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.
1036 Do not execute commands found in any initialization files. Normally,
1037 @value{GDBN} executes the commands in these files after all the command
1038 options and arguments have been processed. @xref{Command Files,,Command
1044 @cindex @code{--quiet}
1045 @cindex @code{--silent}
1047 ``Quiet''. Do not print the introductory and copyright messages. These
1048 messages are also suppressed in batch mode.
1051 @cindex @code{--batch}
1052 Run in batch mode. Exit with status @code{0} after processing all the
1053 command files specified with @samp{-x} (and all commands from
1054 initialization files, if not inhibited with @samp{-n}). Exit with
1055 nonzero status if an error occurs in executing the @value{GDBN} commands
1056 in the command files. Batch mode also disables pagination, sets unlimited
1057 terminal width and height @pxref{Screen Size}, and acts as if @kbd{set confirm
1058 off} were in effect (@pxref{Messages/Warnings}).
1060 Batch mode may be useful for running @value{GDBN} as a filter, for
1061 example to download and run a program on another computer; in order to
1062 make this more useful, the message
1065 Program exited normally.
1069 (which is ordinarily issued whenever a program running under
1070 @value{GDBN} control terminates) is not issued when running in batch
1074 @cindex @code{--batch-silent}
1075 Run in batch mode exactly like @samp{-batch}, but totally silently. All
1076 @value{GDBN} output to @code{stdout} is prevented (@code{stderr} is
1077 unaffected). This is much quieter than @samp{-silent} and would be useless
1078 for an interactive session.
1080 This is particularly useful when using targets that give @samp{Loading section}
1081 messages, for example.
1083 Note that targets that give their output via @value{GDBN}, as opposed to
1084 writing directly to @code{stdout}, will also be made silent.
1086 @item -return-child-result
1087 @cindex @code{--return-child-result}
1088 The return code from @value{GDBN} will be the return code from the child
1089 process (the process being debugged), with the following exceptions:
1093 @value{GDBN} exits abnormally. E.g., due to an incorrect argument or an
1094 internal error. In this case the exit code is the same as it would have been
1095 without @samp{-return-child-result}.
1097 The user quits with an explicit value. E.g., @samp{quit 1}.
1099 The child process never runs, or is not allowed to terminate, in which case
1100 the exit code will be -1.
1103 This option is useful in conjunction with @samp{-batch} or @samp{-batch-silent},
1104 when @value{GDBN} is being used as a remote program loader or simulator
1109 @cindex @code{--nowindows}
1111 ``No windows''. If @value{GDBN} comes with a graphical user interface
1112 (GUI) built in, then this option tells @value{GDBN} to only use the command-line
1113 interface. If no GUI is available, this option has no effect.
1117 @cindex @code{--windows}
1119 If @value{GDBN} includes a GUI, then this option requires it to be
1122 @item -cd @var{directory}
1124 Run @value{GDBN} using @var{directory} as its working directory,
1125 instead of the current directory.
1127 @item -data-directory @var{directory}
1128 @cindex @code{--data-directory}
1129 Run @value{GDBN} using @var{directory} as its data directory.
1130 The data directory is where @value{GDBN} searches for its
1131 auxiliary files. @xref{Data Files}.
1135 @cindex @code{--fullname}
1137 @sc{gnu} Emacs sets this option when it runs @value{GDBN} as a
1138 subprocess. It tells @value{GDBN} to output the full file name and line
1139 number in a standard, recognizable fashion each time a stack frame is
1140 displayed (which includes each time your program stops). This
1141 recognizable format looks like two @samp{\032} characters, followed by
1142 the file name, line number and character position separated by colons,
1143 and a newline. The Emacs-to-@value{GDBN} interface program uses the two
1144 @samp{\032} characters as a signal to display the source code for the
1148 @cindex @code{--epoch}
1149 The Epoch Emacs-@value{GDBN} interface sets this option when it runs
1150 @value{GDBN} as a subprocess. It tells @value{GDBN} to modify its print
1151 routines so as to allow Epoch to display values of expressions in a
1154 @item -annotate @var{level}
1155 @cindex @code{--annotate}
1156 This option sets the @dfn{annotation level} inside @value{GDBN}. Its
1157 effect is identical to using @samp{set annotate @var{level}}
1158 (@pxref{Annotations}). The annotation @var{level} controls how much
1159 information @value{GDBN} prints together with its prompt, values of
1160 expressions, source lines, and other types of output. Level 0 is the
1161 normal, level 1 is for use when @value{GDBN} is run as a subprocess of
1162 @sc{gnu} Emacs, level 3 is the maximum annotation suitable for programs
1163 that control @value{GDBN}, and level 2 has been deprecated.
1165 The annotation mechanism has largely been superseded by @sc{gdb/mi}
1169 @cindex @code{--args}
1170 Change interpretation of command line so that arguments following the
1171 executable file are passed as command line arguments to the inferior.
1172 This option stops option processing.
1174 @item -baud @var{bps}
1176 @cindex @code{--baud}
1178 Set the line speed (baud rate or bits per second) of any serial
1179 interface used by @value{GDBN} for remote debugging.
1181 @item -l @var{timeout}
1183 Set the timeout (in seconds) of any communication used by @value{GDBN}
1184 for remote debugging.
1186 @item -tty @var{device}
1187 @itemx -t @var{device}
1188 @cindex @code{--tty}
1190 Run using @var{device} for your program's standard input and output.
1191 @c FIXME: kingdon thinks there is more to -tty. Investigate.
1193 @c resolve the situation of these eventually
1195 @cindex @code{--tui}
1196 Activate the @dfn{Text User Interface} when starting. The Text User
1197 Interface manages several text windows on the terminal, showing
1198 source, assembly, registers and @value{GDBN} command outputs
1199 (@pxref{TUI, ,@value{GDBN} Text User Interface}). Do not use this
1200 option if you run @value{GDBN} from Emacs (@pxref{Emacs, ,
1201 Using @value{GDBN} under @sc{gnu} Emacs}).
1204 @c @cindex @code{--xdb}
1205 @c Run in XDB compatibility mode, allowing the use of certain XDB commands.
1206 @c For information, see the file @file{xdb_trans.html}, which is usually
1207 @c installed in the directory @code{/opt/langtools/wdb/doc} on HP-UX
1210 @item -interpreter @var{interp}
1211 @cindex @code{--interpreter}
1212 Use the interpreter @var{interp} for interface with the controlling
1213 program or device. This option is meant to be set by programs which
1214 communicate with @value{GDBN} using it as a back end.
1215 @xref{Interpreters, , Command Interpreters}.
1217 @samp{--interpreter=mi} (or @samp{--interpreter=mi2}) causes
1218 @value{GDBN} to use the @dfn{@sc{gdb/mi} interface} (@pxref{GDB/MI, ,
1219 The @sc{gdb/mi} Interface}) included since @value{GDBN} version 6.0. The
1220 previous @sc{gdb/mi} interface, included in @value{GDBN} version 5.3 and
1221 selected with @samp{--interpreter=mi1}, is deprecated. Earlier
1222 @sc{gdb/mi} interfaces are no longer supported.
1225 @cindex @code{--write}
1226 Open the executable and core files for both reading and writing. This
1227 is equivalent to the @samp{set write on} command inside @value{GDBN}
1231 @cindex @code{--statistics}
1232 This option causes @value{GDBN} to print statistics about time and
1233 memory usage after it completes each command and returns to the prompt.
1236 @cindex @code{--version}
1237 This option causes @value{GDBN} to print its version number and
1238 no-warranty blurb, and exit.
1240 @item -use-deprecated-index-sections
1241 @cindex @code{--use-deprecated-index-sections}
1242 This option causes @value{GDBN} to read and use deprecated
1243 @samp{.gdb_index} sections from symbol files. This can speed up
1244 startup, but may result in some functionality being lost.
1245 @xref{Index Section Format}.
1250 @subsection What @value{GDBN} Does During Startup
1251 @cindex @value{GDBN} startup
1253 Here's the description of what @value{GDBN} does during session startup:
1257 Sets up the command interpreter as specified by the command line
1258 (@pxref{Mode Options, interpreter}).
1261 Executes commands and command files specified by the @samp{-iex} and
1262 @samp{-ix} options in their specified order. Usually you should use the
1263 @samp{-ex} and @samp{-x} options instead, but this way you can apply
1264 settings before @value{GDBN} init files get executed and before inferior
1269 Reads the system-wide @dfn{init file} (if @option{--with-system-gdbinit} was
1270 used when building @value{GDBN}; @pxref{System-wide configuration,
1271 ,System-wide configuration and settings}) and executes all the commands in
1275 Reads the init file (if any) in your home directory@footnote{On
1276 DOS/Windows systems, the home directory is the one pointed to by the
1277 @code{HOME} environment variable.} and executes all the commands in
1281 Processes command line options and operands.
1284 Reads and executes the commands from init file (if any) in the current
1285 working directory. This is only done if the current directory is
1286 different from your home directory. Thus, you can have more than one
1287 init file, one generic in your home directory, and another, specific
1288 to the program you are debugging, in the directory where you invoke
1292 If the command line specified a program to debug, or a process to
1293 attach to, or a core file, @value{GDBN} loads any auto-loaded
1294 scripts provided for the program or for its loaded shared libraries.
1295 @xref{Auto-loading}.
1297 If you wish to disable the auto-loading during startup,
1298 you must do something like the following:
1301 $ gdb -iex "set auto-load-scripts off" myprogram
1304 Option @samp{-ex} does not work because the auto-loading is then turned
1308 Executes commands and command files specified by the @samp{-ex} and
1309 @samp{-x} options in their specified order. @xref{Command Files}, for
1310 more details about @value{GDBN} command files.
1313 Reads the command history recorded in the @dfn{history file}.
1314 @xref{Command History}, for more details about the command history and the
1315 files where @value{GDBN} records it.
1318 Init files use the same syntax as @dfn{command files} (@pxref{Command
1319 Files}) and are processed by @value{GDBN} in the same way. The init
1320 file in your home directory can set options (such as @samp{set
1321 complaints}) that affect subsequent processing of command line options
1322 and operands. Init files are not executed if you use the @samp{-nx}
1323 option (@pxref{Mode Options, ,Choosing Modes}).
1325 To display the list of init files loaded by gdb at startup, you
1326 can use @kbd{gdb --help}.
1328 @cindex init file name
1329 @cindex @file{.gdbinit}
1330 @cindex @file{gdb.ini}
1331 The @value{GDBN} init files are normally called @file{.gdbinit}.
1332 The DJGPP port of @value{GDBN} uses the name @file{gdb.ini}, due to
1333 the limitations of file names imposed by DOS filesystems. The Windows
1334 ports of @value{GDBN} use the standard name, but if they find a
1335 @file{gdb.ini} file, they warn you about that and suggest to rename
1336 the file to the standard name.
1340 @section Quitting @value{GDBN}
1341 @cindex exiting @value{GDBN}
1342 @cindex leaving @value{GDBN}
1345 @kindex quit @r{[}@var{expression}@r{]}
1346 @kindex q @r{(@code{quit})}
1347 @item quit @r{[}@var{expression}@r{]}
1349 To exit @value{GDBN}, use the @code{quit} command (abbreviated
1350 @code{q}), or type an end-of-file character (usually @kbd{Ctrl-d}). If you
1351 do not supply @var{expression}, @value{GDBN} will terminate normally;
1352 otherwise it will terminate using the result of @var{expression} as the
1357 An interrupt (often @kbd{Ctrl-c}) does not exit from @value{GDBN}, but rather
1358 terminates the action of any @value{GDBN} command that is in progress and
1359 returns to @value{GDBN} command level. It is safe to type the interrupt
1360 character at any time because @value{GDBN} does not allow it to take effect
1361 until a time when it is safe.
1363 If you have been using @value{GDBN} to control an attached process or
1364 device, you can release it with the @code{detach} command
1365 (@pxref{Attach, ,Debugging an Already-running Process}).
1367 @node Shell Commands
1368 @section Shell Commands
1370 If you need to execute occasional shell commands during your
1371 debugging session, there is no need to leave or suspend @value{GDBN}; you can
1372 just use the @code{shell} command.
1377 @cindex shell escape
1378 @item shell @var{command-string}
1379 @itemx !@var{command-string}
1380 Invoke a standard shell to execute @var{command-string}.
1381 Note that no space is needed between @code{!} and @var{command-string}.
1382 If it exists, the environment variable @code{SHELL} determines which
1383 shell to run. Otherwise @value{GDBN} uses the default shell
1384 (@file{/bin/sh} on Unix systems, @file{COMMAND.COM} on MS-DOS, etc.).
1387 The utility @code{make} is often needed in development environments.
1388 You do not have to use the @code{shell} command for this purpose in
1393 @cindex calling make
1394 @item make @var{make-args}
1395 Execute the @code{make} program with the specified
1396 arguments. This is equivalent to @samp{shell make @var{make-args}}.
1399 @node Logging Output
1400 @section Logging Output
1401 @cindex logging @value{GDBN} output
1402 @cindex save @value{GDBN} output to a file
1404 You may want to save the output of @value{GDBN} commands to a file.
1405 There are several commands to control @value{GDBN}'s logging.
1409 @item set logging on
1411 @item set logging off
1413 @cindex logging file name
1414 @item set logging file @var{file}
1415 Change the name of the current logfile. The default logfile is @file{gdb.txt}.
1416 @item set logging overwrite [on|off]
1417 By default, @value{GDBN} will append to the logfile. Set @code{overwrite} if
1418 you want @code{set logging on} to overwrite the logfile instead.
1419 @item set logging redirect [on|off]
1420 By default, @value{GDBN} output will go to both the terminal and the logfile.
1421 Set @code{redirect} if you want output to go only to the log file.
1422 @kindex show logging
1424 Show the current values of the logging settings.
1428 @chapter @value{GDBN} Commands
1430 You can abbreviate a @value{GDBN} command to the first few letters of the command
1431 name, if that abbreviation is unambiguous; and you can repeat certain
1432 @value{GDBN} commands by typing just @key{RET}. You can also use the @key{TAB}
1433 key to get @value{GDBN} to fill out the rest of a word in a command (or to
1434 show you the alternatives available, if there is more than one possibility).
1437 * Command Syntax:: How to give commands to @value{GDBN}
1438 * Completion:: Command completion
1439 * Help:: How to ask @value{GDBN} for help
1442 @node Command Syntax
1443 @section Command Syntax
1445 A @value{GDBN} command is a single line of input. There is no limit on
1446 how long it can be. It starts with a command name, which is followed by
1447 arguments whose meaning depends on the command name. For example, the
1448 command @code{step} accepts an argument which is the number of times to
1449 step, as in @samp{step 5}. You can also use the @code{step} command
1450 with no arguments. Some commands do not allow any arguments.
1452 @cindex abbreviation
1453 @value{GDBN} command names may always be truncated if that abbreviation is
1454 unambiguous. Other possible command abbreviations are listed in the
1455 documentation for individual commands. In some cases, even ambiguous
1456 abbreviations are allowed; for example, @code{s} is specially defined as
1457 equivalent to @code{step} even though there are other commands whose
1458 names start with @code{s}. You can test abbreviations by using them as
1459 arguments to the @code{help} command.
1461 @cindex repeating commands
1462 @kindex RET @r{(repeat last command)}
1463 A blank line as input to @value{GDBN} (typing just @key{RET}) means to
1464 repeat the previous command. Certain commands (for example, @code{run})
1465 will not repeat this way; these are commands whose unintentional
1466 repetition might cause trouble and which you are unlikely to want to
1467 repeat. User-defined commands can disable this feature; see
1468 @ref{Define, dont-repeat}.
1470 The @code{list} and @code{x} commands, when you repeat them with
1471 @key{RET}, construct new arguments rather than repeating
1472 exactly as typed. This permits easy scanning of source or memory.
1474 @value{GDBN} can also use @key{RET} in another way: to partition lengthy
1475 output, in a way similar to the common utility @code{more}
1476 (@pxref{Screen Size,,Screen Size}). Since it is easy to press one
1477 @key{RET} too many in this situation, @value{GDBN} disables command
1478 repetition after any command that generates this sort of display.
1480 @kindex # @r{(a comment)}
1482 Any text from a @kbd{#} to the end of the line is a comment; it does
1483 nothing. This is useful mainly in command files (@pxref{Command
1484 Files,,Command Files}).
1486 @cindex repeating command sequences
1487 @kindex Ctrl-o @r{(operate-and-get-next)}
1488 The @kbd{Ctrl-o} binding is useful for repeating a complex sequence of
1489 commands. This command accepts the current line, like @key{RET}, and
1490 then fetches the next line relative to the current line from the history
1494 @section Command Completion
1497 @cindex word completion
1498 @value{GDBN} can fill in the rest of a word in a command for you, if there is
1499 only one possibility; it can also show you what the valid possibilities
1500 are for the next word in a command, at any time. This works for @value{GDBN}
1501 commands, @value{GDBN} subcommands, and the names of symbols in your program.
1503 Press the @key{TAB} key whenever you want @value{GDBN} to fill out the rest
1504 of a word. If there is only one possibility, @value{GDBN} fills in the
1505 word, and waits for you to finish the command (or press @key{RET} to
1506 enter it). For example, if you type
1508 @c FIXME "@key" does not distinguish its argument sufficiently to permit
1509 @c complete accuracy in these examples; space introduced for clarity.
1510 @c If texinfo enhancements make it unnecessary, it would be nice to
1511 @c replace " @key" by "@key" in the following...
1513 (@value{GDBP}) info bre @key{TAB}
1517 @value{GDBN} fills in the rest of the word @samp{breakpoints}, since that is
1518 the only @code{info} subcommand beginning with @samp{bre}:
1521 (@value{GDBP}) info breakpoints
1525 You can either press @key{RET} at this point, to run the @code{info
1526 breakpoints} command, or backspace and enter something else, if
1527 @samp{breakpoints} does not look like the command you expected. (If you
1528 were sure you wanted @code{info breakpoints} in the first place, you
1529 might as well just type @key{RET} immediately after @samp{info bre},
1530 to exploit command abbreviations rather than command completion).
1532 If there is more than one possibility for the next word when you press
1533 @key{TAB}, @value{GDBN} sounds a bell. You can either supply more
1534 characters and try again, or just press @key{TAB} a second time;
1535 @value{GDBN} displays all the possible completions for that word. For
1536 example, you might want to set a breakpoint on a subroutine whose name
1537 begins with @samp{make_}, but when you type @kbd{b make_@key{TAB}} @value{GDBN}
1538 just sounds the bell. Typing @key{TAB} again displays all the
1539 function names in your program that begin with those characters, for
1543 (@value{GDBP}) b make_ @key{TAB}
1544 @exdent @value{GDBN} sounds bell; press @key{TAB} again, to see:
1545 make_a_section_from_file make_environ
1546 make_abs_section make_function_type
1547 make_blockvector make_pointer_type
1548 make_cleanup make_reference_type
1549 make_command make_symbol_completion_list
1550 (@value{GDBP}) b make_
1554 After displaying the available possibilities, @value{GDBN} copies your
1555 partial input (@samp{b make_} in the example) so you can finish the
1558 If you just want to see the list of alternatives in the first place, you
1559 can press @kbd{M-?} rather than pressing @key{TAB} twice. @kbd{M-?}
1560 means @kbd{@key{META} ?}. You can type this either by holding down a
1561 key designated as the @key{META} shift on your keyboard (if there is
1562 one) while typing @kbd{?}, or as @key{ESC} followed by @kbd{?}.
1564 @cindex quotes in commands
1565 @cindex completion of quoted strings
1566 Sometimes the string you need, while logically a ``word'', may contain
1567 parentheses or other characters that @value{GDBN} normally excludes from
1568 its notion of a word. To permit word completion to work in this
1569 situation, you may enclose words in @code{'} (single quote marks) in
1570 @value{GDBN} commands.
1572 The most likely situation where you might need this is in typing the
1573 name of a C@t{++} function. This is because C@t{++} allows function
1574 overloading (multiple definitions of the same function, distinguished
1575 by argument type). For example, when you want to set a breakpoint you
1576 may need to distinguish whether you mean the version of @code{name}
1577 that takes an @code{int} parameter, @code{name(int)}, or the version
1578 that takes a @code{float} parameter, @code{name(float)}. To use the
1579 word-completion facilities in this situation, type a single quote
1580 @code{'} at the beginning of the function name. This alerts
1581 @value{GDBN} that it may need to consider more information than usual
1582 when you press @key{TAB} or @kbd{M-?} to request word completion:
1585 (@value{GDBP}) b 'bubble( @kbd{M-?}
1586 bubble(double,double) bubble(int,int)
1587 (@value{GDBP}) b 'bubble(
1590 In some cases, @value{GDBN} can tell that completing a name requires using
1591 quotes. When this happens, @value{GDBN} inserts the quote for you (while
1592 completing as much as it can) if you do not type the quote in the first
1596 (@value{GDBP}) b bub @key{TAB}
1597 @exdent @value{GDBN} alters your input line to the following, and rings a bell:
1598 (@value{GDBP}) b 'bubble(
1602 In general, @value{GDBN} can tell that a quote is needed (and inserts it) if
1603 you have not yet started typing the argument list when you ask for
1604 completion on an overloaded symbol.
1606 For more information about overloaded functions, see @ref{C Plus Plus
1607 Expressions, ,C@t{++} Expressions}. You can use the command @code{set
1608 overload-resolution off} to disable overload resolution;
1609 see @ref{Debugging C Plus Plus, ,@value{GDBN} Features for C@t{++}}.
1611 @cindex completion of structure field names
1612 @cindex structure field name completion
1613 @cindex completion of union field names
1614 @cindex union field name completion
1615 When completing in an expression which looks up a field in a
1616 structure, @value{GDBN} also tries@footnote{The completer can be
1617 confused by certain kinds of invalid expressions. Also, it only
1618 examines the static type of the expression, not the dynamic type.} to
1619 limit completions to the field names available in the type of the
1623 (@value{GDBP}) p gdb_stdout.@kbd{M-?}
1624 magic to_fputs to_rewind
1625 to_data to_isatty to_write
1626 to_delete to_put to_write_async_safe
1631 This is because the @code{gdb_stdout} is a variable of the type
1632 @code{struct ui_file} that is defined in @value{GDBN} sources as
1639 ui_file_flush_ftype *to_flush;
1640 ui_file_write_ftype *to_write;
1641 ui_file_write_async_safe_ftype *to_write_async_safe;
1642 ui_file_fputs_ftype *to_fputs;
1643 ui_file_read_ftype *to_read;
1644 ui_file_delete_ftype *to_delete;
1645 ui_file_isatty_ftype *to_isatty;
1646 ui_file_rewind_ftype *to_rewind;
1647 ui_file_put_ftype *to_put;
1654 @section Getting Help
1655 @cindex online documentation
1658 You can always ask @value{GDBN} itself for information on its commands,
1659 using the command @code{help}.
1662 @kindex h @r{(@code{help})}
1665 You can use @code{help} (abbreviated @code{h}) with no arguments to
1666 display a short list of named classes of commands:
1670 List of classes of commands:
1672 aliases -- Aliases of other commands
1673 breakpoints -- Making program stop at certain points
1674 data -- Examining data
1675 files -- Specifying and examining files
1676 internals -- Maintenance commands
1677 obscure -- Obscure features
1678 running -- Running the program
1679 stack -- Examining the stack
1680 status -- Status inquiries
1681 support -- Support facilities
1682 tracepoints -- Tracing of program execution without
1683 stopping the program
1684 user-defined -- User-defined commands
1686 Type "help" followed by a class name for a list of
1687 commands in that class.
1688 Type "help" followed by command name for full
1690 Command name abbreviations are allowed if unambiguous.
1693 @c the above line break eliminates huge line overfull...
1695 @item help @var{class}
1696 Using one of the general help classes as an argument, you can get a
1697 list of the individual commands in that class. For example, here is the
1698 help display for the class @code{status}:
1701 (@value{GDBP}) help status
1706 @c Line break in "show" line falsifies real output, but needed
1707 @c to fit in smallbook page size.
1708 info -- Generic command for showing things
1709 about the program being debugged
1710 show -- Generic command for showing things
1713 Type "help" followed by command name for full
1715 Command name abbreviations are allowed if unambiguous.
1719 @item help @var{command}
1720 With a command name as @code{help} argument, @value{GDBN} displays a
1721 short paragraph on how to use that command.
1724 @item apropos @var{args}
1725 The @code{apropos} command searches through all of the @value{GDBN}
1726 commands, and their documentation, for the regular expression specified in
1727 @var{args}. It prints out all matches found. For example:
1738 alias -- Define a new command that is an alias of an existing command
1739 aliases -- Aliases of other commands
1740 d -- Delete some breakpoints or auto-display expressions
1741 del -- Delete some breakpoints or auto-display expressions
1742 delete -- Delete some breakpoints or auto-display expressions
1747 @item complete @var{args}
1748 The @code{complete @var{args}} command lists all the possible completions
1749 for the beginning of a command. Use @var{args} to specify the beginning of the
1750 command you want completed. For example:
1756 @noindent results in:
1767 @noindent This is intended for use by @sc{gnu} Emacs.
1770 In addition to @code{help}, you can use the @value{GDBN} commands @code{info}
1771 and @code{show} to inquire about the state of your program, or the state
1772 of @value{GDBN} itself. Each command supports many topics of inquiry; this
1773 manual introduces each of them in the appropriate context. The listings
1774 under @code{info} and under @code{show} in the Index point to
1775 all the sub-commands. @xref{Index}.
1780 @kindex i @r{(@code{info})}
1782 This command (abbreviated @code{i}) is for describing the state of your
1783 program. For example, you can show the arguments passed to a function
1784 with @code{info args}, list the registers currently in use with @code{info
1785 registers}, or list the breakpoints you have set with @code{info breakpoints}.
1786 You can get a complete list of the @code{info} sub-commands with
1787 @w{@code{help info}}.
1791 You can assign the result of an expression to an environment variable with
1792 @code{set}. For example, you can set the @value{GDBN} prompt to a $-sign with
1793 @code{set prompt $}.
1797 In contrast to @code{info}, @code{show} is for describing the state of
1798 @value{GDBN} itself.
1799 You can change most of the things you can @code{show}, by using the
1800 related command @code{set}; for example, you can control what number
1801 system is used for displays with @code{set radix}, or simply inquire
1802 which is currently in use with @code{show radix}.
1805 To display all the settable parameters and their current
1806 values, you can use @code{show} with no arguments; you may also use
1807 @code{info set}. Both commands produce the same display.
1808 @c FIXME: "info set" violates the rule that "info" is for state of
1809 @c FIXME...program. Ck w/ GNU: "info set" to be called something else,
1810 @c FIXME...or change desc of rule---eg "state of prog and debugging session"?
1814 Here are three miscellaneous @code{show} subcommands, all of which are
1815 exceptional in lacking corresponding @code{set} commands:
1818 @kindex show version
1819 @cindex @value{GDBN} version number
1821 Show what version of @value{GDBN} is running. You should include this
1822 information in @value{GDBN} bug-reports. If multiple versions of
1823 @value{GDBN} are in use at your site, you may need to determine which
1824 version of @value{GDBN} you are running; as @value{GDBN} evolves, new
1825 commands are introduced, and old ones may wither away. Also, many
1826 system vendors ship variant versions of @value{GDBN}, and there are
1827 variant versions of @value{GDBN} in @sc{gnu}/Linux distributions as well.
1828 The version number is the same as the one announced when you start
1831 @kindex show copying
1832 @kindex info copying
1833 @cindex display @value{GDBN} copyright
1836 Display information about permission for copying @value{GDBN}.
1838 @kindex show warranty
1839 @kindex info warranty
1841 @itemx info warranty
1842 Display the @sc{gnu} ``NO WARRANTY'' statement, or a warranty,
1843 if your version of @value{GDBN} comes with one.
1848 @chapter Running Programs Under @value{GDBN}
1850 When you run a program under @value{GDBN}, you must first generate
1851 debugging information when you compile it.
1853 You may start @value{GDBN} with its arguments, if any, in an environment
1854 of your choice. If you are doing native debugging, you may redirect
1855 your program's input and output, debug an already running process, or
1856 kill a child process.
1859 * Compilation:: Compiling for debugging
1860 * Starting:: Starting your program
1861 * Arguments:: Your program's arguments
1862 * Environment:: Your program's environment
1864 * Working Directory:: Your program's working directory
1865 * Input/Output:: Your program's input and output
1866 * Attach:: Debugging an already-running process
1867 * Kill Process:: Killing the child process
1869 * Inferiors and Programs:: Debugging multiple inferiors and programs
1870 * Threads:: Debugging programs with multiple threads
1871 * Forks:: Debugging forks
1872 * Checkpoint/Restart:: Setting a @emph{bookmark} to return to later
1876 @section Compiling for Debugging
1878 In order to debug a program effectively, you need to generate
1879 debugging information when you compile it. This debugging information
1880 is stored in the object file; it describes the data type of each
1881 variable or function and the correspondence between source line numbers
1882 and addresses in the executable code.
1884 To request debugging information, specify the @samp{-g} option when you run
1887 Programs that are to be shipped to your customers are compiled with
1888 optimizations, using the @samp{-O} compiler option. However, some
1889 compilers are unable to handle the @samp{-g} and @samp{-O} options
1890 together. Using those compilers, you cannot generate optimized
1891 executables containing debugging information.
1893 @value{NGCC}, the @sc{gnu} C/C@t{++} compiler, supports @samp{-g} with or
1894 without @samp{-O}, making it possible to debug optimized code. We
1895 recommend that you @emph{always} use @samp{-g} whenever you compile a
1896 program. You may think your program is correct, but there is no sense
1897 in pushing your luck. For more information, see @ref{Optimized Code}.
1899 Older versions of the @sc{gnu} C compiler permitted a variant option
1900 @w{@samp{-gg}} for debugging information. @value{GDBN} no longer supports this
1901 format; if your @sc{gnu} C compiler has this option, do not use it.
1903 @value{GDBN} knows about preprocessor macros and can show you their
1904 expansion (@pxref{Macros}). Most compilers do not include information
1905 about preprocessor macros in the debugging information if you specify
1906 the @option{-g} flag alone. Version 3.1 and later of @value{NGCC},
1907 the @sc{gnu} C compiler, provides macro information if you are using
1908 the DWARF debugging format, and specify the option @option{-g3}.
1910 @xref{Debugging Options,,Options for Debugging Your Program or GCC,
1911 gcc.info, Using the @sc{gnu} Compiler Collection (GCC)}, for more
1912 information on @value{NGCC} options affecting debug information.
1914 You will have the best debugging experience if you use the latest
1915 version of the DWARF debugging format that your compiler supports.
1916 DWARF is currently the most expressive and best supported debugging
1917 format in @value{GDBN}.
1921 @section Starting your Program
1927 @kindex r @r{(@code{run})}
1930 Use the @code{run} command to start your program under @value{GDBN}.
1931 You must first specify the program name (except on VxWorks) with an
1932 argument to @value{GDBN} (@pxref{Invocation, ,Getting In and Out of
1933 @value{GDBN}}), or by using the @code{file} or @code{exec-file} command
1934 (@pxref{Files, ,Commands to Specify Files}).
1938 If you are running your program in an execution environment that
1939 supports processes, @code{run} creates an inferior process and makes
1940 that process run your program. In some environments without processes,
1941 @code{run} jumps to the start of your program. Other targets,
1942 like @samp{remote}, are always running. If you get an error
1943 message like this one:
1946 The "remote" target does not support "run".
1947 Try "help target" or "continue".
1951 then use @code{continue} to run your program. You may need @code{load}
1952 first (@pxref{load}).
1954 The execution of a program is affected by certain information it
1955 receives from its superior. @value{GDBN} provides ways to specify this
1956 information, which you must do @emph{before} starting your program. (You
1957 can change it after starting your program, but such changes only affect
1958 your program the next time you start it.) This information may be
1959 divided into four categories:
1962 @item The @emph{arguments.}
1963 Specify the arguments to give your program as the arguments of the
1964 @code{run} command. If a shell is available on your target, the shell
1965 is used to pass the arguments, so that you may use normal conventions
1966 (such as wildcard expansion or variable substitution) in describing
1968 In Unix systems, you can control which shell is used with the
1969 @code{SHELL} environment variable.
1970 @xref{Arguments, ,Your Program's Arguments}.
1972 @item The @emph{environment.}
1973 Your program normally inherits its environment from @value{GDBN}, but you can
1974 use the @value{GDBN} commands @code{set environment} and @code{unset
1975 environment} to change parts of the environment that affect
1976 your program. @xref{Environment, ,Your Program's Environment}.
1978 @item The @emph{working directory.}
1979 Your program inherits its working directory from @value{GDBN}. You can set
1980 the @value{GDBN} working directory with the @code{cd} command in @value{GDBN}.
1981 @xref{Working Directory, ,Your Program's Working Directory}.
1983 @item The @emph{standard input and output.}
1984 Your program normally uses the same device for standard input and
1985 standard output as @value{GDBN} is using. You can redirect input and output
1986 in the @code{run} command line, or you can use the @code{tty} command to
1987 set a different device for your program.
1988 @xref{Input/Output, ,Your Program's Input and Output}.
1991 @emph{Warning:} While input and output redirection work, you cannot use
1992 pipes to pass the output of the program you are debugging to another
1993 program; if you attempt this, @value{GDBN} is likely to wind up debugging the
1997 When you issue the @code{run} command, your program begins to execute
1998 immediately. @xref{Stopping, ,Stopping and Continuing}, for discussion
1999 of how to arrange for your program to stop. Once your program has
2000 stopped, you may call functions in your program, using the @code{print}
2001 or @code{call} commands. @xref{Data, ,Examining Data}.
2003 If the modification time of your symbol file has changed since the last
2004 time @value{GDBN} read its symbols, @value{GDBN} discards its symbol
2005 table, and reads it again. When it does this, @value{GDBN} tries to retain
2006 your current breakpoints.
2011 @cindex run to main procedure
2012 The name of the main procedure can vary from language to language.
2013 With C or C@t{++}, the main procedure name is always @code{main}, but
2014 other languages such as Ada do not require a specific name for their
2015 main procedure. The debugger provides a convenient way to start the
2016 execution of the program and to stop at the beginning of the main
2017 procedure, depending on the language used.
2019 The @samp{start} command does the equivalent of setting a temporary
2020 breakpoint at the beginning of the main procedure and then invoking
2021 the @samp{run} command.
2023 @cindex elaboration phase
2024 Some programs contain an @dfn{elaboration} phase where some startup code is
2025 executed before the main procedure is called. This depends on the
2026 languages used to write your program. In C@t{++}, for instance,
2027 constructors for static and global objects are executed before
2028 @code{main} is called. It is therefore possible that the debugger stops
2029 before reaching the main procedure. However, the temporary breakpoint
2030 will remain to halt execution.
2032 Specify the arguments to give to your program as arguments to the
2033 @samp{start} command. These arguments will be given verbatim to the
2034 underlying @samp{run} command. Note that the same arguments will be
2035 reused if no argument is provided during subsequent calls to
2036 @samp{start} or @samp{run}.
2038 It is sometimes necessary to debug the program during elaboration. In
2039 these cases, using the @code{start} command would stop the execution of
2040 your program too late, as the program would have already completed the
2041 elaboration phase. Under these circumstances, insert breakpoints in your
2042 elaboration code before running your program.
2044 @kindex set exec-wrapper
2045 @item set exec-wrapper @var{wrapper}
2046 @itemx show exec-wrapper
2047 @itemx unset exec-wrapper
2048 When @samp{exec-wrapper} is set, the specified wrapper is used to
2049 launch programs for debugging. @value{GDBN} starts your program
2050 with a shell command of the form @kbd{exec @var{wrapper}
2051 @var{program}}. Quoting is added to @var{program} and its
2052 arguments, but not to @var{wrapper}, so you should add quotes if
2053 appropriate for your shell. The wrapper runs until it executes
2054 your program, and then @value{GDBN} takes control.
2056 You can use any program that eventually calls @code{execve} with
2057 its arguments as a wrapper. Several standard Unix utilities do
2058 this, e.g.@: @code{env} and @code{nohup}. Any Unix shell script ending
2059 with @code{exec "$@@"} will also work.
2061 For example, you can use @code{env} to pass an environment variable to
2062 the debugged program, without setting the variable in your shell's
2066 (@value{GDBP}) set exec-wrapper env 'LD_PRELOAD=libtest.so'
2070 This command is available when debugging locally on most targets, excluding
2071 @sc{djgpp}, Cygwin, MS Windows, and QNX Neutrino.
2073 @kindex set disable-randomization
2074 @item set disable-randomization
2075 @itemx set disable-randomization on
2076 This option (enabled by default in @value{GDBN}) will turn off the native
2077 randomization of the virtual address space of the started program. This option
2078 is useful for multiple debugging sessions to make the execution better
2079 reproducible and memory addresses reusable across debugging sessions.
2081 This feature is implemented only on certain targets, including @sc{gnu}/Linux.
2082 On @sc{gnu}/Linux you can get the same behavior using
2085 (@value{GDBP}) set exec-wrapper setarch `uname -m` -R
2088 @item set disable-randomization off
2089 Leave the behavior of the started executable unchanged. Some bugs rear their
2090 ugly heads only when the program is loaded at certain addresses. If your bug
2091 disappears when you run the program under @value{GDBN}, that might be because
2092 @value{GDBN} by default disables the address randomization on platforms, such
2093 as @sc{gnu}/Linux, which do that for stand-alone programs. Use @kbd{set
2094 disable-randomization off} to try to reproduce such elusive bugs.
2096 On targets where it is available, virtual address space randomization
2097 protects the programs against certain kinds of security attacks. In these
2098 cases the attacker needs to know the exact location of a concrete executable
2099 code. Randomizing its location makes it impossible to inject jumps misusing
2100 a code at its expected addresses.
2102 Prelinking shared libraries provides a startup performance advantage but it
2103 makes addresses in these libraries predictable for privileged processes by
2104 having just unprivileged access at the target system. Reading the shared
2105 library binary gives enough information for assembling the malicious code
2106 misusing it. Still even a prelinked shared library can get loaded at a new
2107 random address just requiring the regular relocation process during the
2108 startup. Shared libraries not already prelinked are always loaded at
2109 a randomly chosen address.
2111 Position independent executables (PIE) contain position independent code
2112 similar to the shared libraries and therefore such executables get loaded at
2113 a randomly chosen address upon startup. PIE executables always load even
2114 already prelinked shared libraries at a random address. You can build such
2115 executable using @command{gcc -fPIE -pie}.
2117 Heap (malloc storage), stack and custom mmap areas are always placed randomly
2118 (as long as the randomization is enabled).
2120 @item show disable-randomization
2121 Show the current setting of the explicit disable of the native randomization of
2122 the virtual address space of the started program.
2127 @section Your Program's Arguments
2129 @cindex arguments (to your program)
2130 The arguments to your program can be specified by the arguments of the
2132 They are passed to a shell, which expands wildcard characters and
2133 performs redirection of I/O, and thence to your program. Your
2134 @code{SHELL} environment variable (if it exists) specifies what shell
2135 @value{GDBN} uses. If you do not define @code{SHELL}, @value{GDBN} uses
2136 the default shell (@file{/bin/sh} on Unix).
2138 On non-Unix systems, the program is usually invoked directly by
2139 @value{GDBN}, which emulates I/O redirection via the appropriate system
2140 calls, and the wildcard characters are expanded by the startup code of
2141 the program, not by the shell.
2143 @code{run} with no arguments uses the same arguments used by the previous
2144 @code{run}, or those set by the @code{set args} command.
2149 Specify the arguments to be used the next time your program is run. If
2150 @code{set args} has no arguments, @code{run} executes your program
2151 with no arguments. Once you have run your program with arguments,
2152 using @code{set args} before the next @code{run} is the only way to run
2153 it again without arguments.
2157 Show the arguments to give your program when it is started.
2161 @section Your Program's Environment
2163 @cindex environment (of your program)
2164 The @dfn{environment} consists of a set of environment variables and
2165 their values. Environment variables conventionally record such things as
2166 your user name, your home directory, your terminal type, and your search
2167 path for programs to run. Usually you set up environment variables with
2168 the shell and they are inherited by all the other programs you run. When
2169 debugging, it can be useful to try running your program with a modified
2170 environment without having to start @value{GDBN} over again.
2174 @item path @var{directory}
2175 Add @var{directory} to the front of the @code{PATH} environment variable
2176 (the search path for executables) that will be passed to your program.
2177 The value of @code{PATH} used by @value{GDBN} does not change.
2178 You may specify several directory names, separated by whitespace or by a
2179 system-dependent separator character (@samp{:} on Unix, @samp{;} on
2180 MS-DOS and MS-Windows). If @var{directory} is already in the path, it
2181 is moved to the front, so it is searched sooner.
2183 You can use the string @samp{$cwd} to refer to whatever is the current
2184 working directory at the time @value{GDBN} searches the path. If you
2185 use @samp{.} instead, it refers to the directory where you executed the
2186 @code{path} command. @value{GDBN} replaces @samp{.} in the
2187 @var{directory} argument (with the current path) before adding
2188 @var{directory} to the search path.
2189 @c 'path' is explicitly nonrepeatable, but RMS points out it is silly to
2190 @c document that, since repeating it would be a no-op.
2194 Display the list of search paths for executables (the @code{PATH}
2195 environment variable).
2197 @kindex show environment
2198 @item show environment @r{[}@var{varname}@r{]}
2199 Print the value of environment variable @var{varname} to be given to
2200 your program when it starts. If you do not supply @var{varname},
2201 print the names and values of all environment variables to be given to
2202 your program. You can abbreviate @code{environment} as @code{env}.
2204 @kindex set environment
2205 @item set environment @var{varname} @r{[}=@var{value}@r{]}
2206 Set environment variable @var{varname} to @var{value}. The value
2207 changes for your program only, not for @value{GDBN} itself. @var{value} may
2208 be any string; the values of environment variables are just strings, and
2209 any interpretation is supplied by your program itself. The @var{value}
2210 parameter is optional; if it is eliminated, the variable is set to a
2212 @c "any string" here does not include leading, trailing
2213 @c blanks. Gnu asks: does anyone care?
2215 For example, this command:
2222 tells the debugged program, when subsequently run, that its user is named
2223 @samp{foo}. (The spaces around @samp{=} are used for clarity here; they
2224 are not actually required.)
2226 @kindex unset environment
2227 @item unset environment @var{varname}
2228 Remove variable @var{varname} from the environment to be passed to your
2229 program. This is different from @samp{set env @var{varname} =};
2230 @code{unset environment} removes the variable from the environment,
2231 rather than assigning it an empty value.
2234 @emph{Warning:} On Unix systems, @value{GDBN} runs your program using
2236 by your @code{SHELL} environment variable if it exists (or
2237 @code{/bin/sh} if not). If your @code{SHELL} variable names a shell
2238 that runs an initialization file---such as @file{.cshrc} for C-shell, or
2239 @file{.bashrc} for BASH---any variables you set in that file affect
2240 your program. You may wish to move setting of environment variables to
2241 files that are only run when you sign on, such as @file{.login} or
2244 @node Working Directory
2245 @section Your Program's Working Directory
2247 @cindex working directory (of your program)
2248 Each time you start your program with @code{run}, it inherits its
2249 working directory from the current working directory of @value{GDBN}.
2250 The @value{GDBN} working directory is initially whatever it inherited
2251 from its parent process (typically the shell), but you can specify a new
2252 working directory in @value{GDBN} with the @code{cd} command.
2254 The @value{GDBN} working directory also serves as a default for the commands
2255 that specify files for @value{GDBN} to operate on. @xref{Files, ,Commands to
2260 @cindex change working directory
2261 @item cd @var{directory}
2262 Set the @value{GDBN} working directory to @var{directory}.
2266 Print the @value{GDBN} working directory.
2269 It is generally impossible to find the current working directory of
2270 the process being debugged (since a program can change its directory
2271 during its run). If you work on a system where @value{GDBN} is
2272 configured with the @file{/proc} support, you can use the @code{info
2273 proc} command (@pxref{SVR4 Process Information}) to find out the
2274 current working directory of the debuggee.
2277 @section Your Program's Input and Output
2282 By default, the program you run under @value{GDBN} does input and output to
2283 the same terminal that @value{GDBN} uses. @value{GDBN} switches the terminal
2284 to its own terminal modes to interact with you, but it records the terminal
2285 modes your program was using and switches back to them when you continue
2286 running your program.
2289 @kindex info terminal
2291 Displays information recorded by @value{GDBN} about the terminal modes your
2295 You can redirect your program's input and/or output using shell
2296 redirection with the @code{run} command. For example,
2303 starts your program, diverting its output to the file @file{outfile}.
2306 @cindex controlling terminal
2307 Another way to specify where your program should do input and output is
2308 with the @code{tty} command. This command accepts a file name as
2309 argument, and causes this file to be the default for future @code{run}
2310 commands. It also resets the controlling terminal for the child
2311 process, for future @code{run} commands. For example,
2318 directs that processes started with subsequent @code{run} commands
2319 default to do input and output on the terminal @file{/dev/ttyb} and have
2320 that as their controlling terminal.
2322 An explicit redirection in @code{run} overrides the @code{tty} command's
2323 effect on the input/output device, but not its effect on the controlling
2326 When you use the @code{tty} command or redirect input in the @code{run}
2327 command, only the input @emph{for your program} is affected. The input
2328 for @value{GDBN} still comes from your terminal. @code{tty} is an alias
2329 for @code{set inferior-tty}.
2331 @cindex inferior tty
2332 @cindex set inferior controlling terminal
2333 You can use the @code{show inferior-tty} command to tell @value{GDBN} to
2334 display the name of the terminal that will be used for future runs of your
2338 @item set inferior-tty /dev/ttyb
2339 @kindex set inferior-tty
2340 Set the tty for the program being debugged to /dev/ttyb.
2342 @item show inferior-tty
2343 @kindex show inferior-tty
2344 Show the current tty for the program being debugged.
2348 @section Debugging an Already-running Process
2353 @item attach @var{process-id}
2354 This command attaches to a running process---one that was started
2355 outside @value{GDBN}. (@code{info files} shows your active
2356 targets.) The command takes as argument a process ID. The usual way to
2357 find out the @var{process-id} of a Unix process is with the @code{ps} utility,
2358 or with the @samp{jobs -l} shell command.
2360 @code{attach} does not repeat if you press @key{RET} a second time after
2361 executing the command.
2364 To use @code{attach}, your program must be running in an environment
2365 which supports processes; for example, @code{attach} does not work for
2366 programs on bare-board targets that lack an operating system. You must
2367 also have permission to send the process a signal.
2369 When you use @code{attach}, the debugger finds the program running in
2370 the process first by looking in the current working directory, then (if
2371 the program is not found) by using the source file search path
2372 (@pxref{Source Path, ,Specifying Source Directories}). You can also use
2373 the @code{file} command to load the program. @xref{Files, ,Commands to
2376 The first thing @value{GDBN} does after arranging to debug the specified
2377 process is to stop it. You can examine and modify an attached process
2378 with all the @value{GDBN} commands that are ordinarily available when
2379 you start processes with @code{run}. You can insert breakpoints; you
2380 can step and continue; you can modify storage. If you would rather the
2381 process continue running, you may use the @code{continue} command after
2382 attaching @value{GDBN} to the process.
2387 When you have finished debugging the attached process, you can use the
2388 @code{detach} command to release it from @value{GDBN} control. Detaching
2389 the process continues its execution. After the @code{detach} command,
2390 that process and @value{GDBN} become completely independent once more, and you
2391 are ready to @code{attach} another process or start one with @code{run}.
2392 @code{detach} does not repeat if you press @key{RET} again after
2393 executing the command.
2396 If you exit @value{GDBN} while you have an attached process, you detach
2397 that process. If you use the @code{run} command, you kill that process.
2398 By default, @value{GDBN} asks for confirmation if you try to do either of these
2399 things; you can control whether or not you need to confirm by using the
2400 @code{set confirm} command (@pxref{Messages/Warnings, ,Optional Warnings and
2404 @section Killing the Child Process
2409 Kill the child process in which your program is running under @value{GDBN}.
2412 This command is useful if you wish to debug a core dump instead of a
2413 running process. @value{GDBN} ignores any core dump file while your program
2416 On some operating systems, a program cannot be executed outside @value{GDBN}
2417 while you have breakpoints set on it inside @value{GDBN}. You can use the
2418 @code{kill} command in this situation to permit running your program
2419 outside the debugger.
2421 The @code{kill} command is also useful if you wish to recompile and
2422 relink your program, since on many systems it is impossible to modify an
2423 executable file while it is running in a process. In this case, when you
2424 next type @code{run}, @value{GDBN} notices that the file has changed, and
2425 reads the symbol table again (while trying to preserve your current
2426 breakpoint settings).
2428 @node Inferiors and Programs
2429 @section Debugging Multiple Inferiors and Programs
2431 @value{GDBN} lets you run and debug multiple programs in a single
2432 session. In addition, @value{GDBN} on some systems may let you run
2433 several programs simultaneously (otherwise you have to exit from one
2434 before starting another). In the most general case, you can have
2435 multiple threads of execution in each of multiple processes, launched
2436 from multiple executables.
2439 @value{GDBN} represents the state of each program execution with an
2440 object called an @dfn{inferior}. An inferior typically corresponds to
2441 a process, but is more general and applies also to targets that do not
2442 have processes. Inferiors may be created before a process runs, and
2443 may be retained after a process exits. Inferiors have unique
2444 identifiers that are different from process ids. Usually each
2445 inferior will also have its own distinct address space, although some
2446 embedded targets may have several inferiors running in different parts
2447 of a single address space. Each inferior may in turn have multiple
2448 threads running in it.
2450 To find out what inferiors exist at any moment, use @w{@code{info
2454 @kindex info inferiors
2455 @item info inferiors
2456 Print a list of all inferiors currently being managed by @value{GDBN}.
2458 @value{GDBN} displays for each inferior (in this order):
2462 the inferior number assigned by @value{GDBN}
2465 the target system's inferior identifier
2468 the name of the executable the inferior is running.
2473 An asterisk @samp{*} preceding the @value{GDBN} inferior number
2474 indicates the current inferior.
2478 @c end table here to get a little more width for example
2481 (@value{GDBP}) info inferiors
2482 Num Description Executable
2483 2 process 2307 hello
2484 * 1 process 3401 goodbye
2487 To switch focus between inferiors, use the @code{inferior} command:
2490 @kindex inferior @var{infno}
2491 @item inferior @var{infno}
2492 Make inferior number @var{infno} the current inferior. The argument
2493 @var{infno} is the inferior number assigned by @value{GDBN}, as shown
2494 in the first field of the @samp{info inferiors} display.
2498 You can get multiple executables into a debugging session via the
2499 @code{add-inferior} and @w{@code{clone-inferior}} commands. On some
2500 systems @value{GDBN} can add inferiors to the debug session
2501 automatically by following calls to @code{fork} and @code{exec}. To
2502 remove inferiors from the debugging session use the
2503 @w{@code{remove-inferiors}} command.
2506 @kindex add-inferior
2507 @item add-inferior [ -copies @var{n} ] [ -exec @var{executable} ]
2508 Adds @var{n} inferiors to be run using @var{executable} as the
2509 executable. @var{n} defaults to 1. If no executable is specified,
2510 the inferiors begins empty, with no program. You can still assign or
2511 change the program assigned to the inferior at any time by using the
2512 @code{file} command with the executable name as its argument.
2514 @kindex clone-inferior
2515 @item clone-inferior [ -copies @var{n} ] [ @var{infno} ]
2516 Adds @var{n} inferiors ready to execute the same program as inferior
2517 @var{infno}. @var{n} defaults to 1. @var{infno} defaults to the
2518 number of the current inferior. This is a convenient command when you
2519 want to run another instance of the inferior you are debugging.
2522 (@value{GDBP}) info inferiors
2523 Num Description Executable
2524 * 1 process 29964 helloworld
2525 (@value{GDBP}) clone-inferior
2528 (@value{GDBP}) info inferiors
2529 Num Description Executable
2531 * 1 process 29964 helloworld
2534 You can now simply switch focus to inferior 2 and run it.
2536 @kindex remove-inferiors
2537 @item remove-inferiors @var{infno}@dots{}
2538 Removes the inferior or inferiors @var{infno}@dots{}. It is not
2539 possible to remove an inferior that is running with this command. For
2540 those, use the @code{kill} or @code{detach} command first.
2544 To quit debugging one of the running inferiors that is not the current
2545 inferior, you can either detach from it by using the @w{@code{detach
2546 inferior}} command (allowing it to run independently), or kill it
2547 using the @w{@code{kill inferiors}} command:
2550 @kindex detach inferiors @var{infno}@dots{}
2551 @item detach inferior @var{infno}@dots{}
2552 Detach from the inferior or inferiors identified by @value{GDBN}
2553 inferior number(s) @var{infno}@dots{}. Note that the inferior's entry
2554 still stays on the list of inferiors shown by @code{info inferiors},
2555 but its Description will show @samp{<null>}.
2557 @kindex kill inferiors @var{infno}@dots{}
2558 @item kill inferiors @var{infno}@dots{}
2559 Kill the inferior or inferiors identified by @value{GDBN} inferior
2560 number(s) @var{infno}@dots{}. Note that the inferior's entry still
2561 stays on the list of inferiors shown by @code{info inferiors}, but its
2562 Description will show @samp{<null>}.
2565 After the successful completion of a command such as @code{detach},
2566 @code{detach inferiors}, @code{kill} or @code{kill inferiors}, or after
2567 a normal process exit, the inferior is still valid and listed with
2568 @code{info inferiors}, ready to be restarted.
2571 To be notified when inferiors are started or exit under @value{GDBN}'s
2572 control use @w{@code{set print inferior-events}}:
2575 @kindex set print inferior-events
2576 @cindex print messages on inferior start and exit
2577 @item set print inferior-events
2578 @itemx set print inferior-events on
2579 @itemx set print inferior-events off
2580 The @code{set print inferior-events} command allows you to enable or
2581 disable printing of messages when @value{GDBN} notices that new
2582 inferiors have started or that inferiors have exited or have been
2583 detached. By default, these messages will not be printed.
2585 @kindex show print inferior-events
2586 @item show print inferior-events
2587 Show whether messages will be printed when @value{GDBN} detects that
2588 inferiors have started, exited or have been detached.
2591 Many commands will work the same with multiple programs as with a
2592 single program: e.g., @code{print myglobal} will simply display the
2593 value of @code{myglobal} in the current inferior.
2596 Occasionaly, when debugging @value{GDBN} itself, it may be useful to
2597 get more info about the relationship of inferiors, programs, address
2598 spaces in a debug session. You can do that with the @w{@code{maint
2599 info program-spaces}} command.
2602 @kindex maint info program-spaces
2603 @item maint info program-spaces
2604 Print a list of all program spaces currently being managed by
2607 @value{GDBN} displays for each program space (in this order):
2611 the program space number assigned by @value{GDBN}
2614 the name of the executable loaded into the program space, with e.g.,
2615 the @code{file} command.
2620 An asterisk @samp{*} preceding the @value{GDBN} program space number
2621 indicates the current program space.
2623 In addition, below each program space line, @value{GDBN} prints extra
2624 information that isn't suitable to display in tabular form. For
2625 example, the list of inferiors bound to the program space.
2628 (@value{GDBP}) maint info program-spaces
2631 Bound inferiors: ID 1 (process 21561)
2635 Here we can see that no inferior is running the program @code{hello},
2636 while @code{process 21561} is running the program @code{goodbye}. On
2637 some targets, it is possible that multiple inferiors are bound to the
2638 same program space. The most common example is that of debugging both
2639 the parent and child processes of a @code{vfork} call. For example,
2642 (@value{GDBP}) maint info program-spaces
2645 Bound inferiors: ID 2 (process 18050), ID 1 (process 18045)
2648 Here, both inferior 2 and inferior 1 are running in the same program
2649 space as a result of inferior 1 having executed a @code{vfork} call.
2653 @section Debugging Programs with Multiple Threads
2655 @cindex threads of execution
2656 @cindex multiple threads
2657 @cindex switching threads
2658 In some operating systems, such as HP-UX and Solaris, a single program
2659 may have more than one @dfn{thread} of execution. The precise semantics
2660 of threads differ from one operating system to another, but in general
2661 the threads of a single program are akin to multiple processes---except
2662 that they share one address space (that is, they can all examine and
2663 modify the same variables). On the other hand, each thread has its own
2664 registers and execution stack, and perhaps private memory.
2666 @value{GDBN} provides these facilities for debugging multi-thread
2670 @item automatic notification of new threads
2671 @item @samp{thread @var{threadno}}, a command to switch among threads
2672 @item @samp{info threads}, a command to inquire about existing threads
2673 @item @samp{thread apply [@var{threadno}] [@var{all}] @var{args}},
2674 a command to apply a command to a list of threads
2675 @item thread-specific breakpoints
2676 @item @samp{set print thread-events}, which controls printing of
2677 messages on thread start and exit.
2678 @item @samp{set libthread-db-search-path @var{path}}, which lets
2679 the user specify which @code{libthread_db} to use if the default choice
2680 isn't compatible with the program.
2684 @emph{Warning:} These facilities are not yet available on every
2685 @value{GDBN} configuration where the operating system supports threads.
2686 If your @value{GDBN} does not support threads, these commands have no
2687 effect. For example, a system without thread support shows no output
2688 from @samp{info threads}, and always rejects the @code{thread} command,
2692 (@value{GDBP}) info threads
2693 (@value{GDBP}) thread 1
2694 Thread ID 1 not known. Use the "info threads" command to
2695 see the IDs of currently known threads.
2697 @c FIXME to implementors: how hard would it be to say "sorry, this GDB
2698 @c doesn't support threads"?
2701 @cindex focus of debugging
2702 @cindex current thread
2703 The @value{GDBN} thread debugging facility allows you to observe all
2704 threads while your program runs---but whenever @value{GDBN} takes
2705 control, one thread in particular is always the focus of debugging.
2706 This thread is called the @dfn{current thread}. Debugging commands show
2707 program information from the perspective of the current thread.
2709 @cindex @code{New} @var{systag} message
2710 @cindex thread identifier (system)
2711 @c FIXME-implementors!! It would be more helpful if the [New...] message
2712 @c included GDB's numeric thread handle, so you could just go to that
2713 @c thread without first checking `info threads'.
2714 Whenever @value{GDBN} detects a new thread in your program, it displays
2715 the target system's identification for the thread with a message in the
2716 form @samp{[New @var{systag}]}. @var{systag} is a thread identifier
2717 whose form varies depending on the particular system. For example, on
2718 @sc{gnu}/Linux, you might see
2721 [New Thread 0x41e02940 (LWP 25582)]
2725 when @value{GDBN} notices a new thread. In contrast, on an SGI system,
2726 the @var{systag} is simply something like @samp{process 368}, with no
2729 @c FIXME!! (1) Does the [New...] message appear even for the very first
2730 @c thread of a program, or does it only appear for the
2731 @c second---i.e.@: when it becomes obvious we have a multithread
2733 @c (2) *Is* there necessarily a first thread always? Or do some
2734 @c multithread systems permit starting a program with multiple
2735 @c threads ab initio?
2737 @cindex thread number
2738 @cindex thread identifier (GDB)
2739 For debugging purposes, @value{GDBN} associates its own thread
2740 number---always a single integer---with each thread in your program.
2743 @kindex info threads
2744 @item info threads @r{[}@var{id}@dots{}@r{]}
2745 Display a summary of all threads currently in your program. Optional
2746 argument @var{id}@dots{} is one or more thread ids separated by spaces, and
2747 means to print information only about the specified thread or threads.
2748 @value{GDBN} displays for each thread (in this order):
2752 the thread number assigned by @value{GDBN}
2755 the target system's thread identifier (@var{systag})
2758 the thread's name, if one is known. A thread can either be named by
2759 the user (see @code{thread name}, below), or, in some cases, by the
2763 the current stack frame summary for that thread
2767 An asterisk @samp{*} to the left of the @value{GDBN} thread number
2768 indicates the current thread.
2772 @c end table here to get a little more width for example
2775 (@value{GDBP}) info threads
2777 3 process 35 thread 27 0x34e5 in sigpause ()
2778 2 process 35 thread 23 0x34e5 in sigpause ()
2779 * 1 process 35 thread 13 main (argc=1, argv=0x7ffffff8)
2783 On Solaris, you can display more information about user threads with a
2784 Solaris-specific command:
2787 @item maint info sol-threads
2788 @kindex maint info sol-threads
2789 @cindex thread info (Solaris)
2790 Display info on Solaris user threads.
2794 @kindex thread @var{threadno}
2795 @item thread @var{threadno}
2796 Make thread number @var{threadno} the current thread. The command
2797 argument @var{threadno} is the internal @value{GDBN} thread number, as
2798 shown in the first field of the @samp{info threads} display.
2799 @value{GDBN} responds by displaying the system identifier of the thread
2800 you selected, and its current stack frame summary:
2803 (@value{GDBP}) thread 2
2804 [Switching to thread 2 (Thread 0xb7fdab70 (LWP 12747))]
2805 #0 some_function (ignore=0x0) at example.c:8
2806 8 printf ("hello\n");
2810 As with the @samp{[New @dots{}]} message, the form of the text after
2811 @samp{Switching to} depends on your system's conventions for identifying
2814 @vindex $_thread@r{, convenience variable}
2815 The debugger convenience variable @samp{$_thread} contains the number
2816 of the current thread. You may find this useful in writing breakpoint
2817 conditional expressions, command scripts, and so forth. See
2818 @xref{Convenience Vars,, Convenience Variables}, for general
2819 information on convenience variables.
2821 @kindex thread apply
2822 @cindex apply command to several threads
2823 @item thread apply [@var{threadno} | all] @var{command}
2824 The @code{thread apply} command allows you to apply the named
2825 @var{command} to one or more threads. Specify the numbers of the
2826 threads that you want affected with the command argument
2827 @var{threadno}. It can be a single thread number, one of the numbers
2828 shown in the first field of the @samp{info threads} display; or it
2829 could be a range of thread numbers, as in @code{2-4}. To apply a
2830 command to all threads, type @kbd{thread apply all @var{command}}.
2833 @cindex name a thread
2834 @item thread name [@var{name}]
2835 This command assigns a name to the current thread. If no argument is
2836 given, any existing user-specified name is removed. The thread name
2837 appears in the @samp{info threads} display.
2839 On some systems, such as @sc{gnu}/Linux, @value{GDBN} is able to
2840 determine the name of the thread as given by the OS. On these
2841 systems, a name specified with @samp{thread name} will override the
2842 system-give name, and removing the user-specified name will cause
2843 @value{GDBN} to once again display the system-specified name.
2846 @cindex search for a thread
2847 @item thread find [@var{regexp}]
2848 Search for and display thread ids whose name or @var{systag}
2849 matches the supplied regular expression.
2851 As well as being the complement to the @samp{thread name} command,
2852 this command also allows you to identify a thread by its target
2853 @var{systag}. For instance, on @sc{gnu}/Linux, the target @var{systag}
2857 (@value{GDBN}) thread find 26688
2858 Thread 4 has target id 'Thread 0x41e02940 (LWP 26688)'
2859 (@value{GDBN}) info thread 4
2861 4 Thread 0x41e02940 (LWP 26688) 0x00000031ca6cd372 in select ()
2864 @kindex set print thread-events
2865 @cindex print messages on thread start and exit
2866 @item set print thread-events
2867 @itemx set print thread-events on
2868 @itemx set print thread-events off
2869 The @code{set print thread-events} command allows you to enable or
2870 disable printing of messages when @value{GDBN} notices that new threads have
2871 started or that threads have exited. By default, these messages will
2872 be printed if detection of these events is supported by the target.
2873 Note that these messages cannot be disabled on all targets.
2875 @kindex show print thread-events
2876 @item show print thread-events
2877 Show whether messages will be printed when @value{GDBN} detects that threads
2878 have started and exited.
2881 @xref{Thread Stops,,Stopping and Starting Multi-thread Programs}, for
2882 more information about how @value{GDBN} behaves when you stop and start
2883 programs with multiple threads.
2885 @xref{Set Watchpoints,,Setting Watchpoints}, for information about
2886 watchpoints in programs with multiple threads.
2889 @kindex set libthread-db-search-path
2890 @cindex search path for @code{libthread_db}
2891 @item set libthread-db-search-path @r{[}@var{path}@r{]}
2892 If this variable is set, @var{path} is a colon-separated list of
2893 directories @value{GDBN} will use to search for @code{libthread_db}.
2894 If you omit @var{path}, @samp{libthread-db-search-path} will be reset to
2895 its default value (@code{$sdir:$pdir} on @sc{gnu}/Linux and Solaris systems).
2896 Internally, the default value comes from the @code{LIBTHREAD_DB_SEARCH_PATH}
2899 On @sc{gnu}/Linux and Solaris systems, @value{GDBN} uses a ``helper''
2900 @code{libthread_db} library to obtain information about threads in the
2901 inferior process. @value{GDBN} will use @samp{libthread-db-search-path}
2902 to find @code{libthread_db}.
2904 A special entry @samp{$sdir} for @samp{libthread-db-search-path}
2905 refers to the default system directories that are
2906 normally searched for loading shared libraries.
2908 A special entry @samp{$pdir} for @samp{libthread-db-search-path}
2909 refers to the directory from which @code{libpthread}
2910 was loaded in the inferior process.
2912 For any @code{libthread_db} library @value{GDBN} finds in above directories,
2913 @value{GDBN} attempts to initialize it with the current inferior process.
2914 If this initialization fails (which could happen because of a version
2915 mismatch between @code{libthread_db} and @code{libpthread}), @value{GDBN}
2916 will unload @code{libthread_db}, and continue with the next directory.
2917 If none of @code{libthread_db} libraries initialize successfully,
2918 @value{GDBN} will issue a warning and thread debugging will be disabled.
2920 Setting @code{libthread-db-search-path} is currently implemented
2921 only on some platforms.
2923 @kindex show libthread-db-search-path
2924 @item show libthread-db-search-path
2925 Display current libthread_db search path.
2927 @kindex set debug libthread-db
2928 @kindex show debug libthread-db
2929 @cindex debugging @code{libthread_db}
2930 @item set debug libthread-db
2931 @itemx show debug libthread-db
2932 Turns on or off display of @code{libthread_db}-related events.
2933 Use @code{1} to enable, @code{0} to disable.
2937 @section Debugging Forks
2939 @cindex fork, debugging programs which call
2940 @cindex multiple processes
2941 @cindex processes, multiple
2942 On most systems, @value{GDBN} has no special support for debugging
2943 programs which create additional processes using the @code{fork}
2944 function. When a program forks, @value{GDBN} will continue to debug the
2945 parent process and the child process will run unimpeded. If you have
2946 set a breakpoint in any code which the child then executes, the child
2947 will get a @code{SIGTRAP} signal which (unless it catches the signal)
2948 will cause it to terminate.
2950 However, if you want to debug the child process there is a workaround
2951 which isn't too painful. Put a call to @code{sleep} in the code which
2952 the child process executes after the fork. It may be useful to sleep
2953 only if a certain environment variable is set, or a certain file exists,
2954 so that the delay need not occur when you don't want to run @value{GDBN}
2955 on the child. While the child is sleeping, use the @code{ps} program to
2956 get its process ID. Then tell @value{GDBN} (a new invocation of
2957 @value{GDBN} if you are also debugging the parent process) to attach to
2958 the child process (@pxref{Attach}). From that point on you can debug
2959 the child process just like any other process which you attached to.
2961 On some systems, @value{GDBN} provides support for debugging programs that
2962 create additional processes using the @code{fork} or @code{vfork} functions.
2963 Currently, the only platforms with this feature are HP-UX (11.x and later
2964 only?) and @sc{gnu}/Linux (kernel version 2.5.60 and later).
2966 By default, when a program forks, @value{GDBN} will continue to debug
2967 the parent process and the child process will run unimpeded.
2969 If you want to follow the child process instead of the parent process,
2970 use the command @w{@code{set follow-fork-mode}}.
2973 @kindex set follow-fork-mode
2974 @item set follow-fork-mode @var{mode}
2975 Set the debugger response to a program call of @code{fork} or
2976 @code{vfork}. A call to @code{fork} or @code{vfork} creates a new
2977 process. The @var{mode} argument can be:
2981 The original process is debugged after a fork. The child process runs
2982 unimpeded. This is the default.
2985 The new process is debugged after a fork. The parent process runs
2990 @kindex show follow-fork-mode
2991 @item show follow-fork-mode
2992 Display the current debugger response to a @code{fork} or @code{vfork} call.
2995 @cindex debugging multiple processes
2996 On Linux, if you want to debug both the parent and child processes, use the
2997 command @w{@code{set detach-on-fork}}.
3000 @kindex set detach-on-fork
3001 @item set detach-on-fork @var{mode}
3002 Tells gdb whether to detach one of the processes after a fork, or
3003 retain debugger control over them both.
3007 The child process (or parent process, depending on the value of
3008 @code{follow-fork-mode}) will be detached and allowed to run
3009 independently. This is the default.
3012 Both processes will be held under the control of @value{GDBN}.
3013 One process (child or parent, depending on the value of
3014 @code{follow-fork-mode}) is debugged as usual, while the other
3019 @kindex show detach-on-fork
3020 @item show detach-on-fork
3021 Show whether detach-on-fork mode is on/off.
3024 If you choose to set @samp{detach-on-fork} mode off, then @value{GDBN}
3025 will retain control of all forked processes (including nested forks).
3026 You can list the forked processes under the control of @value{GDBN} by
3027 using the @w{@code{info inferiors}} command, and switch from one fork
3028 to another by using the @code{inferior} command (@pxref{Inferiors and
3029 Programs, ,Debugging Multiple Inferiors and Programs}).
3031 To quit debugging one of the forked processes, you can either detach
3032 from it by using the @w{@code{detach inferiors}} command (allowing it
3033 to run independently), or kill it using the @w{@code{kill inferiors}}
3034 command. @xref{Inferiors and Programs, ,Debugging Multiple Inferiors
3037 If you ask to debug a child process and a @code{vfork} is followed by an
3038 @code{exec}, @value{GDBN} executes the new target up to the first
3039 breakpoint in the new target. If you have a breakpoint set on
3040 @code{main} in your original program, the breakpoint will also be set on
3041 the child process's @code{main}.
3043 On some systems, when a child process is spawned by @code{vfork}, you
3044 cannot debug the child or parent until an @code{exec} call completes.
3046 If you issue a @code{run} command to @value{GDBN} after an @code{exec}
3047 call executes, the new target restarts. To restart the parent
3048 process, use the @code{file} command with the parent executable name
3049 as its argument. By default, after an @code{exec} call executes,
3050 @value{GDBN} discards the symbols of the previous executable image.
3051 You can change this behaviour with the @w{@code{set follow-exec-mode}}
3055 @kindex set follow-exec-mode
3056 @item set follow-exec-mode @var{mode}
3058 Set debugger response to a program call of @code{exec}. An
3059 @code{exec} call replaces the program image of a process.
3061 @code{follow-exec-mode} can be:
3065 @value{GDBN} creates a new inferior and rebinds the process to this
3066 new inferior. The program the process was running before the
3067 @code{exec} call can be restarted afterwards by restarting the
3073 (@value{GDBP}) info inferiors
3075 Id Description Executable
3078 process 12020 is executing new program: prog2
3079 Program exited normally.
3080 (@value{GDBP}) info inferiors
3081 Id Description Executable
3087 @value{GDBN} keeps the process bound to the same inferior. The new
3088 executable image replaces the previous executable loaded in the
3089 inferior. Restarting the inferior after the @code{exec} call, with
3090 e.g., the @code{run} command, restarts the executable the process was
3091 running after the @code{exec} call. This is the default mode.
3096 (@value{GDBP}) info inferiors
3097 Id Description Executable
3100 process 12020 is executing new program: prog2
3101 Program exited normally.
3102 (@value{GDBP}) info inferiors
3103 Id Description Executable
3110 You can use the @code{catch} command to make @value{GDBN} stop whenever
3111 a @code{fork}, @code{vfork}, or @code{exec} call is made. @xref{Set
3112 Catchpoints, ,Setting Catchpoints}.
3114 @node Checkpoint/Restart
3115 @section Setting a @emph{Bookmark} to Return to Later
3120 @cindex snapshot of a process
3121 @cindex rewind program state
3123 On certain operating systems@footnote{Currently, only
3124 @sc{gnu}/Linux.}, @value{GDBN} is able to save a @dfn{snapshot} of a
3125 program's state, called a @dfn{checkpoint}, and come back to it
3128 Returning to a checkpoint effectively undoes everything that has
3129 happened in the program since the @code{checkpoint} was saved. This
3130 includes changes in memory, registers, and even (within some limits)
3131 system state. Effectively, it is like going back in time to the
3132 moment when the checkpoint was saved.
3134 Thus, if you're stepping thru a program and you think you're
3135 getting close to the point where things go wrong, you can save
3136 a checkpoint. Then, if you accidentally go too far and miss
3137 the critical statement, instead of having to restart your program
3138 from the beginning, you can just go back to the checkpoint and
3139 start again from there.
3141 This can be especially useful if it takes a lot of time or
3142 steps to reach the point where you think the bug occurs.
3144 To use the @code{checkpoint}/@code{restart} method of debugging:
3149 Save a snapshot of the debugged program's current execution state.
3150 The @code{checkpoint} command takes no arguments, but each checkpoint
3151 is assigned a small integer id, similar to a breakpoint id.
3153 @kindex info checkpoints
3154 @item info checkpoints
3155 List the checkpoints that have been saved in the current debugging
3156 session. For each checkpoint, the following information will be
3163 @item Source line, or label
3166 @kindex restart @var{checkpoint-id}
3167 @item restart @var{checkpoint-id}
3168 Restore the program state that was saved as checkpoint number
3169 @var{checkpoint-id}. All program variables, registers, stack frames
3170 etc.@: will be returned to the values that they had when the checkpoint
3171 was saved. In essence, gdb will ``wind back the clock'' to the point
3172 in time when the checkpoint was saved.
3174 Note that breakpoints, @value{GDBN} variables, command history etc.
3175 are not affected by restoring a checkpoint. In general, a checkpoint
3176 only restores things that reside in the program being debugged, not in
3179 @kindex delete checkpoint @var{checkpoint-id}
3180 @item delete checkpoint @var{checkpoint-id}
3181 Delete the previously-saved checkpoint identified by @var{checkpoint-id}.
3185 Returning to a previously saved checkpoint will restore the user state
3186 of the program being debugged, plus a significant subset of the system
3187 (OS) state, including file pointers. It won't ``un-write'' data from
3188 a file, but it will rewind the file pointer to the previous location,
3189 so that the previously written data can be overwritten. For files
3190 opened in read mode, the pointer will also be restored so that the
3191 previously read data can be read again.
3193 Of course, characters that have been sent to a printer (or other
3194 external device) cannot be ``snatched back'', and characters received
3195 from eg.@: a serial device can be removed from internal program buffers,
3196 but they cannot be ``pushed back'' into the serial pipeline, ready to
3197 be received again. Similarly, the actual contents of files that have
3198 been changed cannot be restored (at this time).
3200 However, within those constraints, you actually can ``rewind'' your
3201 program to a previously saved point in time, and begin debugging it
3202 again --- and you can change the course of events so as to debug a
3203 different execution path this time.
3205 @cindex checkpoints and process id
3206 Finally, there is one bit of internal program state that will be
3207 different when you return to a checkpoint --- the program's process
3208 id. Each checkpoint will have a unique process id (or @var{pid}),
3209 and each will be different from the program's original @var{pid}.
3210 If your program has saved a local copy of its process id, this could
3211 potentially pose a problem.
3213 @subsection A Non-obvious Benefit of Using Checkpoints
3215 On some systems such as @sc{gnu}/Linux, address space randomization
3216 is performed on new processes for security reasons. This makes it
3217 difficult or impossible to set a breakpoint, or watchpoint, on an
3218 absolute address if you have to restart the program, since the
3219 absolute location of a symbol will change from one execution to the
3222 A checkpoint, however, is an @emph{identical} copy of a process.
3223 Therefore if you create a checkpoint at (eg.@:) the start of main,
3224 and simply return to that checkpoint instead of restarting the
3225 process, you can avoid the effects of address randomization and
3226 your symbols will all stay in the same place.
3229 @chapter Stopping and Continuing
3231 The principal purposes of using a debugger are so that you can stop your
3232 program before it terminates; or so that, if your program runs into
3233 trouble, you can investigate and find out why.
3235 Inside @value{GDBN}, your program may stop for any of several reasons,
3236 such as a signal, a breakpoint, or reaching a new line after a
3237 @value{GDBN} command such as @code{step}. You may then examine and
3238 change variables, set new breakpoints or remove old ones, and then
3239 continue execution. Usually, the messages shown by @value{GDBN} provide
3240 ample explanation of the status of your program---but you can also
3241 explicitly request this information at any time.
3244 @kindex info program
3246 Display information about the status of your program: whether it is
3247 running or not, what process it is, and why it stopped.
3251 * Breakpoints:: Breakpoints, watchpoints, and catchpoints
3252 * Continuing and Stepping:: Resuming execution
3253 * Skipping Over Functions and Files::
3254 Skipping over functions and files
3256 * Thread Stops:: Stopping and starting multi-thread programs
3260 @section Breakpoints, Watchpoints, and Catchpoints
3263 A @dfn{breakpoint} makes your program stop whenever a certain point in
3264 the program is reached. For each breakpoint, you can add conditions to
3265 control in finer detail whether your program stops. You can set
3266 breakpoints with the @code{break} command and its variants (@pxref{Set
3267 Breaks, ,Setting Breakpoints}), to specify the place where your program
3268 should stop by line number, function name or exact address in the
3271 On some systems, you can set breakpoints in shared libraries before
3272 the executable is run. There is a minor limitation on HP-UX systems:
3273 you must wait until the executable is run in order to set breakpoints
3274 in shared library routines that are not called directly by the program
3275 (for example, routines that are arguments in a @code{pthread_create}
3279 @cindex data breakpoints
3280 @cindex memory tracing
3281 @cindex breakpoint on memory address
3282 @cindex breakpoint on variable modification
3283 A @dfn{watchpoint} is a special breakpoint that stops your program
3284 when the value of an expression changes. The expression may be a value
3285 of a variable, or it could involve values of one or more variables
3286 combined by operators, such as @samp{a + b}. This is sometimes called
3287 @dfn{data breakpoints}. You must use a different command to set
3288 watchpoints (@pxref{Set Watchpoints, ,Setting Watchpoints}), but aside
3289 from that, you can manage a watchpoint like any other breakpoint: you
3290 enable, disable, and delete both breakpoints and watchpoints using the
3293 You can arrange to have values from your program displayed automatically
3294 whenever @value{GDBN} stops at a breakpoint. @xref{Auto Display,,
3298 @cindex breakpoint on events
3299 A @dfn{catchpoint} is another special breakpoint that stops your program
3300 when a certain kind of event occurs, such as the throwing of a C@t{++}
3301 exception or the loading of a library. As with watchpoints, you use a
3302 different command to set a catchpoint (@pxref{Set Catchpoints, ,Setting
3303 Catchpoints}), but aside from that, you can manage a catchpoint like any
3304 other breakpoint. (To stop when your program receives a signal, use the
3305 @code{handle} command; see @ref{Signals, ,Signals}.)
3307 @cindex breakpoint numbers
3308 @cindex numbers for breakpoints
3309 @value{GDBN} assigns a number to each breakpoint, watchpoint, or
3310 catchpoint when you create it; these numbers are successive integers
3311 starting with one. In many of the commands for controlling various
3312 features of breakpoints you use the breakpoint number to say which
3313 breakpoint you want to change. Each breakpoint may be @dfn{enabled} or
3314 @dfn{disabled}; if disabled, it has no effect on your program until you
3317 @cindex breakpoint ranges
3318 @cindex ranges of breakpoints
3319 Some @value{GDBN} commands accept a range of breakpoints on which to
3320 operate. A breakpoint range is either a single breakpoint number, like
3321 @samp{5}, or two such numbers, in increasing order, separated by a
3322 hyphen, like @samp{5-7}. When a breakpoint range is given to a command,
3323 all breakpoints in that range are operated on.
3326 * Set Breaks:: Setting breakpoints
3327 * Set Watchpoints:: Setting watchpoints
3328 * Set Catchpoints:: Setting catchpoints
3329 * Delete Breaks:: Deleting breakpoints
3330 * Disabling:: Disabling breakpoints
3331 * Conditions:: Break conditions
3332 * Break Commands:: Breakpoint command lists
3333 * Save Breakpoints:: How to save breakpoints in a file
3334 * Error in Breakpoints:: ``Cannot insert breakpoints''
3335 * Breakpoint-related Warnings:: ``Breakpoint address adjusted...''
3339 @subsection Setting Breakpoints
3341 @c FIXME LMB what does GDB do if no code on line of breakpt?
3342 @c consider in particular declaration with/without initialization.
3344 @c FIXME 2 is there stuff on this already? break at fun start, already init?
3347 @kindex b @r{(@code{break})}
3348 @vindex $bpnum@r{, convenience variable}
3349 @cindex latest breakpoint
3350 Breakpoints are set with the @code{break} command (abbreviated
3351 @code{b}). The debugger convenience variable @samp{$bpnum} records the
3352 number of the breakpoint you've set most recently; see @ref{Convenience
3353 Vars,, Convenience Variables}, for a discussion of what you can do with
3354 convenience variables.
3357 @item break @var{location}
3358 Set a breakpoint at the given @var{location}, which can specify a
3359 function name, a line number, or an address of an instruction.
3360 (@xref{Specify Location}, for a list of all the possible ways to
3361 specify a @var{location}.) The breakpoint will stop your program just
3362 before it executes any of the code in the specified @var{location}.
3364 When using source languages that permit overloading of symbols, such as
3365 C@t{++}, a function name may refer to more than one possible place to break.
3366 @xref{Ambiguous Expressions,,Ambiguous Expressions}, for a discussion of
3369 It is also possible to insert a breakpoint that will stop the program
3370 only if a specific thread (@pxref{Thread-Specific Breakpoints})
3371 or a specific task (@pxref{Ada Tasks}) hits that breakpoint.
3374 When called without any arguments, @code{break} sets a breakpoint at
3375 the next instruction to be executed in the selected stack frame
3376 (@pxref{Stack, ,Examining the Stack}). In any selected frame but the
3377 innermost, this makes your program stop as soon as control
3378 returns to that frame. This is similar to the effect of a
3379 @code{finish} command in the frame inside the selected frame---except
3380 that @code{finish} does not leave an active breakpoint. If you use
3381 @code{break} without an argument in the innermost frame, @value{GDBN} stops
3382 the next time it reaches the current location; this may be useful
3385 @value{GDBN} normally ignores breakpoints when it resumes execution, until at
3386 least one instruction has been executed. If it did not do this, you
3387 would be unable to proceed past a breakpoint without first disabling the
3388 breakpoint. This rule applies whether or not the breakpoint already
3389 existed when your program stopped.
3391 @item break @dots{} if @var{cond}
3392 Set a breakpoint with condition @var{cond}; evaluate the expression
3393 @var{cond} each time the breakpoint is reached, and stop only if the
3394 value is nonzero---that is, if @var{cond} evaluates as true.
3395 @samp{@dots{}} stands for one of the possible arguments described
3396 above (or no argument) specifying where to break. @xref{Conditions,
3397 ,Break Conditions}, for more information on breakpoint conditions.
3400 @item tbreak @var{args}
3401 Set a breakpoint enabled only for one stop. @var{args} are the
3402 same as for the @code{break} command, and the breakpoint is set in the same
3403 way, but the breakpoint is automatically deleted after the first time your
3404 program stops there. @xref{Disabling, ,Disabling Breakpoints}.
3407 @cindex hardware breakpoints
3408 @item hbreak @var{args}
3409 Set a hardware-assisted breakpoint. @var{args} are the same as for the
3410 @code{break} command and the breakpoint is set in the same way, but the
3411 breakpoint requires hardware support and some target hardware may not
3412 have this support. The main purpose of this is EPROM/ROM code
3413 debugging, so you can set a breakpoint at an instruction without
3414 changing the instruction. This can be used with the new trap-generation
3415 provided by SPARClite DSU and most x86-based targets. These targets
3416 will generate traps when a program accesses some data or instruction
3417 address that is assigned to the debug registers. However the hardware
3418 breakpoint registers can take a limited number of breakpoints. For
3419 example, on the DSU, only two data breakpoints can be set at a time, and
3420 @value{GDBN} will reject this command if more than two are used. Delete
3421 or disable unused hardware breakpoints before setting new ones
3422 (@pxref{Disabling, ,Disabling Breakpoints}).
3423 @xref{Conditions, ,Break Conditions}.
3424 For remote targets, you can restrict the number of hardware
3425 breakpoints @value{GDBN} will use, see @ref{set remote
3426 hardware-breakpoint-limit}.
3429 @item thbreak @var{args}
3430 Set a hardware-assisted breakpoint enabled only for one stop. @var{args}
3431 are the same as for the @code{hbreak} command and the breakpoint is set in
3432 the same way. However, like the @code{tbreak} command,
3433 the breakpoint is automatically deleted after the
3434 first time your program stops there. Also, like the @code{hbreak}
3435 command, the breakpoint requires hardware support and some target hardware
3436 may not have this support. @xref{Disabling, ,Disabling Breakpoints}.
3437 See also @ref{Conditions, ,Break Conditions}.
3440 @cindex regular expression
3441 @cindex breakpoints at functions matching a regexp
3442 @cindex set breakpoints in many functions
3443 @item rbreak @var{regex}
3444 Set breakpoints on all functions matching the regular expression
3445 @var{regex}. This command sets an unconditional breakpoint on all
3446 matches, printing a list of all breakpoints it set. Once these
3447 breakpoints are set, they are treated just like the breakpoints set with
3448 the @code{break} command. You can delete them, disable them, or make
3449 them conditional the same way as any other breakpoint.
3451 The syntax of the regular expression is the standard one used with tools
3452 like @file{grep}. Note that this is different from the syntax used by
3453 shells, so for instance @code{foo*} matches all functions that include
3454 an @code{fo} followed by zero or more @code{o}s. There is an implicit
3455 @code{.*} leading and trailing the regular expression you supply, so to
3456 match only functions that begin with @code{foo}, use @code{^foo}.
3458 @cindex non-member C@t{++} functions, set breakpoint in
3459 When debugging C@t{++} programs, @code{rbreak} is useful for setting
3460 breakpoints on overloaded functions that are not members of any special
3463 @cindex set breakpoints on all functions
3464 The @code{rbreak} command can be used to set breakpoints in
3465 @strong{all} the functions in a program, like this:
3468 (@value{GDBP}) rbreak .
3471 @item rbreak @var{file}:@var{regex}
3472 If @code{rbreak} is called with a filename qualification, it limits
3473 the search for functions matching the given regular expression to the
3474 specified @var{file}. This can be used, for example, to set breakpoints on
3475 every function in a given file:
3478 (@value{GDBP}) rbreak file.c:.
3481 The colon separating the filename qualifier from the regex may
3482 optionally be surrounded by spaces.
3484 @kindex info breakpoints
3485 @cindex @code{$_} and @code{info breakpoints}
3486 @item info breakpoints @r{[}@var{n}@dots{}@r{]}
3487 @itemx info break @r{[}@var{n}@dots{}@r{]}
3488 Print a table of all breakpoints, watchpoints, and catchpoints set and
3489 not deleted. Optional argument @var{n} means print information only
3490 about the specified breakpoint(s) (or watchpoint(s) or catchpoint(s)).
3491 For each breakpoint, following columns are printed:
3494 @item Breakpoint Numbers
3496 Breakpoint, watchpoint, or catchpoint.
3498 Whether the breakpoint is marked to be disabled or deleted when hit.
3499 @item Enabled or Disabled
3500 Enabled breakpoints are marked with @samp{y}. @samp{n} marks breakpoints
3501 that are not enabled.
3503 Where the breakpoint is in your program, as a memory address. For a
3504 pending breakpoint whose address is not yet known, this field will
3505 contain @samp{<PENDING>}. Such breakpoint won't fire until a shared
3506 library that has the symbol or line referred by breakpoint is loaded.
3507 See below for details. A breakpoint with several locations will
3508 have @samp{<MULTIPLE>} in this field---see below for details.
3510 Where the breakpoint is in the source for your program, as a file and
3511 line number. For a pending breakpoint, the original string passed to
3512 the breakpoint command will be listed as it cannot be resolved until
3513 the appropriate shared library is loaded in the future.
3517 If a breakpoint is conditional, there are two evaluation modes: ``host'' and
3518 ``target''. If mode is ``host'', breakpoint condition evaluation is done by
3519 @value{GDBN} on the host's side. If it is ``target'', then the condition
3520 is evaluated by the target. The @code{info break} command shows
3521 the condition on the line following the affected breakpoint, together with
3522 its condition evaluation mode in between parentheses.
3524 Breakpoint commands, if any, are listed after that. A pending breakpoint is
3525 allowed to have a condition specified for it. The condition is not parsed for
3526 validity until a shared library is loaded that allows the pending
3527 breakpoint to resolve to a valid location.
3530 @code{info break} with a breakpoint
3531 number @var{n} as argument lists only that breakpoint. The
3532 convenience variable @code{$_} and the default examining-address for
3533 the @code{x} command are set to the address of the last breakpoint
3534 listed (@pxref{Memory, ,Examining Memory}).
3537 @code{info break} displays a count of the number of times the breakpoint
3538 has been hit. This is especially useful in conjunction with the
3539 @code{ignore} command. You can ignore a large number of breakpoint
3540 hits, look at the breakpoint info to see how many times the breakpoint
3541 was hit, and then run again, ignoring one less than that number. This
3542 will get you quickly to the last hit of that breakpoint.
3545 For a breakpoints with an enable count (xref) greater than 1,
3546 @code{info break} also displays that count.
3550 @value{GDBN} allows you to set any number of breakpoints at the same place in
3551 your program. There is nothing silly or meaningless about this. When
3552 the breakpoints are conditional, this is even useful
3553 (@pxref{Conditions, ,Break Conditions}).
3555 @cindex multiple locations, breakpoints
3556 @cindex breakpoints, multiple locations
3557 It is possible that a breakpoint corresponds to several locations
3558 in your program. Examples of this situation are:
3562 Multiple functions in the program may have the same name.
3565 For a C@t{++} constructor, the @value{NGCC} compiler generates several
3566 instances of the function body, used in different cases.
3569 For a C@t{++} template function, a given line in the function can
3570 correspond to any number of instantiations.
3573 For an inlined function, a given source line can correspond to
3574 several places where that function is inlined.
3577 In all those cases, @value{GDBN} will insert a breakpoint at all
3578 the relevant locations.
3580 A breakpoint with multiple locations is displayed in the breakpoint
3581 table using several rows---one header row, followed by one row for
3582 each breakpoint location. The header row has @samp{<MULTIPLE>} in the
3583 address column. The rows for individual locations contain the actual
3584 addresses for locations, and show the functions to which those
3585 locations belong. The number column for a location is of the form
3586 @var{breakpoint-number}.@var{location-number}.
3591 Num Type Disp Enb Address What
3592 1 breakpoint keep y <MULTIPLE>
3594 breakpoint already hit 1 time
3595 1.1 y 0x080486a2 in void foo<int>() at t.cc:8
3596 1.2 y 0x080486ca in void foo<double>() at t.cc:8
3599 Each location can be individually enabled or disabled by passing
3600 @var{breakpoint-number}.@var{location-number} as argument to the
3601 @code{enable} and @code{disable} commands. Note that you cannot
3602 delete the individual locations from the list, you can only delete the
3603 entire list of locations that belong to their parent breakpoint (with
3604 the @kbd{delete @var{num}} command, where @var{num} is the number of
3605 the parent breakpoint, 1 in the above example). Disabling or enabling
3606 the parent breakpoint (@pxref{Disabling}) affects all of the locations
3607 that belong to that breakpoint.
3609 @cindex pending breakpoints
3610 It's quite common to have a breakpoint inside a shared library.
3611 Shared libraries can be loaded and unloaded explicitly,
3612 and possibly repeatedly, as the program is executed. To support
3613 this use case, @value{GDBN} updates breakpoint locations whenever
3614 any shared library is loaded or unloaded. Typically, you would
3615 set a breakpoint in a shared library at the beginning of your
3616 debugging session, when the library is not loaded, and when the
3617 symbols from the library are not available. When you try to set
3618 breakpoint, @value{GDBN} will ask you if you want to set
3619 a so called @dfn{pending breakpoint}---breakpoint whose address
3620 is not yet resolved.
3622 After the program is run, whenever a new shared library is loaded,
3623 @value{GDBN} reevaluates all the breakpoints. When a newly loaded
3624 shared library contains the symbol or line referred to by some
3625 pending breakpoint, that breakpoint is resolved and becomes an
3626 ordinary breakpoint. When a library is unloaded, all breakpoints
3627 that refer to its symbols or source lines become pending again.
3629 This logic works for breakpoints with multiple locations, too. For
3630 example, if you have a breakpoint in a C@t{++} template function, and
3631 a newly loaded shared library has an instantiation of that template,
3632 a new location is added to the list of locations for the breakpoint.
3634 Except for having unresolved address, pending breakpoints do not
3635 differ from regular breakpoints. You can set conditions or commands,
3636 enable and disable them and perform other breakpoint operations.
3638 @value{GDBN} provides some additional commands for controlling what
3639 happens when the @samp{break} command cannot resolve breakpoint
3640 address specification to an address:
3642 @kindex set breakpoint pending
3643 @kindex show breakpoint pending
3645 @item set breakpoint pending auto
3646 This is the default behavior. When @value{GDBN} cannot find the breakpoint
3647 location, it queries you whether a pending breakpoint should be created.
3649 @item set breakpoint pending on
3650 This indicates that an unrecognized breakpoint location should automatically
3651 result in a pending breakpoint being created.
3653 @item set breakpoint pending off
3654 This indicates that pending breakpoints are not to be created. Any
3655 unrecognized breakpoint location results in an error. This setting does
3656 not affect any pending breakpoints previously created.
3658 @item show breakpoint pending
3659 Show the current behavior setting for creating pending breakpoints.
3662 The settings above only affect the @code{break} command and its
3663 variants. Once breakpoint is set, it will be automatically updated
3664 as shared libraries are loaded and unloaded.
3666 @cindex automatic hardware breakpoints
3667 For some targets, @value{GDBN} can automatically decide if hardware or
3668 software breakpoints should be used, depending on whether the
3669 breakpoint address is read-only or read-write. This applies to
3670 breakpoints set with the @code{break} command as well as to internal
3671 breakpoints set by commands like @code{next} and @code{finish}. For
3672 breakpoints set with @code{hbreak}, @value{GDBN} will always use hardware
3675 You can control this automatic behaviour with the following commands::
3677 @kindex set breakpoint auto-hw
3678 @kindex show breakpoint auto-hw
3680 @item set breakpoint auto-hw on
3681 This is the default behavior. When @value{GDBN} sets a breakpoint, it
3682 will try to use the target memory map to decide if software or hardware
3683 breakpoint must be used.
3685 @item set breakpoint auto-hw off
3686 This indicates @value{GDBN} should not automatically select breakpoint
3687 type. If the target provides a memory map, @value{GDBN} will warn when
3688 trying to set software breakpoint at a read-only address.
3691 @value{GDBN} normally implements breakpoints by replacing the program code
3692 at the breakpoint address with a special instruction, which, when
3693 executed, given control to the debugger. By default, the program
3694 code is so modified only when the program is resumed. As soon as
3695 the program stops, @value{GDBN} restores the original instructions. This
3696 behaviour guards against leaving breakpoints inserted in the
3697 target should gdb abrubptly disconnect. However, with slow remote
3698 targets, inserting and removing breakpoint can reduce the performance.
3699 This behavior can be controlled with the following commands::
3701 @kindex set breakpoint always-inserted
3702 @kindex show breakpoint always-inserted
3704 @item set breakpoint always-inserted off
3705 All breakpoints, including newly added by the user, are inserted in
3706 the target only when the target is resumed. All breakpoints are
3707 removed from the target when it stops.
3709 @item set breakpoint always-inserted on
3710 Causes all breakpoints to be inserted in the target at all times. If
3711 the user adds a new breakpoint, or changes an existing breakpoint, the
3712 breakpoints in the target are updated immediately. A breakpoint is
3713 removed from the target only when breakpoint itself is removed.
3715 @cindex non-stop mode, and @code{breakpoint always-inserted}
3716 @item set breakpoint always-inserted auto
3717 This is the default mode. If @value{GDBN} is controlling the inferior
3718 in non-stop mode (@pxref{Non-Stop Mode}), gdb behaves as if
3719 @code{breakpoint always-inserted} mode is on. If @value{GDBN} is
3720 controlling the inferior in all-stop mode, @value{GDBN} behaves as if
3721 @code{breakpoint always-inserted} mode is off.
3724 @value{GDBN} handles conditional breakpoints by evaluating these conditions
3725 when a breakpoint breaks. If the condition is true, then the process being
3726 debugged stops, otherwise the process is resumed.
3728 If the target supports evaluating conditions on its end, @value{GDBN} may
3729 download the breakpoint, together with its conditions, to it.
3731 This feature can be controlled via the following commands:
3733 @kindex set breakpoint condition-evaluation
3734 @kindex show breakpoint condition-evaluation
3736 @item set breakpoint condition-evaluation host
3737 This option commands @value{GDBN} to evaluate the breakpoint
3738 conditions on the host's side. Unconditional breakpoints are sent to
3739 the target which in turn receives the triggers and reports them back to GDB
3740 for condition evaluation. This is the standard evaluation mode.
3742 @item set breakpoint condition-evaluation target
3743 This option commands @value{GDBN} to download breakpoint conditions
3744 to the target at the moment of their insertion. The target
3745 is responsible for evaluating the conditional expression and reporting
3746 breakpoint stop events back to @value{GDBN} whenever the condition
3747 is true. Due to limitations of target-side evaluation, some conditions
3748 cannot be evaluated there, e.g., conditions that depend on local data
3749 that is only known to the host. Examples include
3750 conditional expressions involving convenience variables, complex types
3751 that cannot be handled by the agent expression parser and expressions
3752 that are too long to be sent over to the target, specially when the
3753 target is a remote system. In these cases, the conditions will be
3754 evaluated by @value{GDBN}.
3756 @item set breakpoint condition-evaluation auto
3757 This is the default mode. If the target supports evaluating breakpoint
3758 conditions on its end, @value{GDBN} will download breakpoint conditions to
3759 the target (limitations mentioned previously apply). If the target does
3760 not support breakpoint condition evaluation, then @value{GDBN} will fallback
3761 to evaluating all these conditions on the host's side.
3765 @cindex negative breakpoint numbers
3766 @cindex internal @value{GDBN} breakpoints
3767 @value{GDBN} itself sometimes sets breakpoints in your program for
3768 special purposes, such as proper handling of @code{longjmp} (in C
3769 programs). These internal breakpoints are assigned negative numbers,
3770 starting with @code{-1}; @samp{info breakpoints} does not display them.
3771 You can see these breakpoints with the @value{GDBN} maintenance command
3772 @samp{maint info breakpoints} (@pxref{maint info breakpoints}).
3775 @node Set Watchpoints
3776 @subsection Setting Watchpoints
3778 @cindex setting watchpoints
3779 You can use a watchpoint to stop execution whenever the value of an
3780 expression changes, without having to predict a particular place where
3781 this may happen. (This is sometimes called a @dfn{data breakpoint}.)
3782 The expression may be as simple as the value of a single variable, or
3783 as complex as many variables combined by operators. Examples include:
3787 A reference to the value of a single variable.
3790 An address cast to an appropriate data type. For example,
3791 @samp{*(int *)0x12345678} will watch a 4-byte region at the specified
3792 address (assuming an @code{int} occupies 4 bytes).
3795 An arbitrarily complex expression, such as @samp{a*b + c/d}. The
3796 expression can use any operators valid in the program's native
3797 language (@pxref{Languages}).
3800 You can set a watchpoint on an expression even if the expression can
3801 not be evaluated yet. For instance, you can set a watchpoint on
3802 @samp{*global_ptr} before @samp{global_ptr} is initialized.
3803 @value{GDBN} will stop when your program sets @samp{global_ptr} and
3804 the expression produces a valid value. If the expression becomes
3805 valid in some other way than changing a variable (e.g.@: if the memory
3806 pointed to by @samp{*global_ptr} becomes readable as the result of a
3807 @code{malloc} call), @value{GDBN} may not stop until the next time
3808 the expression changes.
3810 @cindex software watchpoints
3811 @cindex hardware watchpoints
3812 Depending on your system, watchpoints may be implemented in software or
3813 hardware. @value{GDBN} does software watchpointing by single-stepping your
3814 program and testing the variable's value each time, which is hundreds of
3815 times slower than normal execution. (But this may still be worth it, to
3816 catch errors where you have no clue what part of your program is the
3819 On some systems, such as HP-UX, PowerPC, @sc{gnu}/Linux and most other
3820 x86-based targets, @value{GDBN} includes support for hardware
3821 watchpoints, which do not slow down the running of your program.
3825 @item watch @r{[}-l@r{|}-location@r{]} @var{expr} @r{[}thread @var{threadnum}@r{]} @r{[}mask @var{maskvalue}@r{]}
3826 Set a watchpoint for an expression. @value{GDBN} will break when the
3827 expression @var{expr} is written into by the program and its value
3828 changes. The simplest (and the most popular) use of this command is
3829 to watch the value of a single variable:
3832 (@value{GDBP}) watch foo
3835 If the command includes a @code{@r{[}thread @var{threadnum}@r{]}}
3836 argument, @value{GDBN} breaks only when the thread identified by
3837 @var{threadnum} changes the value of @var{expr}. If any other threads
3838 change the value of @var{expr}, @value{GDBN} will not break. Note
3839 that watchpoints restricted to a single thread in this way only work
3840 with Hardware Watchpoints.
3842 Ordinarily a watchpoint respects the scope of variables in @var{expr}
3843 (see below). The @code{-location} argument tells @value{GDBN} to
3844 instead watch the memory referred to by @var{expr}. In this case,
3845 @value{GDBN} will evaluate @var{expr}, take the address of the result,
3846 and watch the memory at that address. The type of the result is used
3847 to determine the size of the watched memory. If the expression's
3848 result does not have an address, then @value{GDBN} will print an
3851 The @code{@r{[}mask @var{maskvalue}@r{]}} argument allows creation
3852 of masked watchpoints, if the current architecture supports this
3853 feature (e.g., PowerPC Embedded architecture, see @ref{PowerPC
3854 Embedded}.) A @dfn{masked watchpoint} specifies a mask in addition
3855 to an address to watch. The mask specifies that some bits of an address
3856 (the bits which are reset in the mask) should be ignored when matching
3857 the address accessed by the inferior against the watchpoint address.
3858 Thus, a masked watchpoint watches many addresses simultaneously---those
3859 addresses whose unmasked bits are identical to the unmasked bits in the
3860 watchpoint address. The @code{mask} argument implies @code{-location}.
3864 (@value{GDBP}) watch foo mask 0xffff00ff
3865 (@value{GDBP}) watch *0xdeadbeef mask 0xffffff00
3869 @item rwatch @r{[}-l@r{|}-location@r{]} @var{expr} @r{[}thread @var{threadnum}@r{]} @r{[}mask @var{maskvalue}@r{]}
3870 Set a watchpoint that will break when the value of @var{expr} is read
3874 @item awatch @r{[}-l@r{|}-location@r{]} @var{expr} @r{[}thread @var{threadnum}@r{]} @r{[}mask @var{maskvalue}@r{]}
3875 Set a watchpoint that will break when @var{expr} is either read from
3876 or written into by the program.
3878 @kindex info watchpoints @r{[}@var{n}@dots{}@r{]}
3879 @item info watchpoints @r{[}@var{n}@dots{}@r{]}
3880 This command prints a list of watchpoints, using the same format as
3881 @code{info break} (@pxref{Set Breaks}).
3884 If you watch for a change in a numerically entered address you need to
3885 dereference it, as the address itself is just a constant number which will
3886 never change. @value{GDBN} refuses to create a watchpoint that watches
3887 a never-changing value:
3890 (@value{GDBP}) watch 0x600850
3891 Cannot watch constant value 0x600850.
3892 (@value{GDBP}) watch *(int *) 0x600850
3893 Watchpoint 1: *(int *) 6293584
3896 @value{GDBN} sets a @dfn{hardware watchpoint} if possible. Hardware
3897 watchpoints execute very quickly, and the debugger reports a change in
3898 value at the exact instruction where the change occurs. If @value{GDBN}
3899 cannot set a hardware watchpoint, it sets a software watchpoint, which
3900 executes more slowly and reports the change in value at the next
3901 @emph{statement}, not the instruction, after the change occurs.
3903 @cindex use only software watchpoints
3904 You can force @value{GDBN} to use only software watchpoints with the
3905 @kbd{set can-use-hw-watchpoints 0} command. With this variable set to
3906 zero, @value{GDBN} will never try to use hardware watchpoints, even if
3907 the underlying system supports them. (Note that hardware-assisted
3908 watchpoints that were set @emph{before} setting
3909 @code{can-use-hw-watchpoints} to zero will still use the hardware
3910 mechanism of watching expression values.)
3913 @item set can-use-hw-watchpoints
3914 @kindex set can-use-hw-watchpoints
3915 Set whether or not to use hardware watchpoints.
3917 @item show can-use-hw-watchpoints
3918 @kindex show can-use-hw-watchpoints
3919 Show the current mode of using hardware watchpoints.
3922 For remote targets, you can restrict the number of hardware
3923 watchpoints @value{GDBN} will use, see @ref{set remote
3924 hardware-breakpoint-limit}.
3926 When you issue the @code{watch} command, @value{GDBN} reports
3929 Hardware watchpoint @var{num}: @var{expr}
3933 if it was able to set a hardware watchpoint.
3935 Currently, the @code{awatch} and @code{rwatch} commands can only set
3936 hardware watchpoints, because accesses to data that don't change the
3937 value of the watched expression cannot be detected without examining
3938 every instruction as it is being executed, and @value{GDBN} does not do
3939 that currently. If @value{GDBN} finds that it is unable to set a
3940 hardware breakpoint with the @code{awatch} or @code{rwatch} command, it
3941 will print a message like this:
3944 Expression cannot be implemented with read/access watchpoint.
3947 Sometimes, @value{GDBN} cannot set a hardware watchpoint because the
3948 data type of the watched expression is wider than what a hardware
3949 watchpoint on the target machine can handle. For example, some systems
3950 can only watch regions that are up to 4 bytes wide; on such systems you
3951 cannot set hardware watchpoints for an expression that yields a
3952 double-precision floating-point number (which is typically 8 bytes
3953 wide). As a work-around, it might be possible to break the large region
3954 into a series of smaller ones and watch them with separate watchpoints.
3956 If you set too many hardware watchpoints, @value{GDBN} might be unable
3957 to insert all of them when you resume the execution of your program.
3958 Since the precise number of active watchpoints is unknown until such
3959 time as the program is about to be resumed, @value{GDBN} might not be
3960 able to warn you about this when you set the watchpoints, and the
3961 warning will be printed only when the program is resumed:
3964 Hardware watchpoint @var{num}: Could not insert watchpoint
3968 If this happens, delete or disable some of the watchpoints.
3970 Watching complex expressions that reference many variables can also
3971 exhaust the resources available for hardware-assisted watchpoints.
3972 That's because @value{GDBN} needs to watch every variable in the
3973 expression with separately allocated resources.
3975 If you call a function interactively using @code{print} or @code{call},
3976 any watchpoints you have set will be inactive until @value{GDBN} reaches another
3977 kind of breakpoint or the call completes.
3979 @value{GDBN} automatically deletes watchpoints that watch local
3980 (automatic) variables, or expressions that involve such variables, when
3981 they go out of scope, that is, when the execution leaves the block in
3982 which these variables were defined. In particular, when the program
3983 being debugged terminates, @emph{all} local variables go out of scope,
3984 and so only watchpoints that watch global variables remain set. If you
3985 rerun the program, you will need to set all such watchpoints again. One
3986 way of doing that would be to set a code breakpoint at the entry to the
3987 @code{main} function and when it breaks, set all the watchpoints.
3989 @cindex watchpoints and threads
3990 @cindex threads and watchpoints
3991 In multi-threaded programs, watchpoints will detect changes to the
3992 watched expression from every thread.
3995 @emph{Warning:} In multi-threaded programs, software watchpoints
3996 have only limited usefulness. If @value{GDBN} creates a software
3997 watchpoint, it can only watch the value of an expression @emph{in a
3998 single thread}. If you are confident that the expression can only
3999 change due to the current thread's activity (and if you are also
4000 confident that no other thread can become current), then you can use
4001 software watchpoints as usual. However, @value{GDBN} may not notice
4002 when a non-current thread's activity changes the expression. (Hardware
4003 watchpoints, in contrast, watch an expression in all threads.)
4006 @xref{set remote hardware-watchpoint-limit}.
4008 @node Set Catchpoints
4009 @subsection Setting Catchpoints
4010 @cindex catchpoints, setting
4011 @cindex exception handlers
4012 @cindex event handling
4014 You can use @dfn{catchpoints} to cause the debugger to stop for certain
4015 kinds of program events, such as C@t{++} exceptions or the loading of a
4016 shared library. Use the @code{catch} command to set a catchpoint.
4020 @item catch @var{event}
4021 Stop when @var{event} occurs. @var{event} can be any of the following:
4024 @cindex stop on C@t{++} exceptions
4025 The throwing of a C@t{++} exception.
4028 The catching of a C@t{++} exception.
4031 @cindex Ada exception catching
4032 @cindex catch Ada exceptions
4033 An Ada exception being raised. If an exception name is specified
4034 at the end of the command (eg @code{catch exception Program_Error}),
4035 the debugger will stop only when this specific exception is raised.
4036 Otherwise, the debugger stops execution when any Ada exception is raised.
4038 When inserting an exception catchpoint on a user-defined exception whose
4039 name is identical to one of the exceptions defined by the language, the
4040 fully qualified name must be used as the exception name. Otherwise,
4041 @value{GDBN} will assume that it should stop on the pre-defined exception
4042 rather than the user-defined one. For instance, assuming an exception
4043 called @code{Constraint_Error} is defined in package @code{Pck}, then
4044 the command to use to catch such exceptions is @kbd{catch exception
4045 Pck.Constraint_Error}.
4047 @item exception unhandled
4048 An exception that was raised but is not handled by the program.
4051 A failed Ada assertion.
4054 @cindex break on fork/exec
4055 A call to @code{exec}. This is currently only available for HP-UX
4059 @itemx syscall @r{[}@var{name} @r{|} @var{number}@r{]} @dots{}
4060 @cindex break on a system call.
4061 A call to or return from a system call, a.k.a.@: @dfn{syscall}. A
4062 syscall is a mechanism for application programs to request a service
4063 from the operating system (OS) or one of the OS system services.
4064 @value{GDBN} can catch some or all of the syscalls issued by the
4065 debuggee, and show the related information for each syscall. If no
4066 argument is specified, calls to and returns from all system calls
4069 @var{name} can be any system call name that is valid for the
4070 underlying OS. Just what syscalls are valid depends on the OS. On
4071 GNU and Unix systems, you can find the full list of valid syscall
4072 names on @file{/usr/include/asm/unistd.h}.
4074 @c For MS-Windows, the syscall names and the corresponding numbers
4075 @c can be found, e.g., on this URL:
4076 @c http://www.metasploit.com/users/opcode/syscalls.html
4077 @c but we don't support Windows syscalls yet.
4079 Normally, @value{GDBN} knows in advance which syscalls are valid for
4080 each OS, so you can use the @value{GDBN} command-line completion
4081 facilities (@pxref{Completion,, command completion}) to list the
4084 You may also specify the system call numerically. A syscall's
4085 number is the value passed to the OS's syscall dispatcher to
4086 identify the requested service. When you specify the syscall by its
4087 name, @value{GDBN} uses its database of syscalls to convert the name
4088 into the corresponding numeric code, but using the number directly
4089 may be useful if @value{GDBN}'s database does not have the complete
4090 list of syscalls on your system (e.g., because @value{GDBN} lags
4091 behind the OS upgrades).
4093 The example below illustrates how this command works if you don't provide
4097 (@value{GDBP}) catch syscall
4098 Catchpoint 1 (syscall)
4100 Starting program: /tmp/catch-syscall
4102 Catchpoint 1 (call to syscall 'close'), \
4103 0xffffe424 in __kernel_vsyscall ()
4107 Catchpoint 1 (returned from syscall 'close'), \
4108 0xffffe424 in __kernel_vsyscall ()
4112 Here is an example of catching a system call by name:
4115 (@value{GDBP}) catch syscall chroot
4116 Catchpoint 1 (syscall 'chroot' [61])
4118 Starting program: /tmp/catch-syscall
4120 Catchpoint 1 (call to syscall 'chroot'), \
4121 0xffffe424 in __kernel_vsyscall ()
4125 Catchpoint 1 (returned from syscall 'chroot'), \
4126 0xffffe424 in __kernel_vsyscall ()
4130 An example of specifying a system call numerically. In the case
4131 below, the syscall number has a corresponding entry in the XML
4132 file, so @value{GDBN} finds its name and prints it:
4135 (@value{GDBP}) catch syscall 252
4136 Catchpoint 1 (syscall(s) 'exit_group')
4138 Starting program: /tmp/catch-syscall
4140 Catchpoint 1 (call to syscall 'exit_group'), \
4141 0xffffe424 in __kernel_vsyscall ()
4145 Program exited normally.
4149 However, there can be situations when there is no corresponding name
4150 in XML file for that syscall number. In this case, @value{GDBN} prints
4151 a warning message saying that it was not able to find the syscall name,
4152 but the catchpoint will be set anyway. See the example below:
4155 (@value{GDBP}) catch syscall 764
4156 warning: The number '764' does not represent a known syscall.
4157 Catchpoint 2 (syscall 764)
4161 If you configure @value{GDBN} using the @samp{--without-expat} option,
4162 it will not be able to display syscall names. Also, if your
4163 architecture does not have an XML file describing its system calls,
4164 you will not be able to see the syscall names. It is important to
4165 notice that these two features are used for accessing the syscall
4166 name database. In either case, you will see a warning like this:
4169 (@value{GDBP}) catch syscall
4170 warning: Could not open "syscalls/i386-linux.xml"
4171 warning: Could not load the syscall XML file 'syscalls/i386-linux.xml'.
4172 GDB will not be able to display syscall names.
4173 Catchpoint 1 (syscall)
4177 Of course, the file name will change depending on your architecture and system.
4179 Still using the example above, you can also try to catch a syscall by its
4180 number. In this case, you would see something like:
4183 (@value{GDBP}) catch syscall 252
4184 Catchpoint 1 (syscall(s) 252)
4187 Again, in this case @value{GDBN} would not be able to display syscall's names.
4190 A call to @code{fork}. This is currently only available for HP-UX
4194 A call to @code{vfork}. This is currently only available for HP-UX
4197 @item load @r{[}regexp@r{]}
4198 @itemx unload @r{[}regexp@r{]}
4199 The loading or unloading of a shared library. If @var{regexp} is
4200 given, then the catchpoint will stop only if the regular expression
4201 matches one of the affected libraries.
4205 @item tcatch @var{event}
4206 Set a catchpoint that is enabled only for one stop. The catchpoint is
4207 automatically deleted after the first time the event is caught.
4211 Use the @code{info break} command to list the current catchpoints.
4213 There are currently some limitations to C@t{++} exception handling
4214 (@code{catch throw} and @code{catch catch}) in @value{GDBN}:
4218 If you call a function interactively, @value{GDBN} normally returns
4219 control to you when the function has finished executing. If the call
4220 raises an exception, however, the call may bypass the mechanism that
4221 returns control to you and cause your program either to abort or to
4222 simply continue running until it hits a breakpoint, catches a signal
4223 that @value{GDBN} is listening for, or exits. This is the case even if
4224 you set a catchpoint for the exception; catchpoints on exceptions are
4225 disabled within interactive calls.
4228 You cannot raise an exception interactively.
4231 You cannot install an exception handler interactively.
4234 @cindex raise exceptions
4235 Sometimes @code{catch} is not the best way to debug exception handling:
4236 if you need to know exactly where an exception is raised, it is better to
4237 stop @emph{before} the exception handler is called, since that way you
4238 can see the stack before any unwinding takes place. If you set a
4239 breakpoint in an exception handler instead, it may not be easy to find
4240 out where the exception was raised.
4242 To stop just before an exception handler is called, you need some
4243 knowledge of the implementation. In the case of @sc{gnu} C@t{++}, exceptions are
4244 raised by calling a library function named @code{__raise_exception}
4245 which has the following ANSI C interface:
4248 /* @var{addr} is where the exception identifier is stored.
4249 @var{id} is the exception identifier. */
4250 void __raise_exception (void **addr, void *id);
4254 To make the debugger catch all exceptions before any stack
4255 unwinding takes place, set a breakpoint on @code{__raise_exception}
4256 (@pxref{Breakpoints, ,Breakpoints; Watchpoints; and Exceptions}).
4258 With a conditional breakpoint (@pxref{Conditions, ,Break Conditions})
4259 that depends on the value of @var{id}, you can stop your program when
4260 a specific exception is raised. You can use multiple conditional
4261 breakpoints to stop your program when any of a number of exceptions are
4266 @subsection Deleting Breakpoints
4268 @cindex clearing breakpoints, watchpoints, catchpoints
4269 @cindex deleting breakpoints, watchpoints, catchpoints
4270 It is often necessary to eliminate a breakpoint, watchpoint, or
4271 catchpoint once it has done its job and you no longer want your program
4272 to stop there. This is called @dfn{deleting} the breakpoint. A
4273 breakpoint that has been deleted no longer exists; it is forgotten.
4275 With the @code{clear} command you can delete breakpoints according to
4276 where they are in your program. With the @code{delete} command you can
4277 delete individual breakpoints, watchpoints, or catchpoints by specifying
4278 their breakpoint numbers.
4280 It is not necessary to delete a breakpoint to proceed past it. @value{GDBN}
4281 automatically ignores breakpoints on the first instruction to be executed
4282 when you continue execution without changing the execution address.
4287 Delete any breakpoints at the next instruction to be executed in the
4288 selected stack frame (@pxref{Selection, ,Selecting a Frame}). When
4289 the innermost frame is selected, this is a good way to delete a
4290 breakpoint where your program just stopped.
4292 @item clear @var{location}
4293 Delete any breakpoints set at the specified @var{location}.
4294 @xref{Specify Location}, for the various forms of @var{location}; the
4295 most useful ones are listed below:
4298 @item clear @var{function}
4299 @itemx clear @var{filename}:@var{function}
4300 Delete any breakpoints set at entry to the named @var{function}.
4302 @item clear @var{linenum}
4303 @itemx clear @var{filename}:@var{linenum}
4304 Delete any breakpoints set at or within the code of the specified
4305 @var{linenum} of the specified @var{filename}.
4308 @cindex delete breakpoints
4310 @kindex d @r{(@code{delete})}
4311 @item delete @r{[}breakpoints@r{]} @r{[}@var{range}@dots{}@r{]}
4312 Delete the breakpoints, watchpoints, or catchpoints of the breakpoint
4313 ranges specified as arguments. If no argument is specified, delete all
4314 breakpoints (@value{GDBN} asks confirmation, unless you have @code{set
4315 confirm off}). You can abbreviate this command as @code{d}.
4319 @subsection Disabling Breakpoints
4321 @cindex enable/disable a breakpoint
4322 Rather than deleting a breakpoint, watchpoint, or catchpoint, you might
4323 prefer to @dfn{disable} it. This makes the breakpoint inoperative as if
4324 it had been deleted, but remembers the information on the breakpoint so
4325 that you can @dfn{enable} it again later.
4327 You disable and enable breakpoints, watchpoints, and catchpoints with
4328 the @code{enable} and @code{disable} commands, optionally specifying
4329 one or more breakpoint numbers as arguments. Use @code{info break} to
4330 print a list of all breakpoints, watchpoints, and catchpoints if you
4331 do not know which numbers to use.
4333 Disabling and enabling a breakpoint that has multiple locations
4334 affects all of its locations.
4336 A breakpoint, watchpoint, or catchpoint can have any of several
4337 different states of enablement:
4341 Enabled. The breakpoint stops your program. A breakpoint set
4342 with the @code{break} command starts out in this state.
4344 Disabled. The breakpoint has no effect on your program.
4346 Enabled once. The breakpoint stops your program, but then becomes
4349 Enabled for a count. The breakpoint stops your program for the next
4350 N times, then becomes disabled.
4352 Enabled for deletion. The breakpoint stops your program, but
4353 immediately after it does so it is deleted permanently. A breakpoint
4354 set with the @code{tbreak} command starts out in this state.
4357 You can use the following commands to enable or disable breakpoints,
4358 watchpoints, and catchpoints:
4362 @kindex dis @r{(@code{disable})}
4363 @item disable @r{[}breakpoints@r{]} @r{[}@var{range}@dots{}@r{]}
4364 Disable the specified breakpoints---or all breakpoints, if none are
4365 listed. A disabled breakpoint has no effect but is not forgotten. All
4366 options such as ignore-counts, conditions and commands are remembered in
4367 case the breakpoint is enabled again later. You may abbreviate
4368 @code{disable} as @code{dis}.
4371 @item enable @r{[}breakpoints@r{]} @r{[}@var{range}@dots{}@r{]}
4372 Enable the specified breakpoints (or all defined breakpoints). They
4373 become effective once again in stopping your program.
4375 @item enable @r{[}breakpoints@r{]} once @var{range}@dots{}
4376 Enable the specified breakpoints temporarily. @value{GDBN} disables any
4377 of these breakpoints immediately after stopping your program.
4379 @item enable @r{[}breakpoints@r{]} count @var{count} @var{range}@dots{}
4380 Enable the specified breakpoints temporarily. @value{GDBN} records
4381 @var{count} with each of the specified breakpoints, and decrements a
4382 breakpoint's count when it is hit. When any count reaches 0,
4383 @value{GDBN} disables that breakpoint. If a breakpoint has an ignore
4384 count (@pxref{Conditions, ,Break Conditions}), that will be
4385 decremented to 0 before @var{count} is affected.
4387 @item enable @r{[}breakpoints@r{]} delete @var{range}@dots{}
4388 Enable the specified breakpoints to work once, then die. @value{GDBN}
4389 deletes any of these breakpoints as soon as your program stops there.
4390 Breakpoints set by the @code{tbreak} command start out in this state.
4393 @c FIXME: I think the following ``Except for [...] @code{tbreak}'' is
4394 @c confusing: tbreak is also initially enabled.
4395 Except for a breakpoint set with @code{tbreak} (@pxref{Set Breaks,
4396 ,Setting Breakpoints}), breakpoints that you set are initially enabled;
4397 subsequently, they become disabled or enabled only when you use one of
4398 the commands above. (The command @code{until} can set and delete a
4399 breakpoint of its own, but it does not change the state of your other
4400 breakpoints; see @ref{Continuing and Stepping, ,Continuing and
4404 @subsection Break Conditions
4405 @cindex conditional breakpoints
4406 @cindex breakpoint conditions
4408 @c FIXME what is scope of break condition expr? Context where wanted?
4409 @c in particular for a watchpoint?
4410 The simplest sort of breakpoint breaks every time your program reaches a
4411 specified place. You can also specify a @dfn{condition} for a
4412 breakpoint. A condition is just a Boolean expression in your
4413 programming language (@pxref{Expressions, ,Expressions}). A breakpoint with
4414 a condition evaluates the expression each time your program reaches it,
4415 and your program stops only if the condition is @emph{true}.
4417 This is the converse of using assertions for program validation; in that
4418 situation, you want to stop when the assertion is violated---that is,
4419 when the condition is false. In C, if you want to test an assertion expressed
4420 by the condition @var{assert}, you should set the condition
4421 @samp{! @var{assert}} on the appropriate breakpoint.
4423 Conditions are also accepted for watchpoints; you may not need them,
4424 since a watchpoint is inspecting the value of an expression anyhow---but
4425 it might be simpler, say, to just set a watchpoint on a variable name,
4426 and specify a condition that tests whether the new value is an interesting
4429 Break conditions can have side effects, and may even call functions in
4430 your program. This can be useful, for example, to activate functions
4431 that log program progress, or to use your own print functions to
4432 format special data structures. The effects are completely predictable
4433 unless there is another enabled breakpoint at the same address. (In
4434 that case, @value{GDBN} might see the other breakpoint first and stop your
4435 program without checking the condition of this one.) Note that
4436 breakpoint commands are usually more convenient and flexible than break
4438 purpose of performing side effects when a breakpoint is reached
4439 (@pxref{Break Commands, ,Breakpoint Command Lists}).
4441 Breakpoint conditions can also be evaluated on the target's side if
4442 the target supports it. Instead of evaluating the conditions locally,
4443 @value{GDBN} encodes the expression into an agent expression
4444 (@pxref{Agent Expressions}) suitable for execution on the target,
4445 independently of @value{GDBN}. Global variables become raw memory
4446 locations, locals become stack accesses, and so forth.
4448 In this case, @value{GDBN} will only be notified of a breakpoint trigger
4449 when its condition evaluates to true. This mechanism may provide faster
4450 response times depending on the performance characteristics of the target
4451 since it does not need to keep @value{GDBN} informed about
4452 every breakpoint trigger, even those with false conditions.
4454 Break conditions can be specified when a breakpoint is set, by using
4455 @samp{if} in the arguments to the @code{break} command. @xref{Set
4456 Breaks, ,Setting Breakpoints}. They can also be changed at any time
4457 with the @code{condition} command.
4459 You can also use the @code{if} keyword with the @code{watch} command.
4460 The @code{catch} command does not recognize the @code{if} keyword;
4461 @code{condition} is the only way to impose a further condition on a
4466 @item condition @var{bnum} @var{expression}
4467 Specify @var{expression} as the break condition for breakpoint,
4468 watchpoint, or catchpoint number @var{bnum}. After you set a condition,
4469 breakpoint @var{bnum} stops your program only if the value of
4470 @var{expression} is true (nonzero, in C). When you use
4471 @code{condition}, @value{GDBN} checks @var{expression} immediately for
4472 syntactic correctness, and to determine whether symbols in it have
4473 referents in the context of your breakpoint. If @var{expression} uses
4474 symbols not referenced in the context of the breakpoint, @value{GDBN}
4475 prints an error message:
4478 No symbol "foo" in current context.
4483 not actually evaluate @var{expression} at the time the @code{condition}
4484 command (or a command that sets a breakpoint with a condition, like
4485 @code{break if @dots{}}) is given, however. @xref{Expressions, ,Expressions}.
4487 @item condition @var{bnum}
4488 Remove the condition from breakpoint number @var{bnum}. It becomes
4489 an ordinary unconditional breakpoint.
4492 @cindex ignore count (of breakpoint)
4493 A special case of a breakpoint condition is to stop only when the
4494 breakpoint has been reached a certain number of times. This is so
4495 useful that there is a special way to do it, using the @dfn{ignore
4496 count} of the breakpoint. Every breakpoint has an ignore count, which
4497 is an integer. Most of the time, the ignore count is zero, and
4498 therefore has no effect. But if your program reaches a breakpoint whose
4499 ignore count is positive, then instead of stopping, it just decrements
4500 the ignore count by one and continues. As a result, if the ignore count
4501 value is @var{n}, the breakpoint does not stop the next @var{n} times
4502 your program reaches it.
4506 @item ignore @var{bnum} @var{count}
4507 Set the ignore count of breakpoint number @var{bnum} to @var{count}.
4508 The next @var{count} times the breakpoint is reached, your program's
4509 execution does not stop; other than to decrement the ignore count, @value{GDBN}
4512 To make the breakpoint stop the next time it is reached, specify
4515 When you use @code{continue} to resume execution of your program from a
4516 breakpoint, you can specify an ignore count directly as an argument to
4517 @code{continue}, rather than using @code{ignore}. @xref{Continuing and
4518 Stepping,,Continuing and Stepping}.
4520 If a breakpoint has a positive ignore count and a condition, the
4521 condition is not checked. Once the ignore count reaches zero,
4522 @value{GDBN} resumes checking the condition.
4524 You could achieve the effect of the ignore count with a condition such
4525 as @w{@samp{$foo-- <= 0}} using a debugger convenience variable that
4526 is decremented each time. @xref{Convenience Vars, ,Convenience
4530 Ignore counts apply to breakpoints, watchpoints, and catchpoints.
4533 @node Break Commands
4534 @subsection Breakpoint Command Lists
4536 @cindex breakpoint commands
4537 You can give any breakpoint (or watchpoint or catchpoint) a series of
4538 commands to execute when your program stops due to that breakpoint. For
4539 example, you might want to print the values of certain expressions, or
4540 enable other breakpoints.
4544 @kindex end@r{ (breakpoint commands)}
4545 @item commands @r{[}@var{range}@dots{}@r{]}
4546 @itemx @dots{} @var{command-list} @dots{}
4548 Specify a list of commands for the given breakpoints. The commands
4549 themselves appear on the following lines. Type a line containing just
4550 @code{end} to terminate the commands.
4552 To remove all commands from a breakpoint, type @code{commands} and
4553 follow it immediately with @code{end}; that is, give no commands.
4555 With no argument, @code{commands} refers to the last breakpoint,
4556 watchpoint, or catchpoint set (not to the breakpoint most recently
4557 encountered). If the most recent breakpoints were set with a single
4558 command, then the @code{commands} will apply to all the breakpoints
4559 set by that command. This applies to breakpoints set by
4560 @code{rbreak}, and also applies when a single @code{break} command
4561 creates multiple breakpoints (@pxref{Ambiguous Expressions,,Ambiguous
4565 Pressing @key{RET} as a means of repeating the last @value{GDBN} command is
4566 disabled within a @var{command-list}.
4568 You can use breakpoint commands to start your program up again. Simply
4569 use the @code{continue} command, or @code{step}, or any other command
4570 that resumes execution.
4572 Any other commands in the command list, after a command that resumes
4573 execution, are ignored. This is because any time you resume execution
4574 (even with a simple @code{next} or @code{step}), you may encounter
4575 another breakpoint---which could have its own command list, leading to
4576 ambiguities about which list to execute.
4579 If the first command you specify in a command list is @code{silent}, the
4580 usual message about stopping at a breakpoint is not printed. This may
4581 be desirable for breakpoints that are to print a specific message and
4582 then continue. If none of the remaining commands print anything, you
4583 see no sign that the breakpoint was reached. @code{silent} is
4584 meaningful only at the beginning of a breakpoint command list.
4586 The commands @code{echo}, @code{output}, and @code{printf} allow you to
4587 print precisely controlled output, and are often useful in silent
4588 breakpoints. @xref{Output, ,Commands for Controlled Output}.
4590 For example, here is how you could use breakpoint commands to print the
4591 value of @code{x} at entry to @code{foo} whenever @code{x} is positive.
4597 printf "x is %d\n",x
4602 One application for breakpoint commands is to compensate for one bug so
4603 you can test for another. Put a breakpoint just after the erroneous line
4604 of code, give it a condition to detect the case in which something
4605 erroneous has been done, and give it commands to assign correct values
4606 to any variables that need them. End with the @code{continue} command
4607 so that your program does not stop, and start with the @code{silent}
4608 command so that no output is produced. Here is an example:
4619 @node Save Breakpoints
4620 @subsection How to save breakpoints to a file
4622 To save breakpoint definitions to a file use the @w{@code{save
4623 breakpoints}} command.
4626 @kindex save breakpoints
4627 @cindex save breakpoints to a file for future sessions
4628 @item save breakpoints [@var{filename}]
4629 This command saves all current breakpoint definitions together with
4630 their commands and ignore counts, into a file @file{@var{filename}}
4631 suitable for use in a later debugging session. This includes all
4632 types of breakpoints (breakpoints, watchpoints, catchpoints,
4633 tracepoints). To read the saved breakpoint definitions, use the
4634 @code{source} command (@pxref{Command Files}). Note that watchpoints
4635 with expressions involving local variables may fail to be recreated
4636 because it may not be possible to access the context where the
4637 watchpoint is valid anymore. Because the saved breakpoint definitions
4638 are simply a sequence of @value{GDBN} commands that recreate the
4639 breakpoints, you can edit the file in your favorite editing program,
4640 and remove the breakpoint definitions you're not interested in, or
4641 that can no longer be recreated.
4644 @c @ifclear BARETARGET
4645 @node Error in Breakpoints
4646 @subsection ``Cannot insert breakpoints''
4648 If you request too many active hardware-assisted breakpoints and
4649 watchpoints, you will see this error message:
4651 @c FIXME: the precise wording of this message may change; the relevant
4652 @c source change is not committed yet (Sep 3, 1999).
4654 Stopped; cannot insert breakpoints.
4655 You may have requested too many hardware breakpoints and watchpoints.
4659 This message is printed when you attempt to resume the program, since
4660 only then @value{GDBN} knows exactly how many hardware breakpoints and
4661 watchpoints it needs to insert.
4663 When this message is printed, you need to disable or remove some of the
4664 hardware-assisted breakpoints and watchpoints, and then continue.
4666 @node Breakpoint-related Warnings
4667 @subsection ``Breakpoint address adjusted...''
4668 @cindex breakpoint address adjusted
4670 Some processor architectures place constraints on the addresses at
4671 which breakpoints may be placed. For architectures thus constrained,
4672 @value{GDBN} will attempt to adjust the breakpoint's address to comply
4673 with the constraints dictated by the architecture.
4675 One example of such an architecture is the Fujitsu FR-V. The FR-V is
4676 a VLIW architecture in which a number of RISC-like instructions may be
4677 bundled together for parallel execution. The FR-V architecture
4678 constrains the location of a breakpoint instruction within such a
4679 bundle to the instruction with the lowest address. @value{GDBN}
4680 honors this constraint by adjusting a breakpoint's address to the
4681 first in the bundle.
4683 It is not uncommon for optimized code to have bundles which contain
4684 instructions from different source statements, thus it may happen that
4685 a breakpoint's address will be adjusted from one source statement to
4686 another. Since this adjustment may significantly alter @value{GDBN}'s
4687 breakpoint related behavior from what the user expects, a warning is
4688 printed when the breakpoint is first set and also when the breakpoint
4691 A warning like the one below is printed when setting a breakpoint
4692 that's been subject to address adjustment:
4695 warning: Breakpoint address adjusted from 0x00010414 to 0x00010410.
4698 Such warnings are printed both for user settable and @value{GDBN}'s
4699 internal breakpoints. If you see one of these warnings, you should
4700 verify that a breakpoint set at the adjusted address will have the
4701 desired affect. If not, the breakpoint in question may be removed and
4702 other breakpoints may be set which will have the desired behavior.
4703 E.g., it may be sufficient to place the breakpoint at a later
4704 instruction. A conditional breakpoint may also be useful in some
4705 cases to prevent the breakpoint from triggering too often.
4707 @value{GDBN} will also issue a warning when stopping at one of these
4708 adjusted breakpoints:
4711 warning: Breakpoint 1 address previously adjusted from 0x00010414
4715 When this warning is encountered, it may be too late to take remedial
4716 action except in cases where the breakpoint is hit earlier or more
4717 frequently than expected.
4719 @node Continuing and Stepping
4720 @section Continuing and Stepping
4724 @cindex resuming execution
4725 @dfn{Continuing} means resuming program execution until your program
4726 completes normally. In contrast, @dfn{stepping} means executing just
4727 one more ``step'' of your program, where ``step'' may mean either one
4728 line of source code, or one machine instruction (depending on what
4729 particular command you use). Either when continuing or when stepping,
4730 your program may stop even sooner, due to a breakpoint or a signal. (If
4731 it stops due to a signal, you may want to use @code{handle}, or use
4732 @samp{signal 0} to resume execution. @xref{Signals, ,Signals}.)
4736 @kindex c @r{(@code{continue})}
4737 @kindex fg @r{(resume foreground execution)}
4738 @item continue @r{[}@var{ignore-count}@r{]}
4739 @itemx c @r{[}@var{ignore-count}@r{]}
4740 @itemx fg @r{[}@var{ignore-count}@r{]}
4741 Resume program execution, at the address where your program last stopped;
4742 any breakpoints set at that address are bypassed. The optional argument
4743 @var{ignore-count} allows you to specify a further number of times to
4744 ignore a breakpoint at this location; its effect is like that of
4745 @code{ignore} (@pxref{Conditions, ,Break Conditions}).
4747 The argument @var{ignore-count} is meaningful only when your program
4748 stopped due to a breakpoint. At other times, the argument to
4749 @code{continue} is ignored.
4751 The synonyms @code{c} and @code{fg} (for @dfn{foreground}, as the
4752 debugged program is deemed to be the foreground program) are provided
4753 purely for convenience, and have exactly the same behavior as
4757 To resume execution at a different place, you can use @code{return}
4758 (@pxref{Returning, ,Returning from a Function}) to go back to the
4759 calling function; or @code{jump} (@pxref{Jumping, ,Continuing at a
4760 Different Address}) to go to an arbitrary location in your program.
4762 A typical technique for using stepping is to set a breakpoint
4763 (@pxref{Breakpoints, ,Breakpoints; Watchpoints; and Catchpoints}) at the
4764 beginning of the function or the section of your program where a problem
4765 is believed to lie, run your program until it stops at that breakpoint,
4766 and then step through the suspect area, examining the variables that are
4767 interesting, until you see the problem happen.
4771 @kindex s @r{(@code{step})}
4773 Continue running your program until control reaches a different source
4774 line, then stop it and return control to @value{GDBN}. This command is
4775 abbreviated @code{s}.
4778 @c "without debugging information" is imprecise; actually "without line
4779 @c numbers in the debugging information". (gcc -g1 has debugging info but
4780 @c not line numbers). But it seems complex to try to make that
4781 @c distinction here.
4782 @emph{Warning:} If you use the @code{step} command while control is
4783 within a function that was compiled without debugging information,
4784 execution proceeds until control reaches a function that does have
4785 debugging information. Likewise, it will not step into a function which
4786 is compiled without debugging information. To step through functions
4787 without debugging information, use the @code{stepi} command, described
4791 The @code{step} command only stops at the first instruction of a source
4792 line. This prevents the multiple stops that could otherwise occur in
4793 @code{switch} statements, @code{for} loops, etc. @code{step} continues
4794 to stop if a function that has debugging information is called within
4795 the line. In other words, @code{step} @emph{steps inside} any functions
4796 called within the line.
4798 Also, the @code{step} command only enters a function if there is line
4799 number information for the function. Otherwise it acts like the
4800 @code{next} command. This avoids problems when using @code{cc -gl}
4801 on MIPS machines. Previously, @code{step} entered subroutines if there
4802 was any debugging information about the routine.
4804 @item step @var{count}
4805 Continue running as in @code{step}, but do so @var{count} times. If a
4806 breakpoint is reached, or a signal not related to stepping occurs before
4807 @var{count} steps, stepping stops right away.
4810 @kindex n @r{(@code{next})}
4811 @item next @r{[}@var{count}@r{]}
4812 Continue to the next source line in the current (innermost) stack frame.
4813 This is similar to @code{step}, but function calls that appear within
4814 the line of code are executed without stopping. Execution stops when
4815 control reaches a different line of code at the original stack level
4816 that was executing when you gave the @code{next} command. This command
4817 is abbreviated @code{n}.
4819 An argument @var{count} is a repeat count, as for @code{step}.
4822 @c FIX ME!! Do we delete this, or is there a way it fits in with
4823 @c the following paragraph? --- Vctoria
4825 @c @code{next} within a function that lacks debugging information acts like
4826 @c @code{step}, but any function calls appearing within the code of the
4827 @c function are executed without stopping.
4829 The @code{next} command only stops at the first instruction of a
4830 source line. This prevents multiple stops that could otherwise occur in
4831 @code{switch} statements, @code{for} loops, etc.
4833 @kindex set step-mode
4835 @cindex functions without line info, and stepping
4836 @cindex stepping into functions with no line info
4837 @itemx set step-mode on
4838 The @code{set step-mode on} command causes the @code{step} command to
4839 stop at the first instruction of a function which contains no debug line
4840 information rather than stepping over it.
4842 This is useful in cases where you may be interested in inspecting the
4843 machine instructions of a function which has no symbolic info and do not
4844 want @value{GDBN} to automatically skip over this function.
4846 @item set step-mode off
4847 Causes the @code{step} command to step over any functions which contains no
4848 debug information. This is the default.
4850 @item show step-mode
4851 Show whether @value{GDBN} will stop in or step over functions without
4852 source line debug information.
4855 @kindex fin @r{(@code{finish})}
4857 Continue running until just after function in the selected stack frame
4858 returns. Print the returned value (if any). This command can be
4859 abbreviated as @code{fin}.
4861 Contrast this with the @code{return} command (@pxref{Returning,
4862 ,Returning from a Function}).
4865 @kindex u @r{(@code{until})}
4866 @cindex run until specified location
4869 Continue running until a source line past the current line, in the
4870 current stack frame, is reached. This command is used to avoid single
4871 stepping through a loop more than once. It is like the @code{next}
4872 command, except that when @code{until} encounters a jump, it
4873 automatically continues execution until the program counter is greater
4874 than the address of the jump.
4876 This means that when you reach the end of a loop after single stepping
4877 though it, @code{until} makes your program continue execution until it
4878 exits the loop. In contrast, a @code{next} command at the end of a loop
4879 simply steps back to the beginning of the loop, which forces you to step
4880 through the next iteration.
4882 @code{until} always stops your program if it attempts to exit the current
4885 @code{until} may produce somewhat counterintuitive results if the order
4886 of machine code does not match the order of the source lines. For
4887 example, in the following excerpt from a debugging session, the @code{f}
4888 (@code{frame}) command shows that execution is stopped at line
4889 @code{206}; yet when we use @code{until}, we get to line @code{195}:
4893 #0 main (argc=4, argv=0xf7fffae8) at m4.c:206
4895 (@value{GDBP}) until
4896 195 for ( ; argc > 0; NEXTARG) @{
4899 This happened because, for execution efficiency, the compiler had
4900 generated code for the loop closure test at the end, rather than the
4901 start, of the loop---even though the test in a C @code{for}-loop is
4902 written before the body of the loop. The @code{until} command appeared
4903 to step back to the beginning of the loop when it advanced to this
4904 expression; however, it has not really gone to an earlier
4905 statement---not in terms of the actual machine code.
4907 @code{until} with no argument works by means of single
4908 instruction stepping, and hence is slower than @code{until} with an
4911 @item until @var{location}
4912 @itemx u @var{location}
4913 Continue running your program until either the specified location is
4914 reached, or the current stack frame returns. @var{location} is any of
4915 the forms described in @ref{Specify Location}.
4916 This form of the command uses temporary breakpoints, and
4917 hence is quicker than @code{until} without an argument. The specified
4918 location is actually reached only if it is in the current frame. This
4919 implies that @code{until} can be used to skip over recursive function
4920 invocations. For instance in the code below, if the current location is
4921 line @code{96}, issuing @code{until 99} will execute the program up to
4922 line @code{99} in the same invocation of factorial, i.e., after the inner
4923 invocations have returned.
4926 94 int factorial (int value)
4928 96 if (value > 1) @{
4929 97 value *= factorial (value - 1);
4936 @kindex advance @var{location}
4937 @itemx advance @var{location}
4938 Continue running the program up to the given @var{location}. An argument is
4939 required, which should be of one of the forms described in
4940 @ref{Specify Location}.
4941 Execution will also stop upon exit from the current stack
4942 frame. This command is similar to @code{until}, but @code{advance} will
4943 not skip over recursive function calls, and the target location doesn't
4944 have to be in the same frame as the current one.
4948 @kindex si @r{(@code{stepi})}
4950 @itemx stepi @var{arg}
4952 Execute one machine instruction, then stop and return to the debugger.
4954 It is often useful to do @samp{display/i $pc} when stepping by machine
4955 instructions. This makes @value{GDBN} automatically display the next
4956 instruction to be executed, each time your program stops. @xref{Auto
4957 Display,, Automatic Display}.
4959 An argument is a repeat count, as in @code{step}.
4963 @kindex ni @r{(@code{nexti})}
4965 @itemx nexti @var{arg}
4967 Execute one machine instruction, but if it is a function call,
4968 proceed until the function returns.
4970 An argument is a repeat count, as in @code{next}.
4973 @node Skipping Over Functions and Files
4974 @section Skipping Over Functions and Files
4975 @cindex skipping over functions and files
4977 The program you are debugging may contain some functions which are
4978 uninteresting to debug. The @code{skip} comand lets you tell @value{GDBN} to
4979 skip a function or all functions in a file when stepping.
4981 For example, consider the following C function:
4992 Suppose you wish to step into the functions @code{foo} and @code{bar}, but you
4993 are not interested in stepping through @code{boring}. If you run @code{step}
4994 at line 103, you'll enter @code{boring()}, but if you run @code{next}, you'll
4995 step over both @code{foo} and @code{boring}!
4997 One solution is to @code{step} into @code{boring} and use the @code{finish}
4998 command to immediately exit it. But this can become tedious if @code{boring}
4999 is called from many places.
5001 A more flexible solution is to execute @kbd{skip boring}. This instructs
5002 @value{GDBN} never to step into @code{boring}. Now when you execute
5003 @code{step} at line 103, you'll step over @code{boring} and directly into
5006 You can also instruct @value{GDBN} to skip all functions in a file, with, for
5007 example, @code{skip file boring.c}.
5010 @kindex skip function
5011 @item skip @r{[}@var{linespec}@r{]}
5012 @itemx skip function @r{[}@var{linespec}@r{]}
5013 After running this command, the function named by @var{linespec} or the
5014 function containing the line named by @var{linespec} will be skipped over when
5015 stepping. @xref{Specify Location}.
5017 If you do not specify @var{linespec}, the function you're currently debugging
5020 (If you have a function called @code{file} that you want to skip, use
5021 @kbd{skip function file}.)
5024 @item skip file @r{[}@var{filename}@r{]}
5025 After running this command, any function whose source lives in @var{filename}
5026 will be skipped over when stepping.
5028 If you do not specify @var{filename}, functions whose source lives in the file
5029 you're currently debugging will be skipped.
5032 Skips can be listed, deleted, disabled, and enabled, much like breakpoints.
5033 These are the commands for managing your list of skips:
5037 @item info skip @r{[}@var{range}@r{]}
5038 Print details about the specified skip(s). If @var{range} is not specified,
5039 print a table with details about all functions and files marked for skipping.
5040 @code{info skip} prints the following information about each skip:
5044 A number identifying this skip.
5046 The type of this skip, either @samp{function} or @samp{file}.
5047 @item Enabled or Disabled
5048 Enabled skips are marked with @samp{y}. Disabled skips are marked with @samp{n}.
5050 For function skips, this column indicates the address in memory of the function
5051 being skipped. If you've set a function skip on a function which has not yet
5052 been loaded, this field will contain @samp{<PENDING>}. Once a shared library
5053 which has the function is loaded, @code{info skip} will show the function's
5056 For file skips, this field contains the filename being skipped. For functions
5057 skips, this field contains the function name and its line number in the file
5058 where it is defined.
5062 @item skip delete @r{[}@var{range}@r{]}
5063 Delete the specified skip(s). If @var{range} is not specified, delete all
5067 @item skip enable @r{[}@var{range}@r{]}
5068 Enable the specified skip(s). If @var{range} is not specified, enable all
5071 @kindex skip disable
5072 @item skip disable @r{[}@var{range}@r{]}
5073 Disable the specified skip(s). If @var{range} is not specified, disable all
5082 A signal is an asynchronous event that can happen in a program. The
5083 operating system defines the possible kinds of signals, and gives each
5084 kind a name and a number. For example, in Unix @code{SIGINT} is the
5085 signal a program gets when you type an interrupt character (often @kbd{Ctrl-c});
5086 @code{SIGSEGV} is the signal a program gets from referencing a place in
5087 memory far away from all the areas in use; @code{SIGALRM} occurs when
5088 the alarm clock timer goes off (which happens only if your program has
5089 requested an alarm).
5091 @cindex fatal signals
5092 Some signals, including @code{SIGALRM}, are a normal part of the
5093 functioning of your program. Others, such as @code{SIGSEGV}, indicate
5094 errors; these signals are @dfn{fatal} (they kill your program immediately) if the
5095 program has not specified in advance some other way to handle the signal.
5096 @code{SIGINT} does not indicate an error in your program, but it is normally
5097 fatal so it can carry out the purpose of the interrupt: to kill the program.
5099 @value{GDBN} has the ability to detect any occurrence of a signal in your
5100 program. You can tell @value{GDBN} in advance what to do for each kind of
5103 @cindex handling signals
5104 Normally, @value{GDBN} is set up to let the non-erroneous signals like
5105 @code{SIGALRM} be silently passed to your program
5106 (so as not to interfere with their role in the program's functioning)
5107 but to stop your program immediately whenever an error signal happens.
5108 You can change these settings with the @code{handle} command.
5111 @kindex info signals
5115 Print a table of all the kinds of signals and how @value{GDBN} has been told to
5116 handle each one. You can use this to see the signal numbers of all
5117 the defined types of signals.
5119 @item info signals @var{sig}
5120 Similar, but print information only about the specified signal number.
5122 @code{info handle} is an alias for @code{info signals}.
5125 @item handle @var{signal} @r{[}@var{keywords}@dots{}@r{]}
5126 Change the way @value{GDBN} handles signal @var{signal}. @var{signal}
5127 can be the number of a signal or its name (with or without the
5128 @samp{SIG} at the beginning); a list of signal numbers of the form
5129 @samp{@var{low}-@var{high}}; or the word @samp{all}, meaning all the
5130 known signals. Optional arguments @var{keywords}, described below,
5131 say what change to make.
5135 The keywords allowed by the @code{handle} command can be abbreviated.
5136 Their full names are:
5140 @value{GDBN} should not stop your program when this signal happens. It may
5141 still print a message telling you that the signal has come in.
5144 @value{GDBN} should stop your program when this signal happens. This implies
5145 the @code{print} keyword as well.
5148 @value{GDBN} should print a message when this signal happens.
5151 @value{GDBN} should not mention the occurrence of the signal at all. This
5152 implies the @code{nostop} keyword as well.
5156 @value{GDBN} should allow your program to see this signal; your program
5157 can handle the signal, or else it may terminate if the signal is fatal
5158 and not handled. @code{pass} and @code{noignore} are synonyms.
5162 @value{GDBN} should not allow your program to see this signal.
5163 @code{nopass} and @code{ignore} are synonyms.
5167 When a signal stops your program, the signal is not visible to the
5169 continue. Your program sees the signal then, if @code{pass} is in
5170 effect for the signal in question @emph{at that time}. In other words,
5171 after @value{GDBN} reports a signal, you can use the @code{handle}
5172 command with @code{pass} or @code{nopass} to control whether your
5173 program sees that signal when you continue.
5175 The default is set to @code{nostop}, @code{noprint}, @code{pass} for
5176 non-erroneous signals such as @code{SIGALRM}, @code{SIGWINCH} and
5177 @code{SIGCHLD}, and to @code{stop}, @code{print}, @code{pass} for the
5180 You can also use the @code{signal} command to prevent your program from
5181 seeing a signal, or cause it to see a signal it normally would not see,
5182 or to give it any signal at any time. For example, if your program stopped
5183 due to some sort of memory reference error, you might store correct
5184 values into the erroneous variables and continue, hoping to see more
5185 execution; but your program would probably terminate immediately as
5186 a result of the fatal signal once it saw the signal. To prevent this,
5187 you can continue with @samp{signal 0}. @xref{Signaling, ,Giving your
5190 @cindex extra signal information
5191 @anchor{extra signal information}
5193 On some targets, @value{GDBN} can inspect extra signal information
5194 associated with the intercepted signal, before it is actually
5195 delivered to the program being debugged. This information is exported
5196 by the convenience variable @code{$_siginfo}, and consists of data
5197 that is passed by the kernel to the signal handler at the time of the
5198 receipt of a signal. The data type of the information itself is
5199 target dependent. You can see the data type using the @code{ptype
5200 $_siginfo} command. On Unix systems, it typically corresponds to the
5201 standard @code{siginfo_t} type, as defined in the @file{signal.h}
5204 Here's an example, on a @sc{gnu}/Linux system, printing the stray
5205 referenced address that raised a segmentation fault.
5209 (@value{GDBP}) continue
5210 Program received signal SIGSEGV, Segmentation fault.
5211 0x0000000000400766 in main ()
5213 (@value{GDBP}) ptype $_siginfo
5220 struct @{...@} _kill;
5221 struct @{...@} _timer;
5223 struct @{...@} _sigchld;
5224 struct @{...@} _sigfault;
5225 struct @{...@} _sigpoll;
5228 (@value{GDBP}) ptype $_siginfo._sifields._sigfault
5232 (@value{GDBP}) p $_siginfo._sifields._sigfault.si_addr
5233 $1 = (void *) 0x7ffff7ff7000
5237 Depending on target support, @code{$_siginfo} may also be writable.
5240 @section Stopping and Starting Multi-thread Programs
5242 @cindex stopped threads
5243 @cindex threads, stopped
5245 @cindex continuing threads
5246 @cindex threads, continuing
5248 @value{GDBN} supports debugging programs with multiple threads
5249 (@pxref{Threads,, Debugging Programs with Multiple Threads}). There
5250 are two modes of controlling execution of your program within the
5251 debugger. In the default mode, referred to as @dfn{all-stop mode},
5252 when any thread in your program stops (for example, at a breakpoint
5253 or while being stepped), all other threads in the program are also stopped by
5254 @value{GDBN}. On some targets, @value{GDBN} also supports
5255 @dfn{non-stop mode}, in which other threads can continue to run freely while
5256 you examine the stopped thread in the debugger.
5259 * All-Stop Mode:: All threads stop when GDB takes control
5260 * Non-Stop Mode:: Other threads continue to execute
5261 * Background Execution:: Running your program asynchronously
5262 * Thread-Specific Breakpoints:: Controlling breakpoints
5263 * Interrupted System Calls:: GDB may interfere with system calls
5264 * Observer Mode:: GDB does not alter program behavior
5268 @subsection All-Stop Mode
5270 @cindex all-stop mode
5272 In all-stop mode, whenever your program stops under @value{GDBN} for any reason,
5273 @emph{all} threads of execution stop, not just the current thread. This
5274 allows you to examine the overall state of the program, including
5275 switching between threads, without worrying that things may change
5278 Conversely, whenever you restart the program, @emph{all} threads start
5279 executing. @emph{This is true even when single-stepping} with commands
5280 like @code{step} or @code{next}.
5282 In particular, @value{GDBN} cannot single-step all threads in lockstep.
5283 Since thread scheduling is up to your debugging target's operating
5284 system (not controlled by @value{GDBN}), other threads may
5285 execute more than one statement while the current thread completes a
5286 single step. Moreover, in general other threads stop in the middle of a
5287 statement, rather than at a clean statement boundary, when the program
5290 You might even find your program stopped in another thread after
5291 continuing or even single-stepping. This happens whenever some other
5292 thread runs into a breakpoint, a signal, or an exception before the
5293 first thread completes whatever you requested.
5295 @cindex automatic thread selection
5296 @cindex switching threads automatically
5297 @cindex threads, automatic switching
5298 Whenever @value{GDBN} stops your program, due to a breakpoint or a
5299 signal, it automatically selects the thread where that breakpoint or
5300 signal happened. @value{GDBN} alerts you to the context switch with a
5301 message such as @samp{[Switching to Thread @var{n}]} to identify the
5304 On some OSes, you can modify @value{GDBN}'s default behavior by
5305 locking the OS scheduler to allow only a single thread to run.
5308 @item set scheduler-locking @var{mode}
5309 @cindex scheduler locking mode
5310 @cindex lock scheduler
5311 Set the scheduler locking mode. If it is @code{off}, then there is no
5312 locking and any thread may run at any time. If @code{on}, then only the
5313 current thread may run when the inferior is resumed. The @code{step}
5314 mode optimizes for single-stepping; it prevents other threads
5315 from preempting the current thread while you are stepping, so that
5316 the focus of debugging does not change unexpectedly.
5317 Other threads only rarely (or never) get a chance to run
5318 when you step. They are more likely to run when you @samp{next} over a
5319 function call, and they are completely free to run when you use commands
5320 like @samp{continue}, @samp{until}, or @samp{finish}. However, unless another
5321 thread hits a breakpoint during its timeslice, @value{GDBN} does not change
5322 the current thread away from the thread that you are debugging.
5324 @item show scheduler-locking
5325 Display the current scheduler locking mode.
5328 @cindex resume threads of multiple processes simultaneously
5329 By default, when you issue one of the execution commands such as
5330 @code{continue}, @code{next} or @code{step}, @value{GDBN} allows only
5331 threads of the current inferior to run. For example, if @value{GDBN}
5332 is attached to two inferiors, each with two threads, the
5333 @code{continue} command resumes only the two threads of the current
5334 inferior. This is useful, for example, when you debug a program that
5335 forks and you want to hold the parent stopped (so that, for instance,
5336 it doesn't run to exit), while you debug the child. In other
5337 situations, you may not be interested in inspecting the current state
5338 of any of the processes @value{GDBN} is attached to, and you may want
5339 to resume them all until some breakpoint is hit. In the latter case,
5340 you can instruct @value{GDBN} to allow all threads of all the
5341 inferiors to run with the @w{@code{set schedule-multiple}} command.
5344 @kindex set schedule-multiple
5345 @item set schedule-multiple
5346 Set the mode for allowing threads of multiple processes to be resumed
5347 when an execution command is issued. When @code{on}, all threads of
5348 all processes are allowed to run. When @code{off}, only the threads
5349 of the current process are resumed. The default is @code{off}. The
5350 @code{scheduler-locking} mode takes precedence when set to @code{on},
5351 or while you are stepping and set to @code{step}.
5353 @item show schedule-multiple
5354 Display the current mode for resuming the execution of threads of
5359 @subsection Non-Stop Mode
5361 @cindex non-stop mode
5363 @c This section is really only a place-holder, and needs to be expanded
5364 @c with more details.
5366 For some multi-threaded targets, @value{GDBN} supports an optional
5367 mode of operation in which you can examine stopped program threads in
5368 the debugger while other threads continue to execute freely. This
5369 minimizes intrusion when debugging live systems, such as programs
5370 where some threads have real-time constraints or must continue to
5371 respond to external events. This is referred to as @dfn{non-stop} mode.
5373 In non-stop mode, when a thread stops to report a debugging event,
5374 @emph{only} that thread is stopped; @value{GDBN} does not stop other
5375 threads as well, in contrast to the all-stop mode behavior. Additionally,
5376 execution commands such as @code{continue} and @code{step} apply by default
5377 only to the current thread in non-stop mode, rather than all threads as
5378 in all-stop mode. This allows you to control threads explicitly in
5379 ways that are not possible in all-stop mode --- for example, stepping
5380 one thread while allowing others to run freely, stepping
5381 one thread while holding all others stopped, or stepping several threads
5382 independently and simultaneously.
5384 To enter non-stop mode, use this sequence of commands before you run
5385 or attach to your program:
5388 # Enable the async interface.
5391 # If using the CLI, pagination breaks non-stop.
5394 # Finally, turn it on!
5398 You can use these commands to manipulate the non-stop mode setting:
5401 @kindex set non-stop
5402 @item set non-stop on
5403 Enable selection of non-stop mode.
5404 @item set non-stop off
5405 Disable selection of non-stop mode.
5406 @kindex show non-stop
5408 Show the current non-stop enablement setting.
5411 Note these commands only reflect whether non-stop mode is enabled,
5412 not whether the currently-executing program is being run in non-stop mode.
5413 In particular, the @code{set non-stop} preference is only consulted when
5414 @value{GDBN} starts or connects to the target program, and it is generally
5415 not possible to switch modes once debugging has started. Furthermore,
5416 since not all targets support non-stop mode, even when you have enabled
5417 non-stop mode, @value{GDBN} may still fall back to all-stop operation by
5420 In non-stop mode, all execution commands apply only to the current thread
5421 by default. That is, @code{continue} only continues one thread.
5422 To continue all threads, issue @code{continue -a} or @code{c -a}.
5424 You can use @value{GDBN}'s background execution commands
5425 (@pxref{Background Execution}) to run some threads in the background
5426 while you continue to examine or step others from @value{GDBN}.
5427 The MI execution commands (@pxref{GDB/MI Program Execution}) are
5428 always executed asynchronously in non-stop mode.
5430 Suspending execution is done with the @code{interrupt} command when
5431 running in the background, or @kbd{Ctrl-c} during foreground execution.
5432 In all-stop mode, this stops the whole process;
5433 but in non-stop mode the interrupt applies only to the current thread.
5434 To stop the whole program, use @code{interrupt -a}.
5436 Other execution commands do not currently support the @code{-a} option.
5438 In non-stop mode, when a thread stops, @value{GDBN} doesn't automatically make
5439 that thread current, as it does in all-stop mode. This is because the
5440 thread stop notifications are asynchronous with respect to @value{GDBN}'s
5441 command interpreter, and it would be confusing if @value{GDBN} unexpectedly
5442 changed to a different thread just as you entered a command to operate on the
5443 previously current thread.
5445 @node Background Execution
5446 @subsection Background Execution
5448 @cindex foreground execution
5449 @cindex background execution
5450 @cindex asynchronous execution
5451 @cindex execution, foreground, background and asynchronous
5453 @value{GDBN}'s execution commands have two variants: the normal
5454 foreground (synchronous) behavior, and a background
5455 (asynchronous) behavior. In foreground execution, @value{GDBN} waits for
5456 the program to report that some thread has stopped before prompting for
5457 another command. In background execution, @value{GDBN} immediately gives
5458 a command prompt so that you can issue other commands while your program runs.
5460 You need to explicitly enable asynchronous mode before you can use
5461 background execution commands. You can use these commands to
5462 manipulate the asynchronous mode setting:
5465 @kindex set target-async
5466 @item set target-async on
5467 Enable asynchronous mode.
5468 @item set target-async off
5469 Disable asynchronous mode.
5470 @kindex show target-async
5471 @item show target-async
5472 Show the current target-async setting.
5475 If the target doesn't support async mode, @value{GDBN} issues an error
5476 message if you attempt to use the background execution commands.
5478 To specify background execution, add a @code{&} to the command. For example,
5479 the background form of the @code{continue} command is @code{continue&}, or
5480 just @code{c&}. The execution commands that accept background execution
5486 @xref{Starting, , Starting your Program}.
5490 @xref{Attach, , Debugging an Already-running Process}.
5494 @xref{Continuing and Stepping, step}.
5498 @xref{Continuing and Stepping, stepi}.
5502 @xref{Continuing and Stepping, next}.
5506 @xref{Continuing and Stepping, nexti}.
5510 @xref{Continuing and Stepping, continue}.
5514 @xref{Continuing and Stepping, finish}.
5518 @xref{Continuing and Stepping, until}.
5522 Background execution is especially useful in conjunction with non-stop
5523 mode for debugging programs with multiple threads; see @ref{Non-Stop Mode}.
5524 However, you can also use these commands in the normal all-stop mode with
5525 the restriction that you cannot issue another execution command until the
5526 previous one finishes. Examples of commands that are valid in all-stop
5527 mode while the program is running include @code{help} and @code{info break}.
5529 You can interrupt your program while it is running in the background by
5530 using the @code{interrupt} command.
5537 Suspend execution of the running program. In all-stop mode,
5538 @code{interrupt} stops the whole process, but in non-stop mode, it stops
5539 only the current thread. To stop the whole program in non-stop mode,
5540 use @code{interrupt -a}.
5543 @node Thread-Specific Breakpoints
5544 @subsection Thread-Specific Breakpoints
5546 When your program has multiple threads (@pxref{Threads,, Debugging
5547 Programs with Multiple Threads}), you can choose whether to set
5548 breakpoints on all threads, or on a particular thread.
5551 @cindex breakpoints and threads
5552 @cindex thread breakpoints
5553 @kindex break @dots{} thread @var{threadno}
5554 @item break @var{linespec} thread @var{threadno}
5555 @itemx break @var{linespec} thread @var{threadno} if @dots{}
5556 @var{linespec} specifies source lines; there are several ways of
5557 writing them (@pxref{Specify Location}), but the effect is always to
5558 specify some source line.
5560 Use the qualifier @samp{thread @var{threadno}} with a breakpoint command
5561 to specify that you only want @value{GDBN} to stop the program when a
5562 particular thread reaches this breakpoint. @var{threadno} is one of the
5563 numeric thread identifiers assigned by @value{GDBN}, shown in the first
5564 column of the @samp{info threads} display.
5566 If you do not specify @samp{thread @var{threadno}} when you set a
5567 breakpoint, the breakpoint applies to @emph{all} threads of your
5570 You can use the @code{thread} qualifier on conditional breakpoints as
5571 well; in this case, place @samp{thread @var{threadno}} before or
5572 after the breakpoint condition, like this:
5575 (@value{GDBP}) break frik.c:13 thread 28 if bartab > lim
5580 @node Interrupted System Calls
5581 @subsection Interrupted System Calls
5583 @cindex thread breakpoints and system calls
5584 @cindex system calls and thread breakpoints
5585 @cindex premature return from system calls
5586 There is an unfortunate side effect when using @value{GDBN} to debug
5587 multi-threaded programs. If one thread stops for a
5588 breakpoint, or for some other reason, and another thread is blocked in a
5589 system call, then the system call may return prematurely. This is a
5590 consequence of the interaction between multiple threads and the signals
5591 that @value{GDBN} uses to implement breakpoints and other events that
5594 To handle this problem, your program should check the return value of
5595 each system call and react appropriately. This is good programming
5598 For example, do not write code like this:
5604 The call to @code{sleep} will return early if a different thread stops
5605 at a breakpoint or for some other reason.
5607 Instead, write this:
5612 unslept = sleep (unslept);
5615 A system call is allowed to return early, so the system is still
5616 conforming to its specification. But @value{GDBN} does cause your
5617 multi-threaded program to behave differently than it would without
5620 Also, @value{GDBN} uses internal breakpoints in the thread library to
5621 monitor certain events such as thread creation and thread destruction.
5622 When such an event happens, a system call in another thread may return
5623 prematurely, even though your program does not appear to stop.
5626 @subsection Observer Mode
5628 If you want to build on non-stop mode and observe program behavior
5629 without any chance of disruption by @value{GDBN}, you can set
5630 variables to disable all of the debugger's attempts to modify state,
5631 whether by writing memory, inserting breakpoints, etc. These operate
5632 at a low level, intercepting operations from all commands.
5634 When all of these are set to @code{off}, then @value{GDBN} is said to
5635 be @dfn{observer mode}. As a convenience, the variable
5636 @code{observer} can be set to disable these, plus enable non-stop
5639 Note that @value{GDBN} will not prevent you from making nonsensical
5640 combinations of these settings. For instance, if you have enabled
5641 @code{may-insert-breakpoints} but disabled @code{may-write-memory},
5642 then breakpoints that work by writing trap instructions into the code
5643 stream will still not be able to be placed.
5648 @item set observer on
5649 @itemx set observer off
5650 When set to @code{on}, this disables all the permission variables
5651 below (except for @code{insert-fast-tracepoints}), plus enables
5652 non-stop debugging. Setting this to @code{off} switches back to
5653 normal debugging, though remaining in non-stop mode.
5656 Show whether observer mode is on or off.
5658 @kindex may-write-registers
5659 @item set may-write-registers on
5660 @itemx set may-write-registers off
5661 This controls whether @value{GDBN} will attempt to alter the values of
5662 registers, such as with assignment expressions in @code{print}, or the
5663 @code{jump} command. It defaults to @code{on}.
5665 @item show may-write-registers
5666 Show the current permission to write registers.
5668 @kindex may-write-memory
5669 @item set may-write-memory on
5670 @itemx set may-write-memory off
5671 This controls whether @value{GDBN} will attempt to alter the contents
5672 of memory, such as with assignment expressions in @code{print}. It
5673 defaults to @code{on}.
5675 @item show may-write-memory
5676 Show the current permission to write memory.
5678 @kindex may-insert-breakpoints
5679 @item set may-insert-breakpoints on
5680 @itemx set may-insert-breakpoints off
5681 This controls whether @value{GDBN} will attempt to insert breakpoints.
5682 This affects all breakpoints, including internal breakpoints defined
5683 by @value{GDBN}. It defaults to @code{on}.
5685 @item show may-insert-breakpoints
5686 Show the current permission to insert breakpoints.
5688 @kindex may-insert-tracepoints
5689 @item set may-insert-tracepoints on
5690 @itemx set may-insert-tracepoints off
5691 This controls whether @value{GDBN} will attempt to insert (regular)
5692 tracepoints at the beginning of a tracing experiment. It affects only
5693 non-fast tracepoints, fast tracepoints being under the control of
5694 @code{may-insert-fast-tracepoints}. It defaults to @code{on}.
5696 @item show may-insert-tracepoints
5697 Show the current permission to insert tracepoints.
5699 @kindex may-insert-fast-tracepoints
5700 @item set may-insert-fast-tracepoints on
5701 @itemx set may-insert-fast-tracepoints off
5702 This controls whether @value{GDBN} will attempt to insert fast
5703 tracepoints at the beginning of a tracing experiment. It affects only
5704 fast tracepoints, regular (non-fast) tracepoints being under the
5705 control of @code{may-insert-tracepoints}. It defaults to @code{on}.
5707 @item show may-insert-fast-tracepoints
5708 Show the current permission to insert fast tracepoints.
5710 @kindex may-interrupt
5711 @item set may-interrupt on
5712 @itemx set may-interrupt off
5713 This controls whether @value{GDBN} will attempt to interrupt or stop
5714 program execution. When this variable is @code{off}, the
5715 @code{interrupt} command will have no effect, nor will
5716 @kbd{Ctrl-c}. It defaults to @code{on}.
5718 @item show may-interrupt
5719 Show the current permission to interrupt or stop the program.
5723 @node Reverse Execution
5724 @chapter Running programs backward
5725 @cindex reverse execution
5726 @cindex running programs backward
5728 When you are debugging a program, it is not unusual to realize that
5729 you have gone too far, and some event of interest has already happened.
5730 If the target environment supports it, @value{GDBN} can allow you to
5731 ``rewind'' the program by running it backward.
5733 A target environment that supports reverse execution should be able
5734 to ``undo'' the changes in machine state that have taken place as the
5735 program was executing normally. Variables, registers etc.@: should
5736 revert to their previous values. Obviously this requires a great
5737 deal of sophistication on the part of the target environment; not
5738 all target environments can support reverse execution.
5740 When a program is executed in reverse, the instructions that
5741 have most recently been executed are ``un-executed'', in reverse
5742 order. The program counter runs backward, following the previous
5743 thread of execution in reverse. As each instruction is ``un-executed'',
5744 the values of memory and/or registers that were changed by that
5745 instruction are reverted to their previous states. After executing
5746 a piece of source code in reverse, all side effects of that code
5747 should be ``undone'', and all variables should be returned to their
5748 prior values@footnote{
5749 Note that some side effects are easier to undo than others. For instance,
5750 memory and registers are relatively easy, but device I/O is hard. Some
5751 targets may be able undo things like device I/O, and some may not.
5753 The contract between @value{GDBN} and the reverse executing target
5754 requires only that the target do something reasonable when
5755 @value{GDBN} tells it to execute backwards, and then report the
5756 results back to @value{GDBN}. Whatever the target reports back to
5757 @value{GDBN}, @value{GDBN} will report back to the user. @value{GDBN}
5758 assumes that the memory and registers that the target reports are in a
5759 consistant state, but @value{GDBN} accepts whatever it is given.
5762 If you are debugging in a target environment that supports
5763 reverse execution, @value{GDBN} provides the following commands.
5766 @kindex reverse-continue
5767 @kindex rc @r{(@code{reverse-continue})}
5768 @item reverse-continue @r{[}@var{ignore-count}@r{]}
5769 @itemx rc @r{[}@var{ignore-count}@r{]}
5770 Beginning at the point where your program last stopped, start executing
5771 in reverse. Reverse execution will stop for breakpoints and synchronous
5772 exceptions (signals), just like normal execution. Behavior of
5773 asynchronous signals depends on the target environment.
5775 @kindex reverse-step
5776 @kindex rs @r{(@code{step})}
5777 @item reverse-step @r{[}@var{count}@r{]}
5778 Run the program backward until control reaches the start of a
5779 different source line; then stop it, and return control to @value{GDBN}.
5781 Like the @code{step} command, @code{reverse-step} will only stop
5782 at the beginning of a source line. It ``un-executes'' the previously
5783 executed source line. If the previous source line included calls to
5784 debuggable functions, @code{reverse-step} will step (backward) into
5785 the called function, stopping at the beginning of the @emph{last}
5786 statement in the called function (typically a return statement).
5788 Also, as with the @code{step} command, if non-debuggable functions are
5789 called, @code{reverse-step} will run thru them backward without stopping.
5791 @kindex reverse-stepi
5792 @kindex rsi @r{(@code{reverse-stepi})}
5793 @item reverse-stepi @r{[}@var{count}@r{]}
5794 Reverse-execute one machine instruction. Note that the instruction
5795 to be reverse-executed is @emph{not} the one pointed to by the program
5796 counter, but the instruction executed prior to that one. For instance,
5797 if the last instruction was a jump, @code{reverse-stepi} will take you
5798 back from the destination of the jump to the jump instruction itself.
5800 @kindex reverse-next
5801 @kindex rn @r{(@code{reverse-next})}
5802 @item reverse-next @r{[}@var{count}@r{]}
5803 Run backward to the beginning of the previous line executed in
5804 the current (innermost) stack frame. If the line contains function
5805 calls, they will be ``un-executed'' without stopping. Starting from
5806 the first line of a function, @code{reverse-next} will take you back
5807 to the caller of that function, @emph{before} the function was called,
5808 just as the normal @code{next} command would take you from the last
5809 line of a function back to its return to its caller
5810 @footnote{Unless the code is too heavily optimized.}.
5812 @kindex reverse-nexti
5813 @kindex rni @r{(@code{reverse-nexti})}
5814 @item reverse-nexti @r{[}@var{count}@r{]}
5815 Like @code{nexti}, @code{reverse-nexti} executes a single instruction
5816 in reverse, except that called functions are ``un-executed'' atomically.
5817 That is, if the previously executed instruction was a return from
5818 another function, @code{reverse-nexti} will continue to execute
5819 in reverse until the call to that function (from the current stack
5822 @kindex reverse-finish
5823 @item reverse-finish
5824 Just as the @code{finish} command takes you to the point where the
5825 current function returns, @code{reverse-finish} takes you to the point
5826 where it was called. Instead of ending up at the end of the current
5827 function invocation, you end up at the beginning.
5829 @kindex set exec-direction
5830 @item set exec-direction
5831 Set the direction of target execution.
5832 @itemx set exec-direction reverse
5833 @cindex execute forward or backward in time
5834 @value{GDBN} will perform all execution commands in reverse, until the
5835 exec-direction mode is changed to ``forward''. Affected commands include
5836 @code{step, stepi, next, nexti, continue, and finish}. The @code{return}
5837 command cannot be used in reverse mode.
5838 @item set exec-direction forward
5839 @value{GDBN} will perform all execution commands in the normal fashion.
5840 This is the default.
5844 @node Process Record and Replay
5845 @chapter Recording Inferior's Execution and Replaying It
5846 @cindex process record and replay
5847 @cindex recording inferior's execution and replaying it
5849 On some platforms, @value{GDBN} provides a special @dfn{process record
5850 and replay} target that can record a log of the process execution, and
5851 replay it later with both forward and reverse execution commands.
5854 When this target is in use, if the execution log includes the record
5855 for the next instruction, @value{GDBN} will debug in @dfn{replay
5856 mode}. In the replay mode, the inferior does not really execute code
5857 instructions. Instead, all the events that normally happen during
5858 code execution are taken from the execution log. While code is not
5859 really executed in replay mode, the values of registers (including the
5860 program counter register) and the memory of the inferior are still
5861 changed as they normally would. Their contents are taken from the
5865 If the record for the next instruction is not in the execution log,
5866 @value{GDBN} will debug in @dfn{record mode}. In this mode, the
5867 inferior executes normally, and @value{GDBN} records the execution log
5870 The process record and replay target supports reverse execution
5871 (@pxref{Reverse Execution}), even if the platform on which the
5872 inferior runs does not. However, the reverse execution is limited in
5873 this case by the range of the instructions recorded in the execution
5874 log. In other words, reverse execution on platforms that don't
5875 support it directly can only be done in the replay mode.
5877 When debugging in the reverse direction, @value{GDBN} will work in
5878 replay mode as long as the execution log includes the record for the
5879 previous instruction; otherwise, it will work in record mode, if the
5880 platform supports reverse execution, or stop if not.
5882 For architecture environments that support process record and replay,
5883 @value{GDBN} provides the following commands:
5886 @kindex target record
5890 This command starts the process record and replay target. The process
5891 record and replay target can only debug a process that is already
5892 running. Therefore, you need first to start the process with the
5893 @kbd{run} or @kbd{start} commands, and then start the recording with
5894 the @kbd{target record} command.
5896 Both @code{record} and @code{rec} are aliases of @code{target record}.
5898 @cindex displaced stepping, and process record and replay
5899 Displaced stepping (@pxref{Maintenance Commands,, displaced stepping})
5900 will be automatically disabled when process record and replay target
5901 is started. That's because the process record and replay target
5902 doesn't support displaced stepping.
5904 @cindex non-stop mode, and process record and replay
5905 @cindex asynchronous execution, and process record and replay
5906 If the inferior is in the non-stop mode (@pxref{Non-Stop Mode}) or in
5907 the asynchronous execution mode (@pxref{Background Execution}), the
5908 process record and replay target cannot be started because it doesn't
5909 support these two modes.
5914 Stop the process record and replay target. When process record and
5915 replay target stops, the entire execution log will be deleted and the
5916 inferior will either be terminated, or will remain in its final state.
5918 When you stop the process record and replay target in record mode (at
5919 the end of the execution log), the inferior will be stopped at the
5920 next instruction that would have been recorded. In other words, if
5921 you record for a while and then stop recording, the inferior process
5922 will be left in the same state as if the recording never happened.
5924 On the other hand, if the process record and replay target is stopped
5925 while in replay mode (that is, not at the end of the execution log,
5926 but at some earlier point), the inferior process will become ``live''
5927 at that earlier state, and it will then be possible to continue the
5928 usual ``live'' debugging of the process from that state.
5930 When the inferior process exits, or @value{GDBN} detaches from it,
5931 process record and replay target will automatically stop itself.
5934 @item record save @var{filename}
5935 Save the execution log to a file @file{@var{filename}}.
5936 Default filename is @file{gdb_record.@var{process_id}}, where
5937 @var{process_id} is the process ID of the inferior.
5939 @kindex record restore
5940 @item record restore @var{filename}
5941 Restore the execution log from a file @file{@var{filename}}.
5942 File must have been created with @code{record save}.
5944 @kindex set record insn-number-max
5945 @item set record insn-number-max @var{limit}
5946 Set the limit of instructions to be recorded. Default value is 200000.
5948 If @var{limit} is a positive number, then @value{GDBN} will start
5949 deleting instructions from the log once the number of the record
5950 instructions becomes greater than @var{limit}. For every new recorded
5951 instruction, @value{GDBN} will delete the earliest recorded
5952 instruction to keep the number of recorded instructions at the limit.
5953 (Since deleting recorded instructions loses information, @value{GDBN}
5954 lets you control what happens when the limit is reached, by means of
5955 the @code{stop-at-limit} option, described below.)
5957 If @var{limit} is zero, @value{GDBN} will never delete recorded
5958 instructions from the execution log. The number of recorded
5959 instructions is unlimited in this case.
5961 @kindex show record insn-number-max
5962 @item show record insn-number-max
5963 Show the limit of instructions to be recorded.
5965 @kindex set record stop-at-limit
5966 @item set record stop-at-limit
5967 Control the behavior when the number of recorded instructions reaches
5968 the limit. If ON (the default), @value{GDBN} will stop when the limit
5969 is reached for the first time and ask you whether you want to stop the
5970 inferior or continue running it and recording the execution log. If
5971 you decide to continue recording, each new recorded instruction will
5972 cause the oldest one to be deleted.
5974 If this option is OFF, @value{GDBN} will automatically delete the
5975 oldest record to make room for each new one, without asking.
5977 @kindex show record stop-at-limit
5978 @item show record stop-at-limit
5979 Show the current setting of @code{stop-at-limit}.
5981 @kindex set record memory-query
5982 @item set record memory-query
5983 Control the behavior when @value{GDBN} is unable to record memory
5984 changes caused by an instruction. If ON, @value{GDBN} will query
5985 whether to stop the inferior in that case.
5987 If this option is OFF (the default), @value{GDBN} will automatically
5988 ignore the effect of such instructions on memory. Later, when
5989 @value{GDBN} replays this execution log, it will mark the log of this
5990 instruction as not accessible, and it will not affect the replay
5993 @kindex show record memory-query
5994 @item show record memory-query
5995 Show the current setting of @code{memory-query}.
5999 Show various statistics about the state of process record and its
6000 in-memory execution log buffer, including:
6004 Whether in record mode or replay mode.
6006 Lowest recorded instruction number (counting from when the current execution log started recording instructions).
6008 Highest recorded instruction number.
6010 Current instruction about to be replayed (if in replay mode).
6012 Number of instructions contained in the execution log.
6014 Maximum number of instructions that may be contained in the execution log.
6017 @kindex record delete
6020 When record target runs in replay mode (``in the past''), delete the
6021 subsequent execution log and begin to record a new execution log starting
6022 from the current address. This means you will abandon the previously
6023 recorded ``future'' and begin recording a new ``future''.
6028 @chapter Examining the Stack
6030 When your program has stopped, the first thing you need to know is where it
6031 stopped and how it got there.
6034 Each time your program performs a function call, information about the call
6036 That information includes the location of the call in your program,
6037 the arguments of the call,
6038 and the local variables of the function being called.
6039 The information is saved in a block of data called a @dfn{stack frame}.
6040 The stack frames are allocated in a region of memory called the @dfn{call
6043 When your program stops, the @value{GDBN} commands for examining the
6044 stack allow you to see all of this information.
6046 @cindex selected frame
6047 One of the stack frames is @dfn{selected} by @value{GDBN} and many
6048 @value{GDBN} commands refer implicitly to the selected frame. In
6049 particular, whenever you ask @value{GDBN} for the value of a variable in
6050 your program, the value is found in the selected frame. There are
6051 special @value{GDBN} commands to select whichever frame you are
6052 interested in. @xref{Selection, ,Selecting a Frame}.
6054 When your program stops, @value{GDBN} automatically selects the
6055 currently executing frame and describes it briefly, similar to the
6056 @code{frame} command (@pxref{Frame Info, ,Information about a Frame}).
6059 * Frames:: Stack frames
6060 * Backtrace:: Backtraces
6061 * Selection:: Selecting a frame
6062 * Frame Info:: Information on a frame
6067 @section Stack Frames
6069 @cindex frame, definition
6071 The call stack is divided up into contiguous pieces called @dfn{stack
6072 frames}, or @dfn{frames} for short; each frame is the data associated
6073 with one call to one function. The frame contains the arguments given
6074 to the function, the function's local variables, and the address at
6075 which the function is executing.
6077 @cindex initial frame
6078 @cindex outermost frame
6079 @cindex innermost frame
6080 When your program is started, the stack has only one frame, that of the
6081 function @code{main}. This is called the @dfn{initial} frame or the
6082 @dfn{outermost} frame. Each time a function is called, a new frame is
6083 made. Each time a function returns, the frame for that function invocation
6084 is eliminated. If a function is recursive, there can be many frames for
6085 the same function. The frame for the function in which execution is
6086 actually occurring is called the @dfn{innermost} frame. This is the most
6087 recently created of all the stack frames that still exist.
6089 @cindex frame pointer
6090 Inside your program, stack frames are identified by their addresses. A
6091 stack frame consists of many bytes, each of which has its own address; each
6092 kind of computer has a convention for choosing one byte whose
6093 address serves as the address of the frame. Usually this address is kept
6094 in a register called the @dfn{frame pointer register}
6095 (@pxref{Registers, $fp}) while execution is going on in that frame.
6097 @cindex frame number
6098 @value{GDBN} assigns numbers to all existing stack frames, starting with
6099 zero for the innermost frame, one for the frame that called it,
6100 and so on upward. These numbers do not really exist in your program;
6101 they are assigned by @value{GDBN} to give you a way of designating stack
6102 frames in @value{GDBN} commands.
6104 @c The -fomit-frame-pointer below perennially causes hbox overflow
6105 @c underflow problems.
6106 @cindex frameless execution
6107 Some compilers provide a way to compile functions so that they operate
6108 without stack frames. (For example, the @value{NGCC} option
6110 @samp{-fomit-frame-pointer}
6112 generates functions without a frame.)
6113 This is occasionally done with heavily used library functions to save
6114 the frame setup time. @value{GDBN} has limited facilities for dealing
6115 with these function invocations. If the innermost function invocation
6116 has no stack frame, @value{GDBN} nevertheless regards it as though
6117 it had a separate frame, which is numbered zero as usual, allowing
6118 correct tracing of the function call chain. However, @value{GDBN} has
6119 no provision for frameless functions elsewhere in the stack.
6122 @kindex frame@r{, command}
6123 @cindex current stack frame
6124 @item frame @var{args}
6125 The @code{frame} command allows you to move from one stack frame to another,
6126 and to print the stack frame you select. @var{args} may be either the
6127 address of the frame or the stack frame number. Without an argument,
6128 @code{frame} prints the current stack frame.
6130 @kindex select-frame
6131 @cindex selecting frame silently
6133 The @code{select-frame} command allows you to move from one stack frame
6134 to another without printing the frame. This is the silent version of
6142 @cindex call stack traces
6143 A backtrace is a summary of how your program got where it is. It shows one
6144 line per frame, for many frames, starting with the currently executing
6145 frame (frame zero), followed by its caller (frame one), and on up the
6150 @kindex bt @r{(@code{backtrace})}
6153 Print a backtrace of the entire stack: one line per frame for all
6154 frames in the stack.
6156 You can stop the backtrace at any time by typing the system interrupt
6157 character, normally @kbd{Ctrl-c}.
6159 @item backtrace @var{n}
6161 Similar, but print only the innermost @var{n} frames.
6163 @item backtrace -@var{n}
6165 Similar, but print only the outermost @var{n} frames.
6167 @item backtrace full
6169 @itemx bt full @var{n}
6170 @itemx bt full -@var{n}
6171 Print the values of the local variables also. @var{n} specifies the
6172 number of frames to print, as described above.
6177 The names @code{where} and @code{info stack} (abbreviated @code{info s})
6178 are additional aliases for @code{backtrace}.
6180 @cindex multiple threads, backtrace
6181 In a multi-threaded program, @value{GDBN} by default shows the
6182 backtrace only for the current thread. To display the backtrace for
6183 several or all of the threads, use the command @code{thread apply}
6184 (@pxref{Threads, thread apply}). For example, if you type @kbd{thread
6185 apply all backtrace}, @value{GDBN} will display the backtrace for all
6186 the threads; this is handy when you debug a core dump of a
6187 multi-threaded program.
6189 Each line in the backtrace shows the frame number and the function name.
6190 The program counter value is also shown---unless you use @code{set
6191 print address off}. The backtrace also shows the source file name and
6192 line number, as well as the arguments to the function. The program
6193 counter value is omitted if it is at the beginning of the code for that
6196 Here is an example of a backtrace. It was made with the command
6197 @samp{bt 3}, so it shows the innermost three frames.
6201 #0 m4_traceon (obs=0x24eb0, argc=1, argv=0x2b8c8)
6203 #1 0x6e38 in expand_macro (sym=0x2b600, data=...) at macro.c:242
6204 #2 0x6840 in expand_token (obs=0x0, t=177664, td=0xf7fffb08)
6206 (More stack frames follow...)
6211 The display for frame zero does not begin with a program counter
6212 value, indicating that your program has stopped at the beginning of the
6213 code for line @code{993} of @code{builtin.c}.
6216 The value of parameter @code{data} in frame 1 has been replaced by
6217 @code{@dots{}}. By default, @value{GDBN} prints the value of a parameter
6218 only if it is a scalar (integer, pointer, enumeration, etc). See command
6219 @kbd{set print frame-arguments} in @ref{Print Settings} for more details
6220 on how to configure the way function parameter values are printed.
6222 @cindex optimized out, in backtrace
6223 @cindex function call arguments, optimized out
6224 If your program was compiled with optimizations, some compilers will
6225 optimize away arguments passed to functions if those arguments are
6226 never used after the call. Such optimizations generate code that
6227 passes arguments through registers, but doesn't store those arguments
6228 in the stack frame. @value{GDBN} has no way of displaying such
6229 arguments in stack frames other than the innermost one. Here's what
6230 such a backtrace might look like:
6234 #0 m4_traceon (obs=0x24eb0, argc=1, argv=0x2b8c8)
6236 #1 0x6e38 in expand_macro (sym=<optimized out>) at macro.c:242
6237 #2 0x6840 in expand_token (obs=0x0, t=<optimized out>, td=0xf7fffb08)
6239 (More stack frames follow...)
6244 The values of arguments that were not saved in their stack frames are
6245 shown as @samp{<optimized out>}.
6247 If you need to display the values of such optimized-out arguments,
6248 either deduce that from other variables whose values depend on the one
6249 you are interested in, or recompile without optimizations.
6251 @cindex backtrace beyond @code{main} function
6252 @cindex program entry point
6253 @cindex startup code, and backtrace
6254 Most programs have a standard user entry point---a place where system
6255 libraries and startup code transition into user code. For C this is
6256 @code{main}@footnote{
6257 Note that embedded programs (the so-called ``free-standing''
6258 environment) are not required to have a @code{main} function as the
6259 entry point. They could even have multiple entry points.}.
6260 When @value{GDBN} finds the entry function in a backtrace
6261 it will terminate the backtrace, to avoid tracing into highly
6262 system-specific (and generally uninteresting) code.
6264 If you need to examine the startup code, or limit the number of levels
6265 in a backtrace, you can change this behavior:
6268 @item set backtrace past-main
6269 @itemx set backtrace past-main on
6270 @kindex set backtrace
6271 Backtraces will continue past the user entry point.
6273 @item set backtrace past-main off
6274 Backtraces will stop when they encounter the user entry point. This is the
6277 @item show backtrace past-main
6278 @kindex show backtrace
6279 Display the current user entry point backtrace policy.
6281 @item set backtrace past-entry
6282 @itemx set backtrace past-entry on
6283 Backtraces will continue past the internal entry point of an application.
6284 This entry point is encoded by the linker when the application is built,
6285 and is likely before the user entry point @code{main} (or equivalent) is called.
6287 @item set backtrace past-entry off
6288 Backtraces will stop when they encounter the internal entry point of an
6289 application. This is the default.
6291 @item show backtrace past-entry
6292 Display the current internal entry point backtrace policy.
6294 @item set backtrace limit @var{n}
6295 @itemx set backtrace limit 0
6296 @cindex backtrace limit
6297 Limit the backtrace to @var{n} levels. A value of zero means
6300 @item show backtrace limit
6301 Display the current limit on backtrace levels.
6305 @section Selecting a Frame
6307 Most commands for examining the stack and other data in your program work on
6308 whichever stack frame is selected at the moment. Here are the commands for
6309 selecting a stack frame; all of them finish by printing a brief description
6310 of the stack frame just selected.
6313 @kindex frame@r{, selecting}
6314 @kindex f @r{(@code{frame})}
6317 Select frame number @var{n}. Recall that frame zero is the innermost
6318 (currently executing) frame, frame one is the frame that called the
6319 innermost one, and so on. The highest-numbered frame is the one for
6322 @item frame @var{addr}
6324 Select the frame at address @var{addr}. This is useful mainly if the
6325 chaining of stack frames has been damaged by a bug, making it
6326 impossible for @value{GDBN} to assign numbers properly to all frames. In
6327 addition, this can be useful when your program has multiple stacks and
6328 switches between them.
6330 On the SPARC architecture, @code{frame} needs two addresses to
6331 select an arbitrary frame: a frame pointer and a stack pointer.
6333 On the MIPS and Alpha architecture, it needs two addresses: a stack
6334 pointer and a program counter.
6336 On the 29k architecture, it needs three addresses: a register stack
6337 pointer, a program counter, and a memory stack pointer.
6341 Move @var{n} frames up the stack. For positive numbers @var{n}, this
6342 advances toward the outermost frame, to higher frame numbers, to frames
6343 that have existed longer. @var{n} defaults to one.
6346 @kindex do @r{(@code{down})}
6348 Move @var{n} frames down the stack. For positive numbers @var{n}, this
6349 advances toward the innermost frame, to lower frame numbers, to frames
6350 that were created more recently. @var{n} defaults to one. You may
6351 abbreviate @code{down} as @code{do}.
6354 All of these commands end by printing two lines of output describing the
6355 frame. The first line shows the frame number, the function name, the
6356 arguments, and the source file and line number of execution in that
6357 frame. The second line shows the text of that source line.
6365 #1 0x22f0 in main (argc=1, argv=0xf7fffbf4, env=0xf7fffbfc)
6367 10 read_input_file (argv[i]);
6371 After such a printout, the @code{list} command with no arguments
6372 prints ten lines centered on the point of execution in the frame.
6373 You can also edit the program at the point of execution with your favorite
6374 editing program by typing @code{edit}.
6375 @xref{List, ,Printing Source Lines},
6379 @kindex down-silently
6381 @item up-silently @var{n}
6382 @itemx down-silently @var{n}
6383 These two commands are variants of @code{up} and @code{down},
6384 respectively; they differ in that they do their work silently, without
6385 causing display of the new frame. They are intended primarily for use
6386 in @value{GDBN} command scripts, where the output might be unnecessary and
6391 @section Information About a Frame
6393 There are several other commands to print information about the selected
6399 When used without any argument, this command does not change which
6400 frame is selected, but prints a brief description of the currently
6401 selected stack frame. It can be abbreviated @code{f}. With an
6402 argument, this command is used to select a stack frame.
6403 @xref{Selection, ,Selecting a Frame}.
6406 @kindex info f @r{(@code{info frame})}
6409 This command prints a verbose description of the selected stack frame,
6414 the address of the frame
6416 the address of the next frame down (called by this frame)
6418 the address of the next frame up (caller of this frame)
6420 the language in which the source code corresponding to this frame is written
6422 the address of the frame's arguments
6424 the address of the frame's local variables
6426 the program counter saved in it (the address of execution in the caller frame)
6428 which registers were saved in the frame
6431 @noindent The verbose description is useful when
6432 something has gone wrong that has made the stack format fail to fit
6433 the usual conventions.
6435 @item info frame @var{addr}
6436 @itemx info f @var{addr}
6437 Print a verbose description of the frame at address @var{addr}, without
6438 selecting that frame. The selected frame remains unchanged by this
6439 command. This requires the same kind of address (more than one for some
6440 architectures) that you specify in the @code{frame} command.
6441 @xref{Selection, ,Selecting a Frame}.
6445 Print the arguments of the selected frame, each on a separate line.
6449 Print the local variables of the selected frame, each on a separate
6450 line. These are all variables (declared either static or automatic)
6451 accessible at the point of execution of the selected frame.
6457 @chapter Examining Source Files
6459 @value{GDBN} can print parts of your program's source, since the debugging
6460 information recorded in the program tells @value{GDBN} what source files were
6461 used to build it. When your program stops, @value{GDBN} spontaneously prints
6462 the line where it stopped. Likewise, when you select a stack frame
6463 (@pxref{Selection, ,Selecting a Frame}), @value{GDBN} prints the line where
6464 execution in that frame has stopped. You can print other portions of
6465 source files by explicit command.
6467 If you use @value{GDBN} through its @sc{gnu} Emacs interface, you may
6468 prefer to use Emacs facilities to view source; see @ref{Emacs, ,Using
6469 @value{GDBN} under @sc{gnu} Emacs}.
6472 * List:: Printing source lines
6473 * Specify Location:: How to specify code locations
6474 * Edit:: Editing source files
6475 * Search:: Searching source files
6476 * Source Path:: Specifying source directories
6477 * Machine Code:: Source and machine code
6481 @section Printing Source Lines
6484 @kindex l @r{(@code{list})}
6485 To print lines from a source file, use the @code{list} command
6486 (abbreviated @code{l}). By default, ten lines are printed.
6487 There are several ways to specify what part of the file you want to
6488 print; see @ref{Specify Location}, for the full list.
6490 Here are the forms of the @code{list} command most commonly used:
6493 @item list @var{linenum}
6494 Print lines centered around line number @var{linenum} in the
6495 current source file.
6497 @item list @var{function}
6498 Print lines centered around the beginning of function
6502 Print more lines. If the last lines printed were printed with a
6503 @code{list} command, this prints lines following the last lines
6504 printed; however, if the last line printed was a solitary line printed
6505 as part of displaying a stack frame (@pxref{Stack, ,Examining the
6506 Stack}), this prints lines centered around that line.
6509 Print lines just before the lines last printed.
6512 @cindex @code{list}, how many lines to display
6513 By default, @value{GDBN} prints ten source lines with any of these forms of
6514 the @code{list} command. You can change this using @code{set listsize}:
6517 @kindex set listsize
6518 @item set listsize @var{count}
6519 Make the @code{list} command display @var{count} source lines (unless
6520 the @code{list} argument explicitly specifies some other number).
6522 @kindex show listsize
6524 Display the number of lines that @code{list} prints.
6527 Repeating a @code{list} command with @key{RET} discards the argument,
6528 so it is equivalent to typing just @code{list}. This is more useful
6529 than listing the same lines again. An exception is made for an
6530 argument of @samp{-}; that argument is preserved in repetition so that
6531 each repetition moves up in the source file.
6533 In general, the @code{list} command expects you to supply zero, one or two
6534 @dfn{linespecs}. Linespecs specify source lines; there are several ways
6535 of writing them (@pxref{Specify Location}), but the effect is always
6536 to specify some source line.
6538 Here is a complete description of the possible arguments for @code{list}:
6541 @item list @var{linespec}
6542 Print lines centered around the line specified by @var{linespec}.
6544 @item list @var{first},@var{last}
6545 Print lines from @var{first} to @var{last}. Both arguments are
6546 linespecs. When a @code{list} command has two linespecs, and the
6547 source file of the second linespec is omitted, this refers to
6548 the same source file as the first linespec.
6550 @item list ,@var{last}
6551 Print lines ending with @var{last}.
6553 @item list @var{first},
6554 Print lines starting with @var{first}.
6557 Print lines just after the lines last printed.
6560 Print lines just before the lines last printed.
6563 As described in the preceding table.
6566 @node Specify Location
6567 @section Specifying a Location
6568 @cindex specifying location
6571 Several @value{GDBN} commands accept arguments that specify a location
6572 of your program's code. Since @value{GDBN} is a source-level
6573 debugger, a location usually specifies some line in the source code;
6574 for that reason, locations are also known as @dfn{linespecs}.
6576 Here are all the different ways of specifying a code location that
6577 @value{GDBN} understands:
6581 Specifies the line number @var{linenum} of the current source file.
6584 @itemx +@var{offset}
6585 Specifies the line @var{offset} lines before or after the @dfn{current
6586 line}. For the @code{list} command, the current line is the last one
6587 printed; for the breakpoint commands, this is the line at which
6588 execution stopped in the currently selected @dfn{stack frame}
6589 (@pxref{Frames, ,Frames}, for a description of stack frames.) When
6590 used as the second of the two linespecs in a @code{list} command,
6591 this specifies the line @var{offset} lines up or down from the first
6594 @item @var{filename}:@var{linenum}
6595 Specifies the line @var{linenum} in the source file @var{filename}.
6596 If @var{filename} is a relative file name, then it will match any
6597 source file name with the same trailing components. For example, if
6598 @var{filename} is @samp{gcc/expr.c}, then it will match source file
6599 name of @file{/build/trunk/gcc/expr.c}, but not
6600 @file{/build/trunk/libcpp/expr.c} or @file{/build/trunk/gcc/x-expr.c}.
6602 @item @var{function}
6603 Specifies the line that begins the body of the function @var{function}.
6604 For example, in C, this is the line with the open brace.
6606 @item @var{function}:@var{label}
6607 Specifies the line where @var{label} appears in @var{function}.
6609 @item @var{filename}:@var{function}
6610 Specifies the line that begins the body of the function @var{function}
6611 in the file @var{filename}. You only need the file name with a
6612 function name to avoid ambiguity when there are identically named
6613 functions in different source files.
6616 Specifies the line at which the label named @var{label} appears.
6617 @value{GDBN} searches for the label in the function corresponding to
6618 the currently selected stack frame. If there is no current selected
6619 stack frame (for instance, if the inferior is not running), then
6620 @value{GDBN} will not search for a label.
6622 @item *@var{address}
6623 Specifies the program address @var{address}. For line-oriented
6624 commands, such as @code{list} and @code{edit}, this specifies a source
6625 line that contains @var{address}. For @code{break} and other
6626 breakpoint oriented commands, this can be used to set breakpoints in
6627 parts of your program which do not have debugging information or
6630 Here @var{address} may be any expression valid in the current working
6631 language (@pxref{Languages, working language}) that specifies a code
6632 address. In addition, as a convenience, @value{GDBN} extends the
6633 semantics of expressions used in locations to cover the situations
6634 that frequently happen during debugging. Here are the various forms
6638 @item @var{expression}
6639 Any expression valid in the current working language.
6641 @item @var{funcaddr}
6642 An address of a function or procedure derived from its name. In C,
6643 C@t{++}, Java, Objective-C, Fortran, minimal, and assembly, this is
6644 simply the function's name @var{function} (and actually a special case
6645 of a valid expression). In Pascal and Modula-2, this is
6646 @code{&@var{function}}. In Ada, this is @code{@var{function}'Address}
6647 (although the Pascal form also works).
6649 This form specifies the address of the function's first instruction,
6650 before the stack frame and arguments have been set up.
6652 @item '@var{filename}'::@var{funcaddr}
6653 Like @var{funcaddr} above, but also specifies the name of the source
6654 file explicitly. This is useful if the name of the function does not
6655 specify the function unambiguously, e.g., if there are several
6656 functions with identical names in different source files.
6663 @section Editing Source Files
6664 @cindex editing source files
6667 @kindex e @r{(@code{edit})}
6668 To edit the lines in a source file, use the @code{edit} command.
6669 The editing program of your choice
6670 is invoked with the current line set to
6671 the active line in the program.
6672 Alternatively, there are several ways to specify what part of the file you
6673 want to print if you want to see other parts of the program:
6676 @item edit @var{location}
6677 Edit the source file specified by @code{location}. Editing starts at
6678 that @var{location}, e.g., at the specified source line of the
6679 specified file. @xref{Specify Location}, for all the possible forms
6680 of the @var{location} argument; here are the forms of the @code{edit}
6681 command most commonly used:
6684 @item edit @var{number}
6685 Edit the current source file with @var{number} as the active line number.
6687 @item edit @var{function}
6688 Edit the file containing @var{function} at the beginning of its definition.
6693 @subsection Choosing your Editor
6694 You can customize @value{GDBN} to use any editor you want
6696 The only restriction is that your editor (say @code{ex}), recognizes the
6697 following command-line syntax:
6699 ex +@var{number} file
6701 The optional numeric value +@var{number} specifies the number of the line in
6702 the file where to start editing.}.
6703 By default, it is @file{@value{EDITOR}}, but you can change this
6704 by setting the environment variable @code{EDITOR} before using
6705 @value{GDBN}. For example, to configure @value{GDBN} to use the
6706 @code{vi} editor, you could use these commands with the @code{sh} shell:
6712 or in the @code{csh} shell,
6714 setenv EDITOR /usr/bin/vi
6719 @section Searching Source Files
6720 @cindex searching source files
6722 There are two commands for searching through the current source file for a
6727 @kindex forward-search
6728 @item forward-search @var{regexp}
6729 @itemx search @var{regexp}
6730 The command @samp{forward-search @var{regexp}} checks each line,
6731 starting with the one following the last line listed, for a match for
6732 @var{regexp}. It lists the line that is found. You can use the
6733 synonym @samp{search @var{regexp}} or abbreviate the command name as
6736 @kindex reverse-search
6737 @item reverse-search @var{regexp}
6738 The command @samp{reverse-search @var{regexp}} checks each line, starting
6739 with the one before the last line listed and going backward, for a match
6740 for @var{regexp}. It lists the line that is found. You can abbreviate
6741 this command as @code{rev}.
6745 @section Specifying Source Directories
6748 @cindex directories for source files
6749 Executable programs sometimes do not record the directories of the source
6750 files from which they were compiled, just the names. Even when they do,
6751 the directories could be moved between the compilation and your debugging
6752 session. @value{GDBN} has a list of directories to search for source files;
6753 this is called the @dfn{source path}. Each time @value{GDBN} wants a source file,
6754 it tries all the directories in the list, in the order they are present
6755 in the list, until it finds a file with the desired name.
6757 For example, suppose an executable references the file
6758 @file{/usr/src/foo-1.0/lib/foo.c}, and our source path is
6759 @file{/mnt/cross}. The file is first looked up literally; if this
6760 fails, @file{/mnt/cross/usr/src/foo-1.0/lib/foo.c} is tried; if this
6761 fails, @file{/mnt/cross/foo.c} is opened; if this fails, an error
6762 message is printed. @value{GDBN} does not look up the parts of the
6763 source file name, such as @file{/mnt/cross/src/foo-1.0/lib/foo.c}.
6764 Likewise, the subdirectories of the source path are not searched: if
6765 the source path is @file{/mnt/cross}, and the binary refers to
6766 @file{foo.c}, @value{GDBN} would not find it under
6767 @file{/mnt/cross/usr/src/foo-1.0/lib}.
6769 Plain file names, relative file names with leading directories, file
6770 names containing dots, etc.@: are all treated as described above; for
6771 instance, if the source path is @file{/mnt/cross}, and the source file
6772 is recorded as @file{../lib/foo.c}, @value{GDBN} would first try
6773 @file{../lib/foo.c}, then @file{/mnt/cross/../lib/foo.c}, and after
6774 that---@file{/mnt/cross/foo.c}.
6776 Note that the executable search path is @emph{not} used to locate the
6779 Whenever you reset or rearrange the source path, @value{GDBN} clears out
6780 any information it has cached about where source files are found and where
6781 each line is in the file.
6785 When you start @value{GDBN}, its source path includes only @samp{cdir}
6786 and @samp{cwd}, in that order.
6787 To add other directories, use the @code{directory} command.
6789 The search path is used to find both program source files and @value{GDBN}
6790 script files (read using the @samp{-command} option and @samp{source} command).
6792 In addition to the source path, @value{GDBN} provides a set of commands
6793 that manage a list of source path substitution rules. A @dfn{substitution
6794 rule} specifies how to rewrite source directories stored in the program's
6795 debug information in case the sources were moved to a different
6796 directory between compilation and debugging. A rule is made of
6797 two strings, the first specifying what needs to be rewritten in
6798 the path, and the second specifying how it should be rewritten.
6799 In @ref{set substitute-path}, we name these two parts @var{from} and
6800 @var{to} respectively. @value{GDBN} does a simple string replacement
6801 of @var{from} with @var{to} at the start of the directory part of the
6802 source file name, and uses that result instead of the original file
6803 name to look up the sources.
6805 Using the previous example, suppose the @file{foo-1.0} tree has been
6806 moved from @file{/usr/src} to @file{/mnt/cross}, then you can tell
6807 @value{GDBN} to replace @file{/usr/src} in all source path names with
6808 @file{/mnt/cross}. The first lookup will then be
6809 @file{/mnt/cross/foo-1.0/lib/foo.c} in place of the original location
6810 of @file{/usr/src/foo-1.0/lib/foo.c}. To define a source path
6811 substitution rule, use the @code{set substitute-path} command
6812 (@pxref{set substitute-path}).
6814 To avoid unexpected substitution results, a rule is applied only if the
6815 @var{from} part of the directory name ends at a directory separator.
6816 For instance, a rule substituting @file{/usr/source} into
6817 @file{/mnt/cross} will be applied to @file{/usr/source/foo-1.0} but
6818 not to @file{/usr/sourceware/foo-2.0}. And because the substitution
6819 is applied only at the beginning of the directory name, this rule will
6820 not be applied to @file{/root/usr/source/baz.c} either.
6822 In many cases, you can achieve the same result using the @code{directory}
6823 command. However, @code{set substitute-path} can be more efficient in
6824 the case where the sources are organized in a complex tree with multiple
6825 subdirectories. With the @code{directory} command, you need to add each
6826 subdirectory of your project. If you moved the entire tree while
6827 preserving its internal organization, then @code{set substitute-path}
6828 allows you to direct the debugger to all the sources with one single
6831 @code{set substitute-path} is also more than just a shortcut command.
6832 The source path is only used if the file at the original location no
6833 longer exists. On the other hand, @code{set substitute-path} modifies
6834 the debugger behavior to look at the rewritten location instead. So, if
6835 for any reason a source file that is not relevant to your executable is
6836 located at the original location, a substitution rule is the only
6837 method available to point @value{GDBN} at the new location.
6839 @cindex @samp{--with-relocated-sources}
6840 @cindex default source path substitution
6841 You can configure a default source path substitution rule by
6842 configuring @value{GDBN} with the
6843 @samp{--with-relocated-sources=@var{dir}} option. The @var{dir}
6844 should be the name of a directory under @value{GDBN}'s configured
6845 prefix (set with @samp{--prefix} or @samp{--exec-prefix}), and
6846 directory names in debug information under @var{dir} will be adjusted
6847 automatically if the installed @value{GDBN} is moved to a new
6848 location. This is useful if @value{GDBN}, libraries or executables
6849 with debug information and corresponding source code are being moved
6853 @item directory @var{dirname} @dots{}
6854 @item dir @var{dirname} @dots{}
6855 Add directory @var{dirname} to the front of the source path. Several
6856 directory names may be given to this command, separated by @samp{:}
6857 (@samp{;} on MS-DOS and MS-Windows, where @samp{:} usually appears as
6858 part of absolute file names) or
6859 whitespace. You may specify a directory that is already in the source
6860 path; this moves it forward, so @value{GDBN} searches it sooner.
6864 @vindex $cdir@r{, convenience variable}
6865 @vindex $cwd@r{, convenience variable}
6866 @cindex compilation directory
6867 @cindex current directory
6868 @cindex working directory
6869 @cindex directory, current
6870 @cindex directory, compilation
6871 You can use the string @samp{$cdir} to refer to the compilation
6872 directory (if one is recorded), and @samp{$cwd} to refer to the current
6873 working directory. @samp{$cwd} is not the same as @samp{.}---the former
6874 tracks the current working directory as it changes during your @value{GDBN}
6875 session, while the latter is immediately expanded to the current
6876 directory at the time you add an entry to the source path.
6879 Reset the source path to its default value (@samp{$cdir:$cwd} on Unix systems). This requires confirmation.
6881 @c RET-repeat for @code{directory} is explicitly disabled, but since
6882 @c repeating it would be a no-op we do not say that. (thanks to RMS)
6884 @item set directories @var{path-list}
6885 @kindex set directories
6886 Set the source path to @var{path-list}.
6887 @samp{$cdir:$cwd} are added if missing.
6889 @item show directories
6890 @kindex show directories
6891 Print the source path: show which directories it contains.
6893 @anchor{set substitute-path}
6894 @item set substitute-path @var{from} @var{to}
6895 @kindex set substitute-path
6896 Define a source path substitution rule, and add it at the end of the
6897 current list of existing substitution rules. If a rule with the same
6898 @var{from} was already defined, then the old rule is also deleted.
6900 For example, if the file @file{/foo/bar/baz.c} was moved to
6901 @file{/mnt/cross/baz.c}, then the command
6904 (@value{GDBP}) set substitute-path /usr/src /mnt/cross
6908 will tell @value{GDBN} to replace @samp{/usr/src} with
6909 @samp{/mnt/cross}, which will allow @value{GDBN} to find the file
6910 @file{baz.c} even though it was moved.
6912 In the case when more than one substitution rule have been defined,
6913 the rules are evaluated one by one in the order where they have been
6914 defined. The first one matching, if any, is selected to perform
6917 For instance, if we had entered the following commands:
6920 (@value{GDBP}) set substitute-path /usr/src/include /mnt/include
6921 (@value{GDBP}) set substitute-path /usr/src /mnt/src
6925 @value{GDBN} would then rewrite @file{/usr/src/include/defs.h} into
6926 @file{/mnt/include/defs.h} by using the first rule. However, it would
6927 use the second rule to rewrite @file{/usr/src/lib/foo.c} into
6928 @file{/mnt/src/lib/foo.c}.
6931 @item unset substitute-path [path]
6932 @kindex unset substitute-path
6933 If a path is specified, search the current list of substitution rules
6934 for a rule that would rewrite that path. Delete that rule if found.
6935 A warning is emitted by the debugger if no rule could be found.
6937 If no path is specified, then all substitution rules are deleted.
6939 @item show substitute-path [path]
6940 @kindex show substitute-path
6941 If a path is specified, then print the source path substitution rule
6942 which would rewrite that path, if any.
6944 If no path is specified, then print all existing source path substitution
6949 If your source path is cluttered with directories that are no longer of
6950 interest, @value{GDBN} may sometimes cause confusion by finding the wrong
6951 versions of source. You can correct the situation as follows:
6955 Use @code{directory} with no argument to reset the source path to its default value.
6958 Use @code{directory} with suitable arguments to reinstall the
6959 directories you want in the source path. You can add all the
6960 directories in one command.
6964 @section Source and Machine Code
6965 @cindex source line and its code address
6967 You can use the command @code{info line} to map source lines to program
6968 addresses (and vice versa), and the command @code{disassemble} to display
6969 a range of addresses as machine instructions. You can use the command
6970 @code{set disassemble-next-line} to set whether to disassemble next
6971 source line when execution stops. When run under @sc{gnu} Emacs
6972 mode, the @code{info line} command causes the arrow to point to the
6973 line specified. Also, @code{info line} prints addresses in symbolic form as
6978 @item info line @var{linespec}
6979 Print the starting and ending addresses of the compiled code for
6980 source line @var{linespec}. You can specify source lines in any of
6981 the ways documented in @ref{Specify Location}.
6984 For example, we can use @code{info line} to discover the location of
6985 the object code for the first line of function
6986 @code{m4_changequote}:
6988 @c FIXME: I think this example should also show the addresses in
6989 @c symbolic form, as they usually would be displayed.
6991 (@value{GDBP}) info line m4_changequote
6992 Line 895 of "builtin.c" starts at pc 0x634c and ends at 0x6350.
6996 @cindex code address and its source line
6997 We can also inquire (using @code{*@var{addr}} as the form for
6998 @var{linespec}) what source line covers a particular address:
7000 (@value{GDBP}) info line *0x63ff
7001 Line 926 of "builtin.c" starts at pc 0x63e4 and ends at 0x6404.
7004 @cindex @code{$_} and @code{info line}
7005 @cindex @code{x} command, default address
7006 @kindex x@r{(examine), and} info line
7007 After @code{info line}, the default address for the @code{x} command
7008 is changed to the starting address of the line, so that @samp{x/i} is
7009 sufficient to begin examining the machine code (@pxref{Memory,
7010 ,Examining Memory}). Also, this address is saved as the value of the
7011 convenience variable @code{$_} (@pxref{Convenience Vars, ,Convenience
7016 @cindex assembly instructions
7017 @cindex instructions, assembly
7018 @cindex machine instructions
7019 @cindex listing machine instructions
7021 @itemx disassemble /m
7022 @itemx disassemble /r
7023 This specialized command dumps a range of memory as machine
7024 instructions. It can also print mixed source+disassembly by specifying
7025 the @code{/m} modifier and print the raw instructions in hex as well as
7026 in symbolic form by specifying the @code{/r}.
7027 The default memory range is the function surrounding the
7028 program counter of the selected frame. A single argument to this
7029 command is a program counter value; @value{GDBN} dumps the function
7030 surrounding this value. When two arguments are given, they should
7031 be separated by a comma, possibly surrounded by whitespace. The
7032 arguments specify a range of addresses to dump, in one of two forms:
7035 @item @var{start},@var{end}
7036 the addresses from @var{start} (inclusive) to @var{end} (exclusive)
7037 @item @var{start},+@var{length}
7038 the addresses from @var{start} (inclusive) to
7039 @code{@var{start}+@var{length}} (exclusive).
7043 When 2 arguments are specified, the name of the function is also
7044 printed (since there could be several functions in the given range).
7046 The argument(s) can be any expression yielding a numeric value, such as
7047 @samp{0x32c4}, @samp{&main+10} or @samp{$pc - 8}.
7049 If the range of memory being disassembled contains current program counter,
7050 the instruction at that location is shown with a @code{=>} marker.
7053 The following example shows the disassembly of a range of addresses of
7054 HP PA-RISC 2.0 code:
7057 (@value{GDBP}) disas 0x32c4, 0x32e4
7058 Dump of assembler code from 0x32c4 to 0x32e4:
7059 0x32c4 <main+204>: addil 0,dp
7060 0x32c8 <main+208>: ldw 0x22c(sr0,r1),r26
7061 0x32cc <main+212>: ldil 0x3000,r31
7062 0x32d0 <main+216>: ble 0x3f8(sr4,r31)
7063 0x32d4 <main+220>: ldo 0(r31),rp
7064 0x32d8 <main+224>: addil -0x800,dp
7065 0x32dc <main+228>: ldo 0x588(r1),r26
7066 0x32e0 <main+232>: ldil 0x3000,r31
7067 End of assembler dump.
7070 Here is an example showing mixed source+assembly for Intel x86, when the
7071 program is stopped just after function prologue:
7074 (@value{GDBP}) disas /m main
7075 Dump of assembler code for function main:
7077 0x08048330 <+0>: push %ebp
7078 0x08048331 <+1>: mov %esp,%ebp
7079 0x08048333 <+3>: sub $0x8,%esp
7080 0x08048336 <+6>: and $0xfffffff0,%esp
7081 0x08048339 <+9>: sub $0x10,%esp
7083 6 printf ("Hello.\n");
7084 => 0x0804833c <+12>: movl $0x8048440,(%esp)
7085 0x08048343 <+19>: call 0x8048284 <puts@@plt>
7089 0x08048348 <+24>: mov $0x0,%eax
7090 0x0804834d <+29>: leave
7091 0x0804834e <+30>: ret
7093 End of assembler dump.
7096 Here is another example showing raw instructions in hex for AMD x86-64,
7099 (gdb) disas /r 0x400281,+10
7100 Dump of assembler code from 0x400281 to 0x40028b:
7101 0x0000000000400281: 38 36 cmp %dh,(%rsi)
7102 0x0000000000400283: 2d 36 34 2e 73 sub $0x732e3436,%eax
7103 0x0000000000400288: 6f outsl %ds:(%rsi),(%dx)
7104 0x0000000000400289: 2e 32 00 xor %cs:(%rax),%al
7105 End of assembler dump.
7108 Some architectures have more than one commonly-used set of instruction
7109 mnemonics or other syntax.
7111 For programs that were dynamically linked and use shared libraries,
7112 instructions that call functions or branch to locations in the shared
7113 libraries might show a seemingly bogus location---it's actually a
7114 location of the relocation table. On some architectures, @value{GDBN}
7115 might be able to resolve these to actual function names.
7118 @kindex set disassembly-flavor
7119 @cindex Intel disassembly flavor
7120 @cindex AT&T disassembly flavor
7121 @item set disassembly-flavor @var{instruction-set}
7122 Select the instruction set to use when disassembling the
7123 program via the @code{disassemble} or @code{x/i} commands.
7125 Currently this command is only defined for the Intel x86 family. You
7126 can set @var{instruction-set} to either @code{intel} or @code{att}.
7127 The default is @code{att}, the AT&T flavor used by default by Unix
7128 assemblers for x86-based targets.
7130 @kindex show disassembly-flavor
7131 @item show disassembly-flavor
7132 Show the current setting of the disassembly flavor.
7136 @kindex set disassemble-next-line
7137 @kindex show disassemble-next-line
7138 @item set disassemble-next-line
7139 @itemx show disassemble-next-line
7140 Control whether or not @value{GDBN} will disassemble the next source
7141 line or instruction when execution stops. If ON, @value{GDBN} will
7142 display disassembly of the next source line when execution of the
7143 program being debugged stops. This is @emph{in addition} to
7144 displaying the source line itself, which @value{GDBN} always does if
7145 possible. If the next source line cannot be displayed for some reason
7146 (e.g., if @value{GDBN} cannot find the source file, or there's no line
7147 info in the debug info), @value{GDBN} will display disassembly of the
7148 next @emph{instruction} instead of showing the next source line. If
7149 AUTO, @value{GDBN} will display disassembly of next instruction only
7150 if the source line cannot be displayed. This setting causes
7151 @value{GDBN} to display some feedback when you step through a function
7152 with no line info or whose source file is unavailable. The default is
7153 OFF, which means never display the disassembly of the next line or
7159 @chapter Examining Data
7161 @cindex printing data
7162 @cindex examining data
7165 @c "inspect" is not quite a synonym if you are using Epoch, which we do not
7166 @c document because it is nonstandard... Under Epoch it displays in a
7167 @c different window or something like that.
7168 The usual way to examine data in your program is with the @code{print}
7169 command (abbreviated @code{p}), or its synonym @code{inspect}. It
7170 evaluates and prints the value of an expression of the language your
7171 program is written in (@pxref{Languages, ,Using @value{GDBN} with
7172 Different Languages}). It may also print the expression using a
7173 Python-based pretty-printer (@pxref{Pretty Printing}).
7176 @item print @var{expr}
7177 @itemx print /@var{f} @var{expr}
7178 @var{expr} is an expression (in the source language). By default the
7179 value of @var{expr} is printed in a format appropriate to its data type;
7180 you can choose a different format by specifying @samp{/@var{f}}, where
7181 @var{f} is a letter specifying the format; see @ref{Output Formats,,Output
7185 @itemx print /@var{f}
7186 @cindex reprint the last value
7187 If you omit @var{expr}, @value{GDBN} displays the last value again (from the
7188 @dfn{value history}; @pxref{Value History, ,Value History}). This allows you to
7189 conveniently inspect the same value in an alternative format.
7192 A more low-level way of examining data is with the @code{x} command.
7193 It examines data in memory at a specified address and prints it in a
7194 specified format. @xref{Memory, ,Examining Memory}.
7196 If you are interested in information about types, or about how the
7197 fields of a struct or a class are declared, use the @code{ptype @var{exp}}
7198 command rather than @code{print}. @xref{Symbols, ,Examining the Symbol
7201 @cindex exploring hierarchical data structures
7203 Another way of examining values of expressions and type information is
7204 through the Python extension command @code{explore} (available only if
7205 the @value{GDBN} build is configured with @code{--with-python}). It
7206 offers an interactive way to start at the highest level (or, the most
7207 abstract level) of the data type of an expression (or, the data type
7208 itself) and explore all the way down to leaf scalar values/fields
7209 embedded in the higher level data types.
7212 @item explore @var{arg}
7213 @var{arg} is either an expression (in the source language), or a type
7214 visible in the current context of the program being debugged.
7217 The working of the @code{explore} command can be illustrated with an
7218 example. If a data type @code{struct ComplexStruct} is defined in your
7228 struct ComplexStruct
7230 struct SimpleStruct *ss_p;
7236 followed by variable declarations as
7239 struct SimpleStruct ss = @{ 10, 1.11 @};
7240 struct ComplexStruct cs = @{ &ss, @{ 0, 1, 2, 3, 4, 5, 6, 7, 8, 9 @} @};
7244 then, the value of the variable @code{cs} can be explored using the
7245 @code{explore} command as follows.
7249 The value of `cs' is a struct/class of type `struct ComplexStruct' with
7250 the following fields:
7252 ss_p = <Enter 0 to explore this field of type `struct SimpleStruct *'>
7253 arr = <Enter 1 to explore this field of type `int [10]'>
7255 Enter the field number of choice:
7259 Since the fields of @code{cs} are not scalar values, you are being
7260 prompted to chose the field you want to explore. Let's say you choose
7261 the field @code{ss_p} by entering @code{0}. Then, since this field is a
7262 pointer, you will be asked if it is pointing to a single value. From
7263 the declaration of @code{cs} above, it is indeed pointing to a single
7264 value, hence you enter @code{y}. If you enter @code{n}, then you will
7265 be asked if it were pointing to an array of values, in which case this
7266 field will be explored as if it were an array.
7269 `cs.ss_p' is a pointer to a value of type `struct SimpleStruct'
7270 Continue exploring it as a pointer to a single value [y/n]: y
7271 The value of `*(cs.ss_p)' is a struct/class of type `struct
7272 SimpleStruct' with the following fields:
7274 i = 10 .. (Value of type `int')
7275 d = 1.1100000000000001 .. (Value of type `double')
7277 Press enter to return to parent value:
7281 If the field @code{arr} of @code{cs} was chosen for exploration by
7282 entering @code{1} earlier, then since it is as array, you will be
7283 prompted to enter the index of the element in the array that you want
7287 `cs.arr' is an array of `int'.
7288 Enter the index of the element you want to explore in `cs.arr': 5
7290 `(cs.arr)[5]' is a scalar value of type `int'.
7294 Press enter to return to parent value:
7297 In general, at any stage of exploration, you can go deeper towards the
7298 leaf values by responding to the prompts appropriately, or hit the
7299 return key to return to the enclosing data structure (the @i{higher}
7300 level data structure).
7302 Similar to exploring values, you can use the @code{explore} command to
7303 explore types. Instead of specifying a value (which is typically a
7304 variable name or an expression valid in the current context of the
7305 program being debugged), you specify a type name. If you consider the
7306 same example as above, your can explore the type
7307 @code{struct ComplexStruct} by passing the argument
7308 @code{struct ComplexStruct} to the @code{explore} command.
7311 (gdb) explore struct ComplexStruct
7315 By responding to the prompts appropriately in the subsequent interactive
7316 session, you can explore the type @code{struct ComplexStruct} in a
7317 manner similar to how the value @code{cs} was explored in the above
7320 The @code{explore} command also has two sub-commands,
7321 @code{explore value} and @code{explore type}. The former sub-command is
7322 a way to explicitly specify that value exploration of the argument is
7323 being invoked, while the latter is a way to explicitly specify that type
7324 exploration of the argument is being invoked.
7327 @item explore value @var{expr}
7328 @cindex explore value
7329 This sub-command of @code{explore} explores the value of the
7330 expression @var{expr} (if @var{expr} is an expression valid in the
7331 current context of the program being debugged). The behavior of this
7332 command is identical to that of the behavior of the @code{explore}
7333 command being passed the argument @var{expr}.
7335 @item explore type @var{arg}
7336 @cindex explore type
7337 This sub-command of @code{explore} explores the type of @var{arg} (if
7338 @var{arg} is a type visible in the current context of program being
7339 debugged), or the type of the value/expression @var{arg} (if @var{arg}
7340 is an expression valid in the current context of the program being
7341 debugged). If @var{arg} is a type, then the behavior of this command is
7342 identical to that of the @code{explore} command being passed the
7343 argument @var{arg}. If @var{arg} is an expression, then the behavior of
7344 this command will be identical to that of the @code{explore} command
7345 being passed the type of @var{arg} as the argument.
7349 * Expressions:: Expressions
7350 * Ambiguous Expressions:: Ambiguous Expressions
7351 * Variables:: Program variables
7352 * Arrays:: Artificial arrays
7353 * Output Formats:: Output formats
7354 * Memory:: Examining memory
7355 * Auto Display:: Automatic display
7356 * Print Settings:: Print settings
7357 * Pretty Printing:: Python pretty printing
7358 * Value History:: Value history
7359 * Convenience Vars:: Convenience variables
7360 * Registers:: Registers
7361 * Floating Point Hardware:: Floating point hardware
7362 * Vector Unit:: Vector Unit
7363 * OS Information:: Auxiliary data provided by operating system
7364 * Memory Region Attributes:: Memory region attributes
7365 * Dump/Restore Files:: Copy between memory and a file
7366 * Core File Generation:: Cause a program dump its core
7367 * Character Sets:: Debugging programs that use a different
7368 character set than GDB does
7369 * Caching Remote Data:: Data caching for remote targets
7370 * Searching Memory:: Searching memory for a sequence of bytes
7374 @section Expressions
7377 @code{print} and many other @value{GDBN} commands accept an expression and
7378 compute its value. Any kind of constant, variable or operator defined
7379 by the programming language you are using is valid in an expression in
7380 @value{GDBN}. This includes conditional expressions, function calls,
7381 casts, and string constants. It also includes preprocessor macros, if
7382 you compiled your program to include this information; see
7385 @cindex arrays in expressions
7386 @value{GDBN} supports array constants in expressions input by
7387 the user. The syntax is @{@var{element}, @var{element}@dots{}@}. For example,
7388 you can use the command @code{print @{1, 2, 3@}} to create an array
7389 of three integers. If you pass an array to a function or assign it
7390 to a program variable, @value{GDBN} copies the array to memory that
7391 is @code{malloc}ed in the target program.
7393 Because C is so widespread, most of the expressions shown in examples in
7394 this manual are in C. @xref{Languages, , Using @value{GDBN} with Different
7395 Languages}, for information on how to use expressions in other
7398 In this section, we discuss operators that you can use in @value{GDBN}
7399 expressions regardless of your programming language.
7401 @cindex casts, in expressions
7402 Casts are supported in all languages, not just in C, because it is so
7403 useful to cast a number into a pointer in order to examine a structure
7404 at that address in memory.
7405 @c FIXME: casts supported---Mod2 true?
7407 @value{GDBN} supports these operators, in addition to those common
7408 to programming languages:
7412 @samp{@@} is a binary operator for treating parts of memory as arrays.
7413 @xref{Arrays, ,Artificial Arrays}, for more information.
7416 @samp{::} allows you to specify a variable in terms of the file or
7417 function where it is defined. @xref{Variables, ,Program Variables}.
7419 @cindex @{@var{type}@}
7420 @cindex type casting memory
7421 @cindex memory, viewing as typed object
7422 @cindex casts, to view memory
7423 @item @{@var{type}@} @var{addr}
7424 Refers to an object of type @var{type} stored at address @var{addr} in
7425 memory. @var{addr} may be any expression whose value is an integer or
7426 pointer (but parentheses are required around binary operators, just as in
7427 a cast). This construct is allowed regardless of what kind of data is
7428 normally supposed to reside at @var{addr}.
7431 @node Ambiguous Expressions
7432 @section Ambiguous Expressions
7433 @cindex ambiguous expressions
7435 Expressions can sometimes contain some ambiguous elements. For instance,
7436 some programming languages (notably Ada, C@t{++} and Objective-C) permit
7437 a single function name to be defined several times, for application in
7438 different contexts. This is called @dfn{overloading}. Another example
7439 involving Ada is generics. A @dfn{generic package} is similar to C@t{++}
7440 templates and is typically instantiated several times, resulting in
7441 the same function name being defined in different contexts.
7443 In some cases and depending on the language, it is possible to adjust
7444 the expression to remove the ambiguity. For instance in C@t{++}, you
7445 can specify the signature of the function you want to break on, as in
7446 @kbd{break @var{function}(@var{types})}. In Ada, using the fully
7447 qualified name of your function often makes the expression unambiguous
7450 When an ambiguity that needs to be resolved is detected, the debugger
7451 has the capability to display a menu of numbered choices for each
7452 possibility, and then waits for the selection with the prompt @samp{>}.
7453 The first option is always @samp{[0] cancel}, and typing @kbd{0 @key{RET}}
7454 aborts the current command. If the command in which the expression was
7455 used allows more than one choice to be selected, the next option in the
7456 menu is @samp{[1] all}, and typing @kbd{1 @key{RET}} selects all possible
7459 For example, the following session excerpt shows an attempt to set a
7460 breakpoint at the overloaded symbol @code{String::after}.
7461 We choose three particular definitions of that function name:
7463 @c FIXME! This is likely to change to show arg type lists, at least
7466 (@value{GDBP}) b String::after
7469 [2] file:String.cc; line number:867
7470 [3] file:String.cc; line number:860
7471 [4] file:String.cc; line number:875
7472 [5] file:String.cc; line number:853
7473 [6] file:String.cc; line number:846
7474 [7] file:String.cc; line number:735
7476 Breakpoint 1 at 0xb26c: file String.cc, line 867.
7477 Breakpoint 2 at 0xb344: file String.cc, line 875.
7478 Breakpoint 3 at 0xafcc: file String.cc, line 846.
7479 Multiple breakpoints were set.
7480 Use the "delete" command to delete unwanted
7487 @kindex set multiple-symbols
7488 @item set multiple-symbols @var{mode}
7489 @cindex multiple-symbols menu
7491 This option allows you to adjust the debugger behavior when an expression
7494 By default, @var{mode} is set to @code{all}. If the command with which
7495 the expression is used allows more than one choice, then @value{GDBN}
7496 automatically selects all possible choices. For instance, inserting
7497 a breakpoint on a function using an ambiguous name results in a breakpoint
7498 inserted on each possible match. However, if a unique choice must be made,
7499 then @value{GDBN} uses the menu to help you disambiguate the expression.
7500 For instance, printing the address of an overloaded function will result
7501 in the use of the menu.
7503 When @var{mode} is set to @code{ask}, the debugger always uses the menu
7504 when an ambiguity is detected.
7506 Finally, when @var{mode} is set to @code{cancel}, the debugger reports
7507 an error due to the ambiguity and the command is aborted.
7509 @kindex show multiple-symbols
7510 @item show multiple-symbols
7511 Show the current value of the @code{multiple-symbols} setting.
7515 @section Program Variables
7517 The most common kind of expression to use is the name of a variable
7520 Variables in expressions are understood in the selected stack frame
7521 (@pxref{Selection, ,Selecting a Frame}); they must be either:
7525 global (or file-static)
7532 visible according to the scope rules of the
7533 programming language from the point of execution in that frame
7536 @noindent This means that in the function
7551 you can examine and use the variable @code{a} whenever your program is
7552 executing within the function @code{foo}, but you can only use or
7553 examine the variable @code{b} while your program is executing inside
7554 the block where @code{b} is declared.
7556 @cindex variable name conflict
7557 There is an exception: you can refer to a variable or function whose
7558 scope is a single source file even if the current execution point is not
7559 in this file. But it is possible to have more than one such variable or
7560 function with the same name (in different source files). If that
7561 happens, referring to that name has unpredictable effects. If you wish,
7562 you can specify a static variable in a particular function or file by
7563 using the colon-colon (@code{::}) notation:
7565 @cindex colon-colon, context for variables/functions
7567 @c info cannot cope with a :: index entry, but why deprive hard copy readers?
7568 @cindex @code{::}, context for variables/functions
7571 @var{file}::@var{variable}
7572 @var{function}::@var{variable}
7576 Here @var{file} or @var{function} is the name of the context for the
7577 static @var{variable}. In the case of file names, you can use quotes to
7578 make sure @value{GDBN} parses the file name as a single word---for example,
7579 to print a global value of @code{x} defined in @file{f2.c}:
7582 (@value{GDBP}) p 'f2.c'::x
7585 The @code{::} notation is normally used for referring to
7586 static variables, since you typically disambiguate uses of local variables
7587 in functions by selecting the appropriate frame and using the
7588 simple name of the variable. However, you may also use this notation
7589 to refer to local variables in frames enclosing the selected frame:
7598 process (a); /* Stop here */
7609 For example, if there is a breakpoint at the commented line,
7610 here is what you might see
7611 when the program stops after executing the call @code{bar(0)}:
7616 (@value{GDBP}) p bar::a
7619 #2 0x080483d0 in foo (a=5) at foobar.c:12
7622 (@value{GDBP}) p bar::a
7626 @cindex C@t{++} scope resolution
7627 These uses of @samp{::} are very rarely in conflict with the very similar
7628 use of the same notation in C@t{++}. @value{GDBN} also supports use of the C@t{++}
7629 scope resolution operator in @value{GDBN} expressions.
7630 @c FIXME: Um, so what happens in one of those rare cases where it's in
7633 @cindex wrong values
7634 @cindex variable values, wrong
7635 @cindex function entry/exit, wrong values of variables
7636 @cindex optimized code, wrong values of variables
7638 @emph{Warning:} Occasionally, a local variable may appear to have the
7639 wrong value at certain points in a function---just after entry to a new
7640 scope, and just before exit.
7642 You may see this problem when you are stepping by machine instructions.
7643 This is because, on most machines, it takes more than one instruction to
7644 set up a stack frame (including local variable definitions); if you are
7645 stepping by machine instructions, variables may appear to have the wrong
7646 values until the stack frame is completely built. On exit, it usually
7647 also takes more than one machine instruction to destroy a stack frame;
7648 after you begin stepping through that group of instructions, local
7649 variable definitions may be gone.
7651 This may also happen when the compiler does significant optimizations.
7652 To be sure of always seeing accurate values, turn off all optimization
7655 @cindex ``No symbol "foo" in current context''
7656 Another possible effect of compiler optimizations is to optimize
7657 unused variables out of existence, or assign variables to registers (as
7658 opposed to memory addresses). Depending on the support for such cases
7659 offered by the debug info format used by the compiler, @value{GDBN}
7660 might not be able to display values for such local variables. If that
7661 happens, @value{GDBN} will print a message like this:
7664 No symbol "foo" in current context.
7667 To solve such problems, either recompile without optimizations, or use a
7668 different debug info format, if the compiler supports several such
7669 formats. @xref{Compilation}, for more information on choosing compiler
7670 options. @xref{C, ,C and C@t{++}}, for more information about debug
7671 info formats that are best suited to C@t{++} programs.
7673 If you ask to print an object whose contents are unknown to
7674 @value{GDBN}, e.g., because its data type is not completely specified
7675 by the debug information, @value{GDBN} will say @samp{<incomplete
7676 type>}. @xref{Symbols, incomplete type}, for more about this.
7678 If you append @kbd{@@entry} string to a function parameter name you get its
7679 value at the time the function got called. If the value is not available an
7680 error message is printed. Entry values are available only with some compilers.
7681 Entry values are normally also printed at the function parameter list according
7682 to @ref{set print entry-values}.
7685 Breakpoint 1, d (i=30) at gdb.base/entry-value.c:29
7691 (gdb) print i@@entry
7695 Strings are identified as arrays of @code{char} values without specified
7696 signedness. Arrays of either @code{signed char} or @code{unsigned char} get
7697 printed as arrays of 1 byte sized integers. @code{-fsigned-char} or
7698 @code{-funsigned-char} @value{NGCC} options have no effect as @value{GDBN}
7699 defines literal string type @code{"char"} as @code{char} without a sign.
7704 signed char var1[] = "A";
7707 You get during debugging
7712 $2 = @{65 'A', 0 '\0'@}
7716 @section Artificial Arrays
7718 @cindex artificial array
7720 @kindex @@@r{, referencing memory as an array}
7721 It is often useful to print out several successive objects of the
7722 same type in memory; a section of an array, or an array of
7723 dynamically determined size for which only a pointer exists in the
7726 You can do this by referring to a contiguous span of memory as an
7727 @dfn{artificial array}, using the binary operator @samp{@@}. The left
7728 operand of @samp{@@} should be the first element of the desired array
7729 and be an individual object. The right operand should be the desired length
7730 of the array. The result is an array value whose elements are all of
7731 the type of the left argument. The first element is actually the left
7732 argument; the second element comes from bytes of memory immediately
7733 following those that hold the first element, and so on. Here is an
7734 example. If a program says
7737 int *array = (int *) malloc (len * sizeof (int));
7741 you can print the contents of @code{array} with
7747 The left operand of @samp{@@} must reside in memory. Array values made
7748 with @samp{@@} in this way behave just like other arrays in terms of
7749 subscripting, and are coerced to pointers when used in expressions.
7750 Artificial arrays most often appear in expressions via the value history
7751 (@pxref{Value History, ,Value History}), after printing one out.
7753 Another way to create an artificial array is to use a cast.
7754 This re-interprets a value as if it were an array.
7755 The value need not be in memory:
7757 (@value{GDBP}) p/x (short[2])0x12345678
7758 $1 = @{0x1234, 0x5678@}
7761 As a convenience, if you leave the array length out (as in
7762 @samp{(@var{type}[])@var{value}}) @value{GDBN} calculates the size to fill
7763 the value (as @samp{sizeof(@var{value})/sizeof(@var{type})}:
7765 (@value{GDBP}) p/x (short[])0x12345678
7766 $2 = @{0x1234, 0x5678@}
7769 Sometimes the artificial array mechanism is not quite enough; in
7770 moderately complex data structures, the elements of interest may not
7771 actually be adjacent---for example, if you are interested in the values
7772 of pointers in an array. One useful work-around in this situation is
7773 to use a convenience variable (@pxref{Convenience Vars, ,Convenience
7774 Variables}) as a counter in an expression that prints the first
7775 interesting value, and then repeat that expression via @key{RET}. For
7776 instance, suppose you have an array @code{dtab} of pointers to
7777 structures, and you are interested in the values of a field @code{fv}
7778 in each structure. Here is an example of what you might type:
7788 @node Output Formats
7789 @section Output Formats
7791 @cindex formatted output
7792 @cindex output formats
7793 By default, @value{GDBN} prints a value according to its data type. Sometimes
7794 this is not what you want. For example, you might want to print a number
7795 in hex, or a pointer in decimal. Or you might want to view data in memory
7796 at a certain address as a character string or as an instruction. To do
7797 these things, specify an @dfn{output format} when you print a value.
7799 The simplest use of output formats is to say how to print a value
7800 already computed. This is done by starting the arguments of the
7801 @code{print} command with a slash and a format letter. The format
7802 letters supported are:
7806 Regard the bits of the value as an integer, and print the integer in
7810 Print as integer in signed decimal.
7813 Print as integer in unsigned decimal.
7816 Print as integer in octal.
7819 Print as integer in binary. The letter @samp{t} stands for ``two''.
7820 @footnote{@samp{b} cannot be used because these format letters are also
7821 used with the @code{x} command, where @samp{b} stands for ``byte'';
7822 see @ref{Memory,,Examining Memory}.}
7825 @cindex unknown address, locating
7826 @cindex locate address
7827 Print as an address, both absolute in hexadecimal and as an offset from
7828 the nearest preceding symbol. You can use this format used to discover
7829 where (in what function) an unknown address is located:
7832 (@value{GDBP}) p/a 0x54320
7833 $3 = 0x54320 <_initialize_vx+396>
7837 The command @code{info symbol 0x54320} yields similar results.
7838 @xref{Symbols, info symbol}.
7841 Regard as an integer and print it as a character constant. This
7842 prints both the numerical value and its character representation. The
7843 character representation is replaced with the octal escape @samp{\nnn}
7844 for characters outside the 7-bit @sc{ascii} range.
7846 Without this format, @value{GDBN} displays @code{char},
7847 @w{@code{unsigned char}}, and @w{@code{signed char}} data as character
7848 constants. Single-byte members of vectors are displayed as integer
7852 Regard the bits of the value as a floating point number and print
7853 using typical floating point syntax.
7856 @cindex printing strings
7857 @cindex printing byte arrays
7858 Regard as a string, if possible. With this format, pointers to single-byte
7859 data are displayed as null-terminated strings and arrays of single-byte data
7860 are displayed as fixed-length strings. Other values are displayed in their
7863 Without this format, @value{GDBN} displays pointers to and arrays of
7864 @code{char}, @w{@code{unsigned char}}, and @w{@code{signed char}} as
7865 strings. Single-byte members of a vector are displayed as an integer
7869 @cindex raw printing
7870 Print using the @samp{raw} formatting. By default, @value{GDBN} will
7871 use a Python-based pretty-printer, if one is available (@pxref{Pretty
7872 Printing}). This typically results in a higher-level display of the
7873 value's contents. The @samp{r} format bypasses any Python
7874 pretty-printer which might exist.
7877 For example, to print the program counter in hex (@pxref{Registers}), type
7884 Note that no space is required before the slash; this is because command
7885 names in @value{GDBN} cannot contain a slash.
7887 To reprint the last value in the value history with a different format,
7888 you can use the @code{print} command with just a format and no
7889 expression. For example, @samp{p/x} reprints the last value in hex.
7892 @section Examining Memory
7894 You can use the command @code{x} (for ``examine'') to examine memory in
7895 any of several formats, independently of your program's data types.
7897 @cindex examining memory
7899 @kindex x @r{(examine memory)}
7900 @item x/@var{nfu} @var{addr}
7903 Use the @code{x} command to examine memory.
7906 @var{n}, @var{f}, and @var{u} are all optional parameters that specify how
7907 much memory to display and how to format it; @var{addr} is an
7908 expression giving the address where you want to start displaying memory.
7909 If you use defaults for @var{nfu}, you need not type the slash @samp{/}.
7910 Several commands set convenient defaults for @var{addr}.
7913 @item @var{n}, the repeat count
7914 The repeat count is a decimal integer; the default is 1. It specifies
7915 how much memory (counting by units @var{u}) to display.
7916 @c This really is **decimal**; unaffected by 'set radix' as of GDB
7919 @item @var{f}, the display format
7920 The display format is one of the formats used by @code{print}
7921 (@samp{x}, @samp{d}, @samp{u}, @samp{o}, @samp{t}, @samp{a}, @samp{c},
7922 @samp{f}, @samp{s}), and in addition @samp{i} (for machine instructions).
7923 The default is @samp{x} (hexadecimal) initially. The default changes
7924 each time you use either @code{x} or @code{print}.
7926 @item @var{u}, the unit size
7927 The unit size is any of
7933 Halfwords (two bytes).
7935 Words (four bytes). This is the initial default.
7937 Giant words (eight bytes).
7940 Each time you specify a unit size with @code{x}, that size becomes the
7941 default unit the next time you use @code{x}. For the @samp{i} format,
7942 the unit size is ignored and is normally not written. For the @samp{s} format,
7943 the unit size defaults to @samp{b}, unless it is explicitly given.
7944 Use @kbd{x /hs} to display 16-bit char strings and @kbd{x /ws} to display
7945 32-bit strings. The next use of @kbd{x /s} will again display 8-bit strings.
7946 Note that the results depend on the programming language of the
7947 current compilation unit. If the language is C, the @samp{s}
7948 modifier will use the UTF-16 encoding while @samp{w} will use
7949 UTF-32. The encoding is set by the programming language and cannot
7952 @item @var{addr}, starting display address
7953 @var{addr} is the address where you want @value{GDBN} to begin displaying
7954 memory. The expression need not have a pointer value (though it may);
7955 it is always interpreted as an integer address of a byte of memory.
7956 @xref{Expressions, ,Expressions}, for more information on expressions. The default for
7957 @var{addr} is usually just after the last address examined---but several
7958 other commands also set the default address: @code{info breakpoints} (to
7959 the address of the last breakpoint listed), @code{info line} (to the
7960 starting address of a line), and @code{print} (if you use it to display
7961 a value from memory).
7964 For example, @samp{x/3uh 0x54320} is a request to display three halfwords
7965 (@code{h}) of memory, formatted as unsigned decimal integers (@samp{u}),
7966 starting at address @code{0x54320}. @samp{x/4xw $sp} prints the four
7967 words (@samp{w}) of memory above the stack pointer (here, @samp{$sp};
7968 @pxref{Registers, ,Registers}) in hexadecimal (@samp{x}).
7970 Since the letters indicating unit sizes are all distinct from the
7971 letters specifying output formats, you do not have to remember whether
7972 unit size or format comes first; either order works. The output
7973 specifications @samp{4xw} and @samp{4wx} mean exactly the same thing.
7974 (However, the count @var{n} must come first; @samp{wx4} does not work.)
7976 Even though the unit size @var{u} is ignored for the formats @samp{s}
7977 and @samp{i}, you might still want to use a count @var{n}; for example,
7978 @samp{3i} specifies that you want to see three machine instructions,
7979 including any operands. For convenience, especially when used with
7980 the @code{display} command, the @samp{i} format also prints branch delay
7981 slot instructions, if any, beyond the count specified, which immediately
7982 follow the last instruction that is within the count. The command
7983 @code{disassemble} gives an alternative way of inspecting machine
7984 instructions; see @ref{Machine Code,,Source and Machine Code}.
7986 All the defaults for the arguments to @code{x} are designed to make it
7987 easy to continue scanning memory with minimal specifications each time
7988 you use @code{x}. For example, after you have inspected three machine
7989 instructions with @samp{x/3i @var{addr}}, you can inspect the next seven
7990 with just @samp{x/7}. If you use @key{RET} to repeat the @code{x} command,
7991 the repeat count @var{n} is used again; the other arguments default as
7992 for successive uses of @code{x}.
7994 When examining machine instructions, the instruction at current program
7995 counter is shown with a @code{=>} marker. For example:
7998 (@value{GDBP}) x/5i $pc-6
7999 0x804837f <main+11>: mov %esp,%ebp
8000 0x8048381 <main+13>: push %ecx
8001 0x8048382 <main+14>: sub $0x4,%esp
8002 => 0x8048385 <main+17>: movl $0x8048460,(%esp)
8003 0x804838c <main+24>: call 0x80482d4 <puts@@plt>
8006 @cindex @code{$_}, @code{$__}, and value history
8007 The addresses and contents printed by the @code{x} command are not saved
8008 in the value history because there is often too much of them and they
8009 would get in the way. Instead, @value{GDBN} makes these values available for
8010 subsequent use in expressions as values of the convenience variables
8011 @code{$_} and @code{$__}. After an @code{x} command, the last address
8012 examined is available for use in expressions in the convenience variable
8013 @code{$_}. The contents of that address, as examined, are available in
8014 the convenience variable @code{$__}.
8016 If the @code{x} command has a repeat count, the address and contents saved
8017 are from the last memory unit printed; this is not the same as the last
8018 address printed if several units were printed on the last line of output.
8020 @cindex remote memory comparison
8021 @cindex verify remote memory image
8022 When you are debugging a program running on a remote target machine
8023 (@pxref{Remote Debugging}), you may wish to verify the program's image in the
8024 remote machine's memory against the executable file you downloaded to
8025 the target. The @code{compare-sections} command is provided for such
8029 @kindex compare-sections
8030 @item compare-sections @r{[}@var{section-name}@r{]}
8031 Compare the data of a loadable section @var{section-name} in the
8032 executable file of the program being debugged with the same section in
8033 the remote machine's memory, and report any mismatches. With no
8034 arguments, compares all loadable sections. This command's
8035 availability depends on the target's support for the @code{"qCRC"}
8040 @section Automatic Display
8041 @cindex automatic display
8042 @cindex display of expressions
8044 If you find that you want to print the value of an expression frequently
8045 (to see how it changes), you might want to add it to the @dfn{automatic
8046 display list} so that @value{GDBN} prints its value each time your program stops.
8047 Each expression added to the list is given a number to identify it;
8048 to remove an expression from the list, you specify that number.
8049 The automatic display looks like this:
8053 3: bar[5] = (struct hack *) 0x3804
8057 This display shows item numbers, expressions and their current values. As with
8058 displays you request manually using @code{x} or @code{print}, you can
8059 specify the output format you prefer; in fact, @code{display} decides
8060 whether to use @code{print} or @code{x} depending your format
8061 specification---it uses @code{x} if you specify either the @samp{i}
8062 or @samp{s} format, or a unit size; otherwise it uses @code{print}.
8066 @item display @var{expr}
8067 Add the expression @var{expr} to the list of expressions to display
8068 each time your program stops. @xref{Expressions, ,Expressions}.
8070 @code{display} does not repeat if you press @key{RET} again after using it.
8072 @item display/@var{fmt} @var{expr}
8073 For @var{fmt} specifying only a display format and not a size or
8074 count, add the expression @var{expr} to the auto-display list but
8075 arrange to display it each time in the specified format @var{fmt}.
8076 @xref{Output Formats,,Output Formats}.
8078 @item display/@var{fmt} @var{addr}
8079 For @var{fmt} @samp{i} or @samp{s}, or including a unit-size or a
8080 number of units, add the expression @var{addr} as a memory address to
8081 be examined each time your program stops. Examining means in effect
8082 doing @samp{x/@var{fmt} @var{addr}}. @xref{Memory, ,Examining Memory}.
8085 For example, @samp{display/i $pc} can be helpful, to see the machine
8086 instruction about to be executed each time execution stops (@samp{$pc}
8087 is a common name for the program counter; @pxref{Registers, ,Registers}).
8090 @kindex delete display
8092 @item undisplay @var{dnums}@dots{}
8093 @itemx delete display @var{dnums}@dots{}
8094 Remove items from the list of expressions to display. Specify the
8095 numbers of the displays that you want affected with the command
8096 argument @var{dnums}. It can be a single display number, one of the
8097 numbers shown in the first field of the @samp{info display} display;
8098 or it could be a range of display numbers, as in @code{2-4}.
8100 @code{undisplay} does not repeat if you press @key{RET} after using it.
8101 (Otherwise you would just get the error @samp{No display number @dots{}}.)
8103 @kindex disable display
8104 @item disable display @var{dnums}@dots{}
8105 Disable the display of item numbers @var{dnums}. A disabled display
8106 item is not printed automatically, but is not forgotten. It may be
8107 enabled again later. Specify the numbers of the displays that you
8108 want affected with the command argument @var{dnums}. It can be a
8109 single display number, one of the numbers shown in the first field of
8110 the @samp{info display} display; or it could be a range of display
8111 numbers, as in @code{2-4}.
8113 @kindex enable display
8114 @item enable display @var{dnums}@dots{}
8115 Enable display of item numbers @var{dnums}. It becomes effective once
8116 again in auto display of its expression, until you specify otherwise.
8117 Specify the numbers of the displays that you want affected with the
8118 command argument @var{dnums}. It can be a single display number, one
8119 of the numbers shown in the first field of the @samp{info display}
8120 display; or it could be a range of display numbers, as in @code{2-4}.
8123 Display the current values of the expressions on the list, just as is
8124 done when your program stops.
8126 @kindex info display
8128 Print the list of expressions previously set up to display
8129 automatically, each one with its item number, but without showing the
8130 values. This includes disabled expressions, which are marked as such.
8131 It also includes expressions which would not be displayed right now
8132 because they refer to automatic variables not currently available.
8135 @cindex display disabled out of scope
8136 If a display expression refers to local variables, then it does not make
8137 sense outside the lexical context for which it was set up. Such an
8138 expression is disabled when execution enters a context where one of its
8139 variables is not defined. For example, if you give the command
8140 @code{display last_char} while inside a function with an argument
8141 @code{last_char}, @value{GDBN} displays this argument while your program
8142 continues to stop inside that function. When it stops elsewhere---where
8143 there is no variable @code{last_char}---the display is disabled
8144 automatically. The next time your program stops where @code{last_char}
8145 is meaningful, you can enable the display expression once again.
8147 @node Print Settings
8148 @section Print Settings
8150 @cindex format options
8151 @cindex print settings
8152 @value{GDBN} provides the following ways to control how arrays, structures,
8153 and symbols are printed.
8156 These settings are useful for debugging programs in any language:
8160 @item set print address
8161 @itemx set print address on
8162 @cindex print/don't print memory addresses
8163 @value{GDBN} prints memory addresses showing the location of stack
8164 traces, structure values, pointer values, breakpoints, and so forth,
8165 even when it also displays the contents of those addresses. The default
8166 is @code{on}. For example, this is what a stack frame display looks like with
8167 @code{set print address on}:
8172 #0 set_quotes (lq=0x34c78 "<<", rq=0x34c88 ">>")
8174 530 if (lquote != def_lquote)
8178 @item set print address off
8179 Do not print addresses when displaying their contents. For example,
8180 this is the same stack frame displayed with @code{set print address off}:
8184 (@value{GDBP}) set print addr off
8186 #0 set_quotes (lq="<<", rq=">>") at input.c:530
8187 530 if (lquote != def_lquote)
8191 You can use @samp{set print address off} to eliminate all machine
8192 dependent displays from the @value{GDBN} interface. For example, with
8193 @code{print address off}, you should get the same text for backtraces on
8194 all machines---whether or not they involve pointer arguments.
8197 @item show print address
8198 Show whether or not addresses are to be printed.
8201 When @value{GDBN} prints a symbolic address, it normally prints the
8202 closest earlier symbol plus an offset. If that symbol does not uniquely
8203 identify the address (for example, it is a name whose scope is a single
8204 source file), you may need to clarify. One way to do this is with
8205 @code{info line}, for example @samp{info line *0x4537}. Alternately,
8206 you can set @value{GDBN} to print the source file and line number when
8207 it prints a symbolic address:
8210 @item set print symbol-filename on
8211 @cindex source file and line of a symbol
8212 @cindex symbol, source file and line
8213 Tell @value{GDBN} to print the source file name and line number of a
8214 symbol in the symbolic form of an address.
8216 @item set print symbol-filename off
8217 Do not print source file name and line number of a symbol. This is the
8220 @item show print symbol-filename
8221 Show whether or not @value{GDBN} will print the source file name and
8222 line number of a symbol in the symbolic form of an address.
8225 Another situation where it is helpful to show symbol filenames and line
8226 numbers is when disassembling code; @value{GDBN} shows you the line
8227 number and source file that corresponds to each instruction.
8229 Also, you may wish to see the symbolic form only if the address being
8230 printed is reasonably close to the closest earlier symbol:
8233 @item set print max-symbolic-offset @var{max-offset}
8234 @cindex maximum value for offset of closest symbol
8235 Tell @value{GDBN} to only display the symbolic form of an address if the
8236 offset between the closest earlier symbol and the address is less than
8237 @var{max-offset}. The default is 0, which tells @value{GDBN}
8238 to always print the symbolic form of an address if any symbol precedes it.
8240 @item show print max-symbolic-offset
8241 Ask how large the maximum offset is that @value{GDBN} prints in a
8245 @cindex wild pointer, interpreting
8246 @cindex pointer, finding referent
8247 If you have a pointer and you are not sure where it points, try
8248 @samp{set print symbol-filename on}. Then you can determine the name
8249 and source file location of the variable where it points, using
8250 @samp{p/a @var{pointer}}. This interprets the address in symbolic form.
8251 For example, here @value{GDBN} shows that a variable @code{ptt} points
8252 at another variable @code{t}, defined in @file{hi2.c}:
8255 (@value{GDBP}) set print symbol-filename on
8256 (@value{GDBP}) p/a ptt
8257 $4 = 0xe008 <t in hi2.c>
8261 @emph{Warning:} For pointers that point to a local variable, @samp{p/a}
8262 does not show the symbol name and filename of the referent, even with
8263 the appropriate @code{set print} options turned on.
8266 Other settings control how different kinds of objects are printed:
8269 @item set print array
8270 @itemx set print array on
8271 @cindex pretty print arrays
8272 Pretty print arrays. This format is more convenient to read,
8273 but uses more space. The default is off.
8275 @item set print array off
8276 Return to compressed format for arrays.
8278 @item show print array
8279 Show whether compressed or pretty format is selected for displaying
8282 @cindex print array indexes
8283 @item set print array-indexes
8284 @itemx set print array-indexes on
8285 Print the index of each element when displaying arrays. May be more
8286 convenient to locate a given element in the array or quickly find the
8287 index of a given element in that printed array. The default is off.
8289 @item set print array-indexes off
8290 Stop printing element indexes when displaying arrays.
8292 @item show print array-indexes
8293 Show whether the index of each element is printed when displaying
8296 @item set print elements @var{number-of-elements}
8297 @cindex number of array elements to print
8298 @cindex limit on number of printed array elements
8299 Set a limit on how many elements of an array @value{GDBN} will print.
8300 If @value{GDBN} is printing a large array, it stops printing after it has
8301 printed the number of elements set by the @code{set print elements} command.
8302 This limit also applies to the display of strings.
8303 When @value{GDBN} starts, this limit is set to 200.
8304 Setting @var{number-of-elements} to zero means that the printing is unlimited.
8306 @item show print elements
8307 Display the number of elements of a large array that @value{GDBN} will print.
8308 If the number is 0, then the printing is unlimited.
8310 @item set print frame-arguments @var{value}
8311 @kindex set print frame-arguments
8312 @cindex printing frame argument values
8313 @cindex print all frame argument values
8314 @cindex print frame argument values for scalars only
8315 @cindex do not print frame argument values
8316 This command allows to control how the values of arguments are printed
8317 when the debugger prints a frame (@pxref{Frames}). The possible
8322 The values of all arguments are printed.
8325 Print the value of an argument only if it is a scalar. The value of more
8326 complex arguments such as arrays, structures, unions, etc, is replaced
8327 by @code{@dots{}}. This is the default. Here is an example where
8328 only scalar arguments are shown:
8331 #1 0x08048361 in call_me (i=3, s=@dots{}, ss=0xbf8d508c, u=@dots{}, e=green)
8336 None of the argument values are printed. Instead, the value of each argument
8337 is replaced by @code{@dots{}}. In this case, the example above now becomes:
8340 #1 0x08048361 in call_me (i=@dots{}, s=@dots{}, ss=@dots{}, u=@dots{}, e=@dots{})
8345 By default, only scalar arguments are printed. This command can be used
8346 to configure the debugger to print the value of all arguments, regardless
8347 of their type. However, it is often advantageous to not print the value
8348 of more complex parameters. For instance, it reduces the amount of
8349 information printed in each frame, making the backtrace more readable.
8350 Also, it improves performance when displaying Ada frames, because
8351 the computation of large arguments can sometimes be CPU-intensive,
8352 especially in large applications. Setting @code{print frame-arguments}
8353 to @code{scalars} (the default) or @code{none} avoids this computation,
8354 thus speeding up the display of each Ada frame.
8356 @item show print frame-arguments
8357 Show how the value of arguments should be displayed when printing a frame.
8359 @anchor{set print entry-values}
8360 @item set print entry-values @var{value}
8361 @kindex set print entry-values
8362 Set printing of frame argument values at function entry. In some cases
8363 @value{GDBN} can determine the value of function argument which was passed by
8364 the function caller, even if the value was modified inside the called function
8365 and therefore is different. With optimized code, the current value could be
8366 unavailable, but the entry value may still be known.
8368 The default value is @code{default} (see below for its description). Older
8369 @value{GDBN} behaved as with the setting @code{no}. Compilers not supporting
8370 this feature will behave in the @code{default} setting the same way as with the
8373 This functionality is currently supported only by DWARF 2 debugging format and
8374 the compiler has to produce @samp{DW_TAG_GNU_call_site} tags. With
8375 @value{NGCC}, you need to specify @option{-O -g} during compilation, to get
8378 The @var{value} parameter can be one of the following:
8382 Print only actual parameter values, never print values from function entry
8386 #0 different (val=6)
8387 #0 lost (val=<optimized out>)
8389 #0 invalid (val=<optimized out>)
8393 Print only parameter values from function entry point. The actual parameter
8394 values are never printed.
8396 #0 equal (val@@entry=5)
8397 #0 different (val@@entry=5)
8398 #0 lost (val@@entry=5)
8399 #0 born (val@@entry=<optimized out>)
8400 #0 invalid (val@@entry=<optimized out>)
8404 Print only parameter values from function entry point. If value from function
8405 entry point is not known while the actual value is known, print the actual
8406 value for such parameter.
8408 #0 equal (val@@entry=5)
8409 #0 different (val@@entry=5)
8410 #0 lost (val@@entry=5)
8412 #0 invalid (val@@entry=<optimized out>)
8416 Print actual parameter values. If actual parameter value is not known while
8417 value from function entry point is known, print the entry point value for such
8421 #0 different (val=6)
8422 #0 lost (val@@entry=5)
8424 #0 invalid (val=<optimized out>)
8428 Always print both the actual parameter value and its value from function entry
8429 point, even if values of one or both are not available due to compiler
8432 #0 equal (val=5, val@@entry=5)
8433 #0 different (val=6, val@@entry=5)
8434 #0 lost (val=<optimized out>, val@@entry=5)
8435 #0 born (val=10, val@@entry=<optimized out>)
8436 #0 invalid (val=<optimized out>, val@@entry=<optimized out>)
8440 Print the actual parameter value if it is known and also its value from
8441 function entry point if it is known. If neither is known, print for the actual
8442 value @code{<optimized out>}. If not in MI mode (@pxref{GDB/MI}) and if both
8443 values are known and identical, print the shortened
8444 @code{param=param@@entry=VALUE} notation.
8446 #0 equal (val=val@@entry=5)
8447 #0 different (val=6, val@@entry=5)
8448 #0 lost (val@@entry=5)
8450 #0 invalid (val=<optimized out>)
8454 Always print the actual parameter value. Print also its value from function
8455 entry point, but only if it is known. If not in MI mode (@pxref{GDB/MI}) and
8456 if both values are known and identical, print the shortened
8457 @code{param=param@@entry=VALUE} notation.
8459 #0 equal (val=val@@entry=5)
8460 #0 different (val=6, val@@entry=5)
8461 #0 lost (val=<optimized out>, val@@entry=5)
8463 #0 invalid (val=<optimized out>)
8467 For analysis messages on possible failures of frame argument values at function
8468 entry resolution see @ref{set debug entry-values}.
8470 @item show print entry-values
8471 Show the method being used for printing of frame argument values at function
8474 @item set print repeats
8475 @cindex repeated array elements
8476 Set the threshold for suppressing display of repeated array
8477 elements. When the number of consecutive identical elements of an
8478 array exceeds the threshold, @value{GDBN} prints the string
8479 @code{"<repeats @var{n} times>"}, where @var{n} is the number of
8480 identical repetitions, instead of displaying the identical elements
8481 themselves. Setting the threshold to zero will cause all elements to
8482 be individually printed. The default threshold is 10.
8484 @item show print repeats
8485 Display the current threshold for printing repeated identical
8488 @item set print null-stop
8489 @cindex @sc{null} elements in arrays
8490 Cause @value{GDBN} to stop printing the characters of an array when the first
8491 @sc{null} is encountered. This is useful when large arrays actually
8492 contain only short strings.
8495 @item show print null-stop
8496 Show whether @value{GDBN} stops printing an array on the first
8497 @sc{null} character.
8499 @item set print pretty on
8500 @cindex print structures in indented form
8501 @cindex indentation in structure display
8502 Cause @value{GDBN} to print structures in an indented format with one member
8503 per line, like this:
8518 @item set print pretty off
8519 Cause @value{GDBN} to print structures in a compact format, like this:
8523 $1 = @{next = 0x0, flags = @{sweet = 1, sour = 1@}, \
8524 meat = 0x54 "Pork"@}
8529 This is the default format.
8531 @item show print pretty
8532 Show which format @value{GDBN} is using to print structures.
8534 @item set print sevenbit-strings on
8535 @cindex eight-bit characters in strings
8536 @cindex octal escapes in strings
8537 Print using only seven-bit characters; if this option is set,
8538 @value{GDBN} displays any eight-bit characters (in strings or
8539 character values) using the notation @code{\}@var{nnn}. This setting is
8540 best if you are working in English (@sc{ascii}) and you use the
8541 high-order bit of characters as a marker or ``meta'' bit.
8543 @item set print sevenbit-strings off
8544 Print full eight-bit characters. This allows the use of more
8545 international character sets, and is the default.
8547 @item show print sevenbit-strings
8548 Show whether or not @value{GDBN} is printing only seven-bit characters.
8550 @item set print union on
8551 @cindex unions in structures, printing
8552 Tell @value{GDBN} to print unions which are contained in structures
8553 and other unions. This is the default setting.
8555 @item set print union off
8556 Tell @value{GDBN} not to print unions which are contained in
8557 structures and other unions. @value{GDBN} will print @code{"@{...@}"}
8560 @item show print union
8561 Ask @value{GDBN} whether or not it will print unions which are contained in
8562 structures and other unions.
8564 For example, given the declarations
8567 typedef enum @{Tree, Bug@} Species;
8568 typedef enum @{Big_tree, Acorn, Seedling@} Tree_forms;
8569 typedef enum @{Caterpillar, Cocoon, Butterfly@}
8580 struct thing foo = @{Tree, @{Acorn@}@};
8584 with @code{set print union on} in effect @samp{p foo} would print
8587 $1 = @{it = Tree, form = @{tree = Acorn, bug = Cocoon@}@}
8591 and with @code{set print union off} in effect it would print
8594 $1 = @{it = Tree, form = @{...@}@}
8598 @code{set print union} affects programs written in C-like languages
8604 These settings are of interest when debugging C@t{++} programs:
8607 @cindex demangling C@t{++} names
8608 @item set print demangle
8609 @itemx set print demangle on
8610 Print C@t{++} names in their source form rather than in the encoded
8611 (``mangled'') form passed to the assembler and linker for type-safe
8612 linkage. The default is on.
8614 @item show print demangle
8615 Show whether C@t{++} names are printed in mangled or demangled form.
8617 @item set print asm-demangle
8618 @itemx set print asm-demangle on
8619 Print C@t{++} names in their source form rather than their mangled form, even
8620 in assembler code printouts such as instruction disassemblies.
8623 @item show print asm-demangle
8624 Show whether C@t{++} names in assembly listings are printed in mangled
8627 @cindex C@t{++} symbol decoding style
8628 @cindex symbol decoding style, C@t{++}
8629 @kindex set demangle-style
8630 @item set demangle-style @var{style}
8631 Choose among several encoding schemes used by different compilers to
8632 represent C@t{++} names. The choices for @var{style} are currently:
8636 Allow @value{GDBN} to choose a decoding style by inspecting your program.
8639 Decode based on the @sc{gnu} C@t{++} compiler (@code{g++}) encoding algorithm.
8640 This is the default.
8643 Decode based on the HP ANSI C@t{++} (@code{aCC}) encoding algorithm.
8646 Decode based on the Lucid C@t{++} compiler (@code{lcc}) encoding algorithm.
8649 Decode using the algorithm in the @cite{C@t{++} Annotated Reference Manual}.
8650 @strong{Warning:} this setting alone is not sufficient to allow
8651 debugging @code{cfront}-generated executables. @value{GDBN} would
8652 require further enhancement to permit that.
8655 If you omit @var{style}, you will see a list of possible formats.
8657 @item show demangle-style
8658 Display the encoding style currently in use for decoding C@t{++} symbols.
8660 @item set print object
8661 @itemx set print object on
8662 @cindex derived type of an object, printing
8663 @cindex display derived types
8664 When displaying a pointer to an object, identify the @emph{actual}
8665 (derived) type of the object rather than the @emph{declared} type, using
8666 the virtual function table. Note that the virtual function table is
8667 required---this feature can only work for objects that have run-time
8668 type identification; a single virtual method in the object's declared
8669 type is sufficient. Note that this setting is also taken into account when
8670 working with variable objects via MI (@pxref{GDB/MI}).
8672 @item set print object off
8673 Display only the declared type of objects, without reference to the
8674 virtual function table. This is the default setting.
8676 @item show print object
8677 Show whether actual, or declared, object types are displayed.
8679 @item set print static-members
8680 @itemx set print static-members on
8681 @cindex static members of C@t{++} objects
8682 Print static members when displaying a C@t{++} object. The default is on.
8684 @item set print static-members off
8685 Do not print static members when displaying a C@t{++} object.
8687 @item show print static-members
8688 Show whether C@t{++} static members are printed or not.
8690 @item set print pascal_static-members
8691 @itemx set print pascal_static-members on
8692 @cindex static members of Pascal objects
8693 @cindex Pascal objects, static members display
8694 Print static members when displaying a Pascal object. The default is on.
8696 @item set print pascal_static-members off
8697 Do not print static members when displaying a Pascal object.
8699 @item show print pascal_static-members
8700 Show whether Pascal static members are printed or not.
8702 @c These don't work with HP ANSI C++ yet.
8703 @item set print vtbl
8704 @itemx set print vtbl on
8705 @cindex pretty print C@t{++} virtual function tables
8706 @cindex virtual functions (C@t{++}) display
8707 @cindex VTBL display
8708 Pretty print C@t{++} virtual function tables. The default is off.
8709 (The @code{vtbl} commands do not work on programs compiled with the HP
8710 ANSI C@t{++} compiler (@code{aCC}).)
8712 @item set print vtbl off
8713 Do not pretty print C@t{++} virtual function tables.
8715 @item show print vtbl
8716 Show whether C@t{++} virtual function tables are pretty printed, or not.
8719 @node Pretty Printing
8720 @section Pretty Printing
8722 @value{GDBN} provides a mechanism to allow pretty-printing of values using
8723 Python code. It greatly simplifies the display of complex objects. This
8724 mechanism works for both MI and the CLI.
8727 * Pretty-Printer Introduction:: Introduction to pretty-printers
8728 * Pretty-Printer Example:: An example pretty-printer
8729 * Pretty-Printer Commands:: Pretty-printer commands
8732 @node Pretty-Printer Introduction
8733 @subsection Pretty-Printer Introduction
8735 When @value{GDBN} prints a value, it first sees if there is a pretty-printer
8736 registered for the value. If there is then @value{GDBN} invokes the
8737 pretty-printer to print the value. Otherwise the value is printed normally.
8739 Pretty-printers are normally named. This makes them easy to manage.
8740 The @samp{info pretty-printer} command will list all the installed
8741 pretty-printers with their names.
8742 If a pretty-printer can handle multiple data types, then its
8743 @dfn{subprinters} are the printers for the individual data types.
8744 Each such subprinter has its own name.
8745 The format of the name is @var{printer-name};@var{subprinter-name}.
8747 Pretty-printers are installed by @dfn{registering} them with @value{GDBN}.
8748 Typically they are automatically loaded and registered when the corresponding
8749 debug information is loaded, thus making them available without having to
8750 do anything special.
8752 There are three places where a pretty-printer can be registered.
8756 Pretty-printers registered globally are available when debugging
8760 Pretty-printers registered with a program space are available only
8761 when debugging that program.
8762 @xref{Progspaces In Python}, for more details on program spaces in Python.
8765 Pretty-printers registered with an objfile are loaded and unloaded
8766 with the corresponding objfile (e.g., shared library).
8767 @xref{Objfiles In Python}, for more details on objfiles in Python.
8770 @xref{Selecting Pretty-Printers}, for further information on how
8771 pretty-printers are selected,
8773 @xref{Writing a Pretty-Printer}, for implementing pretty printers
8776 @node Pretty-Printer Example
8777 @subsection Pretty-Printer Example
8779 Here is how a C@t{++} @code{std::string} looks without a pretty-printer:
8782 (@value{GDBP}) print s
8784 static npos = 4294967295,
8786 <std::allocator<char>> = @{
8787 <__gnu_cxx::new_allocator<char>> = @{
8788 <No data fields>@}, <No data fields>
8790 members of std::basic_string<char, std::char_traits<char>,
8791 std::allocator<char> >::_Alloc_hider:
8792 _M_p = 0x804a014 "abcd"
8797 With a pretty-printer for @code{std::string} only the contents are printed:
8800 (@value{GDBP}) print s
8804 @node Pretty-Printer Commands
8805 @subsection Pretty-Printer Commands
8806 @cindex pretty-printer commands
8809 @kindex info pretty-printer
8810 @item info pretty-printer [@var{object-regexp} [@var{name-regexp}]]
8811 Print the list of installed pretty-printers.
8812 This includes disabled pretty-printers, which are marked as such.
8814 @var{object-regexp} is a regular expression matching the objects
8815 whose pretty-printers to list.
8816 Objects can be @code{global}, the program space's file
8817 (@pxref{Progspaces In Python}),
8818 and the object files within that program space (@pxref{Objfiles In Python}).
8819 @xref{Selecting Pretty-Printers}, for details on how @value{GDBN}
8820 looks up a printer from these three objects.
8822 @var{name-regexp} is a regular expression matching the name of the printers
8825 @kindex disable pretty-printer
8826 @item disable pretty-printer [@var{object-regexp} [@var{name-regexp}]]
8827 Disable pretty-printers matching @var{object-regexp} and @var{name-regexp}.
8828 A disabled pretty-printer is not forgotten, it may be enabled again later.
8830 @kindex enable pretty-printer
8831 @item enable pretty-printer [@var{object-regexp} [@var{name-regexp}]]
8832 Enable pretty-printers matching @var{object-regexp} and @var{name-regexp}.
8837 Suppose we have three pretty-printers installed: one from library1.so
8838 named @code{foo} that prints objects of type @code{foo}, and
8839 another from library2.so named @code{bar} that prints two types of objects,
8840 @code{bar1} and @code{bar2}.
8843 (gdb) info pretty-printer
8850 (gdb) info pretty-printer library2
8855 (gdb) disable pretty-printer library1
8857 2 of 3 printers enabled
8858 (gdb) info pretty-printer
8865 (gdb) disable pretty-printer library2 bar:bar1
8867 1 of 3 printers enabled
8868 (gdb) info pretty-printer library2
8875 (gdb) disable pretty-printer library2 bar
8877 0 of 3 printers enabled
8878 (gdb) info pretty-printer library2
8887 Note that for @code{bar} the entire printer can be disabled,
8888 as can each individual subprinter.
8891 @section Value History
8893 @cindex value history
8894 @cindex history of values printed by @value{GDBN}
8895 Values printed by the @code{print} command are saved in the @value{GDBN}
8896 @dfn{value history}. This allows you to refer to them in other expressions.
8897 Values are kept until the symbol table is re-read or discarded
8898 (for example with the @code{file} or @code{symbol-file} commands).
8899 When the symbol table changes, the value history is discarded,
8900 since the values may contain pointers back to the types defined in the
8905 @cindex history number
8906 The values printed are given @dfn{history numbers} by which you can
8907 refer to them. These are successive integers starting with one.
8908 @code{print} shows you the history number assigned to a value by
8909 printing @samp{$@var{num} = } before the value; here @var{num} is the
8912 To refer to any previous value, use @samp{$} followed by the value's
8913 history number. The way @code{print} labels its output is designed to
8914 remind you of this. Just @code{$} refers to the most recent value in
8915 the history, and @code{$$} refers to the value before that.
8916 @code{$$@var{n}} refers to the @var{n}th value from the end; @code{$$2}
8917 is the value just prior to @code{$$}, @code{$$1} is equivalent to
8918 @code{$$}, and @code{$$0} is equivalent to @code{$}.
8920 For example, suppose you have just printed a pointer to a structure and
8921 want to see the contents of the structure. It suffices to type
8927 If you have a chain of structures where the component @code{next} points
8928 to the next one, you can print the contents of the next one with this:
8935 You can print successive links in the chain by repeating this
8936 command---which you can do by just typing @key{RET}.
8938 Note that the history records values, not expressions. If the value of
8939 @code{x} is 4 and you type these commands:
8947 then the value recorded in the value history by the @code{print} command
8948 remains 4 even though the value of @code{x} has changed.
8953 Print the last ten values in the value history, with their item numbers.
8954 This is like @samp{p@ $$9} repeated ten times, except that @code{show
8955 values} does not change the history.
8957 @item show values @var{n}
8958 Print ten history values centered on history item number @var{n}.
8961 Print ten history values just after the values last printed. If no more
8962 values are available, @code{show values +} produces no display.
8965 Pressing @key{RET} to repeat @code{show values @var{n}} has exactly the
8966 same effect as @samp{show values +}.
8968 @node Convenience Vars
8969 @section Convenience Variables
8971 @cindex convenience variables
8972 @cindex user-defined variables
8973 @value{GDBN} provides @dfn{convenience variables} that you can use within
8974 @value{GDBN} to hold on to a value and refer to it later. These variables
8975 exist entirely within @value{GDBN}; they are not part of your program, and
8976 setting a convenience variable has no direct effect on further execution
8977 of your program. That is why you can use them freely.
8979 Convenience variables are prefixed with @samp{$}. Any name preceded by
8980 @samp{$} can be used for a convenience variable, unless it is one of
8981 the predefined machine-specific register names (@pxref{Registers, ,Registers}).
8982 (Value history references, in contrast, are @emph{numbers} preceded
8983 by @samp{$}. @xref{Value History, ,Value History}.)
8985 You can save a value in a convenience variable with an assignment
8986 expression, just as you would set a variable in your program.
8990 set $foo = *object_ptr
8994 would save in @code{$foo} the value contained in the object pointed to by
8997 Using a convenience variable for the first time creates it, but its
8998 value is @code{void} until you assign a new value. You can alter the
8999 value with another assignment at any time.
9001 Convenience variables have no fixed types. You can assign a convenience
9002 variable any type of value, including structures and arrays, even if
9003 that variable already has a value of a different type. The convenience
9004 variable, when used as an expression, has the type of its current value.
9007 @kindex show convenience
9008 @cindex show all user variables
9009 @item show convenience
9010 Print a list of convenience variables used so far, and their values.
9011 Abbreviated @code{show conv}.
9013 @kindex init-if-undefined
9014 @cindex convenience variables, initializing
9015 @item init-if-undefined $@var{variable} = @var{expression}
9016 Set a convenience variable if it has not already been set. This is useful
9017 for user-defined commands that keep some state. It is similar, in concept,
9018 to using local static variables with initializers in C (except that
9019 convenience variables are global). It can also be used to allow users to
9020 override default values used in a command script.
9022 If the variable is already defined then the expression is not evaluated so
9023 any side-effects do not occur.
9026 One of the ways to use a convenience variable is as a counter to be
9027 incremented or a pointer to be advanced. For example, to print
9028 a field from successive elements of an array of structures:
9032 print bar[$i++]->contents
9036 Repeat that command by typing @key{RET}.
9038 Some convenience variables are created automatically by @value{GDBN} and given
9039 values likely to be useful.
9042 @vindex $_@r{, convenience variable}
9044 The variable @code{$_} is automatically set by the @code{x} command to
9045 the last address examined (@pxref{Memory, ,Examining Memory}). Other
9046 commands which provide a default address for @code{x} to examine also
9047 set @code{$_} to that address; these commands include @code{info line}
9048 and @code{info breakpoint}. The type of @code{$_} is @code{void *}
9049 except when set by the @code{x} command, in which case it is a pointer
9050 to the type of @code{$__}.
9052 @vindex $__@r{, convenience variable}
9054 The variable @code{$__} is automatically set by the @code{x} command
9055 to the value found in the last address examined. Its type is chosen
9056 to match the format in which the data was printed.
9059 @vindex $_exitcode@r{, convenience variable}
9060 The variable @code{$_exitcode} is automatically set to the exit code when
9061 the program being debugged terminates.
9064 @vindex $_sdata@r{, inspect, convenience variable}
9065 The variable @code{$_sdata} contains extra collected static tracepoint
9066 data. @xref{Tracepoint Actions,,Tracepoint Action Lists}. Note that
9067 @code{$_sdata} could be empty, if not inspecting a trace buffer, or
9068 if extra static tracepoint data has not been collected.
9071 @vindex $_siginfo@r{, convenience variable}
9072 The variable @code{$_siginfo} contains extra signal information
9073 (@pxref{extra signal information}). Note that @code{$_siginfo}
9074 could be empty, if the application has not yet received any signals.
9075 For example, it will be empty before you execute the @code{run} command.
9078 @vindex $_tlb@r{, convenience variable}
9079 The variable @code{$_tlb} is automatically set when debugging
9080 applications running on MS-Windows in native mode or connected to
9081 gdbserver that supports the @code{qGetTIBAddr} request.
9082 @xref{General Query Packets}.
9083 This variable contains the address of the thread information block.
9087 On HP-UX systems, if you refer to a function or variable name that
9088 begins with a dollar sign, @value{GDBN} searches for a user or system
9089 name first, before it searches for a convenience variable.
9091 @cindex convenience functions
9092 @value{GDBN} also supplies some @dfn{convenience functions}. These
9093 have a syntax similar to convenience variables. A convenience
9094 function can be used in an expression just like an ordinary function;
9095 however, a convenience function is implemented internally to
9100 @kindex help function
9101 @cindex show all convenience functions
9102 Print a list of all convenience functions.
9109 You can refer to machine register contents, in expressions, as variables
9110 with names starting with @samp{$}. The names of registers are different
9111 for each machine; use @code{info registers} to see the names used on
9115 @kindex info registers
9116 @item info registers
9117 Print the names and values of all registers except floating-point
9118 and vector registers (in the selected stack frame).
9120 @kindex info all-registers
9121 @cindex floating point registers
9122 @item info all-registers
9123 Print the names and values of all registers, including floating-point
9124 and vector registers (in the selected stack frame).
9126 @item info registers @var{regname} @dots{}
9127 Print the @dfn{relativized} value of each specified register @var{regname}.
9128 As discussed in detail below, register values are normally relative to
9129 the selected stack frame. @var{regname} may be any register name valid on
9130 the machine you are using, with or without the initial @samp{$}.
9133 @cindex stack pointer register
9134 @cindex program counter register
9135 @cindex process status register
9136 @cindex frame pointer register
9137 @cindex standard registers
9138 @value{GDBN} has four ``standard'' register names that are available (in
9139 expressions) on most machines---whenever they do not conflict with an
9140 architecture's canonical mnemonics for registers. The register names
9141 @code{$pc} and @code{$sp} are used for the program counter register and
9142 the stack pointer. @code{$fp} is used for a register that contains a
9143 pointer to the current stack frame, and @code{$ps} is used for a
9144 register that contains the processor status. For example,
9145 you could print the program counter in hex with
9152 or print the instruction to be executed next with
9159 or add four to the stack pointer@footnote{This is a way of removing
9160 one word from the stack, on machines where stacks grow downward in
9161 memory (most machines, nowadays). This assumes that the innermost
9162 stack frame is selected; setting @code{$sp} is not allowed when other
9163 stack frames are selected. To pop entire frames off the stack,
9164 regardless of machine architecture, use @code{return};
9165 see @ref{Returning, ,Returning from a Function}.} with
9171 Whenever possible, these four standard register names are available on
9172 your machine even though the machine has different canonical mnemonics,
9173 so long as there is no conflict. The @code{info registers} command
9174 shows the canonical names. For example, on the SPARC, @code{info
9175 registers} displays the processor status register as @code{$psr} but you
9176 can also refer to it as @code{$ps}; and on x86-based machines @code{$ps}
9177 is an alias for the @sc{eflags} register.
9179 @value{GDBN} always considers the contents of an ordinary register as an
9180 integer when the register is examined in this way. Some machines have
9181 special registers which can hold nothing but floating point; these
9182 registers are considered to have floating point values. There is no way
9183 to refer to the contents of an ordinary register as floating point value
9184 (although you can @emph{print} it as a floating point value with
9185 @samp{print/f $@var{regname}}).
9187 Some registers have distinct ``raw'' and ``virtual'' data formats. This
9188 means that the data format in which the register contents are saved by
9189 the operating system is not the same one that your program normally
9190 sees. For example, the registers of the 68881 floating point
9191 coprocessor are always saved in ``extended'' (raw) format, but all C
9192 programs expect to work with ``double'' (virtual) format. In such
9193 cases, @value{GDBN} normally works with the virtual format only (the format
9194 that makes sense for your program), but the @code{info registers} command
9195 prints the data in both formats.
9197 @cindex SSE registers (x86)
9198 @cindex MMX registers (x86)
9199 Some machines have special registers whose contents can be interpreted
9200 in several different ways. For example, modern x86-based machines
9201 have SSE and MMX registers that can hold several values packed
9202 together in several different formats. @value{GDBN} refers to such
9203 registers in @code{struct} notation:
9206 (@value{GDBP}) print $xmm1
9208 v4_float = @{0, 3.43859137e-038, 1.54142831e-044, 1.821688e-044@},
9209 v2_double = @{9.92129282474342e-303, 2.7585945287983262e-313@},
9210 v16_int8 = "\000\000\000\000\3706;\001\v\000\000\000\r\000\000",
9211 v8_int16 = @{0, 0, 14072, 315, 11, 0, 13, 0@},
9212 v4_int32 = @{0, 20657912, 11, 13@},
9213 v2_int64 = @{88725056443645952, 55834574859@},
9214 uint128 = 0x0000000d0000000b013b36f800000000
9219 To set values of such registers, you need to tell @value{GDBN} which
9220 view of the register you wish to change, as if you were assigning
9221 value to a @code{struct} member:
9224 (@value{GDBP}) set $xmm1.uint128 = 0x000000000000000000000000FFFFFFFF
9227 Normally, register values are relative to the selected stack frame
9228 (@pxref{Selection, ,Selecting a Frame}). This means that you get the
9229 value that the register would contain if all stack frames farther in
9230 were exited and their saved registers restored. In order to see the
9231 true contents of hardware registers, you must select the innermost
9232 frame (with @samp{frame 0}).
9234 However, @value{GDBN} must deduce where registers are saved, from the machine
9235 code generated by your compiler. If some registers are not saved, or if
9236 @value{GDBN} is unable to locate the saved registers, the selected stack
9237 frame makes no difference.
9239 @node Floating Point Hardware
9240 @section Floating Point Hardware
9241 @cindex floating point
9243 Depending on the configuration, @value{GDBN} may be able to give
9244 you more information about the status of the floating point hardware.
9249 Display hardware-dependent information about the floating
9250 point unit. The exact contents and layout vary depending on the
9251 floating point chip. Currently, @samp{info float} is supported on
9252 the ARM and x86 machines.
9256 @section Vector Unit
9259 Depending on the configuration, @value{GDBN} may be able to give you
9260 more information about the status of the vector unit.
9265 Display information about the vector unit. The exact contents and
9266 layout vary depending on the hardware.
9269 @node OS Information
9270 @section Operating System Auxiliary Information
9271 @cindex OS information
9273 @value{GDBN} provides interfaces to useful OS facilities that can help
9274 you debug your program.
9276 @cindex @code{ptrace} system call
9277 @cindex @code{struct user} contents
9278 When @value{GDBN} runs on a @dfn{Posix system} (such as GNU or Unix
9279 machines), it interfaces with the inferior via the @code{ptrace}
9280 system call. The operating system creates a special sata structure,
9281 called @code{struct user}, for this interface. You can use the
9282 command @code{info udot} to display the contents of this data
9288 Display the contents of the @code{struct user} maintained by the OS
9289 kernel for the program being debugged. @value{GDBN} displays the
9290 contents of @code{struct user} as a list of hex numbers, similar to
9291 the @code{examine} command.
9294 @cindex auxiliary vector
9295 @cindex vector, auxiliary
9296 Some operating systems supply an @dfn{auxiliary vector} to programs at
9297 startup. This is akin to the arguments and environment that you
9298 specify for a program, but contains a system-dependent variety of
9299 binary values that tell system libraries important details about the
9300 hardware, operating system, and process. Each value's purpose is
9301 identified by an integer tag; the meanings are well-known but system-specific.
9302 Depending on the configuration and operating system facilities,
9303 @value{GDBN} may be able to show you this information. For remote
9304 targets, this functionality may further depend on the remote stub's
9305 support of the @samp{qXfer:auxv:read} packet, see
9306 @ref{qXfer auxiliary vector read}.
9311 Display the auxiliary vector of the inferior, which can be either a
9312 live process or a core dump file. @value{GDBN} prints each tag value
9313 numerically, and also shows names and text descriptions for recognized
9314 tags. Some values in the vector are numbers, some bit masks, and some
9315 pointers to strings or other data. @value{GDBN} displays each value in the
9316 most appropriate form for a recognized tag, and in hexadecimal for
9317 an unrecognized tag.
9320 On some targets, @value{GDBN} can access operating-system-specific information
9321 and display it to user, without interpretation. For remote targets,
9322 this functionality depends on the remote stub's support of the
9323 @samp{qXfer:osdata:read} packet, see @ref{qXfer osdata read}.
9328 List the types of OS information available for the target. If the
9329 target does not return a list of possible types, this command will
9332 @kindex info os processes
9333 @item info os processes
9334 Display the list of processes on the target. For each process,
9335 @value{GDBN} prints the process identifier, the name of the user, and
9336 the command corresponding to the process.
9339 @node Memory Region Attributes
9340 @section Memory Region Attributes
9341 @cindex memory region attributes
9343 @dfn{Memory region attributes} allow you to describe special handling
9344 required by regions of your target's memory. @value{GDBN} uses
9345 attributes to determine whether to allow certain types of memory
9346 accesses; whether to use specific width accesses; and whether to cache
9347 target memory. By default the description of memory regions is
9348 fetched from the target (if the current target supports this), but the
9349 user can override the fetched regions.
9351 Defined memory regions can be individually enabled and disabled. When a
9352 memory region is disabled, @value{GDBN} uses the default attributes when
9353 accessing memory in that region. Similarly, if no memory regions have
9354 been defined, @value{GDBN} uses the default attributes when accessing
9357 When a memory region is defined, it is given a number to identify it;
9358 to enable, disable, or remove a memory region, you specify that number.
9362 @item mem @var{lower} @var{upper} @var{attributes}@dots{}
9363 Define a memory region bounded by @var{lower} and @var{upper} with
9364 attributes @var{attributes}@dots{}, and add it to the list of regions
9365 monitored by @value{GDBN}. Note that @var{upper} == 0 is a special
9366 case: it is treated as the target's maximum memory address.
9367 (0xffff on 16 bit targets, 0xffffffff on 32 bit targets, etc.)
9370 Discard any user changes to the memory regions and use target-supplied
9371 regions, if available, or no regions if the target does not support.
9374 @item delete mem @var{nums}@dots{}
9375 Remove memory regions @var{nums}@dots{} from the list of regions
9376 monitored by @value{GDBN}.
9379 @item disable mem @var{nums}@dots{}
9380 Disable monitoring of memory regions @var{nums}@dots{}.
9381 A disabled memory region is not forgotten.
9382 It may be enabled again later.
9385 @item enable mem @var{nums}@dots{}
9386 Enable monitoring of memory regions @var{nums}@dots{}.
9390 Print a table of all defined memory regions, with the following columns
9394 @item Memory Region Number
9395 @item Enabled or Disabled.
9396 Enabled memory regions are marked with @samp{y}.
9397 Disabled memory regions are marked with @samp{n}.
9400 The address defining the inclusive lower bound of the memory region.
9403 The address defining the exclusive upper bound of the memory region.
9406 The list of attributes set for this memory region.
9411 @subsection Attributes
9413 @subsubsection Memory Access Mode
9414 The access mode attributes set whether @value{GDBN} may make read or
9415 write accesses to a memory region.
9417 While these attributes prevent @value{GDBN} from performing invalid
9418 memory accesses, they do nothing to prevent the target system, I/O DMA,
9419 etc.@: from accessing memory.
9423 Memory is read only.
9425 Memory is write only.
9427 Memory is read/write. This is the default.
9430 @subsubsection Memory Access Size
9431 The access size attribute tells @value{GDBN} to use specific sized
9432 accesses in the memory region. Often memory mapped device registers
9433 require specific sized accesses. If no access size attribute is
9434 specified, @value{GDBN} may use accesses of any size.
9438 Use 8 bit memory accesses.
9440 Use 16 bit memory accesses.
9442 Use 32 bit memory accesses.
9444 Use 64 bit memory accesses.
9447 @c @subsubsection Hardware/Software Breakpoints
9448 @c The hardware/software breakpoint attributes set whether @value{GDBN}
9449 @c will use hardware or software breakpoints for the internal breakpoints
9450 @c used by the step, next, finish, until, etc. commands.
9454 @c Always use hardware breakpoints
9455 @c @item swbreak (default)
9458 @subsubsection Data Cache
9459 The data cache attributes set whether @value{GDBN} will cache target
9460 memory. While this generally improves performance by reducing debug
9461 protocol overhead, it can lead to incorrect results because @value{GDBN}
9462 does not know about volatile variables or memory mapped device
9467 Enable @value{GDBN} to cache target memory.
9469 Disable @value{GDBN} from caching target memory. This is the default.
9472 @subsection Memory Access Checking
9473 @value{GDBN} can be instructed to refuse accesses to memory that is
9474 not explicitly described. This can be useful if accessing such
9475 regions has undesired effects for a specific target, or to provide
9476 better error checking. The following commands control this behaviour.
9479 @kindex set mem inaccessible-by-default
9480 @item set mem inaccessible-by-default [on|off]
9481 If @code{on} is specified, make @value{GDBN} treat memory not
9482 explicitly described by the memory ranges as non-existent and refuse accesses
9483 to such memory. The checks are only performed if there's at least one
9484 memory range defined. If @code{off} is specified, make @value{GDBN}
9485 treat the memory not explicitly described by the memory ranges as RAM.
9486 The default value is @code{on}.
9487 @kindex show mem inaccessible-by-default
9488 @item show mem inaccessible-by-default
9489 Show the current handling of accesses to unknown memory.
9493 @c @subsubsection Memory Write Verification
9494 @c The memory write verification attributes set whether @value{GDBN}
9495 @c will re-reads data after each write to verify the write was successful.
9499 @c @item noverify (default)
9502 @node Dump/Restore Files
9503 @section Copy Between Memory and a File
9504 @cindex dump/restore files
9505 @cindex append data to a file
9506 @cindex dump data to a file
9507 @cindex restore data from a file
9509 You can use the commands @code{dump}, @code{append}, and
9510 @code{restore} to copy data between target memory and a file. The
9511 @code{dump} and @code{append} commands write data to a file, and the
9512 @code{restore} command reads data from a file back into the inferior's
9513 memory. Files may be in binary, Motorola S-record, Intel hex, or
9514 Tektronix Hex format; however, @value{GDBN} can only append to binary
9520 @item dump @r{[}@var{format}@r{]} memory @var{filename} @var{start_addr} @var{end_addr}
9521 @itemx dump @r{[}@var{format}@r{]} value @var{filename} @var{expr}
9522 Dump the contents of memory from @var{start_addr} to @var{end_addr},
9523 or the value of @var{expr}, to @var{filename} in the given format.
9525 The @var{format} parameter may be any one of:
9532 Motorola S-record format.
9534 Tektronix Hex format.
9537 @value{GDBN} uses the same definitions of these formats as the
9538 @sc{gnu} binary utilities, like @samp{objdump} and @samp{objcopy}. If
9539 @var{format} is omitted, @value{GDBN} dumps the data in raw binary
9543 @item append @r{[}binary@r{]} memory @var{filename} @var{start_addr} @var{end_addr}
9544 @itemx append @r{[}binary@r{]} value @var{filename} @var{expr}
9545 Append the contents of memory from @var{start_addr} to @var{end_addr},
9546 or the value of @var{expr}, to the file @var{filename}, in raw binary form.
9547 (@value{GDBN} can only append data to files in raw binary form.)
9550 @item restore @var{filename} @r{[}binary@r{]} @var{bias} @var{start} @var{end}
9551 Restore the contents of file @var{filename} into memory. The
9552 @code{restore} command can automatically recognize any known @sc{bfd}
9553 file format, except for raw binary. To restore a raw binary file you
9554 must specify the optional keyword @code{binary} after the filename.
9556 If @var{bias} is non-zero, its value will be added to the addresses
9557 contained in the file. Binary files always start at address zero, so
9558 they will be restored at address @var{bias}. Other bfd files have
9559 a built-in location; they will be restored at offset @var{bias}
9562 If @var{start} and/or @var{end} are non-zero, then only data between
9563 file offset @var{start} and file offset @var{end} will be restored.
9564 These offsets are relative to the addresses in the file, before
9565 the @var{bias} argument is applied.
9569 @node Core File Generation
9570 @section How to Produce a Core File from Your Program
9571 @cindex dump core from inferior
9573 A @dfn{core file} or @dfn{core dump} is a file that records the memory
9574 image of a running process and its process status (register values
9575 etc.). Its primary use is post-mortem debugging of a program that
9576 crashed while it ran outside a debugger. A program that crashes
9577 automatically produces a core file, unless this feature is disabled by
9578 the user. @xref{Files}, for information on invoking @value{GDBN} in
9579 the post-mortem debugging mode.
9581 Occasionally, you may wish to produce a core file of the program you
9582 are debugging in order to preserve a snapshot of its state.
9583 @value{GDBN} has a special command for that.
9587 @kindex generate-core-file
9588 @item generate-core-file [@var{file}]
9589 @itemx gcore [@var{file}]
9590 Produce a core dump of the inferior process. The optional argument
9591 @var{file} specifies the file name where to put the core dump. If not
9592 specified, the file name defaults to @file{core.@var{pid}}, where
9593 @var{pid} is the inferior process ID.
9595 Note that this command is implemented only for some systems (as of
9596 this writing, @sc{gnu}/Linux, FreeBSD, Solaris, Unixware, and S390).
9599 @node Character Sets
9600 @section Character Sets
9601 @cindex character sets
9603 @cindex translating between character sets
9604 @cindex host character set
9605 @cindex target character set
9607 If the program you are debugging uses a different character set to
9608 represent characters and strings than the one @value{GDBN} uses itself,
9609 @value{GDBN} can automatically translate between the character sets for
9610 you. The character set @value{GDBN} uses we call the @dfn{host
9611 character set}; the one the inferior program uses we call the
9612 @dfn{target character set}.
9614 For example, if you are running @value{GDBN} on a @sc{gnu}/Linux system, which
9615 uses the ISO Latin 1 character set, but you are using @value{GDBN}'s
9616 remote protocol (@pxref{Remote Debugging}) to debug a program
9617 running on an IBM mainframe, which uses the @sc{ebcdic} character set,
9618 then the host character set is Latin-1, and the target character set is
9619 @sc{ebcdic}. If you give @value{GDBN} the command @code{set
9620 target-charset EBCDIC-US}, then @value{GDBN} translates between
9621 @sc{ebcdic} and Latin 1 as you print character or string values, or use
9622 character and string literals in expressions.
9624 @value{GDBN} has no way to automatically recognize which character set
9625 the inferior program uses; you must tell it, using the @code{set
9626 target-charset} command, described below.
9628 Here are the commands for controlling @value{GDBN}'s character set
9632 @item set target-charset @var{charset}
9633 @kindex set target-charset
9634 Set the current target character set to @var{charset}. To display the
9635 list of supported target character sets, type
9636 @kbd{@w{set target-charset @key{TAB}@key{TAB}}}.
9638 @item set host-charset @var{charset}
9639 @kindex set host-charset
9640 Set the current host character set to @var{charset}.
9642 By default, @value{GDBN} uses a host character set appropriate to the
9643 system it is running on; you can override that default using the
9644 @code{set host-charset} command. On some systems, @value{GDBN} cannot
9645 automatically determine the appropriate host character set. In this
9646 case, @value{GDBN} uses @samp{UTF-8}.
9648 @value{GDBN} can only use certain character sets as its host character
9649 set. If you type @kbd{@w{set host-charset @key{TAB}@key{TAB}}},
9650 @value{GDBN} will list the host character sets it supports.
9652 @item set charset @var{charset}
9654 Set the current host and target character sets to @var{charset}. As
9655 above, if you type @kbd{@w{set charset @key{TAB}@key{TAB}}},
9656 @value{GDBN} will list the names of the character sets that can be used
9657 for both host and target.
9660 @kindex show charset
9661 Show the names of the current host and target character sets.
9663 @item show host-charset
9664 @kindex show host-charset
9665 Show the name of the current host character set.
9667 @item show target-charset
9668 @kindex show target-charset
9669 Show the name of the current target character set.
9671 @item set target-wide-charset @var{charset}
9672 @kindex set target-wide-charset
9673 Set the current target's wide character set to @var{charset}. This is
9674 the character set used by the target's @code{wchar_t} type. To
9675 display the list of supported wide character sets, type
9676 @kbd{@w{set target-wide-charset @key{TAB}@key{TAB}}}.
9678 @item show target-wide-charset
9679 @kindex show target-wide-charset
9680 Show the name of the current target's wide character set.
9683 Here is an example of @value{GDBN}'s character set support in action.
9684 Assume that the following source code has been placed in the file
9685 @file{charset-test.c}:
9691 = @{72, 101, 108, 108, 111, 44, 32, 119,
9692 111, 114, 108, 100, 33, 10, 0@};
9693 char ibm1047_hello[]
9694 = @{200, 133, 147, 147, 150, 107, 64, 166,
9695 150, 153, 147, 132, 90, 37, 0@};
9699 printf ("Hello, world!\n");
9703 In this program, @code{ascii_hello} and @code{ibm1047_hello} are arrays
9704 containing the string @samp{Hello, world!} followed by a newline,
9705 encoded in the @sc{ascii} and @sc{ibm1047} character sets.
9707 We compile the program, and invoke the debugger on it:
9710 $ gcc -g charset-test.c -o charset-test
9711 $ gdb -nw charset-test
9712 GNU gdb 2001-12-19-cvs
9713 Copyright 2001 Free Software Foundation, Inc.
9718 We can use the @code{show charset} command to see what character sets
9719 @value{GDBN} is currently using to interpret and display characters and
9723 (@value{GDBP}) show charset
9724 The current host and target character set is `ISO-8859-1'.
9728 For the sake of printing this manual, let's use @sc{ascii} as our
9729 initial character set:
9731 (@value{GDBP}) set charset ASCII
9732 (@value{GDBP}) show charset
9733 The current host and target character set is `ASCII'.
9737 Let's assume that @sc{ascii} is indeed the correct character set for our
9738 host system --- in other words, let's assume that if @value{GDBN} prints
9739 characters using the @sc{ascii} character set, our terminal will display
9740 them properly. Since our current target character set is also
9741 @sc{ascii}, the contents of @code{ascii_hello} print legibly:
9744 (@value{GDBP}) print ascii_hello
9745 $1 = 0x401698 "Hello, world!\n"
9746 (@value{GDBP}) print ascii_hello[0]
9751 @value{GDBN} uses the target character set for character and string
9752 literals you use in expressions:
9755 (@value{GDBP}) print '+'
9760 The @sc{ascii} character set uses the number 43 to encode the @samp{+}
9763 @value{GDBN} relies on the user to tell it which character set the
9764 target program uses. If we print @code{ibm1047_hello} while our target
9765 character set is still @sc{ascii}, we get jibberish:
9768 (@value{GDBP}) print ibm1047_hello
9769 $4 = 0x4016a8 "\310\205\223\223\226k@@\246\226\231\223\204Z%"
9770 (@value{GDBP}) print ibm1047_hello[0]
9775 If we invoke the @code{set target-charset} followed by @key{TAB}@key{TAB},
9776 @value{GDBN} tells us the character sets it supports:
9779 (@value{GDBP}) set target-charset
9780 ASCII EBCDIC-US IBM1047 ISO-8859-1
9781 (@value{GDBP}) set target-charset
9784 We can select @sc{ibm1047} as our target character set, and examine the
9785 program's strings again. Now the @sc{ascii} string is wrong, but
9786 @value{GDBN} translates the contents of @code{ibm1047_hello} from the
9787 target character set, @sc{ibm1047}, to the host character set,
9788 @sc{ascii}, and they display correctly:
9791 (@value{GDBP}) set target-charset IBM1047
9792 (@value{GDBP}) show charset
9793 The current host character set is `ASCII'.
9794 The current target character set is `IBM1047'.
9795 (@value{GDBP}) print ascii_hello
9796 $6 = 0x401698 "\110\145%%?\054\040\167?\162%\144\041\012"
9797 (@value{GDBP}) print ascii_hello[0]
9799 (@value{GDBP}) print ibm1047_hello
9800 $8 = 0x4016a8 "Hello, world!\n"
9801 (@value{GDBP}) print ibm1047_hello[0]
9806 As above, @value{GDBN} uses the target character set for character and
9807 string literals you use in expressions:
9810 (@value{GDBP}) print '+'
9815 The @sc{ibm1047} character set uses the number 78 to encode the @samp{+}
9818 @node Caching Remote Data
9819 @section Caching Data of Remote Targets
9820 @cindex caching data of remote targets
9822 @value{GDBN} caches data exchanged between the debugger and a
9823 remote target (@pxref{Remote Debugging}). Such caching generally improves
9824 performance, because it reduces the overhead of the remote protocol by
9825 bundling memory reads and writes into large chunks. Unfortunately, simply
9826 caching everything would lead to incorrect results, since @value{GDBN}
9827 does not necessarily know anything about volatile values, memory-mapped I/O
9828 addresses, etc. Furthermore, in non-stop mode (@pxref{Non-Stop Mode})
9829 memory can be changed @emph{while} a gdb command is executing.
9830 Therefore, by default, @value{GDBN} only caches data
9831 known to be on the stack@footnote{In non-stop mode, it is moderately
9832 rare for a running thread to modify the stack of a stopped thread
9833 in a way that would interfere with a backtrace, and caching of
9834 stack reads provides a significant speed up of remote backtraces.}.
9835 Other regions of memory can be explicitly marked as
9836 cacheable; see @pxref{Memory Region Attributes}.
9839 @kindex set remotecache
9840 @item set remotecache on
9841 @itemx set remotecache off
9842 This option no longer does anything; it exists for compatibility
9845 @kindex show remotecache
9846 @item show remotecache
9847 Show the current state of the obsolete remotecache flag.
9849 @kindex set stack-cache
9850 @item set stack-cache on
9851 @itemx set stack-cache off
9852 Enable or disable caching of stack accesses. When @code{ON}, use
9853 caching. By default, this option is @code{ON}.
9855 @kindex show stack-cache
9856 @item show stack-cache
9857 Show the current state of data caching for memory accesses.
9860 @item info dcache @r{[}line@r{]}
9861 Print the information about the data cache performance. The
9862 information displayed includes the dcache width and depth, and for
9863 each cache line, its number, address, and how many times it was
9864 referenced. This command is useful for debugging the data cache
9867 If a line number is specified, the contents of that line will be
9870 @item set dcache size @var{size}
9872 @kindex set dcache size
9873 Set maximum number of entries in dcache (dcache depth above).
9875 @item set dcache line-size @var{line-size}
9876 @cindex dcache line-size
9877 @kindex set dcache line-size
9878 Set number of bytes each dcache entry caches (dcache width above).
9879 Must be a power of 2.
9881 @item show dcache size
9882 @kindex show dcache size
9883 Show maximum number of dcache entries. See also @ref{Caching Remote Data, info dcache}.
9885 @item show dcache line-size
9886 @kindex show dcache line-size
9887 Show default size of dcache lines. See also @ref{Caching Remote Data, info dcache}.
9891 @node Searching Memory
9892 @section Search Memory
9893 @cindex searching memory
9895 Memory can be searched for a particular sequence of bytes with the
9896 @code{find} command.
9900 @item find @r{[}/@var{sn}@r{]} @var{start_addr}, +@var{len}, @var{val1} @r{[}, @var{val2}, @dots{}@r{]}
9901 @itemx find @r{[}/@var{sn}@r{]} @var{start_addr}, @var{end_addr}, @var{val1} @r{[}, @var{val2}, @dots{}@r{]}
9902 Search memory for the sequence of bytes specified by @var{val1}, @var{val2},
9903 etc. The search begins at address @var{start_addr} and continues for either
9904 @var{len} bytes or through to @var{end_addr} inclusive.
9907 @var{s} and @var{n} are optional parameters.
9908 They may be specified in either order, apart or together.
9911 @item @var{s}, search query size
9912 The size of each search query value.
9918 halfwords (two bytes)
9922 giant words (eight bytes)
9925 All values are interpreted in the current language.
9926 This means, for example, that if the current source language is C/C@t{++}
9927 then searching for the string ``hello'' includes the trailing '\0'.
9929 If the value size is not specified, it is taken from the
9930 value's type in the current language.
9931 This is useful when one wants to specify the search
9932 pattern as a mixture of types.
9933 Note that this means, for example, that in the case of C-like languages
9934 a search for an untyped 0x42 will search for @samp{(int) 0x42}
9935 which is typically four bytes.
9937 @item @var{n}, maximum number of finds
9938 The maximum number of matches to print. The default is to print all finds.
9941 You can use strings as search values. Quote them with double-quotes
9943 The string value is copied into the search pattern byte by byte,
9944 regardless of the endianness of the target and the size specification.
9946 The address of each match found is printed as well as a count of the
9947 number of matches found.
9949 The address of the last value found is stored in convenience variable
9951 A count of the number of matches is stored in @samp{$numfound}.
9953 For example, if stopped at the @code{printf} in this function:
9959 static char hello[] = "hello-hello";
9960 static struct @{ char c; short s; int i; @}
9961 __attribute__ ((packed)) mixed
9962 = @{ 'c', 0x1234, 0x87654321 @};
9963 printf ("%s\n", hello);
9968 you get during debugging:
9971 (gdb) find &hello[0], +sizeof(hello), "hello"
9972 0x804956d <hello.1620+6>
9974 (gdb) find &hello[0], +sizeof(hello), 'h', 'e', 'l', 'l', 'o'
9975 0x8049567 <hello.1620>
9976 0x804956d <hello.1620+6>
9978 (gdb) find /b1 &hello[0], +sizeof(hello), 'h', 0x65, 'l'
9979 0x8049567 <hello.1620>
9981 (gdb) find &mixed, +sizeof(mixed), (char) 'c', (short) 0x1234, (int) 0x87654321
9982 0x8049560 <mixed.1625>
9984 (gdb) print $numfound
9987 $2 = (void *) 0x8049560
9990 @node Optimized Code
9991 @chapter Debugging Optimized Code
9992 @cindex optimized code, debugging
9993 @cindex debugging optimized code
9995 Almost all compilers support optimization. With optimization
9996 disabled, the compiler generates assembly code that corresponds
9997 directly to your source code, in a simplistic way. As the compiler
9998 applies more powerful optimizations, the generated assembly code
9999 diverges from your original source code. With help from debugging
10000 information generated by the compiler, @value{GDBN} can map from
10001 the running program back to constructs from your original source.
10003 @value{GDBN} is more accurate with optimization disabled. If you
10004 can recompile without optimization, it is easier to follow the
10005 progress of your program during debugging. But, there are many cases
10006 where you may need to debug an optimized version.
10008 When you debug a program compiled with @samp{-g -O}, remember that the
10009 optimizer has rearranged your code; the debugger shows you what is
10010 really there. Do not be too surprised when the execution path does not
10011 exactly match your source file! An extreme example: if you define a
10012 variable, but never use it, @value{GDBN} never sees that
10013 variable---because the compiler optimizes it out of existence.
10015 Some things do not work as well with @samp{-g -O} as with just
10016 @samp{-g}, particularly on machines with instruction scheduling. If in
10017 doubt, recompile with @samp{-g} alone, and if this fixes the problem,
10018 please report it to us as a bug (including a test case!).
10019 @xref{Variables}, for more information about debugging optimized code.
10022 * Inline Functions:: How @value{GDBN} presents inlining
10023 * Tail Call Frames:: @value{GDBN} analysis of jumps to functions
10026 @node Inline Functions
10027 @section Inline Functions
10028 @cindex inline functions, debugging
10030 @dfn{Inlining} is an optimization that inserts a copy of the function
10031 body directly at each call site, instead of jumping to a shared
10032 routine. @value{GDBN} displays inlined functions just like
10033 non-inlined functions. They appear in backtraces. You can view their
10034 arguments and local variables, step into them with @code{step}, skip
10035 them with @code{next}, and escape from them with @code{finish}.
10036 You can check whether a function was inlined by using the
10037 @code{info frame} command.
10039 For @value{GDBN} to support inlined functions, the compiler must
10040 record information about inlining in the debug information ---
10041 @value{NGCC} using the @sc{dwarf 2} format does this, and several
10042 other compilers do also. @value{GDBN} only supports inlined functions
10043 when using @sc{dwarf 2}. Versions of @value{NGCC} before 4.1
10044 do not emit two required attributes (@samp{DW_AT_call_file} and
10045 @samp{DW_AT_call_line}); @value{GDBN} does not display inlined
10046 function calls with earlier versions of @value{NGCC}. It instead
10047 displays the arguments and local variables of inlined functions as
10048 local variables in the caller.
10050 The body of an inlined function is directly included at its call site;
10051 unlike a non-inlined function, there are no instructions devoted to
10052 the call. @value{GDBN} still pretends that the call site and the
10053 start of the inlined function are different instructions. Stepping to
10054 the call site shows the call site, and then stepping again shows
10055 the first line of the inlined function, even though no additional
10056 instructions are executed.
10058 This makes source-level debugging much clearer; you can see both the
10059 context of the call and then the effect of the call. Only stepping by
10060 a single instruction using @code{stepi} or @code{nexti} does not do
10061 this; single instruction steps always show the inlined body.
10063 There are some ways that @value{GDBN} does not pretend that inlined
10064 function calls are the same as normal calls:
10068 Setting breakpoints at the call site of an inlined function may not
10069 work, because the call site does not contain any code. @value{GDBN}
10070 may incorrectly move the breakpoint to the next line of the enclosing
10071 function, after the call. This limitation will be removed in a future
10072 version of @value{GDBN}; until then, set a breakpoint on an earlier line
10073 or inside the inlined function instead.
10076 @value{GDBN} cannot locate the return value of inlined calls after
10077 using the @code{finish} command. This is a limitation of compiler-generated
10078 debugging information; after @code{finish}, you can step to the next line
10079 and print a variable where your program stored the return value.
10083 @node Tail Call Frames
10084 @section Tail Call Frames
10085 @cindex tail call frames, debugging
10087 Function @code{B} can call function @code{C} in its very last statement. In
10088 unoptimized compilation the call of @code{C} is immediately followed by return
10089 instruction at the end of @code{B} code. Optimizing compiler may replace the
10090 call and return in function @code{B} into one jump to function @code{C}
10091 instead. Such use of a jump instruction is called @dfn{tail call}.
10093 During execution of function @code{C}, there will be no indication in the
10094 function call stack frames that it was tail-called from @code{B}. If function
10095 @code{A} regularly calls function @code{B} which tail-calls function @code{C},
10096 then @value{GDBN} will see @code{A} as the caller of @code{C}. However, in
10097 some cases @value{GDBN} can determine that @code{C} was tail-called from
10098 @code{B}, and it will then create fictitious call frame for that, with the
10099 return address set up as if @code{B} called @code{C} normally.
10101 This functionality is currently supported only by DWARF 2 debugging format and
10102 the compiler has to produce @samp{DW_TAG_GNU_call_site} tags. With
10103 @value{NGCC}, you need to specify @option{-O -g} during compilation, to get
10106 @kbd{info frame} command (@pxref{Frame Info}) will indicate the tail call frame
10107 kind by text @code{tail call frame} such as in this sample @value{GDBN} output:
10111 0x40066b <b(int, double)+11>: jmp 0x400640 <c(int, double)>
10113 Stack level 1, frame at 0x7fffffffda30:
10114 rip = 0x40066d in b (amd64-entry-value.cc:59); saved rip 0x4004c5
10115 tail call frame, caller of frame at 0x7fffffffda30
10116 source language c++.
10117 Arglist at unknown address.
10118 Locals at unknown address, Previous frame's sp is 0x7fffffffda30
10121 The detection of all the possible code path executions can find them ambiguous.
10122 There is no execution history stored (possible @ref{Reverse Execution} is never
10123 used for this purpose) and the last known caller could have reached the known
10124 callee by multiple different jump sequences. In such case @value{GDBN} still
10125 tries to show at least all the unambiguous top tail callers and all the
10126 unambiguous bottom tail calees, if any.
10129 @anchor{set debug entry-values}
10130 @item set debug entry-values
10131 @kindex set debug entry-values
10132 When set to on, enables printing of analysis messages for both frame argument
10133 values at function entry and tail calls. It will show all the possible valid
10134 tail calls code paths it has considered. It will also print the intersection
10135 of them with the final unambiguous (possibly partial or even empty) code path
10138 @item show debug entry-values
10139 @kindex show debug entry-values
10140 Show the current state of analysis messages printing for both frame argument
10141 values at function entry and tail calls.
10144 The analysis messages for tail calls can for example show why the virtual tail
10145 call frame for function @code{c} has not been recognized (due to the indirect
10146 reference by variable @code{x}):
10149 static void __attribute__((noinline, noclone)) c (void);
10150 void (*x) (void) = c;
10151 static void __attribute__((noinline, noclone)) a (void) @{ x++; @}
10152 static void __attribute__((noinline, noclone)) c (void) @{ a (); @}
10153 int main (void) @{ x (); return 0; @}
10155 Breakpoint 1, DW_OP_GNU_entry_value resolving cannot find
10156 DW_TAG_GNU_call_site 0x40039a in main
10158 3 static void __attribute__((noinline, noclone)) a (void) @{ x++; @}
10161 #1 0x000000000040039a in main () at t.c:5
10164 Another possibility is an ambiguous virtual tail call frames resolution:
10168 static void __attribute__((noinline, noclone)) f (void) @{ i++; @}
10169 static void __attribute__((noinline, noclone)) e (void) @{ f (); @}
10170 static void __attribute__((noinline, noclone)) d (void) @{ f (); @}
10171 static void __attribute__((noinline, noclone)) c (void) @{ d (); @}
10172 static void __attribute__((noinline, noclone)) b (void)
10173 @{ if (i) c (); else e (); @}
10174 static void __attribute__((noinline, noclone)) a (void) @{ b (); @}
10175 int main (void) @{ a (); return 0; @}
10177 tailcall: initial: 0x4004d2(a) 0x4004ce(b) 0x4004b2(c) 0x4004a2(d)
10178 tailcall: compare: 0x4004d2(a) 0x4004cc(b) 0x400492(e)
10179 tailcall: reduced: 0x4004d2(a) |
10182 #1 0x00000000004004d2 in a () at t.c:8
10183 #2 0x0000000000400395 in main () at t.c:9
10186 @set CALLSEQ1A @code{main@value{ARROW}a@value{ARROW}b@value{ARROW}c@value{ARROW}d@value{ARROW}f}
10187 @set CALLSEQ2A @code{main@value{ARROW}a@value{ARROW}b@value{ARROW}e@value{ARROW}f}
10189 @c Convert CALLSEQ#A to CALLSEQ#B depending on HAVE_MAKEINFO_CLICK.
10190 @ifset HAVE_MAKEINFO_CLICK
10191 @set ARROW @click{}
10192 @set CALLSEQ1B @clicksequence{@value{CALLSEQ1A}}
10193 @set CALLSEQ2B @clicksequence{@value{CALLSEQ2A}}
10195 @ifclear HAVE_MAKEINFO_CLICK
10197 @set CALLSEQ1B @value{CALLSEQ1A}
10198 @set CALLSEQ2B @value{CALLSEQ2A}
10201 Frames #0 and #2 are real, #1 is a virtual tail call frame.
10202 The code can have possible execution paths @value{CALLSEQ1B} or
10203 @value{CALLSEQ2B}, @value{GDBN} cannot find which one from the inferior state.
10205 @code{initial:} state shows some random possible calling sequence @value{GDBN}
10206 has found. It then finds another possible calling sequcen - that one is
10207 prefixed by @code{compare:}. The non-ambiguous intersection of these two is
10208 printed as the @code{reduced:} calling sequence. That one could have many
10209 futher @code{compare:} and @code{reduced:} statements as long as there remain
10210 any non-ambiguous sequence entries.
10212 For the frame of function @code{b} in both cases there are different possible
10213 @code{$pc} values (@code{0x4004cc} or @code{0x4004ce}), therefore this frame is
10214 also ambigous. The only non-ambiguous frame is the one for function @code{a},
10215 therefore this one is displayed to the user while the ambiguous frames are
10218 There can be also reasons why printing of frame argument values at function
10223 static void __attribute__((noinline, noclone)) c (int i) @{ v++; @}
10224 static void __attribute__((noinline, noclone)) a (int i);
10225 static void __attribute__((noinline, noclone)) b (int i) @{ a (i); @}
10226 static void __attribute__((noinline, noclone)) a (int i)
10227 @{ if (i) b (i - 1); else c (0); @}
10228 int main (void) @{ a (5); return 0; @}
10231 #0 c (i=i@@entry=0) at t.c:2
10232 #1 0x0000000000400428 in a (DW_OP_GNU_entry_value resolving has found
10233 function "a" at 0x400420 can call itself via tail calls
10234 i=<optimized out>) at t.c:6
10235 #2 0x000000000040036e in main () at t.c:7
10238 @value{GDBN} cannot find out from the inferior state if and how many times did
10239 function @code{a} call itself (via function @code{b}) as these calls would be
10240 tail calls. Such tail calls would modify thue @code{i} variable, therefore
10241 @value{GDBN} cannot be sure the value it knows would be right - @value{GDBN}
10242 prints @code{<optimized out>} instead.
10245 @chapter C Preprocessor Macros
10247 Some languages, such as C and C@t{++}, provide a way to define and invoke
10248 ``preprocessor macros'' which expand into strings of tokens.
10249 @value{GDBN} can evaluate expressions containing macro invocations, show
10250 the result of macro expansion, and show a macro's definition, including
10251 where it was defined.
10253 You may need to compile your program specially to provide @value{GDBN}
10254 with information about preprocessor macros. Most compilers do not
10255 include macros in their debugging information, even when you compile
10256 with the @option{-g} flag. @xref{Compilation}.
10258 A program may define a macro at one point, remove that definition later,
10259 and then provide a different definition after that. Thus, at different
10260 points in the program, a macro may have different definitions, or have
10261 no definition at all. If there is a current stack frame, @value{GDBN}
10262 uses the macros in scope at that frame's source code line. Otherwise,
10263 @value{GDBN} uses the macros in scope at the current listing location;
10266 Whenever @value{GDBN} evaluates an expression, it always expands any
10267 macro invocations present in the expression. @value{GDBN} also provides
10268 the following commands for working with macros explicitly.
10272 @kindex macro expand
10273 @cindex macro expansion, showing the results of preprocessor
10274 @cindex preprocessor macro expansion, showing the results of
10275 @cindex expanding preprocessor macros
10276 @item macro expand @var{expression}
10277 @itemx macro exp @var{expression}
10278 Show the results of expanding all preprocessor macro invocations in
10279 @var{expression}. Since @value{GDBN} simply expands macros, but does
10280 not parse the result, @var{expression} need not be a valid expression;
10281 it can be any string of tokens.
10284 @item macro expand-once @var{expression}
10285 @itemx macro exp1 @var{expression}
10286 @cindex expand macro once
10287 @i{(This command is not yet implemented.)} Show the results of
10288 expanding those preprocessor macro invocations that appear explicitly in
10289 @var{expression}. Macro invocations appearing in that expansion are
10290 left unchanged. This command allows you to see the effect of a
10291 particular macro more clearly, without being confused by further
10292 expansions. Since @value{GDBN} simply expands macros, but does not
10293 parse the result, @var{expression} need not be a valid expression; it
10294 can be any string of tokens.
10297 @cindex macro definition, showing
10298 @cindex definition of a macro, showing
10299 @cindex macros, from debug info
10300 @item info macro [-a|-all] [--] @var{macro}
10301 Show the current definition or all definitions of the named @var{macro},
10302 and describe the source location or compiler command-line where that
10303 definition was established. The optional double dash is to signify the end of
10304 argument processing and the beginning of @var{macro} for non C-like macros where
10305 the macro may begin with a hyphen.
10307 @kindex info macros
10308 @item info macros @var{linespec}
10309 Show all macro definitions that are in effect at the location specified
10310 by @var{linespec}, and describe the source location or compiler
10311 command-line where those definitions were established.
10313 @kindex macro define
10314 @cindex user-defined macros
10315 @cindex defining macros interactively
10316 @cindex macros, user-defined
10317 @item macro define @var{macro} @var{replacement-list}
10318 @itemx macro define @var{macro}(@var{arglist}) @var{replacement-list}
10319 Introduce a definition for a preprocessor macro named @var{macro},
10320 invocations of which are replaced by the tokens given in
10321 @var{replacement-list}. The first form of this command defines an
10322 ``object-like'' macro, which takes no arguments; the second form
10323 defines a ``function-like'' macro, which takes the arguments given in
10326 A definition introduced by this command is in scope in every
10327 expression evaluated in @value{GDBN}, until it is removed with the
10328 @code{macro undef} command, described below. The definition overrides
10329 all definitions for @var{macro} present in the program being debugged,
10330 as well as any previous user-supplied definition.
10332 @kindex macro undef
10333 @item macro undef @var{macro}
10334 Remove any user-supplied definition for the macro named @var{macro}.
10335 This command only affects definitions provided with the @code{macro
10336 define} command, described above; it cannot remove definitions present
10337 in the program being debugged.
10341 List all the macros defined using the @code{macro define} command.
10344 @cindex macros, example of debugging with
10345 Here is a transcript showing the above commands in action. First, we
10346 show our source files:
10351 #include "sample.h"
10354 #define ADD(x) (M + x)
10359 printf ("Hello, world!\n");
10361 printf ("We're so creative.\n");
10363 printf ("Goodbye, world!\n");
10370 Now, we compile the program using the @sc{gnu} C compiler,
10371 @value{NGCC}. We pass the @option{-gdwarf-2}@footnote{This is the
10372 minimum. Recent versions of @value{NGCC} support @option{-gdwarf-3}
10373 and @option{-gdwarf-4}; we recommend always choosing the most recent
10374 version of DWARF.} @emph{and} @option{-g3} flags to ensure the compiler
10375 includes information about preprocessor macros in the debugging
10379 $ gcc -gdwarf-2 -g3 sample.c -o sample
10383 Now, we start @value{GDBN} on our sample program:
10387 GNU gdb 2002-05-06-cvs
10388 Copyright 2002 Free Software Foundation, Inc.
10389 GDB is free software, @dots{}
10393 We can expand macros and examine their definitions, even when the
10394 program is not running. @value{GDBN} uses the current listing position
10395 to decide which macro definitions are in scope:
10398 (@value{GDBP}) list main
10401 5 #define ADD(x) (M + x)
10406 10 printf ("Hello, world!\n");
10408 12 printf ("We're so creative.\n");
10409 (@value{GDBP}) info macro ADD
10410 Defined at /home/jimb/gdb/macros/play/sample.c:5
10411 #define ADD(x) (M + x)
10412 (@value{GDBP}) info macro Q
10413 Defined at /home/jimb/gdb/macros/play/sample.h:1
10414 included at /home/jimb/gdb/macros/play/sample.c:2
10416 (@value{GDBP}) macro expand ADD(1)
10417 expands to: (42 + 1)
10418 (@value{GDBP}) macro expand-once ADD(1)
10419 expands to: once (M + 1)
10423 In the example above, note that @code{macro expand-once} expands only
10424 the macro invocation explicit in the original text --- the invocation of
10425 @code{ADD} --- but does not expand the invocation of the macro @code{M},
10426 which was introduced by @code{ADD}.
10428 Once the program is running, @value{GDBN} uses the macro definitions in
10429 force at the source line of the current stack frame:
10432 (@value{GDBP}) break main
10433 Breakpoint 1 at 0x8048370: file sample.c, line 10.
10435 Starting program: /home/jimb/gdb/macros/play/sample
10437 Breakpoint 1, main () at sample.c:10
10438 10 printf ("Hello, world!\n");
10442 At line 10, the definition of the macro @code{N} at line 9 is in force:
10445 (@value{GDBP}) info macro N
10446 Defined at /home/jimb/gdb/macros/play/sample.c:9
10448 (@value{GDBP}) macro expand N Q M
10449 expands to: 28 < 42
10450 (@value{GDBP}) print N Q M
10455 As we step over directives that remove @code{N}'s definition, and then
10456 give it a new definition, @value{GDBN} finds the definition (or lack
10457 thereof) in force at each point:
10460 (@value{GDBP}) next
10462 12 printf ("We're so creative.\n");
10463 (@value{GDBP}) info macro N
10464 The symbol `N' has no definition as a C/C++ preprocessor macro
10465 at /home/jimb/gdb/macros/play/sample.c:12
10466 (@value{GDBP}) next
10468 14 printf ("Goodbye, world!\n");
10469 (@value{GDBP}) info macro N
10470 Defined at /home/jimb/gdb/macros/play/sample.c:13
10472 (@value{GDBP}) macro expand N Q M
10473 expands to: 1729 < 42
10474 (@value{GDBP}) print N Q M
10479 In addition to source files, macros can be defined on the compilation command
10480 line using the @option{-D@var{name}=@var{value}} syntax. For macros defined in
10481 such a way, @value{GDBN} displays the location of their definition as line zero
10482 of the source file submitted to the compiler.
10485 (@value{GDBP}) info macro __STDC__
10486 Defined at /home/jimb/gdb/macros/play/sample.c:0
10493 @chapter Tracepoints
10494 @c This chapter is based on the documentation written by Michael
10495 @c Snyder, David Taylor, Jim Blandy, and Elena Zannoni.
10497 @cindex tracepoints
10498 In some applications, it is not feasible for the debugger to interrupt
10499 the program's execution long enough for the developer to learn
10500 anything helpful about its behavior. If the program's correctness
10501 depends on its real-time behavior, delays introduced by a debugger
10502 might cause the program to change its behavior drastically, or perhaps
10503 fail, even when the code itself is correct. It is useful to be able
10504 to observe the program's behavior without interrupting it.
10506 Using @value{GDBN}'s @code{trace} and @code{collect} commands, you can
10507 specify locations in the program, called @dfn{tracepoints}, and
10508 arbitrary expressions to evaluate when those tracepoints are reached.
10509 Later, using the @code{tfind} command, you can examine the values
10510 those expressions had when the program hit the tracepoints. The
10511 expressions may also denote objects in memory---structures or arrays,
10512 for example---whose values @value{GDBN} should record; while visiting
10513 a particular tracepoint, you may inspect those objects as if they were
10514 in memory at that moment. However, because @value{GDBN} records these
10515 values without interacting with you, it can do so quickly and
10516 unobtrusively, hopefully not disturbing the program's behavior.
10518 The tracepoint facility is currently available only for remote
10519 targets. @xref{Targets}. In addition, your remote target must know
10520 how to collect trace data. This functionality is implemented in the
10521 remote stub; however, none of the stubs distributed with @value{GDBN}
10522 support tracepoints as of this writing. The format of the remote
10523 packets used to implement tracepoints are described in @ref{Tracepoint
10526 It is also possible to get trace data from a file, in a manner reminiscent
10527 of corefiles; you specify the filename, and use @code{tfind} to search
10528 through the file. @xref{Trace Files}, for more details.
10530 This chapter describes the tracepoint commands and features.
10533 * Set Tracepoints::
10534 * Analyze Collected Data::
10535 * Tracepoint Variables::
10539 @node Set Tracepoints
10540 @section Commands to Set Tracepoints
10542 Before running such a @dfn{trace experiment}, an arbitrary number of
10543 tracepoints can be set. A tracepoint is actually a special type of
10544 breakpoint (@pxref{Set Breaks}), so you can manipulate it using
10545 standard breakpoint commands. For instance, as with breakpoints,
10546 tracepoint numbers are successive integers starting from one, and many
10547 of the commands associated with tracepoints take the tracepoint number
10548 as their argument, to identify which tracepoint to work on.
10550 For each tracepoint, you can specify, in advance, some arbitrary set
10551 of data that you want the target to collect in the trace buffer when
10552 it hits that tracepoint. The collected data can include registers,
10553 local variables, or global data. Later, you can use @value{GDBN}
10554 commands to examine the values these data had at the time the
10555 tracepoint was hit.
10557 Tracepoints do not support every breakpoint feature. Ignore counts on
10558 tracepoints have no effect, and tracepoints cannot run @value{GDBN}
10559 commands when they are hit. Tracepoints may not be thread-specific
10562 @cindex fast tracepoints
10563 Some targets may support @dfn{fast tracepoints}, which are inserted in
10564 a different way (such as with a jump instead of a trap), that is
10565 faster but possibly restricted in where they may be installed.
10567 @cindex static tracepoints
10568 @cindex markers, static tracepoints
10569 @cindex probing markers, static tracepoints
10570 Regular and fast tracepoints are dynamic tracing facilities, meaning
10571 that they can be used to insert tracepoints at (almost) any location
10572 in the target. Some targets may also support controlling @dfn{static
10573 tracepoints} from @value{GDBN}. With static tracing, a set of
10574 instrumentation points, also known as @dfn{markers}, are embedded in
10575 the target program, and can be activated or deactivated by name or
10576 address. These are usually placed at locations which facilitate
10577 investigating what the target is actually doing. @value{GDBN}'s
10578 support for static tracing includes being able to list instrumentation
10579 points, and attach them with @value{GDBN} defined high level
10580 tracepoints that expose the whole range of convenience of
10581 @value{GDBN}'s tracepoints support. Namely, support for collecting
10582 registers values and values of global or local (to the instrumentation
10583 point) variables; tracepoint conditions and trace state variables.
10584 The act of installing a @value{GDBN} static tracepoint on an
10585 instrumentation point, or marker, is referred to as @dfn{probing} a
10586 static tracepoint marker.
10588 @code{gdbserver} supports tracepoints on some target systems.
10589 @xref{Server,,Tracepoints support in @code{gdbserver}}.
10591 This section describes commands to set tracepoints and associated
10592 conditions and actions.
10595 * Create and Delete Tracepoints::
10596 * Enable and Disable Tracepoints::
10597 * Tracepoint Passcounts::
10598 * Tracepoint Conditions::
10599 * Trace State Variables::
10600 * Tracepoint Actions::
10601 * Listing Tracepoints::
10602 * Listing Static Tracepoint Markers::
10603 * Starting and Stopping Trace Experiments::
10604 * Tracepoint Restrictions::
10607 @node Create and Delete Tracepoints
10608 @subsection Create and Delete Tracepoints
10611 @cindex set tracepoint
10613 @item trace @var{location}
10614 The @code{trace} command is very similar to the @code{break} command.
10615 Its argument @var{location} can be a source line, a function name, or
10616 an address in the target program. @xref{Specify Location}. The
10617 @code{trace} command defines a tracepoint, which is a point in the
10618 target program where the debugger will briefly stop, collect some
10619 data, and then allow the program to continue. Setting a tracepoint or
10620 changing its actions takes effect immediately if the remote stub
10621 supports the @samp{InstallInTrace} feature (@pxref{install tracepoint
10623 If remote stub doesn't support the @samp{InstallInTrace} feature, all
10624 these changes don't take effect until the next @code{tstart}
10625 command, and once a trace experiment is running, further changes will
10626 not have any effect until the next trace experiment starts. In addition,
10627 @value{GDBN} supports @dfn{pending tracepoints}---tracepoints whose
10628 address is not yet resolved. (This is similar to pending breakpoints.)
10629 Pending tracepoints are not downloaded to the target and not installed
10630 until they are resolved. The resolution of pending tracepoints requires
10631 @value{GDBN} support---when debugging with the remote target, and
10632 @value{GDBN} disconnects from the remote stub (@pxref{disconnected
10633 tracing}), pending tracepoints can not be resolved (and downloaded to
10634 the remote stub) while @value{GDBN} is disconnected.
10636 Here are some examples of using the @code{trace} command:
10639 (@value{GDBP}) @b{trace foo.c:121} // a source file and line number
10641 (@value{GDBP}) @b{trace +2} // 2 lines forward
10643 (@value{GDBP}) @b{trace my_function} // first source line of function
10645 (@value{GDBP}) @b{trace *my_function} // EXACT start address of function
10647 (@value{GDBP}) @b{trace *0x2117c4} // an address
10651 You can abbreviate @code{trace} as @code{tr}.
10653 @item trace @var{location} if @var{cond}
10654 Set a tracepoint with condition @var{cond}; evaluate the expression
10655 @var{cond} each time the tracepoint is reached, and collect data only
10656 if the value is nonzero---that is, if @var{cond} evaluates as true.
10657 @xref{Tracepoint Conditions, ,Tracepoint Conditions}, for more
10658 information on tracepoint conditions.
10660 @item ftrace @var{location} [ if @var{cond} ]
10661 @cindex set fast tracepoint
10662 @cindex fast tracepoints, setting
10664 The @code{ftrace} command sets a fast tracepoint. For targets that
10665 support them, fast tracepoints will use a more efficient but possibly
10666 less general technique to trigger data collection, such as a jump
10667 instruction instead of a trap, or some sort of hardware support. It
10668 may not be possible to create a fast tracepoint at the desired
10669 location, in which case the command will exit with an explanatory
10672 @value{GDBN} handles arguments to @code{ftrace} exactly as for
10675 On 32-bit x86-architecture systems, fast tracepoints normally need to
10676 be placed at an instruction that is 5 bytes or longer, but can be
10677 placed at 4-byte instructions if the low 64K of memory of the target
10678 program is available to install trampolines. Some Unix-type systems,
10679 such as @sc{gnu}/Linux, exclude low addresses from the program's
10680 address space; but for instance with the Linux kernel it is possible
10681 to let @value{GDBN} use this area by doing a @command{sysctl} command
10682 to set the @code{mmap_min_addr} kernel parameter, as in
10685 sudo sysctl -w vm.mmap_min_addr=32768
10689 which sets the low address to 32K, which leaves plenty of room for
10690 trampolines. The minimum address should be set to a page boundary.
10692 @item strace @var{location} [ if @var{cond} ]
10693 @cindex set static tracepoint
10694 @cindex static tracepoints, setting
10695 @cindex probe static tracepoint marker
10697 The @code{strace} command sets a static tracepoint. For targets that
10698 support it, setting a static tracepoint probes a static
10699 instrumentation point, or marker, found at @var{location}. It may not
10700 be possible to set a static tracepoint at the desired location, in
10701 which case the command will exit with an explanatory message.
10703 @value{GDBN} handles arguments to @code{strace} exactly as for
10704 @code{trace}, with the addition that the user can also specify
10705 @code{-m @var{marker}} as @var{location}. This probes the marker
10706 identified by the @var{marker} string identifier. This identifier
10707 depends on the static tracepoint backend library your program is
10708 using. You can find all the marker identifiers in the @samp{ID} field
10709 of the @code{info static-tracepoint-markers} command output.
10710 @xref{Listing Static Tracepoint Markers,,Listing Static Tracepoint
10711 Markers}. For example, in the following small program using the UST
10717 trace_mark(ust, bar33, "str %s", "FOOBAZ");
10722 the marker id is composed of joining the first two arguments to the
10723 @code{trace_mark} call with a slash, which translates to:
10726 (@value{GDBP}) info static-tracepoint-markers
10727 Cnt Enb ID Address What
10728 1 n ust/bar33 0x0000000000400ddc in main at stexample.c:22
10734 so you may probe the marker above with:
10737 (@value{GDBP}) strace -m ust/bar33
10740 Static tracepoints accept an extra collect action --- @code{collect
10741 $_sdata}. This collects arbitrary user data passed in the probe point
10742 call to the tracing library. In the UST example above, you'll see
10743 that the third argument to @code{trace_mark} is a printf-like format
10744 string. The user data is then the result of running that formating
10745 string against the following arguments. Note that @code{info
10746 static-tracepoint-markers} command output lists that format string in
10747 the @samp{Data:} field.
10749 You can inspect this data when analyzing the trace buffer, by printing
10750 the $_sdata variable like any other variable available to
10751 @value{GDBN}. @xref{Tracepoint Actions,,Tracepoint Action Lists}.
10754 @cindex last tracepoint number
10755 @cindex recent tracepoint number
10756 @cindex tracepoint number
10757 The convenience variable @code{$tpnum} records the tracepoint number
10758 of the most recently set tracepoint.
10760 @kindex delete tracepoint
10761 @cindex tracepoint deletion
10762 @item delete tracepoint @r{[}@var{num}@r{]}
10763 Permanently delete one or more tracepoints. With no argument, the
10764 default is to delete all tracepoints. Note that the regular
10765 @code{delete} command can remove tracepoints also.
10770 (@value{GDBP}) @b{delete trace 1 2 3} // remove three tracepoints
10772 (@value{GDBP}) @b{delete trace} // remove all tracepoints
10776 You can abbreviate this command as @code{del tr}.
10779 @node Enable and Disable Tracepoints
10780 @subsection Enable and Disable Tracepoints
10782 These commands are deprecated; they are equivalent to plain @code{disable} and @code{enable}.
10785 @kindex disable tracepoint
10786 @item disable tracepoint @r{[}@var{num}@r{]}
10787 Disable tracepoint @var{num}, or all tracepoints if no argument
10788 @var{num} is given. A disabled tracepoint will have no effect during
10789 a trace experiment, but it is not forgotten. You can re-enable
10790 a disabled tracepoint using the @code{enable tracepoint} command.
10791 If the command is issued during a trace experiment and the debug target
10792 has support for disabling tracepoints during a trace experiment, then the
10793 change will be effective immediately. Otherwise, it will be applied to the
10794 next trace experiment.
10796 @kindex enable tracepoint
10797 @item enable tracepoint @r{[}@var{num}@r{]}
10798 Enable tracepoint @var{num}, or all tracepoints. If this command is
10799 issued during a trace experiment and the debug target supports enabling
10800 tracepoints during a trace experiment, then the enabled tracepoints will
10801 become effective immediately. Otherwise, they will become effective the
10802 next time a trace experiment is run.
10805 @node Tracepoint Passcounts
10806 @subsection Tracepoint Passcounts
10810 @cindex tracepoint pass count
10811 @item passcount @r{[}@var{n} @r{[}@var{num}@r{]]}
10812 Set the @dfn{passcount} of a tracepoint. The passcount is a way to
10813 automatically stop a trace experiment. If a tracepoint's passcount is
10814 @var{n}, then the trace experiment will be automatically stopped on
10815 the @var{n}'th time that tracepoint is hit. If the tracepoint number
10816 @var{num} is not specified, the @code{passcount} command sets the
10817 passcount of the most recently defined tracepoint. If no passcount is
10818 given, the trace experiment will run until stopped explicitly by the
10824 (@value{GDBP}) @b{passcount 5 2} // Stop on the 5th execution of
10825 @exdent @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @code{// tracepoint 2}
10827 (@value{GDBP}) @b{passcount 12} // Stop on the 12th execution of the
10828 @exdent @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @code{// most recently defined tracepoint.}
10829 (@value{GDBP}) @b{trace foo}
10830 (@value{GDBP}) @b{pass 3}
10831 (@value{GDBP}) @b{trace bar}
10832 (@value{GDBP}) @b{pass 2}
10833 (@value{GDBP}) @b{trace baz}
10834 (@value{GDBP}) @b{pass 1} // Stop tracing when foo has been
10835 @exdent @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @code{// executed 3 times OR when bar has}
10836 @exdent @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @code{// been executed 2 times}
10837 @exdent @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @code{// OR when baz has been executed 1 time.}
10841 @node Tracepoint Conditions
10842 @subsection Tracepoint Conditions
10843 @cindex conditional tracepoints
10844 @cindex tracepoint conditions
10846 The simplest sort of tracepoint collects data every time your program
10847 reaches a specified place. You can also specify a @dfn{condition} for
10848 a tracepoint. A condition is just a Boolean expression in your
10849 programming language (@pxref{Expressions, ,Expressions}). A
10850 tracepoint with a condition evaluates the expression each time your
10851 program reaches it, and data collection happens only if the condition
10854 Tracepoint conditions can be specified when a tracepoint is set, by
10855 using @samp{if} in the arguments to the @code{trace} command.
10856 @xref{Create and Delete Tracepoints, ,Setting Tracepoints}. They can
10857 also be set or changed at any time with the @code{condition} command,
10858 just as with breakpoints.
10860 Unlike breakpoint conditions, @value{GDBN} does not actually evaluate
10861 the conditional expression itself. Instead, @value{GDBN} encodes the
10862 expression into an agent expression (@pxref{Agent Expressions})
10863 suitable for execution on the target, independently of @value{GDBN}.
10864 Global variables become raw memory locations, locals become stack
10865 accesses, and so forth.
10867 For instance, suppose you have a function that is usually called
10868 frequently, but should not be called after an error has occurred. You
10869 could use the following tracepoint command to collect data about calls
10870 of that function that happen while the error code is propagating
10871 through the program; an unconditional tracepoint could end up
10872 collecting thousands of useless trace frames that you would have to
10876 (@value{GDBP}) @kbd{trace normal_operation if errcode > 0}
10879 @node Trace State Variables
10880 @subsection Trace State Variables
10881 @cindex trace state variables
10883 A @dfn{trace state variable} is a special type of variable that is
10884 created and managed by target-side code. The syntax is the same as
10885 that for GDB's convenience variables (a string prefixed with ``$''),
10886 but they are stored on the target. They must be created explicitly,
10887 using a @code{tvariable} command. They are always 64-bit signed
10890 Trace state variables are remembered by @value{GDBN}, and downloaded
10891 to the target along with tracepoint information when the trace
10892 experiment starts. There are no intrinsic limits on the number of
10893 trace state variables, beyond memory limitations of the target.
10895 @cindex convenience variables, and trace state variables
10896 Although trace state variables are managed by the target, you can use
10897 them in print commands and expressions as if they were convenience
10898 variables; @value{GDBN} will get the current value from the target
10899 while the trace experiment is running. Trace state variables share
10900 the same namespace as other ``$'' variables, which means that you
10901 cannot have trace state variables with names like @code{$23} or
10902 @code{$pc}, nor can you have a trace state variable and a convenience
10903 variable with the same name.
10907 @item tvariable $@var{name} [ = @var{expression} ]
10909 The @code{tvariable} command creates a new trace state variable named
10910 @code{$@var{name}}, and optionally gives it an initial value of
10911 @var{expression}. @var{expression} is evaluated when this command is
10912 entered; the result will be converted to an integer if possible,
10913 otherwise @value{GDBN} will report an error. A subsequent
10914 @code{tvariable} command specifying the same name does not create a
10915 variable, but instead assigns the supplied initial value to the
10916 existing variable of that name, overwriting any previous initial
10917 value. The default initial value is 0.
10919 @item info tvariables
10920 @kindex info tvariables
10921 List all the trace state variables along with their initial values.
10922 Their current values may also be displayed, if the trace experiment is
10925 @item delete tvariable @r{[} $@var{name} @dots{} @r{]}
10926 @kindex delete tvariable
10927 Delete the given trace state variables, or all of them if no arguments
10932 @node Tracepoint Actions
10933 @subsection Tracepoint Action Lists
10937 @cindex tracepoint actions
10938 @item actions @r{[}@var{num}@r{]}
10939 This command will prompt for a list of actions to be taken when the
10940 tracepoint is hit. If the tracepoint number @var{num} is not
10941 specified, this command sets the actions for the one that was most
10942 recently defined (so that you can define a tracepoint and then say
10943 @code{actions} without bothering about its number). You specify the
10944 actions themselves on the following lines, one action at a time, and
10945 terminate the actions list with a line containing just @code{end}. So
10946 far, the only defined actions are @code{collect}, @code{teval}, and
10947 @code{while-stepping}.
10949 @code{actions} is actually equivalent to @code{commands} (@pxref{Break
10950 Commands, ,Breakpoint Command Lists}), except that only the defined
10951 actions are allowed; any other @value{GDBN} command is rejected.
10953 @cindex remove actions from a tracepoint
10954 To remove all actions from a tracepoint, type @samp{actions @var{num}}
10955 and follow it immediately with @samp{end}.
10958 (@value{GDBP}) @b{collect @var{data}} // collect some data
10960 (@value{GDBP}) @b{while-stepping 5} // single-step 5 times, collect data
10962 (@value{GDBP}) @b{end} // signals the end of actions.
10965 In the following example, the action list begins with @code{collect}
10966 commands indicating the things to be collected when the tracepoint is
10967 hit. Then, in order to single-step and collect additional data
10968 following the tracepoint, a @code{while-stepping} command is used,
10969 followed by the list of things to be collected after each step in a
10970 sequence of single steps. The @code{while-stepping} command is
10971 terminated by its own separate @code{end} command. Lastly, the action
10972 list is terminated by an @code{end} command.
10975 (@value{GDBP}) @b{trace foo}
10976 (@value{GDBP}) @b{actions}
10977 Enter actions for tracepoint 1, one per line:
10980 > while-stepping 12
10981 > collect $pc, arr[i]
10986 @kindex collect @r{(tracepoints)}
10987 @item collect@r{[}/@var{mods}@r{]} @var{expr1}, @var{expr2}, @dots{}
10988 Collect values of the given expressions when the tracepoint is hit.
10989 This command accepts a comma-separated list of any valid expressions.
10990 In addition to global, static, or local variables, the following
10991 special arguments are supported:
10995 Collect all registers.
10998 Collect all function arguments.
11001 Collect all local variables.
11004 Collect the return address. This is helpful if you want to see more
11008 @vindex $_sdata@r{, collect}
11009 Collect static tracepoint marker specific data. Only available for
11010 static tracepoints. @xref{Tracepoint Actions,,Tracepoint Action
11011 Lists}. On the UST static tracepoints library backend, an
11012 instrumentation point resembles a @code{printf} function call. The
11013 tracing library is able to collect user specified data formatted to a
11014 character string using the format provided by the programmer that
11015 instrumented the program. Other backends have similar mechanisms.
11016 Here's an example of a UST marker call:
11019 const char master_name[] = "$your_name";
11020 trace_mark(channel1, marker1, "hello %s", master_name)
11023 In this case, collecting @code{$_sdata} collects the string
11024 @samp{hello $yourname}. When analyzing the trace buffer, you can
11025 inspect @samp{$_sdata} like any other variable available to
11029 You can give several consecutive @code{collect} commands, each one
11030 with a single argument, or one @code{collect} command with several
11031 arguments separated by commas; the effect is the same.
11033 The optional @var{mods} changes the usual handling of the arguments.
11034 @code{s} requests that pointers to chars be handled as strings, in
11035 particular collecting the contents of the memory being pointed at, up
11036 to the first zero. The upper bound is by default the value of the
11037 @code{print elements} variable; if @code{s} is followed by a decimal
11038 number, that is the upper bound instead. So for instance
11039 @samp{collect/s25 mystr} collects as many as 25 characters at
11042 The command @code{info scope} (@pxref{Symbols, info scope}) is
11043 particularly useful for figuring out what data to collect.
11045 @kindex teval @r{(tracepoints)}
11046 @item teval @var{expr1}, @var{expr2}, @dots{}
11047 Evaluate the given expressions when the tracepoint is hit. This
11048 command accepts a comma-separated list of expressions. The results
11049 are discarded, so this is mainly useful for assigning values to trace
11050 state variables (@pxref{Trace State Variables}) without adding those
11051 values to the trace buffer, as would be the case if the @code{collect}
11054 @kindex while-stepping @r{(tracepoints)}
11055 @item while-stepping @var{n}
11056 Perform @var{n} single-step instruction traces after the tracepoint,
11057 collecting new data after each step. The @code{while-stepping}
11058 command is followed by the list of what to collect while stepping
11059 (followed by its own @code{end} command):
11062 > while-stepping 12
11063 > collect $regs, myglobal
11069 Note that @code{$pc} is not automatically collected by
11070 @code{while-stepping}; you need to explicitly collect that register if
11071 you need it. You may abbreviate @code{while-stepping} as @code{ws} or
11074 @item set default-collect @var{expr1}, @var{expr2}, @dots{}
11075 @kindex set default-collect
11076 @cindex default collection action
11077 This variable is a list of expressions to collect at each tracepoint
11078 hit. It is effectively an additional @code{collect} action prepended
11079 to every tracepoint action list. The expressions are parsed
11080 individually for each tracepoint, so for instance a variable named
11081 @code{xyz} may be interpreted as a global for one tracepoint, and a
11082 local for another, as appropriate to the tracepoint's location.
11084 @item show default-collect
11085 @kindex show default-collect
11086 Show the list of expressions that are collected by default at each
11091 @node Listing Tracepoints
11092 @subsection Listing Tracepoints
11095 @kindex info tracepoints @r{[}@var{n}@dots{}@r{]}
11096 @kindex info tp @r{[}@var{n}@dots{}@r{]}
11097 @cindex information about tracepoints
11098 @item info tracepoints @r{[}@var{num}@dots{}@r{]}
11099 Display information about the tracepoint @var{num}. If you don't
11100 specify a tracepoint number, displays information about all the
11101 tracepoints defined so far. The format is similar to that used for
11102 @code{info breakpoints}; in fact, @code{info tracepoints} is the same
11103 command, simply restricting itself to tracepoints.
11105 A tracepoint's listing may include additional information specific to
11110 its passcount as given by the @code{passcount @var{n}} command
11114 (@value{GDBP}) @b{info trace}
11115 Num Type Disp Enb Address What
11116 1 tracepoint keep y 0x0804ab57 in foo() at main.cxx:7
11118 collect globfoo, $regs
11127 This command can be abbreviated @code{info tp}.
11130 @node Listing Static Tracepoint Markers
11131 @subsection Listing Static Tracepoint Markers
11134 @kindex info static-tracepoint-markers
11135 @cindex information about static tracepoint markers
11136 @item info static-tracepoint-markers
11137 Display information about all static tracepoint markers defined in the
11140 For each marker, the following columns are printed:
11144 An incrementing counter, output to help readability. This is not a
11147 The marker ID, as reported by the target.
11148 @item Enabled or Disabled
11149 Probed markers are tagged with @samp{y}. @samp{n} identifies marks
11150 that are not enabled.
11152 Where the marker is in your program, as a memory address.
11154 Where the marker is in the source for your program, as a file and line
11155 number. If the debug information included in the program does not
11156 allow @value{GDBN} to locate the source of the marker, this column
11157 will be left blank.
11161 In addition, the following information may be printed for each marker:
11165 User data passed to the tracing library by the marker call. In the
11166 UST backend, this is the format string passed as argument to the
11168 @item Static tracepoints probing the marker
11169 The list of static tracepoints attached to the marker.
11173 (@value{GDBP}) info static-tracepoint-markers
11174 Cnt ID Enb Address What
11175 1 ust/bar2 y 0x0000000000400e1a in main at stexample.c:25
11176 Data: number1 %d number2 %d
11177 Probed by static tracepoints: #2
11178 2 ust/bar33 n 0x0000000000400c87 in main at stexample.c:24
11184 @node Starting and Stopping Trace Experiments
11185 @subsection Starting and Stopping Trace Experiments
11188 @kindex tstart [ @var{notes} ]
11189 @cindex start a new trace experiment
11190 @cindex collected data discarded
11192 This command starts the trace experiment, and begins collecting data.
11193 It has the side effect of discarding all the data collected in the
11194 trace buffer during the previous trace experiment. If any arguments
11195 are supplied, they are taken as a note and stored with the trace
11196 experiment's state. The notes may be arbitrary text, and are
11197 especially useful with disconnected tracing in a multi-user context;
11198 the notes can explain what the trace is doing, supply user contact
11199 information, and so forth.
11201 @kindex tstop [ @var{notes} ]
11202 @cindex stop a running trace experiment
11204 This command stops the trace experiment. If any arguments are
11205 supplied, they are recorded with the experiment as a note. This is
11206 useful if you are stopping a trace started by someone else, for
11207 instance if the trace is interfering with the system's behavior and
11208 needs to be stopped quickly.
11210 @strong{Note}: a trace experiment and data collection may stop
11211 automatically if any tracepoint's passcount is reached
11212 (@pxref{Tracepoint Passcounts}), or if the trace buffer becomes full.
11215 @cindex status of trace data collection
11216 @cindex trace experiment, status of
11218 This command displays the status of the current trace data
11222 Here is an example of the commands we described so far:
11225 (@value{GDBP}) @b{trace gdb_c_test}
11226 (@value{GDBP}) @b{actions}
11227 Enter actions for tracepoint #1, one per line.
11228 > collect $regs,$locals,$args
11229 > while-stepping 11
11233 (@value{GDBP}) @b{tstart}
11234 [time passes @dots{}]
11235 (@value{GDBP}) @b{tstop}
11238 @anchor{disconnected tracing}
11239 @cindex disconnected tracing
11240 You can choose to continue running the trace experiment even if
11241 @value{GDBN} disconnects from the target, voluntarily or
11242 involuntarily. For commands such as @code{detach}, the debugger will
11243 ask what you want to do with the trace. But for unexpected
11244 terminations (@value{GDBN} crash, network outage), it would be
11245 unfortunate to lose hard-won trace data, so the variable
11246 @code{disconnected-tracing} lets you decide whether the trace should
11247 continue running without @value{GDBN}.
11250 @item set disconnected-tracing on
11251 @itemx set disconnected-tracing off
11252 @kindex set disconnected-tracing
11253 Choose whether a tracing run should continue to run if @value{GDBN}
11254 has disconnected from the target. Note that @code{detach} or
11255 @code{quit} will ask you directly what to do about a running trace no
11256 matter what this variable's setting, so the variable is mainly useful
11257 for handling unexpected situations, such as loss of the network.
11259 @item show disconnected-tracing
11260 @kindex show disconnected-tracing
11261 Show the current choice for disconnected tracing.
11265 When you reconnect to the target, the trace experiment may or may not
11266 still be running; it might have filled the trace buffer in the
11267 meantime, or stopped for one of the other reasons. If it is running,
11268 it will continue after reconnection.
11270 Upon reconnection, the target will upload information about the
11271 tracepoints in effect. @value{GDBN} will then compare that
11272 information to the set of tracepoints currently defined, and attempt
11273 to match them up, allowing for the possibility that the numbers may
11274 have changed due to creation and deletion in the meantime. If one of
11275 the target's tracepoints does not match any in @value{GDBN}, the
11276 debugger will create a new tracepoint, so that you have a number with
11277 which to specify that tracepoint. This matching-up process is
11278 necessarily heuristic, and it may result in useless tracepoints being
11279 created; you may simply delete them if they are of no use.
11281 @cindex circular trace buffer
11282 If your target agent supports a @dfn{circular trace buffer}, then you
11283 can run a trace experiment indefinitely without filling the trace
11284 buffer; when space runs out, the agent deletes already-collected trace
11285 frames, oldest first, until there is enough room to continue
11286 collecting. This is especially useful if your tracepoints are being
11287 hit too often, and your trace gets terminated prematurely because the
11288 buffer is full. To ask for a circular trace buffer, simply set
11289 @samp{circular-trace-buffer} to on. You can set this at any time,
11290 including during tracing; if the agent can do it, it will change
11291 buffer handling on the fly, otherwise it will not take effect until
11295 @item set circular-trace-buffer on
11296 @itemx set circular-trace-buffer off
11297 @kindex set circular-trace-buffer
11298 Choose whether a tracing run should use a linear or circular buffer
11299 for trace data. A linear buffer will not lose any trace data, but may
11300 fill up prematurely, while a circular buffer will discard old trace
11301 data, but it will have always room for the latest tracepoint hits.
11303 @item show circular-trace-buffer
11304 @kindex show circular-trace-buffer
11305 Show the current choice for the trace buffer. Note that this may not
11306 match the agent's current buffer handling, nor is it guaranteed to
11307 match the setting that might have been in effect during a past run,
11308 for instance if you are looking at frames from a trace file.
11313 @item set trace-user @var{text}
11314 @kindex set trace-user
11316 @item show trace-user
11317 @kindex show trace-user
11319 @item set trace-notes @var{text}
11320 @kindex set trace-notes
11321 Set the trace run's notes.
11323 @item show trace-notes
11324 @kindex show trace-notes
11325 Show the trace run's notes.
11327 @item set trace-stop-notes @var{text}
11328 @kindex set trace-stop-notes
11329 Set the trace run's stop notes. The handling of the note is as for
11330 @code{tstop} arguments; the set command is convenient way to fix a
11331 stop note that is mistaken or incomplete.
11333 @item show trace-stop-notes
11334 @kindex show trace-stop-notes
11335 Show the trace run's stop notes.
11339 @node Tracepoint Restrictions
11340 @subsection Tracepoint Restrictions
11342 @cindex tracepoint restrictions
11343 There are a number of restrictions on the use of tracepoints. As
11344 described above, tracepoint data gathering occurs on the target
11345 without interaction from @value{GDBN}. Thus the full capabilities of
11346 the debugger are not available during data gathering, and then at data
11347 examination time, you will be limited by only having what was
11348 collected. The following items describe some common problems, but it
11349 is not exhaustive, and you may run into additional difficulties not
11355 Tracepoint expressions are intended to gather objects (lvalues). Thus
11356 the full flexibility of GDB's expression evaluator is not available.
11357 You cannot call functions, cast objects to aggregate types, access
11358 convenience variables or modify values (except by assignment to trace
11359 state variables). Some language features may implicitly call
11360 functions (for instance Objective-C fields with accessors), and therefore
11361 cannot be collected either.
11364 Collection of local variables, either individually or in bulk with
11365 @code{$locals} or @code{$args}, during @code{while-stepping} may
11366 behave erratically. The stepping action may enter a new scope (for
11367 instance by stepping into a function), or the location of the variable
11368 may change (for instance it is loaded into a register). The
11369 tracepoint data recorded uses the location information for the
11370 variables that is correct for the tracepoint location. When the
11371 tracepoint is created, it is not possible, in general, to determine
11372 where the steps of a @code{while-stepping} sequence will advance the
11373 program---particularly if a conditional branch is stepped.
11376 Collection of an incompletely-initialized or partially-destroyed object
11377 may result in something that @value{GDBN} cannot display, or displays
11378 in a misleading way.
11381 When @value{GDBN} displays a pointer to character it automatically
11382 dereferences the pointer to also display characters of the string
11383 being pointed to. However, collecting the pointer during tracing does
11384 not automatically collect the string. You need to explicitly
11385 dereference the pointer and provide size information if you want to
11386 collect not only the pointer, but the memory pointed to. For example,
11387 @code{*ptr@@50} can be used to collect the 50 element array pointed to
11391 It is not possible to collect a complete stack backtrace at a
11392 tracepoint. Instead, you may collect the registers and a few hundred
11393 bytes from the stack pointer with something like @code{*(unsigned char *)$esp@@300}
11394 (adjust to use the name of the actual stack pointer register on your
11395 target architecture, and the amount of stack you wish to capture).
11396 Then the @code{backtrace} command will show a partial backtrace when
11397 using a trace frame. The number of stack frames that can be examined
11398 depends on the sizes of the frames in the collected stack. Note that
11399 if you ask for a block so large that it goes past the bottom of the
11400 stack, the target agent may report an error trying to read from an
11404 If you do not collect registers at a tracepoint, @value{GDBN} can
11405 infer that the value of @code{$pc} must be the same as the address of
11406 the tracepoint and use that when you are looking at a trace frame
11407 for that tracepoint. However, this cannot work if the tracepoint has
11408 multiple locations (for instance if it was set in a function that was
11409 inlined), or if it has a @code{while-stepping} loop. In those cases
11410 @value{GDBN} will warn you that it can't infer @code{$pc}, and default
11415 @node Analyze Collected Data
11416 @section Using the Collected Data
11418 After the tracepoint experiment ends, you use @value{GDBN} commands
11419 for examining the trace data. The basic idea is that each tracepoint
11420 collects a trace @dfn{snapshot} every time it is hit and another
11421 snapshot every time it single-steps. All these snapshots are
11422 consecutively numbered from zero and go into a buffer, and you can
11423 examine them later. The way you examine them is to @dfn{focus} on a
11424 specific trace snapshot. When the remote stub is focused on a trace
11425 snapshot, it will respond to all @value{GDBN} requests for memory and
11426 registers by reading from the buffer which belongs to that snapshot,
11427 rather than from @emph{real} memory or registers of the program being
11428 debugged. This means that @strong{all} @value{GDBN} commands
11429 (@code{print}, @code{info registers}, @code{backtrace}, etc.) will
11430 behave as if we were currently debugging the program state as it was
11431 when the tracepoint occurred. Any requests for data that are not in
11432 the buffer will fail.
11435 * tfind:: How to select a trace snapshot
11436 * tdump:: How to display all data for a snapshot
11437 * save tracepoints:: How to save tracepoints for a future run
11441 @subsection @code{tfind @var{n}}
11444 @cindex select trace snapshot
11445 @cindex find trace snapshot
11446 The basic command for selecting a trace snapshot from the buffer is
11447 @code{tfind @var{n}}, which finds trace snapshot number @var{n},
11448 counting from zero. If no argument @var{n} is given, the next
11449 snapshot is selected.
11451 Here are the various forms of using the @code{tfind} command.
11455 Find the first snapshot in the buffer. This is a synonym for
11456 @code{tfind 0} (since 0 is the number of the first snapshot).
11459 Stop debugging trace snapshots, resume @emph{live} debugging.
11462 Same as @samp{tfind none}.
11465 No argument means find the next trace snapshot.
11468 Find the previous trace snapshot before the current one. This permits
11469 retracing earlier steps.
11471 @item tfind tracepoint @var{num}
11472 Find the next snapshot associated with tracepoint @var{num}. Search
11473 proceeds forward from the last examined trace snapshot. If no
11474 argument @var{num} is given, it means find the next snapshot collected
11475 for the same tracepoint as the current snapshot.
11477 @item tfind pc @var{addr}
11478 Find the next snapshot associated with the value @var{addr} of the
11479 program counter. Search proceeds forward from the last examined trace
11480 snapshot. If no argument @var{addr} is given, it means find the next
11481 snapshot with the same value of PC as the current snapshot.
11483 @item tfind outside @var{addr1}, @var{addr2}
11484 Find the next snapshot whose PC is outside the given range of
11485 addresses (exclusive).
11487 @item tfind range @var{addr1}, @var{addr2}
11488 Find the next snapshot whose PC is between @var{addr1} and
11489 @var{addr2} (inclusive).
11491 @item tfind line @r{[}@var{file}:@r{]}@var{n}
11492 Find the next snapshot associated with the source line @var{n}. If
11493 the optional argument @var{file} is given, refer to line @var{n} in
11494 that source file. Search proceeds forward from the last examined
11495 trace snapshot. If no argument @var{n} is given, it means find the
11496 next line other than the one currently being examined; thus saying
11497 @code{tfind line} repeatedly can appear to have the same effect as
11498 stepping from line to line in a @emph{live} debugging session.
11501 The default arguments for the @code{tfind} commands are specifically
11502 designed to make it easy to scan through the trace buffer. For
11503 instance, @code{tfind} with no argument selects the next trace
11504 snapshot, and @code{tfind -} with no argument selects the previous
11505 trace snapshot. So, by giving one @code{tfind} command, and then
11506 simply hitting @key{RET} repeatedly you can examine all the trace
11507 snapshots in order. Or, by saying @code{tfind -} and then hitting
11508 @key{RET} repeatedly you can examine the snapshots in reverse order.
11509 The @code{tfind line} command with no argument selects the snapshot
11510 for the next source line executed. The @code{tfind pc} command with
11511 no argument selects the next snapshot with the same program counter
11512 (PC) as the current frame. The @code{tfind tracepoint} command with
11513 no argument selects the next trace snapshot collected by the same
11514 tracepoint as the current one.
11516 In addition to letting you scan through the trace buffer manually,
11517 these commands make it easy to construct @value{GDBN} scripts that
11518 scan through the trace buffer and print out whatever collected data
11519 you are interested in. Thus, if we want to examine the PC, FP, and SP
11520 registers from each trace frame in the buffer, we can say this:
11523 (@value{GDBP}) @b{tfind start}
11524 (@value{GDBP}) @b{while ($trace_frame != -1)}
11525 > printf "Frame %d, PC = %08X, SP = %08X, FP = %08X\n", \
11526 $trace_frame, $pc, $sp, $fp
11530 Frame 0, PC = 0020DC64, SP = 0030BF3C, FP = 0030BF44
11531 Frame 1, PC = 0020DC6C, SP = 0030BF38, FP = 0030BF44
11532 Frame 2, PC = 0020DC70, SP = 0030BF34, FP = 0030BF44
11533 Frame 3, PC = 0020DC74, SP = 0030BF30, FP = 0030BF44
11534 Frame 4, PC = 0020DC78, SP = 0030BF2C, FP = 0030BF44
11535 Frame 5, PC = 0020DC7C, SP = 0030BF28, FP = 0030BF44
11536 Frame 6, PC = 0020DC80, SP = 0030BF24, FP = 0030BF44
11537 Frame 7, PC = 0020DC84, SP = 0030BF20, FP = 0030BF44
11538 Frame 8, PC = 0020DC88, SP = 0030BF1C, FP = 0030BF44
11539 Frame 9, PC = 0020DC8E, SP = 0030BF18, FP = 0030BF44
11540 Frame 10, PC = 00203F6C, SP = 0030BE3C, FP = 0030BF14
11543 Or, if we want to examine the variable @code{X} at each source line in
11547 (@value{GDBP}) @b{tfind start}
11548 (@value{GDBP}) @b{while ($trace_frame != -1)}
11549 > printf "Frame %d, X == %d\n", $trace_frame, X
11559 @subsection @code{tdump}
11561 @cindex dump all data collected at tracepoint
11562 @cindex tracepoint data, display
11564 This command takes no arguments. It prints all the data collected at
11565 the current trace snapshot.
11568 (@value{GDBP}) @b{trace 444}
11569 (@value{GDBP}) @b{actions}
11570 Enter actions for tracepoint #2, one per line:
11571 > collect $regs, $locals, $args, gdb_long_test
11574 (@value{GDBP}) @b{tstart}
11576 (@value{GDBP}) @b{tfind line 444}
11577 #0 gdb_test (p1=0x11, p2=0x22, p3=0x33, p4=0x44, p5=0x55, p6=0x66)
11579 444 printp( "%s: arguments = 0x%X 0x%X 0x%X 0x%X 0x%X 0x%X\n", )
11581 (@value{GDBP}) @b{tdump}
11582 Data collected at tracepoint 2, trace frame 1:
11583 d0 0xc4aa0085 -995491707
11587 d4 0x71aea3d 119204413
11590 d7 0x380035 3670069
11591 a0 0x19e24a 1696330
11592 a1 0x3000668 50333288
11594 a3 0x322000 3284992
11595 a4 0x3000698 50333336
11596 a5 0x1ad3cc 1758156
11597 fp 0x30bf3c 0x30bf3c
11598 sp 0x30bf34 0x30bf34
11600 pc 0x20b2c8 0x20b2c8
11604 p = 0x20e5b4 "gdb-test"
11611 gdb_long_test = 17 '\021'
11616 @code{tdump} works by scanning the tracepoint's current collection
11617 actions and printing the value of each expression listed. So
11618 @code{tdump} can fail, if after a run, you change the tracepoint's
11619 actions to mention variables that were not collected during the run.
11621 Also, for tracepoints with @code{while-stepping} loops, @code{tdump}
11622 uses the collected value of @code{$pc} to distinguish between trace
11623 frames that were collected at the tracepoint hit, and frames that were
11624 collected while stepping. This allows it to correctly choose whether
11625 to display the basic list of collections, or the collections from the
11626 body of the while-stepping loop. However, if @code{$pc} was not collected,
11627 then @code{tdump} will always attempt to dump using the basic collection
11628 list, and may fail if a while-stepping frame does not include all the
11629 same data that is collected at the tracepoint hit.
11630 @c This is getting pretty arcane, example would be good.
11632 @node save tracepoints
11633 @subsection @code{save tracepoints @var{filename}}
11634 @kindex save tracepoints
11635 @kindex save-tracepoints
11636 @cindex save tracepoints for future sessions
11638 This command saves all current tracepoint definitions together with
11639 their actions and passcounts, into a file @file{@var{filename}}
11640 suitable for use in a later debugging session. To read the saved
11641 tracepoint definitions, use the @code{source} command (@pxref{Command
11642 Files}). The @w{@code{save-tracepoints}} command is a deprecated
11643 alias for @w{@code{save tracepoints}}
11645 @node Tracepoint Variables
11646 @section Convenience Variables for Tracepoints
11647 @cindex tracepoint variables
11648 @cindex convenience variables for tracepoints
11651 @vindex $trace_frame
11652 @item (int) $trace_frame
11653 The current trace snapshot (a.k.a.@: @dfn{frame}) number, or -1 if no
11654 snapshot is selected.
11656 @vindex $tracepoint
11657 @item (int) $tracepoint
11658 The tracepoint for the current trace snapshot.
11660 @vindex $trace_line
11661 @item (int) $trace_line
11662 The line number for the current trace snapshot.
11664 @vindex $trace_file
11665 @item (char []) $trace_file
11666 The source file for the current trace snapshot.
11668 @vindex $trace_func
11669 @item (char []) $trace_func
11670 The name of the function containing @code{$tracepoint}.
11673 Note: @code{$trace_file} is not suitable for use in @code{printf},
11674 use @code{output} instead.
11676 Here's a simple example of using these convenience variables for
11677 stepping through all the trace snapshots and printing some of their
11678 data. Note that these are not the same as trace state variables,
11679 which are managed by the target.
11682 (@value{GDBP}) @b{tfind start}
11684 (@value{GDBP}) @b{while $trace_frame != -1}
11685 > output $trace_file
11686 > printf ", line %d (tracepoint #%d)\n", $trace_line, $tracepoint
11692 @section Using Trace Files
11693 @cindex trace files
11695 In some situations, the target running a trace experiment may no
11696 longer be available; perhaps it crashed, or the hardware was needed
11697 for a different activity. To handle these cases, you can arrange to
11698 dump the trace data into a file, and later use that file as a source
11699 of trace data, via the @code{target tfile} command.
11704 @item tsave [ -r ] @var{filename}
11705 Save the trace data to @var{filename}. By default, this command
11706 assumes that @var{filename} refers to the host filesystem, so if
11707 necessary @value{GDBN} will copy raw trace data up from the target and
11708 then save it. If the target supports it, you can also supply the
11709 optional argument @code{-r} (``remote'') to direct the target to save
11710 the data directly into @var{filename} in its own filesystem, which may be
11711 more efficient if the trace buffer is very large. (Note, however, that
11712 @code{target tfile} can only read from files accessible to the host.)
11714 @kindex target tfile
11716 @item target tfile @var{filename}
11717 Use the file named @var{filename} as a source of trace data. Commands
11718 that examine data work as they do with a live target, but it is not
11719 possible to run any new trace experiments. @code{tstatus} will report
11720 the state of the trace run at the moment the data was saved, as well
11721 as the current trace frame you are examining. @var{filename} must be
11722 on a filesystem accessible to the host.
11727 @chapter Debugging Programs That Use Overlays
11730 If your program is too large to fit completely in your target system's
11731 memory, you can sometimes use @dfn{overlays} to work around this
11732 problem. @value{GDBN} provides some support for debugging programs that
11736 * How Overlays Work:: A general explanation of overlays.
11737 * Overlay Commands:: Managing overlays in @value{GDBN}.
11738 * Automatic Overlay Debugging:: @value{GDBN} can find out which overlays are
11739 mapped by asking the inferior.
11740 * Overlay Sample Program:: A sample program using overlays.
11743 @node How Overlays Work
11744 @section How Overlays Work
11745 @cindex mapped overlays
11746 @cindex unmapped overlays
11747 @cindex load address, overlay's
11748 @cindex mapped address
11749 @cindex overlay area
11751 Suppose you have a computer whose instruction address space is only 64
11752 kilobytes long, but which has much more memory which can be accessed by
11753 other means: special instructions, segment registers, or memory
11754 management hardware, for example. Suppose further that you want to
11755 adapt a program which is larger than 64 kilobytes to run on this system.
11757 One solution is to identify modules of your program which are relatively
11758 independent, and need not call each other directly; call these modules
11759 @dfn{overlays}. Separate the overlays from the main program, and place
11760 their machine code in the larger memory. Place your main program in
11761 instruction memory, but leave at least enough space there to hold the
11762 largest overlay as well.
11764 Now, to call a function located in an overlay, you must first copy that
11765 overlay's machine code from the large memory into the space set aside
11766 for it in the instruction memory, and then jump to its entry point
11769 @c NB: In the below the mapped area's size is greater or equal to the
11770 @c size of all overlays. This is intentional to remind the developer
11771 @c that overlays don't necessarily need to be the same size.
11775 Data Instruction Larger
11776 Address Space Address Space Address Space
11777 +-----------+ +-----------+ +-----------+
11779 +-----------+ +-----------+ +-----------+<-- overlay 1
11780 | program | | main | .----| overlay 1 | load address
11781 | variables | | program | | +-----------+
11782 | and heap | | | | | |
11783 +-----------+ | | | +-----------+<-- overlay 2
11784 | | +-----------+ | | | load address
11785 +-----------+ | | | .-| overlay 2 |
11787 mapped --->+-----------+ | | +-----------+
11788 address | | | | | |
11789 | overlay | <-' | | |
11790 | area | <---' +-----------+<-- overlay 3
11791 | | <---. | | load address
11792 +-----------+ `--| overlay 3 |
11799 @anchor{A code overlay}A code overlay
11803 The diagram (@pxref{A code overlay}) shows a system with separate data
11804 and instruction address spaces. To map an overlay, the program copies
11805 its code from the larger address space to the instruction address space.
11806 Since the overlays shown here all use the same mapped address, only one
11807 may be mapped at a time. For a system with a single address space for
11808 data and instructions, the diagram would be similar, except that the
11809 program variables and heap would share an address space with the main
11810 program and the overlay area.
11812 An overlay loaded into instruction memory and ready for use is called a
11813 @dfn{mapped} overlay; its @dfn{mapped address} is its address in the
11814 instruction memory. An overlay not present (or only partially present)
11815 in instruction memory is called @dfn{unmapped}; its @dfn{load address}
11816 is its address in the larger memory. The mapped address is also called
11817 the @dfn{virtual memory address}, or @dfn{VMA}; the load address is also
11818 called the @dfn{load memory address}, or @dfn{LMA}.
11820 Unfortunately, overlays are not a completely transparent way to adapt a
11821 program to limited instruction memory. They introduce a new set of
11822 global constraints you must keep in mind as you design your program:
11827 Before calling or returning to a function in an overlay, your program
11828 must make sure that overlay is actually mapped. Otherwise, the call or
11829 return will transfer control to the right address, but in the wrong
11830 overlay, and your program will probably crash.
11833 If the process of mapping an overlay is expensive on your system, you
11834 will need to choose your overlays carefully to minimize their effect on
11835 your program's performance.
11838 The executable file you load onto your system must contain each
11839 overlay's instructions, appearing at the overlay's load address, not its
11840 mapped address. However, each overlay's instructions must be relocated
11841 and its symbols defined as if the overlay were at its mapped address.
11842 You can use GNU linker scripts to specify different load and relocation
11843 addresses for pieces of your program; see @ref{Overlay Description,,,
11844 ld.info, Using ld: the GNU linker}.
11847 The procedure for loading executable files onto your system must be able
11848 to load their contents into the larger address space as well as the
11849 instruction and data spaces.
11853 The overlay system described above is rather simple, and could be
11854 improved in many ways:
11859 If your system has suitable bank switch registers or memory management
11860 hardware, you could use those facilities to make an overlay's load area
11861 contents simply appear at their mapped address in instruction space.
11862 This would probably be faster than copying the overlay to its mapped
11863 area in the usual way.
11866 If your overlays are small enough, you could set aside more than one
11867 overlay area, and have more than one overlay mapped at a time.
11870 You can use overlays to manage data, as well as instructions. In
11871 general, data overlays are even less transparent to your design than
11872 code overlays: whereas code overlays only require care when you call or
11873 return to functions, data overlays require care every time you access
11874 the data. Also, if you change the contents of a data overlay, you
11875 must copy its contents back out to its load address before you can copy a
11876 different data overlay into the same mapped area.
11881 @node Overlay Commands
11882 @section Overlay Commands
11884 To use @value{GDBN}'s overlay support, each overlay in your program must
11885 correspond to a separate section of the executable file. The section's
11886 virtual memory address and load memory address must be the overlay's
11887 mapped and load addresses. Identifying overlays with sections allows
11888 @value{GDBN} to determine the appropriate address of a function or
11889 variable, depending on whether the overlay is mapped or not.
11891 @value{GDBN}'s overlay commands all start with the word @code{overlay};
11892 you can abbreviate this as @code{ov} or @code{ovly}. The commands are:
11897 Disable @value{GDBN}'s overlay support. When overlay support is
11898 disabled, @value{GDBN} assumes that all functions and variables are
11899 always present at their mapped addresses. By default, @value{GDBN}'s
11900 overlay support is disabled.
11902 @item overlay manual
11903 @cindex manual overlay debugging
11904 Enable @dfn{manual} overlay debugging. In this mode, @value{GDBN}
11905 relies on you to tell it which overlays are mapped, and which are not,
11906 using the @code{overlay map-overlay} and @code{overlay unmap-overlay}
11907 commands described below.
11909 @item overlay map-overlay @var{overlay}
11910 @itemx overlay map @var{overlay}
11911 @cindex map an overlay
11912 Tell @value{GDBN} that @var{overlay} is now mapped; @var{overlay} must
11913 be the name of the object file section containing the overlay. When an
11914 overlay is mapped, @value{GDBN} assumes it can find the overlay's
11915 functions and variables at their mapped addresses. @value{GDBN} assumes
11916 that any other overlays whose mapped ranges overlap that of
11917 @var{overlay} are now unmapped.
11919 @item overlay unmap-overlay @var{overlay}
11920 @itemx overlay unmap @var{overlay}
11921 @cindex unmap an overlay
11922 Tell @value{GDBN} that @var{overlay} is no longer mapped; @var{overlay}
11923 must be the name of the object file section containing the overlay.
11924 When an overlay is unmapped, @value{GDBN} assumes it can find the
11925 overlay's functions and variables at their load addresses.
11928 Enable @dfn{automatic} overlay debugging. In this mode, @value{GDBN}
11929 consults a data structure the overlay manager maintains in the inferior
11930 to see which overlays are mapped. For details, see @ref{Automatic
11931 Overlay Debugging}.
11933 @item overlay load-target
11934 @itemx overlay load
11935 @cindex reloading the overlay table
11936 Re-read the overlay table from the inferior. Normally, @value{GDBN}
11937 re-reads the table @value{GDBN} automatically each time the inferior
11938 stops, so this command should only be necessary if you have changed the
11939 overlay mapping yourself using @value{GDBN}. This command is only
11940 useful when using automatic overlay debugging.
11942 @item overlay list-overlays
11943 @itemx overlay list
11944 @cindex listing mapped overlays
11945 Display a list of the overlays currently mapped, along with their mapped
11946 addresses, load addresses, and sizes.
11950 Normally, when @value{GDBN} prints a code address, it includes the name
11951 of the function the address falls in:
11954 (@value{GDBP}) print main
11955 $3 = @{int ()@} 0x11a0 <main>
11958 When overlay debugging is enabled, @value{GDBN} recognizes code in
11959 unmapped overlays, and prints the names of unmapped functions with
11960 asterisks around them. For example, if @code{foo} is a function in an
11961 unmapped overlay, @value{GDBN} prints it this way:
11964 (@value{GDBP}) overlay list
11965 No sections are mapped.
11966 (@value{GDBP}) print foo
11967 $5 = @{int (int)@} 0x100000 <*foo*>
11970 When @code{foo}'s overlay is mapped, @value{GDBN} prints the function's
11974 (@value{GDBP}) overlay list
11975 Section .ov.foo.text, loaded at 0x100000 - 0x100034,
11976 mapped at 0x1016 - 0x104a
11977 (@value{GDBP}) print foo
11978 $6 = @{int (int)@} 0x1016 <foo>
11981 When overlay debugging is enabled, @value{GDBN} can find the correct
11982 address for functions and variables in an overlay, whether or not the
11983 overlay is mapped. This allows most @value{GDBN} commands, like
11984 @code{break} and @code{disassemble}, to work normally, even on unmapped
11985 code. However, @value{GDBN}'s breakpoint support has some limitations:
11989 @cindex breakpoints in overlays
11990 @cindex overlays, setting breakpoints in
11991 You can set breakpoints in functions in unmapped overlays, as long as
11992 @value{GDBN} can write to the overlay at its load address.
11994 @value{GDBN} can not set hardware or simulator-based breakpoints in
11995 unmapped overlays. However, if you set a breakpoint at the end of your
11996 overlay manager (and tell @value{GDBN} which overlays are now mapped, if
11997 you are using manual overlay management), @value{GDBN} will re-set its
11998 breakpoints properly.
12002 @node Automatic Overlay Debugging
12003 @section Automatic Overlay Debugging
12004 @cindex automatic overlay debugging
12006 @value{GDBN} can automatically track which overlays are mapped and which
12007 are not, given some simple co-operation from the overlay manager in the
12008 inferior. If you enable automatic overlay debugging with the
12009 @code{overlay auto} command (@pxref{Overlay Commands}), @value{GDBN}
12010 looks in the inferior's memory for certain variables describing the
12011 current state of the overlays.
12013 Here are the variables your overlay manager must define to support
12014 @value{GDBN}'s automatic overlay debugging:
12018 @item @code{_ovly_table}:
12019 This variable must be an array of the following structures:
12024 /* The overlay's mapped address. */
12027 /* The size of the overlay, in bytes. */
12028 unsigned long size;
12030 /* The overlay's load address. */
12033 /* Non-zero if the overlay is currently mapped;
12035 unsigned long mapped;
12039 @item @code{_novlys}:
12040 This variable must be a four-byte signed integer, holding the total
12041 number of elements in @code{_ovly_table}.
12045 To decide whether a particular overlay is mapped or not, @value{GDBN}
12046 looks for an entry in @w{@code{_ovly_table}} whose @code{vma} and
12047 @code{lma} members equal the VMA and LMA of the overlay's section in the
12048 executable file. When @value{GDBN} finds a matching entry, it consults
12049 the entry's @code{mapped} member to determine whether the overlay is
12052 In addition, your overlay manager may define a function called
12053 @code{_ovly_debug_event}. If this function is defined, @value{GDBN}
12054 will silently set a breakpoint there. If the overlay manager then
12055 calls this function whenever it has changed the overlay table, this
12056 will enable @value{GDBN} to accurately keep track of which overlays
12057 are in program memory, and update any breakpoints that may be set
12058 in overlays. This will allow breakpoints to work even if the
12059 overlays are kept in ROM or other non-writable memory while they
12060 are not being executed.
12062 @node Overlay Sample Program
12063 @section Overlay Sample Program
12064 @cindex overlay example program
12066 When linking a program which uses overlays, you must place the overlays
12067 at their load addresses, while relocating them to run at their mapped
12068 addresses. To do this, you must write a linker script (@pxref{Overlay
12069 Description,,, ld.info, Using ld: the GNU linker}). Unfortunately,
12070 since linker scripts are specific to a particular host system, target
12071 architecture, and target memory layout, this manual cannot provide
12072 portable sample code demonstrating @value{GDBN}'s overlay support.
12074 However, the @value{GDBN} source distribution does contain an overlaid
12075 program, with linker scripts for a few systems, as part of its test
12076 suite. The program consists of the following files from
12077 @file{gdb/testsuite/gdb.base}:
12081 The main program file.
12083 A simple overlay manager, used by @file{overlays.c}.
12088 Overlay modules, loaded and used by @file{overlays.c}.
12091 Linker scripts for linking the test program on the @code{d10v-elf}
12092 and @code{m32r-elf} targets.
12095 You can build the test program using the @code{d10v-elf} GCC
12096 cross-compiler like this:
12099 $ d10v-elf-gcc -g -c overlays.c
12100 $ d10v-elf-gcc -g -c ovlymgr.c
12101 $ d10v-elf-gcc -g -c foo.c
12102 $ d10v-elf-gcc -g -c bar.c
12103 $ d10v-elf-gcc -g -c baz.c
12104 $ d10v-elf-gcc -g -c grbx.c
12105 $ d10v-elf-gcc -g overlays.o ovlymgr.o foo.o bar.o \
12106 baz.o grbx.o -Wl,-Td10v.ld -o overlays
12109 The build process is identical for any other architecture, except that
12110 you must substitute the appropriate compiler and linker script for the
12111 target system for @code{d10v-elf-gcc} and @code{d10v.ld}.
12115 @chapter Using @value{GDBN} with Different Languages
12118 Although programming languages generally have common aspects, they are
12119 rarely expressed in the same manner. For instance, in ANSI C,
12120 dereferencing a pointer @code{p} is accomplished by @code{*p}, but in
12121 Modula-2, it is accomplished by @code{p^}. Values can also be
12122 represented (and displayed) differently. Hex numbers in C appear as
12123 @samp{0x1ae}, while in Modula-2 they appear as @samp{1AEH}.
12125 @cindex working language
12126 Language-specific information is built into @value{GDBN} for some languages,
12127 allowing you to express operations like the above in your program's
12128 native language, and allowing @value{GDBN} to output values in a manner
12129 consistent with the syntax of your program's native language. The
12130 language you use to build expressions is called the @dfn{working
12134 * Setting:: Switching between source languages
12135 * Show:: Displaying the language
12136 * Checks:: Type and range checks
12137 * Supported Languages:: Supported languages
12138 * Unsupported Languages:: Unsupported languages
12142 @section Switching Between Source Languages
12144 There are two ways to control the working language---either have @value{GDBN}
12145 set it automatically, or select it manually yourself. You can use the
12146 @code{set language} command for either purpose. On startup, @value{GDBN}
12147 defaults to setting the language automatically. The working language is
12148 used to determine how expressions you type are interpreted, how values
12151 In addition to the working language, every source file that
12152 @value{GDBN} knows about has its own working language. For some object
12153 file formats, the compiler might indicate which language a particular
12154 source file is in. However, most of the time @value{GDBN} infers the
12155 language from the name of the file. The language of a source file
12156 controls whether C@t{++} names are demangled---this way @code{backtrace} can
12157 show each frame appropriately for its own language. There is no way to
12158 set the language of a source file from within @value{GDBN}, but you can
12159 set the language associated with a filename extension. @xref{Show, ,
12160 Displaying the Language}.
12162 This is most commonly a problem when you use a program, such
12163 as @code{cfront} or @code{f2c}, that generates C but is written in
12164 another language. In that case, make the
12165 program use @code{#line} directives in its C output; that way
12166 @value{GDBN} will know the correct language of the source code of the original
12167 program, and will display that source code, not the generated C code.
12170 * Filenames:: Filename extensions and languages.
12171 * Manually:: Setting the working language manually
12172 * Automatically:: Having @value{GDBN} infer the source language
12176 @subsection List of Filename Extensions and Languages
12178 If a source file name ends in one of the following extensions, then
12179 @value{GDBN} infers that its language is the one indicated.
12197 C@t{++} source file
12203 Objective-C source file
12207 Fortran source file
12210 Modula-2 source file
12214 Assembler source file. This actually behaves almost like C, but
12215 @value{GDBN} does not skip over function prologues when stepping.
12218 In addition, you may set the language associated with a filename
12219 extension. @xref{Show, , Displaying the Language}.
12222 @subsection Setting the Working Language
12224 If you allow @value{GDBN} to set the language automatically,
12225 expressions are interpreted the same way in your debugging session and
12228 @kindex set language
12229 If you wish, you may set the language manually. To do this, issue the
12230 command @samp{set language @var{lang}}, where @var{lang} is the name of
12231 a language, such as
12232 @code{c} or @code{modula-2}.
12233 For a list of the supported languages, type @samp{set language}.
12235 Setting the language manually prevents @value{GDBN} from updating the working
12236 language automatically. This can lead to confusion if you try
12237 to debug a program when the working language is not the same as the
12238 source language, when an expression is acceptable to both
12239 languages---but means different things. For instance, if the current
12240 source file were written in C, and @value{GDBN} was parsing Modula-2, a
12248 might not have the effect you intended. In C, this means to add
12249 @code{b} and @code{c} and place the result in @code{a}. The result
12250 printed would be the value of @code{a}. In Modula-2, this means to compare
12251 @code{a} to the result of @code{b+c}, yielding a @code{BOOLEAN} value.
12253 @node Automatically
12254 @subsection Having @value{GDBN} Infer the Source Language
12256 To have @value{GDBN} set the working language automatically, use
12257 @samp{set language local} or @samp{set language auto}. @value{GDBN}
12258 then infers the working language. That is, when your program stops in a
12259 frame (usually by encountering a breakpoint), @value{GDBN} sets the
12260 working language to the language recorded for the function in that
12261 frame. If the language for a frame is unknown (that is, if the function
12262 or block corresponding to the frame was defined in a source file that
12263 does not have a recognized extension), the current working language is
12264 not changed, and @value{GDBN} issues a warning.
12266 This may not seem necessary for most programs, which are written
12267 entirely in one source language. However, program modules and libraries
12268 written in one source language can be used by a main program written in
12269 a different source language. Using @samp{set language auto} in this
12270 case frees you from having to set the working language manually.
12273 @section Displaying the Language
12275 The following commands help you find out which language is the
12276 working language, and also what language source files were written in.
12279 @item show language
12280 @kindex show language
12281 Display the current working language. This is the
12282 language you can use with commands such as @code{print} to
12283 build and compute expressions that may involve variables in your program.
12286 @kindex info frame@r{, show the source language}
12287 Display the source language for this frame. This language becomes the
12288 working language if you use an identifier from this frame.
12289 @xref{Frame Info, ,Information about a Frame}, to identify the other
12290 information listed here.
12293 @kindex info source@r{, show the source language}
12294 Display the source language of this source file.
12295 @xref{Symbols, ,Examining the Symbol Table}, to identify the other
12296 information listed here.
12299 In unusual circumstances, you may have source files with extensions
12300 not in the standard list. You can then set the extension associated
12301 with a language explicitly:
12304 @item set extension-language @var{ext} @var{language}
12305 @kindex set extension-language
12306 Tell @value{GDBN} that source files with extension @var{ext} are to be
12307 assumed as written in the source language @var{language}.
12309 @item info extensions
12310 @kindex info extensions
12311 List all the filename extensions and the associated languages.
12315 @section Type and Range Checking
12318 @emph{Warning:} In this release, the @value{GDBN} commands for type and range
12319 checking are included, but they do not yet have any effect. This
12320 section documents the intended facilities.
12322 @c FIXME remove warning when type/range code added
12324 Some languages are designed to guard you against making seemingly common
12325 errors through a series of compile- and run-time checks. These include
12326 checking the type of arguments to functions and operators, and making
12327 sure mathematical overflows are caught at run time. Checks such as
12328 these help to ensure a program's correctness once it has been compiled
12329 by eliminating type mismatches, and providing active checks for range
12330 errors when your program is running.
12332 @value{GDBN} can check for conditions like the above if you wish.
12333 Although @value{GDBN} does not check the statements in your program,
12334 it can check expressions entered directly into @value{GDBN} for
12335 evaluation via the @code{print} command, for example. As with the
12336 working language, @value{GDBN} can also decide whether or not to check
12337 automatically based on your program's source language.
12338 @xref{Supported Languages, ,Supported Languages}, for the default
12339 settings of supported languages.
12342 * Type Checking:: An overview of type checking
12343 * Range Checking:: An overview of range checking
12346 @cindex type checking
12347 @cindex checks, type
12348 @node Type Checking
12349 @subsection An Overview of Type Checking
12351 Some languages, such as Modula-2, are strongly typed, meaning that the
12352 arguments to operators and functions have to be of the correct type,
12353 otherwise an error occurs. These checks prevent type mismatch
12354 errors from ever causing any run-time problems. For example,
12362 The second example fails because the @code{CARDINAL} 1 is not
12363 type-compatible with the @code{REAL} 2.3.
12365 For the expressions you use in @value{GDBN} commands, you can tell the
12366 @value{GDBN} type checker to skip checking;
12367 to treat any mismatches as errors and abandon the expression;
12368 or to only issue warnings when type mismatches occur,
12369 but evaluate the expression anyway. When you choose the last of
12370 these, @value{GDBN} evaluates expressions like the second example above, but
12371 also issues a warning.
12373 Even if you turn type checking off, there may be other reasons
12374 related to type that prevent @value{GDBN} from evaluating an expression.
12375 For instance, @value{GDBN} does not know how to add an @code{int} and
12376 a @code{struct foo}. These particular type errors have nothing to do
12377 with the language in use, and usually arise from expressions, such as
12378 the one described above, which make little sense to evaluate anyway.
12380 Each language defines to what degree it is strict about type. For
12381 instance, both Modula-2 and C require the arguments to arithmetical
12382 operators to be numbers. In C, enumerated types and pointers can be
12383 represented as numbers, so that they are valid arguments to mathematical
12384 operators. @xref{Supported Languages, ,Supported Languages}, for further
12385 details on specific languages.
12387 @value{GDBN} provides some additional commands for controlling the type checker:
12389 @kindex set check type
12390 @kindex show check type
12392 @item set check type auto
12393 Set type checking on or off based on the current working language.
12394 @xref{Supported Languages, ,Supported Languages}, for the default settings for
12397 @item set check type on
12398 @itemx set check type off
12399 Set type checking on or off, overriding the default setting for the
12400 current working language. Issue a warning if the setting does not
12401 match the language default. If any type mismatches occur in
12402 evaluating an expression while type checking is on, @value{GDBN} prints a
12403 message and aborts evaluation of the expression.
12405 @item set check type warn
12406 Cause the type checker to issue warnings, but to always attempt to
12407 evaluate the expression. Evaluating the expression may still
12408 be impossible for other reasons. For example, @value{GDBN} cannot add
12409 numbers and structures.
12412 Show the current setting of the type checker, and whether or not @value{GDBN}
12413 is setting it automatically.
12416 @cindex range checking
12417 @cindex checks, range
12418 @node Range Checking
12419 @subsection An Overview of Range Checking
12421 In some languages (such as Modula-2), it is an error to exceed the
12422 bounds of a type; this is enforced with run-time checks. Such range
12423 checking is meant to ensure program correctness by making sure
12424 computations do not overflow, or indices on an array element access do
12425 not exceed the bounds of the array.
12427 For expressions you use in @value{GDBN} commands, you can tell
12428 @value{GDBN} to treat range errors in one of three ways: ignore them,
12429 always treat them as errors and abandon the expression, or issue
12430 warnings but evaluate the expression anyway.
12432 A range error can result from numerical overflow, from exceeding an
12433 array index bound, or when you type a constant that is not a member
12434 of any type. Some languages, however, do not treat overflows as an
12435 error. In many implementations of C, mathematical overflow causes the
12436 result to ``wrap around'' to lower values---for example, if @var{m} is
12437 the largest integer value, and @var{s} is the smallest, then
12440 @var{m} + 1 @result{} @var{s}
12443 This, too, is specific to individual languages, and in some cases
12444 specific to individual compilers or machines. @xref{Supported Languages, ,
12445 Supported Languages}, for further details on specific languages.
12447 @value{GDBN} provides some additional commands for controlling the range checker:
12449 @kindex set check range
12450 @kindex show check range
12452 @item set check range auto
12453 Set range checking on or off based on the current working language.
12454 @xref{Supported Languages, ,Supported Languages}, for the default settings for
12457 @item set check range on
12458 @itemx set check range off
12459 Set range checking on or off, overriding the default setting for the
12460 current working language. A warning is issued if the setting does not
12461 match the language default. If a range error occurs and range checking is on,
12462 then a message is printed and evaluation of the expression is aborted.
12464 @item set check range warn
12465 Output messages when the @value{GDBN} range checker detects a range error,
12466 but attempt to evaluate the expression anyway. Evaluating the
12467 expression may still be impossible for other reasons, such as accessing
12468 memory that the process does not own (a typical example from many Unix
12472 Show the current setting of the range checker, and whether or not it is
12473 being set automatically by @value{GDBN}.
12476 @node Supported Languages
12477 @section Supported Languages
12479 @value{GDBN} supports C, C@t{++}, D, Objective-C, Fortran, Java, OpenCL C, Pascal,
12480 assembly, Modula-2, and Ada.
12481 @c This is false ...
12482 Some @value{GDBN} features may be used in expressions regardless of the
12483 language you use: the @value{GDBN} @code{@@} and @code{::} operators,
12484 and the @samp{@{type@}addr} construct (@pxref{Expressions,
12485 ,Expressions}) can be used with the constructs of any supported
12488 The following sections detail to what degree each source language is
12489 supported by @value{GDBN}. These sections are not meant to be language
12490 tutorials or references, but serve only as a reference guide to what the
12491 @value{GDBN} expression parser accepts, and what input and output
12492 formats should look like for different languages. There are many good
12493 books written on each of these languages; please look to these for a
12494 language reference or tutorial.
12497 * C:: C and C@t{++}
12499 * Objective-C:: Objective-C
12500 * OpenCL C:: OpenCL C
12501 * Fortran:: Fortran
12503 * Modula-2:: Modula-2
12508 @subsection C and C@t{++}
12510 @cindex C and C@t{++}
12511 @cindex expressions in C or C@t{++}
12513 Since C and C@t{++} are so closely related, many features of @value{GDBN} apply
12514 to both languages. Whenever this is the case, we discuss those languages
12518 @cindex @code{g++}, @sc{gnu} C@t{++} compiler
12519 @cindex @sc{gnu} C@t{++}
12520 The C@t{++} debugging facilities are jointly implemented by the C@t{++}
12521 compiler and @value{GDBN}. Therefore, to debug your C@t{++} code
12522 effectively, you must compile your C@t{++} programs with a supported
12523 C@t{++} compiler, such as @sc{gnu} @code{g++}, or the HP ANSI C@t{++}
12524 compiler (@code{aCC}).
12527 * C Operators:: C and C@t{++} operators
12528 * C Constants:: C and C@t{++} constants
12529 * C Plus Plus Expressions:: C@t{++} expressions
12530 * C Defaults:: Default settings for C and C@t{++}
12531 * C Checks:: C and C@t{++} type and range checks
12532 * Debugging C:: @value{GDBN} and C
12533 * Debugging C Plus Plus:: @value{GDBN} features for C@t{++}
12534 * Decimal Floating Point:: Numbers in Decimal Floating Point format
12538 @subsubsection C and C@t{++} Operators
12540 @cindex C and C@t{++} operators
12542 Operators must be defined on values of specific types. For instance,
12543 @code{+} is defined on numbers, but not on structures. Operators are
12544 often defined on groups of types.
12546 For the purposes of C and C@t{++}, the following definitions hold:
12551 @emph{Integral types} include @code{int} with any of its storage-class
12552 specifiers; @code{char}; @code{enum}; and, for C@t{++}, @code{bool}.
12555 @emph{Floating-point types} include @code{float}, @code{double}, and
12556 @code{long double} (if supported by the target platform).
12559 @emph{Pointer types} include all types defined as @code{(@var{type} *)}.
12562 @emph{Scalar types} include all of the above.
12567 The following operators are supported. They are listed here
12568 in order of increasing precedence:
12572 The comma or sequencing operator. Expressions in a comma-separated list
12573 are evaluated from left to right, with the result of the entire
12574 expression being the last expression evaluated.
12577 Assignment. The value of an assignment expression is the value
12578 assigned. Defined on scalar types.
12581 Used in an expression of the form @w{@code{@var{a} @var{op}= @var{b}}},
12582 and translated to @w{@code{@var{a} = @var{a op b}}}.
12583 @w{@code{@var{op}=}} and @code{=} have the same precedence.
12584 @var{op} is any one of the operators @code{|}, @code{^}, @code{&},
12585 @code{<<}, @code{>>}, @code{+}, @code{-}, @code{*}, @code{/}, @code{%}.
12588 The ternary operator. @code{@var{a} ? @var{b} : @var{c}} can be thought
12589 of as: if @var{a} then @var{b} else @var{c}. @var{a} should be of an
12593 Logical @sc{or}. Defined on integral types.
12596 Logical @sc{and}. Defined on integral types.
12599 Bitwise @sc{or}. Defined on integral types.
12602 Bitwise exclusive-@sc{or}. Defined on integral types.
12605 Bitwise @sc{and}. Defined on integral types.
12608 Equality and inequality. Defined on scalar types. The value of these
12609 expressions is 0 for false and non-zero for true.
12611 @item <@r{, }>@r{, }<=@r{, }>=
12612 Less than, greater than, less than or equal, greater than or equal.
12613 Defined on scalar types. The value of these expressions is 0 for false
12614 and non-zero for true.
12617 left shift, and right shift. Defined on integral types.
12620 The @value{GDBN} ``artificial array'' operator (@pxref{Expressions, ,Expressions}).
12623 Addition and subtraction. Defined on integral types, floating-point types and
12626 @item *@r{, }/@r{, }%
12627 Multiplication, division, and modulus. Multiplication and division are
12628 defined on integral and floating-point types. Modulus is defined on
12632 Increment and decrement. When appearing before a variable, the
12633 operation is performed before the variable is used in an expression;
12634 when appearing after it, the variable's value is used before the
12635 operation takes place.
12638 Pointer dereferencing. Defined on pointer types. Same precedence as
12642 Address operator. Defined on variables. Same precedence as @code{++}.
12644 For debugging C@t{++}, @value{GDBN} implements a use of @samp{&} beyond what is
12645 allowed in the C@t{++} language itself: you can use @samp{&(&@var{ref})}
12646 to examine the address
12647 where a C@t{++} reference variable (declared with @samp{&@var{ref}}) is
12651 Negative. Defined on integral and floating-point types. Same
12652 precedence as @code{++}.
12655 Logical negation. Defined on integral types. Same precedence as
12659 Bitwise complement operator. Defined on integral types. Same precedence as
12664 Structure member, and pointer-to-structure member. For convenience,
12665 @value{GDBN} regards the two as equivalent, choosing whether to dereference a
12666 pointer based on the stored type information.
12667 Defined on @code{struct} and @code{union} data.
12670 Dereferences of pointers to members.
12673 Array indexing. @code{@var{a}[@var{i}]} is defined as
12674 @code{*(@var{a}+@var{i})}. Same precedence as @code{->}.
12677 Function parameter list. Same precedence as @code{->}.
12680 C@t{++} scope resolution operator. Defined on @code{struct}, @code{union},
12681 and @code{class} types.
12684 Doubled colons also represent the @value{GDBN} scope operator
12685 (@pxref{Expressions, ,Expressions}). Same precedence as @code{::},
12689 If an operator is redefined in the user code, @value{GDBN} usually
12690 attempts to invoke the redefined version instead of using the operator's
12691 predefined meaning.
12694 @subsubsection C and C@t{++} Constants
12696 @cindex C and C@t{++} constants
12698 @value{GDBN} allows you to express the constants of C and C@t{++} in the
12703 Integer constants are a sequence of digits. Octal constants are
12704 specified by a leading @samp{0} (i.e.@: zero), and hexadecimal constants
12705 by a leading @samp{0x} or @samp{0X}. Constants may also end with a letter
12706 @samp{l}, specifying that the constant should be treated as a
12710 Floating point constants are a sequence of digits, followed by a decimal
12711 point, followed by a sequence of digits, and optionally followed by an
12712 exponent. An exponent is of the form:
12713 @samp{@w{e@r{[[}+@r{]|}-@r{]}@var{nnn}}}, where @var{nnn} is another
12714 sequence of digits. The @samp{+} is optional for positive exponents.
12715 A floating-point constant may also end with a letter @samp{f} or
12716 @samp{F}, specifying that the constant should be treated as being of
12717 the @code{float} (as opposed to the default @code{double}) type; or with
12718 a letter @samp{l} or @samp{L}, which specifies a @code{long double}
12722 Enumerated constants consist of enumerated identifiers, or their
12723 integral equivalents.
12726 Character constants are a single character surrounded by single quotes
12727 (@code{'}), or a number---the ordinal value of the corresponding character
12728 (usually its @sc{ascii} value). Within quotes, the single character may
12729 be represented by a letter or by @dfn{escape sequences}, which are of
12730 the form @samp{\@var{nnn}}, where @var{nnn} is the octal representation
12731 of the character's ordinal value; or of the form @samp{\@var{x}}, where
12732 @samp{@var{x}} is a predefined special character---for example,
12733 @samp{\n} for newline.
12735 Wide character constants can be written by prefixing a character
12736 constant with @samp{L}, as in C. For example, @samp{L'x'} is the wide
12737 form of @samp{x}. The target wide character set is used when
12738 computing the value of this constant (@pxref{Character Sets}).
12741 String constants are a sequence of character constants surrounded by
12742 double quotes (@code{"}). Any valid character constant (as described
12743 above) may appear. Double quotes within the string must be preceded by
12744 a backslash, so for instance @samp{"a\"b'c"} is a string of five
12747 Wide string constants can be written by prefixing a string constant
12748 with @samp{L}, as in C. The target wide character set is used when
12749 computing the value of this constant (@pxref{Character Sets}).
12752 Pointer constants are an integral value. You can also write pointers
12753 to constants using the C operator @samp{&}.
12756 Array constants are comma-separated lists surrounded by braces @samp{@{}
12757 and @samp{@}}; for example, @samp{@{1,2,3@}} is a three-element array of
12758 integers, @samp{@{@{1,2@}, @{3,4@}, @{5,6@}@}} is a three-by-two array,
12759 and @samp{@{&"hi", &"there", &"fred"@}} is a three-element array of pointers.
12762 @node C Plus Plus Expressions
12763 @subsubsection C@t{++} Expressions
12765 @cindex expressions in C@t{++}
12766 @value{GDBN} expression handling can interpret most C@t{++} expressions.
12768 @cindex debugging C@t{++} programs
12769 @cindex C@t{++} compilers
12770 @cindex debug formats and C@t{++}
12771 @cindex @value{NGCC} and C@t{++}
12773 @emph{Warning:} @value{GDBN} can only debug C@t{++} code if you use
12774 the proper compiler and the proper debug format. Currently,
12775 @value{GDBN} works best when debugging C@t{++} code that is compiled
12776 with the most recent version of @value{NGCC} possible. The DWARF
12777 debugging format is preferred; @value{NGCC} defaults to this on most
12778 popular platforms. Other compilers and/or debug formats are likely to
12779 work badly or not at all when using @value{GDBN} to debug C@t{++}
12780 code. @xref{Compilation}.
12785 @cindex member functions
12787 Member function calls are allowed; you can use expressions like
12790 count = aml->GetOriginal(x, y)
12793 @vindex this@r{, inside C@t{++} member functions}
12794 @cindex namespace in C@t{++}
12796 While a member function is active (in the selected stack frame), your
12797 expressions have the same namespace available as the member function;
12798 that is, @value{GDBN} allows implicit references to the class instance
12799 pointer @code{this} following the same rules as C@t{++}. @code{using}
12800 declarations in the current scope are also respected by @value{GDBN}.
12802 @cindex call overloaded functions
12803 @cindex overloaded functions, calling
12804 @cindex type conversions in C@t{++}
12806 You can call overloaded functions; @value{GDBN} resolves the function
12807 call to the right definition, with some restrictions. @value{GDBN} does not
12808 perform overload resolution involving user-defined type conversions,
12809 calls to constructors, or instantiations of templates that do not exist
12810 in the program. It also cannot handle ellipsis argument lists or
12813 It does perform integral conversions and promotions, floating-point
12814 promotions, arithmetic conversions, pointer conversions, conversions of
12815 class objects to base classes, and standard conversions such as those of
12816 functions or arrays to pointers; it requires an exact match on the
12817 number of function arguments.
12819 Overload resolution is always performed, unless you have specified
12820 @code{set overload-resolution off}. @xref{Debugging C Plus Plus,
12821 ,@value{GDBN} Features for C@t{++}}.
12823 You must specify @code{set overload-resolution off} in order to use an
12824 explicit function signature to call an overloaded function, as in
12826 p 'foo(char,int)'('x', 13)
12829 The @value{GDBN} command-completion facility can simplify this;
12830 see @ref{Completion, ,Command Completion}.
12832 @cindex reference declarations
12834 @value{GDBN} understands variables declared as C@t{++} references; you can use
12835 them in expressions just as you do in C@t{++} source---they are automatically
12838 In the parameter list shown when @value{GDBN} displays a frame, the values of
12839 reference variables are not displayed (unlike other variables); this
12840 avoids clutter, since references are often used for large structures.
12841 The @emph{address} of a reference variable is always shown, unless
12842 you have specified @samp{set print address off}.
12845 @value{GDBN} supports the C@t{++} name resolution operator @code{::}---your
12846 expressions can use it just as expressions in your program do. Since
12847 one scope may be defined in another, you can use @code{::} repeatedly if
12848 necessary, for example in an expression like
12849 @samp{@var{scope1}::@var{scope2}::@var{name}}. @value{GDBN} also allows
12850 resolving name scope by reference to source files, in both C and C@t{++}
12851 debugging (@pxref{Variables, ,Program Variables}).
12854 @value{GDBN} performs argument-dependent lookup, following the C@t{++}
12859 @subsubsection C and C@t{++} Defaults
12861 @cindex C and C@t{++} defaults
12863 If you allow @value{GDBN} to set type and range checking automatically, they
12864 both default to @code{off} whenever the working language changes to
12865 C or C@t{++}. This happens regardless of whether you or @value{GDBN}
12866 selects the working language.
12868 If you allow @value{GDBN} to set the language automatically, it
12869 recognizes source files whose names end with @file{.c}, @file{.C}, or
12870 @file{.cc}, etc, and when @value{GDBN} enters code compiled from one of
12871 these files, it sets the working language to C or C@t{++}.
12872 @xref{Automatically, ,Having @value{GDBN} Infer the Source Language},
12873 for further details.
12875 @c Type checking is (a) primarily motivated by Modula-2, and (b)
12876 @c unimplemented. If (b) changes, it might make sense to let this node
12877 @c appear even if Mod-2 does not, but meanwhile ignore it. roland 16jul93.
12880 @subsubsection C and C@t{++} Type and Range Checks
12882 @cindex C and C@t{++} checks
12884 By default, when @value{GDBN} parses C or C@t{++} expressions, type checking
12885 is not used. However, if you turn type checking on, @value{GDBN}
12886 considers two variables type equivalent if:
12890 The two variables are structured and have the same structure, union, or
12894 The two variables have the same type name, or types that have been
12895 declared equivalent through @code{typedef}.
12898 @c leaving this out because neither J Gilmore nor R Pesch understand it.
12901 The two @code{struct}, @code{union}, or @code{enum} variables are
12902 declared in the same declaration. (Note: this may not be true for all C
12907 Range checking, if turned on, is done on mathematical operations. Array
12908 indices are not checked, since they are often used to index a pointer
12909 that is not itself an array.
12912 @subsubsection @value{GDBN} and C
12914 The @code{set print union} and @code{show print union} commands apply to
12915 the @code{union} type. When set to @samp{on}, any @code{union} that is
12916 inside a @code{struct} or @code{class} is also printed. Otherwise, it
12917 appears as @samp{@{...@}}.
12919 The @code{@@} operator aids in the debugging of dynamic arrays, formed
12920 with pointers and a memory allocation function. @xref{Expressions,
12923 @node Debugging C Plus Plus
12924 @subsubsection @value{GDBN} Features for C@t{++}
12926 @cindex commands for C@t{++}
12928 Some @value{GDBN} commands are particularly useful with C@t{++}, and some are
12929 designed specifically for use with C@t{++}. Here is a summary:
12932 @cindex break in overloaded functions
12933 @item @r{breakpoint menus}
12934 When you want a breakpoint in a function whose name is overloaded,
12935 @value{GDBN} has the capability to display a menu of possible breakpoint
12936 locations to help you specify which function definition you want.
12937 @xref{Ambiguous Expressions,,Ambiguous Expressions}.
12939 @cindex overloading in C@t{++}
12940 @item rbreak @var{regex}
12941 Setting breakpoints using regular expressions is helpful for setting
12942 breakpoints on overloaded functions that are not members of any special
12944 @xref{Set Breaks, ,Setting Breakpoints}.
12946 @cindex C@t{++} exception handling
12949 Debug C@t{++} exception handling using these commands. @xref{Set
12950 Catchpoints, , Setting Catchpoints}.
12952 @cindex inheritance
12953 @item ptype @var{typename}
12954 Print inheritance relationships as well as other information for type
12956 @xref{Symbols, ,Examining the Symbol Table}.
12958 @item info vtbl @var{expression}.
12959 The @code{info vtbl} command can be used to display the virtual
12960 method tables of the object computed by @var{expression}. This shows
12961 one entry per virtual table; there may be multiple virtual tables when
12962 multiple inheritance is in use.
12964 @cindex C@t{++} symbol display
12965 @item set print demangle
12966 @itemx show print demangle
12967 @itemx set print asm-demangle
12968 @itemx show print asm-demangle
12969 Control whether C@t{++} symbols display in their source form, both when
12970 displaying code as C@t{++} source and when displaying disassemblies.
12971 @xref{Print Settings, ,Print Settings}.
12973 @item set print object
12974 @itemx show print object
12975 Choose whether to print derived (actual) or declared types of objects.
12976 @xref{Print Settings, ,Print Settings}.
12978 @item set print vtbl
12979 @itemx show print vtbl
12980 Control the format for printing virtual function tables.
12981 @xref{Print Settings, ,Print Settings}.
12982 (The @code{vtbl} commands do not work on programs compiled with the HP
12983 ANSI C@t{++} compiler (@code{aCC}).)
12985 @kindex set overload-resolution
12986 @cindex overloaded functions, overload resolution
12987 @item set overload-resolution on
12988 Enable overload resolution for C@t{++} expression evaluation. The default
12989 is on. For overloaded functions, @value{GDBN} evaluates the arguments
12990 and searches for a function whose signature matches the argument types,
12991 using the standard C@t{++} conversion rules (see @ref{C Plus Plus
12992 Expressions, ,C@t{++} Expressions}, for details).
12993 If it cannot find a match, it emits a message.
12995 @item set overload-resolution off
12996 Disable overload resolution for C@t{++} expression evaluation. For
12997 overloaded functions that are not class member functions, @value{GDBN}
12998 chooses the first function of the specified name that it finds in the
12999 symbol table, whether or not its arguments are of the correct type. For
13000 overloaded functions that are class member functions, @value{GDBN}
13001 searches for a function whose signature @emph{exactly} matches the
13004 @kindex show overload-resolution
13005 @item show overload-resolution
13006 Show the current setting of overload resolution.
13008 @item @r{Overloaded symbol names}
13009 You can specify a particular definition of an overloaded symbol, using
13010 the same notation that is used to declare such symbols in C@t{++}: type
13011 @code{@var{symbol}(@var{types})} rather than just @var{symbol}. You can
13012 also use the @value{GDBN} command-line word completion facilities to list the
13013 available choices, or to finish the type list for you.
13014 @xref{Completion,, Command Completion}, for details on how to do this.
13017 @node Decimal Floating Point
13018 @subsubsection Decimal Floating Point format
13019 @cindex decimal floating point format
13021 @value{GDBN} can examine, set and perform computations with numbers in
13022 decimal floating point format, which in the C language correspond to the
13023 @code{_Decimal32}, @code{_Decimal64} and @code{_Decimal128} types as
13024 specified by the extension to support decimal floating-point arithmetic.
13026 There are two encodings in use, depending on the architecture: BID (Binary
13027 Integer Decimal) for x86 and x86-64, and DPD (Densely Packed Decimal) for
13028 PowerPC. @value{GDBN} will use the appropriate encoding for the configured
13031 Because of a limitation in @file{libdecnumber}, the library used by @value{GDBN}
13032 to manipulate decimal floating point numbers, it is not possible to convert
13033 (using a cast, for example) integers wider than 32-bit to decimal float.
13035 In addition, in order to imitate @value{GDBN}'s behaviour with binary floating
13036 point computations, error checking in decimal float operations ignores
13037 underflow, overflow and divide by zero exceptions.
13039 In the PowerPC architecture, @value{GDBN} provides a set of pseudo-registers
13040 to inspect @code{_Decimal128} values stored in floating point registers.
13041 See @ref{PowerPC,,PowerPC} for more details.
13047 @value{GDBN} can be used to debug programs written in D and compiled with
13048 GDC, LDC or DMD compilers. Currently @value{GDBN} supports only one D
13049 specific feature --- dynamic arrays.
13052 @subsection Objective-C
13054 @cindex Objective-C
13055 This section provides information about some commands and command
13056 options that are useful for debugging Objective-C code. See also
13057 @ref{Symbols, info classes}, and @ref{Symbols, info selectors}, for a
13058 few more commands specific to Objective-C support.
13061 * Method Names in Commands::
13062 * The Print Command with Objective-C::
13065 @node Method Names in Commands
13066 @subsubsection Method Names in Commands
13068 The following commands have been extended to accept Objective-C method
13069 names as line specifications:
13071 @kindex clear@r{, and Objective-C}
13072 @kindex break@r{, and Objective-C}
13073 @kindex info line@r{, and Objective-C}
13074 @kindex jump@r{, and Objective-C}
13075 @kindex list@r{, and Objective-C}
13079 @item @code{info line}
13084 A fully qualified Objective-C method name is specified as
13087 -[@var{Class} @var{methodName}]
13090 where the minus sign is used to indicate an instance method and a
13091 plus sign (not shown) is used to indicate a class method. The class
13092 name @var{Class} and method name @var{methodName} are enclosed in
13093 brackets, similar to the way messages are specified in Objective-C
13094 source code. For example, to set a breakpoint at the @code{create}
13095 instance method of class @code{Fruit} in the program currently being
13099 break -[Fruit create]
13102 To list ten program lines around the @code{initialize} class method,
13106 list +[NSText initialize]
13109 In the current version of @value{GDBN}, the plus or minus sign is
13110 required. In future versions of @value{GDBN}, the plus or minus
13111 sign will be optional, but you can use it to narrow the search. It
13112 is also possible to specify just a method name:
13118 You must specify the complete method name, including any colons. If
13119 your program's source files contain more than one @code{create} method,
13120 you'll be presented with a numbered list of classes that implement that
13121 method. Indicate your choice by number, or type @samp{0} to exit if
13124 As another example, to clear a breakpoint established at the
13125 @code{makeKeyAndOrderFront:} method of the @code{NSWindow} class, enter:
13128 clear -[NSWindow makeKeyAndOrderFront:]
13131 @node The Print Command with Objective-C
13132 @subsubsection The Print Command With Objective-C
13133 @cindex Objective-C, print objects
13134 @kindex print-object
13135 @kindex po @r{(@code{print-object})}
13137 The print command has also been extended to accept methods. For example:
13140 print -[@var{object} hash]
13143 @cindex print an Objective-C object description
13144 @cindex @code{_NSPrintForDebugger}, and printing Objective-C objects
13146 will tell @value{GDBN} to send the @code{hash} message to @var{object}
13147 and print the result. Also, an additional command has been added,
13148 @code{print-object} or @code{po} for short, which is meant to print
13149 the description of an object. However, this command may only work
13150 with certain Objective-C libraries that have a particular hook
13151 function, @code{_NSPrintForDebugger}, defined.
13154 @subsection OpenCL C
13157 This section provides information about @value{GDBN}s OpenCL C support.
13160 * OpenCL C Datatypes::
13161 * OpenCL C Expressions::
13162 * OpenCL C Operators::
13165 @node OpenCL C Datatypes
13166 @subsubsection OpenCL C Datatypes
13168 @cindex OpenCL C Datatypes
13169 @value{GDBN} supports the builtin scalar and vector datatypes specified
13170 by OpenCL 1.1. In addition the half- and double-precision floating point
13171 data types of the @code{cl_khr_fp16} and @code{cl_khr_fp64} OpenCL
13172 extensions are also known to @value{GDBN}.
13174 @node OpenCL C Expressions
13175 @subsubsection OpenCL C Expressions
13177 @cindex OpenCL C Expressions
13178 @value{GDBN} supports accesses to vector components including the access as
13179 lvalue where possible. Since OpenCL C is based on C99 most C expressions
13180 supported by @value{GDBN} can be used as well.
13182 @node OpenCL C Operators
13183 @subsubsection OpenCL C Operators
13185 @cindex OpenCL C Operators
13186 @value{GDBN} supports the operators specified by OpenCL 1.1 for scalar and
13190 @subsection Fortran
13191 @cindex Fortran-specific support in @value{GDBN}
13193 @value{GDBN} can be used to debug programs written in Fortran, but it
13194 currently supports only the features of Fortran 77 language.
13196 @cindex trailing underscore, in Fortran symbols
13197 Some Fortran compilers (@sc{gnu} Fortran 77 and Fortran 95 compilers
13198 among them) append an underscore to the names of variables and
13199 functions. When you debug programs compiled by those compilers, you
13200 will need to refer to variables and functions with a trailing
13204 * Fortran Operators:: Fortran operators and expressions
13205 * Fortran Defaults:: Default settings for Fortran
13206 * Special Fortran Commands:: Special @value{GDBN} commands for Fortran
13209 @node Fortran Operators
13210 @subsubsection Fortran Operators and Expressions
13212 @cindex Fortran operators and expressions
13214 Operators must be defined on values of specific types. For instance,
13215 @code{+} is defined on numbers, but not on characters or other non-
13216 arithmetic types. Operators are often defined on groups of types.
13220 The exponentiation operator. It raises the first operand to the power
13224 The range operator. Normally used in the form of array(low:high) to
13225 represent a section of array.
13228 The access component operator. Normally used to access elements in derived
13229 types. Also suitable for unions. As unions aren't part of regular Fortran,
13230 this can only happen when accessing a register that uses a gdbarch-defined
13234 @node Fortran Defaults
13235 @subsubsection Fortran Defaults
13237 @cindex Fortran Defaults
13239 Fortran symbols are usually case-insensitive, so @value{GDBN} by
13240 default uses case-insensitive matches for Fortran symbols. You can
13241 change that with the @samp{set case-insensitive} command, see
13242 @ref{Symbols}, for the details.
13244 @node Special Fortran Commands
13245 @subsubsection Special Fortran Commands
13247 @cindex Special Fortran commands
13249 @value{GDBN} has some commands to support Fortran-specific features,
13250 such as displaying common blocks.
13253 @cindex @code{COMMON} blocks, Fortran
13254 @kindex info common
13255 @item info common @r{[}@var{common-name}@r{]}
13256 This command prints the values contained in the Fortran @code{COMMON}
13257 block whose name is @var{common-name}. With no argument, the names of
13258 all @code{COMMON} blocks visible at the current program location are
13265 @cindex Pascal support in @value{GDBN}, limitations
13266 Debugging Pascal programs which use sets, subranges, file variables, or
13267 nested functions does not currently work. @value{GDBN} does not support
13268 entering expressions, printing values, or similar features using Pascal
13271 The Pascal-specific command @code{set print pascal_static-members}
13272 controls whether static members of Pascal objects are displayed.
13273 @xref{Print Settings, pascal_static-members}.
13276 @subsection Modula-2
13278 @cindex Modula-2, @value{GDBN} support
13280 The extensions made to @value{GDBN} to support Modula-2 only support
13281 output from the @sc{gnu} Modula-2 compiler (which is currently being
13282 developed). Other Modula-2 compilers are not currently supported, and
13283 attempting to debug executables produced by them is most likely
13284 to give an error as @value{GDBN} reads in the executable's symbol
13287 @cindex expressions in Modula-2
13289 * M2 Operators:: Built-in operators
13290 * Built-In Func/Proc:: Built-in functions and procedures
13291 * M2 Constants:: Modula-2 constants
13292 * M2 Types:: Modula-2 types
13293 * M2 Defaults:: Default settings for Modula-2
13294 * Deviations:: Deviations from standard Modula-2
13295 * M2 Checks:: Modula-2 type and range checks
13296 * M2 Scope:: The scope operators @code{::} and @code{.}
13297 * GDB/M2:: @value{GDBN} and Modula-2
13301 @subsubsection Operators
13302 @cindex Modula-2 operators
13304 Operators must be defined on values of specific types. For instance,
13305 @code{+} is defined on numbers, but not on structures. Operators are
13306 often defined on groups of types. For the purposes of Modula-2, the
13307 following definitions hold:
13312 @emph{Integral types} consist of @code{INTEGER}, @code{CARDINAL}, and
13316 @emph{Character types} consist of @code{CHAR} and its subranges.
13319 @emph{Floating-point types} consist of @code{REAL}.
13322 @emph{Pointer types} consist of anything declared as @code{POINTER TO
13326 @emph{Scalar types} consist of all of the above.
13329 @emph{Set types} consist of @code{SET} and @code{BITSET} types.
13332 @emph{Boolean types} consist of @code{BOOLEAN}.
13336 The following operators are supported, and appear in order of
13337 increasing precedence:
13341 Function argument or array index separator.
13344 Assignment. The value of @var{var} @code{:=} @var{value} is
13348 Less than, greater than on integral, floating-point, or enumerated
13352 Less than or equal to, greater than or equal to
13353 on integral, floating-point and enumerated types, or set inclusion on
13354 set types. Same precedence as @code{<}.
13356 @item =@r{, }<>@r{, }#
13357 Equality and two ways of expressing inequality, valid on scalar types.
13358 Same precedence as @code{<}. In @value{GDBN} scripts, only @code{<>} is
13359 available for inequality, since @code{#} conflicts with the script
13363 Set membership. Defined on set types and the types of their members.
13364 Same precedence as @code{<}.
13367 Boolean disjunction. Defined on boolean types.
13370 Boolean conjunction. Defined on boolean types.
13373 The @value{GDBN} ``artificial array'' operator (@pxref{Expressions, ,Expressions}).
13376 Addition and subtraction on integral and floating-point types, or union
13377 and difference on set types.
13380 Multiplication on integral and floating-point types, or set intersection
13384 Division on floating-point types, or symmetric set difference on set
13385 types. Same precedence as @code{*}.
13388 Integer division and remainder. Defined on integral types. Same
13389 precedence as @code{*}.
13392 Negative. Defined on @code{INTEGER} and @code{REAL} data.
13395 Pointer dereferencing. Defined on pointer types.
13398 Boolean negation. Defined on boolean types. Same precedence as
13402 @code{RECORD} field selector. Defined on @code{RECORD} data. Same
13403 precedence as @code{^}.
13406 Array indexing. Defined on @code{ARRAY} data. Same precedence as @code{^}.
13409 Procedure argument list. Defined on @code{PROCEDURE} objects. Same precedence
13413 @value{GDBN} and Modula-2 scope operators.
13417 @emph{Warning:} Set expressions and their operations are not yet supported, so @value{GDBN}
13418 treats the use of the operator @code{IN}, or the use of operators
13419 @code{+}, @code{-}, @code{*}, @code{/}, @code{=}, , @code{<>}, @code{#},
13420 @code{<=}, and @code{>=} on sets as an error.
13424 @node Built-In Func/Proc
13425 @subsubsection Built-in Functions and Procedures
13426 @cindex Modula-2 built-ins
13428 Modula-2 also makes available several built-in procedures and functions.
13429 In describing these, the following metavariables are used:
13434 represents an @code{ARRAY} variable.
13437 represents a @code{CHAR} constant or variable.
13440 represents a variable or constant of integral type.
13443 represents an identifier that belongs to a set. Generally used in the
13444 same function with the metavariable @var{s}. The type of @var{s} should
13445 be @code{SET OF @var{mtype}} (where @var{mtype} is the type of @var{m}).
13448 represents a variable or constant of integral or floating-point type.
13451 represents a variable or constant of floating-point type.
13457 represents a variable.
13460 represents a variable or constant of one of many types. See the
13461 explanation of the function for details.
13464 All Modula-2 built-in procedures also return a result, described below.
13468 Returns the absolute value of @var{n}.
13471 If @var{c} is a lower case letter, it returns its upper case
13472 equivalent, otherwise it returns its argument.
13475 Returns the character whose ordinal value is @var{i}.
13478 Decrements the value in the variable @var{v} by one. Returns the new value.
13480 @item DEC(@var{v},@var{i})
13481 Decrements the value in the variable @var{v} by @var{i}. Returns the
13484 @item EXCL(@var{m},@var{s})
13485 Removes the element @var{m} from the set @var{s}. Returns the new
13488 @item FLOAT(@var{i})
13489 Returns the floating point equivalent of the integer @var{i}.
13491 @item HIGH(@var{a})
13492 Returns the index of the last member of @var{a}.
13495 Increments the value in the variable @var{v} by one. Returns the new value.
13497 @item INC(@var{v},@var{i})
13498 Increments the value in the variable @var{v} by @var{i}. Returns the
13501 @item INCL(@var{m},@var{s})
13502 Adds the element @var{m} to the set @var{s} if it is not already
13503 there. Returns the new set.
13506 Returns the maximum value of the type @var{t}.
13509 Returns the minimum value of the type @var{t}.
13512 Returns boolean TRUE if @var{i} is an odd number.
13515 Returns the ordinal value of its argument. For example, the ordinal
13516 value of a character is its @sc{ascii} value (on machines supporting the
13517 @sc{ascii} character set). @var{x} must be of an ordered type, which include
13518 integral, character and enumerated types.
13520 @item SIZE(@var{x})
13521 Returns the size of its argument. @var{x} can be a variable or a type.
13523 @item TRUNC(@var{r})
13524 Returns the integral part of @var{r}.
13526 @item TSIZE(@var{x})
13527 Returns the size of its argument. @var{x} can be a variable or a type.
13529 @item VAL(@var{t},@var{i})
13530 Returns the member of the type @var{t} whose ordinal value is @var{i}.
13534 @emph{Warning:} Sets and their operations are not yet supported, so
13535 @value{GDBN} treats the use of procedures @code{INCL} and @code{EXCL} as
13539 @cindex Modula-2 constants
13541 @subsubsection Constants
13543 @value{GDBN} allows you to express the constants of Modula-2 in the following
13549 Integer constants are simply a sequence of digits. When used in an
13550 expression, a constant is interpreted to be type-compatible with the
13551 rest of the expression. Hexadecimal integers are specified by a
13552 trailing @samp{H}, and octal integers by a trailing @samp{B}.
13555 Floating point constants appear as a sequence of digits, followed by a
13556 decimal point and another sequence of digits. An optional exponent can
13557 then be specified, in the form @samp{E@r{[}+@r{|}-@r{]}@var{nnn}}, where
13558 @samp{@r{[}+@r{|}-@r{]}@var{nnn}} is the desired exponent. All of the
13559 digits of the floating point constant must be valid decimal (base 10)
13563 Character constants consist of a single character enclosed by a pair of
13564 like quotes, either single (@code{'}) or double (@code{"}). They may
13565 also be expressed by their ordinal value (their @sc{ascii} value, usually)
13566 followed by a @samp{C}.
13569 String constants consist of a sequence of characters enclosed by a
13570 pair of like quotes, either single (@code{'}) or double (@code{"}).
13571 Escape sequences in the style of C are also allowed. @xref{C
13572 Constants, ,C and C@t{++} Constants}, for a brief explanation of escape
13576 Enumerated constants consist of an enumerated identifier.
13579 Boolean constants consist of the identifiers @code{TRUE} and
13583 Pointer constants consist of integral values only.
13586 Set constants are not yet supported.
13590 @subsubsection Modula-2 Types
13591 @cindex Modula-2 types
13593 Currently @value{GDBN} can print the following data types in Modula-2
13594 syntax: array types, record types, set types, pointer types, procedure
13595 types, enumerated types, subrange types and base types. You can also
13596 print the contents of variables declared using these type.
13597 This section gives a number of simple source code examples together with
13598 sample @value{GDBN} sessions.
13600 The first example contains the following section of code:
13609 and you can request @value{GDBN} to interrogate the type and value of
13610 @code{r} and @code{s}.
13613 (@value{GDBP}) print s
13615 (@value{GDBP}) ptype s
13617 (@value{GDBP}) print r
13619 (@value{GDBP}) ptype r
13624 Likewise if your source code declares @code{s} as:
13628 s: SET ['A'..'Z'] ;
13632 then you may query the type of @code{s} by:
13635 (@value{GDBP}) ptype s
13636 type = SET ['A'..'Z']
13640 Note that at present you cannot interactively manipulate set
13641 expressions using the debugger.
13643 The following example shows how you might declare an array in Modula-2
13644 and how you can interact with @value{GDBN} to print its type and contents:
13648 s: ARRAY [-10..10] OF CHAR ;
13652 (@value{GDBP}) ptype s
13653 ARRAY [-10..10] OF CHAR
13656 Note that the array handling is not yet complete and although the type
13657 is printed correctly, expression handling still assumes that all
13658 arrays have a lower bound of zero and not @code{-10} as in the example
13661 Here are some more type related Modula-2 examples:
13665 colour = (blue, red, yellow, green) ;
13666 t = [blue..yellow] ;
13674 The @value{GDBN} interaction shows how you can query the data type
13675 and value of a variable.
13678 (@value{GDBP}) print s
13680 (@value{GDBP}) ptype t
13681 type = [blue..yellow]
13685 In this example a Modula-2 array is declared and its contents
13686 displayed. Observe that the contents are written in the same way as
13687 their @code{C} counterparts.
13691 s: ARRAY [1..5] OF CARDINAL ;
13697 (@value{GDBP}) print s
13698 $1 = @{1, 0, 0, 0, 0@}
13699 (@value{GDBP}) ptype s
13700 type = ARRAY [1..5] OF CARDINAL
13703 The Modula-2 language interface to @value{GDBN} also understands
13704 pointer types as shown in this example:
13708 s: POINTER TO ARRAY [1..5] OF CARDINAL ;
13715 and you can request that @value{GDBN} describes the type of @code{s}.
13718 (@value{GDBP}) ptype s
13719 type = POINTER TO ARRAY [1..5] OF CARDINAL
13722 @value{GDBN} handles compound types as we can see in this example.
13723 Here we combine array types, record types, pointer types and subrange
13734 myarray = ARRAY myrange OF CARDINAL ;
13735 myrange = [-2..2] ;
13737 s: POINTER TO ARRAY myrange OF foo ;
13741 and you can ask @value{GDBN} to describe the type of @code{s} as shown
13745 (@value{GDBP}) ptype s
13746 type = POINTER TO ARRAY [-2..2] OF foo = RECORD
13749 f3 : ARRAY [-2..2] OF CARDINAL;
13754 @subsubsection Modula-2 Defaults
13755 @cindex Modula-2 defaults
13757 If type and range checking are set automatically by @value{GDBN}, they
13758 both default to @code{on} whenever the working language changes to
13759 Modula-2. This happens regardless of whether you or @value{GDBN}
13760 selected the working language.
13762 If you allow @value{GDBN} to set the language automatically, then entering
13763 code compiled from a file whose name ends with @file{.mod} sets the
13764 working language to Modula-2. @xref{Automatically, ,Having @value{GDBN}
13765 Infer the Source Language}, for further details.
13768 @subsubsection Deviations from Standard Modula-2
13769 @cindex Modula-2, deviations from
13771 A few changes have been made to make Modula-2 programs easier to debug.
13772 This is done primarily via loosening its type strictness:
13776 Unlike in standard Modula-2, pointer constants can be formed by
13777 integers. This allows you to modify pointer variables during
13778 debugging. (In standard Modula-2, the actual address contained in a
13779 pointer variable is hidden from you; it can only be modified
13780 through direct assignment to another pointer variable or expression that
13781 returned a pointer.)
13784 C escape sequences can be used in strings and characters to represent
13785 non-printable characters. @value{GDBN} prints out strings with these
13786 escape sequences embedded. Single non-printable characters are
13787 printed using the @samp{CHR(@var{nnn})} format.
13790 The assignment operator (@code{:=}) returns the value of its right-hand
13794 All built-in procedures both modify @emph{and} return their argument.
13798 @subsubsection Modula-2 Type and Range Checks
13799 @cindex Modula-2 checks
13802 @emph{Warning:} in this release, @value{GDBN} does not yet perform type or
13805 @c FIXME remove warning when type/range checks added
13807 @value{GDBN} considers two Modula-2 variables type equivalent if:
13811 They are of types that have been declared equivalent via a @code{TYPE
13812 @var{t1} = @var{t2}} statement
13815 They have been declared on the same line. (Note: This is true of the
13816 @sc{gnu} Modula-2 compiler, but it may not be true of other compilers.)
13819 As long as type checking is enabled, any attempt to combine variables
13820 whose types are not equivalent is an error.
13822 Range checking is done on all mathematical operations, assignment, array
13823 index bounds, and all built-in functions and procedures.
13826 @subsubsection The Scope Operators @code{::} and @code{.}
13828 @cindex @code{.}, Modula-2 scope operator
13829 @cindex colon, doubled as scope operator
13831 @vindex colon-colon@r{, in Modula-2}
13832 @c Info cannot handle :: but TeX can.
13835 @vindex ::@r{, in Modula-2}
13838 There are a few subtle differences between the Modula-2 scope operator
13839 (@code{.}) and the @value{GDBN} scope operator (@code{::}). The two have
13844 @var{module} . @var{id}
13845 @var{scope} :: @var{id}
13849 where @var{scope} is the name of a module or a procedure,
13850 @var{module} the name of a module, and @var{id} is any declared
13851 identifier within your program, except another module.
13853 Using the @code{::} operator makes @value{GDBN} search the scope
13854 specified by @var{scope} for the identifier @var{id}. If it is not
13855 found in the specified scope, then @value{GDBN} searches all scopes
13856 enclosing the one specified by @var{scope}.
13858 Using the @code{.} operator makes @value{GDBN} search the current scope for
13859 the identifier specified by @var{id} that was imported from the
13860 definition module specified by @var{module}. With this operator, it is
13861 an error if the identifier @var{id} was not imported from definition
13862 module @var{module}, or if @var{id} is not an identifier in
13866 @subsubsection @value{GDBN} and Modula-2
13868 Some @value{GDBN} commands have little use when debugging Modula-2 programs.
13869 Five subcommands of @code{set print} and @code{show print} apply
13870 specifically to C and C@t{++}: @samp{vtbl}, @samp{demangle},
13871 @samp{asm-demangle}, @samp{object}, and @samp{union}. The first four
13872 apply to C@t{++}, and the last to the C @code{union} type, which has no direct
13873 analogue in Modula-2.
13875 The @code{@@} operator (@pxref{Expressions, ,Expressions}), while available
13876 with any language, is not useful with Modula-2. Its
13877 intent is to aid the debugging of @dfn{dynamic arrays}, which cannot be
13878 created in Modula-2 as they can in C or C@t{++}. However, because an
13879 address can be specified by an integral constant, the construct
13880 @samp{@{@var{type}@}@var{adrexp}} is still useful.
13882 @cindex @code{#} in Modula-2
13883 In @value{GDBN} scripts, the Modula-2 inequality operator @code{#} is
13884 interpreted as the beginning of a comment. Use @code{<>} instead.
13890 The extensions made to @value{GDBN} for Ada only support
13891 output from the @sc{gnu} Ada (GNAT) compiler.
13892 Other Ada compilers are not currently supported, and
13893 attempting to debug executables produced by them is most likely
13897 @cindex expressions in Ada
13899 * Ada Mode Intro:: General remarks on the Ada syntax
13900 and semantics supported by Ada mode
13902 * Omissions from Ada:: Restrictions on the Ada expression syntax.
13903 * Additions to Ada:: Extensions of the Ada expression syntax.
13904 * Stopping Before Main Program:: Debugging the program during elaboration.
13905 * Ada Tasks:: Listing and setting breakpoints in tasks.
13906 * Ada Tasks and Core Files:: Tasking Support when Debugging Core Files
13907 * Ravenscar Profile:: Tasking Support when using the Ravenscar
13909 * Ada Glitches:: Known peculiarities of Ada mode.
13912 @node Ada Mode Intro
13913 @subsubsection Introduction
13914 @cindex Ada mode, general
13916 The Ada mode of @value{GDBN} supports a fairly large subset of Ada expression
13917 syntax, with some extensions.
13918 The philosophy behind the design of this subset is
13922 That @value{GDBN} should provide basic literals and access to operations for
13923 arithmetic, dereferencing, field selection, indexing, and subprogram calls,
13924 leaving more sophisticated computations to subprograms written into the
13925 program (which therefore may be called from @value{GDBN}).
13928 That type safety and strict adherence to Ada language restrictions
13929 are not particularly important to the @value{GDBN} user.
13932 That brevity is important to the @value{GDBN} user.
13935 Thus, for brevity, the debugger acts as if all names declared in
13936 user-written packages are directly visible, even if they are not visible
13937 according to Ada rules, thus making it unnecessary to fully qualify most
13938 names with their packages, regardless of context. Where this causes
13939 ambiguity, @value{GDBN} asks the user's intent.
13941 The debugger will start in Ada mode if it detects an Ada main program.
13942 As for other languages, it will enter Ada mode when stopped in a program that
13943 was translated from an Ada source file.
13945 While in Ada mode, you may use `@t{--}' for comments. This is useful
13946 mostly for documenting command files. The standard @value{GDBN} comment
13947 (@samp{#}) still works at the beginning of a line in Ada mode, but not in the
13948 middle (to allow based literals).
13950 The debugger supports limited overloading. Given a subprogram call in which
13951 the function symbol has multiple definitions, it will use the number of
13952 actual parameters and some information about their types to attempt to narrow
13953 the set of definitions. It also makes very limited use of context, preferring
13954 procedures to functions in the context of the @code{call} command, and
13955 functions to procedures elsewhere.
13957 @node Omissions from Ada
13958 @subsubsection Omissions from Ada
13959 @cindex Ada, omissions from
13961 Here are the notable omissions from the subset:
13965 Only a subset of the attributes are supported:
13969 @t{'First}, @t{'Last}, and @t{'Length}
13970 on array objects (not on types and subtypes).
13973 @t{'Min} and @t{'Max}.
13976 @t{'Pos} and @t{'Val}.
13982 @t{'Range} on array objects (not subtypes), but only as the right
13983 operand of the membership (@code{in}) operator.
13986 @t{'Access}, @t{'Unchecked_Access}, and
13987 @t{'Unrestricted_Access} (a GNAT extension).
13995 @code{Characters.Latin_1} are not available and
13996 concatenation is not implemented. Thus, escape characters in strings are
13997 not currently available.
14000 Equality tests (@samp{=} and @samp{/=}) on arrays test for bitwise
14001 equality of representations. They will generally work correctly
14002 for strings and arrays whose elements have integer or enumeration types.
14003 They may not work correctly for arrays whose element
14004 types have user-defined equality, for arrays of real values
14005 (in particular, IEEE-conformant floating point, because of negative
14006 zeroes and NaNs), and for arrays whose elements contain unused bits with
14007 indeterminate values.
14010 The other component-by-component array operations (@code{and}, @code{or},
14011 @code{xor}, @code{not}, and relational tests other than equality)
14012 are not implemented.
14015 @cindex array aggregates (Ada)
14016 @cindex record aggregates (Ada)
14017 @cindex aggregates (Ada)
14018 There is limited support for array and record aggregates. They are
14019 permitted only on the right sides of assignments, as in these examples:
14022 (@value{GDBP}) set An_Array := (1, 2, 3, 4, 5, 6)
14023 (@value{GDBP}) set An_Array := (1, others => 0)
14024 (@value{GDBP}) set An_Array := (0|4 => 1, 1..3 => 2, 5 => 6)
14025 (@value{GDBP}) set A_2D_Array := ((1, 2, 3), (4, 5, 6), (7, 8, 9))
14026 (@value{GDBP}) set A_Record := (1, "Peter", True);
14027 (@value{GDBP}) set A_Record := (Name => "Peter", Id => 1, Alive => True)
14031 discriminant's value by assigning an aggregate has an
14032 undefined effect if that discriminant is used within the record.
14033 However, you can first modify discriminants by directly assigning to
14034 them (which normally would not be allowed in Ada), and then performing an
14035 aggregate assignment. For example, given a variable @code{A_Rec}
14036 declared to have a type such as:
14039 type Rec (Len : Small_Integer := 0) is record
14041 Vals : IntArray (1 .. Len);
14045 you can assign a value with a different size of @code{Vals} with two
14049 (@value{GDBP}) set A_Rec.Len := 4
14050 (@value{GDBP}) set A_Rec := (Id => 42, Vals => (1, 2, 3, 4))
14053 As this example also illustrates, @value{GDBN} is very loose about the usual
14054 rules concerning aggregates. You may leave out some of the
14055 components of an array or record aggregate (such as the @code{Len}
14056 component in the assignment to @code{A_Rec} above); they will retain their
14057 original values upon assignment. You may freely use dynamic values as
14058 indices in component associations. You may even use overlapping or
14059 redundant component associations, although which component values are
14060 assigned in such cases is not defined.
14063 Calls to dispatching subprograms are not implemented.
14066 The overloading algorithm is much more limited (i.e., less selective)
14067 than that of real Ada. It makes only limited use of the context in
14068 which a subexpression appears to resolve its meaning, and it is much
14069 looser in its rules for allowing type matches. As a result, some
14070 function calls will be ambiguous, and the user will be asked to choose
14071 the proper resolution.
14074 The @code{new} operator is not implemented.
14077 Entry calls are not implemented.
14080 Aside from printing, arithmetic operations on the native VAX floating-point
14081 formats are not supported.
14084 It is not possible to slice a packed array.
14087 The names @code{True} and @code{False}, when not part of a qualified name,
14088 are interpreted as if implicitly prefixed by @code{Standard}, regardless of
14090 Should your program
14091 redefine these names in a package or procedure (at best a dubious practice),
14092 you will have to use fully qualified names to access their new definitions.
14095 @node Additions to Ada
14096 @subsubsection Additions to Ada
14097 @cindex Ada, deviations from
14099 As it does for other languages, @value{GDBN} makes certain generic
14100 extensions to Ada (@pxref{Expressions}):
14104 If the expression @var{E} is a variable residing in memory (typically
14105 a local variable or array element) and @var{N} is a positive integer,
14106 then @code{@var{E}@@@var{N}} displays the values of @var{E} and the
14107 @var{N}-1 adjacent variables following it in memory as an array. In
14108 Ada, this operator is generally not necessary, since its prime use is
14109 in displaying parts of an array, and slicing will usually do this in
14110 Ada. However, there are occasional uses when debugging programs in
14111 which certain debugging information has been optimized away.
14114 @code{@var{B}::@var{var}} means ``the variable named @var{var} that
14115 appears in function or file @var{B}.'' When @var{B} is a file name,
14116 you must typically surround it in single quotes.
14119 The expression @code{@{@var{type}@} @var{addr}} means ``the variable of type
14120 @var{type} that appears at address @var{addr}.''
14123 A name starting with @samp{$} is a convenience variable
14124 (@pxref{Convenience Vars}) or a machine register (@pxref{Registers}).
14127 In addition, @value{GDBN} provides a few other shortcuts and outright
14128 additions specific to Ada:
14132 The assignment statement is allowed as an expression, returning
14133 its right-hand operand as its value. Thus, you may enter
14136 (@value{GDBP}) set x := y + 3
14137 (@value{GDBP}) print A(tmp := y + 1)
14141 The semicolon is allowed as an ``operator,'' returning as its value
14142 the value of its right-hand operand.
14143 This allows, for example,
14144 complex conditional breaks:
14147 (@value{GDBP}) break f
14148 (@value{GDBP}) condition 1 (report(i); k += 1; A(k) > 100)
14152 Rather than use catenation and symbolic character names to introduce special
14153 characters into strings, one may instead use a special bracket notation,
14154 which is also used to print strings. A sequence of characters of the form
14155 @samp{["@var{XX}"]} within a string or character literal denotes the
14156 (single) character whose numeric encoding is @var{XX} in hexadecimal. The
14157 sequence of characters @samp{["""]} also denotes a single quotation mark
14158 in strings. For example,
14160 "One line.["0a"]Next line.["0a"]"
14163 contains an ASCII newline character (@code{Ada.Characters.Latin_1.LF})
14167 The subtype used as a prefix for the attributes @t{'Pos}, @t{'Min}, and
14168 @t{'Max} is optional (and is ignored in any case). For example, it is valid
14172 (@value{GDBP}) print 'max(x, y)
14176 When printing arrays, @value{GDBN} uses positional notation when the
14177 array has a lower bound of 1, and uses a modified named notation otherwise.
14178 For example, a one-dimensional array of three integers with a lower bound
14179 of 3 might print as
14186 That is, in contrast to valid Ada, only the first component has a @code{=>}
14190 You may abbreviate attributes in expressions with any unique,
14191 multi-character subsequence of
14192 their names (an exact match gets preference).
14193 For example, you may use @t{a'len}, @t{a'gth}, or @t{a'lh}
14194 in place of @t{a'length}.
14197 @cindex quoting Ada internal identifiers
14198 Since Ada is case-insensitive, the debugger normally maps identifiers you type
14199 to lower case. The GNAT compiler uses upper-case characters for
14200 some of its internal identifiers, which are normally of no interest to users.
14201 For the rare occasions when you actually have to look at them,
14202 enclose them in angle brackets to avoid the lower-case mapping.
14205 (@value{GDBP}) print <JMPBUF_SAVE>[0]
14209 Printing an object of class-wide type or dereferencing an
14210 access-to-class-wide value will display all the components of the object's
14211 specific type (as indicated by its run-time tag). Likewise, component
14212 selection on such a value will operate on the specific type of the
14217 @node Stopping Before Main Program
14218 @subsubsection Stopping at the Very Beginning
14220 @cindex breakpointing Ada elaboration code
14221 It is sometimes necessary to debug the program during elaboration, and
14222 before reaching the main procedure.
14223 As defined in the Ada Reference
14224 Manual, the elaboration code is invoked from a procedure called
14225 @code{adainit}. To run your program up to the beginning of
14226 elaboration, simply use the following two commands:
14227 @code{tbreak adainit} and @code{run}.
14230 @subsubsection Extensions for Ada Tasks
14231 @cindex Ada, tasking
14233 Support for Ada tasks is analogous to that for threads (@pxref{Threads}).
14234 @value{GDBN} provides the following task-related commands:
14239 This command shows a list of current Ada tasks, as in the following example:
14246 (@value{GDBP}) info tasks
14247 ID TID P-ID Pri State Name
14248 1 8088000 0 15 Child Activation Wait main_task
14249 2 80a4000 1 15 Accept Statement b
14250 3 809a800 1 15 Child Activation Wait a
14251 * 4 80ae800 3 15 Runnable c
14256 In this listing, the asterisk before the last task indicates it to be the
14257 task currently being inspected.
14261 Represents @value{GDBN}'s internal task number.
14267 The parent's task ID (@value{GDBN}'s internal task number).
14270 The base priority of the task.
14273 Current state of the task.
14277 The task has been created but has not been activated. It cannot be
14281 The task is not blocked for any reason known to Ada. (It may be waiting
14282 for a mutex, though.) It is conceptually "executing" in normal mode.
14285 The task is terminated, in the sense of ARM 9.3 (5). Any dependents
14286 that were waiting on terminate alternatives have been awakened and have
14287 terminated themselves.
14289 @item Child Activation Wait
14290 The task is waiting for created tasks to complete activation.
14292 @item Accept Statement
14293 The task is waiting on an accept or selective wait statement.
14295 @item Waiting on entry call
14296 The task is waiting on an entry call.
14298 @item Async Select Wait
14299 The task is waiting to start the abortable part of an asynchronous
14303 The task is waiting on a select statement with only a delay
14306 @item Child Termination Wait
14307 The task is sleeping having completed a master within itself, and is
14308 waiting for the tasks dependent on that master to become terminated or
14309 waiting on a terminate Phase.
14311 @item Wait Child in Term Alt
14312 The task is sleeping waiting for tasks on terminate alternatives to
14313 finish terminating.
14315 @item Accepting RV with @var{taskno}
14316 The task is accepting a rendez-vous with the task @var{taskno}.
14320 Name of the task in the program.
14324 @kindex info task @var{taskno}
14325 @item info task @var{taskno}
14326 This command shows detailled informations on the specified task, as in
14327 the following example:
14332 (@value{GDBP}) info tasks
14333 ID TID P-ID Pri State Name
14334 1 8077880 0 15 Child Activation Wait main_task
14335 * 2 807c468 1 15 Runnable task_1
14336 (@value{GDBP}) info task 2
14337 Ada Task: 0x807c468
14340 Parent: 1 (main_task)
14346 @kindex task@r{ (Ada)}
14347 @cindex current Ada task ID
14348 This command prints the ID of the current task.
14354 (@value{GDBP}) info tasks
14355 ID TID P-ID Pri State Name
14356 1 8077870 0 15 Child Activation Wait main_task
14357 * 2 807c458 1 15 Runnable t
14358 (@value{GDBP}) task
14359 [Current task is 2]
14362 @item task @var{taskno}
14363 @cindex Ada task switching
14364 This command is like the @code{thread @var{threadno}}
14365 command (@pxref{Threads}). It switches the context of debugging
14366 from the current task to the given task.
14372 (@value{GDBP}) info tasks
14373 ID TID P-ID Pri State Name
14374 1 8077870 0 15 Child Activation Wait main_task
14375 * 2 807c458 1 15 Runnable t
14376 (@value{GDBP}) task 1
14377 [Switching to task 1]
14378 #0 0x8067726 in pthread_cond_wait ()
14380 #0 0x8067726 in pthread_cond_wait ()
14381 #1 0x8056714 in system.os_interface.pthread_cond_wait ()
14382 #2 0x805cb63 in system.task_primitives.operations.sleep ()
14383 #3 0x806153e in system.tasking.stages.activate_tasks ()
14384 #4 0x804aacc in un () at un.adb:5
14387 @item break @var{linespec} task @var{taskno}
14388 @itemx break @var{linespec} task @var{taskno} if @dots{}
14389 @cindex breakpoints and tasks, in Ada
14390 @cindex task breakpoints, in Ada
14391 @kindex break @dots{} task @var{taskno}@r{ (Ada)}
14392 These commands are like the @code{break @dots{} thread @dots{}}
14393 command (@pxref{Thread Stops}).
14394 @var{linespec} specifies source lines, as described
14395 in @ref{Specify Location}.
14397 Use the qualifier @samp{task @var{taskno}} with a breakpoint command
14398 to specify that you only want @value{GDBN} to stop the program when a
14399 particular Ada task reaches this breakpoint. @var{taskno} is one of the
14400 numeric task identifiers assigned by @value{GDBN}, shown in the first
14401 column of the @samp{info tasks} display.
14403 If you do not specify @samp{task @var{taskno}} when you set a
14404 breakpoint, the breakpoint applies to @emph{all} tasks of your
14407 You can use the @code{task} qualifier on conditional breakpoints as
14408 well; in this case, place @samp{task @var{taskno}} before the
14409 breakpoint condition (before the @code{if}).
14417 (@value{GDBP}) info tasks
14418 ID TID P-ID Pri State Name
14419 1 140022020 0 15 Child Activation Wait main_task
14420 2 140045060 1 15 Accept/Select Wait t2
14421 3 140044840 1 15 Runnable t1
14422 * 4 140056040 1 15 Runnable t3
14423 (@value{GDBP}) b 15 task 2
14424 Breakpoint 5 at 0x120044cb0: file test_task_debug.adb, line 15.
14425 (@value{GDBP}) cont
14430 Breakpoint 5, test_task_debug () at test_task_debug.adb:15
14432 (@value{GDBP}) info tasks
14433 ID TID P-ID Pri State Name
14434 1 140022020 0 15 Child Activation Wait main_task
14435 * 2 140045060 1 15 Runnable t2
14436 3 140044840 1 15 Runnable t1
14437 4 140056040 1 15 Delay Sleep t3
14441 @node Ada Tasks and Core Files
14442 @subsubsection Tasking Support when Debugging Core Files
14443 @cindex Ada tasking and core file debugging
14445 When inspecting a core file, as opposed to debugging a live program,
14446 tasking support may be limited or even unavailable, depending on
14447 the platform being used.
14448 For instance, on x86-linux, the list of tasks is available, but task
14449 switching is not supported. On Tru64, however, task switching will work
14452 On certain platforms, including Tru64, the debugger needs to perform some
14453 memory writes in order to provide Ada tasking support. When inspecting
14454 a core file, this means that the core file must be opened with read-write
14455 privileges, using the command @samp{"set write on"} (@pxref{Patching}).
14456 Under these circumstances, you should make a backup copy of the core
14457 file before inspecting it with @value{GDBN}.
14459 @node Ravenscar Profile
14460 @subsubsection Tasking Support when using the Ravenscar Profile
14461 @cindex Ravenscar Profile
14463 The @dfn{Ravenscar Profile} is a subset of the Ada tasking features,
14464 specifically designed for systems with safety-critical real-time
14468 @kindex set ravenscar task-switching on
14469 @cindex task switching with program using Ravenscar Profile
14470 @item set ravenscar task-switching on
14471 Allows task switching when debugging a program that uses the Ravenscar
14472 Profile. This is the default.
14474 @kindex set ravenscar task-switching off
14475 @item set ravenscar task-switching off
14476 Turn off task switching when debugging a program that uses the Ravenscar
14477 Profile. This is mostly intended to disable the code that adds support
14478 for the Ravenscar Profile, in case a bug in either @value{GDBN} or in
14479 the Ravenscar runtime is preventing @value{GDBN} from working properly.
14480 To be effective, this command should be run before the program is started.
14482 @kindex show ravenscar task-switching
14483 @item show ravenscar task-switching
14484 Show whether it is possible to switch from task to task in a program
14485 using the Ravenscar Profile.
14490 @subsubsection Known Peculiarities of Ada Mode
14491 @cindex Ada, problems
14493 Besides the omissions listed previously (@pxref{Omissions from Ada}),
14494 we know of several problems with and limitations of Ada mode in
14496 some of which will be fixed with planned future releases of the debugger
14497 and the GNU Ada compiler.
14501 Static constants that the compiler chooses not to materialize as objects in
14502 storage are invisible to the debugger.
14505 Named parameter associations in function argument lists are ignored (the
14506 argument lists are treated as positional).
14509 Many useful library packages are currently invisible to the debugger.
14512 Fixed-point arithmetic, conversions, input, and output is carried out using
14513 floating-point arithmetic, and may give results that only approximate those on
14517 The GNAT compiler never generates the prefix @code{Standard} for any of
14518 the standard symbols defined by the Ada language. @value{GDBN} knows about
14519 this: it will strip the prefix from names when you use it, and will never
14520 look for a name you have so qualified among local symbols, nor match against
14521 symbols in other packages or subprograms. If you have
14522 defined entities anywhere in your program other than parameters and
14523 local variables whose simple names match names in @code{Standard},
14524 GNAT's lack of qualification here can cause confusion. When this happens,
14525 you can usually resolve the confusion
14526 by qualifying the problematic names with package
14527 @code{Standard} explicitly.
14530 Older versions of the compiler sometimes generate erroneous debugging
14531 information, resulting in the debugger incorrectly printing the value
14532 of affected entities. In some cases, the debugger is able to work
14533 around an issue automatically. In other cases, the debugger is able
14534 to work around the issue, but the work-around has to be specifically
14537 @kindex set ada trust-PAD-over-XVS
14538 @kindex show ada trust-PAD-over-XVS
14541 @item set ada trust-PAD-over-XVS on
14542 Configure GDB to strictly follow the GNAT encoding when computing the
14543 value of Ada entities, particularly when @code{PAD} and @code{PAD___XVS}
14544 types are involved (see @code{ada/exp_dbug.ads} in the GCC sources for
14545 a complete description of the encoding used by the GNAT compiler).
14546 This is the default.
14548 @item set ada trust-PAD-over-XVS off
14549 This is related to the encoding using by the GNAT compiler. If @value{GDBN}
14550 sometimes prints the wrong value for certain entities, changing @code{ada
14551 trust-PAD-over-XVS} to @code{off} activates a work-around which may fix
14552 the issue. It is always safe to set @code{ada trust-PAD-over-XVS} to
14553 @code{off}, but this incurs a slight performance penalty, so it is
14554 recommended to leave this setting to @code{on} unless necessary.
14558 @node Unsupported Languages
14559 @section Unsupported Languages
14561 @cindex unsupported languages
14562 @cindex minimal language
14563 In addition to the other fully-supported programming languages,
14564 @value{GDBN} also provides a pseudo-language, called @code{minimal}.
14565 It does not represent a real programming language, but provides a set
14566 of capabilities close to what the C or assembly languages provide.
14567 This should allow most simple operations to be performed while debugging
14568 an application that uses a language currently not supported by @value{GDBN}.
14570 If the language is set to @code{auto}, @value{GDBN} will automatically
14571 select this language if the current frame corresponds to an unsupported
14575 @chapter Examining the Symbol Table
14577 The commands described in this chapter allow you to inquire about the
14578 symbols (names of variables, functions and types) defined in your
14579 program. This information is inherent in the text of your program and
14580 does not change as your program executes. @value{GDBN} finds it in your
14581 program's symbol table, in the file indicated when you started @value{GDBN}
14582 (@pxref{File Options, ,Choosing Files}), or by one of the
14583 file-management commands (@pxref{Files, ,Commands to Specify Files}).
14585 @cindex symbol names
14586 @cindex names of symbols
14587 @cindex quoting names
14588 Occasionally, you may need to refer to symbols that contain unusual
14589 characters, which @value{GDBN} ordinarily treats as word delimiters. The
14590 most frequent case is in referring to static variables in other
14591 source files (@pxref{Variables,,Program Variables}). File names
14592 are recorded in object files as debugging symbols, but @value{GDBN} would
14593 ordinarily parse a typical file name, like @file{foo.c}, as the three words
14594 @samp{foo} @samp{.} @samp{c}. To allow @value{GDBN} to recognize
14595 @samp{foo.c} as a single symbol, enclose it in single quotes; for example,
14602 looks up the value of @code{x} in the scope of the file @file{foo.c}.
14605 @cindex case-insensitive symbol names
14606 @cindex case sensitivity in symbol names
14607 @kindex set case-sensitive
14608 @item set case-sensitive on
14609 @itemx set case-sensitive off
14610 @itemx set case-sensitive auto
14611 Normally, when @value{GDBN} looks up symbols, it matches their names
14612 with case sensitivity determined by the current source language.
14613 Occasionally, you may wish to control that. The command @code{set
14614 case-sensitive} lets you do that by specifying @code{on} for
14615 case-sensitive matches or @code{off} for case-insensitive ones. If
14616 you specify @code{auto}, case sensitivity is reset to the default
14617 suitable for the source language. The default is case-sensitive
14618 matches for all languages except for Fortran, for which the default is
14619 case-insensitive matches.
14621 @kindex show case-sensitive
14622 @item show case-sensitive
14623 This command shows the current setting of case sensitivity for symbols
14626 @kindex info address
14627 @cindex address of a symbol
14628 @item info address @var{symbol}
14629 Describe where the data for @var{symbol} is stored. For a register
14630 variable, this says which register it is kept in. For a non-register
14631 local variable, this prints the stack-frame offset at which the variable
14634 Note the contrast with @samp{print &@var{symbol}}, which does not work
14635 at all for a register variable, and for a stack local variable prints
14636 the exact address of the current instantiation of the variable.
14638 @kindex info symbol
14639 @cindex symbol from address
14640 @cindex closest symbol and offset for an address
14641 @item info symbol @var{addr}
14642 Print the name of a symbol which is stored at the address @var{addr}.
14643 If no symbol is stored exactly at @var{addr}, @value{GDBN} prints the
14644 nearest symbol and an offset from it:
14647 (@value{GDBP}) info symbol 0x54320
14648 _initialize_vx + 396 in section .text
14652 This is the opposite of the @code{info address} command. You can use
14653 it to find out the name of a variable or a function given its address.
14655 For dynamically linked executables, the name of executable or shared
14656 library containing the symbol is also printed:
14659 (@value{GDBP}) info symbol 0x400225
14660 _start + 5 in section .text of /tmp/a.out
14661 (@value{GDBP}) info symbol 0x2aaaac2811cf
14662 __read_nocancel + 6 in section .text of /usr/lib64/libc.so.6
14666 @item whatis [@var{arg}]
14667 Print the data type of @var{arg}, which can be either an expression
14668 or a name of a data type. With no argument, print the data type of
14669 @code{$}, the last value in the value history.
14671 If @var{arg} is an expression (@pxref{Expressions, ,Expressions}), it
14672 is not actually evaluated, and any side-effecting operations (such as
14673 assignments or function calls) inside it do not take place.
14675 If @var{arg} is a variable or an expression, @code{whatis} prints its
14676 literal type as it is used in the source code. If the type was
14677 defined using a @code{typedef}, @code{whatis} will @emph{not} print
14678 the data type underlying the @code{typedef}. If the type of the
14679 variable or the expression is a compound data type, such as
14680 @code{struct} or @code{class}, @code{whatis} never prints their
14681 fields or methods. It just prints the @code{struct}/@code{class}
14682 name (a.k.a.@: its @dfn{tag}). If you want to see the members of
14683 such a compound data type, use @code{ptype}.
14685 If @var{arg} is a type name that was defined using @code{typedef},
14686 @code{whatis} @dfn{unrolls} only one level of that @code{typedef}.
14687 Unrolling means that @code{whatis} will show the underlying type used
14688 in the @code{typedef} declaration of @var{arg}. However, if that
14689 underlying type is also a @code{typedef}, @code{whatis} will not
14692 For C code, the type names may also have the form @samp{class
14693 @var{class-name}}, @samp{struct @var{struct-tag}}, @samp{union
14694 @var{union-tag}} or @samp{enum @var{enum-tag}}.
14697 @item ptype [@var{arg}]
14698 @code{ptype} accepts the same arguments as @code{whatis}, but prints a
14699 detailed description of the type, instead of just the name of the type.
14700 @xref{Expressions, ,Expressions}.
14702 Contrary to @code{whatis}, @code{ptype} always unrolls any
14703 @code{typedef}s in its argument declaration, whether the argument is
14704 a variable, expression, or a data type. This means that @code{ptype}
14705 of a variable or an expression will not print literally its type as
14706 present in the source code---use @code{whatis} for that. @code{typedef}s at
14707 the pointer or reference targets are also unrolled. Only @code{typedef}s of
14708 fields, methods and inner @code{class typedef}s of @code{struct}s,
14709 @code{class}es and @code{union}s are not unrolled even with @code{ptype}.
14711 For example, for this variable declaration:
14714 typedef double real_t;
14715 struct complex @{ real_t real; double imag; @};
14716 typedef struct complex complex_t;
14718 real_t *real_pointer_var;
14722 the two commands give this output:
14726 (@value{GDBP}) whatis var
14728 (@value{GDBP}) ptype var
14729 type = struct complex @{
14733 (@value{GDBP}) whatis complex_t
14734 type = struct complex
14735 (@value{GDBP}) whatis struct complex
14736 type = struct complex
14737 (@value{GDBP}) ptype struct complex
14738 type = struct complex @{
14742 (@value{GDBP}) whatis real_pointer_var
14744 (@value{GDBP}) ptype real_pointer_var
14750 As with @code{whatis}, using @code{ptype} without an argument refers to
14751 the type of @code{$}, the last value in the value history.
14753 @cindex incomplete type
14754 Sometimes, programs use opaque data types or incomplete specifications
14755 of complex data structure. If the debug information included in the
14756 program does not allow @value{GDBN} to display a full declaration of
14757 the data type, it will say @samp{<incomplete type>}. For example,
14758 given these declarations:
14762 struct foo *fooptr;
14766 but no definition for @code{struct foo} itself, @value{GDBN} will say:
14769 (@value{GDBP}) ptype foo
14770 $1 = <incomplete type>
14774 ``Incomplete type'' is C terminology for data types that are not
14775 completely specified.
14778 @item info types @var{regexp}
14780 Print a brief description of all types whose names match the regular
14781 expression @var{regexp} (or all types in your program, if you supply
14782 no argument). Each complete typename is matched as though it were a
14783 complete line; thus, @samp{i type value} gives information on all
14784 types in your program whose names include the string @code{value}, but
14785 @samp{i type ^value$} gives information only on types whose complete
14786 name is @code{value}.
14788 This command differs from @code{ptype} in two ways: first, like
14789 @code{whatis}, it does not print a detailed description; second, it
14790 lists all source files where a type is defined.
14793 @cindex local variables
14794 @item info scope @var{location}
14795 List all the variables local to a particular scope. This command
14796 accepts a @var{location} argument---a function name, a source line, or
14797 an address preceded by a @samp{*}, and prints all the variables local
14798 to the scope defined by that location. (@xref{Specify Location}, for
14799 details about supported forms of @var{location}.) For example:
14802 (@value{GDBP}) @b{info scope command_line_handler}
14803 Scope for command_line_handler:
14804 Symbol rl is an argument at stack/frame offset 8, length 4.
14805 Symbol linebuffer is in static storage at address 0x150a18, length 4.
14806 Symbol linelength is in static storage at address 0x150a1c, length 4.
14807 Symbol p is a local variable in register $esi, length 4.
14808 Symbol p1 is a local variable in register $ebx, length 4.
14809 Symbol nline is a local variable in register $edx, length 4.
14810 Symbol repeat is a local variable at frame offset -8, length 4.
14814 This command is especially useful for determining what data to collect
14815 during a @dfn{trace experiment}, see @ref{Tracepoint Actions,
14818 @kindex info source
14820 Show information about the current source file---that is, the source file for
14821 the function containing the current point of execution:
14824 the name of the source file, and the directory containing it,
14826 the directory it was compiled in,
14828 its length, in lines,
14830 which programming language it is written in,
14832 whether the executable includes debugging information for that file, and
14833 if so, what format the information is in (e.g., STABS, Dwarf 2, etc.), and
14835 whether the debugging information includes information about
14836 preprocessor macros.
14840 @kindex info sources
14842 Print the names of all source files in your program for which there is
14843 debugging information, organized into two lists: files whose symbols
14844 have already been read, and files whose symbols will be read when needed.
14846 @kindex info functions
14847 @item info functions
14848 Print the names and data types of all defined functions.
14850 @item info functions @var{regexp}
14851 Print the names and data types of all defined functions
14852 whose names contain a match for regular expression @var{regexp}.
14853 Thus, @samp{info fun step} finds all functions whose names
14854 include @code{step}; @samp{info fun ^step} finds those whose names
14855 start with @code{step}. If a function name contains characters
14856 that conflict with the regular expression language (e.g.@:
14857 @samp{operator*()}), they may be quoted with a backslash.
14859 @kindex info variables
14860 @item info variables
14861 Print the names and data types of all variables that are defined
14862 outside of functions (i.e.@: excluding local variables).
14864 @item info variables @var{regexp}
14865 Print the names and data types of all variables (except for local
14866 variables) whose names contain a match for regular expression
14869 @kindex info classes
14870 @cindex Objective-C, classes and selectors
14872 @itemx info classes @var{regexp}
14873 Display all Objective-C classes in your program, or
14874 (with the @var{regexp} argument) all those matching a particular regular
14877 @kindex info selectors
14878 @item info selectors
14879 @itemx info selectors @var{regexp}
14880 Display all Objective-C selectors in your program, or
14881 (with the @var{regexp} argument) all those matching a particular regular
14885 This was never implemented.
14886 @kindex info methods
14888 @itemx info methods @var{regexp}
14889 The @code{info methods} command permits the user to examine all defined
14890 methods within C@t{++} program, or (with the @var{regexp} argument) a
14891 specific set of methods found in the various C@t{++} classes. Many
14892 C@t{++} classes provide a large number of methods. Thus, the output
14893 from the @code{ptype} command can be overwhelming and hard to use. The
14894 @code{info-methods} command filters the methods, printing only those
14895 which match the regular-expression @var{regexp}.
14898 @cindex opaque data types
14899 @kindex set opaque-type-resolution
14900 @item set opaque-type-resolution on
14901 Tell @value{GDBN} to resolve opaque types. An opaque type is a type
14902 declared as a pointer to a @code{struct}, @code{class}, or
14903 @code{union}---for example, @code{struct MyType *}---that is used in one
14904 source file although the full declaration of @code{struct MyType} is in
14905 another source file. The default is on.
14907 A change in the setting of this subcommand will not take effect until
14908 the next time symbols for a file are loaded.
14910 @item set opaque-type-resolution off
14911 Tell @value{GDBN} not to resolve opaque types. In this case, the type
14912 is printed as follows:
14914 @{<no data fields>@}
14917 @kindex show opaque-type-resolution
14918 @item show opaque-type-resolution
14919 Show whether opaque types are resolved or not.
14921 @kindex maint print symbols
14922 @cindex symbol dump
14923 @kindex maint print psymbols
14924 @cindex partial symbol dump
14925 @item maint print symbols @var{filename}
14926 @itemx maint print psymbols @var{filename}
14927 @itemx maint print msymbols @var{filename}
14928 Write a dump of debugging symbol data into the file @var{filename}.
14929 These commands are used to debug the @value{GDBN} symbol-reading code. Only
14930 symbols with debugging data are included. If you use @samp{maint print
14931 symbols}, @value{GDBN} includes all the symbols for which it has already
14932 collected full details: that is, @var{filename} reflects symbols for
14933 only those files whose symbols @value{GDBN} has read. You can use the
14934 command @code{info sources} to find out which files these are. If you
14935 use @samp{maint print psymbols} instead, the dump shows information about
14936 symbols that @value{GDBN} only knows partially---that is, symbols defined in
14937 files that @value{GDBN} has skimmed, but not yet read completely. Finally,
14938 @samp{maint print msymbols} dumps just the minimal symbol information
14939 required for each object file from which @value{GDBN} has read some symbols.
14940 @xref{Files, ,Commands to Specify Files}, for a discussion of how
14941 @value{GDBN} reads symbols (in the description of @code{symbol-file}).
14943 @kindex maint info symtabs
14944 @kindex maint info psymtabs
14945 @cindex listing @value{GDBN}'s internal symbol tables
14946 @cindex symbol tables, listing @value{GDBN}'s internal
14947 @cindex full symbol tables, listing @value{GDBN}'s internal
14948 @cindex partial symbol tables, listing @value{GDBN}'s internal
14949 @item maint info symtabs @r{[} @var{regexp} @r{]}
14950 @itemx maint info psymtabs @r{[} @var{regexp} @r{]}
14952 List the @code{struct symtab} or @code{struct partial_symtab}
14953 structures whose names match @var{regexp}. If @var{regexp} is not
14954 given, list them all. The output includes expressions which you can
14955 copy into a @value{GDBN} debugging this one to examine a particular
14956 structure in more detail. For example:
14959 (@value{GDBP}) maint info psymtabs dwarf2read
14960 @{ objfile /home/gnu/build/gdb/gdb
14961 ((struct objfile *) 0x82e69d0)
14962 @{ psymtab /home/gnu/src/gdb/dwarf2read.c
14963 ((struct partial_symtab *) 0x8474b10)
14966 text addresses 0x814d3c8 -- 0x8158074
14967 globals (* (struct partial_symbol **) 0x8507a08 @@ 9)
14968 statics (* (struct partial_symbol **) 0x40e95b78 @@ 2882)
14969 dependencies (none)
14972 (@value{GDBP}) maint info symtabs
14976 We see that there is one partial symbol table whose filename contains
14977 the string @samp{dwarf2read}, belonging to the @samp{gdb} executable;
14978 and we see that @value{GDBN} has not read in any symtabs yet at all.
14979 If we set a breakpoint on a function, that will cause @value{GDBN} to
14980 read the symtab for the compilation unit containing that function:
14983 (@value{GDBP}) break dwarf2_psymtab_to_symtab
14984 Breakpoint 1 at 0x814e5da: file /home/gnu/src/gdb/dwarf2read.c,
14986 (@value{GDBP}) maint info symtabs
14987 @{ objfile /home/gnu/build/gdb/gdb
14988 ((struct objfile *) 0x82e69d0)
14989 @{ symtab /home/gnu/src/gdb/dwarf2read.c
14990 ((struct symtab *) 0x86c1f38)
14993 blockvector ((struct blockvector *) 0x86c1bd0) (primary)
14994 linetable ((struct linetable *) 0x8370fa0)
14995 debugformat DWARF 2
15004 @chapter Altering Execution
15006 Once you think you have found an error in your program, you might want to
15007 find out for certain whether correcting the apparent error would lead to
15008 correct results in the rest of the run. You can find the answer by
15009 experiment, using the @value{GDBN} features for altering execution of the
15012 For example, you can store new values into variables or memory
15013 locations, give your program a signal, restart it at a different
15014 address, or even return prematurely from a function.
15017 * Assignment:: Assignment to variables
15018 * Jumping:: Continuing at a different address
15019 * Signaling:: Giving your program a signal
15020 * Returning:: Returning from a function
15021 * Calling:: Calling your program's functions
15022 * Patching:: Patching your program
15026 @section Assignment to Variables
15029 @cindex setting variables
15030 To alter the value of a variable, evaluate an assignment expression.
15031 @xref{Expressions, ,Expressions}. For example,
15038 stores the value 4 into the variable @code{x}, and then prints the
15039 value of the assignment expression (which is 4).
15040 @xref{Languages, ,Using @value{GDBN} with Different Languages}, for more
15041 information on operators in supported languages.
15043 @kindex set variable
15044 @cindex variables, setting
15045 If you are not interested in seeing the value of the assignment, use the
15046 @code{set} command instead of the @code{print} command. @code{set} is
15047 really the same as @code{print} except that the expression's value is
15048 not printed and is not put in the value history (@pxref{Value History,
15049 ,Value History}). The expression is evaluated only for its effects.
15051 If the beginning of the argument string of the @code{set} command
15052 appears identical to a @code{set} subcommand, use the @code{set
15053 variable} command instead of just @code{set}. This command is identical
15054 to @code{set} except for its lack of subcommands. For example, if your
15055 program has a variable @code{width}, you get an error if you try to set
15056 a new value with just @samp{set width=13}, because @value{GDBN} has the
15057 command @code{set width}:
15060 (@value{GDBP}) whatis width
15062 (@value{GDBP}) p width
15064 (@value{GDBP}) set width=47
15065 Invalid syntax in expression.
15069 The invalid expression, of course, is @samp{=47}. In
15070 order to actually set the program's variable @code{width}, use
15073 (@value{GDBP}) set var width=47
15076 Because the @code{set} command has many subcommands that can conflict
15077 with the names of program variables, it is a good idea to use the
15078 @code{set variable} command instead of just @code{set}. For example, if
15079 your program has a variable @code{g}, you run into problems if you try
15080 to set a new value with just @samp{set g=4}, because @value{GDBN} has
15081 the command @code{set gnutarget}, abbreviated @code{set g}:
15085 (@value{GDBP}) whatis g
15089 (@value{GDBP}) set g=4
15093 The program being debugged has been started already.
15094 Start it from the beginning? (y or n) y
15095 Starting program: /home/smith/cc_progs/a.out
15096 "/home/smith/cc_progs/a.out": can't open to read symbols:
15097 Invalid bfd target.
15098 (@value{GDBP}) show g
15099 The current BFD target is "=4".
15104 The program variable @code{g} did not change, and you silently set the
15105 @code{gnutarget} to an invalid value. In order to set the variable
15109 (@value{GDBP}) set var g=4
15112 @value{GDBN} allows more implicit conversions in assignments than C; you can
15113 freely store an integer value into a pointer variable or vice versa,
15114 and you can convert any structure to any other structure that is the
15115 same length or shorter.
15116 @comment FIXME: how do structs align/pad in these conversions?
15117 @comment /doc@cygnus.com 18dec1990
15119 To store values into arbitrary places in memory, use the @samp{@{@dots{}@}}
15120 construct to generate a value of specified type at a specified address
15121 (@pxref{Expressions, ,Expressions}). For example, @code{@{int@}0x83040} refers
15122 to memory location @code{0x83040} as an integer (which implies a certain size
15123 and representation in memory), and
15126 set @{int@}0x83040 = 4
15130 stores the value 4 into that memory location.
15133 @section Continuing at a Different Address
15135 Ordinarily, when you continue your program, you do so at the place where
15136 it stopped, with the @code{continue} command. You can instead continue at
15137 an address of your own choosing, with the following commands:
15141 @item jump @var{linespec}
15142 @itemx jump @var{location}
15143 Resume execution at line @var{linespec} or at address given by
15144 @var{location}. Execution stops again immediately if there is a
15145 breakpoint there. @xref{Specify Location}, for a description of the
15146 different forms of @var{linespec} and @var{location}. It is common
15147 practice to use the @code{tbreak} command in conjunction with
15148 @code{jump}. @xref{Set Breaks, ,Setting Breakpoints}.
15150 The @code{jump} command does not change the current stack frame, or
15151 the stack pointer, or the contents of any memory location or any
15152 register other than the program counter. If line @var{linespec} is in
15153 a different function from the one currently executing, the results may
15154 be bizarre if the two functions expect different patterns of arguments or
15155 of local variables. For this reason, the @code{jump} command requests
15156 confirmation if the specified line is not in the function currently
15157 executing. However, even bizarre results are predictable if you are
15158 well acquainted with the machine-language code of your program.
15161 @c Doesn't work on HP-UX; have to set $pcoqh and $pcoqt.
15162 On many systems, you can get much the same effect as the @code{jump}
15163 command by storing a new value into the register @code{$pc}. The
15164 difference is that this does not start your program running; it only
15165 changes the address of where it @emph{will} run when you continue. For
15173 makes the next @code{continue} command or stepping command execute at
15174 address @code{0x485}, rather than at the address where your program stopped.
15175 @xref{Continuing and Stepping, ,Continuing and Stepping}.
15177 The most common occasion to use the @code{jump} command is to back
15178 up---perhaps with more breakpoints set---over a portion of a program
15179 that has already executed, in order to examine its execution in more
15184 @section Giving your Program a Signal
15185 @cindex deliver a signal to a program
15189 @item signal @var{signal}
15190 Resume execution where your program stopped, but immediately give it the
15191 signal @var{signal}. @var{signal} can be the name or the number of a
15192 signal. For example, on many systems @code{signal 2} and @code{signal
15193 SIGINT} are both ways of sending an interrupt signal.
15195 Alternatively, if @var{signal} is zero, continue execution without
15196 giving a signal. This is useful when your program stopped on account of
15197 a signal and would ordinary see the signal when resumed with the
15198 @code{continue} command; @samp{signal 0} causes it to resume without a
15201 @code{signal} does not repeat when you press @key{RET} a second time
15202 after executing the command.
15206 Invoking the @code{signal} command is not the same as invoking the
15207 @code{kill} utility from the shell. Sending a signal with @code{kill}
15208 causes @value{GDBN} to decide what to do with the signal depending on
15209 the signal handling tables (@pxref{Signals}). The @code{signal} command
15210 passes the signal directly to your program.
15214 @section Returning from a Function
15217 @cindex returning from a function
15220 @itemx return @var{expression}
15221 You can cancel execution of a function call with the @code{return}
15222 command. If you give an
15223 @var{expression} argument, its value is used as the function's return
15227 When you use @code{return}, @value{GDBN} discards the selected stack frame
15228 (and all frames within it). You can think of this as making the
15229 discarded frame return prematurely. If you wish to specify a value to
15230 be returned, give that value as the argument to @code{return}.
15232 This pops the selected stack frame (@pxref{Selection, ,Selecting a
15233 Frame}), and any other frames inside of it, leaving its caller as the
15234 innermost remaining frame. That frame becomes selected. The
15235 specified value is stored in the registers used for returning values
15238 The @code{return} command does not resume execution; it leaves the
15239 program stopped in the state that would exist if the function had just
15240 returned. In contrast, the @code{finish} command (@pxref{Continuing
15241 and Stepping, ,Continuing and Stepping}) resumes execution until the
15242 selected stack frame returns naturally.
15244 @value{GDBN} needs to know how the @var{expression} argument should be set for
15245 the inferior. The concrete registers assignment depends on the OS ABI and the
15246 type being returned by the selected stack frame. For example it is common for
15247 OS ABI to return floating point values in FPU registers while integer values in
15248 CPU registers. Still some ABIs return even floating point values in CPU
15249 registers. Larger integer widths (such as @code{long long int}) also have
15250 specific placement rules. @value{GDBN} already knows the OS ABI from its
15251 current target so it needs to find out also the type being returned to make the
15252 assignment into the right register(s).
15254 Normally, the selected stack frame has debug info. @value{GDBN} will always
15255 use the debug info instead of the implicit type of @var{expression} when the
15256 debug info is available. For example, if you type @kbd{return -1}, and the
15257 function in the current stack frame is declared to return a @code{long long
15258 int}, @value{GDBN} transparently converts the implicit @code{int} value of -1
15259 into a @code{long long int}:
15262 Breakpoint 1, func () at gdb.base/return-nodebug.c:29
15264 (@value{GDBP}) return -1
15265 Make func return now? (y or n) y
15266 #0 0x004004f6 in main () at gdb.base/return-nodebug.c:43
15267 43 printf ("result=%lld\n", func ());
15271 However, if the selected stack frame does not have a debug info, e.g., if the
15272 function was compiled without debug info, @value{GDBN} has to find out the type
15273 to return from user. Specifying a different type by mistake may set the value
15274 in different inferior registers than the caller code expects. For example,
15275 typing @kbd{return -1} with its implicit type @code{int} would set only a part
15276 of a @code{long long int} result for a debug info less function (on 32-bit
15277 architectures). Therefore the user is required to specify the return type by
15278 an appropriate cast explicitly:
15281 Breakpoint 2, 0x0040050b in func ()
15282 (@value{GDBP}) return -1
15283 Return value type not available for selected stack frame.
15284 Please use an explicit cast of the value to return.
15285 (@value{GDBP}) return (long long int) -1
15286 Make selected stack frame return now? (y or n) y
15287 #0 0x00400526 in main ()
15292 @section Calling Program Functions
15295 @cindex calling functions
15296 @cindex inferior functions, calling
15297 @item print @var{expr}
15298 Evaluate the expression @var{expr} and display the resulting value.
15299 @var{expr} may include calls to functions in the program being
15303 @item call @var{expr}
15304 Evaluate the expression @var{expr} without displaying @code{void}
15307 You can use this variant of the @code{print} command if you want to
15308 execute a function from your program that does not return anything
15309 (a.k.a.@: @dfn{a void function}), but without cluttering the output
15310 with @code{void} returned values that @value{GDBN} will otherwise
15311 print. If the result is not void, it is printed and saved in the
15315 It is possible for the function you call via the @code{print} or
15316 @code{call} command to generate a signal (e.g., if there's a bug in
15317 the function, or if you passed it incorrect arguments). What happens
15318 in that case is controlled by the @code{set unwindonsignal} command.
15320 Similarly, with a C@t{++} program it is possible for the function you
15321 call via the @code{print} or @code{call} command to generate an
15322 exception that is not handled due to the constraints of the dummy
15323 frame. In this case, any exception that is raised in the frame, but has
15324 an out-of-frame exception handler will not be found. GDB builds a
15325 dummy-frame for the inferior function call, and the unwinder cannot
15326 seek for exception handlers outside of this dummy-frame. What happens
15327 in that case is controlled by the
15328 @code{set unwind-on-terminating-exception} command.
15331 @item set unwindonsignal
15332 @kindex set unwindonsignal
15333 @cindex unwind stack in called functions
15334 @cindex call dummy stack unwinding
15335 Set unwinding of the stack if a signal is received while in a function
15336 that @value{GDBN} called in the program being debugged. If set to on,
15337 @value{GDBN} unwinds the stack it created for the call and restores
15338 the context to what it was before the call. If set to off (the
15339 default), @value{GDBN} stops in the frame where the signal was
15342 @item show unwindonsignal
15343 @kindex show unwindonsignal
15344 Show the current setting of stack unwinding in the functions called by
15347 @item set unwind-on-terminating-exception
15348 @kindex set unwind-on-terminating-exception
15349 @cindex unwind stack in called functions with unhandled exceptions
15350 @cindex call dummy stack unwinding on unhandled exception.
15351 Set unwinding of the stack if a C@t{++} exception is raised, but left
15352 unhandled while in a function that @value{GDBN} called in the program being
15353 debugged. If set to on (the default), @value{GDBN} unwinds the stack
15354 it created for the call and restores the context to what it was before
15355 the call. If set to off, @value{GDBN} the exception is delivered to
15356 the default C@t{++} exception handler and the inferior terminated.
15358 @item show unwind-on-terminating-exception
15359 @kindex show unwind-on-terminating-exception
15360 Show the current setting of stack unwinding in the functions called by
15365 @cindex weak alias functions
15366 Sometimes, a function you wish to call is actually a @dfn{weak alias}
15367 for another function. In such case, @value{GDBN} might not pick up
15368 the type information, including the types of the function arguments,
15369 which causes @value{GDBN} to call the inferior function incorrectly.
15370 As a result, the called function will function erroneously and may
15371 even crash. A solution to that is to use the name of the aliased
15375 @section Patching Programs
15377 @cindex patching binaries
15378 @cindex writing into executables
15379 @cindex writing into corefiles
15381 By default, @value{GDBN} opens the file containing your program's
15382 executable code (or the corefile) read-only. This prevents accidental
15383 alterations to machine code; but it also prevents you from intentionally
15384 patching your program's binary.
15386 If you'd like to be able to patch the binary, you can specify that
15387 explicitly with the @code{set write} command. For example, you might
15388 want to turn on internal debugging flags, or even to make emergency
15394 @itemx set write off
15395 If you specify @samp{set write on}, @value{GDBN} opens executable and
15396 core files for both reading and writing; if you specify @kbd{set write
15397 off} (the default), @value{GDBN} opens them read-only.
15399 If you have already loaded a file, you must load it again (using the
15400 @code{exec-file} or @code{core-file} command) after changing @code{set
15401 write}, for your new setting to take effect.
15405 Display whether executable files and core files are opened for writing
15406 as well as reading.
15410 @chapter @value{GDBN} Files
15412 @value{GDBN} needs to know the file name of the program to be debugged,
15413 both in order to read its symbol table and in order to start your
15414 program. To debug a core dump of a previous run, you must also tell
15415 @value{GDBN} the name of the core dump file.
15418 * Files:: Commands to specify files
15419 * Separate Debug Files:: Debugging information in separate files
15420 * Index Files:: Index files speed up GDB
15421 * Symbol Errors:: Errors reading symbol files
15422 * Data Files:: GDB data files
15426 @section Commands to Specify Files
15428 @cindex symbol table
15429 @cindex core dump file
15431 You may want to specify executable and core dump file names. The usual
15432 way to do this is at start-up time, using the arguments to
15433 @value{GDBN}'s start-up commands (@pxref{Invocation, , Getting In and
15434 Out of @value{GDBN}}).
15436 Occasionally it is necessary to change to a different file during a
15437 @value{GDBN} session. Or you may run @value{GDBN} and forget to
15438 specify a file you want to use. Or you are debugging a remote target
15439 via @code{gdbserver} (@pxref{Server, file, Using the @code{gdbserver}
15440 Program}). In these situations the @value{GDBN} commands to specify
15441 new files are useful.
15444 @cindex executable file
15446 @item file @var{filename}
15447 Use @var{filename} as the program to be debugged. It is read for its
15448 symbols and for the contents of pure memory. It is also the program
15449 executed when you use the @code{run} command. If you do not specify a
15450 directory and the file is not found in the @value{GDBN} working directory,
15451 @value{GDBN} uses the environment variable @code{PATH} as a list of
15452 directories to search, just as the shell does when looking for a program
15453 to run. You can change the value of this variable, for both @value{GDBN}
15454 and your program, using the @code{path} command.
15456 @cindex unlinked object files
15457 @cindex patching object files
15458 You can load unlinked object @file{.o} files into @value{GDBN} using
15459 the @code{file} command. You will not be able to ``run'' an object
15460 file, but you can disassemble functions and inspect variables. Also,
15461 if the underlying BFD functionality supports it, you could use
15462 @kbd{gdb -write} to patch object files using this technique. Note
15463 that @value{GDBN} can neither interpret nor modify relocations in this
15464 case, so branches and some initialized variables will appear to go to
15465 the wrong place. But this feature is still handy from time to time.
15468 @code{file} with no argument makes @value{GDBN} discard any information it
15469 has on both executable file and the symbol table.
15472 @item exec-file @r{[} @var{filename} @r{]}
15473 Specify that the program to be run (but not the symbol table) is found
15474 in @var{filename}. @value{GDBN} searches the environment variable @code{PATH}
15475 if necessary to locate your program. Omitting @var{filename} means to
15476 discard information on the executable file.
15478 @kindex symbol-file
15479 @item symbol-file @r{[} @var{filename} @r{]}
15480 Read symbol table information from file @var{filename}. @code{PATH} is
15481 searched when necessary. Use the @code{file} command to get both symbol
15482 table and program to run from the same file.
15484 @code{symbol-file} with no argument clears out @value{GDBN} information on your
15485 program's symbol table.
15487 The @code{symbol-file} command causes @value{GDBN} to forget the contents of
15488 some breakpoints and auto-display expressions. This is because they may
15489 contain pointers to the internal data recording symbols and data types,
15490 which are part of the old symbol table data being discarded inside
15493 @code{symbol-file} does not repeat if you press @key{RET} again after
15496 When @value{GDBN} is configured for a particular environment, it
15497 understands debugging information in whatever format is the standard
15498 generated for that environment; you may use either a @sc{gnu} compiler, or
15499 other compilers that adhere to the local conventions.
15500 Best results are usually obtained from @sc{gnu} compilers; for example,
15501 using @code{@value{NGCC}} you can generate debugging information for
15504 For most kinds of object files, with the exception of old SVR3 systems
15505 using COFF, the @code{symbol-file} command does not normally read the
15506 symbol table in full right away. Instead, it scans the symbol table
15507 quickly to find which source files and which symbols are present. The
15508 details are read later, one source file at a time, as they are needed.
15510 The purpose of this two-stage reading strategy is to make @value{GDBN}
15511 start up faster. For the most part, it is invisible except for
15512 occasional pauses while the symbol table details for a particular source
15513 file are being read. (The @code{set verbose} command can turn these
15514 pauses into messages if desired. @xref{Messages/Warnings, ,Optional
15515 Warnings and Messages}.)
15517 We have not implemented the two-stage strategy for COFF yet. When the
15518 symbol table is stored in COFF format, @code{symbol-file} reads the
15519 symbol table data in full right away. Note that ``stabs-in-COFF''
15520 still does the two-stage strategy, since the debug info is actually
15524 @cindex reading symbols immediately
15525 @cindex symbols, reading immediately
15526 @item symbol-file @r{[} -readnow @r{]} @var{filename}
15527 @itemx file @r{[} -readnow @r{]} @var{filename}
15528 You can override the @value{GDBN} two-stage strategy for reading symbol
15529 tables by using the @samp{-readnow} option with any of the commands that
15530 load symbol table information, if you want to be sure @value{GDBN} has the
15531 entire symbol table available.
15533 @c FIXME: for now no mention of directories, since this seems to be in
15534 @c flux. 13mar1992 status is that in theory GDB would look either in
15535 @c current dir or in same dir as myprog; but issues like competing
15536 @c GDB's, or clutter in system dirs, mean that in practice right now
15537 @c only current dir is used. FFish says maybe a special GDB hierarchy
15538 @c (eg rooted in val of env var GDBSYMS) could exist for mappable symbol
15542 @item core-file @r{[}@var{filename}@r{]}
15544 Specify the whereabouts of a core dump file to be used as the ``contents
15545 of memory''. Traditionally, core files contain only some parts of the
15546 address space of the process that generated them; @value{GDBN} can access the
15547 executable file itself for other parts.
15549 @code{core-file} with no argument specifies that no core file is
15552 Note that the core file is ignored when your program is actually running
15553 under @value{GDBN}. So, if you have been running your program and you
15554 wish to debug a core file instead, you must kill the subprocess in which
15555 the program is running. To do this, use the @code{kill} command
15556 (@pxref{Kill Process, ,Killing the Child Process}).
15558 @kindex add-symbol-file
15559 @cindex dynamic linking
15560 @item add-symbol-file @var{filename} @var{address}
15561 @itemx add-symbol-file @var{filename} @var{address} @r{[} -readnow @r{]}
15562 @itemx add-symbol-file @var{filename} @var{address} -s @var{section} @var{address} @dots{}
15563 The @code{add-symbol-file} command reads additional symbol table
15564 information from the file @var{filename}. You would use this command
15565 when @var{filename} has been dynamically loaded (by some other means)
15566 into the program that is running. @var{address} should be the memory
15567 address at which the file has been loaded; @value{GDBN} cannot figure
15568 this out for itself. You can additionally specify an arbitrary number
15569 of @samp{-s @var{section} @var{address}} pairs, to give an explicit
15570 section name and base address for that section. You can specify any
15571 @var{address} as an expression.
15573 The symbol table of the file @var{filename} is added to the symbol table
15574 originally read with the @code{symbol-file} command. You can use the
15575 @code{add-symbol-file} command any number of times; the new symbol data
15576 thus read keeps adding to the old. To discard all old symbol data
15577 instead, use the @code{symbol-file} command without any arguments.
15579 @cindex relocatable object files, reading symbols from
15580 @cindex object files, relocatable, reading symbols from
15581 @cindex reading symbols from relocatable object files
15582 @cindex symbols, reading from relocatable object files
15583 @cindex @file{.o} files, reading symbols from
15584 Although @var{filename} is typically a shared library file, an
15585 executable file, or some other object file which has been fully
15586 relocated for loading into a process, you can also load symbolic
15587 information from relocatable @file{.o} files, as long as:
15591 the file's symbolic information refers only to linker symbols defined in
15592 that file, not to symbols defined by other object files,
15594 every section the file's symbolic information refers to has actually
15595 been loaded into the inferior, as it appears in the file, and
15597 you can determine the address at which every section was loaded, and
15598 provide these to the @code{add-symbol-file} command.
15602 Some embedded operating systems, like Sun Chorus and VxWorks, can load
15603 relocatable files into an already running program; such systems
15604 typically make the requirements above easy to meet. However, it's
15605 important to recognize that many native systems use complex link
15606 procedures (@code{.linkonce} section factoring and C@t{++} constructor table
15607 assembly, for example) that make the requirements difficult to meet. In
15608 general, one cannot assume that using @code{add-symbol-file} to read a
15609 relocatable object file's symbolic information will have the same effect
15610 as linking the relocatable object file into the program in the normal
15613 @code{add-symbol-file} does not repeat if you press @key{RET} after using it.
15615 @kindex add-symbol-file-from-memory
15616 @cindex @code{syscall DSO}
15617 @cindex load symbols from memory
15618 @item add-symbol-file-from-memory @var{address}
15619 Load symbols from the given @var{address} in a dynamically loaded
15620 object file whose image is mapped directly into the inferior's memory.
15621 For example, the Linux kernel maps a @code{syscall DSO} into each
15622 process's address space; this DSO provides kernel-specific code for
15623 some system calls. The argument can be any expression whose
15624 evaluation yields the address of the file's shared object file header.
15625 For this command to work, you must have used @code{symbol-file} or
15626 @code{exec-file} commands in advance.
15628 @kindex add-shared-symbol-files
15630 @item add-shared-symbol-files @var{library-file}
15631 @itemx assf @var{library-file}
15632 The @code{add-shared-symbol-files} command can currently be used only
15633 in the Cygwin build of @value{GDBN} on MS-Windows OS, where it is an
15634 alias for the @code{dll-symbols} command (@pxref{Cygwin Native}).
15635 @value{GDBN} automatically looks for shared libraries, however if
15636 @value{GDBN} does not find yours, you can invoke
15637 @code{add-shared-symbol-files}. It takes one argument: the shared
15638 library's file name. @code{assf} is a shorthand alias for
15639 @code{add-shared-symbol-files}.
15642 @item section @var{section} @var{addr}
15643 The @code{section} command changes the base address of the named
15644 @var{section} of the exec file to @var{addr}. This can be used if the
15645 exec file does not contain section addresses, (such as in the
15646 @code{a.out} format), or when the addresses specified in the file
15647 itself are wrong. Each section must be changed separately. The
15648 @code{info files} command, described below, lists all the sections and
15652 @kindex info target
15655 @code{info files} and @code{info target} are synonymous; both print the
15656 current target (@pxref{Targets, ,Specifying a Debugging Target}),
15657 including the names of the executable and core dump files currently in
15658 use by @value{GDBN}, and the files from which symbols were loaded. The
15659 command @code{help target} lists all possible targets rather than
15662 @kindex maint info sections
15663 @item maint info sections
15664 Another command that can give you extra information about program sections
15665 is @code{maint info sections}. In addition to the section information
15666 displayed by @code{info files}, this command displays the flags and file
15667 offset of each section in the executable and core dump files. In addition,
15668 @code{maint info sections} provides the following command options (which
15669 may be arbitrarily combined):
15673 Display sections for all loaded object files, including shared libraries.
15674 @item @var{sections}
15675 Display info only for named @var{sections}.
15676 @item @var{section-flags}
15677 Display info only for sections for which @var{section-flags} are true.
15678 The section flags that @value{GDBN} currently knows about are:
15681 Section will have space allocated in the process when loaded.
15682 Set for all sections except those containing debug information.
15684 Section will be loaded from the file into the child process memory.
15685 Set for pre-initialized code and data, clear for @code{.bss} sections.
15687 Section needs to be relocated before loading.
15689 Section cannot be modified by the child process.
15691 Section contains executable code only.
15693 Section contains data only (no executable code).
15695 Section will reside in ROM.
15697 Section contains data for constructor/destructor lists.
15699 Section is not empty.
15701 An instruction to the linker to not output the section.
15702 @item COFF_SHARED_LIBRARY
15703 A notification to the linker that the section contains
15704 COFF shared library information.
15706 Section contains common symbols.
15709 @kindex set trust-readonly-sections
15710 @cindex read-only sections
15711 @item set trust-readonly-sections on
15712 Tell @value{GDBN} that readonly sections in your object file
15713 really are read-only (i.e.@: that their contents will not change).
15714 In that case, @value{GDBN} can fetch values from these sections
15715 out of the object file, rather than from the target program.
15716 For some targets (notably embedded ones), this can be a significant
15717 enhancement to debugging performance.
15719 The default is off.
15721 @item set trust-readonly-sections off
15722 Tell @value{GDBN} not to trust readonly sections. This means that
15723 the contents of the section might change while the program is running,
15724 and must therefore be fetched from the target when needed.
15726 @item show trust-readonly-sections
15727 Show the current setting of trusting readonly sections.
15730 All file-specifying commands allow both absolute and relative file names
15731 as arguments. @value{GDBN} always converts the file name to an absolute file
15732 name and remembers it that way.
15734 @cindex shared libraries
15735 @anchor{Shared Libraries}
15736 @value{GDBN} supports @sc{gnu}/Linux, MS-Windows, HP-UX, SunOS, SVr4, Irix,
15737 and IBM RS/6000 AIX shared libraries.
15739 On MS-Windows @value{GDBN} must be linked with the Expat library to support
15740 shared libraries. @xref{Expat}.
15742 @value{GDBN} automatically loads symbol definitions from shared libraries
15743 when you use the @code{run} command, or when you examine a core file.
15744 (Before you issue the @code{run} command, @value{GDBN} does not understand
15745 references to a function in a shared library, however---unless you are
15746 debugging a core file).
15748 On HP-UX, if the program loads a library explicitly, @value{GDBN}
15749 automatically loads the symbols at the time of the @code{shl_load} call.
15751 @c FIXME: some @value{GDBN} release may permit some refs to undef
15752 @c FIXME...symbols---eg in a break cmd---assuming they are from a shared
15753 @c FIXME...lib; check this from time to time when updating manual
15755 There are times, however, when you may wish to not automatically load
15756 symbol definitions from shared libraries, such as when they are
15757 particularly large or there are many of them.
15759 To control the automatic loading of shared library symbols, use the
15763 @kindex set auto-solib-add
15764 @item set auto-solib-add @var{mode}
15765 If @var{mode} is @code{on}, symbols from all shared object libraries
15766 will be loaded automatically when the inferior begins execution, you
15767 attach to an independently started inferior, or when the dynamic linker
15768 informs @value{GDBN} that a new library has been loaded. If @var{mode}
15769 is @code{off}, symbols must be loaded manually, using the
15770 @code{sharedlibrary} command. The default value is @code{on}.
15772 @cindex memory used for symbol tables
15773 If your program uses lots of shared libraries with debug info that
15774 takes large amounts of memory, you can decrease the @value{GDBN}
15775 memory footprint by preventing it from automatically loading the
15776 symbols from shared libraries. To that end, type @kbd{set
15777 auto-solib-add off} before running the inferior, then load each
15778 library whose debug symbols you do need with @kbd{sharedlibrary
15779 @var{regexp}}, where @var{regexp} is a regular expression that matches
15780 the libraries whose symbols you want to be loaded.
15782 @kindex show auto-solib-add
15783 @item show auto-solib-add
15784 Display the current autoloading mode.
15787 @cindex load shared library
15788 To explicitly load shared library symbols, use the @code{sharedlibrary}
15792 @kindex info sharedlibrary
15794 @item info share @var{regex}
15795 @itemx info sharedlibrary @var{regex}
15796 Print the names of the shared libraries which are currently loaded
15797 that match @var{regex}. If @var{regex} is omitted then print
15798 all shared libraries that are loaded.
15800 @kindex sharedlibrary
15802 @item sharedlibrary @var{regex}
15803 @itemx share @var{regex}
15804 Load shared object library symbols for files matching a
15805 Unix regular expression.
15806 As with files loaded automatically, it only loads shared libraries
15807 required by your program for a core file or after typing @code{run}. If
15808 @var{regex} is omitted all shared libraries required by your program are
15811 @item nosharedlibrary
15812 @kindex nosharedlibrary
15813 @cindex unload symbols from shared libraries
15814 Unload all shared object library symbols. This discards all symbols
15815 that have been loaded from all shared libraries. Symbols from shared
15816 libraries that were loaded by explicit user requests are not
15820 Sometimes you may wish that @value{GDBN} stops and gives you control
15821 when any of shared library events happen. The best way to do this is
15822 to use @code{catch load} and @code{catch unload} (@pxref{Set
15825 @value{GDBN} also supports the the @code{set stop-on-solib-events}
15826 command for this. This command exists for historical reasons. It is
15827 less useful than setting a catchpoint, because it does not allow for
15828 conditions or commands as a catchpoint does.
15831 @item set stop-on-solib-events
15832 @kindex set stop-on-solib-events
15833 This command controls whether @value{GDBN} should give you control
15834 when the dynamic linker notifies it about some shared library event.
15835 The most common event of interest is loading or unloading of a new
15838 @item show stop-on-solib-events
15839 @kindex show stop-on-solib-events
15840 Show whether @value{GDBN} stops and gives you control when shared
15841 library events happen.
15844 Shared libraries are also supported in many cross or remote debugging
15845 configurations. @value{GDBN} needs to have access to the target's libraries;
15846 this can be accomplished either by providing copies of the libraries
15847 on the host system, or by asking @value{GDBN} to automatically retrieve the
15848 libraries from the target. If copies of the target libraries are
15849 provided, they need to be the same as the target libraries, although the
15850 copies on the target can be stripped as long as the copies on the host are
15853 @cindex where to look for shared libraries
15854 For remote debugging, you need to tell @value{GDBN} where the target
15855 libraries are, so that it can load the correct copies---otherwise, it
15856 may try to load the host's libraries. @value{GDBN} has two variables
15857 to specify the search directories for target libraries.
15860 @cindex prefix for shared library file names
15861 @cindex system root, alternate
15862 @kindex set solib-absolute-prefix
15863 @kindex set sysroot
15864 @item set sysroot @var{path}
15865 Use @var{path} as the system root for the program being debugged. Any
15866 absolute shared library paths will be prefixed with @var{path}; many
15867 runtime loaders store the absolute paths to the shared library in the
15868 target program's memory. If you use @code{set sysroot} to find shared
15869 libraries, they need to be laid out in the same way that they are on
15870 the target, with e.g.@: a @file{/lib} and @file{/usr/lib} hierarchy
15873 If @var{path} starts with the sequence @file{remote:}, @value{GDBN} will
15874 retrieve the target libraries from the remote system. This is only
15875 supported when using a remote target that supports the @code{remote get}
15876 command (@pxref{File Transfer,,Sending files to a remote system}).
15877 The part of @var{path} following the initial @file{remote:}
15878 (if present) is used as system root prefix on the remote file system.
15879 @footnote{If you want to specify a local system root using a directory
15880 that happens to be named @file{remote:}, you need to use some equivalent
15881 variant of the name like @file{./remote:}.}
15883 For targets with an MS-DOS based filesystem, such as MS-Windows and
15884 SymbianOS, @value{GDBN} tries prefixing a few variants of the target
15885 absolute file name with @var{path}. But first, on Unix hosts,
15886 @value{GDBN} converts all backslash directory separators into forward
15887 slashes, because the backslash is not a directory separator on Unix:
15890 c:\foo\bar.dll @result{} c:/foo/bar.dll
15893 Then, @value{GDBN} attempts prefixing the target file name with
15894 @var{path}, and looks for the resulting file name in the host file
15898 c:/foo/bar.dll @result{} /path/to/sysroot/c:/foo/bar.dll
15901 If that does not find the shared library, @value{GDBN} tries removing
15902 the @samp{:} character from the drive spec, both for convenience, and,
15903 for the case of the host file system not supporting file names with
15907 c:/foo/bar.dll @result{} /path/to/sysroot/c/foo/bar.dll
15910 This makes it possible to have a system root that mirrors a target
15911 with more than one drive. E.g., you may want to setup your local
15912 copies of the target system shared libraries like so (note @samp{c} vs
15916 @file{/path/to/sysroot/c/sys/bin/foo.dll}
15917 @file{/path/to/sysroot/c/sys/bin/bar.dll}
15918 @file{/path/to/sysroot/z/sys/bin/bar.dll}
15922 and point the system root at @file{/path/to/sysroot}, so that
15923 @value{GDBN} can find the correct copies of both
15924 @file{c:\sys\bin\foo.dll}, and @file{z:\sys\bin\bar.dll}.
15926 If that still does not find the shared library, @value{GDBN} tries
15927 removing the whole drive spec from the target file name:
15930 c:/foo/bar.dll @result{} /path/to/sysroot/foo/bar.dll
15933 This last lookup makes it possible to not care about the drive name,
15934 if you don't want or need to.
15936 The @code{set solib-absolute-prefix} command is an alias for @code{set
15939 @cindex default system root
15940 @cindex @samp{--with-sysroot}
15941 You can set the default system root by using the configure-time
15942 @samp{--with-sysroot} option. If the system root is inside
15943 @value{GDBN}'s configured binary prefix (set with @samp{--prefix} or
15944 @samp{--exec-prefix}), then the default system root will be updated
15945 automatically if the installed @value{GDBN} is moved to a new
15948 @kindex show sysroot
15950 Display the current shared library prefix.
15952 @kindex set solib-search-path
15953 @item set solib-search-path @var{path}
15954 If this variable is set, @var{path} is a colon-separated list of
15955 directories to search for shared libraries. @samp{solib-search-path}
15956 is used after @samp{sysroot} fails to locate the library, or if the
15957 path to the library is relative instead of absolute. If you want to
15958 use @samp{solib-search-path} instead of @samp{sysroot}, be sure to set
15959 @samp{sysroot} to a nonexistent directory to prevent @value{GDBN} from
15960 finding your host's libraries. @samp{sysroot} is preferred; setting
15961 it to a nonexistent directory may interfere with automatic loading
15962 of shared library symbols.
15964 @kindex show solib-search-path
15965 @item show solib-search-path
15966 Display the current shared library search path.
15968 @cindex DOS file-name semantics of file names.
15969 @kindex set target-file-system-kind (unix|dos-based|auto)
15970 @kindex show target-file-system-kind
15971 @item set target-file-system-kind @var{kind}
15972 Set assumed file system kind for target reported file names.
15974 Shared library file names as reported by the target system may not
15975 make sense as is on the system @value{GDBN} is running on. For
15976 example, when remote debugging a target that has MS-DOS based file
15977 system semantics, from a Unix host, the target may be reporting to
15978 @value{GDBN} a list of loaded shared libraries with file names such as
15979 @file{c:\Windows\kernel32.dll}. On Unix hosts, there's no concept of
15980 drive letters, so the @samp{c:\} prefix is not normally understood as
15981 indicating an absolute file name, and neither is the backslash
15982 normally considered a directory separator character. In that case,
15983 the native file system would interpret this whole absolute file name
15984 as a relative file name with no directory components. This would make
15985 it impossible to point @value{GDBN} at a copy of the remote target's
15986 shared libraries on the host using @code{set sysroot}, and impractical
15987 with @code{set solib-search-path}. Setting
15988 @code{target-file-system-kind} to @code{dos-based} tells @value{GDBN}
15989 to interpret such file names similarly to how the target would, and to
15990 map them to file names valid on @value{GDBN}'s native file system
15991 semantics. The value of @var{kind} can be @code{"auto"}, in addition
15992 to one of the supported file system kinds. In that case, @value{GDBN}
15993 tries to determine the appropriate file system variant based on the
15994 current target's operating system (@pxref{ABI, ,Configuring the
15995 Current ABI}). The supported file system settings are:
15999 Instruct @value{GDBN} to assume the target file system is of Unix
16000 kind. Only file names starting the forward slash (@samp{/}) character
16001 are considered absolute, and the directory separator character is also
16005 Instruct @value{GDBN} to assume the target file system is DOS based.
16006 File names starting with either a forward slash, or a drive letter
16007 followed by a colon (e.g., @samp{c:}), are considered absolute, and
16008 both the slash (@samp{/}) and the backslash (@samp{\\}) characters are
16009 considered directory separators.
16012 Instruct @value{GDBN} to use the file system kind associated with the
16013 target operating system (@pxref{ABI, ,Configuring the Current ABI}).
16014 This is the default.
16018 @cindex file name canonicalization
16019 @cindex base name differences
16020 When processing file names provided by the user, @value{GDBN}
16021 frequently needs to compare them to the file names recorded in the
16022 program's debug info. Normally, @value{GDBN} compares just the
16023 @dfn{base names} of the files as strings, which is reasonably fast
16024 even for very large programs. (The base name of a file is the last
16025 portion of its name, after stripping all the leading directories.)
16026 This shortcut in comparison is based upon the assumption that files
16027 cannot have more than one base name. This is usually true, but
16028 references to files that use symlinks or similar filesystem
16029 facilities violate that assumption. If your program records files
16030 using such facilities, or if you provide file names to @value{GDBN}
16031 using symlinks etc., you can set @code{basenames-may-differ} to
16032 @code{true} to instruct @value{GDBN} to completely canonicalize each
16033 pair of file names it needs to compare. This will make file-name
16034 comparisons accurate, but at a price of a significant slowdown.
16037 @item set basenames-may-differ
16038 @kindex set basenames-may-differ
16039 Set whether a source file may have multiple base names.
16041 @item show basenames-may-differ
16042 @kindex show basenames-may-differ
16043 Show whether a source file may have multiple base names.
16046 @node Separate Debug Files
16047 @section Debugging Information in Separate Files
16048 @cindex separate debugging information files
16049 @cindex debugging information in separate files
16050 @cindex @file{.debug} subdirectories
16051 @cindex debugging information directory, global
16052 @cindex global debugging information directory
16053 @cindex build ID, and separate debugging files
16054 @cindex @file{.build-id} directory
16056 @value{GDBN} allows you to put a program's debugging information in a
16057 file separate from the executable itself, in a way that allows
16058 @value{GDBN} to find and load the debugging information automatically.
16059 Since debugging information can be very large---sometimes larger
16060 than the executable code itself---some systems distribute debugging
16061 information for their executables in separate files, which users can
16062 install only when they need to debug a problem.
16064 @value{GDBN} supports two ways of specifying the separate debug info
16069 The executable contains a @dfn{debug link} that specifies the name of
16070 the separate debug info file. The separate debug file's name is
16071 usually @file{@var{executable}.debug}, where @var{executable} is the
16072 name of the corresponding executable file without leading directories
16073 (e.g., @file{ls.debug} for @file{/usr/bin/ls}). In addition, the
16074 debug link specifies a 32-bit @dfn{Cyclic Redundancy Check} (CRC)
16075 checksum for the debug file, which @value{GDBN} uses to validate that
16076 the executable and the debug file came from the same build.
16079 The executable contains a @dfn{build ID}, a unique bit string that is
16080 also present in the corresponding debug info file. (This is supported
16081 only on some operating systems, notably those which use the ELF format
16082 for binary files and the @sc{gnu} Binutils.) For more details about
16083 this feature, see the description of the @option{--build-id}
16084 command-line option in @ref{Options, , Command Line Options, ld.info,
16085 The GNU Linker}. The debug info file's name is not specified
16086 explicitly by the build ID, but can be computed from the build ID, see
16090 Depending on the way the debug info file is specified, @value{GDBN}
16091 uses two different methods of looking for the debug file:
16095 For the ``debug link'' method, @value{GDBN} looks up the named file in
16096 the directory of the executable file, then in a subdirectory of that
16097 directory named @file{.debug}, and finally under the global debug
16098 directory, in a subdirectory whose name is identical to the leading
16099 directories of the executable's absolute file name.
16102 For the ``build ID'' method, @value{GDBN} looks in the
16103 @file{.build-id} subdirectory of the global debug directory for a file
16104 named @file{@var{nn}/@var{nnnnnnnn}.debug}, where @var{nn} are the
16105 first 2 hex characters of the build ID bit string, and @var{nnnnnnnn}
16106 are the rest of the bit string. (Real build ID strings are 32 or more
16107 hex characters, not 10.)
16110 So, for example, suppose you ask @value{GDBN} to debug
16111 @file{/usr/bin/ls}, which has a debug link that specifies the
16112 file @file{ls.debug}, and a build ID whose value in hex is
16113 @code{abcdef1234}. If the global debug directory is
16114 @file{/usr/lib/debug}, then @value{GDBN} will look for the following
16115 debug information files, in the indicated order:
16119 @file{/usr/lib/debug/.build-id/ab/cdef1234.debug}
16121 @file{/usr/bin/ls.debug}
16123 @file{/usr/bin/.debug/ls.debug}
16125 @file{/usr/lib/debug/usr/bin/ls.debug}.
16128 You can set the global debugging info directory's name, and view the
16129 name @value{GDBN} is currently using.
16133 @kindex set debug-file-directory
16134 @item set debug-file-directory @var{directories}
16135 Set the directories which @value{GDBN} searches for separate debugging
16136 information files to @var{directory}. Multiple directory components can be set
16137 concatenating them by a directory separator.
16139 @kindex show debug-file-directory
16140 @item show debug-file-directory
16141 Show the directories @value{GDBN} searches for separate debugging
16146 @cindex @code{.gnu_debuglink} sections
16147 @cindex debug link sections
16148 A debug link is a special section of the executable file named
16149 @code{.gnu_debuglink}. The section must contain:
16153 A filename, with any leading directory components removed, followed by
16156 zero to three bytes of padding, as needed to reach the next four-byte
16157 boundary within the section, and
16159 a four-byte CRC checksum, stored in the same endianness used for the
16160 executable file itself. The checksum is computed on the debugging
16161 information file's full contents by the function given below, passing
16162 zero as the @var{crc} argument.
16165 Any executable file format can carry a debug link, as long as it can
16166 contain a section named @code{.gnu_debuglink} with the contents
16169 @cindex @code{.note.gnu.build-id} sections
16170 @cindex build ID sections
16171 The build ID is a special section in the executable file (and in other
16172 ELF binary files that @value{GDBN} may consider). This section is
16173 often named @code{.note.gnu.build-id}, but that name is not mandatory.
16174 It contains unique identification for the built files---the ID remains
16175 the same across multiple builds of the same build tree. The default
16176 algorithm SHA1 produces 160 bits (40 hexadecimal characters) of the
16177 content for the build ID string. The same section with an identical
16178 value is present in the original built binary with symbols, in its
16179 stripped variant, and in the separate debugging information file.
16181 The debugging information file itself should be an ordinary
16182 executable, containing a full set of linker symbols, sections, and
16183 debugging information. The sections of the debugging information file
16184 should have the same names, addresses, and sizes as the original file,
16185 but they need not contain any data---much like a @code{.bss} section
16186 in an ordinary executable.
16188 The @sc{gnu} binary utilities (Binutils) package includes the
16189 @samp{objcopy} utility that can produce
16190 the separated executable / debugging information file pairs using the
16191 following commands:
16194 @kbd{objcopy --only-keep-debug foo foo.debug}
16199 These commands remove the debugging
16200 information from the executable file @file{foo} and place it in the file
16201 @file{foo.debug}. You can use the first, second or both methods to link the
16206 The debug link method needs the following additional command to also leave
16207 behind a debug link in @file{foo}:
16210 @kbd{objcopy --add-gnu-debuglink=foo.debug foo}
16213 Ulrich Drepper's @file{elfutils} package, starting with version 0.53, contains
16214 a version of the @code{strip} command such that the command @kbd{strip foo -f
16215 foo.debug} has the same functionality as the two @code{objcopy} commands and
16216 the @code{ln -s} command above, together.
16219 Build ID gets embedded into the main executable using @code{ld --build-id} or
16220 the @value{NGCC} counterpart @code{gcc -Wl,--build-id}. Build ID support plus
16221 compatibility fixes for debug files separation are present in @sc{gnu} binary
16222 utilities (Binutils) package since version 2.18.
16227 @cindex CRC algorithm definition
16228 The CRC used in @code{.gnu_debuglink} is the CRC-32 defined in
16229 IEEE 802.3 using the polynomial:
16231 @c TexInfo requires naked braces for multi-digit exponents for Tex
16232 @c output, but this causes HTML output to barf. HTML has to be set using
16233 @c raw commands. So we end up having to specify this equation in 2
16238 <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>
16239 + <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
16245 @math{x^{32} + x^{26} + x^{23} + x^{22} + x^{16} + x^{12} + x^{11}}
16246 @math{+ x^{10} + x^8 + x^7 + x^5 + x^4 + x^2 + x + 1}
16250 The function is computed byte at a time, taking the least
16251 significant bit of each byte first. The initial pattern
16252 @code{0xffffffff} is used, to ensure leading zeros affect the CRC and
16253 the final result is inverted to ensure trailing zeros also affect the
16256 @emph{Note:} This is the same CRC polynomial as used in handling the
16257 @dfn{Remote Serial Protocol} @code{qCRC} packet (@pxref{Remote Protocol,
16258 , @value{GDBN} Remote Serial Protocol}). However in the
16259 case of the Remote Serial Protocol, the CRC is computed @emph{most}
16260 significant bit first, and the result is not inverted, so trailing
16261 zeros have no effect on the CRC value.
16263 To complete the description, we show below the code of the function
16264 which produces the CRC used in @code{.gnu_debuglink}. Inverting the
16265 initially supplied @code{crc} argument means that an initial call to
16266 this function passing in zero will start computing the CRC using
16269 @kindex gnu_debuglink_crc32
16272 gnu_debuglink_crc32 (unsigned long crc,
16273 unsigned char *buf, size_t len)
16275 static const unsigned long crc32_table[256] =
16277 0x00000000, 0x77073096, 0xee0e612c, 0x990951ba, 0x076dc419,
16278 0x706af48f, 0xe963a535, 0x9e6495a3, 0x0edb8832, 0x79dcb8a4,
16279 0xe0d5e91e, 0x97d2d988, 0x09b64c2b, 0x7eb17cbd, 0xe7b82d07,
16280 0x90bf1d91, 0x1db71064, 0x6ab020f2, 0xf3b97148, 0x84be41de,
16281 0x1adad47d, 0x6ddde4eb, 0xf4d4b551, 0x83d385c7, 0x136c9856,
16282 0x646ba8c0, 0xfd62f97a, 0x8a65c9ec, 0x14015c4f, 0x63066cd9,
16283 0xfa0f3d63, 0x8d080df5, 0x3b6e20c8, 0x4c69105e, 0xd56041e4,
16284 0xa2677172, 0x3c03e4d1, 0x4b04d447, 0xd20d85fd, 0xa50ab56b,
16285 0x35b5a8fa, 0x42b2986c, 0xdbbbc9d6, 0xacbcf940, 0x32d86ce3,
16286 0x45df5c75, 0xdcd60dcf, 0xabd13d59, 0x26d930ac, 0x51de003a,
16287 0xc8d75180, 0xbfd06116, 0x21b4f4b5, 0x56b3c423, 0xcfba9599,
16288 0xb8bda50f, 0x2802b89e, 0x5f058808, 0xc60cd9b2, 0xb10be924,
16289 0x2f6f7c87, 0x58684c11, 0xc1611dab, 0xb6662d3d, 0x76dc4190,
16290 0x01db7106, 0x98d220bc, 0xefd5102a, 0x71b18589, 0x06b6b51f,
16291 0x9fbfe4a5, 0xe8b8d433, 0x7807c9a2, 0x0f00f934, 0x9609a88e,
16292 0xe10e9818, 0x7f6a0dbb, 0x086d3d2d, 0x91646c97, 0xe6635c01,
16293 0x6b6b51f4, 0x1c6c6162, 0x856530d8, 0xf262004e, 0x6c0695ed,
16294 0x1b01a57b, 0x8208f4c1, 0xf50fc457, 0x65b0d9c6, 0x12b7e950,
16295 0x8bbeb8ea, 0xfcb9887c, 0x62dd1ddf, 0x15da2d49, 0x8cd37cf3,
16296 0xfbd44c65, 0x4db26158, 0x3ab551ce, 0xa3bc0074, 0xd4bb30e2,
16297 0x4adfa541, 0x3dd895d7, 0xa4d1c46d, 0xd3d6f4fb, 0x4369e96a,
16298 0x346ed9fc, 0xad678846, 0xda60b8d0, 0x44042d73, 0x33031de5,
16299 0xaa0a4c5f, 0xdd0d7cc9, 0x5005713c, 0x270241aa, 0xbe0b1010,
16300 0xc90c2086, 0x5768b525, 0x206f85b3, 0xb966d409, 0xce61e49f,
16301 0x5edef90e, 0x29d9c998, 0xb0d09822, 0xc7d7a8b4, 0x59b33d17,
16302 0x2eb40d81, 0xb7bd5c3b, 0xc0ba6cad, 0xedb88320, 0x9abfb3b6,
16303 0x03b6e20c, 0x74b1d29a, 0xead54739, 0x9dd277af, 0x04db2615,
16304 0x73dc1683, 0xe3630b12, 0x94643b84, 0x0d6d6a3e, 0x7a6a5aa8,
16305 0xe40ecf0b, 0x9309ff9d, 0x0a00ae27, 0x7d079eb1, 0xf00f9344,
16306 0x8708a3d2, 0x1e01f268, 0x6906c2fe, 0xf762575d, 0x806567cb,
16307 0x196c3671, 0x6e6b06e7, 0xfed41b76, 0x89d32be0, 0x10da7a5a,
16308 0x67dd4acc, 0xf9b9df6f, 0x8ebeeff9, 0x17b7be43, 0x60b08ed5,
16309 0xd6d6a3e8, 0xa1d1937e, 0x38d8c2c4, 0x4fdff252, 0xd1bb67f1,
16310 0xa6bc5767, 0x3fb506dd, 0x48b2364b, 0xd80d2bda, 0xaf0a1b4c,
16311 0x36034af6, 0x41047a60, 0xdf60efc3, 0xa867df55, 0x316e8eef,
16312 0x4669be79, 0xcb61b38c, 0xbc66831a, 0x256fd2a0, 0x5268e236,
16313 0xcc0c7795, 0xbb0b4703, 0x220216b9, 0x5505262f, 0xc5ba3bbe,
16314 0xb2bd0b28, 0x2bb45a92, 0x5cb36a04, 0xc2d7ffa7, 0xb5d0cf31,
16315 0x2cd99e8b, 0x5bdeae1d, 0x9b64c2b0, 0xec63f226, 0x756aa39c,
16316 0x026d930a, 0x9c0906a9, 0xeb0e363f, 0x72076785, 0x05005713,
16317 0x95bf4a82, 0xe2b87a14, 0x7bb12bae, 0x0cb61b38, 0x92d28e9b,
16318 0xe5d5be0d, 0x7cdcefb7, 0x0bdbdf21, 0x86d3d2d4, 0xf1d4e242,
16319 0x68ddb3f8, 0x1fda836e, 0x81be16cd, 0xf6b9265b, 0x6fb077e1,
16320 0x18b74777, 0x88085ae6, 0xff0f6a70, 0x66063bca, 0x11010b5c,
16321 0x8f659eff, 0xf862ae69, 0x616bffd3, 0x166ccf45, 0xa00ae278,
16322 0xd70dd2ee, 0x4e048354, 0x3903b3c2, 0xa7672661, 0xd06016f7,
16323 0x4969474d, 0x3e6e77db, 0xaed16a4a, 0xd9d65adc, 0x40df0b66,
16324 0x37d83bf0, 0xa9bcae53, 0xdebb9ec5, 0x47b2cf7f, 0x30b5ffe9,
16325 0xbdbdf21c, 0xcabac28a, 0x53b39330, 0x24b4a3a6, 0xbad03605,
16326 0xcdd70693, 0x54de5729, 0x23d967bf, 0xb3667a2e, 0xc4614ab8,
16327 0x5d681b02, 0x2a6f2b94, 0xb40bbe37, 0xc30c8ea1, 0x5a05df1b,
16330 unsigned char *end;
16332 crc = ~crc & 0xffffffff;
16333 for (end = buf + len; buf < end; ++buf)
16334 crc = crc32_table[(crc ^ *buf) & 0xff] ^ (crc >> 8);
16335 return ~crc & 0xffffffff;
16340 This computation does not apply to the ``build ID'' method.
16344 @section Index Files Speed Up @value{GDBN}
16345 @cindex index files
16346 @cindex @samp{.gdb_index} section
16348 When @value{GDBN} finds a symbol file, it scans the symbols in the
16349 file in order to construct an internal symbol table. This lets most
16350 @value{GDBN} operations work quickly---at the cost of a delay early
16351 on. For large programs, this delay can be quite lengthy, so
16352 @value{GDBN} provides a way to build an index, which speeds up
16355 The index is stored as a section in the symbol file. @value{GDBN} can
16356 write the index to a file, then you can put it into the symbol file
16357 using @command{objcopy}.
16359 To create an index file, use the @code{save gdb-index} command:
16362 @item save gdb-index @var{directory}
16363 @kindex save gdb-index
16364 Create an index file for each symbol file currently known by
16365 @value{GDBN}. Each file is named after its corresponding symbol file,
16366 with @samp{.gdb-index} appended, and is written into the given
16370 Once you have created an index file you can merge it into your symbol
16371 file, here named @file{symfile}, using @command{objcopy}:
16374 $ objcopy --add-section .gdb_index=symfile.gdb-index \
16375 --set-section-flags .gdb_index=readonly symfile symfile
16378 There are currently some limitation on indices. They only work when
16379 for DWARF debugging information, not stabs. And, they do not
16380 currently work for programs using Ada.
16382 @node Symbol Errors
16383 @section Errors Reading Symbol Files
16385 While reading a symbol file, @value{GDBN} occasionally encounters problems,
16386 such as symbol types it does not recognize, or known bugs in compiler
16387 output. By default, @value{GDBN} does not notify you of such problems, since
16388 they are relatively common and primarily of interest to people
16389 debugging compilers. If you are interested in seeing information
16390 about ill-constructed symbol tables, you can either ask @value{GDBN} to print
16391 only one message about each such type of problem, no matter how many
16392 times the problem occurs; or you can ask @value{GDBN} to print more messages,
16393 to see how many times the problems occur, with the @code{set
16394 complaints} command (@pxref{Messages/Warnings, ,Optional Warnings and
16397 The messages currently printed, and their meanings, include:
16400 @item inner block not inside outer block in @var{symbol}
16402 The symbol information shows where symbol scopes begin and end
16403 (such as at the start of a function or a block of statements). This
16404 error indicates that an inner scope block is not fully contained
16405 in its outer scope blocks.
16407 @value{GDBN} circumvents the problem by treating the inner block as if it had
16408 the same scope as the outer block. In the error message, @var{symbol}
16409 may be shown as ``@code{(don't know)}'' if the outer block is not a
16412 @item block at @var{address} out of order
16414 The symbol information for symbol scope blocks should occur in
16415 order of increasing addresses. This error indicates that it does not
16418 @value{GDBN} does not circumvent this problem, and has trouble
16419 locating symbols in the source file whose symbols it is reading. (You
16420 can often determine what source file is affected by specifying
16421 @code{set verbose on}. @xref{Messages/Warnings, ,Optional Warnings and
16424 @item bad block start address patched
16426 The symbol information for a symbol scope block has a start address
16427 smaller than the address of the preceding source line. This is known
16428 to occur in the SunOS 4.1.1 (and earlier) C compiler.
16430 @value{GDBN} circumvents the problem by treating the symbol scope block as
16431 starting on the previous source line.
16433 @item bad string table offset in symbol @var{n}
16436 Symbol number @var{n} contains a pointer into the string table which is
16437 larger than the size of the string table.
16439 @value{GDBN} circumvents the problem by considering the symbol to have the
16440 name @code{foo}, which may cause other problems if many symbols end up
16443 @item unknown symbol type @code{0x@var{nn}}
16445 The symbol information contains new data types that @value{GDBN} does
16446 not yet know how to read. @code{0x@var{nn}} is the symbol type of the
16447 uncomprehended information, in hexadecimal.
16449 @value{GDBN} circumvents the error by ignoring this symbol information.
16450 This usually allows you to debug your program, though certain symbols
16451 are not accessible. If you encounter such a problem and feel like
16452 debugging it, you can debug @code{@value{GDBP}} with itself, breakpoint
16453 on @code{complain}, then go up to the function @code{read_dbx_symtab}
16454 and examine @code{*bufp} to see the symbol.
16456 @item stub type has NULL name
16458 @value{GDBN} could not find the full definition for a struct or class.
16460 @item const/volatile indicator missing (ok if using g++ v1.x), got@dots{}
16461 The symbol information for a C@t{++} member function is missing some
16462 information that recent versions of the compiler should have output for
16465 @item info mismatch between compiler and debugger
16467 @value{GDBN} could not parse a type specification output by the compiler.
16472 @section GDB Data Files
16474 @cindex prefix for data files
16475 @value{GDBN} will sometimes read an auxiliary data file. These files
16476 are kept in a directory known as the @dfn{data directory}.
16478 You can set the data directory's name, and view the name @value{GDBN}
16479 is currently using.
16482 @kindex set data-directory
16483 @item set data-directory @var{directory}
16484 Set the directory which @value{GDBN} searches for auxiliary data files
16485 to @var{directory}.
16487 @kindex show data-directory
16488 @item show data-directory
16489 Show the directory @value{GDBN} searches for auxiliary data files.
16492 @cindex default data directory
16493 @cindex @samp{--with-gdb-datadir}
16494 You can set the default data directory by using the configure-time
16495 @samp{--with-gdb-datadir} option. If the data directory is inside
16496 @value{GDBN}'s configured binary prefix (set with @samp{--prefix} or
16497 @samp{--exec-prefix}), then the default data directory will be updated
16498 automatically if the installed @value{GDBN} is moved to a new
16501 The data directory may also be specified with the
16502 @code{--data-directory} command line option.
16503 @xref{Mode Options}.
16506 @chapter Specifying a Debugging Target
16508 @cindex debugging target
16509 A @dfn{target} is the execution environment occupied by your program.
16511 Often, @value{GDBN} runs in the same host environment as your program;
16512 in that case, the debugging target is specified as a side effect when
16513 you use the @code{file} or @code{core} commands. When you need more
16514 flexibility---for example, running @value{GDBN} on a physically separate
16515 host, or controlling a standalone system over a serial port or a
16516 realtime system over a TCP/IP connection---you can use the @code{target}
16517 command to specify one of the target types configured for @value{GDBN}
16518 (@pxref{Target Commands, ,Commands for Managing Targets}).
16520 @cindex target architecture
16521 It is possible to build @value{GDBN} for several different @dfn{target
16522 architectures}. When @value{GDBN} is built like that, you can choose
16523 one of the available architectures with the @kbd{set architecture}
16527 @kindex set architecture
16528 @kindex show architecture
16529 @item set architecture @var{arch}
16530 This command sets the current target architecture to @var{arch}. The
16531 value of @var{arch} can be @code{"auto"}, in addition to one of the
16532 supported architectures.
16534 @item show architecture
16535 Show the current target architecture.
16537 @item set processor
16539 @kindex set processor
16540 @kindex show processor
16541 These are alias commands for, respectively, @code{set architecture}
16542 and @code{show architecture}.
16546 * Active Targets:: Active targets
16547 * Target Commands:: Commands for managing targets
16548 * Byte Order:: Choosing target byte order
16551 @node Active Targets
16552 @section Active Targets
16554 @cindex stacking targets
16555 @cindex active targets
16556 @cindex multiple targets
16558 There are multiple classes of targets such as: processes, executable files or
16559 recording sessions. Core files belong to the process class, making core file
16560 and process mutually exclusive. Otherwise, @value{GDBN} can work concurrently
16561 on multiple active targets, one in each class. This allows you to (for
16562 example) start a process and inspect its activity, while still having access to
16563 the executable file after the process finishes. Or if you start process
16564 recording (@pxref{Reverse Execution}) and @code{reverse-step} there, you are
16565 presented a virtual layer of the recording target, while the process target
16566 remains stopped at the chronologically last point of the process execution.
16568 Use the @code{core-file} and @code{exec-file} commands to select a new core
16569 file or executable target (@pxref{Files, ,Commands to Specify Files}). To
16570 specify as a target a process that is already running, use the @code{attach}
16571 command (@pxref{Attach, ,Debugging an Already-running Process}).
16573 @node Target Commands
16574 @section Commands for Managing Targets
16577 @item target @var{type} @var{parameters}
16578 Connects the @value{GDBN} host environment to a target machine or
16579 process. A target is typically a protocol for talking to debugging
16580 facilities. You use the argument @var{type} to specify the type or
16581 protocol of the target machine.
16583 Further @var{parameters} are interpreted by the target protocol, but
16584 typically include things like device names or host names to connect
16585 with, process numbers, and baud rates.
16587 The @code{target} command does not repeat if you press @key{RET} again
16588 after executing the command.
16590 @kindex help target
16592 Displays the names of all targets available. To display targets
16593 currently selected, use either @code{info target} or @code{info files}
16594 (@pxref{Files, ,Commands to Specify Files}).
16596 @item help target @var{name}
16597 Describe a particular target, including any parameters necessary to
16600 @kindex set gnutarget
16601 @item set gnutarget @var{args}
16602 @value{GDBN} uses its own library BFD to read your files. @value{GDBN}
16603 knows whether it is reading an @dfn{executable},
16604 a @dfn{core}, or a @dfn{.o} file; however, you can specify the file format
16605 with the @code{set gnutarget} command. Unlike most @code{target} commands,
16606 with @code{gnutarget} the @code{target} refers to a program, not a machine.
16609 @emph{Warning:} To specify a file format with @code{set gnutarget},
16610 you must know the actual BFD name.
16614 @xref{Files, , Commands to Specify Files}.
16616 @kindex show gnutarget
16617 @item show gnutarget
16618 Use the @code{show gnutarget} command to display what file format
16619 @code{gnutarget} is set to read. If you have not set @code{gnutarget},
16620 @value{GDBN} will determine the file format for each file automatically,
16621 and @code{show gnutarget} displays @samp{The current BDF target is "auto"}.
16624 @cindex common targets
16625 Here are some common targets (available, or not, depending on the GDB
16630 @item target exec @var{program}
16631 @cindex executable file target
16632 An executable file. @samp{target exec @var{program}} is the same as
16633 @samp{exec-file @var{program}}.
16635 @item target core @var{filename}
16636 @cindex core dump file target
16637 A core dump file. @samp{target core @var{filename}} is the same as
16638 @samp{core-file @var{filename}}.
16640 @item target remote @var{medium}
16641 @cindex remote target
16642 A remote system connected to @value{GDBN} via a serial line or network
16643 connection. This command tells @value{GDBN} to use its own remote
16644 protocol over @var{medium} for debugging. @xref{Remote Debugging}.
16646 For example, if you have a board connected to @file{/dev/ttya} on the
16647 machine running @value{GDBN}, you could say:
16650 target remote /dev/ttya
16653 @code{target remote} supports the @code{load} command. This is only
16654 useful if you have some other way of getting the stub to the target
16655 system, and you can put it somewhere in memory where it won't get
16656 clobbered by the download.
16658 @item target sim @r{[}@var{simargs}@r{]} @dots{}
16659 @cindex built-in simulator target
16660 Builtin CPU simulator. @value{GDBN} includes simulators for most architectures.
16668 works; however, you cannot assume that a specific memory map, device
16669 drivers, or even basic I/O is available, although some simulators do
16670 provide these. For info about any processor-specific simulator details,
16671 see the appropriate section in @ref{Embedded Processors, ,Embedded
16676 Some configurations may include these targets as well:
16680 @item target nrom @var{dev}
16681 @cindex NetROM ROM emulator target
16682 NetROM ROM emulator. This target only supports downloading.
16686 Different targets are available on different configurations of @value{GDBN};
16687 your configuration may have more or fewer targets.
16689 Many remote targets require you to download the executable's code once
16690 you've successfully established a connection. You may wish to control
16691 various aspects of this process.
16696 @kindex set hash@r{, for remote monitors}
16697 @cindex hash mark while downloading
16698 This command controls whether a hash mark @samp{#} is displayed while
16699 downloading a file to the remote monitor. If on, a hash mark is
16700 displayed after each S-record is successfully downloaded to the
16704 @kindex show hash@r{, for remote monitors}
16705 Show the current status of displaying the hash mark.
16707 @item set debug monitor
16708 @kindex set debug monitor
16709 @cindex display remote monitor communications
16710 Enable or disable display of communications messages between
16711 @value{GDBN} and the remote monitor.
16713 @item show debug monitor
16714 @kindex show debug monitor
16715 Show the current status of displaying communications between
16716 @value{GDBN} and the remote monitor.
16721 @kindex load @var{filename}
16722 @item load @var{filename}
16724 Depending on what remote debugging facilities are configured into
16725 @value{GDBN}, the @code{load} command may be available. Where it exists, it
16726 is meant to make @var{filename} (an executable) available for debugging
16727 on the remote system---by downloading, or dynamic linking, for example.
16728 @code{load} also records the @var{filename} symbol table in @value{GDBN}, like
16729 the @code{add-symbol-file} command.
16731 If your @value{GDBN} does not have a @code{load} command, attempting to
16732 execute it gets the error message ``@code{You can't do that when your
16733 target is @dots{}}''
16735 The file is loaded at whatever address is specified in the executable.
16736 For some object file formats, you can specify the load address when you
16737 link the program; for other formats, like a.out, the object file format
16738 specifies a fixed address.
16739 @c FIXME! This would be a good place for an xref to the GNU linker doc.
16741 Depending on the remote side capabilities, @value{GDBN} may be able to
16742 load programs into flash memory.
16744 @code{load} does not repeat if you press @key{RET} again after using it.
16748 @section Choosing Target Byte Order
16750 @cindex choosing target byte order
16751 @cindex target byte order
16753 Some types of processors, such as the MIPS, PowerPC, and Renesas SH,
16754 offer the ability to run either big-endian or little-endian byte
16755 orders. Usually the executable or symbol will include a bit to
16756 designate the endian-ness, and you will not need to worry about
16757 which to use. However, you may still find it useful to adjust
16758 @value{GDBN}'s idea of processor endian-ness manually.
16762 @item set endian big
16763 Instruct @value{GDBN} to assume the target is big-endian.
16765 @item set endian little
16766 Instruct @value{GDBN} to assume the target is little-endian.
16768 @item set endian auto
16769 Instruct @value{GDBN} to use the byte order associated with the
16773 Display @value{GDBN}'s current idea of the target byte order.
16777 Note that these commands merely adjust interpretation of symbolic
16778 data on the host, and that they have absolutely no effect on the
16782 @node Remote Debugging
16783 @chapter Debugging Remote Programs
16784 @cindex remote debugging
16786 If you are trying to debug a program running on a machine that cannot run
16787 @value{GDBN} in the usual way, it is often useful to use remote debugging.
16788 For example, you might use remote debugging on an operating system kernel,
16789 or on a small system which does not have a general purpose operating system
16790 powerful enough to run a full-featured debugger.
16792 Some configurations of @value{GDBN} have special serial or TCP/IP interfaces
16793 to make this work with particular debugging targets. In addition,
16794 @value{GDBN} comes with a generic serial protocol (specific to @value{GDBN},
16795 but not specific to any particular target system) which you can use if you
16796 write the remote stubs---the code that runs on the remote system to
16797 communicate with @value{GDBN}.
16799 Other remote targets may be available in your
16800 configuration of @value{GDBN}; use @code{help target} to list them.
16803 * Connecting:: Connecting to a remote target
16804 * File Transfer:: Sending files to a remote system
16805 * Server:: Using the gdbserver program
16806 * Remote Configuration:: Remote configuration
16807 * Remote Stub:: Implementing a remote stub
16811 @section Connecting to a Remote Target
16813 On the @value{GDBN} host machine, you will need an unstripped copy of
16814 your program, since @value{GDBN} needs symbol and debugging information.
16815 Start up @value{GDBN} as usual, using the name of the local copy of your
16816 program as the first argument.
16818 @cindex @code{target remote}
16819 @value{GDBN} can communicate with the target over a serial line, or
16820 over an @acronym{IP} network using @acronym{TCP} or @acronym{UDP}. In
16821 each case, @value{GDBN} uses the same protocol for debugging your
16822 program; only the medium carrying the debugging packets varies. The
16823 @code{target remote} command establishes a connection to the target.
16824 Its arguments indicate which medium to use:
16828 @item target remote @var{serial-device}
16829 @cindex serial line, @code{target remote}
16830 Use @var{serial-device} to communicate with the target. For example,
16831 to use a serial line connected to the device named @file{/dev/ttyb}:
16834 target remote /dev/ttyb
16837 If you're using a serial line, you may want to give @value{GDBN} the
16838 @w{@samp{--baud}} option, or use the @code{set remotebaud} command
16839 (@pxref{Remote Configuration, set remotebaud}) before the
16840 @code{target} command.
16842 @item target remote @code{@var{host}:@var{port}}
16843 @itemx target remote @code{tcp:@var{host}:@var{port}}
16844 @cindex @acronym{TCP} port, @code{target remote}
16845 Debug using a @acronym{TCP} connection to @var{port} on @var{host}.
16846 The @var{host} may be either a host name or a numeric @acronym{IP}
16847 address; @var{port} must be a decimal number. The @var{host} could be
16848 the target machine itself, if it is directly connected to the net, or
16849 it might be a terminal server which in turn has a serial line to the
16852 For example, to connect to port 2828 on a terminal server named
16856 target remote manyfarms:2828
16859 If your remote target is actually running on the same machine as your
16860 debugger session (e.g.@: a simulator for your target running on the
16861 same host), you can omit the hostname. For example, to connect to
16862 port 1234 on your local machine:
16865 target remote :1234
16869 Note that the colon is still required here.
16871 @item target remote @code{udp:@var{host}:@var{port}}
16872 @cindex @acronym{UDP} port, @code{target remote}
16873 Debug using @acronym{UDP} packets to @var{port} on @var{host}. For example, to
16874 connect to @acronym{UDP} port 2828 on a terminal server named @code{manyfarms}:
16877 target remote udp:manyfarms:2828
16880 When using a @acronym{UDP} connection for remote debugging, you should
16881 keep in mind that the `U' stands for ``Unreliable''. @acronym{UDP}
16882 can silently drop packets on busy or unreliable networks, which will
16883 cause havoc with your debugging session.
16885 @item target remote | @var{command}
16886 @cindex pipe, @code{target remote} to
16887 Run @var{command} in the background and communicate with it using a
16888 pipe. The @var{command} is a shell command, to be parsed and expanded
16889 by the system's command shell, @code{/bin/sh}; it should expect remote
16890 protocol packets on its standard input, and send replies on its
16891 standard output. You could use this to run a stand-alone simulator
16892 that speaks the remote debugging protocol, to make net connections
16893 using programs like @code{ssh}, or for other similar tricks.
16895 If @var{command} closes its standard output (perhaps by exiting),
16896 @value{GDBN} will try to send it a @code{SIGTERM} signal. (If the
16897 program has already exited, this will have no effect.)
16901 Once the connection has been established, you can use all the usual
16902 commands to examine and change data. The remote program is already
16903 running; you can use @kbd{step} and @kbd{continue}, and you do not
16904 need to use @kbd{run}.
16906 @cindex interrupting remote programs
16907 @cindex remote programs, interrupting
16908 Whenever @value{GDBN} is waiting for the remote program, if you type the
16909 interrupt character (often @kbd{Ctrl-c}), @value{GDBN} attempts to stop the
16910 program. This may or may not succeed, depending in part on the hardware
16911 and the serial drivers the remote system uses. If you type the
16912 interrupt character once again, @value{GDBN} displays this prompt:
16915 Interrupted while waiting for the program.
16916 Give up (and stop debugging it)? (y or n)
16919 If you type @kbd{y}, @value{GDBN} abandons the remote debugging session.
16920 (If you decide you want to try again later, you can use @samp{target
16921 remote} again to connect once more.) If you type @kbd{n}, @value{GDBN}
16922 goes back to waiting.
16925 @kindex detach (remote)
16927 When you have finished debugging the remote program, you can use the
16928 @code{detach} command to release it from @value{GDBN} control.
16929 Detaching from the target normally resumes its execution, but the results
16930 will depend on your particular remote stub. After the @code{detach}
16931 command, @value{GDBN} is free to connect to another target.
16935 The @code{disconnect} command behaves like @code{detach}, except that
16936 the target is generally not resumed. It will wait for @value{GDBN}
16937 (this instance or another one) to connect and continue debugging. After
16938 the @code{disconnect} command, @value{GDBN} is again free to connect to
16941 @cindex send command to remote monitor
16942 @cindex extend @value{GDBN} for remote targets
16943 @cindex add new commands for external monitor
16945 @item monitor @var{cmd}
16946 This command allows you to send arbitrary commands directly to the
16947 remote monitor. Since @value{GDBN} doesn't care about the commands it
16948 sends like this, this command is the way to extend @value{GDBN}---you
16949 can add new commands that only the external monitor will understand
16953 @node File Transfer
16954 @section Sending files to a remote system
16955 @cindex remote target, file transfer
16956 @cindex file transfer
16957 @cindex sending files to remote systems
16959 Some remote targets offer the ability to transfer files over the same
16960 connection used to communicate with @value{GDBN}. This is convenient
16961 for targets accessible through other means, e.g.@: @sc{gnu}/Linux systems
16962 running @code{gdbserver} over a network interface. For other targets,
16963 e.g.@: embedded devices with only a single serial port, this may be
16964 the only way to upload or download files.
16966 Not all remote targets support these commands.
16970 @item remote put @var{hostfile} @var{targetfile}
16971 Copy file @var{hostfile} from the host system (the machine running
16972 @value{GDBN}) to @var{targetfile} on the target system.
16975 @item remote get @var{targetfile} @var{hostfile}
16976 Copy file @var{targetfile} from the target system to @var{hostfile}
16977 on the host system.
16979 @kindex remote delete
16980 @item remote delete @var{targetfile}
16981 Delete @var{targetfile} from the target system.
16986 @section Using the @code{gdbserver} Program
16989 @cindex remote connection without stubs
16990 @code{gdbserver} is a control program for Unix-like systems, which
16991 allows you to connect your program with a remote @value{GDBN} via
16992 @code{target remote}---but without linking in the usual debugging stub.
16994 @code{gdbserver} is not a complete replacement for the debugging stubs,
16995 because it requires essentially the same operating-system facilities
16996 that @value{GDBN} itself does. In fact, a system that can run
16997 @code{gdbserver} to connect to a remote @value{GDBN} could also run
16998 @value{GDBN} locally! @code{gdbserver} is sometimes useful nevertheless,
16999 because it is a much smaller program than @value{GDBN} itself. It is
17000 also easier to port than all of @value{GDBN}, so you may be able to get
17001 started more quickly on a new system by using @code{gdbserver}.
17002 Finally, if you develop code for real-time systems, you may find that
17003 the tradeoffs involved in real-time operation make it more convenient to
17004 do as much development work as possible on another system, for example
17005 by cross-compiling. You can use @code{gdbserver} to make a similar
17006 choice for debugging.
17008 @value{GDBN} and @code{gdbserver} communicate via either a serial line
17009 or a TCP connection, using the standard @value{GDBN} remote serial
17013 @emph{Warning:} @code{gdbserver} does not have any built-in security.
17014 Do not run @code{gdbserver} connected to any public network; a
17015 @value{GDBN} connection to @code{gdbserver} provides access to the
17016 target system with the same privileges as the user running
17020 @subsection Running @code{gdbserver}
17021 @cindex arguments, to @code{gdbserver}
17022 @cindex @code{gdbserver}, command-line arguments
17024 Run @code{gdbserver} on the target system. You need a copy of the
17025 program you want to debug, including any libraries it requires.
17026 @code{gdbserver} does not need your program's symbol table, so you can
17027 strip the program if necessary to save space. @value{GDBN} on the host
17028 system does all the symbol handling.
17030 To use the server, you must tell it how to communicate with @value{GDBN};
17031 the name of your program; and the arguments for your program. The usual
17035 target> gdbserver @var{comm} @var{program} [ @var{args} @dots{} ]
17038 @var{comm} is either a device name (to use a serial line), or a TCP
17039 hostname and portnumber, or @code{-} or @code{stdio} to use
17040 stdin/stdout of @code{gdbserver}.
17041 For example, to debug Emacs with the argument
17042 @samp{foo.txt} and communicate with @value{GDBN} over the serial port
17046 target> gdbserver /dev/com1 emacs foo.txt
17049 @code{gdbserver} waits passively for the host @value{GDBN} to communicate
17052 To use a TCP connection instead of a serial line:
17055 target> gdbserver host:2345 emacs foo.txt
17058 The only difference from the previous example is the first argument,
17059 specifying that you are communicating with the host @value{GDBN} via
17060 TCP. The @samp{host:2345} argument means that @code{gdbserver} is to
17061 expect a TCP connection from machine @samp{host} to local TCP port 2345.
17062 (Currently, the @samp{host} part is ignored.) You can choose any number
17063 you want for the port number as long as it does not conflict with any
17064 TCP ports already in use on the target system (for example, @code{23} is
17065 reserved for @code{telnet}).@footnote{If you choose a port number that
17066 conflicts with another service, @code{gdbserver} prints an error message
17067 and exits.} You must use the same port number with the host @value{GDBN}
17068 @code{target remote} command.
17070 The @code{stdio} connection is useful when starting @code{gdbserver}
17074 (gdb) target remote | ssh -T hostname gdbserver - hello
17077 The @samp{-T} option to ssh is provided because we don't need a remote pty,
17078 and we don't want escape-character handling. Ssh does this by default when
17079 a command is provided, the flag is provided to make it explicit.
17080 You could elide it if you want to.
17082 Programs started with stdio-connected gdbserver have @file{/dev/null} for
17083 @code{stdin}, and @code{stdout},@code{stderr} are sent back to gdb for
17084 display through a pipe connected to gdbserver.
17085 Both @code{stdout} and @code{stderr} use the same pipe.
17087 @subsubsection Attaching to a Running Program
17088 @cindex attach to a program, @code{gdbserver}
17089 @cindex @option{--attach}, @code{gdbserver} option
17091 On some targets, @code{gdbserver} can also attach to running programs.
17092 This is accomplished via the @code{--attach} argument. The syntax is:
17095 target> gdbserver --attach @var{comm} @var{pid}
17098 @var{pid} is the process ID of a currently running process. It isn't necessary
17099 to point @code{gdbserver} at a binary for the running process.
17102 You can debug processes by name instead of process ID if your target has the
17103 @code{pidof} utility:
17106 target> gdbserver --attach @var{comm} `pidof @var{program}`
17109 In case more than one copy of @var{program} is running, or @var{program}
17110 has multiple threads, most versions of @code{pidof} support the
17111 @code{-s} option to only return the first process ID.
17113 @subsubsection Multi-Process Mode for @code{gdbserver}
17114 @cindex @code{gdbserver}, multiple processes
17115 @cindex multiple processes with @code{gdbserver}
17117 When you connect to @code{gdbserver} using @code{target remote},
17118 @code{gdbserver} debugs the specified program only once. When the
17119 program exits, or you detach from it, @value{GDBN} closes the connection
17120 and @code{gdbserver} exits.
17122 If you connect using @kbd{target extended-remote}, @code{gdbserver}
17123 enters multi-process mode. When the debugged program exits, or you
17124 detach from it, @value{GDBN} stays connected to @code{gdbserver} even
17125 though no program is running. The @code{run} and @code{attach}
17126 commands instruct @code{gdbserver} to run or attach to a new program.
17127 The @code{run} command uses @code{set remote exec-file} (@pxref{set
17128 remote exec-file}) to select the program to run. Command line
17129 arguments are supported, except for wildcard expansion and I/O
17130 redirection (@pxref{Arguments}).
17132 @cindex @option{--multi}, @code{gdbserver} option
17133 To start @code{gdbserver} without supplying an initial command to run
17134 or process ID to attach, use the @option{--multi} command line option.
17135 Then you can connect using @kbd{target extended-remote} and start
17136 the program you want to debug.
17138 In multi-process mode @code{gdbserver} does not automatically exit unless you
17139 use the option @option{--once}. You can terminate it by using
17140 @code{monitor exit} (@pxref{Monitor Commands for gdbserver}). Note that the
17141 conditions under which @code{gdbserver} terminates depend on how @value{GDBN}
17142 connects to it (@kbd{target remote} or @kbd{target extended-remote}). The
17143 @option{--multi} option to @code{gdbserver} has no influence on that.
17145 @subsubsection TCP port allocation lifecycle of @code{gdbserver}
17147 This section applies only when @code{gdbserver} is run to listen on a TCP port.
17149 @code{gdbserver} normally terminates after all of its debugged processes have
17150 terminated in @kbd{target remote} mode. On the other hand, for @kbd{target
17151 extended-remote}, @code{gdbserver} stays running even with no processes left.
17152 @value{GDBN} normally terminates the spawned debugged process on its exit,
17153 which normally also terminates @code{gdbserver} in the @kbd{target remote}
17154 mode. Therefore, when the connection drops unexpectedly, and @value{GDBN}
17155 cannot ask @code{gdbserver} to kill its debugged processes, @code{gdbserver}
17156 stays running even in the @kbd{target remote} mode.
17158 When @code{gdbserver} stays running, @value{GDBN} can connect to it again later.
17159 Such reconnecting is useful for features like @ref{disconnected tracing}. For
17160 completeness, at most one @value{GDBN} can be connected at a time.
17162 @cindex @option{--once}, @code{gdbserver} option
17163 By default, @code{gdbserver} keeps the listening TCP port open, so that
17164 additional connections are possible. However, if you start @code{gdbserver}
17165 with the @option{--once} option, it will stop listening for any further
17166 connection attempts after connecting to the first @value{GDBN} session. This
17167 means no further connections to @code{gdbserver} will be possible after the
17168 first one. It also means @code{gdbserver} will terminate after the first
17169 connection with remote @value{GDBN} has closed, even for unexpectedly closed
17170 connections and even in the @kbd{target extended-remote} mode. The
17171 @option{--once} option allows reusing the same port number for connecting to
17172 multiple instances of @code{gdbserver} running on the same host, since each
17173 instance closes its port after the first connection.
17175 @subsubsection Other Command-Line Arguments for @code{gdbserver}
17177 @cindex @option{--debug}, @code{gdbserver} option
17178 The @option{--debug} option tells @code{gdbserver} to display extra
17179 status information about the debugging process.
17180 @cindex @option{--remote-debug}, @code{gdbserver} option
17181 The @option{--remote-debug} option tells @code{gdbserver} to display
17182 remote protocol debug output. These options are intended for
17183 @code{gdbserver} development and for bug reports to the developers.
17185 @cindex @option{--wrapper}, @code{gdbserver} option
17186 The @option{--wrapper} option specifies a wrapper to launch programs
17187 for debugging. The option should be followed by the name of the
17188 wrapper, then any command-line arguments to pass to the wrapper, then
17189 @kbd{--} indicating the end of the wrapper arguments.
17191 @code{gdbserver} runs the specified wrapper program with a combined
17192 command line including the wrapper arguments, then the name of the
17193 program to debug, then any arguments to the program. The wrapper
17194 runs until it executes your program, and then @value{GDBN} gains control.
17196 You can use any program that eventually calls @code{execve} with
17197 its arguments as a wrapper. Several standard Unix utilities do
17198 this, e.g.@: @code{env} and @code{nohup}. Any Unix shell script ending
17199 with @code{exec "$@@"} will also work.
17201 For example, you can use @code{env} to pass an environment variable to
17202 the debugged program, without setting the variable in @code{gdbserver}'s
17206 $ gdbserver --wrapper env LD_PRELOAD=libtest.so -- :2222 ./testprog
17209 @subsection Connecting to @code{gdbserver}
17211 Run @value{GDBN} on the host system.
17213 First make sure you have the necessary symbol files. Load symbols for
17214 your application using the @code{file} command before you connect. Use
17215 @code{set sysroot} to locate target libraries (unless your @value{GDBN}
17216 was compiled with the correct sysroot using @code{--with-sysroot}).
17218 The symbol file and target libraries must exactly match the executable
17219 and libraries on the target, with one exception: the files on the host
17220 system should not be stripped, even if the files on the target system
17221 are. Mismatched or missing files will lead to confusing results
17222 during debugging. On @sc{gnu}/Linux targets, mismatched or missing
17223 files may also prevent @code{gdbserver} from debugging multi-threaded
17226 Connect to your target (@pxref{Connecting,,Connecting to a Remote Target}).
17227 For TCP connections, you must start up @code{gdbserver} prior to using
17228 the @code{target remote} command. Otherwise you may get an error whose
17229 text depends on the host system, but which usually looks something like
17230 @samp{Connection refused}. Don't use the @code{load}
17231 command in @value{GDBN} when using @code{gdbserver}, since the program is
17232 already on the target.
17234 @subsection Monitor Commands for @code{gdbserver}
17235 @cindex monitor commands, for @code{gdbserver}
17236 @anchor{Monitor Commands for gdbserver}
17238 During a @value{GDBN} session using @code{gdbserver}, you can use the
17239 @code{monitor} command to send special requests to @code{gdbserver}.
17240 Here are the available commands.
17244 List the available monitor commands.
17246 @item monitor set debug 0
17247 @itemx monitor set debug 1
17248 Disable or enable general debugging messages.
17250 @item monitor set remote-debug 0
17251 @itemx monitor set remote-debug 1
17252 Disable or enable specific debugging messages associated with the remote
17253 protocol (@pxref{Remote Protocol}).
17255 @item monitor set libthread-db-search-path [PATH]
17256 @cindex gdbserver, search path for @code{libthread_db}
17257 When this command is issued, @var{path} is a colon-separated list of
17258 directories to search for @code{libthread_db} (@pxref{Threads,,set
17259 libthread-db-search-path}). If you omit @var{path},
17260 @samp{libthread-db-search-path} will be reset to its default value.
17262 The special entry @samp{$pdir} for @samp{libthread-db-search-path} is
17263 not supported in @code{gdbserver}.
17266 Tell gdbserver to exit immediately. This command should be followed by
17267 @code{disconnect} to close the debugging session. @code{gdbserver} will
17268 detach from any attached processes and kill any processes it created.
17269 Use @code{monitor exit} to terminate @code{gdbserver} at the end
17270 of a multi-process mode debug session.
17274 @subsection Tracepoints support in @code{gdbserver}
17275 @cindex tracepoints support in @code{gdbserver}
17277 On some targets, @code{gdbserver} supports tracepoints, fast
17278 tracepoints and static tracepoints.
17280 For fast or static tracepoints to work, a special library called the
17281 @dfn{in-process agent} (IPA), must be loaded in the inferior process.
17282 This library is built and distributed as an integral part of
17283 @code{gdbserver}. In addition, support for static tracepoints
17284 requires building the in-process agent library with static tracepoints
17285 support. At present, the UST (LTTng Userspace Tracer,
17286 @url{http://lttng.org/ust}) tracing engine is supported. This support
17287 is automatically available if UST development headers are found in the
17288 standard include path when @code{gdbserver} is built, or if
17289 @code{gdbserver} was explicitly configured using @option{--with-ust}
17290 to point at such headers. You can explicitly disable the support
17291 using @option{--with-ust=no}.
17293 There are several ways to load the in-process agent in your program:
17296 @item Specifying it as dependency at link time
17298 You can link your program dynamically with the in-process agent
17299 library. On most systems, this is accomplished by adding
17300 @code{-linproctrace} to the link command.
17302 @item Using the system's preloading mechanisms
17304 You can force loading the in-process agent at startup time by using
17305 your system's support for preloading shared libraries. Many Unixes
17306 support the concept of preloading user defined libraries. In most
17307 cases, you do that by specifying @code{LD_PRELOAD=libinproctrace.so}
17308 in the environment. See also the description of @code{gdbserver}'s
17309 @option{--wrapper} command line option.
17311 @item Using @value{GDBN} to force loading the agent at run time
17313 On some systems, you can force the inferior to load a shared library,
17314 by calling a dynamic loader function in the inferior that takes care
17315 of dynamically looking up and loading a shared library. On most Unix
17316 systems, the function is @code{dlopen}. You'll use the @code{call}
17317 command for that. For example:
17320 (@value{GDBP}) call dlopen ("libinproctrace.so", ...)
17323 Note that on most Unix systems, for the @code{dlopen} function to be
17324 available, the program needs to be linked with @code{-ldl}.
17327 On systems that have a userspace dynamic loader, like most Unix
17328 systems, when you connect to @code{gdbserver} using @code{target
17329 remote}, you'll find that the program is stopped at the dynamic
17330 loader's entry point, and no shared library has been loaded in the
17331 program's address space yet, including the in-process agent. In that
17332 case, before being able to use any of the fast or static tracepoints
17333 features, you need to let the loader run and load the shared
17334 libraries. The simplest way to do that is to run the program to the
17335 main procedure. E.g., if debugging a C or C@t{++} program, start
17336 @code{gdbserver} like so:
17339 $ gdbserver :9999 myprogram
17342 Start GDB and connect to @code{gdbserver} like so, and run to main:
17346 (@value{GDBP}) target remote myhost:9999
17347 0x00007f215893ba60 in ?? () from /lib64/ld-linux-x86-64.so.2
17348 (@value{GDBP}) b main
17349 (@value{GDBP}) continue
17352 The in-process tracing agent library should now be loaded into the
17353 process; you can confirm it with the @code{info sharedlibrary}
17354 command, which will list @file{libinproctrace.so} as loaded in the
17355 process. You are now ready to install fast tracepoints, list static
17356 tracepoint markers, probe static tracepoints markers, and start
17359 @node Remote Configuration
17360 @section Remote Configuration
17363 @kindex show remote
17364 This section documents the configuration options available when
17365 debugging remote programs. For the options related to the File I/O
17366 extensions of the remote protocol, see @ref{system,
17367 system-call-allowed}.
17370 @item set remoteaddresssize @var{bits}
17371 @cindex address size for remote targets
17372 @cindex bits in remote address
17373 Set the maximum size of address in a memory packet to the specified
17374 number of bits. @value{GDBN} will mask off the address bits above
17375 that number, when it passes addresses to the remote target. The
17376 default value is the number of bits in the target's address.
17378 @item show remoteaddresssize
17379 Show the current value of remote address size in bits.
17381 @item set remotebaud @var{n}
17382 @cindex baud rate for remote targets
17383 Set the baud rate for the remote serial I/O to @var{n} baud. The
17384 value is used to set the speed of the serial port used for debugging
17387 @item show remotebaud
17388 Show the current speed of the remote connection.
17390 @item set remotebreak
17391 @cindex interrupt remote programs
17392 @cindex BREAK signal instead of Ctrl-C
17393 @anchor{set remotebreak}
17394 If set to on, @value{GDBN} sends a @code{BREAK} signal to the remote
17395 when you type @kbd{Ctrl-c} to interrupt the program running
17396 on the remote. If set to off, @value{GDBN} sends the @samp{Ctrl-C}
17397 character instead. The default is off, since most remote systems
17398 expect to see @samp{Ctrl-C} as the interrupt signal.
17400 @item show remotebreak
17401 Show whether @value{GDBN} sends @code{BREAK} or @samp{Ctrl-C} to
17402 interrupt the remote program.
17404 @item set remoteflow on
17405 @itemx set remoteflow off
17406 @kindex set remoteflow
17407 Enable or disable hardware flow control (@code{RTS}/@code{CTS})
17408 on the serial port used to communicate to the remote target.
17410 @item show remoteflow
17411 @kindex show remoteflow
17412 Show the current setting of hardware flow control.
17414 @item set remotelogbase @var{base}
17415 Set the base (a.k.a.@: radix) of logging serial protocol
17416 communications to @var{base}. Supported values of @var{base} are:
17417 @code{ascii}, @code{octal}, and @code{hex}. The default is
17420 @item show remotelogbase
17421 Show the current setting of the radix for logging remote serial
17424 @item set remotelogfile @var{file}
17425 @cindex record serial communications on file
17426 Record remote serial communications on the named @var{file}. The
17427 default is not to record at all.
17429 @item show remotelogfile.
17430 Show the current setting of the file name on which to record the
17431 serial communications.
17433 @item set remotetimeout @var{num}
17434 @cindex timeout for serial communications
17435 @cindex remote timeout
17436 Set the timeout limit to wait for the remote target to respond to
17437 @var{num} seconds. The default is 2 seconds.
17439 @item show remotetimeout
17440 Show the current number of seconds to wait for the remote target
17443 @cindex limit hardware breakpoints and watchpoints
17444 @cindex remote target, limit break- and watchpoints
17445 @anchor{set remote hardware-watchpoint-limit}
17446 @anchor{set remote hardware-breakpoint-limit}
17447 @item set remote hardware-watchpoint-limit @var{limit}
17448 @itemx set remote hardware-breakpoint-limit @var{limit}
17449 Restrict @value{GDBN} to using @var{limit} remote hardware breakpoint or
17450 watchpoints. A limit of -1, the default, is treated as unlimited.
17452 @cindex limit hardware watchpoints length
17453 @cindex remote target, limit watchpoints length
17454 @anchor{set remote hardware-watchpoint-length-limit}
17455 @item set remote hardware-watchpoint-length-limit @var{limit}
17456 Restrict @value{GDBN} to using @var{limit} bytes for the maximum length of
17457 a remote hardware watchpoint. A limit of -1, the default, is treated
17460 @item show remote hardware-watchpoint-length-limit
17461 Show the current limit (in bytes) of the maximum length of
17462 a remote hardware watchpoint.
17464 @item set remote exec-file @var{filename}
17465 @itemx show remote exec-file
17466 @anchor{set remote exec-file}
17467 @cindex executable file, for remote target
17468 Select the file used for @code{run} with @code{target
17469 extended-remote}. This should be set to a filename valid on the
17470 target system. If it is not set, the target will use a default
17471 filename (e.g.@: the last program run).
17473 @item set remote interrupt-sequence
17474 @cindex interrupt remote programs
17475 @cindex select Ctrl-C, BREAK or BREAK-g
17476 Allow the user to select one of @samp{Ctrl-C}, a @code{BREAK} or
17477 @samp{BREAK-g} as the
17478 sequence to the remote target in order to interrupt the execution.
17479 @samp{Ctrl-C} is a default. Some system prefers @code{BREAK} which
17480 is high level of serial line for some certain time.
17481 Linux kernel prefers @samp{BREAK-g}, a.k.a Magic SysRq g.
17482 It is @code{BREAK} signal followed by character @code{g}.
17484 @item show interrupt-sequence
17485 Show which of @samp{Ctrl-C}, @code{BREAK} or @code{BREAK-g}
17486 is sent by @value{GDBN} to interrupt the remote program.
17487 @code{BREAK-g} is BREAK signal followed by @code{g} and
17488 also known as Magic SysRq g.
17490 @item set remote interrupt-on-connect
17491 @cindex send interrupt-sequence on start
17492 Specify whether interrupt-sequence is sent to remote target when
17493 @value{GDBN} connects to it. This is mostly needed when you debug
17494 Linux kernel. Linux kernel expects @code{BREAK} followed by @code{g}
17495 which is known as Magic SysRq g in order to connect @value{GDBN}.
17497 @item show interrupt-on-connect
17498 Show whether interrupt-sequence is sent
17499 to remote target when @value{GDBN} connects to it.
17503 @item set tcp auto-retry on
17504 @cindex auto-retry, for remote TCP target
17505 Enable auto-retry for remote TCP connections. This is useful if the remote
17506 debugging agent is launched in parallel with @value{GDBN}; there is a race
17507 condition because the agent may not become ready to accept the connection
17508 before @value{GDBN} attempts to connect. When auto-retry is
17509 enabled, if the initial attempt to connect fails, @value{GDBN} reattempts
17510 to establish the connection using the timeout specified by
17511 @code{set tcp connect-timeout}.
17513 @item set tcp auto-retry off
17514 Do not auto-retry failed TCP connections.
17516 @item show tcp auto-retry
17517 Show the current auto-retry setting.
17519 @item set tcp connect-timeout @var{seconds}
17520 @cindex connection timeout, for remote TCP target
17521 @cindex timeout, for remote target connection
17522 Set the timeout for establishing a TCP connection to the remote target to
17523 @var{seconds}. The timeout affects both polling to retry failed connections
17524 (enabled by @code{set tcp auto-retry on}) and waiting for connections
17525 that are merely slow to complete, and represents an approximate cumulative
17528 @item show tcp connect-timeout
17529 Show the current connection timeout setting.
17532 @cindex remote packets, enabling and disabling
17533 The @value{GDBN} remote protocol autodetects the packets supported by
17534 your debugging stub. If you need to override the autodetection, you
17535 can use these commands to enable or disable individual packets. Each
17536 packet can be set to @samp{on} (the remote target supports this
17537 packet), @samp{off} (the remote target does not support this packet),
17538 or @samp{auto} (detect remote target support for this packet). They
17539 all default to @samp{auto}. For more information about each packet,
17540 see @ref{Remote Protocol}.
17542 During normal use, you should not have to use any of these commands.
17543 If you do, that may be a bug in your remote debugging stub, or a bug
17544 in @value{GDBN}. You may want to report the problem to the
17545 @value{GDBN} developers.
17547 For each packet @var{name}, the command to enable or disable the
17548 packet is @code{set remote @var{name}-packet}. The available settings
17551 @multitable @columnfractions 0.28 0.32 0.25
17554 @tab Related Features
17556 @item @code{fetch-register}
17558 @tab @code{info registers}
17560 @item @code{set-register}
17564 @item @code{binary-download}
17566 @tab @code{load}, @code{set}
17568 @item @code{read-aux-vector}
17569 @tab @code{qXfer:auxv:read}
17570 @tab @code{info auxv}
17572 @item @code{symbol-lookup}
17573 @tab @code{qSymbol}
17574 @tab Detecting multiple threads
17576 @item @code{attach}
17577 @tab @code{vAttach}
17580 @item @code{verbose-resume}
17582 @tab Stepping or resuming multiple threads
17588 @item @code{software-breakpoint}
17592 @item @code{hardware-breakpoint}
17596 @item @code{write-watchpoint}
17600 @item @code{read-watchpoint}
17604 @item @code{access-watchpoint}
17608 @item @code{target-features}
17609 @tab @code{qXfer:features:read}
17610 @tab @code{set architecture}
17612 @item @code{library-info}
17613 @tab @code{qXfer:libraries:read}
17614 @tab @code{info sharedlibrary}
17616 @item @code{memory-map}
17617 @tab @code{qXfer:memory-map:read}
17618 @tab @code{info mem}
17620 @item @code{read-sdata-object}
17621 @tab @code{qXfer:sdata:read}
17622 @tab @code{print $_sdata}
17624 @item @code{read-spu-object}
17625 @tab @code{qXfer:spu:read}
17626 @tab @code{info spu}
17628 @item @code{write-spu-object}
17629 @tab @code{qXfer:spu:write}
17630 @tab @code{info spu}
17632 @item @code{read-siginfo-object}
17633 @tab @code{qXfer:siginfo:read}
17634 @tab @code{print $_siginfo}
17636 @item @code{write-siginfo-object}
17637 @tab @code{qXfer:siginfo:write}
17638 @tab @code{set $_siginfo}
17640 @item @code{threads}
17641 @tab @code{qXfer:threads:read}
17642 @tab @code{info threads}
17644 @item @code{get-thread-local-@*storage-address}
17645 @tab @code{qGetTLSAddr}
17646 @tab Displaying @code{__thread} variables
17648 @item @code{get-thread-information-block-address}
17649 @tab @code{qGetTIBAddr}
17650 @tab Display MS-Windows Thread Information Block.
17652 @item @code{search-memory}
17653 @tab @code{qSearch:memory}
17656 @item @code{supported-packets}
17657 @tab @code{qSupported}
17658 @tab Remote communications parameters
17660 @item @code{pass-signals}
17661 @tab @code{QPassSignals}
17662 @tab @code{handle @var{signal}}
17664 @item @code{program-signals}
17665 @tab @code{QProgramSignals}
17666 @tab @code{handle @var{signal}}
17668 @item @code{hostio-close-packet}
17669 @tab @code{vFile:close}
17670 @tab @code{remote get}, @code{remote put}
17672 @item @code{hostio-open-packet}
17673 @tab @code{vFile:open}
17674 @tab @code{remote get}, @code{remote put}
17676 @item @code{hostio-pread-packet}
17677 @tab @code{vFile:pread}
17678 @tab @code{remote get}, @code{remote put}
17680 @item @code{hostio-pwrite-packet}
17681 @tab @code{vFile:pwrite}
17682 @tab @code{remote get}, @code{remote put}
17684 @item @code{hostio-unlink-packet}
17685 @tab @code{vFile:unlink}
17686 @tab @code{remote delete}
17688 @item @code{hostio-readlink-packet}
17689 @tab @code{vFile:readlink}
17692 @item @code{noack-packet}
17693 @tab @code{QStartNoAckMode}
17694 @tab Packet acknowledgment
17696 @item @code{osdata}
17697 @tab @code{qXfer:osdata:read}
17698 @tab @code{info os}
17700 @item @code{query-attached}
17701 @tab @code{qAttached}
17702 @tab Querying remote process attach state.
17704 @item @code{traceframe-info}
17705 @tab @code{qXfer:traceframe-info:read}
17706 @tab Traceframe info
17708 @item @code{install-in-trace}
17709 @tab @code{InstallInTrace}
17710 @tab Install tracepoint in tracing
17712 @item @code{disable-randomization}
17713 @tab @code{QDisableRandomization}
17714 @tab @code{set disable-randomization}
17716 @item @code{conditional-breakpoints-packet}
17717 @tab @code{Z0 and Z1}
17718 @tab @code{Support for target-side breakpoint condition evaluation}
17722 @section Implementing a Remote Stub
17724 @cindex debugging stub, example
17725 @cindex remote stub, example
17726 @cindex stub example, remote debugging
17727 The stub files provided with @value{GDBN} implement the target side of the
17728 communication protocol, and the @value{GDBN} side is implemented in the
17729 @value{GDBN} source file @file{remote.c}. Normally, you can simply allow
17730 these subroutines to communicate, and ignore the details. (If you're
17731 implementing your own stub file, you can still ignore the details: start
17732 with one of the existing stub files. @file{sparc-stub.c} is the best
17733 organized, and therefore the easiest to read.)
17735 @cindex remote serial debugging, overview
17736 To debug a program running on another machine (the debugging
17737 @dfn{target} machine), you must first arrange for all the usual
17738 prerequisites for the program to run by itself. For example, for a C
17743 A startup routine to set up the C runtime environment; these usually
17744 have a name like @file{crt0}. The startup routine may be supplied by
17745 your hardware supplier, or you may have to write your own.
17748 A C subroutine library to support your program's
17749 subroutine calls, notably managing input and output.
17752 A way of getting your program to the other machine---for example, a
17753 download program. These are often supplied by the hardware
17754 manufacturer, but you may have to write your own from hardware
17758 The next step is to arrange for your program to use a serial port to
17759 communicate with the machine where @value{GDBN} is running (the @dfn{host}
17760 machine). In general terms, the scheme looks like this:
17764 @value{GDBN} already understands how to use this protocol; when everything
17765 else is set up, you can simply use the @samp{target remote} command
17766 (@pxref{Targets,,Specifying a Debugging Target}).
17768 @item On the target,
17769 you must link with your program a few special-purpose subroutines that
17770 implement the @value{GDBN} remote serial protocol. The file containing these
17771 subroutines is called a @dfn{debugging stub}.
17773 On certain remote targets, you can use an auxiliary program
17774 @code{gdbserver} instead of linking a stub into your program.
17775 @xref{Server,,Using the @code{gdbserver} Program}, for details.
17778 The debugging stub is specific to the architecture of the remote
17779 machine; for example, use @file{sparc-stub.c} to debug programs on
17782 @cindex remote serial stub list
17783 These working remote stubs are distributed with @value{GDBN}:
17788 @cindex @file{i386-stub.c}
17791 For Intel 386 and compatible architectures.
17794 @cindex @file{m68k-stub.c}
17795 @cindex Motorola 680x0
17797 For Motorola 680x0 architectures.
17800 @cindex @file{sh-stub.c}
17803 For Renesas SH architectures.
17806 @cindex @file{sparc-stub.c}
17808 For @sc{sparc} architectures.
17810 @item sparcl-stub.c
17811 @cindex @file{sparcl-stub.c}
17814 For Fujitsu @sc{sparclite} architectures.
17818 The @file{README} file in the @value{GDBN} distribution may list other
17819 recently added stubs.
17822 * Stub Contents:: What the stub can do for you
17823 * Bootstrapping:: What you must do for the stub
17824 * Debug Session:: Putting it all together
17827 @node Stub Contents
17828 @subsection What the Stub Can Do for You
17830 @cindex remote serial stub
17831 The debugging stub for your architecture supplies these three
17835 @item set_debug_traps
17836 @findex set_debug_traps
17837 @cindex remote serial stub, initialization
17838 This routine arranges for @code{handle_exception} to run when your
17839 program stops. You must call this subroutine explicitly in your
17840 program's startup code.
17842 @item handle_exception
17843 @findex handle_exception
17844 @cindex remote serial stub, main routine
17845 This is the central workhorse, but your program never calls it
17846 explicitly---the setup code arranges for @code{handle_exception} to
17847 run when a trap is triggered.
17849 @code{handle_exception} takes control when your program stops during
17850 execution (for example, on a breakpoint), and mediates communications
17851 with @value{GDBN} on the host machine. This is where the communications
17852 protocol is implemented; @code{handle_exception} acts as the @value{GDBN}
17853 representative on the target machine. It begins by sending summary
17854 information on the state of your program, then continues to execute,
17855 retrieving and transmitting any information @value{GDBN} needs, until you
17856 execute a @value{GDBN} command that makes your program resume; at that point,
17857 @code{handle_exception} returns control to your own code on the target
17861 @cindex @code{breakpoint} subroutine, remote
17862 Use this auxiliary subroutine to make your program contain a
17863 breakpoint. Depending on the particular situation, this may be the only
17864 way for @value{GDBN} to get control. For instance, if your target
17865 machine has some sort of interrupt button, you won't need to call this;
17866 pressing the interrupt button transfers control to
17867 @code{handle_exception}---in effect, to @value{GDBN}. On some machines,
17868 simply receiving characters on the serial port may also trigger a trap;
17869 again, in that situation, you don't need to call @code{breakpoint} from
17870 your own program---simply running @samp{target remote} from the host
17871 @value{GDBN} session gets control.
17873 Call @code{breakpoint} if none of these is true, or if you simply want
17874 to make certain your program stops at a predetermined point for the
17875 start of your debugging session.
17878 @node Bootstrapping
17879 @subsection What You Must Do for the Stub
17881 @cindex remote stub, support routines
17882 The debugging stubs that come with @value{GDBN} are set up for a particular
17883 chip architecture, but they have no information about the rest of your
17884 debugging target machine.
17886 First of all you need to tell the stub how to communicate with the
17890 @item int getDebugChar()
17891 @findex getDebugChar
17892 Write this subroutine to read a single character from the serial port.
17893 It may be identical to @code{getchar} for your target system; a
17894 different name is used to allow you to distinguish the two if you wish.
17896 @item void putDebugChar(int)
17897 @findex putDebugChar
17898 Write this subroutine to write a single character to the serial port.
17899 It may be identical to @code{putchar} for your target system; a
17900 different name is used to allow you to distinguish the two if you wish.
17903 @cindex control C, and remote debugging
17904 @cindex interrupting remote targets
17905 If you want @value{GDBN} to be able to stop your program while it is
17906 running, you need to use an interrupt-driven serial driver, and arrange
17907 for it to stop when it receives a @code{^C} (@samp{\003}, the control-C
17908 character). That is the character which @value{GDBN} uses to tell the
17909 remote system to stop.
17911 Getting the debugging target to return the proper status to @value{GDBN}
17912 probably requires changes to the standard stub; one quick and dirty way
17913 is to just execute a breakpoint instruction (the ``dirty'' part is that
17914 @value{GDBN} reports a @code{SIGTRAP} instead of a @code{SIGINT}).
17916 Other routines you need to supply are:
17919 @item void exceptionHandler (int @var{exception_number}, void *@var{exception_address})
17920 @findex exceptionHandler
17921 Write this function to install @var{exception_address} in the exception
17922 handling tables. You need to do this because the stub does not have any
17923 way of knowing what the exception handling tables on your target system
17924 are like (for example, the processor's table might be in @sc{rom},
17925 containing entries which point to a table in @sc{ram}).
17926 @var{exception_number} is the exception number which should be changed;
17927 its meaning is architecture-dependent (for example, different numbers
17928 might represent divide by zero, misaligned access, etc). When this
17929 exception occurs, control should be transferred directly to
17930 @var{exception_address}, and the processor state (stack, registers,
17931 and so on) should be just as it is when a processor exception occurs. So if
17932 you want to use a jump instruction to reach @var{exception_address}, it
17933 should be a simple jump, not a jump to subroutine.
17935 For the 386, @var{exception_address} should be installed as an interrupt
17936 gate so that interrupts are masked while the handler runs. The gate
17937 should be at privilege level 0 (the most privileged level). The
17938 @sc{sparc} and 68k stubs are able to mask interrupts themselves without
17939 help from @code{exceptionHandler}.
17941 @item void flush_i_cache()
17942 @findex flush_i_cache
17943 On @sc{sparc} and @sc{sparclite} only, write this subroutine to flush the
17944 instruction cache, if any, on your target machine. If there is no
17945 instruction cache, this subroutine may be a no-op.
17947 On target machines that have instruction caches, @value{GDBN} requires this
17948 function to make certain that the state of your program is stable.
17952 You must also make sure this library routine is available:
17955 @item void *memset(void *, int, int)
17957 This is the standard library function @code{memset} that sets an area of
17958 memory to a known value. If you have one of the free versions of
17959 @code{libc.a}, @code{memset} can be found there; otherwise, you must
17960 either obtain it from your hardware manufacturer, or write your own.
17963 If you do not use the GNU C compiler, you may need other standard
17964 library subroutines as well; this varies from one stub to another,
17965 but in general the stubs are likely to use any of the common library
17966 subroutines which @code{@value{NGCC}} generates as inline code.
17969 @node Debug Session
17970 @subsection Putting it All Together
17972 @cindex remote serial debugging summary
17973 In summary, when your program is ready to debug, you must follow these
17978 Make sure you have defined the supporting low-level routines
17979 (@pxref{Bootstrapping,,What You Must Do for the Stub}):
17981 @code{getDebugChar}, @code{putDebugChar},
17982 @code{flush_i_cache}, @code{memset}, @code{exceptionHandler}.
17986 Insert these lines in your program's startup code, before the main
17987 procedure is called:
17994 On some machines, when a breakpoint trap is raised, the hardware
17995 automatically makes the PC point to the instruction after the
17996 breakpoint. If your machine doesn't do that, you may need to adjust
17997 @code{handle_exception} to arrange for it to return to the instruction
17998 after the breakpoint on this first invocation, so that your program
17999 doesn't keep hitting the initial breakpoint instead of making
18003 For the 680x0 stub only, you need to provide a variable called
18004 @code{exceptionHook}. Normally you just use:
18007 void (*exceptionHook)() = 0;
18011 but if before calling @code{set_debug_traps}, you set it to point to a
18012 function in your program, that function is called when
18013 @code{@value{GDBN}} continues after stopping on a trap (for example, bus
18014 error). The function indicated by @code{exceptionHook} is called with
18015 one parameter: an @code{int} which is the exception number.
18018 Compile and link together: your program, the @value{GDBN} debugging stub for
18019 your target architecture, and the supporting subroutines.
18022 Make sure you have a serial connection between your target machine and
18023 the @value{GDBN} host, and identify the serial port on the host.
18026 @c The "remote" target now provides a `load' command, so we should
18027 @c document that. FIXME.
18028 Download your program to your target machine (or get it there by
18029 whatever means the manufacturer provides), and start it.
18032 Start @value{GDBN} on the host, and connect to the target
18033 (@pxref{Connecting,,Connecting to a Remote Target}).
18037 @node Configurations
18038 @chapter Configuration-Specific Information
18040 While nearly all @value{GDBN} commands are available for all native and
18041 cross versions of the debugger, there are some exceptions. This chapter
18042 describes things that are only available in certain configurations.
18044 There are three major categories of configurations: native
18045 configurations, where the host and target are the same, embedded
18046 operating system configurations, which are usually the same for several
18047 different processor architectures, and bare embedded processors, which
18048 are quite different from each other.
18053 * Embedded Processors::
18060 This section describes details specific to particular native
18065 * BSD libkvm Interface:: Debugging BSD kernel memory images
18066 * SVR4 Process Information:: SVR4 process information
18067 * DJGPP Native:: Features specific to the DJGPP port
18068 * Cygwin Native:: Features specific to the Cygwin port
18069 * Hurd Native:: Features specific to @sc{gnu} Hurd
18070 * Neutrino:: Features specific to QNX Neutrino
18071 * Darwin:: Features specific to Darwin
18077 On HP-UX systems, if you refer to a function or variable name that
18078 begins with a dollar sign, @value{GDBN} searches for a user or system
18079 name first, before it searches for a convenience variable.
18082 @node BSD libkvm Interface
18083 @subsection BSD libkvm Interface
18086 @cindex kernel memory image
18087 @cindex kernel crash dump
18089 BSD-derived systems (FreeBSD/NetBSD/OpenBSD) have a kernel memory
18090 interface that provides a uniform interface for accessing kernel virtual
18091 memory images, including live systems and crash dumps. @value{GDBN}
18092 uses this interface to allow you to debug live kernels and kernel crash
18093 dumps on many native BSD configurations. This is implemented as a
18094 special @code{kvm} debugging target. For debugging a live system, load
18095 the currently running kernel into @value{GDBN} and connect to the
18099 (@value{GDBP}) @b{target kvm}
18102 For debugging crash dumps, provide the file name of the crash dump as an
18106 (@value{GDBP}) @b{target kvm /var/crash/bsd.0}
18109 Once connected to the @code{kvm} target, the following commands are
18115 Set current context from the @dfn{Process Control Block} (PCB) address.
18118 Set current context from proc address. This command isn't available on
18119 modern FreeBSD systems.
18122 @node SVR4 Process Information
18123 @subsection SVR4 Process Information
18125 @cindex examine process image
18126 @cindex process info via @file{/proc}
18128 Many versions of SVR4 and compatible systems provide a facility called
18129 @samp{/proc} that can be used to examine the image of a running
18130 process using file-system subroutines. If @value{GDBN} is configured
18131 for an operating system with this facility, the command @code{info
18132 proc} is available to report information about the process running
18133 your program, or about any process running on your system. @code{info
18134 proc} works only on SVR4 systems that include the @code{procfs} code.
18135 This includes, as of this writing, @sc{gnu}/Linux, OSF/1 (Digital
18136 Unix), Solaris, Irix, and Unixware, but not HP-UX, for example.
18142 @itemx info proc @var{process-id}
18143 Summarize available information about any running process. If a
18144 process ID is specified by @var{process-id}, display information about
18145 that process; otherwise display information about the program being
18146 debugged. The summary includes the debugged process ID, the command
18147 line used to invoke it, its current working directory, and its
18148 executable file's absolute file name.
18150 On some systems, @var{process-id} can be of the form
18151 @samp{[@var{pid}]/@var{tid}} which specifies a certain thread ID
18152 within a process. If the optional @var{pid} part is missing, it means
18153 a thread from the process being debugged (the leading @samp{/} still
18154 needs to be present, or else @value{GDBN} will interpret the number as
18155 a process ID rather than a thread ID).
18157 @item info proc mappings
18158 @cindex memory address space mappings
18159 Report the memory address space ranges accessible in the program, with
18160 information on whether the process has read, write, or execute access
18161 rights to each range. On @sc{gnu}/Linux systems, each memory range
18162 includes the object file which is mapped to that range, instead of the
18163 memory access rights to that range.
18165 @item info proc stat
18166 @itemx info proc status
18167 @cindex process detailed status information
18168 These subcommands are specific to @sc{gnu}/Linux systems. They show
18169 the process-related information, including the user ID and group ID;
18170 how many threads are there in the process; its virtual memory usage;
18171 the signals that are pending, blocked, and ignored; its TTY; its
18172 consumption of system and user time; its stack size; its @samp{nice}
18173 value; etc. For more information, see the @samp{proc} man page
18174 (type @kbd{man 5 proc} from your shell prompt).
18176 @item info proc all
18177 Show all the information about the process described under all of the
18178 above @code{info proc} subcommands.
18181 @comment These sub-options of 'info proc' were not included when
18182 @comment procfs.c was re-written. Keep their descriptions around
18183 @comment against the day when someone finds the time to put them back in.
18184 @kindex info proc times
18185 @item info proc times
18186 Starting time, user CPU time, and system CPU time for your program and
18189 @kindex info proc id
18191 Report on the process IDs related to your program: its own process ID,
18192 the ID of its parent, the process group ID, and the session ID.
18195 @item set procfs-trace
18196 @kindex set procfs-trace
18197 @cindex @code{procfs} API calls
18198 This command enables and disables tracing of @code{procfs} API calls.
18200 @item show procfs-trace
18201 @kindex show procfs-trace
18202 Show the current state of @code{procfs} API call tracing.
18204 @item set procfs-file @var{file}
18205 @kindex set procfs-file
18206 Tell @value{GDBN} to write @code{procfs} API trace to the named
18207 @var{file}. @value{GDBN} appends the trace info to the previous
18208 contents of the file. The default is to display the trace on the
18211 @item show procfs-file
18212 @kindex show procfs-file
18213 Show the file to which @code{procfs} API trace is written.
18215 @item proc-trace-entry
18216 @itemx proc-trace-exit
18217 @itemx proc-untrace-entry
18218 @itemx proc-untrace-exit
18219 @kindex proc-trace-entry
18220 @kindex proc-trace-exit
18221 @kindex proc-untrace-entry
18222 @kindex proc-untrace-exit
18223 These commands enable and disable tracing of entries into and exits
18224 from the @code{syscall} interface.
18227 @kindex info pidlist
18228 @cindex process list, QNX Neutrino
18229 For QNX Neutrino only, this command displays the list of all the
18230 processes and all the threads within each process.
18233 @kindex info meminfo
18234 @cindex mapinfo list, QNX Neutrino
18235 For QNX Neutrino only, this command displays the list of all mapinfos.
18239 @subsection Features for Debugging @sc{djgpp} Programs
18240 @cindex @sc{djgpp} debugging
18241 @cindex native @sc{djgpp} debugging
18242 @cindex MS-DOS-specific commands
18245 @sc{djgpp} is a port of the @sc{gnu} development tools to MS-DOS and
18246 MS-Windows. @sc{djgpp} programs are 32-bit protected-mode programs
18247 that use the @dfn{DPMI} (DOS Protected-Mode Interface) API to run on
18248 top of real-mode DOS systems and their emulations.
18250 @value{GDBN} supports native debugging of @sc{djgpp} programs, and
18251 defines a few commands specific to the @sc{djgpp} port. This
18252 subsection describes those commands.
18257 This is a prefix of @sc{djgpp}-specific commands which print
18258 information about the target system and important OS structures.
18261 @cindex MS-DOS system info
18262 @cindex free memory information (MS-DOS)
18263 @item info dos sysinfo
18264 This command displays assorted information about the underlying
18265 platform: the CPU type and features, the OS version and flavor, the
18266 DPMI version, and the available conventional and DPMI memory.
18271 @cindex segment descriptor tables
18272 @cindex descriptor tables display
18274 @itemx info dos ldt
18275 @itemx info dos idt
18276 These 3 commands display entries from, respectively, Global, Local,
18277 and Interrupt Descriptor Tables (GDT, LDT, and IDT). The descriptor
18278 tables are data structures which store a descriptor for each segment
18279 that is currently in use. The segment's selector is an index into a
18280 descriptor table; the table entry for that index holds the
18281 descriptor's base address and limit, and its attributes and access
18284 A typical @sc{djgpp} program uses 3 segments: a code segment, a data
18285 segment (used for both data and the stack), and a DOS segment (which
18286 allows access to DOS/BIOS data structures and absolute addresses in
18287 conventional memory). However, the DPMI host will usually define
18288 additional segments in order to support the DPMI environment.
18290 @cindex garbled pointers
18291 These commands allow to display entries from the descriptor tables.
18292 Without an argument, all entries from the specified table are
18293 displayed. An argument, which should be an integer expression, means
18294 display a single entry whose index is given by the argument. For
18295 example, here's a convenient way to display information about the
18296 debugged program's data segment:
18299 @exdent @code{(@value{GDBP}) info dos ldt $ds}
18300 @exdent @code{0x13f: base=0x11970000 limit=0x0009ffff 32-Bit Data (Read/Write, Exp-up)}
18304 This comes in handy when you want to see whether a pointer is outside
18305 the data segment's limit (i.e.@: @dfn{garbled}).
18307 @cindex page tables display (MS-DOS)
18309 @itemx info dos pte
18310 These two commands display entries from, respectively, the Page
18311 Directory and the Page Tables. Page Directories and Page Tables are
18312 data structures which control how virtual memory addresses are mapped
18313 into physical addresses. A Page Table includes an entry for every
18314 page of memory that is mapped into the program's address space; there
18315 may be several Page Tables, each one holding up to 4096 entries. A
18316 Page Directory has up to 4096 entries, one each for every Page Table
18317 that is currently in use.
18319 Without an argument, @kbd{info dos pde} displays the entire Page
18320 Directory, and @kbd{info dos pte} displays all the entries in all of
18321 the Page Tables. An argument, an integer expression, given to the
18322 @kbd{info dos pde} command means display only that entry from the Page
18323 Directory table. An argument given to the @kbd{info dos pte} command
18324 means display entries from a single Page Table, the one pointed to by
18325 the specified entry in the Page Directory.
18327 @cindex direct memory access (DMA) on MS-DOS
18328 These commands are useful when your program uses @dfn{DMA} (Direct
18329 Memory Access), which needs physical addresses to program the DMA
18332 These commands are supported only with some DPMI servers.
18334 @cindex physical address from linear address
18335 @item info dos address-pte @var{addr}
18336 This command displays the Page Table entry for a specified linear
18337 address. The argument @var{addr} is a linear address which should
18338 already have the appropriate segment's base address added to it,
18339 because this command accepts addresses which may belong to @emph{any}
18340 segment. For example, here's how to display the Page Table entry for
18341 the page where a variable @code{i} is stored:
18344 @exdent @code{(@value{GDBP}) info dos address-pte __djgpp_base_address + (char *)&i}
18345 @exdent @code{Page Table entry for address 0x11a00d30:}
18346 @exdent @code{Base=0x02698000 Dirty Acc. Not-Cached Write-Back Usr Read-Write +0xd30}
18350 This says that @code{i} is stored at offset @code{0xd30} from the page
18351 whose physical base address is @code{0x02698000}, and shows all the
18352 attributes of that page.
18354 Note that you must cast the addresses of variables to a @code{char *},
18355 since otherwise the value of @code{__djgpp_base_address}, the base
18356 address of all variables and functions in a @sc{djgpp} program, will
18357 be added using the rules of C pointer arithmetics: if @code{i} is
18358 declared an @code{int}, @value{GDBN} will add 4 times the value of
18359 @code{__djgpp_base_address} to the address of @code{i}.
18361 Here's another example, it displays the Page Table entry for the
18365 @exdent @code{(@value{GDBP}) info dos address-pte *((unsigned *)&_go32_info_block + 3)}
18366 @exdent @code{Page Table entry for address 0x29110:}
18367 @exdent @code{Base=0x00029000 Dirty Acc. Not-Cached Write-Back Usr Read-Write +0x110}
18371 (The @code{+ 3} offset is because the transfer buffer's address is the
18372 3rd member of the @code{_go32_info_block} structure.) The output
18373 clearly shows that this DPMI server maps the addresses in conventional
18374 memory 1:1, i.e.@: the physical (@code{0x00029000} + @code{0x110}) and
18375 linear (@code{0x29110}) addresses are identical.
18377 This command is supported only with some DPMI servers.
18380 @cindex DOS serial data link, remote debugging
18381 In addition to native debugging, the DJGPP port supports remote
18382 debugging via a serial data link. The following commands are specific
18383 to remote serial debugging in the DJGPP port of @value{GDBN}.
18386 @kindex set com1base
18387 @kindex set com1irq
18388 @kindex set com2base
18389 @kindex set com2irq
18390 @kindex set com3base
18391 @kindex set com3irq
18392 @kindex set com4base
18393 @kindex set com4irq
18394 @item set com1base @var{addr}
18395 This command sets the base I/O port address of the @file{COM1} serial
18398 @item set com1irq @var{irq}
18399 This command sets the @dfn{Interrupt Request} (@code{IRQ}) line to use
18400 for the @file{COM1} serial port.
18402 There are similar commands @samp{set com2base}, @samp{set com3irq},
18403 etc.@: for setting the port address and the @code{IRQ} lines for the
18406 @kindex show com1base
18407 @kindex show com1irq
18408 @kindex show com2base
18409 @kindex show com2irq
18410 @kindex show com3base
18411 @kindex show com3irq
18412 @kindex show com4base
18413 @kindex show com4irq
18414 The related commands @samp{show com1base}, @samp{show com1irq} etc.@:
18415 display the current settings of the base address and the @code{IRQ}
18416 lines used by the COM ports.
18419 @kindex info serial
18420 @cindex DOS serial port status
18421 This command prints the status of the 4 DOS serial ports. For each
18422 port, it prints whether it's active or not, its I/O base address and
18423 IRQ number, whether it uses a 16550-style FIFO, its baudrate, and the
18424 counts of various errors encountered so far.
18428 @node Cygwin Native
18429 @subsection Features for Debugging MS Windows PE Executables
18430 @cindex MS Windows debugging
18431 @cindex native Cygwin debugging
18432 @cindex Cygwin-specific commands
18434 @value{GDBN} supports native debugging of MS Windows programs, including
18435 DLLs with and without symbolic debugging information.
18437 @cindex Ctrl-BREAK, MS-Windows
18438 @cindex interrupt debuggee on MS-Windows
18439 MS-Windows programs that call @code{SetConsoleMode} to switch off the
18440 special meaning of the @samp{Ctrl-C} keystroke cannot be interrupted
18441 by typing @kbd{C-c}. For this reason, @value{GDBN} on MS-Windows
18442 supports @kbd{C-@key{BREAK}} as an alternative interrupt key
18443 sequence, which can be used to interrupt the debuggee even if it
18446 There are various additional Cygwin-specific commands, described in
18447 this section. Working with DLLs that have no debugging symbols is
18448 described in @ref{Non-debug DLL Symbols}.
18453 This is a prefix of MS Windows-specific commands which print
18454 information about the target system and important OS structures.
18456 @item info w32 selector
18457 This command displays information returned by
18458 the Win32 API @code{GetThreadSelectorEntry} function.
18459 It takes an optional argument that is evaluated to
18460 a long value to give the information about this given selector.
18461 Without argument, this command displays information
18462 about the six segment registers.
18464 @item info w32 thread-information-block
18465 This command displays thread specific information stored in the
18466 Thread Information Block (readable on the X86 CPU family using @code{$fs}
18467 selector for 32-bit programs and @code{$gs} for 64-bit programs).
18471 This is a Cygwin-specific alias of @code{info shared}.
18473 @kindex dll-symbols
18475 This command loads symbols from a dll similarly to
18476 add-sym command but without the need to specify a base address.
18478 @kindex set cygwin-exceptions
18479 @cindex debugging the Cygwin DLL
18480 @cindex Cygwin DLL, debugging
18481 @item set cygwin-exceptions @var{mode}
18482 If @var{mode} is @code{on}, @value{GDBN} will break on exceptions that
18483 happen inside the Cygwin DLL. If @var{mode} is @code{off},
18484 @value{GDBN} will delay recognition of exceptions, and may ignore some
18485 exceptions which seem to be caused by internal Cygwin DLL
18486 ``bookkeeping''. This option is meant primarily for debugging the
18487 Cygwin DLL itself; the default value is @code{off} to avoid annoying
18488 @value{GDBN} users with false @code{SIGSEGV} signals.
18490 @kindex show cygwin-exceptions
18491 @item show cygwin-exceptions
18492 Displays whether @value{GDBN} will break on exceptions that happen
18493 inside the Cygwin DLL itself.
18495 @kindex set new-console
18496 @item set new-console @var{mode}
18497 If @var{mode} is @code{on} the debuggee will
18498 be started in a new console on next start.
18499 If @var{mode} is @code{off}, the debuggee will
18500 be started in the same console as the debugger.
18502 @kindex show new-console
18503 @item show new-console
18504 Displays whether a new console is used
18505 when the debuggee is started.
18507 @kindex set new-group
18508 @item set new-group @var{mode}
18509 This boolean value controls whether the debuggee should
18510 start a new group or stay in the same group as the debugger.
18511 This affects the way the Windows OS handles
18514 @kindex show new-group
18515 @item show new-group
18516 Displays current value of new-group boolean.
18518 @kindex set debugevents
18519 @item set debugevents
18520 This boolean value adds debug output concerning kernel events related
18521 to the debuggee seen by the debugger. This includes events that
18522 signal thread and process creation and exit, DLL loading and
18523 unloading, console interrupts, and debugging messages produced by the
18524 Windows @code{OutputDebugString} API call.
18526 @kindex set debugexec
18527 @item set debugexec
18528 This boolean value adds debug output concerning execute events
18529 (such as resume thread) seen by the debugger.
18531 @kindex set debugexceptions
18532 @item set debugexceptions
18533 This boolean value adds debug output concerning exceptions in the
18534 debuggee seen by the debugger.
18536 @kindex set debugmemory
18537 @item set debugmemory
18538 This boolean value adds debug output concerning debuggee memory reads
18539 and writes by the debugger.
18543 This boolean values specifies whether the debuggee is called
18544 via a shell or directly (default value is on).
18548 Displays if the debuggee will be started with a shell.
18553 * Non-debug DLL Symbols:: Support for DLLs without debugging symbols
18556 @node Non-debug DLL Symbols
18557 @subsubsection Support for DLLs without Debugging Symbols
18558 @cindex DLLs with no debugging symbols
18559 @cindex Minimal symbols and DLLs
18561 Very often on windows, some of the DLLs that your program relies on do
18562 not include symbolic debugging information (for example,
18563 @file{kernel32.dll}). When @value{GDBN} doesn't recognize any debugging
18564 symbols in a DLL, it relies on the minimal amount of symbolic
18565 information contained in the DLL's export table. This section
18566 describes working with such symbols, known internally to @value{GDBN} as
18567 ``minimal symbols''.
18569 Note that before the debugged program has started execution, no DLLs
18570 will have been loaded. The easiest way around this problem is simply to
18571 start the program --- either by setting a breakpoint or letting the
18572 program run once to completion. It is also possible to force
18573 @value{GDBN} to load a particular DLL before starting the executable ---
18574 see the shared library information in @ref{Files}, or the
18575 @code{dll-symbols} command in @ref{Cygwin Native}. Currently,
18576 explicitly loading symbols from a DLL with no debugging information will
18577 cause the symbol names to be duplicated in @value{GDBN}'s lookup table,
18578 which may adversely affect symbol lookup performance.
18580 @subsubsection DLL Name Prefixes
18582 In keeping with the naming conventions used by the Microsoft debugging
18583 tools, DLL export symbols are made available with a prefix based on the
18584 DLL name, for instance @code{KERNEL32!CreateFileA}. The plain name is
18585 also entered into the symbol table, so @code{CreateFileA} is often
18586 sufficient. In some cases there will be name clashes within a program
18587 (particularly if the executable itself includes full debugging symbols)
18588 necessitating the use of the fully qualified name when referring to the
18589 contents of the DLL. Use single-quotes around the name to avoid the
18590 exclamation mark (``!'') being interpreted as a language operator.
18592 Note that the internal name of the DLL may be all upper-case, even
18593 though the file name of the DLL is lower-case, or vice-versa. Since
18594 symbols within @value{GDBN} are @emph{case-sensitive} this may cause
18595 some confusion. If in doubt, try the @code{info functions} and
18596 @code{info variables} commands or even @code{maint print msymbols}
18597 (@pxref{Symbols}). Here's an example:
18600 (@value{GDBP}) info function CreateFileA
18601 All functions matching regular expression "CreateFileA":
18603 Non-debugging symbols:
18604 0x77e885f4 CreateFileA
18605 0x77e885f4 KERNEL32!CreateFileA
18609 (@value{GDBP}) info function !
18610 All functions matching regular expression "!":
18612 Non-debugging symbols:
18613 0x6100114c cygwin1!__assert
18614 0x61004034 cygwin1!_dll_crt0@@0
18615 0x61004240 cygwin1!dll_crt0(per_process *)
18619 @subsubsection Working with Minimal Symbols
18621 Symbols extracted from a DLL's export table do not contain very much
18622 type information. All that @value{GDBN} can do is guess whether a symbol
18623 refers to a function or variable depending on the linker section that
18624 contains the symbol. Also note that the actual contents of the memory
18625 contained in a DLL are not available unless the program is running. This
18626 means that you cannot examine the contents of a variable or disassemble
18627 a function within a DLL without a running program.
18629 Variables are generally treated as pointers and dereferenced
18630 automatically. For this reason, it is often necessary to prefix a
18631 variable name with the address-of operator (``&'') and provide explicit
18632 type information in the command. Here's an example of the type of
18636 (@value{GDBP}) print 'cygwin1!__argv'
18641 (@value{GDBP}) x 'cygwin1!__argv'
18642 0x10021610: "\230y\""
18645 And two possible solutions:
18648 (@value{GDBP}) print ((char **)'cygwin1!__argv')[0]
18649 $2 = 0x22fd98 "/cygdrive/c/mydirectory/myprogram"
18653 (@value{GDBP}) x/2x &'cygwin1!__argv'
18654 0x610c0aa8 <cygwin1!__argv>: 0x10021608 0x00000000
18655 (@value{GDBP}) x/x 0x10021608
18656 0x10021608: 0x0022fd98
18657 (@value{GDBP}) x/s 0x0022fd98
18658 0x22fd98: "/cygdrive/c/mydirectory/myprogram"
18661 Setting a break point within a DLL is possible even before the program
18662 starts execution. However, under these circumstances, @value{GDBN} can't
18663 examine the initial instructions of the function in order to skip the
18664 function's frame set-up code. You can work around this by using ``*&''
18665 to set the breakpoint at a raw memory address:
18668 (@value{GDBP}) break *&'python22!PyOS_Readline'
18669 Breakpoint 1 at 0x1e04eff0
18672 The author of these extensions is not entirely convinced that setting a
18673 break point within a shared DLL like @file{kernel32.dll} is completely
18677 @subsection Commands Specific to @sc{gnu} Hurd Systems
18678 @cindex @sc{gnu} Hurd debugging
18680 This subsection describes @value{GDBN} commands specific to the
18681 @sc{gnu} Hurd native debugging.
18686 @kindex set signals@r{, Hurd command}
18687 @kindex set sigs@r{, Hurd command}
18688 This command toggles the state of inferior signal interception by
18689 @value{GDBN}. Mach exceptions, such as breakpoint traps, are not
18690 affected by this command. @code{sigs} is a shorthand alias for
18695 @kindex show signals@r{, Hurd command}
18696 @kindex show sigs@r{, Hurd command}
18697 Show the current state of intercepting inferior's signals.
18699 @item set signal-thread
18700 @itemx set sigthread
18701 @kindex set signal-thread
18702 @kindex set sigthread
18703 This command tells @value{GDBN} which thread is the @code{libc} signal
18704 thread. That thread is run when a signal is delivered to a running
18705 process. @code{set sigthread} is the shorthand alias of @code{set
18708 @item show signal-thread
18709 @itemx show sigthread
18710 @kindex show signal-thread
18711 @kindex show sigthread
18712 These two commands show which thread will run when the inferior is
18713 delivered a signal.
18716 @kindex set stopped@r{, Hurd command}
18717 This commands tells @value{GDBN} that the inferior process is stopped,
18718 as with the @code{SIGSTOP} signal. The stopped process can be
18719 continued by delivering a signal to it.
18722 @kindex show stopped@r{, Hurd command}
18723 This command shows whether @value{GDBN} thinks the debuggee is
18726 @item set exceptions
18727 @kindex set exceptions@r{, Hurd command}
18728 Use this command to turn off trapping of exceptions in the inferior.
18729 When exception trapping is off, neither breakpoints nor
18730 single-stepping will work. To restore the default, set exception
18733 @item show exceptions
18734 @kindex show exceptions@r{, Hurd command}
18735 Show the current state of trapping exceptions in the inferior.
18737 @item set task pause
18738 @kindex set task@r{, Hurd commands}
18739 @cindex task attributes (@sc{gnu} Hurd)
18740 @cindex pause current task (@sc{gnu} Hurd)
18741 This command toggles task suspension when @value{GDBN} has control.
18742 Setting it to on takes effect immediately, and the task is suspended
18743 whenever @value{GDBN} gets control. Setting it to off will take
18744 effect the next time the inferior is continued. If this option is set
18745 to off, you can use @code{set thread default pause on} or @code{set
18746 thread pause on} (see below) to pause individual threads.
18748 @item show task pause
18749 @kindex show task@r{, Hurd commands}
18750 Show the current state of task suspension.
18752 @item set task detach-suspend-count
18753 @cindex task suspend count
18754 @cindex detach from task, @sc{gnu} Hurd
18755 This command sets the suspend count the task will be left with when
18756 @value{GDBN} detaches from it.
18758 @item show task detach-suspend-count
18759 Show the suspend count the task will be left with when detaching.
18761 @item set task exception-port
18762 @itemx set task excp
18763 @cindex task exception port, @sc{gnu} Hurd
18764 This command sets the task exception port to which @value{GDBN} will
18765 forward exceptions. The argument should be the value of the @dfn{send
18766 rights} of the task. @code{set task excp} is a shorthand alias.
18768 @item set noninvasive
18769 @cindex noninvasive task options
18770 This command switches @value{GDBN} to a mode that is the least
18771 invasive as far as interfering with the inferior is concerned. This
18772 is the same as using @code{set task pause}, @code{set exceptions}, and
18773 @code{set signals} to values opposite to the defaults.
18775 @item info send-rights
18776 @itemx info receive-rights
18777 @itemx info port-rights
18778 @itemx info port-sets
18779 @itemx info dead-names
18782 @cindex send rights, @sc{gnu} Hurd
18783 @cindex receive rights, @sc{gnu} Hurd
18784 @cindex port rights, @sc{gnu} Hurd
18785 @cindex port sets, @sc{gnu} Hurd
18786 @cindex dead names, @sc{gnu} Hurd
18787 These commands display information about, respectively, send rights,
18788 receive rights, port rights, port sets, and dead names of a task.
18789 There are also shorthand aliases: @code{info ports} for @code{info
18790 port-rights} and @code{info psets} for @code{info port-sets}.
18792 @item set thread pause
18793 @kindex set thread@r{, Hurd command}
18794 @cindex thread properties, @sc{gnu} Hurd
18795 @cindex pause current thread (@sc{gnu} Hurd)
18796 This command toggles current thread suspension when @value{GDBN} has
18797 control. Setting it to on takes effect immediately, and the current
18798 thread is suspended whenever @value{GDBN} gets control. Setting it to
18799 off will take effect the next time the inferior is continued.
18800 Normally, this command has no effect, since when @value{GDBN} has
18801 control, the whole task is suspended. However, if you used @code{set
18802 task pause off} (see above), this command comes in handy to suspend
18803 only the current thread.
18805 @item show thread pause
18806 @kindex show thread@r{, Hurd command}
18807 This command shows the state of current thread suspension.
18809 @item set thread run
18810 This command sets whether the current thread is allowed to run.
18812 @item show thread run
18813 Show whether the current thread is allowed to run.
18815 @item set thread detach-suspend-count
18816 @cindex thread suspend count, @sc{gnu} Hurd
18817 @cindex detach from thread, @sc{gnu} Hurd
18818 This command sets the suspend count @value{GDBN} will leave on a
18819 thread when detaching. This number is relative to the suspend count
18820 found by @value{GDBN} when it notices the thread; use @code{set thread
18821 takeover-suspend-count} to force it to an absolute value.
18823 @item show thread detach-suspend-count
18824 Show the suspend count @value{GDBN} will leave on the thread when
18827 @item set thread exception-port
18828 @itemx set thread excp
18829 Set the thread exception port to which to forward exceptions. This
18830 overrides the port set by @code{set task exception-port} (see above).
18831 @code{set thread excp} is the shorthand alias.
18833 @item set thread takeover-suspend-count
18834 Normally, @value{GDBN}'s thread suspend counts are relative to the
18835 value @value{GDBN} finds when it notices each thread. This command
18836 changes the suspend counts to be absolute instead.
18838 @item set thread default
18839 @itemx show thread default
18840 @cindex thread default settings, @sc{gnu} Hurd
18841 Each of the above @code{set thread} commands has a @code{set thread
18842 default} counterpart (e.g., @code{set thread default pause}, @code{set
18843 thread default exception-port}, etc.). The @code{thread default}
18844 variety of commands sets the default thread properties for all
18845 threads; you can then change the properties of individual threads with
18846 the non-default commands.
18851 @subsection QNX Neutrino
18852 @cindex QNX Neutrino
18854 @value{GDBN} provides the following commands specific to the QNX
18858 @item set debug nto-debug
18859 @kindex set debug nto-debug
18860 When set to on, enables debugging messages specific to the QNX
18863 @item show debug nto-debug
18864 @kindex show debug nto-debug
18865 Show the current state of QNX Neutrino messages.
18872 @value{GDBN} provides the following commands specific to the Darwin target:
18875 @item set debug darwin @var{num}
18876 @kindex set debug darwin
18877 When set to a non zero value, enables debugging messages specific to
18878 the Darwin support. Higher values produce more verbose output.
18880 @item show debug darwin
18881 @kindex show debug darwin
18882 Show the current state of Darwin messages.
18884 @item set debug mach-o @var{num}
18885 @kindex set debug mach-o
18886 When set to a non zero value, enables debugging messages while
18887 @value{GDBN} is reading Darwin object files. (@dfn{Mach-O} is the
18888 file format used on Darwin for object and executable files.) Higher
18889 values produce more verbose output. This is a command to diagnose
18890 problems internal to @value{GDBN} and should not be needed in normal
18893 @item show debug mach-o
18894 @kindex show debug mach-o
18895 Show the current state of Mach-O file messages.
18897 @item set mach-exceptions on
18898 @itemx set mach-exceptions off
18899 @kindex set mach-exceptions
18900 On Darwin, faults are first reported as a Mach exception and are then
18901 mapped to a Posix signal. Use this command to turn on trapping of
18902 Mach exceptions in the inferior. This might be sometimes useful to
18903 better understand the cause of a fault. The default is off.
18905 @item show mach-exceptions
18906 @kindex show mach-exceptions
18907 Show the current state of exceptions trapping.
18912 @section Embedded Operating Systems
18914 This section describes configurations involving the debugging of
18915 embedded operating systems that are available for several different
18919 * VxWorks:: Using @value{GDBN} with VxWorks
18922 @value{GDBN} includes the ability to debug programs running on
18923 various real-time operating systems.
18926 @subsection Using @value{GDBN} with VxWorks
18932 @kindex target vxworks
18933 @item target vxworks @var{machinename}
18934 A VxWorks system, attached via TCP/IP. The argument @var{machinename}
18935 is the target system's machine name or IP address.
18939 On VxWorks, @code{load} links @var{filename} dynamically on the
18940 current target system as well as adding its symbols in @value{GDBN}.
18942 @value{GDBN} enables developers to spawn and debug tasks running on networked
18943 VxWorks targets from a Unix host. Already-running tasks spawned from
18944 the VxWorks shell can also be debugged. @value{GDBN} uses code that runs on
18945 both the Unix host and on the VxWorks target. The program
18946 @code{@value{GDBP}} is installed and executed on the Unix host. (It may be
18947 installed with the name @code{vxgdb}, to distinguish it from a
18948 @value{GDBN} for debugging programs on the host itself.)
18951 @item VxWorks-timeout @var{args}
18952 @kindex vxworks-timeout
18953 All VxWorks-based targets now support the option @code{vxworks-timeout}.
18954 This option is set by the user, and @var{args} represents the number of
18955 seconds @value{GDBN} waits for responses to rpc's. You might use this if
18956 your VxWorks target is a slow software simulator or is on the far side
18957 of a thin network line.
18960 The following information on connecting to VxWorks was current when
18961 this manual was produced; newer releases of VxWorks may use revised
18964 @findex INCLUDE_RDB
18965 To use @value{GDBN} with VxWorks, you must rebuild your VxWorks kernel
18966 to include the remote debugging interface routines in the VxWorks
18967 library @file{rdb.a}. To do this, define @code{INCLUDE_RDB} in the
18968 VxWorks configuration file @file{configAll.h} and rebuild your VxWorks
18969 kernel. The resulting kernel contains @file{rdb.a}, and spawns the
18970 source debugging task @code{tRdbTask} when VxWorks is booted. For more
18971 information on configuring and remaking VxWorks, see the manufacturer's
18973 @c VxWorks, see the @cite{VxWorks Programmer's Guide}.
18975 Once you have included @file{rdb.a} in your VxWorks system image and set
18976 your Unix execution search path to find @value{GDBN}, you are ready to
18977 run @value{GDBN}. From your Unix host, run @code{@value{GDBP}} (or
18978 @code{vxgdb}, depending on your installation).
18980 @value{GDBN} comes up showing the prompt:
18987 * VxWorks Connection:: Connecting to VxWorks
18988 * VxWorks Download:: VxWorks download
18989 * VxWorks Attach:: Running tasks
18992 @node VxWorks Connection
18993 @subsubsection Connecting to VxWorks
18995 The @value{GDBN} command @code{target} lets you connect to a VxWorks target on the
18996 network. To connect to a target whose host name is ``@code{tt}'', type:
18999 (vxgdb) target vxworks tt
19003 @value{GDBN} displays messages like these:
19006 Attaching remote machine across net...
19011 @value{GDBN} then attempts to read the symbol tables of any object modules
19012 loaded into the VxWorks target since it was last booted. @value{GDBN} locates
19013 these files by searching the directories listed in the command search
19014 path (@pxref{Environment, ,Your Program's Environment}); if it fails
19015 to find an object file, it displays a message such as:
19018 prog.o: No such file or directory.
19021 When this happens, add the appropriate directory to the search path with
19022 the @value{GDBN} command @code{path}, and execute the @code{target}
19025 @node VxWorks Download
19026 @subsubsection VxWorks Download
19028 @cindex download to VxWorks
19029 If you have connected to the VxWorks target and you want to debug an
19030 object that has not yet been loaded, you can use the @value{GDBN}
19031 @code{load} command to download a file from Unix to VxWorks
19032 incrementally. The object file given as an argument to the @code{load}
19033 command is actually opened twice: first by the VxWorks target in order
19034 to download the code, then by @value{GDBN} in order to read the symbol
19035 table. This can lead to problems if the current working directories on
19036 the two systems differ. If both systems have NFS mounted the same
19037 filesystems, you can avoid these problems by using absolute paths.
19038 Otherwise, it is simplest to set the working directory on both systems
19039 to the directory in which the object file resides, and then to reference
19040 the file by its name, without any path. For instance, a program
19041 @file{prog.o} may reside in @file{@var{vxpath}/vw/demo/rdb} in VxWorks
19042 and in @file{@var{hostpath}/vw/demo/rdb} on the host. To load this
19043 program, type this on VxWorks:
19046 -> cd "@var{vxpath}/vw/demo/rdb"
19050 Then, in @value{GDBN}, type:
19053 (vxgdb) cd @var{hostpath}/vw/demo/rdb
19054 (vxgdb) load prog.o
19057 @value{GDBN} displays a response similar to this:
19060 Reading symbol data from wherever/vw/demo/rdb/prog.o... done.
19063 You can also use the @code{load} command to reload an object module
19064 after editing and recompiling the corresponding source file. Note that
19065 this makes @value{GDBN} delete all currently-defined breakpoints,
19066 auto-displays, and convenience variables, and to clear the value
19067 history. (This is necessary in order to preserve the integrity of
19068 debugger's data structures that reference the target system's symbol
19071 @node VxWorks Attach
19072 @subsubsection Running Tasks
19074 @cindex running VxWorks tasks
19075 You can also attach to an existing task using the @code{attach} command as
19079 (vxgdb) attach @var{task}
19083 where @var{task} is the VxWorks hexadecimal task ID. The task can be running
19084 or suspended when you attach to it. Running tasks are suspended at
19085 the time of attachment.
19087 @node Embedded Processors
19088 @section Embedded Processors
19090 This section goes into details specific to particular embedded
19093 @cindex send command to simulator
19094 Whenever a specific embedded processor has a simulator, @value{GDBN}
19095 allows to send an arbitrary command to the simulator.
19098 @item sim @var{command}
19099 @kindex sim@r{, a command}
19100 Send an arbitrary @var{command} string to the simulator. Consult the
19101 documentation for the specific simulator in use for information about
19102 acceptable commands.
19108 * M32R/D:: Renesas M32R/D
19109 * M68K:: Motorola M68K
19110 * MicroBlaze:: Xilinx MicroBlaze
19111 * MIPS Embedded:: MIPS Embedded
19112 * OpenRISC 1000:: OpenRisc 1000
19113 * PA:: HP PA Embedded
19114 * PowerPC Embedded:: PowerPC Embedded
19115 * Sparclet:: Tsqware Sparclet
19116 * Sparclite:: Fujitsu Sparclite
19117 * Z8000:: Zilog Z8000
19120 * Super-H:: Renesas Super-H
19129 @item target rdi @var{dev}
19130 ARM Angel monitor, via RDI library interface to ADP protocol. You may
19131 use this target to communicate with both boards running the Angel
19132 monitor, or with the EmbeddedICE JTAG debug device.
19135 @item target rdp @var{dev}
19140 @value{GDBN} provides the following ARM-specific commands:
19143 @item set arm disassembler
19145 This commands selects from a list of disassembly styles. The
19146 @code{"std"} style is the standard style.
19148 @item show arm disassembler
19150 Show the current disassembly style.
19152 @item set arm apcs32
19153 @cindex ARM 32-bit mode
19154 This command toggles ARM operation mode between 32-bit and 26-bit.
19156 @item show arm apcs32
19157 Display the current usage of the ARM 32-bit mode.
19159 @item set arm fpu @var{fputype}
19160 This command sets the ARM floating-point unit (FPU) type. The
19161 argument @var{fputype} can be one of these:
19165 Determine the FPU type by querying the OS ABI.
19167 Software FPU, with mixed-endian doubles on little-endian ARM
19170 GCC-compiled FPA co-processor.
19172 Software FPU with pure-endian doubles.
19178 Show the current type of the FPU.
19181 This command forces @value{GDBN} to use the specified ABI.
19184 Show the currently used ABI.
19186 @item set arm fallback-mode (arm|thumb|auto)
19187 @value{GDBN} uses the symbol table, when available, to determine
19188 whether instructions are ARM or Thumb. This command controls
19189 @value{GDBN}'s default behavior when the symbol table is not
19190 available. The default is @samp{auto}, which causes @value{GDBN} to
19191 use the current execution mode (from the @code{T} bit in the @code{CPSR}
19194 @item show arm fallback-mode
19195 Show the current fallback instruction mode.
19197 @item set arm force-mode (arm|thumb|auto)
19198 This command overrides use of the symbol table to determine whether
19199 instructions are ARM or Thumb. The default is @samp{auto}, which
19200 causes @value{GDBN} to use the symbol table and then the setting
19201 of @samp{set arm fallback-mode}.
19203 @item show arm force-mode
19204 Show the current forced instruction mode.
19206 @item set debug arm
19207 Toggle whether to display ARM-specific debugging messages from the ARM
19208 target support subsystem.
19210 @item show debug arm
19211 Show whether ARM-specific debugging messages are enabled.
19214 The following commands are available when an ARM target is debugged
19215 using the RDI interface:
19218 @item rdilogfile @r{[}@var{file}@r{]}
19220 @cindex ADP (Angel Debugger Protocol) logging
19221 Set the filename for the ADP (Angel Debugger Protocol) packet log.
19222 With an argument, sets the log file to the specified @var{file}. With
19223 no argument, show the current log file name. The default log file is
19226 @item rdilogenable @r{[}@var{arg}@r{]}
19227 @kindex rdilogenable
19228 Control logging of ADP packets. With an argument of 1 or @code{"yes"}
19229 enables logging, with an argument 0 or @code{"no"} disables it. With
19230 no arguments displays the current setting. When logging is enabled,
19231 ADP packets exchanged between @value{GDBN} and the RDI target device
19232 are logged to a file.
19234 @item set rdiromatzero
19235 @kindex set rdiromatzero
19236 @cindex ROM at zero address, RDI
19237 Tell @value{GDBN} whether the target has ROM at address 0. If on,
19238 vector catching is disabled, so that zero address can be used. If off
19239 (the default), vector catching is enabled. For this command to take
19240 effect, it needs to be invoked prior to the @code{target rdi} command.
19242 @item show rdiromatzero
19243 @kindex show rdiromatzero
19244 Show the current setting of ROM at zero address.
19246 @item set rdiheartbeat
19247 @kindex set rdiheartbeat
19248 @cindex RDI heartbeat
19249 Enable or disable RDI heartbeat packets. It is not recommended to
19250 turn on this option, since it confuses ARM and EPI JTAG interface, as
19251 well as the Angel monitor.
19253 @item show rdiheartbeat
19254 @kindex show rdiheartbeat
19255 Show the setting of RDI heartbeat packets.
19259 @item target sim @r{[}@var{simargs}@r{]} @dots{}
19260 The @value{GDBN} ARM simulator accepts the following optional arguments.
19263 @item --swi-support=@var{type}
19264 Tell the simulator which SWI interfaces to support.
19265 @var{type} may be a comma separated list of the following values.
19266 The default value is @code{all}.
19279 @subsection Renesas M32R/D and M32R/SDI
19282 @kindex target m32r
19283 @item target m32r @var{dev}
19284 Renesas M32R/D ROM monitor.
19286 @kindex target m32rsdi
19287 @item target m32rsdi @var{dev}
19288 Renesas M32R SDI server, connected via parallel port to the board.
19291 The following @value{GDBN} commands are specific to the M32R monitor:
19294 @item set download-path @var{path}
19295 @kindex set download-path
19296 @cindex find downloadable @sc{srec} files (M32R)
19297 Set the default path for finding downloadable @sc{srec} files.
19299 @item show download-path
19300 @kindex show download-path
19301 Show the default path for downloadable @sc{srec} files.
19303 @item set board-address @var{addr}
19304 @kindex set board-address
19305 @cindex M32-EVA target board address
19306 Set the IP address for the M32R-EVA target board.
19308 @item show board-address
19309 @kindex show board-address
19310 Show the current IP address of the target board.
19312 @item set server-address @var{addr}
19313 @kindex set server-address
19314 @cindex download server address (M32R)
19315 Set the IP address for the download server, which is the @value{GDBN}'s
19318 @item show server-address
19319 @kindex show server-address
19320 Display the IP address of the download server.
19322 @item upload @r{[}@var{file}@r{]}
19323 @kindex upload@r{, M32R}
19324 Upload the specified @sc{srec} @var{file} via the monitor's Ethernet
19325 upload capability. If no @var{file} argument is given, the current
19326 executable file is uploaded.
19328 @item tload @r{[}@var{file}@r{]}
19329 @kindex tload@r{, M32R}
19330 Test the @code{upload} command.
19333 The following commands are available for M32R/SDI:
19338 @cindex reset SDI connection, M32R
19339 This command resets the SDI connection.
19343 This command shows the SDI connection status.
19346 @kindex debug_chaos
19347 @cindex M32R/Chaos debugging
19348 Instructs the remote that M32R/Chaos debugging is to be used.
19350 @item use_debug_dma
19351 @kindex use_debug_dma
19352 Instructs the remote to use the DEBUG_DMA method of accessing memory.
19355 @kindex use_mon_code
19356 Instructs the remote to use the MON_CODE method of accessing memory.
19359 @kindex use_ib_break
19360 Instructs the remote to set breakpoints by IB break.
19362 @item use_dbt_break
19363 @kindex use_dbt_break
19364 Instructs the remote to set breakpoints by DBT.
19370 The Motorola m68k configuration includes ColdFire support, and a
19371 target command for the following ROM monitor.
19375 @kindex target dbug
19376 @item target dbug @var{dev}
19377 dBUG ROM monitor for Motorola ColdFire.
19382 @subsection MicroBlaze
19383 @cindex Xilinx MicroBlaze
19384 @cindex XMD, Xilinx Microprocessor Debugger
19386 The MicroBlaze is a soft-core processor supported on various Xilinx
19387 FPGAs, such as Spartan or Virtex series. Boards with these processors
19388 usually have JTAG ports which connect to a host system running the Xilinx
19389 Embedded Development Kit (EDK) or Software Development Kit (SDK).
19390 This host system is used to download the configuration bitstream to
19391 the target FPGA. The Xilinx Microprocessor Debugger (XMD) program
19392 communicates with the target board using the JTAG interface and
19393 presents a @code{gdbserver} interface to the board. By default
19394 @code{xmd} uses port @code{1234}. (While it is possible to change
19395 this default port, it requires the use of undocumented @code{xmd}
19396 commands. Contact Xilinx support if you need to do this.)
19398 Use these GDB commands to connect to the MicroBlaze target processor.
19401 @item target remote :1234
19402 Use this command to connect to the target if you are running @value{GDBN}
19403 on the same system as @code{xmd}.
19405 @item target remote @var{xmd-host}:1234
19406 Use this command to connect to the target if it is connected to @code{xmd}
19407 running on a different system named @var{xmd-host}.
19410 Use this command to download a program to the MicroBlaze target.
19412 @item set debug microblaze @var{n}
19413 Enable MicroBlaze-specific debugging messages if non-zero.
19415 @item show debug microblaze @var{n}
19416 Show MicroBlaze-specific debugging level.
19419 @node MIPS Embedded
19420 @subsection MIPS Embedded
19422 @cindex MIPS boards
19423 @value{GDBN} can use the MIPS remote debugging protocol to talk to a
19424 MIPS board attached to a serial line. This is available when
19425 you configure @value{GDBN} with @samp{--target=mips-elf}.
19428 Use these @value{GDBN} commands to specify the connection to your target board:
19431 @item target mips @var{port}
19432 @kindex target mips @var{port}
19433 To run a program on the board, start up @code{@value{GDBP}} with the
19434 name of your program as the argument. To connect to the board, use the
19435 command @samp{target mips @var{port}}, where @var{port} is the name of
19436 the serial port connected to the board. If the program has not already
19437 been downloaded to the board, you may use the @code{load} command to
19438 download it. You can then use all the usual @value{GDBN} commands.
19440 For example, this sequence connects to the target board through a serial
19441 port, and loads and runs a program called @var{prog} through the
19445 host$ @value{GDBP} @var{prog}
19446 @value{GDBN} is free software and @dots{}
19447 (@value{GDBP}) target mips /dev/ttyb
19448 (@value{GDBP}) load @var{prog}
19452 @item target mips @var{hostname}:@var{portnumber}
19453 On some @value{GDBN} host configurations, you can specify a TCP
19454 connection (for instance, to a serial line managed by a terminal
19455 concentrator) instead of a serial port, using the syntax
19456 @samp{@var{hostname}:@var{portnumber}}.
19458 @item target pmon @var{port}
19459 @kindex target pmon @var{port}
19462 @item target ddb @var{port}
19463 @kindex target ddb @var{port}
19464 NEC's DDB variant of PMON for Vr4300.
19466 @item target lsi @var{port}
19467 @kindex target lsi @var{port}
19468 LSI variant of PMON.
19470 @kindex target r3900
19471 @item target r3900 @var{dev}
19472 Densan DVE-R3900 ROM monitor for Toshiba R3900 Mips.
19474 @kindex target array
19475 @item target array @var{dev}
19476 Array Tech LSI33K RAID controller board.
19482 @value{GDBN} also supports these special commands for MIPS targets:
19485 @item set mipsfpu double
19486 @itemx set mipsfpu single
19487 @itemx set mipsfpu none
19488 @itemx set mipsfpu auto
19489 @itemx show mipsfpu
19490 @kindex set mipsfpu
19491 @kindex show mipsfpu
19492 @cindex MIPS remote floating point
19493 @cindex floating point, MIPS remote
19494 If your target board does not support the MIPS floating point
19495 coprocessor, you should use the command @samp{set mipsfpu none} (if you
19496 need this, you may wish to put the command in your @value{GDBN} init
19497 file). This tells @value{GDBN} how to find the return value of
19498 functions which return floating point values. It also allows
19499 @value{GDBN} to avoid saving the floating point registers when calling
19500 functions on the board. If you are using a floating point coprocessor
19501 with only single precision floating point support, as on the @sc{r4650}
19502 processor, use the command @samp{set mipsfpu single}. The default
19503 double precision floating point coprocessor may be selected using
19504 @samp{set mipsfpu double}.
19506 In previous versions the only choices were double precision or no
19507 floating point, so @samp{set mipsfpu on} will select double precision
19508 and @samp{set mipsfpu off} will select no floating point.
19510 As usual, you can inquire about the @code{mipsfpu} variable with
19511 @samp{show mipsfpu}.
19513 @item set timeout @var{seconds}
19514 @itemx set retransmit-timeout @var{seconds}
19515 @itemx show timeout
19516 @itemx show retransmit-timeout
19517 @cindex @code{timeout}, MIPS protocol
19518 @cindex @code{retransmit-timeout}, MIPS protocol
19519 @kindex set timeout
19520 @kindex show timeout
19521 @kindex set retransmit-timeout
19522 @kindex show retransmit-timeout
19523 You can control the timeout used while waiting for a packet, in the MIPS
19524 remote protocol, with the @code{set timeout @var{seconds}} command. The
19525 default is 5 seconds. Similarly, you can control the timeout used while
19526 waiting for an acknowledgment of a packet with the @code{set
19527 retransmit-timeout @var{seconds}} command. The default is 3 seconds.
19528 You can inspect both values with @code{show timeout} and @code{show
19529 retransmit-timeout}. (These commands are @emph{only} available when
19530 @value{GDBN} is configured for @samp{--target=mips-elf}.)
19532 The timeout set by @code{set timeout} does not apply when @value{GDBN}
19533 is waiting for your program to stop. In that case, @value{GDBN} waits
19534 forever because it has no way of knowing how long the program is going
19535 to run before stopping.
19537 @item set syn-garbage-limit @var{num}
19538 @kindex set syn-garbage-limit@r{, MIPS remote}
19539 @cindex synchronize with remote MIPS target
19540 Limit the maximum number of characters @value{GDBN} should ignore when
19541 it tries to synchronize with the remote target. The default is 10
19542 characters. Setting the limit to -1 means there's no limit.
19544 @item show syn-garbage-limit
19545 @kindex show syn-garbage-limit@r{, MIPS remote}
19546 Show the current limit on the number of characters to ignore when
19547 trying to synchronize with the remote system.
19549 @item set monitor-prompt @var{prompt}
19550 @kindex set monitor-prompt@r{, MIPS remote}
19551 @cindex remote monitor prompt
19552 Tell @value{GDBN} to expect the specified @var{prompt} string from the
19553 remote monitor. The default depends on the target:
19563 @item show monitor-prompt
19564 @kindex show monitor-prompt@r{, MIPS remote}
19565 Show the current strings @value{GDBN} expects as the prompt from the
19568 @item set monitor-warnings
19569 @kindex set monitor-warnings@r{, MIPS remote}
19570 Enable or disable monitor warnings about hardware breakpoints. This
19571 has effect only for the @code{lsi} target. When on, @value{GDBN} will
19572 display warning messages whose codes are returned by the @code{lsi}
19573 PMON monitor for breakpoint commands.
19575 @item show monitor-warnings
19576 @kindex show monitor-warnings@r{, MIPS remote}
19577 Show the current setting of printing monitor warnings.
19579 @item pmon @var{command}
19580 @kindex pmon@r{, MIPS remote}
19581 @cindex send PMON command
19582 This command allows sending an arbitrary @var{command} string to the
19583 monitor. The monitor must be in debug mode for this to work.
19586 @node OpenRISC 1000
19587 @subsection OpenRISC 1000
19588 @cindex OpenRISC 1000
19590 @cindex or1k boards
19591 See OR1k Architecture document (@uref{www.opencores.org}) for more information
19592 about platform and commands.
19596 @kindex target jtag
19597 @item target jtag jtag://@var{host}:@var{port}
19599 Connects to remote JTAG server.
19600 JTAG remote server can be either an or1ksim or JTAG server,
19601 connected via parallel port to the board.
19603 Example: @code{target jtag jtag://localhost:9999}
19606 @item or1ksim @var{command}
19607 If connected to @code{or1ksim} OpenRISC 1000 Architectural
19608 Simulator, proprietary commands can be executed.
19610 @kindex info or1k spr
19611 @item info or1k spr
19612 Displays spr groups.
19614 @item info or1k spr @var{group}
19615 @itemx info or1k spr @var{groupno}
19616 Displays register names in selected group.
19618 @item info or1k spr @var{group} @var{register}
19619 @itemx info or1k spr @var{register}
19620 @itemx info or1k spr @var{groupno} @var{registerno}
19621 @itemx info or1k spr @var{registerno}
19622 Shows information about specified spr register.
19625 @item spr @var{group} @var{register} @var{value}
19626 @itemx spr @var{register @var{value}}
19627 @itemx spr @var{groupno} @var{registerno @var{value}}
19628 @itemx spr @var{registerno @var{value}}
19629 Writes @var{value} to specified spr register.
19632 Some implementations of OpenRISC 1000 Architecture also have hardware trace.
19633 It is very similar to @value{GDBN} trace, except it does not interfere with normal
19634 program execution and is thus much faster. Hardware breakpoints/watchpoint
19635 triggers can be set using:
19638 Load effective address/data
19640 Store effective address/data
19642 Access effective address ($SEA or $LEA) or data ($SDATA/$LDATA)
19647 When triggered, it can capture low level data, like: @code{PC}, @code{LSEA},
19648 @code{LDATA}, @code{SDATA}, @code{READSPR}, @code{WRITESPR}, @code{INSTR}.
19650 @code{htrace} commands:
19651 @cindex OpenRISC 1000 htrace
19654 @item hwatch @var{conditional}
19655 Set hardware watchpoint on combination of Load/Store Effective Address(es)
19656 or Data. For example:
19658 @code{hwatch ($LEA == my_var) && ($LDATA < 50) || ($SEA == my_var) && ($SDATA >= 50)}
19660 @code{hwatch ($LEA == my_var) && ($LDATA < 50) || ($SEA == my_var) && ($SDATA >= 50)}
19664 Display information about current HW trace configuration.
19666 @item htrace trigger @var{conditional}
19667 Set starting criteria for HW trace.
19669 @item htrace qualifier @var{conditional}
19670 Set acquisition qualifier for HW trace.
19672 @item htrace stop @var{conditional}
19673 Set HW trace stopping criteria.
19675 @item htrace record [@var{data}]*
19676 Selects the data to be recorded, when qualifier is met and HW trace was
19679 @item htrace enable
19680 @itemx htrace disable
19681 Enables/disables the HW trace.
19683 @item htrace rewind [@var{filename}]
19684 Clears currently recorded trace data.
19686 If filename is specified, new trace file is made and any newly collected data
19687 will be written there.
19689 @item htrace print [@var{start} [@var{len}]]
19690 Prints trace buffer, using current record configuration.
19692 @item htrace mode continuous
19693 Set continuous trace mode.
19695 @item htrace mode suspend
19696 Set suspend trace mode.
19700 @node PowerPC Embedded
19701 @subsection PowerPC Embedded
19703 @cindex DVC register
19704 @value{GDBN} supports using the DVC (Data Value Compare) register to
19705 implement in hardware simple hardware watchpoint conditions of the form:
19708 (@value{GDBP}) watch @var{ADDRESS|VARIABLE} \
19709 if @var{ADDRESS|VARIABLE} == @var{CONSTANT EXPRESSION}
19712 The DVC register will be automatically used when @value{GDBN} detects
19713 such pattern in a condition expression, and the created watchpoint uses one
19714 debug register (either the @code{exact-watchpoints} option is on and the
19715 variable is scalar, or the variable has a length of one byte). This feature
19716 is available in native @value{GDBN} running on a Linux kernel version 2.6.34
19719 When running on PowerPC embedded processors, @value{GDBN} automatically uses
19720 ranged hardware watchpoints, unless the @code{exact-watchpoints} option is on,
19721 in which case watchpoints using only one debug register are created when
19722 watching variables of scalar types.
19724 You can create an artificial array to watch an arbitrary memory
19725 region using one of the following commands (@pxref{Expressions}):
19728 (@value{GDBP}) watch *((char *) @var{address})@@@var{length}
19729 (@value{GDBP}) watch @{char[@var{length}]@} @var{address}
19732 PowerPC embedded processors support masked watchpoints. See the discussion
19733 about the @code{mask} argument in @ref{Set Watchpoints}.
19735 @cindex ranged breakpoint
19736 PowerPC embedded processors support hardware accelerated
19737 @dfn{ranged breakpoints}. A ranged breakpoint stops execution of
19738 the inferior whenever it executes an instruction at any address within
19739 the range it specifies. To set a ranged breakpoint in @value{GDBN},
19740 use the @code{break-range} command.
19742 @value{GDBN} provides the following PowerPC-specific commands:
19745 @kindex break-range
19746 @item break-range @var{start-location}, @var{end-location}
19747 Set a breakpoint for an address range.
19748 @var{start-location} and @var{end-location} can specify a function name,
19749 a line number, an offset of lines from the current line or from the start
19750 location, or an address of an instruction (see @ref{Specify Location},
19751 for a list of all the possible ways to specify a @var{location}.)
19752 The breakpoint will stop execution of the inferior whenever it
19753 executes an instruction at any address within the specified range,
19754 (including @var{start-location} and @var{end-location}.)
19756 @kindex set powerpc
19757 @item set powerpc soft-float
19758 @itemx show powerpc soft-float
19759 Force @value{GDBN} to use (or not use) a software floating point calling
19760 convention. By default, @value{GDBN} selects the calling convention based
19761 on the selected architecture and the provided executable file.
19763 @item set powerpc vector-abi
19764 @itemx show powerpc vector-abi
19765 Force @value{GDBN} to use the specified calling convention for vector
19766 arguments and return values. The valid options are @samp{auto};
19767 @samp{generic}, to avoid vector registers even if they are present;
19768 @samp{altivec}, to use AltiVec registers; and @samp{spe} to use SPE
19769 registers. By default, @value{GDBN} selects the calling convention
19770 based on the selected architecture and the provided executable file.
19772 @item set powerpc exact-watchpoints
19773 @itemx show powerpc exact-watchpoints
19774 Allow @value{GDBN} to use only one debug register when watching a variable
19775 of scalar type, thus assuming that the variable is accessed through the
19776 address of its first byte.
19778 @kindex target dink32
19779 @item target dink32 @var{dev}
19780 DINK32 ROM monitor.
19782 @kindex target ppcbug
19783 @item target ppcbug @var{dev}
19784 @kindex target ppcbug1
19785 @item target ppcbug1 @var{dev}
19786 PPCBUG ROM monitor for PowerPC.
19789 @item target sds @var{dev}
19790 SDS monitor, running on a PowerPC board (such as Motorola's ADS).
19793 @cindex SDS protocol
19794 The following commands specific to the SDS protocol are supported
19798 @item set sdstimeout @var{nsec}
19799 @kindex set sdstimeout
19800 Set the timeout for SDS protocol reads to be @var{nsec} seconds. The
19801 default is 2 seconds.
19803 @item show sdstimeout
19804 @kindex show sdstimeout
19805 Show the current value of the SDS timeout.
19807 @item sds @var{command}
19808 @kindex sds@r{, a command}
19809 Send the specified @var{command} string to the SDS monitor.
19814 @subsection HP PA Embedded
19818 @kindex target op50n
19819 @item target op50n @var{dev}
19820 OP50N monitor, running on an OKI HPPA board.
19822 @kindex target w89k
19823 @item target w89k @var{dev}
19824 W89K monitor, running on a Winbond HPPA board.
19829 @subsection Tsqware Sparclet
19833 @value{GDBN} enables developers to debug tasks running on
19834 Sparclet targets from a Unix host.
19835 @value{GDBN} uses code that runs on
19836 both the Unix host and on the Sparclet target. The program
19837 @code{@value{GDBP}} is installed and executed on the Unix host.
19840 @item remotetimeout @var{args}
19841 @kindex remotetimeout
19842 @value{GDBN} supports the option @code{remotetimeout}.
19843 This option is set by the user, and @var{args} represents the number of
19844 seconds @value{GDBN} waits for responses.
19847 @cindex compiling, on Sparclet
19848 When compiling for debugging, include the options @samp{-g} to get debug
19849 information and @samp{-Ttext} to relocate the program to where you wish to
19850 load it on the target. You may also want to add the options @samp{-n} or
19851 @samp{-N} in order to reduce the size of the sections. Example:
19854 sparclet-aout-gcc prog.c -Ttext 0x12010000 -g -o prog -N
19857 You can use @code{objdump} to verify that the addresses are what you intended:
19860 sparclet-aout-objdump --headers --syms prog
19863 @cindex running, on Sparclet
19865 your Unix execution search path to find @value{GDBN}, you are ready to
19866 run @value{GDBN}. From your Unix host, run @code{@value{GDBP}}
19867 (or @code{sparclet-aout-gdb}, depending on your installation).
19869 @value{GDBN} comes up showing the prompt:
19876 * Sparclet File:: Setting the file to debug
19877 * Sparclet Connection:: Connecting to Sparclet
19878 * Sparclet Download:: Sparclet download
19879 * Sparclet Execution:: Running and debugging
19882 @node Sparclet File
19883 @subsubsection Setting File to Debug
19885 The @value{GDBN} command @code{file} lets you choose with program to debug.
19888 (gdbslet) file prog
19892 @value{GDBN} then attempts to read the symbol table of @file{prog}.
19893 @value{GDBN} locates
19894 the file by searching the directories listed in the command search
19896 If the file was compiled with debug information (option @samp{-g}), source
19897 files will be searched as well.
19898 @value{GDBN} locates
19899 the source files by searching the directories listed in the directory search
19900 path (@pxref{Environment, ,Your Program's Environment}).
19902 to find a file, it displays a message such as:
19905 prog: No such file or directory.
19908 When this happens, add the appropriate directories to the search paths with
19909 the @value{GDBN} commands @code{path} and @code{dir}, and execute the
19910 @code{target} command again.
19912 @node Sparclet Connection
19913 @subsubsection Connecting to Sparclet
19915 The @value{GDBN} command @code{target} lets you connect to a Sparclet target.
19916 To connect to a target on serial port ``@code{ttya}'', type:
19919 (gdbslet) target sparclet /dev/ttya
19920 Remote target sparclet connected to /dev/ttya
19921 main () at ../prog.c:3
19925 @value{GDBN} displays messages like these:
19931 @node Sparclet Download
19932 @subsubsection Sparclet Download
19934 @cindex download to Sparclet
19935 Once connected to the Sparclet target,
19936 you can use the @value{GDBN}
19937 @code{load} command to download the file from the host to the target.
19938 The file name and load offset should be given as arguments to the @code{load}
19940 Since the file format is aout, the program must be loaded to the starting
19941 address. You can use @code{objdump} to find out what this value is. The load
19942 offset is an offset which is added to the VMA (virtual memory address)
19943 of each of the file's sections.
19944 For instance, if the program
19945 @file{prog} was linked to text address 0x1201000, with data at 0x12010160
19946 and bss at 0x12010170, in @value{GDBN}, type:
19949 (gdbslet) load prog 0x12010000
19950 Loading section .text, size 0xdb0 vma 0x12010000
19953 If the code is loaded at a different address then what the program was linked
19954 to, you may need to use the @code{section} and @code{add-symbol-file} commands
19955 to tell @value{GDBN} where to map the symbol table.
19957 @node Sparclet Execution
19958 @subsubsection Running and Debugging
19960 @cindex running and debugging Sparclet programs
19961 You can now begin debugging the task using @value{GDBN}'s execution control
19962 commands, @code{b}, @code{step}, @code{run}, etc. See the @value{GDBN}
19963 manual for the list of commands.
19967 Breakpoint 1 at 0x12010000: file prog.c, line 3.
19969 Starting program: prog
19970 Breakpoint 1, main (argc=1, argv=0xeffff21c) at prog.c:3
19971 3 char *symarg = 0;
19973 4 char *execarg = "hello!";
19978 @subsection Fujitsu Sparclite
19982 @kindex target sparclite
19983 @item target sparclite @var{dev}
19984 Fujitsu sparclite boards, used only for the purpose of loading.
19985 You must use an additional command to debug the program.
19986 For example: target remote @var{dev} using @value{GDBN} standard
19992 @subsection Zilog Z8000
19995 @cindex simulator, Z8000
19996 @cindex Zilog Z8000 simulator
19998 When configured for debugging Zilog Z8000 targets, @value{GDBN} includes
20001 For the Z8000 family, @samp{target sim} simulates either the Z8002 (the
20002 unsegmented variant of the Z8000 architecture) or the Z8001 (the
20003 segmented variant). The simulator recognizes which architecture is
20004 appropriate by inspecting the object code.
20007 @item target sim @var{args}
20009 @kindex target sim@r{, with Z8000}
20010 Debug programs on a simulated CPU. If the simulator supports setup
20011 options, specify them via @var{args}.
20015 After specifying this target, you can debug programs for the simulated
20016 CPU in the same style as programs for your host computer; use the
20017 @code{file} command to load a new program image, the @code{run} command
20018 to run your program, and so on.
20020 As well as making available all the usual machine registers
20021 (@pxref{Registers, ,Registers}), the Z8000 simulator provides three
20022 additional items of information as specially named registers:
20027 Counts clock-ticks in the simulator.
20030 Counts instructions run in the simulator.
20033 Execution time in 60ths of a second.
20037 You can refer to these values in @value{GDBN} expressions with the usual
20038 conventions; for example, @w{@samp{b fputc if $cycles>5000}} sets a
20039 conditional breakpoint that suspends only after at least 5000
20040 simulated clock ticks.
20043 @subsection Atmel AVR
20046 When configured for debugging the Atmel AVR, @value{GDBN} supports the
20047 following AVR-specific commands:
20050 @item info io_registers
20051 @kindex info io_registers@r{, AVR}
20052 @cindex I/O registers (Atmel AVR)
20053 This command displays information about the AVR I/O registers. For
20054 each register, @value{GDBN} prints its number and value.
20061 When configured for debugging CRIS, @value{GDBN} provides the
20062 following CRIS-specific commands:
20065 @item set cris-version @var{ver}
20066 @cindex CRIS version
20067 Set the current CRIS version to @var{ver}, either @samp{10} or @samp{32}.
20068 The CRIS version affects register names and sizes. This command is useful in
20069 case autodetection of the CRIS version fails.
20071 @item show cris-version
20072 Show the current CRIS version.
20074 @item set cris-dwarf2-cfi
20075 @cindex DWARF-2 CFI and CRIS
20076 Set the usage of DWARF-2 CFI for CRIS debugging. The default is @samp{on}.
20077 Change to @samp{off} when using @code{gcc-cris} whose version is below
20080 @item show cris-dwarf2-cfi
20081 Show the current state of using DWARF-2 CFI.
20083 @item set cris-mode @var{mode}
20085 Set the current CRIS mode to @var{mode}. It should only be changed when
20086 debugging in guru mode, in which case it should be set to
20087 @samp{guru} (the default is @samp{normal}).
20089 @item show cris-mode
20090 Show the current CRIS mode.
20094 @subsection Renesas Super-H
20097 For the Renesas Super-H processor, @value{GDBN} provides these
20102 @kindex regs@r{, Super-H}
20103 Show the values of all Super-H registers.
20105 @item set sh calling-convention @var{convention}
20106 @kindex set sh calling-convention
20107 Set the calling-convention used when calling functions from @value{GDBN}.
20108 Allowed values are @samp{gcc}, which is the default setting, and @samp{renesas}.
20109 With the @samp{gcc} setting, functions are called using the @value{NGCC} calling
20110 convention. If the DWARF-2 information of the called function specifies
20111 that the function follows the Renesas calling convention, the function
20112 is called using the Renesas calling convention. If the calling convention
20113 is set to @samp{renesas}, the Renesas calling convention is always used,
20114 regardless of the DWARF-2 information. This can be used to override the
20115 default of @samp{gcc} if debug information is missing, or the compiler
20116 does not emit the DWARF-2 calling convention entry for a function.
20118 @item show sh calling-convention
20119 @kindex show sh calling-convention
20120 Show the current calling convention setting.
20125 @node Architectures
20126 @section Architectures
20128 This section describes characteristics of architectures that affect
20129 all uses of @value{GDBN} with the architecture, both native and cross.
20136 * HPPA:: HP PA architecture
20137 * SPU:: Cell Broadband Engine SPU architecture
20142 @subsection x86 Architecture-specific Issues
20145 @item set struct-convention @var{mode}
20146 @kindex set struct-convention
20147 @cindex struct return convention
20148 @cindex struct/union returned in registers
20149 Set the convention used by the inferior to return @code{struct}s and
20150 @code{union}s from functions to @var{mode}. Possible values of
20151 @var{mode} are @code{"pcc"}, @code{"reg"}, and @code{"default"} (the
20152 default). @code{"default"} or @code{"pcc"} means that @code{struct}s
20153 are returned on the stack, while @code{"reg"} means that a
20154 @code{struct} or a @code{union} whose size is 1, 2, 4, or 8 bytes will
20155 be returned in a register.
20157 @item show struct-convention
20158 @kindex show struct-convention
20159 Show the current setting of the convention to return @code{struct}s
20168 @kindex set rstack_high_address
20169 @cindex AMD 29K register stack
20170 @cindex register stack, AMD29K
20171 @item set rstack_high_address @var{address}
20172 On AMD 29000 family processors, registers are saved in a separate
20173 @dfn{register stack}. There is no way for @value{GDBN} to determine the
20174 extent of this stack. Normally, @value{GDBN} just assumes that the
20175 stack is ``large enough''. This may result in @value{GDBN} referencing
20176 memory locations that do not exist. If necessary, you can get around
20177 this problem by specifying the ending address of the register stack with
20178 the @code{set rstack_high_address} command. The argument should be an
20179 address, which you probably want to precede with @samp{0x} to specify in
20182 @kindex show rstack_high_address
20183 @item show rstack_high_address
20184 Display the current limit of the register stack, on AMD 29000 family
20192 See the following section.
20197 @cindex stack on Alpha
20198 @cindex stack on MIPS
20199 @cindex Alpha stack
20201 Alpha- and MIPS-based computers use an unusual stack frame, which
20202 sometimes requires @value{GDBN} to search backward in the object code to
20203 find the beginning of a function.
20205 @cindex response time, MIPS debugging
20206 To improve response time (especially for embedded applications, where
20207 @value{GDBN} may be restricted to a slow serial line for this search)
20208 you may want to limit the size of this search, using one of these
20212 @cindex @code{heuristic-fence-post} (Alpha, MIPS)
20213 @item set heuristic-fence-post @var{limit}
20214 Restrict @value{GDBN} to examining at most @var{limit} bytes in its
20215 search for the beginning of a function. A value of @var{0} (the
20216 default) means there is no limit. However, except for @var{0}, the
20217 larger the limit the more bytes @code{heuristic-fence-post} must search
20218 and therefore the longer it takes to run. You should only need to use
20219 this command when debugging a stripped executable.
20221 @item show heuristic-fence-post
20222 Display the current limit.
20226 These commands are available @emph{only} when @value{GDBN} is configured
20227 for debugging programs on Alpha or MIPS processors.
20229 Several MIPS-specific commands are available when debugging MIPS
20233 @item set mips abi @var{arg}
20234 @kindex set mips abi
20235 @cindex set ABI for MIPS
20236 Tell @value{GDBN} which MIPS ABI is used by the inferior. Possible
20237 values of @var{arg} are:
20241 The default ABI associated with the current binary (this is the
20251 @item show mips abi
20252 @kindex show mips abi
20253 Show the MIPS ABI used by @value{GDBN} to debug the inferior.
20256 @itemx show mipsfpu
20257 @xref{MIPS Embedded, set mipsfpu}.
20259 @item set mips mask-address @var{arg}
20260 @kindex set mips mask-address
20261 @cindex MIPS addresses, masking
20262 This command determines whether the most-significant 32 bits of 64-bit
20263 MIPS addresses are masked off. The argument @var{arg} can be
20264 @samp{on}, @samp{off}, or @samp{auto}. The latter is the default
20265 setting, which lets @value{GDBN} determine the correct value.
20267 @item show mips mask-address
20268 @kindex show mips mask-address
20269 Show whether the upper 32 bits of MIPS addresses are masked off or
20272 @item set remote-mips64-transfers-32bit-regs
20273 @kindex set remote-mips64-transfers-32bit-regs
20274 This command controls compatibility with 64-bit MIPS targets that
20275 transfer data in 32-bit quantities. If you have an old MIPS 64 target
20276 that transfers 32 bits for some registers, like @sc{sr} and @sc{fsr},
20277 and 64 bits for other registers, set this option to @samp{on}.
20279 @item show remote-mips64-transfers-32bit-regs
20280 @kindex show remote-mips64-transfers-32bit-regs
20281 Show the current setting of compatibility with older MIPS 64 targets.
20283 @item set debug mips
20284 @kindex set debug mips
20285 This command turns on and off debugging messages for the MIPS-specific
20286 target code in @value{GDBN}.
20288 @item show debug mips
20289 @kindex show debug mips
20290 Show the current setting of MIPS debugging messages.
20296 @cindex HPPA support
20298 When @value{GDBN} is debugging the HP PA architecture, it provides the
20299 following special commands:
20302 @item set debug hppa
20303 @kindex set debug hppa
20304 This command determines whether HPPA architecture-specific debugging
20305 messages are to be displayed.
20307 @item show debug hppa
20308 Show whether HPPA debugging messages are displayed.
20310 @item maint print unwind @var{address}
20311 @kindex maint print unwind@r{, HPPA}
20312 This command displays the contents of the unwind table entry at the
20313 given @var{address}.
20319 @subsection Cell Broadband Engine SPU architecture
20320 @cindex Cell Broadband Engine
20323 When @value{GDBN} is debugging the Cell Broadband Engine SPU architecture,
20324 it provides the following special commands:
20327 @item info spu event
20329 Display SPU event facility status. Shows current event mask
20330 and pending event status.
20332 @item info spu signal
20333 Display SPU signal notification facility status. Shows pending
20334 signal-control word and signal notification mode of both signal
20335 notification channels.
20337 @item info spu mailbox
20338 Display SPU mailbox facility status. Shows all pending entries,
20339 in order of processing, in each of the SPU Write Outbound,
20340 SPU Write Outbound Interrupt, and SPU Read Inbound mailboxes.
20343 Display MFC DMA status. Shows all pending commands in the MFC
20344 DMA queue. For each entry, opcode, tag, class IDs, effective
20345 and local store addresses and transfer size are shown.
20347 @item info spu proxydma
20348 Display MFC Proxy-DMA status. Shows all pending commands in the MFC
20349 Proxy-DMA queue. For each entry, opcode, tag, class IDs, effective
20350 and local store addresses and transfer size are shown.
20354 When @value{GDBN} is debugging a combined PowerPC/SPU application
20355 on the Cell Broadband Engine, it provides in addition the following
20359 @item set spu stop-on-load @var{arg}
20361 Set whether to stop for new SPE threads. When set to @code{on}, @value{GDBN}
20362 will give control to the user when a new SPE thread enters its @code{main}
20363 function. The default is @code{off}.
20365 @item show spu stop-on-load
20367 Show whether to stop for new SPE threads.
20369 @item set spu auto-flush-cache @var{arg}
20370 Set whether to automatically flush the software-managed cache. When set to
20371 @code{on}, @value{GDBN} will automatically cause the SPE software-managed
20372 cache to be flushed whenever SPE execution stops. This provides a consistent
20373 view of PowerPC memory that is accessed via the cache. If an application
20374 does not use the software-managed cache, this option has no effect.
20376 @item show spu auto-flush-cache
20377 Show whether to automatically flush the software-managed cache.
20382 @subsection PowerPC
20383 @cindex PowerPC architecture
20385 When @value{GDBN} is debugging the PowerPC architecture, it provides a set of
20386 pseudo-registers to enable inspection of 128-bit wide Decimal Floating Point
20387 numbers stored in the floating point registers. These values must be stored
20388 in two consecutive registers, always starting at an even register like
20389 @code{f0} or @code{f2}.
20391 The pseudo-registers go from @code{$dl0} through @code{$dl15}, and are formed
20392 by joining the even/odd register pairs @code{f0} and @code{f1} for @code{$dl0},
20393 @code{f2} and @code{f3} for @code{$dl1} and so on.
20395 For POWER7 processors, @value{GDBN} provides a set of pseudo-registers, the 64-bit
20396 wide Extended Floating Point Registers (@samp{f32} through @samp{f63}).
20399 @node Controlling GDB
20400 @chapter Controlling @value{GDBN}
20402 You can alter the way @value{GDBN} interacts with you by using the
20403 @code{set} command. For commands controlling how @value{GDBN} displays
20404 data, see @ref{Print Settings, ,Print Settings}. Other settings are
20409 * Editing:: Command editing
20410 * Command History:: Command history
20411 * Screen Size:: Screen size
20412 * Numbers:: Numbers
20413 * ABI:: Configuring the current ABI
20414 * Messages/Warnings:: Optional warnings and messages
20415 * Debugging Output:: Optional messages about internal happenings
20416 * Other Misc Settings:: Other Miscellaneous Settings
20424 @value{GDBN} indicates its readiness to read a command by printing a string
20425 called the @dfn{prompt}. This string is normally @samp{(@value{GDBP})}. You
20426 can change the prompt string with the @code{set prompt} command. For
20427 instance, when debugging @value{GDBN} with @value{GDBN}, it is useful to change
20428 the prompt in one of the @value{GDBN} sessions so that you can always tell
20429 which one you are talking to.
20431 @emph{Note:} @code{set prompt} does not add a space for you after the
20432 prompt you set. This allows you to set a prompt which ends in a space
20433 or a prompt that does not.
20437 @item set prompt @var{newprompt}
20438 Directs @value{GDBN} to use @var{newprompt} as its prompt string henceforth.
20440 @kindex show prompt
20442 Prints a line of the form: @samp{Gdb's prompt is: @var{your-prompt}}
20445 Versions of @value{GDBN} that ship with Python scripting enabled have
20446 prompt extensions. The commands for interacting with these extensions
20450 @kindex set extended-prompt
20451 @item set extended-prompt @var{prompt}
20452 Set an extended prompt that allows for substitutions.
20453 @xref{gdb.prompt}, for a list of escape sequences that can be used for
20454 substitution. Any escape sequences specified as part of the prompt
20455 string are replaced with the corresponding strings each time the prompt
20461 set extended-prompt Current working directory: \w (gdb)
20464 Note that when an extended-prompt is set, it takes control of the
20465 @var{prompt_hook} hook. @xref{prompt_hook}, for further information.
20467 @kindex show extended-prompt
20468 @item show extended-prompt
20469 Prints the extended prompt. Any escape sequences specified as part of
20470 the prompt string with @code{set extended-prompt}, are replaced with the
20471 corresponding strings each time the prompt is displayed.
20475 @section Command Editing
20477 @cindex command line editing
20479 @value{GDBN} reads its input commands via the @dfn{Readline} interface. This
20480 @sc{gnu} library provides consistent behavior for programs which provide a
20481 command line interface to the user. Advantages are @sc{gnu} Emacs-style
20482 or @dfn{vi}-style inline editing of commands, @code{csh}-like history
20483 substitution, and a storage and recall of command history across
20484 debugging sessions.
20486 You may control the behavior of command line editing in @value{GDBN} with the
20487 command @code{set}.
20490 @kindex set editing
20493 @itemx set editing on
20494 Enable command line editing (enabled by default).
20496 @item set editing off
20497 Disable command line editing.
20499 @kindex show editing
20501 Show whether command line editing is enabled.
20504 @ifset SYSTEM_READLINE
20505 @xref{Command Line Editing, , , rluserman, GNU Readline Library},
20507 @ifclear SYSTEM_READLINE
20508 @xref{Command Line Editing},
20510 for more details about the Readline
20511 interface. Users unfamiliar with @sc{gnu} Emacs or @code{vi} are
20512 encouraged to read that chapter.
20514 @node Command History
20515 @section Command History
20516 @cindex command history
20518 @value{GDBN} can keep track of the commands you type during your
20519 debugging sessions, so that you can be certain of precisely what
20520 happened. Use these commands to manage the @value{GDBN} command
20523 @value{GDBN} uses the @sc{gnu} History library, a part of the Readline
20524 package, to provide the history facility.
20525 @ifset SYSTEM_READLINE
20526 @xref{Using History Interactively, , , history, GNU History Library},
20528 @ifclear SYSTEM_READLINE
20529 @xref{Using History Interactively},
20531 for the detailed description of the History library.
20533 To issue a command to @value{GDBN} without affecting certain aspects of
20534 the state which is seen by users, prefix it with @samp{server }
20535 (@pxref{Server Prefix}). This
20536 means that this command will not affect the command history, nor will it
20537 affect @value{GDBN}'s notion of which command to repeat if @key{RET} is
20538 pressed on a line by itself.
20540 @cindex @code{server}, command prefix
20541 The server prefix does not affect the recording of values into the value
20542 history; to print a value without recording it into the value history,
20543 use the @code{output} command instead of the @code{print} command.
20545 Here is the description of @value{GDBN} commands related to command
20549 @cindex history substitution
20550 @cindex history file
20551 @kindex set history filename
20552 @cindex @env{GDBHISTFILE}, environment variable
20553 @item set history filename @var{fname}
20554 Set the name of the @value{GDBN} command history file to @var{fname}.
20555 This is the file where @value{GDBN} reads an initial command history
20556 list, and where it writes the command history from this session when it
20557 exits. You can access this list through history expansion or through
20558 the history command editing characters listed below. This file defaults
20559 to the value of the environment variable @code{GDBHISTFILE}, or to
20560 @file{./.gdb_history} (@file{./_gdb_history} on MS-DOS) if this variable
20563 @cindex save command history
20564 @kindex set history save
20565 @item set history save
20566 @itemx set history save on
20567 Record command history in a file, whose name may be specified with the
20568 @code{set history filename} command. By default, this option is disabled.
20570 @item set history save off
20571 Stop recording command history in a file.
20573 @cindex history size
20574 @kindex set history size
20575 @cindex @env{HISTSIZE}, environment variable
20576 @item set history size @var{size}
20577 Set the number of commands which @value{GDBN} keeps in its history list.
20578 This defaults to the value of the environment variable
20579 @code{HISTSIZE}, or to 256 if this variable is not set.
20582 History expansion assigns special meaning to the character @kbd{!}.
20583 @ifset SYSTEM_READLINE
20584 @xref{Event Designators, , , history, GNU History Library},
20586 @ifclear SYSTEM_READLINE
20587 @xref{Event Designators},
20591 @cindex history expansion, turn on/off
20592 Since @kbd{!} is also the logical not operator in C, history expansion
20593 is off by default. If you decide to enable history expansion with the
20594 @code{set history expansion on} command, you may sometimes need to
20595 follow @kbd{!} (when it is used as logical not, in an expression) with
20596 a space or a tab to prevent it from being expanded. The readline
20597 history facilities do not attempt substitution on the strings
20598 @kbd{!=} and @kbd{!(}, even when history expansion is enabled.
20600 The commands to control history expansion are:
20603 @item set history expansion on
20604 @itemx set history expansion
20605 @kindex set history expansion
20606 Enable history expansion. History expansion is off by default.
20608 @item set history expansion off
20609 Disable history expansion.
20612 @kindex show history
20614 @itemx show history filename
20615 @itemx show history save
20616 @itemx show history size
20617 @itemx show history expansion
20618 These commands display the state of the @value{GDBN} history parameters.
20619 @code{show history} by itself displays all four states.
20624 @kindex show commands
20625 @cindex show last commands
20626 @cindex display command history
20627 @item show commands
20628 Display the last ten commands in the command history.
20630 @item show commands @var{n}
20631 Print ten commands centered on command number @var{n}.
20633 @item show commands +
20634 Print ten commands just after the commands last printed.
20638 @section Screen Size
20639 @cindex size of screen
20640 @cindex pauses in output
20642 Certain commands to @value{GDBN} may produce large amounts of
20643 information output to the screen. To help you read all of it,
20644 @value{GDBN} pauses and asks you for input at the end of each page of
20645 output. Type @key{RET} when you want to continue the output, or @kbd{q}
20646 to discard the remaining output. Also, the screen width setting
20647 determines when to wrap lines of output. Depending on what is being
20648 printed, @value{GDBN} tries to break the line at a readable place,
20649 rather than simply letting it overflow onto the following line.
20651 Normally @value{GDBN} knows the size of the screen from the terminal
20652 driver software. For example, on Unix @value{GDBN} uses the termcap data base
20653 together with the value of the @code{TERM} environment variable and the
20654 @code{stty rows} and @code{stty cols} settings. If this is not correct,
20655 you can override it with the @code{set height} and @code{set
20662 @kindex show height
20663 @item set height @var{lpp}
20665 @itemx set width @var{cpl}
20667 These @code{set} commands specify a screen height of @var{lpp} lines and
20668 a screen width of @var{cpl} characters. The associated @code{show}
20669 commands display the current settings.
20671 If you specify a height of zero lines, @value{GDBN} does not pause during
20672 output no matter how long the output is. This is useful if output is to a
20673 file or to an editor buffer.
20675 Likewise, you can specify @samp{set width 0} to prevent @value{GDBN}
20676 from wrapping its output.
20678 @item set pagination on
20679 @itemx set pagination off
20680 @kindex set pagination
20681 Turn the output pagination on or off; the default is on. Turning
20682 pagination off is the alternative to @code{set height 0}. Note that
20683 running @value{GDBN} with the @option{--batch} option (@pxref{Mode
20684 Options, -batch}) also automatically disables pagination.
20686 @item show pagination
20687 @kindex show pagination
20688 Show the current pagination mode.
20693 @cindex number representation
20694 @cindex entering numbers
20696 You can always enter numbers in octal, decimal, or hexadecimal in
20697 @value{GDBN} by the usual conventions: octal numbers begin with
20698 @samp{0}, decimal numbers end with @samp{.}, and hexadecimal numbers
20699 begin with @samp{0x}. Numbers that neither begin with @samp{0} or
20700 @samp{0x}, nor end with a @samp{.} are, by default, entered in base
20701 10; likewise, the default display for numbers---when no particular
20702 format is specified---is base 10. You can change the default base for
20703 both input and output with the commands described below.
20706 @kindex set input-radix
20707 @item set input-radix @var{base}
20708 Set the default base for numeric input. Supported choices
20709 for @var{base} are decimal 8, 10, or 16. @var{base} must itself be
20710 specified either unambiguously or using the current input radix; for
20714 set input-radix 012
20715 set input-radix 10.
20716 set input-radix 0xa
20720 sets the input base to decimal. On the other hand, @samp{set input-radix 10}
20721 leaves the input radix unchanged, no matter what it was, since
20722 @samp{10}, being without any leading or trailing signs of its base, is
20723 interpreted in the current radix. Thus, if the current radix is 16,
20724 @samp{10} is interpreted in hex, i.e.@: as 16 decimal, which doesn't
20727 @kindex set output-radix
20728 @item set output-radix @var{base}
20729 Set the default base for numeric display. Supported choices
20730 for @var{base} are decimal 8, 10, or 16. @var{base} must itself be
20731 specified either unambiguously or using the current input radix.
20733 @kindex show input-radix
20734 @item show input-radix
20735 Display the current default base for numeric input.
20737 @kindex show output-radix
20738 @item show output-radix
20739 Display the current default base for numeric display.
20741 @item set radix @r{[}@var{base}@r{]}
20745 These commands set and show the default base for both input and output
20746 of numbers. @code{set radix} sets the radix of input and output to
20747 the same base; without an argument, it resets the radix back to its
20748 default value of 10.
20753 @section Configuring the Current ABI
20755 @value{GDBN} can determine the @dfn{ABI} (Application Binary Interface) of your
20756 application automatically. However, sometimes you need to override its
20757 conclusions. Use these commands to manage @value{GDBN}'s view of the
20764 One @value{GDBN} configuration can debug binaries for multiple operating
20765 system targets, either via remote debugging or native emulation.
20766 @value{GDBN} will autodetect the @dfn{OS ABI} (Operating System ABI) in use,
20767 but you can override its conclusion using the @code{set osabi} command.
20768 One example where this is useful is in debugging of binaries which use
20769 an alternate C library (e.g.@: @sc{uClibc} for @sc{gnu}/Linux) which does
20770 not have the same identifying marks that the standard C library for your
20775 Show the OS ABI currently in use.
20778 With no argument, show the list of registered available OS ABI's.
20780 @item set osabi @var{abi}
20781 Set the current OS ABI to @var{abi}.
20784 @cindex float promotion
20786 Generally, the way that an argument of type @code{float} is passed to a
20787 function depends on whether the function is prototyped. For a prototyped
20788 (i.e.@: ANSI/ISO style) function, @code{float} arguments are passed unchanged,
20789 according to the architecture's convention for @code{float}. For unprototyped
20790 (i.e.@: K&R style) functions, @code{float} arguments are first promoted to type
20791 @code{double} and then passed.
20793 Unfortunately, some forms of debug information do not reliably indicate whether
20794 a function is prototyped. If @value{GDBN} calls a function that is not marked
20795 as prototyped, it consults @kbd{set coerce-float-to-double}.
20798 @kindex set coerce-float-to-double
20799 @item set coerce-float-to-double
20800 @itemx set coerce-float-to-double on
20801 Arguments of type @code{float} will be promoted to @code{double} when passed
20802 to an unprototyped function. This is the default setting.
20804 @item set coerce-float-to-double off
20805 Arguments of type @code{float} will be passed directly to unprototyped
20808 @kindex show coerce-float-to-double
20809 @item show coerce-float-to-double
20810 Show the current setting of promoting @code{float} to @code{double}.
20814 @kindex show cp-abi
20815 @value{GDBN} needs to know the ABI used for your program's C@t{++}
20816 objects. The correct C@t{++} ABI depends on which C@t{++} compiler was
20817 used to build your application. @value{GDBN} only fully supports
20818 programs with a single C@t{++} ABI; if your program contains code using
20819 multiple C@t{++} ABI's or if @value{GDBN} can not identify your
20820 program's ABI correctly, you can tell @value{GDBN} which ABI to use.
20821 Currently supported ABI's include ``gnu-v2'', for @code{g++} versions
20822 before 3.0, ``gnu-v3'', for @code{g++} versions 3.0 and later, and
20823 ``hpaCC'' for the HP ANSI C@t{++} compiler. Other C@t{++} compilers may
20824 use the ``gnu-v2'' or ``gnu-v3'' ABI's as well. The default setting is
20829 Show the C@t{++} ABI currently in use.
20832 With no argument, show the list of supported C@t{++} ABI's.
20834 @item set cp-abi @var{abi}
20835 @itemx set cp-abi auto
20836 Set the current C@t{++} ABI to @var{abi}, or return to automatic detection.
20839 @node Messages/Warnings
20840 @section Optional Warnings and Messages
20842 @cindex verbose operation
20843 @cindex optional warnings
20844 By default, @value{GDBN} is silent about its inner workings. If you are
20845 running on a slow machine, you may want to use the @code{set verbose}
20846 command. This makes @value{GDBN} tell you when it does a lengthy
20847 internal operation, so you will not think it has crashed.
20849 Currently, the messages controlled by @code{set verbose} are those
20850 which announce that the symbol table for a source file is being read;
20851 see @code{symbol-file} in @ref{Files, ,Commands to Specify Files}.
20854 @kindex set verbose
20855 @item set verbose on
20856 Enables @value{GDBN} output of certain informational messages.
20858 @item set verbose off
20859 Disables @value{GDBN} output of certain informational messages.
20861 @kindex show verbose
20863 Displays whether @code{set verbose} is on or off.
20866 By default, if @value{GDBN} encounters bugs in the symbol table of an
20867 object file, it is silent; but if you are debugging a compiler, you may
20868 find this information useful (@pxref{Symbol Errors, ,Errors Reading
20873 @kindex set complaints
20874 @item set complaints @var{limit}
20875 Permits @value{GDBN} to output @var{limit} complaints about each type of
20876 unusual symbols before becoming silent about the problem. Set
20877 @var{limit} to zero to suppress all complaints; set it to a large number
20878 to prevent complaints from being suppressed.
20880 @kindex show complaints
20881 @item show complaints
20882 Displays how many symbol complaints @value{GDBN} is permitted to produce.
20886 @anchor{confirmation requests}
20887 By default, @value{GDBN} is cautious, and asks what sometimes seems to be a
20888 lot of stupid questions to confirm certain commands. For example, if
20889 you try to run a program which is already running:
20893 The program being debugged has been started already.
20894 Start it from the beginning? (y or n)
20897 If you are willing to unflinchingly face the consequences of your own
20898 commands, you can disable this ``feature'':
20902 @kindex set confirm
20904 @cindex confirmation
20905 @cindex stupid questions
20906 @item set confirm off
20907 Disables confirmation requests. Note that running @value{GDBN} with
20908 the @option{--batch} option (@pxref{Mode Options, -batch}) also
20909 automatically disables confirmation requests.
20911 @item set confirm on
20912 Enables confirmation requests (the default).
20914 @kindex show confirm
20916 Displays state of confirmation requests.
20920 @cindex command tracing
20921 If you need to debug user-defined commands or sourced files you may find it
20922 useful to enable @dfn{command tracing}. In this mode each command will be
20923 printed as it is executed, prefixed with one or more @samp{+} symbols, the
20924 quantity denoting the call depth of each command.
20927 @kindex set trace-commands
20928 @cindex command scripts, debugging
20929 @item set trace-commands on
20930 Enable command tracing.
20931 @item set trace-commands off
20932 Disable command tracing.
20933 @item show trace-commands
20934 Display the current state of command tracing.
20937 @node Debugging Output
20938 @section Optional Messages about Internal Happenings
20939 @cindex optional debugging messages
20941 @value{GDBN} has commands that enable optional debugging messages from
20942 various @value{GDBN} subsystems; normally these commands are of
20943 interest to @value{GDBN} maintainers, or when reporting a bug. This
20944 section documents those commands.
20947 @kindex set exec-done-display
20948 @item set exec-done-display
20949 Turns on or off the notification of asynchronous commands'
20950 completion. When on, @value{GDBN} will print a message when an
20951 asynchronous command finishes its execution. The default is off.
20952 @kindex show exec-done-display
20953 @item show exec-done-display
20954 Displays the current setting of asynchronous command completion
20957 @cindex gdbarch debugging info
20958 @cindex architecture debugging info
20959 @item set debug arch
20960 Turns on or off display of gdbarch debugging info. The default is off
20962 @item show debug arch
20963 Displays the current state of displaying gdbarch debugging info.
20964 @item set debug aix-thread
20965 @cindex AIX threads
20966 Display debugging messages about inner workings of the AIX thread
20968 @item show debug aix-thread
20969 Show the current state of AIX thread debugging info display.
20970 @item set debug check-physname
20972 Check the results of the ``physname'' computation. When reading DWARF
20973 debugging information for C@t{++}, @value{GDBN} attempts to compute
20974 each entity's name. @value{GDBN} can do this computation in two
20975 different ways, depending on exactly what information is present.
20976 When enabled, this setting causes @value{GDBN} to compute the names
20977 both ways and display any discrepancies.
20978 @item show debug check-physname
20979 Show the current state of ``physname'' checking.
20980 @item set debug dwarf2-die
20981 @cindex DWARF2 DIEs
20982 Dump DWARF2 DIEs after they are read in.
20983 The value is the number of nesting levels to print.
20984 A value of zero turns off the display.
20985 @item show debug dwarf2-die
20986 Show the current state of DWARF2 DIE debugging.
20987 @item set debug displaced
20988 @cindex displaced stepping debugging info
20989 Turns on or off display of @value{GDBN} debugging info for the
20990 displaced stepping support. The default is off.
20991 @item show debug displaced
20992 Displays the current state of displaying @value{GDBN} debugging info
20993 related to displaced stepping.
20994 @item set debug event
20995 @cindex event debugging info
20996 Turns on or off display of @value{GDBN} event debugging info. The
20998 @item show debug event
20999 Displays the current state of displaying @value{GDBN} event debugging
21001 @item set debug expression
21002 @cindex expression debugging info
21003 Turns on or off display of debugging info about @value{GDBN}
21004 expression parsing. The default is off.
21005 @item show debug expression
21006 Displays the current state of displaying debugging info about
21007 @value{GDBN} expression parsing.
21008 @item set debug frame
21009 @cindex frame debugging info
21010 Turns on or off display of @value{GDBN} frame debugging info. The
21012 @item show debug frame
21013 Displays the current state of displaying @value{GDBN} frame debugging
21015 @item set debug gnu-nat
21016 @cindex @sc{gnu}/Hurd debug messages
21017 Turns on or off debugging messages from the @sc{gnu}/Hurd debug support.
21018 @item show debug gnu-nat
21019 Show the current state of @sc{gnu}/Hurd debugging messages.
21020 @item set debug infrun
21021 @cindex inferior debugging info
21022 Turns on or off display of @value{GDBN} debugging info for running the inferior.
21023 The default is off. @file{infrun.c} contains GDB's runtime state machine used
21024 for implementing operations such as single-stepping the inferior.
21025 @item show debug infrun
21026 Displays the current state of @value{GDBN} inferior debugging.
21027 @item set debug jit
21028 @cindex just-in-time compilation, debugging messages
21029 Turns on or off debugging messages from JIT debug support.
21030 @item show debug jit
21031 Displays the current state of @value{GDBN} JIT debugging.
21032 @item set debug lin-lwp
21033 @cindex @sc{gnu}/Linux LWP debug messages
21034 @cindex Linux lightweight processes
21035 Turns on or off debugging messages from the Linux LWP debug support.
21036 @item show debug lin-lwp
21037 Show the current state of Linux LWP debugging messages.
21038 @item set debug observer
21039 @cindex observer debugging info
21040 Turns on or off display of @value{GDBN} observer debugging. This
21041 includes info such as the notification of observable events.
21042 @item show debug observer
21043 Displays the current state of observer debugging.
21044 @item set debug overload
21045 @cindex C@t{++} overload debugging info
21046 Turns on or off display of @value{GDBN} C@t{++} overload debugging
21047 info. This includes info such as ranking of functions, etc. The default
21049 @item show debug overload
21050 Displays the current state of displaying @value{GDBN} C@t{++} overload
21052 @cindex expression parser, debugging info
21053 @cindex debug expression parser
21054 @item set debug parser
21055 Turns on or off the display of expression parser debugging output.
21056 Internally, this sets the @code{yydebug} variable in the expression
21057 parser. @xref{Tracing, , Tracing Your Parser, bison, Bison}, for
21058 details. The default is off.
21059 @item show debug parser
21060 Show the current state of expression parser debugging.
21061 @cindex packets, reporting on stdout
21062 @cindex serial connections, debugging
21063 @cindex debug remote protocol
21064 @cindex remote protocol debugging
21065 @cindex display remote packets
21066 @item set debug remote
21067 Turns on or off display of reports on all packets sent back and forth across
21068 the serial line to the remote machine. The info is printed on the
21069 @value{GDBN} standard output stream. The default is off.
21070 @item show debug remote
21071 Displays the state of display of remote packets.
21072 @item set debug serial
21073 Turns on or off display of @value{GDBN} serial debugging info. The
21075 @item show debug serial
21076 Displays the current state of displaying @value{GDBN} serial debugging
21078 @item set debug solib-frv
21079 @cindex FR-V shared-library debugging
21080 Turns on or off debugging messages for FR-V shared-library code.
21081 @item show debug solib-frv
21082 Display the current state of FR-V shared-library code debugging
21084 @item set debug target
21085 @cindex target debugging info
21086 Turns on or off display of @value{GDBN} target debugging info. This info
21087 includes what is going on at the target level of GDB, as it happens. The
21088 default is 0. Set it to 1 to track events, and to 2 to also track the
21089 value of large memory transfers. Changes to this flag do not take effect
21090 until the next time you connect to a target or use the @code{run} command.
21091 @item show debug target
21092 Displays the current state of displaying @value{GDBN} target debugging
21094 @item set debug timestamp
21095 @cindex timestampping debugging info
21096 Turns on or off display of timestamps with @value{GDBN} debugging info.
21097 When enabled, seconds and microseconds are displayed before each debugging
21099 @item show debug timestamp
21100 Displays the current state of displaying timestamps with @value{GDBN}
21102 @item set debugvarobj
21103 @cindex variable object debugging info
21104 Turns on or off display of @value{GDBN} variable object debugging
21105 info. The default is off.
21106 @item show debugvarobj
21107 Displays the current state of displaying @value{GDBN} variable object
21109 @item set debug xml
21110 @cindex XML parser debugging
21111 Turns on or off debugging messages for built-in XML parsers.
21112 @item show debug xml
21113 Displays the current state of XML debugging messages.
21116 @node Other Misc Settings
21117 @section Other Miscellaneous Settings
21118 @cindex miscellaneous settings
21121 @kindex set interactive-mode
21122 @item set interactive-mode
21123 If @code{on}, forces @value{GDBN} to assume that GDB was started
21124 in a terminal. In practice, this means that @value{GDBN} should wait
21125 for the user to answer queries generated by commands entered at
21126 the command prompt. If @code{off}, forces @value{GDBN} to operate
21127 in the opposite mode, and it uses the default answers to all queries.
21128 If @code{auto} (the default), @value{GDBN} tries to determine whether
21129 its standard input is a terminal, and works in interactive-mode if it
21130 is, non-interactively otherwise.
21132 In the vast majority of cases, the debugger should be able to guess
21133 correctly which mode should be used. But this setting can be useful
21134 in certain specific cases, such as running a MinGW @value{GDBN}
21135 inside a cygwin window.
21137 @kindex show interactive-mode
21138 @item show interactive-mode
21139 Displays whether the debugger is operating in interactive mode or not.
21142 @node Extending GDB
21143 @chapter Extending @value{GDBN}
21144 @cindex extending GDB
21146 @value{GDBN} provides three mechanisms for extension. The first is based
21147 on composition of @value{GDBN} commands, the second is based on the
21148 Python scripting language, and the third is for defining new aliases of
21151 To facilitate the use of the first two extensions, @value{GDBN} is capable
21152 of evaluating the contents of a file. When doing so, @value{GDBN}
21153 can recognize which scripting language is being used by looking at
21154 the filename extension. Files with an unrecognized filename extension
21155 are always treated as a @value{GDBN} Command Files.
21156 @xref{Command Files,, Command files}.
21158 You can control how @value{GDBN} evaluates these files with the following
21162 @kindex set script-extension
21163 @kindex show script-extension
21164 @item set script-extension off
21165 All scripts are always evaluated as @value{GDBN} Command Files.
21167 @item set script-extension soft
21168 The debugger determines the scripting language based on filename
21169 extension. If this scripting language is supported, @value{GDBN}
21170 evaluates the script using that language. Otherwise, it evaluates
21171 the file as a @value{GDBN} Command File.
21173 @item set script-extension strict
21174 The debugger determines the scripting language based on filename
21175 extension, and evaluates the script using that language. If the
21176 language is not supported, then the evaluation fails.
21178 @item show script-extension
21179 Display the current value of the @code{script-extension} option.
21184 * Sequences:: Canned Sequences of Commands
21185 * Python:: Scripting @value{GDBN} using Python
21186 * Aliases:: Creating new spellings of existing commands
21190 @section Canned Sequences of Commands
21192 Aside from breakpoint commands (@pxref{Break Commands, ,Breakpoint
21193 Command Lists}), @value{GDBN} provides two ways to store sequences of
21194 commands for execution as a unit: user-defined commands and command
21198 * Define:: How to define your own commands
21199 * Hooks:: Hooks for user-defined commands
21200 * Command Files:: How to write scripts of commands to be stored in a file
21201 * Output:: Commands for controlled output
21205 @subsection User-defined Commands
21207 @cindex user-defined command
21208 @cindex arguments, to user-defined commands
21209 A @dfn{user-defined command} is a sequence of @value{GDBN} commands to
21210 which you assign a new name as a command. This is done with the
21211 @code{define} command. User commands may accept up to 10 arguments
21212 separated by whitespace. Arguments are accessed within the user command
21213 via @code{$arg0@dots{}$arg9}. A trivial example:
21217 print $arg0 + $arg1 + $arg2
21222 To execute the command use:
21229 This defines the command @code{adder}, which prints the sum of
21230 its three arguments. Note the arguments are text substitutions, so they may
21231 reference variables, use complex expressions, or even perform inferior
21234 @cindex argument count in user-defined commands
21235 @cindex how many arguments (user-defined commands)
21236 In addition, @code{$argc} may be used to find out how many arguments have
21237 been passed. This expands to a number in the range 0@dots{}10.
21242 print $arg0 + $arg1
21245 print $arg0 + $arg1 + $arg2
21253 @item define @var{commandname}
21254 Define a command named @var{commandname}. If there is already a command
21255 by that name, you are asked to confirm that you want to redefine it.
21256 @var{commandname} may be a bare command name consisting of letters,
21257 numbers, dashes, and underscores. It may also start with any predefined
21258 prefix command. For example, @samp{define target my-target} creates
21259 a user-defined @samp{target my-target} command.
21261 The definition of the command is made up of other @value{GDBN} command lines,
21262 which are given following the @code{define} command. The end of these
21263 commands is marked by a line containing @code{end}.
21266 @kindex end@r{ (user-defined commands)}
21267 @item document @var{commandname}
21268 Document the user-defined command @var{commandname}, so that it can be
21269 accessed by @code{help}. The command @var{commandname} must already be
21270 defined. This command reads lines of documentation just as @code{define}
21271 reads the lines of the command definition, ending with @code{end}.
21272 After the @code{document} command is finished, @code{help} on command
21273 @var{commandname} displays the documentation you have written.
21275 You may use the @code{document} command again to change the
21276 documentation of a command. Redefining the command with @code{define}
21277 does not change the documentation.
21279 @kindex dont-repeat
21280 @cindex don't repeat command
21282 Used inside a user-defined command, this tells @value{GDBN} that this
21283 command should not be repeated when the user hits @key{RET}
21284 (@pxref{Command Syntax, repeat last command}).
21286 @kindex help user-defined
21287 @item help user-defined
21288 List all user-defined commands and all python commands defined in class
21289 COMAND_USER. The first line of the documentation or docstring is
21294 @itemx show user @var{commandname}
21295 Display the @value{GDBN} commands used to define @var{commandname} (but
21296 not its documentation). If no @var{commandname} is given, display the
21297 definitions for all user-defined commands.
21298 This does not work for user-defined python commands.
21300 @cindex infinite recursion in user-defined commands
21301 @kindex show max-user-call-depth
21302 @kindex set max-user-call-depth
21303 @item show max-user-call-depth
21304 @itemx set max-user-call-depth
21305 The value of @code{max-user-call-depth} controls how many recursion
21306 levels are allowed in user-defined commands before @value{GDBN} suspects an
21307 infinite recursion and aborts the command.
21308 This does not apply to user-defined python commands.
21311 In addition to the above commands, user-defined commands frequently
21312 use control flow commands, described in @ref{Command Files}.
21314 When user-defined commands are executed, the
21315 commands of the definition are not printed. An error in any command
21316 stops execution of the user-defined command.
21318 If used interactively, commands that would ask for confirmation proceed
21319 without asking when used inside a user-defined command. Many @value{GDBN}
21320 commands that normally print messages to say what they are doing omit the
21321 messages when used in a user-defined command.
21324 @subsection User-defined Command Hooks
21325 @cindex command hooks
21326 @cindex hooks, for commands
21327 @cindex hooks, pre-command
21330 You may define @dfn{hooks}, which are a special kind of user-defined
21331 command. Whenever you run the command @samp{foo}, if the user-defined
21332 command @samp{hook-foo} exists, it is executed (with no arguments)
21333 before that command.
21335 @cindex hooks, post-command
21337 A hook may also be defined which is run after the command you executed.
21338 Whenever you run the command @samp{foo}, if the user-defined command
21339 @samp{hookpost-foo} exists, it is executed (with no arguments) after
21340 that command. Post-execution hooks may exist simultaneously with
21341 pre-execution hooks, for the same command.
21343 It is valid for a hook to call the command which it hooks. If this
21344 occurs, the hook is not re-executed, thereby avoiding infinite recursion.
21346 @c It would be nice if hookpost could be passed a parameter indicating
21347 @c if the command it hooks executed properly or not. FIXME!
21349 @kindex stop@r{, a pseudo-command}
21350 In addition, a pseudo-command, @samp{stop} exists. Defining
21351 (@samp{hook-stop}) makes the associated commands execute every time
21352 execution stops in your program: before breakpoint commands are run,
21353 displays are printed, or the stack frame is printed.
21355 For example, to ignore @code{SIGALRM} signals while
21356 single-stepping, but treat them normally during normal execution,
21361 handle SIGALRM nopass
21365 handle SIGALRM pass
21368 define hook-continue
21369 handle SIGALRM pass
21373 As a further example, to hook at the beginning and end of the @code{echo}
21374 command, and to add extra text to the beginning and end of the message,
21382 define hookpost-echo
21386 (@value{GDBP}) echo Hello World
21387 <<<---Hello World--->>>
21392 You can define a hook for any single-word command in @value{GDBN}, but
21393 not for command aliases; you should define a hook for the basic command
21394 name, e.g.@: @code{backtrace} rather than @code{bt}.
21395 @c FIXME! So how does Joe User discover whether a command is an alias
21397 You can hook a multi-word command by adding @code{hook-} or
21398 @code{hookpost-} to the last word of the command, e.g.@:
21399 @samp{define target hook-remote} to add a hook to @samp{target remote}.
21401 If an error occurs during the execution of your hook, execution of
21402 @value{GDBN} commands stops and @value{GDBN} issues a prompt
21403 (before the command that you actually typed had a chance to run).
21405 If you try to define a hook which does not match any known command, you
21406 get a warning from the @code{define} command.
21408 @node Command Files
21409 @subsection Command Files
21411 @cindex command files
21412 @cindex scripting commands
21413 A command file for @value{GDBN} is a text file made of lines that are
21414 @value{GDBN} commands. Comments (lines starting with @kbd{#}) may
21415 also be included. An empty line in a command file does nothing; it
21416 does not mean to repeat the last command, as it would from the
21419 You can request the execution of a command file with the @code{source}
21420 command. Note that the @code{source} command is also used to evaluate
21421 scripts that are not Command Files. The exact behavior can be configured
21422 using the @code{script-extension} setting.
21423 @xref{Extending GDB,, Extending GDB}.
21427 @cindex execute commands from a file
21428 @item source [-s] [-v] @var{filename}
21429 Execute the command file @var{filename}.
21432 The lines in a command file are generally executed sequentially,
21433 unless the order of execution is changed by one of the
21434 @emph{flow-control commands} described below. The commands are not
21435 printed as they are executed. An error in any command terminates
21436 execution of the command file and control is returned to the console.
21438 @value{GDBN} first searches for @var{filename} in the current directory.
21439 If the file is not found there, and @var{filename} does not specify a
21440 directory, then @value{GDBN} also looks for the file on the source search path
21441 (specified with the @samp{directory} command);
21442 except that @file{$cdir} is not searched because the compilation directory
21443 is not relevant to scripts.
21445 If @code{-s} is specified, then @value{GDBN} searches for @var{filename}
21446 on the search path even if @var{filename} specifies a directory.
21447 The search is done by appending @var{filename} to each element of the
21448 search path. So, for example, if @var{filename} is @file{mylib/myscript}
21449 and the search path contains @file{/home/user} then @value{GDBN} will
21450 look for the script @file{/home/user/mylib/myscript}.
21451 The search is also done if @var{filename} is an absolute path.
21452 For example, if @var{filename} is @file{/tmp/myscript} and
21453 the search path contains @file{/home/user} then @value{GDBN} will
21454 look for the script @file{/home/user/tmp/myscript}.
21455 For DOS-like systems, if @var{filename} contains a drive specification,
21456 it is stripped before concatenation. For example, if @var{filename} is
21457 @file{d:myscript} and the search path contains @file{c:/tmp} then @value{GDBN}
21458 will look for the script @file{c:/tmp/myscript}.
21460 If @code{-v}, for verbose mode, is given then @value{GDBN} displays
21461 each command as it is executed. The option must be given before
21462 @var{filename}, and is interpreted as part of the filename anywhere else.
21464 Commands that would ask for confirmation if used interactively proceed
21465 without asking when used in a command file. Many @value{GDBN} commands that
21466 normally print messages to say what they are doing omit the messages
21467 when called from command files.
21469 @value{GDBN} also accepts command input from standard input. In this
21470 mode, normal output goes to standard output and error output goes to
21471 standard error. Errors in a command file supplied on standard input do
21472 not terminate execution of the command file---execution continues with
21476 gdb < cmds > log 2>&1
21479 (The syntax above will vary depending on the shell used.) This example
21480 will execute commands from the file @file{cmds}. All output and errors
21481 would be directed to @file{log}.
21483 Since commands stored on command files tend to be more general than
21484 commands typed interactively, they frequently need to deal with
21485 complicated situations, such as different or unexpected values of
21486 variables and symbols, changes in how the program being debugged is
21487 built, etc. @value{GDBN} provides a set of flow-control commands to
21488 deal with these complexities. Using these commands, you can write
21489 complex scripts that loop over data structures, execute commands
21490 conditionally, etc.
21497 This command allows to include in your script conditionally executed
21498 commands. The @code{if} command takes a single argument, which is an
21499 expression to evaluate. It is followed by a series of commands that
21500 are executed only if the expression is true (its value is nonzero).
21501 There can then optionally be an @code{else} line, followed by a series
21502 of commands that are only executed if the expression was false. The
21503 end of the list is marked by a line containing @code{end}.
21507 This command allows to write loops. Its syntax is similar to
21508 @code{if}: the command takes a single argument, which is an expression
21509 to evaluate, and must be followed by the commands to execute, one per
21510 line, terminated by an @code{end}. These commands are called the
21511 @dfn{body} of the loop. The commands in the body of @code{while} are
21512 executed repeatedly as long as the expression evaluates to true.
21516 This command exits the @code{while} loop in whose body it is included.
21517 Execution of the script continues after that @code{while}s @code{end}
21520 @kindex loop_continue
21521 @item loop_continue
21522 This command skips the execution of the rest of the body of commands
21523 in the @code{while} loop in whose body it is included. Execution
21524 branches to the beginning of the @code{while} loop, where it evaluates
21525 the controlling expression.
21527 @kindex end@r{ (if/else/while commands)}
21529 Terminate the block of commands that are the body of @code{if},
21530 @code{else}, or @code{while} flow-control commands.
21535 @subsection Commands for Controlled Output
21537 During the execution of a command file or a user-defined command, normal
21538 @value{GDBN} output is suppressed; the only output that appears is what is
21539 explicitly printed by the commands in the definition. This section
21540 describes three commands useful for generating exactly the output you
21545 @item echo @var{text}
21546 @c I do not consider backslash-space a standard C escape sequence
21547 @c because it is not in ANSI.
21548 Print @var{text}. Nonprinting characters can be included in
21549 @var{text} using C escape sequences, such as @samp{\n} to print a
21550 newline. @strong{No newline is printed unless you specify one.}
21551 In addition to the standard C escape sequences, a backslash followed
21552 by a space stands for a space. This is useful for displaying a
21553 string with spaces at the beginning or the end, since leading and
21554 trailing spaces are otherwise trimmed from all arguments.
21555 To print @samp{@w{ }and foo =@w{ }}, use the command
21556 @samp{echo \@w{ }and foo = \@w{ }}.
21558 A backslash at the end of @var{text} can be used, as in C, to continue
21559 the command onto subsequent lines. For example,
21562 echo This is some text\n\
21563 which is continued\n\
21564 onto several lines.\n
21567 produces the same output as
21570 echo This is some text\n
21571 echo which is continued\n
21572 echo onto several lines.\n
21576 @item output @var{expression}
21577 Print the value of @var{expression} and nothing but that value: no
21578 newlines, no @samp{$@var{nn} = }. The value is not entered in the
21579 value history either. @xref{Expressions, ,Expressions}, for more information
21582 @item output/@var{fmt} @var{expression}
21583 Print the value of @var{expression} in format @var{fmt}. You can use
21584 the same formats as for @code{print}. @xref{Output Formats,,Output
21585 Formats}, for more information.
21588 @item printf @var{template}, @var{expressions}@dots{}
21589 Print the values of one or more @var{expressions} under the control of
21590 the string @var{template}. To print several values, make
21591 @var{expressions} be a comma-separated list of individual expressions,
21592 which may be either numbers or pointers. Their values are printed as
21593 specified by @var{template}, exactly as a C program would do by
21594 executing the code below:
21597 printf (@var{template}, @var{expressions}@dots{});
21600 As in @code{C} @code{printf}, ordinary characters in @var{template}
21601 are printed verbatim, while @dfn{conversion specification} introduced
21602 by the @samp{%} character cause subsequent @var{expressions} to be
21603 evaluated, their values converted and formatted according to type and
21604 style information encoded in the conversion specifications, and then
21607 For example, you can print two values in hex like this:
21610 printf "foo, bar-foo = 0x%x, 0x%x\n", foo, bar-foo
21613 @code{printf} supports all the standard @code{C} conversion
21614 specifications, including the flags and modifiers between the @samp{%}
21615 character and the conversion letter, with the following exceptions:
21619 The argument-ordering modifiers, such as @samp{2$}, are not supported.
21622 The modifier @samp{*} is not supported for specifying precision or
21626 The @samp{'} flag (for separation of digits into groups according to
21627 @code{LC_NUMERIC'}) is not supported.
21630 The type modifiers @samp{hh}, @samp{j}, @samp{t}, and @samp{z} are not
21634 The conversion letter @samp{n} (as in @samp{%n}) is not supported.
21637 The conversion letters @samp{a} and @samp{A} are not supported.
21641 Note that the @samp{ll} type modifier is supported only if the
21642 underlying @code{C} implementation used to build @value{GDBN} supports
21643 the @code{long long int} type, and the @samp{L} type modifier is
21644 supported only if @code{long double} type is available.
21646 As in @code{C}, @code{printf} supports simple backslash-escape
21647 sequences, such as @code{\n}, @samp{\t}, @samp{\\}, @samp{\"},
21648 @samp{\a}, and @samp{\f}, that consist of backslash followed by a
21649 single character. Octal and hexadecimal escape sequences are not
21652 Additionally, @code{printf} supports conversion specifications for DFP
21653 (@dfn{Decimal Floating Point}) types using the following length modifiers
21654 together with a floating point specifier.
21659 @samp{H} for printing @code{Decimal32} types.
21662 @samp{D} for printing @code{Decimal64} types.
21665 @samp{DD} for printing @code{Decimal128} types.
21668 If the underlying @code{C} implementation used to build @value{GDBN} has
21669 support for the three length modifiers for DFP types, other modifiers
21670 such as width and precision will also be available for @value{GDBN} to use.
21672 In case there is no such @code{C} support, no additional modifiers will be
21673 available and the value will be printed in the standard way.
21675 Here's an example of printing DFP types using the above conversion letters:
21677 printf "D32: %Hf - D64: %Df - D128: %DDf\n",1.2345df,1.2E10dd,1.2E1dl
21681 @item eval @var{template}, @var{expressions}@dots{}
21682 Convert the values of one or more @var{expressions} under the control of
21683 the string @var{template} to a command line, and call it.
21688 @section Scripting @value{GDBN} using Python
21689 @cindex python scripting
21690 @cindex scripting with python
21692 You can script @value{GDBN} using the @uref{http://www.python.org/,
21693 Python programming language}. This feature is available only if
21694 @value{GDBN} was configured using @option{--with-python}.
21696 @cindex python directory
21697 Python scripts used by @value{GDBN} should be installed in
21698 @file{@var{data-directory}/python}, where @var{data-directory} is
21699 the data directory as determined at @value{GDBN} startup (@pxref{Data Files}).
21700 This directory, known as the @dfn{python directory},
21701 is automatically added to the Python Search Path in order to allow
21702 the Python interpreter to locate all scripts installed at this location.
21704 Additionally, @value{GDBN} commands and convenience functions which
21705 are written in Python and are located in the
21706 @file{@var{data-directory}/python/gdb/command} or
21707 @file{@var{data-directory}/python/gdb/function} directories are
21708 automatically imported when @value{GDBN} starts.
21711 * Python Commands:: Accessing Python from @value{GDBN}.
21712 * Python API:: Accessing @value{GDBN} from Python.
21713 * Auto-loading:: Automatically loading Python code.
21714 * Python modules:: Python modules provided by @value{GDBN}.
21717 @node Python Commands
21718 @subsection Python Commands
21719 @cindex python commands
21720 @cindex commands to access python
21722 @value{GDBN} provides one command for accessing the Python interpreter,
21723 and one related setting:
21727 @item python @r{[}@var{code}@r{]}
21728 The @code{python} command can be used to evaluate Python code.
21730 If given an argument, the @code{python} command will evaluate the
21731 argument as a Python command. For example:
21734 (@value{GDBP}) python print 23
21738 If you do not provide an argument to @code{python}, it will act as a
21739 multi-line command, like @code{define}. In this case, the Python
21740 script is made up of subsequent command lines, given after the
21741 @code{python} command. This command list is terminated using a line
21742 containing @code{end}. For example:
21745 (@value{GDBP}) python
21747 End with a line saying just "end".
21753 @kindex set python print-stack
21754 @item set python print-stack
21755 By default, @value{GDBN} will print only the message component of a
21756 Python exception when an error occurs in a Python script. This can be
21757 controlled using @code{set python print-stack}: if @code{full}, then
21758 full Python stack printing is enabled; if @code{none}, then Python stack
21759 and message printing is disabled; if @code{message}, the default, only
21760 the message component of the error is printed.
21763 It is also possible to execute a Python script from the @value{GDBN}
21767 @item source @file{script-name}
21768 The script name must end with @samp{.py} and @value{GDBN} must be configured
21769 to recognize the script language based on filename extension using
21770 the @code{script-extension} setting. @xref{Extending GDB, ,Extending GDB}.
21772 @item python execfile ("script-name")
21773 This method is based on the @code{execfile} Python built-in function,
21774 and thus is always available.
21778 @subsection Python API
21780 @cindex programming in python
21782 @cindex python stdout
21783 @cindex python pagination
21784 At startup, @value{GDBN} overrides Python's @code{sys.stdout} and
21785 @code{sys.stderr} to print using @value{GDBN}'s output-paging streams.
21786 A Python program which outputs to one of these streams may have its
21787 output interrupted by the user (@pxref{Screen Size}). In this
21788 situation, a Python @code{KeyboardInterrupt} exception is thrown.
21791 * Basic Python:: Basic Python Functions.
21792 * Exception Handling:: How Python exceptions are translated.
21793 * Values From Inferior:: Python representation of values.
21794 * Types In Python:: Python representation of types.
21795 * Pretty Printing API:: Pretty-printing values.
21796 * Selecting Pretty-Printers:: How GDB chooses a pretty-printer.
21797 * Writing a Pretty-Printer:: Writing a Pretty-Printer.
21798 * Inferiors In Python:: Python representation of inferiors (processes)
21799 * Events In Python:: Listening for events from @value{GDBN}.
21800 * Threads In Python:: Accessing inferior threads from Python.
21801 * Commands In Python:: Implementing new commands in Python.
21802 * Parameters In Python:: Adding new @value{GDBN} parameters.
21803 * Functions In Python:: Writing new convenience functions.
21804 * Progspaces In Python:: Program spaces.
21805 * Objfiles In Python:: Object files.
21806 * Frames In Python:: Accessing inferior stack frames from Python.
21807 * Blocks In Python:: Accessing frame blocks from Python.
21808 * Symbols In Python:: Python representation of symbols.
21809 * Symbol Tables In Python:: Python representation of symbol tables.
21810 * Lazy Strings In Python:: Python representation of lazy strings.
21811 * Breakpoints In Python:: Manipulating breakpoints using Python.
21812 * Finish Breakpoints in Python:: Setting Breakpoints on function return
21817 @subsubsection Basic Python
21819 @cindex python functions
21820 @cindex python module
21822 @value{GDBN} introduces a new Python module, named @code{gdb}. All
21823 methods and classes added by @value{GDBN} are placed in this module.
21824 @value{GDBN} automatically @code{import}s the @code{gdb} module for
21825 use in all scripts evaluated by the @code{python} command.
21827 @findex gdb.PYTHONDIR
21828 @defvar gdb.PYTHONDIR
21829 A string containing the python directory (@pxref{Python}).
21832 @findex gdb.execute
21833 @defun gdb.execute (command @r{[}, from_tty @r{[}, to_string@r{]]})
21834 Evaluate @var{command}, a string, as a @value{GDBN} CLI command.
21835 If a GDB exception happens while @var{command} runs, it is
21836 translated as described in @ref{Exception Handling,,Exception Handling}.
21838 @var{from_tty} specifies whether @value{GDBN} ought to consider this
21839 command as having originated from the user invoking it interactively.
21840 It must be a boolean value. If omitted, it defaults to @code{False}.
21842 By default, any output produced by @var{command} is sent to
21843 @value{GDBN}'s standard output. If the @var{to_string} parameter is
21844 @code{True}, then output will be collected by @code{gdb.execute} and
21845 returned as a string. The default is @code{False}, in which case the
21846 return value is @code{None}. If @var{to_string} is @code{True}, the
21847 @value{GDBN} virtual terminal will be temporarily set to unlimited width
21848 and height, and its pagination will be disabled; @pxref{Screen Size}.
21851 @findex gdb.breakpoints
21852 @defun gdb.breakpoints ()
21853 Return a sequence holding all of @value{GDBN}'s breakpoints.
21854 @xref{Breakpoints In Python}, for more information.
21857 @findex gdb.parameter
21858 @defun gdb.parameter (parameter)
21859 Return the value of a @value{GDBN} parameter. @var{parameter} is a
21860 string naming the parameter to look up; @var{parameter} may contain
21861 spaces if the parameter has a multi-part name. For example,
21862 @samp{print object} is a valid parameter name.
21864 If the named parameter does not exist, this function throws a
21865 @code{gdb.error} (@pxref{Exception Handling}). Otherwise, the
21866 parameter's value is converted to a Python value of the appropriate
21867 type, and returned.
21870 @findex gdb.history
21871 @defun gdb.history (number)
21872 Return a value from @value{GDBN}'s value history (@pxref{Value
21873 History}). @var{number} indicates which history element to return.
21874 If @var{number} is negative, then @value{GDBN} will take its absolute value
21875 and count backward from the last element (i.e., the most recent element) to
21876 find the value to return. If @var{number} is zero, then @value{GDBN} will
21877 return the most recent element. If the element specified by @var{number}
21878 doesn't exist in the value history, a @code{gdb.error} exception will be
21881 If no exception is raised, the return value is always an instance of
21882 @code{gdb.Value} (@pxref{Values From Inferior}).
21885 @findex gdb.parse_and_eval
21886 @defun gdb.parse_and_eval (expression)
21887 Parse @var{expression} as an expression in the current language,
21888 evaluate it, and return the result as a @code{gdb.Value}.
21889 @var{expression} must be a string.
21891 This function can be useful when implementing a new command
21892 (@pxref{Commands In Python}), as it provides a way to parse the
21893 command's argument as an expression. It is also useful simply to
21894 compute values, for example, it is the only way to get the value of a
21895 convenience variable (@pxref{Convenience Vars}) as a @code{gdb.Value}.
21898 @findex gdb.post_event
21899 @defun gdb.post_event (event)
21900 Put @var{event}, a callable object taking no arguments, into
21901 @value{GDBN}'s internal event queue. This callable will be invoked at
21902 some later point, during @value{GDBN}'s event processing. Events
21903 posted using @code{post_event} will be run in the order in which they
21904 were posted; however, there is no way to know when they will be
21905 processed relative to other events inside @value{GDBN}.
21907 @value{GDBN} is not thread-safe. If your Python program uses multiple
21908 threads, you must be careful to only call @value{GDBN}-specific
21909 functions in the main @value{GDBN} thread. @code{post_event} ensures
21913 (@value{GDBP}) python
21917 > def __init__(self, message):
21918 > self.message = message;
21919 > def __call__(self):
21920 > gdb.write(self.message)
21922 >class MyThread1 (threading.Thread):
21924 > gdb.post_event(Writer("Hello "))
21926 >class MyThread2 (threading.Thread):
21928 > gdb.post_event(Writer("World\n"))
21930 >MyThread1().start()
21931 >MyThread2().start()
21933 (@value{GDBP}) Hello World
21938 @defun gdb.write (string @r{[}, stream{]})
21939 Print a string to @value{GDBN}'s paginated output stream. The
21940 optional @var{stream} determines the stream to print to. The default
21941 stream is @value{GDBN}'s standard output stream. Possible stream
21948 @value{GDBN}'s standard output stream.
21953 @value{GDBN}'s standard error stream.
21958 @value{GDBN}'s log stream (@pxref{Logging Output}).
21961 Writing to @code{sys.stdout} or @code{sys.stderr} will automatically
21962 call this function and will automatically direct the output to the
21967 @defun gdb.flush ()
21968 Flush the buffer of a @value{GDBN} paginated stream so that the
21969 contents are displayed immediately. @value{GDBN} will flush the
21970 contents of a stream automatically when it encounters a newline in the
21971 buffer. The optional @var{stream} determines the stream to flush. The
21972 default stream is @value{GDBN}'s standard output stream. Possible
21979 @value{GDBN}'s standard output stream.
21984 @value{GDBN}'s standard error stream.
21989 @value{GDBN}'s log stream (@pxref{Logging Output}).
21993 Flushing @code{sys.stdout} or @code{sys.stderr} will automatically
21994 call this function for the relevant stream.
21997 @findex gdb.target_charset
21998 @defun gdb.target_charset ()
21999 Return the name of the current target character set (@pxref{Character
22000 Sets}). This differs from @code{gdb.parameter('target-charset')} in
22001 that @samp{auto} is never returned.
22004 @findex gdb.target_wide_charset
22005 @defun gdb.target_wide_charset ()
22006 Return the name of the current target wide character set
22007 (@pxref{Character Sets}). This differs from
22008 @code{gdb.parameter('target-wide-charset')} in that @samp{auto} is
22012 @findex gdb.solib_name
22013 @defun gdb.solib_name (address)
22014 Return the name of the shared library holding the given @var{address}
22015 as a string, or @code{None}.
22018 @findex gdb.decode_line
22019 @defun gdb.decode_line @r{[}expression@r{]}
22020 Return locations of the line specified by @var{expression}, or of the
22021 current line if no argument was given. This function returns a Python
22022 tuple containing two elements. The first element contains a string
22023 holding any unparsed section of @var{expression} (or @code{None} if
22024 the expression has been fully parsed). The second element contains
22025 either @code{None} or another tuple that contains all the locations
22026 that match the expression represented as @code{gdb.Symtab_and_line}
22027 objects (@pxref{Symbol Tables In Python}). If @var{expression} is
22028 provided, it is decoded the way that @value{GDBN}'s inbuilt
22029 @code{break} or @code{edit} commands do (@pxref{Specify Location}).
22032 @defun gdb.prompt_hook (current_prompt)
22033 @anchor{prompt_hook}
22035 If @var{prompt_hook} is callable, @value{GDBN} will call the method
22036 assigned to this operation before a prompt is displayed by
22039 The parameter @code{current_prompt} contains the current @value{GDBN}
22040 prompt. This method must return a Python string, or @code{None}. If
22041 a string is returned, the @value{GDBN} prompt will be set to that
22042 string. If @code{None} is returned, @value{GDBN} will continue to use
22043 the current prompt.
22045 Some prompts cannot be substituted in @value{GDBN}. Secondary prompts
22046 such as those used by readline for command input, and annotation
22047 related prompts are prohibited from being changed.
22050 @node Exception Handling
22051 @subsubsection Exception Handling
22052 @cindex python exceptions
22053 @cindex exceptions, python
22055 When executing the @code{python} command, Python exceptions
22056 uncaught within the Python code are translated to calls to
22057 @value{GDBN} error-reporting mechanism. If the command that called
22058 @code{python} does not handle the error, @value{GDBN} will
22059 terminate it and print an error message containing the Python
22060 exception name, the associated value, and the Python call stack
22061 backtrace at the point where the exception was raised. Example:
22064 (@value{GDBP}) python print foo
22065 Traceback (most recent call last):
22066 File "<string>", line 1, in <module>
22067 NameError: name 'foo' is not defined
22070 @value{GDBN} errors that happen in @value{GDBN} commands invoked by
22071 Python code are converted to Python exceptions. The type of the
22072 Python exception depends on the error.
22076 This is the base class for most exceptions generated by @value{GDBN}.
22077 It is derived from @code{RuntimeError}, for compatibility with earlier
22078 versions of @value{GDBN}.
22080 If an error occurring in @value{GDBN} does not fit into some more
22081 specific category, then the generated exception will have this type.
22083 @item gdb.MemoryError
22084 This is a subclass of @code{gdb.error} which is thrown when an
22085 operation tried to access invalid memory in the inferior.
22087 @item KeyboardInterrupt
22088 User interrupt (via @kbd{C-c} or by typing @kbd{q} at a pagination
22089 prompt) is translated to a Python @code{KeyboardInterrupt} exception.
22092 In all cases, your exception handler will see the @value{GDBN} error
22093 message as its value and the Python call stack backtrace at the Python
22094 statement closest to where the @value{GDBN} error occured as the
22097 @findex gdb.GdbError
22098 When implementing @value{GDBN} commands in Python via @code{gdb.Command},
22099 it is useful to be able to throw an exception that doesn't cause a
22100 traceback to be printed. For example, the user may have invoked the
22101 command incorrectly. Use the @code{gdb.GdbError} exception
22102 to handle this case. Example:
22106 >class HelloWorld (gdb.Command):
22107 > """Greet the whole world."""
22108 > def __init__ (self):
22109 > super (HelloWorld, self).__init__ ("hello-world", gdb.COMMAND_USER)
22110 > def invoke (self, args, from_tty):
22111 > argv = gdb.string_to_argv (args)
22112 > if len (argv) != 0:
22113 > raise gdb.GdbError ("hello-world takes no arguments")
22114 > print "Hello, World!"
22117 (gdb) hello-world 42
22118 hello-world takes no arguments
22121 @node Values From Inferior
22122 @subsubsection Values From Inferior
22123 @cindex values from inferior, with Python
22124 @cindex python, working with values from inferior
22126 @cindex @code{gdb.Value}
22127 @value{GDBN} provides values it obtains from the inferior program in
22128 an object of type @code{gdb.Value}. @value{GDBN} uses this object
22129 for its internal bookkeeping of the inferior's values, and for
22130 fetching values when necessary.
22132 Inferior values that are simple scalars can be used directly in
22133 Python expressions that are valid for the value's data type. Here's
22134 an example for an integer or floating-point value @code{some_val}:
22141 As result of this, @code{bar} will also be a @code{gdb.Value} object
22142 whose values are of the same type as those of @code{some_val}.
22144 Inferior values that are structures or instances of some class can
22145 be accessed using the Python @dfn{dictionary syntax}. For example, if
22146 @code{some_val} is a @code{gdb.Value} instance holding a structure, you
22147 can access its @code{foo} element with:
22150 bar = some_val['foo']
22153 Again, @code{bar} will also be a @code{gdb.Value} object.
22155 A @code{gdb.Value} that represents a function can be executed via
22156 inferior function call. Any arguments provided to the call must match
22157 the function's prototype, and must be provided in the order specified
22160 For example, @code{some_val} is a @code{gdb.Value} instance
22161 representing a function that takes two integers as arguments. To
22162 execute this function, call it like so:
22165 result = some_val (10,20)
22168 Any values returned from a function call will be stored as a
22171 The following attributes are provided:
22174 @defvar Value.address
22175 If this object is addressable, this read-only attribute holds a
22176 @code{gdb.Value} object representing the address. Otherwise,
22177 this attribute holds @code{None}.
22180 @cindex optimized out value in Python
22181 @defvar Value.is_optimized_out
22182 This read-only boolean attribute is true if the compiler optimized out
22183 this value, thus it is not available for fetching from the inferior.
22187 The type of this @code{gdb.Value}. The value of this attribute is a
22188 @code{gdb.Type} object (@pxref{Types In Python}).
22191 @defvar Value.dynamic_type
22192 The dynamic type of this @code{gdb.Value}. This uses C@t{++} run-time
22193 type information (@acronym{RTTI}) to determine the dynamic type of the
22194 value. If this value is of class type, it will return the class in
22195 which the value is embedded, if any. If this value is of pointer or
22196 reference to a class type, it will compute the dynamic type of the
22197 referenced object, and return a pointer or reference to that type,
22198 respectively. In all other cases, it will return the value's static
22201 Note that this feature will only work when debugging a C@t{++} program
22202 that includes @acronym{RTTI} for the object in question. Otherwise,
22203 it will just return the static type of the value as in @kbd{ptype foo}
22204 (@pxref{Symbols, ptype}).
22207 @defvar Value.is_lazy
22208 The value of this read-only boolean attribute is @code{True} if this
22209 @code{gdb.Value} has not yet been fetched from the inferior.
22210 @value{GDBN} does not fetch values until necessary, for efficiency.
22214 myval = gdb.parse_and_eval ('somevar')
22217 The value of @code{somevar} is not fetched at this time. It will be
22218 fetched when the value is needed, or when the @code{fetch_lazy}
22223 The following methods are provided:
22226 @defun Value.__init__ (@var{val})
22227 Many Python values can be converted directly to a @code{gdb.Value} via
22228 this object initializer. Specifically:
22231 @item Python boolean
22232 A Python boolean is converted to the boolean type from the current
22235 @item Python integer
22236 A Python integer is converted to the C @code{long} type for the
22237 current architecture.
22240 A Python long is converted to the C @code{long long} type for the
22241 current architecture.
22244 A Python float is converted to the C @code{double} type for the
22245 current architecture.
22247 @item Python string
22248 A Python string is converted to a target string, using the current
22251 @item @code{gdb.Value}
22252 If @code{val} is a @code{gdb.Value}, then a copy of the value is made.
22254 @item @code{gdb.LazyString}
22255 If @code{val} is a @code{gdb.LazyString} (@pxref{Lazy Strings In
22256 Python}), then the lazy string's @code{value} method is called, and
22257 its result is used.
22261 @defun Value.cast (type)
22262 Return a new instance of @code{gdb.Value} that is the result of
22263 casting this instance to the type described by @var{type}, which must
22264 be a @code{gdb.Type} object. If the cast cannot be performed for some
22265 reason, this method throws an exception.
22268 @defun Value.dereference ()
22269 For pointer data types, this method returns a new @code{gdb.Value} object
22270 whose contents is the object pointed to by the pointer. For example, if
22271 @code{foo} is a C pointer to an @code{int}, declared in your C program as
22278 then you can use the corresponding @code{gdb.Value} to access what
22279 @code{foo} points to like this:
22282 bar = foo.dereference ()
22285 The result @code{bar} will be a @code{gdb.Value} object holding the
22286 value pointed to by @code{foo}.
22288 A similar function @code{Value.referenced_value} exists which also
22289 returns @code{gdb.Value} objects corresonding to the values pointed to
22290 by pointer values (and additionally, values referenced by reference
22291 values). However, the behavior of @code{Value.dereference}
22292 differs from @code{Value.referenced_value} by the fact that the
22293 behavior of @code{Value.dereference} is identical to applying the C
22294 unary operator @code{*} on a given value. For example, consider a
22295 reference to a pointer @code{ptrref}, declared in your C@t{++} program
22299 typedef int *intptr;
22303 intptr &ptrref = ptr;
22306 Though @code{ptrref} is a reference value, one can apply the method
22307 @code{Value.dereference} to the @code{gdb.Value} object corresponding
22308 to it and obtain a @code{gdb.Value} which is identical to that
22309 corresponding to @code{val}. However, if you apply the method
22310 @code{Value.referenced_value}, the result would be a @code{gdb.Value}
22311 object identical to that corresponding to @code{ptr}.
22314 py_ptrref = gdb.parse_and_eval ("ptrref")
22315 py_val = py_ptrref.dereference ()
22316 py_ptr = py_ptrref.referenced_value ()
22319 The @code{gdb.Value} object @code{py_val} is identical to that
22320 corresponding to @code{val}, and @code{py_ptr} is identical to that
22321 corresponding to @code{ptr}. In general, @code{Value.dereference} can
22322 be applied whenever the C unary operator @code{*} can be applied
22323 to the corresponding C value. For those cases where applying both
22324 @code{Value.dereference} and @code{Value.referenced_value} is allowed,
22325 the results obtained need not be identical (as we have seen in the above
22326 example). The results are however identical when applied on
22327 @code{gdb.Value} objects corresponding to pointers (@code{gdb.Value}
22328 objects with type code @code{TYPE_CODE_PTR}) in a C/C@t{++} program.
22331 @defun Value.referenced_value ()
22332 For pointer or reference data types, this method returns a new
22333 @code{gdb.Value} object corresponding to the value referenced by the
22334 pointer/reference value. For pointer data types,
22335 @code{Value.dereference} and @code{Value.referenced_value} produce
22336 identical results. The difference between these methods is that
22337 @code{Value.dereference} cannot get the values referenced by reference
22338 values. For example, consider a reference to an @code{int}, declared
22339 in your C@t{++} program as
22347 then applying @code{Value.dereference} to the @code{gdb.Value} object
22348 corresponding to @code{ref} will result in an error, while applying
22349 @code{Value.referenced_value} will result in a @code{gdb.Value} object
22350 identical to that corresponding to @code{val}.
22353 py_ref = gdb.parse_and_eval ("ref")
22354 er_ref = py_ref.dereference () # Results in error
22355 py_val = py_ref.referenced_value () # Returns the referenced value
22358 The @code{gdb.Value} object @code{py_val} is identical to that
22359 corresponding to @code{val}.
22362 @defun Value.dynamic_cast (type)
22363 Like @code{Value.cast}, but works as if the C@t{++} @code{dynamic_cast}
22364 operator were used. Consult a C@t{++} reference for details.
22367 @defun Value.reinterpret_cast (type)
22368 Like @code{Value.cast}, but works as if the C@t{++} @code{reinterpret_cast}
22369 operator were used. Consult a C@t{++} reference for details.
22372 @defun Value.string (@r{[}encoding@r{[}, errors@r{[}, length@r{]]]})
22373 If this @code{gdb.Value} represents a string, then this method
22374 converts the contents to a Python string. Otherwise, this method will
22375 throw an exception.
22377 Strings are recognized in a language-specific way; whether a given
22378 @code{gdb.Value} represents a string is determined by the current
22381 For C-like languages, a value is a string if it is a pointer to or an
22382 array of characters or ints. The string is assumed to be terminated
22383 by a zero of the appropriate width. However if the optional length
22384 argument is given, the string will be converted to that given length,
22385 ignoring any embedded zeros that the string may contain.
22387 If the optional @var{encoding} argument is given, it must be a string
22388 naming the encoding of the string in the @code{gdb.Value}, such as
22389 @code{"ascii"}, @code{"iso-8859-6"} or @code{"utf-8"}. It accepts
22390 the same encodings as the corresponding argument to Python's
22391 @code{string.decode} method, and the Python codec machinery will be used
22392 to convert the string. If @var{encoding} is not given, or if
22393 @var{encoding} is the empty string, then either the @code{target-charset}
22394 (@pxref{Character Sets}) will be used, or a language-specific encoding
22395 will be used, if the current language is able to supply one.
22397 The optional @var{errors} argument is the same as the corresponding
22398 argument to Python's @code{string.decode} method.
22400 If the optional @var{length} argument is given, the string will be
22401 fetched and converted to the given length.
22404 @defun Value.lazy_string (@r{[}encoding @r{[}, length@r{]]})
22405 If this @code{gdb.Value} represents a string, then this method
22406 converts the contents to a @code{gdb.LazyString} (@pxref{Lazy Strings
22407 In Python}). Otherwise, this method will throw an exception.
22409 If the optional @var{encoding} argument is given, it must be a string
22410 naming the encoding of the @code{gdb.LazyString}. Some examples are:
22411 @samp{ascii}, @samp{iso-8859-6} or @samp{utf-8}. If the
22412 @var{encoding} argument is an encoding that @value{GDBN} does
22413 recognize, @value{GDBN} will raise an error.
22415 When a lazy string is printed, the @value{GDBN} encoding machinery is
22416 used to convert the string during printing. If the optional
22417 @var{encoding} argument is not provided, or is an empty string,
22418 @value{GDBN} will automatically select the encoding most suitable for
22419 the string type. For further information on encoding in @value{GDBN}
22420 please see @ref{Character Sets}.
22422 If the optional @var{length} argument is given, the string will be
22423 fetched and encoded to the length of characters specified. If
22424 the @var{length} argument is not provided, the string will be fetched
22425 and encoded until a null of appropriate width is found.
22428 @defun Value.fetch_lazy ()
22429 If the @code{gdb.Value} object is currently a lazy value
22430 (@code{gdb.Value.is_lazy} is @code{True}), then the value is
22431 fetched from the inferior. Any errors that occur in the process
22432 will produce a Python exception.
22434 If the @code{gdb.Value} object is not a lazy value, this method
22437 This method does not return a value.
22442 @node Types In Python
22443 @subsubsection Types In Python
22444 @cindex types in Python
22445 @cindex Python, working with types
22448 @value{GDBN} represents types from the inferior using the class
22451 The following type-related functions are available in the @code{gdb}
22454 @findex gdb.lookup_type
22455 @defun gdb.lookup_type (name @r{[}, block@r{]})
22456 This function looks up a type by name. @var{name} is the name of the
22457 type to look up. It must be a string.
22459 If @var{block} is given, then @var{name} is looked up in that scope.
22460 Otherwise, it is searched for globally.
22462 Ordinarily, this function will return an instance of @code{gdb.Type}.
22463 If the named type cannot be found, it will throw an exception.
22466 If the type is a structure or class type, or an enum type, the fields
22467 of that type can be accessed using the Python @dfn{dictionary syntax}.
22468 For example, if @code{some_type} is a @code{gdb.Type} instance holding
22469 a structure type, you can access its @code{foo} field with:
22472 bar = some_type['foo']
22475 @code{bar} will be a @code{gdb.Field} object; see below under the
22476 description of the @code{Type.fields} method for a description of the
22477 @code{gdb.Field} class.
22479 An instance of @code{Type} has the following attributes:
22483 The type code for this type. The type code will be one of the
22484 @code{TYPE_CODE_} constants defined below.
22487 @defvar Type.sizeof
22488 The size of this type, in target @code{char} units. Usually, a
22489 target's @code{char} type will be an 8-bit byte. However, on some
22490 unusual platforms, this type may have a different size.
22494 The tag name for this type. The tag name is the name after
22495 @code{struct}, @code{union}, or @code{enum} in C and C@t{++}; not all
22496 languages have this concept. If this type has no tag name, then
22497 @code{None} is returned.
22501 The following methods are provided:
22504 @defun Type.fields ()
22505 For structure and union types, this method returns the fields. Range
22506 types have two fields, the minimum and maximum values. Enum types
22507 have one field per enum constant. Function and method types have one
22508 field per parameter. The base types of C@t{++} classes are also
22509 represented as fields. If the type has no fields, or does not fit
22510 into one of these categories, an empty sequence will be returned.
22512 Each field is a @code{gdb.Field} object, with some pre-defined attributes:
22515 This attribute is not available for @code{static} fields (as in
22516 C@t{++} or Java). For non-@code{static} fields, the value is the bit
22517 position of the field. For @code{enum} fields, the value is the
22518 enumeration member's integer representation.
22521 The name of the field, or @code{None} for anonymous fields.
22524 This is @code{True} if the field is artificial, usually meaning that
22525 it was provided by the compiler and not the user. This attribute is
22526 always provided, and is @code{False} if the field is not artificial.
22528 @item is_base_class
22529 This is @code{True} if the field represents a base class of a C@t{++}
22530 structure. This attribute is always provided, and is @code{False}
22531 if the field is not a base class of the type that is the argument of
22532 @code{fields}, or if that type was not a C@t{++} class.
22535 If the field is packed, or is a bitfield, then this will have a
22536 non-zero value, which is the size of the field in bits. Otherwise,
22537 this will be zero; in this case the field's size is given by its type.
22540 The type of the field. This is usually an instance of @code{Type},
22541 but it can be @code{None} in some situations.
22545 @defun Type.array (@var{n1} @r{[}, @var{n2}@r{]})
22546 Return a new @code{gdb.Type} object which represents an array of this
22547 type. If one argument is given, it is the inclusive upper bound of
22548 the array; in this case the lower bound is zero. If two arguments are
22549 given, the first argument is the lower bound of the array, and the
22550 second argument is the upper bound of the array. An array's length
22551 must not be negative, but the bounds can be.
22554 @defun Type.const ()
22555 Return a new @code{gdb.Type} object which represents a
22556 @code{const}-qualified variant of this type.
22559 @defun Type.volatile ()
22560 Return a new @code{gdb.Type} object which represents a
22561 @code{volatile}-qualified variant of this type.
22564 @defun Type.unqualified ()
22565 Return a new @code{gdb.Type} object which represents an unqualified
22566 variant of this type. That is, the result is neither @code{const} nor
22570 @defun Type.range ()
22571 Return a Python @code{Tuple} object that contains two elements: the
22572 low bound of the argument type and the high bound of that type. If
22573 the type does not have a range, @value{GDBN} will raise a
22574 @code{gdb.error} exception (@pxref{Exception Handling}).
22577 @defun Type.reference ()
22578 Return a new @code{gdb.Type} object which represents a reference to this
22582 @defun Type.pointer ()
22583 Return a new @code{gdb.Type} object which represents a pointer to this
22587 @defun Type.strip_typedefs ()
22588 Return a new @code{gdb.Type} that represents the real type,
22589 after removing all layers of typedefs.
22592 @defun Type.target ()
22593 Return a new @code{gdb.Type} object which represents the target type
22596 For a pointer type, the target type is the type of the pointed-to
22597 object. For an array type (meaning C-like arrays), the target type is
22598 the type of the elements of the array. For a function or method type,
22599 the target type is the type of the return value. For a complex type,
22600 the target type is the type of the elements. For a typedef, the
22601 target type is the aliased type.
22603 If the type does not have a target, this method will throw an
22607 @defun Type.template_argument (n @r{[}, block@r{]})
22608 If this @code{gdb.Type} is an instantiation of a template, this will
22609 return a new @code{gdb.Type} which represents the type of the
22610 @var{n}th template argument.
22612 If this @code{gdb.Type} is not a template type, this will throw an
22613 exception. Ordinarily, only C@t{++} code will have template types.
22615 If @var{block} is given, then @var{name} is looked up in that scope.
22616 Otherwise, it is searched for globally.
22621 Each type has a code, which indicates what category this type falls
22622 into. The available type categories are represented by constants
22623 defined in the @code{gdb} module:
22626 @findex TYPE_CODE_PTR
22627 @findex gdb.TYPE_CODE_PTR
22628 @item gdb.TYPE_CODE_PTR
22629 The type is a pointer.
22631 @findex TYPE_CODE_ARRAY
22632 @findex gdb.TYPE_CODE_ARRAY
22633 @item gdb.TYPE_CODE_ARRAY
22634 The type is an array.
22636 @findex TYPE_CODE_STRUCT
22637 @findex gdb.TYPE_CODE_STRUCT
22638 @item gdb.TYPE_CODE_STRUCT
22639 The type is a structure.
22641 @findex TYPE_CODE_UNION
22642 @findex gdb.TYPE_CODE_UNION
22643 @item gdb.TYPE_CODE_UNION
22644 The type is a union.
22646 @findex TYPE_CODE_ENUM
22647 @findex gdb.TYPE_CODE_ENUM
22648 @item gdb.TYPE_CODE_ENUM
22649 The type is an enum.
22651 @findex TYPE_CODE_FLAGS
22652 @findex gdb.TYPE_CODE_FLAGS
22653 @item gdb.TYPE_CODE_FLAGS
22654 A bit flags type, used for things such as status registers.
22656 @findex TYPE_CODE_FUNC
22657 @findex gdb.TYPE_CODE_FUNC
22658 @item gdb.TYPE_CODE_FUNC
22659 The type is a function.
22661 @findex TYPE_CODE_INT
22662 @findex gdb.TYPE_CODE_INT
22663 @item gdb.TYPE_CODE_INT
22664 The type is an integer type.
22666 @findex TYPE_CODE_FLT
22667 @findex gdb.TYPE_CODE_FLT
22668 @item gdb.TYPE_CODE_FLT
22669 A floating point type.
22671 @findex TYPE_CODE_VOID
22672 @findex gdb.TYPE_CODE_VOID
22673 @item gdb.TYPE_CODE_VOID
22674 The special type @code{void}.
22676 @findex TYPE_CODE_SET
22677 @findex gdb.TYPE_CODE_SET
22678 @item gdb.TYPE_CODE_SET
22681 @findex TYPE_CODE_RANGE
22682 @findex gdb.TYPE_CODE_RANGE
22683 @item gdb.TYPE_CODE_RANGE
22684 A range type, that is, an integer type with bounds.
22686 @findex TYPE_CODE_STRING
22687 @findex gdb.TYPE_CODE_STRING
22688 @item gdb.TYPE_CODE_STRING
22689 A string type. Note that this is only used for certain languages with
22690 language-defined string types; C strings are not represented this way.
22692 @findex TYPE_CODE_BITSTRING
22693 @findex gdb.TYPE_CODE_BITSTRING
22694 @item gdb.TYPE_CODE_BITSTRING
22697 @findex TYPE_CODE_ERROR
22698 @findex gdb.TYPE_CODE_ERROR
22699 @item gdb.TYPE_CODE_ERROR
22700 An unknown or erroneous type.
22702 @findex TYPE_CODE_METHOD
22703 @findex gdb.TYPE_CODE_METHOD
22704 @item gdb.TYPE_CODE_METHOD
22705 A method type, as found in C@t{++} or Java.
22707 @findex TYPE_CODE_METHODPTR
22708 @findex gdb.TYPE_CODE_METHODPTR
22709 @item gdb.TYPE_CODE_METHODPTR
22710 A pointer-to-member-function.
22712 @findex TYPE_CODE_MEMBERPTR
22713 @findex gdb.TYPE_CODE_MEMBERPTR
22714 @item gdb.TYPE_CODE_MEMBERPTR
22715 A pointer-to-member.
22717 @findex TYPE_CODE_REF
22718 @findex gdb.TYPE_CODE_REF
22719 @item gdb.TYPE_CODE_REF
22722 @findex TYPE_CODE_CHAR
22723 @findex gdb.TYPE_CODE_CHAR
22724 @item gdb.TYPE_CODE_CHAR
22727 @findex TYPE_CODE_BOOL
22728 @findex gdb.TYPE_CODE_BOOL
22729 @item gdb.TYPE_CODE_BOOL
22732 @findex TYPE_CODE_COMPLEX
22733 @findex gdb.TYPE_CODE_COMPLEX
22734 @item gdb.TYPE_CODE_COMPLEX
22735 A complex float type.
22737 @findex TYPE_CODE_TYPEDEF
22738 @findex gdb.TYPE_CODE_TYPEDEF
22739 @item gdb.TYPE_CODE_TYPEDEF
22740 A typedef to some other type.
22742 @findex TYPE_CODE_NAMESPACE
22743 @findex gdb.TYPE_CODE_NAMESPACE
22744 @item gdb.TYPE_CODE_NAMESPACE
22745 A C@t{++} namespace.
22747 @findex TYPE_CODE_DECFLOAT
22748 @findex gdb.TYPE_CODE_DECFLOAT
22749 @item gdb.TYPE_CODE_DECFLOAT
22750 A decimal floating point type.
22752 @findex TYPE_CODE_INTERNAL_FUNCTION
22753 @findex gdb.TYPE_CODE_INTERNAL_FUNCTION
22754 @item gdb.TYPE_CODE_INTERNAL_FUNCTION
22755 A function internal to @value{GDBN}. This is the type used to represent
22756 convenience functions.
22759 Further support for types is provided in the @code{gdb.types}
22760 Python module (@pxref{gdb.types}).
22762 @node Pretty Printing API
22763 @subsubsection Pretty Printing API
22765 An example output is provided (@pxref{Pretty Printing}).
22767 A pretty-printer is just an object that holds a value and implements a
22768 specific interface, defined here.
22770 @defun pretty_printer.children (self)
22771 @value{GDBN} will call this method on a pretty-printer to compute the
22772 children of the pretty-printer's value.
22774 This method must return an object conforming to the Python iterator
22775 protocol. Each item returned by the iterator must be a tuple holding
22776 two elements. The first element is the ``name'' of the child; the
22777 second element is the child's value. The value can be any Python
22778 object which is convertible to a @value{GDBN} value.
22780 This method is optional. If it does not exist, @value{GDBN} will act
22781 as though the value has no children.
22784 @defun pretty_printer.display_hint (self)
22785 The CLI may call this method and use its result to change the
22786 formatting of a value. The result will also be supplied to an MI
22787 consumer as a @samp{displayhint} attribute of the variable being
22790 This method is optional. If it does exist, this method must return a
22793 Some display hints are predefined by @value{GDBN}:
22797 Indicate that the object being printed is ``array-like''. The CLI
22798 uses this to respect parameters such as @code{set print elements} and
22799 @code{set print array}.
22802 Indicate that the object being printed is ``map-like'', and that the
22803 children of this value can be assumed to alternate between keys and
22807 Indicate that the object being printed is ``string-like''. If the
22808 printer's @code{to_string} method returns a Python string of some
22809 kind, then @value{GDBN} will call its internal language-specific
22810 string-printing function to format the string. For the CLI this means
22811 adding quotation marks, possibly escaping some characters, respecting
22812 @code{set print elements}, and the like.
22816 @defun pretty_printer.to_string (self)
22817 @value{GDBN} will call this method to display the string
22818 representation of the value passed to the object's constructor.
22820 When printing from the CLI, if the @code{to_string} method exists,
22821 then @value{GDBN} will prepend its result to the values returned by
22822 @code{children}. Exactly how this formatting is done is dependent on
22823 the display hint, and may change as more hints are added. Also,
22824 depending on the print settings (@pxref{Print Settings}), the CLI may
22825 print just the result of @code{to_string} in a stack trace, omitting
22826 the result of @code{children}.
22828 If this method returns a string, it is printed verbatim.
22830 Otherwise, if this method returns an instance of @code{gdb.Value},
22831 then @value{GDBN} prints this value. This may result in a call to
22832 another pretty-printer.
22834 If instead the method returns a Python value which is convertible to a
22835 @code{gdb.Value}, then @value{GDBN} performs the conversion and prints
22836 the resulting value. Again, this may result in a call to another
22837 pretty-printer. Python scalars (integers, floats, and booleans) and
22838 strings are convertible to @code{gdb.Value}; other types are not.
22840 Finally, if this method returns @code{None} then no further operations
22841 are peformed in this method and nothing is printed.
22843 If the result is not one of these types, an exception is raised.
22846 @value{GDBN} provides a function which can be used to look up the
22847 default pretty-printer for a @code{gdb.Value}:
22849 @findex gdb.default_visualizer
22850 @defun gdb.default_visualizer (value)
22851 This function takes a @code{gdb.Value} object as an argument. If a
22852 pretty-printer for this value exists, then it is returned. If no such
22853 printer exists, then this returns @code{None}.
22856 @node Selecting Pretty-Printers
22857 @subsubsection Selecting Pretty-Printers
22859 The Python list @code{gdb.pretty_printers} contains an array of
22860 functions or callable objects that have been registered via addition
22861 as a pretty-printer. Printers in this list are called @code{global}
22862 printers, they're available when debugging all inferiors.
22863 Each @code{gdb.Progspace} contains a @code{pretty_printers} attribute.
22864 Each @code{gdb.Objfile} also contains a @code{pretty_printers}
22867 Each function on these lists is passed a single @code{gdb.Value}
22868 argument and should return a pretty-printer object conforming to the
22869 interface definition above (@pxref{Pretty Printing API}). If a function
22870 cannot create a pretty-printer for the value, it should return
22873 @value{GDBN} first checks the @code{pretty_printers} attribute of each
22874 @code{gdb.Objfile} in the current program space and iteratively calls
22875 each enabled lookup routine in the list for that @code{gdb.Objfile}
22876 until it receives a pretty-printer object.
22877 If no pretty-printer is found in the objfile lists, @value{GDBN} then
22878 searches the pretty-printer list of the current program space,
22879 calling each enabled function until an object is returned.
22880 After these lists have been exhausted, it tries the global
22881 @code{gdb.pretty_printers} list, again calling each enabled function until an
22882 object is returned.
22884 The order in which the objfiles are searched is not specified. For a
22885 given list, functions are always invoked from the head of the list,
22886 and iterated over sequentially until the end of the list, or a printer
22887 object is returned.
22889 For various reasons a pretty-printer may not work.
22890 For example, the underlying data structure may have changed and
22891 the pretty-printer is out of date.
22893 The consequences of a broken pretty-printer are severe enough that
22894 @value{GDBN} provides support for enabling and disabling individual
22895 printers. For example, if @code{print frame-arguments} is on,
22896 a backtrace can become highly illegible if any argument is printed
22897 with a broken printer.
22899 Pretty-printers are enabled and disabled by attaching an @code{enabled}
22900 attribute to the registered function or callable object. If this attribute
22901 is present and its value is @code{False}, the printer is disabled, otherwise
22902 the printer is enabled.
22904 @node Writing a Pretty-Printer
22905 @subsubsection Writing a Pretty-Printer
22906 @cindex writing a pretty-printer
22908 A pretty-printer consists of two parts: a lookup function to detect
22909 if the type is supported, and the printer itself.
22911 Here is an example showing how a @code{std::string} printer might be
22912 written. @xref{Pretty Printing API}, for details on the API this class
22916 class StdStringPrinter(object):
22917 "Print a std::string"
22919 def __init__(self, val):
22922 def to_string(self):
22923 return self.val['_M_dataplus']['_M_p']
22925 def display_hint(self):
22929 And here is an example showing how a lookup function for the printer
22930 example above might be written.
22933 def str_lookup_function(val):
22934 lookup_tag = val.type.tag
22935 if lookup_tag == None:
22937 regex = re.compile("^std::basic_string<char,.*>$")
22938 if regex.match(lookup_tag):
22939 return StdStringPrinter(val)
22943 The example lookup function extracts the value's type, and attempts to
22944 match it to a type that it can pretty-print. If it is a type the
22945 printer can pretty-print, it will return a printer object. If not, it
22946 returns @code{None}.
22948 We recommend that you put your core pretty-printers into a Python
22949 package. If your pretty-printers are for use with a library, we
22950 further recommend embedding a version number into the package name.
22951 This practice will enable @value{GDBN} to load multiple versions of
22952 your pretty-printers at the same time, because they will have
22955 You should write auto-loaded code (@pxref{Auto-loading}) such that it
22956 can be evaluated multiple times without changing its meaning. An
22957 ideal auto-load file will consist solely of @code{import}s of your
22958 printer modules, followed by a call to a register pretty-printers with
22959 the current objfile.
22961 Taken as a whole, this approach will scale nicely to multiple
22962 inferiors, each potentially using a different library version.
22963 Embedding a version number in the Python package name will ensure that
22964 @value{GDBN} is able to load both sets of printers simultaneously.
22965 Then, because the search for pretty-printers is done by objfile, and
22966 because your auto-loaded code took care to register your library's
22967 printers with a specific objfile, @value{GDBN} will find the correct
22968 printers for the specific version of the library used by each
22971 To continue the @code{std::string} example (@pxref{Pretty Printing API}),
22972 this code might appear in @code{gdb.libstdcxx.v6}:
22975 def register_printers(objfile):
22976 objfile.pretty_printers.append(str_lookup_function)
22980 And then the corresponding contents of the auto-load file would be:
22983 import gdb.libstdcxx.v6
22984 gdb.libstdcxx.v6.register_printers(gdb.current_objfile())
22987 The previous example illustrates a basic pretty-printer.
22988 There are a few things that can be improved on.
22989 The printer doesn't have a name, making it hard to identify in a
22990 list of installed printers. The lookup function has a name, but
22991 lookup functions can have arbitrary, even identical, names.
22993 Second, the printer only handles one type, whereas a library typically has
22994 several types. One could install a lookup function for each desired type
22995 in the library, but one could also have a single lookup function recognize
22996 several types. The latter is the conventional way this is handled.
22997 If a pretty-printer can handle multiple data types, then its
22998 @dfn{subprinters} are the printers for the individual data types.
23000 The @code{gdb.printing} module provides a formal way of solving these
23001 problems (@pxref{gdb.printing}).
23002 Here is another example that handles multiple types.
23004 These are the types we are going to pretty-print:
23007 struct foo @{ int a, b; @};
23008 struct bar @{ struct foo x, y; @};
23011 Here are the printers:
23015 """Print a foo object."""
23017 def __init__(self, val):
23020 def to_string(self):
23021 return ("a=<" + str(self.val["a"]) +
23022 "> b=<" + str(self.val["b"]) + ">")
23025 """Print a bar object."""
23027 def __init__(self, val):
23030 def to_string(self):
23031 return ("x=<" + str(self.val["x"]) +
23032 "> y=<" + str(self.val["y"]) + ">")
23035 This example doesn't need a lookup function, that is handled by the
23036 @code{gdb.printing} module. Instead a function is provided to build up
23037 the object that handles the lookup.
23040 import gdb.printing
23042 def build_pretty_printer():
23043 pp = gdb.printing.RegexpCollectionPrettyPrinter(
23045 pp.add_printer('foo', '^foo$', fooPrinter)
23046 pp.add_printer('bar', '^bar$', barPrinter)
23050 And here is the autoload support:
23053 import gdb.printing
23055 gdb.printing.register_pretty_printer(
23056 gdb.current_objfile(),
23057 my_library.build_pretty_printer())
23060 Finally, when this printer is loaded into @value{GDBN}, here is the
23061 corresponding output of @samp{info pretty-printer}:
23064 (gdb) info pretty-printer
23071 @node Inferiors In Python
23072 @subsubsection Inferiors In Python
23073 @cindex inferiors in Python
23075 @findex gdb.Inferior
23076 Programs which are being run under @value{GDBN} are called inferiors
23077 (@pxref{Inferiors and Programs}). Python scripts can access
23078 information about and manipulate inferiors controlled by @value{GDBN}
23079 via objects of the @code{gdb.Inferior} class.
23081 The following inferior-related functions are available in the @code{gdb}
23084 @defun gdb.inferiors ()
23085 Return a tuple containing all inferior objects.
23088 @defun gdb.selected_inferior ()
23089 Return an object representing the current inferior.
23092 A @code{gdb.Inferior} object has the following attributes:
23095 @defvar Inferior.num
23096 ID of inferior, as assigned by GDB.
23099 @defvar Inferior.pid
23100 Process ID of the inferior, as assigned by the underlying operating
23104 @defvar Inferior.was_attached
23105 Boolean signaling whether the inferior was created using `attach', or
23106 started by @value{GDBN} itself.
23110 A @code{gdb.Inferior} object has the following methods:
23113 @defun Inferior.is_valid ()
23114 Returns @code{True} if the @code{gdb.Inferior} object is valid,
23115 @code{False} if not. A @code{gdb.Inferior} object will become invalid
23116 if the inferior no longer exists within @value{GDBN}. All other
23117 @code{gdb.Inferior} methods will throw an exception if it is invalid
23118 at the time the method is called.
23121 @defun Inferior.threads ()
23122 This method returns a tuple holding all the threads which are valid
23123 when it is called. If there are no valid threads, the method will
23124 return an empty tuple.
23127 @findex gdb.read_memory
23128 @defun Inferior.read_memory (address, length)
23129 Read @var{length} bytes of memory from the inferior, starting at
23130 @var{address}. Returns a buffer object, which behaves much like an array
23131 or a string. It can be modified and given to the @code{gdb.write_memory}
23135 @findex gdb.write_memory
23136 @defun Inferior.write_memory (address, buffer @r{[}, length@r{]})
23137 Write the contents of @var{buffer} to the inferior, starting at
23138 @var{address}. The @var{buffer} parameter must be a Python object
23139 which supports the buffer protocol, i.e., a string, an array or the
23140 object returned from @code{gdb.read_memory}. If given, @var{length}
23141 determines the number of bytes from @var{buffer} to be written.
23144 @findex gdb.search_memory
23145 @defun Inferior.search_memory (address, length, pattern)
23146 Search a region of the inferior memory starting at @var{address} with
23147 the given @var{length} using the search pattern supplied in
23148 @var{pattern}. The @var{pattern} parameter must be a Python object
23149 which supports the buffer protocol, i.e., a string, an array or the
23150 object returned from @code{gdb.read_memory}. Returns a Python @code{Long}
23151 containing the address where the pattern was found, or @code{None} if
23152 the pattern could not be found.
23156 @node Events In Python
23157 @subsubsection Events In Python
23158 @cindex inferior events in Python
23160 @value{GDBN} provides a general event facility so that Python code can be
23161 notified of various state changes, particularly changes that occur in
23164 An @dfn{event} is just an object that describes some state change. The
23165 type of the object and its attributes will vary depending on the details
23166 of the change. All the existing events are described below.
23168 In order to be notified of an event, you must register an event handler
23169 with an @dfn{event registry}. An event registry is an object in the
23170 @code{gdb.events} module which dispatches particular events. A registry
23171 provides methods to register and unregister event handlers:
23174 @defun EventRegistry.connect (object)
23175 Add the given callable @var{object} to the registry. This object will be
23176 called when an event corresponding to this registry occurs.
23179 @defun EventRegistry.disconnect (object)
23180 Remove the given @var{object} from the registry. Once removed, the object
23181 will no longer receive notifications of events.
23185 Here is an example:
23188 def exit_handler (event):
23189 print "event type: exit"
23190 print "exit code: %d" % (event.exit_code)
23192 gdb.events.exited.connect (exit_handler)
23195 In the above example we connect our handler @code{exit_handler} to the
23196 registry @code{events.exited}. Once connected, @code{exit_handler} gets
23197 called when the inferior exits. The argument @dfn{event} in this example is
23198 of type @code{gdb.ExitedEvent}. As you can see in the example the
23199 @code{ExitedEvent} object has an attribute which indicates the exit code of
23202 The following is a listing of the event registries that are available and
23203 details of the events they emit:
23208 Emits @code{gdb.ThreadEvent}.
23210 Some events can be thread specific when @value{GDBN} is running in non-stop
23211 mode. When represented in Python, these events all extend
23212 @code{gdb.ThreadEvent}. Note, this event is not emitted directly; instead,
23213 events which are emitted by this or other modules might extend this event.
23214 Examples of these events are @code{gdb.BreakpointEvent} and
23215 @code{gdb.ContinueEvent}.
23218 @defvar ThreadEvent.inferior_thread
23219 In non-stop mode this attribute will be set to the specific thread which was
23220 involved in the emitted event. Otherwise, it will be set to @code{None}.
23224 Emits @code{gdb.ContinueEvent} which extends @code{gdb.ThreadEvent}.
23226 This event indicates that the inferior has been continued after a stop. For
23227 inherited attribute refer to @code{gdb.ThreadEvent} above.
23229 @item events.exited
23230 Emits @code{events.ExitedEvent} which indicates that the inferior has exited.
23231 @code{events.ExitedEvent} has two attributes:
23233 @defvar ExitedEvent.exit_code
23234 An integer representing the exit code, if available, which the inferior
23235 has returned. (The exit code could be unavailable if, for example,
23236 @value{GDBN} detaches from the inferior.) If the exit code is unavailable,
23237 the attribute does not exist.
23239 @defvar ExitedEvent inferior
23240 A reference to the inferior which triggered the @code{exited} event.
23245 Emits @code{gdb.StopEvent} which extends @code{gdb.ThreadEvent}.
23247 Indicates that the inferior has stopped. All events emitted by this registry
23248 extend StopEvent. As a child of @code{gdb.ThreadEvent}, @code{gdb.StopEvent}
23249 will indicate the stopped thread when @value{GDBN} is running in non-stop
23250 mode. Refer to @code{gdb.ThreadEvent} above for more details.
23252 Emits @code{gdb.SignalEvent} which extends @code{gdb.StopEvent}.
23254 This event indicates that the inferior or one of its threads has received as
23255 signal. @code{gdb.SignalEvent} has the following attributes:
23258 @defvar SignalEvent.stop_signal
23259 A string representing the signal received by the inferior. A list of possible
23260 signal values can be obtained by running the command @code{info signals} in
23261 the @value{GDBN} command prompt.
23265 Also emits @code{gdb.BreakpointEvent} which extends @code{gdb.StopEvent}.
23267 @code{gdb.BreakpointEvent} event indicates that one or more breakpoints have
23268 been hit, and has the following attributes:
23271 @defvar BreakpointEvent.breakpoints
23272 A sequence containing references to all the breakpoints (type
23273 @code{gdb.Breakpoint}) that were hit.
23274 @xref{Breakpoints In Python}, for details of the @code{gdb.Breakpoint} object.
23276 @defvar BreakpointEvent.breakpoint
23277 A reference to the first breakpoint that was hit.
23278 This function is maintained for backward compatibility and is now deprecated
23279 in favor of the @code{gdb.BreakpointEvent.breakpoints} attribute.
23283 @item events.new_objfile
23284 Emits @code{gdb.NewObjFileEvent} which indicates that a new object file has
23285 been loaded by @value{GDBN}. @code{gdb.NewObjFileEvent} has one attribute:
23288 @defvar NewObjFileEvent.new_objfile
23289 A reference to the object file (@code{gdb.Objfile}) which has been loaded.
23290 @xref{Objfiles In Python}, for details of the @code{gdb.Objfile} object.
23296 @node Threads In Python
23297 @subsubsection Threads In Python
23298 @cindex threads in python
23300 @findex gdb.InferiorThread
23301 Python scripts can access information about, and manipulate inferior threads
23302 controlled by @value{GDBN}, via objects of the @code{gdb.InferiorThread} class.
23304 The following thread-related functions are available in the @code{gdb}
23307 @findex gdb.selected_thread
23308 @defun gdb.selected_thread ()
23309 This function returns the thread object for the selected thread. If there
23310 is no selected thread, this will return @code{None}.
23313 A @code{gdb.InferiorThread} object has the following attributes:
23316 @defvar InferiorThread.name
23317 The name of the thread. If the user specified a name using
23318 @code{thread name}, then this returns that name. Otherwise, if an
23319 OS-supplied name is available, then it is returned. Otherwise, this
23320 returns @code{None}.
23322 This attribute can be assigned to. The new value must be a string
23323 object, which sets the new name, or @code{None}, which removes any
23324 user-specified thread name.
23327 @defvar InferiorThread.num
23328 ID of the thread, as assigned by GDB.
23331 @defvar InferiorThread.ptid
23332 ID of the thread, as assigned by the operating system. This attribute is a
23333 tuple containing three integers. The first is the Process ID (PID); the second
23334 is the Lightweight Process ID (LWPID), and the third is the Thread ID (TID).
23335 Either the LWPID or TID may be 0, which indicates that the operating system
23336 does not use that identifier.
23340 A @code{gdb.InferiorThread} object has the following methods:
23343 @defun InferiorThread.is_valid ()
23344 Returns @code{True} if the @code{gdb.InferiorThread} object is valid,
23345 @code{False} if not. A @code{gdb.InferiorThread} object will become
23346 invalid if the thread exits, or the inferior that the thread belongs
23347 is deleted. All other @code{gdb.InferiorThread} methods will throw an
23348 exception if it is invalid at the time the method is called.
23351 @defun InferiorThread.switch ()
23352 This changes @value{GDBN}'s currently selected thread to the one represented
23356 @defun InferiorThread.is_stopped ()
23357 Return a Boolean indicating whether the thread is stopped.
23360 @defun InferiorThread.is_running ()
23361 Return a Boolean indicating whether the thread is running.
23364 @defun InferiorThread.is_exited ()
23365 Return a Boolean indicating whether the thread is exited.
23369 @node Commands In Python
23370 @subsubsection Commands In Python
23372 @cindex commands in python
23373 @cindex python commands
23374 You can implement new @value{GDBN} CLI commands in Python. A CLI
23375 command is implemented using an instance of the @code{gdb.Command}
23376 class, most commonly using a subclass.
23378 @defun Command.__init__ (name, @var{command_class} @r{[}, @var{completer_class} @r{[}, @var{prefix}@r{]]})
23379 The object initializer for @code{Command} registers the new command
23380 with @value{GDBN}. This initializer is normally invoked from the
23381 subclass' own @code{__init__} method.
23383 @var{name} is the name of the command. If @var{name} consists of
23384 multiple words, then the initial words are looked for as prefix
23385 commands. In this case, if one of the prefix commands does not exist,
23386 an exception is raised.
23388 There is no support for multi-line commands.
23390 @var{command_class} should be one of the @samp{COMMAND_} constants
23391 defined below. This argument tells @value{GDBN} how to categorize the
23392 new command in the help system.
23394 @var{completer_class} is an optional argument. If given, it should be
23395 one of the @samp{COMPLETE_} constants defined below. This argument
23396 tells @value{GDBN} how to perform completion for this command. If not
23397 given, @value{GDBN} will attempt to complete using the object's
23398 @code{complete} method (see below); if no such method is found, an
23399 error will occur when completion is attempted.
23401 @var{prefix} is an optional argument. If @code{True}, then the new
23402 command is a prefix command; sub-commands of this command may be
23405 The help text for the new command is taken from the Python
23406 documentation string for the command's class, if there is one. If no
23407 documentation string is provided, the default value ``This command is
23408 not documented.'' is used.
23411 @cindex don't repeat Python command
23412 @defun Command.dont_repeat ()
23413 By default, a @value{GDBN} command is repeated when the user enters a
23414 blank line at the command prompt. A command can suppress this
23415 behavior by invoking the @code{dont_repeat} method. This is similar
23416 to the user command @code{dont-repeat}, see @ref{Define, dont-repeat}.
23419 @defun Command.invoke (argument, from_tty)
23420 This method is called by @value{GDBN} when this command is invoked.
23422 @var{argument} is a string. It is the argument to the command, after
23423 leading and trailing whitespace has been stripped.
23425 @var{from_tty} is a boolean argument. When true, this means that the
23426 command was entered by the user at the terminal; when false it means
23427 that the command came from elsewhere.
23429 If this method throws an exception, it is turned into a @value{GDBN}
23430 @code{error} call. Otherwise, the return value is ignored.
23432 @findex gdb.string_to_argv
23433 To break @var{argument} up into an argv-like string use
23434 @code{gdb.string_to_argv}. This function behaves identically to
23435 @value{GDBN}'s internal argument lexer @code{buildargv}.
23436 It is recommended to use this for consistency.
23437 Arguments are separated by spaces and may be quoted.
23441 print gdb.string_to_argv ("1 2\ \\\"3 '4 \"5' \"6 '7\"")
23442 ['1', '2 "3', '4 "5', "6 '7"]
23447 @cindex completion of Python commands
23448 @defun Command.complete (text, word)
23449 This method is called by @value{GDBN} when the user attempts
23450 completion on this command. All forms of completion are handled by
23451 this method, that is, the @key{TAB} and @key{M-?} key bindings
23452 (@pxref{Completion}), and the @code{complete} command (@pxref{Help,
23455 The arguments @var{text} and @var{word} are both strings. @var{text}
23456 holds the complete command line up to the cursor's location.
23457 @var{word} holds the last word of the command line; this is computed
23458 using a word-breaking heuristic.
23460 The @code{complete} method can return several values:
23463 If the return value is a sequence, the contents of the sequence are
23464 used as the completions. It is up to @code{complete} to ensure that the
23465 contents actually do complete the word. A zero-length sequence is
23466 allowed, it means that there were no completions available. Only
23467 string elements of the sequence are used; other elements in the
23468 sequence are ignored.
23471 If the return value is one of the @samp{COMPLETE_} constants defined
23472 below, then the corresponding @value{GDBN}-internal completion
23473 function is invoked, and its result is used.
23476 All other results are treated as though there were no available
23481 When a new command is registered, it must be declared as a member of
23482 some general class of commands. This is used to classify top-level
23483 commands in the on-line help system; note that prefix commands are not
23484 listed under their own category but rather that of their top-level
23485 command. The available classifications are represented by constants
23486 defined in the @code{gdb} module:
23489 @findex COMMAND_NONE
23490 @findex gdb.COMMAND_NONE
23491 @item gdb.COMMAND_NONE
23492 The command does not belong to any particular class. A command in
23493 this category will not be displayed in any of the help categories.
23495 @findex COMMAND_RUNNING
23496 @findex gdb.COMMAND_RUNNING
23497 @item gdb.COMMAND_RUNNING
23498 The command is related to running the inferior. For example,
23499 @code{start}, @code{step}, and @code{continue} are in this category.
23500 Type @kbd{help running} at the @value{GDBN} prompt to see a list of
23501 commands in this category.
23503 @findex COMMAND_DATA
23504 @findex gdb.COMMAND_DATA
23505 @item gdb.COMMAND_DATA
23506 The command is related to data or variables. For example,
23507 @code{call}, @code{find}, and @code{print} are in this category. Type
23508 @kbd{help data} at the @value{GDBN} prompt to see a list of commands
23511 @findex COMMAND_STACK
23512 @findex gdb.COMMAND_STACK
23513 @item gdb.COMMAND_STACK
23514 The command has to do with manipulation of the stack. For example,
23515 @code{backtrace}, @code{frame}, and @code{return} are in this
23516 category. Type @kbd{help stack} at the @value{GDBN} prompt to see a
23517 list of commands in this category.
23519 @findex COMMAND_FILES
23520 @findex gdb.COMMAND_FILES
23521 @item gdb.COMMAND_FILES
23522 This class is used for file-related commands. For example,
23523 @code{file}, @code{list} and @code{section} are in this category.
23524 Type @kbd{help files} at the @value{GDBN} prompt to see a list of
23525 commands in this category.
23527 @findex COMMAND_SUPPORT
23528 @findex gdb.COMMAND_SUPPORT
23529 @item gdb.COMMAND_SUPPORT
23530 This should be used for ``support facilities'', generally meaning
23531 things that are useful to the user when interacting with @value{GDBN},
23532 but not related to the state of the inferior. For example,
23533 @code{help}, @code{make}, and @code{shell} are in this category. Type
23534 @kbd{help support} at the @value{GDBN} prompt to see a list of
23535 commands in this category.
23537 @findex COMMAND_STATUS
23538 @findex gdb.COMMAND_STATUS
23539 @item gdb.COMMAND_STATUS
23540 The command is an @samp{info}-related command, that is, related to the
23541 state of @value{GDBN} itself. For example, @code{info}, @code{macro},
23542 and @code{show} are in this category. Type @kbd{help status} at the
23543 @value{GDBN} prompt to see a list of commands in this category.
23545 @findex COMMAND_BREAKPOINTS
23546 @findex gdb.COMMAND_BREAKPOINTS
23547 @item gdb.COMMAND_BREAKPOINTS
23548 The command has to do with breakpoints. For example, @code{break},
23549 @code{clear}, and @code{delete} are in this category. Type @kbd{help
23550 breakpoints} at the @value{GDBN} prompt to see a list of commands in
23553 @findex COMMAND_TRACEPOINTS
23554 @findex gdb.COMMAND_TRACEPOINTS
23555 @item gdb.COMMAND_TRACEPOINTS
23556 The command has to do with tracepoints. For example, @code{trace},
23557 @code{actions}, and @code{tfind} are in this category. Type
23558 @kbd{help tracepoints} at the @value{GDBN} prompt to see a list of
23559 commands in this category.
23561 @findex COMMAND_USER
23562 @findex gdb.COMMAND_USER
23563 @item gdb.COMMAND_USER
23564 The command is a general purpose command for the user, and typically
23565 does not fit in one of the other categories.
23566 Type @kbd{help user-defined} at the @value{GDBN} prompt to see
23567 a list of commands in this category, as well as the list of gdb macros
23568 (@pxref{Sequences}).
23570 @findex COMMAND_OBSCURE
23571 @findex gdb.COMMAND_OBSCURE
23572 @item gdb.COMMAND_OBSCURE
23573 The command is only used in unusual circumstances, or is not of
23574 general interest to users. For example, @code{checkpoint},
23575 @code{fork}, and @code{stop} are in this category. Type @kbd{help
23576 obscure} at the @value{GDBN} prompt to see a list of commands in this
23579 @findex COMMAND_MAINTENANCE
23580 @findex gdb.COMMAND_MAINTENANCE
23581 @item gdb.COMMAND_MAINTENANCE
23582 The command is only useful to @value{GDBN} maintainers. The
23583 @code{maintenance} and @code{flushregs} commands are in this category.
23584 Type @kbd{help internals} at the @value{GDBN} prompt to see a list of
23585 commands in this category.
23588 A new command can use a predefined completion function, either by
23589 specifying it via an argument at initialization, or by returning it
23590 from the @code{complete} method. These predefined completion
23591 constants are all defined in the @code{gdb} module:
23594 @findex COMPLETE_NONE
23595 @findex gdb.COMPLETE_NONE
23596 @item gdb.COMPLETE_NONE
23597 This constant means that no completion should be done.
23599 @findex COMPLETE_FILENAME
23600 @findex gdb.COMPLETE_FILENAME
23601 @item gdb.COMPLETE_FILENAME
23602 This constant means that filename completion should be performed.
23604 @findex COMPLETE_LOCATION
23605 @findex gdb.COMPLETE_LOCATION
23606 @item gdb.COMPLETE_LOCATION
23607 This constant means that location completion should be done.
23608 @xref{Specify Location}.
23610 @findex COMPLETE_COMMAND
23611 @findex gdb.COMPLETE_COMMAND
23612 @item gdb.COMPLETE_COMMAND
23613 This constant means that completion should examine @value{GDBN}
23616 @findex COMPLETE_SYMBOL
23617 @findex gdb.COMPLETE_SYMBOL
23618 @item gdb.COMPLETE_SYMBOL
23619 This constant means that completion should be done using symbol names
23623 The following code snippet shows how a trivial CLI command can be
23624 implemented in Python:
23627 class HelloWorld (gdb.Command):
23628 """Greet the whole world."""
23630 def __init__ (self):
23631 super (HelloWorld, self).__init__ ("hello-world", gdb.COMMAND_USER)
23633 def invoke (self, arg, from_tty):
23634 print "Hello, World!"
23639 The last line instantiates the class, and is necessary to trigger the
23640 registration of the command with @value{GDBN}. Depending on how the
23641 Python code is read into @value{GDBN}, you may need to import the
23642 @code{gdb} module explicitly.
23644 @node Parameters In Python
23645 @subsubsection Parameters In Python
23647 @cindex parameters in python
23648 @cindex python parameters
23649 @tindex gdb.Parameter
23651 You can implement new @value{GDBN} parameters using Python. A new
23652 parameter is implemented as an instance of the @code{gdb.Parameter}
23655 Parameters are exposed to the user via the @code{set} and
23656 @code{show} commands. @xref{Help}.
23658 There are many parameters that already exist and can be set in
23659 @value{GDBN}. Two examples are: @code{set follow fork} and
23660 @code{set charset}. Setting these parameters influences certain
23661 behavior in @value{GDBN}. Similarly, you can define parameters that
23662 can be used to influence behavior in custom Python scripts and commands.
23664 @defun Parameter.__init__ (name, @var{command-class}, @var{parameter-class} @r{[}, @var{enum-sequence}@r{]})
23665 The object initializer for @code{Parameter} registers the new
23666 parameter with @value{GDBN}. This initializer is normally invoked
23667 from the subclass' own @code{__init__} method.
23669 @var{name} is the name of the new parameter. If @var{name} consists
23670 of multiple words, then the initial words are looked for as prefix
23671 parameters. An example of this can be illustrated with the
23672 @code{set print} set of parameters. If @var{name} is
23673 @code{print foo}, then @code{print} will be searched as the prefix
23674 parameter. In this case the parameter can subsequently be accessed in
23675 @value{GDBN} as @code{set print foo}.
23677 If @var{name} consists of multiple words, and no prefix parameter group
23678 can be found, an exception is raised.
23680 @var{command-class} should be one of the @samp{COMMAND_} constants
23681 (@pxref{Commands In Python}). This argument tells @value{GDBN} how to
23682 categorize the new parameter in the help system.
23684 @var{parameter-class} should be one of the @samp{PARAM_} constants
23685 defined below. This argument tells @value{GDBN} the type of the new
23686 parameter; this information is used for input validation and
23689 If @var{parameter-class} is @code{PARAM_ENUM}, then
23690 @var{enum-sequence} must be a sequence of strings. These strings
23691 represent the possible values for the parameter.
23693 If @var{parameter-class} is not @code{PARAM_ENUM}, then the presence
23694 of a fourth argument will cause an exception to be thrown.
23696 The help text for the new parameter is taken from the Python
23697 documentation string for the parameter's class, if there is one. If
23698 there is no documentation string, a default value is used.
23701 @defvar Parameter.set_doc
23702 If this attribute exists, and is a string, then its value is used as
23703 the help text for this parameter's @code{set} command. The value is
23704 examined when @code{Parameter.__init__} is invoked; subsequent changes
23708 @defvar Parameter.show_doc
23709 If this attribute exists, and is a string, then its value is used as
23710 the help text for this parameter's @code{show} command. The value is
23711 examined when @code{Parameter.__init__} is invoked; subsequent changes
23715 @defvar Parameter.value
23716 The @code{value} attribute holds the underlying value of the
23717 parameter. It can be read and assigned to just as any other
23718 attribute. @value{GDBN} does validation when assignments are made.
23721 There are two methods that should be implemented in any
23722 @code{Parameter} class. These are:
23724 @defun Parameter.get_set_string (self)
23725 @value{GDBN} will call this method when a @var{parameter}'s value has
23726 been changed via the @code{set} API (for example, @kbd{set foo off}).
23727 The @code{value} attribute has already been populated with the new
23728 value and may be used in output. This method must return a string.
23731 @defun Parameter.get_show_string (self, svalue)
23732 @value{GDBN} will call this method when a @var{parameter}'s
23733 @code{show} API has been invoked (for example, @kbd{show foo}). The
23734 argument @code{svalue} receives the string representation of the
23735 current value. This method must return a string.
23738 When a new parameter is defined, its type must be specified. The
23739 available types are represented by constants defined in the @code{gdb}
23743 @findex PARAM_BOOLEAN
23744 @findex gdb.PARAM_BOOLEAN
23745 @item gdb.PARAM_BOOLEAN
23746 The value is a plain boolean. The Python boolean values, @code{True}
23747 and @code{False} are the only valid values.
23749 @findex PARAM_AUTO_BOOLEAN
23750 @findex gdb.PARAM_AUTO_BOOLEAN
23751 @item gdb.PARAM_AUTO_BOOLEAN
23752 The value has three possible states: true, false, and @samp{auto}. In
23753 Python, true and false are represented using boolean constants, and
23754 @samp{auto} is represented using @code{None}.
23756 @findex PARAM_UINTEGER
23757 @findex gdb.PARAM_UINTEGER
23758 @item gdb.PARAM_UINTEGER
23759 The value is an unsigned integer. The value of 0 should be
23760 interpreted to mean ``unlimited''.
23762 @findex PARAM_INTEGER
23763 @findex gdb.PARAM_INTEGER
23764 @item gdb.PARAM_INTEGER
23765 The value is a signed integer. The value of 0 should be interpreted
23766 to mean ``unlimited''.
23768 @findex PARAM_STRING
23769 @findex gdb.PARAM_STRING
23770 @item gdb.PARAM_STRING
23771 The value is a string. When the user modifies the string, any escape
23772 sequences, such as @samp{\t}, @samp{\f}, and octal escapes, are
23773 translated into corresponding characters and encoded into the current
23776 @findex PARAM_STRING_NOESCAPE
23777 @findex gdb.PARAM_STRING_NOESCAPE
23778 @item gdb.PARAM_STRING_NOESCAPE
23779 The value is a string. When the user modifies the string, escapes are
23780 passed through untranslated.
23782 @findex PARAM_OPTIONAL_FILENAME
23783 @findex gdb.PARAM_OPTIONAL_FILENAME
23784 @item gdb.PARAM_OPTIONAL_FILENAME
23785 The value is a either a filename (a string), or @code{None}.
23787 @findex PARAM_FILENAME
23788 @findex gdb.PARAM_FILENAME
23789 @item gdb.PARAM_FILENAME
23790 The value is a filename. This is just like
23791 @code{PARAM_STRING_NOESCAPE}, but uses file names for completion.
23793 @findex PARAM_ZINTEGER
23794 @findex gdb.PARAM_ZINTEGER
23795 @item gdb.PARAM_ZINTEGER
23796 The value is an integer. This is like @code{PARAM_INTEGER}, except 0
23797 is interpreted as itself.
23800 @findex gdb.PARAM_ENUM
23801 @item gdb.PARAM_ENUM
23802 The value is a string, which must be one of a collection string
23803 constants provided when the parameter is created.
23806 @node Functions In Python
23807 @subsubsection Writing new convenience functions
23809 @cindex writing convenience functions
23810 @cindex convenience functions in python
23811 @cindex python convenience functions
23812 @tindex gdb.Function
23814 You can implement new convenience functions (@pxref{Convenience Vars})
23815 in Python. A convenience function is an instance of a subclass of the
23816 class @code{gdb.Function}.
23818 @defun Function.__init__ (name)
23819 The initializer for @code{Function} registers the new function with
23820 @value{GDBN}. The argument @var{name} is the name of the function,
23821 a string. The function will be visible to the user as a convenience
23822 variable of type @code{internal function}, whose name is the same as
23823 the given @var{name}.
23825 The documentation for the new function is taken from the documentation
23826 string for the new class.
23829 @defun Function.invoke (@var{*args})
23830 When a convenience function is evaluated, its arguments are converted
23831 to instances of @code{gdb.Value}, and then the function's
23832 @code{invoke} method is called. Note that @value{GDBN} does not
23833 predetermine the arity of convenience functions. Instead, all
23834 available arguments are passed to @code{invoke}, following the
23835 standard Python calling convention. In particular, a convenience
23836 function can have default values for parameters without ill effect.
23838 The return value of this method is used as its value in the enclosing
23839 expression. If an ordinary Python value is returned, it is converted
23840 to a @code{gdb.Value} following the usual rules.
23843 The following code snippet shows how a trivial convenience function can
23844 be implemented in Python:
23847 class Greet (gdb.Function):
23848 """Return string to greet someone.
23849 Takes a name as argument."""
23851 def __init__ (self):
23852 super (Greet, self).__init__ ("greet")
23854 def invoke (self, name):
23855 return "Hello, %s!" % name.string ()
23860 The last line instantiates the class, and is necessary to trigger the
23861 registration of the function with @value{GDBN}. Depending on how the
23862 Python code is read into @value{GDBN}, you may need to import the
23863 @code{gdb} module explicitly.
23865 @node Progspaces In Python
23866 @subsubsection Program Spaces In Python
23868 @cindex progspaces in python
23869 @tindex gdb.Progspace
23871 A program space, or @dfn{progspace}, represents a symbolic view
23872 of an address space.
23873 It consists of all of the objfiles of the program.
23874 @xref{Objfiles In Python}.
23875 @xref{Inferiors and Programs, program spaces}, for more details
23876 about program spaces.
23878 The following progspace-related functions are available in the
23881 @findex gdb.current_progspace
23882 @defun gdb.current_progspace ()
23883 This function returns the program space of the currently selected inferior.
23884 @xref{Inferiors and Programs}.
23887 @findex gdb.progspaces
23888 @defun gdb.progspaces ()
23889 Return a sequence of all the progspaces currently known to @value{GDBN}.
23892 Each progspace is represented by an instance of the @code{gdb.Progspace}
23895 @defvar Progspace.filename
23896 The file name of the progspace as a string.
23899 @defvar Progspace.pretty_printers
23900 The @code{pretty_printers} attribute is a list of functions. It is
23901 used to look up pretty-printers. A @code{Value} is passed to each
23902 function in order; if the function returns @code{None}, then the
23903 search continues. Otherwise, the return value should be an object
23904 which is used to format the value. @xref{Pretty Printing API}, for more
23908 @node Objfiles In Python
23909 @subsubsection Objfiles In Python
23911 @cindex objfiles in python
23912 @tindex gdb.Objfile
23914 @value{GDBN} loads symbols for an inferior from various
23915 symbol-containing files (@pxref{Files}). These include the primary
23916 executable file, any shared libraries used by the inferior, and any
23917 separate debug info files (@pxref{Separate Debug Files}).
23918 @value{GDBN} calls these symbol-containing files @dfn{objfiles}.
23920 The following objfile-related functions are available in the
23923 @findex gdb.current_objfile
23924 @defun gdb.current_objfile ()
23925 When auto-loading a Python script (@pxref{Auto-loading}), @value{GDBN}
23926 sets the ``current objfile'' to the corresponding objfile. This
23927 function returns the current objfile. If there is no current objfile,
23928 this function returns @code{None}.
23931 @findex gdb.objfiles
23932 @defun gdb.objfiles ()
23933 Return a sequence of all the objfiles current known to @value{GDBN}.
23934 @xref{Objfiles In Python}.
23937 Each objfile is represented by an instance of the @code{gdb.Objfile}
23940 @defvar Objfile.filename
23941 The file name of the objfile as a string.
23944 @defvar Objfile.pretty_printers
23945 The @code{pretty_printers} attribute is a list of functions. It is
23946 used to look up pretty-printers. A @code{Value} is passed to each
23947 function in order; if the function returns @code{None}, then the
23948 search continues. Otherwise, the return value should be an object
23949 which is used to format the value. @xref{Pretty Printing API}, for more
23953 A @code{gdb.Objfile} object has the following methods:
23955 @defun Objfile.is_valid ()
23956 Returns @code{True} if the @code{gdb.Objfile} object is valid,
23957 @code{False} if not. A @code{gdb.Objfile} object can become invalid
23958 if the object file it refers to is not loaded in @value{GDBN} any
23959 longer. All other @code{gdb.Objfile} methods will throw an exception
23960 if it is invalid at the time the method is called.
23963 @node Frames In Python
23964 @subsubsection Accessing inferior stack frames from Python.
23966 @cindex frames in python
23967 When the debugged program stops, @value{GDBN} is able to analyze its call
23968 stack (@pxref{Frames,,Stack frames}). The @code{gdb.Frame} class
23969 represents a frame in the stack. A @code{gdb.Frame} object is only valid
23970 while its corresponding frame exists in the inferior's stack. If you try
23971 to use an invalid frame object, @value{GDBN} will throw a @code{gdb.error}
23972 exception (@pxref{Exception Handling}).
23974 Two @code{gdb.Frame} objects can be compared for equality with the @code{==}
23978 (@value{GDBP}) python print gdb.newest_frame() == gdb.selected_frame ()
23982 The following frame-related functions are available in the @code{gdb} module:
23984 @findex gdb.selected_frame
23985 @defun gdb.selected_frame ()
23986 Return the selected frame object. (@pxref{Selection,,Selecting a Frame}).
23989 @findex gdb.newest_frame
23990 @defun gdb.newest_frame ()
23991 Return the newest frame object for the selected thread.
23994 @defun gdb.frame_stop_reason_string (reason)
23995 Return a string explaining the reason why @value{GDBN} stopped unwinding
23996 frames, as expressed by the given @var{reason} code (an integer, see the
23997 @code{unwind_stop_reason} method further down in this section).
24000 A @code{gdb.Frame} object has the following methods:
24003 @defun Frame.is_valid ()
24004 Returns true if the @code{gdb.Frame} object is valid, false if not.
24005 A frame object can become invalid if the frame it refers to doesn't
24006 exist anymore in the inferior. All @code{gdb.Frame} methods will throw
24007 an exception if it is invalid at the time the method is called.
24010 @defun Frame.name ()
24011 Returns the function name of the frame, or @code{None} if it can't be
24015 @defun Frame.type ()
24016 Returns the type of the frame. The value can be one of:
24018 @item gdb.NORMAL_FRAME
24019 An ordinary stack frame.
24021 @item gdb.DUMMY_FRAME
24022 A fake stack frame that was created by @value{GDBN} when performing an
24023 inferior function call.
24025 @item gdb.INLINE_FRAME
24026 A frame representing an inlined function. The function was inlined
24027 into a @code{gdb.NORMAL_FRAME} that is older than this one.
24029 @item gdb.TAILCALL_FRAME
24030 A frame representing a tail call. @xref{Tail Call Frames}.
24032 @item gdb.SIGTRAMP_FRAME
24033 A signal trampoline frame. This is the frame created by the OS when
24034 it calls into a signal handler.
24036 @item gdb.ARCH_FRAME
24037 A fake stack frame representing a cross-architecture call.
24039 @item gdb.SENTINEL_FRAME
24040 This is like @code{gdb.NORMAL_FRAME}, but it is only used for the
24045 @defun Frame.unwind_stop_reason ()
24046 Return an integer representing the reason why it's not possible to find
24047 more frames toward the outermost frame. Use
24048 @code{gdb.frame_stop_reason_string} to convert the value returned by this
24049 function to a string. The value can be one of:
24052 @item gdb.FRAME_UNWIND_NO_REASON
24053 No particular reason (older frames should be available).
24055 @item gdb.FRAME_UNWIND_NULL_ID
24056 The previous frame's analyzer returns an invalid result.
24058 @item gdb.FRAME_UNWIND_OUTERMOST
24059 This frame is the outermost.
24061 @item gdb.FRAME_UNWIND_UNAVAILABLE
24062 Cannot unwind further, because that would require knowing the
24063 values of registers or memory that have not been collected.
24065 @item gdb.FRAME_UNWIND_INNER_ID
24066 This frame ID looks like it ought to belong to a NEXT frame,
24067 but we got it for a PREV frame. Normally, this is a sign of
24068 unwinder failure. It could also indicate stack corruption.
24070 @item gdb.FRAME_UNWIND_SAME_ID
24071 This frame has the same ID as the previous one. That means
24072 that unwinding further would almost certainly give us another
24073 frame with exactly the same ID, so break the chain. Normally,
24074 this is a sign of unwinder failure. It could also indicate
24077 @item gdb.FRAME_UNWIND_NO_SAVED_PC
24078 The frame unwinder did not find any saved PC, but we needed
24079 one to unwind further.
24081 @item gdb.FRAME_UNWIND_FIRST_ERROR
24082 Any stop reason greater or equal to this value indicates some kind
24083 of error. This special value facilitates writing code that tests
24084 for errors in unwinding in a way that will work correctly even if
24085 the list of the other values is modified in future @value{GDBN}
24086 versions. Using it, you could write:
24088 reason = gdb.selected_frame().unwind_stop_reason ()
24089 reason_str = gdb.frame_stop_reason_string (reason)
24090 if reason >= gdb.FRAME_UNWIND_FIRST_ERROR:
24091 print "An error occured: %s" % reason_str
24098 Returns the frame's resume address.
24101 @defun Frame.block ()
24102 Return the frame's code block. @xref{Blocks In Python}.
24105 @defun Frame.function ()
24106 Return the symbol for the function corresponding to this frame.
24107 @xref{Symbols In Python}.
24110 @defun Frame.older ()
24111 Return the frame that called this frame.
24114 @defun Frame.newer ()
24115 Return the frame called by this frame.
24118 @defun Frame.find_sal ()
24119 Return the frame's symtab and line object.
24120 @xref{Symbol Tables In Python}.
24123 @defun Frame.read_var (variable @r{[}, block@r{]})
24124 Return the value of @var{variable} in this frame. If the optional
24125 argument @var{block} is provided, search for the variable from that
24126 block; otherwise start at the frame's current block (which is
24127 determined by the frame's current program counter). @var{variable}
24128 must be a string or a @code{gdb.Symbol} object. @var{block} must be a
24129 @code{gdb.Block} object.
24132 @defun Frame.select ()
24133 Set this frame to be the selected frame. @xref{Stack, ,Examining the
24138 @node Blocks In Python
24139 @subsubsection Accessing frame blocks from Python.
24141 @cindex blocks in python
24144 Within each frame, @value{GDBN} maintains information on each block
24145 stored in that frame. These blocks are organized hierarchically, and
24146 are represented individually in Python as a @code{gdb.Block}.
24147 Please see @ref{Frames In Python}, for a more in-depth discussion on
24148 frames. Furthermore, see @ref{Stack, ,Examining the Stack}, for more
24149 detailed technical information on @value{GDBN}'s book-keeping of the
24152 A @code{gdb.Block} is iterable. The iterator returns the symbols
24153 (@pxref{Symbols In Python}) local to the block.
24155 The following block-related functions are available in the @code{gdb}
24158 @findex gdb.block_for_pc
24159 @defun gdb.block_for_pc (pc)
24160 Return the @code{gdb.Block} containing the given @var{pc} value. If the
24161 block cannot be found for the @var{pc} value specified, the function
24162 will return @code{None}.
24165 A @code{gdb.Block} object has the following methods:
24168 @defun Block.is_valid ()
24169 Returns @code{True} if the @code{gdb.Block} object is valid,
24170 @code{False} if not. A block object can become invalid if the block it
24171 refers to doesn't exist anymore in the inferior. All other
24172 @code{gdb.Block} methods will throw an exception if it is invalid at
24173 the time the method is called. The block's validity is also checked
24174 during iteration over symbols of the block.
24178 A @code{gdb.Block} object has the following attributes:
24181 @defvar Block.start
24182 The start address of the block. This attribute is not writable.
24186 The end address of the block. This attribute is not writable.
24189 @defvar Block.function
24190 The name of the block represented as a @code{gdb.Symbol}. If the
24191 block is not named, then this attribute holds @code{None}. This
24192 attribute is not writable.
24195 @defvar Block.superblock
24196 The block containing this block. If this parent block does not exist,
24197 this attribute holds @code{None}. This attribute is not writable.
24200 @defvar Block.global_block
24201 The global block associated with this block. This attribute is not
24205 @defvar Block.static_block
24206 The static block associated with this block. This attribute is not
24210 @defvar Block.is_global
24211 @code{True} if the @code{gdb.Block} object is a global block,
24212 @code{False} if not. This attribute is not
24216 @defvar Block.is_static
24217 @code{True} if the @code{gdb.Block} object is a static block,
24218 @code{False} if not. This attribute is not writable.
24222 @node Symbols In Python
24223 @subsubsection Python representation of Symbols.
24225 @cindex symbols in python
24228 @value{GDBN} represents every variable, function and type as an
24229 entry in a symbol table. @xref{Symbols, ,Examining the Symbol Table}.
24230 Similarly, Python represents these symbols in @value{GDBN} with the
24231 @code{gdb.Symbol} object.
24233 The following symbol-related functions are available in the @code{gdb}
24236 @findex gdb.lookup_symbol
24237 @defun gdb.lookup_symbol (name @r{[}, block @r{[}, domain@r{]]})
24238 This function searches for a symbol by name. The search scope can be
24239 restricted to the parameters defined in the optional domain and block
24242 @var{name} is the name of the symbol. It must be a string. The
24243 optional @var{block} argument restricts the search to symbols visible
24244 in that @var{block}. The @var{block} argument must be a
24245 @code{gdb.Block} object. If omitted, the block for the current frame
24246 is used. The optional @var{domain} argument restricts
24247 the search to the domain type. The @var{domain} argument must be a
24248 domain constant defined in the @code{gdb} module and described later
24251 The result is a tuple of two elements.
24252 The first element is a @code{gdb.Symbol} object or @code{None} if the symbol
24254 If the symbol is found, the second element is @code{True} if the symbol
24255 is a field of a method's object (e.g., @code{this} in C@t{++}),
24256 otherwise it is @code{False}.
24257 If the symbol is not found, the second element is @code{False}.
24260 @findex gdb.lookup_global_symbol
24261 @defun gdb.lookup_global_symbol (name @r{[}, domain@r{]})
24262 This function searches for a global symbol by name.
24263 The search scope can be restricted to by the domain argument.
24265 @var{name} is the name of the symbol. It must be a string.
24266 The optional @var{domain} argument restricts the search to the domain type.
24267 The @var{domain} argument must be a domain constant defined in the @code{gdb}
24268 module and described later in this chapter.
24270 The result is a @code{gdb.Symbol} object or @code{None} if the symbol
24274 A @code{gdb.Symbol} object has the following attributes:
24277 @defvar Symbol.type
24278 The type of the symbol or @code{None} if no type is recorded.
24279 This attribute is represented as a @code{gdb.Type} object.
24280 @xref{Types In Python}. This attribute is not writable.
24283 @defvar Symbol.symtab
24284 The symbol table in which the symbol appears. This attribute is
24285 represented as a @code{gdb.Symtab} object. @xref{Symbol Tables In
24286 Python}. This attribute is not writable.
24289 @defvar Symbol.line
24290 The line number in the source code at which the symbol was defined.
24291 This is an integer.
24294 @defvar Symbol.name
24295 The name of the symbol as a string. This attribute is not writable.
24298 @defvar Symbol.linkage_name
24299 The name of the symbol, as used by the linker (i.e., may be mangled).
24300 This attribute is not writable.
24303 @defvar Symbol.print_name
24304 The name of the symbol in a form suitable for output. This is either
24305 @code{name} or @code{linkage_name}, depending on whether the user
24306 asked @value{GDBN} to display demangled or mangled names.
24309 @defvar Symbol.addr_class
24310 The address class of the symbol. This classifies how to find the value
24311 of a symbol. Each address class is a constant defined in the
24312 @code{gdb} module and described later in this chapter.
24315 @defvar Symbol.needs_frame
24316 This is @code{True} if evaluating this symbol's value requires a frame
24317 (@pxref{Frames In Python}) and @code{False} otherwise. Typically,
24318 local variables will require a frame, but other symbols will not.
24321 @defvar Symbol.is_argument
24322 @code{True} if the symbol is an argument of a function.
24325 @defvar Symbol.is_constant
24326 @code{True} if the symbol is a constant.
24329 @defvar Symbol.is_function
24330 @code{True} if the symbol is a function or a method.
24333 @defvar Symbol.is_variable
24334 @code{True} if the symbol is a variable.
24338 A @code{gdb.Symbol} object has the following methods:
24341 @defun Symbol.is_valid ()
24342 Returns @code{True} if the @code{gdb.Symbol} object is valid,
24343 @code{False} if not. A @code{gdb.Symbol} object can become invalid if
24344 the symbol it refers to does not exist in @value{GDBN} any longer.
24345 All other @code{gdb.Symbol} methods will throw an exception if it is
24346 invalid at the time the method is called.
24349 @defun Symbol.value (@r{[}frame@r{]})
24350 Compute the value of the symbol, as a @code{gdb.Value}. For
24351 functions, this computes the address of the function, cast to the
24352 appropriate type. If the symbol requires a frame in order to compute
24353 its value, then @var{frame} must be given. If @var{frame} is not
24354 given, or if @var{frame} is invalid, then this method will throw an
24359 The available domain categories in @code{gdb.Symbol} are represented
24360 as constants in the @code{gdb} module:
24363 @findex SYMBOL_UNDEF_DOMAIN
24364 @findex gdb.SYMBOL_UNDEF_DOMAIN
24365 @item gdb.SYMBOL_UNDEF_DOMAIN
24366 This is used when a domain has not been discovered or none of the
24367 following domains apply. This usually indicates an error either
24368 in the symbol information or in @value{GDBN}'s handling of symbols.
24369 @findex SYMBOL_VAR_DOMAIN
24370 @findex gdb.SYMBOL_VAR_DOMAIN
24371 @item gdb.SYMBOL_VAR_DOMAIN
24372 This domain contains variables, function names, typedef names and enum
24374 @findex SYMBOL_STRUCT_DOMAIN
24375 @findex gdb.SYMBOL_STRUCT_DOMAIN
24376 @item gdb.SYMBOL_STRUCT_DOMAIN
24377 This domain holds struct, union and enum type names.
24378 @findex SYMBOL_LABEL_DOMAIN
24379 @findex gdb.SYMBOL_LABEL_DOMAIN
24380 @item gdb.SYMBOL_LABEL_DOMAIN
24381 This domain contains names of labels (for gotos).
24382 @findex SYMBOL_VARIABLES_DOMAIN
24383 @findex gdb.SYMBOL_VARIABLES_DOMAIN
24384 @item gdb.SYMBOL_VARIABLES_DOMAIN
24385 This domain holds a subset of the @code{SYMBOLS_VAR_DOMAIN}; it
24386 contains everything minus functions and types.
24387 @findex SYMBOL_FUNCTIONS_DOMAIN
24388 @findex gdb.SYMBOL_FUNCTIONS_DOMAIN
24389 @item gdb.SYMBOL_FUNCTION_DOMAIN
24390 This domain contains all functions.
24391 @findex SYMBOL_TYPES_DOMAIN
24392 @findex gdb.SYMBOL_TYPES_DOMAIN
24393 @item gdb.SYMBOL_TYPES_DOMAIN
24394 This domain contains all types.
24397 The available address class categories in @code{gdb.Symbol} are represented
24398 as constants in the @code{gdb} module:
24401 @findex SYMBOL_LOC_UNDEF
24402 @findex gdb.SYMBOL_LOC_UNDEF
24403 @item gdb.SYMBOL_LOC_UNDEF
24404 If this is returned by address class, it indicates an error either in
24405 the symbol information or in @value{GDBN}'s handling of symbols.
24406 @findex SYMBOL_LOC_CONST
24407 @findex gdb.SYMBOL_LOC_CONST
24408 @item gdb.SYMBOL_LOC_CONST
24409 Value is constant int.
24410 @findex SYMBOL_LOC_STATIC
24411 @findex gdb.SYMBOL_LOC_STATIC
24412 @item gdb.SYMBOL_LOC_STATIC
24413 Value is at a fixed address.
24414 @findex SYMBOL_LOC_REGISTER
24415 @findex gdb.SYMBOL_LOC_REGISTER
24416 @item gdb.SYMBOL_LOC_REGISTER
24417 Value is in a register.
24418 @findex SYMBOL_LOC_ARG
24419 @findex gdb.SYMBOL_LOC_ARG
24420 @item gdb.SYMBOL_LOC_ARG
24421 Value is an argument. This value is at the offset stored within the
24422 symbol inside the frame's argument list.
24423 @findex SYMBOL_LOC_REF_ARG
24424 @findex gdb.SYMBOL_LOC_REF_ARG
24425 @item gdb.SYMBOL_LOC_REF_ARG
24426 Value address is stored in the frame's argument list. Just like
24427 @code{LOC_ARG} except that the value's address is stored at the
24428 offset, not the value itself.
24429 @findex SYMBOL_LOC_REGPARM_ADDR
24430 @findex gdb.SYMBOL_LOC_REGPARM_ADDR
24431 @item gdb.SYMBOL_LOC_REGPARM_ADDR
24432 Value is a specified register. Just like @code{LOC_REGISTER} except
24433 the register holds the address of the argument instead of the argument
24435 @findex SYMBOL_LOC_LOCAL
24436 @findex gdb.SYMBOL_LOC_LOCAL
24437 @item gdb.SYMBOL_LOC_LOCAL
24438 Value is a local variable.
24439 @findex SYMBOL_LOC_TYPEDEF
24440 @findex gdb.SYMBOL_LOC_TYPEDEF
24441 @item gdb.SYMBOL_LOC_TYPEDEF
24442 Value not used. Symbols in the domain @code{SYMBOL_STRUCT_DOMAIN} all
24444 @findex SYMBOL_LOC_BLOCK
24445 @findex gdb.SYMBOL_LOC_BLOCK
24446 @item gdb.SYMBOL_LOC_BLOCK
24448 @findex SYMBOL_LOC_CONST_BYTES
24449 @findex gdb.SYMBOL_LOC_CONST_BYTES
24450 @item gdb.SYMBOL_LOC_CONST_BYTES
24451 Value is a byte-sequence.
24452 @findex SYMBOL_LOC_UNRESOLVED
24453 @findex gdb.SYMBOL_LOC_UNRESOLVED
24454 @item gdb.SYMBOL_LOC_UNRESOLVED
24455 Value is at a fixed address, but the address of the variable has to be
24456 determined from the minimal symbol table whenever the variable is
24458 @findex SYMBOL_LOC_OPTIMIZED_OUT
24459 @findex gdb.SYMBOL_LOC_OPTIMIZED_OUT
24460 @item gdb.SYMBOL_LOC_OPTIMIZED_OUT
24461 The value does not actually exist in the program.
24462 @findex SYMBOL_LOC_COMPUTED
24463 @findex gdb.SYMBOL_LOC_COMPUTED
24464 @item gdb.SYMBOL_LOC_COMPUTED
24465 The value's address is a computed location.
24468 @node Symbol Tables In Python
24469 @subsubsection Symbol table representation in Python.
24471 @cindex symbol tables in python
24473 @tindex gdb.Symtab_and_line
24475 Access to symbol table data maintained by @value{GDBN} on the inferior
24476 is exposed to Python via two objects: @code{gdb.Symtab_and_line} and
24477 @code{gdb.Symtab}. Symbol table and line data for a frame is returned
24478 from the @code{find_sal} method in @code{gdb.Frame} object.
24479 @xref{Frames In Python}.
24481 For more information on @value{GDBN}'s symbol table management, see
24482 @ref{Symbols, ,Examining the Symbol Table}, for more information.
24484 A @code{gdb.Symtab_and_line} object has the following attributes:
24487 @defvar Symtab_and_line.symtab
24488 The symbol table object (@code{gdb.Symtab}) for this frame.
24489 This attribute is not writable.
24492 @defvar Symtab_and_line.pc
24493 Indicates the current program counter address. This attribute is not
24497 @defvar Symtab_and_line.line
24498 Indicates the current line number for this object. This
24499 attribute is not writable.
24503 A @code{gdb.Symtab_and_line} object has the following methods:
24506 @defun Symtab_and_line.is_valid ()
24507 Returns @code{True} if the @code{gdb.Symtab_and_line} object is valid,
24508 @code{False} if not. A @code{gdb.Symtab_and_line} object can become
24509 invalid if the Symbol table and line object it refers to does not
24510 exist in @value{GDBN} any longer. All other
24511 @code{gdb.Symtab_and_line} methods will throw an exception if it is
24512 invalid at the time the method is called.
24516 A @code{gdb.Symtab} object has the following attributes:
24519 @defvar Symtab.filename
24520 The symbol table's source filename. This attribute is not writable.
24523 @defvar Symtab.objfile
24524 The symbol table's backing object file. @xref{Objfiles In Python}.
24525 This attribute is not writable.
24529 A @code{gdb.Symtab} object has the following methods:
24532 @defun Symtab.is_valid ()
24533 Returns @code{True} if the @code{gdb.Symtab} object is valid,
24534 @code{False} if not. A @code{gdb.Symtab} object can become invalid if
24535 the symbol table it refers to does not exist in @value{GDBN} any
24536 longer. All other @code{gdb.Symtab} methods will throw an exception
24537 if it is invalid at the time the method is called.
24540 @defun Symtab.fullname ()
24541 Return the symbol table's source absolute file name.
24545 @node Breakpoints In Python
24546 @subsubsection Manipulating breakpoints using Python
24548 @cindex breakpoints in python
24549 @tindex gdb.Breakpoint
24551 Python code can manipulate breakpoints via the @code{gdb.Breakpoint}
24554 @defun Breakpoint.__init__ (spec @r{[}, type @r{[}, wp_class @r{[},internal@r{]]]})
24555 Create a new breakpoint. @var{spec} is a string naming the
24556 location of the breakpoint, or an expression that defines a
24557 watchpoint. The contents can be any location recognized by the
24558 @code{break} command, or in the case of a watchpoint, by the @code{watch}
24559 command. The optional @var{type} denotes the breakpoint to create
24560 from the types defined later in this chapter. This argument can be
24561 either: @code{gdb.BP_BREAKPOINT} or @code{gdb.BP_WATCHPOINT}. @var{type}
24562 defaults to @code{gdb.BP_BREAKPOINT}. The optional @var{internal} argument
24563 allows the breakpoint to become invisible to the user. The breakpoint
24564 will neither be reported when created, nor will it be listed in the
24565 output from @code{info breakpoints} (but will be listed with the
24566 @code{maint info breakpoints} command). The optional @var{wp_class}
24567 argument defines the class of watchpoint to create, if @var{type} is
24568 @code{gdb.BP_WATCHPOINT}. If a watchpoint class is not provided, it is
24569 assumed to be a @code{gdb.WP_WRITE} class.
24572 @defun Breakpoint.stop (self)
24573 The @code{gdb.Breakpoint} class can be sub-classed and, in
24574 particular, you may choose to implement the @code{stop} method.
24575 If this method is defined as a sub-class of @code{gdb.Breakpoint},
24576 it will be called when the inferior reaches any location of a
24577 breakpoint which instantiates that sub-class. If the method returns
24578 @code{True}, the inferior will be stopped at the location of the
24579 breakpoint, otherwise the inferior will continue.
24581 If there are multiple breakpoints at the same location with a
24582 @code{stop} method, each one will be called regardless of the
24583 return status of the previous. This ensures that all @code{stop}
24584 methods have a chance to execute at that location. In this scenario
24585 if one of the methods returns @code{True} but the others return
24586 @code{False}, the inferior will still be stopped.
24588 You should not alter the execution state of the inferior (i.e.@:, step,
24589 next, etc.), alter the current frame context (i.e.@:, change the current
24590 active frame), or alter, add or delete any breakpoint. As a general
24591 rule, you should not alter any data within @value{GDBN} or the inferior
24594 Example @code{stop} implementation:
24597 class MyBreakpoint (gdb.Breakpoint):
24599 inf_val = gdb.parse_and_eval("foo")
24606 The available watchpoint types represented by constants are defined in the
24611 @findex gdb.WP_READ
24613 Read only watchpoint.
24616 @findex gdb.WP_WRITE
24618 Write only watchpoint.
24621 @findex gdb.WP_ACCESS
24622 @item gdb.WP_ACCESS
24623 Read/Write watchpoint.
24626 @defun Breakpoint.is_valid ()
24627 Return @code{True} if this @code{Breakpoint} object is valid,
24628 @code{False} otherwise. A @code{Breakpoint} object can become invalid
24629 if the user deletes the breakpoint. In this case, the object still
24630 exists, but the underlying breakpoint does not. In the cases of
24631 watchpoint scope, the watchpoint remains valid even if execution of the
24632 inferior leaves the scope of that watchpoint.
24635 @defun Breakpoint.delete
24636 Permanently deletes the @value{GDBN} breakpoint. This also
24637 invalidates the Python @code{Breakpoint} object. Any further access
24638 to this object's attributes or methods will raise an error.
24641 @defvar Breakpoint.enabled
24642 This attribute is @code{True} if the breakpoint is enabled, and
24643 @code{False} otherwise. This attribute is writable.
24646 @defvar Breakpoint.silent
24647 This attribute is @code{True} if the breakpoint is silent, and
24648 @code{False} otherwise. This attribute is writable.
24650 Note that a breakpoint can also be silent if it has commands and the
24651 first command is @code{silent}. This is not reported by the
24652 @code{silent} attribute.
24655 @defvar Breakpoint.thread
24656 If the breakpoint is thread-specific, this attribute holds the thread
24657 id. If the breakpoint is not thread-specific, this attribute is
24658 @code{None}. This attribute is writable.
24661 @defvar Breakpoint.task
24662 If the breakpoint is Ada task-specific, this attribute holds the Ada task
24663 id. If the breakpoint is not task-specific (or the underlying
24664 language is not Ada), this attribute is @code{None}. This attribute
24668 @defvar Breakpoint.ignore_count
24669 This attribute holds the ignore count for the breakpoint, an integer.
24670 This attribute is writable.
24673 @defvar Breakpoint.number
24674 This attribute holds the breakpoint's number --- the identifier used by
24675 the user to manipulate the breakpoint. This attribute is not writable.
24678 @defvar Breakpoint.type
24679 This attribute holds the breakpoint's type --- the identifier used to
24680 determine the actual breakpoint type or use-case. This attribute is not
24684 @defvar Breakpoint.visible
24685 This attribute tells whether the breakpoint is visible to the user
24686 when set, or when the @samp{info breakpoints} command is run. This
24687 attribute is not writable.
24690 The available types are represented by constants defined in the @code{gdb}
24694 @findex BP_BREAKPOINT
24695 @findex gdb.BP_BREAKPOINT
24696 @item gdb.BP_BREAKPOINT
24697 Normal code breakpoint.
24699 @findex BP_WATCHPOINT
24700 @findex gdb.BP_WATCHPOINT
24701 @item gdb.BP_WATCHPOINT
24702 Watchpoint breakpoint.
24704 @findex BP_HARDWARE_WATCHPOINT
24705 @findex gdb.BP_HARDWARE_WATCHPOINT
24706 @item gdb.BP_HARDWARE_WATCHPOINT
24707 Hardware assisted watchpoint.
24709 @findex BP_READ_WATCHPOINT
24710 @findex gdb.BP_READ_WATCHPOINT
24711 @item gdb.BP_READ_WATCHPOINT
24712 Hardware assisted read watchpoint.
24714 @findex BP_ACCESS_WATCHPOINT
24715 @findex gdb.BP_ACCESS_WATCHPOINT
24716 @item gdb.BP_ACCESS_WATCHPOINT
24717 Hardware assisted access watchpoint.
24720 @defvar Breakpoint.hit_count
24721 This attribute holds the hit count for the breakpoint, an integer.
24722 This attribute is writable, but currently it can only be set to zero.
24725 @defvar Breakpoint.location
24726 This attribute holds the location of the breakpoint, as specified by
24727 the user. It is a string. If the breakpoint does not have a location
24728 (that is, it is a watchpoint) the attribute's value is @code{None}. This
24729 attribute is not writable.
24732 @defvar Breakpoint.expression
24733 This attribute holds a breakpoint expression, as specified by
24734 the user. It is a string. If the breakpoint does not have an
24735 expression (the breakpoint is not a watchpoint) the attribute's value
24736 is @code{None}. This attribute is not writable.
24739 @defvar Breakpoint.condition
24740 This attribute holds the condition of the breakpoint, as specified by
24741 the user. It is a string. If there is no condition, this attribute's
24742 value is @code{None}. This attribute is writable.
24745 @defvar Breakpoint.commands
24746 This attribute holds the commands attached to the breakpoint. If
24747 there are commands, this attribute's value is a string holding all the
24748 commands, separated by newlines. If there are no commands, this
24749 attribute is @code{None}. This attribute is not writable.
24752 @node Finish Breakpoints in Python
24753 @subsubsection Finish Breakpoints
24755 @cindex python finish breakpoints
24756 @tindex gdb.FinishBreakpoint
24758 A finish breakpoint is a temporary breakpoint set at the return address of
24759 a frame, based on the @code{finish} command. @code{gdb.FinishBreakpoint}
24760 extends @code{gdb.Breakpoint}. The underlying breakpoint will be disabled
24761 and deleted when the execution will run out of the breakpoint scope (i.e.@:
24762 @code{Breakpoint.stop} or @code{FinishBreakpoint.out_of_scope} triggered).
24763 Finish breakpoints are thread specific and must be create with the right
24766 @defun FinishBreakpoint.__init__ (@r{[}frame@r{]} @r{[}, internal@r{]})
24767 Create a finish breakpoint at the return address of the @code{gdb.Frame}
24768 object @var{frame}. If @var{frame} is not provided, this defaults to the
24769 newest frame. The optional @var{internal} argument allows the breakpoint to
24770 become invisible to the user. @xref{Breakpoints In Python}, for further
24771 details about this argument.
24774 @defun FinishBreakpoint.out_of_scope (self)
24775 In some circumstances (e.g.@: @code{longjmp}, C@t{++} exceptions, @value{GDBN}
24776 @code{return} command, @dots{}), a function may not properly terminate, and
24777 thus never hit the finish breakpoint. When @value{GDBN} notices such a
24778 situation, the @code{out_of_scope} callback will be triggered.
24780 You may want to sub-class @code{gdb.FinishBreakpoint} and override this
24784 class MyFinishBreakpoint (gdb.FinishBreakpoint)
24786 print "normal finish"
24789 def out_of_scope ():
24790 print "abnormal finish"
24794 @defvar FinishBreakpoint.return_value
24795 When @value{GDBN} is stopped at a finish breakpoint and the frame
24796 used to build the @code{gdb.FinishBreakpoint} object had debug symbols, this
24797 attribute will contain a @code{gdb.Value} object corresponding to the return
24798 value of the function. The value will be @code{None} if the function return
24799 type is @code{void} or if the return value was not computable. This attribute
24803 @node Lazy Strings In Python
24804 @subsubsection Python representation of lazy strings.
24806 @cindex lazy strings in python
24807 @tindex gdb.LazyString
24809 A @dfn{lazy string} is a string whose contents is not retrieved or
24810 encoded until it is needed.
24812 A @code{gdb.LazyString} is represented in @value{GDBN} as an
24813 @code{address} that points to a region of memory, an @code{encoding}
24814 that will be used to encode that region of memory, and a @code{length}
24815 to delimit the region of memory that represents the string. The
24816 difference between a @code{gdb.LazyString} and a string wrapped within
24817 a @code{gdb.Value} is that a @code{gdb.LazyString} will be treated
24818 differently by @value{GDBN} when printing. A @code{gdb.LazyString} is
24819 retrieved and encoded during printing, while a @code{gdb.Value}
24820 wrapping a string is immediately retrieved and encoded on creation.
24822 A @code{gdb.LazyString} object has the following functions:
24824 @defun LazyString.value ()
24825 Convert the @code{gdb.LazyString} to a @code{gdb.Value}. This value
24826 will point to the string in memory, but will lose all the delayed
24827 retrieval, encoding and handling that @value{GDBN} applies to a
24828 @code{gdb.LazyString}.
24831 @defvar LazyString.address
24832 This attribute holds the address of the string. This attribute is not
24836 @defvar LazyString.length
24837 This attribute holds the length of the string in characters. If the
24838 length is -1, then the string will be fetched and encoded up to the
24839 first null of appropriate width. This attribute is not writable.
24842 @defvar LazyString.encoding
24843 This attribute holds the encoding that will be applied to the string
24844 when the string is printed by @value{GDBN}. If the encoding is not
24845 set, or contains an empty string, then @value{GDBN} will select the
24846 most appropriate encoding when the string is printed. This attribute
24850 @defvar LazyString.type
24851 This attribute holds the type that is represented by the lazy string's
24852 type. For a lazy string this will always be a pointer type. To
24853 resolve this to the lazy string's character type, use the type's
24854 @code{target} method. @xref{Types In Python}. This attribute is not
24859 @subsection Auto-loading
24860 @cindex auto-loading, Python
24862 When a new object file is read (for example, due to the @code{file}
24863 command, or because the inferior has loaded a shared library),
24864 @value{GDBN} will look for Python support scripts in several ways:
24865 @file{@var{objfile}-gdb.py} (@pxref{objfile-gdb.py file})
24866 and @code{.debug_gdb_scripts} section
24867 (@pxref{dotdebug_gdb_scripts section}).
24869 The auto-loading feature is useful for supplying application-specific
24870 debugging commands and scripts.
24872 Auto-loading can be enabled or disabled,
24873 and the list of auto-loaded scripts can be printed.
24876 @kindex set auto-load-scripts
24877 @item set auto-load-scripts [yes|no]
24878 Enable or disable the auto-loading of Python scripts.
24880 @kindex show auto-load-scripts
24881 @item show auto-load-scripts
24882 Show whether auto-loading of Python scripts is enabled or disabled.
24884 @kindex info auto-load-scripts
24885 @cindex print list of auto-loaded scripts
24886 @item info auto-load-scripts [@var{regexp}]
24887 Print the list of all scripts that @value{GDBN} auto-loaded.
24889 Also printed is the list of scripts that were mentioned in
24890 the @code{.debug_gdb_scripts} section and were not found
24891 (@pxref{dotdebug_gdb_scripts section}).
24892 This is useful because their names are not printed when @value{GDBN}
24893 tries to load them and fails. There may be many of them, and printing
24894 an error message for each one is problematic.
24896 If @var{regexp} is supplied only scripts with matching names are printed.
24901 (gdb) info auto-load-scripts
24903 Yes py-section-script.py
24904 full name: /tmp/py-section-script.py
24905 Missing my-foo-pretty-printers.py
24909 When reading an auto-loaded file, @value{GDBN} sets the
24910 @dfn{current objfile}. This is available via the @code{gdb.current_objfile}
24911 function (@pxref{Objfiles In Python}). This can be useful for
24912 registering objfile-specific pretty-printers.
24915 * objfile-gdb.py file:: The @file{@var{objfile}-gdb.py} file
24916 * dotdebug_gdb_scripts section:: The @code{.debug_gdb_scripts} section
24917 * Which flavor to choose?::
24920 @node objfile-gdb.py file
24921 @subsubsection The @file{@var{objfile}-gdb.py} file
24922 @cindex @file{@var{objfile}-gdb.py}
24924 When a new object file is read, @value{GDBN} looks for
24925 a file named @file{@var{objfile}-gdb.py},
24926 where @var{objfile} is the object file's real name, formed by ensuring
24927 that the file name is absolute, following all symlinks, and resolving
24928 @code{.} and @code{..} components. If this file exists and is
24929 readable, @value{GDBN} will evaluate it as a Python script.
24931 If this file does not exist, and if the parameter
24932 @code{debug-file-directory} is set (@pxref{Separate Debug Files}),
24933 then @value{GDBN} will look for @var{real-name} in all of the
24934 directories mentioned in the value of @code{debug-file-directory}.
24936 Finally, if this file does not exist, then @value{GDBN} will look for
24937 a file named @file{@var{data-directory}/auto-load/@var{real-name}}, where
24938 @var{data-directory} is @value{GDBN}'s data directory (available via
24939 @code{show data-directory}, @pxref{Data Files}), and @var{real-name}
24940 is the object file's real name, as described above.
24942 @value{GDBN} does not track which files it has already auto-loaded this way.
24943 @value{GDBN} will load the associated script every time the corresponding
24944 @var{objfile} is opened.
24945 So your @file{-gdb.py} file should be careful to avoid errors if it
24946 is evaluated more than once.
24948 @node dotdebug_gdb_scripts section
24949 @subsubsection The @code{.debug_gdb_scripts} section
24950 @cindex @code{.debug_gdb_scripts} section
24952 For systems using file formats like ELF and COFF,
24953 when @value{GDBN} loads a new object file
24954 it will look for a special section named @samp{.debug_gdb_scripts}.
24955 If this section exists, its contents is a list of names of scripts to load.
24957 @value{GDBN} will look for each specified script file first in the
24958 current directory and then along the source search path
24959 (@pxref{Source Path, ,Specifying Source Directories}),
24960 except that @file{$cdir} is not searched, since the compilation
24961 directory is not relevant to scripts.
24963 Entries can be placed in section @code{.debug_gdb_scripts} with,
24964 for example, this GCC macro:
24967 /* Note: The "MS" section flags are to remove duplicates. */
24968 #define DEFINE_GDB_SCRIPT(script_name) \
24970 .pushsection \".debug_gdb_scripts\", \"MS\",@@progbits,1\n\
24972 .asciz \"" script_name "\"\n\
24978 Then one can reference the macro in a header or source file like this:
24981 DEFINE_GDB_SCRIPT ("my-app-scripts.py")
24984 The script name may include directories if desired.
24986 If the macro is put in a header, any application or library
24987 using this header will get a reference to the specified script.
24989 @node Which flavor to choose?
24990 @subsubsection Which flavor to choose?
24992 Given the multiple ways of auto-loading Python scripts, it might not always
24993 be clear which one to choose. This section provides some guidance.
24995 Benefits of the @file{-gdb.py} way:
24999 Can be used with file formats that don't support multiple sections.
25002 Ease of finding scripts for public libraries.
25004 Scripts specified in the @code{.debug_gdb_scripts} section are searched for
25005 in the source search path.
25006 For publicly installed libraries, e.g., @file{libstdc++}, there typically
25007 isn't a source directory in which to find the script.
25010 Doesn't require source code additions.
25013 Benefits of the @code{.debug_gdb_scripts} way:
25017 Works with static linking.
25019 Scripts for libraries done the @file{-gdb.py} way require an objfile to
25020 trigger their loading. When an application is statically linked the only
25021 objfile available is the executable, and it is cumbersome to attach all the
25022 scripts from all the input libraries to the executable's @file{-gdb.py} script.
25025 Works with classes that are entirely inlined.
25027 Some classes can be entirely inlined, and thus there may not be an associated
25028 shared library to attach a @file{-gdb.py} script to.
25031 Scripts needn't be copied out of the source tree.
25033 In some circumstances, apps can be built out of large collections of internal
25034 libraries, and the build infrastructure necessary to install the
25035 @file{-gdb.py} scripts in a place where @value{GDBN} can find them is
25036 cumbersome. It may be easier to specify the scripts in the
25037 @code{.debug_gdb_scripts} section as relative paths, and add a path to the
25038 top of the source tree to the source search path.
25041 @node Python modules
25042 @subsection Python modules
25043 @cindex python modules
25045 @value{GDBN} comes with several modules to assist writing Python code.
25048 * gdb.printing:: Building and registering pretty-printers.
25049 * gdb.types:: Utilities for working with types.
25050 * gdb.prompt:: Utilities for prompt value substitution.
25054 @subsubsection gdb.printing
25055 @cindex gdb.printing
25057 This module provides a collection of utilities for working with
25061 @item PrettyPrinter (@var{name}, @var{subprinters}=None)
25062 This class specifies the API that makes @samp{info pretty-printer},
25063 @samp{enable pretty-printer} and @samp{disable pretty-printer} work.
25064 Pretty-printers should generally inherit from this class.
25066 @item SubPrettyPrinter (@var{name})
25067 For printers that handle multiple types, this class specifies the
25068 corresponding API for the subprinters.
25070 @item RegexpCollectionPrettyPrinter (@var{name})
25071 Utility class for handling multiple printers, all recognized via
25072 regular expressions.
25073 @xref{Writing a Pretty-Printer}, for an example.
25075 @item FlagEnumerationPrinter (@var{name})
25076 A pretty-printer which handles printing of @code{enum} values. Unlike
25077 @value{GDBN}'s built-in @code{enum} printing, this printer attempts to
25078 work properly when there is some overlap between the enumeration
25079 constants. @var{name} is the name of the printer and also the name of
25080 the @code{enum} type to look up.
25082 @item register_pretty_printer (@var{obj}, @var{printer}, @var{replace}=False)
25083 Register @var{printer} with the pretty-printer list of @var{obj}.
25084 If @var{replace} is @code{True} then any existing copy of the printer
25085 is replaced. Otherwise a @code{RuntimeError} exception is raised
25086 if a printer with the same name already exists.
25090 @subsubsection gdb.types
25093 This module provides a collection of utilities for working with
25094 @code{gdb.Types} objects.
25097 @item get_basic_type (@var{type})
25098 Return @var{type} with const and volatile qualifiers stripped,
25099 and with typedefs and C@t{++} references converted to the underlying type.
25104 typedef const int const_int;
25106 const_int& foo_ref (foo);
25107 int main () @{ return 0; @}
25114 (gdb) python import gdb.types
25115 (gdb) python foo_ref = gdb.parse_and_eval("foo_ref")
25116 (gdb) python print gdb.types.get_basic_type(foo_ref.type)
25120 @item has_field (@var{type}, @var{field})
25121 Return @code{True} if @var{type}, assumed to be a type with fields
25122 (e.g., a structure or union), has field @var{field}.
25124 @item make_enum_dict (@var{enum_type})
25125 Return a Python @code{dictionary} type produced from @var{enum_type}.
25127 @item deep_items (@var{type})
25128 Returns a Python iterator similar to the standard
25129 @code{gdb.Type.iteritems} method, except that the iterator returned
25130 by @code{deep_items} will recursively traverse anonymous struct or
25131 union fields. For example:
25145 Then in @value{GDBN}:
25147 (@value{GDBP}) python import gdb.types
25148 (@value{GDBP}) python struct_a = gdb.lookup_type("struct A")
25149 (@value{GDBP}) python print struct_a.keys ()
25151 (@value{GDBP}) python print [k for k,v in gdb.types.deep_items(struct_a)]
25152 @{['a', 'b0', 'b1']@}
25158 @subsubsection gdb.prompt
25161 This module provides a method for prompt value-substitution.
25164 @item substitute_prompt (@var{string})
25165 Return @var{string} with escape sequences substituted by values. Some
25166 escape sequences take arguments. You can specify arguments inside
25167 ``@{@}'' immediately following the escape sequence.
25169 The escape sequences you can pass to this function are:
25173 Substitute a backslash.
25175 Substitute an ESC character.
25177 Substitute the selected frame; an argument names a frame parameter.
25179 Substitute a newline.
25181 Substitute a parameter's value; the argument names the parameter.
25183 Substitute a carriage return.
25185 Substitute the selected thread; an argument names a thread parameter.
25187 Substitute the version of GDB.
25189 Substitute the current working directory.
25191 Begin a sequence of non-printing characters. These sequences are
25192 typically used with the ESC character, and are not counted in the string
25193 length. Example: ``\[\e[0;34m\](gdb)\[\e[0m\]'' will return a
25194 blue-colored ``(gdb)'' prompt where the length is five.
25196 End a sequence of non-printing characters.
25202 substitute_prompt (``frame: \f,
25203 print arguments: \p@{print frame-arguments@}'')
25206 @exdent will return the string:
25209 "frame: main, print arguments: scalars"
25214 @section Creating new spellings of existing commands
25215 @cindex aliases for commands
25217 It is often useful to define alternate spellings of existing commands.
25218 For example, if a new @value{GDBN} command defined in Python has
25219 a long name to type, it is handy to have an abbreviated version of it
25220 that involves less typing.
25222 @value{GDBN} itself uses aliases. For example @samp{s} is an alias
25223 of the @samp{step} command even though it is otherwise an ambiguous
25224 abbreviation of other commands like @samp{set} and @samp{show}.
25226 Aliases are also used to provide shortened or more common versions
25227 of multi-word commands. For example, @value{GDBN} provides the
25228 @samp{tty} alias of the @samp{set inferior-tty} command.
25230 You can define a new alias with the @samp{alias} command.
25235 @item alias [-a] [--] @var{ALIAS} = @var{COMMAND}
25239 @var{ALIAS} specifies the name of the new alias.
25240 Each word of @var{ALIAS} must consist of letters, numbers, dashes and
25243 @var{COMMAND} specifies the name of an existing command
25244 that is being aliased.
25246 The @samp{-a} option specifies that the new alias is an abbreviation
25247 of the command. Abbreviations are not shown in command
25248 lists displayed by the @samp{help} command.
25250 The @samp{--} option specifies the end of options,
25251 and is useful when @var{ALIAS} begins with a dash.
25253 Here is a simple example showing how to make an abbreviation
25254 of a command so that there is less to type.
25255 Suppose you were tired of typing @samp{disas}, the current
25256 shortest unambiguous abbreviation of the @samp{disassemble} command
25257 and you wanted an even shorter version named @samp{di}.
25258 The following will accomplish this.
25261 (gdb) alias -a di = disas
25264 Note that aliases are different from user-defined commands.
25265 With a user-defined command, you also need to write documentation
25266 for it with the @samp{document} command.
25267 An alias automatically picks up the documentation of the existing command.
25269 Here is an example where we make @samp{elms} an abbreviation of
25270 @samp{elements} in the @samp{set print elements} command.
25271 This is to show that you can make an abbreviation of any part
25275 (gdb) alias -a set print elms = set print elements
25276 (gdb) alias -a show print elms = show print elements
25277 (gdb) set p elms 20
25279 Limit on string chars or array elements to print is 200.
25282 Note that if you are defining an alias of a @samp{set} command,
25283 and you want to have an alias for the corresponding @samp{show}
25284 command, then you need to define the latter separately.
25286 Unambiguously abbreviated commands are allowed in @var{COMMAND} and
25287 @var{ALIAS}, just as they are normally.
25290 (gdb) alias -a set pr elms = set p ele
25293 Finally, here is an example showing the creation of a one word
25294 alias for a more complex command.
25295 This creates alias @samp{spe} of the command @samp{set print elements}.
25298 (gdb) alias spe = set print elements
25303 @chapter Command Interpreters
25304 @cindex command interpreters
25306 @value{GDBN} supports multiple command interpreters, and some command
25307 infrastructure to allow users or user interface writers to switch
25308 between interpreters or run commands in other interpreters.
25310 @value{GDBN} currently supports two command interpreters, the console
25311 interpreter (sometimes called the command-line interpreter or @sc{cli})
25312 and the machine interface interpreter (or @sc{gdb/mi}). This manual
25313 describes both of these interfaces in great detail.
25315 By default, @value{GDBN} will start with the console interpreter.
25316 However, the user may choose to start @value{GDBN} with another
25317 interpreter by specifying the @option{-i} or @option{--interpreter}
25318 startup options. Defined interpreters include:
25322 @cindex console interpreter
25323 The traditional console or command-line interpreter. This is the most often
25324 used interpreter with @value{GDBN}. With no interpreter specified at runtime,
25325 @value{GDBN} will use this interpreter.
25328 @cindex mi interpreter
25329 The newest @sc{gdb/mi} interface (currently @code{mi2}). Used primarily
25330 by programs wishing to use @value{GDBN} as a backend for a debugger GUI
25331 or an IDE. For more information, see @ref{GDB/MI, ,The @sc{gdb/mi}
25335 @cindex mi2 interpreter
25336 The current @sc{gdb/mi} interface.
25339 @cindex mi1 interpreter
25340 The @sc{gdb/mi} interface included in @value{GDBN} 5.1, 5.2, and 5.3.
25344 @cindex invoke another interpreter
25345 The interpreter being used by @value{GDBN} may not be dynamically
25346 switched at runtime. Although possible, this could lead to a very
25347 precarious situation. Consider an IDE using @sc{gdb/mi}. If a user
25348 enters the command "interpreter-set console" in a console view,
25349 @value{GDBN} would switch to using the console interpreter, rendering
25350 the IDE inoperable!
25352 @kindex interpreter-exec
25353 Although you may only choose a single interpreter at startup, you may execute
25354 commands in any interpreter from the current interpreter using the appropriate
25355 command. If you are running the console interpreter, simply use the
25356 @code{interpreter-exec} command:
25359 interpreter-exec mi "-data-list-register-names"
25362 @sc{gdb/mi} has a similar command, although it is only available in versions of
25363 @value{GDBN} which support @sc{gdb/mi} version 2 (or greater).
25366 @chapter @value{GDBN} Text User Interface
25368 @cindex Text User Interface
25371 * TUI Overview:: TUI overview
25372 * TUI Keys:: TUI key bindings
25373 * TUI Single Key Mode:: TUI single key mode
25374 * TUI Commands:: TUI-specific commands
25375 * TUI Configuration:: TUI configuration variables
25378 The @value{GDBN} Text User Interface (TUI) is a terminal
25379 interface which uses the @code{curses} library to show the source
25380 file, the assembly output, the program registers and @value{GDBN}
25381 commands in separate text windows. The TUI mode is supported only
25382 on platforms where a suitable version of the @code{curses} library
25385 The TUI mode is enabled by default when you invoke @value{GDBN} as
25386 @samp{@value{GDBP} -tui}.
25387 You can also switch in and out of TUI mode while @value{GDBN} runs by
25388 using various TUI commands and key bindings, such as @kbd{C-x C-a}.
25389 @xref{TUI Keys, ,TUI Key Bindings}.
25392 @section TUI Overview
25394 In TUI mode, @value{GDBN} can display several text windows:
25398 This window is the @value{GDBN} command window with the @value{GDBN}
25399 prompt and the @value{GDBN} output. The @value{GDBN} input is still
25400 managed using readline.
25403 The source window shows the source file of the program. The current
25404 line and active breakpoints are displayed in this window.
25407 The assembly window shows the disassembly output of the program.
25410 This window shows the processor registers. Registers are highlighted
25411 when their values change.
25414 The source and assembly windows show the current program position
25415 by highlighting the current line and marking it with a @samp{>} marker.
25416 Breakpoints are indicated with two markers. The first marker
25417 indicates the breakpoint type:
25421 Breakpoint which was hit at least once.
25424 Breakpoint which was never hit.
25427 Hardware breakpoint which was hit at least once.
25430 Hardware breakpoint which was never hit.
25433 The second marker indicates whether the breakpoint is enabled or not:
25437 Breakpoint is enabled.
25440 Breakpoint is disabled.
25443 The source, assembly and register windows are updated when the current
25444 thread changes, when the frame changes, or when the program counter
25447 These windows are not all visible at the same time. The command
25448 window is always visible. The others can be arranged in several
25459 source and assembly,
25462 source and registers, or
25465 assembly and registers.
25468 A status line above the command window shows the following information:
25472 Indicates the current @value{GDBN} target.
25473 (@pxref{Targets, ,Specifying a Debugging Target}).
25476 Gives the current process or thread number.
25477 When no process is being debugged, this field is set to @code{No process}.
25480 Gives the current function name for the selected frame.
25481 The name is demangled if demangling is turned on (@pxref{Print Settings}).
25482 When there is no symbol corresponding to the current program counter,
25483 the string @code{??} is displayed.
25486 Indicates the current line number for the selected frame.
25487 When the current line number is not known, the string @code{??} is displayed.
25490 Indicates the current program counter address.
25494 @section TUI Key Bindings
25495 @cindex TUI key bindings
25497 The TUI installs several key bindings in the readline keymaps
25498 @ifset SYSTEM_READLINE
25499 (@pxref{Command Line Editing, , , rluserman, GNU Readline Library}).
25501 @ifclear SYSTEM_READLINE
25502 (@pxref{Command Line Editing}).
25504 The following key bindings are installed for both TUI mode and the
25505 @value{GDBN} standard mode.
25514 Enter or leave the TUI mode. When leaving the TUI mode,
25515 the curses window management stops and @value{GDBN} operates using
25516 its standard mode, writing on the terminal directly. When reentering
25517 the TUI mode, control is given back to the curses windows.
25518 The screen is then refreshed.
25522 Use a TUI layout with only one window. The layout will
25523 either be @samp{source} or @samp{assembly}. When the TUI mode
25524 is not active, it will switch to the TUI mode.
25526 Think of this key binding as the Emacs @kbd{C-x 1} binding.
25530 Use a TUI layout with at least two windows. When the current
25531 layout already has two windows, the next layout with two windows is used.
25532 When a new layout is chosen, one window will always be common to the
25533 previous layout and the new one.
25535 Think of it as the Emacs @kbd{C-x 2} binding.
25539 Change the active window. The TUI associates several key bindings
25540 (like scrolling and arrow keys) with the active window. This command
25541 gives the focus to the next TUI window.
25543 Think of it as the Emacs @kbd{C-x o} binding.
25547 Switch in and out of the TUI SingleKey mode that binds single
25548 keys to @value{GDBN} commands (@pxref{TUI Single Key Mode}).
25551 The following key bindings only work in the TUI mode:
25556 Scroll the active window one page up.
25560 Scroll the active window one page down.
25564 Scroll the active window one line up.
25568 Scroll the active window one line down.
25572 Scroll the active window one column left.
25576 Scroll the active window one column right.
25580 Refresh the screen.
25583 Because the arrow keys scroll the active window in the TUI mode, they
25584 are not available for their normal use by readline unless the command
25585 window has the focus. When another window is active, you must use
25586 other readline key bindings such as @kbd{C-p}, @kbd{C-n}, @kbd{C-b}
25587 and @kbd{C-f} to control the command window.
25589 @node TUI Single Key Mode
25590 @section TUI Single Key Mode
25591 @cindex TUI single key mode
25593 The TUI also provides a @dfn{SingleKey} mode, which binds several
25594 frequently used @value{GDBN} commands to single keys. Type @kbd{C-x s} to
25595 switch into this mode, where the following key bindings are used:
25598 @kindex c @r{(SingleKey TUI key)}
25602 @kindex d @r{(SingleKey TUI key)}
25606 @kindex f @r{(SingleKey TUI key)}
25610 @kindex n @r{(SingleKey TUI key)}
25614 @kindex q @r{(SingleKey TUI key)}
25616 exit the SingleKey mode.
25618 @kindex r @r{(SingleKey TUI key)}
25622 @kindex s @r{(SingleKey TUI key)}
25626 @kindex u @r{(SingleKey TUI key)}
25630 @kindex v @r{(SingleKey TUI key)}
25634 @kindex w @r{(SingleKey TUI key)}
25639 Other keys temporarily switch to the @value{GDBN} command prompt.
25640 The key that was pressed is inserted in the editing buffer so that
25641 it is possible to type most @value{GDBN} commands without interaction
25642 with the TUI SingleKey mode. Once the command is entered the TUI
25643 SingleKey mode is restored. The only way to permanently leave
25644 this mode is by typing @kbd{q} or @kbd{C-x s}.
25648 @section TUI-specific Commands
25649 @cindex TUI commands
25651 The TUI has specific commands to control the text windows.
25652 These commands are always available, even when @value{GDBN} is not in
25653 the TUI mode. When @value{GDBN} is in the standard mode, most
25654 of these commands will automatically switch to the TUI mode.
25656 Note that if @value{GDBN}'s @code{stdout} is not connected to a
25657 terminal, or @value{GDBN} has been started with the machine interface
25658 interpreter (@pxref{GDB/MI, ,The @sc{gdb/mi} Interface}), most of
25659 these commands will fail with an error, because it would not be
25660 possible or desirable to enable curses window management.
25665 List and give the size of all displayed windows.
25669 Display the next layout.
25672 Display the previous layout.
25675 Display the source window only.
25678 Display the assembly window only.
25681 Display the source and assembly window.
25684 Display the register window together with the source or assembly window.
25688 Make the next window active for scrolling.
25691 Make the previous window active for scrolling.
25694 Make the source window active for scrolling.
25697 Make the assembly window active for scrolling.
25700 Make the register window active for scrolling.
25703 Make the command window active for scrolling.
25707 Refresh the screen. This is similar to typing @kbd{C-L}.
25709 @item tui reg float
25711 Show the floating point registers in the register window.
25713 @item tui reg general
25714 Show the general registers in the register window.
25717 Show the next register group. The list of register groups as well as
25718 their order is target specific. The predefined register groups are the
25719 following: @code{general}, @code{float}, @code{system}, @code{vector},
25720 @code{all}, @code{save}, @code{restore}.
25722 @item tui reg system
25723 Show the system registers in the register window.
25727 Update the source window and the current execution point.
25729 @item winheight @var{name} +@var{count}
25730 @itemx winheight @var{name} -@var{count}
25732 Change the height of the window @var{name} by @var{count}
25733 lines. Positive counts increase the height, while negative counts
25736 @item tabset @var{nchars}
25738 Set the width of tab stops to be @var{nchars} characters.
25741 @node TUI Configuration
25742 @section TUI Configuration Variables
25743 @cindex TUI configuration variables
25745 Several configuration variables control the appearance of TUI windows.
25748 @item set tui border-kind @var{kind}
25749 @kindex set tui border-kind
25750 Select the border appearance for the source, assembly and register windows.
25751 The possible values are the following:
25754 Use a space character to draw the border.
25757 Use @sc{ascii} characters @samp{+}, @samp{-} and @samp{|} to draw the border.
25760 Use the Alternate Character Set to draw the border. The border is
25761 drawn using character line graphics if the terminal supports them.
25764 @item set tui border-mode @var{mode}
25765 @kindex set tui border-mode
25766 @itemx set tui active-border-mode @var{mode}
25767 @kindex set tui active-border-mode
25768 Select the display attributes for the borders of the inactive windows
25769 or the active window. The @var{mode} can be one of the following:
25772 Use normal attributes to display the border.
25778 Use reverse video mode.
25781 Use half bright mode.
25783 @item half-standout
25784 Use half bright and standout mode.
25787 Use extra bright or bold mode.
25789 @item bold-standout
25790 Use extra bright or bold and standout mode.
25795 @chapter Using @value{GDBN} under @sc{gnu} Emacs
25798 @cindex @sc{gnu} Emacs
25799 A special interface allows you to use @sc{gnu} Emacs to view (and
25800 edit) the source files for the program you are debugging with
25803 To use this interface, use the command @kbd{M-x gdb} in Emacs. Give the
25804 executable file you want to debug as an argument. This command starts
25805 @value{GDBN} as a subprocess of Emacs, with input and output through a newly
25806 created Emacs buffer.
25807 @c (Do not use the @code{-tui} option to run @value{GDBN} from Emacs.)
25809 Running @value{GDBN} under Emacs can be just like running @value{GDBN} normally except for two
25814 All ``terminal'' input and output goes through an Emacs buffer, called
25817 This applies both to @value{GDBN} commands and their output, and to the input
25818 and output done by the program you are debugging.
25820 This is useful because it means that you can copy the text of previous
25821 commands and input them again; you can even use parts of the output
25824 All the facilities of Emacs' Shell mode are available for interacting
25825 with your program. In particular, you can send signals the usual
25826 way---for example, @kbd{C-c C-c} for an interrupt, @kbd{C-c C-z} for a
25830 @value{GDBN} displays source code through Emacs.
25832 Each time @value{GDBN} displays a stack frame, Emacs automatically finds the
25833 source file for that frame and puts an arrow (@samp{=>}) at the
25834 left margin of the current line. Emacs uses a separate buffer for
25835 source display, and splits the screen to show both your @value{GDBN} session
25838 Explicit @value{GDBN} @code{list} or search commands still produce output as
25839 usual, but you probably have no reason to use them from Emacs.
25842 We call this @dfn{text command mode}. Emacs 22.1, and later, also uses
25843 a graphical mode, enabled by default, which provides further buffers
25844 that can control the execution and describe the state of your program.
25845 @xref{GDB Graphical Interface,,, Emacs, The @sc{gnu} Emacs Manual}.
25847 If you specify an absolute file name when prompted for the @kbd{M-x
25848 gdb} argument, then Emacs sets your current working directory to where
25849 your program resides. If you only specify the file name, then Emacs
25850 sets your current working directory to the directory associated
25851 with the previous buffer. In this case, @value{GDBN} may find your
25852 program by searching your environment's @code{PATH} variable, but on
25853 some operating systems it might not find the source. So, although the
25854 @value{GDBN} input and output session proceeds normally, the auxiliary
25855 buffer does not display the current source and line of execution.
25857 The initial working directory of @value{GDBN} is printed on the top
25858 line of the GUD buffer and this serves as a default for the commands
25859 that specify files for @value{GDBN} to operate on. @xref{Files,
25860 ,Commands to Specify Files}.
25862 By default, @kbd{M-x gdb} calls the program called @file{gdb}. If you
25863 need to call @value{GDBN} by a different name (for example, if you
25864 keep several configurations around, with different names) you can
25865 customize the Emacs variable @code{gud-gdb-command-name} to run the
25868 In the GUD buffer, you can use these special Emacs commands in
25869 addition to the standard Shell mode commands:
25873 Describe the features of Emacs' GUD Mode.
25876 Execute to another source line, like the @value{GDBN} @code{step} command; also
25877 update the display window to show the current file and location.
25880 Execute to next source line in this function, skipping all function
25881 calls, like the @value{GDBN} @code{next} command. Then update the display window
25882 to show the current file and location.
25885 Execute one instruction, like the @value{GDBN} @code{stepi} command; update
25886 display window accordingly.
25889 Execute until exit from the selected stack frame, like the @value{GDBN}
25890 @code{finish} command.
25893 Continue execution of your program, like the @value{GDBN} @code{continue}
25897 Go up the number of frames indicated by the numeric argument
25898 (@pxref{Arguments, , Numeric Arguments, Emacs, The @sc{gnu} Emacs Manual}),
25899 like the @value{GDBN} @code{up} command.
25902 Go down the number of frames indicated by the numeric argument, like the
25903 @value{GDBN} @code{down} command.
25906 In any source file, the Emacs command @kbd{C-x @key{SPC}} (@code{gud-break})
25907 tells @value{GDBN} to set a breakpoint on the source line point is on.
25909 In text command mode, if you type @kbd{M-x speedbar}, Emacs displays a
25910 separate frame which shows a backtrace when the GUD buffer is current.
25911 Move point to any frame in the stack and type @key{RET} to make it
25912 become the current frame and display the associated source in the
25913 source buffer. Alternatively, click @kbd{Mouse-2} to make the
25914 selected frame become the current one. In graphical mode, the
25915 speedbar displays watch expressions.
25917 If you accidentally delete the source-display buffer, an easy way to get
25918 it back is to type the command @code{f} in the @value{GDBN} buffer, to
25919 request a frame display; when you run under Emacs, this recreates
25920 the source buffer if necessary to show you the context of the current
25923 The source files displayed in Emacs are in ordinary Emacs buffers
25924 which are visiting the source files in the usual way. You can edit
25925 the files with these buffers if you wish; but keep in mind that @value{GDBN}
25926 communicates with Emacs in terms of line numbers. If you add or
25927 delete lines from the text, the line numbers that @value{GDBN} knows cease
25928 to correspond properly with the code.
25930 A more detailed description of Emacs' interaction with @value{GDBN} is
25931 given in the Emacs manual (@pxref{Debuggers,,, Emacs, The @sc{gnu}
25934 @c The following dropped because Epoch is nonstandard. Reactivate
25935 @c if/when v19 does something similar. ---doc@cygnus.com 19dec1990
25937 @kindex Emacs Epoch environment
25941 Version 18 of @sc{gnu} Emacs has a built-in window system
25942 called the @code{epoch}
25943 environment. Users of this environment can use a new command,
25944 @code{inspect} which performs identically to @code{print} except that
25945 each value is printed in its own window.
25950 @chapter The @sc{gdb/mi} Interface
25952 @unnumberedsec Function and Purpose
25954 @cindex @sc{gdb/mi}, its purpose
25955 @sc{gdb/mi} is a line based machine oriented text interface to
25956 @value{GDBN} and is activated by specifying using the
25957 @option{--interpreter} command line option (@pxref{Mode Options}). It
25958 is specifically intended to support the development of systems which
25959 use the debugger as just one small component of a larger system.
25961 This chapter is a specification of the @sc{gdb/mi} interface. It is written
25962 in the form of a reference manual.
25964 Note that @sc{gdb/mi} is still under construction, so some of the
25965 features described below are incomplete and subject to change
25966 (@pxref{GDB/MI Development and Front Ends, , @sc{gdb/mi} Development and Front Ends}).
25968 @unnumberedsec Notation and Terminology
25970 @cindex notational conventions, for @sc{gdb/mi}
25971 This chapter uses the following notation:
25975 @code{|} separates two alternatives.
25978 @code{[ @var{something} ]} indicates that @var{something} is optional:
25979 it may or may not be given.
25982 @code{( @var{group} )*} means that @var{group} inside the parentheses
25983 may repeat zero or more times.
25986 @code{( @var{group} )+} means that @var{group} inside the parentheses
25987 may repeat one or more times.
25990 @code{"@var{string}"} means a literal @var{string}.
25994 @heading Dependencies
25998 * GDB/MI General Design::
25999 * GDB/MI Command Syntax::
26000 * GDB/MI Compatibility with CLI::
26001 * GDB/MI Development and Front Ends::
26002 * GDB/MI Output Records::
26003 * GDB/MI Simple Examples::
26004 * GDB/MI Command Description Format::
26005 * GDB/MI Breakpoint Commands::
26006 * GDB/MI Program Context::
26007 * GDB/MI Thread Commands::
26008 * GDB/MI Ada Tasking Commands::
26009 * GDB/MI Program Execution::
26010 * GDB/MI Stack Manipulation::
26011 * GDB/MI Variable Objects::
26012 * GDB/MI Data Manipulation::
26013 * GDB/MI Tracepoint Commands::
26014 * GDB/MI Symbol Query::
26015 * GDB/MI File Commands::
26017 * GDB/MI Kod Commands::
26018 * GDB/MI Memory Overlay Commands::
26019 * GDB/MI Signal Handling Commands::
26021 * GDB/MI Target Manipulation::
26022 * GDB/MI File Transfer Commands::
26023 * GDB/MI Miscellaneous Commands::
26026 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
26027 @node GDB/MI General Design
26028 @section @sc{gdb/mi} General Design
26029 @cindex GDB/MI General Design
26031 Interaction of a @sc{GDB/MI} frontend with @value{GDBN} involves three
26032 parts---commands sent to @value{GDBN}, responses to those commands
26033 and notifications. Each command results in exactly one response,
26034 indicating either successful completion of the command, or an error.
26035 For the commands that do not resume the target, the response contains the
26036 requested information. For the commands that resume the target, the
26037 response only indicates whether the target was successfully resumed.
26038 Notifications is the mechanism for reporting changes in the state of the
26039 target, or in @value{GDBN} state, that cannot conveniently be associated with
26040 a command and reported as part of that command response.
26042 The important examples of notifications are:
26046 Exec notifications. These are used to report changes in
26047 target state---when a target is resumed, or stopped. It would not
26048 be feasible to include this information in response of resuming
26049 commands, because one resume commands can result in multiple events in
26050 different threads. Also, quite some time may pass before any event
26051 happens in the target, while a frontend needs to know whether the resuming
26052 command itself was successfully executed.
26055 Console output, and status notifications. Console output
26056 notifications are used to report output of CLI commands, as well as
26057 diagnostics for other commands. Status notifications are used to
26058 report the progress of a long-running operation. Naturally, including
26059 this information in command response would mean no output is produced
26060 until the command is finished, which is undesirable.
26063 General notifications. Commands may have various side effects on
26064 the @value{GDBN} or target state beyond their official purpose. For example,
26065 a command may change the selected thread. Although such changes can
26066 be included in command response, using notification allows for more
26067 orthogonal frontend design.
26071 There's no guarantee that whenever an MI command reports an error,
26072 @value{GDBN} or the target are in any specific state, and especially,
26073 the state is not reverted to the state before the MI command was
26074 processed. Therefore, whenever an MI command results in an error,
26075 we recommend that the frontend refreshes all the information shown in
26076 the user interface.
26080 * Context management::
26081 * Asynchronous and non-stop modes::
26085 @node Context management
26086 @subsection Context management
26088 In most cases when @value{GDBN} accesses the target, this access is
26089 done in context of a specific thread and frame (@pxref{Frames}).
26090 Often, even when accessing global data, the target requires that a thread
26091 be specified. The CLI interface maintains the selected thread and frame,
26092 and supplies them to target on each command. This is convenient,
26093 because a command line user would not want to specify that information
26094 explicitly on each command, and because user interacts with
26095 @value{GDBN} via a single terminal, so no confusion is possible as
26096 to what thread and frame are the current ones.
26098 In the case of MI, the concept of selected thread and frame is less
26099 useful. First, a frontend can easily remember this information
26100 itself. Second, a graphical frontend can have more than one window,
26101 each one used for debugging a different thread, and the frontend might
26102 want to access additional threads for internal purposes. This
26103 increases the risk that by relying on implicitly selected thread, the
26104 frontend may be operating on a wrong one. Therefore, each MI command
26105 should explicitly specify which thread and frame to operate on. To
26106 make it possible, each MI command accepts the @samp{--thread} and
26107 @samp{--frame} options, the value to each is @value{GDBN} identifier
26108 for thread and frame to operate on.
26110 Usually, each top-level window in a frontend allows the user to select
26111 a thread and a frame, and remembers the user selection for further
26112 operations. However, in some cases @value{GDBN} may suggest that the
26113 current thread be changed. For example, when stopping on a breakpoint
26114 it is reasonable to switch to the thread where breakpoint is hit. For
26115 another example, if the user issues the CLI @samp{thread} command via
26116 the frontend, it is desirable to change the frontend's selected thread to the
26117 one specified by user. @value{GDBN} communicates the suggestion to
26118 change current thread using the @samp{=thread-selected} notification.
26119 No such notification is available for the selected frame at the moment.
26121 Note that historically, MI shares the selected thread with CLI, so
26122 frontends used the @code{-thread-select} to execute commands in the
26123 right context. However, getting this to work right is cumbersome. The
26124 simplest way is for frontend to emit @code{-thread-select} command
26125 before every command. This doubles the number of commands that need
26126 to be sent. The alternative approach is to suppress @code{-thread-select}
26127 if the selected thread in @value{GDBN} is supposed to be identical to the
26128 thread the frontend wants to operate on. However, getting this
26129 optimization right can be tricky. In particular, if the frontend
26130 sends several commands to @value{GDBN}, and one of the commands changes the
26131 selected thread, then the behaviour of subsequent commands will
26132 change. So, a frontend should either wait for response from such
26133 problematic commands, or explicitly add @code{-thread-select} for
26134 all subsequent commands. No frontend is known to do this exactly
26135 right, so it is suggested to just always pass the @samp{--thread} and
26136 @samp{--frame} options.
26138 @node Asynchronous and non-stop modes
26139 @subsection Asynchronous command execution and non-stop mode
26141 On some targets, @value{GDBN} is capable of processing MI commands
26142 even while the target is running. This is called @dfn{asynchronous
26143 command execution} (@pxref{Background Execution}). The frontend may
26144 specify a preferrence for asynchronous execution using the
26145 @code{-gdb-set target-async 1} command, which should be emitted before
26146 either running the executable or attaching to the target. After the
26147 frontend has started the executable or attached to the target, it can
26148 find if asynchronous execution is enabled using the
26149 @code{-list-target-features} command.
26151 Even if @value{GDBN} can accept a command while target is running,
26152 many commands that access the target do not work when the target is
26153 running. Therefore, asynchronous command execution is most useful
26154 when combined with non-stop mode (@pxref{Non-Stop Mode}). Then,
26155 it is possible to examine the state of one thread, while other threads
26158 When a given thread is running, MI commands that try to access the
26159 target in the context of that thread may not work, or may work only on
26160 some targets. In particular, commands that try to operate on thread's
26161 stack will not work, on any target. Commands that read memory, or
26162 modify breakpoints, may work or not work, depending on the target. Note
26163 that even commands that operate on global state, such as @code{print},
26164 @code{set}, and breakpoint commands, still access the target in the
26165 context of a specific thread, so frontend should try to find a
26166 stopped thread and perform the operation on that thread (using the
26167 @samp{--thread} option).
26169 Which commands will work in the context of a running thread is
26170 highly target dependent. However, the two commands
26171 @code{-exec-interrupt}, to stop a thread, and @code{-thread-info},
26172 to find the state of a thread, will always work.
26174 @node Thread groups
26175 @subsection Thread groups
26176 @value{GDBN} may be used to debug several processes at the same time.
26177 On some platfroms, @value{GDBN} may support debugging of several
26178 hardware systems, each one having several cores with several different
26179 processes running on each core. This section describes the MI
26180 mechanism to support such debugging scenarios.
26182 The key observation is that regardless of the structure of the
26183 target, MI can have a global list of threads, because most commands that
26184 accept the @samp{--thread} option do not need to know what process that
26185 thread belongs to. Therefore, it is not necessary to introduce
26186 neither additional @samp{--process} option, nor an notion of the
26187 current process in the MI interface. The only strictly new feature
26188 that is required is the ability to find how the threads are grouped
26191 To allow the user to discover such grouping, and to support arbitrary
26192 hierarchy of machines/cores/processes, MI introduces the concept of a
26193 @dfn{thread group}. Thread group is a collection of threads and other
26194 thread groups. A thread group always has a string identifier, a type,
26195 and may have additional attributes specific to the type. A new
26196 command, @code{-list-thread-groups}, returns the list of top-level
26197 thread groups, which correspond to processes that @value{GDBN} is
26198 debugging at the moment. By passing an identifier of a thread group
26199 to the @code{-list-thread-groups} command, it is possible to obtain
26200 the members of specific thread group.
26202 To allow the user to easily discover processes, and other objects, he
26203 wishes to debug, a concept of @dfn{available thread group} is
26204 introduced. Available thread group is an thread group that
26205 @value{GDBN} is not debugging, but that can be attached to, using the
26206 @code{-target-attach} command. The list of available top-level thread
26207 groups can be obtained using @samp{-list-thread-groups --available}.
26208 In general, the content of a thread group may be only retrieved only
26209 after attaching to that thread group.
26211 Thread groups are related to inferiors (@pxref{Inferiors and
26212 Programs}). Each inferior corresponds to a thread group of a special
26213 type @samp{process}, and some additional operations are permitted on
26214 such thread groups.
26216 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
26217 @node GDB/MI Command Syntax
26218 @section @sc{gdb/mi} Command Syntax
26221 * GDB/MI Input Syntax::
26222 * GDB/MI Output Syntax::
26225 @node GDB/MI Input Syntax
26226 @subsection @sc{gdb/mi} Input Syntax
26228 @cindex input syntax for @sc{gdb/mi}
26229 @cindex @sc{gdb/mi}, input syntax
26231 @item @var{command} @expansion{}
26232 @code{@var{cli-command} | @var{mi-command}}
26234 @item @var{cli-command} @expansion{}
26235 @code{[ @var{token} ] @var{cli-command} @var{nl}}, where
26236 @var{cli-command} is any existing @value{GDBN} CLI command.
26238 @item @var{mi-command} @expansion{}
26239 @code{[ @var{token} ] "-" @var{operation} ( " " @var{option} )*
26240 @code{[} " --" @code{]} ( " " @var{parameter} )* @var{nl}}
26242 @item @var{token} @expansion{}
26243 "any sequence of digits"
26245 @item @var{option} @expansion{}
26246 @code{"-" @var{parameter} [ " " @var{parameter} ]}
26248 @item @var{parameter} @expansion{}
26249 @code{@var{non-blank-sequence} | @var{c-string}}
26251 @item @var{operation} @expansion{}
26252 @emph{any of the operations described in this chapter}
26254 @item @var{non-blank-sequence} @expansion{}
26255 @emph{anything, provided it doesn't contain special characters such as
26256 "-", @var{nl}, """ and of course " "}
26258 @item @var{c-string} @expansion{}
26259 @code{""" @var{seven-bit-iso-c-string-content} """}
26261 @item @var{nl} @expansion{}
26270 The CLI commands are still handled by the @sc{mi} interpreter; their
26271 output is described below.
26274 The @code{@var{token}}, when present, is passed back when the command
26278 Some @sc{mi} commands accept optional arguments as part of the parameter
26279 list. Each option is identified by a leading @samp{-} (dash) and may be
26280 followed by an optional argument parameter. Options occur first in the
26281 parameter list and can be delimited from normal parameters using
26282 @samp{--} (this is useful when some parameters begin with a dash).
26289 We want easy access to the existing CLI syntax (for debugging).
26292 We want it to be easy to spot a @sc{mi} operation.
26295 @node GDB/MI Output Syntax
26296 @subsection @sc{gdb/mi} Output Syntax
26298 @cindex output syntax of @sc{gdb/mi}
26299 @cindex @sc{gdb/mi}, output syntax
26300 The output from @sc{gdb/mi} consists of zero or more out-of-band records
26301 followed, optionally, by a single result record. This result record
26302 is for the most recent command. The sequence of output records is
26303 terminated by @samp{(gdb)}.
26305 If an input command was prefixed with a @code{@var{token}} then the
26306 corresponding output for that command will also be prefixed by that same
26310 @item @var{output} @expansion{}
26311 @code{( @var{out-of-band-record} )* [ @var{result-record} ] "(gdb)" @var{nl}}
26313 @item @var{result-record} @expansion{}
26314 @code{ [ @var{token} ] "^" @var{result-class} ( "," @var{result} )* @var{nl}}
26316 @item @var{out-of-band-record} @expansion{}
26317 @code{@var{async-record} | @var{stream-record}}
26319 @item @var{async-record} @expansion{}
26320 @code{@var{exec-async-output} | @var{status-async-output} | @var{notify-async-output}}
26322 @item @var{exec-async-output} @expansion{}
26323 @code{[ @var{token} ] "*" @var{async-output}}
26325 @item @var{status-async-output} @expansion{}
26326 @code{[ @var{token} ] "+" @var{async-output}}
26328 @item @var{notify-async-output} @expansion{}
26329 @code{[ @var{token} ] "=" @var{async-output}}
26331 @item @var{async-output} @expansion{}
26332 @code{@var{async-class} ( "," @var{result} )* @var{nl}}
26334 @item @var{result-class} @expansion{}
26335 @code{"done" | "running" | "connected" | "error" | "exit"}
26337 @item @var{async-class} @expansion{}
26338 @code{"stopped" | @var{others}} (where @var{others} will be added
26339 depending on the needs---this is still in development).
26341 @item @var{result} @expansion{}
26342 @code{ @var{variable} "=" @var{value}}
26344 @item @var{variable} @expansion{}
26345 @code{ @var{string} }
26347 @item @var{value} @expansion{}
26348 @code{ @var{const} | @var{tuple} | @var{list} }
26350 @item @var{const} @expansion{}
26351 @code{@var{c-string}}
26353 @item @var{tuple} @expansion{}
26354 @code{ "@{@}" | "@{" @var{result} ( "," @var{result} )* "@}" }
26356 @item @var{list} @expansion{}
26357 @code{ "[]" | "[" @var{value} ( "," @var{value} )* "]" | "["
26358 @var{result} ( "," @var{result} )* "]" }
26360 @item @var{stream-record} @expansion{}
26361 @code{@var{console-stream-output} | @var{target-stream-output} | @var{log-stream-output}}
26363 @item @var{console-stream-output} @expansion{}
26364 @code{"~" @var{c-string}}
26366 @item @var{target-stream-output} @expansion{}
26367 @code{"@@" @var{c-string}}
26369 @item @var{log-stream-output} @expansion{}
26370 @code{"&" @var{c-string}}
26372 @item @var{nl} @expansion{}
26375 @item @var{token} @expansion{}
26376 @emph{any sequence of digits}.
26384 All output sequences end in a single line containing a period.
26387 The @code{@var{token}} is from the corresponding request. Note that
26388 for all async output, while the token is allowed by the grammar and
26389 may be output by future versions of @value{GDBN} for select async
26390 output messages, it is generally omitted. Frontends should treat
26391 all async output as reporting general changes in the state of the
26392 target and there should be no need to associate async output to any
26396 @cindex status output in @sc{gdb/mi}
26397 @var{status-async-output} contains on-going status information about the
26398 progress of a slow operation. It can be discarded. All status output is
26399 prefixed by @samp{+}.
26402 @cindex async output in @sc{gdb/mi}
26403 @var{exec-async-output} contains asynchronous state change on the target
26404 (stopped, started, disappeared). All async output is prefixed by
26408 @cindex notify output in @sc{gdb/mi}
26409 @var{notify-async-output} contains supplementary information that the
26410 client should handle (e.g., a new breakpoint information). All notify
26411 output is prefixed by @samp{=}.
26414 @cindex console output in @sc{gdb/mi}
26415 @var{console-stream-output} is output that should be displayed as is in the
26416 console. It is the textual response to a CLI command. All the console
26417 output is prefixed by @samp{~}.
26420 @cindex target output in @sc{gdb/mi}
26421 @var{target-stream-output} is the output produced by the target program.
26422 All the target output is prefixed by @samp{@@}.
26425 @cindex log output in @sc{gdb/mi}
26426 @var{log-stream-output} is output text coming from @value{GDBN}'s internals, for
26427 instance messages that should be displayed as part of an error log. All
26428 the log output is prefixed by @samp{&}.
26431 @cindex list output in @sc{gdb/mi}
26432 New @sc{gdb/mi} commands should only output @var{lists} containing
26438 @xref{GDB/MI Stream Records, , @sc{gdb/mi} Stream Records}, for more
26439 details about the various output records.
26441 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
26442 @node GDB/MI Compatibility with CLI
26443 @section @sc{gdb/mi} Compatibility with CLI
26445 @cindex compatibility, @sc{gdb/mi} and CLI
26446 @cindex @sc{gdb/mi}, compatibility with CLI
26448 For the developers convenience CLI commands can be entered directly,
26449 but there may be some unexpected behaviour. For example, commands
26450 that query the user will behave as if the user replied yes, breakpoint
26451 command lists are not executed and some CLI commands, such as
26452 @code{if}, @code{when} and @code{define}, prompt for further input with
26453 @samp{>}, which is not valid MI output.
26455 This feature may be removed at some stage in the future and it is
26456 recommended that front ends use the @code{-interpreter-exec} command
26457 (@pxref{-interpreter-exec}).
26459 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
26460 @node GDB/MI Development and Front Ends
26461 @section @sc{gdb/mi} Development and Front Ends
26462 @cindex @sc{gdb/mi} development
26464 The application which takes the MI output and presents the state of the
26465 program being debugged to the user is called a @dfn{front end}.
26467 Although @sc{gdb/mi} is still incomplete, it is currently being used
26468 by a variety of front ends to @value{GDBN}. This makes it difficult
26469 to introduce new functionality without breaking existing usage. This
26470 section tries to minimize the problems by describing how the protocol
26473 Some changes in MI need not break a carefully designed front end, and
26474 for these the MI version will remain unchanged. The following is a
26475 list of changes that may occur within one level, so front ends should
26476 parse MI output in a way that can handle them:
26480 New MI commands may be added.
26483 New fields may be added to the output of any MI command.
26486 The range of values for fields with specified values, e.g.,
26487 @code{in_scope} (@pxref{-var-update}) may be extended.
26489 @c The format of field's content e.g type prefix, may change so parse it
26490 @c at your own risk. Yes, in general?
26492 @c The order of fields may change? Shouldn't really matter but it might
26493 @c resolve inconsistencies.
26496 If the changes are likely to break front ends, the MI version level
26497 will be increased by one. This will allow the front end to parse the
26498 output according to the MI version. Apart from mi0, new versions of
26499 @value{GDBN} will not support old versions of MI and it will be the
26500 responsibility of the front end to work with the new one.
26502 @c Starting with mi3, add a new command -mi-version that prints the MI
26505 The best way to avoid unexpected changes in MI that might break your front
26506 end is to make your project known to @value{GDBN} developers and
26507 follow development on @email{gdb@@sourceware.org} and
26508 @email{gdb-patches@@sourceware.org}.
26509 @cindex mailing lists
26511 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
26512 @node GDB/MI Output Records
26513 @section @sc{gdb/mi} Output Records
26516 * GDB/MI Result Records::
26517 * GDB/MI Stream Records::
26518 * GDB/MI Async Records::
26519 * GDB/MI Frame Information::
26520 * GDB/MI Thread Information::
26521 * GDB/MI Ada Exception Information::
26524 @node GDB/MI Result Records
26525 @subsection @sc{gdb/mi} Result Records
26527 @cindex result records in @sc{gdb/mi}
26528 @cindex @sc{gdb/mi}, result records
26529 In addition to a number of out-of-band notifications, the response to a
26530 @sc{gdb/mi} command includes one of the following result indications:
26534 @item "^done" [ "," @var{results} ]
26535 The synchronous operation was successful, @code{@var{results}} are the return
26540 This result record is equivalent to @samp{^done}. Historically, it
26541 was output instead of @samp{^done} if the command has resumed the
26542 target. This behaviour is maintained for backward compatibility, but
26543 all frontends should treat @samp{^done} and @samp{^running}
26544 identically and rely on the @samp{*running} output record to determine
26545 which threads are resumed.
26549 @value{GDBN} has connected to a remote target.
26551 @item "^error" "," @var{c-string}
26553 The operation failed. The @code{@var{c-string}} contains the corresponding
26558 @value{GDBN} has terminated.
26562 @node GDB/MI Stream Records
26563 @subsection @sc{gdb/mi} Stream Records
26565 @cindex @sc{gdb/mi}, stream records
26566 @cindex stream records in @sc{gdb/mi}
26567 @value{GDBN} internally maintains a number of output streams: the console, the
26568 target, and the log. The output intended for each of these streams is
26569 funneled through the @sc{gdb/mi} interface using @dfn{stream records}.
26571 Each stream record begins with a unique @dfn{prefix character} which
26572 identifies its stream (@pxref{GDB/MI Output Syntax, , @sc{gdb/mi} Output
26573 Syntax}). In addition to the prefix, each stream record contains a
26574 @code{@var{string-output}}. This is either raw text (with an implicit new
26575 line) or a quoted C string (which does not contain an implicit newline).
26578 @item "~" @var{string-output}
26579 The console output stream contains text that should be displayed in the
26580 CLI console window. It contains the textual responses to CLI commands.
26582 @item "@@" @var{string-output}
26583 The target output stream contains any textual output from the running
26584 target. This is only present when GDB's event loop is truly
26585 asynchronous, which is currently only the case for remote targets.
26587 @item "&" @var{string-output}
26588 The log stream contains debugging messages being produced by @value{GDBN}'s
26592 @node GDB/MI Async Records
26593 @subsection @sc{gdb/mi} Async Records
26595 @cindex async records in @sc{gdb/mi}
26596 @cindex @sc{gdb/mi}, async records
26597 @dfn{Async} records are used to notify the @sc{gdb/mi} client of
26598 additional changes that have occurred. Those changes can either be a
26599 consequence of @sc{gdb/mi} commands (e.g., a breakpoint modified) or a result of
26600 target activity (e.g., target stopped).
26602 The following is the list of possible async records:
26606 @item *running,thread-id="@var{thread}"
26607 The target is now running. The @var{thread} field tells which
26608 specific thread is now running, and can be @samp{all} if all threads
26609 are running. The frontend should assume that no interaction with a
26610 running thread is possible after this notification is produced.
26611 The frontend should not assume that this notification is output
26612 only once for any command. @value{GDBN} may emit this notification
26613 several times, either for different threads, because it cannot resume
26614 all threads together, or even for a single thread, if the thread must
26615 be stepped though some code before letting it run freely.
26617 @item *stopped,reason="@var{reason}",thread-id="@var{id}",stopped-threads="@var{stopped}",core="@var{core}"
26618 The target has stopped. The @var{reason} field can have one of the
26622 @item breakpoint-hit
26623 A breakpoint was reached.
26624 @item watchpoint-trigger
26625 A watchpoint was triggered.
26626 @item read-watchpoint-trigger
26627 A read watchpoint was triggered.
26628 @item access-watchpoint-trigger
26629 An access watchpoint was triggered.
26630 @item function-finished
26631 An -exec-finish or similar CLI command was accomplished.
26632 @item location-reached
26633 An -exec-until or similar CLI command was accomplished.
26634 @item watchpoint-scope
26635 A watchpoint has gone out of scope.
26636 @item end-stepping-range
26637 An -exec-next, -exec-next-instruction, -exec-step, -exec-step-instruction or
26638 similar CLI command was accomplished.
26639 @item exited-signalled
26640 The inferior exited because of a signal.
26642 The inferior exited.
26643 @item exited-normally
26644 The inferior exited normally.
26645 @item signal-received
26646 A signal was received by the inferior.
26648 The inferior has stopped due to a library being loaded or unloaded.
26649 This can happen when @code{stop-on-solib-events} (@pxref{Files}) is
26650 set or when a @code{catch load} or @code{catch unload} catchpoint is
26651 in use (@pxref{Set Catchpoints}).
26653 The inferior has forked. This is reported when @code{catch fork}
26654 (@pxref{Set Catchpoints}) has been used.
26656 The inferior has vforked. This is reported in when @code{catch vfork}
26657 (@pxref{Set Catchpoints}) has been used.
26658 @item syscall-entry
26659 The inferior entered a system call. This is reported when @code{catch
26660 syscall} (@pxref{Set Catchpoints}) has been used.
26661 @item syscall-entry
26662 The inferior returned from a system call. This is reported when
26663 @code{catch syscall} (@pxref{Set Catchpoints}) has been used.
26665 The inferior called @code{exec}. This is reported when @code{catch exec}
26666 (@pxref{Set Catchpoints}) has been used.
26669 The @var{id} field identifies the thread that directly caused the stop
26670 -- for example by hitting a breakpoint. Depending on whether all-stop
26671 mode is in effect (@pxref{All-Stop Mode}), @value{GDBN} may either
26672 stop all threads, or only the thread that directly triggered the stop.
26673 If all threads are stopped, the @var{stopped} field will have the
26674 value of @code{"all"}. Otherwise, the value of the @var{stopped}
26675 field will be a list of thread identifiers. Presently, this list will
26676 always include a single thread, but frontend should be prepared to see
26677 several threads in the list. The @var{core} field reports the
26678 processor core on which the stop event has happened. This field may be absent
26679 if such information is not available.
26681 @item =thread-group-added,id="@var{id}"
26682 @itemx =thread-group-removed,id="@var{id}"
26683 A thread group was either added or removed. The @var{id} field
26684 contains the @value{GDBN} identifier of the thread group. When a thread
26685 group is added, it generally might not be associated with a running
26686 process. When a thread group is removed, its id becomes invalid and
26687 cannot be used in any way.
26689 @item =thread-group-started,id="@var{id}",pid="@var{pid}"
26690 A thread group became associated with a running program,
26691 either because the program was just started or the thread group
26692 was attached to a program. The @var{id} field contains the
26693 @value{GDBN} identifier of the thread group. The @var{pid} field
26694 contains process identifier, specific to the operating system.
26696 @item =thread-group-exited,id="@var{id}"[,exit-code="@var{code}"]
26697 A thread group is no longer associated with a running program,
26698 either because the program has exited, or because it was detached
26699 from. The @var{id} field contains the @value{GDBN} identifier of the
26700 thread group. @var{code} is the exit code of the inferior; it exists
26701 only when the inferior exited with some code.
26703 @item =thread-created,id="@var{id}",group-id="@var{gid}"
26704 @itemx =thread-exited,id="@var{id}",group-id="@var{gid}"
26705 A thread either was created, or has exited. The @var{id} field
26706 contains the @value{GDBN} identifier of the thread. The @var{gid}
26707 field identifies the thread group this thread belongs to.
26709 @item =thread-selected,id="@var{id}"
26710 Informs that the selected thread was changed as result of the last
26711 command. This notification is not emitted as result of @code{-thread-select}
26712 command but is emitted whenever an MI command that is not documented
26713 to change the selected thread actually changes it. In particular,
26714 invoking, directly or indirectly (via user-defined command), the CLI
26715 @code{thread} command, will generate this notification.
26717 We suggest that in response to this notification, front ends
26718 highlight the selected thread and cause subsequent commands to apply to
26721 @item =library-loaded,...
26722 Reports that a new library file was loaded by the program. This
26723 notification has 4 fields---@var{id}, @var{target-name},
26724 @var{host-name}, and @var{symbols-loaded}. The @var{id} field is an
26725 opaque identifier of the library. For remote debugging case,
26726 @var{target-name} and @var{host-name} fields give the name of the
26727 library file on the target, and on the host respectively. For native
26728 debugging, both those fields have the same value. The
26729 @var{symbols-loaded} field is emitted only for backward compatibility
26730 and should not be relied on to convey any useful information. The
26731 @var{thread-group} field, if present, specifies the id of the thread
26732 group in whose context the library was loaded. If the field is
26733 absent, it means the library was loaded in the context of all present
26736 @item =library-unloaded,...
26737 Reports that a library was unloaded by the program. This notification
26738 has 3 fields---@var{id}, @var{target-name} and @var{host-name} with
26739 the same meaning as for the @code{=library-loaded} notification.
26740 The @var{thread-group} field, if present, specifies the id of the
26741 thread group in whose context the library was unloaded. If the field is
26742 absent, it means the library was unloaded in the context of all present
26745 @item =breakpoint-created,bkpt=@{...@}
26746 @itemx =breakpoint-modified,bkpt=@{...@}
26747 @itemx =breakpoint-deleted,bkpt=@{...@}
26748 Reports that a breakpoint was created, modified, or deleted,
26749 respectively. Only user-visible breakpoints are reported to the MI
26752 The @var{bkpt} argument is of the same form as returned by the various
26753 breakpoint commands; @xref{GDB/MI Breakpoint Commands}.
26755 Note that if a breakpoint is emitted in the result record of a
26756 command, then it will not also be emitted in an async record.
26760 @node GDB/MI Frame Information
26761 @subsection @sc{gdb/mi} Frame Information
26763 Response from many MI commands includes an information about stack
26764 frame. This information is a tuple that may have the following
26769 The level of the stack frame. The innermost frame has the level of
26770 zero. This field is always present.
26773 The name of the function corresponding to the frame. This field may
26774 be absent if @value{GDBN} is unable to determine the function name.
26777 The code address for the frame. This field is always present.
26780 The name of the source files that correspond to the frame's code
26781 address. This field may be absent.
26784 The source line corresponding to the frames' code address. This field
26788 The name of the binary file (either executable or shared library) the
26789 corresponds to the frame's code address. This field may be absent.
26793 @node GDB/MI Thread Information
26794 @subsection @sc{gdb/mi} Thread Information
26796 Whenever @value{GDBN} has to report an information about a thread, it
26797 uses a tuple with the following fields:
26801 The numeric id assigned to the thread by @value{GDBN}. This field is
26805 Target-specific string identifying the thread. This field is always present.
26808 Additional information about the thread provided by the target.
26809 It is supposed to be human-readable and not interpreted by the
26810 frontend. This field is optional.
26813 Either @samp{stopped} or @samp{running}, depending on whether the
26814 thread is presently running. This field is always present.
26817 The value of this field is an integer number of the processor core the
26818 thread was last seen on. This field is optional.
26821 @node GDB/MI Ada Exception Information
26822 @subsection @sc{gdb/mi} Ada Exception Information
26824 Whenever a @code{*stopped} record is emitted because the program
26825 stopped after hitting an exception catchpoint (@pxref{Set Catchpoints}),
26826 @value{GDBN} provides the name of the exception that was raised via
26827 the @code{exception-name} field.
26829 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
26830 @node GDB/MI Simple Examples
26831 @section Simple Examples of @sc{gdb/mi} Interaction
26832 @cindex @sc{gdb/mi}, simple examples
26834 This subsection presents several simple examples of interaction using
26835 the @sc{gdb/mi} interface. In these examples, @samp{->} means that the
26836 following line is passed to @sc{gdb/mi} as input, while @samp{<-} means
26837 the output received from @sc{gdb/mi}.
26839 Note the line breaks shown in the examples are here only for
26840 readability, they don't appear in the real output.
26842 @subheading Setting a Breakpoint
26844 Setting a breakpoint generates synchronous output which contains detailed
26845 information of the breakpoint.
26848 -> -break-insert main
26849 <- ^done,bkpt=@{number="1",type="breakpoint",disp="keep",
26850 enabled="y",addr="0x08048564",func="main",file="myprog.c",
26851 fullname="/home/nickrob/myprog.c",line="68",times="0"@}
26855 @subheading Program Execution
26857 Program execution generates asynchronous records and MI gives the
26858 reason that execution stopped.
26864 <- *stopped,reason="breakpoint-hit",disp="keep",bkptno="1",thread-id="0",
26865 frame=@{addr="0x08048564",func="main",
26866 args=[@{name="argc",value="1"@},@{name="argv",value="0xbfc4d4d4"@}],
26867 file="myprog.c",fullname="/home/nickrob/myprog.c",line="68"@}
26872 <- *stopped,reason="exited-normally"
26876 @subheading Quitting @value{GDBN}
26878 Quitting @value{GDBN} just prints the result class @samp{^exit}.
26886 Please note that @samp{^exit} is printed immediately, but it might
26887 take some time for @value{GDBN} to actually exit. During that time, @value{GDBN}
26888 performs necessary cleanups, including killing programs being debugged
26889 or disconnecting from debug hardware, so the frontend should wait till
26890 @value{GDBN} exits and should only forcibly kill @value{GDBN} if it
26891 fails to exit in reasonable time.
26893 @subheading A Bad Command
26895 Here's what happens if you pass a non-existent command:
26899 <- ^error,msg="Undefined MI command: rubbish"
26904 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
26905 @node GDB/MI Command Description Format
26906 @section @sc{gdb/mi} Command Description Format
26908 The remaining sections describe blocks of commands. Each block of
26909 commands is laid out in a fashion similar to this section.
26911 @subheading Motivation
26913 The motivation for this collection of commands.
26915 @subheading Introduction
26917 A brief introduction to this collection of commands as a whole.
26919 @subheading Commands
26921 For each command in the block, the following is described:
26923 @subsubheading Synopsis
26926 -command @var{args}@dots{}
26929 @subsubheading Result
26931 @subsubheading @value{GDBN} Command
26933 The corresponding @value{GDBN} CLI command(s), if any.
26935 @subsubheading Example
26937 Example(s) formatted for readability. Some of the described commands have
26938 not been implemented yet and these are labeled N.A.@: (not available).
26941 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
26942 @node GDB/MI Breakpoint Commands
26943 @section @sc{gdb/mi} Breakpoint Commands
26945 @cindex breakpoint commands for @sc{gdb/mi}
26946 @cindex @sc{gdb/mi}, breakpoint commands
26947 This section documents @sc{gdb/mi} commands for manipulating
26950 @subheading The @code{-break-after} Command
26951 @findex -break-after
26953 @subsubheading Synopsis
26956 -break-after @var{number} @var{count}
26959 The breakpoint number @var{number} is not in effect until it has been
26960 hit @var{count} times. To see how this is reflected in the output of
26961 the @samp{-break-list} command, see the description of the
26962 @samp{-break-list} command below.
26964 @subsubheading @value{GDBN} Command
26966 The corresponding @value{GDBN} command is @samp{ignore}.
26968 @subsubheading Example
26973 ^done,bkpt=@{number="1",type="breakpoint",disp="keep",
26974 enabled="y",addr="0x000100d0",func="main",file="hello.c",
26975 fullname="/home/foo/hello.c",line="5",times="0"@}
26982 ^done,BreakpointTable=@{nr_rows="1",nr_cols="6",
26983 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
26984 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
26985 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
26986 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
26987 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
26988 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
26989 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
26990 addr="0x000100d0",func="main",file="hello.c",fullname="/home/foo/hello.c",
26991 line="5",times="0",ignore="3"@}]@}
26996 @subheading The @code{-break-catch} Command
26997 @findex -break-catch
27000 @subheading The @code{-break-commands} Command
27001 @findex -break-commands
27003 @subsubheading Synopsis
27006 -break-commands @var{number} [ @var{command1} ... @var{commandN} ]
27009 Specifies the CLI commands that should be executed when breakpoint
27010 @var{number} is hit. The parameters @var{command1} to @var{commandN}
27011 are the commands. If no command is specified, any previously-set
27012 commands are cleared. @xref{Break Commands}. Typical use of this
27013 functionality is tracing a program, that is, printing of values of
27014 some variables whenever breakpoint is hit and then continuing.
27016 @subsubheading @value{GDBN} Command
27018 The corresponding @value{GDBN} command is @samp{commands}.
27020 @subsubheading Example
27025 ^done,bkpt=@{number="1",type="breakpoint",disp="keep",
27026 enabled="y",addr="0x000100d0",func="main",file="hello.c",
27027 fullname="/home/foo/hello.c",line="5",times="0"@}
27029 -break-commands 1 "print v" "continue"
27034 @subheading The @code{-break-condition} Command
27035 @findex -break-condition
27037 @subsubheading Synopsis
27040 -break-condition @var{number} @var{expr}
27043 Breakpoint @var{number} will stop the program only if the condition in
27044 @var{expr} is true. The condition becomes part of the
27045 @samp{-break-list} output (see the description of the @samp{-break-list}
27048 @subsubheading @value{GDBN} Command
27050 The corresponding @value{GDBN} command is @samp{condition}.
27052 @subsubheading Example
27056 -break-condition 1 1
27060 ^done,BreakpointTable=@{nr_rows="1",nr_cols="6",
27061 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
27062 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
27063 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
27064 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
27065 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
27066 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
27067 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
27068 addr="0x000100d0",func="main",file="hello.c",fullname="/home/foo/hello.c",
27069 line="5",cond="1",times="0",ignore="3"@}]@}
27073 @subheading The @code{-break-delete} Command
27074 @findex -break-delete
27076 @subsubheading Synopsis
27079 -break-delete ( @var{breakpoint} )+
27082 Delete the breakpoint(s) whose number(s) are specified in the argument
27083 list. This is obviously reflected in the breakpoint list.
27085 @subsubheading @value{GDBN} Command
27087 The corresponding @value{GDBN} command is @samp{delete}.
27089 @subsubheading Example
27097 ^done,BreakpointTable=@{nr_rows="0",nr_cols="6",
27098 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
27099 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
27100 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
27101 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
27102 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
27103 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
27108 @subheading The @code{-break-disable} Command
27109 @findex -break-disable
27111 @subsubheading Synopsis
27114 -break-disable ( @var{breakpoint} )+
27117 Disable the named @var{breakpoint}(s). The field @samp{enabled} in the
27118 break list is now set to @samp{n} for the named @var{breakpoint}(s).
27120 @subsubheading @value{GDBN} Command
27122 The corresponding @value{GDBN} command is @samp{disable}.
27124 @subsubheading Example
27132 ^done,BreakpointTable=@{nr_rows="1",nr_cols="6",
27133 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
27134 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
27135 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
27136 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
27137 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
27138 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
27139 body=[bkpt=@{number="2",type="breakpoint",disp="keep",enabled="n",
27140 addr="0x000100d0",func="main",file="hello.c",fullname="/home/foo/hello.c",
27141 line="5",times="0"@}]@}
27145 @subheading The @code{-break-enable} Command
27146 @findex -break-enable
27148 @subsubheading Synopsis
27151 -break-enable ( @var{breakpoint} )+
27154 Enable (previously disabled) @var{breakpoint}(s).
27156 @subsubheading @value{GDBN} Command
27158 The corresponding @value{GDBN} command is @samp{enable}.
27160 @subsubheading Example
27168 ^done,BreakpointTable=@{nr_rows="1",nr_cols="6",
27169 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
27170 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
27171 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
27172 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
27173 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
27174 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
27175 body=[bkpt=@{number="2",type="breakpoint",disp="keep",enabled="y",
27176 addr="0x000100d0",func="main",file="hello.c",fullname="/home/foo/hello.c",
27177 line="5",times="0"@}]@}
27181 @subheading The @code{-break-info} Command
27182 @findex -break-info
27184 @subsubheading Synopsis
27187 -break-info @var{breakpoint}
27191 Get information about a single breakpoint.
27193 @subsubheading @value{GDBN} Command
27195 The corresponding @value{GDBN} command is @samp{info break @var{breakpoint}}.
27197 @subsubheading Example
27200 @subheading The @code{-break-insert} Command
27201 @findex -break-insert
27203 @subsubheading Synopsis
27206 -break-insert [ -t ] [ -h ] [ -f ] [ -d ] [ -a ]
27207 [ -c @var{condition} ] [ -i @var{ignore-count} ]
27208 [ -p @var{thread} ] [ @var{location} ]
27212 If specified, @var{location}, can be one of:
27219 @item filename:linenum
27220 @item filename:function
27224 The possible optional parameters of this command are:
27228 Insert a temporary breakpoint.
27230 Insert a hardware breakpoint.
27231 @item -c @var{condition}
27232 Make the breakpoint conditional on @var{condition}.
27233 @item -i @var{ignore-count}
27234 Initialize the @var{ignore-count}.
27236 If @var{location} cannot be parsed (for example if it
27237 refers to unknown files or functions), create a pending
27238 breakpoint. Without this flag, @value{GDBN} will report
27239 an error, and won't create a breakpoint, if @var{location}
27242 Create a disabled breakpoint.
27244 Create a tracepoint. @xref{Tracepoints}. When this parameter
27245 is used together with @samp{-h}, a fast tracepoint is created.
27248 @subsubheading Result
27250 The result is in the form:
27253 ^done,bkpt=@{number="@var{number}",type="@var{type}",disp="del"|"keep",
27254 enabled="y"|"n",addr="@var{hex}",func="@var{funcname}",file="@var{filename}",
27255 fullname="@var{full_filename}",line="@var{lineno}",[thread="@var{threadno},]
27256 times="@var{times}"@}
27260 where @var{number} is the @value{GDBN} number for this breakpoint,
27261 @var{funcname} is the name of the function where the breakpoint was
27262 inserted, @var{filename} is the name of the source file which contains
27263 this function, @var{lineno} is the source line number within that file
27264 and @var{times} the number of times that the breakpoint has been hit
27265 (always 0 for -break-insert but may be greater for -break-info or -break-list
27266 which use the same output).
27268 Note: this format is open to change.
27269 @c An out-of-band breakpoint instead of part of the result?
27271 @subsubheading @value{GDBN} Command
27273 The corresponding @value{GDBN} commands are @samp{break}, @samp{tbreak},
27274 @samp{hbreak}, @samp{thbreak}, and @samp{rbreak}.
27276 @subsubheading Example
27281 ^done,bkpt=@{number="1",addr="0x0001072c",file="recursive2.c",
27282 fullname="/home/foo/recursive2.c,line="4",times="0"@}
27284 -break-insert -t foo
27285 ^done,bkpt=@{number="2",addr="0x00010774",file="recursive2.c",
27286 fullname="/home/foo/recursive2.c,line="11",times="0"@}
27289 ^done,BreakpointTable=@{nr_rows="2",nr_cols="6",
27290 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
27291 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
27292 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
27293 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
27294 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
27295 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
27296 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
27297 addr="0x0001072c", func="main",file="recursive2.c",
27298 fullname="/home/foo/recursive2.c,"line="4",times="0"@},
27299 bkpt=@{number="2",type="breakpoint",disp="del",enabled="y",
27300 addr="0x00010774",func="foo",file="recursive2.c",
27301 fullname="/home/foo/recursive2.c",line="11",times="0"@}]@}
27303 -break-insert -r foo.*
27304 ~int foo(int, int);
27305 ^done,bkpt=@{number="3",addr="0x00010774",file="recursive2.c,
27306 "fullname="/home/foo/recursive2.c",line="11",times="0"@}
27310 @subheading The @code{-break-list} Command
27311 @findex -break-list
27313 @subsubheading Synopsis
27319 Displays the list of inserted breakpoints, showing the following fields:
27323 number of the breakpoint
27325 type of the breakpoint: @samp{breakpoint} or @samp{watchpoint}
27327 should the breakpoint be deleted or disabled when it is hit: @samp{keep}
27330 is the breakpoint enabled or no: @samp{y} or @samp{n}
27332 memory location at which the breakpoint is set
27334 logical location of the breakpoint, expressed by function name, file
27337 number of times the breakpoint has been hit
27340 If there are no breakpoints or watchpoints, the @code{BreakpointTable}
27341 @code{body} field is an empty list.
27343 @subsubheading @value{GDBN} Command
27345 The corresponding @value{GDBN} command is @samp{info break}.
27347 @subsubheading Example
27352 ^done,BreakpointTable=@{nr_rows="2",nr_cols="6",
27353 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
27354 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
27355 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
27356 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
27357 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
27358 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
27359 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
27360 addr="0x000100d0",func="main",file="hello.c",line="5",times="0"@},
27361 bkpt=@{number="2",type="breakpoint",disp="keep",enabled="y",
27362 addr="0x00010114",func="foo",file="hello.c",fullname="/home/foo/hello.c",
27363 line="13",times="0"@}]@}
27367 Here's an example of the result when there are no breakpoints:
27372 ^done,BreakpointTable=@{nr_rows="0",nr_cols="6",
27373 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
27374 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
27375 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
27376 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
27377 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
27378 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
27383 @subheading The @code{-break-passcount} Command
27384 @findex -break-passcount
27386 @subsubheading Synopsis
27389 -break-passcount @var{tracepoint-number} @var{passcount}
27392 Set the passcount for tracepoint @var{tracepoint-number} to
27393 @var{passcount}. If the breakpoint referred to by @var{tracepoint-number}
27394 is not a tracepoint, error is emitted. This corresponds to CLI
27395 command @samp{passcount}.
27397 @subheading The @code{-break-watch} Command
27398 @findex -break-watch
27400 @subsubheading Synopsis
27403 -break-watch [ -a | -r ]
27406 Create a watchpoint. With the @samp{-a} option it will create an
27407 @dfn{access} watchpoint, i.e., a watchpoint that triggers either on a
27408 read from or on a write to the memory location. With the @samp{-r}
27409 option, the watchpoint created is a @dfn{read} watchpoint, i.e., it will
27410 trigger only when the memory location is accessed for reading. Without
27411 either of the options, the watchpoint created is a regular watchpoint,
27412 i.e., it will trigger when the memory location is accessed for writing.
27413 @xref{Set Watchpoints, , Setting Watchpoints}.
27415 Note that @samp{-break-list} will report a single list of watchpoints and
27416 breakpoints inserted.
27418 @subsubheading @value{GDBN} Command
27420 The corresponding @value{GDBN} commands are @samp{watch}, @samp{awatch}, and
27423 @subsubheading Example
27425 Setting a watchpoint on a variable in the @code{main} function:
27430 ^done,wpt=@{number="2",exp="x"@}
27435 *stopped,reason="watchpoint-trigger",wpt=@{number="2",exp="x"@},
27436 value=@{old="-268439212",new="55"@},
27437 frame=@{func="main",args=[],file="recursive2.c",
27438 fullname="/home/foo/bar/recursive2.c",line="5"@}
27442 Setting a watchpoint on a variable local to a function. @value{GDBN} will stop
27443 the program execution twice: first for the variable changing value, then
27444 for the watchpoint going out of scope.
27449 ^done,wpt=@{number="5",exp="C"@}
27454 *stopped,reason="watchpoint-trigger",
27455 wpt=@{number="5",exp="C"@},value=@{old="-276895068",new="3"@},
27456 frame=@{func="callee4",args=[],
27457 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
27458 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="13"@}
27463 *stopped,reason="watchpoint-scope",wpnum="5",
27464 frame=@{func="callee3",args=[@{name="strarg",
27465 value="0x11940 \"A string argument.\""@}],
27466 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
27467 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="18"@}
27471 Listing breakpoints and watchpoints, at different points in the program
27472 execution. Note that once the watchpoint goes out of scope, it is
27478 ^done,wpt=@{number="2",exp="C"@}
27481 ^done,BreakpointTable=@{nr_rows="2",nr_cols="6",
27482 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
27483 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
27484 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
27485 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
27486 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
27487 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
27488 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
27489 addr="0x00010734",func="callee4",
27490 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
27491 fullname="/home/foo/devo/gdb/testsuite/gdb.mi/basics.c"line="8",times="1"@},
27492 bkpt=@{number="2",type="watchpoint",disp="keep",
27493 enabled="y",addr="",what="C",times="0"@}]@}
27498 *stopped,reason="watchpoint-trigger",wpt=@{number="2",exp="C"@},
27499 value=@{old="-276895068",new="3"@},
27500 frame=@{func="callee4",args=[],
27501 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
27502 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="13"@}
27505 ^done,BreakpointTable=@{nr_rows="2",nr_cols="6",
27506 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
27507 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
27508 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
27509 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
27510 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
27511 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
27512 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
27513 addr="0x00010734",func="callee4",
27514 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
27515 fullname="/home/foo/devo/gdb/testsuite/gdb.mi/basics.c",line="8",times="1"@},
27516 bkpt=@{number="2",type="watchpoint",disp="keep",
27517 enabled="y",addr="",what="C",times="-5"@}]@}
27521 ^done,reason="watchpoint-scope",wpnum="2",
27522 frame=@{func="callee3",args=[@{name="strarg",
27523 value="0x11940 \"A string argument.\""@}],
27524 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
27525 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="18"@}
27528 ^done,BreakpointTable=@{nr_rows="1",nr_cols="6",
27529 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
27530 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
27531 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
27532 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
27533 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
27534 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
27535 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
27536 addr="0x00010734",func="callee4",
27537 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
27538 fullname="/home/foo/devo/gdb/testsuite/gdb.mi/basics.c",line="8",
27543 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
27544 @node GDB/MI Program Context
27545 @section @sc{gdb/mi} Program Context
27547 @subheading The @code{-exec-arguments} Command
27548 @findex -exec-arguments
27551 @subsubheading Synopsis
27554 -exec-arguments @var{args}
27557 Set the inferior program arguments, to be used in the next
27560 @subsubheading @value{GDBN} Command
27562 The corresponding @value{GDBN} command is @samp{set args}.
27564 @subsubheading Example
27568 -exec-arguments -v word
27575 @subheading The @code{-exec-show-arguments} Command
27576 @findex -exec-show-arguments
27578 @subsubheading Synopsis
27581 -exec-show-arguments
27584 Print the arguments of the program.
27586 @subsubheading @value{GDBN} Command
27588 The corresponding @value{GDBN} command is @samp{show args}.
27590 @subsubheading Example
27595 @subheading The @code{-environment-cd} Command
27596 @findex -environment-cd
27598 @subsubheading Synopsis
27601 -environment-cd @var{pathdir}
27604 Set @value{GDBN}'s working directory.
27606 @subsubheading @value{GDBN} Command
27608 The corresponding @value{GDBN} command is @samp{cd}.
27610 @subsubheading Example
27614 -environment-cd /kwikemart/marge/ezannoni/flathead-dev/devo/gdb
27620 @subheading The @code{-environment-directory} Command
27621 @findex -environment-directory
27623 @subsubheading Synopsis
27626 -environment-directory [ -r ] [ @var{pathdir} ]+
27629 Add directories @var{pathdir} to beginning of search path for source files.
27630 If the @samp{-r} option is used, the search path is reset to the default
27631 search path. If directories @var{pathdir} are supplied in addition to the
27632 @samp{-r} option, the search path is first reset and then addition
27634 Multiple directories may be specified, separated by blanks. Specifying
27635 multiple directories in a single command
27636 results in the directories added to the beginning of the
27637 search path in the same order they were presented in the command.
27638 If blanks are needed as
27639 part of a directory name, double-quotes should be used around
27640 the name. In the command output, the path will show up separated
27641 by the system directory-separator character. The directory-separator
27642 character must not be used
27643 in any directory name.
27644 If no directories are specified, the current search path is displayed.
27646 @subsubheading @value{GDBN} Command
27648 The corresponding @value{GDBN} command is @samp{dir}.
27650 @subsubheading Example
27654 -environment-directory /kwikemart/marge/ezannoni/flathead-dev/devo/gdb
27655 ^done,source-path="/kwikemart/marge/ezannoni/flathead-dev/devo/gdb:$cdir:$cwd"
27657 -environment-directory ""
27658 ^done,source-path="/kwikemart/marge/ezannoni/flathead-dev/devo/gdb:$cdir:$cwd"
27660 -environment-directory -r /home/jjohnstn/src/gdb /usr/src
27661 ^done,source-path="/home/jjohnstn/src/gdb:/usr/src:$cdir:$cwd"
27663 -environment-directory -r
27664 ^done,source-path="$cdir:$cwd"
27669 @subheading The @code{-environment-path} Command
27670 @findex -environment-path
27672 @subsubheading Synopsis
27675 -environment-path [ -r ] [ @var{pathdir} ]+
27678 Add directories @var{pathdir} to beginning of search path for object files.
27679 If the @samp{-r} option is used, the search path is reset to the original
27680 search path that existed at gdb start-up. If directories @var{pathdir} are
27681 supplied in addition to the
27682 @samp{-r} option, the search path is first reset and then addition
27684 Multiple directories may be specified, separated by blanks. Specifying
27685 multiple directories in a single command
27686 results in the directories added to the beginning of the
27687 search path in the same order they were presented in the command.
27688 If blanks are needed as
27689 part of a directory name, double-quotes should be used around
27690 the name. In the command output, the path will show up separated
27691 by the system directory-separator character. The directory-separator
27692 character must not be used
27693 in any directory name.
27694 If no directories are specified, the current path is displayed.
27697 @subsubheading @value{GDBN} Command
27699 The corresponding @value{GDBN} command is @samp{path}.
27701 @subsubheading Example
27706 ^done,path="/usr/bin"
27708 -environment-path /kwikemart/marge/ezannoni/flathead-dev/ppc-eabi/gdb /bin
27709 ^done,path="/kwikemart/marge/ezannoni/flathead-dev/ppc-eabi/gdb:/bin:/usr/bin"
27711 -environment-path -r /usr/local/bin
27712 ^done,path="/usr/local/bin:/usr/bin"
27717 @subheading The @code{-environment-pwd} Command
27718 @findex -environment-pwd
27720 @subsubheading Synopsis
27726 Show the current working directory.
27728 @subsubheading @value{GDBN} Command
27730 The corresponding @value{GDBN} command is @samp{pwd}.
27732 @subsubheading Example
27737 ^done,cwd="/kwikemart/marge/ezannoni/flathead-dev/devo/gdb"
27741 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
27742 @node GDB/MI Thread Commands
27743 @section @sc{gdb/mi} Thread Commands
27746 @subheading The @code{-thread-info} Command
27747 @findex -thread-info
27749 @subsubheading Synopsis
27752 -thread-info [ @var{thread-id} ]
27755 Reports information about either a specific thread, if
27756 the @var{thread-id} parameter is present, or about all
27757 threads. When printing information about all threads,
27758 also reports the current thread.
27760 @subsubheading @value{GDBN} Command
27762 The @samp{info thread} command prints the same information
27765 @subsubheading Result
27767 The result is a list of threads. The following attributes are
27768 defined for a given thread:
27772 This field exists only for the current thread. It has the value @samp{*}.
27775 The identifier that @value{GDBN} uses to refer to the thread.
27778 The identifier that the target uses to refer to the thread.
27781 Extra information about the thread, in a target-specific format. This
27785 The name of the thread. If the user specified a name using the
27786 @code{thread name} command, then this name is given. Otherwise, if
27787 @value{GDBN} can extract the thread name from the target, then that
27788 name is given. If @value{GDBN} cannot find the thread name, then this
27792 The stack frame currently executing in the thread.
27795 The thread's state. The @samp{state} field may have the following
27800 The thread is stopped. Frame information is available for stopped
27804 The thread is running. There's no frame information for running
27810 If @value{GDBN} can find the CPU core on which this thread is running,
27811 then this field is the core identifier. This field is optional.
27815 @subsubheading Example
27820 @{id="2",target-id="Thread 0xb7e14b90 (LWP 21257)",
27821 frame=@{level="0",addr="0xffffe410",func="__kernel_vsyscall",
27822 args=[]@},state="running"@},
27823 @{id="1",target-id="Thread 0xb7e156b0 (LWP 21254)",
27824 frame=@{level="0",addr="0x0804891f",func="foo",
27825 args=[@{name="i",value="10"@}],
27826 file="/tmp/a.c",fullname="/tmp/a.c",line="158"@},
27827 state="running"@}],
27828 current-thread-id="1"
27832 @subheading The @code{-thread-list-ids} Command
27833 @findex -thread-list-ids
27835 @subsubheading Synopsis
27841 Produces a list of the currently known @value{GDBN} thread ids. At the
27842 end of the list it also prints the total number of such threads.
27844 This command is retained for historical reasons, the
27845 @code{-thread-info} command should be used instead.
27847 @subsubheading @value{GDBN} Command
27849 Part of @samp{info threads} supplies the same information.
27851 @subsubheading Example
27856 ^done,thread-ids=@{thread-id="3",thread-id="2",thread-id="1"@},
27857 current-thread-id="1",number-of-threads="3"
27862 @subheading The @code{-thread-select} Command
27863 @findex -thread-select
27865 @subsubheading Synopsis
27868 -thread-select @var{threadnum}
27871 Make @var{threadnum} the current thread. It prints the number of the new
27872 current thread, and the topmost frame for that thread.
27874 This command is deprecated in favor of explicitly using the
27875 @samp{--thread} option to each command.
27877 @subsubheading @value{GDBN} Command
27879 The corresponding @value{GDBN} command is @samp{thread}.
27881 @subsubheading Example
27888 *stopped,reason="end-stepping-range",thread-id="2",line="187",
27889 file="../../../devo/gdb/testsuite/gdb.threads/linux-dp.c"
27893 thread-ids=@{thread-id="3",thread-id="2",thread-id="1"@},
27894 number-of-threads="3"
27897 ^done,new-thread-id="3",
27898 frame=@{level="0",func="vprintf",
27899 args=[@{name="format",value="0x8048e9c \"%*s%c %d %c\\n\""@},
27900 @{name="arg",value="0x2"@}],file="vprintf.c",line="31"@}
27904 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
27905 @node GDB/MI Ada Tasking Commands
27906 @section @sc{gdb/mi} Ada Tasking Commands
27908 @subheading The @code{-ada-task-info} Command
27909 @findex -ada-task-info
27911 @subsubheading Synopsis
27914 -ada-task-info [ @var{task-id} ]
27917 Reports information about either a specific Ada task, if the
27918 @var{task-id} parameter is present, or about all Ada tasks.
27920 @subsubheading @value{GDBN} Command
27922 The @samp{info tasks} command prints the same information
27923 about all Ada tasks (@pxref{Ada Tasks}).
27925 @subsubheading Result
27927 The result is a table of Ada tasks. The following columns are
27928 defined for each Ada task:
27932 This field exists only for the current thread. It has the value @samp{*}.
27935 The identifier that @value{GDBN} uses to refer to the Ada task.
27938 The identifier that the target uses to refer to the Ada task.
27941 The identifier of the thread corresponding to the Ada task.
27943 This field should always exist, as Ada tasks are always implemented
27944 on top of a thread. But if @value{GDBN} cannot find this corresponding
27945 thread for any reason, the field is omitted.
27948 This field exists only when the task was created by another task.
27949 In this case, it provides the ID of the parent task.
27952 The base priority of the task.
27955 The current state of the task. For a detailed description of the
27956 possible states, see @ref{Ada Tasks}.
27959 The name of the task.
27963 @subsubheading Example
27967 ^done,tasks=@{nr_rows="3",nr_cols="8",
27968 hdr=[@{width="1",alignment="-1",col_name="current",colhdr=""@},
27969 @{width="3",alignment="1",col_name="id",colhdr="ID"@},
27970 @{width="9",alignment="1",col_name="task-id",colhdr="TID"@},
27971 @{width="4",alignment="1",col_name="thread-id",colhdr=""@},
27972 @{width="4",alignment="1",col_name="parent-id",colhdr="P-ID"@},
27973 @{width="3",alignment="1",col_name="priority",colhdr="Pri"@},
27974 @{width="22",alignment="-1",col_name="state",colhdr="State"@},
27975 @{width="1",alignment="2",col_name="name",colhdr="Name"@}],
27976 body=[@{current="*",id="1",task-id=" 644010",thread-id="1",priority="48",
27977 state="Child Termination Wait",name="main_task"@}]@}
27981 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
27982 @node GDB/MI Program Execution
27983 @section @sc{gdb/mi} Program Execution
27985 These are the asynchronous commands which generate the out-of-band
27986 record @samp{*stopped}. Currently @value{GDBN} only really executes
27987 asynchronously with remote targets and this interaction is mimicked in
27990 @subheading The @code{-exec-continue} Command
27991 @findex -exec-continue
27993 @subsubheading Synopsis
27996 -exec-continue [--reverse] [--all|--thread-group N]
27999 Resumes the execution of the inferior program, which will continue
28000 to execute until it reaches a debugger stop event. If the
28001 @samp{--reverse} option is specified, execution resumes in reverse until
28002 it reaches a stop event. Stop events may include
28005 breakpoints or watchpoints
28007 signals or exceptions
28009 the end of the process (or its beginning under @samp{--reverse})
28011 the end or beginning of a replay log if one is being used.
28013 In all-stop mode (@pxref{All-Stop
28014 Mode}), may resume only one thread, or all threads, depending on the
28015 value of the @samp{scheduler-locking} variable. If @samp{--all} is
28016 specified, all threads (in all inferiors) will be resumed. The @samp{--all} option is
28017 ignored in all-stop mode. If the @samp{--thread-group} options is
28018 specified, then all threads in that thread group are resumed.
28020 @subsubheading @value{GDBN} Command
28022 The corresponding @value{GDBN} corresponding is @samp{continue}.
28024 @subsubheading Example
28031 *stopped,reason="breakpoint-hit",disp="keep",bkptno="2",frame=@{
28032 func="foo",args=[],file="hello.c",fullname="/home/foo/bar/hello.c",
28038 @subheading The @code{-exec-finish} Command
28039 @findex -exec-finish
28041 @subsubheading Synopsis
28044 -exec-finish [--reverse]
28047 Resumes the execution of the inferior program until the current
28048 function is exited. Displays the results returned by the function.
28049 If the @samp{--reverse} option is specified, resumes the reverse
28050 execution of the inferior program until the point where current
28051 function was called.
28053 @subsubheading @value{GDBN} Command
28055 The corresponding @value{GDBN} command is @samp{finish}.
28057 @subsubheading Example
28059 Function returning @code{void}.
28066 *stopped,reason="function-finished",frame=@{func="main",args=[],
28067 file="hello.c",fullname="/home/foo/bar/hello.c",line="7"@}
28071 Function returning other than @code{void}. The name of the internal
28072 @value{GDBN} variable storing the result is printed, together with the
28079 *stopped,reason="function-finished",frame=@{addr="0x000107b0",func="foo",
28080 args=[@{name="a",value="1"],@{name="b",value="9"@}@},
28081 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
28082 gdb-result-var="$1",return-value="0"
28087 @subheading The @code{-exec-interrupt} Command
28088 @findex -exec-interrupt
28090 @subsubheading Synopsis
28093 -exec-interrupt [--all|--thread-group N]
28096 Interrupts the background execution of the target. Note how the token
28097 associated with the stop message is the one for the execution command
28098 that has been interrupted. The token for the interrupt itself only
28099 appears in the @samp{^done} output. If the user is trying to
28100 interrupt a non-running program, an error message will be printed.
28102 Note that when asynchronous execution is enabled, this command is
28103 asynchronous just like other execution commands. That is, first the
28104 @samp{^done} response will be printed, and the target stop will be
28105 reported after that using the @samp{*stopped} notification.
28107 In non-stop mode, only the context thread is interrupted by default.
28108 All threads (in all inferiors) will be interrupted if the
28109 @samp{--all} option is specified. If the @samp{--thread-group}
28110 option is specified, all threads in that group will be interrupted.
28112 @subsubheading @value{GDBN} Command
28114 The corresponding @value{GDBN} command is @samp{interrupt}.
28116 @subsubheading Example
28127 111*stopped,signal-name="SIGINT",signal-meaning="Interrupt",
28128 frame=@{addr="0x00010140",func="foo",args=[],file="try.c",
28129 fullname="/home/foo/bar/try.c",line="13"@}
28134 ^error,msg="mi_cmd_exec_interrupt: Inferior not executing."
28138 @subheading The @code{-exec-jump} Command
28141 @subsubheading Synopsis
28144 -exec-jump @var{location}
28147 Resumes execution of the inferior program at the location specified by
28148 parameter. @xref{Specify Location}, for a description of the
28149 different forms of @var{location}.
28151 @subsubheading @value{GDBN} Command
28153 The corresponding @value{GDBN} command is @samp{jump}.
28155 @subsubheading Example
28158 -exec-jump foo.c:10
28159 *running,thread-id="all"
28164 @subheading The @code{-exec-next} Command
28167 @subsubheading Synopsis
28170 -exec-next [--reverse]
28173 Resumes execution of the inferior program, stopping when the beginning
28174 of the next source line is reached.
28176 If the @samp{--reverse} option is specified, resumes reverse execution
28177 of the inferior program, stopping at the beginning of the previous
28178 source line. If you issue this command on the first line of a
28179 function, it will take you back to the caller of that function, to the
28180 source line where the function was called.
28183 @subsubheading @value{GDBN} Command
28185 The corresponding @value{GDBN} command is @samp{next}.
28187 @subsubheading Example
28193 *stopped,reason="end-stepping-range",line="8",file="hello.c"
28198 @subheading The @code{-exec-next-instruction} Command
28199 @findex -exec-next-instruction
28201 @subsubheading Synopsis
28204 -exec-next-instruction [--reverse]
28207 Executes one machine instruction. If the instruction is a function
28208 call, continues until the function returns. If the program stops at an
28209 instruction in the middle of a source line, the address will be
28212 If the @samp{--reverse} option is specified, resumes reverse execution
28213 of the inferior program, stopping at the previous instruction. If the
28214 previously executed instruction was a return from another function,
28215 it will continue to execute in reverse until the call to that function
28216 (from the current stack frame) is reached.
28218 @subsubheading @value{GDBN} Command
28220 The corresponding @value{GDBN} command is @samp{nexti}.
28222 @subsubheading Example
28226 -exec-next-instruction
28230 *stopped,reason="end-stepping-range",
28231 addr="0x000100d4",line="5",file="hello.c"
28236 @subheading The @code{-exec-return} Command
28237 @findex -exec-return
28239 @subsubheading Synopsis
28245 Makes current function return immediately. Doesn't execute the inferior.
28246 Displays the new current frame.
28248 @subsubheading @value{GDBN} Command
28250 The corresponding @value{GDBN} command is @samp{return}.
28252 @subsubheading Example
28256 200-break-insert callee4
28257 200^done,bkpt=@{number="1",addr="0x00010734",
28258 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",line="8"@}
28263 000*stopped,reason="breakpoint-hit",disp="keep",bkptno="1",
28264 frame=@{func="callee4",args=[],
28265 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
28266 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="8"@}
28272 111^done,frame=@{level="0",func="callee3",
28273 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"@}
28281 @subheading The @code{-exec-run} Command
28284 @subsubheading Synopsis
28287 -exec-run [--all | --thread-group N]
28290 Starts execution of the inferior from the beginning. The inferior
28291 executes until either a breakpoint is encountered or the program
28292 exits. In the latter case the output will include an exit code, if
28293 the program has exited exceptionally.
28295 When no option is specified, the current inferior is started. If the
28296 @samp{--thread-group} option is specified, it should refer to a thread
28297 group of type @samp{process}, and that thread group will be started.
28298 If the @samp{--all} option is specified, then all inferiors will be started.
28300 @subsubheading @value{GDBN} Command
28302 The corresponding @value{GDBN} command is @samp{run}.
28304 @subsubheading Examples
28309 ^done,bkpt=@{number="1",addr="0x0001072c",file="recursive2.c",line="4"@}
28314 *stopped,reason="breakpoint-hit",disp="keep",bkptno="1",
28315 frame=@{func="main",args=[],file="recursive2.c",
28316 fullname="/home/foo/bar/recursive2.c",line="4"@}
28321 Program exited normally:
28329 *stopped,reason="exited-normally"
28334 Program exited exceptionally:
28342 *stopped,reason="exited",exit-code="01"
28346 Another way the program can terminate is if it receives a signal such as
28347 @code{SIGINT}. In this case, @sc{gdb/mi} displays this:
28351 *stopped,reason="exited-signalled",signal-name="SIGINT",
28352 signal-meaning="Interrupt"
28356 @c @subheading -exec-signal
28359 @subheading The @code{-exec-step} Command
28362 @subsubheading Synopsis
28365 -exec-step [--reverse]
28368 Resumes execution of the inferior program, stopping when the beginning
28369 of the next source line is reached, if the next source line is not a
28370 function call. If it is, stop at the first instruction of the called
28371 function. If the @samp{--reverse} option is specified, resumes reverse
28372 execution of the inferior program, stopping at the beginning of the
28373 previously executed source line.
28375 @subsubheading @value{GDBN} Command
28377 The corresponding @value{GDBN} command is @samp{step}.
28379 @subsubheading Example
28381 Stepping into a function:
28387 *stopped,reason="end-stepping-range",
28388 frame=@{func="foo",args=[@{name="a",value="10"@},
28389 @{name="b",value="0"@}],file="recursive2.c",
28390 fullname="/home/foo/bar/recursive2.c",line="11"@}
28400 *stopped,reason="end-stepping-range",line="14",file="recursive2.c"
28405 @subheading The @code{-exec-step-instruction} Command
28406 @findex -exec-step-instruction
28408 @subsubheading Synopsis
28411 -exec-step-instruction [--reverse]
28414 Resumes the inferior which executes one machine instruction. If the
28415 @samp{--reverse} option is specified, resumes reverse execution of the
28416 inferior program, stopping at the previously executed instruction.
28417 The output, once @value{GDBN} has stopped, will vary depending on
28418 whether we have stopped in the middle of a source line or not. In the
28419 former case, the address at which the program stopped will be printed
28422 @subsubheading @value{GDBN} Command
28424 The corresponding @value{GDBN} command is @samp{stepi}.
28426 @subsubheading Example
28430 -exec-step-instruction
28434 *stopped,reason="end-stepping-range",
28435 frame=@{func="foo",args=[],file="try.c",
28436 fullname="/home/foo/bar/try.c",line="10"@}
28438 -exec-step-instruction
28442 *stopped,reason="end-stepping-range",
28443 frame=@{addr="0x000100f4",func="foo",args=[],file="try.c",
28444 fullname="/home/foo/bar/try.c",line="10"@}
28449 @subheading The @code{-exec-until} Command
28450 @findex -exec-until
28452 @subsubheading Synopsis
28455 -exec-until [ @var{location} ]
28458 Executes the inferior until the @var{location} specified in the
28459 argument is reached. If there is no argument, the inferior executes
28460 until a source line greater than the current one is reached. The
28461 reason for stopping in this case will be @samp{location-reached}.
28463 @subsubheading @value{GDBN} Command
28465 The corresponding @value{GDBN} command is @samp{until}.
28467 @subsubheading Example
28471 -exec-until recursive2.c:6
28475 *stopped,reason="location-reached",frame=@{func="main",args=[],
28476 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="6"@}
28481 @subheading -file-clear
28482 Is this going away????
28485 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
28486 @node GDB/MI Stack Manipulation
28487 @section @sc{gdb/mi} Stack Manipulation Commands
28490 @subheading The @code{-stack-info-frame} Command
28491 @findex -stack-info-frame
28493 @subsubheading Synopsis
28499 Get info on the selected frame.
28501 @subsubheading @value{GDBN} Command
28503 The corresponding @value{GDBN} command is @samp{info frame} or @samp{frame}
28504 (without arguments).
28506 @subsubheading Example
28511 ^done,frame=@{level="1",addr="0x0001076c",func="callee3",
28512 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
28513 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="17"@}
28517 @subheading The @code{-stack-info-depth} Command
28518 @findex -stack-info-depth
28520 @subsubheading Synopsis
28523 -stack-info-depth [ @var{max-depth} ]
28526 Return the depth of the stack. If the integer argument @var{max-depth}
28527 is specified, do not count beyond @var{max-depth} frames.
28529 @subsubheading @value{GDBN} Command
28531 There's no equivalent @value{GDBN} command.
28533 @subsubheading Example
28535 For a stack with frame levels 0 through 11:
28542 -stack-info-depth 4
28545 -stack-info-depth 12
28548 -stack-info-depth 11
28551 -stack-info-depth 13
28556 @subheading The @code{-stack-list-arguments} Command
28557 @findex -stack-list-arguments
28559 @subsubheading Synopsis
28562 -stack-list-arguments @var{print-values}
28563 [ @var{low-frame} @var{high-frame} ]
28566 Display a list of the arguments for the frames between @var{low-frame}
28567 and @var{high-frame} (inclusive). If @var{low-frame} and
28568 @var{high-frame} are not provided, list the arguments for the whole
28569 call stack. If the two arguments are equal, show the single frame
28570 at the corresponding level. It is an error if @var{low-frame} is
28571 larger than the actual number of frames. On the other hand,
28572 @var{high-frame} may be larger than the actual number of frames, in
28573 which case only existing frames will be returned.
28575 If @var{print-values} is 0 or @code{--no-values}, print only the names of
28576 the variables; if it is 1 or @code{--all-values}, print also their
28577 values; and if it is 2 or @code{--simple-values}, print the name,
28578 type and value for simple data types, and the name and type for arrays,
28579 structures and unions.
28581 Use of this command to obtain arguments in a single frame is
28582 deprecated in favor of the @samp{-stack-list-variables} command.
28584 @subsubheading @value{GDBN} Command
28586 @value{GDBN} does not have an equivalent command. @code{gdbtk} has a
28587 @samp{gdb_get_args} command which partially overlaps with the
28588 functionality of @samp{-stack-list-arguments}.
28590 @subsubheading Example
28597 frame=@{level="0",addr="0x00010734",func="callee4",
28598 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
28599 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="8"@},
28600 frame=@{level="1",addr="0x0001076c",func="callee3",
28601 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
28602 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="17"@},
28603 frame=@{level="2",addr="0x0001078c",func="callee2",
28604 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
28605 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="22"@},
28606 frame=@{level="3",addr="0x000107b4",func="callee1",
28607 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
28608 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="27"@},
28609 frame=@{level="4",addr="0x000107e0",func="main",
28610 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
28611 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="32"@}]
28613 -stack-list-arguments 0
28616 frame=@{level="0",args=[]@},
28617 frame=@{level="1",args=[name="strarg"]@},
28618 frame=@{level="2",args=[name="intarg",name="strarg"]@},
28619 frame=@{level="3",args=[name="intarg",name="strarg",name="fltarg"]@},
28620 frame=@{level="4",args=[]@}]
28622 -stack-list-arguments 1
28625 frame=@{level="0",args=[]@},
28627 args=[@{name="strarg",value="0x11940 \"A string argument.\""@}]@},
28628 frame=@{level="2",args=[
28629 @{name="intarg",value="2"@},
28630 @{name="strarg",value="0x11940 \"A string argument.\""@}]@},
28631 @{frame=@{level="3",args=[
28632 @{name="intarg",value="2"@},
28633 @{name="strarg",value="0x11940 \"A string argument.\""@},
28634 @{name="fltarg",value="3.5"@}]@},
28635 frame=@{level="4",args=[]@}]
28637 -stack-list-arguments 0 2 2
28638 ^done,stack-args=[frame=@{level="2",args=[name="intarg",name="strarg"]@}]
28640 -stack-list-arguments 1 2 2
28641 ^done,stack-args=[frame=@{level="2",
28642 args=[@{name="intarg",value="2"@},
28643 @{name="strarg",value="0x11940 \"A string argument.\""@}]@}]
28647 @c @subheading -stack-list-exception-handlers
28650 @subheading The @code{-stack-list-frames} Command
28651 @findex -stack-list-frames
28653 @subsubheading Synopsis
28656 -stack-list-frames [ @var{low-frame} @var{high-frame} ]
28659 List the frames currently on the stack. For each frame it displays the
28664 The frame number, 0 being the topmost frame, i.e., the innermost function.
28666 The @code{$pc} value for that frame.
28670 File name of the source file where the function lives.
28671 @item @var{fullname}
28672 The full file name of the source file where the function lives.
28674 Line number corresponding to the @code{$pc}.
28676 The shared library where this function is defined. This is only given
28677 if the frame's function is not known.
28680 If invoked without arguments, this command prints a backtrace for the
28681 whole stack. If given two integer arguments, it shows the frames whose
28682 levels are between the two arguments (inclusive). If the two arguments
28683 are equal, it shows the single frame at the corresponding level. It is
28684 an error if @var{low-frame} is larger than the actual number of
28685 frames. On the other hand, @var{high-frame} may be larger than the
28686 actual number of frames, in which case only existing frames will be returned.
28688 @subsubheading @value{GDBN} Command
28690 The corresponding @value{GDBN} commands are @samp{backtrace} and @samp{where}.
28692 @subsubheading Example
28694 Full stack backtrace:
28700 [frame=@{level="0",addr="0x0001076c",func="foo",
28701 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="11"@},
28702 frame=@{level="1",addr="0x000107a4",func="foo",
28703 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
28704 frame=@{level="2",addr="0x000107a4",func="foo",
28705 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
28706 frame=@{level="3",addr="0x000107a4",func="foo",
28707 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
28708 frame=@{level="4",addr="0x000107a4",func="foo",
28709 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
28710 frame=@{level="5",addr="0x000107a4",func="foo",
28711 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
28712 frame=@{level="6",addr="0x000107a4",func="foo",
28713 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
28714 frame=@{level="7",addr="0x000107a4",func="foo",
28715 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
28716 frame=@{level="8",addr="0x000107a4",func="foo",
28717 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
28718 frame=@{level="9",addr="0x000107a4",func="foo",
28719 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
28720 frame=@{level="10",addr="0x000107a4",func="foo",
28721 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
28722 frame=@{level="11",addr="0x00010738",func="main",
28723 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="4"@}]
28727 Show frames between @var{low_frame} and @var{high_frame}:
28731 -stack-list-frames 3 5
28733 [frame=@{level="3",addr="0x000107a4",func="foo",
28734 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
28735 frame=@{level="4",addr="0x000107a4",func="foo",
28736 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
28737 frame=@{level="5",addr="0x000107a4",func="foo",
28738 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@}]
28742 Show a single frame:
28746 -stack-list-frames 3 3
28748 [frame=@{level="3",addr="0x000107a4",func="foo",
28749 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@}]
28754 @subheading The @code{-stack-list-locals} Command
28755 @findex -stack-list-locals
28757 @subsubheading Synopsis
28760 -stack-list-locals @var{print-values}
28763 Display the local variable names for the selected frame. If
28764 @var{print-values} is 0 or @code{--no-values}, print only the names of
28765 the variables; if it is 1 or @code{--all-values}, print also their
28766 values; and if it is 2 or @code{--simple-values}, print the name,
28767 type and value for simple data types, and the name and type for arrays,
28768 structures and unions. In this last case, a frontend can immediately
28769 display the value of simple data types and create variable objects for
28770 other data types when the user wishes to explore their values in
28773 This command is deprecated in favor of the
28774 @samp{-stack-list-variables} command.
28776 @subsubheading @value{GDBN} Command
28778 @samp{info locals} in @value{GDBN}, @samp{gdb_get_locals} in @code{gdbtk}.
28780 @subsubheading Example
28784 -stack-list-locals 0
28785 ^done,locals=[name="A",name="B",name="C"]
28787 -stack-list-locals --all-values
28788 ^done,locals=[@{name="A",value="1"@},@{name="B",value="2"@},
28789 @{name="C",value="@{1, 2, 3@}"@}]
28790 -stack-list-locals --simple-values
28791 ^done,locals=[@{name="A",type="int",value="1"@},
28792 @{name="B",type="int",value="2"@},@{name="C",type="int [3]"@}]
28796 @subheading The @code{-stack-list-variables} Command
28797 @findex -stack-list-variables
28799 @subsubheading Synopsis
28802 -stack-list-variables @var{print-values}
28805 Display the names of local variables and function arguments for the selected frame. If
28806 @var{print-values} is 0 or @code{--no-values}, print only the names of
28807 the variables; if it is 1 or @code{--all-values}, print also their
28808 values; and if it is 2 or @code{--simple-values}, print the name,
28809 type and value for simple data types, and the name and type for arrays,
28810 structures and unions.
28812 @subsubheading Example
28816 -stack-list-variables --thread 1 --frame 0 --all-values
28817 ^done,variables=[@{name="x",value="11"@},@{name="s",value="@{a = 1, b = 2@}"@}]
28822 @subheading The @code{-stack-select-frame} Command
28823 @findex -stack-select-frame
28825 @subsubheading Synopsis
28828 -stack-select-frame @var{framenum}
28831 Change the selected frame. Select a different frame @var{framenum} on
28834 This command in deprecated in favor of passing the @samp{--frame}
28835 option to every command.
28837 @subsubheading @value{GDBN} Command
28839 The corresponding @value{GDBN} commands are @samp{frame}, @samp{up},
28840 @samp{down}, @samp{select-frame}, @samp{up-silent}, and @samp{down-silent}.
28842 @subsubheading Example
28846 -stack-select-frame 2
28851 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
28852 @node GDB/MI Variable Objects
28853 @section @sc{gdb/mi} Variable Objects
28857 @subheading Motivation for Variable Objects in @sc{gdb/mi}
28859 For the implementation of a variable debugger window (locals, watched
28860 expressions, etc.), we are proposing the adaptation of the existing code
28861 used by @code{Insight}.
28863 The two main reasons for that are:
28867 It has been proven in practice (it is already on its second generation).
28870 It will shorten development time (needless to say how important it is
28874 The original interface was designed to be used by Tcl code, so it was
28875 slightly changed so it could be used through @sc{gdb/mi}. This section
28876 describes the @sc{gdb/mi} operations that will be available and gives some
28877 hints about their use.
28879 @emph{Note}: In addition to the set of operations described here, we
28880 expect the @sc{gui} implementation of a variable window to require, at
28881 least, the following operations:
28884 @item @code{-gdb-show} @code{output-radix}
28885 @item @code{-stack-list-arguments}
28886 @item @code{-stack-list-locals}
28887 @item @code{-stack-select-frame}
28892 @subheading Introduction to Variable Objects
28894 @cindex variable objects in @sc{gdb/mi}
28896 Variable objects are "object-oriented" MI interface for examining and
28897 changing values of expressions. Unlike some other MI interfaces that
28898 work with expressions, variable objects are specifically designed for
28899 simple and efficient presentation in the frontend. A variable object
28900 is identified by string name. When a variable object is created, the
28901 frontend specifies the expression for that variable object. The
28902 expression can be a simple variable, or it can be an arbitrary complex
28903 expression, and can even involve CPU registers. After creating a
28904 variable object, the frontend can invoke other variable object
28905 operations---for example to obtain or change the value of a variable
28906 object, or to change display format.
28908 Variable objects have hierarchical tree structure. Any variable object
28909 that corresponds to a composite type, such as structure in C, has
28910 a number of child variable objects, for example corresponding to each
28911 element of a structure. A child variable object can itself have
28912 children, recursively. Recursion ends when we reach
28913 leaf variable objects, which always have built-in types. Child variable
28914 objects are created only by explicit request, so if a frontend
28915 is not interested in the children of a particular variable object, no
28916 child will be created.
28918 For a leaf variable object it is possible to obtain its value as a
28919 string, or set the value from a string. String value can be also
28920 obtained for a non-leaf variable object, but it's generally a string
28921 that only indicates the type of the object, and does not list its
28922 contents. Assignment to a non-leaf variable object is not allowed.
28924 A frontend does not need to read the values of all variable objects each time
28925 the program stops. Instead, MI provides an update command that lists all
28926 variable objects whose values has changed since the last update
28927 operation. This considerably reduces the amount of data that must
28928 be transferred to the frontend. As noted above, children variable
28929 objects are created on demand, and only leaf variable objects have a
28930 real value. As result, gdb will read target memory only for leaf
28931 variables that frontend has created.
28933 The automatic update is not always desirable. For example, a frontend
28934 might want to keep a value of some expression for future reference,
28935 and never update it. For another example, fetching memory is
28936 relatively slow for embedded targets, so a frontend might want
28937 to disable automatic update for the variables that are either not
28938 visible on the screen, or ``closed''. This is possible using so
28939 called ``frozen variable objects''. Such variable objects are never
28940 implicitly updated.
28942 Variable objects can be either @dfn{fixed} or @dfn{floating}. For the
28943 fixed variable object, the expression is parsed when the variable
28944 object is created, including associating identifiers to specific
28945 variables. The meaning of expression never changes. For a floating
28946 variable object the values of variables whose names appear in the
28947 expressions are re-evaluated every time in the context of the current
28948 frame. Consider this example:
28953 struct work_state state;
28960 If a fixed variable object for the @code{state} variable is created in
28961 this function, and we enter the recursive call, the variable
28962 object will report the value of @code{state} in the top-level
28963 @code{do_work} invocation. On the other hand, a floating variable
28964 object will report the value of @code{state} in the current frame.
28966 If an expression specified when creating a fixed variable object
28967 refers to a local variable, the variable object becomes bound to the
28968 thread and frame in which the variable object is created. When such
28969 variable object is updated, @value{GDBN} makes sure that the
28970 thread/frame combination the variable object is bound to still exists,
28971 and re-evaluates the variable object in context of that thread/frame.
28973 The following is the complete set of @sc{gdb/mi} operations defined to
28974 access this functionality:
28976 @multitable @columnfractions .4 .6
28977 @item @strong{Operation}
28978 @tab @strong{Description}
28980 @item @code{-enable-pretty-printing}
28981 @tab enable Python-based pretty-printing
28982 @item @code{-var-create}
28983 @tab create a variable object
28984 @item @code{-var-delete}
28985 @tab delete the variable object and/or its children
28986 @item @code{-var-set-format}
28987 @tab set the display format of this variable
28988 @item @code{-var-show-format}
28989 @tab show the display format of this variable
28990 @item @code{-var-info-num-children}
28991 @tab tells how many children this object has
28992 @item @code{-var-list-children}
28993 @tab return a list of the object's children
28994 @item @code{-var-info-type}
28995 @tab show the type of this variable object
28996 @item @code{-var-info-expression}
28997 @tab print parent-relative expression that this variable object represents
28998 @item @code{-var-info-path-expression}
28999 @tab print full expression that this variable object represents
29000 @item @code{-var-show-attributes}
29001 @tab is this variable editable? does it exist here?
29002 @item @code{-var-evaluate-expression}
29003 @tab get the value of this variable
29004 @item @code{-var-assign}
29005 @tab set the value of this variable
29006 @item @code{-var-update}
29007 @tab update the variable and its children
29008 @item @code{-var-set-frozen}
29009 @tab set frozeness attribute
29010 @item @code{-var-set-update-range}
29011 @tab set range of children to display on update
29014 In the next subsection we describe each operation in detail and suggest
29015 how it can be used.
29017 @subheading Description And Use of Operations on Variable Objects
29019 @subheading The @code{-enable-pretty-printing} Command
29020 @findex -enable-pretty-printing
29023 -enable-pretty-printing
29026 @value{GDBN} allows Python-based visualizers to affect the output of the
29027 MI variable object commands. However, because there was no way to
29028 implement this in a fully backward-compatible way, a front end must
29029 request that this functionality be enabled.
29031 Once enabled, this feature cannot be disabled.
29033 Note that if Python support has not been compiled into @value{GDBN},
29034 this command will still succeed (and do nothing).
29036 This feature is currently (as of @value{GDBN} 7.0) experimental, and
29037 may work differently in future versions of @value{GDBN}.
29039 @subheading The @code{-var-create} Command
29040 @findex -var-create
29042 @subsubheading Synopsis
29045 -var-create @{@var{name} | "-"@}
29046 @{@var{frame-addr} | "*" | "@@"@} @var{expression}
29049 This operation creates a variable object, which allows the monitoring of
29050 a variable, the result of an expression, a memory cell or a CPU
29053 The @var{name} parameter is the string by which the object can be
29054 referenced. It must be unique. If @samp{-} is specified, the varobj
29055 system will generate a string ``varNNNNNN'' automatically. It will be
29056 unique provided that one does not specify @var{name} of that format.
29057 The command fails if a duplicate name is found.
29059 The frame under which the expression should be evaluated can be
29060 specified by @var{frame-addr}. A @samp{*} indicates that the current
29061 frame should be used. A @samp{@@} indicates that a floating variable
29062 object must be created.
29064 @var{expression} is any expression valid on the current language set (must not
29065 begin with a @samp{*}), or one of the following:
29069 @samp{*@var{addr}}, where @var{addr} is the address of a memory cell
29072 @samp{*@var{addr}-@var{addr}} --- a memory address range (TBD)
29075 @samp{$@var{regname}} --- a CPU register name
29078 @cindex dynamic varobj
29079 A varobj's contents may be provided by a Python-based pretty-printer. In this
29080 case the varobj is known as a @dfn{dynamic varobj}. Dynamic varobjs
29081 have slightly different semantics in some cases. If the
29082 @code{-enable-pretty-printing} command is not sent, then @value{GDBN}
29083 will never create a dynamic varobj. This ensures backward
29084 compatibility for existing clients.
29086 @subsubheading Result
29088 This operation returns attributes of the newly-created varobj. These
29093 The name of the varobj.
29096 The number of children of the varobj. This number is not necessarily
29097 reliable for a dynamic varobj. Instead, you must examine the
29098 @samp{has_more} attribute.
29101 The varobj's scalar value. For a varobj whose type is some sort of
29102 aggregate (e.g., a @code{struct}), or for a dynamic varobj, this value
29103 will not be interesting.
29106 The varobj's type. This is a string representation of the type, as
29107 would be printed by the @value{GDBN} CLI. If @samp{print object}
29108 (@pxref{Print Settings, set print object}) is set to @code{on}, the
29109 @emph{actual} (derived) type of the object is shown rather than the
29110 @emph{declared} one.
29113 If a variable object is bound to a specific thread, then this is the
29114 thread's identifier.
29117 For a dynamic varobj, this indicates whether there appear to be any
29118 children available. For a non-dynamic varobj, this will be 0.
29121 This attribute will be present and have the value @samp{1} if the
29122 varobj is a dynamic varobj. If the varobj is not a dynamic varobj,
29123 then this attribute will not be present.
29126 A dynamic varobj can supply a display hint to the front end. The
29127 value comes directly from the Python pretty-printer object's
29128 @code{display_hint} method. @xref{Pretty Printing API}.
29131 Typical output will look like this:
29134 name="@var{name}",numchild="@var{N}",type="@var{type}",thread-id="@var{M}",
29135 has_more="@var{has_more}"
29139 @subheading The @code{-var-delete} Command
29140 @findex -var-delete
29142 @subsubheading Synopsis
29145 -var-delete [ -c ] @var{name}
29148 Deletes a previously created variable object and all of its children.
29149 With the @samp{-c} option, just deletes the children.
29151 Returns an error if the object @var{name} is not found.
29154 @subheading The @code{-var-set-format} Command
29155 @findex -var-set-format
29157 @subsubheading Synopsis
29160 -var-set-format @var{name} @var{format-spec}
29163 Sets the output format for the value of the object @var{name} to be
29166 @anchor{-var-set-format}
29167 The syntax for the @var{format-spec} is as follows:
29170 @var{format-spec} @expansion{}
29171 @{binary | decimal | hexadecimal | octal | natural@}
29174 The natural format is the default format choosen automatically
29175 based on the variable type (like decimal for an @code{int}, hex
29176 for pointers, etc.).
29178 For a variable with children, the format is set only on the
29179 variable itself, and the children are not affected.
29181 @subheading The @code{-var-show-format} Command
29182 @findex -var-show-format
29184 @subsubheading Synopsis
29187 -var-show-format @var{name}
29190 Returns the format used to display the value of the object @var{name}.
29193 @var{format} @expansion{}
29198 @subheading The @code{-var-info-num-children} Command
29199 @findex -var-info-num-children
29201 @subsubheading Synopsis
29204 -var-info-num-children @var{name}
29207 Returns the number of children of a variable object @var{name}:
29213 Note that this number is not completely reliable for a dynamic varobj.
29214 It will return the current number of children, but more children may
29218 @subheading The @code{-var-list-children} Command
29219 @findex -var-list-children
29221 @subsubheading Synopsis
29224 -var-list-children [@var{print-values}] @var{name} [@var{from} @var{to}]
29226 @anchor{-var-list-children}
29228 Return a list of the children of the specified variable object and
29229 create variable objects for them, if they do not already exist. With
29230 a single argument or if @var{print-values} has a value of 0 or
29231 @code{--no-values}, print only the names of the variables; if
29232 @var{print-values} is 1 or @code{--all-values}, also print their
29233 values; and if it is 2 or @code{--simple-values} print the name and
29234 value for simple data types and just the name for arrays, structures
29237 @var{from} and @var{to}, if specified, indicate the range of children
29238 to report. If @var{from} or @var{to} is less than zero, the range is
29239 reset and all children will be reported. Otherwise, children starting
29240 at @var{from} (zero-based) and up to and excluding @var{to} will be
29243 If a child range is requested, it will only affect the current call to
29244 @code{-var-list-children}, but not future calls to @code{-var-update}.
29245 For this, you must instead use @code{-var-set-update-range}. The
29246 intent of this approach is to enable a front end to implement any
29247 update approach it likes; for example, scrolling a view may cause the
29248 front end to request more children with @code{-var-list-children}, and
29249 then the front end could call @code{-var-set-update-range} with a
29250 different range to ensure that future updates are restricted to just
29253 For each child the following results are returned:
29258 Name of the variable object created for this child.
29261 The expression to be shown to the user by the front end to designate this child.
29262 For example this may be the name of a structure member.
29264 For a dynamic varobj, this value cannot be used to form an
29265 expression. There is no way to do this at all with a dynamic varobj.
29267 For C/C@t{++} structures there are several pseudo children returned to
29268 designate access qualifiers. For these pseudo children @var{exp} is
29269 @samp{public}, @samp{private}, or @samp{protected}. In this case the
29270 type and value are not present.
29272 A dynamic varobj will not report the access qualifying
29273 pseudo-children, regardless of the language. This information is not
29274 available at all with a dynamic varobj.
29277 Number of children this child has. For a dynamic varobj, this will be
29281 The type of the child. If @samp{print object}
29282 (@pxref{Print Settings, set print object}) is set to @code{on}, the
29283 @emph{actual} (derived) type of the object is shown rather than the
29284 @emph{declared} one.
29287 If values were requested, this is the value.
29290 If this variable object is associated with a thread, this is the thread id.
29291 Otherwise this result is not present.
29294 If the variable object is frozen, this variable will be present with a value of 1.
29297 The result may have its own attributes:
29301 A dynamic varobj can supply a display hint to the front end. The
29302 value comes directly from the Python pretty-printer object's
29303 @code{display_hint} method. @xref{Pretty Printing API}.
29306 This is an integer attribute which is nonzero if there are children
29307 remaining after the end of the selected range.
29310 @subsubheading Example
29314 -var-list-children n
29315 ^done,numchild=@var{n},children=[child=@{name=@var{name},exp=@var{exp},
29316 numchild=@var{n},type=@var{type}@},@r{(repeats N times)}]
29318 -var-list-children --all-values n
29319 ^done,numchild=@var{n},children=[child=@{name=@var{name},exp=@var{exp},
29320 numchild=@var{n},value=@var{value},type=@var{type}@},@r{(repeats N times)}]
29324 @subheading The @code{-var-info-type} Command
29325 @findex -var-info-type
29327 @subsubheading Synopsis
29330 -var-info-type @var{name}
29333 Returns the type of the specified variable @var{name}. The type is
29334 returned as a string in the same format as it is output by the
29338 type=@var{typename}
29342 @subheading The @code{-var-info-expression} Command
29343 @findex -var-info-expression
29345 @subsubheading Synopsis
29348 -var-info-expression @var{name}
29351 Returns a string that is suitable for presenting this
29352 variable object in user interface. The string is generally
29353 not valid expression in the current language, and cannot be evaluated.
29355 For example, if @code{a} is an array, and variable object
29356 @code{A} was created for @code{a}, then we'll get this output:
29359 (gdb) -var-info-expression A.1
29360 ^done,lang="C",exp="1"
29364 Here, the values of @code{lang} can be @code{@{"C" | "C++" | "Java"@}}.
29366 Note that the output of the @code{-var-list-children} command also
29367 includes those expressions, so the @code{-var-info-expression} command
29370 @subheading The @code{-var-info-path-expression} Command
29371 @findex -var-info-path-expression
29373 @subsubheading Synopsis
29376 -var-info-path-expression @var{name}
29379 Returns an expression that can be evaluated in the current
29380 context and will yield the same value that a variable object has.
29381 Compare this with the @code{-var-info-expression} command, which
29382 result can be used only for UI presentation. Typical use of
29383 the @code{-var-info-path-expression} command is creating a
29384 watchpoint from a variable object.
29386 This command is currently not valid for children of a dynamic varobj,
29387 and will give an error when invoked on one.
29389 For example, suppose @code{C} is a C@t{++} class, derived from class
29390 @code{Base}, and that the @code{Base} class has a member called
29391 @code{m_size}. Assume a variable @code{c} is has the type of
29392 @code{C} and a variable object @code{C} was created for variable
29393 @code{c}. Then, we'll get this output:
29395 (gdb) -var-info-path-expression C.Base.public.m_size
29396 ^done,path_expr=((Base)c).m_size)
29399 @subheading The @code{-var-show-attributes} Command
29400 @findex -var-show-attributes
29402 @subsubheading Synopsis
29405 -var-show-attributes @var{name}
29408 List attributes of the specified variable object @var{name}:
29411 status=@var{attr} [ ( ,@var{attr} )* ]
29415 where @var{attr} is @code{@{ @{ editable | noneditable @} | TBD @}}.
29417 @subheading The @code{-var-evaluate-expression} Command
29418 @findex -var-evaluate-expression
29420 @subsubheading Synopsis
29423 -var-evaluate-expression [-f @var{format-spec}] @var{name}
29426 Evaluates the expression that is represented by the specified variable
29427 object and returns its value as a string. The format of the string
29428 can be specified with the @samp{-f} option. The possible values of
29429 this option are the same as for @code{-var-set-format}
29430 (@pxref{-var-set-format}). If the @samp{-f} option is not specified,
29431 the current display format will be used. The current display format
29432 can be changed using the @code{-var-set-format} command.
29438 Note that one must invoke @code{-var-list-children} for a variable
29439 before the value of a child variable can be evaluated.
29441 @subheading The @code{-var-assign} Command
29442 @findex -var-assign
29444 @subsubheading Synopsis
29447 -var-assign @var{name} @var{expression}
29450 Assigns the value of @var{expression} to the variable object specified
29451 by @var{name}. The object must be @samp{editable}. If the variable's
29452 value is altered by the assign, the variable will show up in any
29453 subsequent @code{-var-update} list.
29455 @subsubheading Example
29463 ^done,changelist=[@{name="var1",in_scope="true",type_changed="false"@}]
29467 @subheading The @code{-var-update} Command
29468 @findex -var-update
29470 @subsubheading Synopsis
29473 -var-update [@var{print-values}] @{@var{name} | "*"@}
29476 Reevaluate the expressions corresponding to the variable object
29477 @var{name} and all its direct and indirect children, and return the
29478 list of variable objects whose values have changed; @var{name} must
29479 be a root variable object. Here, ``changed'' means that the result of
29480 @code{-var-evaluate-expression} before and after the
29481 @code{-var-update} is different. If @samp{*} is used as the variable
29482 object names, all existing variable objects are updated, except
29483 for frozen ones (@pxref{-var-set-frozen}). The option
29484 @var{print-values} determines whether both names and values, or just
29485 names are printed. The possible values of this option are the same
29486 as for @code{-var-list-children} (@pxref{-var-list-children}). It is
29487 recommended to use the @samp{--all-values} option, to reduce the
29488 number of MI commands needed on each program stop.
29490 With the @samp{*} parameter, if a variable object is bound to a
29491 currently running thread, it will not be updated, without any
29494 If @code{-var-set-update-range} was previously used on a varobj, then
29495 only the selected range of children will be reported.
29497 @code{-var-update} reports all the changed varobjs in a tuple named
29500 Each item in the change list is itself a tuple holding:
29504 The name of the varobj.
29507 If values were requested for this update, then this field will be
29508 present and will hold the value of the varobj.
29511 @anchor{-var-update}
29512 This field is a string which may take one of three values:
29516 The variable object's current value is valid.
29519 The variable object does not currently hold a valid value but it may
29520 hold one in the future if its associated expression comes back into
29524 The variable object no longer holds a valid value.
29525 This can occur when the executable file being debugged has changed,
29526 either through recompilation or by using the @value{GDBN} @code{file}
29527 command. The front end should normally choose to delete these variable
29531 In the future new values may be added to this list so the front should
29532 be prepared for this possibility. @xref{GDB/MI Development and Front Ends, ,@sc{GDB/MI} Development and Front Ends}.
29535 This is only present if the varobj is still valid. If the type
29536 changed, then this will be the string @samp{true}; otherwise it will
29539 When a varobj's type changes, its children are also likely to have
29540 become incorrect. Therefore, the varobj's children are automatically
29541 deleted when this attribute is @samp{true}. Also, the varobj's update
29542 range, when set using the @code{-var-set-update-range} command, is
29546 If the varobj's type changed, then this field will be present and will
29549 @item new_num_children
29550 For a dynamic varobj, if the number of children changed, or if the
29551 type changed, this will be the new number of children.
29553 The @samp{numchild} field in other varobj responses is generally not
29554 valid for a dynamic varobj -- it will show the number of children that
29555 @value{GDBN} knows about, but because dynamic varobjs lazily
29556 instantiate their children, this will not reflect the number of
29557 children which may be available.
29559 The @samp{new_num_children} attribute only reports changes to the
29560 number of children known by @value{GDBN}. This is the only way to
29561 detect whether an update has removed children (which necessarily can
29562 only happen at the end of the update range).
29565 The display hint, if any.
29568 This is an integer value, which will be 1 if there are more children
29569 available outside the varobj's update range.
29572 This attribute will be present and have the value @samp{1} if the
29573 varobj is a dynamic varobj. If the varobj is not a dynamic varobj,
29574 then this attribute will not be present.
29577 If new children were added to a dynamic varobj within the selected
29578 update range (as set by @code{-var-set-update-range}), then they will
29579 be listed in this attribute.
29582 @subsubheading Example
29589 -var-update --all-values var1
29590 ^done,changelist=[@{name="var1",value="3",in_scope="true",
29591 type_changed="false"@}]
29595 @subheading The @code{-var-set-frozen} Command
29596 @findex -var-set-frozen
29597 @anchor{-var-set-frozen}
29599 @subsubheading Synopsis
29602 -var-set-frozen @var{name} @var{flag}
29605 Set the frozenness flag on the variable object @var{name}. The
29606 @var{flag} parameter should be either @samp{1} to make the variable
29607 frozen or @samp{0} to make it unfrozen. If a variable object is
29608 frozen, then neither itself, nor any of its children, are
29609 implicitly updated by @code{-var-update} of
29610 a parent variable or by @code{-var-update *}. Only
29611 @code{-var-update} of the variable itself will update its value and
29612 values of its children. After a variable object is unfrozen, it is
29613 implicitly updated by all subsequent @code{-var-update} operations.
29614 Unfreezing a variable does not update it, only subsequent
29615 @code{-var-update} does.
29617 @subsubheading Example
29621 -var-set-frozen V 1
29626 @subheading The @code{-var-set-update-range} command
29627 @findex -var-set-update-range
29628 @anchor{-var-set-update-range}
29630 @subsubheading Synopsis
29633 -var-set-update-range @var{name} @var{from} @var{to}
29636 Set the range of children to be returned by future invocations of
29637 @code{-var-update}.
29639 @var{from} and @var{to} indicate the range of children to report. If
29640 @var{from} or @var{to} is less than zero, the range is reset and all
29641 children will be reported. Otherwise, children starting at @var{from}
29642 (zero-based) and up to and excluding @var{to} will be reported.
29644 @subsubheading Example
29648 -var-set-update-range V 1 2
29652 @subheading The @code{-var-set-visualizer} command
29653 @findex -var-set-visualizer
29654 @anchor{-var-set-visualizer}
29656 @subsubheading Synopsis
29659 -var-set-visualizer @var{name} @var{visualizer}
29662 Set a visualizer for the variable object @var{name}.
29664 @var{visualizer} is the visualizer to use. The special value
29665 @samp{None} means to disable any visualizer in use.
29667 If not @samp{None}, @var{visualizer} must be a Python expression.
29668 This expression must evaluate to a callable object which accepts a
29669 single argument. @value{GDBN} will call this object with the value of
29670 the varobj @var{name} as an argument (this is done so that the same
29671 Python pretty-printing code can be used for both the CLI and MI).
29672 When called, this object must return an object which conforms to the
29673 pretty-printing interface (@pxref{Pretty Printing API}).
29675 The pre-defined function @code{gdb.default_visualizer} may be used to
29676 select a visualizer by following the built-in process
29677 (@pxref{Selecting Pretty-Printers}). This is done automatically when
29678 a varobj is created, and so ordinarily is not needed.
29680 This feature is only available if Python support is enabled. The MI
29681 command @code{-list-features} (@pxref{GDB/MI Miscellaneous Commands})
29682 can be used to check this.
29684 @subsubheading Example
29686 Resetting the visualizer:
29690 -var-set-visualizer V None
29694 Reselecting the default (type-based) visualizer:
29698 -var-set-visualizer V gdb.default_visualizer
29702 Suppose @code{SomeClass} is a visualizer class. A lambda expression
29703 can be used to instantiate this class for a varobj:
29707 -var-set-visualizer V "lambda val: SomeClass()"
29711 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
29712 @node GDB/MI Data Manipulation
29713 @section @sc{gdb/mi} Data Manipulation
29715 @cindex data manipulation, in @sc{gdb/mi}
29716 @cindex @sc{gdb/mi}, data manipulation
29717 This section describes the @sc{gdb/mi} commands that manipulate data:
29718 examine memory and registers, evaluate expressions, etc.
29720 @c REMOVED FROM THE INTERFACE.
29721 @c @subheading -data-assign
29722 @c Change the value of a program variable. Plenty of side effects.
29723 @c @subsubheading GDB Command
29725 @c @subsubheading Example
29728 @subheading The @code{-data-disassemble} Command
29729 @findex -data-disassemble
29731 @subsubheading Synopsis
29735 [ -s @var{start-addr} -e @var{end-addr} ]
29736 | [ -f @var{filename} -l @var{linenum} [ -n @var{lines} ] ]
29744 @item @var{start-addr}
29745 is the beginning address (or @code{$pc})
29746 @item @var{end-addr}
29748 @item @var{filename}
29749 is the name of the file to disassemble
29750 @item @var{linenum}
29751 is the line number to disassemble around
29753 is the number of disassembly lines to be produced. If it is -1,
29754 the whole function will be disassembled, in case no @var{end-addr} is
29755 specified. If @var{end-addr} is specified as a non-zero value, and
29756 @var{lines} is lower than the number of disassembly lines between
29757 @var{start-addr} and @var{end-addr}, only @var{lines} lines are
29758 displayed; if @var{lines} is higher than the number of lines between
29759 @var{start-addr} and @var{end-addr}, only the lines up to @var{end-addr}
29762 is either 0 (meaning only disassembly), 1 (meaning mixed source and
29763 disassembly), 2 (meaning disassembly with raw opcodes), or 3 (meaning
29764 mixed source and disassembly with raw opcodes).
29767 @subsubheading Result
29769 The output for each instruction is composed of four fields:
29778 Note that whatever included in the instruction field, is not manipulated
29779 directly by @sc{gdb/mi}, i.e., it is not possible to adjust its format.
29781 @subsubheading @value{GDBN} Command
29783 There's no direct mapping from this command to the CLI.
29785 @subsubheading Example
29787 Disassemble from the current value of @code{$pc} to @code{$pc + 20}:
29791 -data-disassemble -s $pc -e "$pc + 20" -- 0
29794 @{address="0x000107c0",func-name="main",offset="4",
29795 inst="mov 2, %o0"@},
29796 @{address="0x000107c4",func-name="main",offset="8",
29797 inst="sethi %hi(0x11800), %o2"@},
29798 @{address="0x000107c8",func-name="main",offset="12",
29799 inst="or %o2, 0x140, %o1\t! 0x11940 <_lib_version+8>"@},
29800 @{address="0x000107cc",func-name="main",offset="16",
29801 inst="sethi %hi(0x11800), %o2"@},
29802 @{address="0x000107d0",func-name="main",offset="20",
29803 inst="or %o2, 0x168, %o4\t! 0x11968 <_lib_version+48>"@}]
29807 Disassemble the whole @code{main} function. Line 32 is part of
29811 -data-disassemble -f basics.c -l 32 -- 0
29813 @{address="0x000107bc",func-name="main",offset="0",
29814 inst="save %sp, -112, %sp"@},
29815 @{address="0x000107c0",func-name="main",offset="4",
29816 inst="mov 2, %o0"@},
29817 @{address="0x000107c4",func-name="main",offset="8",
29818 inst="sethi %hi(0x11800), %o2"@},
29820 @{address="0x0001081c",func-name="main",offset="96",inst="ret "@},
29821 @{address="0x00010820",func-name="main",offset="100",inst="restore "@}]
29825 Disassemble 3 instructions from the start of @code{main}:
29829 -data-disassemble -f basics.c -l 32 -n 3 -- 0
29831 @{address="0x000107bc",func-name="main",offset="0",
29832 inst="save %sp, -112, %sp"@},
29833 @{address="0x000107c0",func-name="main",offset="4",
29834 inst="mov 2, %o0"@},
29835 @{address="0x000107c4",func-name="main",offset="8",
29836 inst="sethi %hi(0x11800), %o2"@}]
29840 Disassemble 3 instructions from the start of @code{main} in mixed mode:
29844 -data-disassemble -f basics.c -l 32 -n 3 -- 1
29846 src_and_asm_line=@{line="31",
29847 file="/kwikemart/marge/ezannoni/flathead-dev/devo/gdb/ \
29848 testsuite/gdb.mi/basics.c",line_asm_insn=[
29849 @{address="0x000107bc",func-name="main",offset="0",
29850 inst="save %sp, -112, %sp"@}]@},
29851 src_and_asm_line=@{line="32",
29852 file="/kwikemart/marge/ezannoni/flathead-dev/devo/gdb/ \
29853 testsuite/gdb.mi/basics.c",line_asm_insn=[
29854 @{address="0x000107c0",func-name="main",offset="4",
29855 inst="mov 2, %o0"@},
29856 @{address="0x000107c4",func-name="main",offset="8",
29857 inst="sethi %hi(0x11800), %o2"@}]@}]
29862 @subheading The @code{-data-evaluate-expression} Command
29863 @findex -data-evaluate-expression
29865 @subsubheading Synopsis
29868 -data-evaluate-expression @var{expr}
29871 Evaluate @var{expr} as an expression. The expression could contain an
29872 inferior function call. The function call will execute synchronously.
29873 If the expression contains spaces, it must be enclosed in double quotes.
29875 @subsubheading @value{GDBN} Command
29877 The corresponding @value{GDBN} commands are @samp{print}, @samp{output}, and
29878 @samp{call}. In @code{gdbtk} only, there's a corresponding
29879 @samp{gdb_eval} command.
29881 @subsubheading Example
29883 In the following example, the numbers that precede the commands are the
29884 @dfn{tokens} described in @ref{GDB/MI Command Syntax, ,@sc{gdb/mi}
29885 Command Syntax}. Notice how @sc{gdb/mi} returns the same tokens in its
29889 211-data-evaluate-expression A
29892 311-data-evaluate-expression &A
29893 311^done,value="0xefffeb7c"
29895 411-data-evaluate-expression A+3
29898 511-data-evaluate-expression "A + 3"
29904 @subheading The @code{-data-list-changed-registers} Command
29905 @findex -data-list-changed-registers
29907 @subsubheading Synopsis
29910 -data-list-changed-registers
29913 Display a list of the registers that have changed.
29915 @subsubheading @value{GDBN} Command
29917 @value{GDBN} doesn't have a direct analog for this command; @code{gdbtk}
29918 has the corresponding command @samp{gdb_changed_register_list}.
29920 @subsubheading Example
29922 On a PPC MBX board:
29930 *stopped,reason="breakpoint-hit",disp="keep",bkptno="1",frame=@{
29931 func="main",args=[],file="try.c",fullname="/home/foo/bar/try.c",
29934 -data-list-changed-registers
29935 ^done,changed-registers=["0","1","2","4","5","6","7","8","9",
29936 "10","11","13","14","15","16","17","18","19","20","21","22","23",
29937 "24","25","26","27","28","30","31","64","65","66","67","69"]
29942 @subheading The @code{-data-list-register-names} Command
29943 @findex -data-list-register-names
29945 @subsubheading Synopsis
29948 -data-list-register-names [ ( @var{regno} )+ ]
29951 Show a list of register names for the current target. If no arguments
29952 are given, it shows a list of the names of all the registers. If
29953 integer numbers are given as arguments, it will print a list of the
29954 names of the registers corresponding to the arguments. To ensure
29955 consistency between a register name and its number, the output list may
29956 include empty register names.
29958 @subsubheading @value{GDBN} Command
29960 @value{GDBN} does not have a command which corresponds to
29961 @samp{-data-list-register-names}. In @code{gdbtk} there is a
29962 corresponding command @samp{gdb_regnames}.
29964 @subsubheading Example
29966 For the PPC MBX board:
29969 -data-list-register-names
29970 ^done,register-names=["r0","r1","r2","r3","r4","r5","r6","r7",
29971 "r8","r9","r10","r11","r12","r13","r14","r15","r16","r17","r18",
29972 "r19","r20","r21","r22","r23","r24","r25","r26","r27","r28","r29",
29973 "r30","r31","f0","f1","f2","f3","f4","f5","f6","f7","f8","f9",
29974 "f10","f11","f12","f13","f14","f15","f16","f17","f18","f19","f20",
29975 "f21","f22","f23","f24","f25","f26","f27","f28","f29","f30","f31",
29976 "", "pc","ps","cr","lr","ctr","xer"]
29978 -data-list-register-names 1 2 3
29979 ^done,register-names=["r1","r2","r3"]
29983 @subheading The @code{-data-list-register-values} Command
29984 @findex -data-list-register-values
29986 @subsubheading Synopsis
29989 -data-list-register-values @var{fmt} [ ( @var{regno} )*]
29992 Display the registers' contents. @var{fmt} is the format according to
29993 which the registers' contents are to be returned, followed by an optional
29994 list of numbers specifying the registers to display. A missing list of
29995 numbers indicates that the contents of all the registers must be returned.
29997 Allowed formats for @var{fmt} are:
30014 @subsubheading @value{GDBN} Command
30016 The corresponding @value{GDBN} commands are @samp{info reg}, @samp{info
30017 all-reg}, and (in @code{gdbtk}) @samp{gdb_fetch_registers}.
30019 @subsubheading Example
30021 For a PPC MBX board (note: line breaks are for readability only, they
30022 don't appear in the actual output):
30026 -data-list-register-values r 64 65
30027 ^done,register-values=[@{number="64",value="0xfe00a300"@},
30028 @{number="65",value="0x00029002"@}]
30030 -data-list-register-values x
30031 ^done,register-values=[@{number="0",value="0xfe0043c8"@},
30032 @{number="1",value="0x3fff88"@},@{number="2",value="0xfffffffe"@},
30033 @{number="3",value="0x0"@},@{number="4",value="0xa"@},
30034 @{number="5",value="0x3fff68"@},@{number="6",value="0x3fff58"@},
30035 @{number="7",value="0xfe011e98"@},@{number="8",value="0x2"@},
30036 @{number="9",value="0xfa202820"@},@{number="10",value="0xfa202808"@},
30037 @{number="11",value="0x1"@},@{number="12",value="0x0"@},
30038 @{number="13",value="0x4544"@},@{number="14",value="0xffdfffff"@},
30039 @{number="15",value="0xffffffff"@},@{number="16",value="0xfffffeff"@},
30040 @{number="17",value="0xefffffed"@},@{number="18",value="0xfffffffe"@},
30041 @{number="19",value="0xffffffff"@},@{number="20",value="0xffffffff"@},
30042 @{number="21",value="0xffffffff"@},@{number="22",value="0xfffffff7"@},
30043 @{number="23",value="0xffffffff"@},@{number="24",value="0xffffffff"@},
30044 @{number="25",value="0xffffffff"@},@{number="26",value="0xfffffffb"@},
30045 @{number="27",value="0xffffffff"@},@{number="28",value="0xf7bfffff"@},
30046 @{number="29",value="0x0"@},@{number="30",value="0xfe010000"@},
30047 @{number="31",value="0x0"@},@{number="32",value="0x0"@},
30048 @{number="33",value="0x0"@},@{number="34",value="0x0"@},
30049 @{number="35",value="0x0"@},@{number="36",value="0x0"@},
30050 @{number="37",value="0x0"@},@{number="38",value="0x0"@},
30051 @{number="39",value="0x0"@},@{number="40",value="0x0"@},
30052 @{number="41",value="0x0"@},@{number="42",value="0x0"@},
30053 @{number="43",value="0x0"@},@{number="44",value="0x0"@},
30054 @{number="45",value="0x0"@},@{number="46",value="0x0"@},
30055 @{number="47",value="0x0"@},@{number="48",value="0x0"@},
30056 @{number="49",value="0x0"@},@{number="50",value="0x0"@},
30057 @{number="51",value="0x0"@},@{number="52",value="0x0"@},
30058 @{number="53",value="0x0"@},@{number="54",value="0x0"@},
30059 @{number="55",value="0x0"@},@{number="56",value="0x0"@},
30060 @{number="57",value="0x0"@},@{number="58",value="0x0"@},
30061 @{number="59",value="0x0"@},@{number="60",value="0x0"@},
30062 @{number="61",value="0x0"@},@{number="62",value="0x0"@},
30063 @{number="63",value="0x0"@},@{number="64",value="0xfe00a300"@},
30064 @{number="65",value="0x29002"@},@{number="66",value="0x202f04b5"@},
30065 @{number="67",value="0xfe0043b0"@},@{number="68",value="0xfe00b3e4"@},
30066 @{number="69",value="0x20002b03"@}]
30071 @subheading The @code{-data-read-memory} Command
30072 @findex -data-read-memory
30074 This command is deprecated, use @code{-data-read-memory-bytes} instead.
30076 @subsubheading Synopsis
30079 -data-read-memory [ -o @var{byte-offset} ]
30080 @var{address} @var{word-format} @var{word-size}
30081 @var{nr-rows} @var{nr-cols} [ @var{aschar} ]
30088 @item @var{address}
30089 An expression specifying the address of the first memory word to be
30090 read. Complex expressions containing embedded white space should be
30091 quoted using the C convention.
30093 @item @var{word-format}
30094 The format to be used to print the memory words. The notation is the
30095 same as for @value{GDBN}'s @code{print} command (@pxref{Output Formats,
30098 @item @var{word-size}
30099 The size of each memory word in bytes.
30101 @item @var{nr-rows}
30102 The number of rows in the output table.
30104 @item @var{nr-cols}
30105 The number of columns in the output table.
30108 If present, indicates that each row should include an @sc{ascii} dump. The
30109 value of @var{aschar} is used as a padding character when a byte is not a
30110 member of the printable @sc{ascii} character set (printable @sc{ascii}
30111 characters are those whose code is between 32 and 126, inclusively).
30113 @item @var{byte-offset}
30114 An offset to add to the @var{address} before fetching memory.
30117 This command displays memory contents as a table of @var{nr-rows} by
30118 @var{nr-cols} words, each word being @var{word-size} bytes. In total,
30119 @code{@var{nr-rows} * @var{nr-cols} * @var{word-size}} bytes are read
30120 (returned as @samp{total-bytes}). Should less than the requested number
30121 of bytes be returned by the target, the missing words are identified
30122 using @samp{N/A}. The number of bytes read from the target is returned
30123 in @samp{nr-bytes} and the starting address used to read memory in
30126 The address of the next/previous row or page is available in
30127 @samp{next-row} and @samp{prev-row}, @samp{next-page} and
30130 @subsubheading @value{GDBN} Command
30132 The corresponding @value{GDBN} command is @samp{x}. @code{gdbtk} has
30133 @samp{gdb_get_mem} memory read command.
30135 @subsubheading Example
30137 Read six bytes of memory starting at @code{bytes+6} but then offset by
30138 @code{-6} bytes. Format as three rows of two columns. One byte per
30139 word. Display each word in hex.
30143 9-data-read-memory -o -6 -- bytes+6 x 1 3 2
30144 9^done,addr="0x00001390",nr-bytes="6",total-bytes="6",
30145 next-row="0x00001396",prev-row="0x0000138e",next-page="0x00001396",
30146 prev-page="0x0000138a",memory=[
30147 @{addr="0x00001390",data=["0x00","0x01"]@},
30148 @{addr="0x00001392",data=["0x02","0x03"]@},
30149 @{addr="0x00001394",data=["0x04","0x05"]@}]
30153 Read two bytes of memory starting at address @code{shorts + 64} and
30154 display as a single word formatted in decimal.
30158 5-data-read-memory shorts+64 d 2 1 1
30159 5^done,addr="0x00001510",nr-bytes="2",total-bytes="2",
30160 next-row="0x00001512",prev-row="0x0000150e",
30161 next-page="0x00001512",prev-page="0x0000150e",memory=[
30162 @{addr="0x00001510",data=["128"]@}]
30166 Read thirty two bytes of memory starting at @code{bytes+16} and format
30167 as eight rows of four columns. Include a string encoding with @samp{x}
30168 used as the non-printable character.
30172 4-data-read-memory bytes+16 x 1 8 4 x
30173 4^done,addr="0x000013a0",nr-bytes="32",total-bytes="32",
30174 next-row="0x000013c0",prev-row="0x0000139c",
30175 next-page="0x000013c0",prev-page="0x00001380",memory=[
30176 @{addr="0x000013a0",data=["0x10","0x11","0x12","0x13"],ascii="xxxx"@},
30177 @{addr="0x000013a4",data=["0x14","0x15","0x16","0x17"],ascii="xxxx"@},
30178 @{addr="0x000013a8",data=["0x18","0x19","0x1a","0x1b"],ascii="xxxx"@},
30179 @{addr="0x000013ac",data=["0x1c","0x1d","0x1e","0x1f"],ascii="xxxx"@},
30180 @{addr="0x000013b0",data=["0x20","0x21","0x22","0x23"],ascii=" !\"#"@},
30181 @{addr="0x000013b4",data=["0x24","0x25","0x26","0x27"],ascii="$%&'"@},
30182 @{addr="0x000013b8",data=["0x28","0x29","0x2a","0x2b"],ascii="()*+"@},
30183 @{addr="0x000013bc",data=["0x2c","0x2d","0x2e","0x2f"],ascii=",-./"@}]
30187 @subheading The @code{-data-read-memory-bytes} Command
30188 @findex -data-read-memory-bytes
30190 @subsubheading Synopsis
30193 -data-read-memory-bytes [ -o @var{byte-offset} ]
30194 @var{address} @var{count}
30201 @item @var{address}
30202 An expression specifying the address of the first memory word to be
30203 read. Complex expressions containing embedded white space should be
30204 quoted using the C convention.
30207 The number of bytes to read. This should be an integer literal.
30209 @item @var{byte-offset}
30210 The offsets in bytes relative to @var{address} at which to start
30211 reading. This should be an integer literal. This option is provided
30212 so that a frontend is not required to first evaluate address and then
30213 perform address arithmetics itself.
30217 This command attempts to read all accessible memory regions in the
30218 specified range. First, all regions marked as unreadable in the memory
30219 map (if one is defined) will be skipped. @xref{Memory Region
30220 Attributes}. Second, @value{GDBN} will attempt to read the remaining
30221 regions. For each one, if reading full region results in an errors,
30222 @value{GDBN} will try to read a subset of the region.
30224 In general, every single byte in the region may be readable or not,
30225 and the only way to read every readable byte is to try a read at
30226 every address, which is not practical. Therefore, @value{GDBN} will
30227 attempt to read all accessible bytes at either beginning or the end
30228 of the region, using a binary division scheme. This heuristic works
30229 well for reading accross a memory map boundary. Note that if a region
30230 has a readable range that is neither at the beginning or the end,
30231 @value{GDBN} will not read it.
30233 The result record (@pxref{GDB/MI Result Records}) that is output of
30234 the command includes a field named @samp{memory} whose content is a
30235 list of tuples. Each tuple represent a successfully read memory block
30236 and has the following fields:
30240 The start address of the memory block, as hexadecimal literal.
30243 The end address of the memory block, as hexadecimal literal.
30246 The offset of the memory block, as hexadecimal literal, relative to
30247 the start address passed to @code{-data-read-memory-bytes}.
30250 The contents of the memory block, in hex.
30256 @subsubheading @value{GDBN} Command
30258 The corresponding @value{GDBN} command is @samp{x}.
30260 @subsubheading Example
30264 -data-read-memory-bytes &a 10
30265 ^done,memory=[@{begin="0xbffff154",offset="0x00000000",
30267 contents="01000000020000000300"@}]
30272 @subheading The @code{-data-write-memory-bytes} Command
30273 @findex -data-write-memory-bytes
30275 @subsubheading Synopsis
30278 -data-write-memory-bytes @var{address} @var{contents}
30285 @item @var{address}
30286 An expression specifying the address of the first memory word to be
30287 read. Complex expressions containing embedded white space should be
30288 quoted using the C convention.
30290 @item @var{contents}
30291 The hex-encoded bytes to write.
30295 @subsubheading @value{GDBN} Command
30297 There's no corresponding @value{GDBN} command.
30299 @subsubheading Example
30303 -data-write-memory-bytes &a "aabbccdd"
30309 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
30310 @node GDB/MI Tracepoint Commands
30311 @section @sc{gdb/mi} Tracepoint Commands
30313 The commands defined in this section implement MI support for
30314 tracepoints. For detailed introduction, see @ref{Tracepoints}.
30316 @subheading The @code{-trace-find} Command
30317 @findex -trace-find
30319 @subsubheading Synopsis
30322 -trace-find @var{mode} [@var{parameters}@dots{}]
30325 Find a trace frame using criteria defined by @var{mode} and
30326 @var{parameters}. The following table lists permissible
30327 modes and their parameters. For details of operation, see @ref{tfind}.
30332 No parameters are required. Stops examining trace frames.
30335 An integer is required as parameter. Selects tracepoint frame with
30338 @item tracepoint-number
30339 An integer is required as parameter. Finds next
30340 trace frame that corresponds to tracepoint with the specified number.
30343 An address is required as parameter. Finds
30344 next trace frame that corresponds to any tracepoint at the specified
30347 @item pc-inside-range
30348 Two addresses are required as parameters. Finds next trace
30349 frame that corresponds to a tracepoint at an address inside the
30350 specified range. Both bounds are considered to be inside the range.
30352 @item pc-outside-range
30353 Two addresses are required as parameters. Finds
30354 next trace frame that corresponds to a tracepoint at an address outside
30355 the specified range. Both bounds are considered to be inside the range.
30358 Line specification is required as parameter. @xref{Specify Location}.
30359 Finds next trace frame that corresponds to a tracepoint at
30360 the specified location.
30364 If @samp{none} was passed as @var{mode}, the response does not
30365 have fields. Otherwise, the response may have the following fields:
30369 This field has either @samp{0} or @samp{1} as the value, depending
30370 on whether a matching tracepoint was found.
30373 The index of the found traceframe. This field is present iff
30374 the @samp{found} field has value of @samp{1}.
30377 The index of the found tracepoint. This field is present iff
30378 the @samp{found} field has value of @samp{1}.
30381 The information about the frame corresponding to the found trace
30382 frame. This field is present only if a trace frame was found.
30383 @xref{GDB/MI Frame Information}, for description of this field.
30387 @subsubheading @value{GDBN} Command
30389 The corresponding @value{GDBN} command is @samp{tfind}.
30391 @subheading -trace-define-variable
30392 @findex -trace-define-variable
30394 @subsubheading Synopsis
30397 -trace-define-variable @var{name} [ @var{value} ]
30400 Create trace variable @var{name} if it does not exist. If
30401 @var{value} is specified, sets the initial value of the specified
30402 trace variable to that value. Note that the @var{name} should start
30403 with the @samp{$} character.
30405 @subsubheading @value{GDBN} Command
30407 The corresponding @value{GDBN} command is @samp{tvariable}.
30409 @subheading -trace-list-variables
30410 @findex -trace-list-variables
30412 @subsubheading Synopsis
30415 -trace-list-variables
30418 Return a table of all defined trace variables. Each element of the
30419 table has the following fields:
30423 The name of the trace variable. This field is always present.
30426 The initial value. This is a 64-bit signed integer. This
30427 field is always present.
30430 The value the trace variable has at the moment. This is a 64-bit
30431 signed integer. This field is absent iff current value is
30432 not defined, for example if the trace was never run, or is
30437 @subsubheading @value{GDBN} Command
30439 The corresponding @value{GDBN} command is @samp{tvariables}.
30441 @subsubheading Example
30445 -trace-list-variables
30446 ^done,trace-variables=@{nr_rows="1",nr_cols="3",
30447 hdr=[@{width="15",alignment="-1",col_name="name",colhdr="Name"@},
30448 @{width="11",alignment="-1",col_name="initial",colhdr="Initial"@},
30449 @{width="11",alignment="-1",col_name="current",colhdr="Current"@}],
30450 body=[variable=@{name="$trace_timestamp",initial="0"@}
30451 variable=@{name="$foo",initial="10",current="15"@}]@}
30455 @subheading -trace-save
30456 @findex -trace-save
30458 @subsubheading Synopsis
30461 -trace-save [-r ] @var{filename}
30464 Saves the collected trace data to @var{filename}. Without the
30465 @samp{-r} option, the data is downloaded from the target and saved
30466 in a local file. With the @samp{-r} option the target is asked
30467 to perform the save.
30469 @subsubheading @value{GDBN} Command
30471 The corresponding @value{GDBN} command is @samp{tsave}.
30474 @subheading -trace-start
30475 @findex -trace-start
30477 @subsubheading Synopsis
30483 Starts a tracing experiments. The result of this command does not
30486 @subsubheading @value{GDBN} Command
30488 The corresponding @value{GDBN} command is @samp{tstart}.
30490 @subheading -trace-status
30491 @findex -trace-status
30493 @subsubheading Synopsis
30499 Obtains the status of a tracing experiment. The result may include
30500 the following fields:
30505 May have a value of either @samp{0}, when no tracing operations are
30506 supported, @samp{1}, when all tracing operations are supported, or
30507 @samp{file} when examining trace file. In the latter case, examining
30508 of trace frame is possible but new tracing experiement cannot be
30509 started. This field is always present.
30512 May have a value of either @samp{0} or @samp{1} depending on whether
30513 tracing experiement is in progress on target. This field is present
30514 if @samp{supported} field is not @samp{0}.
30517 Report the reason why the tracing was stopped last time. This field
30518 may be absent iff tracing was never stopped on target yet. The
30519 value of @samp{request} means the tracing was stopped as result of
30520 the @code{-trace-stop} command. The value of @samp{overflow} means
30521 the tracing buffer is full. The value of @samp{disconnection} means
30522 tracing was automatically stopped when @value{GDBN} has disconnected.
30523 The value of @samp{passcount} means tracing was stopped when a
30524 tracepoint was passed a maximal number of times for that tracepoint.
30525 This field is present if @samp{supported} field is not @samp{0}.
30527 @item stopping-tracepoint
30528 The number of tracepoint whose passcount as exceeded. This field is
30529 present iff the @samp{stop-reason} field has the value of
30533 @itemx frames-created
30534 The @samp{frames} field is a count of the total number of trace frames
30535 in the trace buffer, while @samp{frames-created} is the total created
30536 during the run, including ones that were discarded, such as when a
30537 circular trace buffer filled up. Both fields are optional.
30541 These fields tell the current size of the tracing buffer and the
30542 remaining space. These fields are optional.
30545 The value of the circular trace buffer flag. @code{1} means that the
30546 trace buffer is circular and old trace frames will be discarded if
30547 necessary to make room, @code{0} means that the trace buffer is linear
30551 The value of the disconnected tracing flag. @code{1} means that
30552 tracing will continue after @value{GDBN} disconnects, @code{0} means
30553 that the trace run will stop.
30557 @subsubheading @value{GDBN} Command
30559 The corresponding @value{GDBN} command is @samp{tstatus}.
30561 @subheading -trace-stop
30562 @findex -trace-stop
30564 @subsubheading Synopsis
30570 Stops a tracing experiment. The result of this command has the same
30571 fields as @code{-trace-status}, except that the @samp{supported} and
30572 @samp{running} fields are not output.
30574 @subsubheading @value{GDBN} Command
30576 The corresponding @value{GDBN} command is @samp{tstop}.
30579 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
30580 @node GDB/MI Symbol Query
30581 @section @sc{gdb/mi} Symbol Query Commands
30585 @subheading The @code{-symbol-info-address} Command
30586 @findex -symbol-info-address
30588 @subsubheading Synopsis
30591 -symbol-info-address @var{symbol}
30594 Describe where @var{symbol} is stored.
30596 @subsubheading @value{GDBN} Command
30598 The corresponding @value{GDBN} command is @samp{info address}.
30600 @subsubheading Example
30604 @subheading The @code{-symbol-info-file} Command
30605 @findex -symbol-info-file
30607 @subsubheading Synopsis
30613 Show the file for the symbol.
30615 @subsubheading @value{GDBN} Command
30617 There's no equivalent @value{GDBN} command. @code{gdbtk} has
30618 @samp{gdb_find_file}.
30620 @subsubheading Example
30624 @subheading The @code{-symbol-info-function} Command
30625 @findex -symbol-info-function
30627 @subsubheading Synopsis
30630 -symbol-info-function
30633 Show which function the symbol lives in.
30635 @subsubheading @value{GDBN} Command
30637 @samp{gdb_get_function} in @code{gdbtk}.
30639 @subsubheading Example
30643 @subheading The @code{-symbol-info-line} Command
30644 @findex -symbol-info-line
30646 @subsubheading Synopsis
30652 Show the core addresses of the code for a source line.
30654 @subsubheading @value{GDBN} Command
30656 The corresponding @value{GDBN} command is @samp{info line}.
30657 @code{gdbtk} has the @samp{gdb_get_line} and @samp{gdb_get_file} commands.
30659 @subsubheading Example
30663 @subheading The @code{-symbol-info-symbol} Command
30664 @findex -symbol-info-symbol
30666 @subsubheading Synopsis
30669 -symbol-info-symbol @var{addr}
30672 Describe what symbol is at location @var{addr}.
30674 @subsubheading @value{GDBN} Command
30676 The corresponding @value{GDBN} command is @samp{info symbol}.
30678 @subsubheading Example
30682 @subheading The @code{-symbol-list-functions} Command
30683 @findex -symbol-list-functions
30685 @subsubheading Synopsis
30688 -symbol-list-functions
30691 List the functions in the executable.
30693 @subsubheading @value{GDBN} Command
30695 @samp{info functions} in @value{GDBN}, @samp{gdb_listfunc} and
30696 @samp{gdb_search} in @code{gdbtk}.
30698 @subsubheading Example
30703 @subheading The @code{-symbol-list-lines} Command
30704 @findex -symbol-list-lines
30706 @subsubheading Synopsis
30709 -symbol-list-lines @var{filename}
30712 Print the list of lines that contain code and their associated program
30713 addresses for the given source filename. The entries are sorted in
30714 ascending PC order.
30716 @subsubheading @value{GDBN} Command
30718 There is no corresponding @value{GDBN} command.
30720 @subsubheading Example
30723 -symbol-list-lines basics.c
30724 ^done,lines=[@{pc="0x08048554",line="7"@},@{pc="0x0804855a",line="8"@}]
30730 @subheading The @code{-symbol-list-types} Command
30731 @findex -symbol-list-types
30733 @subsubheading Synopsis
30739 List all the type names.
30741 @subsubheading @value{GDBN} Command
30743 The corresponding commands are @samp{info types} in @value{GDBN},
30744 @samp{gdb_search} in @code{gdbtk}.
30746 @subsubheading Example
30750 @subheading The @code{-symbol-list-variables} Command
30751 @findex -symbol-list-variables
30753 @subsubheading Synopsis
30756 -symbol-list-variables
30759 List all the global and static variable names.
30761 @subsubheading @value{GDBN} Command
30763 @samp{info variables} in @value{GDBN}, @samp{gdb_search} in @code{gdbtk}.
30765 @subsubheading Example
30769 @subheading The @code{-symbol-locate} Command
30770 @findex -symbol-locate
30772 @subsubheading Synopsis
30778 @subsubheading @value{GDBN} Command
30780 @samp{gdb_loc} in @code{gdbtk}.
30782 @subsubheading Example
30786 @subheading The @code{-symbol-type} Command
30787 @findex -symbol-type
30789 @subsubheading Synopsis
30792 -symbol-type @var{variable}
30795 Show type of @var{variable}.
30797 @subsubheading @value{GDBN} Command
30799 The corresponding @value{GDBN} command is @samp{ptype}, @code{gdbtk} has
30800 @samp{gdb_obj_variable}.
30802 @subsubheading Example
30807 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
30808 @node GDB/MI File Commands
30809 @section @sc{gdb/mi} File Commands
30811 This section describes the GDB/MI commands to specify executable file names
30812 and to read in and obtain symbol table information.
30814 @subheading The @code{-file-exec-and-symbols} Command
30815 @findex -file-exec-and-symbols
30817 @subsubheading Synopsis
30820 -file-exec-and-symbols @var{file}
30823 Specify the executable file to be debugged. This file is the one from
30824 which the symbol table is also read. If no file is specified, the
30825 command clears the executable and symbol information. If breakpoints
30826 are set when using this command with no arguments, @value{GDBN} will produce
30827 error messages. Otherwise, no output is produced, except a completion
30830 @subsubheading @value{GDBN} Command
30832 The corresponding @value{GDBN} command is @samp{file}.
30834 @subsubheading Example
30838 -file-exec-and-symbols /kwikemart/marge/ezannoni/TRUNK/mbx/hello.mbx
30844 @subheading The @code{-file-exec-file} Command
30845 @findex -file-exec-file
30847 @subsubheading Synopsis
30850 -file-exec-file @var{file}
30853 Specify the executable file to be debugged. Unlike
30854 @samp{-file-exec-and-symbols}, the symbol table is @emph{not} read
30855 from this file. If used without argument, @value{GDBN} clears the information
30856 about the executable file. No output is produced, except a completion
30859 @subsubheading @value{GDBN} Command
30861 The corresponding @value{GDBN} command is @samp{exec-file}.
30863 @subsubheading Example
30867 -file-exec-file /kwikemart/marge/ezannoni/TRUNK/mbx/hello.mbx
30874 @subheading The @code{-file-list-exec-sections} Command
30875 @findex -file-list-exec-sections
30877 @subsubheading Synopsis
30880 -file-list-exec-sections
30883 List the sections of the current executable file.
30885 @subsubheading @value{GDBN} Command
30887 The @value{GDBN} command @samp{info file} shows, among the rest, the same
30888 information as this command. @code{gdbtk} has a corresponding command
30889 @samp{gdb_load_info}.
30891 @subsubheading Example
30896 @subheading The @code{-file-list-exec-source-file} Command
30897 @findex -file-list-exec-source-file
30899 @subsubheading Synopsis
30902 -file-list-exec-source-file
30905 List the line number, the current source file, and the absolute path
30906 to the current source file for the current executable. The macro
30907 information field has a value of @samp{1} or @samp{0} depending on
30908 whether or not the file includes preprocessor macro information.
30910 @subsubheading @value{GDBN} Command
30912 The @value{GDBN} equivalent is @samp{info source}
30914 @subsubheading Example
30918 123-file-list-exec-source-file
30919 123^done,line="1",file="foo.c",fullname="/home/bar/foo.c,macro-info="1"
30924 @subheading The @code{-file-list-exec-source-files} Command
30925 @findex -file-list-exec-source-files
30927 @subsubheading Synopsis
30930 -file-list-exec-source-files
30933 List the source files for the current executable.
30935 It will always output the filename, but only when @value{GDBN} can find
30936 the absolute file name of a source file, will it output the fullname.
30938 @subsubheading @value{GDBN} Command
30940 The @value{GDBN} equivalent is @samp{info sources}.
30941 @code{gdbtk} has an analogous command @samp{gdb_listfiles}.
30943 @subsubheading Example
30946 -file-list-exec-source-files
30948 @{file=foo.c,fullname=/home/foo.c@},
30949 @{file=/home/bar.c,fullname=/home/bar.c@},
30950 @{file=gdb_could_not_find_fullpath.c@}]
30955 @subheading The @code{-file-list-shared-libraries} Command
30956 @findex -file-list-shared-libraries
30958 @subsubheading Synopsis
30961 -file-list-shared-libraries
30964 List the shared libraries in the program.
30966 @subsubheading @value{GDBN} Command
30968 The corresponding @value{GDBN} command is @samp{info shared}.
30970 @subsubheading Example
30974 @subheading The @code{-file-list-symbol-files} Command
30975 @findex -file-list-symbol-files
30977 @subsubheading Synopsis
30980 -file-list-symbol-files
30985 @subsubheading @value{GDBN} Command
30987 The corresponding @value{GDBN} command is @samp{info file} (part of it).
30989 @subsubheading Example
30994 @subheading The @code{-file-symbol-file} Command
30995 @findex -file-symbol-file
30997 @subsubheading Synopsis
31000 -file-symbol-file @var{file}
31003 Read symbol table info from the specified @var{file} argument. When
31004 used without arguments, clears @value{GDBN}'s symbol table info. No output is
31005 produced, except for a completion notification.
31007 @subsubheading @value{GDBN} Command
31009 The corresponding @value{GDBN} command is @samp{symbol-file}.
31011 @subsubheading Example
31015 -file-symbol-file /kwikemart/marge/ezannoni/TRUNK/mbx/hello.mbx
31021 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
31022 @node GDB/MI Memory Overlay Commands
31023 @section @sc{gdb/mi} Memory Overlay Commands
31025 The memory overlay commands are not implemented.
31027 @c @subheading -overlay-auto
31029 @c @subheading -overlay-list-mapping-state
31031 @c @subheading -overlay-list-overlays
31033 @c @subheading -overlay-map
31035 @c @subheading -overlay-off
31037 @c @subheading -overlay-on
31039 @c @subheading -overlay-unmap
31041 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
31042 @node GDB/MI Signal Handling Commands
31043 @section @sc{gdb/mi} Signal Handling Commands
31045 Signal handling commands are not implemented.
31047 @c @subheading -signal-handle
31049 @c @subheading -signal-list-handle-actions
31051 @c @subheading -signal-list-signal-types
31055 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
31056 @node GDB/MI Target Manipulation
31057 @section @sc{gdb/mi} Target Manipulation Commands
31060 @subheading The @code{-target-attach} Command
31061 @findex -target-attach
31063 @subsubheading Synopsis
31066 -target-attach @var{pid} | @var{gid} | @var{file}
31069 Attach to a process @var{pid} or a file @var{file} outside of
31070 @value{GDBN}, or a thread group @var{gid}. If attaching to a thread
31071 group, the id previously returned by
31072 @samp{-list-thread-groups --available} must be used.
31074 @subsubheading @value{GDBN} Command
31076 The corresponding @value{GDBN} command is @samp{attach}.
31078 @subsubheading Example
31082 =thread-created,id="1"
31083 *stopped,thread-id="1",frame=@{addr="0xb7f7e410",func="bar",args=[]@}
31089 @subheading The @code{-target-compare-sections} Command
31090 @findex -target-compare-sections
31092 @subsubheading Synopsis
31095 -target-compare-sections [ @var{section} ]
31098 Compare data of section @var{section} on target to the exec file.
31099 Without the argument, all sections are compared.
31101 @subsubheading @value{GDBN} Command
31103 The @value{GDBN} equivalent is @samp{compare-sections}.
31105 @subsubheading Example
31110 @subheading The @code{-target-detach} Command
31111 @findex -target-detach
31113 @subsubheading Synopsis
31116 -target-detach [ @var{pid} | @var{gid} ]
31119 Detach from the remote target which normally resumes its execution.
31120 If either @var{pid} or @var{gid} is specified, detaches from either
31121 the specified process, or specified thread group. There's no output.
31123 @subsubheading @value{GDBN} Command
31125 The corresponding @value{GDBN} command is @samp{detach}.
31127 @subsubheading Example
31137 @subheading The @code{-target-disconnect} Command
31138 @findex -target-disconnect
31140 @subsubheading Synopsis
31146 Disconnect from the remote target. There's no output and the target is
31147 generally not resumed.
31149 @subsubheading @value{GDBN} Command
31151 The corresponding @value{GDBN} command is @samp{disconnect}.
31153 @subsubheading Example
31163 @subheading The @code{-target-download} Command
31164 @findex -target-download
31166 @subsubheading Synopsis
31172 Loads the executable onto the remote target.
31173 It prints out an update message every half second, which includes the fields:
31177 The name of the section.
31179 The size of what has been sent so far for that section.
31181 The size of the section.
31183 The total size of what was sent so far (the current and the previous sections).
31185 The size of the overall executable to download.
31189 Each message is sent as status record (@pxref{GDB/MI Output Syntax, ,
31190 @sc{gdb/mi} Output Syntax}).
31192 In addition, it prints the name and size of the sections, as they are
31193 downloaded. These messages include the following fields:
31197 The name of the section.
31199 The size of the section.
31201 The size of the overall executable to download.
31205 At the end, a summary is printed.
31207 @subsubheading @value{GDBN} Command
31209 The corresponding @value{GDBN} command is @samp{load}.
31211 @subsubheading Example
31213 Note: each status message appears on a single line. Here the messages
31214 have been broken down so that they can fit onto a page.
31219 +download,@{section=".text",section-size="6668",total-size="9880"@}
31220 +download,@{section=".text",section-sent="512",section-size="6668",
31221 total-sent="512",total-size="9880"@}
31222 +download,@{section=".text",section-sent="1024",section-size="6668",
31223 total-sent="1024",total-size="9880"@}
31224 +download,@{section=".text",section-sent="1536",section-size="6668",
31225 total-sent="1536",total-size="9880"@}
31226 +download,@{section=".text",section-sent="2048",section-size="6668",
31227 total-sent="2048",total-size="9880"@}
31228 +download,@{section=".text",section-sent="2560",section-size="6668",
31229 total-sent="2560",total-size="9880"@}
31230 +download,@{section=".text",section-sent="3072",section-size="6668",
31231 total-sent="3072",total-size="9880"@}
31232 +download,@{section=".text",section-sent="3584",section-size="6668",
31233 total-sent="3584",total-size="9880"@}
31234 +download,@{section=".text",section-sent="4096",section-size="6668",
31235 total-sent="4096",total-size="9880"@}
31236 +download,@{section=".text",section-sent="4608",section-size="6668",
31237 total-sent="4608",total-size="9880"@}
31238 +download,@{section=".text",section-sent="5120",section-size="6668",
31239 total-sent="5120",total-size="9880"@}
31240 +download,@{section=".text",section-sent="5632",section-size="6668",
31241 total-sent="5632",total-size="9880"@}
31242 +download,@{section=".text",section-sent="6144",section-size="6668",
31243 total-sent="6144",total-size="9880"@}
31244 +download,@{section=".text",section-sent="6656",section-size="6668",
31245 total-sent="6656",total-size="9880"@}
31246 +download,@{section=".init",section-size="28",total-size="9880"@}
31247 +download,@{section=".fini",section-size="28",total-size="9880"@}
31248 +download,@{section=".data",section-size="3156",total-size="9880"@}
31249 +download,@{section=".data",section-sent="512",section-size="3156",
31250 total-sent="7236",total-size="9880"@}
31251 +download,@{section=".data",section-sent="1024",section-size="3156",
31252 total-sent="7748",total-size="9880"@}
31253 +download,@{section=".data",section-sent="1536",section-size="3156",
31254 total-sent="8260",total-size="9880"@}
31255 +download,@{section=".data",section-sent="2048",section-size="3156",
31256 total-sent="8772",total-size="9880"@}
31257 +download,@{section=".data",section-sent="2560",section-size="3156",
31258 total-sent="9284",total-size="9880"@}
31259 +download,@{section=".data",section-sent="3072",section-size="3156",
31260 total-sent="9796",total-size="9880"@}
31261 ^done,address="0x10004",load-size="9880",transfer-rate="6586",
31268 @subheading The @code{-target-exec-status} Command
31269 @findex -target-exec-status
31271 @subsubheading Synopsis
31274 -target-exec-status
31277 Provide information on the state of the target (whether it is running or
31278 not, for instance).
31280 @subsubheading @value{GDBN} Command
31282 There's no equivalent @value{GDBN} command.
31284 @subsubheading Example
31288 @subheading The @code{-target-list-available-targets} Command
31289 @findex -target-list-available-targets
31291 @subsubheading Synopsis
31294 -target-list-available-targets
31297 List the possible targets to connect to.
31299 @subsubheading @value{GDBN} Command
31301 The corresponding @value{GDBN} command is @samp{help target}.
31303 @subsubheading Example
31307 @subheading The @code{-target-list-current-targets} Command
31308 @findex -target-list-current-targets
31310 @subsubheading Synopsis
31313 -target-list-current-targets
31316 Describe the current target.
31318 @subsubheading @value{GDBN} Command
31320 The corresponding information is printed by @samp{info file} (among
31323 @subsubheading Example
31327 @subheading The @code{-target-list-parameters} Command
31328 @findex -target-list-parameters
31330 @subsubheading Synopsis
31333 -target-list-parameters
31339 @subsubheading @value{GDBN} Command
31343 @subsubheading Example
31347 @subheading The @code{-target-select} Command
31348 @findex -target-select
31350 @subsubheading Synopsis
31353 -target-select @var{type} @var{parameters @dots{}}
31356 Connect @value{GDBN} to the remote target. This command takes two args:
31360 The type of target, for instance @samp{remote}, etc.
31361 @item @var{parameters}
31362 Device names, host names and the like. @xref{Target Commands, ,
31363 Commands for Managing Targets}, for more details.
31366 The output is a connection notification, followed by the address at
31367 which the target program is, in the following form:
31370 ^connected,addr="@var{address}",func="@var{function name}",
31371 args=[@var{arg list}]
31374 @subsubheading @value{GDBN} Command
31376 The corresponding @value{GDBN} command is @samp{target}.
31378 @subsubheading Example
31382 -target-select remote /dev/ttya
31383 ^connected,addr="0xfe00a300",func="??",args=[]
31387 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
31388 @node GDB/MI File Transfer Commands
31389 @section @sc{gdb/mi} File Transfer Commands
31392 @subheading The @code{-target-file-put} Command
31393 @findex -target-file-put
31395 @subsubheading Synopsis
31398 -target-file-put @var{hostfile} @var{targetfile}
31401 Copy file @var{hostfile} from the host system (the machine running
31402 @value{GDBN}) to @var{targetfile} on the target system.
31404 @subsubheading @value{GDBN} Command
31406 The corresponding @value{GDBN} command is @samp{remote put}.
31408 @subsubheading Example
31412 -target-file-put localfile remotefile
31418 @subheading The @code{-target-file-get} Command
31419 @findex -target-file-get
31421 @subsubheading Synopsis
31424 -target-file-get @var{targetfile} @var{hostfile}
31427 Copy file @var{targetfile} from the target system to @var{hostfile}
31428 on the host system.
31430 @subsubheading @value{GDBN} Command
31432 The corresponding @value{GDBN} command is @samp{remote get}.
31434 @subsubheading Example
31438 -target-file-get remotefile localfile
31444 @subheading The @code{-target-file-delete} Command
31445 @findex -target-file-delete
31447 @subsubheading Synopsis
31450 -target-file-delete @var{targetfile}
31453 Delete @var{targetfile} from the target system.
31455 @subsubheading @value{GDBN} Command
31457 The corresponding @value{GDBN} command is @samp{remote delete}.
31459 @subsubheading Example
31463 -target-file-delete remotefile
31469 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
31470 @node GDB/MI Miscellaneous Commands
31471 @section Miscellaneous @sc{gdb/mi} Commands
31473 @c @subheading -gdb-complete
31475 @subheading The @code{-gdb-exit} Command
31478 @subsubheading Synopsis
31484 Exit @value{GDBN} immediately.
31486 @subsubheading @value{GDBN} Command
31488 Approximately corresponds to @samp{quit}.
31490 @subsubheading Example
31500 @subheading The @code{-exec-abort} Command
31501 @findex -exec-abort
31503 @subsubheading Synopsis
31509 Kill the inferior running program.
31511 @subsubheading @value{GDBN} Command
31513 The corresponding @value{GDBN} command is @samp{kill}.
31515 @subsubheading Example
31520 @subheading The @code{-gdb-set} Command
31523 @subsubheading Synopsis
31529 Set an internal @value{GDBN} variable.
31530 @c IS THIS A DOLLAR VARIABLE? OR SOMETHING LIKE ANNOTATE ?????
31532 @subsubheading @value{GDBN} Command
31534 The corresponding @value{GDBN} command is @samp{set}.
31536 @subsubheading Example
31546 @subheading The @code{-gdb-show} Command
31549 @subsubheading Synopsis
31555 Show the current value of a @value{GDBN} variable.
31557 @subsubheading @value{GDBN} Command
31559 The corresponding @value{GDBN} command is @samp{show}.
31561 @subsubheading Example
31570 @c @subheading -gdb-source
31573 @subheading The @code{-gdb-version} Command
31574 @findex -gdb-version
31576 @subsubheading Synopsis
31582 Show version information for @value{GDBN}. Used mostly in testing.
31584 @subsubheading @value{GDBN} Command
31586 The @value{GDBN} equivalent is @samp{show version}. @value{GDBN} by
31587 default shows this information when you start an interactive session.
31589 @subsubheading Example
31591 @c This example modifies the actual output from GDB to avoid overfull
31597 ~Copyright 2000 Free Software Foundation, Inc.
31598 ~GDB is free software, covered by the GNU General Public License, and
31599 ~you are welcome to change it and/or distribute copies of it under
31600 ~ certain conditions.
31601 ~Type "show copying" to see the conditions.
31602 ~There is absolutely no warranty for GDB. Type "show warranty" for
31604 ~This GDB was configured as
31605 "--host=sparc-sun-solaris2.5.1 --target=ppc-eabi".
31610 @subheading The @code{-list-features} Command
31611 @findex -list-features
31613 Returns a list of particular features of the MI protocol that
31614 this version of gdb implements. A feature can be a command,
31615 or a new field in an output of some command, or even an
31616 important bugfix. While a frontend can sometimes detect presence
31617 of a feature at runtime, it is easier to perform detection at debugger
31620 The command returns a list of strings, with each string naming an
31621 available feature. Each returned string is just a name, it does not
31622 have any internal structure. The list of possible feature names
31628 (gdb) -list-features
31629 ^done,result=["feature1","feature2"]
31632 The current list of features is:
31635 @item frozen-varobjs
31636 Indicates support for the @code{-var-set-frozen} command, as well
31637 as possible presense of the @code{frozen} field in the output
31638 of @code{-varobj-create}.
31639 @item pending-breakpoints
31640 Indicates support for the @option{-f} option to the @code{-break-insert}
31643 Indicates Python scripting support, Python-based
31644 pretty-printing commands, and possible presence of the
31645 @samp{display_hint} field in the output of @code{-var-list-children}
31647 Indicates support for the @code{-thread-info} command.
31648 @item data-read-memory-bytes
31649 Indicates support for the @code{-data-read-memory-bytes} and the
31650 @code{-data-write-memory-bytes} commands.
31651 @item breakpoint-notifications
31652 Indicates that changes to breakpoints and breakpoints created via the
31653 CLI will be announced via async records.
31654 @item ada-task-info
31655 Indicates support for the @code{-ada-task-info} command.
31658 @subheading The @code{-list-target-features} Command
31659 @findex -list-target-features
31661 Returns a list of particular features that are supported by the
31662 target. Those features affect the permitted MI commands, but
31663 unlike the features reported by the @code{-list-features} command, the
31664 features depend on which target GDB is using at the moment. Whenever
31665 a target can change, due to commands such as @code{-target-select},
31666 @code{-target-attach} or @code{-exec-run}, the list of target features
31667 may change, and the frontend should obtain it again.
31671 (gdb) -list-features
31672 ^done,result=["async"]
31675 The current list of features is:
31679 Indicates that the target is capable of asynchronous command
31680 execution, which means that @value{GDBN} will accept further commands
31681 while the target is running.
31684 Indicates that the target is capable of reverse execution.
31685 @xref{Reverse Execution}, for more information.
31689 @subheading The @code{-list-thread-groups} Command
31690 @findex -list-thread-groups
31692 @subheading Synopsis
31695 -list-thread-groups [ --available ] [ --recurse 1 ] [ @var{group} ... ]
31698 Lists thread groups (@pxref{Thread groups}). When a single thread
31699 group is passed as the argument, lists the children of that group.
31700 When several thread group are passed, lists information about those
31701 thread groups. Without any parameters, lists information about all
31702 top-level thread groups.
31704 Normally, thread groups that are being debugged are reported.
31705 With the @samp{--available} option, @value{GDBN} reports thread groups
31706 available on the target.
31708 The output of this command may have either a @samp{threads} result or
31709 a @samp{groups} result. The @samp{thread} result has a list of tuples
31710 as value, with each tuple describing a thread (@pxref{GDB/MI Thread
31711 Information}). The @samp{groups} result has a list of tuples as value,
31712 each tuple describing a thread group. If top-level groups are
31713 requested (that is, no parameter is passed), or when several groups
31714 are passed, the output always has a @samp{groups} result. The format
31715 of the @samp{group} result is described below.
31717 To reduce the number of roundtrips it's possible to list thread groups
31718 together with their children, by passing the @samp{--recurse} option
31719 and the recursion depth. Presently, only recursion depth of 1 is
31720 permitted. If this option is present, then every reported thread group
31721 will also include its children, either as @samp{group} or
31722 @samp{threads} field.
31724 In general, any combination of option and parameters is permitted, with
31725 the following caveats:
31729 When a single thread group is passed, the output will typically
31730 be the @samp{threads} result. Because threads may not contain
31731 anything, the @samp{recurse} option will be ignored.
31734 When the @samp{--available} option is passed, limited information may
31735 be available. In particular, the list of threads of a process might
31736 be inaccessible. Further, specifying specific thread groups might
31737 not give any performance advantage over listing all thread groups.
31738 The frontend should assume that @samp{-list-thread-groups --available}
31739 is always an expensive operation and cache the results.
31743 The @samp{groups} result is a list of tuples, where each tuple may
31744 have the following fields:
31748 Identifier of the thread group. This field is always present.
31749 The identifier is an opaque string; frontends should not try to
31750 convert it to an integer, even though it might look like one.
31753 The type of the thread group. At present, only @samp{process} is a
31757 The target-specific process identifier. This field is only present
31758 for thread groups of type @samp{process} and only if the process exists.
31761 The number of children this thread group has. This field may be
31762 absent for an available thread group.
31765 This field has a list of tuples as value, each tuple describing a
31766 thread. It may be present if the @samp{--recurse} option is
31767 specified, and it's actually possible to obtain the threads.
31770 This field is a list of integers, each identifying a core that one
31771 thread of the group is running on. This field may be absent if
31772 such information is not available.
31775 The name of the executable file that corresponds to this thread group.
31776 The field is only present for thread groups of type @samp{process},
31777 and only if there is a corresponding executable file.
31781 @subheading Example
31785 -list-thread-groups
31786 ^done,groups=[@{id="17",type="process",pid="yyy",num_children="2"@}]
31787 -list-thread-groups 17
31788 ^done,threads=[@{id="2",target-id="Thread 0xb7e14b90 (LWP 21257)",
31789 frame=@{level="0",addr="0xffffe410",func="__kernel_vsyscall",args=[]@},state="running"@},
31790 @{id="1",target-id="Thread 0xb7e156b0 (LWP 21254)",
31791 frame=@{level="0",addr="0x0804891f",func="foo",args=[@{name="i",value="10"@}],
31792 file="/tmp/a.c",fullname="/tmp/a.c",line="158"@},state="running"@}]]
31793 -list-thread-groups --available
31794 ^done,groups=[@{id="17",type="process",pid="yyy",num_children="2",cores=[1,2]@}]
31795 -list-thread-groups --available --recurse 1
31796 ^done,groups=[@{id="17", types="process",pid="yyy",num_children="2",cores=[1,2],
31797 threads=[@{id="1",target-id="Thread 0xb7e14b90",cores=[1]@},
31798 @{id="2",target-id="Thread 0xb7e14b90",cores=[2]@}]@},..]
31799 -list-thread-groups --available --recurse 1 17 18
31800 ^done,groups=[@{id="17", types="process",pid="yyy",num_children="2",cores=[1,2],
31801 threads=[@{id="1",target-id="Thread 0xb7e14b90",cores=[1]@},
31802 @{id="2",target-id="Thread 0xb7e14b90",cores=[2]@}]@},...]
31806 @subheading The @code{-add-inferior} Command
31807 @findex -add-inferior
31809 @subheading Synopsis
31815 Creates a new inferior (@pxref{Inferiors and Programs}). The created
31816 inferior is not associated with any executable. Such association may
31817 be established with the @samp{-file-exec-and-symbols} command
31818 (@pxref{GDB/MI File Commands}). The command response has a single
31819 field, @samp{thread-group}, whose value is the identifier of the
31820 thread group corresponding to the new inferior.
31822 @subheading Example
31827 ^done,thread-group="i3"
31830 @subheading The @code{-interpreter-exec} Command
31831 @findex -interpreter-exec
31833 @subheading Synopsis
31836 -interpreter-exec @var{interpreter} @var{command}
31838 @anchor{-interpreter-exec}
31840 Execute the specified @var{command} in the given @var{interpreter}.
31842 @subheading @value{GDBN} Command
31844 The corresponding @value{GDBN} command is @samp{interpreter-exec}.
31846 @subheading Example
31850 -interpreter-exec console "break main"
31851 &"During symbol reading, couldn't parse type; debugger out of date?.\n"
31852 &"During symbol reading, bad structure-type format.\n"
31853 ~"Breakpoint 1 at 0x8074fc6: file ../../src/gdb/main.c, line 743.\n"
31858 @subheading The @code{-inferior-tty-set} Command
31859 @findex -inferior-tty-set
31861 @subheading Synopsis
31864 -inferior-tty-set /dev/pts/1
31867 Set terminal for future runs of the program being debugged.
31869 @subheading @value{GDBN} Command
31871 The corresponding @value{GDBN} command is @samp{set inferior-tty} /dev/pts/1.
31873 @subheading Example
31877 -inferior-tty-set /dev/pts/1
31882 @subheading The @code{-inferior-tty-show} Command
31883 @findex -inferior-tty-show
31885 @subheading Synopsis
31891 Show terminal for future runs of program being debugged.
31893 @subheading @value{GDBN} Command
31895 The corresponding @value{GDBN} command is @samp{show inferior-tty}.
31897 @subheading Example
31901 -inferior-tty-set /dev/pts/1
31905 ^done,inferior_tty_terminal="/dev/pts/1"
31909 @subheading The @code{-enable-timings} Command
31910 @findex -enable-timings
31912 @subheading Synopsis
31915 -enable-timings [yes | no]
31918 Toggle the printing of the wallclock, user and system times for an MI
31919 command as a field in its output. This command is to help frontend
31920 developers optimize the performance of their code. No argument is
31921 equivalent to @samp{yes}.
31923 @subheading @value{GDBN} Command
31927 @subheading Example
31935 ^done,bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
31936 addr="0x080484ed",func="main",file="myprog.c",
31937 fullname="/home/nickrob/myprog.c",line="73",times="0"@},
31938 time=@{wallclock="0.05185",user="0.00800",system="0.00000"@}
31946 *stopped,reason="breakpoint-hit",disp="keep",bkptno="1",thread-id="0",
31947 frame=@{addr="0x080484ed",func="main",args=[@{name="argc",value="1"@},
31948 @{name="argv",value="0xbfb60364"@}],file="myprog.c",
31949 fullname="/home/nickrob/myprog.c",line="73"@}
31954 @chapter @value{GDBN} Annotations
31956 This chapter describes annotations in @value{GDBN}. Annotations were
31957 designed to interface @value{GDBN} to graphical user interfaces or other
31958 similar programs which want to interact with @value{GDBN} at a
31959 relatively high level.
31961 The annotation mechanism has largely been superseded by @sc{gdb/mi}
31965 This is Edition @value{EDITION}, @value{DATE}.
31969 * Annotations Overview:: What annotations are; the general syntax.
31970 * Server Prefix:: Issuing a command without affecting user state.
31971 * Prompting:: Annotations marking @value{GDBN}'s need for input.
31972 * Errors:: Annotations for error messages.
31973 * Invalidation:: Some annotations describe things now invalid.
31974 * Annotations for Running::
31975 Whether the program is running, how it stopped, etc.
31976 * Source Annotations:: Annotations describing source code.
31979 @node Annotations Overview
31980 @section What is an Annotation?
31981 @cindex annotations
31983 Annotations start with a newline character, two @samp{control-z}
31984 characters, and the name of the annotation. If there is no additional
31985 information associated with this annotation, the name of the annotation
31986 is followed immediately by a newline. If there is additional
31987 information, the name of the annotation is followed by a space, the
31988 additional information, and a newline. The additional information
31989 cannot contain newline characters.
31991 Any output not beginning with a newline and two @samp{control-z}
31992 characters denotes literal output from @value{GDBN}. Currently there is
31993 no need for @value{GDBN} to output a newline followed by two
31994 @samp{control-z} characters, but if there was such a need, the
31995 annotations could be extended with an @samp{escape} annotation which
31996 means those three characters as output.
31998 The annotation @var{level}, which is specified using the
31999 @option{--annotate} command line option (@pxref{Mode Options}), controls
32000 how much information @value{GDBN} prints together with its prompt,
32001 values of expressions, source lines, and other types of output. Level 0
32002 is for no annotations, level 1 is for use when @value{GDBN} is run as a
32003 subprocess of @sc{gnu} Emacs, level 3 is the maximum annotation suitable
32004 for programs that control @value{GDBN}, and level 2 annotations have
32005 been made obsolete (@pxref{Limitations, , Limitations of the Annotation
32006 Interface, annotate, GDB's Obsolete Annotations}).
32009 @kindex set annotate
32010 @item set annotate @var{level}
32011 The @value{GDBN} command @code{set annotate} sets the level of
32012 annotations to the specified @var{level}.
32014 @item show annotate
32015 @kindex show annotate
32016 Show the current annotation level.
32019 This chapter describes level 3 annotations.
32021 A simple example of starting up @value{GDBN} with annotations is:
32024 $ @kbd{gdb --annotate=3}
32026 Copyright 2003 Free Software Foundation, Inc.
32027 GDB is free software, covered by the GNU General Public License,
32028 and you are welcome to change it and/or distribute copies of it
32029 under certain conditions.
32030 Type "show copying" to see the conditions.
32031 There is absolutely no warranty for GDB. Type "show warranty"
32033 This GDB was configured as "i386-pc-linux-gnu"
32044 Here @samp{quit} is input to @value{GDBN}; the rest is output from
32045 @value{GDBN}. The three lines beginning @samp{^Z^Z} (where @samp{^Z}
32046 denotes a @samp{control-z} character) are annotations; the rest is
32047 output from @value{GDBN}.
32049 @node Server Prefix
32050 @section The Server Prefix
32051 @cindex server prefix
32053 If you prefix a command with @samp{server } then it will not affect
32054 the command history, nor will it affect @value{GDBN}'s notion of which
32055 command to repeat if @key{RET} is pressed on a line by itself. This
32056 means that commands can be run behind a user's back by a front-end in
32057 a transparent manner.
32059 The @code{server } prefix does not affect the recording of values into
32060 the value history; to print a value without recording it into the
32061 value history, use the @code{output} command instead of the
32062 @code{print} command.
32064 Using this prefix also disables confirmation requests
32065 (@pxref{confirmation requests}).
32068 @section Annotation for @value{GDBN} Input
32070 @cindex annotations for prompts
32071 When @value{GDBN} prompts for input, it annotates this fact so it is possible
32072 to know when to send output, when the output from a given command is
32075 Different kinds of input each have a different @dfn{input type}. Each
32076 input type has three annotations: a @code{pre-} annotation, which
32077 denotes the beginning of any prompt which is being output, a plain
32078 annotation, which denotes the end of the prompt, and then a @code{post-}
32079 annotation which denotes the end of any echo which may (or may not) be
32080 associated with the input. For example, the @code{prompt} input type
32081 features the following annotations:
32089 The input types are
32092 @findex pre-prompt annotation
32093 @findex prompt annotation
32094 @findex post-prompt annotation
32096 When @value{GDBN} is prompting for a command (the main @value{GDBN} prompt).
32098 @findex pre-commands annotation
32099 @findex commands annotation
32100 @findex post-commands annotation
32102 When @value{GDBN} prompts for a set of commands, like in the @code{commands}
32103 command. The annotations are repeated for each command which is input.
32105 @findex pre-overload-choice annotation
32106 @findex overload-choice annotation
32107 @findex post-overload-choice annotation
32108 @item overload-choice
32109 When @value{GDBN} wants the user to select between various overloaded functions.
32111 @findex pre-query annotation
32112 @findex query annotation
32113 @findex post-query annotation
32115 When @value{GDBN} wants the user to confirm a potentially dangerous operation.
32117 @findex pre-prompt-for-continue annotation
32118 @findex prompt-for-continue annotation
32119 @findex post-prompt-for-continue annotation
32120 @item prompt-for-continue
32121 When @value{GDBN} is asking the user to press return to continue. Note: Don't
32122 expect this to work well; instead use @code{set height 0} to disable
32123 prompting. This is because the counting of lines is buggy in the
32124 presence of annotations.
32129 @cindex annotations for errors, warnings and interrupts
32131 @findex quit annotation
32136 This annotation occurs right before @value{GDBN} responds to an interrupt.
32138 @findex error annotation
32143 This annotation occurs right before @value{GDBN} responds to an error.
32145 Quit and error annotations indicate that any annotations which @value{GDBN} was
32146 in the middle of may end abruptly. For example, if a
32147 @code{value-history-begin} annotation is followed by a @code{error}, one
32148 cannot expect to receive the matching @code{value-history-end}. One
32149 cannot expect not to receive it either, however; an error annotation
32150 does not necessarily mean that @value{GDBN} is immediately returning all the way
32153 @findex error-begin annotation
32154 A quit or error annotation may be preceded by
32160 Any output between that and the quit or error annotation is the error
32163 Warning messages are not yet annotated.
32164 @c If we want to change that, need to fix warning(), type_error(),
32165 @c range_error(), and possibly other places.
32168 @section Invalidation Notices
32170 @cindex annotations for invalidation messages
32171 The following annotations say that certain pieces of state may have
32175 @findex frames-invalid annotation
32176 @item ^Z^Zframes-invalid
32178 The frames (for example, output from the @code{backtrace} command) may
32181 @findex breakpoints-invalid annotation
32182 @item ^Z^Zbreakpoints-invalid
32184 The breakpoints may have changed. For example, the user just added or
32185 deleted a breakpoint.
32188 @node Annotations for Running
32189 @section Running the Program
32190 @cindex annotations for running programs
32192 @findex starting annotation
32193 @findex stopping annotation
32194 When the program starts executing due to a @value{GDBN} command such as
32195 @code{step} or @code{continue},
32201 is output. When the program stops,
32207 is output. Before the @code{stopped} annotation, a variety of
32208 annotations describe how the program stopped.
32211 @findex exited annotation
32212 @item ^Z^Zexited @var{exit-status}
32213 The program exited, and @var{exit-status} is the exit status (zero for
32214 successful exit, otherwise nonzero).
32216 @findex signalled annotation
32217 @findex signal-name annotation
32218 @findex signal-name-end annotation
32219 @findex signal-string annotation
32220 @findex signal-string-end annotation
32221 @item ^Z^Zsignalled
32222 The program exited with a signal. After the @code{^Z^Zsignalled}, the
32223 annotation continues:
32229 ^Z^Zsignal-name-end
32233 ^Z^Zsignal-string-end
32238 where @var{name} is the name of the signal, such as @code{SIGILL} or
32239 @code{SIGSEGV}, and @var{string} is the explanation of the signal, such
32240 as @code{Illegal Instruction} or @code{Segmentation fault}.
32241 @var{intro-text}, @var{middle-text}, and @var{end-text} are for the
32242 user's benefit and have no particular format.
32244 @findex signal annotation
32246 The syntax of this annotation is just like @code{signalled}, but @value{GDBN} is
32247 just saying that the program received the signal, not that it was
32248 terminated with it.
32250 @findex breakpoint annotation
32251 @item ^Z^Zbreakpoint @var{number}
32252 The program hit breakpoint number @var{number}.
32254 @findex watchpoint annotation
32255 @item ^Z^Zwatchpoint @var{number}
32256 The program hit watchpoint number @var{number}.
32259 @node Source Annotations
32260 @section Displaying Source
32261 @cindex annotations for source display
32263 @findex source annotation
32264 The following annotation is used instead of displaying source code:
32267 ^Z^Zsource @var{filename}:@var{line}:@var{character}:@var{middle}:@var{addr}
32270 where @var{filename} is an absolute file name indicating which source
32271 file, @var{line} is the line number within that file (where 1 is the
32272 first line in the file), @var{character} is the character position
32273 within the file (where 0 is the first character in the file) (for most
32274 debug formats this will necessarily point to the beginning of a line),
32275 @var{middle} is @samp{middle} if @var{addr} is in the middle of the
32276 line, or @samp{beg} if @var{addr} is at the beginning of the line, and
32277 @var{addr} is the address in the target program associated with the
32278 source which is being displayed. @var{addr} is in the form @samp{0x}
32279 followed by one or more lowercase hex digits (note that this does not
32280 depend on the language).
32282 @node JIT Interface
32283 @chapter JIT Compilation Interface
32284 @cindex just-in-time compilation
32285 @cindex JIT compilation interface
32287 This chapter documents @value{GDBN}'s @dfn{just-in-time} (JIT) compilation
32288 interface. A JIT compiler is a program or library that generates native
32289 executable code at runtime and executes it, usually in order to achieve good
32290 performance while maintaining platform independence.
32292 Programs that use JIT compilation are normally difficult to debug because
32293 portions of their code are generated at runtime, instead of being loaded from
32294 object files, which is where @value{GDBN} normally finds the program's symbols
32295 and debug information. In order to debug programs that use JIT compilation,
32296 @value{GDBN} has an interface that allows the program to register in-memory
32297 symbol files with @value{GDBN} at runtime.
32299 If you are using @value{GDBN} to debug a program that uses this interface, then
32300 it should work transparently so long as you have not stripped the binary. If
32301 you are developing a JIT compiler, then the interface is documented in the rest
32302 of this chapter. At this time, the only known client of this interface is the
32305 Broadly speaking, the JIT interface mirrors the dynamic loader interface. The
32306 JIT compiler communicates with @value{GDBN} by writing data into a global
32307 variable and calling a fuction at a well-known symbol. When @value{GDBN}
32308 attaches, it reads a linked list of symbol files from the global variable to
32309 find existing code, and puts a breakpoint in the function so that it can find
32310 out about additional code.
32313 * Declarations:: Relevant C struct declarations
32314 * Registering Code:: Steps to register code
32315 * Unregistering Code:: Steps to unregister code
32316 * Custom Debug Info:: Emit debug information in a custom format
32320 @section JIT Declarations
32322 These are the relevant struct declarations that a C program should include to
32323 implement the interface:
32333 struct jit_code_entry
32335 struct jit_code_entry *next_entry;
32336 struct jit_code_entry *prev_entry;
32337 const char *symfile_addr;
32338 uint64_t symfile_size;
32341 struct jit_descriptor
32344 /* This type should be jit_actions_t, but we use uint32_t
32345 to be explicit about the bitwidth. */
32346 uint32_t action_flag;
32347 struct jit_code_entry *relevant_entry;
32348 struct jit_code_entry *first_entry;
32351 /* GDB puts a breakpoint in this function. */
32352 void __attribute__((noinline)) __jit_debug_register_code() @{ @};
32354 /* Make sure to specify the version statically, because the
32355 debugger may check the version before we can set it. */
32356 struct jit_descriptor __jit_debug_descriptor = @{ 1, 0, 0, 0 @};
32359 If the JIT is multi-threaded, then it is important that the JIT synchronize any
32360 modifications to this global data properly, which can easily be done by putting
32361 a global mutex around modifications to these structures.
32363 @node Registering Code
32364 @section Registering Code
32366 To register code with @value{GDBN}, the JIT should follow this protocol:
32370 Generate an object file in memory with symbols and other desired debug
32371 information. The file must include the virtual addresses of the sections.
32374 Create a code entry for the file, which gives the start and size of the symbol
32378 Add it to the linked list in the JIT descriptor.
32381 Point the relevant_entry field of the descriptor at the entry.
32384 Set @code{action_flag} to @code{JIT_REGISTER} and call
32385 @code{__jit_debug_register_code}.
32388 When @value{GDBN} is attached and the breakpoint fires, @value{GDBN} uses the
32389 @code{relevant_entry} pointer so it doesn't have to walk the list looking for
32390 new code. However, the linked list must still be maintained in order to allow
32391 @value{GDBN} to attach to a running process and still find the symbol files.
32393 @node Unregistering Code
32394 @section Unregistering Code
32396 If code is freed, then the JIT should use the following protocol:
32400 Remove the code entry corresponding to the code from the linked list.
32403 Point the @code{relevant_entry} field of the descriptor at the code entry.
32406 Set @code{action_flag} to @code{JIT_UNREGISTER} and call
32407 @code{__jit_debug_register_code}.
32410 If the JIT frees or recompiles code without unregistering it, then @value{GDBN}
32411 and the JIT will leak the memory used for the associated symbol files.
32413 @node Custom Debug Info
32414 @section Custom Debug Info
32415 @cindex custom JIT debug info
32416 @cindex JIT debug info reader
32418 Generating debug information in platform-native file formats (like ELF
32419 or COFF) may be an overkill for JIT compilers; especially if all the
32420 debug info is used for is displaying a meaningful backtrace. The
32421 issue can be resolved by having the JIT writers decide on a debug info
32422 format and also provide a reader that parses the debug info generated
32423 by the JIT compiler. This section gives a brief overview on writing
32424 such a parser. More specific details can be found in the source file
32425 @file{gdb/jit-reader.in}, which is also installed as a header at
32426 @file{@var{includedir}/gdb/jit-reader.h} for easy inclusion.
32428 The reader is implemented as a shared object (so this functionality is
32429 not available on platforms which don't allow loading shared objects at
32430 runtime). Two @value{GDBN} commands, @code{jit-reader-load} and
32431 @code{jit-reader-unload} are provided, to be used to load and unload
32432 the readers from a preconfigured directory. Once loaded, the shared
32433 object is used the parse the debug information emitted by the JIT
32437 * Using JIT Debug Info Readers:: How to use supplied readers correctly
32438 * Writing JIT Debug Info Readers:: Creating a debug-info reader
32441 @node Using JIT Debug Info Readers
32442 @subsection Using JIT Debug Info Readers
32443 @kindex jit-reader-load
32444 @kindex jit-reader-unload
32446 Readers can be loaded and unloaded using the @code{jit-reader-load}
32447 and @code{jit-reader-unload} commands.
32450 @item jit-reader-load @var{reader-name}
32451 Load the JIT reader named @var{reader-name}. On a UNIX system, this
32452 will usually load @file{@var{libdir}/gdb/@var{reader-name}}, where
32453 @var{libdir} is the system library directory, usually
32454 @file{/usr/local/lib}. Only one reader can be active at a time;
32455 trying to load a second reader when one is already loaded will result
32456 in @value{GDBN} reporting an error. A new JIT reader can be loaded by
32457 first unloading the current one using @code{jit-reader-load} and then
32458 invoking @code{jit-reader-load}.
32460 @item jit-reader-unload
32461 Unload the currently loaded JIT reader.
32465 @node Writing JIT Debug Info Readers
32466 @subsection Writing JIT Debug Info Readers
32467 @cindex writing JIT debug info readers
32469 As mentioned, a reader is essentially a shared object conforming to a
32470 certain ABI. This ABI is described in @file{jit-reader.h}.
32472 @file{jit-reader.h} defines the structures, macros and functions
32473 required to write a reader. It is installed (along with
32474 @value{GDBN}), in @file{@var{includedir}/gdb} where @var{includedir} is
32475 the system include directory.
32477 Readers need to be released under a GPL compatible license. A reader
32478 can be declared as released under such a license by placing the macro
32479 @code{GDB_DECLARE_GPL_COMPATIBLE_READER} in a source file.
32481 The entry point for readers is the symbol @code{gdb_init_reader},
32482 which is expected to be a function with the prototype
32484 @findex gdb_init_reader
32486 extern struct gdb_reader_funcs *gdb_init_reader (void);
32489 @cindex @code{struct gdb_reader_funcs}
32491 @code{struct gdb_reader_funcs} contains a set of pointers to callback
32492 functions. These functions are executed to read the debug info
32493 generated by the JIT compiler (@code{read}), to unwind stack frames
32494 (@code{unwind}) and to create canonical frame IDs
32495 (@code{get_Frame_id}). It also has a callback that is called when the
32496 reader is being unloaded (@code{destroy}). The struct looks like this
32499 struct gdb_reader_funcs
32501 /* Must be set to GDB_READER_INTERFACE_VERSION. */
32502 int reader_version;
32504 /* For use by the reader. */
32507 gdb_read_debug_info *read;
32508 gdb_unwind_frame *unwind;
32509 gdb_get_frame_id *get_frame_id;
32510 gdb_destroy_reader *destroy;
32514 @cindex @code{struct gdb_symbol_callbacks}
32515 @cindex @code{struct gdb_unwind_callbacks}
32517 The callbacks are provided with another set of callbacks by
32518 @value{GDBN} to do their job. For @code{read}, these callbacks are
32519 passed in a @code{struct gdb_symbol_callbacks} and for @code{unwind}
32520 and @code{get_frame_id}, in a @code{struct gdb_unwind_callbacks}.
32521 @code{struct gdb_symbol_callbacks} has callbacks to create new object
32522 files and new symbol tables inside those object files. @code{struct
32523 gdb_unwind_callbacks} has callbacks to read registers off the current
32524 frame and to write out the values of the registers in the previous
32525 frame. Both have a callback (@code{target_read}) to read bytes off the
32526 target's address space.
32528 @node In-Process Agent
32529 @chapter In-Process Agent
32530 @cindex debugging agent
32531 The traditional debugging model is conceptually low-speed, but works fine,
32532 because most bugs can be reproduced in debugging-mode execution. However,
32533 as multi-core or many-core processors are becoming mainstream, and
32534 multi-threaded programs become more and more popular, there should be more
32535 and more bugs that only manifest themselves at normal-mode execution, for
32536 example, thread races, because debugger's interference with the program's
32537 timing may conceal the bugs. On the other hand, in some applications,
32538 it is not feasible for the debugger to interrupt the program's execution
32539 long enough for the developer to learn anything helpful about its behavior.
32540 If the program's correctness depends on its real-time behavior, delays
32541 introduced by a debugger might cause the program to fail, even when the
32542 code itself is correct. It is useful to be able to observe the program's
32543 behavior without interrupting it.
32545 Therefore, traditional debugging model is too intrusive to reproduce
32546 some bugs. In order to reduce the interference with the program, we can
32547 reduce the number of operations performed by debugger. The
32548 @dfn{In-Process Agent}, a shared library, is running within the same
32549 process with inferior, and is able to perform some debugging operations
32550 itself. As a result, debugger is only involved when necessary, and
32551 performance of debugging can be improved accordingly. Note that
32552 interference with program can be reduced but can't be removed completely,
32553 because the in-process agent will still stop or slow down the program.
32555 The in-process agent can interpret and execute Agent Expressions
32556 (@pxref{Agent Expressions}) during performing debugging operations. The
32557 agent expressions can be used for different purposes, such as collecting
32558 data in tracepoints, and condition evaluation in breakpoints.
32560 @anchor{Control Agent}
32561 You can control whether the in-process agent is used as an aid for
32562 debugging with the following commands:
32565 @kindex set agent on
32567 Causes the in-process agent to perform some operations on behalf of the
32568 debugger. Just which operations requested by the user will be done
32569 by the in-process agent depends on the its capabilities. For example,
32570 if you request to evaluate breakpoint conditions in the in-process agent,
32571 and the in-process agent has such capability as well, then breakpoint
32572 conditions will be evaluated in the in-process agent.
32574 @kindex set agent off
32575 @item set agent off
32576 Disables execution of debugging operations by the in-process agent. All
32577 of the operations will be performed by @value{GDBN}.
32581 Display the current setting of execution of debugging operations by
32582 the in-process agent.
32586 @chapter Reporting Bugs in @value{GDBN}
32587 @cindex bugs in @value{GDBN}
32588 @cindex reporting bugs in @value{GDBN}
32590 Your bug reports play an essential role in making @value{GDBN} reliable.
32592 Reporting a bug may help you by bringing a solution to your problem, or it
32593 may not. But in any case the principal function of a bug report is to help
32594 the entire community by making the next version of @value{GDBN} work better. Bug
32595 reports are your contribution to the maintenance of @value{GDBN}.
32597 In order for a bug report to serve its purpose, you must include the
32598 information that enables us to fix the bug.
32601 * Bug Criteria:: Have you found a bug?
32602 * Bug Reporting:: How to report bugs
32606 @section Have You Found a Bug?
32607 @cindex bug criteria
32609 If you are not sure whether you have found a bug, here are some guidelines:
32612 @cindex fatal signal
32613 @cindex debugger crash
32614 @cindex crash of debugger
32616 If the debugger gets a fatal signal, for any input whatever, that is a
32617 @value{GDBN} bug. Reliable debuggers never crash.
32619 @cindex error on valid input
32621 If @value{GDBN} produces an error message for valid input, that is a
32622 bug. (Note that if you're cross debugging, the problem may also be
32623 somewhere in the connection to the target.)
32625 @cindex invalid input
32627 If @value{GDBN} does not produce an error message for invalid input,
32628 that is a bug. However, you should note that your idea of
32629 ``invalid input'' might be our idea of ``an extension'' or ``support
32630 for traditional practice''.
32633 If you are an experienced user of debugging tools, your suggestions
32634 for improvement of @value{GDBN} are welcome in any case.
32637 @node Bug Reporting
32638 @section How to Report Bugs
32639 @cindex bug reports
32640 @cindex @value{GDBN} bugs, reporting
32642 A number of companies and individuals offer support for @sc{gnu} products.
32643 If you obtained @value{GDBN} from a support organization, we recommend you
32644 contact that organization first.
32646 You can find contact information for many support companies and
32647 individuals in the file @file{etc/SERVICE} in the @sc{gnu} Emacs
32649 @c should add a web page ref...
32652 @ifset BUGURL_DEFAULT
32653 In any event, we also recommend that you submit bug reports for
32654 @value{GDBN}. The preferred method is to submit them directly using
32655 @uref{http://www.gnu.org/software/gdb/bugs/, @value{GDBN}'s Bugs web
32656 page}. Alternatively, the @email{bug-gdb@@gnu.org, e-mail gateway} can
32659 @strong{Do not send bug reports to @samp{info-gdb}, or to
32660 @samp{help-gdb}, or to any newsgroups.} Most users of @value{GDBN} do
32661 not want to receive bug reports. Those that do have arranged to receive
32664 The mailing list @samp{bug-gdb} has a newsgroup @samp{gnu.gdb.bug} which
32665 serves as a repeater. The mailing list and the newsgroup carry exactly
32666 the same messages. Often people think of posting bug reports to the
32667 newsgroup instead of mailing them. This appears to work, but it has one
32668 problem which can be crucial: a newsgroup posting often lacks a mail
32669 path back to the sender. Thus, if we need to ask for more information,
32670 we may be unable to reach you. For this reason, it is better to send
32671 bug reports to the mailing list.
32673 @ifclear BUGURL_DEFAULT
32674 In any event, we also recommend that you submit bug reports for
32675 @value{GDBN} to @value{BUGURL}.
32679 The fundamental principle of reporting bugs usefully is this:
32680 @strong{report all the facts}. If you are not sure whether to state a
32681 fact or leave it out, state it!
32683 Often people omit facts because they think they know what causes the
32684 problem and assume that some details do not matter. Thus, you might
32685 assume that the name of the variable you use in an example does not matter.
32686 Well, probably it does not, but one cannot be sure. Perhaps the bug is a
32687 stray memory reference which happens to fetch from the location where that
32688 name is stored in memory; perhaps, if the name were different, the contents
32689 of that location would fool the debugger into doing the right thing despite
32690 the bug. Play it safe and give a specific, complete example. That is the
32691 easiest thing for you to do, and the most helpful.
32693 Keep in mind that the purpose of a bug report is to enable us to fix the
32694 bug. It may be that the bug has been reported previously, but neither
32695 you nor we can know that unless your bug report is complete and
32698 Sometimes people give a few sketchy facts and ask, ``Does this ring a
32699 bell?'' Those bug reports are useless, and we urge everyone to
32700 @emph{refuse to respond to them} except to chide the sender to report
32703 To enable us to fix the bug, you should include all these things:
32707 The version of @value{GDBN}. @value{GDBN} announces it if you start
32708 with no arguments; you can also print it at any time using @code{show
32711 Without this, we will not know whether there is any point in looking for
32712 the bug in the current version of @value{GDBN}.
32715 The type of machine you are using, and the operating system name and
32719 What compiler (and its version) was used to compile @value{GDBN}---e.g.@:
32720 ``@value{GCC}--2.8.1''.
32723 What compiler (and its version) was used to compile the program you are
32724 debugging---e.g.@: ``@value{GCC}--2.8.1'', or ``HP92453-01 A.10.32.03 HP
32725 C Compiler''. For @value{NGCC}, you can say @kbd{@value{GCC} --version}
32726 to get this information; for other compilers, see the documentation for
32730 The command arguments you gave the compiler to compile your example and
32731 observe the bug. For example, did you use @samp{-O}? To guarantee
32732 you will not omit something important, list them all. A copy of the
32733 Makefile (or the output from make) is sufficient.
32735 If we were to try to guess the arguments, we would probably guess wrong
32736 and then we might not encounter the bug.
32739 A complete input script, and all necessary source files, that will
32743 A description of what behavior you observe that you believe is
32744 incorrect. For example, ``It gets a fatal signal.''
32746 Of course, if the bug is that @value{GDBN} gets a fatal signal, then we
32747 will certainly notice it. But if the bug is incorrect output, we might
32748 not notice unless it is glaringly wrong. You might as well not give us
32749 a chance to make a mistake.
32751 Even if the problem you experience is a fatal signal, you should still
32752 say so explicitly. Suppose something strange is going on, such as, your
32753 copy of @value{GDBN} is out of synch, or you have encountered a bug in
32754 the C library on your system. (This has happened!) Your copy might
32755 crash and ours would not. If you told us to expect a crash, then when
32756 ours fails to crash, we would know that the bug was not happening for
32757 us. If you had not told us to expect a crash, then we would not be able
32758 to draw any conclusion from our observations.
32761 @cindex recording a session script
32762 To collect all this information, you can use a session recording program
32763 such as @command{script}, which is available on many Unix systems.
32764 Just run your @value{GDBN} session inside @command{script} and then
32765 include the @file{typescript} file with your bug report.
32767 Another way to record a @value{GDBN} session is to run @value{GDBN}
32768 inside Emacs and then save the entire buffer to a file.
32771 If you wish to suggest changes to the @value{GDBN} source, send us context
32772 diffs. If you even discuss something in the @value{GDBN} source, refer to
32773 it by context, not by line number.
32775 The line numbers in our development sources will not match those in your
32776 sources. Your line numbers would convey no useful information to us.
32780 Here are some things that are not necessary:
32784 A description of the envelope of the bug.
32786 Often people who encounter a bug spend a lot of time investigating
32787 which changes to the input file will make the bug go away and which
32788 changes will not affect it.
32790 This is often time consuming and not very useful, because the way we
32791 will find the bug is by running a single example under the debugger
32792 with breakpoints, not by pure deduction from a series of examples.
32793 We recommend that you save your time for something else.
32795 Of course, if you can find a simpler example to report @emph{instead}
32796 of the original one, that is a convenience for us. Errors in the
32797 output will be easier to spot, running under the debugger will take
32798 less time, and so on.
32800 However, simplification is not vital; if you do not want to do this,
32801 report the bug anyway and send us the entire test case you used.
32804 A patch for the bug.
32806 A patch for the bug does help us if it is a good one. But do not omit
32807 the necessary information, such as the test case, on the assumption that
32808 a patch is all we need. We might see problems with your patch and decide
32809 to fix the problem another way, or we might not understand it at all.
32811 Sometimes with a program as complicated as @value{GDBN} it is very hard to
32812 construct an example that will make the program follow a certain path
32813 through the code. If you do not send us the example, we will not be able
32814 to construct one, so we will not be able to verify that the bug is fixed.
32816 And if we cannot understand what bug you are trying to fix, or why your
32817 patch should be an improvement, we will not install it. A test case will
32818 help us to understand.
32821 A guess about what the bug is or what it depends on.
32823 Such guesses are usually wrong. Even we cannot guess right about such
32824 things without first using the debugger to find the facts.
32827 @c The readline documentation is distributed with the readline code
32828 @c and consists of the two following files:
32831 @c Use -I with makeinfo to point to the appropriate directory,
32832 @c environment var TEXINPUTS with TeX.
32833 @ifclear SYSTEM_READLINE
32834 @include rluser.texi
32835 @include hsuser.texi
32839 @appendix In Memoriam
32841 The @value{GDBN} project mourns the loss of the following long-time
32846 Fred was a long-standing contributor to @value{GDBN} (1991-2006), and
32847 to Free Software in general. Outside of @value{GDBN}, he was known in
32848 the Amiga world for his series of Fish Disks, and the GeekGadget project.
32850 @item Michael Snyder
32851 Michael was one of the Global Maintainers of the @value{GDBN} project,
32852 with contributions recorded as early as 1996, until 2011. In addition
32853 to his day to day participation, he was a large driving force behind
32854 adding Reverse Debugging to @value{GDBN}.
32857 Beyond their technical contributions to the project, they were also
32858 enjoyable members of the Free Software Community. We will miss them.
32860 @node Formatting Documentation
32861 @appendix Formatting Documentation
32863 @cindex @value{GDBN} reference card
32864 @cindex reference card
32865 The @value{GDBN} 4 release includes an already-formatted reference card, ready
32866 for printing with PostScript or Ghostscript, in the @file{gdb}
32867 subdirectory of the main source directory@footnote{In
32868 @file{gdb-@value{GDBVN}/gdb/refcard.ps} of the version @value{GDBVN}
32869 release.}. If you can use PostScript or Ghostscript with your printer,
32870 you can print the reference card immediately with @file{refcard.ps}.
32872 The release also includes the source for the reference card. You
32873 can format it, using @TeX{}, by typing:
32879 The @value{GDBN} reference card is designed to print in @dfn{landscape}
32880 mode on US ``letter'' size paper;
32881 that is, on a sheet 11 inches wide by 8.5 inches
32882 high. You will need to specify this form of printing as an option to
32883 your @sc{dvi} output program.
32885 @cindex documentation
32887 All the documentation for @value{GDBN} comes as part of the machine-readable
32888 distribution. The documentation is written in Texinfo format, which is
32889 a documentation system that uses a single source file to produce both
32890 on-line information and a printed manual. You can use one of the Info
32891 formatting commands to create the on-line version of the documentation
32892 and @TeX{} (or @code{texi2roff}) to typeset the printed version.
32894 @value{GDBN} includes an already formatted copy of the on-line Info
32895 version of this manual in the @file{gdb} subdirectory. The main Info
32896 file is @file{gdb-@value{GDBVN}/gdb/gdb.info}, and it refers to
32897 subordinate files matching @samp{gdb.info*} in the same directory. If
32898 necessary, you can print out these files, or read them with any editor;
32899 but they are easier to read using the @code{info} subsystem in @sc{gnu}
32900 Emacs or the standalone @code{info} program, available as part of the
32901 @sc{gnu} Texinfo distribution.
32903 If you want to format these Info files yourself, you need one of the
32904 Info formatting programs, such as @code{texinfo-format-buffer} or
32907 If you have @code{makeinfo} installed, and are in the top level
32908 @value{GDBN} source directory (@file{gdb-@value{GDBVN}}, in the case of
32909 version @value{GDBVN}), you can make the Info file by typing:
32916 If you want to typeset and print copies of this manual, you need @TeX{},
32917 a program to print its @sc{dvi} output files, and @file{texinfo.tex}, the
32918 Texinfo definitions file.
32920 @TeX{} is a typesetting program; it does not print files directly, but
32921 produces output files called @sc{dvi} files. To print a typeset
32922 document, you need a program to print @sc{dvi} files. If your system
32923 has @TeX{} installed, chances are it has such a program. The precise
32924 command to use depends on your system; @kbd{lpr -d} is common; another
32925 (for PostScript devices) is @kbd{dvips}. The @sc{dvi} print command may
32926 require a file name without any extension or a @samp{.dvi} extension.
32928 @TeX{} also requires a macro definitions file called
32929 @file{texinfo.tex}. This file tells @TeX{} how to typeset a document
32930 written in Texinfo format. On its own, @TeX{} cannot either read or
32931 typeset a Texinfo file. @file{texinfo.tex} is distributed with GDB
32932 and is located in the @file{gdb-@var{version-number}/texinfo}
32935 If you have @TeX{} and a @sc{dvi} printer program installed, you can
32936 typeset and print this manual. First switch to the @file{gdb}
32937 subdirectory of the main source directory (for example, to
32938 @file{gdb-@value{GDBVN}/gdb}) and type:
32944 Then give @file{gdb.dvi} to your @sc{dvi} printing program.
32946 @node Installing GDB
32947 @appendix Installing @value{GDBN}
32948 @cindex installation
32951 * Requirements:: Requirements for building @value{GDBN}
32952 * Running Configure:: Invoking the @value{GDBN} @file{configure} script
32953 * Separate Objdir:: Compiling @value{GDBN} in another directory
32954 * Config Names:: Specifying names for hosts and targets
32955 * Configure Options:: Summary of options for configure
32956 * System-wide configuration:: Having a system-wide init file
32960 @section Requirements for Building @value{GDBN}
32961 @cindex building @value{GDBN}, requirements for
32963 Building @value{GDBN} requires various tools and packages to be available.
32964 Other packages will be used only if they are found.
32966 @heading Tools/Packages Necessary for Building @value{GDBN}
32968 @item ISO C90 compiler
32969 @value{GDBN} is written in ISO C90. It should be buildable with any
32970 working C90 compiler, e.g.@: GCC.
32974 @heading Tools/Packages Optional for Building @value{GDBN}
32978 @value{GDBN} can use the Expat XML parsing library. This library may be
32979 included with your operating system distribution; if it is not, you
32980 can get the latest version from @url{http://expat.sourceforge.net}.
32981 The @file{configure} script will search for this library in several
32982 standard locations; if it is installed in an unusual path, you can
32983 use the @option{--with-libexpat-prefix} option to specify its location.
32989 Remote protocol memory maps (@pxref{Memory Map Format})
32991 Target descriptions (@pxref{Target Descriptions})
32993 Remote shared library lists (@xref{Library List Format},
32994 or alternatively @pxref{Library List Format for SVR4 Targets})
32996 MS-Windows shared libraries (@pxref{Shared Libraries})
32998 Traceframe info (@pxref{Traceframe Info Format})
33002 @cindex compressed debug sections
33003 @value{GDBN} will use the @samp{zlib} library, if available, to read
33004 compressed debug sections. Some linkers, such as GNU gold, are capable
33005 of producing binaries with compressed debug sections. If @value{GDBN}
33006 is compiled with @samp{zlib}, it will be able to read the debug
33007 information in such binaries.
33009 The @samp{zlib} library is likely included with your operating system
33010 distribution; if it is not, you can get the latest version from
33011 @url{http://zlib.net}.
33014 @value{GDBN}'s features related to character sets (@pxref{Character
33015 Sets}) require a functioning @code{iconv} implementation. If you are
33016 on a GNU system, then this is provided by the GNU C Library. Some
33017 other systems also provide a working @code{iconv}.
33019 If @value{GDBN} is using the @code{iconv} program which is installed
33020 in a non-standard place, you will need to tell @value{GDBN} where to find it.
33021 This is done with @option{--with-iconv-bin} which specifies the
33022 directory that contains the @code{iconv} program.
33024 On systems without @code{iconv}, you can install GNU Libiconv. If you
33025 have previously installed Libiconv, you can use the
33026 @option{--with-libiconv-prefix} option to configure.
33028 @value{GDBN}'s top-level @file{configure} and @file{Makefile} will
33029 arrange to build Libiconv if a directory named @file{libiconv} appears
33030 in the top-most source directory. If Libiconv is built this way, and
33031 if the operating system does not provide a suitable @code{iconv}
33032 implementation, then the just-built library will automatically be used
33033 by @value{GDBN}. One easy way to set this up is to download GNU
33034 Libiconv, unpack it, and then rename the directory holding the
33035 Libiconv source code to @samp{libiconv}.
33038 @node Running Configure
33039 @section Invoking the @value{GDBN} @file{configure} Script
33040 @cindex configuring @value{GDBN}
33041 @value{GDBN} comes with a @file{configure} script that automates the process
33042 of preparing @value{GDBN} for installation; you can then use @code{make} to
33043 build the @code{gdb} program.
33045 @c irrelevant in info file; it's as current as the code it lives with.
33046 @footnote{If you have a more recent version of @value{GDBN} than @value{GDBVN},
33047 look at the @file{README} file in the sources; we may have improved the
33048 installation procedures since publishing this manual.}
33051 The @value{GDBN} distribution includes all the source code you need for
33052 @value{GDBN} in a single directory, whose name is usually composed by
33053 appending the version number to @samp{gdb}.
33055 For example, the @value{GDBN} version @value{GDBVN} distribution is in the
33056 @file{gdb-@value{GDBVN}} directory. That directory contains:
33059 @item gdb-@value{GDBVN}/configure @r{(and supporting files)}
33060 script for configuring @value{GDBN} and all its supporting libraries
33062 @item gdb-@value{GDBVN}/gdb
33063 the source specific to @value{GDBN} itself
33065 @item gdb-@value{GDBVN}/bfd
33066 source for the Binary File Descriptor library
33068 @item gdb-@value{GDBVN}/include
33069 @sc{gnu} include files
33071 @item gdb-@value{GDBVN}/libiberty
33072 source for the @samp{-liberty} free software library
33074 @item gdb-@value{GDBVN}/opcodes
33075 source for the library of opcode tables and disassemblers
33077 @item gdb-@value{GDBVN}/readline
33078 source for the @sc{gnu} command-line interface
33080 @item gdb-@value{GDBVN}/glob
33081 source for the @sc{gnu} filename pattern-matching subroutine
33083 @item gdb-@value{GDBVN}/mmalloc
33084 source for the @sc{gnu} memory-mapped malloc package
33087 The simplest way to configure and build @value{GDBN} is to run @file{configure}
33088 from the @file{gdb-@var{version-number}} source directory, which in
33089 this example is the @file{gdb-@value{GDBVN}} directory.
33091 First switch to the @file{gdb-@var{version-number}} source directory
33092 if you are not already in it; then run @file{configure}. Pass the
33093 identifier for the platform on which @value{GDBN} will run as an
33099 cd gdb-@value{GDBVN}
33100 ./configure @var{host}
33105 where @var{host} is an identifier such as @samp{sun4} or
33106 @samp{decstation}, that identifies the platform where @value{GDBN} will run.
33107 (You can often leave off @var{host}; @file{configure} tries to guess the
33108 correct value by examining your system.)
33110 Running @samp{configure @var{host}} and then running @code{make} builds the
33111 @file{bfd}, @file{readline}, @file{mmalloc}, and @file{libiberty}
33112 libraries, then @code{gdb} itself. The configured source files, and the
33113 binaries, are left in the corresponding source directories.
33116 @file{configure} is a Bourne-shell (@code{/bin/sh}) script; if your
33117 system does not recognize this automatically when you run a different
33118 shell, you may need to run @code{sh} on it explicitly:
33121 sh configure @var{host}
33124 If you run @file{configure} from a directory that contains source
33125 directories for multiple libraries or programs, such as the
33126 @file{gdb-@value{GDBVN}} source directory for version @value{GDBVN},
33128 creates configuration files for every directory level underneath (unless
33129 you tell it not to, with the @samp{--norecursion} option).
33131 You should run the @file{configure} script from the top directory in the
33132 source tree, the @file{gdb-@var{version-number}} directory. If you run
33133 @file{configure} from one of the subdirectories, you will configure only
33134 that subdirectory. That is usually not what you want. In particular,
33135 if you run the first @file{configure} from the @file{gdb} subdirectory
33136 of the @file{gdb-@var{version-number}} directory, you will omit the
33137 configuration of @file{bfd}, @file{readline}, and other sibling
33138 directories of the @file{gdb} subdirectory. This leads to build errors
33139 about missing include files such as @file{bfd/bfd.h}.
33141 You can install @code{@value{GDBP}} anywhere; it has no hardwired paths.
33142 However, you should make sure that the shell on your path (named by
33143 the @samp{SHELL} environment variable) is publicly readable. Remember
33144 that @value{GDBN} uses the shell to start your program---some systems refuse to
33145 let @value{GDBN} debug child processes whose programs are not readable.
33147 @node Separate Objdir
33148 @section Compiling @value{GDBN} in Another Directory
33150 If you want to run @value{GDBN} versions for several host or target machines,
33151 you need a different @code{gdb} compiled for each combination of
33152 host and target. @file{configure} is designed to make this easy by
33153 allowing you to generate each configuration in a separate subdirectory,
33154 rather than in the source directory. If your @code{make} program
33155 handles the @samp{VPATH} feature (@sc{gnu} @code{make} does), running
33156 @code{make} in each of these directories builds the @code{gdb}
33157 program specified there.
33159 To build @code{gdb} in a separate directory, run @file{configure}
33160 with the @samp{--srcdir} option to specify where to find the source.
33161 (You also need to specify a path to find @file{configure}
33162 itself from your working directory. If the path to @file{configure}
33163 would be the same as the argument to @samp{--srcdir}, you can leave out
33164 the @samp{--srcdir} option; it is assumed.)
33166 For example, with version @value{GDBVN}, you can build @value{GDBN} in a
33167 separate directory for a Sun 4 like this:
33171 cd gdb-@value{GDBVN}
33174 ../gdb-@value{GDBVN}/configure sun4
33179 When @file{configure} builds a configuration using a remote source
33180 directory, it creates a tree for the binaries with the same structure
33181 (and using the same names) as the tree under the source directory. In
33182 the example, you'd find the Sun 4 library @file{libiberty.a} in the
33183 directory @file{gdb-sun4/libiberty}, and @value{GDBN} itself in
33184 @file{gdb-sun4/gdb}.
33186 Make sure that your path to the @file{configure} script has just one
33187 instance of @file{gdb} in it. If your path to @file{configure} looks
33188 like @file{../gdb-@value{GDBVN}/gdb/configure}, you are configuring only
33189 one subdirectory of @value{GDBN}, not the whole package. This leads to
33190 build errors about missing include files such as @file{bfd/bfd.h}.
33192 One popular reason to build several @value{GDBN} configurations in separate
33193 directories is to configure @value{GDBN} for cross-compiling (where
33194 @value{GDBN} runs on one machine---the @dfn{host}---while debugging
33195 programs that run on another machine---the @dfn{target}).
33196 You specify a cross-debugging target by
33197 giving the @samp{--target=@var{target}} option to @file{configure}.
33199 When you run @code{make} to build a program or library, you must run
33200 it in a configured directory---whatever directory you were in when you
33201 called @file{configure} (or one of its subdirectories).
33203 The @code{Makefile} that @file{configure} generates in each source
33204 directory also runs recursively. If you type @code{make} in a source
33205 directory such as @file{gdb-@value{GDBVN}} (or in a separate configured
33206 directory configured with @samp{--srcdir=@var{dirname}/gdb-@value{GDBVN}}), you
33207 will build all the required libraries, and then build GDB.
33209 When you have multiple hosts or targets configured in separate
33210 directories, you can run @code{make} on them in parallel (for example,
33211 if they are NFS-mounted on each of the hosts); they will not interfere
33215 @section Specifying Names for Hosts and Targets
33217 The specifications used for hosts and targets in the @file{configure}
33218 script are based on a three-part naming scheme, but some short predefined
33219 aliases are also supported. The full naming scheme encodes three pieces
33220 of information in the following pattern:
33223 @var{architecture}-@var{vendor}-@var{os}
33226 For example, you can use the alias @code{sun4} as a @var{host} argument,
33227 or as the value for @var{target} in a @code{--target=@var{target}}
33228 option. The equivalent full name is @samp{sparc-sun-sunos4}.
33230 The @file{configure} script accompanying @value{GDBN} does not provide
33231 any query facility to list all supported host and target names or
33232 aliases. @file{configure} calls the Bourne shell script
33233 @code{config.sub} to map abbreviations to full names; you can read the
33234 script, if you wish, or you can use it to test your guesses on
33235 abbreviations---for example:
33238 % sh config.sub i386-linux
33240 % sh config.sub alpha-linux
33241 alpha-unknown-linux-gnu
33242 % sh config.sub hp9k700
33244 % sh config.sub sun4
33245 sparc-sun-sunos4.1.1
33246 % sh config.sub sun3
33247 m68k-sun-sunos4.1.1
33248 % sh config.sub i986v
33249 Invalid configuration `i986v': machine `i986v' not recognized
33253 @code{config.sub} is also distributed in the @value{GDBN} source
33254 directory (@file{gdb-@value{GDBVN}}, for version @value{GDBVN}).
33256 @node Configure Options
33257 @section @file{configure} Options
33259 Here is a summary of the @file{configure} options and arguments that
33260 are most often useful for building @value{GDBN}. @file{configure} also has
33261 several other options not listed here. @inforef{What Configure
33262 Does,,configure.info}, for a full explanation of @file{configure}.
33265 configure @r{[}--help@r{]}
33266 @r{[}--prefix=@var{dir}@r{]}
33267 @r{[}--exec-prefix=@var{dir}@r{]}
33268 @r{[}--srcdir=@var{dirname}@r{]}
33269 @r{[}--norecursion@r{]} @r{[}--rm@r{]}
33270 @r{[}--target=@var{target}@r{]}
33275 You may introduce options with a single @samp{-} rather than
33276 @samp{--} if you prefer; but you may abbreviate option names if you use
33281 Display a quick summary of how to invoke @file{configure}.
33283 @item --prefix=@var{dir}
33284 Configure the source to install programs and files under directory
33287 @item --exec-prefix=@var{dir}
33288 Configure the source to install programs under directory
33291 @c avoid splitting the warning from the explanation:
33293 @item --srcdir=@var{dirname}
33294 @strong{Warning: using this option requires @sc{gnu} @code{make}, or another
33295 @code{make} that implements the @code{VPATH} feature.}@*
33296 Use this option to make configurations in directories separate from the
33297 @value{GDBN} source directories. Among other things, you can use this to
33298 build (or maintain) several configurations simultaneously, in separate
33299 directories. @file{configure} writes configuration-specific files in
33300 the current directory, but arranges for them to use the source in the
33301 directory @var{dirname}. @file{configure} creates directories under
33302 the working directory in parallel to the source directories below
33305 @item --norecursion
33306 Configure only the directory level where @file{configure} is executed; do not
33307 propagate configuration to subdirectories.
33309 @item --target=@var{target}
33310 Configure @value{GDBN} for cross-debugging programs running on the specified
33311 @var{target}. Without this option, @value{GDBN} is configured to debug
33312 programs that run on the same machine (@var{host}) as @value{GDBN} itself.
33314 There is no convenient way to generate a list of all available targets.
33316 @item @var{host} @dots{}
33317 Configure @value{GDBN} to run on the specified @var{host}.
33319 There is no convenient way to generate a list of all available hosts.
33322 There are many other options available as well, but they are generally
33323 needed for special purposes only.
33325 @node System-wide configuration
33326 @section System-wide configuration and settings
33327 @cindex system-wide init file
33329 @value{GDBN} can be configured to have a system-wide init file;
33330 this file will be read and executed at startup (@pxref{Startup, , What
33331 @value{GDBN} does during startup}).
33333 Here is the corresponding configure option:
33336 @item --with-system-gdbinit=@var{file}
33337 Specify that the default location of the system-wide init file is
33341 If @value{GDBN} has been configured with the option @option{--prefix=$prefix},
33342 it may be subject to relocation. Two possible cases:
33346 If the default location of this init file contains @file{$prefix},
33347 it will be subject to relocation. Suppose that the configure options
33348 are @option{--prefix=$prefix --with-system-gdbinit=$prefix/etc/gdbinit};
33349 if @value{GDBN} is moved from @file{$prefix} to @file{$install}, the system
33350 init file is looked for as @file{$install/etc/gdbinit} instead of
33351 @file{$prefix/etc/gdbinit}.
33354 By contrast, if the default location does not contain the prefix,
33355 it will not be relocated. E.g.@: if @value{GDBN} has been configured with
33356 @option{--prefix=/usr/local --with-system-gdbinit=/usr/share/gdb/gdbinit},
33357 then @value{GDBN} will always look for @file{/usr/share/gdb/gdbinit},
33358 wherever @value{GDBN} is installed.
33361 @node Maintenance Commands
33362 @appendix Maintenance Commands
33363 @cindex maintenance commands
33364 @cindex internal commands
33366 In addition to commands intended for @value{GDBN} users, @value{GDBN}
33367 includes a number of commands intended for @value{GDBN} developers,
33368 that are not documented elsewhere in this manual. These commands are
33369 provided here for reference. (For commands that turn on debugging
33370 messages, see @ref{Debugging Output}.)
33373 @kindex maint agent
33374 @kindex maint agent-eval
33375 @item maint agent @var{expression}
33376 @itemx maint agent-eval @var{expression}
33377 Translate the given @var{expression} into remote agent bytecodes.
33378 This command is useful for debugging the Agent Expression mechanism
33379 (@pxref{Agent Expressions}). The @samp{agent} version produces an
33380 expression useful for data collection, such as by tracepoints, while
33381 @samp{maint agent-eval} produces an expression that evaluates directly
33382 to a result. For instance, a collection expression for @code{globa +
33383 globb} will include bytecodes to record four bytes of memory at each
33384 of the addresses of @code{globa} and @code{globb}, while discarding
33385 the result of the addition, while an evaluation expression will do the
33386 addition and return the sum.
33388 @kindex maint info breakpoints
33389 @item @anchor{maint info breakpoints}maint info breakpoints
33390 Using the same format as @samp{info breakpoints}, display both the
33391 breakpoints you've set explicitly, and those @value{GDBN} is using for
33392 internal purposes. Internal breakpoints are shown with negative
33393 breakpoint numbers. The type column identifies what kind of breakpoint
33398 Normal, explicitly set breakpoint.
33401 Normal, explicitly set watchpoint.
33404 Internal breakpoint, used to handle correctly stepping through
33405 @code{longjmp} calls.
33407 @item longjmp resume
33408 Internal breakpoint at the target of a @code{longjmp}.
33411 Temporary internal breakpoint used by the @value{GDBN} @code{until} command.
33414 Temporary internal breakpoint used by the @value{GDBN} @code{finish} command.
33417 Shared library events.
33421 @kindex set displaced-stepping
33422 @kindex show displaced-stepping
33423 @cindex displaced stepping support
33424 @cindex out-of-line single-stepping
33425 @item set displaced-stepping
33426 @itemx show displaced-stepping
33427 Control whether or not @value{GDBN} will do @dfn{displaced stepping}
33428 if the target supports it. Displaced stepping is a way to single-step
33429 over breakpoints without removing them from the inferior, by executing
33430 an out-of-line copy of the instruction that was originally at the
33431 breakpoint location. It is also known as out-of-line single-stepping.
33434 @item set displaced-stepping on
33435 If the target architecture supports it, @value{GDBN} will use
33436 displaced stepping to step over breakpoints.
33438 @item set displaced-stepping off
33439 @value{GDBN} will not use displaced stepping to step over breakpoints,
33440 even if such is supported by the target architecture.
33442 @cindex non-stop mode, and @samp{set displaced-stepping}
33443 @item set displaced-stepping auto
33444 This is the default mode. @value{GDBN} will use displaced stepping
33445 only if non-stop mode is active (@pxref{Non-Stop Mode}) and the target
33446 architecture supports displaced stepping.
33449 @kindex maint check-symtabs
33450 @item maint check-symtabs
33451 Check the consistency of psymtabs and symtabs.
33453 @kindex maint cplus first_component
33454 @item maint cplus first_component @var{name}
33455 Print the first C@t{++} class/namespace component of @var{name}.
33457 @kindex maint cplus namespace
33458 @item maint cplus namespace
33459 Print the list of possible C@t{++} namespaces.
33461 @kindex maint demangle
33462 @item maint demangle @var{name}
33463 Demangle a C@t{++} or Objective-C mangled @var{name}.
33465 @kindex maint deprecate
33466 @kindex maint undeprecate
33467 @cindex deprecated commands
33468 @item maint deprecate @var{command} @r{[}@var{replacement}@r{]}
33469 @itemx maint undeprecate @var{command}
33470 Deprecate or undeprecate the named @var{command}. Deprecated commands
33471 cause @value{GDBN} to issue a warning when you use them. The optional
33472 argument @var{replacement} says which newer command should be used in
33473 favor of the deprecated one; if it is given, @value{GDBN} will mention
33474 the replacement as part of the warning.
33476 @kindex maint dump-me
33477 @item maint dump-me
33478 @cindex @code{SIGQUIT} signal, dump core of @value{GDBN}
33479 Cause a fatal signal in the debugger and force it to dump its core.
33480 This is supported only on systems which support aborting a program
33481 with the @code{SIGQUIT} signal.
33483 @kindex maint internal-error
33484 @kindex maint internal-warning
33485 @item maint internal-error @r{[}@var{message-text}@r{]}
33486 @itemx maint internal-warning @r{[}@var{message-text}@r{]}
33487 Cause @value{GDBN} to call the internal function @code{internal_error}
33488 or @code{internal_warning} and hence behave as though an internal error
33489 or internal warning has been detected. In addition to reporting the
33490 internal problem, these functions give the user the opportunity to
33491 either quit @value{GDBN} or create a core file of the current
33492 @value{GDBN} session.
33494 These commands take an optional parameter @var{message-text} that is
33495 used as the text of the error or warning message.
33497 Here's an example of using @code{internal-error}:
33500 (@value{GDBP}) @kbd{maint internal-error testing, 1, 2}
33501 @dots{}/maint.c:121: internal-error: testing, 1, 2
33502 A problem internal to GDB has been detected. Further
33503 debugging may prove unreliable.
33504 Quit this debugging session? (y or n) @kbd{n}
33505 Create a core file? (y or n) @kbd{n}
33509 @cindex @value{GDBN} internal error
33510 @cindex internal errors, control of @value{GDBN} behavior
33512 @kindex maint set internal-error
33513 @kindex maint show internal-error
33514 @kindex maint set internal-warning
33515 @kindex maint show internal-warning
33516 @item maint set internal-error @var{action} [ask|yes|no]
33517 @itemx maint show internal-error @var{action}
33518 @itemx maint set internal-warning @var{action} [ask|yes|no]
33519 @itemx maint show internal-warning @var{action}
33520 When @value{GDBN} reports an internal problem (error or warning) it
33521 gives the user the opportunity to both quit @value{GDBN} and create a
33522 core file of the current @value{GDBN} session. These commands let you
33523 override the default behaviour for each particular @var{action},
33524 described in the table below.
33528 You can specify that @value{GDBN} should always (yes) or never (no)
33529 quit. The default is to ask the user what to do.
33532 You can specify that @value{GDBN} should always (yes) or never (no)
33533 create a core file. The default is to ask the user what to do.
33536 @kindex maint packet
33537 @item maint packet @var{text}
33538 If @value{GDBN} is talking to an inferior via the serial protocol,
33539 then this command sends the string @var{text} to the inferior, and
33540 displays the response packet. @value{GDBN} supplies the initial
33541 @samp{$} character, the terminating @samp{#} character, and the
33544 @kindex maint print architecture
33545 @item maint print architecture @r{[}@var{file}@r{]}
33546 Print the entire architecture configuration. The optional argument
33547 @var{file} names the file where the output goes.
33549 @kindex maint print c-tdesc
33550 @item maint print c-tdesc
33551 Print the current target description (@pxref{Target Descriptions}) as
33552 a C source file. The created source file can be used in @value{GDBN}
33553 when an XML parser is not available to parse the description.
33555 @kindex maint print dummy-frames
33556 @item maint print dummy-frames
33557 Prints the contents of @value{GDBN}'s internal dummy-frame stack.
33560 (@value{GDBP}) @kbd{b add}
33562 (@value{GDBP}) @kbd{print add(2,3)}
33563 Breakpoint 2, add (a=2, b=3) at @dots{}
33565 The program being debugged stopped while in a function called from GDB.
33567 (@value{GDBP}) @kbd{maint print dummy-frames}
33568 0x1a57c80: pc=0x01014068 fp=0x0200bddc sp=0x0200bdd6
33569 top=0x0200bdd4 id=@{stack=0x200bddc,code=0x101405c@}
33570 call_lo=0x01014000 call_hi=0x01014001
33574 Takes an optional file parameter.
33576 @kindex maint print registers
33577 @kindex maint print raw-registers
33578 @kindex maint print cooked-registers
33579 @kindex maint print register-groups
33580 @kindex maint print remote-registers
33581 @item maint print registers @r{[}@var{file}@r{]}
33582 @itemx maint print raw-registers @r{[}@var{file}@r{]}
33583 @itemx maint print cooked-registers @r{[}@var{file}@r{]}
33584 @itemx maint print register-groups @r{[}@var{file}@r{]}
33585 @itemx maint print remote-registers @r{[}@var{file}@r{]}
33586 Print @value{GDBN}'s internal register data structures.
33588 The command @code{maint print raw-registers} includes the contents of
33589 the raw register cache; the command @code{maint print
33590 cooked-registers} includes the (cooked) value of all registers,
33591 including registers which aren't available on the target nor visible
33592 to user; the command @code{maint print register-groups} includes the
33593 groups that each register is a member of; and the command @code{maint
33594 print remote-registers} includes the remote target's register numbers
33595 and offsets in the `G' packets. @xref{Registers,, Registers, gdbint,
33596 @value{GDBN} Internals}.
33598 These commands take an optional parameter, a file name to which to
33599 write the information.
33601 @kindex maint print reggroups
33602 @item maint print reggroups @r{[}@var{file}@r{]}
33603 Print @value{GDBN}'s internal register group data structures. The
33604 optional argument @var{file} tells to what file to write the
33607 The register groups info looks like this:
33610 (@value{GDBP}) @kbd{maint print reggroups}
33623 This command forces @value{GDBN} to flush its internal register cache.
33625 @kindex maint print objfiles
33626 @cindex info for known object files
33627 @item maint print objfiles
33628 Print a dump of all known object files. For each object file, this
33629 command prints its name, address in memory, and all of its psymtabs
33632 @kindex maint print section-scripts
33633 @cindex info for known .debug_gdb_scripts-loaded scripts
33634 @item maint print section-scripts [@var{regexp}]
33635 Print a dump of scripts specified in the @code{.debug_gdb_section} section.
33636 If @var{regexp} is specified, only print scripts loaded by object files
33637 matching @var{regexp}.
33638 For each script, this command prints its name as specified in the objfile,
33639 and the full path if known.
33640 @xref{dotdebug_gdb_scripts section}.
33642 @kindex maint print statistics
33643 @cindex bcache statistics
33644 @item maint print statistics
33645 This command prints, for each object file in the program, various data
33646 about that object file followed by the byte cache (@dfn{bcache})
33647 statistics for the object file. The objfile data includes the number
33648 of minimal, partial, full, and stabs symbols, the number of types
33649 defined by the objfile, the number of as yet unexpanded psym tables,
33650 the number of line tables and string tables, and the amount of memory
33651 used by the various tables. The bcache statistics include the counts,
33652 sizes, and counts of duplicates of all and unique objects, max,
33653 average, and median entry size, total memory used and its overhead and
33654 savings, and various measures of the hash table size and chain
33657 @kindex maint print target-stack
33658 @cindex target stack description
33659 @item maint print target-stack
33660 A @dfn{target} is an interface between the debugger and a particular
33661 kind of file or process. Targets can be stacked in @dfn{strata},
33662 so that more than one target can potentially respond to a request.
33663 In particular, memory accesses will walk down the stack of targets
33664 until they find a target that is interested in handling that particular
33667 This command prints a short description of each layer that was pushed on
33668 the @dfn{target stack}, starting from the top layer down to the bottom one.
33670 @kindex maint print type
33671 @cindex type chain of a data type
33672 @item maint print type @var{expr}
33673 Print the type chain for a type specified by @var{expr}. The argument
33674 can be either a type name or a symbol. If it is a symbol, the type of
33675 that symbol is described. The type chain produced by this command is
33676 a recursive definition of the data type as stored in @value{GDBN}'s
33677 data structures, including its flags and contained types.
33679 @kindex maint set dwarf2 always-disassemble
33680 @kindex maint show dwarf2 always-disassemble
33681 @item maint set dwarf2 always-disassemble
33682 @item maint show dwarf2 always-disassemble
33683 Control the behavior of @code{info address} when using DWARF debugging
33686 The default is @code{off}, which means that @value{GDBN} should try to
33687 describe a variable's location in an easily readable format. When
33688 @code{on}, @value{GDBN} will instead display the DWARF location
33689 expression in an assembly-like format. Note that some locations are
33690 too complex for @value{GDBN} to describe simply; in this case you will
33691 always see the disassembly form.
33693 Here is an example of the resulting disassembly:
33696 (gdb) info addr argc
33697 Symbol "argc" is a complex DWARF expression:
33701 For more information on these expressions, see
33702 @uref{http://www.dwarfstd.org/, the DWARF standard}.
33704 @kindex maint set dwarf2 max-cache-age
33705 @kindex maint show dwarf2 max-cache-age
33706 @item maint set dwarf2 max-cache-age
33707 @itemx maint show dwarf2 max-cache-age
33708 Control the DWARF 2 compilation unit cache.
33710 @cindex DWARF 2 compilation units cache
33711 In object files with inter-compilation-unit references, such as those
33712 produced by the GCC option @samp{-feliminate-dwarf2-dups}, the DWARF 2
33713 reader needs to frequently refer to previously read compilation units.
33714 This setting controls how long a compilation unit will remain in the
33715 cache if it is not referenced. A higher limit means that cached
33716 compilation units will be stored in memory longer, and more total
33717 memory will be used. Setting it to zero disables caching, which will
33718 slow down @value{GDBN} startup, but reduce memory consumption.
33720 @kindex maint set profile
33721 @kindex maint show profile
33722 @cindex profiling GDB
33723 @item maint set profile
33724 @itemx maint show profile
33725 Control profiling of @value{GDBN}.
33727 Profiling will be disabled until you use the @samp{maint set profile}
33728 command to enable it. When you enable profiling, the system will begin
33729 collecting timing and execution count data; when you disable profiling or
33730 exit @value{GDBN}, the results will be written to a log file. Remember that
33731 if you use profiling, @value{GDBN} will overwrite the profiling log file
33732 (often called @file{gmon.out}). If you have a record of important profiling
33733 data in a @file{gmon.out} file, be sure to move it to a safe location.
33735 Configuring with @samp{--enable-profiling} arranges for @value{GDBN} to be
33736 compiled with the @samp{-pg} compiler option.
33738 @kindex maint set show-debug-regs
33739 @kindex maint show show-debug-regs
33740 @cindex hardware debug registers
33741 @item maint set show-debug-regs
33742 @itemx maint show show-debug-regs
33743 Control whether to show variables that mirror the hardware debug
33744 registers. Use @code{ON} to enable, @code{OFF} to disable. If
33745 enabled, the debug registers values are shown when @value{GDBN} inserts or
33746 removes a hardware breakpoint or watchpoint, and when the inferior
33747 triggers a hardware-assisted breakpoint or watchpoint.
33749 @kindex maint set show-all-tib
33750 @kindex maint show show-all-tib
33751 @item maint set show-all-tib
33752 @itemx maint show show-all-tib
33753 Control whether to show all non zero areas within a 1k block starting
33754 at thread local base, when using the @samp{info w32 thread-information-block}
33757 @kindex maint space
33758 @cindex memory used by commands
33760 Control whether to display memory usage for each command. If set to a
33761 nonzero value, @value{GDBN} will display how much memory each command
33762 took, following the command's own output. This can also be requested
33763 by invoking @value{GDBN} with the @option{--statistics} command-line
33764 switch (@pxref{Mode Options}).
33767 @cindex time of command execution
33769 Control whether to display the execution time of @value{GDBN} for each command.
33770 If set to a nonzero value, @value{GDBN} will display how much time it
33771 took to execute each command, following the command's own output.
33772 Both CPU time and wallclock time are printed.
33773 Printing both is useful when trying to determine whether the cost is
33774 CPU or, e.g., disk/network, latency.
33775 Note that the CPU time printed is for @value{GDBN} only, it does not include
33776 the execution time of the inferior because there's no mechanism currently
33777 to compute how much time was spent by @value{GDBN} and how much time was
33778 spent by the program been debugged.
33779 This can also be requested by invoking @value{GDBN} with the
33780 @option{--statistics} command-line switch (@pxref{Mode Options}).
33782 @kindex maint translate-address
33783 @item maint translate-address @r{[}@var{section}@r{]} @var{addr}
33784 Find the symbol stored at the location specified by the address
33785 @var{addr} and an optional section name @var{section}. If found,
33786 @value{GDBN} prints the name of the closest symbol and an offset from
33787 the symbol's location to the specified address. This is similar to
33788 the @code{info address} command (@pxref{Symbols}), except that this
33789 command also allows to find symbols in other sections.
33791 If section was not specified, the section in which the symbol was found
33792 is also printed. For dynamically linked executables, the name of
33793 executable or shared library containing the symbol is printed as well.
33797 The following command is useful for non-interactive invocations of
33798 @value{GDBN}, such as in the test suite.
33801 @item set watchdog @var{nsec}
33802 @kindex set watchdog
33803 @cindex watchdog timer
33804 @cindex timeout for commands
33805 Set the maximum number of seconds @value{GDBN} will wait for the
33806 target operation to finish. If this time expires, @value{GDBN}
33807 reports and error and the command is aborted.
33809 @item show watchdog
33810 Show the current setting of the target wait timeout.
33813 @node Remote Protocol
33814 @appendix @value{GDBN} Remote Serial Protocol
33819 * Stop Reply Packets::
33820 * General Query Packets::
33821 * Architecture-Specific Protocol Details::
33822 * Tracepoint Packets::
33823 * Host I/O Packets::
33825 * Notification Packets::
33826 * Remote Non-Stop::
33827 * Packet Acknowledgment::
33829 * File-I/O Remote Protocol Extension::
33830 * Library List Format::
33831 * Library List Format for SVR4 Targets::
33832 * Memory Map Format::
33833 * Thread List Format::
33834 * Traceframe Info Format::
33840 There may be occasions when you need to know something about the
33841 protocol---for example, if there is only one serial port to your target
33842 machine, you might want your program to do something special if it
33843 recognizes a packet meant for @value{GDBN}.
33845 In the examples below, @samp{->} and @samp{<-} are used to indicate
33846 transmitted and received data, respectively.
33848 @cindex protocol, @value{GDBN} remote serial
33849 @cindex serial protocol, @value{GDBN} remote
33850 @cindex remote serial protocol
33851 All @value{GDBN} commands and responses (other than acknowledgments
33852 and notifications, see @ref{Notification Packets}) are sent as a
33853 @var{packet}. A @var{packet} is introduced with the character
33854 @samp{$}, the actual @var{packet-data}, and the terminating character
33855 @samp{#} followed by a two-digit @var{checksum}:
33858 @code{$}@var{packet-data}@code{#}@var{checksum}
33862 @cindex checksum, for @value{GDBN} remote
33864 The two-digit @var{checksum} is computed as the modulo 256 sum of all
33865 characters between the leading @samp{$} and the trailing @samp{#} (an
33866 eight bit unsigned checksum).
33868 Implementors should note that prior to @value{GDBN} 5.0 the protocol
33869 specification also included an optional two-digit @var{sequence-id}:
33872 @code{$}@var{sequence-id}@code{:}@var{packet-data}@code{#}@var{checksum}
33875 @cindex sequence-id, for @value{GDBN} remote
33877 That @var{sequence-id} was appended to the acknowledgment. @value{GDBN}
33878 has never output @var{sequence-id}s. Stubs that handle packets added
33879 since @value{GDBN} 5.0 must not accept @var{sequence-id}.
33881 When either the host or the target machine receives a packet, the first
33882 response expected is an acknowledgment: either @samp{+} (to indicate
33883 the package was received correctly) or @samp{-} (to request
33887 -> @code{$}@var{packet-data}@code{#}@var{checksum}
33892 The @samp{+}/@samp{-} acknowledgments can be disabled
33893 once a connection is established.
33894 @xref{Packet Acknowledgment}, for details.
33896 The host (@value{GDBN}) sends @var{command}s, and the target (the
33897 debugging stub incorporated in your program) sends a @var{response}. In
33898 the case of step and continue @var{command}s, the response is only sent
33899 when the operation has completed, and the target has again stopped all
33900 threads in all attached processes. This is the default all-stop mode
33901 behavior, but the remote protocol also supports @value{GDBN}'s non-stop
33902 execution mode; see @ref{Remote Non-Stop}, for details.
33904 @var{packet-data} consists of a sequence of characters with the
33905 exception of @samp{#} and @samp{$} (see @samp{X} packet for additional
33908 @cindex remote protocol, field separator
33909 Fields within the packet should be separated using @samp{,} @samp{;} or
33910 @samp{:}. Except where otherwise noted all numbers are represented in
33911 @sc{hex} with leading zeros suppressed.
33913 Implementors should note that prior to @value{GDBN} 5.0, the character
33914 @samp{:} could not appear as the third character in a packet (as it
33915 would potentially conflict with the @var{sequence-id}).
33917 @cindex remote protocol, binary data
33918 @anchor{Binary Data}
33919 Binary data in most packets is encoded either as two hexadecimal
33920 digits per byte of binary data. This allowed the traditional remote
33921 protocol to work over connections which were only seven-bit clean.
33922 Some packets designed more recently assume an eight-bit clean
33923 connection, and use a more efficient encoding to send and receive
33926 The binary data representation uses @code{7d} (@sc{ascii} @samp{@}})
33927 as an escape character. Any escaped byte is transmitted as the escape
33928 character followed by the original character XORed with @code{0x20}.
33929 For example, the byte @code{0x7d} would be transmitted as the two
33930 bytes @code{0x7d 0x5d}. The bytes @code{0x23} (@sc{ascii} @samp{#}),
33931 @code{0x24} (@sc{ascii} @samp{$}), and @code{0x7d} (@sc{ascii}
33932 @samp{@}}) must always be escaped. Responses sent by the stub
33933 must also escape @code{0x2a} (@sc{ascii} @samp{*}), so that it
33934 is not interpreted as the start of a run-length encoded sequence
33937 Response @var{data} can be run-length encoded to save space.
33938 Run-length encoding replaces runs of identical characters with one
33939 instance of the repeated character, followed by a @samp{*} and a
33940 repeat count. The repeat count is itself sent encoded, to avoid
33941 binary characters in @var{data}: a value of @var{n} is sent as
33942 @code{@var{n}+29}. For a repeat count greater or equal to 3, this
33943 produces a printable @sc{ascii} character, e.g.@: a space (@sc{ascii}
33944 code 32) for a repeat count of 3. (This is because run-length
33945 encoding starts to win for counts 3 or more.) Thus, for example,
33946 @samp{0* } is a run-length encoding of ``0000'': the space character
33947 after @samp{*} means repeat the leading @code{0} @w{@code{32 - 29 =
33950 The printable characters @samp{#} and @samp{$} or with a numeric value
33951 greater than 126 must not be used. Runs of six repeats (@samp{#}) or
33952 seven repeats (@samp{$}) can be expanded using a repeat count of only
33953 five (@samp{"}). For example, @samp{00000000} can be encoded as
33956 The error response returned for some packets includes a two character
33957 error number. That number is not well defined.
33959 @cindex empty response, for unsupported packets
33960 For any @var{command} not supported by the stub, an empty response
33961 (@samp{$#00}) should be returned. That way it is possible to extend the
33962 protocol. A newer @value{GDBN} can tell if a packet is supported based
33965 At a minimum, a stub is required to support the @samp{g} and @samp{G}
33966 commands for register access, and the @samp{m} and @samp{M} commands
33967 for memory access. Stubs that only control single-threaded targets
33968 can implement run control with the @samp{c} (continue), and @samp{s}
33969 (step) commands. Stubs that support multi-threading targets should
33970 support the @samp{vCont} command. All other commands are optional.
33975 The following table provides a complete list of all currently defined
33976 @var{command}s and their corresponding response @var{data}.
33977 @xref{File-I/O Remote Protocol Extension}, for details about the File
33978 I/O extension of the remote protocol.
33980 Each packet's description has a template showing the packet's overall
33981 syntax, followed by an explanation of the packet's meaning. We
33982 include spaces in some of the templates for clarity; these are not
33983 part of the packet's syntax. No @value{GDBN} packet uses spaces to
33984 separate its components. For example, a template like @samp{foo
33985 @var{bar} @var{baz}} describes a packet beginning with the three ASCII
33986 bytes @samp{foo}, followed by a @var{bar}, followed directly by a
33987 @var{baz}. @value{GDBN} does not transmit a space character between the
33988 @samp{foo} and the @var{bar}, or between the @var{bar} and the
33991 @cindex @var{thread-id}, in remote protocol
33992 @anchor{thread-id syntax}
33993 Several packets and replies include a @var{thread-id} field to identify
33994 a thread. Normally these are positive numbers with a target-specific
33995 interpretation, formatted as big-endian hex strings. A @var{thread-id}
33996 can also be a literal @samp{-1} to indicate all threads, or @samp{0} to
33999 In addition, the remote protocol supports a multiprocess feature in
34000 which the @var{thread-id} syntax is extended to optionally include both
34001 process and thread ID fields, as @samp{p@var{pid}.@var{tid}}.
34002 The @var{pid} (process) and @var{tid} (thread) components each have the
34003 format described above: a positive number with target-specific
34004 interpretation formatted as a big-endian hex string, literal @samp{-1}
34005 to indicate all processes or threads (respectively), or @samp{0} to
34006 indicate an arbitrary process or thread. Specifying just a process, as
34007 @samp{p@var{pid}}, is equivalent to @samp{p@var{pid}.-1}. It is an
34008 error to specify all processes but a specific thread, such as
34009 @samp{p-1.@var{tid}}. Note that the @samp{p} prefix is @emph{not} used
34010 for those packets and replies explicitly documented to include a process
34011 ID, rather than a @var{thread-id}.
34013 The multiprocess @var{thread-id} syntax extensions are only used if both
34014 @value{GDBN} and the stub report support for the @samp{multiprocess}
34015 feature using @samp{qSupported}. @xref{multiprocess extensions}, for
34018 Note that all packet forms beginning with an upper- or lower-case
34019 letter, other than those described here, are reserved for future use.
34021 Here are the packet descriptions.
34026 @cindex @samp{!} packet
34027 @anchor{extended mode}
34028 Enable extended mode. In extended mode, the remote server is made
34029 persistent. The @samp{R} packet is used to restart the program being
34035 The remote target both supports and has enabled extended mode.
34039 @cindex @samp{?} packet
34040 Indicate the reason the target halted. The reply is the same as for
34041 step and continue. This packet has a special interpretation when the
34042 target is in non-stop mode; see @ref{Remote Non-Stop}.
34045 @xref{Stop Reply Packets}, for the reply specifications.
34047 @item A @var{arglen},@var{argnum},@var{arg},@dots{}
34048 @cindex @samp{A} packet
34049 Initialized @code{argv[]} array passed into program. @var{arglen}
34050 specifies the number of bytes in the hex encoded byte stream
34051 @var{arg}. See @code{gdbserver} for more details.
34056 The arguments were set.
34062 @cindex @samp{b} packet
34063 (Don't use this packet; its behavior is not well-defined.)
34064 Change the serial line speed to @var{baud}.
34066 JTC: @emph{When does the transport layer state change? When it's
34067 received, or after the ACK is transmitted. In either case, there are
34068 problems if the command or the acknowledgment packet is dropped.}
34070 Stan: @emph{If people really wanted to add something like this, and get
34071 it working for the first time, they ought to modify ser-unix.c to send
34072 some kind of out-of-band message to a specially-setup stub and have the
34073 switch happen "in between" packets, so that from remote protocol's point
34074 of view, nothing actually happened.}
34076 @item B @var{addr},@var{mode}
34077 @cindex @samp{B} packet
34078 Set (@var{mode} is @samp{S}) or clear (@var{mode} is @samp{C}) a
34079 breakpoint at @var{addr}.
34081 Don't use this packet. Use the @samp{Z} and @samp{z} packets instead
34082 (@pxref{insert breakpoint or watchpoint packet}).
34084 @cindex @samp{bc} packet
34087 Backward continue. Execute the target system in reverse. No parameter.
34088 @xref{Reverse Execution}, for more information.
34091 @xref{Stop Reply Packets}, for the reply specifications.
34093 @cindex @samp{bs} packet
34096 Backward single step. Execute one instruction in reverse. No parameter.
34097 @xref{Reverse Execution}, for more information.
34100 @xref{Stop Reply Packets}, for the reply specifications.
34102 @item c @r{[}@var{addr}@r{]}
34103 @cindex @samp{c} packet
34104 Continue. @var{addr} is address to resume. If @var{addr} is omitted,
34105 resume at current address.
34107 This packet is deprecated for multi-threading support. @xref{vCont
34111 @xref{Stop Reply Packets}, for the reply specifications.
34113 @item C @var{sig}@r{[};@var{addr}@r{]}
34114 @cindex @samp{C} packet
34115 Continue with signal @var{sig} (hex signal number). If
34116 @samp{;@var{addr}} is omitted, resume at same address.
34118 This packet is deprecated for multi-threading support. @xref{vCont
34122 @xref{Stop Reply Packets}, for the reply specifications.
34125 @cindex @samp{d} packet
34128 Don't use this packet; instead, define a general set packet
34129 (@pxref{General Query Packets}).
34133 @cindex @samp{D} packet
34134 The first form of the packet is used to detach @value{GDBN} from the
34135 remote system. It is sent to the remote target
34136 before @value{GDBN} disconnects via the @code{detach} command.
34138 The second form, including a process ID, is used when multiprocess
34139 protocol extensions are enabled (@pxref{multiprocess extensions}), to
34140 detach only a specific process. The @var{pid} is specified as a
34141 big-endian hex string.
34151 @item F @var{RC},@var{EE},@var{CF};@var{XX}
34152 @cindex @samp{F} packet
34153 A reply from @value{GDBN} to an @samp{F} packet sent by the target.
34154 This is part of the File-I/O protocol extension. @xref{File-I/O
34155 Remote Protocol Extension}, for the specification.
34158 @anchor{read registers packet}
34159 @cindex @samp{g} packet
34160 Read general registers.
34164 @item @var{XX@dots{}}
34165 Each byte of register data is described by two hex digits. The bytes
34166 with the register are transmitted in target byte order. The size of
34167 each register and their position within the @samp{g} packet are
34168 determined by the @value{GDBN} internal gdbarch functions
34169 @code{DEPRECATED_REGISTER_RAW_SIZE} and @code{gdbarch_register_name}. The
34170 specification of several standard @samp{g} packets is specified below.
34172 When reading registers from a trace frame (@pxref{Analyze Collected
34173 Data,,Using the Collected Data}), the stub may also return a string of
34174 literal @samp{x}'s in place of the register data digits, to indicate
34175 that the corresponding register has not been collected, thus its value
34176 is unavailable. For example, for an architecture with 4 registers of
34177 4 bytes each, the following reply indicates to @value{GDBN} that
34178 registers 0 and 2 have not been collected, while registers 1 and 3
34179 have been collected, and both have zero value:
34183 <- @code{xxxxxxxx00000000xxxxxxxx00000000}
34190 @item G @var{XX@dots{}}
34191 @cindex @samp{G} packet
34192 Write general registers. @xref{read registers packet}, for a
34193 description of the @var{XX@dots{}} data.
34203 @item H @var{op} @var{thread-id}
34204 @cindex @samp{H} packet
34205 Set thread for subsequent operations (@samp{m}, @samp{M}, @samp{g},
34206 @samp{G}, et.al.). @var{op} depends on the operation to be performed:
34207 it should be @samp{c} for step and continue operations (note that this
34208 is deprecated, supporting the @samp{vCont} command is a better
34209 option), @samp{g} for other operations. The thread designator
34210 @var{thread-id} has the format and interpretation described in
34211 @ref{thread-id syntax}.
34222 @c 'H': How restrictive (or permissive) is the thread model. If a
34223 @c thread is selected and stopped, are other threads allowed
34224 @c to continue to execute? As I mentioned above, I think the
34225 @c semantics of each command when a thread is selected must be
34226 @c described. For example:
34228 @c 'g': If the stub supports threads and a specific thread is
34229 @c selected, returns the register block from that thread;
34230 @c otherwise returns current registers.
34232 @c 'G' If the stub supports threads and a specific thread is
34233 @c selected, sets the registers of the register block of
34234 @c that thread; otherwise sets current registers.
34236 @item i @r{[}@var{addr}@r{[},@var{nnn}@r{]]}
34237 @anchor{cycle step packet}
34238 @cindex @samp{i} packet
34239 Step the remote target by a single clock cycle. If @samp{,@var{nnn}} is
34240 present, cycle step @var{nnn} cycles. If @var{addr} is present, cycle
34241 step starting at that address.
34244 @cindex @samp{I} packet
34245 Signal, then cycle step. @xref{step with signal packet}. @xref{cycle
34249 @cindex @samp{k} packet
34252 FIXME: @emph{There is no description of how to operate when a specific
34253 thread context has been selected (i.e.@: does 'k' kill only that
34256 @item m @var{addr},@var{length}
34257 @cindex @samp{m} packet
34258 Read @var{length} bytes of memory starting at address @var{addr}.
34259 Note that @var{addr} may not be aligned to any particular boundary.
34261 The stub need not use any particular size or alignment when gathering
34262 data from memory for the response; even if @var{addr} is word-aligned
34263 and @var{length} is a multiple of the word size, the stub is free to
34264 use byte accesses, or not. For this reason, this packet may not be
34265 suitable for accessing memory-mapped I/O devices.
34266 @cindex alignment of remote memory accesses
34267 @cindex size of remote memory accesses
34268 @cindex memory, alignment and size of remote accesses
34272 @item @var{XX@dots{}}
34273 Memory contents; each byte is transmitted as a two-digit hexadecimal
34274 number. The reply may contain fewer bytes than requested if the
34275 server was able to read only part of the region of memory.
34280 @item M @var{addr},@var{length}:@var{XX@dots{}}
34281 @cindex @samp{M} packet
34282 Write @var{length} bytes of memory starting at address @var{addr}.
34283 @var{XX@dots{}} is the data; each byte is transmitted as a two-digit
34284 hexadecimal number.
34291 for an error (this includes the case where only part of the data was
34296 @cindex @samp{p} packet
34297 Read the value of register @var{n}; @var{n} is in hex.
34298 @xref{read registers packet}, for a description of how the returned
34299 register value is encoded.
34303 @item @var{XX@dots{}}
34304 the register's value
34308 Indicating an unrecognized @var{query}.
34311 @item P @var{n@dots{}}=@var{r@dots{}}
34312 @anchor{write register packet}
34313 @cindex @samp{P} packet
34314 Write register @var{n@dots{}} with value @var{r@dots{}}. The register
34315 number @var{n} is in hexadecimal, and @var{r@dots{}} contains two hex
34316 digits for each byte in the register (target byte order).
34326 @item q @var{name} @var{params}@dots{}
34327 @itemx Q @var{name} @var{params}@dots{}
34328 @cindex @samp{q} packet
34329 @cindex @samp{Q} packet
34330 General query (@samp{q}) and set (@samp{Q}). These packets are
34331 described fully in @ref{General Query Packets}.
34334 @cindex @samp{r} packet
34335 Reset the entire system.
34337 Don't use this packet; use the @samp{R} packet instead.
34340 @cindex @samp{R} packet
34341 Restart the program being debugged. @var{XX}, while needed, is ignored.
34342 This packet is only available in extended mode (@pxref{extended mode}).
34344 The @samp{R} packet has no reply.
34346 @item s @r{[}@var{addr}@r{]}
34347 @cindex @samp{s} packet
34348 Single step. @var{addr} is the address at which to resume. If
34349 @var{addr} is omitted, resume at same address.
34351 This packet is deprecated for multi-threading support. @xref{vCont
34355 @xref{Stop Reply Packets}, for the reply specifications.
34357 @item S @var{sig}@r{[};@var{addr}@r{]}
34358 @anchor{step with signal packet}
34359 @cindex @samp{S} packet
34360 Step with signal. This is analogous to the @samp{C} packet, but
34361 requests a single-step, rather than a normal resumption of execution.
34363 This packet is deprecated for multi-threading support. @xref{vCont
34367 @xref{Stop Reply Packets}, for the reply specifications.
34369 @item t @var{addr}:@var{PP},@var{MM}
34370 @cindex @samp{t} packet
34371 Search backwards starting at address @var{addr} for a match with pattern
34372 @var{PP} and mask @var{MM}. @var{PP} and @var{MM} are 4 bytes.
34373 @var{addr} must be at least 3 digits.
34375 @item T @var{thread-id}
34376 @cindex @samp{T} packet
34377 Find out if the thread @var{thread-id} is alive. @xref{thread-id syntax}.
34382 thread is still alive
34388 Packets starting with @samp{v} are identified by a multi-letter name,
34389 up to the first @samp{;} or @samp{?} (or the end of the packet).
34391 @item vAttach;@var{pid}
34392 @cindex @samp{vAttach} packet
34393 Attach to a new process with the specified process ID @var{pid}.
34394 The process ID is a
34395 hexadecimal integer identifying the process. In all-stop mode, all
34396 threads in the attached process are stopped; in non-stop mode, it may be
34397 attached without being stopped if that is supported by the target.
34399 @c In non-stop mode, on a successful vAttach, the stub should set the
34400 @c current thread to a thread of the newly-attached process. After
34401 @c attaching, GDB queries for the attached process's thread ID with qC.
34402 @c Also note that, from a user perspective, whether or not the
34403 @c target is stopped on attach in non-stop mode depends on whether you
34404 @c use the foreground or background version of the attach command, not
34405 @c on what vAttach does; GDB does the right thing with respect to either
34406 @c stopping or restarting threads.
34408 This packet is only available in extended mode (@pxref{extended mode}).
34414 @item @r{Any stop packet}
34415 for success in all-stop mode (@pxref{Stop Reply Packets})
34417 for success in non-stop mode (@pxref{Remote Non-Stop})
34420 @item vCont@r{[};@var{action}@r{[}:@var{thread-id}@r{]]}@dots{}
34421 @cindex @samp{vCont} packet
34422 @anchor{vCont packet}
34423 Resume the inferior, specifying different actions for each thread.
34424 If an action is specified with no @var{thread-id}, then it is applied to any
34425 threads that don't have a specific action specified; if no default action is
34426 specified then other threads should remain stopped in all-stop mode and
34427 in their current state in non-stop mode.
34428 Specifying multiple
34429 default actions is an error; specifying no actions is also an error.
34430 Thread IDs are specified using the syntax described in @ref{thread-id syntax}.
34432 Currently supported actions are:
34438 Continue with signal @var{sig}. The signal @var{sig} should be two hex digits.
34442 Step with signal @var{sig}. The signal @var{sig} should be two hex digits.
34447 The optional argument @var{addr} normally associated with the
34448 @samp{c}, @samp{C}, @samp{s}, and @samp{S} packets is
34449 not supported in @samp{vCont}.
34451 The @samp{t} action is only relevant in non-stop mode
34452 (@pxref{Remote Non-Stop}) and may be ignored by the stub otherwise.
34453 A stop reply should be generated for any affected thread not already stopped.
34454 When a thread is stopped by means of a @samp{t} action,
34455 the corresponding stop reply should indicate that the thread has stopped with
34456 signal @samp{0}, regardless of whether the target uses some other signal
34457 as an implementation detail.
34459 The stub must support @samp{vCont} if it reports support for
34460 multiprocess extensions (@pxref{multiprocess extensions}). Note that in
34461 this case @samp{vCont} actions can be specified to apply to all threads
34462 in a process by using the @samp{p@var{pid}.-1} form of the
34466 @xref{Stop Reply Packets}, for the reply specifications.
34469 @cindex @samp{vCont?} packet
34470 Request a list of actions supported by the @samp{vCont} packet.
34474 @item vCont@r{[};@var{action}@dots{}@r{]}
34475 The @samp{vCont} packet is supported. Each @var{action} is a supported
34476 command in the @samp{vCont} packet.
34478 The @samp{vCont} packet is not supported.
34481 @item vFile:@var{operation}:@var{parameter}@dots{}
34482 @cindex @samp{vFile} packet
34483 Perform a file operation on the target system. For details,
34484 see @ref{Host I/O Packets}.
34486 @item vFlashErase:@var{addr},@var{length}
34487 @cindex @samp{vFlashErase} packet
34488 Direct the stub to erase @var{length} bytes of flash starting at
34489 @var{addr}. The region may enclose any number of flash blocks, but
34490 its start and end must fall on block boundaries, as indicated by the
34491 flash block size appearing in the memory map (@pxref{Memory Map
34492 Format}). @value{GDBN} groups flash memory programming operations
34493 together, and sends a @samp{vFlashDone} request after each group; the
34494 stub is allowed to delay erase operation until the @samp{vFlashDone}
34495 packet is received.
34505 @item vFlashWrite:@var{addr}:@var{XX@dots{}}
34506 @cindex @samp{vFlashWrite} packet
34507 Direct the stub to write data to flash address @var{addr}. The data
34508 is passed in binary form using the same encoding as for the @samp{X}
34509 packet (@pxref{Binary Data}). The memory ranges specified by
34510 @samp{vFlashWrite} packets preceding a @samp{vFlashDone} packet must
34511 not overlap, and must appear in order of increasing addresses
34512 (although @samp{vFlashErase} packets for higher addresses may already
34513 have been received; the ordering is guaranteed only between
34514 @samp{vFlashWrite} packets). If a packet writes to an address that was
34515 neither erased by a preceding @samp{vFlashErase} packet nor by some other
34516 target-specific method, the results are unpredictable.
34524 for vFlashWrite addressing non-flash memory
34530 @cindex @samp{vFlashDone} packet
34531 Indicate to the stub that flash programming operation is finished.
34532 The stub is permitted to delay or batch the effects of a group of
34533 @samp{vFlashErase} and @samp{vFlashWrite} packets until a
34534 @samp{vFlashDone} packet is received. The contents of the affected
34535 regions of flash memory are unpredictable until the @samp{vFlashDone}
34536 request is completed.
34538 @item vKill;@var{pid}
34539 @cindex @samp{vKill} packet
34540 Kill the process with the specified process ID. @var{pid} is a
34541 hexadecimal integer identifying the process. This packet is used in
34542 preference to @samp{k} when multiprocess protocol extensions are
34543 supported; see @ref{multiprocess extensions}.
34553 @item vRun;@var{filename}@r{[};@var{argument}@r{]}@dots{}
34554 @cindex @samp{vRun} packet
34555 Run the program @var{filename}, passing it each @var{argument} on its
34556 command line. The file and arguments are hex-encoded strings. If
34557 @var{filename} is an empty string, the stub may use a default program
34558 (e.g.@: the last program run). The program is created in the stopped
34561 @c FIXME: What about non-stop mode?
34563 This packet is only available in extended mode (@pxref{extended mode}).
34569 @item @r{Any stop packet}
34570 for success (@pxref{Stop Reply Packets})
34574 @anchor{vStopped packet}
34575 @cindex @samp{vStopped} packet
34577 In non-stop mode (@pxref{Remote Non-Stop}), acknowledge a previous stop
34578 reply and prompt for the stub to report another one.
34582 @item @r{Any stop packet}
34583 if there is another unreported stop event (@pxref{Stop Reply Packets})
34585 if there are no unreported stop events
34588 @item X @var{addr},@var{length}:@var{XX@dots{}}
34590 @cindex @samp{X} packet
34591 Write data to memory, where the data is transmitted in binary.
34592 @var{addr} is address, @var{length} is number of bytes,
34593 @samp{@var{XX}@dots{}} is binary data (@pxref{Binary Data}).
34603 @item z @var{type},@var{addr},@var{kind}
34604 @itemx Z @var{type},@var{addr},@var{kind}
34605 @anchor{insert breakpoint or watchpoint packet}
34606 @cindex @samp{z} packet
34607 @cindex @samp{Z} packets
34608 Insert (@samp{Z}) or remove (@samp{z}) a @var{type} breakpoint or
34609 watchpoint starting at address @var{address} of kind @var{kind}.
34611 Each breakpoint and watchpoint packet @var{type} is documented
34614 @emph{Implementation notes: A remote target shall return an empty string
34615 for an unrecognized breakpoint or watchpoint packet @var{type}. A
34616 remote target shall support either both or neither of a given
34617 @samp{Z@var{type}@dots{}} and @samp{z@var{type}@dots{}} packet pair. To
34618 avoid potential problems with duplicate packets, the operations should
34619 be implemented in an idempotent way.}
34621 @item z0,@var{addr},@var{kind}
34622 @itemx Z0,@var{addr},@var{kind}@r{[};@var{cond_list}@dots{}@r{]}
34623 @cindex @samp{z0} packet
34624 @cindex @samp{Z0} packet
34625 Insert (@samp{Z0}) or remove (@samp{z0}) a memory breakpoint at address
34626 @var{addr} of type @var{kind}.
34628 A memory breakpoint is implemented by replacing the instruction at
34629 @var{addr} with a software breakpoint or trap instruction. The
34630 @var{kind} is target-specific and typically indicates the size of
34631 the breakpoint in bytes that should be inserted. E.g., the @sc{arm}
34632 and @sc{mips} can insert either a 2 or 4 byte breakpoint. Some
34633 architectures have additional meanings for @var{kind};
34634 @var{cond_list} is an optional list of conditional expressions in bytecode
34635 form that should be evaluated on the target's side. These are the
34636 conditions that should be taken into consideration when deciding if
34637 the breakpoint trigger should be reported back to @var{GDBN}.
34639 The @var{cond_list} parameter is comprised of a series of expressions,
34640 concatenated without separators. Each expression has the following form:
34644 @item X @var{len},@var{expr}
34645 @var{len} is the length of the bytecode expression and @var{expr} is the
34646 actual conditional expression in bytecode form.
34650 see @ref{Architecture-Specific Protocol Details}.
34652 @emph{Implementation note: It is possible for a target to copy or move
34653 code that contains memory breakpoints (e.g., when implementing
34654 overlays). The behavior of this packet, in the presence of such a
34655 target, is not defined.}
34667 @item z1,@var{addr},@var{kind}
34668 @itemx Z1,@var{addr},@var{kind}@r{[};@var{cond_list}@dots{}@r{]}
34669 @cindex @samp{z1} packet
34670 @cindex @samp{Z1} packet
34671 Insert (@samp{Z1}) or remove (@samp{z1}) a hardware breakpoint at
34672 address @var{addr}.
34674 A hardware breakpoint is implemented using a mechanism that is not
34675 dependant on being able to modify the target's memory. @var{kind}
34676 and @var{cond_list} have the same meaning as in @samp{Z0} packets.
34678 @emph{Implementation note: A hardware breakpoint is not affected by code
34691 @item z2,@var{addr},@var{kind}
34692 @itemx Z2,@var{addr},@var{kind}
34693 @cindex @samp{z2} packet
34694 @cindex @samp{Z2} packet
34695 Insert (@samp{Z2}) or remove (@samp{z2}) a write watchpoint at @var{addr}.
34696 @var{kind} is interpreted as the number of bytes to watch.
34708 @item z3,@var{addr},@var{kind}
34709 @itemx Z3,@var{addr},@var{kind}
34710 @cindex @samp{z3} packet
34711 @cindex @samp{Z3} packet
34712 Insert (@samp{Z3}) or remove (@samp{z3}) a read watchpoint at @var{addr}.
34713 @var{kind} is interpreted as the number of bytes to watch.
34725 @item z4,@var{addr},@var{kind}
34726 @itemx Z4,@var{addr},@var{kind}
34727 @cindex @samp{z4} packet
34728 @cindex @samp{Z4} packet
34729 Insert (@samp{Z4}) or remove (@samp{z4}) an access watchpoint at @var{addr}.
34730 @var{kind} is interpreted as the number of bytes to watch.
34744 @node Stop Reply Packets
34745 @section Stop Reply Packets
34746 @cindex stop reply packets
34748 The @samp{C}, @samp{c}, @samp{S}, @samp{s}, @samp{vCont},
34749 @samp{vAttach}, @samp{vRun}, @samp{vStopped}, and @samp{?} packets can
34750 receive any of the below as a reply. Except for @samp{?}
34751 and @samp{vStopped}, that reply is only returned
34752 when the target halts. In the below the exact meaning of @dfn{signal
34753 number} is defined by the header @file{include/gdb/signals.h} in the
34754 @value{GDBN} source code.
34756 As in the description of request packets, we include spaces in the
34757 reply templates for clarity; these are not part of the reply packet's
34758 syntax. No @value{GDBN} stop reply packet uses spaces to separate its
34764 The program received signal number @var{AA} (a two-digit hexadecimal
34765 number). This is equivalent to a @samp{T} response with no
34766 @var{n}:@var{r} pairs.
34768 @item T @var{AA} @var{n1}:@var{r1};@var{n2}:@var{r2};@dots{}
34769 @cindex @samp{T} packet reply
34770 The program received signal number @var{AA} (a two-digit hexadecimal
34771 number). This is equivalent to an @samp{S} response, except that the
34772 @samp{@var{n}:@var{r}} pairs can carry values of important registers
34773 and other information directly in the stop reply packet, reducing
34774 round-trip latency. Single-step and breakpoint traps are reported
34775 this way. Each @samp{@var{n}:@var{r}} pair is interpreted as follows:
34779 If @var{n} is a hexadecimal number, it is a register number, and the
34780 corresponding @var{r} gives that register's value. @var{r} is a
34781 series of bytes in target byte order, with each byte given by a
34782 two-digit hex number.
34785 If @var{n} is @samp{thread}, then @var{r} is the @var{thread-id} of
34786 the stopped thread, as specified in @ref{thread-id syntax}.
34789 If @var{n} is @samp{core}, then @var{r} is the hexadecimal number of
34790 the core on which the stop event was detected.
34793 If @var{n} is a recognized @dfn{stop reason}, it describes a more
34794 specific event that stopped the target. The currently defined stop
34795 reasons are listed below. @var{aa} should be @samp{05}, the trap
34796 signal. At most one stop reason should be present.
34799 Otherwise, @value{GDBN} should ignore this @samp{@var{n}:@var{r}} pair
34800 and go on to the next; this allows us to extend the protocol in the
34804 The currently defined stop reasons are:
34810 The packet indicates a watchpoint hit, and @var{r} is the data address, in
34813 @cindex shared library events, remote reply
34815 The packet indicates that the loaded libraries have changed.
34816 @value{GDBN} should use @samp{qXfer:libraries:read} to fetch a new
34817 list of loaded libraries. @var{r} is ignored.
34819 @cindex replay log events, remote reply
34821 The packet indicates that the target cannot continue replaying
34822 logged execution events, because it has reached the end (or the
34823 beginning when executing backward) of the log. The value of @var{r}
34824 will be either @samp{begin} or @samp{end}. @xref{Reverse Execution},
34825 for more information.
34829 @itemx W @var{AA} ; process:@var{pid}
34830 The process exited, and @var{AA} is the exit status. This is only
34831 applicable to certain targets.
34833 The second form of the response, including the process ID of the exited
34834 process, can be used only when @value{GDBN} has reported support for
34835 multiprocess protocol extensions; see @ref{multiprocess extensions}.
34836 The @var{pid} is formatted as a big-endian hex string.
34839 @itemx X @var{AA} ; process:@var{pid}
34840 The process terminated with signal @var{AA}.
34842 The second form of the response, including the process ID of the
34843 terminated process, can be used only when @value{GDBN} has reported
34844 support for multiprocess protocol extensions; see @ref{multiprocess
34845 extensions}. The @var{pid} is formatted as a big-endian hex string.
34847 @item O @var{XX}@dots{}
34848 @samp{@var{XX}@dots{}} is hex encoding of @sc{ascii} data, to be
34849 written as the program's console output. This can happen at any time
34850 while the program is running and the debugger should continue to wait
34851 for @samp{W}, @samp{T}, etc. This reply is not permitted in non-stop mode.
34853 @item F @var{call-id},@var{parameter}@dots{}
34854 @var{call-id} is the identifier which says which host system call should
34855 be called. This is just the name of the function. Translation into the
34856 correct system call is only applicable as it's defined in @value{GDBN}.
34857 @xref{File-I/O Remote Protocol Extension}, for a list of implemented
34860 @samp{@var{parameter}@dots{}} is a list of parameters as defined for
34861 this very system call.
34863 The target replies with this packet when it expects @value{GDBN} to
34864 call a host system call on behalf of the target. @value{GDBN} replies
34865 with an appropriate @samp{F} packet and keeps up waiting for the next
34866 reply packet from the target. The latest @samp{C}, @samp{c}, @samp{S}
34867 or @samp{s} action is expected to be continued. @xref{File-I/O Remote
34868 Protocol Extension}, for more details.
34872 @node General Query Packets
34873 @section General Query Packets
34874 @cindex remote query requests
34876 Packets starting with @samp{q} are @dfn{general query packets};
34877 packets starting with @samp{Q} are @dfn{general set packets}. General
34878 query and set packets are a semi-unified form for retrieving and
34879 sending information to and from the stub.
34881 The initial letter of a query or set packet is followed by a name
34882 indicating what sort of thing the packet applies to. For example,
34883 @value{GDBN} may use a @samp{qSymbol} packet to exchange symbol
34884 definitions with the stub. These packet names follow some
34889 The name must not contain commas, colons or semicolons.
34891 Most @value{GDBN} query and set packets have a leading upper case
34894 The names of custom vendor packets should use a company prefix, in
34895 lower case, followed by a period. For example, packets designed at
34896 the Acme Corporation might begin with @samp{qacme.foo} (for querying
34897 foos) or @samp{Qacme.bar} (for setting bars).
34900 The name of a query or set packet should be separated from any
34901 parameters by a @samp{:}; the parameters themselves should be
34902 separated by @samp{,} or @samp{;}. Stubs must be careful to match the
34903 full packet name, and check for a separator or the end of the packet,
34904 in case two packet names share a common prefix. New packets should not begin
34905 with @samp{qC}, @samp{qP}, or @samp{qL}@footnote{The @samp{qP} and @samp{qL}
34906 packets predate these conventions, and have arguments without any terminator
34907 for the packet name; we suspect they are in widespread use in places that
34908 are difficult to upgrade. The @samp{qC} packet has no arguments, but some
34909 existing stubs (e.g.@: RedBoot) are known to not check for the end of the
34912 Like the descriptions of the other packets, each description here
34913 has a template showing the packet's overall syntax, followed by an
34914 explanation of the packet's meaning. We include spaces in some of the
34915 templates for clarity; these are not part of the packet's syntax. No
34916 @value{GDBN} packet uses spaces to separate its components.
34918 Here are the currently defined query and set packets:
34924 Turn on or off the agent as a helper to perform some debugging operations
34925 delegated from @value{GDBN} (@pxref{Control Agent}).
34927 @item QAllow:@var{op}:@var{val}@dots{}
34928 @cindex @samp{QAllow} packet
34929 Specify which operations @value{GDBN} expects to request of the
34930 target, as a semicolon-separated list of operation name and value
34931 pairs. Possible values for @var{op} include @samp{WriteReg},
34932 @samp{WriteMem}, @samp{InsertBreak}, @samp{InsertTrace},
34933 @samp{InsertFastTrace}, and @samp{Stop}. @var{val} is either 0,
34934 indicating that @value{GDBN} will not request the operation, or 1,
34935 indicating that it may. (The target can then use this to set up its
34936 own internals optimally, for instance if the debugger never expects to
34937 insert breakpoints, it may not need to install its own trap handler.)
34940 @cindex current thread, remote request
34941 @cindex @samp{qC} packet
34942 Return the current thread ID.
34946 @item QC @var{thread-id}
34947 Where @var{thread-id} is a thread ID as documented in
34948 @ref{thread-id syntax}.
34949 @item @r{(anything else)}
34950 Any other reply implies the old thread ID.
34953 @item qCRC:@var{addr},@var{length}
34954 @cindex CRC of memory block, remote request
34955 @cindex @samp{qCRC} packet
34956 Compute the CRC checksum of a block of memory using CRC-32 defined in
34957 IEEE 802.3. The CRC is computed byte at a time, taking the most
34958 significant bit of each byte first. The initial pattern code
34959 @code{0xffffffff} is used to ensure leading zeros affect the CRC.
34961 @emph{Note:} This is the same CRC used in validating separate debug
34962 files (@pxref{Separate Debug Files, , Debugging Information in Separate
34963 Files}). However the algorithm is slightly different. When validating
34964 separate debug files, the CRC is computed taking the @emph{least}
34965 significant bit of each byte first, and the final result is inverted to
34966 detect trailing zeros.
34971 An error (such as memory fault)
34972 @item C @var{crc32}
34973 The specified memory region's checksum is @var{crc32}.
34976 @item QDisableRandomization:@var{value}
34977 @cindex disable address space randomization, remote request
34978 @cindex @samp{QDisableRandomization} packet
34979 Some target operating systems will randomize the virtual address space
34980 of the inferior process as a security feature, but provide a feature
34981 to disable such randomization, e.g.@: to allow for a more deterministic
34982 debugging experience. On such systems, this packet with a @var{value}
34983 of 1 directs the target to disable address space randomization for
34984 processes subsequently started via @samp{vRun} packets, while a packet
34985 with a @var{value} of 0 tells the target to enable address space
34988 This packet is only available in extended mode (@pxref{extended mode}).
34993 The request succeeded.
34996 An error occurred. @var{nn} are hex digits.
34999 An empty reply indicates that @samp{QDisableRandomization} is not supported
35003 This packet is not probed by default; the remote stub must request it,
35004 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
35005 This should only be done on targets that actually support disabling
35006 address space randomization.
35009 @itemx qsThreadInfo
35010 @cindex list active threads, remote request
35011 @cindex @samp{qfThreadInfo} packet
35012 @cindex @samp{qsThreadInfo} packet
35013 Obtain a list of all active thread IDs from the target (OS). Since there
35014 may be too many active threads to fit into one reply packet, this query
35015 works iteratively: it may require more than one query/reply sequence to
35016 obtain the entire list of threads. The first query of the sequence will
35017 be the @samp{qfThreadInfo} query; subsequent queries in the
35018 sequence will be the @samp{qsThreadInfo} query.
35020 NOTE: This packet replaces the @samp{qL} query (see below).
35024 @item m @var{thread-id}
35026 @item m @var{thread-id},@var{thread-id}@dots{}
35027 a comma-separated list of thread IDs
35029 (lower case letter @samp{L}) denotes end of list.
35032 In response to each query, the target will reply with a list of one or
35033 more thread IDs, separated by commas.
35034 @value{GDBN} will respond to each reply with a request for more thread
35035 ids (using the @samp{qs} form of the query), until the target responds
35036 with @samp{l} (lower-case ell, for @dfn{last}).
35037 Refer to @ref{thread-id syntax}, for the format of the @var{thread-id}
35040 @item qGetTLSAddr:@var{thread-id},@var{offset},@var{lm}
35041 @cindex get thread-local storage address, remote request
35042 @cindex @samp{qGetTLSAddr} packet
35043 Fetch the address associated with thread local storage specified
35044 by @var{thread-id}, @var{offset}, and @var{lm}.
35046 @var{thread-id} is the thread ID associated with the
35047 thread for which to fetch the TLS address. @xref{thread-id syntax}.
35049 @var{offset} is the (big endian, hex encoded) offset associated with the
35050 thread local variable. (This offset is obtained from the debug
35051 information associated with the variable.)
35053 @var{lm} is the (big endian, hex encoded) OS/ABI-specific encoding of the
35054 load module associated with the thread local storage. For example,
35055 a @sc{gnu}/Linux system will pass the link map address of the shared
35056 object associated with the thread local storage under consideration.
35057 Other operating environments may choose to represent the load module
35058 differently, so the precise meaning of this parameter will vary.
35062 @item @var{XX}@dots{}
35063 Hex encoded (big endian) bytes representing the address of the thread
35064 local storage requested.
35067 An error occurred. @var{nn} are hex digits.
35070 An empty reply indicates that @samp{qGetTLSAddr} is not supported by the stub.
35073 @item qGetTIBAddr:@var{thread-id}
35074 @cindex get thread information block address
35075 @cindex @samp{qGetTIBAddr} packet
35076 Fetch address of the Windows OS specific Thread Information Block.
35078 @var{thread-id} is the thread ID associated with the thread.
35082 @item @var{XX}@dots{}
35083 Hex encoded (big endian) bytes representing the linear address of the
35084 thread information block.
35087 An error occured. This means that either the thread was not found, or the
35088 address could not be retrieved.
35091 An empty reply indicates that @samp{qGetTIBAddr} is not supported by the stub.
35094 @item qL @var{startflag} @var{threadcount} @var{nextthread}
35095 Obtain thread information from RTOS. Where: @var{startflag} (one hex
35096 digit) is one to indicate the first query and zero to indicate a
35097 subsequent query; @var{threadcount} (two hex digits) is the maximum
35098 number of threads the response packet can contain; and @var{nextthread}
35099 (eight hex digits), for subsequent queries (@var{startflag} is zero), is
35100 returned in the response as @var{argthread}.
35102 Don't use this packet; use the @samp{qfThreadInfo} query instead (see above).
35106 @item qM @var{count} @var{done} @var{argthread} @var{thread}@dots{}
35107 Where: @var{count} (two hex digits) is the number of threads being
35108 returned; @var{done} (one hex digit) is zero to indicate more threads
35109 and one indicates no further threads; @var{argthreadid} (eight hex
35110 digits) is @var{nextthread} from the request packet; @var{thread}@dots{}
35111 is a sequence of thread IDs from the target. @var{threadid} (eight hex
35112 digits). See @code{remote.c:parse_threadlist_response()}.
35116 @cindex section offsets, remote request
35117 @cindex @samp{qOffsets} packet
35118 Get section offsets that the target used when relocating the downloaded
35123 @item Text=@var{xxx};Data=@var{yyy}@r{[};Bss=@var{zzz}@r{]}
35124 Relocate the @code{Text} section by @var{xxx} from its original address.
35125 Relocate the @code{Data} section by @var{yyy} from its original address.
35126 If the object file format provides segment information (e.g.@: @sc{elf}
35127 @samp{PT_LOAD} program headers), @value{GDBN} will relocate entire
35128 segments by the supplied offsets.
35130 @emph{Note: while a @code{Bss} offset may be included in the response,
35131 @value{GDBN} ignores this and instead applies the @code{Data} offset
35132 to the @code{Bss} section.}
35134 @item TextSeg=@var{xxx}@r{[};DataSeg=@var{yyy}@r{]}
35135 Relocate the first segment of the object file, which conventionally
35136 contains program code, to a starting address of @var{xxx}. If
35137 @samp{DataSeg} is specified, relocate the second segment, which
35138 conventionally contains modifiable data, to a starting address of
35139 @var{yyy}. @value{GDBN} will report an error if the object file
35140 does not contain segment information, or does not contain at least
35141 as many segments as mentioned in the reply. Extra segments are
35142 kept at fixed offsets relative to the last relocated segment.
35145 @item qP @var{mode} @var{thread-id}
35146 @cindex thread information, remote request
35147 @cindex @samp{qP} packet
35148 Returns information on @var{thread-id}. Where: @var{mode} is a hex
35149 encoded 32 bit mode; @var{thread-id} is a thread ID
35150 (@pxref{thread-id syntax}).
35152 Don't use this packet; use the @samp{qThreadExtraInfo} query instead
35155 Reply: see @code{remote.c:remote_unpack_thread_info_response()}.
35159 @cindex non-stop mode, remote request
35160 @cindex @samp{QNonStop} packet
35162 Enter non-stop (@samp{QNonStop:1}) or all-stop (@samp{QNonStop:0}) mode.
35163 @xref{Remote Non-Stop}, for more information.
35168 The request succeeded.
35171 An error occurred. @var{nn} are hex digits.
35174 An empty reply indicates that @samp{QNonStop} is not supported by
35178 This packet is not probed by default; the remote stub must request it,
35179 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
35180 Use of this packet is controlled by the @code{set non-stop} command;
35181 @pxref{Non-Stop Mode}.
35183 @item QPassSignals: @var{signal} @r{[};@var{signal}@r{]}@dots{}
35184 @cindex pass signals to inferior, remote request
35185 @cindex @samp{QPassSignals} packet
35186 @anchor{QPassSignals}
35187 Each listed @var{signal} should be passed directly to the inferior process.
35188 Signals are numbered identically to continue packets and stop replies
35189 (@pxref{Stop Reply Packets}). Each @var{signal} list item should be
35190 strictly greater than the previous item. These signals do not need to stop
35191 the inferior, or be reported to @value{GDBN}. All other signals should be
35192 reported to @value{GDBN}. Multiple @samp{QPassSignals} packets do not
35193 combine; any earlier @samp{QPassSignals} list is completely replaced by the
35194 new list. This packet improves performance when using @samp{handle
35195 @var{signal} nostop noprint pass}.
35200 The request succeeded.
35203 An error occurred. @var{nn} are hex digits.
35206 An empty reply indicates that @samp{QPassSignals} is not supported by
35210 Use of this packet is controlled by the @code{set remote pass-signals}
35211 command (@pxref{Remote Configuration, set remote pass-signals}).
35212 This packet is not probed by default; the remote stub must request it,
35213 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
35215 @item QProgramSignals: @var{signal} @r{[};@var{signal}@r{]}@dots{}
35216 @cindex signals the inferior may see, remote request
35217 @cindex @samp{QProgramSignals} packet
35218 @anchor{QProgramSignals}
35219 Each listed @var{signal} may be delivered to the inferior process.
35220 Others should be silently discarded.
35222 In some cases, the remote stub may need to decide whether to deliver a
35223 signal to the program or not without @value{GDBN} involvement. One
35224 example of that is while detaching --- the program's threads may have
35225 stopped for signals that haven't yet had a chance of being reported to
35226 @value{GDBN}, and so the remote stub can use the signal list specified
35227 by this packet to know whether to deliver or ignore those pending
35230 This does not influence whether to deliver a signal as requested by a
35231 resumption packet (@pxref{vCont packet}).
35233 Signals are numbered identically to continue packets and stop replies
35234 (@pxref{Stop Reply Packets}). Each @var{signal} list item should be
35235 strictly greater than the previous item. Multiple
35236 @samp{QProgramSignals} packets do not combine; any earlier
35237 @samp{QProgramSignals} list is completely replaced by the new list.
35242 The request succeeded.
35245 An error occurred. @var{nn} are hex digits.
35248 An empty reply indicates that @samp{QProgramSignals} is not supported
35252 Use of this packet is controlled by the @code{set remote program-signals}
35253 command (@pxref{Remote Configuration, set remote program-signals}).
35254 This packet is not probed by default; the remote stub must request it,
35255 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
35257 @item qRcmd,@var{command}
35258 @cindex execute remote command, remote request
35259 @cindex @samp{qRcmd} packet
35260 @var{command} (hex encoded) is passed to the local interpreter for
35261 execution. Invalid commands should be reported using the output
35262 string. Before the final result packet, the target may also respond
35263 with a number of intermediate @samp{O@var{output}} console output
35264 packets. @emph{Implementors should note that providing access to a
35265 stubs's interpreter may have security implications}.
35270 A command response with no output.
35272 A command response with the hex encoded output string @var{OUTPUT}.
35274 Indicate a badly formed request.
35276 An empty reply indicates that @samp{qRcmd} is not recognized.
35279 (Note that the @code{qRcmd} packet's name is separated from the
35280 command by a @samp{,}, not a @samp{:}, contrary to the naming
35281 conventions above. Please don't use this packet as a model for new
35284 @item qSearch:memory:@var{address};@var{length};@var{search-pattern}
35285 @cindex searching memory, in remote debugging
35286 @cindex @samp{qSearch:memory} packet
35287 @anchor{qSearch memory}
35288 Search @var{length} bytes at @var{address} for @var{search-pattern}.
35289 @var{address} and @var{length} are encoded in hex.
35290 @var{search-pattern} is a sequence of bytes, hex encoded.
35295 The pattern was not found.
35297 The pattern was found at @var{address}.
35299 A badly formed request or an error was encountered while searching memory.
35301 An empty reply indicates that @samp{qSearch:memory} is not recognized.
35304 @item QStartNoAckMode
35305 @cindex @samp{QStartNoAckMode} packet
35306 @anchor{QStartNoAckMode}
35307 Request that the remote stub disable the normal @samp{+}/@samp{-}
35308 protocol acknowledgments (@pxref{Packet Acknowledgment}).
35313 The stub has switched to no-acknowledgment mode.
35314 @value{GDBN} acknowledges this reponse,
35315 but neither the stub nor @value{GDBN} shall send or expect further
35316 @samp{+}/@samp{-} acknowledgments in the current connection.
35318 An empty reply indicates that the stub does not support no-acknowledgment mode.
35321 @item qSupported @r{[}:@var{gdbfeature} @r{[};@var{gdbfeature}@r{]}@dots{} @r{]}
35322 @cindex supported packets, remote query
35323 @cindex features of the remote protocol
35324 @cindex @samp{qSupported} packet
35325 @anchor{qSupported}
35326 Tell the remote stub about features supported by @value{GDBN}, and
35327 query the stub for features it supports. This packet allows
35328 @value{GDBN} and the remote stub to take advantage of each others'
35329 features. @samp{qSupported} also consolidates multiple feature probes
35330 at startup, to improve @value{GDBN} performance---a single larger
35331 packet performs better than multiple smaller probe packets on
35332 high-latency links. Some features may enable behavior which must not
35333 be on by default, e.g.@: because it would confuse older clients or
35334 stubs. Other features may describe packets which could be
35335 automatically probed for, but are not. These features must be
35336 reported before @value{GDBN} will use them. This ``default
35337 unsupported'' behavior is not appropriate for all packets, but it
35338 helps to keep the initial connection time under control with new
35339 versions of @value{GDBN} which support increasing numbers of packets.
35343 @item @var{stubfeature} @r{[};@var{stubfeature}@r{]}@dots{}
35344 The stub supports or does not support each returned @var{stubfeature},
35345 depending on the form of each @var{stubfeature} (see below for the
35348 An empty reply indicates that @samp{qSupported} is not recognized,
35349 or that no features needed to be reported to @value{GDBN}.
35352 The allowed forms for each feature (either a @var{gdbfeature} in the
35353 @samp{qSupported} packet, or a @var{stubfeature} in the response)
35357 @item @var{name}=@var{value}
35358 The remote protocol feature @var{name} is supported, and associated
35359 with the specified @var{value}. The format of @var{value} depends
35360 on the feature, but it must not include a semicolon.
35362 The remote protocol feature @var{name} is supported, and does not
35363 need an associated value.
35365 The remote protocol feature @var{name} is not supported.
35367 The remote protocol feature @var{name} may be supported, and
35368 @value{GDBN} should auto-detect support in some other way when it is
35369 needed. This form will not be used for @var{gdbfeature} notifications,
35370 but may be used for @var{stubfeature} responses.
35373 Whenever the stub receives a @samp{qSupported} request, the
35374 supplied set of @value{GDBN} features should override any previous
35375 request. This allows @value{GDBN} to put the stub in a known
35376 state, even if the stub had previously been communicating with
35377 a different version of @value{GDBN}.
35379 The following values of @var{gdbfeature} (for the packet sent by @value{GDBN})
35384 This feature indicates whether @value{GDBN} supports multiprocess
35385 extensions to the remote protocol. @value{GDBN} does not use such
35386 extensions unless the stub also reports that it supports them by
35387 including @samp{multiprocess+} in its @samp{qSupported} reply.
35388 @xref{multiprocess extensions}, for details.
35391 This feature indicates that @value{GDBN} supports the XML target
35392 description. If the stub sees @samp{xmlRegisters=} with target
35393 specific strings separated by a comma, it will report register
35397 This feature indicates whether @value{GDBN} supports the
35398 @samp{qRelocInsn} packet (@pxref{Tracepoint Packets,,Relocate
35399 instruction reply packet}).
35402 Stubs should ignore any unknown values for
35403 @var{gdbfeature}. Any @value{GDBN} which sends a @samp{qSupported}
35404 packet supports receiving packets of unlimited length (earlier
35405 versions of @value{GDBN} may reject overly long responses). Additional values
35406 for @var{gdbfeature} may be defined in the future to let the stub take
35407 advantage of new features in @value{GDBN}, e.g.@: incompatible
35408 improvements in the remote protocol---the @samp{multiprocess} feature is
35409 an example of such a feature. The stub's reply should be independent
35410 of the @var{gdbfeature} entries sent by @value{GDBN}; first @value{GDBN}
35411 describes all the features it supports, and then the stub replies with
35412 all the features it supports.
35414 Similarly, @value{GDBN} will silently ignore unrecognized stub feature
35415 responses, as long as each response uses one of the standard forms.
35417 Some features are flags. A stub which supports a flag feature
35418 should respond with a @samp{+} form response. Other features
35419 require values, and the stub should respond with an @samp{=}
35422 Each feature has a default value, which @value{GDBN} will use if
35423 @samp{qSupported} is not available or if the feature is not mentioned
35424 in the @samp{qSupported} response. The default values are fixed; a
35425 stub is free to omit any feature responses that match the defaults.
35427 Not all features can be probed, but for those which can, the probing
35428 mechanism is useful: in some cases, a stub's internal
35429 architecture may not allow the protocol layer to know some information
35430 about the underlying target in advance. This is especially common in
35431 stubs which may be configured for multiple targets.
35433 These are the currently defined stub features and their properties:
35435 @multitable @columnfractions 0.35 0.2 0.12 0.2
35436 @c NOTE: The first row should be @headitem, but we do not yet require
35437 @c a new enough version of Texinfo (4.7) to use @headitem.
35439 @tab Value Required
35443 @item @samp{PacketSize}
35448 @item @samp{qXfer:auxv:read}
35453 @item @samp{qXfer:features:read}
35458 @item @samp{qXfer:libraries:read}
35463 @item @samp{qXfer:memory-map:read}
35468 @item @samp{qXfer:sdata:read}
35473 @item @samp{qXfer:spu:read}
35478 @item @samp{qXfer:spu:write}
35483 @item @samp{qXfer:siginfo:read}
35488 @item @samp{qXfer:siginfo:write}
35493 @item @samp{qXfer:threads:read}
35498 @item @samp{qXfer:traceframe-info:read}
35503 @item @samp{qXfer:uib:read}
35508 @item @samp{qXfer:fdpic:read}
35513 @item @samp{QNonStop}
35518 @item @samp{QPassSignals}
35523 @item @samp{QStartNoAckMode}
35528 @item @samp{multiprocess}
35533 @item @samp{ConditionalBreakpoints}
35538 @item @samp{ConditionalTracepoints}
35543 @item @samp{ReverseContinue}
35548 @item @samp{ReverseStep}
35553 @item @samp{TracepointSource}
35558 @item @samp{QAgent}
35563 @item @samp{QAllow}
35568 @item @samp{QDisableRandomization}
35573 @item @samp{EnableDisableTracepoints}
35578 @item @samp{tracenz}
35585 These are the currently defined stub features, in more detail:
35588 @cindex packet size, remote protocol
35589 @item PacketSize=@var{bytes}
35590 The remote stub can accept packets up to at least @var{bytes} in
35591 length. @value{GDBN} will send packets up to this size for bulk
35592 transfers, and will never send larger packets. This is a limit on the
35593 data characters in the packet, including the frame and checksum.
35594 There is no trailing NUL byte in a remote protocol packet; if the stub
35595 stores packets in a NUL-terminated format, it should allow an extra
35596 byte in its buffer for the NUL. If this stub feature is not supported,
35597 @value{GDBN} guesses based on the size of the @samp{g} packet response.
35599 @item qXfer:auxv:read
35600 The remote stub understands the @samp{qXfer:auxv:read} packet
35601 (@pxref{qXfer auxiliary vector read}).
35603 @item qXfer:features:read
35604 The remote stub understands the @samp{qXfer:features:read} packet
35605 (@pxref{qXfer target description read}).
35607 @item qXfer:libraries:read
35608 The remote stub understands the @samp{qXfer:libraries:read} packet
35609 (@pxref{qXfer library list read}).
35611 @item qXfer:libraries-svr4:read
35612 The remote stub understands the @samp{qXfer:libraries-svr4:read} packet
35613 (@pxref{qXfer svr4 library list read}).
35615 @item qXfer:memory-map:read
35616 The remote stub understands the @samp{qXfer:memory-map:read} packet
35617 (@pxref{qXfer memory map read}).
35619 @item qXfer:sdata:read
35620 The remote stub understands the @samp{qXfer:sdata:read} packet
35621 (@pxref{qXfer sdata read}).
35623 @item qXfer:spu:read
35624 The remote stub understands the @samp{qXfer:spu:read} packet
35625 (@pxref{qXfer spu read}).
35627 @item qXfer:spu:write
35628 The remote stub understands the @samp{qXfer:spu:write} packet
35629 (@pxref{qXfer spu write}).
35631 @item qXfer:siginfo:read
35632 The remote stub understands the @samp{qXfer:siginfo:read} packet
35633 (@pxref{qXfer siginfo read}).
35635 @item qXfer:siginfo:write
35636 The remote stub understands the @samp{qXfer:siginfo:write} packet
35637 (@pxref{qXfer siginfo write}).
35639 @item qXfer:threads:read
35640 The remote stub understands the @samp{qXfer:threads:read} packet
35641 (@pxref{qXfer threads read}).
35643 @item qXfer:traceframe-info:read
35644 The remote stub understands the @samp{qXfer:traceframe-info:read}
35645 packet (@pxref{qXfer traceframe info read}).
35647 @item qXfer:uib:read
35648 The remote stub understands the @samp{qXfer:uib:read}
35649 packet (@pxref{qXfer unwind info block}).
35651 @item qXfer:fdpic:read
35652 The remote stub understands the @samp{qXfer:fdpic:read}
35653 packet (@pxref{qXfer fdpic loadmap read}).
35656 The remote stub understands the @samp{QNonStop} packet
35657 (@pxref{QNonStop}).
35660 The remote stub understands the @samp{QPassSignals} packet
35661 (@pxref{QPassSignals}).
35663 @item QStartNoAckMode
35664 The remote stub understands the @samp{QStartNoAckMode} packet and
35665 prefers to operate in no-acknowledgment mode. @xref{Packet Acknowledgment}.
35668 @anchor{multiprocess extensions}
35669 @cindex multiprocess extensions, in remote protocol
35670 The remote stub understands the multiprocess extensions to the remote
35671 protocol syntax. The multiprocess extensions affect the syntax of
35672 thread IDs in both packets and replies (@pxref{thread-id syntax}), and
35673 add process IDs to the @samp{D} packet and @samp{W} and @samp{X}
35674 replies. Note that reporting this feature indicates support for the
35675 syntactic extensions only, not that the stub necessarily supports
35676 debugging of more than one process at a time. The stub must not use
35677 multiprocess extensions in packet replies unless @value{GDBN} has also
35678 indicated it supports them in its @samp{qSupported} request.
35680 @item qXfer:osdata:read
35681 The remote stub understands the @samp{qXfer:osdata:read} packet
35682 ((@pxref{qXfer osdata read}).
35684 @item ConditionalBreakpoints
35685 The target accepts and implements evaluation of conditional expressions
35686 defined for breakpoints. The target will only report breakpoint triggers
35687 when such conditions are true (@pxref{Conditions, ,Break Conditions}).
35689 @item ConditionalTracepoints
35690 The remote stub accepts and implements conditional expressions defined
35691 for tracepoints (@pxref{Tracepoint Conditions}).
35693 @item ReverseContinue
35694 The remote stub accepts and implements the reverse continue packet
35698 The remote stub accepts and implements the reverse step packet
35701 @item TracepointSource
35702 The remote stub understands the @samp{QTDPsrc} packet that supplies
35703 the source form of tracepoint definitions.
35706 The remote stub understands the @samp{QAgent} packet.
35709 The remote stub understands the @samp{QAllow} packet.
35711 @item QDisableRandomization
35712 The remote stub understands the @samp{QDisableRandomization} packet.
35714 @item StaticTracepoint
35715 @cindex static tracepoints, in remote protocol
35716 The remote stub supports static tracepoints.
35718 @item InstallInTrace
35719 @anchor{install tracepoint in tracing}
35720 The remote stub supports installing tracepoint in tracing.
35722 @item EnableDisableTracepoints
35723 The remote stub supports the @samp{QTEnable} (@pxref{QTEnable}) and
35724 @samp{QTDisable} (@pxref{QTDisable}) packets that allow tracepoints
35725 to be enabled and disabled while a trace experiment is running.
35728 @cindex string tracing, in remote protocol
35729 The remote stub supports the @samp{tracenz} bytecode for collecting strings.
35730 See @ref{Bytecode Descriptions} for details about the bytecode.
35735 @cindex symbol lookup, remote request
35736 @cindex @samp{qSymbol} packet
35737 Notify the target that @value{GDBN} is prepared to serve symbol lookup
35738 requests. Accept requests from the target for the values of symbols.
35743 The target does not need to look up any (more) symbols.
35744 @item qSymbol:@var{sym_name}
35745 The target requests the value of symbol @var{sym_name} (hex encoded).
35746 @value{GDBN} may provide the value by using the
35747 @samp{qSymbol:@var{sym_value}:@var{sym_name}} message, described
35751 @item qSymbol:@var{sym_value}:@var{sym_name}
35752 Set the value of @var{sym_name} to @var{sym_value}.
35754 @var{sym_name} (hex encoded) is the name of a symbol whose value the
35755 target has previously requested.
35757 @var{sym_value} (hex) is the value for symbol @var{sym_name}. If
35758 @value{GDBN} cannot supply a value for @var{sym_name}, then this field
35764 The target does not need to look up any (more) symbols.
35765 @item qSymbol:@var{sym_name}
35766 The target requests the value of a new symbol @var{sym_name} (hex
35767 encoded). @value{GDBN} will continue to supply the values of symbols
35768 (if available), until the target ceases to request them.
35773 @item QTDisconnected
35780 @itemx qTMinFTPILen
35782 @xref{Tracepoint Packets}.
35784 @item qThreadExtraInfo,@var{thread-id}
35785 @cindex thread attributes info, remote request
35786 @cindex @samp{qThreadExtraInfo} packet
35787 Obtain a printable string description of a thread's attributes from
35788 the target OS. @var{thread-id} is a thread ID;
35789 see @ref{thread-id syntax}. This
35790 string may contain anything that the target OS thinks is interesting
35791 for @value{GDBN} to tell the user about the thread. The string is
35792 displayed in @value{GDBN}'s @code{info threads} display. Some
35793 examples of possible thread extra info strings are @samp{Runnable}, or
35794 @samp{Blocked on Mutex}.
35798 @item @var{XX}@dots{}
35799 Where @samp{@var{XX}@dots{}} is a hex encoding of @sc{ascii} data,
35800 comprising the printable string containing the extra information about
35801 the thread's attributes.
35804 (Note that the @code{qThreadExtraInfo} packet's name is separated from
35805 the command by a @samp{,}, not a @samp{:}, contrary to the naming
35806 conventions above. Please don't use this packet as a model for new
35825 @xref{Tracepoint Packets}.
35827 @item qXfer:@var{object}:read:@var{annex}:@var{offset},@var{length}
35828 @cindex read special object, remote request
35829 @cindex @samp{qXfer} packet
35830 @anchor{qXfer read}
35831 Read uninterpreted bytes from the target's special data area
35832 identified by the keyword @var{object}. Request @var{length} bytes
35833 starting at @var{offset} bytes into the data. The content and
35834 encoding of @var{annex} is specific to @var{object}; it can supply
35835 additional details about what data to access.
35837 Here are the specific requests of this form defined so far. All
35838 @samp{qXfer:@var{object}:read:@dots{}} requests use the same reply
35839 formats, listed below.
35842 @item qXfer:auxv:read::@var{offset},@var{length}
35843 @anchor{qXfer auxiliary vector read}
35844 Access the target's @dfn{auxiliary vector}. @xref{OS Information,
35845 auxiliary vector}. Note @var{annex} must be empty.
35847 This packet is not probed by default; the remote stub must request it,
35848 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
35850 @item qXfer:features:read:@var{annex}:@var{offset},@var{length}
35851 @anchor{qXfer target description read}
35852 Access the @dfn{target description}. @xref{Target Descriptions}. The
35853 annex specifies which XML document to access. The main description is
35854 always loaded from the @samp{target.xml} annex.
35856 This packet is not probed by default; the remote stub must request it,
35857 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
35859 @item qXfer:libraries:read:@var{annex}:@var{offset},@var{length}
35860 @anchor{qXfer library list read}
35861 Access the target's list of loaded libraries. @xref{Library List Format}.
35862 The annex part of the generic @samp{qXfer} packet must be empty
35863 (@pxref{qXfer read}).
35865 Targets which maintain a list of libraries in the program's memory do
35866 not need to implement this packet; it is designed for platforms where
35867 the operating system manages the list of loaded libraries.
35869 This packet is not probed by default; the remote stub must request it,
35870 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
35872 @item qXfer:libraries-svr4:read:@var{annex}:@var{offset},@var{length}
35873 @anchor{qXfer svr4 library list read}
35874 Access the target's list of loaded libraries when the target is an SVR4
35875 platform. @xref{Library List Format for SVR4 Targets}. The annex part
35876 of the generic @samp{qXfer} packet must be empty (@pxref{qXfer read}).
35878 This packet is optional for better performance on SVR4 targets.
35879 @value{GDBN} uses memory read packets to read the SVR4 library list otherwise.
35881 This packet is not probed by default; the remote stub must request it,
35882 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
35884 @item qXfer:memory-map:read::@var{offset},@var{length}
35885 @anchor{qXfer memory map read}
35886 Access the target's @dfn{memory-map}. @xref{Memory Map Format}. The
35887 annex part of the generic @samp{qXfer} packet must be empty
35888 (@pxref{qXfer read}).
35890 This packet is not probed by default; the remote stub must request it,
35891 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
35893 @item qXfer:sdata:read::@var{offset},@var{length}
35894 @anchor{qXfer sdata read}
35896 Read contents of the extra collected static tracepoint marker
35897 information. The annex part of the generic @samp{qXfer} packet must
35898 be empty (@pxref{qXfer read}). @xref{Tracepoint Actions,,Tracepoint
35901 This packet is not probed by default; the remote stub must request it,
35902 by supplying an appropriate @samp{qSupported} response
35903 (@pxref{qSupported}).
35905 @item qXfer:siginfo:read::@var{offset},@var{length}
35906 @anchor{qXfer siginfo read}
35907 Read contents of the extra signal information on the target
35908 system. The annex part of the generic @samp{qXfer} packet must be
35909 empty (@pxref{qXfer read}).
35911 This packet is not probed by default; the remote stub must request it,
35912 by supplying an appropriate @samp{qSupported} response
35913 (@pxref{qSupported}).
35915 @item qXfer:spu:read:@var{annex}:@var{offset},@var{length}
35916 @anchor{qXfer spu read}
35917 Read contents of an @code{spufs} file on the target system. The
35918 annex specifies which file to read; it must be of the form
35919 @file{@var{id}/@var{name}}, where @var{id} specifies an SPU context ID
35920 in the target process, and @var{name} identifes the @code{spufs} file
35921 in that context to be accessed.
35923 This packet is not probed by default; the remote stub must request it,
35924 by supplying an appropriate @samp{qSupported} response
35925 (@pxref{qSupported}).
35927 @item qXfer:threads:read::@var{offset},@var{length}
35928 @anchor{qXfer threads read}
35929 Access the list of threads on target. @xref{Thread List Format}. The
35930 annex part of the generic @samp{qXfer} packet must be empty
35931 (@pxref{qXfer read}).
35933 This packet is not probed by default; the remote stub must request it,
35934 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
35936 @item qXfer:traceframe-info:read::@var{offset},@var{length}
35937 @anchor{qXfer traceframe info read}
35939 Return a description of the current traceframe's contents.
35940 @xref{Traceframe Info Format}. The annex part of the generic
35941 @samp{qXfer} packet must be empty (@pxref{qXfer read}).
35943 This packet is not probed by default; the remote stub must request it,
35944 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
35946 @item qXfer:uib:read:@var{pc}:@var{offset},@var{length}
35947 @anchor{qXfer unwind info block}
35949 Return the unwind information block for @var{pc}. This packet is used
35950 on OpenVMS/ia64 to ask the kernel unwind information.
35952 This packet is not probed by default.
35954 @item qXfer:fdpic:read:@var{annex}:@var{offset},@var{length}
35955 @anchor{qXfer fdpic loadmap read}
35956 Read contents of @code{loadmap}s on the target system. The
35957 annex, either @samp{exec} or @samp{interp}, specifies which @code{loadmap},
35958 executable @code{loadmap} or interpreter @code{loadmap} to read.
35960 This packet is not probed by default; the remote stub must request it,
35961 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
35963 @item qXfer:osdata:read::@var{offset},@var{length}
35964 @anchor{qXfer osdata read}
35965 Access the target's @dfn{operating system information}.
35966 @xref{Operating System Information}.
35973 Data @var{data} (@pxref{Binary Data}) has been read from the
35974 target. There may be more data at a higher address (although
35975 it is permitted to return @samp{m} even for the last valid
35976 block of data, as long as at least one byte of data was read).
35977 @var{data} may have fewer bytes than the @var{length} in the
35981 Data @var{data} (@pxref{Binary Data}) has been read from the target.
35982 There is no more data to be read. @var{data} may have fewer bytes
35983 than the @var{length} in the request.
35986 The @var{offset} in the request is at the end of the data.
35987 There is no more data to be read.
35990 The request was malformed, or @var{annex} was invalid.
35993 The offset was invalid, or there was an error encountered reading the data.
35994 @var{nn} is a hex-encoded @code{errno} value.
35997 An empty reply indicates the @var{object} string was not recognized by
35998 the stub, or that the object does not support reading.
36001 @item qXfer:@var{object}:write:@var{annex}:@var{offset}:@var{data}@dots{}
36002 @cindex write data into object, remote request
36003 @anchor{qXfer write}
36004 Write uninterpreted bytes into the target's special data area
36005 identified by the keyword @var{object}, starting at @var{offset} bytes
36006 into the data. @var{data}@dots{} is the binary-encoded data
36007 (@pxref{Binary Data}) to be written. The content and encoding of @var{annex}
36008 is specific to @var{object}; it can supply additional details about what data
36011 Here are the specific requests of this form defined so far. All
36012 @samp{qXfer:@var{object}:write:@dots{}} requests use the same reply
36013 formats, listed below.
36016 @item qXfer:siginfo:write::@var{offset}:@var{data}@dots{}
36017 @anchor{qXfer siginfo write}
36018 Write @var{data} to the extra signal information on the target system.
36019 The annex part of the generic @samp{qXfer} packet must be
36020 empty (@pxref{qXfer write}).
36022 This packet is not probed by default; the remote stub must request it,
36023 by supplying an appropriate @samp{qSupported} response
36024 (@pxref{qSupported}).
36026 @item qXfer:spu:write:@var{annex}:@var{offset}:@var{data}@dots{}
36027 @anchor{qXfer spu write}
36028 Write @var{data} to an @code{spufs} file on the target system. The
36029 annex specifies which file to write; it must be of the form
36030 @file{@var{id}/@var{name}}, where @var{id} specifies an SPU context ID
36031 in the target process, and @var{name} identifes the @code{spufs} file
36032 in that context to be accessed.
36034 This packet is not probed by default; the remote stub must request it,
36035 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
36041 @var{nn} (hex encoded) is the number of bytes written.
36042 This may be fewer bytes than supplied in the request.
36045 The request was malformed, or @var{annex} was invalid.
36048 The offset was invalid, or there was an error encountered writing the data.
36049 @var{nn} is a hex-encoded @code{errno} value.
36052 An empty reply indicates the @var{object} string was not
36053 recognized by the stub, or that the object does not support writing.
36056 @item qXfer:@var{object}:@var{operation}:@dots{}
36057 Requests of this form may be added in the future. When a stub does
36058 not recognize the @var{object} keyword, or its support for
36059 @var{object} does not recognize the @var{operation} keyword, the stub
36060 must respond with an empty packet.
36062 @item qAttached:@var{pid}
36063 @cindex query attached, remote request
36064 @cindex @samp{qAttached} packet
36065 Return an indication of whether the remote server attached to an
36066 existing process or created a new process. When the multiprocess
36067 protocol extensions are supported (@pxref{multiprocess extensions}),
36068 @var{pid} is an integer in hexadecimal format identifying the target
36069 process. Otherwise, @value{GDBN} will omit the @var{pid} field and
36070 the query packet will be simplified as @samp{qAttached}.
36072 This query is used, for example, to know whether the remote process
36073 should be detached or killed when a @value{GDBN} session is ended with
36074 the @code{quit} command.
36079 The remote server attached to an existing process.
36081 The remote server created a new process.
36083 A badly formed request or an error was encountered.
36088 @node Architecture-Specific Protocol Details
36089 @section Architecture-Specific Protocol Details
36091 This section describes how the remote protocol is applied to specific
36092 target architectures. Also see @ref{Standard Target Features}, for
36093 details of XML target descriptions for each architecture.
36097 @subsubsection Breakpoint Kinds
36099 These breakpoint kinds are defined for the @samp{Z0} and @samp{Z1} packets.
36104 16-bit Thumb mode breakpoint.
36107 32-bit Thumb mode (Thumb-2) breakpoint.
36110 32-bit ARM mode breakpoint.
36116 @subsubsection Register Packet Format
36118 The following @code{g}/@code{G} packets have previously been defined.
36119 In the below, some thirty-two bit registers are transferred as
36120 sixty-four bits. Those registers should be zero/sign extended (which?)
36121 to fill the space allocated. Register bytes are transferred in target
36122 byte order. The two nibbles within a register byte are transferred
36123 most-significant - least-significant.
36129 All registers are transferred as thirty-two bit quantities in the order:
36130 32 general-purpose; sr; lo; hi; bad; cause; pc; 32 floating-point
36131 registers; fsr; fir; fp.
36135 All registers are transferred as sixty-four bit quantities (including
36136 thirty-two bit registers such as @code{sr}). The ordering is the same
36141 @node Tracepoint Packets
36142 @section Tracepoint Packets
36143 @cindex tracepoint packets
36144 @cindex packets, tracepoint
36146 Here we describe the packets @value{GDBN} uses to implement
36147 tracepoints (@pxref{Tracepoints}).
36151 @item QTDP:@var{n}:@var{addr}:@var{ena}:@var{step}:@var{pass}[:F@var{flen}][:X@var{len},@var{bytes}]@r{[}-@r{]}
36152 Create a new tracepoint, number @var{n}, at @var{addr}. If @var{ena}
36153 is @samp{E}, then the tracepoint is enabled; if it is @samp{D}, then
36154 the tracepoint is disabled. @var{step} is the tracepoint's step
36155 count, and @var{pass} is its pass count. If an @samp{F} is present,
36156 then the tracepoint is to be a fast tracepoint, and the @var{flen} is
36157 the number of bytes that the target should copy elsewhere to make room
36158 for the tracepoint. If an @samp{X} is present, it introduces a
36159 tracepoint condition, which consists of a hexadecimal length, followed
36160 by a comma and hex-encoded bytes, in a manner similar to action
36161 encodings as described below. If the trailing @samp{-} is present,
36162 further @samp{QTDP} packets will follow to specify this tracepoint's
36168 The packet was understood and carried out.
36170 @xref{Tracepoint Packets,,Relocate instruction reply packet}.
36172 The packet was not recognized.
36175 @item QTDP:-@var{n}:@var{addr}:@r{[}S@r{]}@var{action}@dots{}@r{[}-@r{]}
36176 Define actions to be taken when a tracepoint is hit. @var{n} and
36177 @var{addr} must be the same as in the initial @samp{QTDP} packet for
36178 this tracepoint. This packet may only be sent immediately after
36179 another @samp{QTDP} packet that ended with a @samp{-}. If the
36180 trailing @samp{-} is present, further @samp{QTDP} packets will follow,
36181 specifying more actions for this tracepoint.
36183 In the series of action packets for a given tracepoint, at most one
36184 can have an @samp{S} before its first @var{action}. If such a packet
36185 is sent, it and the following packets define ``while-stepping''
36186 actions. Any prior packets define ordinary actions --- that is, those
36187 taken when the tracepoint is first hit. If no action packet has an
36188 @samp{S}, then all the packets in the series specify ordinary
36189 tracepoint actions.
36191 The @samp{@var{action}@dots{}} portion of the packet is a series of
36192 actions, concatenated without separators. Each action has one of the
36198 Collect the registers whose bits are set in @var{mask}. @var{mask} is
36199 a hexadecimal number whose @var{i}'th bit is set if register number
36200 @var{i} should be collected. (The least significant bit is numbered
36201 zero.) Note that @var{mask} may be any number of digits long; it may
36202 not fit in a 32-bit word.
36204 @item M @var{basereg},@var{offset},@var{len}
36205 Collect @var{len} bytes of memory starting at the address in register
36206 number @var{basereg}, plus @var{offset}. If @var{basereg} is
36207 @samp{-1}, then the range has a fixed address: @var{offset} is the
36208 address of the lowest byte to collect. The @var{basereg},
36209 @var{offset}, and @var{len} parameters are all unsigned hexadecimal
36210 values (the @samp{-1} value for @var{basereg} is a special case).
36212 @item X @var{len},@var{expr}
36213 Evaluate @var{expr}, whose length is @var{len}, and collect memory as
36214 it directs. @var{expr} is an agent expression, as described in
36215 @ref{Agent Expressions}. Each byte of the expression is encoded as a
36216 two-digit hex number in the packet; @var{len} is the number of bytes
36217 in the expression (and thus one-half the number of hex digits in the
36222 Any number of actions may be packed together in a single @samp{QTDP}
36223 packet, as long as the packet does not exceed the maximum packet
36224 length (400 bytes, for many stubs). There may be only one @samp{R}
36225 action per tracepoint, and it must precede any @samp{M} or @samp{X}
36226 actions. Any registers referred to by @samp{M} and @samp{X} actions
36227 must be collected by a preceding @samp{R} action. (The
36228 ``while-stepping'' actions are treated as if they were attached to a
36229 separate tracepoint, as far as these restrictions are concerned.)
36234 The packet was understood and carried out.
36236 @xref{Tracepoint Packets,,Relocate instruction reply packet}.
36238 The packet was not recognized.
36241 @item QTDPsrc:@var{n}:@var{addr}:@var{type}:@var{start}:@var{slen}:@var{bytes}
36242 @cindex @samp{QTDPsrc} packet
36243 Specify a source string of tracepoint @var{n} at address @var{addr}.
36244 This is useful to get accurate reproduction of the tracepoints
36245 originally downloaded at the beginning of the trace run. @var{type}
36246 is the name of the tracepoint part, such as @samp{cond} for the
36247 tracepoint's conditional expression (see below for a list of types), while
36248 @var{bytes} is the string, encoded in hexadecimal.
36250 @var{start} is the offset of the @var{bytes} within the overall source
36251 string, while @var{slen} is the total length of the source string.
36252 This is intended for handling source strings that are longer than will
36253 fit in a single packet.
36254 @c Add detailed example when this info is moved into a dedicated
36255 @c tracepoint descriptions section.
36257 The available string types are @samp{at} for the location,
36258 @samp{cond} for the conditional, and @samp{cmd} for an action command.
36259 @value{GDBN} sends a separate packet for each command in the action
36260 list, in the same order in which the commands are stored in the list.
36262 The target does not need to do anything with source strings except
36263 report them back as part of the replies to the @samp{qTfP}/@samp{qTsP}
36266 Although this packet is optional, and @value{GDBN} will only send it
36267 if the target replies with @samp{TracepointSource} @xref{General
36268 Query Packets}, it makes both disconnected tracing and trace files
36269 much easier to use. Otherwise the user must be careful that the
36270 tracepoints in effect while looking at trace frames are identical to
36271 the ones in effect during the trace run; even a small discrepancy
36272 could cause @samp{tdump} not to work, or a particular trace frame not
36275 @item QTDV:@var{n}:@var{value}
36276 @cindex define trace state variable, remote request
36277 @cindex @samp{QTDV} packet
36278 Create a new trace state variable, number @var{n}, with an initial
36279 value of @var{value}, which is a 64-bit signed integer. Both @var{n}
36280 and @var{value} are encoded as hexadecimal values. @value{GDBN} has
36281 the option of not using this packet for initial values of zero; the
36282 target should simply create the trace state variables as they are
36283 mentioned in expressions.
36285 @item QTFrame:@var{n}
36286 Select the @var{n}'th tracepoint frame from the buffer, and use the
36287 register and memory contents recorded there to answer subsequent
36288 request packets from @value{GDBN}.
36290 A successful reply from the stub indicates that the stub has found the
36291 requested frame. The response is a series of parts, concatenated
36292 without separators, describing the frame we selected. Each part has
36293 one of the following forms:
36297 The selected frame is number @var{n} in the trace frame buffer;
36298 @var{f} is a hexadecimal number. If @var{f} is @samp{-1}, then there
36299 was no frame matching the criteria in the request packet.
36302 The selected trace frame records a hit of tracepoint number @var{t};
36303 @var{t} is a hexadecimal number.
36307 @item QTFrame:pc:@var{addr}
36308 Like @samp{QTFrame:@var{n}}, but select the first tracepoint frame after the
36309 currently selected frame whose PC is @var{addr};
36310 @var{addr} is a hexadecimal number.
36312 @item QTFrame:tdp:@var{t}
36313 Like @samp{QTFrame:@var{n}}, but select the first tracepoint frame after the
36314 currently selected frame that is a hit of tracepoint @var{t}; @var{t}
36315 is a hexadecimal number.
36317 @item QTFrame:range:@var{start}:@var{end}
36318 Like @samp{QTFrame:@var{n}}, but select the first tracepoint frame after the
36319 currently selected frame whose PC is between @var{start} (inclusive)
36320 and @var{end} (inclusive); @var{start} and @var{end} are hexadecimal
36323 @item QTFrame:outside:@var{start}:@var{end}
36324 Like @samp{QTFrame:range:@var{start}:@var{end}}, but select the first
36325 frame @emph{outside} the given range of addresses (exclusive).
36328 This packet requests the minimum length of instruction at which a fast
36329 tracepoint (@pxref{Set Tracepoints}) may be placed. For instance, on
36330 the 32-bit x86 architecture, it is possible to use a 4-byte jump, but
36331 it depends on the target system being able to create trampolines in
36332 the first 64K of memory, which might or might not be possible for that
36333 system. So the reply to this packet will be 4 if it is able to
36340 The minimum instruction length is currently unknown.
36342 The minimum instruction length is @var{length}, where @var{length} is greater
36343 or equal to 1. @var{length} is a hexadecimal number. A reply of 1 means
36344 that a fast tracepoint may be placed on any instruction regardless of size.
36346 An error has occurred.
36348 An empty reply indicates that the request is not supported by the stub.
36352 Begin the tracepoint experiment. Begin collecting data from
36353 tracepoint hits in the trace frame buffer. This packet supports the
36354 @samp{qRelocInsn} reply (@pxref{Tracepoint Packets,,Relocate
36355 instruction reply packet}).
36358 End the tracepoint experiment. Stop collecting trace frames.
36360 @item QTEnable:@var{n}:@var{addr}
36362 Enable tracepoint @var{n} at address @var{addr} in a started tracepoint
36363 experiment. If the tracepoint was previously disabled, then collection
36364 of data from it will resume.
36366 @item QTDisable:@var{n}:@var{addr}
36368 Disable tracepoint @var{n} at address @var{addr} in a started tracepoint
36369 experiment. No more data will be collected from the tracepoint unless
36370 @samp{QTEnable:@var{n}:@var{addr}} is subsequently issued.
36373 Clear the table of tracepoints, and empty the trace frame buffer.
36375 @item QTro:@var{start1},@var{end1}:@var{start2},@var{end2}:@dots{}
36376 Establish the given ranges of memory as ``transparent''. The stub
36377 will answer requests for these ranges from memory's current contents,
36378 if they were not collected as part of the tracepoint hit.
36380 @value{GDBN} uses this to mark read-only regions of memory, like those
36381 containing program code. Since these areas never change, they should
36382 still have the same contents they did when the tracepoint was hit, so
36383 there's no reason for the stub to refuse to provide their contents.
36385 @item QTDisconnected:@var{value}
36386 Set the choice to what to do with the tracing run when @value{GDBN}
36387 disconnects from the target. A @var{value} of 1 directs the target to
36388 continue the tracing run, while 0 tells the target to stop tracing if
36389 @value{GDBN} is no longer in the picture.
36392 Ask the stub if there is a trace experiment running right now.
36394 The reply has the form:
36398 @item T@var{running}@r{[};@var{field}@r{]}@dots{}
36399 @var{running} is a single digit @code{1} if the trace is presently
36400 running, or @code{0} if not. It is followed by semicolon-separated
36401 optional fields that an agent may use to report additional status.
36405 If the trace is not running, the agent may report any of several
36406 explanations as one of the optional fields:
36411 No trace has been run yet.
36413 @item tstop[:@var{text}]:0
36414 The trace was stopped by a user-originated stop command. The optional
36415 @var{text} field is a user-supplied string supplied as part of the
36416 stop command (for instance, an explanation of why the trace was
36417 stopped manually). It is hex-encoded.
36420 The trace stopped because the trace buffer filled up.
36422 @item tdisconnected:0
36423 The trace stopped because @value{GDBN} disconnected from the target.
36425 @item tpasscount:@var{tpnum}
36426 The trace stopped because tracepoint @var{tpnum} exceeded its pass count.
36428 @item terror:@var{text}:@var{tpnum}
36429 The trace stopped because tracepoint @var{tpnum} had an error. The
36430 string @var{text} is available to describe the nature of the error
36431 (for instance, a divide by zero in the condition expression).
36432 @var{text} is hex encoded.
36435 The trace stopped for some other reason.
36439 Additional optional fields supply statistical and other information.
36440 Although not required, they are extremely useful for users monitoring
36441 the progress of a trace run. If a trace has stopped, and these
36442 numbers are reported, they must reflect the state of the just-stopped
36447 @item tframes:@var{n}
36448 The number of trace frames in the buffer.
36450 @item tcreated:@var{n}
36451 The total number of trace frames created during the run. This may
36452 be larger than the trace frame count, if the buffer is circular.
36454 @item tsize:@var{n}
36455 The total size of the trace buffer, in bytes.
36457 @item tfree:@var{n}
36458 The number of bytes still unused in the buffer.
36460 @item circular:@var{n}
36461 The value of the circular trace buffer flag. @code{1} means that the
36462 trace buffer is circular and old trace frames will be discarded if
36463 necessary to make room, @code{0} means that the trace buffer is linear
36466 @item disconn:@var{n}
36467 The value of the disconnected tracing flag. @code{1} means that
36468 tracing will continue after @value{GDBN} disconnects, @code{0} means
36469 that the trace run will stop.
36473 @item qTP:@var{tp}:@var{addr}
36474 @cindex tracepoint status, remote request
36475 @cindex @samp{qTP} packet
36476 Ask the stub for the current state of tracepoint number @var{tp} at
36477 address @var{addr}.
36481 @item V@var{hits}:@var{usage}
36482 The tracepoint has been hit @var{hits} times so far during the trace
36483 run, and accounts for @var{usage} in the trace buffer. Note that
36484 @code{while-stepping} steps are not counted as separate hits, but the
36485 steps' space consumption is added into the usage number.
36489 @item qTV:@var{var}
36490 @cindex trace state variable value, remote request
36491 @cindex @samp{qTV} packet
36492 Ask the stub for the value of the trace state variable number @var{var}.
36497 The value of the variable is @var{value}. This will be the current
36498 value of the variable if the user is examining a running target, or a
36499 saved value if the variable was collected in the trace frame that the
36500 user is looking at. Note that multiple requests may result in
36501 different reply values, such as when requesting values while the
36502 program is running.
36505 The value of the variable is unknown. This would occur, for example,
36506 if the user is examining a trace frame in which the requested variable
36512 These packets request data about tracepoints that are being used by
36513 the target. @value{GDBN} sends @code{qTfP} to get the first piece
36514 of data, and multiple @code{qTsP} to get additional pieces. Replies
36515 to these packets generally take the form of the @code{QTDP} packets
36516 that define tracepoints. (FIXME add detailed syntax)
36520 These packets request data about trace state variables that are on the
36521 target. @value{GDBN} sends @code{qTfV} to get the first vari of data,
36522 and multiple @code{qTsV} to get additional variables. Replies to
36523 these packets follow the syntax of the @code{QTDV} packets that define
36524 trace state variables.
36528 These packets request data about static tracepoint markers that exist
36529 in the target program. @value{GDBN} sends @code{qTfSTM} to get the
36530 first piece of data, and multiple @code{qTsSTM} to get additional
36531 pieces. Replies to these packets take the following form:
36535 @item m @var{address}:@var{id}:@var{extra}
36537 @item m @var{address}:@var{id}:@var{extra},@var{address}:@var{id}:@var{extra}@dots{}
36538 a comma-separated list of markers
36540 (lower case letter @samp{L}) denotes end of list.
36542 An error occurred. @var{nn} are hex digits.
36544 An empty reply indicates that the request is not supported by the
36548 @var{address} is encoded in hex.
36549 @var{id} and @var{extra} are strings encoded in hex.
36551 In response to each query, the target will reply with a list of one or
36552 more markers, separated by commas. @value{GDBN} will respond to each
36553 reply with a request for more markers (using the @samp{qs} form of the
36554 query), until the target responds with @samp{l} (lower-case ell, for
36557 @item qTSTMat:@var{address}
36558 This packets requests data about static tracepoint markers in the
36559 target program at @var{address}. Replies to this packet follow the
36560 syntax of the @samp{qTfSTM} and @code{qTsSTM} packets that list static
36561 tracepoint markers.
36563 @item QTSave:@var{filename}
36564 This packet directs the target to save trace data to the file name
36565 @var{filename} in the target's filesystem. @var{filename} is encoded
36566 as a hex string; the interpretation of the file name (relative vs
36567 absolute, wild cards, etc) is up to the target.
36569 @item qTBuffer:@var{offset},@var{len}
36570 Return up to @var{len} bytes of the current contents of trace buffer,
36571 starting at @var{offset}. The trace buffer is treated as if it were
36572 a contiguous collection of traceframes, as per the trace file format.
36573 The reply consists as many hex-encoded bytes as the target can deliver
36574 in a packet; it is not an error to return fewer than were asked for.
36575 A reply consisting of just @code{l} indicates that no bytes are
36578 @item QTBuffer:circular:@var{value}
36579 This packet directs the target to use a circular trace buffer if
36580 @var{value} is 1, or a linear buffer if the value is 0.
36582 @item QTNotes:@r{[}@var{type}:@var{text}@r{]}@r{[};@var{type}:@var{text}@r{]}@dots{}
36583 This packet adds optional textual notes to the trace run. Allowable
36584 types include @code{user}, @code{notes}, and @code{tstop}, the
36585 @var{text} fields are arbitrary strings, hex-encoded.
36589 @subsection Relocate instruction reply packet
36590 When installing fast tracepoints in memory, the target may need to
36591 relocate the instruction currently at the tracepoint address to a
36592 different address in memory. For most instructions, a simple copy is
36593 enough, but, for example, call instructions that implicitly push the
36594 return address on the stack, and relative branches or other
36595 PC-relative instructions require offset adjustment, so that the effect
36596 of executing the instruction at a different address is the same as if
36597 it had executed in the original location.
36599 In response to several of the tracepoint packets, the target may also
36600 respond with a number of intermediate @samp{qRelocInsn} request
36601 packets before the final result packet, to have @value{GDBN} handle
36602 this relocation operation. If a packet supports this mechanism, its
36603 documentation will explicitly say so. See for example the above
36604 descriptions for the @samp{QTStart} and @samp{QTDP} packets. The
36605 format of the request is:
36608 @item qRelocInsn:@var{from};@var{to}
36610 This requests @value{GDBN} to copy instruction at address @var{from}
36611 to address @var{to}, possibly adjusted so that executing the
36612 instruction at @var{to} has the same effect as executing it at
36613 @var{from}. @value{GDBN} writes the adjusted instruction to target
36614 memory starting at @var{to}.
36619 @item qRelocInsn:@var{adjusted_size}
36620 Informs the stub the relocation is complete. @var{adjusted_size} is
36621 the length in bytes of resulting relocated instruction sequence.
36623 A badly formed request was detected, or an error was encountered while
36624 relocating the instruction.
36627 @node Host I/O Packets
36628 @section Host I/O Packets
36629 @cindex Host I/O, remote protocol
36630 @cindex file transfer, remote protocol
36632 The @dfn{Host I/O} packets allow @value{GDBN} to perform I/O
36633 operations on the far side of a remote link. For example, Host I/O is
36634 used to upload and download files to a remote target with its own
36635 filesystem. Host I/O uses the same constant values and data structure
36636 layout as the target-initiated File-I/O protocol. However, the
36637 Host I/O packets are structured differently. The target-initiated
36638 protocol relies on target memory to store parameters and buffers.
36639 Host I/O requests are initiated by @value{GDBN}, and the
36640 target's memory is not involved. @xref{File-I/O Remote Protocol
36641 Extension}, for more details on the target-initiated protocol.
36643 The Host I/O request packets all encode a single operation along with
36644 its arguments. They have this format:
36648 @item vFile:@var{operation}: @var{parameter}@dots{}
36649 @var{operation} is the name of the particular request; the target
36650 should compare the entire packet name up to the second colon when checking
36651 for a supported operation. The format of @var{parameter} depends on
36652 the operation. Numbers are always passed in hexadecimal. Negative
36653 numbers have an explicit minus sign (i.e.@: two's complement is not
36654 used). Strings (e.g.@: filenames) are encoded as a series of
36655 hexadecimal bytes. The last argument to a system call may be a
36656 buffer of escaped binary data (@pxref{Binary Data}).
36660 The valid responses to Host I/O packets are:
36664 @item F @var{result} [, @var{errno}] [; @var{attachment}]
36665 @var{result} is the integer value returned by this operation, usually
36666 non-negative for success and -1 for errors. If an error has occured,
36667 @var{errno} will be included in the result. @var{errno} will have a
36668 value defined by the File-I/O protocol (@pxref{Errno Values}). For
36669 operations which return data, @var{attachment} supplies the data as a
36670 binary buffer. Binary buffers in response packets are escaped in the
36671 normal way (@pxref{Binary Data}). See the individual packet
36672 documentation for the interpretation of @var{result} and
36676 An empty response indicates that this operation is not recognized.
36680 These are the supported Host I/O operations:
36683 @item vFile:open: @var{pathname}, @var{flags}, @var{mode}
36684 Open a file at @var{pathname} and return a file descriptor for it, or
36685 return -1 if an error occurs. @var{pathname} is a string,
36686 @var{flags} is an integer indicating a mask of open flags
36687 (@pxref{Open Flags}), and @var{mode} is an integer indicating a mask
36688 of mode bits to use if the file is created (@pxref{mode_t Values}).
36689 @xref{open}, for details of the open flags and mode values.
36691 @item vFile:close: @var{fd}
36692 Close the open file corresponding to @var{fd} and return 0, or
36693 -1 if an error occurs.
36695 @item vFile:pread: @var{fd}, @var{count}, @var{offset}
36696 Read data from the open file corresponding to @var{fd}. Up to
36697 @var{count} bytes will be read from the file, starting at @var{offset}
36698 relative to the start of the file. The target may read fewer bytes;
36699 common reasons include packet size limits and an end-of-file
36700 condition. The number of bytes read is returned. Zero should only be
36701 returned for a successful read at the end of the file, or if
36702 @var{count} was zero.
36704 The data read should be returned as a binary attachment on success.
36705 If zero bytes were read, the response should include an empty binary
36706 attachment (i.e.@: a trailing semicolon). The return value is the
36707 number of target bytes read; the binary attachment may be longer if
36708 some characters were escaped.
36710 @item vFile:pwrite: @var{fd}, @var{offset}, @var{data}
36711 Write @var{data} (a binary buffer) to the open file corresponding
36712 to @var{fd}. Start the write at @var{offset} from the start of the
36713 file. Unlike many @code{write} system calls, there is no
36714 separate @var{count} argument; the length of @var{data} in the
36715 packet is used. @samp{vFile:write} returns the number of bytes written,
36716 which may be shorter than the length of @var{data}, or -1 if an
36719 @item vFile:unlink: @var{pathname}
36720 Delete the file at @var{pathname} on the target. Return 0,
36721 or -1 if an error occurs. @var{pathname} is a string.
36723 @item vFile:readlink: @var{filename}
36724 Read value of symbolic link @var{filename} on the target. Return
36725 the number of bytes read, or -1 if an error occurs.
36727 The data read should be returned as a binary attachment on success.
36728 If zero bytes were read, the response should include an empty binary
36729 attachment (i.e.@: a trailing semicolon). The return value is the
36730 number of target bytes read; the binary attachment may be longer if
36731 some characters were escaped.
36736 @section Interrupts
36737 @cindex interrupts (remote protocol)
36739 When a program on the remote target is running, @value{GDBN} may
36740 attempt to interrupt it by sending a @samp{Ctrl-C}, @code{BREAK} or
36741 a @code{BREAK} followed by @code{g},
36742 control of which is specified via @value{GDBN}'s @samp{interrupt-sequence}.
36744 The precise meaning of @code{BREAK} is defined by the transport
36745 mechanism and may, in fact, be undefined. @value{GDBN} does not
36746 currently define a @code{BREAK} mechanism for any of the network
36747 interfaces except for TCP, in which case @value{GDBN} sends the
36748 @code{telnet} BREAK sequence.
36750 @samp{Ctrl-C}, on the other hand, is defined and implemented for all
36751 transport mechanisms. It is represented by sending the single byte
36752 @code{0x03} without any of the usual packet overhead described in
36753 the Overview section (@pxref{Overview}). When a @code{0x03} byte is
36754 transmitted as part of a packet, it is considered to be packet data
36755 and does @emph{not} represent an interrupt. E.g., an @samp{X} packet
36756 (@pxref{X packet}), used for binary downloads, may include an unescaped
36757 @code{0x03} as part of its packet.
36759 @code{BREAK} followed by @code{g} is also known as Magic SysRq g.
36760 When Linux kernel receives this sequence from serial port,
36761 it stops execution and connects to gdb.
36763 Stubs are not required to recognize these interrupt mechanisms and the
36764 precise meaning associated with receipt of the interrupt is
36765 implementation defined. If the target supports debugging of multiple
36766 threads and/or processes, it should attempt to interrupt all
36767 currently-executing threads and processes.
36768 If the stub is successful at interrupting the
36769 running program, it should send one of the stop
36770 reply packets (@pxref{Stop Reply Packets}) to @value{GDBN} as a result
36771 of successfully stopping the program in all-stop mode, and a stop reply
36772 for each stopped thread in non-stop mode.
36773 Interrupts received while the
36774 program is stopped are discarded.
36776 @node Notification Packets
36777 @section Notification Packets
36778 @cindex notification packets
36779 @cindex packets, notification
36781 The @value{GDBN} remote serial protocol includes @dfn{notifications},
36782 packets that require no acknowledgment. Both the GDB and the stub
36783 may send notifications (although the only notifications defined at
36784 present are sent by the stub). Notifications carry information
36785 without incurring the round-trip latency of an acknowledgment, and so
36786 are useful for low-impact communications where occasional packet loss
36789 A notification packet has the form @samp{% @var{data} #
36790 @var{checksum}}, where @var{data} is the content of the notification,
36791 and @var{checksum} is a checksum of @var{data}, computed and formatted
36792 as for ordinary @value{GDBN} packets. A notification's @var{data}
36793 never contains @samp{$}, @samp{%} or @samp{#} characters. Upon
36794 receiving a notification, the recipient sends no @samp{+} or @samp{-}
36795 to acknowledge the notification's receipt or to report its corruption.
36797 Every notification's @var{data} begins with a name, which contains no
36798 colon characters, followed by a colon character.
36800 Recipients should silently ignore corrupted notifications and
36801 notifications they do not understand. Recipients should restart
36802 timeout periods on receipt of a well-formed notification, whether or
36803 not they understand it.
36805 Senders should only send the notifications described here when this
36806 protocol description specifies that they are permitted. In the
36807 future, we may extend the protocol to permit existing notifications in
36808 new contexts; this rule helps older senders avoid confusing newer
36811 (Older versions of @value{GDBN} ignore bytes received until they see
36812 the @samp{$} byte that begins an ordinary packet, so new stubs may
36813 transmit notifications without fear of confusing older clients. There
36814 are no notifications defined for @value{GDBN} to send at the moment, but we
36815 assume that most older stubs would ignore them, as well.)
36817 The following notification packets from the stub to @value{GDBN} are
36821 @item Stop: @var{reply}
36822 Report an asynchronous stop event in non-stop mode.
36823 The @var{reply} has the form of a stop reply, as
36824 described in @ref{Stop Reply Packets}. Refer to @ref{Remote Non-Stop},
36825 for information on how these notifications are acknowledged by
36829 @node Remote Non-Stop
36830 @section Remote Protocol Support for Non-Stop Mode
36832 @value{GDBN}'s remote protocol supports non-stop debugging of
36833 multi-threaded programs, as described in @ref{Non-Stop Mode}. If the stub
36834 supports non-stop mode, it should report that to @value{GDBN} by including
36835 @samp{QNonStop+} in its @samp{qSupported} response (@pxref{qSupported}).
36837 @value{GDBN} typically sends a @samp{QNonStop} packet only when
36838 establishing a new connection with the stub. Entering non-stop mode
36839 does not alter the state of any currently-running threads, but targets
36840 must stop all threads in any already-attached processes when entering
36841 all-stop mode. @value{GDBN} uses the @samp{?} packet as necessary to
36842 probe the target state after a mode change.
36844 In non-stop mode, when an attached process encounters an event that
36845 would otherwise be reported with a stop reply, it uses the
36846 asynchronous notification mechanism (@pxref{Notification Packets}) to
36847 inform @value{GDBN}. In contrast to all-stop mode, where all threads
36848 in all processes are stopped when a stop reply is sent, in non-stop
36849 mode only the thread reporting the stop event is stopped. That is,
36850 when reporting a @samp{S} or @samp{T} response to indicate completion
36851 of a step operation, hitting a breakpoint, or a fault, only the
36852 affected thread is stopped; any other still-running threads continue
36853 to run. When reporting a @samp{W} or @samp{X} response, all running
36854 threads belonging to other attached processes continue to run.
36856 Only one stop reply notification at a time may be pending; if
36857 additional stop events occur before @value{GDBN} has acknowledged the
36858 previous notification, they must be queued by the stub for later
36859 synchronous transmission in response to @samp{vStopped} packets from
36860 @value{GDBN}. Because the notification mechanism is unreliable,
36861 the stub is permitted to resend a stop reply notification
36862 if it believes @value{GDBN} may not have received it. @value{GDBN}
36863 ignores additional stop reply notifications received before it has
36864 finished processing a previous notification and the stub has completed
36865 sending any queued stop events.
36867 Otherwise, @value{GDBN} must be prepared to receive a stop reply
36868 notification at any time. Specifically, they may appear when
36869 @value{GDBN} is not otherwise reading input from the stub, or when
36870 @value{GDBN} is expecting to read a normal synchronous response or a
36871 @samp{+}/@samp{-} acknowledgment to a packet it has sent.
36872 Notification packets are distinct from any other communication from
36873 the stub so there is no ambiguity.
36875 After receiving a stop reply notification, @value{GDBN} shall
36876 acknowledge it by sending a @samp{vStopped} packet (@pxref{vStopped packet})
36877 as a regular, synchronous request to the stub. Such acknowledgment
36878 is not required to happen immediately, as @value{GDBN} is permitted to
36879 send other, unrelated packets to the stub first, which the stub should
36882 Upon receiving a @samp{vStopped} packet, if the stub has other queued
36883 stop events to report to @value{GDBN}, it shall respond by sending a
36884 normal stop reply response. @value{GDBN} shall then send another
36885 @samp{vStopped} packet to solicit further responses; again, it is
36886 permitted to send other, unrelated packets as well which the stub
36887 should process normally.
36889 If the stub receives a @samp{vStopped} packet and there are no
36890 additional stop events to report, the stub shall return an @samp{OK}
36891 response. At this point, if further stop events occur, the stub shall
36892 send a new stop reply notification, @value{GDBN} shall accept the
36893 notification, and the process shall be repeated.
36895 In non-stop mode, the target shall respond to the @samp{?} packet as
36896 follows. First, any incomplete stop reply notification/@samp{vStopped}
36897 sequence in progress is abandoned. The target must begin a new
36898 sequence reporting stop events for all stopped threads, whether or not
36899 it has previously reported those events to @value{GDBN}. The first
36900 stop reply is sent as a synchronous reply to the @samp{?} packet, and
36901 subsequent stop replies are sent as responses to @samp{vStopped} packets
36902 using the mechanism described above. The target must not send
36903 asynchronous stop reply notifications until the sequence is complete.
36904 If all threads are running when the target receives the @samp{?} packet,
36905 or if the target is not attached to any process, it shall respond
36908 @node Packet Acknowledgment
36909 @section Packet Acknowledgment
36911 @cindex acknowledgment, for @value{GDBN} remote
36912 @cindex packet acknowledgment, for @value{GDBN} remote
36913 By default, when either the host or the target machine receives a packet,
36914 the first response expected is an acknowledgment: either @samp{+} (to indicate
36915 the package was received correctly) or @samp{-} (to request retransmission).
36916 This mechanism allows the @value{GDBN} remote protocol to operate over
36917 unreliable transport mechanisms, such as a serial line.
36919 In cases where the transport mechanism is itself reliable (such as a pipe or
36920 TCP connection), the @samp{+}/@samp{-} acknowledgments are redundant.
36921 It may be desirable to disable them in that case to reduce communication
36922 overhead, or for other reasons. This can be accomplished by means of the
36923 @samp{QStartNoAckMode} packet; @pxref{QStartNoAckMode}.
36925 When in no-acknowledgment mode, neither the stub nor @value{GDBN} shall send or
36926 expect @samp{+}/@samp{-} protocol acknowledgments. The packet
36927 and response format still includes the normal checksum, as described in
36928 @ref{Overview}, but the checksum may be ignored by the receiver.
36930 If the stub supports @samp{QStartNoAckMode} and prefers to operate in
36931 no-acknowledgment mode, it should report that to @value{GDBN}
36932 by including @samp{QStartNoAckMode+} in its response to @samp{qSupported};
36933 @pxref{qSupported}.
36934 If @value{GDBN} also supports @samp{QStartNoAckMode} and it has not been
36935 disabled via the @code{set remote noack-packet off} command
36936 (@pxref{Remote Configuration}),
36937 @value{GDBN} may then send a @samp{QStartNoAckMode} packet to the stub.
36938 Only then may the stub actually turn off packet acknowledgments.
36939 @value{GDBN} sends a final @samp{+} acknowledgment of the stub's @samp{OK}
36940 response, which can be safely ignored by the stub.
36942 Note that @code{set remote noack-packet} command only affects negotiation
36943 between @value{GDBN} and the stub when subsequent connections are made;
36944 it does not affect the protocol acknowledgment state for any current
36946 Since @samp{+}/@samp{-} acknowledgments are enabled by default when a
36947 new connection is established,
36948 there is also no protocol request to re-enable the acknowledgments
36949 for the current connection, once disabled.
36954 Example sequence of a target being re-started. Notice how the restart
36955 does not get any direct output:
36960 @emph{target restarts}
36963 <- @code{T001:1234123412341234}
36967 Example sequence of a target being stepped by a single instruction:
36970 -> @code{G1445@dots{}}
36975 <- @code{T001:1234123412341234}
36979 <- @code{1455@dots{}}
36983 @node File-I/O Remote Protocol Extension
36984 @section File-I/O Remote Protocol Extension
36985 @cindex File-I/O remote protocol extension
36988 * File-I/O Overview::
36989 * Protocol Basics::
36990 * The F Request Packet::
36991 * The F Reply Packet::
36992 * The Ctrl-C Message::
36994 * List of Supported Calls::
36995 * Protocol-specific Representation of Datatypes::
36997 * File-I/O Examples::
37000 @node File-I/O Overview
37001 @subsection File-I/O Overview
37002 @cindex file-i/o overview
37004 The @dfn{File I/O remote protocol extension} (short: File-I/O) allows the
37005 target to use the host's file system and console I/O to perform various
37006 system calls. System calls on the target system are translated into a
37007 remote protocol packet to the host system, which then performs the needed
37008 actions and returns a response packet to the target system.
37009 This simulates file system operations even on targets that lack file systems.
37011 The protocol is defined to be independent of both the host and target systems.
37012 It uses its own internal representation of datatypes and values. Both
37013 @value{GDBN} and the target's @value{GDBN} stub are responsible for
37014 translating the system-dependent value representations into the internal
37015 protocol representations when data is transmitted.
37017 The communication is synchronous. A system call is possible only when
37018 @value{GDBN} is waiting for a response from the @samp{C}, @samp{c}, @samp{S}
37019 or @samp{s} packets. While @value{GDBN} handles the request for a system call,
37020 the target is stopped to allow deterministic access to the target's
37021 memory. Therefore File-I/O is not interruptible by target signals. On
37022 the other hand, it is possible to interrupt File-I/O by a user interrupt
37023 (@samp{Ctrl-C}) within @value{GDBN}.
37025 The target's request to perform a host system call does not finish
37026 the latest @samp{C}, @samp{c}, @samp{S} or @samp{s} action. That means,
37027 after finishing the system call, the target returns to continuing the
37028 previous activity (continue, step). No additional continue or step
37029 request from @value{GDBN} is required.
37032 (@value{GDBP}) continue
37033 <- target requests 'system call X'
37034 target is stopped, @value{GDBN} executes system call
37035 -> @value{GDBN} returns result
37036 ... target continues, @value{GDBN} returns to wait for the target
37037 <- target hits breakpoint and sends a Txx packet
37040 The protocol only supports I/O on the console and to regular files on
37041 the host file system. Character or block special devices, pipes,
37042 named pipes, sockets or any other communication method on the host
37043 system are not supported by this protocol.
37045 File I/O is not supported in non-stop mode.
37047 @node Protocol Basics
37048 @subsection Protocol Basics
37049 @cindex protocol basics, file-i/o
37051 The File-I/O protocol uses the @code{F} packet as the request as well
37052 as reply packet. Since a File-I/O system call can only occur when
37053 @value{GDBN} is waiting for a response from the continuing or stepping target,
37054 the File-I/O request is a reply that @value{GDBN} has to expect as a result
37055 of a previous @samp{C}, @samp{c}, @samp{S} or @samp{s} packet.
37056 This @code{F} packet contains all information needed to allow @value{GDBN}
37057 to call the appropriate host system call:
37061 A unique identifier for the requested system call.
37064 All parameters to the system call. Pointers are given as addresses
37065 in the target memory address space. Pointers to strings are given as
37066 pointer/length pair. Numerical values are given as they are.
37067 Numerical control flags are given in a protocol-specific representation.
37071 At this point, @value{GDBN} has to perform the following actions.
37075 If the parameters include pointer values to data needed as input to a
37076 system call, @value{GDBN} requests this data from the target with a
37077 standard @code{m} packet request. This additional communication has to be
37078 expected by the target implementation and is handled as any other @code{m}
37082 @value{GDBN} translates all value from protocol representation to host
37083 representation as needed. Datatypes are coerced into the host types.
37086 @value{GDBN} calls the system call.
37089 It then coerces datatypes back to protocol representation.
37092 If the system call is expected to return data in buffer space specified
37093 by pointer parameters to the call, the data is transmitted to the
37094 target using a @code{M} or @code{X} packet. This packet has to be expected
37095 by the target implementation and is handled as any other @code{M} or @code{X}
37100 Eventually @value{GDBN} replies with another @code{F} packet which contains all
37101 necessary information for the target to continue. This at least contains
37108 @code{errno}, if has been changed by the system call.
37115 After having done the needed type and value coercion, the target continues
37116 the latest continue or step action.
37118 @node The F Request Packet
37119 @subsection The @code{F} Request Packet
37120 @cindex file-i/o request packet
37121 @cindex @code{F} request packet
37123 The @code{F} request packet has the following format:
37126 @item F@var{call-id},@var{parameter@dots{}}
37128 @var{call-id} is the identifier to indicate the host system call to be called.
37129 This is just the name of the function.
37131 @var{parameter@dots{}} are the parameters to the system call.
37132 Parameters are hexadecimal integer values, either the actual values in case
37133 of scalar datatypes, pointers to target buffer space in case of compound
37134 datatypes and unspecified memory areas, or pointer/length pairs in case
37135 of string parameters. These are appended to the @var{call-id} as a
37136 comma-delimited list. All values are transmitted in ASCII
37137 string representation, pointer/length pairs separated by a slash.
37143 @node The F Reply Packet
37144 @subsection The @code{F} Reply Packet
37145 @cindex file-i/o reply packet
37146 @cindex @code{F} reply packet
37148 The @code{F} reply packet has the following format:
37152 @item F@var{retcode},@var{errno},@var{Ctrl-C flag};@var{call-specific attachment}
37154 @var{retcode} is the return code of the system call as hexadecimal value.
37156 @var{errno} is the @code{errno} set by the call, in protocol-specific
37158 This parameter can be omitted if the call was successful.
37160 @var{Ctrl-C flag} is only sent if the user requested a break. In this
37161 case, @var{errno} must be sent as well, even if the call was successful.
37162 The @var{Ctrl-C flag} itself consists of the character @samp{C}:
37169 or, if the call was interrupted before the host call has been performed:
37176 assuming 4 is the protocol-specific representation of @code{EINTR}.
37181 @node The Ctrl-C Message
37182 @subsection The @samp{Ctrl-C} Message
37183 @cindex ctrl-c message, in file-i/o protocol
37185 If the @samp{Ctrl-C} flag is set in the @value{GDBN}
37186 reply packet (@pxref{The F Reply Packet}),
37187 the target should behave as if it had
37188 gotten a break message. The meaning for the target is ``system call
37189 interrupted by @code{SIGINT}''. Consequentially, the target should actually stop
37190 (as with a break message) and return to @value{GDBN} with a @code{T02}
37193 It's important for the target to know in which
37194 state the system call was interrupted. There are two possible cases:
37198 The system call hasn't been performed on the host yet.
37201 The system call on the host has been finished.
37205 These two states can be distinguished by the target by the value of the
37206 returned @code{errno}. If it's the protocol representation of @code{EINTR}, the system
37207 call hasn't been performed. This is equivalent to the @code{EINTR} handling
37208 on POSIX systems. In any other case, the target may presume that the
37209 system call has been finished --- successfully or not --- and should behave
37210 as if the break message arrived right after the system call.
37212 @value{GDBN} must behave reliably. If the system call has not been called
37213 yet, @value{GDBN} may send the @code{F} reply immediately, setting @code{EINTR} as
37214 @code{errno} in the packet. If the system call on the host has been finished
37215 before the user requests a break, the full action must be finished by
37216 @value{GDBN}. This requires sending @code{M} or @code{X} packets as necessary.
37217 The @code{F} packet may only be sent when either nothing has happened
37218 or the full action has been completed.
37221 @subsection Console I/O
37222 @cindex console i/o as part of file-i/o
37224 By default and if not explicitly closed by the target system, the file
37225 descriptors 0, 1 and 2 are connected to the @value{GDBN} console. Output
37226 on the @value{GDBN} console is handled as any other file output operation
37227 (@code{write(1, @dots{})} or @code{write(2, @dots{})}). Console input is handled
37228 by @value{GDBN} so that after the target read request from file descriptor
37229 0 all following typing is buffered until either one of the following
37234 The user types @kbd{Ctrl-c}. The behaviour is as explained above, and the
37236 system call is treated as finished.
37239 The user presses @key{RET}. This is treated as end of input with a trailing
37243 The user types @kbd{Ctrl-d}. This is treated as end of input. No trailing
37244 character (neither newline nor @samp{Ctrl-D}) is appended to the input.
37248 If the user has typed more characters than fit in the buffer given to
37249 the @code{read} call, the trailing characters are buffered in @value{GDBN} until
37250 either another @code{read(0, @dots{})} is requested by the target, or debugging
37251 is stopped at the user's request.
37254 @node List of Supported Calls
37255 @subsection List of Supported Calls
37256 @cindex list of supported file-i/o calls
37273 @unnumberedsubsubsec open
37274 @cindex open, file-i/o system call
37279 int open(const char *pathname, int flags);
37280 int open(const char *pathname, int flags, mode_t mode);
37284 @samp{Fopen,@var{pathptr}/@var{len},@var{flags},@var{mode}}
37287 @var{flags} is the bitwise @code{OR} of the following values:
37291 If the file does not exist it will be created. The host
37292 rules apply as far as file ownership and time stamps
37296 When used with @code{O_CREAT}, if the file already exists it is
37297 an error and open() fails.
37300 If the file already exists and the open mode allows
37301 writing (@code{O_RDWR} or @code{O_WRONLY} is given) it will be
37302 truncated to zero length.
37305 The file is opened in append mode.
37308 The file is opened for reading only.
37311 The file is opened for writing only.
37314 The file is opened for reading and writing.
37318 Other bits are silently ignored.
37322 @var{mode} is the bitwise @code{OR} of the following values:
37326 User has read permission.
37329 User has write permission.
37332 Group has read permission.
37335 Group has write permission.
37338 Others have read permission.
37341 Others have write permission.
37345 Other bits are silently ignored.
37348 @item Return value:
37349 @code{open} returns the new file descriptor or -1 if an error
37356 @var{pathname} already exists and @code{O_CREAT} and @code{O_EXCL} were used.
37359 @var{pathname} refers to a directory.
37362 The requested access is not allowed.
37365 @var{pathname} was too long.
37368 A directory component in @var{pathname} does not exist.
37371 @var{pathname} refers to a device, pipe, named pipe or socket.
37374 @var{pathname} refers to a file on a read-only filesystem and
37375 write access was requested.
37378 @var{pathname} is an invalid pointer value.
37381 No space on device to create the file.
37384 The process already has the maximum number of files open.
37387 The limit on the total number of files open on the system
37391 The call was interrupted by the user.
37397 @unnumberedsubsubsec close
37398 @cindex close, file-i/o system call
37407 @samp{Fclose,@var{fd}}
37409 @item Return value:
37410 @code{close} returns zero on success, or -1 if an error occurred.
37416 @var{fd} isn't a valid open file descriptor.
37419 The call was interrupted by the user.
37425 @unnumberedsubsubsec read
37426 @cindex read, file-i/o system call
37431 int read(int fd, void *buf, unsigned int count);
37435 @samp{Fread,@var{fd},@var{bufptr},@var{count}}
37437 @item Return value:
37438 On success, the number of bytes read is returned.
37439 Zero indicates end of file. If count is zero, read
37440 returns zero as well. On error, -1 is returned.
37446 @var{fd} is not a valid file descriptor or is not open for
37450 @var{bufptr} is an invalid pointer value.
37453 The call was interrupted by the user.
37459 @unnumberedsubsubsec write
37460 @cindex write, file-i/o system call
37465 int write(int fd, const void *buf, unsigned int count);
37469 @samp{Fwrite,@var{fd},@var{bufptr},@var{count}}
37471 @item Return value:
37472 On success, the number of bytes written are returned.
37473 Zero indicates nothing was written. On error, -1
37480 @var{fd} is not a valid file descriptor or is not open for
37484 @var{bufptr} is an invalid pointer value.
37487 An attempt was made to write a file that exceeds the
37488 host-specific maximum file size allowed.
37491 No space on device to write the data.
37494 The call was interrupted by the user.
37500 @unnumberedsubsubsec lseek
37501 @cindex lseek, file-i/o system call
37506 long lseek (int fd, long offset, int flag);
37510 @samp{Flseek,@var{fd},@var{offset},@var{flag}}
37512 @var{flag} is one of:
37516 The offset is set to @var{offset} bytes.
37519 The offset is set to its current location plus @var{offset}
37523 The offset is set to the size of the file plus @var{offset}
37527 @item Return value:
37528 On success, the resulting unsigned offset in bytes from
37529 the beginning of the file is returned. Otherwise, a
37530 value of -1 is returned.
37536 @var{fd} is not a valid open file descriptor.
37539 @var{fd} is associated with the @value{GDBN} console.
37542 @var{flag} is not a proper value.
37545 The call was interrupted by the user.
37551 @unnumberedsubsubsec rename
37552 @cindex rename, file-i/o system call
37557 int rename(const char *oldpath, const char *newpath);
37561 @samp{Frename,@var{oldpathptr}/@var{len},@var{newpathptr}/@var{len}}
37563 @item Return value:
37564 On success, zero is returned. On error, -1 is returned.
37570 @var{newpath} is an existing directory, but @var{oldpath} is not a
37574 @var{newpath} is a non-empty directory.
37577 @var{oldpath} or @var{newpath} is a directory that is in use by some
37581 An attempt was made to make a directory a subdirectory
37585 A component used as a directory in @var{oldpath} or new
37586 path is not a directory. Or @var{oldpath} is a directory
37587 and @var{newpath} exists but is not a directory.
37590 @var{oldpathptr} or @var{newpathptr} are invalid pointer values.
37593 No access to the file or the path of the file.
37597 @var{oldpath} or @var{newpath} was too long.
37600 A directory component in @var{oldpath} or @var{newpath} does not exist.
37603 The file is on a read-only filesystem.
37606 The device containing the file has no room for the new
37610 The call was interrupted by the user.
37616 @unnumberedsubsubsec unlink
37617 @cindex unlink, file-i/o system call
37622 int unlink(const char *pathname);
37626 @samp{Funlink,@var{pathnameptr}/@var{len}}
37628 @item Return value:
37629 On success, zero is returned. On error, -1 is returned.
37635 No access to the file or the path of the file.
37638 The system does not allow unlinking of directories.
37641 The file @var{pathname} cannot be unlinked because it's
37642 being used by another process.
37645 @var{pathnameptr} is an invalid pointer value.
37648 @var{pathname} was too long.
37651 A directory component in @var{pathname} does not exist.
37654 A component of the path is not a directory.
37657 The file is on a read-only filesystem.
37660 The call was interrupted by the user.
37666 @unnumberedsubsubsec stat/fstat
37667 @cindex fstat, file-i/o system call
37668 @cindex stat, file-i/o system call
37673 int stat(const char *pathname, struct stat *buf);
37674 int fstat(int fd, struct stat *buf);
37678 @samp{Fstat,@var{pathnameptr}/@var{len},@var{bufptr}}@*
37679 @samp{Ffstat,@var{fd},@var{bufptr}}
37681 @item Return value:
37682 On success, zero is returned. On error, -1 is returned.
37688 @var{fd} is not a valid open file.
37691 A directory component in @var{pathname} does not exist or the
37692 path is an empty string.
37695 A component of the path is not a directory.
37698 @var{pathnameptr} is an invalid pointer value.
37701 No access to the file or the path of the file.
37704 @var{pathname} was too long.
37707 The call was interrupted by the user.
37713 @unnumberedsubsubsec gettimeofday
37714 @cindex gettimeofday, file-i/o system call
37719 int gettimeofday(struct timeval *tv, void *tz);
37723 @samp{Fgettimeofday,@var{tvptr},@var{tzptr}}
37725 @item Return value:
37726 On success, 0 is returned, -1 otherwise.
37732 @var{tz} is a non-NULL pointer.
37735 @var{tvptr} and/or @var{tzptr} is an invalid pointer value.
37741 @unnumberedsubsubsec isatty
37742 @cindex isatty, file-i/o system call
37747 int isatty(int fd);
37751 @samp{Fisatty,@var{fd}}
37753 @item Return value:
37754 Returns 1 if @var{fd} refers to the @value{GDBN} console, 0 otherwise.
37760 The call was interrupted by the user.
37765 Note that the @code{isatty} call is treated as a special case: it returns
37766 1 to the target if the file descriptor is attached
37767 to the @value{GDBN} console, 0 otherwise. Implementing through system calls
37768 would require implementing @code{ioctl} and would be more complex than
37773 @unnumberedsubsubsec system
37774 @cindex system, file-i/o system call
37779 int system(const char *command);
37783 @samp{Fsystem,@var{commandptr}/@var{len}}
37785 @item Return value:
37786 If @var{len} is zero, the return value indicates whether a shell is
37787 available. A zero return value indicates a shell is not available.
37788 For non-zero @var{len}, the value returned is -1 on error and the
37789 return status of the command otherwise. Only the exit status of the
37790 command is returned, which is extracted from the host's @code{system}
37791 return value by calling @code{WEXITSTATUS(retval)}. In case
37792 @file{/bin/sh} could not be executed, 127 is returned.
37798 The call was interrupted by the user.
37803 @value{GDBN} takes over the full task of calling the necessary host calls
37804 to perform the @code{system} call. The return value of @code{system} on
37805 the host is simplified before it's returned
37806 to the target. Any termination signal information from the child process
37807 is discarded, and the return value consists
37808 entirely of the exit status of the called command.
37810 Due to security concerns, the @code{system} call is by default refused
37811 by @value{GDBN}. The user has to allow this call explicitly with the
37812 @code{set remote system-call-allowed 1} command.
37815 @item set remote system-call-allowed
37816 @kindex set remote system-call-allowed
37817 Control whether to allow the @code{system} calls in the File I/O
37818 protocol for the remote target. The default is zero (disabled).
37820 @item show remote system-call-allowed
37821 @kindex show remote system-call-allowed
37822 Show whether the @code{system} calls are allowed in the File I/O
37826 @node Protocol-specific Representation of Datatypes
37827 @subsection Protocol-specific Representation of Datatypes
37828 @cindex protocol-specific representation of datatypes, in file-i/o protocol
37831 * Integral Datatypes::
37833 * Memory Transfer::
37838 @node Integral Datatypes
37839 @unnumberedsubsubsec Integral Datatypes
37840 @cindex integral datatypes, in file-i/o protocol
37842 The integral datatypes used in the system calls are @code{int},
37843 @code{unsigned int}, @code{long}, @code{unsigned long},
37844 @code{mode_t}, and @code{time_t}.
37846 @code{int}, @code{unsigned int}, @code{mode_t} and @code{time_t} are
37847 implemented as 32 bit values in this protocol.
37849 @code{long} and @code{unsigned long} are implemented as 64 bit types.
37851 @xref{Limits}, for corresponding MIN and MAX values (similar to those
37852 in @file{limits.h}) to allow range checking on host and target.
37854 @code{time_t} datatypes are defined as seconds since the Epoch.
37856 All integral datatypes transferred as part of a memory read or write of a
37857 structured datatype e.g.@: a @code{struct stat} have to be given in big endian
37860 @node Pointer Values
37861 @unnumberedsubsubsec Pointer Values
37862 @cindex pointer values, in file-i/o protocol
37864 Pointers to target data are transmitted as they are. An exception
37865 is made for pointers to buffers for which the length isn't
37866 transmitted as part of the function call, namely strings. Strings
37867 are transmitted as a pointer/length pair, both as hex values, e.g.@:
37874 which is a pointer to data of length 18 bytes at position 0x1aaf.
37875 The length is defined as the full string length in bytes, including
37876 the trailing null byte. For example, the string @code{"hello world"}
37877 at address 0x123456 is transmitted as
37883 @node Memory Transfer
37884 @unnumberedsubsubsec Memory Transfer
37885 @cindex memory transfer, in file-i/o protocol
37887 Structured data which is transferred using a memory read or write (for
37888 example, a @code{struct stat}) is expected to be in a protocol-specific format
37889 with all scalar multibyte datatypes being big endian. Translation to
37890 this representation needs to be done both by the target before the @code{F}
37891 packet is sent, and by @value{GDBN} before
37892 it transfers memory to the target. Transferred pointers to structured
37893 data should point to the already-coerced data at any time.
37897 @unnumberedsubsubsec struct stat
37898 @cindex struct stat, in file-i/o protocol
37900 The buffer of type @code{struct stat} used by the target and @value{GDBN}
37901 is defined as follows:
37905 unsigned int st_dev; /* device */
37906 unsigned int st_ino; /* inode */
37907 mode_t st_mode; /* protection */
37908 unsigned int st_nlink; /* number of hard links */
37909 unsigned int st_uid; /* user ID of owner */
37910 unsigned int st_gid; /* group ID of owner */
37911 unsigned int st_rdev; /* device type (if inode device) */
37912 unsigned long st_size; /* total size, in bytes */
37913 unsigned long st_blksize; /* blocksize for filesystem I/O */
37914 unsigned long st_blocks; /* number of blocks allocated */
37915 time_t st_atime; /* time of last access */
37916 time_t st_mtime; /* time of last modification */
37917 time_t st_ctime; /* time of last change */
37921 The integral datatypes conform to the definitions given in the
37922 appropriate section (see @ref{Integral Datatypes}, for details) so this
37923 structure is of size 64 bytes.
37925 The values of several fields have a restricted meaning and/or
37931 A value of 0 represents a file, 1 the console.
37934 No valid meaning for the target. Transmitted unchanged.
37937 Valid mode bits are described in @ref{Constants}. Any other
37938 bits have currently no meaning for the target.
37943 No valid meaning for the target. Transmitted unchanged.
37948 These values have a host and file system dependent
37949 accuracy. Especially on Windows hosts, the file system may not
37950 support exact timing values.
37953 The target gets a @code{struct stat} of the above representation and is
37954 responsible for coercing it to the target representation before
37957 Note that due to size differences between the host, target, and protocol
37958 representations of @code{struct stat} members, these members could eventually
37959 get truncated on the target.
37961 @node struct timeval
37962 @unnumberedsubsubsec struct timeval
37963 @cindex struct timeval, in file-i/o protocol
37965 The buffer of type @code{struct timeval} used by the File-I/O protocol
37966 is defined as follows:
37970 time_t tv_sec; /* second */
37971 long tv_usec; /* microsecond */
37975 The integral datatypes conform to the definitions given in the
37976 appropriate section (see @ref{Integral Datatypes}, for details) so this
37977 structure is of size 8 bytes.
37980 @subsection Constants
37981 @cindex constants, in file-i/o protocol
37983 The following values are used for the constants inside of the
37984 protocol. @value{GDBN} and target are responsible for translating these
37985 values before and after the call as needed.
37996 @unnumberedsubsubsec Open Flags
37997 @cindex open flags, in file-i/o protocol
37999 All values are given in hexadecimal representation.
38011 @node mode_t Values
38012 @unnumberedsubsubsec mode_t Values
38013 @cindex mode_t values, in file-i/o protocol
38015 All values are given in octal representation.
38032 @unnumberedsubsubsec Errno Values
38033 @cindex errno values, in file-i/o protocol
38035 All values are given in decimal representation.
38060 @code{EUNKNOWN} is used as a fallback error value if a host system returns
38061 any error value not in the list of supported error numbers.
38064 @unnumberedsubsubsec Lseek Flags
38065 @cindex lseek flags, in file-i/o protocol
38074 @unnumberedsubsubsec Limits
38075 @cindex limits, in file-i/o protocol
38077 All values are given in decimal representation.
38080 INT_MIN -2147483648
38082 UINT_MAX 4294967295
38083 LONG_MIN -9223372036854775808
38084 LONG_MAX 9223372036854775807
38085 ULONG_MAX 18446744073709551615
38088 @node File-I/O Examples
38089 @subsection File-I/O Examples
38090 @cindex file-i/o examples
38092 Example sequence of a write call, file descriptor 3, buffer is at target
38093 address 0x1234, 6 bytes should be written:
38096 <- @code{Fwrite,3,1234,6}
38097 @emph{request memory read from target}
38100 @emph{return "6 bytes written"}
38104 Example sequence of a read call, file descriptor 3, buffer is at target
38105 address 0x1234, 6 bytes should be read:
38108 <- @code{Fread,3,1234,6}
38109 @emph{request memory write to target}
38110 -> @code{X1234,6:XXXXXX}
38111 @emph{return "6 bytes read"}
38115 Example sequence of a read call, call fails on the host due to invalid
38116 file descriptor (@code{EBADF}):
38119 <- @code{Fread,3,1234,6}
38123 Example sequence of a read call, user presses @kbd{Ctrl-c} before syscall on
38127 <- @code{Fread,3,1234,6}
38132 Example sequence of a read call, user presses @kbd{Ctrl-c} after syscall on
38136 <- @code{Fread,3,1234,6}
38137 -> @code{X1234,6:XXXXXX}
38141 @node Library List Format
38142 @section Library List Format
38143 @cindex library list format, remote protocol
38145 On some platforms, a dynamic loader (e.g.@: @file{ld.so}) runs in the
38146 same process as your application to manage libraries. In this case,
38147 @value{GDBN} can use the loader's symbol table and normal memory
38148 operations to maintain a list of shared libraries. On other
38149 platforms, the operating system manages loaded libraries.
38150 @value{GDBN} can not retrieve the list of currently loaded libraries
38151 through memory operations, so it uses the @samp{qXfer:libraries:read}
38152 packet (@pxref{qXfer library list read}) instead. The remote stub
38153 queries the target's operating system and reports which libraries
38156 The @samp{qXfer:libraries:read} packet returns an XML document which
38157 lists loaded libraries and their offsets. Each library has an
38158 associated name and one or more segment or section base addresses,
38159 which report where the library was loaded in memory.
38161 For the common case of libraries that are fully linked binaries, the
38162 library should have a list of segments. If the target supports
38163 dynamic linking of a relocatable object file, its library XML element
38164 should instead include a list of allocated sections. The segment or
38165 section bases are start addresses, not relocation offsets; they do not
38166 depend on the library's link-time base addresses.
38168 @value{GDBN} must be linked with the Expat library to support XML
38169 library lists. @xref{Expat}.
38171 A simple memory map, with one loaded library relocated by a single
38172 offset, looks like this:
38176 <library name="/lib/libc.so.6">
38177 <segment address="0x10000000"/>
38182 Another simple memory map, with one loaded library with three
38183 allocated sections (.text, .data, .bss), looks like this:
38187 <library name="sharedlib.o">
38188 <section address="0x10000000"/>
38189 <section address="0x20000000"/>
38190 <section address="0x30000000"/>
38195 The format of a library list is described by this DTD:
38198 <!-- library-list: Root element with versioning -->
38199 <!ELEMENT library-list (library)*>
38200 <!ATTLIST library-list version CDATA #FIXED "1.0">
38201 <!ELEMENT library (segment*, section*)>
38202 <!ATTLIST library name CDATA #REQUIRED>
38203 <!ELEMENT segment EMPTY>
38204 <!ATTLIST segment address CDATA #REQUIRED>
38205 <!ELEMENT section EMPTY>
38206 <!ATTLIST section address CDATA #REQUIRED>
38209 In addition, segments and section descriptors cannot be mixed within a
38210 single library element, and you must supply at least one segment or
38211 section for each library.
38213 @node Library List Format for SVR4 Targets
38214 @section Library List Format for SVR4 Targets
38215 @cindex library list format, remote protocol
38217 On SVR4 platforms @value{GDBN} can use the symbol table of a dynamic loader
38218 (e.g.@: @file{ld.so}) and normal memory operations to maintain a list of
38219 shared libraries. Still a special library list provided by this packet is
38220 more efficient for the @value{GDBN} remote protocol.
38222 The @samp{qXfer:libraries-svr4:read} packet returns an XML document which lists
38223 loaded libraries and their SVR4 linker parameters. For each library on SVR4
38224 target, the following parameters are reported:
38228 @code{name}, the absolute file name from the @code{l_name} field of
38229 @code{struct link_map}.
38231 @code{lm} with address of @code{struct link_map} used for TLS
38232 (Thread Local Storage) access.
38234 @code{l_addr}, the displacement as read from the field @code{l_addr} of
38235 @code{struct link_map}. For prelinked libraries this is not an absolute
38236 memory address. It is a displacement of absolute memory address against
38237 address the file was prelinked to during the library load.
38239 @code{l_ld}, which is memory address of the @code{PT_DYNAMIC} segment
38242 Additionally the single @code{main-lm} attribute specifies address of
38243 @code{struct link_map} used for the main executable. This parameter is used
38244 for TLS access and its presence is optional.
38246 @value{GDBN} must be linked with the Expat library to support XML
38247 SVR4 library lists. @xref{Expat}.
38249 A simple memory map, with two loaded libraries (which do not use prelink),
38253 <library-list-svr4 version="1.0" main-lm="0xe4f8f8">
38254 <library name="/lib/ld-linux.so.2" lm="0xe4f51c" l_addr="0xe2d000"
38256 <library name="/lib/libc.so.6" lm="0xe4fbe8" l_addr="0x154000"
38258 </library-list-svr>
38261 The format of an SVR4 library list is described by this DTD:
38264 <!-- library-list-svr4: Root element with versioning -->
38265 <!ELEMENT library-list-svr4 (library)*>
38266 <!ATTLIST library-list-svr4 version CDATA #FIXED "1.0">
38267 <!ATTLIST library-list-svr4 main-lm CDATA #IMPLIED>
38268 <!ELEMENT library EMPTY>
38269 <!ATTLIST library name CDATA #REQUIRED>
38270 <!ATTLIST library lm CDATA #REQUIRED>
38271 <!ATTLIST library l_addr CDATA #REQUIRED>
38272 <!ATTLIST library l_ld CDATA #REQUIRED>
38275 @node Memory Map Format
38276 @section Memory Map Format
38277 @cindex memory map format
38279 To be able to write into flash memory, @value{GDBN} needs to obtain a
38280 memory map from the target. This section describes the format of the
38283 The memory map is obtained using the @samp{qXfer:memory-map:read}
38284 (@pxref{qXfer memory map read}) packet and is an XML document that
38285 lists memory regions.
38287 @value{GDBN} must be linked with the Expat library to support XML
38288 memory maps. @xref{Expat}.
38290 The top-level structure of the document is shown below:
38293 <?xml version="1.0"?>
38294 <!DOCTYPE memory-map
38295 PUBLIC "+//IDN gnu.org//DTD GDB Memory Map V1.0//EN"
38296 "http://sourceware.org/gdb/gdb-memory-map.dtd">
38302 Each region can be either:
38307 A region of RAM starting at @var{addr} and extending for @var{length}
38311 <memory type="ram" start="@var{addr}" length="@var{length}"/>
38316 A region of read-only memory:
38319 <memory type="rom" start="@var{addr}" length="@var{length}"/>
38324 A region of flash memory, with erasure blocks @var{blocksize}
38328 <memory type="flash" start="@var{addr}" length="@var{length}">
38329 <property name="blocksize">@var{blocksize}</property>
38335 Regions must not overlap. @value{GDBN} assumes that areas of memory not covered
38336 by the memory map are RAM, and uses the ordinary @samp{M} and @samp{X}
38337 packets to write to addresses in such ranges.
38339 The formal DTD for memory map format is given below:
38342 <!-- ................................................... -->
38343 <!-- Memory Map XML DTD ................................ -->
38344 <!-- File: memory-map.dtd .............................. -->
38345 <!-- .................................... .............. -->
38346 <!-- memory-map.dtd -->
38347 <!-- memory-map: Root element with versioning -->
38348 <!ELEMENT memory-map (memory | property)>
38349 <!ATTLIST memory-map version CDATA #FIXED "1.0.0">
38350 <!ELEMENT memory (property)>
38351 <!-- memory: Specifies a memory region,
38352 and its type, or device. -->
38353 <!ATTLIST memory type CDATA #REQUIRED
38354 start CDATA #REQUIRED
38355 length CDATA #REQUIRED
38356 device CDATA #IMPLIED>
38357 <!-- property: Generic attribute tag -->
38358 <!ELEMENT property (#PCDATA | property)*>
38359 <!ATTLIST property name CDATA #REQUIRED>
38362 @node Thread List Format
38363 @section Thread List Format
38364 @cindex thread list format
38366 To efficiently update the list of threads and their attributes,
38367 @value{GDBN} issues the @samp{qXfer:threads:read} packet
38368 (@pxref{qXfer threads read}) and obtains the XML document with
38369 the following structure:
38372 <?xml version="1.0"?>
38374 <thread id="id" core="0">
38375 ... description ...
38380 Each @samp{thread} element must have the @samp{id} attribute that
38381 identifies the thread (@pxref{thread-id syntax}). The
38382 @samp{core} attribute, if present, specifies which processor core
38383 the thread was last executing on. The content of the of @samp{thread}
38384 element is interpreted as human-readable auxilliary information.
38386 @node Traceframe Info Format
38387 @section Traceframe Info Format
38388 @cindex traceframe info format
38390 To be able to know which objects in the inferior can be examined when
38391 inspecting a tracepoint hit, @value{GDBN} needs to obtain the list of
38392 memory ranges, registers and trace state variables that have been
38393 collected in a traceframe.
38395 This list is obtained using the @samp{qXfer:traceframe-info:read}
38396 (@pxref{qXfer traceframe info read}) packet and is an XML document.
38398 @value{GDBN} must be linked with the Expat library to support XML
38399 traceframe info discovery. @xref{Expat}.
38401 The top-level structure of the document is shown below:
38404 <?xml version="1.0"?>
38405 <!DOCTYPE traceframe-info
38406 PUBLIC "+//IDN gnu.org//DTD GDB Memory Map V1.0//EN"
38407 "http://sourceware.org/gdb/gdb-traceframe-info.dtd">
38413 Each traceframe block can be either:
38418 A region of collected memory starting at @var{addr} and extending for
38419 @var{length} bytes from there:
38422 <memory start="@var{addr}" length="@var{length}"/>
38427 The formal DTD for the traceframe info format is given below:
38430 <!ELEMENT traceframe-info (memory)* >
38431 <!ATTLIST traceframe-info version CDATA #FIXED "1.0">
38433 <!ELEMENT memory EMPTY>
38434 <!ATTLIST memory start CDATA #REQUIRED
38435 length CDATA #REQUIRED>
38438 @include agentexpr.texi
38440 @node Target Descriptions
38441 @appendix Target Descriptions
38442 @cindex target descriptions
38444 One of the challenges of using @value{GDBN} to debug embedded systems
38445 is that there are so many minor variants of each processor
38446 architecture in use. It is common practice for vendors to start with
38447 a standard processor core --- ARM, PowerPC, or MIPS, for example ---
38448 and then make changes to adapt it to a particular market niche. Some
38449 architectures have hundreds of variants, available from dozens of
38450 vendors. This leads to a number of problems:
38454 With so many different customized processors, it is difficult for
38455 the @value{GDBN} maintainers to keep up with the changes.
38457 Since individual variants may have short lifetimes or limited
38458 audiences, it may not be worthwhile to carry information about every
38459 variant in the @value{GDBN} source tree.
38461 When @value{GDBN} does support the architecture of the embedded system
38462 at hand, the task of finding the correct architecture name to give the
38463 @command{set architecture} command can be error-prone.
38466 To address these problems, the @value{GDBN} remote protocol allows a
38467 target system to not only identify itself to @value{GDBN}, but to
38468 actually describe its own features. This lets @value{GDBN} support
38469 processor variants it has never seen before --- to the extent that the
38470 descriptions are accurate, and that @value{GDBN} understands them.
38472 @value{GDBN} must be linked with the Expat library to support XML
38473 target descriptions. @xref{Expat}.
38476 * Retrieving Descriptions:: How descriptions are fetched from a target.
38477 * Target Description Format:: The contents of a target description.
38478 * Predefined Target Types:: Standard types available for target
38480 * Standard Target Features:: Features @value{GDBN} knows about.
38483 @node Retrieving Descriptions
38484 @section Retrieving Descriptions
38486 Target descriptions can be read from the target automatically, or
38487 specified by the user manually. The default behavior is to read the
38488 description from the target. @value{GDBN} retrieves it via the remote
38489 protocol using @samp{qXfer} requests (@pxref{General Query Packets,
38490 qXfer}). The @var{annex} in the @samp{qXfer} packet will be
38491 @samp{target.xml}. The contents of the @samp{target.xml} annex are an
38492 XML document, of the form described in @ref{Target Description
38495 Alternatively, you can specify a file to read for the target description.
38496 If a file is set, the target will not be queried. The commands to
38497 specify a file are:
38500 @cindex set tdesc filename
38501 @item set tdesc filename @var{path}
38502 Read the target description from @var{path}.
38504 @cindex unset tdesc filename
38505 @item unset tdesc filename
38506 Do not read the XML target description from a file. @value{GDBN}
38507 will use the description supplied by the current target.
38509 @cindex show tdesc filename
38510 @item show tdesc filename
38511 Show the filename to read for a target description, if any.
38515 @node Target Description Format
38516 @section Target Description Format
38517 @cindex target descriptions, XML format
38519 A target description annex is an @uref{http://www.w3.org/XML/, XML}
38520 document which complies with the Document Type Definition provided in
38521 the @value{GDBN} sources in @file{gdb/features/gdb-target.dtd}. This
38522 means you can use generally available tools like @command{xmllint} to
38523 check that your feature descriptions are well-formed and valid.
38524 However, to help people unfamiliar with XML write descriptions for
38525 their targets, we also describe the grammar here.
38527 Target descriptions can identify the architecture of the remote target
38528 and (for some architectures) provide information about custom register
38529 sets. They can also identify the OS ABI of the remote target.
38530 @value{GDBN} can use this information to autoconfigure for your
38531 target, or to warn you if you connect to an unsupported target.
38533 Here is a simple target description:
38536 <target version="1.0">
38537 <architecture>i386:x86-64</architecture>
38542 This minimal description only says that the target uses
38543 the x86-64 architecture.
38545 A target description has the following overall form, with [ ] marking
38546 optional elements and @dots{} marking repeatable elements. The elements
38547 are explained further below.
38550 <?xml version="1.0"?>
38551 <!DOCTYPE target SYSTEM "gdb-target.dtd">
38552 <target version="1.0">
38553 @r{[}@var{architecture}@r{]}
38554 @r{[}@var{osabi}@r{]}
38555 @r{[}@var{compatible}@r{]}
38556 @r{[}@var{feature}@dots{}@r{]}
38561 The description is generally insensitive to whitespace and line
38562 breaks, under the usual common-sense rules. The XML version
38563 declaration and document type declaration can generally be omitted
38564 (@value{GDBN} does not require them), but specifying them may be
38565 useful for XML validation tools. The @samp{version} attribute for
38566 @samp{<target>} may also be omitted, but we recommend
38567 including it; if future versions of @value{GDBN} use an incompatible
38568 revision of @file{gdb-target.dtd}, they will detect and report
38569 the version mismatch.
38571 @subsection Inclusion
38572 @cindex target descriptions, inclusion
38575 @cindex <xi:include>
38578 It can sometimes be valuable to split a target description up into
38579 several different annexes, either for organizational purposes, or to
38580 share files between different possible target descriptions. You can
38581 divide a description into multiple files by replacing any element of
38582 the target description with an inclusion directive of the form:
38585 <xi:include href="@var{document}"/>
38589 When @value{GDBN} encounters an element of this form, it will retrieve
38590 the named XML @var{document}, and replace the inclusion directive with
38591 the contents of that document. If the current description was read
38592 using @samp{qXfer}, then so will be the included document;
38593 @var{document} will be interpreted as the name of an annex. If the
38594 current description was read from a file, @value{GDBN} will look for
38595 @var{document} as a file in the same directory where it found the
38596 original description.
38598 @subsection Architecture
38599 @cindex <architecture>
38601 An @samp{<architecture>} element has this form:
38604 <architecture>@var{arch}</architecture>
38607 @var{arch} is one of the architectures from the set accepted by
38608 @code{set architecture} (@pxref{Targets, ,Specifying a Debugging Target}).
38611 @cindex @code{<osabi>}
38613 This optional field was introduced in @value{GDBN} version 7.0.
38614 Previous versions of @value{GDBN} ignore it.
38616 An @samp{<osabi>} element has this form:
38619 <osabi>@var{abi-name}</osabi>
38622 @var{abi-name} is an OS ABI name from the same selection accepted by
38623 @w{@code{set osabi}} (@pxref{ABI, ,Configuring the Current ABI}).
38625 @subsection Compatible Architecture
38626 @cindex @code{<compatible>}
38628 This optional field was introduced in @value{GDBN} version 7.0.
38629 Previous versions of @value{GDBN} ignore it.
38631 A @samp{<compatible>} element has this form:
38634 <compatible>@var{arch}</compatible>
38637 @var{arch} is one of the architectures from the set accepted by
38638 @code{set architecture} (@pxref{Targets, ,Specifying a Debugging Target}).
38640 A @samp{<compatible>} element is used to specify that the target
38641 is able to run binaries in some other than the main target architecture
38642 given by the @samp{<architecture>} element. For example, on the
38643 Cell Broadband Engine, the main architecture is @code{powerpc:common}
38644 or @code{powerpc:common64}, but the system is able to run binaries
38645 in the @code{spu} architecture as well. The way to describe this
38646 capability with @samp{<compatible>} is as follows:
38649 <architecture>powerpc:common</architecture>
38650 <compatible>spu</compatible>
38653 @subsection Features
38656 Each @samp{<feature>} describes some logical portion of the target
38657 system. Features are currently used to describe available CPU
38658 registers and the types of their contents. A @samp{<feature>} element
38662 <feature name="@var{name}">
38663 @r{[}@var{type}@dots{}@r{]}
38669 Each feature's name should be unique within the description. The name
38670 of a feature does not matter unless @value{GDBN} has some special
38671 knowledge of the contents of that feature; if it does, the feature
38672 should have its standard name. @xref{Standard Target Features}.
38676 Any register's value is a collection of bits which @value{GDBN} must
38677 interpret. The default interpretation is a two's complement integer,
38678 but other types can be requested by name in the register description.
38679 Some predefined types are provided by @value{GDBN} (@pxref{Predefined
38680 Target Types}), and the description can define additional composite types.
38682 Each type element must have an @samp{id} attribute, which gives
38683 a unique (within the containing @samp{<feature>}) name to the type.
38684 Types must be defined before they are used.
38687 Some targets offer vector registers, which can be treated as arrays
38688 of scalar elements. These types are written as @samp{<vector>} elements,
38689 specifying the array element type, @var{type}, and the number of elements,
38693 <vector id="@var{id}" type="@var{type}" count="@var{count}"/>
38697 If a register's value is usefully viewed in multiple ways, define it
38698 with a union type containing the useful representations. The
38699 @samp{<union>} element contains one or more @samp{<field>} elements,
38700 each of which has a @var{name} and a @var{type}:
38703 <union id="@var{id}">
38704 <field name="@var{name}" type="@var{type}"/>
38710 If a register's value is composed from several separate values, define
38711 it with a structure type. There are two forms of the @samp{<struct>}
38712 element; a @samp{<struct>} element must either contain only bitfields
38713 or contain no bitfields. If the structure contains only bitfields,
38714 its total size in bytes must be specified, each bitfield must have an
38715 explicit start and end, and bitfields are automatically assigned an
38716 integer type. The field's @var{start} should be less than or
38717 equal to its @var{end}, and zero represents the least significant bit.
38720 <struct id="@var{id}" size="@var{size}">
38721 <field name="@var{name}" start="@var{start}" end="@var{end}"/>
38726 If the structure contains no bitfields, then each field has an
38727 explicit type, and no implicit padding is added.
38730 <struct id="@var{id}">
38731 <field name="@var{name}" type="@var{type}"/>
38737 If a register's value is a series of single-bit flags, define it with
38738 a flags type. The @samp{<flags>} element has an explicit @var{size}
38739 and contains one or more @samp{<field>} elements. Each field has a
38740 @var{name}, a @var{start}, and an @var{end}. Only single-bit flags
38744 <flags id="@var{id}" size="@var{size}">
38745 <field name="@var{name}" start="@var{start}" end="@var{end}"/>
38750 @subsection Registers
38753 Each register is represented as an element with this form:
38756 <reg name="@var{name}"
38757 bitsize="@var{size}"
38758 @r{[}regnum="@var{num}"@r{]}
38759 @r{[}save-restore="@var{save-restore}"@r{]}
38760 @r{[}type="@var{type}"@r{]}
38761 @r{[}group="@var{group}"@r{]}/>
38765 The components are as follows:
38770 The register's name; it must be unique within the target description.
38773 The register's size, in bits.
38776 The register's number. If omitted, a register's number is one greater
38777 than that of the previous register (either in the current feature or in
38778 a preceding feature); the first register in the target description
38779 defaults to zero. This register number is used to read or write
38780 the register; e.g.@: it is used in the remote @code{p} and @code{P}
38781 packets, and registers appear in the @code{g} and @code{G} packets
38782 in order of increasing register number.
38785 Whether the register should be preserved across inferior function
38786 calls; this must be either @code{yes} or @code{no}. The default is
38787 @code{yes}, which is appropriate for most registers except for
38788 some system control registers; this is not related to the target's
38792 The type of the register. @var{type} may be a predefined type, a type
38793 defined in the current feature, or one of the special types @code{int}
38794 and @code{float}. @code{int} is an integer type of the correct size
38795 for @var{bitsize}, and @code{float} is a floating point type (in the
38796 architecture's normal floating point format) of the correct size for
38797 @var{bitsize}. The default is @code{int}.
38800 The register group to which this register belongs. @var{group} must
38801 be either @code{general}, @code{float}, or @code{vector}. If no
38802 @var{group} is specified, @value{GDBN} will not display the register
38803 in @code{info registers}.
38807 @node Predefined Target Types
38808 @section Predefined Target Types
38809 @cindex target descriptions, predefined types
38811 Type definitions in the self-description can build up composite types
38812 from basic building blocks, but can not define fundamental types. Instead,
38813 standard identifiers are provided by @value{GDBN} for the fundamental
38814 types. The currently supported types are:
38823 Signed integer types holding the specified number of bits.
38830 Unsigned integer types holding the specified number of bits.
38834 Pointers to unspecified code and data. The program counter and
38835 any dedicated return address register may be marked as code
38836 pointers; printing a code pointer converts it into a symbolic
38837 address. The stack pointer and any dedicated address registers
38838 may be marked as data pointers.
38841 Single precision IEEE floating point.
38844 Double precision IEEE floating point.
38847 The 12-byte extended precision format used by ARM FPA registers.
38850 The 10-byte extended precision format used by x87 registers.
38853 32bit @sc{eflags} register used by x86.
38856 32bit @sc{mxcsr} register used by x86.
38860 @node Standard Target Features
38861 @section Standard Target Features
38862 @cindex target descriptions, standard features
38864 A target description must contain either no registers or all the
38865 target's registers. If the description contains no registers, then
38866 @value{GDBN} will assume a default register layout, selected based on
38867 the architecture. If the description contains any registers, the
38868 default layout will not be used; the standard registers must be
38869 described in the target description, in such a way that @value{GDBN}
38870 can recognize them.
38872 This is accomplished by giving specific names to feature elements
38873 which contain standard registers. @value{GDBN} will look for features
38874 with those names and verify that they contain the expected registers;
38875 if any known feature is missing required registers, or if any required
38876 feature is missing, @value{GDBN} will reject the target
38877 description. You can add additional registers to any of the
38878 standard features --- @value{GDBN} will display them just as if
38879 they were added to an unrecognized feature.
38881 This section lists the known features and their expected contents.
38882 Sample XML documents for these features are included in the
38883 @value{GDBN} source tree, in the directory @file{gdb/features}.
38885 Names recognized by @value{GDBN} should include the name of the
38886 company or organization which selected the name, and the overall
38887 architecture to which the feature applies; so e.g.@: the feature
38888 containing ARM core registers is named @samp{org.gnu.gdb.arm.core}.
38890 The names of registers are not case sensitive for the purpose
38891 of recognizing standard features, but @value{GDBN} will only display
38892 registers using the capitalization used in the description.
38899 * PowerPC Features::
38905 @subsection ARM Features
38906 @cindex target descriptions, ARM features
38908 The @samp{org.gnu.gdb.arm.core} feature is required for non-M-profile
38910 It should contain registers @samp{r0} through @samp{r13}, @samp{sp},
38911 @samp{lr}, @samp{pc}, and @samp{cpsr}.
38913 For M-profile targets (e.g. Cortex-M3), the @samp{org.gnu.gdb.arm.core}
38914 feature is replaced by @samp{org.gnu.gdb.arm.m-profile}. It should contain
38915 registers @samp{r0} through @samp{r13}, @samp{sp}, @samp{lr}, @samp{pc},
38918 The @samp{org.gnu.gdb.arm.fpa} feature is optional. If present, it
38919 should contain registers @samp{f0} through @samp{f7} and @samp{fps}.
38921 The @samp{org.gnu.gdb.xscale.iwmmxt} feature is optional. If present,
38922 it should contain at least registers @samp{wR0} through @samp{wR15} and
38923 @samp{wCGR0} through @samp{wCGR3}. The @samp{wCID}, @samp{wCon},
38924 @samp{wCSSF}, and @samp{wCASF} registers are optional.
38926 The @samp{org.gnu.gdb.arm.vfp} feature is optional. If present, it
38927 should contain at least registers @samp{d0} through @samp{d15}. If
38928 they are present, @samp{d16} through @samp{d31} should also be included.
38929 @value{GDBN} will synthesize the single-precision registers from
38930 halves of the double-precision registers.
38932 The @samp{org.gnu.gdb.arm.neon} feature is optional. It does not
38933 need to contain registers; it instructs @value{GDBN} to display the
38934 VFP double-precision registers as vectors and to synthesize the
38935 quad-precision registers from pairs of double-precision registers.
38936 If this feature is present, @samp{org.gnu.gdb.arm.vfp} must also
38937 be present and include 32 double-precision registers.
38939 @node i386 Features
38940 @subsection i386 Features
38941 @cindex target descriptions, i386 features
38943 The @samp{org.gnu.gdb.i386.core} feature is required for i386/amd64
38944 targets. It should describe the following registers:
38948 @samp{eax} through @samp{edi} plus @samp{eip} for i386
38950 @samp{rax} through @samp{r15} plus @samp{rip} for amd64
38952 @samp{eflags}, @samp{cs}, @samp{ss}, @samp{ds}, @samp{es},
38953 @samp{fs}, @samp{gs}
38955 @samp{st0} through @samp{st7}
38957 @samp{fctrl}, @samp{fstat}, @samp{ftag}, @samp{fiseg}, @samp{fioff},
38958 @samp{foseg}, @samp{fooff} and @samp{fop}
38961 The register sets may be different, depending on the target.
38963 The @samp{org.gnu.gdb.i386.sse} feature is optional. It should
38964 describe registers:
38968 @samp{xmm0} through @samp{xmm7} for i386
38970 @samp{xmm0} through @samp{xmm15} for amd64
38975 The @samp{org.gnu.gdb.i386.avx} feature is optional and requires the
38976 @samp{org.gnu.gdb.i386.sse} feature. It should
38977 describe the upper 128 bits of @sc{ymm} registers:
38981 @samp{ymm0h} through @samp{ymm7h} for i386
38983 @samp{ymm0h} through @samp{ymm15h} for amd64
38986 The @samp{org.gnu.gdb.i386.linux} feature is optional. It should
38987 describe a single register, @samp{orig_eax}.
38989 @node MIPS Features
38990 @subsection MIPS Features
38991 @cindex target descriptions, MIPS features
38993 The @samp{org.gnu.gdb.mips.cpu} feature is required for MIPS targets.
38994 It should contain registers @samp{r0} through @samp{r31}, @samp{lo},
38995 @samp{hi}, and @samp{pc}. They may be 32-bit or 64-bit depending
38998 The @samp{org.gnu.gdb.mips.cp0} feature is also required. It should
38999 contain at least the @samp{status}, @samp{badvaddr}, and @samp{cause}
39000 registers. They may be 32-bit or 64-bit depending on the target.
39002 The @samp{org.gnu.gdb.mips.fpu} feature is currently required, though
39003 it may be optional in a future version of @value{GDBN}. It should
39004 contain registers @samp{f0} through @samp{f31}, @samp{fcsr}, and
39005 @samp{fir}. They may be 32-bit or 64-bit depending on the target.
39007 The @samp{org.gnu.gdb.mips.dsp} feature is optional. It should
39008 contain registers @samp{hi1} through @samp{hi3}, @samp{lo1} through
39009 @samp{lo3}, and @samp{dspctl}. The @samp{dspctl} register should
39010 be 32-bit and the rest may be 32-bit or 64-bit depending on the target.
39012 The @samp{org.gnu.gdb.mips.linux} feature is optional. It should
39013 contain a single register, @samp{restart}, which is used by the
39014 Linux kernel to control restartable syscalls.
39016 @node M68K Features
39017 @subsection M68K Features
39018 @cindex target descriptions, M68K features
39021 @item @samp{org.gnu.gdb.m68k.core}
39022 @itemx @samp{org.gnu.gdb.coldfire.core}
39023 @itemx @samp{org.gnu.gdb.fido.core}
39024 One of those features must be always present.
39025 The feature that is present determines which flavor of m68k is
39026 used. The feature that is present should contain registers
39027 @samp{d0} through @samp{d7}, @samp{a0} through @samp{a5}, @samp{fp},
39028 @samp{sp}, @samp{ps} and @samp{pc}.
39030 @item @samp{org.gnu.gdb.coldfire.fp}
39031 This feature is optional. If present, it should contain registers
39032 @samp{fp0} through @samp{fp7}, @samp{fpcontrol}, @samp{fpstatus} and
39036 @node PowerPC Features
39037 @subsection PowerPC Features
39038 @cindex target descriptions, PowerPC features
39040 The @samp{org.gnu.gdb.power.core} feature is required for PowerPC
39041 targets. It should contain registers @samp{r0} through @samp{r31},
39042 @samp{pc}, @samp{msr}, @samp{cr}, @samp{lr}, @samp{ctr}, and
39043 @samp{xer}. They may be 32-bit or 64-bit depending on the target.
39045 The @samp{org.gnu.gdb.power.fpu} feature is optional. It should
39046 contain registers @samp{f0} through @samp{f31} and @samp{fpscr}.
39048 The @samp{org.gnu.gdb.power.altivec} feature is optional. It should
39049 contain registers @samp{vr0} through @samp{vr31}, @samp{vscr},
39052 The @samp{org.gnu.gdb.power.vsx} feature is optional. It should
39053 contain registers @samp{vs0h} through @samp{vs31h}. @value{GDBN}
39054 will combine these registers with the floating point registers
39055 (@samp{f0} through @samp{f31}) and the altivec registers (@samp{vr0}
39056 through @samp{vr31}) to present the 128-bit wide registers @samp{vs0}
39057 through @samp{vs63}, the set of vector registers for POWER7.
39059 The @samp{org.gnu.gdb.power.spe} feature is optional. It should
39060 contain registers @samp{ev0h} through @samp{ev31h}, @samp{acc}, and
39061 @samp{spefscr}. SPE targets should provide 32-bit registers in
39062 @samp{org.gnu.gdb.power.core} and provide the upper halves in
39063 @samp{ev0h} through @samp{ev31h}. @value{GDBN} will combine
39064 these to present registers @samp{ev0} through @samp{ev31} to the
39067 @node TIC6x Features
39068 @subsection TMS320C6x Features
39069 @cindex target descriptions, TIC6x features
39070 @cindex target descriptions, TMS320C6x features
39071 The @samp{org.gnu.gdb.tic6x.core} feature is required for TMS320C6x
39072 targets. It should contain registers @samp{A0} through @samp{A15},
39073 registers @samp{B0} through @samp{B15}, @samp{CSR} and @samp{PC}.
39075 The @samp{org.gnu.gdb.tic6x.gp} feature is optional. It should
39076 contain registers @samp{A16} through @samp{A31} and @samp{B16}
39077 through @samp{B31}.
39079 The @samp{org.gnu.gdb.tic6x.c6xp} feature is optional. It should
39080 contain registers @samp{TSR}, @samp{ILC} and @samp{RILC}.
39082 @node Operating System Information
39083 @appendix Operating System Information
39084 @cindex operating system information
39090 Users of @value{GDBN} often wish to obtain information about the state of
39091 the operating system running on the target---for example the list of
39092 processes, or the list of open files. This section describes the
39093 mechanism that makes it possible. This mechanism is similar to the
39094 target features mechanism (@pxref{Target Descriptions}), but focuses
39095 on a different aspect of target.
39097 Operating system information is retrived from the target via the
39098 remote protocol, using @samp{qXfer} requests (@pxref{qXfer osdata
39099 read}). The object name in the request should be @samp{osdata}, and
39100 the @var{annex} identifies the data to be fetched.
39103 @appendixsection Process list
39104 @cindex operating system information, process list
39106 When requesting the process list, the @var{annex} field in the
39107 @samp{qXfer} request should be @samp{processes}. The returned data is
39108 an XML document. The formal syntax of this document is defined in
39109 @file{gdb/features/osdata.dtd}.
39111 An example document is:
39114 <?xml version="1.0"?>
39115 <!DOCTYPE target SYSTEM "osdata.dtd">
39116 <osdata type="processes">
39118 <column name="pid">1</column>
39119 <column name="user">root</column>
39120 <column name="command">/sbin/init</column>
39121 <column name="cores">1,2,3</column>
39126 Each item should include a column whose name is @samp{pid}. The value
39127 of that column should identify the process on the target. The
39128 @samp{user} and @samp{command} columns are optional, and will be
39129 displayed by @value{GDBN}. The @samp{cores} column, if present,
39130 should contain a comma-separated list of cores that this process
39131 is running on. Target may provide additional columns,
39132 which @value{GDBN} currently ignores.
39134 @node Trace File Format
39135 @appendix Trace File Format
39136 @cindex trace file format
39138 The trace file comes in three parts: a header, a textual description
39139 section, and a trace frame section with binary data.
39141 The header has the form @code{\x7fTRACE0\n}. The first byte is
39142 @code{0x7f} so as to indicate that the file contains binary data,
39143 while the @code{0} is a version number that may have different values
39146 The description section consists of multiple lines of @sc{ascii} text
39147 separated by newline characters (@code{0xa}). The lines may include a
39148 variety of optional descriptive or context-setting information, such
39149 as tracepoint definitions or register set size. @value{GDBN} will
39150 ignore any line that it does not recognize. An empty line marks the end
39153 @c FIXME add some specific types of data
39155 The trace frame section consists of a number of consecutive frames.
39156 Each frame begins with a two-byte tracepoint number, followed by a
39157 four-byte size giving the amount of data in the frame. The data in
39158 the frame consists of a number of blocks, each introduced by a
39159 character indicating its type (at least register, memory, and trace
39160 state variable). The data in this section is raw binary, not a
39161 hexadecimal or other encoding; its endianness matches the target's
39164 @c FIXME bi-arch may require endianness/arch info in description section
39167 @item R @var{bytes}
39168 Register block. The number and ordering of bytes matches that of a
39169 @code{g} packet in the remote protocol. Note that these are the
39170 actual bytes, in target order and @value{GDBN} register order, not a
39171 hexadecimal encoding.
39173 @item M @var{address} @var{length} @var{bytes}...
39174 Memory block. This is a contiguous block of memory, at the 8-byte
39175 address @var{address}, with a 2-byte length @var{length}, followed by
39176 @var{length} bytes.
39178 @item V @var{number} @var{value}
39179 Trace state variable block. This records the 8-byte signed value
39180 @var{value} of trace state variable numbered @var{number}.
39184 Future enhancements of the trace file format may include additional types
39187 @node Index Section Format
39188 @appendix @code{.gdb_index} section format
39189 @cindex .gdb_index section format
39190 @cindex index section format
39192 This section documents the index section that is created by @code{save
39193 gdb-index} (@pxref{Index Files}). The index section is
39194 DWARF-specific; some knowledge of DWARF is assumed in this
39197 The mapped index file format is designed to be directly
39198 @code{mmap}able on any architecture. In most cases, a datum is
39199 represented using a little-endian 32-bit integer value, called an
39200 @code{offset_type}. Big endian machines must byte-swap the values
39201 before using them. Exceptions to this rule are noted. The data is
39202 laid out such that alignment is always respected.
39204 A mapped index consists of several areas, laid out in order.
39208 The file header. This is a sequence of values, of @code{offset_type}
39209 unless otherwise noted:
39213 The version number, currently 6. Versions 1, 2 and 3 are obsolete.
39214 Version 4 uses a different hashing function from versions 5 and 6.
39215 Version 6 includes symbols for inlined functions, whereas versions
39216 4 and 5 do not. @value{GDBN} will only read version 4 and 5 indices
39217 if the @code{--use-deprecated-index-sections} option is used.
39220 The offset, from the start of the file, of the CU list.
39223 The offset, from the start of the file, of the types CU list. Note
39224 that this area can be empty, in which case this offset will be equal
39225 to the next offset.
39228 The offset, from the start of the file, of the address area.
39231 The offset, from the start of the file, of the symbol table.
39234 The offset, from the start of the file, of the constant pool.
39238 The CU list. This is a sequence of pairs of 64-bit little-endian
39239 values, sorted by the CU offset. The first element in each pair is
39240 the offset of a CU in the @code{.debug_info} section. The second
39241 element in each pair is the length of that CU. References to a CU
39242 elsewhere in the map are done using a CU index, which is just the
39243 0-based index into this table. Note that if there are type CUs, then
39244 conceptually CUs and type CUs form a single list for the purposes of
39248 The types CU list. This is a sequence of triplets of 64-bit
39249 little-endian values. In a triplet, the first value is the CU offset,
39250 the second value is the type offset in the CU, and the third value is
39251 the type signature. The types CU list is not sorted.
39254 The address area. The address area consists of a sequence of address
39255 entries. Each address entry has three elements:
39259 The low address. This is a 64-bit little-endian value.
39262 The high address. This is a 64-bit little-endian value. Like
39263 @code{DW_AT_high_pc}, the value is one byte beyond the end.
39266 The CU index. This is an @code{offset_type} value.
39270 The symbol table. This is an open-addressed hash table. The size of
39271 the hash table is always a power of 2.
39273 Each slot in the hash table consists of a pair of @code{offset_type}
39274 values. The first value is the offset of the symbol's name in the
39275 constant pool. The second value is the offset of the CU vector in the
39278 If both values are 0, then this slot in the hash table is empty. This
39279 is ok because while 0 is a valid constant pool index, it cannot be a
39280 valid index for both a string and a CU vector.
39282 The hash value for a table entry is computed by applying an
39283 iterative hash function to the symbol's name. Starting with an
39284 initial value of @code{r = 0}, each (unsigned) character @samp{c} in
39285 the string is incorporated into the hash using the formula depending on the
39290 The formula is @code{r = r * 67 + c - 113}.
39292 @item Versions 5 and 6
39293 The formula is @code{r = r * 67 + tolower (c) - 113}.
39296 The terminating @samp{\0} is not incorporated into the hash.
39298 The step size used in the hash table is computed via
39299 @code{((hash * 17) & (size - 1)) | 1}, where @samp{hash} is the hash
39300 value, and @samp{size} is the size of the hash table. The step size
39301 is used to find the next candidate slot when handling a hash
39304 The names of C@t{++} symbols in the hash table are canonicalized. We
39305 don't currently have a simple description of the canonicalization
39306 algorithm; if you intend to create new index sections, you must read
39310 The constant pool. This is simply a bunch of bytes. It is organized
39311 so that alignment is correct: CU vectors are stored first, followed by
39314 A CU vector in the constant pool is a sequence of @code{offset_type}
39315 values. The first value is the number of CU indices in the vector.
39316 Each subsequent value is the index of a CU in the CU list. This
39317 element in the hash table is used to indicate which CUs define the
39320 A string in the constant pool is zero-terminated.
39325 @node GNU Free Documentation License
39326 @appendix GNU Free Documentation License
39335 % I think something like @colophon should be in texinfo. In the
39337 \long\def\colophon{\hbox to0pt{}\vfill
39338 \centerline{The body of this manual is set in}
39339 \centerline{\fontname\tenrm,}
39340 \centerline{with headings in {\bf\fontname\tenbf}}
39341 \centerline{and examples in {\tt\fontname\tentt}.}
39342 \centerline{{\it\fontname\tenit\/},}
39343 \centerline{{\bf\fontname\tenbf}, and}
39344 \centerline{{\sl\fontname\tensl\/}}
39345 \centerline{are used for emphasis.}\vfill}
39347 % Blame: doc@cygnus.com, 1991.