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 -directory @var{directory}
994 @itemx -d @var{directory}
995 @cindex @code{--directory}
997 Add @var{directory} to the path to search for source and script files.
1001 @cindex @code{--readnow}
1003 Read each symbol file's entire symbol table immediately, rather than
1004 the default, which is to read it incrementally as it is needed.
1005 This makes startup slower, but makes future operations faster.
1010 @subsection Choosing Modes
1012 You can run @value{GDBN} in various alternative modes---for example, in
1013 batch mode or quiet mode.
1020 Do not execute commands found in any initialization files. Normally,
1021 @value{GDBN} executes the commands in these files after all the command
1022 options and arguments have been processed. @xref{Command Files,,Command
1028 @cindex @code{--quiet}
1029 @cindex @code{--silent}
1031 ``Quiet''. Do not print the introductory and copyright messages. These
1032 messages are also suppressed in batch mode.
1035 @cindex @code{--batch}
1036 Run in batch mode. Exit with status @code{0} after processing all the
1037 command files specified with @samp{-x} (and all commands from
1038 initialization files, if not inhibited with @samp{-n}). Exit with
1039 nonzero status if an error occurs in executing the @value{GDBN} commands
1040 in the command files. Batch mode also disables pagination, sets unlimited
1041 terminal width and height @pxref{Screen Size}, and acts as if @kbd{set confirm
1042 off} were in effect (@pxref{Messages/Warnings}).
1044 Batch mode may be useful for running @value{GDBN} as a filter, for
1045 example to download and run a program on another computer; in order to
1046 make this more useful, the message
1049 Program exited normally.
1053 (which is ordinarily issued whenever a program running under
1054 @value{GDBN} control terminates) is not issued when running in batch
1058 @cindex @code{--batch-silent}
1059 Run in batch mode exactly like @samp{-batch}, but totally silently. All
1060 @value{GDBN} output to @code{stdout} is prevented (@code{stderr} is
1061 unaffected). This is much quieter than @samp{-silent} and would be useless
1062 for an interactive session.
1064 This is particularly useful when using targets that give @samp{Loading section}
1065 messages, for example.
1067 Note that targets that give their output via @value{GDBN}, as opposed to
1068 writing directly to @code{stdout}, will also be made silent.
1070 @item -return-child-result
1071 @cindex @code{--return-child-result}
1072 The return code from @value{GDBN} will be the return code from the child
1073 process (the process being debugged), with the following exceptions:
1077 @value{GDBN} exits abnormally. E.g., due to an incorrect argument or an
1078 internal error. In this case the exit code is the same as it would have been
1079 without @samp{-return-child-result}.
1081 The user quits with an explicit value. E.g., @samp{quit 1}.
1083 The child process never runs, or is not allowed to terminate, in which case
1084 the exit code will be -1.
1087 This option is useful in conjunction with @samp{-batch} or @samp{-batch-silent},
1088 when @value{GDBN} is being used as a remote program loader or simulator
1093 @cindex @code{--nowindows}
1095 ``No windows''. If @value{GDBN} comes with a graphical user interface
1096 (GUI) built in, then this option tells @value{GDBN} to only use the command-line
1097 interface. If no GUI is available, this option has no effect.
1101 @cindex @code{--windows}
1103 If @value{GDBN} includes a GUI, then this option requires it to be
1106 @item -cd @var{directory}
1108 Run @value{GDBN} using @var{directory} as its working directory,
1109 instead of the current directory.
1111 @item -data-directory @var{directory}
1112 @cindex @code{--data-directory}
1113 Run @value{GDBN} using @var{directory} as its data directory.
1114 The data directory is where @value{GDBN} searches for its
1115 auxiliary files. @xref{Data Files}.
1119 @cindex @code{--fullname}
1121 @sc{gnu} Emacs sets this option when it runs @value{GDBN} as a
1122 subprocess. It tells @value{GDBN} to output the full file name and line
1123 number in a standard, recognizable fashion each time a stack frame is
1124 displayed (which includes each time your program stops). This
1125 recognizable format looks like two @samp{\032} characters, followed by
1126 the file name, line number and character position separated by colons,
1127 and a newline. The Emacs-to-@value{GDBN} interface program uses the two
1128 @samp{\032} characters as a signal to display the source code for the
1132 @cindex @code{--epoch}
1133 The Epoch Emacs-@value{GDBN} interface sets this option when it runs
1134 @value{GDBN} as a subprocess. It tells @value{GDBN} to modify its print
1135 routines so as to allow Epoch to display values of expressions in a
1138 @item -annotate @var{level}
1139 @cindex @code{--annotate}
1140 This option sets the @dfn{annotation level} inside @value{GDBN}. Its
1141 effect is identical to using @samp{set annotate @var{level}}
1142 (@pxref{Annotations}). The annotation @var{level} controls how much
1143 information @value{GDBN} prints together with its prompt, values of
1144 expressions, source lines, and other types of output. Level 0 is the
1145 normal, level 1 is for use when @value{GDBN} is run as a subprocess of
1146 @sc{gnu} Emacs, level 3 is the maximum annotation suitable for programs
1147 that control @value{GDBN}, and level 2 has been deprecated.
1149 The annotation mechanism has largely been superseded by @sc{gdb/mi}
1153 @cindex @code{--args}
1154 Change interpretation of command line so that arguments following the
1155 executable file are passed as command line arguments to the inferior.
1156 This option stops option processing.
1158 @item -baud @var{bps}
1160 @cindex @code{--baud}
1162 Set the line speed (baud rate or bits per second) of any serial
1163 interface used by @value{GDBN} for remote debugging.
1165 @item -l @var{timeout}
1167 Set the timeout (in seconds) of any communication used by @value{GDBN}
1168 for remote debugging.
1170 @item -tty @var{device}
1171 @itemx -t @var{device}
1172 @cindex @code{--tty}
1174 Run using @var{device} for your program's standard input and output.
1175 @c FIXME: kingdon thinks there is more to -tty. Investigate.
1177 @c resolve the situation of these eventually
1179 @cindex @code{--tui}
1180 Activate the @dfn{Text User Interface} when starting. The Text User
1181 Interface manages several text windows on the terminal, showing
1182 source, assembly, registers and @value{GDBN} command outputs
1183 (@pxref{TUI, ,@value{GDBN} Text User Interface}). Do not use this
1184 option if you run @value{GDBN} from Emacs (@pxref{Emacs, ,
1185 Using @value{GDBN} under @sc{gnu} Emacs}).
1188 @c @cindex @code{--xdb}
1189 @c Run in XDB compatibility mode, allowing the use of certain XDB commands.
1190 @c For information, see the file @file{xdb_trans.html}, which is usually
1191 @c installed in the directory @code{/opt/langtools/wdb/doc} on HP-UX
1194 @item -interpreter @var{interp}
1195 @cindex @code{--interpreter}
1196 Use the interpreter @var{interp} for interface with the controlling
1197 program or device. This option is meant to be set by programs which
1198 communicate with @value{GDBN} using it as a back end.
1199 @xref{Interpreters, , Command Interpreters}.
1201 @samp{--interpreter=mi} (or @samp{--interpreter=mi2}) causes
1202 @value{GDBN} to use the @dfn{@sc{gdb/mi} interface} (@pxref{GDB/MI, ,
1203 The @sc{gdb/mi} Interface}) included since @value{GDBN} version 6.0. The
1204 previous @sc{gdb/mi} interface, included in @value{GDBN} version 5.3 and
1205 selected with @samp{--interpreter=mi1}, is deprecated. Earlier
1206 @sc{gdb/mi} interfaces are no longer supported.
1209 @cindex @code{--write}
1210 Open the executable and core files for both reading and writing. This
1211 is equivalent to the @samp{set write on} command inside @value{GDBN}
1215 @cindex @code{--statistics}
1216 This option causes @value{GDBN} to print statistics about time and
1217 memory usage after it completes each command and returns to the prompt.
1220 @cindex @code{--version}
1221 This option causes @value{GDBN} to print its version number and
1222 no-warranty blurb, and exit.
1227 @subsection What @value{GDBN} Does During Startup
1228 @cindex @value{GDBN} startup
1230 Here's the description of what @value{GDBN} does during session startup:
1234 Sets up the command interpreter as specified by the command line
1235 (@pxref{Mode Options, interpreter}).
1239 Reads the system-wide @dfn{init file} (if @option{--with-system-gdbinit} was
1240 used when building @value{GDBN}; @pxref{System-wide configuration,
1241 ,System-wide configuration and settings}) and executes all the commands in
1245 Reads the init file (if any) in your home directory@footnote{On
1246 DOS/Windows systems, the home directory is the one pointed to by the
1247 @code{HOME} environment variable.} and executes all the commands in
1251 Processes command line options and operands.
1254 Reads and executes the commands from init file (if any) in the current
1255 working directory. This is only done if the current directory is
1256 different from your home directory. Thus, you can have more than one
1257 init file, one generic in your home directory, and another, specific
1258 to the program you are debugging, in the directory where you invoke
1262 If the command line specified a program to debug, or a process to
1263 attach to, or a core file, @value{GDBN} loads any auto-loaded
1264 scripts provided for the program or for its loaded shared libraries.
1265 @xref{Auto-loading}.
1267 If you wish to disable the auto-loading during startup,
1268 you must do something like the following:
1271 $ gdb -ex "set auto-load-scripts off" -ex "file myprogram"
1274 The following does not work because the auto-loading is turned off too late:
1277 $ gdb -ex "set auto-load-scripts off" myprogram
1281 Executes commands and command files specified by the @samp{-ex} and
1282 @samp{-x} options in their specified order. @xref{Command Files}, for
1283 more details about @value{GDBN} command files.
1286 Reads the command history recorded in the @dfn{history file}.
1287 @xref{Command History}, for more details about the command history and the
1288 files where @value{GDBN} records it.
1291 Init files use the same syntax as @dfn{command files} (@pxref{Command
1292 Files}) and are processed by @value{GDBN} in the same way. The init
1293 file in your home directory can set options (such as @samp{set
1294 complaints}) that affect subsequent processing of command line options
1295 and operands. Init files are not executed if you use the @samp{-nx}
1296 option (@pxref{Mode Options, ,Choosing Modes}).
1298 To display the list of init files loaded by gdb at startup, you
1299 can use @kbd{gdb --help}.
1301 @cindex init file name
1302 @cindex @file{.gdbinit}
1303 @cindex @file{gdb.ini}
1304 The @value{GDBN} init files are normally called @file{.gdbinit}.
1305 The DJGPP port of @value{GDBN} uses the name @file{gdb.ini}, due to
1306 the limitations of file names imposed by DOS filesystems. The Windows
1307 ports of @value{GDBN} use the standard name, but if they find a
1308 @file{gdb.ini} file, they warn you about that and suggest to rename
1309 the file to the standard name.
1313 @section Quitting @value{GDBN}
1314 @cindex exiting @value{GDBN}
1315 @cindex leaving @value{GDBN}
1318 @kindex quit @r{[}@var{expression}@r{]}
1319 @kindex q @r{(@code{quit})}
1320 @item quit @r{[}@var{expression}@r{]}
1322 To exit @value{GDBN}, use the @code{quit} command (abbreviated
1323 @code{q}), or type an end-of-file character (usually @kbd{Ctrl-d}). If you
1324 do not supply @var{expression}, @value{GDBN} will terminate normally;
1325 otherwise it will terminate using the result of @var{expression} as the
1330 An interrupt (often @kbd{Ctrl-c}) does not exit from @value{GDBN}, but rather
1331 terminates the action of any @value{GDBN} command that is in progress and
1332 returns to @value{GDBN} command level. It is safe to type the interrupt
1333 character at any time because @value{GDBN} does not allow it to take effect
1334 until a time when it is safe.
1336 If you have been using @value{GDBN} to control an attached process or
1337 device, you can release it with the @code{detach} command
1338 (@pxref{Attach, ,Debugging an Already-running Process}).
1340 @node Shell Commands
1341 @section Shell Commands
1343 If you need to execute occasional shell commands during your
1344 debugging session, there is no need to leave or suspend @value{GDBN}; you can
1345 just use the @code{shell} command.
1350 @cindex shell escape
1351 @item shell @var{command-string}
1352 @itemx !@var{command-string}
1353 Invoke a standard shell to execute @var{command-string}.
1354 Note that no space is needed between @code{!} and @var{command-string}.
1355 If it exists, the environment variable @code{SHELL} determines which
1356 shell to run. Otherwise @value{GDBN} uses the default shell
1357 (@file{/bin/sh} on Unix systems, @file{COMMAND.COM} on MS-DOS, etc.).
1360 The utility @code{make} is often needed in development environments.
1361 You do not have to use the @code{shell} command for this purpose in
1366 @cindex calling make
1367 @item make @var{make-args}
1368 Execute the @code{make} program with the specified
1369 arguments. This is equivalent to @samp{shell make @var{make-args}}.
1372 @node Logging Output
1373 @section Logging Output
1374 @cindex logging @value{GDBN} output
1375 @cindex save @value{GDBN} output to a file
1377 You may want to save the output of @value{GDBN} commands to a file.
1378 There are several commands to control @value{GDBN}'s logging.
1382 @item set logging on
1384 @item set logging off
1386 @cindex logging file name
1387 @item set logging file @var{file}
1388 Change the name of the current logfile. The default logfile is @file{gdb.txt}.
1389 @item set logging overwrite [on|off]
1390 By default, @value{GDBN} will append to the logfile. Set @code{overwrite} if
1391 you want @code{set logging on} to overwrite the logfile instead.
1392 @item set logging redirect [on|off]
1393 By default, @value{GDBN} output will go to both the terminal and the logfile.
1394 Set @code{redirect} if you want output to go only to the log file.
1395 @kindex show logging
1397 Show the current values of the logging settings.
1401 @chapter @value{GDBN} Commands
1403 You can abbreviate a @value{GDBN} command to the first few letters of the command
1404 name, if that abbreviation is unambiguous; and you can repeat certain
1405 @value{GDBN} commands by typing just @key{RET}. You can also use the @key{TAB}
1406 key to get @value{GDBN} to fill out the rest of a word in a command (or to
1407 show you the alternatives available, if there is more than one possibility).
1410 * Command Syntax:: How to give commands to @value{GDBN}
1411 * Completion:: Command completion
1412 * Help:: How to ask @value{GDBN} for help
1415 @node Command Syntax
1416 @section Command Syntax
1418 A @value{GDBN} command is a single line of input. There is no limit on
1419 how long it can be. It starts with a command name, which is followed by
1420 arguments whose meaning depends on the command name. For example, the
1421 command @code{step} accepts an argument which is the number of times to
1422 step, as in @samp{step 5}. You can also use the @code{step} command
1423 with no arguments. Some commands do not allow any arguments.
1425 @cindex abbreviation
1426 @value{GDBN} command names may always be truncated if that abbreviation is
1427 unambiguous. Other possible command abbreviations are listed in the
1428 documentation for individual commands. In some cases, even ambiguous
1429 abbreviations are allowed; for example, @code{s} is specially defined as
1430 equivalent to @code{step} even though there are other commands whose
1431 names start with @code{s}. You can test abbreviations by using them as
1432 arguments to the @code{help} command.
1434 @cindex repeating commands
1435 @kindex RET @r{(repeat last command)}
1436 A blank line as input to @value{GDBN} (typing just @key{RET}) means to
1437 repeat the previous command. Certain commands (for example, @code{run})
1438 will not repeat this way; these are commands whose unintentional
1439 repetition might cause trouble and which you are unlikely to want to
1440 repeat. User-defined commands can disable this feature; see
1441 @ref{Define, dont-repeat}.
1443 The @code{list} and @code{x} commands, when you repeat them with
1444 @key{RET}, construct new arguments rather than repeating
1445 exactly as typed. This permits easy scanning of source or memory.
1447 @value{GDBN} can also use @key{RET} in another way: to partition lengthy
1448 output, in a way similar to the common utility @code{more}
1449 (@pxref{Screen Size,,Screen Size}). Since it is easy to press one
1450 @key{RET} too many in this situation, @value{GDBN} disables command
1451 repetition after any command that generates this sort of display.
1453 @kindex # @r{(a comment)}
1455 Any text from a @kbd{#} to the end of the line is a comment; it does
1456 nothing. This is useful mainly in command files (@pxref{Command
1457 Files,,Command Files}).
1459 @cindex repeating command sequences
1460 @kindex Ctrl-o @r{(operate-and-get-next)}
1461 The @kbd{Ctrl-o} binding is useful for repeating a complex sequence of
1462 commands. This command accepts the current line, like @key{RET}, and
1463 then fetches the next line relative to the current line from the history
1467 @section Command Completion
1470 @cindex word completion
1471 @value{GDBN} can fill in the rest of a word in a command for you, if there is
1472 only one possibility; it can also show you what the valid possibilities
1473 are for the next word in a command, at any time. This works for @value{GDBN}
1474 commands, @value{GDBN} subcommands, and the names of symbols in your program.
1476 Press the @key{TAB} key whenever you want @value{GDBN} to fill out the rest
1477 of a word. If there is only one possibility, @value{GDBN} fills in the
1478 word, and waits for you to finish the command (or press @key{RET} to
1479 enter it). For example, if you type
1481 @c FIXME "@key" does not distinguish its argument sufficiently to permit
1482 @c complete accuracy in these examples; space introduced for clarity.
1483 @c If texinfo enhancements make it unnecessary, it would be nice to
1484 @c replace " @key" by "@key" in the following...
1486 (@value{GDBP}) info bre @key{TAB}
1490 @value{GDBN} fills in the rest of the word @samp{breakpoints}, since that is
1491 the only @code{info} subcommand beginning with @samp{bre}:
1494 (@value{GDBP}) info breakpoints
1498 You can either press @key{RET} at this point, to run the @code{info
1499 breakpoints} command, or backspace and enter something else, if
1500 @samp{breakpoints} does not look like the command you expected. (If you
1501 were sure you wanted @code{info breakpoints} in the first place, you
1502 might as well just type @key{RET} immediately after @samp{info bre},
1503 to exploit command abbreviations rather than command completion).
1505 If there is more than one possibility for the next word when you press
1506 @key{TAB}, @value{GDBN} sounds a bell. You can either supply more
1507 characters and try again, or just press @key{TAB} a second time;
1508 @value{GDBN} displays all the possible completions for that word. For
1509 example, you might want to set a breakpoint on a subroutine whose name
1510 begins with @samp{make_}, but when you type @kbd{b make_@key{TAB}} @value{GDBN}
1511 just sounds the bell. Typing @key{TAB} again displays all the
1512 function names in your program that begin with those characters, for
1516 (@value{GDBP}) b make_ @key{TAB}
1517 @exdent @value{GDBN} sounds bell; press @key{TAB} again, to see:
1518 make_a_section_from_file make_environ
1519 make_abs_section make_function_type
1520 make_blockvector make_pointer_type
1521 make_cleanup make_reference_type
1522 make_command make_symbol_completion_list
1523 (@value{GDBP}) b make_
1527 After displaying the available possibilities, @value{GDBN} copies your
1528 partial input (@samp{b make_} in the example) so you can finish the
1531 If you just want to see the list of alternatives in the first place, you
1532 can press @kbd{M-?} rather than pressing @key{TAB} twice. @kbd{M-?}
1533 means @kbd{@key{META} ?}. You can type this either by holding down a
1534 key designated as the @key{META} shift on your keyboard (if there is
1535 one) while typing @kbd{?}, or as @key{ESC} followed by @kbd{?}.
1537 @cindex quotes in commands
1538 @cindex completion of quoted strings
1539 Sometimes the string you need, while logically a ``word'', may contain
1540 parentheses or other characters that @value{GDBN} normally excludes from
1541 its notion of a word. To permit word completion to work in this
1542 situation, you may enclose words in @code{'} (single quote marks) in
1543 @value{GDBN} commands.
1545 The most likely situation where you might need this is in typing the
1546 name of a C@t{++} function. This is because C@t{++} allows function
1547 overloading (multiple definitions of the same function, distinguished
1548 by argument type). For example, when you want to set a breakpoint you
1549 may need to distinguish whether you mean the version of @code{name}
1550 that takes an @code{int} parameter, @code{name(int)}, or the version
1551 that takes a @code{float} parameter, @code{name(float)}. To use the
1552 word-completion facilities in this situation, type a single quote
1553 @code{'} at the beginning of the function name. This alerts
1554 @value{GDBN} that it may need to consider more information than usual
1555 when you press @key{TAB} or @kbd{M-?} to request word completion:
1558 (@value{GDBP}) b 'bubble( @kbd{M-?}
1559 bubble(double,double) bubble(int,int)
1560 (@value{GDBP}) b 'bubble(
1563 In some cases, @value{GDBN} can tell that completing a name requires using
1564 quotes. When this happens, @value{GDBN} inserts the quote for you (while
1565 completing as much as it can) if you do not type the quote in the first
1569 (@value{GDBP}) b bub @key{TAB}
1570 @exdent @value{GDBN} alters your input line to the following, and rings a bell:
1571 (@value{GDBP}) b 'bubble(
1575 In general, @value{GDBN} can tell that a quote is needed (and inserts it) if
1576 you have not yet started typing the argument list when you ask for
1577 completion on an overloaded symbol.
1579 For more information about overloaded functions, see @ref{C Plus Plus
1580 Expressions, ,C@t{++} Expressions}. You can use the command @code{set
1581 overload-resolution off} to disable overload resolution;
1582 see @ref{Debugging C Plus Plus, ,@value{GDBN} Features for C@t{++}}.
1584 @cindex completion of structure field names
1585 @cindex structure field name completion
1586 @cindex completion of union field names
1587 @cindex union field name completion
1588 When completing in an expression which looks up a field in a
1589 structure, @value{GDBN} also tries@footnote{The completer can be
1590 confused by certain kinds of invalid expressions. Also, it only
1591 examines the static type of the expression, not the dynamic type.} to
1592 limit completions to the field names available in the type of the
1596 (@value{GDBP}) p gdb_stdout.@kbd{M-?}
1597 magic to_fputs to_rewind
1598 to_data to_isatty to_write
1599 to_delete to_put to_write_async_safe
1604 This is because the @code{gdb_stdout} is a variable of the type
1605 @code{struct ui_file} that is defined in @value{GDBN} sources as
1612 ui_file_flush_ftype *to_flush;
1613 ui_file_write_ftype *to_write;
1614 ui_file_write_async_safe_ftype *to_write_async_safe;
1615 ui_file_fputs_ftype *to_fputs;
1616 ui_file_read_ftype *to_read;
1617 ui_file_delete_ftype *to_delete;
1618 ui_file_isatty_ftype *to_isatty;
1619 ui_file_rewind_ftype *to_rewind;
1620 ui_file_put_ftype *to_put;
1627 @section Getting Help
1628 @cindex online documentation
1631 You can always ask @value{GDBN} itself for information on its commands,
1632 using the command @code{help}.
1635 @kindex h @r{(@code{help})}
1638 You can use @code{help} (abbreviated @code{h}) with no arguments to
1639 display a short list of named classes of commands:
1643 List of classes of commands:
1645 aliases -- Aliases of other commands
1646 breakpoints -- Making program stop at certain points
1647 data -- Examining data
1648 files -- Specifying and examining files
1649 internals -- Maintenance commands
1650 obscure -- Obscure features
1651 running -- Running the program
1652 stack -- Examining the stack
1653 status -- Status inquiries
1654 support -- Support facilities
1655 tracepoints -- Tracing of program execution without
1656 stopping the program
1657 user-defined -- User-defined commands
1659 Type "help" followed by a class name for a list of
1660 commands in that class.
1661 Type "help" followed by command name for full
1663 Command name abbreviations are allowed if unambiguous.
1666 @c the above line break eliminates huge line overfull...
1668 @item help @var{class}
1669 Using one of the general help classes as an argument, you can get a
1670 list of the individual commands in that class. For example, here is the
1671 help display for the class @code{status}:
1674 (@value{GDBP}) help status
1679 @c Line break in "show" line falsifies real output, but needed
1680 @c to fit in smallbook page size.
1681 info -- Generic command for showing things
1682 about the program being debugged
1683 show -- Generic command for showing things
1686 Type "help" followed by command name for full
1688 Command name abbreviations are allowed if unambiguous.
1692 @item help @var{command}
1693 With a command name as @code{help} argument, @value{GDBN} displays a
1694 short paragraph on how to use that command.
1697 @item apropos @var{args}
1698 The @code{apropos} command searches through all of the @value{GDBN}
1699 commands, and their documentation, for the regular expression specified in
1700 @var{args}. It prints out all matches found. For example:
1711 alias -- Define a new command that is an alias of an existing command
1712 aliases -- Aliases of other commands
1713 d -- Delete some breakpoints or auto-display expressions
1714 del -- Delete some breakpoints or auto-display expressions
1715 delete -- Delete some breakpoints or auto-display expressions
1720 @item complete @var{args}
1721 The @code{complete @var{args}} command lists all the possible completions
1722 for the beginning of a command. Use @var{args} to specify the beginning of the
1723 command you want completed. For example:
1729 @noindent results in:
1740 @noindent This is intended for use by @sc{gnu} Emacs.
1743 In addition to @code{help}, you can use the @value{GDBN} commands @code{info}
1744 and @code{show} to inquire about the state of your program, or the state
1745 of @value{GDBN} itself. Each command supports many topics of inquiry; this
1746 manual introduces each of them in the appropriate context. The listings
1747 under @code{info} and under @code{show} in the Index point to
1748 all the sub-commands. @xref{Index}.
1753 @kindex i @r{(@code{info})}
1755 This command (abbreviated @code{i}) is for describing the state of your
1756 program. For example, you can show the arguments passed to a function
1757 with @code{info args}, list the registers currently in use with @code{info
1758 registers}, or list the breakpoints you have set with @code{info breakpoints}.
1759 You can get a complete list of the @code{info} sub-commands with
1760 @w{@code{help info}}.
1764 You can assign the result of an expression to an environment variable with
1765 @code{set}. For example, you can set the @value{GDBN} prompt to a $-sign with
1766 @code{set prompt $}.
1770 In contrast to @code{info}, @code{show} is for describing the state of
1771 @value{GDBN} itself.
1772 You can change most of the things you can @code{show}, by using the
1773 related command @code{set}; for example, you can control what number
1774 system is used for displays with @code{set radix}, or simply inquire
1775 which is currently in use with @code{show radix}.
1778 To display all the settable parameters and their current
1779 values, you can use @code{show} with no arguments; you may also use
1780 @code{info set}. Both commands produce the same display.
1781 @c FIXME: "info set" violates the rule that "info" is for state of
1782 @c FIXME...program. Ck w/ GNU: "info set" to be called something else,
1783 @c FIXME...or change desc of rule---eg "state of prog and debugging session"?
1787 Here are three miscellaneous @code{show} subcommands, all of which are
1788 exceptional in lacking corresponding @code{set} commands:
1791 @kindex show version
1792 @cindex @value{GDBN} version number
1794 Show what version of @value{GDBN} is running. You should include this
1795 information in @value{GDBN} bug-reports. If multiple versions of
1796 @value{GDBN} are in use at your site, you may need to determine which
1797 version of @value{GDBN} you are running; as @value{GDBN} evolves, new
1798 commands are introduced, and old ones may wither away. Also, many
1799 system vendors ship variant versions of @value{GDBN}, and there are
1800 variant versions of @value{GDBN} in @sc{gnu}/Linux distributions as well.
1801 The version number is the same as the one announced when you start
1804 @kindex show copying
1805 @kindex info copying
1806 @cindex display @value{GDBN} copyright
1809 Display information about permission for copying @value{GDBN}.
1811 @kindex show warranty
1812 @kindex info warranty
1814 @itemx info warranty
1815 Display the @sc{gnu} ``NO WARRANTY'' statement, or a warranty,
1816 if your version of @value{GDBN} comes with one.
1821 @chapter Running Programs Under @value{GDBN}
1823 When you run a program under @value{GDBN}, you must first generate
1824 debugging information when you compile it.
1826 You may start @value{GDBN} with its arguments, if any, in an environment
1827 of your choice. If you are doing native debugging, you may redirect
1828 your program's input and output, debug an already running process, or
1829 kill a child process.
1832 * Compilation:: Compiling for debugging
1833 * Starting:: Starting your program
1834 * Arguments:: Your program's arguments
1835 * Environment:: Your program's environment
1837 * Working Directory:: Your program's working directory
1838 * Input/Output:: Your program's input and output
1839 * Attach:: Debugging an already-running process
1840 * Kill Process:: Killing the child process
1842 * Inferiors and Programs:: Debugging multiple inferiors and programs
1843 * Threads:: Debugging programs with multiple threads
1844 * Forks:: Debugging forks
1845 * Checkpoint/Restart:: Setting a @emph{bookmark} to return to later
1849 @section Compiling for Debugging
1851 In order to debug a program effectively, you need to generate
1852 debugging information when you compile it. This debugging information
1853 is stored in the object file; it describes the data type of each
1854 variable or function and the correspondence between source line numbers
1855 and addresses in the executable code.
1857 To request debugging information, specify the @samp{-g} option when you run
1860 Programs that are to be shipped to your customers are compiled with
1861 optimizations, using the @samp{-O} compiler option. However, some
1862 compilers are unable to handle the @samp{-g} and @samp{-O} options
1863 together. Using those compilers, you cannot generate optimized
1864 executables containing debugging information.
1866 @value{NGCC}, the @sc{gnu} C/C@t{++} compiler, supports @samp{-g} with or
1867 without @samp{-O}, making it possible to debug optimized code. We
1868 recommend that you @emph{always} use @samp{-g} whenever you compile a
1869 program. You may think your program is correct, but there is no sense
1870 in pushing your luck. For more information, see @ref{Optimized Code}.
1872 Older versions of the @sc{gnu} C compiler permitted a variant option
1873 @w{@samp{-gg}} for debugging information. @value{GDBN} no longer supports this
1874 format; if your @sc{gnu} C compiler has this option, do not use it.
1876 @value{GDBN} knows about preprocessor macros and can show you their
1877 expansion (@pxref{Macros}). Most compilers do not include information
1878 about preprocessor macros in the debugging information if you specify
1879 the @option{-g} flag alone. Version 3.1 and later of @value{NGCC},
1880 the @sc{gnu} C compiler, provides macro information if you are using
1881 the DWARF debugging format, and specify the option @option{-g3}.
1883 @xref{Debugging Options,,Options for Debugging Your Program or GCC,
1884 gcc.info, Using the @sc{gnu} Compiler Collection (GCC)}, for more
1885 information on @value{NGCC} options affecting debug information.
1887 You will have the best debugging experience if you use the latest
1888 version of the DWARF debugging format that your compiler supports.
1889 DWARF is currently the most expressive and best supported debugging
1890 format in @value{GDBN}.
1894 @section Starting your Program
1900 @kindex r @r{(@code{run})}
1903 Use the @code{run} command to start your program under @value{GDBN}.
1904 You must first specify the program name (except on VxWorks) with an
1905 argument to @value{GDBN} (@pxref{Invocation, ,Getting In and Out of
1906 @value{GDBN}}), or by using the @code{file} or @code{exec-file} command
1907 (@pxref{Files, ,Commands to Specify Files}).
1911 If you are running your program in an execution environment that
1912 supports processes, @code{run} creates an inferior process and makes
1913 that process run your program. In some environments without processes,
1914 @code{run} jumps to the start of your program. Other targets,
1915 like @samp{remote}, are always running. If you get an error
1916 message like this one:
1919 The "remote" target does not support "run".
1920 Try "help target" or "continue".
1924 then use @code{continue} to run your program. You may need @code{load}
1925 first (@pxref{load}).
1927 The execution of a program is affected by certain information it
1928 receives from its superior. @value{GDBN} provides ways to specify this
1929 information, which you must do @emph{before} starting your program. (You
1930 can change it after starting your program, but such changes only affect
1931 your program the next time you start it.) This information may be
1932 divided into four categories:
1935 @item The @emph{arguments.}
1936 Specify the arguments to give your program as the arguments of the
1937 @code{run} command. If a shell is available on your target, the shell
1938 is used to pass the arguments, so that you may use normal conventions
1939 (such as wildcard expansion or variable substitution) in describing
1941 In Unix systems, you can control which shell is used with the
1942 @code{SHELL} environment variable.
1943 @xref{Arguments, ,Your Program's Arguments}.
1945 @item The @emph{environment.}
1946 Your program normally inherits its environment from @value{GDBN}, but you can
1947 use the @value{GDBN} commands @code{set environment} and @code{unset
1948 environment} to change parts of the environment that affect
1949 your program. @xref{Environment, ,Your Program's Environment}.
1951 @item The @emph{working directory.}
1952 Your program inherits its working directory from @value{GDBN}. You can set
1953 the @value{GDBN} working directory with the @code{cd} command in @value{GDBN}.
1954 @xref{Working Directory, ,Your Program's Working Directory}.
1956 @item The @emph{standard input and output.}
1957 Your program normally uses the same device for standard input and
1958 standard output as @value{GDBN} is using. You can redirect input and output
1959 in the @code{run} command line, or you can use the @code{tty} command to
1960 set a different device for your program.
1961 @xref{Input/Output, ,Your Program's Input and Output}.
1964 @emph{Warning:} While input and output redirection work, you cannot use
1965 pipes to pass the output of the program you are debugging to another
1966 program; if you attempt this, @value{GDBN} is likely to wind up debugging the
1970 When you issue the @code{run} command, your program begins to execute
1971 immediately. @xref{Stopping, ,Stopping and Continuing}, for discussion
1972 of how to arrange for your program to stop. Once your program has
1973 stopped, you may call functions in your program, using the @code{print}
1974 or @code{call} commands. @xref{Data, ,Examining Data}.
1976 If the modification time of your symbol file has changed since the last
1977 time @value{GDBN} read its symbols, @value{GDBN} discards its symbol
1978 table, and reads it again. When it does this, @value{GDBN} tries to retain
1979 your current breakpoints.
1984 @cindex run to main procedure
1985 The name of the main procedure can vary from language to language.
1986 With C or C@t{++}, the main procedure name is always @code{main}, but
1987 other languages such as Ada do not require a specific name for their
1988 main procedure. The debugger provides a convenient way to start the
1989 execution of the program and to stop at the beginning of the main
1990 procedure, depending on the language used.
1992 The @samp{start} command does the equivalent of setting a temporary
1993 breakpoint at the beginning of the main procedure and then invoking
1994 the @samp{run} command.
1996 @cindex elaboration phase
1997 Some programs contain an @dfn{elaboration} phase where some startup code is
1998 executed before the main procedure is called. This depends on the
1999 languages used to write your program. In C@t{++}, for instance,
2000 constructors for static and global objects are executed before
2001 @code{main} is called. It is therefore possible that the debugger stops
2002 before reaching the main procedure. However, the temporary breakpoint
2003 will remain to halt execution.
2005 Specify the arguments to give to your program as arguments to the
2006 @samp{start} command. These arguments will be given verbatim to the
2007 underlying @samp{run} command. Note that the same arguments will be
2008 reused if no argument is provided during subsequent calls to
2009 @samp{start} or @samp{run}.
2011 It is sometimes necessary to debug the program during elaboration. In
2012 these cases, using the @code{start} command would stop the execution of
2013 your program too late, as the program would have already completed the
2014 elaboration phase. Under these circumstances, insert breakpoints in your
2015 elaboration code before running your program.
2017 @kindex set exec-wrapper
2018 @item set exec-wrapper @var{wrapper}
2019 @itemx show exec-wrapper
2020 @itemx unset exec-wrapper
2021 When @samp{exec-wrapper} is set, the specified wrapper is used to
2022 launch programs for debugging. @value{GDBN} starts your program
2023 with a shell command of the form @kbd{exec @var{wrapper}
2024 @var{program}}. Quoting is added to @var{program} and its
2025 arguments, but not to @var{wrapper}, so you should add quotes if
2026 appropriate for your shell. The wrapper runs until it executes
2027 your program, and then @value{GDBN} takes control.
2029 You can use any program that eventually calls @code{execve} with
2030 its arguments as a wrapper. Several standard Unix utilities do
2031 this, e.g.@: @code{env} and @code{nohup}. Any Unix shell script ending
2032 with @code{exec "$@@"} will also work.
2034 For example, you can use @code{env} to pass an environment variable to
2035 the debugged program, without setting the variable in your shell's
2039 (@value{GDBP}) set exec-wrapper env 'LD_PRELOAD=libtest.so'
2043 This command is available when debugging locally on most targets, excluding
2044 @sc{djgpp}, Cygwin, MS Windows, and QNX Neutrino.
2046 @kindex set disable-randomization
2047 @item set disable-randomization
2048 @itemx set disable-randomization on
2049 This option (enabled by default in @value{GDBN}) will turn off the native
2050 randomization of the virtual address space of the started program. This option
2051 is useful for multiple debugging sessions to make the execution better
2052 reproducible and memory addresses reusable across debugging sessions.
2054 This feature is implemented only on certain targets, including @sc{gnu}/Linux.
2055 On @sc{gnu}/Linux you can get the same behavior using
2058 (@value{GDBP}) set exec-wrapper setarch `uname -m` -R
2061 @item set disable-randomization off
2062 Leave the behavior of the started executable unchanged. Some bugs rear their
2063 ugly heads only when the program is loaded at certain addresses. If your bug
2064 disappears when you run the program under @value{GDBN}, that might be because
2065 @value{GDBN} by default disables the address randomization on platforms, such
2066 as @sc{gnu}/Linux, which do that for stand-alone programs. Use @kbd{set
2067 disable-randomization off} to try to reproduce such elusive bugs.
2069 On targets where it is available, virtual address space randomization
2070 protects the programs against certain kinds of security attacks. In these
2071 cases the attacker needs to know the exact location of a concrete executable
2072 code. Randomizing its location makes it impossible to inject jumps misusing
2073 a code at its expected addresses.
2075 Prelinking shared libraries provides a startup performance advantage but it
2076 makes addresses in these libraries predictable for privileged processes by
2077 having just unprivileged access at the target system. Reading the shared
2078 library binary gives enough information for assembling the malicious code
2079 misusing it. Still even a prelinked shared library can get loaded at a new
2080 random address just requiring the regular relocation process during the
2081 startup. Shared libraries not already prelinked are always loaded at
2082 a randomly chosen address.
2084 Position independent executables (PIE) contain position independent code
2085 similar to the shared libraries and therefore such executables get loaded at
2086 a randomly chosen address upon startup. PIE executables always load even
2087 already prelinked shared libraries at a random address. You can build such
2088 executable using @command{gcc -fPIE -pie}.
2090 Heap (malloc storage), stack and custom mmap areas are always placed randomly
2091 (as long as the randomization is enabled).
2093 @item show disable-randomization
2094 Show the current setting of the explicit disable of the native randomization of
2095 the virtual address space of the started program.
2100 @section Your Program's Arguments
2102 @cindex arguments (to your program)
2103 The arguments to your program can be specified by the arguments of the
2105 They are passed to a shell, which expands wildcard characters and
2106 performs redirection of I/O, and thence to your program. Your
2107 @code{SHELL} environment variable (if it exists) specifies what shell
2108 @value{GDBN} uses. If you do not define @code{SHELL}, @value{GDBN} uses
2109 the default shell (@file{/bin/sh} on Unix).
2111 On non-Unix systems, the program is usually invoked directly by
2112 @value{GDBN}, which emulates I/O redirection via the appropriate system
2113 calls, and the wildcard characters are expanded by the startup code of
2114 the program, not by the shell.
2116 @code{run} with no arguments uses the same arguments used by the previous
2117 @code{run}, or those set by the @code{set args} command.
2122 Specify the arguments to be used the next time your program is run. If
2123 @code{set args} has no arguments, @code{run} executes your program
2124 with no arguments. Once you have run your program with arguments,
2125 using @code{set args} before the next @code{run} is the only way to run
2126 it again without arguments.
2130 Show the arguments to give your program when it is started.
2134 @section Your Program's Environment
2136 @cindex environment (of your program)
2137 The @dfn{environment} consists of a set of environment variables and
2138 their values. Environment variables conventionally record such things as
2139 your user name, your home directory, your terminal type, and your search
2140 path for programs to run. Usually you set up environment variables with
2141 the shell and they are inherited by all the other programs you run. When
2142 debugging, it can be useful to try running your program with a modified
2143 environment without having to start @value{GDBN} over again.
2147 @item path @var{directory}
2148 Add @var{directory} to the front of the @code{PATH} environment variable
2149 (the search path for executables) that will be passed to your program.
2150 The value of @code{PATH} used by @value{GDBN} does not change.
2151 You may specify several directory names, separated by whitespace or by a
2152 system-dependent separator character (@samp{:} on Unix, @samp{;} on
2153 MS-DOS and MS-Windows). If @var{directory} is already in the path, it
2154 is moved to the front, so it is searched sooner.
2156 You can use the string @samp{$cwd} to refer to whatever is the current
2157 working directory at the time @value{GDBN} searches the path. If you
2158 use @samp{.} instead, it refers to the directory where you executed the
2159 @code{path} command. @value{GDBN} replaces @samp{.} in the
2160 @var{directory} argument (with the current path) before adding
2161 @var{directory} to the search path.
2162 @c 'path' is explicitly nonrepeatable, but RMS points out it is silly to
2163 @c document that, since repeating it would be a no-op.
2167 Display the list of search paths for executables (the @code{PATH}
2168 environment variable).
2170 @kindex show environment
2171 @item show environment @r{[}@var{varname}@r{]}
2172 Print the value of environment variable @var{varname} to be given to
2173 your program when it starts. If you do not supply @var{varname},
2174 print the names and values of all environment variables to be given to
2175 your program. You can abbreviate @code{environment} as @code{env}.
2177 @kindex set environment
2178 @item set environment @var{varname} @r{[}=@var{value}@r{]}
2179 Set environment variable @var{varname} to @var{value}. The value
2180 changes for your program only, not for @value{GDBN} itself. @var{value} may
2181 be any string; the values of environment variables are just strings, and
2182 any interpretation is supplied by your program itself. The @var{value}
2183 parameter is optional; if it is eliminated, the variable is set to a
2185 @c "any string" here does not include leading, trailing
2186 @c blanks. Gnu asks: does anyone care?
2188 For example, this command:
2195 tells the debugged program, when subsequently run, that its user is named
2196 @samp{foo}. (The spaces around @samp{=} are used for clarity here; they
2197 are not actually required.)
2199 @kindex unset environment
2200 @item unset environment @var{varname}
2201 Remove variable @var{varname} from the environment to be passed to your
2202 program. This is different from @samp{set env @var{varname} =};
2203 @code{unset environment} removes the variable from the environment,
2204 rather than assigning it an empty value.
2207 @emph{Warning:} On Unix systems, @value{GDBN} runs your program using
2209 by your @code{SHELL} environment variable if it exists (or
2210 @code{/bin/sh} if not). If your @code{SHELL} variable names a shell
2211 that runs an initialization file---such as @file{.cshrc} for C-shell, or
2212 @file{.bashrc} for BASH---any variables you set in that file affect
2213 your program. You may wish to move setting of environment variables to
2214 files that are only run when you sign on, such as @file{.login} or
2217 @node Working Directory
2218 @section Your Program's Working Directory
2220 @cindex working directory (of your program)
2221 Each time you start your program with @code{run}, it inherits its
2222 working directory from the current working directory of @value{GDBN}.
2223 The @value{GDBN} working directory is initially whatever it inherited
2224 from its parent process (typically the shell), but you can specify a new
2225 working directory in @value{GDBN} with the @code{cd} command.
2227 The @value{GDBN} working directory also serves as a default for the commands
2228 that specify files for @value{GDBN} to operate on. @xref{Files, ,Commands to
2233 @cindex change working directory
2234 @item cd @var{directory}
2235 Set the @value{GDBN} working directory to @var{directory}.
2239 Print the @value{GDBN} working directory.
2242 It is generally impossible to find the current working directory of
2243 the process being debugged (since a program can change its directory
2244 during its run). If you work on a system where @value{GDBN} is
2245 configured with the @file{/proc} support, you can use the @code{info
2246 proc} command (@pxref{SVR4 Process Information}) to find out the
2247 current working directory of the debuggee.
2250 @section Your Program's Input and Output
2255 By default, the program you run under @value{GDBN} does input and output to
2256 the same terminal that @value{GDBN} uses. @value{GDBN} switches the terminal
2257 to its own terminal modes to interact with you, but it records the terminal
2258 modes your program was using and switches back to them when you continue
2259 running your program.
2262 @kindex info terminal
2264 Displays information recorded by @value{GDBN} about the terminal modes your
2268 You can redirect your program's input and/or output using shell
2269 redirection with the @code{run} command. For example,
2276 starts your program, diverting its output to the file @file{outfile}.
2279 @cindex controlling terminal
2280 Another way to specify where your program should do input and output is
2281 with the @code{tty} command. This command accepts a file name as
2282 argument, and causes this file to be the default for future @code{run}
2283 commands. It also resets the controlling terminal for the child
2284 process, for future @code{run} commands. For example,
2291 directs that processes started with subsequent @code{run} commands
2292 default to do input and output on the terminal @file{/dev/ttyb} and have
2293 that as their controlling terminal.
2295 An explicit redirection in @code{run} overrides the @code{tty} command's
2296 effect on the input/output device, but not its effect on the controlling
2299 When you use the @code{tty} command or redirect input in the @code{run}
2300 command, only the input @emph{for your program} is affected. The input
2301 for @value{GDBN} still comes from your terminal. @code{tty} is an alias
2302 for @code{set inferior-tty}.
2304 @cindex inferior tty
2305 @cindex set inferior controlling terminal
2306 You can use the @code{show inferior-tty} command to tell @value{GDBN} to
2307 display the name of the terminal that will be used for future runs of your
2311 @item set inferior-tty /dev/ttyb
2312 @kindex set inferior-tty
2313 Set the tty for the program being debugged to /dev/ttyb.
2315 @item show inferior-tty
2316 @kindex show inferior-tty
2317 Show the current tty for the program being debugged.
2321 @section Debugging an Already-running Process
2326 @item attach @var{process-id}
2327 This command attaches to a running process---one that was started
2328 outside @value{GDBN}. (@code{info files} shows your active
2329 targets.) The command takes as argument a process ID. The usual way to
2330 find out the @var{process-id} of a Unix process is with the @code{ps} utility,
2331 or with the @samp{jobs -l} shell command.
2333 @code{attach} does not repeat if you press @key{RET} a second time after
2334 executing the command.
2337 To use @code{attach}, your program must be running in an environment
2338 which supports processes; for example, @code{attach} does not work for
2339 programs on bare-board targets that lack an operating system. You must
2340 also have permission to send the process a signal.
2342 When you use @code{attach}, the debugger finds the program running in
2343 the process first by looking in the current working directory, then (if
2344 the program is not found) by using the source file search path
2345 (@pxref{Source Path, ,Specifying Source Directories}). You can also use
2346 the @code{file} command to load the program. @xref{Files, ,Commands to
2349 The first thing @value{GDBN} does after arranging to debug the specified
2350 process is to stop it. You can examine and modify an attached process
2351 with all the @value{GDBN} commands that are ordinarily available when
2352 you start processes with @code{run}. You can insert breakpoints; you
2353 can step and continue; you can modify storage. If you would rather the
2354 process continue running, you may use the @code{continue} command after
2355 attaching @value{GDBN} to the process.
2360 When you have finished debugging the attached process, you can use the
2361 @code{detach} command to release it from @value{GDBN} control. Detaching
2362 the process continues its execution. After the @code{detach} command,
2363 that process and @value{GDBN} become completely independent once more, and you
2364 are ready to @code{attach} another process or start one with @code{run}.
2365 @code{detach} does not repeat if you press @key{RET} again after
2366 executing the command.
2369 If you exit @value{GDBN} while you have an attached process, you detach
2370 that process. If you use the @code{run} command, you kill that process.
2371 By default, @value{GDBN} asks for confirmation if you try to do either of these
2372 things; you can control whether or not you need to confirm by using the
2373 @code{set confirm} command (@pxref{Messages/Warnings, ,Optional Warnings and
2377 @section Killing the Child Process
2382 Kill the child process in which your program is running under @value{GDBN}.
2385 This command is useful if you wish to debug a core dump instead of a
2386 running process. @value{GDBN} ignores any core dump file while your program
2389 On some operating systems, a program cannot be executed outside @value{GDBN}
2390 while you have breakpoints set on it inside @value{GDBN}. You can use the
2391 @code{kill} command in this situation to permit running your program
2392 outside the debugger.
2394 The @code{kill} command is also useful if you wish to recompile and
2395 relink your program, since on many systems it is impossible to modify an
2396 executable file while it is running in a process. In this case, when you
2397 next type @code{run}, @value{GDBN} notices that the file has changed, and
2398 reads the symbol table again (while trying to preserve your current
2399 breakpoint settings).
2401 @node Inferiors and Programs
2402 @section Debugging Multiple Inferiors and Programs
2404 @value{GDBN} lets you run and debug multiple programs in a single
2405 session. In addition, @value{GDBN} on some systems may let you run
2406 several programs simultaneously (otherwise you have to exit from one
2407 before starting another). In the most general case, you can have
2408 multiple threads of execution in each of multiple processes, launched
2409 from multiple executables.
2412 @value{GDBN} represents the state of each program execution with an
2413 object called an @dfn{inferior}. An inferior typically corresponds to
2414 a process, but is more general and applies also to targets that do not
2415 have processes. Inferiors may be created before a process runs, and
2416 may be retained after a process exits. Inferiors have unique
2417 identifiers that are different from process ids. Usually each
2418 inferior will also have its own distinct address space, although some
2419 embedded targets may have several inferiors running in different parts
2420 of a single address space. Each inferior may in turn have multiple
2421 threads running in it.
2423 To find out what inferiors exist at any moment, use @w{@code{info
2427 @kindex info inferiors
2428 @item info inferiors
2429 Print a list of all inferiors currently being managed by @value{GDBN}.
2431 @value{GDBN} displays for each inferior (in this order):
2435 the inferior number assigned by @value{GDBN}
2438 the target system's inferior identifier
2441 the name of the executable the inferior is running.
2446 An asterisk @samp{*} preceding the @value{GDBN} inferior number
2447 indicates the current inferior.
2451 @c end table here to get a little more width for example
2454 (@value{GDBP}) info inferiors
2455 Num Description Executable
2456 2 process 2307 hello
2457 * 1 process 3401 goodbye
2460 To switch focus between inferiors, use the @code{inferior} command:
2463 @kindex inferior @var{infno}
2464 @item inferior @var{infno}
2465 Make inferior number @var{infno} the current inferior. The argument
2466 @var{infno} is the inferior number assigned by @value{GDBN}, as shown
2467 in the first field of the @samp{info inferiors} display.
2471 You can get multiple executables into a debugging session via the
2472 @code{add-inferior} and @w{@code{clone-inferior}} commands. On some
2473 systems @value{GDBN} can add inferiors to the debug session
2474 automatically by following calls to @code{fork} and @code{exec}. To
2475 remove inferiors from the debugging session use the
2476 @w{@code{remove-inferiors}} command.
2479 @kindex add-inferior
2480 @item add-inferior [ -copies @var{n} ] [ -exec @var{executable} ]
2481 Adds @var{n} inferiors to be run using @var{executable} as the
2482 executable. @var{n} defaults to 1. If no executable is specified,
2483 the inferiors begins empty, with no program. You can still assign or
2484 change the program assigned to the inferior at any time by using the
2485 @code{file} command with the executable name as its argument.
2487 @kindex clone-inferior
2488 @item clone-inferior [ -copies @var{n} ] [ @var{infno} ]
2489 Adds @var{n} inferiors ready to execute the same program as inferior
2490 @var{infno}. @var{n} defaults to 1. @var{infno} defaults to the
2491 number of the current inferior. This is a convenient command when you
2492 want to run another instance of the inferior you are debugging.
2495 (@value{GDBP}) info inferiors
2496 Num Description Executable
2497 * 1 process 29964 helloworld
2498 (@value{GDBP}) clone-inferior
2501 (@value{GDBP}) info inferiors
2502 Num Description Executable
2504 * 1 process 29964 helloworld
2507 You can now simply switch focus to inferior 2 and run it.
2509 @kindex remove-inferiors
2510 @item remove-inferiors @var{infno}@dots{}
2511 Removes the inferior or inferiors @var{infno}@dots{}. It is not
2512 possible to remove an inferior that is running with this command. For
2513 those, use the @code{kill} or @code{detach} command first.
2517 To quit debugging one of the running inferiors that is not the current
2518 inferior, you can either detach from it by using the @w{@code{detach
2519 inferior}} command (allowing it to run independently), or kill it
2520 using the @w{@code{kill inferiors}} command:
2523 @kindex detach inferiors @var{infno}@dots{}
2524 @item detach inferior @var{infno}@dots{}
2525 Detach from the inferior or inferiors identified by @value{GDBN}
2526 inferior number(s) @var{infno}@dots{}. Note that the inferior's entry
2527 still stays on the list of inferiors shown by @code{info inferiors},
2528 but its Description will show @samp{<null>}.
2530 @kindex kill inferiors @var{infno}@dots{}
2531 @item kill inferiors @var{infno}@dots{}
2532 Kill the inferior or inferiors identified by @value{GDBN} inferior
2533 number(s) @var{infno}@dots{}. Note that the inferior's entry still
2534 stays on the list of inferiors shown by @code{info inferiors}, but its
2535 Description will show @samp{<null>}.
2538 After the successful completion of a command such as @code{detach},
2539 @code{detach inferiors}, @code{kill} or @code{kill inferiors}, or after
2540 a normal process exit, the inferior is still valid and listed with
2541 @code{info inferiors}, ready to be restarted.
2544 To be notified when inferiors are started or exit under @value{GDBN}'s
2545 control use @w{@code{set print inferior-events}}:
2548 @kindex set print inferior-events
2549 @cindex print messages on inferior start and exit
2550 @item set print inferior-events
2551 @itemx set print inferior-events on
2552 @itemx set print inferior-events off
2553 The @code{set print inferior-events} command allows you to enable or
2554 disable printing of messages when @value{GDBN} notices that new
2555 inferiors have started or that inferiors have exited or have been
2556 detached. By default, these messages will not be printed.
2558 @kindex show print inferior-events
2559 @item show print inferior-events
2560 Show whether messages will be printed when @value{GDBN} detects that
2561 inferiors have started, exited or have been detached.
2564 Many commands will work the same with multiple programs as with a
2565 single program: e.g., @code{print myglobal} will simply display the
2566 value of @code{myglobal} in the current inferior.
2569 Occasionaly, when debugging @value{GDBN} itself, it may be useful to
2570 get more info about the relationship of inferiors, programs, address
2571 spaces in a debug session. You can do that with the @w{@code{maint
2572 info program-spaces}} command.
2575 @kindex maint info program-spaces
2576 @item maint info program-spaces
2577 Print a list of all program spaces currently being managed by
2580 @value{GDBN} displays for each program space (in this order):
2584 the program space number assigned by @value{GDBN}
2587 the name of the executable loaded into the program space, with e.g.,
2588 the @code{file} command.
2593 An asterisk @samp{*} preceding the @value{GDBN} program space number
2594 indicates the current program space.
2596 In addition, below each program space line, @value{GDBN} prints extra
2597 information that isn't suitable to display in tabular form. For
2598 example, the list of inferiors bound to the program space.
2601 (@value{GDBP}) maint info program-spaces
2604 Bound inferiors: ID 1 (process 21561)
2608 Here we can see that no inferior is running the program @code{hello},
2609 while @code{process 21561} is running the program @code{goodbye}. On
2610 some targets, it is possible that multiple inferiors are bound to the
2611 same program space. The most common example is that of debugging both
2612 the parent and child processes of a @code{vfork} call. For example,
2615 (@value{GDBP}) maint info program-spaces
2618 Bound inferiors: ID 2 (process 18050), ID 1 (process 18045)
2621 Here, both inferior 2 and inferior 1 are running in the same program
2622 space as a result of inferior 1 having executed a @code{vfork} call.
2626 @section Debugging Programs with Multiple Threads
2628 @cindex threads of execution
2629 @cindex multiple threads
2630 @cindex switching threads
2631 In some operating systems, such as HP-UX and Solaris, a single program
2632 may have more than one @dfn{thread} of execution. The precise semantics
2633 of threads differ from one operating system to another, but in general
2634 the threads of a single program are akin to multiple processes---except
2635 that they share one address space (that is, they can all examine and
2636 modify the same variables). On the other hand, each thread has its own
2637 registers and execution stack, and perhaps private memory.
2639 @value{GDBN} provides these facilities for debugging multi-thread
2643 @item automatic notification of new threads
2644 @item @samp{thread @var{threadno}}, a command to switch among threads
2645 @item @samp{info threads}, a command to inquire about existing threads
2646 @item @samp{thread apply [@var{threadno}] [@var{all}] @var{args}},
2647 a command to apply a command to a list of threads
2648 @item thread-specific breakpoints
2649 @item @samp{set print thread-events}, which controls printing of
2650 messages on thread start and exit.
2651 @item @samp{set libthread-db-search-path @var{path}}, which lets
2652 the user specify which @code{libthread_db} to use if the default choice
2653 isn't compatible with the program.
2657 @emph{Warning:} These facilities are not yet available on every
2658 @value{GDBN} configuration where the operating system supports threads.
2659 If your @value{GDBN} does not support threads, these commands have no
2660 effect. For example, a system without thread support shows no output
2661 from @samp{info threads}, and always rejects the @code{thread} command,
2665 (@value{GDBP}) info threads
2666 (@value{GDBP}) thread 1
2667 Thread ID 1 not known. Use the "info threads" command to
2668 see the IDs of currently known threads.
2670 @c FIXME to implementors: how hard would it be to say "sorry, this GDB
2671 @c doesn't support threads"?
2674 @cindex focus of debugging
2675 @cindex current thread
2676 The @value{GDBN} thread debugging facility allows you to observe all
2677 threads while your program runs---but whenever @value{GDBN} takes
2678 control, one thread in particular is always the focus of debugging.
2679 This thread is called the @dfn{current thread}. Debugging commands show
2680 program information from the perspective of the current thread.
2682 @cindex @code{New} @var{systag} message
2683 @cindex thread identifier (system)
2684 @c FIXME-implementors!! It would be more helpful if the [New...] message
2685 @c included GDB's numeric thread handle, so you could just go to that
2686 @c thread without first checking `info threads'.
2687 Whenever @value{GDBN} detects a new thread in your program, it displays
2688 the target system's identification for the thread with a message in the
2689 form @samp{[New @var{systag}]}. @var{systag} is a thread identifier
2690 whose form varies depending on the particular system. For example, on
2691 @sc{gnu}/Linux, you might see
2694 [New Thread 0x41e02940 (LWP 25582)]
2698 when @value{GDBN} notices a new thread. In contrast, on an SGI system,
2699 the @var{systag} is simply something like @samp{process 368}, with no
2702 @c FIXME!! (1) Does the [New...] message appear even for the very first
2703 @c thread of a program, or does it only appear for the
2704 @c second---i.e.@: when it becomes obvious we have a multithread
2706 @c (2) *Is* there necessarily a first thread always? Or do some
2707 @c multithread systems permit starting a program with multiple
2708 @c threads ab initio?
2710 @cindex thread number
2711 @cindex thread identifier (GDB)
2712 For debugging purposes, @value{GDBN} associates its own thread
2713 number---always a single integer---with each thread in your program.
2716 @kindex info threads
2717 @item info threads @r{[}@var{id}@dots{}@r{]}
2718 Display a summary of all threads currently in your program. Optional
2719 argument @var{id}@dots{} is one or more thread ids separated by spaces, and
2720 means to print information only about the specified thread or threads.
2721 @value{GDBN} displays for each thread (in this order):
2725 the thread number assigned by @value{GDBN}
2728 the target system's thread identifier (@var{systag})
2731 the thread's name, if one is known. A thread can either be named by
2732 the user (see @code{thread name}, below), or, in some cases, by the
2736 the current stack frame summary for that thread
2740 An asterisk @samp{*} to the left of the @value{GDBN} thread number
2741 indicates the current thread.
2745 @c end table here to get a little more width for example
2748 (@value{GDBP}) info threads
2750 3 process 35 thread 27 0x34e5 in sigpause ()
2751 2 process 35 thread 23 0x34e5 in sigpause ()
2752 * 1 process 35 thread 13 main (argc=1, argv=0x7ffffff8)
2756 On Solaris, you can display more information about user threads with a
2757 Solaris-specific command:
2760 @item maint info sol-threads
2761 @kindex maint info sol-threads
2762 @cindex thread info (Solaris)
2763 Display info on Solaris user threads.
2767 @kindex thread @var{threadno}
2768 @item thread @var{threadno}
2769 Make thread number @var{threadno} the current thread. The command
2770 argument @var{threadno} is the internal @value{GDBN} thread number, as
2771 shown in the first field of the @samp{info threads} display.
2772 @value{GDBN} responds by displaying the system identifier of the thread
2773 you selected, and its current stack frame summary:
2776 (@value{GDBP}) thread 2
2777 [Switching to thread 2 (Thread 0xb7fdab70 (LWP 12747))]
2778 #0 some_function (ignore=0x0) at example.c:8
2779 8 printf ("hello\n");
2783 As with the @samp{[New @dots{}]} message, the form of the text after
2784 @samp{Switching to} depends on your system's conventions for identifying
2787 @vindex $_thread@r{, convenience variable}
2788 The debugger convenience variable @samp{$_thread} contains the number
2789 of the current thread. You may find this useful in writing breakpoint
2790 conditional expressions, command scripts, and so forth. See
2791 @xref{Convenience Vars,, Convenience Variables}, for general
2792 information on convenience variables.
2794 @kindex thread apply
2795 @cindex apply command to several threads
2796 @item thread apply [@var{threadno} | all] @var{command}
2797 The @code{thread apply} command allows you to apply the named
2798 @var{command} to one or more threads. Specify the numbers of the
2799 threads that you want affected with the command argument
2800 @var{threadno}. It can be a single thread number, one of the numbers
2801 shown in the first field of the @samp{info threads} display; or it
2802 could be a range of thread numbers, as in @code{2-4}. To apply a
2803 command to all threads, type @kbd{thread apply all @var{command}}.
2806 @cindex name a thread
2807 @item thread name [@var{name}]
2808 This command assigns a name to the current thread. If no argument is
2809 given, any existing user-specified name is removed. The thread name
2810 appears in the @samp{info threads} display.
2812 On some systems, such as @sc{gnu}/Linux, @value{GDBN} is able to
2813 determine the name of the thread as given by the OS. On these
2814 systems, a name specified with @samp{thread name} will override the
2815 system-give name, and removing the user-specified name will cause
2816 @value{GDBN} to once again display the system-specified name.
2819 @cindex search for a thread
2820 @item thread find [@var{regexp}]
2821 Search for and display thread ids whose name or @var{systag}
2822 matches the supplied regular expression.
2824 As well as being the complement to the @samp{thread name} command,
2825 this command also allows you to identify a thread by its target
2826 @var{systag}. For instance, on @sc{gnu}/Linux, the target @var{systag}
2830 (@value{GDBN}) thread find 26688
2831 Thread 4 has target id 'Thread 0x41e02940 (LWP 26688)'
2832 (@value{GDBN}) info thread 4
2834 4 Thread 0x41e02940 (LWP 26688) 0x00000031ca6cd372 in select ()
2837 @kindex set print thread-events
2838 @cindex print messages on thread start and exit
2839 @item set print thread-events
2840 @itemx set print thread-events on
2841 @itemx set print thread-events off
2842 The @code{set print thread-events} command allows you to enable or
2843 disable printing of messages when @value{GDBN} notices that new threads have
2844 started or that threads have exited. By default, these messages will
2845 be printed if detection of these events is supported by the target.
2846 Note that these messages cannot be disabled on all targets.
2848 @kindex show print thread-events
2849 @item show print thread-events
2850 Show whether messages will be printed when @value{GDBN} detects that threads
2851 have started and exited.
2854 @xref{Thread Stops,,Stopping and Starting Multi-thread Programs}, for
2855 more information about how @value{GDBN} behaves when you stop and start
2856 programs with multiple threads.
2858 @xref{Set Watchpoints,,Setting Watchpoints}, for information about
2859 watchpoints in programs with multiple threads.
2862 @kindex set libthread-db-search-path
2863 @cindex search path for @code{libthread_db}
2864 @item set libthread-db-search-path @r{[}@var{path}@r{]}
2865 If this variable is set, @var{path} is a colon-separated list of
2866 directories @value{GDBN} will use to search for @code{libthread_db}.
2867 If you omit @var{path}, @samp{libthread-db-search-path} will be reset to
2868 its default value (@code{$sdir:$pdir} on @sc{gnu}/Linux and Solaris systems).
2869 Internally, the default value comes from the @code{LIBTHREAD_DB_SEARCH_PATH}
2872 On @sc{gnu}/Linux and Solaris systems, @value{GDBN} uses a ``helper''
2873 @code{libthread_db} library to obtain information about threads in the
2874 inferior process. @value{GDBN} will use @samp{libthread-db-search-path}
2875 to find @code{libthread_db}.
2877 A special entry @samp{$sdir} for @samp{libthread-db-search-path}
2878 refers to the default system directories that are
2879 normally searched for loading shared libraries.
2881 A special entry @samp{$pdir} for @samp{libthread-db-search-path}
2882 refers to the directory from which @code{libpthread}
2883 was loaded in the inferior process.
2885 For any @code{libthread_db} library @value{GDBN} finds in above directories,
2886 @value{GDBN} attempts to initialize it with the current inferior process.
2887 If this initialization fails (which could happen because of a version
2888 mismatch between @code{libthread_db} and @code{libpthread}), @value{GDBN}
2889 will unload @code{libthread_db}, and continue with the next directory.
2890 If none of @code{libthread_db} libraries initialize successfully,
2891 @value{GDBN} will issue a warning and thread debugging will be disabled.
2893 Setting @code{libthread-db-search-path} is currently implemented
2894 only on some platforms.
2896 @kindex show libthread-db-search-path
2897 @item show libthread-db-search-path
2898 Display current libthread_db search path.
2900 @kindex set debug libthread-db
2901 @kindex show debug libthread-db
2902 @cindex debugging @code{libthread_db}
2903 @item set debug libthread-db
2904 @itemx show debug libthread-db
2905 Turns on or off display of @code{libthread_db}-related events.
2906 Use @code{1} to enable, @code{0} to disable.
2910 @section Debugging Forks
2912 @cindex fork, debugging programs which call
2913 @cindex multiple processes
2914 @cindex processes, multiple
2915 On most systems, @value{GDBN} has no special support for debugging
2916 programs which create additional processes using the @code{fork}
2917 function. When a program forks, @value{GDBN} will continue to debug the
2918 parent process and the child process will run unimpeded. If you have
2919 set a breakpoint in any code which the child then executes, the child
2920 will get a @code{SIGTRAP} signal which (unless it catches the signal)
2921 will cause it to terminate.
2923 However, if you want to debug the child process there is a workaround
2924 which isn't too painful. Put a call to @code{sleep} in the code which
2925 the child process executes after the fork. It may be useful to sleep
2926 only if a certain environment variable is set, or a certain file exists,
2927 so that the delay need not occur when you don't want to run @value{GDBN}
2928 on the child. While the child is sleeping, use the @code{ps} program to
2929 get its process ID. Then tell @value{GDBN} (a new invocation of
2930 @value{GDBN} if you are also debugging the parent process) to attach to
2931 the child process (@pxref{Attach}). From that point on you can debug
2932 the child process just like any other process which you attached to.
2934 On some systems, @value{GDBN} provides support for debugging programs that
2935 create additional processes using the @code{fork} or @code{vfork} functions.
2936 Currently, the only platforms with this feature are HP-UX (11.x and later
2937 only?) and @sc{gnu}/Linux (kernel version 2.5.60 and later).
2939 By default, when a program forks, @value{GDBN} will continue to debug
2940 the parent process and the child process will run unimpeded.
2942 If you want to follow the child process instead of the parent process,
2943 use the command @w{@code{set follow-fork-mode}}.
2946 @kindex set follow-fork-mode
2947 @item set follow-fork-mode @var{mode}
2948 Set the debugger response to a program call of @code{fork} or
2949 @code{vfork}. A call to @code{fork} or @code{vfork} creates a new
2950 process. The @var{mode} argument can be:
2954 The original process is debugged after a fork. The child process runs
2955 unimpeded. This is the default.
2958 The new process is debugged after a fork. The parent process runs
2963 @kindex show follow-fork-mode
2964 @item show follow-fork-mode
2965 Display the current debugger response to a @code{fork} or @code{vfork} call.
2968 @cindex debugging multiple processes
2969 On Linux, if you want to debug both the parent and child processes, use the
2970 command @w{@code{set detach-on-fork}}.
2973 @kindex set detach-on-fork
2974 @item set detach-on-fork @var{mode}
2975 Tells gdb whether to detach one of the processes after a fork, or
2976 retain debugger control over them both.
2980 The child process (or parent process, depending on the value of
2981 @code{follow-fork-mode}) will be detached and allowed to run
2982 independently. This is the default.
2985 Both processes will be held under the control of @value{GDBN}.
2986 One process (child or parent, depending on the value of
2987 @code{follow-fork-mode}) is debugged as usual, while the other
2992 @kindex show detach-on-fork
2993 @item show detach-on-fork
2994 Show whether detach-on-fork mode is on/off.
2997 If you choose to set @samp{detach-on-fork} mode off, then @value{GDBN}
2998 will retain control of all forked processes (including nested forks).
2999 You can list the forked processes under the control of @value{GDBN} by
3000 using the @w{@code{info inferiors}} command, and switch from one fork
3001 to another by using the @code{inferior} command (@pxref{Inferiors and
3002 Programs, ,Debugging Multiple Inferiors and Programs}).
3004 To quit debugging one of the forked processes, you can either detach
3005 from it by using the @w{@code{detach inferiors}} command (allowing it
3006 to run independently), or kill it using the @w{@code{kill inferiors}}
3007 command. @xref{Inferiors and Programs, ,Debugging Multiple Inferiors
3010 If you ask to debug a child process and a @code{vfork} is followed by an
3011 @code{exec}, @value{GDBN} executes the new target up to the first
3012 breakpoint in the new target. If you have a breakpoint set on
3013 @code{main} in your original program, the breakpoint will also be set on
3014 the child process's @code{main}.
3016 On some systems, when a child process is spawned by @code{vfork}, you
3017 cannot debug the child or parent until an @code{exec} call completes.
3019 If you issue a @code{run} command to @value{GDBN} after an @code{exec}
3020 call executes, the new target restarts. To restart the parent
3021 process, use the @code{file} command with the parent executable name
3022 as its argument. By default, after an @code{exec} call executes,
3023 @value{GDBN} discards the symbols of the previous executable image.
3024 You can change this behaviour with the @w{@code{set follow-exec-mode}}
3028 @kindex set follow-exec-mode
3029 @item set follow-exec-mode @var{mode}
3031 Set debugger response to a program call of @code{exec}. An
3032 @code{exec} call replaces the program image of a process.
3034 @code{follow-exec-mode} can be:
3038 @value{GDBN} creates a new inferior and rebinds the process to this
3039 new inferior. The program the process was running before the
3040 @code{exec} call can be restarted afterwards by restarting the
3046 (@value{GDBP}) info inferiors
3048 Id Description Executable
3051 process 12020 is executing new program: prog2
3052 Program exited normally.
3053 (@value{GDBP}) info inferiors
3054 Id Description Executable
3060 @value{GDBN} keeps the process bound to the same inferior. The new
3061 executable image replaces the previous executable loaded in the
3062 inferior. Restarting the inferior after the @code{exec} call, with
3063 e.g., the @code{run} command, restarts the executable the process was
3064 running after the @code{exec} call. This is the default mode.
3069 (@value{GDBP}) info inferiors
3070 Id Description Executable
3073 process 12020 is executing new program: prog2
3074 Program exited normally.
3075 (@value{GDBP}) info inferiors
3076 Id Description Executable
3083 You can use the @code{catch} command to make @value{GDBN} stop whenever
3084 a @code{fork}, @code{vfork}, or @code{exec} call is made. @xref{Set
3085 Catchpoints, ,Setting Catchpoints}.
3087 @node Checkpoint/Restart
3088 @section Setting a @emph{Bookmark} to Return to Later
3093 @cindex snapshot of a process
3094 @cindex rewind program state
3096 On certain operating systems@footnote{Currently, only
3097 @sc{gnu}/Linux.}, @value{GDBN} is able to save a @dfn{snapshot} of a
3098 program's state, called a @dfn{checkpoint}, and come back to it
3101 Returning to a checkpoint effectively undoes everything that has
3102 happened in the program since the @code{checkpoint} was saved. This
3103 includes changes in memory, registers, and even (within some limits)
3104 system state. Effectively, it is like going back in time to the
3105 moment when the checkpoint was saved.
3107 Thus, if you're stepping thru a program and you think you're
3108 getting close to the point where things go wrong, you can save
3109 a checkpoint. Then, if you accidentally go too far and miss
3110 the critical statement, instead of having to restart your program
3111 from the beginning, you can just go back to the checkpoint and
3112 start again from there.
3114 This can be especially useful if it takes a lot of time or
3115 steps to reach the point where you think the bug occurs.
3117 To use the @code{checkpoint}/@code{restart} method of debugging:
3122 Save a snapshot of the debugged program's current execution state.
3123 The @code{checkpoint} command takes no arguments, but each checkpoint
3124 is assigned a small integer id, similar to a breakpoint id.
3126 @kindex info checkpoints
3127 @item info checkpoints
3128 List the checkpoints that have been saved in the current debugging
3129 session. For each checkpoint, the following information will be
3136 @item Source line, or label
3139 @kindex restart @var{checkpoint-id}
3140 @item restart @var{checkpoint-id}
3141 Restore the program state that was saved as checkpoint number
3142 @var{checkpoint-id}. All program variables, registers, stack frames
3143 etc.@: will be returned to the values that they had when the checkpoint
3144 was saved. In essence, gdb will ``wind back the clock'' to the point
3145 in time when the checkpoint was saved.
3147 Note that breakpoints, @value{GDBN} variables, command history etc.
3148 are not affected by restoring a checkpoint. In general, a checkpoint
3149 only restores things that reside in the program being debugged, not in
3152 @kindex delete checkpoint @var{checkpoint-id}
3153 @item delete checkpoint @var{checkpoint-id}
3154 Delete the previously-saved checkpoint identified by @var{checkpoint-id}.
3158 Returning to a previously saved checkpoint will restore the user state
3159 of the program being debugged, plus a significant subset of the system
3160 (OS) state, including file pointers. It won't ``un-write'' data from
3161 a file, but it will rewind the file pointer to the previous location,
3162 so that the previously written data can be overwritten. For files
3163 opened in read mode, the pointer will also be restored so that the
3164 previously read data can be read again.
3166 Of course, characters that have been sent to a printer (or other
3167 external device) cannot be ``snatched back'', and characters received
3168 from eg.@: a serial device can be removed from internal program buffers,
3169 but they cannot be ``pushed back'' into the serial pipeline, ready to
3170 be received again. Similarly, the actual contents of files that have
3171 been changed cannot be restored (at this time).
3173 However, within those constraints, you actually can ``rewind'' your
3174 program to a previously saved point in time, and begin debugging it
3175 again --- and you can change the course of events so as to debug a
3176 different execution path this time.
3178 @cindex checkpoints and process id
3179 Finally, there is one bit of internal program state that will be
3180 different when you return to a checkpoint --- the program's process
3181 id. Each checkpoint will have a unique process id (or @var{pid}),
3182 and each will be different from the program's original @var{pid}.
3183 If your program has saved a local copy of its process id, this could
3184 potentially pose a problem.
3186 @subsection A Non-obvious Benefit of Using Checkpoints
3188 On some systems such as @sc{gnu}/Linux, address space randomization
3189 is performed on new processes for security reasons. This makes it
3190 difficult or impossible to set a breakpoint, or watchpoint, on an
3191 absolute address if you have to restart the program, since the
3192 absolute location of a symbol will change from one execution to the
3195 A checkpoint, however, is an @emph{identical} copy of a process.
3196 Therefore if you create a checkpoint at (eg.@:) the start of main,
3197 and simply return to that checkpoint instead of restarting the
3198 process, you can avoid the effects of address randomization and
3199 your symbols will all stay in the same place.
3202 @chapter Stopping and Continuing
3204 The principal purposes of using a debugger are so that you can stop your
3205 program before it terminates; or so that, if your program runs into
3206 trouble, you can investigate and find out why.
3208 Inside @value{GDBN}, your program may stop for any of several reasons,
3209 such as a signal, a breakpoint, or reaching a new line after a
3210 @value{GDBN} command such as @code{step}. You may then examine and
3211 change variables, set new breakpoints or remove old ones, and then
3212 continue execution. Usually, the messages shown by @value{GDBN} provide
3213 ample explanation of the status of your program---but you can also
3214 explicitly request this information at any time.
3217 @kindex info program
3219 Display information about the status of your program: whether it is
3220 running or not, what process it is, and why it stopped.
3224 * Breakpoints:: Breakpoints, watchpoints, and catchpoints
3225 * Continuing and Stepping:: Resuming execution
3226 * Skipping Over Functions and Files::
3227 Skipping over functions and files
3229 * Thread Stops:: Stopping and starting multi-thread programs
3233 @section Breakpoints, Watchpoints, and Catchpoints
3236 A @dfn{breakpoint} makes your program stop whenever a certain point in
3237 the program is reached. For each breakpoint, you can add conditions to
3238 control in finer detail whether your program stops. You can set
3239 breakpoints with the @code{break} command and its variants (@pxref{Set
3240 Breaks, ,Setting Breakpoints}), to specify the place where your program
3241 should stop by line number, function name or exact address in the
3244 On some systems, you can set breakpoints in shared libraries before
3245 the executable is run. There is a minor limitation on HP-UX systems:
3246 you must wait until the executable is run in order to set breakpoints
3247 in shared library routines that are not called directly by the program
3248 (for example, routines that are arguments in a @code{pthread_create}
3252 @cindex data breakpoints
3253 @cindex memory tracing
3254 @cindex breakpoint on memory address
3255 @cindex breakpoint on variable modification
3256 A @dfn{watchpoint} is a special breakpoint that stops your program
3257 when the value of an expression changes. The expression may be a value
3258 of a variable, or it could involve values of one or more variables
3259 combined by operators, such as @samp{a + b}. This is sometimes called
3260 @dfn{data breakpoints}. You must use a different command to set
3261 watchpoints (@pxref{Set Watchpoints, ,Setting Watchpoints}), but aside
3262 from that, you can manage a watchpoint like any other breakpoint: you
3263 enable, disable, and delete both breakpoints and watchpoints using the
3266 You can arrange to have values from your program displayed automatically
3267 whenever @value{GDBN} stops at a breakpoint. @xref{Auto Display,,
3271 @cindex breakpoint on events
3272 A @dfn{catchpoint} is another special breakpoint that stops your program
3273 when a certain kind of event occurs, such as the throwing of a C@t{++}
3274 exception or the loading of a library. As with watchpoints, you use a
3275 different command to set a catchpoint (@pxref{Set Catchpoints, ,Setting
3276 Catchpoints}), but aside from that, you can manage a catchpoint like any
3277 other breakpoint. (To stop when your program receives a signal, use the
3278 @code{handle} command; see @ref{Signals, ,Signals}.)
3280 @cindex breakpoint numbers
3281 @cindex numbers for breakpoints
3282 @value{GDBN} assigns a number to each breakpoint, watchpoint, or
3283 catchpoint when you create it; these numbers are successive integers
3284 starting with one. In many of the commands for controlling various
3285 features of breakpoints you use the breakpoint number to say which
3286 breakpoint you want to change. Each breakpoint may be @dfn{enabled} or
3287 @dfn{disabled}; if disabled, it has no effect on your program until you
3290 @cindex breakpoint ranges
3291 @cindex ranges of breakpoints
3292 Some @value{GDBN} commands accept a range of breakpoints on which to
3293 operate. A breakpoint range is either a single breakpoint number, like
3294 @samp{5}, or two such numbers, in increasing order, separated by a
3295 hyphen, like @samp{5-7}. When a breakpoint range is given to a command,
3296 all breakpoints in that range are operated on.
3299 * Set Breaks:: Setting breakpoints
3300 * Set Watchpoints:: Setting watchpoints
3301 * Set Catchpoints:: Setting catchpoints
3302 * Delete Breaks:: Deleting breakpoints
3303 * Disabling:: Disabling breakpoints
3304 * Conditions:: Break conditions
3305 * Break Commands:: Breakpoint command lists
3306 * Save Breakpoints:: How to save breakpoints in a file
3307 * Error in Breakpoints:: ``Cannot insert breakpoints''
3308 * Breakpoint-related Warnings:: ``Breakpoint address adjusted...''
3312 @subsection Setting Breakpoints
3314 @c FIXME LMB what does GDB do if no code on line of breakpt?
3315 @c consider in particular declaration with/without initialization.
3317 @c FIXME 2 is there stuff on this already? break at fun start, already init?
3320 @kindex b @r{(@code{break})}
3321 @vindex $bpnum@r{, convenience variable}
3322 @cindex latest breakpoint
3323 Breakpoints are set with the @code{break} command (abbreviated
3324 @code{b}). The debugger convenience variable @samp{$bpnum} records the
3325 number of the breakpoint you've set most recently; see @ref{Convenience
3326 Vars,, Convenience Variables}, for a discussion of what you can do with
3327 convenience variables.
3330 @item break @var{location}
3331 Set a breakpoint at the given @var{location}, which can specify a
3332 function name, a line number, or an address of an instruction.
3333 (@xref{Specify Location}, for a list of all the possible ways to
3334 specify a @var{location}.) The breakpoint will stop your program just
3335 before it executes any of the code in the specified @var{location}.
3337 When using source languages that permit overloading of symbols, such as
3338 C@t{++}, a function name may refer to more than one possible place to break.
3339 @xref{Ambiguous Expressions,,Ambiguous Expressions}, for a discussion of
3342 It is also possible to insert a breakpoint that will stop the program
3343 only if a specific thread (@pxref{Thread-Specific Breakpoints})
3344 or a specific task (@pxref{Ada Tasks}) hits that breakpoint.
3347 When called without any arguments, @code{break} sets a breakpoint at
3348 the next instruction to be executed in the selected stack frame
3349 (@pxref{Stack, ,Examining the Stack}). In any selected frame but the
3350 innermost, this makes your program stop as soon as control
3351 returns to that frame. This is similar to the effect of a
3352 @code{finish} command in the frame inside the selected frame---except
3353 that @code{finish} does not leave an active breakpoint. If you use
3354 @code{break} without an argument in the innermost frame, @value{GDBN} stops
3355 the next time it reaches the current location; this may be useful
3358 @value{GDBN} normally ignores breakpoints when it resumes execution, until at
3359 least one instruction has been executed. If it did not do this, you
3360 would be unable to proceed past a breakpoint without first disabling the
3361 breakpoint. This rule applies whether or not the breakpoint already
3362 existed when your program stopped.
3364 @item break @dots{} if @var{cond}
3365 Set a breakpoint with condition @var{cond}; evaluate the expression
3366 @var{cond} each time the breakpoint is reached, and stop only if the
3367 value is nonzero---that is, if @var{cond} evaluates as true.
3368 @samp{@dots{}} stands for one of the possible arguments described
3369 above (or no argument) specifying where to break. @xref{Conditions,
3370 ,Break Conditions}, for more information on breakpoint conditions.
3373 @item tbreak @var{args}
3374 Set a breakpoint enabled only for one stop. @var{args} are the
3375 same as for the @code{break} command, and the breakpoint is set in the same
3376 way, but the breakpoint is automatically deleted after the first time your
3377 program stops there. @xref{Disabling, ,Disabling Breakpoints}.
3380 @cindex hardware breakpoints
3381 @item hbreak @var{args}
3382 Set a hardware-assisted breakpoint. @var{args} are the same as for the
3383 @code{break} command and the breakpoint is set in the same way, but the
3384 breakpoint requires hardware support and some target hardware may not
3385 have this support. The main purpose of this is EPROM/ROM code
3386 debugging, so you can set a breakpoint at an instruction without
3387 changing the instruction. This can be used with the new trap-generation
3388 provided by SPARClite DSU and most x86-based targets. These targets
3389 will generate traps when a program accesses some data or instruction
3390 address that is assigned to the debug registers. However the hardware
3391 breakpoint registers can take a limited number of breakpoints. For
3392 example, on the DSU, only two data breakpoints can be set at a time, and
3393 @value{GDBN} will reject this command if more than two are used. Delete
3394 or disable unused hardware breakpoints before setting new ones
3395 (@pxref{Disabling, ,Disabling Breakpoints}).
3396 @xref{Conditions, ,Break Conditions}.
3397 For remote targets, you can restrict the number of hardware
3398 breakpoints @value{GDBN} will use, see @ref{set remote
3399 hardware-breakpoint-limit}.
3402 @item thbreak @var{args}
3403 Set a hardware-assisted breakpoint enabled only for one stop. @var{args}
3404 are the same as for the @code{hbreak} command and the breakpoint is set in
3405 the same way. However, like the @code{tbreak} command,
3406 the breakpoint is automatically deleted after the
3407 first time your program stops there. Also, like the @code{hbreak}
3408 command, the breakpoint requires hardware support and some target hardware
3409 may not have this support. @xref{Disabling, ,Disabling Breakpoints}.
3410 See also @ref{Conditions, ,Break Conditions}.
3413 @cindex regular expression
3414 @cindex breakpoints at functions matching a regexp
3415 @cindex set breakpoints in many functions
3416 @item rbreak @var{regex}
3417 Set breakpoints on all functions matching the regular expression
3418 @var{regex}. This command sets an unconditional breakpoint on all
3419 matches, printing a list of all breakpoints it set. Once these
3420 breakpoints are set, they are treated just like the breakpoints set with
3421 the @code{break} command. You can delete them, disable them, or make
3422 them conditional the same way as any other breakpoint.
3424 The syntax of the regular expression is the standard one used with tools
3425 like @file{grep}. Note that this is different from the syntax used by
3426 shells, so for instance @code{foo*} matches all functions that include
3427 an @code{fo} followed by zero or more @code{o}s. There is an implicit
3428 @code{.*} leading and trailing the regular expression you supply, so to
3429 match only functions that begin with @code{foo}, use @code{^foo}.
3431 @cindex non-member C@t{++} functions, set breakpoint in
3432 When debugging C@t{++} programs, @code{rbreak} is useful for setting
3433 breakpoints on overloaded functions that are not members of any special
3436 @cindex set breakpoints on all functions
3437 The @code{rbreak} command can be used to set breakpoints in
3438 @strong{all} the functions in a program, like this:
3441 (@value{GDBP}) rbreak .
3444 @item rbreak @var{file}:@var{regex}
3445 If @code{rbreak} is called with a filename qualification, it limits
3446 the search for functions matching the given regular expression to the
3447 specified @var{file}. This can be used, for example, to set breakpoints on
3448 every function in a given file:
3451 (@value{GDBP}) rbreak file.c:.
3454 The colon separating the filename qualifier from the regex may
3455 optionally be surrounded by spaces.
3457 @kindex info breakpoints
3458 @cindex @code{$_} and @code{info breakpoints}
3459 @item info breakpoints @r{[}@var{n}@dots{}@r{]}
3460 @itemx info break @r{[}@var{n}@dots{}@r{]}
3461 Print a table of all breakpoints, watchpoints, and catchpoints set and
3462 not deleted. Optional argument @var{n} means print information only
3463 about the specified breakpoint(s) (or watchpoint(s) or catchpoint(s)).
3464 For each breakpoint, following columns are printed:
3467 @item Breakpoint Numbers
3469 Breakpoint, watchpoint, or catchpoint.
3471 Whether the breakpoint is marked to be disabled or deleted when hit.
3472 @item Enabled or Disabled
3473 Enabled breakpoints are marked with @samp{y}. @samp{n} marks breakpoints
3474 that are not enabled.
3476 Where the breakpoint is in your program, as a memory address. For a
3477 pending breakpoint whose address is not yet known, this field will
3478 contain @samp{<PENDING>}. Such breakpoint won't fire until a shared
3479 library that has the symbol or line referred by breakpoint is loaded.
3480 See below for details. A breakpoint with several locations will
3481 have @samp{<MULTIPLE>} in this field---see below for details.
3483 Where the breakpoint is in the source for your program, as a file and
3484 line number. For a pending breakpoint, the original string passed to
3485 the breakpoint command will be listed as it cannot be resolved until
3486 the appropriate shared library is loaded in the future.
3490 If a breakpoint is conditional, there are two evaluation modes: ``host'' and
3491 ``target''. If mode is ``host'', breakpoint condition evaluation is done by
3492 @value{GDBN} on the host's side. If it is ``target'', then the condition
3493 is evaluated by the target. The @code{info break} command shows
3494 the condition on the line following the affected breakpoint, together with
3495 its condition evaluation mode in between parentheses.
3497 Breakpoint commands, if any, are listed after that. A pending breakpoint is
3498 allowed to have a condition specified for it. The condition is not parsed for
3499 validity until a shared library is loaded that allows the pending
3500 breakpoint to resolve to a valid location.
3503 @code{info break} with a breakpoint
3504 number @var{n} as argument lists only that breakpoint. The
3505 convenience variable @code{$_} and the default examining-address for
3506 the @code{x} command are set to the address of the last breakpoint
3507 listed (@pxref{Memory, ,Examining Memory}).
3510 @code{info break} displays a count of the number of times the breakpoint
3511 has been hit. This is especially useful in conjunction with the
3512 @code{ignore} command. You can ignore a large number of breakpoint
3513 hits, look at the breakpoint info to see how many times the breakpoint
3514 was hit, and then run again, ignoring one less than that number. This
3515 will get you quickly to the last hit of that breakpoint.
3518 For a breakpoints with an enable count (xref) greater than 1,
3519 @code{info break} also displays that count.
3523 @value{GDBN} allows you to set any number of breakpoints at the same place in
3524 your program. There is nothing silly or meaningless about this. When
3525 the breakpoints are conditional, this is even useful
3526 (@pxref{Conditions, ,Break Conditions}).
3528 @cindex multiple locations, breakpoints
3529 @cindex breakpoints, multiple locations
3530 It is possible that a breakpoint corresponds to several locations
3531 in your program. Examples of this situation are:
3535 Multiple functions in the program may have the same name.
3538 For a C@t{++} constructor, the @value{NGCC} compiler generates several
3539 instances of the function body, used in different cases.
3542 For a C@t{++} template function, a given line in the function can
3543 correspond to any number of instantiations.
3546 For an inlined function, a given source line can correspond to
3547 several places where that function is inlined.
3550 In all those cases, @value{GDBN} will insert a breakpoint at all
3551 the relevant locations.
3553 A breakpoint with multiple locations is displayed in the breakpoint
3554 table using several rows---one header row, followed by one row for
3555 each breakpoint location. The header row has @samp{<MULTIPLE>} in the
3556 address column. The rows for individual locations contain the actual
3557 addresses for locations, and show the functions to which those
3558 locations belong. The number column for a location is of the form
3559 @var{breakpoint-number}.@var{location-number}.
3564 Num Type Disp Enb Address What
3565 1 breakpoint keep y <MULTIPLE>
3567 breakpoint already hit 1 time
3568 1.1 y 0x080486a2 in void foo<int>() at t.cc:8
3569 1.2 y 0x080486ca in void foo<double>() at t.cc:8
3572 Each location can be individually enabled or disabled by passing
3573 @var{breakpoint-number}.@var{location-number} as argument to the
3574 @code{enable} and @code{disable} commands. Note that you cannot
3575 delete the individual locations from the list, you can only delete the
3576 entire list of locations that belong to their parent breakpoint (with
3577 the @kbd{delete @var{num}} command, where @var{num} is the number of
3578 the parent breakpoint, 1 in the above example). Disabling or enabling
3579 the parent breakpoint (@pxref{Disabling}) affects all of the locations
3580 that belong to that breakpoint.
3582 @cindex pending breakpoints
3583 It's quite common to have a breakpoint inside a shared library.
3584 Shared libraries can be loaded and unloaded explicitly,
3585 and possibly repeatedly, as the program is executed. To support
3586 this use case, @value{GDBN} updates breakpoint locations whenever
3587 any shared library is loaded or unloaded. Typically, you would
3588 set a breakpoint in a shared library at the beginning of your
3589 debugging session, when the library is not loaded, and when the
3590 symbols from the library are not available. When you try to set
3591 breakpoint, @value{GDBN} will ask you if you want to set
3592 a so called @dfn{pending breakpoint}---breakpoint whose address
3593 is not yet resolved.
3595 After the program is run, whenever a new shared library is loaded,
3596 @value{GDBN} reevaluates all the breakpoints. When a newly loaded
3597 shared library contains the symbol or line referred to by some
3598 pending breakpoint, that breakpoint is resolved and becomes an
3599 ordinary breakpoint. When a library is unloaded, all breakpoints
3600 that refer to its symbols or source lines become pending again.
3602 This logic works for breakpoints with multiple locations, too. For
3603 example, if you have a breakpoint in a C@t{++} template function, and
3604 a newly loaded shared library has an instantiation of that template,
3605 a new location is added to the list of locations for the breakpoint.
3607 Except for having unresolved address, pending breakpoints do not
3608 differ from regular breakpoints. You can set conditions or commands,
3609 enable and disable them and perform other breakpoint operations.
3611 @value{GDBN} provides some additional commands for controlling what
3612 happens when the @samp{break} command cannot resolve breakpoint
3613 address specification to an address:
3615 @kindex set breakpoint pending
3616 @kindex show breakpoint pending
3618 @item set breakpoint pending auto
3619 This is the default behavior. When @value{GDBN} cannot find the breakpoint
3620 location, it queries you whether a pending breakpoint should be created.
3622 @item set breakpoint pending on
3623 This indicates that an unrecognized breakpoint location should automatically
3624 result in a pending breakpoint being created.
3626 @item set breakpoint pending off
3627 This indicates that pending breakpoints are not to be created. Any
3628 unrecognized breakpoint location results in an error. This setting does
3629 not affect any pending breakpoints previously created.
3631 @item show breakpoint pending
3632 Show the current behavior setting for creating pending breakpoints.
3635 The settings above only affect the @code{break} command and its
3636 variants. Once breakpoint is set, it will be automatically updated
3637 as shared libraries are loaded and unloaded.
3639 @cindex automatic hardware breakpoints
3640 For some targets, @value{GDBN} can automatically decide if hardware or
3641 software breakpoints should be used, depending on whether the
3642 breakpoint address is read-only or read-write. This applies to
3643 breakpoints set with the @code{break} command as well as to internal
3644 breakpoints set by commands like @code{next} and @code{finish}. For
3645 breakpoints set with @code{hbreak}, @value{GDBN} will always use hardware
3648 You can control this automatic behaviour with the following commands::
3650 @kindex set breakpoint auto-hw
3651 @kindex show breakpoint auto-hw
3653 @item set breakpoint auto-hw on
3654 This is the default behavior. When @value{GDBN} sets a breakpoint, it
3655 will try to use the target memory map to decide if software or hardware
3656 breakpoint must be used.
3658 @item set breakpoint auto-hw off
3659 This indicates @value{GDBN} should not automatically select breakpoint
3660 type. If the target provides a memory map, @value{GDBN} will warn when
3661 trying to set software breakpoint at a read-only address.
3664 @value{GDBN} normally implements breakpoints by replacing the program code
3665 at the breakpoint address with a special instruction, which, when
3666 executed, given control to the debugger. By default, the program
3667 code is so modified only when the program is resumed. As soon as
3668 the program stops, @value{GDBN} restores the original instructions. This
3669 behaviour guards against leaving breakpoints inserted in the
3670 target should gdb abrubptly disconnect. However, with slow remote
3671 targets, inserting and removing breakpoint can reduce the performance.
3672 This behavior can be controlled with the following commands::
3674 @kindex set breakpoint always-inserted
3675 @kindex show breakpoint always-inserted
3677 @item set breakpoint always-inserted off
3678 All breakpoints, including newly added by the user, are inserted in
3679 the target only when the target is resumed. All breakpoints are
3680 removed from the target when it stops.
3682 @item set breakpoint always-inserted on
3683 Causes all breakpoints to be inserted in the target at all times. If
3684 the user adds a new breakpoint, or changes an existing breakpoint, the
3685 breakpoints in the target are updated immediately. A breakpoint is
3686 removed from the target only when breakpoint itself is removed.
3688 @cindex non-stop mode, and @code{breakpoint always-inserted}
3689 @item set breakpoint always-inserted auto
3690 This is the default mode. If @value{GDBN} is controlling the inferior
3691 in non-stop mode (@pxref{Non-Stop Mode}), gdb behaves as if
3692 @code{breakpoint always-inserted} mode is on. If @value{GDBN} is
3693 controlling the inferior in all-stop mode, @value{GDBN} behaves as if
3694 @code{breakpoint always-inserted} mode is off.
3697 @value{GDBN} handles conditional breakpoints by evaluating these conditions
3698 when a breakpoint breaks. If the condition is true, then the process being
3699 debugged stops, otherwise the process is resumed.
3701 If the target supports evaluating conditions on its end, @value{GDBN} may
3702 download the breakpoint, together with its conditions, to it.
3704 This feature can be controlled via the following commands:
3706 @kindex set breakpoint condition-evaluation
3707 @kindex show breakpoint condition-evaluation
3709 @item set breakpoint condition-evaluation host
3710 This option commands @value{GDBN} to evaluate the breakpoint
3711 conditions on the host's side. Unconditional breakpoints are sent to
3712 the target which in turn receives the triggers and reports them back to GDB
3713 for condition evaluation. This is the standard evaluation mode.
3715 @item set breakpoint condition-evaluation target
3716 This option commands @value{GDBN} to download breakpoint conditions
3717 to the target at the moment of their insertion. The target
3718 is responsible for evaluating the conditional expression and reporting
3719 breakpoint stop events back to @value{GDBN} whenever the condition
3720 is true. Due to limitations of target-side evaluation, some conditions
3721 cannot be evaluated there, e.g., conditions that depend on local data
3722 that is only known to the host. Examples include
3723 conditional expressions involving convenience variables, complex types
3724 that cannot be handled by the agent expression parser and expressions
3725 that are too long to be sent over to the target, specially when the
3726 target is a remote system. In these cases, the conditions will be
3727 evaluated by @value{GDBN}.
3729 @item set breakpoint condition-evaluation auto
3730 This is the default mode. If the target supports evaluating breakpoint
3731 conditions on its end, @value{GDBN} will download breakpoint conditions to
3732 the target (limitations mentioned previously apply). If the target does
3733 not support breakpoint condition evaluation, then @value{GDBN} will fallback
3734 to evaluating all these conditions on the host's side.
3738 @cindex negative breakpoint numbers
3739 @cindex internal @value{GDBN} breakpoints
3740 @value{GDBN} itself sometimes sets breakpoints in your program for
3741 special purposes, such as proper handling of @code{longjmp} (in C
3742 programs). These internal breakpoints are assigned negative numbers,
3743 starting with @code{-1}; @samp{info breakpoints} does not display them.
3744 You can see these breakpoints with the @value{GDBN} maintenance command
3745 @samp{maint info breakpoints} (@pxref{maint info breakpoints}).
3748 @node Set Watchpoints
3749 @subsection Setting Watchpoints
3751 @cindex setting watchpoints
3752 You can use a watchpoint to stop execution whenever the value of an
3753 expression changes, without having to predict a particular place where
3754 this may happen. (This is sometimes called a @dfn{data breakpoint}.)
3755 The expression may be as simple as the value of a single variable, or
3756 as complex as many variables combined by operators. Examples include:
3760 A reference to the value of a single variable.
3763 An address cast to an appropriate data type. For example,
3764 @samp{*(int *)0x12345678} will watch a 4-byte region at the specified
3765 address (assuming an @code{int} occupies 4 bytes).
3768 An arbitrarily complex expression, such as @samp{a*b + c/d}. The
3769 expression can use any operators valid in the program's native
3770 language (@pxref{Languages}).
3773 You can set a watchpoint on an expression even if the expression can
3774 not be evaluated yet. For instance, you can set a watchpoint on
3775 @samp{*global_ptr} before @samp{global_ptr} is initialized.
3776 @value{GDBN} will stop when your program sets @samp{global_ptr} and
3777 the expression produces a valid value. If the expression becomes
3778 valid in some other way than changing a variable (e.g.@: if the memory
3779 pointed to by @samp{*global_ptr} becomes readable as the result of a
3780 @code{malloc} call), @value{GDBN} may not stop until the next time
3781 the expression changes.
3783 @cindex software watchpoints
3784 @cindex hardware watchpoints
3785 Depending on your system, watchpoints may be implemented in software or
3786 hardware. @value{GDBN} does software watchpointing by single-stepping your
3787 program and testing the variable's value each time, which is hundreds of
3788 times slower than normal execution. (But this may still be worth it, to
3789 catch errors where you have no clue what part of your program is the
3792 On some systems, such as HP-UX, PowerPC, @sc{gnu}/Linux and most other
3793 x86-based targets, @value{GDBN} includes support for hardware
3794 watchpoints, which do not slow down the running of your program.
3798 @item watch @r{[}-l@r{|}-location@r{]} @var{expr} @r{[}thread @var{threadnum}@r{]} @r{[}mask @var{maskvalue}@r{]}
3799 Set a watchpoint for an expression. @value{GDBN} will break when the
3800 expression @var{expr} is written into by the program and its value
3801 changes. The simplest (and the most popular) use of this command is
3802 to watch the value of a single variable:
3805 (@value{GDBP}) watch foo
3808 If the command includes a @code{@r{[}thread @var{threadnum}@r{]}}
3809 argument, @value{GDBN} breaks only when the thread identified by
3810 @var{threadnum} changes the value of @var{expr}. If any other threads
3811 change the value of @var{expr}, @value{GDBN} will not break. Note
3812 that watchpoints restricted to a single thread in this way only work
3813 with Hardware Watchpoints.
3815 Ordinarily a watchpoint respects the scope of variables in @var{expr}
3816 (see below). The @code{-location} argument tells @value{GDBN} to
3817 instead watch the memory referred to by @var{expr}. In this case,
3818 @value{GDBN} will evaluate @var{expr}, take the address of the result,
3819 and watch the memory at that address. The type of the result is used
3820 to determine the size of the watched memory. If the expression's
3821 result does not have an address, then @value{GDBN} will print an
3824 The @code{@r{[}mask @var{maskvalue}@r{]}} argument allows creation
3825 of masked watchpoints, if the current architecture supports this
3826 feature (e.g., PowerPC Embedded architecture, see @ref{PowerPC
3827 Embedded}.) A @dfn{masked watchpoint} specifies a mask in addition
3828 to an address to watch. The mask specifies that some bits of an address
3829 (the bits which are reset in the mask) should be ignored when matching
3830 the address accessed by the inferior against the watchpoint address.
3831 Thus, a masked watchpoint watches many addresses simultaneously---those
3832 addresses whose unmasked bits are identical to the unmasked bits in the
3833 watchpoint address. The @code{mask} argument implies @code{-location}.
3837 (@value{GDBP}) watch foo mask 0xffff00ff
3838 (@value{GDBP}) watch *0xdeadbeef mask 0xffffff00
3842 @item rwatch @r{[}-l@r{|}-location@r{]} @var{expr} @r{[}thread @var{threadnum}@r{]} @r{[}mask @var{maskvalue}@r{]}
3843 Set a watchpoint that will break when the value of @var{expr} is read
3847 @item awatch @r{[}-l@r{|}-location@r{]} @var{expr} @r{[}thread @var{threadnum}@r{]} @r{[}mask @var{maskvalue}@r{]}
3848 Set a watchpoint that will break when @var{expr} is either read from
3849 or written into by the program.
3851 @kindex info watchpoints @r{[}@var{n}@dots{}@r{]}
3852 @item info watchpoints @r{[}@var{n}@dots{}@r{]}
3853 This command prints a list of watchpoints, using the same format as
3854 @code{info break} (@pxref{Set Breaks}).
3857 If you watch for a change in a numerically entered address you need to
3858 dereference it, as the address itself is just a constant number which will
3859 never change. @value{GDBN} refuses to create a watchpoint that watches
3860 a never-changing value:
3863 (@value{GDBP}) watch 0x600850
3864 Cannot watch constant value 0x600850.
3865 (@value{GDBP}) watch *(int *) 0x600850
3866 Watchpoint 1: *(int *) 6293584
3869 @value{GDBN} sets a @dfn{hardware watchpoint} if possible. Hardware
3870 watchpoints execute very quickly, and the debugger reports a change in
3871 value at the exact instruction where the change occurs. If @value{GDBN}
3872 cannot set a hardware watchpoint, it sets a software watchpoint, which
3873 executes more slowly and reports the change in value at the next
3874 @emph{statement}, not the instruction, after the change occurs.
3876 @cindex use only software watchpoints
3877 You can force @value{GDBN} to use only software watchpoints with the
3878 @kbd{set can-use-hw-watchpoints 0} command. With this variable set to
3879 zero, @value{GDBN} will never try to use hardware watchpoints, even if
3880 the underlying system supports them. (Note that hardware-assisted
3881 watchpoints that were set @emph{before} setting
3882 @code{can-use-hw-watchpoints} to zero will still use the hardware
3883 mechanism of watching expression values.)
3886 @item set can-use-hw-watchpoints
3887 @kindex set can-use-hw-watchpoints
3888 Set whether or not to use hardware watchpoints.
3890 @item show can-use-hw-watchpoints
3891 @kindex show can-use-hw-watchpoints
3892 Show the current mode of using hardware watchpoints.
3895 For remote targets, you can restrict the number of hardware
3896 watchpoints @value{GDBN} will use, see @ref{set remote
3897 hardware-breakpoint-limit}.
3899 When you issue the @code{watch} command, @value{GDBN} reports
3902 Hardware watchpoint @var{num}: @var{expr}
3906 if it was able to set a hardware watchpoint.
3908 Currently, the @code{awatch} and @code{rwatch} commands can only set
3909 hardware watchpoints, because accesses to data that don't change the
3910 value of the watched expression cannot be detected without examining
3911 every instruction as it is being executed, and @value{GDBN} does not do
3912 that currently. If @value{GDBN} finds that it is unable to set a
3913 hardware breakpoint with the @code{awatch} or @code{rwatch} command, it
3914 will print a message like this:
3917 Expression cannot be implemented with read/access watchpoint.
3920 Sometimes, @value{GDBN} cannot set a hardware watchpoint because the
3921 data type of the watched expression is wider than what a hardware
3922 watchpoint on the target machine can handle. For example, some systems
3923 can only watch regions that are up to 4 bytes wide; on such systems you
3924 cannot set hardware watchpoints for an expression that yields a
3925 double-precision floating-point number (which is typically 8 bytes
3926 wide). As a work-around, it might be possible to break the large region
3927 into a series of smaller ones and watch them with separate watchpoints.
3929 If you set too many hardware watchpoints, @value{GDBN} might be unable
3930 to insert all of them when you resume the execution of your program.
3931 Since the precise number of active watchpoints is unknown until such
3932 time as the program is about to be resumed, @value{GDBN} might not be
3933 able to warn you about this when you set the watchpoints, and the
3934 warning will be printed only when the program is resumed:
3937 Hardware watchpoint @var{num}: Could not insert watchpoint
3941 If this happens, delete or disable some of the watchpoints.
3943 Watching complex expressions that reference many variables can also
3944 exhaust the resources available for hardware-assisted watchpoints.
3945 That's because @value{GDBN} needs to watch every variable in the
3946 expression with separately allocated resources.
3948 If you call a function interactively using @code{print} or @code{call},
3949 any watchpoints you have set will be inactive until @value{GDBN} reaches another
3950 kind of breakpoint or the call completes.
3952 @value{GDBN} automatically deletes watchpoints that watch local
3953 (automatic) variables, or expressions that involve such variables, when
3954 they go out of scope, that is, when the execution leaves the block in
3955 which these variables were defined. In particular, when the program
3956 being debugged terminates, @emph{all} local variables go out of scope,
3957 and so only watchpoints that watch global variables remain set. If you
3958 rerun the program, you will need to set all such watchpoints again. One
3959 way of doing that would be to set a code breakpoint at the entry to the
3960 @code{main} function and when it breaks, set all the watchpoints.
3962 @cindex watchpoints and threads
3963 @cindex threads and watchpoints
3964 In multi-threaded programs, watchpoints will detect changes to the
3965 watched expression from every thread.
3968 @emph{Warning:} In multi-threaded programs, software watchpoints
3969 have only limited usefulness. If @value{GDBN} creates a software
3970 watchpoint, it can only watch the value of an expression @emph{in a
3971 single thread}. If you are confident that the expression can only
3972 change due to the current thread's activity (and if you are also
3973 confident that no other thread can become current), then you can use
3974 software watchpoints as usual. However, @value{GDBN} may not notice
3975 when a non-current thread's activity changes the expression. (Hardware
3976 watchpoints, in contrast, watch an expression in all threads.)
3979 @xref{set remote hardware-watchpoint-limit}.
3981 @node Set Catchpoints
3982 @subsection Setting Catchpoints
3983 @cindex catchpoints, setting
3984 @cindex exception handlers
3985 @cindex event handling
3987 You can use @dfn{catchpoints} to cause the debugger to stop for certain
3988 kinds of program events, such as C@t{++} exceptions or the loading of a
3989 shared library. Use the @code{catch} command to set a catchpoint.
3993 @item catch @var{event}
3994 Stop when @var{event} occurs. @var{event} can be any of the following:
3997 @cindex stop on C@t{++} exceptions
3998 The throwing of a C@t{++} exception.
4001 The catching of a C@t{++} exception.
4004 @cindex Ada exception catching
4005 @cindex catch Ada exceptions
4006 An Ada exception being raised. If an exception name is specified
4007 at the end of the command (eg @code{catch exception Program_Error}),
4008 the debugger will stop only when this specific exception is raised.
4009 Otherwise, the debugger stops execution when any Ada exception is raised.
4011 When inserting an exception catchpoint on a user-defined exception whose
4012 name is identical to one of the exceptions defined by the language, the
4013 fully qualified name must be used as the exception name. Otherwise,
4014 @value{GDBN} will assume that it should stop on the pre-defined exception
4015 rather than the user-defined one. For instance, assuming an exception
4016 called @code{Constraint_Error} is defined in package @code{Pck}, then
4017 the command to use to catch such exceptions is @kbd{catch exception
4018 Pck.Constraint_Error}.
4020 @item exception unhandled
4021 An exception that was raised but is not handled by the program.
4024 A failed Ada assertion.
4027 @cindex break on fork/exec
4028 A call to @code{exec}. This is currently only available for HP-UX
4032 @itemx syscall @r{[}@var{name} @r{|} @var{number}@r{]} @dots{}
4033 @cindex break on a system call.
4034 A call to or return from a system call, a.k.a.@: @dfn{syscall}. A
4035 syscall is a mechanism for application programs to request a service
4036 from the operating system (OS) or one of the OS system services.
4037 @value{GDBN} can catch some or all of the syscalls issued by the
4038 debuggee, and show the related information for each syscall. If no
4039 argument is specified, calls to and returns from all system calls
4042 @var{name} can be any system call name that is valid for the
4043 underlying OS. Just what syscalls are valid depends on the OS. On
4044 GNU and Unix systems, you can find the full list of valid syscall
4045 names on @file{/usr/include/asm/unistd.h}.
4047 @c For MS-Windows, the syscall names and the corresponding numbers
4048 @c can be found, e.g., on this URL:
4049 @c http://www.metasploit.com/users/opcode/syscalls.html
4050 @c but we don't support Windows syscalls yet.
4052 Normally, @value{GDBN} knows in advance which syscalls are valid for
4053 each OS, so you can use the @value{GDBN} command-line completion
4054 facilities (@pxref{Completion,, command completion}) to list the
4057 You may also specify the system call numerically. A syscall's
4058 number is the value passed to the OS's syscall dispatcher to
4059 identify the requested service. When you specify the syscall by its
4060 name, @value{GDBN} uses its database of syscalls to convert the name
4061 into the corresponding numeric code, but using the number directly
4062 may be useful if @value{GDBN}'s database does not have the complete
4063 list of syscalls on your system (e.g., because @value{GDBN} lags
4064 behind the OS upgrades).
4066 The example below illustrates how this command works if you don't provide
4070 (@value{GDBP}) catch syscall
4071 Catchpoint 1 (syscall)
4073 Starting program: /tmp/catch-syscall
4075 Catchpoint 1 (call to syscall 'close'), \
4076 0xffffe424 in __kernel_vsyscall ()
4080 Catchpoint 1 (returned from syscall 'close'), \
4081 0xffffe424 in __kernel_vsyscall ()
4085 Here is an example of catching a system call by name:
4088 (@value{GDBP}) catch syscall chroot
4089 Catchpoint 1 (syscall 'chroot' [61])
4091 Starting program: /tmp/catch-syscall
4093 Catchpoint 1 (call to syscall 'chroot'), \
4094 0xffffe424 in __kernel_vsyscall ()
4098 Catchpoint 1 (returned from syscall 'chroot'), \
4099 0xffffe424 in __kernel_vsyscall ()
4103 An example of specifying a system call numerically. In the case
4104 below, the syscall number has a corresponding entry in the XML
4105 file, so @value{GDBN} finds its name and prints it:
4108 (@value{GDBP}) catch syscall 252
4109 Catchpoint 1 (syscall(s) 'exit_group')
4111 Starting program: /tmp/catch-syscall
4113 Catchpoint 1 (call to syscall 'exit_group'), \
4114 0xffffe424 in __kernel_vsyscall ()
4118 Program exited normally.
4122 However, there can be situations when there is no corresponding name
4123 in XML file for that syscall number. In this case, @value{GDBN} prints
4124 a warning message saying that it was not able to find the syscall name,
4125 but the catchpoint will be set anyway. See the example below:
4128 (@value{GDBP}) catch syscall 764
4129 warning: The number '764' does not represent a known syscall.
4130 Catchpoint 2 (syscall 764)
4134 If you configure @value{GDBN} using the @samp{--without-expat} option,
4135 it will not be able to display syscall names. Also, if your
4136 architecture does not have an XML file describing its system calls,
4137 you will not be able to see the syscall names. It is important to
4138 notice that these two features are used for accessing the syscall
4139 name database. In either case, you will see a warning like this:
4142 (@value{GDBP}) catch syscall
4143 warning: Could not open "syscalls/i386-linux.xml"
4144 warning: Could not load the syscall XML file 'syscalls/i386-linux.xml'.
4145 GDB will not be able to display syscall names.
4146 Catchpoint 1 (syscall)
4150 Of course, the file name will change depending on your architecture and system.
4152 Still using the example above, you can also try to catch a syscall by its
4153 number. In this case, you would see something like:
4156 (@value{GDBP}) catch syscall 252
4157 Catchpoint 1 (syscall(s) 252)
4160 Again, in this case @value{GDBN} would not be able to display syscall's names.
4163 A call to @code{fork}. This is currently only available for HP-UX
4167 A call to @code{vfork}. This is currently only available for HP-UX
4170 @item load @r{[}regexp@r{]}
4171 @itemx unload @r{[}regexp@r{]}
4172 The loading or unloading of a shared library. If @var{regexp} is
4173 given, then the catchpoint will stop only if the regular expression
4174 matches one of the affected libraries.
4178 @item tcatch @var{event}
4179 Set a catchpoint that is enabled only for one stop. The catchpoint is
4180 automatically deleted after the first time the event is caught.
4184 Use the @code{info break} command to list the current catchpoints.
4186 There are currently some limitations to C@t{++} exception handling
4187 (@code{catch throw} and @code{catch catch}) in @value{GDBN}:
4191 If you call a function interactively, @value{GDBN} normally returns
4192 control to you when the function has finished executing. If the call
4193 raises an exception, however, the call may bypass the mechanism that
4194 returns control to you and cause your program either to abort or to
4195 simply continue running until it hits a breakpoint, catches a signal
4196 that @value{GDBN} is listening for, or exits. This is the case even if
4197 you set a catchpoint for the exception; catchpoints on exceptions are
4198 disabled within interactive calls.
4201 You cannot raise an exception interactively.
4204 You cannot install an exception handler interactively.
4207 @cindex raise exceptions
4208 Sometimes @code{catch} is not the best way to debug exception handling:
4209 if you need to know exactly where an exception is raised, it is better to
4210 stop @emph{before} the exception handler is called, since that way you
4211 can see the stack before any unwinding takes place. If you set a
4212 breakpoint in an exception handler instead, it may not be easy to find
4213 out where the exception was raised.
4215 To stop just before an exception handler is called, you need some
4216 knowledge of the implementation. In the case of @sc{gnu} C@t{++}, exceptions are
4217 raised by calling a library function named @code{__raise_exception}
4218 which has the following ANSI C interface:
4221 /* @var{addr} is where the exception identifier is stored.
4222 @var{id} is the exception identifier. */
4223 void __raise_exception (void **addr, void *id);
4227 To make the debugger catch all exceptions before any stack
4228 unwinding takes place, set a breakpoint on @code{__raise_exception}
4229 (@pxref{Breakpoints, ,Breakpoints; Watchpoints; and Exceptions}).
4231 With a conditional breakpoint (@pxref{Conditions, ,Break Conditions})
4232 that depends on the value of @var{id}, you can stop your program when
4233 a specific exception is raised. You can use multiple conditional
4234 breakpoints to stop your program when any of a number of exceptions are
4239 @subsection Deleting Breakpoints
4241 @cindex clearing breakpoints, watchpoints, catchpoints
4242 @cindex deleting breakpoints, watchpoints, catchpoints
4243 It is often necessary to eliminate a breakpoint, watchpoint, or
4244 catchpoint once it has done its job and you no longer want your program
4245 to stop there. This is called @dfn{deleting} the breakpoint. A
4246 breakpoint that has been deleted no longer exists; it is forgotten.
4248 With the @code{clear} command you can delete breakpoints according to
4249 where they are in your program. With the @code{delete} command you can
4250 delete individual breakpoints, watchpoints, or catchpoints by specifying
4251 their breakpoint numbers.
4253 It is not necessary to delete a breakpoint to proceed past it. @value{GDBN}
4254 automatically ignores breakpoints on the first instruction to be executed
4255 when you continue execution without changing the execution address.
4260 Delete any breakpoints at the next instruction to be executed in the
4261 selected stack frame (@pxref{Selection, ,Selecting a Frame}). When
4262 the innermost frame is selected, this is a good way to delete a
4263 breakpoint where your program just stopped.
4265 @item clear @var{location}
4266 Delete any breakpoints set at the specified @var{location}.
4267 @xref{Specify Location}, for the various forms of @var{location}; the
4268 most useful ones are listed below:
4271 @item clear @var{function}
4272 @itemx clear @var{filename}:@var{function}
4273 Delete any breakpoints set at entry to the named @var{function}.
4275 @item clear @var{linenum}
4276 @itemx clear @var{filename}:@var{linenum}
4277 Delete any breakpoints set at or within the code of the specified
4278 @var{linenum} of the specified @var{filename}.
4281 @cindex delete breakpoints
4283 @kindex d @r{(@code{delete})}
4284 @item delete @r{[}breakpoints@r{]} @r{[}@var{range}@dots{}@r{]}
4285 Delete the breakpoints, watchpoints, or catchpoints of the breakpoint
4286 ranges specified as arguments. If no argument is specified, delete all
4287 breakpoints (@value{GDBN} asks confirmation, unless you have @code{set
4288 confirm off}). You can abbreviate this command as @code{d}.
4292 @subsection Disabling Breakpoints
4294 @cindex enable/disable a breakpoint
4295 Rather than deleting a breakpoint, watchpoint, or catchpoint, you might
4296 prefer to @dfn{disable} it. This makes the breakpoint inoperative as if
4297 it had been deleted, but remembers the information on the breakpoint so
4298 that you can @dfn{enable} it again later.
4300 You disable and enable breakpoints, watchpoints, and catchpoints with
4301 the @code{enable} and @code{disable} commands, optionally specifying
4302 one or more breakpoint numbers as arguments. Use @code{info break} to
4303 print a list of all breakpoints, watchpoints, and catchpoints if you
4304 do not know which numbers to use.
4306 Disabling and enabling a breakpoint that has multiple locations
4307 affects all of its locations.
4309 A breakpoint, watchpoint, or catchpoint can have any of several
4310 different states of enablement:
4314 Enabled. The breakpoint stops your program. A breakpoint set
4315 with the @code{break} command starts out in this state.
4317 Disabled. The breakpoint has no effect on your program.
4319 Enabled once. The breakpoint stops your program, but then becomes
4322 Enabled for a count. The breakpoint stops your program for the next
4323 N times, then becomes disabled.
4325 Enabled for deletion. The breakpoint stops your program, but
4326 immediately after it does so it is deleted permanently. A breakpoint
4327 set with the @code{tbreak} command starts out in this state.
4330 You can use the following commands to enable or disable breakpoints,
4331 watchpoints, and catchpoints:
4335 @kindex dis @r{(@code{disable})}
4336 @item disable @r{[}breakpoints@r{]} @r{[}@var{range}@dots{}@r{]}
4337 Disable the specified breakpoints---or all breakpoints, if none are
4338 listed. A disabled breakpoint has no effect but is not forgotten. All
4339 options such as ignore-counts, conditions and commands are remembered in
4340 case the breakpoint is enabled again later. You may abbreviate
4341 @code{disable} as @code{dis}.
4344 @item enable @r{[}breakpoints@r{]} @r{[}@var{range}@dots{}@r{]}
4345 Enable the specified breakpoints (or all defined breakpoints). They
4346 become effective once again in stopping your program.
4348 @item enable @r{[}breakpoints@r{]} once @var{range}@dots{}
4349 Enable the specified breakpoints temporarily. @value{GDBN} disables any
4350 of these breakpoints immediately after stopping your program.
4352 @item enable @r{[}breakpoints@r{]} count @var{count} @var{range}@dots{}
4353 Enable the specified breakpoints temporarily. @value{GDBN} records
4354 @var{count} with each of the specified breakpoints, and decrements a
4355 breakpoint's count when it is hit. When any count reaches 0,
4356 @value{GDBN} disables that breakpoint. If a breakpoint has an ignore
4357 count (@pxref{Conditions, ,Break Conditions}), that will be
4358 decremented to 0 before @var{count} is affected.
4360 @item enable @r{[}breakpoints@r{]} delete @var{range}@dots{}
4361 Enable the specified breakpoints to work once, then die. @value{GDBN}
4362 deletes any of these breakpoints as soon as your program stops there.
4363 Breakpoints set by the @code{tbreak} command start out in this state.
4366 @c FIXME: I think the following ``Except for [...] @code{tbreak}'' is
4367 @c confusing: tbreak is also initially enabled.
4368 Except for a breakpoint set with @code{tbreak} (@pxref{Set Breaks,
4369 ,Setting Breakpoints}), breakpoints that you set are initially enabled;
4370 subsequently, they become disabled or enabled only when you use one of
4371 the commands above. (The command @code{until} can set and delete a
4372 breakpoint of its own, but it does not change the state of your other
4373 breakpoints; see @ref{Continuing and Stepping, ,Continuing and
4377 @subsection Break Conditions
4378 @cindex conditional breakpoints
4379 @cindex breakpoint conditions
4381 @c FIXME what is scope of break condition expr? Context where wanted?
4382 @c in particular for a watchpoint?
4383 The simplest sort of breakpoint breaks every time your program reaches a
4384 specified place. You can also specify a @dfn{condition} for a
4385 breakpoint. A condition is just a Boolean expression in your
4386 programming language (@pxref{Expressions, ,Expressions}). A breakpoint with
4387 a condition evaluates the expression each time your program reaches it,
4388 and your program stops only if the condition is @emph{true}.
4390 This is the converse of using assertions for program validation; in that
4391 situation, you want to stop when the assertion is violated---that is,
4392 when the condition is false. In C, if you want to test an assertion expressed
4393 by the condition @var{assert}, you should set the condition
4394 @samp{! @var{assert}} on the appropriate breakpoint.
4396 Conditions are also accepted for watchpoints; you may not need them,
4397 since a watchpoint is inspecting the value of an expression anyhow---but
4398 it might be simpler, say, to just set a watchpoint on a variable name,
4399 and specify a condition that tests whether the new value is an interesting
4402 Break conditions can have side effects, and may even call functions in
4403 your program. This can be useful, for example, to activate functions
4404 that log program progress, or to use your own print functions to
4405 format special data structures. The effects are completely predictable
4406 unless there is another enabled breakpoint at the same address. (In
4407 that case, @value{GDBN} might see the other breakpoint first and stop your
4408 program without checking the condition of this one.) Note that
4409 breakpoint commands are usually more convenient and flexible than break
4411 purpose of performing side effects when a breakpoint is reached
4412 (@pxref{Break Commands, ,Breakpoint Command Lists}).
4414 Breakpoint conditions can also be evaluated on the target's side if
4415 the target supports it. Instead of evaluating the conditions locally,
4416 @value{GDBN} encodes the expression into an agent expression
4417 (@pxref{Agent Expressions}) suitable for execution on the target,
4418 independently of @value{GDBN}. Global variables become raw memory
4419 locations, locals become stack accesses, and so forth.
4421 In this case, @value{GDBN} will only be notified of a breakpoint trigger
4422 when its condition evaluates to true. This mechanism may provide faster
4423 response times depending on the performance characteristics of the target
4424 since it does not need to keep @value{GDBN} informed about
4425 every breakpoint trigger, even those with false conditions.
4427 Break conditions can be specified when a breakpoint is set, by using
4428 @samp{if} in the arguments to the @code{break} command. @xref{Set
4429 Breaks, ,Setting Breakpoints}. They can also be changed at any time
4430 with the @code{condition} command.
4432 You can also use the @code{if} keyword with the @code{watch} command.
4433 The @code{catch} command does not recognize the @code{if} keyword;
4434 @code{condition} is the only way to impose a further condition on a
4439 @item condition @var{bnum} @var{expression}
4440 Specify @var{expression} as the break condition for breakpoint,
4441 watchpoint, or catchpoint number @var{bnum}. After you set a condition,
4442 breakpoint @var{bnum} stops your program only if the value of
4443 @var{expression} is true (nonzero, in C). When you use
4444 @code{condition}, @value{GDBN} checks @var{expression} immediately for
4445 syntactic correctness, and to determine whether symbols in it have
4446 referents in the context of your breakpoint. If @var{expression} uses
4447 symbols not referenced in the context of the breakpoint, @value{GDBN}
4448 prints an error message:
4451 No symbol "foo" in current context.
4456 not actually evaluate @var{expression} at the time the @code{condition}
4457 command (or a command that sets a breakpoint with a condition, like
4458 @code{break if @dots{}}) is given, however. @xref{Expressions, ,Expressions}.
4460 @item condition @var{bnum}
4461 Remove the condition from breakpoint number @var{bnum}. It becomes
4462 an ordinary unconditional breakpoint.
4465 @cindex ignore count (of breakpoint)
4466 A special case of a breakpoint condition is to stop only when the
4467 breakpoint has been reached a certain number of times. This is so
4468 useful that there is a special way to do it, using the @dfn{ignore
4469 count} of the breakpoint. Every breakpoint has an ignore count, which
4470 is an integer. Most of the time, the ignore count is zero, and
4471 therefore has no effect. But if your program reaches a breakpoint whose
4472 ignore count is positive, then instead of stopping, it just decrements
4473 the ignore count by one and continues. As a result, if the ignore count
4474 value is @var{n}, the breakpoint does not stop the next @var{n} times
4475 your program reaches it.
4479 @item ignore @var{bnum} @var{count}
4480 Set the ignore count of breakpoint number @var{bnum} to @var{count}.
4481 The next @var{count} times the breakpoint is reached, your program's
4482 execution does not stop; other than to decrement the ignore count, @value{GDBN}
4485 To make the breakpoint stop the next time it is reached, specify
4488 When you use @code{continue} to resume execution of your program from a
4489 breakpoint, you can specify an ignore count directly as an argument to
4490 @code{continue}, rather than using @code{ignore}. @xref{Continuing and
4491 Stepping,,Continuing and Stepping}.
4493 If a breakpoint has a positive ignore count and a condition, the
4494 condition is not checked. Once the ignore count reaches zero,
4495 @value{GDBN} resumes checking the condition.
4497 You could achieve the effect of the ignore count with a condition such
4498 as @w{@samp{$foo-- <= 0}} using a debugger convenience variable that
4499 is decremented each time. @xref{Convenience Vars, ,Convenience
4503 Ignore counts apply to breakpoints, watchpoints, and catchpoints.
4506 @node Break Commands
4507 @subsection Breakpoint Command Lists
4509 @cindex breakpoint commands
4510 You can give any breakpoint (or watchpoint or catchpoint) a series of
4511 commands to execute when your program stops due to that breakpoint. For
4512 example, you might want to print the values of certain expressions, or
4513 enable other breakpoints.
4517 @kindex end@r{ (breakpoint commands)}
4518 @item commands @r{[}@var{range}@dots{}@r{]}
4519 @itemx @dots{} @var{command-list} @dots{}
4521 Specify a list of commands for the given breakpoints. The commands
4522 themselves appear on the following lines. Type a line containing just
4523 @code{end} to terminate the commands.
4525 To remove all commands from a breakpoint, type @code{commands} and
4526 follow it immediately with @code{end}; that is, give no commands.
4528 With no argument, @code{commands} refers to the last breakpoint,
4529 watchpoint, or catchpoint set (not to the breakpoint most recently
4530 encountered). If the most recent breakpoints were set with a single
4531 command, then the @code{commands} will apply to all the breakpoints
4532 set by that command. This applies to breakpoints set by
4533 @code{rbreak}, and also applies when a single @code{break} command
4534 creates multiple breakpoints (@pxref{Ambiguous Expressions,,Ambiguous
4538 Pressing @key{RET} as a means of repeating the last @value{GDBN} command is
4539 disabled within a @var{command-list}.
4541 You can use breakpoint commands to start your program up again. Simply
4542 use the @code{continue} command, or @code{step}, or any other command
4543 that resumes execution.
4545 Any other commands in the command list, after a command that resumes
4546 execution, are ignored. This is because any time you resume execution
4547 (even with a simple @code{next} or @code{step}), you may encounter
4548 another breakpoint---which could have its own command list, leading to
4549 ambiguities about which list to execute.
4552 If the first command you specify in a command list is @code{silent}, the
4553 usual message about stopping at a breakpoint is not printed. This may
4554 be desirable for breakpoints that are to print a specific message and
4555 then continue. If none of the remaining commands print anything, you
4556 see no sign that the breakpoint was reached. @code{silent} is
4557 meaningful only at the beginning of a breakpoint command list.
4559 The commands @code{echo}, @code{output}, and @code{printf} allow you to
4560 print precisely controlled output, and are often useful in silent
4561 breakpoints. @xref{Output, ,Commands for Controlled Output}.
4563 For example, here is how you could use breakpoint commands to print the
4564 value of @code{x} at entry to @code{foo} whenever @code{x} is positive.
4570 printf "x is %d\n",x
4575 One application for breakpoint commands is to compensate for one bug so
4576 you can test for another. Put a breakpoint just after the erroneous line
4577 of code, give it a condition to detect the case in which something
4578 erroneous has been done, and give it commands to assign correct values
4579 to any variables that need them. End with the @code{continue} command
4580 so that your program does not stop, and start with the @code{silent}
4581 command so that no output is produced. Here is an example:
4592 @node Save Breakpoints
4593 @subsection How to save breakpoints to a file
4595 To save breakpoint definitions to a file use the @w{@code{save
4596 breakpoints}} command.
4599 @kindex save breakpoints
4600 @cindex save breakpoints to a file for future sessions
4601 @item save breakpoints [@var{filename}]
4602 This command saves all current breakpoint definitions together with
4603 their commands and ignore counts, into a file @file{@var{filename}}
4604 suitable for use in a later debugging session. This includes all
4605 types of breakpoints (breakpoints, watchpoints, catchpoints,
4606 tracepoints). To read the saved breakpoint definitions, use the
4607 @code{source} command (@pxref{Command Files}). Note that watchpoints
4608 with expressions involving local variables may fail to be recreated
4609 because it may not be possible to access the context where the
4610 watchpoint is valid anymore. Because the saved breakpoint definitions
4611 are simply a sequence of @value{GDBN} commands that recreate the
4612 breakpoints, you can edit the file in your favorite editing program,
4613 and remove the breakpoint definitions you're not interested in, or
4614 that can no longer be recreated.
4617 @c @ifclear BARETARGET
4618 @node Error in Breakpoints
4619 @subsection ``Cannot insert breakpoints''
4621 If you request too many active hardware-assisted breakpoints and
4622 watchpoints, you will see this error message:
4624 @c FIXME: the precise wording of this message may change; the relevant
4625 @c source change is not committed yet (Sep 3, 1999).
4627 Stopped; cannot insert breakpoints.
4628 You may have requested too many hardware breakpoints and watchpoints.
4632 This message is printed when you attempt to resume the program, since
4633 only then @value{GDBN} knows exactly how many hardware breakpoints and
4634 watchpoints it needs to insert.
4636 When this message is printed, you need to disable or remove some of the
4637 hardware-assisted breakpoints and watchpoints, and then continue.
4639 @node Breakpoint-related Warnings
4640 @subsection ``Breakpoint address adjusted...''
4641 @cindex breakpoint address adjusted
4643 Some processor architectures place constraints on the addresses at
4644 which breakpoints may be placed. For architectures thus constrained,
4645 @value{GDBN} will attempt to adjust the breakpoint's address to comply
4646 with the constraints dictated by the architecture.
4648 One example of such an architecture is the Fujitsu FR-V. The FR-V is
4649 a VLIW architecture in which a number of RISC-like instructions may be
4650 bundled together for parallel execution. The FR-V architecture
4651 constrains the location of a breakpoint instruction within such a
4652 bundle to the instruction with the lowest address. @value{GDBN}
4653 honors this constraint by adjusting a breakpoint's address to the
4654 first in the bundle.
4656 It is not uncommon for optimized code to have bundles which contain
4657 instructions from different source statements, thus it may happen that
4658 a breakpoint's address will be adjusted from one source statement to
4659 another. Since this adjustment may significantly alter @value{GDBN}'s
4660 breakpoint related behavior from what the user expects, a warning is
4661 printed when the breakpoint is first set and also when the breakpoint
4664 A warning like the one below is printed when setting a breakpoint
4665 that's been subject to address adjustment:
4668 warning: Breakpoint address adjusted from 0x00010414 to 0x00010410.
4671 Such warnings are printed both for user settable and @value{GDBN}'s
4672 internal breakpoints. If you see one of these warnings, you should
4673 verify that a breakpoint set at the adjusted address will have the
4674 desired affect. If not, the breakpoint in question may be removed and
4675 other breakpoints may be set which will have the desired behavior.
4676 E.g., it may be sufficient to place the breakpoint at a later
4677 instruction. A conditional breakpoint may also be useful in some
4678 cases to prevent the breakpoint from triggering too often.
4680 @value{GDBN} will also issue a warning when stopping at one of these
4681 adjusted breakpoints:
4684 warning: Breakpoint 1 address previously adjusted from 0x00010414
4688 When this warning is encountered, it may be too late to take remedial
4689 action except in cases where the breakpoint is hit earlier or more
4690 frequently than expected.
4692 @node Continuing and Stepping
4693 @section Continuing and Stepping
4697 @cindex resuming execution
4698 @dfn{Continuing} means resuming program execution until your program
4699 completes normally. In contrast, @dfn{stepping} means executing just
4700 one more ``step'' of your program, where ``step'' may mean either one
4701 line of source code, or one machine instruction (depending on what
4702 particular command you use). Either when continuing or when stepping,
4703 your program may stop even sooner, due to a breakpoint or a signal. (If
4704 it stops due to a signal, you may want to use @code{handle}, or use
4705 @samp{signal 0} to resume execution. @xref{Signals, ,Signals}.)
4709 @kindex c @r{(@code{continue})}
4710 @kindex fg @r{(resume foreground execution)}
4711 @item continue @r{[}@var{ignore-count}@r{]}
4712 @itemx c @r{[}@var{ignore-count}@r{]}
4713 @itemx fg @r{[}@var{ignore-count}@r{]}
4714 Resume program execution, at the address where your program last stopped;
4715 any breakpoints set at that address are bypassed. The optional argument
4716 @var{ignore-count} allows you to specify a further number of times to
4717 ignore a breakpoint at this location; its effect is like that of
4718 @code{ignore} (@pxref{Conditions, ,Break Conditions}).
4720 The argument @var{ignore-count} is meaningful only when your program
4721 stopped due to a breakpoint. At other times, the argument to
4722 @code{continue} is ignored.
4724 The synonyms @code{c} and @code{fg} (for @dfn{foreground}, as the
4725 debugged program is deemed to be the foreground program) are provided
4726 purely for convenience, and have exactly the same behavior as
4730 To resume execution at a different place, you can use @code{return}
4731 (@pxref{Returning, ,Returning from a Function}) to go back to the
4732 calling function; or @code{jump} (@pxref{Jumping, ,Continuing at a
4733 Different Address}) to go to an arbitrary location in your program.
4735 A typical technique for using stepping is to set a breakpoint
4736 (@pxref{Breakpoints, ,Breakpoints; Watchpoints; and Catchpoints}) at the
4737 beginning of the function or the section of your program where a problem
4738 is believed to lie, run your program until it stops at that breakpoint,
4739 and then step through the suspect area, examining the variables that are
4740 interesting, until you see the problem happen.
4744 @kindex s @r{(@code{step})}
4746 Continue running your program until control reaches a different source
4747 line, then stop it and return control to @value{GDBN}. This command is
4748 abbreviated @code{s}.
4751 @c "without debugging information" is imprecise; actually "without line
4752 @c numbers in the debugging information". (gcc -g1 has debugging info but
4753 @c not line numbers). But it seems complex to try to make that
4754 @c distinction here.
4755 @emph{Warning:} If you use the @code{step} command while control is
4756 within a function that was compiled without debugging information,
4757 execution proceeds until control reaches a function that does have
4758 debugging information. Likewise, it will not step into a function which
4759 is compiled without debugging information. To step through functions
4760 without debugging information, use the @code{stepi} command, described
4764 The @code{step} command only stops at the first instruction of a source
4765 line. This prevents the multiple stops that could otherwise occur in
4766 @code{switch} statements, @code{for} loops, etc. @code{step} continues
4767 to stop if a function that has debugging information is called within
4768 the line. In other words, @code{step} @emph{steps inside} any functions
4769 called within the line.
4771 Also, the @code{step} command only enters a function if there is line
4772 number information for the function. Otherwise it acts like the
4773 @code{next} command. This avoids problems when using @code{cc -gl}
4774 on MIPS machines. Previously, @code{step} entered subroutines if there
4775 was any debugging information about the routine.
4777 @item step @var{count}
4778 Continue running as in @code{step}, but do so @var{count} times. If a
4779 breakpoint is reached, or a signal not related to stepping occurs before
4780 @var{count} steps, stepping stops right away.
4783 @kindex n @r{(@code{next})}
4784 @item next @r{[}@var{count}@r{]}
4785 Continue to the next source line in the current (innermost) stack frame.
4786 This is similar to @code{step}, but function calls that appear within
4787 the line of code are executed without stopping. Execution stops when
4788 control reaches a different line of code at the original stack level
4789 that was executing when you gave the @code{next} command. This command
4790 is abbreviated @code{n}.
4792 An argument @var{count} is a repeat count, as for @code{step}.
4795 @c FIX ME!! Do we delete this, or is there a way it fits in with
4796 @c the following paragraph? --- Vctoria
4798 @c @code{next} within a function that lacks debugging information acts like
4799 @c @code{step}, but any function calls appearing within the code of the
4800 @c function are executed without stopping.
4802 The @code{next} command only stops at the first instruction of a
4803 source line. This prevents multiple stops that could otherwise occur in
4804 @code{switch} statements, @code{for} loops, etc.
4806 @kindex set step-mode
4808 @cindex functions without line info, and stepping
4809 @cindex stepping into functions with no line info
4810 @itemx set step-mode on
4811 The @code{set step-mode on} command causes the @code{step} command to
4812 stop at the first instruction of a function which contains no debug line
4813 information rather than stepping over it.
4815 This is useful in cases where you may be interested in inspecting the
4816 machine instructions of a function which has no symbolic info and do not
4817 want @value{GDBN} to automatically skip over this function.
4819 @item set step-mode off
4820 Causes the @code{step} command to step over any functions which contains no
4821 debug information. This is the default.
4823 @item show step-mode
4824 Show whether @value{GDBN} will stop in or step over functions without
4825 source line debug information.
4828 @kindex fin @r{(@code{finish})}
4830 Continue running until just after function in the selected stack frame
4831 returns. Print the returned value (if any). This command can be
4832 abbreviated as @code{fin}.
4834 Contrast this with the @code{return} command (@pxref{Returning,
4835 ,Returning from a Function}).
4838 @kindex u @r{(@code{until})}
4839 @cindex run until specified location
4842 Continue running until a source line past the current line, in the
4843 current stack frame, is reached. This command is used to avoid single
4844 stepping through a loop more than once. It is like the @code{next}
4845 command, except that when @code{until} encounters a jump, it
4846 automatically continues execution until the program counter is greater
4847 than the address of the jump.
4849 This means that when you reach the end of a loop after single stepping
4850 though it, @code{until} makes your program continue execution until it
4851 exits the loop. In contrast, a @code{next} command at the end of a loop
4852 simply steps back to the beginning of the loop, which forces you to step
4853 through the next iteration.
4855 @code{until} always stops your program if it attempts to exit the current
4858 @code{until} may produce somewhat counterintuitive results if the order
4859 of machine code does not match the order of the source lines. For
4860 example, in the following excerpt from a debugging session, the @code{f}
4861 (@code{frame}) command shows that execution is stopped at line
4862 @code{206}; yet when we use @code{until}, we get to line @code{195}:
4866 #0 main (argc=4, argv=0xf7fffae8) at m4.c:206
4868 (@value{GDBP}) until
4869 195 for ( ; argc > 0; NEXTARG) @{
4872 This happened because, for execution efficiency, the compiler had
4873 generated code for the loop closure test at the end, rather than the
4874 start, of the loop---even though the test in a C @code{for}-loop is
4875 written before the body of the loop. The @code{until} command appeared
4876 to step back to the beginning of the loop when it advanced to this
4877 expression; however, it has not really gone to an earlier
4878 statement---not in terms of the actual machine code.
4880 @code{until} with no argument works by means of single
4881 instruction stepping, and hence is slower than @code{until} with an
4884 @item until @var{location}
4885 @itemx u @var{location}
4886 Continue running your program until either the specified location is
4887 reached, or the current stack frame returns. @var{location} is any of
4888 the forms described in @ref{Specify Location}.
4889 This form of the command uses temporary breakpoints, and
4890 hence is quicker than @code{until} without an argument. The specified
4891 location is actually reached only if it is in the current frame. This
4892 implies that @code{until} can be used to skip over recursive function
4893 invocations. For instance in the code below, if the current location is
4894 line @code{96}, issuing @code{until 99} will execute the program up to
4895 line @code{99} in the same invocation of factorial, i.e., after the inner
4896 invocations have returned.
4899 94 int factorial (int value)
4901 96 if (value > 1) @{
4902 97 value *= factorial (value - 1);
4909 @kindex advance @var{location}
4910 @itemx advance @var{location}
4911 Continue running the program up to the given @var{location}. An argument is
4912 required, which should be of one of the forms described in
4913 @ref{Specify Location}.
4914 Execution will also stop upon exit from the current stack
4915 frame. This command is similar to @code{until}, but @code{advance} will
4916 not skip over recursive function calls, and the target location doesn't
4917 have to be in the same frame as the current one.
4921 @kindex si @r{(@code{stepi})}
4923 @itemx stepi @var{arg}
4925 Execute one machine instruction, then stop and return to the debugger.
4927 It is often useful to do @samp{display/i $pc} when stepping by machine
4928 instructions. This makes @value{GDBN} automatically display the next
4929 instruction to be executed, each time your program stops. @xref{Auto
4930 Display,, Automatic Display}.
4932 An argument is a repeat count, as in @code{step}.
4936 @kindex ni @r{(@code{nexti})}
4938 @itemx nexti @var{arg}
4940 Execute one machine instruction, but if it is a function call,
4941 proceed until the function returns.
4943 An argument is a repeat count, as in @code{next}.
4946 @node Skipping Over Functions and Files
4947 @section Skipping Over Functions and Files
4948 @cindex skipping over functions and files
4950 The program you are debugging may contain some functions which are
4951 uninteresting to debug. The @code{skip} comand lets you tell @value{GDBN} to
4952 skip a function or all functions in a file when stepping.
4954 For example, consider the following C function:
4965 Suppose you wish to step into the functions @code{foo} and @code{bar}, but you
4966 are not interested in stepping through @code{boring}. If you run @code{step}
4967 at line 103, you'll enter @code{boring()}, but if you run @code{next}, you'll
4968 step over both @code{foo} and @code{boring}!
4970 One solution is to @code{step} into @code{boring} and use the @code{finish}
4971 command to immediately exit it. But this can become tedious if @code{boring}
4972 is called from many places.
4974 A more flexible solution is to execute @kbd{skip boring}. This instructs
4975 @value{GDBN} never to step into @code{boring}. Now when you execute
4976 @code{step} at line 103, you'll step over @code{boring} and directly into
4979 You can also instruct @value{GDBN} to skip all functions in a file, with, for
4980 example, @code{skip file boring.c}.
4983 @kindex skip function
4984 @item skip @r{[}@var{linespec}@r{]}
4985 @itemx skip function @r{[}@var{linespec}@r{]}
4986 After running this command, the function named by @var{linespec} or the
4987 function containing the line named by @var{linespec} will be skipped over when
4988 stepping. @xref{Specify Location}.
4990 If you do not specify @var{linespec}, the function you're currently debugging
4993 (If you have a function called @code{file} that you want to skip, use
4994 @kbd{skip function file}.)
4997 @item skip file @r{[}@var{filename}@r{]}
4998 After running this command, any function whose source lives in @var{filename}
4999 will be skipped over when stepping.
5001 If you do not specify @var{filename}, functions whose source lives in the file
5002 you're currently debugging will be skipped.
5005 Skips can be listed, deleted, disabled, and enabled, much like breakpoints.
5006 These are the commands for managing your list of skips:
5010 @item info skip @r{[}@var{range}@r{]}
5011 Print details about the specified skip(s). If @var{range} is not specified,
5012 print a table with details about all functions and files marked for skipping.
5013 @code{info skip} prints the following information about each skip:
5017 A number identifying this skip.
5019 The type of this skip, either @samp{function} or @samp{file}.
5020 @item Enabled or Disabled
5021 Enabled skips are marked with @samp{y}. Disabled skips are marked with @samp{n}.
5023 For function skips, this column indicates the address in memory of the function
5024 being skipped. If you've set a function skip on a function which has not yet
5025 been loaded, this field will contain @samp{<PENDING>}. Once a shared library
5026 which has the function is loaded, @code{info skip} will show the function's
5029 For file skips, this field contains the filename being skipped. For functions
5030 skips, this field contains the function name and its line number in the file
5031 where it is defined.
5035 @item skip delete @r{[}@var{range}@r{]}
5036 Delete the specified skip(s). If @var{range} is not specified, delete all
5040 @item skip enable @r{[}@var{range}@r{]}
5041 Enable the specified skip(s). If @var{range} is not specified, enable all
5044 @kindex skip disable
5045 @item skip disable @r{[}@var{range}@r{]}
5046 Disable the specified skip(s). If @var{range} is not specified, disable all
5055 A signal is an asynchronous event that can happen in a program. The
5056 operating system defines the possible kinds of signals, and gives each
5057 kind a name and a number. For example, in Unix @code{SIGINT} is the
5058 signal a program gets when you type an interrupt character (often @kbd{Ctrl-c});
5059 @code{SIGSEGV} is the signal a program gets from referencing a place in
5060 memory far away from all the areas in use; @code{SIGALRM} occurs when
5061 the alarm clock timer goes off (which happens only if your program has
5062 requested an alarm).
5064 @cindex fatal signals
5065 Some signals, including @code{SIGALRM}, are a normal part of the
5066 functioning of your program. Others, such as @code{SIGSEGV}, indicate
5067 errors; these signals are @dfn{fatal} (they kill your program immediately) if the
5068 program has not specified in advance some other way to handle the signal.
5069 @code{SIGINT} does not indicate an error in your program, but it is normally
5070 fatal so it can carry out the purpose of the interrupt: to kill the program.
5072 @value{GDBN} has the ability to detect any occurrence of a signal in your
5073 program. You can tell @value{GDBN} in advance what to do for each kind of
5076 @cindex handling signals
5077 Normally, @value{GDBN} is set up to let the non-erroneous signals like
5078 @code{SIGALRM} be silently passed to your program
5079 (so as not to interfere with their role in the program's functioning)
5080 but to stop your program immediately whenever an error signal happens.
5081 You can change these settings with the @code{handle} command.
5084 @kindex info signals
5088 Print a table of all the kinds of signals and how @value{GDBN} has been told to
5089 handle each one. You can use this to see the signal numbers of all
5090 the defined types of signals.
5092 @item info signals @var{sig}
5093 Similar, but print information only about the specified signal number.
5095 @code{info handle} is an alias for @code{info signals}.
5098 @item handle @var{signal} @r{[}@var{keywords}@dots{}@r{]}
5099 Change the way @value{GDBN} handles signal @var{signal}. @var{signal}
5100 can be the number of a signal or its name (with or without the
5101 @samp{SIG} at the beginning); a list of signal numbers of the form
5102 @samp{@var{low}-@var{high}}; or the word @samp{all}, meaning all the
5103 known signals. Optional arguments @var{keywords}, described below,
5104 say what change to make.
5108 The keywords allowed by the @code{handle} command can be abbreviated.
5109 Their full names are:
5113 @value{GDBN} should not stop your program when this signal happens. It may
5114 still print a message telling you that the signal has come in.
5117 @value{GDBN} should stop your program when this signal happens. This implies
5118 the @code{print} keyword as well.
5121 @value{GDBN} should print a message when this signal happens.
5124 @value{GDBN} should not mention the occurrence of the signal at all. This
5125 implies the @code{nostop} keyword as well.
5129 @value{GDBN} should allow your program to see this signal; your program
5130 can handle the signal, or else it may terminate if the signal is fatal
5131 and not handled. @code{pass} and @code{noignore} are synonyms.
5135 @value{GDBN} should not allow your program to see this signal.
5136 @code{nopass} and @code{ignore} are synonyms.
5140 When a signal stops your program, the signal is not visible to the
5142 continue. Your program sees the signal then, if @code{pass} is in
5143 effect for the signal in question @emph{at that time}. In other words,
5144 after @value{GDBN} reports a signal, you can use the @code{handle}
5145 command with @code{pass} or @code{nopass} to control whether your
5146 program sees that signal when you continue.
5148 The default is set to @code{nostop}, @code{noprint}, @code{pass} for
5149 non-erroneous signals such as @code{SIGALRM}, @code{SIGWINCH} and
5150 @code{SIGCHLD}, and to @code{stop}, @code{print}, @code{pass} for the
5153 You can also use the @code{signal} command to prevent your program from
5154 seeing a signal, or cause it to see a signal it normally would not see,
5155 or to give it any signal at any time. For example, if your program stopped
5156 due to some sort of memory reference error, you might store correct
5157 values into the erroneous variables and continue, hoping to see more
5158 execution; but your program would probably terminate immediately as
5159 a result of the fatal signal once it saw the signal. To prevent this,
5160 you can continue with @samp{signal 0}. @xref{Signaling, ,Giving your
5163 @cindex extra signal information
5164 @anchor{extra signal information}
5166 On some targets, @value{GDBN} can inspect extra signal information
5167 associated with the intercepted signal, before it is actually
5168 delivered to the program being debugged. This information is exported
5169 by the convenience variable @code{$_siginfo}, and consists of data
5170 that is passed by the kernel to the signal handler at the time of the
5171 receipt of a signal. The data type of the information itself is
5172 target dependent. You can see the data type using the @code{ptype
5173 $_siginfo} command. On Unix systems, it typically corresponds to the
5174 standard @code{siginfo_t} type, as defined in the @file{signal.h}
5177 Here's an example, on a @sc{gnu}/Linux system, printing the stray
5178 referenced address that raised a segmentation fault.
5182 (@value{GDBP}) continue
5183 Program received signal SIGSEGV, Segmentation fault.
5184 0x0000000000400766 in main ()
5186 (@value{GDBP}) ptype $_siginfo
5193 struct @{...@} _kill;
5194 struct @{...@} _timer;
5196 struct @{...@} _sigchld;
5197 struct @{...@} _sigfault;
5198 struct @{...@} _sigpoll;
5201 (@value{GDBP}) ptype $_siginfo._sifields._sigfault
5205 (@value{GDBP}) p $_siginfo._sifields._sigfault.si_addr
5206 $1 = (void *) 0x7ffff7ff7000
5210 Depending on target support, @code{$_siginfo} may also be writable.
5213 @section Stopping and Starting Multi-thread Programs
5215 @cindex stopped threads
5216 @cindex threads, stopped
5218 @cindex continuing threads
5219 @cindex threads, continuing
5221 @value{GDBN} supports debugging programs with multiple threads
5222 (@pxref{Threads,, Debugging Programs with Multiple Threads}). There
5223 are two modes of controlling execution of your program within the
5224 debugger. In the default mode, referred to as @dfn{all-stop mode},
5225 when any thread in your program stops (for example, at a breakpoint
5226 or while being stepped), all other threads in the program are also stopped by
5227 @value{GDBN}. On some targets, @value{GDBN} also supports
5228 @dfn{non-stop mode}, in which other threads can continue to run freely while
5229 you examine the stopped thread in the debugger.
5232 * All-Stop Mode:: All threads stop when GDB takes control
5233 * Non-Stop Mode:: Other threads continue to execute
5234 * Background Execution:: Running your program asynchronously
5235 * Thread-Specific Breakpoints:: Controlling breakpoints
5236 * Interrupted System Calls:: GDB may interfere with system calls
5237 * Observer Mode:: GDB does not alter program behavior
5241 @subsection All-Stop Mode
5243 @cindex all-stop mode
5245 In all-stop mode, whenever your program stops under @value{GDBN} for any reason,
5246 @emph{all} threads of execution stop, not just the current thread. This
5247 allows you to examine the overall state of the program, including
5248 switching between threads, without worrying that things may change
5251 Conversely, whenever you restart the program, @emph{all} threads start
5252 executing. @emph{This is true even when single-stepping} with commands
5253 like @code{step} or @code{next}.
5255 In particular, @value{GDBN} cannot single-step all threads in lockstep.
5256 Since thread scheduling is up to your debugging target's operating
5257 system (not controlled by @value{GDBN}), other threads may
5258 execute more than one statement while the current thread completes a
5259 single step. Moreover, in general other threads stop in the middle of a
5260 statement, rather than at a clean statement boundary, when the program
5263 You might even find your program stopped in another thread after
5264 continuing or even single-stepping. This happens whenever some other
5265 thread runs into a breakpoint, a signal, or an exception before the
5266 first thread completes whatever you requested.
5268 @cindex automatic thread selection
5269 @cindex switching threads automatically
5270 @cindex threads, automatic switching
5271 Whenever @value{GDBN} stops your program, due to a breakpoint or a
5272 signal, it automatically selects the thread where that breakpoint or
5273 signal happened. @value{GDBN} alerts you to the context switch with a
5274 message such as @samp{[Switching to Thread @var{n}]} to identify the
5277 On some OSes, you can modify @value{GDBN}'s default behavior by
5278 locking the OS scheduler to allow only a single thread to run.
5281 @item set scheduler-locking @var{mode}
5282 @cindex scheduler locking mode
5283 @cindex lock scheduler
5284 Set the scheduler locking mode. If it is @code{off}, then there is no
5285 locking and any thread may run at any time. If @code{on}, then only the
5286 current thread may run when the inferior is resumed. The @code{step}
5287 mode optimizes for single-stepping; it prevents other threads
5288 from preempting the current thread while you are stepping, so that
5289 the focus of debugging does not change unexpectedly.
5290 Other threads only rarely (or never) get a chance to run
5291 when you step. They are more likely to run when you @samp{next} over a
5292 function call, and they are completely free to run when you use commands
5293 like @samp{continue}, @samp{until}, or @samp{finish}. However, unless another
5294 thread hits a breakpoint during its timeslice, @value{GDBN} does not change
5295 the current thread away from the thread that you are debugging.
5297 @item show scheduler-locking
5298 Display the current scheduler locking mode.
5301 @cindex resume threads of multiple processes simultaneously
5302 By default, when you issue one of the execution commands such as
5303 @code{continue}, @code{next} or @code{step}, @value{GDBN} allows only
5304 threads of the current inferior to run. For example, if @value{GDBN}
5305 is attached to two inferiors, each with two threads, the
5306 @code{continue} command resumes only the two threads of the current
5307 inferior. This is useful, for example, when you debug a program that
5308 forks and you want to hold the parent stopped (so that, for instance,
5309 it doesn't run to exit), while you debug the child. In other
5310 situations, you may not be interested in inspecting the current state
5311 of any of the processes @value{GDBN} is attached to, and you may want
5312 to resume them all until some breakpoint is hit. In the latter case,
5313 you can instruct @value{GDBN} to allow all threads of all the
5314 inferiors to run with the @w{@code{set schedule-multiple}} command.
5317 @kindex set schedule-multiple
5318 @item set schedule-multiple
5319 Set the mode for allowing threads of multiple processes to be resumed
5320 when an execution command is issued. When @code{on}, all threads of
5321 all processes are allowed to run. When @code{off}, only the threads
5322 of the current process are resumed. The default is @code{off}. The
5323 @code{scheduler-locking} mode takes precedence when set to @code{on},
5324 or while you are stepping and set to @code{step}.
5326 @item show schedule-multiple
5327 Display the current mode for resuming the execution of threads of
5332 @subsection Non-Stop Mode
5334 @cindex non-stop mode
5336 @c This section is really only a place-holder, and needs to be expanded
5337 @c with more details.
5339 For some multi-threaded targets, @value{GDBN} supports an optional
5340 mode of operation in which you can examine stopped program threads in
5341 the debugger while other threads continue to execute freely. This
5342 minimizes intrusion when debugging live systems, such as programs
5343 where some threads have real-time constraints or must continue to
5344 respond to external events. This is referred to as @dfn{non-stop} mode.
5346 In non-stop mode, when a thread stops to report a debugging event,
5347 @emph{only} that thread is stopped; @value{GDBN} does not stop other
5348 threads as well, in contrast to the all-stop mode behavior. Additionally,
5349 execution commands such as @code{continue} and @code{step} apply by default
5350 only to the current thread in non-stop mode, rather than all threads as
5351 in all-stop mode. This allows you to control threads explicitly in
5352 ways that are not possible in all-stop mode --- for example, stepping
5353 one thread while allowing others to run freely, stepping
5354 one thread while holding all others stopped, or stepping several threads
5355 independently and simultaneously.
5357 To enter non-stop mode, use this sequence of commands before you run
5358 or attach to your program:
5361 # Enable the async interface.
5364 # If using the CLI, pagination breaks non-stop.
5367 # Finally, turn it on!
5371 You can use these commands to manipulate the non-stop mode setting:
5374 @kindex set non-stop
5375 @item set non-stop on
5376 Enable selection of non-stop mode.
5377 @item set non-stop off
5378 Disable selection of non-stop mode.
5379 @kindex show non-stop
5381 Show the current non-stop enablement setting.
5384 Note these commands only reflect whether non-stop mode is enabled,
5385 not whether the currently-executing program is being run in non-stop mode.
5386 In particular, the @code{set non-stop} preference is only consulted when
5387 @value{GDBN} starts or connects to the target program, and it is generally
5388 not possible to switch modes once debugging has started. Furthermore,
5389 since not all targets support non-stop mode, even when you have enabled
5390 non-stop mode, @value{GDBN} may still fall back to all-stop operation by
5393 In non-stop mode, all execution commands apply only to the current thread
5394 by default. That is, @code{continue} only continues one thread.
5395 To continue all threads, issue @code{continue -a} or @code{c -a}.
5397 You can use @value{GDBN}'s background execution commands
5398 (@pxref{Background Execution}) to run some threads in the background
5399 while you continue to examine or step others from @value{GDBN}.
5400 The MI execution commands (@pxref{GDB/MI Program Execution}) are
5401 always executed asynchronously in non-stop mode.
5403 Suspending execution is done with the @code{interrupt} command when
5404 running in the background, or @kbd{Ctrl-c} during foreground execution.
5405 In all-stop mode, this stops the whole process;
5406 but in non-stop mode the interrupt applies only to the current thread.
5407 To stop the whole program, use @code{interrupt -a}.
5409 Other execution commands do not currently support the @code{-a} option.
5411 In non-stop mode, when a thread stops, @value{GDBN} doesn't automatically make
5412 that thread current, as it does in all-stop mode. This is because the
5413 thread stop notifications are asynchronous with respect to @value{GDBN}'s
5414 command interpreter, and it would be confusing if @value{GDBN} unexpectedly
5415 changed to a different thread just as you entered a command to operate on the
5416 previously current thread.
5418 @node Background Execution
5419 @subsection Background Execution
5421 @cindex foreground execution
5422 @cindex background execution
5423 @cindex asynchronous execution
5424 @cindex execution, foreground, background and asynchronous
5426 @value{GDBN}'s execution commands have two variants: the normal
5427 foreground (synchronous) behavior, and a background
5428 (asynchronous) behavior. In foreground execution, @value{GDBN} waits for
5429 the program to report that some thread has stopped before prompting for
5430 another command. In background execution, @value{GDBN} immediately gives
5431 a command prompt so that you can issue other commands while your program runs.
5433 You need to explicitly enable asynchronous mode before you can use
5434 background execution commands. You can use these commands to
5435 manipulate the asynchronous mode setting:
5438 @kindex set target-async
5439 @item set target-async on
5440 Enable asynchronous mode.
5441 @item set target-async off
5442 Disable asynchronous mode.
5443 @kindex show target-async
5444 @item show target-async
5445 Show the current target-async setting.
5448 If the target doesn't support async mode, @value{GDBN} issues an error
5449 message if you attempt to use the background execution commands.
5451 To specify background execution, add a @code{&} to the command. For example,
5452 the background form of the @code{continue} command is @code{continue&}, or
5453 just @code{c&}. The execution commands that accept background execution
5459 @xref{Starting, , Starting your Program}.
5463 @xref{Attach, , Debugging an Already-running Process}.
5467 @xref{Continuing and Stepping, step}.
5471 @xref{Continuing and Stepping, stepi}.
5475 @xref{Continuing and Stepping, next}.
5479 @xref{Continuing and Stepping, nexti}.
5483 @xref{Continuing and Stepping, continue}.
5487 @xref{Continuing and Stepping, finish}.
5491 @xref{Continuing and Stepping, until}.
5495 Background execution is especially useful in conjunction with non-stop
5496 mode for debugging programs with multiple threads; see @ref{Non-Stop Mode}.
5497 However, you can also use these commands in the normal all-stop mode with
5498 the restriction that you cannot issue another execution command until the
5499 previous one finishes. Examples of commands that are valid in all-stop
5500 mode while the program is running include @code{help} and @code{info break}.
5502 You can interrupt your program while it is running in the background by
5503 using the @code{interrupt} command.
5510 Suspend execution of the running program. In all-stop mode,
5511 @code{interrupt} stops the whole process, but in non-stop mode, it stops
5512 only the current thread. To stop the whole program in non-stop mode,
5513 use @code{interrupt -a}.
5516 @node Thread-Specific Breakpoints
5517 @subsection Thread-Specific Breakpoints
5519 When your program has multiple threads (@pxref{Threads,, Debugging
5520 Programs with Multiple Threads}), you can choose whether to set
5521 breakpoints on all threads, or on a particular thread.
5524 @cindex breakpoints and threads
5525 @cindex thread breakpoints
5526 @kindex break @dots{} thread @var{threadno}
5527 @item break @var{linespec} thread @var{threadno}
5528 @itemx break @var{linespec} thread @var{threadno} if @dots{}
5529 @var{linespec} specifies source lines; there are several ways of
5530 writing them (@pxref{Specify Location}), but the effect is always to
5531 specify some source line.
5533 Use the qualifier @samp{thread @var{threadno}} with a breakpoint command
5534 to specify that you only want @value{GDBN} to stop the program when a
5535 particular thread reaches this breakpoint. @var{threadno} is one of the
5536 numeric thread identifiers assigned by @value{GDBN}, shown in the first
5537 column of the @samp{info threads} display.
5539 If you do not specify @samp{thread @var{threadno}} when you set a
5540 breakpoint, the breakpoint applies to @emph{all} threads of your
5543 You can use the @code{thread} qualifier on conditional breakpoints as
5544 well; in this case, place @samp{thread @var{threadno}} before or
5545 after the breakpoint condition, like this:
5548 (@value{GDBP}) break frik.c:13 thread 28 if bartab > lim
5553 @node Interrupted System Calls
5554 @subsection Interrupted System Calls
5556 @cindex thread breakpoints and system calls
5557 @cindex system calls and thread breakpoints
5558 @cindex premature return from system calls
5559 There is an unfortunate side effect when using @value{GDBN} to debug
5560 multi-threaded programs. If one thread stops for a
5561 breakpoint, or for some other reason, and another thread is blocked in a
5562 system call, then the system call may return prematurely. This is a
5563 consequence of the interaction between multiple threads and the signals
5564 that @value{GDBN} uses to implement breakpoints and other events that
5567 To handle this problem, your program should check the return value of
5568 each system call and react appropriately. This is good programming
5571 For example, do not write code like this:
5577 The call to @code{sleep} will return early if a different thread stops
5578 at a breakpoint or for some other reason.
5580 Instead, write this:
5585 unslept = sleep (unslept);
5588 A system call is allowed to return early, so the system is still
5589 conforming to its specification. But @value{GDBN} does cause your
5590 multi-threaded program to behave differently than it would without
5593 Also, @value{GDBN} uses internal breakpoints in the thread library to
5594 monitor certain events such as thread creation and thread destruction.
5595 When such an event happens, a system call in another thread may return
5596 prematurely, even though your program does not appear to stop.
5599 @subsection Observer Mode
5601 If you want to build on non-stop mode and observe program behavior
5602 without any chance of disruption by @value{GDBN}, you can set
5603 variables to disable all of the debugger's attempts to modify state,
5604 whether by writing memory, inserting breakpoints, etc. These operate
5605 at a low level, intercepting operations from all commands.
5607 When all of these are set to @code{off}, then @value{GDBN} is said to
5608 be @dfn{observer mode}. As a convenience, the variable
5609 @code{observer} can be set to disable these, plus enable non-stop
5612 Note that @value{GDBN} will not prevent you from making nonsensical
5613 combinations of these settings. For instance, if you have enabled
5614 @code{may-insert-breakpoints} but disabled @code{may-write-memory},
5615 then breakpoints that work by writing trap instructions into the code
5616 stream will still not be able to be placed.
5621 @item set observer on
5622 @itemx set observer off
5623 When set to @code{on}, this disables all the permission variables
5624 below (except for @code{insert-fast-tracepoints}), plus enables
5625 non-stop debugging. Setting this to @code{off} switches back to
5626 normal debugging, though remaining in non-stop mode.
5629 Show whether observer mode is on or off.
5631 @kindex may-write-registers
5632 @item set may-write-registers on
5633 @itemx set may-write-registers off
5634 This controls whether @value{GDBN} will attempt to alter the values of
5635 registers, such as with assignment expressions in @code{print}, or the
5636 @code{jump} command. It defaults to @code{on}.
5638 @item show may-write-registers
5639 Show the current permission to write registers.
5641 @kindex may-write-memory
5642 @item set may-write-memory on
5643 @itemx set may-write-memory off
5644 This controls whether @value{GDBN} will attempt to alter the contents
5645 of memory, such as with assignment expressions in @code{print}. It
5646 defaults to @code{on}.
5648 @item show may-write-memory
5649 Show the current permission to write memory.
5651 @kindex may-insert-breakpoints
5652 @item set may-insert-breakpoints on
5653 @itemx set may-insert-breakpoints off
5654 This controls whether @value{GDBN} will attempt to insert breakpoints.
5655 This affects all breakpoints, including internal breakpoints defined
5656 by @value{GDBN}. It defaults to @code{on}.
5658 @item show may-insert-breakpoints
5659 Show the current permission to insert breakpoints.
5661 @kindex may-insert-tracepoints
5662 @item set may-insert-tracepoints on
5663 @itemx set may-insert-tracepoints off
5664 This controls whether @value{GDBN} will attempt to insert (regular)
5665 tracepoints at the beginning of a tracing experiment. It affects only
5666 non-fast tracepoints, fast tracepoints being under the control of
5667 @code{may-insert-fast-tracepoints}. It defaults to @code{on}.
5669 @item show may-insert-tracepoints
5670 Show the current permission to insert tracepoints.
5672 @kindex may-insert-fast-tracepoints
5673 @item set may-insert-fast-tracepoints on
5674 @itemx set may-insert-fast-tracepoints off
5675 This controls whether @value{GDBN} will attempt to insert fast
5676 tracepoints at the beginning of a tracing experiment. It affects only
5677 fast tracepoints, regular (non-fast) tracepoints being under the
5678 control of @code{may-insert-tracepoints}. It defaults to @code{on}.
5680 @item show may-insert-fast-tracepoints
5681 Show the current permission to insert fast tracepoints.
5683 @kindex may-interrupt
5684 @item set may-interrupt on
5685 @itemx set may-interrupt off
5686 This controls whether @value{GDBN} will attempt to interrupt or stop
5687 program execution. When this variable is @code{off}, the
5688 @code{interrupt} command will have no effect, nor will
5689 @kbd{Ctrl-c}. It defaults to @code{on}.
5691 @item show may-interrupt
5692 Show the current permission to interrupt or stop the program.
5696 @node Reverse Execution
5697 @chapter Running programs backward
5698 @cindex reverse execution
5699 @cindex running programs backward
5701 When you are debugging a program, it is not unusual to realize that
5702 you have gone too far, and some event of interest has already happened.
5703 If the target environment supports it, @value{GDBN} can allow you to
5704 ``rewind'' the program by running it backward.
5706 A target environment that supports reverse execution should be able
5707 to ``undo'' the changes in machine state that have taken place as the
5708 program was executing normally. Variables, registers etc.@: should
5709 revert to their previous values. Obviously this requires a great
5710 deal of sophistication on the part of the target environment; not
5711 all target environments can support reverse execution.
5713 When a program is executed in reverse, the instructions that
5714 have most recently been executed are ``un-executed'', in reverse
5715 order. The program counter runs backward, following the previous
5716 thread of execution in reverse. As each instruction is ``un-executed'',
5717 the values of memory and/or registers that were changed by that
5718 instruction are reverted to their previous states. After executing
5719 a piece of source code in reverse, all side effects of that code
5720 should be ``undone'', and all variables should be returned to their
5721 prior values@footnote{
5722 Note that some side effects are easier to undo than others. For instance,
5723 memory and registers are relatively easy, but device I/O is hard. Some
5724 targets may be able undo things like device I/O, and some may not.
5726 The contract between @value{GDBN} and the reverse executing target
5727 requires only that the target do something reasonable when
5728 @value{GDBN} tells it to execute backwards, and then report the
5729 results back to @value{GDBN}. Whatever the target reports back to
5730 @value{GDBN}, @value{GDBN} will report back to the user. @value{GDBN}
5731 assumes that the memory and registers that the target reports are in a
5732 consistant state, but @value{GDBN} accepts whatever it is given.
5735 If you are debugging in a target environment that supports
5736 reverse execution, @value{GDBN} provides the following commands.
5739 @kindex reverse-continue
5740 @kindex rc @r{(@code{reverse-continue})}
5741 @item reverse-continue @r{[}@var{ignore-count}@r{]}
5742 @itemx rc @r{[}@var{ignore-count}@r{]}
5743 Beginning at the point where your program last stopped, start executing
5744 in reverse. Reverse execution will stop for breakpoints and synchronous
5745 exceptions (signals), just like normal execution. Behavior of
5746 asynchronous signals depends on the target environment.
5748 @kindex reverse-step
5749 @kindex rs @r{(@code{step})}
5750 @item reverse-step @r{[}@var{count}@r{]}
5751 Run the program backward until control reaches the start of a
5752 different source line; then stop it, and return control to @value{GDBN}.
5754 Like the @code{step} command, @code{reverse-step} will only stop
5755 at the beginning of a source line. It ``un-executes'' the previously
5756 executed source line. If the previous source line included calls to
5757 debuggable functions, @code{reverse-step} will step (backward) into
5758 the called function, stopping at the beginning of the @emph{last}
5759 statement in the called function (typically a return statement).
5761 Also, as with the @code{step} command, if non-debuggable functions are
5762 called, @code{reverse-step} will run thru them backward without stopping.
5764 @kindex reverse-stepi
5765 @kindex rsi @r{(@code{reverse-stepi})}
5766 @item reverse-stepi @r{[}@var{count}@r{]}
5767 Reverse-execute one machine instruction. Note that the instruction
5768 to be reverse-executed is @emph{not} the one pointed to by the program
5769 counter, but the instruction executed prior to that one. For instance,
5770 if the last instruction was a jump, @code{reverse-stepi} will take you
5771 back from the destination of the jump to the jump instruction itself.
5773 @kindex reverse-next
5774 @kindex rn @r{(@code{reverse-next})}
5775 @item reverse-next @r{[}@var{count}@r{]}
5776 Run backward to the beginning of the previous line executed in
5777 the current (innermost) stack frame. If the line contains function
5778 calls, they will be ``un-executed'' without stopping. Starting from
5779 the first line of a function, @code{reverse-next} will take you back
5780 to the caller of that function, @emph{before} the function was called,
5781 just as the normal @code{next} command would take you from the last
5782 line of a function back to its return to its caller
5783 @footnote{Unless the code is too heavily optimized.}.
5785 @kindex reverse-nexti
5786 @kindex rni @r{(@code{reverse-nexti})}
5787 @item reverse-nexti @r{[}@var{count}@r{]}
5788 Like @code{nexti}, @code{reverse-nexti} executes a single instruction
5789 in reverse, except that called functions are ``un-executed'' atomically.
5790 That is, if the previously executed instruction was a return from
5791 another function, @code{reverse-nexti} will continue to execute
5792 in reverse until the call to that function (from the current stack
5795 @kindex reverse-finish
5796 @item reverse-finish
5797 Just as the @code{finish} command takes you to the point where the
5798 current function returns, @code{reverse-finish} takes you to the point
5799 where it was called. Instead of ending up at the end of the current
5800 function invocation, you end up at the beginning.
5802 @kindex set exec-direction
5803 @item set exec-direction
5804 Set the direction of target execution.
5805 @itemx set exec-direction reverse
5806 @cindex execute forward or backward in time
5807 @value{GDBN} will perform all execution commands in reverse, until the
5808 exec-direction mode is changed to ``forward''. Affected commands include
5809 @code{step, stepi, next, nexti, continue, and finish}. The @code{return}
5810 command cannot be used in reverse mode.
5811 @item set exec-direction forward
5812 @value{GDBN} will perform all execution commands in the normal fashion.
5813 This is the default.
5817 @node Process Record and Replay
5818 @chapter Recording Inferior's Execution and Replaying It
5819 @cindex process record and replay
5820 @cindex recording inferior's execution and replaying it
5822 On some platforms, @value{GDBN} provides a special @dfn{process record
5823 and replay} target that can record a log of the process execution, and
5824 replay it later with both forward and reverse execution commands.
5827 When this target is in use, if the execution log includes the record
5828 for the next instruction, @value{GDBN} will debug in @dfn{replay
5829 mode}. In the replay mode, the inferior does not really execute code
5830 instructions. Instead, all the events that normally happen during
5831 code execution are taken from the execution log. While code is not
5832 really executed in replay mode, the values of registers (including the
5833 program counter register) and the memory of the inferior are still
5834 changed as they normally would. Their contents are taken from the
5838 If the record for the next instruction is not in the execution log,
5839 @value{GDBN} will debug in @dfn{record mode}. In this mode, the
5840 inferior executes normally, and @value{GDBN} records the execution log
5843 The process record and replay target supports reverse execution
5844 (@pxref{Reverse Execution}), even if the platform on which the
5845 inferior runs does not. However, the reverse execution is limited in
5846 this case by the range of the instructions recorded in the execution
5847 log. In other words, reverse execution on platforms that don't
5848 support it directly can only be done in the replay mode.
5850 When debugging in the reverse direction, @value{GDBN} will work in
5851 replay mode as long as the execution log includes the record for the
5852 previous instruction; otherwise, it will work in record mode, if the
5853 platform supports reverse execution, or stop if not.
5855 For architecture environments that support process record and replay,
5856 @value{GDBN} provides the following commands:
5859 @kindex target record
5863 This command starts the process record and replay target. The process
5864 record and replay target can only debug a process that is already
5865 running. Therefore, you need first to start the process with the
5866 @kbd{run} or @kbd{start} commands, and then start the recording with
5867 the @kbd{target record} command.
5869 Both @code{record} and @code{rec} are aliases of @code{target record}.
5871 @cindex displaced stepping, and process record and replay
5872 Displaced stepping (@pxref{Maintenance Commands,, displaced stepping})
5873 will be automatically disabled when process record and replay target
5874 is started. That's because the process record and replay target
5875 doesn't support displaced stepping.
5877 @cindex non-stop mode, and process record and replay
5878 @cindex asynchronous execution, and process record and replay
5879 If the inferior is in the non-stop mode (@pxref{Non-Stop Mode}) or in
5880 the asynchronous execution mode (@pxref{Background Execution}), the
5881 process record and replay target cannot be started because it doesn't
5882 support these two modes.
5887 Stop the process record and replay target. When process record and
5888 replay target stops, the entire execution log will be deleted and the
5889 inferior will either be terminated, or will remain in its final state.
5891 When you stop the process record and replay target in record mode (at
5892 the end of the execution log), the inferior will be stopped at the
5893 next instruction that would have been recorded. In other words, if
5894 you record for a while and then stop recording, the inferior process
5895 will be left in the same state as if the recording never happened.
5897 On the other hand, if the process record and replay target is stopped
5898 while in replay mode (that is, not at the end of the execution log,
5899 but at some earlier point), the inferior process will become ``live''
5900 at that earlier state, and it will then be possible to continue the
5901 usual ``live'' debugging of the process from that state.
5903 When the inferior process exits, or @value{GDBN} detaches from it,
5904 process record and replay target will automatically stop itself.
5907 @item record save @var{filename}
5908 Save the execution log to a file @file{@var{filename}}.
5909 Default filename is @file{gdb_record.@var{process_id}}, where
5910 @var{process_id} is the process ID of the inferior.
5912 @kindex record restore
5913 @item record restore @var{filename}
5914 Restore the execution log from a file @file{@var{filename}}.
5915 File must have been created with @code{record save}.
5917 @kindex set record insn-number-max
5918 @item set record insn-number-max @var{limit}
5919 Set the limit of instructions to be recorded. Default value is 200000.
5921 If @var{limit} is a positive number, then @value{GDBN} will start
5922 deleting instructions from the log once the number of the record
5923 instructions becomes greater than @var{limit}. For every new recorded
5924 instruction, @value{GDBN} will delete the earliest recorded
5925 instruction to keep the number of recorded instructions at the limit.
5926 (Since deleting recorded instructions loses information, @value{GDBN}
5927 lets you control what happens when the limit is reached, by means of
5928 the @code{stop-at-limit} option, described below.)
5930 If @var{limit} is zero, @value{GDBN} will never delete recorded
5931 instructions from the execution log. The number of recorded
5932 instructions is unlimited in this case.
5934 @kindex show record insn-number-max
5935 @item show record insn-number-max
5936 Show the limit of instructions to be recorded.
5938 @kindex set record stop-at-limit
5939 @item set record stop-at-limit
5940 Control the behavior when the number of recorded instructions reaches
5941 the limit. If ON (the default), @value{GDBN} will stop when the limit
5942 is reached for the first time and ask you whether you want to stop the
5943 inferior or continue running it and recording the execution log. If
5944 you decide to continue recording, each new recorded instruction will
5945 cause the oldest one to be deleted.
5947 If this option is OFF, @value{GDBN} will automatically delete the
5948 oldest record to make room for each new one, without asking.
5950 @kindex show record stop-at-limit
5951 @item show record stop-at-limit
5952 Show the current setting of @code{stop-at-limit}.
5954 @kindex set record memory-query
5955 @item set record memory-query
5956 Control the behavior when @value{GDBN} is unable to record memory
5957 changes caused by an instruction. If ON, @value{GDBN} will query
5958 whether to stop the inferior in that case.
5960 If this option is OFF (the default), @value{GDBN} will automatically
5961 ignore the effect of such instructions on memory. Later, when
5962 @value{GDBN} replays this execution log, it will mark the log of this
5963 instruction as not accessible, and it will not affect the replay
5966 @kindex show record memory-query
5967 @item show record memory-query
5968 Show the current setting of @code{memory-query}.
5972 Show various statistics about the state of process record and its
5973 in-memory execution log buffer, including:
5977 Whether in record mode or replay mode.
5979 Lowest recorded instruction number (counting from when the current execution log started recording instructions).
5981 Highest recorded instruction number.
5983 Current instruction about to be replayed (if in replay mode).
5985 Number of instructions contained in the execution log.
5987 Maximum number of instructions that may be contained in the execution log.
5990 @kindex record delete
5993 When record target runs in replay mode (``in the past''), delete the
5994 subsequent execution log and begin to record a new execution log starting
5995 from the current address. This means you will abandon the previously
5996 recorded ``future'' and begin recording a new ``future''.
6001 @chapter Examining the Stack
6003 When your program has stopped, the first thing you need to know is where it
6004 stopped and how it got there.
6007 Each time your program performs a function call, information about the call
6009 That information includes the location of the call in your program,
6010 the arguments of the call,
6011 and the local variables of the function being called.
6012 The information is saved in a block of data called a @dfn{stack frame}.
6013 The stack frames are allocated in a region of memory called the @dfn{call
6016 When your program stops, the @value{GDBN} commands for examining the
6017 stack allow you to see all of this information.
6019 @cindex selected frame
6020 One of the stack frames is @dfn{selected} by @value{GDBN} and many
6021 @value{GDBN} commands refer implicitly to the selected frame. In
6022 particular, whenever you ask @value{GDBN} for the value of a variable in
6023 your program, the value is found in the selected frame. There are
6024 special @value{GDBN} commands to select whichever frame you are
6025 interested in. @xref{Selection, ,Selecting a Frame}.
6027 When your program stops, @value{GDBN} automatically selects the
6028 currently executing frame and describes it briefly, similar to the
6029 @code{frame} command (@pxref{Frame Info, ,Information about a Frame}).
6032 * Frames:: Stack frames
6033 * Backtrace:: Backtraces
6034 * Selection:: Selecting a frame
6035 * Frame Info:: Information on a frame
6040 @section Stack Frames
6042 @cindex frame, definition
6044 The call stack is divided up into contiguous pieces called @dfn{stack
6045 frames}, or @dfn{frames} for short; each frame is the data associated
6046 with one call to one function. The frame contains the arguments given
6047 to the function, the function's local variables, and the address at
6048 which the function is executing.
6050 @cindex initial frame
6051 @cindex outermost frame
6052 @cindex innermost frame
6053 When your program is started, the stack has only one frame, that of the
6054 function @code{main}. This is called the @dfn{initial} frame or the
6055 @dfn{outermost} frame. Each time a function is called, a new frame is
6056 made. Each time a function returns, the frame for that function invocation
6057 is eliminated. If a function is recursive, there can be many frames for
6058 the same function. The frame for the function in which execution is
6059 actually occurring is called the @dfn{innermost} frame. This is the most
6060 recently created of all the stack frames that still exist.
6062 @cindex frame pointer
6063 Inside your program, stack frames are identified by their addresses. A
6064 stack frame consists of many bytes, each of which has its own address; each
6065 kind of computer has a convention for choosing one byte whose
6066 address serves as the address of the frame. Usually this address is kept
6067 in a register called the @dfn{frame pointer register}
6068 (@pxref{Registers, $fp}) while execution is going on in that frame.
6070 @cindex frame number
6071 @value{GDBN} assigns numbers to all existing stack frames, starting with
6072 zero for the innermost frame, one for the frame that called it,
6073 and so on upward. These numbers do not really exist in your program;
6074 they are assigned by @value{GDBN} to give you a way of designating stack
6075 frames in @value{GDBN} commands.
6077 @c The -fomit-frame-pointer below perennially causes hbox overflow
6078 @c underflow problems.
6079 @cindex frameless execution
6080 Some compilers provide a way to compile functions so that they operate
6081 without stack frames. (For example, the @value{NGCC} option
6083 @samp{-fomit-frame-pointer}
6085 generates functions without a frame.)
6086 This is occasionally done with heavily used library functions to save
6087 the frame setup time. @value{GDBN} has limited facilities for dealing
6088 with these function invocations. If the innermost function invocation
6089 has no stack frame, @value{GDBN} nevertheless regards it as though
6090 it had a separate frame, which is numbered zero as usual, allowing
6091 correct tracing of the function call chain. However, @value{GDBN} has
6092 no provision for frameless functions elsewhere in the stack.
6095 @kindex frame@r{, command}
6096 @cindex current stack frame
6097 @item frame @var{args}
6098 The @code{frame} command allows you to move from one stack frame to another,
6099 and to print the stack frame you select. @var{args} may be either the
6100 address of the frame or the stack frame number. Without an argument,
6101 @code{frame} prints the current stack frame.
6103 @kindex select-frame
6104 @cindex selecting frame silently
6106 The @code{select-frame} command allows you to move from one stack frame
6107 to another without printing the frame. This is the silent version of
6115 @cindex call stack traces
6116 A backtrace is a summary of how your program got where it is. It shows one
6117 line per frame, for many frames, starting with the currently executing
6118 frame (frame zero), followed by its caller (frame one), and on up the
6123 @kindex bt @r{(@code{backtrace})}
6126 Print a backtrace of the entire stack: one line per frame for all
6127 frames in the stack.
6129 You can stop the backtrace at any time by typing the system interrupt
6130 character, normally @kbd{Ctrl-c}.
6132 @item backtrace @var{n}
6134 Similar, but print only the innermost @var{n} frames.
6136 @item backtrace -@var{n}
6138 Similar, but print only the outermost @var{n} frames.
6140 @item backtrace full
6142 @itemx bt full @var{n}
6143 @itemx bt full -@var{n}
6144 Print the values of the local variables also. @var{n} specifies the
6145 number of frames to print, as described above.
6150 The names @code{where} and @code{info stack} (abbreviated @code{info s})
6151 are additional aliases for @code{backtrace}.
6153 @cindex multiple threads, backtrace
6154 In a multi-threaded program, @value{GDBN} by default shows the
6155 backtrace only for the current thread. To display the backtrace for
6156 several or all of the threads, use the command @code{thread apply}
6157 (@pxref{Threads, thread apply}). For example, if you type @kbd{thread
6158 apply all backtrace}, @value{GDBN} will display the backtrace for all
6159 the threads; this is handy when you debug a core dump of a
6160 multi-threaded program.
6162 Each line in the backtrace shows the frame number and the function name.
6163 The program counter value is also shown---unless you use @code{set
6164 print address off}. The backtrace also shows the source file name and
6165 line number, as well as the arguments to the function. The program
6166 counter value is omitted if it is at the beginning of the code for that
6169 Here is an example of a backtrace. It was made with the command
6170 @samp{bt 3}, so it shows the innermost three frames.
6174 #0 m4_traceon (obs=0x24eb0, argc=1, argv=0x2b8c8)
6176 #1 0x6e38 in expand_macro (sym=0x2b600, data=...) at macro.c:242
6177 #2 0x6840 in expand_token (obs=0x0, t=177664, td=0xf7fffb08)
6179 (More stack frames follow...)
6184 The display for frame zero does not begin with a program counter
6185 value, indicating that your program has stopped at the beginning of the
6186 code for line @code{993} of @code{builtin.c}.
6189 The value of parameter @code{data} in frame 1 has been replaced by
6190 @code{@dots{}}. By default, @value{GDBN} prints the value of a parameter
6191 only if it is a scalar (integer, pointer, enumeration, etc). See command
6192 @kbd{set print frame-arguments} in @ref{Print Settings} for more details
6193 on how to configure the way function parameter values are printed.
6195 @cindex optimized out, in backtrace
6196 @cindex function call arguments, optimized out
6197 If your program was compiled with optimizations, some compilers will
6198 optimize away arguments passed to functions if those arguments are
6199 never used after the call. Such optimizations generate code that
6200 passes arguments through registers, but doesn't store those arguments
6201 in the stack frame. @value{GDBN} has no way of displaying such
6202 arguments in stack frames other than the innermost one. Here's what
6203 such a backtrace might look like:
6207 #0 m4_traceon (obs=0x24eb0, argc=1, argv=0x2b8c8)
6209 #1 0x6e38 in expand_macro (sym=<optimized out>) at macro.c:242
6210 #2 0x6840 in expand_token (obs=0x0, t=<optimized out>, td=0xf7fffb08)
6212 (More stack frames follow...)
6217 The values of arguments that were not saved in their stack frames are
6218 shown as @samp{<optimized out>}.
6220 If you need to display the values of such optimized-out arguments,
6221 either deduce that from other variables whose values depend on the one
6222 you are interested in, or recompile without optimizations.
6224 @cindex backtrace beyond @code{main} function
6225 @cindex program entry point
6226 @cindex startup code, and backtrace
6227 Most programs have a standard user entry point---a place where system
6228 libraries and startup code transition into user code. For C this is
6229 @code{main}@footnote{
6230 Note that embedded programs (the so-called ``free-standing''
6231 environment) are not required to have a @code{main} function as the
6232 entry point. They could even have multiple entry points.}.
6233 When @value{GDBN} finds the entry function in a backtrace
6234 it will terminate the backtrace, to avoid tracing into highly
6235 system-specific (and generally uninteresting) code.
6237 If you need to examine the startup code, or limit the number of levels
6238 in a backtrace, you can change this behavior:
6241 @item set backtrace past-main
6242 @itemx set backtrace past-main on
6243 @kindex set backtrace
6244 Backtraces will continue past the user entry point.
6246 @item set backtrace past-main off
6247 Backtraces will stop when they encounter the user entry point. This is the
6250 @item show backtrace past-main
6251 @kindex show backtrace
6252 Display the current user entry point backtrace policy.
6254 @item set backtrace past-entry
6255 @itemx set backtrace past-entry on
6256 Backtraces will continue past the internal entry point of an application.
6257 This entry point is encoded by the linker when the application is built,
6258 and is likely before the user entry point @code{main} (or equivalent) is called.
6260 @item set backtrace past-entry off
6261 Backtraces will stop when they encounter the internal entry point of an
6262 application. This is the default.
6264 @item show backtrace past-entry
6265 Display the current internal entry point backtrace policy.
6267 @item set backtrace limit @var{n}
6268 @itemx set backtrace limit 0
6269 @cindex backtrace limit
6270 Limit the backtrace to @var{n} levels. A value of zero means
6273 @item show backtrace limit
6274 Display the current limit on backtrace levels.
6278 @section Selecting a Frame
6280 Most commands for examining the stack and other data in your program work on
6281 whichever stack frame is selected at the moment. Here are the commands for
6282 selecting a stack frame; all of them finish by printing a brief description
6283 of the stack frame just selected.
6286 @kindex frame@r{, selecting}
6287 @kindex f @r{(@code{frame})}
6290 Select frame number @var{n}. Recall that frame zero is the innermost
6291 (currently executing) frame, frame one is the frame that called the
6292 innermost one, and so on. The highest-numbered frame is the one for
6295 @item frame @var{addr}
6297 Select the frame at address @var{addr}. This is useful mainly if the
6298 chaining of stack frames has been damaged by a bug, making it
6299 impossible for @value{GDBN} to assign numbers properly to all frames. In
6300 addition, this can be useful when your program has multiple stacks and
6301 switches between them.
6303 On the SPARC architecture, @code{frame} needs two addresses to
6304 select an arbitrary frame: a frame pointer and a stack pointer.
6306 On the MIPS and Alpha architecture, it needs two addresses: a stack
6307 pointer and a program counter.
6309 On the 29k architecture, it needs three addresses: a register stack
6310 pointer, a program counter, and a memory stack pointer.
6314 Move @var{n} frames up the stack. For positive numbers @var{n}, this
6315 advances toward the outermost frame, to higher frame numbers, to frames
6316 that have existed longer. @var{n} defaults to one.
6319 @kindex do @r{(@code{down})}
6321 Move @var{n} frames down the stack. For positive numbers @var{n}, this
6322 advances toward the innermost frame, to lower frame numbers, to frames
6323 that were created more recently. @var{n} defaults to one. You may
6324 abbreviate @code{down} as @code{do}.
6327 All of these commands end by printing two lines of output describing the
6328 frame. The first line shows the frame number, the function name, the
6329 arguments, and the source file and line number of execution in that
6330 frame. The second line shows the text of that source line.
6338 #1 0x22f0 in main (argc=1, argv=0xf7fffbf4, env=0xf7fffbfc)
6340 10 read_input_file (argv[i]);
6344 After such a printout, the @code{list} command with no arguments
6345 prints ten lines centered on the point of execution in the frame.
6346 You can also edit the program at the point of execution with your favorite
6347 editing program by typing @code{edit}.
6348 @xref{List, ,Printing Source Lines},
6352 @kindex down-silently
6354 @item up-silently @var{n}
6355 @itemx down-silently @var{n}
6356 These two commands are variants of @code{up} and @code{down},
6357 respectively; they differ in that they do their work silently, without
6358 causing display of the new frame. They are intended primarily for use
6359 in @value{GDBN} command scripts, where the output might be unnecessary and
6364 @section Information About a Frame
6366 There are several other commands to print information about the selected
6372 When used without any argument, this command does not change which
6373 frame is selected, but prints a brief description of the currently
6374 selected stack frame. It can be abbreviated @code{f}. With an
6375 argument, this command is used to select a stack frame.
6376 @xref{Selection, ,Selecting a Frame}.
6379 @kindex info f @r{(@code{info frame})}
6382 This command prints a verbose description of the selected stack frame,
6387 the address of the frame
6389 the address of the next frame down (called by this frame)
6391 the address of the next frame up (caller of this frame)
6393 the language in which the source code corresponding to this frame is written
6395 the address of the frame's arguments
6397 the address of the frame's local variables
6399 the program counter saved in it (the address of execution in the caller frame)
6401 which registers were saved in the frame
6404 @noindent The verbose description is useful when
6405 something has gone wrong that has made the stack format fail to fit
6406 the usual conventions.
6408 @item info frame @var{addr}
6409 @itemx info f @var{addr}
6410 Print a verbose description of the frame at address @var{addr}, without
6411 selecting that frame. The selected frame remains unchanged by this
6412 command. This requires the same kind of address (more than one for some
6413 architectures) that you specify in the @code{frame} command.
6414 @xref{Selection, ,Selecting a Frame}.
6418 Print the arguments of the selected frame, each on a separate line.
6422 Print the local variables of the selected frame, each on a separate
6423 line. These are all variables (declared either static or automatic)
6424 accessible at the point of execution of the selected frame.
6430 @chapter Examining Source Files
6432 @value{GDBN} can print parts of your program's source, since the debugging
6433 information recorded in the program tells @value{GDBN} what source files were
6434 used to build it. When your program stops, @value{GDBN} spontaneously prints
6435 the line where it stopped. Likewise, when you select a stack frame
6436 (@pxref{Selection, ,Selecting a Frame}), @value{GDBN} prints the line where
6437 execution in that frame has stopped. You can print other portions of
6438 source files by explicit command.
6440 If you use @value{GDBN} through its @sc{gnu} Emacs interface, you may
6441 prefer to use Emacs facilities to view source; see @ref{Emacs, ,Using
6442 @value{GDBN} under @sc{gnu} Emacs}.
6445 * List:: Printing source lines
6446 * Specify Location:: How to specify code locations
6447 * Edit:: Editing source files
6448 * Search:: Searching source files
6449 * Source Path:: Specifying source directories
6450 * Machine Code:: Source and machine code
6454 @section Printing Source Lines
6457 @kindex l @r{(@code{list})}
6458 To print lines from a source file, use the @code{list} command
6459 (abbreviated @code{l}). By default, ten lines are printed.
6460 There are several ways to specify what part of the file you want to
6461 print; see @ref{Specify Location}, for the full list.
6463 Here are the forms of the @code{list} command most commonly used:
6466 @item list @var{linenum}
6467 Print lines centered around line number @var{linenum} in the
6468 current source file.
6470 @item list @var{function}
6471 Print lines centered around the beginning of function
6475 Print more lines. If the last lines printed were printed with a
6476 @code{list} command, this prints lines following the last lines
6477 printed; however, if the last line printed was a solitary line printed
6478 as part of displaying a stack frame (@pxref{Stack, ,Examining the
6479 Stack}), this prints lines centered around that line.
6482 Print lines just before the lines last printed.
6485 @cindex @code{list}, how many lines to display
6486 By default, @value{GDBN} prints ten source lines with any of these forms of
6487 the @code{list} command. You can change this using @code{set listsize}:
6490 @kindex set listsize
6491 @item set listsize @var{count}
6492 Make the @code{list} command display @var{count} source lines (unless
6493 the @code{list} argument explicitly specifies some other number).
6495 @kindex show listsize
6497 Display the number of lines that @code{list} prints.
6500 Repeating a @code{list} command with @key{RET} discards the argument,
6501 so it is equivalent to typing just @code{list}. This is more useful
6502 than listing the same lines again. An exception is made for an
6503 argument of @samp{-}; that argument is preserved in repetition so that
6504 each repetition moves up in the source file.
6506 In general, the @code{list} command expects you to supply zero, one or two
6507 @dfn{linespecs}. Linespecs specify source lines; there are several ways
6508 of writing them (@pxref{Specify Location}), but the effect is always
6509 to specify some source line.
6511 Here is a complete description of the possible arguments for @code{list}:
6514 @item list @var{linespec}
6515 Print lines centered around the line specified by @var{linespec}.
6517 @item list @var{first},@var{last}
6518 Print lines from @var{first} to @var{last}. Both arguments are
6519 linespecs. When a @code{list} command has two linespecs, and the
6520 source file of the second linespec is omitted, this refers to
6521 the same source file as the first linespec.
6523 @item list ,@var{last}
6524 Print lines ending with @var{last}.
6526 @item list @var{first},
6527 Print lines starting with @var{first}.
6530 Print lines just after the lines last printed.
6533 Print lines just before the lines last printed.
6536 As described in the preceding table.
6539 @node Specify Location
6540 @section Specifying a Location
6541 @cindex specifying location
6544 Several @value{GDBN} commands accept arguments that specify a location
6545 of your program's code. Since @value{GDBN} is a source-level
6546 debugger, a location usually specifies some line in the source code;
6547 for that reason, locations are also known as @dfn{linespecs}.
6549 Here are all the different ways of specifying a code location that
6550 @value{GDBN} understands:
6554 Specifies the line number @var{linenum} of the current source file.
6557 @itemx +@var{offset}
6558 Specifies the line @var{offset} lines before or after the @dfn{current
6559 line}. For the @code{list} command, the current line is the last one
6560 printed; for the breakpoint commands, this is the line at which
6561 execution stopped in the currently selected @dfn{stack frame}
6562 (@pxref{Frames, ,Frames}, for a description of stack frames.) When
6563 used as the second of the two linespecs in a @code{list} command,
6564 this specifies the line @var{offset} lines up or down from the first
6567 @item @var{filename}:@var{linenum}
6568 Specifies the line @var{linenum} in the source file @var{filename}.
6569 If @var{filename} is a relative file name, then it will match any
6570 source file name with the same trailing components. For example, if
6571 @var{filename} is @samp{gcc/expr.c}, then it will match source file
6572 name of @file{/build/trunk/gcc/expr.c}, but not
6573 @file{/build/trunk/libcpp/expr.c} or @file{/build/trunk/gcc/x-expr.c}.
6575 @item @var{function}
6576 Specifies the line that begins the body of the function @var{function}.
6577 For example, in C, this is the line with the open brace.
6579 @item @var{function}:@var{label}
6580 Specifies the line where @var{label} appears in @var{function}.
6582 @item @var{filename}:@var{function}
6583 Specifies the line that begins the body of the function @var{function}
6584 in the file @var{filename}. You only need the file name with a
6585 function name to avoid ambiguity when there are identically named
6586 functions in different source files.
6589 Specifies the line at which the label named @var{label} appears.
6590 @value{GDBN} searches for the label in the function corresponding to
6591 the currently selected stack frame. If there is no current selected
6592 stack frame (for instance, if the inferior is not running), then
6593 @value{GDBN} will not search for a label.
6595 @item *@var{address}
6596 Specifies the program address @var{address}. For line-oriented
6597 commands, such as @code{list} and @code{edit}, this specifies a source
6598 line that contains @var{address}. For @code{break} and other
6599 breakpoint oriented commands, this can be used to set breakpoints in
6600 parts of your program which do not have debugging information or
6603 Here @var{address} may be any expression valid in the current working
6604 language (@pxref{Languages, working language}) that specifies a code
6605 address. In addition, as a convenience, @value{GDBN} extends the
6606 semantics of expressions used in locations to cover the situations
6607 that frequently happen during debugging. Here are the various forms
6611 @item @var{expression}
6612 Any expression valid in the current working language.
6614 @item @var{funcaddr}
6615 An address of a function or procedure derived from its name. In C,
6616 C@t{++}, Java, Objective-C, Fortran, minimal, and assembly, this is
6617 simply the function's name @var{function} (and actually a special case
6618 of a valid expression). In Pascal and Modula-2, this is
6619 @code{&@var{function}}. In Ada, this is @code{@var{function}'Address}
6620 (although the Pascal form also works).
6622 This form specifies the address of the function's first instruction,
6623 before the stack frame and arguments have been set up.
6625 @item '@var{filename}'::@var{funcaddr}
6626 Like @var{funcaddr} above, but also specifies the name of the source
6627 file explicitly. This is useful if the name of the function does not
6628 specify the function unambiguously, e.g., if there are several
6629 functions with identical names in different source files.
6636 @section Editing Source Files
6637 @cindex editing source files
6640 @kindex e @r{(@code{edit})}
6641 To edit the lines in a source file, use the @code{edit} command.
6642 The editing program of your choice
6643 is invoked with the current line set to
6644 the active line in the program.
6645 Alternatively, there are several ways to specify what part of the file you
6646 want to print if you want to see other parts of the program:
6649 @item edit @var{location}
6650 Edit the source file specified by @code{location}. Editing starts at
6651 that @var{location}, e.g., at the specified source line of the
6652 specified file. @xref{Specify Location}, for all the possible forms
6653 of the @var{location} argument; here are the forms of the @code{edit}
6654 command most commonly used:
6657 @item edit @var{number}
6658 Edit the current source file with @var{number} as the active line number.
6660 @item edit @var{function}
6661 Edit the file containing @var{function} at the beginning of its definition.
6666 @subsection Choosing your Editor
6667 You can customize @value{GDBN} to use any editor you want
6669 The only restriction is that your editor (say @code{ex}), recognizes the
6670 following command-line syntax:
6672 ex +@var{number} file
6674 The optional numeric value +@var{number} specifies the number of the line in
6675 the file where to start editing.}.
6676 By default, it is @file{@value{EDITOR}}, but you can change this
6677 by setting the environment variable @code{EDITOR} before using
6678 @value{GDBN}. For example, to configure @value{GDBN} to use the
6679 @code{vi} editor, you could use these commands with the @code{sh} shell:
6685 or in the @code{csh} shell,
6687 setenv EDITOR /usr/bin/vi
6692 @section Searching Source Files
6693 @cindex searching source files
6695 There are two commands for searching through the current source file for a
6700 @kindex forward-search
6701 @item forward-search @var{regexp}
6702 @itemx search @var{regexp}
6703 The command @samp{forward-search @var{regexp}} checks each line,
6704 starting with the one following the last line listed, for a match for
6705 @var{regexp}. It lists the line that is found. You can use the
6706 synonym @samp{search @var{regexp}} or abbreviate the command name as
6709 @kindex reverse-search
6710 @item reverse-search @var{regexp}
6711 The command @samp{reverse-search @var{regexp}} checks each line, starting
6712 with the one before the last line listed and going backward, for a match
6713 for @var{regexp}. It lists the line that is found. You can abbreviate
6714 this command as @code{rev}.
6718 @section Specifying Source Directories
6721 @cindex directories for source files
6722 Executable programs sometimes do not record the directories of the source
6723 files from which they were compiled, just the names. Even when they do,
6724 the directories could be moved between the compilation and your debugging
6725 session. @value{GDBN} has a list of directories to search for source files;
6726 this is called the @dfn{source path}. Each time @value{GDBN} wants a source file,
6727 it tries all the directories in the list, in the order they are present
6728 in the list, until it finds a file with the desired name.
6730 For example, suppose an executable references the file
6731 @file{/usr/src/foo-1.0/lib/foo.c}, and our source path is
6732 @file{/mnt/cross}. The file is first looked up literally; if this
6733 fails, @file{/mnt/cross/usr/src/foo-1.0/lib/foo.c} is tried; if this
6734 fails, @file{/mnt/cross/foo.c} is opened; if this fails, an error
6735 message is printed. @value{GDBN} does not look up the parts of the
6736 source file name, such as @file{/mnt/cross/src/foo-1.0/lib/foo.c}.
6737 Likewise, the subdirectories of the source path are not searched: if
6738 the source path is @file{/mnt/cross}, and the binary refers to
6739 @file{foo.c}, @value{GDBN} would not find it under
6740 @file{/mnt/cross/usr/src/foo-1.0/lib}.
6742 Plain file names, relative file names with leading directories, file
6743 names containing dots, etc.@: are all treated as described above; for
6744 instance, if the source path is @file{/mnt/cross}, and the source file
6745 is recorded as @file{../lib/foo.c}, @value{GDBN} would first try
6746 @file{../lib/foo.c}, then @file{/mnt/cross/../lib/foo.c}, and after
6747 that---@file{/mnt/cross/foo.c}.
6749 Note that the executable search path is @emph{not} used to locate the
6752 Whenever you reset or rearrange the source path, @value{GDBN} clears out
6753 any information it has cached about where source files are found and where
6754 each line is in the file.
6758 When you start @value{GDBN}, its source path includes only @samp{cdir}
6759 and @samp{cwd}, in that order.
6760 To add other directories, use the @code{directory} command.
6762 The search path is used to find both program source files and @value{GDBN}
6763 script files (read using the @samp{-command} option and @samp{source} command).
6765 In addition to the source path, @value{GDBN} provides a set of commands
6766 that manage a list of source path substitution rules. A @dfn{substitution
6767 rule} specifies how to rewrite source directories stored in the program's
6768 debug information in case the sources were moved to a different
6769 directory between compilation and debugging. A rule is made of
6770 two strings, the first specifying what needs to be rewritten in
6771 the path, and the second specifying how it should be rewritten.
6772 In @ref{set substitute-path}, we name these two parts @var{from} and
6773 @var{to} respectively. @value{GDBN} does a simple string replacement
6774 of @var{from} with @var{to} at the start of the directory part of the
6775 source file name, and uses that result instead of the original file
6776 name to look up the sources.
6778 Using the previous example, suppose the @file{foo-1.0} tree has been
6779 moved from @file{/usr/src} to @file{/mnt/cross}, then you can tell
6780 @value{GDBN} to replace @file{/usr/src} in all source path names with
6781 @file{/mnt/cross}. The first lookup will then be
6782 @file{/mnt/cross/foo-1.0/lib/foo.c} in place of the original location
6783 of @file{/usr/src/foo-1.0/lib/foo.c}. To define a source path
6784 substitution rule, use the @code{set substitute-path} command
6785 (@pxref{set substitute-path}).
6787 To avoid unexpected substitution results, a rule is applied only if the
6788 @var{from} part of the directory name ends at a directory separator.
6789 For instance, a rule substituting @file{/usr/source} into
6790 @file{/mnt/cross} will be applied to @file{/usr/source/foo-1.0} but
6791 not to @file{/usr/sourceware/foo-2.0}. And because the substitution
6792 is applied only at the beginning of the directory name, this rule will
6793 not be applied to @file{/root/usr/source/baz.c} either.
6795 In many cases, you can achieve the same result using the @code{directory}
6796 command. However, @code{set substitute-path} can be more efficient in
6797 the case where the sources are organized in a complex tree with multiple
6798 subdirectories. With the @code{directory} command, you need to add each
6799 subdirectory of your project. If you moved the entire tree while
6800 preserving its internal organization, then @code{set substitute-path}
6801 allows you to direct the debugger to all the sources with one single
6804 @code{set substitute-path} is also more than just a shortcut command.
6805 The source path is only used if the file at the original location no
6806 longer exists. On the other hand, @code{set substitute-path} modifies
6807 the debugger behavior to look at the rewritten location instead. So, if
6808 for any reason a source file that is not relevant to your executable is
6809 located at the original location, a substitution rule is the only
6810 method available to point @value{GDBN} at the new location.
6812 @cindex @samp{--with-relocated-sources}
6813 @cindex default source path substitution
6814 You can configure a default source path substitution rule by
6815 configuring @value{GDBN} with the
6816 @samp{--with-relocated-sources=@var{dir}} option. The @var{dir}
6817 should be the name of a directory under @value{GDBN}'s configured
6818 prefix (set with @samp{--prefix} or @samp{--exec-prefix}), and
6819 directory names in debug information under @var{dir} will be adjusted
6820 automatically if the installed @value{GDBN} is moved to a new
6821 location. This is useful if @value{GDBN}, libraries or executables
6822 with debug information and corresponding source code are being moved
6826 @item directory @var{dirname} @dots{}
6827 @item dir @var{dirname} @dots{}
6828 Add directory @var{dirname} to the front of the source path. Several
6829 directory names may be given to this command, separated by @samp{:}
6830 (@samp{;} on MS-DOS and MS-Windows, where @samp{:} usually appears as
6831 part of absolute file names) or
6832 whitespace. You may specify a directory that is already in the source
6833 path; this moves it forward, so @value{GDBN} searches it sooner.
6837 @vindex $cdir@r{, convenience variable}
6838 @vindex $cwd@r{, convenience variable}
6839 @cindex compilation directory
6840 @cindex current directory
6841 @cindex working directory
6842 @cindex directory, current
6843 @cindex directory, compilation
6844 You can use the string @samp{$cdir} to refer to the compilation
6845 directory (if one is recorded), and @samp{$cwd} to refer to the current
6846 working directory. @samp{$cwd} is not the same as @samp{.}---the former
6847 tracks the current working directory as it changes during your @value{GDBN}
6848 session, while the latter is immediately expanded to the current
6849 directory at the time you add an entry to the source path.
6852 Reset the source path to its default value (@samp{$cdir:$cwd} on Unix systems). This requires confirmation.
6854 @c RET-repeat for @code{directory} is explicitly disabled, but since
6855 @c repeating it would be a no-op we do not say that. (thanks to RMS)
6857 @item set directories @var{path-list}
6858 @kindex set directories
6859 Set the source path to @var{path-list}.
6860 @samp{$cdir:$cwd} are added if missing.
6862 @item show directories
6863 @kindex show directories
6864 Print the source path: show which directories it contains.
6866 @anchor{set substitute-path}
6867 @item set substitute-path @var{from} @var{to}
6868 @kindex set substitute-path
6869 Define a source path substitution rule, and add it at the end of the
6870 current list of existing substitution rules. If a rule with the same
6871 @var{from} was already defined, then the old rule is also deleted.
6873 For example, if the file @file{/foo/bar/baz.c} was moved to
6874 @file{/mnt/cross/baz.c}, then the command
6877 (@value{GDBP}) set substitute-path /usr/src /mnt/cross
6881 will tell @value{GDBN} to replace @samp{/usr/src} with
6882 @samp{/mnt/cross}, which will allow @value{GDBN} to find the file
6883 @file{baz.c} even though it was moved.
6885 In the case when more than one substitution rule have been defined,
6886 the rules are evaluated one by one in the order where they have been
6887 defined. The first one matching, if any, is selected to perform
6890 For instance, if we had entered the following commands:
6893 (@value{GDBP}) set substitute-path /usr/src/include /mnt/include
6894 (@value{GDBP}) set substitute-path /usr/src /mnt/src
6898 @value{GDBN} would then rewrite @file{/usr/src/include/defs.h} into
6899 @file{/mnt/include/defs.h} by using the first rule. However, it would
6900 use the second rule to rewrite @file{/usr/src/lib/foo.c} into
6901 @file{/mnt/src/lib/foo.c}.
6904 @item unset substitute-path [path]
6905 @kindex unset substitute-path
6906 If a path is specified, search the current list of substitution rules
6907 for a rule that would rewrite that path. Delete that rule if found.
6908 A warning is emitted by the debugger if no rule could be found.
6910 If no path is specified, then all substitution rules are deleted.
6912 @item show substitute-path [path]
6913 @kindex show substitute-path
6914 If a path is specified, then print the source path substitution rule
6915 which would rewrite that path, if any.
6917 If no path is specified, then print all existing source path substitution
6922 If your source path is cluttered with directories that are no longer of
6923 interest, @value{GDBN} may sometimes cause confusion by finding the wrong
6924 versions of source. You can correct the situation as follows:
6928 Use @code{directory} with no argument to reset the source path to its default value.
6931 Use @code{directory} with suitable arguments to reinstall the
6932 directories you want in the source path. You can add all the
6933 directories in one command.
6937 @section Source and Machine Code
6938 @cindex source line and its code address
6940 You can use the command @code{info line} to map source lines to program
6941 addresses (and vice versa), and the command @code{disassemble} to display
6942 a range of addresses as machine instructions. You can use the command
6943 @code{set disassemble-next-line} to set whether to disassemble next
6944 source line when execution stops. When run under @sc{gnu} Emacs
6945 mode, the @code{info line} command causes the arrow to point to the
6946 line specified. Also, @code{info line} prints addresses in symbolic form as
6951 @item info line @var{linespec}
6952 Print the starting and ending addresses of the compiled code for
6953 source line @var{linespec}. You can specify source lines in any of
6954 the ways documented in @ref{Specify Location}.
6957 For example, we can use @code{info line} to discover the location of
6958 the object code for the first line of function
6959 @code{m4_changequote}:
6961 @c FIXME: I think this example should also show the addresses in
6962 @c symbolic form, as they usually would be displayed.
6964 (@value{GDBP}) info line m4_changequote
6965 Line 895 of "builtin.c" starts at pc 0x634c and ends at 0x6350.
6969 @cindex code address and its source line
6970 We can also inquire (using @code{*@var{addr}} as the form for
6971 @var{linespec}) what source line covers a particular address:
6973 (@value{GDBP}) info line *0x63ff
6974 Line 926 of "builtin.c" starts at pc 0x63e4 and ends at 0x6404.
6977 @cindex @code{$_} and @code{info line}
6978 @cindex @code{x} command, default address
6979 @kindex x@r{(examine), and} info line
6980 After @code{info line}, the default address for the @code{x} command
6981 is changed to the starting address of the line, so that @samp{x/i} is
6982 sufficient to begin examining the machine code (@pxref{Memory,
6983 ,Examining Memory}). Also, this address is saved as the value of the
6984 convenience variable @code{$_} (@pxref{Convenience Vars, ,Convenience
6989 @cindex assembly instructions
6990 @cindex instructions, assembly
6991 @cindex machine instructions
6992 @cindex listing machine instructions
6994 @itemx disassemble /m
6995 @itemx disassemble /r
6996 This specialized command dumps a range of memory as machine
6997 instructions. It can also print mixed source+disassembly by specifying
6998 the @code{/m} modifier and print the raw instructions in hex as well as
6999 in symbolic form by specifying the @code{/r}.
7000 The default memory range is the function surrounding the
7001 program counter of the selected frame. A single argument to this
7002 command is a program counter value; @value{GDBN} dumps the function
7003 surrounding this value. When two arguments are given, they should
7004 be separated by a comma, possibly surrounded by whitespace. The
7005 arguments specify a range of addresses to dump, in one of two forms:
7008 @item @var{start},@var{end}
7009 the addresses from @var{start} (inclusive) to @var{end} (exclusive)
7010 @item @var{start},+@var{length}
7011 the addresses from @var{start} (inclusive) to
7012 @code{@var{start}+@var{length}} (exclusive).
7016 When 2 arguments are specified, the name of the function is also
7017 printed (since there could be several functions in the given range).
7019 The argument(s) can be any expression yielding a numeric value, such as
7020 @samp{0x32c4}, @samp{&main+10} or @samp{$pc - 8}.
7022 If the range of memory being disassembled contains current program counter,
7023 the instruction at that location is shown with a @code{=>} marker.
7026 The following example shows the disassembly of a range of addresses of
7027 HP PA-RISC 2.0 code:
7030 (@value{GDBP}) disas 0x32c4, 0x32e4
7031 Dump of assembler code from 0x32c4 to 0x32e4:
7032 0x32c4 <main+204>: addil 0,dp
7033 0x32c8 <main+208>: ldw 0x22c(sr0,r1),r26
7034 0x32cc <main+212>: ldil 0x3000,r31
7035 0x32d0 <main+216>: ble 0x3f8(sr4,r31)
7036 0x32d4 <main+220>: ldo 0(r31),rp
7037 0x32d8 <main+224>: addil -0x800,dp
7038 0x32dc <main+228>: ldo 0x588(r1),r26
7039 0x32e0 <main+232>: ldil 0x3000,r31
7040 End of assembler dump.
7043 Here is an example showing mixed source+assembly for Intel x86, when the
7044 program is stopped just after function prologue:
7047 (@value{GDBP}) disas /m main
7048 Dump of assembler code for function main:
7050 0x08048330 <+0>: push %ebp
7051 0x08048331 <+1>: mov %esp,%ebp
7052 0x08048333 <+3>: sub $0x8,%esp
7053 0x08048336 <+6>: and $0xfffffff0,%esp
7054 0x08048339 <+9>: sub $0x10,%esp
7056 6 printf ("Hello.\n");
7057 => 0x0804833c <+12>: movl $0x8048440,(%esp)
7058 0x08048343 <+19>: call 0x8048284 <puts@@plt>
7062 0x08048348 <+24>: mov $0x0,%eax
7063 0x0804834d <+29>: leave
7064 0x0804834e <+30>: ret
7066 End of assembler dump.
7069 Here is another example showing raw instructions in hex for AMD x86-64,
7072 (gdb) disas /r 0x400281,+10
7073 Dump of assembler code from 0x400281 to 0x40028b:
7074 0x0000000000400281: 38 36 cmp %dh,(%rsi)
7075 0x0000000000400283: 2d 36 34 2e 73 sub $0x732e3436,%eax
7076 0x0000000000400288: 6f outsl %ds:(%rsi),(%dx)
7077 0x0000000000400289: 2e 32 00 xor %cs:(%rax),%al
7078 End of assembler dump.
7081 Some architectures have more than one commonly-used set of instruction
7082 mnemonics or other syntax.
7084 For programs that were dynamically linked and use shared libraries,
7085 instructions that call functions or branch to locations in the shared
7086 libraries might show a seemingly bogus location---it's actually a
7087 location of the relocation table. On some architectures, @value{GDBN}
7088 might be able to resolve these to actual function names.
7091 @kindex set disassembly-flavor
7092 @cindex Intel disassembly flavor
7093 @cindex AT&T disassembly flavor
7094 @item set disassembly-flavor @var{instruction-set}
7095 Select the instruction set to use when disassembling the
7096 program via the @code{disassemble} or @code{x/i} commands.
7098 Currently this command is only defined for the Intel x86 family. You
7099 can set @var{instruction-set} to either @code{intel} or @code{att}.
7100 The default is @code{att}, the AT&T flavor used by default by Unix
7101 assemblers for x86-based targets.
7103 @kindex show disassembly-flavor
7104 @item show disassembly-flavor
7105 Show the current setting of the disassembly flavor.
7109 @kindex set disassemble-next-line
7110 @kindex show disassemble-next-line
7111 @item set disassemble-next-line
7112 @itemx show disassemble-next-line
7113 Control whether or not @value{GDBN} will disassemble the next source
7114 line or instruction when execution stops. If ON, @value{GDBN} will
7115 display disassembly of the next source line when execution of the
7116 program being debugged stops. This is @emph{in addition} to
7117 displaying the source line itself, which @value{GDBN} always does if
7118 possible. If the next source line cannot be displayed for some reason
7119 (e.g., if @value{GDBN} cannot find the source file, or there's no line
7120 info in the debug info), @value{GDBN} will display disassembly of the
7121 next @emph{instruction} instead of showing the next source line. If
7122 AUTO, @value{GDBN} will display disassembly of next instruction only
7123 if the source line cannot be displayed. This setting causes
7124 @value{GDBN} to display some feedback when you step through a function
7125 with no line info or whose source file is unavailable. The default is
7126 OFF, which means never display the disassembly of the next line or
7132 @chapter Examining Data
7134 @cindex printing data
7135 @cindex examining data
7138 @c "inspect" is not quite a synonym if you are using Epoch, which we do not
7139 @c document because it is nonstandard... Under Epoch it displays in a
7140 @c different window or something like that.
7141 The usual way to examine data in your program is with the @code{print}
7142 command (abbreviated @code{p}), or its synonym @code{inspect}. It
7143 evaluates and prints the value of an expression of the language your
7144 program is written in (@pxref{Languages, ,Using @value{GDBN} with
7145 Different Languages}). It may also print the expression using a
7146 Python-based pretty-printer (@pxref{Pretty Printing}).
7149 @item print @var{expr}
7150 @itemx print /@var{f} @var{expr}
7151 @var{expr} is an expression (in the source language). By default the
7152 value of @var{expr} is printed in a format appropriate to its data type;
7153 you can choose a different format by specifying @samp{/@var{f}}, where
7154 @var{f} is a letter specifying the format; see @ref{Output Formats,,Output
7158 @itemx print /@var{f}
7159 @cindex reprint the last value
7160 If you omit @var{expr}, @value{GDBN} displays the last value again (from the
7161 @dfn{value history}; @pxref{Value History, ,Value History}). This allows you to
7162 conveniently inspect the same value in an alternative format.
7165 A more low-level way of examining data is with the @code{x} command.
7166 It examines data in memory at a specified address and prints it in a
7167 specified format. @xref{Memory, ,Examining Memory}.
7169 If you are interested in information about types, or about how the
7170 fields of a struct or a class are declared, use the @code{ptype @var{exp}}
7171 command rather than @code{print}. @xref{Symbols, ,Examining the Symbol
7175 * Expressions:: Expressions
7176 * Ambiguous Expressions:: Ambiguous Expressions
7177 * Variables:: Program variables
7178 * Arrays:: Artificial arrays
7179 * Output Formats:: Output formats
7180 * Memory:: Examining memory
7181 * Auto Display:: Automatic display
7182 * Print Settings:: Print settings
7183 * Pretty Printing:: Python pretty printing
7184 * Value History:: Value history
7185 * Convenience Vars:: Convenience variables
7186 * Registers:: Registers
7187 * Floating Point Hardware:: Floating point hardware
7188 * Vector Unit:: Vector Unit
7189 * OS Information:: Auxiliary data provided by operating system
7190 * Memory Region Attributes:: Memory region attributes
7191 * Dump/Restore Files:: Copy between memory and a file
7192 * Core File Generation:: Cause a program dump its core
7193 * Character Sets:: Debugging programs that use a different
7194 character set than GDB does
7195 * Caching Remote Data:: Data caching for remote targets
7196 * Searching Memory:: Searching memory for a sequence of bytes
7200 @section Expressions
7203 @code{print} and many other @value{GDBN} commands accept an expression and
7204 compute its value. Any kind of constant, variable or operator defined
7205 by the programming language you are using is valid in an expression in
7206 @value{GDBN}. This includes conditional expressions, function calls,
7207 casts, and string constants. It also includes preprocessor macros, if
7208 you compiled your program to include this information; see
7211 @cindex arrays in expressions
7212 @value{GDBN} supports array constants in expressions input by
7213 the user. The syntax is @{@var{element}, @var{element}@dots{}@}. For example,
7214 you can use the command @code{print @{1, 2, 3@}} to create an array
7215 of three integers. If you pass an array to a function or assign it
7216 to a program variable, @value{GDBN} copies the array to memory that
7217 is @code{malloc}ed in the target program.
7219 Because C is so widespread, most of the expressions shown in examples in
7220 this manual are in C. @xref{Languages, , Using @value{GDBN} with Different
7221 Languages}, for information on how to use expressions in other
7224 In this section, we discuss operators that you can use in @value{GDBN}
7225 expressions regardless of your programming language.
7227 @cindex casts, in expressions
7228 Casts are supported in all languages, not just in C, because it is so
7229 useful to cast a number into a pointer in order to examine a structure
7230 at that address in memory.
7231 @c FIXME: casts supported---Mod2 true?
7233 @value{GDBN} supports these operators, in addition to those common
7234 to programming languages:
7238 @samp{@@} is a binary operator for treating parts of memory as arrays.
7239 @xref{Arrays, ,Artificial Arrays}, for more information.
7242 @samp{::} allows you to specify a variable in terms of the file or
7243 function where it is defined. @xref{Variables, ,Program Variables}.
7245 @cindex @{@var{type}@}
7246 @cindex type casting memory
7247 @cindex memory, viewing as typed object
7248 @cindex casts, to view memory
7249 @item @{@var{type}@} @var{addr}
7250 Refers to an object of type @var{type} stored at address @var{addr} in
7251 memory. @var{addr} may be any expression whose value is an integer or
7252 pointer (but parentheses are required around binary operators, just as in
7253 a cast). This construct is allowed regardless of what kind of data is
7254 normally supposed to reside at @var{addr}.
7257 @node Ambiguous Expressions
7258 @section Ambiguous Expressions
7259 @cindex ambiguous expressions
7261 Expressions can sometimes contain some ambiguous elements. For instance,
7262 some programming languages (notably Ada, C@t{++} and Objective-C) permit
7263 a single function name to be defined several times, for application in
7264 different contexts. This is called @dfn{overloading}. Another example
7265 involving Ada is generics. A @dfn{generic package} is similar to C@t{++}
7266 templates and is typically instantiated several times, resulting in
7267 the same function name being defined in different contexts.
7269 In some cases and depending on the language, it is possible to adjust
7270 the expression to remove the ambiguity. For instance in C@t{++}, you
7271 can specify the signature of the function you want to break on, as in
7272 @kbd{break @var{function}(@var{types})}. In Ada, using the fully
7273 qualified name of your function often makes the expression unambiguous
7276 When an ambiguity that needs to be resolved is detected, the debugger
7277 has the capability to display a menu of numbered choices for each
7278 possibility, and then waits for the selection with the prompt @samp{>}.
7279 The first option is always @samp{[0] cancel}, and typing @kbd{0 @key{RET}}
7280 aborts the current command. If the command in which the expression was
7281 used allows more than one choice to be selected, the next option in the
7282 menu is @samp{[1] all}, and typing @kbd{1 @key{RET}} selects all possible
7285 For example, the following session excerpt shows an attempt to set a
7286 breakpoint at the overloaded symbol @code{String::after}.
7287 We choose three particular definitions of that function name:
7289 @c FIXME! This is likely to change to show arg type lists, at least
7292 (@value{GDBP}) b String::after
7295 [2] file:String.cc; line number:867
7296 [3] file:String.cc; line number:860
7297 [4] file:String.cc; line number:875
7298 [5] file:String.cc; line number:853
7299 [6] file:String.cc; line number:846
7300 [7] file:String.cc; line number:735
7302 Breakpoint 1 at 0xb26c: file String.cc, line 867.
7303 Breakpoint 2 at 0xb344: file String.cc, line 875.
7304 Breakpoint 3 at 0xafcc: file String.cc, line 846.
7305 Multiple breakpoints were set.
7306 Use the "delete" command to delete unwanted
7313 @kindex set multiple-symbols
7314 @item set multiple-symbols @var{mode}
7315 @cindex multiple-symbols menu
7317 This option allows you to adjust the debugger behavior when an expression
7320 By default, @var{mode} is set to @code{all}. If the command with which
7321 the expression is used allows more than one choice, then @value{GDBN}
7322 automatically selects all possible choices. For instance, inserting
7323 a breakpoint on a function using an ambiguous name results in a breakpoint
7324 inserted on each possible match. However, if a unique choice must be made,
7325 then @value{GDBN} uses the menu to help you disambiguate the expression.
7326 For instance, printing the address of an overloaded function will result
7327 in the use of the menu.
7329 When @var{mode} is set to @code{ask}, the debugger always uses the menu
7330 when an ambiguity is detected.
7332 Finally, when @var{mode} is set to @code{cancel}, the debugger reports
7333 an error due to the ambiguity and the command is aborted.
7335 @kindex show multiple-symbols
7336 @item show multiple-symbols
7337 Show the current value of the @code{multiple-symbols} setting.
7341 @section Program Variables
7343 The most common kind of expression to use is the name of a variable
7346 Variables in expressions are understood in the selected stack frame
7347 (@pxref{Selection, ,Selecting a Frame}); they must be either:
7351 global (or file-static)
7358 visible according to the scope rules of the
7359 programming language from the point of execution in that frame
7362 @noindent This means that in the function
7377 you can examine and use the variable @code{a} whenever your program is
7378 executing within the function @code{foo}, but you can only use or
7379 examine the variable @code{b} while your program is executing inside
7380 the block where @code{b} is declared.
7382 @cindex variable name conflict
7383 There is an exception: you can refer to a variable or function whose
7384 scope is a single source file even if the current execution point is not
7385 in this file. But it is possible to have more than one such variable or
7386 function with the same name (in different source files). If that
7387 happens, referring to that name has unpredictable effects. If you wish,
7388 you can specify a static variable in a particular function or file by
7389 using the colon-colon (@code{::}) notation:
7391 @cindex colon-colon, context for variables/functions
7393 @c info cannot cope with a :: index entry, but why deprive hard copy readers?
7394 @cindex @code{::}, context for variables/functions
7397 @var{file}::@var{variable}
7398 @var{function}::@var{variable}
7402 Here @var{file} or @var{function} is the name of the context for the
7403 static @var{variable}. In the case of file names, you can use quotes to
7404 make sure @value{GDBN} parses the file name as a single word---for example,
7405 to print a global value of @code{x} defined in @file{f2.c}:
7408 (@value{GDBP}) p 'f2.c'::x
7411 The @code{::} notation is normally used for referring to
7412 static variables, since you typically disambiguate uses of local variables
7413 in functions by selecting the appropriate frame and using the
7414 simple name of the variable. However, you may also use this notation
7415 to refer to local variables in frames enclosing the selected frame:
7424 process (a); /* Stop here */
7435 For example, if there is a breakpoint at the commented line,
7436 here is what you might see
7437 when the program stops after executing the call @code{bar(0)}:
7442 (@value{GDBP}) p bar::a
7445 #2 0x080483d0 in foo (a=5) at foobar.c:12
7448 (@value{GDBP}) p bar::a
7452 @cindex C@t{++} scope resolution
7453 These uses of @samp{::} are very rarely in conflict with the very similar
7454 use of the same notation in C@t{++}. @value{GDBN} also supports use of the C@t{++}
7455 scope resolution operator in @value{GDBN} expressions.
7456 @c FIXME: Um, so what happens in one of those rare cases where it's in
7459 @cindex wrong values
7460 @cindex variable values, wrong
7461 @cindex function entry/exit, wrong values of variables
7462 @cindex optimized code, wrong values of variables
7464 @emph{Warning:} Occasionally, a local variable may appear to have the
7465 wrong value at certain points in a function---just after entry to a new
7466 scope, and just before exit.
7468 You may see this problem when you are stepping by machine instructions.
7469 This is because, on most machines, it takes more than one instruction to
7470 set up a stack frame (including local variable definitions); if you are
7471 stepping by machine instructions, variables may appear to have the wrong
7472 values until the stack frame is completely built. On exit, it usually
7473 also takes more than one machine instruction to destroy a stack frame;
7474 after you begin stepping through that group of instructions, local
7475 variable definitions may be gone.
7477 This may also happen when the compiler does significant optimizations.
7478 To be sure of always seeing accurate values, turn off all optimization
7481 @cindex ``No symbol "foo" in current context''
7482 Another possible effect of compiler optimizations is to optimize
7483 unused variables out of existence, or assign variables to registers (as
7484 opposed to memory addresses). Depending on the support for such cases
7485 offered by the debug info format used by the compiler, @value{GDBN}
7486 might not be able to display values for such local variables. If that
7487 happens, @value{GDBN} will print a message like this:
7490 No symbol "foo" in current context.
7493 To solve such problems, either recompile without optimizations, or use a
7494 different debug info format, if the compiler supports several such
7495 formats. @xref{Compilation}, for more information on choosing compiler
7496 options. @xref{C, ,C and C@t{++}}, for more information about debug
7497 info formats that are best suited to C@t{++} programs.
7499 If you ask to print an object whose contents are unknown to
7500 @value{GDBN}, e.g., because its data type is not completely specified
7501 by the debug information, @value{GDBN} will say @samp{<incomplete
7502 type>}. @xref{Symbols, incomplete type}, for more about this.
7504 If you append @kbd{@@entry} string to a function parameter name you get its
7505 value at the time the function got called. If the value is not available an
7506 error message is printed. Entry values are available only with some compilers.
7507 Entry values are normally also printed at the function parameter list according
7508 to @ref{set print entry-values}.
7511 Breakpoint 1, d (i=30) at gdb.base/entry-value.c:29
7517 (gdb) print i@@entry
7521 Strings are identified as arrays of @code{char} values without specified
7522 signedness. Arrays of either @code{signed char} or @code{unsigned char} get
7523 printed as arrays of 1 byte sized integers. @code{-fsigned-char} or
7524 @code{-funsigned-char} @value{NGCC} options have no effect as @value{GDBN}
7525 defines literal string type @code{"char"} as @code{char} without a sign.
7530 signed char var1[] = "A";
7533 You get during debugging
7538 $2 = @{65 'A', 0 '\0'@}
7542 @section Artificial Arrays
7544 @cindex artificial array
7546 @kindex @@@r{, referencing memory as an array}
7547 It is often useful to print out several successive objects of the
7548 same type in memory; a section of an array, or an array of
7549 dynamically determined size for which only a pointer exists in the
7552 You can do this by referring to a contiguous span of memory as an
7553 @dfn{artificial array}, using the binary operator @samp{@@}. The left
7554 operand of @samp{@@} should be the first element of the desired array
7555 and be an individual object. The right operand should be the desired length
7556 of the array. The result is an array value whose elements are all of
7557 the type of the left argument. The first element is actually the left
7558 argument; the second element comes from bytes of memory immediately
7559 following those that hold the first element, and so on. Here is an
7560 example. If a program says
7563 int *array = (int *) malloc (len * sizeof (int));
7567 you can print the contents of @code{array} with
7573 The left operand of @samp{@@} must reside in memory. Array values made
7574 with @samp{@@} in this way behave just like other arrays in terms of
7575 subscripting, and are coerced to pointers when used in expressions.
7576 Artificial arrays most often appear in expressions via the value history
7577 (@pxref{Value History, ,Value History}), after printing one out.
7579 Another way to create an artificial array is to use a cast.
7580 This re-interprets a value as if it were an array.
7581 The value need not be in memory:
7583 (@value{GDBP}) p/x (short[2])0x12345678
7584 $1 = @{0x1234, 0x5678@}
7587 As a convenience, if you leave the array length out (as in
7588 @samp{(@var{type}[])@var{value}}) @value{GDBN} calculates the size to fill
7589 the value (as @samp{sizeof(@var{value})/sizeof(@var{type})}:
7591 (@value{GDBP}) p/x (short[])0x12345678
7592 $2 = @{0x1234, 0x5678@}
7595 Sometimes the artificial array mechanism is not quite enough; in
7596 moderately complex data structures, the elements of interest may not
7597 actually be adjacent---for example, if you are interested in the values
7598 of pointers in an array. One useful work-around in this situation is
7599 to use a convenience variable (@pxref{Convenience Vars, ,Convenience
7600 Variables}) as a counter in an expression that prints the first
7601 interesting value, and then repeat that expression via @key{RET}. For
7602 instance, suppose you have an array @code{dtab} of pointers to
7603 structures, and you are interested in the values of a field @code{fv}
7604 in each structure. Here is an example of what you might type:
7614 @node Output Formats
7615 @section Output Formats
7617 @cindex formatted output
7618 @cindex output formats
7619 By default, @value{GDBN} prints a value according to its data type. Sometimes
7620 this is not what you want. For example, you might want to print a number
7621 in hex, or a pointer in decimal. Or you might want to view data in memory
7622 at a certain address as a character string or as an instruction. To do
7623 these things, specify an @dfn{output format} when you print a value.
7625 The simplest use of output formats is to say how to print a value
7626 already computed. This is done by starting the arguments of the
7627 @code{print} command with a slash and a format letter. The format
7628 letters supported are:
7632 Regard the bits of the value as an integer, and print the integer in
7636 Print as integer in signed decimal.
7639 Print as integer in unsigned decimal.
7642 Print as integer in octal.
7645 Print as integer in binary. The letter @samp{t} stands for ``two''.
7646 @footnote{@samp{b} cannot be used because these format letters are also
7647 used with the @code{x} command, where @samp{b} stands for ``byte'';
7648 see @ref{Memory,,Examining Memory}.}
7651 @cindex unknown address, locating
7652 @cindex locate address
7653 Print as an address, both absolute in hexadecimal and as an offset from
7654 the nearest preceding symbol. You can use this format used to discover
7655 where (in what function) an unknown address is located:
7658 (@value{GDBP}) p/a 0x54320
7659 $3 = 0x54320 <_initialize_vx+396>
7663 The command @code{info symbol 0x54320} yields similar results.
7664 @xref{Symbols, info symbol}.
7667 Regard as an integer and print it as a character constant. This
7668 prints both the numerical value and its character representation. The
7669 character representation is replaced with the octal escape @samp{\nnn}
7670 for characters outside the 7-bit @sc{ascii} range.
7672 Without this format, @value{GDBN} displays @code{char},
7673 @w{@code{unsigned char}}, and @w{@code{signed char}} data as character
7674 constants. Single-byte members of vectors are displayed as integer
7678 Regard the bits of the value as a floating point number and print
7679 using typical floating point syntax.
7682 @cindex printing strings
7683 @cindex printing byte arrays
7684 Regard as a string, if possible. With this format, pointers to single-byte
7685 data are displayed as null-terminated strings and arrays of single-byte data
7686 are displayed as fixed-length strings. Other values are displayed in their
7689 Without this format, @value{GDBN} displays pointers to and arrays of
7690 @code{char}, @w{@code{unsigned char}}, and @w{@code{signed char}} as
7691 strings. Single-byte members of a vector are displayed as an integer
7695 @cindex raw printing
7696 Print using the @samp{raw} formatting. By default, @value{GDBN} will
7697 use a Python-based pretty-printer, if one is available (@pxref{Pretty
7698 Printing}). This typically results in a higher-level display of the
7699 value's contents. The @samp{r} format bypasses any Python
7700 pretty-printer which might exist.
7703 For example, to print the program counter in hex (@pxref{Registers}), type
7710 Note that no space is required before the slash; this is because command
7711 names in @value{GDBN} cannot contain a slash.
7713 To reprint the last value in the value history with a different format,
7714 you can use the @code{print} command with just a format and no
7715 expression. For example, @samp{p/x} reprints the last value in hex.
7718 @section Examining Memory
7720 You can use the command @code{x} (for ``examine'') to examine memory in
7721 any of several formats, independently of your program's data types.
7723 @cindex examining memory
7725 @kindex x @r{(examine memory)}
7726 @item x/@var{nfu} @var{addr}
7729 Use the @code{x} command to examine memory.
7732 @var{n}, @var{f}, and @var{u} are all optional parameters that specify how
7733 much memory to display and how to format it; @var{addr} is an
7734 expression giving the address where you want to start displaying memory.
7735 If you use defaults for @var{nfu}, you need not type the slash @samp{/}.
7736 Several commands set convenient defaults for @var{addr}.
7739 @item @var{n}, the repeat count
7740 The repeat count is a decimal integer; the default is 1. It specifies
7741 how much memory (counting by units @var{u}) to display.
7742 @c This really is **decimal**; unaffected by 'set radix' as of GDB
7745 @item @var{f}, the display format
7746 The display format is one of the formats used by @code{print}
7747 (@samp{x}, @samp{d}, @samp{u}, @samp{o}, @samp{t}, @samp{a}, @samp{c},
7748 @samp{f}, @samp{s}), and in addition @samp{i} (for machine instructions).
7749 The default is @samp{x} (hexadecimal) initially. The default changes
7750 each time you use either @code{x} or @code{print}.
7752 @item @var{u}, the unit size
7753 The unit size is any of
7759 Halfwords (two bytes).
7761 Words (four bytes). This is the initial default.
7763 Giant words (eight bytes).
7766 Each time you specify a unit size with @code{x}, that size becomes the
7767 default unit the next time you use @code{x}. For the @samp{i} format,
7768 the unit size is ignored and is normally not written. For the @samp{s} format,
7769 the unit size defaults to @samp{b}, unless it is explicitly given.
7770 Use @kbd{x /hs} to display 16-bit char strings and @kbd{x /ws} to display
7771 32-bit strings. The next use of @kbd{x /s} will again display 8-bit strings.
7772 Note that the results depend on the programming language of the
7773 current compilation unit. If the language is C, the @samp{s}
7774 modifier will use the UTF-16 encoding while @samp{w} will use
7775 UTF-32. The encoding is set by the programming language and cannot
7778 @item @var{addr}, starting display address
7779 @var{addr} is the address where you want @value{GDBN} to begin displaying
7780 memory. The expression need not have a pointer value (though it may);
7781 it is always interpreted as an integer address of a byte of memory.
7782 @xref{Expressions, ,Expressions}, for more information on expressions. The default for
7783 @var{addr} is usually just after the last address examined---but several
7784 other commands also set the default address: @code{info breakpoints} (to
7785 the address of the last breakpoint listed), @code{info line} (to the
7786 starting address of a line), and @code{print} (if you use it to display
7787 a value from memory).
7790 For example, @samp{x/3uh 0x54320} is a request to display three halfwords
7791 (@code{h}) of memory, formatted as unsigned decimal integers (@samp{u}),
7792 starting at address @code{0x54320}. @samp{x/4xw $sp} prints the four
7793 words (@samp{w}) of memory above the stack pointer (here, @samp{$sp};
7794 @pxref{Registers, ,Registers}) in hexadecimal (@samp{x}).
7796 Since the letters indicating unit sizes are all distinct from the
7797 letters specifying output formats, you do not have to remember whether
7798 unit size or format comes first; either order works. The output
7799 specifications @samp{4xw} and @samp{4wx} mean exactly the same thing.
7800 (However, the count @var{n} must come first; @samp{wx4} does not work.)
7802 Even though the unit size @var{u} is ignored for the formats @samp{s}
7803 and @samp{i}, you might still want to use a count @var{n}; for example,
7804 @samp{3i} specifies that you want to see three machine instructions,
7805 including any operands. For convenience, especially when used with
7806 the @code{display} command, the @samp{i} format also prints branch delay
7807 slot instructions, if any, beyond the count specified, which immediately
7808 follow the last instruction that is within the count. The command
7809 @code{disassemble} gives an alternative way of inspecting machine
7810 instructions; see @ref{Machine Code,,Source and Machine Code}.
7812 All the defaults for the arguments to @code{x} are designed to make it
7813 easy to continue scanning memory with minimal specifications each time
7814 you use @code{x}. For example, after you have inspected three machine
7815 instructions with @samp{x/3i @var{addr}}, you can inspect the next seven
7816 with just @samp{x/7}. If you use @key{RET} to repeat the @code{x} command,
7817 the repeat count @var{n} is used again; the other arguments default as
7818 for successive uses of @code{x}.
7820 When examining machine instructions, the instruction at current program
7821 counter is shown with a @code{=>} marker. For example:
7824 (@value{GDBP}) x/5i $pc-6
7825 0x804837f <main+11>: mov %esp,%ebp
7826 0x8048381 <main+13>: push %ecx
7827 0x8048382 <main+14>: sub $0x4,%esp
7828 => 0x8048385 <main+17>: movl $0x8048460,(%esp)
7829 0x804838c <main+24>: call 0x80482d4 <puts@@plt>
7832 @cindex @code{$_}, @code{$__}, and value history
7833 The addresses and contents printed by the @code{x} command are not saved
7834 in the value history because there is often too much of them and they
7835 would get in the way. Instead, @value{GDBN} makes these values available for
7836 subsequent use in expressions as values of the convenience variables
7837 @code{$_} and @code{$__}. After an @code{x} command, the last address
7838 examined is available for use in expressions in the convenience variable
7839 @code{$_}. The contents of that address, as examined, are available in
7840 the convenience variable @code{$__}.
7842 If the @code{x} command has a repeat count, the address and contents saved
7843 are from the last memory unit printed; this is not the same as the last
7844 address printed if several units were printed on the last line of output.
7846 @cindex remote memory comparison
7847 @cindex verify remote memory image
7848 When you are debugging a program running on a remote target machine
7849 (@pxref{Remote Debugging}), you may wish to verify the program's image in the
7850 remote machine's memory against the executable file you downloaded to
7851 the target. The @code{compare-sections} command is provided for such
7855 @kindex compare-sections
7856 @item compare-sections @r{[}@var{section-name}@r{]}
7857 Compare the data of a loadable section @var{section-name} in the
7858 executable file of the program being debugged with the same section in
7859 the remote machine's memory, and report any mismatches. With no
7860 arguments, compares all loadable sections. This command's
7861 availability depends on the target's support for the @code{"qCRC"}
7866 @section Automatic Display
7867 @cindex automatic display
7868 @cindex display of expressions
7870 If you find that you want to print the value of an expression frequently
7871 (to see how it changes), you might want to add it to the @dfn{automatic
7872 display list} so that @value{GDBN} prints its value each time your program stops.
7873 Each expression added to the list is given a number to identify it;
7874 to remove an expression from the list, you specify that number.
7875 The automatic display looks like this:
7879 3: bar[5] = (struct hack *) 0x3804
7883 This display shows item numbers, expressions and their current values. As with
7884 displays you request manually using @code{x} or @code{print}, you can
7885 specify the output format you prefer; in fact, @code{display} decides
7886 whether to use @code{print} or @code{x} depending your format
7887 specification---it uses @code{x} if you specify either the @samp{i}
7888 or @samp{s} format, or a unit size; otherwise it uses @code{print}.
7892 @item display @var{expr}
7893 Add the expression @var{expr} to the list of expressions to display
7894 each time your program stops. @xref{Expressions, ,Expressions}.
7896 @code{display} does not repeat if you press @key{RET} again after using it.
7898 @item display/@var{fmt} @var{expr}
7899 For @var{fmt} specifying only a display format and not a size or
7900 count, add the expression @var{expr} to the auto-display list but
7901 arrange to display it each time in the specified format @var{fmt}.
7902 @xref{Output Formats,,Output Formats}.
7904 @item display/@var{fmt} @var{addr}
7905 For @var{fmt} @samp{i} or @samp{s}, or including a unit-size or a
7906 number of units, add the expression @var{addr} as a memory address to
7907 be examined each time your program stops. Examining means in effect
7908 doing @samp{x/@var{fmt} @var{addr}}. @xref{Memory, ,Examining Memory}.
7911 For example, @samp{display/i $pc} can be helpful, to see the machine
7912 instruction about to be executed each time execution stops (@samp{$pc}
7913 is a common name for the program counter; @pxref{Registers, ,Registers}).
7916 @kindex delete display
7918 @item undisplay @var{dnums}@dots{}
7919 @itemx delete display @var{dnums}@dots{}
7920 Remove items from the list of expressions to display. Specify the
7921 numbers of the displays that you want affected with the command
7922 argument @var{dnums}. It can be a single display number, one of the
7923 numbers shown in the first field of the @samp{info display} display;
7924 or it could be a range of display numbers, as in @code{2-4}.
7926 @code{undisplay} does not repeat if you press @key{RET} after using it.
7927 (Otherwise you would just get the error @samp{No display number @dots{}}.)
7929 @kindex disable display
7930 @item disable display @var{dnums}@dots{}
7931 Disable the display of item numbers @var{dnums}. A disabled display
7932 item is not printed automatically, but is not forgotten. It may be
7933 enabled again later. Specify the numbers of the displays that you
7934 want affected with the command argument @var{dnums}. It can be a
7935 single display number, one of the numbers shown in the first field of
7936 the @samp{info display} display; or it could be a range of display
7937 numbers, as in @code{2-4}.
7939 @kindex enable display
7940 @item enable display @var{dnums}@dots{}
7941 Enable display of item numbers @var{dnums}. It becomes effective once
7942 again in auto display of its expression, until you specify otherwise.
7943 Specify the numbers of the displays that you want affected with the
7944 command argument @var{dnums}. It can be a single display number, one
7945 of the numbers shown in the first field of the @samp{info display}
7946 display; or it could be a range of display numbers, as in @code{2-4}.
7949 Display the current values of the expressions on the list, just as is
7950 done when your program stops.
7952 @kindex info display
7954 Print the list of expressions previously set up to display
7955 automatically, each one with its item number, but without showing the
7956 values. This includes disabled expressions, which are marked as such.
7957 It also includes expressions which would not be displayed right now
7958 because they refer to automatic variables not currently available.
7961 @cindex display disabled out of scope
7962 If a display expression refers to local variables, then it does not make
7963 sense outside the lexical context for which it was set up. Such an
7964 expression is disabled when execution enters a context where one of its
7965 variables is not defined. For example, if you give the command
7966 @code{display last_char} while inside a function with an argument
7967 @code{last_char}, @value{GDBN} displays this argument while your program
7968 continues to stop inside that function. When it stops elsewhere---where
7969 there is no variable @code{last_char}---the display is disabled
7970 automatically. The next time your program stops where @code{last_char}
7971 is meaningful, you can enable the display expression once again.
7973 @node Print Settings
7974 @section Print Settings
7976 @cindex format options
7977 @cindex print settings
7978 @value{GDBN} provides the following ways to control how arrays, structures,
7979 and symbols are printed.
7982 These settings are useful for debugging programs in any language:
7986 @item set print address
7987 @itemx set print address on
7988 @cindex print/don't print memory addresses
7989 @value{GDBN} prints memory addresses showing the location of stack
7990 traces, structure values, pointer values, breakpoints, and so forth,
7991 even when it also displays the contents of those addresses. The default
7992 is @code{on}. For example, this is what a stack frame display looks like with
7993 @code{set print address on}:
7998 #0 set_quotes (lq=0x34c78 "<<", rq=0x34c88 ">>")
8000 530 if (lquote != def_lquote)
8004 @item set print address off
8005 Do not print addresses when displaying their contents. For example,
8006 this is the same stack frame displayed with @code{set print address off}:
8010 (@value{GDBP}) set print addr off
8012 #0 set_quotes (lq="<<", rq=">>") at input.c:530
8013 530 if (lquote != def_lquote)
8017 You can use @samp{set print address off} to eliminate all machine
8018 dependent displays from the @value{GDBN} interface. For example, with
8019 @code{print address off}, you should get the same text for backtraces on
8020 all machines---whether or not they involve pointer arguments.
8023 @item show print address
8024 Show whether or not addresses are to be printed.
8027 When @value{GDBN} prints a symbolic address, it normally prints the
8028 closest earlier symbol plus an offset. If that symbol does not uniquely
8029 identify the address (for example, it is a name whose scope is a single
8030 source file), you may need to clarify. One way to do this is with
8031 @code{info line}, for example @samp{info line *0x4537}. Alternately,
8032 you can set @value{GDBN} to print the source file and line number when
8033 it prints a symbolic address:
8036 @item set print symbol-filename on
8037 @cindex source file and line of a symbol
8038 @cindex symbol, source file and line
8039 Tell @value{GDBN} to print the source file name and line number of a
8040 symbol in the symbolic form of an address.
8042 @item set print symbol-filename off
8043 Do not print source file name and line number of a symbol. This is the
8046 @item show print symbol-filename
8047 Show whether or not @value{GDBN} will print the source file name and
8048 line number of a symbol in the symbolic form of an address.
8051 Another situation where it is helpful to show symbol filenames and line
8052 numbers is when disassembling code; @value{GDBN} shows you the line
8053 number and source file that corresponds to each instruction.
8055 Also, you may wish to see the symbolic form only if the address being
8056 printed is reasonably close to the closest earlier symbol:
8059 @item set print max-symbolic-offset @var{max-offset}
8060 @cindex maximum value for offset of closest symbol
8061 Tell @value{GDBN} to only display the symbolic form of an address if the
8062 offset between the closest earlier symbol and the address is less than
8063 @var{max-offset}. The default is 0, which tells @value{GDBN}
8064 to always print the symbolic form of an address if any symbol precedes it.
8066 @item show print max-symbolic-offset
8067 Ask how large the maximum offset is that @value{GDBN} prints in a
8071 @cindex wild pointer, interpreting
8072 @cindex pointer, finding referent
8073 If you have a pointer and you are not sure where it points, try
8074 @samp{set print symbol-filename on}. Then you can determine the name
8075 and source file location of the variable where it points, using
8076 @samp{p/a @var{pointer}}. This interprets the address in symbolic form.
8077 For example, here @value{GDBN} shows that a variable @code{ptt} points
8078 at another variable @code{t}, defined in @file{hi2.c}:
8081 (@value{GDBP}) set print symbol-filename on
8082 (@value{GDBP}) p/a ptt
8083 $4 = 0xe008 <t in hi2.c>
8087 @emph{Warning:} For pointers that point to a local variable, @samp{p/a}
8088 does not show the symbol name and filename of the referent, even with
8089 the appropriate @code{set print} options turned on.
8092 Other settings control how different kinds of objects are printed:
8095 @item set print array
8096 @itemx set print array on
8097 @cindex pretty print arrays
8098 Pretty print arrays. This format is more convenient to read,
8099 but uses more space. The default is off.
8101 @item set print array off
8102 Return to compressed format for arrays.
8104 @item show print array
8105 Show whether compressed or pretty format is selected for displaying
8108 @cindex print array indexes
8109 @item set print array-indexes
8110 @itemx set print array-indexes on
8111 Print the index of each element when displaying arrays. May be more
8112 convenient to locate a given element in the array or quickly find the
8113 index of a given element in that printed array. The default is off.
8115 @item set print array-indexes off
8116 Stop printing element indexes when displaying arrays.
8118 @item show print array-indexes
8119 Show whether the index of each element is printed when displaying
8122 @item set print elements @var{number-of-elements}
8123 @cindex number of array elements to print
8124 @cindex limit on number of printed array elements
8125 Set a limit on how many elements of an array @value{GDBN} will print.
8126 If @value{GDBN} is printing a large array, it stops printing after it has
8127 printed the number of elements set by the @code{set print elements} command.
8128 This limit also applies to the display of strings.
8129 When @value{GDBN} starts, this limit is set to 200.
8130 Setting @var{number-of-elements} to zero means that the printing is unlimited.
8132 @item show print elements
8133 Display the number of elements of a large array that @value{GDBN} will print.
8134 If the number is 0, then the printing is unlimited.
8136 @item set print frame-arguments @var{value}
8137 @kindex set print frame-arguments
8138 @cindex printing frame argument values
8139 @cindex print all frame argument values
8140 @cindex print frame argument values for scalars only
8141 @cindex do not print frame argument values
8142 This command allows to control how the values of arguments are printed
8143 when the debugger prints a frame (@pxref{Frames}). The possible
8148 The values of all arguments are printed.
8151 Print the value of an argument only if it is a scalar. The value of more
8152 complex arguments such as arrays, structures, unions, etc, is replaced
8153 by @code{@dots{}}. This is the default. Here is an example where
8154 only scalar arguments are shown:
8157 #1 0x08048361 in call_me (i=3, s=@dots{}, ss=0xbf8d508c, u=@dots{}, e=green)
8162 None of the argument values are printed. Instead, the value of each argument
8163 is replaced by @code{@dots{}}. In this case, the example above now becomes:
8166 #1 0x08048361 in call_me (i=@dots{}, s=@dots{}, ss=@dots{}, u=@dots{}, e=@dots{})
8171 By default, only scalar arguments are printed. This command can be used
8172 to configure the debugger to print the value of all arguments, regardless
8173 of their type. However, it is often advantageous to not print the value
8174 of more complex parameters. For instance, it reduces the amount of
8175 information printed in each frame, making the backtrace more readable.
8176 Also, it improves performance when displaying Ada frames, because
8177 the computation of large arguments can sometimes be CPU-intensive,
8178 especially in large applications. Setting @code{print frame-arguments}
8179 to @code{scalars} (the default) or @code{none} avoids this computation,
8180 thus speeding up the display of each Ada frame.
8182 @item show print frame-arguments
8183 Show how the value of arguments should be displayed when printing a frame.
8185 @anchor{set print entry-values}
8186 @item set print entry-values @var{value}
8187 @kindex set print entry-values
8188 Set printing of frame argument values at function entry. In some cases
8189 @value{GDBN} can determine the value of function argument which was passed by
8190 the function caller, even if the value was modified inside the called function
8191 and therefore is different. With optimized code, the current value could be
8192 unavailable, but the entry value may still be known.
8194 The default value is @code{default} (see below for its description). Older
8195 @value{GDBN} behaved as with the setting @code{no}. Compilers not supporting
8196 this feature will behave in the @code{default} setting the same way as with the
8199 This functionality is currently supported only by DWARF 2 debugging format and
8200 the compiler has to produce @samp{DW_TAG_GNU_call_site} tags. With
8201 @value{NGCC}, you need to specify @option{-O -g} during compilation, to get
8204 The @var{value} parameter can be one of the following:
8208 Print only actual parameter values, never print values from function entry
8212 #0 different (val=6)
8213 #0 lost (val=<optimized out>)
8215 #0 invalid (val=<optimized out>)
8219 Print only parameter values from function entry point. The actual parameter
8220 values are never printed.
8222 #0 equal (val@@entry=5)
8223 #0 different (val@@entry=5)
8224 #0 lost (val@@entry=5)
8225 #0 born (val@@entry=<optimized out>)
8226 #0 invalid (val@@entry=<optimized out>)
8230 Print only parameter values from function entry point. If value from function
8231 entry point is not known while the actual value is known, print the actual
8232 value for such parameter.
8234 #0 equal (val@@entry=5)
8235 #0 different (val@@entry=5)
8236 #0 lost (val@@entry=5)
8238 #0 invalid (val@@entry=<optimized out>)
8242 Print actual parameter values. If actual parameter value is not known while
8243 value from function entry point is known, print the entry point value for such
8247 #0 different (val=6)
8248 #0 lost (val@@entry=5)
8250 #0 invalid (val=<optimized out>)
8254 Always print both the actual parameter value and its value from function entry
8255 point, even if values of one or both are not available due to compiler
8258 #0 equal (val=5, val@@entry=5)
8259 #0 different (val=6, val@@entry=5)
8260 #0 lost (val=<optimized out>, val@@entry=5)
8261 #0 born (val=10, val@@entry=<optimized out>)
8262 #0 invalid (val=<optimized out>, val@@entry=<optimized out>)
8266 Print the actual parameter value if it is known and also its value from
8267 function entry point if it is known. If neither is known, print for the actual
8268 value @code{<optimized out>}. If not in MI mode (@pxref{GDB/MI}) and if both
8269 values are known and identical, print the shortened
8270 @code{param=param@@entry=VALUE} notation.
8272 #0 equal (val=val@@entry=5)
8273 #0 different (val=6, val@@entry=5)
8274 #0 lost (val@@entry=5)
8276 #0 invalid (val=<optimized out>)
8280 Always print the actual parameter value. Print also its value from function
8281 entry point, but only if it is known. If not in MI mode (@pxref{GDB/MI}) and
8282 if both values are known and identical, print the shortened
8283 @code{param=param@@entry=VALUE} notation.
8285 #0 equal (val=val@@entry=5)
8286 #0 different (val=6, val@@entry=5)
8287 #0 lost (val=<optimized out>, val@@entry=5)
8289 #0 invalid (val=<optimized out>)
8293 For analysis messages on possible failures of frame argument values at function
8294 entry resolution see @ref{set debug entry-values}.
8296 @item show print entry-values
8297 Show the method being used for printing of frame argument values at function
8300 @item set print repeats
8301 @cindex repeated array elements
8302 Set the threshold for suppressing display of repeated array
8303 elements. When the number of consecutive identical elements of an
8304 array exceeds the threshold, @value{GDBN} prints the string
8305 @code{"<repeats @var{n} times>"}, where @var{n} is the number of
8306 identical repetitions, instead of displaying the identical elements
8307 themselves. Setting the threshold to zero will cause all elements to
8308 be individually printed. The default threshold is 10.
8310 @item show print repeats
8311 Display the current threshold for printing repeated identical
8314 @item set print null-stop
8315 @cindex @sc{null} elements in arrays
8316 Cause @value{GDBN} to stop printing the characters of an array when the first
8317 @sc{null} is encountered. This is useful when large arrays actually
8318 contain only short strings.
8321 @item show print null-stop
8322 Show whether @value{GDBN} stops printing an array on the first
8323 @sc{null} character.
8325 @item set print pretty on
8326 @cindex print structures in indented form
8327 @cindex indentation in structure display
8328 Cause @value{GDBN} to print structures in an indented format with one member
8329 per line, like this:
8344 @item set print pretty off
8345 Cause @value{GDBN} to print structures in a compact format, like this:
8349 $1 = @{next = 0x0, flags = @{sweet = 1, sour = 1@}, \
8350 meat = 0x54 "Pork"@}
8355 This is the default format.
8357 @item show print pretty
8358 Show which format @value{GDBN} is using to print structures.
8360 @item set print sevenbit-strings on
8361 @cindex eight-bit characters in strings
8362 @cindex octal escapes in strings
8363 Print using only seven-bit characters; if this option is set,
8364 @value{GDBN} displays any eight-bit characters (in strings or
8365 character values) using the notation @code{\}@var{nnn}. This setting is
8366 best if you are working in English (@sc{ascii}) and you use the
8367 high-order bit of characters as a marker or ``meta'' bit.
8369 @item set print sevenbit-strings off
8370 Print full eight-bit characters. This allows the use of more
8371 international character sets, and is the default.
8373 @item show print sevenbit-strings
8374 Show whether or not @value{GDBN} is printing only seven-bit characters.
8376 @item set print union on
8377 @cindex unions in structures, printing
8378 Tell @value{GDBN} to print unions which are contained in structures
8379 and other unions. This is the default setting.
8381 @item set print union off
8382 Tell @value{GDBN} not to print unions which are contained in
8383 structures and other unions. @value{GDBN} will print @code{"@{...@}"}
8386 @item show print union
8387 Ask @value{GDBN} whether or not it will print unions which are contained in
8388 structures and other unions.
8390 For example, given the declarations
8393 typedef enum @{Tree, Bug@} Species;
8394 typedef enum @{Big_tree, Acorn, Seedling@} Tree_forms;
8395 typedef enum @{Caterpillar, Cocoon, Butterfly@}
8406 struct thing foo = @{Tree, @{Acorn@}@};
8410 with @code{set print union on} in effect @samp{p foo} would print
8413 $1 = @{it = Tree, form = @{tree = Acorn, bug = Cocoon@}@}
8417 and with @code{set print union off} in effect it would print
8420 $1 = @{it = Tree, form = @{...@}@}
8424 @code{set print union} affects programs written in C-like languages
8430 These settings are of interest when debugging C@t{++} programs:
8433 @cindex demangling C@t{++} names
8434 @item set print demangle
8435 @itemx set print demangle on
8436 Print C@t{++} names in their source form rather than in the encoded
8437 (``mangled'') form passed to the assembler and linker for type-safe
8438 linkage. The default is on.
8440 @item show print demangle
8441 Show whether C@t{++} names are printed in mangled or demangled form.
8443 @item set print asm-demangle
8444 @itemx set print asm-demangle on
8445 Print C@t{++} names in their source form rather than their mangled form, even
8446 in assembler code printouts such as instruction disassemblies.
8449 @item show print asm-demangle
8450 Show whether C@t{++} names in assembly listings are printed in mangled
8453 @cindex C@t{++} symbol decoding style
8454 @cindex symbol decoding style, C@t{++}
8455 @kindex set demangle-style
8456 @item set demangle-style @var{style}
8457 Choose among several encoding schemes used by different compilers to
8458 represent C@t{++} names. The choices for @var{style} are currently:
8462 Allow @value{GDBN} to choose a decoding style by inspecting your program.
8465 Decode based on the @sc{gnu} C@t{++} compiler (@code{g++}) encoding algorithm.
8466 This is the default.
8469 Decode based on the HP ANSI C@t{++} (@code{aCC}) encoding algorithm.
8472 Decode based on the Lucid C@t{++} compiler (@code{lcc}) encoding algorithm.
8475 Decode using the algorithm in the @cite{C@t{++} Annotated Reference Manual}.
8476 @strong{Warning:} this setting alone is not sufficient to allow
8477 debugging @code{cfront}-generated executables. @value{GDBN} would
8478 require further enhancement to permit that.
8481 If you omit @var{style}, you will see a list of possible formats.
8483 @item show demangle-style
8484 Display the encoding style currently in use for decoding C@t{++} symbols.
8486 @item set print object
8487 @itemx set print object on
8488 @cindex derived type of an object, printing
8489 @cindex display derived types
8490 When displaying a pointer to an object, identify the @emph{actual}
8491 (derived) type of the object rather than the @emph{declared} type, using
8492 the virtual function table. Note that the virtual function table is
8493 required---this feature can only work for objects that have run-time
8494 type identification; a single virtual method in the object's declared
8497 @item set print object off
8498 Display only the declared type of objects, without reference to the
8499 virtual function table. This is the default setting.
8501 @item show print object
8502 Show whether actual, or declared, object types are displayed.
8504 @item set print static-members
8505 @itemx set print static-members on
8506 @cindex static members of C@t{++} objects
8507 Print static members when displaying a C@t{++} object. The default is on.
8509 @item set print static-members off
8510 Do not print static members when displaying a C@t{++} object.
8512 @item show print static-members
8513 Show whether C@t{++} static members are printed or not.
8515 @item set print pascal_static-members
8516 @itemx set print pascal_static-members on
8517 @cindex static members of Pascal objects
8518 @cindex Pascal objects, static members display
8519 Print static members when displaying a Pascal object. The default is on.
8521 @item set print pascal_static-members off
8522 Do not print static members when displaying a Pascal object.
8524 @item show print pascal_static-members
8525 Show whether Pascal static members are printed or not.
8527 @c These don't work with HP ANSI C++ yet.
8528 @item set print vtbl
8529 @itemx set print vtbl on
8530 @cindex pretty print C@t{++} virtual function tables
8531 @cindex virtual functions (C@t{++}) display
8532 @cindex VTBL display
8533 Pretty print C@t{++} virtual function tables. The default is off.
8534 (The @code{vtbl} commands do not work on programs compiled with the HP
8535 ANSI C@t{++} compiler (@code{aCC}).)
8537 @item set print vtbl off
8538 Do not pretty print C@t{++} virtual function tables.
8540 @item show print vtbl
8541 Show whether C@t{++} virtual function tables are pretty printed, or not.
8544 @node Pretty Printing
8545 @section Pretty Printing
8547 @value{GDBN} provides a mechanism to allow pretty-printing of values using
8548 Python code. It greatly simplifies the display of complex objects. This
8549 mechanism works for both MI and the CLI.
8552 * Pretty-Printer Introduction:: Introduction to pretty-printers
8553 * Pretty-Printer Example:: An example pretty-printer
8554 * Pretty-Printer Commands:: Pretty-printer commands
8557 @node Pretty-Printer Introduction
8558 @subsection Pretty-Printer Introduction
8560 When @value{GDBN} prints a value, it first sees if there is a pretty-printer
8561 registered for the value. If there is then @value{GDBN} invokes the
8562 pretty-printer to print the value. Otherwise the value is printed normally.
8564 Pretty-printers are normally named. This makes them easy to manage.
8565 The @samp{info pretty-printer} command will list all the installed
8566 pretty-printers with their names.
8567 If a pretty-printer can handle multiple data types, then its
8568 @dfn{subprinters} are the printers for the individual data types.
8569 Each such subprinter has its own name.
8570 The format of the name is @var{printer-name};@var{subprinter-name}.
8572 Pretty-printers are installed by @dfn{registering} them with @value{GDBN}.
8573 Typically they are automatically loaded and registered when the corresponding
8574 debug information is loaded, thus making them available without having to
8575 do anything special.
8577 There are three places where a pretty-printer can be registered.
8581 Pretty-printers registered globally are available when debugging
8585 Pretty-printers registered with a program space are available only
8586 when debugging that program.
8587 @xref{Progspaces In Python}, for more details on program spaces in Python.
8590 Pretty-printers registered with an objfile are loaded and unloaded
8591 with the corresponding objfile (e.g., shared library).
8592 @xref{Objfiles In Python}, for more details on objfiles in Python.
8595 @xref{Selecting Pretty-Printers}, for further information on how
8596 pretty-printers are selected,
8598 @xref{Writing a Pretty-Printer}, for implementing pretty printers
8601 @node Pretty-Printer Example
8602 @subsection Pretty-Printer Example
8604 Here is how a C@t{++} @code{std::string} looks without a pretty-printer:
8607 (@value{GDBP}) print s
8609 static npos = 4294967295,
8611 <std::allocator<char>> = @{
8612 <__gnu_cxx::new_allocator<char>> = @{
8613 <No data fields>@}, <No data fields>
8615 members of std::basic_string<char, std::char_traits<char>,
8616 std::allocator<char> >::_Alloc_hider:
8617 _M_p = 0x804a014 "abcd"
8622 With a pretty-printer for @code{std::string} only the contents are printed:
8625 (@value{GDBP}) print s
8629 @node Pretty-Printer Commands
8630 @subsection Pretty-Printer Commands
8631 @cindex pretty-printer commands
8634 @kindex info pretty-printer
8635 @item info pretty-printer [@var{object-regexp} [@var{name-regexp}]]
8636 Print the list of installed pretty-printers.
8637 This includes disabled pretty-printers, which are marked as such.
8639 @var{object-regexp} is a regular expression matching the objects
8640 whose pretty-printers to list.
8641 Objects can be @code{global}, the program space's file
8642 (@pxref{Progspaces In Python}),
8643 and the object files within that program space (@pxref{Objfiles In Python}).
8644 @xref{Selecting Pretty-Printers}, for details on how @value{GDBN}
8645 looks up a printer from these three objects.
8647 @var{name-regexp} is a regular expression matching the name of the printers
8650 @kindex disable pretty-printer
8651 @item disable pretty-printer [@var{object-regexp} [@var{name-regexp}]]
8652 Disable pretty-printers matching @var{object-regexp} and @var{name-regexp}.
8653 A disabled pretty-printer is not forgotten, it may be enabled again later.
8655 @kindex enable pretty-printer
8656 @item enable pretty-printer [@var{object-regexp} [@var{name-regexp}]]
8657 Enable pretty-printers matching @var{object-regexp} and @var{name-regexp}.
8662 Suppose we have three pretty-printers installed: one from library1.so
8663 named @code{foo} that prints objects of type @code{foo}, and
8664 another from library2.so named @code{bar} that prints two types of objects,
8665 @code{bar1} and @code{bar2}.
8668 (gdb) info pretty-printer
8675 (gdb) info pretty-printer library2
8680 (gdb) disable pretty-printer library1
8682 2 of 3 printers enabled
8683 (gdb) info pretty-printer
8690 (gdb) disable pretty-printer library2 bar:bar1
8692 1 of 3 printers enabled
8693 (gdb) info pretty-printer library2
8700 (gdb) disable pretty-printer library2 bar
8702 0 of 3 printers enabled
8703 (gdb) info pretty-printer library2
8712 Note that for @code{bar} the entire printer can be disabled,
8713 as can each individual subprinter.
8716 @section Value History
8718 @cindex value history
8719 @cindex history of values printed by @value{GDBN}
8720 Values printed by the @code{print} command are saved in the @value{GDBN}
8721 @dfn{value history}. This allows you to refer to them in other expressions.
8722 Values are kept until the symbol table is re-read or discarded
8723 (for example with the @code{file} or @code{symbol-file} commands).
8724 When the symbol table changes, the value history is discarded,
8725 since the values may contain pointers back to the types defined in the
8730 @cindex history number
8731 The values printed are given @dfn{history numbers} by which you can
8732 refer to them. These are successive integers starting with one.
8733 @code{print} shows you the history number assigned to a value by
8734 printing @samp{$@var{num} = } before the value; here @var{num} is the
8737 To refer to any previous value, use @samp{$} followed by the value's
8738 history number. The way @code{print} labels its output is designed to
8739 remind you of this. Just @code{$} refers to the most recent value in
8740 the history, and @code{$$} refers to the value before that.
8741 @code{$$@var{n}} refers to the @var{n}th value from the end; @code{$$2}
8742 is the value just prior to @code{$$}, @code{$$1} is equivalent to
8743 @code{$$}, and @code{$$0} is equivalent to @code{$}.
8745 For example, suppose you have just printed a pointer to a structure and
8746 want to see the contents of the structure. It suffices to type
8752 If you have a chain of structures where the component @code{next} points
8753 to the next one, you can print the contents of the next one with this:
8760 You can print successive links in the chain by repeating this
8761 command---which you can do by just typing @key{RET}.
8763 Note that the history records values, not expressions. If the value of
8764 @code{x} is 4 and you type these commands:
8772 then the value recorded in the value history by the @code{print} command
8773 remains 4 even though the value of @code{x} has changed.
8778 Print the last ten values in the value history, with their item numbers.
8779 This is like @samp{p@ $$9} repeated ten times, except that @code{show
8780 values} does not change the history.
8782 @item show values @var{n}
8783 Print ten history values centered on history item number @var{n}.
8786 Print ten history values just after the values last printed. If no more
8787 values are available, @code{show values +} produces no display.
8790 Pressing @key{RET} to repeat @code{show values @var{n}} has exactly the
8791 same effect as @samp{show values +}.
8793 @node Convenience Vars
8794 @section Convenience Variables
8796 @cindex convenience variables
8797 @cindex user-defined variables
8798 @value{GDBN} provides @dfn{convenience variables} that you can use within
8799 @value{GDBN} to hold on to a value and refer to it later. These variables
8800 exist entirely within @value{GDBN}; they are not part of your program, and
8801 setting a convenience variable has no direct effect on further execution
8802 of your program. That is why you can use them freely.
8804 Convenience variables are prefixed with @samp{$}. Any name preceded by
8805 @samp{$} can be used for a convenience variable, unless it is one of
8806 the predefined machine-specific register names (@pxref{Registers, ,Registers}).
8807 (Value history references, in contrast, are @emph{numbers} preceded
8808 by @samp{$}. @xref{Value History, ,Value History}.)
8810 You can save a value in a convenience variable with an assignment
8811 expression, just as you would set a variable in your program.
8815 set $foo = *object_ptr
8819 would save in @code{$foo} the value contained in the object pointed to by
8822 Using a convenience variable for the first time creates it, but its
8823 value is @code{void} until you assign a new value. You can alter the
8824 value with another assignment at any time.
8826 Convenience variables have no fixed types. You can assign a convenience
8827 variable any type of value, including structures and arrays, even if
8828 that variable already has a value of a different type. The convenience
8829 variable, when used as an expression, has the type of its current value.
8832 @kindex show convenience
8833 @cindex show all user variables
8834 @item show convenience
8835 Print a list of convenience variables used so far, and their values.
8836 Abbreviated @code{show conv}.
8838 @kindex init-if-undefined
8839 @cindex convenience variables, initializing
8840 @item init-if-undefined $@var{variable} = @var{expression}
8841 Set a convenience variable if it has not already been set. This is useful
8842 for user-defined commands that keep some state. It is similar, in concept,
8843 to using local static variables with initializers in C (except that
8844 convenience variables are global). It can also be used to allow users to
8845 override default values used in a command script.
8847 If the variable is already defined then the expression is not evaluated so
8848 any side-effects do not occur.
8851 One of the ways to use a convenience variable is as a counter to be
8852 incremented or a pointer to be advanced. For example, to print
8853 a field from successive elements of an array of structures:
8857 print bar[$i++]->contents
8861 Repeat that command by typing @key{RET}.
8863 Some convenience variables are created automatically by @value{GDBN} and given
8864 values likely to be useful.
8867 @vindex $_@r{, convenience variable}
8869 The variable @code{$_} is automatically set by the @code{x} command to
8870 the last address examined (@pxref{Memory, ,Examining Memory}). Other
8871 commands which provide a default address for @code{x} to examine also
8872 set @code{$_} to that address; these commands include @code{info line}
8873 and @code{info breakpoint}. The type of @code{$_} is @code{void *}
8874 except when set by the @code{x} command, in which case it is a pointer
8875 to the type of @code{$__}.
8877 @vindex $__@r{, convenience variable}
8879 The variable @code{$__} is automatically set by the @code{x} command
8880 to the value found in the last address examined. Its type is chosen
8881 to match the format in which the data was printed.
8884 @vindex $_exitcode@r{, convenience variable}
8885 The variable @code{$_exitcode} is automatically set to the exit code when
8886 the program being debugged terminates.
8889 @vindex $_sdata@r{, inspect, convenience variable}
8890 The variable @code{$_sdata} contains extra collected static tracepoint
8891 data. @xref{Tracepoint Actions,,Tracepoint Action Lists}. Note that
8892 @code{$_sdata} could be empty, if not inspecting a trace buffer, or
8893 if extra static tracepoint data has not been collected.
8896 @vindex $_siginfo@r{, convenience variable}
8897 The variable @code{$_siginfo} contains extra signal information
8898 (@pxref{extra signal information}). Note that @code{$_siginfo}
8899 could be empty, if the application has not yet received any signals.
8900 For example, it will be empty before you execute the @code{run} command.
8903 @vindex $_tlb@r{, convenience variable}
8904 The variable @code{$_tlb} is automatically set when debugging
8905 applications running on MS-Windows in native mode or connected to
8906 gdbserver that supports the @code{qGetTIBAddr} request.
8907 @xref{General Query Packets}.
8908 This variable contains the address of the thread information block.
8912 On HP-UX systems, if you refer to a function or variable name that
8913 begins with a dollar sign, @value{GDBN} searches for a user or system
8914 name first, before it searches for a convenience variable.
8916 @cindex convenience functions
8917 @value{GDBN} also supplies some @dfn{convenience functions}. These
8918 have a syntax similar to convenience variables. A convenience
8919 function can be used in an expression just like an ordinary function;
8920 however, a convenience function is implemented internally to
8925 @kindex help function
8926 @cindex show all convenience functions
8927 Print a list of all convenience functions.
8934 You can refer to machine register contents, in expressions, as variables
8935 with names starting with @samp{$}. The names of registers are different
8936 for each machine; use @code{info registers} to see the names used on
8940 @kindex info registers
8941 @item info registers
8942 Print the names and values of all registers except floating-point
8943 and vector registers (in the selected stack frame).
8945 @kindex info all-registers
8946 @cindex floating point registers
8947 @item info all-registers
8948 Print the names and values of all registers, including floating-point
8949 and vector registers (in the selected stack frame).
8951 @item info registers @var{regname} @dots{}
8952 Print the @dfn{relativized} value of each specified register @var{regname}.
8953 As discussed in detail below, register values are normally relative to
8954 the selected stack frame. @var{regname} may be any register name valid on
8955 the machine you are using, with or without the initial @samp{$}.
8958 @cindex stack pointer register
8959 @cindex program counter register
8960 @cindex process status register
8961 @cindex frame pointer register
8962 @cindex standard registers
8963 @value{GDBN} has four ``standard'' register names that are available (in
8964 expressions) on most machines---whenever they do not conflict with an
8965 architecture's canonical mnemonics for registers. The register names
8966 @code{$pc} and @code{$sp} are used for the program counter register and
8967 the stack pointer. @code{$fp} is used for a register that contains a
8968 pointer to the current stack frame, and @code{$ps} is used for a
8969 register that contains the processor status. For example,
8970 you could print the program counter in hex with
8977 or print the instruction to be executed next with
8984 or add four to the stack pointer@footnote{This is a way of removing
8985 one word from the stack, on machines where stacks grow downward in
8986 memory (most machines, nowadays). This assumes that the innermost
8987 stack frame is selected; setting @code{$sp} is not allowed when other
8988 stack frames are selected. To pop entire frames off the stack,
8989 regardless of machine architecture, use @code{return};
8990 see @ref{Returning, ,Returning from a Function}.} with
8996 Whenever possible, these four standard register names are available on
8997 your machine even though the machine has different canonical mnemonics,
8998 so long as there is no conflict. The @code{info registers} command
8999 shows the canonical names. For example, on the SPARC, @code{info
9000 registers} displays the processor status register as @code{$psr} but you
9001 can also refer to it as @code{$ps}; and on x86-based machines @code{$ps}
9002 is an alias for the @sc{eflags} register.
9004 @value{GDBN} always considers the contents of an ordinary register as an
9005 integer when the register is examined in this way. Some machines have
9006 special registers which can hold nothing but floating point; these
9007 registers are considered to have floating point values. There is no way
9008 to refer to the contents of an ordinary register as floating point value
9009 (although you can @emph{print} it as a floating point value with
9010 @samp{print/f $@var{regname}}).
9012 Some registers have distinct ``raw'' and ``virtual'' data formats. This
9013 means that the data format in which the register contents are saved by
9014 the operating system is not the same one that your program normally
9015 sees. For example, the registers of the 68881 floating point
9016 coprocessor are always saved in ``extended'' (raw) format, but all C
9017 programs expect to work with ``double'' (virtual) format. In such
9018 cases, @value{GDBN} normally works with the virtual format only (the format
9019 that makes sense for your program), but the @code{info registers} command
9020 prints the data in both formats.
9022 @cindex SSE registers (x86)
9023 @cindex MMX registers (x86)
9024 Some machines have special registers whose contents can be interpreted
9025 in several different ways. For example, modern x86-based machines
9026 have SSE and MMX registers that can hold several values packed
9027 together in several different formats. @value{GDBN} refers to such
9028 registers in @code{struct} notation:
9031 (@value{GDBP}) print $xmm1
9033 v4_float = @{0, 3.43859137e-038, 1.54142831e-044, 1.821688e-044@},
9034 v2_double = @{9.92129282474342e-303, 2.7585945287983262e-313@},
9035 v16_int8 = "\000\000\000\000\3706;\001\v\000\000\000\r\000\000",
9036 v8_int16 = @{0, 0, 14072, 315, 11, 0, 13, 0@},
9037 v4_int32 = @{0, 20657912, 11, 13@},
9038 v2_int64 = @{88725056443645952, 55834574859@},
9039 uint128 = 0x0000000d0000000b013b36f800000000
9044 To set values of such registers, you need to tell @value{GDBN} which
9045 view of the register you wish to change, as if you were assigning
9046 value to a @code{struct} member:
9049 (@value{GDBP}) set $xmm1.uint128 = 0x000000000000000000000000FFFFFFFF
9052 Normally, register values are relative to the selected stack frame
9053 (@pxref{Selection, ,Selecting a Frame}). This means that you get the
9054 value that the register would contain if all stack frames farther in
9055 were exited and their saved registers restored. In order to see the
9056 true contents of hardware registers, you must select the innermost
9057 frame (with @samp{frame 0}).
9059 However, @value{GDBN} must deduce where registers are saved, from the machine
9060 code generated by your compiler. If some registers are not saved, or if
9061 @value{GDBN} is unable to locate the saved registers, the selected stack
9062 frame makes no difference.
9064 @node Floating Point Hardware
9065 @section Floating Point Hardware
9066 @cindex floating point
9068 Depending on the configuration, @value{GDBN} may be able to give
9069 you more information about the status of the floating point hardware.
9074 Display hardware-dependent information about the floating
9075 point unit. The exact contents and layout vary depending on the
9076 floating point chip. Currently, @samp{info float} is supported on
9077 the ARM and x86 machines.
9081 @section Vector Unit
9084 Depending on the configuration, @value{GDBN} may be able to give you
9085 more information about the status of the vector unit.
9090 Display information about the vector unit. The exact contents and
9091 layout vary depending on the hardware.
9094 @node OS Information
9095 @section Operating System Auxiliary Information
9096 @cindex OS information
9098 @value{GDBN} provides interfaces to useful OS facilities that can help
9099 you debug your program.
9101 @cindex @code{ptrace} system call
9102 @cindex @code{struct user} contents
9103 When @value{GDBN} runs on a @dfn{Posix system} (such as GNU or Unix
9104 machines), it interfaces with the inferior via the @code{ptrace}
9105 system call. The operating system creates a special sata structure,
9106 called @code{struct user}, for this interface. You can use the
9107 command @code{info udot} to display the contents of this data
9113 Display the contents of the @code{struct user} maintained by the OS
9114 kernel for the program being debugged. @value{GDBN} displays the
9115 contents of @code{struct user} as a list of hex numbers, similar to
9116 the @code{examine} command.
9119 @cindex auxiliary vector
9120 @cindex vector, auxiliary
9121 Some operating systems supply an @dfn{auxiliary vector} to programs at
9122 startup. This is akin to the arguments and environment that you
9123 specify for a program, but contains a system-dependent variety of
9124 binary values that tell system libraries important details about the
9125 hardware, operating system, and process. Each value's purpose is
9126 identified by an integer tag; the meanings are well-known but system-specific.
9127 Depending on the configuration and operating system facilities,
9128 @value{GDBN} may be able to show you this information. For remote
9129 targets, this functionality may further depend on the remote stub's
9130 support of the @samp{qXfer:auxv:read} packet, see
9131 @ref{qXfer auxiliary vector read}.
9136 Display the auxiliary vector of the inferior, which can be either a
9137 live process or a core dump file. @value{GDBN} prints each tag value
9138 numerically, and also shows names and text descriptions for recognized
9139 tags. Some values in the vector are numbers, some bit masks, and some
9140 pointers to strings or other data. @value{GDBN} displays each value in the
9141 most appropriate form for a recognized tag, and in hexadecimal for
9142 an unrecognized tag.
9145 On some targets, @value{GDBN} can access operating-system-specific information
9146 and display it to user, without interpretation. For remote targets,
9147 this functionality depends on the remote stub's support of the
9148 @samp{qXfer:osdata:read} packet, see @ref{qXfer osdata read}.
9153 List the types of OS information available for the target. If the
9154 target does not return a list of possible types, this command will
9157 @kindex info os processes
9158 @item info os processes
9159 Display the list of processes on the target. For each process,
9160 @value{GDBN} prints the process identifier, the name of the user, and
9161 the command corresponding to the process.
9164 @node Memory Region Attributes
9165 @section Memory Region Attributes
9166 @cindex memory region attributes
9168 @dfn{Memory region attributes} allow you to describe special handling
9169 required by regions of your target's memory. @value{GDBN} uses
9170 attributes to determine whether to allow certain types of memory
9171 accesses; whether to use specific width accesses; and whether to cache
9172 target memory. By default the description of memory regions is
9173 fetched from the target (if the current target supports this), but the
9174 user can override the fetched regions.
9176 Defined memory regions can be individually enabled and disabled. When a
9177 memory region is disabled, @value{GDBN} uses the default attributes when
9178 accessing memory in that region. Similarly, if no memory regions have
9179 been defined, @value{GDBN} uses the default attributes when accessing
9182 When a memory region is defined, it is given a number to identify it;
9183 to enable, disable, or remove a memory region, you specify that number.
9187 @item mem @var{lower} @var{upper} @var{attributes}@dots{}
9188 Define a memory region bounded by @var{lower} and @var{upper} with
9189 attributes @var{attributes}@dots{}, and add it to the list of regions
9190 monitored by @value{GDBN}. Note that @var{upper} == 0 is a special
9191 case: it is treated as the target's maximum memory address.
9192 (0xffff on 16 bit targets, 0xffffffff on 32 bit targets, etc.)
9195 Discard any user changes to the memory regions and use target-supplied
9196 regions, if available, or no regions if the target does not support.
9199 @item delete mem @var{nums}@dots{}
9200 Remove memory regions @var{nums}@dots{} from the list of regions
9201 monitored by @value{GDBN}.
9204 @item disable mem @var{nums}@dots{}
9205 Disable monitoring of memory regions @var{nums}@dots{}.
9206 A disabled memory region is not forgotten.
9207 It may be enabled again later.
9210 @item enable mem @var{nums}@dots{}
9211 Enable monitoring of memory regions @var{nums}@dots{}.
9215 Print a table of all defined memory regions, with the following columns
9219 @item Memory Region Number
9220 @item Enabled or Disabled.
9221 Enabled memory regions are marked with @samp{y}.
9222 Disabled memory regions are marked with @samp{n}.
9225 The address defining the inclusive lower bound of the memory region.
9228 The address defining the exclusive upper bound of the memory region.
9231 The list of attributes set for this memory region.
9236 @subsection Attributes
9238 @subsubsection Memory Access Mode
9239 The access mode attributes set whether @value{GDBN} may make read or
9240 write accesses to a memory region.
9242 While these attributes prevent @value{GDBN} from performing invalid
9243 memory accesses, they do nothing to prevent the target system, I/O DMA,
9244 etc.@: from accessing memory.
9248 Memory is read only.
9250 Memory is write only.
9252 Memory is read/write. This is the default.
9255 @subsubsection Memory Access Size
9256 The access size attribute tells @value{GDBN} to use specific sized
9257 accesses in the memory region. Often memory mapped device registers
9258 require specific sized accesses. If no access size attribute is
9259 specified, @value{GDBN} may use accesses of any size.
9263 Use 8 bit memory accesses.
9265 Use 16 bit memory accesses.
9267 Use 32 bit memory accesses.
9269 Use 64 bit memory accesses.
9272 @c @subsubsection Hardware/Software Breakpoints
9273 @c The hardware/software breakpoint attributes set whether @value{GDBN}
9274 @c will use hardware or software breakpoints for the internal breakpoints
9275 @c used by the step, next, finish, until, etc. commands.
9279 @c Always use hardware breakpoints
9280 @c @item swbreak (default)
9283 @subsubsection Data Cache
9284 The data cache attributes set whether @value{GDBN} will cache target
9285 memory. While this generally improves performance by reducing debug
9286 protocol overhead, it can lead to incorrect results because @value{GDBN}
9287 does not know about volatile variables or memory mapped device
9292 Enable @value{GDBN} to cache target memory.
9294 Disable @value{GDBN} from caching target memory. This is the default.
9297 @subsection Memory Access Checking
9298 @value{GDBN} can be instructed to refuse accesses to memory that is
9299 not explicitly described. This can be useful if accessing such
9300 regions has undesired effects for a specific target, or to provide
9301 better error checking. The following commands control this behaviour.
9304 @kindex set mem inaccessible-by-default
9305 @item set mem inaccessible-by-default [on|off]
9306 If @code{on} is specified, make @value{GDBN} treat memory not
9307 explicitly described by the memory ranges as non-existent and refuse accesses
9308 to such memory. The checks are only performed if there's at least one
9309 memory range defined. If @code{off} is specified, make @value{GDBN}
9310 treat the memory not explicitly described by the memory ranges as RAM.
9311 The default value is @code{on}.
9312 @kindex show mem inaccessible-by-default
9313 @item show mem inaccessible-by-default
9314 Show the current handling of accesses to unknown memory.
9318 @c @subsubsection Memory Write Verification
9319 @c The memory write verification attributes set whether @value{GDBN}
9320 @c will re-reads data after each write to verify the write was successful.
9324 @c @item noverify (default)
9327 @node Dump/Restore Files
9328 @section Copy Between Memory and a File
9329 @cindex dump/restore files
9330 @cindex append data to a file
9331 @cindex dump data to a file
9332 @cindex restore data from a file
9334 You can use the commands @code{dump}, @code{append}, and
9335 @code{restore} to copy data between target memory and a file. The
9336 @code{dump} and @code{append} commands write data to a file, and the
9337 @code{restore} command reads data from a file back into the inferior's
9338 memory. Files may be in binary, Motorola S-record, Intel hex, or
9339 Tektronix Hex format; however, @value{GDBN} can only append to binary
9345 @item dump @r{[}@var{format}@r{]} memory @var{filename} @var{start_addr} @var{end_addr}
9346 @itemx dump @r{[}@var{format}@r{]} value @var{filename} @var{expr}
9347 Dump the contents of memory from @var{start_addr} to @var{end_addr},
9348 or the value of @var{expr}, to @var{filename} in the given format.
9350 The @var{format} parameter may be any one of:
9357 Motorola S-record format.
9359 Tektronix Hex format.
9362 @value{GDBN} uses the same definitions of these formats as the
9363 @sc{gnu} binary utilities, like @samp{objdump} and @samp{objcopy}. If
9364 @var{format} is omitted, @value{GDBN} dumps the data in raw binary
9368 @item append @r{[}binary@r{]} memory @var{filename} @var{start_addr} @var{end_addr}
9369 @itemx append @r{[}binary@r{]} value @var{filename} @var{expr}
9370 Append the contents of memory from @var{start_addr} to @var{end_addr},
9371 or the value of @var{expr}, to the file @var{filename}, in raw binary form.
9372 (@value{GDBN} can only append data to files in raw binary form.)
9375 @item restore @var{filename} @r{[}binary@r{]} @var{bias} @var{start} @var{end}
9376 Restore the contents of file @var{filename} into memory. The
9377 @code{restore} command can automatically recognize any known @sc{bfd}
9378 file format, except for raw binary. To restore a raw binary file you
9379 must specify the optional keyword @code{binary} after the filename.
9381 If @var{bias} is non-zero, its value will be added to the addresses
9382 contained in the file. Binary files always start at address zero, so
9383 they will be restored at address @var{bias}. Other bfd files have
9384 a built-in location; they will be restored at offset @var{bias}
9387 If @var{start} and/or @var{end} are non-zero, then only data between
9388 file offset @var{start} and file offset @var{end} will be restored.
9389 These offsets are relative to the addresses in the file, before
9390 the @var{bias} argument is applied.
9394 @node Core File Generation
9395 @section How to Produce a Core File from Your Program
9396 @cindex dump core from inferior
9398 A @dfn{core file} or @dfn{core dump} is a file that records the memory
9399 image of a running process and its process status (register values
9400 etc.). Its primary use is post-mortem debugging of a program that
9401 crashed while it ran outside a debugger. A program that crashes
9402 automatically produces a core file, unless this feature is disabled by
9403 the user. @xref{Files}, for information on invoking @value{GDBN} in
9404 the post-mortem debugging mode.
9406 Occasionally, you may wish to produce a core file of the program you
9407 are debugging in order to preserve a snapshot of its state.
9408 @value{GDBN} has a special command for that.
9412 @kindex generate-core-file
9413 @item generate-core-file [@var{file}]
9414 @itemx gcore [@var{file}]
9415 Produce a core dump of the inferior process. The optional argument
9416 @var{file} specifies the file name where to put the core dump. If not
9417 specified, the file name defaults to @file{core.@var{pid}}, where
9418 @var{pid} is the inferior process ID.
9420 Note that this command is implemented only for some systems (as of
9421 this writing, @sc{gnu}/Linux, FreeBSD, Solaris, Unixware, and S390).
9424 @node Character Sets
9425 @section Character Sets
9426 @cindex character sets
9428 @cindex translating between character sets
9429 @cindex host character set
9430 @cindex target character set
9432 If the program you are debugging uses a different character set to
9433 represent characters and strings than the one @value{GDBN} uses itself,
9434 @value{GDBN} can automatically translate between the character sets for
9435 you. The character set @value{GDBN} uses we call the @dfn{host
9436 character set}; the one the inferior program uses we call the
9437 @dfn{target character set}.
9439 For example, if you are running @value{GDBN} on a @sc{gnu}/Linux system, which
9440 uses the ISO Latin 1 character set, but you are using @value{GDBN}'s
9441 remote protocol (@pxref{Remote Debugging}) to debug a program
9442 running on an IBM mainframe, which uses the @sc{ebcdic} character set,
9443 then the host character set is Latin-1, and the target character set is
9444 @sc{ebcdic}. If you give @value{GDBN} the command @code{set
9445 target-charset EBCDIC-US}, then @value{GDBN} translates between
9446 @sc{ebcdic} and Latin 1 as you print character or string values, or use
9447 character and string literals in expressions.
9449 @value{GDBN} has no way to automatically recognize which character set
9450 the inferior program uses; you must tell it, using the @code{set
9451 target-charset} command, described below.
9453 Here are the commands for controlling @value{GDBN}'s character set
9457 @item set target-charset @var{charset}
9458 @kindex set target-charset
9459 Set the current target character set to @var{charset}. To display the
9460 list of supported target character sets, type
9461 @kbd{@w{set target-charset @key{TAB}@key{TAB}}}.
9463 @item set host-charset @var{charset}
9464 @kindex set host-charset
9465 Set the current host character set to @var{charset}.
9467 By default, @value{GDBN} uses a host character set appropriate to the
9468 system it is running on; you can override that default using the
9469 @code{set host-charset} command. On some systems, @value{GDBN} cannot
9470 automatically determine the appropriate host character set. In this
9471 case, @value{GDBN} uses @samp{UTF-8}.
9473 @value{GDBN} can only use certain character sets as its host character
9474 set. If you type @kbd{@w{set host-charset @key{TAB}@key{TAB}}},
9475 @value{GDBN} will list the host character sets it supports.
9477 @item set charset @var{charset}
9479 Set the current host and target character sets to @var{charset}. As
9480 above, if you type @kbd{@w{set charset @key{TAB}@key{TAB}}},
9481 @value{GDBN} will list the names of the character sets that can be used
9482 for both host and target.
9485 @kindex show charset
9486 Show the names of the current host and target character sets.
9488 @item show host-charset
9489 @kindex show host-charset
9490 Show the name of the current host character set.
9492 @item show target-charset
9493 @kindex show target-charset
9494 Show the name of the current target character set.
9496 @item set target-wide-charset @var{charset}
9497 @kindex set target-wide-charset
9498 Set the current target's wide character set to @var{charset}. This is
9499 the character set used by the target's @code{wchar_t} type. To
9500 display the list of supported wide character sets, type
9501 @kbd{@w{set target-wide-charset @key{TAB}@key{TAB}}}.
9503 @item show target-wide-charset
9504 @kindex show target-wide-charset
9505 Show the name of the current target's wide character set.
9508 Here is an example of @value{GDBN}'s character set support in action.
9509 Assume that the following source code has been placed in the file
9510 @file{charset-test.c}:
9516 = @{72, 101, 108, 108, 111, 44, 32, 119,
9517 111, 114, 108, 100, 33, 10, 0@};
9518 char ibm1047_hello[]
9519 = @{200, 133, 147, 147, 150, 107, 64, 166,
9520 150, 153, 147, 132, 90, 37, 0@};
9524 printf ("Hello, world!\n");
9528 In this program, @code{ascii_hello} and @code{ibm1047_hello} are arrays
9529 containing the string @samp{Hello, world!} followed by a newline,
9530 encoded in the @sc{ascii} and @sc{ibm1047} character sets.
9532 We compile the program, and invoke the debugger on it:
9535 $ gcc -g charset-test.c -o charset-test
9536 $ gdb -nw charset-test
9537 GNU gdb 2001-12-19-cvs
9538 Copyright 2001 Free Software Foundation, Inc.
9543 We can use the @code{show charset} command to see what character sets
9544 @value{GDBN} is currently using to interpret and display characters and
9548 (@value{GDBP}) show charset
9549 The current host and target character set is `ISO-8859-1'.
9553 For the sake of printing this manual, let's use @sc{ascii} as our
9554 initial character set:
9556 (@value{GDBP}) set charset ASCII
9557 (@value{GDBP}) show charset
9558 The current host and target character set is `ASCII'.
9562 Let's assume that @sc{ascii} is indeed the correct character set for our
9563 host system --- in other words, let's assume that if @value{GDBN} prints
9564 characters using the @sc{ascii} character set, our terminal will display
9565 them properly. Since our current target character set is also
9566 @sc{ascii}, the contents of @code{ascii_hello} print legibly:
9569 (@value{GDBP}) print ascii_hello
9570 $1 = 0x401698 "Hello, world!\n"
9571 (@value{GDBP}) print ascii_hello[0]
9576 @value{GDBN} uses the target character set for character and string
9577 literals you use in expressions:
9580 (@value{GDBP}) print '+'
9585 The @sc{ascii} character set uses the number 43 to encode the @samp{+}
9588 @value{GDBN} relies on the user to tell it which character set the
9589 target program uses. If we print @code{ibm1047_hello} while our target
9590 character set is still @sc{ascii}, we get jibberish:
9593 (@value{GDBP}) print ibm1047_hello
9594 $4 = 0x4016a8 "\310\205\223\223\226k@@\246\226\231\223\204Z%"
9595 (@value{GDBP}) print ibm1047_hello[0]
9600 If we invoke the @code{set target-charset} followed by @key{TAB}@key{TAB},
9601 @value{GDBN} tells us the character sets it supports:
9604 (@value{GDBP}) set target-charset
9605 ASCII EBCDIC-US IBM1047 ISO-8859-1
9606 (@value{GDBP}) set target-charset
9609 We can select @sc{ibm1047} as our target character set, and examine the
9610 program's strings again. Now the @sc{ascii} string is wrong, but
9611 @value{GDBN} translates the contents of @code{ibm1047_hello} from the
9612 target character set, @sc{ibm1047}, to the host character set,
9613 @sc{ascii}, and they display correctly:
9616 (@value{GDBP}) set target-charset IBM1047
9617 (@value{GDBP}) show charset
9618 The current host character set is `ASCII'.
9619 The current target character set is `IBM1047'.
9620 (@value{GDBP}) print ascii_hello
9621 $6 = 0x401698 "\110\145%%?\054\040\167?\162%\144\041\012"
9622 (@value{GDBP}) print ascii_hello[0]
9624 (@value{GDBP}) print ibm1047_hello
9625 $8 = 0x4016a8 "Hello, world!\n"
9626 (@value{GDBP}) print ibm1047_hello[0]
9631 As above, @value{GDBN} uses the target character set for character and
9632 string literals you use in expressions:
9635 (@value{GDBP}) print '+'
9640 The @sc{ibm1047} character set uses the number 78 to encode the @samp{+}
9643 @node Caching Remote Data
9644 @section Caching Data of Remote Targets
9645 @cindex caching data of remote targets
9647 @value{GDBN} caches data exchanged between the debugger and a
9648 remote target (@pxref{Remote Debugging}). Such caching generally improves
9649 performance, because it reduces the overhead of the remote protocol by
9650 bundling memory reads and writes into large chunks. Unfortunately, simply
9651 caching everything would lead to incorrect results, since @value{GDBN}
9652 does not necessarily know anything about volatile values, memory-mapped I/O
9653 addresses, etc. Furthermore, in non-stop mode (@pxref{Non-Stop Mode})
9654 memory can be changed @emph{while} a gdb command is executing.
9655 Therefore, by default, @value{GDBN} only caches data
9656 known to be on the stack@footnote{In non-stop mode, it is moderately
9657 rare for a running thread to modify the stack of a stopped thread
9658 in a way that would interfere with a backtrace, and caching of
9659 stack reads provides a significant speed up of remote backtraces.}.
9660 Other regions of memory can be explicitly marked as
9661 cacheable; see @pxref{Memory Region Attributes}.
9664 @kindex set remotecache
9665 @item set remotecache on
9666 @itemx set remotecache off
9667 This option no longer does anything; it exists for compatibility
9670 @kindex show remotecache
9671 @item show remotecache
9672 Show the current state of the obsolete remotecache flag.
9674 @kindex set stack-cache
9675 @item set stack-cache on
9676 @itemx set stack-cache off
9677 Enable or disable caching of stack accesses. When @code{ON}, use
9678 caching. By default, this option is @code{ON}.
9680 @kindex show stack-cache
9681 @item show stack-cache
9682 Show the current state of data caching for memory accesses.
9685 @item info dcache @r{[}line@r{]}
9686 Print the information about the data cache performance. The
9687 information displayed includes the dcache width and depth, and for
9688 each cache line, its number, address, and how many times it was
9689 referenced. This command is useful for debugging the data cache
9692 If a line number is specified, the contents of that line will be
9695 @item set dcache size @var{size}
9697 @kindex set dcache size
9698 Set maximum number of entries in dcache (dcache depth above).
9700 @item set dcache line-size @var{line-size}
9701 @cindex dcache line-size
9702 @kindex set dcache line-size
9703 Set number of bytes each dcache entry caches (dcache width above).
9704 Must be a power of 2.
9706 @item show dcache size
9707 @kindex show dcache size
9708 Show maximum number of dcache entries. See also @ref{Caching Remote Data, info dcache}.
9710 @item show dcache line-size
9711 @kindex show dcache line-size
9712 Show default size of dcache lines. See also @ref{Caching Remote Data, info dcache}.
9716 @node Searching Memory
9717 @section Search Memory
9718 @cindex searching memory
9720 Memory can be searched for a particular sequence of bytes with the
9721 @code{find} command.
9725 @item find @r{[}/@var{sn}@r{]} @var{start_addr}, +@var{len}, @var{val1} @r{[}, @var{val2}, @dots{}@r{]}
9726 @itemx find @r{[}/@var{sn}@r{]} @var{start_addr}, @var{end_addr}, @var{val1} @r{[}, @var{val2}, @dots{}@r{]}
9727 Search memory for the sequence of bytes specified by @var{val1}, @var{val2},
9728 etc. The search begins at address @var{start_addr} and continues for either
9729 @var{len} bytes or through to @var{end_addr} inclusive.
9732 @var{s} and @var{n} are optional parameters.
9733 They may be specified in either order, apart or together.
9736 @item @var{s}, search query size
9737 The size of each search query value.
9743 halfwords (two bytes)
9747 giant words (eight bytes)
9750 All values are interpreted in the current language.
9751 This means, for example, that if the current source language is C/C@t{++}
9752 then searching for the string ``hello'' includes the trailing '\0'.
9754 If the value size is not specified, it is taken from the
9755 value's type in the current language.
9756 This is useful when one wants to specify the search
9757 pattern as a mixture of types.
9758 Note that this means, for example, that in the case of C-like languages
9759 a search for an untyped 0x42 will search for @samp{(int) 0x42}
9760 which is typically four bytes.
9762 @item @var{n}, maximum number of finds
9763 The maximum number of matches to print. The default is to print all finds.
9766 You can use strings as search values. Quote them with double-quotes
9768 The string value is copied into the search pattern byte by byte,
9769 regardless of the endianness of the target and the size specification.
9771 The address of each match found is printed as well as a count of the
9772 number of matches found.
9774 The address of the last value found is stored in convenience variable
9776 A count of the number of matches is stored in @samp{$numfound}.
9778 For example, if stopped at the @code{printf} in this function:
9784 static char hello[] = "hello-hello";
9785 static struct @{ char c; short s; int i; @}
9786 __attribute__ ((packed)) mixed
9787 = @{ 'c', 0x1234, 0x87654321 @};
9788 printf ("%s\n", hello);
9793 you get during debugging:
9796 (gdb) find &hello[0], +sizeof(hello), "hello"
9797 0x804956d <hello.1620+6>
9799 (gdb) find &hello[0], +sizeof(hello), 'h', 'e', 'l', 'l', 'o'
9800 0x8049567 <hello.1620>
9801 0x804956d <hello.1620+6>
9803 (gdb) find /b1 &hello[0], +sizeof(hello), 'h', 0x65, 'l'
9804 0x8049567 <hello.1620>
9806 (gdb) find &mixed, +sizeof(mixed), (char) 'c', (short) 0x1234, (int) 0x87654321
9807 0x8049560 <mixed.1625>
9809 (gdb) print $numfound
9812 $2 = (void *) 0x8049560
9815 @node Optimized Code
9816 @chapter Debugging Optimized Code
9817 @cindex optimized code, debugging
9818 @cindex debugging optimized code
9820 Almost all compilers support optimization. With optimization
9821 disabled, the compiler generates assembly code that corresponds
9822 directly to your source code, in a simplistic way. As the compiler
9823 applies more powerful optimizations, the generated assembly code
9824 diverges from your original source code. With help from debugging
9825 information generated by the compiler, @value{GDBN} can map from
9826 the running program back to constructs from your original source.
9828 @value{GDBN} is more accurate with optimization disabled. If you
9829 can recompile without optimization, it is easier to follow the
9830 progress of your program during debugging. But, there are many cases
9831 where you may need to debug an optimized version.
9833 When you debug a program compiled with @samp{-g -O}, remember that the
9834 optimizer has rearranged your code; the debugger shows you what is
9835 really there. Do not be too surprised when the execution path does not
9836 exactly match your source file! An extreme example: if you define a
9837 variable, but never use it, @value{GDBN} never sees that
9838 variable---because the compiler optimizes it out of existence.
9840 Some things do not work as well with @samp{-g -O} as with just
9841 @samp{-g}, particularly on machines with instruction scheduling. If in
9842 doubt, recompile with @samp{-g} alone, and if this fixes the problem,
9843 please report it to us as a bug (including a test case!).
9844 @xref{Variables}, for more information about debugging optimized code.
9847 * Inline Functions:: How @value{GDBN} presents inlining
9848 * Tail Call Frames:: @value{GDBN} analysis of jumps to functions
9851 @node Inline Functions
9852 @section Inline Functions
9853 @cindex inline functions, debugging
9855 @dfn{Inlining} is an optimization that inserts a copy of the function
9856 body directly at each call site, instead of jumping to a shared
9857 routine. @value{GDBN} displays inlined functions just like
9858 non-inlined functions. They appear in backtraces. You can view their
9859 arguments and local variables, step into them with @code{step}, skip
9860 them with @code{next}, and escape from them with @code{finish}.
9861 You can check whether a function was inlined by using the
9862 @code{info frame} command.
9864 For @value{GDBN} to support inlined functions, the compiler must
9865 record information about inlining in the debug information ---
9866 @value{NGCC} using the @sc{dwarf 2} format does this, and several
9867 other compilers do also. @value{GDBN} only supports inlined functions
9868 when using @sc{dwarf 2}. Versions of @value{NGCC} before 4.1
9869 do not emit two required attributes (@samp{DW_AT_call_file} and
9870 @samp{DW_AT_call_line}); @value{GDBN} does not display inlined
9871 function calls with earlier versions of @value{NGCC}. It instead
9872 displays the arguments and local variables of inlined functions as
9873 local variables in the caller.
9875 The body of an inlined function is directly included at its call site;
9876 unlike a non-inlined function, there are no instructions devoted to
9877 the call. @value{GDBN} still pretends that the call site and the
9878 start of the inlined function are different instructions. Stepping to
9879 the call site shows the call site, and then stepping again shows
9880 the first line of the inlined function, even though no additional
9881 instructions are executed.
9883 This makes source-level debugging much clearer; you can see both the
9884 context of the call and then the effect of the call. Only stepping by
9885 a single instruction using @code{stepi} or @code{nexti} does not do
9886 this; single instruction steps always show the inlined body.
9888 There are some ways that @value{GDBN} does not pretend that inlined
9889 function calls are the same as normal calls:
9893 You cannot set breakpoints on inlined functions. @value{GDBN}
9894 either reports that there is no symbol with that name, or else sets the
9895 breakpoint only on non-inlined copies of the function. This limitation
9896 will be removed in a future version of @value{GDBN}; until then,
9897 set a breakpoint by line number on the first line of the inlined
9901 Setting breakpoints at the call site of an inlined function may not
9902 work, because the call site does not contain any code. @value{GDBN}
9903 may incorrectly move the breakpoint to the next line of the enclosing
9904 function, after the call. This limitation will be removed in a future
9905 version of @value{GDBN}; until then, set a breakpoint on an earlier line
9906 or inside the inlined function instead.
9909 @value{GDBN} cannot locate the return value of inlined calls after
9910 using the @code{finish} command. This is a limitation of compiler-generated
9911 debugging information; after @code{finish}, you can step to the next line
9912 and print a variable where your program stored the return value.
9916 @node Tail Call Frames
9917 @section Tail Call Frames
9918 @cindex tail call frames, debugging
9920 Function @code{B} can call function @code{C} in its very last statement. In
9921 unoptimized compilation the call of @code{C} is immediately followed by return
9922 instruction at the end of @code{B} code. Optimizing compiler may replace the
9923 call and return in function @code{B} into one jump to function @code{C}
9924 instead. Such use of a jump instruction is called @dfn{tail call}.
9926 During execution of function @code{C}, there will be no indication in the
9927 function call stack frames that it was tail-called from @code{B}. If function
9928 @code{A} regularly calls function @code{B} which tail-calls function @code{C},
9929 then @value{GDBN} will see @code{A} as the caller of @code{C}. However, in
9930 some cases @value{GDBN} can determine that @code{C} was tail-called from
9931 @code{B}, and it will then create fictitious call frame for that, with the
9932 return address set up as if @code{B} called @code{C} normally.
9934 This functionality is currently supported only by DWARF 2 debugging format and
9935 the compiler has to produce @samp{DW_TAG_GNU_call_site} tags. With
9936 @value{NGCC}, you need to specify @option{-O -g} during compilation, to get
9939 @kbd{info frame} command (@pxref{Frame Info}) will indicate the tail call frame
9940 kind by text @code{tail call frame} such as in this sample @value{GDBN} output:
9944 0x40066b <b(int, double)+11>: jmp 0x400640 <c(int, double)>
9946 Stack level 1, frame at 0x7fffffffda30:
9947 rip = 0x40066d in b (amd64-entry-value.cc:59); saved rip 0x4004c5
9948 tail call frame, caller of frame at 0x7fffffffda30
9949 source language c++.
9950 Arglist at unknown address.
9951 Locals at unknown address, Previous frame's sp is 0x7fffffffda30
9954 The detection of all the possible code path executions can find them ambiguous.
9955 There is no execution history stored (possible @ref{Reverse Execution} is never
9956 used for this purpose) and the last known caller could have reached the known
9957 callee by multiple different jump sequences. In such case @value{GDBN} still
9958 tries to show at least all the unambiguous top tail callers and all the
9959 unambiguous bottom tail calees, if any.
9962 @anchor{set debug entry-values}
9963 @item set debug entry-values
9964 @kindex set debug entry-values
9965 When set to on, enables printing of analysis messages for both frame argument
9966 values at function entry and tail calls. It will show all the possible valid
9967 tail calls code paths it has considered. It will also print the intersection
9968 of them with the final unambiguous (possibly partial or even empty) code path
9971 @item show debug entry-values
9972 @kindex show debug entry-values
9973 Show the current state of analysis messages printing for both frame argument
9974 values at function entry and tail calls.
9977 The analysis messages for tail calls can for example show why the virtual tail
9978 call frame for function @code{c} has not been recognized (due to the indirect
9979 reference by variable @code{x}):
9982 static void __attribute__((noinline, noclone)) c (void);
9983 void (*x) (void) = c;
9984 static void __attribute__((noinline, noclone)) a (void) @{ x++; @}
9985 static void __attribute__((noinline, noclone)) c (void) @{ a (); @}
9986 int main (void) @{ x (); return 0; @}
9988 Breakpoint 1, DW_OP_GNU_entry_value resolving cannot find
9989 DW_TAG_GNU_call_site 0x40039a in main
9991 3 static void __attribute__((noinline, noclone)) a (void) @{ x++; @}
9994 #1 0x000000000040039a in main () at t.c:5
9997 Another possibility is an ambiguous virtual tail call frames resolution:
10001 static void __attribute__((noinline, noclone)) f (void) @{ i++; @}
10002 static void __attribute__((noinline, noclone)) e (void) @{ f (); @}
10003 static void __attribute__((noinline, noclone)) d (void) @{ f (); @}
10004 static void __attribute__((noinline, noclone)) c (void) @{ d (); @}
10005 static void __attribute__((noinline, noclone)) b (void)
10006 @{ if (i) c (); else e (); @}
10007 static void __attribute__((noinline, noclone)) a (void) @{ b (); @}
10008 int main (void) @{ a (); return 0; @}
10010 tailcall: initial: 0x4004d2(a) 0x4004ce(b) 0x4004b2(c) 0x4004a2(d)
10011 tailcall: compare: 0x4004d2(a) 0x4004cc(b) 0x400492(e)
10012 tailcall: reduced: 0x4004d2(a) |
10015 #1 0x00000000004004d2 in a () at t.c:8
10016 #2 0x0000000000400395 in main () at t.c:9
10019 @set CALLSEQ1A @code{main@value{ARROW}a@value{ARROW}b@value{ARROW}c@value{ARROW}d@value{ARROW}f}
10020 @set CALLSEQ2A @code{main@value{ARROW}a@value{ARROW}b@value{ARROW}e@value{ARROW}f}
10022 @c Convert CALLSEQ#A to CALLSEQ#B depending on HAVE_MAKEINFO_CLICK.
10023 @ifset HAVE_MAKEINFO_CLICK
10024 @set ARROW @click{}
10025 @set CALLSEQ1B @clicksequence{@value{CALLSEQ1A}}
10026 @set CALLSEQ2B @clicksequence{@value{CALLSEQ2A}}
10028 @ifclear HAVE_MAKEINFO_CLICK
10030 @set CALLSEQ1B @value{CALLSEQ1A}
10031 @set CALLSEQ2B @value{CALLSEQ2A}
10034 Frames #0 and #2 are real, #1 is a virtual tail call frame.
10035 The code can have possible execution paths @value{CALLSEQ1B} or
10036 @value{CALLSEQ2B}, @value{GDBN} cannot find which one from the inferior state.
10038 @code{initial:} state shows some random possible calling sequence @value{GDBN}
10039 has found. It then finds another possible calling sequcen - that one is
10040 prefixed by @code{compare:}. The non-ambiguous intersection of these two is
10041 printed as the @code{reduced:} calling sequence. That one could have many
10042 futher @code{compare:} and @code{reduced:} statements as long as there remain
10043 any non-ambiguous sequence entries.
10045 For the frame of function @code{b} in both cases there are different possible
10046 @code{$pc} values (@code{0x4004cc} or @code{0x4004ce}), therefore this frame is
10047 also ambigous. The only non-ambiguous frame is the one for function @code{a},
10048 therefore this one is displayed to the user while the ambiguous frames are
10051 There can be also reasons why printing of frame argument values at function
10056 static void __attribute__((noinline, noclone)) c (int i) @{ v++; @}
10057 static void __attribute__((noinline, noclone)) a (int i);
10058 static void __attribute__((noinline, noclone)) b (int i) @{ a (i); @}
10059 static void __attribute__((noinline, noclone)) a (int i)
10060 @{ if (i) b (i - 1); else c (0); @}
10061 int main (void) @{ a (5); return 0; @}
10064 #0 c (i=i@@entry=0) at t.c:2
10065 #1 0x0000000000400428 in a (DW_OP_GNU_entry_value resolving has found
10066 function "a" at 0x400420 can call itself via tail calls
10067 i=<optimized out>) at t.c:6
10068 #2 0x000000000040036e in main () at t.c:7
10071 @value{GDBN} cannot find out from the inferior state if and how many times did
10072 function @code{a} call itself (via function @code{b}) as these calls would be
10073 tail calls. Such tail calls would modify thue @code{i} variable, therefore
10074 @value{GDBN} cannot be sure the value it knows would be right - @value{GDBN}
10075 prints @code{<optimized out>} instead.
10078 @chapter C Preprocessor Macros
10080 Some languages, such as C and C@t{++}, provide a way to define and invoke
10081 ``preprocessor macros'' which expand into strings of tokens.
10082 @value{GDBN} can evaluate expressions containing macro invocations, show
10083 the result of macro expansion, and show a macro's definition, including
10084 where it was defined.
10086 You may need to compile your program specially to provide @value{GDBN}
10087 with information about preprocessor macros. Most compilers do not
10088 include macros in their debugging information, even when you compile
10089 with the @option{-g} flag. @xref{Compilation}.
10091 A program may define a macro at one point, remove that definition later,
10092 and then provide a different definition after that. Thus, at different
10093 points in the program, a macro may have different definitions, or have
10094 no definition at all. If there is a current stack frame, @value{GDBN}
10095 uses the macros in scope at that frame's source code line. Otherwise,
10096 @value{GDBN} uses the macros in scope at the current listing location;
10099 Whenever @value{GDBN} evaluates an expression, it always expands any
10100 macro invocations present in the expression. @value{GDBN} also provides
10101 the following commands for working with macros explicitly.
10105 @kindex macro expand
10106 @cindex macro expansion, showing the results of preprocessor
10107 @cindex preprocessor macro expansion, showing the results of
10108 @cindex expanding preprocessor macros
10109 @item macro expand @var{expression}
10110 @itemx macro exp @var{expression}
10111 Show the results of expanding all preprocessor macro invocations in
10112 @var{expression}. Since @value{GDBN} simply expands macros, but does
10113 not parse the result, @var{expression} need not be a valid expression;
10114 it can be any string of tokens.
10117 @item macro expand-once @var{expression}
10118 @itemx macro exp1 @var{expression}
10119 @cindex expand macro once
10120 @i{(This command is not yet implemented.)} Show the results of
10121 expanding those preprocessor macro invocations that appear explicitly in
10122 @var{expression}. Macro invocations appearing in that expansion are
10123 left unchanged. This command allows you to see the effect of a
10124 particular macro more clearly, without being confused by further
10125 expansions. Since @value{GDBN} simply expands macros, but does not
10126 parse the result, @var{expression} need not be a valid expression; it
10127 can be any string of tokens.
10130 @cindex macro definition, showing
10131 @cindex definition of a macro, showing
10132 @cindex macros, from debug info
10133 @item info macro [-a|-all] [--] @var{macro}
10134 Show the current definition or all definitions of the named @var{macro},
10135 and describe the source location or compiler command-line where that
10136 definition was established. The optional double dash is to signify the end of
10137 argument processing and the beginning of @var{macro} for non C-like macros where
10138 the macro may begin with a hyphen.
10140 @kindex info macros
10141 @item info macros @var{linespec}
10142 Show all macro definitions that are in effect at the location specified
10143 by @var{linespec}, and describe the source location or compiler
10144 command-line where those definitions were established.
10146 @kindex macro define
10147 @cindex user-defined macros
10148 @cindex defining macros interactively
10149 @cindex macros, user-defined
10150 @item macro define @var{macro} @var{replacement-list}
10151 @itemx macro define @var{macro}(@var{arglist}) @var{replacement-list}
10152 Introduce a definition for a preprocessor macro named @var{macro},
10153 invocations of which are replaced by the tokens given in
10154 @var{replacement-list}. The first form of this command defines an
10155 ``object-like'' macro, which takes no arguments; the second form
10156 defines a ``function-like'' macro, which takes the arguments given in
10159 A definition introduced by this command is in scope in every
10160 expression evaluated in @value{GDBN}, until it is removed with the
10161 @code{macro undef} command, described below. The definition overrides
10162 all definitions for @var{macro} present in the program being debugged,
10163 as well as any previous user-supplied definition.
10165 @kindex macro undef
10166 @item macro undef @var{macro}
10167 Remove any user-supplied definition for the macro named @var{macro}.
10168 This command only affects definitions provided with the @code{macro
10169 define} command, described above; it cannot remove definitions present
10170 in the program being debugged.
10174 List all the macros defined using the @code{macro define} command.
10177 @cindex macros, example of debugging with
10178 Here is a transcript showing the above commands in action. First, we
10179 show our source files:
10184 #include "sample.h"
10187 #define ADD(x) (M + x)
10192 printf ("Hello, world!\n");
10194 printf ("We're so creative.\n");
10196 printf ("Goodbye, world!\n");
10203 Now, we compile the program using the @sc{gnu} C compiler,
10204 @value{NGCC}. We pass the @option{-gdwarf-2}@footnote{This is the
10205 minimum. Recent versions of @value{NGCC} support @option{-gdwarf-3}
10206 and @option{-gdwarf-4}; we recommend always choosing the most recent
10207 version of DWARF.} @emph{and} @option{-g3} flags to ensure the compiler
10208 includes information about preprocessor macros in the debugging
10212 $ gcc -gdwarf-2 -g3 sample.c -o sample
10216 Now, we start @value{GDBN} on our sample program:
10220 GNU gdb 2002-05-06-cvs
10221 Copyright 2002 Free Software Foundation, Inc.
10222 GDB is free software, @dots{}
10226 We can expand macros and examine their definitions, even when the
10227 program is not running. @value{GDBN} uses the current listing position
10228 to decide which macro definitions are in scope:
10231 (@value{GDBP}) list main
10234 5 #define ADD(x) (M + x)
10239 10 printf ("Hello, world!\n");
10241 12 printf ("We're so creative.\n");
10242 (@value{GDBP}) info macro ADD
10243 Defined at /home/jimb/gdb/macros/play/sample.c:5
10244 #define ADD(x) (M + x)
10245 (@value{GDBP}) info macro Q
10246 Defined at /home/jimb/gdb/macros/play/sample.h:1
10247 included at /home/jimb/gdb/macros/play/sample.c:2
10249 (@value{GDBP}) macro expand ADD(1)
10250 expands to: (42 + 1)
10251 (@value{GDBP}) macro expand-once ADD(1)
10252 expands to: once (M + 1)
10256 In the example above, note that @code{macro expand-once} expands only
10257 the macro invocation explicit in the original text --- the invocation of
10258 @code{ADD} --- but does not expand the invocation of the macro @code{M},
10259 which was introduced by @code{ADD}.
10261 Once the program is running, @value{GDBN} uses the macro definitions in
10262 force at the source line of the current stack frame:
10265 (@value{GDBP}) break main
10266 Breakpoint 1 at 0x8048370: file sample.c, line 10.
10268 Starting program: /home/jimb/gdb/macros/play/sample
10270 Breakpoint 1, main () at sample.c:10
10271 10 printf ("Hello, world!\n");
10275 At line 10, the definition of the macro @code{N} at line 9 is in force:
10278 (@value{GDBP}) info macro N
10279 Defined at /home/jimb/gdb/macros/play/sample.c:9
10281 (@value{GDBP}) macro expand N Q M
10282 expands to: 28 < 42
10283 (@value{GDBP}) print N Q M
10288 As we step over directives that remove @code{N}'s definition, and then
10289 give it a new definition, @value{GDBN} finds the definition (or lack
10290 thereof) in force at each point:
10293 (@value{GDBP}) next
10295 12 printf ("We're so creative.\n");
10296 (@value{GDBP}) info macro N
10297 The symbol `N' has no definition as a C/C++ preprocessor macro
10298 at /home/jimb/gdb/macros/play/sample.c:12
10299 (@value{GDBP}) next
10301 14 printf ("Goodbye, world!\n");
10302 (@value{GDBP}) info macro N
10303 Defined at /home/jimb/gdb/macros/play/sample.c:13
10305 (@value{GDBP}) macro expand N Q M
10306 expands to: 1729 < 42
10307 (@value{GDBP}) print N Q M
10312 In addition to source files, macros can be defined on the compilation command
10313 line using the @option{-D@var{name}=@var{value}} syntax. For macros defined in
10314 such a way, @value{GDBN} displays the location of their definition as line zero
10315 of the source file submitted to the compiler.
10318 (@value{GDBP}) info macro __STDC__
10319 Defined at /home/jimb/gdb/macros/play/sample.c:0
10326 @chapter Tracepoints
10327 @c This chapter is based on the documentation written by Michael
10328 @c Snyder, David Taylor, Jim Blandy, and Elena Zannoni.
10330 @cindex tracepoints
10331 In some applications, it is not feasible for the debugger to interrupt
10332 the program's execution long enough for the developer to learn
10333 anything helpful about its behavior. If the program's correctness
10334 depends on its real-time behavior, delays introduced by a debugger
10335 might cause the program to change its behavior drastically, or perhaps
10336 fail, even when the code itself is correct. It is useful to be able
10337 to observe the program's behavior without interrupting it.
10339 Using @value{GDBN}'s @code{trace} and @code{collect} commands, you can
10340 specify locations in the program, called @dfn{tracepoints}, and
10341 arbitrary expressions to evaluate when those tracepoints are reached.
10342 Later, using the @code{tfind} command, you can examine the values
10343 those expressions had when the program hit the tracepoints. The
10344 expressions may also denote objects in memory---structures or arrays,
10345 for example---whose values @value{GDBN} should record; while visiting
10346 a particular tracepoint, you may inspect those objects as if they were
10347 in memory at that moment. However, because @value{GDBN} records these
10348 values without interacting with you, it can do so quickly and
10349 unobtrusively, hopefully not disturbing the program's behavior.
10351 The tracepoint facility is currently available only for remote
10352 targets. @xref{Targets}. In addition, your remote target must know
10353 how to collect trace data. This functionality is implemented in the
10354 remote stub; however, none of the stubs distributed with @value{GDBN}
10355 support tracepoints as of this writing. The format of the remote
10356 packets used to implement tracepoints are described in @ref{Tracepoint
10359 It is also possible to get trace data from a file, in a manner reminiscent
10360 of corefiles; you specify the filename, and use @code{tfind} to search
10361 through the file. @xref{Trace Files}, for more details.
10363 This chapter describes the tracepoint commands and features.
10366 * Set Tracepoints::
10367 * Analyze Collected Data::
10368 * Tracepoint Variables::
10372 @node Set Tracepoints
10373 @section Commands to Set Tracepoints
10375 Before running such a @dfn{trace experiment}, an arbitrary number of
10376 tracepoints can be set. A tracepoint is actually a special type of
10377 breakpoint (@pxref{Set Breaks}), so you can manipulate it using
10378 standard breakpoint commands. For instance, as with breakpoints,
10379 tracepoint numbers are successive integers starting from one, and many
10380 of the commands associated with tracepoints take the tracepoint number
10381 as their argument, to identify which tracepoint to work on.
10383 For each tracepoint, you can specify, in advance, some arbitrary set
10384 of data that you want the target to collect in the trace buffer when
10385 it hits that tracepoint. The collected data can include registers,
10386 local variables, or global data. Later, you can use @value{GDBN}
10387 commands to examine the values these data had at the time the
10388 tracepoint was hit.
10390 Tracepoints do not support every breakpoint feature. Ignore counts on
10391 tracepoints have no effect, and tracepoints cannot run @value{GDBN}
10392 commands when they are hit. Tracepoints may not be thread-specific
10395 @cindex fast tracepoints
10396 Some targets may support @dfn{fast tracepoints}, which are inserted in
10397 a different way (such as with a jump instead of a trap), that is
10398 faster but possibly restricted in where they may be installed.
10400 @cindex static tracepoints
10401 @cindex markers, static tracepoints
10402 @cindex probing markers, static tracepoints
10403 Regular and fast tracepoints are dynamic tracing facilities, meaning
10404 that they can be used to insert tracepoints at (almost) any location
10405 in the target. Some targets may also support controlling @dfn{static
10406 tracepoints} from @value{GDBN}. With static tracing, a set of
10407 instrumentation points, also known as @dfn{markers}, are embedded in
10408 the target program, and can be activated or deactivated by name or
10409 address. These are usually placed at locations which facilitate
10410 investigating what the target is actually doing. @value{GDBN}'s
10411 support for static tracing includes being able to list instrumentation
10412 points, and attach them with @value{GDBN} defined high level
10413 tracepoints that expose the whole range of convenience of
10414 @value{GDBN}'s tracepoints support. Namely, support for collecting
10415 registers values and values of global or local (to the instrumentation
10416 point) variables; tracepoint conditions and trace state variables.
10417 The act of installing a @value{GDBN} static tracepoint on an
10418 instrumentation point, or marker, is referred to as @dfn{probing} a
10419 static tracepoint marker.
10421 @code{gdbserver} supports tracepoints on some target systems.
10422 @xref{Server,,Tracepoints support in @code{gdbserver}}.
10424 This section describes commands to set tracepoints and associated
10425 conditions and actions.
10428 * Create and Delete Tracepoints::
10429 * Enable and Disable Tracepoints::
10430 * Tracepoint Passcounts::
10431 * Tracepoint Conditions::
10432 * Trace State Variables::
10433 * Tracepoint Actions::
10434 * Listing Tracepoints::
10435 * Listing Static Tracepoint Markers::
10436 * Starting and Stopping Trace Experiments::
10437 * Tracepoint Restrictions::
10440 @node Create and Delete Tracepoints
10441 @subsection Create and Delete Tracepoints
10444 @cindex set tracepoint
10446 @item trace @var{location}
10447 The @code{trace} command is very similar to the @code{break} command.
10448 Its argument @var{location} can be a source line, a function name, or
10449 an address in the target program. @xref{Specify Location}. The
10450 @code{trace} command defines a tracepoint, which is a point in the
10451 target program where the debugger will briefly stop, collect some
10452 data, and then allow the program to continue. Setting a tracepoint or
10453 changing its actions takes effect immediately if the remote stub
10454 supports the @samp{InstallInTrace} feature (@pxref{install tracepoint
10456 If remote stub doesn't support the @samp{InstallInTrace} feature, all
10457 these changes don't take effect until the next @code{tstart}
10458 command, and once a trace experiment is running, further changes will
10459 not have any effect until the next trace experiment starts. In addition,
10460 @value{GDBN} supports @dfn{pending tracepoints}---tracepoints whose
10461 address is not yet resolved. (This is similar to pending breakpoints.)
10462 Pending tracepoints are not downloaded to the target and not installed
10463 until they are resolved. The resolution of pending tracepoints requires
10464 @value{GDBN} support---when debugging with the remote target, and
10465 @value{GDBN} disconnects from the remote stub (@pxref{disconnected
10466 tracing}), pending tracepoints can not be resolved (and downloaded to
10467 the remote stub) while @value{GDBN} is disconnected.
10469 Here are some examples of using the @code{trace} command:
10472 (@value{GDBP}) @b{trace foo.c:121} // a source file and line number
10474 (@value{GDBP}) @b{trace +2} // 2 lines forward
10476 (@value{GDBP}) @b{trace my_function} // first source line of function
10478 (@value{GDBP}) @b{trace *my_function} // EXACT start address of function
10480 (@value{GDBP}) @b{trace *0x2117c4} // an address
10484 You can abbreviate @code{trace} as @code{tr}.
10486 @item trace @var{location} if @var{cond}
10487 Set a tracepoint with condition @var{cond}; evaluate the expression
10488 @var{cond} each time the tracepoint is reached, and collect data only
10489 if the value is nonzero---that is, if @var{cond} evaluates as true.
10490 @xref{Tracepoint Conditions, ,Tracepoint Conditions}, for more
10491 information on tracepoint conditions.
10493 @item ftrace @var{location} [ if @var{cond} ]
10494 @cindex set fast tracepoint
10495 @cindex fast tracepoints, setting
10497 The @code{ftrace} command sets a fast tracepoint. For targets that
10498 support them, fast tracepoints will use a more efficient but possibly
10499 less general technique to trigger data collection, such as a jump
10500 instruction instead of a trap, or some sort of hardware support. It
10501 may not be possible to create a fast tracepoint at the desired
10502 location, in which case the command will exit with an explanatory
10505 @value{GDBN} handles arguments to @code{ftrace} exactly as for
10508 On 32-bit x86-architecture systems, fast tracepoints normally need to
10509 be placed at an instruction that is 5 bytes or longer, but can be
10510 placed at 4-byte instructions if the low 64K of memory of the target
10511 program is available to install trampolines. Some Unix-type systems,
10512 such as @sc{gnu}/Linux, exclude low addresses from the program's
10513 address space; but for instance with the Linux kernel it is possible
10514 to let @value{GDBN} use this area by doing a @command{sysctl} command
10515 to set the @code{mmap_min_addr} kernel parameter, as in
10518 sudo sysctl -w vm.mmap_min_addr=32768
10522 which sets the low address to 32K, which leaves plenty of room for
10523 trampolines. The minimum address should be set to a page boundary.
10525 @item strace @var{location} [ if @var{cond} ]
10526 @cindex set static tracepoint
10527 @cindex static tracepoints, setting
10528 @cindex probe static tracepoint marker
10530 The @code{strace} command sets a static tracepoint. For targets that
10531 support it, setting a static tracepoint probes a static
10532 instrumentation point, or marker, found at @var{location}. It may not
10533 be possible to set a static tracepoint at the desired location, in
10534 which case the command will exit with an explanatory message.
10536 @value{GDBN} handles arguments to @code{strace} exactly as for
10537 @code{trace}, with the addition that the user can also specify
10538 @code{-m @var{marker}} as @var{location}. This probes the marker
10539 identified by the @var{marker} string identifier. This identifier
10540 depends on the static tracepoint backend library your program is
10541 using. You can find all the marker identifiers in the @samp{ID} field
10542 of the @code{info static-tracepoint-markers} command output.
10543 @xref{Listing Static Tracepoint Markers,,Listing Static Tracepoint
10544 Markers}. For example, in the following small program using the UST
10550 trace_mark(ust, bar33, "str %s", "FOOBAZ");
10555 the marker id is composed of joining the first two arguments to the
10556 @code{trace_mark} call with a slash, which translates to:
10559 (@value{GDBP}) info static-tracepoint-markers
10560 Cnt Enb ID Address What
10561 1 n ust/bar33 0x0000000000400ddc in main at stexample.c:22
10567 so you may probe the marker above with:
10570 (@value{GDBP}) strace -m ust/bar33
10573 Static tracepoints accept an extra collect action --- @code{collect
10574 $_sdata}. This collects arbitrary user data passed in the probe point
10575 call to the tracing library. In the UST example above, you'll see
10576 that the third argument to @code{trace_mark} is a printf-like format
10577 string. The user data is then the result of running that formating
10578 string against the following arguments. Note that @code{info
10579 static-tracepoint-markers} command output lists that format string in
10580 the @samp{Data:} field.
10582 You can inspect this data when analyzing the trace buffer, by printing
10583 the $_sdata variable like any other variable available to
10584 @value{GDBN}. @xref{Tracepoint Actions,,Tracepoint Action Lists}.
10587 @cindex last tracepoint number
10588 @cindex recent tracepoint number
10589 @cindex tracepoint number
10590 The convenience variable @code{$tpnum} records the tracepoint number
10591 of the most recently set tracepoint.
10593 @kindex delete tracepoint
10594 @cindex tracepoint deletion
10595 @item delete tracepoint @r{[}@var{num}@r{]}
10596 Permanently delete one or more tracepoints. With no argument, the
10597 default is to delete all tracepoints. Note that the regular
10598 @code{delete} command can remove tracepoints also.
10603 (@value{GDBP}) @b{delete trace 1 2 3} // remove three tracepoints
10605 (@value{GDBP}) @b{delete trace} // remove all tracepoints
10609 You can abbreviate this command as @code{del tr}.
10612 @node Enable and Disable Tracepoints
10613 @subsection Enable and Disable Tracepoints
10615 These commands are deprecated; they are equivalent to plain @code{disable} and @code{enable}.
10618 @kindex disable tracepoint
10619 @item disable tracepoint @r{[}@var{num}@r{]}
10620 Disable tracepoint @var{num}, or all tracepoints if no argument
10621 @var{num} is given. A disabled tracepoint will have no effect during
10622 a trace experiment, but it is not forgotten. You can re-enable
10623 a disabled tracepoint using the @code{enable tracepoint} command.
10624 If the command is issued during a trace experiment and the debug target
10625 has support for disabling tracepoints during a trace experiment, then the
10626 change will be effective immediately. Otherwise, it will be applied to the
10627 next trace experiment.
10629 @kindex enable tracepoint
10630 @item enable tracepoint @r{[}@var{num}@r{]}
10631 Enable tracepoint @var{num}, or all tracepoints. If this command is
10632 issued during a trace experiment and the debug target supports enabling
10633 tracepoints during a trace experiment, then the enabled tracepoints will
10634 become effective immediately. Otherwise, they will become effective the
10635 next time a trace experiment is run.
10638 @node Tracepoint Passcounts
10639 @subsection Tracepoint Passcounts
10643 @cindex tracepoint pass count
10644 @item passcount @r{[}@var{n} @r{[}@var{num}@r{]]}
10645 Set the @dfn{passcount} of a tracepoint. The passcount is a way to
10646 automatically stop a trace experiment. If a tracepoint's passcount is
10647 @var{n}, then the trace experiment will be automatically stopped on
10648 the @var{n}'th time that tracepoint is hit. If the tracepoint number
10649 @var{num} is not specified, the @code{passcount} command sets the
10650 passcount of the most recently defined tracepoint. If no passcount is
10651 given, the trace experiment will run until stopped explicitly by the
10657 (@value{GDBP}) @b{passcount 5 2} // Stop on the 5th execution of
10658 @exdent @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @code{// tracepoint 2}
10660 (@value{GDBP}) @b{passcount 12} // Stop on the 12th execution of the
10661 @exdent @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @code{// most recently defined tracepoint.}
10662 (@value{GDBP}) @b{trace foo}
10663 (@value{GDBP}) @b{pass 3}
10664 (@value{GDBP}) @b{trace bar}
10665 (@value{GDBP}) @b{pass 2}
10666 (@value{GDBP}) @b{trace baz}
10667 (@value{GDBP}) @b{pass 1} // Stop tracing when foo has been
10668 @exdent @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @code{// executed 3 times OR when bar has}
10669 @exdent @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @code{// been executed 2 times}
10670 @exdent @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @code{// OR when baz has been executed 1 time.}
10674 @node Tracepoint Conditions
10675 @subsection Tracepoint Conditions
10676 @cindex conditional tracepoints
10677 @cindex tracepoint conditions
10679 The simplest sort of tracepoint collects data every time your program
10680 reaches a specified place. You can also specify a @dfn{condition} for
10681 a tracepoint. A condition is just a Boolean expression in your
10682 programming language (@pxref{Expressions, ,Expressions}). A
10683 tracepoint with a condition evaluates the expression each time your
10684 program reaches it, and data collection happens only if the condition
10687 Tracepoint conditions can be specified when a tracepoint is set, by
10688 using @samp{if} in the arguments to the @code{trace} command.
10689 @xref{Create and Delete Tracepoints, ,Setting Tracepoints}. They can
10690 also be set or changed at any time with the @code{condition} command,
10691 just as with breakpoints.
10693 Unlike breakpoint conditions, @value{GDBN} does not actually evaluate
10694 the conditional expression itself. Instead, @value{GDBN} encodes the
10695 expression into an agent expression (@pxref{Agent Expressions})
10696 suitable for execution on the target, independently of @value{GDBN}.
10697 Global variables become raw memory locations, locals become stack
10698 accesses, and so forth.
10700 For instance, suppose you have a function that is usually called
10701 frequently, but should not be called after an error has occurred. You
10702 could use the following tracepoint command to collect data about calls
10703 of that function that happen while the error code is propagating
10704 through the program; an unconditional tracepoint could end up
10705 collecting thousands of useless trace frames that you would have to
10709 (@value{GDBP}) @kbd{trace normal_operation if errcode > 0}
10712 @node Trace State Variables
10713 @subsection Trace State Variables
10714 @cindex trace state variables
10716 A @dfn{trace state variable} is a special type of variable that is
10717 created and managed by target-side code. The syntax is the same as
10718 that for GDB's convenience variables (a string prefixed with ``$''),
10719 but they are stored on the target. They must be created explicitly,
10720 using a @code{tvariable} command. They are always 64-bit signed
10723 Trace state variables are remembered by @value{GDBN}, and downloaded
10724 to the target along with tracepoint information when the trace
10725 experiment starts. There are no intrinsic limits on the number of
10726 trace state variables, beyond memory limitations of the target.
10728 @cindex convenience variables, and trace state variables
10729 Although trace state variables are managed by the target, you can use
10730 them in print commands and expressions as if they were convenience
10731 variables; @value{GDBN} will get the current value from the target
10732 while the trace experiment is running. Trace state variables share
10733 the same namespace as other ``$'' variables, which means that you
10734 cannot have trace state variables with names like @code{$23} or
10735 @code{$pc}, nor can you have a trace state variable and a convenience
10736 variable with the same name.
10740 @item tvariable $@var{name} [ = @var{expression} ]
10742 The @code{tvariable} command creates a new trace state variable named
10743 @code{$@var{name}}, and optionally gives it an initial value of
10744 @var{expression}. @var{expression} is evaluated when this command is
10745 entered; the result will be converted to an integer if possible,
10746 otherwise @value{GDBN} will report an error. A subsequent
10747 @code{tvariable} command specifying the same name does not create a
10748 variable, but instead assigns the supplied initial value to the
10749 existing variable of that name, overwriting any previous initial
10750 value. The default initial value is 0.
10752 @item info tvariables
10753 @kindex info tvariables
10754 List all the trace state variables along with their initial values.
10755 Their current values may also be displayed, if the trace experiment is
10758 @item delete tvariable @r{[} $@var{name} @dots{} @r{]}
10759 @kindex delete tvariable
10760 Delete the given trace state variables, or all of them if no arguments
10765 @node Tracepoint Actions
10766 @subsection Tracepoint Action Lists
10770 @cindex tracepoint actions
10771 @item actions @r{[}@var{num}@r{]}
10772 This command will prompt for a list of actions to be taken when the
10773 tracepoint is hit. If the tracepoint number @var{num} is not
10774 specified, this command sets the actions for the one that was most
10775 recently defined (so that you can define a tracepoint and then say
10776 @code{actions} without bothering about its number). You specify the
10777 actions themselves on the following lines, one action at a time, and
10778 terminate the actions list with a line containing just @code{end}. So
10779 far, the only defined actions are @code{collect}, @code{teval}, and
10780 @code{while-stepping}.
10782 @code{actions} is actually equivalent to @code{commands} (@pxref{Break
10783 Commands, ,Breakpoint Command Lists}), except that only the defined
10784 actions are allowed; any other @value{GDBN} command is rejected.
10786 @cindex remove actions from a tracepoint
10787 To remove all actions from a tracepoint, type @samp{actions @var{num}}
10788 and follow it immediately with @samp{end}.
10791 (@value{GDBP}) @b{collect @var{data}} // collect some data
10793 (@value{GDBP}) @b{while-stepping 5} // single-step 5 times, collect data
10795 (@value{GDBP}) @b{end} // signals the end of actions.
10798 In the following example, the action list begins with @code{collect}
10799 commands indicating the things to be collected when the tracepoint is
10800 hit. Then, in order to single-step and collect additional data
10801 following the tracepoint, a @code{while-stepping} command is used,
10802 followed by the list of things to be collected after each step in a
10803 sequence of single steps. The @code{while-stepping} command is
10804 terminated by its own separate @code{end} command. Lastly, the action
10805 list is terminated by an @code{end} command.
10808 (@value{GDBP}) @b{trace foo}
10809 (@value{GDBP}) @b{actions}
10810 Enter actions for tracepoint 1, one per line:
10813 > while-stepping 12
10814 > collect $pc, arr[i]
10819 @kindex collect @r{(tracepoints)}
10820 @item collect@r{[}/@var{mods}@r{]} @var{expr1}, @var{expr2}, @dots{}
10821 Collect values of the given expressions when the tracepoint is hit.
10822 This command accepts a comma-separated list of any valid expressions.
10823 In addition to global, static, or local variables, the following
10824 special arguments are supported:
10828 Collect all registers.
10831 Collect all function arguments.
10834 Collect all local variables.
10837 Collect the return address. This is helpful if you want to see more
10841 @vindex $_sdata@r{, collect}
10842 Collect static tracepoint marker specific data. Only available for
10843 static tracepoints. @xref{Tracepoint Actions,,Tracepoint Action
10844 Lists}. On the UST static tracepoints library backend, an
10845 instrumentation point resembles a @code{printf} function call. The
10846 tracing library is able to collect user specified data formatted to a
10847 character string using the format provided by the programmer that
10848 instrumented the program. Other backends have similar mechanisms.
10849 Here's an example of a UST marker call:
10852 const char master_name[] = "$your_name";
10853 trace_mark(channel1, marker1, "hello %s", master_name)
10856 In this case, collecting @code{$_sdata} collects the string
10857 @samp{hello $yourname}. When analyzing the trace buffer, you can
10858 inspect @samp{$_sdata} like any other variable available to
10862 You can give several consecutive @code{collect} commands, each one
10863 with a single argument, or one @code{collect} command with several
10864 arguments separated by commas; the effect is the same.
10866 The optional @var{mods} changes the usual handling of the arguments.
10867 @code{s} requests that pointers to chars be handled as strings, in
10868 particular collecting the contents of the memory being pointed at, up
10869 to the first zero. The upper bound is by default the value of the
10870 @code{print elements} variable; if @code{s} is followed by a decimal
10871 number, that is the upper bound instead. So for instance
10872 @samp{collect/s25 mystr} collects as many as 25 characters at
10875 The command @code{info scope} (@pxref{Symbols, info scope}) is
10876 particularly useful for figuring out what data to collect.
10878 @kindex teval @r{(tracepoints)}
10879 @item teval @var{expr1}, @var{expr2}, @dots{}
10880 Evaluate the given expressions when the tracepoint is hit. This
10881 command accepts a comma-separated list of expressions. The results
10882 are discarded, so this is mainly useful for assigning values to trace
10883 state variables (@pxref{Trace State Variables}) without adding those
10884 values to the trace buffer, as would be the case if the @code{collect}
10887 @kindex while-stepping @r{(tracepoints)}
10888 @item while-stepping @var{n}
10889 Perform @var{n} single-step instruction traces after the tracepoint,
10890 collecting new data after each step. The @code{while-stepping}
10891 command is followed by the list of what to collect while stepping
10892 (followed by its own @code{end} command):
10895 > while-stepping 12
10896 > collect $regs, myglobal
10902 Note that @code{$pc} is not automatically collected by
10903 @code{while-stepping}; you need to explicitly collect that register if
10904 you need it. You may abbreviate @code{while-stepping} as @code{ws} or
10907 @item set default-collect @var{expr1}, @var{expr2}, @dots{}
10908 @kindex set default-collect
10909 @cindex default collection action
10910 This variable is a list of expressions to collect at each tracepoint
10911 hit. It is effectively an additional @code{collect} action prepended
10912 to every tracepoint action list. The expressions are parsed
10913 individually for each tracepoint, so for instance a variable named
10914 @code{xyz} may be interpreted as a global for one tracepoint, and a
10915 local for another, as appropriate to the tracepoint's location.
10917 @item show default-collect
10918 @kindex show default-collect
10919 Show the list of expressions that are collected by default at each
10924 @node Listing Tracepoints
10925 @subsection Listing Tracepoints
10928 @kindex info tracepoints @r{[}@var{n}@dots{}@r{]}
10929 @kindex info tp @r{[}@var{n}@dots{}@r{]}
10930 @cindex information about tracepoints
10931 @item info tracepoints @r{[}@var{num}@dots{}@r{]}
10932 Display information about the tracepoint @var{num}. If you don't
10933 specify a tracepoint number, displays information about all the
10934 tracepoints defined so far. The format is similar to that used for
10935 @code{info breakpoints}; in fact, @code{info tracepoints} is the same
10936 command, simply restricting itself to tracepoints.
10938 A tracepoint's listing may include additional information specific to
10943 its passcount as given by the @code{passcount @var{n}} command
10947 (@value{GDBP}) @b{info trace}
10948 Num Type Disp Enb Address What
10949 1 tracepoint keep y 0x0804ab57 in foo() at main.cxx:7
10951 collect globfoo, $regs
10960 This command can be abbreviated @code{info tp}.
10963 @node Listing Static Tracepoint Markers
10964 @subsection Listing Static Tracepoint Markers
10967 @kindex info static-tracepoint-markers
10968 @cindex information about static tracepoint markers
10969 @item info static-tracepoint-markers
10970 Display information about all static tracepoint markers defined in the
10973 For each marker, the following columns are printed:
10977 An incrementing counter, output to help readability. This is not a
10980 The marker ID, as reported by the target.
10981 @item Enabled or Disabled
10982 Probed markers are tagged with @samp{y}. @samp{n} identifies marks
10983 that are not enabled.
10985 Where the marker is in your program, as a memory address.
10987 Where the marker is in the source for your program, as a file and line
10988 number. If the debug information included in the program does not
10989 allow @value{GDBN} to locate the source of the marker, this column
10990 will be left blank.
10994 In addition, the following information may be printed for each marker:
10998 User data passed to the tracing library by the marker call. In the
10999 UST backend, this is the format string passed as argument to the
11001 @item Static tracepoints probing the marker
11002 The list of static tracepoints attached to the marker.
11006 (@value{GDBP}) info static-tracepoint-markers
11007 Cnt ID Enb Address What
11008 1 ust/bar2 y 0x0000000000400e1a in main at stexample.c:25
11009 Data: number1 %d number2 %d
11010 Probed by static tracepoints: #2
11011 2 ust/bar33 n 0x0000000000400c87 in main at stexample.c:24
11017 @node Starting and Stopping Trace Experiments
11018 @subsection Starting and Stopping Trace Experiments
11021 @kindex tstart [ @var{notes} ]
11022 @cindex start a new trace experiment
11023 @cindex collected data discarded
11025 This command starts the trace experiment, and begins collecting data.
11026 It has the side effect of discarding all the data collected in the
11027 trace buffer during the previous trace experiment. If any arguments
11028 are supplied, they are taken as a note and stored with the trace
11029 experiment's state. The notes may be arbitrary text, and are
11030 especially useful with disconnected tracing in a multi-user context;
11031 the notes can explain what the trace is doing, supply user contact
11032 information, and so forth.
11034 @kindex tstop [ @var{notes} ]
11035 @cindex stop a running trace experiment
11037 This command stops the trace experiment. If any arguments are
11038 supplied, they are recorded with the experiment as a note. This is
11039 useful if you are stopping a trace started by someone else, for
11040 instance if the trace is interfering with the system's behavior and
11041 needs to be stopped quickly.
11043 @strong{Note}: a trace experiment and data collection may stop
11044 automatically if any tracepoint's passcount is reached
11045 (@pxref{Tracepoint Passcounts}), or if the trace buffer becomes full.
11048 @cindex status of trace data collection
11049 @cindex trace experiment, status of
11051 This command displays the status of the current trace data
11055 Here is an example of the commands we described so far:
11058 (@value{GDBP}) @b{trace gdb_c_test}
11059 (@value{GDBP}) @b{actions}
11060 Enter actions for tracepoint #1, one per line.
11061 > collect $regs,$locals,$args
11062 > while-stepping 11
11066 (@value{GDBP}) @b{tstart}
11067 [time passes @dots{}]
11068 (@value{GDBP}) @b{tstop}
11071 @anchor{disconnected tracing}
11072 @cindex disconnected tracing
11073 You can choose to continue running the trace experiment even if
11074 @value{GDBN} disconnects from the target, voluntarily or
11075 involuntarily. For commands such as @code{detach}, the debugger will
11076 ask what you want to do with the trace. But for unexpected
11077 terminations (@value{GDBN} crash, network outage), it would be
11078 unfortunate to lose hard-won trace data, so the variable
11079 @code{disconnected-tracing} lets you decide whether the trace should
11080 continue running without @value{GDBN}.
11083 @item set disconnected-tracing on
11084 @itemx set disconnected-tracing off
11085 @kindex set disconnected-tracing
11086 Choose whether a tracing run should continue to run if @value{GDBN}
11087 has disconnected from the target. Note that @code{detach} or
11088 @code{quit} will ask you directly what to do about a running trace no
11089 matter what this variable's setting, so the variable is mainly useful
11090 for handling unexpected situations, such as loss of the network.
11092 @item show disconnected-tracing
11093 @kindex show disconnected-tracing
11094 Show the current choice for disconnected tracing.
11098 When you reconnect to the target, the trace experiment may or may not
11099 still be running; it might have filled the trace buffer in the
11100 meantime, or stopped for one of the other reasons. If it is running,
11101 it will continue after reconnection.
11103 Upon reconnection, the target will upload information about the
11104 tracepoints in effect. @value{GDBN} will then compare that
11105 information to the set of tracepoints currently defined, and attempt
11106 to match them up, allowing for the possibility that the numbers may
11107 have changed due to creation and deletion in the meantime. If one of
11108 the target's tracepoints does not match any in @value{GDBN}, the
11109 debugger will create a new tracepoint, so that you have a number with
11110 which to specify that tracepoint. This matching-up process is
11111 necessarily heuristic, and it may result in useless tracepoints being
11112 created; you may simply delete them if they are of no use.
11114 @cindex circular trace buffer
11115 If your target agent supports a @dfn{circular trace buffer}, then you
11116 can run a trace experiment indefinitely without filling the trace
11117 buffer; when space runs out, the agent deletes already-collected trace
11118 frames, oldest first, until there is enough room to continue
11119 collecting. This is especially useful if your tracepoints are being
11120 hit too often, and your trace gets terminated prematurely because the
11121 buffer is full. To ask for a circular trace buffer, simply set
11122 @samp{circular-trace-buffer} to on. You can set this at any time,
11123 including during tracing; if the agent can do it, it will change
11124 buffer handling on the fly, otherwise it will not take effect until
11128 @item set circular-trace-buffer on
11129 @itemx set circular-trace-buffer off
11130 @kindex set circular-trace-buffer
11131 Choose whether a tracing run should use a linear or circular buffer
11132 for trace data. A linear buffer will not lose any trace data, but may
11133 fill up prematurely, while a circular buffer will discard old trace
11134 data, but it will have always room for the latest tracepoint hits.
11136 @item show circular-trace-buffer
11137 @kindex show circular-trace-buffer
11138 Show the current choice for the trace buffer. Note that this may not
11139 match the agent's current buffer handling, nor is it guaranteed to
11140 match the setting that might have been in effect during a past run,
11141 for instance if you are looking at frames from a trace file.
11146 @item set trace-user @var{text}
11147 @kindex set trace-user
11149 @item show trace-user
11150 @kindex show trace-user
11152 @item set trace-notes @var{text}
11153 @kindex set trace-notes
11154 Set the trace run's notes.
11156 @item show trace-notes
11157 @kindex show trace-notes
11158 Show the trace run's notes.
11160 @item set trace-stop-notes @var{text}
11161 @kindex set trace-stop-notes
11162 Set the trace run's stop notes. The handling of the note is as for
11163 @code{tstop} arguments; the set command is convenient way to fix a
11164 stop note that is mistaken or incomplete.
11166 @item show trace-stop-notes
11167 @kindex show trace-stop-notes
11168 Show the trace run's stop notes.
11172 @node Tracepoint Restrictions
11173 @subsection Tracepoint Restrictions
11175 @cindex tracepoint restrictions
11176 There are a number of restrictions on the use of tracepoints. As
11177 described above, tracepoint data gathering occurs on the target
11178 without interaction from @value{GDBN}. Thus the full capabilities of
11179 the debugger are not available during data gathering, and then at data
11180 examination time, you will be limited by only having what was
11181 collected. The following items describe some common problems, but it
11182 is not exhaustive, and you may run into additional difficulties not
11188 Tracepoint expressions are intended to gather objects (lvalues). Thus
11189 the full flexibility of GDB's expression evaluator is not available.
11190 You cannot call functions, cast objects to aggregate types, access
11191 convenience variables or modify values (except by assignment to trace
11192 state variables). Some language features may implicitly call
11193 functions (for instance Objective-C fields with accessors), and therefore
11194 cannot be collected either.
11197 Collection of local variables, either individually or in bulk with
11198 @code{$locals} or @code{$args}, during @code{while-stepping} may
11199 behave erratically. The stepping action may enter a new scope (for
11200 instance by stepping into a function), or the location of the variable
11201 may change (for instance it is loaded into a register). The
11202 tracepoint data recorded uses the location information for the
11203 variables that is correct for the tracepoint location. When the
11204 tracepoint is created, it is not possible, in general, to determine
11205 where the steps of a @code{while-stepping} sequence will advance the
11206 program---particularly if a conditional branch is stepped.
11209 Collection of an incompletely-initialized or partially-destroyed object
11210 may result in something that @value{GDBN} cannot display, or displays
11211 in a misleading way.
11214 When @value{GDBN} displays a pointer to character it automatically
11215 dereferences the pointer to also display characters of the string
11216 being pointed to. However, collecting the pointer during tracing does
11217 not automatically collect the string. You need to explicitly
11218 dereference the pointer and provide size information if you want to
11219 collect not only the pointer, but the memory pointed to. For example,
11220 @code{*ptr@@50} can be used to collect the 50 element array pointed to
11224 It is not possible to collect a complete stack backtrace at a
11225 tracepoint. Instead, you may collect the registers and a few hundred
11226 bytes from the stack pointer with something like @code{*(unsigned char *)$esp@@300}
11227 (adjust to use the name of the actual stack pointer register on your
11228 target architecture, and the amount of stack you wish to capture).
11229 Then the @code{backtrace} command will show a partial backtrace when
11230 using a trace frame. The number of stack frames that can be examined
11231 depends on the sizes of the frames in the collected stack. Note that
11232 if you ask for a block so large that it goes past the bottom of the
11233 stack, the target agent may report an error trying to read from an
11237 If you do not collect registers at a tracepoint, @value{GDBN} can
11238 infer that the value of @code{$pc} must be the same as the address of
11239 the tracepoint and use that when you are looking at a trace frame
11240 for that tracepoint. However, this cannot work if the tracepoint has
11241 multiple locations (for instance if it was set in a function that was
11242 inlined), or if it has a @code{while-stepping} loop. In those cases
11243 @value{GDBN} will warn you that it can't infer @code{$pc}, and default
11248 @node Analyze Collected Data
11249 @section Using the Collected Data
11251 After the tracepoint experiment ends, you use @value{GDBN} commands
11252 for examining the trace data. The basic idea is that each tracepoint
11253 collects a trace @dfn{snapshot} every time it is hit and another
11254 snapshot every time it single-steps. All these snapshots are
11255 consecutively numbered from zero and go into a buffer, and you can
11256 examine them later. The way you examine them is to @dfn{focus} on a
11257 specific trace snapshot. When the remote stub is focused on a trace
11258 snapshot, it will respond to all @value{GDBN} requests for memory and
11259 registers by reading from the buffer which belongs to that snapshot,
11260 rather than from @emph{real} memory or registers of the program being
11261 debugged. This means that @strong{all} @value{GDBN} commands
11262 (@code{print}, @code{info registers}, @code{backtrace}, etc.) will
11263 behave as if we were currently debugging the program state as it was
11264 when the tracepoint occurred. Any requests for data that are not in
11265 the buffer will fail.
11268 * tfind:: How to select a trace snapshot
11269 * tdump:: How to display all data for a snapshot
11270 * save tracepoints:: How to save tracepoints for a future run
11274 @subsection @code{tfind @var{n}}
11277 @cindex select trace snapshot
11278 @cindex find trace snapshot
11279 The basic command for selecting a trace snapshot from the buffer is
11280 @code{tfind @var{n}}, which finds trace snapshot number @var{n},
11281 counting from zero. If no argument @var{n} is given, the next
11282 snapshot is selected.
11284 Here are the various forms of using the @code{tfind} command.
11288 Find the first snapshot in the buffer. This is a synonym for
11289 @code{tfind 0} (since 0 is the number of the first snapshot).
11292 Stop debugging trace snapshots, resume @emph{live} debugging.
11295 Same as @samp{tfind none}.
11298 No argument means find the next trace snapshot.
11301 Find the previous trace snapshot before the current one. This permits
11302 retracing earlier steps.
11304 @item tfind tracepoint @var{num}
11305 Find the next snapshot associated with tracepoint @var{num}. Search
11306 proceeds forward from the last examined trace snapshot. If no
11307 argument @var{num} is given, it means find the next snapshot collected
11308 for the same tracepoint as the current snapshot.
11310 @item tfind pc @var{addr}
11311 Find the next snapshot associated with the value @var{addr} of the
11312 program counter. Search proceeds forward from the last examined trace
11313 snapshot. If no argument @var{addr} is given, it means find the next
11314 snapshot with the same value of PC as the current snapshot.
11316 @item tfind outside @var{addr1}, @var{addr2}
11317 Find the next snapshot whose PC is outside the given range of
11318 addresses (exclusive).
11320 @item tfind range @var{addr1}, @var{addr2}
11321 Find the next snapshot whose PC is between @var{addr1} and
11322 @var{addr2} (inclusive).
11324 @item tfind line @r{[}@var{file}:@r{]}@var{n}
11325 Find the next snapshot associated with the source line @var{n}. If
11326 the optional argument @var{file} is given, refer to line @var{n} in
11327 that source file. Search proceeds forward from the last examined
11328 trace snapshot. If no argument @var{n} is given, it means find the
11329 next line other than the one currently being examined; thus saying
11330 @code{tfind line} repeatedly can appear to have the same effect as
11331 stepping from line to line in a @emph{live} debugging session.
11334 The default arguments for the @code{tfind} commands are specifically
11335 designed to make it easy to scan through the trace buffer. For
11336 instance, @code{tfind} with no argument selects the next trace
11337 snapshot, and @code{tfind -} with no argument selects the previous
11338 trace snapshot. So, by giving one @code{tfind} command, and then
11339 simply hitting @key{RET} repeatedly you can examine all the trace
11340 snapshots in order. Or, by saying @code{tfind -} and then hitting
11341 @key{RET} repeatedly you can examine the snapshots in reverse order.
11342 The @code{tfind line} command with no argument selects the snapshot
11343 for the next source line executed. The @code{tfind pc} command with
11344 no argument selects the next snapshot with the same program counter
11345 (PC) as the current frame. The @code{tfind tracepoint} command with
11346 no argument selects the next trace snapshot collected by the same
11347 tracepoint as the current one.
11349 In addition to letting you scan through the trace buffer manually,
11350 these commands make it easy to construct @value{GDBN} scripts that
11351 scan through the trace buffer and print out whatever collected data
11352 you are interested in. Thus, if we want to examine the PC, FP, and SP
11353 registers from each trace frame in the buffer, we can say this:
11356 (@value{GDBP}) @b{tfind start}
11357 (@value{GDBP}) @b{while ($trace_frame != -1)}
11358 > printf "Frame %d, PC = %08X, SP = %08X, FP = %08X\n", \
11359 $trace_frame, $pc, $sp, $fp
11363 Frame 0, PC = 0020DC64, SP = 0030BF3C, FP = 0030BF44
11364 Frame 1, PC = 0020DC6C, SP = 0030BF38, FP = 0030BF44
11365 Frame 2, PC = 0020DC70, SP = 0030BF34, FP = 0030BF44
11366 Frame 3, PC = 0020DC74, SP = 0030BF30, FP = 0030BF44
11367 Frame 4, PC = 0020DC78, SP = 0030BF2C, FP = 0030BF44
11368 Frame 5, PC = 0020DC7C, SP = 0030BF28, FP = 0030BF44
11369 Frame 6, PC = 0020DC80, SP = 0030BF24, FP = 0030BF44
11370 Frame 7, PC = 0020DC84, SP = 0030BF20, FP = 0030BF44
11371 Frame 8, PC = 0020DC88, SP = 0030BF1C, FP = 0030BF44
11372 Frame 9, PC = 0020DC8E, SP = 0030BF18, FP = 0030BF44
11373 Frame 10, PC = 00203F6C, SP = 0030BE3C, FP = 0030BF14
11376 Or, if we want to examine the variable @code{X} at each source line in
11380 (@value{GDBP}) @b{tfind start}
11381 (@value{GDBP}) @b{while ($trace_frame != -1)}
11382 > printf "Frame %d, X == %d\n", $trace_frame, X
11392 @subsection @code{tdump}
11394 @cindex dump all data collected at tracepoint
11395 @cindex tracepoint data, display
11397 This command takes no arguments. It prints all the data collected at
11398 the current trace snapshot.
11401 (@value{GDBP}) @b{trace 444}
11402 (@value{GDBP}) @b{actions}
11403 Enter actions for tracepoint #2, one per line:
11404 > collect $regs, $locals, $args, gdb_long_test
11407 (@value{GDBP}) @b{tstart}
11409 (@value{GDBP}) @b{tfind line 444}
11410 #0 gdb_test (p1=0x11, p2=0x22, p3=0x33, p4=0x44, p5=0x55, p6=0x66)
11412 444 printp( "%s: arguments = 0x%X 0x%X 0x%X 0x%X 0x%X 0x%X\n", )
11414 (@value{GDBP}) @b{tdump}
11415 Data collected at tracepoint 2, trace frame 1:
11416 d0 0xc4aa0085 -995491707
11420 d4 0x71aea3d 119204413
11423 d7 0x380035 3670069
11424 a0 0x19e24a 1696330
11425 a1 0x3000668 50333288
11427 a3 0x322000 3284992
11428 a4 0x3000698 50333336
11429 a5 0x1ad3cc 1758156
11430 fp 0x30bf3c 0x30bf3c
11431 sp 0x30bf34 0x30bf34
11433 pc 0x20b2c8 0x20b2c8
11437 p = 0x20e5b4 "gdb-test"
11444 gdb_long_test = 17 '\021'
11449 @code{tdump} works by scanning the tracepoint's current collection
11450 actions and printing the value of each expression listed. So
11451 @code{tdump} can fail, if after a run, you change the tracepoint's
11452 actions to mention variables that were not collected during the run.
11454 Also, for tracepoints with @code{while-stepping} loops, @code{tdump}
11455 uses the collected value of @code{$pc} to distinguish between trace
11456 frames that were collected at the tracepoint hit, and frames that were
11457 collected while stepping. This allows it to correctly choose whether
11458 to display the basic list of collections, or the collections from the
11459 body of the while-stepping loop. However, if @code{$pc} was not collected,
11460 then @code{tdump} will always attempt to dump using the basic collection
11461 list, and may fail if a while-stepping frame does not include all the
11462 same data that is collected at the tracepoint hit.
11463 @c This is getting pretty arcane, example would be good.
11465 @node save tracepoints
11466 @subsection @code{save tracepoints @var{filename}}
11467 @kindex save tracepoints
11468 @kindex save-tracepoints
11469 @cindex save tracepoints for future sessions
11471 This command saves all current tracepoint definitions together with
11472 their actions and passcounts, into a file @file{@var{filename}}
11473 suitable for use in a later debugging session. To read the saved
11474 tracepoint definitions, use the @code{source} command (@pxref{Command
11475 Files}). The @w{@code{save-tracepoints}} command is a deprecated
11476 alias for @w{@code{save tracepoints}}
11478 @node Tracepoint Variables
11479 @section Convenience Variables for Tracepoints
11480 @cindex tracepoint variables
11481 @cindex convenience variables for tracepoints
11484 @vindex $trace_frame
11485 @item (int) $trace_frame
11486 The current trace snapshot (a.k.a.@: @dfn{frame}) number, or -1 if no
11487 snapshot is selected.
11489 @vindex $tracepoint
11490 @item (int) $tracepoint
11491 The tracepoint for the current trace snapshot.
11493 @vindex $trace_line
11494 @item (int) $trace_line
11495 The line number for the current trace snapshot.
11497 @vindex $trace_file
11498 @item (char []) $trace_file
11499 The source file for the current trace snapshot.
11501 @vindex $trace_func
11502 @item (char []) $trace_func
11503 The name of the function containing @code{$tracepoint}.
11506 Note: @code{$trace_file} is not suitable for use in @code{printf},
11507 use @code{output} instead.
11509 Here's a simple example of using these convenience variables for
11510 stepping through all the trace snapshots and printing some of their
11511 data. Note that these are not the same as trace state variables,
11512 which are managed by the target.
11515 (@value{GDBP}) @b{tfind start}
11517 (@value{GDBP}) @b{while $trace_frame != -1}
11518 > output $trace_file
11519 > printf ", line %d (tracepoint #%d)\n", $trace_line, $tracepoint
11525 @section Using Trace Files
11526 @cindex trace files
11528 In some situations, the target running a trace experiment may no
11529 longer be available; perhaps it crashed, or the hardware was needed
11530 for a different activity. To handle these cases, you can arrange to
11531 dump the trace data into a file, and later use that file as a source
11532 of trace data, via the @code{target tfile} command.
11537 @item tsave [ -r ] @var{filename}
11538 Save the trace data to @var{filename}. By default, this command
11539 assumes that @var{filename} refers to the host filesystem, so if
11540 necessary @value{GDBN} will copy raw trace data up from the target and
11541 then save it. If the target supports it, you can also supply the
11542 optional argument @code{-r} (``remote'') to direct the target to save
11543 the data directly into @var{filename} in its own filesystem, which may be
11544 more efficient if the trace buffer is very large. (Note, however, that
11545 @code{target tfile} can only read from files accessible to the host.)
11547 @kindex target tfile
11549 @item target tfile @var{filename}
11550 Use the file named @var{filename} as a source of trace data. Commands
11551 that examine data work as they do with a live target, but it is not
11552 possible to run any new trace experiments. @code{tstatus} will report
11553 the state of the trace run at the moment the data was saved, as well
11554 as the current trace frame you are examining. @var{filename} must be
11555 on a filesystem accessible to the host.
11560 @chapter Debugging Programs That Use Overlays
11563 If your program is too large to fit completely in your target system's
11564 memory, you can sometimes use @dfn{overlays} to work around this
11565 problem. @value{GDBN} provides some support for debugging programs that
11569 * How Overlays Work:: A general explanation of overlays.
11570 * Overlay Commands:: Managing overlays in @value{GDBN}.
11571 * Automatic Overlay Debugging:: @value{GDBN} can find out which overlays are
11572 mapped by asking the inferior.
11573 * Overlay Sample Program:: A sample program using overlays.
11576 @node How Overlays Work
11577 @section How Overlays Work
11578 @cindex mapped overlays
11579 @cindex unmapped overlays
11580 @cindex load address, overlay's
11581 @cindex mapped address
11582 @cindex overlay area
11584 Suppose you have a computer whose instruction address space is only 64
11585 kilobytes long, but which has much more memory which can be accessed by
11586 other means: special instructions, segment registers, or memory
11587 management hardware, for example. Suppose further that you want to
11588 adapt a program which is larger than 64 kilobytes to run on this system.
11590 One solution is to identify modules of your program which are relatively
11591 independent, and need not call each other directly; call these modules
11592 @dfn{overlays}. Separate the overlays from the main program, and place
11593 their machine code in the larger memory. Place your main program in
11594 instruction memory, but leave at least enough space there to hold the
11595 largest overlay as well.
11597 Now, to call a function located in an overlay, you must first copy that
11598 overlay's machine code from the large memory into the space set aside
11599 for it in the instruction memory, and then jump to its entry point
11602 @c NB: In the below the mapped area's size is greater or equal to the
11603 @c size of all overlays. This is intentional to remind the developer
11604 @c that overlays don't necessarily need to be the same size.
11608 Data Instruction Larger
11609 Address Space Address Space Address Space
11610 +-----------+ +-----------+ +-----------+
11612 +-----------+ +-----------+ +-----------+<-- overlay 1
11613 | program | | main | .----| overlay 1 | load address
11614 | variables | | program | | +-----------+
11615 | and heap | | | | | |
11616 +-----------+ | | | +-----------+<-- overlay 2
11617 | | +-----------+ | | | load address
11618 +-----------+ | | | .-| overlay 2 |
11620 mapped --->+-----------+ | | +-----------+
11621 address | | | | | |
11622 | overlay | <-' | | |
11623 | area | <---' +-----------+<-- overlay 3
11624 | | <---. | | load address
11625 +-----------+ `--| overlay 3 |
11632 @anchor{A code overlay}A code overlay
11636 The diagram (@pxref{A code overlay}) shows a system with separate data
11637 and instruction address spaces. To map an overlay, the program copies
11638 its code from the larger address space to the instruction address space.
11639 Since the overlays shown here all use the same mapped address, only one
11640 may be mapped at a time. For a system with a single address space for
11641 data and instructions, the diagram would be similar, except that the
11642 program variables and heap would share an address space with the main
11643 program and the overlay area.
11645 An overlay loaded into instruction memory and ready for use is called a
11646 @dfn{mapped} overlay; its @dfn{mapped address} is its address in the
11647 instruction memory. An overlay not present (or only partially present)
11648 in instruction memory is called @dfn{unmapped}; its @dfn{load address}
11649 is its address in the larger memory. The mapped address is also called
11650 the @dfn{virtual memory address}, or @dfn{VMA}; the load address is also
11651 called the @dfn{load memory address}, or @dfn{LMA}.
11653 Unfortunately, overlays are not a completely transparent way to adapt a
11654 program to limited instruction memory. They introduce a new set of
11655 global constraints you must keep in mind as you design your program:
11660 Before calling or returning to a function in an overlay, your program
11661 must make sure that overlay is actually mapped. Otherwise, the call or
11662 return will transfer control to the right address, but in the wrong
11663 overlay, and your program will probably crash.
11666 If the process of mapping an overlay is expensive on your system, you
11667 will need to choose your overlays carefully to minimize their effect on
11668 your program's performance.
11671 The executable file you load onto your system must contain each
11672 overlay's instructions, appearing at the overlay's load address, not its
11673 mapped address. However, each overlay's instructions must be relocated
11674 and its symbols defined as if the overlay were at its mapped address.
11675 You can use GNU linker scripts to specify different load and relocation
11676 addresses for pieces of your program; see @ref{Overlay Description,,,
11677 ld.info, Using ld: the GNU linker}.
11680 The procedure for loading executable files onto your system must be able
11681 to load their contents into the larger address space as well as the
11682 instruction and data spaces.
11686 The overlay system described above is rather simple, and could be
11687 improved in many ways:
11692 If your system has suitable bank switch registers or memory management
11693 hardware, you could use those facilities to make an overlay's load area
11694 contents simply appear at their mapped address in instruction space.
11695 This would probably be faster than copying the overlay to its mapped
11696 area in the usual way.
11699 If your overlays are small enough, you could set aside more than one
11700 overlay area, and have more than one overlay mapped at a time.
11703 You can use overlays to manage data, as well as instructions. In
11704 general, data overlays are even less transparent to your design than
11705 code overlays: whereas code overlays only require care when you call or
11706 return to functions, data overlays require care every time you access
11707 the data. Also, if you change the contents of a data overlay, you
11708 must copy its contents back out to its load address before you can copy a
11709 different data overlay into the same mapped area.
11714 @node Overlay Commands
11715 @section Overlay Commands
11717 To use @value{GDBN}'s overlay support, each overlay in your program must
11718 correspond to a separate section of the executable file. The section's
11719 virtual memory address and load memory address must be the overlay's
11720 mapped and load addresses. Identifying overlays with sections allows
11721 @value{GDBN} to determine the appropriate address of a function or
11722 variable, depending on whether the overlay is mapped or not.
11724 @value{GDBN}'s overlay commands all start with the word @code{overlay};
11725 you can abbreviate this as @code{ov} or @code{ovly}. The commands are:
11730 Disable @value{GDBN}'s overlay support. When overlay support is
11731 disabled, @value{GDBN} assumes that all functions and variables are
11732 always present at their mapped addresses. By default, @value{GDBN}'s
11733 overlay support is disabled.
11735 @item overlay manual
11736 @cindex manual overlay debugging
11737 Enable @dfn{manual} overlay debugging. In this mode, @value{GDBN}
11738 relies on you to tell it which overlays are mapped, and which are not,
11739 using the @code{overlay map-overlay} and @code{overlay unmap-overlay}
11740 commands described below.
11742 @item overlay map-overlay @var{overlay}
11743 @itemx overlay map @var{overlay}
11744 @cindex map an overlay
11745 Tell @value{GDBN} that @var{overlay} is now mapped; @var{overlay} must
11746 be the name of the object file section containing the overlay. When an
11747 overlay is mapped, @value{GDBN} assumes it can find the overlay's
11748 functions and variables at their mapped addresses. @value{GDBN} assumes
11749 that any other overlays whose mapped ranges overlap that of
11750 @var{overlay} are now unmapped.
11752 @item overlay unmap-overlay @var{overlay}
11753 @itemx overlay unmap @var{overlay}
11754 @cindex unmap an overlay
11755 Tell @value{GDBN} that @var{overlay} is no longer mapped; @var{overlay}
11756 must be the name of the object file section containing the overlay.
11757 When an overlay is unmapped, @value{GDBN} assumes it can find the
11758 overlay's functions and variables at their load addresses.
11761 Enable @dfn{automatic} overlay debugging. In this mode, @value{GDBN}
11762 consults a data structure the overlay manager maintains in the inferior
11763 to see which overlays are mapped. For details, see @ref{Automatic
11764 Overlay Debugging}.
11766 @item overlay load-target
11767 @itemx overlay load
11768 @cindex reloading the overlay table
11769 Re-read the overlay table from the inferior. Normally, @value{GDBN}
11770 re-reads the table @value{GDBN} automatically each time the inferior
11771 stops, so this command should only be necessary if you have changed the
11772 overlay mapping yourself using @value{GDBN}. This command is only
11773 useful when using automatic overlay debugging.
11775 @item overlay list-overlays
11776 @itemx overlay list
11777 @cindex listing mapped overlays
11778 Display a list of the overlays currently mapped, along with their mapped
11779 addresses, load addresses, and sizes.
11783 Normally, when @value{GDBN} prints a code address, it includes the name
11784 of the function the address falls in:
11787 (@value{GDBP}) print main
11788 $3 = @{int ()@} 0x11a0 <main>
11791 When overlay debugging is enabled, @value{GDBN} recognizes code in
11792 unmapped overlays, and prints the names of unmapped functions with
11793 asterisks around them. For example, if @code{foo} is a function in an
11794 unmapped overlay, @value{GDBN} prints it this way:
11797 (@value{GDBP}) overlay list
11798 No sections are mapped.
11799 (@value{GDBP}) print foo
11800 $5 = @{int (int)@} 0x100000 <*foo*>
11803 When @code{foo}'s overlay is mapped, @value{GDBN} prints the function's
11807 (@value{GDBP}) overlay list
11808 Section .ov.foo.text, loaded at 0x100000 - 0x100034,
11809 mapped at 0x1016 - 0x104a
11810 (@value{GDBP}) print foo
11811 $6 = @{int (int)@} 0x1016 <foo>
11814 When overlay debugging is enabled, @value{GDBN} can find the correct
11815 address for functions and variables in an overlay, whether or not the
11816 overlay is mapped. This allows most @value{GDBN} commands, like
11817 @code{break} and @code{disassemble}, to work normally, even on unmapped
11818 code. However, @value{GDBN}'s breakpoint support has some limitations:
11822 @cindex breakpoints in overlays
11823 @cindex overlays, setting breakpoints in
11824 You can set breakpoints in functions in unmapped overlays, as long as
11825 @value{GDBN} can write to the overlay at its load address.
11827 @value{GDBN} can not set hardware or simulator-based breakpoints in
11828 unmapped overlays. However, if you set a breakpoint at the end of your
11829 overlay manager (and tell @value{GDBN} which overlays are now mapped, if
11830 you are using manual overlay management), @value{GDBN} will re-set its
11831 breakpoints properly.
11835 @node Automatic Overlay Debugging
11836 @section Automatic Overlay Debugging
11837 @cindex automatic overlay debugging
11839 @value{GDBN} can automatically track which overlays are mapped and which
11840 are not, given some simple co-operation from the overlay manager in the
11841 inferior. If you enable automatic overlay debugging with the
11842 @code{overlay auto} command (@pxref{Overlay Commands}), @value{GDBN}
11843 looks in the inferior's memory for certain variables describing the
11844 current state of the overlays.
11846 Here are the variables your overlay manager must define to support
11847 @value{GDBN}'s automatic overlay debugging:
11851 @item @code{_ovly_table}:
11852 This variable must be an array of the following structures:
11857 /* The overlay's mapped address. */
11860 /* The size of the overlay, in bytes. */
11861 unsigned long size;
11863 /* The overlay's load address. */
11866 /* Non-zero if the overlay is currently mapped;
11868 unsigned long mapped;
11872 @item @code{_novlys}:
11873 This variable must be a four-byte signed integer, holding the total
11874 number of elements in @code{_ovly_table}.
11878 To decide whether a particular overlay is mapped or not, @value{GDBN}
11879 looks for an entry in @w{@code{_ovly_table}} whose @code{vma} and
11880 @code{lma} members equal the VMA and LMA of the overlay's section in the
11881 executable file. When @value{GDBN} finds a matching entry, it consults
11882 the entry's @code{mapped} member to determine whether the overlay is
11885 In addition, your overlay manager may define a function called
11886 @code{_ovly_debug_event}. If this function is defined, @value{GDBN}
11887 will silently set a breakpoint there. If the overlay manager then
11888 calls this function whenever it has changed the overlay table, this
11889 will enable @value{GDBN} to accurately keep track of which overlays
11890 are in program memory, and update any breakpoints that may be set
11891 in overlays. This will allow breakpoints to work even if the
11892 overlays are kept in ROM or other non-writable memory while they
11893 are not being executed.
11895 @node Overlay Sample Program
11896 @section Overlay Sample Program
11897 @cindex overlay example program
11899 When linking a program which uses overlays, you must place the overlays
11900 at their load addresses, while relocating them to run at their mapped
11901 addresses. To do this, you must write a linker script (@pxref{Overlay
11902 Description,,, ld.info, Using ld: the GNU linker}). Unfortunately,
11903 since linker scripts are specific to a particular host system, target
11904 architecture, and target memory layout, this manual cannot provide
11905 portable sample code demonstrating @value{GDBN}'s overlay support.
11907 However, the @value{GDBN} source distribution does contain an overlaid
11908 program, with linker scripts for a few systems, as part of its test
11909 suite. The program consists of the following files from
11910 @file{gdb/testsuite/gdb.base}:
11914 The main program file.
11916 A simple overlay manager, used by @file{overlays.c}.
11921 Overlay modules, loaded and used by @file{overlays.c}.
11924 Linker scripts for linking the test program on the @code{d10v-elf}
11925 and @code{m32r-elf} targets.
11928 You can build the test program using the @code{d10v-elf} GCC
11929 cross-compiler like this:
11932 $ d10v-elf-gcc -g -c overlays.c
11933 $ d10v-elf-gcc -g -c ovlymgr.c
11934 $ d10v-elf-gcc -g -c foo.c
11935 $ d10v-elf-gcc -g -c bar.c
11936 $ d10v-elf-gcc -g -c baz.c
11937 $ d10v-elf-gcc -g -c grbx.c
11938 $ d10v-elf-gcc -g overlays.o ovlymgr.o foo.o bar.o \
11939 baz.o grbx.o -Wl,-Td10v.ld -o overlays
11942 The build process is identical for any other architecture, except that
11943 you must substitute the appropriate compiler and linker script for the
11944 target system for @code{d10v-elf-gcc} and @code{d10v.ld}.
11948 @chapter Using @value{GDBN} with Different Languages
11951 Although programming languages generally have common aspects, they are
11952 rarely expressed in the same manner. For instance, in ANSI C,
11953 dereferencing a pointer @code{p} is accomplished by @code{*p}, but in
11954 Modula-2, it is accomplished by @code{p^}. Values can also be
11955 represented (and displayed) differently. Hex numbers in C appear as
11956 @samp{0x1ae}, while in Modula-2 they appear as @samp{1AEH}.
11958 @cindex working language
11959 Language-specific information is built into @value{GDBN} for some languages,
11960 allowing you to express operations like the above in your program's
11961 native language, and allowing @value{GDBN} to output values in a manner
11962 consistent with the syntax of your program's native language. The
11963 language you use to build expressions is called the @dfn{working
11967 * Setting:: Switching between source languages
11968 * Show:: Displaying the language
11969 * Checks:: Type and range checks
11970 * Supported Languages:: Supported languages
11971 * Unsupported Languages:: Unsupported languages
11975 @section Switching Between Source Languages
11977 There are two ways to control the working language---either have @value{GDBN}
11978 set it automatically, or select it manually yourself. You can use the
11979 @code{set language} command for either purpose. On startup, @value{GDBN}
11980 defaults to setting the language automatically. The working language is
11981 used to determine how expressions you type are interpreted, how values
11984 In addition to the working language, every source file that
11985 @value{GDBN} knows about has its own working language. For some object
11986 file formats, the compiler might indicate which language a particular
11987 source file is in. However, most of the time @value{GDBN} infers the
11988 language from the name of the file. The language of a source file
11989 controls whether C@t{++} names are demangled---this way @code{backtrace} can
11990 show each frame appropriately for its own language. There is no way to
11991 set the language of a source file from within @value{GDBN}, but you can
11992 set the language associated with a filename extension. @xref{Show, ,
11993 Displaying the Language}.
11995 This is most commonly a problem when you use a program, such
11996 as @code{cfront} or @code{f2c}, that generates C but is written in
11997 another language. In that case, make the
11998 program use @code{#line} directives in its C output; that way
11999 @value{GDBN} will know the correct language of the source code of the original
12000 program, and will display that source code, not the generated C code.
12003 * Filenames:: Filename extensions and languages.
12004 * Manually:: Setting the working language manually
12005 * Automatically:: Having @value{GDBN} infer the source language
12009 @subsection List of Filename Extensions and Languages
12011 If a source file name ends in one of the following extensions, then
12012 @value{GDBN} infers that its language is the one indicated.
12030 C@t{++} source file
12036 Objective-C source file
12040 Fortran source file
12043 Modula-2 source file
12047 Assembler source file. This actually behaves almost like C, but
12048 @value{GDBN} does not skip over function prologues when stepping.
12051 In addition, you may set the language associated with a filename
12052 extension. @xref{Show, , Displaying the Language}.
12055 @subsection Setting the Working Language
12057 If you allow @value{GDBN} to set the language automatically,
12058 expressions are interpreted the same way in your debugging session and
12061 @kindex set language
12062 If you wish, you may set the language manually. To do this, issue the
12063 command @samp{set language @var{lang}}, where @var{lang} is the name of
12064 a language, such as
12065 @code{c} or @code{modula-2}.
12066 For a list of the supported languages, type @samp{set language}.
12068 Setting the language manually prevents @value{GDBN} from updating the working
12069 language automatically. This can lead to confusion if you try
12070 to debug a program when the working language is not the same as the
12071 source language, when an expression is acceptable to both
12072 languages---but means different things. For instance, if the current
12073 source file were written in C, and @value{GDBN} was parsing Modula-2, a
12081 might not have the effect you intended. In C, this means to add
12082 @code{b} and @code{c} and place the result in @code{a}. The result
12083 printed would be the value of @code{a}. In Modula-2, this means to compare
12084 @code{a} to the result of @code{b+c}, yielding a @code{BOOLEAN} value.
12086 @node Automatically
12087 @subsection Having @value{GDBN} Infer the Source Language
12089 To have @value{GDBN} set the working language automatically, use
12090 @samp{set language local} or @samp{set language auto}. @value{GDBN}
12091 then infers the working language. That is, when your program stops in a
12092 frame (usually by encountering a breakpoint), @value{GDBN} sets the
12093 working language to the language recorded for the function in that
12094 frame. If the language for a frame is unknown (that is, if the function
12095 or block corresponding to the frame was defined in a source file that
12096 does not have a recognized extension), the current working language is
12097 not changed, and @value{GDBN} issues a warning.
12099 This may not seem necessary for most programs, which are written
12100 entirely in one source language. However, program modules and libraries
12101 written in one source language can be used by a main program written in
12102 a different source language. Using @samp{set language auto} in this
12103 case frees you from having to set the working language manually.
12106 @section Displaying the Language
12108 The following commands help you find out which language is the
12109 working language, and also what language source files were written in.
12112 @item show language
12113 @kindex show language
12114 Display the current working language. This is the
12115 language you can use with commands such as @code{print} to
12116 build and compute expressions that may involve variables in your program.
12119 @kindex info frame@r{, show the source language}
12120 Display the source language for this frame. This language becomes the
12121 working language if you use an identifier from this frame.
12122 @xref{Frame Info, ,Information about a Frame}, to identify the other
12123 information listed here.
12126 @kindex info source@r{, show the source language}
12127 Display the source language of this source file.
12128 @xref{Symbols, ,Examining the Symbol Table}, to identify the other
12129 information listed here.
12132 In unusual circumstances, you may have source files with extensions
12133 not in the standard list. You can then set the extension associated
12134 with a language explicitly:
12137 @item set extension-language @var{ext} @var{language}
12138 @kindex set extension-language
12139 Tell @value{GDBN} that source files with extension @var{ext} are to be
12140 assumed as written in the source language @var{language}.
12142 @item info extensions
12143 @kindex info extensions
12144 List all the filename extensions and the associated languages.
12148 @section Type and Range Checking
12151 @emph{Warning:} In this release, the @value{GDBN} commands for type and range
12152 checking are included, but they do not yet have any effect. This
12153 section documents the intended facilities.
12155 @c FIXME remove warning when type/range code added
12157 Some languages are designed to guard you against making seemingly common
12158 errors through a series of compile- and run-time checks. These include
12159 checking the type of arguments to functions and operators, and making
12160 sure mathematical overflows are caught at run time. Checks such as
12161 these help to ensure a program's correctness once it has been compiled
12162 by eliminating type mismatches, and providing active checks for range
12163 errors when your program is running.
12165 @value{GDBN} can check for conditions like the above if you wish.
12166 Although @value{GDBN} does not check the statements in your program,
12167 it can check expressions entered directly into @value{GDBN} for
12168 evaluation via the @code{print} command, for example. As with the
12169 working language, @value{GDBN} can also decide whether or not to check
12170 automatically based on your program's source language.
12171 @xref{Supported Languages, ,Supported Languages}, for the default
12172 settings of supported languages.
12175 * Type Checking:: An overview of type checking
12176 * Range Checking:: An overview of range checking
12179 @cindex type checking
12180 @cindex checks, type
12181 @node Type Checking
12182 @subsection An Overview of Type Checking
12184 Some languages, such as Modula-2, are strongly typed, meaning that the
12185 arguments to operators and functions have to be of the correct type,
12186 otherwise an error occurs. These checks prevent type mismatch
12187 errors from ever causing any run-time problems. For example,
12195 The second example fails because the @code{CARDINAL} 1 is not
12196 type-compatible with the @code{REAL} 2.3.
12198 For the expressions you use in @value{GDBN} commands, you can tell the
12199 @value{GDBN} type checker to skip checking;
12200 to treat any mismatches as errors and abandon the expression;
12201 or to only issue warnings when type mismatches occur,
12202 but evaluate the expression anyway. When you choose the last of
12203 these, @value{GDBN} evaluates expressions like the second example above, but
12204 also issues a warning.
12206 Even if you turn type checking off, there may be other reasons
12207 related to type that prevent @value{GDBN} from evaluating an expression.
12208 For instance, @value{GDBN} does not know how to add an @code{int} and
12209 a @code{struct foo}. These particular type errors have nothing to do
12210 with the language in use, and usually arise from expressions, such as
12211 the one described above, which make little sense to evaluate anyway.
12213 Each language defines to what degree it is strict about type. For
12214 instance, both Modula-2 and C require the arguments to arithmetical
12215 operators to be numbers. In C, enumerated types and pointers can be
12216 represented as numbers, so that they are valid arguments to mathematical
12217 operators. @xref{Supported Languages, ,Supported Languages}, for further
12218 details on specific languages.
12220 @value{GDBN} provides some additional commands for controlling the type checker:
12222 @kindex set check type
12223 @kindex show check type
12225 @item set check type auto
12226 Set type checking on or off based on the current working language.
12227 @xref{Supported Languages, ,Supported Languages}, for the default settings for
12230 @item set check type on
12231 @itemx set check type off
12232 Set type checking on or off, overriding the default setting for the
12233 current working language. Issue a warning if the setting does not
12234 match the language default. If any type mismatches occur in
12235 evaluating an expression while type checking is on, @value{GDBN} prints a
12236 message and aborts evaluation of the expression.
12238 @item set check type warn
12239 Cause the type checker to issue warnings, but to always attempt to
12240 evaluate the expression. Evaluating the expression may still
12241 be impossible for other reasons. For example, @value{GDBN} cannot add
12242 numbers and structures.
12245 Show the current setting of the type checker, and whether or not @value{GDBN}
12246 is setting it automatically.
12249 @cindex range checking
12250 @cindex checks, range
12251 @node Range Checking
12252 @subsection An Overview of Range Checking
12254 In some languages (such as Modula-2), it is an error to exceed the
12255 bounds of a type; this is enforced with run-time checks. Such range
12256 checking is meant to ensure program correctness by making sure
12257 computations do not overflow, or indices on an array element access do
12258 not exceed the bounds of the array.
12260 For expressions you use in @value{GDBN} commands, you can tell
12261 @value{GDBN} to treat range errors in one of three ways: ignore them,
12262 always treat them as errors and abandon the expression, or issue
12263 warnings but evaluate the expression anyway.
12265 A range error can result from numerical overflow, from exceeding an
12266 array index bound, or when you type a constant that is not a member
12267 of any type. Some languages, however, do not treat overflows as an
12268 error. In many implementations of C, mathematical overflow causes the
12269 result to ``wrap around'' to lower values---for example, if @var{m} is
12270 the largest integer value, and @var{s} is the smallest, then
12273 @var{m} + 1 @result{} @var{s}
12276 This, too, is specific to individual languages, and in some cases
12277 specific to individual compilers or machines. @xref{Supported Languages, ,
12278 Supported Languages}, for further details on specific languages.
12280 @value{GDBN} provides some additional commands for controlling the range checker:
12282 @kindex set check range
12283 @kindex show check range
12285 @item set check range auto
12286 Set range checking on or off based on the current working language.
12287 @xref{Supported Languages, ,Supported Languages}, for the default settings for
12290 @item set check range on
12291 @itemx set check range off
12292 Set range checking on or off, overriding the default setting for the
12293 current working language. A warning is issued if the setting does not
12294 match the language default. If a range error occurs and range checking is on,
12295 then a message is printed and evaluation of the expression is aborted.
12297 @item set check range warn
12298 Output messages when the @value{GDBN} range checker detects a range error,
12299 but attempt to evaluate the expression anyway. Evaluating the
12300 expression may still be impossible for other reasons, such as accessing
12301 memory that the process does not own (a typical example from many Unix
12305 Show the current setting of the range checker, and whether or not it is
12306 being set automatically by @value{GDBN}.
12309 @node Supported Languages
12310 @section Supported Languages
12312 @value{GDBN} supports C, C@t{++}, D, Objective-C, Fortran, Java, OpenCL C, Pascal,
12313 assembly, Modula-2, and Ada.
12314 @c This is false ...
12315 Some @value{GDBN} features may be used in expressions regardless of the
12316 language you use: the @value{GDBN} @code{@@} and @code{::} operators,
12317 and the @samp{@{type@}addr} construct (@pxref{Expressions,
12318 ,Expressions}) can be used with the constructs of any supported
12321 The following sections detail to what degree each source language is
12322 supported by @value{GDBN}. These sections are not meant to be language
12323 tutorials or references, but serve only as a reference guide to what the
12324 @value{GDBN} expression parser accepts, and what input and output
12325 formats should look like for different languages. There are many good
12326 books written on each of these languages; please look to these for a
12327 language reference or tutorial.
12330 * C:: C and C@t{++}
12332 * Objective-C:: Objective-C
12333 * OpenCL C:: OpenCL C
12334 * Fortran:: Fortran
12336 * Modula-2:: Modula-2
12341 @subsection C and C@t{++}
12343 @cindex C and C@t{++}
12344 @cindex expressions in C or C@t{++}
12346 Since C and C@t{++} are so closely related, many features of @value{GDBN} apply
12347 to both languages. Whenever this is the case, we discuss those languages
12351 @cindex @code{g++}, @sc{gnu} C@t{++} compiler
12352 @cindex @sc{gnu} C@t{++}
12353 The C@t{++} debugging facilities are jointly implemented by the C@t{++}
12354 compiler and @value{GDBN}. Therefore, to debug your C@t{++} code
12355 effectively, you must compile your C@t{++} programs with a supported
12356 C@t{++} compiler, such as @sc{gnu} @code{g++}, or the HP ANSI C@t{++}
12357 compiler (@code{aCC}).
12360 * C Operators:: C and C@t{++} operators
12361 * C Constants:: C and C@t{++} constants
12362 * C Plus Plus Expressions:: C@t{++} expressions
12363 * C Defaults:: Default settings for C and C@t{++}
12364 * C Checks:: C and C@t{++} type and range checks
12365 * Debugging C:: @value{GDBN} and C
12366 * Debugging C Plus Plus:: @value{GDBN} features for C@t{++}
12367 * Decimal Floating Point:: Numbers in Decimal Floating Point format
12371 @subsubsection C and C@t{++} Operators
12373 @cindex C and C@t{++} operators
12375 Operators must be defined on values of specific types. For instance,
12376 @code{+} is defined on numbers, but not on structures. Operators are
12377 often defined on groups of types.
12379 For the purposes of C and C@t{++}, the following definitions hold:
12384 @emph{Integral types} include @code{int} with any of its storage-class
12385 specifiers; @code{char}; @code{enum}; and, for C@t{++}, @code{bool}.
12388 @emph{Floating-point types} include @code{float}, @code{double}, and
12389 @code{long double} (if supported by the target platform).
12392 @emph{Pointer types} include all types defined as @code{(@var{type} *)}.
12395 @emph{Scalar types} include all of the above.
12400 The following operators are supported. They are listed here
12401 in order of increasing precedence:
12405 The comma or sequencing operator. Expressions in a comma-separated list
12406 are evaluated from left to right, with the result of the entire
12407 expression being the last expression evaluated.
12410 Assignment. The value of an assignment expression is the value
12411 assigned. Defined on scalar types.
12414 Used in an expression of the form @w{@code{@var{a} @var{op}= @var{b}}},
12415 and translated to @w{@code{@var{a} = @var{a op b}}}.
12416 @w{@code{@var{op}=}} and @code{=} have the same precedence.
12417 @var{op} is any one of the operators @code{|}, @code{^}, @code{&},
12418 @code{<<}, @code{>>}, @code{+}, @code{-}, @code{*}, @code{/}, @code{%}.
12421 The ternary operator. @code{@var{a} ? @var{b} : @var{c}} can be thought
12422 of as: if @var{a} then @var{b} else @var{c}. @var{a} should be of an
12426 Logical @sc{or}. Defined on integral types.
12429 Logical @sc{and}. Defined on integral types.
12432 Bitwise @sc{or}. Defined on integral types.
12435 Bitwise exclusive-@sc{or}. Defined on integral types.
12438 Bitwise @sc{and}. Defined on integral types.
12441 Equality and inequality. Defined on scalar types. The value of these
12442 expressions is 0 for false and non-zero for true.
12444 @item <@r{, }>@r{, }<=@r{, }>=
12445 Less than, greater than, less than or equal, greater than or equal.
12446 Defined on scalar types. The value of these expressions is 0 for false
12447 and non-zero for true.
12450 left shift, and right shift. Defined on integral types.
12453 The @value{GDBN} ``artificial array'' operator (@pxref{Expressions, ,Expressions}).
12456 Addition and subtraction. Defined on integral types, floating-point types and
12459 @item *@r{, }/@r{, }%
12460 Multiplication, division, and modulus. Multiplication and division are
12461 defined on integral and floating-point types. Modulus is defined on
12465 Increment and decrement. When appearing before a variable, the
12466 operation is performed before the variable is used in an expression;
12467 when appearing after it, the variable's value is used before the
12468 operation takes place.
12471 Pointer dereferencing. Defined on pointer types. Same precedence as
12475 Address operator. Defined on variables. Same precedence as @code{++}.
12477 For debugging C@t{++}, @value{GDBN} implements a use of @samp{&} beyond what is
12478 allowed in the C@t{++} language itself: you can use @samp{&(&@var{ref})}
12479 to examine the address
12480 where a C@t{++} reference variable (declared with @samp{&@var{ref}}) is
12484 Negative. Defined on integral and floating-point types. Same
12485 precedence as @code{++}.
12488 Logical negation. Defined on integral types. Same precedence as
12492 Bitwise complement operator. Defined on integral types. Same precedence as
12497 Structure member, and pointer-to-structure member. For convenience,
12498 @value{GDBN} regards the two as equivalent, choosing whether to dereference a
12499 pointer based on the stored type information.
12500 Defined on @code{struct} and @code{union} data.
12503 Dereferences of pointers to members.
12506 Array indexing. @code{@var{a}[@var{i}]} is defined as
12507 @code{*(@var{a}+@var{i})}. Same precedence as @code{->}.
12510 Function parameter list. Same precedence as @code{->}.
12513 C@t{++} scope resolution operator. Defined on @code{struct}, @code{union},
12514 and @code{class} types.
12517 Doubled colons also represent the @value{GDBN} scope operator
12518 (@pxref{Expressions, ,Expressions}). Same precedence as @code{::},
12522 If an operator is redefined in the user code, @value{GDBN} usually
12523 attempts to invoke the redefined version instead of using the operator's
12524 predefined meaning.
12527 @subsubsection C and C@t{++} Constants
12529 @cindex C and C@t{++} constants
12531 @value{GDBN} allows you to express the constants of C and C@t{++} in the
12536 Integer constants are a sequence of digits. Octal constants are
12537 specified by a leading @samp{0} (i.e.@: zero), and hexadecimal constants
12538 by a leading @samp{0x} or @samp{0X}. Constants may also end with a letter
12539 @samp{l}, specifying that the constant should be treated as a
12543 Floating point constants are a sequence of digits, followed by a decimal
12544 point, followed by a sequence of digits, and optionally followed by an
12545 exponent. An exponent is of the form:
12546 @samp{@w{e@r{[[}+@r{]|}-@r{]}@var{nnn}}}, where @var{nnn} is another
12547 sequence of digits. The @samp{+} is optional for positive exponents.
12548 A floating-point constant may also end with a letter @samp{f} or
12549 @samp{F}, specifying that the constant should be treated as being of
12550 the @code{float} (as opposed to the default @code{double}) type; or with
12551 a letter @samp{l} or @samp{L}, which specifies a @code{long double}
12555 Enumerated constants consist of enumerated identifiers, or their
12556 integral equivalents.
12559 Character constants are a single character surrounded by single quotes
12560 (@code{'}), or a number---the ordinal value of the corresponding character
12561 (usually its @sc{ascii} value). Within quotes, the single character may
12562 be represented by a letter or by @dfn{escape sequences}, which are of
12563 the form @samp{\@var{nnn}}, where @var{nnn} is the octal representation
12564 of the character's ordinal value; or of the form @samp{\@var{x}}, where
12565 @samp{@var{x}} is a predefined special character---for example,
12566 @samp{\n} for newline.
12568 Wide character constants can be written by prefixing a character
12569 constant with @samp{L}, as in C. For example, @samp{L'x'} is the wide
12570 form of @samp{x}. The target wide character set is used when
12571 computing the value of this constant (@pxref{Character Sets}).
12574 String constants are a sequence of character constants surrounded by
12575 double quotes (@code{"}). Any valid character constant (as described
12576 above) may appear. Double quotes within the string must be preceded by
12577 a backslash, so for instance @samp{"a\"b'c"} is a string of five
12580 Wide string constants can be written by prefixing a string constant
12581 with @samp{L}, as in C. The target wide character set is used when
12582 computing the value of this constant (@pxref{Character Sets}).
12585 Pointer constants are an integral value. You can also write pointers
12586 to constants using the C operator @samp{&}.
12589 Array constants are comma-separated lists surrounded by braces @samp{@{}
12590 and @samp{@}}; for example, @samp{@{1,2,3@}} is a three-element array of
12591 integers, @samp{@{@{1,2@}, @{3,4@}, @{5,6@}@}} is a three-by-two array,
12592 and @samp{@{&"hi", &"there", &"fred"@}} is a three-element array of pointers.
12595 @node C Plus Plus Expressions
12596 @subsubsection C@t{++} Expressions
12598 @cindex expressions in C@t{++}
12599 @value{GDBN} expression handling can interpret most C@t{++} expressions.
12601 @cindex debugging C@t{++} programs
12602 @cindex C@t{++} compilers
12603 @cindex debug formats and C@t{++}
12604 @cindex @value{NGCC} and C@t{++}
12606 @emph{Warning:} @value{GDBN} can only debug C@t{++} code if you use
12607 the proper compiler and the proper debug format. Currently,
12608 @value{GDBN} works best when debugging C@t{++} code that is compiled
12609 with the most recent version of @value{NGCC} possible. The DWARF
12610 debugging format is preferred; @value{NGCC} defaults to this on most
12611 popular platforms. Other compilers and/or debug formats are likely to
12612 work badly or not at all when using @value{GDBN} to debug C@t{++}
12613 code. @xref{Compilation}.
12618 @cindex member functions
12620 Member function calls are allowed; you can use expressions like
12623 count = aml->GetOriginal(x, y)
12626 @vindex this@r{, inside C@t{++} member functions}
12627 @cindex namespace in C@t{++}
12629 While a member function is active (in the selected stack frame), your
12630 expressions have the same namespace available as the member function;
12631 that is, @value{GDBN} allows implicit references to the class instance
12632 pointer @code{this} following the same rules as C@t{++}. @code{using}
12633 declarations in the current scope are also respected by @value{GDBN}.
12635 @cindex call overloaded functions
12636 @cindex overloaded functions, calling
12637 @cindex type conversions in C@t{++}
12639 You can call overloaded functions; @value{GDBN} resolves the function
12640 call to the right definition, with some restrictions. @value{GDBN} does not
12641 perform overload resolution involving user-defined type conversions,
12642 calls to constructors, or instantiations of templates that do not exist
12643 in the program. It also cannot handle ellipsis argument lists or
12646 It does perform integral conversions and promotions, floating-point
12647 promotions, arithmetic conversions, pointer conversions, conversions of
12648 class objects to base classes, and standard conversions such as those of
12649 functions or arrays to pointers; it requires an exact match on the
12650 number of function arguments.
12652 Overload resolution is always performed, unless you have specified
12653 @code{set overload-resolution off}. @xref{Debugging C Plus Plus,
12654 ,@value{GDBN} Features for C@t{++}}.
12656 You must specify @code{set overload-resolution off} in order to use an
12657 explicit function signature to call an overloaded function, as in
12659 p 'foo(char,int)'('x', 13)
12662 The @value{GDBN} command-completion facility can simplify this;
12663 see @ref{Completion, ,Command Completion}.
12665 @cindex reference declarations
12667 @value{GDBN} understands variables declared as C@t{++} references; you can use
12668 them in expressions just as you do in C@t{++} source---they are automatically
12671 In the parameter list shown when @value{GDBN} displays a frame, the values of
12672 reference variables are not displayed (unlike other variables); this
12673 avoids clutter, since references are often used for large structures.
12674 The @emph{address} of a reference variable is always shown, unless
12675 you have specified @samp{set print address off}.
12678 @value{GDBN} supports the C@t{++} name resolution operator @code{::}---your
12679 expressions can use it just as expressions in your program do. Since
12680 one scope may be defined in another, you can use @code{::} repeatedly if
12681 necessary, for example in an expression like
12682 @samp{@var{scope1}::@var{scope2}::@var{name}}. @value{GDBN} also allows
12683 resolving name scope by reference to source files, in both C and C@t{++}
12684 debugging (@pxref{Variables, ,Program Variables}).
12687 @value{GDBN} performs argument-dependent lookup, following the C@t{++}
12692 @subsubsection C and C@t{++} Defaults
12694 @cindex C and C@t{++} defaults
12696 If you allow @value{GDBN} to set type and range checking automatically, they
12697 both default to @code{off} whenever the working language changes to
12698 C or C@t{++}. This happens regardless of whether you or @value{GDBN}
12699 selects the working language.
12701 If you allow @value{GDBN} to set the language automatically, it
12702 recognizes source files whose names end with @file{.c}, @file{.C}, or
12703 @file{.cc}, etc, and when @value{GDBN} enters code compiled from one of
12704 these files, it sets the working language to C or C@t{++}.
12705 @xref{Automatically, ,Having @value{GDBN} Infer the Source Language},
12706 for further details.
12708 @c Type checking is (a) primarily motivated by Modula-2, and (b)
12709 @c unimplemented. If (b) changes, it might make sense to let this node
12710 @c appear even if Mod-2 does not, but meanwhile ignore it. roland 16jul93.
12713 @subsubsection C and C@t{++} Type and Range Checks
12715 @cindex C and C@t{++} checks
12717 By default, when @value{GDBN} parses C or C@t{++} expressions, type checking
12718 is not used. However, if you turn type checking on, @value{GDBN}
12719 considers two variables type equivalent if:
12723 The two variables are structured and have the same structure, union, or
12727 The two variables have the same type name, or types that have been
12728 declared equivalent through @code{typedef}.
12731 @c leaving this out because neither J Gilmore nor R Pesch understand it.
12734 The two @code{struct}, @code{union}, or @code{enum} variables are
12735 declared in the same declaration. (Note: this may not be true for all C
12740 Range checking, if turned on, is done on mathematical operations. Array
12741 indices are not checked, since they are often used to index a pointer
12742 that is not itself an array.
12745 @subsubsection @value{GDBN} and C
12747 The @code{set print union} and @code{show print union} commands apply to
12748 the @code{union} type. When set to @samp{on}, any @code{union} that is
12749 inside a @code{struct} or @code{class} is also printed. Otherwise, it
12750 appears as @samp{@{...@}}.
12752 The @code{@@} operator aids in the debugging of dynamic arrays, formed
12753 with pointers and a memory allocation function. @xref{Expressions,
12756 @node Debugging C Plus Plus
12757 @subsubsection @value{GDBN} Features for C@t{++}
12759 @cindex commands for C@t{++}
12761 Some @value{GDBN} commands are particularly useful with C@t{++}, and some are
12762 designed specifically for use with C@t{++}. Here is a summary:
12765 @cindex break in overloaded functions
12766 @item @r{breakpoint menus}
12767 When you want a breakpoint in a function whose name is overloaded,
12768 @value{GDBN} has the capability to display a menu of possible breakpoint
12769 locations to help you specify which function definition you want.
12770 @xref{Ambiguous Expressions,,Ambiguous Expressions}.
12772 @cindex overloading in C@t{++}
12773 @item rbreak @var{regex}
12774 Setting breakpoints using regular expressions is helpful for setting
12775 breakpoints on overloaded functions that are not members of any special
12777 @xref{Set Breaks, ,Setting Breakpoints}.
12779 @cindex C@t{++} exception handling
12782 Debug C@t{++} exception handling using these commands. @xref{Set
12783 Catchpoints, , Setting Catchpoints}.
12785 @cindex inheritance
12786 @item ptype @var{typename}
12787 Print inheritance relationships as well as other information for type
12789 @xref{Symbols, ,Examining the Symbol Table}.
12791 @item info vtbl @var{expression}.
12792 The @code{info vtbl} command can be used to display the virtual
12793 method tables of the object computed by @var{expression}. This shows
12794 one entry per virtual table; there may be multiple virtual tables when
12795 multiple inheritance is in use.
12797 @cindex C@t{++} symbol display
12798 @item set print demangle
12799 @itemx show print demangle
12800 @itemx set print asm-demangle
12801 @itemx show print asm-demangle
12802 Control whether C@t{++} symbols display in their source form, both when
12803 displaying code as C@t{++} source and when displaying disassemblies.
12804 @xref{Print Settings, ,Print Settings}.
12806 @item set print object
12807 @itemx show print object
12808 Choose whether to print derived (actual) or declared types of objects.
12809 @xref{Print Settings, ,Print Settings}.
12811 @item set print vtbl
12812 @itemx show print vtbl
12813 Control the format for printing virtual function tables.
12814 @xref{Print Settings, ,Print Settings}.
12815 (The @code{vtbl} commands do not work on programs compiled with the HP
12816 ANSI C@t{++} compiler (@code{aCC}).)
12818 @kindex set overload-resolution
12819 @cindex overloaded functions, overload resolution
12820 @item set overload-resolution on
12821 Enable overload resolution for C@t{++} expression evaluation. The default
12822 is on. For overloaded functions, @value{GDBN} evaluates the arguments
12823 and searches for a function whose signature matches the argument types,
12824 using the standard C@t{++} conversion rules (see @ref{C Plus Plus
12825 Expressions, ,C@t{++} Expressions}, for details).
12826 If it cannot find a match, it emits a message.
12828 @item set overload-resolution off
12829 Disable overload resolution for C@t{++} expression evaluation. For
12830 overloaded functions that are not class member functions, @value{GDBN}
12831 chooses the first function of the specified name that it finds in the
12832 symbol table, whether or not its arguments are of the correct type. For
12833 overloaded functions that are class member functions, @value{GDBN}
12834 searches for a function whose signature @emph{exactly} matches the
12837 @kindex show overload-resolution
12838 @item show overload-resolution
12839 Show the current setting of overload resolution.
12841 @item @r{Overloaded symbol names}
12842 You can specify a particular definition of an overloaded symbol, using
12843 the same notation that is used to declare such symbols in C@t{++}: type
12844 @code{@var{symbol}(@var{types})} rather than just @var{symbol}. You can
12845 also use the @value{GDBN} command-line word completion facilities to list the
12846 available choices, or to finish the type list for you.
12847 @xref{Completion,, Command Completion}, for details on how to do this.
12850 @node Decimal Floating Point
12851 @subsubsection Decimal Floating Point format
12852 @cindex decimal floating point format
12854 @value{GDBN} can examine, set and perform computations with numbers in
12855 decimal floating point format, which in the C language correspond to the
12856 @code{_Decimal32}, @code{_Decimal64} and @code{_Decimal128} types as
12857 specified by the extension to support decimal floating-point arithmetic.
12859 There are two encodings in use, depending on the architecture: BID (Binary
12860 Integer Decimal) for x86 and x86-64, and DPD (Densely Packed Decimal) for
12861 PowerPC. @value{GDBN} will use the appropriate encoding for the configured
12864 Because of a limitation in @file{libdecnumber}, the library used by @value{GDBN}
12865 to manipulate decimal floating point numbers, it is not possible to convert
12866 (using a cast, for example) integers wider than 32-bit to decimal float.
12868 In addition, in order to imitate @value{GDBN}'s behaviour with binary floating
12869 point computations, error checking in decimal float operations ignores
12870 underflow, overflow and divide by zero exceptions.
12872 In the PowerPC architecture, @value{GDBN} provides a set of pseudo-registers
12873 to inspect @code{_Decimal128} values stored in floating point registers.
12874 See @ref{PowerPC,,PowerPC} for more details.
12880 @value{GDBN} can be used to debug programs written in D and compiled with
12881 GDC, LDC or DMD compilers. Currently @value{GDBN} supports only one D
12882 specific feature --- dynamic arrays.
12885 @subsection Objective-C
12887 @cindex Objective-C
12888 This section provides information about some commands and command
12889 options that are useful for debugging Objective-C code. See also
12890 @ref{Symbols, info classes}, and @ref{Symbols, info selectors}, for a
12891 few more commands specific to Objective-C support.
12894 * Method Names in Commands::
12895 * The Print Command with Objective-C::
12898 @node Method Names in Commands
12899 @subsubsection Method Names in Commands
12901 The following commands have been extended to accept Objective-C method
12902 names as line specifications:
12904 @kindex clear@r{, and Objective-C}
12905 @kindex break@r{, and Objective-C}
12906 @kindex info line@r{, and Objective-C}
12907 @kindex jump@r{, and Objective-C}
12908 @kindex list@r{, and Objective-C}
12912 @item @code{info line}
12917 A fully qualified Objective-C method name is specified as
12920 -[@var{Class} @var{methodName}]
12923 where the minus sign is used to indicate an instance method and a
12924 plus sign (not shown) is used to indicate a class method. The class
12925 name @var{Class} and method name @var{methodName} are enclosed in
12926 brackets, similar to the way messages are specified in Objective-C
12927 source code. For example, to set a breakpoint at the @code{create}
12928 instance method of class @code{Fruit} in the program currently being
12932 break -[Fruit create]
12935 To list ten program lines around the @code{initialize} class method,
12939 list +[NSText initialize]
12942 In the current version of @value{GDBN}, the plus or minus sign is
12943 required. In future versions of @value{GDBN}, the plus or minus
12944 sign will be optional, but you can use it to narrow the search. It
12945 is also possible to specify just a method name:
12951 You must specify the complete method name, including any colons. If
12952 your program's source files contain more than one @code{create} method,
12953 you'll be presented with a numbered list of classes that implement that
12954 method. Indicate your choice by number, or type @samp{0} to exit if
12957 As another example, to clear a breakpoint established at the
12958 @code{makeKeyAndOrderFront:} method of the @code{NSWindow} class, enter:
12961 clear -[NSWindow makeKeyAndOrderFront:]
12964 @node The Print Command with Objective-C
12965 @subsubsection The Print Command With Objective-C
12966 @cindex Objective-C, print objects
12967 @kindex print-object
12968 @kindex po @r{(@code{print-object})}
12970 The print command has also been extended to accept methods. For example:
12973 print -[@var{object} hash]
12976 @cindex print an Objective-C object description
12977 @cindex @code{_NSPrintForDebugger}, and printing Objective-C objects
12979 will tell @value{GDBN} to send the @code{hash} message to @var{object}
12980 and print the result. Also, an additional command has been added,
12981 @code{print-object} or @code{po} for short, which is meant to print
12982 the description of an object. However, this command may only work
12983 with certain Objective-C libraries that have a particular hook
12984 function, @code{_NSPrintForDebugger}, defined.
12987 @subsection OpenCL C
12990 This section provides information about @value{GDBN}s OpenCL C support.
12993 * OpenCL C Datatypes::
12994 * OpenCL C Expressions::
12995 * OpenCL C Operators::
12998 @node OpenCL C Datatypes
12999 @subsubsection OpenCL C Datatypes
13001 @cindex OpenCL C Datatypes
13002 @value{GDBN} supports the builtin scalar and vector datatypes specified
13003 by OpenCL 1.1. In addition the half- and double-precision floating point
13004 data types of the @code{cl_khr_fp16} and @code{cl_khr_fp64} OpenCL
13005 extensions are also known to @value{GDBN}.
13007 @node OpenCL C Expressions
13008 @subsubsection OpenCL C Expressions
13010 @cindex OpenCL C Expressions
13011 @value{GDBN} supports accesses to vector components including the access as
13012 lvalue where possible. Since OpenCL C is based on C99 most C expressions
13013 supported by @value{GDBN} can be used as well.
13015 @node OpenCL C Operators
13016 @subsubsection OpenCL C Operators
13018 @cindex OpenCL C Operators
13019 @value{GDBN} supports the operators specified by OpenCL 1.1 for scalar and
13023 @subsection Fortran
13024 @cindex Fortran-specific support in @value{GDBN}
13026 @value{GDBN} can be used to debug programs written in Fortran, but it
13027 currently supports only the features of Fortran 77 language.
13029 @cindex trailing underscore, in Fortran symbols
13030 Some Fortran compilers (@sc{gnu} Fortran 77 and Fortran 95 compilers
13031 among them) append an underscore to the names of variables and
13032 functions. When you debug programs compiled by those compilers, you
13033 will need to refer to variables and functions with a trailing
13037 * Fortran Operators:: Fortran operators and expressions
13038 * Fortran Defaults:: Default settings for Fortran
13039 * Special Fortran Commands:: Special @value{GDBN} commands for Fortran
13042 @node Fortran Operators
13043 @subsubsection Fortran Operators and Expressions
13045 @cindex Fortran operators and expressions
13047 Operators must be defined on values of specific types. For instance,
13048 @code{+} is defined on numbers, but not on characters or other non-
13049 arithmetic types. Operators are often defined on groups of types.
13053 The exponentiation operator. It raises the first operand to the power
13057 The range operator. Normally used in the form of array(low:high) to
13058 represent a section of array.
13061 The access component operator. Normally used to access elements in derived
13062 types. Also suitable for unions. As unions aren't part of regular Fortran,
13063 this can only happen when accessing a register that uses a gdbarch-defined
13067 @node Fortran Defaults
13068 @subsubsection Fortran Defaults
13070 @cindex Fortran Defaults
13072 Fortran symbols are usually case-insensitive, so @value{GDBN} by
13073 default uses case-insensitive matches for Fortran symbols. You can
13074 change that with the @samp{set case-insensitive} command, see
13075 @ref{Symbols}, for the details.
13077 @node Special Fortran Commands
13078 @subsubsection Special Fortran Commands
13080 @cindex Special Fortran commands
13082 @value{GDBN} has some commands to support Fortran-specific features,
13083 such as displaying common blocks.
13086 @cindex @code{COMMON} blocks, Fortran
13087 @kindex info common
13088 @item info common @r{[}@var{common-name}@r{]}
13089 This command prints the values contained in the Fortran @code{COMMON}
13090 block whose name is @var{common-name}. With no argument, the names of
13091 all @code{COMMON} blocks visible at the current program location are
13098 @cindex Pascal support in @value{GDBN}, limitations
13099 Debugging Pascal programs which use sets, subranges, file variables, or
13100 nested functions does not currently work. @value{GDBN} does not support
13101 entering expressions, printing values, or similar features using Pascal
13104 The Pascal-specific command @code{set print pascal_static-members}
13105 controls whether static members of Pascal objects are displayed.
13106 @xref{Print Settings, pascal_static-members}.
13109 @subsection Modula-2
13111 @cindex Modula-2, @value{GDBN} support
13113 The extensions made to @value{GDBN} to support Modula-2 only support
13114 output from the @sc{gnu} Modula-2 compiler (which is currently being
13115 developed). Other Modula-2 compilers are not currently supported, and
13116 attempting to debug executables produced by them is most likely
13117 to give an error as @value{GDBN} reads in the executable's symbol
13120 @cindex expressions in Modula-2
13122 * M2 Operators:: Built-in operators
13123 * Built-In Func/Proc:: Built-in functions and procedures
13124 * M2 Constants:: Modula-2 constants
13125 * M2 Types:: Modula-2 types
13126 * M2 Defaults:: Default settings for Modula-2
13127 * Deviations:: Deviations from standard Modula-2
13128 * M2 Checks:: Modula-2 type and range checks
13129 * M2 Scope:: The scope operators @code{::} and @code{.}
13130 * GDB/M2:: @value{GDBN} and Modula-2
13134 @subsubsection Operators
13135 @cindex Modula-2 operators
13137 Operators must be defined on values of specific types. For instance,
13138 @code{+} is defined on numbers, but not on structures. Operators are
13139 often defined on groups of types. For the purposes of Modula-2, the
13140 following definitions hold:
13145 @emph{Integral types} consist of @code{INTEGER}, @code{CARDINAL}, and
13149 @emph{Character types} consist of @code{CHAR} and its subranges.
13152 @emph{Floating-point types} consist of @code{REAL}.
13155 @emph{Pointer types} consist of anything declared as @code{POINTER TO
13159 @emph{Scalar types} consist of all of the above.
13162 @emph{Set types} consist of @code{SET} and @code{BITSET} types.
13165 @emph{Boolean types} consist of @code{BOOLEAN}.
13169 The following operators are supported, and appear in order of
13170 increasing precedence:
13174 Function argument or array index separator.
13177 Assignment. The value of @var{var} @code{:=} @var{value} is
13181 Less than, greater than on integral, floating-point, or enumerated
13185 Less than or equal to, greater than or equal to
13186 on integral, floating-point and enumerated types, or set inclusion on
13187 set types. Same precedence as @code{<}.
13189 @item =@r{, }<>@r{, }#
13190 Equality and two ways of expressing inequality, valid on scalar types.
13191 Same precedence as @code{<}. In @value{GDBN} scripts, only @code{<>} is
13192 available for inequality, since @code{#} conflicts with the script
13196 Set membership. Defined on set types and the types of their members.
13197 Same precedence as @code{<}.
13200 Boolean disjunction. Defined on boolean types.
13203 Boolean conjunction. Defined on boolean types.
13206 The @value{GDBN} ``artificial array'' operator (@pxref{Expressions, ,Expressions}).
13209 Addition and subtraction on integral and floating-point types, or union
13210 and difference on set types.
13213 Multiplication on integral and floating-point types, or set intersection
13217 Division on floating-point types, or symmetric set difference on set
13218 types. Same precedence as @code{*}.
13221 Integer division and remainder. Defined on integral types. Same
13222 precedence as @code{*}.
13225 Negative. Defined on @code{INTEGER} and @code{REAL} data.
13228 Pointer dereferencing. Defined on pointer types.
13231 Boolean negation. Defined on boolean types. Same precedence as
13235 @code{RECORD} field selector. Defined on @code{RECORD} data. Same
13236 precedence as @code{^}.
13239 Array indexing. Defined on @code{ARRAY} data. Same precedence as @code{^}.
13242 Procedure argument list. Defined on @code{PROCEDURE} objects. Same precedence
13246 @value{GDBN} and Modula-2 scope operators.
13250 @emph{Warning:} Set expressions and their operations are not yet supported, so @value{GDBN}
13251 treats the use of the operator @code{IN}, or the use of operators
13252 @code{+}, @code{-}, @code{*}, @code{/}, @code{=}, , @code{<>}, @code{#},
13253 @code{<=}, and @code{>=} on sets as an error.
13257 @node Built-In Func/Proc
13258 @subsubsection Built-in Functions and Procedures
13259 @cindex Modula-2 built-ins
13261 Modula-2 also makes available several built-in procedures and functions.
13262 In describing these, the following metavariables are used:
13267 represents an @code{ARRAY} variable.
13270 represents a @code{CHAR} constant or variable.
13273 represents a variable or constant of integral type.
13276 represents an identifier that belongs to a set. Generally used in the
13277 same function with the metavariable @var{s}. The type of @var{s} should
13278 be @code{SET OF @var{mtype}} (where @var{mtype} is the type of @var{m}).
13281 represents a variable or constant of integral or floating-point type.
13284 represents a variable or constant of floating-point type.
13290 represents a variable.
13293 represents a variable or constant of one of many types. See the
13294 explanation of the function for details.
13297 All Modula-2 built-in procedures also return a result, described below.
13301 Returns the absolute value of @var{n}.
13304 If @var{c} is a lower case letter, it returns its upper case
13305 equivalent, otherwise it returns its argument.
13308 Returns the character whose ordinal value is @var{i}.
13311 Decrements the value in the variable @var{v} by one. Returns the new value.
13313 @item DEC(@var{v},@var{i})
13314 Decrements the value in the variable @var{v} by @var{i}. Returns the
13317 @item EXCL(@var{m},@var{s})
13318 Removes the element @var{m} from the set @var{s}. Returns the new
13321 @item FLOAT(@var{i})
13322 Returns the floating point equivalent of the integer @var{i}.
13324 @item HIGH(@var{a})
13325 Returns the index of the last member of @var{a}.
13328 Increments the value in the variable @var{v} by one. Returns the new value.
13330 @item INC(@var{v},@var{i})
13331 Increments the value in the variable @var{v} by @var{i}. Returns the
13334 @item INCL(@var{m},@var{s})
13335 Adds the element @var{m} to the set @var{s} if it is not already
13336 there. Returns the new set.
13339 Returns the maximum value of the type @var{t}.
13342 Returns the minimum value of the type @var{t}.
13345 Returns boolean TRUE if @var{i} is an odd number.
13348 Returns the ordinal value of its argument. For example, the ordinal
13349 value of a character is its @sc{ascii} value (on machines supporting the
13350 @sc{ascii} character set). @var{x} must be of an ordered type, which include
13351 integral, character and enumerated types.
13353 @item SIZE(@var{x})
13354 Returns the size of its argument. @var{x} can be a variable or a type.
13356 @item TRUNC(@var{r})
13357 Returns the integral part of @var{r}.
13359 @item TSIZE(@var{x})
13360 Returns the size of its argument. @var{x} can be a variable or a type.
13362 @item VAL(@var{t},@var{i})
13363 Returns the member of the type @var{t} whose ordinal value is @var{i}.
13367 @emph{Warning:} Sets and their operations are not yet supported, so
13368 @value{GDBN} treats the use of procedures @code{INCL} and @code{EXCL} as
13372 @cindex Modula-2 constants
13374 @subsubsection Constants
13376 @value{GDBN} allows you to express the constants of Modula-2 in the following
13382 Integer constants are simply a sequence of digits. When used in an
13383 expression, a constant is interpreted to be type-compatible with the
13384 rest of the expression. Hexadecimal integers are specified by a
13385 trailing @samp{H}, and octal integers by a trailing @samp{B}.
13388 Floating point constants appear as a sequence of digits, followed by a
13389 decimal point and another sequence of digits. An optional exponent can
13390 then be specified, in the form @samp{E@r{[}+@r{|}-@r{]}@var{nnn}}, where
13391 @samp{@r{[}+@r{|}-@r{]}@var{nnn}} is the desired exponent. All of the
13392 digits of the floating point constant must be valid decimal (base 10)
13396 Character constants consist of a single character enclosed by a pair of
13397 like quotes, either single (@code{'}) or double (@code{"}). They may
13398 also be expressed by their ordinal value (their @sc{ascii} value, usually)
13399 followed by a @samp{C}.
13402 String constants consist of a sequence of characters enclosed by a
13403 pair of like quotes, either single (@code{'}) or double (@code{"}).
13404 Escape sequences in the style of C are also allowed. @xref{C
13405 Constants, ,C and C@t{++} Constants}, for a brief explanation of escape
13409 Enumerated constants consist of an enumerated identifier.
13412 Boolean constants consist of the identifiers @code{TRUE} and
13416 Pointer constants consist of integral values only.
13419 Set constants are not yet supported.
13423 @subsubsection Modula-2 Types
13424 @cindex Modula-2 types
13426 Currently @value{GDBN} can print the following data types in Modula-2
13427 syntax: array types, record types, set types, pointer types, procedure
13428 types, enumerated types, subrange types and base types. You can also
13429 print the contents of variables declared using these type.
13430 This section gives a number of simple source code examples together with
13431 sample @value{GDBN} sessions.
13433 The first example contains the following section of code:
13442 and you can request @value{GDBN} to interrogate the type and value of
13443 @code{r} and @code{s}.
13446 (@value{GDBP}) print s
13448 (@value{GDBP}) ptype s
13450 (@value{GDBP}) print r
13452 (@value{GDBP}) ptype r
13457 Likewise if your source code declares @code{s} as:
13461 s: SET ['A'..'Z'] ;
13465 then you may query the type of @code{s} by:
13468 (@value{GDBP}) ptype s
13469 type = SET ['A'..'Z']
13473 Note that at present you cannot interactively manipulate set
13474 expressions using the debugger.
13476 The following example shows how you might declare an array in Modula-2
13477 and how you can interact with @value{GDBN} to print its type and contents:
13481 s: ARRAY [-10..10] OF CHAR ;
13485 (@value{GDBP}) ptype s
13486 ARRAY [-10..10] OF CHAR
13489 Note that the array handling is not yet complete and although the type
13490 is printed correctly, expression handling still assumes that all
13491 arrays have a lower bound of zero and not @code{-10} as in the example
13494 Here are some more type related Modula-2 examples:
13498 colour = (blue, red, yellow, green) ;
13499 t = [blue..yellow] ;
13507 The @value{GDBN} interaction shows how you can query the data type
13508 and value of a variable.
13511 (@value{GDBP}) print s
13513 (@value{GDBP}) ptype t
13514 type = [blue..yellow]
13518 In this example a Modula-2 array is declared and its contents
13519 displayed. Observe that the contents are written in the same way as
13520 their @code{C} counterparts.
13524 s: ARRAY [1..5] OF CARDINAL ;
13530 (@value{GDBP}) print s
13531 $1 = @{1, 0, 0, 0, 0@}
13532 (@value{GDBP}) ptype s
13533 type = ARRAY [1..5] OF CARDINAL
13536 The Modula-2 language interface to @value{GDBN} also understands
13537 pointer types as shown in this example:
13541 s: POINTER TO ARRAY [1..5] OF CARDINAL ;
13548 and you can request that @value{GDBN} describes the type of @code{s}.
13551 (@value{GDBP}) ptype s
13552 type = POINTER TO ARRAY [1..5] OF CARDINAL
13555 @value{GDBN} handles compound types as we can see in this example.
13556 Here we combine array types, record types, pointer types and subrange
13567 myarray = ARRAY myrange OF CARDINAL ;
13568 myrange = [-2..2] ;
13570 s: POINTER TO ARRAY myrange OF foo ;
13574 and you can ask @value{GDBN} to describe the type of @code{s} as shown
13578 (@value{GDBP}) ptype s
13579 type = POINTER TO ARRAY [-2..2] OF foo = RECORD
13582 f3 : ARRAY [-2..2] OF CARDINAL;
13587 @subsubsection Modula-2 Defaults
13588 @cindex Modula-2 defaults
13590 If type and range checking are set automatically by @value{GDBN}, they
13591 both default to @code{on} whenever the working language changes to
13592 Modula-2. This happens regardless of whether you or @value{GDBN}
13593 selected the working language.
13595 If you allow @value{GDBN} to set the language automatically, then entering
13596 code compiled from a file whose name ends with @file{.mod} sets the
13597 working language to Modula-2. @xref{Automatically, ,Having @value{GDBN}
13598 Infer the Source Language}, for further details.
13601 @subsubsection Deviations from Standard Modula-2
13602 @cindex Modula-2, deviations from
13604 A few changes have been made to make Modula-2 programs easier to debug.
13605 This is done primarily via loosening its type strictness:
13609 Unlike in standard Modula-2, pointer constants can be formed by
13610 integers. This allows you to modify pointer variables during
13611 debugging. (In standard Modula-2, the actual address contained in a
13612 pointer variable is hidden from you; it can only be modified
13613 through direct assignment to another pointer variable or expression that
13614 returned a pointer.)
13617 C escape sequences can be used in strings and characters to represent
13618 non-printable characters. @value{GDBN} prints out strings with these
13619 escape sequences embedded. Single non-printable characters are
13620 printed using the @samp{CHR(@var{nnn})} format.
13623 The assignment operator (@code{:=}) returns the value of its right-hand
13627 All built-in procedures both modify @emph{and} return their argument.
13631 @subsubsection Modula-2 Type and Range Checks
13632 @cindex Modula-2 checks
13635 @emph{Warning:} in this release, @value{GDBN} does not yet perform type or
13638 @c FIXME remove warning when type/range checks added
13640 @value{GDBN} considers two Modula-2 variables type equivalent if:
13644 They are of types that have been declared equivalent via a @code{TYPE
13645 @var{t1} = @var{t2}} statement
13648 They have been declared on the same line. (Note: This is true of the
13649 @sc{gnu} Modula-2 compiler, but it may not be true of other compilers.)
13652 As long as type checking is enabled, any attempt to combine variables
13653 whose types are not equivalent is an error.
13655 Range checking is done on all mathematical operations, assignment, array
13656 index bounds, and all built-in functions and procedures.
13659 @subsubsection The Scope Operators @code{::} and @code{.}
13661 @cindex @code{.}, Modula-2 scope operator
13662 @cindex colon, doubled as scope operator
13664 @vindex colon-colon@r{, in Modula-2}
13665 @c Info cannot handle :: but TeX can.
13668 @vindex ::@r{, in Modula-2}
13671 There are a few subtle differences between the Modula-2 scope operator
13672 (@code{.}) and the @value{GDBN} scope operator (@code{::}). The two have
13677 @var{module} . @var{id}
13678 @var{scope} :: @var{id}
13682 where @var{scope} is the name of a module or a procedure,
13683 @var{module} the name of a module, and @var{id} is any declared
13684 identifier within your program, except another module.
13686 Using the @code{::} operator makes @value{GDBN} search the scope
13687 specified by @var{scope} for the identifier @var{id}. If it is not
13688 found in the specified scope, then @value{GDBN} searches all scopes
13689 enclosing the one specified by @var{scope}.
13691 Using the @code{.} operator makes @value{GDBN} search the current scope for
13692 the identifier specified by @var{id} that was imported from the
13693 definition module specified by @var{module}. With this operator, it is
13694 an error if the identifier @var{id} was not imported from definition
13695 module @var{module}, or if @var{id} is not an identifier in
13699 @subsubsection @value{GDBN} and Modula-2
13701 Some @value{GDBN} commands have little use when debugging Modula-2 programs.
13702 Five subcommands of @code{set print} and @code{show print} apply
13703 specifically to C and C@t{++}: @samp{vtbl}, @samp{demangle},
13704 @samp{asm-demangle}, @samp{object}, and @samp{union}. The first four
13705 apply to C@t{++}, and the last to the C @code{union} type, which has no direct
13706 analogue in Modula-2.
13708 The @code{@@} operator (@pxref{Expressions, ,Expressions}), while available
13709 with any language, is not useful with Modula-2. Its
13710 intent is to aid the debugging of @dfn{dynamic arrays}, which cannot be
13711 created in Modula-2 as they can in C or C@t{++}. However, because an
13712 address can be specified by an integral constant, the construct
13713 @samp{@{@var{type}@}@var{adrexp}} is still useful.
13715 @cindex @code{#} in Modula-2
13716 In @value{GDBN} scripts, the Modula-2 inequality operator @code{#} is
13717 interpreted as the beginning of a comment. Use @code{<>} instead.
13723 The extensions made to @value{GDBN} for Ada only support
13724 output from the @sc{gnu} Ada (GNAT) compiler.
13725 Other Ada compilers are not currently supported, and
13726 attempting to debug executables produced by them is most likely
13730 @cindex expressions in Ada
13732 * Ada Mode Intro:: General remarks on the Ada syntax
13733 and semantics supported by Ada mode
13735 * Omissions from Ada:: Restrictions on the Ada expression syntax.
13736 * Additions to Ada:: Extensions of the Ada expression syntax.
13737 * Stopping Before Main Program:: Debugging the program during elaboration.
13738 * Ada Tasks:: Listing and setting breakpoints in tasks.
13739 * Ada Tasks and Core Files:: Tasking Support when Debugging Core Files
13740 * Ravenscar Profile:: Tasking Support when using the Ravenscar
13742 * Ada Glitches:: Known peculiarities of Ada mode.
13745 @node Ada Mode Intro
13746 @subsubsection Introduction
13747 @cindex Ada mode, general
13749 The Ada mode of @value{GDBN} supports a fairly large subset of Ada expression
13750 syntax, with some extensions.
13751 The philosophy behind the design of this subset is
13755 That @value{GDBN} should provide basic literals and access to operations for
13756 arithmetic, dereferencing, field selection, indexing, and subprogram calls,
13757 leaving more sophisticated computations to subprograms written into the
13758 program (which therefore may be called from @value{GDBN}).
13761 That type safety and strict adherence to Ada language restrictions
13762 are not particularly important to the @value{GDBN} user.
13765 That brevity is important to the @value{GDBN} user.
13768 Thus, for brevity, the debugger acts as if all names declared in
13769 user-written packages are directly visible, even if they are not visible
13770 according to Ada rules, thus making it unnecessary to fully qualify most
13771 names with their packages, regardless of context. Where this causes
13772 ambiguity, @value{GDBN} asks the user's intent.
13774 The debugger will start in Ada mode if it detects an Ada main program.
13775 As for other languages, it will enter Ada mode when stopped in a program that
13776 was translated from an Ada source file.
13778 While in Ada mode, you may use `@t{--}' for comments. This is useful
13779 mostly for documenting command files. The standard @value{GDBN} comment
13780 (@samp{#}) still works at the beginning of a line in Ada mode, but not in the
13781 middle (to allow based literals).
13783 The debugger supports limited overloading. Given a subprogram call in which
13784 the function symbol has multiple definitions, it will use the number of
13785 actual parameters and some information about their types to attempt to narrow
13786 the set of definitions. It also makes very limited use of context, preferring
13787 procedures to functions in the context of the @code{call} command, and
13788 functions to procedures elsewhere.
13790 @node Omissions from Ada
13791 @subsubsection Omissions from Ada
13792 @cindex Ada, omissions from
13794 Here are the notable omissions from the subset:
13798 Only a subset of the attributes are supported:
13802 @t{'First}, @t{'Last}, and @t{'Length}
13803 on array objects (not on types and subtypes).
13806 @t{'Min} and @t{'Max}.
13809 @t{'Pos} and @t{'Val}.
13815 @t{'Range} on array objects (not subtypes), but only as the right
13816 operand of the membership (@code{in}) operator.
13819 @t{'Access}, @t{'Unchecked_Access}, and
13820 @t{'Unrestricted_Access} (a GNAT extension).
13828 @code{Characters.Latin_1} are not available and
13829 concatenation is not implemented. Thus, escape characters in strings are
13830 not currently available.
13833 Equality tests (@samp{=} and @samp{/=}) on arrays test for bitwise
13834 equality of representations. They will generally work correctly
13835 for strings and arrays whose elements have integer or enumeration types.
13836 They may not work correctly for arrays whose element
13837 types have user-defined equality, for arrays of real values
13838 (in particular, IEEE-conformant floating point, because of negative
13839 zeroes and NaNs), and for arrays whose elements contain unused bits with
13840 indeterminate values.
13843 The other component-by-component array operations (@code{and}, @code{or},
13844 @code{xor}, @code{not}, and relational tests other than equality)
13845 are not implemented.
13848 @cindex array aggregates (Ada)
13849 @cindex record aggregates (Ada)
13850 @cindex aggregates (Ada)
13851 There is limited support for array and record aggregates. They are
13852 permitted only on the right sides of assignments, as in these examples:
13855 (@value{GDBP}) set An_Array := (1, 2, 3, 4, 5, 6)
13856 (@value{GDBP}) set An_Array := (1, others => 0)
13857 (@value{GDBP}) set An_Array := (0|4 => 1, 1..3 => 2, 5 => 6)
13858 (@value{GDBP}) set A_2D_Array := ((1, 2, 3), (4, 5, 6), (7, 8, 9))
13859 (@value{GDBP}) set A_Record := (1, "Peter", True);
13860 (@value{GDBP}) set A_Record := (Name => "Peter", Id => 1, Alive => True)
13864 discriminant's value by assigning an aggregate has an
13865 undefined effect if that discriminant is used within the record.
13866 However, you can first modify discriminants by directly assigning to
13867 them (which normally would not be allowed in Ada), and then performing an
13868 aggregate assignment. For example, given a variable @code{A_Rec}
13869 declared to have a type such as:
13872 type Rec (Len : Small_Integer := 0) is record
13874 Vals : IntArray (1 .. Len);
13878 you can assign a value with a different size of @code{Vals} with two
13882 (@value{GDBP}) set A_Rec.Len := 4
13883 (@value{GDBP}) set A_Rec := (Id => 42, Vals => (1, 2, 3, 4))
13886 As this example also illustrates, @value{GDBN} is very loose about the usual
13887 rules concerning aggregates. You may leave out some of the
13888 components of an array or record aggregate (such as the @code{Len}
13889 component in the assignment to @code{A_Rec} above); they will retain their
13890 original values upon assignment. You may freely use dynamic values as
13891 indices in component associations. You may even use overlapping or
13892 redundant component associations, although which component values are
13893 assigned in such cases is not defined.
13896 Calls to dispatching subprograms are not implemented.
13899 The overloading algorithm is much more limited (i.e., less selective)
13900 than that of real Ada. It makes only limited use of the context in
13901 which a subexpression appears to resolve its meaning, and it is much
13902 looser in its rules for allowing type matches. As a result, some
13903 function calls will be ambiguous, and the user will be asked to choose
13904 the proper resolution.
13907 The @code{new} operator is not implemented.
13910 Entry calls are not implemented.
13913 Aside from printing, arithmetic operations on the native VAX floating-point
13914 formats are not supported.
13917 It is not possible to slice a packed array.
13920 The names @code{True} and @code{False}, when not part of a qualified name,
13921 are interpreted as if implicitly prefixed by @code{Standard}, regardless of
13923 Should your program
13924 redefine these names in a package or procedure (at best a dubious practice),
13925 you will have to use fully qualified names to access their new definitions.
13928 @node Additions to Ada
13929 @subsubsection Additions to Ada
13930 @cindex Ada, deviations from
13932 As it does for other languages, @value{GDBN} makes certain generic
13933 extensions to Ada (@pxref{Expressions}):
13937 If the expression @var{E} is a variable residing in memory (typically
13938 a local variable or array element) and @var{N} is a positive integer,
13939 then @code{@var{E}@@@var{N}} displays the values of @var{E} and the
13940 @var{N}-1 adjacent variables following it in memory as an array. In
13941 Ada, this operator is generally not necessary, since its prime use is
13942 in displaying parts of an array, and slicing will usually do this in
13943 Ada. However, there are occasional uses when debugging programs in
13944 which certain debugging information has been optimized away.
13947 @code{@var{B}::@var{var}} means ``the variable named @var{var} that
13948 appears in function or file @var{B}.'' When @var{B} is a file name,
13949 you must typically surround it in single quotes.
13952 The expression @code{@{@var{type}@} @var{addr}} means ``the variable of type
13953 @var{type} that appears at address @var{addr}.''
13956 A name starting with @samp{$} is a convenience variable
13957 (@pxref{Convenience Vars}) or a machine register (@pxref{Registers}).
13960 In addition, @value{GDBN} provides a few other shortcuts and outright
13961 additions specific to Ada:
13965 The assignment statement is allowed as an expression, returning
13966 its right-hand operand as its value. Thus, you may enter
13969 (@value{GDBP}) set x := y + 3
13970 (@value{GDBP}) print A(tmp := y + 1)
13974 The semicolon is allowed as an ``operator,'' returning as its value
13975 the value of its right-hand operand.
13976 This allows, for example,
13977 complex conditional breaks:
13980 (@value{GDBP}) break f
13981 (@value{GDBP}) condition 1 (report(i); k += 1; A(k) > 100)
13985 Rather than use catenation and symbolic character names to introduce special
13986 characters into strings, one may instead use a special bracket notation,
13987 which is also used to print strings. A sequence of characters of the form
13988 @samp{["@var{XX}"]} within a string or character literal denotes the
13989 (single) character whose numeric encoding is @var{XX} in hexadecimal. The
13990 sequence of characters @samp{["""]} also denotes a single quotation mark
13991 in strings. For example,
13993 "One line.["0a"]Next line.["0a"]"
13996 contains an ASCII newline character (@code{Ada.Characters.Latin_1.LF})
14000 The subtype used as a prefix for the attributes @t{'Pos}, @t{'Min}, and
14001 @t{'Max} is optional (and is ignored in any case). For example, it is valid
14005 (@value{GDBP}) print 'max(x, y)
14009 When printing arrays, @value{GDBN} uses positional notation when the
14010 array has a lower bound of 1, and uses a modified named notation otherwise.
14011 For example, a one-dimensional array of three integers with a lower bound
14012 of 3 might print as
14019 That is, in contrast to valid Ada, only the first component has a @code{=>}
14023 You may abbreviate attributes in expressions with any unique,
14024 multi-character subsequence of
14025 their names (an exact match gets preference).
14026 For example, you may use @t{a'len}, @t{a'gth}, or @t{a'lh}
14027 in place of @t{a'length}.
14030 @cindex quoting Ada internal identifiers
14031 Since Ada is case-insensitive, the debugger normally maps identifiers you type
14032 to lower case. The GNAT compiler uses upper-case characters for
14033 some of its internal identifiers, which are normally of no interest to users.
14034 For the rare occasions when you actually have to look at them,
14035 enclose them in angle brackets to avoid the lower-case mapping.
14038 (@value{GDBP}) print <JMPBUF_SAVE>[0]
14042 Printing an object of class-wide type or dereferencing an
14043 access-to-class-wide value will display all the components of the object's
14044 specific type (as indicated by its run-time tag). Likewise, component
14045 selection on such a value will operate on the specific type of the
14050 @node Stopping Before Main Program
14051 @subsubsection Stopping at the Very Beginning
14053 @cindex breakpointing Ada elaboration code
14054 It is sometimes necessary to debug the program during elaboration, and
14055 before reaching the main procedure.
14056 As defined in the Ada Reference
14057 Manual, the elaboration code is invoked from a procedure called
14058 @code{adainit}. To run your program up to the beginning of
14059 elaboration, simply use the following two commands:
14060 @code{tbreak adainit} and @code{run}.
14063 @subsubsection Extensions for Ada Tasks
14064 @cindex Ada, tasking
14066 Support for Ada tasks is analogous to that for threads (@pxref{Threads}).
14067 @value{GDBN} provides the following task-related commands:
14072 This command shows a list of current Ada tasks, as in the following example:
14079 (@value{GDBP}) info tasks
14080 ID TID P-ID Pri State Name
14081 1 8088000 0 15 Child Activation Wait main_task
14082 2 80a4000 1 15 Accept Statement b
14083 3 809a800 1 15 Child Activation Wait a
14084 * 4 80ae800 3 15 Runnable c
14089 In this listing, the asterisk before the last task indicates it to be the
14090 task currently being inspected.
14094 Represents @value{GDBN}'s internal task number.
14100 The parent's task ID (@value{GDBN}'s internal task number).
14103 The base priority of the task.
14106 Current state of the task.
14110 The task has been created but has not been activated. It cannot be
14114 The task is not blocked for any reason known to Ada. (It may be waiting
14115 for a mutex, though.) It is conceptually "executing" in normal mode.
14118 The task is terminated, in the sense of ARM 9.3 (5). Any dependents
14119 that were waiting on terminate alternatives have been awakened and have
14120 terminated themselves.
14122 @item Child Activation Wait
14123 The task is waiting for created tasks to complete activation.
14125 @item Accept Statement
14126 The task is waiting on an accept or selective wait statement.
14128 @item Waiting on entry call
14129 The task is waiting on an entry call.
14131 @item Async Select Wait
14132 The task is waiting to start the abortable part of an asynchronous
14136 The task is waiting on a select statement with only a delay
14139 @item Child Termination Wait
14140 The task is sleeping having completed a master within itself, and is
14141 waiting for the tasks dependent on that master to become terminated or
14142 waiting on a terminate Phase.
14144 @item Wait Child in Term Alt
14145 The task is sleeping waiting for tasks on terminate alternatives to
14146 finish terminating.
14148 @item Accepting RV with @var{taskno}
14149 The task is accepting a rendez-vous with the task @var{taskno}.
14153 Name of the task in the program.
14157 @kindex info task @var{taskno}
14158 @item info task @var{taskno}
14159 This command shows detailled informations on the specified task, as in
14160 the following example:
14165 (@value{GDBP}) info tasks
14166 ID TID P-ID Pri State Name
14167 1 8077880 0 15 Child Activation Wait main_task
14168 * 2 807c468 1 15 Runnable task_1
14169 (@value{GDBP}) info task 2
14170 Ada Task: 0x807c468
14173 Parent: 1 (main_task)
14179 @kindex task@r{ (Ada)}
14180 @cindex current Ada task ID
14181 This command prints the ID of the current task.
14187 (@value{GDBP}) info tasks
14188 ID TID P-ID Pri State Name
14189 1 8077870 0 15 Child Activation Wait main_task
14190 * 2 807c458 1 15 Runnable t
14191 (@value{GDBP}) task
14192 [Current task is 2]
14195 @item task @var{taskno}
14196 @cindex Ada task switching
14197 This command is like the @code{thread @var{threadno}}
14198 command (@pxref{Threads}). It switches the context of debugging
14199 from the current task to the given task.
14205 (@value{GDBP}) info tasks
14206 ID TID P-ID Pri State Name
14207 1 8077870 0 15 Child Activation Wait main_task
14208 * 2 807c458 1 15 Runnable t
14209 (@value{GDBP}) task 1
14210 [Switching to task 1]
14211 #0 0x8067726 in pthread_cond_wait ()
14213 #0 0x8067726 in pthread_cond_wait ()
14214 #1 0x8056714 in system.os_interface.pthread_cond_wait ()
14215 #2 0x805cb63 in system.task_primitives.operations.sleep ()
14216 #3 0x806153e in system.tasking.stages.activate_tasks ()
14217 #4 0x804aacc in un () at un.adb:5
14220 @item break @var{linespec} task @var{taskno}
14221 @itemx break @var{linespec} task @var{taskno} if @dots{}
14222 @cindex breakpoints and tasks, in Ada
14223 @cindex task breakpoints, in Ada
14224 @kindex break @dots{} task @var{taskno}@r{ (Ada)}
14225 These commands are like the @code{break @dots{} thread @dots{}}
14226 command (@pxref{Thread Stops}).
14227 @var{linespec} specifies source lines, as described
14228 in @ref{Specify Location}.
14230 Use the qualifier @samp{task @var{taskno}} with a breakpoint command
14231 to specify that you only want @value{GDBN} to stop the program when a
14232 particular Ada task reaches this breakpoint. @var{taskno} is one of the
14233 numeric task identifiers assigned by @value{GDBN}, shown in the first
14234 column of the @samp{info tasks} display.
14236 If you do not specify @samp{task @var{taskno}} when you set a
14237 breakpoint, the breakpoint applies to @emph{all} tasks of your
14240 You can use the @code{task} qualifier on conditional breakpoints as
14241 well; in this case, place @samp{task @var{taskno}} before the
14242 breakpoint condition (before the @code{if}).
14250 (@value{GDBP}) info tasks
14251 ID TID P-ID Pri State Name
14252 1 140022020 0 15 Child Activation Wait main_task
14253 2 140045060 1 15 Accept/Select Wait t2
14254 3 140044840 1 15 Runnable t1
14255 * 4 140056040 1 15 Runnable t3
14256 (@value{GDBP}) b 15 task 2
14257 Breakpoint 5 at 0x120044cb0: file test_task_debug.adb, line 15.
14258 (@value{GDBP}) cont
14263 Breakpoint 5, test_task_debug () at test_task_debug.adb:15
14265 (@value{GDBP}) info tasks
14266 ID TID P-ID Pri State Name
14267 1 140022020 0 15 Child Activation Wait main_task
14268 * 2 140045060 1 15 Runnable t2
14269 3 140044840 1 15 Runnable t1
14270 4 140056040 1 15 Delay Sleep t3
14274 @node Ada Tasks and Core Files
14275 @subsubsection Tasking Support when Debugging Core Files
14276 @cindex Ada tasking and core file debugging
14278 When inspecting a core file, as opposed to debugging a live program,
14279 tasking support may be limited or even unavailable, depending on
14280 the platform being used.
14281 For instance, on x86-linux, the list of tasks is available, but task
14282 switching is not supported. On Tru64, however, task switching will work
14285 On certain platforms, including Tru64, the debugger needs to perform some
14286 memory writes in order to provide Ada tasking support. When inspecting
14287 a core file, this means that the core file must be opened with read-write
14288 privileges, using the command @samp{"set write on"} (@pxref{Patching}).
14289 Under these circumstances, you should make a backup copy of the core
14290 file before inspecting it with @value{GDBN}.
14292 @node Ravenscar Profile
14293 @subsubsection Tasking Support when using the Ravenscar Profile
14294 @cindex Ravenscar Profile
14296 The @dfn{Ravenscar Profile} is a subset of the Ada tasking features,
14297 specifically designed for systems with safety-critical real-time
14301 @kindex set ravenscar task-switching on
14302 @cindex task switching with program using Ravenscar Profile
14303 @item set ravenscar task-switching on
14304 Allows task switching when debugging a program that uses the Ravenscar
14305 Profile. This is the default.
14307 @kindex set ravenscar task-switching off
14308 @item set ravenscar task-switching off
14309 Turn off task switching when debugging a program that uses the Ravenscar
14310 Profile. This is mostly intended to disable the code that adds support
14311 for the Ravenscar Profile, in case a bug in either @value{GDBN} or in
14312 the Ravenscar runtime is preventing @value{GDBN} from working properly.
14313 To be effective, this command should be run before the program is started.
14315 @kindex show ravenscar task-switching
14316 @item show ravenscar task-switching
14317 Show whether it is possible to switch from task to task in a program
14318 using the Ravenscar Profile.
14323 @subsubsection Known Peculiarities of Ada Mode
14324 @cindex Ada, problems
14326 Besides the omissions listed previously (@pxref{Omissions from Ada}),
14327 we know of several problems with and limitations of Ada mode in
14329 some of which will be fixed with planned future releases of the debugger
14330 and the GNU Ada compiler.
14334 Static constants that the compiler chooses not to materialize as objects in
14335 storage are invisible to the debugger.
14338 Named parameter associations in function argument lists are ignored (the
14339 argument lists are treated as positional).
14342 Many useful library packages are currently invisible to the debugger.
14345 Fixed-point arithmetic, conversions, input, and output is carried out using
14346 floating-point arithmetic, and may give results that only approximate those on
14350 The GNAT compiler never generates the prefix @code{Standard} for any of
14351 the standard symbols defined by the Ada language. @value{GDBN} knows about
14352 this: it will strip the prefix from names when you use it, and will never
14353 look for a name you have so qualified among local symbols, nor match against
14354 symbols in other packages or subprograms. If you have
14355 defined entities anywhere in your program other than parameters and
14356 local variables whose simple names match names in @code{Standard},
14357 GNAT's lack of qualification here can cause confusion. When this happens,
14358 you can usually resolve the confusion
14359 by qualifying the problematic names with package
14360 @code{Standard} explicitly.
14363 Older versions of the compiler sometimes generate erroneous debugging
14364 information, resulting in the debugger incorrectly printing the value
14365 of affected entities. In some cases, the debugger is able to work
14366 around an issue automatically. In other cases, the debugger is able
14367 to work around the issue, but the work-around has to be specifically
14370 @kindex set ada trust-PAD-over-XVS
14371 @kindex show ada trust-PAD-over-XVS
14374 @item set ada trust-PAD-over-XVS on
14375 Configure GDB to strictly follow the GNAT encoding when computing the
14376 value of Ada entities, particularly when @code{PAD} and @code{PAD___XVS}
14377 types are involved (see @code{ada/exp_dbug.ads} in the GCC sources for
14378 a complete description of the encoding used by the GNAT compiler).
14379 This is the default.
14381 @item set ada trust-PAD-over-XVS off
14382 This is related to the encoding using by the GNAT compiler. If @value{GDBN}
14383 sometimes prints the wrong value for certain entities, changing @code{ada
14384 trust-PAD-over-XVS} to @code{off} activates a work-around which may fix
14385 the issue. It is always safe to set @code{ada trust-PAD-over-XVS} to
14386 @code{off}, but this incurs a slight performance penalty, so it is
14387 recommended to leave this setting to @code{on} unless necessary.
14391 @node Unsupported Languages
14392 @section Unsupported Languages
14394 @cindex unsupported languages
14395 @cindex minimal language
14396 In addition to the other fully-supported programming languages,
14397 @value{GDBN} also provides a pseudo-language, called @code{minimal}.
14398 It does not represent a real programming language, but provides a set
14399 of capabilities close to what the C or assembly languages provide.
14400 This should allow most simple operations to be performed while debugging
14401 an application that uses a language currently not supported by @value{GDBN}.
14403 If the language is set to @code{auto}, @value{GDBN} will automatically
14404 select this language if the current frame corresponds to an unsupported
14408 @chapter Examining the Symbol Table
14410 The commands described in this chapter allow you to inquire about the
14411 symbols (names of variables, functions and types) defined in your
14412 program. This information is inherent in the text of your program and
14413 does not change as your program executes. @value{GDBN} finds it in your
14414 program's symbol table, in the file indicated when you started @value{GDBN}
14415 (@pxref{File Options, ,Choosing Files}), or by one of the
14416 file-management commands (@pxref{Files, ,Commands to Specify Files}).
14418 @cindex symbol names
14419 @cindex names of symbols
14420 @cindex quoting names
14421 Occasionally, you may need to refer to symbols that contain unusual
14422 characters, which @value{GDBN} ordinarily treats as word delimiters. The
14423 most frequent case is in referring to static variables in other
14424 source files (@pxref{Variables,,Program Variables}). File names
14425 are recorded in object files as debugging symbols, but @value{GDBN} would
14426 ordinarily parse a typical file name, like @file{foo.c}, as the three words
14427 @samp{foo} @samp{.} @samp{c}. To allow @value{GDBN} to recognize
14428 @samp{foo.c} as a single symbol, enclose it in single quotes; for example,
14435 looks up the value of @code{x} in the scope of the file @file{foo.c}.
14438 @cindex case-insensitive symbol names
14439 @cindex case sensitivity in symbol names
14440 @kindex set case-sensitive
14441 @item set case-sensitive on
14442 @itemx set case-sensitive off
14443 @itemx set case-sensitive auto
14444 Normally, when @value{GDBN} looks up symbols, it matches their names
14445 with case sensitivity determined by the current source language.
14446 Occasionally, you may wish to control that. The command @code{set
14447 case-sensitive} lets you do that by specifying @code{on} for
14448 case-sensitive matches or @code{off} for case-insensitive ones. If
14449 you specify @code{auto}, case sensitivity is reset to the default
14450 suitable for the source language. The default is case-sensitive
14451 matches for all languages except for Fortran, for which the default is
14452 case-insensitive matches.
14454 @kindex show case-sensitive
14455 @item show case-sensitive
14456 This command shows the current setting of case sensitivity for symbols
14459 @kindex info address
14460 @cindex address of a symbol
14461 @item info address @var{symbol}
14462 Describe where the data for @var{symbol} is stored. For a register
14463 variable, this says which register it is kept in. For a non-register
14464 local variable, this prints the stack-frame offset at which the variable
14467 Note the contrast with @samp{print &@var{symbol}}, which does not work
14468 at all for a register variable, and for a stack local variable prints
14469 the exact address of the current instantiation of the variable.
14471 @kindex info symbol
14472 @cindex symbol from address
14473 @cindex closest symbol and offset for an address
14474 @item info symbol @var{addr}
14475 Print the name of a symbol which is stored at the address @var{addr}.
14476 If no symbol is stored exactly at @var{addr}, @value{GDBN} prints the
14477 nearest symbol and an offset from it:
14480 (@value{GDBP}) info symbol 0x54320
14481 _initialize_vx + 396 in section .text
14485 This is the opposite of the @code{info address} command. You can use
14486 it to find out the name of a variable or a function given its address.
14488 For dynamically linked executables, the name of executable or shared
14489 library containing the symbol is also printed:
14492 (@value{GDBP}) info symbol 0x400225
14493 _start + 5 in section .text of /tmp/a.out
14494 (@value{GDBP}) info symbol 0x2aaaac2811cf
14495 __read_nocancel + 6 in section .text of /usr/lib64/libc.so.6
14499 @item whatis [@var{arg}]
14500 Print the data type of @var{arg}, which can be either an expression
14501 or a name of a data type. With no argument, print the data type of
14502 @code{$}, the last value in the value history.
14504 If @var{arg} is an expression (@pxref{Expressions, ,Expressions}), it
14505 is not actually evaluated, and any side-effecting operations (such as
14506 assignments or function calls) inside it do not take place.
14508 If @var{arg} is a variable or an expression, @code{whatis} prints its
14509 literal type as it is used in the source code. If the type was
14510 defined using a @code{typedef}, @code{whatis} will @emph{not} print
14511 the data type underlying the @code{typedef}. If the type of the
14512 variable or the expression is a compound data type, such as
14513 @code{struct} or @code{class}, @code{whatis} never prints their
14514 fields or methods. It just prints the @code{struct}/@code{class}
14515 name (a.k.a.@: its @dfn{tag}). If you want to see the members of
14516 such a compound data type, use @code{ptype}.
14518 If @var{arg} is a type name that was defined using @code{typedef},
14519 @code{whatis} @dfn{unrolls} only one level of that @code{typedef}.
14520 Unrolling means that @code{whatis} will show the underlying type used
14521 in the @code{typedef} declaration of @var{arg}. However, if that
14522 underlying type is also a @code{typedef}, @code{whatis} will not
14525 For C code, the type names may also have the form @samp{class
14526 @var{class-name}}, @samp{struct @var{struct-tag}}, @samp{union
14527 @var{union-tag}} or @samp{enum @var{enum-tag}}.
14530 @item ptype [@var{arg}]
14531 @code{ptype} accepts the same arguments as @code{whatis}, but prints a
14532 detailed description of the type, instead of just the name of the type.
14533 @xref{Expressions, ,Expressions}.
14535 Contrary to @code{whatis}, @code{ptype} always unrolls any
14536 @code{typedef}s in its argument declaration, whether the argument is
14537 a variable, expression, or a data type. This means that @code{ptype}
14538 of a variable or an expression will not print literally its type as
14539 present in the source code---use @code{whatis} for that. @code{typedef}s at
14540 the pointer or reference targets are also unrolled. Only @code{typedef}s of
14541 fields, methods and inner @code{class typedef}s of @code{struct}s,
14542 @code{class}es and @code{union}s are not unrolled even with @code{ptype}.
14544 For example, for this variable declaration:
14547 typedef double real_t;
14548 struct complex @{ real_t real; double imag; @};
14549 typedef struct complex complex_t;
14551 real_t *real_pointer_var;
14555 the two commands give this output:
14559 (@value{GDBP}) whatis var
14561 (@value{GDBP}) ptype var
14562 type = struct complex @{
14566 (@value{GDBP}) whatis complex_t
14567 type = struct complex
14568 (@value{GDBP}) whatis struct complex
14569 type = struct complex
14570 (@value{GDBP}) ptype struct complex
14571 type = struct complex @{
14575 (@value{GDBP}) whatis real_pointer_var
14577 (@value{GDBP}) ptype real_pointer_var
14583 As with @code{whatis}, using @code{ptype} without an argument refers to
14584 the type of @code{$}, the last value in the value history.
14586 @cindex incomplete type
14587 Sometimes, programs use opaque data types or incomplete specifications
14588 of complex data structure. If the debug information included in the
14589 program does not allow @value{GDBN} to display a full declaration of
14590 the data type, it will say @samp{<incomplete type>}. For example,
14591 given these declarations:
14595 struct foo *fooptr;
14599 but no definition for @code{struct foo} itself, @value{GDBN} will say:
14602 (@value{GDBP}) ptype foo
14603 $1 = <incomplete type>
14607 ``Incomplete type'' is C terminology for data types that are not
14608 completely specified.
14611 @item info types @var{regexp}
14613 Print a brief description of all types whose names match the regular
14614 expression @var{regexp} (or all types in your program, if you supply
14615 no argument). Each complete typename is matched as though it were a
14616 complete line; thus, @samp{i type value} gives information on all
14617 types in your program whose names include the string @code{value}, but
14618 @samp{i type ^value$} gives information only on types whose complete
14619 name is @code{value}.
14621 This command differs from @code{ptype} in two ways: first, like
14622 @code{whatis}, it does not print a detailed description; second, it
14623 lists all source files where a type is defined.
14626 @cindex local variables
14627 @item info scope @var{location}
14628 List all the variables local to a particular scope. This command
14629 accepts a @var{location} argument---a function name, a source line, or
14630 an address preceded by a @samp{*}, and prints all the variables local
14631 to the scope defined by that location. (@xref{Specify Location}, for
14632 details about supported forms of @var{location}.) For example:
14635 (@value{GDBP}) @b{info scope command_line_handler}
14636 Scope for command_line_handler:
14637 Symbol rl is an argument at stack/frame offset 8, length 4.
14638 Symbol linebuffer is in static storage at address 0x150a18, length 4.
14639 Symbol linelength is in static storage at address 0x150a1c, length 4.
14640 Symbol p is a local variable in register $esi, length 4.
14641 Symbol p1 is a local variable in register $ebx, length 4.
14642 Symbol nline is a local variable in register $edx, length 4.
14643 Symbol repeat is a local variable at frame offset -8, length 4.
14647 This command is especially useful for determining what data to collect
14648 during a @dfn{trace experiment}, see @ref{Tracepoint Actions,
14651 @kindex info source
14653 Show information about the current source file---that is, the source file for
14654 the function containing the current point of execution:
14657 the name of the source file, and the directory containing it,
14659 the directory it was compiled in,
14661 its length, in lines,
14663 which programming language it is written in,
14665 whether the executable includes debugging information for that file, and
14666 if so, what format the information is in (e.g., STABS, Dwarf 2, etc.), and
14668 whether the debugging information includes information about
14669 preprocessor macros.
14673 @kindex info sources
14675 Print the names of all source files in your program for which there is
14676 debugging information, organized into two lists: files whose symbols
14677 have already been read, and files whose symbols will be read when needed.
14679 @kindex info functions
14680 @item info functions
14681 Print the names and data types of all defined functions.
14683 @item info functions @var{regexp}
14684 Print the names and data types of all defined functions
14685 whose names contain a match for regular expression @var{regexp}.
14686 Thus, @samp{info fun step} finds all functions whose names
14687 include @code{step}; @samp{info fun ^step} finds those whose names
14688 start with @code{step}. If a function name contains characters
14689 that conflict with the regular expression language (e.g.@:
14690 @samp{operator*()}), they may be quoted with a backslash.
14692 @kindex info variables
14693 @item info variables
14694 Print the names and data types of all variables that are defined
14695 outside of functions (i.e.@: excluding local variables).
14697 @item info variables @var{regexp}
14698 Print the names and data types of all variables (except for local
14699 variables) whose names contain a match for regular expression
14702 @kindex info classes
14703 @cindex Objective-C, classes and selectors
14705 @itemx info classes @var{regexp}
14706 Display all Objective-C classes in your program, or
14707 (with the @var{regexp} argument) all those matching a particular regular
14710 @kindex info selectors
14711 @item info selectors
14712 @itemx info selectors @var{regexp}
14713 Display all Objective-C selectors in your program, or
14714 (with the @var{regexp} argument) all those matching a particular regular
14718 This was never implemented.
14719 @kindex info methods
14721 @itemx info methods @var{regexp}
14722 The @code{info methods} command permits the user to examine all defined
14723 methods within C@t{++} program, or (with the @var{regexp} argument) a
14724 specific set of methods found in the various C@t{++} classes. Many
14725 C@t{++} classes provide a large number of methods. Thus, the output
14726 from the @code{ptype} command can be overwhelming and hard to use. The
14727 @code{info-methods} command filters the methods, printing only those
14728 which match the regular-expression @var{regexp}.
14731 @cindex opaque data types
14732 @kindex set opaque-type-resolution
14733 @item set opaque-type-resolution on
14734 Tell @value{GDBN} to resolve opaque types. An opaque type is a type
14735 declared as a pointer to a @code{struct}, @code{class}, or
14736 @code{union}---for example, @code{struct MyType *}---that is used in one
14737 source file although the full declaration of @code{struct MyType} is in
14738 another source file. The default is on.
14740 A change in the setting of this subcommand will not take effect until
14741 the next time symbols for a file are loaded.
14743 @item set opaque-type-resolution off
14744 Tell @value{GDBN} not to resolve opaque types. In this case, the type
14745 is printed as follows:
14747 @{<no data fields>@}
14750 @kindex show opaque-type-resolution
14751 @item show opaque-type-resolution
14752 Show whether opaque types are resolved or not.
14754 @kindex maint print symbols
14755 @cindex symbol dump
14756 @kindex maint print psymbols
14757 @cindex partial symbol dump
14758 @item maint print symbols @var{filename}
14759 @itemx maint print psymbols @var{filename}
14760 @itemx maint print msymbols @var{filename}
14761 Write a dump of debugging symbol data into the file @var{filename}.
14762 These commands are used to debug the @value{GDBN} symbol-reading code. Only
14763 symbols with debugging data are included. If you use @samp{maint print
14764 symbols}, @value{GDBN} includes all the symbols for which it has already
14765 collected full details: that is, @var{filename} reflects symbols for
14766 only those files whose symbols @value{GDBN} has read. You can use the
14767 command @code{info sources} to find out which files these are. If you
14768 use @samp{maint print psymbols} instead, the dump shows information about
14769 symbols that @value{GDBN} only knows partially---that is, symbols defined in
14770 files that @value{GDBN} has skimmed, but not yet read completely. Finally,
14771 @samp{maint print msymbols} dumps just the minimal symbol information
14772 required for each object file from which @value{GDBN} has read some symbols.
14773 @xref{Files, ,Commands to Specify Files}, for a discussion of how
14774 @value{GDBN} reads symbols (in the description of @code{symbol-file}).
14776 @kindex maint info symtabs
14777 @kindex maint info psymtabs
14778 @cindex listing @value{GDBN}'s internal symbol tables
14779 @cindex symbol tables, listing @value{GDBN}'s internal
14780 @cindex full symbol tables, listing @value{GDBN}'s internal
14781 @cindex partial symbol tables, listing @value{GDBN}'s internal
14782 @item maint info symtabs @r{[} @var{regexp} @r{]}
14783 @itemx maint info psymtabs @r{[} @var{regexp} @r{]}
14785 List the @code{struct symtab} or @code{struct partial_symtab}
14786 structures whose names match @var{regexp}. If @var{regexp} is not
14787 given, list them all. The output includes expressions which you can
14788 copy into a @value{GDBN} debugging this one to examine a particular
14789 structure in more detail. For example:
14792 (@value{GDBP}) maint info psymtabs dwarf2read
14793 @{ objfile /home/gnu/build/gdb/gdb
14794 ((struct objfile *) 0x82e69d0)
14795 @{ psymtab /home/gnu/src/gdb/dwarf2read.c
14796 ((struct partial_symtab *) 0x8474b10)
14799 text addresses 0x814d3c8 -- 0x8158074
14800 globals (* (struct partial_symbol **) 0x8507a08 @@ 9)
14801 statics (* (struct partial_symbol **) 0x40e95b78 @@ 2882)
14802 dependencies (none)
14805 (@value{GDBP}) maint info symtabs
14809 We see that there is one partial symbol table whose filename contains
14810 the string @samp{dwarf2read}, belonging to the @samp{gdb} executable;
14811 and we see that @value{GDBN} has not read in any symtabs yet at all.
14812 If we set a breakpoint on a function, that will cause @value{GDBN} to
14813 read the symtab for the compilation unit containing that function:
14816 (@value{GDBP}) break dwarf2_psymtab_to_symtab
14817 Breakpoint 1 at 0x814e5da: file /home/gnu/src/gdb/dwarf2read.c,
14819 (@value{GDBP}) maint info symtabs
14820 @{ objfile /home/gnu/build/gdb/gdb
14821 ((struct objfile *) 0x82e69d0)
14822 @{ symtab /home/gnu/src/gdb/dwarf2read.c
14823 ((struct symtab *) 0x86c1f38)
14826 blockvector ((struct blockvector *) 0x86c1bd0) (primary)
14827 linetable ((struct linetable *) 0x8370fa0)
14828 debugformat DWARF 2
14837 @chapter Altering Execution
14839 Once you think you have found an error in your program, you might want to
14840 find out for certain whether correcting the apparent error would lead to
14841 correct results in the rest of the run. You can find the answer by
14842 experiment, using the @value{GDBN} features for altering execution of the
14845 For example, you can store new values into variables or memory
14846 locations, give your program a signal, restart it at a different
14847 address, or even return prematurely from a function.
14850 * Assignment:: Assignment to variables
14851 * Jumping:: Continuing at a different address
14852 * Signaling:: Giving your program a signal
14853 * Returning:: Returning from a function
14854 * Calling:: Calling your program's functions
14855 * Patching:: Patching your program
14859 @section Assignment to Variables
14862 @cindex setting variables
14863 To alter the value of a variable, evaluate an assignment expression.
14864 @xref{Expressions, ,Expressions}. For example,
14871 stores the value 4 into the variable @code{x}, and then prints the
14872 value of the assignment expression (which is 4).
14873 @xref{Languages, ,Using @value{GDBN} with Different Languages}, for more
14874 information on operators in supported languages.
14876 @kindex set variable
14877 @cindex variables, setting
14878 If you are not interested in seeing the value of the assignment, use the
14879 @code{set} command instead of the @code{print} command. @code{set} is
14880 really the same as @code{print} except that the expression's value is
14881 not printed and is not put in the value history (@pxref{Value History,
14882 ,Value History}). The expression is evaluated only for its effects.
14884 If the beginning of the argument string of the @code{set} command
14885 appears identical to a @code{set} subcommand, use the @code{set
14886 variable} command instead of just @code{set}. This command is identical
14887 to @code{set} except for its lack of subcommands. For example, if your
14888 program has a variable @code{width}, you get an error if you try to set
14889 a new value with just @samp{set width=13}, because @value{GDBN} has the
14890 command @code{set width}:
14893 (@value{GDBP}) whatis width
14895 (@value{GDBP}) p width
14897 (@value{GDBP}) set width=47
14898 Invalid syntax in expression.
14902 The invalid expression, of course, is @samp{=47}. In
14903 order to actually set the program's variable @code{width}, use
14906 (@value{GDBP}) set var width=47
14909 Because the @code{set} command has many subcommands that can conflict
14910 with the names of program variables, it is a good idea to use the
14911 @code{set variable} command instead of just @code{set}. For example, if
14912 your program has a variable @code{g}, you run into problems if you try
14913 to set a new value with just @samp{set g=4}, because @value{GDBN} has
14914 the command @code{set gnutarget}, abbreviated @code{set g}:
14918 (@value{GDBP}) whatis g
14922 (@value{GDBP}) set g=4
14926 The program being debugged has been started already.
14927 Start it from the beginning? (y or n) y
14928 Starting program: /home/smith/cc_progs/a.out
14929 "/home/smith/cc_progs/a.out": can't open to read symbols:
14930 Invalid bfd target.
14931 (@value{GDBP}) show g
14932 The current BFD target is "=4".
14937 The program variable @code{g} did not change, and you silently set the
14938 @code{gnutarget} to an invalid value. In order to set the variable
14942 (@value{GDBP}) set var g=4
14945 @value{GDBN} allows more implicit conversions in assignments than C; you can
14946 freely store an integer value into a pointer variable or vice versa,
14947 and you can convert any structure to any other structure that is the
14948 same length or shorter.
14949 @comment FIXME: how do structs align/pad in these conversions?
14950 @comment /doc@cygnus.com 18dec1990
14952 To store values into arbitrary places in memory, use the @samp{@{@dots{}@}}
14953 construct to generate a value of specified type at a specified address
14954 (@pxref{Expressions, ,Expressions}). For example, @code{@{int@}0x83040} refers
14955 to memory location @code{0x83040} as an integer (which implies a certain size
14956 and representation in memory), and
14959 set @{int@}0x83040 = 4
14963 stores the value 4 into that memory location.
14966 @section Continuing at a Different Address
14968 Ordinarily, when you continue your program, you do so at the place where
14969 it stopped, with the @code{continue} command. You can instead continue at
14970 an address of your own choosing, with the following commands:
14974 @item jump @var{linespec}
14975 @itemx jump @var{location}
14976 Resume execution at line @var{linespec} or at address given by
14977 @var{location}. Execution stops again immediately if there is a
14978 breakpoint there. @xref{Specify Location}, for a description of the
14979 different forms of @var{linespec} and @var{location}. It is common
14980 practice to use the @code{tbreak} command in conjunction with
14981 @code{jump}. @xref{Set Breaks, ,Setting Breakpoints}.
14983 The @code{jump} command does not change the current stack frame, or
14984 the stack pointer, or the contents of any memory location or any
14985 register other than the program counter. If line @var{linespec} is in
14986 a different function from the one currently executing, the results may
14987 be bizarre if the two functions expect different patterns of arguments or
14988 of local variables. For this reason, the @code{jump} command requests
14989 confirmation if the specified line is not in the function currently
14990 executing. However, even bizarre results are predictable if you are
14991 well acquainted with the machine-language code of your program.
14994 @c Doesn't work on HP-UX; have to set $pcoqh and $pcoqt.
14995 On many systems, you can get much the same effect as the @code{jump}
14996 command by storing a new value into the register @code{$pc}. The
14997 difference is that this does not start your program running; it only
14998 changes the address of where it @emph{will} run when you continue. For
15006 makes the next @code{continue} command or stepping command execute at
15007 address @code{0x485}, rather than at the address where your program stopped.
15008 @xref{Continuing and Stepping, ,Continuing and Stepping}.
15010 The most common occasion to use the @code{jump} command is to back
15011 up---perhaps with more breakpoints set---over a portion of a program
15012 that has already executed, in order to examine its execution in more
15017 @section Giving your Program a Signal
15018 @cindex deliver a signal to a program
15022 @item signal @var{signal}
15023 Resume execution where your program stopped, but immediately give it the
15024 signal @var{signal}. @var{signal} can be the name or the number of a
15025 signal. For example, on many systems @code{signal 2} and @code{signal
15026 SIGINT} are both ways of sending an interrupt signal.
15028 Alternatively, if @var{signal} is zero, continue execution without
15029 giving a signal. This is useful when your program stopped on account of
15030 a signal and would ordinary see the signal when resumed with the
15031 @code{continue} command; @samp{signal 0} causes it to resume without a
15034 @code{signal} does not repeat when you press @key{RET} a second time
15035 after executing the command.
15039 Invoking the @code{signal} command is not the same as invoking the
15040 @code{kill} utility from the shell. Sending a signal with @code{kill}
15041 causes @value{GDBN} to decide what to do with the signal depending on
15042 the signal handling tables (@pxref{Signals}). The @code{signal} command
15043 passes the signal directly to your program.
15047 @section Returning from a Function
15050 @cindex returning from a function
15053 @itemx return @var{expression}
15054 You can cancel execution of a function call with the @code{return}
15055 command. If you give an
15056 @var{expression} argument, its value is used as the function's return
15060 When you use @code{return}, @value{GDBN} discards the selected stack frame
15061 (and all frames within it). You can think of this as making the
15062 discarded frame return prematurely. If you wish to specify a value to
15063 be returned, give that value as the argument to @code{return}.
15065 This pops the selected stack frame (@pxref{Selection, ,Selecting a
15066 Frame}), and any other frames inside of it, leaving its caller as the
15067 innermost remaining frame. That frame becomes selected. The
15068 specified value is stored in the registers used for returning values
15071 The @code{return} command does not resume execution; it leaves the
15072 program stopped in the state that would exist if the function had just
15073 returned. In contrast, the @code{finish} command (@pxref{Continuing
15074 and Stepping, ,Continuing and Stepping}) resumes execution until the
15075 selected stack frame returns naturally.
15077 @value{GDBN} needs to know how the @var{expression} argument should be set for
15078 the inferior. The concrete registers assignment depends on the OS ABI and the
15079 type being returned by the selected stack frame. For example it is common for
15080 OS ABI to return floating point values in FPU registers while integer values in
15081 CPU registers. Still some ABIs return even floating point values in CPU
15082 registers. Larger integer widths (such as @code{long long int}) also have
15083 specific placement rules. @value{GDBN} already knows the OS ABI from its
15084 current target so it needs to find out also the type being returned to make the
15085 assignment into the right register(s).
15087 Normally, the selected stack frame has debug info. @value{GDBN} will always
15088 use the debug info instead of the implicit type of @var{expression} when the
15089 debug info is available. For example, if you type @kbd{return -1}, and the
15090 function in the current stack frame is declared to return a @code{long long
15091 int}, @value{GDBN} transparently converts the implicit @code{int} value of -1
15092 into a @code{long long int}:
15095 Breakpoint 1, func () at gdb.base/return-nodebug.c:29
15097 (@value{GDBP}) return -1
15098 Make func return now? (y or n) y
15099 #0 0x004004f6 in main () at gdb.base/return-nodebug.c:43
15100 43 printf ("result=%lld\n", func ());
15104 However, if the selected stack frame does not have a debug info, e.g., if the
15105 function was compiled without debug info, @value{GDBN} has to find out the type
15106 to return from user. Specifying a different type by mistake may set the value
15107 in different inferior registers than the caller code expects. For example,
15108 typing @kbd{return -1} with its implicit type @code{int} would set only a part
15109 of a @code{long long int} result for a debug info less function (on 32-bit
15110 architectures). Therefore the user is required to specify the return type by
15111 an appropriate cast explicitly:
15114 Breakpoint 2, 0x0040050b in func ()
15115 (@value{GDBP}) return -1
15116 Return value type not available for selected stack frame.
15117 Please use an explicit cast of the value to return.
15118 (@value{GDBP}) return (long long int) -1
15119 Make selected stack frame return now? (y or n) y
15120 #0 0x00400526 in main ()
15125 @section Calling Program Functions
15128 @cindex calling functions
15129 @cindex inferior functions, calling
15130 @item print @var{expr}
15131 Evaluate the expression @var{expr} and display the resulting value.
15132 @var{expr} may include calls to functions in the program being
15136 @item call @var{expr}
15137 Evaluate the expression @var{expr} without displaying @code{void}
15140 You can use this variant of the @code{print} command if you want to
15141 execute a function from your program that does not return anything
15142 (a.k.a.@: @dfn{a void function}), but without cluttering the output
15143 with @code{void} returned values that @value{GDBN} will otherwise
15144 print. If the result is not void, it is printed and saved in the
15148 It is possible for the function you call via the @code{print} or
15149 @code{call} command to generate a signal (e.g., if there's a bug in
15150 the function, or if you passed it incorrect arguments). What happens
15151 in that case is controlled by the @code{set unwindonsignal} command.
15153 Similarly, with a C@t{++} program it is possible for the function you
15154 call via the @code{print} or @code{call} command to generate an
15155 exception that is not handled due to the constraints of the dummy
15156 frame. In this case, any exception that is raised in the frame, but has
15157 an out-of-frame exception handler will not be found. GDB builds a
15158 dummy-frame for the inferior function call, and the unwinder cannot
15159 seek for exception handlers outside of this dummy-frame. What happens
15160 in that case is controlled by the
15161 @code{set unwind-on-terminating-exception} command.
15164 @item set unwindonsignal
15165 @kindex set unwindonsignal
15166 @cindex unwind stack in called functions
15167 @cindex call dummy stack unwinding
15168 Set unwinding of the stack if a signal is received while in a function
15169 that @value{GDBN} called in the program being debugged. If set to on,
15170 @value{GDBN} unwinds the stack it created for the call and restores
15171 the context to what it was before the call. If set to off (the
15172 default), @value{GDBN} stops in the frame where the signal was
15175 @item show unwindonsignal
15176 @kindex show unwindonsignal
15177 Show the current setting of stack unwinding in the functions called by
15180 @item set unwind-on-terminating-exception
15181 @kindex set unwind-on-terminating-exception
15182 @cindex unwind stack in called functions with unhandled exceptions
15183 @cindex call dummy stack unwinding on unhandled exception.
15184 Set unwinding of the stack if a C@t{++} exception is raised, but left
15185 unhandled while in a function that @value{GDBN} called in the program being
15186 debugged. If set to on (the default), @value{GDBN} unwinds the stack
15187 it created for the call and restores the context to what it was before
15188 the call. If set to off, @value{GDBN} the exception is delivered to
15189 the default C@t{++} exception handler and the inferior terminated.
15191 @item show unwind-on-terminating-exception
15192 @kindex show unwind-on-terminating-exception
15193 Show the current setting of stack unwinding in the functions called by
15198 @cindex weak alias functions
15199 Sometimes, a function you wish to call is actually a @dfn{weak alias}
15200 for another function. In such case, @value{GDBN} might not pick up
15201 the type information, including the types of the function arguments,
15202 which causes @value{GDBN} to call the inferior function incorrectly.
15203 As a result, the called function will function erroneously and may
15204 even crash. A solution to that is to use the name of the aliased
15208 @section Patching Programs
15210 @cindex patching binaries
15211 @cindex writing into executables
15212 @cindex writing into corefiles
15214 By default, @value{GDBN} opens the file containing your program's
15215 executable code (or the corefile) read-only. This prevents accidental
15216 alterations to machine code; but it also prevents you from intentionally
15217 patching your program's binary.
15219 If you'd like to be able to patch the binary, you can specify that
15220 explicitly with the @code{set write} command. For example, you might
15221 want to turn on internal debugging flags, or even to make emergency
15227 @itemx set write off
15228 If you specify @samp{set write on}, @value{GDBN} opens executable and
15229 core files for both reading and writing; if you specify @kbd{set write
15230 off} (the default), @value{GDBN} opens them read-only.
15232 If you have already loaded a file, you must load it again (using the
15233 @code{exec-file} or @code{core-file} command) after changing @code{set
15234 write}, for your new setting to take effect.
15238 Display whether executable files and core files are opened for writing
15239 as well as reading.
15243 @chapter @value{GDBN} Files
15245 @value{GDBN} needs to know the file name of the program to be debugged,
15246 both in order to read its symbol table and in order to start your
15247 program. To debug a core dump of a previous run, you must also tell
15248 @value{GDBN} the name of the core dump file.
15251 * Files:: Commands to specify files
15252 * Separate Debug Files:: Debugging information in separate files
15253 * Index Files:: Index files speed up GDB
15254 * Symbol Errors:: Errors reading symbol files
15255 * Data Files:: GDB data files
15259 @section Commands to Specify Files
15261 @cindex symbol table
15262 @cindex core dump file
15264 You may want to specify executable and core dump file names. The usual
15265 way to do this is at start-up time, using the arguments to
15266 @value{GDBN}'s start-up commands (@pxref{Invocation, , Getting In and
15267 Out of @value{GDBN}}).
15269 Occasionally it is necessary to change to a different file during a
15270 @value{GDBN} session. Or you may run @value{GDBN} and forget to
15271 specify a file you want to use. Or you are debugging a remote target
15272 via @code{gdbserver} (@pxref{Server, file, Using the @code{gdbserver}
15273 Program}). In these situations the @value{GDBN} commands to specify
15274 new files are useful.
15277 @cindex executable file
15279 @item file @var{filename}
15280 Use @var{filename} as the program to be debugged. It is read for its
15281 symbols and for the contents of pure memory. It is also the program
15282 executed when you use the @code{run} command. If you do not specify a
15283 directory and the file is not found in the @value{GDBN} working directory,
15284 @value{GDBN} uses the environment variable @code{PATH} as a list of
15285 directories to search, just as the shell does when looking for a program
15286 to run. You can change the value of this variable, for both @value{GDBN}
15287 and your program, using the @code{path} command.
15289 @cindex unlinked object files
15290 @cindex patching object files
15291 You can load unlinked object @file{.o} files into @value{GDBN} using
15292 the @code{file} command. You will not be able to ``run'' an object
15293 file, but you can disassemble functions and inspect variables. Also,
15294 if the underlying BFD functionality supports it, you could use
15295 @kbd{gdb -write} to patch object files using this technique. Note
15296 that @value{GDBN} can neither interpret nor modify relocations in this
15297 case, so branches and some initialized variables will appear to go to
15298 the wrong place. But this feature is still handy from time to time.
15301 @code{file} with no argument makes @value{GDBN} discard any information it
15302 has on both executable file and the symbol table.
15305 @item exec-file @r{[} @var{filename} @r{]}
15306 Specify that the program to be run (but not the symbol table) is found
15307 in @var{filename}. @value{GDBN} searches the environment variable @code{PATH}
15308 if necessary to locate your program. Omitting @var{filename} means to
15309 discard information on the executable file.
15311 @kindex symbol-file
15312 @item symbol-file @r{[} @var{filename} @r{]}
15313 Read symbol table information from file @var{filename}. @code{PATH} is
15314 searched when necessary. Use the @code{file} command to get both symbol
15315 table and program to run from the same file.
15317 @code{symbol-file} with no argument clears out @value{GDBN} information on your
15318 program's symbol table.
15320 The @code{symbol-file} command causes @value{GDBN} to forget the contents of
15321 some breakpoints and auto-display expressions. This is because they may
15322 contain pointers to the internal data recording symbols and data types,
15323 which are part of the old symbol table data being discarded inside
15326 @code{symbol-file} does not repeat if you press @key{RET} again after
15329 When @value{GDBN} is configured for a particular environment, it
15330 understands debugging information in whatever format is the standard
15331 generated for that environment; you may use either a @sc{gnu} compiler, or
15332 other compilers that adhere to the local conventions.
15333 Best results are usually obtained from @sc{gnu} compilers; for example,
15334 using @code{@value{NGCC}} you can generate debugging information for
15337 For most kinds of object files, with the exception of old SVR3 systems
15338 using COFF, the @code{symbol-file} command does not normally read the
15339 symbol table in full right away. Instead, it scans the symbol table
15340 quickly to find which source files and which symbols are present. The
15341 details are read later, one source file at a time, as they are needed.
15343 The purpose of this two-stage reading strategy is to make @value{GDBN}
15344 start up faster. For the most part, it is invisible except for
15345 occasional pauses while the symbol table details for a particular source
15346 file are being read. (The @code{set verbose} command can turn these
15347 pauses into messages if desired. @xref{Messages/Warnings, ,Optional
15348 Warnings and Messages}.)
15350 We have not implemented the two-stage strategy for COFF yet. When the
15351 symbol table is stored in COFF format, @code{symbol-file} reads the
15352 symbol table data in full right away. Note that ``stabs-in-COFF''
15353 still does the two-stage strategy, since the debug info is actually
15357 @cindex reading symbols immediately
15358 @cindex symbols, reading immediately
15359 @item symbol-file @r{[} -readnow @r{]} @var{filename}
15360 @itemx file @r{[} -readnow @r{]} @var{filename}
15361 You can override the @value{GDBN} two-stage strategy for reading symbol
15362 tables by using the @samp{-readnow} option with any of the commands that
15363 load symbol table information, if you want to be sure @value{GDBN} has the
15364 entire symbol table available.
15366 @c FIXME: for now no mention of directories, since this seems to be in
15367 @c flux. 13mar1992 status is that in theory GDB would look either in
15368 @c current dir or in same dir as myprog; but issues like competing
15369 @c GDB's, or clutter in system dirs, mean that in practice right now
15370 @c only current dir is used. FFish says maybe a special GDB hierarchy
15371 @c (eg rooted in val of env var GDBSYMS) could exist for mappable symbol
15375 @item core-file @r{[}@var{filename}@r{]}
15377 Specify the whereabouts of a core dump file to be used as the ``contents
15378 of memory''. Traditionally, core files contain only some parts of the
15379 address space of the process that generated them; @value{GDBN} can access the
15380 executable file itself for other parts.
15382 @code{core-file} with no argument specifies that no core file is
15385 Note that the core file is ignored when your program is actually running
15386 under @value{GDBN}. So, if you have been running your program and you
15387 wish to debug a core file instead, you must kill the subprocess in which
15388 the program is running. To do this, use the @code{kill} command
15389 (@pxref{Kill Process, ,Killing the Child Process}).
15391 @kindex add-symbol-file
15392 @cindex dynamic linking
15393 @item add-symbol-file @var{filename} @var{address}
15394 @itemx add-symbol-file @var{filename} @var{address} @r{[} -readnow @r{]}
15395 @itemx add-symbol-file @var{filename} @var{address} -s @var{section} @var{address} @dots{}
15396 The @code{add-symbol-file} command reads additional symbol table
15397 information from the file @var{filename}. You would use this command
15398 when @var{filename} has been dynamically loaded (by some other means)
15399 into the program that is running. @var{address} should be the memory
15400 address at which the file has been loaded; @value{GDBN} cannot figure
15401 this out for itself. You can additionally specify an arbitrary number
15402 of @samp{-s @var{section} @var{address}} pairs, to give an explicit
15403 section name and base address for that section. You can specify any
15404 @var{address} as an expression.
15406 The symbol table of the file @var{filename} is added to the symbol table
15407 originally read with the @code{symbol-file} command. You can use the
15408 @code{add-symbol-file} command any number of times; the new symbol data
15409 thus read keeps adding to the old. To discard all old symbol data
15410 instead, use the @code{symbol-file} command without any arguments.
15412 @cindex relocatable object files, reading symbols from
15413 @cindex object files, relocatable, reading symbols from
15414 @cindex reading symbols from relocatable object files
15415 @cindex symbols, reading from relocatable object files
15416 @cindex @file{.o} files, reading symbols from
15417 Although @var{filename} is typically a shared library file, an
15418 executable file, or some other object file which has been fully
15419 relocated for loading into a process, you can also load symbolic
15420 information from relocatable @file{.o} files, as long as:
15424 the file's symbolic information refers only to linker symbols defined in
15425 that file, not to symbols defined by other object files,
15427 every section the file's symbolic information refers to has actually
15428 been loaded into the inferior, as it appears in the file, and
15430 you can determine the address at which every section was loaded, and
15431 provide these to the @code{add-symbol-file} command.
15435 Some embedded operating systems, like Sun Chorus and VxWorks, can load
15436 relocatable files into an already running program; such systems
15437 typically make the requirements above easy to meet. However, it's
15438 important to recognize that many native systems use complex link
15439 procedures (@code{.linkonce} section factoring and C@t{++} constructor table
15440 assembly, for example) that make the requirements difficult to meet. In
15441 general, one cannot assume that using @code{add-symbol-file} to read a
15442 relocatable object file's symbolic information will have the same effect
15443 as linking the relocatable object file into the program in the normal
15446 @code{add-symbol-file} does not repeat if you press @key{RET} after using it.
15448 @kindex add-symbol-file-from-memory
15449 @cindex @code{syscall DSO}
15450 @cindex load symbols from memory
15451 @item add-symbol-file-from-memory @var{address}
15452 Load symbols from the given @var{address} in a dynamically loaded
15453 object file whose image is mapped directly into the inferior's memory.
15454 For example, the Linux kernel maps a @code{syscall DSO} into each
15455 process's address space; this DSO provides kernel-specific code for
15456 some system calls. The argument can be any expression whose
15457 evaluation yields the address of the file's shared object file header.
15458 For this command to work, you must have used @code{symbol-file} or
15459 @code{exec-file} commands in advance.
15461 @kindex add-shared-symbol-files
15463 @item add-shared-symbol-files @var{library-file}
15464 @itemx assf @var{library-file}
15465 The @code{add-shared-symbol-files} command can currently be used only
15466 in the Cygwin build of @value{GDBN} on MS-Windows OS, where it is an
15467 alias for the @code{dll-symbols} command (@pxref{Cygwin Native}).
15468 @value{GDBN} automatically looks for shared libraries, however if
15469 @value{GDBN} does not find yours, you can invoke
15470 @code{add-shared-symbol-files}. It takes one argument: the shared
15471 library's file name. @code{assf} is a shorthand alias for
15472 @code{add-shared-symbol-files}.
15475 @item section @var{section} @var{addr}
15476 The @code{section} command changes the base address of the named
15477 @var{section} of the exec file to @var{addr}. This can be used if the
15478 exec file does not contain section addresses, (such as in the
15479 @code{a.out} format), or when the addresses specified in the file
15480 itself are wrong. Each section must be changed separately. The
15481 @code{info files} command, described below, lists all the sections and
15485 @kindex info target
15488 @code{info files} and @code{info target} are synonymous; both print the
15489 current target (@pxref{Targets, ,Specifying a Debugging Target}),
15490 including the names of the executable and core dump files currently in
15491 use by @value{GDBN}, and the files from which symbols were loaded. The
15492 command @code{help target} lists all possible targets rather than
15495 @kindex maint info sections
15496 @item maint info sections
15497 Another command that can give you extra information about program sections
15498 is @code{maint info sections}. In addition to the section information
15499 displayed by @code{info files}, this command displays the flags and file
15500 offset of each section in the executable and core dump files. In addition,
15501 @code{maint info sections} provides the following command options (which
15502 may be arbitrarily combined):
15506 Display sections for all loaded object files, including shared libraries.
15507 @item @var{sections}
15508 Display info only for named @var{sections}.
15509 @item @var{section-flags}
15510 Display info only for sections for which @var{section-flags} are true.
15511 The section flags that @value{GDBN} currently knows about are:
15514 Section will have space allocated in the process when loaded.
15515 Set for all sections except those containing debug information.
15517 Section will be loaded from the file into the child process memory.
15518 Set for pre-initialized code and data, clear for @code{.bss} sections.
15520 Section needs to be relocated before loading.
15522 Section cannot be modified by the child process.
15524 Section contains executable code only.
15526 Section contains data only (no executable code).
15528 Section will reside in ROM.
15530 Section contains data for constructor/destructor lists.
15532 Section is not empty.
15534 An instruction to the linker to not output the section.
15535 @item COFF_SHARED_LIBRARY
15536 A notification to the linker that the section contains
15537 COFF shared library information.
15539 Section contains common symbols.
15542 @kindex set trust-readonly-sections
15543 @cindex read-only sections
15544 @item set trust-readonly-sections on
15545 Tell @value{GDBN} that readonly sections in your object file
15546 really are read-only (i.e.@: that their contents will not change).
15547 In that case, @value{GDBN} can fetch values from these sections
15548 out of the object file, rather than from the target program.
15549 For some targets (notably embedded ones), this can be a significant
15550 enhancement to debugging performance.
15552 The default is off.
15554 @item set trust-readonly-sections off
15555 Tell @value{GDBN} not to trust readonly sections. This means that
15556 the contents of the section might change while the program is running,
15557 and must therefore be fetched from the target when needed.
15559 @item show trust-readonly-sections
15560 Show the current setting of trusting readonly sections.
15563 All file-specifying commands allow both absolute and relative file names
15564 as arguments. @value{GDBN} always converts the file name to an absolute file
15565 name and remembers it that way.
15567 @cindex shared libraries
15568 @anchor{Shared Libraries}
15569 @value{GDBN} supports @sc{gnu}/Linux, MS-Windows, HP-UX, SunOS, SVr4, Irix,
15570 and IBM RS/6000 AIX shared libraries.
15572 On MS-Windows @value{GDBN} must be linked with the Expat library to support
15573 shared libraries. @xref{Expat}.
15575 @value{GDBN} automatically loads symbol definitions from shared libraries
15576 when you use the @code{run} command, or when you examine a core file.
15577 (Before you issue the @code{run} command, @value{GDBN} does not understand
15578 references to a function in a shared library, however---unless you are
15579 debugging a core file).
15581 On HP-UX, if the program loads a library explicitly, @value{GDBN}
15582 automatically loads the symbols at the time of the @code{shl_load} call.
15584 @c FIXME: some @value{GDBN} release may permit some refs to undef
15585 @c FIXME...symbols---eg in a break cmd---assuming they are from a shared
15586 @c FIXME...lib; check this from time to time when updating manual
15588 There are times, however, when you may wish to not automatically load
15589 symbol definitions from shared libraries, such as when they are
15590 particularly large or there are many of them.
15592 To control the automatic loading of shared library symbols, use the
15596 @kindex set auto-solib-add
15597 @item set auto-solib-add @var{mode}
15598 If @var{mode} is @code{on}, symbols from all shared object libraries
15599 will be loaded automatically when the inferior begins execution, you
15600 attach to an independently started inferior, or when the dynamic linker
15601 informs @value{GDBN} that a new library has been loaded. If @var{mode}
15602 is @code{off}, symbols must be loaded manually, using the
15603 @code{sharedlibrary} command. The default value is @code{on}.
15605 @cindex memory used for symbol tables
15606 If your program uses lots of shared libraries with debug info that
15607 takes large amounts of memory, you can decrease the @value{GDBN}
15608 memory footprint by preventing it from automatically loading the
15609 symbols from shared libraries. To that end, type @kbd{set
15610 auto-solib-add off} before running the inferior, then load each
15611 library whose debug symbols you do need with @kbd{sharedlibrary
15612 @var{regexp}}, where @var{regexp} is a regular expression that matches
15613 the libraries whose symbols you want to be loaded.
15615 @kindex show auto-solib-add
15616 @item show auto-solib-add
15617 Display the current autoloading mode.
15620 @cindex load shared library
15621 To explicitly load shared library symbols, use the @code{sharedlibrary}
15625 @kindex info sharedlibrary
15627 @item info share @var{regex}
15628 @itemx info sharedlibrary @var{regex}
15629 Print the names of the shared libraries which are currently loaded
15630 that match @var{regex}. If @var{regex} is omitted then print
15631 all shared libraries that are loaded.
15633 @kindex sharedlibrary
15635 @item sharedlibrary @var{regex}
15636 @itemx share @var{regex}
15637 Load shared object library symbols for files matching a
15638 Unix regular expression.
15639 As with files loaded automatically, it only loads shared libraries
15640 required by your program for a core file or after typing @code{run}. If
15641 @var{regex} is omitted all shared libraries required by your program are
15644 @item nosharedlibrary
15645 @kindex nosharedlibrary
15646 @cindex unload symbols from shared libraries
15647 Unload all shared object library symbols. This discards all symbols
15648 that have been loaded from all shared libraries. Symbols from shared
15649 libraries that were loaded by explicit user requests are not
15653 Sometimes you may wish that @value{GDBN} stops and gives you control
15654 when any of shared library events happen. The best way to do this is
15655 to use @code{catch load} and @code{catch unload} (@pxref{Set
15658 @value{GDBN} also supports the the @code{set stop-on-solib-events}
15659 command for this. This command exists for historical reasons. It is
15660 less useful than setting a catchpoint, because it does not allow for
15661 conditions or commands as a catchpoint does.
15664 @item set stop-on-solib-events
15665 @kindex set stop-on-solib-events
15666 This command controls whether @value{GDBN} should give you control
15667 when the dynamic linker notifies it about some shared library event.
15668 The most common event of interest is loading or unloading of a new
15671 @item show stop-on-solib-events
15672 @kindex show stop-on-solib-events
15673 Show whether @value{GDBN} stops and gives you control when shared
15674 library events happen.
15677 Shared libraries are also supported in many cross or remote debugging
15678 configurations. @value{GDBN} needs to have access to the target's libraries;
15679 this can be accomplished either by providing copies of the libraries
15680 on the host system, or by asking @value{GDBN} to automatically retrieve the
15681 libraries from the target. If copies of the target libraries are
15682 provided, they need to be the same as the target libraries, although the
15683 copies on the target can be stripped as long as the copies on the host are
15686 @cindex where to look for shared libraries
15687 For remote debugging, you need to tell @value{GDBN} where the target
15688 libraries are, so that it can load the correct copies---otherwise, it
15689 may try to load the host's libraries. @value{GDBN} has two variables
15690 to specify the search directories for target libraries.
15693 @cindex prefix for shared library file names
15694 @cindex system root, alternate
15695 @kindex set solib-absolute-prefix
15696 @kindex set sysroot
15697 @item set sysroot @var{path}
15698 Use @var{path} as the system root for the program being debugged. Any
15699 absolute shared library paths will be prefixed with @var{path}; many
15700 runtime loaders store the absolute paths to the shared library in the
15701 target program's memory. If you use @code{set sysroot} to find shared
15702 libraries, they need to be laid out in the same way that they are on
15703 the target, with e.g.@: a @file{/lib} and @file{/usr/lib} hierarchy
15706 If @var{path} starts with the sequence @file{remote:}, @value{GDBN} will
15707 retrieve the target libraries from the remote system. This is only
15708 supported when using a remote target that supports the @code{remote get}
15709 command (@pxref{File Transfer,,Sending files to a remote system}).
15710 The part of @var{path} following the initial @file{remote:}
15711 (if present) is used as system root prefix on the remote file system.
15712 @footnote{If you want to specify a local system root using a directory
15713 that happens to be named @file{remote:}, you need to use some equivalent
15714 variant of the name like @file{./remote:}.}
15716 For targets with an MS-DOS based filesystem, such as MS-Windows and
15717 SymbianOS, @value{GDBN} tries prefixing a few variants of the target
15718 absolute file name with @var{path}. But first, on Unix hosts,
15719 @value{GDBN} converts all backslash directory separators into forward
15720 slashes, because the backslash is not a directory separator on Unix:
15723 c:\foo\bar.dll @result{} c:/foo/bar.dll
15726 Then, @value{GDBN} attempts prefixing the target file name with
15727 @var{path}, and looks for the resulting file name in the host file
15731 c:/foo/bar.dll @result{} /path/to/sysroot/c:/foo/bar.dll
15734 If that does not find the shared library, @value{GDBN} tries removing
15735 the @samp{:} character from the drive spec, both for convenience, and,
15736 for the case of the host file system not supporting file names with
15740 c:/foo/bar.dll @result{} /path/to/sysroot/c/foo/bar.dll
15743 This makes it possible to have a system root that mirrors a target
15744 with more than one drive. E.g., you may want to setup your local
15745 copies of the target system shared libraries like so (note @samp{c} vs
15749 @file{/path/to/sysroot/c/sys/bin/foo.dll}
15750 @file{/path/to/sysroot/c/sys/bin/bar.dll}
15751 @file{/path/to/sysroot/z/sys/bin/bar.dll}
15755 and point the system root at @file{/path/to/sysroot}, so that
15756 @value{GDBN} can find the correct copies of both
15757 @file{c:\sys\bin\foo.dll}, and @file{z:\sys\bin\bar.dll}.
15759 If that still does not find the shared library, @value{GDBN} tries
15760 removing the whole drive spec from the target file name:
15763 c:/foo/bar.dll @result{} /path/to/sysroot/foo/bar.dll
15766 This last lookup makes it possible to not care about the drive name,
15767 if you don't want or need to.
15769 The @code{set solib-absolute-prefix} command is an alias for @code{set
15772 @cindex default system root
15773 @cindex @samp{--with-sysroot}
15774 You can set the default system root by using the configure-time
15775 @samp{--with-sysroot} option. If the system root is inside
15776 @value{GDBN}'s configured binary prefix (set with @samp{--prefix} or
15777 @samp{--exec-prefix}), then the default system root will be updated
15778 automatically if the installed @value{GDBN} is moved to a new
15781 @kindex show sysroot
15783 Display the current shared library prefix.
15785 @kindex set solib-search-path
15786 @item set solib-search-path @var{path}
15787 If this variable is set, @var{path} is a colon-separated list of
15788 directories to search for shared libraries. @samp{solib-search-path}
15789 is used after @samp{sysroot} fails to locate the library, or if the
15790 path to the library is relative instead of absolute. If you want to
15791 use @samp{solib-search-path} instead of @samp{sysroot}, be sure to set
15792 @samp{sysroot} to a nonexistent directory to prevent @value{GDBN} from
15793 finding your host's libraries. @samp{sysroot} is preferred; setting
15794 it to a nonexistent directory may interfere with automatic loading
15795 of shared library symbols.
15797 @kindex show solib-search-path
15798 @item show solib-search-path
15799 Display the current shared library search path.
15801 @cindex DOS file-name semantics of file names.
15802 @kindex set target-file-system-kind (unix|dos-based|auto)
15803 @kindex show target-file-system-kind
15804 @item set target-file-system-kind @var{kind}
15805 Set assumed file system kind for target reported file names.
15807 Shared library file names as reported by the target system may not
15808 make sense as is on the system @value{GDBN} is running on. For
15809 example, when remote debugging a target that has MS-DOS based file
15810 system semantics, from a Unix host, the target may be reporting to
15811 @value{GDBN} a list of loaded shared libraries with file names such as
15812 @file{c:\Windows\kernel32.dll}. On Unix hosts, there's no concept of
15813 drive letters, so the @samp{c:\} prefix is not normally understood as
15814 indicating an absolute file name, and neither is the backslash
15815 normally considered a directory separator character. In that case,
15816 the native file system would interpret this whole absolute file name
15817 as a relative file name with no directory components. This would make
15818 it impossible to point @value{GDBN} at a copy of the remote target's
15819 shared libraries on the host using @code{set sysroot}, and impractical
15820 with @code{set solib-search-path}. Setting
15821 @code{target-file-system-kind} to @code{dos-based} tells @value{GDBN}
15822 to interpret such file names similarly to how the target would, and to
15823 map them to file names valid on @value{GDBN}'s native file system
15824 semantics. The value of @var{kind} can be @code{"auto"}, in addition
15825 to one of the supported file system kinds. In that case, @value{GDBN}
15826 tries to determine the appropriate file system variant based on the
15827 current target's operating system (@pxref{ABI, ,Configuring the
15828 Current ABI}). The supported file system settings are:
15832 Instruct @value{GDBN} to assume the target file system is of Unix
15833 kind. Only file names starting the forward slash (@samp{/}) character
15834 are considered absolute, and the directory separator character is also
15838 Instruct @value{GDBN} to assume the target file system is DOS based.
15839 File names starting with either a forward slash, or a drive letter
15840 followed by a colon (e.g., @samp{c:}), are considered absolute, and
15841 both the slash (@samp{/}) and the backslash (@samp{\\}) characters are
15842 considered directory separators.
15845 Instruct @value{GDBN} to use the file system kind associated with the
15846 target operating system (@pxref{ABI, ,Configuring the Current ABI}).
15847 This is the default.
15851 @cindex file name canonicalization
15852 @cindex base name differences
15853 When processing file names provided by the user, @value{GDBN}
15854 frequently needs to compare them to the file names recorded in the
15855 program's debug info. Normally, @value{GDBN} compares just the
15856 @dfn{base names} of the files as strings, which is reasonably fast
15857 even for very large programs. (The base name of a file is the last
15858 portion of its name, after stripping all the leading directories.)
15859 This shortcut in comparison is based upon the assumption that files
15860 cannot have more than one base name. This is usually true, but
15861 references to files that use symlinks or similar filesystem
15862 facilities violate that assumption. If your program records files
15863 using such facilities, or if you provide file names to @value{GDBN}
15864 using symlinks etc., you can set @code{basenames-may-differ} to
15865 @code{true} to instruct @value{GDBN} to completely canonicalize each
15866 pair of file names it needs to compare. This will make file-name
15867 comparisons accurate, but at a price of a significant slowdown.
15870 @item set basenames-may-differ
15871 @kindex set basenames-may-differ
15872 Set whether a source file may have multiple base names.
15874 @item show basenames-may-differ
15875 @kindex show basenames-may-differ
15876 Show whether a source file may have multiple base names.
15879 @node Separate Debug Files
15880 @section Debugging Information in Separate Files
15881 @cindex separate debugging information files
15882 @cindex debugging information in separate files
15883 @cindex @file{.debug} subdirectories
15884 @cindex debugging information directory, global
15885 @cindex global debugging information directory
15886 @cindex build ID, and separate debugging files
15887 @cindex @file{.build-id} directory
15889 @value{GDBN} allows you to put a program's debugging information in a
15890 file separate from the executable itself, in a way that allows
15891 @value{GDBN} to find and load the debugging information automatically.
15892 Since debugging information can be very large---sometimes larger
15893 than the executable code itself---some systems distribute debugging
15894 information for their executables in separate files, which users can
15895 install only when they need to debug a problem.
15897 @value{GDBN} supports two ways of specifying the separate debug info
15902 The executable contains a @dfn{debug link} that specifies the name of
15903 the separate debug info file. The separate debug file's name is
15904 usually @file{@var{executable}.debug}, where @var{executable} is the
15905 name of the corresponding executable file without leading directories
15906 (e.g., @file{ls.debug} for @file{/usr/bin/ls}). In addition, the
15907 debug link specifies a 32-bit @dfn{Cyclic Redundancy Check} (CRC)
15908 checksum for the debug file, which @value{GDBN} uses to validate that
15909 the executable and the debug file came from the same build.
15912 The executable contains a @dfn{build ID}, a unique bit string that is
15913 also present in the corresponding debug info file. (This is supported
15914 only on some operating systems, notably those which use the ELF format
15915 for binary files and the @sc{gnu} Binutils.) For more details about
15916 this feature, see the description of the @option{--build-id}
15917 command-line option in @ref{Options, , Command Line Options, ld.info,
15918 The GNU Linker}. The debug info file's name is not specified
15919 explicitly by the build ID, but can be computed from the build ID, see
15923 Depending on the way the debug info file is specified, @value{GDBN}
15924 uses two different methods of looking for the debug file:
15928 For the ``debug link'' method, @value{GDBN} looks up the named file in
15929 the directory of the executable file, then in a subdirectory of that
15930 directory named @file{.debug}, and finally under the global debug
15931 directory, in a subdirectory whose name is identical to the leading
15932 directories of the executable's absolute file name.
15935 For the ``build ID'' method, @value{GDBN} looks in the
15936 @file{.build-id} subdirectory of the global debug directory for a file
15937 named @file{@var{nn}/@var{nnnnnnnn}.debug}, where @var{nn} are the
15938 first 2 hex characters of the build ID bit string, and @var{nnnnnnnn}
15939 are the rest of the bit string. (Real build ID strings are 32 or more
15940 hex characters, not 10.)
15943 So, for example, suppose you ask @value{GDBN} to debug
15944 @file{/usr/bin/ls}, which has a debug link that specifies the
15945 file @file{ls.debug}, and a build ID whose value in hex is
15946 @code{abcdef1234}. If the global debug directory is
15947 @file{/usr/lib/debug}, then @value{GDBN} will look for the following
15948 debug information files, in the indicated order:
15952 @file{/usr/lib/debug/.build-id/ab/cdef1234.debug}
15954 @file{/usr/bin/ls.debug}
15956 @file{/usr/bin/.debug/ls.debug}
15958 @file{/usr/lib/debug/usr/bin/ls.debug}.
15961 You can set the global debugging info directory's name, and view the
15962 name @value{GDBN} is currently using.
15966 @kindex set debug-file-directory
15967 @item set debug-file-directory @var{directories}
15968 Set the directories which @value{GDBN} searches for separate debugging
15969 information files to @var{directory}. Multiple directory components can be set
15970 concatenating them by a directory separator.
15972 @kindex show debug-file-directory
15973 @item show debug-file-directory
15974 Show the directories @value{GDBN} searches for separate debugging
15979 @cindex @code{.gnu_debuglink} sections
15980 @cindex debug link sections
15981 A debug link is a special section of the executable file named
15982 @code{.gnu_debuglink}. The section must contain:
15986 A filename, with any leading directory components removed, followed by
15989 zero to three bytes of padding, as needed to reach the next four-byte
15990 boundary within the section, and
15992 a four-byte CRC checksum, stored in the same endianness used for the
15993 executable file itself. The checksum is computed on the debugging
15994 information file's full contents by the function given below, passing
15995 zero as the @var{crc} argument.
15998 Any executable file format can carry a debug link, as long as it can
15999 contain a section named @code{.gnu_debuglink} with the contents
16002 @cindex @code{.note.gnu.build-id} sections
16003 @cindex build ID sections
16004 The build ID is a special section in the executable file (and in other
16005 ELF binary files that @value{GDBN} may consider). This section is
16006 often named @code{.note.gnu.build-id}, but that name is not mandatory.
16007 It contains unique identification for the built files---the ID remains
16008 the same across multiple builds of the same build tree. The default
16009 algorithm SHA1 produces 160 bits (40 hexadecimal characters) of the
16010 content for the build ID string. The same section with an identical
16011 value is present in the original built binary with symbols, in its
16012 stripped variant, and in the separate debugging information file.
16014 The debugging information file itself should be an ordinary
16015 executable, containing a full set of linker symbols, sections, and
16016 debugging information. The sections of the debugging information file
16017 should have the same names, addresses, and sizes as the original file,
16018 but they need not contain any data---much like a @code{.bss} section
16019 in an ordinary executable.
16021 The @sc{gnu} binary utilities (Binutils) package includes the
16022 @samp{objcopy} utility that can produce
16023 the separated executable / debugging information file pairs using the
16024 following commands:
16027 @kbd{objcopy --only-keep-debug foo foo.debug}
16032 These commands remove the debugging
16033 information from the executable file @file{foo} and place it in the file
16034 @file{foo.debug}. You can use the first, second or both methods to link the
16039 The debug link method needs the following additional command to also leave
16040 behind a debug link in @file{foo}:
16043 @kbd{objcopy --add-gnu-debuglink=foo.debug foo}
16046 Ulrich Drepper's @file{elfutils} package, starting with version 0.53, contains
16047 a version of the @code{strip} command such that the command @kbd{strip foo -f
16048 foo.debug} has the same functionality as the two @code{objcopy} commands and
16049 the @code{ln -s} command above, together.
16052 Build ID gets embedded into the main executable using @code{ld --build-id} or
16053 the @value{NGCC} counterpart @code{gcc -Wl,--build-id}. Build ID support plus
16054 compatibility fixes for debug files separation are present in @sc{gnu} binary
16055 utilities (Binutils) package since version 2.18.
16060 @cindex CRC algorithm definition
16061 The CRC used in @code{.gnu_debuglink} is the CRC-32 defined in
16062 IEEE 802.3 using the polynomial:
16064 @c TexInfo requires naked braces for multi-digit exponents for Tex
16065 @c output, but this causes HTML output to barf. HTML has to be set using
16066 @c raw commands. So we end up having to specify this equation in 2
16071 <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>
16072 + <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
16078 @math{x^{32} + x^{26} + x^{23} + x^{22} + x^{16} + x^{12} + x^{11}}
16079 @math{+ x^{10} + x^8 + x^7 + x^5 + x^4 + x^2 + x + 1}
16083 The function is computed byte at a time, taking the least
16084 significant bit of each byte first. The initial pattern
16085 @code{0xffffffff} is used, to ensure leading zeros affect the CRC and
16086 the final result is inverted to ensure trailing zeros also affect the
16089 @emph{Note:} This is the same CRC polynomial as used in handling the
16090 @dfn{Remote Serial Protocol} @code{qCRC} packet (@pxref{Remote Protocol,
16091 , @value{GDBN} Remote Serial Protocol}). However in the
16092 case of the Remote Serial Protocol, the CRC is computed @emph{most}
16093 significant bit first, and the result is not inverted, so trailing
16094 zeros have no effect on the CRC value.
16096 To complete the description, we show below the code of the function
16097 which produces the CRC used in @code{.gnu_debuglink}. Inverting the
16098 initially supplied @code{crc} argument means that an initial call to
16099 this function passing in zero will start computing the CRC using
16102 @kindex gnu_debuglink_crc32
16105 gnu_debuglink_crc32 (unsigned long crc,
16106 unsigned char *buf, size_t len)
16108 static const unsigned long crc32_table[256] =
16110 0x00000000, 0x77073096, 0xee0e612c, 0x990951ba, 0x076dc419,
16111 0x706af48f, 0xe963a535, 0x9e6495a3, 0x0edb8832, 0x79dcb8a4,
16112 0xe0d5e91e, 0x97d2d988, 0x09b64c2b, 0x7eb17cbd, 0xe7b82d07,
16113 0x90bf1d91, 0x1db71064, 0x6ab020f2, 0xf3b97148, 0x84be41de,
16114 0x1adad47d, 0x6ddde4eb, 0xf4d4b551, 0x83d385c7, 0x136c9856,
16115 0x646ba8c0, 0xfd62f97a, 0x8a65c9ec, 0x14015c4f, 0x63066cd9,
16116 0xfa0f3d63, 0x8d080df5, 0x3b6e20c8, 0x4c69105e, 0xd56041e4,
16117 0xa2677172, 0x3c03e4d1, 0x4b04d447, 0xd20d85fd, 0xa50ab56b,
16118 0x35b5a8fa, 0x42b2986c, 0xdbbbc9d6, 0xacbcf940, 0x32d86ce3,
16119 0x45df5c75, 0xdcd60dcf, 0xabd13d59, 0x26d930ac, 0x51de003a,
16120 0xc8d75180, 0xbfd06116, 0x21b4f4b5, 0x56b3c423, 0xcfba9599,
16121 0xb8bda50f, 0x2802b89e, 0x5f058808, 0xc60cd9b2, 0xb10be924,
16122 0x2f6f7c87, 0x58684c11, 0xc1611dab, 0xb6662d3d, 0x76dc4190,
16123 0x01db7106, 0x98d220bc, 0xefd5102a, 0x71b18589, 0x06b6b51f,
16124 0x9fbfe4a5, 0xe8b8d433, 0x7807c9a2, 0x0f00f934, 0x9609a88e,
16125 0xe10e9818, 0x7f6a0dbb, 0x086d3d2d, 0x91646c97, 0xe6635c01,
16126 0x6b6b51f4, 0x1c6c6162, 0x856530d8, 0xf262004e, 0x6c0695ed,
16127 0x1b01a57b, 0x8208f4c1, 0xf50fc457, 0x65b0d9c6, 0x12b7e950,
16128 0x8bbeb8ea, 0xfcb9887c, 0x62dd1ddf, 0x15da2d49, 0x8cd37cf3,
16129 0xfbd44c65, 0x4db26158, 0x3ab551ce, 0xa3bc0074, 0xd4bb30e2,
16130 0x4adfa541, 0x3dd895d7, 0xa4d1c46d, 0xd3d6f4fb, 0x4369e96a,
16131 0x346ed9fc, 0xad678846, 0xda60b8d0, 0x44042d73, 0x33031de5,
16132 0xaa0a4c5f, 0xdd0d7cc9, 0x5005713c, 0x270241aa, 0xbe0b1010,
16133 0xc90c2086, 0x5768b525, 0x206f85b3, 0xb966d409, 0xce61e49f,
16134 0x5edef90e, 0x29d9c998, 0xb0d09822, 0xc7d7a8b4, 0x59b33d17,
16135 0x2eb40d81, 0xb7bd5c3b, 0xc0ba6cad, 0xedb88320, 0x9abfb3b6,
16136 0x03b6e20c, 0x74b1d29a, 0xead54739, 0x9dd277af, 0x04db2615,
16137 0x73dc1683, 0xe3630b12, 0x94643b84, 0x0d6d6a3e, 0x7a6a5aa8,
16138 0xe40ecf0b, 0x9309ff9d, 0x0a00ae27, 0x7d079eb1, 0xf00f9344,
16139 0x8708a3d2, 0x1e01f268, 0x6906c2fe, 0xf762575d, 0x806567cb,
16140 0x196c3671, 0x6e6b06e7, 0xfed41b76, 0x89d32be0, 0x10da7a5a,
16141 0x67dd4acc, 0xf9b9df6f, 0x8ebeeff9, 0x17b7be43, 0x60b08ed5,
16142 0xd6d6a3e8, 0xa1d1937e, 0x38d8c2c4, 0x4fdff252, 0xd1bb67f1,
16143 0xa6bc5767, 0x3fb506dd, 0x48b2364b, 0xd80d2bda, 0xaf0a1b4c,
16144 0x36034af6, 0x41047a60, 0xdf60efc3, 0xa867df55, 0x316e8eef,
16145 0x4669be79, 0xcb61b38c, 0xbc66831a, 0x256fd2a0, 0x5268e236,
16146 0xcc0c7795, 0xbb0b4703, 0x220216b9, 0x5505262f, 0xc5ba3bbe,
16147 0xb2bd0b28, 0x2bb45a92, 0x5cb36a04, 0xc2d7ffa7, 0xb5d0cf31,
16148 0x2cd99e8b, 0x5bdeae1d, 0x9b64c2b0, 0xec63f226, 0x756aa39c,
16149 0x026d930a, 0x9c0906a9, 0xeb0e363f, 0x72076785, 0x05005713,
16150 0x95bf4a82, 0xe2b87a14, 0x7bb12bae, 0x0cb61b38, 0x92d28e9b,
16151 0xe5d5be0d, 0x7cdcefb7, 0x0bdbdf21, 0x86d3d2d4, 0xf1d4e242,
16152 0x68ddb3f8, 0x1fda836e, 0x81be16cd, 0xf6b9265b, 0x6fb077e1,
16153 0x18b74777, 0x88085ae6, 0xff0f6a70, 0x66063bca, 0x11010b5c,
16154 0x8f659eff, 0xf862ae69, 0x616bffd3, 0x166ccf45, 0xa00ae278,
16155 0xd70dd2ee, 0x4e048354, 0x3903b3c2, 0xa7672661, 0xd06016f7,
16156 0x4969474d, 0x3e6e77db, 0xaed16a4a, 0xd9d65adc, 0x40df0b66,
16157 0x37d83bf0, 0xa9bcae53, 0xdebb9ec5, 0x47b2cf7f, 0x30b5ffe9,
16158 0xbdbdf21c, 0xcabac28a, 0x53b39330, 0x24b4a3a6, 0xbad03605,
16159 0xcdd70693, 0x54de5729, 0x23d967bf, 0xb3667a2e, 0xc4614ab8,
16160 0x5d681b02, 0x2a6f2b94, 0xb40bbe37, 0xc30c8ea1, 0x5a05df1b,
16163 unsigned char *end;
16165 crc = ~crc & 0xffffffff;
16166 for (end = buf + len; buf < end; ++buf)
16167 crc = crc32_table[(crc ^ *buf) & 0xff] ^ (crc >> 8);
16168 return ~crc & 0xffffffff;
16173 This computation does not apply to the ``build ID'' method.
16177 @section Index Files Speed Up @value{GDBN}
16178 @cindex index files
16179 @cindex @samp{.gdb_index} section
16181 When @value{GDBN} finds a symbol file, it scans the symbols in the
16182 file in order to construct an internal symbol table. This lets most
16183 @value{GDBN} operations work quickly---at the cost of a delay early
16184 on. For large programs, this delay can be quite lengthy, so
16185 @value{GDBN} provides a way to build an index, which speeds up
16188 The index is stored as a section in the symbol file. @value{GDBN} can
16189 write the index to a file, then you can put it into the symbol file
16190 using @command{objcopy}.
16192 To create an index file, use the @code{save gdb-index} command:
16195 @item save gdb-index @var{directory}
16196 @kindex save gdb-index
16197 Create an index file for each symbol file currently known by
16198 @value{GDBN}. Each file is named after its corresponding symbol file,
16199 with @samp{.gdb-index} appended, and is written into the given
16203 Once you have created an index file you can merge it into your symbol
16204 file, here named @file{symfile}, using @command{objcopy}:
16207 $ objcopy --add-section .gdb_index=symfile.gdb-index \
16208 --set-section-flags .gdb_index=readonly symfile symfile
16211 There are currently some limitation on indices. They only work when
16212 for DWARF debugging information, not stabs. And, they do not
16213 currently work for programs using Ada.
16215 @node Symbol Errors
16216 @section Errors Reading Symbol Files
16218 While reading a symbol file, @value{GDBN} occasionally encounters problems,
16219 such as symbol types it does not recognize, or known bugs in compiler
16220 output. By default, @value{GDBN} does not notify you of such problems, since
16221 they are relatively common and primarily of interest to people
16222 debugging compilers. If you are interested in seeing information
16223 about ill-constructed symbol tables, you can either ask @value{GDBN} to print
16224 only one message about each such type of problem, no matter how many
16225 times the problem occurs; or you can ask @value{GDBN} to print more messages,
16226 to see how many times the problems occur, with the @code{set
16227 complaints} command (@pxref{Messages/Warnings, ,Optional Warnings and
16230 The messages currently printed, and their meanings, include:
16233 @item inner block not inside outer block in @var{symbol}
16235 The symbol information shows where symbol scopes begin and end
16236 (such as at the start of a function or a block of statements). This
16237 error indicates that an inner scope block is not fully contained
16238 in its outer scope blocks.
16240 @value{GDBN} circumvents the problem by treating the inner block as if it had
16241 the same scope as the outer block. In the error message, @var{symbol}
16242 may be shown as ``@code{(don't know)}'' if the outer block is not a
16245 @item block at @var{address} out of order
16247 The symbol information for symbol scope blocks should occur in
16248 order of increasing addresses. This error indicates that it does not
16251 @value{GDBN} does not circumvent this problem, and has trouble
16252 locating symbols in the source file whose symbols it is reading. (You
16253 can often determine what source file is affected by specifying
16254 @code{set verbose on}. @xref{Messages/Warnings, ,Optional Warnings and
16257 @item bad block start address patched
16259 The symbol information for a symbol scope block has a start address
16260 smaller than the address of the preceding source line. This is known
16261 to occur in the SunOS 4.1.1 (and earlier) C compiler.
16263 @value{GDBN} circumvents the problem by treating the symbol scope block as
16264 starting on the previous source line.
16266 @item bad string table offset in symbol @var{n}
16269 Symbol number @var{n} contains a pointer into the string table which is
16270 larger than the size of the string table.
16272 @value{GDBN} circumvents the problem by considering the symbol to have the
16273 name @code{foo}, which may cause other problems if many symbols end up
16276 @item unknown symbol type @code{0x@var{nn}}
16278 The symbol information contains new data types that @value{GDBN} does
16279 not yet know how to read. @code{0x@var{nn}} is the symbol type of the
16280 uncomprehended information, in hexadecimal.
16282 @value{GDBN} circumvents the error by ignoring this symbol information.
16283 This usually allows you to debug your program, though certain symbols
16284 are not accessible. If you encounter such a problem and feel like
16285 debugging it, you can debug @code{@value{GDBP}} with itself, breakpoint
16286 on @code{complain}, then go up to the function @code{read_dbx_symtab}
16287 and examine @code{*bufp} to see the symbol.
16289 @item stub type has NULL name
16291 @value{GDBN} could not find the full definition for a struct or class.
16293 @item const/volatile indicator missing (ok if using g++ v1.x), got@dots{}
16294 The symbol information for a C@t{++} member function is missing some
16295 information that recent versions of the compiler should have output for
16298 @item info mismatch between compiler and debugger
16300 @value{GDBN} could not parse a type specification output by the compiler.
16305 @section GDB Data Files
16307 @cindex prefix for data files
16308 @value{GDBN} will sometimes read an auxiliary data file. These files
16309 are kept in a directory known as the @dfn{data directory}.
16311 You can set the data directory's name, and view the name @value{GDBN}
16312 is currently using.
16315 @kindex set data-directory
16316 @item set data-directory @var{directory}
16317 Set the directory which @value{GDBN} searches for auxiliary data files
16318 to @var{directory}.
16320 @kindex show data-directory
16321 @item show data-directory
16322 Show the directory @value{GDBN} searches for auxiliary data files.
16325 @cindex default data directory
16326 @cindex @samp{--with-gdb-datadir}
16327 You can set the default data directory by using the configure-time
16328 @samp{--with-gdb-datadir} option. If the data directory is inside
16329 @value{GDBN}'s configured binary prefix (set with @samp{--prefix} or
16330 @samp{--exec-prefix}), then the default data directory will be updated
16331 automatically if the installed @value{GDBN} is moved to a new
16334 The data directory may also be specified with the
16335 @code{--data-directory} command line option.
16336 @xref{Mode Options}.
16339 @chapter Specifying a Debugging Target
16341 @cindex debugging target
16342 A @dfn{target} is the execution environment occupied by your program.
16344 Often, @value{GDBN} runs in the same host environment as your program;
16345 in that case, the debugging target is specified as a side effect when
16346 you use the @code{file} or @code{core} commands. When you need more
16347 flexibility---for example, running @value{GDBN} on a physically separate
16348 host, or controlling a standalone system over a serial port or a
16349 realtime system over a TCP/IP connection---you can use the @code{target}
16350 command to specify one of the target types configured for @value{GDBN}
16351 (@pxref{Target Commands, ,Commands for Managing Targets}).
16353 @cindex target architecture
16354 It is possible to build @value{GDBN} for several different @dfn{target
16355 architectures}. When @value{GDBN} is built like that, you can choose
16356 one of the available architectures with the @kbd{set architecture}
16360 @kindex set architecture
16361 @kindex show architecture
16362 @item set architecture @var{arch}
16363 This command sets the current target architecture to @var{arch}. The
16364 value of @var{arch} can be @code{"auto"}, in addition to one of the
16365 supported architectures.
16367 @item show architecture
16368 Show the current target architecture.
16370 @item set processor
16372 @kindex set processor
16373 @kindex show processor
16374 These are alias commands for, respectively, @code{set architecture}
16375 and @code{show architecture}.
16379 * Active Targets:: Active targets
16380 * Target Commands:: Commands for managing targets
16381 * Byte Order:: Choosing target byte order
16384 @node Active Targets
16385 @section Active Targets
16387 @cindex stacking targets
16388 @cindex active targets
16389 @cindex multiple targets
16391 There are multiple classes of targets such as: processes, executable files or
16392 recording sessions. Core files belong to the process class, making core file
16393 and process mutually exclusive. Otherwise, @value{GDBN} can work concurrently
16394 on multiple active targets, one in each class. This allows you to (for
16395 example) start a process and inspect its activity, while still having access to
16396 the executable file after the process finishes. Or if you start process
16397 recording (@pxref{Reverse Execution}) and @code{reverse-step} there, you are
16398 presented a virtual layer of the recording target, while the process target
16399 remains stopped at the chronologically last point of the process execution.
16401 Use the @code{core-file} and @code{exec-file} commands to select a new core
16402 file or executable target (@pxref{Files, ,Commands to Specify Files}). To
16403 specify as a target a process that is already running, use the @code{attach}
16404 command (@pxref{Attach, ,Debugging an Already-running Process}).
16406 @node Target Commands
16407 @section Commands for Managing Targets
16410 @item target @var{type} @var{parameters}
16411 Connects the @value{GDBN} host environment to a target machine or
16412 process. A target is typically a protocol for talking to debugging
16413 facilities. You use the argument @var{type} to specify the type or
16414 protocol of the target machine.
16416 Further @var{parameters} are interpreted by the target protocol, but
16417 typically include things like device names or host names to connect
16418 with, process numbers, and baud rates.
16420 The @code{target} command does not repeat if you press @key{RET} again
16421 after executing the command.
16423 @kindex help target
16425 Displays the names of all targets available. To display targets
16426 currently selected, use either @code{info target} or @code{info files}
16427 (@pxref{Files, ,Commands to Specify Files}).
16429 @item help target @var{name}
16430 Describe a particular target, including any parameters necessary to
16433 @kindex set gnutarget
16434 @item set gnutarget @var{args}
16435 @value{GDBN} uses its own library BFD to read your files. @value{GDBN}
16436 knows whether it is reading an @dfn{executable},
16437 a @dfn{core}, or a @dfn{.o} file; however, you can specify the file format
16438 with the @code{set gnutarget} command. Unlike most @code{target} commands,
16439 with @code{gnutarget} the @code{target} refers to a program, not a machine.
16442 @emph{Warning:} To specify a file format with @code{set gnutarget},
16443 you must know the actual BFD name.
16447 @xref{Files, , Commands to Specify Files}.
16449 @kindex show gnutarget
16450 @item show gnutarget
16451 Use the @code{show gnutarget} command to display what file format
16452 @code{gnutarget} is set to read. If you have not set @code{gnutarget},
16453 @value{GDBN} will determine the file format for each file automatically,
16454 and @code{show gnutarget} displays @samp{The current BDF target is "auto"}.
16457 @cindex common targets
16458 Here are some common targets (available, or not, depending on the GDB
16463 @item target exec @var{program}
16464 @cindex executable file target
16465 An executable file. @samp{target exec @var{program}} is the same as
16466 @samp{exec-file @var{program}}.
16468 @item target core @var{filename}
16469 @cindex core dump file target
16470 A core dump file. @samp{target core @var{filename}} is the same as
16471 @samp{core-file @var{filename}}.
16473 @item target remote @var{medium}
16474 @cindex remote target
16475 A remote system connected to @value{GDBN} via a serial line or network
16476 connection. This command tells @value{GDBN} to use its own remote
16477 protocol over @var{medium} for debugging. @xref{Remote Debugging}.
16479 For example, if you have a board connected to @file{/dev/ttya} on the
16480 machine running @value{GDBN}, you could say:
16483 target remote /dev/ttya
16486 @code{target remote} supports the @code{load} command. This is only
16487 useful if you have some other way of getting the stub to the target
16488 system, and you can put it somewhere in memory where it won't get
16489 clobbered by the download.
16491 @item target sim @r{[}@var{simargs}@r{]} @dots{}
16492 @cindex built-in simulator target
16493 Builtin CPU simulator. @value{GDBN} includes simulators for most architectures.
16501 works; however, you cannot assume that a specific memory map, device
16502 drivers, or even basic I/O is available, although some simulators do
16503 provide these. For info about any processor-specific simulator details,
16504 see the appropriate section in @ref{Embedded Processors, ,Embedded
16509 Some configurations may include these targets as well:
16513 @item target nrom @var{dev}
16514 @cindex NetROM ROM emulator target
16515 NetROM ROM emulator. This target only supports downloading.
16519 Different targets are available on different configurations of @value{GDBN};
16520 your configuration may have more or fewer targets.
16522 Many remote targets require you to download the executable's code once
16523 you've successfully established a connection. You may wish to control
16524 various aspects of this process.
16529 @kindex set hash@r{, for remote monitors}
16530 @cindex hash mark while downloading
16531 This command controls whether a hash mark @samp{#} is displayed while
16532 downloading a file to the remote monitor. If on, a hash mark is
16533 displayed after each S-record is successfully downloaded to the
16537 @kindex show hash@r{, for remote monitors}
16538 Show the current status of displaying the hash mark.
16540 @item set debug monitor
16541 @kindex set debug monitor
16542 @cindex display remote monitor communications
16543 Enable or disable display of communications messages between
16544 @value{GDBN} and the remote monitor.
16546 @item show debug monitor
16547 @kindex show debug monitor
16548 Show the current status of displaying communications between
16549 @value{GDBN} and the remote monitor.
16554 @kindex load @var{filename}
16555 @item load @var{filename}
16557 Depending on what remote debugging facilities are configured into
16558 @value{GDBN}, the @code{load} command may be available. Where it exists, it
16559 is meant to make @var{filename} (an executable) available for debugging
16560 on the remote system---by downloading, or dynamic linking, for example.
16561 @code{load} also records the @var{filename} symbol table in @value{GDBN}, like
16562 the @code{add-symbol-file} command.
16564 If your @value{GDBN} does not have a @code{load} command, attempting to
16565 execute it gets the error message ``@code{You can't do that when your
16566 target is @dots{}}''
16568 The file is loaded at whatever address is specified in the executable.
16569 For some object file formats, you can specify the load address when you
16570 link the program; for other formats, like a.out, the object file format
16571 specifies a fixed address.
16572 @c FIXME! This would be a good place for an xref to the GNU linker doc.
16574 Depending on the remote side capabilities, @value{GDBN} may be able to
16575 load programs into flash memory.
16577 @code{load} does not repeat if you press @key{RET} again after using it.
16581 @section Choosing Target Byte Order
16583 @cindex choosing target byte order
16584 @cindex target byte order
16586 Some types of processors, such as the MIPS, PowerPC, and Renesas SH,
16587 offer the ability to run either big-endian or little-endian byte
16588 orders. Usually the executable or symbol will include a bit to
16589 designate the endian-ness, and you will not need to worry about
16590 which to use. However, you may still find it useful to adjust
16591 @value{GDBN}'s idea of processor endian-ness manually.
16595 @item set endian big
16596 Instruct @value{GDBN} to assume the target is big-endian.
16598 @item set endian little
16599 Instruct @value{GDBN} to assume the target is little-endian.
16601 @item set endian auto
16602 Instruct @value{GDBN} to use the byte order associated with the
16606 Display @value{GDBN}'s current idea of the target byte order.
16610 Note that these commands merely adjust interpretation of symbolic
16611 data on the host, and that they have absolutely no effect on the
16615 @node Remote Debugging
16616 @chapter Debugging Remote Programs
16617 @cindex remote debugging
16619 If you are trying to debug a program running on a machine that cannot run
16620 @value{GDBN} in the usual way, it is often useful to use remote debugging.
16621 For example, you might use remote debugging on an operating system kernel,
16622 or on a small system which does not have a general purpose operating system
16623 powerful enough to run a full-featured debugger.
16625 Some configurations of @value{GDBN} have special serial or TCP/IP interfaces
16626 to make this work with particular debugging targets. In addition,
16627 @value{GDBN} comes with a generic serial protocol (specific to @value{GDBN},
16628 but not specific to any particular target system) which you can use if you
16629 write the remote stubs---the code that runs on the remote system to
16630 communicate with @value{GDBN}.
16632 Other remote targets may be available in your
16633 configuration of @value{GDBN}; use @code{help target} to list them.
16636 * Connecting:: Connecting to a remote target
16637 * File Transfer:: Sending files to a remote system
16638 * Server:: Using the gdbserver program
16639 * Remote Configuration:: Remote configuration
16640 * Remote Stub:: Implementing a remote stub
16644 @section Connecting to a Remote Target
16646 On the @value{GDBN} host machine, you will need an unstripped copy of
16647 your program, since @value{GDBN} needs symbol and debugging information.
16648 Start up @value{GDBN} as usual, using the name of the local copy of your
16649 program as the first argument.
16651 @cindex @code{target remote}
16652 @value{GDBN} can communicate with the target over a serial line, or
16653 over an @acronym{IP} network using @acronym{TCP} or @acronym{UDP}. In
16654 each case, @value{GDBN} uses the same protocol for debugging your
16655 program; only the medium carrying the debugging packets varies. The
16656 @code{target remote} command establishes a connection to the target.
16657 Its arguments indicate which medium to use:
16661 @item target remote @var{serial-device}
16662 @cindex serial line, @code{target remote}
16663 Use @var{serial-device} to communicate with the target. For example,
16664 to use a serial line connected to the device named @file{/dev/ttyb}:
16667 target remote /dev/ttyb
16670 If you're using a serial line, you may want to give @value{GDBN} the
16671 @w{@samp{--baud}} option, or use the @code{set remotebaud} command
16672 (@pxref{Remote Configuration, set remotebaud}) before the
16673 @code{target} command.
16675 @item target remote @code{@var{host}:@var{port}}
16676 @itemx target remote @code{tcp:@var{host}:@var{port}}
16677 @cindex @acronym{TCP} port, @code{target remote}
16678 Debug using a @acronym{TCP} connection to @var{port} on @var{host}.
16679 The @var{host} may be either a host name or a numeric @acronym{IP}
16680 address; @var{port} must be a decimal number. The @var{host} could be
16681 the target machine itself, if it is directly connected to the net, or
16682 it might be a terminal server which in turn has a serial line to the
16685 For example, to connect to port 2828 on a terminal server named
16689 target remote manyfarms:2828
16692 If your remote target is actually running on the same machine as your
16693 debugger session (e.g.@: a simulator for your target running on the
16694 same host), you can omit the hostname. For example, to connect to
16695 port 1234 on your local machine:
16698 target remote :1234
16702 Note that the colon is still required here.
16704 @item target remote @code{udp:@var{host}:@var{port}}
16705 @cindex @acronym{UDP} port, @code{target remote}
16706 Debug using @acronym{UDP} packets to @var{port} on @var{host}. For example, to
16707 connect to @acronym{UDP} port 2828 on a terminal server named @code{manyfarms}:
16710 target remote udp:manyfarms:2828
16713 When using a @acronym{UDP} connection for remote debugging, you should
16714 keep in mind that the `U' stands for ``Unreliable''. @acronym{UDP}
16715 can silently drop packets on busy or unreliable networks, which will
16716 cause havoc with your debugging session.
16718 @item target remote | @var{command}
16719 @cindex pipe, @code{target remote} to
16720 Run @var{command} in the background and communicate with it using a
16721 pipe. The @var{command} is a shell command, to be parsed and expanded
16722 by the system's command shell, @code{/bin/sh}; it should expect remote
16723 protocol packets on its standard input, and send replies on its
16724 standard output. You could use this to run a stand-alone simulator
16725 that speaks the remote debugging protocol, to make net connections
16726 using programs like @code{ssh}, or for other similar tricks.
16728 If @var{command} closes its standard output (perhaps by exiting),
16729 @value{GDBN} will try to send it a @code{SIGTERM} signal. (If the
16730 program has already exited, this will have no effect.)
16734 Once the connection has been established, you can use all the usual
16735 commands to examine and change data. The remote program is already
16736 running; you can use @kbd{step} and @kbd{continue}, and you do not
16737 need to use @kbd{run}.
16739 @cindex interrupting remote programs
16740 @cindex remote programs, interrupting
16741 Whenever @value{GDBN} is waiting for the remote program, if you type the
16742 interrupt character (often @kbd{Ctrl-c}), @value{GDBN} attempts to stop the
16743 program. This may or may not succeed, depending in part on the hardware
16744 and the serial drivers the remote system uses. If you type the
16745 interrupt character once again, @value{GDBN} displays this prompt:
16748 Interrupted while waiting for the program.
16749 Give up (and stop debugging it)? (y or n)
16752 If you type @kbd{y}, @value{GDBN} abandons the remote debugging session.
16753 (If you decide you want to try again later, you can use @samp{target
16754 remote} again to connect once more.) If you type @kbd{n}, @value{GDBN}
16755 goes back to waiting.
16758 @kindex detach (remote)
16760 When you have finished debugging the remote program, you can use the
16761 @code{detach} command to release it from @value{GDBN} control.
16762 Detaching from the target normally resumes its execution, but the results
16763 will depend on your particular remote stub. After the @code{detach}
16764 command, @value{GDBN} is free to connect to another target.
16768 The @code{disconnect} command behaves like @code{detach}, except that
16769 the target is generally not resumed. It will wait for @value{GDBN}
16770 (this instance or another one) to connect and continue debugging. After
16771 the @code{disconnect} command, @value{GDBN} is again free to connect to
16774 @cindex send command to remote monitor
16775 @cindex extend @value{GDBN} for remote targets
16776 @cindex add new commands for external monitor
16778 @item monitor @var{cmd}
16779 This command allows you to send arbitrary commands directly to the
16780 remote monitor. Since @value{GDBN} doesn't care about the commands it
16781 sends like this, this command is the way to extend @value{GDBN}---you
16782 can add new commands that only the external monitor will understand
16786 @node File Transfer
16787 @section Sending files to a remote system
16788 @cindex remote target, file transfer
16789 @cindex file transfer
16790 @cindex sending files to remote systems
16792 Some remote targets offer the ability to transfer files over the same
16793 connection used to communicate with @value{GDBN}. This is convenient
16794 for targets accessible through other means, e.g.@: @sc{gnu}/Linux systems
16795 running @code{gdbserver} over a network interface. For other targets,
16796 e.g.@: embedded devices with only a single serial port, this may be
16797 the only way to upload or download files.
16799 Not all remote targets support these commands.
16803 @item remote put @var{hostfile} @var{targetfile}
16804 Copy file @var{hostfile} from the host system (the machine running
16805 @value{GDBN}) to @var{targetfile} on the target system.
16808 @item remote get @var{targetfile} @var{hostfile}
16809 Copy file @var{targetfile} from the target system to @var{hostfile}
16810 on the host system.
16812 @kindex remote delete
16813 @item remote delete @var{targetfile}
16814 Delete @var{targetfile} from the target system.
16819 @section Using the @code{gdbserver} Program
16822 @cindex remote connection without stubs
16823 @code{gdbserver} is a control program for Unix-like systems, which
16824 allows you to connect your program with a remote @value{GDBN} via
16825 @code{target remote}---but without linking in the usual debugging stub.
16827 @code{gdbserver} is not a complete replacement for the debugging stubs,
16828 because it requires essentially the same operating-system facilities
16829 that @value{GDBN} itself does. In fact, a system that can run
16830 @code{gdbserver} to connect to a remote @value{GDBN} could also run
16831 @value{GDBN} locally! @code{gdbserver} is sometimes useful nevertheless,
16832 because it is a much smaller program than @value{GDBN} itself. It is
16833 also easier to port than all of @value{GDBN}, so you may be able to get
16834 started more quickly on a new system by using @code{gdbserver}.
16835 Finally, if you develop code for real-time systems, you may find that
16836 the tradeoffs involved in real-time operation make it more convenient to
16837 do as much development work as possible on another system, for example
16838 by cross-compiling. You can use @code{gdbserver} to make a similar
16839 choice for debugging.
16841 @value{GDBN} and @code{gdbserver} communicate via either a serial line
16842 or a TCP connection, using the standard @value{GDBN} remote serial
16846 @emph{Warning:} @code{gdbserver} does not have any built-in security.
16847 Do not run @code{gdbserver} connected to any public network; a
16848 @value{GDBN} connection to @code{gdbserver} provides access to the
16849 target system with the same privileges as the user running
16853 @subsection Running @code{gdbserver}
16854 @cindex arguments, to @code{gdbserver}
16855 @cindex @code{gdbserver}, command-line arguments
16857 Run @code{gdbserver} on the target system. You need a copy of the
16858 program you want to debug, including any libraries it requires.
16859 @code{gdbserver} does not need your program's symbol table, so you can
16860 strip the program if necessary to save space. @value{GDBN} on the host
16861 system does all the symbol handling.
16863 To use the server, you must tell it how to communicate with @value{GDBN};
16864 the name of your program; and the arguments for your program. The usual
16868 target> gdbserver @var{comm} @var{program} [ @var{args} @dots{} ]
16871 @var{comm} is either a device name (to use a serial line), or a TCP
16872 hostname and portnumber, or @code{-} or @code{stdio} to use
16873 stdin/stdout of @code{gdbserver}.
16874 For example, to debug Emacs with the argument
16875 @samp{foo.txt} and communicate with @value{GDBN} over the serial port
16879 target> gdbserver /dev/com1 emacs foo.txt
16882 @code{gdbserver} waits passively for the host @value{GDBN} to communicate
16885 To use a TCP connection instead of a serial line:
16888 target> gdbserver host:2345 emacs foo.txt
16891 The only difference from the previous example is the first argument,
16892 specifying that you are communicating with the host @value{GDBN} via
16893 TCP. The @samp{host:2345} argument means that @code{gdbserver} is to
16894 expect a TCP connection from machine @samp{host} to local TCP port 2345.
16895 (Currently, the @samp{host} part is ignored.) You can choose any number
16896 you want for the port number as long as it does not conflict with any
16897 TCP ports already in use on the target system (for example, @code{23} is
16898 reserved for @code{telnet}).@footnote{If you choose a port number that
16899 conflicts with another service, @code{gdbserver} prints an error message
16900 and exits.} You must use the same port number with the host @value{GDBN}
16901 @code{target remote} command.
16903 The @code{stdio} connection is useful when starting @code{gdbserver}
16907 (gdb) target remote | ssh -T hostname gdbserver - hello
16910 The @samp{-T} option to ssh is provided because we don't need a remote pty,
16911 and we don't want escape-character handling. Ssh does this by default when
16912 a command is provided, the flag is provided to make it explicit.
16913 You could elide it if you want to.
16915 Programs started with stdio-connected gdbserver have @file{/dev/null} for
16916 @code{stdin}, and @code{stdout},@code{stderr} are sent back to gdb for
16917 display through a pipe connected to gdbserver.
16918 Both @code{stdout} and @code{stderr} use the same pipe.
16920 @subsubsection Attaching to a Running Program
16921 @cindex attach to a program, @code{gdbserver}
16922 @cindex @option{--attach}, @code{gdbserver} option
16924 On some targets, @code{gdbserver} can also attach to running programs.
16925 This is accomplished via the @code{--attach} argument. The syntax is:
16928 target> gdbserver --attach @var{comm} @var{pid}
16931 @var{pid} is the process ID of a currently running process. It isn't necessary
16932 to point @code{gdbserver} at a binary for the running process.
16935 You can debug processes by name instead of process ID if your target has the
16936 @code{pidof} utility:
16939 target> gdbserver --attach @var{comm} `pidof @var{program}`
16942 In case more than one copy of @var{program} is running, or @var{program}
16943 has multiple threads, most versions of @code{pidof} support the
16944 @code{-s} option to only return the first process ID.
16946 @subsubsection Multi-Process Mode for @code{gdbserver}
16947 @cindex @code{gdbserver}, multiple processes
16948 @cindex multiple processes with @code{gdbserver}
16950 When you connect to @code{gdbserver} using @code{target remote},
16951 @code{gdbserver} debugs the specified program only once. When the
16952 program exits, or you detach from it, @value{GDBN} closes the connection
16953 and @code{gdbserver} exits.
16955 If you connect using @kbd{target extended-remote}, @code{gdbserver}
16956 enters multi-process mode. When the debugged program exits, or you
16957 detach from it, @value{GDBN} stays connected to @code{gdbserver} even
16958 though no program is running. The @code{run} and @code{attach}
16959 commands instruct @code{gdbserver} to run or attach to a new program.
16960 The @code{run} command uses @code{set remote exec-file} (@pxref{set
16961 remote exec-file}) to select the program to run. Command line
16962 arguments are supported, except for wildcard expansion and I/O
16963 redirection (@pxref{Arguments}).
16965 @cindex @option{--multi}, @code{gdbserver} option
16966 To start @code{gdbserver} without supplying an initial command to run
16967 or process ID to attach, use the @option{--multi} command line option.
16968 Then you can connect using @kbd{target extended-remote} and start
16969 the program you want to debug.
16971 In multi-process mode @code{gdbserver} does not automatically exit unless you
16972 use the option @option{--once}. You can terminate it by using
16973 @code{monitor exit} (@pxref{Monitor Commands for gdbserver}). Note that the
16974 conditions under which @code{gdbserver} terminates depend on how @value{GDBN}
16975 connects to it (@kbd{target remote} or @kbd{target extended-remote}). The
16976 @option{--multi} option to @code{gdbserver} has no influence on that.
16978 @subsubsection TCP port allocation lifecycle of @code{gdbserver}
16980 This section applies only when @code{gdbserver} is run to listen on a TCP port.
16982 @code{gdbserver} normally terminates after all of its debugged processes have
16983 terminated in @kbd{target remote} mode. On the other hand, for @kbd{target
16984 extended-remote}, @code{gdbserver} stays running even with no processes left.
16985 @value{GDBN} normally terminates the spawned debugged process on its exit,
16986 which normally also terminates @code{gdbserver} in the @kbd{target remote}
16987 mode. Therefore, when the connection drops unexpectedly, and @value{GDBN}
16988 cannot ask @code{gdbserver} to kill its debugged processes, @code{gdbserver}
16989 stays running even in the @kbd{target remote} mode.
16991 When @code{gdbserver} stays running, @value{GDBN} can connect to it again later.
16992 Such reconnecting is useful for features like @ref{disconnected tracing}. For
16993 completeness, at most one @value{GDBN} can be connected at a time.
16995 @cindex @option{--once}, @code{gdbserver} option
16996 By default, @code{gdbserver} keeps the listening TCP port open, so that
16997 additional connections are possible. However, if you start @code{gdbserver}
16998 with the @option{--once} option, it will stop listening for any further
16999 connection attempts after connecting to the first @value{GDBN} session. This
17000 means no further connections to @code{gdbserver} will be possible after the
17001 first one. It also means @code{gdbserver} will terminate after the first
17002 connection with remote @value{GDBN} has closed, even for unexpectedly closed
17003 connections and even in the @kbd{target extended-remote} mode. The
17004 @option{--once} option allows reusing the same port number for connecting to
17005 multiple instances of @code{gdbserver} running on the same host, since each
17006 instance closes its port after the first connection.
17008 @subsubsection Other Command-Line Arguments for @code{gdbserver}
17010 @cindex @option{--debug}, @code{gdbserver} option
17011 The @option{--debug} option tells @code{gdbserver} to display extra
17012 status information about the debugging process.
17013 @cindex @option{--remote-debug}, @code{gdbserver} option
17014 The @option{--remote-debug} option tells @code{gdbserver} to display
17015 remote protocol debug output. These options are intended for
17016 @code{gdbserver} development and for bug reports to the developers.
17018 @cindex @option{--wrapper}, @code{gdbserver} option
17019 The @option{--wrapper} option specifies a wrapper to launch programs
17020 for debugging. The option should be followed by the name of the
17021 wrapper, then any command-line arguments to pass to the wrapper, then
17022 @kbd{--} indicating the end of the wrapper arguments.
17024 @code{gdbserver} runs the specified wrapper program with a combined
17025 command line including the wrapper arguments, then the name of the
17026 program to debug, then any arguments to the program. The wrapper
17027 runs until it executes your program, and then @value{GDBN} gains control.
17029 You can use any program that eventually calls @code{execve} with
17030 its arguments as a wrapper. Several standard Unix utilities do
17031 this, e.g.@: @code{env} and @code{nohup}. Any Unix shell script ending
17032 with @code{exec "$@@"} will also work.
17034 For example, you can use @code{env} to pass an environment variable to
17035 the debugged program, without setting the variable in @code{gdbserver}'s
17039 $ gdbserver --wrapper env LD_PRELOAD=libtest.so -- :2222 ./testprog
17042 @subsection Connecting to @code{gdbserver}
17044 Run @value{GDBN} on the host system.
17046 First make sure you have the necessary symbol files. Load symbols for
17047 your application using the @code{file} command before you connect. Use
17048 @code{set sysroot} to locate target libraries (unless your @value{GDBN}
17049 was compiled with the correct sysroot using @code{--with-sysroot}).
17051 The symbol file and target libraries must exactly match the executable
17052 and libraries on the target, with one exception: the files on the host
17053 system should not be stripped, even if the files on the target system
17054 are. Mismatched or missing files will lead to confusing results
17055 during debugging. On @sc{gnu}/Linux targets, mismatched or missing
17056 files may also prevent @code{gdbserver} from debugging multi-threaded
17059 Connect to your target (@pxref{Connecting,,Connecting to a Remote Target}).
17060 For TCP connections, you must start up @code{gdbserver} prior to using
17061 the @code{target remote} command. Otherwise you may get an error whose
17062 text depends on the host system, but which usually looks something like
17063 @samp{Connection refused}. Don't use the @code{load}
17064 command in @value{GDBN} when using @code{gdbserver}, since the program is
17065 already on the target.
17067 @subsection Monitor Commands for @code{gdbserver}
17068 @cindex monitor commands, for @code{gdbserver}
17069 @anchor{Monitor Commands for gdbserver}
17071 During a @value{GDBN} session using @code{gdbserver}, you can use the
17072 @code{monitor} command to send special requests to @code{gdbserver}.
17073 Here are the available commands.
17077 List the available monitor commands.
17079 @item monitor set debug 0
17080 @itemx monitor set debug 1
17081 Disable or enable general debugging messages.
17083 @item monitor set remote-debug 0
17084 @itemx monitor set remote-debug 1
17085 Disable or enable specific debugging messages associated with the remote
17086 protocol (@pxref{Remote Protocol}).
17088 @item monitor set libthread-db-search-path [PATH]
17089 @cindex gdbserver, search path for @code{libthread_db}
17090 When this command is issued, @var{path} is a colon-separated list of
17091 directories to search for @code{libthread_db} (@pxref{Threads,,set
17092 libthread-db-search-path}). If you omit @var{path},
17093 @samp{libthread-db-search-path} will be reset to its default value.
17095 The special entry @samp{$pdir} for @samp{libthread-db-search-path} is
17096 not supported in @code{gdbserver}.
17099 Tell gdbserver to exit immediately. This command should be followed by
17100 @code{disconnect} to close the debugging session. @code{gdbserver} will
17101 detach from any attached processes and kill any processes it created.
17102 Use @code{monitor exit} to terminate @code{gdbserver} at the end
17103 of a multi-process mode debug session.
17107 @subsection Tracepoints support in @code{gdbserver}
17108 @cindex tracepoints support in @code{gdbserver}
17110 On some targets, @code{gdbserver} supports tracepoints, fast
17111 tracepoints and static tracepoints.
17113 For fast or static tracepoints to work, a special library called the
17114 @dfn{in-process agent} (IPA), must be loaded in the inferior process.
17115 This library is built and distributed as an integral part of
17116 @code{gdbserver}. In addition, support for static tracepoints
17117 requires building the in-process agent library with static tracepoints
17118 support. At present, the UST (LTTng Userspace Tracer,
17119 @url{http://lttng.org/ust}) tracing engine is supported. This support
17120 is automatically available if UST development headers are found in the
17121 standard include path when @code{gdbserver} is built, or if
17122 @code{gdbserver} was explicitly configured using @option{--with-ust}
17123 to point at such headers. You can explicitly disable the support
17124 using @option{--with-ust=no}.
17126 There are several ways to load the in-process agent in your program:
17129 @item Specifying it as dependency at link time
17131 You can link your program dynamically with the in-process agent
17132 library. On most systems, this is accomplished by adding
17133 @code{-linproctrace} to the link command.
17135 @item Using the system's preloading mechanisms
17137 You can force loading the in-process agent at startup time by using
17138 your system's support for preloading shared libraries. Many Unixes
17139 support the concept of preloading user defined libraries. In most
17140 cases, you do that by specifying @code{LD_PRELOAD=libinproctrace.so}
17141 in the environment. See also the description of @code{gdbserver}'s
17142 @option{--wrapper} command line option.
17144 @item Using @value{GDBN} to force loading the agent at run time
17146 On some systems, you can force the inferior to load a shared library,
17147 by calling a dynamic loader function in the inferior that takes care
17148 of dynamically looking up and loading a shared library. On most Unix
17149 systems, the function is @code{dlopen}. You'll use the @code{call}
17150 command for that. For example:
17153 (@value{GDBP}) call dlopen ("libinproctrace.so", ...)
17156 Note that on most Unix systems, for the @code{dlopen} function to be
17157 available, the program needs to be linked with @code{-ldl}.
17160 On systems that have a userspace dynamic loader, like most Unix
17161 systems, when you connect to @code{gdbserver} using @code{target
17162 remote}, you'll find that the program is stopped at the dynamic
17163 loader's entry point, and no shared library has been loaded in the
17164 program's address space yet, including the in-process agent. In that
17165 case, before being able to use any of the fast or static tracepoints
17166 features, you need to let the loader run and load the shared
17167 libraries. The simplest way to do that is to run the program to the
17168 main procedure. E.g., if debugging a C or C@t{++} program, start
17169 @code{gdbserver} like so:
17172 $ gdbserver :9999 myprogram
17175 Start GDB and connect to @code{gdbserver} like so, and run to main:
17179 (@value{GDBP}) target remote myhost:9999
17180 0x00007f215893ba60 in ?? () from /lib64/ld-linux-x86-64.so.2
17181 (@value{GDBP}) b main
17182 (@value{GDBP}) continue
17185 The in-process tracing agent library should now be loaded into the
17186 process; you can confirm it with the @code{info sharedlibrary}
17187 command, which will list @file{libinproctrace.so} as loaded in the
17188 process. You are now ready to install fast tracepoints, list static
17189 tracepoint markers, probe static tracepoints markers, and start
17192 @node Remote Configuration
17193 @section Remote Configuration
17196 @kindex show remote
17197 This section documents the configuration options available when
17198 debugging remote programs. For the options related to the File I/O
17199 extensions of the remote protocol, see @ref{system,
17200 system-call-allowed}.
17203 @item set remoteaddresssize @var{bits}
17204 @cindex address size for remote targets
17205 @cindex bits in remote address
17206 Set the maximum size of address in a memory packet to the specified
17207 number of bits. @value{GDBN} will mask off the address bits above
17208 that number, when it passes addresses to the remote target. The
17209 default value is the number of bits in the target's address.
17211 @item show remoteaddresssize
17212 Show the current value of remote address size in bits.
17214 @item set remotebaud @var{n}
17215 @cindex baud rate for remote targets
17216 Set the baud rate for the remote serial I/O to @var{n} baud. The
17217 value is used to set the speed of the serial port used for debugging
17220 @item show remotebaud
17221 Show the current speed of the remote connection.
17223 @item set remotebreak
17224 @cindex interrupt remote programs
17225 @cindex BREAK signal instead of Ctrl-C
17226 @anchor{set remotebreak}
17227 If set to on, @value{GDBN} sends a @code{BREAK} signal to the remote
17228 when you type @kbd{Ctrl-c} to interrupt the program running
17229 on the remote. If set to off, @value{GDBN} sends the @samp{Ctrl-C}
17230 character instead. The default is off, since most remote systems
17231 expect to see @samp{Ctrl-C} as the interrupt signal.
17233 @item show remotebreak
17234 Show whether @value{GDBN} sends @code{BREAK} or @samp{Ctrl-C} to
17235 interrupt the remote program.
17237 @item set remoteflow on
17238 @itemx set remoteflow off
17239 @kindex set remoteflow
17240 Enable or disable hardware flow control (@code{RTS}/@code{CTS})
17241 on the serial port used to communicate to the remote target.
17243 @item show remoteflow
17244 @kindex show remoteflow
17245 Show the current setting of hardware flow control.
17247 @item set remotelogbase @var{base}
17248 Set the base (a.k.a.@: radix) of logging serial protocol
17249 communications to @var{base}. Supported values of @var{base} are:
17250 @code{ascii}, @code{octal}, and @code{hex}. The default is
17253 @item show remotelogbase
17254 Show the current setting of the radix for logging remote serial
17257 @item set remotelogfile @var{file}
17258 @cindex record serial communications on file
17259 Record remote serial communications on the named @var{file}. The
17260 default is not to record at all.
17262 @item show remotelogfile.
17263 Show the current setting of the file name on which to record the
17264 serial communications.
17266 @item set remotetimeout @var{num}
17267 @cindex timeout for serial communications
17268 @cindex remote timeout
17269 Set the timeout limit to wait for the remote target to respond to
17270 @var{num} seconds. The default is 2 seconds.
17272 @item show remotetimeout
17273 Show the current number of seconds to wait for the remote target
17276 @cindex limit hardware breakpoints and watchpoints
17277 @cindex remote target, limit break- and watchpoints
17278 @anchor{set remote hardware-watchpoint-limit}
17279 @anchor{set remote hardware-breakpoint-limit}
17280 @item set remote hardware-watchpoint-limit @var{limit}
17281 @itemx set remote hardware-breakpoint-limit @var{limit}
17282 Restrict @value{GDBN} to using @var{limit} remote hardware breakpoint or
17283 watchpoints. A limit of -1, the default, is treated as unlimited.
17285 @cindex limit hardware watchpoints length
17286 @cindex remote target, limit watchpoints length
17287 @anchor{set remote hardware-watchpoint-length-limit}
17288 @item set remote hardware-watchpoint-length-limit @var{limit}
17289 Restrict @value{GDBN} to using @var{limit} bytes for the maximum length of
17290 a remote hardware watchpoint. A limit of -1, the default, is treated
17293 @item show remote hardware-watchpoint-length-limit
17294 Show the current limit (in bytes) of the maximum length of
17295 a remote hardware watchpoint.
17297 @item set remote exec-file @var{filename}
17298 @itemx show remote exec-file
17299 @anchor{set remote exec-file}
17300 @cindex executable file, for remote target
17301 Select the file used for @code{run} with @code{target
17302 extended-remote}. This should be set to a filename valid on the
17303 target system. If it is not set, the target will use a default
17304 filename (e.g.@: the last program run).
17306 @item set remote interrupt-sequence
17307 @cindex interrupt remote programs
17308 @cindex select Ctrl-C, BREAK or BREAK-g
17309 Allow the user to select one of @samp{Ctrl-C}, a @code{BREAK} or
17310 @samp{BREAK-g} as the
17311 sequence to the remote target in order to interrupt the execution.
17312 @samp{Ctrl-C} is a default. Some system prefers @code{BREAK} which
17313 is high level of serial line for some certain time.
17314 Linux kernel prefers @samp{BREAK-g}, a.k.a Magic SysRq g.
17315 It is @code{BREAK} signal followed by character @code{g}.
17317 @item show interrupt-sequence
17318 Show which of @samp{Ctrl-C}, @code{BREAK} or @code{BREAK-g}
17319 is sent by @value{GDBN} to interrupt the remote program.
17320 @code{BREAK-g} is BREAK signal followed by @code{g} and
17321 also known as Magic SysRq g.
17323 @item set remote interrupt-on-connect
17324 @cindex send interrupt-sequence on start
17325 Specify whether interrupt-sequence is sent to remote target when
17326 @value{GDBN} connects to it. This is mostly needed when you debug
17327 Linux kernel. Linux kernel expects @code{BREAK} followed by @code{g}
17328 which is known as Magic SysRq g in order to connect @value{GDBN}.
17330 @item show interrupt-on-connect
17331 Show whether interrupt-sequence is sent
17332 to remote target when @value{GDBN} connects to it.
17336 @item set tcp auto-retry on
17337 @cindex auto-retry, for remote TCP target
17338 Enable auto-retry for remote TCP connections. This is useful if the remote
17339 debugging agent is launched in parallel with @value{GDBN}; there is a race
17340 condition because the agent may not become ready to accept the connection
17341 before @value{GDBN} attempts to connect. When auto-retry is
17342 enabled, if the initial attempt to connect fails, @value{GDBN} reattempts
17343 to establish the connection using the timeout specified by
17344 @code{set tcp connect-timeout}.
17346 @item set tcp auto-retry off
17347 Do not auto-retry failed TCP connections.
17349 @item show tcp auto-retry
17350 Show the current auto-retry setting.
17352 @item set tcp connect-timeout @var{seconds}
17353 @cindex connection timeout, for remote TCP target
17354 @cindex timeout, for remote target connection
17355 Set the timeout for establishing a TCP connection to the remote target to
17356 @var{seconds}. The timeout affects both polling to retry failed connections
17357 (enabled by @code{set tcp auto-retry on}) and waiting for connections
17358 that are merely slow to complete, and represents an approximate cumulative
17361 @item show tcp connect-timeout
17362 Show the current connection timeout setting.
17365 @cindex remote packets, enabling and disabling
17366 The @value{GDBN} remote protocol autodetects the packets supported by
17367 your debugging stub. If you need to override the autodetection, you
17368 can use these commands to enable or disable individual packets. Each
17369 packet can be set to @samp{on} (the remote target supports this
17370 packet), @samp{off} (the remote target does not support this packet),
17371 or @samp{auto} (detect remote target support for this packet). They
17372 all default to @samp{auto}. For more information about each packet,
17373 see @ref{Remote Protocol}.
17375 During normal use, you should not have to use any of these commands.
17376 If you do, that may be a bug in your remote debugging stub, or a bug
17377 in @value{GDBN}. You may want to report the problem to the
17378 @value{GDBN} developers.
17380 For each packet @var{name}, the command to enable or disable the
17381 packet is @code{set remote @var{name}-packet}. The available settings
17384 @multitable @columnfractions 0.28 0.32 0.25
17387 @tab Related Features
17389 @item @code{fetch-register}
17391 @tab @code{info registers}
17393 @item @code{set-register}
17397 @item @code{binary-download}
17399 @tab @code{load}, @code{set}
17401 @item @code{read-aux-vector}
17402 @tab @code{qXfer:auxv:read}
17403 @tab @code{info auxv}
17405 @item @code{symbol-lookup}
17406 @tab @code{qSymbol}
17407 @tab Detecting multiple threads
17409 @item @code{attach}
17410 @tab @code{vAttach}
17413 @item @code{verbose-resume}
17415 @tab Stepping or resuming multiple threads
17421 @item @code{software-breakpoint}
17425 @item @code{hardware-breakpoint}
17429 @item @code{write-watchpoint}
17433 @item @code{read-watchpoint}
17437 @item @code{access-watchpoint}
17441 @item @code{target-features}
17442 @tab @code{qXfer:features:read}
17443 @tab @code{set architecture}
17445 @item @code{library-info}
17446 @tab @code{qXfer:libraries:read}
17447 @tab @code{info sharedlibrary}
17449 @item @code{memory-map}
17450 @tab @code{qXfer:memory-map:read}
17451 @tab @code{info mem}
17453 @item @code{read-sdata-object}
17454 @tab @code{qXfer:sdata:read}
17455 @tab @code{print $_sdata}
17457 @item @code{read-spu-object}
17458 @tab @code{qXfer:spu:read}
17459 @tab @code{info spu}
17461 @item @code{write-spu-object}
17462 @tab @code{qXfer:spu:write}
17463 @tab @code{info spu}
17465 @item @code{read-siginfo-object}
17466 @tab @code{qXfer:siginfo:read}
17467 @tab @code{print $_siginfo}
17469 @item @code{write-siginfo-object}
17470 @tab @code{qXfer:siginfo:write}
17471 @tab @code{set $_siginfo}
17473 @item @code{threads}
17474 @tab @code{qXfer:threads:read}
17475 @tab @code{info threads}
17477 @item @code{get-thread-local-@*storage-address}
17478 @tab @code{qGetTLSAddr}
17479 @tab Displaying @code{__thread} variables
17481 @item @code{get-thread-information-block-address}
17482 @tab @code{qGetTIBAddr}
17483 @tab Display MS-Windows Thread Information Block.
17485 @item @code{search-memory}
17486 @tab @code{qSearch:memory}
17489 @item @code{supported-packets}
17490 @tab @code{qSupported}
17491 @tab Remote communications parameters
17493 @item @code{pass-signals}
17494 @tab @code{QPassSignals}
17495 @tab @code{handle @var{signal}}
17497 @item @code{program-signals}
17498 @tab @code{QProgramSignals}
17499 @tab @code{handle @var{signal}}
17501 @item @code{hostio-close-packet}
17502 @tab @code{vFile:close}
17503 @tab @code{remote get}, @code{remote put}
17505 @item @code{hostio-open-packet}
17506 @tab @code{vFile:open}
17507 @tab @code{remote get}, @code{remote put}
17509 @item @code{hostio-pread-packet}
17510 @tab @code{vFile:pread}
17511 @tab @code{remote get}, @code{remote put}
17513 @item @code{hostio-pwrite-packet}
17514 @tab @code{vFile:pwrite}
17515 @tab @code{remote get}, @code{remote put}
17517 @item @code{hostio-unlink-packet}
17518 @tab @code{vFile:unlink}
17519 @tab @code{remote delete}
17521 @item @code{hostio-readlink-packet}
17522 @tab @code{vFile:readlink}
17525 @item @code{noack-packet}
17526 @tab @code{QStartNoAckMode}
17527 @tab Packet acknowledgment
17529 @item @code{osdata}
17530 @tab @code{qXfer:osdata:read}
17531 @tab @code{info os}
17533 @item @code{query-attached}
17534 @tab @code{qAttached}
17535 @tab Querying remote process attach state.
17537 @item @code{traceframe-info}
17538 @tab @code{qXfer:traceframe-info:read}
17539 @tab Traceframe info
17541 @item @code{install-in-trace}
17542 @tab @code{InstallInTrace}
17543 @tab Install tracepoint in tracing
17545 @item @code{disable-randomization}
17546 @tab @code{QDisableRandomization}
17547 @tab @code{set disable-randomization}
17549 @item @code{conditional-breakpoints-packet}
17550 @tab @code{Z0 and Z1}
17551 @tab @code{Support for target-side breakpoint condition evaluation}
17555 @section Implementing a Remote Stub
17557 @cindex debugging stub, example
17558 @cindex remote stub, example
17559 @cindex stub example, remote debugging
17560 The stub files provided with @value{GDBN} implement the target side of the
17561 communication protocol, and the @value{GDBN} side is implemented in the
17562 @value{GDBN} source file @file{remote.c}. Normally, you can simply allow
17563 these subroutines to communicate, and ignore the details. (If you're
17564 implementing your own stub file, you can still ignore the details: start
17565 with one of the existing stub files. @file{sparc-stub.c} is the best
17566 organized, and therefore the easiest to read.)
17568 @cindex remote serial debugging, overview
17569 To debug a program running on another machine (the debugging
17570 @dfn{target} machine), you must first arrange for all the usual
17571 prerequisites for the program to run by itself. For example, for a C
17576 A startup routine to set up the C runtime environment; these usually
17577 have a name like @file{crt0}. The startup routine may be supplied by
17578 your hardware supplier, or you may have to write your own.
17581 A C subroutine library to support your program's
17582 subroutine calls, notably managing input and output.
17585 A way of getting your program to the other machine---for example, a
17586 download program. These are often supplied by the hardware
17587 manufacturer, but you may have to write your own from hardware
17591 The next step is to arrange for your program to use a serial port to
17592 communicate with the machine where @value{GDBN} is running (the @dfn{host}
17593 machine). In general terms, the scheme looks like this:
17597 @value{GDBN} already understands how to use this protocol; when everything
17598 else is set up, you can simply use the @samp{target remote} command
17599 (@pxref{Targets,,Specifying a Debugging Target}).
17601 @item On the target,
17602 you must link with your program a few special-purpose subroutines that
17603 implement the @value{GDBN} remote serial protocol. The file containing these
17604 subroutines is called a @dfn{debugging stub}.
17606 On certain remote targets, you can use an auxiliary program
17607 @code{gdbserver} instead of linking a stub into your program.
17608 @xref{Server,,Using the @code{gdbserver} Program}, for details.
17611 The debugging stub is specific to the architecture of the remote
17612 machine; for example, use @file{sparc-stub.c} to debug programs on
17615 @cindex remote serial stub list
17616 These working remote stubs are distributed with @value{GDBN}:
17621 @cindex @file{i386-stub.c}
17624 For Intel 386 and compatible architectures.
17627 @cindex @file{m68k-stub.c}
17628 @cindex Motorola 680x0
17630 For Motorola 680x0 architectures.
17633 @cindex @file{sh-stub.c}
17636 For Renesas SH architectures.
17639 @cindex @file{sparc-stub.c}
17641 For @sc{sparc} architectures.
17643 @item sparcl-stub.c
17644 @cindex @file{sparcl-stub.c}
17647 For Fujitsu @sc{sparclite} architectures.
17651 The @file{README} file in the @value{GDBN} distribution may list other
17652 recently added stubs.
17655 * Stub Contents:: What the stub can do for you
17656 * Bootstrapping:: What you must do for the stub
17657 * Debug Session:: Putting it all together
17660 @node Stub Contents
17661 @subsection What the Stub Can Do for You
17663 @cindex remote serial stub
17664 The debugging stub for your architecture supplies these three
17668 @item set_debug_traps
17669 @findex set_debug_traps
17670 @cindex remote serial stub, initialization
17671 This routine arranges for @code{handle_exception} to run when your
17672 program stops. You must call this subroutine explicitly in your
17673 program's startup code.
17675 @item handle_exception
17676 @findex handle_exception
17677 @cindex remote serial stub, main routine
17678 This is the central workhorse, but your program never calls it
17679 explicitly---the setup code arranges for @code{handle_exception} to
17680 run when a trap is triggered.
17682 @code{handle_exception} takes control when your program stops during
17683 execution (for example, on a breakpoint), and mediates communications
17684 with @value{GDBN} on the host machine. This is where the communications
17685 protocol is implemented; @code{handle_exception} acts as the @value{GDBN}
17686 representative on the target machine. It begins by sending summary
17687 information on the state of your program, then continues to execute,
17688 retrieving and transmitting any information @value{GDBN} needs, until you
17689 execute a @value{GDBN} command that makes your program resume; at that point,
17690 @code{handle_exception} returns control to your own code on the target
17694 @cindex @code{breakpoint} subroutine, remote
17695 Use this auxiliary subroutine to make your program contain a
17696 breakpoint. Depending on the particular situation, this may be the only
17697 way for @value{GDBN} to get control. For instance, if your target
17698 machine has some sort of interrupt button, you won't need to call this;
17699 pressing the interrupt button transfers control to
17700 @code{handle_exception}---in effect, to @value{GDBN}. On some machines,
17701 simply receiving characters on the serial port may also trigger a trap;
17702 again, in that situation, you don't need to call @code{breakpoint} from
17703 your own program---simply running @samp{target remote} from the host
17704 @value{GDBN} session gets control.
17706 Call @code{breakpoint} if none of these is true, or if you simply want
17707 to make certain your program stops at a predetermined point for the
17708 start of your debugging session.
17711 @node Bootstrapping
17712 @subsection What You Must Do for the Stub
17714 @cindex remote stub, support routines
17715 The debugging stubs that come with @value{GDBN} are set up for a particular
17716 chip architecture, but they have no information about the rest of your
17717 debugging target machine.
17719 First of all you need to tell the stub how to communicate with the
17723 @item int getDebugChar()
17724 @findex getDebugChar
17725 Write this subroutine to read a single character from the serial port.
17726 It may be identical to @code{getchar} for your target system; a
17727 different name is used to allow you to distinguish the two if you wish.
17729 @item void putDebugChar(int)
17730 @findex putDebugChar
17731 Write this subroutine to write a single character to the serial port.
17732 It may be identical to @code{putchar} for your target system; a
17733 different name is used to allow you to distinguish the two if you wish.
17736 @cindex control C, and remote debugging
17737 @cindex interrupting remote targets
17738 If you want @value{GDBN} to be able to stop your program while it is
17739 running, you need to use an interrupt-driven serial driver, and arrange
17740 for it to stop when it receives a @code{^C} (@samp{\003}, the control-C
17741 character). That is the character which @value{GDBN} uses to tell the
17742 remote system to stop.
17744 Getting the debugging target to return the proper status to @value{GDBN}
17745 probably requires changes to the standard stub; one quick and dirty way
17746 is to just execute a breakpoint instruction (the ``dirty'' part is that
17747 @value{GDBN} reports a @code{SIGTRAP} instead of a @code{SIGINT}).
17749 Other routines you need to supply are:
17752 @item void exceptionHandler (int @var{exception_number}, void *@var{exception_address})
17753 @findex exceptionHandler
17754 Write this function to install @var{exception_address} in the exception
17755 handling tables. You need to do this because the stub does not have any
17756 way of knowing what the exception handling tables on your target system
17757 are like (for example, the processor's table might be in @sc{rom},
17758 containing entries which point to a table in @sc{ram}).
17759 @var{exception_number} is the exception number which should be changed;
17760 its meaning is architecture-dependent (for example, different numbers
17761 might represent divide by zero, misaligned access, etc). When this
17762 exception occurs, control should be transferred directly to
17763 @var{exception_address}, and the processor state (stack, registers,
17764 and so on) should be just as it is when a processor exception occurs. So if
17765 you want to use a jump instruction to reach @var{exception_address}, it
17766 should be a simple jump, not a jump to subroutine.
17768 For the 386, @var{exception_address} should be installed as an interrupt
17769 gate so that interrupts are masked while the handler runs. The gate
17770 should be at privilege level 0 (the most privileged level). The
17771 @sc{sparc} and 68k stubs are able to mask interrupts themselves without
17772 help from @code{exceptionHandler}.
17774 @item void flush_i_cache()
17775 @findex flush_i_cache
17776 On @sc{sparc} and @sc{sparclite} only, write this subroutine to flush the
17777 instruction cache, if any, on your target machine. If there is no
17778 instruction cache, this subroutine may be a no-op.
17780 On target machines that have instruction caches, @value{GDBN} requires this
17781 function to make certain that the state of your program is stable.
17785 You must also make sure this library routine is available:
17788 @item void *memset(void *, int, int)
17790 This is the standard library function @code{memset} that sets an area of
17791 memory to a known value. If you have one of the free versions of
17792 @code{libc.a}, @code{memset} can be found there; otherwise, you must
17793 either obtain it from your hardware manufacturer, or write your own.
17796 If you do not use the GNU C compiler, you may need other standard
17797 library subroutines as well; this varies from one stub to another,
17798 but in general the stubs are likely to use any of the common library
17799 subroutines which @code{@value{NGCC}} generates as inline code.
17802 @node Debug Session
17803 @subsection Putting it All Together
17805 @cindex remote serial debugging summary
17806 In summary, when your program is ready to debug, you must follow these
17811 Make sure you have defined the supporting low-level routines
17812 (@pxref{Bootstrapping,,What You Must Do for the Stub}):
17814 @code{getDebugChar}, @code{putDebugChar},
17815 @code{flush_i_cache}, @code{memset}, @code{exceptionHandler}.
17819 Insert these lines in your program's startup code, before the main
17820 procedure is called:
17827 On some machines, when a breakpoint trap is raised, the hardware
17828 automatically makes the PC point to the instruction after the
17829 breakpoint. If your machine doesn't do that, you may need to adjust
17830 @code{handle_exception} to arrange for it to return to the instruction
17831 after the breakpoint on this first invocation, so that your program
17832 doesn't keep hitting the initial breakpoint instead of making
17836 For the 680x0 stub only, you need to provide a variable called
17837 @code{exceptionHook}. Normally you just use:
17840 void (*exceptionHook)() = 0;
17844 but if before calling @code{set_debug_traps}, you set it to point to a
17845 function in your program, that function is called when
17846 @code{@value{GDBN}} continues after stopping on a trap (for example, bus
17847 error). The function indicated by @code{exceptionHook} is called with
17848 one parameter: an @code{int} which is the exception number.
17851 Compile and link together: your program, the @value{GDBN} debugging stub for
17852 your target architecture, and the supporting subroutines.
17855 Make sure you have a serial connection between your target machine and
17856 the @value{GDBN} host, and identify the serial port on the host.
17859 @c The "remote" target now provides a `load' command, so we should
17860 @c document that. FIXME.
17861 Download your program to your target machine (or get it there by
17862 whatever means the manufacturer provides), and start it.
17865 Start @value{GDBN} on the host, and connect to the target
17866 (@pxref{Connecting,,Connecting to a Remote Target}).
17870 @node Configurations
17871 @chapter Configuration-Specific Information
17873 While nearly all @value{GDBN} commands are available for all native and
17874 cross versions of the debugger, there are some exceptions. This chapter
17875 describes things that are only available in certain configurations.
17877 There are three major categories of configurations: native
17878 configurations, where the host and target are the same, embedded
17879 operating system configurations, which are usually the same for several
17880 different processor architectures, and bare embedded processors, which
17881 are quite different from each other.
17886 * Embedded Processors::
17893 This section describes details specific to particular native
17898 * BSD libkvm Interface:: Debugging BSD kernel memory images
17899 * SVR4 Process Information:: SVR4 process information
17900 * DJGPP Native:: Features specific to the DJGPP port
17901 * Cygwin Native:: Features specific to the Cygwin port
17902 * Hurd Native:: Features specific to @sc{gnu} Hurd
17903 * Neutrino:: Features specific to QNX Neutrino
17904 * Darwin:: Features specific to Darwin
17910 On HP-UX systems, if you refer to a function or variable name that
17911 begins with a dollar sign, @value{GDBN} searches for a user or system
17912 name first, before it searches for a convenience variable.
17915 @node BSD libkvm Interface
17916 @subsection BSD libkvm Interface
17919 @cindex kernel memory image
17920 @cindex kernel crash dump
17922 BSD-derived systems (FreeBSD/NetBSD/OpenBSD) have a kernel memory
17923 interface that provides a uniform interface for accessing kernel virtual
17924 memory images, including live systems and crash dumps. @value{GDBN}
17925 uses this interface to allow you to debug live kernels and kernel crash
17926 dumps on many native BSD configurations. This is implemented as a
17927 special @code{kvm} debugging target. For debugging a live system, load
17928 the currently running kernel into @value{GDBN} and connect to the
17932 (@value{GDBP}) @b{target kvm}
17935 For debugging crash dumps, provide the file name of the crash dump as an
17939 (@value{GDBP}) @b{target kvm /var/crash/bsd.0}
17942 Once connected to the @code{kvm} target, the following commands are
17948 Set current context from the @dfn{Process Control Block} (PCB) address.
17951 Set current context from proc address. This command isn't available on
17952 modern FreeBSD systems.
17955 @node SVR4 Process Information
17956 @subsection SVR4 Process Information
17958 @cindex examine process image
17959 @cindex process info via @file{/proc}
17961 Many versions of SVR4 and compatible systems provide a facility called
17962 @samp{/proc} that can be used to examine the image of a running
17963 process using file-system subroutines. If @value{GDBN} is configured
17964 for an operating system with this facility, the command @code{info
17965 proc} is available to report information about the process running
17966 your program, or about any process running on your system. @code{info
17967 proc} works only on SVR4 systems that include the @code{procfs} code.
17968 This includes, as of this writing, @sc{gnu}/Linux, OSF/1 (Digital
17969 Unix), Solaris, Irix, and Unixware, but not HP-UX, for example.
17975 @itemx info proc @var{process-id}
17976 Summarize available information about any running process. If a
17977 process ID is specified by @var{process-id}, display information about
17978 that process; otherwise display information about the program being
17979 debugged. The summary includes the debugged process ID, the command
17980 line used to invoke it, its current working directory, and its
17981 executable file's absolute file name.
17983 On some systems, @var{process-id} can be of the form
17984 @samp{[@var{pid}]/@var{tid}} which specifies a certain thread ID
17985 within a process. If the optional @var{pid} part is missing, it means
17986 a thread from the process being debugged (the leading @samp{/} still
17987 needs to be present, or else @value{GDBN} will interpret the number as
17988 a process ID rather than a thread ID).
17990 @item info proc mappings
17991 @cindex memory address space mappings
17992 Report the memory address space ranges accessible in the program, with
17993 information on whether the process has read, write, or execute access
17994 rights to each range. On @sc{gnu}/Linux systems, each memory range
17995 includes the object file which is mapped to that range, instead of the
17996 memory access rights to that range.
17998 @item info proc stat
17999 @itemx info proc status
18000 @cindex process detailed status information
18001 These subcommands are specific to @sc{gnu}/Linux systems. They show
18002 the process-related information, including the user ID and group ID;
18003 how many threads are there in the process; its virtual memory usage;
18004 the signals that are pending, blocked, and ignored; its TTY; its
18005 consumption of system and user time; its stack size; its @samp{nice}
18006 value; etc. For more information, see the @samp{proc} man page
18007 (type @kbd{man 5 proc} from your shell prompt).
18009 @item info proc all
18010 Show all the information about the process described under all of the
18011 above @code{info proc} subcommands.
18014 @comment These sub-options of 'info proc' were not included when
18015 @comment procfs.c was re-written. Keep their descriptions around
18016 @comment against the day when someone finds the time to put them back in.
18017 @kindex info proc times
18018 @item info proc times
18019 Starting time, user CPU time, and system CPU time for your program and
18022 @kindex info proc id
18024 Report on the process IDs related to your program: its own process ID,
18025 the ID of its parent, the process group ID, and the session ID.
18028 @item set procfs-trace
18029 @kindex set procfs-trace
18030 @cindex @code{procfs} API calls
18031 This command enables and disables tracing of @code{procfs} API calls.
18033 @item show procfs-trace
18034 @kindex show procfs-trace
18035 Show the current state of @code{procfs} API call tracing.
18037 @item set procfs-file @var{file}
18038 @kindex set procfs-file
18039 Tell @value{GDBN} to write @code{procfs} API trace to the named
18040 @var{file}. @value{GDBN} appends the trace info to the previous
18041 contents of the file. The default is to display the trace on the
18044 @item show procfs-file
18045 @kindex show procfs-file
18046 Show the file to which @code{procfs} API trace is written.
18048 @item proc-trace-entry
18049 @itemx proc-trace-exit
18050 @itemx proc-untrace-entry
18051 @itemx proc-untrace-exit
18052 @kindex proc-trace-entry
18053 @kindex proc-trace-exit
18054 @kindex proc-untrace-entry
18055 @kindex proc-untrace-exit
18056 These commands enable and disable tracing of entries into and exits
18057 from the @code{syscall} interface.
18060 @kindex info pidlist
18061 @cindex process list, QNX Neutrino
18062 For QNX Neutrino only, this command displays the list of all the
18063 processes and all the threads within each process.
18066 @kindex info meminfo
18067 @cindex mapinfo list, QNX Neutrino
18068 For QNX Neutrino only, this command displays the list of all mapinfos.
18072 @subsection Features for Debugging @sc{djgpp} Programs
18073 @cindex @sc{djgpp} debugging
18074 @cindex native @sc{djgpp} debugging
18075 @cindex MS-DOS-specific commands
18078 @sc{djgpp} is a port of the @sc{gnu} development tools to MS-DOS and
18079 MS-Windows. @sc{djgpp} programs are 32-bit protected-mode programs
18080 that use the @dfn{DPMI} (DOS Protected-Mode Interface) API to run on
18081 top of real-mode DOS systems and their emulations.
18083 @value{GDBN} supports native debugging of @sc{djgpp} programs, and
18084 defines a few commands specific to the @sc{djgpp} port. This
18085 subsection describes those commands.
18090 This is a prefix of @sc{djgpp}-specific commands which print
18091 information about the target system and important OS structures.
18094 @cindex MS-DOS system info
18095 @cindex free memory information (MS-DOS)
18096 @item info dos sysinfo
18097 This command displays assorted information about the underlying
18098 platform: the CPU type and features, the OS version and flavor, the
18099 DPMI version, and the available conventional and DPMI memory.
18104 @cindex segment descriptor tables
18105 @cindex descriptor tables display
18107 @itemx info dos ldt
18108 @itemx info dos idt
18109 These 3 commands display entries from, respectively, Global, Local,
18110 and Interrupt Descriptor Tables (GDT, LDT, and IDT). The descriptor
18111 tables are data structures which store a descriptor for each segment
18112 that is currently in use. The segment's selector is an index into a
18113 descriptor table; the table entry for that index holds the
18114 descriptor's base address and limit, and its attributes and access
18117 A typical @sc{djgpp} program uses 3 segments: a code segment, a data
18118 segment (used for both data and the stack), and a DOS segment (which
18119 allows access to DOS/BIOS data structures and absolute addresses in
18120 conventional memory). However, the DPMI host will usually define
18121 additional segments in order to support the DPMI environment.
18123 @cindex garbled pointers
18124 These commands allow to display entries from the descriptor tables.
18125 Without an argument, all entries from the specified table are
18126 displayed. An argument, which should be an integer expression, means
18127 display a single entry whose index is given by the argument. For
18128 example, here's a convenient way to display information about the
18129 debugged program's data segment:
18132 @exdent @code{(@value{GDBP}) info dos ldt $ds}
18133 @exdent @code{0x13f: base=0x11970000 limit=0x0009ffff 32-Bit Data (Read/Write, Exp-up)}
18137 This comes in handy when you want to see whether a pointer is outside
18138 the data segment's limit (i.e.@: @dfn{garbled}).
18140 @cindex page tables display (MS-DOS)
18142 @itemx info dos pte
18143 These two commands display entries from, respectively, the Page
18144 Directory and the Page Tables. Page Directories and Page Tables are
18145 data structures which control how virtual memory addresses are mapped
18146 into physical addresses. A Page Table includes an entry for every
18147 page of memory that is mapped into the program's address space; there
18148 may be several Page Tables, each one holding up to 4096 entries. A
18149 Page Directory has up to 4096 entries, one each for every Page Table
18150 that is currently in use.
18152 Without an argument, @kbd{info dos pde} displays the entire Page
18153 Directory, and @kbd{info dos pte} displays all the entries in all of
18154 the Page Tables. An argument, an integer expression, given to the
18155 @kbd{info dos pde} command means display only that entry from the Page
18156 Directory table. An argument given to the @kbd{info dos pte} command
18157 means display entries from a single Page Table, the one pointed to by
18158 the specified entry in the Page Directory.
18160 @cindex direct memory access (DMA) on MS-DOS
18161 These commands are useful when your program uses @dfn{DMA} (Direct
18162 Memory Access), which needs physical addresses to program the DMA
18165 These commands are supported only with some DPMI servers.
18167 @cindex physical address from linear address
18168 @item info dos address-pte @var{addr}
18169 This command displays the Page Table entry for a specified linear
18170 address. The argument @var{addr} is a linear address which should
18171 already have the appropriate segment's base address added to it,
18172 because this command accepts addresses which may belong to @emph{any}
18173 segment. For example, here's how to display the Page Table entry for
18174 the page where a variable @code{i} is stored:
18177 @exdent @code{(@value{GDBP}) info dos address-pte __djgpp_base_address + (char *)&i}
18178 @exdent @code{Page Table entry for address 0x11a00d30:}
18179 @exdent @code{Base=0x02698000 Dirty Acc. Not-Cached Write-Back Usr Read-Write +0xd30}
18183 This says that @code{i} is stored at offset @code{0xd30} from the page
18184 whose physical base address is @code{0x02698000}, and shows all the
18185 attributes of that page.
18187 Note that you must cast the addresses of variables to a @code{char *},
18188 since otherwise the value of @code{__djgpp_base_address}, the base
18189 address of all variables and functions in a @sc{djgpp} program, will
18190 be added using the rules of C pointer arithmetics: if @code{i} is
18191 declared an @code{int}, @value{GDBN} will add 4 times the value of
18192 @code{__djgpp_base_address} to the address of @code{i}.
18194 Here's another example, it displays the Page Table entry for the
18198 @exdent @code{(@value{GDBP}) info dos address-pte *((unsigned *)&_go32_info_block + 3)}
18199 @exdent @code{Page Table entry for address 0x29110:}
18200 @exdent @code{Base=0x00029000 Dirty Acc. Not-Cached Write-Back Usr Read-Write +0x110}
18204 (The @code{+ 3} offset is because the transfer buffer's address is the
18205 3rd member of the @code{_go32_info_block} structure.) The output
18206 clearly shows that this DPMI server maps the addresses in conventional
18207 memory 1:1, i.e.@: the physical (@code{0x00029000} + @code{0x110}) and
18208 linear (@code{0x29110}) addresses are identical.
18210 This command is supported only with some DPMI servers.
18213 @cindex DOS serial data link, remote debugging
18214 In addition to native debugging, the DJGPP port supports remote
18215 debugging via a serial data link. The following commands are specific
18216 to remote serial debugging in the DJGPP port of @value{GDBN}.
18219 @kindex set com1base
18220 @kindex set com1irq
18221 @kindex set com2base
18222 @kindex set com2irq
18223 @kindex set com3base
18224 @kindex set com3irq
18225 @kindex set com4base
18226 @kindex set com4irq
18227 @item set com1base @var{addr}
18228 This command sets the base I/O port address of the @file{COM1} serial
18231 @item set com1irq @var{irq}
18232 This command sets the @dfn{Interrupt Request} (@code{IRQ}) line to use
18233 for the @file{COM1} serial port.
18235 There are similar commands @samp{set com2base}, @samp{set com3irq},
18236 etc.@: for setting the port address and the @code{IRQ} lines for the
18239 @kindex show com1base
18240 @kindex show com1irq
18241 @kindex show com2base
18242 @kindex show com2irq
18243 @kindex show com3base
18244 @kindex show com3irq
18245 @kindex show com4base
18246 @kindex show com4irq
18247 The related commands @samp{show com1base}, @samp{show com1irq} etc.@:
18248 display the current settings of the base address and the @code{IRQ}
18249 lines used by the COM ports.
18252 @kindex info serial
18253 @cindex DOS serial port status
18254 This command prints the status of the 4 DOS serial ports. For each
18255 port, it prints whether it's active or not, its I/O base address and
18256 IRQ number, whether it uses a 16550-style FIFO, its baudrate, and the
18257 counts of various errors encountered so far.
18261 @node Cygwin Native
18262 @subsection Features for Debugging MS Windows PE Executables
18263 @cindex MS Windows debugging
18264 @cindex native Cygwin debugging
18265 @cindex Cygwin-specific commands
18267 @value{GDBN} supports native debugging of MS Windows programs, including
18268 DLLs with and without symbolic debugging information.
18270 @cindex Ctrl-BREAK, MS-Windows
18271 @cindex interrupt debuggee on MS-Windows
18272 MS-Windows programs that call @code{SetConsoleMode} to switch off the
18273 special meaning of the @samp{Ctrl-C} keystroke cannot be interrupted
18274 by typing @kbd{C-c}. For this reason, @value{GDBN} on MS-Windows
18275 supports @kbd{C-@key{BREAK}} as an alternative interrupt key
18276 sequence, which can be used to interrupt the debuggee even if it
18279 There are various additional Cygwin-specific commands, described in
18280 this section. Working with DLLs that have no debugging symbols is
18281 described in @ref{Non-debug DLL Symbols}.
18286 This is a prefix of MS Windows-specific commands which print
18287 information about the target system and important OS structures.
18289 @item info w32 selector
18290 This command displays information returned by
18291 the Win32 API @code{GetThreadSelectorEntry} function.
18292 It takes an optional argument that is evaluated to
18293 a long value to give the information about this given selector.
18294 Without argument, this command displays information
18295 about the six segment registers.
18297 @item info w32 thread-information-block
18298 This command displays thread specific information stored in the
18299 Thread Information Block (readable on the X86 CPU family using @code{$fs}
18300 selector for 32-bit programs and @code{$gs} for 64-bit programs).
18304 This is a Cygwin-specific alias of @code{info shared}.
18306 @kindex dll-symbols
18308 This command loads symbols from a dll similarly to
18309 add-sym command but without the need to specify a base address.
18311 @kindex set cygwin-exceptions
18312 @cindex debugging the Cygwin DLL
18313 @cindex Cygwin DLL, debugging
18314 @item set cygwin-exceptions @var{mode}
18315 If @var{mode} is @code{on}, @value{GDBN} will break on exceptions that
18316 happen inside the Cygwin DLL. If @var{mode} is @code{off},
18317 @value{GDBN} will delay recognition of exceptions, and may ignore some
18318 exceptions which seem to be caused by internal Cygwin DLL
18319 ``bookkeeping''. This option is meant primarily for debugging the
18320 Cygwin DLL itself; the default value is @code{off} to avoid annoying
18321 @value{GDBN} users with false @code{SIGSEGV} signals.
18323 @kindex show cygwin-exceptions
18324 @item show cygwin-exceptions
18325 Displays whether @value{GDBN} will break on exceptions that happen
18326 inside the Cygwin DLL itself.
18328 @kindex set new-console
18329 @item set new-console @var{mode}
18330 If @var{mode} is @code{on} the debuggee will
18331 be started in a new console on next start.
18332 If @var{mode} is @code{off}, the debuggee will
18333 be started in the same console as the debugger.
18335 @kindex show new-console
18336 @item show new-console
18337 Displays whether a new console is used
18338 when the debuggee is started.
18340 @kindex set new-group
18341 @item set new-group @var{mode}
18342 This boolean value controls whether the debuggee should
18343 start a new group or stay in the same group as the debugger.
18344 This affects the way the Windows OS handles
18347 @kindex show new-group
18348 @item show new-group
18349 Displays current value of new-group boolean.
18351 @kindex set debugevents
18352 @item set debugevents
18353 This boolean value adds debug output concerning kernel events related
18354 to the debuggee seen by the debugger. This includes events that
18355 signal thread and process creation and exit, DLL loading and
18356 unloading, console interrupts, and debugging messages produced by the
18357 Windows @code{OutputDebugString} API call.
18359 @kindex set debugexec
18360 @item set debugexec
18361 This boolean value adds debug output concerning execute events
18362 (such as resume thread) seen by the debugger.
18364 @kindex set debugexceptions
18365 @item set debugexceptions
18366 This boolean value adds debug output concerning exceptions in the
18367 debuggee seen by the debugger.
18369 @kindex set debugmemory
18370 @item set debugmemory
18371 This boolean value adds debug output concerning debuggee memory reads
18372 and writes by the debugger.
18376 This boolean values specifies whether the debuggee is called
18377 via a shell or directly (default value is on).
18381 Displays if the debuggee will be started with a shell.
18386 * Non-debug DLL Symbols:: Support for DLLs without debugging symbols
18389 @node Non-debug DLL Symbols
18390 @subsubsection Support for DLLs without Debugging Symbols
18391 @cindex DLLs with no debugging symbols
18392 @cindex Minimal symbols and DLLs
18394 Very often on windows, some of the DLLs that your program relies on do
18395 not include symbolic debugging information (for example,
18396 @file{kernel32.dll}). When @value{GDBN} doesn't recognize any debugging
18397 symbols in a DLL, it relies on the minimal amount of symbolic
18398 information contained in the DLL's export table. This section
18399 describes working with such symbols, known internally to @value{GDBN} as
18400 ``minimal symbols''.
18402 Note that before the debugged program has started execution, no DLLs
18403 will have been loaded. The easiest way around this problem is simply to
18404 start the program --- either by setting a breakpoint or letting the
18405 program run once to completion. It is also possible to force
18406 @value{GDBN} to load a particular DLL before starting the executable ---
18407 see the shared library information in @ref{Files}, or the
18408 @code{dll-symbols} command in @ref{Cygwin Native}. Currently,
18409 explicitly loading symbols from a DLL with no debugging information will
18410 cause the symbol names to be duplicated in @value{GDBN}'s lookup table,
18411 which may adversely affect symbol lookup performance.
18413 @subsubsection DLL Name Prefixes
18415 In keeping with the naming conventions used by the Microsoft debugging
18416 tools, DLL export symbols are made available with a prefix based on the
18417 DLL name, for instance @code{KERNEL32!CreateFileA}. The plain name is
18418 also entered into the symbol table, so @code{CreateFileA} is often
18419 sufficient. In some cases there will be name clashes within a program
18420 (particularly if the executable itself includes full debugging symbols)
18421 necessitating the use of the fully qualified name when referring to the
18422 contents of the DLL. Use single-quotes around the name to avoid the
18423 exclamation mark (``!'') being interpreted as a language operator.
18425 Note that the internal name of the DLL may be all upper-case, even
18426 though the file name of the DLL is lower-case, or vice-versa. Since
18427 symbols within @value{GDBN} are @emph{case-sensitive} this may cause
18428 some confusion. If in doubt, try the @code{info functions} and
18429 @code{info variables} commands or even @code{maint print msymbols}
18430 (@pxref{Symbols}). Here's an example:
18433 (@value{GDBP}) info function CreateFileA
18434 All functions matching regular expression "CreateFileA":
18436 Non-debugging symbols:
18437 0x77e885f4 CreateFileA
18438 0x77e885f4 KERNEL32!CreateFileA
18442 (@value{GDBP}) info function !
18443 All functions matching regular expression "!":
18445 Non-debugging symbols:
18446 0x6100114c cygwin1!__assert
18447 0x61004034 cygwin1!_dll_crt0@@0
18448 0x61004240 cygwin1!dll_crt0(per_process *)
18452 @subsubsection Working with Minimal Symbols
18454 Symbols extracted from a DLL's export table do not contain very much
18455 type information. All that @value{GDBN} can do is guess whether a symbol
18456 refers to a function or variable depending on the linker section that
18457 contains the symbol. Also note that the actual contents of the memory
18458 contained in a DLL are not available unless the program is running. This
18459 means that you cannot examine the contents of a variable or disassemble
18460 a function within a DLL without a running program.
18462 Variables are generally treated as pointers and dereferenced
18463 automatically. For this reason, it is often necessary to prefix a
18464 variable name with the address-of operator (``&'') and provide explicit
18465 type information in the command. Here's an example of the type of
18469 (@value{GDBP}) print 'cygwin1!__argv'
18474 (@value{GDBP}) x 'cygwin1!__argv'
18475 0x10021610: "\230y\""
18478 And two possible solutions:
18481 (@value{GDBP}) print ((char **)'cygwin1!__argv')[0]
18482 $2 = 0x22fd98 "/cygdrive/c/mydirectory/myprogram"
18486 (@value{GDBP}) x/2x &'cygwin1!__argv'
18487 0x610c0aa8 <cygwin1!__argv>: 0x10021608 0x00000000
18488 (@value{GDBP}) x/x 0x10021608
18489 0x10021608: 0x0022fd98
18490 (@value{GDBP}) x/s 0x0022fd98
18491 0x22fd98: "/cygdrive/c/mydirectory/myprogram"
18494 Setting a break point within a DLL is possible even before the program
18495 starts execution. However, under these circumstances, @value{GDBN} can't
18496 examine the initial instructions of the function in order to skip the
18497 function's frame set-up code. You can work around this by using ``*&''
18498 to set the breakpoint at a raw memory address:
18501 (@value{GDBP}) break *&'python22!PyOS_Readline'
18502 Breakpoint 1 at 0x1e04eff0
18505 The author of these extensions is not entirely convinced that setting a
18506 break point within a shared DLL like @file{kernel32.dll} is completely
18510 @subsection Commands Specific to @sc{gnu} Hurd Systems
18511 @cindex @sc{gnu} Hurd debugging
18513 This subsection describes @value{GDBN} commands specific to the
18514 @sc{gnu} Hurd native debugging.
18519 @kindex set signals@r{, Hurd command}
18520 @kindex set sigs@r{, Hurd command}
18521 This command toggles the state of inferior signal interception by
18522 @value{GDBN}. Mach exceptions, such as breakpoint traps, are not
18523 affected by this command. @code{sigs} is a shorthand alias for
18528 @kindex show signals@r{, Hurd command}
18529 @kindex show sigs@r{, Hurd command}
18530 Show the current state of intercepting inferior's signals.
18532 @item set signal-thread
18533 @itemx set sigthread
18534 @kindex set signal-thread
18535 @kindex set sigthread
18536 This command tells @value{GDBN} which thread is the @code{libc} signal
18537 thread. That thread is run when a signal is delivered to a running
18538 process. @code{set sigthread} is the shorthand alias of @code{set
18541 @item show signal-thread
18542 @itemx show sigthread
18543 @kindex show signal-thread
18544 @kindex show sigthread
18545 These two commands show which thread will run when the inferior is
18546 delivered a signal.
18549 @kindex set stopped@r{, Hurd command}
18550 This commands tells @value{GDBN} that the inferior process is stopped,
18551 as with the @code{SIGSTOP} signal. The stopped process can be
18552 continued by delivering a signal to it.
18555 @kindex show stopped@r{, Hurd command}
18556 This command shows whether @value{GDBN} thinks the debuggee is
18559 @item set exceptions
18560 @kindex set exceptions@r{, Hurd command}
18561 Use this command to turn off trapping of exceptions in the inferior.
18562 When exception trapping is off, neither breakpoints nor
18563 single-stepping will work. To restore the default, set exception
18566 @item show exceptions
18567 @kindex show exceptions@r{, Hurd command}
18568 Show the current state of trapping exceptions in the inferior.
18570 @item set task pause
18571 @kindex set task@r{, Hurd commands}
18572 @cindex task attributes (@sc{gnu} Hurd)
18573 @cindex pause current task (@sc{gnu} Hurd)
18574 This command toggles task suspension when @value{GDBN} has control.
18575 Setting it to on takes effect immediately, and the task is suspended
18576 whenever @value{GDBN} gets control. Setting it to off will take
18577 effect the next time the inferior is continued. If this option is set
18578 to off, you can use @code{set thread default pause on} or @code{set
18579 thread pause on} (see below) to pause individual threads.
18581 @item show task pause
18582 @kindex show task@r{, Hurd commands}
18583 Show the current state of task suspension.
18585 @item set task detach-suspend-count
18586 @cindex task suspend count
18587 @cindex detach from task, @sc{gnu} Hurd
18588 This command sets the suspend count the task will be left with when
18589 @value{GDBN} detaches from it.
18591 @item show task detach-suspend-count
18592 Show the suspend count the task will be left with when detaching.
18594 @item set task exception-port
18595 @itemx set task excp
18596 @cindex task exception port, @sc{gnu} Hurd
18597 This command sets the task exception port to which @value{GDBN} will
18598 forward exceptions. The argument should be the value of the @dfn{send
18599 rights} of the task. @code{set task excp} is a shorthand alias.
18601 @item set noninvasive
18602 @cindex noninvasive task options
18603 This command switches @value{GDBN} to a mode that is the least
18604 invasive as far as interfering with the inferior is concerned. This
18605 is the same as using @code{set task pause}, @code{set exceptions}, and
18606 @code{set signals} to values opposite to the defaults.
18608 @item info send-rights
18609 @itemx info receive-rights
18610 @itemx info port-rights
18611 @itemx info port-sets
18612 @itemx info dead-names
18615 @cindex send rights, @sc{gnu} Hurd
18616 @cindex receive rights, @sc{gnu} Hurd
18617 @cindex port rights, @sc{gnu} Hurd
18618 @cindex port sets, @sc{gnu} Hurd
18619 @cindex dead names, @sc{gnu} Hurd
18620 These commands display information about, respectively, send rights,
18621 receive rights, port rights, port sets, and dead names of a task.
18622 There are also shorthand aliases: @code{info ports} for @code{info
18623 port-rights} and @code{info psets} for @code{info port-sets}.
18625 @item set thread pause
18626 @kindex set thread@r{, Hurd command}
18627 @cindex thread properties, @sc{gnu} Hurd
18628 @cindex pause current thread (@sc{gnu} Hurd)
18629 This command toggles current thread suspension when @value{GDBN} has
18630 control. Setting it to on takes effect immediately, and the current
18631 thread is suspended whenever @value{GDBN} gets control. Setting it to
18632 off will take effect the next time the inferior is continued.
18633 Normally, this command has no effect, since when @value{GDBN} has
18634 control, the whole task is suspended. However, if you used @code{set
18635 task pause off} (see above), this command comes in handy to suspend
18636 only the current thread.
18638 @item show thread pause
18639 @kindex show thread@r{, Hurd command}
18640 This command shows the state of current thread suspension.
18642 @item set thread run
18643 This command sets whether the current thread is allowed to run.
18645 @item show thread run
18646 Show whether the current thread is allowed to run.
18648 @item set thread detach-suspend-count
18649 @cindex thread suspend count, @sc{gnu} Hurd
18650 @cindex detach from thread, @sc{gnu} Hurd
18651 This command sets the suspend count @value{GDBN} will leave on a
18652 thread when detaching. This number is relative to the suspend count
18653 found by @value{GDBN} when it notices the thread; use @code{set thread
18654 takeover-suspend-count} to force it to an absolute value.
18656 @item show thread detach-suspend-count
18657 Show the suspend count @value{GDBN} will leave on the thread when
18660 @item set thread exception-port
18661 @itemx set thread excp
18662 Set the thread exception port to which to forward exceptions. This
18663 overrides the port set by @code{set task exception-port} (see above).
18664 @code{set thread excp} is the shorthand alias.
18666 @item set thread takeover-suspend-count
18667 Normally, @value{GDBN}'s thread suspend counts are relative to the
18668 value @value{GDBN} finds when it notices each thread. This command
18669 changes the suspend counts to be absolute instead.
18671 @item set thread default
18672 @itemx show thread default
18673 @cindex thread default settings, @sc{gnu} Hurd
18674 Each of the above @code{set thread} commands has a @code{set thread
18675 default} counterpart (e.g., @code{set thread default pause}, @code{set
18676 thread default exception-port}, etc.). The @code{thread default}
18677 variety of commands sets the default thread properties for all
18678 threads; you can then change the properties of individual threads with
18679 the non-default commands.
18684 @subsection QNX Neutrino
18685 @cindex QNX Neutrino
18687 @value{GDBN} provides the following commands specific to the QNX
18691 @item set debug nto-debug
18692 @kindex set debug nto-debug
18693 When set to on, enables debugging messages specific to the QNX
18696 @item show debug nto-debug
18697 @kindex show debug nto-debug
18698 Show the current state of QNX Neutrino messages.
18705 @value{GDBN} provides the following commands specific to the Darwin target:
18708 @item set debug darwin @var{num}
18709 @kindex set debug darwin
18710 When set to a non zero value, enables debugging messages specific to
18711 the Darwin support. Higher values produce more verbose output.
18713 @item show debug darwin
18714 @kindex show debug darwin
18715 Show the current state of Darwin messages.
18717 @item set debug mach-o @var{num}
18718 @kindex set debug mach-o
18719 When set to a non zero value, enables debugging messages while
18720 @value{GDBN} is reading Darwin object files. (@dfn{Mach-O} is the
18721 file format used on Darwin for object and executable files.) Higher
18722 values produce more verbose output. This is a command to diagnose
18723 problems internal to @value{GDBN} and should not be needed in normal
18726 @item show debug mach-o
18727 @kindex show debug mach-o
18728 Show the current state of Mach-O file messages.
18730 @item set mach-exceptions on
18731 @itemx set mach-exceptions off
18732 @kindex set mach-exceptions
18733 On Darwin, faults are first reported as a Mach exception and are then
18734 mapped to a Posix signal. Use this command to turn on trapping of
18735 Mach exceptions in the inferior. This might be sometimes useful to
18736 better understand the cause of a fault. The default is off.
18738 @item show mach-exceptions
18739 @kindex show mach-exceptions
18740 Show the current state of exceptions trapping.
18745 @section Embedded Operating Systems
18747 This section describes configurations involving the debugging of
18748 embedded operating systems that are available for several different
18752 * VxWorks:: Using @value{GDBN} with VxWorks
18755 @value{GDBN} includes the ability to debug programs running on
18756 various real-time operating systems.
18759 @subsection Using @value{GDBN} with VxWorks
18765 @kindex target vxworks
18766 @item target vxworks @var{machinename}
18767 A VxWorks system, attached via TCP/IP. The argument @var{machinename}
18768 is the target system's machine name or IP address.
18772 On VxWorks, @code{load} links @var{filename} dynamically on the
18773 current target system as well as adding its symbols in @value{GDBN}.
18775 @value{GDBN} enables developers to spawn and debug tasks running on networked
18776 VxWorks targets from a Unix host. Already-running tasks spawned from
18777 the VxWorks shell can also be debugged. @value{GDBN} uses code that runs on
18778 both the Unix host and on the VxWorks target. The program
18779 @code{@value{GDBP}} is installed and executed on the Unix host. (It may be
18780 installed with the name @code{vxgdb}, to distinguish it from a
18781 @value{GDBN} for debugging programs on the host itself.)
18784 @item VxWorks-timeout @var{args}
18785 @kindex vxworks-timeout
18786 All VxWorks-based targets now support the option @code{vxworks-timeout}.
18787 This option is set by the user, and @var{args} represents the number of
18788 seconds @value{GDBN} waits for responses to rpc's. You might use this if
18789 your VxWorks target is a slow software simulator or is on the far side
18790 of a thin network line.
18793 The following information on connecting to VxWorks was current when
18794 this manual was produced; newer releases of VxWorks may use revised
18797 @findex INCLUDE_RDB
18798 To use @value{GDBN} with VxWorks, you must rebuild your VxWorks kernel
18799 to include the remote debugging interface routines in the VxWorks
18800 library @file{rdb.a}. To do this, define @code{INCLUDE_RDB} in the
18801 VxWorks configuration file @file{configAll.h} and rebuild your VxWorks
18802 kernel. The resulting kernel contains @file{rdb.a}, and spawns the
18803 source debugging task @code{tRdbTask} when VxWorks is booted. For more
18804 information on configuring and remaking VxWorks, see the manufacturer's
18806 @c VxWorks, see the @cite{VxWorks Programmer's Guide}.
18808 Once you have included @file{rdb.a} in your VxWorks system image and set
18809 your Unix execution search path to find @value{GDBN}, you are ready to
18810 run @value{GDBN}. From your Unix host, run @code{@value{GDBP}} (or
18811 @code{vxgdb}, depending on your installation).
18813 @value{GDBN} comes up showing the prompt:
18820 * VxWorks Connection:: Connecting to VxWorks
18821 * VxWorks Download:: VxWorks download
18822 * VxWorks Attach:: Running tasks
18825 @node VxWorks Connection
18826 @subsubsection Connecting to VxWorks
18828 The @value{GDBN} command @code{target} lets you connect to a VxWorks target on the
18829 network. To connect to a target whose host name is ``@code{tt}'', type:
18832 (vxgdb) target vxworks tt
18836 @value{GDBN} displays messages like these:
18839 Attaching remote machine across net...
18844 @value{GDBN} then attempts to read the symbol tables of any object modules
18845 loaded into the VxWorks target since it was last booted. @value{GDBN} locates
18846 these files by searching the directories listed in the command search
18847 path (@pxref{Environment, ,Your Program's Environment}); if it fails
18848 to find an object file, it displays a message such as:
18851 prog.o: No such file or directory.
18854 When this happens, add the appropriate directory to the search path with
18855 the @value{GDBN} command @code{path}, and execute the @code{target}
18858 @node VxWorks Download
18859 @subsubsection VxWorks Download
18861 @cindex download to VxWorks
18862 If you have connected to the VxWorks target and you want to debug an
18863 object that has not yet been loaded, you can use the @value{GDBN}
18864 @code{load} command to download a file from Unix to VxWorks
18865 incrementally. The object file given as an argument to the @code{load}
18866 command is actually opened twice: first by the VxWorks target in order
18867 to download the code, then by @value{GDBN} in order to read the symbol
18868 table. This can lead to problems if the current working directories on
18869 the two systems differ. If both systems have NFS mounted the same
18870 filesystems, you can avoid these problems by using absolute paths.
18871 Otherwise, it is simplest to set the working directory on both systems
18872 to the directory in which the object file resides, and then to reference
18873 the file by its name, without any path. For instance, a program
18874 @file{prog.o} may reside in @file{@var{vxpath}/vw/demo/rdb} in VxWorks
18875 and in @file{@var{hostpath}/vw/demo/rdb} on the host. To load this
18876 program, type this on VxWorks:
18879 -> cd "@var{vxpath}/vw/demo/rdb"
18883 Then, in @value{GDBN}, type:
18886 (vxgdb) cd @var{hostpath}/vw/demo/rdb
18887 (vxgdb) load prog.o
18890 @value{GDBN} displays a response similar to this:
18893 Reading symbol data from wherever/vw/demo/rdb/prog.o... done.
18896 You can also use the @code{load} command to reload an object module
18897 after editing and recompiling the corresponding source file. Note that
18898 this makes @value{GDBN} delete all currently-defined breakpoints,
18899 auto-displays, and convenience variables, and to clear the value
18900 history. (This is necessary in order to preserve the integrity of
18901 debugger's data structures that reference the target system's symbol
18904 @node VxWorks Attach
18905 @subsubsection Running Tasks
18907 @cindex running VxWorks tasks
18908 You can also attach to an existing task using the @code{attach} command as
18912 (vxgdb) attach @var{task}
18916 where @var{task} is the VxWorks hexadecimal task ID. The task can be running
18917 or suspended when you attach to it. Running tasks are suspended at
18918 the time of attachment.
18920 @node Embedded Processors
18921 @section Embedded Processors
18923 This section goes into details specific to particular embedded
18926 @cindex send command to simulator
18927 Whenever a specific embedded processor has a simulator, @value{GDBN}
18928 allows to send an arbitrary command to the simulator.
18931 @item sim @var{command}
18932 @kindex sim@r{, a command}
18933 Send an arbitrary @var{command} string to the simulator. Consult the
18934 documentation for the specific simulator in use for information about
18935 acceptable commands.
18941 * M32R/D:: Renesas M32R/D
18942 * M68K:: Motorola M68K
18943 * MicroBlaze:: Xilinx MicroBlaze
18944 * MIPS Embedded:: MIPS Embedded
18945 * OpenRISC 1000:: OpenRisc 1000
18946 * PA:: HP PA Embedded
18947 * PowerPC Embedded:: PowerPC Embedded
18948 * Sparclet:: Tsqware Sparclet
18949 * Sparclite:: Fujitsu Sparclite
18950 * Z8000:: Zilog Z8000
18953 * Super-H:: Renesas Super-H
18962 @item target rdi @var{dev}
18963 ARM Angel monitor, via RDI library interface to ADP protocol. You may
18964 use this target to communicate with both boards running the Angel
18965 monitor, or with the EmbeddedICE JTAG debug device.
18968 @item target rdp @var{dev}
18973 @value{GDBN} provides the following ARM-specific commands:
18976 @item set arm disassembler
18978 This commands selects from a list of disassembly styles. The
18979 @code{"std"} style is the standard style.
18981 @item show arm disassembler
18983 Show the current disassembly style.
18985 @item set arm apcs32
18986 @cindex ARM 32-bit mode
18987 This command toggles ARM operation mode between 32-bit and 26-bit.
18989 @item show arm apcs32
18990 Display the current usage of the ARM 32-bit mode.
18992 @item set arm fpu @var{fputype}
18993 This command sets the ARM floating-point unit (FPU) type. The
18994 argument @var{fputype} can be one of these:
18998 Determine the FPU type by querying the OS ABI.
19000 Software FPU, with mixed-endian doubles on little-endian ARM
19003 GCC-compiled FPA co-processor.
19005 Software FPU with pure-endian doubles.
19011 Show the current type of the FPU.
19014 This command forces @value{GDBN} to use the specified ABI.
19017 Show the currently used ABI.
19019 @item set arm fallback-mode (arm|thumb|auto)
19020 @value{GDBN} uses the symbol table, when available, to determine
19021 whether instructions are ARM or Thumb. This command controls
19022 @value{GDBN}'s default behavior when the symbol table is not
19023 available. The default is @samp{auto}, which causes @value{GDBN} to
19024 use the current execution mode (from the @code{T} bit in the @code{CPSR}
19027 @item show arm fallback-mode
19028 Show the current fallback instruction mode.
19030 @item set arm force-mode (arm|thumb|auto)
19031 This command overrides use of the symbol table to determine whether
19032 instructions are ARM or Thumb. The default is @samp{auto}, which
19033 causes @value{GDBN} to use the symbol table and then the setting
19034 of @samp{set arm fallback-mode}.
19036 @item show arm force-mode
19037 Show the current forced instruction mode.
19039 @item set debug arm
19040 Toggle whether to display ARM-specific debugging messages from the ARM
19041 target support subsystem.
19043 @item show debug arm
19044 Show whether ARM-specific debugging messages are enabled.
19047 The following commands are available when an ARM target is debugged
19048 using the RDI interface:
19051 @item rdilogfile @r{[}@var{file}@r{]}
19053 @cindex ADP (Angel Debugger Protocol) logging
19054 Set the filename for the ADP (Angel Debugger Protocol) packet log.
19055 With an argument, sets the log file to the specified @var{file}. With
19056 no argument, show the current log file name. The default log file is
19059 @item rdilogenable @r{[}@var{arg}@r{]}
19060 @kindex rdilogenable
19061 Control logging of ADP packets. With an argument of 1 or @code{"yes"}
19062 enables logging, with an argument 0 or @code{"no"} disables it. With
19063 no arguments displays the current setting. When logging is enabled,
19064 ADP packets exchanged between @value{GDBN} and the RDI target device
19065 are logged to a file.
19067 @item set rdiromatzero
19068 @kindex set rdiromatzero
19069 @cindex ROM at zero address, RDI
19070 Tell @value{GDBN} whether the target has ROM at address 0. If on,
19071 vector catching is disabled, so that zero address can be used. If off
19072 (the default), vector catching is enabled. For this command to take
19073 effect, it needs to be invoked prior to the @code{target rdi} command.
19075 @item show rdiromatzero
19076 @kindex show rdiromatzero
19077 Show the current setting of ROM at zero address.
19079 @item set rdiheartbeat
19080 @kindex set rdiheartbeat
19081 @cindex RDI heartbeat
19082 Enable or disable RDI heartbeat packets. It is not recommended to
19083 turn on this option, since it confuses ARM and EPI JTAG interface, as
19084 well as the Angel monitor.
19086 @item show rdiheartbeat
19087 @kindex show rdiheartbeat
19088 Show the setting of RDI heartbeat packets.
19092 @item target sim @r{[}@var{simargs}@r{]} @dots{}
19093 The @value{GDBN} ARM simulator accepts the following optional arguments.
19096 @item --swi-support=@var{type}
19097 Tell the simulator which SWI interfaces to support.
19098 @var{type} may be a comma separated list of the following values.
19099 The default value is @code{all}.
19112 @subsection Renesas M32R/D and M32R/SDI
19115 @kindex target m32r
19116 @item target m32r @var{dev}
19117 Renesas M32R/D ROM monitor.
19119 @kindex target m32rsdi
19120 @item target m32rsdi @var{dev}
19121 Renesas M32R SDI server, connected via parallel port to the board.
19124 The following @value{GDBN} commands are specific to the M32R monitor:
19127 @item set download-path @var{path}
19128 @kindex set download-path
19129 @cindex find downloadable @sc{srec} files (M32R)
19130 Set the default path for finding downloadable @sc{srec} files.
19132 @item show download-path
19133 @kindex show download-path
19134 Show the default path for downloadable @sc{srec} files.
19136 @item set board-address @var{addr}
19137 @kindex set board-address
19138 @cindex M32-EVA target board address
19139 Set the IP address for the M32R-EVA target board.
19141 @item show board-address
19142 @kindex show board-address
19143 Show the current IP address of the target board.
19145 @item set server-address @var{addr}
19146 @kindex set server-address
19147 @cindex download server address (M32R)
19148 Set the IP address for the download server, which is the @value{GDBN}'s
19151 @item show server-address
19152 @kindex show server-address
19153 Display the IP address of the download server.
19155 @item upload @r{[}@var{file}@r{]}
19156 @kindex upload@r{, M32R}
19157 Upload the specified @sc{srec} @var{file} via the monitor's Ethernet
19158 upload capability. If no @var{file} argument is given, the current
19159 executable file is uploaded.
19161 @item tload @r{[}@var{file}@r{]}
19162 @kindex tload@r{, M32R}
19163 Test the @code{upload} command.
19166 The following commands are available for M32R/SDI:
19171 @cindex reset SDI connection, M32R
19172 This command resets the SDI connection.
19176 This command shows the SDI connection status.
19179 @kindex debug_chaos
19180 @cindex M32R/Chaos debugging
19181 Instructs the remote that M32R/Chaos debugging is to be used.
19183 @item use_debug_dma
19184 @kindex use_debug_dma
19185 Instructs the remote to use the DEBUG_DMA method of accessing memory.
19188 @kindex use_mon_code
19189 Instructs the remote to use the MON_CODE method of accessing memory.
19192 @kindex use_ib_break
19193 Instructs the remote to set breakpoints by IB break.
19195 @item use_dbt_break
19196 @kindex use_dbt_break
19197 Instructs the remote to set breakpoints by DBT.
19203 The Motorola m68k configuration includes ColdFire support, and a
19204 target command for the following ROM monitor.
19208 @kindex target dbug
19209 @item target dbug @var{dev}
19210 dBUG ROM monitor for Motorola ColdFire.
19215 @subsection MicroBlaze
19216 @cindex Xilinx MicroBlaze
19217 @cindex XMD, Xilinx Microprocessor Debugger
19219 The MicroBlaze is a soft-core processor supported on various Xilinx
19220 FPGAs, such as Spartan or Virtex series. Boards with these processors
19221 usually have JTAG ports which connect to a host system running the Xilinx
19222 Embedded Development Kit (EDK) or Software Development Kit (SDK).
19223 This host system is used to download the configuration bitstream to
19224 the target FPGA. The Xilinx Microprocessor Debugger (XMD) program
19225 communicates with the target board using the JTAG interface and
19226 presents a @code{gdbserver} interface to the board. By default
19227 @code{xmd} uses port @code{1234}. (While it is possible to change
19228 this default port, it requires the use of undocumented @code{xmd}
19229 commands. Contact Xilinx support if you need to do this.)
19231 Use these GDB commands to connect to the MicroBlaze target processor.
19234 @item target remote :1234
19235 Use this command to connect to the target if you are running @value{GDBN}
19236 on the same system as @code{xmd}.
19238 @item target remote @var{xmd-host}:1234
19239 Use this command to connect to the target if it is connected to @code{xmd}
19240 running on a different system named @var{xmd-host}.
19243 Use this command to download a program to the MicroBlaze target.
19245 @item set debug microblaze @var{n}
19246 Enable MicroBlaze-specific debugging messages if non-zero.
19248 @item show debug microblaze @var{n}
19249 Show MicroBlaze-specific debugging level.
19252 @node MIPS Embedded
19253 @subsection MIPS Embedded
19255 @cindex MIPS boards
19256 @value{GDBN} can use the MIPS remote debugging protocol to talk to a
19257 MIPS board attached to a serial line. This is available when
19258 you configure @value{GDBN} with @samp{--target=mips-elf}.
19261 Use these @value{GDBN} commands to specify the connection to your target board:
19264 @item target mips @var{port}
19265 @kindex target mips @var{port}
19266 To run a program on the board, start up @code{@value{GDBP}} with the
19267 name of your program as the argument. To connect to the board, use the
19268 command @samp{target mips @var{port}}, where @var{port} is the name of
19269 the serial port connected to the board. If the program has not already
19270 been downloaded to the board, you may use the @code{load} command to
19271 download it. You can then use all the usual @value{GDBN} commands.
19273 For example, this sequence connects to the target board through a serial
19274 port, and loads and runs a program called @var{prog} through the
19278 host$ @value{GDBP} @var{prog}
19279 @value{GDBN} is free software and @dots{}
19280 (@value{GDBP}) target mips /dev/ttyb
19281 (@value{GDBP}) load @var{prog}
19285 @item target mips @var{hostname}:@var{portnumber}
19286 On some @value{GDBN} host configurations, you can specify a TCP
19287 connection (for instance, to a serial line managed by a terminal
19288 concentrator) instead of a serial port, using the syntax
19289 @samp{@var{hostname}:@var{portnumber}}.
19291 @item target pmon @var{port}
19292 @kindex target pmon @var{port}
19295 @item target ddb @var{port}
19296 @kindex target ddb @var{port}
19297 NEC's DDB variant of PMON for Vr4300.
19299 @item target lsi @var{port}
19300 @kindex target lsi @var{port}
19301 LSI variant of PMON.
19303 @kindex target r3900
19304 @item target r3900 @var{dev}
19305 Densan DVE-R3900 ROM monitor for Toshiba R3900 Mips.
19307 @kindex target array
19308 @item target array @var{dev}
19309 Array Tech LSI33K RAID controller board.
19315 @value{GDBN} also supports these special commands for MIPS targets:
19318 @item set mipsfpu double
19319 @itemx set mipsfpu single
19320 @itemx set mipsfpu none
19321 @itemx set mipsfpu auto
19322 @itemx show mipsfpu
19323 @kindex set mipsfpu
19324 @kindex show mipsfpu
19325 @cindex MIPS remote floating point
19326 @cindex floating point, MIPS remote
19327 If your target board does not support the MIPS floating point
19328 coprocessor, you should use the command @samp{set mipsfpu none} (if you
19329 need this, you may wish to put the command in your @value{GDBN} init
19330 file). This tells @value{GDBN} how to find the return value of
19331 functions which return floating point values. It also allows
19332 @value{GDBN} to avoid saving the floating point registers when calling
19333 functions on the board. If you are using a floating point coprocessor
19334 with only single precision floating point support, as on the @sc{r4650}
19335 processor, use the command @samp{set mipsfpu single}. The default
19336 double precision floating point coprocessor may be selected using
19337 @samp{set mipsfpu double}.
19339 In previous versions the only choices were double precision or no
19340 floating point, so @samp{set mipsfpu on} will select double precision
19341 and @samp{set mipsfpu off} will select no floating point.
19343 As usual, you can inquire about the @code{mipsfpu} variable with
19344 @samp{show mipsfpu}.
19346 @item set timeout @var{seconds}
19347 @itemx set retransmit-timeout @var{seconds}
19348 @itemx show timeout
19349 @itemx show retransmit-timeout
19350 @cindex @code{timeout}, MIPS protocol
19351 @cindex @code{retransmit-timeout}, MIPS protocol
19352 @kindex set timeout
19353 @kindex show timeout
19354 @kindex set retransmit-timeout
19355 @kindex show retransmit-timeout
19356 You can control the timeout used while waiting for a packet, in the MIPS
19357 remote protocol, with the @code{set timeout @var{seconds}} command. The
19358 default is 5 seconds. Similarly, you can control the timeout used while
19359 waiting for an acknowledgment of a packet with the @code{set
19360 retransmit-timeout @var{seconds}} command. The default is 3 seconds.
19361 You can inspect both values with @code{show timeout} and @code{show
19362 retransmit-timeout}. (These commands are @emph{only} available when
19363 @value{GDBN} is configured for @samp{--target=mips-elf}.)
19365 The timeout set by @code{set timeout} does not apply when @value{GDBN}
19366 is waiting for your program to stop. In that case, @value{GDBN} waits
19367 forever because it has no way of knowing how long the program is going
19368 to run before stopping.
19370 @item set syn-garbage-limit @var{num}
19371 @kindex set syn-garbage-limit@r{, MIPS remote}
19372 @cindex synchronize with remote MIPS target
19373 Limit the maximum number of characters @value{GDBN} should ignore when
19374 it tries to synchronize with the remote target. The default is 10
19375 characters. Setting the limit to -1 means there's no limit.
19377 @item show syn-garbage-limit
19378 @kindex show syn-garbage-limit@r{, MIPS remote}
19379 Show the current limit on the number of characters to ignore when
19380 trying to synchronize with the remote system.
19382 @item set monitor-prompt @var{prompt}
19383 @kindex set monitor-prompt@r{, MIPS remote}
19384 @cindex remote monitor prompt
19385 Tell @value{GDBN} to expect the specified @var{prompt} string from the
19386 remote monitor. The default depends on the target:
19396 @item show monitor-prompt
19397 @kindex show monitor-prompt@r{, MIPS remote}
19398 Show the current strings @value{GDBN} expects as the prompt from the
19401 @item set monitor-warnings
19402 @kindex set monitor-warnings@r{, MIPS remote}
19403 Enable or disable monitor warnings about hardware breakpoints. This
19404 has effect only for the @code{lsi} target. When on, @value{GDBN} will
19405 display warning messages whose codes are returned by the @code{lsi}
19406 PMON monitor for breakpoint commands.
19408 @item show monitor-warnings
19409 @kindex show monitor-warnings@r{, MIPS remote}
19410 Show the current setting of printing monitor warnings.
19412 @item pmon @var{command}
19413 @kindex pmon@r{, MIPS remote}
19414 @cindex send PMON command
19415 This command allows sending an arbitrary @var{command} string to the
19416 monitor. The monitor must be in debug mode for this to work.
19419 @node OpenRISC 1000
19420 @subsection OpenRISC 1000
19421 @cindex OpenRISC 1000
19423 @cindex or1k boards
19424 See OR1k Architecture document (@uref{www.opencores.org}) for more information
19425 about platform and commands.
19429 @kindex target jtag
19430 @item target jtag jtag://@var{host}:@var{port}
19432 Connects to remote JTAG server.
19433 JTAG remote server can be either an or1ksim or JTAG server,
19434 connected via parallel port to the board.
19436 Example: @code{target jtag jtag://localhost:9999}
19439 @item or1ksim @var{command}
19440 If connected to @code{or1ksim} OpenRISC 1000 Architectural
19441 Simulator, proprietary commands can be executed.
19443 @kindex info or1k spr
19444 @item info or1k spr
19445 Displays spr groups.
19447 @item info or1k spr @var{group}
19448 @itemx info or1k spr @var{groupno}
19449 Displays register names in selected group.
19451 @item info or1k spr @var{group} @var{register}
19452 @itemx info or1k spr @var{register}
19453 @itemx info or1k spr @var{groupno} @var{registerno}
19454 @itemx info or1k spr @var{registerno}
19455 Shows information about specified spr register.
19458 @item spr @var{group} @var{register} @var{value}
19459 @itemx spr @var{register @var{value}}
19460 @itemx spr @var{groupno} @var{registerno @var{value}}
19461 @itemx spr @var{registerno @var{value}}
19462 Writes @var{value} to specified spr register.
19465 Some implementations of OpenRISC 1000 Architecture also have hardware trace.
19466 It is very similar to @value{GDBN} trace, except it does not interfere with normal
19467 program execution and is thus much faster. Hardware breakpoints/watchpoint
19468 triggers can be set using:
19471 Load effective address/data
19473 Store effective address/data
19475 Access effective address ($SEA or $LEA) or data ($SDATA/$LDATA)
19480 When triggered, it can capture low level data, like: @code{PC}, @code{LSEA},
19481 @code{LDATA}, @code{SDATA}, @code{READSPR}, @code{WRITESPR}, @code{INSTR}.
19483 @code{htrace} commands:
19484 @cindex OpenRISC 1000 htrace
19487 @item hwatch @var{conditional}
19488 Set hardware watchpoint on combination of Load/Store Effective Address(es)
19489 or Data. For example:
19491 @code{hwatch ($LEA == my_var) && ($LDATA < 50) || ($SEA == my_var) && ($SDATA >= 50)}
19493 @code{hwatch ($LEA == my_var) && ($LDATA < 50) || ($SEA == my_var) && ($SDATA >= 50)}
19497 Display information about current HW trace configuration.
19499 @item htrace trigger @var{conditional}
19500 Set starting criteria for HW trace.
19502 @item htrace qualifier @var{conditional}
19503 Set acquisition qualifier for HW trace.
19505 @item htrace stop @var{conditional}
19506 Set HW trace stopping criteria.
19508 @item htrace record [@var{data}]*
19509 Selects the data to be recorded, when qualifier is met and HW trace was
19512 @item htrace enable
19513 @itemx htrace disable
19514 Enables/disables the HW trace.
19516 @item htrace rewind [@var{filename}]
19517 Clears currently recorded trace data.
19519 If filename is specified, new trace file is made and any newly collected data
19520 will be written there.
19522 @item htrace print [@var{start} [@var{len}]]
19523 Prints trace buffer, using current record configuration.
19525 @item htrace mode continuous
19526 Set continuous trace mode.
19528 @item htrace mode suspend
19529 Set suspend trace mode.
19533 @node PowerPC Embedded
19534 @subsection PowerPC Embedded
19536 @cindex DVC register
19537 @value{GDBN} supports using the DVC (Data Value Compare) register to
19538 implement in hardware simple hardware watchpoint conditions of the form:
19541 (@value{GDBP}) watch @var{ADDRESS|VARIABLE} \
19542 if @var{ADDRESS|VARIABLE} == @var{CONSTANT EXPRESSION}
19545 The DVC register will be automatically used when @value{GDBN} detects
19546 such pattern in a condition expression, and the created watchpoint uses one
19547 debug register (either the @code{exact-watchpoints} option is on and the
19548 variable is scalar, or the variable has a length of one byte). This feature
19549 is available in native @value{GDBN} running on a Linux kernel version 2.6.34
19552 When running on PowerPC embedded processors, @value{GDBN} automatically uses
19553 ranged hardware watchpoints, unless the @code{exact-watchpoints} option is on,
19554 in which case watchpoints using only one debug register are created when
19555 watching variables of scalar types.
19557 You can create an artificial array to watch an arbitrary memory
19558 region using one of the following commands (@pxref{Expressions}):
19561 (@value{GDBP}) watch *((char *) @var{address})@@@var{length}
19562 (@value{GDBP}) watch @{char[@var{length}]@} @var{address}
19565 PowerPC embedded processors support masked watchpoints. See the discussion
19566 about the @code{mask} argument in @ref{Set Watchpoints}.
19568 @cindex ranged breakpoint
19569 PowerPC embedded processors support hardware accelerated
19570 @dfn{ranged breakpoints}. A ranged breakpoint stops execution of
19571 the inferior whenever it executes an instruction at any address within
19572 the range it specifies. To set a ranged breakpoint in @value{GDBN},
19573 use the @code{break-range} command.
19575 @value{GDBN} provides the following PowerPC-specific commands:
19578 @kindex break-range
19579 @item break-range @var{start-location}, @var{end-location}
19580 Set a breakpoint for an address range.
19581 @var{start-location} and @var{end-location} can specify a function name,
19582 a line number, an offset of lines from the current line or from the start
19583 location, or an address of an instruction (see @ref{Specify Location},
19584 for a list of all the possible ways to specify a @var{location}.)
19585 The breakpoint will stop execution of the inferior whenever it
19586 executes an instruction at any address within the specified range,
19587 (including @var{start-location} and @var{end-location}.)
19589 @kindex set powerpc
19590 @item set powerpc soft-float
19591 @itemx show powerpc soft-float
19592 Force @value{GDBN} to use (or not use) a software floating point calling
19593 convention. By default, @value{GDBN} selects the calling convention based
19594 on the selected architecture and the provided executable file.
19596 @item set powerpc vector-abi
19597 @itemx show powerpc vector-abi
19598 Force @value{GDBN} to use the specified calling convention for vector
19599 arguments and return values. The valid options are @samp{auto};
19600 @samp{generic}, to avoid vector registers even if they are present;
19601 @samp{altivec}, to use AltiVec registers; and @samp{spe} to use SPE
19602 registers. By default, @value{GDBN} selects the calling convention
19603 based on the selected architecture and the provided executable file.
19605 @item set powerpc exact-watchpoints
19606 @itemx show powerpc exact-watchpoints
19607 Allow @value{GDBN} to use only one debug register when watching a variable
19608 of scalar type, thus assuming that the variable is accessed through the
19609 address of its first byte.
19611 @kindex target dink32
19612 @item target dink32 @var{dev}
19613 DINK32 ROM monitor.
19615 @kindex target ppcbug
19616 @item target ppcbug @var{dev}
19617 @kindex target ppcbug1
19618 @item target ppcbug1 @var{dev}
19619 PPCBUG ROM monitor for PowerPC.
19622 @item target sds @var{dev}
19623 SDS monitor, running on a PowerPC board (such as Motorola's ADS).
19626 @cindex SDS protocol
19627 The following commands specific to the SDS protocol are supported
19631 @item set sdstimeout @var{nsec}
19632 @kindex set sdstimeout
19633 Set the timeout for SDS protocol reads to be @var{nsec} seconds. The
19634 default is 2 seconds.
19636 @item show sdstimeout
19637 @kindex show sdstimeout
19638 Show the current value of the SDS timeout.
19640 @item sds @var{command}
19641 @kindex sds@r{, a command}
19642 Send the specified @var{command} string to the SDS monitor.
19647 @subsection HP PA Embedded
19651 @kindex target op50n
19652 @item target op50n @var{dev}
19653 OP50N monitor, running on an OKI HPPA board.
19655 @kindex target w89k
19656 @item target w89k @var{dev}
19657 W89K monitor, running on a Winbond HPPA board.
19662 @subsection Tsqware Sparclet
19666 @value{GDBN} enables developers to debug tasks running on
19667 Sparclet targets from a Unix host.
19668 @value{GDBN} uses code that runs on
19669 both the Unix host and on the Sparclet target. The program
19670 @code{@value{GDBP}} is installed and executed on the Unix host.
19673 @item remotetimeout @var{args}
19674 @kindex remotetimeout
19675 @value{GDBN} supports the option @code{remotetimeout}.
19676 This option is set by the user, and @var{args} represents the number of
19677 seconds @value{GDBN} waits for responses.
19680 @cindex compiling, on Sparclet
19681 When compiling for debugging, include the options @samp{-g} to get debug
19682 information and @samp{-Ttext} to relocate the program to where you wish to
19683 load it on the target. You may also want to add the options @samp{-n} or
19684 @samp{-N} in order to reduce the size of the sections. Example:
19687 sparclet-aout-gcc prog.c -Ttext 0x12010000 -g -o prog -N
19690 You can use @code{objdump} to verify that the addresses are what you intended:
19693 sparclet-aout-objdump --headers --syms prog
19696 @cindex running, on Sparclet
19698 your Unix execution search path to find @value{GDBN}, you are ready to
19699 run @value{GDBN}. From your Unix host, run @code{@value{GDBP}}
19700 (or @code{sparclet-aout-gdb}, depending on your installation).
19702 @value{GDBN} comes up showing the prompt:
19709 * Sparclet File:: Setting the file to debug
19710 * Sparclet Connection:: Connecting to Sparclet
19711 * Sparclet Download:: Sparclet download
19712 * Sparclet Execution:: Running and debugging
19715 @node Sparclet File
19716 @subsubsection Setting File to Debug
19718 The @value{GDBN} command @code{file} lets you choose with program to debug.
19721 (gdbslet) file prog
19725 @value{GDBN} then attempts to read the symbol table of @file{prog}.
19726 @value{GDBN} locates
19727 the file by searching the directories listed in the command search
19729 If the file was compiled with debug information (option @samp{-g}), source
19730 files will be searched as well.
19731 @value{GDBN} locates
19732 the source files by searching the directories listed in the directory search
19733 path (@pxref{Environment, ,Your Program's Environment}).
19735 to find a file, it displays a message such as:
19738 prog: No such file or directory.
19741 When this happens, add the appropriate directories to the search paths with
19742 the @value{GDBN} commands @code{path} and @code{dir}, and execute the
19743 @code{target} command again.
19745 @node Sparclet Connection
19746 @subsubsection Connecting to Sparclet
19748 The @value{GDBN} command @code{target} lets you connect to a Sparclet target.
19749 To connect to a target on serial port ``@code{ttya}'', type:
19752 (gdbslet) target sparclet /dev/ttya
19753 Remote target sparclet connected to /dev/ttya
19754 main () at ../prog.c:3
19758 @value{GDBN} displays messages like these:
19764 @node Sparclet Download
19765 @subsubsection Sparclet Download
19767 @cindex download to Sparclet
19768 Once connected to the Sparclet target,
19769 you can use the @value{GDBN}
19770 @code{load} command to download the file from the host to the target.
19771 The file name and load offset should be given as arguments to the @code{load}
19773 Since the file format is aout, the program must be loaded to the starting
19774 address. You can use @code{objdump} to find out what this value is. The load
19775 offset is an offset which is added to the VMA (virtual memory address)
19776 of each of the file's sections.
19777 For instance, if the program
19778 @file{prog} was linked to text address 0x1201000, with data at 0x12010160
19779 and bss at 0x12010170, in @value{GDBN}, type:
19782 (gdbslet) load prog 0x12010000
19783 Loading section .text, size 0xdb0 vma 0x12010000
19786 If the code is loaded at a different address then what the program was linked
19787 to, you may need to use the @code{section} and @code{add-symbol-file} commands
19788 to tell @value{GDBN} where to map the symbol table.
19790 @node Sparclet Execution
19791 @subsubsection Running and Debugging
19793 @cindex running and debugging Sparclet programs
19794 You can now begin debugging the task using @value{GDBN}'s execution control
19795 commands, @code{b}, @code{step}, @code{run}, etc. See the @value{GDBN}
19796 manual for the list of commands.
19800 Breakpoint 1 at 0x12010000: file prog.c, line 3.
19802 Starting program: prog
19803 Breakpoint 1, main (argc=1, argv=0xeffff21c) at prog.c:3
19804 3 char *symarg = 0;
19806 4 char *execarg = "hello!";
19811 @subsection Fujitsu Sparclite
19815 @kindex target sparclite
19816 @item target sparclite @var{dev}
19817 Fujitsu sparclite boards, used only for the purpose of loading.
19818 You must use an additional command to debug the program.
19819 For example: target remote @var{dev} using @value{GDBN} standard
19825 @subsection Zilog Z8000
19828 @cindex simulator, Z8000
19829 @cindex Zilog Z8000 simulator
19831 When configured for debugging Zilog Z8000 targets, @value{GDBN} includes
19834 For the Z8000 family, @samp{target sim} simulates either the Z8002 (the
19835 unsegmented variant of the Z8000 architecture) or the Z8001 (the
19836 segmented variant). The simulator recognizes which architecture is
19837 appropriate by inspecting the object code.
19840 @item target sim @var{args}
19842 @kindex target sim@r{, with Z8000}
19843 Debug programs on a simulated CPU. If the simulator supports setup
19844 options, specify them via @var{args}.
19848 After specifying this target, you can debug programs for the simulated
19849 CPU in the same style as programs for your host computer; use the
19850 @code{file} command to load a new program image, the @code{run} command
19851 to run your program, and so on.
19853 As well as making available all the usual machine registers
19854 (@pxref{Registers, ,Registers}), the Z8000 simulator provides three
19855 additional items of information as specially named registers:
19860 Counts clock-ticks in the simulator.
19863 Counts instructions run in the simulator.
19866 Execution time in 60ths of a second.
19870 You can refer to these values in @value{GDBN} expressions with the usual
19871 conventions; for example, @w{@samp{b fputc if $cycles>5000}} sets a
19872 conditional breakpoint that suspends only after at least 5000
19873 simulated clock ticks.
19876 @subsection Atmel AVR
19879 When configured for debugging the Atmel AVR, @value{GDBN} supports the
19880 following AVR-specific commands:
19883 @item info io_registers
19884 @kindex info io_registers@r{, AVR}
19885 @cindex I/O registers (Atmel AVR)
19886 This command displays information about the AVR I/O registers. For
19887 each register, @value{GDBN} prints its number and value.
19894 When configured for debugging CRIS, @value{GDBN} provides the
19895 following CRIS-specific commands:
19898 @item set cris-version @var{ver}
19899 @cindex CRIS version
19900 Set the current CRIS version to @var{ver}, either @samp{10} or @samp{32}.
19901 The CRIS version affects register names and sizes. This command is useful in
19902 case autodetection of the CRIS version fails.
19904 @item show cris-version
19905 Show the current CRIS version.
19907 @item set cris-dwarf2-cfi
19908 @cindex DWARF-2 CFI and CRIS
19909 Set the usage of DWARF-2 CFI for CRIS debugging. The default is @samp{on}.
19910 Change to @samp{off} when using @code{gcc-cris} whose version is below
19913 @item show cris-dwarf2-cfi
19914 Show the current state of using DWARF-2 CFI.
19916 @item set cris-mode @var{mode}
19918 Set the current CRIS mode to @var{mode}. It should only be changed when
19919 debugging in guru mode, in which case it should be set to
19920 @samp{guru} (the default is @samp{normal}).
19922 @item show cris-mode
19923 Show the current CRIS mode.
19927 @subsection Renesas Super-H
19930 For the Renesas Super-H processor, @value{GDBN} provides these
19935 @kindex regs@r{, Super-H}
19936 Show the values of all Super-H registers.
19938 @item set sh calling-convention @var{convention}
19939 @kindex set sh calling-convention
19940 Set the calling-convention used when calling functions from @value{GDBN}.
19941 Allowed values are @samp{gcc}, which is the default setting, and @samp{renesas}.
19942 With the @samp{gcc} setting, functions are called using the @value{NGCC} calling
19943 convention. If the DWARF-2 information of the called function specifies
19944 that the function follows the Renesas calling convention, the function
19945 is called using the Renesas calling convention. If the calling convention
19946 is set to @samp{renesas}, the Renesas calling convention is always used,
19947 regardless of the DWARF-2 information. This can be used to override the
19948 default of @samp{gcc} if debug information is missing, or the compiler
19949 does not emit the DWARF-2 calling convention entry for a function.
19951 @item show sh calling-convention
19952 @kindex show sh calling-convention
19953 Show the current calling convention setting.
19958 @node Architectures
19959 @section Architectures
19961 This section describes characteristics of architectures that affect
19962 all uses of @value{GDBN} with the architecture, both native and cross.
19969 * HPPA:: HP PA architecture
19970 * SPU:: Cell Broadband Engine SPU architecture
19975 @subsection x86 Architecture-specific Issues
19978 @item set struct-convention @var{mode}
19979 @kindex set struct-convention
19980 @cindex struct return convention
19981 @cindex struct/union returned in registers
19982 Set the convention used by the inferior to return @code{struct}s and
19983 @code{union}s from functions to @var{mode}. Possible values of
19984 @var{mode} are @code{"pcc"}, @code{"reg"}, and @code{"default"} (the
19985 default). @code{"default"} or @code{"pcc"} means that @code{struct}s
19986 are returned on the stack, while @code{"reg"} means that a
19987 @code{struct} or a @code{union} whose size is 1, 2, 4, or 8 bytes will
19988 be returned in a register.
19990 @item show struct-convention
19991 @kindex show struct-convention
19992 Show the current setting of the convention to return @code{struct}s
20001 @kindex set rstack_high_address
20002 @cindex AMD 29K register stack
20003 @cindex register stack, AMD29K
20004 @item set rstack_high_address @var{address}
20005 On AMD 29000 family processors, registers are saved in a separate
20006 @dfn{register stack}. There is no way for @value{GDBN} to determine the
20007 extent of this stack. Normally, @value{GDBN} just assumes that the
20008 stack is ``large enough''. This may result in @value{GDBN} referencing
20009 memory locations that do not exist. If necessary, you can get around
20010 this problem by specifying the ending address of the register stack with
20011 the @code{set rstack_high_address} command. The argument should be an
20012 address, which you probably want to precede with @samp{0x} to specify in
20015 @kindex show rstack_high_address
20016 @item show rstack_high_address
20017 Display the current limit of the register stack, on AMD 29000 family
20025 See the following section.
20030 @cindex stack on Alpha
20031 @cindex stack on MIPS
20032 @cindex Alpha stack
20034 Alpha- and MIPS-based computers use an unusual stack frame, which
20035 sometimes requires @value{GDBN} to search backward in the object code to
20036 find the beginning of a function.
20038 @cindex response time, MIPS debugging
20039 To improve response time (especially for embedded applications, where
20040 @value{GDBN} may be restricted to a slow serial line for this search)
20041 you may want to limit the size of this search, using one of these
20045 @cindex @code{heuristic-fence-post} (Alpha, MIPS)
20046 @item set heuristic-fence-post @var{limit}
20047 Restrict @value{GDBN} to examining at most @var{limit} bytes in its
20048 search for the beginning of a function. A value of @var{0} (the
20049 default) means there is no limit. However, except for @var{0}, the
20050 larger the limit the more bytes @code{heuristic-fence-post} must search
20051 and therefore the longer it takes to run. You should only need to use
20052 this command when debugging a stripped executable.
20054 @item show heuristic-fence-post
20055 Display the current limit.
20059 These commands are available @emph{only} when @value{GDBN} is configured
20060 for debugging programs on Alpha or MIPS processors.
20062 Several MIPS-specific commands are available when debugging MIPS
20066 @item set mips abi @var{arg}
20067 @kindex set mips abi
20068 @cindex set ABI for MIPS
20069 Tell @value{GDBN} which MIPS ABI is used by the inferior. Possible
20070 values of @var{arg} are:
20074 The default ABI associated with the current binary (this is the
20084 @item show mips abi
20085 @kindex show mips abi
20086 Show the MIPS ABI used by @value{GDBN} to debug the inferior.
20089 @itemx show mipsfpu
20090 @xref{MIPS Embedded, set mipsfpu}.
20092 @item set mips mask-address @var{arg}
20093 @kindex set mips mask-address
20094 @cindex MIPS addresses, masking
20095 This command determines whether the most-significant 32 bits of 64-bit
20096 MIPS addresses are masked off. The argument @var{arg} can be
20097 @samp{on}, @samp{off}, or @samp{auto}. The latter is the default
20098 setting, which lets @value{GDBN} determine the correct value.
20100 @item show mips mask-address
20101 @kindex show mips mask-address
20102 Show whether the upper 32 bits of MIPS addresses are masked off or
20105 @item set remote-mips64-transfers-32bit-regs
20106 @kindex set remote-mips64-transfers-32bit-regs
20107 This command controls compatibility with 64-bit MIPS targets that
20108 transfer data in 32-bit quantities. If you have an old MIPS 64 target
20109 that transfers 32 bits for some registers, like @sc{sr} and @sc{fsr},
20110 and 64 bits for other registers, set this option to @samp{on}.
20112 @item show remote-mips64-transfers-32bit-regs
20113 @kindex show remote-mips64-transfers-32bit-regs
20114 Show the current setting of compatibility with older MIPS 64 targets.
20116 @item set debug mips
20117 @kindex set debug mips
20118 This command turns on and off debugging messages for the MIPS-specific
20119 target code in @value{GDBN}.
20121 @item show debug mips
20122 @kindex show debug mips
20123 Show the current setting of MIPS debugging messages.
20129 @cindex HPPA support
20131 When @value{GDBN} is debugging the HP PA architecture, it provides the
20132 following special commands:
20135 @item set debug hppa
20136 @kindex set debug hppa
20137 This command determines whether HPPA architecture-specific debugging
20138 messages are to be displayed.
20140 @item show debug hppa
20141 Show whether HPPA debugging messages are displayed.
20143 @item maint print unwind @var{address}
20144 @kindex maint print unwind@r{, HPPA}
20145 This command displays the contents of the unwind table entry at the
20146 given @var{address}.
20152 @subsection Cell Broadband Engine SPU architecture
20153 @cindex Cell Broadband Engine
20156 When @value{GDBN} is debugging the Cell Broadband Engine SPU architecture,
20157 it provides the following special commands:
20160 @item info spu event
20162 Display SPU event facility status. Shows current event mask
20163 and pending event status.
20165 @item info spu signal
20166 Display SPU signal notification facility status. Shows pending
20167 signal-control word and signal notification mode of both signal
20168 notification channels.
20170 @item info spu mailbox
20171 Display SPU mailbox facility status. Shows all pending entries,
20172 in order of processing, in each of the SPU Write Outbound,
20173 SPU Write Outbound Interrupt, and SPU Read Inbound mailboxes.
20176 Display MFC DMA status. Shows all pending commands in the MFC
20177 DMA queue. For each entry, opcode, tag, class IDs, effective
20178 and local store addresses and transfer size are shown.
20180 @item info spu proxydma
20181 Display MFC Proxy-DMA status. Shows all pending commands in the MFC
20182 Proxy-DMA queue. For each entry, opcode, tag, class IDs, effective
20183 and local store addresses and transfer size are shown.
20187 When @value{GDBN} is debugging a combined PowerPC/SPU application
20188 on the Cell Broadband Engine, it provides in addition the following
20192 @item set spu stop-on-load @var{arg}
20194 Set whether to stop for new SPE threads. When set to @code{on}, @value{GDBN}
20195 will give control to the user when a new SPE thread enters its @code{main}
20196 function. The default is @code{off}.
20198 @item show spu stop-on-load
20200 Show whether to stop for new SPE threads.
20202 @item set spu auto-flush-cache @var{arg}
20203 Set whether to automatically flush the software-managed cache. When set to
20204 @code{on}, @value{GDBN} will automatically cause the SPE software-managed
20205 cache to be flushed whenever SPE execution stops. This provides a consistent
20206 view of PowerPC memory that is accessed via the cache. If an application
20207 does not use the software-managed cache, this option has no effect.
20209 @item show spu auto-flush-cache
20210 Show whether to automatically flush the software-managed cache.
20215 @subsection PowerPC
20216 @cindex PowerPC architecture
20218 When @value{GDBN} is debugging the PowerPC architecture, it provides a set of
20219 pseudo-registers to enable inspection of 128-bit wide Decimal Floating Point
20220 numbers stored in the floating point registers. These values must be stored
20221 in two consecutive registers, always starting at an even register like
20222 @code{f0} or @code{f2}.
20224 The pseudo-registers go from @code{$dl0} through @code{$dl15}, and are formed
20225 by joining the even/odd register pairs @code{f0} and @code{f1} for @code{$dl0},
20226 @code{f2} and @code{f3} for @code{$dl1} and so on.
20228 For POWER7 processors, @value{GDBN} provides a set of pseudo-registers, the 64-bit
20229 wide Extended Floating Point Registers (@samp{f32} through @samp{f63}).
20232 @node Controlling GDB
20233 @chapter Controlling @value{GDBN}
20235 You can alter the way @value{GDBN} interacts with you by using the
20236 @code{set} command. For commands controlling how @value{GDBN} displays
20237 data, see @ref{Print Settings, ,Print Settings}. Other settings are
20242 * Editing:: Command editing
20243 * Command History:: Command history
20244 * Screen Size:: Screen size
20245 * Numbers:: Numbers
20246 * ABI:: Configuring the current ABI
20247 * Messages/Warnings:: Optional warnings and messages
20248 * Debugging Output:: Optional messages about internal happenings
20249 * Other Misc Settings:: Other Miscellaneous Settings
20257 @value{GDBN} indicates its readiness to read a command by printing a string
20258 called the @dfn{prompt}. This string is normally @samp{(@value{GDBP})}. You
20259 can change the prompt string with the @code{set prompt} command. For
20260 instance, when debugging @value{GDBN} with @value{GDBN}, it is useful to change
20261 the prompt in one of the @value{GDBN} sessions so that you can always tell
20262 which one you are talking to.
20264 @emph{Note:} @code{set prompt} does not add a space for you after the
20265 prompt you set. This allows you to set a prompt which ends in a space
20266 or a prompt that does not.
20270 @item set prompt @var{newprompt}
20271 Directs @value{GDBN} to use @var{newprompt} as its prompt string henceforth.
20273 @kindex show prompt
20275 Prints a line of the form: @samp{Gdb's prompt is: @var{your-prompt}}
20278 Versions of @value{GDBN} that ship with Python scripting enabled have
20279 prompt extensions. The commands for interacting with these extensions
20283 @kindex set extended-prompt
20284 @item set extended-prompt @var{prompt}
20285 Set an extended prompt that allows for substitutions.
20286 @xref{gdb.prompt}, for a list of escape sequences that can be used for
20287 substitution. Any escape sequences specified as part of the prompt
20288 string are replaced with the corresponding strings each time the prompt
20294 set extended-prompt Current working directory: \w (gdb)
20297 Note that when an extended-prompt is set, it takes control of the
20298 @var{prompt_hook} hook. @xref{prompt_hook}, for further information.
20300 @kindex show extended-prompt
20301 @item show extended-prompt
20302 Prints the extended prompt. Any escape sequences specified as part of
20303 the prompt string with @code{set extended-prompt}, are replaced with the
20304 corresponding strings each time the prompt is displayed.
20308 @section Command Editing
20310 @cindex command line editing
20312 @value{GDBN} reads its input commands via the @dfn{Readline} interface. This
20313 @sc{gnu} library provides consistent behavior for programs which provide a
20314 command line interface to the user. Advantages are @sc{gnu} Emacs-style
20315 or @dfn{vi}-style inline editing of commands, @code{csh}-like history
20316 substitution, and a storage and recall of command history across
20317 debugging sessions.
20319 You may control the behavior of command line editing in @value{GDBN} with the
20320 command @code{set}.
20323 @kindex set editing
20326 @itemx set editing on
20327 Enable command line editing (enabled by default).
20329 @item set editing off
20330 Disable command line editing.
20332 @kindex show editing
20334 Show whether command line editing is enabled.
20337 @ifset SYSTEM_READLINE
20338 @xref{Command Line Editing, , , rluserman, GNU Readline Library},
20340 @ifclear SYSTEM_READLINE
20341 @xref{Command Line Editing},
20343 for more details about the Readline
20344 interface. Users unfamiliar with @sc{gnu} Emacs or @code{vi} are
20345 encouraged to read that chapter.
20347 @node Command History
20348 @section Command History
20349 @cindex command history
20351 @value{GDBN} can keep track of the commands you type during your
20352 debugging sessions, so that you can be certain of precisely what
20353 happened. Use these commands to manage the @value{GDBN} command
20356 @value{GDBN} uses the @sc{gnu} History library, a part of the Readline
20357 package, to provide the history facility.
20358 @ifset SYSTEM_READLINE
20359 @xref{Using History Interactively, , , history, GNU History Library},
20361 @ifclear SYSTEM_READLINE
20362 @xref{Using History Interactively},
20364 for the detailed description of the History library.
20366 To issue a command to @value{GDBN} without affecting certain aspects of
20367 the state which is seen by users, prefix it with @samp{server }
20368 (@pxref{Server Prefix}). This
20369 means that this command will not affect the command history, nor will it
20370 affect @value{GDBN}'s notion of which command to repeat if @key{RET} is
20371 pressed on a line by itself.
20373 @cindex @code{server}, command prefix
20374 The server prefix does not affect the recording of values into the value
20375 history; to print a value without recording it into the value history,
20376 use the @code{output} command instead of the @code{print} command.
20378 Here is the description of @value{GDBN} commands related to command
20382 @cindex history substitution
20383 @cindex history file
20384 @kindex set history filename
20385 @cindex @env{GDBHISTFILE}, environment variable
20386 @item set history filename @var{fname}
20387 Set the name of the @value{GDBN} command history file to @var{fname}.
20388 This is the file where @value{GDBN} reads an initial command history
20389 list, and where it writes the command history from this session when it
20390 exits. You can access this list through history expansion or through
20391 the history command editing characters listed below. This file defaults
20392 to the value of the environment variable @code{GDBHISTFILE}, or to
20393 @file{./.gdb_history} (@file{./_gdb_history} on MS-DOS) if this variable
20396 @cindex save command history
20397 @kindex set history save
20398 @item set history save
20399 @itemx set history save on
20400 Record command history in a file, whose name may be specified with the
20401 @code{set history filename} command. By default, this option is disabled.
20403 @item set history save off
20404 Stop recording command history in a file.
20406 @cindex history size
20407 @kindex set history size
20408 @cindex @env{HISTSIZE}, environment variable
20409 @item set history size @var{size}
20410 Set the number of commands which @value{GDBN} keeps in its history list.
20411 This defaults to the value of the environment variable
20412 @code{HISTSIZE}, or to 256 if this variable is not set.
20415 History expansion assigns special meaning to the character @kbd{!}.
20416 @ifset SYSTEM_READLINE
20417 @xref{Event Designators, , , history, GNU History Library},
20419 @ifclear SYSTEM_READLINE
20420 @xref{Event Designators},
20424 @cindex history expansion, turn on/off
20425 Since @kbd{!} is also the logical not operator in C, history expansion
20426 is off by default. If you decide to enable history expansion with the
20427 @code{set history expansion on} command, you may sometimes need to
20428 follow @kbd{!} (when it is used as logical not, in an expression) with
20429 a space or a tab to prevent it from being expanded. The readline
20430 history facilities do not attempt substitution on the strings
20431 @kbd{!=} and @kbd{!(}, even when history expansion is enabled.
20433 The commands to control history expansion are:
20436 @item set history expansion on
20437 @itemx set history expansion
20438 @kindex set history expansion
20439 Enable history expansion. History expansion is off by default.
20441 @item set history expansion off
20442 Disable history expansion.
20445 @kindex show history
20447 @itemx show history filename
20448 @itemx show history save
20449 @itemx show history size
20450 @itemx show history expansion
20451 These commands display the state of the @value{GDBN} history parameters.
20452 @code{show history} by itself displays all four states.
20457 @kindex show commands
20458 @cindex show last commands
20459 @cindex display command history
20460 @item show commands
20461 Display the last ten commands in the command history.
20463 @item show commands @var{n}
20464 Print ten commands centered on command number @var{n}.
20466 @item show commands +
20467 Print ten commands just after the commands last printed.
20471 @section Screen Size
20472 @cindex size of screen
20473 @cindex pauses in output
20475 Certain commands to @value{GDBN} may produce large amounts of
20476 information output to the screen. To help you read all of it,
20477 @value{GDBN} pauses and asks you for input at the end of each page of
20478 output. Type @key{RET} when you want to continue the output, or @kbd{q}
20479 to discard the remaining output. Also, the screen width setting
20480 determines when to wrap lines of output. Depending on what is being
20481 printed, @value{GDBN} tries to break the line at a readable place,
20482 rather than simply letting it overflow onto the following line.
20484 Normally @value{GDBN} knows the size of the screen from the terminal
20485 driver software. For example, on Unix @value{GDBN} uses the termcap data base
20486 together with the value of the @code{TERM} environment variable and the
20487 @code{stty rows} and @code{stty cols} settings. If this is not correct,
20488 you can override it with the @code{set height} and @code{set
20495 @kindex show height
20496 @item set height @var{lpp}
20498 @itemx set width @var{cpl}
20500 These @code{set} commands specify a screen height of @var{lpp} lines and
20501 a screen width of @var{cpl} characters. The associated @code{show}
20502 commands display the current settings.
20504 If you specify a height of zero lines, @value{GDBN} does not pause during
20505 output no matter how long the output is. This is useful if output is to a
20506 file or to an editor buffer.
20508 Likewise, you can specify @samp{set width 0} to prevent @value{GDBN}
20509 from wrapping its output.
20511 @item set pagination on
20512 @itemx set pagination off
20513 @kindex set pagination
20514 Turn the output pagination on or off; the default is on. Turning
20515 pagination off is the alternative to @code{set height 0}. Note that
20516 running @value{GDBN} with the @option{--batch} option (@pxref{Mode
20517 Options, -batch}) also automatically disables pagination.
20519 @item show pagination
20520 @kindex show pagination
20521 Show the current pagination mode.
20526 @cindex number representation
20527 @cindex entering numbers
20529 You can always enter numbers in octal, decimal, or hexadecimal in
20530 @value{GDBN} by the usual conventions: octal numbers begin with
20531 @samp{0}, decimal numbers end with @samp{.}, and hexadecimal numbers
20532 begin with @samp{0x}. Numbers that neither begin with @samp{0} or
20533 @samp{0x}, nor end with a @samp{.} are, by default, entered in base
20534 10; likewise, the default display for numbers---when no particular
20535 format is specified---is base 10. You can change the default base for
20536 both input and output with the commands described below.
20539 @kindex set input-radix
20540 @item set input-radix @var{base}
20541 Set the default base for numeric input. Supported choices
20542 for @var{base} are decimal 8, 10, or 16. @var{base} must itself be
20543 specified either unambiguously or using the current input radix; for
20547 set input-radix 012
20548 set input-radix 10.
20549 set input-radix 0xa
20553 sets the input base to decimal. On the other hand, @samp{set input-radix 10}
20554 leaves the input radix unchanged, no matter what it was, since
20555 @samp{10}, being without any leading or trailing signs of its base, is
20556 interpreted in the current radix. Thus, if the current radix is 16,
20557 @samp{10} is interpreted in hex, i.e.@: as 16 decimal, which doesn't
20560 @kindex set output-radix
20561 @item set output-radix @var{base}
20562 Set the default base for numeric display. Supported choices
20563 for @var{base} are decimal 8, 10, or 16. @var{base} must itself be
20564 specified either unambiguously or using the current input radix.
20566 @kindex show input-radix
20567 @item show input-radix
20568 Display the current default base for numeric input.
20570 @kindex show output-radix
20571 @item show output-radix
20572 Display the current default base for numeric display.
20574 @item set radix @r{[}@var{base}@r{]}
20578 These commands set and show the default base for both input and output
20579 of numbers. @code{set radix} sets the radix of input and output to
20580 the same base; without an argument, it resets the radix back to its
20581 default value of 10.
20586 @section Configuring the Current ABI
20588 @value{GDBN} can determine the @dfn{ABI} (Application Binary Interface) of your
20589 application automatically. However, sometimes you need to override its
20590 conclusions. Use these commands to manage @value{GDBN}'s view of the
20597 One @value{GDBN} configuration can debug binaries for multiple operating
20598 system targets, either via remote debugging or native emulation.
20599 @value{GDBN} will autodetect the @dfn{OS ABI} (Operating System ABI) in use,
20600 but you can override its conclusion using the @code{set osabi} command.
20601 One example where this is useful is in debugging of binaries which use
20602 an alternate C library (e.g.@: @sc{uClibc} for @sc{gnu}/Linux) which does
20603 not have the same identifying marks that the standard C library for your
20608 Show the OS ABI currently in use.
20611 With no argument, show the list of registered available OS ABI's.
20613 @item set osabi @var{abi}
20614 Set the current OS ABI to @var{abi}.
20617 @cindex float promotion
20619 Generally, the way that an argument of type @code{float} is passed to a
20620 function depends on whether the function is prototyped. For a prototyped
20621 (i.e.@: ANSI/ISO style) function, @code{float} arguments are passed unchanged,
20622 according to the architecture's convention for @code{float}. For unprototyped
20623 (i.e.@: K&R style) functions, @code{float} arguments are first promoted to type
20624 @code{double} and then passed.
20626 Unfortunately, some forms of debug information do not reliably indicate whether
20627 a function is prototyped. If @value{GDBN} calls a function that is not marked
20628 as prototyped, it consults @kbd{set coerce-float-to-double}.
20631 @kindex set coerce-float-to-double
20632 @item set coerce-float-to-double
20633 @itemx set coerce-float-to-double on
20634 Arguments of type @code{float} will be promoted to @code{double} when passed
20635 to an unprototyped function. This is the default setting.
20637 @item set coerce-float-to-double off
20638 Arguments of type @code{float} will be passed directly to unprototyped
20641 @kindex show coerce-float-to-double
20642 @item show coerce-float-to-double
20643 Show the current setting of promoting @code{float} to @code{double}.
20647 @kindex show cp-abi
20648 @value{GDBN} needs to know the ABI used for your program's C@t{++}
20649 objects. The correct C@t{++} ABI depends on which C@t{++} compiler was
20650 used to build your application. @value{GDBN} only fully supports
20651 programs with a single C@t{++} ABI; if your program contains code using
20652 multiple C@t{++} ABI's or if @value{GDBN} can not identify your
20653 program's ABI correctly, you can tell @value{GDBN} which ABI to use.
20654 Currently supported ABI's include ``gnu-v2'', for @code{g++} versions
20655 before 3.0, ``gnu-v3'', for @code{g++} versions 3.0 and later, and
20656 ``hpaCC'' for the HP ANSI C@t{++} compiler. Other C@t{++} compilers may
20657 use the ``gnu-v2'' or ``gnu-v3'' ABI's as well. The default setting is
20662 Show the C@t{++} ABI currently in use.
20665 With no argument, show the list of supported C@t{++} ABI's.
20667 @item set cp-abi @var{abi}
20668 @itemx set cp-abi auto
20669 Set the current C@t{++} ABI to @var{abi}, or return to automatic detection.
20672 @node Messages/Warnings
20673 @section Optional Warnings and Messages
20675 @cindex verbose operation
20676 @cindex optional warnings
20677 By default, @value{GDBN} is silent about its inner workings. If you are
20678 running on a slow machine, you may want to use the @code{set verbose}
20679 command. This makes @value{GDBN} tell you when it does a lengthy
20680 internal operation, so you will not think it has crashed.
20682 Currently, the messages controlled by @code{set verbose} are those
20683 which announce that the symbol table for a source file is being read;
20684 see @code{symbol-file} in @ref{Files, ,Commands to Specify Files}.
20687 @kindex set verbose
20688 @item set verbose on
20689 Enables @value{GDBN} output of certain informational messages.
20691 @item set verbose off
20692 Disables @value{GDBN} output of certain informational messages.
20694 @kindex show verbose
20696 Displays whether @code{set verbose} is on or off.
20699 By default, if @value{GDBN} encounters bugs in the symbol table of an
20700 object file, it is silent; but if you are debugging a compiler, you may
20701 find this information useful (@pxref{Symbol Errors, ,Errors Reading
20706 @kindex set complaints
20707 @item set complaints @var{limit}
20708 Permits @value{GDBN} to output @var{limit} complaints about each type of
20709 unusual symbols before becoming silent about the problem. Set
20710 @var{limit} to zero to suppress all complaints; set it to a large number
20711 to prevent complaints from being suppressed.
20713 @kindex show complaints
20714 @item show complaints
20715 Displays how many symbol complaints @value{GDBN} is permitted to produce.
20719 @anchor{confirmation requests}
20720 By default, @value{GDBN} is cautious, and asks what sometimes seems to be a
20721 lot of stupid questions to confirm certain commands. For example, if
20722 you try to run a program which is already running:
20726 The program being debugged has been started already.
20727 Start it from the beginning? (y or n)
20730 If you are willing to unflinchingly face the consequences of your own
20731 commands, you can disable this ``feature'':
20735 @kindex set confirm
20737 @cindex confirmation
20738 @cindex stupid questions
20739 @item set confirm off
20740 Disables confirmation requests. Note that running @value{GDBN} with
20741 the @option{--batch} option (@pxref{Mode Options, -batch}) also
20742 automatically disables confirmation requests.
20744 @item set confirm on
20745 Enables confirmation requests (the default).
20747 @kindex show confirm
20749 Displays state of confirmation requests.
20753 @cindex command tracing
20754 If you need to debug user-defined commands or sourced files you may find it
20755 useful to enable @dfn{command tracing}. In this mode each command will be
20756 printed as it is executed, prefixed with one or more @samp{+} symbols, the
20757 quantity denoting the call depth of each command.
20760 @kindex set trace-commands
20761 @cindex command scripts, debugging
20762 @item set trace-commands on
20763 Enable command tracing.
20764 @item set trace-commands off
20765 Disable command tracing.
20766 @item show trace-commands
20767 Display the current state of command tracing.
20770 @node Debugging Output
20771 @section Optional Messages about Internal Happenings
20772 @cindex optional debugging messages
20774 @value{GDBN} has commands that enable optional debugging messages from
20775 various @value{GDBN} subsystems; normally these commands are of
20776 interest to @value{GDBN} maintainers, or when reporting a bug. This
20777 section documents those commands.
20780 @kindex set exec-done-display
20781 @item set exec-done-display
20782 Turns on or off the notification of asynchronous commands'
20783 completion. When on, @value{GDBN} will print a message when an
20784 asynchronous command finishes its execution. The default is off.
20785 @kindex show exec-done-display
20786 @item show exec-done-display
20787 Displays the current setting of asynchronous command completion
20790 @cindex gdbarch debugging info
20791 @cindex architecture debugging info
20792 @item set debug arch
20793 Turns on or off display of gdbarch debugging info. The default is off
20795 @item show debug arch
20796 Displays the current state of displaying gdbarch debugging info.
20797 @item set debug aix-thread
20798 @cindex AIX threads
20799 Display debugging messages about inner workings of the AIX thread
20801 @item show debug aix-thread
20802 Show the current state of AIX thread debugging info display.
20803 @item set debug check-physname
20805 Check the results of the ``physname'' computation. When reading DWARF
20806 debugging information for C@t{++}, @value{GDBN} attempts to compute
20807 each entity's name. @value{GDBN} can do this computation in two
20808 different ways, depending on exactly what information is present.
20809 When enabled, this setting causes @value{GDBN} to compute the names
20810 both ways and display any discrepancies.
20811 @item show debug check-physname
20812 Show the current state of ``physname'' checking.
20813 @item set debug dwarf2-die
20814 @cindex DWARF2 DIEs
20815 Dump DWARF2 DIEs after they are read in.
20816 The value is the number of nesting levels to print.
20817 A value of zero turns off the display.
20818 @item show debug dwarf2-die
20819 Show the current state of DWARF2 DIE debugging.
20820 @item set debug displaced
20821 @cindex displaced stepping debugging info
20822 Turns on or off display of @value{GDBN} debugging info for the
20823 displaced stepping support. The default is off.
20824 @item show debug displaced
20825 Displays the current state of displaying @value{GDBN} debugging info
20826 related to displaced stepping.
20827 @item set debug event
20828 @cindex event debugging info
20829 Turns on or off display of @value{GDBN} event debugging info. The
20831 @item show debug event
20832 Displays the current state of displaying @value{GDBN} event debugging
20834 @item set debug expression
20835 @cindex expression debugging info
20836 Turns on or off display of debugging info about @value{GDBN}
20837 expression parsing. The default is off.
20838 @item show debug expression
20839 Displays the current state of displaying debugging info about
20840 @value{GDBN} expression parsing.
20841 @item set debug frame
20842 @cindex frame debugging info
20843 Turns on or off display of @value{GDBN} frame debugging info. The
20845 @item show debug frame
20846 Displays the current state of displaying @value{GDBN} frame debugging
20848 @item set debug gnu-nat
20849 @cindex @sc{gnu}/Hurd debug messages
20850 Turns on or off debugging messages from the @sc{gnu}/Hurd debug support.
20851 @item show debug gnu-nat
20852 Show the current state of @sc{gnu}/Hurd debugging messages.
20853 @item set debug infrun
20854 @cindex inferior debugging info
20855 Turns on or off display of @value{GDBN} debugging info for running the inferior.
20856 The default is off. @file{infrun.c} contains GDB's runtime state machine used
20857 for implementing operations such as single-stepping the inferior.
20858 @item show debug infrun
20859 Displays the current state of @value{GDBN} inferior debugging.
20860 @item set debug jit
20861 @cindex just-in-time compilation, debugging messages
20862 Turns on or off debugging messages from JIT debug support.
20863 @item show debug jit
20864 Displays the current state of @value{GDBN} JIT debugging.
20865 @item set debug lin-lwp
20866 @cindex @sc{gnu}/Linux LWP debug messages
20867 @cindex Linux lightweight processes
20868 Turns on or off debugging messages from the Linux LWP debug support.
20869 @item show debug lin-lwp
20870 Show the current state of Linux LWP debugging messages.
20871 @item set debug observer
20872 @cindex observer debugging info
20873 Turns on or off display of @value{GDBN} observer debugging. This
20874 includes info such as the notification of observable events.
20875 @item show debug observer
20876 Displays the current state of observer debugging.
20877 @item set debug overload
20878 @cindex C@t{++} overload debugging info
20879 Turns on or off display of @value{GDBN} C@t{++} overload debugging
20880 info. This includes info such as ranking of functions, etc. The default
20882 @item show debug overload
20883 Displays the current state of displaying @value{GDBN} C@t{++} overload
20885 @cindex expression parser, debugging info
20886 @cindex debug expression parser
20887 @item set debug parser
20888 Turns on or off the display of expression parser debugging output.
20889 Internally, this sets the @code{yydebug} variable in the expression
20890 parser. @xref{Tracing, , Tracing Your Parser, bison, Bison}, for
20891 details. The default is off.
20892 @item show debug parser
20893 Show the current state of expression parser debugging.
20894 @cindex packets, reporting on stdout
20895 @cindex serial connections, debugging
20896 @cindex debug remote protocol
20897 @cindex remote protocol debugging
20898 @cindex display remote packets
20899 @item set debug remote
20900 Turns on or off display of reports on all packets sent back and forth across
20901 the serial line to the remote machine. The info is printed on the
20902 @value{GDBN} standard output stream. The default is off.
20903 @item show debug remote
20904 Displays the state of display of remote packets.
20905 @item set debug serial
20906 Turns on or off display of @value{GDBN} serial debugging info. The
20908 @item show debug serial
20909 Displays the current state of displaying @value{GDBN} serial debugging
20911 @item set debug solib-frv
20912 @cindex FR-V shared-library debugging
20913 Turns on or off debugging messages for FR-V shared-library code.
20914 @item show debug solib-frv
20915 Display the current state of FR-V shared-library code debugging
20917 @item set debug target
20918 @cindex target debugging info
20919 Turns on or off display of @value{GDBN} target debugging info. This info
20920 includes what is going on at the target level of GDB, as it happens. The
20921 default is 0. Set it to 1 to track events, and to 2 to also track the
20922 value of large memory transfers. Changes to this flag do not take effect
20923 until the next time you connect to a target or use the @code{run} command.
20924 @item show debug target
20925 Displays the current state of displaying @value{GDBN} target debugging
20927 @item set debug timestamp
20928 @cindex timestampping debugging info
20929 Turns on or off display of timestamps with @value{GDBN} debugging info.
20930 When enabled, seconds and microseconds are displayed before each debugging
20932 @item show debug timestamp
20933 Displays the current state of displaying timestamps with @value{GDBN}
20935 @item set debugvarobj
20936 @cindex variable object debugging info
20937 Turns on or off display of @value{GDBN} variable object debugging
20938 info. The default is off.
20939 @item show debugvarobj
20940 Displays the current state of displaying @value{GDBN} variable object
20942 @item set debug xml
20943 @cindex XML parser debugging
20944 Turns on or off debugging messages for built-in XML parsers.
20945 @item show debug xml
20946 Displays the current state of XML debugging messages.
20949 @node Other Misc Settings
20950 @section Other Miscellaneous Settings
20951 @cindex miscellaneous settings
20954 @kindex set interactive-mode
20955 @item set interactive-mode
20956 If @code{on}, forces @value{GDBN} to assume that GDB was started
20957 in a terminal. In practice, this means that @value{GDBN} should wait
20958 for the user to answer queries generated by commands entered at
20959 the command prompt. If @code{off}, forces @value{GDBN} to operate
20960 in the opposite mode, and it uses the default answers to all queries.
20961 If @code{auto} (the default), @value{GDBN} tries to determine whether
20962 its standard input is a terminal, and works in interactive-mode if it
20963 is, non-interactively otherwise.
20965 In the vast majority of cases, the debugger should be able to guess
20966 correctly which mode should be used. But this setting can be useful
20967 in certain specific cases, such as running a MinGW @value{GDBN}
20968 inside a cygwin window.
20970 @kindex show interactive-mode
20971 @item show interactive-mode
20972 Displays whether the debugger is operating in interactive mode or not.
20975 @node Extending GDB
20976 @chapter Extending @value{GDBN}
20977 @cindex extending GDB
20979 @value{GDBN} provides three mechanisms for extension. The first is based
20980 on composition of @value{GDBN} commands, the second is based on the
20981 Python scripting language, and the third is for defining new aliases of
20984 To facilitate the use of the first two extensions, @value{GDBN} is capable
20985 of evaluating the contents of a file. When doing so, @value{GDBN}
20986 can recognize which scripting language is being used by looking at
20987 the filename extension. Files with an unrecognized filename extension
20988 are always treated as a @value{GDBN} Command Files.
20989 @xref{Command Files,, Command files}.
20991 You can control how @value{GDBN} evaluates these files with the following
20995 @kindex set script-extension
20996 @kindex show script-extension
20997 @item set script-extension off
20998 All scripts are always evaluated as @value{GDBN} Command Files.
21000 @item set script-extension soft
21001 The debugger determines the scripting language based on filename
21002 extension. If this scripting language is supported, @value{GDBN}
21003 evaluates the script using that language. Otherwise, it evaluates
21004 the file as a @value{GDBN} Command File.
21006 @item set script-extension strict
21007 The debugger determines the scripting language based on filename
21008 extension, and evaluates the script using that language. If the
21009 language is not supported, then the evaluation fails.
21011 @item show script-extension
21012 Display the current value of the @code{script-extension} option.
21017 * Sequences:: Canned Sequences of Commands
21018 * Python:: Scripting @value{GDBN} using Python
21019 * Aliases:: Creating new spellings of existing commands
21023 @section Canned Sequences of Commands
21025 Aside from breakpoint commands (@pxref{Break Commands, ,Breakpoint
21026 Command Lists}), @value{GDBN} provides two ways to store sequences of
21027 commands for execution as a unit: user-defined commands and command
21031 * Define:: How to define your own commands
21032 * Hooks:: Hooks for user-defined commands
21033 * Command Files:: How to write scripts of commands to be stored in a file
21034 * Output:: Commands for controlled output
21038 @subsection User-defined Commands
21040 @cindex user-defined command
21041 @cindex arguments, to user-defined commands
21042 A @dfn{user-defined command} is a sequence of @value{GDBN} commands to
21043 which you assign a new name as a command. This is done with the
21044 @code{define} command. User commands may accept up to 10 arguments
21045 separated by whitespace. Arguments are accessed within the user command
21046 via @code{$arg0@dots{}$arg9}. A trivial example:
21050 print $arg0 + $arg1 + $arg2
21055 To execute the command use:
21062 This defines the command @code{adder}, which prints the sum of
21063 its three arguments. Note the arguments are text substitutions, so they may
21064 reference variables, use complex expressions, or even perform inferior
21067 @cindex argument count in user-defined commands
21068 @cindex how many arguments (user-defined commands)
21069 In addition, @code{$argc} may be used to find out how many arguments have
21070 been passed. This expands to a number in the range 0@dots{}10.
21075 print $arg0 + $arg1
21078 print $arg0 + $arg1 + $arg2
21086 @item define @var{commandname}
21087 Define a command named @var{commandname}. If there is already a command
21088 by that name, you are asked to confirm that you want to redefine it.
21089 @var{commandname} may be a bare command name consisting of letters,
21090 numbers, dashes, and underscores. It may also start with any predefined
21091 prefix command. For example, @samp{define target my-target} creates
21092 a user-defined @samp{target my-target} command.
21094 The definition of the command is made up of other @value{GDBN} command lines,
21095 which are given following the @code{define} command. The end of these
21096 commands is marked by a line containing @code{end}.
21099 @kindex end@r{ (user-defined commands)}
21100 @item document @var{commandname}
21101 Document the user-defined command @var{commandname}, so that it can be
21102 accessed by @code{help}. The command @var{commandname} must already be
21103 defined. This command reads lines of documentation just as @code{define}
21104 reads the lines of the command definition, ending with @code{end}.
21105 After the @code{document} command is finished, @code{help} on command
21106 @var{commandname} displays the documentation you have written.
21108 You may use the @code{document} command again to change the
21109 documentation of a command. Redefining the command with @code{define}
21110 does not change the documentation.
21112 @kindex dont-repeat
21113 @cindex don't repeat command
21115 Used inside a user-defined command, this tells @value{GDBN} that this
21116 command should not be repeated when the user hits @key{RET}
21117 (@pxref{Command Syntax, repeat last command}).
21119 @kindex help user-defined
21120 @item help user-defined
21121 List all user-defined commands and all python commands defined in class
21122 COMAND_USER. The first line of the documentation or docstring is
21127 @itemx show user @var{commandname}
21128 Display the @value{GDBN} commands used to define @var{commandname} (but
21129 not its documentation). If no @var{commandname} is given, display the
21130 definitions for all user-defined commands.
21131 This does not work for user-defined python commands.
21133 @cindex infinite recursion in user-defined commands
21134 @kindex show max-user-call-depth
21135 @kindex set max-user-call-depth
21136 @item show max-user-call-depth
21137 @itemx set max-user-call-depth
21138 The value of @code{max-user-call-depth} controls how many recursion
21139 levels are allowed in user-defined commands before @value{GDBN} suspects an
21140 infinite recursion and aborts the command.
21141 This does not apply to user-defined python commands.
21144 In addition to the above commands, user-defined commands frequently
21145 use control flow commands, described in @ref{Command Files}.
21147 When user-defined commands are executed, the
21148 commands of the definition are not printed. An error in any command
21149 stops execution of the user-defined command.
21151 If used interactively, commands that would ask for confirmation proceed
21152 without asking when used inside a user-defined command. Many @value{GDBN}
21153 commands that normally print messages to say what they are doing omit the
21154 messages when used in a user-defined command.
21157 @subsection User-defined Command Hooks
21158 @cindex command hooks
21159 @cindex hooks, for commands
21160 @cindex hooks, pre-command
21163 You may define @dfn{hooks}, which are a special kind of user-defined
21164 command. Whenever you run the command @samp{foo}, if the user-defined
21165 command @samp{hook-foo} exists, it is executed (with no arguments)
21166 before that command.
21168 @cindex hooks, post-command
21170 A hook may also be defined which is run after the command you executed.
21171 Whenever you run the command @samp{foo}, if the user-defined command
21172 @samp{hookpost-foo} exists, it is executed (with no arguments) after
21173 that command. Post-execution hooks may exist simultaneously with
21174 pre-execution hooks, for the same command.
21176 It is valid for a hook to call the command which it hooks. If this
21177 occurs, the hook is not re-executed, thereby avoiding infinite recursion.
21179 @c It would be nice if hookpost could be passed a parameter indicating
21180 @c if the command it hooks executed properly or not. FIXME!
21182 @kindex stop@r{, a pseudo-command}
21183 In addition, a pseudo-command, @samp{stop} exists. Defining
21184 (@samp{hook-stop}) makes the associated commands execute every time
21185 execution stops in your program: before breakpoint commands are run,
21186 displays are printed, or the stack frame is printed.
21188 For example, to ignore @code{SIGALRM} signals while
21189 single-stepping, but treat them normally during normal execution,
21194 handle SIGALRM nopass
21198 handle SIGALRM pass
21201 define hook-continue
21202 handle SIGALRM pass
21206 As a further example, to hook at the beginning and end of the @code{echo}
21207 command, and to add extra text to the beginning and end of the message,
21215 define hookpost-echo
21219 (@value{GDBP}) echo Hello World
21220 <<<---Hello World--->>>
21225 You can define a hook for any single-word command in @value{GDBN}, but
21226 not for command aliases; you should define a hook for the basic command
21227 name, e.g.@: @code{backtrace} rather than @code{bt}.
21228 @c FIXME! So how does Joe User discover whether a command is an alias
21230 You can hook a multi-word command by adding @code{hook-} or
21231 @code{hookpost-} to the last word of the command, e.g.@:
21232 @samp{define target hook-remote} to add a hook to @samp{target remote}.
21234 If an error occurs during the execution of your hook, execution of
21235 @value{GDBN} commands stops and @value{GDBN} issues a prompt
21236 (before the command that you actually typed had a chance to run).
21238 If you try to define a hook which does not match any known command, you
21239 get a warning from the @code{define} command.
21241 @node Command Files
21242 @subsection Command Files
21244 @cindex command files
21245 @cindex scripting commands
21246 A command file for @value{GDBN} is a text file made of lines that are
21247 @value{GDBN} commands. Comments (lines starting with @kbd{#}) may
21248 also be included. An empty line in a command file does nothing; it
21249 does not mean to repeat the last command, as it would from the
21252 You can request the execution of a command file with the @code{source}
21253 command. Note that the @code{source} command is also used to evaluate
21254 scripts that are not Command Files. The exact behavior can be configured
21255 using the @code{script-extension} setting.
21256 @xref{Extending GDB,, Extending GDB}.
21260 @cindex execute commands from a file
21261 @item source [-s] [-v] @var{filename}
21262 Execute the command file @var{filename}.
21265 The lines in a command file are generally executed sequentially,
21266 unless the order of execution is changed by one of the
21267 @emph{flow-control commands} described below. The commands are not
21268 printed as they are executed. An error in any command terminates
21269 execution of the command file and control is returned to the console.
21271 @value{GDBN} first searches for @var{filename} in the current directory.
21272 If the file is not found there, and @var{filename} does not specify a
21273 directory, then @value{GDBN} also looks for the file on the source search path
21274 (specified with the @samp{directory} command);
21275 except that @file{$cdir} is not searched because the compilation directory
21276 is not relevant to scripts.
21278 If @code{-s} is specified, then @value{GDBN} searches for @var{filename}
21279 on the search path even if @var{filename} specifies a directory.
21280 The search is done by appending @var{filename} to each element of the
21281 search path. So, for example, if @var{filename} is @file{mylib/myscript}
21282 and the search path contains @file{/home/user} then @value{GDBN} will
21283 look for the script @file{/home/user/mylib/myscript}.
21284 The search is also done if @var{filename} is an absolute path.
21285 For example, if @var{filename} is @file{/tmp/myscript} and
21286 the search path contains @file{/home/user} then @value{GDBN} will
21287 look for the script @file{/home/user/tmp/myscript}.
21288 For DOS-like systems, if @var{filename} contains a drive specification,
21289 it is stripped before concatenation. For example, if @var{filename} is
21290 @file{d:myscript} and the search path contains @file{c:/tmp} then @value{GDBN}
21291 will look for the script @file{c:/tmp/myscript}.
21293 If @code{-v}, for verbose mode, is given then @value{GDBN} displays
21294 each command as it is executed. The option must be given before
21295 @var{filename}, and is interpreted as part of the filename anywhere else.
21297 Commands that would ask for confirmation if used interactively proceed
21298 without asking when used in a command file. Many @value{GDBN} commands that
21299 normally print messages to say what they are doing omit the messages
21300 when called from command files.
21302 @value{GDBN} also accepts command input from standard input. In this
21303 mode, normal output goes to standard output and error output goes to
21304 standard error. Errors in a command file supplied on standard input do
21305 not terminate execution of the command file---execution continues with
21309 gdb < cmds > log 2>&1
21312 (The syntax above will vary depending on the shell used.) This example
21313 will execute commands from the file @file{cmds}. All output and errors
21314 would be directed to @file{log}.
21316 Since commands stored on command files tend to be more general than
21317 commands typed interactively, they frequently need to deal with
21318 complicated situations, such as different or unexpected values of
21319 variables and symbols, changes in how the program being debugged is
21320 built, etc. @value{GDBN} provides a set of flow-control commands to
21321 deal with these complexities. Using these commands, you can write
21322 complex scripts that loop over data structures, execute commands
21323 conditionally, etc.
21330 This command allows to include in your script conditionally executed
21331 commands. The @code{if} command takes a single argument, which is an
21332 expression to evaluate. It is followed by a series of commands that
21333 are executed only if the expression is true (its value is nonzero).
21334 There can then optionally be an @code{else} line, followed by a series
21335 of commands that are only executed if the expression was false. The
21336 end of the list is marked by a line containing @code{end}.
21340 This command allows to write loops. Its syntax is similar to
21341 @code{if}: the command takes a single argument, which is an expression
21342 to evaluate, and must be followed by the commands to execute, one per
21343 line, terminated by an @code{end}. These commands are called the
21344 @dfn{body} of the loop. The commands in the body of @code{while} are
21345 executed repeatedly as long as the expression evaluates to true.
21349 This command exits the @code{while} loop in whose body it is included.
21350 Execution of the script continues after that @code{while}s @code{end}
21353 @kindex loop_continue
21354 @item loop_continue
21355 This command skips the execution of the rest of the body of commands
21356 in the @code{while} loop in whose body it is included. Execution
21357 branches to the beginning of the @code{while} loop, where it evaluates
21358 the controlling expression.
21360 @kindex end@r{ (if/else/while commands)}
21362 Terminate the block of commands that are the body of @code{if},
21363 @code{else}, or @code{while} flow-control commands.
21368 @subsection Commands for Controlled Output
21370 During the execution of a command file or a user-defined command, normal
21371 @value{GDBN} output is suppressed; the only output that appears is what is
21372 explicitly printed by the commands in the definition. This section
21373 describes three commands useful for generating exactly the output you
21378 @item echo @var{text}
21379 @c I do not consider backslash-space a standard C escape sequence
21380 @c because it is not in ANSI.
21381 Print @var{text}. Nonprinting characters can be included in
21382 @var{text} using C escape sequences, such as @samp{\n} to print a
21383 newline. @strong{No newline is printed unless you specify one.}
21384 In addition to the standard C escape sequences, a backslash followed
21385 by a space stands for a space. This is useful for displaying a
21386 string with spaces at the beginning or the end, since leading and
21387 trailing spaces are otherwise trimmed from all arguments.
21388 To print @samp{@w{ }and foo =@w{ }}, use the command
21389 @samp{echo \@w{ }and foo = \@w{ }}.
21391 A backslash at the end of @var{text} can be used, as in C, to continue
21392 the command onto subsequent lines. For example,
21395 echo This is some text\n\
21396 which is continued\n\
21397 onto several lines.\n
21400 produces the same output as
21403 echo This is some text\n
21404 echo which is continued\n
21405 echo onto several lines.\n
21409 @item output @var{expression}
21410 Print the value of @var{expression} and nothing but that value: no
21411 newlines, no @samp{$@var{nn} = }. The value is not entered in the
21412 value history either. @xref{Expressions, ,Expressions}, for more information
21415 @item output/@var{fmt} @var{expression}
21416 Print the value of @var{expression} in format @var{fmt}. You can use
21417 the same formats as for @code{print}. @xref{Output Formats,,Output
21418 Formats}, for more information.
21421 @item printf @var{template}, @var{expressions}@dots{}
21422 Print the values of one or more @var{expressions} under the control of
21423 the string @var{template}. To print several values, make
21424 @var{expressions} be a comma-separated list of individual expressions,
21425 which may be either numbers or pointers. Their values are printed as
21426 specified by @var{template}, exactly as a C program would do by
21427 executing the code below:
21430 printf (@var{template}, @var{expressions}@dots{});
21433 As in @code{C} @code{printf}, ordinary characters in @var{template}
21434 are printed verbatim, while @dfn{conversion specification} introduced
21435 by the @samp{%} character cause subsequent @var{expressions} to be
21436 evaluated, their values converted and formatted according to type and
21437 style information encoded in the conversion specifications, and then
21440 For example, you can print two values in hex like this:
21443 printf "foo, bar-foo = 0x%x, 0x%x\n", foo, bar-foo
21446 @code{printf} supports all the standard @code{C} conversion
21447 specifications, including the flags and modifiers between the @samp{%}
21448 character and the conversion letter, with the following exceptions:
21452 The argument-ordering modifiers, such as @samp{2$}, are not supported.
21455 The modifier @samp{*} is not supported for specifying precision or
21459 The @samp{'} flag (for separation of digits into groups according to
21460 @code{LC_NUMERIC'}) is not supported.
21463 The type modifiers @samp{hh}, @samp{j}, @samp{t}, and @samp{z} are not
21467 The conversion letter @samp{n} (as in @samp{%n}) is not supported.
21470 The conversion letters @samp{a} and @samp{A} are not supported.
21474 Note that the @samp{ll} type modifier is supported only if the
21475 underlying @code{C} implementation used to build @value{GDBN} supports
21476 the @code{long long int} type, and the @samp{L} type modifier is
21477 supported only if @code{long double} type is available.
21479 As in @code{C}, @code{printf} supports simple backslash-escape
21480 sequences, such as @code{\n}, @samp{\t}, @samp{\\}, @samp{\"},
21481 @samp{\a}, and @samp{\f}, that consist of backslash followed by a
21482 single character. Octal and hexadecimal escape sequences are not
21485 Additionally, @code{printf} supports conversion specifications for DFP
21486 (@dfn{Decimal Floating Point}) types using the following length modifiers
21487 together with a floating point specifier.
21492 @samp{H} for printing @code{Decimal32} types.
21495 @samp{D} for printing @code{Decimal64} types.
21498 @samp{DD} for printing @code{Decimal128} types.
21501 If the underlying @code{C} implementation used to build @value{GDBN} has
21502 support for the three length modifiers for DFP types, other modifiers
21503 such as width and precision will also be available for @value{GDBN} to use.
21505 In case there is no such @code{C} support, no additional modifiers will be
21506 available and the value will be printed in the standard way.
21508 Here's an example of printing DFP types using the above conversion letters:
21510 printf "D32: %Hf - D64: %Df - D128: %DDf\n",1.2345df,1.2E10dd,1.2E1dl
21514 @item eval @var{template}, @var{expressions}@dots{}
21515 Convert the values of one or more @var{expressions} under the control of
21516 the string @var{template} to a command line, and call it.
21521 @section Scripting @value{GDBN} using Python
21522 @cindex python scripting
21523 @cindex scripting with python
21525 You can script @value{GDBN} using the @uref{http://www.python.org/,
21526 Python programming language}. This feature is available only if
21527 @value{GDBN} was configured using @option{--with-python}.
21529 @cindex python directory
21530 Python scripts used by @value{GDBN} should be installed in
21531 @file{@var{data-directory}/python}, where @var{data-directory} is
21532 the data directory as determined at @value{GDBN} startup (@pxref{Data Files}).
21533 This directory, known as the @dfn{python directory},
21534 is automatically added to the Python Search Path in order to allow
21535 the Python interpreter to locate all scripts installed at this location.
21537 Additionally, @value{GDBN} commands and convenience functions which
21538 are written in Python and are located in the
21539 @file{@var{data-directory}/python/gdb/command} or
21540 @file{@var{data-directory}/python/gdb/function} directories are
21541 automatically imported when @value{GDBN} starts.
21544 * Python Commands:: Accessing Python from @value{GDBN}.
21545 * Python API:: Accessing @value{GDBN} from Python.
21546 * Auto-loading:: Automatically loading Python code.
21547 * Python modules:: Python modules provided by @value{GDBN}.
21550 @node Python Commands
21551 @subsection Python Commands
21552 @cindex python commands
21553 @cindex commands to access python
21555 @value{GDBN} provides one command for accessing the Python interpreter,
21556 and one related setting:
21560 @item python @r{[}@var{code}@r{]}
21561 The @code{python} command can be used to evaluate Python code.
21563 If given an argument, the @code{python} command will evaluate the
21564 argument as a Python command. For example:
21567 (@value{GDBP}) python print 23
21571 If you do not provide an argument to @code{python}, it will act as a
21572 multi-line command, like @code{define}. In this case, the Python
21573 script is made up of subsequent command lines, given after the
21574 @code{python} command. This command list is terminated using a line
21575 containing @code{end}. For example:
21578 (@value{GDBP}) python
21580 End with a line saying just "end".
21586 @kindex set python print-stack
21587 @item set python print-stack
21588 By default, @value{GDBN} will print only the message component of a
21589 Python exception when an error occurs in a Python script. This can be
21590 controlled using @code{set python print-stack}: if @code{full}, then
21591 full Python stack printing is enabled; if @code{none}, then Python stack
21592 and message printing is disabled; if @code{message}, the default, only
21593 the message component of the error is printed.
21596 It is also possible to execute a Python script from the @value{GDBN}
21600 @item source @file{script-name}
21601 The script name must end with @samp{.py} and @value{GDBN} must be configured
21602 to recognize the script language based on filename extension using
21603 the @code{script-extension} setting. @xref{Extending GDB, ,Extending GDB}.
21605 @item python execfile ("script-name")
21606 This method is based on the @code{execfile} Python built-in function,
21607 and thus is always available.
21611 @subsection Python API
21613 @cindex programming in python
21615 @cindex python stdout
21616 @cindex python pagination
21617 At startup, @value{GDBN} overrides Python's @code{sys.stdout} and
21618 @code{sys.stderr} to print using @value{GDBN}'s output-paging streams.
21619 A Python program which outputs to one of these streams may have its
21620 output interrupted by the user (@pxref{Screen Size}). In this
21621 situation, a Python @code{KeyboardInterrupt} exception is thrown.
21624 * Basic Python:: Basic Python Functions.
21625 * Exception Handling:: How Python exceptions are translated.
21626 * Values From Inferior:: Python representation of values.
21627 * Types In Python:: Python representation of types.
21628 * Pretty Printing API:: Pretty-printing values.
21629 * Selecting Pretty-Printers:: How GDB chooses a pretty-printer.
21630 * Writing a Pretty-Printer:: Writing a Pretty-Printer.
21631 * Inferiors In Python:: Python representation of inferiors (processes)
21632 * Events In Python:: Listening for events from @value{GDBN}.
21633 * Threads In Python:: Accessing inferior threads from Python.
21634 * Commands In Python:: Implementing new commands in Python.
21635 * Parameters In Python:: Adding new @value{GDBN} parameters.
21636 * Functions In Python:: Writing new convenience functions.
21637 * Progspaces In Python:: Program spaces.
21638 * Objfiles In Python:: Object files.
21639 * Frames In Python:: Accessing inferior stack frames from Python.
21640 * Blocks In Python:: Accessing frame blocks from Python.
21641 * Symbols In Python:: Python representation of symbols.
21642 * Symbol Tables In Python:: Python representation of symbol tables.
21643 * Lazy Strings In Python:: Python representation of lazy strings.
21644 * Breakpoints In Python:: Manipulating breakpoints using Python.
21645 * Finish Breakpoints in Python:: Setting Breakpoints on function return
21650 @subsubsection Basic Python
21652 @cindex python functions
21653 @cindex python module
21655 @value{GDBN} introduces a new Python module, named @code{gdb}. All
21656 methods and classes added by @value{GDBN} are placed in this module.
21657 @value{GDBN} automatically @code{import}s the @code{gdb} module for
21658 use in all scripts evaluated by the @code{python} command.
21660 @findex gdb.PYTHONDIR
21661 @defvar gdb.PYTHONDIR
21662 A string containing the python directory (@pxref{Python}).
21665 @findex gdb.execute
21666 @defun gdb.execute (command @r{[}, from_tty @r{[}, to_string@r{]]})
21667 Evaluate @var{command}, a string, as a @value{GDBN} CLI command.
21668 If a GDB exception happens while @var{command} runs, it is
21669 translated as described in @ref{Exception Handling,,Exception Handling}.
21671 @var{from_tty} specifies whether @value{GDBN} ought to consider this
21672 command as having originated from the user invoking it interactively.
21673 It must be a boolean value. If omitted, it defaults to @code{False}.
21675 By default, any output produced by @var{command} is sent to
21676 @value{GDBN}'s standard output. If the @var{to_string} parameter is
21677 @code{True}, then output will be collected by @code{gdb.execute} and
21678 returned as a string. The default is @code{False}, in which case the
21679 return value is @code{None}. If @var{to_string} is @code{True}, the
21680 @value{GDBN} virtual terminal will be temporarily set to unlimited width
21681 and height, and its pagination will be disabled; @pxref{Screen Size}.
21684 @findex gdb.breakpoints
21685 @defun gdb.breakpoints ()
21686 Return a sequence holding all of @value{GDBN}'s breakpoints.
21687 @xref{Breakpoints In Python}, for more information.
21690 @findex gdb.parameter
21691 @defun gdb.parameter (parameter)
21692 Return the value of a @value{GDBN} parameter. @var{parameter} is a
21693 string naming the parameter to look up; @var{parameter} may contain
21694 spaces if the parameter has a multi-part name. For example,
21695 @samp{print object} is a valid parameter name.
21697 If the named parameter does not exist, this function throws a
21698 @code{gdb.error} (@pxref{Exception Handling}). Otherwise, the
21699 parameter's value is converted to a Python value of the appropriate
21700 type, and returned.
21703 @findex gdb.history
21704 @defun gdb.history (number)
21705 Return a value from @value{GDBN}'s value history (@pxref{Value
21706 History}). @var{number} indicates which history element to return.
21707 If @var{number} is negative, then @value{GDBN} will take its absolute value
21708 and count backward from the last element (i.e., the most recent element) to
21709 find the value to return. If @var{number} is zero, then @value{GDBN} will
21710 return the most recent element. If the element specified by @var{number}
21711 doesn't exist in the value history, a @code{gdb.error} exception will be
21714 If no exception is raised, the return value is always an instance of
21715 @code{gdb.Value} (@pxref{Values From Inferior}).
21718 @findex gdb.parse_and_eval
21719 @defun gdb.parse_and_eval (expression)
21720 Parse @var{expression} as an expression in the current language,
21721 evaluate it, and return the result as a @code{gdb.Value}.
21722 @var{expression} must be a string.
21724 This function can be useful when implementing a new command
21725 (@pxref{Commands In Python}), as it provides a way to parse the
21726 command's argument as an expression. It is also useful simply to
21727 compute values, for example, it is the only way to get the value of a
21728 convenience variable (@pxref{Convenience Vars}) as a @code{gdb.Value}.
21731 @findex gdb.post_event
21732 @defun gdb.post_event (event)
21733 Put @var{event}, a callable object taking no arguments, into
21734 @value{GDBN}'s internal event queue. This callable will be invoked at
21735 some later point, during @value{GDBN}'s event processing. Events
21736 posted using @code{post_event} will be run in the order in which they
21737 were posted; however, there is no way to know when they will be
21738 processed relative to other events inside @value{GDBN}.
21740 @value{GDBN} is not thread-safe. If your Python program uses multiple
21741 threads, you must be careful to only call @value{GDBN}-specific
21742 functions in the main @value{GDBN} thread. @code{post_event} ensures
21746 (@value{GDBP}) python
21750 > def __init__(self, message):
21751 > self.message = message;
21752 > def __call__(self):
21753 > gdb.write(self.message)
21755 >class MyThread1 (threading.Thread):
21757 > gdb.post_event(Writer("Hello "))
21759 >class MyThread2 (threading.Thread):
21761 > gdb.post_event(Writer("World\n"))
21763 >MyThread1().start()
21764 >MyThread2().start()
21766 (@value{GDBP}) Hello World
21771 @defun gdb.write (string @r{[}, stream{]})
21772 Print a string to @value{GDBN}'s paginated output stream. The
21773 optional @var{stream} determines the stream to print to. The default
21774 stream is @value{GDBN}'s standard output stream. Possible stream
21781 @value{GDBN}'s standard output stream.
21786 @value{GDBN}'s standard error stream.
21791 @value{GDBN}'s log stream (@pxref{Logging Output}).
21794 Writing to @code{sys.stdout} or @code{sys.stderr} will automatically
21795 call this function and will automatically direct the output to the
21800 @defun gdb.flush ()
21801 Flush the buffer of a @value{GDBN} paginated stream so that the
21802 contents are displayed immediately. @value{GDBN} will flush the
21803 contents of a stream automatically when it encounters a newline in the
21804 buffer. The optional @var{stream} determines the stream to flush. The
21805 default stream is @value{GDBN}'s standard output stream. Possible
21812 @value{GDBN}'s standard output stream.
21817 @value{GDBN}'s standard error stream.
21822 @value{GDBN}'s log stream (@pxref{Logging Output}).
21826 Flushing @code{sys.stdout} or @code{sys.stderr} will automatically
21827 call this function for the relevant stream.
21830 @findex gdb.target_charset
21831 @defun gdb.target_charset ()
21832 Return the name of the current target character set (@pxref{Character
21833 Sets}). This differs from @code{gdb.parameter('target-charset')} in
21834 that @samp{auto} is never returned.
21837 @findex gdb.target_wide_charset
21838 @defun gdb.target_wide_charset ()
21839 Return the name of the current target wide character set
21840 (@pxref{Character Sets}). This differs from
21841 @code{gdb.parameter('target-wide-charset')} in that @samp{auto} is
21845 @findex gdb.solib_name
21846 @defun gdb.solib_name (address)
21847 Return the name of the shared library holding the given @var{address}
21848 as a string, or @code{None}.
21851 @findex gdb.decode_line
21852 @defun gdb.decode_line @r{[}expression@r{]}
21853 Return locations of the line specified by @var{expression}, or of the
21854 current line if no argument was given. This function returns a Python
21855 tuple containing two elements. The first element contains a string
21856 holding any unparsed section of @var{expression} (or @code{None} if
21857 the expression has been fully parsed). The second element contains
21858 either @code{None} or another tuple that contains all the locations
21859 that match the expression represented as @code{gdb.Symtab_and_line}
21860 objects (@pxref{Symbol Tables In Python}). If @var{expression} is
21861 provided, it is decoded the way that @value{GDBN}'s inbuilt
21862 @code{break} or @code{edit} commands do (@pxref{Specify Location}).
21865 @defun gdb.prompt_hook (current_prompt)
21866 @anchor{prompt_hook}
21868 If @var{prompt_hook} is callable, @value{GDBN} will call the method
21869 assigned to this operation before a prompt is displayed by
21872 The parameter @code{current_prompt} contains the current @value{GDBN}
21873 prompt. This method must return a Python string, or @code{None}. If
21874 a string is returned, the @value{GDBN} prompt will be set to that
21875 string. If @code{None} is returned, @value{GDBN} will continue to use
21876 the current prompt.
21878 Some prompts cannot be substituted in @value{GDBN}. Secondary prompts
21879 such as those used by readline for command input, and annotation
21880 related prompts are prohibited from being changed.
21883 @node Exception Handling
21884 @subsubsection Exception Handling
21885 @cindex python exceptions
21886 @cindex exceptions, python
21888 When executing the @code{python} command, Python exceptions
21889 uncaught within the Python code are translated to calls to
21890 @value{GDBN} error-reporting mechanism. If the command that called
21891 @code{python} does not handle the error, @value{GDBN} will
21892 terminate it and print an error message containing the Python
21893 exception name, the associated value, and the Python call stack
21894 backtrace at the point where the exception was raised. Example:
21897 (@value{GDBP}) python print foo
21898 Traceback (most recent call last):
21899 File "<string>", line 1, in <module>
21900 NameError: name 'foo' is not defined
21903 @value{GDBN} errors that happen in @value{GDBN} commands invoked by
21904 Python code are converted to Python exceptions. The type of the
21905 Python exception depends on the error.
21909 This is the base class for most exceptions generated by @value{GDBN}.
21910 It is derived from @code{RuntimeError}, for compatibility with earlier
21911 versions of @value{GDBN}.
21913 If an error occurring in @value{GDBN} does not fit into some more
21914 specific category, then the generated exception will have this type.
21916 @item gdb.MemoryError
21917 This is a subclass of @code{gdb.error} which is thrown when an
21918 operation tried to access invalid memory in the inferior.
21920 @item KeyboardInterrupt
21921 User interrupt (via @kbd{C-c} or by typing @kbd{q} at a pagination
21922 prompt) is translated to a Python @code{KeyboardInterrupt} exception.
21925 In all cases, your exception handler will see the @value{GDBN} error
21926 message as its value and the Python call stack backtrace at the Python
21927 statement closest to where the @value{GDBN} error occured as the
21930 @findex gdb.GdbError
21931 When implementing @value{GDBN} commands in Python via @code{gdb.Command},
21932 it is useful to be able to throw an exception that doesn't cause a
21933 traceback to be printed. For example, the user may have invoked the
21934 command incorrectly. Use the @code{gdb.GdbError} exception
21935 to handle this case. Example:
21939 >class HelloWorld (gdb.Command):
21940 > """Greet the whole world."""
21941 > def __init__ (self):
21942 > super (HelloWorld, self).__init__ ("hello-world", gdb.COMMAND_USER)
21943 > def invoke (self, args, from_tty):
21944 > argv = gdb.string_to_argv (args)
21945 > if len (argv) != 0:
21946 > raise gdb.GdbError ("hello-world takes no arguments")
21947 > print "Hello, World!"
21950 (gdb) hello-world 42
21951 hello-world takes no arguments
21954 @node Values From Inferior
21955 @subsubsection Values From Inferior
21956 @cindex values from inferior, with Python
21957 @cindex python, working with values from inferior
21959 @cindex @code{gdb.Value}
21960 @value{GDBN} provides values it obtains from the inferior program in
21961 an object of type @code{gdb.Value}. @value{GDBN} uses this object
21962 for its internal bookkeeping of the inferior's values, and for
21963 fetching values when necessary.
21965 Inferior values that are simple scalars can be used directly in
21966 Python expressions that are valid for the value's data type. Here's
21967 an example for an integer or floating-point value @code{some_val}:
21974 As result of this, @code{bar} will also be a @code{gdb.Value} object
21975 whose values are of the same type as those of @code{some_val}.
21977 Inferior values that are structures or instances of some class can
21978 be accessed using the Python @dfn{dictionary syntax}. For example, if
21979 @code{some_val} is a @code{gdb.Value} instance holding a structure, you
21980 can access its @code{foo} element with:
21983 bar = some_val['foo']
21986 Again, @code{bar} will also be a @code{gdb.Value} object.
21988 A @code{gdb.Value} that represents a function can be executed via
21989 inferior function call. Any arguments provided to the call must match
21990 the function's prototype, and must be provided in the order specified
21993 For example, @code{some_val} is a @code{gdb.Value} instance
21994 representing a function that takes two integers as arguments. To
21995 execute this function, call it like so:
21998 result = some_val (10,20)
22001 Any values returned from a function call will be stored as a
22004 The following attributes are provided:
22007 @defvar Value.address
22008 If this object is addressable, this read-only attribute holds a
22009 @code{gdb.Value} object representing the address. Otherwise,
22010 this attribute holds @code{None}.
22013 @cindex optimized out value in Python
22014 @defvar Value.is_optimized_out
22015 This read-only boolean attribute is true if the compiler optimized out
22016 this value, thus it is not available for fetching from the inferior.
22020 The type of this @code{gdb.Value}. The value of this attribute is a
22021 @code{gdb.Type} object (@pxref{Types In Python}).
22024 @defvar Value.dynamic_type
22025 The dynamic type of this @code{gdb.Value}. This uses C@t{++} run-time
22026 type information (@acronym{RTTI}) to determine the dynamic type of the
22027 value. If this value is of class type, it will return the class in
22028 which the value is embedded, if any. If this value is of pointer or
22029 reference to a class type, it will compute the dynamic type of the
22030 referenced object, and return a pointer or reference to that type,
22031 respectively. In all other cases, it will return the value's static
22034 Note that this feature will only work when debugging a C@t{++} program
22035 that includes @acronym{RTTI} for the object in question. Otherwise,
22036 it will just return the static type of the value as in @kbd{ptype foo}
22037 (@pxref{Symbols, ptype}).
22040 @defvar Value.is_lazy
22041 The value of this read-only boolean attribute is @code{True} if this
22042 @code{gdb.Value} has not yet been fetched from the inferior.
22043 @value{GDBN} does not fetch values until necessary, for efficiency.
22047 myval = gdb.parse_and_eval ('somevar')
22050 The value of @code{somevar} is not fetched at this time. It will be
22051 fetched when the value is needed, or when the @code{fetch_lazy}
22056 The following methods are provided:
22059 @defun Value.__init__ (@var{val})
22060 Many Python values can be converted directly to a @code{gdb.Value} via
22061 this object initializer. Specifically:
22064 @item Python boolean
22065 A Python boolean is converted to the boolean type from the current
22068 @item Python integer
22069 A Python integer is converted to the C @code{long} type for the
22070 current architecture.
22073 A Python long is converted to the C @code{long long} type for the
22074 current architecture.
22077 A Python float is converted to the C @code{double} type for the
22078 current architecture.
22080 @item Python string
22081 A Python string is converted to a target string, using the current
22084 @item @code{gdb.Value}
22085 If @code{val} is a @code{gdb.Value}, then a copy of the value is made.
22087 @item @code{gdb.LazyString}
22088 If @code{val} is a @code{gdb.LazyString} (@pxref{Lazy Strings In
22089 Python}), then the lazy string's @code{value} method is called, and
22090 its result is used.
22094 @defun Value.cast (type)
22095 Return a new instance of @code{gdb.Value} that is the result of
22096 casting this instance to the type described by @var{type}, which must
22097 be a @code{gdb.Type} object. If the cast cannot be performed for some
22098 reason, this method throws an exception.
22101 @defun Value.dereference ()
22102 For pointer data types, this method returns a new @code{gdb.Value} object
22103 whose contents is the object pointed to by the pointer. For example, if
22104 @code{foo} is a C pointer to an @code{int}, declared in your C program as
22111 then you can use the corresponding @code{gdb.Value} to access what
22112 @code{foo} points to like this:
22115 bar = foo.dereference ()
22118 The result @code{bar} will be a @code{gdb.Value} object holding the
22119 value pointed to by @code{foo}.
22122 @defun Value.dynamic_cast (type)
22123 Like @code{Value.cast}, but works as if the C@t{++} @code{dynamic_cast}
22124 operator were used. Consult a C@t{++} reference for details.
22127 @defun Value.reinterpret_cast (type)
22128 Like @code{Value.cast}, but works as if the C@t{++} @code{reinterpret_cast}
22129 operator were used. Consult a C@t{++} reference for details.
22132 @defun Value.string (@r{[}encoding@r{[}, errors@r{[}, length@r{]]]})
22133 If this @code{gdb.Value} represents a string, then this method
22134 converts the contents to a Python string. Otherwise, this method will
22135 throw an exception.
22137 Strings are recognized in a language-specific way; whether a given
22138 @code{gdb.Value} represents a string is determined by the current
22141 For C-like languages, a value is a string if it is a pointer to or an
22142 array of characters or ints. The string is assumed to be terminated
22143 by a zero of the appropriate width. However if the optional length
22144 argument is given, the string will be converted to that given length,
22145 ignoring any embedded zeros that the string may contain.
22147 If the optional @var{encoding} argument is given, it must be a string
22148 naming the encoding of the string in the @code{gdb.Value}, such as
22149 @code{"ascii"}, @code{"iso-8859-6"} or @code{"utf-8"}. It accepts
22150 the same encodings as the corresponding argument to Python's
22151 @code{string.decode} method, and the Python codec machinery will be used
22152 to convert the string. If @var{encoding} is not given, or if
22153 @var{encoding} is the empty string, then either the @code{target-charset}
22154 (@pxref{Character Sets}) will be used, or a language-specific encoding
22155 will be used, if the current language is able to supply one.
22157 The optional @var{errors} argument is the same as the corresponding
22158 argument to Python's @code{string.decode} method.
22160 If the optional @var{length} argument is given, the string will be
22161 fetched and converted to the given length.
22164 @defun Value.lazy_string (@r{[}encoding @r{[}, length@r{]]})
22165 If this @code{gdb.Value} represents a string, then this method
22166 converts the contents to a @code{gdb.LazyString} (@pxref{Lazy Strings
22167 In Python}). Otherwise, this method will throw an exception.
22169 If the optional @var{encoding} argument is given, it must be a string
22170 naming the encoding of the @code{gdb.LazyString}. Some examples are:
22171 @samp{ascii}, @samp{iso-8859-6} or @samp{utf-8}. If the
22172 @var{encoding} argument is an encoding that @value{GDBN} does
22173 recognize, @value{GDBN} will raise an error.
22175 When a lazy string is printed, the @value{GDBN} encoding machinery is
22176 used to convert the string during printing. If the optional
22177 @var{encoding} argument is not provided, or is an empty string,
22178 @value{GDBN} will automatically select the encoding most suitable for
22179 the string type. For further information on encoding in @value{GDBN}
22180 please see @ref{Character Sets}.
22182 If the optional @var{length} argument is given, the string will be
22183 fetched and encoded to the length of characters specified. If
22184 the @var{length} argument is not provided, the string will be fetched
22185 and encoded until a null of appropriate width is found.
22188 @defun Value.fetch_lazy ()
22189 If the @code{gdb.Value} object is currently a lazy value
22190 (@code{gdb.Value.is_lazy} is @code{True}), then the value is
22191 fetched from the inferior. Any errors that occur in the process
22192 will produce a Python exception.
22194 If the @code{gdb.Value} object is not a lazy value, this method
22197 This method does not return a value.
22202 @node Types In Python
22203 @subsubsection Types In Python
22204 @cindex types in Python
22205 @cindex Python, working with types
22208 @value{GDBN} represents types from the inferior using the class
22211 The following type-related functions are available in the @code{gdb}
22214 @findex gdb.lookup_type
22215 @defun gdb.lookup_type (name @r{[}, block@r{]})
22216 This function looks up a type by name. @var{name} is the name of the
22217 type to look up. It must be a string.
22219 If @var{block} is given, then @var{name} is looked up in that scope.
22220 Otherwise, it is searched for globally.
22222 Ordinarily, this function will return an instance of @code{gdb.Type}.
22223 If the named type cannot be found, it will throw an exception.
22226 If the type is a structure or class type, or an enum type, the fields
22227 of that type can be accessed using the Python @dfn{dictionary syntax}.
22228 For example, if @code{some_type} is a @code{gdb.Type} instance holding
22229 a structure type, you can access its @code{foo} field with:
22232 bar = some_type['foo']
22235 @code{bar} will be a @code{gdb.Field} object; see below under the
22236 description of the @code{Type.fields} method for a description of the
22237 @code{gdb.Field} class.
22239 An instance of @code{Type} has the following attributes:
22243 The type code for this type. The type code will be one of the
22244 @code{TYPE_CODE_} constants defined below.
22247 @defvar Type.sizeof
22248 The size of this type, in target @code{char} units. Usually, a
22249 target's @code{char} type will be an 8-bit byte. However, on some
22250 unusual platforms, this type may have a different size.
22254 The tag name for this type. The tag name is the name after
22255 @code{struct}, @code{union}, or @code{enum} in C and C@t{++}; not all
22256 languages have this concept. If this type has no tag name, then
22257 @code{None} is returned.
22261 The following methods are provided:
22264 @defun Type.fields ()
22265 For structure and union types, this method returns the fields. Range
22266 types have two fields, the minimum and maximum values. Enum types
22267 have one field per enum constant. Function and method types have one
22268 field per parameter. The base types of C@t{++} classes are also
22269 represented as fields. If the type has no fields, or does not fit
22270 into one of these categories, an empty sequence will be returned.
22272 Each field is a @code{gdb.Field} object, with some pre-defined attributes:
22275 This attribute is not available for @code{static} fields (as in
22276 C@t{++} or Java). For non-@code{static} fields, the value is the bit
22277 position of the field. For @code{enum} fields, the value is the
22278 enumeration member's integer representation.
22281 The name of the field, or @code{None} for anonymous fields.
22284 This is @code{True} if the field is artificial, usually meaning that
22285 it was provided by the compiler and not the user. This attribute is
22286 always provided, and is @code{False} if the field is not artificial.
22288 @item is_base_class
22289 This is @code{True} if the field represents a base class of a C@t{++}
22290 structure. This attribute is always provided, and is @code{False}
22291 if the field is not a base class of the type that is the argument of
22292 @code{fields}, or if that type was not a C@t{++} class.
22295 If the field is packed, or is a bitfield, then this will have a
22296 non-zero value, which is the size of the field in bits. Otherwise,
22297 this will be zero; in this case the field's size is given by its type.
22300 The type of the field. This is usually an instance of @code{Type},
22301 but it can be @code{None} in some situations.
22305 @defun Type.array (@var{n1} @r{[}, @var{n2}@r{]})
22306 Return a new @code{gdb.Type} object which represents an array of this
22307 type. If one argument is given, it is the inclusive upper bound of
22308 the array; in this case the lower bound is zero. If two arguments are
22309 given, the first argument is the lower bound of the array, and the
22310 second argument is the upper bound of the array. An array's length
22311 must not be negative, but the bounds can be.
22314 @defun Type.const ()
22315 Return a new @code{gdb.Type} object which represents a
22316 @code{const}-qualified variant of this type.
22319 @defun Type.volatile ()
22320 Return a new @code{gdb.Type} object which represents a
22321 @code{volatile}-qualified variant of this type.
22324 @defun Type.unqualified ()
22325 Return a new @code{gdb.Type} object which represents an unqualified
22326 variant of this type. That is, the result is neither @code{const} nor
22330 @defun Type.range ()
22331 Return a Python @code{Tuple} object that contains two elements: the
22332 low bound of the argument type and the high bound of that type. If
22333 the type does not have a range, @value{GDBN} will raise a
22334 @code{gdb.error} exception (@pxref{Exception Handling}).
22337 @defun Type.reference ()
22338 Return a new @code{gdb.Type} object which represents a reference to this
22342 @defun Type.pointer ()
22343 Return a new @code{gdb.Type} object which represents a pointer to this
22347 @defun Type.strip_typedefs ()
22348 Return a new @code{gdb.Type} that represents the real type,
22349 after removing all layers of typedefs.
22352 @defun Type.target ()
22353 Return a new @code{gdb.Type} object which represents the target type
22356 For a pointer type, the target type is the type of the pointed-to
22357 object. For an array type (meaning C-like arrays), the target type is
22358 the type of the elements of the array. For a function or method type,
22359 the target type is the type of the return value. For a complex type,
22360 the target type is the type of the elements. For a typedef, the
22361 target type is the aliased type.
22363 If the type does not have a target, this method will throw an
22367 @defun Type.template_argument (n @r{[}, block@r{]})
22368 If this @code{gdb.Type} is an instantiation of a template, this will
22369 return a new @code{gdb.Type} which represents the type of the
22370 @var{n}th template argument.
22372 If this @code{gdb.Type} is not a template type, this will throw an
22373 exception. Ordinarily, only C@t{++} code will have template types.
22375 If @var{block} is given, then @var{name} is looked up in that scope.
22376 Otherwise, it is searched for globally.
22381 Each type has a code, which indicates what category this type falls
22382 into. The available type categories are represented by constants
22383 defined in the @code{gdb} module:
22386 @findex TYPE_CODE_PTR
22387 @findex gdb.TYPE_CODE_PTR
22388 @item gdb.TYPE_CODE_PTR
22389 The type is a pointer.
22391 @findex TYPE_CODE_ARRAY
22392 @findex gdb.TYPE_CODE_ARRAY
22393 @item gdb.TYPE_CODE_ARRAY
22394 The type is an array.
22396 @findex TYPE_CODE_STRUCT
22397 @findex gdb.TYPE_CODE_STRUCT
22398 @item gdb.TYPE_CODE_STRUCT
22399 The type is a structure.
22401 @findex TYPE_CODE_UNION
22402 @findex gdb.TYPE_CODE_UNION
22403 @item gdb.TYPE_CODE_UNION
22404 The type is a union.
22406 @findex TYPE_CODE_ENUM
22407 @findex gdb.TYPE_CODE_ENUM
22408 @item gdb.TYPE_CODE_ENUM
22409 The type is an enum.
22411 @findex TYPE_CODE_FLAGS
22412 @findex gdb.TYPE_CODE_FLAGS
22413 @item gdb.TYPE_CODE_FLAGS
22414 A bit flags type, used for things such as status registers.
22416 @findex TYPE_CODE_FUNC
22417 @findex gdb.TYPE_CODE_FUNC
22418 @item gdb.TYPE_CODE_FUNC
22419 The type is a function.
22421 @findex TYPE_CODE_INT
22422 @findex gdb.TYPE_CODE_INT
22423 @item gdb.TYPE_CODE_INT
22424 The type is an integer type.
22426 @findex TYPE_CODE_FLT
22427 @findex gdb.TYPE_CODE_FLT
22428 @item gdb.TYPE_CODE_FLT
22429 A floating point type.
22431 @findex TYPE_CODE_VOID
22432 @findex gdb.TYPE_CODE_VOID
22433 @item gdb.TYPE_CODE_VOID
22434 The special type @code{void}.
22436 @findex TYPE_CODE_SET
22437 @findex gdb.TYPE_CODE_SET
22438 @item gdb.TYPE_CODE_SET
22441 @findex TYPE_CODE_RANGE
22442 @findex gdb.TYPE_CODE_RANGE
22443 @item gdb.TYPE_CODE_RANGE
22444 A range type, that is, an integer type with bounds.
22446 @findex TYPE_CODE_STRING
22447 @findex gdb.TYPE_CODE_STRING
22448 @item gdb.TYPE_CODE_STRING
22449 A string type. Note that this is only used for certain languages with
22450 language-defined string types; C strings are not represented this way.
22452 @findex TYPE_CODE_BITSTRING
22453 @findex gdb.TYPE_CODE_BITSTRING
22454 @item gdb.TYPE_CODE_BITSTRING
22457 @findex TYPE_CODE_ERROR
22458 @findex gdb.TYPE_CODE_ERROR
22459 @item gdb.TYPE_CODE_ERROR
22460 An unknown or erroneous type.
22462 @findex TYPE_CODE_METHOD
22463 @findex gdb.TYPE_CODE_METHOD
22464 @item gdb.TYPE_CODE_METHOD
22465 A method type, as found in C@t{++} or Java.
22467 @findex TYPE_CODE_METHODPTR
22468 @findex gdb.TYPE_CODE_METHODPTR
22469 @item gdb.TYPE_CODE_METHODPTR
22470 A pointer-to-member-function.
22472 @findex TYPE_CODE_MEMBERPTR
22473 @findex gdb.TYPE_CODE_MEMBERPTR
22474 @item gdb.TYPE_CODE_MEMBERPTR
22475 A pointer-to-member.
22477 @findex TYPE_CODE_REF
22478 @findex gdb.TYPE_CODE_REF
22479 @item gdb.TYPE_CODE_REF
22482 @findex TYPE_CODE_CHAR
22483 @findex gdb.TYPE_CODE_CHAR
22484 @item gdb.TYPE_CODE_CHAR
22487 @findex TYPE_CODE_BOOL
22488 @findex gdb.TYPE_CODE_BOOL
22489 @item gdb.TYPE_CODE_BOOL
22492 @findex TYPE_CODE_COMPLEX
22493 @findex gdb.TYPE_CODE_COMPLEX
22494 @item gdb.TYPE_CODE_COMPLEX
22495 A complex float type.
22497 @findex TYPE_CODE_TYPEDEF
22498 @findex gdb.TYPE_CODE_TYPEDEF
22499 @item gdb.TYPE_CODE_TYPEDEF
22500 A typedef to some other type.
22502 @findex TYPE_CODE_NAMESPACE
22503 @findex gdb.TYPE_CODE_NAMESPACE
22504 @item gdb.TYPE_CODE_NAMESPACE
22505 A C@t{++} namespace.
22507 @findex TYPE_CODE_DECFLOAT
22508 @findex gdb.TYPE_CODE_DECFLOAT
22509 @item gdb.TYPE_CODE_DECFLOAT
22510 A decimal floating point type.
22512 @findex TYPE_CODE_INTERNAL_FUNCTION
22513 @findex gdb.TYPE_CODE_INTERNAL_FUNCTION
22514 @item gdb.TYPE_CODE_INTERNAL_FUNCTION
22515 A function internal to @value{GDBN}. This is the type used to represent
22516 convenience functions.
22519 Further support for types is provided in the @code{gdb.types}
22520 Python module (@pxref{gdb.types}).
22522 @node Pretty Printing API
22523 @subsubsection Pretty Printing API
22525 An example output is provided (@pxref{Pretty Printing}).
22527 A pretty-printer is just an object that holds a value and implements a
22528 specific interface, defined here.
22530 @defun pretty_printer.children (self)
22531 @value{GDBN} will call this method on a pretty-printer to compute the
22532 children of the pretty-printer's value.
22534 This method must return an object conforming to the Python iterator
22535 protocol. Each item returned by the iterator must be a tuple holding
22536 two elements. The first element is the ``name'' of the child; the
22537 second element is the child's value. The value can be any Python
22538 object which is convertible to a @value{GDBN} value.
22540 This method is optional. If it does not exist, @value{GDBN} will act
22541 as though the value has no children.
22544 @defun pretty_printer.display_hint (self)
22545 The CLI may call this method and use its result to change the
22546 formatting of a value. The result will also be supplied to an MI
22547 consumer as a @samp{displayhint} attribute of the variable being
22550 This method is optional. If it does exist, this method must return a
22553 Some display hints are predefined by @value{GDBN}:
22557 Indicate that the object being printed is ``array-like''. The CLI
22558 uses this to respect parameters such as @code{set print elements} and
22559 @code{set print array}.
22562 Indicate that the object being printed is ``map-like'', and that the
22563 children of this value can be assumed to alternate between keys and
22567 Indicate that the object being printed is ``string-like''. If the
22568 printer's @code{to_string} method returns a Python string of some
22569 kind, then @value{GDBN} will call its internal language-specific
22570 string-printing function to format the string. For the CLI this means
22571 adding quotation marks, possibly escaping some characters, respecting
22572 @code{set print elements}, and the like.
22576 @defun pretty_printer.to_string (self)
22577 @value{GDBN} will call this method to display the string
22578 representation of the value passed to the object's constructor.
22580 When printing from the CLI, if the @code{to_string} method exists,
22581 then @value{GDBN} will prepend its result to the values returned by
22582 @code{children}. Exactly how this formatting is done is dependent on
22583 the display hint, and may change as more hints are added. Also,
22584 depending on the print settings (@pxref{Print Settings}), the CLI may
22585 print just the result of @code{to_string} in a stack trace, omitting
22586 the result of @code{children}.
22588 If this method returns a string, it is printed verbatim.
22590 Otherwise, if this method returns an instance of @code{gdb.Value},
22591 then @value{GDBN} prints this value. This may result in a call to
22592 another pretty-printer.
22594 If instead the method returns a Python value which is convertible to a
22595 @code{gdb.Value}, then @value{GDBN} performs the conversion and prints
22596 the resulting value. Again, this may result in a call to another
22597 pretty-printer. Python scalars (integers, floats, and booleans) and
22598 strings are convertible to @code{gdb.Value}; other types are not.
22600 Finally, if this method returns @code{None} then no further operations
22601 are peformed in this method and nothing is printed.
22603 If the result is not one of these types, an exception is raised.
22606 @value{GDBN} provides a function which can be used to look up the
22607 default pretty-printer for a @code{gdb.Value}:
22609 @findex gdb.default_visualizer
22610 @defun gdb.default_visualizer (value)
22611 This function takes a @code{gdb.Value} object as an argument. If a
22612 pretty-printer for this value exists, then it is returned. If no such
22613 printer exists, then this returns @code{None}.
22616 @node Selecting Pretty-Printers
22617 @subsubsection Selecting Pretty-Printers
22619 The Python list @code{gdb.pretty_printers} contains an array of
22620 functions or callable objects that have been registered via addition
22621 as a pretty-printer. Printers in this list are called @code{global}
22622 printers, they're available when debugging all inferiors.
22623 Each @code{gdb.Progspace} contains a @code{pretty_printers} attribute.
22624 Each @code{gdb.Objfile} also contains a @code{pretty_printers}
22627 Each function on these lists is passed a single @code{gdb.Value}
22628 argument and should return a pretty-printer object conforming to the
22629 interface definition above (@pxref{Pretty Printing API}). If a function
22630 cannot create a pretty-printer for the value, it should return
22633 @value{GDBN} first checks the @code{pretty_printers} attribute of each
22634 @code{gdb.Objfile} in the current program space and iteratively calls
22635 each enabled lookup routine in the list for that @code{gdb.Objfile}
22636 until it receives a pretty-printer object.
22637 If no pretty-printer is found in the objfile lists, @value{GDBN} then
22638 searches the pretty-printer list of the current program space,
22639 calling each enabled function until an object is returned.
22640 After these lists have been exhausted, it tries the global
22641 @code{gdb.pretty_printers} list, again calling each enabled function until an
22642 object is returned.
22644 The order in which the objfiles are searched is not specified. For a
22645 given list, functions are always invoked from the head of the list,
22646 and iterated over sequentially until the end of the list, or a printer
22647 object is returned.
22649 For various reasons a pretty-printer may not work.
22650 For example, the underlying data structure may have changed and
22651 the pretty-printer is out of date.
22653 The consequences of a broken pretty-printer are severe enough that
22654 @value{GDBN} provides support for enabling and disabling individual
22655 printers. For example, if @code{print frame-arguments} is on,
22656 a backtrace can become highly illegible if any argument is printed
22657 with a broken printer.
22659 Pretty-printers are enabled and disabled by attaching an @code{enabled}
22660 attribute to the registered function or callable object. If this attribute
22661 is present and its value is @code{False}, the printer is disabled, otherwise
22662 the printer is enabled.
22664 @node Writing a Pretty-Printer
22665 @subsubsection Writing a Pretty-Printer
22666 @cindex writing a pretty-printer
22668 A pretty-printer consists of two parts: a lookup function to detect
22669 if the type is supported, and the printer itself.
22671 Here is an example showing how a @code{std::string} printer might be
22672 written. @xref{Pretty Printing API}, for details on the API this class
22676 class StdStringPrinter(object):
22677 "Print a std::string"
22679 def __init__(self, val):
22682 def to_string(self):
22683 return self.val['_M_dataplus']['_M_p']
22685 def display_hint(self):
22689 And here is an example showing how a lookup function for the printer
22690 example above might be written.
22693 def str_lookup_function(val):
22694 lookup_tag = val.type.tag
22695 if lookup_tag == None:
22697 regex = re.compile("^std::basic_string<char,.*>$")
22698 if regex.match(lookup_tag):
22699 return StdStringPrinter(val)
22703 The example lookup function extracts the value's type, and attempts to
22704 match it to a type that it can pretty-print. If it is a type the
22705 printer can pretty-print, it will return a printer object. If not, it
22706 returns @code{None}.
22708 We recommend that you put your core pretty-printers into a Python
22709 package. If your pretty-printers are for use with a library, we
22710 further recommend embedding a version number into the package name.
22711 This practice will enable @value{GDBN} to load multiple versions of
22712 your pretty-printers at the same time, because they will have
22715 You should write auto-loaded code (@pxref{Auto-loading}) such that it
22716 can be evaluated multiple times without changing its meaning. An
22717 ideal auto-load file will consist solely of @code{import}s of your
22718 printer modules, followed by a call to a register pretty-printers with
22719 the current objfile.
22721 Taken as a whole, this approach will scale nicely to multiple
22722 inferiors, each potentially using a different library version.
22723 Embedding a version number in the Python package name will ensure that
22724 @value{GDBN} is able to load both sets of printers simultaneously.
22725 Then, because the search for pretty-printers is done by objfile, and
22726 because your auto-loaded code took care to register your library's
22727 printers with a specific objfile, @value{GDBN} will find the correct
22728 printers for the specific version of the library used by each
22731 To continue the @code{std::string} example (@pxref{Pretty Printing API}),
22732 this code might appear in @code{gdb.libstdcxx.v6}:
22735 def register_printers(objfile):
22736 objfile.pretty_printers.append(str_lookup_function)
22740 And then the corresponding contents of the auto-load file would be:
22743 import gdb.libstdcxx.v6
22744 gdb.libstdcxx.v6.register_printers(gdb.current_objfile())
22747 The previous example illustrates a basic pretty-printer.
22748 There are a few things that can be improved on.
22749 The printer doesn't have a name, making it hard to identify in a
22750 list of installed printers. The lookup function has a name, but
22751 lookup functions can have arbitrary, even identical, names.
22753 Second, the printer only handles one type, whereas a library typically has
22754 several types. One could install a lookup function for each desired type
22755 in the library, but one could also have a single lookup function recognize
22756 several types. The latter is the conventional way this is handled.
22757 If a pretty-printer can handle multiple data types, then its
22758 @dfn{subprinters} are the printers for the individual data types.
22760 The @code{gdb.printing} module provides a formal way of solving these
22761 problems (@pxref{gdb.printing}).
22762 Here is another example that handles multiple types.
22764 These are the types we are going to pretty-print:
22767 struct foo @{ int a, b; @};
22768 struct bar @{ struct foo x, y; @};
22771 Here are the printers:
22775 """Print a foo object."""
22777 def __init__(self, val):
22780 def to_string(self):
22781 return ("a=<" + str(self.val["a"]) +
22782 "> b=<" + str(self.val["b"]) + ">")
22785 """Print a bar object."""
22787 def __init__(self, val):
22790 def to_string(self):
22791 return ("x=<" + str(self.val["x"]) +
22792 "> y=<" + str(self.val["y"]) + ">")
22795 This example doesn't need a lookup function, that is handled by the
22796 @code{gdb.printing} module. Instead a function is provided to build up
22797 the object that handles the lookup.
22800 import gdb.printing
22802 def build_pretty_printer():
22803 pp = gdb.printing.RegexpCollectionPrettyPrinter(
22805 pp.add_printer('foo', '^foo$', fooPrinter)
22806 pp.add_printer('bar', '^bar$', barPrinter)
22810 And here is the autoload support:
22813 import gdb.printing
22815 gdb.printing.register_pretty_printer(
22816 gdb.current_objfile(),
22817 my_library.build_pretty_printer())
22820 Finally, when this printer is loaded into @value{GDBN}, here is the
22821 corresponding output of @samp{info pretty-printer}:
22824 (gdb) info pretty-printer
22831 @node Inferiors In Python
22832 @subsubsection Inferiors In Python
22833 @cindex inferiors in Python
22835 @findex gdb.Inferior
22836 Programs which are being run under @value{GDBN} are called inferiors
22837 (@pxref{Inferiors and Programs}). Python scripts can access
22838 information about and manipulate inferiors controlled by @value{GDBN}
22839 via objects of the @code{gdb.Inferior} class.
22841 The following inferior-related functions are available in the @code{gdb}
22844 @defun gdb.inferiors ()
22845 Return a tuple containing all inferior objects.
22848 @defun gdb.selected_inferior ()
22849 Return an object representing the current inferior.
22852 A @code{gdb.Inferior} object has the following attributes:
22855 @defvar Inferior.num
22856 ID of inferior, as assigned by GDB.
22859 @defvar Inferior.pid
22860 Process ID of the inferior, as assigned by the underlying operating
22864 @defvar Inferior.was_attached
22865 Boolean signaling whether the inferior was created using `attach', or
22866 started by @value{GDBN} itself.
22870 A @code{gdb.Inferior} object has the following methods:
22873 @defun Inferior.is_valid ()
22874 Returns @code{True} if the @code{gdb.Inferior} object is valid,
22875 @code{False} if not. A @code{gdb.Inferior} object will become invalid
22876 if the inferior no longer exists within @value{GDBN}. All other
22877 @code{gdb.Inferior} methods will throw an exception if it is invalid
22878 at the time the method is called.
22881 @defun Inferior.threads ()
22882 This method returns a tuple holding all the threads which are valid
22883 when it is called. If there are no valid threads, the method will
22884 return an empty tuple.
22887 @findex gdb.read_memory
22888 @defun Inferior.read_memory (address, length)
22889 Read @var{length} bytes of memory from the inferior, starting at
22890 @var{address}. Returns a buffer object, which behaves much like an array
22891 or a string. It can be modified and given to the @code{gdb.write_memory}
22895 @findex gdb.write_memory
22896 @defun Inferior.write_memory (address, buffer @r{[}, length@r{]})
22897 Write the contents of @var{buffer} to the inferior, starting at
22898 @var{address}. The @var{buffer} parameter must be a Python object
22899 which supports the buffer protocol, i.e., a string, an array or the
22900 object returned from @code{gdb.read_memory}. If given, @var{length}
22901 determines the number of bytes from @var{buffer} to be written.
22904 @findex gdb.search_memory
22905 @defun Inferior.search_memory (address, length, pattern)
22906 Search a region of the inferior memory starting at @var{address} with
22907 the given @var{length} using the search pattern supplied in
22908 @var{pattern}. The @var{pattern} parameter must be a Python object
22909 which supports the buffer protocol, i.e., a string, an array or the
22910 object returned from @code{gdb.read_memory}. Returns a Python @code{Long}
22911 containing the address where the pattern was found, or @code{None} if
22912 the pattern could not be found.
22916 @node Events In Python
22917 @subsubsection Events In Python
22918 @cindex inferior events in Python
22920 @value{GDBN} provides a general event facility so that Python code can be
22921 notified of various state changes, particularly changes that occur in
22924 An @dfn{event} is just an object that describes some state change. The
22925 type of the object and its attributes will vary depending on the details
22926 of the change. All the existing events are described below.
22928 In order to be notified of an event, you must register an event handler
22929 with an @dfn{event registry}. An event registry is an object in the
22930 @code{gdb.events} module which dispatches particular events. A registry
22931 provides methods to register and unregister event handlers:
22934 @defun EventRegistry.connect (object)
22935 Add the given callable @var{object} to the registry. This object will be
22936 called when an event corresponding to this registry occurs.
22939 @defun EventRegistry.disconnect (object)
22940 Remove the given @var{object} from the registry. Once removed, the object
22941 will no longer receive notifications of events.
22945 Here is an example:
22948 def exit_handler (event):
22949 print "event type: exit"
22950 print "exit code: %d" % (event.exit_code)
22952 gdb.events.exited.connect (exit_handler)
22955 In the above example we connect our handler @code{exit_handler} to the
22956 registry @code{events.exited}. Once connected, @code{exit_handler} gets
22957 called when the inferior exits. The argument @dfn{event} in this example is
22958 of type @code{gdb.ExitedEvent}. As you can see in the example the
22959 @code{ExitedEvent} object has an attribute which indicates the exit code of
22962 The following is a listing of the event registries that are available and
22963 details of the events they emit:
22968 Emits @code{gdb.ThreadEvent}.
22970 Some events can be thread specific when @value{GDBN} is running in non-stop
22971 mode. When represented in Python, these events all extend
22972 @code{gdb.ThreadEvent}. Note, this event is not emitted directly; instead,
22973 events which are emitted by this or other modules might extend this event.
22974 Examples of these events are @code{gdb.BreakpointEvent} and
22975 @code{gdb.ContinueEvent}.
22978 @defvar ThreadEvent.inferior_thread
22979 In non-stop mode this attribute will be set to the specific thread which was
22980 involved in the emitted event. Otherwise, it will be set to @code{None}.
22984 Emits @code{gdb.ContinueEvent} which extends @code{gdb.ThreadEvent}.
22986 This event indicates that the inferior has been continued after a stop. For
22987 inherited attribute refer to @code{gdb.ThreadEvent} above.
22989 @item events.exited
22990 Emits @code{events.ExitedEvent} which indicates that the inferior has exited.
22991 @code{events.ExitedEvent} has two attributes:
22993 @defvar ExitedEvent.exit_code
22994 An integer representing the exit code, if available, which the inferior
22995 has returned. (The exit code could be unavailable if, for example,
22996 @value{GDBN} detaches from the inferior.) If the exit code is unavailable,
22997 the attribute does not exist.
22999 @defvar ExitedEvent inferior
23000 A reference to the inferior which triggered the @code{exited} event.
23005 Emits @code{gdb.StopEvent} which extends @code{gdb.ThreadEvent}.
23007 Indicates that the inferior has stopped. All events emitted by this registry
23008 extend StopEvent. As a child of @code{gdb.ThreadEvent}, @code{gdb.StopEvent}
23009 will indicate the stopped thread when @value{GDBN} is running in non-stop
23010 mode. Refer to @code{gdb.ThreadEvent} above for more details.
23012 Emits @code{gdb.SignalEvent} which extends @code{gdb.StopEvent}.
23014 This event indicates that the inferior or one of its threads has received as
23015 signal. @code{gdb.SignalEvent} has the following attributes:
23018 @defvar SignalEvent.stop_signal
23019 A string representing the signal received by the inferior. A list of possible
23020 signal values can be obtained by running the command @code{info signals} in
23021 the @value{GDBN} command prompt.
23025 Also emits @code{gdb.BreakpointEvent} which extends @code{gdb.StopEvent}.
23027 @code{gdb.BreakpointEvent} event indicates that one or more breakpoints have
23028 been hit, and has the following attributes:
23031 @defvar BreakpointEvent.breakpoints
23032 A sequence containing references to all the breakpoints (type
23033 @code{gdb.Breakpoint}) that were hit.
23034 @xref{Breakpoints In Python}, for details of the @code{gdb.Breakpoint} object.
23036 @defvar BreakpointEvent.breakpoint
23037 A reference to the first breakpoint that was hit.
23038 This function is maintained for backward compatibility and is now deprecated
23039 in favor of the @code{gdb.BreakpointEvent.breakpoints} attribute.
23043 @item events.new_objfile
23044 Emits @code{gdb.NewObjFileEvent} which indicates that a new object file has
23045 been loaded by @value{GDBN}. @code{gdb.NewObjFileEvent} has one attribute:
23048 @defvar NewObjFileEvent.new_objfile
23049 A reference to the object file (@code{gdb.Objfile}) which has been loaded.
23050 @xref{Objfiles In Python}, for details of the @code{gdb.Objfile} object.
23056 @node Threads In Python
23057 @subsubsection Threads In Python
23058 @cindex threads in python
23060 @findex gdb.InferiorThread
23061 Python scripts can access information about, and manipulate inferior threads
23062 controlled by @value{GDBN}, via objects of the @code{gdb.InferiorThread} class.
23064 The following thread-related functions are available in the @code{gdb}
23067 @findex gdb.selected_thread
23068 @defun gdb.selected_thread ()
23069 This function returns the thread object for the selected thread. If there
23070 is no selected thread, this will return @code{None}.
23073 A @code{gdb.InferiorThread} object has the following attributes:
23076 @defvar InferiorThread.name
23077 The name of the thread. If the user specified a name using
23078 @code{thread name}, then this returns that name. Otherwise, if an
23079 OS-supplied name is available, then it is returned. Otherwise, this
23080 returns @code{None}.
23082 This attribute can be assigned to. The new value must be a string
23083 object, which sets the new name, or @code{None}, which removes any
23084 user-specified thread name.
23087 @defvar InferiorThread.num
23088 ID of the thread, as assigned by GDB.
23091 @defvar InferiorThread.ptid
23092 ID of the thread, as assigned by the operating system. This attribute is a
23093 tuple containing three integers. The first is the Process ID (PID); the second
23094 is the Lightweight Process ID (LWPID), and the third is the Thread ID (TID).
23095 Either the LWPID or TID may be 0, which indicates that the operating system
23096 does not use that identifier.
23100 A @code{gdb.InferiorThread} object has the following methods:
23103 @defun InferiorThread.is_valid ()
23104 Returns @code{True} if the @code{gdb.InferiorThread} object is valid,
23105 @code{False} if not. A @code{gdb.InferiorThread} object will become
23106 invalid if the thread exits, or the inferior that the thread belongs
23107 is deleted. All other @code{gdb.InferiorThread} methods will throw an
23108 exception if it is invalid at the time the method is called.
23111 @defun InferiorThread.switch ()
23112 This changes @value{GDBN}'s currently selected thread to the one represented
23116 @defun InferiorThread.is_stopped ()
23117 Return a Boolean indicating whether the thread is stopped.
23120 @defun InferiorThread.is_running ()
23121 Return a Boolean indicating whether the thread is running.
23124 @defun InferiorThread.is_exited ()
23125 Return a Boolean indicating whether the thread is exited.
23129 @node Commands In Python
23130 @subsubsection Commands In Python
23132 @cindex commands in python
23133 @cindex python commands
23134 You can implement new @value{GDBN} CLI commands in Python. A CLI
23135 command is implemented using an instance of the @code{gdb.Command}
23136 class, most commonly using a subclass.
23138 @defun Command.__init__ (name, @var{command_class} @r{[}, @var{completer_class} @r{[}, @var{prefix}@r{]]})
23139 The object initializer for @code{Command} registers the new command
23140 with @value{GDBN}. This initializer is normally invoked from the
23141 subclass' own @code{__init__} method.
23143 @var{name} is the name of the command. If @var{name} consists of
23144 multiple words, then the initial words are looked for as prefix
23145 commands. In this case, if one of the prefix commands does not exist,
23146 an exception is raised.
23148 There is no support for multi-line commands.
23150 @var{command_class} should be one of the @samp{COMMAND_} constants
23151 defined below. This argument tells @value{GDBN} how to categorize the
23152 new command in the help system.
23154 @var{completer_class} is an optional argument. If given, it should be
23155 one of the @samp{COMPLETE_} constants defined below. This argument
23156 tells @value{GDBN} how to perform completion for this command. If not
23157 given, @value{GDBN} will attempt to complete using the object's
23158 @code{complete} method (see below); if no such method is found, an
23159 error will occur when completion is attempted.
23161 @var{prefix} is an optional argument. If @code{True}, then the new
23162 command is a prefix command; sub-commands of this command may be
23165 The help text for the new command is taken from the Python
23166 documentation string for the command's class, if there is one. If no
23167 documentation string is provided, the default value ``This command is
23168 not documented.'' is used.
23171 @cindex don't repeat Python command
23172 @defun Command.dont_repeat ()
23173 By default, a @value{GDBN} command is repeated when the user enters a
23174 blank line at the command prompt. A command can suppress this
23175 behavior by invoking the @code{dont_repeat} method. This is similar
23176 to the user command @code{dont-repeat}, see @ref{Define, dont-repeat}.
23179 @defun Command.invoke (argument, from_tty)
23180 This method is called by @value{GDBN} when this command is invoked.
23182 @var{argument} is a string. It is the argument to the command, after
23183 leading and trailing whitespace has been stripped.
23185 @var{from_tty} is a boolean argument. When true, this means that the
23186 command was entered by the user at the terminal; when false it means
23187 that the command came from elsewhere.
23189 If this method throws an exception, it is turned into a @value{GDBN}
23190 @code{error} call. Otherwise, the return value is ignored.
23192 @findex gdb.string_to_argv
23193 To break @var{argument} up into an argv-like string use
23194 @code{gdb.string_to_argv}. This function behaves identically to
23195 @value{GDBN}'s internal argument lexer @code{buildargv}.
23196 It is recommended to use this for consistency.
23197 Arguments are separated by spaces and may be quoted.
23201 print gdb.string_to_argv ("1 2\ \\\"3 '4 \"5' \"6 '7\"")
23202 ['1', '2 "3', '4 "5', "6 '7"]
23207 @cindex completion of Python commands
23208 @defun Command.complete (text, word)
23209 This method is called by @value{GDBN} when the user attempts
23210 completion on this command. All forms of completion are handled by
23211 this method, that is, the @key{TAB} and @key{M-?} key bindings
23212 (@pxref{Completion}), and the @code{complete} command (@pxref{Help,
23215 The arguments @var{text} and @var{word} are both strings. @var{text}
23216 holds the complete command line up to the cursor's location.
23217 @var{word} holds the last word of the command line; this is computed
23218 using a word-breaking heuristic.
23220 The @code{complete} method can return several values:
23223 If the return value is a sequence, the contents of the sequence are
23224 used as the completions. It is up to @code{complete} to ensure that the
23225 contents actually do complete the word. A zero-length sequence is
23226 allowed, it means that there were no completions available. Only
23227 string elements of the sequence are used; other elements in the
23228 sequence are ignored.
23231 If the return value is one of the @samp{COMPLETE_} constants defined
23232 below, then the corresponding @value{GDBN}-internal completion
23233 function is invoked, and its result is used.
23236 All other results are treated as though there were no available
23241 When a new command is registered, it must be declared as a member of
23242 some general class of commands. This is used to classify top-level
23243 commands in the on-line help system; note that prefix commands are not
23244 listed under their own category but rather that of their top-level
23245 command. The available classifications are represented by constants
23246 defined in the @code{gdb} module:
23249 @findex COMMAND_NONE
23250 @findex gdb.COMMAND_NONE
23251 @item gdb.COMMAND_NONE
23252 The command does not belong to any particular class. A command in
23253 this category will not be displayed in any of the help categories.
23255 @findex COMMAND_RUNNING
23256 @findex gdb.COMMAND_RUNNING
23257 @item gdb.COMMAND_RUNNING
23258 The command is related to running the inferior. For example,
23259 @code{start}, @code{step}, and @code{continue} are in this category.
23260 Type @kbd{help running} at the @value{GDBN} prompt to see a list of
23261 commands in this category.
23263 @findex COMMAND_DATA
23264 @findex gdb.COMMAND_DATA
23265 @item gdb.COMMAND_DATA
23266 The command is related to data or variables. For example,
23267 @code{call}, @code{find}, and @code{print} are in this category. Type
23268 @kbd{help data} at the @value{GDBN} prompt to see a list of commands
23271 @findex COMMAND_STACK
23272 @findex gdb.COMMAND_STACK
23273 @item gdb.COMMAND_STACK
23274 The command has to do with manipulation of the stack. For example,
23275 @code{backtrace}, @code{frame}, and @code{return} are in this
23276 category. Type @kbd{help stack} at the @value{GDBN} prompt to see a
23277 list of commands in this category.
23279 @findex COMMAND_FILES
23280 @findex gdb.COMMAND_FILES
23281 @item gdb.COMMAND_FILES
23282 This class is used for file-related commands. For example,
23283 @code{file}, @code{list} and @code{section} are in this category.
23284 Type @kbd{help files} at the @value{GDBN} prompt to see a list of
23285 commands in this category.
23287 @findex COMMAND_SUPPORT
23288 @findex gdb.COMMAND_SUPPORT
23289 @item gdb.COMMAND_SUPPORT
23290 This should be used for ``support facilities'', generally meaning
23291 things that are useful to the user when interacting with @value{GDBN},
23292 but not related to the state of the inferior. For example,
23293 @code{help}, @code{make}, and @code{shell} are in this category. Type
23294 @kbd{help support} at the @value{GDBN} prompt to see a list of
23295 commands in this category.
23297 @findex COMMAND_STATUS
23298 @findex gdb.COMMAND_STATUS
23299 @item gdb.COMMAND_STATUS
23300 The command is an @samp{info}-related command, that is, related to the
23301 state of @value{GDBN} itself. For example, @code{info}, @code{macro},
23302 and @code{show} are in this category. Type @kbd{help status} at the
23303 @value{GDBN} prompt to see a list of commands in this category.
23305 @findex COMMAND_BREAKPOINTS
23306 @findex gdb.COMMAND_BREAKPOINTS
23307 @item gdb.COMMAND_BREAKPOINTS
23308 The command has to do with breakpoints. For example, @code{break},
23309 @code{clear}, and @code{delete} are in this category. Type @kbd{help
23310 breakpoints} at the @value{GDBN} prompt to see a list of commands in
23313 @findex COMMAND_TRACEPOINTS
23314 @findex gdb.COMMAND_TRACEPOINTS
23315 @item gdb.COMMAND_TRACEPOINTS
23316 The command has to do with tracepoints. For example, @code{trace},
23317 @code{actions}, and @code{tfind} are in this category. Type
23318 @kbd{help tracepoints} at the @value{GDBN} prompt to see a list of
23319 commands in this category.
23321 @findex COMMAND_USER
23322 @findex gdb.COMMAND_USER
23323 @item gdb.COMMAND_USER
23324 The command is a general purpose command for the user, and typically
23325 does not fit in one of the other categories.
23326 Type @kbd{help user-defined} at the @value{GDBN} prompt to see
23327 a list of commands in this category, as well as the list of gdb macros
23328 (@pxref{Sequences}).
23330 @findex COMMAND_OBSCURE
23331 @findex gdb.COMMAND_OBSCURE
23332 @item gdb.COMMAND_OBSCURE
23333 The command is only used in unusual circumstances, or is not of
23334 general interest to users. For example, @code{checkpoint},
23335 @code{fork}, and @code{stop} are in this category. Type @kbd{help
23336 obscure} at the @value{GDBN} prompt to see a list of commands in this
23339 @findex COMMAND_MAINTENANCE
23340 @findex gdb.COMMAND_MAINTENANCE
23341 @item gdb.COMMAND_MAINTENANCE
23342 The command is only useful to @value{GDBN} maintainers. The
23343 @code{maintenance} and @code{flushregs} commands are in this category.
23344 Type @kbd{help internals} at the @value{GDBN} prompt to see a list of
23345 commands in this category.
23348 A new command can use a predefined completion function, either by
23349 specifying it via an argument at initialization, or by returning it
23350 from the @code{complete} method. These predefined completion
23351 constants are all defined in the @code{gdb} module:
23354 @findex COMPLETE_NONE
23355 @findex gdb.COMPLETE_NONE
23356 @item gdb.COMPLETE_NONE
23357 This constant means that no completion should be done.
23359 @findex COMPLETE_FILENAME
23360 @findex gdb.COMPLETE_FILENAME
23361 @item gdb.COMPLETE_FILENAME
23362 This constant means that filename completion should be performed.
23364 @findex COMPLETE_LOCATION
23365 @findex gdb.COMPLETE_LOCATION
23366 @item gdb.COMPLETE_LOCATION
23367 This constant means that location completion should be done.
23368 @xref{Specify Location}.
23370 @findex COMPLETE_COMMAND
23371 @findex gdb.COMPLETE_COMMAND
23372 @item gdb.COMPLETE_COMMAND
23373 This constant means that completion should examine @value{GDBN}
23376 @findex COMPLETE_SYMBOL
23377 @findex gdb.COMPLETE_SYMBOL
23378 @item gdb.COMPLETE_SYMBOL
23379 This constant means that completion should be done using symbol names
23383 The following code snippet shows how a trivial CLI command can be
23384 implemented in Python:
23387 class HelloWorld (gdb.Command):
23388 """Greet the whole world."""
23390 def __init__ (self):
23391 super (HelloWorld, self).__init__ ("hello-world", gdb.COMMAND_USER)
23393 def invoke (self, arg, from_tty):
23394 print "Hello, World!"
23399 The last line instantiates the class, and is necessary to trigger the
23400 registration of the command with @value{GDBN}. Depending on how the
23401 Python code is read into @value{GDBN}, you may need to import the
23402 @code{gdb} module explicitly.
23404 @node Parameters In Python
23405 @subsubsection Parameters In Python
23407 @cindex parameters in python
23408 @cindex python parameters
23409 @tindex gdb.Parameter
23411 You can implement new @value{GDBN} parameters using Python. A new
23412 parameter is implemented as an instance of the @code{gdb.Parameter}
23415 Parameters are exposed to the user via the @code{set} and
23416 @code{show} commands. @xref{Help}.
23418 There are many parameters that already exist and can be set in
23419 @value{GDBN}. Two examples are: @code{set follow fork} and
23420 @code{set charset}. Setting these parameters influences certain
23421 behavior in @value{GDBN}. Similarly, you can define parameters that
23422 can be used to influence behavior in custom Python scripts and commands.
23424 @defun Parameter.__init__ (name, @var{command-class}, @var{parameter-class} @r{[}, @var{enum-sequence}@r{]})
23425 The object initializer for @code{Parameter} registers the new
23426 parameter with @value{GDBN}. This initializer is normally invoked
23427 from the subclass' own @code{__init__} method.
23429 @var{name} is the name of the new parameter. If @var{name} consists
23430 of multiple words, then the initial words are looked for as prefix
23431 parameters. An example of this can be illustrated with the
23432 @code{set print} set of parameters. If @var{name} is
23433 @code{print foo}, then @code{print} will be searched as the prefix
23434 parameter. In this case the parameter can subsequently be accessed in
23435 @value{GDBN} as @code{set print foo}.
23437 If @var{name} consists of multiple words, and no prefix parameter group
23438 can be found, an exception is raised.
23440 @var{command-class} should be one of the @samp{COMMAND_} constants
23441 (@pxref{Commands In Python}). This argument tells @value{GDBN} how to
23442 categorize the new parameter in the help system.
23444 @var{parameter-class} should be one of the @samp{PARAM_} constants
23445 defined below. This argument tells @value{GDBN} the type of the new
23446 parameter; this information is used for input validation and
23449 If @var{parameter-class} is @code{PARAM_ENUM}, then
23450 @var{enum-sequence} must be a sequence of strings. These strings
23451 represent the possible values for the parameter.
23453 If @var{parameter-class} is not @code{PARAM_ENUM}, then the presence
23454 of a fourth argument will cause an exception to be thrown.
23456 The help text for the new parameter is taken from the Python
23457 documentation string for the parameter's class, if there is one. If
23458 there is no documentation string, a default value is used.
23461 @defvar Parameter.set_doc
23462 If this attribute exists, and is a string, then its value is used as
23463 the help text for this parameter's @code{set} command. The value is
23464 examined when @code{Parameter.__init__} is invoked; subsequent changes
23468 @defvar Parameter.show_doc
23469 If this attribute exists, and is a string, then its value is used as
23470 the help text for this parameter's @code{show} command. The value is
23471 examined when @code{Parameter.__init__} is invoked; subsequent changes
23475 @defvar Parameter.value
23476 The @code{value} attribute holds the underlying value of the
23477 parameter. It can be read and assigned to just as any other
23478 attribute. @value{GDBN} does validation when assignments are made.
23481 There are two methods that should be implemented in any
23482 @code{Parameter} class. These are:
23484 @defun Parameter.get_set_string (self)
23485 @value{GDBN} will call this method when a @var{parameter}'s value has
23486 been changed via the @code{set} API (for example, @kbd{set foo off}).
23487 The @code{value} attribute has already been populated with the new
23488 value and may be used in output. This method must return a string.
23491 @defun Parameter.get_show_string (self, svalue)
23492 @value{GDBN} will call this method when a @var{parameter}'s
23493 @code{show} API has been invoked (for example, @kbd{show foo}). The
23494 argument @code{svalue} receives the string representation of the
23495 current value. This method must return a string.
23498 When a new parameter is defined, its type must be specified. The
23499 available types are represented by constants defined in the @code{gdb}
23503 @findex PARAM_BOOLEAN
23504 @findex gdb.PARAM_BOOLEAN
23505 @item gdb.PARAM_BOOLEAN
23506 The value is a plain boolean. The Python boolean values, @code{True}
23507 and @code{False} are the only valid values.
23509 @findex PARAM_AUTO_BOOLEAN
23510 @findex gdb.PARAM_AUTO_BOOLEAN
23511 @item gdb.PARAM_AUTO_BOOLEAN
23512 The value has three possible states: true, false, and @samp{auto}. In
23513 Python, true and false are represented using boolean constants, and
23514 @samp{auto} is represented using @code{None}.
23516 @findex PARAM_UINTEGER
23517 @findex gdb.PARAM_UINTEGER
23518 @item gdb.PARAM_UINTEGER
23519 The value is an unsigned integer. The value of 0 should be
23520 interpreted to mean ``unlimited''.
23522 @findex PARAM_INTEGER
23523 @findex gdb.PARAM_INTEGER
23524 @item gdb.PARAM_INTEGER
23525 The value is a signed integer. The value of 0 should be interpreted
23526 to mean ``unlimited''.
23528 @findex PARAM_STRING
23529 @findex gdb.PARAM_STRING
23530 @item gdb.PARAM_STRING
23531 The value is a string. When the user modifies the string, any escape
23532 sequences, such as @samp{\t}, @samp{\f}, and octal escapes, are
23533 translated into corresponding characters and encoded into the current
23536 @findex PARAM_STRING_NOESCAPE
23537 @findex gdb.PARAM_STRING_NOESCAPE
23538 @item gdb.PARAM_STRING_NOESCAPE
23539 The value is a string. When the user modifies the string, escapes are
23540 passed through untranslated.
23542 @findex PARAM_OPTIONAL_FILENAME
23543 @findex gdb.PARAM_OPTIONAL_FILENAME
23544 @item gdb.PARAM_OPTIONAL_FILENAME
23545 The value is a either a filename (a string), or @code{None}.
23547 @findex PARAM_FILENAME
23548 @findex gdb.PARAM_FILENAME
23549 @item gdb.PARAM_FILENAME
23550 The value is a filename. This is just like
23551 @code{PARAM_STRING_NOESCAPE}, but uses file names for completion.
23553 @findex PARAM_ZINTEGER
23554 @findex gdb.PARAM_ZINTEGER
23555 @item gdb.PARAM_ZINTEGER
23556 The value is an integer. This is like @code{PARAM_INTEGER}, except 0
23557 is interpreted as itself.
23560 @findex gdb.PARAM_ENUM
23561 @item gdb.PARAM_ENUM
23562 The value is a string, which must be one of a collection string
23563 constants provided when the parameter is created.
23566 @node Functions In Python
23567 @subsubsection Writing new convenience functions
23569 @cindex writing convenience functions
23570 @cindex convenience functions in python
23571 @cindex python convenience functions
23572 @tindex gdb.Function
23574 You can implement new convenience functions (@pxref{Convenience Vars})
23575 in Python. A convenience function is an instance of a subclass of the
23576 class @code{gdb.Function}.
23578 @defun Function.__init__ (name)
23579 The initializer for @code{Function} registers the new function with
23580 @value{GDBN}. The argument @var{name} is the name of the function,
23581 a string. The function will be visible to the user as a convenience
23582 variable of type @code{internal function}, whose name is the same as
23583 the given @var{name}.
23585 The documentation for the new function is taken from the documentation
23586 string for the new class.
23589 @defun Function.invoke (@var{*args})
23590 When a convenience function is evaluated, its arguments are converted
23591 to instances of @code{gdb.Value}, and then the function's
23592 @code{invoke} method is called. Note that @value{GDBN} does not
23593 predetermine the arity of convenience functions. Instead, all
23594 available arguments are passed to @code{invoke}, following the
23595 standard Python calling convention. In particular, a convenience
23596 function can have default values for parameters without ill effect.
23598 The return value of this method is used as its value in the enclosing
23599 expression. If an ordinary Python value is returned, it is converted
23600 to a @code{gdb.Value} following the usual rules.
23603 The following code snippet shows how a trivial convenience function can
23604 be implemented in Python:
23607 class Greet (gdb.Function):
23608 """Return string to greet someone.
23609 Takes a name as argument."""
23611 def __init__ (self):
23612 super (Greet, self).__init__ ("greet")
23614 def invoke (self, name):
23615 return "Hello, %s!" % name.string ()
23620 The last line instantiates the class, and is necessary to trigger the
23621 registration of the function with @value{GDBN}. Depending on how the
23622 Python code is read into @value{GDBN}, you may need to import the
23623 @code{gdb} module explicitly.
23625 @node Progspaces In Python
23626 @subsubsection Program Spaces In Python
23628 @cindex progspaces in python
23629 @tindex gdb.Progspace
23631 A program space, or @dfn{progspace}, represents a symbolic view
23632 of an address space.
23633 It consists of all of the objfiles of the program.
23634 @xref{Objfiles In Python}.
23635 @xref{Inferiors and Programs, program spaces}, for more details
23636 about program spaces.
23638 The following progspace-related functions are available in the
23641 @findex gdb.current_progspace
23642 @defun gdb.current_progspace ()
23643 This function returns the program space of the currently selected inferior.
23644 @xref{Inferiors and Programs}.
23647 @findex gdb.progspaces
23648 @defun gdb.progspaces ()
23649 Return a sequence of all the progspaces currently known to @value{GDBN}.
23652 Each progspace is represented by an instance of the @code{gdb.Progspace}
23655 @defvar Progspace.filename
23656 The file name of the progspace as a string.
23659 @defvar Progspace.pretty_printers
23660 The @code{pretty_printers} attribute is a list of functions. It is
23661 used to look up pretty-printers. A @code{Value} is passed to each
23662 function in order; if the function returns @code{None}, then the
23663 search continues. Otherwise, the return value should be an object
23664 which is used to format the value. @xref{Pretty Printing API}, for more
23668 @node Objfiles In Python
23669 @subsubsection Objfiles In Python
23671 @cindex objfiles in python
23672 @tindex gdb.Objfile
23674 @value{GDBN} loads symbols for an inferior from various
23675 symbol-containing files (@pxref{Files}). These include the primary
23676 executable file, any shared libraries used by the inferior, and any
23677 separate debug info files (@pxref{Separate Debug Files}).
23678 @value{GDBN} calls these symbol-containing files @dfn{objfiles}.
23680 The following objfile-related functions are available in the
23683 @findex gdb.current_objfile
23684 @defun gdb.current_objfile ()
23685 When auto-loading a Python script (@pxref{Auto-loading}), @value{GDBN}
23686 sets the ``current objfile'' to the corresponding objfile. This
23687 function returns the current objfile. If there is no current objfile,
23688 this function returns @code{None}.
23691 @findex gdb.objfiles
23692 @defun gdb.objfiles ()
23693 Return a sequence of all the objfiles current known to @value{GDBN}.
23694 @xref{Objfiles In Python}.
23697 Each objfile is represented by an instance of the @code{gdb.Objfile}
23700 @defvar Objfile.filename
23701 The file name of the objfile as a string.
23704 @defvar Objfile.pretty_printers
23705 The @code{pretty_printers} attribute is a list of functions. It is
23706 used to look up pretty-printers. A @code{Value} is passed to each
23707 function in order; if the function returns @code{None}, then the
23708 search continues. Otherwise, the return value should be an object
23709 which is used to format the value. @xref{Pretty Printing API}, for more
23713 A @code{gdb.Objfile} object has the following methods:
23715 @defun Objfile.is_valid ()
23716 Returns @code{True} if the @code{gdb.Objfile} object is valid,
23717 @code{False} if not. A @code{gdb.Objfile} object can become invalid
23718 if the object file it refers to is not loaded in @value{GDBN} any
23719 longer. All other @code{gdb.Objfile} methods will throw an exception
23720 if it is invalid at the time the method is called.
23723 @node Frames In Python
23724 @subsubsection Accessing inferior stack frames from Python.
23726 @cindex frames in python
23727 When the debugged program stops, @value{GDBN} is able to analyze its call
23728 stack (@pxref{Frames,,Stack frames}). The @code{gdb.Frame} class
23729 represents a frame in the stack. A @code{gdb.Frame} object is only valid
23730 while its corresponding frame exists in the inferior's stack. If you try
23731 to use an invalid frame object, @value{GDBN} will throw a @code{gdb.error}
23732 exception (@pxref{Exception Handling}).
23734 Two @code{gdb.Frame} objects can be compared for equality with the @code{==}
23738 (@value{GDBP}) python print gdb.newest_frame() == gdb.selected_frame ()
23742 The following frame-related functions are available in the @code{gdb} module:
23744 @findex gdb.selected_frame
23745 @defun gdb.selected_frame ()
23746 Return the selected frame object. (@pxref{Selection,,Selecting a Frame}).
23749 @findex gdb.newest_frame
23750 @defun gdb.newest_frame ()
23751 Return the newest frame object for the selected thread.
23754 @defun gdb.frame_stop_reason_string (reason)
23755 Return a string explaining the reason why @value{GDBN} stopped unwinding
23756 frames, as expressed by the given @var{reason} code (an integer, see the
23757 @code{unwind_stop_reason} method further down in this section).
23760 A @code{gdb.Frame} object has the following methods:
23763 @defun Frame.is_valid ()
23764 Returns true if the @code{gdb.Frame} object is valid, false if not.
23765 A frame object can become invalid if the frame it refers to doesn't
23766 exist anymore in the inferior. All @code{gdb.Frame} methods will throw
23767 an exception if it is invalid at the time the method is called.
23770 @defun Frame.name ()
23771 Returns the function name of the frame, or @code{None} if it can't be
23775 @defun Frame.type ()
23776 Returns the type of the frame. The value can be one of:
23778 @item gdb.NORMAL_FRAME
23779 An ordinary stack frame.
23781 @item gdb.DUMMY_FRAME
23782 A fake stack frame that was created by @value{GDBN} when performing an
23783 inferior function call.
23785 @item gdb.INLINE_FRAME
23786 A frame representing an inlined function. The function was inlined
23787 into a @code{gdb.NORMAL_FRAME} that is older than this one.
23789 @item gdb.TAILCALL_FRAME
23790 A frame representing a tail call. @xref{Tail Call Frames}.
23792 @item gdb.SIGTRAMP_FRAME
23793 A signal trampoline frame. This is the frame created by the OS when
23794 it calls into a signal handler.
23796 @item gdb.ARCH_FRAME
23797 A fake stack frame representing a cross-architecture call.
23799 @item gdb.SENTINEL_FRAME
23800 This is like @code{gdb.NORMAL_FRAME}, but it is only used for the
23805 @defun Frame.unwind_stop_reason ()
23806 Return an integer representing the reason why it's not possible to find
23807 more frames toward the outermost frame. Use
23808 @code{gdb.frame_stop_reason_string} to convert the value returned by this
23809 function to a string. The value can be one of:
23812 @item gdb.FRAME_UNWIND_NO_REASON
23813 No particular reason (older frames should be available).
23815 @item gdb.FRAME_UNWIND_NULL_ID
23816 The previous frame's analyzer returns an invalid result.
23818 @item gdb.FRAME_UNWIND_OUTERMOST
23819 This frame is the outermost.
23821 @item gdb.FRAME_UNWIND_UNAVAILABLE
23822 Cannot unwind further, because that would require knowing the
23823 values of registers or memory that have not been collected.
23825 @item gdb.FRAME_UNWIND_INNER_ID
23826 This frame ID looks like it ought to belong to a NEXT frame,
23827 but we got it for a PREV frame. Normally, this is a sign of
23828 unwinder failure. It could also indicate stack corruption.
23830 @item gdb.FRAME_UNWIND_SAME_ID
23831 This frame has the same ID as the previous one. That means
23832 that unwinding further would almost certainly give us another
23833 frame with exactly the same ID, so break the chain. Normally,
23834 this is a sign of unwinder failure. It could also indicate
23837 @item gdb.FRAME_UNWIND_NO_SAVED_PC
23838 The frame unwinder did not find any saved PC, but we needed
23839 one to unwind further.
23841 @item gdb.FRAME_UNWIND_FIRST_ERROR
23842 Any stop reason greater or equal to this value indicates some kind
23843 of error. This special value facilitates writing code that tests
23844 for errors in unwinding in a way that will work correctly even if
23845 the list of the other values is modified in future @value{GDBN}
23846 versions. Using it, you could write:
23848 reason = gdb.selected_frame().unwind_stop_reason ()
23849 reason_str = gdb.frame_stop_reason_string (reason)
23850 if reason >= gdb.FRAME_UNWIND_FIRST_ERROR:
23851 print "An error occured: %s" % reason_str
23858 Returns the frame's resume address.
23861 @defun Frame.block ()
23862 Return the frame's code block. @xref{Blocks In Python}.
23865 @defun Frame.function ()
23866 Return the symbol for the function corresponding to this frame.
23867 @xref{Symbols In Python}.
23870 @defun Frame.older ()
23871 Return the frame that called this frame.
23874 @defun Frame.newer ()
23875 Return the frame called by this frame.
23878 @defun Frame.find_sal ()
23879 Return the frame's symtab and line object.
23880 @xref{Symbol Tables In Python}.
23883 @defun Frame.read_var (variable @r{[}, block@r{]})
23884 Return the value of @var{variable} in this frame. If the optional
23885 argument @var{block} is provided, search for the variable from that
23886 block; otherwise start at the frame's current block (which is
23887 determined by the frame's current program counter). @var{variable}
23888 must be a string or a @code{gdb.Symbol} object. @var{block} must be a
23889 @code{gdb.Block} object.
23892 @defun Frame.select ()
23893 Set this frame to be the selected frame. @xref{Stack, ,Examining the
23898 @node Blocks In Python
23899 @subsubsection Accessing frame blocks from Python.
23901 @cindex blocks in python
23904 Within each frame, @value{GDBN} maintains information on each block
23905 stored in that frame. These blocks are organized hierarchically, and
23906 are represented individually in Python as a @code{gdb.Block}.
23907 Please see @ref{Frames In Python}, for a more in-depth discussion on
23908 frames. Furthermore, see @ref{Stack, ,Examining the Stack}, for more
23909 detailed technical information on @value{GDBN}'s book-keeping of the
23912 A @code{gdb.Block} is iterable. The iterator returns the symbols
23913 (@pxref{Symbols In Python}) local to the block.
23915 The following block-related functions are available in the @code{gdb}
23918 @findex gdb.block_for_pc
23919 @defun gdb.block_for_pc (pc)
23920 Return the @code{gdb.Block} containing the given @var{pc} value. If the
23921 block cannot be found for the @var{pc} value specified, the function
23922 will return @code{None}.
23925 A @code{gdb.Block} object has the following methods:
23928 @defun Block.is_valid ()
23929 Returns @code{True} if the @code{gdb.Block} object is valid,
23930 @code{False} if not. A block object can become invalid if the block it
23931 refers to doesn't exist anymore in the inferior. All other
23932 @code{gdb.Block} methods will throw an exception if it is invalid at
23933 the time the method is called. The block's validity is also checked
23934 during iteration over symbols of the block.
23938 A @code{gdb.Block} object has the following attributes:
23941 @defvar Block.start
23942 The start address of the block. This attribute is not writable.
23946 The end address of the block. This attribute is not writable.
23949 @defvar Block.function
23950 The name of the block represented as a @code{gdb.Symbol}. If the
23951 block is not named, then this attribute holds @code{None}. This
23952 attribute is not writable.
23955 @defvar Block.superblock
23956 The block containing this block. If this parent block does not exist,
23957 this attribute holds @code{None}. This attribute is not writable.
23960 @defvar Block.global_block
23961 The global block associated with this block. This attribute is not
23965 @defvar Block.static_block
23966 The static block associated with this block. This attribute is not
23970 @defvar Block.is_global
23971 @code{True} if the @code{gdb.Block} object is a global block,
23972 @code{False} if not. This attribute is not
23976 @defvar Block.is_static
23977 @code{True} if the @code{gdb.Block} object is a static block,
23978 @code{False} if not. This attribute is not writable.
23982 @node Symbols In Python
23983 @subsubsection Python representation of Symbols.
23985 @cindex symbols in python
23988 @value{GDBN} represents every variable, function and type as an
23989 entry in a symbol table. @xref{Symbols, ,Examining the Symbol Table}.
23990 Similarly, Python represents these symbols in @value{GDBN} with the
23991 @code{gdb.Symbol} object.
23993 The following symbol-related functions are available in the @code{gdb}
23996 @findex gdb.lookup_symbol
23997 @defun gdb.lookup_symbol (name @r{[}, block @r{[}, domain@r{]]})
23998 This function searches for a symbol by name. The search scope can be
23999 restricted to the parameters defined in the optional domain and block
24002 @var{name} is the name of the symbol. It must be a string. The
24003 optional @var{block} argument restricts the search to symbols visible
24004 in that @var{block}. The @var{block} argument must be a
24005 @code{gdb.Block} object. If omitted, the block for the current frame
24006 is used. The optional @var{domain} argument restricts
24007 the search to the domain type. The @var{domain} argument must be a
24008 domain constant defined in the @code{gdb} module and described later
24011 The result is a tuple of two elements.
24012 The first element is a @code{gdb.Symbol} object or @code{None} if the symbol
24014 If the symbol is found, the second element is @code{True} if the symbol
24015 is a field of a method's object (e.g., @code{this} in C@t{++}),
24016 otherwise it is @code{False}.
24017 If the symbol is not found, the second element is @code{False}.
24020 @findex gdb.lookup_global_symbol
24021 @defun gdb.lookup_global_symbol (name @r{[}, domain@r{]})
24022 This function searches for a global symbol by name.
24023 The search scope can be restricted to by the domain argument.
24025 @var{name} is the name of the symbol. It must be a string.
24026 The optional @var{domain} argument restricts the search to the domain type.
24027 The @var{domain} argument must be a domain constant defined in the @code{gdb}
24028 module and described later in this chapter.
24030 The result is a @code{gdb.Symbol} object or @code{None} if the symbol
24034 A @code{gdb.Symbol} object has the following attributes:
24037 @defvar Symbol.type
24038 The type of the symbol or @code{None} if no type is recorded.
24039 This attribute is represented as a @code{gdb.Type} object.
24040 @xref{Types In Python}. This attribute is not writable.
24043 @defvar Symbol.symtab
24044 The symbol table in which the symbol appears. This attribute is
24045 represented as a @code{gdb.Symtab} object. @xref{Symbol Tables In
24046 Python}. This attribute is not writable.
24049 @defvar Symbol.line
24050 The line number in the source code at which the symbol was defined.
24051 This is an integer.
24054 @defvar Symbol.name
24055 The name of the symbol as a string. This attribute is not writable.
24058 @defvar Symbol.linkage_name
24059 The name of the symbol, as used by the linker (i.e., may be mangled).
24060 This attribute is not writable.
24063 @defvar Symbol.print_name
24064 The name of the symbol in a form suitable for output. This is either
24065 @code{name} or @code{linkage_name}, depending on whether the user
24066 asked @value{GDBN} to display demangled or mangled names.
24069 @defvar Symbol.addr_class
24070 The address class of the symbol. This classifies how to find the value
24071 of a symbol. Each address class is a constant defined in the
24072 @code{gdb} module and described later in this chapter.
24075 @defvar Symbol.needs_frame
24076 This is @code{True} if evaluating this symbol's value requires a frame
24077 (@pxref{Frames In Python}) and @code{False} otherwise. Typically,
24078 local variables will require a frame, but other symbols will not.
24081 @defvar Symbol.is_argument
24082 @code{True} if the symbol is an argument of a function.
24085 @defvar Symbol.is_constant
24086 @code{True} if the symbol is a constant.
24089 @defvar Symbol.is_function
24090 @code{True} if the symbol is a function or a method.
24093 @defvar Symbol.is_variable
24094 @code{True} if the symbol is a variable.
24098 A @code{gdb.Symbol} object has the following methods:
24101 @defun Symbol.is_valid ()
24102 Returns @code{True} if the @code{gdb.Symbol} object is valid,
24103 @code{False} if not. A @code{gdb.Symbol} object can become invalid if
24104 the symbol it refers to does not exist in @value{GDBN} any longer.
24105 All other @code{gdb.Symbol} methods will throw an exception if it is
24106 invalid at the time the method is called.
24109 @defun Symbol.value (@r{[}frame@r{]})
24110 Compute the value of the symbol, as a @code{gdb.Value}. For
24111 functions, this computes the address of the function, cast to the
24112 appropriate type. If the symbol requires a frame in order to compute
24113 its value, then @var{frame} must be given. If @var{frame} is not
24114 given, or if @var{frame} is invalid, then this method will throw an
24119 The available domain categories in @code{gdb.Symbol} are represented
24120 as constants in the @code{gdb} module:
24123 @findex SYMBOL_UNDEF_DOMAIN
24124 @findex gdb.SYMBOL_UNDEF_DOMAIN
24125 @item gdb.SYMBOL_UNDEF_DOMAIN
24126 This is used when a domain has not been discovered or none of the
24127 following domains apply. This usually indicates an error either
24128 in the symbol information or in @value{GDBN}'s handling of symbols.
24129 @findex SYMBOL_VAR_DOMAIN
24130 @findex gdb.SYMBOL_VAR_DOMAIN
24131 @item gdb.SYMBOL_VAR_DOMAIN
24132 This domain contains variables, function names, typedef names and enum
24134 @findex SYMBOL_STRUCT_DOMAIN
24135 @findex gdb.SYMBOL_STRUCT_DOMAIN
24136 @item gdb.SYMBOL_STRUCT_DOMAIN
24137 This domain holds struct, union and enum type names.
24138 @findex SYMBOL_LABEL_DOMAIN
24139 @findex gdb.SYMBOL_LABEL_DOMAIN
24140 @item gdb.SYMBOL_LABEL_DOMAIN
24141 This domain contains names of labels (for gotos).
24142 @findex SYMBOL_VARIABLES_DOMAIN
24143 @findex gdb.SYMBOL_VARIABLES_DOMAIN
24144 @item gdb.SYMBOL_VARIABLES_DOMAIN
24145 This domain holds a subset of the @code{SYMBOLS_VAR_DOMAIN}; it
24146 contains everything minus functions and types.
24147 @findex SYMBOL_FUNCTIONS_DOMAIN
24148 @findex gdb.SYMBOL_FUNCTIONS_DOMAIN
24149 @item gdb.SYMBOL_FUNCTION_DOMAIN
24150 This domain contains all functions.
24151 @findex SYMBOL_TYPES_DOMAIN
24152 @findex gdb.SYMBOL_TYPES_DOMAIN
24153 @item gdb.SYMBOL_TYPES_DOMAIN
24154 This domain contains all types.
24157 The available address class categories in @code{gdb.Symbol} are represented
24158 as constants in the @code{gdb} module:
24161 @findex SYMBOL_LOC_UNDEF
24162 @findex gdb.SYMBOL_LOC_UNDEF
24163 @item gdb.SYMBOL_LOC_UNDEF
24164 If this is returned by address class, it indicates an error either in
24165 the symbol information or in @value{GDBN}'s handling of symbols.
24166 @findex SYMBOL_LOC_CONST
24167 @findex gdb.SYMBOL_LOC_CONST
24168 @item gdb.SYMBOL_LOC_CONST
24169 Value is constant int.
24170 @findex SYMBOL_LOC_STATIC
24171 @findex gdb.SYMBOL_LOC_STATIC
24172 @item gdb.SYMBOL_LOC_STATIC
24173 Value is at a fixed address.
24174 @findex SYMBOL_LOC_REGISTER
24175 @findex gdb.SYMBOL_LOC_REGISTER
24176 @item gdb.SYMBOL_LOC_REGISTER
24177 Value is in a register.
24178 @findex SYMBOL_LOC_ARG
24179 @findex gdb.SYMBOL_LOC_ARG
24180 @item gdb.SYMBOL_LOC_ARG
24181 Value is an argument. This value is at the offset stored within the
24182 symbol inside the frame's argument list.
24183 @findex SYMBOL_LOC_REF_ARG
24184 @findex gdb.SYMBOL_LOC_REF_ARG
24185 @item gdb.SYMBOL_LOC_REF_ARG
24186 Value address is stored in the frame's argument list. Just like
24187 @code{LOC_ARG} except that the value's address is stored at the
24188 offset, not the value itself.
24189 @findex SYMBOL_LOC_REGPARM_ADDR
24190 @findex gdb.SYMBOL_LOC_REGPARM_ADDR
24191 @item gdb.SYMBOL_LOC_REGPARM_ADDR
24192 Value is a specified register. Just like @code{LOC_REGISTER} except
24193 the register holds the address of the argument instead of the argument
24195 @findex SYMBOL_LOC_LOCAL
24196 @findex gdb.SYMBOL_LOC_LOCAL
24197 @item gdb.SYMBOL_LOC_LOCAL
24198 Value is a local variable.
24199 @findex SYMBOL_LOC_TYPEDEF
24200 @findex gdb.SYMBOL_LOC_TYPEDEF
24201 @item gdb.SYMBOL_LOC_TYPEDEF
24202 Value not used. Symbols in the domain @code{SYMBOL_STRUCT_DOMAIN} all
24204 @findex SYMBOL_LOC_BLOCK
24205 @findex gdb.SYMBOL_LOC_BLOCK
24206 @item gdb.SYMBOL_LOC_BLOCK
24208 @findex SYMBOL_LOC_CONST_BYTES
24209 @findex gdb.SYMBOL_LOC_CONST_BYTES
24210 @item gdb.SYMBOL_LOC_CONST_BYTES
24211 Value is a byte-sequence.
24212 @findex SYMBOL_LOC_UNRESOLVED
24213 @findex gdb.SYMBOL_LOC_UNRESOLVED
24214 @item gdb.SYMBOL_LOC_UNRESOLVED
24215 Value is at a fixed address, but the address of the variable has to be
24216 determined from the minimal symbol table whenever the variable is
24218 @findex SYMBOL_LOC_OPTIMIZED_OUT
24219 @findex gdb.SYMBOL_LOC_OPTIMIZED_OUT
24220 @item gdb.SYMBOL_LOC_OPTIMIZED_OUT
24221 The value does not actually exist in the program.
24222 @findex SYMBOL_LOC_COMPUTED
24223 @findex gdb.SYMBOL_LOC_COMPUTED
24224 @item gdb.SYMBOL_LOC_COMPUTED
24225 The value's address is a computed location.
24228 @node Symbol Tables In Python
24229 @subsubsection Symbol table representation in Python.
24231 @cindex symbol tables in python
24233 @tindex gdb.Symtab_and_line
24235 Access to symbol table data maintained by @value{GDBN} on the inferior
24236 is exposed to Python via two objects: @code{gdb.Symtab_and_line} and
24237 @code{gdb.Symtab}. Symbol table and line data for a frame is returned
24238 from the @code{find_sal} method in @code{gdb.Frame} object.
24239 @xref{Frames In Python}.
24241 For more information on @value{GDBN}'s symbol table management, see
24242 @ref{Symbols, ,Examining the Symbol Table}, for more information.
24244 A @code{gdb.Symtab_and_line} object has the following attributes:
24247 @defvar Symtab_and_line.symtab
24248 The symbol table object (@code{gdb.Symtab}) for this frame.
24249 This attribute is not writable.
24252 @defvar Symtab_and_line.pc
24253 Indicates the current program counter address. This attribute is not
24257 @defvar Symtab_and_line.line
24258 Indicates the current line number for this object. This
24259 attribute is not writable.
24263 A @code{gdb.Symtab_and_line} object has the following methods:
24266 @defun Symtab_and_line.is_valid ()
24267 Returns @code{True} if the @code{gdb.Symtab_and_line} object is valid,
24268 @code{False} if not. A @code{gdb.Symtab_and_line} object can become
24269 invalid if the Symbol table and line object it refers to does not
24270 exist in @value{GDBN} any longer. All other
24271 @code{gdb.Symtab_and_line} methods will throw an exception if it is
24272 invalid at the time the method is called.
24276 A @code{gdb.Symtab} object has the following attributes:
24279 @defvar Symtab.filename
24280 The symbol table's source filename. This attribute is not writable.
24283 @defvar Symtab.objfile
24284 The symbol table's backing object file. @xref{Objfiles In Python}.
24285 This attribute is not writable.
24289 A @code{gdb.Symtab} object has the following methods:
24292 @defun Symtab.is_valid ()
24293 Returns @code{True} if the @code{gdb.Symtab} object is valid,
24294 @code{False} if not. A @code{gdb.Symtab} object can become invalid if
24295 the symbol table it refers to does not exist in @value{GDBN} any
24296 longer. All other @code{gdb.Symtab} methods will throw an exception
24297 if it is invalid at the time the method is called.
24300 @defun Symtab.fullname ()
24301 Return the symbol table's source absolute file name.
24305 @node Breakpoints In Python
24306 @subsubsection Manipulating breakpoints using Python
24308 @cindex breakpoints in python
24309 @tindex gdb.Breakpoint
24311 Python code can manipulate breakpoints via the @code{gdb.Breakpoint}
24314 @defun Breakpoint.__init__ (spec @r{[}, type @r{[}, wp_class @r{[},internal@r{]]]})
24315 Create a new breakpoint. @var{spec} is a string naming the
24316 location of the breakpoint, or an expression that defines a
24317 watchpoint. The contents can be any location recognized by the
24318 @code{break} command, or in the case of a watchpoint, by the @code{watch}
24319 command. The optional @var{type} denotes the breakpoint to create
24320 from the types defined later in this chapter. This argument can be
24321 either: @code{gdb.BP_BREAKPOINT} or @code{gdb.BP_WATCHPOINT}. @var{type}
24322 defaults to @code{gdb.BP_BREAKPOINT}. The optional @var{internal} argument
24323 allows the breakpoint to become invisible to the user. The breakpoint
24324 will neither be reported when created, nor will it be listed in the
24325 output from @code{info breakpoints} (but will be listed with the
24326 @code{maint info breakpoints} command). The optional @var{wp_class}
24327 argument defines the class of watchpoint to create, if @var{type} is
24328 @code{gdb.BP_WATCHPOINT}. If a watchpoint class is not provided, it is
24329 assumed to be a @code{gdb.WP_WRITE} class.
24332 @defun Breakpoint.stop (self)
24333 The @code{gdb.Breakpoint} class can be sub-classed and, in
24334 particular, you may choose to implement the @code{stop} method.
24335 If this method is defined as a sub-class of @code{gdb.Breakpoint},
24336 it will be called when the inferior reaches any location of a
24337 breakpoint which instantiates that sub-class. If the method returns
24338 @code{True}, the inferior will be stopped at the location of the
24339 breakpoint, otherwise the inferior will continue.
24341 If there are multiple breakpoints at the same location with a
24342 @code{stop} method, each one will be called regardless of the
24343 return status of the previous. This ensures that all @code{stop}
24344 methods have a chance to execute at that location. In this scenario
24345 if one of the methods returns @code{True} but the others return
24346 @code{False}, the inferior will still be stopped.
24348 You should not alter the execution state of the inferior (i.e.@:, step,
24349 next, etc.), alter the current frame context (i.e.@:, change the current
24350 active frame), or alter, add or delete any breakpoint. As a general
24351 rule, you should not alter any data within @value{GDBN} or the inferior
24354 Example @code{stop} implementation:
24357 class MyBreakpoint (gdb.Breakpoint):
24359 inf_val = gdb.parse_and_eval("foo")
24366 The available watchpoint types represented by constants are defined in the
24371 @findex gdb.WP_READ
24373 Read only watchpoint.
24376 @findex gdb.WP_WRITE
24378 Write only watchpoint.
24381 @findex gdb.WP_ACCESS
24382 @item gdb.WP_ACCESS
24383 Read/Write watchpoint.
24386 @defun Breakpoint.is_valid ()
24387 Return @code{True} if this @code{Breakpoint} object is valid,
24388 @code{False} otherwise. A @code{Breakpoint} object can become invalid
24389 if the user deletes the breakpoint. In this case, the object still
24390 exists, but the underlying breakpoint does not. In the cases of
24391 watchpoint scope, the watchpoint remains valid even if execution of the
24392 inferior leaves the scope of that watchpoint.
24395 @defun Breakpoint.delete
24396 Permanently deletes the @value{GDBN} breakpoint. This also
24397 invalidates the Python @code{Breakpoint} object. Any further access
24398 to this object's attributes or methods will raise an error.
24401 @defvar Breakpoint.enabled
24402 This attribute is @code{True} if the breakpoint is enabled, and
24403 @code{False} otherwise. This attribute is writable.
24406 @defvar Breakpoint.silent
24407 This attribute is @code{True} if the breakpoint is silent, and
24408 @code{False} otherwise. This attribute is writable.
24410 Note that a breakpoint can also be silent if it has commands and the
24411 first command is @code{silent}. This is not reported by the
24412 @code{silent} attribute.
24415 @defvar Breakpoint.thread
24416 If the breakpoint is thread-specific, this attribute holds the thread
24417 id. If the breakpoint is not thread-specific, this attribute is
24418 @code{None}. This attribute is writable.
24421 @defvar Breakpoint.task
24422 If the breakpoint is Ada task-specific, this attribute holds the Ada task
24423 id. If the breakpoint is not task-specific (or the underlying
24424 language is not Ada), this attribute is @code{None}. This attribute
24428 @defvar Breakpoint.ignore_count
24429 This attribute holds the ignore count for the breakpoint, an integer.
24430 This attribute is writable.
24433 @defvar Breakpoint.number
24434 This attribute holds the breakpoint's number --- the identifier used by
24435 the user to manipulate the breakpoint. This attribute is not writable.
24438 @defvar Breakpoint.type
24439 This attribute holds the breakpoint's type --- the identifier used to
24440 determine the actual breakpoint type or use-case. This attribute is not
24444 @defvar Breakpoint.visible
24445 This attribute tells whether the breakpoint is visible to the user
24446 when set, or when the @samp{info breakpoints} command is run. This
24447 attribute is not writable.
24450 The available types are represented by constants defined in the @code{gdb}
24454 @findex BP_BREAKPOINT
24455 @findex gdb.BP_BREAKPOINT
24456 @item gdb.BP_BREAKPOINT
24457 Normal code breakpoint.
24459 @findex BP_WATCHPOINT
24460 @findex gdb.BP_WATCHPOINT
24461 @item gdb.BP_WATCHPOINT
24462 Watchpoint breakpoint.
24464 @findex BP_HARDWARE_WATCHPOINT
24465 @findex gdb.BP_HARDWARE_WATCHPOINT
24466 @item gdb.BP_HARDWARE_WATCHPOINT
24467 Hardware assisted watchpoint.
24469 @findex BP_READ_WATCHPOINT
24470 @findex gdb.BP_READ_WATCHPOINT
24471 @item gdb.BP_READ_WATCHPOINT
24472 Hardware assisted read watchpoint.
24474 @findex BP_ACCESS_WATCHPOINT
24475 @findex gdb.BP_ACCESS_WATCHPOINT
24476 @item gdb.BP_ACCESS_WATCHPOINT
24477 Hardware assisted access watchpoint.
24480 @defvar Breakpoint.hit_count
24481 This attribute holds the hit count for the breakpoint, an integer.
24482 This attribute is writable, but currently it can only be set to zero.
24485 @defvar Breakpoint.location
24486 This attribute holds the location of the breakpoint, as specified by
24487 the user. It is a string. If the breakpoint does not have a location
24488 (that is, it is a watchpoint) the attribute's value is @code{None}. This
24489 attribute is not writable.
24492 @defvar Breakpoint.expression
24493 This attribute holds a breakpoint expression, as specified by
24494 the user. It is a string. If the breakpoint does not have an
24495 expression (the breakpoint is not a watchpoint) the attribute's value
24496 is @code{None}. This attribute is not writable.
24499 @defvar Breakpoint.condition
24500 This attribute holds the condition of the breakpoint, as specified by
24501 the user. It is a string. If there is no condition, this attribute's
24502 value is @code{None}. This attribute is writable.
24505 @defvar Breakpoint.commands
24506 This attribute holds the commands attached to the breakpoint. If
24507 there are commands, this attribute's value is a string holding all the
24508 commands, separated by newlines. If there are no commands, this
24509 attribute is @code{None}. This attribute is not writable.
24512 @node Finish Breakpoints in Python
24513 @subsubsection Finish Breakpoints
24515 @cindex python finish breakpoints
24516 @tindex gdb.FinishBreakpoint
24518 A finish breakpoint is a temporary breakpoint set at the return address of
24519 a frame, based on the @code{finish} command. @code{gdb.FinishBreakpoint}
24520 extends @code{gdb.Breakpoint}. The underlying breakpoint will be disabled
24521 and deleted when the execution will run out of the breakpoint scope (i.e.@:
24522 @code{Breakpoint.stop} or @code{FinishBreakpoint.out_of_scope} triggered).
24523 Finish breakpoints are thread specific and must be create with the right
24526 @defun FinishBreakpoint.__init__ (@r{[}frame@r{]} @r{[}, internal@r{]})
24527 Create a finish breakpoint at the return address of the @code{gdb.Frame}
24528 object @var{frame}. If @var{frame} is not provided, this defaults to the
24529 newest frame. The optional @var{internal} argument allows the breakpoint to
24530 become invisible to the user. @xref{Breakpoints In Python}, for further
24531 details about this argument.
24534 @defun FinishBreakpoint.out_of_scope (self)
24535 In some circumstances (e.g.@: @code{longjmp}, C@t{++} exceptions, @value{GDBN}
24536 @code{return} command, @dots{}), a function may not properly terminate, and
24537 thus never hit the finish breakpoint. When @value{GDBN} notices such a
24538 situation, the @code{out_of_scope} callback will be triggered.
24540 You may want to sub-class @code{gdb.FinishBreakpoint} and override this
24544 class MyFinishBreakpoint (gdb.FinishBreakpoint)
24546 print "normal finish"
24549 def out_of_scope ():
24550 print "abnormal finish"
24554 @defvar FinishBreakpoint.return_value
24555 When @value{GDBN} is stopped at a finish breakpoint and the frame
24556 used to build the @code{gdb.FinishBreakpoint} object had debug symbols, this
24557 attribute will contain a @code{gdb.Value} object corresponding to the return
24558 value of the function. The value will be @code{None} if the function return
24559 type is @code{void} or if the return value was not computable. This attribute
24563 @node Lazy Strings In Python
24564 @subsubsection Python representation of lazy strings.
24566 @cindex lazy strings in python
24567 @tindex gdb.LazyString
24569 A @dfn{lazy string} is a string whose contents is not retrieved or
24570 encoded until it is needed.
24572 A @code{gdb.LazyString} is represented in @value{GDBN} as an
24573 @code{address} that points to a region of memory, an @code{encoding}
24574 that will be used to encode that region of memory, and a @code{length}
24575 to delimit the region of memory that represents the string. The
24576 difference between a @code{gdb.LazyString} and a string wrapped within
24577 a @code{gdb.Value} is that a @code{gdb.LazyString} will be treated
24578 differently by @value{GDBN} when printing. A @code{gdb.LazyString} is
24579 retrieved and encoded during printing, while a @code{gdb.Value}
24580 wrapping a string is immediately retrieved and encoded on creation.
24582 A @code{gdb.LazyString} object has the following functions:
24584 @defun LazyString.value ()
24585 Convert the @code{gdb.LazyString} to a @code{gdb.Value}. This value
24586 will point to the string in memory, but will lose all the delayed
24587 retrieval, encoding and handling that @value{GDBN} applies to a
24588 @code{gdb.LazyString}.
24591 @defvar LazyString.address
24592 This attribute holds the address of the string. This attribute is not
24596 @defvar LazyString.length
24597 This attribute holds the length of the string in characters. If the
24598 length is -1, then the string will be fetched and encoded up to the
24599 first null of appropriate width. This attribute is not writable.
24602 @defvar LazyString.encoding
24603 This attribute holds the encoding that will be applied to the string
24604 when the string is printed by @value{GDBN}. If the encoding is not
24605 set, or contains an empty string, then @value{GDBN} will select the
24606 most appropriate encoding when the string is printed. This attribute
24610 @defvar LazyString.type
24611 This attribute holds the type that is represented by the lazy string's
24612 type. For a lazy string this will always be a pointer type. To
24613 resolve this to the lazy string's character type, use the type's
24614 @code{target} method. @xref{Types In Python}. This attribute is not
24619 @subsection Auto-loading
24620 @cindex auto-loading, Python
24622 When a new object file is read (for example, due to the @code{file}
24623 command, or because the inferior has loaded a shared library),
24624 @value{GDBN} will look for Python support scripts in several ways:
24625 @file{@var{objfile}-gdb.py} and @code{.debug_gdb_scripts} section.
24628 * objfile-gdb.py file:: The @file{@var{objfile}-gdb.py} file
24629 * .debug_gdb_scripts section:: The @code{.debug_gdb_scripts} section
24630 * Which flavor to choose?::
24633 The auto-loading feature is useful for supplying application-specific
24634 debugging commands and scripts.
24636 Auto-loading can be enabled or disabled,
24637 and the list of auto-loaded scripts can be printed.
24640 @kindex set auto-load-scripts
24641 @item set auto-load-scripts [yes|no]
24642 Enable or disable the auto-loading of Python scripts.
24644 @kindex show auto-load-scripts
24645 @item show auto-load-scripts
24646 Show whether auto-loading of Python scripts is enabled or disabled.
24648 @kindex info auto-load-scripts
24649 @cindex print list of auto-loaded scripts
24650 @item info auto-load-scripts [@var{regexp}]
24651 Print the list of all scripts that @value{GDBN} auto-loaded.
24653 Also printed is the list of scripts that were mentioned in
24654 the @code{.debug_gdb_scripts} section and were not found
24655 (@pxref{.debug_gdb_scripts section}).
24656 This is useful because their names are not printed when @value{GDBN}
24657 tries to load them and fails. There may be many of them, and printing
24658 an error message for each one is problematic.
24660 If @var{regexp} is supplied only scripts with matching names are printed.
24665 (gdb) info auto-load-scripts
24667 Yes py-section-script.py
24668 full name: /tmp/py-section-script.py
24669 Missing my-foo-pretty-printers.py
24673 When reading an auto-loaded file, @value{GDBN} sets the
24674 @dfn{current objfile}. This is available via the @code{gdb.current_objfile}
24675 function (@pxref{Objfiles In Python}). This can be useful for
24676 registering objfile-specific pretty-printers.
24678 @node objfile-gdb.py file
24679 @subsubsection The @file{@var{objfile}-gdb.py} file
24680 @cindex @file{@var{objfile}-gdb.py}
24682 When a new object file is read, @value{GDBN} looks for
24683 a file named @file{@var{objfile}-gdb.py},
24684 where @var{objfile} is the object file's real name, formed by ensuring
24685 that the file name is absolute, following all symlinks, and resolving
24686 @code{.} and @code{..} components. If this file exists and is
24687 readable, @value{GDBN} will evaluate it as a Python script.
24689 If this file does not exist, and if the parameter
24690 @code{debug-file-directory} is set (@pxref{Separate Debug Files}),
24691 then @value{GDBN} will look for @var{real-name} in all of the
24692 directories mentioned in the value of @code{debug-file-directory}.
24694 Finally, if this file does not exist, then @value{GDBN} will look for
24695 a file named @file{@var{data-directory}/auto-load/@var{real-name}}, where
24696 @var{data-directory} is @value{GDBN}'s data directory (available via
24697 @code{show data-directory}, @pxref{Data Files}), and @var{real-name}
24698 is the object file's real name, as described above.
24700 @value{GDBN} does not track which files it has already auto-loaded this way.
24701 @value{GDBN} will load the associated script every time the corresponding
24702 @var{objfile} is opened.
24703 So your @file{-gdb.py} file should be careful to avoid errors if it
24704 is evaluated more than once.
24706 @node .debug_gdb_scripts section
24707 @subsubsection The @code{.debug_gdb_scripts} section
24708 @cindex @code{.debug_gdb_scripts} section
24710 For systems using file formats like ELF and COFF,
24711 when @value{GDBN} loads a new object file
24712 it will look for a special section named @samp{.debug_gdb_scripts}.
24713 If this section exists, its contents is a list of names of scripts to load.
24715 @value{GDBN} will look for each specified script file first in the
24716 current directory and then along the source search path
24717 (@pxref{Source Path, ,Specifying Source Directories}),
24718 except that @file{$cdir} is not searched, since the compilation
24719 directory is not relevant to scripts.
24721 Entries can be placed in section @code{.debug_gdb_scripts} with,
24722 for example, this GCC macro:
24725 /* Note: The "MS" section flags are to remove duplicates. */
24726 #define DEFINE_GDB_SCRIPT(script_name) \
24728 .pushsection \".debug_gdb_scripts\", \"MS\",@@progbits,1\n\
24730 .asciz \"" script_name "\"\n\
24736 Then one can reference the macro in a header or source file like this:
24739 DEFINE_GDB_SCRIPT ("my-app-scripts.py")
24742 The script name may include directories if desired.
24744 If the macro is put in a header, any application or library
24745 using this header will get a reference to the specified script.
24747 @node Which flavor to choose?
24748 @subsubsection Which flavor to choose?
24750 Given the multiple ways of auto-loading Python scripts, it might not always
24751 be clear which one to choose. This section provides some guidance.
24753 Benefits of the @file{-gdb.py} way:
24757 Can be used with file formats that don't support multiple sections.
24760 Ease of finding scripts for public libraries.
24762 Scripts specified in the @code{.debug_gdb_scripts} section are searched for
24763 in the source search path.
24764 For publicly installed libraries, e.g., @file{libstdc++}, there typically
24765 isn't a source directory in which to find the script.
24768 Doesn't require source code additions.
24771 Benefits of the @code{.debug_gdb_scripts} way:
24775 Works with static linking.
24777 Scripts for libraries done the @file{-gdb.py} way require an objfile to
24778 trigger their loading. When an application is statically linked the only
24779 objfile available is the executable, and it is cumbersome to attach all the
24780 scripts from all the input libraries to the executable's @file{-gdb.py} script.
24783 Works with classes that are entirely inlined.
24785 Some classes can be entirely inlined, and thus there may not be an associated
24786 shared library to attach a @file{-gdb.py} script to.
24789 Scripts needn't be copied out of the source tree.
24791 In some circumstances, apps can be built out of large collections of internal
24792 libraries, and the build infrastructure necessary to install the
24793 @file{-gdb.py} scripts in a place where @value{GDBN} can find them is
24794 cumbersome. It may be easier to specify the scripts in the
24795 @code{.debug_gdb_scripts} section as relative paths, and add a path to the
24796 top of the source tree to the source search path.
24799 @node Python modules
24800 @subsection Python modules
24801 @cindex python modules
24803 @value{GDBN} comes with several modules to assist writing Python code.
24806 * gdb.printing:: Building and registering pretty-printers.
24807 * gdb.types:: Utilities for working with types.
24808 * gdb.prompt:: Utilities for prompt value substitution.
24812 @subsubsection gdb.printing
24813 @cindex gdb.printing
24815 This module provides a collection of utilities for working with
24819 @item PrettyPrinter (@var{name}, @var{subprinters}=None)
24820 This class specifies the API that makes @samp{info pretty-printer},
24821 @samp{enable pretty-printer} and @samp{disable pretty-printer} work.
24822 Pretty-printers should generally inherit from this class.
24824 @item SubPrettyPrinter (@var{name})
24825 For printers that handle multiple types, this class specifies the
24826 corresponding API for the subprinters.
24828 @item RegexpCollectionPrettyPrinter (@var{name})
24829 Utility class for handling multiple printers, all recognized via
24830 regular expressions.
24831 @xref{Writing a Pretty-Printer}, for an example.
24833 @item FlagEnumerationPrinter (@var{name})
24834 A pretty-printer which handles printing of @code{enum} values. Unlike
24835 @value{GDBN}'s built-in @code{enum} printing, this printer attempts to
24836 work properly when there is some overlap between the enumeration
24837 constants. @var{name} is the name of the printer and also the name of
24838 the @code{enum} type to look up.
24840 @item register_pretty_printer (@var{obj}, @var{printer}, @var{replace}=False)
24841 Register @var{printer} with the pretty-printer list of @var{obj}.
24842 If @var{replace} is @code{True} then any existing copy of the printer
24843 is replaced. Otherwise a @code{RuntimeError} exception is raised
24844 if a printer with the same name already exists.
24848 @subsubsection gdb.types
24851 This module provides a collection of utilities for working with
24852 @code{gdb.Types} objects.
24855 @item get_basic_type (@var{type})
24856 Return @var{type} with const and volatile qualifiers stripped,
24857 and with typedefs and C@t{++} references converted to the underlying type.
24862 typedef const int const_int;
24864 const_int& foo_ref (foo);
24865 int main () @{ return 0; @}
24872 (gdb) python import gdb.types
24873 (gdb) python foo_ref = gdb.parse_and_eval("foo_ref")
24874 (gdb) python print gdb.types.get_basic_type(foo_ref.type)
24878 @item has_field (@var{type}, @var{field})
24879 Return @code{True} if @var{type}, assumed to be a type with fields
24880 (e.g., a structure or union), has field @var{field}.
24882 @item make_enum_dict (@var{enum_type})
24883 Return a Python @code{dictionary} type produced from @var{enum_type}.
24885 @item deep_items (@var{type})
24886 Returns a Python iterator similar to the standard
24887 @code{gdb.Type.iteritems} method, except that the iterator returned
24888 by @code{deep_items} will recursively traverse anonymous struct or
24889 union fields. For example:
24903 Then in @value{GDBN}:
24905 (@value{GDBP}) python import gdb.types
24906 (@value{GDBP}) python struct_a = gdb.lookup_type("struct A")
24907 (@value{GDBP}) python print struct_a.keys ()
24909 (@value{GDBP}) python print [k for k,v in gdb.types.deep_items(struct_a)]
24910 @{['a', 'b0', 'b1']@}
24916 @subsubsection gdb.prompt
24919 This module provides a method for prompt value-substitution.
24922 @item substitute_prompt (@var{string})
24923 Return @var{string} with escape sequences substituted by values. Some
24924 escape sequences take arguments. You can specify arguments inside
24925 ``@{@}'' immediately following the escape sequence.
24927 The escape sequences you can pass to this function are:
24931 Substitute a backslash.
24933 Substitute an ESC character.
24935 Substitute the selected frame; an argument names a frame parameter.
24937 Substitute a newline.
24939 Substitute a parameter's value; the argument names the parameter.
24941 Substitute a carriage return.
24943 Substitute the selected thread; an argument names a thread parameter.
24945 Substitute the version of GDB.
24947 Substitute the current working directory.
24949 Begin a sequence of non-printing characters. These sequences are
24950 typically used with the ESC character, and are not counted in the string
24951 length. Example: ``\[\e[0;34m\](gdb)\[\e[0m\]'' will return a
24952 blue-colored ``(gdb)'' prompt where the length is five.
24954 End a sequence of non-printing characters.
24960 substitute_prompt (``frame: \f,
24961 print arguments: \p@{print frame-arguments@}'')
24964 @exdent will return the string:
24967 "frame: main, print arguments: scalars"
24972 @section Creating new spellings of existing commands
24973 @cindex aliases for commands
24975 It is often useful to define alternate spellings of existing commands.
24976 For example, if a new @value{GDBN} command defined in Python has
24977 a long name to type, it is handy to have an abbreviated version of it
24978 that involves less typing.
24980 @value{GDBN} itself uses aliases. For example @samp{s} is an alias
24981 of the @samp{step} command even though it is otherwise an ambiguous
24982 abbreviation of other commands like @samp{set} and @samp{show}.
24984 Aliases are also used to provide shortened or more common versions
24985 of multi-word commands. For example, @value{GDBN} provides the
24986 @samp{tty} alias of the @samp{set inferior-tty} command.
24988 You can define a new alias with the @samp{alias} command.
24993 @item alias [-a] [--] @var{ALIAS} = @var{COMMAND}
24997 @var{ALIAS} specifies the name of the new alias.
24998 Each word of @var{ALIAS} must consist of letters, numbers, dashes and
25001 @var{COMMAND} specifies the name of an existing command
25002 that is being aliased.
25004 The @samp{-a} option specifies that the new alias is an abbreviation
25005 of the command. Abbreviations are not shown in command
25006 lists displayed by the @samp{help} command.
25008 The @samp{--} option specifies the end of options,
25009 and is useful when @var{ALIAS} begins with a dash.
25011 Here is a simple example showing how to make an abbreviation
25012 of a command so that there is less to type.
25013 Suppose you were tired of typing @samp{disas}, the current
25014 shortest unambiguous abbreviation of the @samp{disassemble} command
25015 and you wanted an even shorter version named @samp{di}.
25016 The following will accomplish this.
25019 (gdb) alias -a di = disas
25022 Note that aliases are different from user-defined commands.
25023 With a user-defined command, you also need to write documentation
25024 for it with the @samp{document} command.
25025 An alias automatically picks up the documentation of the existing command.
25027 Here is an example where we make @samp{elms} an abbreviation of
25028 @samp{elements} in the @samp{set print elements} command.
25029 This is to show that you can make an abbreviation of any part
25033 (gdb) alias -a set print elms = set print elements
25034 (gdb) alias -a show print elms = show print elements
25035 (gdb) set p elms 20
25037 Limit on string chars or array elements to print is 200.
25040 Note that if you are defining an alias of a @samp{set} command,
25041 and you want to have an alias for the corresponding @samp{show}
25042 command, then you need to define the latter separately.
25044 Unambiguously abbreviated commands are allowed in @var{COMMAND} and
25045 @var{ALIAS}, just as they are normally.
25048 (gdb) alias -a set pr elms = set p ele
25051 Finally, here is an example showing the creation of a one word
25052 alias for a more complex command.
25053 This creates alias @samp{spe} of the command @samp{set print elements}.
25056 (gdb) alias spe = set print elements
25061 @chapter Command Interpreters
25062 @cindex command interpreters
25064 @value{GDBN} supports multiple command interpreters, and some command
25065 infrastructure to allow users or user interface writers to switch
25066 between interpreters or run commands in other interpreters.
25068 @value{GDBN} currently supports two command interpreters, the console
25069 interpreter (sometimes called the command-line interpreter or @sc{cli})
25070 and the machine interface interpreter (or @sc{gdb/mi}). This manual
25071 describes both of these interfaces in great detail.
25073 By default, @value{GDBN} will start with the console interpreter.
25074 However, the user may choose to start @value{GDBN} with another
25075 interpreter by specifying the @option{-i} or @option{--interpreter}
25076 startup options. Defined interpreters include:
25080 @cindex console interpreter
25081 The traditional console or command-line interpreter. This is the most often
25082 used interpreter with @value{GDBN}. With no interpreter specified at runtime,
25083 @value{GDBN} will use this interpreter.
25086 @cindex mi interpreter
25087 The newest @sc{gdb/mi} interface (currently @code{mi2}). Used primarily
25088 by programs wishing to use @value{GDBN} as a backend for a debugger GUI
25089 or an IDE. For more information, see @ref{GDB/MI, ,The @sc{gdb/mi}
25093 @cindex mi2 interpreter
25094 The current @sc{gdb/mi} interface.
25097 @cindex mi1 interpreter
25098 The @sc{gdb/mi} interface included in @value{GDBN} 5.1, 5.2, and 5.3.
25102 @cindex invoke another interpreter
25103 The interpreter being used by @value{GDBN} may not be dynamically
25104 switched at runtime. Although possible, this could lead to a very
25105 precarious situation. Consider an IDE using @sc{gdb/mi}. If a user
25106 enters the command "interpreter-set console" in a console view,
25107 @value{GDBN} would switch to using the console interpreter, rendering
25108 the IDE inoperable!
25110 @kindex interpreter-exec
25111 Although you may only choose a single interpreter at startup, you may execute
25112 commands in any interpreter from the current interpreter using the appropriate
25113 command. If you are running the console interpreter, simply use the
25114 @code{interpreter-exec} command:
25117 interpreter-exec mi "-data-list-register-names"
25120 @sc{gdb/mi} has a similar command, although it is only available in versions of
25121 @value{GDBN} which support @sc{gdb/mi} version 2 (or greater).
25124 @chapter @value{GDBN} Text User Interface
25126 @cindex Text User Interface
25129 * TUI Overview:: TUI overview
25130 * TUI Keys:: TUI key bindings
25131 * TUI Single Key Mode:: TUI single key mode
25132 * TUI Commands:: TUI-specific commands
25133 * TUI Configuration:: TUI configuration variables
25136 The @value{GDBN} Text User Interface (TUI) is a terminal
25137 interface which uses the @code{curses} library to show the source
25138 file, the assembly output, the program registers and @value{GDBN}
25139 commands in separate text windows. The TUI mode is supported only
25140 on platforms where a suitable version of the @code{curses} library
25143 The TUI mode is enabled by default when you invoke @value{GDBN} as
25144 @samp{@value{GDBP} -tui}.
25145 You can also switch in and out of TUI mode while @value{GDBN} runs by
25146 using various TUI commands and key bindings, such as @kbd{C-x C-a}.
25147 @xref{TUI Keys, ,TUI Key Bindings}.
25150 @section TUI Overview
25152 In TUI mode, @value{GDBN} can display several text windows:
25156 This window is the @value{GDBN} command window with the @value{GDBN}
25157 prompt and the @value{GDBN} output. The @value{GDBN} input is still
25158 managed using readline.
25161 The source window shows the source file of the program. The current
25162 line and active breakpoints are displayed in this window.
25165 The assembly window shows the disassembly output of the program.
25168 This window shows the processor registers. Registers are highlighted
25169 when their values change.
25172 The source and assembly windows show the current program position
25173 by highlighting the current line and marking it with a @samp{>} marker.
25174 Breakpoints are indicated with two markers. The first marker
25175 indicates the breakpoint type:
25179 Breakpoint which was hit at least once.
25182 Breakpoint which was never hit.
25185 Hardware breakpoint which was hit at least once.
25188 Hardware breakpoint which was never hit.
25191 The second marker indicates whether the breakpoint is enabled or not:
25195 Breakpoint is enabled.
25198 Breakpoint is disabled.
25201 The source, assembly and register windows are updated when the current
25202 thread changes, when the frame changes, or when the program counter
25205 These windows are not all visible at the same time. The command
25206 window is always visible. The others can be arranged in several
25217 source and assembly,
25220 source and registers, or
25223 assembly and registers.
25226 A status line above the command window shows the following information:
25230 Indicates the current @value{GDBN} target.
25231 (@pxref{Targets, ,Specifying a Debugging Target}).
25234 Gives the current process or thread number.
25235 When no process is being debugged, this field is set to @code{No process}.
25238 Gives the current function name for the selected frame.
25239 The name is demangled if demangling is turned on (@pxref{Print Settings}).
25240 When there is no symbol corresponding to the current program counter,
25241 the string @code{??} is displayed.
25244 Indicates the current line number for the selected frame.
25245 When the current line number is not known, the string @code{??} is displayed.
25248 Indicates the current program counter address.
25252 @section TUI Key Bindings
25253 @cindex TUI key bindings
25255 The TUI installs several key bindings in the readline keymaps
25256 @ifset SYSTEM_READLINE
25257 (@pxref{Command Line Editing, , , rluserman, GNU Readline Library}).
25259 @ifclear SYSTEM_READLINE
25260 (@pxref{Command Line Editing}).
25262 The following key bindings are installed for both TUI mode and the
25263 @value{GDBN} standard mode.
25272 Enter or leave the TUI mode. When leaving the TUI mode,
25273 the curses window management stops and @value{GDBN} operates using
25274 its standard mode, writing on the terminal directly. When reentering
25275 the TUI mode, control is given back to the curses windows.
25276 The screen is then refreshed.
25280 Use a TUI layout with only one window. The layout will
25281 either be @samp{source} or @samp{assembly}. When the TUI mode
25282 is not active, it will switch to the TUI mode.
25284 Think of this key binding as the Emacs @kbd{C-x 1} binding.
25288 Use a TUI layout with at least two windows. When the current
25289 layout already has two windows, the next layout with two windows is used.
25290 When a new layout is chosen, one window will always be common to the
25291 previous layout and the new one.
25293 Think of it as the Emacs @kbd{C-x 2} binding.
25297 Change the active window. The TUI associates several key bindings
25298 (like scrolling and arrow keys) with the active window. This command
25299 gives the focus to the next TUI window.
25301 Think of it as the Emacs @kbd{C-x o} binding.
25305 Switch in and out of the TUI SingleKey mode that binds single
25306 keys to @value{GDBN} commands (@pxref{TUI Single Key Mode}).
25309 The following key bindings only work in the TUI mode:
25314 Scroll the active window one page up.
25318 Scroll the active window one page down.
25322 Scroll the active window one line up.
25326 Scroll the active window one line down.
25330 Scroll the active window one column left.
25334 Scroll the active window one column right.
25338 Refresh the screen.
25341 Because the arrow keys scroll the active window in the TUI mode, they
25342 are not available for their normal use by readline unless the command
25343 window has the focus. When another window is active, you must use
25344 other readline key bindings such as @kbd{C-p}, @kbd{C-n}, @kbd{C-b}
25345 and @kbd{C-f} to control the command window.
25347 @node TUI Single Key Mode
25348 @section TUI Single Key Mode
25349 @cindex TUI single key mode
25351 The TUI also provides a @dfn{SingleKey} mode, which binds several
25352 frequently used @value{GDBN} commands to single keys. Type @kbd{C-x s} to
25353 switch into this mode, where the following key bindings are used:
25356 @kindex c @r{(SingleKey TUI key)}
25360 @kindex d @r{(SingleKey TUI key)}
25364 @kindex f @r{(SingleKey TUI key)}
25368 @kindex n @r{(SingleKey TUI key)}
25372 @kindex q @r{(SingleKey TUI key)}
25374 exit the SingleKey mode.
25376 @kindex r @r{(SingleKey TUI key)}
25380 @kindex s @r{(SingleKey TUI key)}
25384 @kindex u @r{(SingleKey TUI key)}
25388 @kindex v @r{(SingleKey TUI key)}
25392 @kindex w @r{(SingleKey TUI key)}
25397 Other keys temporarily switch to the @value{GDBN} command prompt.
25398 The key that was pressed is inserted in the editing buffer so that
25399 it is possible to type most @value{GDBN} commands without interaction
25400 with the TUI SingleKey mode. Once the command is entered the TUI
25401 SingleKey mode is restored. The only way to permanently leave
25402 this mode is by typing @kbd{q} or @kbd{C-x s}.
25406 @section TUI-specific Commands
25407 @cindex TUI commands
25409 The TUI has specific commands to control the text windows.
25410 These commands are always available, even when @value{GDBN} is not in
25411 the TUI mode. When @value{GDBN} is in the standard mode, most
25412 of these commands will automatically switch to the TUI mode.
25414 Note that if @value{GDBN}'s @code{stdout} is not connected to a
25415 terminal, or @value{GDBN} has been started with the machine interface
25416 interpreter (@pxref{GDB/MI, ,The @sc{gdb/mi} Interface}), most of
25417 these commands will fail with an error, because it would not be
25418 possible or desirable to enable curses window management.
25423 List and give the size of all displayed windows.
25427 Display the next layout.
25430 Display the previous layout.
25433 Display the source window only.
25436 Display the assembly window only.
25439 Display the source and assembly window.
25442 Display the register window together with the source or assembly window.
25446 Make the next window active for scrolling.
25449 Make the previous window active for scrolling.
25452 Make the source window active for scrolling.
25455 Make the assembly window active for scrolling.
25458 Make the register window active for scrolling.
25461 Make the command window active for scrolling.
25465 Refresh the screen. This is similar to typing @kbd{C-L}.
25467 @item tui reg float
25469 Show the floating point registers in the register window.
25471 @item tui reg general
25472 Show the general registers in the register window.
25475 Show the next register group. The list of register groups as well as
25476 their order is target specific. The predefined register groups are the
25477 following: @code{general}, @code{float}, @code{system}, @code{vector},
25478 @code{all}, @code{save}, @code{restore}.
25480 @item tui reg system
25481 Show the system registers in the register window.
25485 Update the source window and the current execution point.
25487 @item winheight @var{name} +@var{count}
25488 @itemx winheight @var{name} -@var{count}
25490 Change the height of the window @var{name} by @var{count}
25491 lines. Positive counts increase the height, while negative counts
25494 @item tabset @var{nchars}
25496 Set the width of tab stops to be @var{nchars} characters.
25499 @node TUI Configuration
25500 @section TUI Configuration Variables
25501 @cindex TUI configuration variables
25503 Several configuration variables control the appearance of TUI windows.
25506 @item set tui border-kind @var{kind}
25507 @kindex set tui border-kind
25508 Select the border appearance for the source, assembly and register windows.
25509 The possible values are the following:
25512 Use a space character to draw the border.
25515 Use @sc{ascii} characters @samp{+}, @samp{-} and @samp{|} to draw the border.
25518 Use the Alternate Character Set to draw the border. The border is
25519 drawn using character line graphics if the terminal supports them.
25522 @item set tui border-mode @var{mode}
25523 @kindex set tui border-mode
25524 @itemx set tui active-border-mode @var{mode}
25525 @kindex set tui active-border-mode
25526 Select the display attributes for the borders of the inactive windows
25527 or the active window. The @var{mode} can be one of the following:
25530 Use normal attributes to display the border.
25536 Use reverse video mode.
25539 Use half bright mode.
25541 @item half-standout
25542 Use half bright and standout mode.
25545 Use extra bright or bold mode.
25547 @item bold-standout
25548 Use extra bright or bold and standout mode.
25553 @chapter Using @value{GDBN} under @sc{gnu} Emacs
25556 @cindex @sc{gnu} Emacs
25557 A special interface allows you to use @sc{gnu} Emacs to view (and
25558 edit) the source files for the program you are debugging with
25561 To use this interface, use the command @kbd{M-x gdb} in Emacs. Give the
25562 executable file you want to debug as an argument. This command starts
25563 @value{GDBN} as a subprocess of Emacs, with input and output through a newly
25564 created Emacs buffer.
25565 @c (Do not use the @code{-tui} option to run @value{GDBN} from Emacs.)
25567 Running @value{GDBN} under Emacs can be just like running @value{GDBN} normally except for two
25572 All ``terminal'' input and output goes through an Emacs buffer, called
25575 This applies both to @value{GDBN} commands and their output, and to the input
25576 and output done by the program you are debugging.
25578 This is useful because it means that you can copy the text of previous
25579 commands and input them again; you can even use parts of the output
25582 All the facilities of Emacs' Shell mode are available for interacting
25583 with your program. In particular, you can send signals the usual
25584 way---for example, @kbd{C-c C-c} for an interrupt, @kbd{C-c C-z} for a
25588 @value{GDBN} displays source code through Emacs.
25590 Each time @value{GDBN} displays a stack frame, Emacs automatically finds the
25591 source file for that frame and puts an arrow (@samp{=>}) at the
25592 left margin of the current line. Emacs uses a separate buffer for
25593 source display, and splits the screen to show both your @value{GDBN} session
25596 Explicit @value{GDBN} @code{list} or search commands still produce output as
25597 usual, but you probably have no reason to use them from Emacs.
25600 We call this @dfn{text command mode}. Emacs 22.1, and later, also uses
25601 a graphical mode, enabled by default, which provides further buffers
25602 that can control the execution and describe the state of your program.
25603 @xref{GDB Graphical Interface,,, Emacs, The @sc{gnu} Emacs Manual}.
25605 If you specify an absolute file name when prompted for the @kbd{M-x
25606 gdb} argument, then Emacs sets your current working directory to where
25607 your program resides. If you only specify the file name, then Emacs
25608 sets your current working directory to the directory associated
25609 with the previous buffer. In this case, @value{GDBN} may find your
25610 program by searching your environment's @code{PATH} variable, but on
25611 some operating systems it might not find the source. So, although the
25612 @value{GDBN} input and output session proceeds normally, the auxiliary
25613 buffer does not display the current source and line of execution.
25615 The initial working directory of @value{GDBN} is printed on the top
25616 line of the GUD buffer and this serves as a default for the commands
25617 that specify files for @value{GDBN} to operate on. @xref{Files,
25618 ,Commands to Specify Files}.
25620 By default, @kbd{M-x gdb} calls the program called @file{gdb}. If you
25621 need to call @value{GDBN} by a different name (for example, if you
25622 keep several configurations around, with different names) you can
25623 customize the Emacs variable @code{gud-gdb-command-name} to run the
25626 In the GUD buffer, you can use these special Emacs commands in
25627 addition to the standard Shell mode commands:
25631 Describe the features of Emacs' GUD Mode.
25634 Execute to another source line, like the @value{GDBN} @code{step} command; also
25635 update the display window to show the current file and location.
25638 Execute to next source line in this function, skipping all function
25639 calls, like the @value{GDBN} @code{next} command. Then update the display window
25640 to show the current file and location.
25643 Execute one instruction, like the @value{GDBN} @code{stepi} command; update
25644 display window accordingly.
25647 Execute until exit from the selected stack frame, like the @value{GDBN}
25648 @code{finish} command.
25651 Continue execution of your program, like the @value{GDBN} @code{continue}
25655 Go up the number of frames indicated by the numeric argument
25656 (@pxref{Arguments, , Numeric Arguments, Emacs, The @sc{gnu} Emacs Manual}),
25657 like the @value{GDBN} @code{up} command.
25660 Go down the number of frames indicated by the numeric argument, like the
25661 @value{GDBN} @code{down} command.
25664 In any source file, the Emacs command @kbd{C-x @key{SPC}} (@code{gud-break})
25665 tells @value{GDBN} to set a breakpoint on the source line point is on.
25667 In text command mode, if you type @kbd{M-x speedbar}, Emacs displays a
25668 separate frame which shows a backtrace when the GUD buffer is current.
25669 Move point to any frame in the stack and type @key{RET} to make it
25670 become the current frame and display the associated source in the
25671 source buffer. Alternatively, click @kbd{Mouse-2} to make the
25672 selected frame become the current one. In graphical mode, the
25673 speedbar displays watch expressions.
25675 If you accidentally delete the source-display buffer, an easy way to get
25676 it back is to type the command @code{f} in the @value{GDBN} buffer, to
25677 request a frame display; when you run under Emacs, this recreates
25678 the source buffer if necessary to show you the context of the current
25681 The source files displayed in Emacs are in ordinary Emacs buffers
25682 which are visiting the source files in the usual way. You can edit
25683 the files with these buffers if you wish; but keep in mind that @value{GDBN}
25684 communicates with Emacs in terms of line numbers. If you add or
25685 delete lines from the text, the line numbers that @value{GDBN} knows cease
25686 to correspond properly with the code.
25688 A more detailed description of Emacs' interaction with @value{GDBN} is
25689 given in the Emacs manual (@pxref{Debuggers,,, Emacs, The @sc{gnu}
25692 @c The following dropped because Epoch is nonstandard. Reactivate
25693 @c if/when v19 does something similar. ---doc@cygnus.com 19dec1990
25695 @kindex Emacs Epoch environment
25699 Version 18 of @sc{gnu} Emacs has a built-in window system
25700 called the @code{epoch}
25701 environment. Users of this environment can use a new command,
25702 @code{inspect} which performs identically to @code{print} except that
25703 each value is printed in its own window.
25708 @chapter The @sc{gdb/mi} Interface
25710 @unnumberedsec Function and Purpose
25712 @cindex @sc{gdb/mi}, its purpose
25713 @sc{gdb/mi} is a line based machine oriented text interface to
25714 @value{GDBN} and is activated by specifying using the
25715 @option{--interpreter} command line option (@pxref{Mode Options}). It
25716 is specifically intended to support the development of systems which
25717 use the debugger as just one small component of a larger system.
25719 This chapter is a specification of the @sc{gdb/mi} interface. It is written
25720 in the form of a reference manual.
25722 Note that @sc{gdb/mi} is still under construction, so some of the
25723 features described below are incomplete and subject to change
25724 (@pxref{GDB/MI Development and Front Ends, , @sc{gdb/mi} Development and Front Ends}).
25726 @unnumberedsec Notation and Terminology
25728 @cindex notational conventions, for @sc{gdb/mi}
25729 This chapter uses the following notation:
25733 @code{|} separates two alternatives.
25736 @code{[ @var{something} ]} indicates that @var{something} is optional:
25737 it may or may not be given.
25740 @code{( @var{group} )*} means that @var{group} inside the parentheses
25741 may repeat zero or more times.
25744 @code{( @var{group} )+} means that @var{group} inside the parentheses
25745 may repeat one or more times.
25748 @code{"@var{string}"} means a literal @var{string}.
25752 @heading Dependencies
25756 * GDB/MI General Design::
25757 * GDB/MI Command Syntax::
25758 * GDB/MI Compatibility with CLI::
25759 * GDB/MI Development and Front Ends::
25760 * GDB/MI Output Records::
25761 * GDB/MI Simple Examples::
25762 * GDB/MI Command Description Format::
25763 * GDB/MI Breakpoint Commands::
25764 * GDB/MI Program Context::
25765 * GDB/MI Thread Commands::
25766 * GDB/MI Ada Tasking Commands::
25767 * GDB/MI Program Execution::
25768 * GDB/MI Stack Manipulation::
25769 * GDB/MI Variable Objects::
25770 * GDB/MI Data Manipulation::
25771 * GDB/MI Tracepoint Commands::
25772 * GDB/MI Symbol Query::
25773 * GDB/MI File Commands::
25775 * GDB/MI Kod Commands::
25776 * GDB/MI Memory Overlay Commands::
25777 * GDB/MI Signal Handling Commands::
25779 * GDB/MI Target Manipulation::
25780 * GDB/MI File Transfer Commands::
25781 * GDB/MI Miscellaneous Commands::
25784 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
25785 @node GDB/MI General Design
25786 @section @sc{gdb/mi} General Design
25787 @cindex GDB/MI General Design
25789 Interaction of a @sc{GDB/MI} frontend with @value{GDBN} involves three
25790 parts---commands sent to @value{GDBN}, responses to those commands
25791 and notifications. Each command results in exactly one response,
25792 indicating either successful completion of the command, or an error.
25793 For the commands that do not resume the target, the response contains the
25794 requested information. For the commands that resume the target, the
25795 response only indicates whether the target was successfully resumed.
25796 Notifications is the mechanism for reporting changes in the state of the
25797 target, or in @value{GDBN} state, that cannot conveniently be associated with
25798 a command and reported as part of that command response.
25800 The important examples of notifications are:
25804 Exec notifications. These are used to report changes in
25805 target state---when a target is resumed, or stopped. It would not
25806 be feasible to include this information in response of resuming
25807 commands, because one resume commands can result in multiple events in
25808 different threads. Also, quite some time may pass before any event
25809 happens in the target, while a frontend needs to know whether the resuming
25810 command itself was successfully executed.
25813 Console output, and status notifications. Console output
25814 notifications are used to report output of CLI commands, as well as
25815 diagnostics for other commands. Status notifications are used to
25816 report the progress of a long-running operation. Naturally, including
25817 this information in command response would mean no output is produced
25818 until the command is finished, which is undesirable.
25821 General notifications. Commands may have various side effects on
25822 the @value{GDBN} or target state beyond their official purpose. For example,
25823 a command may change the selected thread. Although such changes can
25824 be included in command response, using notification allows for more
25825 orthogonal frontend design.
25829 There's no guarantee that whenever an MI command reports an error,
25830 @value{GDBN} or the target are in any specific state, and especially,
25831 the state is not reverted to the state before the MI command was
25832 processed. Therefore, whenever an MI command results in an error,
25833 we recommend that the frontend refreshes all the information shown in
25834 the user interface.
25838 * Context management::
25839 * Asynchronous and non-stop modes::
25843 @node Context management
25844 @subsection Context management
25846 In most cases when @value{GDBN} accesses the target, this access is
25847 done in context of a specific thread and frame (@pxref{Frames}).
25848 Often, even when accessing global data, the target requires that a thread
25849 be specified. The CLI interface maintains the selected thread and frame,
25850 and supplies them to target on each command. This is convenient,
25851 because a command line user would not want to specify that information
25852 explicitly on each command, and because user interacts with
25853 @value{GDBN} via a single terminal, so no confusion is possible as
25854 to what thread and frame are the current ones.
25856 In the case of MI, the concept of selected thread and frame is less
25857 useful. First, a frontend can easily remember this information
25858 itself. Second, a graphical frontend can have more than one window,
25859 each one used for debugging a different thread, and the frontend might
25860 want to access additional threads for internal purposes. This
25861 increases the risk that by relying on implicitly selected thread, the
25862 frontend may be operating on a wrong one. Therefore, each MI command
25863 should explicitly specify which thread and frame to operate on. To
25864 make it possible, each MI command accepts the @samp{--thread} and
25865 @samp{--frame} options, the value to each is @value{GDBN} identifier
25866 for thread and frame to operate on.
25868 Usually, each top-level window in a frontend allows the user to select
25869 a thread and a frame, and remembers the user selection for further
25870 operations. However, in some cases @value{GDBN} may suggest that the
25871 current thread be changed. For example, when stopping on a breakpoint
25872 it is reasonable to switch to the thread where breakpoint is hit. For
25873 another example, if the user issues the CLI @samp{thread} command via
25874 the frontend, it is desirable to change the frontend's selected thread to the
25875 one specified by user. @value{GDBN} communicates the suggestion to
25876 change current thread using the @samp{=thread-selected} notification.
25877 No such notification is available for the selected frame at the moment.
25879 Note that historically, MI shares the selected thread with CLI, so
25880 frontends used the @code{-thread-select} to execute commands in the
25881 right context. However, getting this to work right is cumbersome. The
25882 simplest way is for frontend to emit @code{-thread-select} command
25883 before every command. This doubles the number of commands that need
25884 to be sent. The alternative approach is to suppress @code{-thread-select}
25885 if the selected thread in @value{GDBN} is supposed to be identical to the
25886 thread the frontend wants to operate on. However, getting this
25887 optimization right can be tricky. In particular, if the frontend
25888 sends several commands to @value{GDBN}, and one of the commands changes the
25889 selected thread, then the behaviour of subsequent commands will
25890 change. So, a frontend should either wait for response from such
25891 problematic commands, or explicitly add @code{-thread-select} for
25892 all subsequent commands. No frontend is known to do this exactly
25893 right, so it is suggested to just always pass the @samp{--thread} and
25894 @samp{--frame} options.
25896 @node Asynchronous and non-stop modes
25897 @subsection Asynchronous command execution and non-stop mode
25899 On some targets, @value{GDBN} is capable of processing MI commands
25900 even while the target is running. This is called @dfn{asynchronous
25901 command execution} (@pxref{Background Execution}). The frontend may
25902 specify a preferrence for asynchronous execution using the
25903 @code{-gdb-set target-async 1} command, which should be emitted before
25904 either running the executable or attaching to the target. After the
25905 frontend has started the executable or attached to the target, it can
25906 find if asynchronous execution is enabled using the
25907 @code{-list-target-features} command.
25909 Even if @value{GDBN} can accept a command while target is running,
25910 many commands that access the target do not work when the target is
25911 running. Therefore, asynchronous command execution is most useful
25912 when combined with non-stop mode (@pxref{Non-Stop Mode}). Then,
25913 it is possible to examine the state of one thread, while other threads
25916 When a given thread is running, MI commands that try to access the
25917 target in the context of that thread may not work, or may work only on
25918 some targets. In particular, commands that try to operate on thread's
25919 stack will not work, on any target. Commands that read memory, or
25920 modify breakpoints, may work or not work, depending on the target. Note
25921 that even commands that operate on global state, such as @code{print},
25922 @code{set}, and breakpoint commands, still access the target in the
25923 context of a specific thread, so frontend should try to find a
25924 stopped thread and perform the operation on that thread (using the
25925 @samp{--thread} option).
25927 Which commands will work in the context of a running thread is
25928 highly target dependent. However, the two commands
25929 @code{-exec-interrupt}, to stop a thread, and @code{-thread-info},
25930 to find the state of a thread, will always work.
25932 @node Thread groups
25933 @subsection Thread groups
25934 @value{GDBN} may be used to debug several processes at the same time.
25935 On some platfroms, @value{GDBN} may support debugging of several
25936 hardware systems, each one having several cores with several different
25937 processes running on each core. This section describes the MI
25938 mechanism to support such debugging scenarios.
25940 The key observation is that regardless of the structure of the
25941 target, MI can have a global list of threads, because most commands that
25942 accept the @samp{--thread} option do not need to know what process that
25943 thread belongs to. Therefore, it is not necessary to introduce
25944 neither additional @samp{--process} option, nor an notion of the
25945 current process in the MI interface. The only strictly new feature
25946 that is required is the ability to find how the threads are grouped
25949 To allow the user to discover such grouping, and to support arbitrary
25950 hierarchy of machines/cores/processes, MI introduces the concept of a
25951 @dfn{thread group}. Thread group is a collection of threads and other
25952 thread groups. A thread group always has a string identifier, a type,
25953 and may have additional attributes specific to the type. A new
25954 command, @code{-list-thread-groups}, returns the list of top-level
25955 thread groups, which correspond to processes that @value{GDBN} is
25956 debugging at the moment. By passing an identifier of a thread group
25957 to the @code{-list-thread-groups} command, it is possible to obtain
25958 the members of specific thread group.
25960 To allow the user to easily discover processes, and other objects, he
25961 wishes to debug, a concept of @dfn{available thread group} is
25962 introduced. Available thread group is an thread group that
25963 @value{GDBN} is not debugging, but that can be attached to, using the
25964 @code{-target-attach} command. The list of available top-level thread
25965 groups can be obtained using @samp{-list-thread-groups --available}.
25966 In general, the content of a thread group may be only retrieved only
25967 after attaching to that thread group.
25969 Thread groups are related to inferiors (@pxref{Inferiors and
25970 Programs}). Each inferior corresponds to a thread group of a special
25971 type @samp{process}, and some additional operations are permitted on
25972 such thread groups.
25974 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
25975 @node GDB/MI Command Syntax
25976 @section @sc{gdb/mi} Command Syntax
25979 * GDB/MI Input Syntax::
25980 * GDB/MI Output Syntax::
25983 @node GDB/MI Input Syntax
25984 @subsection @sc{gdb/mi} Input Syntax
25986 @cindex input syntax for @sc{gdb/mi}
25987 @cindex @sc{gdb/mi}, input syntax
25989 @item @var{command} @expansion{}
25990 @code{@var{cli-command} | @var{mi-command}}
25992 @item @var{cli-command} @expansion{}
25993 @code{[ @var{token} ] @var{cli-command} @var{nl}}, where
25994 @var{cli-command} is any existing @value{GDBN} CLI command.
25996 @item @var{mi-command} @expansion{}
25997 @code{[ @var{token} ] "-" @var{operation} ( " " @var{option} )*
25998 @code{[} " --" @code{]} ( " " @var{parameter} )* @var{nl}}
26000 @item @var{token} @expansion{}
26001 "any sequence of digits"
26003 @item @var{option} @expansion{}
26004 @code{"-" @var{parameter} [ " " @var{parameter} ]}
26006 @item @var{parameter} @expansion{}
26007 @code{@var{non-blank-sequence} | @var{c-string}}
26009 @item @var{operation} @expansion{}
26010 @emph{any of the operations described in this chapter}
26012 @item @var{non-blank-sequence} @expansion{}
26013 @emph{anything, provided it doesn't contain special characters such as
26014 "-", @var{nl}, """ and of course " "}
26016 @item @var{c-string} @expansion{}
26017 @code{""" @var{seven-bit-iso-c-string-content} """}
26019 @item @var{nl} @expansion{}
26028 The CLI commands are still handled by the @sc{mi} interpreter; their
26029 output is described below.
26032 The @code{@var{token}}, when present, is passed back when the command
26036 Some @sc{mi} commands accept optional arguments as part of the parameter
26037 list. Each option is identified by a leading @samp{-} (dash) and may be
26038 followed by an optional argument parameter. Options occur first in the
26039 parameter list and can be delimited from normal parameters using
26040 @samp{--} (this is useful when some parameters begin with a dash).
26047 We want easy access to the existing CLI syntax (for debugging).
26050 We want it to be easy to spot a @sc{mi} operation.
26053 @node GDB/MI Output Syntax
26054 @subsection @sc{gdb/mi} Output Syntax
26056 @cindex output syntax of @sc{gdb/mi}
26057 @cindex @sc{gdb/mi}, output syntax
26058 The output from @sc{gdb/mi} consists of zero or more out-of-band records
26059 followed, optionally, by a single result record. This result record
26060 is for the most recent command. The sequence of output records is
26061 terminated by @samp{(gdb)}.
26063 If an input command was prefixed with a @code{@var{token}} then the
26064 corresponding output for that command will also be prefixed by that same
26068 @item @var{output} @expansion{}
26069 @code{( @var{out-of-band-record} )* [ @var{result-record} ] "(gdb)" @var{nl}}
26071 @item @var{result-record} @expansion{}
26072 @code{ [ @var{token} ] "^" @var{result-class} ( "," @var{result} )* @var{nl}}
26074 @item @var{out-of-band-record} @expansion{}
26075 @code{@var{async-record} | @var{stream-record}}
26077 @item @var{async-record} @expansion{}
26078 @code{@var{exec-async-output} | @var{status-async-output} | @var{notify-async-output}}
26080 @item @var{exec-async-output} @expansion{}
26081 @code{[ @var{token} ] "*" @var{async-output}}
26083 @item @var{status-async-output} @expansion{}
26084 @code{[ @var{token} ] "+" @var{async-output}}
26086 @item @var{notify-async-output} @expansion{}
26087 @code{[ @var{token} ] "=" @var{async-output}}
26089 @item @var{async-output} @expansion{}
26090 @code{@var{async-class} ( "," @var{result} )* @var{nl}}
26092 @item @var{result-class} @expansion{}
26093 @code{"done" | "running" | "connected" | "error" | "exit"}
26095 @item @var{async-class} @expansion{}
26096 @code{"stopped" | @var{others}} (where @var{others} will be added
26097 depending on the needs---this is still in development).
26099 @item @var{result} @expansion{}
26100 @code{ @var{variable} "=" @var{value}}
26102 @item @var{variable} @expansion{}
26103 @code{ @var{string} }
26105 @item @var{value} @expansion{}
26106 @code{ @var{const} | @var{tuple} | @var{list} }
26108 @item @var{const} @expansion{}
26109 @code{@var{c-string}}
26111 @item @var{tuple} @expansion{}
26112 @code{ "@{@}" | "@{" @var{result} ( "," @var{result} )* "@}" }
26114 @item @var{list} @expansion{}
26115 @code{ "[]" | "[" @var{value} ( "," @var{value} )* "]" | "["
26116 @var{result} ( "," @var{result} )* "]" }
26118 @item @var{stream-record} @expansion{}
26119 @code{@var{console-stream-output} | @var{target-stream-output} | @var{log-stream-output}}
26121 @item @var{console-stream-output} @expansion{}
26122 @code{"~" @var{c-string}}
26124 @item @var{target-stream-output} @expansion{}
26125 @code{"@@" @var{c-string}}
26127 @item @var{log-stream-output} @expansion{}
26128 @code{"&" @var{c-string}}
26130 @item @var{nl} @expansion{}
26133 @item @var{token} @expansion{}
26134 @emph{any sequence of digits}.
26142 All output sequences end in a single line containing a period.
26145 The @code{@var{token}} is from the corresponding request. Note that
26146 for all async output, while the token is allowed by the grammar and
26147 may be output by future versions of @value{GDBN} for select async
26148 output messages, it is generally omitted. Frontends should treat
26149 all async output as reporting general changes in the state of the
26150 target and there should be no need to associate async output to any
26154 @cindex status output in @sc{gdb/mi}
26155 @var{status-async-output} contains on-going status information about the
26156 progress of a slow operation. It can be discarded. All status output is
26157 prefixed by @samp{+}.
26160 @cindex async output in @sc{gdb/mi}
26161 @var{exec-async-output} contains asynchronous state change on the target
26162 (stopped, started, disappeared). All async output is prefixed by
26166 @cindex notify output in @sc{gdb/mi}
26167 @var{notify-async-output} contains supplementary information that the
26168 client should handle (e.g., a new breakpoint information). All notify
26169 output is prefixed by @samp{=}.
26172 @cindex console output in @sc{gdb/mi}
26173 @var{console-stream-output} is output that should be displayed as is in the
26174 console. It is the textual response to a CLI command. All the console
26175 output is prefixed by @samp{~}.
26178 @cindex target output in @sc{gdb/mi}
26179 @var{target-stream-output} is the output produced by the target program.
26180 All the target output is prefixed by @samp{@@}.
26183 @cindex log output in @sc{gdb/mi}
26184 @var{log-stream-output} is output text coming from @value{GDBN}'s internals, for
26185 instance messages that should be displayed as part of an error log. All
26186 the log output is prefixed by @samp{&}.
26189 @cindex list output in @sc{gdb/mi}
26190 New @sc{gdb/mi} commands should only output @var{lists} containing
26196 @xref{GDB/MI Stream Records, , @sc{gdb/mi} Stream Records}, for more
26197 details about the various output records.
26199 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
26200 @node GDB/MI Compatibility with CLI
26201 @section @sc{gdb/mi} Compatibility with CLI
26203 @cindex compatibility, @sc{gdb/mi} and CLI
26204 @cindex @sc{gdb/mi}, compatibility with CLI
26206 For the developers convenience CLI commands can be entered directly,
26207 but there may be some unexpected behaviour. For example, commands
26208 that query the user will behave as if the user replied yes, breakpoint
26209 command lists are not executed and some CLI commands, such as
26210 @code{if}, @code{when} and @code{define}, prompt for further input with
26211 @samp{>}, which is not valid MI output.
26213 This feature may be removed at some stage in the future and it is
26214 recommended that front ends use the @code{-interpreter-exec} command
26215 (@pxref{-interpreter-exec}).
26217 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
26218 @node GDB/MI Development and Front Ends
26219 @section @sc{gdb/mi} Development and Front Ends
26220 @cindex @sc{gdb/mi} development
26222 The application which takes the MI output and presents the state of the
26223 program being debugged to the user is called a @dfn{front end}.
26225 Although @sc{gdb/mi} is still incomplete, it is currently being used
26226 by a variety of front ends to @value{GDBN}. This makes it difficult
26227 to introduce new functionality without breaking existing usage. This
26228 section tries to minimize the problems by describing how the protocol
26231 Some changes in MI need not break a carefully designed front end, and
26232 for these the MI version will remain unchanged. The following is a
26233 list of changes that may occur within one level, so front ends should
26234 parse MI output in a way that can handle them:
26238 New MI commands may be added.
26241 New fields may be added to the output of any MI command.
26244 The range of values for fields with specified values, e.g.,
26245 @code{in_scope} (@pxref{-var-update}) may be extended.
26247 @c The format of field's content e.g type prefix, may change so parse it
26248 @c at your own risk. Yes, in general?
26250 @c The order of fields may change? Shouldn't really matter but it might
26251 @c resolve inconsistencies.
26254 If the changes are likely to break front ends, the MI version level
26255 will be increased by one. This will allow the front end to parse the
26256 output according to the MI version. Apart from mi0, new versions of
26257 @value{GDBN} will not support old versions of MI and it will be the
26258 responsibility of the front end to work with the new one.
26260 @c Starting with mi3, add a new command -mi-version that prints the MI
26263 The best way to avoid unexpected changes in MI that might break your front
26264 end is to make your project known to @value{GDBN} developers and
26265 follow development on @email{gdb@@sourceware.org} and
26266 @email{gdb-patches@@sourceware.org}.
26267 @cindex mailing lists
26269 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
26270 @node GDB/MI Output Records
26271 @section @sc{gdb/mi} Output Records
26274 * GDB/MI Result Records::
26275 * GDB/MI Stream Records::
26276 * GDB/MI Async Records::
26277 * GDB/MI Frame Information::
26278 * GDB/MI Thread Information::
26279 * GDB/MI Ada Exception Information::
26282 @node GDB/MI Result Records
26283 @subsection @sc{gdb/mi} Result Records
26285 @cindex result records in @sc{gdb/mi}
26286 @cindex @sc{gdb/mi}, result records
26287 In addition to a number of out-of-band notifications, the response to a
26288 @sc{gdb/mi} command includes one of the following result indications:
26292 @item "^done" [ "," @var{results} ]
26293 The synchronous operation was successful, @code{@var{results}} are the return
26298 This result record is equivalent to @samp{^done}. Historically, it
26299 was output instead of @samp{^done} if the command has resumed the
26300 target. This behaviour is maintained for backward compatibility, but
26301 all frontends should treat @samp{^done} and @samp{^running}
26302 identically and rely on the @samp{*running} output record to determine
26303 which threads are resumed.
26307 @value{GDBN} has connected to a remote target.
26309 @item "^error" "," @var{c-string}
26311 The operation failed. The @code{@var{c-string}} contains the corresponding
26316 @value{GDBN} has terminated.
26320 @node GDB/MI Stream Records
26321 @subsection @sc{gdb/mi} Stream Records
26323 @cindex @sc{gdb/mi}, stream records
26324 @cindex stream records in @sc{gdb/mi}
26325 @value{GDBN} internally maintains a number of output streams: the console, the
26326 target, and the log. The output intended for each of these streams is
26327 funneled through the @sc{gdb/mi} interface using @dfn{stream records}.
26329 Each stream record begins with a unique @dfn{prefix character} which
26330 identifies its stream (@pxref{GDB/MI Output Syntax, , @sc{gdb/mi} Output
26331 Syntax}). In addition to the prefix, each stream record contains a
26332 @code{@var{string-output}}. This is either raw text (with an implicit new
26333 line) or a quoted C string (which does not contain an implicit newline).
26336 @item "~" @var{string-output}
26337 The console output stream contains text that should be displayed in the
26338 CLI console window. It contains the textual responses to CLI commands.
26340 @item "@@" @var{string-output}
26341 The target output stream contains any textual output from the running
26342 target. This is only present when GDB's event loop is truly
26343 asynchronous, which is currently only the case for remote targets.
26345 @item "&" @var{string-output}
26346 The log stream contains debugging messages being produced by @value{GDBN}'s
26350 @node GDB/MI Async Records
26351 @subsection @sc{gdb/mi} Async Records
26353 @cindex async records in @sc{gdb/mi}
26354 @cindex @sc{gdb/mi}, async records
26355 @dfn{Async} records are used to notify the @sc{gdb/mi} client of
26356 additional changes that have occurred. Those changes can either be a
26357 consequence of @sc{gdb/mi} commands (e.g., a breakpoint modified) or a result of
26358 target activity (e.g., target stopped).
26360 The following is the list of possible async records:
26364 @item *running,thread-id="@var{thread}"
26365 The target is now running. The @var{thread} field tells which
26366 specific thread is now running, and can be @samp{all} if all threads
26367 are running. The frontend should assume that no interaction with a
26368 running thread is possible after this notification is produced.
26369 The frontend should not assume that this notification is output
26370 only once for any command. @value{GDBN} may emit this notification
26371 several times, either for different threads, because it cannot resume
26372 all threads together, or even for a single thread, if the thread must
26373 be stepped though some code before letting it run freely.
26375 @item *stopped,reason="@var{reason}",thread-id="@var{id}",stopped-threads="@var{stopped}",core="@var{core}"
26376 The target has stopped. The @var{reason} field can have one of the
26380 @item breakpoint-hit
26381 A breakpoint was reached.
26382 @item watchpoint-trigger
26383 A watchpoint was triggered.
26384 @item read-watchpoint-trigger
26385 A read watchpoint was triggered.
26386 @item access-watchpoint-trigger
26387 An access watchpoint was triggered.
26388 @item function-finished
26389 An -exec-finish or similar CLI command was accomplished.
26390 @item location-reached
26391 An -exec-until or similar CLI command was accomplished.
26392 @item watchpoint-scope
26393 A watchpoint has gone out of scope.
26394 @item end-stepping-range
26395 An -exec-next, -exec-next-instruction, -exec-step, -exec-step-instruction or
26396 similar CLI command was accomplished.
26397 @item exited-signalled
26398 The inferior exited because of a signal.
26400 The inferior exited.
26401 @item exited-normally
26402 The inferior exited normally.
26403 @item signal-received
26404 A signal was received by the inferior.
26406 The inferior has stopped due to a library being loaded or unloaded.
26407 This can happen when @code{stop-on-solib-events} (@pxref{Files}) is
26408 set or when a @code{catch load} or @code{catch unload} catchpoint is
26409 in use (@pxref{Set Catchpoints}).
26411 The inferior has forked. This is reported when @code{catch fork}
26412 (@pxref{Set Catchpoints}) has been used.
26414 The inferior has vforked. This is reported in when @code{catch vfork}
26415 (@pxref{Set Catchpoints}) has been used.
26416 @item syscall-entry
26417 The inferior entered a system call. This is reported when @code{catch
26418 syscall} (@pxref{Set Catchpoints}) has been used.
26419 @item syscall-entry
26420 The inferior returned from a system call. This is reported when
26421 @code{catch syscall} (@pxref{Set Catchpoints}) has been used.
26423 The inferior called @code{exec}. This is reported when @code{catch exec}
26424 (@pxref{Set Catchpoints}) has been used.
26427 The @var{id} field identifies the thread that directly caused the stop
26428 -- for example by hitting a breakpoint. Depending on whether all-stop
26429 mode is in effect (@pxref{All-Stop Mode}), @value{GDBN} may either
26430 stop all threads, or only the thread that directly triggered the stop.
26431 If all threads are stopped, the @var{stopped} field will have the
26432 value of @code{"all"}. Otherwise, the value of the @var{stopped}
26433 field will be a list of thread identifiers. Presently, this list will
26434 always include a single thread, but frontend should be prepared to see
26435 several threads in the list. The @var{core} field reports the
26436 processor core on which the stop event has happened. This field may be absent
26437 if such information is not available.
26439 @item =thread-group-added,id="@var{id}"
26440 @itemx =thread-group-removed,id="@var{id}"
26441 A thread group was either added or removed. The @var{id} field
26442 contains the @value{GDBN} identifier of the thread group. When a thread
26443 group is added, it generally might not be associated with a running
26444 process. When a thread group is removed, its id becomes invalid and
26445 cannot be used in any way.
26447 @item =thread-group-started,id="@var{id}",pid="@var{pid}"
26448 A thread group became associated with a running program,
26449 either because the program was just started or the thread group
26450 was attached to a program. The @var{id} field contains the
26451 @value{GDBN} identifier of the thread group. The @var{pid} field
26452 contains process identifier, specific to the operating system.
26454 @item =thread-group-exited,id="@var{id}"[,exit-code="@var{code}"]
26455 A thread group is no longer associated with a running program,
26456 either because the program has exited, or because it was detached
26457 from. The @var{id} field contains the @value{GDBN} identifier of the
26458 thread group. @var{code} is the exit code of the inferior; it exists
26459 only when the inferior exited with some code.
26461 @item =thread-created,id="@var{id}",group-id="@var{gid}"
26462 @itemx =thread-exited,id="@var{id}",group-id="@var{gid}"
26463 A thread either was created, or has exited. The @var{id} field
26464 contains the @value{GDBN} identifier of the thread. The @var{gid}
26465 field identifies the thread group this thread belongs to.
26467 @item =thread-selected,id="@var{id}"
26468 Informs that the selected thread was changed as result of the last
26469 command. This notification is not emitted as result of @code{-thread-select}
26470 command but is emitted whenever an MI command that is not documented
26471 to change the selected thread actually changes it. In particular,
26472 invoking, directly or indirectly (via user-defined command), the CLI
26473 @code{thread} command, will generate this notification.
26475 We suggest that in response to this notification, front ends
26476 highlight the selected thread and cause subsequent commands to apply to
26479 @item =library-loaded,...
26480 Reports that a new library file was loaded by the program. This
26481 notification has 4 fields---@var{id}, @var{target-name},
26482 @var{host-name}, and @var{symbols-loaded}. The @var{id} field is an
26483 opaque identifier of the library. For remote debugging case,
26484 @var{target-name} and @var{host-name} fields give the name of the
26485 library file on the target, and on the host respectively. For native
26486 debugging, both those fields have the same value. The
26487 @var{symbols-loaded} field is emitted only for backward compatibility
26488 and should not be relied on to convey any useful information. The
26489 @var{thread-group} field, if present, specifies the id of the thread
26490 group in whose context the library was loaded. If the field is
26491 absent, it means the library was loaded in the context of all present
26494 @item =library-unloaded,...
26495 Reports that a library was unloaded by the program. This notification
26496 has 3 fields---@var{id}, @var{target-name} and @var{host-name} with
26497 the same meaning as for the @code{=library-loaded} notification.
26498 The @var{thread-group} field, if present, specifies the id of the
26499 thread group in whose context the library was unloaded. If the field is
26500 absent, it means the library was unloaded in the context of all present
26503 @item =breakpoint-created,bkpt=@{...@}
26504 @itemx =breakpoint-modified,bkpt=@{...@}
26505 @itemx =breakpoint-deleted,bkpt=@{...@}
26506 Reports that a breakpoint was created, modified, or deleted,
26507 respectively. Only user-visible breakpoints are reported to the MI
26510 The @var{bkpt} argument is of the same form as returned by the various
26511 breakpoint commands; @xref{GDB/MI Breakpoint Commands}.
26513 Note that if a breakpoint is emitted in the result record of a
26514 command, then it will not also be emitted in an async record.
26518 @node GDB/MI Frame Information
26519 @subsection @sc{gdb/mi} Frame Information
26521 Response from many MI commands includes an information about stack
26522 frame. This information is a tuple that may have the following
26527 The level of the stack frame. The innermost frame has the level of
26528 zero. This field is always present.
26531 The name of the function corresponding to the frame. This field may
26532 be absent if @value{GDBN} is unable to determine the function name.
26535 The code address for the frame. This field is always present.
26538 The name of the source files that correspond to the frame's code
26539 address. This field may be absent.
26542 The source line corresponding to the frames' code address. This field
26546 The name of the binary file (either executable or shared library) the
26547 corresponds to the frame's code address. This field may be absent.
26551 @node GDB/MI Thread Information
26552 @subsection @sc{gdb/mi} Thread Information
26554 Whenever @value{GDBN} has to report an information about a thread, it
26555 uses a tuple with the following fields:
26559 The numeric id assigned to the thread by @value{GDBN}. This field is
26563 Target-specific string identifying the thread. This field is always present.
26566 Additional information about the thread provided by the target.
26567 It is supposed to be human-readable and not interpreted by the
26568 frontend. This field is optional.
26571 Either @samp{stopped} or @samp{running}, depending on whether the
26572 thread is presently running. This field is always present.
26575 The value of this field is an integer number of the processor core the
26576 thread was last seen on. This field is optional.
26579 @node GDB/MI Ada Exception Information
26580 @subsection @sc{gdb/mi} Ada Exception Information
26582 Whenever a @code{*stopped} record is emitted because the program
26583 stopped after hitting an exception catchpoint (@pxref{Set Catchpoints}),
26584 @value{GDBN} provides the name of the exception that was raised via
26585 the @code{exception-name} field.
26587 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
26588 @node GDB/MI Simple Examples
26589 @section Simple Examples of @sc{gdb/mi} Interaction
26590 @cindex @sc{gdb/mi}, simple examples
26592 This subsection presents several simple examples of interaction using
26593 the @sc{gdb/mi} interface. In these examples, @samp{->} means that the
26594 following line is passed to @sc{gdb/mi} as input, while @samp{<-} means
26595 the output received from @sc{gdb/mi}.
26597 Note the line breaks shown in the examples are here only for
26598 readability, they don't appear in the real output.
26600 @subheading Setting a Breakpoint
26602 Setting a breakpoint generates synchronous output which contains detailed
26603 information of the breakpoint.
26606 -> -break-insert main
26607 <- ^done,bkpt=@{number="1",type="breakpoint",disp="keep",
26608 enabled="y",addr="0x08048564",func="main",file="myprog.c",
26609 fullname="/home/nickrob/myprog.c",line="68",times="0"@}
26613 @subheading Program Execution
26615 Program execution generates asynchronous records and MI gives the
26616 reason that execution stopped.
26622 <- *stopped,reason="breakpoint-hit",disp="keep",bkptno="1",thread-id="0",
26623 frame=@{addr="0x08048564",func="main",
26624 args=[@{name="argc",value="1"@},@{name="argv",value="0xbfc4d4d4"@}],
26625 file="myprog.c",fullname="/home/nickrob/myprog.c",line="68"@}
26630 <- *stopped,reason="exited-normally"
26634 @subheading Quitting @value{GDBN}
26636 Quitting @value{GDBN} just prints the result class @samp{^exit}.
26644 Please note that @samp{^exit} is printed immediately, but it might
26645 take some time for @value{GDBN} to actually exit. During that time, @value{GDBN}
26646 performs necessary cleanups, including killing programs being debugged
26647 or disconnecting from debug hardware, so the frontend should wait till
26648 @value{GDBN} exits and should only forcibly kill @value{GDBN} if it
26649 fails to exit in reasonable time.
26651 @subheading A Bad Command
26653 Here's what happens if you pass a non-existent command:
26657 <- ^error,msg="Undefined MI command: rubbish"
26662 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
26663 @node GDB/MI Command Description Format
26664 @section @sc{gdb/mi} Command Description Format
26666 The remaining sections describe blocks of commands. Each block of
26667 commands is laid out in a fashion similar to this section.
26669 @subheading Motivation
26671 The motivation for this collection of commands.
26673 @subheading Introduction
26675 A brief introduction to this collection of commands as a whole.
26677 @subheading Commands
26679 For each command in the block, the following is described:
26681 @subsubheading Synopsis
26684 -command @var{args}@dots{}
26687 @subsubheading Result
26689 @subsubheading @value{GDBN} Command
26691 The corresponding @value{GDBN} CLI command(s), if any.
26693 @subsubheading Example
26695 Example(s) formatted for readability. Some of the described commands have
26696 not been implemented yet and these are labeled N.A.@: (not available).
26699 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
26700 @node GDB/MI Breakpoint Commands
26701 @section @sc{gdb/mi} Breakpoint Commands
26703 @cindex breakpoint commands for @sc{gdb/mi}
26704 @cindex @sc{gdb/mi}, breakpoint commands
26705 This section documents @sc{gdb/mi} commands for manipulating
26708 @subheading The @code{-break-after} Command
26709 @findex -break-after
26711 @subsubheading Synopsis
26714 -break-after @var{number} @var{count}
26717 The breakpoint number @var{number} is not in effect until it has been
26718 hit @var{count} times. To see how this is reflected in the output of
26719 the @samp{-break-list} command, see the description of the
26720 @samp{-break-list} command below.
26722 @subsubheading @value{GDBN} Command
26724 The corresponding @value{GDBN} command is @samp{ignore}.
26726 @subsubheading Example
26731 ^done,bkpt=@{number="1",type="breakpoint",disp="keep",
26732 enabled="y",addr="0x000100d0",func="main",file="hello.c",
26733 fullname="/home/foo/hello.c",line="5",times="0"@}
26740 ^done,BreakpointTable=@{nr_rows="1",nr_cols="6",
26741 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
26742 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
26743 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
26744 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
26745 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
26746 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
26747 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
26748 addr="0x000100d0",func="main",file="hello.c",fullname="/home/foo/hello.c",
26749 line="5",times="0",ignore="3"@}]@}
26754 @subheading The @code{-break-catch} Command
26755 @findex -break-catch
26758 @subheading The @code{-break-commands} Command
26759 @findex -break-commands
26761 @subsubheading Synopsis
26764 -break-commands @var{number} [ @var{command1} ... @var{commandN} ]
26767 Specifies the CLI commands that should be executed when breakpoint
26768 @var{number} is hit. The parameters @var{command1} to @var{commandN}
26769 are the commands. If no command is specified, any previously-set
26770 commands are cleared. @xref{Break Commands}. Typical use of this
26771 functionality is tracing a program, that is, printing of values of
26772 some variables whenever breakpoint is hit and then continuing.
26774 @subsubheading @value{GDBN} Command
26776 The corresponding @value{GDBN} command is @samp{commands}.
26778 @subsubheading Example
26783 ^done,bkpt=@{number="1",type="breakpoint",disp="keep",
26784 enabled="y",addr="0x000100d0",func="main",file="hello.c",
26785 fullname="/home/foo/hello.c",line="5",times="0"@}
26787 -break-commands 1 "print v" "continue"
26792 @subheading The @code{-break-condition} Command
26793 @findex -break-condition
26795 @subsubheading Synopsis
26798 -break-condition @var{number} @var{expr}
26801 Breakpoint @var{number} will stop the program only if the condition in
26802 @var{expr} is true. The condition becomes part of the
26803 @samp{-break-list} output (see the description of the @samp{-break-list}
26806 @subsubheading @value{GDBN} Command
26808 The corresponding @value{GDBN} command is @samp{condition}.
26810 @subsubheading Example
26814 -break-condition 1 1
26818 ^done,BreakpointTable=@{nr_rows="1",nr_cols="6",
26819 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
26820 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
26821 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
26822 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
26823 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
26824 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
26825 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
26826 addr="0x000100d0",func="main",file="hello.c",fullname="/home/foo/hello.c",
26827 line="5",cond="1",times="0",ignore="3"@}]@}
26831 @subheading The @code{-break-delete} Command
26832 @findex -break-delete
26834 @subsubheading Synopsis
26837 -break-delete ( @var{breakpoint} )+
26840 Delete the breakpoint(s) whose number(s) are specified in the argument
26841 list. This is obviously reflected in the breakpoint list.
26843 @subsubheading @value{GDBN} Command
26845 The corresponding @value{GDBN} command is @samp{delete}.
26847 @subsubheading Example
26855 ^done,BreakpointTable=@{nr_rows="0",nr_cols="6",
26856 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
26857 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
26858 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
26859 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
26860 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
26861 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
26866 @subheading The @code{-break-disable} Command
26867 @findex -break-disable
26869 @subsubheading Synopsis
26872 -break-disable ( @var{breakpoint} )+
26875 Disable the named @var{breakpoint}(s). The field @samp{enabled} in the
26876 break list is now set to @samp{n} for the named @var{breakpoint}(s).
26878 @subsubheading @value{GDBN} Command
26880 The corresponding @value{GDBN} command is @samp{disable}.
26882 @subsubheading Example
26890 ^done,BreakpointTable=@{nr_rows="1",nr_cols="6",
26891 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
26892 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
26893 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
26894 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
26895 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
26896 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
26897 body=[bkpt=@{number="2",type="breakpoint",disp="keep",enabled="n",
26898 addr="0x000100d0",func="main",file="hello.c",fullname="/home/foo/hello.c",
26899 line="5",times="0"@}]@}
26903 @subheading The @code{-break-enable} Command
26904 @findex -break-enable
26906 @subsubheading Synopsis
26909 -break-enable ( @var{breakpoint} )+
26912 Enable (previously disabled) @var{breakpoint}(s).
26914 @subsubheading @value{GDBN} Command
26916 The corresponding @value{GDBN} command is @samp{enable}.
26918 @subsubheading Example
26926 ^done,BreakpointTable=@{nr_rows="1",nr_cols="6",
26927 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
26928 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
26929 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
26930 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
26931 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
26932 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
26933 body=[bkpt=@{number="2",type="breakpoint",disp="keep",enabled="y",
26934 addr="0x000100d0",func="main",file="hello.c",fullname="/home/foo/hello.c",
26935 line="5",times="0"@}]@}
26939 @subheading The @code{-break-info} Command
26940 @findex -break-info
26942 @subsubheading Synopsis
26945 -break-info @var{breakpoint}
26949 Get information about a single breakpoint.
26951 @subsubheading @value{GDBN} Command
26953 The corresponding @value{GDBN} command is @samp{info break @var{breakpoint}}.
26955 @subsubheading Example
26958 @subheading The @code{-break-insert} Command
26959 @findex -break-insert
26961 @subsubheading Synopsis
26964 -break-insert [ -t ] [ -h ] [ -f ] [ -d ] [ -a ]
26965 [ -c @var{condition} ] [ -i @var{ignore-count} ]
26966 [ -p @var{thread} ] [ @var{location} ]
26970 If specified, @var{location}, can be one of:
26977 @item filename:linenum
26978 @item filename:function
26982 The possible optional parameters of this command are:
26986 Insert a temporary breakpoint.
26988 Insert a hardware breakpoint.
26989 @item -c @var{condition}
26990 Make the breakpoint conditional on @var{condition}.
26991 @item -i @var{ignore-count}
26992 Initialize the @var{ignore-count}.
26994 If @var{location} cannot be parsed (for example if it
26995 refers to unknown files or functions), create a pending
26996 breakpoint. Without this flag, @value{GDBN} will report
26997 an error, and won't create a breakpoint, if @var{location}
27000 Create a disabled breakpoint.
27002 Create a tracepoint. @xref{Tracepoints}. When this parameter
27003 is used together with @samp{-h}, a fast tracepoint is created.
27006 @subsubheading Result
27008 The result is in the form:
27011 ^done,bkpt=@{number="@var{number}",type="@var{type}",disp="del"|"keep",
27012 enabled="y"|"n",addr="@var{hex}",func="@var{funcname}",file="@var{filename}",
27013 fullname="@var{full_filename}",line="@var{lineno}",[thread="@var{threadno},]
27014 times="@var{times}"@}
27018 where @var{number} is the @value{GDBN} number for this breakpoint,
27019 @var{funcname} is the name of the function where the breakpoint was
27020 inserted, @var{filename} is the name of the source file which contains
27021 this function, @var{lineno} is the source line number within that file
27022 and @var{times} the number of times that the breakpoint has been hit
27023 (always 0 for -break-insert but may be greater for -break-info or -break-list
27024 which use the same output).
27026 Note: this format is open to change.
27027 @c An out-of-band breakpoint instead of part of the result?
27029 @subsubheading @value{GDBN} Command
27031 The corresponding @value{GDBN} commands are @samp{break}, @samp{tbreak},
27032 @samp{hbreak}, @samp{thbreak}, and @samp{rbreak}.
27034 @subsubheading Example
27039 ^done,bkpt=@{number="1",addr="0x0001072c",file="recursive2.c",
27040 fullname="/home/foo/recursive2.c,line="4",times="0"@}
27042 -break-insert -t foo
27043 ^done,bkpt=@{number="2",addr="0x00010774",file="recursive2.c",
27044 fullname="/home/foo/recursive2.c,line="11",times="0"@}
27047 ^done,BreakpointTable=@{nr_rows="2",nr_cols="6",
27048 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
27049 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
27050 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
27051 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
27052 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
27053 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
27054 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
27055 addr="0x0001072c", func="main",file="recursive2.c",
27056 fullname="/home/foo/recursive2.c,"line="4",times="0"@},
27057 bkpt=@{number="2",type="breakpoint",disp="del",enabled="y",
27058 addr="0x00010774",func="foo",file="recursive2.c",
27059 fullname="/home/foo/recursive2.c",line="11",times="0"@}]@}
27061 -break-insert -r foo.*
27062 ~int foo(int, int);
27063 ^done,bkpt=@{number="3",addr="0x00010774",file="recursive2.c,
27064 "fullname="/home/foo/recursive2.c",line="11",times="0"@}
27068 @subheading The @code{-break-list} Command
27069 @findex -break-list
27071 @subsubheading Synopsis
27077 Displays the list of inserted breakpoints, showing the following fields:
27081 number of the breakpoint
27083 type of the breakpoint: @samp{breakpoint} or @samp{watchpoint}
27085 should the breakpoint be deleted or disabled when it is hit: @samp{keep}
27088 is the breakpoint enabled or no: @samp{y} or @samp{n}
27090 memory location at which the breakpoint is set
27092 logical location of the breakpoint, expressed by function name, file
27095 number of times the breakpoint has been hit
27098 If there are no breakpoints or watchpoints, the @code{BreakpointTable}
27099 @code{body} field is an empty list.
27101 @subsubheading @value{GDBN} Command
27103 The corresponding @value{GDBN} command is @samp{info break}.
27105 @subsubheading Example
27110 ^done,BreakpointTable=@{nr_rows="2",nr_cols="6",
27111 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
27112 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
27113 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
27114 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
27115 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
27116 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
27117 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
27118 addr="0x000100d0",func="main",file="hello.c",line="5",times="0"@},
27119 bkpt=@{number="2",type="breakpoint",disp="keep",enabled="y",
27120 addr="0x00010114",func="foo",file="hello.c",fullname="/home/foo/hello.c",
27121 line="13",times="0"@}]@}
27125 Here's an example of the result when there are no breakpoints:
27130 ^done,BreakpointTable=@{nr_rows="0",nr_cols="6",
27131 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
27132 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
27133 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
27134 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
27135 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
27136 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
27141 @subheading The @code{-break-passcount} Command
27142 @findex -break-passcount
27144 @subsubheading Synopsis
27147 -break-passcount @var{tracepoint-number} @var{passcount}
27150 Set the passcount for tracepoint @var{tracepoint-number} to
27151 @var{passcount}. If the breakpoint referred to by @var{tracepoint-number}
27152 is not a tracepoint, error is emitted. This corresponds to CLI
27153 command @samp{passcount}.
27155 @subheading The @code{-break-watch} Command
27156 @findex -break-watch
27158 @subsubheading Synopsis
27161 -break-watch [ -a | -r ]
27164 Create a watchpoint. With the @samp{-a} option it will create an
27165 @dfn{access} watchpoint, i.e., a watchpoint that triggers either on a
27166 read from or on a write to the memory location. With the @samp{-r}
27167 option, the watchpoint created is a @dfn{read} watchpoint, i.e., it will
27168 trigger only when the memory location is accessed for reading. Without
27169 either of the options, the watchpoint created is a regular watchpoint,
27170 i.e., it will trigger when the memory location is accessed for writing.
27171 @xref{Set Watchpoints, , Setting Watchpoints}.
27173 Note that @samp{-break-list} will report a single list of watchpoints and
27174 breakpoints inserted.
27176 @subsubheading @value{GDBN} Command
27178 The corresponding @value{GDBN} commands are @samp{watch}, @samp{awatch}, and
27181 @subsubheading Example
27183 Setting a watchpoint on a variable in the @code{main} function:
27188 ^done,wpt=@{number="2",exp="x"@}
27193 *stopped,reason="watchpoint-trigger",wpt=@{number="2",exp="x"@},
27194 value=@{old="-268439212",new="55"@},
27195 frame=@{func="main",args=[],file="recursive2.c",
27196 fullname="/home/foo/bar/recursive2.c",line="5"@}
27200 Setting a watchpoint on a variable local to a function. @value{GDBN} will stop
27201 the program execution twice: first for the variable changing value, then
27202 for the watchpoint going out of scope.
27207 ^done,wpt=@{number="5",exp="C"@}
27212 *stopped,reason="watchpoint-trigger",
27213 wpt=@{number="5",exp="C"@},value=@{old="-276895068",new="3"@},
27214 frame=@{func="callee4",args=[],
27215 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
27216 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="13"@}
27221 *stopped,reason="watchpoint-scope",wpnum="5",
27222 frame=@{func="callee3",args=[@{name="strarg",
27223 value="0x11940 \"A string argument.\""@}],
27224 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
27225 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="18"@}
27229 Listing breakpoints and watchpoints, at different points in the program
27230 execution. Note that once the watchpoint goes out of scope, it is
27236 ^done,wpt=@{number="2",exp="C"@}
27239 ^done,BreakpointTable=@{nr_rows="2",nr_cols="6",
27240 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
27241 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
27242 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
27243 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
27244 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
27245 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
27246 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
27247 addr="0x00010734",func="callee4",
27248 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
27249 fullname="/home/foo/devo/gdb/testsuite/gdb.mi/basics.c"line="8",times="1"@},
27250 bkpt=@{number="2",type="watchpoint",disp="keep",
27251 enabled="y",addr="",what="C",times="0"@}]@}
27256 *stopped,reason="watchpoint-trigger",wpt=@{number="2",exp="C"@},
27257 value=@{old="-276895068",new="3"@},
27258 frame=@{func="callee4",args=[],
27259 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
27260 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="13"@}
27263 ^done,BreakpointTable=@{nr_rows="2",nr_cols="6",
27264 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
27265 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
27266 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
27267 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
27268 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
27269 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
27270 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
27271 addr="0x00010734",func="callee4",
27272 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
27273 fullname="/home/foo/devo/gdb/testsuite/gdb.mi/basics.c",line="8",times="1"@},
27274 bkpt=@{number="2",type="watchpoint",disp="keep",
27275 enabled="y",addr="",what="C",times="-5"@}]@}
27279 ^done,reason="watchpoint-scope",wpnum="2",
27280 frame=@{func="callee3",args=[@{name="strarg",
27281 value="0x11940 \"A string argument.\""@}],
27282 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
27283 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="18"@}
27286 ^done,BreakpointTable=@{nr_rows="1",nr_cols="6",
27287 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
27288 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
27289 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
27290 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
27291 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
27292 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
27293 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
27294 addr="0x00010734",func="callee4",
27295 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
27296 fullname="/home/foo/devo/gdb/testsuite/gdb.mi/basics.c",line="8",
27301 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
27302 @node GDB/MI Program Context
27303 @section @sc{gdb/mi} Program Context
27305 @subheading The @code{-exec-arguments} Command
27306 @findex -exec-arguments
27309 @subsubheading Synopsis
27312 -exec-arguments @var{args}
27315 Set the inferior program arguments, to be used in the next
27318 @subsubheading @value{GDBN} Command
27320 The corresponding @value{GDBN} command is @samp{set args}.
27322 @subsubheading Example
27326 -exec-arguments -v word
27333 @subheading The @code{-exec-show-arguments} Command
27334 @findex -exec-show-arguments
27336 @subsubheading Synopsis
27339 -exec-show-arguments
27342 Print the arguments of the program.
27344 @subsubheading @value{GDBN} Command
27346 The corresponding @value{GDBN} command is @samp{show args}.
27348 @subsubheading Example
27353 @subheading The @code{-environment-cd} Command
27354 @findex -environment-cd
27356 @subsubheading Synopsis
27359 -environment-cd @var{pathdir}
27362 Set @value{GDBN}'s working directory.
27364 @subsubheading @value{GDBN} Command
27366 The corresponding @value{GDBN} command is @samp{cd}.
27368 @subsubheading Example
27372 -environment-cd /kwikemart/marge/ezannoni/flathead-dev/devo/gdb
27378 @subheading The @code{-environment-directory} Command
27379 @findex -environment-directory
27381 @subsubheading Synopsis
27384 -environment-directory [ -r ] [ @var{pathdir} ]+
27387 Add directories @var{pathdir} to beginning of search path for source files.
27388 If the @samp{-r} option is used, the search path is reset to the default
27389 search path. If directories @var{pathdir} are supplied in addition to the
27390 @samp{-r} option, the search path is first reset and then addition
27392 Multiple directories may be specified, separated by blanks. Specifying
27393 multiple directories in a single command
27394 results in the directories added to the beginning of the
27395 search path in the same order they were presented in the command.
27396 If blanks are needed as
27397 part of a directory name, double-quotes should be used around
27398 the name. In the command output, the path will show up separated
27399 by the system directory-separator character. The directory-separator
27400 character must not be used
27401 in any directory name.
27402 If no directories are specified, the current search path is displayed.
27404 @subsubheading @value{GDBN} Command
27406 The corresponding @value{GDBN} command is @samp{dir}.
27408 @subsubheading Example
27412 -environment-directory /kwikemart/marge/ezannoni/flathead-dev/devo/gdb
27413 ^done,source-path="/kwikemart/marge/ezannoni/flathead-dev/devo/gdb:$cdir:$cwd"
27415 -environment-directory ""
27416 ^done,source-path="/kwikemart/marge/ezannoni/flathead-dev/devo/gdb:$cdir:$cwd"
27418 -environment-directory -r /home/jjohnstn/src/gdb /usr/src
27419 ^done,source-path="/home/jjohnstn/src/gdb:/usr/src:$cdir:$cwd"
27421 -environment-directory -r
27422 ^done,source-path="$cdir:$cwd"
27427 @subheading The @code{-environment-path} Command
27428 @findex -environment-path
27430 @subsubheading Synopsis
27433 -environment-path [ -r ] [ @var{pathdir} ]+
27436 Add directories @var{pathdir} to beginning of search path for object files.
27437 If the @samp{-r} option is used, the search path is reset to the original
27438 search path that existed at gdb start-up. If directories @var{pathdir} are
27439 supplied in addition to the
27440 @samp{-r} option, the search path is first reset and then addition
27442 Multiple directories may be specified, separated by blanks. Specifying
27443 multiple directories in a single command
27444 results in the directories added to the beginning of the
27445 search path in the same order they were presented in the command.
27446 If blanks are needed as
27447 part of a directory name, double-quotes should be used around
27448 the name. In the command output, the path will show up separated
27449 by the system directory-separator character. The directory-separator
27450 character must not be used
27451 in any directory name.
27452 If no directories are specified, the current path is displayed.
27455 @subsubheading @value{GDBN} Command
27457 The corresponding @value{GDBN} command is @samp{path}.
27459 @subsubheading Example
27464 ^done,path="/usr/bin"
27466 -environment-path /kwikemart/marge/ezannoni/flathead-dev/ppc-eabi/gdb /bin
27467 ^done,path="/kwikemart/marge/ezannoni/flathead-dev/ppc-eabi/gdb:/bin:/usr/bin"
27469 -environment-path -r /usr/local/bin
27470 ^done,path="/usr/local/bin:/usr/bin"
27475 @subheading The @code{-environment-pwd} Command
27476 @findex -environment-pwd
27478 @subsubheading Synopsis
27484 Show the current working directory.
27486 @subsubheading @value{GDBN} Command
27488 The corresponding @value{GDBN} command is @samp{pwd}.
27490 @subsubheading Example
27495 ^done,cwd="/kwikemart/marge/ezannoni/flathead-dev/devo/gdb"
27499 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
27500 @node GDB/MI Thread Commands
27501 @section @sc{gdb/mi} Thread Commands
27504 @subheading The @code{-thread-info} Command
27505 @findex -thread-info
27507 @subsubheading Synopsis
27510 -thread-info [ @var{thread-id} ]
27513 Reports information about either a specific thread, if
27514 the @var{thread-id} parameter is present, or about all
27515 threads. When printing information about all threads,
27516 also reports the current thread.
27518 @subsubheading @value{GDBN} Command
27520 The @samp{info thread} command prints the same information
27523 @subsubheading Result
27525 The result is a list of threads. The following attributes are
27526 defined for a given thread:
27530 This field exists only for the current thread. It has the value @samp{*}.
27533 The identifier that @value{GDBN} uses to refer to the thread.
27536 The identifier that the target uses to refer to the thread.
27539 Extra information about the thread, in a target-specific format. This
27543 The name of the thread. If the user specified a name using the
27544 @code{thread name} command, then this name is given. Otherwise, if
27545 @value{GDBN} can extract the thread name from the target, then that
27546 name is given. If @value{GDBN} cannot find the thread name, then this
27550 The stack frame currently executing in the thread.
27553 The thread's state. The @samp{state} field may have the following
27558 The thread is stopped. Frame information is available for stopped
27562 The thread is running. There's no frame information for running
27568 If @value{GDBN} can find the CPU core on which this thread is running,
27569 then this field is the core identifier. This field is optional.
27573 @subsubheading Example
27578 @{id="2",target-id="Thread 0xb7e14b90 (LWP 21257)",
27579 frame=@{level="0",addr="0xffffe410",func="__kernel_vsyscall",
27580 args=[]@},state="running"@},
27581 @{id="1",target-id="Thread 0xb7e156b0 (LWP 21254)",
27582 frame=@{level="0",addr="0x0804891f",func="foo",
27583 args=[@{name="i",value="10"@}],
27584 file="/tmp/a.c",fullname="/tmp/a.c",line="158"@},
27585 state="running"@}],
27586 current-thread-id="1"
27590 @subheading The @code{-thread-list-ids} Command
27591 @findex -thread-list-ids
27593 @subsubheading Synopsis
27599 Produces a list of the currently known @value{GDBN} thread ids. At the
27600 end of the list it also prints the total number of such threads.
27602 This command is retained for historical reasons, the
27603 @code{-thread-info} command should be used instead.
27605 @subsubheading @value{GDBN} Command
27607 Part of @samp{info threads} supplies the same information.
27609 @subsubheading Example
27614 ^done,thread-ids=@{thread-id="3",thread-id="2",thread-id="1"@},
27615 current-thread-id="1",number-of-threads="3"
27620 @subheading The @code{-thread-select} Command
27621 @findex -thread-select
27623 @subsubheading Synopsis
27626 -thread-select @var{threadnum}
27629 Make @var{threadnum} the current thread. It prints the number of the new
27630 current thread, and the topmost frame for that thread.
27632 This command is deprecated in favor of explicitly using the
27633 @samp{--thread} option to each command.
27635 @subsubheading @value{GDBN} Command
27637 The corresponding @value{GDBN} command is @samp{thread}.
27639 @subsubheading Example
27646 *stopped,reason="end-stepping-range",thread-id="2",line="187",
27647 file="../../../devo/gdb/testsuite/gdb.threads/linux-dp.c"
27651 thread-ids=@{thread-id="3",thread-id="2",thread-id="1"@},
27652 number-of-threads="3"
27655 ^done,new-thread-id="3",
27656 frame=@{level="0",func="vprintf",
27657 args=[@{name="format",value="0x8048e9c \"%*s%c %d %c\\n\""@},
27658 @{name="arg",value="0x2"@}],file="vprintf.c",line="31"@}
27662 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
27663 @node GDB/MI Ada Tasking Commands
27664 @section @sc{gdb/mi} Ada Tasking Commands
27666 @subheading The @code{-ada-task-info} Command
27667 @findex -ada-task-info
27669 @subsubheading Synopsis
27672 -ada-task-info [ @var{task-id} ]
27675 Reports information about either a specific Ada task, if the
27676 @var{task-id} parameter is present, or about all Ada tasks.
27678 @subsubheading @value{GDBN} Command
27680 The @samp{info tasks} command prints the same information
27681 about all Ada tasks (@pxref{Ada Tasks}).
27683 @subsubheading Result
27685 The result is a table of Ada tasks. The following columns are
27686 defined for each Ada task:
27690 This field exists only for the current thread. It has the value @samp{*}.
27693 The identifier that @value{GDBN} uses to refer to the Ada task.
27696 The identifier that the target uses to refer to the Ada task.
27699 The identifier of the thread corresponding to the Ada task.
27701 This field should always exist, as Ada tasks are always implemented
27702 on top of a thread. But if @value{GDBN} cannot find this corresponding
27703 thread for any reason, the field is omitted.
27706 This field exists only when the task was created by another task.
27707 In this case, it provides the ID of the parent task.
27710 The base priority of the task.
27713 The current state of the task. For a detailed description of the
27714 possible states, see @ref{Ada Tasks}.
27717 The name of the task.
27721 @subsubheading Example
27725 ^done,tasks=@{nr_rows="3",nr_cols="8",
27726 hdr=[@{width="1",alignment="-1",col_name="current",colhdr=""@},
27727 @{width="3",alignment="1",col_name="id",colhdr="ID"@},
27728 @{width="9",alignment="1",col_name="task-id",colhdr="TID"@},
27729 @{width="4",alignment="1",col_name="thread-id",colhdr=""@},
27730 @{width="4",alignment="1",col_name="parent-id",colhdr="P-ID"@},
27731 @{width="3",alignment="1",col_name="priority",colhdr="Pri"@},
27732 @{width="22",alignment="-1",col_name="state",colhdr="State"@},
27733 @{width="1",alignment="2",col_name="name",colhdr="Name"@}],
27734 body=[@{current="*",id="1",task-id=" 644010",thread-id="1",priority="48",
27735 state="Child Termination Wait",name="main_task"@}]@}
27739 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
27740 @node GDB/MI Program Execution
27741 @section @sc{gdb/mi} Program Execution
27743 These are the asynchronous commands which generate the out-of-band
27744 record @samp{*stopped}. Currently @value{GDBN} only really executes
27745 asynchronously with remote targets and this interaction is mimicked in
27748 @subheading The @code{-exec-continue} Command
27749 @findex -exec-continue
27751 @subsubheading Synopsis
27754 -exec-continue [--reverse] [--all|--thread-group N]
27757 Resumes the execution of the inferior program, which will continue
27758 to execute until it reaches a debugger stop event. If the
27759 @samp{--reverse} option is specified, execution resumes in reverse until
27760 it reaches a stop event. Stop events may include
27763 breakpoints or watchpoints
27765 signals or exceptions
27767 the end of the process (or its beginning under @samp{--reverse})
27769 the end or beginning of a replay log if one is being used.
27771 In all-stop mode (@pxref{All-Stop
27772 Mode}), may resume only one thread, or all threads, depending on the
27773 value of the @samp{scheduler-locking} variable. If @samp{--all} is
27774 specified, all threads (in all inferiors) will be resumed. The @samp{--all} option is
27775 ignored in all-stop mode. If the @samp{--thread-group} options is
27776 specified, then all threads in that thread group are resumed.
27778 @subsubheading @value{GDBN} Command
27780 The corresponding @value{GDBN} corresponding is @samp{continue}.
27782 @subsubheading Example
27789 *stopped,reason="breakpoint-hit",disp="keep",bkptno="2",frame=@{
27790 func="foo",args=[],file="hello.c",fullname="/home/foo/bar/hello.c",
27796 @subheading The @code{-exec-finish} Command
27797 @findex -exec-finish
27799 @subsubheading Synopsis
27802 -exec-finish [--reverse]
27805 Resumes the execution of the inferior program until the current
27806 function is exited. Displays the results returned by the function.
27807 If the @samp{--reverse} option is specified, resumes the reverse
27808 execution of the inferior program until the point where current
27809 function was called.
27811 @subsubheading @value{GDBN} Command
27813 The corresponding @value{GDBN} command is @samp{finish}.
27815 @subsubheading Example
27817 Function returning @code{void}.
27824 *stopped,reason="function-finished",frame=@{func="main",args=[],
27825 file="hello.c",fullname="/home/foo/bar/hello.c",line="7"@}
27829 Function returning other than @code{void}. The name of the internal
27830 @value{GDBN} variable storing the result is printed, together with the
27837 *stopped,reason="function-finished",frame=@{addr="0x000107b0",func="foo",
27838 args=[@{name="a",value="1"],@{name="b",value="9"@}@},
27839 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
27840 gdb-result-var="$1",return-value="0"
27845 @subheading The @code{-exec-interrupt} Command
27846 @findex -exec-interrupt
27848 @subsubheading Synopsis
27851 -exec-interrupt [--all|--thread-group N]
27854 Interrupts the background execution of the target. Note how the token
27855 associated with the stop message is the one for the execution command
27856 that has been interrupted. The token for the interrupt itself only
27857 appears in the @samp{^done} output. If the user is trying to
27858 interrupt a non-running program, an error message will be printed.
27860 Note that when asynchronous execution is enabled, this command is
27861 asynchronous just like other execution commands. That is, first the
27862 @samp{^done} response will be printed, and the target stop will be
27863 reported after that using the @samp{*stopped} notification.
27865 In non-stop mode, only the context thread is interrupted by default.
27866 All threads (in all inferiors) will be interrupted if the
27867 @samp{--all} option is specified. If the @samp{--thread-group}
27868 option is specified, all threads in that group will be interrupted.
27870 @subsubheading @value{GDBN} Command
27872 The corresponding @value{GDBN} command is @samp{interrupt}.
27874 @subsubheading Example
27885 111*stopped,signal-name="SIGINT",signal-meaning="Interrupt",
27886 frame=@{addr="0x00010140",func="foo",args=[],file="try.c",
27887 fullname="/home/foo/bar/try.c",line="13"@}
27892 ^error,msg="mi_cmd_exec_interrupt: Inferior not executing."
27896 @subheading The @code{-exec-jump} Command
27899 @subsubheading Synopsis
27902 -exec-jump @var{location}
27905 Resumes execution of the inferior program at the location specified by
27906 parameter. @xref{Specify Location}, for a description of the
27907 different forms of @var{location}.
27909 @subsubheading @value{GDBN} Command
27911 The corresponding @value{GDBN} command is @samp{jump}.
27913 @subsubheading Example
27916 -exec-jump foo.c:10
27917 *running,thread-id="all"
27922 @subheading The @code{-exec-next} Command
27925 @subsubheading Synopsis
27928 -exec-next [--reverse]
27931 Resumes execution of the inferior program, stopping when the beginning
27932 of the next source line is reached.
27934 If the @samp{--reverse} option is specified, resumes reverse execution
27935 of the inferior program, stopping at the beginning of the previous
27936 source line. If you issue this command on the first line of a
27937 function, it will take you back to the caller of that function, to the
27938 source line where the function was called.
27941 @subsubheading @value{GDBN} Command
27943 The corresponding @value{GDBN} command is @samp{next}.
27945 @subsubheading Example
27951 *stopped,reason="end-stepping-range",line="8",file="hello.c"
27956 @subheading The @code{-exec-next-instruction} Command
27957 @findex -exec-next-instruction
27959 @subsubheading Synopsis
27962 -exec-next-instruction [--reverse]
27965 Executes one machine instruction. If the instruction is a function
27966 call, continues until the function returns. If the program stops at an
27967 instruction in the middle of a source line, the address will be
27970 If the @samp{--reverse} option is specified, resumes reverse execution
27971 of the inferior program, stopping at the previous instruction. If the
27972 previously executed instruction was a return from another function,
27973 it will continue to execute in reverse until the call to that function
27974 (from the current stack frame) is reached.
27976 @subsubheading @value{GDBN} Command
27978 The corresponding @value{GDBN} command is @samp{nexti}.
27980 @subsubheading Example
27984 -exec-next-instruction
27988 *stopped,reason="end-stepping-range",
27989 addr="0x000100d4",line="5",file="hello.c"
27994 @subheading The @code{-exec-return} Command
27995 @findex -exec-return
27997 @subsubheading Synopsis
28003 Makes current function return immediately. Doesn't execute the inferior.
28004 Displays the new current frame.
28006 @subsubheading @value{GDBN} Command
28008 The corresponding @value{GDBN} command is @samp{return}.
28010 @subsubheading Example
28014 200-break-insert callee4
28015 200^done,bkpt=@{number="1",addr="0x00010734",
28016 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",line="8"@}
28021 000*stopped,reason="breakpoint-hit",disp="keep",bkptno="1",
28022 frame=@{func="callee4",args=[],
28023 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
28024 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="8"@}
28030 111^done,frame=@{level="0",func="callee3",
28031 args=[@{name="strarg",
28032 value="0x11940 \"A string argument.\""@}],
28033 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
28034 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="18"@}
28039 @subheading The @code{-exec-run} Command
28042 @subsubheading Synopsis
28045 -exec-run [--all | --thread-group N]
28048 Starts execution of the inferior from the beginning. The inferior
28049 executes until either a breakpoint is encountered or the program
28050 exits. In the latter case the output will include an exit code, if
28051 the program has exited exceptionally.
28053 When no option is specified, the current inferior is started. If the
28054 @samp{--thread-group} option is specified, it should refer to a thread
28055 group of type @samp{process}, and that thread group will be started.
28056 If the @samp{--all} option is specified, then all inferiors will be started.
28058 @subsubheading @value{GDBN} Command
28060 The corresponding @value{GDBN} command is @samp{run}.
28062 @subsubheading Examples
28067 ^done,bkpt=@{number="1",addr="0x0001072c",file="recursive2.c",line="4"@}
28072 *stopped,reason="breakpoint-hit",disp="keep",bkptno="1",
28073 frame=@{func="main",args=[],file="recursive2.c",
28074 fullname="/home/foo/bar/recursive2.c",line="4"@}
28079 Program exited normally:
28087 *stopped,reason="exited-normally"
28092 Program exited exceptionally:
28100 *stopped,reason="exited",exit-code="01"
28104 Another way the program can terminate is if it receives a signal such as
28105 @code{SIGINT}. In this case, @sc{gdb/mi} displays this:
28109 *stopped,reason="exited-signalled",signal-name="SIGINT",
28110 signal-meaning="Interrupt"
28114 @c @subheading -exec-signal
28117 @subheading The @code{-exec-step} Command
28120 @subsubheading Synopsis
28123 -exec-step [--reverse]
28126 Resumes execution of the inferior program, stopping when the beginning
28127 of the next source line is reached, if the next source line is not a
28128 function call. If it is, stop at the first instruction of the called
28129 function. If the @samp{--reverse} option is specified, resumes reverse
28130 execution of the inferior program, stopping at the beginning of the
28131 previously executed source line.
28133 @subsubheading @value{GDBN} Command
28135 The corresponding @value{GDBN} command is @samp{step}.
28137 @subsubheading Example
28139 Stepping into a function:
28145 *stopped,reason="end-stepping-range",
28146 frame=@{func="foo",args=[@{name="a",value="10"@},
28147 @{name="b",value="0"@}],file="recursive2.c",
28148 fullname="/home/foo/bar/recursive2.c",line="11"@}
28158 *stopped,reason="end-stepping-range",line="14",file="recursive2.c"
28163 @subheading The @code{-exec-step-instruction} Command
28164 @findex -exec-step-instruction
28166 @subsubheading Synopsis
28169 -exec-step-instruction [--reverse]
28172 Resumes the inferior which executes one machine instruction. If the
28173 @samp{--reverse} option is specified, resumes reverse execution of the
28174 inferior program, stopping at the previously executed instruction.
28175 The output, once @value{GDBN} has stopped, will vary depending on
28176 whether we have stopped in the middle of a source line or not. In the
28177 former case, the address at which the program stopped will be printed
28180 @subsubheading @value{GDBN} Command
28182 The corresponding @value{GDBN} command is @samp{stepi}.
28184 @subsubheading Example
28188 -exec-step-instruction
28192 *stopped,reason="end-stepping-range",
28193 frame=@{func="foo",args=[],file="try.c",
28194 fullname="/home/foo/bar/try.c",line="10"@}
28196 -exec-step-instruction
28200 *stopped,reason="end-stepping-range",
28201 frame=@{addr="0x000100f4",func="foo",args=[],file="try.c",
28202 fullname="/home/foo/bar/try.c",line="10"@}
28207 @subheading The @code{-exec-until} Command
28208 @findex -exec-until
28210 @subsubheading Synopsis
28213 -exec-until [ @var{location} ]
28216 Executes the inferior until the @var{location} specified in the
28217 argument is reached. If there is no argument, the inferior executes
28218 until a source line greater than the current one is reached. The
28219 reason for stopping in this case will be @samp{location-reached}.
28221 @subsubheading @value{GDBN} Command
28223 The corresponding @value{GDBN} command is @samp{until}.
28225 @subsubheading Example
28229 -exec-until recursive2.c:6
28233 *stopped,reason="location-reached",frame=@{func="main",args=[],
28234 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="6"@}
28239 @subheading -file-clear
28240 Is this going away????
28243 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
28244 @node GDB/MI Stack Manipulation
28245 @section @sc{gdb/mi} Stack Manipulation Commands
28248 @subheading The @code{-stack-info-frame} Command
28249 @findex -stack-info-frame
28251 @subsubheading Synopsis
28257 Get info on the selected frame.
28259 @subsubheading @value{GDBN} Command
28261 The corresponding @value{GDBN} command is @samp{info frame} or @samp{frame}
28262 (without arguments).
28264 @subsubheading Example
28269 ^done,frame=@{level="1",addr="0x0001076c",func="callee3",
28270 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
28271 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="17"@}
28275 @subheading The @code{-stack-info-depth} Command
28276 @findex -stack-info-depth
28278 @subsubheading Synopsis
28281 -stack-info-depth [ @var{max-depth} ]
28284 Return the depth of the stack. If the integer argument @var{max-depth}
28285 is specified, do not count beyond @var{max-depth} frames.
28287 @subsubheading @value{GDBN} Command
28289 There's no equivalent @value{GDBN} command.
28291 @subsubheading Example
28293 For a stack with frame levels 0 through 11:
28300 -stack-info-depth 4
28303 -stack-info-depth 12
28306 -stack-info-depth 11
28309 -stack-info-depth 13
28314 @subheading The @code{-stack-list-arguments} Command
28315 @findex -stack-list-arguments
28317 @subsubheading Synopsis
28320 -stack-list-arguments @var{print-values}
28321 [ @var{low-frame} @var{high-frame} ]
28324 Display a list of the arguments for the frames between @var{low-frame}
28325 and @var{high-frame} (inclusive). If @var{low-frame} and
28326 @var{high-frame} are not provided, list the arguments for the whole
28327 call stack. If the two arguments are equal, show the single frame
28328 at the corresponding level. It is an error if @var{low-frame} is
28329 larger than the actual number of frames. On the other hand,
28330 @var{high-frame} may be larger than the actual number of frames, in
28331 which case only existing frames will be returned.
28333 If @var{print-values} is 0 or @code{--no-values}, print only the names of
28334 the variables; if it is 1 or @code{--all-values}, print also their
28335 values; and if it is 2 or @code{--simple-values}, print the name,
28336 type and value for simple data types, and the name and type for arrays,
28337 structures and unions.
28339 Use of this command to obtain arguments in a single frame is
28340 deprecated in favor of the @samp{-stack-list-variables} command.
28342 @subsubheading @value{GDBN} Command
28344 @value{GDBN} does not have an equivalent command. @code{gdbtk} has a
28345 @samp{gdb_get_args} command which partially overlaps with the
28346 functionality of @samp{-stack-list-arguments}.
28348 @subsubheading Example
28355 frame=@{level="0",addr="0x00010734",func="callee4",
28356 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
28357 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="8"@},
28358 frame=@{level="1",addr="0x0001076c",func="callee3",
28359 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
28360 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="17"@},
28361 frame=@{level="2",addr="0x0001078c",func="callee2",
28362 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
28363 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="22"@},
28364 frame=@{level="3",addr="0x000107b4",func="callee1",
28365 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
28366 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="27"@},
28367 frame=@{level="4",addr="0x000107e0",func="main",
28368 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
28369 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="32"@}]
28371 -stack-list-arguments 0
28374 frame=@{level="0",args=[]@},
28375 frame=@{level="1",args=[name="strarg"]@},
28376 frame=@{level="2",args=[name="intarg",name="strarg"]@},
28377 frame=@{level="3",args=[name="intarg",name="strarg",name="fltarg"]@},
28378 frame=@{level="4",args=[]@}]
28380 -stack-list-arguments 1
28383 frame=@{level="0",args=[]@},
28385 args=[@{name="strarg",value="0x11940 \"A string argument.\""@}]@},
28386 frame=@{level="2",args=[
28387 @{name="intarg",value="2"@},
28388 @{name="strarg",value="0x11940 \"A string argument.\""@}]@},
28389 @{frame=@{level="3",args=[
28390 @{name="intarg",value="2"@},
28391 @{name="strarg",value="0x11940 \"A string argument.\""@},
28392 @{name="fltarg",value="3.5"@}]@},
28393 frame=@{level="4",args=[]@}]
28395 -stack-list-arguments 0 2 2
28396 ^done,stack-args=[frame=@{level="2",args=[name="intarg",name="strarg"]@}]
28398 -stack-list-arguments 1 2 2
28399 ^done,stack-args=[frame=@{level="2",
28400 args=[@{name="intarg",value="2"@},
28401 @{name="strarg",value="0x11940 \"A string argument.\""@}]@}]
28405 @c @subheading -stack-list-exception-handlers
28408 @subheading The @code{-stack-list-frames} Command
28409 @findex -stack-list-frames
28411 @subsubheading Synopsis
28414 -stack-list-frames [ @var{low-frame} @var{high-frame} ]
28417 List the frames currently on the stack. For each frame it displays the
28422 The frame number, 0 being the topmost frame, i.e., the innermost function.
28424 The @code{$pc} value for that frame.
28428 File name of the source file where the function lives.
28429 @item @var{fullname}
28430 The full file name of the source file where the function lives.
28432 Line number corresponding to the @code{$pc}.
28434 The shared library where this function is defined. This is only given
28435 if the frame's function is not known.
28438 If invoked without arguments, this command prints a backtrace for the
28439 whole stack. If given two integer arguments, it shows the frames whose
28440 levels are between the two arguments (inclusive). If the two arguments
28441 are equal, it shows the single frame at the corresponding level. It is
28442 an error if @var{low-frame} is larger than the actual number of
28443 frames. On the other hand, @var{high-frame} may be larger than the
28444 actual number of frames, in which case only existing frames will be returned.
28446 @subsubheading @value{GDBN} Command
28448 The corresponding @value{GDBN} commands are @samp{backtrace} and @samp{where}.
28450 @subsubheading Example
28452 Full stack backtrace:
28458 [frame=@{level="0",addr="0x0001076c",func="foo",
28459 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="11"@},
28460 frame=@{level="1",addr="0x000107a4",func="foo",
28461 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
28462 frame=@{level="2",addr="0x000107a4",func="foo",
28463 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
28464 frame=@{level="3",addr="0x000107a4",func="foo",
28465 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
28466 frame=@{level="4",addr="0x000107a4",func="foo",
28467 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
28468 frame=@{level="5",addr="0x000107a4",func="foo",
28469 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
28470 frame=@{level="6",addr="0x000107a4",func="foo",
28471 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
28472 frame=@{level="7",addr="0x000107a4",func="foo",
28473 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
28474 frame=@{level="8",addr="0x000107a4",func="foo",
28475 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
28476 frame=@{level="9",addr="0x000107a4",func="foo",
28477 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
28478 frame=@{level="10",addr="0x000107a4",func="foo",
28479 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
28480 frame=@{level="11",addr="0x00010738",func="main",
28481 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="4"@}]
28485 Show frames between @var{low_frame} and @var{high_frame}:
28489 -stack-list-frames 3 5
28491 [frame=@{level="3",addr="0x000107a4",func="foo",
28492 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
28493 frame=@{level="4",addr="0x000107a4",func="foo",
28494 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
28495 frame=@{level="5",addr="0x000107a4",func="foo",
28496 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@}]
28500 Show a single frame:
28504 -stack-list-frames 3 3
28506 [frame=@{level="3",addr="0x000107a4",func="foo",
28507 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@}]
28512 @subheading The @code{-stack-list-locals} Command
28513 @findex -stack-list-locals
28515 @subsubheading Synopsis
28518 -stack-list-locals @var{print-values}
28521 Display the local variable names for the selected frame. If
28522 @var{print-values} is 0 or @code{--no-values}, print only the names of
28523 the variables; if it is 1 or @code{--all-values}, print also their
28524 values; and if it is 2 or @code{--simple-values}, print the name,
28525 type and value for simple data types, and the name and type for arrays,
28526 structures and unions. In this last case, a frontend can immediately
28527 display the value of simple data types and create variable objects for
28528 other data types when the user wishes to explore their values in
28531 This command is deprecated in favor of the
28532 @samp{-stack-list-variables} command.
28534 @subsubheading @value{GDBN} Command
28536 @samp{info locals} in @value{GDBN}, @samp{gdb_get_locals} in @code{gdbtk}.
28538 @subsubheading Example
28542 -stack-list-locals 0
28543 ^done,locals=[name="A",name="B",name="C"]
28545 -stack-list-locals --all-values
28546 ^done,locals=[@{name="A",value="1"@},@{name="B",value="2"@},
28547 @{name="C",value="@{1, 2, 3@}"@}]
28548 -stack-list-locals --simple-values
28549 ^done,locals=[@{name="A",type="int",value="1"@},
28550 @{name="B",type="int",value="2"@},@{name="C",type="int [3]"@}]
28554 @subheading The @code{-stack-list-variables} Command
28555 @findex -stack-list-variables
28557 @subsubheading Synopsis
28560 -stack-list-variables @var{print-values}
28563 Display the names of local variables and function arguments for the selected frame. If
28564 @var{print-values} is 0 or @code{--no-values}, print only the names of
28565 the variables; if it is 1 or @code{--all-values}, print also their
28566 values; and if it is 2 or @code{--simple-values}, print the name,
28567 type and value for simple data types, and the name and type for arrays,
28568 structures and unions.
28570 @subsubheading Example
28574 -stack-list-variables --thread 1 --frame 0 --all-values
28575 ^done,variables=[@{name="x",value="11"@},@{name="s",value="@{a = 1, b = 2@}"@}]
28580 @subheading The @code{-stack-select-frame} Command
28581 @findex -stack-select-frame
28583 @subsubheading Synopsis
28586 -stack-select-frame @var{framenum}
28589 Change the selected frame. Select a different frame @var{framenum} on
28592 This command in deprecated in favor of passing the @samp{--frame}
28593 option to every command.
28595 @subsubheading @value{GDBN} Command
28597 The corresponding @value{GDBN} commands are @samp{frame}, @samp{up},
28598 @samp{down}, @samp{select-frame}, @samp{up-silent}, and @samp{down-silent}.
28600 @subsubheading Example
28604 -stack-select-frame 2
28609 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
28610 @node GDB/MI Variable Objects
28611 @section @sc{gdb/mi} Variable Objects
28615 @subheading Motivation for Variable Objects in @sc{gdb/mi}
28617 For the implementation of a variable debugger window (locals, watched
28618 expressions, etc.), we are proposing the adaptation of the existing code
28619 used by @code{Insight}.
28621 The two main reasons for that are:
28625 It has been proven in practice (it is already on its second generation).
28628 It will shorten development time (needless to say how important it is
28632 The original interface was designed to be used by Tcl code, so it was
28633 slightly changed so it could be used through @sc{gdb/mi}. This section
28634 describes the @sc{gdb/mi} operations that will be available and gives some
28635 hints about their use.
28637 @emph{Note}: In addition to the set of operations described here, we
28638 expect the @sc{gui} implementation of a variable window to require, at
28639 least, the following operations:
28642 @item @code{-gdb-show} @code{output-radix}
28643 @item @code{-stack-list-arguments}
28644 @item @code{-stack-list-locals}
28645 @item @code{-stack-select-frame}
28650 @subheading Introduction to Variable Objects
28652 @cindex variable objects in @sc{gdb/mi}
28654 Variable objects are "object-oriented" MI interface for examining and
28655 changing values of expressions. Unlike some other MI interfaces that
28656 work with expressions, variable objects are specifically designed for
28657 simple and efficient presentation in the frontend. A variable object
28658 is identified by string name. When a variable object is created, the
28659 frontend specifies the expression for that variable object. The
28660 expression can be a simple variable, or it can be an arbitrary complex
28661 expression, and can even involve CPU registers. After creating a
28662 variable object, the frontend can invoke other variable object
28663 operations---for example to obtain or change the value of a variable
28664 object, or to change display format.
28666 Variable objects have hierarchical tree structure. Any variable object
28667 that corresponds to a composite type, such as structure in C, has
28668 a number of child variable objects, for example corresponding to each
28669 element of a structure. A child variable object can itself have
28670 children, recursively. Recursion ends when we reach
28671 leaf variable objects, which always have built-in types. Child variable
28672 objects are created only by explicit request, so if a frontend
28673 is not interested in the children of a particular variable object, no
28674 child will be created.
28676 For a leaf variable object it is possible to obtain its value as a
28677 string, or set the value from a string. String value can be also
28678 obtained for a non-leaf variable object, but it's generally a string
28679 that only indicates the type of the object, and does not list its
28680 contents. Assignment to a non-leaf variable object is not allowed.
28682 A frontend does not need to read the values of all variable objects each time
28683 the program stops. Instead, MI provides an update command that lists all
28684 variable objects whose values has changed since the last update
28685 operation. This considerably reduces the amount of data that must
28686 be transferred to the frontend. As noted above, children variable
28687 objects are created on demand, and only leaf variable objects have a
28688 real value. As result, gdb will read target memory only for leaf
28689 variables that frontend has created.
28691 The automatic update is not always desirable. For example, a frontend
28692 might want to keep a value of some expression for future reference,
28693 and never update it. For another example, fetching memory is
28694 relatively slow for embedded targets, so a frontend might want
28695 to disable automatic update for the variables that are either not
28696 visible on the screen, or ``closed''. This is possible using so
28697 called ``frozen variable objects''. Such variable objects are never
28698 implicitly updated.
28700 Variable objects can be either @dfn{fixed} or @dfn{floating}. For the
28701 fixed variable object, the expression is parsed when the variable
28702 object is created, including associating identifiers to specific
28703 variables. The meaning of expression never changes. For a floating
28704 variable object the values of variables whose names appear in the
28705 expressions are re-evaluated every time in the context of the current
28706 frame. Consider this example:
28711 struct work_state state;
28718 If a fixed variable object for the @code{state} variable is created in
28719 this function, and we enter the recursive call, the variable
28720 object will report the value of @code{state} in the top-level
28721 @code{do_work} invocation. On the other hand, a floating variable
28722 object will report the value of @code{state} in the current frame.
28724 If an expression specified when creating a fixed variable object
28725 refers to a local variable, the variable object becomes bound to the
28726 thread and frame in which the variable object is created. When such
28727 variable object is updated, @value{GDBN} makes sure that the
28728 thread/frame combination the variable object is bound to still exists,
28729 and re-evaluates the variable object in context of that thread/frame.
28731 The following is the complete set of @sc{gdb/mi} operations defined to
28732 access this functionality:
28734 @multitable @columnfractions .4 .6
28735 @item @strong{Operation}
28736 @tab @strong{Description}
28738 @item @code{-enable-pretty-printing}
28739 @tab enable Python-based pretty-printing
28740 @item @code{-var-create}
28741 @tab create a variable object
28742 @item @code{-var-delete}
28743 @tab delete the variable object and/or its children
28744 @item @code{-var-set-format}
28745 @tab set the display format of this variable
28746 @item @code{-var-show-format}
28747 @tab show the display format of this variable
28748 @item @code{-var-info-num-children}
28749 @tab tells how many children this object has
28750 @item @code{-var-list-children}
28751 @tab return a list of the object's children
28752 @item @code{-var-info-type}
28753 @tab show the type of this variable object
28754 @item @code{-var-info-expression}
28755 @tab print parent-relative expression that this variable object represents
28756 @item @code{-var-info-path-expression}
28757 @tab print full expression that this variable object represents
28758 @item @code{-var-show-attributes}
28759 @tab is this variable editable? does it exist here?
28760 @item @code{-var-evaluate-expression}
28761 @tab get the value of this variable
28762 @item @code{-var-assign}
28763 @tab set the value of this variable
28764 @item @code{-var-update}
28765 @tab update the variable and its children
28766 @item @code{-var-set-frozen}
28767 @tab set frozeness attribute
28768 @item @code{-var-set-update-range}
28769 @tab set range of children to display on update
28772 In the next subsection we describe each operation in detail and suggest
28773 how it can be used.
28775 @subheading Description And Use of Operations on Variable Objects
28777 @subheading The @code{-enable-pretty-printing} Command
28778 @findex -enable-pretty-printing
28781 -enable-pretty-printing
28784 @value{GDBN} allows Python-based visualizers to affect the output of the
28785 MI variable object commands. However, because there was no way to
28786 implement this in a fully backward-compatible way, a front end must
28787 request that this functionality be enabled.
28789 Once enabled, this feature cannot be disabled.
28791 Note that if Python support has not been compiled into @value{GDBN},
28792 this command will still succeed (and do nothing).
28794 This feature is currently (as of @value{GDBN} 7.0) experimental, and
28795 may work differently in future versions of @value{GDBN}.
28797 @subheading The @code{-var-create} Command
28798 @findex -var-create
28800 @subsubheading Synopsis
28803 -var-create @{@var{name} | "-"@}
28804 @{@var{frame-addr} | "*" | "@@"@} @var{expression}
28807 This operation creates a variable object, which allows the monitoring of
28808 a variable, the result of an expression, a memory cell or a CPU
28811 The @var{name} parameter is the string by which the object can be
28812 referenced. It must be unique. If @samp{-} is specified, the varobj
28813 system will generate a string ``varNNNNNN'' automatically. It will be
28814 unique provided that one does not specify @var{name} of that format.
28815 The command fails if a duplicate name is found.
28817 The frame under which the expression should be evaluated can be
28818 specified by @var{frame-addr}. A @samp{*} indicates that the current
28819 frame should be used. A @samp{@@} indicates that a floating variable
28820 object must be created.
28822 @var{expression} is any expression valid on the current language set (must not
28823 begin with a @samp{*}), or one of the following:
28827 @samp{*@var{addr}}, where @var{addr} is the address of a memory cell
28830 @samp{*@var{addr}-@var{addr}} --- a memory address range (TBD)
28833 @samp{$@var{regname}} --- a CPU register name
28836 @cindex dynamic varobj
28837 A varobj's contents may be provided by a Python-based pretty-printer. In this
28838 case the varobj is known as a @dfn{dynamic varobj}. Dynamic varobjs
28839 have slightly different semantics in some cases. If the
28840 @code{-enable-pretty-printing} command is not sent, then @value{GDBN}
28841 will never create a dynamic varobj. This ensures backward
28842 compatibility for existing clients.
28844 @subsubheading Result
28846 This operation returns attributes of the newly-created varobj. These
28851 The name of the varobj.
28854 The number of children of the varobj. This number is not necessarily
28855 reliable for a dynamic varobj. Instead, you must examine the
28856 @samp{has_more} attribute.
28859 The varobj's scalar value. For a varobj whose type is some sort of
28860 aggregate (e.g., a @code{struct}), or for a dynamic varobj, this value
28861 will not be interesting.
28864 The varobj's type. This is a string representation of the type, as
28865 would be printed by the @value{GDBN} CLI.
28868 If a variable object is bound to a specific thread, then this is the
28869 thread's identifier.
28872 For a dynamic varobj, this indicates whether there appear to be any
28873 children available. For a non-dynamic varobj, this will be 0.
28876 This attribute will be present and have the value @samp{1} if the
28877 varobj is a dynamic varobj. If the varobj is not a dynamic varobj,
28878 then this attribute will not be present.
28881 A dynamic varobj can supply a display hint to the front end. The
28882 value comes directly from the Python pretty-printer object's
28883 @code{display_hint} method. @xref{Pretty Printing API}.
28886 Typical output will look like this:
28889 name="@var{name}",numchild="@var{N}",type="@var{type}",thread-id="@var{M}",
28890 has_more="@var{has_more}"
28894 @subheading The @code{-var-delete} Command
28895 @findex -var-delete
28897 @subsubheading Synopsis
28900 -var-delete [ -c ] @var{name}
28903 Deletes a previously created variable object and all of its children.
28904 With the @samp{-c} option, just deletes the children.
28906 Returns an error if the object @var{name} is not found.
28909 @subheading The @code{-var-set-format} Command
28910 @findex -var-set-format
28912 @subsubheading Synopsis
28915 -var-set-format @var{name} @var{format-spec}
28918 Sets the output format for the value of the object @var{name} to be
28921 @anchor{-var-set-format}
28922 The syntax for the @var{format-spec} is as follows:
28925 @var{format-spec} @expansion{}
28926 @{binary | decimal | hexadecimal | octal | natural@}
28929 The natural format is the default format choosen automatically
28930 based on the variable type (like decimal for an @code{int}, hex
28931 for pointers, etc.).
28933 For a variable with children, the format is set only on the
28934 variable itself, and the children are not affected.
28936 @subheading The @code{-var-show-format} Command
28937 @findex -var-show-format
28939 @subsubheading Synopsis
28942 -var-show-format @var{name}
28945 Returns the format used to display the value of the object @var{name}.
28948 @var{format} @expansion{}
28953 @subheading The @code{-var-info-num-children} Command
28954 @findex -var-info-num-children
28956 @subsubheading Synopsis
28959 -var-info-num-children @var{name}
28962 Returns the number of children of a variable object @var{name}:
28968 Note that this number is not completely reliable for a dynamic varobj.
28969 It will return the current number of children, but more children may
28973 @subheading The @code{-var-list-children} Command
28974 @findex -var-list-children
28976 @subsubheading Synopsis
28979 -var-list-children [@var{print-values}] @var{name} [@var{from} @var{to}]
28981 @anchor{-var-list-children}
28983 Return a list of the children of the specified variable object and
28984 create variable objects for them, if they do not already exist. With
28985 a single argument or if @var{print-values} has a value of 0 or
28986 @code{--no-values}, print only the names of the variables; if
28987 @var{print-values} is 1 or @code{--all-values}, also print their
28988 values; and if it is 2 or @code{--simple-values} print the name and
28989 value for simple data types and just the name for arrays, structures
28992 @var{from} and @var{to}, if specified, indicate the range of children
28993 to report. If @var{from} or @var{to} is less than zero, the range is
28994 reset and all children will be reported. Otherwise, children starting
28995 at @var{from} (zero-based) and up to and excluding @var{to} will be
28998 If a child range is requested, it will only affect the current call to
28999 @code{-var-list-children}, but not future calls to @code{-var-update}.
29000 For this, you must instead use @code{-var-set-update-range}. The
29001 intent of this approach is to enable a front end to implement any
29002 update approach it likes; for example, scrolling a view may cause the
29003 front end to request more children with @code{-var-list-children}, and
29004 then the front end could call @code{-var-set-update-range} with a
29005 different range to ensure that future updates are restricted to just
29008 For each child the following results are returned:
29013 Name of the variable object created for this child.
29016 The expression to be shown to the user by the front end to designate this child.
29017 For example this may be the name of a structure member.
29019 For a dynamic varobj, this value cannot be used to form an
29020 expression. There is no way to do this at all with a dynamic varobj.
29022 For C/C@t{++} structures there are several pseudo children returned to
29023 designate access qualifiers. For these pseudo children @var{exp} is
29024 @samp{public}, @samp{private}, or @samp{protected}. In this case the
29025 type and value are not present.
29027 A dynamic varobj will not report the access qualifying
29028 pseudo-children, regardless of the language. This information is not
29029 available at all with a dynamic varobj.
29032 Number of children this child has. For a dynamic varobj, this will be
29036 The type of the child.
29039 If values were requested, this is the value.
29042 If this variable object is associated with a thread, this is the thread id.
29043 Otherwise this result is not present.
29046 If the variable object is frozen, this variable will be present with a value of 1.
29049 The result may have its own attributes:
29053 A dynamic varobj can supply a display hint to the front end. The
29054 value comes directly from the Python pretty-printer object's
29055 @code{display_hint} method. @xref{Pretty Printing API}.
29058 This is an integer attribute which is nonzero if there are children
29059 remaining after the end of the selected range.
29062 @subsubheading Example
29066 -var-list-children n
29067 ^done,numchild=@var{n},children=[child=@{name=@var{name},exp=@var{exp},
29068 numchild=@var{n},type=@var{type}@},@r{(repeats N times)}]
29070 -var-list-children --all-values n
29071 ^done,numchild=@var{n},children=[child=@{name=@var{name},exp=@var{exp},
29072 numchild=@var{n},value=@var{value},type=@var{type}@},@r{(repeats N times)}]
29076 @subheading The @code{-var-info-type} Command
29077 @findex -var-info-type
29079 @subsubheading Synopsis
29082 -var-info-type @var{name}
29085 Returns the type of the specified variable @var{name}. The type is
29086 returned as a string in the same format as it is output by the
29090 type=@var{typename}
29094 @subheading The @code{-var-info-expression} Command
29095 @findex -var-info-expression
29097 @subsubheading Synopsis
29100 -var-info-expression @var{name}
29103 Returns a string that is suitable for presenting this
29104 variable object in user interface. The string is generally
29105 not valid expression in the current language, and cannot be evaluated.
29107 For example, if @code{a} is an array, and variable object
29108 @code{A} was created for @code{a}, then we'll get this output:
29111 (gdb) -var-info-expression A.1
29112 ^done,lang="C",exp="1"
29116 Here, the values of @code{lang} can be @code{@{"C" | "C++" | "Java"@}}.
29118 Note that the output of the @code{-var-list-children} command also
29119 includes those expressions, so the @code{-var-info-expression} command
29122 @subheading The @code{-var-info-path-expression} Command
29123 @findex -var-info-path-expression
29125 @subsubheading Synopsis
29128 -var-info-path-expression @var{name}
29131 Returns an expression that can be evaluated in the current
29132 context and will yield the same value that a variable object has.
29133 Compare this with the @code{-var-info-expression} command, which
29134 result can be used only for UI presentation. Typical use of
29135 the @code{-var-info-path-expression} command is creating a
29136 watchpoint from a variable object.
29138 This command is currently not valid for children of a dynamic varobj,
29139 and will give an error when invoked on one.
29141 For example, suppose @code{C} is a C@t{++} class, derived from class
29142 @code{Base}, and that the @code{Base} class has a member called
29143 @code{m_size}. Assume a variable @code{c} is has the type of
29144 @code{C} and a variable object @code{C} was created for variable
29145 @code{c}. Then, we'll get this output:
29147 (gdb) -var-info-path-expression C.Base.public.m_size
29148 ^done,path_expr=((Base)c).m_size)
29151 @subheading The @code{-var-show-attributes} Command
29152 @findex -var-show-attributes
29154 @subsubheading Synopsis
29157 -var-show-attributes @var{name}
29160 List attributes of the specified variable object @var{name}:
29163 status=@var{attr} [ ( ,@var{attr} )* ]
29167 where @var{attr} is @code{@{ @{ editable | noneditable @} | TBD @}}.
29169 @subheading The @code{-var-evaluate-expression} Command
29170 @findex -var-evaluate-expression
29172 @subsubheading Synopsis
29175 -var-evaluate-expression [-f @var{format-spec}] @var{name}
29178 Evaluates the expression that is represented by the specified variable
29179 object and returns its value as a string. The format of the string
29180 can be specified with the @samp{-f} option. The possible values of
29181 this option are the same as for @code{-var-set-format}
29182 (@pxref{-var-set-format}). If the @samp{-f} option is not specified,
29183 the current display format will be used. The current display format
29184 can be changed using the @code{-var-set-format} command.
29190 Note that one must invoke @code{-var-list-children} for a variable
29191 before the value of a child variable can be evaluated.
29193 @subheading The @code{-var-assign} Command
29194 @findex -var-assign
29196 @subsubheading Synopsis
29199 -var-assign @var{name} @var{expression}
29202 Assigns the value of @var{expression} to the variable object specified
29203 by @var{name}. The object must be @samp{editable}. If the variable's
29204 value is altered by the assign, the variable will show up in any
29205 subsequent @code{-var-update} list.
29207 @subsubheading Example
29215 ^done,changelist=[@{name="var1",in_scope="true",type_changed="false"@}]
29219 @subheading The @code{-var-update} Command
29220 @findex -var-update
29222 @subsubheading Synopsis
29225 -var-update [@var{print-values}] @{@var{name} | "*"@}
29228 Reevaluate the expressions corresponding to the variable object
29229 @var{name} and all its direct and indirect children, and return the
29230 list of variable objects whose values have changed; @var{name} must
29231 be a root variable object. Here, ``changed'' means that the result of
29232 @code{-var-evaluate-expression} before and after the
29233 @code{-var-update} is different. If @samp{*} is used as the variable
29234 object names, all existing variable objects are updated, except
29235 for frozen ones (@pxref{-var-set-frozen}). The option
29236 @var{print-values} determines whether both names and values, or just
29237 names are printed. The possible values of this option are the same
29238 as for @code{-var-list-children} (@pxref{-var-list-children}). It is
29239 recommended to use the @samp{--all-values} option, to reduce the
29240 number of MI commands needed on each program stop.
29242 With the @samp{*} parameter, if a variable object is bound to a
29243 currently running thread, it will not be updated, without any
29246 If @code{-var-set-update-range} was previously used on a varobj, then
29247 only the selected range of children will be reported.
29249 @code{-var-update} reports all the changed varobjs in a tuple named
29252 Each item in the change list is itself a tuple holding:
29256 The name of the varobj.
29259 If values were requested for this update, then this field will be
29260 present and will hold the value of the varobj.
29263 @anchor{-var-update}
29264 This field is a string which may take one of three values:
29268 The variable object's current value is valid.
29271 The variable object does not currently hold a valid value but it may
29272 hold one in the future if its associated expression comes back into
29276 The variable object no longer holds a valid value.
29277 This can occur when the executable file being debugged has changed,
29278 either through recompilation or by using the @value{GDBN} @code{file}
29279 command. The front end should normally choose to delete these variable
29283 In the future new values may be added to this list so the front should
29284 be prepared for this possibility. @xref{GDB/MI Development and Front Ends, ,@sc{GDB/MI} Development and Front Ends}.
29287 This is only present if the varobj is still valid. If the type
29288 changed, then this will be the string @samp{true}; otherwise it will
29292 If the varobj's type changed, then this field will be present and will
29295 @item new_num_children
29296 For a dynamic varobj, if the number of children changed, or if the
29297 type changed, this will be the new number of children.
29299 The @samp{numchild} field in other varobj responses is generally not
29300 valid for a dynamic varobj -- it will show the number of children that
29301 @value{GDBN} knows about, but because dynamic varobjs lazily
29302 instantiate their children, this will not reflect the number of
29303 children which may be available.
29305 The @samp{new_num_children} attribute only reports changes to the
29306 number of children known by @value{GDBN}. This is the only way to
29307 detect whether an update has removed children (which necessarily can
29308 only happen at the end of the update range).
29311 The display hint, if any.
29314 This is an integer value, which will be 1 if there are more children
29315 available outside the varobj's update range.
29318 This attribute will be present and have the value @samp{1} if the
29319 varobj is a dynamic varobj. If the varobj is not a dynamic varobj,
29320 then this attribute will not be present.
29323 If new children were added to a dynamic varobj within the selected
29324 update range (as set by @code{-var-set-update-range}), then they will
29325 be listed in this attribute.
29328 @subsubheading Example
29335 -var-update --all-values var1
29336 ^done,changelist=[@{name="var1",value="3",in_scope="true",
29337 type_changed="false"@}]
29341 @subheading The @code{-var-set-frozen} Command
29342 @findex -var-set-frozen
29343 @anchor{-var-set-frozen}
29345 @subsubheading Synopsis
29348 -var-set-frozen @var{name} @var{flag}
29351 Set the frozenness flag on the variable object @var{name}. The
29352 @var{flag} parameter should be either @samp{1} to make the variable
29353 frozen or @samp{0} to make it unfrozen. If a variable object is
29354 frozen, then neither itself, nor any of its children, are
29355 implicitly updated by @code{-var-update} of
29356 a parent variable or by @code{-var-update *}. Only
29357 @code{-var-update} of the variable itself will update its value and
29358 values of its children. After a variable object is unfrozen, it is
29359 implicitly updated by all subsequent @code{-var-update} operations.
29360 Unfreezing a variable does not update it, only subsequent
29361 @code{-var-update} does.
29363 @subsubheading Example
29367 -var-set-frozen V 1
29372 @subheading The @code{-var-set-update-range} command
29373 @findex -var-set-update-range
29374 @anchor{-var-set-update-range}
29376 @subsubheading Synopsis
29379 -var-set-update-range @var{name} @var{from} @var{to}
29382 Set the range of children to be returned by future invocations of
29383 @code{-var-update}.
29385 @var{from} and @var{to} indicate the range of children to report. If
29386 @var{from} or @var{to} is less than zero, the range is reset and all
29387 children will be reported. Otherwise, children starting at @var{from}
29388 (zero-based) and up to and excluding @var{to} will be reported.
29390 @subsubheading Example
29394 -var-set-update-range V 1 2
29398 @subheading The @code{-var-set-visualizer} command
29399 @findex -var-set-visualizer
29400 @anchor{-var-set-visualizer}
29402 @subsubheading Synopsis
29405 -var-set-visualizer @var{name} @var{visualizer}
29408 Set a visualizer for the variable object @var{name}.
29410 @var{visualizer} is the visualizer to use. The special value
29411 @samp{None} means to disable any visualizer in use.
29413 If not @samp{None}, @var{visualizer} must be a Python expression.
29414 This expression must evaluate to a callable object which accepts a
29415 single argument. @value{GDBN} will call this object with the value of
29416 the varobj @var{name} as an argument (this is done so that the same
29417 Python pretty-printing code can be used for both the CLI and MI).
29418 When called, this object must return an object which conforms to the
29419 pretty-printing interface (@pxref{Pretty Printing API}).
29421 The pre-defined function @code{gdb.default_visualizer} may be used to
29422 select a visualizer by following the built-in process
29423 (@pxref{Selecting Pretty-Printers}). This is done automatically when
29424 a varobj is created, and so ordinarily is not needed.
29426 This feature is only available if Python support is enabled. The MI
29427 command @code{-list-features} (@pxref{GDB/MI Miscellaneous Commands})
29428 can be used to check this.
29430 @subsubheading Example
29432 Resetting the visualizer:
29436 -var-set-visualizer V None
29440 Reselecting the default (type-based) visualizer:
29444 -var-set-visualizer V gdb.default_visualizer
29448 Suppose @code{SomeClass} is a visualizer class. A lambda expression
29449 can be used to instantiate this class for a varobj:
29453 -var-set-visualizer V "lambda val: SomeClass()"
29457 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
29458 @node GDB/MI Data Manipulation
29459 @section @sc{gdb/mi} Data Manipulation
29461 @cindex data manipulation, in @sc{gdb/mi}
29462 @cindex @sc{gdb/mi}, data manipulation
29463 This section describes the @sc{gdb/mi} commands that manipulate data:
29464 examine memory and registers, evaluate expressions, etc.
29466 @c REMOVED FROM THE INTERFACE.
29467 @c @subheading -data-assign
29468 @c Change the value of a program variable. Plenty of side effects.
29469 @c @subsubheading GDB Command
29471 @c @subsubheading Example
29474 @subheading The @code{-data-disassemble} Command
29475 @findex -data-disassemble
29477 @subsubheading Synopsis
29481 [ -s @var{start-addr} -e @var{end-addr} ]
29482 | [ -f @var{filename} -l @var{linenum} [ -n @var{lines} ] ]
29490 @item @var{start-addr}
29491 is the beginning address (or @code{$pc})
29492 @item @var{end-addr}
29494 @item @var{filename}
29495 is the name of the file to disassemble
29496 @item @var{linenum}
29497 is the line number to disassemble around
29499 is the number of disassembly lines to be produced. If it is -1,
29500 the whole function will be disassembled, in case no @var{end-addr} is
29501 specified. If @var{end-addr} is specified as a non-zero value, and
29502 @var{lines} is lower than the number of disassembly lines between
29503 @var{start-addr} and @var{end-addr}, only @var{lines} lines are
29504 displayed; if @var{lines} is higher than the number of lines between
29505 @var{start-addr} and @var{end-addr}, only the lines up to @var{end-addr}
29508 is either 0 (meaning only disassembly), 1 (meaning mixed source and
29509 disassembly), 2 (meaning disassembly with raw opcodes), or 3 (meaning
29510 mixed source and disassembly with raw opcodes).
29513 @subsubheading Result
29515 The output for each instruction is composed of four fields:
29524 Note that whatever included in the instruction field, is not manipulated
29525 directly by @sc{gdb/mi}, i.e., it is not possible to adjust its format.
29527 @subsubheading @value{GDBN} Command
29529 There's no direct mapping from this command to the CLI.
29531 @subsubheading Example
29533 Disassemble from the current value of @code{$pc} to @code{$pc + 20}:
29537 -data-disassemble -s $pc -e "$pc + 20" -- 0
29540 @{address="0x000107c0",func-name="main",offset="4",
29541 inst="mov 2, %o0"@},
29542 @{address="0x000107c4",func-name="main",offset="8",
29543 inst="sethi %hi(0x11800), %o2"@},
29544 @{address="0x000107c8",func-name="main",offset="12",
29545 inst="or %o2, 0x140, %o1\t! 0x11940 <_lib_version+8>"@},
29546 @{address="0x000107cc",func-name="main",offset="16",
29547 inst="sethi %hi(0x11800), %o2"@},
29548 @{address="0x000107d0",func-name="main",offset="20",
29549 inst="or %o2, 0x168, %o4\t! 0x11968 <_lib_version+48>"@}]
29553 Disassemble the whole @code{main} function. Line 32 is part of
29557 -data-disassemble -f basics.c -l 32 -- 0
29559 @{address="0x000107bc",func-name="main",offset="0",
29560 inst="save %sp, -112, %sp"@},
29561 @{address="0x000107c0",func-name="main",offset="4",
29562 inst="mov 2, %o0"@},
29563 @{address="0x000107c4",func-name="main",offset="8",
29564 inst="sethi %hi(0x11800), %o2"@},
29566 @{address="0x0001081c",func-name="main",offset="96",inst="ret "@},
29567 @{address="0x00010820",func-name="main",offset="100",inst="restore "@}]
29571 Disassemble 3 instructions from the start of @code{main}:
29575 -data-disassemble -f basics.c -l 32 -n 3 -- 0
29577 @{address="0x000107bc",func-name="main",offset="0",
29578 inst="save %sp, -112, %sp"@},
29579 @{address="0x000107c0",func-name="main",offset="4",
29580 inst="mov 2, %o0"@},
29581 @{address="0x000107c4",func-name="main",offset="8",
29582 inst="sethi %hi(0x11800), %o2"@}]
29586 Disassemble 3 instructions from the start of @code{main} in mixed mode:
29590 -data-disassemble -f basics.c -l 32 -n 3 -- 1
29592 src_and_asm_line=@{line="31",
29593 file="/kwikemart/marge/ezannoni/flathead-dev/devo/gdb/ \
29594 testsuite/gdb.mi/basics.c",line_asm_insn=[
29595 @{address="0x000107bc",func-name="main",offset="0",
29596 inst="save %sp, -112, %sp"@}]@},
29597 src_and_asm_line=@{line="32",
29598 file="/kwikemart/marge/ezannoni/flathead-dev/devo/gdb/ \
29599 testsuite/gdb.mi/basics.c",line_asm_insn=[
29600 @{address="0x000107c0",func-name="main",offset="4",
29601 inst="mov 2, %o0"@},
29602 @{address="0x000107c4",func-name="main",offset="8",
29603 inst="sethi %hi(0x11800), %o2"@}]@}]
29608 @subheading The @code{-data-evaluate-expression} Command
29609 @findex -data-evaluate-expression
29611 @subsubheading Synopsis
29614 -data-evaluate-expression @var{expr}
29617 Evaluate @var{expr} as an expression. The expression could contain an
29618 inferior function call. The function call will execute synchronously.
29619 If the expression contains spaces, it must be enclosed in double quotes.
29621 @subsubheading @value{GDBN} Command
29623 The corresponding @value{GDBN} commands are @samp{print}, @samp{output}, and
29624 @samp{call}. In @code{gdbtk} only, there's a corresponding
29625 @samp{gdb_eval} command.
29627 @subsubheading Example
29629 In the following example, the numbers that precede the commands are the
29630 @dfn{tokens} described in @ref{GDB/MI Command Syntax, ,@sc{gdb/mi}
29631 Command Syntax}. Notice how @sc{gdb/mi} returns the same tokens in its
29635 211-data-evaluate-expression A
29638 311-data-evaluate-expression &A
29639 311^done,value="0xefffeb7c"
29641 411-data-evaluate-expression A+3
29644 511-data-evaluate-expression "A + 3"
29650 @subheading The @code{-data-list-changed-registers} Command
29651 @findex -data-list-changed-registers
29653 @subsubheading Synopsis
29656 -data-list-changed-registers
29659 Display a list of the registers that have changed.
29661 @subsubheading @value{GDBN} Command
29663 @value{GDBN} doesn't have a direct analog for this command; @code{gdbtk}
29664 has the corresponding command @samp{gdb_changed_register_list}.
29666 @subsubheading Example
29668 On a PPC MBX board:
29676 *stopped,reason="breakpoint-hit",disp="keep",bkptno="1",frame=@{
29677 func="main",args=[],file="try.c",fullname="/home/foo/bar/try.c",
29680 -data-list-changed-registers
29681 ^done,changed-registers=["0","1","2","4","5","6","7","8","9",
29682 "10","11","13","14","15","16","17","18","19","20","21","22","23",
29683 "24","25","26","27","28","30","31","64","65","66","67","69"]
29688 @subheading The @code{-data-list-register-names} Command
29689 @findex -data-list-register-names
29691 @subsubheading Synopsis
29694 -data-list-register-names [ ( @var{regno} )+ ]
29697 Show a list of register names for the current target. If no arguments
29698 are given, it shows a list of the names of all the registers. If
29699 integer numbers are given as arguments, it will print a list of the
29700 names of the registers corresponding to the arguments. To ensure
29701 consistency between a register name and its number, the output list may
29702 include empty register names.
29704 @subsubheading @value{GDBN} Command
29706 @value{GDBN} does not have a command which corresponds to
29707 @samp{-data-list-register-names}. In @code{gdbtk} there is a
29708 corresponding command @samp{gdb_regnames}.
29710 @subsubheading Example
29712 For the PPC MBX board:
29715 -data-list-register-names
29716 ^done,register-names=["r0","r1","r2","r3","r4","r5","r6","r7",
29717 "r8","r9","r10","r11","r12","r13","r14","r15","r16","r17","r18",
29718 "r19","r20","r21","r22","r23","r24","r25","r26","r27","r28","r29",
29719 "r30","r31","f0","f1","f2","f3","f4","f5","f6","f7","f8","f9",
29720 "f10","f11","f12","f13","f14","f15","f16","f17","f18","f19","f20",
29721 "f21","f22","f23","f24","f25","f26","f27","f28","f29","f30","f31",
29722 "", "pc","ps","cr","lr","ctr","xer"]
29724 -data-list-register-names 1 2 3
29725 ^done,register-names=["r1","r2","r3"]
29729 @subheading The @code{-data-list-register-values} Command
29730 @findex -data-list-register-values
29732 @subsubheading Synopsis
29735 -data-list-register-values @var{fmt} [ ( @var{regno} )*]
29738 Display the registers' contents. @var{fmt} is the format according to
29739 which the registers' contents are to be returned, followed by an optional
29740 list of numbers specifying the registers to display. A missing list of
29741 numbers indicates that the contents of all the registers must be returned.
29743 Allowed formats for @var{fmt} are:
29760 @subsubheading @value{GDBN} Command
29762 The corresponding @value{GDBN} commands are @samp{info reg}, @samp{info
29763 all-reg}, and (in @code{gdbtk}) @samp{gdb_fetch_registers}.
29765 @subsubheading Example
29767 For a PPC MBX board (note: line breaks are for readability only, they
29768 don't appear in the actual output):
29772 -data-list-register-values r 64 65
29773 ^done,register-values=[@{number="64",value="0xfe00a300"@},
29774 @{number="65",value="0x00029002"@}]
29776 -data-list-register-values x
29777 ^done,register-values=[@{number="0",value="0xfe0043c8"@},
29778 @{number="1",value="0x3fff88"@},@{number="2",value="0xfffffffe"@},
29779 @{number="3",value="0x0"@},@{number="4",value="0xa"@},
29780 @{number="5",value="0x3fff68"@},@{number="6",value="0x3fff58"@},
29781 @{number="7",value="0xfe011e98"@},@{number="8",value="0x2"@},
29782 @{number="9",value="0xfa202820"@},@{number="10",value="0xfa202808"@},
29783 @{number="11",value="0x1"@},@{number="12",value="0x0"@},
29784 @{number="13",value="0x4544"@},@{number="14",value="0xffdfffff"@},
29785 @{number="15",value="0xffffffff"@},@{number="16",value="0xfffffeff"@},
29786 @{number="17",value="0xefffffed"@},@{number="18",value="0xfffffffe"@},
29787 @{number="19",value="0xffffffff"@},@{number="20",value="0xffffffff"@},
29788 @{number="21",value="0xffffffff"@},@{number="22",value="0xfffffff7"@},
29789 @{number="23",value="0xffffffff"@},@{number="24",value="0xffffffff"@},
29790 @{number="25",value="0xffffffff"@},@{number="26",value="0xfffffffb"@},
29791 @{number="27",value="0xffffffff"@},@{number="28",value="0xf7bfffff"@},
29792 @{number="29",value="0x0"@},@{number="30",value="0xfe010000"@},
29793 @{number="31",value="0x0"@},@{number="32",value="0x0"@},
29794 @{number="33",value="0x0"@},@{number="34",value="0x0"@},
29795 @{number="35",value="0x0"@},@{number="36",value="0x0"@},
29796 @{number="37",value="0x0"@},@{number="38",value="0x0"@},
29797 @{number="39",value="0x0"@},@{number="40",value="0x0"@},
29798 @{number="41",value="0x0"@},@{number="42",value="0x0"@},
29799 @{number="43",value="0x0"@},@{number="44",value="0x0"@},
29800 @{number="45",value="0x0"@},@{number="46",value="0x0"@},
29801 @{number="47",value="0x0"@},@{number="48",value="0x0"@},
29802 @{number="49",value="0x0"@},@{number="50",value="0x0"@},
29803 @{number="51",value="0x0"@},@{number="52",value="0x0"@},
29804 @{number="53",value="0x0"@},@{number="54",value="0x0"@},
29805 @{number="55",value="0x0"@},@{number="56",value="0x0"@},
29806 @{number="57",value="0x0"@},@{number="58",value="0x0"@},
29807 @{number="59",value="0x0"@},@{number="60",value="0x0"@},
29808 @{number="61",value="0x0"@},@{number="62",value="0x0"@},
29809 @{number="63",value="0x0"@},@{number="64",value="0xfe00a300"@},
29810 @{number="65",value="0x29002"@},@{number="66",value="0x202f04b5"@},
29811 @{number="67",value="0xfe0043b0"@},@{number="68",value="0xfe00b3e4"@},
29812 @{number="69",value="0x20002b03"@}]
29817 @subheading The @code{-data-read-memory} Command
29818 @findex -data-read-memory
29820 This command is deprecated, use @code{-data-read-memory-bytes} instead.
29822 @subsubheading Synopsis
29825 -data-read-memory [ -o @var{byte-offset} ]
29826 @var{address} @var{word-format} @var{word-size}
29827 @var{nr-rows} @var{nr-cols} [ @var{aschar} ]
29834 @item @var{address}
29835 An expression specifying the address of the first memory word to be
29836 read. Complex expressions containing embedded white space should be
29837 quoted using the C convention.
29839 @item @var{word-format}
29840 The format to be used to print the memory words. The notation is the
29841 same as for @value{GDBN}'s @code{print} command (@pxref{Output Formats,
29844 @item @var{word-size}
29845 The size of each memory word in bytes.
29847 @item @var{nr-rows}
29848 The number of rows in the output table.
29850 @item @var{nr-cols}
29851 The number of columns in the output table.
29854 If present, indicates that each row should include an @sc{ascii} dump. The
29855 value of @var{aschar} is used as a padding character when a byte is not a
29856 member of the printable @sc{ascii} character set (printable @sc{ascii}
29857 characters are those whose code is between 32 and 126, inclusively).
29859 @item @var{byte-offset}
29860 An offset to add to the @var{address} before fetching memory.
29863 This command displays memory contents as a table of @var{nr-rows} by
29864 @var{nr-cols} words, each word being @var{word-size} bytes. In total,
29865 @code{@var{nr-rows} * @var{nr-cols} * @var{word-size}} bytes are read
29866 (returned as @samp{total-bytes}). Should less than the requested number
29867 of bytes be returned by the target, the missing words are identified
29868 using @samp{N/A}. The number of bytes read from the target is returned
29869 in @samp{nr-bytes} and the starting address used to read memory in
29872 The address of the next/previous row or page is available in
29873 @samp{next-row} and @samp{prev-row}, @samp{next-page} and
29876 @subsubheading @value{GDBN} Command
29878 The corresponding @value{GDBN} command is @samp{x}. @code{gdbtk} has
29879 @samp{gdb_get_mem} memory read command.
29881 @subsubheading Example
29883 Read six bytes of memory starting at @code{bytes+6} but then offset by
29884 @code{-6} bytes. Format as three rows of two columns. One byte per
29885 word. Display each word in hex.
29889 9-data-read-memory -o -6 -- bytes+6 x 1 3 2
29890 9^done,addr="0x00001390",nr-bytes="6",total-bytes="6",
29891 next-row="0x00001396",prev-row="0x0000138e",next-page="0x00001396",
29892 prev-page="0x0000138a",memory=[
29893 @{addr="0x00001390",data=["0x00","0x01"]@},
29894 @{addr="0x00001392",data=["0x02","0x03"]@},
29895 @{addr="0x00001394",data=["0x04","0x05"]@}]
29899 Read two bytes of memory starting at address @code{shorts + 64} and
29900 display as a single word formatted in decimal.
29904 5-data-read-memory shorts+64 d 2 1 1
29905 5^done,addr="0x00001510",nr-bytes="2",total-bytes="2",
29906 next-row="0x00001512",prev-row="0x0000150e",
29907 next-page="0x00001512",prev-page="0x0000150e",memory=[
29908 @{addr="0x00001510",data=["128"]@}]
29912 Read thirty two bytes of memory starting at @code{bytes+16} and format
29913 as eight rows of four columns. Include a string encoding with @samp{x}
29914 used as the non-printable character.
29918 4-data-read-memory bytes+16 x 1 8 4 x
29919 4^done,addr="0x000013a0",nr-bytes="32",total-bytes="32",
29920 next-row="0x000013c0",prev-row="0x0000139c",
29921 next-page="0x000013c0",prev-page="0x00001380",memory=[
29922 @{addr="0x000013a0",data=["0x10","0x11","0x12","0x13"],ascii="xxxx"@},
29923 @{addr="0x000013a4",data=["0x14","0x15","0x16","0x17"],ascii="xxxx"@},
29924 @{addr="0x000013a8",data=["0x18","0x19","0x1a","0x1b"],ascii="xxxx"@},
29925 @{addr="0x000013ac",data=["0x1c","0x1d","0x1e","0x1f"],ascii="xxxx"@},
29926 @{addr="0x000013b0",data=["0x20","0x21","0x22","0x23"],ascii=" !\"#"@},
29927 @{addr="0x000013b4",data=["0x24","0x25","0x26","0x27"],ascii="$%&'"@},
29928 @{addr="0x000013b8",data=["0x28","0x29","0x2a","0x2b"],ascii="()*+"@},
29929 @{addr="0x000013bc",data=["0x2c","0x2d","0x2e","0x2f"],ascii=",-./"@}]
29933 @subheading The @code{-data-read-memory-bytes} Command
29934 @findex -data-read-memory-bytes
29936 @subsubheading Synopsis
29939 -data-read-memory-bytes [ -o @var{byte-offset} ]
29940 @var{address} @var{count}
29947 @item @var{address}
29948 An expression specifying the address of the first memory word to be
29949 read. Complex expressions containing embedded white space should be
29950 quoted using the C convention.
29953 The number of bytes to read. This should be an integer literal.
29955 @item @var{byte-offset}
29956 The offsets in bytes relative to @var{address} at which to start
29957 reading. This should be an integer literal. This option is provided
29958 so that a frontend is not required to first evaluate address and then
29959 perform address arithmetics itself.
29963 This command attempts to read all accessible memory regions in the
29964 specified range. First, all regions marked as unreadable in the memory
29965 map (if one is defined) will be skipped. @xref{Memory Region
29966 Attributes}. Second, @value{GDBN} will attempt to read the remaining
29967 regions. For each one, if reading full region results in an errors,
29968 @value{GDBN} will try to read a subset of the region.
29970 In general, every single byte in the region may be readable or not,
29971 and the only way to read every readable byte is to try a read at
29972 every address, which is not practical. Therefore, @value{GDBN} will
29973 attempt to read all accessible bytes at either beginning or the end
29974 of the region, using a binary division scheme. This heuristic works
29975 well for reading accross a memory map boundary. Note that if a region
29976 has a readable range that is neither at the beginning or the end,
29977 @value{GDBN} will not read it.
29979 The result record (@pxref{GDB/MI Result Records}) that is output of
29980 the command includes a field named @samp{memory} whose content is a
29981 list of tuples. Each tuple represent a successfully read memory block
29982 and has the following fields:
29986 The start address of the memory block, as hexadecimal literal.
29989 The end address of the memory block, as hexadecimal literal.
29992 The offset of the memory block, as hexadecimal literal, relative to
29993 the start address passed to @code{-data-read-memory-bytes}.
29996 The contents of the memory block, in hex.
30002 @subsubheading @value{GDBN} Command
30004 The corresponding @value{GDBN} command is @samp{x}.
30006 @subsubheading Example
30010 -data-read-memory-bytes &a 10
30011 ^done,memory=[@{begin="0xbffff154",offset="0x00000000",
30013 contents="01000000020000000300"@}]
30018 @subheading The @code{-data-write-memory-bytes} Command
30019 @findex -data-write-memory-bytes
30021 @subsubheading Synopsis
30024 -data-write-memory-bytes @var{address} @var{contents}
30031 @item @var{address}
30032 An expression specifying the address of the first memory word to be
30033 read. Complex expressions containing embedded white space should be
30034 quoted using the C convention.
30036 @item @var{contents}
30037 The hex-encoded bytes to write.
30041 @subsubheading @value{GDBN} Command
30043 There's no corresponding @value{GDBN} command.
30045 @subsubheading Example
30049 -data-write-memory-bytes &a "aabbccdd"
30055 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
30056 @node GDB/MI Tracepoint Commands
30057 @section @sc{gdb/mi} Tracepoint Commands
30059 The commands defined in this section implement MI support for
30060 tracepoints. For detailed introduction, see @ref{Tracepoints}.
30062 @subheading The @code{-trace-find} Command
30063 @findex -trace-find
30065 @subsubheading Synopsis
30068 -trace-find @var{mode} [@var{parameters}@dots{}]
30071 Find a trace frame using criteria defined by @var{mode} and
30072 @var{parameters}. The following table lists permissible
30073 modes and their parameters. For details of operation, see @ref{tfind}.
30078 No parameters are required. Stops examining trace frames.
30081 An integer is required as parameter. Selects tracepoint frame with
30084 @item tracepoint-number
30085 An integer is required as parameter. Finds next
30086 trace frame that corresponds to tracepoint with the specified number.
30089 An address is required as parameter. Finds
30090 next trace frame that corresponds to any tracepoint at the specified
30093 @item pc-inside-range
30094 Two addresses are required as parameters. Finds next trace
30095 frame that corresponds to a tracepoint at an address inside the
30096 specified range. Both bounds are considered to be inside the range.
30098 @item pc-outside-range
30099 Two addresses are required as parameters. Finds
30100 next trace frame that corresponds to a tracepoint at an address outside
30101 the specified range. Both bounds are considered to be inside the range.
30104 Line specification is required as parameter. @xref{Specify Location}.
30105 Finds next trace frame that corresponds to a tracepoint at
30106 the specified location.
30110 If @samp{none} was passed as @var{mode}, the response does not
30111 have fields. Otherwise, the response may have the following fields:
30115 This field has either @samp{0} or @samp{1} as the value, depending
30116 on whether a matching tracepoint was found.
30119 The index of the found traceframe. This field is present iff
30120 the @samp{found} field has value of @samp{1}.
30123 The index of the found tracepoint. This field is present iff
30124 the @samp{found} field has value of @samp{1}.
30127 The information about the frame corresponding to the found trace
30128 frame. This field is present only if a trace frame was found.
30129 @xref{GDB/MI Frame Information}, for description of this field.
30133 @subsubheading @value{GDBN} Command
30135 The corresponding @value{GDBN} command is @samp{tfind}.
30137 @subheading -trace-define-variable
30138 @findex -trace-define-variable
30140 @subsubheading Synopsis
30143 -trace-define-variable @var{name} [ @var{value} ]
30146 Create trace variable @var{name} if it does not exist. If
30147 @var{value} is specified, sets the initial value of the specified
30148 trace variable to that value. Note that the @var{name} should start
30149 with the @samp{$} character.
30151 @subsubheading @value{GDBN} Command
30153 The corresponding @value{GDBN} command is @samp{tvariable}.
30155 @subheading -trace-list-variables
30156 @findex -trace-list-variables
30158 @subsubheading Synopsis
30161 -trace-list-variables
30164 Return a table of all defined trace variables. Each element of the
30165 table has the following fields:
30169 The name of the trace variable. This field is always present.
30172 The initial value. This is a 64-bit signed integer. This
30173 field is always present.
30176 The value the trace variable has at the moment. This is a 64-bit
30177 signed integer. This field is absent iff current value is
30178 not defined, for example if the trace was never run, or is
30183 @subsubheading @value{GDBN} Command
30185 The corresponding @value{GDBN} command is @samp{tvariables}.
30187 @subsubheading Example
30191 -trace-list-variables
30192 ^done,trace-variables=@{nr_rows="1",nr_cols="3",
30193 hdr=[@{width="15",alignment="-1",col_name="name",colhdr="Name"@},
30194 @{width="11",alignment="-1",col_name="initial",colhdr="Initial"@},
30195 @{width="11",alignment="-1",col_name="current",colhdr="Current"@}],
30196 body=[variable=@{name="$trace_timestamp",initial="0"@}
30197 variable=@{name="$foo",initial="10",current="15"@}]@}
30201 @subheading -trace-save
30202 @findex -trace-save
30204 @subsubheading Synopsis
30207 -trace-save [-r ] @var{filename}
30210 Saves the collected trace data to @var{filename}. Without the
30211 @samp{-r} option, the data is downloaded from the target and saved
30212 in a local file. With the @samp{-r} option the target is asked
30213 to perform the save.
30215 @subsubheading @value{GDBN} Command
30217 The corresponding @value{GDBN} command is @samp{tsave}.
30220 @subheading -trace-start
30221 @findex -trace-start
30223 @subsubheading Synopsis
30229 Starts a tracing experiments. The result of this command does not
30232 @subsubheading @value{GDBN} Command
30234 The corresponding @value{GDBN} command is @samp{tstart}.
30236 @subheading -trace-status
30237 @findex -trace-status
30239 @subsubheading Synopsis
30245 Obtains the status of a tracing experiment. The result may include
30246 the following fields:
30251 May have a value of either @samp{0}, when no tracing operations are
30252 supported, @samp{1}, when all tracing operations are supported, or
30253 @samp{file} when examining trace file. In the latter case, examining
30254 of trace frame is possible but new tracing experiement cannot be
30255 started. This field is always present.
30258 May have a value of either @samp{0} or @samp{1} depending on whether
30259 tracing experiement is in progress on target. This field is present
30260 if @samp{supported} field is not @samp{0}.
30263 Report the reason why the tracing was stopped last time. This field
30264 may be absent iff tracing was never stopped on target yet. The
30265 value of @samp{request} means the tracing was stopped as result of
30266 the @code{-trace-stop} command. The value of @samp{overflow} means
30267 the tracing buffer is full. The value of @samp{disconnection} means
30268 tracing was automatically stopped when @value{GDBN} has disconnected.
30269 The value of @samp{passcount} means tracing was stopped when a
30270 tracepoint was passed a maximal number of times for that tracepoint.
30271 This field is present if @samp{supported} field is not @samp{0}.
30273 @item stopping-tracepoint
30274 The number of tracepoint whose passcount as exceeded. This field is
30275 present iff the @samp{stop-reason} field has the value of
30279 @itemx frames-created
30280 The @samp{frames} field is a count of the total number of trace frames
30281 in the trace buffer, while @samp{frames-created} is the total created
30282 during the run, including ones that were discarded, such as when a
30283 circular trace buffer filled up. Both fields are optional.
30287 These fields tell the current size of the tracing buffer and the
30288 remaining space. These fields are optional.
30291 The value of the circular trace buffer flag. @code{1} means that the
30292 trace buffer is circular and old trace frames will be discarded if
30293 necessary to make room, @code{0} means that the trace buffer is linear
30297 The value of the disconnected tracing flag. @code{1} means that
30298 tracing will continue after @value{GDBN} disconnects, @code{0} means
30299 that the trace run will stop.
30303 @subsubheading @value{GDBN} Command
30305 The corresponding @value{GDBN} command is @samp{tstatus}.
30307 @subheading -trace-stop
30308 @findex -trace-stop
30310 @subsubheading Synopsis
30316 Stops a tracing experiment. The result of this command has the same
30317 fields as @code{-trace-status}, except that the @samp{supported} and
30318 @samp{running} fields are not output.
30320 @subsubheading @value{GDBN} Command
30322 The corresponding @value{GDBN} command is @samp{tstop}.
30325 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
30326 @node GDB/MI Symbol Query
30327 @section @sc{gdb/mi} Symbol Query Commands
30331 @subheading The @code{-symbol-info-address} Command
30332 @findex -symbol-info-address
30334 @subsubheading Synopsis
30337 -symbol-info-address @var{symbol}
30340 Describe where @var{symbol} is stored.
30342 @subsubheading @value{GDBN} Command
30344 The corresponding @value{GDBN} command is @samp{info address}.
30346 @subsubheading Example
30350 @subheading The @code{-symbol-info-file} Command
30351 @findex -symbol-info-file
30353 @subsubheading Synopsis
30359 Show the file for the symbol.
30361 @subsubheading @value{GDBN} Command
30363 There's no equivalent @value{GDBN} command. @code{gdbtk} has
30364 @samp{gdb_find_file}.
30366 @subsubheading Example
30370 @subheading The @code{-symbol-info-function} Command
30371 @findex -symbol-info-function
30373 @subsubheading Synopsis
30376 -symbol-info-function
30379 Show which function the symbol lives in.
30381 @subsubheading @value{GDBN} Command
30383 @samp{gdb_get_function} in @code{gdbtk}.
30385 @subsubheading Example
30389 @subheading The @code{-symbol-info-line} Command
30390 @findex -symbol-info-line
30392 @subsubheading Synopsis
30398 Show the core addresses of the code for a source line.
30400 @subsubheading @value{GDBN} Command
30402 The corresponding @value{GDBN} command is @samp{info line}.
30403 @code{gdbtk} has the @samp{gdb_get_line} and @samp{gdb_get_file} commands.
30405 @subsubheading Example
30409 @subheading The @code{-symbol-info-symbol} Command
30410 @findex -symbol-info-symbol
30412 @subsubheading Synopsis
30415 -symbol-info-symbol @var{addr}
30418 Describe what symbol is at location @var{addr}.
30420 @subsubheading @value{GDBN} Command
30422 The corresponding @value{GDBN} command is @samp{info symbol}.
30424 @subsubheading Example
30428 @subheading The @code{-symbol-list-functions} Command
30429 @findex -symbol-list-functions
30431 @subsubheading Synopsis
30434 -symbol-list-functions
30437 List the functions in the executable.
30439 @subsubheading @value{GDBN} Command
30441 @samp{info functions} in @value{GDBN}, @samp{gdb_listfunc} and
30442 @samp{gdb_search} in @code{gdbtk}.
30444 @subsubheading Example
30449 @subheading The @code{-symbol-list-lines} Command
30450 @findex -symbol-list-lines
30452 @subsubheading Synopsis
30455 -symbol-list-lines @var{filename}
30458 Print the list of lines that contain code and their associated program
30459 addresses for the given source filename. The entries are sorted in
30460 ascending PC order.
30462 @subsubheading @value{GDBN} Command
30464 There is no corresponding @value{GDBN} command.
30466 @subsubheading Example
30469 -symbol-list-lines basics.c
30470 ^done,lines=[@{pc="0x08048554",line="7"@},@{pc="0x0804855a",line="8"@}]
30476 @subheading The @code{-symbol-list-types} Command
30477 @findex -symbol-list-types
30479 @subsubheading Synopsis
30485 List all the type names.
30487 @subsubheading @value{GDBN} Command
30489 The corresponding commands are @samp{info types} in @value{GDBN},
30490 @samp{gdb_search} in @code{gdbtk}.
30492 @subsubheading Example
30496 @subheading The @code{-symbol-list-variables} Command
30497 @findex -symbol-list-variables
30499 @subsubheading Synopsis
30502 -symbol-list-variables
30505 List all the global and static variable names.
30507 @subsubheading @value{GDBN} Command
30509 @samp{info variables} in @value{GDBN}, @samp{gdb_search} in @code{gdbtk}.
30511 @subsubheading Example
30515 @subheading The @code{-symbol-locate} Command
30516 @findex -symbol-locate
30518 @subsubheading Synopsis
30524 @subsubheading @value{GDBN} Command
30526 @samp{gdb_loc} in @code{gdbtk}.
30528 @subsubheading Example
30532 @subheading The @code{-symbol-type} Command
30533 @findex -symbol-type
30535 @subsubheading Synopsis
30538 -symbol-type @var{variable}
30541 Show type of @var{variable}.
30543 @subsubheading @value{GDBN} Command
30545 The corresponding @value{GDBN} command is @samp{ptype}, @code{gdbtk} has
30546 @samp{gdb_obj_variable}.
30548 @subsubheading Example
30553 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
30554 @node GDB/MI File Commands
30555 @section @sc{gdb/mi} File Commands
30557 This section describes the GDB/MI commands to specify executable file names
30558 and to read in and obtain symbol table information.
30560 @subheading The @code{-file-exec-and-symbols} Command
30561 @findex -file-exec-and-symbols
30563 @subsubheading Synopsis
30566 -file-exec-and-symbols @var{file}
30569 Specify the executable file to be debugged. This file is the one from
30570 which the symbol table is also read. If no file is specified, the
30571 command clears the executable and symbol information. If breakpoints
30572 are set when using this command with no arguments, @value{GDBN} will produce
30573 error messages. Otherwise, no output is produced, except a completion
30576 @subsubheading @value{GDBN} Command
30578 The corresponding @value{GDBN} command is @samp{file}.
30580 @subsubheading Example
30584 -file-exec-and-symbols /kwikemart/marge/ezannoni/TRUNK/mbx/hello.mbx
30590 @subheading The @code{-file-exec-file} Command
30591 @findex -file-exec-file
30593 @subsubheading Synopsis
30596 -file-exec-file @var{file}
30599 Specify the executable file to be debugged. Unlike
30600 @samp{-file-exec-and-symbols}, the symbol table is @emph{not} read
30601 from this file. If used without argument, @value{GDBN} clears the information
30602 about the executable file. No output is produced, except a completion
30605 @subsubheading @value{GDBN} Command
30607 The corresponding @value{GDBN} command is @samp{exec-file}.
30609 @subsubheading Example
30613 -file-exec-file /kwikemart/marge/ezannoni/TRUNK/mbx/hello.mbx
30620 @subheading The @code{-file-list-exec-sections} Command
30621 @findex -file-list-exec-sections
30623 @subsubheading Synopsis
30626 -file-list-exec-sections
30629 List the sections of the current executable file.
30631 @subsubheading @value{GDBN} Command
30633 The @value{GDBN} command @samp{info file} shows, among the rest, the same
30634 information as this command. @code{gdbtk} has a corresponding command
30635 @samp{gdb_load_info}.
30637 @subsubheading Example
30642 @subheading The @code{-file-list-exec-source-file} Command
30643 @findex -file-list-exec-source-file
30645 @subsubheading Synopsis
30648 -file-list-exec-source-file
30651 List the line number, the current source file, and the absolute path
30652 to the current source file for the current executable. The macro
30653 information field has a value of @samp{1} or @samp{0} depending on
30654 whether or not the file includes preprocessor macro information.
30656 @subsubheading @value{GDBN} Command
30658 The @value{GDBN} equivalent is @samp{info source}
30660 @subsubheading Example
30664 123-file-list-exec-source-file
30665 123^done,line="1",file="foo.c",fullname="/home/bar/foo.c,macro-info="1"
30670 @subheading The @code{-file-list-exec-source-files} Command
30671 @findex -file-list-exec-source-files
30673 @subsubheading Synopsis
30676 -file-list-exec-source-files
30679 List the source files for the current executable.
30681 It will always output the filename, but only when @value{GDBN} can find
30682 the absolute file name of a source file, will it output the fullname.
30684 @subsubheading @value{GDBN} Command
30686 The @value{GDBN} equivalent is @samp{info sources}.
30687 @code{gdbtk} has an analogous command @samp{gdb_listfiles}.
30689 @subsubheading Example
30692 -file-list-exec-source-files
30694 @{file=foo.c,fullname=/home/foo.c@},
30695 @{file=/home/bar.c,fullname=/home/bar.c@},
30696 @{file=gdb_could_not_find_fullpath.c@}]
30701 @subheading The @code{-file-list-shared-libraries} Command
30702 @findex -file-list-shared-libraries
30704 @subsubheading Synopsis
30707 -file-list-shared-libraries
30710 List the shared libraries in the program.
30712 @subsubheading @value{GDBN} Command
30714 The corresponding @value{GDBN} command is @samp{info shared}.
30716 @subsubheading Example
30720 @subheading The @code{-file-list-symbol-files} Command
30721 @findex -file-list-symbol-files
30723 @subsubheading Synopsis
30726 -file-list-symbol-files
30731 @subsubheading @value{GDBN} Command
30733 The corresponding @value{GDBN} command is @samp{info file} (part of it).
30735 @subsubheading Example
30740 @subheading The @code{-file-symbol-file} Command
30741 @findex -file-symbol-file
30743 @subsubheading Synopsis
30746 -file-symbol-file @var{file}
30749 Read symbol table info from the specified @var{file} argument. When
30750 used without arguments, clears @value{GDBN}'s symbol table info. No output is
30751 produced, except for a completion notification.
30753 @subsubheading @value{GDBN} Command
30755 The corresponding @value{GDBN} command is @samp{symbol-file}.
30757 @subsubheading Example
30761 -file-symbol-file /kwikemart/marge/ezannoni/TRUNK/mbx/hello.mbx
30767 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
30768 @node GDB/MI Memory Overlay Commands
30769 @section @sc{gdb/mi} Memory Overlay Commands
30771 The memory overlay commands are not implemented.
30773 @c @subheading -overlay-auto
30775 @c @subheading -overlay-list-mapping-state
30777 @c @subheading -overlay-list-overlays
30779 @c @subheading -overlay-map
30781 @c @subheading -overlay-off
30783 @c @subheading -overlay-on
30785 @c @subheading -overlay-unmap
30787 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
30788 @node GDB/MI Signal Handling Commands
30789 @section @sc{gdb/mi} Signal Handling Commands
30791 Signal handling commands are not implemented.
30793 @c @subheading -signal-handle
30795 @c @subheading -signal-list-handle-actions
30797 @c @subheading -signal-list-signal-types
30801 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
30802 @node GDB/MI Target Manipulation
30803 @section @sc{gdb/mi} Target Manipulation Commands
30806 @subheading The @code{-target-attach} Command
30807 @findex -target-attach
30809 @subsubheading Synopsis
30812 -target-attach @var{pid} | @var{gid} | @var{file}
30815 Attach to a process @var{pid} or a file @var{file} outside of
30816 @value{GDBN}, or a thread group @var{gid}. If attaching to a thread
30817 group, the id previously returned by
30818 @samp{-list-thread-groups --available} must be used.
30820 @subsubheading @value{GDBN} Command
30822 The corresponding @value{GDBN} command is @samp{attach}.
30824 @subsubheading Example
30828 =thread-created,id="1"
30829 *stopped,thread-id="1",frame=@{addr="0xb7f7e410",func="bar",args=[]@}
30835 @subheading The @code{-target-compare-sections} Command
30836 @findex -target-compare-sections
30838 @subsubheading Synopsis
30841 -target-compare-sections [ @var{section} ]
30844 Compare data of section @var{section} on target to the exec file.
30845 Without the argument, all sections are compared.
30847 @subsubheading @value{GDBN} Command
30849 The @value{GDBN} equivalent is @samp{compare-sections}.
30851 @subsubheading Example
30856 @subheading The @code{-target-detach} Command
30857 @findex -target-detach
30859 @subsubheading Synopsis
30862 -target-detach [ @var{pid} | @var{gid} ]
30865 Detach from the remote target which normally resumes its execution.
30866 If either @var{pid} or @var{gid} is specified, detaches from either
30867 the specified process, or specified thread group. There's no output.
30869 @subsubheading @value{GDBN} Command
30871 The corresponding @value{GDBN} command is @samp{detach}.
30873 @subsubheading Example
30883 @subheading The @code{-target-disconnect} Command
30884 @findex -target-disconnect
30886 @subsubheading Synopsis
30892 Disconnect from the remote target. There's no output and the target is
30893 generally not resumed.
30895 @subsubheading @value{GDBN} Command
30897 The corresponding @value{GDBN} command is @samp{disconnect}.
30899 @subsubheading Example
30909 @subheading The @code{-target-download} Command
30910 @findex -target-download
30912 @subsubheading Synopsis
30918 Loads the executable onto the remote target.
30919 It prints out an update message every half second, which includes the fields:
30923 The name of the section.
30925 The size of what has been sent so far for that section.
30927 The size of the section.
30929 The total size of what was sent so far (the current and the previous sections).
30931 The size of the overall executable to download.
30935 Each message is sent as status record (@pxref{GDB/MI Output Syntax, ,
30936 @sc{gdb/mi} Output Syntax}).
30938 In addition, it prints the name and size of the sections, as they are
30939 downloaded. These messages include the following fields:
30943 The name of the section.
30945 The size of the section.
30947 The size of the overall executable to download.
30951 At the end, a summary is printed.
30953 @subsubheading @value{GDBN} Command
30955 The corresponding @value{GDBN} command is @samp{load}.
30957 @subsubheading Example
30959 Note: each status message appears on a single line. Here the messages
30960 have been broken down so that they can fit onto a page.
30965 +download,@{section=".text",section-size="6668",total-size="9880"@}
30966 +download,@{section=".text",section-sent="512",section-size="6668",
30967 total-sent="512",total-size="9880"@}
30968 +download,@{section=".text",section-sent="1024",section-size="6668",
30969 total-sent="1024",total-size="9880"@}
30970 +download,@{section=".text",section-sent="1536",section-size="6668",
30971 total-sent="1536",total-size="9880"@}
30972 +download,@{section=".text",section-sent="2048",section-size="6668",
30973 total-sent="2048",total-size="9880"@}
30974 +download,@{section=".text",section-sent="2560",section-size="6668",
30975 total-sent="2560",total-size="9880"@}
30976 +download,@{section=".text",section-sent="3072",section-size="6668",
30977 total-sent="3072",total-size="9880"@}
30978 +download,@{section=".text",section-sent="3584",section-size="6668",
30979 total-sent="3584",total-size="9880"@}
30980 +download,@{section=".text",section-sent="4096",section-size="6668",
30981 total-sent="4096",total-size="9880"@}
30982 +download,@{section=".text",section-sent="4608",section-size="6668",
30983 total-sent="4608",total-size="9880"@}
30984 +download,@{section=".text",section-sent="5120",section-size="6668",
30985 total-sent="5120",total-size="9880"@}
30986 +download,@{section=".text",section-sent="5632",section-size="6668",
30987 total-sent="5632",total-size="9880"@}
30988 +download,@{section=".text",section-sent="6144",section-size="6668",
30989 total-sent="6144",total-size="9880"@}
30990 +download,@{section=".text",section-sent="6656",section-size="6668",
30991 total-sent="6656",total-size="9880"@}
30992 +download,@{section=".init",section-size="28",total-size="9880"@}
30993 +download,@{section=".fini",section-size="28",total-size="9880"@}
30994 +download,@{section=".data",section-size="3156",total-size="9880"@}
30995 +download,@{section=".data",section-sent="512",section-size="3156",
30996 total-sent="7236",total-size="9880"@}
30997 +download,@{section=".data",section-sent="1024",section-size="3156",
30998 total-sent="7748",total-size="9880"@}
30999 +download,@{section=".data",section-sent="1536",section-size="3156",
31000 total-sent="8260",total-size="9880"@}
31001 +download,@{section=".data",section-sent="2048",section-size="3156",
31002 total-sent="8772",total-size="9880"@}
31003 +download,@{section=".data",section-sent="2560",section-size="3156",
31004 total-sent="9284",total-size="9880"@}
31005 +download,@{section=".data",section-sent="3072",section-size="3156",
31006 total-sent="9796",total-size="9880"@}
31007 ^done,address="0x10004",load-size="9880",transfer-rate="6586",
31014 @subheading The @code{-target-exec-status} Command
31015 @findex -target-exec-status
31017 @subsubheading Synopsis
31020 -target-exec-status
31023 Provide information on the state of the target (whether it is running or
31024 not, for instance).
31026 @subsubheading @value{GDBN} Command
31028 There's no equivalent @value{GDBN} command.
31030 @subsubheading Example
31034 @subheading The @code{-target-list-available-targets} Command
31035 @findex -target-list-available-targets
31037 @subsubheading Synopsis
31040 -target-list-available-targets
31043 List the possible targets to connect to.
31045 @subsubheading @value{GDBN} Command
31047 The corresponding @value{GDBN} command is @samp{help target}.
31049 @subsubheading Example
31053 @subheading The @code{-target-list-current-targets} Command
31054 @findex -target-list-current-targets
31056 @subsubheading Synopsis
31059 -target-list-current-targets
31062 Describe the current target.
31064 @subsubheading @value{GDBN} Command
31066 The corresponding information is printed by @samp{info file} (among
31069 @subsubheading Example
31073 @subheading The @code{-target-list-parameters} Command
31074 @findex -target-list-parameters
31076 @subsubheading Synopsis
31079 -target-list-parameters
31085 @subsubheading @value{GDBN} Command
31089 @subsubheading Example
31093 @subheading The @code{-target-select} Command
31094 @findex -target-select
31096 @subsubheading Synopsis
31099 -target-select @var{type} @var{parameters @dots{}}
31102 Connect @value{GDBN} to the remote target. This command takes two args:
31106 The type of target, for instance @samp{remote}, etc.
31107 @item @var{parameters}
31108 Device names, host names and the like. @xref{Target Commands, ,
31109 Commands for Managing Targets}, for more details.
31112 The output is a connection notification, followed by the address at
31113 which the target program is, in the following form:
31116 ^connected,addr="@var{address}",func="@var{function name}",
31117 args=[@var{arg list}]
31120 @subsubheading @value{GDBN} Command
31122 The corresponding @value{GDBN} command is @samp{target}.
31124 @subsubheading Example
31128 -target-select remote /dev/ttya
31129 ^connected,addr="0xfe00a300",func="??",args=[]
31133 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
31134 @node GDB/MI File Transfer Commands
31135 @section @sc{gdb/mi} File Transfer Commands
31138 @subheading The @code{-target-file-put} Command
31139 @findex -target-file-put
31141 @subsubheading Synopsis
31144 -target-file-put @var{hostfile} @var{targetfile}
31147 Copy file @var{hostfile} from the host system (the machine running
31148 @value{GDBN}) to @var{targetfile} on the target system.
31150 @subsubheading @value{GDBN} Command
31152 The corresponding @value{GDBN} command is @samp{remote put}.
31154 @subsubheading Example
31158 -target-file-put localfile remotefile
31164 @subheading The @code{-target-file-get} Command
31165 @findex -target-file-get
31167 @subsubheading Synopsis
31170 -target-file-get @var{targetfile} @var{hostfile}
31173 Copy file @var{targetfile} from the target system to @var{hostfile}
31174 on the host system.
31176 @subsubheading @value{GDBN} Command
31178 The corresponding @value{GDBN} command is @samp{remote get}.
31180 @subsubheading Example
31184 -target-file-get remotefile localfile
31190 @subheading The @code{-target-file-delete} Command
31191 @findex -target-file-delete
31193 @subsubheading Synopsis
31196 -target-file-delete @var{targetfile}
31199 Delete @var{targetfile} from the target system.
31201 @subsubheading @value{GDBN} Command
31203 The corresponding @value{GDBN} command is @samp{remote delete}.
31205 @subsubheading Example
31209 -target-file-delete remotefile
31215 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
31216 @node GDB/MI Miscellaneous Commands
31217 @section Miscellaneous @sc{gdb/mi} Commands
31219 @c @subheading -gdb-complete
31221 @subheading The @code{-gdb-exit} Command
31224 @subsubheading Synopsis
31230 Exit @value{GDBN} immediately.
31232 @subsubheading @value{GDBN} Command
31234 Approximately corresponds to @samp{quit}.
31236 @subsubheading Example
31246 @subheading The @code{-exec-abort} Command
31247 @findex -exec-abort
31249 @subsubheading Synopsis
31255 Kill the inferior running program.
31257 @subsubheading @value{GDBN} Command
31259 The corresponding @value{GDBN} command is @samp{kill}.
31261 @subsubheading Example
31266 @subheading The @code{-gdb-set} Command
31269 @subsubheading Synopsis
31275 Set an internal @value{GDBN} variable.
31276 @c IS THIS A DOLLAR VARIABLE? OR SOMETHING LIKE ANNOTATE ?????
31278 @subsubheading @value{GDBN} Command
31280 The corresponding @value{GDBN} command is @samp{set}.
31282 @subsubheading Example
31292 @subheading The @code{-gdb-show} Command
31295 @subsubheading Synopsis
31301 Show the current value of a @value{GDBN} variable.
31303 @subsubheading @value{GDBN} Command
31305 The corresponding @value{GDBN} command is @samp{show}.
31307 @subsubheading Example
31316 @c @subheading -gdb-source
31319 @subheading The @code{-gdb-version} Command
31320 @findex -gdb-version
31322 @subsubheading Synopsis
31328 Show version information for @value{GDBN}. Used mostly in testing.
31330 @subsubheading @value{GDBN} Command
31332 The @value{GDBN} equivalent is @samp{show version}. @value{GDBN} by
31333 default shows this information when you start an interactive session.
31335 @subsubheading Example
31337 @c This example modifies the actual output from GDB to avoid overfull
31343 ~Copyright 2000 Free Software Foundation, Inc.
31344 ~GDB is free software, covered by the GNU General Public License, and
31345 ~you are welcome to change it and/or distribute copies of it under
31346 ~ certain conditions.
31347 ~Type "show copying" to see the conditions.
31348 ~There is absolutely no warranty for GDB. Type "show warranty" for
31350 ~This GDB was configured as
31351 "--host=sparc-sun-solaris2.5.1 --target=ppc-eabi".
31356 @subheading The @code{-list-features} Command
31357 @findex -list-features
31359 Returns a list of particular features of the MI protocol that
31360 this version of gdb implements. A feature can be a command,
31361 or a new field in an output of some command, or even an
31362 important bugfix. While a frontend can sometimes detect presence
31363 of a feature at runtime, it is easier to perform detection at debugger
31366 The command returns a list of strings, with each string naming an
31367 available feature. Each returned string is just a name, it does not
31368 have any internal structure. The list of possible feature names
31374 (gdb) -list-features
31375 ^done,result=["feature1","feature2"]
31378 The current list of features is:
31381 @item frozen-varobjs
31382 Indicates support for the @code{-var-set-frozen} command, as well
31383 as possible presense of the @code{frozen} field in the output
31384 of @code{-varobj-create}.
31385 @item pending-breakpoints
31386 Indicates support for the @option{-f} option to the @code{-break-insert}
31389 Indicates Python scripting support, Python-based
31390 pretty-printing commands, and possible presence of the
31391 @samp{display_hint} field in the output of @code{-var-list-children}
31393 Indicates support for the @code{-thread-info} command.
31394 @item data-read-memory-bytes
31395 Indicates support for the @code{-data-read-memory-bytes} and the
31396 @code{-data-write-memory-bytes} commands.
31397 @item breakpoint-notifications
31398 Indicates that changes to breakpoints and breakpoints created via the
31399 CLI will be announced via async records.
31400 @item ada-task-info
31401 Indicates support for the @code{-ada-task-info} command.
31404 @subheading The @code{-list-target-features} Command
31405 @findex -list-target-features
31407 Returns a list of particular features that are supported by the
31408 target. Those features affect the permitted MI commands, but
31409 unlike the features reported by the @code{-list-features} command, the
31410 features depend on which target GDB is using at the moment. Whenever
31411 a target can change, due to commands such as @code{-target-select},
31412 @code{-target-attach} or @code{-exec-run}, the list of target features
31413 may change, and the frontend should obtain it again.
31417 (gdb) -list-features
31418 ^done,result=["async"]
31421 The current list of features is:
31425 Indicates that the target is capable of asynchronous command
31426 execution, which means that @value{GDBN} will accept further commands
31427 while the target is running.
31430 Indicates that the target is capable of reverse execution.
31431 @xref{Reverse Execution}, for more information.
31435 @subheading The @code{-list-thread-groups} Command
31436 @findex -list-thread-groups
31438 @subheading Synopsis
31441 -list-thread-groups [ --available ] [ --recurse 1 ] [ @var{group} ... ]
31444 Lists thread groups (@pxref{Thread groups}). When a single thread
31445 group is passed as the argument, lists the children of that group.
31446 When several thread group are passed, lists information about those
31447 thread groups. Without any parameters, lists information about all
31448 top-level thread groups.
31450 Normally, thread groups that are being debugged are reported.
31451 With the @samp{--available} option, @value{GDBN} reports thread groups
31452 available on the target.
31454 The output of this command may have either a @samp{threads} result or
31455 a @samp{groups} result. The @samp{thread} result has a list of tuples
31456 as value, with each tuple describing a thread (@pxref{GDB/MI Thread
31457 Information}). The @samp{groups} result has a list of tuples as value,
31458 each tuple describing a thread group. If top-level groups are
31459 requested (that is, no parameter is passed), or when several groups
31460 are passed, the output always has a @samp{groups} result. The format
31461 of the @samp{group} result is described below.
31463 To reduce the number of roundtrips it's possible to list thread groups
31464 together with their children, by passing the @samp{--recurse} option
31465 and the recursion depth. Presently, only recursion depth of 1 is
31466 permitted. If this option is present, then every reported thread group
31467 will also include its children, either as @samp{group} or
31468 @samp{threads} field.
31470 In general, any combination of option and parameters is permitted, with
31471 the following caveats:
31475 When a single thread group is passed, the output will typically
31476 be the @samp{threads} result. Because threads may not contain
31477 anything, the @samp{recurse} option will be ignored.
31480 When the @samp{--available} option is passed, limited information may
31481 be available. In particular, the list of threads of a process might
31482 be inaccessible. Further, specifying specific thread groups might
31483 not give any performance advantage over listing all thread groups.
31484 The frontend should assume that @samp{-list-thread-groups --available}
31485 is always an expensive operation and cache the results.
31489 The @samp{groups} result is a list of tuples, where each tuple may
31490 have the following fields:
31494 Identifier of the thread group. This field is always present.
31495 The identifier is an opaque string; frontends should not try to
31496 convert it to an integer, even though it might look like one.
31499 The type of the thread group. At present, only @samp{process} is a
31503 The target-specific process identifier. This field is only present
31504 for thread groups of type @samp{process} and only if the process exists.
31507 The number of children this thread group has. This field may be
31508 absent for an available thread group.
31511 This field has a list of tuples as value, each tuple describing a
31512 thread. It may be present if the @samp{--recurse} option is
31513 specified, and it's actually possible to obtain the threads.
31516 This field is a list of integers, each identifying a core that one
31517 thread of the group is running on. This field may be absent if
31518 such information is not available.
31521 The name of the executable file that corresponds to this thread group.
31522 The field is only present for thread groups of type @samp{process},
31523 and only if there is a corresponding executable file.
31527 @subheading Example
31531 -list-thread-groups
31532 ^done,groups=[@{id="17",type="process",pid="yyy",num_children="2"@}]
31533 -list-thread-groups 17
31534 ^done,threads=[@{id="2",target-id="Thread 0xb7e14b90 (LWP 21257)",
31535 frame=@{level="0",addr="0xffffe410",func="__kernel_vsyscall",args=[]@},state="running"@},
31536 @{id="1",target-id="Thread 0xb7e156b0 (LWP 21254)",
31537 frame=@{level="0",addr="0x0804891f",func="foo",args=[@{name="i",value="10"@}],
31538 file="/tmp/a.c",fullname="/tmp/a.c",line="158"@},state="running"@}]]
31539 -list-thread-groups --available
31540 ^done,groups=[@{id="17",type="process",pid="yyy",num_children="2",cores=[1,2]@}]
31541 -list-thread-groups --available --recurse 1
31542 ^done,groups=[@{id="17", types="process",pid="yyy",num_children="2",cores=[1,2],
31543 threads=[@{id="1",target-id="Thread 0xb7e14b90",cores=[1]@},
31544 @{id="2",target-id="Thread 0xb7e14b90",cores=[2]@}]@},..]
31545 -list-thread-groups --available --recurse 1 17 18
31546 ^done,groups=[@{id="17", types="process",pid="yyy",num_children="2",cores=[1,2],
31547 threads=[@{id="1",target-id="Thread 0xb7e14b90",cores=[1]@},
31548 @{id="2",target-id="Thread 0xb7e14b90",cores=[2]@}]@},...]
31552 @subheading The @code{-add-inferior} Command
31553 @findex -add-inferior
31555 @subheading Synopsis
31561 Creates a new inferior (@pxref{Inferiors and Programs}). The created
31562 inferior is not associated with any executable. Such association may
31563 be established with the @samp{-file-exec-and-symbols} command
31564 (@pxref{GDB/MI File Commands}). The command response has a single
31565 field, @samp{thread-group}, whose value is the identifier of the
31566 thread group corresponding to the new inferior.
31568 @subheading Example
31573 ^done,thread-group="i3"
31576 @subheading The @code{-interpreter-exec} Command
31577 @findex -interpreter-exec
31579 @subheading Synopsis
31582 -interpreter-exec @var{interpreter} @var{command}
31584 @anchor{-interpreter-exec}
31586 Execute the specified @var{command} in the given @var{interpreter}.
31588 @subheading @value{GDBN} Command
31590 The corresponding @value{GDBN} command is @samp{interpreter-exec}.
31592 @subheading Example
31596 -interpreter-exec console "break main"
31597 &"During symbol reading, couldn't parse type; debugger out of date?.\n"
31598 &"During symbol reading, bad structure-type format.\n"
31599 ~"Breakpoint 1 at 0x8074fc6: file ../../src/gdb/main.c, line 743.\n"
31604 @subheading The @code{-inferior-tty-set} Command
31605 @findex -inferior-tty-set
31607 @subheading Synopsis
31610 -inferior-tty-set /dev/pts/1
31613 Set terminal for future runs of the program being debugged.
31615 @subheading @value{GDBN} Command
31617 The corresponding @value{GDBN} command is @samp{set inferior-tty} /dev/pts/1.
31619 @subheading Example
31623 -inferior-tty-set /dev/pts/1
31628 @subheading The @code{-inferior-tty-show} Command
31629 @findex -inferior-tty-show
31631 @subheading Synopsis
31637 Show terminal for future runs of program being debugged.
31639 @subheading @value{GDBN} Command
31641 The corresponding @value{GDBN} command is @samp{show inferior-tty}.
31643 @subheading Example
31647 -inferior-tty-set /dev/pts/1
31651 ^done,inferior_tty_terminal="/dev/pts/1"
31655 @subheading The @code{-enable-timings} Command
31656 @findex -enable-timings
31658 @subheading Synopsis
31661 -enable-timings [yes | no]
31664 Toggle the printing of the wallclock, user and system times for an MI
31665 command as a field in its output. This command is to help frontend
31666 developers optimize the performance of their code. No argument is
31667 equivalent to @samp{yes}.
31669 @subheading @value{GDBN} Command
31673 @subheading Example
31681 ^done,bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
31682 addr="0x080484ed",func="main",file="myprog.c",
31683 fullname="/home/nickrob/myprog.c",line="73",times="0"@},
31684 time=@{wallclock="0.05185",user="0.00800",system="0.00000"@}
31692 *stopped,reason="breakpoint-hit",disp="keep",bkptno="1",thread-id="0",
31693 frame=@{addr="0x080484ed",func="main",args=[@{name="argc",value="1"@},
31694 @{name="argv",value="0xbfb60364"@}],file="myprog.c",
31695 fullname="/home/nickrob/myprog.c",line="73"@}
31700 @chapter @value{GDBN} Annotations
31702 This chapter describes annotations in @value{GDBN}. Annotations were
31703 designed to interface @value{GDBN} to graphical user interfaces or other
31704 similar programs which want to interact with @value{GDBN} at a
31705 relatively high level.
31707 The annotation mechanism has largely been superseded by @sc{gdb/mi}
31711 This is Edition @value{EDITION}, @value{DATE}.
31715 * Annotations Overview:: What annotations are; the general syntax.
31716 * Server Prefix:: Issuing a command without affecting user state.
31717 * Prompting:: Annotations marking @value{GDBN}'s need for input.
31718 * Errors:: Annotations for error messages.
31719 * Invalidation:: Some annotations describe things now invalid.
31720 * Annotations for Running::
31721 Whether the program is running, how it stopped, etc.
31722 * Source Annotations:: Annotations describing source code.
31725 @node Annotations Overview
31726 @section What is an Annotation?
31727 @cindex annotations
31729 Annotations start with a newline character, two @samp{control-z}
31730 characters, and the name of the annotation. If there is no additional
31731 information associated with this annotation, the name of the annotation
31732 is followed immediately by a newline. If there is additional
31733 information, the name of the annotation is followed by a space, the
31734 additional information, and a newline. The additional information
31735 cannot contain newline characters.
31737 Any output not beginning with a newline and two @samp{control-z}
31738 characters denotes literal output from @value{GDBN}. Currently there is
31739 no need for @value{GDBN} to output a newline followed by two
31740 @samp{control-z} characters, but if there was such a need, the
31741 annotations could be extended with an @samp{escape} annotation which
31742 means those three characters as output.
31744 The annotation @var{level}, which is specified using the
31745 @option{--annotate} command line option (@pxref{Mode Options}), controls
31746 how much information @value{GDBN} prints together with its prompt,
31747 values of expressions, source lines, and other types of output. Level 0
31748 is for no annotations, level 1 is for use when @value{GDBN} is run as a
31749 subprocess of @sc{gnu} Emacs, level 3 is the maximum annotation suitable
31750 for programs that control @value{GDBN}, and level 2 annotations have
31751 been made obsolete (@pxref{Limitations, , Limitations of the Annotation
31752 Interface, annotate, GDB's Obsolete Annotations}).
31755 @kindex set annotate
31756 @item set annotate @var{level}
31757 The @value{GDBN} command @code{set annotate} sets the level of
31758 annotations to the specified @var{level}.
31760 @item show annotate
31761 @kindex show annotate
31762 Show the current annotation level.
31765 This chapter describes level 3 annotations.
31767 A simple example of starting up @value{GDBN} with annotations is:
31770 $ @kbd{gdb --annotate=3}
31772 Copyright 2003 Free Software Foundation, Inc.
31773 GDB is free software, covered by the GNU General Public License,
31774 and you are welcome to change it and/or distribute copies of it
31775 under certain conditions.
31776 Type "show copying" to see the conditions.
31777 There is absolutely no warranty for GDB. Type "show warranty"
31779 This GDB was configured as "i386-pc-linux-gnu"
31790 Here @samp{quit} is input to @value{GDBN}; the rest is output from
31791 @value{GDBN}. The three lines beginning @samp{^Z^Z} (where @samp{^Z}
31792 denotes a @samp{control-z} character) are annotations; the rest is
31793 output from @value{GDBN}.
31795 @node Server Prefix
31796 @section The Server Prefix
31797 @cindex server prefix
31799 If you prefix a command with @samp{server } then it will not affect
31800 the command history, nor will it affect @value{GDBN}'s notion of which
31801 command to repeat if @key{RET} is pressed on a line by itself. This
31802 means that commands can be run behind a user's back by a front-end in
31803 a transparent manner.
31805 The @code{server } prefix does not affect the recording of values into
31806 the value history; to print a value without recording it into the
31807 value history, use the @code{output} command instead of the
31808 @code{print} command.
31810 Using this prefix also disables confirmation requests
31811 (@pxref{confirmation requests}).
31814 @section Annotation for @value{GDBN} Input
31816 @cindex annotations for prompts
31817 When @value{GDBN} prompts for input, it annotates this fact so it is possible
31818 to know when to send output, when the output from a given command is
31821 Different kinds of input each have a different @dfn{input type}. Each
31822 input type has three annotations: a @code{pre-} annotation, which
31823 denotes the beginning of any prompt which is being output, a plain
31824 annotation, which denotes the end of the prompt, and then a @code{post-}
31825 annotation which denotes the end of any echo which may (or may not) be
31826 associated with the input. For example, the @code{prompt} input type
31827 features the following annotations:
31835 The input types are
31838 @findex pre-prompt annotation
31839 @findex prompt annotation
31840 @findex post-prompt annotation
31842 When @value{GDBN} is prompting for a command (the main @value{GDBN} prompt).
31844 @findex pre-commands annotation
31845 @findex commands annotation
31846 @findex post-commands annotation
31848 When @value{GDBN} prompts for a set of commands, like in the @code{commands}
31849 command. The annotations are repeated for each command which is input.
31851 @findex pre-overload-choice annotation
31852 @findex overload-choice annotation
31853 @findex post-overload-choice annotation
31854 @item overload-choice
31855 When @value{GDBN} wants the user to select between various overloaded functions.
31857 @findex pre-query annotation
31858 @findex query annotation
31859 @findex post-query annotation
31861 When @value{GDBN} wants the user to confirm a potentially dangerous operation.
31863 @findex pre-prompt-for-continue annotation
31864 @findex prompt-for-continue annotation
31865 @findex post-prompt-for-continue annotation
31866 @item prompt-for-continue
31867 When @value{GDBN} is asking the user to press return to continue. Note: Don't
31868 expect this to work well; instead use @code{set height 0} to disable
31869 prompting. This is because the counting of lines is buggy in the
31870 presence of annotations.
31875 @cindex annotations for errors, warnings and interrupts
31877 @findex quit annotation
31882 This annotation occurs right before @value{GDBN} responds to an interrupt.
31884 @findex error annotation
31889 This annotation occurs right before @value{GDBN} responds to an error.
31891 Quit and error annotations indicate that any annotations which @value{GDBN} was
31892 in the middle of may end abruptly. For example, if a
31893 @code{value-history-begin} annotation is followed by a @code{error}, one
31894 cannot expect to receive the matching @code{value-history-end}. One
31895 cannot expect not to receive it either, however; an error annotation
31896 does not necessarily mean that @value{GDBN} is immediately returning all the way
31899 @findex error-begin annotation
31900 A quit or error annotation may be preceded by
31906 Any output between that and the quit or error annotation is the error
31909 Warning messages are not yet annotated.
31910 @c If we want to change that, need to fix warning(), type_error(),
31911 @c range_error(), and possibly other places.
31914 @section Invalidation Notices
31916 @cindex annotations for invalidation messages
31917 The following annotations say that certain pieces of state may have
31921 @findex frames-invalid annotation
31922 @item ^Z^Zframes-invalid
31924 The frames (for example, output from the @code{backtrace} command) may
31927 @findex breakpoints-invalid annotation
31928 @item ^Z^Zbreakpoints-invalid
31930 The breakpoints may have changed. For example, the user just added or
31931 deleted a breakpoint.
31934 @node Annotations for Running
31935 @section Running the Program
31936 @cindex annotations for running programs
31938 @findex starting annotation
31939 @findex stopping annotation
31940 When the program starts executing due to a @value{GDBN} command such as
31941 @code{step} or @code{continue},
31947 is output. When the program stops,
31953 is output. Before the @code{stopped} annotation, a variety of
31954 annotations describe how the program stopped.
31957 @findex exited annotation
31958 @item ^Z^Zexited @var{exit-status}
31959 The program exited, and @var{exit-status} is the exit status (zero for
31960 successful exit, otherwise nonzero).
31962 @findex signalled annotation
31963 @findex signal-name annotation
31964 @findex signal-name-end annotation
31965 @findex signal-string annotation
31966 @findex signal-string-end annotation
31967 @item ^Z^Zsignalled
31968 The program exited with a signal. After the @code{^Z^Zsignalled}, the
31969 annotation continues:
31975 ^Z^Zsignal-name-end
31979 ^Z^Zsignal-string-end
31984 where @var{name} is the name of the signal, such as @code{SIGILL} or
31985 @code{SIGSEGV}, and @var{string} is the explanation of the signal, such
31986 as @code{Illegal Instruction} or @code{Segmentation fault}.
31987 @var{intro-text}, @var{middle-text}, and @var{end-text} are for the
31988 user's benefit and have no particular format.
31990 @findex signal annotation
31992 The syntax of this annotation is just like @code{signalled}, but @value{GDBN} is
31993 just saying that the program received the signal, not that it was
31994 terminated with it.
31996 @findex breakpoint annotation
31997 @item ^Z^Zbreakpoint @var{number}
31998 The program hit breakpoint number @var{number}.
32000 @findex watchpoint annotation
32001 @item ^Z^Zwatchpoint @var{number}
32002 The program hit watchpoint number @var{number}.
32005 @node Source Annotations
32006 @section Displaying Source
32007 @cindex annotations for source display
32009 @findex source annotation
32010 The following annotation is used instead of displaying source code:
32013 ^Z^Zsource @var{filename}:@var{line}:@var{character}:@var{middle}:@var{addr}
32016 where @var{filename} is an absolute file name indicating which source
32017 file, @var{line} is the line number within that file (where 1 is the
32018 first line in the file), @var{character} is the character position
32019 within the file (where 0 is the first character in the file) (for most
32020 debug formats this will necessarily point to the beginning of a line),
32021 @var{middle} is @samp{middle} if @var{addr} is in the middle of the
32022 line, or @samp{beg} if @var{addr} is at the beginning of the line, and
32023 @var{addr} is the address in the target program associated with the
32024 source which is being displayed. @var{addr} is in the form @samp{0x}
32025 followed by one or more lowercase hex digits (note that this does not
32026 depend on the language).
32028 @node JIT Interface
32029 @chapter JIT Compilation Interface
32030 @cindex just-in-time compilation
32031 @cindex JIT compilation interface
32033 This chapter documents @value{GDBN}'s @dfn{just-in-time} (JIT) compilation
32034 interface. A JIT compiler is a program or library that generates native
32035 executable code at runtime and executes it, usually in order to achieve good
32036 performance while maintaining platform independence.
32038 Programs that use JIT compilation are normally difficult to debug because
32039 portions of their code are generated at runtime, instead of being loaded from
32040 object files, which is where @value{GDBN} normally finds the program's symbols
32041 and debug information. In order to debug programs that use JIT compilation,
32042 @value{GDBN} has an interface that allows the program to register in-memory
32043 symbol files with @value{GDBN} at runtime.
32045 If you are using @value{GDBN} to debug a program that uses this interface, then
32046 it should work transparently so long as you have not stripped the binary. If
32047 you are developing a JIT compiler, then the interface is documented in the rest
32048 of this chapter. At this time, the only known client of this interface is the
32051 Broadly speaking, the JIT interface mirrors the dynamic loader interface. The
32052 JIT compiler communicates with @value{GDBN} by writing data into a global
32053 variable and calling a fuction at a well-known symbol. When @value{GDBN}
32054 attaches, it reads a linked list of symbol files from the global variable to
32055 find existing code, and puts a breakpoint in the function so that it can find
32056 out about additional code.
32059 * Declarations:: Relevant C struct declarations
32060 * Registering Code:: Steps to register code
32061 * Unregistering Code:: Steps to unregister code
32062 * Custom Debug Info:: Emit debug information in a custom format
32066 @section JIT Declarations
32068 These are the relevant struct declarations that a C program should include to
32069 implement the interface:
32079 struct jit_code_entry
32081 struct jit_code_entry *next_entry;
32082 struct jit_code_entry *prev_entry;
32083 const char *symfile_addr;
32084 uint64_t symfile_size;
32087 struct jit_descriptor
32090 /* This type should be jit_actions_t, but we use uint32_t
32091 to be explicit about the bitwidth. */
32092 uint32_t action_flag;
32093 struct jit_code_entry *relevant_entry;
32094 struct jit_code_entry *first_entry;
32097 /* GDB puts a breakpoint in this function. */
32098 void __attribute__((noinline)) __jit_debug_register_code() @{ @};
32100 /* Make sure to specify the version statically, because the
32101 debugger may check the version before we can set it. */
32102 struct jit_descriptor __jit_debug_descriptor = @{ 1, 0, 0, 0 @};
32105 If the JIT is multi-threaded, then it is important that the JIT synchronize any
32106 modifications to this global data properly, which can easily be done by putting
32107 a global mutex around modifications to these structures.
32109 @node Registering Code
32110 @section Registering Code
32112 To register code with @value{GDBN}, the JIT should follow this protocol:
32116 Generate an object file in memory with symbols and other desired debug
32117 information. The file must include the virtual addresses of the sections.
32120 Create a code entry for the file, which gives the start and size of the symbol
32124 Add it to the linked list in the JIT descriptor.
32127 Point the relevant_entry field of the descriptor at the entry.
32130 Set @code{action_flag} to @code{JIT_REGISTER} and call
32131 @code{__jit_debug_register_code}.
32134 When @value{GDBN} is attached and the breakpoint fires, @value{GDBN} uses the
32135 @code{relevant_entry} pointer so it doesn't have to walk the list looking for
32136 new code. However, the linked list must still be maintained in order to allow
32137 @value{GDBN} to attach to a running process and still find the symbol files.
32139 @node Unregistering Code
32140 @section Unregistering Code
32142 If code is freed, then the JIT should use the following protocol:
32146 Remove the code entry corresponding to the code from the linked list.
32149 Point the @code{relevant_entry} field of the descriptor at the code entry.
32152 Set @code{action_flag} to @code{JIT_UNREGISTER} and call
32153 @code{__jit_debug_register_code}.
32156 If the JIT frees or recompiles code without unregistering it, then @value{GDBN}
32157 and the JIT will leak the memory used for the associated symbol files.
32159 @node Custom Debug Info
32160 @section Custom Debug Info
32161 @cindex custom JIT debug info
32162 @cindex JIT debug info reader
32164 Generating debug information in platform-native file formats (like ELF
32165 or COFF) may be an overkill for JIT compilers; especially if all the
32166 debug info is used for is displaying a meaningful backtrace. The
32167 issue can be resolved by having the JIT writers decide on a debug info
32168 format and also provide a reader that parses the debug info generated
32169 by the JIT compiler. This section gives a brief overview on writing
32170 such a parser. More specific details can be found in the source file
32171 @file{gdb/jit-reader.in}, which is also installed as a header at
32172 @file{@var{includedir}/gdb/jit-reader.h} for easy inclusion.
32174 The reader is implemented as a shared object (so this functionality is
32175 not available on platforms which don't allow loading shared objects at
32176 runtime). Two @value{GDBN} commands, @code{jit-reader-load} and
32177 @code{jit-reader-unload} are provided, to be used to load and unload
32178 the readers from a preconfigured directory. Once loaded, the shared
32179 object is used the parse the debug information emitted by the JIT
32183 * Using JIT Debug Info Readers:: How to use supplied readers correctly
32184 * Writing JIT Debug Info Readers:: Creating a debug-info reader
32187 @node Using JIT Debug Info Readers
32188 @subsection Using JIT Debug Info Readers
32189 @kindex jit-reader-load
32190 @kindex jit-reader-unload
32192 Readers can be loaded and unloaded using the @code{jit-reader-load}
32193 and @code{jit-reader-unload} commands.
32196 @item jit-reader-load @var{reader-name}
32197 Load the JIT reader named @var{reader-name}. On a UNIX system, this
32198 will usually load @file{@var{libdir}/gdb/@var{reader-name}}, where
32199 @var{libdir} is the system library directory, usually
32200 @file{/usr/local/lib}. Only one reader can be active at a time;
32201 trying to load a second reader when one is already loaded will result
32202 in @value{GDBN} reporting an error. A new JIT reader can be loaded by
32203 first unloading the current one using @code{jit-reader-load} and then
32204 invoking @code{jit-reader-load}.
32206 @item jit-reader-unload
32207 Unload the currently loaded JIT reader.
32211 @node Writing JIT Debug Info Readers
32212 @subsection Writing JIT Debug Info Readers
32213 @cindex writing JIT debug info readers
32215 As mentioned, a reader is essentially a shared object conforming to a
32216 certain ABI. This ABI is described in @file{jit-reader.h}.
32218 @file{jit-reader.h} defines the structures, macros and functions
32219 required to write a reader. It is installed (along with
32220 @value{GDBN}), in @file{@var{includedir}/gdb} where @var{includedir} is
32221 the system include directory.
32223 Readers need to be released under a GPL compatible license. A reader
32224 can be declared as released under such a license by placing the macro
32225 @code{GDB_DECLARE_GPL_COMPATIBLE_READER} in a source file.
32227 The entry point for readers is the symbol @code{gdb_init_reader},
32228 which is expected to be a function with the prototype
32230 @findex gdb_init_reader
32232 extern struct gdb_reader_funcs *gdb_init_reader (void);
32235 @cindex @code{struct gdb_reader_funcs}
32237 @code{struct gdb_reader_funcs} contains a set of pointers to callback
32238 functions. These functions are executed to read the debug info
32239 generated by the JIT compiler (@code{read}), to unwind stack frames
32240 (@code{unwind}) and to create canonical frame IDs
32241 (@code{get_Frame_id}). It also has a callback that is called when the
32242 reader is being unloaded (@code{destroy}). The struct looks like this
32245 struct gdb_reader_funcs
32247 /* Must be set to GDB_READER_INTERFACE_VERSION. */
32248 int reader_version;
32250 /* For use by the reader. */
32253 gdb_read_debug_info *read;
32254 gdb_unwind_frame *unwind;
32255 gdb_get_frame_id *get_frame_id;
32256 gdb_destroy_reader *destroy;
32260 @cindex @code{struct gdb_symbol_callbacks}
32261 @cindex @code{struct gdb_unwind_callbacks}
32263 The callbacks are provided with another set of callbacks by
32264 @value{GDBN} to do their job. For @code{read}, these callbacks are
32265 passed in a @code{struct gdb_symbol_callbacks} and for @code{unwind}
32266 and @code{get_frame_id}, in a @code{struct gdb_unwind_callbacks}.
32267 @code{struct gdb_symbol_callbacks} has callbacks to create new object
32268 files and new symbol tables inside those object files. @code{struct
32269 gdb_unwind_callbacks} has callbacks to read registers off the current
32270 frame and to write out the values of the registers in the previous
32271 frame. Both have a callback (@code{target_read}) to read bytes off the
32272 target's address space.
32274 @node In-Process Agent
32275 @chapter In-Process Agent
32276 @cindex debugging agent
32277 The traditional debugging model is conceptually low-speed, but works fine,
32278 because most bugs can be reproduced in debugging-mode execution. However,
32279 as multi-core or many-core processors are becoming mainstream, and
32280 multi-threaded programs become more and more popular, there should be more
32281 and more bugs that only manifest themselves at normal-mode execution, for
32282 example, thread races, because debugger's interference with the program's
32283 timing may conceal the bugs. On the other hand, in some applications,
32284 it is not feasible for the debugger to interrupt the program's execution
32285 long enough for the developer to learn anything helpful about its behavior.
32286 If the program's correctness depends on its real-time behavior, delays
32287 introduced by a debugger might cause the program to fail, even when the
32288 code itself is correct. It is useful to be able to observe the program's
32289 behavior without interrupting it.
32291 Therefore, traditional debugging model is too intrusive to reproduce
32292 some bugs. In order to reduce the interference with the program, we can
32293 reduce the number of operations performed by debugger. The
32294 @dfn{In-Process Agent}, a shared library, is running within the same
32295 process with inferior, and is able to perform some debugging operations
32296 itself. As a result, debugger is only involved when necessary, and
32297 performance of debugging can be improved accordingly. Note that
32298 interference with program can be reduced but can't be removed completely,
32299 because the in-process agent will still stop or slow down the program.
32301 The in-process agent can interpret and execute Agent Expressions
32302 (@pxref{Agent Expressions}) during performing debugging operations. The
32303 agent expressions can be used for different purposes, such as collecting
32304 data in tracepoints, and condition evaluation in breakpoints.
32306 @anchor{Control Agent}
32307 You can control whether the in-process agent is used as an aid for
32308 debugging with the following commands:
32311 @kindex set agent on
32313 Causes the in-process agent to perform some operations on behalf of the
32314 debugger. Just which operations requested by the user will be done
32315 by the in-process agent depends on the its capabilities. For example,
32316 if you request to evaluate breakpoint conditions in the in-process agent,
32317 and the in-process agent has such capability as well, then breakpoint
32318 conditions will be evaluated in the in-process agent.
32320 @kindex set agent off
32321 @item set agent off
32322 Disables execution of debugging operations by the in-process agent. All
32323 of the operations will be performed by @value{GDBN}.
32327 Display the current setting of execution of debugging operations by
32328 the in-process agent.
32332 @chapter Reporting Bugs in @value{GDBN}
32333 @cindex bugs in @value{GDBN}
32334 @cindex reporting bugs in @value{GDBN}
32336 Your bug reports play an essential role in making @value{GDBN} reliable.
32338 Reporting a bug may help you by bringing a solution to your problem, or it
32339 may not. But in any case the principal function of a bug report is to help
32340 the entire community by making the next version of @value{GDBN} work better. Bug
32341 reports are your contribution to the maintenance of @value{GDBN}.
32343 In order for a bug report to serve its purpose, you must include the
32344 information that enables us to fix the bug.
32347 * Bug Criteria:: Have you found a bug?
32348 * Bug Reporting:: How to report bugs
32352 @section Have You Found a Bug?
32353 @cindex bug criteria
32355 If you are not sure whether you have found a bug, here are some guidelines:
32358 @cindex fatal signal
32359 @cindex debugger crash
32360 @cindex crash of debugger
32362 If the debugger gets a fatal signal, for any input whatever, that is a
32363 @value{GDBN} bug. Reliable debuggers never crash.
32365 @cindex error on valid input
32367 If @value{GDBN} produces an error message for valid input, that is a
32368 bug. (Note that if you're cross debugging, the problem may also be
32369 somewhere in the connection to the target.)
32371 @cindex invalid input
32373 If @value{GDBN} does not produce an error message for invalid input,
32374 that is a bug. However, you should note that your idea of
32375 ``invalid input'' might be our idea of ``an extension'' or ``support
32376 for traditional practice''.
32379 If you are an experienced user of debugging tools, your suggestions
32380 for improvement of @value{GDBN} are welcome in any case.
32383 @node Bug Reporting
32384 @section How to Report Bugs
32385 @cindex bug reports
32386 @cindex @value{GDBN} bugs, reporting
32388 A number of companies and individuals offer support for @sc{gnu} products.
32389 If you obtained @value{GDBN} from a support organization, we recommend you
32390 contact that organization first.
32392 You can find contact information for many support companies and
32393 individuals in the file @file{etc/SERVICE} in the @sc{gnu} Emacs
32395 @c should add a web page ref...
32398 @ifset BUGURL_DEFAULT
32399 In any event, we also recommend that you submit bug reports for
32400 @value{GDBN}. The preferred method is to submit them directly using
32401 @uref{http://www.gnu.org/software/gdb/bugs/, @value{GDBN}'s Bugs web
32402 page}. Alternatively, the @email{bug-gdb@@gnu.org, e-mail gateway} can
32405 @strong{Do not send bug reports to @samp{info-gdb}, or to
32406 @samp{help-gdb}, or to any newsgroups.} Most users of @value{GDBN} do
32407 not want to receive bug reports. Those that do have arranged to receive
32410 The mailing list @samp{bug-gdb} has a newsgroup @samp{gnu.gdb.bug} which
32411 serves as a repeater. The mailing list and the newsgroup carry exactly
32412 the same messages. Often people think of posting bug reports to the
32413 newsgroup instead of mailing them. This appears to work, but it has one
32414 problem which can be crucial: a newsgroup posting often lacks a mail
32415 path back to the sender. Thus, if we need to ask for more information,
32416 we may be unable to reach you. For this reason, it is better to send
32417 bug reports to the mailing list.
32419 @ifclear BUGURL_DEFAULT
32420 In any event, we also recommend that you submit bug reports for
32421 @value{GDBN} to @value{BUGURL}.
32425 The fundamental principle of reporting bugs usefully is this:
32426 @strong{report all the facts}. If you are not sure whether to state a
32427 fact or leave it out, state it!
32429 Often people omit facts because they think they know what causes the
32430 problem and assume that some details do not matter. Thus, you might
32431 assume that the name of the variable you use in an example does not matter.
32432 Well, probably it does not, but one cannot be sure. Perhaps the bug is a
32433 stray memory reference which happens to fetch from the location where that
32434 name is stored in memory; perhaps, if the name were different, the contents
32435 of that location would fool the debugger into doing the right thing despite
32436 the bug. Play it safe and give a specific, complete example. That is the
32437 easiest thing for you to do, and the most helpful.
32439 Keep in mind that the purpose of a bug report is to enable us to fix the
32440 bug. It may be that the bug has been reported previously, but neither
32441 you nor we can know that unless your bug report is complete and
32444 Sometimes people give a few sketchy facts and ask, ``Does this ring a
32445 bell?'' Those bug reports are useless, and we urge everyone to
32446 @emph{refuse to respond to them} except to chide the sender to report
32449 To enable us to fix the bug, you should include all these things:
32453 The version of @value{GDBN}. @value{GDBN} announces it if you start
32454 with no arguments; you can also print it at any time using @code{show
32457 Without this, we will not know whether there is any point in looking for
32458 the bug in the current version of @value{GDBN}.
32461 The type of machine you are using, and the operating system name and
32465 What compiler (and its version) was used to compile @value{GDBN}---e.g.@:
32466 ``@value{GCC}--2.8.1''.
32469 What compiler (and its version) was used to compile the program you are
32470 debugging---e.g.@: ``@value{GCC}--2.8.1'', or ``HP92453-01 A.10.32.03 HP
32471 C Compiler''. For @value{NGCC}, you can say @kbd{@value{GCC} --version}
32472 to get this information; for other compilers, see the documentation for
32476 The command arguments you gave the compiler to compile your example and
32477 observe the bug. For example, did you use @samp{-O}? To guarantee
32478 you will not omit something important, list them all. A copy of the
32479 Makefile (or the output from make) is sufficient.
32481 If we were to try to guess the arguments, we would probably guess wrong
32482 and then we might not encounter the bug.
32485 A complete input script, and all necessary source files, that will
32489 A description of what behavior you observe that you believe is
32490 incorrect. For example, ``It gets a fatal signal.''
32492 Of course, if the bug is that @value{GDBN} gets a fatal signal, then we
32493 will certainly notice it. But if the bug is incorrect output, we might
32494 not notice unless it is glaringly wrong. You might as well not give us
32495 a chance to make a mistake.
32497 Even if the problem you experience is a fatal signal, you should still
32498 say so explicitly. Suppose something strange is going on, such as, your
32499 copy of @value{GDBN} is out of synch, or you have encountered a bug in
32500 the C library on your system. (This has happened!) Your copy might
32501 crash and ours would not. If you told us to expect a crash, then when
32502 ours fails to crash, we would know that the bug was not happening for
32503 us. If you had not told us to expect a crash, then we would not be able
32504 to draw any conclusion from our observations.
32507 @cindex recording a session script
32508 To collect all this information, you can use a session recording program
32509 such as @command{script}, which is available on many Unix systems.
32510 Just run your @value{GDBN} session inside @command{script} and then
32511 include the @file{typescript} file with your bug report.
32513 Another way to record a @value{GDBN} session is to run @value{GDBN}
32514 inside Emacs and then save the entire buffer to a file.
32517 If you wish to suggest changes to the @value{GDBN} source, send us context
32518 diffs. If you even discuss something in the @value{GDBN} source, refer to
32519 it by context, not by line number.
32521 The line numbers in our development sources will not match those in your
32522 sources. Your line numbers would convey no useful information to us.
32526 Here are some things that are not necessary:
32530 A description of the envelope of the bug.
32532 Often people who encounter a bug spend a lot of time investigating
32533 which changes to the input file will make the bug go away and which
32534 changes will not affect it.
32536 This is often time consuming and not very useful, because the way we
32537 will find the bug is by running a single example under the debugger
32538 with breakpoints, not by pure deduction from a series of examples.
32539 We recommend that you save your time for something else.
32541 Of course, if you can find a simpler example to report @emph{instead}
32542 of the original one, that is a convenience for us. Errors in the
32543 output will be easier to spot, running under the debugger will take
32544 less time, and so on.
32546 However, simplification is not vital; if you do not want to do this,
32547 report the bug anyway and send us the entire test case you used.
32550 A patch for the bug.
32552 A patch for the bug does help us if it is a good one. But do not omit
32553 the necessary information, such as the test case, on the assumption that
32554 a patch is all we need. We might see problems with your patch and decide
32555 to fix the problem another way, or we might not understand it at all.
32557 Sometimes with a program as complicated as @value{GDBN} it is very hard to
32558 construct an example that will make the program follow a certain path
32559 through the code. If you do not send us the example, we will not be able
32560 to construct one, so we will not be able to verify that the bug is fixed.
32562 And if we cannot understand what bug you are trying to fix, or why your
32563 patch should be an improvement, we will not install it. A test case will
32564 help us to understand.
32567 A guess about what the bug is or what it depends on.
32569 Such guesses are usually wrong. Even we cannot guess right about such
32570 things without first using the debugger to find the facts.
32573 @c The readline documentation is distributed with the readline code
32574 @c and consists of the two following files:
32577 @c Use -I with makeinfo to point to the appropriate directory,
32578 @c environment var TEXINPUTS with TeX.
32579 @ifclear SYSTEM_READLINE
32580 @include rluser.texi
32581 @include hsuser.texi
32585 @appendix In Memoriam
32587 The @value{GDBN} project mourns the loss of the following long-time
32592 Fred was a long-standing contributor to @value{GDBN} (1991-2006), and
32593 to Free Software in general. Outside of @value{GDBN}, he was known in
32594 the Amiga world for his series of Fish Disks, and the GeekGadget project.
32596 @item Michael Snyder
32597 Michael was one of the Global Maintainers of the @value{GDBN} project,
32598 with contributions recorded as early as 1996, until 2011. In addition
32599 to his day to day participation, he was a large driving force behind
32600 adding Reverse Debugging to @value{GDBN}.
32603 Beyond their technical contributions to the project, they were also
32604 enjoyable members of the Free Software Community. We will miss them.
32606 @node Formatting Documentation
32607 @appendix Formatting Documentation
32609 @cindex @value{GDBN} reference card
32610 @cindex reference card
32611 The @value{GDBN} 4 release includes an already-formatted reference card, ready
32612 for printing with PostScript or Ghostscript, in the @file{gdb}
32613 subdirectory of the main source directory@footnote{In
32614 @file{gdb-@value{GDBVN}/gdb/refcard.ps} of the version @value{GDBVN}
32615 release.}. If you can use PostScript or Ghostscript with your printer,
32616 you can print the reference card immediately with @file{refcard.ps}.
32618 The release also includes the source for the reference card. You
32619 can format it, using @TeX{}, by typing:
32625 The @value{GDBN} reference card is designed to print in @dfn{landscape}
32626 mode on US ``letter'' size paper;
32627 that is, on a sheet 11 inches wide by 8.5 inches
32628 high. You will need to specify this form of printing as an option to
32629 your @sc{dvi} output program.
32631 @cindex documentation
32633 All the documentation for @value{GDBN} comes as part of the machine-readable
32634 distribution. The documentation is written in Texinfo format, which is
32635 a documentation system that uses a single source file to produce both
32636 on-line information and a printed manual. You can use one of the Info
32637 formatting commands to create the on-line version of the documentation
32638 and @TeX{} (or @code{texi2roff}) to typeset the printed version.
32640 @value{GDBN} includes an already formatted copy of the on-line Info
32641 version of this manual in the @file{gdb} subdirectory. The main Info
32642 file is @file{gdb-@value{GDBVN}/gdb/gdb.info}, and it refers to
32643 subordinate files matching @samp{gdb.info*} in the same directory. If
32644 necessary, you can print out these files, or read them with any editor;
32645 but they are easier to read using the @code{info} subsystem in @sc{gnu}
32646 Emacs or the standalone @code{info} program, available as part of the
32647 @sc{gnu} Texinfo distribution.
32649 If you want to format these Info files yourself, you need one of the
32650 Info formatting programs, such as @code{texinfo-format-buffer} or
32653 If you have @code{makeinfo} installed, and are in the top level
32654 @value{GDBN} source directory (@file{gdb-@value{GDBVN}}, in the case of
32655 version @value{GDBVN}), you can make the Info file by typing:
32662 If you want to typeset and print copies of this manual, you need @TeX{},
32663 a program to print its @sc{dvi} output files, and @file{texinfo.tex}, the
32664 Texinfo definitions file.
32666 @TeX{} is a typesetting program; it does not print files directly, but
32667 produces output files called @sc{dvi} files. To print a typeset
32668 document, you need a program to print @sc{dvi} files. If your system
32669 has @TeX{} installed, chances are it has such a program. The precise
32670 command to use depends on your system; @kbd{lpr -d} is common; another
32671 (for PostScript devices) is @kbd{dvips}. The @sc{dvi} print command may
32672 require a file name without any extension or a @samp{.dvi} extension.
32674 @TeX{} also requires a macro definitions file called
32675 @file{texinfo.tex}. This file tells @TeX{} how to typeset a document
32676 written in Texinfo format. On its own, @TeX{} cannot either read or
32677 typeset a Texinfo file. @file{texinfo.tex} is distributed with GDB
32678 and is located in the @file{gdb-@var{version-number}/texinfo}
32681 If you have @TeX{} and a @sc{dvi} printer program installed, you can
32682 typeset and print this manual. First switch to the @file{gdb}
32683 subdirectory of the main source directory (for example, to
32684 @file{gdb-@value{GDBVN}/gdb}) and type:
32690 Then give @file{gdb.dvi} to your @sc{dvi} printing program.
32692 @node Installing GDB
32693 @appendix Installing @value{GDBN}
32694 @cindex installation
32697 * Requirements:: Requirements for building @value{GDBN}
32698 * Running Configure:: Invoking the @value{GDBN} @file{configure} script
32699 * Separate Objdir:: Compiling @value{GDBN} in another directory
32700 * Config Names:: Specifying names for hosts and targets
32701 * Configure Options:: Summary of options for configure
32702 * System-wide configuration:: Having a system-wide init file
32706 @section Requirements for Building @value{GDBN}
32707 @cindex building @value{GDBN}, requirements for
32709 Building @value{GDBN} requires various tools and packages to be available.
32710 Other packages will be used only if they are found.
32712 @heading Tools/Packages Necessary for Building @value{GDBN}
32714 @item ISO C90 compiler
32715 @value{GDBN} is written in ISO C90. It should be buildable with any
32716 working C90 compiler, e.g.@: GCC.
32720 @heading Tools/Packages Optional for Building @value{GDBN}
32724 @value{GDBN} can use the Expat XML parsing library. This library may be
32725 included with your operating system distribution; if it is not, you
32726 can get the latest version from @url{http://expat.sourceforge.net}.
32727 The @file{configure} script will search for this library in several
32728 standard locations; if it is installed in an unusual path, you can
32729 use the @option{--with-libexpat-prefix} option to specify its location.
32735 Remote protocol memory maps (@pxref{Memory Map Format})
32737 Target descriptions (@pxref{Target Descriptions})
32739 Remote shared library lists (@xref{Library List Format},
32740 or alternatively @pxref{Library List Format for SVR4 Targets})
32742 MS-Windows shared libraries (@pxref{Shared Libraries})
32744 Traceframe info (@pxref{Traceframe Info Format})
32748 @cindex compressed debug sections
32749 @value{GDBN} will use the @samp{zlib} library, if available, to read
32750 compressed debug sections. Some linkers, such as GNU gold, are capable
32751 of producing binaries with compressed debug sections. If @value{GDBN}
32752 is compiled with @samp{zlib}, it will be able to read the debug
32753 information in such binaries.
32755 The @samp{zlib} library is likely included with your operating system
32756 distribution; if it is not, you can get the latest version from
32757 @url{http://zlib.net}.
32760 @value{GDBN}'s features related to character sets (@pxref{Character
32761 Sets}) require a functioning @code{iconv} implementation. If you are
32762 on a GNU system, then this is provided by the GNU C Library. Some
32763 other systems also provide a working @code{iconv}.
32765 If @value{GDBN} is using the @code{iconv} program which is installed
32766 in a non-standard place, you will need to tell @value{GDBN} where to find it.
32767 This is done with @option{--with-iconv-bin} which specifies the
32768 directory that contains the @code{iconv} program.
32770 On systems without @code{iconv}, you can install GNU Libiconv. If you
32771 have previously installed Libiconv, you can use the
32772 @option{--with-libiconv-prefix} option to configure.
32774 @value{GDBN}'s top-level @file{configure} and @file{Makefile} will
32775 arrange to build Libiconv if a directory named @file{libiconv} appears
32776 in the top-most source directory. If Libiconv is built this way, and
32777 if the operating system does not provide a suitable @code{iconv}
32778 implementation, then the just-built library will automatically be used
32779 by @value{GDBN}. One easy way to set this up is to download GNU
32780 Libiconv, unpack it, and then rename the directory holding the
32781 Libiconv source code to @samp{libiconv}.
32784 @node Running Configure
32785 @section Invoking the @value{GDBN} @file{configure} Script
32786 @cindex configuring @value{GDBN}
32787 @value{GDBN} comes with a @file{configure} script that automates the process
32788 of preparing @value{GDBN} for installation; you can then use @code{make} to
32789 build the @code{gdb} program.
32791 @c irrelevant in info file; it's as current as the code it lives with.
32792 @footnote{If you have a more recent version of @value{GDBN} than @value{GDBVN},
32793 look at the @file{README} file in the sources; we may have improved the
32794 installation procedures since publishing this manual.}
32797 The @value{GDBN} distribution includes all the source code you need for
32798 @value{GDBN} in a single directory, whose name is usually composed by
32799 appending the version number to @samp{gdb}.
32801 For example, the @value{GDBN} version @value{GDBVN} distribution is in the
32802 @file{gdb-@value{GDBVN}} directory. That directory contains:
32805 @item gdb-@value{GDBVN}/configure @r{(and supporting files)}
32806 script for configuring @value{GDBN} and all its supporting libraries
32808 @item gdb-@value{GDBVN}/gdb
32809 the source specific to @value{GDBN} itself
32811 @item gdb-@value{GDBVN}/bfd
32812 source for the Binary File Descriptor library
32814 @item gdb-@value{GDBVN}/include
32815 @sc{gnu} include files
32817 @item gdb-@value{GDBVN}/libiberty
32818 source for the @samp{-liberty} free software library
32820 @item gdb-@value{GDBVN}/opcodes
32821 source for the library of opcode tables and disassemblers
32823 @item gdb-@value{GDBVN}/readline
32824 source for the @sc{gnu} command-line interface
32826 @item gdb-@value{GDBVN}/glob
32827 source for the @sc{gnu} filename pattern-matching subroutine
32829 @item gdb-@value{GDBVN}/mmalloc
32830 source for the @sc{gnu} memory-mapped malloc package
32833 The simplest way to configure and build @value{GDBN} is to run @file{configure}
32834 from the @file{gdb-@var{version-number}} source directory, which in
32835 this example is the @file{gdb-@value{GDBVN}} directory.
32837 First switch to the @file{gdb-@var{version-number}} source directory
32838 if you are not already in it; then run @file{configure}. Pass the
32839 identifier for the platform on which @value{GDBN} will run as an
32845 cd gdb-@value{GDBVN}
32846 ./configure @var{host}
32851 where @var{host} is an identifier such as @samp{sun4} or
32852 @samp{decstation}, that identifies the platform where @value{GDBN} will run.
32853 (You can often leave off @var{host}; @file{configure} tries to guess the
32854 correct value by examining your system.)
32856 Running @samp{configure @var{host}} and then running @code{make} builds the
32857 @file{bfd}, @file{readline}, @file{mmalloc}, and @file{libiberty}
32858 libraries, then @code{gdb} itself. The configured source files, and the
32859 binaries, are left in the corresponding source directories.
32862 @file{configure} is a Bourne-shell (@code{/bin/sh}) script; if your
32863 system does not recognize this automatically when you run a different
32864 shell, you may need to run @code{sh} on it explicitly:
32867 sh configure @var{host}
32870 If you run @file{configure} from a directory that contains source
32871 directories for multiple libraries or programs, such as the
32872 @file{gdb-@value{GDBVN}} source directory for version @value{GDBVN},
32874 creates configuration files for every directory level underneath (unless
32875 you tell it not to, with the @samp{--norecursion} option).
32877 You should run the @file{configure} script from the top directory in the
32878 source tree, the @file{gdb-@var{version-number}} directory. If you run
32879 @file{configure} from one of the subdirectories, you will configure only
32880 that subdirectory. That is usually not what you want. In particular,
32881 if you run the first @file{configure} from the @file{gdb} subdirectory
32882 of the @file{gdb-@var{version-number}} directory, you will omit the
32883 configuration of @file{bfd}, @file{readline}, and other sibling
32884 directories of the @file{gdb} subdirectory. This leads to build errors
32885 about missing include files such as @file{bfd/bfd.h}.
32887 You can install @code{@value{GDBP}} anywhere; it has no hardwired paths.
32888 However, you should make sure that the shell on your path (named by
32889 the @samp{SHELL} environment variable) is publicly readable. Remember
32890 that @value{GDBN} uses the shell to start your program---some systems refuse to
32891 let @value{GDBN} debug child processes whose programs are not readable.
32893 @node Separate Objdir
32894 @section Compiling @value{GDBN} in Another Directory
32896 If you want to run @value{GDBN} versions for several host or target machines,
32897 you need a different @code{gdb} compiled for each combination of
32898 host and target. @file{configure} is designed to make this easy by
32899 allowing you to generate each configuration in a separate subdirectory,
32900 rather than in the source directory. If your @code{make} program
32901 handles the @samp{VPATH} feature (@sc{gnu} @code{make} does), running
32902 @code{make} in each of these directories builds the @code{gdb}
32903 program specified there.
32905 To build @code{gdb} in a separate directory, run @file{configure}
32906 with the @samp{--srcdir} option to specify where to find the source.
32907 (You also need to specify a path to find @file{configure}
32908 itself from your working directory. If the path to @file{configure}
32909 would be the same as the argument to @samp{--srcdir}, you can leave out
32910 the @samp{--srcdir} option; it is assumed.)
32912 For example, with version @value{GDBVN}, you can build @value{GDBN} in a
32913 separate directory for a Sun 4 like this:
32917 cd gdb-@value{GDBVN}
32920 ../gdb-@value{GDBVN}/configure sun4
32925 When @file{configure} builds a configuration using a remote source
32926 directory, it creates a tree for the binaries with the same structure
32927 (and using the same names) as the tree under the source directory. In
32928 the example, you'd find the Sun 4 library @file{libiberty.a} in the
32929 directory @file{gdb-sun4/libiberty}, and @value{GDBN} itself in
32930 @file{gdb-sun4/gdb}.
32932 Make sure that your path to the @file{configure} script has just one
32933 instance of @file{gdb} in it. If your path to @file{configure} looks
32934 like @file{../gdb-@value{GDBVN}/gdb/configure}, you are configuring only
32935 one subdirectory of @value{GDBN}, not the whole package. This leads to
32936 build errors about missing include files such as @file{bfd/bfd.h}.
32938 One popular reason to build several @value{GDBN} configurations in separate
32939 directories is to configure @value{GDBN} for cross-compiling (where
32940 @value{GDBN} runs on one machine---the @dfn{host}---while debugging
32941 programs that run on another machine---the @dfn{target}).
32942 You specify a cross-debugging target by
32943 giving the @samp{--target=@var{target}} option to @file{configure}.
32945 When you run @code{make} to build a program or library, you must run
32946 it in a configured directory---whatever directory you were in when you
32947 called @file{configure} (or one of its subdirectories).
32949 The @code{Makefile} that @file{configure} generates in each source
32950 directory also runs recursively. If you type @code{make} in a source
32951 directory such as @file{gdb-@value{GDBVN}} (or in a separate configured
32952 directory configured with @samp{--srcdir=@var{dirname}/gdb-@value{GDBVN}}), you
32953 will build all the required libraries, and then build GDB.
32955 When you have multiple hosts or targets configured in separate
32956 directories, you can run @code{make} on them in parallel (for example,
32957 if they are NFS-mounted on each of the hosts); they will not interfere
32961 @section Specifying Names for Hosts and Targets
32963 The specifications used for hosts and targets in the @file{configure}
32964 script are based on a three-part naming scheme, but some short predefined
32965 aliases are also supported. The full naming scheme encodes three pieces
32966 of information in the following pattern:
32969 @var{architecture}-@var{vendor}-@var{os}
32972 For example, you can use the alias @code{sun4} as a @var{host} argument,
32973 or as the value for @var{target} in a @code{--target=@var{target}}
32974 option. The equivalent full name is @samp{sparc-sun-sunos4}.
32976 The @file{configure} script accompanying @value{GDBN} does not provide
32977 any query facility to list all supported host and target names or
32978 aliases. @file{configure} calls the Bourne shell script
32979 @code{config.sub} to map abbreviations to full names; you can read the
32980 script, if you wish, or you can use it to test your guesses on
32981 abbreviations---for example:
32984 % sh config.sub i386-linux
32986 % sh config.sub alpha-linux
32987 alpha-unknown-linux-gnu
32988 % sh config.sub hp9k700
32990 % sh config.sub sun4
32991 sparc-sun-sunos4.1.1
32992 % sh config.sub sun3
32993 m68k-sun-sunos4.1.1
32994 % sh config.sub i986v
32995 Invalid configuration `i986v': machine `i986v' not recognized
32999 @code{config.sub} is also distributed in the @value{GDBN} source
33000 directory (@file{gdb-@value{GDBVN}}, for version @value{GDBVN}).
33002 @node Configure Options
33003 @section @file{configure} Options
33005 Here is a summary of the @file{configure} options and arguments that
33006 are most often useful for building @value{GDBN}. @file{configure} also has
33007 several other options not listed here. @inforef{What Configure
33008 Does,,configure.info}, for a full explanation of @file{configure}.
33011 configure @r{[}--help@r{]}
33012 @r{[}--prefix=@var{dir}@r{]}
33013 @r{[}--exec-prefix=@var{dir}@r{]}
33014 @r{[}--srcdir=@var{dirname}@r{]}
33015 @r{[}--norecursion@r{]} @r{[}--rm@r{]}
33016 @r{[}--target=@var{target}@r{]}
33021 You may introduce options with a single @samp{-} rather than
33022 @samp{--} if you prefer; but you may abbreviate option names if you use
33027 Display a quick summary of how to invoke @file{configure}.
33029 @item --prefix=@var{dir}
33030 Configure the source to install programs and files under directory
33033 @item --exec-prefix=@var{dir}
33034 Configure the source to install programs under directory
33037 @c avoid splitting the warning from the explanation:
33039 @item --srcdir=@var{dirname}
33040 @strong{Warning: using this option requires @sc{gnu} @code{make}, or another
33041 @code{make} that implements the @code{VPATH} feature.}@*
33042 Use this option to make configurations in directories separate from the
33043 @value{GDBN} source directories. Among other things, you can use this to
33044 build (or maintain) several configurations simultaneously, in separate
33045 directories. @file{configure} writes configuration-specific files in
33046 the current directory, but arranges for them to use the source in the
33047 directory @var{dirname}. @file{configure} creates directories under
33048 the working directory in parallel to the source directories below
33051 @item --norecursion
33052 Configure only the directory level where @file{configure} is executed; do not
33053 propagate configuration to subdirectories.
33055 @item --target=@var{target}
33056 Configure @value{GDBN} for cross-debugging programs running on the specified
33057 @var{target}. Without this option, @value{GDBN} is configured to debug
33058 programs that run on the same machine (@var{host}) as @value{GDBN} itself.
33060 There is no convenient way to generate a list of all available targets.
33062 @item @var{host} @dots{}
33063 Configure @value{GDBN} to run on the specified @var{host}.
33065 There is no convenient way to generate a list of all available hosts.
33068 There are many other options available as well, but they are generally
33069 needed for special purposes only.
33071 @node System-wide configuration
33072 @section System-wide configuration and settings
33073 @cindex system-wide init file
33075 @value{GDBN} can be configured to have a system-wide init file;
33076 this file will be read and executed at startup (@pxref{Startup, , What
33077 @value{GDBN} does during startup}).
33079 Here is the corresponding configure option:
33082 @item --with-system-gdbinit=@var{file}
33083 Specify that the default location of the system-wide init file is
33087 If @value{GDBN} has been configured with the option @option{--prefix=$prefix},
33088 it may be subject to relocation. Two possible cases:
33092 If the default location of this init file contains @file{$prefix},
33093 it will be subject to relocation. Suppose that the configure options
33094 are @option{--prefix=$prefix --with-system-gdbinit=$prefix/etc/gdbinit};
33095 if @value{GDBN} is moved from @file{$prefix} to @file{$install}, the system
33096 init file is looked for as @file{$install/etc/gdbinit} instead of
33097 @file{$prefix/etc/gdbinit}.
33100 By contrast, if the default location does not contain the prefix,
33101 it will not be relocated. E.g.@: if @value{GDBN} has been configured with
33102 @option{--prefix=/usr/local --with-system-gdbinit=/usr/share/gdb/gdbinit},
33103 then @value{GDBN} will always look for @file{/usr/share/gdb/gdbinit},
33104 wherever @value{GDBN} is installed.
33107 @node Maintenance Commands
33108 @appendix Maintenance Commands
33109 @cindex maintenance commands
33110 @cindex internal commands
33112 In addition to commands intended for @value{GDBN} users, @value{GDBN}
33113 includes a number of commands intended for @value{GDBN} developers,
33114 that are not documented elsewhere in this manual. These commands are
33115 provided here for reference. (For commands that turn on debugging
33116 messages, see @ref{Debugging Output}.)
33119 @kindex maint agent
33120 @kindex maint agent-eval
33121 @item maint agent @var{expression}
33122 @itemx maint agent-eval @var{expression}
33123 Translate the given @var{expression} into remote agent bytecodes.
33124 This command is useful for debugging the Agent Expression mechanism
33125 (@pxref{Agent Expressions}). The @samp{agent} version produces an
33126 expression useful for data collection, such as by tracepoints, while
33127 @samp{maint agent-eval} produces an expression that evaluates directly
33128 to a result. For instance, a collection expression for @code{globa +
33129 globb} will include bytecodes to record four bytes of memory at each
33130 of the addresses of @code{globa} and @code{globb}, while discarding
33131 the result of the addition, while an evaluation expression will do the
33132 addition and return the sum.
33134 @kindex maint info breakpoints
33135 @item @anchor{maint info breakpoints}maint info breakpoints
33136 Using the same format as @samp{info breakpoints}, display both the
33137 breakpoints you've set explicitly, and those @value{GDBN} is using for
33138 internal purposes. Internal breakpoints are shown with negative
33139 breakpoint numbers. The type column identifies what kind of breakpoint
33144 Normal, explicitly set breakpoint.
33147 Normal, explicitly set watchpoint.
33150 Internal breakpoint, used to handle correctly stepping through
33151 @code{longjmp} calls.
33153 @item longjmp resume
33154 Internal breakpoint at the target of a @code{longjmp}.
33157 Temporary internal breakpoint used by the @value{GDBN} @code{until} command.
33160 Temporary internal breakpoint used by the @value{GDBN} @code{finish} command.
33163 Shared library events.
33167 @kindex set displaced-stepping
33168 @kindex show displaced-stepping
33169 @cindex displaced stepping support
33170 @cindex out-of-line single-stepping
33171 @item set displaced-stepping
33172 @itemx show displaced-stepping
33173 Control whether or not @value{GDBN} will do @dfn{displaced stepping}
33174 if the target supports it. Displaced stepping is a way to single-step
33175 over breakpoints without removing them from the inferior, by executing
33176 an out-of-line copy of the instruction that was originally at the
33177 breakpoint location. It is also known as out-of-line single-stepping.
33180 @item set displaced-stepping on
33181 If the target architecture supports it, @value{GDBN} will use
33182 displaced stepping to step over breakpoints.
33184 @item set displaced-stepping off
33185 @value{GDBN} will not use displaced stepping to step over breakpoints,
33186 even if such is supported by the target architecture.
33188 @cindex non-stop mode, and @samp{set displaced-stepping}
33189 @item set displaced-stepping auto
33190 This is the default mode. @value{GDBN} will use displaced stepping
33191 only if non-stop mode is active (@pxref{Non-Stop Mode}) and the target
33192 architecture supports displaced stepping.
33195 @kindex maint check-symtabs
33196 @item maint check-symtabs
33197 Check the consistency of psymtabs and symtabs.
33199 @kindex maint cplus first_component
33200 @item maint cplus first_component @var{name}
33201 Print the first C@t{++} class/namespace component of @var{name}.
33203 @kindex maint cplus namespace
33204 @item maint cplus namespace
33205 Print the list of possible C@t{++} namespaces.
33207 @kindex maint demangle
33208 @item maint demangle @var{name}
33209 Demangle a C@t{++} or Objective-C mangled @var{name}.
33211 @kindex maint deprecate
33212 @kindex maint undeprecate
33213 @cindex deprecated commands
33214 @item maint deprecate @var{command} @r{[}@var{replacement}@r{]}
33215 @itemx maint undeprecate @var{command}
33216 Deprecate or undeprecate the named @var{command}. Deprecated commands
33217 cause @value{GDBN} to issue a warning when you use them. The optional
33218 argument @var{replacement} says which newer command should be used in
33219 favor of the deprecated one; if it is given, @value{GDBN} will mention
33220 the replacement as part of the warning.
33222 @kindex maint dump-me
33223 @item maint dump-me
33224 @cindex @code{SIGQUIT} signal, dump core of @value{GDBN}
33225 Cause a fatal signal in the debugger and force it to dump its core.
33226 This is supported only on systems which support aborting a program
33227 with the @code{SIGQUIT} signal.
33229 @kindex maint internal-error
33230 @kindex maint internal-warning
33231 @item maint internal-error @r{[}@var{message-text}@r{]}
33232 @itemx maint internal-warning @r{[}@var{message-text}@r{]}
33233 Cause @value{GDBN} to call the internal function @code{internal_error}
33234 or @code{internal_warning} and hence behave as though an internal error
33235 or internal warning has been detected. In addition to reporting the
33236 internal problem, these functions give the user the opportunity to
33237 either quit @value{GDBN} or create a core file of the current
33238 @value{GDBN} session.
33240 These commands take an optional parameter @var{message-text} that is
33241 used as the text of the error or warning message.
33243 Here's an example of using @code{internal-error}:
33246 (@value{GDBP}) @kbd{maint internal-error testing, 1, 2}
33247 @dots{}/maint.c:121: internal-error: testing, 1, 2
33248 A problem internal to GDB has been detected. Further
33249 debugging may prove unreliable.
33250 Quit this debugging session? (y or n) @kbd{n}
33251 Create a core file? (y or n) @kbd{n}
33255 @cindex @value{GDBN} internal error
33256 @cindex internal errors, control of @value{GDBN} behavior
33258 @kindex maint set internal-error
33259 @kindex maint show internal-error
33260 @kindex maint set internal-warning
33261 @kindex maint show internal-warning
33262 @item maint set internal-error @var{action} [ask|yes|no]
33263 @itemx maint show internal-error @var{action}
33264 @itemx maint set internal-warning @var{action} [ask|yes|no]
33265 @itemx maint show internal-warning @var{action}
33266 When @value{GDBN} reports an internal problem (error or warning) it
33267 gives the user the opportunity to both quit @value{GDBN} and create a
33268 core file of the current @value{GDBN} session. These commands let you
33269 override the default behaviour for each particular @var{action},
33270 described in the table below.
33274 You can specify that @value{GDBN} should always (yes) or never (no)
33275 quit. The default is to ask the user what to do.
33278 You can specify that @value{GDBN} should always (yes) or never (no)
33279 create a core file. The default is to ask the user what to do.
33282 @kindex maint packet
33283 @item maint packet @var{text}
33284 If @value{GDBN} is talking to an inferior via the serial protocol,
33285 then this command sends the string @var{text} to the inferior, and
33286 displays the response packet. @value{GDBN} supplies the initial
33287 @samp{$} character, the terminating @samp{#} character, and the
33290 @kindex maint print architecture
33291 @item maint print architecture @r{[}@var{file}@r{]}
33292 Print the entire architecture configuration. The optional argument
33293 @var{file} names the file where the output goes.
33295 @kindex maint print c-tdesc
33296 @item maint print c-tdesc
33297 Print the current target description (@pxref{Target Descriptions}) as
33298 a C source file. The created source file can be used in @value{GDBN}
33299 when an XML parser is not available to parse the description.
33301 @kindex maint print dummy-frames
33302 @item maint print dummy-frames
33303 Prints the contents of @value{GDBN}'s internal dummy-frame stack.
33306 (@value{GDBP}) @kbd{b add}
33308 (@value{GDBP}) @kbd{print add(2,3)}
33309 Breakpoint 2, add (a=2, b=3) at @dots{}
33311 The program being debugged stopped while in a function called from GDB.
33313 (@value{GDBP}) @kbd{maint print dummy-frames}
33314 0x1a57c80: pc=0x01014068 fp=0x0200bddc sp=0x0200bdd6
33315 top=0x0200bdd4 id=@{stack=0x200bddc,code=0x101405c@}
33316 call_lo=0x01014000 call_hi=0x01014001
33320 Takes an optional file parameter.
33322 @kindex maint print registers
33323 @kindex maint print raw-registers
33324 @kindex maint print cooked-registers
33325 @kindex maint print register-groups
33326 @kindex maint print remote-registers
33327 @item maint print registers @r{[}@var{file}@r{]}
33328 @itemx maint print raw-registers @r{[}@var{file}@r{]}
33329 @itemx maint print cooked-registers @r{[}@var{file}@r{]}
33330 @itemx maint print register-groups @r{[}@var{file}@r{]}
33331 @itemx maint print remote-registers @r{[}@var{file}@r{]}
33332 Print @value{GDBN}'s internal register data structures.
33334 The command @code{maint print raw-registers} includes the contents of
33335 the raw register cache; the command @code{maint print
33336 cooked-registers} includes the (cooked) value of all registers,
33337 including registers which aren't available on the target nor visible
33338 to user; the command @code{maint print register-groups} includes the
33339 groups that each register is a member of; and the command @code{maint
33340 print remote-registers} includes the remote target's register numbers
33341 and offsets in the `G' packets. @xref{Registers,, Registers, gdbint,
33342 @value{GDBN} Internals}.
33344 These commands take an optional parameter, a file name to which to
33345 write the information.
33347 @kindex maint print reggroups
33348 @item maint print reggroups @r{[}@var{file}@r{]}
33349 Print @value{GDBN}'s internal register group data structures. The
33350 optional argument @var{file} tells to what file to write the
33353 The register groups info looks like this:
33356 (@value{GDBP}) @kbd{maint print reggroups}
33369 This command forces @value{GDBN} to flush its internal register cache.
33371 @kindex maint print objfiles
33372 @cindex info for known object files
33373 @item maint print objfiles
33374 Print a dump of all known object files. For each object file, this
33375 command prints its name, address in memory, and all of its psymtabs
33378 @kindex maint print section-scripts
33379 @cindex info for known .debug_gdb_scripts-loaded scripts
33380 @item maint print section-scripts [@var{regexp}]
33381 Print a dump of scripts specified in the @code{.debug_gdb_section} section.
33382 If @var{regexp} is specified, only print scripts loaded by object files
33383 matching @var{regexp}.
33384 For each script, this command prints its name as specified in the objfile,
33385 and the full path if known.
33386 @xref{.debug_gdb_scripts section}.
33388 @kindex maint print statistics
33389 @cindex bcache statistics
33390 @item maint print statistics
33391 This command prints, for each object file in the program, various data
33392 about that object file followed by the byte cache (@dfn{bcache})
33393 statistics for the object file. The objfile data includes the number
33394 of minimal, partial, full, and stabs symbols, the number of types
33395 defined by the objfile, the number of as yet unexpanded psym tables,
33396 the number of line tables and string tables, and the amount of memory
33397 used by the various tables. The bcache statistics include the counts,
33398 sizes, and counts of duplicates of all and unique objects, max,
33399 average, and median entry size, total memory used and its overhead and
33400 savings, and various measures of the hash table size and chain
33403 @kindex maint print target-stack
33404 @cindex target stack description
33405 @item maint print target-stack
33406 A @dfn{target} is an interface between the debugger and a particular
33407 kind of file or process. Targets can be stacked in @dfn{strata},
33408 so that more than one target can potentially respond to a request.
33409 In particular, memory accesses will walk down the stack of targets
33410 until they find a target that is interested in handling that particular
33413 This command prints a short description of each layer that was pushed on
33414 the @dfn{target stack}, starting from the top layer down to the bottom one.
33416 @kindex maint print type
33417 @cindex type chain of a data type
33418 @item maint print type @var{expr}
33419 Print the type chain for a type specified by @var{expr}. The argument
33420 can be either a type name or a symbol. If it is a symbol, the type of
33421 that symbol is described. The type chain produced by this command is
33422 a recursive definition of the data type as stored in @value{GDBN}'s
33423 data structures, including its flags and contained types.
33425 @kindex maint set dwarf2 always-disassemble
33426 @kindex maint show dwarf2 always-disassemble
33427 @item maint set dwarf2 always-disassemble
33428 @item maint show dwarf2 always-disassemble
33429 Control the behavior of @code{info address} when using DWARF debugging
33432 The default is @code{off}, which means that @value{GDBN} should try to
33433 describe a variable's location in an easily readable format. When
33434 @code{on}, @value{GDBN} will instead display the DWARF location
33435 expression in an assembly-like format. Note that some locations are
33436 too complex for @value{GDBN} to describe simply; in this case you will
33437 always see the disassembly form.
33439 Here is an example of the resulting disassembly:
33442 (gdb) info addr argc
33443 Symbol "argc" is a complex DWARF expression:
33447 For more information on these expressions, see
33448 @uref{http://www.dwarfstd.org/, the DWARF standard}.
33450 @kindex maint set dwarf2 max-cache-age
33451 @kindex maint show dwarf2 max-cache-age
33452 @item maint set dwarf2 max-cache-age
33453 @itemx maint show dwarf2 max-cache-age
33454 Control the DWARF 2 compilation unit cache.
33456 @cindex DWARF 2 compilation units cache
33457 In object files with inter-compilation-unit references, such as those
33458 produced by the GCC option @samp{-feliminate-dwarf2-dups}, the DWARF 2
33459 reader needs to frequently refer to previously read compilation units.
33460 This setting controls how long a compilation unit will remain in the
33461 cache if it is not referenced. A higher limit means that cached
33462 compilation units will be stored in memory longer, and more total
33463 memory will be used. Setting it to zero disables caching, which will
33464 slow down @value{GDBN} startup, but reduce memory consumption.
33466 @kindex maint set profile
33467 @kindex maint show profile
33468 @cindex profiling GDB
33469 @item maint set profile
33470 @itemx maint show profile
33471 Control profiling of @value{GDBN}.
33473 Profiling will be disabled until you use the @samp{maint set profile}
33474 command to enable it. When you enable profiling, the system will begin
33475 collecting timing and execution count data; when you disable profiling or
33476 exit @value{GDBN}, the results will be written to a log file. Remember that
33477 if you use profiling, @value{GDBN} will overwrite the profiling log file
33478 (often called @file{gmon.out}). If you have a record of important profiling
33479 data in a @file{gmon.out} file, be sure to move it to a safe location.
33481 Configuring with @samp{--enable-profiling} arranges for @value{GDBN} to be
33482 compiled with the @samp{-pg} compiler option.
33484 @kindex maint set show-debug-regs
33485 @kindex maint show show-debug-regs
33486 @cindex hardware debug registers
33487 @item maint set show-debug-regs
33488 @itemx maint show show-debug-regs
33489 Control whether to show variables that mirror the hardware debug
33490 registers. Use @code{ON} to enable, @code{OFF} to disable. If
33491 enabled, the debug registers values are shown when @value{GDBN} inserts or
33492 removes a hardware breakpoint or watchpoint, and when the inferior
33493 triggers a hardware-assisted breakpoint or watchpoint.
33495 @kindex maint set show-all-tib
33496 @kindex maint show show-all-tib
33497 @item maint set show-all-tib
33498 @itemx maint show show-all-tib
33499 Control whether to show all non zero areas within a 1k block starting
33500 at thread local base, when using the @samp{info w32 thread-information-block}
33503 @kindex maint space
33504 @cindex memory used by commands
33506 Control whether to display memory usage for each command. If set to a
33507 nonzero value, @value{GDBN} will display how much memory each command
33508 took, following the command's own output. This can also be requested
33509 by invoking @value{GDBN} with the @option{--statistics} command-line
33510 switch (@pxref{Mode Options}).
33513 @cindex time of command execution
33515 Control whether to display the execution time of @value{GDBN} for each command.
33516 If set to a nonzero value, @value{GDBN} will display how much time it
33517 took to execute each command, following the command's own output.
33518 Both CPU time and wallclock time are printed.
33519 Printing both is useful when trying to determine whether the cost is
33520 CPU or, e.g., disk/network, latency.
33521 Note that the CPU time printed is for @value{GDBN} only, it does not include
33522 the execution time of the inferior because there's no mechanism currently
33523 to compute how much time was spent by @value{GDBN} and how much time was
33524 spent by the program been debugged.
33525 This can also be requested by invoking @value{GDBN} with the
33526 @option{--statistics} command-line switch (@pxref{Mode Options}).
33528 @kindex maint translate-address
33529 @item maint translate-address @r{[}@var{section}@r{]} @var{addr}
33530 Find the symbol stored at the location specified by the address
33531 @var{addr} and an optional section name @var{section}. If found,
33532 @value{GDBN} prints the name of the closest symbol and an offset from
33533 the symbol's location to the specified address. This is similar to
33534 the @code{info address} command (@pxref{Symbols}), except that this
33535 command also allows to find symbols in other sections.
33537 If section was not specified, the section in which the symbol was found
33538 is also printed. For dynamically linked executables, the name of
33539 executable or shared library containing the symbol is printed as well.
33543 The following command is useful for non-interactive invocations of
33544 @value{GDBN}, such as in the test suite.
33547 @item set watchdog @var{nsec}
33548 @kindex set watchdog
33549 @cindex watchdog timer
33550 @cindex timeout for commands
33551 Set the maximum number of seconds @value{GDBN} will wait for the
33552 target operation to finish. If this time expires, @value{GDBN}
33553 reports and error and the command is aborted.
33555 @item show watchdog
33556 Show the current setting of the target wait timeout.
33559 @node Remote Protocol
33560 @appendix @value{GDBN} Remote Serial Protocol
33565 * Stop Reply Packets::
33566 * General Query Packets::
33567 * Architecture-Specific Protocol Details::
33568 * Tracepoint Packets::
33569 * Host I/O Packets::
33571 * Notification Packets::
33572 * Remote Non-Stop::
33573 * Packet Acknowledgment::
33575 * File-I/O Remote Protocol Extension::
33576 * Library List Format::
33577 * Library List Format for SVR4 Targets::
33578 * Memory Map Format::
33579 * Thread List Format::
33580 * Traceframe Info Format::
33586 There may be occasions when you need to know something about the
33587 protocol---for example, if there is only one serial port to your target
33588 machine, you might want your program to do something special if it
33589 recognizes a packet meant for @value{GDBN}.
33591 In the examples below, @samp{->} and @samp{<-} are used to indicate
33592 transmitted and received data, respectively.
33594 @cindex protocol, @value{GDBN} remote serial
33595 @cindex serial protocol, @value{GDBN} remote
33596 @cindex remote serial protocol
33597 All @value{GDBN} commands and responses (other than acknowledgments
33598 and notifications, see @ref{Notification Packets}) are sent as a
33599 @var{packet}. A @var{packet} is introduced with the character
33600 @samp{$}, the actual @var{packet-data}, and the terminating character
33601 @samp{#} followed by a two-digit @var{checksum}:
33604 @code{$}@var{packet-data}@code{#}@var{checksum}
33608 @cindex checksum, for @value{GDBN} remote
33610 The two-digit @var{checksum} is computed as the modulo 256 sum of all
33611 characters between the leading @samp{$} and the trailing @samp{#} (an
33612 eight bit unsigned checksum).
33614 Implementors should note that prior to @value{GDBN} 5.0 the protocol
33615 specification also included an optional two-digit @var{sequence-id}:
33618 @code{$}@var{sequence-id}@code{:}@var{packet-data}@code{#}@var{checksum}
33621 @cindex sequence-id, for @value{GDBN} remote
33623 That @var{sequence-id} was appended to the acknowledgment. @value{GDBN}
33624 has never output @var{sequence-id}s. Stubs that handle packets added
33625 since @value{GDBN} 5.0 must not accept @var{sequence-id}.
33627 When either the host or the target machine receives a packet, the first
33628 response expected is an acknowledgment: either @samp{+} (to indicate
33629 the package was received correctly) or @samp{-} (to request
33633 -> @code{$}@var{packet-data}@code{#}@var{checksum}
33638 The @samp{+}/@samp{-} acknowledgments can be disabled
33639 once a connection is established.
33640 @xref{Packet Acknowledgment}, for details.
33642 The host (@value{GDBN}) sends @var{command}s, and the target (the
33643 debugging stub incorporated in your program) sends a @var{response}. In
33644 the case of step and continue @var{command}s, the response is only sent
33645 when the operation has completed, and the target has again stopped all
33646 threads in all attached processes. This is the default all-stop mode
33647 behavior, but the remote protocol also supports @value{GDBN}'s non-stop
33648 execution mode; see @ref{Remote Non-Stop}, for details.
33650 @var{packet-data} consists of a sequence of characters with the
33651 exception of @samp{#} and @samp{$} (see @samp{X} packet for additional
33654 @cindex remote protocol, field separator
33655 Fields within the packet should be separated using @samp{,} @samp{;} or
33656 @samp{:}. Except where otherwise noted all numbers are represented in
33657 @sc{hex} with leading zeros suppressed.
33659 Implementors should note that prior to @value{GDBN} 5.0, the character
33660 @samp{:} could not appear as the third character in a packet (as it
33661 would potentially conflict with the @var{sequence-id}).
33663 @cindex remote protocol, binary data
33664 @anchor{Binary Data}
33665 Binary data in most packets is encoded either as two hexadecimal
33666 digits per byte of binary data. This allowed the traditional remote
33667 protocol to work over connections which were only seven-bit clean.
33668 Some packets designed more recently assume an eight-bit clean
33669 connection, and use a more efficient encoding to send and receive
33672 The binary data representation uses @code{7d} (@sc{ascii} @samp{@}})
33673 as an escape character. Any escaped byte is transmitted as the escape
33674 character followed by the original character XORed with @code{0x20}.
33675 For example, the byte @code{0x7d} would be transmitted as the two
33676 bytes @code{0x7d 0x5d}. The bytes @code{0x23} (@sc{ascii} @samp{#}),
33677 @code{0x24} (@sc{ascii} @samp{$}), and @code{0x7d} (@sc{ascii}
33678 @samp{@}}) must always be escaped. Responses sent by the stub
33679 must also escape @code{0x2a} (@sc{ascii} @samp{*}), so that it
33680 is not interpreted as the start of a run-length encoded sequence
33683 Response @var{data} can be run-length encoded to save space.
33684 Run-length encoding replaces runs of identical characters with one
33685 instance of the repeated character, followed by a @samp{*} and a
33686 repeat count. The repeat count is itself sent encoded, to avoid
33687 binary characters in @var{data}: a value of @var{n} is sent as
33688 @code{@var{n}+29}. For a repeat count greater or equal to 3, this
33689 produces a printable @sc{ascii} character, e.g.@: a space (@sc{ascii}
33690 code 32) for a repeat count of 3. (This is because run-length
33691 encoding starts to win for counts 3 or more.) Thus, for example,
33692 @samp{0* } is a run-length encoding of ``0000'': the space character
33693 after @samp{*} means repeat the leading @code{0} @w{@code{32 - 29 =
33696 The printable characters @samp{#} and @samp{$} or with a numeric value
33697 greater than 126 must not be used. Runs of six repeats (@samp{#}) or
33698 seven repeats (@samp{$}) can be expanded using a repeat count of only
33699 five (@samp{"}). For example, @samp{00000000} can be encoded as
33702 The error response returned for some packets includes a two character
33703 error number. That number is not well defined.
33705 @cindex empty response, for unsupported packets
33706 For any @var{command} not supported by the stub, an empty response
33707 (@samp{$#00}) should be returned. That way it is possible to extend the
33708 protocol. A newer @value{GDBN} can tell if a packet is supported based
33711 At a minimum, a stub is required to support the @samp{g} and @samp{G}
33712 commands for register access, and the @samp{m} and @samp{M} commands
33713 for memory access. Stubs that only control single-threaded targets
33714 can implement run control with the @samp{c} (continue), and @samp{s}
33715 (step) commands. Stubs that support multi-threading targets should
33716 support the @samp{vCont} command. All other commands are optional.
33721 The following table provides a complete list of all currently defined
33722 @var{command}s and their corresponding response @var{data}.
33723 @xref{File-I/O Remote Protocol Extension}, for details about the File
33724 I/O extension of the remote protocol.
33726 Each packet's description has a template showing the packet's overall
33727 syntax, followed by an explanation of the packet's meaning. We
33728 include spaces in some of the templates for clarity; these are not
33729 part of the packet's syntax. No @value{GDBN} packet uses spaces to
33730 separate its components. For example, a template like @samp{foo
33731 @var{bar} @var{baz}} describes a packet beginning with the three ASCII
33732 bytes @samp{foo}, followed by a @var{bar}, followed directly by a
33733 @var{baz}. @value{GDBN} does not transmit a space character between the
33734 @samp{foo} and the @var{bar}, or between the @var{bar} and the
33737 @cindex @var{thread-id}, in remote protocol
33738 @anchor{thread-id syntax}
33739 Several packets and replies include a @var{thread-id} field to identify
33740 a thread. Normally these are positive numbers with a target-specific
33741 interpretation, formatted as big-endian hex strings. A @var{thread-id}
33742 can also be a literal @samp{-1} to indicate all threads, or @samp{0} to
33745 In addition, the remote protocol supports a multiprocess feature in
33746 which the @var{thread-id} syntax is extended to optionally include both
33747 process and thread ID fields, as @samp{p@var{pid}.@var{tid}}.
33748 The @var{pid} (process) and @var{tid} (thread) components each have the
33749 format described above: a positive number with target-specific
33750 interpretation formatted as a big-endian hex string, literal @samp{-1}
33751 to indicate all processes or threads (respectively), or @samp{0} to
33752 indicate an arbitrary process or thread. Specifying just a process, as
33753 @samp{p@var{pid}}, is equivalent to @samp{p@var{pid}.-1}. It is an
33754 error to specify all processes but a specific thread, such as
33755 @samp{p-1.@var{tid}}. Note that the @samp{p} prefix is @emph{not} used
33756 for those packets and replies explicitly documented to include a process
33757 ID, rather than a @var{thread-id}.
33759 The multiprocess @var{thread-id} syntax extensions are only used if both
33760 @value{GDBN} and the stub report support for the @samp{multiprocess}
33761 feature using @samp{qSupported}. @xref{multiprocess extensions}, for
33764 Note that all packet forms beginning with an upper- or lower-case
33765 letter, other than those described here, are reserved for future use.
33767 Here are the packet descriptions.
33772 @cindex @samp{!} packet
33773 @anchor{extended mode}
33774 Enable extended mode. In extended mode, the remote server is made
33775 persistent. The @samp{R} packet is used to restart the program being
33781 The remote target both supports and has enabled extended mode.
33785 @cindex @samp{?} packet
33786 Indicate the reason the target halted. The reply is the same as for
33787 step and continue. This packet has a special interpretation when the
33788 target is in non-stop mode; see @ref{Remote Non-Stop}.
33791 @xref{Stop Reply Packets}, for the reply specifications.
33793 @item A @var{arglen},@var{argnum},@var{arg},@dots{}
33794 @cindex @samp{A} packet
33795 Initialized @code{argv[]} array passed into program. @var{arglen}
33796 specifies the number of bytes in the hex encoded byte stream
33797 @var{arg}. See @code{gdbserver} for more details.
33802 The arguments were set.
33808 @cindex @samp{b} packet
33809 (Don't use this packet; its behavior is not well-defined.)
33810 Change the serial line speed to @var{baud}.
33812 JTC: @emph{When does the transport layer state change? When it's
33813 received, or after the ACK is transmitted. In either case, there are
33814 problems if the command or the acknowledgment packet is dropped.}
33816 Stan: @emph{If people really wanted to add something like this, and get
33817 it working for the first time, they ought to modify ser-unix.c to send
33818 some kind of out-of-band message to a specially-setup stub and have the
33819 switch happen "in between" packets, so that from remote protocol's point
33820 of view, nothing actually happened.}
33822 @item B @var{addr},@var{mode}
33823 @cindex @samp{B} packet
33824 Set (@var{mode} is @samp{S}) or clear (@var{mode} is @samp{C}) a
33825 breakpoint at @var{addr}.
33827 Don't use this packet. Use the @samp{Z} and @samp{z} packets instead
33828 (@pxref{insert breakpoint or watchpoint packet}).
33830 @cindex @samp{bc} packet
33833 Backward continue. Execute the target system in reverse. No parameter.
33834 @xref{Reverse Execution}, for more information.
33837 @xref{Stop Reply Packets}, for the reply specifications.
33839 @cindex @samp{bs} packet
33842 Backward single step. Execute one instruction in reverse. No parameter.
33843 @xref{Reverse Execution}, for more information.
33846 @xref{Stop Reply Packets}, for the reply specifications.
33848 @item c @r{[}@var{addr}@r{]}
33849 @cindex @samp{c} packet
33850 Continue. @var{addr} is address to resume. If @var{addr} is omitted,
33851 resume at current address.
33853 This packet is deprecated for multi-threading support. @xref{vCont
33857 @xref{Stop Reply Packets}, for the reply specifications.
33859 @item C @var{sig}@r{[};@var{addr}@r{]}
33860 @cindex @samp{C} packet
33861 Continue with signal @var{sig} (hex signal number). If
33862 @samp{;@var{addr}} is omitted, resume at same address.
33864 This packet is deprecated for multi-threading support. @xref{vCont
33868 @xref{Stop Reply Packets}, for the reply specifications.
33871 @cindex @samp{d} packet
33874 Don't use this packet; instead, define a general set packet
33875 (@pxref{General Query Packets}).
33879 @cindex @samp{D} packet
33880 The first form of the packet is used to detach @value{GDBN} from the
33881 remote system. It is sent to the remote target
33882 before @value{GDBN} disconnects via the @code{detach} command.
33884 The second form, including a process ID, is used when multiprocess
33885 protocol extensions are enabled (@pxref{multiprocess extensions}), to
33886 detach only a specific process. The @var{pid} is specified as a
33887 big-endian hex string.
33897 @item F @var{RC},@var{EE},@var{CF};@var{XX}
33898 @cindex @samp{F} packet
33899 A reply from @value{GDBN} to an @samp{F} packet sent by the target.
33900 This is part of the File-I/O protocol extension. @xref{File-I/O
33901 Remote Protocol Extension}, for the specification.
33904 @anchor{read registers packet}
33905 @cindex @samp{g} packet
33906 Read general registers.
33910 @item @var{XX@dots{}}
33911 Each byte of register data is described by two hex digits. The bytes
33912 with the register are transmitted in target byte order. The size of
33913 each register and their position within the @samp{g} packet are
33914 determined by the @value{GDBN} internal gdbarch functions
33915 @code{DEPRECATED_REGISTER_RAW_SIZE} and @code{gdbarch_register_name}. The
33916 specification of several standard @samp{g} packets is specified below.
33918 When reading registers from a trace frame (@pxref{Analyze Collected
33919 Data,,Using the Collected Data}), the stub may also return a string of
33920 literal @samp{x}'s in place of the register data digits, to indicate
33921 that the corresponding register has not been collected, thus its value
33922 is unavailable. For example, for an architecture with 4 registers of
33923 4 bytes each, the following reply indicates to @value{GDBN} that
33924 registers 0 and 2 have not been collected, while registers 1 and 3
33925 have been collected, and both have zero value:
33929 <- @code{xxxxxxxx00000000xxxxxxxx00000000}
33936 @item G @var{XX@dots{}}
33937 @cindex @samp{G} packet
33938 Write general registers. @xref{read registers packet}, for a
33939 description of the @var{XX@dots{}} data.
33949 @item H @var{op} @var{thread-id}
33950 @cindex @samp{H} packet
33951 Set thread for subsequent operations (@samp{m}, @samp{M}, @samp{g},
33952 @samp{G}, et.al.). @var{op} depends on the operation to be performed:
33953 it should be @samp{c} for step and continue operations (note that this
33954 is deprecated, supporting the @samp{vCont} command is a better
33955 option), @samp{g} for other operations. The thread designator
33956 @var{thread-id} has the format and interpretation described in
33957 @ref{thread-id syntax}.
33968 @c 'H': How restrictive (or permissive) is the thread model. If a
33969 @c thread is selected and stopped, are other threads allowed
33970 @c to continue to execute? As I mentioned above, I think the
33971 @c semantics of each command when a thread is selected must be
33972 @c described. For example:
33974 @c 'g': If the stub supports threads and a specific thread is
33975 @c selected, returns the register block from that thread;
33976 @c otherwise returns current registers.
33978 @c 'G' If the stub supports threads and a specific thread is
33979 @c selected, sets the registers of the register block of
33980 @c that thread; otherwise sets current registers.
33982 @item i @r{[}@var{addr}@r{[},@var{nnn}@r{]]}
33983 @anchor{cycle step packet}
33984 @cindex @samp{i} packet
33985 Step the remote target by a single clock cycle. If @samp{,@var{nnn}} is
33986 present, cycle step @var{nnn} cycles. If @var{addr} is present, cycle
33987 step starting at that address.
33990 @cindex @samp{I} packet
33991 Signal, then cycle step. @xref{step with signal packet}. @xref{cycle
33995 @cindex @samp{k} packet
33998 FIXME: @emph{There is no description of how to operate when a specific
33999 thread context has been selected (i.e.@: does 'k' kill only that
34002 @item m @var{addr},@var{length}
34003 @cindex @samp{m} packet
34004 Read @var{length} bytes of memory starting at address @var{addr}.
34005 Note that @var{addr} may not be aligned to any particular boundary.
34007 The stub need not use any particular size or alignment when gathering
34008 data from memory for the response; even if @var{addr} is word-aligned
34009 and @var{length} is a multiple of the word size, the stub is free to
34010 use byte accesses, or not. For this reason, this packet may not be
34011 suitable for accessing memory-mapped I/O devices.
34012 @cindex alignment of remote memory accesses
34013 @cindex size of remote memory accesses
34014 @cindex memory, alignment and size of remote accesses
34018 @item @var{XX@dots{}}
34019 Memory contents; each byte is transmitted as a two-digit hexadecimal
34020 number. The reply may contain fewer bytes than requested if the
34021 server was able to read only part of the region of memory.
34026 @item M @var{addr},@var{length}:@var{XX@dots{}}
34027 @cindex @samp{M} packet
34028 Write @var{length} bytes of memory starting at address @var{addr}.
34029 @var{XX@dots{}} is the data; each byte is transmitted as a two-digit
34030 hexadecimal number.
34037 for an error (this includes the case where only part of the data was
34042 @cindex @samp{p} packet
34043 Read the value of register @var{n}; @var{n} is in hex.
34044 @xref{read registers packet}, for a description of how the returned
34045 register value is encoded.
34049 @item @var{XX@dots{}}
34050 the register's value
34054 Indicating an unrecognized @var{query}.
34057 @item P @var{n@dots{}}=@var{r@dots{}}
34058 @anchor{write register packet}
34059 @cindex @samp{P} packet
34060 Write register @var{n@dots{}} with value @var{r@dots{}}. The register
34061 number @var{n} is in hexadecimal, and @var{r@dots{}} contains two hex
34062 digits for each byte in the register (target byte order).
34072 @item q @var{name} @var{params}@dots{}
34073 @itemx Q @var{name} @var{params}@dots{}
34074 @cindex @samp{q} packet
34075 @cindex @samp{Q} packet
34076 General query (@samp{q}) and set (@samp{Q}). These packets are
34077 described fully in @ref{General Query Packets}.
34080 @cindex @samp{r} packet
34081 Reset the entire system.
34083 Don't use this packet; use the @samp{R} packet instead.
34086 @cindex @samp{R} packet
34087 Restart the program being debugged. @var{XX}, while needed, is ignored.
34088 This packet is only available in extended mode (@pxref{extended mode}).
34090 The @samp{R} packet has no reply.
34092 @item s @r{[}@var{addr}@r{]}
34093 @cindex @samp{s} packet
34094 Single step. @var{addr} is the address at which to resume. If
34095 @var{addr} is omitted, resume at same address.
34097 This packet is deprecated for multi-threading support. @xref{vCont
34101 @xref{Stop Reply Packets}, for the reply specifications.
34103 @item S @var{sig}@r{[};@var{addr}@r{]}
34104 @anchor{step with signal packet}
34105 @cindex @samp{S} packet
34106 Step with signal. This is analogous to the @samp{C} packet, but
34107 requests a single-step, rather than a normal resumption of execution.
34109 This packet is deprecated for multi-threading support. @xref{vCont
34113 @xref{Stop Reply Packets}, for the reply specifications.
34115 @item t @var{addr}:@var{PP},@var{MM}
34116 @cindex @samp{t} packet
34117 Search backwards starting at address @var{addr} for a match with pattern
34118 @var{PP} and mask @var{MM}. @var{PP} and @var{MM} are 4 bytes.
34119 @var{addr} must be at least 3 digits.
34121 @item T @var{thread-id}
34122 @cindex @samp{T} packet
34123 Find out if the thread @var{thread-id} is alive. @xref{thread-id syntax}.
34128 thread is still alive
34134 Packets starting with @samp{v} are identified by a multi-letter name,
34135 up to the first @samp{;} or @samp{?} (or the end of the packet).
34137 @item vAttach;@var{pid}
34138 @cindex @samp{vAttach} packet
34139 Attach to a new process with the specified process ID @var{pid}.
34140 The process ID is a
34141 hexadecimal integer identifying the process. In all-stop mode, all
34142 threads in the attached process are stopped; in non-stop mode, it may be
34143 attached without being stopped if that is supported by the target.
34145 @c In non-stop mode, on a successful vAttach, the stub should set the
34146 @c current thread to a thread of the newly-attached process. After
34147 @c attaching, GDB queries for the attached process's thread ID with qC.
34148 @c Also note that, from a user perspective, whether or not the
34149 @c target is stopped on attach in non-stop mode depends on whether you
34150 @c use the foreground or background version of the attach command, not
34151 @c on what vAttach does; GDB does the right thing with respect to either
34152 @c stopping or restarting threads.
34154 This packet is only available in extended mode (@pxref{extended mode}).
34160 @item @r{Any stop packet}
34161 for success in all-stop mode (@pxref{Stop Reply Packets})
34163 for success in non-stop mode (@pxref{Remote Non-Stop})
34166 @item vCont@r{[};@var{action}@r{[}:@var{thread-id}@r{]]}@dots{}
34167 @cindex @samp{vCont} packet
34168 @anchor{vCont packet}
34169 Resume the inferior, specifying different actions for each thread.
34170 If an action is specified with no @var{thread-id}, then it is applied to any
34171 threads that don't have a specific action specified; if no default action is
34172 specified then other threads should remain stopped in all-stop mode and
34173 in their current state in non-stop mode.
34174 Specifying multiple
34175 default actions is an error; specifying no actions is also an error.
34176 Thread IDs are specified using the syntax described in @ref{thread-id syntax}.
34178 Currently supported actions are:
34184 Continue with signal @var{sig}. The signal @var{sig} should be two hex digits.
34188 Step with signal @var{sig}. The signal @var{sig} should be two hex digits.
34193 The optional argument @var{addr} normally associated with the
34194 @samp{c}, @samp{C}, @samp{s}, and @samp{S} packets is
34195 not supported in @samp{vCont}.
34197 The @samp{t} action is only relevant in non-stop mode
34198 (@pxref{Remote Non-Stop}) and may be ignored by the stub otherwise.
34199 A stop reply should be generated for any affected thread not already stopped.
34200 When a thread is stopped by means of a @samp{t} action,
34201 the corresponding stop reply should indicate that the thread has stopped with
34202 signal @samp{0}, regardless of whether the target uses some other signal
34203 as an implementation detail.
34205 The stub must support @samp{vCont} if it reports support for
34206 multiprocess extensions (@pxref{multiprocess extensions}). Note that in
34207 this case @samp{vCont} actions can be specified to apply to all threads
34208 in a process by using the @samp{p@var{pid}.-1} form of the
34212 @xref{Stop Reply Packets}, for the reply specifications.
34215 @cindex @samp{vCont?} packet
34216 Request a list of actions supported by the @samp{vCont} packet.
34220 @item vCont@r{[};@var{action}@dots{}@r{]}
34221 The @samp{vCont} packet is supported. Each @var{action} is a supported
34222 command in the @samp{vCont} packet.
34224 The @samp{vCont} packet is not supported.
34227 @item vFile:@var{operation}:@var{parameter}@dots{}
34228 @cindex @samp{vFile} packet
34229 Perform a file operation on the target system. For details,
34230 see @ref{Host I/O Packets}.
34232 @item vFlashErase:@var{addr},@var{length}
34233 @cindex @samp{vFlashErase} packet
34234 Direct the stub to erase @var{length} bytes of flash starting at
34235 @var{addr}. The region may enclose any number of flash blocks, but
34236 its start and end must fall on block boundaries, as indicated by the
34237 flash block size appearing in the memory map (@pxref{Memory Map
34238 Format}). @value{GDBN} groups flash memory programming operations
34239 together, and sends a @samp{vFlashDone} request after each group; the
34240 stub is allowed to delay erase operation until the @samp{vFlashDone}
34241 packet is received.
34251 @item vFlashWrite:@var{addr}:@var{XX@dots{}}
34252 @cindex @samp{vFlashWrite} packet
34253 Direct the stub to write data to flash address @var{addr}. The data
34254 is passed in binary form using the same encoding as for the @samp{X}
34255 packet (@pxref{Binary Data}). The memory ranges specified by
34256 @samp{vFlashWrite} packets preceding a @samp{vFlashDone} packet must
34257 not overlap, and must appear in order of increasing addresses
34258 (although @samp{vFlashErase} packets for higher addresses may already
34259 have been received; the ordering is guaranteed only between
34260 @samp{vFlashWrite} packets). If a packet writes to an address that was
34261 neither erased by a preceding @samp{vFlashErase} packet nor by some other
34262 target-specific method, the results are unpredictable.
34270 for vFlashWrite addressing non-flash memory
34276 @cindex @samp{vFlashDone} packet
34277 Indicate to the stub that flash programming operation is finished.
34278 The stub is permitted to delay or batch the effects of a group of
34279 @samp{vFlashErase} and @samp{vFlashWrite} packets until a
34280 @samp{vFlashDone} packet is received. The contents of the affected
34281 regions of flash memory are unpredictable until the @samp{vFlashDone}
34282 request is completed.
34284 @item vKill;@var{pid}
34285 @cindex @samp{vKill} packet
34286 Kill the process with the specified process ID. @var{pid} is a
34287 hexadecimal integer identifying the process. This packet is used in
34288 preference to @samp{k} when multiprocess protocol extensions are
34289 supported; see @ref{multiprocess extensions}.
34299 @item vRun;@var{filename}@r{[};@var{argument}@r{]}@dots{}
34300 @cindex @samp{vRun} packet
34301 Run the program @var{filename}, passing it each @var{argument} on its
34302 command line. The file and arguments are hex-encoded strings. If
34303 @var{filename} is an empty string, the stub may use a default program
34304 (e.g.@: the last program run). The program is created in the stopped
34307 @c FIXME: What about non-stop mode?
34309 This packet is only available in extended mode (@pxref{extended mode}).
34315 @item @r{Any stop packet}
34316 for success (@pxref{Stop Reply Packets})
34320 @anchor{vStopped packet}
34321 @cindex @samp{vStopped} packet
34323 In non-stop mode (@pxref{Remote Non-Stop}), acknowledge a previous stop
34324 reply and prompt for the stub to report another one.
34328 @item @r{Any stop packet}
34329 if there is another unreported stop event (@pxref{Stop Reply Packets})
34331 if there are no unreported stop events
34334 @item X @var{addr},@var{length}:@var{XX@dots{}}
34336 @cindex @samp{X} packet
34337 Write data to memory, where the data is transmitted in binary.
34338 @var{addr} is address, @var{length} is number of bytes,
34339 @samp{@var{XX}@dots{}} is binary data (@pxref{Binary Data}).
34349 @item z @var{type},@var{addr},@var{kind}
34350 @itemx Z @var{type},@var{addr},@var{kind}
34351 @anchor{insert breakpoint or watchpoint packet}
34352 @cindex @samp{z} packet
34353 @cindex @samp{Z} packets
34354 Insert (@samp{Z}) or remove (@samp{z}) a @var{type} breakpoint or
34355 watchpoint starting at address @var{address} of kind @var{kind}.
34357 Each breakpoint and watchpoint packet @var{type} is documented
34360 @emph{Implementation notes: A remote target shall return an empty string
34361 for an unrecognized breakpoint or watchpoint packet @var{type}. A
34362 remote target shall support either both or neither of a given
34363 @samp{Z@var{type}@dots{}} and @samp{z@var{type}@dots{}} packet pair. To
34364 avoid potential problems with duplicate packets, the operations should
34365 be implemented in an idempotent way.}
34367 @item z0,@var{addr},@var{kind}
34368 @itemx Z0,@var{addr},@var{kind}@r{[};@var{cond_list}@dots{}@r{]}
34369 @cindex @samp{z0} packet
34370 @cindex @samp{Z0} packet
34371 Insert (@samp{Z0}) or remove (@samp{z0}) a memory breakpoint at address
34372 @var{addr} of type @var{kind}.
34374 A memory breakpoint is implemented by replacing the instruction at
34375 @var{addr} with a software breakpoint or trap instruction. The
34376 @var{kind} is target-specific and typically indicates the size of
34377 the breakpoint in bytes that should be inserted. E.g., the @sc{arm}
34378 and @sc{mips} can insert either a 2 or 4 byte breakpoint. Some
34379 architectures have additional meanings for @var{kind};
34380 @var{cond_list} is an optional list of conditional expressions in bytecode
34381 form that should be evaluated on the target's side. These are the
34382 conditions that should be taken into consideration when deciding if
34383 the breakpoint trigger should be reported back to @var{GDBN}.
34385 The @var{cond_list} parameter is comprised of a series of expressions,
34386 concatenated without separators. Each expression has the following form:
34390 @item X @var{len},@var{expr}
34391 @var{len} is the length of the bytecode expression and @var{expr} is the
34392 actual conditional expression in bytecode form.
34396 see @ref{Architecture-Specific Protocol Details}.
34398 @emph{Implementation note: It is possible for a target to copy or move
34399 code that contains memory breakpoints (e.g., when implementing
34400 overlays). The behavior of this packet, in the presence of such a
34401 target, is not defined.}
34413 @item z1,@var{addr},@var{kind}
34414 @itemx Z1,@var{addr},@var{kind}@r{[};@var{cond_list}@dots{}@r{]}
34415 @cindex @samp{z1} packet
34416 @cindex @samp{Z1} packet
34417 Insert (@samp{Z1}) or remove (@samp{z1}) a hardware breakpoint at
34418 address @var{addr}.
34420 A hardware breakpoint is implemented using a mechanism that is not
34421 dependant on being able to modify the target's memory. @var{kind}
34422 and @var{cond_list} have the same meaning as in @samp{Z0} packets.
34424 @emph{Implementation note: A hardware breakpoint is not affected by code
34437 @item z2,@var{addr},@var{kind}
34438 @itemx Z2,@var{addr},@var{kind}
34439 @cindex @samp{z2} packet
34440 @cindex @samp{Z2} packet
34441 Insert (@samp{Z2}) or remove (@samp{z2}) a write watchpoint at @var{addr}.
34442 @var{kind} is interpreted as the number of bytes to watch.
34454 @item z3,@var{addr},@var{kind}
34455 @itemx Z3,@var{addr},@var{kind}
34456 @cindex @samp{z3} packet
34457 @cindex @samp{Z3} packet
34458 Insert (@samp{Z3}) or remove (@samp{z3}) a read watchpoint at @var{addr}.
34459 @var{kind} is interpreted as the number of bytes to watch.
34471 @item z4,@var{addr},@var{kind}
34472 @itemx Z4,@var{addr},@var{kind}
34473 @cindex @samp{z4} packet
34474 @cindex @samp{Z4} packet
34475 Insert (@samp{Z4}) or remove (@samp{z4}) an access watchpoint at @var{addr}.
34476 @var{kind} is interpreted as the number of bytes to watch.
34490 @node Stop Reply Packets
34491 @section Stop Reply Packets
34492 @cindex stop reply packets
34494 The @samp{C}, @samp{c}, @samp{S}, @samp{s}, @samp{vCont},
34495 @samp{vAttach}, @samp{vRun}, @samp{vStopped}, and @samp{?} packets can
34496 receive any of the below as a reply. Except for @samp{?}
34497 and @samp{vStopped}, that reply is only returned
34498 when the target halts. In the below the exact meaning of @dfn{signal
34499 number} is defined by the header @file{include/gdb/signals.h} in the
34500 @value{GDBN} source code.
34502 As in the description of request packets, we include spaces in the
34503 reply templates for clarity; these are not part of the reply packet's
34504 syntax. No @value{GDBN} stop reply packet uses spaces to separate its
34510 The program received signal number @var{AA} (a two-digit hexadecimal
34511 number). This is equivalent to a @samp{T} response with no
34512 @var{n}:@var{r} pairs.
34514 @item T @var{AA} @var{n1}:@var{r1};@var{n2}:@var{r2};@dots{}
34515 @cindex @samp{T} packet reply
34516 The program received signal number @var{AA} (a two-digit hexadecimal
34517 number). This is equivalent to an @samp{S} response, except that the
34518 @samp{@var{n}:@var{r}} pairs can carry values of important registers
34519 and other information directly in the stop reply packet, reducing
34520 round-trip latency. Single-step and breakpoint traps are reported
34521 this way. Each @samp{@var{n}:@var{r}} pair is interpreted as follows:
34525 If @var{n} is a hexadecimal number, it is a register number, and the
34526 corresponding @var{r} gives that register's value. @var{r} is a
34527 series of bytes in target byte order, with each byte given by a
34528 two-digit hex number.
34531 If @var{n} is @samp{thread}, then @var{r} is the @var{thread-id} of
34532 the stopped thread, as specified in @ref{thread-id syntax}.
34535 If @var{n} is @samp{core}, then @var{r} is the hexadecimal number of
34536 the core on which the stop event was detected.
34539 If @var{n} is a recognized @dfn{stop reason}, it describes a more
34540 specific event that stopped the target. The currently defined stop
34541 reasons are listed below. @var{aa} should be @samp{05}, the trap
34542 signal. At most one stop reason should be present.
34545 Otherwise, @value{GDBN} should ignore this @samp{@var{n}:@var{r}} pair
34546 and go on to the next; this allows us to extend the protocol in the
34550 The currently defined stop reasons are:
34556 The packet indicates a watchpoint hit, and @var{r} is the data address, in
34559 @cindex shared library events, remote reply
34561 The packet indicates that the loaded libraries have changed.
34562 @value{GDBN} should use @samp{qXfer:libraries:read} to fetch a new
34563 list of loaded libraries. @var{r} is ignored.
34565 @cindex replay log events, remote reply
34567 The packet indicates that the target cannot continue replaying
34568 logged execution events, because it has reached the end (or the
34569 beginning when executing backward) of the log. The value of @var{r}
34570 will be either @samp{begin} or @samp{end}. @xref{Reverse Execution},
34571 for more information.
34575 @itemx W @var{AA} ; process:@var{pid}
34576 The process exited, and @var{AA} is the exit status. This is only
34577 applicable to certain targets.
34579 The second form of the response, including the process ID of the exited
34580 process, can be used only when @value{GDBN} has reported support for
34581 multiprocess protocol extensions; see @ref{multiprocess extensions}.
34582 The @var{pid} is formatted as a big-endian hex string.
34585 @itemx X @var{AA} ; process:@var{pid}
34586 The process terminated with signal @var{AA}.
34588 The second form of the response, including the process ID of the
34589 terminated process, can be used only when @value{GDBN} has reported
34590 support for multiprocess protocol extensions; see @ref{multiprocess
34591 extensions}. The @var{pid} is formatted as a big-endian hex string.
34593 @item O @var{XX}@dots{}
34594 @samp{@var{XX}@dots{}} is hex encoding of @sc{ascii} data, to be
34595 written as the program's console output. This can happen at any time
34596 while the program is running and the debugger should continue to wait
34597 for @samp{W}, @samp{T}, etc. This reply is not permitted in non-stop mode.
34599 @item F @var{call-id},@var{parameter}@dots{}
34600 @var{call-id} is the identifier which says which host system call should
34601 be called. This is just the name of the function. Translation into the
34602 correct system call is only applicable as it's defined in @value{GDBN}.
34603 @xref{File-I/O Remote Protocol Extension}, for a list of implemented
34606 @samp{@var{parameter}@dots{}} is a list of parameters as defined for
34607 this very system call.
34609 The target replies with this packet when it expects @value{GDBN} to
34610 call a host system call on behalf of the target. @value{GDBN} replies
34611 with an appropriate @samp{F} packet and keeps up waiting for the next
34612 reply packet from the target. The latest @samp{C}, @samp{c}, @samp{S}
34613 or @samp{s} action is expected to be continued. @xref{File-I/O Remote
34614 Protocol Extension}, for more details.
34618 @node General Query Packets
34619 @section General Query Packets
34620 @cindex remote query requests
34622 Packets starting with @samp{q} are @dfn{general query packets};
34623 packets starting with @samp{Q} are @dfn{general set packets}. General
34624 query and set packets are a semi-unified form for retrieving and
34625 sending information to and from the stub.
34627 The initial letter of a query or set packet is followed by a name
34628 indicating what sort of thing the packet applies to. For example,
34629 @value{GDBN} may use a @samp{qSymbol} packet to exchange symbol
34630 definitions with the stub. These packet names follow some
34635 The name must not contain commas, colons or semicolons.
34637 Most @value{GDBN} query and set packets have a leading upper case
34640 The names of custom vendor packets should use a company prefix, in
34641 lower case, followed by a period. For example, packets designed at
34642 the Acme Corporation might begin with @samp{qacme.foo} (for querying
34643 foos) or @samp{Qacme.bar} (for setting bars).
34646 The name of a query or set packet should be separated from any
34647 parameters by a @samp{:}; the parameters themselves should be
34648 separated by @samp{,} or @samp{;}. Stubs must be careful to match the
34649 full packet name, and check for a separator or the end of the packet,
34650 in case two packet names share a common prefix. New packets should not begin
34651 with @samp{qC}, @samp{qP}, or @samp{qL}@footnote{The @samp{qP} and @samp{qL}
34652 packets predate these conventions, and have arguments without any terminator
34653 for the packet name; we suspect they are in widespread use in places that
34654 are difficult to upgrade. The @samp{qC} packet has no arguments, but some
34655 existing stubs (e.g.@: RedBoot) are known to not check for the end of the
34658 Like the descriptions of the other packets, each description here
34659 has a template showing the packet's overall syntax, followed by an
34660 explanation of the packet's meaning. We include spaces in some of the
34661 templates for clarity; these are not part of the packet's syntax. No
34662 @value{GDBN} packet uses spaces to separate its components.
34664 Here are the currently defined query and set packets:
34670 Turn on or off the agent as a helper to perform some debugging operations
34671 delegated from @value{GDBN} (@pxref{Control Agent}).
34673 @item QAllow:@var{op}:@var{val}@dots{}
34674 @cindex @samp{QAllow} packet
34675 Specify which operations @value{GDBN} expects to request of the
34676 target, as a semicolon-separated list of operation name and value
34677 pairs. Possible values for @var{op} include @samp{WriteReg},
34678 @samp{WriteMem}, @samp{InsertBreak}, @samp{InsertTrace},
34679 @samp{InsertFastTrace}, and @samp{Stop}. @var{val} is either 0,
34680 indicating that @value{GDBN} will not request the operation, or 1,
34681 indicating that it may. (The target can then use this to set up its
34682 own internals optimally, for instance if the debugger never expects to
34683 insert breakpoints, it may not need to install its own trap handler.)
34686 @cindex current thread, remote request
34687 @cindex @samp{qC} packet
34688 Return the current thread ID.
34692 @item QC @var{thread-id}
34693 Where @var{thread-id} is a thread ID as documented in
34694 @ref{thread-id syntax}.
34695 @item @r{(anything else)}
34696 Any other reply implies the old thread ID.
34699 @item qCRC:@var{addr},@var{length}
34700 @cindex CRC of memory block, remote request
34701 @cindex @samp{qCRC} packet
34702 Compute the CRC checksum of a block of memory using CRC-32 defined in
34703 IEEE 802.3. The CRC is computed byte at a time, taking the most
34704 significant bit of each byte first. The initial pattern code
34705 @code{0xffffffff} is used to ensure leading zeros affect the CRC.
34707 @emph{Note:} This is the same CRC used in validating separate debug
34708 files (@pxref{Separate Debug Files, , Debugging Information in Separate
34709 Files}). However the algorithm is slightly different. When validating
34710 separate debug files, the CRC is computed taking the @emph{least}
34711 significant bit of each byte first, and the final result is inverted to
34712 detect trailing zeros.
34717 An error (such as memory fault)
34718 @item C @var{crc32}
34719 The specified memory region's checksum is @var{crc32}.
34722 @item QDisableRandomization:@var{value}
34723 @cindex disable address space randomization, remote request
34724 @cindex @samp{QDisableRandomization} packet
34725 Some target operating systems will randomize the virtual address space
34726 of the inferior process as a security feature, but provide a feature
34727 to disable such randomization, e.g.@: to allow for a more deterministic
34728 debugging experience. On such systems, this packet with a @var{value}
34729 of 1 directs the target to disable address space randomization for
34730 processes subsequently started via @samp{vRun} packets, while a packet
34731 with a @var{value} of 0 tells the target to enable address space
34734 This packet is only available in extended mode (@pxref{extended mode}).
34739 The request succeeded.
34742 An error occurred. @var{nn} are hex digits.
34745 An empty reply indicates that @samp{QDisableRandomization} is not supported
34749 This packet is not probed by default; the remote stub must request it,
34750 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
34751 This should only be done on targets that actually support disabling
34752 address space randomization.
34755 @itemx qsThreadInfo
34756 @cindex list active threads, remote request
34757 @cindex @samp{qfThreadInfo} packet
34758 @cindex @samp{qsThreadInfo} packet
34759 Obtain a list of all active thread IDs from the target (OS). Since there
34760 may be too many active threads to fit into one reply packet, this query
34761 works iteratively: it may require more than one query/reply sequence to
34762 obtain the entire list of threads. The first query of the sequence will
34763 be the @samp{qfThreadInfo} query; subsequent queries in the
34764 sequence will be the @samp{qsThreadInfo} query.
34766 NOTE: This packet replaces the @samp{qL} query (see below).
34770 @item m @var{thread-id}
34772 @item m @var{thread-id},@var{thread-id}@dots{}
34773 a comma-separated list of thread IDs
34775 (lower case letter @samp{L}) denotes end of list.
34778 In response to each query, the target will reply with a list of one or
34779 more thread IDs, separated by commas.
34780 @value{GDBN} will respond to each reply with a request for more thread
34781 ids (using the @samp{qs} form of the query), until the target responds
34782 with @samp{l} (lower-case ell, for @dfn{last}).
34783 Refer to @ref{thread-id syntax}, for the format of the @var{thread-id}
34786 @item qGetTLSAddr:@var{thread-id},@var{offset},@var{lm}
34787 @cindex get thread-local storage address, remote request
34788 @cindex @samp{qGetTLSAddr} packet
34789 Fetch the address associated with thread local storage specified
34790 by @var{thread-id}, @var{offset}, and @var{lm}.
34792 @var{thread-id} is the thread ID associated with the
34793 thread for which to fetch the TLS address. @xref{thread-id syntax}.
34795 @var{offset} is the (big endian, hex encoded) offset associated with the
34796 thread local variable. (This offset is obtained from the debug
34797 information associated with the variable.)
34799 @var{lm} is the (big endian, hex encoded) OS/ABI-specific encoding of the
34800 load module associated with the thread local storage. For example,
34801 a @sc{gnu}/Linux system will pass the link map address of the shared
34802 object associated with the thread local storage under consideration.
34803 Other operating environments may choose to represent the load module
34804 differently, so the precise meaning of this parameter will vary.
34808 @item @var{XX}@dots{}
34809 Hex encoded (big endian) bytes representing the address of the thread
34810 local storage requested.
34813 An error occurred. @var{nn} are hex digits.
34816 An empty reply indicates that @samp{qGetTLSAddr} is not supported by the stub.
34819 @item qGetTIBAddr:@var{thread-id}
34820 @cindex get thread information block address
34821 @cindex @samp{qGetTIBAddr} packet
34822 Fetch address of the Windows OS specific Thread Information Block.
34824 @var{thread-id} is the thread ID associated with the thread.
34828 @item @var{XX}@dots{}
34829 Hex encoded (big endian) bytes representing the linear address of the
34830 thread information block.
34833 An error occured. This means that either the thread was not found, or the
34834 address could not be retrieved.
34837 An empty reply indicates that @samp{qGetTIBAddr} is not supported by the stub.
34840 @item qL @var{startflag} @var{threadcount} @var{nextthread}
34841 Obtain thread information from RTOS. Where: @var{startflag} (one hex
34842 digit) is one to indicate the first query and zero to indicate a
34843 subsequent query; @var{threadcount} (two hex digits) is the maximum
34844 number of threads the response packet can contain; and @var{nextthread}
34845 (eight hex digits), for subsequent queries (@var{startflag} is zero), is
34846 returned in the response as @var{argthread}.
34848 Don't use this packet; use the @samp{qfThreadInfo} query instead (see above).
34852 @item qM @var{count} @var{done} @var{argthread} @var{thread}@dots{}
34853 Where: @var{count} (two hex digits) is the number of threads being
34854 returned; @var{done} (one hex digit) is zero to indicate more threads
34855 and one indicates no further threads; @var{argthreadid} (eight hex
34856 digits) is @var{nextthread} from the request packet; @var{thread}@dots{}
34857 is a sequence of thread IDs from the target. @var{threadid} (eight hex
34858 digits). See @code{remote.c:parse_threadlist_response()}.
34862 @cindex section offsets, remote request
34863 @cindex @samp{qOffsets} packet
34864 Get section offsets that the target used when relocating the downloaded
34869 @item Text=@var{xxx};Data=@var{yyy}@r{[};Bss=@var{zzz}@r{]}
34870 Relocate the @code{Text} section by @var{xxx} from its original address.
34871 Relocate the @code{Data} section by @var{yyy} from its original address.
34872 If the object file format provides segment information (e.g.@: @sc{elf}
34873 @samp{PT_LOAD} program headers), @value{GDBN} will relocate entire
34874 segments by the supplied offsets.
34876 @emph{Note: while a @code{Bss} offset may be included in the response,
34877 @value{GDBN} ignores this and instead applies the @code{Data} offset
34878 to the @code{Bss} section.}
34880 @item TextSeg=@var{xxx}@r{[};DataSeg=@var{yyy}@r{]}
34881 Relocate the first segment of the object file, which conventionally
34882 contains program code, to a starting address of @var{xxx}. If
34883 @samp{DataSeg} is specified, relocate the second segment, which
34884 conventionally contains modifiable data, to a starting address of
34885 @var{yyy}. @value{GDBN} will report an error if the object file
34886 does not contain segment information, or does not contain at least
34887 as many segments as mentioned in the reply. Extra segments are
34888 kept at fixed offsets relative to the last relocated segment.
34891 @item qP @var{mode} @var{thread-id}
34892 @cindex thread information, remote request
34893 @cindex @samp{qP} packet
34894 Returns information on @var{thread-id}. Where: @var{mode} is a hex
34895 encoded 32 bit mode; @var{thread-id} is a thread ID
34896 (@pxref{thread-id syntax}).
34898 Don't use this packet; use the @samp{qThreadExtraInfo} query instead
34901 Reply: see @code{remote.c:remote_unpack_thread_info_response()}.
34905 @cindex non-stop mode, remote request
34906 @cindex @samp{QNonStop} packet
34908 Enter non-stop (@samp{QNonStop:1}) or all-stop (@samp{QNonStop:0}) mode.
34909 @xref{Remote Non-Stop}, for more information.
34914 The request succeeded.
34917 An error occurred. @var{nn} are hex digits.
34920 An empty reply indicates that @samp{QNonStop} is not supported by
34924 This packet is not probed by default; the remote stub must request it,
34925 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
34926 Use of this packet is controlled by the @code{set non-stop} command;
34927 @pxref{Non-Stop Mode}.
34929 @item QPassSignals: @var{signal} @r{[};@var{signal}@r{]}@dots{}
34930 @cindex pass signals to inferior, remote request
34931 @cindex @samp{QPassSignals} packet
34932 @anchor{QPassSignals}
34933 Each listed @var{signal} should be passed directly to the inferior process.
34934 Signals are numbered identically to continue packets and stop replies
34935 (@pxref{Stop Reply Packets}). Each @var{signal} list item should be
34936 strictly greater than the previous item. These signals do not need to stop
34937 the inferior, or be reported to @value{GDBN}. All other signals should be
34938 reported to @value{GDBN}. Multiple @samp{QPassSignals} packets do not
34939 combine; any earlier @samp{QPassSignals} list is completely replaced by the
34940 new list. This packet improves performance when using @samp{handle
34941 @var{signal} nostop noprint pass}.
34946 The request succeeded.
34949 An error occurred. @var{nn} are hex digits.
34952 An empty reply indicates that @samp{QPassSignals} is not supported by
34956 Use of this packet is controlled by the @code{set remote pass-signals}
34957 command (@pxref{Remote Configuration, set remote pass-signals}).
34958 This packet is not probed by default; the remote stub must request it,
34959 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
34961 @item QProgramSignals: @var{signal} @r{[};@var{signal}@r{]}@dots{}
34962 @cindex signals the inferior may see, remote request
34963 @cindex @samp{QProgramSignals} packet
34964 @anchor{QProgramSignals}
34965 Each listed @var{signal} may be delivered to the inferior process.
34966 Others should be silently discarded.
34968 In some cases, the remote stub may need to decide whether to deliver a
34969 signal to the program or not without @value{GDBN} involvement. One
34970 example of that is while detaching --- the program's threads may have
34971 stopped for signals that haven't yet had a chance of being reported to
34972 @value{GDBN}, and so the remote stub can use the signal list specified
34973 by this packet to know whether to deliver or ignore those pending
34976 This does not influence whether to deliver a signal as requested by a
34977 resumption packet (@pxref{vCont packet}).
34979 Signals are numbered identically to continue packets and stop replies
34980 (@pxref{Stop Reply Packets}). Each @var{signal} list item should be
34981 strictly greater than the previous item. Multiple
34982 @samp{QProgramSignals} packets do not combine; any earlier
34983 @samp{QProgramSignals} list is completely replaced by the new list.
34988 The request succeeded.
34991 An error occurred. @var{nn} are hex digits.
34994 An empty reply indicates that @samp{QProgramSignals} is not supported
34998 Use of this packet is controlled by the @code{set remote program-signals}
34999 command (@pxref{Remote Configuration, set remote program-signals}).
35000 This packet is not probed by default; the remote stub must request it,
35001 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
35003 @item qRcmd,@var{command}
35004 @cindex execute remote command, remote request
35005 @cindex @samp{qRcmd} packet
35006 @var{command} (hex encoded) is passed to the local interpreter for
35007 execution. Invalid commands should be reported using the output
35008 string. Before the final result packet, the target may also respond
35009 with a number of intermediate @samp{O@var{output}} console output
35010 packets. @emph{Implementors should note that providing access to a
35011 stubs's interpreter may have security implications}.
35016 A command response with no output.
35018 A command response with the hex encoded output string @var{OUTPUT}.
35020 Indicate a badly formed request.
35022 An empty reply indicates that @samp{qRcmd} is not recognized.
35025 (Note that the @code{qRcmd} packet's name is separated from the
35026 command by a @samp{,}, not a @samp{:}, contrary to the naming
35027 conventions above. Please don't use this packet as a model for new
35030 @item qSearch:memory:@var{address};@var{length};@var{search-pattern}
35031 @cindex searching memory, in remote debugging
35032 @cindex @samp{qSearch:memory} packet
35033 @anchor{qSearch memory}
35034 Search @var{length} bytes at @var{address} for @var{search-pattern}.
35035 @var{address} and @var{length} are encoded in hex.
35036 @var{search-pattern} is a sequence of bytes, hex encoded.
35041 The pattern was not found.
35043 The pattern was found at @var{address}.
35045 A badly formed request or an error was encountered while searching memory.
35047 An empty reply indicates that @samp{qSearch:memory} is not recognized.
35050 @item QStartNoAckMode
35051 @cindex @samp{QStartNoAckMode} packet
35052 @anchor{QStartNoAckMode}
35053 Request that the remote stub disable the normal @samp{+}/@samp{-}
35054 protocol acknowledgments (@pxref{Packet Acknowledgment}).
35059 The stub has switched to no-acknowledgment mode.
35060 @value{GDBN} acknowledges this reponse,
35061 but neither the stub nor @value{GDBN} shall send or expect further
35062 @samp{+}/@samp{-} acknowledgments in the current connection.
35064 An empty reply indicates that the stub does not support no-acknowledgment mode.
35067 @item qSupported @r{[}:@var{gdbfeature} @r{[};@var{gdbfeature}@r{]}@dots{} @r{]}
35068 @cindex supported packets, remote query
35069 @cindex features of the remote protocol
35070 @cindex @samp{qSupported} packet
35071 @anchor{qSupported}
35072 Tell the remote stub about features supported by @value{GDBN}, and
35073 query the stub for features it supports. This packet allows
35074 @value{GDBN} and the remote stub to take advantage of each others'
35075 features. @samp{qSupported} also consolidates multiple feature probes
35076 at startup, to improve @value{GDBN} performance---a single larger
35077 packet performs better than multiple smaller probe packets on
35078 high-latency links. Some features may enable behavior which must not
35079 be on by default, e.g.@: because it would confuse older clients or
35080 stubs. Other features may describe packets which could be
35081 automatically probed for, but are not. These features must be
35082 reported before @value{GDBN} will use them. This ``default
35083 unsupported'' behavior is not appropriate for all packets, but it
35084 helps to keep the initial connection time under control with new
35085 versions of @value{GDBN} which support increasing numbers of packets.
35089 @item @var{stubfeature} @r{[};@var{stubfeature}@r{]}@dots{}
35090 The stub supports or does not support each returned @var{stubfeature},
35091 depending on the form of each @var{stubfeature} (see below for the
35094 An empty reply indicates that @samp{qSupported} is not recognized,
35095 or that no features needed to be reported to @value{GDBN}.
35098 The allowed forms for each feature (either a @var{gdbfeature} in the
35099 @samp{qSupported} packet, or a @var{stubfeature} in the response)
35103 @item @var{name}=@var{value}
35104 The remote protocol feature @var{name} is supported, and associated
35105 with the specified @var{value}. The format of @var{value} depends
35106 on the feature, but it must not include a semicolon.
35108 The remote protocol feature @var{name} is supported, and does not
35109 need an associated value.
35111 The remote protocol feature @var{name} is not supported.
35113 The remote protocol feature @var{name} may be supported, and
35114 @value{GDBN} should auto-detect support in some other way when it is
35115 needed. This form will not be used for @var{gdbfeature} notifications,
35116 but may be used for @var{stubfeature} responses.
35119 Whenever the stub receives a @samp{qSupported} request, the
35120 supplied set of @value{GDBN} features should override any previous
35121 request. This allows @value{GDBN} to put the stub in a known
35122 state, even if the stub had previously been communicating with
35123 a different version of @value{GDBN}.
35125 The following values of @var{gdbfeature} (for the packet sent by @value{GDBN})
35130 This feature indicates whether @value{GDBN} supports multiprocess
35131 extensions to the remote protocol. @value{GDBN} does not use such
35132 extensions unless the stub also reports that it supports them by
35133 including @samp{multiprocess+} in its @samp{qSupported} reply.
35134 @xref{multiprocess extensions}, for details.
35137 This feature indicates that @value{GDBN} supports the XML target
35138 description. If the stub sees @samp{xmlRegisters=} with target
35139 specific strings separated by a comma, it will report register
35143 This feature indicates whether @value{GDBN} supports the
35144 @samp{qRelocInsn} packet (@pxref{Tracepoint Packets,,Relocate
35145 instruction reply packet}).
35148 Stubs should ignore any unknown values for
35149 @var{gdbfeature}. Any @value{GDBN} which sends a @samp{qSupported}
35150 packet supports receiving packets of unlimited length (earlier
35151 versions of @value{GDBN} may reject overly long responses). Additional values
35152 for @var{gdbfeature} may be defined in the future to let the stub take
35153 advantage of new features in @value{GDBN}, e.g.@: incompatible
35154 improvements in the remote protocol---the @samp{multiprocess} feature is
35155 an example of such a feature. The stub's reply should be independent
35156 of the @var{gdbfeature} entries sent by @value{GDBN}; first @value{GDBN}
35157 describes all the features it supports, and then the stub replies with
35158 all the features it supports.
35160 Similarly, @value{GDBN} will silently ignore unrecognized stub feature
35161 responses, as long as each response uses one of the standard forms.
35163 Some features are flags. A stub which supports a flag feature
35164 should respond with a @samp{+} form response. Other features
35165 require values, and the stub should respond with an @samp{=}
35168 Each feature has a default value, which @value{GDBN} will use if
35169 @samp{qSupported} is not available or if the feature is not mentioned
35170 in the @samp{qSupported} response. The default values are fixed; a
35171 stub is free to omit any feature responses that match the defaults.
35173 Not all features can be probed, but for those which can, the probing
35174 mechanism is useful: in some cases, a stub's internal
35175 architecture may not allow the protocol layer to know some information
35176 about the underlying target in advance. This is especially common in
35177 stubs which may be configured for multiple targets.
35179 These are the currently defined stub features and their properties:
35181 @multitable @columnfractions 0.35 0.2 0.12 0.2
35182 @c NOTE: The first row should be @headitem, but we do not yet require
35183 @c a new enough version of Texinfo (4.7) to use @headitem.
35185 @tab Value Required
35189 @item @samp{PacketSize}
35194 @item @samp{qXfer:auxv:read}
35199 @item @samp{qXfer:features:read}
35204 @item @samp{qXfer:libraries:read}
35209 @item @samp{qXfer:memory-map:read}
35214 @item @samp{qXfer:sdata:read}
35219 @item @samp{qXfer:spu:read}
35224 @item @samp{qXfer:spu:write}
35229 @item @samp{qXfer:siginfo:read}
35234 @item @samp{qXfer:siginfo:write}
35239 @item @samp{qXfer:threads:read}
35244 @item @samp{qXfer:traceframe-info:read}
35249 @item @samp{qXfer:uib:read}
35254 @item @samp{qXfer:fdpic:read}
35259 @item @samp{QNonStop}
35264 @item @samp{QPassSignals}
35269 @item @samp{QStartNoAckMode}
35274 @item @samp{multiprocess}
35279 @item @samp{ConditionalBreakpoints}
35284 @item @samp{ConditionalTracepoints}
35289 @item @samp{ReverseContinue}
35294 @item @samp{ReverseStep}
35299 @item @samp{TracepointSource}
35304 @item @samp{QAgent}
35309 @item @samp{QAllow}
35314 @item @samp{QDisableRandomization}
35319 @item @samp{EnableDisableTracepoints}
35324 @item @samp{tracenz}
35331 These are the currently defined stub features, in more detail:
35334 @cindex packet size, remote protocol
35335 @item PacketSize=@var{bytes}
35336 The remote stub can accept packets up to at least @var{bytes} in
35337 length. @value{GDBN} will send packets up to this size for bulk
35338 transfers, and will never send larger packets. This is a limit on the
35339 data characters in the packet, including the frame and checksum.
35340 There is no trailing NUL byte in a remote protocol packet; if the stub
35341 stores packets in a NUL-terminated format, it should allow an extra
35342 byte in its buffer for the NUL. If this stub feature is not supported,
35343 @value{GDBN} guesses based on the size of the @samp{g} packet response.
35345 @item qXfer:auxv:read
35346 The remote stub understands the @samp{qXfer:auxv:read} packet
35347 (@pxref{qXfer auxiliary vector read}).
35349 @item qXfer:features:read
35350 The remote stub understands the @samp{qXfer:features:read} packet
35351 (@pxref{qXfer target description read}).
35353 @item qXfer:libraries:read
35354 The remote stub understands the @samp{qXfer:libraries:read} packet
35355 (@pxref{qXfer library list read}).
35357 @item qXfer:libraries-svr4:read
35358 The remote stub understands the @samp{qXfer:libraries-svr4:read} packet
35359 (@pxref{qXfer svr4 library list read}).
35361 @item qXfer:memory-map:read
35362 The remote stub understands the @samp{qXfer:memory-map:read} packet
35363 (@pxref{qXfer memory map read}).
35365 @item qXfer:sdata:read
35366 The remote stub understands the @samp{qXfer:sdata:read} packet
35367 (@pxref{qXfer sdata read}).
35369 @item qXfer:spu:read
35370 The remote stub understands the @samp{qXfer:spu:read} packet
35371 (@pxref{qXfer spu read}).
35373 @item qXfer:spu:write
35374 The remote stub understands the @samp{qXfer:spu:write} packet
35375 (@pxref{qXfer spu write}).
35377 @item qXfer:siginfo:read
35378 The remote stub understands the @samp{qXfer:siginfo:read} packet
35379 (@pxref{qXfer siginfo read}).
35381 @item qXfer:siginfo:write
35382 The remote stub understands the @samp{qXfer:siginfo:write} packet
35383 (@pxref{qXfer siginfo write}).
35385 @item qXfer:threads:read
35386 The remote stub understands the @samp{qXfer:threads:read} packet
35387 (@pxref{qXfer threads read}).
35389 @item qXfer:traceframe-info:read
35390 The remote stub understands the @samp{qXfer:traceframe-info:read}
35391 packet (@pxref{qXfer traceframe info read}).
35393 @item qXfer:uib:read
35394 The remote stub understands the @samp{qXfer:uib:read}
35395 packet (@pxref{qXfer unwind info block}).
35397 @item qXfer:fdpic:read
35398 The remote stub understands the @samp{qXfer:fdpic:read}
35399 packet (@pxref{qXfer fdpic loadmap read}).
35402 The remote stub understands the @samp{QNonStop} packet
35403 (@pxref{QNonStop}).
35406 The remote stub understands the @samp{QPassSignals} packet
35407 (@pxref{QPassSignals}).
35409 @item QStartNoAckMode
35410 The remote stub understands the @samp{QStartNoAckMode} packet and
35411 prefers to operate in no-acknowledgment mode. @xref{Packet Acknowledgment}.
35414 @anchor{multiprocess extensions}
35415 @cindex multiprocess extensions, in remote protocol
35416 The remote stub understands the multiprocess extensions to the remote
35417 protocol syntax. The multiprocess extensions affect the syntax of
35418 thread IDs in both packets and replies (@pxref{thread-id syntax}), and
35419 add process IDs to the @samp{D} packet and @samp{W} and @samp{X}
35420 replies. Note that reporting this feature indicates support for the
35421 syntactic extensions only, not that the stub necessarily supports
35422 debugging of more than one process at a time. The stub must not use
35423 multiprocess extensions in packet replies unless @value{GDBN} has also
35424 indicated it supports them in its @samp{qSupported} request.
35426 @item qXfer:osdata:read
35427 The remote stub understands the @samp{qXfer:osdata:read} packet
35428 ((@pxref{qXfer osdata read}).
35430 @item ConditionalBreakpoints
35431 The target accepts and implements evaluation of conditional expressions
35432 defined for breakpoints. The target will only report breakpoint triggers
35433 when such conditions are true (@pxref{Conditions, ,Break Conditions}).
35435 @item ConditionalTracepoints
35436 The remote stub accepts and implements conditional expressions defined
35437 for tracepoints (@pxref{Tracepoint Conditions}).
35439 @item ReverseContinue
35440 The remote stub accepts and implements the reverse continue packet
35444 The remote stub accepts and implements the reverse step packet
35447 @item TracepointSource
35448 The remote stub understands the @samp{QTDPsrc} packet that supplies
35449 the source form of tracepoint definitions.
35452 The remote stub understands the @samp{QAgent} packet.
35455 The remote stub understands the @samp{QAllow} packet.
35457 @item QDisableRandomization
35458 The remote stub understands the @samp{QDisableRandomization} packet.
35460 @item StaticTracepoint
35461 @cindex static tracepoints, in remote protocol
35462 The remote stub supports static tracepoints.
35464 @item InstallInTrace
35465 @anchor{install tracepoint in tracing}
35466 The remote stub supports installing tracepoint in tracing.
35468 @item EnableDisableTracepoints
35469 The remote stub supports the @samp{QTEnable} (@pxref{QTEnable}) and
35470 @samp{QTDisable} (@pxref{QTDisable}) packets that allow tracepoints
35471 to be enabled and disabled while a trace experiment is running.
35474 @cindex string tracing, in remote protocol
35475 The remote stub supports the @samp{tracenz} bytecode for collecting strings.
35476 See @ref{Bytecode Descriptions} for details about the bytecode.
35481 @cindex symbol lookup, remote request
35482 @cindex @samp{qSymbol} packet
35483 Notify the target that @value{GDBN} is prepared to serve symbol lookup
35484 requests. Accept requests from the target for the values of symbols.
35489 The target does not need to look up any (more) symbols.
35490 @item qSymbol:@var{sym_name}
35491 The target requests the value of symbol @var{sym_name} (hex encoded).
35492 @value{GDBN} may provide the value by using the
35493 @samp{qSymbol:@var{sym_value}:@var{sym_name}} message, described
35497 @item qSymbol:@var{sym_value}:@var{sym_name}
35498 Set the value of @var{sym_name} to @var{sym_value}.
35500 @var{sym_name} (hex encoded) is the name of a symbol whose value the
35501 target has previously requested.
35503 @var{sym_value} (hex) is the value for symbol @var{sym_name}. If
35504 @value{GDBN} cannot supply a value for @var{sym_name}, then this field
35510 The target does not need to look up any (more) symbols.
35511 @item qSymbol:@var{sym_name}
35512 The target requests the value of a new symbol @var{sym_name} (hex
35513 encoded). @value{GDBN} will continue to supply the values of symbols
35514 (if available), until the target ceases to request them.
35519 @item QTDisconnected
35526 @itemx qTMinFTPILen
35528 @xref{Tracepoint Packets}.
35530 @item qThreadExtraInfo,@var{thread-id}
35531 @cindex thread attributes info, remote request
35532 @cindex @samp{qThreadExtraInfo} packet
35533 Obtain a printable string description of a thread's attributes from
35534 the target OS. @var{thread-id} is a thread ID;
35535 see @ref{thread-id syntax}. This
35536 string may contain anything that the target OS thinks is interesting
35537 for @value{GDBN} to tell the user about the thread. The string is
35538 displayed in @value{GDBN}'s @code{info threads} display. Some
35539 examples of possible thread extra info strings are @samp{Runnable}, or
35540 @samp{Blocked on Mutex}.
35544 @item @var{XX}@dots{}
35545 Where @samp{@var{XX}@dots{}} is a hex encoding of @sc{ascii} data,
35546 comprising the printable string containing the extra information about
35547 the thread's attributes.
35550 (Note that the @code{qThreadExtraInfo} packet's name is separated from
35551 the command by a @samp{,}, not a @samp{:}, contrary to the naming
35552 conventions above. Please don't use this packet as a model for new
35571 @xref{Tracepoint Packets}.
35573 @item qXfer:@var{object}:read:@var{annex}:@var{offset},@var{length}
35574 @cindex read special object, remote request
35575 @cindex @samp{qXfer} packet
35576 @anchor{qXfer read}
35577 Read uninterpreted bytes from the target's special data area
35578 identified by the keyword @var{object}. Request @var{length} bytes
35579 starting at @var{offset} bytes into the data. The content and
35580 encoding of @var{annex} is specific to @var{object}; it can supply
35581 additional details about what data to access.
35583 Here are the specific requests of this form defined so far. All
35584 @samp{qXfer:@var{object}:read:@dots{}} requests use the same reply
35585 formats, listed below.
35588 @item qXfer:auxv:read::@var{offset},@var{length}
35589 @anchor{qXfer auxiliary vector read}
35590 Access the target's @dfn{auxiliary vector}. @xref{OS Information,
35591 auxiliary vector}. Note @var{annex} must be empty.
35593 This packet is not probed by default; the remote stub must request it,
35594 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
35596 @item qXfer:features:read:@var{annex}:@var{offset},@var{length}
35597 @anchor{qXfer target description read}
35598 Access the @dfn{target description}. @xref{Target Descriptions}. The
35599 annex specifies which XML document to access. The main description is
35600 always loaded from the @samp{target.xml} annex.
35602 This packet is not probed by default; the remote stub must request it,
35603 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
35605 @item qXfer:libraries:read:@var{annex}:@var{offset},@var{length}
35606 @anchor{qXfer library list read}
35607 Access the target's list of loaded libraries. @xref{Library List Format}.
35608 The annex part of the generic @samp{qXfer} packet must be empty
35609 (@pxref{qXfer read}).
35611 Targets which maintain a list of libraries in the program's memory do
35612 not need to implement this packet; it is designed for platforms where
35613 the operating system manages the list of loaded libraries.
35615 This packet is not probed by default; the remote stub must request it,
35616 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
35618 @item qXfer:libraries-svr4:read:@var{annex}:@var{offset},@var{length}
35619 @anchor{qXfer svr4 library list read}
35620 Access the target's list of loaded libraries when the target is an SVR4
35621 platform. @xref{Library List Format for SVR4 Targets}. The annex part
35622 of the generic @samp{qXfer} packet must be empty (@pxref{qXfer read}).
35624 This packet is optional for better performance on SVR4 targets.
35625 @value{GDBN} uses memory read packets to read the SVR4 library list otherwise.
35627 This packet is not probed by default; the remote stub must request it,
35628 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
35630 @item qXfer:memory-map:read::@var{offset},@var{length}
35631 @anchor{qXfer memory map read}
35632 Access the target's @dfn{memory-map}. @xref{Memory Map Format}. The
35633 annex part of the generic @samp{qXfer} packet must be empty
35634 (@pxref{qXfer read}).
35636 This packet is not probed by default; the remote stub must request it,
35637 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
35639 @item qXfer:sdata:read::@var{offset},@var{length}
35640 @anchor{qXfer sdata read}
35642 Read contents of the extra collected static tracepoint marker
35643 information. The annex part of the generic @samp{qXfer} packet must
35644 be empty (@pxref{qXfer read}). @xref{Tracepoint Actions,,Tracepoint
35647 This packet is not probed by default; the remote stub must request it,
35648 by supplying an appropriate @samp{qSupported} response
35649 (@pxref{qSupported}).
35651 @item qXfer:siginfo:read::@var{offset},@var{length}
35652 @anchor{qXfer siginfo read}
35653 Read contents of the extra signal information on the target
35654 system. The annex part of the generic @samp{qXfer} packet must be
35655 empty (@pxref{qXfer read}).
35657 This packet is not probed by default; the remote stub must request it,
35658 by supplying an appropriate @samp{qSupported} response
35659 (@pxref{qSupported}).
35661 @item qXfer:spu:read:@var{annex}:@var{offset},@var{length}
35662 @anchor{qXfer spu read}
35663 Read contents of an @code{spufs} file on the target system. The
35664 annex specifies which file to read; it must be of the form
35665 @file{@var{id}/@var{name}}, where @var{id} specifies an SPU context ID
35666 in the target process, and @var{name} identifes the @code{spufs} file
35667 in that context to be accessed.
35669 This packet is not probed by default; the remote stub must request it,
35670 by supplying an appropriate @samp{qSupported} response
35671 (@pxref{qSupported}).
35673 @item qXfer:threads:read::@var{offset},@var{length}
35674 @anchor{qXfer threads read}
35675 Access the list of threads on target. @xref{Thread List Format}. The
35676 annex part of the generic @samp{qXfer} packet must be empty
35677 (@pxref{qXfer read}).
35679 This packet is not probed by default; the remote stub must request it,
35680 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
35682 @item qXfer:traceframe-info:read::@var{offset},@var{length}
35683 @anchor{qXfer traceframe info read}
35685 Return a description of the current traceframe's contents.
35686 @xref{Traceframe Info Format}. The annex part of the generic
35687 @samp{qXfer} packet must be empty (@pxref{qXfer read}).
35689 This packet is not probed by default; the remote stub must request it,
35690 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
35692 @item qXfer:uib:read:@var{pc}:@var{offset},@var{length}
35693 @anchor{qXfer unwind info block}
35695 Return the unwind information block for @var{pc}. This packet is used
35696 on OpenVMS/ia64 to ask the kernel unwind information.
35698 This packet is not probed by default.
35700 @item qXfer:fdpic:read:@var{annex}:@var{offset},@var{length}
35701 @anchor{qXfer fdpic loadmap read}
35702 Read contents of @code{loadmap}s on the target system. The
35703 annex, either @samp{exec} or @samp{interp}, specifies which @code{loadmap},
35704 executable @code{loadmap} or interpreter @code{loadmap} to read.
35706 This packet is not probed by default; the remote stub must request it,
35707 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
35709 @item qXfer:osdata:read::@var{offset},@var{length}
35710 @anchor{qXfer osdata read}
35711 Access the target's @dfn{operating system information}.
35712 @xref{Operating System Information}.
35719 Data @var{data} (@pxref{Binary Data}) has been read from the
35720 target. There may be more data at a higher address (although
35721 it is permitted to return @samp{m} even for the last valid
35722 block of data, as long as at least one byte of data was read).
35723 @var{data} may have fewer bytes than the @var{length} in the
35727 Data @var{data} (@pxref{Binary Data}) has been read from the target.
35728 There is no more data to be read. @var{data} may have fewer bytes
35729 than the @var{length} in the request.
35732 The @var{offset} in the request is at the end of the data.
35733 There is no more data to be read.
35736 The request was malformed, or @var{annex} was invalid.
35739 The offset was invalid, or there was an error encountered reading the data.
35740 @var{nn} is a hex-encoded @code{errno} value.
35743 An empty reply indicates the @var{object} string was not recognized by
35744 the stub, or that the object does not support reading.
35747 @item qXfer:@var{object}:write:@var{annex}:@var{offset}:@var{data}@dots{}
35748 @cindex write data into object, remote request
35749 @anchor{qXfer write}
35750 Write uninterpreted bytes into the target's special data area
35751 identified by the keyword @var{object}, starting at @var{offset} bytes
35752 into the data. @var{data}@dots{} is the binary-encoded data
35753 (@pxref{Binary Data}) to be written. The content and encoding of @var{annex}
35754 is specific to @var{object}; it can supply additional details about what data
35757 Here are the specific requests of this form defined so far. All
35758 @samp{qXfer:@var{object}:write:@dots{}} requests use the same reply
35759 formats, listed below.
35762 @item qXfer:siginfo:write::@var{offset}:@var{data}@dots{}
35763 @anchor{qXfer siginfo write}
35764 Write @var{data} to the extra signal information on the target system.
35765 The annex part of the generic @samp{qXfer} packet must be
35766 empty (@pxref{qXfer write}).
35768 This packet is not probed by default; the remote stub must request it,
35769 by supplying an appropriate @samp{qSupported} response
35770 (@pxref{qSupported}).
35772 @item qXfer:spu:write:@var{annex}:@var{offset}:@var{data}@dots{}
35773 @anchor{qXfer spu write}
35774 Write @var{data} to an @code{spufs} file on the target system. The
35775 annex specifies which file to write; it must be of the form
35776 @file{@var{id}/@var{name}}, where @var{id} specifies an SPU context ID
35777 in the target process, and @var{name} identifes the @code{spufs} file
35778 in that context to be accessed.
35780 This packet is not probed by default; the remote stub must request it,
35781 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
35787 @var{nn} (hex encoded) is the number of bytes written.
35788 This may be fewer bytes than supplied in the request.
35791 The request was malformed, or @var{annex} was invalid.
35794 The offset was invalid, or there was an error encountered writing the data.
35795 @var{nn} is a hex-encoded @code{errno} value.
35798 An empty reply indicates the @var{object} string was not
35799 recognized by the stub, or that the object does not support writing.
35802 @item qXfer:@var{object}:@var{operation}:@dots{}
35803 Requests of this form may be added in the future. When a stub does
35804 not recognize the @var{object} keyword, or its support for
35805 @var{object} does not recognize the @var{operation} keyword, the stub
35806 must respond with an empty packet.
35808 @item qAttached:@var{pid}
35809 @cindex query attached, remote request
35810 @cindex @samp{qAttached} packet
35811 Return an indication of whether the remote server attached to an
35812 existing process or created a new process. When the multiprocess
35813 protocol extensions are supported (@pxref{multiprocess extensions}),
35814 @var{pid} is an integer in hexadecimal format identifying the target
35815 process. Otherwise, @value{GDBN} will omit the @var{pid} field and
35816 the query packet will be simplified as @samp{qAttached}.
35818 This query is used, for example, to know whether the remote process
35819 should be detached or killed when a @value{GDBN} session is ended with
35820 the @code{quit} command.
35825 The remote server attached to an existing process.
35827 The remote server created a new process.
35829 A badly formed request or an error was encountered.
35834 @node Architecture-Specific Protocol Details
35835 @section Architecture-Specific Protocol Details
35837 This section describes how the remote protocol is applied to specific
35838 target architectures. Also see @ref{Standard Target Features}, for
35839 details of XML target descriptions for each architecture.
35843 @subsubsection Breakpoint Kinds
35845 These breakpoint kinds are defined for the @samp{Z0} and @samp{Z1} packets.
35850 16-bit Thumb mode breakpoint.
35853 32-bit Thumb mode (Thumb-2) breakpoint.
35856 32-bit ARM mode breakpoint.
35862 @subsubsection Register Packet Format
35864 The following @code{g}/@code{G} packets have previously been defined.
35865 In the below, some thirty-two bit registers are transferred as
35866 sixty-four bits. Those registers should be zero/sign extended (which?)
35867 to fill the space allocated. Register bytes are transferred in target
35868 byte order. The two nibbles within a register byte are transferred
35869 most-significant - least-significant.
35875 All registers are transferred as thirty-two bit quantities in the order:
35876 32 general-purpose; sr; lo; hi; bad; cause; pc; 32 floating-point
35877 registers; fsr; fir; fp.
35881 All registers are transferred as sixty-four bit quantities (including
35882 thirty-two bit registers such as @code{sr}). The ordering is the same
35887 @node Tracepoint Packets
35888 @section Tracepoint Packets
35889 @cindex tracepoint packets
35890 @cindex packets, tracepoint
35892 Here we describe the packets @value{GDBN} uses to implement
35893 tracepoints (@pxref{Tracepoints}).
35897 @item QTDP:@var{n}:@var{addr}:@var{ena}:@var{step}:@var{pass}[:F@var{flen}][:X@var{len},@var{bytes}]@r{[}-@r{]}
35898 Create a new tracepoint, number @var{n}, at @var{addr}. If @var{ena}
35899 is @samp{E}, then the tracepoint is enabled; if it is @samp{D}, then
35900 the tracepoint is disabled. @var{step} is the tracepoint's step
35901 count, and @var{pass} is its pass count. If an @samp{F} is present,
35902 then the tracepoint is to be a fast tracepoint, and the @var{flen} is
35903 the number of bytes that the target should copy elsewhere to make room
35904 for the tracepoint. If an @samp{X} is present, it introduces a
35905 tracepoint condition, which consists of a hexadecimal length, followed
35906 by a comma and hex-encoded bytes, in a manner similar to action
35907 encodings as described below. If the trailing @samp{-} is present,
35908 further @samp{QTDP} packets will follow to specify this tracepoint's
35914 The packet was understood and carried out.
35916 @xref{Tracepoint Packets,,Relocate instruction reply packet}.
35918 The packet was not recognized.
35921 @item QTDP:-@var{n}:@var{addr}:@r{[}S@r{]}@var{action}@dots{}@r{[}-@r{]}
35922 Define actions to be taken when a tracepoint is hit. @var{n} and
35923 @var{addr} must be the same as in the initial @samp{QTDP} packet for
35924 this tracepoint. This packet may only be sent immediately after
35925 another @samp{QTDP} packet that ended with a @samp{-}. If the
35926 trailing @samp{-} is present, further @samp{QTDP} packets will follow,
35927 specifying more actions for this tracepoint.
35929 In the series of action packets for a given tracepoint, at most one
35930 can have an @samp{S} before its first @var{action}. If such a packet
35931 is sent, it and the following packets define ``while-stepping''
35932 actions. Any prior packets define ordinary actions --- that is, those
35933 taken when the tracepoint is first hit. If no action packet has an
35934 @samp{S}, then all the packets in the series specify ordinary
35935 tracepoint actions.
35937 The @samp{@var{action}@dots{}} portion of the packet is a series of
35938 actions, concatenated without separators. Each action has one of the
35944 Collect the registers whose bits are set in @var{mask}. @var{mask} is
35945 a hexadecimal number whose @var{i}'th bit is set if register number
35946 @var{i} should be collected. (The least significant bit is numbered
35947 zero.) Note that @var{mask} may be any number of digits long; it may
35948 not fit in a 32-bit word.
35950 @item M @var{basereg},@var{offset},@var{len}
35951 Collect @var{len} bytes of memory starting at the address in register
35952 number @var{basereg}, plus @var{offset}. If @var{basereg} is
35953 @samp{-1}, then the range has a fixed address: @var{offset} is the
35954 address of the lowest byte to collect. The @var{basereg},
35955 @var{offset}, and @var{len} parameters are all unsigned hexadecimal
35956 values (the @samp{-1} value for @var{basereg} is a special case).
35958 @item X @var{len},@var{expr}
35959 Evaluate @var{expr}, whose length is @var{len}, and collect memory as
35960 it directs. @var{expr} is an agent expression, as described in
35961 @ref{Agent Expressions}. Each byte of the expression is encoded as a
35962 two-digit hex number in the packet; @var{len} is the number of bytes
35963 in the expression (and thus one-half the number of hex digits in the
35968 Any number of actions may be packed together in a single @samp{QTDP}
35969 packet, as long as the packet does not exceed the maximum packet
35970 length (400 bytes, for many stubs). There may be only one @samp{R}
35971 action per tracepoint, and it must precede any @samp{M} or @samp{X}
35972 actions. Any registers referred to by @samp{M} and @samp{X} actions
35973 must be collected by a preceding @samp{R} action. (The
35974 ``while-stepping'' actions are treated as if they were attached to a
35975 separate tracepoint, as far as these restrictions are concerned.)
35980 The packet was understood and carried out.
35982 @xref{Tracepoint Packets,,Relocate instruction reply packet}.
35984 The packet was not recognized.
35987 @item QTDPsrc:@var{n}:@var{addr}:@var{type}:@var{start}:@var{slen}:@var{bytes}
35988 @cindex @samp{QTDPsrc} packet
35989 Specify a source string of tracepoint @var{n} at address @var{addr}.
35990 This is useful to get accurate reproduction of the tracepoints
35991 originally downloaded at the beginning of the trace run. @var{type}
35992 is the name of the tracepoint part, such as @samp{cond} for the
35993 tracepoint's conditional expression (see below for a list of types), while
35994 @var{bytes} is the string, encoded in hexadecimal.
35996 @var{start} is the offset of the @var{bytes} within the overall source
35997 string, while @var{slen} is the total length of the source string.
35998 This is intended for handling source strings that are longer than will
35999 fit in a single packet.
36000 @c Add detailed example when this info is moved into a dedicated
36001 @c tracepoint descriptions section.
36003 The available string types are @samp{at} for the location,
36004 @samp{cond} for the conditional, and @samp{cmd} for an action command.
36005 @value{GDBN} sends a separate packet for each command in the action
36006 list, in the same order in which the commands are stored in the list.
36008 The target does not need to do anything with source strings except
36009 report them back as part of the replies to the @samp{qTfP}/@samp{qTsP}
36012 Although this packet is optional, and @value{GDBN} will only send it
36013 if the target replies with @samp{TracepointSource} @xref{General
36014 Query Packets}, it makes both disconnected tracing and trace files
36015 much easier to use. Otherwise the user must be careful that the
36016 tracepoints in effect while looking at trace frames are identical to
36017 the ones in effect during the trace run; even a small discrepancy
36018 could cause @samp{tdump} not to work, or a particular trace frame not
36021 @item QTDV:@var{n}:@var{value}
36022 @cindex define trace state variable, remote request
36023 @cindex @samp{QTDV} packet
36024 Create a new trace state variable, number @var{n}, with an initial
36025 value of @var{value}, which is a 64-bit signed integer. Both @var{n}
36026 and @var{value} are encoded as hexadecimal values. @value{GDBN} has
36027 the option of not using this packet for initial values of zero; the
36028 target should simply create the trace state variables as they are
36029 mentioned in expressions.
36031 @item QTFrame:@var{n}
36032 Select the @var{n}'th tracepoint frame from the buffer, and use the
36033 register and memory contents recorded there to answer subsequent
36034 request packets from @value{GDBN}.
36036 A successful reply from the stub indicates that the stub has found the
36037 requested frame. The response is a series of parts, concatenated
36038 without separators, describing the frame we selected. Each part has
36039 one of the following forms:
36043 The selected frame is number @var{n} in the trace frame buffer;
36044 @var{f} is a hexadecimal number. If @var{f} is @samp{-1}, then there
36045 was no frame matching the criteria in the request packet.
36048 The selected trace frame records a hit of tracepoint number @var{t};
36049 @var{t} is a hexadecimal number.
36053 @item QTFrame:pc:@var{addr}
36054 Like @samp{QTFrame:@var{n}}, but select the first tracepoint frame after the
36055 currently selected frame whose PC is @var{addr};
36056 @var{addr} is a hexadecimal number.
36058 @item QTFrame:tdp:@var{t}
36059 Like @samp{QTFrame:@var{n}}, but select the first tracepoint frame after the
36060 currently selected frame that is a hit of tracepoint @var{t}; @var{t}
36061 is a hexadecimal number.
36063 @item QTFrame:range:@var{start}:@var{end}
36064 Like @samp{QTFrame:@var{n}}, but select the first tracepoint frame after the
36065 currently selected frame whose PC is between @var{start} (inclusive)
36066 and @var{end} (inclusive); @var{start} and @var{end} are hexadecimal
36069 @item QTFrame:outside:@var{start}:@var{end}
36070 Like @samp{QTFrame:range:@var{start}:@var{end}}, but select the first
36071 frame @emph{outside} the given range of addresses (exclusive).
36074 This packet requests the minimum length of instruction at which a fast
36075 tracepoint (@pxref{Set Tracepoints}) may be placed. For instance, on
36076 the 32-bit x86 architecture, it is possible to use a 4-byte jump, but
36077 it depends on the target system being able to create trampolines in
36078 the first 64K of memory, which might or might not be possible for that
36079 system. So the reply to this packet will be 4 if it is able to
36086 The minimum instruction length is currently unknown.
36088 The minimum instruction length is @var{length}, where @var{length} is greater
36089 or equal to 1. @var{length} is a hexadecimal number. A reply of 1 means
36090 that a fast tracepoint may be placed on any instruction regardless of size.
36092 An error has occurred.
36094 An empty reply indicates that the request is not supported by the stub.
36098 Begin the tracepoint experiment. Begin collecting data from
36099 tracepoint hits in the trace frame buffer. This packet supports the
36100 @samp{qRelocInsn} reply (@pxref{Tracepoint Packets,,Relocate
36101 instruction reply packet}).
36104 End the tracepoint experiment. Stop collecting trace frames.
36106 @item QTEnable:@var{n}:@var{addr}
36108 Enable tracepoint @var{n} at address @var{addr} in a started tracepoint
36109 experiment. If the tracepoint was previously disabled, then collection
36110 of data from it will resume.
36112 @item QTDisable:@var{n}:@var{addr}
36114 Disable tracepoint @var{n} at address @var{addr} in a started tracepoint
36115 experiment. No more data will be collected from the tracepoint unless
36116 @samp{QTEnable:@var{n}:@var{addr}} is subsequently issued.
36119 Clear the table of tracepoints, and empty the trace frame buffer.
36121 @item QTro:@var{start1},@var{end1}:@var{start2},@var{end2}:@dots{}
36122 Establish the given ranges of memory as ``transparent''. The stub
36123 will answer requests for these ranges from memory's current contents,
36124 if they were not collected as part of the tracepoint hit.
36126 @value{GDBN} uses this to mark read-only regions of memory, like those
36127 containing program code. Since these areas never change, they should
36128 still have the same contents they did when the tracepoint was hit, so
36129 there's no reason for the stub to refuse to provide their contents.
36131 @item QTDisconnected:@var{value}
36132 Set the choice to what to do with the tracing run when @value{GDBN}
36133 disconnects from the target. A @var{value} of 1 directs the target to
36134 continue the tracing run, while 0 tells the target to stop tracing if
36135 @value{GDBN} is no longer in the picture.
36138 Ask the stub if there is a trace experiment running right now.
36140 The reply has the form:
36144 @item T@var{running}@r{[};@var{field}@r{]}@dots{}
36145 @var{running} is a single digit @code{1} if the trace is presently
36146 running, or @code{0} if not. It is followed by semicolon-separated
36147 optional fields that an agent may use to report additional status.
36151 If the trace is not running, the agent may report any of several
36152 explanations as one of the optional fields:
36157 No trace has been run yet.
36159 @item tstop[:@var{text}]:0
36160 The trace was stopped by a user-originated stop command. The optional
36161 @var{text} field is a user-supplied string supplied as part of the
36162 stop command (for instance, an explanation of why the trace was
36163 stopped manually). It is hex-encoded.
36166 The trace stopped because the trace buffer filled up.
36168 @item tdisconnected:0
36169 The trace stopped because @value{GDBN} disconnected from the target.
36171 @item tpasscount:@var{tpnum}
36172 The trace stopped because tracepoint @var{tpnum} exceeded its pass count.
36174 @item terror:@var{text}:@var{tpnum}
36175 The trace stopped because tracepoint @var{tpnum} had an error. The
36176 string @var{text} is available to describe the nature of the error
36177 (for instance, a divide by zero in the condition expression).
36178 @var{text} is hex encoded.
36181 The trace stopped for some other reason.
36185 Additional optional fields supply statistical and other information.
36186 Although not required, they are extremely useful for users monitoring
36187 the progress of a trace run. If a trace has stopped, and these
36188 numbers are reported, they must reflect the state of the just-stopped
36193 @item tframes:@var{n}
36194 The number of trace frames in the buffer.
36196 @item tcreated:@var{n}
36197 The total number of trace frames created during the run. This may
36198 be larger than the trace frame count, if the buffer is circular.
36200 @item tsize:@var{n}
36201 The total size of the trace buffer, in bytes.
36203 @item tfree:@var{n}
36204 The number of bytes still unused in the buffer.
36206 @item circular:@var{n}
36207 The value of the circular trace buffer flag. @code{1} means that the
36208 trace buffer is circular and old trace frames will be discarded if
36209 necessary to make room, @code{0} means that the trace buffer is linear
36212 @item disconn:@var{n}
36213 The value of the disconnected tracing flag. @code{1} means that
36214 tracing will continue after @value{GDBN} disconnects, @code{0} means
36215 that the trace run will stop.
36219 @item qTP:@var{tp}:@var{addr}
36220 @cindex tracepoint status, remote request
36221 @cindex @samp{qTP} packet
36222 Ask the stub for the current state of tracepoint number @var{tp} at
36223 address @var{addr}.
36227 @item V@var{hits}:@var{usage}
36228 The tracepoint has been hit @var{hits} times so far during the trace
36229 run, and accounts for @var{usage} in the trace buffer. Note that
36230 @code{while-stepping} steps are not counted as separate hits, but the
36231 steps' space consumption is added into the usage number.
36235 @item qTV:@var{var}
36236 @cindex trace state variable value, remote request
36237 @cindex @samp{qTV} packet
36238 Ask the stub for the value of the trace state variable number @var{var}.
36243 The value of the variable is @var{value}. This will be the current
36244 value of the variable if the user is examining a running target, or a
36245 saved value if the variable was collected in the trace frame that the
36246 user is looking at. Note that multiple requests may result in
36247 different reply values, such as when requesting values while the
36248 program is running.
36251 The value of the variable is unknown. This would occur, for example,
36252 if the user is examining a trace frame in which the requested variable
36258 These packets request data about tracepoints that are being used by
36259 the target. @value{GDBN} sends @code{qTfP} to get the first piece
36260 of data, and multiple @code{qTsP} to get additional pieces. Replies
36261 to these packets generally take the form of the @code{QTDP} packets
36262 that define tracepoints. (FIXME add detailed syntax)
36266 These packets request data about trace state variables that are on the
36267 target. @value{GDBN} sends @code{qTfV} to get the first vari of data,
36268 and multiple @code{qTsV} to get additional variables. Replies to
36269 these packets follow the syntax of the @code{QTDV} packets that define
36270 trace state variables.
36274 These packets request data about static tracepoint markers that exist
36275 in the target program. @value{GDBN} sends @code{qTfSTM} to get the
36276 first piece of data, and multiple @code{qTsSTM} to get additional
36277 pieces. Replies to these packets take the following form:
36281 @item m @var{address}:@var{id}:@var{extra}
36283 @item m @var{address}:@var{id}:@var{extra},@var{address}:@var{id}:@var{extra}@dots{}
36284 a comma-separated list of markers
36286 (lower case letter @samp{L}) denotes end of list.
36288 An error occurred. @var{nn} are hex digits.
36290 An empty reply indicates that the request is not supported by the
36294 @var{address} is encoded in hex.
36295 @var{id} and @var{extra} are strings encoded in hex.
36297 In response to each query, the target will reply with a list of one or
36298 more markers, separated by commas. @value{GDBN} will respond to each
36299 reply with a request for more markers (using the @samp{qs} form of the
36300 query), until the target responds with @samp{l} (lower-case ell, for
36303 @item qTSTMat:@var{address}
36304 This packets requests data about static tracepoint markers in the
36305 target program at @var{address}. Replies to this packet follow the
36306 syntax of the @samp{qTfSTM} and @code{qTsSTM} packets that list static
36307 tracepoint markers.
36309 @item QTSave:@var{filename}
36310 This packet directs the target to save trace data to the file name
36311 @var{filename} in the target's filesystem. @var{filename} is encoded
36312 as a hex string; the interpretation of the file name (relative vs
36313 absolute, wild cards, etc) is up to the target.
36315 @item qTBuffer:@var{offset},@var{len}
36316 Return up to @var{len} bytes of the current contents of trace buffer,
36317 starting at @var{offset}. The trace buffer is treated as if it were
36318 a contiguous collection of traceframes, as per the trace file format.
36319 The reply consists as many hex-encoded bytes as the target can deliver
36320 in a packet; it is not an error to return fewer than were asked for.
36321 A reply consisting of just @code{l} indicates that no bytes are
36324 @item QTBuffer:circular:@var{value}
36325 This packet directs the target to use a circular trace buffer if
36326 @var{value} is 1, or a linear buffer if the value is 0.
36328 @item QTNotes:@r{[}@var{type}:@var{text}@r{]}@r{[};@var{type}:@var{text}@r{]}@dots{}
36329 This packet adds optional textual notes to the trace run. Allowable
36330 types include @code{user}, @code{notes}, and @code{tstop}, the
36331 @var{text} fields are arbitrary strings, hex-encoded.
36335 @subsection Relocate instruction reply packet
36336 When installing fast tracepoints in memory, the target may need to
36337 relocate the instruction currently at the tracepoint address to a
36338 different address in memory. For most instructions, a simple copy is
36339 enough, but, for example, call instructions that implicitly push the
36340 return address on the stack, and relative branches or other
36341 PC-relative instructions require offset adjustment, so that the effect
36342 of executing the instruction at a different address is the same as if
36343 it had executed in the original location.
36345 In response to several of the tracepoint packets, the target may also
36346 respond with a number of intermediate @samp{qRelocInsn} request
36347 packets before the final result packet, to have @value{GDBN} handle
36348 this relocation operation. If a packet supports this mechanism, its
36349 documentation will explicitly say so. See for example the above
36350 descriptions for the @samp{QTStart} and @samp{QTDP} packets. The
36351 format of the request is:
36354 @item qRelocInsn:@var{from};@var{to}
36356 This requests @value{GDBN} to copy instruction at address @var{from}
36357 to address @var{to}, possibly adjusted so that executing the
36358 instruction at @var{to} has the same effect as executing it at
36359 @var{from}. @value{GDBN} writes the adjusted instruction to target
36360 memory starting at @var{to}.
36365 @item qRelocInsn:@var{adjusted_size}
36366 Informs the stub the relocation is complete. @var{adjusted_size} is
36367 the length in bytes of resulting relocated instruction sequence.
36369 A badly formed request was detected, or an error was encountered while
36370 relocating the instruction.
36373 @node Host I/O Packets
36374 @section Host I/O Packets
36375 @cindex Host I/O, remote protocol
36376 @cindex file transfer, remote protocol
36378 The @dfn{Host I/O} packets allow @value{GDBN} to perform I/O
36379 operations on the far side of a remote link. For example, Host I/O is
36380 used to upload and download files to a remote target with its own
36381 filesystem. Host I/O uses the same constant values and data structure
36382 layout as the target-initiated File-I/O protocol. However, the
36383 Host I/O packets are structured differently. The target-initiated
36384 protocol relies on target memory to store parameters and buffers.
36385 Host I/O requests are initiated by @value{GDBN}, and the
36386 target's memory is not involved. @xref{File-I/O Remote Protocol
36387 Extension}, for more details on the target-initiated protocol.
36389 The Host I/O request packets all encode a single operation along with
36390 its arguments. They have this format:
36394 @item vFile:@var{operation}: @var{parameter}@dots{}
36395 @var{operation} is the name of the particular request; the target
36396 should compare the entire packet name up to the second colon when checking
36397 for a supported operation. The format of @var{parameter} depends on
36398 the operation. Numbers are always passed in hexadecimal. Negative
36399 numbers have an explicit minus sign (i.e.@: two's complement is not
36400 used). Strings (e.g.@: filenames) are encoded as a series of
36401 hexadecimal bytes. The last argument to a system call may be a
36402 buffer of escaped binary data (@pxref{Binary Data}).
36406 The valid responses to Host I/O packets are:
36410 @item F @var{result} [, @var{errno}] [; @var{attachment}]
36411 @var{result} is the integer value returned by this operation, usually
36412 non-negative for success and -1 for errors. If an error has occured,
36413 @var{errno} will be included in the result. @var{errno} will have a
36414 value defined by the File-I/O protocol (@pxref{Errno Values}). For
36415 operations which return data, @var{attachment} supplies the data as a
36416 binary buffer. Binary buffers in response packets are escaped in the
36417 normal way (@pxref{Binary Data}). See the individual packet
36418 documentation for the interpretation of @var{result} and
36422 An empty response indicates that this operation is not recognized.
36426 These are the supported Host I/O operations:
36429 @item vFile:open: @var{pathname}, @var{flags}, @var{mode}
36430 Open a file at @var{pathname} and return a file descriptor for it, or
36431 return -1 if an error occurs. @var{pathname} is a string,
36432 @var{flags} is an integer indicating a mask of open flags
36433 (@pxref{Open Flags}), and @var{mode} is an integer indicating a mask
36434 of mode bits to use if the file is created (@pxref{mode_t Values}).
36435 @xref{open}, for details of the open flags and mode values.
36437 @item vFile:close: @var{fd}
36438 Close the open file corresponding to @var{fd} and return 0, or
36439 -1 if an error occurs.
36441 @item vFile:pread: @var{fd}, @var{count}, @var{offset}
36442 Read data from the open file corresponding to @var{fd}. Up to
36443 @var{count} bytes will be read from the file, starting at @var{offset}
36444 relative to the start of the file. The target may read fewer bytes;
36445 common reasons include packet size limits and an end-of-file
36446 condition. The number of bytes read is returned. Zero should only be
36447 returned for a successful read at the end of the file, or if
36448 @var{count} was zero.
36450 The data read should be returned as a binary attachment on success.
36451 If zero bytes were read, the response should include an empty binary
36452 attachment (i.e.@: a trailing semicolon). The return value is the
36453 number of target bytes read; the binary attachment may be longer if
36454 some characters were escaped.
36456 @item vFile:pwrite: @var{fd}, @var{offset}, @var{data}
36457 Write @var{data} (a binary buffer) to the open file corresponding
36458 to @var{fd}. Start the write at @var{offset} from the start of the
36459 file. Unlike many @code{write} system calls, there is no
36460 separate @var{count} argument; the length of @var{data} in the
36461 packet is used. @samp{vFile:write} returns the number of bytes written,
36462 which may be shorter than the length of @var{data}, or -1 if an
36465 @item vFile:unlink: @var{pathname}
36466 Delete the file at @var{pathname} on the target. Return 0,
36467 or -1 if an error occurs. @var{pathname} is a string.
36469 @item vFile:readlink: @var{filename}
36470 Read value of symbolic link @var{filename} on the target. Return
36471 the number of bytes read, or -1 if an error occurs.
36473 The data read should be returned as a binary attachment on success.
36474 If zero bytes were read, the response should include an empty binary
36475 attachment (i.e.@: a trailing semicolon). The return value is the
36476 number of target bytes read; the binary attachment may be longer if
36477 some characters were escaped.
36482 @section Interrupts
36483 @cindex interrupts (remote protocol)
36485 When a program on the remote target is running, @value{GDBN} may
36486 attempt to interrupt it by sending a @samp{Ctrl-C}, @code{BREAK} or
36487 a @code{BREAK} followed by @code{g},
36488 control of which is specified via @value{GDBN}'s @samp{interrupt-sequence}.
36490 The precise meaning of @code{BREAK} is defined by the transport
36491 mechanism and may, in fact, be undefined. @value{GDBN} does not
36492 currently define a @code{BREAK} mechanism for any of the network
36493 interfaces except for TCP, in which case @value{GDBN} sends the
36494 @code{telnet} BREAK sequence.
36496 @samp{Ctrl-C}, on the other hand, is defined and implemented for all
36497 transport mechanisms. It is represented by sending the single byte
36498 @code{0x03} without any of the usual packet overhead described in
36499 the Overview section (@pxref{Overview}). When a @code{0x03} byte is
36500 transmitted as part of a packet, it is considered to be packet data
36501 and does @emph{not} represent an interrupt. E.g., an @samp{X} packet
36502 (@pxref{X packet}), used for binary downloads, may include an unescaped
36503 @code{0x03} as part of its packet.
36505 @code{BREAK} followed by @code{g} is also known as Magic SysRq g.
36506 When Linux kernel receives this sequence from serial port,
36507 it stops execution and connects to gdb.
36509 Stubs are not required to recognize these interrupt mechanisms and the
36510 precise meaning associated with receipt of the interrupt is
36511 implementation defined. If the target supports debugging of multiple
36512 threads and/or processes, it should attempt to interrupt all
36513 currently-executing threads and processes.
36514 If the stub is successful at interrupting the
36515 running program, it should send one of the stop
36516 reply packets (@pxref{Stop Reply Packets}) to @value{GDBN} as a result
36517 of successfully stopping the program in all-stop mode, and a stop reply
36518 for each stopped thread in non-stop mode.
36519 Interrupts received while the
36520 program is stopped are discarded.
36522 @node Notification Packets
36523 @section Notification Packets
36524 @cindex notification packets
36525 @cindex packets, notification
36527 The @value{GDBN} remote serial protocol includes @dfn{notifications},
36528 packets that require no acknowledgment. Both the GDB and the stub
36529 may send notifications (although the only notifications defined at
36530 present are sent by the stub). Notifications carry information
36531 without incurring the round-trip latency of an acknowledgment, and so
36532 are useful for low-impact communications where occasional packet loss
36535 A notification packet has the form @samp{% @var{data} #
36536 @var{checksum}}, where @var{data} is the content of the notification,
36537 and @var{checksum} is a checksum of @var{data}, computed and formatted
36538 as for ordinary @value{GDBN} packets. A notification's @var{data}
36539 never contains @samp{$}, @samp{%} or @samp{#} characters. Upon
36540 receiving a notification, the recipient sends no @samp{+} or @samp{-}
36541 to acknowledge the notification's receipt or to report its corruption.
36543 Every notification's @var{data} begins with a name, which contains no
36544 colon characters, followed by a colon character.
36546 Recipients should silently ignore corrupted notifications and
36547 notifications they do not understand. Recipients should restart
36548 timeout periods on receipt of a well-formed notification, whether or
36549 not they understand it.
36551 Senders should only send the notifications described here when this
36552 protocol description specifies that they are permitted. In the
36553 future, we may extend the protocol to permit existing notifications in
36554 new contexts; this rule helps older senders avoid confusing newer
36557 (Older versions of @value{GDBN} ignore bytes received until they see
36558 the @samp{$} byte that begins an ordinary packet, so new stubs may
36559 transmit notifications without fear of confusing older clients. There
36560 are no notifications defined for @value{GDBN} to send at the moment, but we
36561 assume that most older stubs would ignore them, as well.)
36563 The following notification packets from the stub to @value{GDBN} are
36567 @item Stop: @var{reply}
36568 Report an asynchronous stop event in non-stop mode.
36569 The @var{reply} has the form of a stop reply, as
36570 described in @ref{Stop Reply Packets}. Refer to @ref{Remote Non-Stop},
36571 for information on how these notifications are acknowledged by
36575 @node Remote Non-Stop
36576 @section Remote Protocol Support for Non-Stop Mode
36578 @value{GDBN}'s remote protocol supports non-stop debugging of
36579 multi-threaded programs, as described in @ref{Non-Stop Mode}. If the stub
36580 supports non-stop mode, it should report that to @value{GDBN} by including
36581 @samp{QNonStop+} in its @samp{qSupported} response (@pxref{qSupported}).
36583 @value{GDBN} typically sends a @samp{QNonStop} packet only when
36584 establishing a new connection with the stub. Entering non-stop mode
36585 does not alter the state of any currently-running threads, but targets
36586 must stop all threads in any already-attached processes when entering
36587 all-stop mode. @value{GDBN} uses the @samp{?} packet as necessary to
36588 probe the target state after a mode change.
36590 In non-stop mode, when an attached process encounters an event that
36591 would otherwise be reported with a stop reply, it uses the
36592 asynchronous notification mechanism (@pxref{Notification Packets}) to
36593 inform @value{GDBN}. In contrast to all-stop mode, where all threads
36594 in all processes are stopped when a stop reply is sent, in non-stop
36595 mode only the thread reporting the stop event is stopped. That is,
36596 when reporting a @samp{S} or @samp{T} response to indicate completion
36597 of a step operation, hitting a breakpoint, or a fault, only the
36598 affected thread is stopped; any other still-running threads continue
36599 to run. When reporting a @samp{W} or @samp{X} response, all running
36600 threads belonging to other attached processes continue to run.
36602 Only one stop reply notification at a time may be pending; if
36603 additional stop events occur before @value{GDBN} has acknowledged the
36604 previous notification, they must be queued by the stub for later
36605 synchronous transmission in response to @samp{vStopped} packets from
36606 @value{GDBN}. Because the notification mechanism is unreliable,
36607 the stub is permitted to resend a stop reply notification
36608 if it believes @value{GDBN} may not have received it. @value{GDBN}
36609 ignores additional stop reply notifications received before it has
36610 finished processing a previous notification and the stub has completed
36611 sending any queued stop events.
36613 Otherwise, @value{GDBN} must be prepared to receive a stop reply
36614 notification at any time. Specifically, they may appear when
36615 @value{GDBN} is not otherwise reading input from the stub, or when
36616 @value{GDBN} is expecting to read a normal synchronous response or a
36617 @samp{+}/@samp{-} acknowledgment to a packet it has sent.
36618 Notification packets are distinct from any other communication from
36619 the stub so there is no ambiguity.
36621 After receiving a stop reply notification, @value{GDBN} shall
36622 acknowledge it by sending a @samp{vStopped} packet (@pxref{vStopped packet})
36623 as a regular, synchronous request to the stub. Such acknowledgment
36624 is not required to happen immediately, as @value{GDBN} is permitted to
36625 send other, unrelated packets to the stub first, which the stub should
36628 Upon receiving a @samp{vStopped} packet, if the stub has other queued
36629 stop events to report to @value{GDBN}, it shall respond by sending a
36630 normal stop reply response. @value{GDBN} shall then send another
36631 @samp{vStopped} packet to solicit further responses; again, it is
36632 permitted to send other, unrelated packets as well which the stub
36633 should process normally.
36635 If the stub receives a @samp{vStopped} packet and there are no
36636 additional stop events to report, the stub shall return an @samp{OK}
36637 response. At this point, if further stop events occur, the stub shall
36638 send a new stop reply notification, @value{GDBN} shall accept the
36639 notification, and the process shall be repeated.
36641 In non-stop mode, the target shall respond to the @samp{?} packet as
36642 follows. First, any incomplete stop reply notification/@samp{vStopped}
36643 sequence in progress is abandoned. The target must begin a new
36644 sequence reporting stop events for all stopped threads, whether or not
36645 it has previously reported those events to @value{GDBN}. The first
36646 stop reply is sent as a synchronous reply to the @samp{?} packet, and
36647 subsequent stop replies are sent as responses to @samp{vStopped} packets
36648 using the mechanism described above. The target must not send
36649 asynchronous stop reply notifications until the sequence is complete.
36650 If all threads are running when the target receives the @samp{?} packet,
36651 or if the target is not attached to any process, it shall respond
36654 @node Packet Acknowledgment
36655 @section Packet Acknowledgment
36657 @cindex acknowledgment, for @value{GDBN} remote
36658 @cindex packet acknowledgment, for @value{GDBN} remote
36659 By default, when either the host or the target machine receives a packet,
36660 the first response expected is an acknowledgment: either @samp{+} (to indicate
36661 the package was received correctly) or @samp{-} (to request retransmission).
36662 This mechanism allows the @value{GDBN} remote protocol to operate over
36663 unreliable transport mechanisms, such as a serial line.
36665 In cases where the transport mechanism is itself reliable (such as a pipe or
36666 TCP connection), the @samp{+}/@samp{-} acknowledgments are redundant.
36667 It may be desirable to disable them in that case to reduce communication
36668 overhead, or for other reasons. This can be accomplished by means of the
36669 @samp{QStartNoAckMode} packet; @pxref{QStartNoAckMode}.
36671 When in no-acknowledgment mode, neither the stub nor @value{GDBN} shall send or
36672 expect @samp{+}/@samp{-} protocol acknowledgments. The packet
36673 and response format still includes the normal checksum, as described in
36674 @ref{Overview}, but the checksum may be ignored by the receiver.
36676 If the stub supports @samp{QStartNoAckMode} and prefers to operate in
36677 no-acknowledgment mode, it should report that to @value{GDBN}
36678 by including @samp{QStartNoAckMode+} in its response to @samp{qSupported};
36679 @pxref{qSupported}.
36680 If @value{GDBN} also supports @samp{QStartNoAckMode} and it has not been
36681 disabled via the @code{set remote noack-packet off} command
36682 (@pxref{Remote Configuration}),
36683 @value{GDBN} may then send a @samp{QStartNoAckMode} packet to the stub.
36684 Only then may the stub actually turn off packet acknowledgments.
36685 @value{GDBN} sends a final @samp{+} acknowledgment of the stub's @samp{OK}
36686 response, which can be safely ignored by the stub.
36688 Note that @code{set remote noack-packet} command only affects negotiation
36689 between @value{GDBN} and the stub when subsequent connections are made;
36690 it does not affect the protocol acknowledgment state for any current
36692 Since @samp{+}/@samp{-} acknowledgments are enabled by default when a
36693 new connection is established,
36694 there is also no protocol request to re-enable the acknowledgments
36695 for the current connection, once disabled.
36700 Example sequence of a target being re-started. Notice how the restart
36701 does not get any direct output:
36706 @emph{target restarts}
36709 <- @code{T001:1234123412341234}
36713 Example sequence of a target being stepped by a single instruction:
36716 -> @code{G1445@dots{}}
36721 <- @code{T001:1234123412341234}
36725 <- @code{1455@dots{}}
36729 @node File-I/O Remote Protocol Extension
36730 @section File-I/O Remote Protocol Extension
36731 @cindex File-I/O remote protocol extension
36734 * File-I/O Overview::
36735 * Protocol Basics::
36736 * The F Request Packet::
36737 * The F Reply Packet::
36738 * The Ctrl-C Message::
36740 * List of Supported Calls::
36741 * Protocol-specific Representation of Datatypes::
36743 * File-I/O Examples::
36746 @node File-I/O Overview
36747 @subsection File-I/O Overview
36748 @cindex file-i/o overview
36750 The @dfn{File I/O remote protocol extension} (short: File-I/O) allows the
36751 target to use the host's file system and console I/O to perform various
36752 system calls. System calls on the target system are translated into a
36753 remote protocol packet to the host system, which then performs the needed
36754 actions and returns a response packet to the target system.
36755 This simulates file system operations even on targets that lack file systems.
36757 The protocol is defined to be independent of both the host and target systems.
36758 It uses its own internal representation of datatypes and values. Both
36759 @value{GDBN} and the target's @value{GDBN} stub are responsible for
36760 translating the system-dependent value representations into the internal
36761 protocol representations when data is transmitted.
36763 The communication is synchronous. A system call is possible only when
36764 @value{GDBN} is waiting for a response from the @samp{C}, @samp{c}, @samp{S}
36765 or @samp{s} packets. While @value{GDBN} handles the request for a system call,
36766 the target is stopped to allow deterministic access to the target's
36767 memory. Therefore File-I/O is not interruptible by target signals. On
36768 the other hand, it is possible to interrupt File-I/O by a user interrupt
36769 (@samp{Ctrl-C}) within @value{GDBN}.
36771 The target's request to perform a host system call does not finish
36772 the latest @samp{C}, @samp{c}, @samp{S} or @samp{s} action. That means,
36773 after finishing the system call, the target returns to continuing the
36774 previous activity (continue, step). No additional continue or step
36775 request from @value{GDBN} is required.
36778 (@value{GDBP}) continue
36779 <- target requests 'system call X'
36780 target is stopped, @value{GDBN} executes system call
36781 -> @value{GDBN} returns result
36782 ... target continues, @value{GDBN} returns to wait for the target
36783 <- target hits breakpoint and sends a Txx packet
36786 The protocol only supports I/O on the console and to regular files on
36787 the host file system. Character or block special devices, pipes,
36788 named pipes, sockets or any other communication method on the host
36789 system are not supported by this protocol.
36791 File I/O is not supported in non-stop mode.
36793 @node Protocol Basics
36794 @subsection Protocol Basics
36795 @cindex protocol basics, file-i/o
36797 The File-I/O protocol uses the @code{F} packet as the request as well
36798 as reply packet. Since a File-I/O system call can only occur when
36799 @value{GDBN} is waiting for a response from the continuing or stepping target,
36800 the File-I/O request is a reply that @value{GDBN} has to expect as a result
36801 of a previous @samp{C}, @samp{c}, @samp{S} or @samp{s} packet.
36802 This @code{F} packet contains all information needed to allow @value{GDBN}
36803 to call the appropriate host system call:
36807 A unique identifier for the requested system call.
36810 All parameters to the system call. Pointers are given as addresses
36811 in the target memory address space. Pointers to strings are given as
36812 pointer/length pair. Numerical values are given as they are.
36813 Numerical control flags are given in a protocol-specific representation.
36817 At this point, @value{GDBN} has to perform the following actions.
36821 If the parameters include pointer values to data needed as input to a
36822 system call, @value{GDBN} requests this data from the target with a
36823 standard @code{m} packet request. This additional communication has to be
36824 expected by the target implementation and is handled as any other @code{m}
36828 @value{GDBN} translates all value from protocol representation to host
36829 representation as needed. Datatypes are coerced into the host types.
36832 @value{GDBN} calls the system call.
36835 It then coerces datatypes back to protocol representation.
36838 If the system call is expected to return data in buffer space specified
36839 by pointer parameters to the call, the data is transmitted to the
36840 target using a @code{M} or @code{X} packet. This packet has to be expected
36841 by the target implementation and is handled as any other @code{M} or @code{X}
36846 Eventually @value{GDBN} replies with another @code{F} packet which contains all
36847 necessary information for the target to continue. This at least contains
36854 @code{errno}, if has been changed by the system call.
36861 After having done the needed type and value coercion, the target continues
36862 the latest continue or step action.
36864 @node The F Request Packet
36865 @subsection The @code{F} Request Packet
36866 @cindex file-i/o request packet
36867 @cindex @code{F} request packet
36869 The @code{F} request packet has the following format:
36872 @item F@var{call-id},@var{parameter@dots{}}
36874 @var{call-id} is the identifier to indicate the host system call to be called.
36875 This is just the name of the function.
36877 @var{parameter@dots{}} are the parameters to the system call.
36878 Parameters are hexadecimal integer values, either the actual values in case
36879 of scalar datatypes, pointers to target buffer space in case of compound
36880 datatypes and unspecified memory areas, or pointer/length pairs in case
36881 of string parameters. These are appended to the @var{call-id} as a
36882 comma-delimited list. All values are transmitted in ASCII
36883 string representation, pointer/length pairs separated by a slash.
36889 @node The F Reply Packet
36890 @subsection The @code{F} Reply Packet
36891 @cindex file-i/o reply packet
36892 @cindex @code{F} reply packet
36894 The @code{F} reply packet has the following format:
36898 @item F@var{retcode},@var{errno},@var{Ctrl-C flag};@var{call-specific attachment}
36900 @var{retcode} is the return code of the system call as hexadecimal value.
36902 @var{errno} is the @code{errno} set by the call, in protocol-specific
36904 This parameter can be omitted if the call was successful.
36906 @var{Ctrl-C flag} is only sent if the user requested a break. In this
36907 case, @var{errno} must be sent as well, even if the call was successful.
36908 The @var{Ctrl-C flag} itself consists of the character @samp{C}:
36915 or, if the call was interrupted before the host call has been performed:
36922 assuming 4 is the protocol-specific representation of @code{EINTR}.
36927 @node The Ctrl-C Message
36928 @subsection The @samp{Ctrl-C} Message
36929 @cindex ctrl-c message, in file-i/o protocol
36931 If the @samp{Ctrl-C} flag is set in the @value{GDBN}
36932 reply packet (@pxref{The F Reply Packet}),
36933 the target should behave as if it had
36934 gotten a break message. The meaning for the target is ``system call
36935 interrupted by @code{SIGINT}''. Consequentially, the target should actually stop
36936 (as with a break message) and return to @value{GDBN} with a @code{T02}
36939 It's important for the target to know in which
36940 state the system call was interrupted. There are two possible cases:
36944 The system call hasn't been performed on the host yet.
36947 The system call on the host has been finished.
36951 These two states can be distinguished by the target by the value of the
36952 returned @code{errno}. If it's the protocol representation of @code{EINTR}, the system
36953 call hasn't been performed. This is equivalent to the @code{EINTR} handling
36954 on POSIX systems. In any other case, the target may presume that the
36955 system call has been finished --- successfully or not --- and should behave
36956 as if the break message arrived right after the system call.
36958 @value{GDBN} must behave reliably. If the system call has not been called
36959 yet, @value{GDBN} may send the @code{F} reply immediately, setting @code{EINTR} as
36960 @code{errno} in the packet. If the system call on the host has been finished
36961 before the user requests a break, the full action must be finished by
36962 @value{GDBN}. This requires sending @code{M} or @code{X} packets as necessary.
36963 The @code{F} packet may only be sent when either nothing has happened
36964 or the full action has been completed.
36967 @subsection Console I/O
36968 @cindex console i/o as part of file-i/o
36970 By default and if not explicitly closed by the target system, the file
36971 descriptors 0, 1 and 2 are connected to the @value{GDBN} console. Output
36972 on the @value{GDBN} console is handled as any other file output operation
36973 (@code{write(1, @dots{})} or @code{write(2, @dots{})}). Console input is handled
36974 by @value{GDBN} so that after the target read request from file descriptor
36975 0 all following typing is buffered until either one of the following
36980 The user types @kbd{Ctrl-c}. The behaviour is as explained above, and the
36982 system call is treated as finished.
36985 The user presses @key{RET}. This is treated as end of input with a trailing
36989 The user types @kbd{Ctrl-d}. This is treated as end of input. No trailing
36990 character (neither newline nor @samp{Ctrl-D}) is appended to the input.
36994 If the user has typed more characters than fit in the buffer given to
36995 the @code{read} call, the trailing characters are buffered in @value{GDBN} until
36996 either another @code{read(0, @dots{})} is requested by the target, or debugging
36997 is stopped at the user's request.
37000 @node List of Supported Calls
37001 @subsection List of Supported Calls
37002 @cindex list of supported file-i/o calls
37019 @unnumberedsubsubsec open
37020 @cindex open, file-i/o system call
37025 int open(const char *pathname, int flags);
37026 int open(const char *pathname, int flags, mode_t mode);
37030 @samp{Fopen,@var{pathptr}/@var{len},@var{flags},@var{mode}}
37033 @var{flags} is the bitwise @code{OR} of the following values:
37037 If the file does not exist it will be created. The host
37038 rules apply as far as file ownership and time stamps
37042 When used with @code{O_CREAT}, if the file already exists it is
37043 an error and open() fails.
37046 If the file already exists and the open mode allows
37047 writing (@code{O_RDWR} or @code{O_WRONLY} is given) it will be
37048 truncated to zero length.
37051 The file is opened in append mode.
37054 The file is opened for reading only.
37057 The file is opened for writing only.
37060 The file is opened for reading and writing.
37064 Other bits are silently ignored.
37068 @var{mode} is the bitwise @code{OR} of the following values:
37072 User has read permission.
37075 User has write permission.
37078 Group has read permission.
37081 Group has write permission.
37084 Others have read permission.
37087 Others have write permission.
37091 Other bits are silently ignored.
37094 @item Return value:
37095 @code{open} returns the new file descriptor or -1 if an error
37102 @var{pathname} already exists and @code{O_CREAT} and @code{O_EXCL} were used.
37105 @var{pathname} refers to a directory.
37108 The requested access is not allowed.
37111 @var{pathname} was too long.
37114 A directory component in @var{pathname} does not exist.
37117 @var{pathname} refers to a device, pipe, named pipe or socket.
37120 @var{pathname} refers to a file on a read-only filesystem and
37121 write access was requested.
37124 @var{pathname} is an invalid pointer value.
37127 No space on device to create the file.
37130 The process already has the maximum number of files open.
37133 The limit on the total number of files open on the system
37137 The call was interrupted by the user.
37143 @unnumberedsubsubsec close
37144 @cindex close, file-i/o system call
37153 @samp{Fclose,@var{fd}}
37155 @item Return value:
37156 @code{close} returns zero on success, or -1 if an error occurred.
37162 @var{fd} isn't a valid open file descriptor.
37165 The call was interrupted by the user.
37171 @unnumberedsubsubsec read
37172 @cindex read, file-i/o system call
37177 int read(int fd, void *buf, unsigned int count);
37181 @samp{Fread,@var{fd},@var{bufptr},@var{count}}
37183 @item Return value:
37184 On success, the number of bytes read is returned.
37185 Zero indicates end of file. If count is zero, read
37186 returns zero as well. On error, -1 is returned.
37192 @var{fd} is not a valid file descriptor or is not open for
37196 @var{bufptr} is an invalid pointer value.
37199 The call was interrupted by the user.
37205 @unnumberedsubsubsec write
37206 @cindex write, file-i/o system call
37211 int write(int fd, const void *buf, unsigned int count);
37215 @samp{Fwrite,@var{fd},@var{bufptr},@var{count}}
37217 @item Return value:
37218 On success, the number of bytes written are returned.
37219 Zero indicates nothing was written. On error, -1
37226 @var{fd} is not a valid file descriptor or is not open for
37230 @var{bufptr} is an invalid pointer value.
37233 An attempt was made to write a file that exceeds the
37234 host-specific maximum file size allowed.
37237 No space on device to write the data.
37240 The call was interrupted by the user.
37246 @unnumberedsubsubsec lseek
37247 @cindex lseek, file-i/o system call
37252 long lseek (int fd, long offset, int flag);
37256 @samp{Flseek,@var{fd},@var{offset},@var{flag}}
37258 @var{flag} is one of:
37262 The offset is set to @var{offset} bytes.
37265 The offset is set to its current location plus @var{offset}
37269 The offset is set to the size of the file plus @var{offset}
37273 @item Return value:
37274 On success, the resulting unsigned offset in bytes from
37275 the beginning of the file is returned. Otherwise, a
37276 value of -1 is returned.
37282 @var{fd} is not a valid open file descriptor.
37285 @var{fd} is associated with the @value{GDBN} console.
37288 @var{flag} is not a proper value.
37291 The call was interrupted by the user.
37297 @unnumberedsubsubsec rename
37298 @cindex rename, file-i/o system call
37303 int rename(const char *oldpath, const char *newpath);
37307 @samp{Frename,@var{oldpathptr}/@var{len},@var{newpathptr}/@var{len}}
37309 @item Return value:
37310 On success, zero is returned. On error, -1 is returned.
37316 @var{newpath} is an existing directory, but @var{oldpath} is not a
37320 @var{newpath} is a non-empty directory.
37323 @var{oldpath} or @var{newpath} is a directory that is in use by some
37327 An attempt was made to make a directory a subdirectory
37331 A component used as a directory in @var{oldpath} or new
37332 path is not a directory. Or @var{oldpath} is a directory
37333 and @var{newpath} exists but is not a directory.
37336 @var{oldpathptr} or @var{newpathptr} are invalid pointer values.
37339 No access to the file or the path of the file.
37343 @var{oldpath} or @var{newpath} was too long.
37346 A directory component in @var{oldpath} or @var{newpath} does not exist.
37349 The file is on a read-only filesystem.
37352 The device containing the file has no room for the new
37356 The call was interrupted by the user.
37362 @unnumberedsubsubsec unlink
37363 @cindex unlink, file-i/o system call
37368 int unlink(const char *pathname);
37372 @samp{Funlink,@var{pathnameptr}/@var{len}}
37374 @item Return value:
37375 On success, zero is returned. On error, -1 is returned.
37381 No access to the file or the path of the file.
37384 The system does not allow unlinking of directories.
37387 The file @var{pathname} cannot be unlinked because it's
37388 being used by another process.
37391 @var{pathnameptr} is an invalid pointer value.
37394 @var{pathname} was too long.
37397 A directory component in @var{pathname} does not exist.
37400 A component of the path is not a directory.
37403 The file is on a read-only filesystem.
37406 The call was interrupted by the user.
37412 @unnumberedsubsubsec stat/fstat
37413 @cindex fstat, file-i/o system call
37414 @cindex stat, file-i/o system call
37419 int stat(const char *pathname, struct stat *buf);
37420 int fstat(int fd, struct stat *buf);
37424 @samp{Fstat,@var{pathnameptr}/@var{len},@var{bufptr}}@*
37425 @samp{Ffstat,@var{fd},@var{bufptr}}
37427 @item Return value:
37428 On success, zero is returned. On error, -1 is returned.
37434 @var{fd} is not a valid open file.
37437 A directory component in @var{pathname} does not exist or the
37438 path is an empty string.
37441 A component of the path is not a directory.
37444 @var{pathnameptr} is an invalid pointer value.
37447 No access to the file or the path of the file.
37450 @var{pathname} was too long.
37453 The call was interrupted by the user.
37459 @unnumberedsubsubsec gettimeofday
37460 @cindex gettimeofday, file-i/o system call
37465 int gettimeofday(struct timeval *tv, void *tz);
37469 @samp{Fgettimeofday,@var{tvptr},@var{tzptr}}
37471 @item Return value:
37472 On success, 0 is returned, -1 otherwise.
37478 @var{tz} is a non-NULL pointer.
37481 @var{tvptr} and/or @var{tzptr} is an invalid pointer value.
37487 @unnumberedsubsubsec isatty
37488 @cindex isatty, file-i/o system call
37493 int isatty(int fd);
37497 @samp{Fisatty,@var{fd}}
37499 @item Return value:
37500 Returns 1 if @var{fd} refers to the @value{GDBN} console, 0 otherwise.
37506 The call was interrupted by the user.
37511 Note that the @code{isatty} call is treated as a special case: it returns
37512 1 to the target if the file descriptor is attached
37513 to the @value{GDBN} console, 0 otherwise. Implementing through system calls
37514 would require implementing @code{ioctl} and would be more complex than
37519 @unnumberedsubsubsec system
37520 @cindex system, file-i/o system call
37525 int system(const char *command);
37529 @samp{Fsystem,@var{commandptr}/@var{len}}
37531 @item Return value:
37532 If @var{len} is zero, the return value indicates whether a shell is
37533 available. A zero return value indicates a shell is not available.
37534 For non-zero @var{len}, the value returned is -1 on error and the
37535 return status of the command otherwise. Only the exit status of the
37536 command is returned, which is extracted from the host's @code{system}
37537 return value by calling @code{WEXITSTATUS(retval)}. In case
37538 @file{/bin/sh} could not be executed, 127 is returned.
37544 The call was interrupted by the user.
37549 @value{GDBN} takes over the full task of calling the necessary host calls
37550 to perform the @code{system} call. The return value of @code{system} on
37551 the host is simplified before it's returned
37552 to the target. Any termination signal information from the child process
37553 is discarded, and the return value consists
37554 entirely of the exit status of the called command.
37556 Due to security concerns, the @code{system} call is by default refused
37557 by @value{GDBN}. The user has to allow this call explicitly with the
37558 @code{set remote system-call-allowed 1} command.
37561 @item set remote system-call-allowed
37562 @kindex set remote system-call-allowed
37563 Control whether to allow the @code{system} calls in the File I/O
37564 protocol for the remote target. The default is zero (disabled).
37566 @item show remote system-call-allowed
37567 @kindex show remote system-call-allowed
37568 Show whether the @code{system} calls are allowed in the File I/O
37572 @node Protocol-specific Representation of Datatypes
37573 @subsection Protocol-specific Representation of Datatypes
37574 @cindex protocol-specific representation of datatypes, in file-i/o protocol
37577 * Integral Datatypes::
37579 * Memory Transfer::
37584 @node Integral Datatypes
37585 @unnumberedsubsubsec Integral Datatypes
37586 @cindex integral datatypes, in file-i/o protocol
37588 The integral datatypes used in the system calls are @code{int},
37589 @code{unsigned int}, @code{long}, @code{unsigned long},
37590 @code{mode_t}, and @code{time_t}.
37592 @code{int}, @code{unsigned int}, @code{mode_t} and @code{time_t} are
37593 implemented as 32 bit values in this protocol.
37595 @code{long} and @code{unsigned long} are implemented as 64 bit types.
37597 @xref{Limits}, for corresponding MIN and MAX values (similar to those
37598 in @file{limits.h}) to allow range checking on host and target.
37600 @code{time_t} datatypes are defined as seconds since the Epoch.
37602 All integral datatypes transferred as part of a memory read or write of a
37603 structured datatype e.g.@: a @code{struct stat} have to be given in big endian
37606 @node Pointer Values
37607 @unnumberedsubsubsec Pointer Values
37608 @cindex pointer values, in file-i/o protocol
37610 Pointers to target data are transmitted as they are. An exception
37611 is made for pointers to buffers for which the length isn't
37612 transmitted as part of the function call, namely strings. Strings
37613 are transmitted as a pointer/length pair, both as hex values, e.g.@:
37620 which is a pointer to data of length 18 bytes at position 0x1aaf.
37621 The length is defined as the full string length in bytes, including
37622 the trailing null byte. For example, the string @code{"hello world"}
37623 at address 0x123456 is transmitted as
37629 @node Memory Transfer
37630 @unnumberedsubsubsec Memory Transfer
37631 @cindex memory transfer, in file-i/o protocol
37633 Structured data which is transferred using a memory read or write (for
37634 example, a @code{struct stat}) is expected to be in a protocol-specific format
37635 with all scalar multibyte datatypes being big endian. Translation to
37636 this representation needs to be done both by the target before the @code{F}
37637 packet is sent, and by @value{GDBN} before
37638 it transfers memory to the target. Transferred pointers to structured
37639 data should point to the already-coerced data at any time.
37643 @unnumberedsubsubsec struct stat
37644 @cindex struct stat, in file-i/o protocol
37646 The buffer of type @code{struct stat} used by the target and @value{GDBN}
37647 is defined as follows:
37651 unsigned int st_dev; /* device */
37652 unsigned int st_ino; /* inode */
37653 mode_t st_mode; /* protection */
37654 unsigned int st_nlink; /* number of hard links */
37655 unsigned int st_uid; /* user ID of owner */
37656 unsigned int st_gid; /* group ID of owner */
37657 unsigned int st_rdev; /* device type (if inode device) */
37658 unsigned long st_size; /* total size, in bytes */
37659 unsigned long st_blksize; /* blocksize for filesystem I/O */
37660 unsigned long st_blocks; /* number of blocks allocated */
37661 time_t st_atime; /* time of last access */
37662 time_t st_mtime; /* time of last modification */
37663 time_t st_ctime; /* time of last change */
37667 The integral datatypes conform to the definitions given in the
37668 appropriate section (see @ref{Integral Datatypes}, for details) so this
37669 structure is of size 64 bytes.
37671 The values of several fields have a restricted meaning and/or
37677 A value of 0 represents a file, 1 the console.
37680 No valid meaning for the target. Transmitted unchanged.
37683 Valid mode bits are described in @ref{Constants}. Any other
37684 bits have currently no meaning for the target.
37689 No valid meaning for the target. Transmitted unchanged.
37694 These values have a host and file system dependent
37695 accuracy. Especially on Windows hosts, the file system may not
37696 support exact timing values.
37699 The target gets a @code{struct stat} of the above representation and is
37700 responsible for coercing it to the target representation before
37703 Note that due to size differences between the host, target, and protocol
37704 representations of @code{struct stat} members, these members could eventually
37705 get truncated on the target.
37707 @node struct timeval
37708 @unnumberedsubsubsec struct timeval
37709 @cindex struct timeval, in file-i/o protocol
37711 The buffer of type @code{struct timeval} used by the File-I/O protocol
37712 is defined as follows:
37716 time_t tv_sec; /* second */
37717 long tv_usec; /* microsecond */
37721 The integral datatypes conform to the definitions given in the
37722 appropriate section (see @ref{Integral Datatypes}, for details) so this
37723 structure is of size 8 bytes.
37726 @subsection Constants
37727 @cindex constants, in file-i/o protocol
37729 The following values are used for the constants inside of the
37730 protocol. @value{GDBN} and target are responsible for translating these
37731 values before and after the call as needed.
37742 @unnumberedsubsubsec Open Flags
37743 @cindex open flags, in file-i/o protocol
37745 All values are given in hexadecimal representation.
37757 @node mode_t Values
37758 @unnumberedsubsubsec mode_t Values
37759 @cindex mode_t values, in file-i/o protocol
37761 All values are given in octal representation.
37778 @unnumberedsubsubsec Errno Values
37779 @cindex errno values, in file-i/o protocol
37781 All values are given in decimal representation.
37806 @code{EUNKNOWN} is used as a fallback error value if a host system returns
37807 any error value not in the list of supported error numbers.
37810 @unnumberedsubsubsec Lseek Flags
37811 @cindex lseek flags, in file-i/o protocol
37820 @unnumberedsubsubsec Limits
37821 @cindex limits, in file-i/o protocol
37823 All values are given in decimal representation.
37826 INT_MIN -2147483648
37828 UINT_MAX 4294967295
37829 LONG_MIN -9223372036854775808
37830 LONG_MAX 9223372036854775807
37831 ULONG_MAX 18446744073709551615
37834 @node File-I/O Examples
37835 @subsection File-I/O Examples
37836 @cindex file-i/o examples
37838 Example sequence of a write call, file descriptor 3, buffer is at target
37839 address 0x1234, 6 bytes should be written:
37842 <- @code{Fwrite,3,1234,6}
37843 @emph{request memory read from target}
37846 @emph{return "6 bytes written"}
37850 Example sequence of a read call, file descriptor 3, buffer is at target
37851 address 0x1234, 6 bytes should be read:
37854 <- @code{Fread,3,1234,6}
37855 @emph{request memory write to target}
37856 -> @code{X1234,6:XXXXXX}
37857 @emph{return "6 bytes read"}
37861 Example sequence of a read call, call fails on the host due to invalid
37862 file descriptor (@code{EBADF}):
37865 <- @code{Fread,3,1234,6}
37869 Example sequence of a read call, user presses @kbd{Ctrl-c} before syscall on
37873 <- @code{Fread,3,1234,6}
37878 Example sequence of a read call, user presses @kbd{Ctrl-c} after syscall on
37882 <- @code{Fread,3,1234,6}
37883 -> @code{X1234,6:XXXXXX}
37887 @node Library List Format
37888 @section Library List Format
37889 @cindex library list format, remote protocol
37891 On some platforms, a dynamic loader (e.g.@: @file{ld.so}) runs in the
37892 same process as your application to manage libraries. In this case,
37893 @value{GDBN} can use the loader's symbol table and normal memory
37894 operations to maintain a list of shared libraries. On other
37895 platforms, the operating system manages loaded libraries.
37896 @value{GDBN} can not retrieve the list of currently loaded libraries
37897 through memory operations, so it uses the @samp{qXfer:libraries:read}
37898 packet (@pxref{qXfer library list read}) instead. The remote stub
37899 queries the target's operating system and reports which libraries
37902 The @samp{qXfer:libraries:read} packet returns an XML document which
37903 lists loaded libraries and their offsets. Each library has an
37904 associated name and one or more segment or section base addresses,
37905 which report where the library was loaded in memory.
37907 For the common case of libraries that are fully linked binaries, the
37908 library should have a list of segments. If the target supports
37909 dynamic linking of a relocatable object file, its library XML element
37910 should instead include a list of allocated sections. The segment or
37911 section bases are start addresses, not relocation offsets; they do not
37912 depend on the library's link-time base addresses.
37914 @value{GDBN} must be linked with the Expat library to support XML
37915 library lists. @xref{Expat}.
37917 A simple memory map, with one loaded library relocated by a single
37918 offset, looks like this:
37922 <library name="/lib/libc.so.6">
37923 <segment address="0x10000000"/>
37928 Another simple memory map, with one loaded library with three
37929 allocated sections (.text, .data, .bss), looks like this:
37933 <library name="sharedlib.o">
37934 <section address="0x10000000"/>
37935 <section address="0x20000000"/>
37936 <section address="0x30000000"/>
37941 The format of a library list is described by this DTD:
37944 <!-- library-list: Root element with versioning -->
37945 <!ELEMENT library-list (library)*>
37946 <!ATTLIST library-list version CDATA #FIXED "1.0">
37947 <!ELEMENT library (segment*, section*)>
37948 <!ATTLIST library name CDATA #REQUIRED>
37949 <!ELEMENT segment EMPTY>
37950 <!ATTLIST segment address CDATA #REQUIRED>
37951 <!ELEMENT section EMPTY>
37952 <!ATTLIST section address CDATA #REQUIRED>
37955 In addition, segments and section descriptors cannot be mixed within a
37956 single library element, and you must supply at least one segment or
37957 section for each library.
37959 @node Library List Format for SVR4 Targets
37960 @section Library List Format for SVR4 Targets
37961 @cindex library list format, remote protocol
37963 On SVR4 platforms @value{GDBN} can use the symbol table of a dynamic loader
37964 (e.g.@: @file{ld.so}) and normal memory operations to maintain a list of
37965 shared libraries. Still a special library list provided by this packet is
37966 more efficient for the @value{GDBN} remote protocol.
37968 The @samp{qXfer:libraries-svr4:read} packet returns an XML document which lists
37969 loaded libraries and their SVR4 linker parameters. For each library on SVR4
37970 target, the following parameters are reported:
37974 @code{name}, the absolute file name from the @code{l_name} field of
37975 @code{struct link_map}.
37977 @code{lm} with address of @code{struct link_map} used for TLS
37978 (Thread Local Storage) access.
37980 @code{l_addr}, the displacement as read from the field @code{l_addr} of
37981 @code{struct link_map}. For prelinked libraries this is not an absolute
37982 memory address. It is a displacement of absolute memory address against
37983 address the file was prelinked to during the library load.
37985 @code{l_ld}, which is memory address of the @code{PT_DYNAMIC} segment
37988 Additionally the single @code{main-lm} attribute specifies address of
37989 @code{struct link_map} used for the main executable. This parameter is used
37990 for TLS access and its presence is optional.
37992 @value{GDBN} must be linked with the Expat library to support XML
37993 SVR4 library lists. @xref{Expat}.
37995 A simple memory map, with two loaded libraries (which do not use prelink),
37999 <library-list-svr4 version="1.0" main-lm="0xe4f8f8">
38000 <library name="/lib/ld-linux.so.2" lm="0xe4f51c" l_addr="0xe2d000"
38002 <library name="/lib/libc.so.6" lm="0xe4fbe8" l_addr="0x154000"
38004 </library-list-svr>
38007 The format of an SVR4 library list is described by this DTD:
38010 <!-- library-list-svr4: Root element with versioning -->
38011 <!ELEMENT library-list-svr4 (library)*>
38012 <!ATTLIST library-list-svr4 version CDATA #FIXED "1.0">
38013 <!ATTLIST library-list-svr4 main-lm CDATA #IMPLIED>
38014 <!ELEMENT library EMPTY>
38015 <!ATTLIST library name CDATA #REQUIRED>
38016 <!ATTLIST library lm CDATA #REQUIRED>
38017 <!ATTLIST library l_addr CDATA #REQUIRED>
38018 <!ATTLIST library l_ld CDATA #REQUIRED>
38021 @node Memory Map Format
38022 @section Memory Map Format
38023 @cindex memory map format
38025 To be able to write into flash memory, @value{GDBN} needs to obtain a
38026 memory map from the target. This section describes the format of the
38029 The memory map is obtained using the @samp{qXfer:memory-map:read}
38030 (@pxref{qXfer memory map read}) packet and is an XML document that
38031 lists memory regions.
38033 @value{GDBN} must be linked with the Expat library to support XML
38034 memory maps. @xref{Expat}.
38036 The top-level structure of the document is shown below:
38039 <?xml version="1.0"?>
38040 <!DOCTYPE memory-map
38041 PUBLIC "+//IDN gnu.org//DTD GDB Memory Map V1.0//EN"
38042 "http://sourceware.org/gdb/gdb-memory-map.dtd">
38048 Each region can be either:
38053 A region of RAM starting at @var{addr} and extending for @var{length}
38057 <memory type="ram" start="@var{addr}" length="@var{length}"/>
38062 A region of read-only memory:
38065 <memory type="rom" start="@var{addr}" length="@var{length}"/>
38070 A region of flash memory, with erasure blocks @var{blocksize}
38074 <memory type="flash" start="@var{addr}" length="@var{length}">
38075 <property name="blocksize">@var{blocksize}</property>
38081 Regions must not overlap. @value{GDBN} assumes that areas of memory not covered
38082 by the memory map are RAM, and uses the ordinary @samp{M} and @samp{X}
38083 packets to write to addresses in such ranges.
38085 The formal DTD for memory map format is given below:
38088 <!-- ................................................... -->
38089 <!-- Memory Map XML DTD ................................ -->
38090 <!-- File: memory-map.dtd .............................. -->
38091 <!-- .................................... .............. -->
38092 <!-- memory-map.dtd -->
38093 <!-- memory-map: Root element with versioning -->
38094 <!ELEMENT memory-map (memory | property)>
38095 <!ATTLIST memory-map version CDATA #FIXED "1.0.0">
38096 <!ELEMENT memory (property)>
38097 <!-- memory: Specifies a memory region,
38098 and its type, or device. -->
38099 <!ATTLIST memory type CDATA #REQUIRED
38100 start CDATA #REQUIRED
38101 length CDATA #REQUIRED
38102 device CDATA #IMPLIED>
38103 <!-- property: Generic attribute tag -->
38104 <!ELEMENT property (#PCDATA | property)*>
38105 <!ATTLIST property name CDATA #REQUIRED>
38108 @node Thread List Format
38109 @section Thread List Format
38110 @cindex thread list format
38112 To efficiently update the list of threads and their attributes,
38113 @value{GDBN} issues the @samp{qXfer:threads:read} packet
38114 (@pxref{qXfer threads read}) and obtains the XML document with
38115 the following structure:
38118 <?xml version="1.0"?>
38120 <thread id="id" core="0">
38121 ... description ...
38126 Each @samp{thread} element must have the @samp{id} attribute that
38127 identifies the thread (@pxref{thread-id syntax}). The
38128 @samp{core} attribute, if present, specifies which processor core
38129 the thread was last executing on. The content of the of @samp{thread}
38130 element is interpreted as human-readable auxilliary information.
38132 @node Traceframe Info Format
38133 @section Traceframe Info Format
38134 @cindex traceframe info format
38136 To be able to know which objects in the inferior can be examined when
38137 inspecting a tracepoint hit, @value{GDBN} needs to obtain the list of
38138 memory ranges, registers and trace state variables that have been
38139 collected in a traceframe.
38141 This list is obtained using the @samp{qXfer:traceframe-info:read}
38142 (@pxref{qXfer traceframe info read}) packet and is an XML document.
38144 @value{GDBN} must be linked with the Expat library to support XML
38145 traceframe info discovery. @xref{Expat}.
38147 The top-level structure of the document is shown below:
38150 <?xml version="1.0"?>
38151 <!DOCTYPE traceframe-info
38152 PUBLIC "+//IDN gnu.org//DTD GDB Memory Map V1.0//EN"
38153 "http://sourceware.org/gdb/gdb-traceframe-info.dtd">
38159 Each traceframe block can be either:
38164 A region of collected memory starting at @var{addr} and extending for
38165 @var{length} bytes from there:
38168 <memory start="@var{addr}" length="@var{length}"/>
38173 The formal DTD for the traceframe info format is given below:
38176 <!ELEMENT traceframe-info (memory)* >
38177 <!ATTLIST traceframe-info version CDATA #FIXED "1.0">
38179 <!ELEMENT memory EMPTY>
38180 <!ATTLIST memory start CDATA #REQUIRED
38181 length CDATA #REQUIRED>
38184 @include agentexpr.texi
38186 @node Target Descriptions
38187 @appendix Target Descriptions
38188 @cindex target descriptions
38190 One of the challenges of using @value{GDBN} to debug embedded systems
38191 is that there are so many minor variants of each processor
38192 architecture in use. It is common practice for vendors to start with
38193 a standard processor core --- ARM, PowerPC, or MIPS, for example ---
38194 and then make changes to adapt it to a particular market niche. Some
38195 architectures have hundreds of variants, available from dozens of
38196 vendors. This leads to a number of problems:
38200 With so many different customized processors, it is difficult for
38201 the @value{GDBN} maintainers to keep up with the changes.
38203 Since individual variants may have short lifetimes or limited
38204 audiences, it may not be worthwhile to carry information about every
38205 variant in the @value{GDBN} source tree.
38207 When @value{GDBN} does support the architecture of the embedded system
38208 at hand, the task of finding the correct architecture name to give the
38209 @command{set architecture} command can be error-prone.
38212 To address these problems, the @value{GDBN} remote protocol allows a
38213 target system to not only identify itself to @value{GDBN}, but to
38214 actually describe its own features. This lets @value{GDBN} support
38215 processor variants it has never seen before --- to the extent that the
38216 descriptions are accurate, and that @value{GDBN} understands them.
38218 @value{GDBN} must be linked with the Expat library to support XML
38219 target descriptions. @xref{Expat}.
38222 * Retrieving Descriptions:: How descriptions are fetched from a target.
38223 * Target Description Format:: The contents of a target description.
38224 * Predefined Target Types:: Standard types available for target
38226 * Standard Target Features:: Features @value{GDBN} knows about.
38229 @node Retrieving Descriptions
38230 @section Retrieving Descriptions
38232 Target descriptions can be read from the target automatically, or
38233 specified by the user manually. The default behavior is to read the
38234 description from the target. @value{GDBN} retrieves it via the remote
38235 protocol using @samp{qXfer} requests (@pxref{General Query Packets,
38236 qXfer}). The @var{annex} in the @samp{qXfer} packet will be
38237 @samp{target.xml}. The contents of the @samp{target.xml} annex are an
38238 XML document, of the form described in @ref{Target Description
38241 Alternatively, you can specify a file to read for the target description.
38242 If a file is set, the target will not be queried. The commands to
38243 specify a file are:
38246 @cindex set tdesc filename
38247 @item set tdesc filename @var{path}
38248 Read the target description from @var{path}.
38250 @cindex unset tdesc filename
38251 @item unset tdesc filename
38252 Do not read the XML target description from a file. @value{GDBN}
38253 will use the description supplied by the current target.
38255 @cindex show tdesc filename
38256 @item show tdesc filename
38257 Show the filename to read for a target description, if any.
38261 @node Target Description Format
38262 @section Target Description Format
38263 @cindex target descriptions, XML format
38265 A target description annex is an @uref{http://www.w3.org/XML/, XML}
38266 document which complies with the Document Type Definition provided in
38267 the @value{GDBN} sources in @file{gdb/features/gdb-target.dtd}. This
38268 means you can use generally available tools like @command{xmllint} to
38269 check that your feature descriptions are well-formed and valid.
38270 However, to help people unfamiliar with XML write descriptions for
38271 their targets, we also describe the grammar here.
38273 Target descriptions can identify the architecture of the remote target
38274 and (for some architectures) provide information about custom register
38275 sets. They can also identify the OS ABI of the remote target.
38276 @value{GDBN} can use this information to autoconfigure for your
38277 target, or to warn you if you connect to an unsupported target.
38279 Here is a simple target description:
38282 <target version="1.0">
38283 <architecture>i386:x86-64</architecture>
38288 This minimal description only says that the target uses
38289 the x86-64 architecture.
38291 A target description has the following overall form, with [ ] marking
38292 optional elements and @dots{} marking repeatable elements. The elements
38293 are explained further below.
38296 <?xml version="1.0"?>
38297 <!DOCTYPE target SYSTEM "gdb-target.dtd">
38298 <target version="1.0">
38299 @r{[}@var{architecture}@r{]}
38300 @r{[}@var{osabi}@r{]}
38301 @r{[}@var{compatible}@r{]}
38302 @r{[}@var{feature}@dots{}@r{]}
38307 The description is generally insensitive to whitespace and line
38308 breaks, under the usual common-sense rules. The XML version
38309 declaration and document type declaration can generally be omitted
38310 (@value{GDBN} does not require them), but specifying them may be
38311 useful for XML validation tools. The @samp{version} attribute for
38312 @samp{<target>} may also be omitted, but we recommend
38313 including it; if future versions of @value{GDBN} use an incompatible
38314 revision of @file{gdb-target.dtd}, they will detect and report
38315 the version mismatch.
38317 @subsection Inclusion
38318 @cindex target descriptions, inclusion
38321 @cindex <xi:include>
38324 It can sometimes be valuable to split a target description up into
38325 several different annexes, either for organizational purposes, or to
38326 share files between different possible target descriptions. You can
38327 divide a description into multiple files by replacing any element of
38328 the target description with an inclusion directive of the form:
38331 <xi:include href="@var{document}"/>
38335 When @value{GDBN} encounters an element of this form, it will retrieve
38336 the named XML @var{document}, and replace the inclusion directive with
38337 the contents of that document. If the current description was read
38338 using @samp{qXfer}, then so will be the included document;
38339 @var{document} will be interpreted as the name of an annex. If the
38340 current description was read from a file, @value{GDBN} will look for
38341 @var{document} as a file in the same directory where it found the
38342 original description.
38344 @subsection Architecture
38345 @cindex <architecture>
38347 An @samp{<architecture>} element has this form:
38350 <architecture>@var{arch}</architecture>
38353 @var{arch} is one of the architectures from the set accepted by
38354 @code{set architecture} (@pxref{Targets, ,Specifying a Debugging Target}).
38357 @cindex @code{<osabi>}
38359 This optional field was introduced in @value{GDBN} version 7.0.
38360 Previous versions of @value{GDBN} ignore it.
38362 An @samp{<osabi>} element has this form:
38365 <osabi>@var{abi-name}</osabi>
38368 @var{abi-name} is an OS ABI name from the same selection accepted by
38369 @w{@code{set osabi}} (@pxref{ABI, ,Configuring the Current ABI}).
38371 @subsection Compatible Architecture
38372 @cindex @code{<compatible>}
38374 This optional field was introduced in @value{GDBN} version 7.0.
38375 Previous versions of @value{GDBN} ignore it.
38377 A @samp{<compatible>} element has this form:
38380 <compatible>@var{arch}</compatible>
38383 @var{arch} is one of the architectures from the set accepted by
38384 @code{set architecture} (@pxref{Targets, ,Specifying a Debugging Target}).
38386 A @samp{<compatible>} element is used to specify that the target
38387 is able to run binaries in some other than the main target architecture
38388 given by the @samp{<architecture>} element. For example, on the
38389 Cell Broadband Engine, the main architecture is @code{powerpc:common}
38390 or @code{powerpc:common64}, but the system is able to run binaries
38391 in the @code{spu} architecture as well. The way to describe this
38392 capability with @samp{<compatible>} is as follows:
38395 <architecture>powerpc:common</architecture>
38396 <compatible>spu</compatible>
38399 @subsection Features
38402 Each @samp{<feature>} describes some logical portion of the target
38403 system. Features are currently used to describe available CPU
38404 registers and the types of their contents. A @samp{<feature>} element
38408 <feature name="@var{name}">
38409 @r{[}@var{type}@dots{}@r{]}
38415 Each feature's name should be unique within the description. The name
38416 of a feature does not matter unless @value{GDBN} has some special
38417 knowledge of the contents of that feature; if it does, the feature
38418 should have its standard name. @xref{Standard Target Features}.
38422 Any register's value is a collection of bits which @value{GDBN} must
38423 interpret. The default interpretation is a two's complement integer,
38424 but other types can be requested by name in the register description.
38425 Some predefined types are provided by @value{GDBN} (@pxref{Predefined
38426 Target Types}), and the description can define additional composite types.
38428 Each type element must have an @samp{id} attribute, which gives
38429 a unique (within the containing @samp{<feature>}) name to the type.
38430 Types must be defined before they are used.
38433 Some targets offer vector registers, which can be treated as arrays
38434 of scalar elements. These types are written as @samp{<vector>} elements,
38435 specifying the array element type, @var{type}, and the number of elements,
38439 <vector id="@var{id}" type="@var{type}" count="@var{count}"/>
38443 If a register's value is usefully viewed in multiple ways, define it
38444 with a union type containing the useful representations. The
38445 @samp{<union>} element contains one or more @samp{<field>} elements,
38446 each of which has a @var{name} and a @var{type}:
38449 <union id="@var{id}">
38450 <field name="@var{name}" type="@var{type}"/>
38456 If a register's value is composed from several separate values, define
38457 it with a structure type. There are two forms of the @samp{<struct>}
38458 element; a @samp{<struct>} element must either contain only bitfields
38459 or contain no bitfields. If the structure contains only bitfields,
38460 its total size in bytes must be specified, each bitfield must have an
38461 explicit start and end, and bitfields are automatically assigned an
38462 integer type. The field's @var{start} should be less than or
38463 equal to its @var{end}, and zero represents the least significant bit.
38466 <struct id="@var{id}" size="@var{size}">
38467 <field name="@var{name}" start="@var{start}" end="@var{end}"/>
38472 If the structure contains no bitfields, then each field has an
38473 explicit type, and no implicit padding is added.
38476 <struct id="@var{id}">
38477 <field name="@var{name}" type="@var{type}"/>
38483 If a register's value is a series of single-bit flags, define it with
38484 a flags type. The @samp{<flags>} element has an explicit @var{size}
38485 and contains one or more @samp{<field>} elements. Each field has a
38486 @var{name}, a @var{start}, and an @var{end}. Only single-bit flags
38490 <flags id="@var{id}" size="@var{size}">
38491 <field name="@var{name}" start="@var{start}" end="@var{end}"/>
38496 @subsection Registers
38499 Each register is represented as an element with this form:
38502 <reg name="@var{name}"
38503 bitsize="@var{size}"
38504 @r{[}regnum="@var{num}"@r{]}
38505 @r{[}save-restore="@var{save-restore}"@r{]}
38506 @r{[}type="@var{type}"@r{]}
38507 @r{[}group="@var{group}"@r{]}/>
38511 The components are as follows:
38516 The register's name; it must be unique within the target description.
38519 The register's size, in bits.
38522 The register's number. If omitted, a register's number is one greater
38523 than that of the previous register (either in the current feature or in
38524 a preceding feature); the first register in the target description
38525 defaults to zero. This register number is used to read or write
38526 the register; e.g.@: it is used in the remote @code{p} and @code{P}
38527 packets, and registers appear in the @code{g} and @code{G} packets
38528 in order of increasing register number.
38531 Whether the register should be preserved across inferior function
38532 calls; this must be either @code{yes} or @code{no}. The default is
38533 @code{yes}, which is appropriate for most registers except for
38534 some system control registers; this is not related to the target's
38538 The type of the register. @var{type} may be a predefined type, a type
38539 defined in the current feature, or one of the special types @code{int}
38540 and @code{float}. @code{int} is an integer type of the correct size
38541 for @var{bitsize}, and @code{float} is a floating point type (in the
38542 architecture's normal floating point format) of the correct size for
38543 @var{bitsize}. The default is @code{int}.
38546 The register group to which this register belongs. @var{group} must
38547 be either @code{general}, @code{float}, or @code{vector}. If no
38548 @var{group} is specified, @value{GDBN} will not display the register
38549 in @code{info registers}.
38553 @node Predefined Target Types
38554 @section Predefined Target Types
38555 @cindex target descriptions, predefined types
38557 Type definitions in the self-description can build up composite types
38558 from basic building blocks, but can not define fundamental types. Instead,
38559 standard identifiers are provided by @value{GDBN} for the fundamental
38560 types. The currently supported types are:
38569 Signed integer types holding the specified number of bits.
38576 Unsigned integer types holding the specified number of bits.
38580 Pointers to unspecified code and data. The program counter and
38581 any dedicated return address register may be marked as code
38582 pointers; printing a code pointer converts it into a symbolic
38583 address. The stack pointer and any dedicated address registers
38584 may be marked as data pointers.
38587 Single precision IEEE floating point.
38590 Double precision IEEE floating point.
38593 The 12-byte extended precision format used by ARM FPA registers.
38596 The 10-byte extended precision format used by x87 registers.
38599 32bit @sc{eflags} register used by x86.
38602 32bit @sc{mxcsr} register used by x86.
38606 @node Standard Target Features
38607 @section Standard Target Features
38608 @cindex target descriptions, standard features
38610 A target description must contain either no registers or all the
38611 target's registers. If the description contains no registers, then
38612 @value{GDBN} will assume a default register layout, selected based on
38613 the architecture. If the description contains any registers, the
38614 default layout will not be used; the standard registers must be
38615 described in the target description, in such a way that @value{GDBN}
38616 can recognize them.
38618 This is accomplished by giving specific names to feature elements
38619 which contain standard registers. @value{GDBN} will look for features
38620 with those names and verify that they contain the expected registers;
38621 if any known feature is missing required registers, or if any required
38622 feature is missing, @value{GDBN} will reject the target
38623 description. You can add additional registers to any of the
38624 standard features --- @value{GDBN} will display them just as if
38625 they were added to an unrecognized feature.
38627 This section lists the known features and their expected contents.
38628 Sample XML documents for these features are included in the
38629 @value{GDBN} source tree, in the directory @file{gdb/features}.
38631 Names recognized by @value{GDBN} should include the name of the
38632 company or organization which selected the name, and the overall
38633 architecture to which the feature applies; so e.g.@: the feature
38634 containing ARM core registers is named @samp{org.gnu.gdb.arm.core}.
38636 The names of registers are not case sensitive for the purpose
38637 of recognizing standard features, but @value{GDBN} will only display
38638 registers using the capitalization used in the description.
38645 * PowerPC Features::
38651 @subsection ARM Features
38652 @cindex target descriptions, ARM features
38654 The @samp{org.gnu.gdb.arm.core} feature is required for non-M-profile
38656 It should contain registers @samp{r0} through @samp{r13}, @samp{sp},
38657 @samp{lr}, @samp{pc}, and @samp{cpsr}.
38659 For M-profile targets (e.g. Cortex-M3), the @samp{org.gnu.gdb.arm.core}
38660 feature is replaced by @samp{org.gnu.gdb.arm.m-profile}. It should contain
38661 registers @samp{r0} through @samp{r13}, @samp{sp}, @samp{lr}, @samp{pc},
38664 The @samp{org.gnu.gdb.arm.fpa} feature is optional. If present, it
38665 should contain registers @samp{f0} through @samp{f7} and @samp{fps}.
38667 The @samp{org.gnu.gdb.xscale.iwmmxt} feature is optional. If present,
38668 it should contain at least registers @samp{wR0} through @samp{wR15} and
38669 @samp{wCGR0} through @samp{wCGR3}. The @samp{wCID}, @samp{wCon},
38670 @samp{wCSSF}, and @samp{wCASF} registers are optional.
38672 The @samp{org.gnu.gdb.arm.vfp} feature is optional. If present, it
38673 should contain at least registers @samp{d0} through @samp{d15}. If
38674 they are present, @samp{d16} through @samp{d31} should also be included.
38675 @value{GDBN} will synthesize the single-precision registers from
38676 halves of the double-precision registers.
38678 The @samp{org.gnu.gdb.arm.neon} feature is optional. It does not
38679 need to contain registers; it instructs @value{GDBN} to display the
38680 VFP double-precision registers as vectors and to synthesize the
38681 quad-precision registers from pairs of double-precision registers.
38682 If this feature is present, @samp{org.gnu.gdb.arm.vfp} must also
38683 be present and include 32 double-precision registers.
38685 @node i386 Features
38686 @subsection i386 Features
38687 @cindex target descriptions, i386 features
38689 The @samp{org.gnu.gdb.i386.core} feature is required for i386/amd64
38690 targets. It should describe the following registers:
38694 @samp{eax} through @samp{edi} plus @samp{eip} for i386
38696 @samp{rax} through @samp{r15} plus @samp{rip} for amd64
38698 @samp{eflags}, @samp{cs}, @samp{ss}, @samp{ds}, @samp{es},
38699 @samp{fs}, @samp{gs}
38701 @samp{st0} through @samp{st7}
38703 @samp{fctrl}, @samp{fstat}, @samp{ftag}, @samp{fiseg}, @samp{fioff},
38704 @samp{foseg}, @samp{fooff} and @samp{fop}
38707 The register sets may be different, depending on the target.
38709 The @samp{org.gnu.gdb.i386.sse} feature is optional. It should
38710 describe registers:
38714 @samp{xmm0} through @samp{xmm7} for i386
38716 @samp{xmm0} through @samp{xmm15} for amd64
38721 The @samp{org.gnu.gdb.i386.avx} feature is optional and requires the
38722 @samp{org.gnu.gdb.i386.sse} feature. It should
38723 describe the upper 128 bits of @sc{ymm} registers:
38727 @samp{ymm0h} through @samp{ymm7h} for i386
38729 @samp{ymm0h} through @samp{ymm15h} for amd64
38732 The @samp{org.gnu.gdb.i386.linux} feature is optional. It should
38733 describe a single register, @samp{orig_eax}.
38735 @node MIPS Features
38736 @subsection MIPS Features
38737 @cindex target descriptions, MIPS features
38739 The @samp{org.gnu.gdb.mips.cpu} feature is required for MIPS targets.
38740 It should contain registers @samp{r0} through @samp{r31}, @samp{lo},
38741 @samp{hi}, and @samp{pc}. They may be 32-bit or 64-bit depending
38744 The @samp{org.gnu.gdb.mips.cp0} feature is also required. It should
38745 contain at least the @samp{status}, @samp{badvaddr}, and @samp{cause}
38746 registers. They may be 32-bit or 64-bit depending on the target.
38748 The @samp{org.gnu.gdb.mips.fpu} feature is currently required, though
38749 it may be optional in a future version of @value{GDBN}. It should
38750 contain registers @samp{f0} through @samp{f31}, @samp{fcsr}, and
38751 @samp{fir}. They may be 32-bit or 64-bit depending on the target.
38753 The @samp{org.gnu.gdb.mips.dsp} feature is optional. It should
38754 contain registers @samp{hi1} through @samp{hi3}, @samp{lo1} through
38755 @samp{lo3}, and @samp{dspctl}. The @samp{dspctl} register should
38756 be 32-bit and the rest may be 32-bit or 64-bit depending on the target.
38758 The @samp{org.gnu.gdb.mips.linux} feature is optional. It should
38759 contain a single register, @samp{restart}, which is used by the
38760 Linux kernel to control restartable syscalls.
38762 @node M68K Features
38763 @subsection M68K Features
38764 @cindex target descriptions, M68K features
38767 @item @samp{org.gnu.gdb.m68k.core}
38768 @itemx @samp{org.gnu.gdb.coldfire.core}
38769 @itemx @samp{org.gnu.gdb.fido.core}
38770 One of those features must be always present.
38771 The feature that is present determines which flavor of m68k is
38772 used. The feature that is present should contain registers
38773 @samp{d0} through @samp{d7}, @samp{a0} through @samp{a5}, @samp{fp},
38774 @samp{sp}, @samp{ps} and @samp{pc}.
38776 @item @samp{org.gnu.gdb.coldfire.fp}
38777 This feature is optional. If present, it should contain registers
38778 @samp{fp0} through @samp{fp7}, @samp{fpcontrol}, @samp{fpstatus} and
38782 @node PowerPC Features
38783 @subsection PowerPC Features
38784 @cindex target descriptions, PowerPC features
38786 The @samp{org.gnu.gdb.power.core} feature is required for PowerPC
38787 targets. It should contain registers @samp{r0} through @samp{r31},
38788 @samp{pc}, @samp{msr}, @samp{cr}, @samp{lr}, @samp{ctr}, and
38789 @samp{xer}. They may be 32-bit or 64-bit depending on the target.
38791 The @samp{org.gnu.gdb.power.fpu} feature is optional. It should
38792 contain registers @samp{f0} through @samp{f31} and @samp{fpscr}.
38794 The @samp{org.gnu.gdb.power.altivec} feature is optional. It should
38795 contain registers @samp{vr0} through @samp{vr31}, @samp{vscr},
38798 The @samp{org.gnu.gdb.power.vsx} feature is optional. It should
38799 contain registers @samp{vs0h} through @samp{vs31h}. @value{GDBN}
38800 will combine these registers with the floating point registers
38801 (@samp{f0} through @samp{f31}) and the altivec registers (@samp{vr0}
38802 through @samp{vr31}) to present the 128-bit wide registers @samp{vs0}
38803 through @samp{vs63}, the set of vector registers for POWER7.
38805 The @samp{org.gnu.gdb.power.spe} feature is optional. It should
38806 contain registers @samp{ev0h} through @samp{ev31h}, @samp{acc}, and
38807 @samp{spefscr}. SPE targets should provide 32-bit registers in
38808 @samp{org.gnu.gdb.power.core} and provide the upper halves in
38809 @samp{ev0h} through @samp{ev31h}. @value{GDBN} will combine
38810 these to present registers @samp{ev0} through @samp{ev31} to the
38813 @node TIC6x Features
38814 @subsection TMS320C6x Features
38815 @cindex target descriptions, TIC6x features
38816 @cindex target descriptions, TMS320C6x features
38817 The @samp{org.gnu.gdb.tic6x.core} feature is required for TMS320C6x
38818 targets. It should contain registers @samp{A0} through @samp{A15},
38819 registers @samp{B0} through @samp{B15}, @samp{CSR} and @samp{PC}.
38821 The @samp{org.gnu.gdb.tic6x.gp} feature is optional. It should
38822 contain registers @samp{A16} through @samp{A31} and @samp{B16}
38823 through @samp{B31}.
38825 The @samp{org.gnu.gdb.tic6x.c6xp} feature is optional. It should
38826 contain registers @samp{TSR}, @samp{ILC} and @samp{RILC}.
38828 @node Operating System Information
38829 @appendix Operating System Information
38830 @cindex operating system information
38836 Users of @value{GDBN} often wish to obtain information about the state of
38837 the operating system running on the target---for example the list of
38838 processes, or the list of open files. This section describes the
38839 mechanism that makes it possible. This mechanism is similar to the
38840 target features mechanism (@pxref{Target Descriptions}), but focuses
38841 on a different aspect of target.
38843 Operating system information is retrived from the target via the
38844 remote protocol, using @samp{qXfer} requests (@pxref{qXfer osdata
38845 read}). The object name in the request should be @samp{osdata}, and
38846 the @var{annex} identifies the data to be fetched.
38849 @appendixsection Process list
38850 @cindex operating system information, process list
38852 When requesting the process list, the @var{annex} field in the
38853 @samp{qXfer} request should be @samp{processes}. The returned data is
38854 an XML document. The formal syntax of this document is defined in
38855 @file{gdb/features/osdata.dtd}.
38857 An example document is:
38860 <?xml version="1.0"?>
38861 <!DOCTYPE target SYSTEM "osdata.dtd">
38862 <osdata type="processes">
38864 <column name="pid">1</column>
38865 <column name="user">root</column>
38866 <column name="command">/sbin/init</column>
38867 <column name="cores">1,2,3</column>
38872 Each item should include a column whose name is @samp{pid}. The value
38873 of that column should identify the process on the target. The
38874 @samp{user} and @samp{command} columns are optional, and will be
38875 displayed by @value{GDBN}. The @samp{cores} column, if present,
38876 should contain a comma-separated list of cores that this process
38877 is running on. Target may provide additional columns,
38878 which @value{GDBN} currently ignores.
38880 @node Trace File Format
38881 @appendix Trace File Format
38882 @cindex trace file format
38884 The trace file comes in three parts: a header, a textual description
38885 section, and a trace frame section with binary data.
38887 The header has the form @code{\x7fTRACE0\n}. The first byte is
38888 @code{0x7f} so as to indicate that the file contains binary data,
38889 while the @code{0} is a version number that may have different values
38892 The description section consists of multiple lines of @sc{ascii} text
38893 separated by newline characters (@code{0xa}). The lines may include a
38894 variety of optional descriptive or context-setting information, such
38895 as tracepoint definitions or register set size. @value{GDBN} will
38896 ignore any line that it does not recognize. An empty line marks the end
38899 @c FIXME add some specific types of data
38901 The trace frame section consists of a number of consecutive frames.
38902 Each frame begins with a two-byte tracepoint number, followed by a
38903 four-byte size giving the amount of data in the frame. The data in
38904 the frame consists of a number of blocks, each introduced by a
38905 character indicating its type (at least register, memory, and trace
38906 state variable). The data in this section is raw binary, not a
38907 hexadecimal or other encoding; its endianness matches the target's
38910 @c FIXME bi-arch may require endianness/arch info in description section
38913 @item R @var{bytes}
38914 Register block. The number and ordering of bytes matches that of a
38915 @code{g} packet in the remote protocol. Note that these are the
38916 actual bytes, in target order and @value{GDBN} register order, not a
38917 hexadecimal encoding.
38919 @item M @var{address} @var{length} @var{bytes}...
38920 Memory block. This is a contiguous block of memory, at the 8-byte
38921 address @var{address}, with a 2-byte length @var{length}, followed by
38922 @var{length} bytes.
38924 @item V @var{number} @var{value}
38925 Trace state variable block. This records the 8-byte signed value
38926 @var{value} of trace state variable numbered @var{number}.
38930 Future enhancements of the trace file format may include additional types
38933 @node Index Section Format
38934 @appendix @code{.gdb_index} section format
38935 @cindex .gdb_index section format
38936 @cindex index section format
38938 This section documents the index section that is created by @code{save
38939 gdb-index} (@pxref{Index Files}). The index section is
38940 DWARF-specific; some knowledge of DWARF is assumed in this
38943 The mapped index file format is designed to be directly
38944 @code{mmap}able on any architecture. In most cases, a datum is
38945 represented using a little-endian 32-bit integer value, called an
38946 @code{offset_type}. Big endian machines must byte-swap the values
38947 before using them. Exceptions to this rule are noted. The data is
38948 laid out such that alignment is always respected.
38950 A mapped index consists of several areas, laid out in order.
38954 The file header. This is a sequence of values, of @code{offset_type}
38955 unless otherwise noted:
38959 The version number, currently 5. Versions 1, 2 and 3 are obsolete.
38960 Version 4 differs by its hashing function.
38963 The offset, from the start of the file, of the CU list.
38966 The offset, from the start of the file, of the types CU list. Note
38967 that this area can be empty, in which case this offset will be equal
38968 to the next offset.
38971 The offset, from the start of the file, of the address area.
38974 The offset, from the start of the file, of the symbol table.
38977 The offset, from the start of the file, of the constant pool.
38981 The CU list. This is a sequence of pairs of 64-bit little-endian
38982 values, sorted by the CU offset. The first element in each pair is
38983 the offset of a CU in the @code{.debug_info} section. The second
38984 element in each pair is the length of that CU. References to a CU
38985 elsewhere in the map are done using a CU index, which is just the
38986 0-based index into this table. Note that if there are type CUs, then
38987 conceptually CUs and type CUs form a single list for the purposes of
38991 The types CU list. This is a sequence of triplets of 64-bit
38992 little-endian values. In a triplet, the first value is the CU offset,
38993 the second value is the type offset in the CU, and the third value is
38994 the type signature. The types CU list is not sorted.
38997 The address area. The address area consists of a sequence of address
38998 entries. Each address entry has three elements:
39002 The low address. This is a 64-bit little-endian value.
39005 The high address. This is a 64-bit little-endian value. Like
39006 @code{DW_AT_high_pc}, the value is one byte beyond the end.
39009 The CU index. This is an @code{offset_type} value.
39013 The symbol table. This is an open-addressed hash table. The size of
39014 the hash table is always a power of 2.
39016 Each slot in the hash table consists of a pair of @code{offset_type}
39017 values. The first value is the offset of the symbol's name in the
39018 constant pool. The second value is the offset of the CU vector in the
39021 If both values are 0, then this slot in the hash table is empty. This
39022 is ok because while 0 is a valid constant pool index, it cannot be a
39023 valid index for both a string and a CU vector.
39025 The hash value for a table entry is computed by applying an
39026 iterative hash function to the symbol's name. Starting with an
39027 initial value of @code{r = 0}, each (unsigned) character @samp{c} in
39028 the string is incorporated into the hash using the formula depending on the
39033 The formula is @code{r = r * 67 + c - 113}.
39036 The formula is @code{r = r * 67 + tolower (c) - 113}.
39039 The terminating @samp{\0} is not incorporated into the hash.
39041 The step size used in the hash table is computed via
39042 @code{((hash * 17) & (size - 1)) | 1}, where @samp{hash} is the hash
39043 value, and @samp{size} is the size of the hash table. The step size
39044 is used to find the next candidate slot when handling a hash
39047 The names of C@t{++} symbols in the hash table are canonicalized. We
39048 don't currently have a simple description of the canonicalization
39049 algorithm; if you intend to create new index sections, you must read
39053 The constant pool. This is simply a bunch of bytes. It is organized
39054 so that alignment is correct: CU vectors are stored first, followed by
39057 A CU vector in the constant pool is a sequence of @code{offset_type}
39058 values. The first value is the number of CU indices in the vector.
39059 Each subsequent value is the index of a CU in the CU list. This
39060 element in the hash table is used to indicate which CUs define the
39063 A string in the constant pool is zero-terminated.
39068 @node GNU Free Documentation License
39069 @appendix GNU Free Documentation License
39078 % I think something like @colophon should be in texinfo. In the
39080 \long\def\colophon{\hbox to0pt{}\vfill
39081 \centerline{The body of this manual is set in}
39082 \centerline{\fontname\tenrm,}
39083 \centerline{with headings in {\bf\fontname\tenbf}}
39084 \centerline{and examples in {\tt\fontname\tentt}.}
39085 \centerline{{\it\fontname\tenit\/},}
39086 \centerline{{\bf\fontname\tenbf}, and}
39087 \centerline{{\sl\fontname\tensl\/}}
39088 \centerline{are used for emphasis.}\vfill}
39090 % Blame: doc@cygnus.com, 1991.