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 @cindex C@t{++} symbol display
12792 @item set print demangle
12793 @itemx show print demangle
12794 @itemx set print asm-demangle
12795 @itemx show print asm-demangle
12796 Control whether C@t{++} symbols display in their source form, both when
12797 displaying code as C@t{++} source and when displaying disassemblies.
12798 @xref{Print Settings, ,Print Settings}.
12800 @item set print object
12801 @itemx show print object
12802 Choose whether to print derived (actual) or declared types of objects.
12803 @xref{Print Settings, ,Print Settings}.
12805 @item set print vtbl
12806 @itemx show print vtbl
12807 Control the format for printing virtual function tables.
12808 @xref{Print Settings, ,Print Settings}.
12809 (The @code{vtbl} commands do not work on programs compiled with the HP
12810 ANSI C@t{++} compiler (@code{aCC}).)
12812 @kindex set overload-resolution
12813 @cindex overloaded functions, overload resolution
12814 @item set overload-resolution on
12815 Enable overload resolution for C@t{++} expression evaluation. The default
12816 is on. For overloaded functions, @value{GDBN} evaluates the arguments
12817 and searches for a function whose signature matches the argument types,
12818 using the standard C@t{++} conversion rules (see @ref{C Plus Plus
12819 Expressions, ,C@t{++} Expressions}, for details).
12820 If it cannot find a match, it emits a message.
12822 @item set overload-resolution off
12823 Disable overload resolution for C@t{++} expression evaluation. For
12824 overloaded functions that are not class member functions, @value{GDBN}
12825 chooses the first function of the specified name that it finds in the
12826 symbol table, whether or not its arguments are of the correct type. For
12827 overloaded functions that are class member functions, @value{GDBN}
12828 searches for a function whose signature @emph{exactly} matches the
12831 @kindex show overload-resolution
12832 @item show overload-resolution
12833 Show the current setting of overload resolution.
12835 @item @r{Overloaded symbol names}
12836 You can specify a particular definition of an overloaded symbol, using
12837 the same notation that is used to declare such symbols in C@t{++}: type
12838 @code{@var{symbol}(@var{types})} rather than just @var{symbol}. You can
12839 also use the @value{GDBN} command-line word completion facilities to list the
12840 available choices, or to finish the type list for you.
12841 @xref{Completion,, Command Completion}, for details on how to do this.
12844 @node Decimal Floating Point
12845 @subsubsection Decimal Floating Point format
12846 @cindex decimal floating point format
12848 @value{GDBN} can examine, set and perform computations with numbers in
12849 decimal floating point format, which in the C language correspond to the
12850 @code{_Decimal32}, @code{_Decimal64} and @code{_Decimal128} types as
12851 specified by the extension to support decimal floating-point arithmetic.
12853 There are two encodings in use, depending on the architecture: BID (Binary
12854 Integer Decimal) for x86 and x86-64, and DPD (Densely Packed Decimal) for
12855 PowerPC. @value{GDBN} will use the appropriate encoding for the configured
12858 Because of a limitation in @file{libdecnumber}, the library used by @value{GDBN}
12859 to manipulate decimal floating point numbers, it is not possible to convert
12860 (using a cast, for example) integers wider than 32-bit to decimal float.
12862 In addition, in order to imitate @value{GDBN}'s behaviour with binary floating
12863 point computations, error checking in decimal float operations ignores
12864 underflow, overflow and divide by zero exceptions.
12866 In the PowerPC architecture, @value{GDBN} provides a set of pseudo-registers
12867 to inspect @code{_Decimal128} values stored in floating point registers.
12868 See @ref{PowerPC,,PowerPC} for more details.
12874 @value{GDBN} can be used to debug programs written in D and compiled with
12875 GDC, LDC or DMD compilers. Currently @value{GDBN} supports only one D
12876 specific feature --- dynamic arrays.
12879 @subsection Objective-C
12881 @cindex Objective-C
12882 This section provides information about some commands and command
12883 options that are useful for debugging Objective-C code. See also
12884 @ref{Symbols, info classes}, and @ref{Symbols, info selectors}, for a
12885 few more commands specific to Objective-C support.
12888 * Method Names in Commands::
12889 * The Print Command with Objective-C::
12892 @node Method Names in Commands
12893 @subsubsection Method Names in Commands
12895 The following commands have been extended to accept Objective-C method
12896 names as line specifications:
12898 @kindex clear@r{, and Objective-C}
12899 @kindex break@r{, and Objective-C}
12900 @kindex info line@r{, and Objective-C}
12901 @kindex jump@r{, and Objective-C}
12902 @kindex list@r{, and Objective-C}
12906 @item @code{info line}
12911 A fully qualified Objective-C method name is specified as
12914 -[@var{Class} @var{methodName}]
12917 where the minus sign is used to indicate an instance method and a
12918 plus sign (not shown) is used to indicate a class method. The class
12919 name @var{Class} and method name @var{methodName} are enclosed in
12920 brackets, similar to the way messages are specified in Objective-C
12921 source code. For example, to set a breakpoint at the @code{create}
12922 instance method of class @code{Fruit} in the program currently being
12926 break -[Fruit create]
12929 To list ten program lines around the @code{initialize} class method,
12933 list +[NSText initialize]
12936 In the current version of @value{GDBN}, the plus or minus sign is
12937 required. In future versions of @value{GDBN}, the plus or minus
12938 sign will be optional, but you can use it to narrow the search. It
12939 is also possible to specify just a method name:
12945 You must specify the complete method name, including any colons. If
12946 your program's source files contain more than one @code{create} method,
12947 you'll be presented with a numbered list of classes that implement that
12948 method. Indicate your choice by number, or type @samp{0} to exit if
12951 As another example, to clear a breakpoint established at the
12952 @code{makeKeyAndOrderFront:} method of the @code{NSWindow} class, enter:
12955 clear -[NSWindow makeKeyAndOrderFront:]
12958 @node The Print Command with Objective-C
12959 @subsubsection The Print Command With Objective-C
12960 @cindex Objective-C, print objects
12961 @kindex print-object
12962 @kindex po @r{(@code{print-object})}
12964 The print command has also been extended to accept methods. For example:
12967 print -[@var{object} hash]
12970 @cindex print an Objective-C object description
12971 @cindex @code{_NSPrintForDebugger}, and printing Objective-C objects
12973 will tell @value{GDBN} to send the @code{hash} message to @var{object}
12974 and print the result. Also, an additional command has been added,
12975 @code{print-object} or @code{po} for short, which is meant to print
12976 the description of an object. However, this command may only work
12977 with certain Objective-C libraries that have a particular hook
12978 function, @code{_NSPrintForDebugger}, defined.
12981 @subsection OpenCL C
12984 This section provides information about @value{GDBN}s OpenCL C support.
12987 * OpenCL C Datatypes::
12988 * OpenCL C Expressions::
12989 * OpenCL C Operators::
12992 @node OpenCL C Datatypes
12993 @subsubsection OpenCL C Datatypes
12995 @cindex OpenCL C Datatypes
12996 @value{GDBN} supports the builtin scalar and vector datatypes specified
12997 by OpenCL 1.1. In addition the half- and double-precision floating point
12998 data types of the @code{cl_khr_fp16} and @code{cl_khr_fp64} OpenCL
12999 extensions are also known to @value{GDBN}.
13001 @node OpenCL C Expressions
13002 @subsubsection OpenCL C Expressions
13004 @cindex OpenCL C Expressions
13005 @value{GDBN} supports accesses to vector components including the access as
13006 lvalue where possible. Since OpenCL C is based on C99 most C expressions
13007 supported by @value{GDBN} can be used as well.
13009 @node OpenCL C Operators
13010 @subsubsection OpenCL C Operators
13012 @cindex OpenCL C Operators
13013 @value{GDBN} supports the operators specified by OpenCL 1.1 for scalar and
13017 @subsection Fortran
13018 @cindex Fortran-specific support in @value{GDBN}
13020 @value{GDBN} can be used to debug programs written in Fortran, but it
13021 currently supports only the features of Fortran 77 language.
13023 @cindex trailing underscore, in Fortran symbols
13024 Some Fortran compilers (@sc{gnu} Fortran 77 and Fortran 95 compilers
13025 among them) append an underscore to the names of variables and
13026 functions. When you debug programs compiled by those compilers, you
13027 will need to refer to variables and functions with a trailing
13031 * Fortran Operators:: Fortran operators and expressions
13032 * Fortran Defaults:: Default settings for Fortran
13033 * Special Fortran Commands:: Special @value{GDBN} commands for Fortran
13036 @node Fortran Operators
13037 @subsubsection Fortran Operators and Expressions
13039 @cindex Fortran operators and expressions
13041 Operators must be defined on values of specific types. For instance,
13042 @code{+} is defined on numbers, but not on characters or other non-
13043 arithmetic types. Operators are often defined on groups of types.
13047 The exponentiation operator. It raises the first operand to the power
13051 The range operator. Normally used in the form of array(low:high) to
13052 represent a section of array.
13055 The access component operator. Normally used to access elements in derived
13056 types. Also suitable for unions. As unions aren't part of regular Fortran,
13057 this can only happen when accessing a register that uses a gdbarch-defined
13061 @node Fortran Defaults
13062 @subsubsection Fortran Defaults
13064 @cindex Fortran Defaults
13066 Fortran symbols are usually case-insensitive, so @value{GDBN} by
13067 default uses case-insensitive matches for Fortran symbols. You can
13068 change that with the @samp{set case-insensitive} command, see
13069 @ref{Symbols}, for the details.
13071 @node Special Fortran Commands
13072 @subsubsection Special Fortran Commands
13074 @cindex Special Fortran commands
13076 @value{GDBN} has some commands to support Fortran-specific features,
13077 such as displaying common blocks.
13080 @cindex @code{COMMON} blocks, Fortran
13081 @kindex info common
13082 @item info common @r{[}@var{common-name}@r{]}
13083 This command prints the values contained in the Fortran @code{COMMON}
13084 block whose name is @var{common-name}. With no argument, the names of
13085 all @code{COMMON} blocks visible at the current program location are
13092 @cindex Pascal support in @value{GDBN}, limitations
13093 Debugging Pascal programs which use sets, subranges, file variables, or
13094 nested functions does not currently work. @value{GDBN} does not support
13095 entering expressions, printing values, or similar features using Pascal
13098 The Pascal-specific command @code{set print pascal_static-members}
13099 controls whether static members of Pascal objects are displayed.
13100 @xref{Print Settings, pascal_static-members}.
13103 @subsection Modula-2
13105 @cindex Modula-2, @value{GDBN} support
13107 The extensions made to @value{GDBN} to support Modula-2 only support
13108 output from the @sc{gnu} Modula-2 compiler (which is currently being
13109 developed). Other Modula-2 compilers are not currently supported, and
13110 attempting to debug executables produced by them is most likely
13111 to give an error as @value{GDBN} reads in the executable's symbol
13114 @cindex expressions in Modula-2
13116 * M2 Operators:: Built-in operators
13117 * Built-In Func/Proc:: Built-in functions and procedures
13118 * M2 Constants:: Modula-2 constants
13119 * M2 Types:: Modula-2 types
13120 * M2 Defaults:: Default settings for Modula-2
13121 * Deviations:: Deviations from standard Modula-2
13122 * M2 Checks:: Modula-2 type and range checks
13123 * M2 Scope:: The scope operators @code{::} and @code{.}
13124 * GDB/M2:: @value{GDBN} and Modula-2
13128 @subsubsection Operators
13129 @cindex Modula-2 operators
13131 Operators must be defined on values of specific types. For instance,
13132 @code{+} is defined on numbers, but not on structures. Operators are
13133 often defined on groups of types. For the purposes of Modula-2, the
13134 following definitions hold:
13139 @emph{Integral types} consist of @code{INTEGER}, @code{CARDINAL}, and
13143 @emph{Character types} consist of @code{CHAR} and its subranges.
13146 @emph{Floating-point types} consist of @code{REAL}.
13149 @emph{Pointer types} consist of anything declared as @code{POINTER TO
13153 @emph{Scalar types} consist of all of the above.
13156 @emph{Set types} consist of @code{SET} and @code{BITSET} types.
13159 @emph{Boolean types} consist of @code{BOOLEAN}.
13163 The following operators are supported, and appear in order of
13164 increasing precedence:
13168 Function argument or array index separator.
13171 Assignment. The value of @var{var} @code{:=} @var{value} is
13175 Less than, greater than on integral, floating-point, or enumerated
13179 Less than or equal to, greater than or equal to
13180 on integral, floating-point and enumerated types, or set inclusion on
13181 set types. Same precedence as @code{<}.
13183 @item =@r{, }<>@r{, }#
13184 Equality and two ways of expressing inequality, valid on scalar types.
13185 Same precedence as @code{<}. In @value{GDBN} scripts, only @code{<>} is
13186 available for inequality, since @code{#} conflicts with the script
13190 Set membership. Defined on set types and the types of their members.
13191 Same precedence as @code{<}.
13194 Boolean disjunction. Defined on boolean types.
13197 Boolean conjunction. Defined on boolean types.
13200 The @value{GDBN} ``artificial array'' operator (@pxref{Expressions, ,Expressions}).
13203 Addition and subtraction on integral and floating-point types, or union
13204 and difference on set types.
13207 Multiplication on integral and floating-point types, or set intersection
13211 Division on floating-point types, or symmetric set difference on set
13212 types. Same precedence as @code{*}.
13215 Integer division and remainder. Defined on integral types. Same
13216 precedence as @code{*}.
13219 Negative. Defined on @code{INTEGER} and @code{REAL} data.
13222 Pointer dereferencing. Defined on pointer types.
13225 Boolean negation. Defined on boolean types. Same precedence as
13229 @code{RECORD} field selector. Defined on @code{RECORD} data. Same
13230 precedence as @code{^}.
13233 Array indexing. Defined on @code{ARRAY} data. Same precedence as @code{^}.
13236 Procedure argument list. Defined on @code{PROCEDURE} objects. Same precedence
13240 @value{GDBN} and Modula-2 scope operators.
13244 @emph{Warning:} Set expressions and their operations are not yet supported, so @value{GDBN}
13245 treats the use of the operator @code{IN}, or the use of operators
13246 @code{+}, @code{-}, @code{*}, @code{/}, @code{=}, , @code{<>}, @code{#},
13247 @code{<=}, and @code{>=} on sets as an error.
13251 @node Built-In Func/Proc
13252 @subsubsection Built-in Functions and Procedures
13253 @cindex Modula-2 built-ins
13255 Modula-2 also makes available several built-in procedures and functions.
13256 In describing these, the following metavariables are used:
13261 represents an @code{ARRAY} variable.
13264 represents a @code{CHAR} constant or variable.
13267 represents a variable or constant of integral type.
13270 represents an identifier that belongs to a set. Generally used in the
13271 same function with the metavariable @var{s}. The type of @var{s} should
13272 be @code{SET OF @var{mtype}} (where @var{mtype} is the type of @var{m}).
13275 represents a variable or constant of integral or floating-point type.
13278 represents a variable or constant of floating-point type.
13284 represents a variable.
13287 represents a variable or constant of one of many types. See the
13288 explanation of the function for details.
13291 All Modula-2 built-in procedures also return a result, described below.
13295 Returns the absolute value of @var{n}.
13298 If @var{c} is a lower case letter, it returns its upper case
13299 equivalent, otherwise it returns its argument.
13302 Returns the character whose ordinal value is @var{i}.
13305 Decrements the value in the variable @var{v} by one. Returns the new value.
13307 @item DEC(@var{v},@var{i})
13308 Decrements the value in the variable @var{v} by @var{i}. Returns the
13311 @item EXCL(@var{m},@var{s})
13312 Removes the element @var{m} from the set @var{s}. Returns the new
13315 @item FLOAT(@var{i})
13316 Returns the floating point equivalent of the integer @var{i}.
13318 @item HIGH(@var{a})
13319 Returns the index of the last member of @var{a}.
13322 Increments the value in the variable @var{v} by one. Returns the new value.
13324 @item INC(@var{v},@var{i})
13325 Increments the value in the variable @var{v} by @var{i}. Returns the
13328 @item INCL(@var{m},@var{s})
13329 Adds the element @var{m} to the set @var{s} if it is not already
13330 there. Returns the new set.
13333 Returns the maximum value of the type @var{t}.
13336 Returns the minimum value of the type @var{t}.
13339 Returns boolean TRUE if @var{i} is an odd number.
13342 Returns the ordinal value of its argument. For example, the ordinal
13343 value of a character is its @sc{ascii} value (on machines supporting the
13344 @sc{ascii} character set). @var{x} must be of an ordered type, which include
13345 integral, character and enumerated types.
13347 @item SIZE(@var{x})
13348 Returns the size of its argument. @var{x} can be a variable or a type.
13350 @item TRUNC(@var{r})
13351 Returns the integral part of @var{r}.
13353 @item TSIZE(@var{x})
13354 Returns the size of its argument. @var{x} can be a variable or a type.
13356 @item VAL(@var{t},@var{i})
13357 Returns the member of the type @var{t} whose ordinal value is @var{i}.
13361 @emph{Warning:} Sets and their operations are not yet supported, so
13362 @value{GDBN} treats the use of procedures @code{INCL} and @code{EXCL} as
13366 @cindex Modula-2 constants
13368 @subsubsection Constants
13370 @value{GDBN} allows you to express the constants of Modula-2 in the following
13376 Integer constants are simply a sequence of digits. When used in an
13377 expression, a constant is interpreted to be type-compatible with the
13378 rest of the expression. Hexadecimal integers are specified by a
13379 trailing @samp{H}, and octal integers by a trailing @samp{B}.
13382 Floating point constants appear as a sequence of digits, followed by a
13383 decimal point and another sequence of digits. An optional exponent can
13384 then be specified, in the form @samp{E@r{[}+@r{|}-@r{]}@var{nnn}}, where
13385 @samp{@r{[}+@r{|}-@r{]}@var{nnn}} is the desired exponent. All of the
13386 digits of the floating point constant must be valid decimal (base 10)
13390 Character constants consist of a single character enclosed by a pair of
13391 like quotes, either single (@code{'}) or double (@code{"}). They may
13392 also be expressed by their ordinal value (their @sc{ascii} value, usually)
13393 followed by a @samp{C}.
13396 String constants consist of a sequence of characters enclosed by a
13397 pair of like quotes, either single (@code{'}) or double (@code{"}).
13398 Escape sequences in the style of C are also allowed. @xref{C
13399 Constants, ,C and C@t{++} Constants}, for a brief explanation of escape
13403 Enumerated constants consist of an enumerated identifier.
13406 Boolean constants consist of the identifiers @code{TRUE} and
13410 Pointer constants consist of integral values only.
13413 Set constants are not yet supported.
13417 @subsubsection Modula-2 Types
13418 @cindex Modula-2 types
13420 Currently @value{GDBN} can print the following data types in Modula-2
13421 syntax: array types, record types, set types, pointer types, procedure
13422 types, enumerated types, subrange types and base types. You can also
13423 print the contents of variables declared using these type.
13424 This section gives a number of simple source code examples together with
13425 sample @value{GDBN} sessions.
13427 The first example contains the following section of code:
13436 and you can request @value{GDBN} to interrogate the type and value of
13437 @code{r} and @code{s}.
13440 (@value{GDBP}) print s
13442 (@value{GDBP}) ptype s
13444 (@value{GDBP}) print r
13446 (@value{GDBP}) ptype r
13451 Likewise if your source code declares @code{s} as:
13455 s: SET ['A'..'Z'] ;
13459 then you may query the type of @code{s} by:
13462 (@value{GDBP}) ptype s
13463 type = SET ['A'..'Z']
13467 Note that at present you cannot interactively manipulate set
13468 expressions using the debugger.
13470 The following example shows how you might declare an array in Modula-2
13471 and how you can interact with @value{GDBN} to print its type and contents:
13475 s: ARRAY [-10..10] OF CHAR ;
13479 (@value{GDBP}) ptype s
13480 ARRAY [-10..10] OF CHAR
13483 Note that the array handling is not yet complete and although the type
13484 is printed correctly, expression handling still assumes that all
13485 arrays have a lower bound of zero and not @code{-10} as in the example
13488 Here are some more type related Modula-2 examples:
13492 colour = (blue, red, yellow, green) ;
13493 t = [blue..yellow] ;
13501 The @value{GDBN} interaction shows how you can query the data type
13502 and value of a variable.
13505 (@value{GDBP}) print s
13507 (@value{GDBP}) ptype t
13508 type = [blue..yellow]
13512 In this example a Modula-2 array is declared and its contents
13513 displayed. Observe that the contents are written in the same way as
13514 their @code{C} counterparts.
13518 s: ARRAY [1..5] OF CARDINAL ;
13524 (@value{GDBP}) print s
13525 $1 = @{1, 0, 0, 0, 0@}
13526 (@value{GDBP}) ptype s
13527 type = ARRAY [1..5] OF CARDINAL
13530 The Modula-2 language interface to @value{GDBN} also understands
13531 pointer types as shown in this example:
13535 s: POINTER TO ARRAY [1..5] OF CARDINAL ;
13542 and you can request that @value{GDBN} describes the type of @code{s}.
13545 (@value{GDBP}) ptype s
13546 type = POINTER TO ARRAY [1..5] OF CARDINAL
13549 @value{GDBN} handles compound types as we can see in this example.
13550 Here we combine array types, record types, pointer types and subrange
13561 myarray = ARRAY myrange OF CARDINAL ;
13562 myrange = [-2..2] ;
13564 s: POINTER TO ARRAY myrange OF foo ;
13568 and you can ask @value{GDBN} to describe the type of @code{s} as shown
13572 (@value{GDBP}) ptype s
13573 type = POINTER TO ARRAY [-2..2] OF foo = RECORD
13576 f3 : ARRAY [-2..2] OF CARDINAL;
13581 @subsubsection Modula-2 Defaults
13582 @cindex Modula-2 defaults
13584 If type and range checking are set automatically by @value{GDBN}, they
13585 both default to @code{on} whenever the working language changes to
13586 Modula-2. This happens regardless of whether you or @value{GDBN}
13587 selected the working language.
13589 If you allow @value{GDBN} to set the language automatically, then entering
13590 code compiled from a file whose name ends with @file{.mod} sets the
13591 working language to Modula-2. @xref{Automatically, ,Having @value{GDBN}
13592 Infer the Source Language}, for further details.
13595 @subsubsection Deviations from Standard Modula-2
13596 @cindex Modula-2, deviations from
13598 A few changes have been made to make Modula-2 programs easier to debug.
13599 This is done primarily via loosening its type strictness:
13603 Unlike in standard Modula-2, pointer constants can be formed by
13604 integers. This allows you to modify pointer variables during
13605 debugging. (In standard Modula-2, the actual address contained in a
13606 pointer variable is hidden from you; it can only be modified
13607 through direct assignment to another pointer variable or expression that
13608 returned a pointer.)
13611 C escape sequences can be used in strings and characters to represent
13612 non-printable characters. @value{GDBN} prints out strings with these
13613 escape sequences embedded. Single non-printable characters are
13614 printed using the @samp{CHR(@var{nnn})} format.
13617 The assignment operator (@code{:=}) returns the value of its right-hand
13621 All built-in procedures both modify @emph{and} return their argument.
13625 @subsubsection Modula-2 Type and Range Checks
13626 @cindex Modula-2 checks
13629 @emph{Warning:} in this release, @value{GDBN} does not yet perform type or
13632 @c FIXME remove warning when type/range checks added
13634 @value{GDBN} considers two Modula-2 variables type equivalent if:
13638 They are of types that have been declared equivalent via a @code{TYPE
13639 @var{t1} = @var{t2}} statement
13642 They have been declared on the same line. (Note: This is true of the
13643 @sc{gnu} Modula-2 compiler, but it may not be true of other compilers.)
13646 As long as type checking is enabled, any attempt to combine variables
13647 whose types are not equivalent is an error.
13649 Range checking is done on all mathematical operations, assignment, array
13650 index bounds, and all built-in functions and procedures.
13653 @subsubsection The Scope Operators @code{::} and @code{.}
13655 @cindex @code{.}, Modula-2 scope operator
13656 @cindex colon, doubled as scope operator
13658 @vindex colon-colon@r{, in Modula-2}
13659 @c Info cannot handle :: but TeX can.
13662 @vindex ::@r{, in Modula-2}
13665 There are a few subtle differences between the Modula-2 scope operator
13666 (@code{.}) and the @value{GDBN} scope operator (@code{::}). The two have
13671 @var{module} . @var{id}
13672 @var{scope} :: @var{id}
13676 where @var{scope} is the name of a module or a procedure,
13677 @var{module} the name of a module, and @var{id} is any declared
13678 identifier within your program, except another module.
13680 Using the @code{::} operator makes @value{GDBN} search the scope
13681 specified by @var{scope} for the identifier @var{id}. If it is not
13682 found in the specified scope, then @value{GDBN} searches all scopes
13683 enclosing the one specified by @var{scope}.
13685 Using the @code{.} operator makes @value{GDBN} search the current scope for
13686 the identifier specified by @var{id} that was imported from the
13687 definition module specified by @var{module}. With this operator, it is
13688 an error if the identifier @var{id} was not imported from definition
13689 module @var{module}, or if @var{id} is not an identifier in
13693 @subsubsection @value{GDBN} and Modula-2
13695 Some @value{GDBN} commands have little use when debugging Modula-2 programs.
13696 Five subcommands of @code{set print} and @code{show print} apply
13697 specifically to C and C@t{++}: @samp{vtbl}, @samp{demangle},
13698 @samp{asm-demangle}, @samp{object}, and @samp{union}. The first four
13699 apply to C@t{++}, and the last to the C @code{union} type, which has no direct
13700 analogue in Modula-2.
13702 The @code{@@} operator (@pxref{Expressions, ,Expressions}), while available
13703 with any language, is not useful with Modula-2. Its
13704 intent is to aid the debugging of @dfn{dynamic arrays}, which cannot be
13705 created in Modula-2 as they can in C or C@t{++}. However, because an
13706 address can be specified by an integral constant, the construct
13707 @samp{@{@var{type}@}@var{adrexp}} is still useful.
13709 @cindex @code{#} in Modula-2
13710 In @value{GDBN} scripts, the Modula-2 inequality operator @code{#} is
13711 interpreted as the beginning of a comment. Use @code{<>} instead.
13717 The extensions made to @value{GDBN} for Ada only support
13718 output from the @sc{gnu} Ada (GNAT) compiler.
13719 Other Ada compilers are not currently supported, and
13720 attempting to debug executables produced by them is most likely
13724 @cindex expressions in Ada
13726 * Ada Mode Intro:: General remarks on the Ada syntax
13727 and semantics supported by Ada mode
13729 * Omissions from Ada:: Restrictions on the Ada expression syntax.
13730 * Additions to Ada:: Extensions of the Ada expression syntax.
13731 * Stopping Before Main Program:: Debugging the program during elaboration.
13732 * Ada Tasks:: Listing and setting breakpoints in tasks.
13733 * Ada Tasks and Core Files:: Tasking Support when Debugging Core Files
13734 * Ravenscar Profile:: Tasking Support when using the Ravenscar
13736 * Ada Glitches:: Known peculiarities of Ada mode.
13739 @node Ada Mode Intro
13740 @subsubsection Introduction
13741 @cindex Ada mode, general
13743 The Ada mode of @value{GDBN} supports a fairly large subset of Ada expression
13744 syntax, with some extensions.
13745 The philosophy behind the design of this subset is
13749 That @value{GDBN} should provide basic literals and access to operations for
13750 arithmetic, dereferencing, field selection, indexing, and subprogram calls,
13751 leaving more sophisticated computations to subprograms written into the
13752 program (which therefore may be called from @value{GDBN}).
13755 That type safety and strict adherence to Ada language restrictions
13756 are not particularly important to the @value{GDBN} user.
13759 That brevity is important to the @value{GDBN} user.
13762 Thus, for brevity, the debugger acts as if all names declared in
13763 user-written packages are directly visible, even if they are not visible
13764 according to Ada rules, thus making it unnecessary to fully qualify most
13765 names with their packages, regardless of context. Where this causes
13766 ambiguity, @value{GDBN} asks the user's intent.
13768 The debugger will start in Ada mode if it detects an Ada main program.
13769 As for other languages, it will enter Ada mode when stopped in a program that
13770 was translated from an Ada source file.
13772 While in Ada mode, you may use `@t{--}' for comments. This is useful
13773 mostly for documenting command files. The standard @value{GDBN} comment
13774 (@samp{#}) still works at the beginning of a line in Ada mode, but not in the
13775 middle (to allow based literals).
13777 The debugger supports limited overloading. Given a subprogram call in which
13778 the function symbol has multiple definitions, it will use the number of
13779 actual parameters and some information about their types to attempt to narrow
13780 the set of definitions. It also makes very limited use of context, preferring
13781 procedures to functions in the context of the @code{call} command, and
13782 functions to procedures elsewhere.
13784 @node Omissions from Ada
13785 @subsubsection Omissions from Ada
13786 @cindex Ada, omissions from
13788 Here are the notable omissions from the subset:
13792 Only a subset of the attributes are supported:
13796 @t{'First}, @t{'Last}, and @t{'Length}
13797 on array objects (not on types and subtypes).
13800 @t{'Min} and @t{'Max}.
13803 @t{'Pos} and @t{'Val}.
13809 @t{'Range} on array objects (not subtypes), but only as the right
13810 operand of the membership (@code{in}) operator.
13813 @t{'Access}, @t{'Unchecked_Access}, and
13814 @t{'Unrestricted_Access} (a GNAT extension).
13822 @code{Characters.Latin_1} are not available and
13823 concatenation is not implemented. Thus, escape characters in strings are
13824 not currently available.
13827 Equality tests (@samp{=} and @samp{/=}) on arrays test for bitwise
13828 equality of representations. They will generally work correctly
13829 for strings and arrays whose elements have integer or enumeration types.
13830 They may not work correctly for arrays whose element
13831 types have user-defined equality, for arrays of real values
13832 (in particular, IEEE-conformant floating point, because of negative
13833 zeroes and NaNs), and for arrays whose elements contain unused bits with
13834 indeterminate values.
13837 The other component-by-component array operations (@code{and}, @code{or},
13838 @code{xor}, @code{not}, and relational tests other than equality)
13839 are not implemented.
13842 @cindex array aggregates (Ada)
13843 @cindex record aggregates (Ada)
13844 @cindex aggregates (Ada)
13845 There is limited support for array and record aggregates. They are
13846 permitted only on the right sides of assignments, as in these examples:
13849 (@value{GDBP}) set An_Array := (1, 2, 3, 4, 5, 6)
13850 (@value{GDBP}) set An_Array := (1, others => 0)
13851 (@value{GDBP}) set An_Array := (0|4 => 1, 1..3 => 2, 5 => 6)
13852 (@value{GDBP}) set A_2D_Array := ((1, 2, 3), (4, 5, 6), (7, 8, 9))
13853 (@value{GDBP}) set A_Record := (1, "Peter", True);
13854 (@value{GDBP}) set A_Record := (Name => "Peter", Id => 1, Alive => True)
13858 discriminant's value by assigning an aggregate has an
13859 undefined effect if that discriminant is used within the record.
13860 However, you can first modify discriminants by directly assigning to
13861 them (which normally would not be allowed in Ada), and then performing an
13862 aggregate assignment. For example, given a variable @code{A_Rec}
13863 declared to have a type such as:
13866 type Rec (Len : Small_Integer := 0) is record
13868 Vals : IntArray (1 .. Len);
13872 you can assign a value with a different size of @code{Vals} with two
13876 (@value{GDBP}) set A_Rec.Len := 4
13877 (@value{GDBP}) set A_Rec := (Id => 42, Vals => (1, 2, 3, 4))
13880 As this example also illustrates, @value{GDBN} is very loose about the usual
13881 rules concerning aggregates. You may leave out some of the
13882 components of an array or record aggregate (such as the @code{Len}
13883 component in the assignment to @code{A_Rec} above); they will retain their
13884 original values upon assignment. You may freely use dynamic values as
13885 indices in component associations. You may even use overlapping or
13886 redundant component associations, although which component values are
13887 assigned in such cases is not defined.
13890 Calls to dispatching subprograms are not implemented.
13893 The overloading algorithm is much more limited (i.e., less selective)
13894 than that of real Ada. It makes only limited use of the context in
13895 which a subexpression appears to resolve its meaning, and it is much
13896 looser in its rules for allowing type matches. As a result, some
13897 function calls will be ambiguous, and the user will be asked to choose
13898 the proper resolution.
13901 The @code{new} operator is not implemented.
13904 Entry calls are not implemented.
13907 Aside from printing, arithmetic operations on the native VAX floating-point
13908 formats are not supported.
13911 It is not possible to slice a packed array.
13914 The names @code{True} and @code{False}, when not part of a qualified name,
13915 are interpreted as if implicitly prefixed by @code{Standard}, regardless of
13917 Should your program
13918 redefine these names in a package or procedure (at best a dubious practice),
13919 you will have to use fully qualified names to access their new definitions.
13922 @node Additions to Ada
13923 @subsubsection Additions to Ada
13924 @cindex Ada, deviations from
13926 As it does for other languages, @value{GDBN} makes certain generic
13927 extensions to Ada (@pxref{Expressions}):
13931 If the expression @var{E} is a variable residing in memory (typically
13932 a local variable or array element) and @var{N} is a positive integer,
13933 then @code{@var{E}@@@var{N}} displays the values of @var{E} and the
13934 @var{N}-1 adjacent variables following it in memory as an array. In
13935 Ada, this operator is generally not necessary, since its prime use is
13936 in displaying parts of an array, and slicing will usually do this in
13937 Ada. However, there are occasional uses when debugging programs in
13938 which certain debugging information has been optimized away.
13941 @code{@var{B}::@var{var}} means ``the variable named @var{var} that
13942 appears in function or file @var{B}.'' When @var{B} is a file name,
13943 you must typically surround it in single quotes.
13946 The expression @code{@{@var{type}@} @var{addr}} means ``the variable of type
13947 @var{type} that appears at address @var{addr}.''
13950 A name starting with @samp{$} is a convenience variable
13951 (@pxref{Convenience Vars}) or a machine register (@pxref{Registers}).
13954 In addition, @value{GDBN} provides a few other shortcuts and outright
13955 additions specific to Ada:
13959 The assignment statement is allowed as an expression, returning
13960 its right-hand operand as its value. Thus, you may enter
13963 (@value{GDBP}) set x := y + 3
13964 (@value{GDBP}) print A(tmp := y + 1)
13968 The semicolon is allowed as an ``operator,'' returning as its value
13969 the value of its right-hand operand.
13970 This allows, for example,
13971 complex conditional breaks:
13974 (@value{GDBP}) break f
13975 (@value{GDBP}) condition 1 (report(i); k += 1; A(k) > 100)
13979 Rather than use catenation and symbolic character names to introduce special
13980 characters into strings, one may instead use a special bracket notation,
13981 which is also used to print strings. A sequence of characters of the form
13982 @samp{["@var{XX}"]} within a string or character literal denotes the
13983 (single) character whose numeric encoding is @var{XX} in hexadecimal. The
13984 sequence of characters @samp{["""]} also denotes a single quotation mark
13985 in strings. For example,
13987 "One line.["0a"]Next line.["0a"]"
13990 contains an ASCII newline character (@code{Ada.Characters.Latin_1.LF})
13994 The subtype used as a prefix for the attributes @t{'Pos}, @t{'Min}, and
13995 @t{'Max} is optional (and is ignored in any case). For example, it is valid
13999 (@value{GDBP}) print 'max(x, y)
14003 When printing arrays, @value{GDBN} uses positional notation when the
14004 array has a lower bound of 1, and uses a modified named notation otherwise.
14005 For example, a one-dimensional array of three integers with a lower bound
14006 of 3 might print as
14013 That is, in contrast to valid Ada, only the first component has a @code{=>}
14017 You may abbreviate attributes in expressions with any unique,
14018 multi-character subsequence of
14019 their names (an exact match gets preference).
14020 For example, you may use @t{a'len}, @t{a'gth}, or @t{a'lh}
14021 in place of @t{a'length}.
14024 @cindex quoting Ada internal identifiers
14025 Since Ada is case-insensitive, the debugger normally maps identifiers you type
14026 to lower case. The GNAT compiler uses upper-case characters for
14027 some of its internal identifiers, which are normally of no interest to users.
14028 For the rare occasions when you actually have to look at them,
14029 enclose them in angle brackets to avoid the lower-case mapping.
14032 (@value{GDBP}) print <JMPBUF_SAVE>[0]
14036 Printing an object of class-wide type or dereferencing an
14037 access-to-class-wide value will display all the components of the object's
14038 specific type (as indicated by its run-time tag). Likewise, component
14039 selection on such a value will operate on the specific type of the
14044 @node Stopping Before Main Program
14045 @subsubsection Stopping at the Very Beginning
14047 @cindex breakpointing Ada elaboration code
14048 It is sometimes necessary to debug the program during elaboration, and
14049 before reaching the main procedure.
14050 As defined in the Ada Reference
14051 Manual, the elaboration code is invoked from a procedure called
14052 @code{adainit}. To run your program up to the beginning of
14053 elaboration, simply use the following two commands:
14054 @code{tbreak adainit} and @code{run}.
14057 @subsubsection Extensions for Ada Tasks
14058 @cindex Ada, tasking
14060 Support for Ada tasks is analogous to that for threads (@pxref{Threads}).
14061 @value{GDBN} provides the following task-related commands:
14066 This command shows a list of current Ada tasks, as in the following example:
14073 (@value{GDBP}) info tasks
14074 ID TID P-ID Pri State Name
14075 1 8088000 0 15 Child Activation Wait main_task
14076 2 80a4000 1 15 Accept Statement b
14077 3 809a800 1 15 Child Activation Wait a
14078 * 4 80ae800 3 15 Runnable c
14083 In this listing, the asterisk before the last task indicates it to be the
14084 task currently being inspected.
14088 Represents @value{GDBN}'s internal task number.
14094 The parent's task ID (@value{GDBN}'s internal task number).
14097 The base priority of the task.
14100 Current state of the task.
14104 The task has been created but has not been activated. It cannot be
14108 The task is not blocked for any reason known to Ada. (It may be waiting
14109 for a mutex, though.) It is conceptually "executing" in normal mode.
14112 The task is terminated, in the sense of ARM 9.3 (5). Any dependents
14113 that were waiting on terminate alternatives have been awakened and have
14114 terminated themselves.
14116 @item Child Activation Wait
14117 The task is waiting for created tasks to complete activation.
14119 @item Accept Statement
14120 The task is waiting on an accept or selective wait statement.
14122 @item Waiting on entry call
14123 The task is waiting on an entry call.
14125 @item Async Select Wait
14126 The task is waiting to start the abortable part of an asynchronous
14130 The task is waiting on a select statement with only a delay
14133 @item Child Termination Wait
14134 The task is sleeping having completed a master within itself, and is
14135 waiting for the tasks dependent on that master to become terminated or
14136 waiting on a terminate Phase.
14138 @item Wait Child in Term Alt
14139 The task is sleeping waiting for tasks on terminate alternatives to
14140 finish terminating.
14142 @item Accepting RV with @var{taskno}
14143 The task is accepting a rendez-vous with the task @var{taskno}.
14147 Name of the task in the program.
14151 @kindex info task @var{taskno}
14152 @item info task @var{taskno}
14153 This command shows detailled informations on the specified task, as in
14154 the following example:
14159 (@value{GDBP}) info tasks
14160 ID TID P-ID Pri State Name
14161 1 8077880 0 15 Child Activation Wait main_task
14162 * 2 807c468 1 15 Runnable task_1
14163 (@value{GDBP}) info task 2
14164 Ada Task: 0x807c468
14167 Parent: 1 (main_task)
14173 @kindex task@r{ (Ada)}
14174 @cindex current Ada task ID
14175 This command prints the ID of the current task.
14181 (@value{GDBP}) info tasks
14182 ID TID P-ID Pri State Name
14183 1 8077870 0 15 Child Activation Wait main_task
14184 * 2 807c458 1 15 Runnable t
14185 (@value{GDBP}) task
14186 [Current task is 2]
14189 @item task @var{taskno}
14190 @cindex Ada task switching
14191 This command is like the @code{thread @var{threadno}}
14192 command (@pxref{Threads}). It switches the context of debugging
14193 from the current task to the given task.
14199 (@value{GDBP}) info tasks
14200 ID TID P-ID Pri State Name
14201 1 8077870 0 15 Child Activation Wait main_task
14202 * 2 807c458 1 15 Runnable t
14203 (@value{GDBP}) task 1
14204 [Switching to task 1]
14205 #0 0x8067726 in pthread_cond_wait ()
14207 #0 0x8067726 in pthread_cond_wait ()
14208 #1 0x8056714 in system.os_interface.pthread_cond_wait ()
14209 #2 0x805cb63 in system.task_primitives.operations.sleep ()
14210 #3 0x806153e in system.tasking.stages.activate_tasks ()
14211 #4 0x804aacc in un () at un.adb:5
14214 @item break @var{linespec} task @var{taskno}
14215 @itemx break @var{linespec} task @var{taskno} if @dots{}
14216 @cindex breakpoints and tasks, in Ada
14217 @cindex task breakpoints, in Ada
14218 @kindex break @dots{} task @var{taskno}@r{ (Ada)}
14219 These commands are like the @code{break @dots{} thread @dots{}}
14220 command (@pxref{Thread Stops}).
14221 @var{linespec} specifies source lines, as described
14222 in @ref{Specify Location}.
14224 Use the qualifier @samp{task @var{taskno}} with a breakpoint command
14225 to specify that you only want @value{GDBN} to stop the program when a
14226 particular Ada task reaches this breakpoint. @var{taskno} is one of the
14227 numeric task identifiers assigned by @value{GDBN}, shown in the first
14228 column of the @samp{info tasks} display.
14230 If you do not specify @samp{task @var{taskno}} when you set a
14231 breakpoint, the breakpoint applies to @emph{all} tasks of your
14234 You can use the @code{task} qualifier on conditional breakpoints as
14235 well; in this case, place @samp{task @var{taskno}} before the
14236 breakpoint condition (before the @code{if}).
14244 (@value{GDBP}) info tasks
14245 ID TID P-ID Pri State Name
14246 1 140022020 0 15 Child Activation Wait main_task
14247 2 140045060 1 15 Accept/Select Wait t2
14248 3 140044840 1 15 Runnable t1
14249 * 4 140056040 1 15 Runnable t3
14250 (@value{GDBP}) b 15 task 2
14251 Breakpoint 5 at 0x120044cb0: file test_task_debug.adb, line 15.
14252 (@value{GDBP}) cont
14257 Breakpoint 5, test_task_debug () at test_task_debug.adb:15
14259 (@value{GDBP}) info tasks
14260 ID TID P-ID Pri State Name
14261 1 140022020 0 15 Child Activation Wait main_task
14262 * 2 140045060 1 15 Runnable t2
14263 3 140044840 1 15 Runnable t1
14264 4 140056040 1 15 Delay Sleep t3
14268 @node Ada Tasks and Core Files
14269 @subsubsection Tasking Support when Debugging Core Files
14270 @cindex Ada tasking and core file debugging
14272 When inspecting a core file, as opposed to debugging a live program,
14273 tasking support may be limited or even unavailable, depending on
14274 the platform being used.
14275 For instance, on x86-linux, the list of tasks is available, but task
14276 switching is not supported. On Tru64, however, task switching will work
14279 On certain platforms, including Tru64, the debugger needs to perform some
14280 memory writes in order to provide Ada tasking support. When inspecting
14281 a core file, this means that the core file must be opened with read-write
14282 privileges, using the command @samp{"set write on"} (@pxref{Patching}).
14283 Under these circumstances, you should make a backup copy of the core
14284 file before inspecting it with @value{GDBN}.
14286 @node Ravenscar Profile
14287 @subsubsection Tasking Support when using the Ravenscar Profile
14288 @cindex Ravenscar Profile
14290 The @dfn{Ravenscar Profile} is a subset of the Ada tasking features,
14291 specifically designed for systems with safety-critical real-time
14295 @kindex set ravenscar task-switching on
14296 @cindex task switching with program using Ravenscar Profile
14297 @item set ravenscar task-switching on
14298 Allows task switching when debugging a program that uses the Ravenscar
14299 Profile. This is the default.
14301 @kindex set ravenscar task-switching off
14302 @item set ravenscar task-switching off
14303 Turn off task switching when debugging a program that uses the Ravenscar
14304 Profile. This is mostly intended to disable the code that adds support
14305 for the Ravenscar Profile, in case a bug in either @value{GDBN} or in
14306 the Ravenscar runtime is preventing @value{GDBN} from working properly.
14307 To be effective, this command should be run before the program is started.
14309 @kindex show ravenscar task-switching
14310 @item show ravenscar task-switching
14311 Show whether it is possible to switch from task to task in a program
14312 using the Ravenscar Profile.
14317 @subsubsection Known Peculiarities of Ada Mode
14318 @cindex Ada, problems
14320 Besides the omissions listed previously (@pxref{Omissions from Ada}),
14321 we know of several problems with and limitations of Ada mode in
14323 some of which will be fixed with planned future releases of the debugger
14324 and the GNU Ada compiler.
14328 Static constants that the compiler chooses not to materialize as objects in
14329 storage are invisible to the debugger.
14332 Named parameter associations in function argument lists are ignored (the
14333 argument lists are treated as positional).
14336 Many useful library packages are currently invisible to the debugger.
14339 Fixed-point arithmetic, conversions, input, and output is carried out using
14340 floating-point arithmetic, and may give results that only approximate those on
14344 The GNAT compiler never generates the prefix @code{Standard} for any of
14345 the standard symbols defined by the Ada language. @value{GDBN} knows about
14346 this: it will strip the prefix from names when you use it, and will never
14347 look for a name you have so qualified among local symbols, nor match against
14348 symbols in other packages or subprograms. If you have
14349 defined entities anywhere in your program other than parameters and
14350 local variables whose simple names match names in @code{Standard},
14351 GNAT's lack of qualification here can cause confusion. When this happens,
14352 you can usually resolve the confusion
14353 by qualifying the problematic names with package
14354 @code{Standard} explicitly.
14357 Older versions of the compiler sometimes generate erroneous debugging
14358 information, resulting in the debugger incorrectly printing the value
14359 of affected entities. In some cases, the debugger is able to work
14360 around an issue automatically. In other cases, the debugger is able
14361 to work around the issue, but the work-around has to be specifically
14364 @kindex set ada trust-PAD-over-XVS
14365 @kindex show ada trust-PAD-over-XVS
14368 @item set ada trust-PAD-over-XVS on
14369 Configure GDB to strictly follow the GNAT encoding when computing the
14370 value of Ada entities, particularly when @code{PAD} and @code{PAD___XVS}
14371 types are involved (see @code{ada/exp_dbug.ads} in the GCC sources for
14372 a complete description of the encoding used by the GNAT compiler).
14373 This is the default.
14375 @item set ada trust-PAD-over-XVS off
14376 This is related to the encoding using by the GNAT compiler. If @value{GDBN}
14377 sometimes prints the wrong value for certain entities, changing @code{ada
14378 trust-PAD-over-XVS} to @code{off} activates a work-around which may fix
14379 the issue. It is always safe to set @code{ada trust-PAD-over-XVS} to
14380 @code{off}, but this incurs a slight performance penalty, so it is
14381 recommended to leave this setting to @code{on} unless necessary.
14385 @node Unsupported Languages
14386 @section Unsupported Languages
14388 @cindex unsupported languages
14389 @cindex minimal language
14390 In addition to the other fully-supported programming languages,
14391 @value{GDBN} also provides a pseudo-language, called @code{minimal}.
14392 It does not represent a real programming language, but provides a set
14393 of capabilities close to what the C or assembly languages provide.
14394 This should allow most simple operations to be performed while debugging
14395 an application that uses a language currently not supported by @value{GDBN}.
14397 If the language is set to @code{auto}, @value{GDBN} will automatically
14398 select this language if the current frame corresponds to an unsupported
14402 @chapter Examining the Symbol Table
14404 The commands described in this chapter allow you to inquire about the
14405 symbols (names of variables, functions and types) defined in your
14406 program. This information is inherent in the text of your program and
14407 does not change as your program executes. @value{GDBN} finds it in your
14408 program's symbol table, in the file indicated when you started @value{GDBN}
14409 (@pxref{File Options, ,Choosing Files}), or by one of the
14410 file-management commands (@pxref{Files, ,Commands to Specify Files}).
14412 @cindex symbol names
14413 @cindex names of symbols
14414 @cindex quoting names
14415 Occasionally, you may need to refer to symbols that contain unusual
14416 characters, which @value{GDBN} ordinarily treats as word delimiters. The
14417 most frequent case is in referring to static variables in other
14418 source files (@pxref{Variables,,Program Variables}). File names
14419 are recorded in object files as debugging symbols, but @value{GDBN} would
14420 ordinarily parse a typical file name, like @file{foo.c}, as the three words
14421 @samp{foo} @samp{.} @samp{c}. To allow @value{GDBN} to recognize
14422 @samp{foo.c} as a single symbol, enclose it in single quotes; for example,
14429 looks up the value of @code{x} in the scope of the file @file{foo.c}.
14432 @cindex case-insensitive symbol names
14433 @cindex case sensitivity in symbol names
14434 @kindex set case-sensitive
14435 @item set case-sensitive on
14436 @itemx set case-sensitive off
14437 @itemx set case-sensitive auto
14438 Normally, when @value{GDBN} looks up symbols, it matches their names
14439 with case sensitivity determined by the current source language.
14440 Occasionally, you may wish to control that. The command @code{set
14441 case-sensitive} lets you do that by specifying @code{on} for
14442 case-sensitive matches or @code{off} for case-insensitive ones. If
14443 you specify @code{auto}, case sensitivity is reset to the default
14444 suitable for the source language. The default is case-sensitive
14445 matches for all languages except for Fortran, for which the default is
14446 case-insensitive matches.
14448 @kindex show case-sensitive
14449 @item show case-sensitive
14450 This command shows the current setting of case sensitivity for symbols
14453 @kindex info address
14454 @cindex address of a symbol
14455 @item info address @var{symbol}
14456 Describe where the data for @var{symbol} is stored. For a register
14457 variable, this says which register it is kept in. For a non-register
14458 local variable, this prints the stack-frame offset at which the variable
14461 Note the contrast with @samp{print &@var{symbol}}, which does not work
14462 at all for a register variable, and for a stack local variable prints
14463 the exact address of the current instantiation of the variable.
14465 @kindex info symbol
14466 @cindex symbol from address
14467 @cindex closest symbol and offset for an address
14468 @item info symbol @var{addr}
14469 Print the name of a symbol which is stored at the address @var{addr}.
14470 If no symbol is stored exactly at @var{addr}, @value{GDBN} prints the
14471 nearest symbol and an offset from it:
14474 (@value{GDBP}) info symbol 0x54320
14475 _initialize_vx + 396 in section .text
14479 This is the opposite of the @code{info address} command. You can use
14480 it to find out the name of a variable or a function given its address.
14482 For dynamically linked executables, the name of executable or shared
14483 library containing the symbol is also printed:
14486 (@value{GDBP}) info symbol 0x400225
14487 _start + 5 in section .text of /tmp/a.out
14488 (@value{GDBP}) info symbol 0x2aaaac2811cf
14489 __read_nocancel + 6 in section .text of /usr/lib64/libc.so.6
14493 @item whatis [@var{arg}]
14494 Print the data type of @var{arg}, which can be either an expression
14495 or a name of a data type. With no argument, print the data type of
14496 @code{$}, the last value in the value history.
14498 If @var{arg} is an expression (@pxref{Expressions, ,Expressions}), it
14499 is not actually evaluated, and any side-effecting operations (such as
14500 assignments or function calls) inside it do not take place.
14502 If @var{arg} is a variable or an expression, @code{whatis} prints its
14503 literal type as it is used in the source code. If the type was
14504 defined using a @code{typedef}, @code{whatis} will @emph{not} print
14505 the data type underlying the @code{typedef}. If the type of the
14506 variable or the expression is a compound data type, such as
14507 @code{struct} or @code{class}, @code{whatis} never prints their
14508 fields or methods. It just prints the @code{struct}/@code{class}
14509 name (a.k.a.@: its @dfn{tag}). If you want to see the members of
14510 such a compound data type, use @code{ptype}.
14512 If @var{arg} is a type name that was defined using @code{typedef},
14513 @code{whatis} @dfn{unrolls} only one level of that @code{typedef}.
14514 Unrolling means that @code{whatis} will show the underlying type used
14515 in the @code{typedef} declaration of @var{arg}. However, if that
14516 underlying type is also a @code{typedef}, @code{whatis} will not
14519 For C code, the type names may also have the form @samp{class
14520 @var{class-name}}, @samp{struct @var{struct-tag}}, @samp{union
14521 @var{union-tag}} or @samp{enum @var{enum-tag}}.
14524 @item ptype [@var{arg}]
14525 @code{ptype} accepts the same arguments as @code{whatis}, but prints a
14526 detailed description of the type, instead of just the name of the type.
14527 @xref{Expressions, ,Expressions}.
14529 Contrary to @code{whatis}, @code{ptype} always unrolls any
14530 @code{typedef}s in its argument declaration, whether the argument is
14531 a variable, expression, or a data type. This means that @code{ptype}
14532 of a variable or an expression will not print literally its type as
14533 present in the source code---use @code{whatis} for that. @code{typedef}s at
14534 the pointer or reference targets are also unrolled. Only @code{typedef}s of
14535 fields, methods and inner @code{class typedef}s of @code{struct}s,
14536 @code{class}es and @code{union}s are not unrolled even with @code{ptype}.
14538 For example, for this variable declaration:
14541 typedef double real_t;
14542 struct complex @{ real_t real; double imag; @};
14543 typedef struct complex complex_t;
14545 real_t *real_pointer_var;
14549 the two commands give this output:
14553 (@value{GDBP}) whatis var
14555 (@value{GDBP}) ptype var
14556 type = struct complex @{
14560 (@value{GDBP}) whatis complex_t
14561 type = struct complex
14562 (@value{GDBP}) whatis struct complex
14563 type = struct complex
14564 (@value{GDBP}) ptype struct complex
14565 type = struct complex @{
14569 (@value{GDBP}) whatis real_pointer_var
14571 (@value{GDBP}) ptype real_pointer_var
14577 As with @code{whatis}, using @code{ptype} without an argument refers to
14578 the type of @code{$}, the last value in the value history.
14580 @cindex incomplete type
14581 Sometimes, programs use opaque data types or incomplete specifications
14582 of complex data structure. If the debug information included in the
14583 program does not allow @value{GDBN} to display a full declaration of
14584 the data type, it will say @samp{<incomplete type>}. For example,
14585 given these declarations:
14589 struct foo *fooptr;
14593 but no definition for @code{struct foo} itself, @value{GDBN} will say:
14596 (@value{GDBP}) ptype foo
14597 $1 = <incomplete type>
14601 ``Incomplete type'' is C terminology for data types that are not
14602 completely specified.
14605 @item info types @var{regexp}
14607 Print a brief description of all types whose names match the regular
14608 expression @var{regexp} (or all types in your program, if you supply
14609 no argument). Each complete typename is matched as though it were a
14610 complete line; thus, @samp{i type value} gives information on all
14611 types in your program whose names include the string @code{value}, but
14612 @samp{i type ^value$} gives information only on types whose complete
14613 name is @code{value}.
14615 This command differs from @code{ptype} in two ways: first, like
14616 @code{whatis}, it does not print a detailed description; second, it
14617 lists all source files where a type is defined.
14620 @cindex local variables
14621 @item info scope @var{location}
14622 List all the variables local to a particular scope. This command
14623 accepts a @var{location} argument---a function name, a source line, or
14624 an address preceded by a @samp{*}, and prints all the variables local
14625 to the scope defined by that location. (@xref{Specify Location}, for
14626 details about supported forms of @var{location}.) For example:
14629 (@value{GDBP}) @b{info scope command_line_handler}
14630 Scope for command_line_handler:
14631 Symbol rl is an argument at stack/frame offset 8, length 4.
14632 Symbol linebuffer is in static storage at address 0x150a18, length 4.
14633 Symbol linelength is in static storage at address 0x150a1c, length 4.
14634 Symbol p is a local variable in register $esi, length 4.
14635 Symbol p1 is a local variable in register $ebx, length 4.
14636 Symbol nline is a local variable in register $edx, length 4.
14637 Symbol repeat is a local variable at frame offset -8, length 4.
14641 This command is especially useful for determining what data to collect
14642 during a @dfn{trace experiment}, see @ref{Tracepoint Actions,
14645 @kindex info source
14647 Show information about the current source file---that is, the source file for
14648 the function containing the current point of execution:
14651 the name of the source file, and the directory containing it,
14653 the directory it was compiled in,
14655 its length, in lines,
14657 which programming language it is written in,
14659 whether the executable includes debugging information for that file, and
14660 if so, what format the information is in (e.g., STABS, Dwarf 2, etc.), and
14662 whether the debugging information includes information about
14663 preprocessor macros.
14667 @kindex info sources
14669 Print the names of all source files in your program for which there is
14670 debugging information, organized into two lists: files whose symbols
14671 have already been read, and files whose symbols will be read when needed.
14673 @kindex info functions
14674 @item info functions
14675 Print the names and data types of all defined functions.
14677 @item info functions @var{regexp}
14678 Print the names and data types of all defined functions
14679 whose names contain a match for regular expression @var{regexp}.
14680 Thus, @samp{info fun step} finds all functions whose names
14681 include @code{step}; @samp{info fun ^step} finds those whose names
14682 start with @code{step}. If a function name contains characters
14683 that conflict with the regular expression language (e.g.@:
14684 @samp{operator*()}), they may be quoted with a backslash.
14686 @kindex info variables
14687 @item info variables
14688 Print the names and data types of all variables that are defined
14689 outside of functions (i.e.@: excluding local variables).
14691 @item info variables @var{regexp}
14692 Print the names and data types of all variables (except for local
14693 variables) whose names contain a match for regular expression
14696 @kindex info classes
14697 @cindex Objective-C, classes and selectors
14699 @itemx info classes @var{regexp}
14700 Display all Objective-C classes in your program, or
14701 (with the @var{regexp} argument) all those matching a particular regular
14704 @kindex info selectors
14705 @item info selectors
14706 @itemx info selectors @var{regexp}
14707 Display all Objective-C selectors in your program, or
14708 (with the @var{regexp} argument) all those matching a particular regular
14712 This was never implemented.
14713 @kindex info methods
14715 @itemx info methods @var{regexp}
14716 The @code{info methods} command permits the user to examine all defined
14717 methods within C@t{++} program, or (with the @var{regexp} argument) a
14718 specific set of methods found in the various C@t{++} classes. Many
14719 C@t{++} classes provide a large number of methods. Thus, the output
14720 from the @code{ptype} command can be overwhelming and hard to use. The
14721 @code{info-methods} command filters the methods, printing only those
14722 which match the regular-expression @var{regexp}.
14725 @cindex opaque data types
14726 @kindex set opaque-type-resolution
14727 @item set opaque-type-resolution on
14728 Tell @value{GDBN} to resolve opaque types. An opaque type is a type
14729 declared as a pointer to a @code{struct}, @code{class}, or
14730 @code{union}---for example, @code{struct MyType *}---that is used in one
14731 source file although the full declaration of @code{struct MyType} is in
14732 another source file. The default is on.
14734 A change in the setting of this subcommand will not take effect until
14735 the next time symbols for a file are loaded.
14737 @item set opaque-type-resolution off
14738 Tell @value{GDBN} not to resolve opaque types. In this case, the type
14739 is printed as follows:
14741 @{<no data fields>@}
14744 @kindex show opaque-type-resolution
14745 @item show opaque-type-resolution
14746 Show whether opaque types are resolved or not.
14748 @kindex maint print symbols
14749 @cindex symbol dump
14750 @kindex maint print psymbols
14751 @cindex partial symbol dump
14752 @item maint print symbols @var{filename}
14753 @itemx maint print psymbols @var{filename}
14754 @itemx maint print msymbols @var{filename}
14755 Write a dump of debugging symbol data into the file @var{filename}.
14756 These commands are used to debug the @value{GDBN} symbol-reading code. Only
14757 symbols with debugging data are included. If you use @samp{maint print
14758 symbols}, @value{GDBN} includes all the symbols for which it has already
14759 collected full details: that is, @var{filename} reflects symbols for
14760 only those files whose symbols @value{GDBN} has read. You can use the
14761 command @code{info sources} to find out which files these are. If you
14762 use @samp{maint print psymbols} instead, the dump shows information about
14763 symbols that @value{GDBN} only knows partially---that is, symbols defined in
14764 files that @value{GDBN} has skimmed, but not yet read completely. Finally,
14765 @samp{maint print msymbols} dumps just the minimal symbol information
14766 required for each object file from which @value{GDBN} has read some symbols.
14767 @xref{Files, ,Commands to Specify Files}, for a discussion of how
14768 @value{GDBN} reads symbols (in the description of @code{symbol-file}).
14770 @kindex maint info symtabs
14771 @kindex maint info psymtabs
14772 @cindex listing @value{GDBN}'s internal symbol tables
14773 @cindex symbol tables, listing @value{GDBN}'s internal
14774 @cindex full symbol tables, listing @value{GDBN}'s internal
14775 @cindex partial symbol tables, listing @value{GDBN}'s internal
14776 @item maint info symtabs @r{[} @var{regexp} @r{]}
14777 @itemx maint info psymtabs @r{[} @var{regexp} @r{]}
14779 List the @code{struct symtab} or @code{struct partial_symtab}
14780 structures whose names match @var{regexp}. If @var{regexp} is not
14781 given, list them all. The output includes expressions which you can
14782 copy into a @value{GDBN} debugging this one to examine a particular
14783 structure in more detail. For example:
14786 (@value{GDBP}) maint info psymtabs dwarf2read
14787 @{ objfile /home/gnu/build/gdb/gdb
14788 ((struct objfile *) 0x82e69d0)
14789 @{ psymtab /home/gnu/src/gdb/dwarf2read.c
14790 ((struct partial_symtab *) 0x8474b10)
14793 text addresses 0x814d3c8 -- 0x8158074
14794 globals (* (struct partial_symbol **) 0x8507a08 @@ 9)
14795 statics (* (struct partial_symbol **) 0x40e95b78 @@ 2882)
14796 dependencies (none)
14799 (@value{GDBP}) maint info symtabs
14803 We see that there is one partial symbol table whose filename contains
14804 the string @samp{dwarf2read}, belonging to the @samp{gdb} executable;
14805 and we see that @value{GDBN} has not read in any symtabs yet at all.
14806 If we set a breakpoint on a function, that will cause @value{GDBN} to
14807 read the symtab for the compilation unit containing that function:
14810 (@value{GDBP}) break dwarf2_psymtab_to_symtab
14811 Breakpoint 1 at 0x814e5da: file /home/gnu/src/gdb/dwarf2read.c,
14813 (@value{GDBP}) maint info symtabs
14814 @{ objfile /home/gnu/build/gdb/gdb
14815 ((struct objfile *) 0x82e69d0)
14816 @{ symtab /home/gnu/src/gdb/dwarf2read.c
14817 ((struct symtab *) 0x86c1f38)
14820 blockvector ((struct blockvector *) 0x86c1bd0) (primary)
14821 linetable ((struct linetable *) 0x8370fa0)
14822 debugformat DWARF 2
14831 @chapter Altering Execution
14833 Once you think you have found an error in your program, you might want to
14834 find out for certain whether correcting the apparent error would lead to
14835 correct results in the rest of the run. You can find the answer by
14836 experiment, using the @value{GDBN} features for altering execution of the
14839 For example, you can store new values into variables or memory
14840 locations, give your program a signal, restart it at a different
14841 address, or even return prematurely from a function.
14844 * Assignment:: Assignment to variables
14845 * Jumping:: Continuing at a different address
14846 * Signaling:: Giving your program a signal
14847 * Returning:: Returning from a function
14848 * Calling:: Calling your program's functions
14849 * Patching:: Patching your program
14853 @section Assignment to Variables
14856 @cindex setting variables
14857 To alter the value of a variable, evaluate an assignment expression.
14858 @xref{Expressions, ,Expressions}. For example,
14865 stores the value 4 into the variable @code{x}, and then prints the
14866 value of the assignment expression (which is 4).
14867 @xref{Languages, ,Using @value{GDBN} with Different Languages}, for more
14868 information on operators in supported languages.
14870 @kindex set variable
14871 @cindex variables, setting
14872 If you are not interested in seeing the value of the assignment, use the
14873 @code{set} command instead of the @code{print} command. @code{set} is
14874 really the same as @code{print} except that the expression's value is
14875 not printed and is not put in the value history (@pxref{Value History,
14876 ,Value History}). The expression is evaluated only for its effects.
14878 If the beginning of the argument string of the @code{set} command
14879 appears identical to a @code{set} subcommand, use the @code{set
14880 variable} command instead of just @code{set}. This command is identical
14881 to @code{set} except for its lack of subcommands. For example, if your
14882 program has a variable @code{width}, you get an error if you try to set
14883 a new value with just @samp{set width=13}, because @value{GDBN} has the
14884 command @code{set width}:
14887 (@value{GDBP}) whatis width
14889 (@value{GDBP}) p width
14891 (@value{GDBP}) set width=47
14892 Invalid syntax in expression.
14896 The invalid expression, of course, is @samp{=47}. In
14897 order to actually set the program's variable @code{width}, use
14900 (@value{GDBP}) set var width=47
14903 Because the @code{set} command has many subcommands that can conflict
14904 with the names of program variables, it is a good idea to use the
14905 @code{set variable} command instead of just @code{set}. For example, if
14906 your program has a variable @code{g}, you run into problems if you try
14907 to set a new value with just @samp{set g=4}, because @value{GDBN} has
14908 the command @code{set gnutarget}, abbreviated @code{set g}:
14912 (@value{GDBP}) whatis g
14916 (@value{GDBP}) set g=4
14920 The program being debugged has been started already.
14921 Start it from the beginning? (y or n) y
14922 Starting program: /home/smith/cc_progs/a.out
14923 "/home/smith/cc_progs/a.out": can't open to read symbols:
14924 Invalid bfd target.
14925 (@value{GDBP}) show g
14926 The current BFD target is "=4".
14931 The program variable @code{g} did not change, and you silently set the
14932 @code{gnutarget} to an invalid value. In order to set the variable
14936 (@value{GDBP}) set var g=4
14939 @value{GDBN} allows more implicit conversions in assignments than C; you can
14940 freely store an integer value into a pointer variable or vice versa,
14941 and you can convert any structure to any other structure that is the
14942 same length or shorter.
14943 @comment FIXME: how do structs align/pad in these conversions?
14944 @comment /doc@cygnus.com 18dec1990
14946 To store values into arbitrary places in memory, use the @samp{@{@dots{}@}}
14947 construct to generate a value of specified type at a specified address
14948 (@pxref{Expressions, ,Expressions}). For example, @code{@{int@}0x83040} refers
14949 to memory location @code{0x83040} as an integer (which implies a certain size
14950 and representation in memory), and
14953 set @{int@}0x83040 = 4
14957 stores the value 4 into that memory location.
14960 @section Continuing at a Different Address
14962 Ordinarily, when you continue your program, you do so at the place where
14963 it stopped, with the @code{continue} command. You can instead continue at
14964 an address of your own choosing, with the following commands:
14968 @item jump @var{linespec}
14969 @itemx jump @var{location}
14970 Resume execution at line @var{linespec} or at address given by
14971 @var{location}. Execution stops again immediately if there is a
14972 breakpoint there. @xref{Specify Location}, for a description of the
14973 different forms of @var{linespec} and @var{location}. It is common
14974 practice to use the @code{tbreak} command in conjunction with
14975 @code{jump}. @xref{Set Breaks, ,Setting Breakpoints}.
14977 The @code{jump} command does not change the current stack frame, or
14978 the stack pointer, or the contents of any memory location or any
14979 register other than the program counter. If line @var{linespec} is in
14980 a different function from the one currently executing, the results may
14981 be bizarre if the two functions expect different patterns of arguments or
14982 of local variables. For this reason, the @code{jump} command requests
14983 confirmation if the specified line is not in the function currently
14984 executing. However, even bizarre results are predictable if you are
14985 well acquainted with the machine-language code of your program.
14988 @c Doesn't work on HP-UX; have to set $pcoqh and $pcoqt.
14989 On many systems, you can get much the same effect as the @code{jump}
14990 command by storing a new value into the register @code{$pc}. The
14991 difference is that this does not start your program running; it only
14992 changes the address of where it @emph{will} run when you continue. For
15000 makes the next @code{continue} command or stepping command execute at
15001 address @code{0x485}, rather than at the address where your program stopped.
15002 @xref{Continuing and Stepping, ,Continuing and Stepping}.
15004 The most common occasion to use the @code{jump} command is to back
15005 up---perhaps with more breakpoints set---over a portion of a program
15006 that has already executed, in order to examine its execution in more
15011 @section Giving your Program a Signal
15012 @cindex deliver a signal to a program
15016 @item signal @var{signal}
15017 Resume execution where your program stopped, but immediately give it the
15018 signal @var{signal}. @var{signal} can be the name or the number of a
15019 signal. For example, on many systems @code{signal 2} and @code{signal
15020 SIGINT} are both ways of sending an interrupt signal.
15022 Alternatively, if @var{signal} is zero, continue execution without
15023 giving a signal. This is useful when your program stopped on account of
15024 a signal and would ordinary see the signal when resumed with the
15025 @code{continue} command; @samp{signal 0} causes it to resume without a
15028 @code{signal} does not repeat when you press @key{RET} a second time
15029 after executing the command.
15033 Invoking the @code{signal} command is not the same as invoking the
15034 @code{kill} utility from the shell. Sending a signal with @code{kill}
15035 causes @value{GDBN} to decide what to do with the signal depending on
15036 the signal handling tables (@pxref{Signals}). The @code{signal} command
15037 passes the signal directly to your program.
15041 @section Returning from a Function
15044 @cindex returning from a function
15047 @itemx return @var{expression}
15048 You can cancel execution of a function call with the @code{return}
15049 command. If you give an
15050 @var{expression} argument, its value is used as the function's return
15054 When you use @code{return}, @value{GDBN} discards the selected stack frame
15055 (and all frames within it). You can think of this as making the
15056 discarded frame return prematurely. If you wish to specify a value to
15057 be returned, give that value as the argument to @code{return}.
15059 This pops the selected stack frame (@pxref{Selection, ,Selecting a
15060 Frame}), and any other frames inside of it, leaving its caller as the
15061 innermost remaining frame. That frame becomes selected. The
15062 specified value is stored in the registers used for returning values
15065 The @code{return} command does not resume execution; it leaves the
15066 program stopped in the state that would exist if the function had just
15067 returned. In contrast, the @code{finish} command (@pxref{Continuing
15068 and Stepping, ,Continuing and Stepping}) resumes execution until the
15069 selected stack frame returns naturally.
15071 @value{GDBN} needs to know how the @var{expression} argument should be set for
15072 the inferior. The concrete registers assignment depends on the OS ABI and the
15073 type being returned by the selected stack frame. For example it is common for
15074 OS ABI to return floating point values in FPU registers while integer values in
15075 CPU registers. Still some ABIs return even floating point values in CPU
15076 registers. Larger integer widths (such as @code{long long int}) also have
15077 specific placement rules. @value{GDBN} already knows the OS ABI from its
15078 current target so it needs to find out also the type being returned to make the
15079 assignment into the right register(s).
15081 Normally, the selected stack frame has debug info. @value{GDBN} will always
15082 use the debug info instead of the implicit type of @var{expression} when the
15083 debug info is available. For example, if you type @kbd{return -1}, and the
15084 function in the current stack frame is declared to return a @code{long long
15085 int}, @value{GDBN} transparently converts the implicit @code{int} value of -1
15086 into a @code{long long int}:
15089 Breakpoint 1, func () at gdb.base/return-nodebug.c:29
15091 (@value{GDBP}) return -1
15092 Make func return now? (y or n) y
15093 #0 0x004004f6 in main () at gdb.base/return-nodebug.c:43
15094 43 printf ("result=%lld\n", func ());
15098 However, if the selected stack frame does not have a debug info, e.g., if the
15099 function was compiled without debug info, @value{GDBN} has to find out the type
15100 to return from user. Specifying a different type by mistake may set the value
15101 in different inferior registers than the caller code expects. For example,
15102 typing @kbd{return -1} with its implicit type @code{int} would set only a part
15103 of a @code{long long int} result for a debug info less function (on 32-bit
15104 architectures). Therefore the user is required to specify the return type by
15105 an appropriate cast explicitly:
15108 Breakpoint 2, 0x0040050b in func ()
15109 (@value{GDBP}) return -1
15110 Return value type not available for selected stack frame.
15111 Please use an explicit cast of the value to return.
15112 (@value{GDBP}) return (long long int) -1
15113 Make selected stack frame return now? (y or n) y
15114 #0 0x00400526 in main ()
15119 @section Calling Program Functions
15122 @cindex calling functions
15123 @cindex inferior functions, calling
15124 @item print @var{expr}
15125 Evaluate the expression @var{expr} and display the resulting value.
15126 @var{expr} may include calls to functions in the program being
15130 @item call @var{expr}
15131 Evaluate the expression @var{expr} without displaying @code{void}
15134 You can use this variant of the @code{print} command if you want to
15135 execute a function from your program that does not return anything
15136 (a.k.a.@: @dfn{a void function}), but without cluttering the output
15137 with @code{void} returned values that @value{GDBN} will otherwise
15138 print. If the result is not void, it is printed and saved in the
15142 It is possible for the function you call via the @code{print} or
15143 @code{call} command to generate a signal (e.g., if there's a bug in
15144 the function, or if you passed it incorrect arguments). What happens
15145 in that case is controlled by the @code{set unwindonsignal} command.
15147 Similarly, with a C@t{++} program it is possible for the function you
15148 call via the @code{print} or @code{call} command to generate an
15149 exception that is not handled due to the constraints of the dummy
15150 frame. In this case, any exception that is raised in the frame, but has
15151 an out-of-frame exception handler will not be found. GDB builds a
15152 dummy-frame for the inferior function call, and the unwinder cannot
15153 seek for exception handlers outside of this dummy-frame. What happens
15154 in that case is controlled by the
15155 @code{set unwind-on-terminating-exception} command.
15158 @item set unwindonsignal
15159 @kindex set unwindonsignal
15160 @cindex unwind stack in called functions
15161 @cindex call dummy stack unwinding
15162 Set unwinding of the stack if a signal is received while in a function
15163 that @value{GDBN} called in the program being debugged. If set to on,
15164 @value{GDBN} unwinds the stack it created for the call and restores
15165 the context to what it was before the call. If set to off (the
15166 default), @value{GDBN} stops in the frame where the signal was
15169 @item show unwindonsignal
15170 @kindex show unwindonsignal
15171 Show the current setting of stack unwinding in the functions called by
15174 @item set unwind-on-terminating-exception
15175 @kindex set unwind-on-terminating-exception
15176 @cindex unwind stack in called functions with unhandled exceptions
15177 @cindex call dummy stack unwinding on unhandled exception.
15178 Set unwinding of the stack if a C@t{++} exception is raised, but left
15179 unhandled while in a function that @value{GDBN} called in the program being
15180 debugged. If set to on (the default), @value{GDBN} unwinds the stack
15181 it created for the call and restores the context to what it was before
15182 the call. If set to off, @value{GDBN} the exception is delivered to
15183 the default C@t{++} exception handler and the inferior terminated.
15185 @item show unwind-on-terminating-exception
15186 @kindex show unwind-on-terminating-exception
15187 Show the current setting of stack unwinding in the functions called by
15192 @cindex weak alias functions
15193 Sometimes, a function you wish to call is actually a @dfn{weak alias}
15194 for another function. In such case, @value{GDBN} might not pick up
15195 the type information, including the types of the function arguments,
15196 which causes @value{GDBN} to call the inferior function incorrectly.
15197 As a result, the called function will function erroneously and may
15198 even crash. A solution to that is to use the name of the aliased
15202 @section Patching Programs
15204 @cindex patching binaries
15205 @cindex writing into executables
15206 @cindex writing into corefiles
15208 By default, @value{GDBN} opens the file containing your program's
15209 executable code (or the corefile) read-only. This prevents accidental
15210 alterations to machine code; but it also prevents you from intentionally
15211 patching your program's binary.
15213 If you'd like to be able to patch the binary, you can specify that
15214 explicitly with the @code{set write} command. For example, you might
15215 want to turn on internal debugging flags, or even to make emergency
15221 @itemx set write off
15222 If you specify @samp{set write on}, @value{GDBN} opens executable and
15223 core files for both reading and writing; if you specify @kbd{set write
15224 off} (the default), @value{GDBN} opens them read-only.
15226 If you have already loaded a file, you must load it again (using the
15227 @code{exec-file} or @code{core-file} command) after changing @code{set
15228 write}, for your new setting to take effect.
15232 Display whether executable files and core files are opened for writing
15233 as well as reading.
15237 @chapter @value{GDBN} Files
15239 @value{GDBN} needs to know the file name of the program to be debugged,
15240 both in order to read its symbol table and in order to start your
15241 program. To debug a core dump of a previous run, you must also tell
15242 @value{GDBN} the name of the core dump file.
15245 * Files:: Commands to specify files
15246 * Separate Debug Files:: Debugging information in separate files
15247 * Index Files:: Index files speed up GDB
15248 * Symbol Errors:: Errors reading symbol files
15249 * Data Files:: GDB data files
15253 @section Commands to Specify Files
15255 @cindex symbol table
15256 @cindex core dump file
15258 You may want to specify executable and core dump file names. The usual
15259 way to do this is at start-up time, using the arguments to
15260 @value{GDBN}'s start-up commands (@pxref{Invocation, , Getting In and
15261 Out of @value{GDBN}}).
15263 Occasionally it is necessary to change to a different file during a
15264 @value{GDBN} session. Or you may run @value{GDBN} and forget to
15265 specify a file you want to use. Or you are debugging a remote target
15266 via @code{gdbserver} (@pxref{Server, file, Using the @code{gdbserver}
15267 Program}). In these situations the @value{GDBN} commands to specify
15268 new files are useful.
15271 @cindex executable file
15273 @item file @var{filename}
15274 Use @var{filename} as the program to be debugged. It is read for its
15275 symbols and for the contents of pure memory. It is also the program
15276 executed when you use the @code{run} command. If you do not specify a
15277 directory and the file is not found in the @value{GDBN} working directory,
15278 @value{GDBN} uses the environment variable @code{PATH} as a list of
15279 directories to search, just as the shell does when looking for a program
15280 to run. You can change the value of this variable, for both @value{GDBN}
15281 and your program, using the @code{path} command.
15283 @cindex unlinked object files
15284 @cindex patching object files
15285 You can load unlinked object @file{.o} files into @value{GDBN} using
15286 the @code{file} command. You will not be able to ``run'' an object
15287 file, but you can disassemble functions and inspect variables. Also,
15288 if the underlying BFD functionality supports it, you could use
15289 @kbd{gdb -write} to patch object files using this technique. Note
15290 that @value{GDBN} can neither interpret nor modify relocations in this
15291 case, so branches and some initialized variables will appear to go to
15292 the wrong place. But this feature is still handy from time to time.
15295 @code{file} with no argument makes @value{GDBN} discard any information it
15296 has on both executable file and the symbol table.
15299 @item exec-file @r{[} @var{filename} @r{]}
15300 Specify that the program to be run (but not the symbol table) is found
15301 in @var{filename}. @value{GDBN} searches the environment variable @code{PATH}
15302 if necessary to locate your program. Omitting @var{filename} means to
15303 discard information on the executable file.
15305 @kindex symbol-file
15306 @item symbol-file @r{[} @var{filename} @r{]}
15307 Read symbol table information from file @var{filename}. @code{PATH} is
15308 searched when necessary. Use the @code{file} command to get both symbol
15309 table and program to run from the same file.
15311 @code{symbol-file} with no argument clears out @value{GDBN} information on your
15312 program's symbol table.
15314 The @code{symbol-file} command causes @value{GDBN} to forget the contents of
15315 some breakpoints and auto-display expressions. This is because they may
15316 contain pointers to the internal data recording symbols and data types,
15317 which are part of the old symbol table data being discarded inside
15320 @code{symbol-file} does not repeat if you press @key{RET} again after
15323 When @value{GDBN} is configured for a particular environment, it
15324 understands debugging information in whatever format is the standard
15325 generated for that environment; you may use either a @sc{gnu} compiler, or
15326 other compilers that adhere to the local conventions.
15327 Best results are usually obtained from @sc{gnu} compilers; for example,
15328 using @code{@value{NGCC}} you can generate debugging information for
15331 For most kinds of object files, with the exception of old SVR3 systems
15332 using COFF, the @code{symbol-file} command does not normally read the
15333 symbol table in full right away. Instead, it scans the symbol table
15334 quickly to find which source files and which symbols are present. The
15335 details are read later, one source file at a time, as they are needed.
15337 The purpose of this two-stage reading strategy is to make @value{GDBN}
15338 start up faster. For the most part, it is invisible except for
15339 occasional pauses while the symbol table details for a particular source
15340 file are being read. (The @code{set verbose} command can turn these
15341 pauses into messages if desired. @xref{Messages/Warnings, ,Optional
15342 Warnings and Messages}.)
15344 We have not implemented the two-stage strategy for COFF yet. When the
15345 symbol table is stored in COFF format, @code{symbol-file} reads the
15346 symbol table data in full right away. Note that ``stabs-in-COFF''
15347 still does the two-stage strategy, since the debug info is actually
15351 @cindex reading symbols immediately
15352 @cindex symbols, reading immediately
15353 @item symbol-file @r{[} -readnow @r{]} @var{filename}
15354 @itemx file @r{[} -readnow @r{]} @var{filename}
15355 You can override the @value{GDBN} two-stage strategy for reading symbol
15356 tables by using the @samp{-readnow} option with any of the commands that
15357 load symbol table information, if you want to be sure @value{GDBN} has the
15358 entire symbol table available.
15360 @c FIXME: for now no mention of directories, since this seems to be in
15361 @c flux. 13mar1992 status is that in theory GDB would look either in
15362 @c current dir or in same dir as myprog; but issues like competing
15363 @c GDB's, or clutter in system dirs, mean that in practice right now
15364 @c only current dir is used. FFish says maybe a special GDB hierarchy
15365 @c (eg rooted in val of env var GDBSYMS) could exist for mappable symbol
15369 @item core-file @r{[}@var{filename}@r{]}
15371 Specify the whereabouts of a core dump file to be used as the ``contents
15372 of memory''. Traditionally, core files contain only some parts of the
15373 address space of the process that generated them; @value{GDBN} can access the
15374 executable file itself for other parts.
15376 @code{core-file} with no argument specifies that no core file is
15379 Note that the core file is ignored when your program is actually running
15380 under @value{GDBN}. So, if you have been running your program and you
15381 wish to debug a core file instead, you must kill the subprocess in which
15382 the program is running. To do this, use the @code{kill} command
15383 (@pxref{Kill Process, ,Killing the Child Process}).
15385 @kindex add-symbol-file
15386 @cindex dynamic linking
15387 @item add-symbol-file @var{filename} @var{address}
15388 @itemx add-symbol-file @var{filename} @var{address} @r{[} -readnow @r{]}
15389 @itemx add-symbol-file @var{filename} @var{address} -s @var{section} @var{address} @dots{}
15390 The @code{add-symbol-file} command reads additional symbol table
15391 information from the file @var{filename}. You would use this command
15392 when @var{filename} has been dynamically loaded (by some other means)
15393 into the program that is running. @var{address} should be the memory
15394 address at which the file has been loaded; @value{GDBN} cannot figure
15395 this out for itself. You can additionally specify an arbitrary number
15396 of @samp{-s @var{section} @var{address}} pairs, to give an explicit
15397 section name and base address for that section. You can specify any
15398 @var{address} as an expression.
15400 The symbol table of the file @var{filename} is added to the symbol table
15401 originally read with the @code{symbol-file} command. You can use the
15402 @code{add-symbol-file} command any number of times; the new symbol data
15403 thus read keeps adding to the old. To discard all old symbol data
15404 instead, use the @code{symbol-file} command without any arguments.
15406 @cindex relocatable object files, reading symbols from
15407 @cindex object files, relocatable, reading symbols from
15408 @cindex reading symbols from relocatable object files
15409 @cindex symbols, reading from relocatable object files
15410 @cindex @file{.o} files, reading symbols from
15411 Although @var{filename} is typically a shared library file, an
15412 executable file, or some other object file which has been fully
15413 relocated for loading into a process, you can also load symbolic
15414 information from relocatable @file{.o} files, as long as:
15418 the file's symbolic information refers only to linker symbols defined in
15419 that file, not to symbols defined by other object files,
15421 every section the file's symbolic information refers to has actually
15422 been loaded into the inferior, as it appears in the file, and
15424 you can determine the address at which every section was loaded, and
15425 provide these to the @code{add-symbol-file} command.
15429 Some embedded operating systems, like Sun Chorus and VxWorks, can load
15430 relocatable files into an already running program; such systems
15431 typically make the requirements above easy to meet. However, it's
15432 important to recognize that many native systems use complex link
15433 procedures (@code{.linkonce} section factoring and C@t{++} constructor table
15434 assembly, for example) that make the requirements difficult to meet. In
15435 general, one cannot assume that using @code{add-symbol-file} to read a
15436 relocatable object file's symbolic information will have the same effect
15437 as linking the relocatable object file into the program in the normal
15440 @code{add-symbol-file} does not repeat if you press @key{RET} after using it.
15442 @kindex add-symbol-file-from-memory
15443 @cindex @code{syscall DSO}
15444 @cindex load symbols from memory
15445 @item add-symbol-file-from-memory @var{address}
15446 Load symbols from the given @var{address} in a dynamically loaded
15447 object file whose image is mapped directly into the inferior's memory.
15448 For example, the Linux kernel maps a @code{syscall DSO} into each
15449 process's address space; this DSO provides kernel-specific code for
15450 some system calls. The argument can be any expression whose
15451 evaluation yields the address of the file's shared object file header.
15452 For this command to work, you must have used @code{symbol-file} or
15453 @code{exec-file} commands in advance.
15455 @kindex add-shared-symbol-files
15457 @item add-shared-symbol-files @var{library-file}
15458 @itemx assf @var{library-file}
15459 The @code{add-shared-symbol-files} command can currently be used only
15460 in the Cygwin build of @value{GDBN} on MS-Windows OS, where it is an
15461 alias for the @code{dll-symbols} command (@pxref{Cygwin Native}).
15462 @value{GDBN} automatically looks for shared libraries, however if
15463 @value{GDBN} does not find yours, you can invoke
15464 @code{add-shared-symbol-files}. It takes one argument: the shared
15465 library's file name. @code{assf} is a shorthand alias for
15466 @code{add-shared-symbol-files}.
15469 @item section @var{section} @var{addr}
15470 The @code{section} command changes the base address of the named
15471 @var{section} of the exec file to @var{addr}. This can be used if the
15472 exec file does not contain section addresses, (such as in the
15473 @code{a.out} format), or when the addresses specified in the file
15474 itself are wrong. Each section must be changed separately. The
15475 @code{info files} command, described below, lists all the sections and
15479 @kindex info target
15482 @code{info files} and @code{info target} are synonymous; both print the
15483 current target (@pxref{Targets, ,Specifying a Debugging Target}),
15484 including the names of the executable and core dump files currently in
15485 use by @value{GDBN}, and the files from which symbols were loaded. The
15486 command @code{help target} lists all possible targets rather than
15489 @kindex maint info sections
15490 @item maint info sections
15491 Another command that can give you extra information about program sections
15492 is @code{maint info sections}. In addition to the section information
15493 displayed by @code{info files}, this command displays the flags and file
15494 offset of each section in the executable and core dump files. In addition,
15495 @code{maint info sections} provides the following command options (which
15496 may be arbitrarily combined):
15500 Display sections for all loaded object files, including shared libraries.
15501 @item @var{sections}
15502 Display info only for named @var{sections}.
15503 @item @var{section-flags}
15504 Display info only for sections for which @var{section-flags} are true.
15505 The section flags that @value{GDBN} currently knows about are:
15508 Section will have space allocated in the process when loaded.
15509 Set for all sections except those containing debug information.
15511 Section will be loaded from the file into the child process memory.
15512 Set for pre-initialized code and data, clear for @code{.bss} sections.
15514 Section needs to be relocated before loading.
15516 Section cannot be modified by the child process.
15518 Section contains executable code only.
15520 Section contains data only (no executable code).
15522 Section will reside in ROM.
15524 Section contains data for constructor/destructor lists.
15526 Section is not empty.
15528 An instruction to the linker to not output the section.
15529 @item COFF_SHARED_LIBRARY
15530 A notification to the linker that the section contains
15531 COFF shared library information.
15533 Section contains common symbols.
15536 @kindex set trust-readonly-sections
15537 @cindex read-only sections
15538 @item set trust-readonly-sections on
15539 Tell @value{GDBN} that readonly sections in your object file
15540 really are read-only (i.e.@: that their contents will not change).
15541 In that case, @value{GDBN} can fetch values from these sections
15542 out of the object file, rather than from the target program.
15543 For some targets (notably embedded ones), this can be a significant
15544 enhancement to debugging performance.
15546 The default is off.
15548 @item set trust-readonly-sections off
15549 Tell @value{GDBN} not to trust readonly sections. This means that
15550 the contents of the section might change while the program is running,
15551 and must therefore be fetched from the target when needed.
15553 @item show trust-readonly-sections
15554 Show the current setting of trusting readonly sections.
15557 All file-specifying commands allow both absolute and relative file names
15558 as arguments. @value{GDBN} always converts the file name to an absolute file
15559 name and remembers it that way.
15561 @cindex shared libraries
15562 @anchor{Shared Libraries}
15563 @value{GDBN} supports @sc{gnu}/Linux, MS-Windows, HP-UX, SunOS, SVr4, Irix,
15564 and IBM RS/6000 AIX shared libraries.
15566 On MS-Windows @value{GDBN} must be linked with the Expat library to support
15567 shared libraries. @xref{Expat}.
15569 @value{GDBN} automatically loads symbol definitions from shared libraries
15570 when you use the @code{run} command, or when you examine a core file.
15571 (Before you issue the @code{run} command, @value{GDBN} does not understand
15572 references to a function in a shared library, however---unless you are
15573 debugging a core file).
15575 On HP-UX, if the program loads a library explicitly, @value{GDBN}
15576 automatically loads the symbols at the time of the @code{shl_load} call.
15578 @c FIXME: some @value{GDBN} release may permit some refs to undef
15579 @c FIXME...symbols---eg in a break cmd---assuming they are from a shared
15580 @c FIXME...lib; check this from time to time when updating manual
15582 There are times, however, when you may wish to not automatically load
15583 symbol definitions from shared libraries, such as when they are
15584 particularly large or there are many of them.
15586 To control the automatic loading of shared library symbols, use the
15590 @kindex set auto-solib-add
15591 @item set auto-solib-add @var{mode}
15592 If @var{mode} is @code{on}, symbols from all shared object libraries
15593 will be loaded automatically when the inferior begins execution, you
15594 attach to an independently started inferior, or when the dynamic linker
15595 informs @value{GDBN} that a new library has been loaded. If @var{mode}
15596 is @code{off}, symbols must be loaded manually, using the
15597 @code{sharedlibrary} command. The default value is @code{on}.
15599 @cindex memory used for symbol tables
15600 If your program uses lots of shared libraries with debug info that
15601 takes large amounts of memory, you can decrease the @value{GDBN}
15602 memory footprint by preventing it from automatically loading the
15603 symbols from shared libraries. To that end, type @kbd{set
15604 auto-solib-add off} before running the inferior, then load each
15605 library whose debug symbols you do need with @kbd{sharedlibrary
15606 @var{regexp}}, where @var{regexp} is a regular expression that matches
15607 the libraries whose symbols you want to be loaded.
15609 @kindex show auto-solib-add
15610 @item show auto-solib-add
15611 Display the current autoloading mode.
15614 @cindex load shared library
15615 To explicitly load shared library symbols, use the @code{sharedlibrary}
15619 @kindex info sharedlibrary
15621 @item info share @var{regex}
15622 @itemx info sharedlibrary @var{regex}
15623 Print the names of the shared libraries which are currently loaded
15624 that match @var{regex}. If @var{regex} is omitted then print
15625 all shared libraries that are loaded.
15627 @kindex sharedlibrary
15629 @item sharedlibrary @var{regex}
15630 @itemx share @var{regex}
15631 Load shared object library symbols for files matching a
15632 Unix regular expression.
15633 As with files loaded automatically, it only loads shared libraries
15634 required by your program for a core file or after typing @code{run}. If
15635 @var{regex} is omitted all shared libraries required by your program are
15638 @item nosharedlibrary
15639 @kindex nosharedlibrary
15640 @cindex unload symbols from shared libraries
15641 Unload all shared object library symbols. This discards all symbols
15642 that have been loaded from all shared libraries. Symbols from shared
15643 libraries that were loaded by explicit user requests are not
15647 Sometimes you may wish that @value{GDBN} stops and gives you control
15648 when any of shared library events happen. The best way to do this is
15649 to use @code{catch load} and @code{catch unload} (@pxref{Set
15652 @value{GDBN} also supports the the @code{set stop-on-solib-events}
15653 command for this. This command exists for historical reasons. It is
15654 less useful than setting a catchpoint, because it does not allow for
15655 conditions or commands as a catchpoint does.
15658 @item set stop-on-solib-events
15659 @kindex set stop-on-solib-events
15660 This command controls whether @value{GDBN} should give you control
15661 when the dynamic linker notifies it about some shared library event.
15662 The most common event of interest is loading or unloading of a new
15665 @item show stop-on-solib-events
15666 @kindex show stop-on-solib-events
15667 Show whether @value{GDBN} stops and gives you control when shared
15668 library events happen.
15671 Shared libraries are also supported in many cross or remote debugging
15672 configurations. @value{GDBN} needs to have access to the target's libraries;
15673 this can be accomplished either by providing copies of the libraries
15674 on the host system, or by asking @value{GDBN} to automatically retrieve the
15675 libraries from the target. If copies of the target libraries are
15676 provided, they need to be the same as the target libraries, although the
15677 copies on the target can be stripped as long as the copies on the host are
15680 @cindex where to look for shared libraries
15681 For remote debugging, you need to tell @value{GDBN} where the target
15682 libraries are, so that it can load the correct copies---otherwise, it
15683 may try to load the host's libraries. @value{GDBN} has two variables
15684 to specify the search directories for target libraries.
15687 @cindex prefix for shared library file names
15688 @cindex system root, alternate
15689 @kindex set solib-absolute-prefix
15690 @kindex set sysroot
15691 @item set sysroot @var{path}
15692 Use @var{path} as the system root for the program being debugged. Any
15693 absolute shared library paths will be prefixed with @var{path}; many
15694 runtime loaders store the absolute paths to the shared library in the
15695 target program's memory. If you use @code{set sysroot} to find shared
15696 libraries, they need to be laid out in the same way that they are on
15697 the target, with e.g.@: a @file{/lib} and @file{/usr/lib} hierarchy
15700 If @var{path} starts with the sequence @file{remote:}, @value{GDBN} will
15701 retrieve the target libraries from the remote system. This is only
15702 supported when using a remote target that supports the @code{remote get}
15703 command (@pxref{File Transfer,,Sending files to a remote system}).
15704 The part of @var{path} following the initial @file{remote:}
15705 (if present) is used as system root prefix on the remote file system.
15706 @footnote{If you want to specify a local system root using a directory
15707 that happens to be named @file{remote:}, you need to use some equivalent
15708 variant of the name like @file{./remote:}.}
15710 For targets with an MS-DOS based filesystem, such as MS-Windows and
15711 SymbianOS, @value{GDBN} tries prefixing a few variants of the target
15712 absolute file name with @var{path}. But first, on Unix hosts,
15713 @value{GDBN} converts all backslash directory separators into forward
15714 slashes, because the backslash is not a directory separator on Unix:
15717 c:\foo\bar.dll @result{} c:/foo/bar.dll
15720 Then, @value{GDBN} attempts prefixing the target file name with
15721 @var{path}, and looks for the resulting file name in the host file
15725 c:/foo/bar.dll @result{} /path/to/sysroot/c:/foo/bar.dll
15728 If that does not find the shared library, @value{GDBN} tries removing
15729 the @samp{:} character from the drive spec, both for convenience, and,
15730 for the case of the host file system not supporting file names with
15734 c:/foo/bar.dll @result{} /path/to/sysroot/c/foo/bar.dll
15737 This makes it possible to have a system root that mirrors a target
15738 with more than one drive. E.g., you may want to setup your local
15739 copies of the target system shared libraries like so (note @samp{c} vs
15743 @file{/path/to/sysroot/c/sys/bin/foo.dll}
15744 @file{/path/to/sysroot/c/sys/bin/bar.dll}
15745 @file{/path/to/sysroot/z/sys/bin/bar.dll}
15749 and point the system root at @file{/path/to/sysroot}, so that
15750 @value{GDBN} can find the correct copies of both
15751 @file{c:\sys\bin\foo.dll}, and @file{z:\sys\bin\bar.dll}.
15753 If that still does not find the shared library, @value{GDBN} tries
15754 removing the whole drive spec from the target file name:
15757 c:/foo/bar.dll @result{} /path/to/sysroot/foo/bar.dll
15760 This last lookup makes it possible to not care about the drive name,
15761 if you don't want or need to.
15763 The @code{set solib-absolute-prefix} command is an alias for @code{set
15766 @cindex default system root
15767 @cindex @samp{--with-sysroot}
15768 You can set the default system root by using the configure-time
15769 @samp{--with-sysroot} option. If the system root is inside
15770 @value{GDBN}'s configured binary prefix (set with @samp{--prefix} or
15771 @samp{--exec-prefix}), then the default system root will be updated
15772 automatically if the installed @value{GDBN} is moved to a new
15775 @kindex show sysroot
15777 Display the current shared library prefix.
15779 @kindex set solib-search-path
15780 @item set solib-search-path @var{path}
15781 If this variable is set, @var{path} is a colon-separated list of
15782 directories to search for shared libraries. @samp{solib-search-path}
15783 is used after @samp{sysroot} fails to locate the library, or if the
15784 path to the library is relative instead of absolute. If you want to
15785 use @samp{solib-search-path} instead of @samp{sysroot}, be sure to set
15786 @samp{sysroot} to a nonexistent directory to prevent @value{GDBN} from
15787 finding your host's libraries. @samp{sysroot} is preferred; setting
15788 it to a nonexistent directory may interfere with automatic loading
15789 of shared library symbols.
15791 @kindex show solib-search-path
15792 @item show solib-search-path
15793 Display the current shared library search path.
15795 @cindex DOS file-name semantics of file names.
15796 @kindex set target-file-system-kind (unix|dos-based|auto)
15797 @kindex show target-file-system-kind
15798 @item set target-file-system-kind @var{kind}
15799 Set assumed file system kind for target reported file names.
15801 Shared library file names as reported by the target system may not
15802 make sense as is on the system @value{GDBN} is running on. For
15803 example, when remote debugging a target that has MS-DOS based file
15804 system semantics, from a Unix host, the target may be reporting to
15805 @value{GDBN} a list of loaded shared libraries with file names such as
15806 @file{c:\Windows\kernel32.dll}. On Unix hosts, there's no concept of
15807 drive letters, so the @samp{c:\} prefix is not normally understood as
15808 indicating an absolute file name, and neither is the backslash
15809 normally considered a directory separator character. In that case,
15810 the native file system would interpret this whole absolute file name
15811 as a relative file name with no directory components. This would make
15812 it impossible to point @value{GDBN} at a copy of the remote target's
15813 shared libraries on the host using @code{set sysroot}, and impractical
15814 with @code{set solib-search-path}. Setting
15815 @code{target-file-system-kind} to @code{dos-based} tells @value{GDBN}
15816 to interpret such file names similarly to how the target would, and to
15817 map them to file names valid on @value{GDBN}'s native file system
15818 semantics. The value of @var{kind} can be @code{"auto"}, in addition
15819 to one of the supported file system kinds. In that case, @value{GDBN}
15820 tries to determine the appropriate file system variant based on the
15821 current target's operating system (@pxref{ABI, ,Configuring the
15822 Current ABI}). The supported file system settings are:
15826 Instruct @value{GDBN} to assume the target file system is of Unix
15827 kind. Only file names starting the forward slash (@samp{/}) character
15828 are considered absolute, and the directory separator character is also
15832 Instruct @value{GDBN} to assume the target file system is DOS based.
15833 File names starting with either a forward slash, or a drive letter
15834 followed by a colon (e.g., @samp{c:}), are considered absolute, and
15835 both the slash (@samp{/}) and the backslash (@samp{\\}) characters are
15836 considered directory separators.
15839 Instruct @value{GDBN} to use the file system kind associated with the
15840 target operating system (@pxref{ABI, ,Configuring the Current ABI}).
15841 This is the default.
15845 @cindex file name canonicalization
15846 @cindex base name differences
15847 When processing file names provided by the user, @value{GDBN}
15848 frequently needs to compare them to the file names recorded in the
15849 program's debug info. Normally, @value{GDBN} compares just the
15850 @dfn{base names} of the files as strings, which is reasonably fast
15851 even for very large programs. (The base name of a file is the last
15852 portion of its name, after stripping all the leading directories.)
15853 This shortcut in comparison is based upon the assumption that files
15854 cannot have more than one base name. This is usually true, but
15855 references to files that use symlinks or similar filesystem
15856 facilities violate that assumption. If your program records files
15857 using such facilities, or if you provide file names to @value{GDBN}
15858 using symlinks etc., you can set @code{basenames-may-differ} to
15859 @code{true} to instruct @value{GDBN} to completely canonicalize each
15860 pair of file names it needs to compare. This will make file-name
15861 comparisons accurate, but at a price of a significant slowdown.
15864 @item set basenames-may-differ
15865 @kindex set basenames-may-differ
15866 Set whether a source file may have multiple base names.
15868 @item show basenames-may-differ
15869 @kindex show basenames-may-differ
15870 Show whether a source file may have multiple base names.
15873 @node Separate Debug Files
15874 @section Debugging Information in Separate Files
15875 @cindex separate debugging information files
15876 @cindex debugging information in separate files
15877 @cindex @file{.debug} subdirectories
15878 @cindex debugging information directory, global
15879 @cindex global debugging information directory
15880 @cindex build ID, and separate debugging files
15881 @cindex @file{.build-id} directory
15883 @value{GDBN} allows you to put a program's debugging information in a
15884 file separate from the executable itself, in a way that allows
15885 @value{GDBN} to find and load the debugging information automatically.
15886 Since debugging information can be very large---sometimes larger
15887 than the executable code itself---some systems distribute debugging
15888 information for their executables in separate files, which users can
15889 install only when they need to debug a problem.
15891 @value{GDBN} supports two ways of specifying the separate debug info
15896 The executable contains a @dfn{debug link} that specifies the name of
15897 the separate debug info file. The separate debug file's name is
15898 usually @file{@var{executable}.debug}, where @var{executable} is the
15899 name of the corresponding executable file without leading directories
15900 (e.g., @file{ls.debug} for @file{/usr/bin/ls}). In addition, the
15901 debug link specifies a 32-bit @dfn{Cyclic Redundancy Check} (CRC)
15902 checksum for the debug file, which @value{GDBN} uses to validate that
15903 the executable and the debug file came from the same build.
15906 The executable contains a @dfn{build ID}, a unique bit string that is
15907 also present in the corresponding debug info file. (This is supported
15908 only on some operating systems, notably those which use the ELF format
15909 for binary files and the @sc{gnu} Binutils.) For more details about
15910 this feature, see the description of the @option{--build-id}
15911 command-line option in @ref{Options, , Command Line Options, ld.info,
15912 The GNU Linker}. The debug info file's name is not specified
15913 explicitly by the build ID, but can be computed from the build ID, see
15917 Depending on the way the debug info file is specified, @value{GDBN}
15918 uses two different methods of looking for the debug file:
15922 For the ``debug link'' method, @value{GDBN} looks up the named file in
15923 the directory of the executable file, then in a subdirectory of that
15924 directory named @file{.debug}, and finally under the global debug
15925 directory, in a subdirectory whose name is identical to the leading
15926 directories of the executable's absolute file name.
15929 For the ``build ID'' method, @value{GDBN} looks in the
15930 @file{.build-id} subdirectory of the global debug directory for a file
15931 named @file{@var{nn}/@var{nnnnnnnn}.debug}, where @var{nn} are the
15932 first 2 hex characters of the build ID bit string, and @var{nnnnnnnn}
15933 are the rest of the bit string. (Real build ID strings are 32 or more
15934 hex characters, not 10.)
15937 So, for example, suppose you ask @value{GDBN} to debug
15938 @file{/usr/bin/ls}, which has a debug link that specifies the
15939 file @file{ls.debug}, and a build ID whose value in hex is
15940 @code{abcdef1234}. If the global debug directory is
15941 @file{/usr/lib/debug}, then @value{GDBN} will look for the following
15942 debug information files, in the indicated order:
15946 @file{/usr/lib/debug/.build-id/ab/cdef1234.debug}
15948 @file{/usr/bin/ls.debug}
15950 @file{/usr/bin/.debug/ls.debug}
15952 @file{/usr/lib/debug/usr/bin/ls.debug}.
15955 You can set the global debugging info directory's name, and view the
15956 name @value{GDBN} is currently using.
15960 @kindex set debug-file-directory
15961 @item set debug-file-directory @var{directories}
15962 Set the directories which @value{GDBN} searches for separate debugging
15963 information files to @var{directory}. Multiple directory components can be set
15964 concatenating them by a directory separator.
15966 @kindex show debug-file-directory
15967 @item show debug-file-directory
15968 Show the directories @value{GDBN} searches for separate debugging
15973 @cindex @code{.gnu_debuglink} sections
15974 @cindex debug link sections
15975 A debug link is a special section of the executable file named
15976 @code{.gnu_debuglink}. The section must contain:
15980 A filename, with any leading directory components removed, followed by
15983 zero to three bytes of padding, as needed to reach the next four-byte
15984 boundary within the section, and
15986 a four-byte CRC checksum, stored in the same endianness used for the
15987 executable file itself. The checksum is computed on the debugging
15988 information file's full contents by the function given below, passing
15989 zero as the @var{crc} argument.
15992 Any executable file format can carry a debug link, as long as it can
15993 contain a section named @code{.gnu_debuglink} with the contents
15996 @cindex @code{.note.gnu.build-id} sections
15997 @cindex build ID sections
15998 The build ID is a special section in the executable file (and in other
15999 ELF binary files that @value{GDBN} may consider). This section is
16000 often named @code{.note.gnu.build-id}, but that name is not mandatory.
16001 It contains unique identification for the built files---the ID remains
16002 the same across multiple builds of the same build tree. The default
16003 algorithm SHA1 produces 160 bits (40 hexadecimal characters) of the
16004 content for the build ID string. The same section with an identical
16005 value is present in the original built binary with symbols, in its
16006 stripped variant, and in the separate debugging information file.
16008 The debugging information file itself should be an ordinary
16009 executable, containing a full set of linker symbols, sections, and
16010 debugging information. The sections of the debugging information file
16011 should have the same names, addresses, and sizes as the original file,
16012 but they need not contain any data---much like a @code{.bss} section
16013 in an ordinary executable.
16015 The @sc{gnu} binary utilities (Binutils) package includes the
16016 @samp{objcopy} utility that can produce
16017 the separated executable / debugging information file pairs using the
16018 following commands:
16021 @kbd{objcopy --only-keep-debug foo foo.debug}
16026 These commands remove the debugging
16027 information from the executable file @file{foo} and place it in the file
16028 @file{foo.debug}. You can use the first, second or both methods to link the
16033 The debug link method needs the following additional command to also leave
16034 behind a debug link in @file{foo}:
16037 @kbd{objcopy --add-gnu-debuglink=foo.debug foo}
16040 Ulrich Drepper's @file{elfutils} package, starting with version 0.53, contains
16041 a version of the @code{strip} command such that the command @kbd{strip foo -f
16042 foo.debug} has the same functionality as the two @code{objcopy} commands and
16043 the @code{ln -s} command above, together.
16046 Build ID gets embedded into the main executable using @code{ld --build-id} or
16047 the @value{NGCC} counterpart @code{gcc -Wl,--build-id}. Build ID support plus
16048 compatibility fixes for debug files separation are present in @sc{gnu} binary
16049 utilities (Binutils) package since version 2.18.
16054 @cindex CRC algorithm definition
16055 The CRC used in @code{.gnu_debuglink} is the CRC-32 defined in
16056 IEEE 802.3 using the polynomial:
16058 @c TexInfo requires naked braces for multi-digit exponents for Tex
16059 @c output, but this causes HTML output to barf. HTML has to be set using
16060 @c raw commands. So we end up having to specify this equation in 2
16065 <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>
16066 + <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
16072 @math{x^{32} + x^{26} + x^{23} + x^{22} + x^{16} + x^{12} + x^{11}}
16073 @math{+ x^{10} + x^8 + x^7 + x^5 + x^4 + x^2 + x + 1}
16077 The function is computed byte at a time, taking the least
16078 significant bit of each byte first. The initial pattern
16079 @code{0xffffffff} is used, to ensure leading zeros affect the CRC and
16080 the final result is inverted to ensure trailing zeros also affect the
16083 @emph{Note:} This is the same CRC polynomial as used in handling the
16084 @dfn{Remote Serial Protocol} @code{qCRC} packet (@pxref{Remote Protocol,
16085 , @value{GDBN} Remote Serial Protocol}). However in the
16086 case of the Remote Serial Protocol, the CRC is computed @emph{most}
16087 significant bit first, and the result is not inverted, so trailing
16088 zeros have no effect on the CRC value.
16090 To complete the description, we show below the code of the function
16091 which produces the CRC used in @code{.gnu_debuglink}. Inverting the
16092 initially supplied @code{crc} argument means that an initial call to
16093 this function passing in zero will start computing the CRC using
16096 @kindex gnu_debuglink_crc32
16099 gnu_debuglink_crc32 (unsigned long crc,
16100 unsigned char *buf, size_t len)
16102 static const unsigned long crc32_table[256] =
16104 0x00000000, 0x77073096, 0xee0e612c, 0x990951ba, 0x076dc419,
16105 0x706af48f, 0xe963a535, 0x9e6495a3, 0x0edb8832, 0x79dcb8a4,
16106 0xe0d5e91e, 0x97d2d988, 0x09b64c2b, 0x7eb17cbd, 0xe7b82d07,
16107 0x90bf1d91, 0x1db71064, 0x6ab020f2, 0xf3b97148, 0x84be41de,
16108 0x1adad47d, 0x6ddde4eb, 0xf4d4b551, 0x83d385c7, 0x136c9856,
16109 0x646ba8c0, 0xfd62f97a, 0x8a65c9ec, 0x14015c4f, 0x63066cd9,
16110 0xfa0f3d63, 0x8d080df5, 0x3b6e20c8, 0x4c69105e, 0xd56041e4,
16111 0xa2677172, 0x3c03e4d1, 0x4b04d447, 0xd20d85fd, 0xa50ab56b,
16112 0x35b5a8fa, 0x42b2986c, 0xdbbbc9d6, 0xacbcf940, 0x32d86ce3,
16113 0x45df5c75, 0xdcd60dcf, 0xabd13d59, 0x26d930ac, 0x51de003a,
16114 0xc8d75180, 0xbfd06116, 0x21b4f4b5, 0x56b3c423, 0xcfba9599,
16115 0xb8bda50f, 0x2802b89e, 0x5f058808, 0xc60cd9b2, 0xb10be924,
16116 0x2f6f7c87, 0x58684c11, 0xc1611dab, 0xb6662d3d, 0x76dc4190,
16117 0x01db7106, 0x98d220bc, 0xefd5102a, 0x71b18589, 0x06b6b51f,
16118 0x9fbfe4a5, 0xe8b8d433, 0x7807c9a2, 0x0f00f934, 0x9609a88e,
16119 0xe10e9818, 0x7f6a0dbb, 0x086d3d2d, 0x91646c97, 0xe6635c01,
16120 0x6b6b51f4, 0x1c6c6162, 0x856530d8, 0xf262004e, 0x6c0695ed,
16121 0x1b01a57b, 0x8208f4c1, 0xf50fc457, 0x65b0d9c6, 0x12b7e950,
16122 0x8bbeb8ea, 0xfcb9887c, 0x62dd1ddf, 0x15da2d49, 0x8cd37cf3,
16123 0xfbd44c65, 0x4db26158, 0x3ab551ce, 0xa3bc0074, 0xd4bb30e2,
16124 0x4adfa541, 0x3dd895d7, 0xa4d1c46d, 0xd3d6f4fb, 0x4369e96a,
16125 0x346ed9fc, 0xad678846, 0xda60b8d0, 0x44042d73, 0x33031de5,
16126 0xaa0a4c5f, 0xdd0d7cc9, 0x5005713c, 0x270241aa, 0xbe0b1010,
16127 0xc90c2086, 0x5768b525, 0x206f85b3, 0xb966d409, 0xce61e49f,
16128 0x5edef90e, 0x29d9c998, 0xb0d09822, 0xc7d7a8b4, 0x59b33d17,
16129 0x2eb40d81, 0xb7bd5c3b, 0xc0ba6cad, 0xedb88320, 0x9abfb3b6,
16130 0x03b6e20c, 0x74b1d29a, 0xead54739, 0x9dd277af, 0x04db2615,
16131 0x73dc1683, 0xe3630b12, 0x94643b84, 0x0d6d6a3e, 0x7a6a5aa8,
16132 0xe40ecf0b, 0x9309ff9d, 0x0a00ae27, 0x7d079eb1, 0xf00f9344,
16133 0x8708a3d2, 0x1e01f268, 0x6906c2fe, 0xf762575d, 0x806567cb,
16134 0x196c3671, 0x6e6b06e7, 0xfed41b76, 0x89d32be0, 0x10da7a5a,
16135 0x67dd4acc, 0xf9b9df6f, 0x8ebeeff9, 0x17b7be43, 0x60b08ed5,
16136 0xd6d6a3e8, 0xa1d1937e, 0x38d8c2c4, 0x4fdff252, 0xd1bb67f1,
16137 0xa6bc5767, 0x3fb506dd, 0x48b2364b, 0xd80d2bda, 0xaf0a1b4c,
16138 0x36034af6, 0x41047a60, 0xdf60efc3, 0xa867df55, 0x316e8eef,
16139 0x4669be79, 0xcb61b38c, 0xbc66831a, 0x256fd2a0, 0x5268e236,
16140 0xcc0c7795, 0xbb0b4703, 0x220216b9, 0x5505262f, 0xc5ba3bbe,
16141 0xb2bd0b28, 0x2bb45a92, 0x5cb36a04, 0xc2d7ffa7, 0xb5d0cf31,
16142 0x2cd99e8b, 0x5bdeae1d, 0x9b64c2b0, 0xec63f226, 0x756aa39c,
16143 0x026d930a, 0x9c0906a9, 0xeb0e363f, 0x72076785, 0x05005713,
16144 0x95bf4a82, 0xe2b87a14, 0x7bb12bae, 0x0cb61b38, 0x92d28e9b,
16145 0xe5d5be0d, 0x7cdcefb7, 0x0bdbdf21, 0x86d3d2d4, 0xf1d4e242,
16146 0x68ddb3f8, 0x1fda836e, 0x81be16cd, 0xf6b9265b, 0x6fb077e1,
16147 0x18b74777, 0x88085ae6, 0xff0f6a70, 0x66063bca, 0x11010b5c,
16148 0x8f659eff, 0xf862ae69, 0x616bffd3, 0x166ccf45, 0xa00ae278,
16149 0xd70dd2ee, 0x4e048354, 0x3903b3c2, 0xa7672661, 0xd06016f7,
16150 0x4969474d, 0x3e6e77db, 0xaed16a4a, 0xd9d65adc, 0x40df0b66,
16151 0x37d83bf0, 0xa9bcae53, 0xdebb9ec5, 0x47b2cf7f, 0x30b5ffe9,
16152 0xbdbdf21c, 0xcabac28a, 0x53b39330, 0x24b4a3a6, 0xbad03605,
16153 0xcdd70693, 0x54de5729, 0x23d967bf, 0xb3667a2e, 0xc4614ab8,
16154 0x5d681b02, 0x2a6f2b94, 0xb40bbe37, 0xc30c8ea1, 0x5a05df1b,
16157 unsigned char *end;
16159 crc = ~crc & 0xffffffff;
16160 for (end = buf + len; buf < end; ++buf)
16161 crc = crc32_table[(crc ^ *buf) & 0xff] ^ (crc >> 8);
16162 return ~crc & 0xffffffff;
16167 This computation does not apply to the ``build ID'' method.
16171 @section Index Files Speed Up @value{GDBN}
16172 @cindex index files
16173 @cindex @samp{.gdb_index} section
16175 When @value{GDBN} finds a symbol file, it scans the symbols in the
16176 file in order to construct an internal symbol table. This lets most
16177 @value{GDBN} operations work quickly---at the cost of a delay early
16178 on. For large programs, this delay can be quite lengthy, so
16179 @value{GDBN} provides a way to build an index, which speeds up
16182 The index is stored as a section in the symbol file. @value{GDBN} can
16183 write the index to a file, then you can put it into the symbol file
16184 using @command{objcopy}.
16186 To create an index file, use the @code{save gdb-index} command:
16189 @item save gdb-index @var{directory}
16190 @kindex save gdb-index
16191 Create an index file for each symbol file currently known by
16192 @value{GDBN}. Each file is named after its corresponding symbol file,
16193 with @samp{.gdb-index} appended, and is written into the given
16197 Once you have created an index file you can merge it into your symbol
16198 file, here named @file{symfile}, using @command{objcopy}:
16201 $ objcopy --add-section .gdb_index=symfile.gdb-index \
16202 --set-section-flags .gdb_index=readonly symfile symfile
16205 There are currently some limitation on indices. They only work when
16206 for DWARF debugging information, not stabs. And, they do not
16207 currently work for programs using Ada.
16209 @node Symbol Errors
16210 @section Errors Reading Symbol Files
16212 While reading a symbol file, @value{GDBN} occasionally encounters problems,
16213 such as symbol types it does not recognize, or known bugs in compiler
16214 output. By default, @value{GDBN} does not notify you of such problems, since
16215 they are relatively common and primarily of interest to people
16216 debugging compilers. If you are interested in seeing information
16217 about ill-constructed symbol tables, you can either ask @value{GDBN} to print
16218 only one message about each such type of problem, no matter how many
16219 times the problem occurs; or you can ask @value{GDBN} to print more messages,
16220 to see how many times the problems occur, with the @code{set
16221 complaints} command (@pxref{Messages/Warnings, ,Optional Warnings and
16224 The messages currently printed, and their meanings, include:
16227 @item inner block not inside outer block in @var{symbol}
16229 The symbol information shows where symbol scopes begin and end
16230 (such as at the start of a function or a block of statements). This
16231 error indicates that an inner scope block is not fully contained
16232 in its outer scope blocks.
16234 @value{GDBN} circumvents the problem by treating the inner block as if it had
16235 the same scope as the outer block. In the error message, @var{symbol}
16236 may be shown as ``@code{(don't know)}'' if the outer block is not a
16239 @item block at @var{address} out of order
16241 The symbol information for symbol scope blocks should occur in
16242 order of increasing addresses. This error indicates that it does not
16245 @value{GDBN} does not circumvent this problem, and has trouble
16246 locating symbols in the source file whose symbols it is reading. (You
16247 can often determine what source file is affected by specifying
16248 @code{set verbose on}. @xref{Messages/Warnings, ,Optional Warnings and
16251 @item bad block start address patched
16253 The symbol information for a symbol scope block has a start address
16254 smaller than the address of the preceding source line. This is known
16255 to occur in the SunOS 4.1.1 (and earlier) C compiler.
16257 @value{GDBN} circumvents the problem by treating the symbol scope block as
16258 starting on the previous source line.
16260 @item bad string table offset in symbol @var{n}
16263 Symbol number @var{n} contains a pointer into the string table which is
16264 larger than the size of the string table.
16266 @value{GDBN} circumvents the problem by considering the symbol to have the
16267 name @code{foo}, which may cause other problems if many symbols end up
16270 @item unknown symbol type @code{0x@var{nn}}
16272 The symbol information contains new data types that @value{GDBN} does
16273 not yet know how to read. @code{0x@var{nn}} is the symbol type of the
16274 uncomprehended information, in hexadecimal.
16276 @value{GDBN} circumvents the error by ignoring this symbol information.
16277 This usually allows you to debug your program, though certain symbols
16278 are not accessible. If you encounter such a problem and feel like
16279 debugging it, you can debug @code{@value{GDBP}} with itself, breakpoint
16280 on @code{complain}, then go up to the function @code{read_dbx_symtab}
16281 and examine @code{*bufp} to see the symbol.
16283 @item stub type has NULL name
16285 @value{GDBN} could not find the full definition for a struct or class.
16287 @item const/volatile indicator missing (ok if using g++ v1.x), got@dots{}
16288 The symbol information for a C@t{++} member function is missing some
16289 information that recent versions of the compiler should have output for
16292 @item info mismatch between compiler and debugger
16294 @value{GDBN} could not parse a type specification output by the compiler.
16299 @section GDB Data Files
16301 @cindex prefix for data files
16302 @value{GDBN} will sometimes read an auxiliary data file. These files
16303 are kept in a directory known as the @dfn{data directory}.
16305 You can set the data directory's name, and view the name @value{GDBN}
16306 is currently using.
16309 @kindex set data-directory
16310 @item set data-directory @var{directory}
16311 Set the directory which @value{GDBN} searches for auxiliary data files
16312 to @var{directory}.
16314 @kindex show data-directory
16315 @item show data-directory
16316 Show the directory @value{GDBN} searches for auxiliary data files.
16319 @cindex default data directory
16320 @cindex @samp{--with-gdb-datadir}
16321 You can set the default data directory by using the configure-time
16322 @samp{--with-gdb-datadir} option. If the data directory is inside
16323 @value{GDBN}'s configured binary prefix (set with @samp{--prefix} or
16324 @samp{--exec-prefix}), then the default data directory will be updated
16325 automatically if the installed @value{GDBN} is moved to a new
16328 The data directory may also be specified with the
16329 @code{--data-directory} command line option.
16330 @xref{Mode Options}.
16333 @chapter Specifying a Debugging Target
16335 @cindex debugging target
16336 A @dfn{target} is the execution environment occupied by your program.
16338 Often, @value{GDBN} runs in the same host environment as your program;
16339 in that case, the debugging target is specified as a side effect when
16340 you use the @code{file} or @code{core} commands. When you need more
16341 flexibility---for example, running @value{GDBN} on a physically separate
16342 host, or controlling a standalone system over a serial port or a
16343 realtime system over a TCP/IP connection---you can use the @code{target}
16344 command to specify one of the target types configured for @value{GDBN}
16345 (@pxref{Target Commands, ,Commands for Managing Targets}).
16347 @cindex target architecture
16348 It is possible to build @value{GDBN} for several different @dfn{target
16349 architectures}. When @value{GDBN} is built like that, you can choose
16350 one of the available architectures with the @kbd{set architecture}
16354 @kindex set architecture
16355 @kindex show architecture
16356 @item set architecture @var{arch}
16357 This command sets the current target architecture to @var{arch}. The
16358 value of @var{arch} can be @code{"auto"}, in addition to one of the
16359 supported architectures.
16361 @item show architecture
16362 Show the current target architecture.
16364 @item set processor
16366 @kindex set processor
16367 @kindex show processor
16368 These are alias commands for, respectively, @code{set architecture}
16369 and @code{show architecture}.
16373 * Active Targets:: Active targets
16374 * Target Commands:: Commands for managing targets
16375 * Byte Order:: Choosing target byte order
16378 @node Active Targets
16379 @section Active Targets
16381 @cindex stacking targets
16382 @cindex active targets
16383 @cindex multiple targets
16385 There are multiple classes of targets such as: processes, executable files or
16386 recording sessions. Core files belong to the process class, making core file
16387 and process mutually exclusive. Otherwise, @value{GDBN} can work concurrently
16388 on multiple active targets, one in each class. This allows you to (for
16389 example) start a process and inspect its activity, while still having access to
16390 the executable file after the process finishes. Or if you start process
16391 recording (@pxref{Reverse Execution}) and @code{reverse-step} there, you are
16392 presented a virtual layer of the recording target, while the process target
16393 remains stopped at the chronologically last point of the process execution.
16395 Use the @code{core-file} and @code{exec-file} commands to select a new core
16396 file or executable target (@pxref{Files, ,Commands to Specify Files}). To
16397 specify as a target a process that is already running, use the @code{attach}
16398 command (@pxref{Attach, ,Debugging an Already-running Process}).
16400 @node Target Commands
16401 @section Commands for Managing Targets
16404 @item target @var{type} @var{parameters}
16405 Connects the @value{GDBN} host environment to a target machine or
16406 process. A target is typically a protocol for talking to debugging
16407 facilities. You use the argument @var{type} to specify the type or
16408 protocol of the target machine.
16410 Further @var{parameters} are interpreted by the target protocol, but
16411 typically include things like device names or host names to connect
16412 with, process numbers, and baud rates.
16414 The @code{target} command does not repeat if you press @key{RET} again
16415 after executing the command.
16417 @kindex help target
16419 Displays the names of all targets available. To display targets
16420 currently selected, use either @code{info target} or @code{info files}
16421 (@pxref{Files, ,Commands to Specify Files}).
16423 @item help target @var{name}
16424 Describe a particular target, including any parameters necessary to
16427 @kindex set gnutarget
16428 @item set gnutarget @var{args}
16429 @value{GDBN} uses its own library BFD to read your files. @value{GDBN}
16430 knows whether it is reading an @dfn{executable},
16431 a @dfn{core}, or a @dfn{.o} file; however, you can specify the file format
16432 with the @code{set gnutarget} command. Unlike most @code{target} commands,
16433 with @code{gnutarget} the @code{target} refers to a program, not a machine.
16436 @emph{Warning:} To specify a file format with @code{set gnutarget},
16437 you must know the actual BFD name.
16441 @xref{Files, , Commands to Specify Files}.
16443 @kindex show gnutarget
16444 @item show gnutarget
16445 Use the @code{show gnutarget} command to display what file format
16446 @code{gnutarget} is set to read. If you have not set @code{gnutarget},
16447 @value{GDBN} will determine the file format for each file automatically,
16448 and @code{show gnutarget} displays @samp{The current BDF target is "auto"}.
16451 @cindex common targets
16452 Here are some common targets (available, or not, depending on the GDB
16457 @item target exec @var{program}
16458 @cindex executable file target
16459 An executable file. @samp{target exec @var{program}} is the same as
16460 @samp{exec-file @var{program}}.
16462 @item target core @var{filename}
16463 @cindex core dump file target
16464 A core dump file. @samp{target core @var{filename}} is the same as
16465 @samp{core-file @var{filename}}.
16467 @item target remote @var{medium}
16468 @cindex remote target
16469 A remote system connected to @value{GDBN} via a serial line or network
16470 connection. This command tells @value{GDBN} to use its own remote
16471 protocol over @var{medium} for debugging. @xref{Remote Debugging}.
16473 For example, if you have a board connected to @file{/dev/ttya} on the
16474 machine running @value{GDBN}, you could say:
16477 target remote /dev/ttya
16480 @code{target remote} supports the @code{load} command. This is only
16481 useful if you have some other way of getting the stub to the target
16482 system, and you can put it somewhere in memory where it won't get
16483 clobbered by the download.
16485 @item target sim @r{[}@var{simargs}@r{]} @dots{}
16486 @cindex built-in simulator target
16487 Builtin CPU simulator. @value{GDBN} includes simulators for most architectures.
16495 works; however, you cannot assume that a specific memory map, device
16496 drivers, or even basic I/O is available, although some simulators do
16497 provide these. For info about any processor-specific simulator details,
16498 see the appropriate section in @ref{Embedded Processors, ,Embedded
16503 Some configurations may include these targets as well:
16507 @item target nrom @var{dev}
16508 @cindex NetROM ROM emulator target
16509 NetROM ROM emulator. This target only supports downloading.
16513 Different targets are available on different configurations of @value{GDBN};
16514 your configuration may have more or fewer targets.
16516 Many remote targets require you to download the executable's code once
16517 you've successfully established a connection. You may wish to control
16518 various aspects of this process.
16523 @kindex set hash@r{, for remote monitors}
16524 @cindex hash mark while downloading
16525 This command controls whether a hash mark @samp{#} is displayed while
16526 downloading a file to the remote monitor. If on, a hash mark is
16527 displayed after each S-record is successfully downloaded to the
16531 @kindex show hash@r{, for remote monitors}
16532 Show the current status of displaying the hash mark.
16534 @item set debug monitor
16535 @kindex set debug monitor
16536 @cindex display remote monitor communications
16537 Enable or disable display of communications messages between
16538 @value{GDBN} and the remote monitor.
16540 @item show debug monitor
16541 @kindex show debug monitor
16542 Show the current status of displaying communications between
16543 @value{GDBN} and the remote monitor.
16548 @kindex load @var{filename}
16549 @item load @var{filename}
16551 Depending on what remote debugging facilities are configured into
16552 @value{GDBN}, the @code{load} command may be available. Where it exists, it
16553 is meant to make @var{filename} (an executable) available for debugging
16554 on the remote system---by downloading, or dynamic linking, for example.
16555 @code{load} also records the @var{filename} symbol table in @value{GDBN}, like
16556 the @code{add-symbol-file} command.
16558 If your @value{GDBN} does not have a @code{load} command, attempting to
16559 execute it gets the error message ``@code{You can't do that when your
16560 target is @dots{}}''
16562 The file is loaded at whatever address is specified in the executable.
16563 For some object file formats, you can specify the load address when you
16564 link the program; for other formats, like a.out, the object file format
16565 specifies a fixed address.
16566 @c FIXME! This would be a good place for an xref to the GNU linker doc.
16568 Depending on the remote side capabilities, @value{GDBN} may be able to
16569 load programs into flash memory.
16571 @code{load} does not repeat if you press @key{RET} again after using it.
16575 @section Choosing Target Byte Order
16577 @cindex choosing target byte order
16578 @cindex target byte order
16580 Some types of processors, such as the MIPS, PowerPC, and Renesas SH,
16581 offer the ability to run either big-endian or little-endian byte
16582 orders. Usually the executable or symbol will include a bit to
16583 designate the endian-ness, and you will not need to worry about
16584 which to use. However, you may still find it useful to adjust
16585 @value{GDBN}'s idea of processor endian-ness manually.
16589 @item set endian big
16590 Instruct @value{GDBN} to assume the target is big-endian.
16592 @item set endian little
16593 Instruct @value{GDBN} to assume the target is little-endian.
16595 @item set endian auto
16596 Instruct @value{GDBN} to use the byte order associated with the
16600 Display @value{GDBN}'s current idea of the target byte order.
16604 Note that these commands merely adjust interpretation of symbolic
16605 data on the host, and that they have absolutely no effect on the
16609 @node Remote Debugging
16610 @chapter Debugging Remote Programs
16611 @cindex remote debugging
16613 If you are trying to debug a program running on a machine that cannot run
16614 @value{GDBN} in the usual way, it is often useful to use remote debugging.
16615 For example, you might use remote debugging on an operating system kernel,
16616 or on a small system which does not have a general purpose operating system
16617 powerful enough to run a full-featured debugger.
16619 Some configurations of @value{GDBN} have special serial or TCP/IP interfaces
16620 to make this work with particular debugging targets. In addition,
16621 @value{GDBN} comes with a generic serial protocol (specific to @value{GDBN},
16622 but not specific to any particular target system) which you can use if you
16623 write the remote stubs---the code that runs on the remote system to
16624 communicate with @value{GDBN}.
16626 Other remote targets may be available in your
16627 configuration of @value{GDBN}; use @code{help target} to list them.
16630 * Connecting:: Connecting to a remote target
16631 * File Transfer:: Sending files to a remote system
16632 * Server:: Using the gdbserver program
16633 * Remote Configuration:: Remote configuration
16634 * Remote Stub:: Implementing a remote stub
16638 @section Connecting to a Remote Target
16640 On the @value{GDBN} host machine, you will need an unstripped copy of
16641 your program, since @value{GDBN} needs symbol and debugging information.
16642 Start up @value{GDBN} as usual, using the name of the local copy of your
16643 program as the first argument.
16645 @cindex @code{target remote}
16646 @value{GDBN} can communicate with the target over a serial line, or
16647 over an @acronym{IP} network using @acronym{TCP} or @acronym{UDP}. In
16648 each case, @value{GDBN} uses the same protocol for debugging your
16649 program; only the medium carrying the debugging packets varies. The
16650 @code{target remote} command establishes a connection to the target.
16651 Its arguments indicate which medium to use:
16655 @item target remote @var{serial-device}
16656 @cindex serial line, @code{target remote}
16657 Use @var{serial-device} to communicate with the target. For example,
16658 to use a serial line connected to the device named @file{/dev/ttyb}:
16661 target remote /dev/ttyb
16664 If you're using a serial line, you may want to give @value{GDBN} the
16665 @w{@samp{--baud}} option, or use the @code{set remotebaud} command
16666 (@pxref{Remote Configuration, set remotebaud}) before the
16667 @code{target} command.
16669 @item target remote @code{@var{host}:@var{port}}
16670 @itemx target remote @code{tcp:@var{host}:@var{port}}
16671 @cindex @acronym{TCP} port, @code{target remote}
16672 Debug using a @acronym{TCP} connection to @var{port} on @var{host}.
16673 The @var{host} may be either a host name or a numeric @acronym{IP}
16674 address; @var{port} must be a decimal number. The @var{host} could be
16675 the target machine itself, if it is directly connected to the net, or
16676 it might be a terminal server which in turn has a serial line to the
16679 For example, to connect to port 2828 on a terminal server named
16683 target remote manyfarms:2828
16686 If your remote target is actually running on the same machine as your
16687 debugger session (e.g.@: a simulator for your target running on the
16688 same host), you can omit the hostname. For example, to connect to
16689 port 1234 on your local machine:
16692 target remote :1234
16696 Note that the colon is still required here.
16698 @item target remote @code{udp:@var{host}:@var{port}}
16699 @cindex @acronym{UDP} port, @code{target remote}
16700 Debug using @acronym{UDP} packets to @var{port} on @var{host}. For example, to
16701 connect to @acronym{UDP} port 2828 on a terminal server named @code{manyfarms}:
16704 target remote udp:manyfarms:2828
16707 When using a @acronym{UDP} connection for remote debugging, you should
16708 keep in mind that the `U' stands for ``Unreliable''. @acronym{UDP}
16709 can silently drop packets on busy or unreliable networks, which will
16710 cause havoc with your debugging session.
16712 @item target remote | @var{command}
16713 @cindex pipe, @code{target remote} to
16714 Run @var{command} in the background and communicate with it using a
16715 pipe. The @var{command} is a shell command, to be parsed and expanded
16716 by the system's command shell, @code{/bin/sh}; it should expect remote
16717 protocol packets on its standard input, and send replies on its
16718 standard output. You could use this to run a stand-alone simulator
16719 that speaks the remote debugging protocol, to make net connections
16720 using programs like @code{ssh}, or for other similar tricks.
16722 If @var{command} closes its standard output (perhaps by exiting),
16723 @value{GDBN} will try to send it a @code{SIGTERM} signal. (If the
16724 program has already exited, this will have no effect.)
16728 Once the connection has been established, you can use all the usual
16729 commands to examine and change data. The remote program is already
16730 running; you can use @kbd{step} and @kbd{continue}, and you do not
16731 need to use @kbd{run}.
16733 @cindex interrupting remote programs
16734 @cindex remote programs, interrupting
16735 Whenever @value{GDBN} is waiting for the remote program, if you type the
16736 interrupt character (often @kbd{Ctrl-c}), @value{GDBN} attempts to stop the
16737 program. This may or may not succeed, depending in part on the hardware
16738 and the serial drivers the remote system uses. If you type the
16739 interrupt character once again, @value{GDBN} displays this prompt:
16742 Interrupted while waiting for the program.
16743 Give up (and stop debugging it)? (y or n)
16746 If you type @kbd{y}, @value{GDBN} abandons the remote debugging session.
16747 (If you decide you want to try again later, you can use @samp{target
16748 remote} again to connect once more.) If you type @kbd{n}, @value{GDBN}
16749 goes back to waiting.
16752 @kindex detach (remote)
16754 When you have finished debugging the remote program, you can use the
16755 @code{detach} command to release it from @value{GDBN} control.
16756 Detaching from the target normally resumes its execution, but the results
16757 will depend on your particular remote stub. After the @code{detach}
16758 command, @value{GDBN} is free to connect to another target.
16762 The @code{disconnect} command behaves like @code{detach}, except that
16763 the target is generally not resumed. It will wait for @value{GDBN}
16764 (this instance or another one) to connect and continue debugging. After
16765 the @code{disconnect} command, @value{GDBN} is again free to connect to
16768 @cindex send command to remote monitor
16769 @cindex extend @value{GDBN} for remote targets
16770 @cindex add new commands for external monitor
16772 @item monitor @var{cmd}
16773 This command allows you to send arbitrary commands directly to the
16774 remote monitor. Since @value{GDBN} doesn't care about the commands it
16775 sends like this, this command is the way to extend @value{GDBN}---you
16776 can add new commands that only the external monitor will understand
16780 @node File Transfer
16781 @section Sending files to a remote system
16782 @cindex remote target, file transfer
16783 @cindex file transfer
16784 @cindex sending files to remote systems
16786 Some remote targets offer the ability to transfer files over the same
16787 connection used to communicate with @value{GDBN}. This is convenient
16788 for targets accessible through other means, e.g.@: @sc{gnu}/Linux systems
16789 running @code{gdbserver} over a network interface. For other targets,
16790 e.g.@: embedded devices with only a single serial port, this may be
16791 the only way to upload or download files.
16793 Not all remote targets support these commands.
16797 @item remote put @var{hostfile} @var{targetfile}
16798 Copy file @var{hostfile} from the host system (the machine running
16799 @value{GDBN}) to @var{targetfile} on the target system.
16802 @item remote get @var{targetfile} @var{hostfile}
16803 Copy file @var{targetfile} from the target system to @var{hostfile}
16804 on the host system.
16806 @kindex remote delete
16807 @item remote delete @var{targetfile}
16808 Delete @var{targetfile} from the target system.
16813 @section Using the @code{gdbserver} Program
16816 @cindex remote connection without stubs
16817 @code{gdbserver} is a control program for Unix-like systems, which
16818 allows you to connect your program with a remote @value{GDBN} via
16819 @code{target remote}---but without linking in the usual debugging stub.
16821 @code{gdbserver} is not a complete replacement for the debugging stubs,
16822 because it requires essentially the same operating-system facilities
16823 that @value{GDBN} itself does. In fact, a system that can run
16824 @code{gdbserver} to connect to a remote @value{GDBN} could also run
16825 @value{GDBN} locally! @code{gdbserver} is sometimes useful nevertheless,
16826 because it is a much smaller program than @value{GDBN} itself. It is
16827 also easier to port than all of @value{GDBN}, so you may be able to get
16828 started more quickly on a new system by using @code{gdbserver}.
16829 Finally, if you develop code for real-time systems, you may find that
16830 the tradeoffs involved in real-time operation make it more convenient to
16831 do as much development work as possible on another system, for example
16832 by cross-compiling. You can use @code{gdbserver} to make a similar
16833 choice for debugging.
16835 @value{GDBN} and @code{gdbserver} communicate via either a serial line
16836 or a TCP connection, using the standard @value{GDBN} remote serial
16840 @emph{Warning:} @code{gdbserver} does not have any built-in security.
16841 Do not run @code{gdbserver} connected to any public network; a
16842 @value{GDBN} connection to @code{gdbserver} provides access to the
16843 target system with the same privileges as the user running
16847 @subsection Running @code{gdbserver}
16848 @cindex arguments, to @code{gdbserver}
16849 @cindex @code{gdbserver}, command-line arguments
16851 Run @code{gdbserver} on the target system. You need a copy of the
16852 program you want to debug, including any libraries it requires.
16853 @code{gdbserver} does not need your program's symbol table, so you can
16854 strip the program if necessary to save space. @value{GDBN} on the host
16855 system does all the symbol handling.
16857 To use the server, you must tell it how to communicate with @value{GDBN};
16858 the name of your program; and the arguments for your program. The usual
16862 target> gdbserver @var{comm} @var{program} [ @var{args} @dots{} ]
16865 @var{comm} is either a device name (to use a serial line), or a TCP
16866 hostname and portnumber, or @code{-} or @code{stdio} to use
16867 stdin/stdout of @code{gdbserver}.
16868 For example, to debug Emacs with the argument
16869 @samp{foo.txt} and communicate with @value{GDBN} over the serial port
16873 target> gdbserver /dev/com1 emacs foo.txt
16876 @code{gdbserver} waits passively for the host @value{GDBN} to communicate
16879 To use a TCP connection instead of a serial line:
16882 target> gdbserver host:2345 emacs foo.txt
16885 The only difference from the previous example is the first argument,
16886 specifying that you are communicating with the host @value{GDBN} via
16887 TCP. The @samp{host:2345} argument means that @code{gdbserver} is to
16888 expect a TCP connection from machine @samp{host} to local TCP port 2345.
16889 (Currently, the @samp{host} part is ignored.) You can choose any number
16890 you want for the port number as long as it does not conflict with any
16891 TCP ports already in use on the target system (for example, @code{23} is
16892 reserved for @code{telnet}).@footnote{If you choose a port number that
16893 conflicts with another service, @code{gdbserver} prints an error message
16894 and exits.} You must use the same port number with the host @value{GDBN}
16895 @code{target remote} command.
16897 The @code{stdio} connection is useful when starting @code{gdbserver}
16901 (gdb) target remote | ssh -T hostname gdbserver - hello
16904 The @samp{-T} option to ssh is provided because we don't need a remote pty,
16905 and we don't want escape-character handling. Ssh does this by default when
16906 a command is provided, the flag is provided to make it explicit.
16907 You could elide it if you want to.
16909 Programs started with stdio-connected gdbserver have @file{/dev/null} for
16910 @code{stdin}, and @code{stdout},@code{stderr} are sent back to gdb for
16911 display through a pipe connected to gdbserver.
16912 Both @code{stdout} and @code{stderr} use the same pipe.
16914 @subsubsection Attaching to a Running Program
16915 @cindex attach to a program, @code{gdbserver}
16916 @cindex @option{--attach}, @code{gdbserver} option
16918 On some targets, @code{gdbserver} can also attach to running programs.
16919 This is accomplished via the @code{--attach} argument. The syntax is:
16922 target> gdbserver --attach @var{comm} @var{pid}
16925 @var{pid} is the process ID of a currently running process. It isn't necessary
16926 to point @code{gdbserver} at a binary for the running process.
16929 You can debug processes by name instead of process ID if your target has the
16930 @code{pidof} utility:
16933 target> gdbserver --attach @var{comm} `pidof @var{program}`
16936 In case more than one copy of @var{program} is running, or @var{program}
16937 has multiple threads, most versions of @code{pidof} support the
16938 @code{-s} option to only return the first process ID.
16940 @subsubsection Multi-Process Mode for @code{gdbserver}
16941 @cindex @code{gdbserver}, multiple processes
16942 @cindex multiple processes with @code{gdbserver}
16944 When you connect to @code{gdbserver} using @code{target remote},
16945 @code{gdbserver} debugs the specified program only once. When the
16946 program exits, or you detach from it, @value{GDBN} closes the connection
16947 and @code{gdbserver} exits.
16949 If you connect using @kbd{target extended-remote}, @code{gdbserver}
16950 enters multi-process mode. When the debugged program exits, or you
16951 detach from it, @value{GDBN} stays connected to @code{gdbserver} even
16952 though no program is running. The @code{run} and @code{attach}
16953 commands instruct @code{gdbserver} to run or attach to a new program.
16954 The @code{run} command uses @code{set remote exec-file} (@pxref{set
16955 remote exec-file}) to select the program to run. Command line
16956 arguments are supported, except for wildcard expansion and I/O
16957 redirection (@pxref{Arguments}).
16959 @cindex @option{--multi}, @code{gdbserver} option
16960 To start @code{gdbserver} without supplying an initial command to run
16961 or process ID to attach, use the @option{--multi} command line option.
16962 Then you can connect using @kbd{target extended-remote} and start
16963 the program you want to debug.
16965 In multi-process mode @code{gdbserver} does not automatically exit unless you
16966 use the option @option{--once}. You can terminate it by using
16967 @code{monitor exit} (@pxref{Monitor Commands for gdbserver}). Note that the
16968 conditions under which @code{gdbserver} terminates depend on how @value{GDBN}
16969 connects to it (@kbd{target remote} or @kbd{target extended-remote}). The
16970 @option{--multi} option to @code{gdbserver} has no influence on that.
16972 @subsubsection TCP port allocation lifecycle of @code{gdbserver}
16974 This section applies only when @code{gdbserver} is run to listen on a TCP port.
16976 @code{gdbserver} normally terminates after all of its debugged processes have
16977 terminated in @kbd{target remote} mode. On the other hand, for @kbd{target
16978 extended-remote}, @code{gdbserver} stays running even with no processes left.
16979 @value{GDBN} normally terminates the spawned debugged process on its exit,
16980 which normally also terminates @code{gdbserver} in the @kbd{target remote}
16981 mode. Therefore, when the connection drops unexpectedly, and @value{GDBN}
16982 cannot ask @code{gdbserver} to kill its debugged processes, @code{gdbserver}
16983 stays running even in the @kbd{target remote} mode.
16985 When @code{gdbserver} stays running, @value{GDBN} can connect to it again later.
16986 Such reconnecting is useful for features like @ref{disconnected tracing}. For
16987 completeness, at most one @value{GDBN} can be connected at a time.
16989 @cindex @option{--once}, @code{gdbserver} option
16990 By default, @code{gdbserver} keeps the listening TCP port open, so that
16991 additional connections are possible. However, if you start @code{gdbserver}
16992 with the @option{--once} option, it will stop listening for any further
16993 connection attempts after connecting to the first @value{GDBN} session. This
16994 means no further connections to @code{gdbserver} will be possible after the
16995 first one. It also means @code{gdbserver} will terminate after the first
16996 connection with remote @value{GDBN} has closed, even for unexpectedly closed
16997 connections and even in the @kbd{target extended-remote} mode. The
16998 @option{--once} option allows reusing the same port number for connecting to
16999 multiple instances of @code{gdbserver} running on the same host, since each
17000 instance closes its port after the first connection.
17002 @subsubsection Other Command-Line Arguments for @code{gdbserver}
17004 @cindex @option{--debug}, @code{gdbserver} option
17005 The @option{--debug} option tells @code{gdbserver} to display extra
17006 status information about the debugging process.
17007 @cindex @option{--remote-debug}, @code{gdbserver} option
17008 The @option{--remote-debug} option tells @code{gdbserver} to display
17009 remote protocol debug output. These options are intended for
17010 @code{gdbserver} development and for bug reports to the developers.
17012 @cindex @option{--wrapper}, @code{gdbserver} option
17013 The @option{--wrapper} option specifies a wrapper to launch programs
17014 for debugging. The option should be followed by the name of the
17015 wrapper, then any command-line arguments to pass to the wrapper, then
17016 @kbd{--} indicating the end of the wrapper arguments.
17018 @code{gdbserver} runs the specified wrapper program with a combined
17019 command line including the wrapper arguments, then the name of the
17020 program to debug, then any arguments to the program. The wrapper
17021 runs until it executes your program, and then @value{GDBN} gains control.
17023 You can use any program that eventually calls @code{execve} with
17024 its arguments as a wrapper. Several standard Unix utilities do
17025 this, e.g.@: @code{env} and @code{nohup}. Any Unix shell script ending
17026 with @code{exec "$@@"} will also work.
17028 For example, you can use @code{env} to pass an environment variable to
17029 the debugged program, without setting the variable in @code{gdbserver}'s
17033 $ gdbserver --wrapper env LD_PRELOAD=libtest.so -- :2222 ./testprog
17036 @subsection Connecting to @code{gdbserver}
17038 Run @value{GDBN} on the host system.
17040 First make sure you have the necessary symbol files. Load symbols for
17041 your application using the @code{file} command before you connect. Use
17042 @code{set sysroot} to locate target libraries (unless your @value{GDBN}
17043 was compiled with the correct sysroot using @code{--with-sysroot}).
17045 The symbol file and target libraries must exactly match the executable
17046 and libraries on the target, with one exception: the files on the host
17047 system should not be stripped, even if the files on the target system
17048 are. Mismatched or missing files will lead to confusing results
17049 during debugging. On @sc{gnu}/Linux targets, mismatched or missing
17050 files may also prevent @code{gdbserver} from debugging multi-threaded
17053 Connect to your target (@pxref{Connecting,,Connecting to a Remote Target}).
17054 For TCP connections, you must start up @code{gdbserver} prior to using
17055 the @code{target remote} command. Otherwise you may get an error whose
17056 text depends on the host system, but which usually looks something like
17057 @samp{Connection refused}. Don't use the @code{load}
17058 command in @value{GDBN} when using @code{gdbserver}, since the program is
17059 already on the target.
17061 @subsection Monitor Commands for @code{gdbserver}
17062 @cindex monitor commands, for @code{gdbserver}
17063 @anchor{Monitor Commands for gdbserver}
17065 During a @value{GDBN} session using @code{gdbserver}, you can use the
17066 @code{monitor} command to send special requests to @code{gdbserver}.
17067 Here are the available commands.
17071 List the available monitor commands.
17073 @item monitor set debug 0
17074 @itemx monitor set debug 1
17075 Disable or enable general debugging messages.
17077 @item monitor set remote-debug 0
17078 @itemx monitor set remote-debug 1
17079 Disable or enable specific debugging messages associated with the remote
17080 protocol (@pxref{Remote Protocol}).
17082 @item monitor set libthread-db-search-path [PATH]
17083 @cindex gdbserver, search path for @code{libthread_db}
17084 When this command is issued, @var{path} is a colon-separated list of
17085 directories to search for @code{libthread_db} (@pxref{Threads,,set
17086 libthread-db-search-path}). If you omit @var{path},
17087 @samp{libthread-db-search-path} will be reset to its default value.
17089 The special entry @samp{$pdir} for @samp{libthread-db-search-path} is
17090 not supported in @code{gdbserver}.
17093 Tell gdbserver to exit immediately. This command should be followed by
17094 @code{disconnect} to close the debugging session. @code{gdbserver} will
17095 detach from any attached processes and kill any processes it created.
17096 Use @code{monitor exit} to terminate @code{gdbserver} at the end
17097 of a multi-process mode debug session.
17101 @subsection Tracepoints support in @code{gdbserver}
17102 @cindex tracepoints support in @code{gdbserver}
17104 On some targets, @code{gdbserver} supports tracepoints, fast
17105 tracepoints and static tracepoints.
17107 For fast or static tracepoints to work, a special library called the
17108 @dfn{in-process agent} (IPA), must be loaded in the inferior process.
17109 This library is built and distributed as an integral part of
17110 @code{gdbserver}. In addition, support for static tracepoints
17111 requires building the in-process agent library with static tracepoints
17112 support. At present, the UST (LTTng Userspace Tracer,
17113 @url{http://lttng.org/ust}) tracing engine is supported. This support
17114 is automatically available if UST development headers are found in the
17115 standard include path when @code{gdbserver} is built, or if
17116 @code{gdbserver} was explicitly configured using @option{--with-ust}
17117 to point at such headers. You can explicitly disable the support
17118 using @option{--with-ust=no}.
17120 There are several ways to load the in-process agent in your program:
17123 @item Specifying it as dependency at link time
17125 You can link your program dynamically with the in-process agent
17126 library. On most systems, this is accomplished by adding
17127 @code{-linproctrace} to the link command.
17129 @item Using the system's preloading mechanisms
17131 You can force loading the in-process agent at startup time by using
17132 your system's support for preloading shared libraries. Many Unixes
17133 support the concept of preloading user defined libraries. In most
17134 cases, you do that by specifying @code{LD_PRELOAD=libinproctrace.so}
17135 in the environment. See also the description of @code{gdbserver}'s
17136 @option{--wrapper} command line option.
17138 @item Using @value{GDBN} to force loading the agent at run time
17140 On some systems, you can force the inferior to load a shared library,
17141 by calling a dynamic loader function in the inferior that takes care
17142 of dynamically looking up and loading a shared library. On most Unix
17143 systems, the function is @code{dlopen}. You'll use the @code{call}
17144 command for that. For example:
17147 (@value{GDBP}) call dlopen ("libinproctrace.so", ...)
17150 Note that on most Unix systems, for the @code{dlopen} function to be
17151 available, the program needs to be linked with @code{-ldl}.
17154 On systems that have a userspace dynamic loader, like most Unix
17155 systems, when you connect to @code{gdbserver} using @code{target
17156 remote}, you'll find that the program is stopped at the dynamic
17157 loader's entry point, and no shared library has been loaded in the
17158 program's address space yet, including the in-process agent. In that
17159 case, before being able to use any of the fast or static tracepoints
17160 features, you need to let the loader run and load the shared
17161 libraries. The simplest way to do that is to run the program to the
17162 main procedure. E.g., if debugging a C or C@t{++} program, start
17163 @code{gdbserver} like so:
17166 $ gdbserver :9999 myprogram
17169 Start GDB and connect to @code{gdbserver} like so, and run to main:
17173 (@value{GDBP}) target remote myhost:9999
17174 0x00007f215893ba60 in ?? () from /lib64/ld-linux-x86-64.so.2
17175 (@value{GDBP}) b main
17176 (@value{GDBP}) continue
17179 The in-process tracing agent library should now be loaded into the
17180 process; you can confirm it with the @code{info sharedlibrary}
17181 command, which will list @file{libinproctrace.so} as loaded in the
17182 process. You are now ready to install fast tracepoints, list static
17183 tracepoint markers, probe static tracepoints markers, and start
17186 @node Remote Configuration
17187 @section Remote Configuration
17190 @kindex show remote
17191 This section documents the configuration options available when
17192 debugging remote programs. For the options related to the File I/O
17193 extensions of the remote protocol, see @ref{system,
17194 system-call-allowed}.
17197 @item set remoteaddresssize @var{bits}
17198 @cindex address size for remote targets
17199 @cindex bits in remote address
17200 Set the maximum size of address in a memory packet to the specified
17201 number of bits. @value{GDBN} will mask off the address bits above
17202 that number, when it passes addresses to the remote target. The
17203 default value is the number of bits in the target's address.
17205 @item show remoteaddresssize
17206 Show the current value of remote address size in bits.
17208 @item set remotebaud @var{n}
17209 @cindex baud rate for remote targets
17210 Set the baud rate for the remote serial I/O to @var{n} baud. The
17211 value is used to set the speed of the serial port used for debugging
17214 @item show remotebaud
17215 Show the current speed of the remote connection.
17217 @item set remotebreak
17218 @cindex interrupt remote programs
17219 @cindex BREAK signal instead of Ctrl-C
17220 @anchor{set remotebreak}
17221 If set to on, @value{GDBN} sends a @code{BREAK} signal to the remote
17222 when you type @kbd{Ctrl-c} to interrupt the program running
17223 on the remote. If set to off, @value{GDBN} sends the @samp{Ctrl-C}
17224 character instead. The default is off, since most remote systems
17225 expect to see @samp{Ctrl-C} as the interrupt signal.
17227 @item show remotebreak
17228 Show whether @value{GDBN} sends @code{BREAK} or @samp{Ctrl-C} to
17229 interrupt the remote program.
17231 @item set remoteflow on
17232 @itemx set remoteflow off
17233 @kindex set remoteflow
17234 Enable or disable hardware flow control (@code{RTS}/@code{CTS})
17235 on the serial port used to communicate to the remote target.
17237 @item show remoteflow
17238 @kindex show remoteflow
17239 Show the current setting of hardware flow control.
17241 @item set remotelogbase @var{base}
17242 Set the base (a.k.a.@: radix) of logging serial protocol
17243 communications to @var{base}. Supported values of @var{base} are:
17244 @code{ascii}, @code{octal}, and @code{hex}. The default is
17247 @item show remotelogbase
17248 Show the current setting of the radix for logging remote serial
17251 @item set remotelogfile @var{file}
17252 @cindex record serial communications on file
17253 Record remote serial communications on the named @var{file}. The
17254 default is not to record at all.
17256 @item show remotelogfile.
17257 Show the current setting of the file name on which to record the
17258 serial communications.
17260 @item set remotetimeout @var{num}
17261 @cindex timeout for serial communications
17262 @cindex remote timeout
17263 Set the timeout limit to wait for the remote target to respond to
17264 @var{num} seconds. The default is 2 seconds.
17266 @item show remotetimeout
17267 Show the current number of seconds to wait for the remote target
17270 @cindex limit hardware breakpoints and watchpoints
17271 @cindex remote target, limit break- and watchpoints
17272 @anchor{set remote hardware-watchpoint-limit}
17273 @anchor{set remote hardware-breakpoint-limit}
17274 @item set remote hardware-watchpoint-limit @var{limit}
17275 @itemx set remote hardware-breakpoint-limit @var{limit}
17276 Restrict @value{GDBN} to using @var{limit} remote hardware breakpoint or
17277 watchpoints. A limit of -1, the default, is treated as unlimited.
17279 @cindex limit hardware watchpoints length
17280 @cindex remote target, limit watchpoints length
17281 @anchor{set remote hardware-watchpoint-length-limit}
17282 @item set remote hardware-watchpoint-length-limit @var{limit}
17283 Restrict @value{GDBN} to using @var{limit} bytes for the maximum length of
17284 a remote hardware watchpoint. A limit of -1, the default, is treated
17287 @item show remote hardware-watchpoint-length-limit
17288 Show the current limit (in bytes) of the maximum length of
17289 a remote hardware watchpoint.
17291 @item set remote exec-file @var{filename}
17292 @itemx show remote exec-file
17293 @anchor{set remote exec-file}
17294 @cindex executable file, for remote target
17295 Select the file used for @code{run} with @code{target
17296 extended-remote}. This should be set to a filename valid on the
17297 target system. If it is not set, the target will use a default
17298 filename (e.g.@: the last program run).
17300 @item set remote interrupt-sequence
17301 @cindex interrupt remote programs
17302 @cindex select Ctrl-C, BREAK or BREAK-g
17303 Allow the user to select one of @samp{Ctrl-C}, a @code{BREAK} or
17304 @samp{BREAK-g} as the
17305 sequence to the remote target in order to interrupt the execution.
17306 @samp{Ctrl-C} is a default. Some system prefers @code{BREAK} which
17307 is high level of serial line for some certain time.
17308 Linux kernel prefers @samp{BREAK-g}, a.k.a Magic SysRq g.
17309 It is @code{BREAK} signal followed by character @code{g}.
17311 @item show interrupt-sequence
17312 Show which of @samp{Ctrl-C}, @code{BREAK} or @code{BREAK-g}
17313 is sent by @value{GDBN} to interrupt the remote program.
17314 @code{BREAK-g} is BREAK signal followed by @code{g} and
17315 also known as Magic SysRq g.
17317 @item set remote interrupt-on-connect
17318 @cindex send interrupt-sequence on start
17319 Specify whether interrupt-sequence is sent to remote target when
17320 @value{GDBN} connects to it. This is mostly needed when you debug
17321 Linux kernel. Linux kernel expects @code{BREAK} followed by @code{g}
17322 which is known as Magic SysRq g in order to connect @value{GDBN}.
17324 @item show interrupt-on-connect
17325 Show whether interrupt-sequence is sent
17326 to remote target when @value{GDBN} connects to it.
17330 @item set tcp auto-retry on
17331 @cindex auto-retry, for remote TCP target
17332 Enable auto-retry for remote TCP connections. This is useful if the remote
17333 debugging agent is launched in parallel with @value{GDBN}; there is a race
17334 condition because the agent may not become ready to accept the connection
17335 before @value{GDBN} attempts to connect. When auto-retry is
17336 enabled, if the initial attempt to connect fails, @value{GDBN} reattempts
17337 to establish the connection using the timeout specified by
17338 @code{set tcp connect-timeout}.
17340 @item set tcp auto-retry off
17341 Do not auto-retry failed TCP connections.
17343 @item show tcp auto-retry
17344 Show the current auto-retry setting.
17346 @item set tcp connect-timeout @var{seconds}
17347 @cindex connection timeout, for remote TCP target
17348 @cindex timeout, for remote target connection
17349 Set the timeout for establishing a TCP connection to the remote target to
17350 @var{seconds}. The timeout affects both polling to retry failed connections
17351 (enabled by @code{set tcp auto-retry on}) and waiting for connections
17352 that are merely slow to complete, and represents an approximate cumulative
17355 @item show tcp connect-timeout
17356 Show the current connection timeout setting.
17359 @cindex remote packets, enabling and disabling
17360 The @value{GDBN} remote protocol autodetects the packets supported by
17361 your debugging stub. If you need to override the autodetection, you
17362 can use these commands to enable or disable individual packets. Each
17363 packet can be set to @samp{on} (the remote target supports this
17364 packet), @samp{off} (the remote target does not support this packet),
17365 or @samp{auto} (detect remote target support for this packet). They
17366 all default to @samp{auto}. For more information about each packet,
17367 see @ref{Remote Protocol}.
17369 During normal use, you should not have to use any of these commands.
17370 If you do, that may be a bug in your remote debugging stub, or a bug
17371 in @value{GDBN}. You may want to report the problem to the
17372 @value{GDBN} developers.
17374 For each packet @var{name}, the command to enable or disable the
17375 packet is @code{set remote @var{name}-packet}. The available settings
17378 @multitable @columnfractions 0.28 0.32 0.25
17381 @tab Related Features
17383 @item @code{fetch-register}
17385 @tab @code{info registers}
17387 @item @code{set-register}
17391 @item @code{binary-download}
17393 @tab @code{load}, @code{set}
17395 @item @code{read-aux-vector}
17396 @tab @code{qXfer:auxv:read}
17397 @tab @code{info auxv}
17399 @item @code{symbol-lookup}
17400 @tab @code{qSymbol}
17401 @tab Detecting multiple threads
17403 @item @code{attach}
17404 @tab @code{vAttach}
17407 @item @code{verbose-resume}
17409 @tab Stepping or resuming multiple threads
17415 @item @code{software-breakpoint}
17419 @item @code{hardware-breakpoint}
17423 @item @code{write-watchpoint}
17427 @item @code{read-watchpoint}
17431 @item @code{access-watchpoint}
17435 @item @code{target-features}
17436 @tab @code{qXfer:features:read}
17437 @tab @code{set architecture}
17439 @item @code{library-info}
17440 @tab @code{qXfer:libraries:read}
17441 @tab @code{info sharedlibrary}
17443 @item @code{memory-map}
17444 @tab @code{qXfer:memory-map:read}
17445 @tab @code{info mem}
17447 @item @code{read-sdata-object}
17448 @tab @code{qXfer:sdata:read}
17449 @tab @code{print $_sdata}
17451 @item @code{read-spu-object}
17452 @tab @code{qXfer:spu:read}
17453 @tab @code{info spu}
17455 @item @code{write-spu-object}
17456 @tab @code{qXfer:spu:write}
17457 @tab @code{info spu}
17459 @item @code{read-siginfo-object}
17460 @tab @code{qXfer:siginfo:read}
17461 @tab @code{print $_siginfo}
17463 @item @code{write-siginfo-object}
17464 @tab @code{qXfer:siginfo:write}
17465 @tab @code{set $_siginfo}
17467 @item @code{threads}
17468 @tab @code{qXfer:threads:read}
17469 @tab @code{info threads}
17471 @item @code{get-thread-local-@*storage-address}
17472 @tab @code{qGetTLSAddr}
17473 @tab Displaying @code{__thread} variables
17475 @item @code{get-thread-information-block-address}
17476 @tab @code{qGetTIBAddr}
17477 @tab Display MS-Windows Thread Information Block.
17479 @item @code{search-memory}
17480 @tab @code{qSearch:memory}
17483 @item @code{supported-packets}
17484 @tab @code{qSupported}
17485 @tab Remote communications parameters
17487 @item @code{pass-signals}
17488 @tab @code{QPassSignals}
17489 @tab @code{handle @var{signal}}
17491 @item @code{program-signals}
17492 @tab @code{QProgramSignals}
17493 @tab @code{handle @var{signal}}
17495 @item @code{hostio-close-packet}
17496 @tab @code{vFile:close}
17497 @tab @code{remote get}, @code{remote put}
17499 @item @code{hostio-open-packet}
17500 @tab @code{vFile:open}
17501 @tab @code{remote get}, @code{remote put}
17503 @item @code{hostio-pread-packet}
17504 @tab @code{vFile:pread}
17505 @tab @code{remote get}, @code{remote put}
17507 @item @code{hostio-pwrite-packet}
17508 @tab @code{vFile:pwrite}
17509 @tab @code{remote get}, @code{remote put}
17511 @item @code{hostio-unlink-packet}
17512 @tab @code{vFile:unlink}
17513 @tab @code{remote delete}
17515 @item @code{hostio-readlink-packet}
17516 @tab @code{vFile:readlink}
17519 @item @code{noack-packet}
17520 @tab @code{QStartNoAckMode}
17521 @tab Packet acknowledgment
17523 @item @code{osdata}
17524 @tab @code{qXfer:osdata:read}
17525 @tab @code{info os}
17527 @item @code{query-attached}
17528 @tab @code{qAttached}
17529 @tab Querying remote process attach state.
17531 @item @code{traceframe-info}
17532 @tab @code{qXfer:traceframe-info:read}
17533 @tab Traceframe info
17535 @item @code{install-in-trace}
17536 @tab @code{InstallInTrace}
17537 @tab Install tracepoint in tracing
17539 @item @code{disable-randomization}
17540 @tab @code{QDisableRandomization}
17541 @tab @code{set disable-randomization}
17543 @item @code{conditional-breakpoints-packet}
17544 @tab @code{Z0 and Z1}
17545 @tab @code{Support for target-side breakpoint condition evaluation}
17549 @section Implementing a Remote Stub
17551 @cindex debugging stub, example
17552 @cindex remote stub, example
17553 @cindex stub example, remote debugging
17554 The stub files provided with @value{GDBN} implement the target side of the
17555 communication protocol, and the @value{GDBN} side is implemented in the
17556 @value{GDBN} source file @file{remote.c}. Normally, you can simply allow
17557 these subroutines to communicate, and ignore the details. (If you're
17558 implementing your own stub file, you can still ignore the details: start
17559 with one of the existing stub files. @file{sparc-stub.c} is the best
17560 organized, and therefore the easiest to read.)
17562 @cindex remote serial debugging, overview
17563 To debug a program running on another machine (the debugging
17564 @dfn{target} machine), you must first arrange for all the usual
17565 prerequisites for the program to run by itself. For example, for a C
17570 A startup routine to set up the C runtime environment; these usually
17571 have a name like @file{crt0}. The startup routine may be supplied by
17572 your hardware supplier, or you may have to write your own.
17575 A C subroutine library to support your program's
17576 subroutine calls, notably managing input and output.
17579 A way of getting your program to the other machine---for example, a
17580 download program. These are often supplied by the hardware
17581 manufacturer, but you may have to write your own from hardware
17585 The next step is to arrange for your program to use a serial port to
17586 communicate with the machine where @value{GDBN} is running (the @dfn{host}
17587 machine). In general terms, the scheme looks like this:
17591 @value{GDBN} already understands how to use this protocol; when everything
17592 else is set up, you can simply use the @samp{target remote} command
17593 (@pxref{Targets,,Specifying a Debugging Target}).
17595 @item On the target,
17596 you must link with your program a few special-purpose subroutines that
17597 implement the @value{GDBN} remote serial protocol. The file containing these
17598 subroutines is called a @dfn{debugging stub}.
17600 On certain remote targets, you can use an auxiliary program
17601 @code{gdbserver} instead of linking a stub into your program.
17602 @xref{Server,,Using the @code{gdbserver} Program}, for details.
17605 The debugging stub is specific to the architecture of the remote
17606 machine; for example, use @file{sparc-stub.c} to debug programs on
17609 @cindex remote serial stub list
17610 These working remote stubs are distributed with @value{GDBN}:
17615 @cindex @file{i386-stub.c}
17618 For Intel 386 and compatible architectures.
17621 @cindex @file{m68k-stub.c}
17622 @cindex Motorola 680x0
17624 For Motorola 680x0 architectures.
17627 @cindex @file{sh-stub.c}
17630 For Renesas SH architectures.
17633 @cindex @file{sparc-stub.c}
17635 For @sc{sparc} architectures.
17637 @item sparcl-stub.c
17638 @cindex @file{sparcl-stub.c}
17641 For Fujitsu @sc{sparclite} architectures.
17645 The @file{README} file in the @value{GDBN} distribution may list other
17646 recently added stubs.
17649 * Stub Contents:: What the stub can do for you
17650 * Bootstrapping:: What you must do for the stub
17651 * Debug Session:: Putting it all together
17654 @node Stub Contents
17655 @subsection What the Stub Can Do for You
17657 @cindex remote serial stub
17658 The debugging stub for your architecture supplies these three
17662 @item set_debug_traps
17663 @findex set_debug_traps
17664 @cindex remote serial stub, initialization
17665 This routine arranges for @code{handle_exception} to run when your
17666 program stops. You must call this subroutine explicitly in your
17667 program's startup code.
17669 @item handle_exception
17670 @findex handle_exception
17671 @cindex remote serial stub, main routine
17672 This is the central workhorse, but your program never calls it
17673 explicitly---the setup code arranges for @code{handle_exception} to
17674 run when a trap is triggered.
17676 @code{handle_exception} takes control when your program stops during
17677 execution (for example, on a breakpoint), and mediates communications
17678 with @value{GDBN} on the host machine. This is where the communications
17679 protocol is implemented; @code{handle_exception} acts as the @value{GDBN}
17680 representative on the target machine. It begins by sending summary
17681 information on the state of your program, then continues to execute,
17682 retrieving and transmitting any information @value{GDBN} needs, until you
17683 execute a @value{GDBN} command that makes your program resume; at that point,
17684 @code{handle_exception} returns control to your own code on the target
17688 @cindex @code{breakpoint} subroutine, remote
17689 Use this auxiliary subroutine to make your program contain a
17690 breakpoint. Depending on the particular situation, this may be the only
17691 way for @value{GDBN} to get control. For instance, if your target
17692 machine has some sort of interrupt button, you won't need to call this;
17693 pressing the interrupt button transfers control to
17694 @code{handle_exception}---in effect, to @value{GDBN}. On some machines,
17695 simply receiving characters on the serial port may also trigger a trap;
17696 again, in that situation, you don't need to call @code{breakpoint} from
17697 your own program---simply running @samp{target remote} from the host
17698 @value{GDBN} session gets control.
17700 Call @code{breakpoint} if none of these is true, or if you simply want
17701 to make certain your program stops at a predetermined point for the
17702 start of your debugging session.
17705 @node Bootstrapping
17706 @subsection What You Must Do for the Stub
17708 @cindex remote stub, support routines
17709 The debugging stubs that come with @value{GDBN} are set up for a particular
17710 chip architecture, but they have no information about the rest of your
17711 debugging target machine.
17713 First of all you need to tell the stub how to communicate with the
17717 @item int getDebugChar()
17718 @findex getDebugChar
17719 Write this subroutine to read a single character from the serial port.
17720 It may be identical to @code{getchar} for your target system; a
17721 different name is used to allow you to distinguish the two if you wish.
17723 @item void putDebugChar(int)
17724 @findex putDebugChar
17725 Write this subroutine to write a single character to the serial port.
17726 It may be identical to @code{putchar} for your target system; a
17727 different name is used to allow you to distinguish the two if you wish.
17730 @cindex control C, and remote debugging
17731 @cindex interrupting remote targets
17732 If you want @value{GDBN} to be able to stop your program while it is
17733 running, you need to use an interrupt-driven serial driver, and arrange
17734 for it to stop when it receives a @code{^C} (@samp{\003}, the control-C
17735 character). That is the character which @value{GDBN} uses to tell the
17736 remote system to stop.
17738 Getting the debugging target to return the proper status to @value{GDBN}
17739 probably requires changes to the standard stub; one quick and dirty way
17740 is to just execute a breakpoint instruction (the ``dirty'' part is that
17741 @value{GDBN} reports a @code{SIGTRAP} instead of a @code{SIGINT}).
17743 Other routines you need to supply are:
17746 @item void exceptionHandler (int @var{exception_number}, void *@var{exception_address})
17747 @findex exceptionHandler
17748 Write this function to install @var{exception_address} in the exception
17749 handling tables. You need to do this because the stub does not have any
17750 way of knowing what the exception handling tables on your target system
17751 are like (for example, the processor's table might be in @sc{rom},
17752 containing entries which point to a table in @sc{ram}).
17753 @var{exception_number} is the exception number which should be changed;
17754 its meaning is architecture-dependent (for example, different numbers
17755 might represent divide by zero, misaligned access, etc). When this
17756 exception occurs, control should be transferred directly to
17757 @var{exception_address}, and the processor state (stack, registers,
17758 and so on) should be just as it is when a processor exception occurs. So if
17759 you want to use a jump instruction to reach @var{exception_address}, it
17760 should be a simple jump, not a jump to subroutine.
17762 For the 386, @var{exception_address} should be installed as an interrupt
17763 gate so that interrupts are masked while the handler runs. The gate
17764 should be at privilege level 0 (the most privileged level). The
17765 @sc{sparc} and 68k stubs are able to mask interrupts themselves without
17766 help from @code{exceptionHandler}.
17768 @item void flush_i_cache()
17769 @findex flush_i_cache
17770 On @sc{sparc} and @sc{sparclite} only, write this subroutine to flush the
17771 instruction cache, if any, on your target machine. If there is no
17772 instruction cache, this subroutine may be a no-op.
17774 On target machines that have instruction caches, @value{GDBN} requires this
17775 function to make certain that the state of your program is stable.
17779 You must also make sure this library routine is available:
17782 @item void *memset(void *, int, int)
17784 This is the standard library function @code{memset} that sets an area of
17785 memory to a known value. If you have one of the free versions of
17786 @code{libc.a}, @code{memset} can be found there; otherwise, you must
17787 either obtain it from your hardware manufacturer, or write your own.
17790 If you do not use the GNU C compiler, you may need other standard
17791 library subroutines as well; this varies from one stub to another,
17792 but in general the stubs are likely to use any of the common library
17793 subroutines which @code{@value{NGCC}} generates as inline code.
17796 @node Debug Session
17797 @subsection Putting it All Together
17799 @cindex remote serial debugging summary
17800 In summary, when your program is ready to debug, you must follow these
17805 Make sure you have defined the supporting low-level routines
17806 (@pxref{Bootstrapping,,What You Must Do for the Stub}):
17808 @code{getDebugChar}, @code{putDebugChar},
17809 @code{flush_i_cache}, @code{memset}, @code{exceptionHandler}.
17813 Insert these lines in your program's startup code, before the main
17814 procedure is called:
17821 On some machines, when a breakpoint trap is raised, the hardware
17822 automatically makes the PC point to the instruction after the
17823 breakpoint. If your machine doesn't do that, you may need to adjust
17824 @code{handle_exception} to arrange for it to return to the instruction
17825 after the breakpoint on this first invocation, so that your program
17826 doesn't keep hitting the initial breakpoint instead of making
17830 For the 680x0 stub only, you need to provide a variable called
17831 @code{exceptionHook}. Normally you just use:
17834 void (*exceptionHook)() = 0;
17838 but if before calling @code{set_debug_traps}, you set it to point to a
17839 function in your program, that function is called when
17840 @code{@value{GDBN}} continues after stopping on a trap (for example, bus
17841 error). The function indicated by @code{exceptionHook} is called with
17842 one parameter: an @code{int} which is the exception number.
17845 Compile and link together: your program, the @value{GDBN} debugging stub for
17846 your target architecture, and the supporting subroutines.
17849 Make sure you have a serial connection between your target machine and
17850 the @value{GDBN} host, and identify the serial port on the host.
17853 @c The "remote" target now provides a `load' command, so we should
17854 @c document that. FIXME.
17855 Download your program to your target machine (or get it there by
17856 whatever means the manufacturer provides), and start it.
17859 Start @value{GDBN} on the host, and connect to the target
17860 (@pxref{Connecting,,Connecting to a Remote Target}).
17864 @node Configurations
17865 @chapter Configuration-Specific Information
17867 While nearly all @value{GDBN} commands are available for all native and
17868 cross versions of the debugger, there are some exceptions. This chapter
17869 describes things that are only available in certain configurations.
17871 There are three major categories of configurations: native
17872 configurations, where the host and target are the same, embedded
17873 operating system configurations, which are usually the same for several
17874 different processor architectures, and bare embedded processors, which
17875 are quite different from each other.
17880 * Embedded Processors::
17887 This section describes details specific to particular native
17892 * BSD libkvm Interface:: Debugging BSD kernel memory images
17893 * SVR4 Process Information:: SVR4 process information
17894 * DJGPP Native:: Features specific to the DJGPP port
17895 * Cygwin Native:: Features specific to the Cygwin port
17896 * Hurd Native:: Features specific to @sc{gnu} Hurd
17897 * Neutrino:: Features specific to QNX Neutrino
17898 * Darwin:: Features specific to Darwin
17904 On HP-UX systems, if you refer to a function or variable name that
17905 begins with a dollar sign, @value{GDBN} searches for a user or system
17906 name first, before it searches for a convenience variable.
17909 @node BSD libkvm Interface
17910 @subsection BSD libkvm Interface
17913 @cindex kernel memory image
17914 @cindex kernel crash dump
17916 BSD-derived systems (FreeBSD/NetBSD/OpenBSD) have a kernel memory
17917 interface that provides a uniform interface for accessing kernel virtual
17918 memory images, including live systems and crash dumps. @value{GDBN}
17919 uses this interface to allow you to debug live kernels and kernel crash
17920 dumps on many native BSD configurations. This is implemented as a
17921 special @code{kvm} debugging target. For debugging a live system, load
17922 the currently running kernel into @value{GDBN} and connect to the
17926 (@value{GDBP}) @b{target kvm}
17929 For debugging crash dumps, provide the file name of the crash dump as an
17933 (@value{GDBP}) @b{target kvm /var/crash/bsd.0}
17936 Once connected to the @code{kvm} target, the following commands are
17942 Set current context from the @dfn{Process Control Block} (PCB) address.
17945 Set current context from proc address. This command isn't available on
17946 modern FreeBSD systems.
17949 @node SVR4 Process Information
17950 @subsection SVR4 Process Information
17952 @cindex examine process image
17953 @cindex process info via @file{/proc}
17955 Many versions of SVR4 and compatible systems provide a facility called
17956 @samp{/proc} that can be used to examine the image of a running
17957 process using file-system subroutines. If @value{GDBN} is configured
17958 for an operating system with this facility, the command @code{info
17959 proc} is available to report information about the process running
17960 your program, or about any process running on your system. @code{info
17961 proc} works only on SVR4 systems that include the @code{procfs} code.
17962 This includes, as of this writing, @sc{gnu}/Linux, OSF/1 (Digital
17963 Unix), Solaris, Irix, and Unixware, but not HP-UX, for example.
17969 @itemx info proc @var{process-id}
17970 Summarize available information about any running process. If a
17971 process ID is specified by @var{process-id}, display information about
17972 that process; otherwise display information about the program being
17973 debugged. The summary includes the debugged process ID, the command
17974 line used to invoke it, its current working directory, and its
17975 executable file's absolute file name.
17977 On some systems, @var{process-id} can be of the form
17978 @samp{[@var{pid}]/@var{tid}} which specifies a certain thread ID
17979 within a process. If the optional @var{pid} part is missing, it means
17980 a thread from the process being debugged (the leading @samp{/} still
17981 needs to be present, or else @value{GDBN} will interpret the number as
17982 a process ID rather than a thread ID).
17984 @item info proc mappings
17985 @cindex memory address space mappings
17986 Report the memory address space ranges accessible in the program, with
17987 information on whether the process has read, write, or execute access
17988 rights to each range. On @sc{gnu}/Linux systems, each memory range
17989 includes the object file which is mapped to that range, instead of the
17990 memory access rights to that range.
17992 @item info proc stat
17993 @itemx info proc status
17994 @cindex process detailed status information
17995 These subcommands are specific to @sc{gnu}/Linux systems. They show
17996 the process-related information, including the user ID and group ID;
17997 how many threads are there in the process; its virtual memory usage;
17998 the signals that are pending, blocked, and ignored; its TTY; its
17999 consumption of system and user time; its stack size; its @samp{nice}
18000 value; etc. For more information, see the @samp{proc} man page
18001 (type @kbd{man 5 proc} from your shell prompt).
18003 @item info proc all
18004 Show all the information about the process described under all of the
18005 above @code{info proc} subcommands.
18008 @comment These sub-options of 'info proc' were not included when
18009 @comment procfs.c was re-written. Keep their descriptions around
18010 @comment against the day when someone finds the time to put them back in.
18011 @kindex info proc times
18012 @item info proc times
18013 Starting time, user CPU time, and system CPU time for your program and
18016 @kindex info proc id
18018 Report on the process IDs related to your program: its own process ID,
18019 the ID of its parent, the process group ID, and the session ID.
18022 @item set procfs-trace
18023 @kindex set procfs-trace
18024 @cindex @code{procfs} API calls
18025 This command enables and disables tracing of @code{procfs} API calls.
18027 @item show procfs-trace
18028 @kindex show procfs-trace
18029 Show the current state of @code{procfs} API call tracing.
18031 @item set procfs-file @var{file}
18032 @kindex set procfs-file
18033 Tell @value{GDBN} to write @code{procfs} API trace to the named
18034 @var{file}. @value{GDBN} appends the trace info to the previous
18035 contents of the file. The default is to display the trace on the
18038 @item show procfs-file
18039 @kindex show procfs-file
18040 Show the file to which @code{procfs} API trace is written.
18042 @item proc-trace-entry
18043 @itemx proc-trace-exit
18044 @itemx proc-untrace-entry
18045 @itemx proc-untrace-exit
18046 @kindex proc-trace-entry
18047 @kindex proc-trace-exit
18048 @kindex proc-untrace-entry
18049 @kindex proc-untrace-exit
18050 These commands enable and disable tracing of entries into and exits
18051 from the @code{syscall} interface.
18054 @kindex info pidlist
18055 @cindex process list, QNX Neutrino
18056 For QNX Neutrino only, this command displays the list of all the
18057 processes and all the threads within each process.
18060 @kindex info meminfo
18061 @cindex mapinfo list, QNX Neutrino
18062 For QNX Neutrino only, this command displays the list of all mapinfos.
18066 @subsection Features for Debugging @sc{djgpp} Programs
18067 @cindex @sc{djgpp} debugging
18068 @cindex native @sc{djgpp} debugging
18069 @cindex MS-DOS-specific commands
18072 @sc{djgpp} is a port of the @sc{gnu} development tools to MS-DOS and
18073 MS-Windows. @sc{djgpp} programs are 32-bit protected-mode programs
18074 that use the @dfn{DPMI} (DOS Protected-Mode Interface) API to run on
18075 top of real-mode DOS systems and their emulations.
18077 @value{GDBN} supports native debugging of @sc{djgpp} programs, and
18078 defines a few commands specific to the @sc{djgpp} port. This
18079 subsection describes those commands.
18084 This is a prefix of @sc{djgpp}-specific commands which print
18085 information about the target system and important OS structures.
18088 @cindex MS-DOS system info
18089 @cindex free memory information (MS-DOS)
18090 @item info dos sysinfo
18091 This command displays assorted information about the underlying
18092 platform: the CPU type and features, the OS version and flavor, the
18093 DPMI version, and the available conventional and DPMI memory.
18098 @cindex segment descriptor tables
18099 @cindex descriptor tables display
18101 @itemx info dos ldt
18102 @itemx info dos idt
18103 These 3 commands display entries from, respectively, Global, Local,
18104 and Interrupt Descriptor Tables (GDT, LDT, and IDT). The descriptor
18105 tables are data structures which store a descriptor for each segment
18106 that is currently in use. The segment's selector is an index into a
18107 descriptor table; the table entry for that index holds the
18108 descriptor's base address and limit, and its attributes and access
18111 A typical @sc{djgpp} program uses 3 segments: a code segment, a data
18112 segment (used for both data and the stack), and a DOS segment (which
18113 allows access to DOS/BIOS data structures and absolute addresses in
18114 conventional memory). However, the DPMI host will usually define
18115 additional segments in order to support the DPMI environment.
18117 @cindex garbled pointers
18118 These commands allow to display entries from the descriptor tables.
18119 Without an argument, all entries from the specified table are
18120 displayed. An argument, which should be an integer expression, means
18121 display a single entry whose index is given by the argument. For
18122 example, here's a convenient way to display information about the
18123 debugged program's data segment:
18126 @exdent @code{(@value{GDBP}) info dos ldt $ds}
18127 @exdent @code{0x13f: base=0x11970000 limit=0x0009ffff 32-Bit Data (Read/Write, Exp-up)}
18131 This comes in handy when you want to see whether a pointer is outside
18132 the data segment's limit (i.e.@: @dfn{garbled}).
18134 @cindex page tables display (MS-DOS)
18136 @itemx info dos pte
18137 These two commands display entries from, respectively, the Page
18138 Directory and the Page Tables. Page Directories and Page Tables are
18139 data structures which control how virtual memory addresses are mapped
18140 into physical addresses. A Page Table includes an entry for every
18141 page of memory that is mapped into the program's address space; there
18142 may be several Page Tables, each one holding up to 4096 entries. A
18143 Page Directory has up to 4096 entries, one each for every Page Table
18144 that is currently in use.
18146 Without an argument, @kbd{info dos pde} displays the entire Page
18147 Directory, and @kbd{info dos pte} displays all the entries in all of
18148 the Page Tables. An argument, an integer expression, given to the
18149 @kbd{info dos pde} command means display only that entry from the Page
18150 Directory table. An argument given to the @kbd{info dos pte} command
18151 means display entries from a single Page Table, the one pointed to by
18152 the specified entry in the Page Directory.
18154 @cindex direct memory access (DMA) on MS-DOS
18155 These commands are useful when your program uses @dfn{DMA} (Direct
18156 Memory Access), which needs physical addresses to program the DMA
18159 These commands are supported only with some DPMI servers.
18161 @cindex physical address from linear address
18162 @item info dos address-pte @var{addr}
18163 This command displays the Page Table entry for a specified linear
18164 address. The argument @var{addr} is a linear address which should
18165 already have the appropriate segment's base address added to it,
18166 because this command accepts addresses which may belong to @emph{any}
18167 segment. For example, here's how to display the Page Table entry for
18168 the page where a variable @code{i} is stored:
18171 @exdent @code{(@value{GDBP}) info dos address-pte __djgpp_base_address + (char *)&i}
18172 @exdent @code{Page Table entry for address 0x11a00d30:}
18173 @exdent @code{Base=0x02698000 Dirty Acc. Not-Cached Write-Back Usr Read-Write +0xd30}
18177 This says that @code{i} is stored at offset @code{0xd30} from the page
18178 whose physical base address is @code{0x02698000}, and shows all the
18179 attributes of that page.
18181 Note that you must cast the addresses of variables to a @code{char *},
18182 since otherwise the value of @code{__djgpp_base_address}, the base
18183 address of all variables and functions in a @sc{djgpp} program, will
18184 be added using the rules of C pointer arithmetics: if @code{i} is
18185 declared an @code{int}, @value{GDBN} will add 4 times the value of
18186 @code{__djgpp_base_address} to the address of @code{i}.
18188 Here's another example, it displays the Page Table entry for the
18192 @exdent @code{(@value{GDBP}) info dos address-pte *((unsigned *)&_go32_info_block + 3)}
18193 @exdent @code{Page Table entry for address 0x29110:}
18194 @exdent @code{Base=0x00029000 Dirty Acc. Not-Cached Write-Back Usr Read-Write +0x110}
18198 (The @code{+ 3} offset is because the transfer buffer's address is the
18199 3rd member of the @code{_go32_info_block} structure.) The output
18200 clearly shows that this DPMI server maps the addresses in conventional
18201 memory 1:1, i.e.@: the physical (@code{0x00029000} + @code{0x110}) and
18202 linear (@code{0x29110}) addresses are identical.
18204 This command is supported only with some DPMI servers.
18207 @cindex DOS serial data link, remote debugging
18208 In addition to native debugging, the DJGPP port supports remote
18209 debugging via a serial data link. The following commands are specific
18210 to remote serial debugging in the DJGPP port of @value{GDBN}.
18213 @kindex set com1base
18214 @kindex set com1irq
18215 @kindex set com2base
18216 @kindex set com2irq
18217 @kindex set com3base
18218 @kindex set com3irq
18219 @kindex set com4base
18220 @kindex set com4irq
18221 @item set com1base @var{addr}
18222 This command sets the base I/O port address of the @file{COM1} serial
18225 @item set com1irq @var{irq}
18226 This command sets the @dfn{Interrupt Request} (@code{IRQ}) line to use
18227 for the @file{COM1} serial port.
18229 There are similar commands @samp{set com2base}, @samp{set com3irq},
18230 etc.@: for setting the port address and the @code{IRQ} lines for the
18233 @kindex show com1base
18234 @kindex show com1irq
18235 @kindex show com2base
18236 @kindex show com2irq
18237 @kindex show com3base
18238 @kindex show com3irq
18239 @kindex show com4base
18240 @kindex show com4irq
18241 The related commands @samp{show com1base}, @samp{show com1irq} etc.@:
18242 display the current settings of the base address and the @code{IRQ}
18243 lines used by the COM ports.
18246 @kindex info serial
18247 @cindex DOS serial port status
18248 This command prints the status of the 4 DOS serial ports. For each
18249 port, it prints whether it's active or not, its I/O base address and
18250 IRQ number, whether it uses a 16550-style FIFO, its baudrate, and the
18251 counts of various errors encountered so far.
18255 @node Cygwin Native
18256 @subsection Features for Debugging MS Windows PE Executables
18257 @cindex MS Windows debugging
18258 @cindex native Cygwin debugging
18259 @cindex Cygwin-specific commands
18261 @value{GDBN} supports native debugging of MS Windows programs, including
18262 DLLs with and without symbolic debugging information.
18264 @cindex Ctrl-BREAK, MS-Windows
18265 @cindex interrupt debuggee on MS-Windows
18266 MS-Windows programs that call @code{SetConsoleMode} to switch off the
18267 special meaning of the @samp{Ctrl-C} keystroke cannot be interrupted
18268 by typing @kbd{C-c}. For this reason, @value{GDBN} on MS-Windows
18269 supports @kbd{C-@key{BREAK}} as an alternative interrupt key
18270 sequence, which can be used to interrupt the debuggee even if it
18273 There are various additional Cygwin-specific commands, described in
18274 this section. Working with DLLs that have no debugging symbols is
18275 described in @ref{Non-debug DLL Symbols}.
18280 This is a prefix of MS Windows-specific commands which print
18281 information about the target system and important OS structures.
18283 @item info w32 selector
18284 This command displays information returned by
18285 the Win32 API @code{GetThreadSelectorEntry} function.
18286 It takes an optional argument that is evaluated to
18287 a long value to give the information about this given selector.
18288 Without argument, this command displays information
18289 about the six segment registers.
18291 @item info w32 thread-information-block
18292 This command displays thread specific information stored in the
18293 Thread Information Block (readable on the X86 CPU family using @code{$fs}
18294 selector for 32-bit programs and @code{$gs} for 64-bit programs).
18298 This is a Cygwin-specific alias of @code{info shared}.
18300 @kindex dll-symbols
18302 This command loads symbols from a dll similarly to
18303 add-sym command but without the need to specify a base address.
18305 @kindex set cygwin-exceptions
18306 @cindex debugging the Cygwin DLL
18307 @cindex Cygwin DLL, debugging
18308 @item set cygwin-exceptions @var{mode}
18309 If @var{mode} is @code{on}, @value{GDBN} will break on exceptions that
18310 happen inside the Cygwin DLL. If @var{mode} is @code{off},
18311 @value{GDBN} will delay recognition of exceptions, and may ignore some
18312 exceptions which seem to be caused by internal Cygwin DLL
18313 ``bookkeeping''. This option is meant primarily for debugging the
18314 Cygwin DLL itself; the default value is @code{off} to avoid annoying
18315 @value{GDBN} users with false @code{SIGSEGV} signals.
18317 @kindex show cygwin-exceptions
18318 @item show cygwin-exceptions
18319 Displays whether @value{GDBN} will break on exceptions that happen
18320 inside the Cygwin DLL itself.
18322 @kindex set new-console
18323 @item set new-console @var{mode}
18324 If @var{mode} is @code{on} the debuggee will
18325 be started in a new console on next start.
18326 If @var{mode} is @code{off}, the debuggee will
18327 be started in the same console as the debugger.
18329 @kindex show new-console
18330 @item show new-console
18331 Displays whether a new console is used
18332 when the debuggee is started.
18334 @kindex set new-group
18335 @item set new-group @var{mode}
18336 This boolean value controls whether the debuggee should
18337 start a new group or stay in the same group as the debugger.
18338 This affects the way the Windows OS handles
18341 @kindex show new-group
18342 @item show new-group
18343 Displays current value of new-group boolean.
18345 @kindex set debugevents
18346 @item set debugevents
18347 This boolean value adds debug output concerning kernel events related
18348 to the debuggee seen by the debugger. This includes events that
18349 signal thread and process creation and exit, DLL loading and
18350 unloading, console interrupts, and debugging messages produced by the
18351 Windows @code{OutputDebugString} API call.
18353 @kindex set debugexec
18354 @item set debugexec
18355 This boolean value adds debug output concerning execute events
18356 (such as resume thread) seen by the debugger.
18358 @kindex set debugexceptions
18359 @item set debugexceptions
18360 This boolean value adds debug output concerning exceptions in the
18361 debuggee seen by the debugger.
18363 @kindex set debugmemory
18364 @item set debugmemory
18365 This boolean value adds debug output concerning debuggee memory reads
18366 and writes by the debugger.
18370 This boolean values specifies whether the debuggee is called
18371 via a shell or directly (default value is on).
18375 Displays if the debuggee will be started with a shell.
18380 * Non-debug DLL Symbols:: Support for DLLs without debugging symbols
18383 @node Non-debug DLL Symbols
18384 @subsubsection Support for DLLs without Debugging Symbols
18385 @cindex DLLs with no debugging symbols
18386 @cindex Minimal symbols and DLLs
18388 Very often on windows, some of the DLLs that your program relies on do
18389 not include symbolic debugging information (for example,
18390 @file{kernel32.dll}). When @value{GDBN} doesn't recognize any debugging
18391 symbols in a DLL, it relies on the minimal amount of symbolic
18392 information contained in the DLL's export table. This section
18393 describes working with such symbols, known internally to @value{GDBN} as
18394 ``minimal symbols''.
18396 Note that before the debugged program has started execution, no DLLs
18397 will have been loaded. The easiest way around this problem is simply to
18398 start the program --- either by setting a breakpoint or letting the
18399 program run once to completion. It is also possible to force
18400 @value{GDBN} to load a particular DLL before starting the executable ---
18401 see the shared library information in @ref{Files}, or the
18402 @code{dll-symbols} command in @ref{Cygwin Native}. Currently,
18403 explicitly loading symbols from a DLL with no debugging information will
18404 cause the symbol names to be duplicated in @value{GDBN}'s lookup table,
18405 which may adversely affect symbol lookup performance.
18407 @subsubsection DLL Name Prefixes
18409 In keeping with the naming conventions used by the Microsoft debugging
18410 tools, DLL export symbols are made available with a prefix based on the
18411 DLL name, for instance @code{KERNEL32!CreateFileA}. The plain name is
18412 also entered into the symbol table, so @code{CreateFileA} is often
18413 sufficient. In some cases there will be name clashes within a program
18414 (particularly if the executable itself includes full debugging symbols)
18415 necessitating the use of the fully qualified name when referring to the
18416 contents of the DLL. Use single-quotes around the name to avoid the
18417 exclamation mark (``!'') being interpreted as a language operator.
18419 Note that the internal name of the DLL may be all upper-case, even
18420 though the file name of the DLL is lower-case, or vice-versa. Since
18421 symbols within @value{GDBN} are @emph{case-sensitive} this may cause
18422 some confusion. If in doubt, try the @code{info functions} and
18423 @code{info variables} commands or even @code{maint print msymbols}
18424 (@pxref{Symbols}). Here's an example:
18427 (@value{GDBP}) info function CreateFileA
18428 All functions matching regular expression "CreateFileA":
18430 Non-debugging symbols:
18431 0x77e885f4 CreateFileA
18432 0x77e885f4 KERNEL32!CreateFileA
18436 (@value{GDBP}) info function !
18437 All functions matching regular expression "!":
18439 Non-debugging symbols:
18440 0x6100114c cygwin1!__assert
18441 0x61004034 cygwin1!_dll_crt0@@0
18442 0x61004240 cygwin1!dll_crt0(per_process *)
18446 @subsubsection Working with Minimal Symbols
18448 Symbols extracted from a DLL's export table do not contain very much
18449 type information. All that @value{GDBN} can do is guess whether a symbol
18450 refers to a function or variable depending on the linker section that
18451 contains the symbol. Also note that the actual contents of the memory
18452 contained in a DLL are not available unless the program is running. This
18453 means that you cannot examine the contents of a variable or disassemble
18454 a function within a DLL without a running program.
18456 Variables are generally treated as pointers and dereferenced
18457 automatically. For this reason, it is often necessary to prefix a
18458 variable name with the address-of operator (``&'') and provide explicit
18459 type information in the command. Here's an example of the type of
18463 (@value{GDBP}) print 'cygwin1!__argv'
18468 (@value{GDBP}) x 'cygwin1!__argv'
18469 0x10021610: "\230y\""
18472 And two possible solutions:
18475 (@value{GDBP}) print ((char **)'cygwin1!__argv')[0]
18476 $2 = 0x22fd98 "/cygdrive/c/mydirectory/myprogram"
18480 (@value{GDBP}) x/2x &'cygwin1!__argv'
18481 0x610c0aa8 <cygwin1!__argv>: 0x10021608 0x00000000
18482 (@value{GDBP}) x/x 0x10021608
18483 0x10021608: 0x0022fd98
18484 (@value{GDBP}) x/s 0x0022fd98
18485 0x22fd98: "/cygdrive/c/mydirectory/myprogram"
18488 Setting a break point within a DLL is possible even before the program
18489 starts execution. However, under these circumstances, @value{GDBN} can't
18490 examine the initial instructions of the function in order to skip the
18491 function's frame set-up code. You can work around this by using ``*&''
18492 to set the breakpoint at a raw memory address:
18495 (@value{GDBP}) break *&'python22!PyOS_Readline'
18496 Breakpoint 1 at 0x1e04eff0
18499 The author of these extensions is not entirely convinced that setting a
18500 break point within a shared DLL like @file{kernel32.dll} is completely
18504 @subsection Commands Specific to @sc{gnu} Hurd Systems
18505 @cindex @sc{gnu} Hurd debugging
18507 This subsection describes @value{GDBN} commands specific to the
18508 @sc{gnu} Hurd native debugging.
18513 @kindex set signals@r{, Hurd command}
18514 @kindex set sigs@r{, Hurd command}
18515 This command toggles the state of inferior signal interception by
18516 @value{GDBN}. Mach exceptions, such as breakpoint traps, are not
18517 affected by this command. @code{sigs} is a shorthand alias for
18522 @kindex show signals@r{, Hurd command}
18523 @kindex show sigs@r{, Hurd command}
18524 Show the current state of intercepting inferior's signals.
18526 @item set signal-thread
18527 @itemx set sigthread
18528 @kindex set signal-thread
18529 @kindex set sigthread
18530 This command tells @value{GDBN} which thread is the @code{libc} signal
18531 thread. That thread is run when a signal is delivered to a running
18532 process. @code{set sigthread} is the shorthand alias of @code{set
18535 @item show signal-thread
18536 @itemx show sigthread
18537 @kindex show signal-thread
18538 @kindex show sigthread
18539 These two commands show which thread will run when the inferior is
18540 delivered a signal.
18543 @kindex set stopped@r{, Hurd command}
18544 This commands tells @value{GDBN} that the inferior process is stopped,
18545 as with the @code{SIGSTOP} signal. The stopped process can be
18546 continued by delivering a signal to it.
18549 @kindex show stopped@r{, Hurd command}
18550 This command shows whether @value{GDBN} thinks the debuggee is
18553 @item set exceptions
18554 @kindex set exceptions@r{, Hurd command}
18555 Use this command to turn off trapping of exceptions in the inferior.
18556 When exception trapping is off, neither breakpoints nor
18557 single-stepping will work. To restore the default, set exception
18560 @item show exceptions
18561 @kindex show exceptions@r{, Hurd command}
18562 Show the current state of trapping exceptions in the inferior.
18564 @item set task pause
18565 @kindex set task@r{, Hurd commands}
18566 @cindex task attributes (@sc{gnu} Hurd)
18567 @cindex pause current task (@sc{gnu} Hurd)
18568 This command toggles task suspension when @value{GDBN} has control.
18569 Setting it to on takes effect immediately, and the task is suspended
18570 whenever @value{GDBN} gets control. Setting it to off will take
18571 effect the next time the inferior is continued. If this option is set
18572 to off, you can use @code{set thread default pause on} or @code{set
18573 thread pause on} (see below) to pause individual threads.
18575 @item show task pause
18576 @kindex show task@r{, Hurd commands}
18577 Show the current state of task suspension.
18579 @item set task detach-suspend-count
18580 @cindex task suspend count
18581 @cindex detach from task, @sc{gnu} Hurd
18582 This command sets the suspend count the task will be left with when
18583 @value{GDBN} detaches from it.
18585 @item show task detach-suspend-count
18586 Show the suspend count the task will be left with when detaching.
18588 @item set task exception-port
18589 @itemx set task excp
18590 @cindex task exception port, @sc{gnu} Hurd
18591 This command sets the task exception port to which @value{GDBN} will
18592 forward exceptions. The argument should be the value of the @dfn{send
18593 rights} of the task. @code{set task excp} is a shorthand alias.
18595 @item set noninvasive
18596 @cindex noninvasive task options
18597 This command switches @value{GDBN} to a mode that is the least
18598 invasive as far as interfering with the inferior is concerned. This
18599 is the same as using @code{set task pause}, @code{set exceptions}, and
18600 @code{set signals} to values opposite to the defaults.
18602 @item info send-rights
18603 @itemx info receive-rights
18604 @itemx info port-rights
18605 @itemx info port-sets
18606 @itemx info dead-names
18609 @cindex send rights, @sc{gnu} Hurd
18610 @cindex receive rights, @sc{gnu} Hurd
18611 @cindex port rights, @sc{gnu} Hurd
18612 @cindex port sets, @sc{gnu} Hurd
18613 @cindex dead names, @sc{gnu} Hurd
18614 These commands display information about, respectively, send rights,
18615 receive rights, port rights, port sets, and dead names of a task.
18616 There are also shorthand aliases: @code{info ports} for @code{info
18617 port-rights} and @code{info psets} for @code{info port-sets}.
18619 @item set thread pause
18620 @kindex set thread@r{, Hurd command}
18621 @cindex thread properties, @sc{gnu} Hurd
18622 @cindex pause current thread (@sc{gnu} Hurd)
18623 This command toggles current thread suspension when @value{GDBN} has
18624 control. Setting it to on takes effect immediately, and the current
18625 thread is suspended whenever @value{GDBN} gets control. Setting it to
18626 off will take effect the next time the inferior is continued.
18627 Normally, this command has no effect, since when @value{GDBN} has
18628 control, the whole task is suspended. However, if you used @code{set
18629 task pause off} (see above), this command comes in handy to suspend
18630 only the current thread.
18632 @item show thread pause
18633 @kindex show thread@r{, Hurd command}
18634 This command shows the state of current thread suspension.
18636 @item set thread run
18637 This command sets whether the current thread is allowed to run.
18639 @item show thread run
18640 Show whether the current thread is allowed to run.
18642 @item set thread detach-suspend-count
18643 @cindex thread suspend count, @sc{gnu} Hurd
18644 @cindex detach from thread, @sc{gnu} Hurd
18645 This command sets the suspend count @value{GDBN} will leave on a
18646 thread when detaching. This number is relative to the suspend count
18647 found by @value{GDBN} when it notices the thread; use @code{set thread
18648 takeover-suspend-count} to force it to an absolute value.
18650 @item show thread detach-suspend-count
18651 Show the suspend count @value{GDBN} will leave on the thread when
18654 @item set thread exception-port
18655 @itemx set thread excp
18656 Set the thread exception port to which to forward exceptions. This
18657 overrides the port set by @code{set task exception-port} (see above).
18658 @code{set thread excp} is the shorthand alias.
18660 @item set thread takeover-suspend-count
18661 Normally, @value{GDBN}'s thread suspend counts are relative to the
18662 value @value{GDBN} finds when it notices each thread. This command
18663 changes the suspend counts to be absolute instead.
18665 @item set thread default
18666 @itemx show thread default
18667 @cindex thread default settings, @sc{gnu} Hurd
18668 Each of the above @code{set thread} commands has a @code{set thread
18669 default} counterpart (e.g., @code{set thread default pause}, @code{set
18670 thread default exception-port}, etc.). The @code{thread default}
18671 variety of commands sets the default thread properties for all
18672 threads; you can then change the properties of individual threads with
18673 the non-default commands.
18678 @subsection QNX Neutrino
18679 @cindex QNX Neutrino
18681 @value{GDBN} provides the following commands specific to the QNX
18685 @item set debug nto-debug
18686 @kindex set debug nto-debug
18687 When set to on, enables debugging messages specific to the QNX
18690 @item show debug nto-debug
18691 @kindex show debug nto-debug
18692 Show the current state of QNX Neutrino messages.
18699 @value{GDBN} provides the following commands specific to the Darwin target:
18702 @item set debug darwin @var{num}
18703 @kindex set debug darwin
18704 When set to a non zero value, enables debugging messages specific to
18705 the Darwin support. Higher values produce more verbose output.
18707 @item show debug darwin
18708 @kindex show debug darwin
18709 Show the current state of Darwin messages.
18711 @item set debug mach-o @var{num}
18712 @kindex set debug mach-o
18713 When set to a non zero value, enables debugging messages while
18714 @value{GDBN} is reading Darwin object files. (@dfn{Mach-O} is the
18715 file format used on Darwin for object and executable files.) Higher
18716 values produce more verbose output. This is a command to diagnose
18717 problems internal to @value{GDBN} and should not be needed in normal
18720 @item show debug mach-o
18721 @kindex show debug mach-o
18722 Show the current state of Mach-O file messages.
18724 @item set mach-exceptions on
18725 @itemx set mach-exceptions off
18726 @kindex set mach-exceptions
18727 On Darwin, faults are first reported as a Mach exception and are then
18728 mapped to a Posix signal. Use this command to turn on trapping of
18729 Mach exceptions in the inferior. This might be sometimes useful to
18730 better understand the cause of a fault. The default is off.
18732 @item show mach-exceptions
18733 @kindex show mach-exceptions
18734 Show the current state of exceptions trapping.
18739 @section Embedded Operating Systems
18741 This section describes configurations involving the debugging of
18742 embedded operating systems that are available for several different
18746 * VxWorks:: Using @value{GDBN} with VxWorks
18749 @value{GDBN} includes the ability to debug programs running on
18750 various real-time operating systems.
18753 @subsection Using @value{GDBN} with VxWorks
18759 @kindex target vxworks
18760 @item target vxworks @var{machinename}
18761 A VxWorks system, attached via TCP/IP. The argument @var{machinename}
18762 is the target system's machine name or IP address.
18766 On VxWorks, @code{load} links @var{filename} dynamically on the
18767 current target system as well as adding its symbols in @value{GDBN}.
18769 @value{GDBN} enables developers to spawn and debug tasks running on networked
18770 VxWorks targets from a Unix host. Already-running tasks spawned from
18771 the VxWorks shell can also be debugged. @value{GDBN} uses code that runs on
18772 both the Unix host and on the VxWorks target. The program
18773 @code{@value{GDBP}} is installed and executed on the Unix host. (It may be
18774 installed with the name @code{vxgdb}, to distinguish it from a
18775 @value{GDBN} for debugging programs on the host itself.)
18778 @item VxWorks-timeout @var{args}
18779 @kindex vxworks-timeout
18780 All VxWorks-based targets now support the option @code{vxworks-timeout}.
18781 This option is set by the user, and @var{args} represents the number of
18782 seconds @value{GDBN} waits for responses to rpc's. You might use this if
18783 your VxWorks target is a slow software simulator or is on the far side
18784 of a thin network line.
18787 The following information on connecting to VxWorks was current when
18788 this manual was produced; newer releases of VxWorks may use revised
18791 @findex INCLUDE_RDB
18792 To use @value{GDBN} with VxWorks, you must rebuild your VxWorks kernel
18793 to include the remote debugging interface routines in the VxWorks
18794 library @file{rdb.a}. To do this, define @code{INCLUDE_RDB} in the
18795 VxWorks configuration file @file{configAll.h} and rebuild your VxWorks
18796 kernel. The resulting kernel contains @file{rdb.a}, and spawns the
18797 source debugging task @code{tRdbTask} when VxWorks is booted. For more
18798 information on configuring and remaking VxWorks, see the manufacturer's
18800 @c VxWorks, see the @cite{VxWorks Programmer's Guide}.
18802 Once you have included @file{rdb.a} in your VxWorks system image and set
18803 your Unix execution search path to find @value{GDBN}, you are ready to
18804 run @value{GDBN}. From your Unix host, run @code{@value{GDBP}} (or
18805 @code{vxgdb}, depending on your installation).
18807 @value{GDBN} comes up showing the prompt:
18814 * VxWorks Connection:: Connecting to VxWorks
18815 * VxWorks Download:: VxWorks download
18816 * VxWorks Attach:: Running tasks
18819 @node VxWorks Connection
18820 @subsubsection Connecting to VxWorks
18822 The @value{GDBN} command @code{target} lets you connect to a VxWorks target on the
18823 network. To connect to a target whose host name is ``@code{tt}'', type:
18826 (vxgdb) target vxworks tt
18830 @value{GDBN} displays messages like these:
18833 Attaching remote machine across net...
18838 @value{GDBN} then attempts to read the symbol tables of any object modules
18839 loaded into the VxWorks target since it was last booted. @value{GDBN} locates
18840 these files by searching the directories listed in the command search
18841 path (@pxref{Environment, ,Your Program's Environment}); if it fails
18842 to find an object file, it displays a message such as:
18845 prog.o: No such file or directory.
18848 When this happens, add the appropriate directory to the search path with
18849 the @value{GDBN} command @code{path}, and execute the @code{target}
18852 @node VxWorks Download
18853 @subsubsection VxWorks Download
18855 @cindex download to VxWorks
18856 If you have connected to the VxWorks target and you want to debug an
18857 object that has not yet been loaded, you can use the @value{GDBN}
18858 @code{load} command to download a file from Unix to VxWorks
18859 incrementally. The object file given as an argument to the @code{load}
18860 command is actually opened twice: first by the VxWorks target in order
18861 to download the code, then by @value{GDBN} in order to read the symbol
18862 table. This can lead to problems if the current working directories on
18863 the two systems differ. If both systems have NFS mounted the same
18864 filesystems, you can avoid these problems by using absolute paths.
18865 Otherwise, it is simplest to set the working directory on both systems
18866 to the directory in which the object file resides, and then to reference
18867 the file by its name, without any path. For instance, a program
18868 @file{prog.o} may reside in @file{@var{vxpath}/vw/demo/rdb} in VxWorks
18869 and in @file{@var{hostpath}/vw/demo/rdb} on the host. To load this
18870 program, type this on VxWorks:
18873 -> cd "@var{vxpath}/vw/demo/rdb"
18877 Then, in @value{GDBN}, type:
18880 (vxgdb) cd @var{hostpath}/vw/demo/rdb
18881 (vxgdb) load prog.o
18884 @value{GDBN} displays a response similar to this:
18887 Reading symbol data from wherever/vw/demo/rdb/prog.o... done.
18890 You can also use the @code{load} command to reload an object module
18891 after editing and recompiling the corresponding source file. Note that
18892 this makes @value{GDBN} delete all currently-defined breakpoints,
18893 auto-displays, and convenience variables, and to clear the value
18894 history. (This is necessary in order to preserve the integrity of
18895 debugger's data structures that reference the target system's symbol
18898 @node VxWorks Attach
18899 @subsubsection Running Tasks
18901 @cindex running VxWorks tasks
18902 You can also attach to an existing task using the @code{attach} command as
18906 (vxgdb) attach @var{task}
18910 where @var{task} is the VxWorks hexadecimal task ID. The task can be running
18911 or suspended when you attach to it. Running tasks are suspended at
18912 the time of attachment.
18914 @node Embedded Processors
18915 @section Embedded Processors
18917 This section goes into details specific to particular embedded
18920 @cindex send command to simulator
18921 Whenever a specific embedded processor has a simulator, @value{GDBN}
18922 allows to send an arbitrary command to the simulator.
18925 @item sim @var{command}
18926 @kindex sim@r{, a command}
18927 Send an arbitrary @var{command} string to the simulator. Consult the
18928 documentation for the specific simulator in use for information about
18929 acceptable commands.
18935 * M32R/D:: Renesas M32R/D
18936 * M68K:: Motorola M68K
18937 * MicroBlaze:: Xilinx MicroBlaze
18938 * MIPS Embedded:: MIPS Embedded
18939 * OpenRISC 1000:: OpenRisc 1000
18940 * PA:: HP PA Embedded
18941 * PowerPC Embedded:: PowerPC Embedded
18942 * Sparclet:: Tsqware Sparclet
18943 * Sparclite:: Fujitsu Sparclite
18944 * Z8000:: Zilog Z8000
18947 * Super-H:: Renesas Super-H
18956 @item target rdi @var{dev}
18957 ARM Angel monitor, via RDI library interface to ADP protocol. You may
18958 use this target to communicate with both boards running the Angel
18959 monitor, or with the EmbeddedICE JTAG debug device.
18962 @item target rdp @var{dev}
18967 @value{GDBN} provides the following ARM-specific commands:
18970 @item set arm disassembler
18972 This commands selects from a list of disassembly styles. The
18973 @code{"std"} style is the standard style.
18975 @item show arm disassembler
18977 Show the current disassembly style.
18979 @item set arm apcs32
18980 @cindex ARM 32-bit mode
18981 This command toggles ARM operation mode between 32-bit and 26-bit.
18983 @item show arm apcs32
18984 Display the current usage of the ARM 32-bit mode.
18986 @item set arm fpu @var{fputype}
18987 This command sets the ARM floating-point unit (FPU) type. The
18988 argument @var{fputype} can be one of these:
18992 Determine the FPU type by querying the OS ABI.
18994 Software FPU, with mixed-endian doubles on little-endian ARM
18997 GCC-compiled FPA co-processor.
18999 Software FPU with pure-endian doubles.
19005 Show the current type of the FPU.
19008 This command forces @value{GDBN} to use the specified ABI.
19011 Show the currently used ABI.
19013 @item set arm fallback-mode (arm|thumb|auto)
19014 @value{GDBN} uses the symbol table, when available, to determine
19015 whether instructions are ARM or Thumb. This command controls
19016 @value{GDBN}'s default behavior when the symbol table is not
19017 available. The default is @samp{auto}, which causes @value{GDBN} to
19018 use the current execution mode (from the @code{T} bit in the @code{CPSR}
19021 @item show arm fallback-mode
19022 Show the current fallback instruction mode.
19024 @item set arm force-mode (arm|thumb|auto)
19025 This command overrides use of the symbol table to determine whether
19026 instructions are ARM or Thumb. The default is @samp{auto}, which
19027 causes @value{GDBN} to use the symbol table and then the setting
19028 of @samp{set arm fallback-mode}.
19030 @item show arm force-mode
19031 Show the current forced instruction mode.
19033 @item set debug arm
19034 Toggle whether to display ARM-specific debugging messages from the ARM
19035 target support subsystem.
19037 @item show debug arm
19038 Show whether ARM-specific debugging messages are enabled.
19041 The following commands are available when an ARM target is debugged
19042 using the RDI interface:
19045 @item rdilogfile @r{[}@var{file}@r{]}
19047 @cindex ADP (Angel Debugger Protocol) logging
19048 Set the filename for the ADP (Angel Debugger Protocol) packet log.
19049 With an argument, sets the log file to the specified @var{file}. With
19050 no argument, show the current log file name. The default log file is
19053 @item rdilogenable @r{[}@var{arg}@r{]}
19054 @kindex rdilogenable
19055 Control logging of ADP packets. With an argument of 1 or @code{"yes"}
19056 enables logging, with an argument 0 or @code{"no"} disables it. With
19057 no arguments displays the current setting. When logging is enabled,
19058 ADP packets exchanged between @value{GDBN} and the RDI target device
19059 are logged to a file.
19061 @item set rdiromatzero
19062 @kindex set rdiromatzero
19063 @cindex ROM at zero address, RDI
19064 Tell @value{GDBN} whether the target has ROM at address 0. If on,
19065 vector catching is disabled, so that zero address can be used. If off
19066 (the default), vector catching is enabled. For this command to take
19067 effect, it needs to be invoked prior to the @code{target rdi} command.
19069 @item show rdiromatzero
19070 @kindex show rdiromatzero
19071 Show the current setting of ROM at zero address.
19073 @item set rdiheartbeat
19074 @kindex set rdiheartbeat
19075 @cindex RDI heartbeat
19076 Enable or disable RDI heartbeat packets. It is not recommended to
19077 turn on this option, since it confuses ARM and EPI JTAG interface, as
19078 well as the Angel monitor.
19080 @item show rdiheartbeat
19081 @kindex show rdiheartbeat
19082 Show the setting of RDI heartbeat packets.
19086 @item target sim @r{[}@var{simargs}@r{]} @dots{}
19087 The @value{GDBN} ARM simulator accepts the following optional arguments.
19090 @item --swi-support=@var{type}
19091 Tell the simulator which SWI interfaces to support.
19092 @var{type} may be a comma separated list of the following values.
19093 The default value is @code{all}.
19106 @subsection Renesas M32R/D and M32R/SDI
19109 @kindex target m32r
19110 @item target m32r @var{dev}
19111 Renesas M32R/D ROM monitor.
19113 @kindex target m32rsdi
19114 @item target m32rsdi @var{dev}
19115 Renesas M32R SDI server, connected via parallel port to the board.
19118 The following @value{GDBN} commands are specific to the M32R monitor:
19121 @item set download-path @var{path}
19122 @kindex set download-path
19123 @cindex find downloadable @sc{srec} files (M32R)
19124 Set the default path for finding downloadable @sc{srec} files.
19126 @item show download-path
19127 @kindex show download-path
19128 Show the default path for downloadable @sc{srec} files.
19130 @item set board-address @var{addr}
19131 @kindex set board-address
19132 @cindex M32-EVA target board address
19133 Set the IP address for the M32R-EVA target board.
19135 @item show board-address
19136 @kindex show board-address
19137 Show the current IP address of the target board.
19139 @item set server-address @var{addr}
19140 @kindex set server-address
19141 @cindex download server address (M32R)
19142 Set the IP address for the download server, which is the @value{GDBN}'s
19145 @item show server-address
19146 @kindex show server-address
19147 Display the IP address of the download server.
19149 @item upload @r{[}@var{file}@r{]}
19150 @kindex upload@r{, M32R}
19151 Upload the specified @sc{srec} @var{file} via the monitor's Ethernet
19152 upload capability. If no @var{file} argument is given, the current
19153 executable file is uploaded.
19155 @item tload @r{[}@var{file}@r{]}
19156 @kindex tload@r{, M32R}
19157 Test the @code{upload} command.
19160 The following commands are available for M32R/SDI:
19165 @cindex reset SDI connection, M32R
19166 This command resets the SDI connection.
19170 This command shows the SDI connection status.
19173 @kindex debug_chaos
19174 @cindex M32R/Chaos debugging
19175 Instructs the remote that M32R/Chaos debugging is to be used.
19177 @item use_debug_dma
19178 @kindex use_debug_dma
19179 Instructs the remote to use the DEBUG_DMA method of accessing memory.
19182 @kindex use_mon_code
19183 Instructs the remote to use the MON_CODE method of accessing memory.
19186 @kindex use_ib_break
19187 Instructs the remote to set breakpoints by IB break.
19189 @item use_dbt_break
19190 @kindex use_dbt_break
19191 Instructs the remote to set breakpoints by DBT.
19197 The Motorola m68k configuration includes ColdFire support, and a
19198 target command for the following ROM monitor.
19202 @kindex target dbug
19203 @item target dbug @var{dev}
19204 dBUG ROM monitor for Motorola ColdFire.
19209 @subsection MicroBlaze
19210 @cindex Xilinx MicroBlaze
19211 @cindex XMD, Xilinx Microprocessor Debugger
19213 The MicroBlaze is a soft-core processor supported on various Xilinx
19214 FPGAs, such as Spartan or Virtex series. Boards with these processors
19215 usually have JTAG ports which connect to a host system running the Xilinx
19216 Embedded Development Kit (EDK) or Software Development Kit (SDK).
19217 This host system is used to download the configuration bitstream to
19218 the target FPGA. The Xilinx Microprocessor Debugger (XMD) program
19219 communicates with the target board using the JTAG interface and
19220 presents a @code{gdbserver} interface to the board. By default
19221 @code{xmd} uses port @code{1234}. (While it is possible to change
19222 this default port, it requires the use of undocumented @code{xmd}
19223 commands. Contact Xilinx support if you need to do this.)
19225 Use these GDB commands to connect to the MicroBlaze target processor.
19228 @item target remote :1234
19229 Use this command to connect to the target if you are running @value{GDBN}
19230 on the same system as @code{xmd}.
19232 @item target remote @var{xmd-host}:1234
19233 Use this command to connect to the target if it is connected to @code{xmd}
19234 running on a different system named @var{xmd-host}.
19237 Use this command to download a program to the MicroBlaze target.
19239 @item set debug microblaze @var{n}
19240 Enable MicroBlaze-specific debugging messages if non-zero.
19242 @item show debug microblaze @var{n}
19243 Show MicroBlaze-specific debugging level.
19246 @node MIPS Embedded
19247 @subsection MIPS Embedded
19249 @cindex MIPS boards
19250 @value{GDBN} can use the MIPS remote debugging protocol to talk to a
19251 MIPS board attached to a serial line. This is available when
19252 you configure @value{GDBN} with @samp{--target=mips-elf}.
19255 Use these @value{GDBN} commands to specify the connection to your target board:
19258 @item target mips @var{port}
19259 @kindex target mips @var{port}
19260 To run a program on the board, start up @code{@value{GDBP}} with the
19261 name of your program as the argument. To connect to the board, use the
19262 command @samp{target mips @var{port}}, where @var{port} is the name of
19263 the serial port connected to the board. If the program has not already
19264 been downloaded to the board, you may use the @code{load} command to
19265 download it. You can then use all the usual @value{GDBN} commands.
19267 For example, this sequence connects to the target board through a serial
19268 port, and loads and runs a program called @var{prog} through the
19272 host$ @value{GDBP} @var{prog}
19273 @value{GDBN} is free software and @dots{}
19274 (@value{GDBP}) target mips /dev/ttyb
19275 (@value{GDBP}) load @var{prog}
19279 @item target mips @var{hostname}:@var{portnumber}
19280 On some @value{GDBN} host configurations, you can specify a TCP
19281 connection (for instance, to a serial line managed by a terminal
19282 concentrator) instead of a serial port, using the syntax
19283 @samp{@var{hostname}:@var{portnumber}}.
19285 @item target pmon @var{port}
19286 @kindex target pmon @var{port}
19289 @item target ddb @var{port}
19290 @kindex target ddb @var{port}
19291 NEC's DDB variant of PMON for Vr4300.
19293 @item target lsi @var{port}
19294 @kindex target lsi @var{port}
19295 LSI variant of PMON.
19297 @kindex target r3900
19298 @item target r3900 @var{dev}
19299 Densan DVE-R3900 ROM monitor for Toshiba R3900 Mips.
19301 @kindex target array
19302 @item target array @var{dev}
19303 Array Tech LSI33K RAID controller board.
19309 @value{GDBN} also supports these special commands for MIPS targets:
19312 @item set mipsfpu double
19313 @itemx set mipsfpu single
19314 @itemx set mipsfpu none
19315 @itemx set mipsfpu auto
19316 @itemx show mipsfpu
19317 @kindex set mipsfpu
19318 @kindex show mipsfpu
19319 @cindex MIPS remote floating point
19320 @cindex floating point, MIPS remote
19321 If your target board does not support the MIPS floating point
19322 coprocessor, you should use the command @samp{set mipsfpu none} (if you
19323 need this, you may wish to put the command in your @value{GDBN} init
19324 file). This tells @value{GDBN} how to find the return value of
19325 functions which return floating point values. It also allows
19326 @value{GDBN} to avoid saving the floating point registers when calling
19327 functions on the board. If you are using a floating point coprocessor
19328 with only single precision floating point support, as on the @sc{r4650}
19329 processor, use the command @samp{set mipsfpu single}. The default
19330 double precision floating point coprocessor may be selected using
19331 @samp{set mipsfpu double}.
19333 In previous versions the only choices were double precision or no
19334 floating point, so @samp{set mipsfpu on} will select double precision
19335 and @samp{set mipsfpu off} will select no floating point.
19337 As usual, you can inquire about the @code{mipsfpu} variable with
19338 @samp{show mipsfpu}.
19340 @item set timeout @var{seconds}
19341 @itemx set retransmit-timeout @var{seconds}
19342 @itemx show timeout
19343 @itemx show retransmit-timeout
19344 @cindex @code{timeout}, MIPS protocol
19345 @cindex @code{retransmit-timeout}, MIPS protocol
19346 @kindex set timeout
19347 @kindex show timeout
19348 @kindex set retransmit-timeout
19349 @kindex show retransmit-timeout
19350 You can control the timeout used while waiting for a packet, in the MIPS
19351 remote protocol, with the @code{set timeout @var{seconds}} command. The
19352 default is 5 seconds. Similarly, you can control the timeout used while
19353 waiting for an acknowledgment of a packet with the @code{set
19354 retransmit-timeout @var{seconds}} command. The default is 3 seconds.
19355 You can inspect both values with @code{show timeout} and @code{show
19356 retransmit-timeout}. (These commands are @emph{only} available when
19357 @value{GDBN} is configured for @samp{--target=mips-elf}.)
19359 The timeout set by @code{set timeout} does not apply when @value{GDBN}
19360 is waiting for your program to stop. In that case, @value{GDBN} waits
19361 forever because it has no way of knowing how long the program is going
19362 to run before stopping.
19364 @item set syn-garbage-limit @var{num}
19365 @kindex set syn-garbage-limit@r{, MIPS remote}
19366 @cindex synchronize with remote MIPS target
19367 Limit the maximum number of characters @value{GDBN} should ignore when
19368 it tries to synchronize with the remote target. The default is 10
19369 characters. Setting the limit to -1 means there's no limit.
19371 @item show syn-garbage-limit
19372 @kindex show syn-garbage-limit@r{, MIPS remote}
19373 Show the current limit on the number of characters to ignore when
19374 trying to synchronize with the remote system.
19376 @item set monitor-prompt @var{prompt}
19377 @kindex set monitor-prompt@r{, MIPS remote}
19378 @cindex remote monitor prompt
19379 Tell @value{GDBN} to expect the specified @var{prompt} string from the
19380 remote monitor. The default depends on the target:
19390 @item show monitor-prompt
19391 @kindex show monitor-prompt@r{, MIPS remote}
19392 Show the current strings @value{GDBN} expects as the prompt from the
19395 @item set monitor-warnings
19396 @kindex set monitor-warnings@r{, MIPS remote}
19397 Enable or disable monitor warnings about hardware breakpoints. This
19398 has effect only for the @code{lsi} target. When on, @value{GDBN} will
19399 display warning messages whose codes are returned by the @code{lsi}
19400 PMON monitor for breakpoint commands.
19402 @item show monitor-warnings
19403 @kindex show monitor-warnings@r{, MIPS remote}
19404 Show the current setting of printing monitor warnings.
19406 @item pmon @var{command}
19407 @kindex pmon@r{, MIPS remote}
19408 @cindex send PMON command
19409 This command allows sending an arbitrary @var{command} string to the
19410 monitor. The monitor must be in debug mode for this to work.
19413 @node OpenRISC 1000
19414 @subsection OpenRISC 1000
19415 @cindex OpenRISC 1000
19417 @cindex or1k boards
19418 See OR1k Architecture document (@uref{www.opencores.org}) for more information
19419 about platform and commands.
19423 @kindex target jtag
19424 @item target jtag jtag://@var{host}:@var{port}
19426 Connects to remote JTAG server.
19427 JTAG remote server can be either an or1ksim or JTAG server,
19428 connected via parallel port to the board.
19430 Example: @code{target jtag jtag://localhost:9999}
19433 @item or1ksim @var{command}
19434 If connected to @code{or1ksim} OpenRISC 1000 Architectural
19435 Simulator, proprietary commands can be executed.
19437 @kindex info or1k spr
19438 @item info or1k spr
19439 Displays spr groups.
19441 @item info or1k spr @var{group}
19442 @itemx info or1k spr @var{groupno}
19443 Displays register names in selected group.
19445 @item info or1k spr @var{group} @var{register}
19446 @itemx info or1k spr @var{register}
19447 @itemx info or1k spr @var{groupno} @var{registerno}
19448 @itemx info or1k spr @var{registerno}
19449 Shows information about specified spr register.
19452 @item spr @var{group} @var{register} @var{value}
19453 @itemx spr @var{register @var{value}}
19454 @itemx spr @var{groupno} @var{registerno @var{value}}
19455 @itemx spr @var{registerno @var{value}}
19456 Writes @var{value} to specified spr register.
19459 Some implementations of OpenRISC 1000 Architecture also have hardware trace.
19460 It is very similar to @value{GDBN} trace, except it does not interfere with normal
19461 program execution and is thus much faster. Hardware breakpoints/watchpoint
19462 triggers can be set using:
19465 Load effective address/data
19467 Store effective address/data
19469 Access effective address ($SEA or $LEA) or data ($SDATA/$LDATA)
19474 When triggered, it can capture low level data, like: @code{PC}, @code{LSEA},
19475 @code{LDATA}, @code{SDATA}, @code{READSPR}, @code{WRITESPR}, @code{INSTR}.
19477 @code{htrace} commands:
19478 @cindex OpenRISC 1000 htrace
19481 @item hwatch @var{conditional}
19482 Set hardware watchpoint on combination of Load/Store Effective Address(es)
19483 or Data. For example:
19485 @code{hwatch ($LEA == my_var) && ($LDATA < 50) || ($SEA == my_var) && ($SDATA >= 50)}
19487 @code{hwatch ($LEA == my_var) && ($LDATA < 50) || ($SEA == my_var) && ($SDATA >= 50)}
19491 Display information about current HW trace configuration.
19493 @item htrace trigger @var{conditional}
19494 Set starting criteria for HW trace.
19496 @item htrace qualifier @var{conditional}
19497 Set acquisition qualifier for HW trace.
19499 @item htrace stop @var{conditional}
19500 Set HW trace stopping criteria.
19502 @item htrace record [@var{data}]*
19503 Selects the data to be recorded, when qualifier is met and HW trace was
19506 @item htrace enable
19507 @itemx htrace disable
19508 Enables/disables the HW trace.
19510 @item htrace rewind [@var{filename}]
19511 Clears currently recorded trace data.
19513 If filename is specified, new trace file is made and any newly collected data
19514 will be written there.
19516 @item htrace print [@var{start} [@var{len}]]
19517 Prints trace buffer, using current record configuration.
19519 @item htrace mode continuous
19520 Set continuous trace mode.
19522 @item htrace mode suspend
19523 Set suspend trace mode.
19527 @node PowerPC Embedded
19528 @subsection PowerPC Embedded
19530 @cindex DVC register
19531 @value{GDBN} supports using the DVC (Data Value Compare) register to
19532 implement in hardware simple hardware watchpoint conditions of the form:
19535 (@value{GDBP}) watch @var{ADDRESS|VARIABLE} \
19536 if @var{ADDRESS|VARIABLE} == @var{CONSTANT EXPRESSION}
19539 The DVC register will be automatically used when @value{GDBN} detects
19540 such pattern in a condition expression, and the created watchpoint uses one
19541 debug register (either the @code{exact-watchpoints} option is on and the
19542 variable is scalar, or the variable has a length of one byte). This feature
19543 is available in native @value{GDBN} running on a Linux kernel version 2.6.34
19546 When running on PowerPC embedded processors, @value{GDBN} automatically uses
19547 ranged hardware watchpoints, unless the @code{exact-watchpoints} option is on,
19548 in which case watchpoints using only one debug register are created when
19549 watching variables of scalar types.
19551 You can create an artificial array to watch an arbitrary memory
19552 region using one of the following commands (@pxref{Expressions}):
19555 (@value{GDBP}) watch *((char *) @var{address})@@@var{length}
19556 (@value{GDBP}) watch @{char[@var{length}]@} @var{address}
19559 PowerPC embedded processors support masked watchpoints. See the discussion
19560 about the @code{mask} argument in @ref{Set Watchpoints}.
19562 @cindex ranged breakpoint
19563 PowerPC embedded processors support hardware accelerated
19564 @dfn{ranged breakpoints}. A ranged breakpoint stops execution of
19565 the inferior whenever it executes an instruction at any address within
19566 the range it specifies. To set a ranged breakpoint in @value{GDBN},
19567 use the @code{break-range} command.
19569 @value{GDBN} provides the following PowerPC-specific commands:
19572 @kindex break-range
19573 @item break-range @var{start-location}, @var{end-location}
19574 Set a breakpoint for an address range.
19575 @var{start-location} and @var{end-location} can specify a function name,
19576 a line number, an offset of lines from the current line or from the start
19577 location, or an address of an instruction (see @ref{Specify Location},
19578 for a list of all the possible ways to specify a @var{location}.)
19579 The breakpoint will stop execution of the inferior whenever it
19580 executes an instruction at any address within the specified range,
19581 (including @var{start-location} and @var{end-location}.)
19583 @kindex set powerpc
19584 @item set powerpc soft-float
19585 @itemx show powerpc soft-float
19586 Force @value{GDBN} to use (or not use) a software floating point calling
19587 convention. By default, @value{GDBN} selects the calling convention based
19588 on the selected architecture and the provided executable file.
19590 @item set powerpc vector-abi
19591 @itemx show powerpc vector-abi
19592 Force @value{GDBN} to use the specified calling convention for vector
19593 arguments and return values. The valid options are @samp{auto};
19594 @samp{generic}, to avoid vector registers even if they are present;
19595 @samp{altivec}, to use AltiVec registers; and @samp{spe} to use SPE
19596 registers. By default, @value{GDBN} selects the calling convention
19597 based on the selected architecture and the provided executable file.
19599 @item set powerpc exact-watchpoints
19600 @itemx show powerpc exact-watchpoints
19601 Allow @value{GDBN} to use only one debug register when watching a variable
19602 of scalar type, thus assuming that the variable is accessed through the
19603 address of its first byte.
19605 @kindex target dink32
19606 @item target dink32 @var{dev}
19607 DINK32 ROM monitor.
19609 @kindex target ppcbug
19610 @item target ppcbug @var{dev}
19611 @kindex target ppcbug1
19612 @item target ppcbug1 @var{dev}
19613 PPCBUG ROM monitor for PowerPC.
19616 @item target sds @var{dev}
19617 SDS monitor, running on a PowerPC board (such as Motorola's ADS).
19620 @cindex SDS protocol
19621 The following commands specific to the SDS protocol are supported
19625 @item set sdstimeout @var{nsec}
19626 @kindex set sdstimeout
19627 Set the timeout for SDS protocol reads to be @var{nsec} seconds. The
19628 default is 2 seconds.
19630 @item show sdstimeout
19631 @kindex show sdstimeout
19632 Show the current value of the SDS timeout.
19634 @item sds @var{command}
19635 @kindex sds@r{, a command}
19636 Send the specified @var{command} string to the SDS monitor.
19641 @subsection HP PA Embedded
19645 @kindex target op50n
19646 @item target op50n @var{dev}
19647 OP50N monitor, running on an OKI HPPA board.
19649 @kindex target w89k
19650 @item target w89k @var{dev}
19651 W89K monitor, running on a Winbond HPPA board.
19656 @subsection Tsqware Sparclet
19660 @value{GDBN} enables developers to debug tasks running on
19661 Sparclet targets from a Unix host.
19662 @value{GDBN} uses code that runs on
19663 both the Unix host and on the Sparclet target. The program
19664 @code{@value{GDBP}} is installed and executed on the Unix host.
19667 @item remotetimeout @var{args}
19668 @kindex remotetimeout
19669 @value{GDBN} supports the option @code{remotetimeout}.
19670 This option is set by the user, and @var{args} represents the number of
19671 seconds @value{GDBN} waits for responses.
19674 @cindex compiling, on Sparclet
19675 When compiling for debugging, include the options @samp{-g} to get debug
19676 information and @samp{-Ttext} to relocate the program to where you wish to
19677 load it on the target. You may also want to add the options @samp{-n} or
19678 @samp{-N} in order to reduce the size of the sections. Example:
19681 sparclet-aout-gcc prog.c -Ttext 0x12010000 -g -o prog -N
19684 You can use @code{objdump} to verify that the addresses are what you intended:
19687 sparclet-aout-objdump --headers --syms prog
19690 @cindex running, on Sparclet
19692 your Unix execution search path to find @value{GDBN}, you are ready to
19693 run @value{GDBN}. From your Unix host, run @code{@value{GDBP}}
19694 (or @code{sparclet-aout-gdb}, depending on your installation).
19696 @value{GDBN} comes up showing the prompt:
19703 * Sparclet File:: Setting the file to debug
19704 * Sparclet Connection:: Connecting to Sparclet
19705 * Sparclet Download:: Sparclet download
19706 * Sparclet Execution:: Running and debugging
19709 @node Sparclet File
19710 @subsubsection Setting File to Debug
19712 The @value{GDBN} command @code{file} lets you choose with program to debug.
19715 (gdbslet) file prog
19719 @value{GDBN} then attempts to read the symbol table of @file{prog}.
19720 @value{GDBN} locates
19721 the file by searching the directories listed in the command search
19723 If the file was compiled with debug information (option @samp{-g}), source
19724 files will be searched as well.
19725 @value{GDBN} locates
19726 the source files by searching the directories listed in the directory search
19727 path (@pxref{Environment, ,Your Program's Environment}).
19729 to find a file, it displays a message such as:
19732 prog: No such file or directory.
19735 When this happens, add the appropriate directories to the search paths with
19736 the @value{GDBN} commands @code{path} and @code{dir}, and execute the
19737 @code{target} command again.
19739 @node Sparclet Connection
19740 @subsubsection Connecting to Sparclet
19742 The @value{GDBN} command @code{target} lets you connect to a Sparclet target.
19743 To connect to a target on serial port ``@code{ttya}'', type:
19746 (gdbslet) target sparclet /dev/ttya
19747 Remote target sparclet connected to /dev/ttya
19748 main () at ../prog.c:3
19752 @value{GDBN} displays messages like these:
19758 @node Sparclet Download
19759 @subsubsection Sparclet Download
19761 @cindex download to Sparclet
19762 Once connected to the Sparclet target,
19763 you can use the @value{GDBN}
19764 @code{load} command to download the file from the host to the target.
19765 The file name and load offset should be given as arguments to the @code{load}
19767 Since the file format is aout, the program must be loaded to the starting
19768 address. You can use @code{objdump} to find out what this value is. The load
19769 offset is an offset which is added to the VMA (virtual memory address)
19770 of each of the file's sections.
19771 For instance, if the program
19772 @file{prog} was linked to text address 0x1201000, with data at 0x12010160
19773 and bss at 0x12010170, in @value{GDBN}, type:
19776 (gdbslet) load prog 0x12010000
19777 Loading section .text, size 0xdb0 vma 0x12010000
19780 If the code is loaded at a different address then what the program was linked
19781 to, you may need to use the @code{section} and @code{add-symbol-file} commands
19782 to tell @value{GDBN} where to map the symbol table.
19784 @node Sparclet Execution
19785 @subsubsection Running and Debugging
19787 @cindex running and debugging Sparclet programs
19788 You can now begin debugging the task using @value{GDBN}'s execution control
19789 commands, @code{b}, @code{step}, @code{run}, etc. See the @value{GDBN}
19790 manual for the list of commands.
19794 Breakpoint 1 at 0x12010000: file prog.c, line 3.
19796 Starting program: prog
19797 Breakpoint 1, main (argc=1, argv=0xeffff21c) at prog.c:3
19798 3 char *symarg = 0;
19800 4 char *execarg = "hello!";
19805 @subsection Fujitsu Sparclite
19809 @kindex target sparclite
19810 @item target sparclite @var{dev}
19811 Fujitsu sparclite boards, used only for the purpose of loading.
19812 You must use an additional command to debug the program.
19813 For example: target remote @var{dev} using @value{GDBN} standard
19819 @subsection Zilog Z8000
19822 @cindex simulator, Z8000
19823 @cindex Zilog Z8000 simulator
19825 When configured for debugging Zilog Z8000 targets, @value{GDBN} includes
19828 For the Z8000 family, @samp{target sim} simulates either the Z8002 (the
19829 unsegmented variant of the Z8000 architecture) or the Z8001 (the
19830 segmented variant). The simulator recognizes which architecture is
19831 appropriate by inspecting the object code.
19834 @item target sim @var{args}
19836 @kindex target sim@r{, with Z8000}
19837 Debug programs on a simulated CPU. If the simulator supports setup
19838 options, specify them via @var{args}.
19842 After specifying this target, you can debug programs for the simulated
19843 CPU in the same style as programs for your host computer; use the
19844 @code{file} command to load a new program image, the @code{run} command
19845 to run your program, and so on.
19847 As well as making available all the usual machine registers
19848 (@pxref{Registers, ,Registers}), the Z8000 simulator provides three
19849 additional items of information as specially named registers:
19854 Counts clock-ticks in the simulator.
19857 Counts instructions run in the simulator.
19860 Execution time in 60ths of a second.
19864 You can refer to these values in @value{GDBN} expressions with the usual
19865 conventions; for example, @w{@samp{b fputc if $cycles>5000}} sets a
19866 conditional breakpoint that suspends only after at least 5000
19867 simulated clock ticks.
19870 @subsection Atmel AVR
19873 When configured for debugging the Atmel AVR, @value{GDBN} supports the
19874 following AVR-specific commands:
19877 @item info io_registers
19878 @kindex info io_registers@r{, AVR}
19879 @cindex I/O registers (Atmel AVR)
19880 This command displays information about the AVR I/O registers. For
19881 each register, @value{GDBN} prints its number and value.
19888 When configured for debugging CRIS, @value{GDBN} provides the
19889 following CRIS-specific commands:
19892 @item set cris-version @var{ver}
19893 @cindex CRIS version
19894 Set the current CRIS version to @var{ver}, either @samp{10} or @samp{32}.
19895 The CRIS version affects register names and sizes. This command is useful in
19896 case autodetection of the CRIS version fails.
19898 @item show cris-version
19899 Show the current CRIS version.
19901 @item set cris-dwarf2-cfi
19902 @cindex DWARF-2 CFI and CRIS
19903 Set the usage of DWARF-2 CFI for CRIS debugging. The default is @samp{on}.
19904 Change to @samp{off} when using @code{gcc-cris} whose version is below
19907 @item show cris-dwarf2-cfi
19908 Show the current state of using DWARF-2 CFI.
19910 @item set cris-mode @var{mode}
19912 Set the current CRIS mode to @var{mode}. It should only be changed when
19913 debugging in guru mode, in which case it should be set to
19914 @samp{guru} (the default is @samp{normal}).
19916 @item show cris-mode
19917 Show the current CRIS mode.
19921 @subsection Renesas Super-H
19924 For the Renesas Super-H processor, @value{GDBN} provides these
19929 @kindex regs@r{, Super-H}
19930 Show the values of all Super-H registers.
19932 @item set sh calling-convention @var{convention}
19933 @kindex set sh calling-convention
19934 Set the calling-convention used when calling functions from @value{GDBN}.
19935 Allowed values are @samp{gcc}, which is the default setting, and @samp{renesas}.
19936 With the @samp{gcc} setting, functions are called using the @value{NGCC} calling
19937 convention. If the DWARF-2 information of the called function specifies
19938 that the function follows the Renesas calling convention, the function
19939 is called using the Renesas calling convention. If the calling convention
19940 is set to @samp{renesas}, the Renesas calling convention is always used,
19941 regardless of the DWARF-2 information. This can be used to override the
19942 default of @samp{gcc} if debug information is missing, or the compiler
19943 does not emit the DWARF-2 calling convention entry for a function.
19945 @item show sh calling-convention
19946 @kindex show sh calling-convention
19947 Show the current calling convention setting.
19952 @node Architectures
19953 @section Architectures
19955 This section describes characteristics of architectures that affect
19956 all uses of @value{GDBN} with the architecture, both native and cross.
19963 * HPPA:: HP PA architecture
19964 * SPU:: Cell Broadband Engine SPU architecture
19969 @subsection x86 Architecture-specific Issues
19972 @item set struct-convention @var{mode}
19973 @kindex set struct-convention
19974 @cindex struct return convention
19975 @cindex struct/union returned in registers
19976 Set the convention used by the inferior to return @code{struct}s and
19977 @code{union}s from functions to @var{mode}. Possible values of
19978 @var{mode} are @code{"pcc"}, @code{"reg"}, and @code{"default"} (the
19979 default). @code{"default"} or @code{"pcc"} means that @code{struct}s
19980 are returned on the stack, while @code{"reg"} means that a
19981 @code{struct} or a @code{union} whose size is 1, 2, 4, or 8 bytes will
19982 be returned in a register.
19984 @item show struct-convention
19985 @kindex show struct-convention
19986 Show the current setting of the convention to return @code{struct}s
19995 @kindex set rstack_high_address
19996 @cindex AMD 29K register stack
19997 @cindex register stack, AMD29K
19998 @item set rstack_high_address @var{address}
19999 On AMD 29000 family processors, registers are saved in a separate
20000 @dfn{register stack}. There is no way for @value{GDBN} to determine the
20001 extent of this stack. Normally, @value{GDBN} just assumes that the
20002 stack is ``large enough''. This may result in @value{GDBN} referencing
20003 memory locations that do not exist. If necessary, you can get around
20004 this problem by specifying the ending address of the register stack with
20005 the @code{set rstack_high_address} command. The argument should be an
20006 address, which you probably want to precede with @samp{0x} to specify in
20009 @kindex show rstack_high_address
20010 @item show rstack_high_address
20011 Display the current limit of the register stack, on AMD 29000 family
20019 See the following section.
20024 @cindex stack on Alpha
20025 @cindex stack on MIPS
20026 @cindex Alpha stack
20028 Alpha- and MIPS-based computers use an unusual stack frame, which
20029 sometimes requires @value{GDBN} to search backward in the object code to
20030 find the beginning of a function.
20032 @cindex response time, MIPS debugging
20033 To improve response time (especially for embedded applications, where
20034 @value{GDBN} may be restricted to a slow serial line for this search)
20035 you may want to limit the size of this search, using one of these
20039 @cindex @code{heuristic-fence-post} (Alpha, MIPS)
20040 @item set heuristic-fence-post @var{limit}
20041 Restrict @value{GDBN} to examining at most @var{limit} bytes in its
20042 search for the beginning of a function. A value of @var{0} (the
20043 default) means there is no limit. However, except for @var{0}, the
20044 larger the limit the more bytes @code{heuristic-fence-post} must search
20045 and therefore the longer it takes to run. You should only need to use
20046 this command when debugging a stripped executable.
20048 @item show heuristic-fence-post
20049 Display the current limit.
20053 These commands are available @emph{only} when @value{GDBN} is configured
20054 for debugging programs on Alpha or MIPS processors.
20056 Several MIPS-specific commands are available when debugging MIPS
20060 @item set mips abi @var{arg}
20061 @kindex set mips abi
20062 @cindex set ABI for MIPS
20063 Tell @value{GDBN} which MIPS ABI is used by the inferior. Possible
20064 values of @var{arg} are:
20068 The default ABI associated with the current binary (this is the
20078 @item show mips abi
20079 @kindex show mips abi
20080 Show the MIPS ABI used by @value{GDBN} to debug the inferior.
20083 @itemx show mipsfpu
20084 @xref{MIPS Embedded, set mipsfpu}.
20086 @item set mips mask-address @var{arg}
20087 @kindex set mips mask-address
20088 @cindex MIPS addresses, masking
20089 This command determines whether the most-significant 32 bits of 64-bit
20090 MIPS addresses are masked off. The argument @var{arg} can be
20091 @samp{on}, @samp{off}, or @samp{auto}. The latter is the default
20092 setting, which lets @value{GDBN} determine the correct value.
20094 @item show mips mask-address
20095 @kindex show mips mask-address
20096 Show whether the upper 32 bits of MIPS addresses are masked off or
20099 @item set remote-mips64-transfers-32bit-regs
20100 @kindex set remote-mips64-transfers-32bit-regs
20101 This command controls compatibility with 64-bit MIPS targets that
20102 transfer data in 32-bit quantities. If you have an old MIPS 64 target
20103 that transfers 32 bits for some registers, like @sc{sr} and @sc{fsr},
20104 and 64 bits for other registers, set this option to @samp{on}.
20106 @item show remote-mips64-transfers-32bit-regs
20107 @kindex show remote-mips64-transfers-32bit-regs
20108 Show the current setting of compatibility with older MIPS 64 targets.
20110 @item set debug mips
20111 @kindex set debug mips
20112 This command turns on and off debugging messages for the MIPS-specific
20113 target code in @value{GDBN}.
20115 @item show debug mips
20116 @kindex show debug mips
20117 Show the current setting of MIPS debugging messages.
20123 @cindex HPPA support
20125 When @value{GDBN} is debugging the HP PA architecture, it provides the
20126 following special commands:
20129 @item set debug hppa
20130 @kindex set debug hppa
20131 This command determines whether HPPA architecture-specific debugging
20132 messages are to be displayed.
20134 @item show debug hppa
20135 Show whether HPPA debugging messages are displayed.
20137 @item maint print unwind @var{address}
20138 @kindex maint print unwind@r{, HPPA}
20139 This command displays the contents of the unwind table entry at the
20140 given @var{address}.
20146 @subsection Cell Broadband Engine SPU architecture
20147 @cindex Cell Broadband Engine
20150 When @value{GDBN} is debugging the Cell Broadband Engine SPU architecture,
20151 it provides the following special commands:
20154 @item info spu event
20156 Display SPU event facility status. Shows current event mask
20157 and pending event status.
20159 @item info spu signal
20160 Display SPU signal notification facility status. Shows pending
20161 signal-control word and signal notification mode of both signal
20162 notification channels.
20164 @item info spu mailbox
20165 Display SPU mailbox facility status. Shows all pending entries,
20166 in order of processing, in each of the SPU Write Outbound,
20167 SPU Write Outbound Interrupt, and SPU Read Inbound mailboxes.
20170 Display MFC DMA status. Shows all pending commands in the MFC
20171 DMA queue. For each entry, opcode, tag, class IDs, effective
20172 and local store addresses and transfer size are shown.
20174 @item info spu proxydma
20175 Display MFC Proxy-DMA status. Shows all pending commands in the MFC
20176 Proxy-DMA queue. For each entry, opcode, tag, class IDs, effective
20177 and local store addresses and transfer size are shown.
20181 When @value{GDBN} is debugging a combined PowerPC/SPU application
20182 on the Cell Broadband Engine, it provides in addition the following
20186 @item set spu stop-on-load @var{arg}
20188 Set whether to stop for new SPE threads. When set to @code{on}, @value{GDBN}
20189 will give control to the user when a new SPE thread enters its @code{main}
20190 function. The default is @code{off}.
20192 @item show spu stop-on-load
20194 Show whether to stop for new SPE threads.
20196 @item set spu auto-flush-cache @var{arg}
20197 Set whether to automatically flush the software-managed cache. When set to
20198 @code{on}, @value{GDBN} will automatically cause the SPE software-managed
20199 cache to be flushed whenever SPE execution stops. This provides a consistent
20200 view of PowerPC memory that is accessed via the cache. If an application
20201 does not use the software-managed cache, this option has no effect.
20203 @item show spu auto-flush-cache
20204 Show whether to automatically flush the software-managed cache.
20209 @subsection PowerPC
20210 @cindex PowerPC architecture
20212 When @value{GDBN} is debugging the PowerPC architecture, it provides a set of
20213 pseudo-registers to enable inspection of 128-bit wide Decimal Floating Point
20214 numbers stored in the floating point registers. These values must be stored
20215 in two consecutive registers, always starting at an even register like
20216 @code{f0} or @code{f2}.
20218 The pseudo-registers go from @code{$dl0} through @code{$dl15}, and are formed
20219 by joining the even/odd register pairs @code{f0} and @code{f1} for @code{$dl0},
20220 @code{f2} and @code{f3} for @code{$dl1} and so on.
20222 For POWER7 processors, @value{GDBN} provides a set of pseudo-registers, the 64-bit
20223 wide Extended Floating Point Registers (@samp{f32} through @samp{f63}).
20226 @node Controlling GDB
20227 @chapter Controlling @value{GDBN}
20229 You can alter the way @value{GDBN} interacts with you by using the
20230 @code{set} command. For commands controlling how @value{GDBN} displays
20231 data, see @ref{Print Settings, ,Print Settings}. Other settings are
20236 * Editing:: Command editing
20237 * Command History:: Command history
20238 * Screen Size:: Screen size
20239 * Numbers:: Numbers
20240 * ABI:: Configuring the current ABI
20241 * Messages/Warnings:: Optional warnings and messages
20242 * Debugging Output:: Optional messages about internal happenings
20243 * Other Misc Settings:: Other Miscellaneous Settings
20251 @value{GDBN} indicates its readiness to read a command by printing a string
20252 called the @dfn{prompt}. This string is normally @samp{(@value{GDBP})}. You
20253 can change the prompt string with the @code{set prompt} command. For
20254 instance, when debugging @value{GDBN} with @value{GDBN}, it is useful to change
20255 the prompt in one of the @value{GDBN} sessions so that you can always tell
20256 which one you are talking to.
20258 @emph{Note:} @code{set prompt} does not add a space for you after the
20259 prompt you set. This allows you to set a prompt which ends in a space
20260 or a prompt that does not.
20264 @item set prompt @var{newprompt}
20265 Directs @value{GDBN} to use @var{newprompt} as its prompt string henceforth.
20267 @kindex show prompt
20269 Prints a line of the form: @samp{Gdb's prompt is: @var{your-prompt}}
20272 Versions of @value{GDBN} that ship with Python scripting enabled have
20273 prompt extensions. The commands for interacting with these extensions
20277 @kindex set extended-prompt
20278 @item set extended-prompt @var{prompt}
20279 Set an extended prompt that allows for substitutions.
20280 @xref{gdb.prompt}, for a list of escape sequences that can be used for
20281 substitution. Any escape sequences specified as part of the prompt
20282 string are replaced with the corresponding strings each time the prompt
20288 set extended-prompt Current working directory: \w (gdb)
20291 Note that when an extended-prompt is set, it takes control of the
20292 @var{prompt_hook} hook. @xref{prompt_hook}, for further information.
20294 @kindex show extended-prompt
20295 @item show extended-prompt
20296 Prints the extended prompt. Any escape sequences specified as part of
20297 the prompt string with @code{set extended-prompt}, are replaced with the
20298 corresponding strings each time the prompt is displayed.
20302 @section Command Editing
20304 @cindex command line editing
20306 @value{GDBN} reads its input commands via the @dfn{Readline} interface. This
20307 @sc{gnu} library provides consistent behavior for programs which provide a
20308 command line interface to the user. Advantages are @sc{gnu} Emacs-style
20309 or @dfn{vi}-style inline editing of commands, @code{csh}-like history
20310 substitution, and a storage and recall of command history across
20311 debugging sessions.
20313 You may control the behavior of command line editing in @value{GDBN} with the
20314 command @code{set}.
20317 @kindex set editing
20320 @itemx set editing on
20321 Enable command line editing (enabled by default).
20323 @item set editing off
20324 Disable command line editing.
20326 @kindex show editing
20328 Show whether command line editing is enabled.
20331 @ifset SYSTEM_READLINE
20332 @xref{Command Line Editing, , , rluserman, GNU Readline Library},
20334 @ifclear SYSTEM_READLINE
20335 @xref{Command Line Editing},
20337 for more details about the Readline
20338 interface. Users unfamiliar with @sc{gnu} Emacs or @code{vi} are
20339 encouraged to read that chapter.
20341 @node Command History
20342 @section Command History
20343 @cindex command history
20345 @value{GDBN} can keep track of the commands you type during your
20346 debugging sessions, so that you can be certain of precisely what
20347 happened. Use these commands to manage the @value{GDBN} command
20350 @value{GDBN} uses the @sc{gnu} History library, a part of the Readline
20351 package, to provide the history facility.
20352 @ifset SYSTEM_READLINE
20353 @xref{Using History Interactively, , , history, GNU History Library},
20355 @ifclear SYSTEM_READLINE
20356 @xref{Using History Interactively},
20358 for the detailed description of the History library.
20360 To issue a command to @value{GDBN} without affecting certain aspects of
20361 the state which is seen by users, prefix it with @samp{server }
20362 (@pxref{Server Prefix}). This
20363 means that this command will not affect the command history, nor will it
20364 affect @value{GDBN}'s notion of which command to repeat if @key{RET} is
20365 pressed on a line by itself.
20367 @cindex @code{server}, command prefix
20368 The server prefix does not affect the recording of values into the value
20369 history; to print a value without recording it into the value history,
20370 use the @code{output} command instead of the @code{print} command.
20372 Here is the description of @value{GDBN} commands related to command
20376 @cindex history substitution
20377 @cindex history file
20378 @kindex set history filename
20379 @cindex @env{GDBHISTFILE}, environment variable
20380 @item set history filename @var{fname}
20381 Set the name of the @value{GDBN} command history file to @var{fname}.
20382 This is the file where @value{GDBN} reads an initial command history
20383 list, and where it writes the command history from this session when it
20384 exits. You can access this list through history expansion or through
20385 the history command editing characters listed below. This file defaults
20386 to the value of the environment variable @code{GDBHISTFILE}, or to
20387 @file{./.gdb_history} (@file{./_gdb_history} on MS-DOS) if this variable
20390 @cindex save command history
20391 @kindex set history save
20392 @item set history save
20393 @itemx set history save on
20394 Record command history in a file, whose name may be specified with the
20395 @code{set history filename} command. By default, this option is disabled.
20397 @item set history save off
20398 Stop recording command history in a file.
20400 @cindex history size
20401 @kindex set history size
20402 @cindex @env{HISTSIZE}, environment variable
20403 @item set history size @var{size}
20404 Set the number of commands which @value{GDBN} keeps in its history list.
20405 This defaults to the value of the environment variable
20406 @code{HISTSIZE}, or to 256 if this variable is not set.
20409 History expansion assigns special meaning to the character @kbd{!}.
20410 @ifset SYSTEM_READLINE
20411 @xref{Event Designators, , , history, GNU History Library},
20413 @ifclear SYSTEM_READLINE
20414 @xref{Event Designators},
20418 @cindex history expansion, turn on/off
20419 Since @kbd{!} is also the logical not operator in C, history expansion
20420 is off by default. If you decide to enable history expansion with the
20421 @code{set history expansion on} command, you may sometimes need to
20422 follow @kbd{!} (when it is used as logical not, in an expression) with
20423 a space or a tab to prevent it from being expanded. The readline
20424 history facilities do not attempt substitution on the strings
20425 @kbd{!=} and @kbd{!(}, even when history expansion is enabled.
20427 The commands to control history expansion are:
20430 @item set history expansion on
20431 @itemx set history expansion
20432 @kindex set history expansion
20433 Enable history expansion. History expansion is off by default.
20435 @item set history expansion off
20436 Disable history expansion.
20439 @kindex show history
20441 @itemx show history filename
20442 @itemx show history save
20443 @itemx show history size
20444 @itemx show history expansion
20445 These commands display the state of the @value{GDBN} history parameters.
20446 @code{show history} by itself displays all four states.
20451 @kindex show commands
20452 @cindex show last commands
20453 @cindex display command history
20454 @item show commands
20455 Display the last ten commands in the command history.
20457 @item show commands @var{n}
20458 Print ten commands centered on command number @var{n}.
20460 @item show commands +
20461 Print ten commands just after the commands last printed.
20465 @section Screen Size
20466 @cindex size of screen
20467 @cindex pauses in output
20469 Certain commands to @value{GDBN} may produce large amounts of
20470 information output to the screen. To help you read all of it,
20471 @value{GDBN} pauses and asks you for input at the end of each page of
20472 output. Type @key{RET} when you want to continue the output, or @kbd{q}
20473 to discard the remaining output. Also, the screen width setting
20474 determines when to wrap lines of output. Depending on what is being
20475 printed, @value{GDBN} tries to break the line at a readable place,
20476 rather than simply letting it overflow onto the following line.
20478 Normally @value{GDBN} knows the size of the screen from the terminal
20479 driver software. For example, on Unix @value{GDBN} uses the termcap data base
20480 together with the value of the @code{TERM} environment variable and the
20481 @code{stty rows} and @code{stty cols} settings. If this is not correct,
20482 you can override it with the @code{set height} and @code{set
20489 @kindex show height
20490 @item set height @var{lpp}
20492 @itemx set width @var{cpl}
20494 These @code{set} commands specify a screen height of @var{lpp} lines and
20495 a screen width of @var{cpl} characters. The associated @code{show}
20496 commands display the current settings.
20498 If you specify a height of zero lines, @value{GDBN} does not pause during
20499 output no matter how long the output is. This is useful if output is to a
20500 file or to an editor buffer.
20502 Likewise, you can specify @samp{set width 0} to prevent @value{GDBN}
20503 from wrapping its output.
20505 @item set pagination on
20506 @itemx set pagination off
20507 @kindex set pagination
20508 Turn the output pagination on or off; the default is on. Turning
20509 pagination off is the alternative to @code{set height 0}. Note that
20510 running @value{GDBN} with the @option{--batch} option (@pxref{Mode
20511 Options, -batch}) also automatically disables pagination.
20513 @item show pagination
20514 @kindex show pagination
20515 Show the current pagination mode.
20520 @cindex number representation
20521 @cindex entering numbers
20523 You can always enter numbers in octal, decimal, or hexadecimal in
20524 @value{GDBN} by the usual conventions: octal numbers begin with
20525 @samp{0}, decimal numbers end with @samp{.}, and hexadecimal numbers
20526 begin with @samp{0x}. Numbers that neither begin with @samp{0} or
20527 @samp{0x}, nor end with a @samp{.} are, by default, entered in base
20528 10; likewise, the default display for numbers---when no particular
20529 format is specified---is base 10. You can change the default base for
20530 both input and output with the commands described below.
20533 @kindex set input-radix
20534 @item set input-radix @var{base}
20535 Set the default base for numeric input. Supported choices
20536 for @var{base} are decimal 8, 10, or 16. @var{base} must itself be
20537 specified either unambiguously or using the current input radix; for
20541 set input-radix 012
20542 set input-radix 10.
20543 set input-radix 0xa
20547 sets the input base to decimal. On the other hand, @samp{set input-radix 10}
20548 leaves the input radix unchanged, no matter what it was, since
20549 @samp{10}, being without any leading or trailing signs of its base, is
20550 interpreted in the current radix. Thus, if the current radix is 16,
20551 @samp{10} is interpreted in hex, i.e.@: as 16 decimal, which doesn't
20554 @kindex set output-radix
20555 @item set output-radix @var{base}
20556 Set the default base for numeric display. Supported choices
20557 for @var{base} are decimal 8, 10, or 16. @var{base} must itself be
20558 specified either unambiguously or using the current input radix.
20560 @kindex show input-radix
20561 @item show input-radix
20562 Display the current default base for numeric input.
20564 @kindex show output-radix
20565 @item show output-radix
20566 Display the current default base for numeric display.
20568 @item set radix @r{[}@var{base}@r{]}
20572 These commands set and show the default base for both input and output
20573 of numbers. @code{set radix} sets the radix of input and output to
20574 the same base; without an argument, it resets the radix back to its
20575 default value of 10.
20580 @section Configuring the Current ABI
20582 @value{GDBN} can determine the @dfn{ABI} (Application Binary Interface) of your
20583 application automatically. However, sometimes you need to override its
20584 conclusions. Use these commands to manage @value{GDBN}'s view of the
20591 One @value{GDBN} configuration can debug binaries for multiple operating
20592 system targets, either via remote debugging or native emulation.
20593 @value{GDBN} will autodetect the @dfn{OS ABI} (Operating System ABI) in use,
20594 but you can override its conclusion using the @code{set osabi} command.
20595 One example where this is useful is in debugging of binaries which use
20596 an alternate C library (e.g.@: @sc{uClibc} for @sc{gnu}/Linux) which does
20597 not have the same identifying marks that the standard C library for your
20602 Show the OS ABI currently in use.
20605 With no argument, show the list of registered available OS ABI's.
20607 @item set osabi @var{abi}
20608 Set the current OS ABI to @var{abi}.
20611 @cindex float promotion
20613 Generally, the way that an argument of type @code{float} is passed to a
20614 function depends on whether the function is prototyped. For a prototyped
20615 (i.e.@: ANSI/ISO style) function, @code{float} arguments are passed unchanged,
20616 according to the architecture's convention for @code{float}. For unprototyped
20617 (i.e.@: K&R style) functions, @code{float} arguments are first promoted to type
20618 @code{double} and then passed.
20620 Unfortunately, some forms of debug information do not reliably indicate whether
20621 a function is prototyped. If @value{GDBN} calls a function that is not marked
20622 as prototyped, it consults @kbd{set coerce-float-to-double}.
20625 @kindex set coerce-float-to-double
20626 @item set coerce-float-to-double
20627 @itemx set coerce-float-to-double on
20628 Arguments of type @code{float} will be promoted to @code{double} when passed
20629 to an unprototyped function. This is the default setting.
20631 @item set coerce-float-to-double off
20632 Arguments of type @code{float} will be passed directly to unprototyped
20635 @kindex show coerce-float-to-double
20636 @item show coerce-float-to-double
20637 Show the current setting of promoting @code{float} to @code{double}.
20641 @kindex show cp-abi
20642 @value{GDBN} needs to know the ABI used for your program's C@t{++}
20643 objects. The correct C@t{++} ABI depends on which C@t{++} compiler was
20644 used to build your application. @value{GDBN} only fully supports
20645 programs with a single C@t{++} ABI; if your program contains code using
20646 multiple C@t{++} ABI's or if @value{GDBN} can not identify your
20647 program's ABI correctly, you can tell @value{GDBN} which ABI to use.
20648 Currently supported ABI's include ``gnu-v2'', for @code{g++} versions
20649 before 3.0, ``gnu-v3'', for @code{g++} versions 3.0 and later, and
20650 ``hpaCC'' for the HP ANSI C@t{++} compiler. Other C@t{++} compilers may
20651 use the ``gnu-v2'' or ``gnu-v3'' ABI's as well. The default setting is
20656 Show the C@t{++} ABI currently in use.
20659 With no argument, show the list of supported C@t{++} ABI's.
20661 @item set cp-abi @var{abi}
20662 @itemx set cp-abi auto
20663 Set the current C@t{++} ABI to @var{abi}, or return to automatic detection.
20666 @node Messages/Warnings
20667 @section Optional Warnings and Messages
20669 @cindex verbose operation
20670 @cindex optional warnings
20671 By default, @value{GDBN} is silent about its inner workings. If you are
20672 running on a slow machine, you may want to use the @code{set verbose}
20673 command. This makes @value{GDBN} tell you when it does a lengthy
20674 internal operation, so you will not think it has crashed.
20676 Currently, the messages controlled by @code{set verbose} are those
20677 which announce that the symbol table for a source file is being read;
20678 see @code{symbol-file} in @ref{Files, ,Commands to Specify Files}.
20681 @kindex set verbose
20682 @item set verbose on
20683 Enables @value{GDBN} output of certain informational messages.
20685 @item set verbose off
20686 Disables @value{GDBN} output of certain informational messages.
20688 @kindex show verbose
20690 Displays whether @code{set verbose} is on or off.
20693 By default, if @value{GDBN} encounters bugs in the symbol table of an
20694 object file, it is silent; but if you are debugging a compiler, you may
20695 find this information useful (@pxref{Symbol Errors, ,Errors Reading
20700 @kindex set complaints
20701 @item set complaints @var{limit}
20702 Permits @value{GDBN} to output @var{limit} complaints about each type of
20703 unusual symbols before becoming silent about the problem. Set
20704 @var{limit} to zero to suppress all complaints; set it to a large number
20705 to prevent complaints from being suppressed.
20707 @kindex show complaints
20708 @item show complaints
20709 Displays how many symbol complaints @value{GDBN} is permitted to produce.
20713 @anchor{confirmation requests}
20714 By default, @value{GDBN} is cautious, and asks what sometimes seems to be a
20715 lot of stupid questions to confirm certain commands. For example, if
20716 you try to run a program which is already running:
20720 The program being debugged has been started already.
20721 Start it from the beginning? (y or n)
20724 If you are willing to unflinchingly face the consequences of your own
20725 commands, you can disable this ``feature'':
20729 @kindex set confirm
20731 @cindex confirmation
20732 @cindex stupid questions
20733 @item set confirm off
20734 Disables confirmation requests. Note that running @value{GDBN} with
20735 the @option{--batch} option (@pxref{Mode Options, -batch}) also
20736 automatically disables confirmation requests.
20738 @item set confirm on
20739 Enables confirmation requests (the default).
20741 @kindex show confirm
20743 Displays state of confirmation requests.
20747 @cindex command tracing
20748 If you need to debug user-defined commands or sourced files you may find it
20749 useful to enable @dfn{command tracing}. In this mode each command will be
20750 printed as it is executed, prefixed with one or more @samp{+} symbols, the
20751 quantity denoting the call depth of each command.
20754 @kindex set trace-commands
20755 @cindex command scripts, debugging
20756 @item set trace-commands on
20757 Enable command tracing.
20758 @item set trace-commands off
20759 Disable command tracing.
20760 @item show trace-commands
20761 Display the current state of command tracing.
20764 @node Debugging Output
20765 @section Optional Messages about Internal Happenings
20766 @cindex optional debugging messages
20768 @value{GDBN} has commands that enable optional debugging messages from
20769 various @value{GDBN} subsystems; normally these commands are of
20770 interest to @value{GDBN} maintainers, or when reporting a bug. This
20771 section documents those commands.
20774 @kindex set exec-done-display
20775 @item set exec-done-display
20776 Turns on or off the notification of asynchronous commands'
20777 completion. When on, @value{GDBN} will print a message when an
20778 asynchronous command finishes its execution. The default is off.
20779 @kindex show exec-done-display
20780 @item show exec-done-display
20781 Displays the current setting of asynchronous command completion
20784 @cindex gdbarch debugging info
20785 @cindex architecture debugging info
20786 @item set debug arch
20787 Turns on or off display of gdbarch debugging info. The default is off
20789 @item show debug arch
20790 Displays the current state of displaying gdbarch debugging info.
20791 @item set debug aix-thread
20792 @cindex AIX threads
20793 Display debugging messages about inner workings of the AIX thread
20795 @item show debug aix-thread
20796 Show the current state of AIX thread debugging info display.
20797 @item set debug check-physname
20799 Check the results of the ``physname'' computation. When reading DWARF
20800 debugging information for C@t{++}, @value{GDBN} attempts to compute
20801 each entity's name. @value{GDBN} can do this computation in two
20802 different ways, depending on exactly what information is present.
20803 When enabled, this setting causes @value{GDBN} to compute the names
20804 both ways and display any discrepancies.
20805 @item show debug check-physname
20806 Show the current state of ``physname'' checking.
20807 @item set debug dwarf2-die
20808 @cindex DWARF2 DIEs
20809 Dump DWARF2 DIEs after they are read in.
20810 The value is the number of nesting levels to print.
20811 A value of zero turns off the display.
20812 @item show debug dwarf2-die
20813 Show the current state of DWARF2 DIE debugging.
20814 @item set debug displaced
20815 @cindex displaced stepping debugging info
20816 Turns on or off display of @value{GDBN} debugging info for the
20817 displaced stepping support. The default is off.
20818 @item show debug displaced
20819 Displays the current state of displaying @value{GDBN} debugging info
20820 related to displaced stepping.
20821 @item set debug event
20822 @cindex event debugging info
20823 Turns on or off display of @value{GDBN} event debugging info. The
20825 @item show debug event
20826 Displays the current state of displaying @value{GDBN} event debugging
20828 @item set debug expression
20829 @cindex expression debugging info
20830 Turns on or off display of debugging info about @value{GDBN}
20831 expression parsing. The default is off.
20832 @item show debug expression
20833 Displays the current state of displaying debugging info about
20834 @value{GDBN} expression parsing.
20835 @item set debug frame
20836 @cindex frame debugging info
20837 Turns on or off display of @value{GDBN} frame debugging info. The
20839 @item show debug frame
20840 Displays the current state of displaying @value{GDBN} frame debugging
20842 @item set debug gnu-nat
20843 @cindex @sc{gnu}/Hurd debug messages
20844 Turns on or off debugging messages from the @sc{gnu}/Hurd debug support.
20845 @item show debug gnu-nat
20846 Show the current state of @sc{gnu}/Hurd debugging messages.
20847 @item set debug infrun
20848 @cindex inferior debugging info
20849 Turns on or off display of @value{GDBN} debugging info for running the inferior.
20850 The default is off. @file{infrun.c} contains GDB's runtime state machine used
20851 for implementing operations such as single-stepping the inferior.
20852 @item show debug infrun
20853 Displays the current state of @value{GDBN} inferior debugging.
20854 @item set debug jit
20855 @cindex just-in-time compilation, debugging messages
20856 Turns on or off debugging messages from JIT debug support.
20857 @item show debug jit
20858 Displays the current state of @value{GDBN} JIT debugging.
20859 @item set debug lin-lwp
20860 @cindex @sc{gnu}/Linux LWP debug messages
20861 @cindex Linux lightweight processes
20862 Turns on or off debugging messages from the Linux LWP debug support.
20863 @item show debug lin-lwp
20864 Show the current state of Linux LWP debugging messages.
20865 @item set debug observer
20866 @cindex observer debugging info
20867 Turns on or off display of @value{GDBN} observer debugging. This
20868 includes info such as the notification of observable events.
20869 @item show debug observer
20870 Displays the current state of observer debugging.
20871 @item set debug overload
20872 @cindex C@t{++} overload debugging info
20873 Turns on or off display of @value{GDBN} C@t{++} overload debugging
20874 info. This includes info such as ranking of functions, etc. The default
20876 @item show debug overload
20877 Displays the current state of displaying @value{GDBN} C@t{++} overload
20879 @cindex expression parser, debugging info
20880 @cindex debug expression parser
20881 @item set debug parser
20882 Turns on or off the display of expression parser debugging output.
20883 Internally, this sets the @code{yydebug} variable in the expression
20884 parser. @xref{Tracing, , Tracing Your Parser, bison, Bison}, for
20885 details. The default is off.
20886 @item show debug parser
20887 Show the current state of expression parser debugging.
20888 @cindex packets, reporting on stdout
20889 @cindex serial connections, debugging
20890 @cindex debug remote protocol
20891 @cindex remote protocol debugging
20892 @cindex display remote packets
20893 @item set debug remote
20894 Turns on or off display of reports on all packets sent back and forth across
20895 the serial line to the remote machine. The info is printed on the
20896 @value{GDBN} standard output stream. The default is off.
20897 @item show debug remote
20898 Displays the state of display of remote packets.
20899 @item set debug serial
20900 Turns on or off display of @value{GDBN} serial debugging info. The
20902 @item show debug serial
20903 Displays the current state of displaying @value{GDBN} serial debugging
20905 @item set debug solib-frv
20906 @cindex FR-V shared-library debugging
20907 Turns on or off debugging messages for FR-V shared-library code.
20908 @item show debug solib-frv
20909 Display the current state of FR-V shared-library code debugging
20911 @item set debug target
20912 @cindex target debugging info
20913 Turns on or off display of @value{GDBN} target debugging info. This info
20914 includes what is going on at the target level of GDB, as it happens. The
20915 default is 0. Set it to 1 to track events, and to 2 to also track the
20916 value of large memory transfers. Changes to this flag do not take effect
20917 until the next time you connect to a target or use the @code{run} command.
20918 @item show debug target
20919 Displays the current state of displaying @value{GDBN} target debugging
20921 @item set debug timestamp
20922 @cindex timestampping debugging info
20923 Turns on or off display of timestamps with @value{GDBN} debugging info.
20924 When enabled, seconds and microseconds are displayed before each debugging
20926 @item show debug timestamp
20927 Displays the current state of displaying timestamps with @value{GDBN}
20929 @item set debugvarobj
20930 @cindex variable object debugging info
20931 Turns on or off display of @value{GDBN} variable object debugging
20932 info. The default is off.
20933 @item show debugvarobj
20934 Displays the current state of displaying @value{GDBN} variable object
20936 @item set debug xml
20937 @cindex XML parser debugging
20938 Turns on or off debugging messages for built-in XML parsers.
20939 @item show debug xml
20940 Displays the current state of XML debugging messages.
20943 @node Other Misc Settings
20944 @section Other Miscellaneous Settings
20945 @cindex miscellaneous settings
20948 @kindex set interactive-mode
20949 @item set interactive-mode
20950 If @code{on}, forces @value{GDBN} to assume that GDB was started
20951 in a terminal. In practice, this means that @value{GDBN} should wait
20952 for the user to answer queries generated by commands entered at
20953 the command prompt. If @code{off}, forces @value{GDBN} to operate
20954 in the opposite mode, and it uses the default answers to all queries.
20955 If @code{auto} (the default), @value{GDBN} tries to determine whether
20956 its standard input is a terminal, and works in interactive-mode if it
20957 is, non-interactively otherwise.
20959 In the vast majority of cases, the debugger should be able to guess
20960 correctly which mode should be used. But this setting can be useful
20961 in certain specific cases, such as running a MinGW @value{GDBN}
20962 inside a cygwin window.
20964 @kindex show interactive-mode
20965 @item show interactive-mode
20966 Displays whether the debugger is operating in interactive mode or not.
20969 @node Extending GDB
20970 @chapter Extending @value{GDBN}
20971 @cindex extending GDB
20973 @value{GDBN} provides three mechanisms for extension. The first is based
20974 on composition of @value{GDBN} commands, the second is based on the
20975 Python scripting language, and the third is for defining new aliases of
20978 To facilitate the use of the first two extensions, @value{GDBN} is capable
20979 of evaluating the contents of a file. When doing so, @value{GDBN}
20980 can recognize which scripting language is being used by looking at
20981 the filename extension. Files with an unrecognized filename extension
20982 are always treated as a @value{GDBN} Command Files.
20983 @xref{Command Files,, Command files}.
20985 You can control how @value{GDBN} evaluates these files with the following
20989 @kindex set script-extension
20990 @kindex show script-extension
20991 @item set script-extension off
20992 All scripts are always evaluated as @value{GDBN} Command Files.
20994 @item set script-extension soft
20995 The debugger determines the scripting language based on filename
20996 extension. If this scripting language is supported, @value{GDBN}
20997 evaluates the script using that language. Otherwise, it evaluates
20998 the file as a @value{GDBN} Command File.
21000 @item set script-extension strict
21001 The debugger determines the scripting language based on filename
21002 extension, and evaluates the script using that language. If the
21003 language is not supported, then the evaluation fails.
21005 @item show script-extension
21006 Display the current value of the @code{script-extension} option.
21011 * Sequences:: Canned Sequences of Commands
21012 * Python:: Scripting @value{GDBN} using Python
21013 * Aliases:: Creating new spellings of existing commands
21017 @section Canned Sequences of Commands
21019 Aside from breakpoint commands (@pxref{Break Commands, ,Breakpoint
21020 Command Lists}), @value{GDBN} provides two ways to store sequences of
21021 commands for execution as a unit: user-defined commands and command
21025 * Define:: How to define your own commands
21026 * Hooks:: Hooks for user-defined commands
21027 * Command Files:: How to write scripts of commands to be stored in a file
21028 * Output:: Commands for controlled output
21032 @subsection User-defined Commands
21034 @cindex user-defined command
21035 @cindex arguments, to user-defined commands
21036 A @dfn{user-defined command} is a sequence of @value{GDBN} commands to
21037 which you assign a new name as a command. This is done with the
21038 @code{define} command. User commands may accept up to 10 arguments
21039 separated by whitespace. Arguments are accessed within the user command
21040 via @code{$arg0@dots{}$arg9}. A trivial example:
21044 print $arg0 + $arg1 + $arg2
21049 To execute the command use:
21056 This defines the command @code{adder}, which prints the sum of
21057 its three arguments. Note the arguments are text substitutions, so they may
21058 reference variables, use complex expressions, or even perform inferior
21061 @cindex argument count in user-defined commands
21062 @cindex how many arguments (user-defined commands)
21063 In addition, @code{$argc} may be used to find out how many arguments have
21064 been passed. This expands to a number in the range 0@dots{}10.
21069 print $arg0 + $arg1
21072 print $arg0 + $arg1 + $arg2
21080 @item define @var{commandname}
21081 Define a command named @var{commandname}. If there is already a command
21082 by that name, you are asked to confirm that you want to redefine it.
21083 @var{commandname} may be a bare command name consisting of letters,
21084 numbers, dashes, and underscores. It may also start with any predefined
21085 prefix command. For example, @samp{define target my-target} creates
21086 a user-defined @samp{target my-target} command.
21088 The definition of the command is made up of other @value{GDBN} command lines,
21089 which are given following the @code{define} command. The end of these
21090 commands is marked by a line containing @code{end}.
21093 @kindex end@r{ (user-defined commands)}
21094 @item document @var{commandname}
21095 Document the user-defined command @var{commandname}, so that it can be
21096 accessed by @code{help}. The command @var{commandname} must already be
21097 defined. This command reads lines of documentation just as @code{define}
21098 reads the lines of the command definition, ending with @code{end}.
21099 After the @code{document} command is finished, @code{help} on command
21100 @var{commandname} displays the documentation you have written.
21102 You may use the @code{document} command again to change the
21103 documentation of a command. Redefining the command with @code{define}
21104 does not change the documentation.
21106 @kindex dont-repeat
21107 @cindex don't repeat command
21109 Used inside a user-defined command, this tells @value{GDBN} that this
21110 command should not be repeated when the user hits @key{RET}
21111 (@pxref{Command Syntax, repeat last command}).
21113 @kindex help user-defined
21114 @item help user-defined
21115 List all user-defined commands and all python commands defined in class
21116 COMAND_USER. The first line of the documentation or docstring is
21121 @itemx show user @var{commandname}
21122 Display the @value{GDBN} commands used to define @var{commandname} (but
21123 not its documentation). If no @var{commandname} is given, display the
21124 definitions for all user-defined commands.
21125 This does not work for user-defined python commands.
21127 @cindex infinite recursion in user-defined commands
21128 @kindex show max-user-call-depth
21129 @kindex set max-user-call-depth
21130 @item show max-user-call-depth
21131 @itemx set max-user-call-depth
21132 The value of @code{max-user-call-depth} controls how many recursion
21133 levels are allowed in user-defined commands before @value{GDBN} suspects an
21134 infinite recursion and aborts the command.
21135 This does not apply to user-defined python commands.
21138 In addition to the above commands, user-defined commands frequently
21139 use control flow commands, described in @ref{Command Files}.
21141 When user-defined commands are executed, the
21142 commands of the definition are not printed. An error in any command
21143 stops execution of the user-defined command.
21145 If used interactively, commands that would ask for confirmation proceed
21146 without asking when used inside a user-defined command. Many @value{GDBN}
21147 commands that normally print messages to say what they are doing omit the
21148 messages when used in a user-defined command.
21151 @subsection User-defined Command Hooks
21152 @cindex command hooks
21153 @cindex hooks, for commands
21154 @cindex hooks, pre-command
21157 You may define @dfn{hooks}, which are a special kind of user-defined
21158 command. Whenever you run the command @samp{foo}, if the user-defined
21159 command @samp{hook-foo} exists, it is executed (with no arguments)
21160 before that command.
21162 @cindex hooks, post-command
21164 A hook may also be defined which is run after the command you executed.
21165 Whenever you run the command @samp{foo}, if the user-defined command
21166 @samp{hookpost-foo} exists, it is executed (with no arguments) after
21167 that command. Post-execution hooks may exist simultaneously with
21168 pre-execution hooks, for the same command.
21170 It is valid for a hook to call the command which it hooks. If this
21171 occurs, the hook is not re-executed, thereby avoiding infinite recursion.
21173 @c It would be nice if hookpost could be passed a parameter indicating
21174 @c if the command it hooks executed properly or not. FIXME!
21176 @kindex stop@r{, a pseudo-command}
21177 In addition, a pseudo-command, @samp{stop} exists. Defining
21178 (@samp{hook-stop}) makes the associated commands execute every time
21179 execution stops in your program: before breakpoint commands are run,
21180 displays are printed, or the stack frame is printed.
21182 For example, to ignore @code{SIGALRM} signals while
21183 single-stepping, but treat them normally during normal execution,
21188 handle SIGALRM nopass
21192 handle SIGALRM pass
21195 define hook-continue
21196 handle SIGALRM pass
21200 As a further example, to hook at the beginning and end of the @code{echo}
21201 command, and to add extra text to the beginning and end of the message,
21209 define hookpost-echo
21213 (@value{GDBP}) echo Hello World
21214 <<<---Hello World--->>>
21219 You can define a hook for any single-word command in @value{GDBN}, but
21220 not for command aliases; you should define a hook for the basic command
21221 name, e.g.@: @code{backtrace} rather than @code{bt}.
21222 @c FIXME! So how does Joe User discover whether a command is an alias
21224 You can hook a multi-word command by adding @code{hook-} or
21225 @code{hookpost-} to the last word of the command, e.g.@:
21226 @samp{define target hook-remote} to add a hook to @samp{target remote}.
21228 If an error occurs during the execution of your hook, execution of
21229 @value{GDBN} commands stops and @value{GDBN} issues a prompt
21230 (before the command that you actually typed had a chance to run).
21232 If you try to define a hook which does not match any known command, you
21233 get a warning from the @code{define} command.
21235 @node Command Files
21236 @subsection Command Files
21238 @cindex command files
21239 @cindex scripting commands
21240 A command file for @value{GDBN} is a text file made of lines that are
21241 @value{GDBN} commands. Comments (lines starting with @kbd{#}) may
21242 also be included. An empty line in a command file does nothing; it
21243 does not mean to repeat the last command, as it would from the
21246 You can request the execution of a command file with the @code{source}
21247 command. Note that the @code{source} command is also used to evaluate
21248 scripts that are not Command Files. The exact behavior can be configured
21249 using the @code{script-extension} setting.
21250 @xref{Extending GDB,, Extending GDB}.
21254 @cindex execute commands from a file
21255 @item source [-s] [-v] @var{filename}
21256 Execute the command file @var{filename}.
21259 The lines in a command file are generally executed sequentially,
21260 unless the order of execution is changed by one of the
21261 @emph{flow-control commands} described below. The commands are not
21262 printed as they are executed. An error in any command terminates
21263 execution of the command file and control is returned to the console.
21265 @value{GDBN} first searches for @var{filename} in the current directory.
21266 If the file is not found there, and @var{filename} does not specify a
21267 directory, then @value{GDBN} also looks for the file on the source search path
21268 (specified with the @samp{directory} command);
21269 except that @file{$cdir} is not searched because the compilation directory
21270 is not relevant to scripts.
21272 If @code{-s} is specified, then @value{GDBN} searches for @var{filename}
21273 on the search path even if @var{filename} specifies a directory.
21274 The search is done by appending @var{filename} to each element of the
21275 search path. So, for example, if @var{filename} is @file{mylib/myscript}
21276 and the search path contains @file{/home/user} then @value{GDBN} will
21277 look for the script @file{/home/user/mylib/myscript}.
21278 The search is also done if @var{filename} is an absolute path.
21279 For example, if @var{filename} is @file{/tmp/myscript} and
21280 the search path contains @file{/home/user} then @value{GDBN} will
21281 look for the script @file{/home/user/tmp/myscript}.
21282 For DOS-like systems, if @var{filename} contains a drive specification,
21283 it is stripped before concatenation. For example, if @var{filename} is
21284 @file{d:myscript} and the search path contains @file{c:/tmp} then @value{GDBN}
21285 will look for the script @file{c:/tmp/myscript}.
21287 If @code{-v}, for verbose mode, is given then @value{GDBN} displays
21288 each command as it is executed. The option must be given before
21289 @var{filename}, and is interpreted as part of the filename anywhere else.
21291 Commands that would ask for confirmation if used interactively proceed
21292 without asking when used in a command file. Many @value{GDBN} commands that
21293 normally print messages to say what they are doing omit the messages
21294 when called from command files.
21296 @value{GDBN} also accepts command input from standard input. In this
21297 mode, normal output goes to standard output and error output goes to
21298 standard error. Errors in a command file supplied on standard input do
21299 not terminate execution of the command file---execution continues with
21303 gdb < cmds > log 2>&1
21306 (The syntax above will vary depending on the shell used.) This example
21307 will execute commands from the file @file{cmds}. All output and errors
21308 would be directed to @file{log}.
21310 Since commands stored on command files tend to be more general than
21311 commands typed interactively, they frequently need to deal with
21312 complicated situations, such as different or unexpected values of
21313 variables and symbols, changes in how the program being debugged is
21314 built, etc. @value{GDBN} provides a set of flow-control commands to
21315 deal with these complexities. Using these commands, you can write
21316 complex scripts that loop over data structures, execute commands
21317 conditionally, etc.
21324 This command allows to include in your script conditionally executed
21325 commands. The @code{if} command takes a single argument, which is an
21326 expression to evaluate. It is followed by a series of commands that
21327 are executed only if the expression is true (its value is nonzero).
21328 There can then optionally be an @code{else} line, followed by a series
21329 of commands that are only executed if the expression was false. The
21330 end of the list is marked by a line containing @code{end}.
21334 This command allows to write loops. Its syntax is similar to
21335 @code{if}: the command takes a single argument, which is an expression
21336 to evaluate, and must be followed by the commands to execute, one per
21337 line, terminated by an @code{end}. These commands are called the
21338 @dfn{body} of the loop. The commands in the body of @code{while} are
21339 executed repeatedly as long as the expression evaluates to true.
21343 This command exits the @code{while} loop in whose body it is included.
21344 Execution of the script continues after that @code{while}s @code{end}
21347 @kindex loop_continue
21348 @item loop_continue
21349 This command skips the execution of the rest of the body of commands
21350 in the @code{while} loop in whose body it is included. Execution
21351 branches to the beginning of the @code{while} loop, where it evaluates
21352 the controlling expression.
21354 @kindex end@r{ (if/else/while commands)}
21356 Terminate the block of commands that are the body of @code{if},
21357 @code{else}, or @code{while} flow-control commands.
21362 @subsection Commands for Controlled Output
21364 During the execution of a command file or a user-defined command, normal
21365 @value{GDBN} output is suppressed; the only output that appears is what is
21366 explicitly printed by the commands in the definition. This section
21367 describes three commands useful for generating exactly the output you
21372 @item echo @var{text}
21373 @c I do not consider backslash-space a standard C escape sequence
21374 @c because it is not in ANSI.
21375 Print @var{text}. Nonprinting characters can be included in
21376 @var{text} using C escape sequences, such as @samp{\n} to print a
21377 newline. @strong{No newline is printed unless you specify one.}
21378 In addition to the standard C escape sequences, a backslash followed
21379 by a space stands for a space. This is useful for displaying a
21380 string with spaces at the beginning or the end, since leading and
21381 trailing spaces are otherwise trimmed from all arguments.
21382 To print @samp{@w{ }and foo =@w{ }}, use the command
21383 @samp{echo \@w{ }and foo = \@w{ }}.
21385 A backslash at the end of @var{text} can be used, as in C, to continue
21386 the command onto subsequent lines. For example,
21389 echo This is some text\n\
21390 which is continued\n\
21391 onto several lines.\n
21394 produces the same output as
21397 echo This is some text\n
21398 echo which is continued\n
21399 echo onto several lines.\n
21403 @item output @var{expression}
21404 Print the value of @var{expression} and nothing but that value: no
21405 newlines, no @samp{$@var{nn} = }. The value is not entered in the
21406 value history either. @xref{Expressions, ,Expressions}, for more information
21409 @item output/@var{fmt} @var{expression}
21410 Print the value of @var{expression} in format @var{fmt}. You can use
21411 the same formats as for @code{print}. @xref{Output Formats,,Output
21412 Formats}, for more information.
21415 @item printf @var{template}, @var{expressions}@dots{}
21416 Print the values of one or more @var{expressions} under the control of
21417 the string @var{template}. To print several values, make
21418 @var{expressions} be a comma-separated list of individual expressions,
21419 which may be either numbers or pointers. Their values are printed as
21420 specified by @var{template}, exactly as a C program would do by
21421 executing the code below:
21424 printf (@var{template}, @var{expressions}@dots{});
21427 As in @code{C} @code{printf}, ordinary characters in @var{template}
21428 are printed verbatim, while @dfn{conversion specification} introduced
21429 by the @samp{%} character cause subsequent @var{expressions} to be
21430 evaluated, their values converted and formatted according to type and
21431 style information encoded in the conversion specifications, and then
21434 For example, you can print two values in hex like this:
21437 printf "foo, bar-foo = 0x%x, 0x%x\n", foo, bar-foo
21440 @code{printf} supports all the standard @code{C} conversion
21441 specifications, including the flags and modifiers between the @samp{%}
21442 character and the conversion letter, with the following exceptions:
21446 The argument-ordering modifiers, such as @samp{2$}, are not supported.
21449 The modifier @samp{*} is not supported for specifying precision or
21453 The @samp{'} flag (for separation of digits into groups according to
21454 @code{LC_NUMERIC'}) is not supported.
21457 The type modifiers @samp{hh}, @samp{j}, @samp{t}, and @samp{z} are not
21461 The conversion letter @samp{n} (as in @samp{%n}) is not supported.
21464 The conversion letters @samp{a} and @samp{A} are not supported.
21468 Note that the @samp{ll} type modifier is supported only if the
21469 underlying @code{C} implementation used to build @value{GDBN} supports
21470 the @code{long long int} type, and the @samp{L} type modifier is
21471 supported only if @code{long double} type is available.
21473 As in @code{C}, @code{printf} supports simple backslash-escape
21474 sequences, such as @code{\n}, @samp{\t}, @samp{\\}, @samp{\"},
21475 @samp{\a}, and @samp{\f}, that consist of backslash followed by a
21476 single character. Octal and hexadecimal escape sequences are not
21479 Additionally, @code{printf} supports conversion specifications for DFP
21480 (@dfn{Decimal Floating Point}) types using the following length modifiers
21481 together with a floating point specifier.
21486 @samp{H} for printing @code{Decimal32} types.
21489 @samp{D} for printing @code{Decimal64} types.
21492 @samp{DD} for printing @code{Decimal128} types.
21495 If the underlying @code{C} implementation used to build @value{GDBN} has
21496 support for the three length modifiers for DFP types, other modifiers
21497 such as width and precision will also be available for @value{GDBN} to use.
21499 In case there is no such @code{C} support, no additional modifiers will be
21500 available and the value will be printed in the standard way.
21502 Here's an example of printing DFP types using the above conversion letters:
21504 printf "D32: %Hf - D64: %Df - D128: %DDf\n",1.2345df,1.2E10dd,1.2E1dl
21508 @item eval @var{template}, @var{expressions}@dots{}
21509 Convert the values of one or more @var{expressions} under the control of
21510 the string @var{template} to a command line, and call it.
21515 @section Scripting @value{GDBN} using Python
21516 @cindex python scripting
21517 @cindex scripting with python
21519 You can script @value{GDBN} using the @uref{http://www.python.org/,
21520 Python programming language}. This feature is available only if
21521 @value{GDBN} was configured using @option{--with-python}.
21523 @cindex python directory
21524 Python scripts used by @value{GDBN} should be installed in
21525 @file{@var{data-directory}/python}, where @var{data-directory} is
21526 the data directory as determined at @value{GDBN} startup (@pxref{Data Files}).
21527 This directory, known as the @dfn{python directory},
21528 is automatically added to the Python Search Path in order to allow
21529 the Python interpreter to locate all scripts installed at this location.
21531 Additionally, @value{GDBN} commands and convenience functions which
21532 are written in Python and are located in the
21533 @file{@var{data-directory}/python/gdb/command} or
21534 @file{@var{data-directory}/python/gdb/function} directories are
21535 automatically imported when @value{GDBN} starts.
21538 * Python Commands:: Accessing Python from @value{GDBN}.
21539 * Python API:: Accessing @value{GDBN} from Python.
21540 * Auto-loading:: Automatically loading Python code.
21541 * Python modules:: Python modules provided by @value{GDBN}.
21544 @node Python Commands
21545 @subsection Python Commands
21546 @cindex python commands
21547 @cindex commands to access python
21549 @value{GDBN} provides one command for accessing the Python interpreter,
21550 and one related setting:
21554 @item python @r{[}@var{code}@r{]}
21555 The @code{python} command can be used to evaluate Python code.
21557 If given an argument, the @code{python} command will evaluate the
21558 argument as a Python command. For example:
21561 (@value{GDBP}) python print 23
21565 If you do not provide an argument to @code{python}, it will act as a
21566 multi-line command, like @code{define}. In this case, the Python
21567 script is made up of subsequent command lines, given after the
21568 @code{python} command. This command list is terminated using a line
21569 containing @code{end}. For example:
21572 (@value{GDBP}) python
21574 End with a line saying just "end".
21580 @kindex set python print-stack
21581 @item set python print-stack
21582 By default, @value{GDBN} will print only the message component of a
21583 Python exception when an error occurs in a Python script. This can be
21584 controlled using @code{set python print-stack}: if @code{full}, then
21585 full Python stack printing is enabled; if @code{none}, then Python stack
21586 and message printing is disabled; if @code{message}, the default, only
21587 the message component of the error is printed.
21590 It is also possible to execute a Python script from the @value{GDBN}
21594 @item source @file{script-name}
21595 The script name must end with @samp{.py} and @value{GDBN} must be configured
21596 to recognize the script language based on filename extension using
21597 the @code{script-extension} setting. @xref{Extending GDB, ,Extending GDB}.
21599 @item python execfile ("script-name")
21600 This method is based on the @code{execfile} Python built-in function,
21601 and thus is always available.
21605 @subsection Python API
21607 @cindex programming in python
21609 @cindex python stdout
21610 @cindex python pagination
21611 At startup, @value{GDBN} overrides Python's @code{sys.stdout} and
21612 @code{sys.stderr} to print using @value{GDBN}'s output-paging streams.
21613 A Python program which outputs to one of these streams may have its
21614 output interrupted by the user (@pxref{Screen Size}). In this
21615 situation, a Python @code{KeyboardInterrupt} exception is thrown.
21618 * Basic Python:: Basic Python Functions.
21619 * Exception Handling:: How Python exceptions are translated.
21620 * Values From Inferior:: Python representation of values.
21621 * Types In Python:: Python representation of types.
21622 * Pretty Printing API:: Pretty-printing values.
21623 * Selecting Pretty-Printers:: How GDB chooses a pretty-printer.
21624 * Writing a Pretty-Printer:: Writing a Pretty-Printer.
21625 * Inferiors In Python:: Python representation of inferiors (processes)
21626 * Events In Python:: Listening for events from @value{GDBN}.
21627 * Threads In Python:: Accessing inferior threads from Python.
21628 * Commands In Python:: Implementing new commands in Python.
21629 * Parameters In Python:: Adding new @value{GDBN} parameters.
21630 * Functions In Python:: Writing new convenience functions.
21631 * Progspaces In Python:: Program spaces.
21632 * Objfiles In Python:: Object files.
21633 * Frames In Python:: Accessing inferior stack frames from Python.
21634 * Blocks In Python:: Accessing frame blocks from Python.
21635 * Symbols In Python:: Python representation of symbols.
21636 * Symbol Tables In Python:: Python representation of symbol tables.
21637 * Lazy Strings In Python:: Python representation of lazy strings.
21638 * Breakpoints In Python:: Manipulating breakpoints using Python.
21639 * Finish Breakpoints in Python:: Setting Breakpoints on function return
21644 @subsubsection Basic Python
21646 @cindex python functions
21647 @cindex python module
21649 @value{GDBN} introduces a new Python module, named @code{gdb}. All
21650 methods and classes added by @value{GDBN} are placed in this module.
21651 @value{GDBN} automatically @code{import}s the @code{gdb} module for
21652 use in all scripts evaluated by the @code{python} command.
21654 @findex gdb.PYTHONDIR
21655 @defvar gdb.PYTHONDIR
21656 A string containing the python directory (@pxref{Python}).
21659 @findex gdb.execute
21660 @defun gdb.execute (command @r{[}, from_tty @r{[}, to_string@r{]]})
21661 Evaluate @var{command}, a string, as a @value{GDBN} CLI command.
21662 If a GDB exception happens while @var{command} runs, it is
21663 translated as described in @ref{Exception Handling,,Exception Handling}.
21665 @var{from_tty} specifies whether @value{GDBN} ought to consider this
21666 command as having originated from the user invoking it interactively.
21667 It must be a boolean value. If omitted, it defaults to @code{False}.
21669 By default, any output produced by @var{command} is sent to
21670 @value{GDBN}'s standard output. If the @var{to_string} parameter is
21671 @code{True}, then output will be collected by @code{gdb.execute} and
21672 returned as a string. The default is @code{False}, in which case the
21673 return value is @code{None}. If @var{to_string} is @code{True}, the
21674 @value{GDBN} virtual terminal will be temporarily set to unlimited width
21675 and height, and its pagination will be disabled; @pxref{Screen Size}.
21678 @findex gdb.breakpoints
21679 @defun gdb.breakpoints ()
21680 Return a sequence holding all of @value{GDBN}'s breakpoints.
21681 @xref{Breakpoints In Python}, for more information.
21684 @findex gdb.parameter
21685 @defun gdb.parameter (parameter)
21686 Return the value of a @value{GDBN} parameter. @var{parameter} is a
21687 string naming the parameter to look up; @var{parameter} may contain
21688 spaces if the parameter has a multi-part name. For example,
21689 @samp{print object} is a valid parameter name.
21691 If the named parameter does not exist, this function throws a
21692 @code{gdb.error} (@pxref{Exception Handling}). Otherwise, the
21693 parameter's value is converted to a Python value of the appropriate
21694 type, and returned.
21697 @findex gdb.history
21698 @defun gdb.history (number)
21699 Return a value from @value{GDBN}'s value history (@pxref{Value
21700 History}). @var{number} indicates which history element to return.
21701 If @var{number} is negative, then @value{GDBN} will take its absolute value
21702 and count backward from the last element (i.e., the most recent element) to
21703 find the value to return. If @var{number} is zero, then @value{GDBN} will
21704 return the most recent element. If the element specified by @var{number}
21705 doesn't exist in the value history, a @code{gdb.error} exception will be
21708 If no exception is raised, the return value is always an instance of
21709 @code{gdb.Value} (@pxref{Values From Inferior}).
21712 @findex gdb.parse_and_eval
21713 @defun gdb.parse_and_eval (expression)
21714 Parse @var{expression} as an expression in the current language,
21715 evaluate it, and return the result as a @code{gdb.Value}.
21716 @var{expression} must be a string.
21718 This function can be useful when implementing a new command
21719 (@pxref{Commands In Python}), as it provides a way to parse the
21720 command's argument as an expression. It is also useful simply to
21721 compute values, for example, it is the only way to get the value of a
21722 convenience variable (@pxref{Convenience Vars}) as a @code{gdb.Value}.
21725 @findex gdb.post_event
21726 @defun gdb.post_event (event)
21727 Put @var{event}, a callable object taking no arguments, into
21728 @value{GDBN}'s internal event queue. This callable will be invoked at
21729 some later point, during @value{GDBN}'s event processing. Events
21730 posted using @code{post_event} will be run in the order in which they
21731 were posted; however, there is no way to know when they will be
21732 processed relative to other events inside @value{GDBN}.
21734 @value{GDBN} is not thread-safe. If your Python program uses multiple
21735 threads, you must be careful to only call @value{GDBN}-specific
21736 functions in the main @value{GDBN} thread. @code{post_event} ensures
21740 (@value{GDBP}) python
21744 > def __init__(self, message):
21745 > self.message = message;
21746 > def __call__(self):
21747 > gdb.write(self.message)
21749 >class MyThread1 (threading.Thread):
21751 > gdb.post_event(Writer("Hello "))
21753 >class MyThread2 (threading.Thread):
21755 > gdb.post_event(Writer("World\n"))
21757 >MyThread1().start()
21758 >MyThread2().start()
21760 (@value{GDBP}) Hello World
21765 @defun gdb.write (string @r{[}, stream{]})
21766 Print a string to @value{GDBN}'s paginated output stream. The
21767 optional @var{stream} determines the stream to print to. The default
21768 stream is @value{GDBN}'s standard output stream. Possible stream
21775 @value{GDBN}'s standard output stream.
21780 @value{GDBN}'s standard error stream.
21785 @value{GDBN}'s log stream (@pxref{Logging Output}).
21788 Writing to @code{sys.stdout} or @code{sys.stderr} will automatically
21789 call this function and will automatically direct the output to the
21794 @defun gdb.flush ()
21795 Flush the buffer of a @value{GDBN} paginated stream so that the
21796 contents are displayed immediately. @value{GDBN} will flush the
21797 contents of a stream automatically when it encounters a newline in the
21798 buffer. The optional @var{stream} determines the stream to flush. The
21799 default stream is @value{GDBN}'s standard output stream. Possible
21806 @value{GDBN}'s standard output stream.
21811 @value{GDBN}'s standard error stream.
21816 @value{GDBN}'s log stream (@pxref{Logging Output}).
21820 Flushing @code{sys.stdout} or @code{sys.stderr} will automatically
21821 call this function for the relevant stream.
21824 @findex gdb.target_charset
21825 @defun gdb.target_charset ()
21826 Return the name of the current target character set (@pxref{Character
21827 Sets}). This differs from @code{gdb.parameter('target-charset')} in
21828 that @samp{auto} is never returned.
21831 @findex gdb.target_wide_charset
21832 @defun gdb.target_wide_charset ()
21833 Return the name of the current target wide character set
21834 (@pxref{Character Sets}). This differs from
21835 @code{gdb.parameter('target-wide-charset')} in that @samp{auto} is
21839 @findex gdb.solib_name
21840 @defun gdb.solib_name (address)
21841 Return the name of the shared library holding the given @var{address}
21842 as a string, or @code{None}.
21845 @findex gdb.decode_line
21846 @defun gdb.decode_line @r{[}expression@r{]}
21847 Return locations of the line specified by @var{expression}, or of the
21848 current line if no argument was given. This function returns a Python
21849 tuple containing two elements. The first element contains a string
21850 holding any unparsed section of @var{expression} (or @code{None} if
21851 the expression has been fully parsed). The second element contains
21852 either @code{None} or another tuple that contains all the locations
21853 that match the expression represented as @code{gdb.Symtab_and_line}
21854 objects (@pxref{Symbol Tables In Python}). If @var{expression} is
21855 provided, it is decoded the way that @value{GDBN}'s inbuilt
21856 @code{break} or @code{edit} commands do (@pxref{Specify Location}).
21859 @defun gdb.prompt_hook (current_prompt)
21860 @anchor{prompt_hook}
21862 If @var{prompt_hook} is callable, @value{GDBN} will call the method
21863 assigned to this operation before a prompt is displayed by
21866 The parameter @code{current_prompt} contains the current @value{GDBN}
21867 prompt. This method must return a Python string, or @code{None}. If
21868 a string is returned, the @value{GDBN} prompt will be set to that
21869 string. If @code{None} is returned, @value{GDBN} will continue to use
21870 the current prompt.
21872 Some prompts cannot be substituted in @value{GDBN}. Secondary prompts
21873 such as those used by readline for command input, and annotation
21874 related prompts are prohibited from being changed.
21877 @node Exception Handling
21878 @subsubsection Exception Handling
21879 @cindex python exceptions
21880 @cindex exceptions, python
21882 When executing the @code{python} command, Python exceptions
21883 uncaught within the Python code are translated to calls to
21884 @value{GDBN} error-reporting mechanism. If the command that called
21885 @code{python} does not handle the error, @value{GDBN} will
21886 terminate it and print an error message containing the Python
21887 exception name, the associated value, and the Python call stack
21888 backtrace at the point where the exception was raised. Example:
21891 (@value{GDBP}) python print foo
21892 Traceback (most recent call last):
21893 File "<string>", line 1, in <module>
21894 NameError: name 'foo' is not defined
21897 @value{GDBN} errors that happen in @value{GDBN} commands invoked by
21898 Python code are converted to Python exceptions. The type of the
21899 Python exception depends on the error.
21903 This is the base class for most exceptions generated by @value{GDBN}.
21904 It is derived from @code{RuntimeError}, for compatibility with earlier
21905 versions of @value{GDBN}.
21907 If an error occurring in @value{GDBN} does not fit into some more
21908 specific category, then the generated exception will have this type.
21910 @item gdb.MemoryError
21911 This is a subclass of @code{gdb.error} which is thrown when an
21912 operation tried to access invalid memory in the inferior.
21914 @item KeyboardInterrupt
21915 User interrupt (via @kbd{C-c} or by typing @kbd{q} at a pagination
21916 prompt) is translated to a Python @code{KeyboardInterrupt} exception.
21919 In all cases, your exception handler will see the @value{GDBN} error
21920 message as its value and the Python call stack backtrace at the Python
21921 statement closest to where the @value{GDBN} error occured as the
21924 @findex gdb.GdbError
21925 When implementing @value{GDBN} commands in Python via @code{gdb.Command},
21926 it is useful to be able to throw an exception that doesn't cause a
21927 traceback to be printed. For example, the user may have invoked the
21928 command incorrectly. Use the @code{gdb.GdbError} exception
21929 to handle this case. Example:
21933 >class HelloWorld (gdb.Command):
21934 > """Greet the whole world."""
21935 > def __init__ (self):
21936 > super (HelloWorld, self).__init__ ("hello-world", gdb.COMMAND_USER)
21937 > def invoke (self, args, from_tty):
21938 > argv = gdb.string_to_argv (args)
21939 > if len (argv) != 0:
21940 > raise gdb.GdbError ("hello-world takes no arguments")
21941 > print "Hello, World!"
21944 (gdb) hello-world 42
21945 hello-world takes no arguments
21948 @node Values From Inferior
21949 @subsubsection Values From Inferior
21950 @cindex values from inferior, with Python
21951 @cindex python, working with values from inferior
21953 @cindex @code{gdb.Value}
21954 @value{GDBN} provides values it obtains from the inferior program in
21955 an object of type @code{gdb.Value}. @value{GDBN} uses this object
21956 for its internal bookkeeping of the inferior's values, and for
21957 fetching values when necessary.
21959 Inferior values that are simple scalars can be used directly in
21960 Python expressions that are valid for the value's data type. Here's
21961 an example for an integer or floating-point value @code{some_val}:
21968 As result of this, @code{bar} will also be a @code{gdb.Value} object
21969 whose values are of the same type as those of @code{some_val}.
21971 Inferior values that are structures or instances of some class can
21972 be accessed using the Python @dfn{dictionary syntax}. For example, if
21973 @code{some_val} is a @code{gdb.Value} instance holding a structure, you
21974 can access its @code{foo} element with:
21977 bar = some_val['foo']
21980 Again, @code{bar} will also be a @code{gdb.Value} object.
21982 A @code{gdb.Value} that represents a function can be executed via
21983 inferior function call. Any arguments provided to the call must match
21984 the function's prototype, and must be provided in the order specified
21987 For example, @code{some_val} is a @code{gdb.Value} instance
21988 representing a function that takes two integers as arguments. To
21989 execute this function, call it like so:
21992 result = some_val (10,20)
21995 Any values returned from a function call will be stored as a
21998 The following attributes are provided:
22001 @defvar Value.address
22002 If this object is addressable, this read-only attribute holds a
22003 @code{gdb.Value} object representing the address. Otherwise,
22004 this attribute holds @code{None}.
22007 @cindex optimized out value in Python
22008 @defvar Value.is_optimized_out
22009 This read-only boolean attribute is true if the compiler optimized out
22010 this value, thus it is not available for fetching from the inferior.
22014 The type of this @code{gdb.Value}. The value of this attribute is a
22015 @code{gdb.Type} object (@pxref{Types In Python}).
22018 @defvar Value.dynamic_type
22019 The dynamic type of this @code{gdb.Value}. This uses C@t{++} run-time
22020 type information (@acronym{RTTI}) to determine the dynamic type of the
22021 value. If this value is of class type, it will return the class in
22022 which the value is embedded, if any. If this value is of pointer or
22023 reference to a class type, it will compute the dynamic type of the
22024 referenced object, and return a pointer or reference to that type,
22025 respectively. In all other cases, it will return the value's static
22028 Note that this feature will only work when debugging a C@t{++} program
22029 that includes @acronym{RTTI} for the object in question. Otherwise,
22030 it will just return the static type of the value as in @kbd{ptype foo}
22031 (@pxref{Symbols, ptype}).
22034 @defvar Value.is_lazy
22035 The value of this read-only boolean attribute is @code{True} if this
22036 @code{gdb.Value} has not yet been fetched from the inferior.
22037 @value{GDBN} does not fetch values until necessary, for efficiency.
22041 myval = gdb.parse_and_eval ('somevar')
22044 The value of @code{somevar} is not fetched at this time. It will be
22045 fetched when the value is needed, or when the @code{fetch_lazy}
22050 The following methods are provided:
22053 @defun Value.__init__ (@var{val})
22054 Many Python values can be converted directly to a @code{gdb.Value} via
22055 this object initializer. Specifically:
22058 @item Python boolean
22059 A Python boolean is converted to the boolean type from the current
22062 @item Python integer
22063 A Python integer is converted to the C @code{long} type for the
22064 current architecture.
22067 A Python long is converted to the C @code{long long} type for the
22068 current architecture.
22071 A Python float is converted to the C @code{double} type for the
22072 current architecture.
22074 @item Python string
22075 A Python string is converted to a target string, using the current
22078 @item @code{gdb.Value}
22079 If @code{val} is a @code{gdb.Value}, then a copy of the value is made.
22081 @item @code{gdb.LazyString}
22082 If @code{val} is a @code{gdb.LazyString} (@pxref{Lazy Strings In
22083 Python}), then the lazy string's @code{value} method is called, and
22084 its result is used.
22088 @defun Value.cast (type)
22089 Return a new instance of @code{gdb.Value} that is the result of
22090 casting this instance to the type described by @var{type}, which must
22091 be a @code{gdb.Type} object. If the cast cannot be performed for some
22092 reason, this method throws an exception.
22095 @defun Value.dereference ()
22096 For pointer data types, this method returns a new @code{gdb.Value} object
22097 whose contents is the object pointed to by the pointer. For example, if
22098 @code{foo} is a C pointer to an @code{int}, declared in your C program as
22105 then you can use the corresponding @code{gdb.Value} to access what
22106 @code{foo} points to like this:
22109 bar = foo.dereference ()
22112 The result @code{bar} will be a @code{gdb.Value} object holding the
22113 value pointed to by @code{foo}.
22116 @defun Value.dynamic_cast (type)
22117 Like @code{Value.cast}, but works as if the C@t{++} @code{dynamic_cast}
22118 operator were used. Consult a C@t{++} reference for details.
22121 @defun Value.reinterpret_cast (type)
22122 Like @code{Value.cast}, but works as if the C@t{++} @code{reinterpret_cast}
22123 operator were used. Consult a C@t{++} reference for details.
22126 @defun Value.string (@r{[}encoding@r{[}, errors@r{[}, length@r{]]]})
22127 If this @code{gdb.Value} represents a string, then this method
22128 converts the contents to a Python string. Otherwise, this method will
22129 throw an exception.
22131 Strings are recognized in a language-specific way; whether a given
22132 @code{gdb.Value} represents a string is determined by the current
22135 For C-like languages, a value is a string if it is a pointer to or an
22136 array of characters or ints. The string is assumed to be terminated
22137 by a zero of the appropriate width. However if the optional length
22138 argument is given, the string will be converted to that given length,
22139 ignoring any embedded zeros that the string may contain.
22141 If the optional @var{encoding} argument is given, it must be a string
22142 naming the encoding of the string in the @code{gdb.Value}, such as
22143 @code{"ascii"}, @code{"iso-8859-6"} or @code{"utf-8"}. It accepts
22144 the same encodings as the corresponding argument to Python's
22145 @code{string.decode} method, and the Python codec machinery will be used
22146 to convert the string. If @var{encoding} is not given, or if
22147 @var{encoding} is the empty string, then either the @code{target-charset}
22148 (@pxref{Character Sets}) will be used, or a language-specific encoding
22149 will be used, if the current language is able to supply one.
22151 The optional @var{errors} argument is the same as the corresponding
22152 argument to Python's @code{string.decode} method.
22154 If the optional @var{length} argument is given, the string will be
22155 fetched and converted to the given length.
22158 @defun Value.lazy_string (@r{[}encoding @r{[}, length@r{]]})
22159 If this @code{gdb.Value} represents a string, then this method
22160 converts the contents to a @code{gdb.LazyString} (@pxref{Lazy Strings
22161 In Python}). Otherwise, this method will throw an exception.
22163 If the optional @var{encoding} argument is given, it must be a string
22164 naming the encoding of the @code{gdb.LazyString}. Some examples are:
22165 @samp{ascii}, @samp{iso-8859-6} or @samp{utf-8}. If the
22166 @var{encoding} argument is an encoding that @value{GDBN} does
22167 recognize, @value{GDBN} will raise an error.
22169 When a lazy string is printed, the @value{GDBN} encoding machinery is
22170 used to convert the string during printing. If the optional
22171 @var{encoding} argument is not provided, or is an empty string,
22172 @value{GDBN} will automatically select the encoding most suitable for
22173 the string type. For further information on encoding in @value{GDBN}
22174 please see @ref{Character Sets}.
22176 If the optional @var{length} argument is given, the string will be
22177 fetched and encoded to the length of characters specified. If
22178 the @var{length} argument is not provided, the string will be fetched
22179 and encoded until a null of appropriate width is found.
22182 @defun Value.fetch_lazy ()
22183 If the @code{gdb.Value} object is currently a lazy value
22184 (@code{gdb.Value.is_lazy} is @code{True}), then the value is
22185 fetched from the inferior. Any errors that occur in the process
22186 will produce a Python exception.
22188 If the @code{gdb.Value} object is not a lazy value, this method
22191 This method does not return a value.
22196 @node Types In Python
22197 @subsubsection Types In Python
22198 @cindex types in Python
22199 @cindex Python, working with types
22202 @value{GDBN} represents types from the inferior using the class
22205 The following type-related functions are available in the @code{gdb}
22208 @findex gdb.lookup_type
22209 @defun gdb.lookup_type (name @r{[}, block@r{]})
22210 This function looks up a type by name. @var{name} is the name of the
22211 type to look up. It must be a string.
22213 If @var{block} is given, then @var{name} is looked up in that scope.
22214 Otherwise, it is searched for globally.
22216 Ordinarily, this function will return an instance of @code{gdb.Type}.
22217 If the named type cannot be found, it will throw an exception.
22220 If the type is a structure or class type, or an enum type, the fields
22221 of that type can be accessed using the Python @dfn{dictionary syntax}.
22222 For example, if @code{some_type} is a @code{gdb.Type} instance holding
22223 a structure type, you can access its @code{foo} field with:
22226 bar = some_type['foo']
22229 @code{bar} will be a @code{gdb.Field} object; see below under the
22230 description of the @code{Type.fields} method for a description of the
22231 @code{gdb.Field} class.
22233 An instance of @code{Type} has the following attributes:
22237 The type code for this type. The type code will be one of the
22238 @code{TYPE_CODE_} constants defined below.
22241 @defvar Type.sizeof
22242 The size of this type, in target @code{char} units. Usually, a
22243 target's @code{char} type will be an 8-bit byte. However, on some
22244 unusual platforms, this type may have a different size.
22248 The tag name for this type. The tag name is the name after
22249 @code{struct}, @code{union}, or @code{enum} in C and C@t{++}; not all
22250 languages have this concept. If this type has no tag name, then
22251 @code{None} is returned.
22255 The following methods are provided:
22258 @defun Type.fields ()
22259 For structure and union types, this method returns the fields. Range
22260 types have two fields, the minimum and maximum values. Enum types
22261 have one field per enum constant. Function and method types have one
22262 field per parameter. The base types of C@t{++} classes are also
22263 represented as fields. If the type has no fields, or does not fit
22264 into one of these categories, an empty sequence will be returned.
22266 Each field is a @code{gdb.Field} object, with some pre-defined attributes:
22269 This attribute is not available for @code{static} fields (as in
22270 C@t{++} or Java). For non-@code{static} fields, the value is the bit
22271 position of the field. For @code{enum} fields, the value is the
22272 enumeration member's integer representation.
22275 The name of the field, or @code{None} for anonymous fields.
22278 This is @code{True} if the field is artificial, usually meaning that
22279 it was provided by the compiler and not the user. This attribute is
22280 always provided, and is @code{False} if the field is not artificial.
22282 @item is_base_class
22283 This is @code{True} if the field represents a base class of a C@t{++}
22284 structure. This attribute is always provided, and is @code{False}
22285 if the field is not a base class of the type that is the argument of
22286 @code{fields}, or if that type was not a C@t{++} class.
22289 If the field is packed, or is a bitfield, then this will have a
22290 non-zero value, which is the size of the field in bits. Otherwise,
22291 this will be zero; in this case the field's size is given by its type.
22294 The type of the field. This is usually an instance of @code{Type},
22295 but it can be @code{None} in some situations.
22299 @defun Type.array (@var{n1} @r{[}, @var{n2}@r{]})
22300 Return a new @code{gdb.Type} object which represents an array of this
22301 type. If one argument is given, it is the inclusive upper bound of
22302 the array; in this case the lower bound is zero. If two arguments are
22303 given, the first argument is the lower bound of the array, and the
22304 second argument is the upper bound of the array. An array's length
22305 must not be negative, but the bounds can be.
22308 @defun Type.const ()
22309 Return a new @code{gdb.Type} object which represents a
22310 @code{const}-qualified variant of this type.
22313 @defun Type.volatile ()
22314 Return a new @code{gdb.Type} object which represents a
22315 @code{volatile}-qualified variant of this type.
22318 @defun Type.unqualified ()
22319 Return a new @code{gdb.Type} object which represents an unqualified
22320 variant of this type. That is, the result is neither @code{const} nor
22324 @defun Type.range ()
22325 Return a Python @code{Tuple} object that contains two elements: the
22326 low bound of the argument type and the high bound of that type. If
22327 the type does not have a range, @value{GDBN} will raise a
22328 @code{gdb.error} exception (@pxref{Exception Handling}).
22331 @defun Type.reference ()
22332 Return a new @code{gdb.Type} object which represents a reference to this
22336 @defun Type.pointer ()
22337 Return a new @code{gdb.Type} object which represents a pointer to this
22341 @defun Type.strip_typedefs ()
22342 Return a new @code{gdb.Type} that represents the real type,
22343 after removing all layers of typedefs.
22346 @defun Type.target ()
22347 Return a new @code{gdb.Type} object which represents the target type
22350 For a pointer type, the target type is the type of the pointed-to
22351 object. For an array type (meaning C-like arrays), the target type is
22352 the type of the elements of the array. For a function or method type,
22353 the target type is the type of the return value. For a complex type,
22354 the target type is the type of the elements. For a typedef, the
22355 target type is the aliased type.
22357 If the type does not have a target, this method will throw an
22361 @defun Type.template_argument (n @r{[}, block@r{]})
22362 If this @code{gdb.Type} is an instantiation of a template, this will
22363 return a new @code{gdb.Type} which represents the type of the
22364 @var{n}th template argument.
22366 If this @code{gdb.Type} is not a template type, this will throw an
22367 exception. Ordinarily, only C@t{++} code will have template types.
22369 If @var{block} is given, then @var{name} is looked up in that scope.
22370 Otherwise, it is searched for globally.
22375 Each type has a code, which indicates what category this type falls
22376 into. The available type categories are represented by constants
22377 defined in the @code{gdb} module:
22380 @findex TYPE_CODE_PTR
22381 @findex gdb.TYPE_CODE_PTR
22382 @item gdb.TYPE_CODE_PTR
22383 The type is a pointer.
22385 @findex TYPE_CODE_ARRAY
22386 @findex gdb.TYPE_CODE_ARRAY
22387 @item gdb.TYPE_CODE_ARRAY
22388 The type is an array.
22390 @findex TYPE_CODE_STRUCT
22391 @findex gdb.TYPE_CODE_STRUCT
22392 @item gdb.TYPE_CODE_STRUCT
22393 The type is a structure.
22395 @findex TYPE_CODE_UNION
22396 @findex gdb.TYPE_CODE_UNION
22397 @item gdb.TYPE_CODE_UNION
22398 The type is a union.
22400 @findex TYPE_CODE_ENUM
22401 @findex gdb.TYPE_CODE_ENUM
22402 @item gdb.TYPE_CODE_ENUM
22403 The type is an enum.
22405 @findex TYPE_CODE_FLAGS
22406 @findex gdb.TYPE_CODE_FLAGS
22407 @item gdb.TYPE_CODE_FLAGS
22408 A bit flags type, used for things such as status registers.
22410 @findex TYPE_CODE_FUNC
22411 @findex gdb.TYPE_CODE_FUNC
22412 @item gdb.TYPE_CODE_FUNC
22413 The type is a function.
22415 @findex TYPE_CODE_INT
22416 @findex gdb.TYPE_CODE_INT
22417 @item gdb.TYPE_CODE_INT
22418 The type is an integer type.
22420 @findex TYPE_CODE_FLT
22421 @findex gdb.TYPE_CODE_FLT
22422 @item gdb.TYPE_CODE_FLT
22423 A floating point type.
22425 @findex TYPE_CODE_VOID
22426 @findex gdb.TYPE_CODE_VOID
22427 @item gdb.TYPE_CODE_VOID
22428 The special type @code{void}.
22430 @findex TYPE_CODE_SET
22431 @findex gdb.TYPE_CODE_SET
22432 @item gdb.TYPE_CODE_SET
22435 @findex TYPE_CODE_RANGE
22436 @findex gdb.TYPE_CODE_RANGE
22437 @item gdb.TYPE_CODE_RANGE
22438 A range type, that is, an integer type with bounds.
22440 @findex TYPE_CODE_STRING
22441 @findex gdb.TYPE_CODE_STRING
22442 @item gdb.TYPE_CODE_STRING
22443 A string type. Note that this is only used for certain languages with
22444 language-defined string types; C strings are not represented this way.
22446 @findex TYPE_CODE_BITSTRING
22447 @findex gdb.TYPE_CODE_BITSTRING
22448 @item gdb.TYPE_CODE_BITSTRING
22451 @findex TYPE_CODE_ERROR
22452 @findex gdb.TYPE_CODE_ERROR
22453 @item gdb.TYPE_CODE_ERROR
22454 An unknown or erroneous type.
22456 @findex TYPE_CODE_METHOD
22457 @findex gdb.TYPE_CODE_METHOD
22458 @item gdb.TYPE_CODE_METHOD
22459 A method type, as found in C@t{++} or Java.
22461 @findex TYPE_CODE_METHODPTR
22462 @findex gdb.TYPE_CODE_METHODPTR
22463 @item gdb.TYPE_CODE_METHODPTR
22464 A pointer-to-member-function.
22466 @findex TYPE_CODE_MEMBERPTR
22467 @findex gdb.TYPE_CODE_MEMBERPTR
22468 @item gdb.TYPE_CODE_MEMBERPTR
22469 A pointer-to-member.
22471 @findex TYPE_CODE_REF
22472 @findex gdb.TYPE_CODE_REF
22473 @item gdb.TYPE_CODE_REF
22476 @findex TYPE_CODE_CHAR
22477 @findex gdb.TYPE_CODE_CHAR
22478 @item gdb.TYPE_CODE_CHAR
22481 @findex TYPE_CODE_BOOL
22482 @findex gdb.TYPE_CODE_BOOL
22483 @item gdb.TYPE_CODE_BOOL
22486 @findex TYPE_CODE_COMPLEX
22487 @findex gdb.TYPE_CODE_COMPLEX
22488 @item gdb.TYPE_CODE_COMPLEX
22489 A complex float type.
22491 @findex TYPE_CODE_TYPEDEF
22492 @findex gdb.TYPE_CODE_TYPEDEF
22493 @item gdb.TYPE_CODE_TYPEDEF
22494 A typedef to some other type.
22496 @findex TYPE_CODE_NAMESPACE
22497 @findex gdb.TYPE_CODE_NAMESPACE
22498 @item gdb.TYPE_CODE_NAMESPACE
22499 A C@t{++} namespace.
22501 @findex TYPE_CODE_DECFLOAT
22502 @findex gdb.TYPE_CODE_DECFLOAT
22503 @item gdb.TYPE_CODE_DECFLOAT
22504 A decimal floating point type.
22506 @findex TYPE_CODE_INTERNAL_FUNCTION
22507 @findex gdb.TYPE_CODE_INTERNAL_FUNCTION
22508 @item gdb.TYPE_CODE_INTERNAL_FUNCTION
22509 A function internal to @value{GDBN}. This is the type used to represent
22510 convenience functions.
22513 Further support for types is provided in the @code{gdb.types}
22514 Python module (@pxref{gdb.types}).
22516 @node Pretty Printing API
22517 @subsubsection Pretty Printing API
22519 An example output is provided (@pxref{Pretty Printing}).
22521 A pretty-printer is just an object that holds a value and implements a
22522 specific interface, defined here.
22524 @defun pretty_printer.children (self)
22525 @value{GDBN} will call this method on a pretty-printer to compute the
22526 children of the pretty-printer's value.
22528 This method must return an object conforming to the Python iterator
22529 protocol. Each item returned by the iterator must be a tuple holding
22530 two elements. The first element is the ``name'' of the child; the
22531 second element is the child's value. The value can be any Python
22532 object which is convertible to a @value{GDBN} value.
22534 This method is optional. If it does not exist, @value{GDBN} will act
22535 as though the value has no children.
22538 @defun pretty_printer.display_hint (self)
22539 The CLI may call this method and use its result to change the
22540 formatting of a value. The result will also be supplied to an MI
22541 consumer as a @samp{displayhint} attribute of the variable being
22544 This method is optional. If it does exist, this method must return a
22547 Some display hints are predefined by @value{GDBN}:
22551 Indicate that the object being printed is ``array-like''. The CLI
22552 uses this to respect parameters such as @code{set print elements} and
22553 @code{set print array}.
22556 Indicate that the object being printed is ``map-like'', and that the
22557 children of this value can be assumed to alternate between keys and
22561 Indicate that the object being printed is ``string-like''. If the
22562 printer's @code{to_string} method returns a Python string of some
22563 kind, then @value{GDBN} will call its internal language-specific
22564 string-printing function to format the string. For the CLI this means
22565 adding quotation marks, possibly escaping some characters, respecting
22566 @code{set print elements}, and the like.
22570 @defun pretty_printer.to_string (self)
22571 @value{GDBN} will call this method to display the string
22572 representation of the value passed to the object's constructor.
22574 When printing from the CLI, if the @code{to_string} method exists,
22575 then @value{GDBN} will prepend its result to the values returned by
22576 @code{children}. Exactly how this formatting is done is dependent on
22577 the display hint, and may change as more hints are added. Also,
22578 depending on the print settings (@pxref{Print Settings}), the CLI may
22579 print just the result of @code{to_string} in a stack trace, omitting
22580 the result of @code{children}.
22582 If this method returns a string, it is printed verbatim.
22584 Otherwise, if this method returns an instance of @code{gdb.Value},
22585 then @value{GDBN} prints this value. This may result in a call to
22586 another pretty-printer.
22588 If instead the method returns a Python value which is convertible to a
22589 @code{gdb.Value}, then @value{GDBN} performs the conversion and prints
22590 the resulting value. Again, this may result in a call to another
22591 pretty-printer. Python scalars (integers, floats, and booleans) and
22592 strings are convertible to @code{gdb.Value}; other types are not.
22594 Finally, if this method returns @code{None} then no further operations
22595 are peformed in this method and nothing is printed.
22597 If the result is not one of these types, an exception is raised.
22600 @value{GDBN} provides a function which can be used to look up the
22601 default pretty-printer for a @code{gdb.Value}:
22603 @findex gdb.default_visualizer
22604 @defun gdb.default_visualizer (value)
22605 This function takes a @code{gdb.Value} object as an argument. If a
22606 pretty-printer for this value exists, then it is returned. If no such
22607 printer exists, then this returns @code{None}.
22610 @node Selecting Pretty-Printers
22611 @subsubsection Selecting Pretty-Printers
22613 The Python list @code{gdb.pretty_printers} contains an array of
22614 functions or callable objects that have been registered via addition
22615 as a pretty-printer. Printers in this list are called @code{global}
22616 printers, they're available when debugging all inferiors.
22617 Each @code{gdb.Progspace} contains a @code{pretty_printers} attribute.
22618 Each @code{gdb.Objfile} also contains a @code{pretty_printers}
22621 Each function on these lists is passed a single @code{gdb.Value}
22622 argument and should return a pretty-printer object conforming to the
22623 interface definition above (@pxref{Pretty Printing API}). If a function
22624 cannot create a pretty-printer for the value, it should return
22627 @value{GDBN} first checks the @code{pretty_printers} attribute of each
22628 @code{gdb.Objfile} in the current program space and iteratively calls
22629 each enabled lookup routine in the list for that @code{gdb.Objfile}
22630 until it receives a pretty-printer object.
22631 If no pretty-printer is found in the objfile lists, @value{GDBN} then
22632 searches the pretty-printer list of the current program space,
22633 calling each enabled function until an object is returned.
22634 After these lists have been exhausted, it tries the global
22635 @code{gdb.pretty_printers} list, again calling each enabled function until an
22636 object is returned.
22638 The order in which the objfiles are searched is not specified. For a
22639 given list, functions are always invoked from the head of the list,
22640 and iterated over sequentially until the end of the list, or a printer
22641 object is returned.
22643 For various reasons a pretty-printer may not work.
22644 For example, the underlying data structure may have changed and
22645 the pretty-printer is out of date.
22647 The consequences of a broken pretty-printer are severe enough that
22648 @value{GDBN} provides support for enabling and disabling individual
22649 printers. For example, if @code{print frame-arguments} is on,
22650 a backtrace can become highly illegible if any argument is printed
22651 with a broken printer.
22653 Pretty-printers are enabled and disabled by attaching an @code{enabled}
22654 attribute to the registered function or callable object. If this attribute
22655 is present and its value is @code{False}, the printer is disabled, otherwise
22656 the printer is enabled.
22658 @node Writing a Pretty-Printer
22659 @subsubsection Writing a Pretty-Printer
22660 @cindex writing a pretty-printer
22662 A pretty-printer consists of two parts: a lookup function to detect
22663 if the type is supported, and the printer itself.
22665 Here is an example showing how a @code{std::string} printer might be
22666 written. @xref{Pretty Printing API}, for details on the API this class
22670 class StdStringPrinter(object):
22671 "Print a std::string"
22673 def __init__(self, val):
22676 def to_string(self):
22677 return self.val['_M_dataplus']['_M_p']
22679 def display_hint(self):
22683 And here is an example showing how a lookup function for the printer
22684 example above might be written.
22687 def str_lookup_function(val):
22688 lookup_tag = val.type.tag
22689 if lookup_tag == None:
22691 regex = re.compile("^std::basic_string<char,.*>$")
22692 if regex.match(lookup_tag):
22693 return StdStringPrinter(val)
22697 The example lookup function extracts the value's type, and attempts to
22698 match it to a type that it can pretty-print. If it is a type the
22699 printer can pretty-print, it will return a printer object. If not, it
22700 returns @code{None}.
22702 We recommend that you put your core pretty-printers into a Python
22703 package. If your pretty-printers are for use with a library, we
22704 further recommend embedding a version number into the package name.
22705 This practice will enable @value{GDBN} to load multiple versions of
22706 your pretty-printers at the same time, because they will have
22709 You should write auto-loaded code (@pxref{Auto-loading}) such that it
22710 can be evaluated multiple times without changing its meaning. An
22711 ideal auto-load file will consist solely of @code{import}s of your
22712 printer modules, followed by a call to a register pretty-printers with
22713 the current objfile.
22715 Taken as a whole, this approach will scale nicely to multiple
22716 inferiors, each potentially using a different library version.
22717 Embedding a version number in the Python package name will ensure that
22718 @value{GDBN} is able to load both sets of printers simultaneously.
22719 Then, because the search for pretty-printers is done by objfile, and
22720 because your auto-loaded code took care to register your library's
22721 printers with a specific objfile, @value{GDBN} will find the correct
22722 printers for the specific version of the library used by each
22725 To continue the @code{std::string} example (@pxref{Pretty Printing API}),
22726 this code might appear in @code{gdb.libstdcxx.v6}:
22729 def register_printers(objfile):
22730 objfile.pretty_printers.append(str_lookup_function)
22734 And then the corresponding contents of the auto-load file would be:
22737 import gdb.libstdcxx.v6
22738 gdb.libstdcxx.v6.register_printers(gdb.current_objfile())
22741 The previous example illustrates a basic pretty-printer.
22742 There are a few things that can be improved on.
22743 The printer doesn't have a name, making it hard to identify in a
22744 list of installed printers. The lookup function has a name, but
22745 lookup functions can have arbitrary, even identical, names.
22747 Second, the printer only handles one type, whereas a library typically has
22748 several types. One could install a lookup function for each desired type
22749 in the library, but one could also have a single lookup function recognize
22750 several types. The latter is the conventional way this is handled.
22751 If a pretty-printer can handle multiple data types, then its
22752 @dfn{subprinters} are the printers for the individual data types.
22754 The @code{gdb.printing} module provides a formal way of solving these
22755 problems (@pxref{gdb.printing}).
22756 Here is another example that handles multiple types.
22758 These are the types we are going to pretty-print:
22761 struct foo @{ int a, b; @};
22762 struct bar @{ struct foo x, y; @};
22765 Here are the printers:
22769 """Print a foo object."""
22771 def __init__(self, val):
22774 def to_string(self):
22775 return ("a=<" + str(self.val["a"]) +
22776 "> b=<" + str(self.val["b"]) + ">")
22779 """Print a bar object."""
22781 def __init__(self, val):
22784 def to_string(self):
22785 return ("x=<" + str(self.val["x"]) +
22786 "> y=<" + str(self.val["y"]) + ">")
22789 This example doesn't need a lookup function, that is handled by the
22790 @code{gdb.printing} module. Instead a function is provided to build up
22791 the object that handles the lookup.
22794 import gdb.printing
22796 def build_pretty_printer():
22797 pp = gdb.printing.RegexpCollectionPrettyPrinter(
22799 pp.add_printer('foo', '^foo$', fooPrinter)
22800 pp.add_printer('bar', '^bar$', barPrinter)
22804 And here is the autoload support:
22807 import gdb.printing
22809 gdb.printing.register_pretty_printer(
22810 gdb.current_objfile(),
22811 my_library.build_pretty_printer())
22814 Finally, when this printer is loaded into @value{GDBN}, here is the
22815 corresponding output of @samp{info pretty-printer}:
22818 (gdb) info pretty-printer
22825 @node Inferiors In Python
22826 @subsubsection Inferiors In Python
22827 @cindex inferiors in Python
22829 @findex gdb.Inferior
22830 Programs which are being run under @value{GDBN} are called inferiors
22831 (@pxref{Inferiors and Programs}). Python scripts can access
22832 information about and manipulate inferiors controlled by @value{GDBN}
22833 via objects of the @code{gdb.Inferior} class.
22835 The following inferior-related functions are available in the @code{gdb}
22838 @defun gdb.inferiors ()
22839 Return a tuple containing all inferior objects.
22842 @defun gdb.selected_inferior ()
22843 Return an object representing the current inferior.
22846 A @code{gdb.Inferior} object has the following attributes:
22849 @defvar Inferior.num
22850 ID of inferior, as assigned by GDB.
22853 @defvar Inferior.pid
22854 Process ID of the inferior, as assigned by the underlying operating
22858 @defvar Inferior.was_attached
22859 Boolean signaling whether the inferior was created using `attach', or
22860 started by @value{GDBN} itself.
22864 A @code{gdb.Inferior} object has the following methods:
22867 @defun Inferior.is_valid ()
22868 Returns @code{True} if the @code{gdb.Inferior} object is valid,
22869 @code{False} if not. A @code{gdb.Inferior} object will become invalid
22870 if the inferior no longer exists within @value{GDBN}. All other
22871 @code{gdb.Inferior} methods will throw an exception if it is invalid
22872 at the time the method is called.
22875 @defun Inferior.threads ()
22876 This method returns a tuple holding all the threads which are valid
22877 when it is called. If there are no valid threads, the method will
22878 return an empty tuple.
22881 @findex gdb.read_memory
22882 @defun Inferior.read_memory (address, length)
22883 Read @var{length} bytes of memory from the inferior, starting at
22884 @var{address}. Returns a buffer object, which behaves much like an array
22885 or a string. It can be modified and given to the @code{gdb.write_memory}
22889 @findex gdb.write_memory
22890 @defun Inferior.write_memory (address, buffer @r{[}, length@r{]})
22891 Write the contents of @var{buffer} to the inferior, starting at
22892 @var{address}. The @var{buffer} parameter must be a Python object
22893 which supports the buffer protocol, i.e., a string, an array or the
22894 object returned from @code{gdb.read_memory}. If given, @var{length}
22895 determines the number of bytes from @var{buffer} to be written.
22898 @findex gdb.search_memory
22899 @defun Inferior.search_memory (address, length, pattern)
22900 Search a region of the inferior memory starting at @var{address} with
22901 the given @var{length} using the search pattern supplied in
22902 @var{pattern}. The @var{pattern} parameter must be a Python object
22903 which supports the buffer protocol, i.e., a string, an array or the
22904 object returned from @code{gdb.read_memory}. Returns a Python @code{Long}
22905 containing the address where the pattern was found, or @code{None} if
22906 the pattern could not be found.
22910 @node Events In Python
22911 @subsubsection Events In Python
22912 @cindex inferior events in Python
22914 @value{GDBN} provides a general event facility so that Python code can be
22915 notified of various state changes, particularly changes that occur in
22918 An @dfn{event} is just an object that describes some state change. The
22919 type of the object and its attributes will vary depending on the details
22920 of the change. All the existing events are described below.
22922 In order to be notified of an event, you must register an event handler
22923 with an @dfn{event registry}. An event registry is an object in the
22924 @code{gdb.events} module which dispatches particular events. A registry
22925 provides methods to register and unregister event handlers:
22928 @defun EventRegistry.connect (object)
22929 Add the given callable @var{object} to the registry. This object will be
22930 called when an event corresponding to this registry occurs.
22933 @defun EventRegistry.disconnect (object)
22934 Remove the given @var{object} from the registry. Once removed, the object
22935 will no longer receive notifications of events.
22939 Here is an example:
22942 def exit_handler (event):
22943 print "event type: exit"
22944 print "exit code: %d" % (event.exit_code)
22946 gdb.events.exited.connect (exit_handler)
22949 In the above example we connect our handler @code{exit_handler} to the
22950 registry @code{events.exited}. Once connected, @code{exit_handler} gets
22951 called when the inferior exits. The argument @dfn{event} in this example is
22952 of type @code{gdb.ExitedEvent}. As you can see in the example the
22953 @code{ExitedEvent} object has an attribute which indicates the exit code of
22956 The following is a listing of the event registries that are available and
22957 details of the events they emit:
22962 Emits @code{gdb.ThreadEvent}.
22964 Some events can be thread specific when @value{GDBN} is running in non-stop
22965 mode. When represented in Python, these events all extend
22966 @code{gdb.ThreadEvent}. Note, this event is not emitted directly; instead,
22967 events which are emitted by this or other modules might extend this event.
22968 Examples of these events are @code{gdb.BreakpointEvent} and
22969 @code{gdb.ContinueEvent}.
22972 @defvar ThreadEvent.inferior_thread
22973 In non-stop mode this attribute will be set to the specific thread which was
22974 involved in the emitted event. Otherwise, it will be set to @code{None}.
22978 Emits @code{gdb.ContinueEvent} which extends @code{gdb.ThreadEvent}.
22980 This event indicates that the inferior has been continued after a stop. For
22981 inherited attribute refer to @code{gdb.ThreadEvent} above.
22983 @item events.exited
22984 Emits @code{events.ExitedEvent} which indicates that the inferior has exited.
22985 @code{events.ExitedEvent} has two attributes:
22987 @defvar ExitedEvent.exit_code
22988 An integer representing the exit code, if available, which the inferior
22989 has returned. (The exit code could be unavailable if, for example,
22990 @value{GDBN} detaches from the inferior.) If the exit code is unavailable,
22991 the attribute does not exist.
22993 @defvar ExitedEvent inferior
22994 A reference to the inferior which triggered the @code{exited} event.
22999 Emits @code{gdb.StopEvent} which extends @code{gdb.ThreadEvent}.
23001 Indicates that the inferior has stopped. All events emitted by this registry
23002 extend StopEvent. As a child of @code{gdb.ThreadEvent}, @code{gdb.StopEvent}
23003 will indicate the stopped thread when @value{GDBN} is running in non-stop
23004 mode. Refer to @code{gdb.ThreadEvent} above for more details.
23006 Emits @code{gdb.SignalEvent} which extends @code{gdb.StopEvent}.
23008 This event indicates that the inferior or one of its threads has received as
23009 signal. @code{gdb.SignalEvent} has the following attributes:
23012 @defvar SignalEvent.stop_signal
23013 A string representing the signal received by the inferior. A list of possible
23014 signal values can be obtained by running the command @code{info signals} in
23015 the @value{GDBN} command prompt.
23019 Also emits @code{gdb.BreakpointEvent} which extends @code{gdb.StopEvent}.
23021 @code{gdb.BreakpointEvent} event indicates that one or more breakpoints have
23022 been hit, and has the following attributes:
23025 @defvar BreakpointEvent.breakpoints
23026 A sequence containing references to all the breakpoints (type
23027 @code{gdb.Breakpoint}) that were hit.
23028 @xref{Breakpoints In Python}, for details of the @code{gdb.Breakpoint} object.
23030 @defvar BreakpointEvent.breakpoint
23031 A reference to the first breakpoint that was hit.
23032 This function is maintained for backward compatibility and is now deprecated
23033 in favor of the @code{gdb.BreakpointEvent.breakpoints} attribute.
23037 @item events.new_objfile
23038 Emits @code{gdb.NewObjFileEvent} which indicates that a new object file has
23039 been loaded by @value{GDBN}. @code{gdb.NewObjFileEvent} has one attribute:
23042 @defvar NewObjFileEvent.new_objfile
23043 A reference to the object file (@code{gdb.Objfile}) which has been loaded.
23044 @xref{Objfiles In Python}, for details of the @code{gdb.Objfile} object.
23050 @node Threads In Python
23051 @subsubsection Threads In Python
23052 @cindex threads in python
23054 @findex gdb.InferiorThread
23055 Python scripts can access information about, and manipulate inferior threads
23056 controlled by @value{GDBN}, via objects of the @code{gdb.InferiorThread} class.
23058 The following thread-related functions are available in the @code{gdb}
23061 @findex gdb.selected_thread
23062 @defun gdb.selected_thread ()
23063 This function returns the thread object for the selected thread. If there
23064 is no selected thread, this will return @code{None}.
23067 A @code{gdb.InferiorThread} object has the following attributes:
23070 @defvar InferiorThread.name
23071 The name of the thread. If the user specified a name using
23072 @code{thread name}, then this returns that name. Otherwise, if an
23073 OS-supplied name is available, then it is returned. Otherwise, this
23074 returns @code{None}.
23076 This attribute can be assigned to. The new value must be a string
23077 object, which sets the new name, or @code{None}, which removes any
23078 user-specified thread name.
23081 @defvar InferiorThread.num
23082 ID of the thread, as assigned by GDB.
23085 @defvar InferiorThread.ptid
23086 ID of the thread, as assigned by the operating system. This attribute is a
23087 tuple containing three integers. The first is the Process ID (PID); the second
23088 is the Lightweight Process ID (LWPID), and the third is the Thread ID (TID).
23089 Either the LWPID or TID may be 0, which indicates that the operating system
23090 does not use that identifier.
23094 A @code{gdb.InferiorThread} object has the following methods:
23097 @defun InferiorThread.is_valid ()
23098 Returns @code{True} if the @code{gdb.InferiorThread} object is valid,
23099 @code{False} if not. A @code{gdb.InferiorThread} object will become
23100 invalid if the thread exits, or the inferior that the thread belongs
23101 is deleted. All other @code{gdb.InferiorThread} methods will throw an
23102 exception if it is invalid at the time the method is called.
23105 @defun InferiorThread.switch ()
23106 This changes @value{GDBN}'s currently selected thread to the one represented
23110 @defun InferiorThread.is_stopped ()
23111 Return a Boolean indicating whether the thread is stopped.
23114 @defun InferiorThread.is_running ()
23115 Return a Boolean indicating whether the thread is running.
23118 @defun InferiorThread.is_exited ()
23119 Return a Boolean indicating whether the thread is exited.
23123 @node Commands In Python
23124 @subsubsection Commands In Python
23126 @cindex commands in python
23127 @cindex python commands
23128 You can implement new @value{GDBN} CLI commands in Python. A CLI
23129 command is implemented using an instance of the @code{gdb.Command}
23130 class, most commonly using a subclass.
23132 @defun Command.__init__ (name, @var{command_class} @r{[}, @var{completer_class} @r{[}, @var{prefix}@r{]]})
23133 The object initializer for @code{Command} registers the new command
23134 with @value{GDBN}. This initializer is normally invoked from the
23135 subclass' own @code{__init__} method.
23137 @var{name} is the name of the command. If @var{name} consists of
23138 multiple words, then the initial words are looked for as prefix
23139 commands. In this case, if one of the prefix commands does not exist,
23140 an exception is raised.
23142 There is no support for multi-line commands.
23144 @var{command_class} should be one of the @samp{COMMAND_} constants
23145 defined below. This argument tells @value{GDBN} how to categorize the
23146 new command in the help system.
23148 @var{completer_class} is an optional argument. If given, it should be
23149 one of the @samp{COMPLETE_} constants defined below. This argument
23150 tells @value{GDBN} how to perform completion for this command. If not
23151 given, @value{GDBN} will attempt to complete using the object's
23152 @code{complete} method (see below); if no such method is found, an
23153 error will occur when completion is attempted.
23155 @var{prefix} is an optional argument. If @code{True}, then the new
23156 command is a prefix command; sub-commands of this command may be
23159 The help text for the new command is taken from the Python
23160 documentation string for the command's class, if there is one. If no
23161 documentation string is provided, the default value ``This command is
23162 not documented.'' is used.
23165 @cindex don't repeat Python command
23166 @defun Command.dont_repeat ()
23167 By default, a @value{GDBN} command is repeated when the user enters a
23168 blank line at the command prompt. A command can suppress this
23169 behavior by invoking the @code{dont_repeat} method. This is similar
23170 to the user command @code{dont-repeat}, see @ref{Define, dont-repeat}.
23173 @defun Command.invoke (argument, from_tty)
23174 This method is called by @value{GDBN} when this command is invoked.
23176 @var{argument} is a string. It is the argument to the command, after
23177 leading and trailing whitespace has been stripped.
23179 @var{from_tty} is a boolean argument. When true, this means that the
23180 command was entered by the user at the terminal; when false it means
23181 that the command came from elsewhere.
23183 If this method throws an exception, it is turned into a @value{GDBN}
23184 @code{error} call. Otherwise, the return value is ignored.
23186 @findex gdb.string_to_argv
23187 To break @var{argument} up into an argv-like string use
23188 @code{gdb.string_to_argv}. This function behaves identically to
23189 @value{GDBN}'s internal argument lexer @code{buildargv}.
23190 It is recommended to use this for consistency.
23191 Arguments are separated by spaces and may be quoted.
23195 print gdb.string_to_argv ("1 2\ \\\"3 '4 \"5' \"6 '7\"")
23196 ['1', '2 "3', '4 "5', "6 '7"]
23201 @cindex completion of Python commands
23202 @defun Command.complete (text, word)
23203 This method is called by @value{GDBN} when the user attempts
23204 completion on this command. All forms of completion are handled by
23205 this method, that is, the @key{TAB} and @key{M-?} key bindings
23206 (@pxref{Completion}), and the @code{complete} command (@pxref{Help,
23209 The arguments @var{text} and @var{word} are both strings. @var{text}
23210 holds the complete command line up to the cursor's location.
23211 @var{word} holds the last word of the command line; this is computed
23212 using a word-breaking heuristic.
23214 The @code{complete} method can return several values:
23217 If the return value is a sequence, the contents of the sequence are
23218 used as the completions. It is up to @code{complete} to ensure that the
23219 contents actually do complete the word. A zero-length sequence is
23220 allowed, it means that there were no completions available. Only
23221 string elements of the sequence are used; other elements in the
23222 sequence are ignored.
23225 If the return value is one of the @samp{COMPLETE_} constants defined
23226 below, then the corresponding @value{GDBN}-internal completion
23227 function is invoked, and its result is used.
23230 All other results are treated as though there were no available
23235 When a new command is registered, it must be declared as a member of
23236 some general class of commands. This is used to classify top-level
23237 commands in the on-line help system; note that prefix commands are not
23238 listed under their own category but rather that of their top-level
23239 command. The available classifications are represented by constants
23240 defined in the @code{gdb} module:
23243 @findex COMMAND_NONE
23244 @findex gdb.COMMAND_NONE
23245 @item gdb.COMMAND_NONE
23246 The command does not belong to any particular class. A command in
23247 this category will not be displayed in any of the help categories.
23249 @findex COMMAND_RUNNING
23250 @findex gdb.COMMAND_RUNNING
23251 @item gdb.COMMAND_RUNNING
23252 The command is related to running the inferior. For example,
23253 @code{start}, @code{step}, and @code{continue} are in this category.
23254 Type @kbd{help running} at the @value{GDBN} prompt to see a list of
23255 commands in this category.
23257 @findex COMMAND_DATA
23258 @findex gdb.COMMAND_DATA
23259 @item gdb.COMMAND_DATA
23260 The command is related to data or variables. For example,
23261 @code{call}, @code{find}, and @code{print} are in this category. Type
23262 @kbd{help data} at the @value{GDBN} prompt to see a list of commands
23265 @findex COMMAND_STACK
23266 @findex gdb.COMMAND_STACK
23267 @item gdb.COMMAND_STACK
23268 The command has to do with manipulation of the stack. For example,
23269 @code{backtrace}, @code{frame}, and @code{return} are in this
23270 category. Type @kbd{help stack} at the @value{GDBN} prompt to see a
23271 list of commands in this category.
23273 @findex COMMAND_FILES
23274 @findex gdb.COMMAND_FILES
23275 @item gdb.COMMAND_FILES
23276 This class is used for file-related commands. For example,
23277 @code{file}, @code{list} and @code{section} are in this category.
23278 Type @kbd{help files} at the @value{GDBN} prompt to see a list of
23279 commands in this category.
23281 @findex COMMAND_SUPPORT
23282 @findex gdb.COMMAND_SUPPORT
23283 @item gdb.COMMAND_SUPPORT
23284 This should be used for ``support facilities'', generally meaning
23285 things that are useful to the user when interacting with @value{GDBN},
23286 but not related to the state of the inferior. For example,
23287 @code{help}, @code{make}, and @code{shell} are in this category. Type
23288 @kbd{help support} at the @value{GDBN} prompt to see a list of
23289 commands in this category.
23291 @findex COMMAND_STATUS
23292 @findex gdb.COMMAND_STATUS
23293 @item gdb.COMMAND_STATUS
23294 The command is an @samp{info}-related command, that is, related to the
23295 state of @value{GDBN} itself. For example, @code{info}, @code{macro},
23296 and @code{show} are in this category. Type @kbd{help status} at the
23297 @value{GDBN} prompt to see a list of commands in this category.
23299 @findex COMMAND_BREAKPOINTS
23300 @findex gdb.COMMAND_BREAKPOINTS
23301 @item gdb.COMMAND_BREAKPOINTS
23302 The command has to do with breakpoints. For example, @code{break},
23303 @code{clear}, and @code{delete} are in this category. Type @kbd{help
23304 breakpoints} at the @value{GDBN} prompt to see a list of commands in
23307 @findex COMMAND_TRACEPOINTS
23308 @findex gdb.COMMAND_TRACEPOINTS
23309 @item gdb.COMMAND_TRACEPOINTS
23310 The command has to do with tracepoints. For example, @code{trace},
23311 @code{actions}, and @code{tfind} are in this category. Type
23312 @kbd{help tracepoints} at the @value{GDBN} prompt to see a list of
23313 commands in this category.
23315 @findex COMMAND_USER
23316 @findex gdb.COMMAND_USER
23317 @item gdb.COMMAND_USER
23318 The command is a general purpose command for the user, and typically
23319 does not fit in one of the other categories.
23320 Type @kbd{help user-defined} at the @value{GDBN} prompt to see
23321 a list of commands in this category, as well as the list of gdb macros
23322 (@pxref{Sequences}).
23324 @findex COMMAND_OBSCURE
23325 @findex gdb.COMMAND_OBSCURE
23326 @item gdb.COMMAND_OBSCURE
23327 The command is only used in unusual circumstances, or is not of
23328 general interest to users. For example, @code{checkpoint},
23329 @code{fork}, and @code{stop} are in this category. Type @kbd{help
23330 obscure} at the @value{GDBN} prompt to see a list of commands in this
23333 @findex COMMAND_MAINTENANCE
23334 @findex gdb.COMMAND_MAINTENANCE
23335 @item gdb.COMMAND_MAINTENANCE
23336 The command is only useful to @value{GDBN} maintainers. The
23337 @code{maintenance} and @code{flushregs} commands are in this category.
23338 Type @kbd{help internals} at the @value{GDBN} prompt to see a list of
23339 commands in this category.
23342 A new command can use a predefined completion function, either by
23343 specifying it via an argument at initialization, or by returning it
23344 from the @code{complete} method. These predefined completion
23345 constants are all defined in the @code{gdb} module:
23348 @findex COMPLETE_NONE
23349 @findex gdb.COMPLETE_NONE
23350 @item gdb.COMPLETE_NONE
23351 This constant means that no completion should be done.
23353 @findex COMPLETE_FILENAME
23354 @findex gdb.COMPLETE_FILENAME
23355 @item gdb.COMPLETE_FILENAME
23356 This constant means that filename completion should be performed.
23358 @findex COMPLETE_LOCATION
23359 @findex gdb.COMPLETE_LOCATION
23360 @item gdb.COMPLETE_LOCATION
23361 This constant means that location completion should be done.
23362 @xref{Specify Location}.
23364 @findex COMPLETE_COMMAND
23365 @findex gdb.COMPLETE_COMMAND
23366 @item gdb.COMPLETE_COMMAND
23367 This constant means that completion should examine @value{GDBN}
23370 @findex COMPLETE_SYMBOL
23371 @findex gdb.COMPLETE_SYMBOL
23372 @item gdb.COMPLETE_SYMBOL
23373 This constant means that completion should be done using symbol names
23377 The following code snippet shows how a trivial CLI command can be
23378 implemented in Python:
23381 class HelloWorld (gdb.Command):
23382 """Greet the whole world."""
23384 def __init__ (self):
23385 super (HelloWorld, self).__init__ ("hello-world", gdb.COMMAND_USER)
23387 def invoke (self, arg, from_tty):
23388 print "Hello, World!"
23393 The last line instantiates the class, and is necessary to trigger the
23394 registration of the command with @value{GDBN}. Depending on how the
23395 Python code is read into @value{GDBN}, you may need to import the
23396 @code{gdb} module explicitly.
23398 @node Parameters In Python
23399 @subsubsection Parameters In Python
23401 @cindex parameters in python
23402 @cindex python parameters
23403 @tindex gdb.Parameter
23405 You can implement new @value{GDBN} parameters using Python. A new
23406 parameter is implemented as an instance of the @code{gdb.Parameter}
23409 Parameters are exposed to the user via the @code{set} and
23410 @code{show} commands. @xref{Help}.
23412 There are many parameters that already exist and can be set in
23413 @value{GDBN}. Two examples are: @code{set follow fork} and
23414 @code{set charset}. Setting these parameters influences certain
23415 behavior in @value{GDBN}. Similarly, you can define parameters that
23416 can be used to influence behavior in custom Python scripts and commands.
23418 @defun Parameter.__init__ (name, @var{command-class}, @var{parameter-class} @r{[}, @var{enum-sequence}@r{]})
23419 The object initializer for @code{Parameter} registers the new
23420 parameter with @value{GDBN}. This initializer is normally invoked
23421 from the subclass' own @code{__init__} method.
23423 @var{name} is the name of the new parameter. If @var{name} consists
23424 of multiple words, then the initial words are looked for as prefix
23425 parameters. An example of this can be illustrated with the
23426 @code{set print} set of parameters. If @var{name} is
23427 @code{print foo}, then @code{print} will be searched as the prefix
23428 parameter. In this case the parameter can subsequently be accessed in
23429 @value{GDBN} as @code{set print foo}.
23431 If @var{name} consists of multiple words, and no prefix parameter group
23432 can be found, an exception is raised.
23434 @var{command-class} should be one of the @samp{COMMAND_} constants
23435 (@pxref{Commands In Python}). This argument tells @value{GDBN} how to
23436 categorize the new parameter in the help system.
23438 @var{parameter-class} should be one of the @samp{PARAM_} constants
23439 defined below. This argument tells @value{GDBN} the type of the new
23440 parameter; this information is used for input validation and
23443 If @var{parameter-class} is @code{PARAM_ENUM}, then
23444 @var{enum-sequence} must be a sequence of strings. These strings
23445 represent the possible values for the parameter.
23447 If @var{parameter-class} is not @code{PARAM_ENUM}, then the presence
23448 of a fourth argument will cause an exception to be thrown.
23450 The help text for the new parameter is taken from the Python
23451 documentation string for the parameter's class, if there is one. If
23452 there is no documentation string, a default value is used.
23455 @defvar Parameter.set_doc
23456 If this attribute exists, and is a string, then its value is used as
23457 the help text for this parameter's @code{set} command. The value is
23458 examined when @code{Parameter.__init__} is invoked; subsequent changes
23462 @defvar Parameter.show_doc
23463 If this attribute exists, and is a string, then its value is used as
23464 the help text for this parameter's @code{show} command. The value is
23465 examined when @code{Parameter.__init__} is invoked; subsequent changes
23469 @defvar Parameter.value
23470 The @code{value} attribute holds the underlying value of the
23471 parameter. It can be read and assigned to just as any other
23472 attribute. @value{GDBN} does validation when assignments are made.
23475 There are two methods that should be implemented in any
23476 @code{Parameter} class. These are:
23478 @defun Parameter.get_set_string (self)
23479 @value{GDBN} will call this method when a @var{parameter}'s value has
23480 been changed via the @code{set} API (for example, @kbd{set foo off}).
23481 The @code{value} attribute has already been populated with the new
23482 value and may be used in output. This method must return a string.
23485 @defun Parameter.get_show_string (self, svalue)
23486 @value{GDBN} will call this method when a @var{parameter}'s
23487 @code{show} API has been invoked (for example, @kbd{show foo}). The
23488 argument @code{svalue} receives the string representation of the
23489 current value. This method must return a string.
23492 When a new parameter is defined, its type must be specified. The
23493 available types are represented by constants defined in the @code{gdb}
23497 @findex PARAM_BOOLEAN
23498 @findex gdb.PARAM_BOOLEAN
23499 @item gdb.PARAM_BOOLEAN
23500 The value is a plain boolean. The Python boolean values, @code{True}
23501 and @code{False} are the only valid values.
23503 @findex PARAM_AUTO_BOOLEAN
23504 @findex gdb.PARAM_AUTO_BOOLEAN
23505 @item gdb.PARAM_AUTO_BOOLEAN
23506 The value has three possible states: true, false, and @samp{auto}. In
23507 Python, true and false are represented using boolean constants, and
23508 @samp{auto} is represented using @code{None}.
23510 @findex PARAM_UINTEGER
23511 @findex gdb.PARAM_UINTEGER
23512 @item gdb.PARAM_UINTEGER
23513 The value is an unsigned integer. The value of 0 should be
23514 interpreted to mean ``unlimited''.
23516 @findex PARAM_INTEGER
23517 @findex gdb.PARAM_INTEGER
23518 @item gdb.PARAM_INTEGER
23519 The value is a signed integer. The value of 0 should be interpreted
23520 to mean ``unlimited''.
23522 @findex PARAM_STRING
23523 @findex gdb.PARAM_STRING
23524 @item gdb.PARAM_STRING
23525 The value is a string. When the user modifies the string, any escape
23526 sequences, such as @samp{\t}, @samp{\f}, and octal escapes, are
23527 translated into corresponding characters and encoded into the current
23530 @findex PARAM_STRING_NOESCAPE
23531 @findex gdb.PARAM_STRING_NOESCAPE
23532 @item gdb.PARAM_STRING_NOESCAPE
23533 The value is a string. When the user modifies the string, escapes are
23534 passed through untranslated.
23536 @findex PARAM_OPTIONAL_FILENAME
23537 @findex gdb.PARAM_OPTIONAL_FILENAME
23538 @item gdb.PARAM_OPTIONAL_FILENAME
23539 The value is a either a filename (a string), or @code{None}.
23541 @findex PARAM_FILENAME
23542 @findex gdb.PARAM_FILENAME
23543 @item gdb.PARAM_FILENAME
23544 The value is a filename. This is just like
23545 @code{PARAM_STRING_NOESCAPE}, but uses file names for completion.
23547 @findex PARAM_ZINTEGER
23548 @findex gdb.PARAM_ZINTEGER
23549 @item gdb.PARAM_ZINTEGER
23550 The value is an integer. This is like @code{PARAM_INTEGER}, except 0
23551 is interpreted as itself.
23554 @findex gdb.PARAM_ENUM
23555 @item gdb.PARAM_ENUM
23556 The value is a string, which must be one of a collection string
23557 constants provided when the parameter is created.
23560 @node Functions In Python
23561 @subsubsection Writing new convenience functions
23563 @cindex writing convenience functions
23564 @cindex convenience functions in python
23565 @cindex python convenience functions
23566 @tindex gdb.Function
23568 You can implement new convenience functions (@pxref{Convenience Vars})
23569 in Python. A convenience function is an instance of a subclass of the
23570 class @code{gdb.Function}.
23572 @defun Function.__init__ (name)
23573 The initializer for @code{Function} registers the new function with
23574 @value{GDBN}. The argument @var{name} is the name of the function,
23575 a string. The function will be visible to the user as a convenience
23576 variable of type @code{internal function}, whose name is the same as
23577 the given @var{name}.
23579 The documentation for the new function is taken from the documentation
23580 string for the new class.
23583 @defun Function.invoke (@var{*args})
23584 When a convenience function is evaluated, its arguments are converted
23585 to instances of @code{gdb.Value}, and then the function's
23586 @code{invoke} method is called. Note that @value{GDBN} does not
23587 predetermine the arity of convenience functions. Instead, all
23588 available arguments are passed to @code{invoke}, following the
23589 standard Python calling convention. In particular, a convenience
23590 function can have default values for parameters without ill effect.
23592 The return value of this method is used as its value in the enclosing
23593 expression. If an ordinary Python value is returned, it is converted
23594 to a @code{gdb.Value} following the usual rules.
23597 The following code snippet shows how a trivial convenience function can
23598 be implemented in Python:
23601 class Greet (gdb.Function):
23602 """Return string to greet someone.
23603 Takes a name as argument."""
23605 def __init__ (self):
23606 super (Greet, self).__init__ ("greet")
23608 def invoke (self, name):
23609 return "Hello, %s!" % name.string ()
23614 The last line instantiates the class, and is necessary to trigger the
23615 registration of the function with @value{GDBN}. Depending on how the
23616 Python code is read into @value{GDBN}, you may need to import the
23617 @code{gdb} module explicitly.
23619 @node Progspaces In Python
23620 @subsubsection Program Spaces In Python
23622 @cindex progspaces in python
23623 @tindex gdb.Progspace
23625 A program space, or @dfn{progspace}, represents a symbolic view
23626 of an address space.
23627 It consists of all of the objfiles of the program.
23628 @xref{Objfiles In Python}.
23629 @xref{Inferiors and Programs, program spaces}, for more details
23630 about program spaces.
23632 The following progspace-related functions are available in the
23635 @findex gdb.current_progspace
23636 @defun gdb.current_progspace ()
23637 This function returns the program space of the currently selected inferior.
23638 @xref{Inferiors and Programs}.
23641 @findex gdb.progspaces
23642 @defun gdb.progspaces ()
23643 Return a sequence of all the progspaces currently known to @value{GDBN}.
23646 Each progspace is represented by an instance of the @code{gdb.Progspace}
23649 @defvar Progspace.filename
23650 The file name of the progspace as a string.
23653 @defvar Progspace.pretty_printers
23654 The @code{pretty_printers} attribute is a list of functions. It is
23655 used to look up pretty-printers. A @code{Value} is passed to each
23656 function in order; if the function returns @code{None}, then the
23657 search continues. Otherwise, the return value should be an object
23658 which is used to format the value. @xref{Pretty Printing API}, for more
23662 @node Objfiles In Python
23663 @subsubsection Objfiles In Python
23665 @cindex objfiles in python
23666 @tindex gdb.Objfile
23668 @value{GDBN} loads symbols for an inferior from various
23669 symbol-containing files (@pxref{Files}). These include the primary
23670 executable file, any shared libraries used by the inferior, and any
23671 separate debug info files (@pxref{Separate Debug Files}).
23672 @value{GDBN} calls these symbol-containing files @dfn{objfiles}.
23674 The following objfile-related functions are available in the
23677 @findex gdb.current_objfile
23678 @defun gdb.current_objfile ()
23679 When auto-loading a Python script (@pxref{Auto-loading}), @value{GDBN}
23680 sets the ``current objfile'' to the corresponding objfile. This
23681 function returns the current objfile. If there is no current objfile,
23682 this function returns @code{None}.
23685 @findex gdb.objfiles
23686 @defun gdb.objfiles ()
23687 Return a sequence of all the objfiles current known to @value{GDBN}.
23688 @xref{Objfiles In Python}.
23691 Each objfile is represented by an instance of the @code{gdb.Objfile}
23694 @defvar Objfile.filename
23695 The file name of the objfile as a string.
23698 @defvar Objfile.pretty_printers
23699 The @code{pretty_printers} attribute is a list of functions. It is
23700 used to look up pretty-printers. A @code{Value} is passed to each
23701 function in order; if the function returns @code{None}, then the
23702 search continues. Otherwise, the return value should be an object
23703 which is used to format the value. @xref{Pretty Printing API}, for more
23707 A @code{gdb.Objfile} object has the following methods:
23709 @defun Objfile.is_valid ()
23710 Returns @code{True} if the @code{gdb.Objfile} object is valid,
23711 @code{False} if not. A @code{gdb.Objfile} object can become invalid
23712 if the object file it refers to is not loaded in @value{GDBN} any
23713 longer. All other @code{gdb.Objfile} methods will throw an exception
23714 if it is invalid at the time the method is called.
23717 @node Frames In Python
23718 @subsubsection Accessing inferior stack frames from Python.
23720 @cindex frames in python
23721 When the debugged program stops, @value{GDBN} is able to analyze its call
23722 stack (@pxref{Frames,,Stack frames}). The @code{gdb.Frame} class
23723 represents a frame in the stack. A @code{gdb.Frame} object is only valid
23724 while its corresponding frame exists in the inferior's stack. If you try
23725 to use an invalid frame object, @value{GDBN} will throw a @code{gdb.error}
23726 exception (@pxref{Exception Handling}).
23728 Two @code{gdb.Frame} objects can be compared for equality with the @code{==}
23732 (@value{GDBP}) python print gdb.newest_frame() == gdb.selected_frame ()
23736 The following frame-related functions are available in the @code{gdb} module:
23738 @findex gdb.selected_frame
23739 @defun gdb.selected_frame ()
23740 Return the selected frame object. (@pxref{Selection,,Selecting a Frame}).
23743 @findex gdb.newest_frame
23744 @defun gdb.newest_frame ()
23745 Return the newest frame object for the selected thread.
23748 @defun gdb.frame_stop_reason_string (reason)
23749 Return a string explaining the reason why @value{GDBN} stopped unwinding
23750 frames, as expressed by the given @var{reason} code (an integer, see the
23751 @code{unwind_stop_reason} method further down in this section).
23754 A @code{gdb.Frame} object has the following methods:
23757 @defun Frame.is_valid ()
23758 Returns true if the @code{gdb.Frame} object is valid, false if not.
23759 A frame object can become invalid if the frame it refers to doesn't
23760 exist anymore in the inferior. All @code{gdb.Frame} methods will throw
23761 an exception if it is invalid at the time the method is called.
23764 @defun Frame.name ()
23765 Returns the function name of the frame, or @code{None} if it can't be
23769 @defun Frame.type ()
23770 Returns the type of the frame. The value can be one of:
23772 @item gdb.NORMAL_FRAME
23773 An ordinary stack frame.
23775 @item gdb.DUMMY_FRAME
23776 A fake stack frame that was created by @value{GDBN} when performing an
23777 inferior function call.
23779 @item gdb.INLINE_FRAME
23780 A frame representing an inlined function. The function was inlined
23781 into a @code{gdb.NORMAL_FRAME} that is older than this one.
23783 @item gdb.TAILCALL_FRAME
23784 A frame representing a tail call. @xref{Tail Call Frames}.
23786 @item gdb.SIGTRAMP_FRAME
23787 A signal trampoline frame. This is the frame created by the OS when
23788 it calls into a signal handler.
23790 @item gdb.ARCH_FRAME
23791 A fake stack frame representing a cross-architecture call.
23793 @item gdb.SENTINEL_FRAME
23794 This is like @code{gdb.NORMAL_FRAME}, but it is only used for the
23799 @defun Frame.unwind_stop_reason ()
23800 Return an integer representing the reason why it's not possible to find
23801 more frames toward the outermost frame. Use
23802 @code{gdb.frame_stop_reason_string} to convert the value returned by this
23803 function to a string. The value can be one of:
23806 @item gdb.FRAME_UNWIND_NO_REASON
23807 No particular reason (older frames should be available).
23809 @item gdb.FRAME_UNWIND_NULL_ID
23810 The previous frame's analyzer returns an invalid result.
23812 @item gdb.FRAME_UNWIND_OUTERMOST
23813 This frame is the outermost.
23815 @item gdb.FRAME_UNWIND_UNAVAILABLE
23816 Cannot unwind further, because that would require knowing the
23817 values of registers or memory that have not been collected.
23819 @item gdb.FRAME_UNWIND_INNER_ID
23820 This frame ID looks like it ought to belong to a NEXT frame,
23821 but we got it for a PREV frame. Normally, this is a sign of
23822 unwinder failure. It could also indicate stack corruption.
23824 @item gdb.FRAME_UNWIND_SAME_ID
23825 This frame has the same ID as the previous one. That means
23826 that unwinding further would almost certainly give us another
23827 frame with exactly the same ID, so break the chain. Normally,
23828 this is a sign of unwinder failure. It could also indicate
23831 @item gdb.FRAME_UNWIND_NO_SAVED_PC
23832 The frame unwinder did not find any saved PC, but we needed
23833 one to unwind further.
23835 @item gdb.FRAME_UNWIND_FIRST_ERROR
23836 Any stop reason greater or equal to this value indicates some kind
23837 of error. This special value facilitates writing code that tests
23838 for errors in unwinding in a way that will work correctly even if
23839 the list of the other values is modified in future @value{GDBN}
23840 versions. Using it, you could write:
23842 reason = gdb.selected_frame().unwind_stop_reason ()
23843 reason_str = gdb.frame_stop_reason_string (reason)
23844 if reason >= gdb.FRAME_UNWIND_FIRST_ERROR:
23845 print "An error occured: %s" % reason_str
23852 Returns the frame's resume address.
23855 @defun Frame.block ()
23856 Return the frame's code block. @xref{Blocks In Python}.
23859 @defun Frame.function ()
23860 Return the symbol for the function corresponding to this frame.
23861 @xref{Symbols In Python}.
23864 @defun Frame.older ()
23865 Return the frame that called this frame.
23868 @defun Frame.newer ()
23869 Return the frame called by this frame.
23872 @defun Frame.find_sal ()
23873 Return the frame's symtab and line object.
23874 @xref{Symbol Tables In Python}.
23877 @defun Frame.read_var (variable @r{[}, block@r{]})
23878 Return the value of @var{variable} in this frame. If the optional
23879 argument @var{block} is provided, search for the variable from that
23880 block; otherwise start at the frame's current block (which is
23881 determined by the frame's current program counter). @var{variable}
23882 must be a string or a @code{gdb.Symbol} object. @var{block} must be a
23883 @code{gdb.Block} object.
23886 @defun Frame.select ()
23887 Set this frame to be the selected frame. @xref{Stack, ,Examining the
23892 @node Blocks In Python
23893 @subsubsection Accessing frame blocks from Python.
23895 @cindex blocks in python
23898 Within each frame, @value{GDBN} maintains information on each block
23899 stored in that frame. These blocks are organized hierarchically, and
23900 are represented individually in Python as a @code{gdb.Block}.
23901 Please see @ref{Frames In Python}, for a more in-depth discussion on
23902 frames. Furthermore, see @ref{Stack, ,Examining the Stack}, for more
23903 detailed technical information on @value{GDBN}'s book-keeping of the
23906 A @code{gdb.Block} is iterable. The iterator returns the symbols
23907 (@pxref{Symbols In Python}) local to the block.
23909 The following block-related functions are available in the @code{gdb}
23912 @findex gdb.block_for_pc
23913 @defun gdb.block_for_pc (pc)
23914 Return the @code{gdb.Block} containing the given @var{pc} value. If the
23915 block cannot be found for the @var{pc} value specified, the function
23916 will return @code{None}.
23919 A @code{gdb.Block} object has the following methods:
23922 @defun Block.is_valid ()
23923 Returns @code{True} if the @code{gdb.Block} object is valid,
23924 @code{False} if not. A block object can become invalid if the block it
23925 refers to doesn't exist anymore in the inferior. All other
23926 @code{gdb.Block} methods will throw an exception if it is invalid at
23927 the time the method is called. The block's validity is also checked
23928 during iteration over symbols of the block.
23932 A @code{gdb.Block} object has the following attributes:
23935 @defvar Block.start
23936 The start address of the block. This attribute is not writable.
23940 The end address of the block. This attribute is not writable.
23943 @defvar Block.function
23944 The name of the block represented as a @code{gdb.Symbol}. If the
23945 block is not named, then this attribute holds @code{None}. This
23946 attribute is not writable.
23949 @defvar Block.superblock
23950 The block containing this block. If this parent block does not exist,
23951 this attribute holds @code{None}. This attribute is not writable.
23954 @defvar Block.global_block
23955 The global block associated with this block. This attribute is not
23959 @defvar Block.static_block
23960 The static block associated with this block. This attribute is not
23964 @defvar Block.is_global
23965 @code{True} if the @code{gdb.Block} object is a global block,
23966 @code{False} if not. This attribute is not
23970 @defvar Block.is_static
23971 @code{True} if the @code{gdb.Block} object is a static block,
23972 @code{False} if not. This attribute is not writable.
23976 @node Symbols In Python
23977 @subsubsection Python representation of Symbols.
23979 @cindex symbols in python
23982 @value{GDBN} represents every variable, function and type as an
23983 entry in a symbol table. @xref{Symbols, ,Examining the Symbol Table}.
23984 Similarly, Python represents these symbols in @value{GDBN} with the
23985 @code{gdb.Symbol} object.
23987 The following symbol-related functions are available in the @code{gdb}
23990 @findex gdb.lookup_symbol
23991 @defun gdb.lookup_symbol (name @r{[}, block @r{[}, domain@r{]]})
23992 This function searches for a symbol by name. The search scope can be
23993 restricted to the parameters defined in the optional domain and block
23996 @var{name} is the name of the symbol. It must be a string. The
23997 optional @var{block} argument restricts the search to symbols visible
23998 in that @var{block}. The @var{block} argument must be a
23999 @code{gdb.Block} object. If omitted, the block for the current frame
24000 is used. The optional @var{domain} argument restricts
24001 the search to the domain type. The @var{domain} argument must be a
24002 domain constant defined in the @code{gdb} module and described later
24005 The result is a tuple of two elements.
24006 The first element is a @code{gdb.Symbol} object or @code{None} if the symbol
24008 If the symbol is found, the second element is @code{True} if the symbol
24009 is a field of a method's object (e.g., @code{this} in C@t{++}),
24010 otherwise it is @code{False}.
24011 If the symbol is not found, the second element is @code{False}.
24014 @findex gdb.lookup_global_symbol
24015 @defun gdb.lookup_global_symbol (name @r{[}, domain@r{]})
24016 This function searches for a global symbol by name.
24017 The search scope can be restricted to by the domain argument.
24019 @var{name} is the name of the symbol. It must be a string.
24020 The optional @var{domain} argument restricts the search to the domain type.
24021 The @var{domain} argument must be a domain constant defined in the @code{gdb}
24022 module and described later in this chapter.
24024 The result is a @code{gdb.Symbol} object or @code{None} if the symbol
24028 A @code{gdb.Symbol} object has the following attributes:
24031 @defvar Symbol.type
24032 The type of the symbol or @code{None} if no type is recorded.
24033 This attribute is represented as a @code{gdb.Type} object.
24034 @xref{Types In Python}. This attribute is not writable.
24037 @defvar Symbol.symtab
24038 The symbol table in which the symbol appears. This attribute is
24039 represented as a @code{gdb.Symtab} object. @xref{Symbol Tables In
24040 Python}. This attribute is not writable.
24043 @defvar Symbol.line
24044 The line number in the source code at which the symbol was defined.
24045 This is an integer.
24048 @defvar Symbol.name
24049 The name of the symbol as a string. This attribute is not writable.
24052 @defvar Symbol.linkage_name
24053 The name of the symbol, as used by the linker (i.e., may be mangled).
24054 This attribute is not writable.
24057 @defvar Symbol.print_name
24058 The name of the symbol in a form suitable for output. This is either
24059 @code{name} or @code{linkage_name}, depending on whether the user
24060 asked @value{GDBN} to display demangled or mangled names.
24063 @defvar Symbol.addr_class
24064 The address class of the symbol. This classifies how to find the value
24065 of a symbol. Each address class is a constant defined in the
24066 @code{gdb} module and described later in this chapter.
24069 @defvar Symbol.needs_frame
24070 This is @code{True} if evaluating this symbol's value requires a frame
24071 (@pxref{Frames In Python}) and @code{False} otherwise. Typically,
24072 local variables will require a frame, but other symbols will not.
24075 @defvar Symbol.is_argument
24076 @code{True} if the symbol is an argument of a function.
24079 @defvar Symbol.is_constant
24080 @code{True} if the symbol is a constant.
24083 @defvar Symbol.is_function
24084 @code{True} if the symbol is a function or a method.
24087 @defvar Symbol.is_variable
24088 @code{True} if the symbol is a variable.
24092 A @code{gdb.Symbol} object has the following methods:
24095 @defun Symbol.is_valid ()
24096 Returns @code{True} if the @code{gdb.Symbol} object is valid,
24097 @code{False} if not. A @code{gdb.Symbol} object can become invalid if
24098 the symbol it refers to does not exist in @value{GDBN} any longer.
24099 All other @code{gdb.Symbol} methods will throw an exception if it is
24100 invalid at the time the method is called.
24103 @defun Symbol.value (@r{[}frame@r{]})
24104 Compute the value of the symbol, as a @code{gdb.Value}. For
24105 functions, this computes the address of the function, cast to the
24106 appropriate type. If the symbol requires a frame in order to compute
24107 its value, then @var{frame} must be given. If @var{frame} is not
24108 given, or if @var{frame} is invalid, then this method will throw an
24113 The available domain categories in @code{gdb.Symbol} are represented
24114 as constants in the @code{gdb} module:
24117 @findex SYMBOL_UNDEF_DOMAIN
24118 @findex gdb.SYMBOL_UNDEF_DOMAIN
24119 @item gdb.SYMBOL_UNDEF_DOMAIN
24120 This is used when a domain has not been discovered or none of the
24121 following domains apply. This usually indicates an error either
24122 in the symbol information or in @value{GDBN}'s handling of symbols.
24123 @findex SYMBOL_VAR_DOMAIN
24124 @findex gdb.SYMBOL_VAR_DOMAIN
24125 @item gdb.SYMBOL_VAR_DOMAIN
24126 This domain contains variables, function names, typedef names and enum
24128 @findex SYMBOL_STRUCT_DOMAIN
24129 @findex gdb.SYMBOL_STRUCT_DOMAIN
24130 @item gdb.SYMBOL_STRUCT_DOMAIN
24131 This domain holds struct, union and enum type names.
24132 @findex SYMBOL_LABEL_DOMAIN
24133 @findex gdb.SYMBOL_LABEL_DOMAIN
24134 @item gdb.SYMBOL_LABEL_DOMAIN
24135 This domain contains names of labels (for gotos).
24136 @findex SYMBOL_VARIABLES_DOMAIN
24137 @findex gdb.SYMBOL_VARIABLES_DOMAIN
24138 @item gdb.SYMBOL_VARIABLES_DOMAIN
24139 This domain holds a subset of the @code{SYMBOLS_VAR_DOMAIN}; it
24140 contains everything minus functions and types.
24141 @findex SYMBOL_FUNCTIONS_DOMAIN
24142 @findex gdb.SYMBOL_FUNCTIONS_DOMAIN
24143 @item gdb.SYMBOL_FUNCTION_DOMAIN
24144 This domain contains all functions.
24145 @findex SYMBOL_TYPES_DOMAIN
24146 @findex gdb.SYMBOL_TYPES_DOMAIN
24147 @item gdb.SYMBOL_TYPES_DOMAIN
24148 This domain contains all types.
24151 The available address class categories in @code{gdb.Symbol} are represented
24152 as constants in the @code{gdb} module:
24155 @findex SYMBOL_LOC_UNDEF
24156 @findex gdb.SYMBOL_LOC_UNDEF
24157 @item gdb.SYMBOL_LOC_UNDEF
24158 If this is returned by address class, it indicates an error either in
24159 the symbol information or in @value{GDBN}'s handling of symbols.
24160 @findex SYMBOL_LOC_CONST
24161 @findex gdb.SYMBOL_LOC_CONST
24162 @item gdb.SYMBOL_LOC_CONST
24163 Value is constant int.
24164 @findex SYMBOL_LOC_STATIC
24165 @findex gdb.SYMBOL_LOC_STATIC
24166 @item gdb.SYMBOL_LOC_STATIC
24167 Value is at a fixed address.
24168 @findex SYMBOL_LOC_REGISTER
24169 @findex gdb.SYMBOL_LOC_REGISTER
24170 @item gdb.SYMBOL_LOC_REGISTER
24171 Value is in a register.
24172 @findex SYMBOL_LOC_ARG
24173 @findex gdb.SYMBOL_LOC_ARG
24174 @item gdb.SYMBOL_LOC_ARG
24175 Value is an argument. This value is at the offset stored within the
24176 symbol inside the frame's argument list.
24177 @findex SYMBOL_LOC_REF_ARG
24178 @findex gdb.SYMBOL_LOC_REF_ARG
24179 @item gdb.SYMBOL_LOC_REF_ARG
24180 Value address is stored in the frame's argument list. Just like
24181 @code{LOC_ARG} except that the value's address is stored at the
24182 offset, not the value itself.
24183 @findex SYMBOL_LOC_REGPARM_ADDR
24184 @findex gdb.SYMBOL_LOC_REGPARM_ADDR
24185 @item gdb.SYMBOL_LOC_REGPARM_ADDR
24186 Value is a specified register. Just like @code{LOC_REGISTER} except
24187 the register holds the address of the argument instead of the argument
24189 @findex SYMBOL_LOC_LOCAL
24190 @findex gdb.SYMBOL_LOC_LOCAL
24191 @item gdb.SYMBOL_LOC_LOCAL
24192 Value is a local variable.
24193 @findex SYMBOL_LOC_TYPEDEF
24194 @findex gdb.SYMBOL_LOC_TYPEDEF
24195 @item gdb.SYMBOL_LOC_TYPEDEF
24196 Value not used. Symbols in the domain @code{SYMBOL_STRUCT_DOMAIN} all
24198 @findex SYMBOL_LOC_BLOCK
24199 @findex gdb.SYMBOL_LOC_BLOCK
24200 @item gdb.SYMBOL_LOC_BLOCK
24202 @findex SYMBOL_LOC_CONST_BYTES
24203 @findex gdb.SYMBOL_LOC_CONST_BYTES
24204 @item gdb.SYMBOL_LOC_CONST_BYTES
24205 Value is a byte-sequence.
24206 @findex SYMBOL_LOC_UNRESOLVED
24207 @findex gdb.SYMBOL_LOC_UNRESOLVED
24208 @item gdb.SYMBOL_LOC_UNRESOLVED
24209 Value is at a fixed address, but the address of the variable has to be
24210 determined from the minimal symbol table whenever the variable is
24212 @findex SYMBOL_LOC_OPTIMIZED_OUT
24213 @findex gdb.SYMBOL_LOC_OPTIMIZED_OUT
24214 @item gdb.SYMBOL_LOC_OPTIMIZED_OUT
24215 The value does not actually exist in the program.
24216 @findex SYMBOL_LOC_COMPUTED
24217 @findex gdb.SYMBOL_LOC_COMPUTED
24218 @item gdb.SYMBOL_LOC_COMPUTED
24219 The value's address is a computed location.
24222 @node Symbol Tables In Python
24223 @subsubsection Symbol table representation in Python.
24225 @cindex symbol tables in python
24227 @tindex gdb.Symtab_and_line
24229 Access to symbol table data maintained by @value{GDBN} on the inferior
24230 is exposed to Python via two objects: @code{gdb.Symtab_and_line} and
24231 @code{gdb.Symtab}. Symbol table and line data for a frame is returned
24232 from the @code{find_sal} method in @code{gdb.Frame} object.
24233 @xref{Frames In Python}.
24235 For more information on @value{GDBN}'s symbol table management, see
24236 @ref{Symbols, ,Examining the Symbol Table}, for more information.
24238 A @code{gdb.Symtab_and_line} object has the following attributes:
24241 @defvar Symtab_and_line.symtab
24242 The symbol table object (@code{gdb.Symtab}) for this frame.
24243 This attribute is not writable.
24246 @defvar Symtab_and_line.pc
24247 Indicates the current program counter address. This attribute is not
24251 @defvar Symtab_and_line.line
24252 Indicates the current line number for this object. This
24253 attribute is not writable.
24257 A @code{gdb.Symtab_and_line} object has the following methods:
24260 @defun Symtab_and_line.is_valid ()
24261 Returns @code{True} if the @code{gdb.Symtab_and_line} object is valid,
24262 @code{False} if not. A @code{gdb.Symtab_and_line} object can become
24263 invalid if the Symbol table and line object it refers to does not
24264 exist in @value{GDBN} any longer. All other
24265 @code{gdb.Symtab_and_line} methods will throw an exception if it is
24266 invalid at the time the method is called.
24270 A @code{gdb.Symtab} object has the following attributes:
24273 @defvar Symtab.filename
24274 The symbol table's source filename. This attribute is not writable.
24277 @defvar Symtab.objfile
24278 The symbol table's backing object file. @xref{Objfiles In Python}.
24279 This attribute is not writable.
24283 A @code{gdb.Symtab} object has the following methods:
24286 @defun Symtab.is_valid ()
24287 Returns @code{True} if the @code{gdb.Symtab} object is valid,
24288 @code{False} if not. A @code{gdb.Symtab} object can become invalid if
24289 the symbol table it refers to does not exist in @value{GDBN} any
24290 longer. All other @code{gdb.Symtab} methods will throw an exception
24291 if it is invalid at the time the method is called.
24294 @defun Symtab.fullname ()
24295 Return the symbol table's source absolute file name.
24299 @node Breakpoints In Python
24300 @subsubsection Manipulating breakpoints using Python
24302 @cindex breakpoints in python
24303 @tindex gdb.Breakpoint
24305 Python code can manipulate breakpoints via the @code{gdb.Breakpoint}
24308 @defun Breakpoint.__init__ (spec @r{[}, type @r{[}, wp_class @r{[},internal@r{]]]})
24309 Create a new breakpoint. @var{spec} is a string naming the
24310 location of the breakpoint, or an expression that defines a
24311 watchpoint. The contents can be any location recognized by the
24312 @code{break} command, or in the case of a watchpoint, by the @code{watch}
24313 command. The optional @var{type} denotes the breakpoint to create
24314 from the types defined later in this chapter. This argument can be
24315 either: @code{gdb.BP_BREAKPOINT} or @code{gdb.BP_WATCHPOINT}. @var{type}
24316 defaults to @code{gdb.BP_BREAKPOINT}. The optional @var{internal} argument
24317 allows the breakpoint to become invisible to the user. The breakpoint
24318 will neither be reported when created, nor will it be listed in the
24319 output from @code{info breakpoints} (but will be listed with the
24320 @code{maint info breakpoints} command). The optional @var{wp_class}
24321 argument defines the class of watchpoint to create, if @var{type} is
24322 @code{gdb.BP_WATCHPOINT}. If a watchpoint class is not provided, it is
24323 assumed to be a @code{gdb.WP_WRITE} class.
24326 @defun Breakpoint.stop (self)
24327 The @code{gdb.Breakpoint} class can be sub-classed and, in
24328 particular, you may choose to implement the @code{stop} method.
24329 If this method is defined as a sub-class of @code{gdb.Breakpoint},
24330 it will be called when the inferior reaches any location of a
24331 breakpoint which instantiates that sub-class. If the method returns
24332 @code{True}, the inferior will be stopped at the location of the
24333 breakpoint, otherwise the inferior will continue.
24335 If there are multiple breakpoints at the same location with a
24336 @code{stop} method, each one will be called regardless of the
24337 return status of the previous. This ensures that all @code{stop}
24338 methods have a chance to execute at that location. In this scenario
24339 if one of the methods returns @code{True} but the others return
24340 @code{False}, the inferior will still be stopped.
24342 You should not alter the execution state of the inferior (i.e.@:, step,
24343 next, etc.), alter the current frame context (i.e.@:, change the current
24344 active frame), or alter, add or delete any breakpoint. As a general
24345 rule, you should not alter any data within @value{GDBN} or the inferior
24348 Example @code{stop} implementation:
24351 class MyBreakpoint (gdb.Breakpoint):
24353 inf_val = gdb.parse_and_eval("foo")
24360 The available watchpoint types represented by constants are defined in the
24365 @findex gdb.WP_READ
24367 Read only watchpoint.
24370 @findex gdb.WP_WRITE
24372 Write only watchpoint.
24375 @findex gdb.WP_ACCESS
24376 @item gdb.WP_ACCESS
24377 Read/Write watchpoint.
24380 @defun Breakpoint.is_valid ()
24381 Return @code{True} if this @code{Breakpoint} object is valid,
24382 @code{False} otherwise. A @code{Breakpoint} object can become invalid
24383 if the user deletes the breakpoint. In this case, the object still
24384 exists, but the underlying breakpoint does not. In the cases of
24385 watchpoint scope, the watchpoint remains valid even if execution of the
24386 inferior leaves the scope of that watchpoint.
24389 @defun Breakpoint.delete
24390 Permanently deletes the @value{GDBN} breakpoint. This also
24391 invalidates the Python @code{Breakpoint} object. Any further access
24392 to this object's attributes or methods will raise an error.
24395 @defvar Breakpoint.enabled
24396 This attribute is @code{True} if the breakpoint is enabled, and
24397 @code{False} otherwise. This attribute is writable.
24400 @defvar Breakpoint.silent
24401 This attribute is @code{True} if the breakpoint is silent, and
24402 @code{False} otherwise. This attribute is writable.
24404 Note that a breakpoint can also be silent if it has commands and the
24405 first command is @code{silent}. This is not reported by the
24406 @code{silent} attribute.
24409 @defvar Breakpoint.thread
24410 If the breakpoint is thread-specific, this attribute holds the thread
24411 id. If the breakpoint is not thread-specific, this attribute is
24412 @code{None}. This attribute is writable.
24415 @defvar Breakpoint.task
24416 If the breakpoint is Ada task-specific, this attribute holds the Ada task
24417 id. If the breakpoint is not task-specific (or the underlying
24418 language is not Ada), this attribute is @code{None}. This attribute
24422 @defvar Breakpoint.ignore_count
24423 This attribute holds the ignore count for the breakpoint, an integer.
24424 This attribute is writable.
24427 @defvar Breakpoint.number
24428 This attribute holds the breakpoint's number --- the identifier used by
24429 the user to manipulate the breakpoint. This attribute is not writable.
24432 @defvar Breakpoint.type
24433 This attribute holds the breakpoint's type --- the identifier used to
24434 determine the actual breakpoint type or use-case. This attribute is not
24438 @defvar Breakpoint.visible
24439 This attribute tells whether the breakpoint is visible to the user
24440 when set, or when the @samp{info breakpoints} command is run. This
24441 attribute is not writable.
24444 The available types are represented by constants defined in the @code{gdb}
24448 @findex BP_BREAKPOINT
24449 @findex gdb.BP_BREAKPOINT
24450 @item gdb.BP_BREAKPOINT
24451 Normal code breakpoint.
24453 @findex BP_WATCHPOINT
24454 @findex gdb.BP_WATCHPOINT
24455 @item gdb.BP_WATCHPOINT
24456 Watchpoint breakpoint.
24458 @findex BP_HARDWARE_WATCHPOINT
24459 @findex gdb.BP_HARDWARE_WATCHPOINT
24460 @item gdb.BP_HARDWARE_WATCHPOINT
24461 Hardware assisted watchpoint.
24463 @findex BP_READ_WATCHPOINT
24464 @findex gdb.BP_READ_WATCHPOINT
24465 @item gdb.BP_READ_WATCHPOINT
24466 Hardware assisted read watchpoint.
24468 @findex BP_ACCESS_WATCHPOINT
24469 @findex gdb.BP_ACCESS_WATCHPOINT
24470 @item gdb.BP_ACCESS_WATCHPOINT
24471 Hardware assisted access watchpoint.
24474 @defvar Breakpoint.hit_count
24475 This attribute holds the hit count for the breakpoint, an integer.
24476 This attribute is writable, but currently it can only be set to zero.
24479 @defvar Breakpoint.location
24480 This attribute holds the location of the breakpoint, as specified by
24481 the user. It is a string. If the breakpoint does not have a location
24482 (that is, it is a watchpoint) the attribute's value is @code{None}. This
24483 attribute is not writable.
24486 @defvar Breakpoint.expression
24487 This attribute holds a breakpoint expression, as specified by
24488 the user. It is a string. If the breakpoint does not have an
24489 expression (the breakpoint is not a watchpoint) the attribute's value
24490 is @code{None}. This attribute is not writable.
24493 @defvar Breakpoint.condition
24494 This attribute holds the condition of the breakpoint, as specified by
24495 the user. It is a string. If there is no condition, this attribute's
24496 value is @code{None}. This attribute is writable.
24499 @defvar Breakpoint.commands
24500 This attribute holds the commands attached to the breakpoint. If
24501 there are commands, this attribute's value is a string holding all the
24502 commands, separated by newlines. If there are no commands, this
24503 attribute is @code{None}. This attribute is not writable.
24506 @node Finish Breakpoints in Python
24507 @subsubsection Finish Breakpoints
24509 @cindex python finish breakpoints
24510 @tindex gdb.FinishBreakpoint
24512 A finish breakpoint is a temporary breakpoint set at the return address of
24513 a frame, based on the @code{finish} command. @code{gdb.FinishBreakpoint}
24514 extends @code{gdb.Breakpoint}. The underlying breakpoint will be disabled
24515 and deleted when the execution will run out of the breakpoint scope (i.e.@:
24516 @code{Breakpoint.stop} or @code{FinishBreakpoint.out_of_scope} triggered).
24517 Finish breakpoints are thread specific and must be create with the right
24520 @defun FinishBreakpoint.__init__ (@r{[}frame@r{]} @r{[}, internal@r{]})
24521 Create a finish breakpoint at the return address of the @code{gdb.Frame}
24522 object @var{frame}. If @var{frame} is not provided, this defaults to the
24523 newest frame. The optional @var{internal} argument allows the breakpoint to
24524 become invisible to the user. @xref{Breakpoints In Python}, for further
24525 details about this argument.
24528 @defun FinishBreakpoint.out_of_scope (self)
24529 In some circumstances (e.g.@: @code{longjmp}, C@t{++} exceptions, @value{GDBN}
24530 @code{return} command, @dots{}), a function may not properly terminate, and
24531 thus never hit the finish breakpoint. When @value{GDBN} notices such a
24532 situation, the @code{out_of_scope} callback will be triggered.
24534 You may want to sub-class @code{gdb.FinishBreakpoint} and override this
24538 class MyFinishBreakpoint (gdb.FinishBreakpoint)
24540 print "normal finish"
24543 def out_of_scope ():
24544 print "abnormal finish"
24548 @defvar FinishBreakpoint.return_value
24549 When @value{GDBN} is stopped at a finish breakpoint and the frame
24550 used to build the @code{gdb.FinishBreakpoint} object had debug symbols, this
24551 attribute will contain a @code{gdb.Value} object corresponding to the return
24552 value of the function. The value will be @code{None} if the function return
24553 type is @code{void} or if the return value was not computable. This attribute
24557 @node Lazy Strings In Python
24558 @subsubsection Python representation of lazy strings.
24560 @cindex lazy strings in python
24561 @tindex gdb.LazyString
24563 A @dfn{lazy string} is a string whose contents is not retrieved or
24564 encoded until it is needed.
24566 A @code{gdb.LazyString} is represented in @value{GDBN} as an
24567 @code{address} that points to a region of memory, an @code{encoding}
24568 that will be used to encode that region of memory, and a @code{length}
24569 to delimit the region of memory that represents the string. The
24570 difference between a @code{gdb.LazyString} and a string wrapped within
24571 a @code{gdb.Value} is that a @code{gdb.LazyString} will be treated
24572 differently by @value{GDBN} when printing. A @code{gdb.LazyString} is
24573 retrieved and encoded during printing, while a @code{gdb.Value}
24574 wrapping a string is immediately retrieved and encoded on creation.
24576 A @code{gdb.LazyString} object has the following functions:
24578 @defun LazyString.value ()
24579 Convert the @code{gdb.LazyString} to a @code{gdb.Value}. This value
24580 will point to the string in memory, but will lose all the delayed
24581 retrieval, encoding and handling that @value{GDBN} applies to a
24582 @code{gdb.LazyString}.
24585 @defvar LazyString.address
24586 This attribute holds the address of the string. This attribute is not
24590 @defvar LazyString.length
24591 This attribute holds the length of the string in characters. If the
24592 length is -1, then the string will be fetched and encoded up to the
24593 first null of appropriate width. This attribute is not writable.
24596 @defvar LazyString.encoding
24597 This attribute holds the encoding that will be applied to the string
24598 when the string is printed by @value{GDBN}. If the encoding is not
24599 set, or contains an empty string, then @value{GDBN} will select the
24600 most appropriate encoding when the string is printed. This attribute
24604 @defvar LazyString.type
24605 This attribute holds the type that is represented by the lazy string's
24606 type. For a lazy string this will always be a pointer type. To
24607 resolve this to the lazy string's character type, use the type's
24608 @code{target} method. @xref{Types In Python}. This attribute is not
24613 @subsection Auto-loading
24614 @cindex auto-loading, Python
24616 When a new object file is read (for example, due to the @code{file}
24617 command, or because the inferior has loaded a shared library),
24618 @value{GDBN} will look for Python support scripts in several ways:
24619 @file{@var{objfile}-gdb.py} and @code{.debug_gdb_scripts} section.
24622 * objfile-gdb.py file:: The @file{@var{objfile}-gdb.py} file
24623 * .debug_gdb_scripts section:: The @code{.debug_gdb_scripts} section
24624 * Which flavor to choose?::
24627 The auto-loading feature is useful for supplying application-specific
24628 debugging commands and scripts.
24630 Auto-loading can be enabled or disabled,
24631 and the list of auto-loaded scripts can be printed.
24634 @kindex set auto-load-scripts
24635 @item set auto-load-scripts [yes|no]
24636 Enable or disable the auto-loading of Python scripts.
24638 @kindex show auto-load-scripts
24639 @item show auto-load-scripts
24640 Show whether auto-loading of Python scripts is enabled or disabled.
24642 @kindex info auto-load-scripts
24643 @cindex print list of auto-loaded scripts
24644 @item info auto-load-scripts [@var{regexp}]
24645 Print the list of all scripts that @value{GDBN} auto-loaded.
24647 Also printed is the list of scripts that were mentioned in
24648 the @code{.debug_gdb_scripts} section and were not found
24649 (@pxref{.debug_gdb_scripts section}).
24650 This is useful because their names are not printed when @value{GDBN}
24651 tries to load them and fails. There may be many of them, and printing
24652 an error message for each one is problematic.
24654 If @var{regexp} is supplied only scripts with matching names are printed.
24659 (gdb) info auto-load-scripts
24661 Yes py-section-script.py
24662 full name: /tmp/py-section-script.py
24663 Missing my-foo-pretty-printers.py
24667 When reading an auto-loaded file, @value{GDBN} sets the
24668 @dfn{current objfile}. This is available via the @code{gdb.current_objfile}
24669 function (@pxref{Objfiles In Python}). This can be useful for
24670 registering objfile-specific pretty-printers.
24672 @node objfile-gdb.py file
24673 @subsubsection The @file{@var{objfile}-gdb.py} file
24674 @cindex @file{@var{objfile}-gdb.py}
24676 When a new object file is read, @value{GDBN} looks for
24677 a file named @file{@var{objfile}-gdb.py},
24678 where @var{objfile} is the object file's real name, formed by ensuring
24679 that the file name is absolute, following all symlinks, and resolving
24680 @code{.} and @code{..} components. If this file exists and is
24681 readable, @value{GDBN} will evaluate it as a Python script.
24683 If this file does not exist, and if the parameter
24684 @code{debug-file-directory} is set (@pxref{Separate Debug Files}),
24685 then @value{GDBN} will look for @var{real-name} in all of the
24686 directories mentioned in the value of @code{debug-file-directory}.
24688 Finally, if this file does not exist, then @value{GDBN} will look for
24689 a file named @file{@var{data-directory}/auto-load/@var{real-name}}, where
24690 @var{data-directory} is @value{GDBN}'s data directory (available via
24691 @code{show data-directory}, @pxref{Data Files}), and @var{real-name}
24692 is the object file's real name, as described above.
24694 @value{GDBN} does not track which files it has already auto-loaded this way.
24695 @value{GDBN} will load the associated script every time the corresponding
24696 @var{objfile} is opened.
24697 So your @file{-gdb.py} file should be careful to avoid errors if it
24698 is evaluated more than once.
24700 @node .debug_gdb_scripts section
24701 @subsubsection The @code{.debug_gdb_scripts} section
24702 @cindex @code{.debug_gdb_scripts} section
24704 For systems using file formats like ELF and COFF,
24705 when @value{GDBN} loads a new object file
24706 it will look for a special section named @samp{.debug_gdb_scripts}.
24707 If this section exists, its contents is a list of names of scripts to load.
24709 @value{GDBN} will look for each specified script file first in the
24710 current directory and then along the source search path
24711 (@pxref{Source Path, ,Specifying Source Directories}),
24712 except that @file{$cdir} is not searched, since the compilation
24713 directory is not relevant to scripts.
24715 Entries can be placed in section @code{.debug_gdb_scripts} with,
24716 for example, this GCC macro:
24719 /* Note: The "MS" section flags are to remove duplicates. */
24720 #define DEFINE_GDB_SCRIPT(script_name) \
24722 .pushsection \".debug_gdb_scripts\", \"MS\",@@progbits,1\n\
24724 .asciz \"" script_name "\"\n\
24730 Then one can reference the macro in a header or source file like this:
24733 DEFINE_GDB_SCRIPT ("my-app-scripts.py")
24736 The script name may include directories if desired.
24738 If the macro is put in a header, any application or library
24739 using this header will get a reference to the specified script.
24741 @node Which flavor to choose?
24742 @subsubsection Which flavor to choose?
24744 Given the multiple ways of auto-loading Python scripts, it might not always
24745 be clear which one to choose. This section provides some guidance.
24747 Benefits of the @file{-gdb.py} way:
24751 Can be used with file formats that don't support multiple sections.
24754 Ease of finding scripts for public libraries.
24756 Scripts specified in the @code{.debug_gdb_scripts} section are searched for
24757 in the source search path.
24758 For publicly installed libraries, e.g., @file{libstdc++}, there typically
24759 isn't a source directory in which to find the script.
24762 Doesn't require source code additions.
24765 Benefits of the @code{.debug_gdb_scripts} way:
24769 Works with static linking.
24771 Scripts for libraries done the @file{-gdb.py} way require an objfile to
24772 trigger their loading. When an application is statically linked the only
24773 objfile available is the executable, and it is cumbersome to attach all the
24774 scripts from all the input libraries to the executable's @file{-gdb.py} script.
24777 Works with classes that are entirely inlined.
24779 Some classes can be entirely inlined, and thus there may not be an associated
24780 shared library to attach a @file{-gdb.py} script to.
24783 Scripts needn't be copied out of the source tree.
24785 In some circumstances, apps can be built out of large collections of internal
24786 libraries, and the build infrastructure necessary to install the
24787 @file{-gdb.py} scripts in a place where @value{GDBN} can find them is
24788 cumbersome. It may be easier to specify the scripts in the
24789 @code{.debug_gdb_scripts} section as relative paths, and add a path to the
24790 top of the source tree to the source search path.
24793 @node Python modules
24794 @subsection Python modules
24795 @cindex python modules
24797 @value{GDBN} comes with several modules to assist writing Python code.
24800 * gdb.printing:: Building and registering pretty-printers.
24801 * gdb.types:: Utilities for working with types.
24802 * gdb.prompt:: Utilities for prompt value substitution.
24806 @subsubsection gdb.printing
24807 @cindex gdb.printing
24809 This module provides a collection of utilities for working with
24813 @item PrettyPrinter (@var{name}, @var{subprinters}=None)
24814 This class specifies the API that makes @samp{info pretty-printer},
24815 @samp{enable pretty-printer} and @samp{disable pretty-printer} work.
24816 Pretty-printers should generally inherit from this class.
24818 @item SubPrettyPrinter (@var{name})
24819 For printers that handle multiple types, this class specifies the
24820 corresponding API for the subprinters.
24822 @item RegexpCollectionPrettyPrinter (@var{name})
24823 Utility class for handling multiple printers, all recognized via
24824 regular expressions.
24825 @xref{Writing a Pretty-Printer}, for an example.
24827 @item FlagEnumerationPrinter (@var{name})
24828 A pretty-printer which handles printing of @code{enum} values. Unlike
24829 @value{GDBN}'s built-in @code{enum} printing, this printer attempts to
24830 work properly when there is some overlap between the enumeration
24831 constants. @var{name} is the name of the printer and also the name of
24832 the @code{enum} type to look up.
24834 @item register_pretty_printer (@var{obj}, @var{printer}, @var{replace}=False)
24835 Register @var{printer} with the pretty-printer list of @var{obj}.
24836 If @var{replace} is @code{True} then any existing copy of the printer
24837 is replaced. Otherwise a @code{RuntimeError} exception is raised
24838 if a printer with the same name already exists.
24842 @subsubsection gdb.types
24845 This module provides a collection of utilities for working with
24846 @code{gdb.Types} objects.
24849 @item get_basic_type (@var{type})
24850 Return @var{type} with const and volatile qualifiers stripped,
24851 and with typedefs and C@t{++} references converted to the underlying type.
24856 typedef const int const_int;
24858 const_int& foo_ref (foo);
24859 int main () @{ return 0; @}
24866 (gdb) python import gdb.types
24867 (gdb) python foo_ref = gdb.parse_and_eval("foo_ref")
24868 (gdb) python print gdb.types.get_basic_type(foo_ref.type)
24872 @item has_field (@var{type}, @var{field})
24873 Return @code{True} if @var{type}, assumed to be a type with fields
24874 (e.g., a structure or union), has field @var{field}.
24876 @item make_enum_dict (@var{enum_type})
24877 Return a Python @code{dictionary} type produced from @var{enum_type}.
24879 @item deep_items (@var{type})
24880 Returns a Python iterator similar to the standard
24881 @code{gdb.Type.iteritems} method, except that the iterator returned
24882 by @code{deep_items} will recursively traverse anonymous struct or
24883 union fields. For example:
24897 Then in @value{GDBN}:
24899 (@value{GDBP}) python import gdb.types
24900 (@value{GDBP}) python struct_a = gdb.lookup_type("struct A")
24901 (@value{GDBP}) python print struct_a.keys ()
24903 (@value{GDBP}) python print [k for k,v in gdb.types.deep_items(struct_a)]
24904 @{['a', 'b0', 'b1']@}
24910 @subsubsection gdb.prompt
24913 This module provides a method for prompt value-substitution.
24916 @item substitute_prompt (@var{string})
24917 Return @var{string} with escape sequences substituted by values. Some
24918 escape sequences take arguments. You can specify arguments inside
24919 ``@{@}'' immediately following the escape sequence.
24921 The escape sequences you can pass to this function are:
24925 Substitute a backslash.
24927 Substitute an ESC character.
24929 Substitute the selected frame; an argument names a frame parameter.
24931 Substitute a newline.
24933 Substitute a parameter's value; the argument names the parameter.
24935 Substitute a carriage return.
24937 Substitute the selected thread; an argument names a thread parameter.
24939 Substitute the version of GDB.
24941 Substitute the current working directory.
24943 Begin a sequence of non-printing characters. These sequences are
24944 typically used with the ESC character, and are not counted in the string
24945 length. Example: ``\[\e[0;34m\](gdb)\[\e[0m\]'' will return a
24946 blue-colored ``(gdb)'' prompt where the length is five.
24948 End a sequence of non-printing characters.
24954 substitute_prompt (``frame: \f,
24955 print arguments: \p@{print frame-arguments@}'')
24958 @exdent will return the string:
24961 "frame: main, print arguments: scalars"
24966 @section Creating new spellings of existing commands
24967 @cindex aliases for commands
24969 It is often useful to define alternate spellings of existing commands.
24970 For example, if a new @value{GDBN} command defined in Python has
24971 a long name to type, it is handy to have an abbreviated version of it
24972 that involves less typing.
24974 @value{GDBN} itself uses aliases. For example @samp{s} is an alias
24975 of the @samp{step} command even though it is otherwise an ambiguous
24976 abbreviation of other commands like @samp{set} and @samp{show}.
24978 Aliases are also used to provide shortened or more common versions
24979 of multi-word commands. For example, @value{GDBN} provides the
24980 @samp{tty} alias of the @samp{set inferior-tty} command.
24982 You can define a new alias with the @samp{alias} command.
24987 @item alias [-a] [--] @var{ALIAS} = @var{COMMAND}
24991 @var{ALIAS} specifies the name of the new alias.
24992 Each word of @var{ALIAS} must consist of letters, numbers, dashes and
24995 @var{COMMAND} specifies the name of an existing command
24996 that is being aliased.
24998 The @samp{-a} option specifies that the new alias is an abbreviation
24999 of the command. Abbreviations are not shown in command
25000 lists displayed by the @samp{help} command.
25002 The @samp{--} option specifies the end of options,
25003 and is useful when @var{ALIAS} begins with a dash.
25005 Here is a simple example showing how to make an abbreviation
25006 of a command so that there is less to type.
25007 Suppose you were tired of typing @samp{disas}, the current
25008 shortest unambiguous abbreviation of the @samp{disassemble} command
25009 and you wanted an even shorter version named @samp{di}.
25010 The following will accomplish this.
25013 (gdb) alias -a di = disas
25016 Note that aliases are different from user-defined commands.
25017 With a user-defined command, you also need to write documentation
25018 for it with the @samp{document} command.
25019 An alias automatically picks up the documentation of the existing command.
25021 Here is an example where we make @samp{elms} an abbreviation of
25022 @samp{elements} in the @samp{set print elements} command.
25023 This is to show that you can make an abbreviation of any part
25027 (gdb) alias -a set print elms = set print elements
25028 (gdb) alias -a show print elms = show print elements
25029 (gdb) set p elms 20
25031 Limit on string chars or array elements to print is 200.
25034 Note that if you are defining an alias of a @samp{set} command,
25035 and you want to have an alias for the corresponding @samp{show}
25036 command, then you need to define the latter separately.
25038 Unambiguously abbreviated commands are allowed in @var{COMMAND} and
25039 @var{ALIAS}, just as they are normally.
25042 (gdb) alias -a set pr elms = set p ele
25045 Finally, here is an example showing the creation of a one word
25046 alias for a more complex command.
25047 This creates alias @samp{spe} of the command @samp{set print elements}.
25050 (gdb) alias spe = set print elements
25055 @chapter Command Interpreters
25056 @cindex command interpreters
25058 @value{GDBN} supports multiple command interpreters, and some command
25059 infrastructure to allow users or user interface writers to switch
25060 between interpreters or run commands in other interpreters.
25062 @value{GDBN} currently supports two command interpreters, the console
25063 interpreter (sometimes called the command-line interpreter or @sc{cli})
25064 and the machine interface interpreter (or @sc{gdb/mi}). This manual
25065 describes both of these interfaces in great detail.
25067 By default, @value{GDBN} will start with the console interpreter.
25068 However, the user may choose to start @value{GDBN} with another
25069 interpreter by specifying the @option{-i} or @option{--interpreter}
25070 startup options. Defined interpreters include:
25074 @cindex console interpreter
25075 The traditional console or command-line interpreter. This is the most often
25076 used interpreter with @value{GDBN}. With no interpreter specified at runtime,
25077 @value{GDBN} will use this interpreter.
25080 @cindex mi interpreter
25081 The newest @sc{gdb/mi} interface (currently @code{mi2}). Used primarily
25082 by programs wishing to use @value{GDBN} as a backend for a debugger GUI
25083 or an IDE. For more information, see @ref{GDB/MI, ,The @sc{gdb/mi}
25087 @cindex mi2 interpreter
25088 The current @sc{gdb/mi} interface.
25091 @cindex mi1 interpreter
25092 The @sc{gdb/mi} interface included in @value{GDBN} 5.1, 5.2, and 5.3.
25096 @cindex invoke another interpreter
25097 The interpreter being used by @value{GDBN} may not be dynamically
25098 switched at runtime. Although possible, this could lead to a very
25099 precarious situation. Consider an IDE using @sc{gdb/mi}. If a user
25100 enters the command "interpreter-set console" in a console view,
25101 @value{GDBN} would switch to using the console interpreter, rendering
25102 the IDE inoperable!
25104 @kindex interpreter-exec
25105 Although you may only choose a single interpreter at startup, you may execute
25106 commands in any interpreter from the current interpreter using the appropriate
25107 command. If you are running the console interpreter, simply use the
25108 @code{interpreter-exec} command:
25111 interpreter-exec mi "-data-list-register-names"
25114 @sc{gdb/mi} has a similar command, although it is only available in versions of
25115 @value{GDBN} which support @sc{gdb/mi} version 2 (or greater).
25118 @chapter @value{GDBN} Text User Interface
25120 @cindex Text User Interface
25123 * TUI Overview:: TUI overview
25124 * TUI Keys:: TUI key bindings
25125 * TUI Single Key Mode:: TUI single key mode
25126 * TUI Commands:: TUI-specific commands
25127 * TUI Configuration:: TUI configuration variables
25130 The @value{GDBN} Text User Interface (TUI) is a terminal
25131 interface which uses the @code{curses} library to show the source
25132 file, the assembly output, the program registers and @value{GDBN}
25133 commands in separate text windows. The TUI mode is supported only
25134 on platforms where a suitable version of the @code{curses} library
25137 The TUI mode is enabled by default when you invoke @value{GDBN} as
25138 @samp{@value{GDBP} -tui}.
25139 You can also switch in and out of TUI mode while @value{GDBN} runs by
25140 using various TUI commands and key bindings, such as @kbd{C-x C-a}.
25141 @xref{TUI Keys, ,TUI Key Bindings}.
25144 @section TUI Overview
25146 In TUI mode, @value{GDBN} can display several text windows:
25150 This window is the @value{GDBN} command window with the @value{GDBN}
25151 prompt and the @value{GDBN} output. The @value{GDBN} input is still
25152 managed using readline.
25155 The source window shows the source file of the program. The current
25156 line and active breakpoints are displayed in this window.
25159 The assembly window shows the disassembly output of the program.
25162 This window shows the processor registers. Registers are highlighted
25163 when their values change.
25166 The source and assembly windows show the current program position
25167 by highlighting the current line and marking it with a @samp{>} marker.
25168 Breakpoints are indicated with two markers. The first marker
25169 indicates the breakpoint type:
25173 Breakpoint which was hit at least once.
25176 Breakpoint which was never hit.
25179 Hardware breakpoint which was hit at least once.
25182 Hardware breakpoint which was never hit.
25185 The second marker indicates whether the breakpoint is enabled or not:
25189 Breakpoint is enabled.
25192 Breakpoint is disabled.
25195 The source, assembly and register windows are updated when the current
25196 thread changes, when the frame changes, or when the program counter
25199 These windows are not all visible at the same time. The command
25200 window is always visible. The others can be arranged in several
25211 source and assembly,
25214 source and registers, or
25217 assembly and registers.
25220 A status line above the command window shows the following information:
25224 Indicates the current @value{GDBN} target.
25225 (@pxref{Targets, ,Specifying a Debugging Target}).
25228 Gives the current process or thread number.
25229 When no process is being debugged, this field is set to @code{No process}.
25232 Gives the current function name for the selected frame.
25233 The name is demangled if demangling is turned on (@pxref{Print Settings}).
25234 When there is no symbol corresponding to the current program counter,
25235 the string @code{??} is displayed.
25238 Indicates the current line number for the selected frame.
25239 When the current line number is not known, the string @code{??} is displayed.
25242 Indicates the current program counter address.
25246 @section TUI Key Bindings
25247 @cindex TUI key bindings
25249 The TUI installs several key bindings in the readline keymaps
25250 @ifset SYSTEM_READLINE
25251 (@pxref{Command Line Editing, , , rluserman, GNU Readline Library}).
25253 @ifclear SYSTEM_READLINE
25254 (@pxref{Command Line Editing}).
25256 The following key bindings are installed for both TUI mode and the
25257 @value{GDBN} standard mode.
25266 Enter or leave the TUI mode. When leaving the TUI mode,
25267 the curses window management stops and @value{GDBN} operates using
25268 its standard mode, writing on the terminal directly. When reentering
25269 the TUI mode, control is given back to the curses windows.
25270 The screen is then refreshed.
25274 Use a TUI layout with only one window. The layout will
25275 either be @samp{source} or @samp{assembly}. When the TUI mode
25276 is not active, it will switch to the TUI mode.
25278 Think of this key binding as the Emacs @kbd{C-x 1} binding.
25282 Use a TUI layout with at least two windows. When the current
25283 layout already has two windows, the next layout with two windows is used.
25284 When a new layout is chosen, one window will always be common to the
25285 previous layout and the new one.
25287 Think of it as the Emacs @kbd{C-x 2} binding.
25291 Change the active window. The TUI associates several key bindings
25292 (like scrolling and arrow keys) with the active window. This command
25293 gives the focus to the next TUI window.
25295 Think of it as the Emacs @kbd{C-x o} binding.
25299 Switch in and out of the TUI SingleKey mode that binds single
25300 keys to @value{GDBN} commands (@pxref{TUI Single Key Mode}).
25303 The following key bindings only work in the TUI mode:
25308 Scroll the active window one page up.
25312 Scroll the active window one page down.
25316 Scroll the active window one line up.
25320 Scroll the active window one line down.
25324 Scroll the active window one column left.
25328 Scroll the active window one column right.
25332 Refresh the screen.
25335 Because the arrow keys scroll the active window in the TUI mode, they
25336 are not available for their normal use by readline unless the command
25337 window has the focus. When another window is active, you must use
25338 other readline key bindings such as @kbd{C-p}, @kbd{C-n}, @kbd{C-b}
25339 and @kbd{C-f} to control the command window.
25341 @node TUI Single Key Mode
25342 @section TUI Single Key Mode
25343 @cindex TUI single key mode
25345 The TUI also provides a @dfn{SingleKey} mode, which binds several
25346 frequently used @value{GDBN} commands to single keys. Type @kbd{C-x s} to
25347 switch into this mode, where the following key bindings are used:
25350 @kindex c @r{(SingleKey TUI key)}
25354 @kindex d @r{(SingleKey TUI key)}
25358 @kindex f @r{(SingleKey TUI key)}
25362 @kindex n @r{(SingleKey TUI key)}
25366 @kindex q @r{(SingleKey TUI key)}
25368 exit the SingleKey mode.
25370 @kindex r @r{(SingleKey TUI key)}
25374 @kindex s @r{(SingleKey TUI key)}
25378 @kindex u @r{(SingleKey TUI key)}
25382 @kindex v @r{(SingleKey TUI key)}
25386 @kindex w @r{(SingleKey TUI key)}
25391 Other keys temporarily switch to the @value{GDBN} command prompt.
25392 The key that was pressed is inserted in the editing buffer so that
25393 it is possible to type most @value{GDBN} commands without interaction
25394 with the TUI SingleKey mode. Once the command is entered the TUI
25395 SingleKey mode is restored. The only way to permanently leave
25396 this mode is by typing @kbd{q} or @kbd{C-x s}.
25400 @section TUI-specific Commands
25401 @cindex TUI commands
25403 The TUI has specific commands to control the text windows.
25404 These commands are always available, even when @value{GDBN} is not in
25405 the TUI mode. When @value{GDBN} is in the standard mode, most
25406 of these commands will automatically switch to the TUI mode.
25408 Note that if @value{GDBN}'s @code{stdout} is not connected to a
25409 terminal, or @value{GDBN} has been started with the machine interface
25410 interpreter (@pxref{GDB/MI, ,The @sc{gdb/mi} Interface}), most of
25411 these commands will fail with an error, because it would not be
25412 possible or desirable to enable curses window management.
25417 List and give the size of all displayed windows.
25421 Display the next layout.
25424 Display the previous layout.
25427 Display the source window only.
25430 Display the assembly window only.
25433 Display the source and assembly window.
25436 Display the register window together with the source or assembly window.
25440 Make the next window active for scrolling.
25443 Make the previous window active for scrolling.
25446 Make the source window active for scrolling.
25449 Make the assembly window active for scrolling.
25452 Make the register window active for scrolling.
25455 Make the command window active for scrolling.
25459 Refresh the screen. This is similar to typing @kbd{C-L}.
25461 @item tui reg float
25463 Show the floating point registers in the register window.
25465 @item tui reg general
25466 Show the general registers in the register window.
25469 Show the next register group. The list of register groups as well as
25470 their order is target specific. The predefined register groups are the
25471 following: @code{general}, @code{float}, @code{system}, @code{vector},
25472 @code{all}, @code{save}, @code{restore}.
25474 @item tui reg system
25475 Show the system registers in the register window.
25479 Update the source window and the current execution point.
25481 @item winheight @var{name} +@var{count}
25482 @itemx winheight @var{name} -@var{count}
25484 Change the height of the window @var{name} by @var{count}
25485 lines. Positive counts increase the height, while negative counts
25488 @item tabset @var{nchars}
25490 Set the width of tab stops to be @var{nchars} characters.
25493 @node TUI Configuration
25494 @section TUI Configuration Variables
25495 @cindex TUI configuration variables
25497 Several configuration variables control the appearance of TUI windows.
25500 @item set tui border-kind @var{kind}
25501 @kindex set tui border-kind
25502 Select the border appearance for the source, assembly and register windows.
25503 The possible values are the following:
25506 Use a space character to draw the border.
25509 Use @sc{ascii} characters @samp{+}, @samp{-} and @samp{|} to draw the border.
25512 Use the Alternate Character Set to draw the border. The border is
25513 drawn using character line graphics if the terminal supports them.
25516 @item set tui border-mode @var{mode}
25517 @kindex set tui border-mode
25518 @itemx set tui active-border-mode @var{mode}
25519 @kindex set tui active-border-mode
25520 Select the display attributes for the borders of the inactive windows
25521 or the active window. The @var{mode} can be one of the following:
25524 Use normal attributes to display the border.
25530 Use reverse video mode.
25533 Use half bright mode.
25535 @item half-standout
25536 Use half bright and standout mode.
25539 Use extra bright or bold mode.
25541 @item bold-standout
25542 Use extra bright or bold and standout mode.
25547 @chapter Using @value{GDBN} under @sc{gnu} Emacs
25550 @cindex @sc{gnu} Emacs
25551 A special interface allows you to use @sc{gnu} Emacs to view (and
25552 edit) the source files for the program you are debugging with
25555 To use this interface, use the command @kbd{M-x gdb} in Emacs. Give the
25556 executable file you want to debug as an argument. This command starts
25557 @value{GDBN} as a subprocess of Emacs, with input and output through a newly
25558 created Emacs buffer.
25559 @c (Do not use the @code{-tui} option to run @value{GDBN} from Emacs.)
25561 Running @value{GDBN} under Emacs can be just like running @value{GDBN} normally except for two
25566 All ``terminal'' input and output goes through an Emacs buffer, called
25569 This applies both to @value{GDBN} commands and their output, and to the input
25570 and output done by the program you are debugging.
25572 This is useful because it means that you can copy the text of previous
25573 commands and input them again; you can even use parts of the output
25576 All the facilities of Emacs' Shell mode are available for interacting
25577 with your program. In particular, you can send signals the usual
25578 way---for example, @kbd{C-c C-c} for an interrupt, @kbd{C-c C-z} for a
25582 @value{GDBN} displays source code through Emacs.
25584 Each time @value{GDBN} displays a stack frame, Emacs automatically finds the
25585 source file for that frame and puts an arrow (@samp{=>}) at the
25586 left margin of the current line. Emacs uses a separate buffer for
25587 source display, and splits the screen to show both your @value{GDBN} session
25590 Explicit @value{GDBN} @code{list} or search commands still produce output as
25591 usual, but you probably have no reason to use them from Emacs.
25594 We call this @dfn{text command mode}. Emacs 22.1, and later, also uses
25595 a graphical mode, enabled by default, which provides further buffers
25596 that can control the execution and describe the state of your program.
25597 @xref{GDB Graphical Interface,,, Emacs, The @sc{gnu} Emacs Manual}.
25599 If you specify an absolute file name when prompted for the @kbd{M-x
25600 gdb} argument, then Emacs sets your current working directory to where
25601 your program resides. If you only specify the file name, then Emacs
25602 sets your current working directory to the directory associated
25603 with the previous buffer. In this case, @value{GDBN} may find your
25604 program by searching your environment's @code{PATH} variable, but on
25605 some operating systems it might not find the source. So, although the
25606 @value{GDBN} input and output session proceeds normally, the auxiliary
25607 buffer does not display the current source and line of execution.
25609 The initial working directory of @value{GDBN} is printed on the top
25610 line of the GUD buffer and this serves as a default for the commands
25611 that specify files for @value{GDBN} to operate on. @xref{Files,
25612 ,Commands to Specify Files}.
25614 By default, @kbd{M-x gdb} calls the program called @file{gdb}. If you
25615 need to call @value{GDBN} by a different name (for example, if you
25616 keep several configurations around, with different names) you can
25617 customize the Emacs variable @code{gud-gdb-command-name} to run the
25620 In the GUD buffer, you can use these special Emacs commands in
25621 addition to the standard Shell mode commands:
25625 Describe the features of Emacs' GUD Mode.
25628 Execute to another source line, like the @value{GDBN} @code{step} command; also
25629 update the display window to show the current file and location.
25632 Execute to next source line in this function, skipping all function
25633 calls, like the @value{GDBN} @code{next} command. Then update the display window
25634 to show the current file and location.
25637 Execute one instruction, like the @value{GDBN} @code{stepi} command; update
25638 display window accordingly.
25641 Execute until exit from the selected stack frame, like the @value{GDBN}
25642 @code{finish} command.
25645 Continue execution of your program, like the @value{GDBN} @code{continue}
25649 Go up the number of frames indicated by the numeric argument
25650 (@pxref{Arguments, , Numeric Arguments, Emacs, The @sc{gnu} Emacs Manual}),
25651 like the @value{GDBN} @code{up} command.
25654 Go down the number of frames indicated by the numeric argument, like the
25655 @value{GDBN} @code{down} command.
25658 In any source file, the Emacs command @kbd{C-x @key{SPC}} (@code{gud-break})
25659 tells @value{GDBN} to set a breakpoint on the source line point is on.
25661 In text command mode, if you type @kbd{M-x speedbar}, Emacs displays a
25662 separate frame which shows a backtrace when the GUD buffer is current.
25663 Move point to any frame in the stack and type @key{RET} to make it
25664 become the current frame and display the associated source in the
25665 source buffer. Alternatively, click @kbd{Mouse-2} to make the
25666 selected frame become the current one. In graphical mode, the
25667 speedbar displays watch expressions.
25669 If you accidentally delete the source-display buffer, an easy way to get
25670 it back is to type the command @code{f} in the @value{GDBN} buffer, to
25671 request a frame display; when you run under Emacs, this recreates
25672 the source buffer if necessary to show you the context of the current
25675 The source files displayed in Emacs are in ordinary Emacs buffers
25676 which are visiting the source files in the usual way. You can edit
25677 the files with these buffers if you wish; but keep in mind that @value{GDBN}
25678 communicates with Emacs in terms of line numbers. If you add or
25679 delete lines from the text, the line numbers that @value{GDBN} knows cease
25680 to correspond properly with the code.
25682 A more detailed description of Emacs' interaction with @value{GDBN} is
25683 given in the Emacs manual (@pxref{Debuggers,,, Emacs, The @sc{gnu}
25686 @c The following dropped because Epoch is nonstandard. Reactivate
25687 @c if/when v19 does something similar. ---doc@cygnus.com 19dec1990
25689 @kindex Emacs Epoch environment
25693 Version 18 of @sc{gnu} Emacs has a built-in window system
25694 called the @code{epoch}
25695 environment. Users of this environment can use a new command,
25696 @code{inspect} which performs identically to @code{print} except that
25697 each value is printed in its own window.
25702 @chapter The @sc{gdb/mi} Interface
25704 @unnumberedsec Function and Purpose
25706 @cindex @sc{gdb/mi}, its purpose
25707 @sc{gdb/mi} is a line based machine oriented text interface to
25708 @value{GDBN} and is activated by specifying using the
25709 @option{--interpreter} command line option (@pxref{Mode Options}). It
25710 is specifically intended to support the development of systems which
25711 use the debugger as just one small component of a larger system.
25713 This chapter is a specification of the @sc{gdb/mi} interface. It is written
25714 in the form of a reference manual.
25716 Note that @sc{gdb/mi} is still under construction, so some of the
25717 features described below are incomplete and subject to change
25718 (@pxref{GDB/MI Development and Front Ends, , @sc{gdb/mi} Development and Front Ends}).
25720 @unnumberedsec Notation and Terminology
25722 @cindex notational conventions, for @sc{gdb/mi}
25723 This chapter uses the following notation:
25727 @code{|} separates two alternatives.
25730 @code{[ @var{something} ]} indicates that @var{something} is optional:
25731 it may or may not be given.
25734 @code{( @var{group} )*} means that @var{group} inside the parentheses
25735 may repeat zero or more times.
25738 @code{( @var{group} )+} means that @var{group} inside the parentheses
25739 may repeat one or more times.
25742 @code{"@var{string}"} means a literal @var{string}.
25746 @heading Dependencies
25750 * GDB/MI General Design::
25751 * GDB/MI Command Syntax::
25752 * GDB/MI Compatibility with CLI::
25753 * GDB/MI Development and Front Ends::
25754 * GDB/MI Output Records::
25755 * GDB/MI Simple Examples::
25756 * GDB/MI Command Description Format::
25757 * GDB/MI Breakpoint Commands::
25758 * GDB/MI Program Context::
25759 * GDB/MI Thread Commands::
25760 * GDB/MI Ada Tasking Commands::
25761 * GDB/MI Program Execution::
25762 * GDB/MI Stack Manipulation::
25763 * GDB/MI Variable Objects::
25764 * GDB/MI Data Manipulation::
25765 * GDB/MI Tracepoint Commands::
25766 * GDB/MI Symbol Query::
25767 * GDB/MI File Commands::
25769 * GDB/MI Kod Commands::
25770 * GDB/MI Memory Overlay Commands::
25771 * GDB/MI Signal Handling Commands::
25773 * GDB/MI Target Manipulation::
25774 * GDB/MI File Transfer Commands::
25775 * GDB/MI Miscellaneous Commands::
25778 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
25779 @node GDB/MI General Design
25780 @section @sc{gdb/mi} General Design
25781 @cindex GDB/MI General Design
25783 Interaction of a @sc{GDB/MI} frontend with @value{GDBN} involves three
25784 parts---commands sent to @value{GDBN}, responses to those commands
25785 and notifications. Each command results in exactly one response,
25786 indicating either successful completion of the command, or an error.
25787 For the commands that do not resume the target, the response contains the
25788 requested information. For the commands that resume the target, the
25789 response only indicates whether the target was successfully resumed.
25790 Notifications is the mechanism for reporting changes in the state of the
25791 target, or in @value{GDBN} state, that cannot conveniently be associated with
25792 a command and reported as part of that command response.
25794 The important examples of notifications are:
25798 Exec notifications. These are used to report changes in
25799 target state---when a target is resumed, or stopped. It would not
25800 be feasible to include this information in response of resuming
25801 commands, because one resume commands can result in multiple events in
25802 different threads. Also, quite some time may pass before any event
25803 happens in the target, while a frontend needs to know whether the resuming
25804 command itself was successfully executed.
25807 Console output, and status notifications. Console output
25808 notifications are used to report output of CLI commands, as well as
25809 diagnostics for other commands. Status notifications are used to
25810 report the progress of a long-running operation. Naturally, including
25811 this information in command response would mean no output is produced
25812 until the command is finished, which is undesirable.
25815 General notifications. Commands may have various side effects on
25816 the @value{GDBN} or target state beyond their official purpose. For example,
25817 a command may change the selected thread. Although such changes can
25818 be included in command response, using notification allows for more
25819 orthogonal frontend design.
25823 There's no guarantee that whenever an MI command reports an error,
25824 @value{GDBN} or the target are in any specific state, and especially,
25825 the state is not reverted to the state before the MI command was
25826 processed. Therefore, whenever an MI command results in an error,
25827 we recommend that the frontend refreshes all the information shown in
25828 the user interface.
25832 * Context management::
25833 * Asynchronous and non-stop modes::
25837 @node Context management
25838 @subsection Context management
25840 In most cases when @value{GDBN} accesses the target, this access is
25841 done in context of a specific thread and frame (@pxref{Frames}).
25842 Often, even when accessing global data, the target requires that a thread
25843 be specified. The CLI interface maintains the selected thread and frame,
25844 and supplies them to target on each command. This is convenient,
25845 because a command line user would not want to specify that information
25846 explicitly on each command, and because user interacts with
25847 @value{GDBN} via a single terminal, so no confusion is possible as
25848 to what thread and frame are the current ones.
25850 In the case of MI, the concept of selected thread and frame is less
25851 useful. First, a frontend can easily remember this information
25852 itself. Second, a graphical frontend can have more than one window,
25853 each one used for debugging a different thread, and the frontend might
25854 want to access additional threads for internal purposes. This
25855 increases the risk that by relying on implicitly selected thread, the
25856 frontend may be operating on a wrong one. Therefore, each MI command
25857 should explicitly specify which thread and frame to operate on. To
25858 make it possible, each MI command accepts the @samp{--thread} and
25859 @samp{--frame} options, the value to each is @value{GDBN} identifier
25860 for thread and frame to operate on.
25862 Usually, each top-level window in a frontend allows the user to select
25863 a thread and a frame, and remembers the user selection for further
25864 operations. However, in some cases @value{GDBN} may suggest that the
25865 current thread be changed. For example, when stopping on a breakpoint
25866 it is reasonable to switch to the thread where breakpoint is hit. For
25867 another example, if the user issues the CLI @samp{thread} command via
25868 the frontend, it is desirable to change the frontend's selected thread to the
25869 one specified by user. @value{GDBN} communicates the suggestion to
25870 change current thread using the @samp{=thread-selected} notification.
25871 No such notification is available for the selected frame at the moment.
25873 Note that historically, MI shares the selected thread with CLI, so
25874 frontends used the @code{-thread-select} to execute commands in the
25875 right context. However, getting this to work right is cumbersome. The
25876 simplest way is for frontend to emit @code{-thread-select} command
25877 before every command. This doubles the number of commands that need
25878 to be sent. The alternative approach is to suppress @code{-thread-select}
25879 if the selected thread in @value{GDBN} is supposed to be identical to the
25880 thread the frontend wants to operate on. However, getting this
25881 optimization right can be tricky. In particular, if the frontend
25882 sends several commands to @value{GDBN}, and one of the commands changes the
25883 selected thread, then the behaviour of subsequent commands will
25884 change. So, a frontend should either wait for response from such
25885 problematic commands, or explicitly add @code{-thread-select} for
25886 all subsequent commands. No frontend is known to do this exactly
25887 right, so it is suggested to just always pass the @samp{--thread} and
25888 @samp{--frame} options.
25890 @node Asynchronous and non-stop modes
25891 @subsection Asynchronous command execution and non-stop mode
25893 On some targets, @value{GDBN} is capable of processing MI commands
25894 even while the target is running. This is called @dfn{asynchronous
25895 command execution} (@pxref{Background Execution}). The frontend may
25896 specify a preferrence for asynchronous execution using the
25897 @code{-gdb-set target-async 1} command, which should be emitted before
25898 either running the executable or attaching to the target. After the
25899 frontend has started the executable or attached to the target, it can
25900 find if asynchronous execution is enabled using the
25901 @code{-list-target-features} command.
25903 Even if @value{GDBN} can accept a command while target is running,
25904 many commands that access the target do not work when the target is
25905 running. Therefore, asynchronous command execution is most useful
25906 when combined with non-stop mode (@pxref{Non-Stop Mode}). Then,
25907 it is possible to examine the state of one thread, while other threads
25910 When a given thread is running, MI commands that try to access the
25911 target in the context of that thread may not work, or may work only on
25912 some targets. In particular, commands that try to operate on thread's
25913 stack will not work, on any target. Commands that read memory, or
25914 modify breakpoints, may work or not work, depending on the target. Note
25915 that even commands that operate on global state, such as @code{print},
25916 @code{set}, and breakpoint commands, still access the target in the
25917 context of a specific thread, so frontend should try to find a
25918 stopped thread and perform the operation on that thread (using the
25919 @samp{--thread} option).
25921 Which commands will work in the context of a running thread is
25922 highly target dependent. However, the two commands
25923 @code{-exec-interrupt}, to stop a thread, and @code{-thread-info},
25924 to find the state of a thread, will always work.
25926 @node Thread groups
25927 @subsection Thread groups
25928 @value{GDBN} may be used to debug several processes at the same time.
25929 On some platfroms, @value{GDBN} may support debugging of several
25930 hardware systems, each one having several cores with several different
25931 processes running on each core. This section describes the MI
25932 mechanism to support such debugging scenarios.
25934 The key observation is that regardless of the structure of the
25935 target, MI can have a global list of threads, because most commands that
25936 accept the @samp{--thread} option do not need to know what process that
25937 thread belongs to. Therefore, it is not necessary to introduce
25938 neither additional @samp{--process} option, nor an notion of the
25939 current process in the MI interface. The only strictly new feature
25940 that is required is the ability to find how the threads are grouped
25943 To allow the user to discover such grouping, and to support arbitrary
25944 hierarchy of machines/cores/processes, MI introduces the concept of a
25945 @dfn{thread group}. Thread group is a collection of threads and other
25946 thread groups. A thread group always has a string identifier, a type,
25947 and may have additional attributes specific to the type. A new
25948 command, @code{-list-thread-groups}, returns the list of top-level
25949 thread groups, which correspond to processes that @value{GDBN} is
25950 debugging at the moment. By passing an identifier of a thread group
25951 to the @code{-list-thread-groups} command, it is possible to obtain
25952 the members of specific thread group.
25954 To allow the user to easily discover processes, and other objects, he
25955 wishes to debug, a concept of @dfn{available thread group} is
25956 introduced. Available thread group is an thread group that
25957 @value{GDBN} is not debugging, but that can be attached to, using the
25958 @code{-target-attach} command. The list of available top-level thread
25959 groups can be obtained using @samp{-list-thread-groups --available}.
25960 In general, the content of a thread group may be only retrieved only
25961 after attaching to that thread group.
25963 Thread groups are related to inferiors (@pxref{Inferiors and
25964 Programs}). Each inferior corresponds to a thread group of a special
25965 type @samp{process}, and some additional operations are permitted on
25966 such thread groups.
25968 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
25969 @node GDB/MI Command Syntax
25970 @section @sc{gdb/mi} Command Syntax
25973 * GDB/MI Input Syntax::
25974 * GDB/MI Output Syntax::
25977 @node GDB/MI Input Syntax
25978 @subsection @sc{gdb/mi} Input Syntax
25980 @cindex input syntax for @sc{gdb/mi}
25981 @cindex @sc{gdb/mi}, input syntax
25983 @item @var{command} @expansion{}
25984 @code{@var{cli-command} | @var{mi-command}}
25986 @item @var{cli-command} @expansion{}
25987 @code{[ @var{token} ] @var{cli-command} @var{nl}}, where
25988 @var{cli-command} is any existing @value{GDBN} CLI command.
25990 @item @var{mi-command} @expansion{}
25991 @code{[ @var{token} ] "-" @var{operation} ( " " @var{option} )*
25992 @code{[} " --" @code{]} ( " " @var{parameter} )* @var{nl}}
25994 @item @var{token} @expansion{}
25995 "any sequence of digits"
25997 @item @var{option} @expansion{}
25998 @code{"-" @var{parameter} [ " " @var{parameter} ]}
26000 @item @var{parameter} @expansion{}
26001 @code{@var{non-blank-sequence} | @var{c-string}}
26003 @item @var{operation} @expansion{}
26004 @emph{any of the operations described in this chapter}
26006 @item @var{non-blank-sequence} @expansion{}
26007 @emph{anything, provided it doesn't contain special characters such as
26008 "-", @var{nl}, """ and of course " "}
26010 @item @var{c-string} @expansion{}
26011 @code{""" @var{seven-bit-iso-c-string-content} """}
26013 @item @var{nl} @expansion{}
26022 The CLI commands are still handled by the @sc{mi} interpreter; their
26023 output is described below.
26026 The @code{@var{token}}, when present, is passed back when the command
26030 Some @sc{mi} commands accept optional arguments as part of the parameter
26031 list. Each option is identified by a leading @samp{-} (dash) and may be
26032 followed by an optional argument parameter. Options occur first in the
26033 parameter list and can be delimited from normal parameters using
26034 @samp{--} (this is useful when some parameters begin with a dash).
26041 We want easy access to the existing CLI syntax (for debugging).
26044 We want it to be easy to spot a @sc{mi} operation.
26047 @node GDB/MI Output Syntax
26048 @subsection @sc{gdb/mi} Output Syntax
26050 @cindex output syntax of @sc{gdb/mi}
26051 @cindex @sc{gdb/mi}, output syntax
26052 The output from @sc{gdb/mi} consists of zero or more out-of-band records
26053 followed, optionally, by a single result record. This result record
26054 is for the most recent command. The sequence of output records is
26055 terminated by @samp{(gdb)}.
26057 If an input command was prefixed with a @code{@var{token}} then the
26058 corresponding output for that command will also be prefixed by that same
26062 @item @var{output} @expansion{}
26063 @code{( @var{out-of-band-record} )* [ @var{result-record} ] "(gdb)" @var{nl}}
26065 @item @var{result-record} @expansion{}
26066 @code{ [ @var{token} ] "^" @var{result-class} ( "," @var{result} )* @var{nl}}
26068 @item @var{out-of-band-record} @expansion{}
26069 @code{@var{async-record} | @var{stream-record}}
26071 @item @var{async-record} @expansion{}
26072 @code{@var{exec-async-output} | @var{status-async-output} | @var{notify-async-output}}
26074 @item @var{exec-async-output} @expansion{}
26075 @code{[ @var{token} ] "*" @var{async-output}}
26077 @item @var{status-async-output} @expansion{}
26078 @code{[ @var{token} ] "+" @var{async-output}}
26080 @item @var{notify-async-output} @expansion{}
26081 @code{[ @var{token} ] "=" @var{async-output}}
26083 @item @var{async-output} @expansion{}
26084 @code{@var{async-class} ( "," @var{result} )* @var{nl}}
26086 @item @var{result-class} @expansion{}
26087 @code{"done" | "running" | "connected" | "error" | "exit"}
26089 @item @var{async-class} @expansion{}
26090 @code{"stopped" | @var{others}} (where @var{others} will be added
26091 depending on the needs---this is still in development).
26093 @item @var{result} @expansion{}
26094 @code{ @var{variable} "=" @var{value}}
26096 @item @var{variable} @expansion{}
26097 @code{ @var{string} }
26099 @item @var{value} @expansion{}
26100 @code{ @var{const} | @var{tuple} | @var{list} }
26102 @item @var{const} @expansion{}
26103 @code{@var{c-string}}
26105 @item @var{tuple} @expansion{}
26106 @code{ "@{@}" | "@{" @var{result} ( "," @var{result} )* "@}" }
26108 @item @var{list} @expansion{}
26109 @code{ "[]" | "[" @var{value} ( "," @var{value} )* "]" | "["
26110 @var{result} ( "," @var{result} )* "]" }
26112 @item @var{stream-record} @expansion{}
26113 @code{@var{console-stream-output} | @var{target-stream-output} | @var{log-stream-output}}
26115 @item @var{console-stream-output} @expansion{}
26116 @code{"~" @var{c-string}}
26118 @item @var{target-stream-output} @expansion{}
26119 @code{"@@" @var{c-string}}
26121 @item @var{log-stream-output} @expansion{}
26122 @code{"&" @var{c-string}}
26124 @item @var{nl} @expansion{}
26127 @item @var{token} @expansion{}
26128 @emph{any sequence of digits}.
26136 All output sequences end in a single line containing a period.
26139 The @code{@var{token}} is from the corresponding request. Note that
26140 for all async output, while the token is allowed by the grammar and
26141 may be output by future versions of @value{GDBN} for select async
26142 output messages, it is generally omitted. Frontends should treat
26143 all async output as reporting general changes in the state of the
26144 target and there should be no need to associate async output to any
26148 @cindex status output in @sc{gdb/mi}
26149 @var{status-async-output} contains on-going status information about the
26150 progress of a slow operation. It can be discarded. All status output is
26151 prefixed by @samp{+}.
26154 @cindex async output in @sc{gdb/mi}
26155 @var{exec-async-output} contains asynchronous state change on the target
26156 (stopped, started, disappeared). All async output is prefixed by
26160 @cindex notify output in @sc{gdb/mi}
26161 @var{notify-async-output} contains supplementary information that the
26162 client should handle (e.g., a new breakpoint information). All notify
26163 output is prefixed by @samp{=}.
26166 @cindex console output in @sc{gdb/mi}
26167 @var{console-stream-output} is output that should be displayed as is in the
26168 console. It is the textual response to a CLI command. All the console
26169 output is prefixed by @samp{~}.
26172 @cindex target output in @sc{gdb/mi}
26173 @var{target-stream-output} is the output produced by the target program.
26174 All the target output is prefixed by @samp{@@}.
26177 @cindex log output in @sc{gdb/mi}
26178 @var{log-stream-output} is output text coming from @value{GDBN}'s internals, for
26179 instance messages that should be displayed as part of an error log. All
26180 the log output is prefixed by @samp{&}.
26183 @cindex list output in @sc{gdb/mi}
26184 New @sc{gdb/mi} commands should only output @var{lists} containing
26190 @xref{GDB/MI Stream Records, , @sc{gdb/mi} Stream Records}, for more
26191 details about the various output records.
26193 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
26194 @node GDB/MI Compatibility with CLI
26195 @section @sc{gdb/mi} Compatibility with CLI
26197 @cindex compatibility, @sc{gdb/mi} and CLI
26198 @cindex @sc{gdb/mi}, compatibility with CLI
26200 For the developers convenience CLI commands can be entered directly,
26201 but there may be some unexpected behaviour. For example, commands
26202 that query the user will behave as if the user replied yes, breakpoint
26203 command lists are not executed and some CLI commands, such as
26204 @code{if}, @code{when} and @code{define}, prompt for further input with
26205 @samp{>}, which is not valid MI output.
26207 This feature may be removed at some stage in the future and it is
26208 recommended that front ends use the @code{-interpreter-exec} command
26209 (@pxref{-interpreter-exec}).
26211 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
26212 @node GDB/MI Development and Front Ends
26213 @section @sc{gdb/mi} Development and Front Ends
26214 @cindex @sc{gdb/mi} development
26216 The application which takes the MI output and presents the state of the
26217 program being debugged to the user is called a @dfn{front end}.
26219 Although @sc{gdb/mi} is still incomplete, it is currently being used
26220 by a variety of front ends to @value{GDBN}. This makes it difficult
26221 to introduce new functionality without breaking existing usage. This
26222 section tries to minimize the problems by describing how the protocol
26225 Some changes in MI need not break a carefully designed front end, and
26226 for these the MI version will remain unchanged. The following is a
26227 list of changes that may occur within one level, so front ends should
26228 parse MI output in a way that can handle them:
26232 New MI commands may be added.
26235 New fields may be added to the output of any MI command.
26238 The range of values for fields with specified values, e.g.,
26239 @code{in_scope} (@pxref{-var-update}) may be extended.
26241 @c The format of field's content e.g type prefix, may change so parse it
26242 @c at your own risk. Yes, in general?
26244 @c The order of fields may change? Shouldn't really matter but it might
26245 @c resolve inconsistencies.
26248 If the changes are likely to break front ends, the MI version level
26249 will be increased by one. This will allow the front end to parse the
26250 output according to the MI version. Apart from mi0, new versions of
26251 @value{GDBN} will not support old versions of MI and it will be the
26252 responsibility of the front end to work with the new one.
26254 @c Starting with mi3, add a new command -mi-version that prints the MI
26257 The best way to avoid unexpected changes in MI that might break your front
26258 end is to make your project known to @value{GDBN} developers and
26259 follow development on @email{gdb@@sourceware.org} and
26260 @email{gdb-patches@@sourceware.org}.
26261 @cindex mailing lists
26263 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
26264 @node GDB/MI Output Records
26265 @section @sc{gdb/mi} Output Records
26268 * GDB/MI Result Records::
26269 * GDB/MI Stream Records::
26270 * GDB/MI Async Records::
26271 * GDB/MI Frame Information::
26272 * GDB/MI Thread Information::
26273 * GDB/MI Ada Exception Information::
26276 @node GDB/MI Result Records
26277 @subsection @sc{gdb/mi} Result Records
26279 @cindex result records in @sc{gdb/mi}
26280 @cindex @sc{gdb/mi}, result records
26281 In addition to a number of out-of-band notifications, the response to a
26282 @sc{gdb/mi} command includes one of the following result indications:
26286 @item "^done" [ "," @var{results} ]
26287 The synchronous operation was successful, @code{@var{results}} are the return
26292 This result record is equivalent to @samp{^done}. Historically, it
26293 was output instead of @samp{^done} if the command has resumed the
26294 target. This behaviour is maintained for backward compatibility, but
26295 all frontends should treat @samp{^done} and @samp{^running}
26296 identically and rely on the @samp{*running} output record to determine
26297 which threads are resumed.
26301 @value{GDBN} has connected to a remote target.
26303 @item "^error" "," @var{c-string}
26305 The operation failed. The @code{@var{c-string}} contains the corresponding
26310 @value{GDBN} has terminated.
26314 @node GDB/MI Stream Records
26315 @subsection @sc{gdb/mi} Stream Records
26317 @cindex @sc{gdb/mi}, stream records
26318 @cindex stream records in @sc{gdb/mi}
26319 @value{GDBN} internally maintains a number of output streams: the console, the
26320 target, and the log. The output intended for each of these streams is
26321 funneled through the @sc{gdb/mi} interface using @dfn{stream records}.
26323 Each stream record begins with a unique @dfn{prefix character} which
26324 identifies its stream (@pxref{GDB/MI Output Syntax, , @sc{gdb/mi} Output
26325 Syntax}). In addition to the prefix, each stream record contains a
26326 @code{@var{string-output}}. This is either raw text (with an implicit new
26327 line) or a quoted C string (which does not contain an implicit newline).
26330 @item "~" @var{string-output}
26331 The console output stream contains text that should be displayed in the
26332 CLI console window. It contains the textual responses to CLI commands.
26334 @item "@@" @var{string-output}
26335 The target output stream contains any textual output from the running
26336 target. This is only present when GDB's event loop is truly
26337 asynchronous, which is currently only the case for remote targets.
26339 @item "&" @var{string-output}
26340 The log stream contains debugging messages being produced by @value{GDBN}'s
26344 @node GDB/MI Async Records
26345 @subsection @sc{gdb/mi} Async Records
26347 @cindex async records in @sc{gdb/mi}
26348 @cindex @sc{gdb/mi}, async records
26349 @dfn{Async} records are used to notify the @sc{gdb/mi} client of
26350 additional changes that have occurred. Those changes can either be a
26351 consequence of @sc{gdb/mi} commands (e.g., a breakpoint modified) or a result of
26352 target activity (e.g., target stopped).
26354 The following is the list of possible async records:
26358 @item *running,thread-id="@var{thread}"
26359 The target is now running. The @var{thread} field tells which
26360 specific thread is now running, and can be @samp{all} if all threads
26361 are running. The frontend should assume that no interaction with a
26362 running thread is possible after this notification is produced.
26363 The frontend should not assume that this notification is output
26364 only once for any command. @value{GDBN} may emit this notification
26365 several times, either for different threads, because it cannot resume
26366 all threads together, or even for a single thread, if the thread must
26367 be stepped though some code before letting it run freely.
26369 @item *stopped,reason="@var{reason}",thread-id="@var{id}",stopped-threads="@var{stopped}",core="@var{core}"
26370 The target has stopped. The @var{reason} field can have one of the
26374 @item breakpoint-hit
26375 A breakpoint was reached.
26376 @item watchpoint-trigger
26377 A watchpoint was triggered.
26378 @item read-watchpoint-trigger
26379 A read watchpoint was triggered.
26380 @item access-watchpoint-trigger
26381 An access watchpoint was triggered.
26382 @item function-finished
26383 An -exec-finish or similar CLI command was accomplished.
26384 @item location-reached
26385 An -exec-until or similar CLI command was accomplished.
26386 @item watchpoint-scope
26387 A watchpoint has gone out of scope.
26388 @item end-stepping-range
26389 An -exec-next, -exec-next-instruction, -exec-step, -exec-step-instruction or
26390 similar CLI command was accomplished.
26391 @item exited-signalled
26392 The inferior exited because of a signal.
26394 The inferior exited.
26395 @item exited-normally
26396 The inferior exited normally.
26397 @item signal-received
26398 A signal was received by the inferior.
26400 The inferior has stopped due to a library being loaded or unloaded.
26401 This can happen when @code{stop-on-solib-events} (@pxref{Files}) is
26402 set or when a @code{catch load} or @code{catch unload} catchpoint is
26403 in use (@pxref{Set Catchpoints}).
26405 The inferior has forked. This is reported when @code{catch fork}
26406 (@pxref{Set Catchpoints}) has been used.
26408 The inferior has vforked. This is reported in when @code{catch vfork}
26409 (@pxref{Set Catchpoints}) has been used.
26410 @item syscall-entry
26411 The inferior entered a system call. This is reported when @code{catch
26412 syscall} (@pxref{Set Catchpoints}) has been used.
26413 @item syscall-entry
26414 The inferior returned from a system call. This is reported when
26415 @code{catch syscall} (@pxref{Set Catchpoints}) has been used.
26417 The inferior called @code{exec}. This is reported when @code{catch exec}
26418 (@pxref{Set Catchpoints}) has been used.
26421 The @var{id} field identifies the thread that directly caused the stop
26422 -- for example by hitting a breakpoint. Depending on whether all-stop
26423 mode is in effect (@pxref{All-Stop Mode}), @value{GDBN} may either
26424 stop all threads, or only the thread that directly triggered the stop.
26425 If all threads are stopped, the @var{stopped} field will have the
26426 value of @code{"all"}. Otherwise, the value of the @var{stopped}
26427 field will be a list of thread identifiers. Presently, this list will
26428 always include a single thread, but frontend should be prepared to see
26429 several threads in the list. The @var{core} field reports the
26430 processor core on which the stop event has happened. This field may be absent
26431 if such information is not available.
26433 @item =thread-group-added,id="@var{id}"
26434 @itemx =thread-group-removed,id="@var{id}"
26435 A thread group was either added or removed. The @var{id} field
26436 contains the @value{GDBN} identifier of the thread group. When a thread
26437 group is added, it generally might not be associated with a running
26438 process. When a thread group is removed, its id becomes invalid and
26439 cannot be used in any way.
26441 @item =thread-group-started,id="@var{id}",pid="@var{pid}"
26442 A thread group became associated with a running program,
26443 either because the program was just started or the thread group
26444 was attached to a program. The @var{id} field contains the
26445 @value{GDBN} identifier of the thread group. The @var{pid} field
26446 contains process identifier, specific to the operating system.
26448 @item =thread-group-exited,id="@var{id}"[,exit-code="@var{code}"]
26449 A thread group is no longer associated with a running program,
26450 either because the program has exited, or because it was detached
26451 from. The @var{id} field contains the @value{GDBN} identifier of the
26452 thread group. @var{code} is the exit code of the inferior; it exists
26453 only when the inferior exited with some code.
26455 @item =thread-created,id="@var{id}",group-id="@var{gid}"
26456 @itemx =thread-exited,id="@var{id}",group-id="@var{gid}"
26457 A thread either was created, or has exited. The @var{id} field
26458 contains the @value{GDBN} identifier of the thread. The @var{gid}
26459 field identifies the thread group this thread belongs to.
26461 @item =thread-selected,id="@var{id}"
26462 Informs that the selected thread was changed as result of the last
26463 command. This notification is not emitted as result of @code{-thread-select}
26464 command but is emitted whenever an MI command that is not documented
26465 to change the selected thread actually changes it. In particular,
26466 invoking, directly or indirectly (via user-defined command), the CLI
26467 @code{thread} command, will generate this notification.
26469 We suggest that in response to this notification, front ends
26470 highlight the selected thread and cause subsequent commands to apply to
26473 @item =library-loaded,...
26474 Reports that a new library file was loaded by the program. This
26475 notification has 4 fields---@var{id}, @var{target-name},
26476 @var{host-name}, and @var{symbols-loaded}. The @var{id} field is an
26477 opaque identifier of the library. For remote debugging case,
26478 @var{target-name} and @var{host-name} fields give the name of the
26479 library file on the target, and on the host respectively. For native
26480 debugging, both those fields have the same value. The
26481 @var{symbols-loaded} field is emitted only for backward compatibility
26482 and should not be relied on to convey any useful information. The
26483 @var{thread-group} field, if present, specifies the id of the thread
26484 group in whose context the library was loaded. If the field is
26485 absent, it means the library was loaded in the context of all present
26488 @item =library-unloaded,...
26489 Reports that a library was unloaded by the program. This notification
26490 has 3 fields---@var{id}, @var{target-name} and @var{host-name} with
26491 the same meaning as for the @code{=library-loaded} notification.
26492 The @var{thread-group} field, if present, specifies the id of the
26493 thread group in whose context the library was unloaded. If the field is
26494 absent, it means the library was unloaded in the context of all present
26497 @item =breakpoint-created,bkpt=@{...@}
26498 @itemx =breakpoint-modified,bkpt=@{...@}
26499 @itemx =breakpoint-deleted,bkpt=@{...@}
26500 Reports that a breakpoint was created, modified, or deleted,
26501 respectively. Only user-visible breakpoints are reported to the MI
26504 The @var{bkpt} argument is of the same form as returned by the various
26505 breakpoint commands; @xref{GDB/MI Breakpoint Commands}.
26507 Note that if a breakpoint is emitted in the result record of a
26508 command, then it will not also be emitted in an async record.
26512 @node GDB/MI Frame Information
26513 @subsection @sc{gdb/mi} Frame Information
26515 Response from many MI commands includes an information about stack
26516 frame. This information is a tuple that may have the following
26521 The level of the stack frame. The innermost frame has the level of
26522 zero. This field is always present.
26525 The name of the function corresponding to the frame. This field may
26526 be absent if @value{GDBN} is unable to determine the function name.
26529 The code address for the frame. This field is always present.
26532 The name of the source files that correspond to the frame's code
26533 address. This field may be absent.
26536 The source line corresponding to the frames' code address. This field
26540 The name of the binary file (either executable or shared library) the
26541 corresponds to the frame's code address. This field may be absent.
26545 @node GDB/MI Thread Information
26546 @subsection @sc{gdb/mi} Thread Information
26548 Whenever @value{GDBN} has to report an information about a thread, it
26549 uses a tuple with the following fields:
26553 The numeric id assigned to the thread by @value{GDBN}. This field is
26557 Target-specific string identifying the thread. This field is always present.
26560 Additional information about the thread provided by the target.
26561 It is supposed to be human-readable and not interpreted by the
26562 frontend. This field is optional.
26565 Either @samp{stopped} or @samp{running}, depending on whether the
26566 thread is presently running. This field is always present.
26569 The value of this field is an integer number of the processor core the
26570 thread was last seen on. This field is optional.
26573 @node GDB/MI Ada Exception Information
26574 @subsection @sc{gdb/mi} Ada Exception Information
26576 Whenever a @code{*stopped} record is emitted because the program
26577 stopped after hitting an exception catchpoint (@pxref{Set Catchpoints}),
26578 @value{GDBN} provides the name of the exception that was raised via
26579 the @code{exception-name} field.
26581 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
26582 @node GDB/MI Simple Examples
26583 @section Simple Examples of @sc{gdb/mi} Interaction
26584 @cindex @sc{gdb/mi}, simple examples
26586 This subsection presents several simple examples of interaction using
26587 the @sc{gdb/mi} interface. In these examples, @samp{->} means that the
26588 following line is passed to @sc{gdb/mi} as input, while @samp{<-} means
26589 the output received from @sc{gdb/mi}.
26591 Note the line breaks shown in the examples are here only for
26592 readability, they don't appear in the real output.
26594 @subheading Setting a Breakpoint
26596 Setting a breakpoint generates synchronous output which contains detailed
26597 information of the breakpoint.
26600 -> -break-insert main
26601 <- ^done,bkpt=@{number="1",type="breakpoint",disp="keep",
26602 enabled="y",addr="0x08048564",func="main",file="myprog.c",
26603 fullname="/home/nickrob/myprog.c",line="68",times="0"@}
26607 @subheading Program Execution
26609 Program execution generates asynchronous records and MI gives the
26610 reason that execution stopped.
26616 <- *stopped,reason="breakpoint-hit",disp="keep",bkptno="1",thread-id="0",
26617 frame=@{addr="0x08048564",func="main",
26618 args=[@{name="argc",value="1"@},@{name="argv",value="0xbfc4d4d4"@}],
26619 file="myprog.c",fullname="/home/nickrob/myprog.c",line="68"@}
26624 <- *stopped,reason="exited-normally"
26628 @subheading Quitting @value{GDBN}
26630 Quitting @value{GDBN} just prints the result class @samp{^exit}.
26638 Please note that @samp{^exit} is printed immediately, but it might
26639 take some time for @value{GDBN} to actually exit. During that time, @value{GDBN}
26640 performs necessary cleanups, including killing programs being debugged
26641 or disconnecting from debug hardware, so the frontend should wait till
26642 @value{GDBN} exits and should only forcibly kill @value{GDBN} if it
26643 fails to exit in reasonable time.
26645 @subheading A Bad Command
26647 Here's what happens if you pass a non-existent command:
26651 <- ^error,msg="Undefined MI command: rubbish"
26656 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
26657 @node GDB/MI Command Description Format
26658 @section @sc{gdb/mi} Command Description Format
26660 The remaining sections describe blocks of commands. Each block of
26661 commands is laid out in a fashion similar to this section.
26663 @subheading Motivation
26665 The motivation for this collection of commands.
26667 @subheading Introduction
26669 A brief introduction to this collection of commands as a whole.
26671 @subheading Commands
26673 For each command in the block, the following is described:
26675 @subsubheading Synopsis
26678 -command @var{args}@dots{}
26681 @subsubheading Result
26683 @subsubheading @value{GDBN} Command
26685 The corresponding @value{GDBN} CLI command(s), if any.
26687 @subsubheading Example
26689 Example(s) formatted for readability. Some of the described commands have
26690 not been implemented yet and these are labeled N.A.@: (not available).
26693 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
26694 @node GDB/MI Breakpoint Commands
26695 @section @sc{gdb/mi} Breakpoint Commands
26697 @cindex breakpoint commands for @sc{gdb/mi}
26698 @cindex @sc{gdb/mi}, breakpoint commands
26699 This section documents @sc{gdb/mi} commands for manipulating
26702 @subheading The @code{-break-after} Command
26703 @findex -break-after
26705 @subsubheading Synopsis
26708 -break-after @var{number} @var{count}
26711 The breakpoint number @var{number} is not in effect until it has been
26712 hit @var{count} times. To see how this is reflected in the output of
26713 the @samp{-break-list} command, see the description of the
26714 @samp{-break-list} command below.
26716 @subsubheading @value{GDBN} Command
26718 The corresponding @value{GDBN} command is @samp{ignore}.
26720 @subsubheading Example
26725 ^done,bkpt=@{number="1",type="breakpoint",disp="keep",
26726 enabled="y",addr="0x000100d0",func="main",file="hello.c",
26727 fullname="/home/foo/hello.c",line="5",times="0"@}
26734 ^done,BreakpointTable=@{nr_rows="1",nr_cols="6",
26735 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
26736 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
26737 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
26738 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
26739 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
26740 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
26741 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
26742 addr="0x000100d0",func="main",file="hello.c",fullname="/home/foo/hello.c",
26743 line="5",times="0",ignore="3"@}]@}
26748 @subheading The @code{-break-catch} Command
26749 @findex -break-catch
26752 @subheading The @code{-break-commands} Command
26753 @findex -break-commands
26755 @subsubheading Synopsis
26758 -break-commands @var{number} [ @var{command1} ... @var{commandN} ]
26761 Specifies the CLI commands that should be executed when breakpoint
26762 @var{number} is hit. The parameters @var{command1} to @var{commandN}
26763 are the commands. If no command is specified, any previously-set
26764 commands are cleared. @xref{Break Commands}. Typical use of this
26765 functionality is tracing a program, that is, printing of values of
26766 some variables whenever breakpoint is hit and then continuing.
26768 @subsubheading @value{GDBN} Command
26770 The corresponding @value{GDBN} command is @samp{commands}.
26772 @subsubheading Example
26777 ^done,bkpt=@{number="1",type="breakpoint",disp="keep",
26778 enabled="y",addr="0x000100d0",func="main",file="hello.c",
26779 fullname="/home/foo/hello.c",line="5",times="0"@}
26781 -break-commands 1 "print v" "continue"
26786 @subheading The @code{-break-condition} Command
26787 @findex -break-condition
26789 @subsubheading Synopsis
26792 -break-condition @var{number} @var{expr}
26795 Breakpoint @var{number} will stop the program only if the condition in
26796 @var{expr} is true. The condition becomes part of the
26797 @samp{-break-list} output (see the description of the @samp{-break-list}
26800 @subsubheading @value{GDBN} Command
26802 The corresponding @value{GDBN} command is @samp{condition}.
26804 @subsubheading Example
26808 -break-condition 1 1
26812 ^done,BreakpointTable=@{nr_rows="1",nr_cols="6",
26813 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
26814 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
26815 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
26816 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
26817 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
26818 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
26819 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
26820 addr="0x000100d0",func="main",file="hello.c",fullname="/home/foo/hello.c",
26821 line="5",cond="1",times="0",ignore="3"@}]@}
26825 @subheading The @code{-break-delete} Command
26826 @findex -break-delete
26828 @subsubheading Synopsis
26831 -break-delete ( @var{breakpoint} )+
26834 Delete the breakpoint(s) whose number(s) are specified in the argument
26835 list. This is obviously reflected in the breakpoint list.
26837 @subsubheading @value{GDBN} Command
26839 The corresponding @value{GDBN} command is @samp{delete}.
26841 @subsubheading Example
26849 ^done,BreakpointTable=@{nr_rows="0",nr_cols="6",
26850 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
26851 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
26852 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
26853 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
26854 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
26855 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
26860 @subheading The @code{-break-disable} Command
26861 @findex -break-disable
26863 @subsubheading Synopsis
26866 -break-disable ( @var{breakpoint} )+
26869 Disable the named @var{breakpoint}(s). The field @samp{enabled} in the
26870 break list is now set to @samp{n} for the named @var{breakpoint}(s).
26872 @subsubheading @value{GDBN} Command
26874 The corresponding @value{GDBN} command is @samp{disable}.
26876 @subsubheading Example
26884 ^done,BreakpointTable=@{nr_rows="1",nr_cols="6",
26885 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
26886 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
26887 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
26888 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
26889 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
26890 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
26891 body=[bkpt=@{number="2",type="breakpoint",disp="keep",enabled="n",
26892 addr="0x000100d0",func="main",file="hello.c",fullname="/home/foo/hello.c",
26893 line="5",times="0"@}]@}
26897 @subheading The @code{-break-enable} Command
26898 @findex -break-enable
26900 @subsubheading Synopsis
26903 -break-enable ( @var{breakpoint} )+
26906 Enable (previously disabled) @var{breakpoint}(s).
26908 @subsubheading @value{GDBN} Command
26910 The corresponding @value{GDBN} command is @samp{enable}.
26912 @subsubheading Example
26920 ^done,BreakpointTable=@{nr_rows="1",nr_cols="6",
26921 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
26922 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
26923 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
26924 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
26925 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
26926 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
26927 body=[bkpt=@{number="2",type="breakpoint",disp="keep",enabled="y",
26928 addr="0x000100d0",func="main",file="hello.c",fullname="/home/foo/hello.c",
26929 line="5",times="0"@}]@}
26933 @subheading The @code{-break-info} Command
26934 @findex -break-info
26936 @subsubheading Synopsis
26939 -break-info @var{breakpoint}
26943 Get information about a single breakpoint.
26945 @subsubheading @value{GDBN} Command
26947 The corresponding @value{GDBN} command is @samp{info break @var{breakpoint}}.
26949 @subsubheading Example
26952 @subheading The @code{-break-insert} Command
26953 @findex -break-insert
26955 @subsubheading Synopsis
26958 -break-insert [ -t ] [ -h ] [ -f ] [ -d ] [ -a ]
26959 [ -c @var{condition} ] [ -i @var{ignore-count} ]
26960 [ -p @var{thread} ] [ @var{location} ]
26964 If specified, @var{location}, can be one of:
26971 @item filename:linenum
26972 @item filename:function
26976 The possible optional parameters of this command are:
26980 Insert a temporary breakpoint.
26982 Insert a hardware breakpoint.
26983 @item -c @var{condition}
26984 Make the breakpoint conditional on @var{condition}.
26985 @item -i @var{ignore-count}
26986 Initialize the @var{ignore-count}.
26988 If @var{location} cannot be parsed (for example if it
26989 refers to unknown files or functions), create a pending
26990 breakpoint. Without this flag, @value{GDBN} will report
26991 an error, and won't create a breakpoint, if @var{location}
26994 Create a disabled breakpoint.
26996 Create a tracepoint. @xref{Tracepoints}. When this parameter
26997 is used together with @samp{-h}, a fast tracepoint is created.
27000 @subsubheading Result
27002 The result is in the form:
27005 ^done,bkpt=@{number="@var{number}",type="@var{type}",disp="del"|"keep",
27006 enabled="y"|"n",addr="@var{hex}",func="@var{funcname}",file="@var{filename}",
27007 fullname="@var{full_filename}",line="@var{lineno}",[thread="@var{threadno},]
27008 times="@var{times}"@}
27012 where @var{number} is the @value{GDBN} number for this breakpoint,
27013 @var{funcname} is the name of the function where the breakpoint was
27014 inserted, @var{filename} is the name of the source file which contains
27015 this function, @var{lineno} is the source line number within that file
27016 and @var{times} the number of times that the breakpoint has been hit
27017 (always 0 for -break-insert but may be greater for -break-info or -break-list
27018 which use the same output).
27020 Note: this format is open to change.
27021 @c An out-of-band breakpoint instead of part of the result?
27023 @subsubheading @value{GDBN} Command
27025 The corresponding @value{GDBN} commands are @samp{break}, @samp{tbreak},
27026 @samp{hbreak}, @samp{thbreak}, and @samp{rbreak}.
27028 @subsubheading Example
27033 ^done,bkpt=@{number="1",addr="0x0001072c",file="recursive2.c",
27034 fullname="/home/foo/recursive2.c,line="4",times="0"@}
27036 -break-insert -t foo
27037 ^done,bkpt=@{number="2",addr="0x00010774",file="recursive2.c",
27038 fullname="/home/foo/recursive2.c,line="11",times="0"@}
27041 ^done,BreakpointTable=@{nr_rows="2",nr_cols="6",
27042 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
27043 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
27044 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
27045 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
27046 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
27047 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
27048 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
27049 addr="0x0001072c", func="main",file="recursive2.c",
27050 fullname="/home/foo/recursive2.c,"line="4",times="0"@},
27051 bkpt=@{number="2",type="breakpoint",disp="del",enabled="y",
27052 addr="0x00010774",func="foo",file="recursive2.c",
27053 fullname="/home/foo/recursive2.c",line="11",times="0"@}]@}
27055 -break-insert -r foo.*
27056 ~int foo(int, int);
27057 ^done,bkpt=@{number="3",addr="0x00010774",file="recursive2.c,
27058 "fullname="/home/foo/recursive2.c",line="11",times="0"@}
27062 @subheading The @code{-break-list} Command
27063 @findex -break-list
27065 @subsubheading Synopsis
27071 Displays the list of inserted breakpoints, showing the following fields:
27075 number of the breakpoint
27077 type of the breakpoint: @samp{breakpoint} or @samp{watchpoint}
27079 should the breakpoint be deleted or disabled when it is hit: @samp{keep}
27082 is the breakpoint enabled or no: @samp{y} or @samp{n}
27084 memory location at which the breakpoint is set
27086 logical location of the breakpoint, expressed by function name, file
27089 number of times the breakpoint has been hit
27092 If there are no breakpoints or watchpoints, the @code{BreakpointTable}
27093 @code{body} field is an empty list.
27095 @subsubheading @value{GDBN} Command
27097 The corresponding @value{GDBN} command is @samp{info break}.
27099 @subsubheading Example
27104 ^done,BreakpointTable=@{nr_rows="2",nr_cols="6",
27105 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
27106 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
27107 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
27108 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
27109 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
27110 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
27111 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
27112 addr="0x000100d0",func="main",file="hello.c",line="5",times="0"@},
27113 bkpt=@{number="2",type="breakpoint",disp="keep",enabled="y",
27114 addr="0x00010114",func="foo",file="hello.c",fullname="/home/foo/hello.c",
27115 line="13",times="0"@}]@}
27119 Here's an example of the result when there are no breakpoints:
27124 ^done,BreakpointTable=@{nr_rows="0",nr_cols="6",
27125 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
27126 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
27127 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
27128 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
27129 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
27130 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
27135 @subheading The @code{-break-passcount} Command
27136 @findex -break-passcount
27138 @subsubheading Synopsis
27141 -break-passcount @var{tracepoint-number} @var{passcount}
27144 Set the passcount for tracepoint @var{tracepoint-number} to
27145 @var{passcount}. If the breakpoint referred to by @var{tracepoint-number}
27146 is not a tracepoint, error is emitted. This corresponds to CLI
27147 command @samp{passcount}.
27149 @subheading The @code{-break-watch} Command
27150 @findex -break-watch
27152 @subsubheading Synopsis
27155 -break-watch [ -a | -r ]
27158 Create a watchpoint. With the @samp{-a} option it will create an
27159 @dfn{access} watchpoint, i.e., a watchpoint that triggers either on a
27160 read from or on a write to the memory location. With the @samp{-r}
27161 option, the watchpoint created is a @dfn{read} watchpoint, i.e., it will
27162 trigger only when the memory location is accessed for reading. Without
27163 either of the options, the watchpoint created is a regular watchpoint,
27164 i.e., it will trigger when the memory location is accessed for writing.
27165 @xref{Set Watchpoints, , Setting Watchpoints}.
27167 Note that @samp{-break-list} will report a single list of watchpoints and
27168 breakpoints inserted.
27170 @subsubheading @value{GDBN} Command
27172 The corresponding @value{GDBN} commands are @samp{watch}, @samp{awatch}, and
27175 @subsubheading Example
27177 Setting a watchpoint on a variable in the @code{main} function:
27182 ^done,wpt=@{number="2",exp="x"@}
27187 *stopped,reason="watchpoint-trigger",wpt=@{number="2",exp="x"@},
27188 value=@{old="-268439212",new="55"@},
27189 frame=@{func="main",args=[],file="recursive2.c",
27190 fullname="/home/foo/bar/recursive2.c",line="5"@}
27194 Setting a watchpoint on a variable local to a function. @value{GDBN} will stop
27195 the program execution twice: first for the variable changing value, then
27196 for the watchpoint going out of scope.
27201 ^done,wpt=@{number="5",exp="C"@}
27206 *stopped,reason="watchpoint-trigger",
27207 wpt=@{number="5",exp="C"@},value=@{old="-276895068",new="3"@},
27208 frame=@{func="callee4",args=[],
27209 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
27210 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="13"@}
27215 *stopped,reason="watchpoint-scope",wpnum="5",
27216 frame=@{func="callee3",args=[@{name="strarg",
27217 value="0x11940 \"A string argument.\""@}],
27218 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
27219 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="18"@}
27223 Listing breakpoints and watchpoints, at different points in the program
27224 execution. Note that once the watchpoint goes out of scope, it is
27230 ^done,wpt=@{number="2",exp="C"@}
27233 ^done,BreakpointTable=@{nr_rows="2",nr_cols="6",
27234 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
27235 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
27236 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
27237 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
27238 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
27239 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
27240 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
27241 addr="0x00010734",func="callee4",
27242 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
27243 fullname="/home/foo/devo/gdb/testsuite/gdb.mi/basics.c"line="8",times="1"@},
27244 bkpt=@{number="2",type="watchpoint",disp="keep",
27245 enabled="y",addr="",what="C",times="0"@}]@}
27250 *stopped,reason="watchpoint-trigger",wpt=@{number="2",exp="C"@},
27251 value=@{old="-276895068",new="3"@},
27252 frame=@{func="callee4",args=[],
27253 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
27254 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="13"@}
27257 ^done,BreakpointTable=@{nr_rows="2",nr_cols="6",
27258 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
27259 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
27260 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
27261 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
27262 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
27263 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
27264 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
27265 addr="0x00010734",func="callee4",
27266 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
27267 fullname="/home/foo/devo/gdb/testsuite/gdb.mi/basics.c",line="8",times="1"@},
27268 bkpt=@{number="2",type="watchpoint",disp="keep",
27269 enabled="y",addr="",what="C",times="-5"@}]@}
27273 ^done,reason="watchpoint-scope",wpnum="2",
27274 frame=@{func="callee3",args=[@{name="strarg",
27275 value="0x11940 \"A string argument.\""@}],
27276 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
27277 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="18"@}
27280 ^done,BreakpointTable=@{nr_rows="1",nr_cols="6",
27281 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
27282 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
27283 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
27284 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
27285 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
27286 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
27287 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
27288 addr="0x00010734",func="callee4",
27289 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
27290 fullname="/home/foo/devo/gdb/testsuite/gdb.mi/basics.c",line="8",
27295 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
27296 @node GDB/MI Program Context
27297 @section @sc{gdb/mi} Program Context
27299 @subheading The @code{-exec-arguments} Command
27300 @findex -exec-arguments
27303 @subsubheading Synopsis
27306 -exec-arguments @var{args}
27309 Set the inferior program arguments, to be used in the next
27312 @subsubheading @value{GDBN} Command
27314 The corresponding @value{GDBN} command is @samp{set args}.
27316 @subsubheading Example
27320 -exec-arguments -v word
27327 @subheading The @code{-exec-show-arguments} Command
27328 @findex -exec-show-arguments
27330 @subsubheading Synopsis
27333 -exec-show-arguments
27336 Print the arguments of the program.
27338 @subsubheading @value{GDBN} Command
27340 The corresponding @value{GDBN} command is @samp{show args}.
27342 @subsubheading Example
27347 @subheading The @code{-environment-cd} Command
27348 @findex -environment-cd
27350 @subsubheading Synopsis
27353 -environment-cd @var{pathdir}
27356 Set @value{GDBN}'s working directory.
27358 @subsubheading @value{GDBN} Command
27360 The corresponding @value{GDBN} command is @samp{cd}.
27362 @subsubheading Example
27366 -environment-cd /kwikemart/marge/ezannoni/flathead-dev/devo/gdb
27372 @subheading The @code{-environment-directory} Command
27373 @findex -environment-directory
27375 @subsubheading Synopsis
27378 -environment-directory [ -r ] [ @var{pathdir} ]+
27381 Add directories @var{pathdir} to beginning of search path for source files.
27382 If the @samp{-r} option is used, the search path is reset to the default
27383 search path. If directories @var{pathdir} are supplied in addition to the
27384 @samp{-r} option, the search path is first reset and then addition
27386 Multiple directories may be specified, separated by blanks. Specifying
27387 multiple directories in a single command
27388 results in the directories added to the beginning of the
27389 search path in the same order they were presented in the command.
27390 If blanks are needed as
27391 part of a directory name, double-quotes should be used around
27392 the name. In the command output, the path will show up separated
27393 by the system directory-separator character. The directory-separator
27394 character must not be used
27395 in any directory name.
27396 If no directories are specified, the current search path is displayed.
27398 @subsubheading @value{GDBN} Command
27400 The corresponding @value{GDBN} command is @samp{dir}.
27402 @subsubheading Example
27406 -environment-directory /kwikemart/marge/ezannoni/flathead-dev/devo/gdb
27407 ^done,source-path="/kwikemart/marge/ezannoni/flathead-dev/devo/gdb:$cdir:$cwd"
27409 -environment-directory ""
27410 ^done,source-path="/kwikemart/marge/ezannoni/flathead-dev/devo/gdb:$cdir:$cwd"
27412 -environment-directory -r /home/jjohnstn/src/gdb /usr/src
27413 ^done,source-path="/home/jjohnstn/src/gdb:/usr/src:$cdir:$cwd"
27415 -environment-directory -r
27416 ^done,source-path="$cdir:$cwd"
27421 @subheading The @code{-environment-path} Command
27422 @findex -environment-path
27424 @subsubheading Synopsis
27427 -environment-path [ -r ] [ @var{pathdir} ]+
27430 Add directories @var{pathdir} to beginning of search path for object files.
27431 If the @samp{-r} option is used, the search path is reset to the original
27432 search path that existed at gdb start-up. If directories @var{pathdir} are
27433 supplied in addition to the
27434 @samp{-r} option, the search path is first reset and then addition
27436 Multiple directories may be specified, separated by blanks. Specifying
27437 multiple directories in a single command
27438 results in the directories added to the beginning of the
27439 search path in the same order they were presented in the command.
27440 If blanks are needed as
27441 part of a directory name, double-quotes should be used around
27442 the name. In the command output, the path will show up separated
27443 by the system directory-separator character. The directory-separator
27444 character must not be used
27445 in any directory name.
27446 If no directories are specified, the current path is displayed.
27449 @subsubheading @value{GDBN} Command
27451 The corresponding @value{GDBN} command is @samp{path}.
27453 @subsubheading Example
27458 ^done,path="/usr/bin"
27460 -environment-path /kwikemart/marge/ezannoni/flathead-dev/ppc-eabi/gdb /bin
27461 ^done,path="/kwikemart/marge/ezannoni/flathead-dev/ppc-eabi/gdb:/bin:/usr/bin"
27463 -environment-path -r /usr/local/bin
27464 ^done,path="/usr/local/bin:/usr/bin"
27469 @subheading The @code{-environment-pwd} Command
27470 @findex -environment-pwd
27472 @subsubheading Synopsis
27478 Show the current working directory.
27480 @subsubheading @value{GDBN} Command
27482 The corresponding @value{GDBN} command is @samp{pwd}.
27484 @subsubheading Example
27489 ^done,cwd="/kwikemart/marge/ezannoni/flathead-dev/devo/gdb"
27493 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
27494 @node GDB/MI Thread Commands
27495 @section @sc{gdb/mi} Thread Commands
27498 @subheading The @code{-thread-info} Command
27499 @findex -thread-info
27501 @subsubheading Synopsis
27504 -thread-info [ @var{thread-id} ]
27507 Reports information about either a specific thread, if
27508 the @var{thread-id} parameter is present, or about all
27509 threads. When printing information about all threads,
27510 also reports the current thread.
27512 @subsubheading @value{GDBN} Command
27514 The @samp{info thread} command prints the same information
27517 @subsubheading Result
27519 The result is a list of threads. The following attributes are
27520 defined for a given thread:
27524 This field exists only for the current thread. It has the value @samp{*}.
27527 The identifier that @value{GDBN} uses to refer to the thread.
27530 The identifier that the target uses to refer to the thread.
27533 Extra information about the thread, in a target-specific format. This
27537 The name of the thread. If the user specified a name using the
27538 @code{thread name} command, then this name is given. Otherwise, if
27539 @value{GDBN} can extract the thread name from the target, then that
27540 name is given. If @value{GDBN} cannot find the thread name, then this
27544 The stack frame currently executing in the thread.
27547 The thread's state. The @samp{state} field may have the following
27552 The thread is stopped. Frame information is available for stopped
27556 The thread is running. There's no frame information for running
27562 If @value{GDBN} can find the CPU core on which this thread is running,
27563 then this field is the core identifier. This field is optional.
27567 @subsubheading Example
27572 @{id="2",target-id="Thread 0xb7e14b90 (LWP 21257)",
27573 frame=@{level="0",addr="0xffffe410",func="__kernel_vsyscall",
27574 args=[]@},state="running"@},
27575 @{id="1",target-id="Thread 0xb7e156b0 (LWP 21254)",
27576 frame=@{level="0",addr="0x0804891f",func="foo",
27577 args=[@{name="i",value="10"@}],
27578 file="/tmp/a.c",fullname="/tmp/a.c",line="158"@},
27579 state="running"@}],
27580 current-thread-id="1"
27584 @subheading The @code{-thread-list-ids} Command
27585 @findex -thread-list-ids
27587 @subsubheading Synopsis
27593 Produces a list of the currently known @value{GDBN} thread ids. At the
27594 end of the list it also prints the total number of such threads.
27596 This command is retained for historical reasons, the
27597 @code{-thread-info} command should be used instead.
27599 @subsubheading @value{GDBN} Command
27601 Part of @samp{info threads} supplies the same information.
27603 @subsubheading Example
27608 ^done,thread-ids=@{thread-id="3",thread-id="2",thread-id="1"@},
27609 current-thread-id="1",number-of-threads="3"
27614 @subheading The @code{-thread-select} Command
27615 @findex -thread-select
27617 @subsubheading Synopsis
27620 -thread-select @var{threadnum}
27623 Make @var{threadnum} the current thread. It prints the number of the new
27624 current thread, and the topmost frame for that thread.
27626 This command is deprecated in favor of explicitly using the
27627 @samp{--thread} option to each command.
27629 @subsubheading @value{GDBN} Command
27631 The corresponding @value{GDBN} command is @samp{thread}.
27633 @subsubheading Example
27640 *stopped,reason="end-stepping-range",thread-id="2",line="187",
27641 file="../../../devo/gdb/testsuite/gdb.threads/linux-dp.c"
27645 thread-ids=@{thread-id="3",thread-id="2",thread-id="1"@},
27646 number-of-threads="3"
27649 ^done,new-thread-id="3",
27650 frame=@{level="0",func="vprintf",
27651 args=[@{name="format",value="0x8048e9c \"%*s%c %d %c\\n\""@},
27652 @{name="arg",value="0x2"@}],file="vprintf.c",line="31"@}
27656 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
27657 @node GDB/MI Ada Tasking Commands
27658 @section @sc{gdb/mi} Ada Tasking Commands
27660 @subheading The @code{-ada-task-info} Command
27661 @findex -ada-task-info
27663 @subsubheading Synopsis
27666 -ada-task-info [ @var{task-id} ]
27669 Reports information about either a specific Ada task, if the
27670 @var{task-id} parameter is present, or about all Ada tasks.
27672 @subsubheading @value{GDBN} Command
27674 The @samp{info tasks} command prints the same information
27675 about all Ada tasks (@pxref{Ada Tasks}).
27677 @subsubheading Result
27679 The result is a table of Ada tasks. The following columns are
27680 defined for each Ada task:
27684 This field exists only for the current thread. It has the value @samp{*}.
27687 The identifier that @value{GDBN} uses to refer to the Ada task.
27690 The identifier that the target uses to refer to the Ada task.
27693 The identifier of the thread corresponding to the Ada task.
27695 This field should always exist, as Ada tasks are always implemented
27696 on top of a thread. But if @value{GDBN} cannot find this corresponding
27697 thread for any reason, the field is omitted.
27700 This field exists only when the task was created by another task.
27701 In this case, it provides the ID of the parent task.
27704 The base priority of the task.
27707 The current state of the task. For a detailed description of the
27708 possible states, see @ref{Ada Tasks}.
27711 The name of the task.
27715 @subsubheading Example
27719 ^done,tasks=@{nr_rows="3",nr_cols="8",
27720 hdr=[@{width="1",alignment="-1",col_name="current",colhdr=""@},
27721 @{width="3",alignment="1",col_name="id",colhdr="ID"@},
27722 @{width="9",alignment="1",col_name="task-id",colhdr="TID"@},
27723 @{width="4",alignment="1",col_name="thread-id",colhdr=""@},
27724 @{width="4",alignment="1",col_name="parent-id",colhdr="P-ID"@},
27725 @{width="3",alignment="1",col_name="priority",colhdr="Pri"@},
27726 @{width="22",alignment="-1",col_name="state",colhdr="State"@},
27727 @{width="1",alignment="2",col_name="name",colhdr="Name"@}],
27728 body=[@{current="*",id="1",task-id=" 644010",thread-id="1",priority="48",
27729 state="Child Termination Wait",name="main_task"@}]@}
27733 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
27734 @node GDB/MI Program Execution
27735 @section @sc{gdb/mi} Program Execution
27737 These are the asynchronous commands which generate the out-of-band
27738 record @samp{*stopped}. Currently @value{GDBN} only really executes
27739 asynchronously with remote targets and this interaction is mimicked in
27742 @subheading The @code{-exec-continue} Command
27743 @findex -exec-continue
27745 @subsubheading Synopsis
27748 -exec-continue [--reverse] [--all|--thread-group N]
27751 Resumes the execution of the inferior program, which will continue
27752 to execute until it reaches a debugger stop event. If the
27753 @samp{--reverse} option is specified, execution resumes in reverse until
27754 it reaches a stop event. Stop events may include
27757 breakpoints or watchpoints
27759 signals or exceptions
27761 the end of the process (or its beginning under @samp{--reverse})
27763 the end or beginning of a replay log if one is being used.
27765 In all-stop mode (@pxref{All-Stop
27766 Mode}), may resume only one thread, or all threads, depending on the
27767 value of the @samp{scheduler-locking} variable. If @samp{--all} is
27768 specified, all threads (in all inferiors) will be resumed. The @samp{--all} option is
27769 ignored in all-stop mode. If the @samp{--thread-group} options is
27770 specified, then all threads in that thread group are resumed.
27772 @subsubheading @value{GDBN} Command
27774 The corresponding @value{GDBN} corresponding is @samp{continue}.
27776 @subsubheading Example
27783 *stopped,reason="breakpoint-hit",disp="keep",bkptno="2",frame=@{
27784 func="foo",args=[],file="hello.c",fullname="/home/foo/bar/hello.c",
27790 @subheading The @code{-exec-finish} Command
27791 @findex -exec-finish
27793 @subsubheading Synopsis
27796 -exec-finish [--reverse]
27799 Resumes the execution of the inferior program until the current
27800 function is exited. Displays the results returned by the function.
27801 If the @samp{--reverse} option is specified, resumes the reverse
27802 execution of the inferior program until the point where current
27803 function was called.
27805 @subsubheading @value{GDBN} Command
27807 The corresponding @value{GDBN} command is @samp{finish}.
27809 @subsubheading Example
27811 Function returning @code{void}.
27818 *stopped,reason="function-finished",frame=@{func="main",args=[],
27819 file="hello.c",fullname="/home/foo/bar/hello.c",line="7"@}
27823 Function returning other than @code{void}. The name of the internal
27824 @value{GDBN} variable storing the result is printed, together with the
27831 *stopped,reason="function-finished",frame=@{addr="0x000107b0",func="foo",
27832 args=[@{name="a",value="1"],@{name="b",value="9"@}@},
27833 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
27834 gdb-result-var="$1",return-value="0"
27839 @subheading The @code{-exec-interrupt} Command
27840 @findex -exec-interrupt
27842 @subsubheading Synopsis
27845 -exec-interrupt [--all|--thread-group N]
27848 Interrupts the background execution of the target. Note how the token
27849 associated with the stop message is the one for the execution command
27850 that has been interrupted. The token for the interrupt itself only
27851 appears in the @samp{^done} output. If the user is trying to
27852 interrupt a non-running program, an error message will be printed.
27854 Note that when asynchronous execution is enabled, this command is
27855 asynchronous just like other execution commands. That is, first the
27856 @samp{^done} response will be printed, and the target stop will be
27857 reported after that using the @samp{*stopped} notification.
27859 In non-stop mode, only the context thread is interrupted by default.
27860 All threads (in all inferiors) will be interrupted if the
27861 @samp{--all} option is specified. If the @samp{--thread-group}
27862 option is specified, all threads in that group will be interrupted.
27864 @subsubheading @value{GDBN} Command
27866 The corresponding @value{GDBN} command is @samp{interrupt}.
27868 @subsubheading Example
27879 111*stopped,signal-name="SIGINT",signal-meaning="Interrupt",
27880 frame=@{addr="0x00010140",func="foo",args=[],file="try.c",
27881 fullname="/home/foo/bar/try.c",line="13"@}
27886 ^error,msg="mi_cmd_exec_interrupt: Inferior not executing."
27890 @subheading The @code{-exec-jump} Command
27893 @subsubheading Synopsis
27896 -exec-jump @var{location}
27899 Resumes execution of the inferior program at the location specified by
27900 parameter. @xref{Specify Location}, for a description of the
27901 different forms of @var{location}.
27903 @subsubheading @value{GDBN} Command
27905 The corresponding @value{GDBN} command is @samp{jump}.
27907 @subsubheading Example
27910 -exec-jump foo.c:10
27911 *running,thread-id="all"
27916 @subheading The @code{-exec-next} Command
27919 @subsubheading Synopsis
27922 -exec-next [--reverse]
27925 Resumes execution of the inferior program, stopping when the beginning
27926 of the next source line is reached.
27928 If the @samp{--reverse} option is specified, resumes reverse execution
27929 of the inferior program, stopping at the beginning of the previous
27930 source line. If you issue this command on the first line of a
27931 function, it will take you back to the caller of that function, to the
27932 source line where the function was called.
27935 @subsubheading @value{GDBN} Command
27937 The corresponding @value{GDBN} command is @samp{next}.
27939 @subsubheading Example
27945 *stopped,reason="end-stepping-range",line="8",file="hello.c"
27950 @subheading The @code{-exec-next-instruction} Command
27951 @findex -exec-next-instruction
27953 @subsubheading Synopsis
27956 -exec-next-instruction [--reverse]
27959 Executes one machine instruction. If the instruction is a function
27960 call, continues until the function returns. If the program stops at an
27961 instruction in the middle of a source line, the address will be
27964 If the @samp{--reverse} option is specified, resumes reverse execution
27965 of the inferior program, stopping at the previous instruction. If the
27966 previously executed instruction was a return from another function,
27967 it will continue to execute in reverse until the call to that function
27968 (from the current stack frame) is reached.
27970 @subsubheading @value{GDBN} Command
27972 The corresponding @value{GDBN} command is @samp{nexti}.
27974 @subsubheading Example
27978 -exec-next-instruction
27982 *stopped,reason="end-stepping-range",
27983 addr="0x000100d4",line="5",file="hello.c"
27988 @subheading The @code{-exec-return} Command
27989 @findex -exec-return
27991 @subsubheading Synopsis
27997 Makes current function return immediately. Doesn't execute the inferior.
27998 Displays the new current frame.
28000 @subsubheading @value{GDBN} Command
28002 The corresponding @value{GDBN} command is @samp{return}.
28004 @subsubheading Example
28008 200-break-insert callee4
28009 200^done,bkpt=@{number="1",addr="0x00010734",
28010 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",line="8"@}
28015 000*stopped,reason="breakpoint-hit",disp="keep",bkptno="1",
28016 frame=@{func="callee4",args=[],
28017 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
28018 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="8"@}
28024 111^done,frame=@{level="0",func="callee3",
28025 args=[@{name="strarg",
28026 value="0x11940 \"A string argument.\""@}],
28027 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
28028 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="18"@}
28033 @subheading The @code{-exec-run} Command
28036 @subsubheading Synopsis
28039 -exec-run [--all | --thread-group N]
28042 Starts execution of the inferior from the beginning. The inferior
28043 executes until either a breakpoint is encountered or the program
28044 exits. In the latter case the output will include an exit code, if
28045 the program has exited exceptionally.
28047 When no option is specified, the current inferior is started. If the
28048 @samp{--thread-group} option is specified, it should refer to a thread
28049 group of type @samp{process}, and that thread group will be started.
28050 If the @samp{--all} option is specified, then all inferiors will be started.
28052 @subsubheading @value{GDBN} Command
28054 The corresponding @value{GDBN} command is @samp{run}.
28056 @subsubheading Examples
28061 ^done,bkpt=@{number="1",addr="0x0001072c",file="recursive2.c",line="4"@}
28066 *stopped,reason="breakpoint-hit",disp="keep",bkptno="1",
28067 frame=@{func="main",args=[],file="recursive2.c",
28068 fullname="/home/foo/bar/recursive2.c",line="4"@}
28073 Program exited normally:
28081 *stopped,reason="exited-normally"
28086 Program exited exceptionally:
28094 *stopped,reason="exited",exit-code="01"
28098 Another way the program can terminate is if it receives a signal such as
28099 @code{SIGINT}. In this case, @sc{gdb/mi} displays this:
28103 *stopped,reason="exited-signalled",signal-name="SIGINT",
28104 signal-meaning="Interrupt"
28108 @c @subheading -exec-signal
28111 @subheading The @code{-exec-step} Command
28114 @subsubheading Synopsis
28117 -exec-step [--reverse]
28120 Resumes execution of the inferior program, stopping when the beginning
28121 of the next source line is reached, if the next source line is not a
28122 function call. If it is, stop at the first instruction of the called
28123 function. If the @samp{--reverse} option is specified, resumes reverse
28124 execution of the inferior program, stopping at the beginning of the
28125 previously executed source line.
28127 @subsubheading @value{GDBN} Command
28129 The corresponding @value{GDBN} command is @samp{step}.
28131 @subsubheading Example
28133 Stepping into a function:
28139 *stopped,reason="end-stepping-range",
28140 frame=@{func="foo",args=[@{name="a",value="10"@},
28141 @{name="b",value="0"@}],file="recursive2.c",
28142 fullname="/home/foo/bar/recursive2.c",line="11"@}
28152 *stopped,reason="end-stepping-range",line="14",file="recursive2.c"
28157 @subheading The @code{-exec-step-instruction} Command
28158 @findex -exec-step-instruction
28160 @subsubheading Synopsis
28163 -exec-step-instruction [--reverse]
28166 Resumes the inferior which executes one machine instruction. If the
28167 @samp{--reverse} option is specified, resumes reverse execution of the
28168 inferior program, stopping at the previously executed instruction.
28169 The output, once @value{GDBN} has stopped, will vary depending on
28170 whether we have stopped in the middle of a source line or not. In the
28171 former case, the address at which the program stopped will be printed
28174 @subsubheading @value{GDBN} Command
28176 The corresponding @value{GDBN} command is @samp{stepi}.
28178 @subsubheading Example
28182 -exec-step-instruction
28186 *stopped,reason="end-stepping-range",
28187 frame=@{func="foo",args=[],file="try.c",
28188 fullname="/home/foo/bar/try.c",line="10"@}
28190 -exec-step-instruction
28194 *stopped,reason="end-stepping-range",
28195 frame=@{addr="0x000100f4",func="foo",args=[],file="try.c",
28196 fullname="/home/foo/bar/try.c",line="10"@}
28201 @subheading The @code{-exec-until} Command
28202 @findex -exec-until
28204 @subsubheading Synopsis
28207 -exec-until [ @var{location} ]
28210 Executes the inferior until the @var{location} specified in the
28211 argument is reached. If there is no argument, the inferior executes
28212 until a source line greater than the current one is reached. The
28213 reason for stopping in this case will be @samp{location-reached}.
28215 @subsubheading @value{GDBN} Command
28217 The corresponding @value{GDBN} command is @samp{until}.
28219 @subsubheading Example
28223 -exec-until recursive2.c:6
28227 *stopped,reason="location-reached",frame=@{func="main",args=[],
28228 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="6"@}
28233 @subheading -file-clear
28234 Is this going away????
28237 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
28238 @node GDB/MI Stack Manipulation
28239 @section @sc{gdb/mi} Stack Manipulation Commands
28242 @subheading The @code{-stack-info-frame} Command
28243 @findex -stack-info-frame
28245 @subsubheading Synopsis
28251 Get info on the selected frame.
28253 @subsubheading @value{GDBN} Command
28255 The corresponding @value{GDBN} command is @samp{info frame} or @samp{frame}
28256 (without arguments).
28258 @subsubheading Example
28263 ^done,frame=@{level="1",addr="0x0001076c",func="callee3",
28264 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
28265 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="17"@}
28269 @subheading The @code{-stack-info-depth} Command
28270 @findex -stack-info-depth
28272 @subsubheading Synopsis
28275 -stack-info-depth [ @var{max-depth} ]
28278 Return the depth of the stack. If the integer argument @var{max-depth}
28279 is specified, do not count beyond @var{max-depth} frames.
28281 @subsubheading @value{GDBN} Command
28283 There's no equivalent @value{GDBN} command.
28285 @subsubheading Example
28287 For a stack with frame levels 0 through 11:
28294 -stack-info-depth 4
28297 -stack-info-depth 12
28300 -stack-info-depth 11
28303 -stack-info-depth 13
28308 @subheading The @code{-stack-list-arguments} Command
28309 @findex -stack-list-arguments
28311 @subsubheading Synopsis
28314 -stack-list-arguments @var{print-values}
28315 [ @var{low-frame} @var{high-frame} ]
28318 Display a list of the arguments for the frames between @var{low-frame}
28319 and @var{high-frame} (inclusive). If @var{low-frame} and
28320 @var{high-frame} are not provided, list the arguments for the whole
28321 call stack. If the two arguments are equal, show the single frame
28322 at the corresponding level. It is an error if @var{low-frame} is
28323 larger than the actual number of frames. On the other hand,
28324 @var{high-frame} may be larger than the actual number of frames, in
28325 which case only existing frames will be returned.
28327 If @var{print-values} is 0 or @code{--no-values}, print only the names of
28328 the variables; if it is 1 or @code{--all-values}, print also their
28329 values; and if it is 2 or @code{--simple-values}, print the name,
28330 type and value for simple data types, and the name and type for arrays,
28331 structures and unions.
28333 Use of this command to obtain arguments in a single frame is
28334 deprecated in favor of the @samp{-stack-list-variables} command.
28336 @subsubheading @value{GDBN} Command
28338 @value{GDBN} does not have an equivalent command. @code{gdbtk} has a
28339 @samp{gdb_get_args} command which partially overlaps with the
28340 functionality of @samp{-stack-list-arguments}.
28342 @subsubheading Example
28349 frame=@{level="0",addr="0x00010734",func="callee4",
28350 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
28351 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="8"@},
28352 frame=@{level="1",addr="0x0001076c",func="callee3",
28353 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
28354 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="17"@},
28355 frame=@{level="2",addr="0x0001078c",func="callee2",
28356 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
28357 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="22"@},
28358 frame=@{level="3",addr="0x000107b4",func="callee1",
28359 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
28360 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="27"@},
28361 frame=@{level="4",addr="0x000107e0",func="main",
28362 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
28363 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="32"@}]
28365 -stack-list-arguments 0
28368 frame=@{level="0",args=[]@},
28369 frame=@{level="1",args=[name="strarg"]@},
28370 frame=@{level="2",args=[name="intarg",name="strarg"]@},
28371 frame=@{level="3",args=[name="intarg",name="strarg",name="fltarg"]@},
28372 frame=@{level="4",args=[]@}]
28374 -stack-list-arguments 1
28377 frame=@{level="0",args=[]@},
28379 args=[@{name="strarg",value="0x11940 \"A string argument.\""@}]@},
28380 frame=@{level="2",args=[
28381 @{name="intarg",value="2"@},
28382 @{name="strarg",value="0x11940 \"A string argument.\""@}]@},
28383 @{frame=@{level="3",args=[
28384 @{name="intarg",value="2"@},
28385 @{name="strarg",value="0x11940 \"A string argument.\""@},
28386 @{name="fltarg",value="3.5"@}]@},
28387 frame=@{level="4",args=[]@}]
28389 -stack-list-arguments 0 2 2
28390 ^done,stack-args=[frame=@{level="2",args=[name="intarg",name="strarg"]@}]
28392 -stack-list-arguments 1 2 2
28393 ^done,stack-args=[frame=@{level="2",
28394 args=[@{name="intarg",value="2"@},
28395 @{name="strarg",value="0x11940 \"A string argument.\""@}]@}]
28399 @c @subheading -stack-list-exception-handlers
28402 @subheading The @code{-stack-list-frames} Command
28403 @findex -stack-list-frames
28405 @subsubheading Synopsis
28408 -stack-list-frames [ @var{low-frame} @var{high-frame} ]
28411 List the frames currently on the stack. For each frame it displays the
28416 The frame number, 0 being the topmost frame, i.e., the innermost function.
28418 The @code{$pc} value for that frame.
28422 File name of the source file where the function lives.
28423 @item @var{fullname}
28424 The full file name of the source file where the function lives.
28426 Line number corresponding to the @code{$pc}.
28428 The shared library where this function is defined. This is only given
28429 if the frame's function is not known.
28432 If invoked without arguments, this command prints a backtrace for the
28433 whole stack. If given two integer arguments, it shows the frames whose
28434 levels are between the two arguments (inclusive). If the two arguments
28435 are equal, it shows the single frame at the corresponding level. It is
28436 an error if @var{low-frame} is larger than the actual number of
28437 frames. On the other hand, @var{high-frame} may be larger than the
28438 actual number of frames, in which case only existing frames will be returned.
28440 @subsubheading @value{GDBN} Command
28442 The corresponding @value{GDBN} commands are @samp{backtrace} and @samp{where}.
28444 @subsubheading Example
28446 Full stack backtrace:
28452 [frame=@{level="0",addr="0x0001076c",func="foo",
28453 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="11"@},
28454 frame=@{level="1",addr="0x000107a4",func="foo",
28455 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
28456 frame=@{level="2",addr="0x000107a4",func="foo",
28457 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
28458 frame=@{level="3",addr="0x000107a4",func="foo",
28459 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
28460 frame=@{level="4",addr="0x000107a4",func="foo",
28461 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
28462 frame=@{level="5",addr="0x000107a4",func="foo",
28463 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
28464 frame=@{level="6",addr="0x000107a4",func="foo",
28465 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
28466 frame=@{level="7",addr="0x000107a4",func="foo",
28467 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
28468 frame=@{level="8",addr="0x000107a4",func="foo",
28469 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
28470 frame=@{level="9",addr="0x000107a4",func="foo",
28471 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
28472 frame=@{level="10",addr="0x000107a4",func="foo",
28473 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
28474 frame=@{level="11",addr="0x00010738",func="main",
28475 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="4"@}]
28479 Show frames between @var{low_frame} and @var{high_frame}:
28483 -stack-list-frames 3 5
28485 [frame=@{level="3",addr="0x000107a4",func="foo",
28486 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
28487 frame=@{level="4",addr="0x000107a4",func="foo",
28488 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
28489 frame=@{level="5",addr="0x000107a4",func="foo",
28490 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@}]
28494 Show a single frame:
28498 -stack-list-frames 3 3
28500 [frame=@{level="3",addr="0x000107a4",func="foo",
28501 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@}]
28506 @subheading The @code{-stack-list-locals} Command
28507 @findex -stack-list-locals
28509 @subsubheading Synopsis
28512 -stack-list-locals @var{print-values}
28515 Display the local variable names for the selected frame. If
28516 @var{print-values} is 0 or @code{--no-values}, print only the names of
28517 the variables; if it is 1 or @code{--all-values}, print also their
28518 values; and if it is 2 or @code{--simple-values}, print the name,
28519 type and value for simple data types, and the name and type for arrays,
28520 structures and unions. In this last case, a frontend can immediately
28521 display the value of simple data types and create variable objects for
28522 other data types when the user wishes to explore their values in
28525 This command is deprecated in favor of the
28526 @samp{-stack-list-variables} command.
28528 @subsubheading @value{GDBN} Command
28530 @samp{info locals} in @value{GDBN}, @samp{gdb_get_locals} in @code{gdbtk}.
28532 @subsubheading Example
28536 -stack-list-locals 0
28537 ^done,locals=[name="A",name="B",name="C"]
28539 -stack-list-locals --all-values
28540 ^done,locals=[@{name="A",value="1"@},@{name="B",value="2"@},
28541 @{name="C",value="@{1, 2, 3@}"@}]
28542 -stack-list-locals --simple-values
28543 ^done,locals=[@{name="A",type="int",value="1"@},
28544 @{name="B",type="int",value="2"@},@{name="C",type="int [3]"@}]
28548 @subheading The @code{-stack-list-variables} Command
28549 @findex -stack-list-variables
28551 @subsubheading Synopsis
28554 -stack-list-variables @var{print-values}
28557 Display the names of local variables and function arguments for the selected frame. If
28558 @var{print-values} is 0 or @code{--no-values}, print only the names of
28559 the variables; if it is 1 or @code{--all-values}, print also their
28560 values; and if it is 2 or @code{--simple-values}, print the name,
28561 type and value for simple data types, and the name and type for arrays,
28562 structures and unions.
28564 @subsubheading Example
28568 -stack-list-variables --thread 1 --frame 0 --all-values
28569 ^done,variables=[@{name="x",value="11"@},@{name="s",value="@{a = 1, b = 2@}"@}]
28574 @subheading The @code{-stack-select-frame} Command
28575 @findex -stack-select-frame
28577 @subsubheading Synopsis
28580 -stack-select-frame @var{framenum}
28583 Change the selected frame. Select a different frame @var{framenum} on
28586 This command in deprecated in favor of passing the @samp{--frame}
28587 option to every command.
28589 @subsubheading @value{GDBN} Command
28591 The corresponding @value{GDBN} commands are @samp{frame}, @samp{up},
28592 @samp{down}, @samp{select-frame}, @samp{up-silent}, and @samp{down-silent}.
28594 @subsubheading Example
28598 -stack-select-frame 2
28603 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
28604 @node GDB/MI Variable Objects
28605 @section @sc{gdb/mi} Variable Objects
28609 @subheading Motivation for Variable Objects in @sc{gdb/mi}
28611 For the implementation of a variable debugger window (locals, watched
28612 expressions, etc.), we are proposing the adaptation of the existing code
28613 used by @code{Insight}.
28615 The two main reasons for that are:
28619 It has been proven in practice (it is already on its second generation).
28622 It will shorten development time (needless to say how important it is
28626 The original interface was designed to be used by Tcl code, so it was
28627 slightly changed so it could be used through @sc{gdb/mi}. This section
28628 describes the @sc{gdb/mi} operations that will be available and gives some
28629 hints about their use.
28631 @emph{Note}: In addition to the set of operations described here, we
28632 expect the @sc{gui} implementation of a variable window to require, at
28633 least, the following operations:
28636 @item @code{-gdb-show} @code{output-radix}
28637 @item @code{-stack-list-arguments}
28638 @item @code{-stack-list-locals}
28639 @item @code{-stack-select-frame}
28644 @subheading Introduction to Variable Objects
28646 @cindex variable objects in @sc{gdb/mi}
28648 Variable objects are "object-oriented" MI interface for examining and
28649 changing values of expressions. Unlike some other MI interfaces that
28650 work with expressions, variable objects are specifically designed for
28651 simple and efficient presentation in the frontend. A variable object
28652 is identified by string name. When a variable object is created, the
28653 frontend specifies the expression for that variable object. The
28654 expression can be a simple variable, or it can be an arbitrary complex
28655 expression, and can even involve CPU registers. After creating a
28656 variable object, the frontend can invoke other variable object
28657 operations---for example to obtain or change the value of a variable
28658 object, or to change display format.
28660 Variable objects have hierarchical tree structure. Any variable object
28661 that corresponds to a composite type, such as structure in C, has
28662 a number of child variable objects, for example corresponding to each
28663 element of a structure. A child variable object can itself have
28664 children, recursively. Recursion ends when we reach
28665 leaf variable objects, which always have built-in types. Child variable
28666 objects are created only by explicit request, so if a frontend
28667 is not interested in the children of a particular variable object, no
28668 child will be created.
28670 For a leaf variable object it is possible to obtain its value as a
28671 string, or set the value from a string. String value can be also
28672 obtained for a non-leaf variable object, but it's generally a string
28673 that only indicates the type of the object, and does not list its
28674 contents. Assignment to a non-leaf variable object is not allowed.
28676 A frontend does not need to read the values of all variable objects each time
28677 the program stops. Instead, MI provides an update command that lists all
28678 variable objects whose values has changed since the last update
28679 operation. This considerably reduces the amount of data that must
28680 be transferred to the frontend. As noted above, children variable
28681 objects are created on demand, and only leaf variable objects have a
28682 real value. As result, gdb will read target memory only for leaf
28683 variables that frontend has created.
28685 The automatic update is not always desirable. For example, a frontend
28686 might want to keep a value of some expression for future reference,
28687 and never update it. For another example, fetching memory is
28688 relatively slow for embedded targets, so a frontend might want
28689 to disable automatic update for the variables that are either not
28690 visible on the screen, or ``closed''. This is possible using so
28691 called ``frozen variable objects''. Such variable objects are never
28692 implicitly updated.
28694 Variable objects can be either @dfn{fixed} or @dfn{floating}. For the
28695 fixed variable object, the expression is parsed when the variable
28696 object is created, including associating identifiers to specific
28697 variables. The meaning of expression never changes. For a floating
28698 variable object the values of variables whose names appear in the
28699 expressions are re-evaluated every time in the context of the current
28700 frame. Consider this example:
28705 struct work_state state;
28712 If a fixed variable object for the @code{state} variable is created in
28713 this function, and we enter the recursive call, the variable
28714 object will report the value of @code{state} in the top-level
28715 @code{do_work} invocation. On the other hand, a floating variable
28716 object will report the value of @code{state} in the current frame.
28718 If an expression specified when creating a fixed variable object
28719 refers to a local variable, the variable object becomes bound to the
28720 thread and frame in which the variable object is created. When such
28721 variable object is updated, @value{GDBN} makes sure that the
28722 thread/frame combination the variable object is bound to still exists,
28723 and re-evaluates the variable object in context of that thread/frame.
28725 The following is the complete set of @sc{gdb/mi} operations defined to
28726 access this functionality:
28728 @multitable @columnfractions .4 .6
28729 @item @strong{Operation}
28730 @tab @strong{Description}
28732 @item @code{-enable-pretty-printing}
28733 @tab enable Python-based pretty-printing
28734 @item @code{-var-create}
28735 @tab create a variable object
28736 @item @code{-var-delete}
28737 @tab delete the variable object and/or its children
28738 @item @code{-var-set-format}
28739 @tab set the display format of this variable
28740 @item @code{-var-show-format}
28741 @tab show the display format of this variable
28742 @item @code{-var-info-num-children}
28743 @tab tells how many children this object has
28744 @item @code{-var-list-children}
28745 @tab return a list of the object's children
28746 @item @code{-var-info-type}
28747 @tab show the type of this variable object
28748 @item @code{-var-info-expression}
28749 @tab print parent-relative expression that this variable object represents
28750 @item @code{-var-info-path-expression}
28751 @tab print full expression that this variable object represents
28752 @item @code{-var-show-attributes}
28753 @tab is this variable editable? does it exist here?
28754 @item @code{-var-evaluate-expression}
28755 @tab get the value of this variable
28756 @item @code{-var-assign}
28757 @tab set the value of this variable
28758 @item @code{-var-update}
28759 @tab update the variable and its children
28760 @item @code{-var-set-frozen}
28761 @tab set frozeness attribute
28762 @item @code{-var-set-update-range}
28763 @tab set range of children to display on update
28766 In the next subsection we describe each operation in detail and suggest
28767 how it can be used.
28769 @subheading Description And Use of Operations on Variable Objects
28771 @subheading The @code{-enable-pretty-printing} Command
28772 @findex -enable-pretty-printing
28775 -enable-pretty-printing
28778 @value{GDBN} allows Python-based visualizers to affect the output of the
28779 MI variable object commands. However, because there was no way to
28780 implement this in a fully backward-compatible way, a front end must
28781 request that this functionality be enabled.
28783 Once enabled, this feature cannot be disabled.
28785 Note that if Python support has not been compiled into @value{GDBN},
28786 this command will still succeed (and do nothing).
28788 This feature is currently (as of @value{GDBN} 7.0) experimental, and
28789 may work differently in future versions of @value{GDBN}.
28791 @subheading The @code{-var-create} Command
28792 @findex -var-create
28794 @subsubheading Synopsis
28797 -var-create @{@var{name} | "-"@}
28798 @{@var{frame-addr} | "*" | "@@"@} @var{expression}
28801 This operation creates a variable object, which allows the monitoring of
28802 a variable, the result of an expression, a memory cell or a CPU
28805 The @var{name} parameter is the string by which the object can be
28806 referenced. It must be unique. If @samp{-} is specified, the varobj
28807 system will generate a string ``varNNNNNN'' automatically. It will be
28808 unique provided that one does not specify @var{name} of that format.
28809 The command fails if a duplicate name is found.
28811 The frame under which the expression should be evaluated can be
28812 specified by @var{frame-addr}. A @samp{*} indicates that the current
28813 frame should be used. A @samp{@@} indicates that a floating variable
28814 object must be created.
28816 @var{expression} is any expression valid on the current language set (must not
28817 begin with a @samp{*}), or one of the following:
28821 @samp{*@var{addr}}, where @var{addr} is the address of a memory cell
28824 @samp{*@var{addr}-@var{addr}} --- a memory address range (TBD)
28827 @samp{$@var{regname}} --- a CPU register name
28830 @cindex dynamic varobj
28831 A varobj's contents may be provided by a Python-based pretty-printer. In this
28832 case the varobj is known as a @dfn{dynamic varobj}. Dynamic varobjs
28833 have slightly different semantics in some cases. If the
28834 @code{-enable-pretty-printing} command is not sent, then @value{GDBN}
28835 will never create a dynamic varobj. This ensures backward
28836 compatibility for existing clients.
28838 @subsubheading Result
28840 This operation returns attributes of the newly-created varobj. These
28845 The name of the varobj.
28848 The number of children of the varobj. This number is not necessarily
28849 reliable for a dynamic varobj. Instead, you must examine the
28850 @samp{has_more} attribute.
28853 The varobj's scalar value. For a varobj whose type is some sort of
28854 aggregate (e.g., a @code{struct}), or for a dynamic varobj, this value
28855 will not be interesting.
28858 The varobj's type. This is a string representation of the type, as
28859 would be printed by the @value{GDBN} CLI.
28862 If a variable object is bound to a specific thread, then this is the
28863 thread's identifier.
28866 For a dynamic varobj, this indicates whether there appear to be any
28867 children available. For a non-dynamic varobj, this will be 0.
28870 This attribute will be present and have the value @samp{1} if the
28871 varobj is a dynamic varobj. If the varobj is not a dynamic varobj,
28872 then this attribute will not be present.
28875 A dynamic varobj can supply a display hint to the front end. The
28876 value comes directly from the Python pretty-printer object's
28877 @code{display_hint} method. @xref{Pretty Printing API}.
28880 Typical output will look like this:
28883 name="@var{name}",numchild="@var{N}",type="@var{type}",thread-id="@var{M}",
28884 has_more="@var{has_more}"
28888 @subheading The @code{-var-delete} Command
28889 @findex -var-delete
28891 @subsubheading Synopsis
28894 -var-delete [ -c ] @var{name}
28897 Deletes a previously created variable object and all of its children.
28898 With the @samp{-c} option, just deletes the children.
28900 Returns an error if the object @var{name} is not found.
28903 @subheading The @code{-var-set-format} Command
28904 @findex -var-set-format
28906 @subsubheading Synopsis
28909 -var-set-format @var{name} @var{format-spec}
28912 Sets the output format for the value of the object @var{name} to be
28915 @anchor{-var-set-format}
28916 The syntax for the @var{format-spec} is as follows:
28919 @var{format-spec} @expansion{}
28920 @{binary | decimal | hexadecimal | octal | natural@}
28923 The natural format is the default format choosen automatically
28924 based on the variable type (like decimal for an @code{int}, hex
28925 for pointers, etc.).
28927 For a variable with children, the format is set only on the
28928 variable itself, and the children are not affected.
28930 @subheading The @code{-var-show-format} Command
28931 @findex -var-show-format
28933 @subsubheading Synopsis
28936 -var-show-format @var{name}
28939 Returns the format used to display the value of the object @var{name}.
28942 @var{format} @expansion{}
28947 @subheading The @code{-var-info-num-children} Command
28948 @findex -var-info-num-children
28950 @subsubheading Synopsis
28953 -var-info-num-children @var{name}
28956 Returns the number of children of a variable object @var{name}:
28962 Note that this number is not completely reliable for a dynamic varobj.
28963 It will return the current number of children, but more children may
28967 @subheading The @code{-var-list-children} Command
28968 @findex -var-list-children
28970 @subsubheading Synopsis
28973 -var-list-children [@var{print-values}] @var{name} [@var{from} @var{to}]
28975 @anchor{-var-list-children}
28977 Return a list of the children of the specified variable object and
28978 create variable objects for them, if they do not already exist. With
28979 a single argument or if @var{print-values} has a value of 0 or
28980 @code{--no-values}, print only the names of the variables; if
28981 @var{print-values} is 1 or @code{--all-values}, also print their
28982 values; and if it is 2 or @code{--simple-values} print the name and
28983 value for simple data types and just the name for arrays, structures
28986 @var{from} and @var{to}, if specified, indicate the range of children
28987 to report. If @var{from} or @var{to} is less than zero, the range is
28988 reset and all children will be reported. Otherwise, children starting
28989 at @var{from} (zero-based) and up to and excluding @var{to} will be
28992 If a child range is requested, it will only affect the current call to
28993 @code{-var-list-children}, but not future calls to @code{-var-update}.
28994 For this, you must instead use @code{-var-set-update-range}. The
28995 intent of this approach is to enable a front end to implement any
28996 update approach it likes; for example, scrolling a view may cause the
28997 front end to request more children with @code{-var-list-children}, and
28998 then the front end could call @code{-var-set-update-range} with a
28999 different range to ensure that future updates are restricted to just
29002 For each child the following results are returned:
29007 Name of the variable object created for this child.
29010 The expression to be shown to the user by the front end to designate this child.
29011 For example this may be the name of a structure member.
29013 For a dynamic varobj, this value cannot be used to form an
29014 expression. There is no way to do this at all with a dynamic varobj.
29016 For C/C@t{++} structures there are several pseudo children returned to
29017 designate access qualifiers. For these pseudo children @var{exp} is
29018 @samp{public}, @samp{private}, or @samp{protected}. In this case the
29019 type and value are not present.
29021 A dynamic varobj will not report the access qualifying
29022 pseudo-children, regardless of the language. This information is not
29023 available at all with a dynamic varobj.
29026 Number of children this child has. For a dynamic varobj, this will be
29030 The type of the child.
29033 If values were requested, this is the value.
29036 If this variable object is associated with a thread, this is the thread id.
29037 Otherwise this result is not present.
29040 If the variable object is frozen, this variable will be present with a value of 1.
29043 The result may have its own attributes:
29047 A dynamic varobj can supply a display hint to the front end. The
29048 value comes directly from the Python pretty-printer object's
29049 @code{display_hint} method. @xref{Pretty Printing API}.
29052 This is an integer attribute which is nonzero if there are children
29053 remaining after the end of the selected range.
29056 @subsubheading Example
29060 -var-list-children n
29061 ^done,numchild=@var{n},children=[child=@{name=@var{name},exp=@var{exp},
29062 numchild=@var{n},type=@var{type}@},@r{(repeats N times)}]
29064 -var-list-children --all-values n
29065 ^done,numchild=@var{n},children=[child=@{name=@var{name},exp=@var{exp},
29066 numchild=@var{n},value=@var{value},type=@var{type}@},@r{(repeats N times)}]
29070 @subheading The @code{-var-info-type} Command
29071 @findex -var-info-type
29073 @subsubheading Synopsis
29076 -var-info-type @var{name}
29079 Returns the type of the specified variable @var{name}. The type is
29080 returned as a string in the same format as it is output by the
29084 type=@var{typename}
29088 @subheading The @code{-var-info-expression} Command
29089 @findex -var-info-expression
29091 @subsubheading Synopsis
29094 -var-info-expression @var{name}
29097 Returns a string that is suitable for presenting this
29098 variable object in user interface. The string is generally
29099 not valid expression in the current language, and cannot be evaluated.
29101 For example, if @code{a} is an array, and variable object
29102 @code{A} was created for @code{a}, then we'll get this output:
29105 (gdb) -var-info-expression A.1
29106 ^done,lang="C",exp="1"
29110 Here, the values of @code{lang} can be @code{@{"C" | "C++" | "Java"@}}.
29112 Note that the output of the @code{-var-list-children} command also
29113 includes those expressions, so the @code{-var-info-expression} command
29116 @subheading The @code{-var-info-path-expression} Command
29117 @findex -var-info-path-expression
29119 @subsubheading Synopsis
29122 -var-info-path-expression @var{name}
29125 Returns an expression that can be evaluated in the current
29126 context and will yield the same value that a variable object has.
29127 Compare this with the @code{-var-info-expression} command, which
29128 result can be used only for UI presentation. Typical use of
29129 the @code{-var-info-path-expression} command is creating a
29130 watchpoint from a variable object.
29132 This command is currently not valid for children of a dynamic varobj,
29133 and will give an error when invoked on one.
29135 For example, suppose @code{C} is a C@t{++} class, derived from class
29136 @code{Base}, and that the @code{Base} class has a member called
29137 @code{m_size}. Assume a variable @code{c} is has the type of
29138 @code{C} and a variable object @code{C} was created for variable
29139 @code{c}. Then, we'll get this output:
29141 (gdb) -var-info-path-expression C.Base.public.m_size
29142 ^done,path_expr=((Base)c).m_size)
29145 @subheading The @code{-var-show-attributes} Command
29146 @findex -var-show-attributes
29148 @subsubheading Synopsis
29151 -var-show-attributes @var{name}
29154 List attributes of the specified variable object @var{name}:
29157 status=@var{attr} [ ( ,@var{attr} )* ]
29161 where @var{attr} is @code{@{ @{ editable | noneditable @} | TBD @}}.
29163 @subheading The @code{-var-evaluate-expression} Command
29164 @findex -var-evaluate-expression
29166 @subsubheading Synopsis
29169 -var-evaluate-expression [-f @var{format-spec}] @var{name}
29172 Evaluates the expression that is represented by the specified variable
29173 object and returns its value as a string. The format of the string
29174 can be specified with the @samp{-f} option. The possible values of
29175 this option are the same as for @code{-var-set-format}
29176 (@pxref{-var-set-format}). If the @samp{-f} option is not specified,
29177 the current display format will be used. The current display format
29178 can be changed using the @code{-var-set-format} command.
29184 Note that one must invoke @code{-var-list-children} for a variable
29185 before the value of a child variable can be evaluated.
29187 @subheading The @code{-var-assign} Command
29188 @findex -var-assign
29190 @subsubheading Synopsis
29193 -var-assign @var{name} @var{expression}
29196 Assigns the value of @var{expression} to the variable object specified
29197 by @var{name}. The object must be @samp{editable}. If the variable's
29198 value is altered by the assign, the variable will show up in any
29199 subsequent @code{-var-update} list.
29201 @subsubheading Example
29209 ^done,changelist=[@{name="var1",in_scope="true",type_changed="false"@}]
29213 @subheading The @code{-var-update} Command
29214 @findex -var-update
29216 @subsubheading Synopsis
29219 -var-update [@var{print-values}] @{@var{name} | "*"@}
29222 Reevaluate the expressions corresponding to the variable object
29223 @var{name} and all its direct and indirect children, and return the
29224 list of variable objects whose values have changed; @var{name} must
29225 be a root variable object. Here, ``changed'' means that the result of
29226 @code{-var-evaluate-expression} before and after the
29227 @code{-var-update} is different. If @samp{*} is used as the variable
29228 object names, all existing variable objects are updated, except
29229 for frozen ones (@pxref{-var-set-frozen}). The option
29230 @var{print-values} determines whether both names and values, or just
29231 names are printed. The possible values of this option are the same
29232 as for @code{-var-list-children} (@pxref{-var-list-children}). It is
29233 recommended to use the @samp{--all-values} option, to reduce the
29234 number of MI commands needed on each program stop.
29236 With the @samp{*} parameter, if a variable object is bound to a
29237 currently running thread, it will not be updated, without any
29240 If @code{-var-set-update-range} was previously used on a varobj, then
29241 only the selected range of children will be reported.
29243 @code{-var-update} reports all the changed varobjs in a tuple named
29246 Each item in the change list is itself a tuple holding:
29250 The name of the varobj.
29253 If values were requested for this update, then this field will be
29254 present and will hold the value of the varobj.
29257 @anchor{-var-update}
29258 This field is a string which may take one of three values:
29262 The variable object's current value is valid.
29265 The variable object does not currently hold a valid value but it may
29266 hold one in the future if its associated expression comes back into
29270 The variable object no longer holds a valid value.
29271 This can occur when the executable file being debugged has changed,
29272 either through recompilation or by using the @value{GDBN} @code{file}
29273 command. The front end should normally choose to delete these variable
29277 In the future new values may be added to this list so the front should
29278 be prepared for this possibility. @xref{GDB/MI Development and Front Ends, ,@sc{GDB/MI} Development and Front Ends}.
29281 This is only present if the varobj is still valid. If the type
29282 changed, then this will be the string @samp{true}; otherwise it will
29286 If the varobj's type changed, then this field will be present and will
29289 @item new_num_children
29290 For a dynamic varobj, if the number of children changed, or if the
29291 type changed, this will be the new number of children.
29293 The @samp{numchild} field in other varobj responses is generally not
29294 valid for a dynamic varobj -- it will show the number of children that
29295 @value{GDBN} knows about, but because dynamic varobjs lazily
29296 instantiate their children, this will not reflect the number of
29297 children which may be available.
29299 The @samp{new_num_children} attribute only reports changes to the
29300 number of children known by @value{GDBN}. This is the only way to
29301 detect whether an update has removed children (which necessarily can
29302 only happen at the end of the update range).
29305 The display hint, if any.
29308 This is an integer value, which will be 1 if there are more children
29309 available outside the varobj's update range.
29312 This attribute will be present and have the value @samp{1} if the
29313 varobj is a dynamic varobj. If the varobj is not a dynamic varobj,
29314 then this attribute will not be present.
29317 If new children were added to a dynamic varobj within the selected
29318 update range (as set by @code{-var-set-update-range}), then they will
29319 be listed in this attribute.
29322 @subsubheading Example
29329 -var-update --all-values var1
29330 ^done,changelist=[@{name="var1",value="3",in_scope="true",
29331 type_changed="false"@}]
29335 @subheading The @code{-var-set-frozen} Command
29336 @findex -var-set-frozen
29337 @anchor{-var-set-frozen}
29339 @subsubheading Synopsis
29342 -var-set-frozen @var{name} @var{flag}
29345 Set the frozenness flag on the variable object @var{name}. The
29346 @var{flag} parameter should be either @samp{1} to make the variable
29347 frozen or @samp{0} to make it unfrozen. If a variable object is
29348 frozen, then neither itself, nor any of its children, are
29349 implicitly updated by @code{-var-update} of
29350 a parent variable or by @code{-var-update *}. Only
29351 @code{-var-update} of the variable itself will update its value and
29352 values of its children. After a variable object is unfrozen, it is
29353 implicitly updated by all subsequent @code{-var-update} operations.
29354 Unfreezing a variable does not update it, only subsequent
29355 @code{-var-update} does.
29357 @subsubheading Example
29361 -var-set-frozen V 1
29366 @subheading The @code{-var-set-update-range} command
29367 @findex -var-set-update-range
29368 @anchor{-var-set-update-range}
29370 @subsubheading Synopsis
29373 -var-set-update-range @var{name} @var{from} @var{to}
29376 Set the range of children to be returned by future invocations of
29377 @code{-var-update}.
29379 @var{from} and @var{to} indicate the range of children to report. If
29380 @var{from} or @var{to} is less than zero, the range is reset and all
29381 children will be reported. Otherwise, children starting at @var{from}
29382 (zero-based) and up to and excluding @var{to} will be reported.
29384 @subsubheading Example
29388 -var-set-update-range V 1 2
29392 @subheading The @code{-var-set-visualizer} command
29393 @findex -var-set-visualizer
29394 @anchor{-var-set-visualizer}
29396 @subsubheading Synopsis
29399 -var-set-visualizer @var{name} @var{visualizer}
29402 Set a visualizer for the variable object @var{name}.
29404 @var{visualizer} is the visualizer to use. The special value
29405 @samp{None} means to disable any visualizer in use.
29407 If not @samp{None}, @var{visualizer} must be a Python expression.
29408 This expression must evaluate to a callable object which accepts a
29409 single argument. @value{GDBN} will call this object with the value of
29410 the varobj @var{name} as an argument (this is done so that the same
29411 Python pretty-printing code can be used for both the CLI and MI).
29412 When called, this object must return an object which conforms to the
29413 pretty-printing interface (@pxref{Pretty Printing API}).
29415 The pre-defined function @code{gdb.default_visualizer} may be used to
29416 select a visualizer by following the built-in process
29417 (@pxref{Selecting Pretty-Printers}). This is done automatically when
29418 a varobj is created, and so ordinarily is not needed.
29420 This feature is only available if Python support is enabled. The MI
29421 command @code{-list-features} (@pxref{GDB/MI Miscellaneous Commands})
29422 can be used to check this.
29424 @subsubheading Example
29426 Resetting the visualizer:
29430 -var-set-visualizer V None
29434 Reselecting the default (type-based) visualizer:
29438 -var-set-visualizer V gdb.default_visualizer
29442 Suppose @code{SomeClass} is a visualizer class. A lambda expression
29443 can be used to instantiate this class for a varobj:
29447 -var-set-visualizer V "lambda val: SomeClass()"
29451 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
29452 @node GDB/MI Data Manipulation
29453 @section @sc{gdb/mi} Data Manipulation
29455 @cindex data manipulation, in @sc{gdb/mi}
29456 @cindex @sc{gdb/mi}, data manipulation
29457 This section describes the @sc{gdb/mi} commands that manipulate data:
29458 examine memory and registers, evaluate expressions, etc.
29460 @c REMOVED FROM THE INTERFACE.
29461 @c @subheading -data-assign
29462 @c Change the value of a program variable. Plenty of side effects.
29463 @c @subsubheading GDB Command
29465 @c @subsubheading Example
29468 @subheading The @code{-data-disassemble} Command
29469 @findex -data-disassemble
29471 @subsubheading Synopsis
29475 [ -s @var{start-addr} -e @var{end-addr} ]
29476 | [ -f @var{filename} -l @var{linenum} [ -n @var{lines} ] ]
29484 @item @var{start-addr}
29485 is the beginning address (or @code{$pc})
29486 @item @var{end-addr}
29488 @item @var{filename}
29489 is the name of the file to disassemble
29490 @item @var{linenum}
29491 is the line number to disassemble around
29493 is the number of disassembly lines to be produced. If it is -1,
29494 the whole function will be disassembled, in case no @var{end-addr} is
29495 specified. If @var{end-addr} is specified as a non-zero value, and
29496 @var{lines} is lower than the number of disassembly lines between
29497 @var{start-addr} and @var{end-addr}, only @var{lines} lines are
29498 displayed; if @var{lines} is higher than the number of lines between
29499 @var{start-addr} and @var{end-addr}, only the lines up to @var{end-addr}
29502 is either 0 (meaning only disassembly), 1 (meaning mixed source and
29503 disassembly), 2 (meaning disassembly with raw opcodes), or 3 (meaning
29504 mixed source and disassembly with raw opcodes).
29507 @subsubheading Result
29509 The output for each instruction is composed of four fields:
29518 Note that whatever included in the instruction field, is not manipulated
29519 directly by @sc{gdb/mi}, i.e., it is not possible to adjust its format.
29521 @subsubheading @value{GDBN} Command
29523 There's no direct mapping from this command to the CLI.
29525 @subsubheading Example
29527 Disassemble from the current value of @code{$pc} to @code{$pc + 20}:
29531 -data-disassemble -s $pc -e "$pc + 20" -- 0
29534 @{address="0x000107c0",func-name="main",offset="4",
29535 inst="mov 2, %o0"@},
29536 @{address="0x000107c4",func-name="main",offset="8",
29537 inst="sethi %hi(0x11800), %o2"@},
29538 @{address="0x000107c8",func-name="main",offset="12",
29539 inst="or %o2, 0x140, %o1\t! 0x11940 <_lib_version+8>"@},
29540 @{address="0x000107cc",func-name="main",offset="16",
29541 inst="sethi %hi(0x11800), %o2"@},
29542 @{address="0x000107d0",func-name="main",offset="20",
29543 inst="or %o2, 0x168, %o4\t! 0x11968 <_lib_version+48>"@}]
29547 Disassemble the whole @code{main} function. Line 32 is part of
29551 -data-disassemble -f basics.c -l 32 -- 0
29553 @{address="0x000107bc",func-name="main",offset="0",
29554 inst="save %sp, -112, %sp"@},
29555 @{address="0x000107c0",func-name="main",offset="4",
29556 inst="mov 2, %o0"@},
29557 @{address="0x000107c4",func-name="main",offset="8",
29558 inst="sethi %hi(0x11800), %o2"@},
29560 @{address="0x0001081c",func-name="main",offset="96",inst="ret "@},
29561 @{address="0x00010820",func-name="main",offset="100",inst="restore "@}]
29565 Disassemble 3 instructions from the start of @code{main}:
29569 -data-disassemble -f basics.c -l 32 -n 3 -- 0
29571 @{address="0x000107bc",func-name="main",offset="0",
29572 inst="save %sp, -112, %sp"@},
29573 @{address="0x000107c0",func-name="main",offset="4",
29574 inst="mov 2, %o0"@},
29575 @{address="0x000107c4",func-name="main",offset="8",
29576 inst="sethi %hi(0x11800), %o2"@}]
29580 Disassemble 3 instructions from the start of @code{main} in mixed mode:
29584 -data-disassemble -f basics.c -l 32 -n 3 -- 1
29586 src_and_asm_line=@{line="31",
29587 file="/kwikemart/marge/ezannoni/flathead-dev/devo/gdb/ \
29588 testsuite/gdb.mi/basics.c",line_asm_insn=[
29589 @{address="0x000107bc",func-name="main",offset="0",
29590 inst="save %sp, -112, %sp"@}]@},
29591 src_and_asm_line=@{line="32",
29592 file="/kwikemart/marge/ezannoni/flathead-dev/devo/gdb/ \
29593 testsuite/gdb.mi/basics.c",line_asm_insn=[
29594 @{address="0x000107c0",func-name="main",offset="4",
29595 inst="mov 2, %o0"@},
29596 @{address="0x000107c4",func-name="main",offset="8",
29597 inst="sethi %hi(0x11800), %o2"@}]@}]
29602 @subheading The @code{-data-evaluate-expression} Command
29603 @findex -data-evaluate-expression
29605 @subsubheading Synopsis
29608 -data-evaluate-expression @var{expr}
29611 Evaluate @var{expr} as an expression. The expression could contain an
29612 inferior function call. The function call will execute synchronously.
29613 If the expression contains spaces, it must be enclosed in double quotes.
29615 @subsubheading @value{GDBN} Command
29617 The corresponding @value{GDBN} commands are @samp{print}, @samp{output}, and
29618 @samp{call}. In @code{gdbtk} only, there's a corresponding
29619 @samp{gdb_eval} command.
29621 @subsubheading Example
29623 In the following example, the numbers that precede the commands are the
29624 @dfn{tokens} described in @ref{GDB/MI Command Syntax, ,@sc{gdb/mi}
29625 Command Syntax}. Notice how @sc{gdb/mi} returns the same tokens in its
29629 211-data-evaluate-expression A
29632 311-data-evaluate-expression &A
29633 311^done,value="0xefffeb7c"
29635 411-data-evaluate-expression A+3
29638 511-data-evaluate-expression "A + 3"
29644 @subheading The @code{-data-list-changed-registers} Command
29645 @findex -data-list-changed-registers
29647 @subsubheading Synopsis
29650 -data-list-changed-registers
29653 Display a list of the registers that have changed.
29655 @subsubheading @value{GDBN} Command
29657 @value{GDBN} doesn't have a direct analog for this command; @code{gdbtk}
29658 has the corresponding command @samp{gdb_changed_register_list}.
29660 @subsubheading Example
29662 On a PPC MBX board:
29670 *stopped,reason="breakpoint-hit",disp="keep",bkptno="1",frame=@{
29671 func="main",args=[],file="try.c",fullname="/home/foo/bar/try.c",
29674 -data-list-changed-registers
29675 ^done,changed-registers=["0","1","2","4","5","6","7","8","9",
29676 "10","11","13","14","15","16","17","18","19","20","21","22","23",
29677 "24","25","26","27","28","30","31","64","65","66","67","69"]
29682 @subheading The @code{-data-list-register-names} Command
29683 @findex -data-list-register-names
29685 @subsubheading Synopsis
29688 -data-list-register-names [ ( @var{regno} )+ ]
29691 Show a list of register names for the current target. If no arguments
29692 are given, it shows a list of the names of all the registers. If
29693 integer numbers are given as arguments, it will print a list of the
29694 names of the registers corresponding to the arguments. To ensure
29695 consistency between a register name and its number, the output list may
29696 include empty register names.
29698 @subsubheading @value{GDBN} Command
29700 @value{GDBN} does not have a command which corresponds to
29701 @samp{-data-list-register-names}. In @code{gdbtk} there is a
29702 corresponding command @samp{gdb_regnames}.
29704 @subsubheading Example
29706 For the PPC MBX board:
29709 -data-list-register-names
29710 ^done,register-names=["r0","r1","r2","r3","r4","r5","r6","r7",
29711 "r8","r9","r10","r11","r12","r13","r14","r15","r16","r17","r18",
29712 "r19","r20","r21","r22","r23","r24","r25","r26","r27","r28","r29",
29713 "r30","r31","f0","f1","f2","f3","f4","f5","f6","f7","f8","f9",
29714 "f10","f11","f12","f13","f14","f15","f16","f17","f18","f19","f20",
29715 "f21","f22","f23","f24","f25","f26","f27","f28","f29","f30","f31",
29716 "", "pc","ps","cr","lr","ctr","xer"]
29718 -data-list-register-names 1 2 3
29719 ^done,register-names=["r1","r2","r3"]
29723 @subheading The @code{-data-list-register-values} Command
29724 @findex -data-list-register-values
29726 @subsubheading Synopsis
29729 -data-list-register-values @var{fmt} [ ( @var{regno} )*]
29732 Display the registers' contents. @var{fmt} is the format according to
29733 which the registers' contents are to be returned, followed by an optional
29734 list of numbers specifying the registers to display. A missing list of
29735 numbers indicates that the contents of all the registers must be returned.
29737 Allowed formats for @var{fmt} are:
29754 @subsubheading @value{GDBN} Command
29756 The corresponding @value{GDBN} commands are @samp{info reg}, @samp{info
29757 all-reg}, and (in @code{gdbtk}) @samp{gdb_fetch_registers}.
29759 @subsubheading Example
29761 For a PPC MBX board (note: line breaks are for readability only, they
29762 don't appear in the actual output):
29766 -data-list-register-values r 64 65
29767 ^done,register-values=[@{number="64",value="0xfe00a300"@},
29768 @{number="65",value="0x00029002"@}]
29770 -data-list-register-values x
29771 ^done,register-values=[@{number="0",value="0xfe0043c8"@},
29772 @{number="1",value="0x3fff88"@},@{number="2",value="0xfffffffe"@},
29773 @{number="3",value="0x0"@},@{number="4",value="0xa"@},
29774 @{number="5",value="0x3fff68"@},@{number="6",value="0x3fff58"@},
29775 @{number="7",value="0xfe011e98"@},@{number="8",value="0x2"@},
29776 @{number="9",value="0xfa202820"@},@{number="10",value="0xfa202808"@},
29777 @{number="11",value="0x1"@},@{number="12",value="0x0"@},
29778 @{number="13",value="0x4544"@},@{number="14",value="0xffdfffff"@},
29779 @{number="15",value="0xffffffff"@},@{number="16",value="0xfffffeff"@},
29780 @{number="17",value="0xefffffed"@},@{number="18",value="0xfffffffe"@},
29781 @{number="19",value="0xffffffff"@},@{number="20",value="0xffffffff"@},
29782 @{number="21",value="0xffffffff"@},@{number="22",value="0xfffffff7"@},
29783 @{number="23",value="0xffffffff"@},@{number="24",value="0xffffffff"@},
29784 @{number="25",value="0xffffffff"@},@{number="26",value="0xfffffffb"@},
29785 @{number="27",value="0xffffffff"@},@{number="28",value="0xf7bfffff"@},
29786 @{number="29",value="0x0"@},@{number="30",value="0xfe010000"@},
29787 @{number="31",value="0x0"@},@{number="32",value="0x0"@},
29788 @{number="33",value="0x0"@},@{number="34",value="0x0"@},
29789 @{number="35",value="0x0"@},@{number="36",value="0x0"@},
29790 @{number="37",value="0x0"@},@{number="38",value="0x0"@},
29791 @{number="39",value="0x0"@},@{number="40",value="0x0"@},
29792 @{number="41",value="0x0"@},@{number="42",value="0x0"@},
29793 @{number="43",value="0x0"@},@{number="44",value="0x0"@},
29794 @{number="45",value="0x0"@},@{number="46",value="0x0"@},
29795 @{number="47",value="0x0"@},@{number="48",value="0x0"@},
29796 @{number="49",value="0x0"@},@{number="50",value="0x0"@},
29797 @{number="51",value="0x0"@},@{number="52",value="0x0"@},
29798 @{number="53",value="0x0"@},@{number="54",value="0x0"@},
29799 @{number="55",value="0x0"@},@{number="56",value="0x0"@},
29800 @{number="57",value="0x0"@},@{number="58",value="0x0"@},
29801 @{number="59",value="0x0"@},@{number="60",value="0x0"@},
29802 @{number="61",value="0x0"@},@{number="62",value="0x0"@},
29803 @{number="63",value="0x0"@},@{number="64",value="0xfe00a300"@},
29804 @{number="65",value="0x29002"@},@{number="66",value="0x202f04b5"@},
29805 @{number="67",value="0xfe0043b0"@},@{number="68",value="0xfe00b3e4"@},
29806 @{number="69",value="0x20002b03"@}]
29811 @subheading The @code{-data-read-memory} Command
29812 @findex -data-read-memory
29814 This command is deprecated, use @code{-data-read-memory-bytes} instead.
29816 @subsubheading Synopsis
29819 -data-read-memory [ -o @var{byte-offset} ]
29820 @var{address} @var{word-format} @var{word-size}
29821 @var{nr-rows} @var{nr-cols} [ @var{aschar} ]
29828 @item @var{address}
29829 An expression specifying the address of the first memory word to be
29830 read. Complex expressions containing embedded white space should be
29831 quoted using the C convention.
29833 @item @var{word-format}
29834 The format to be used to print the memory words. The notation is the
29835 same as for @value{GDBN}'s @code{print} command (@pxref{Output Formats,
29838 @item @var{word-size}
29839 The size of each memory word in bytes.
29841 @item @var{nr-rows}
29842 The number of rows in the output table.
29844 @item @var{nr-cols}
29845 The number of columns in the output table.
29848 If present, indicates that each row should include an @sc{ascii} dump. The
29849 value of @var{aschar} is used as a padding character when a byte is not a
29850 member of the printable @sc{ascii} character set (printable @sc{ascii}
29851 characters are those whose code is between 32 and 126, inclusively).
29853 @item @var{byte-offset}
29854 An offset to add to the @var{address} before fetching memory.
29857 This command displays memory contents as a table of @var{nr-rows} by
29858 @var{nr-cols} words, each word being @var{word-size} bytes. In total,
29859 @code{@var{nr-rows} * @var{nr-cols} * @var{word-size}} bytes are read
29860 (returned as @samp{total-bytes}). Should less than the requested number
29861 of bytes be returned by the target, the missing words are identified
29862 using @samp{N/A}. The number of bytes read from the target is returned
29863 in @samp{nr-bytes} and the starting address used to read memory in
29866 The address of the next/previous row or page is available in
29867 @samp{next-row} and @samp{prev-row}, @samp{next-page} and
29870 @subsubheading @value{GDBN} Command
29872 The corresponding @value{GDBN} command is @samp{x}. @code{gdbtk} has
29873 @samp{gdb_get_mem} memory read command.
29875 @subsubheading Example
29877 Read six bytes of memory starting at @code{bytes+6} but then offset by
29878 @code{-6} bytes. Format as three rows of two columns. One byte per
29879 word. Display each word in hex.
29883 9-data-read-memory -o -6 -- bytes+6 x 1 3 2
29884 9^done,addr="0x00001390",nr-bytes="6",total-bytes="6",
29885 next-row="0x00001396",prev-row="0x0000138e",next-page="0x00001396",
29886 prev-page="0x0000138a",memory=[
29887 @{addr="0x00001390",data=["0x00","0x01"]@},
29888 @{addr="0x00001392",data=["0x02","0x03"]@},
29889 @{addr="0x00001394",data=["0x04","0x05"]@}]
29893 Read two bytes of memory starting at address @code{shorts + 64} and
29894 display as a single word formatted in decimal.
29898 5-data-read-memory shorts+64 d 2 1 1
29899 5^done,addr="0x00001510",nr-bytes="2",total-bytes="2",
29900 next-row="0x00001512",prev-row="0x0000150e",
29901 next-page="0x00001512",prev-page="0x0000150e",memory=[
29902 @{addr="0x00001510",data=["128"]@}]
29906 Read thirty two bytes of memory starting at @code{bytes+16} and format
29907 as eight rows of four columns. Include a string encoding with @samp{x}
29908 used as the non-printable character.
29912 4-data-read-memory bytes+16 x 1 8 4 x
29913 4^done,addr="0x000013a0",nr-bytes="32",total-bytes="32",
29914 next-row="0x000013c0",prev-row="0x0000139c",
29915 next-page="0x000013c0",prev-page="0x00001380",memory=[
29916 @{addr="0x000013a0",data=["0x10","0x11","0x12","0x13"],ascii="xxxx"@},
29917 @{addr="0x000013a4",data=["0x14","0x15","0x16","0x17"],ascii="xxxx"@},
29918 @{addr="0x000013a8",data=["0x18","0x19","0x1a","0x1b"],ascii="xxxx"@},
29919 @{addr="0x000013ac",data=["0x1c","0x1d","0x1e","0x1f"],ascii="xxxx"@},
29920 @{addr="0x000013b0",data=["0x20","0x21","0x22","0x23"],ascii=" !\"#"@},
29921 @{addr="0x000013b4",data=["0x24","0x25","0x26","0x27"],ascii="$%&'"@},
29922 @{addr="0x000013b8",data=["0x28","0x29","0x2a","0x2b"],ascii="()*+"@},
29923 @{addr="0x000013bc",data=["0x2c","0x2d","0x2e","0x2f"],ascii=",-./"@}]
29927 @subheading The @code{-data-read-memory-bytes} Command
29928 @findex -data-read-memory-bytes
29930 @subsubheading Synopsis
29933 -data-read-memory-bytes [ -o @var{byte-offset} ]
29934 @var{address} @var{count}
29941 @item @var{address}
29942 An expression specifying the address of the first memory word to be
29943 read. Complex expressions containing embedded white space should be
29944 quoted using the C convention.
29947 The number of bytes to read. This should be an integer literal.
29949 @item @var{byte-offset}
29950 The offsets in bytes relative to @var{address} at which to start
29951 reading. This should be an integer literal. This option is provided
29952 so that a frontend is not required to first evaluate address and then
29953 perform address arithmetics itself.
29957 This command attempts to read all accessible memory regions in the
29958 specified range. First, all regions marked as unreadable in the memory
29959 map (if one is defined) will be skipped. @xref{Memory Region
29960 Attributes}. Second, @value{GDBN} will attempt to read the remaining
29961 regions. For each one, if reading full region results in an errors,
29962 @value{GDBN} will try to read a subset of the region.
29964 In general, every single byte in the region may be readable or not,
29965 and the only way to read every readable byte is to try a read at
29966 every address, which is not practical. Therefore, @value{GDBN} will
29967 attempt to read all accessible bytes at either beginning or the end
29968 of the region, using a binary division scheme. This heuristic works
29969 well for reading accross a memory map boundary. Note that if a region
29970 has a readable range that is neither at the beginning or the end,
29971 @value{GDBN} will not read it.
29973 The result record (@pxref{GDB/MI Result Records}) that is output of
29974 the command includes a field named @samp{memory} whose content is a
29975 list of tuples. Each tuple represent a successfully read memory block
29976 and has the following fields:
29980 The start address of the memory block, as hexadecimal literal.
29983 The end address of the memory block, as hexadecimal literal.
29986 The offset of the memory block, as hexadecimal literal, relative to
29987 the start address passed to @code{-data-read-memory-bytes}.
29990 The contents of the memory block, in hex.
29996 @subsubheading @value{GDBN} Command
29998 The corresponding @value{GDBN} command is @samp{x}.
30000 @subsubheading Example
30004 -data-read-memory-bytes &a 10
30005 ^done,memory=[@{begin="0xbffff154",offset="0x00000000",
30007 contents="01000000020000000300"@}]
30012 @subheading The @code{-data-write-memory-bytes} Command
30013 @findex -data-write-memory-bytes
30015 @subsubheading Synopsis
30018 -data-write-memory-bytes @var{address} @var{contents}
30025 @item @var{address}
30026 An expression specifying the address of the first memory word to be
30027 read. Complex expressions containing embedded white space should be
30028 quoted using the C convention.
30030 @item @var{contents}
30031 The hex-encoded bytes to write.
30035 @subsubheading @value{GDBN} Command
30037 There's no corresponding @value{GDBN} command.
30039 @subsubheading Example
30043 -data-write-memory-bytes &a "aabbccdd"
30049 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
30050 @node GDB/MI Tracepoint Commands
30051 @section @sc{gdb/mi} Tracepoint Commands
30053 The commands defined in this section implement MI support for
30054 tracepoints. For detailed introduction, see @ref{Tracepoints}.
30056 @subheading The @code{-trace-find} Command
30057 @findex -trace-find
30059 @subsubheading Synopsis
30062 -trace-find @var{mode} [@var{parameters}@dots{}]
30065 Find a trace frame using criteria defined by @var{mode} and
30066 @var{parameters}. The following table lists permissible
30067 modes and their parameters. For details of operation, see @ref{tfind}.
30072 No parameters are required. Stops examining trace frames.
30075 An integer is required as parameter. Selects tracepoint frame with
30078 @item tracepoint-number
30079 An integer is required as parameter. Finds next
30080 trace frame that corresponds to tracepoint with the specified number.
30083 An address is required as parameter. Finds
30084 next trace frame that corresponds to any tracepoint at the specified
30087 @item pc-inside-range
30088 Two addresses are required as parameters. Finds next trace
30089 frame that corresponds to a tracepoint at an address inside the
30090 specified range. Both bounds are considered to be inside the range.
30092 @item pc-outside-range
30093 Two addresses are required as parameters. Finds
30094 next trace frame that corresponds to a tracepoint at an address outside
30095 the specified range. Both bounds are considered to be inside the range.
30098 Line specification is required as parameter. @xref{Specify Location}.
30099 Finds next trace frame that corresponds to a tracepoint at
30100 the specified location.
30104 If @samp{none} was passed as @var{mode}, the response does not
30105 have fields. Otherwise, the response may have the following fields:
30109 This field has either @samp{0} or @samp{1} as the value, depending
30110 on whether a matching tracepoint was found.
30113 The index of the found traceframe. This field is present iff
30114 the @samp{found} field has value of @samp{1}.
30117 The index of the found tracepoint. This field is present iff
30118 the @samp{found} field has value of @samp{1}.
30121 The information about the frame corresponding to the found trace
30122 frame. This field is present only if a trace frame was found.
30123 @xref{GDB/MI Frame Information}, for description of this field.
30127 @subsubheading @value{GDBN} Command
30129 The corresponding @value{GDBN} command is @samp{tfind}.
30131 @subheading -trace-define-variable
30132 @findex -trace-define-variable
30134 @subsubheading Synopsis
30137 -trace-define-variable @var{name} [ @var{value} ]
30140 Create trace variable @var{name} if it does not exist. If
30141 @var{value} is specified, sets the initial value of the specified
30142 trace variable to that value. Note that the @var{name} should start
30143 with the @samp{$} character.
30145 @subsubheading @value{GDBN} Command
30147 The corresponding @value{GDBN} command is @samp{tvariable}.
30149 @subheading -trace-list-variables
30150 @findex -trace-list-variables
30152 @subsubheading Synopsis
30155 -trace-list-variables
30158 Return a table of all defined trace variables. Each element of the
30159 table has the following fields:
30163 The name of the trace variable. This field is always present.
30166 The initial value. This is a 64-bit signed integer. This
30167 field is always present.
30170 The value the trace variable has at the moment. This is a 64-bit
30171 signed integer. This field is absent iff current value is
30172 not defined, for example if the trace was never run, or is
30177 @subsubheading @value{GDBN} Command
30179 The corresponding @value{GDBN} command is @samp{tvariables}.
30181 @subsubheading Example
30185 -trace-list-variables
30186 ^done,trace-variables=@{nr_rows="1",nr_cols="3",
30187 hdr=[@{width="15",alignment="-1",col_name="name",colhdr="Name"@},
30188 @{width="11",alignment="-1",col_name="initial",colhdr="Initial"@},
30189 @{width="11",alignment="-1",col_name="current",colhdr="Current"@}],
30190 body=[variable=@{name="$trace_timestamp",initial="0"@}
30191 variable=@{name="$foo",initial="10",current="15"@}]@}
30195 @subheading -trace-save
30196 @findex -trace-save
30198 @subsubheading Synopsis
30201 -trace-save [-r ] @var{filename}
30204 Saves the collected trace data to @var{filename}. Without the
30205 @samp{-r} option, the data is downloaded from the target and saved
30206 in a local file. With the @samp{-r} option the target is asked
30207 to perform the save.
30209 @subsubheading @value{GDBN} Command
30211 The corresponding @value{GDBN} command is @samp{tsave}.
30214 @subheading -trace-start
30215 @findex -trace-start
30217 @subsubheading Synopsis
30223 Starts a tracing experiments. The result of this command does not
30226 @subsubheading @value{GDBN} Command
30228 The corresponding @value{GDBN} command is @samp{tstart}.
30230 @subheading -trace-status
30231 @findex -trace-status
30233 @subsubheading Synopsis
30239 Obtains the status of a tracing experiment. The result may include
30240 the following fields:
30245 May have a value of either @samp{0}, when no tracing operations are
30246 supported, @samp{1}, when all tracing operations are supported, or
30247 @samp{file} when examining trace file. In the latter case, examining
30248 of trace frame is possible but new tracing experiement cannot be
30249 started. This field is always present.
30252 May have a value of either @samp{0} or @samp{1} depending on whether
30253 tracing experiement is in progress on target. This field is present
30254 if @samp{supported} field is not @samp{0}.
30257 Report the reason why the tracing was stopped last time. This field
30258 may be absent iff tracing was never stopped on target yet. The
30259 value of @samp{request} means the tracing was stopped as result of
30260 the @code{-trace-stop} command. The value of @samp{overflow} means
30261 the tracing buffer is full. The value of @samp{disconnection} means
30262 tracing was automatically stopped when @value{GDBN} has disconnected.
30263 The value of @samp{passcount} means tracing was stopped when a
30264 tracepoint was passed a maximal number of times for that tracepoint.
30265 This field is present if @samp{supported} field is not @samp{0}.
30267 @item stopping-tracepoint
30268 The number of tracepoint whose passcount as exceeded. This field is
30269 present iff the @samp{stop-reason} field has the value of
30273 @itemx frames-created
30274 The @samp{frames} field is a count of the total number of trace frames
30275 in the trace buffer, while @samp{frames-created} is the total created
30276 during the run, including ones that were discarded, such as when a
30277 circular trace buffer filled up. Both fields are optional.
30281 These fields tell the current size of the tracing buffer and the
30282 remaining space. These fields are optional.
30285 The value of the circular trace buffer flag. @code{1} means that the
30286 trace buffer is circular and old trace frames will be discarded if
30287 necessary to make room, @code{0} means that the trace buffer is linear
30291 The value of the disconnected tracing flag. @code{1} means that
30292 tracing will continue after @value{GDBN} disconnects, @code{0} means
30293 that the trace run will stop.
30297 @subsubheading @value{GDBN} Command
30299 The corresponding @value{GDBN} command is @samp{tstatus}.
30301 @subheading -trace-stop
30302 @findex -trace-stop
30304 @subsubheading Synopsis
30310 Stops a tracing experiment. The result of this command has the same
30311 fields as @code{-trace-status}, except that the @samp{supported} and
30312 @samp{running} fields are not output.
30314 @subsubheading @value{GDBN} Command
30316 The corresponding @value{GDBN} command is @samp{tstop}.
30319 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
30320 @node GDB/MI Symbol Query
30321 @section @sc{gdb/mi} Symbol Query Commands
30325 @subheading The @code{-symbol-info-address} Command
30326 @findex -symbol-info-address
30328 @subsubheading Synopsis
30331 -symbol-info-address @var{symbol}
30334 Describe where @var{symbol} is stored.
30336 @subsubheading @value{GDBN} Command
30338 The corresponding @value{GDBN} command is @samp{info address}.
30340 @subsubheading Example
30344 @subheading The @code{-symbol-info-file} Command
30345 @findex -symbol-info-file
30347 @subsubheading Synopsis
30353 Show the file for the symbol.
30355 @subsubheading @value{GDBN} Command
30357 There's no equivalent @value{GDBN} command. @code{gdbtk} has
30358 @samp{gdb_find_file}.
30360 @subsubheading Example
30364 @subheading The @code{-symbol-info-function} Command
30365 @findex -symbol-info-function
30367 @subsubheading Synopsis
30370 -symbol-info-function
30373 Show which function the symbol lives in.
30375 @subsubheading @value{GDBN} Command
30377 @samp{gdb_get_function} in @code{gdbtk}.
30379 @subsubheading Example
30383 @subheading The @code{-symbol-info-line} Command
30384 @findex -symbol-info-line
30386 @subsubheading Synopsis
30392 Show the core addresses of the code for a source line.
30394 @subsubheading @value{GDBN} Command
30396 The corresponding @value{GDBN} command is @samp{info line}.
30397 @code{gdbtk} has the @samp{gdb_get_line} and @samp{gdb_get_file} commands.
30399 @subsubheading Example
30403 @subheading The @code{-symbol-info-symbol} Command
30404 @findex -symbol-info-symbol
30406 @subsubheading Synopsis
30409 -symbol-info-symbol @var{addr}
30412 Describe what symbol is at location @var{addr}.
30414 @subsubheading @value{GDBN} Command
30416 The corresponding @value{GDBN} command is @samp{info symbol}.
30418 @subsubheading Example
30422 @subheading The @code{-symbol-list-functions} Command
30423 @findex -symbol-list-functions
30425 @subsubheading Synopsis
30428 -symbol-list-functions
30431 List the functions in the executable.
30433 @subsubheading @value{GDBN} Command
30435 @samp{info functions} in @value{GDBN}, @samp{gdb_listfunc} and
30436 @samp{gdb_search} in @code{gdbtk}.
30438 @subsubheading Example
30443 @subheading The @code{-symbol-list-lines} Command
30444 @findex -symbol-list-lines
30446 @subsubheading Synopsis
30449 -symbol-list-lines @var{filename}
30452 Print the list of lines that contain code and their associated program
30453 addresses for the given source filename. The entries are sorted in
30454 ascending PC order.
30456 @subsubheading @value{GDBN} Command
30458 There is no corresponding @value{GDBN} command.
30460 @subsubheading Example
30463 -symbol-list-lines basics.c
30464 ^done,lines=[@{pc="0x08048554",line="7"@},@{pc="0x0804855a",line="8"@}]
30470 @subheading The @code{-symbol-list-types} Command
30471 @findex -symbol-list-types
30473 @subsubheading Synopsis
30479 List all the type names.
30481 @subsubheading @value{GDBN} Command
30483 The corresponding commands are @samp{info types} in @value{GDBN},
30484 @samp{gdb_search} in @code{gdbtk}.
30486 @subsubheading Example
30490 @subheading The @code{-symbol-list-variables} Command
30491 @findex -symbol-list-variables
30493 @subsubheading Synopsis
30496 -symbol-list-variables
30499 List all the global and static variable names.
30501 @subsubheading @value{GDBN} Command
30503 @samp{info variables} in @value{GDBN}, @samp{gdb_search} in @code{gdbtk}.
30505 @subsubheading Example
30509 @subheading The @code{-symbol-locate} Command
30510 @findex -symbol-locate
30512 @subsubheading Synopsis
30518 @subsubheading @value{GDBN} Command
30520 @samp{gdb_loc} in @code{gdbtk}.
30522 @subsubheading Example
30526 @subheading The @code{-symbol-type} Command
30527 @findex -symbol-type
30529 @subsubheading Synopsis
30532 -symbol-type @var{variable}
30535 Show type of @var{variable}.
30537 @subsubheading @value{GDBN} Command
30539 The corresponding @value{GDBN} command is @samp{ptype}, @code{gdbtk} has
30540 @samp{gdb_obj_variable}.
30542 @subsubheading Example
30547 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
30548 @node GDB/MI File Commands
30549 @section @sc{gdb/mi} File Commands
30551 This section describes the GDB/MI commands to specify executable file names
30552 and to read in and obtain symbol table information.
30554 @subheading The @code{-file-exec-and-symbols} Command
30555 @findex -file-exec-and-symbols
30557 @subsubheading Synopsis
30560 -file-exec-and-symbols @var{file}
30563 Specify the executable file to be debugged. This file is the one from
30564 which the symbol table is also read. If no file is specified, the
30565 command clears the executable and symbol information. If breakpoints
30566 are set when using this command with no arguments, @value{GDBN} will produce
30567 error messages. Otherwise, no output is produced, except a completion
30570 @subsubheading @value{GDBN} Command
30572 The corresponding @value{GDBN} command is @samp{file}.
30574 @subsubheading Example
30578 -file-exec-and-symbols /kwikemart/marge/ezannoni/TRUNK/mbx/hello.mbx
30584 @subheading The @code{-file-exec-file} Command
30585 @findex -file-exec-file
30587 @subsubheading Synopsis
30590 -file-exec-file @var{file}
30593 Specify the executable file to be debugged. Unlike
30594 @samp{-file-exec-and-symbols}, the symbol table is @emph{not} read
30595 from this file. If used without argument, @value{GDBN} clears the information
30596 about the executable file. No output is produced, except a completion
30599 @subsubheading @value{GDBN} Command
30601 The corresponding @value{GDBN} command is @samp{exec-file}.
30603 @subsubheading Example
30607 -file-exec-file /kwikemart/marge/ezannoni/TRUNK/mbx/hello.mbx
30614 @subheading The @code{-file-list-exec-sections} Command
30615 @findex -file-list-exec-sections
30617 @subsubheading Synopsis
30620 -file-list-exec-sections
30623 List the sections of the current executable file.
30625 @subsubheading @value{GDBN} Command
30627 The @value{GDBN} command @samp{info file} shows, among the rest, the same
30628 information as this command. @code{gdbtk} has a corresponding command
30629 @samp{gdb_load_info}.
30631 @subsubheading Example
30636 @subheading The @code{-file-list-exec-source-file} Command
30637 @findex -file-list-exec-source-file
30639 @subsubheading Synopsis
30642 -file-list-exec-source-file
30645 List the line number, the current source file, and the absolute path
30646 to the current source file for the current executable. The macro
30647 information field has a value of @samp{1} or @samp{0} depending on
30648 whether or not the file includes preprocessor macro information.
30650 @subsubheading @value{GDBN} Command
30652 The @value{GDBN} equivalent is @samp{info source}
30654 @subsubheading Example
30658 123-file-list-exec-source-file
30659 123^done,line="1",file="foo.c",fullname="/home/bar/foo.c,macro-info="1"
30664 @subheading The @code{-file-list-exec-source-files} Command
30665 @findex -file-list-exec-source-files
30667 @subsubheading Synopsis
30670 -file-list-exec-source-files
30673 List the source files for the current executable.
30675 It will always output the filename, but only when @value{GDBN} can find
30676 the absolute file name of a source file, will it output the fullname.
30678 @subsubheading @value{GDBN} Command
30680 The @value{GDBN} equivalent is @samp{info sources}.
30681 @code{gdbtk} has an analogous command @samp{gdb_listfiles}.
30683 @subsubheading Example
30686 -file-list-exec-source-files
30688 @{file=foo.c,fullname=/home/foo.c@},
30689 @{file=/home/bar.c,fullname=/home/bar.c@},
30690 @{file=gdb_could_not_find_fullpath.c@}]
30695 @subheading The @code{-file-list-shared-libraries} Command
30696 @findex -file-list-shared-libraries
30698 @subsubheading Synopsis
30701 -file-list-shared-libraries
30704 List the shared libraries in the program.
30706 @subsubheading @value{GDBN} Command
30708 The corresponding @value{GDBN} command is @samp{info shared}.
30710 @subsubheading Example
30714 @subheading The @code{-file-list-symbol-files} Command
30715 @findex -file-list-symbol-files
30717 @subsubheading Synopsis
30720 -file-list-symbol-files
30725 @subsubheading @value{GDBN} Command
30727 The corresponding @value{GDBN} command is @samp{info file} (part of it).
30729 @subsubheading Example
30734 @subheading The @code{-file-symbol-file} Command
30735 @findex -file-symbol-file
30737 @subsubheading Synopsis
30740 -file-symbol-file @var{file}
30743 Read symbol table info from the specified @var{file} argument. When
30744 used without arguments, clears @value{GDBN}'s symbol table info. No output is
30745 produced, except for a completion notification.
30747 @subsubheading @value{GDBN} Command
30749 The corresponding @value{GDBN} command is @samp{symbol-file}.
30751 @subsubheading Example
30755 -file-symbol-file /kwikemart/marge/ezannoni/TRUNK/mbx/hello.mbx
30761 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
30762 @node GDB/MI Memory Overlay Commands
30763 @section @sc{gdb/mi} Memory Overlay Commands
30765 The memory overlay commands are not implemented.
30767 @c @subheading -overlay-auto
30769 @c @subheading -overlay-list-mapping-state
30771 @c @subheading -overlay-list-overlays
30773 @c @subheading -overlay-map
30775 @c @subheading -overlay-off
30777 @c @subheading -overlay-on
30779 @c @subheading -overlay-unmap
30781 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
30782 @node GDB/MI Signal Handling Commands
30783 @section @sc{gdb/mi} Signal Handling Commands
30785 Signal handling commands are not implemented.
30787 @c @subheading -signal-handle
30789 @c @subheading -signal-list-handle-actions
30791 @c @subheading -signal-list-signal-types
30795 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
30796 @node GDB/MI Target Manipulation
30797 @section @sc{gdb/mi} Target Manipulation Commands
30800 @subheading The @code{-target-attach} Command
30801 @findex -target-attach
30803 @subsubheading Synopsis
30806 -target-attach @var{pid} | @var{gid} | @var{file}
30809 Attach to a process @var{pid} or a file @var{file} outside of
30810 @value{GDBN}, or a thread group @var{gid}. If attaching to a thread
30811 group, the id previously returned by
30812 @samp{-list-thread-groups --available} must be used.
30814 @subsubheading @value{GDBN} Command
30816 The corresponding @value{GDBN} command is @samp{attach}.
30818 @subsubheading Example
30822 =thread-created,id="1"
30823 *stopped,thread-id="1",frame=@{addr="0xb7f7e410",func="bar",args=[]@}
30829 @subheading The @code{-target-compare-sections} Command
30830 @findex -target-compare-sections
30832 @subsubheading Synopsis
30835 -target-compare-sections [ @var{section} ]
30838 Compare data of section @var{section} on target to the exec file.
30839 Without the argument, all sections are compared.
30841 @subsubheading @value{GDBN} Command
30843 The @value{GDBN} equivalent is @samp{compare-sections}.
30845 @subsubheading Example
30850 @subheading The @code{-target-detach} Command
30851 @findex -target-detach
30853 @subsubheading Synopsis
30856 -target-detach [ @var{pid} | @var{gid} ]
30859 Detach from the remote target which normally resumes its execution.
30860 If either @var{pid} or @var{gid} is specified, detaches from either
30861 the specified process, or specified thread group. There's no output.
30863 @subsubheading @value{GDBN} Command
30865 The corresponding @value{GDBN} command is @samp{detach}.
30867 @subsubheading Example
30877 @subheading The @code{-target-disconnect} Command
30878 @findex -target-disconnect
30880 @subsubheading Synopsis
30886 Disconnect from the remote target. There's no output and the target is
30887 generally not resumed.
30889 @subsubheading @value{GDBN} Command
30891 The corresponding @value{GDBN} command is @samp{disconnect}.
30893 @subsubheading Example
30903 @subheading The @code{-target-download} Command
30904 @findex -target-download
30906 @subsubheading Synopsis
30912 Loads the executable onto the remote target.
30913 It prints out an update message every half second, which includes the fields:
30917 The name of the section.
30919 The size of what has been sent so far for that section.
30921 The size of the section.
30923 The total size of what was sent so far (the current and the previous sections).
30925 The size of the overall executable to download.
30929 Each message is sent as status record (@pxref{GDB/MI Output Syntax, ,
30930 @sc{gdb/mi} Output Syntax}).
30932 In addition, it prints the name and size of the sections, as they are
30933 downloaded. These messages include the following fields:
30937 The name of the section.
30939 The size of the section.
30941 The size of the overall executable to download.
30945 At the end, a summary is printed.
30947 @subsubheading @value{GDBN} Command
30949 The corresponding @value{GDBN} command is @samp{load}.
30951 @subsubheading Example
30953 Note: each status message appears on a single line. Here the messages
30954 have been broken down so that they can fit onto a page.
30959 +download,@{section=".text",section-size="6668",total-size="9880"@}
30960 +download,@{section=".text",section-sent="512",section-size="6668",
30961 total-sent="512",total-size="9880"@}
30962 +download,@{section=".text",section-sent="1024",section-size="6668",
30963 total-sent="1024",total-size="9880"@}
30964 +download,@{section=".text",section-sent="1536",section-size="6668",
30965 total-sent="1536",total-size="9880"@}
30966 +download,@{section=".text",section-sent="2048",section-size="6668",
30967 total-sent="2048",total-size="9880"@}
30968 +download,@{section=".text",section-sent="2560",section-size="6668",
30969 total-sent="2560",total-size="9880"@}
30970 +download,@{section=".text",section-sent="3072",section-size="6668",
30971 total-sent="3072",total-size="9880"@}
30972 +download,@{section=".text",section-sent="3584",section-size="6668",
30973 total-sent="3584",total-size="9880"@}
30974 +download,@{section=".text",section-sent="4096",section-size="6668",
30975 total-sent="4096",total-size="9880"@}
30976 +download,@{section=".text",section-sent="4608",section-size="6668",
30977 total-sent="4608",total-size="9880"@}
30978 +download,@{section=".text",section-sent="5120",section-size="6668",
30979 total-sent="5120",total-size="9880"@}
30980 +download,@{section=".text",section-sent="5632",section-size="6668",
30981 total-sent="5632",total-size="9880"@}
30982 +download,@{section=".text",section-sent="6144",section-size="6668",
30983 total-sent="6144",total-size="9880"@}
30984 +download,@{section=".text",section-sent="6656",section-size="6668",
30985 total-sent="6656",total-size="9880"@}
30986 +download,@{section=".init",section-size="28",total-size="9880"@}
30987 +download,@{section=".fini",section-size="28",total-size="9880"@}
30988 +download,@{section=".data",section-size="3156",total-size="9880"@}
30989 +download,@{section=".data",section-sent="512",section-size="3156",
30990 total-sent="7236",total-size="9880"@}
30991 +download,@{section=".data",section-sent="1024",section-size="3156",
30992 total-sent="7748",total-size="9880"@}
30993 +download,@{section=".data",section-sent="1536",section-size="3156",
30994 total-sent="8260",total-size="9880"@}
30995 +download,@{section=".data",section-sent="2048",section-size="3156",
30996 total-sent="8772",total-size="9880"@}
30997 +download,@{section=".data",section-sent="2560",section-size="3156",
30998 total-sent="9284",total-size="9880"@}
30999 +download,@{section=".data",section-sent="3072",section-size="3156",
31000 total-sent="9796",total-size="9880"@}
31001 ^done,address="0x10004",load-size="9880",transfer-rate="6586",
31008 @subheading The @code{-target-exec-status} Command
31009 @findex -target-exec-status
31011 @subsubheading Synopsis
31014 -target-exec-status
31017 Provide information on the state of the target (whether it is running or
31018 not, for instance).
31020 @subsubheading @value{GDBN} Command
31022 There's no equivalent @value{GDBN} command.
31024 @subsubheading Example
31028 @subheading The @code{-target-list-available-targets} Command
31029 @findex -target-list-available-targets
31031 @subsubheading Synopsis
31034 -target-list-available-targets
31037 List the possible targets to connect to.
31039 @subsubheading @value{GDBN} Command
31041 The corresponding @value{GDBN} command is @samp{help target}.
31043 @subsubheading Example
31047 @subheading The @code{-target-list-current-targets} Command
31048 @findex -target-list-current-targets
31050 @subsubheading Synopsis
31053 -target-list-current-targets
31056 Describe the current target.
31058 @subsubheading @value{GDBN} Command
31060 The corresponding information is printed by @samp{info file} (among
31063 @subsubheading Example
31067 @subheading The @code{-target-list-parameters} Command
31068 @findex -target-list-parameters
31070 @subsubheading Synopsis
31073 -target-list-parameters
31079 @subsubheading @value{GDBN} Command
31083 @subsubheading Example
31087 @subheading The @code{-target-select} Command
31088 @findex -target-select
31090 @subsubheading Synopsis
31093 -target-select @var{type} @var{parameters @dots{}}
31096 Connect @value{GDBN} to the remote target. This command takes two args:
31100 The type of target, for instance @samp{remote}, etc.
31101 @item @var{parameters}
31102 Device names, host names and the like. @xref{Target Commands, ,
31103 Commands for Managing Targets}, for more details.
31106 The output is a connection notification, followed by the address at
31107 which the target program is, in the following form:
31110 ^connected,addr="@var{address}",func="@var{function name}",
31111 args=[@var{arg list}]
31114 @subsubheading @value{GDBN} Command
31116 The corresponding @value{GDBN} command is @samp{target}.
31118 @subsubheading Example
31122 -target-select remote /dev/ttya
31123 ^connected,addr="0xfe00a300",func="??",args=[]
31127 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
31128 @node GDB/MI File Transfer Commands
31129 @section @sc{gdb/mi} File Transfer Commands
31132 @subheading The @code{-target-file-put} Command
31133 @findex -target-file-put
31135 @subsubheading Synopsis
31138 -target-file-put @var{hostfile} @var{targetfile}
31141 Copy file @var{hostfile} from the host system (the machine running
31142 @value{GDBN}) to @var{targetfile} on the target system.
31144 @subsubheading @value{GDBN} Command
31146 The corresponding @value{GDBN} command is @samp{remote put}.
31148 @subsubheading Example
31152 -target-file-put localfile remotefile
31158 @subheading The @code{-target-file-get} Command
31159 @findex -target-file-get
31161 @subsubheading Synopsis
31164 -target-file-get @var{targetfile} @var{hostfile}
31167 Copy file @var{targetfile} from the target system to @var{hostfile}
31168 on the host system.
31170 @subsubheading @value{GDBN} Command
31172 The corresponding @value{GDBN} command is @samp{remote get}.
31174 @subsubheading Example
31178 -target-file-get remotefile localfile
31184 @subheading The @code{-target-file-delete} Command
31185 @findex -target-file-delete
31187 @subsubheading Synopsis
31190 -target-file-delete @var{targetfile}
31193 Delete @var{targetfile} from the target system.
31195 @subsubheading @value{GDBN} Command
31197 The corresponding @value{GDBN} command is @samp{remote delete}.
31199 @subsubheading Example
31203 -target-file-delete remotefile
31209 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
31210 @node GDB/MI Miscellaneous Commands
31211 @section Miscellaneous @sc{gdb/mi} Commands
31213 @c @subheading -gdb-complete
31215 @subheading The @code{-gdb-exit} Command
31218 @subsubheading Synopsis
31224 Exit @value{GDBN} immediately.
31226 @subsubheading @value{GDBN} Command
31228 Approximately corresponds to @samp{quit}.
31230 @subsubheading Example
31240 @subheading The @code{-exec-abort} Command
31241 @findex -exec-abort
31243 @subsubheading Synopsis
31249 Kill the inferior running program.
31251 @subsubheading @value{GDBN} Command
31253 The corresponding @value{GDBN} command is @samp{kill}.
31255 @subsubheading Example
31260 @subheading The @code{-gdb-set} Command
31263 @subsubheading Synopsis
31269 Set an internal @value{GDBN} variable.
31270 @c IS THIS A DOLLAR VARIABLE? OR SOMETHING LIKE ANNOTATE ?????
31272 @subsubheading @value{GDBN} Command
31274 The corresponding @value{GDBN} command is @samp{set}.
31276 @subsubheading Example
31286 @subheading The @code{-gdb-show} Command
31289 @subsubheading Synopsis
31295 Show the current value of a @value{GDBN} variable.
31297 @subsubheading @value{GDBN} Command
31299 The corresponding @value{GDBN} command is @samp{show}.
31301 @subsubheading Example
31310 @c @subheading -gdb-source
31313 @subheading The @code{-gdb-version} Command
31314 @findex -gdb-version
31316 @subsubheading Synopsis
31322 Show version information for @value{GDBN}. Used mostly in testing.
31324 @subsubheading @value{GDBN} Command
31326 The @value{GDBN} equivalent is @samp{show version}. @value{GDBN} by
31327 default shows this information when you start an interactive session.
31329 @subsubheading Example
31331 @c This example modifies the actual output from GDB to avoid overfull
31337 ~Copyright 2000 Free Software Foundation, Inc.
31338 ~GDB is free software, covered by the GNU General Public License, and
31339 ~you are welcome to change it and/or distribute copies of it under
31340 ~ certain conditions.
31341 ~Type "show copying" to see the conditions.
31342 ~There is absolutely no warranty for GDB. Type "show warranty" for
31344 ~This GDB was configured as
31345 "--host=sparc-sun-solaris2.5.1 --target=ppc-eabi".
31350 @subheading The @code{-list-features} Command
31351 @findex -list-features
31353 Returns a list of particular features of the MI protocol that
31354 this version of gdb implements. A feature can be a command,
31355 or a new field in an output of some command, or even an
31356 important bugfix. While a frontend can sometimes detect presence
31357 of a feature at runtime, it is easier to perform detection at debugger
31360 The command returns a list of strings, with each string naming an
31361 available feature. Each returned string is just a name, it does not
31362 have any internal structure. The list of possible feature names
31368 (gdb) -list-features
31369 ^done,result=["feature1","feature2"]
31372 The current list of features is:
31375 @item frozen-varobjs
31376 Indicates support for the @code{-var-set-frozen} command, as well
31377 as possible presense of the @code{frozen} field in the output
31378 of @code{-varobj-create}.
31379 @item pending-breakpoints
31380 Indicates support for the @option{-f} option to the @code{-break-insert}
31383 Indicates Python scripting support, Python-based
31384 pretty-printing commands, and possible presence of the
31385 @samp{display_hint} field in the output of @code{-var-list-children}
31387 Indicates support for the @code{-thread-info} command.
31388 @item data-read-memory-bytes
31389 Indicates support for the @code{-data-read-memory-bytes} and the
31390 @code{-data-write-memory-bytes} commands.
31391 @item breakpoint-notifications
31392 Indicates that changes to breakpoints and breakpoints created via the
31393 CLI will be announced via async records.
31394 @item ada-task-info
31395 Indicates support for the @code{-ada-task-info} command.
31398 @subheading The @code{-list-target-features} Command
31399 @findex -list-target-features
31401 Returns a list of particular features that are supported by the
31402 target. Those features affect the permitted MI commands, but
31403 unlike the features reported by the @code{-list-features} command, the
31404 features depend on which target GDB is using at the moment. Whenever
31405 a target can change, due to commands such as @code{-target-select},
31406 @code{-target-attach} or @code{-exec-run}, the list of target features
31407 may change, and the frontend should obtain it again.
31411 (gdb) -list-features
31412 ^done,result=["async"]
31415 The current list of features is:
31419 Indicates that the target is capable of asynchronous command
31420 execution, which means that @value{GDBN} will accept further commands
31421 while the target is running.
31424 Indicates that the target is capable of reverse execution.
31425 @xref{Reverse Execution}, for more information.
31429 @subheading The @code{-list-thread-groups} Command
31430 @findex -list-thread-groups
31432 @subheading Synopsis
31435 -list-thread-groups [ --available ] [ --recurse 1 ] [ @var{group} ... ]
31438 Lists thread groups (@pxref{Thread groups}). When a single thread
31439 group is passed as the argument, lists the children of that group.
31440 When several thread group are passed, lists information about those
31441 thread groups. Without any parameters, lists information about all
31442 top-level thread groups.
31444 Normally, thread groups that are being debugged are reported.
31445 With the @samp{--available} option, @value{GDBN} reports thread groups
31446 available on the target.
31448 The output of this command may have either a @samp{threads} result or
31449 a @samp{groups} result. The @samp{thread} result has a list of tuples
31450 as value, with each tuple describing a thread (@pxref{GDB/MI Thread
31451 Information}). The @samp{groups} result has a list of tuples as value,
31452 each tuple describing a thread group. If top-level groups are
31453 requested (that is, no parameter is passed), or when several groups
31454 are passed, the output always has a @samp{groups} result. The format
31455 of the @samp{group} result is described below.
31457 To reduce the number of roundtrips it's possible to list thread groups
31458 together with their children, by passing the @samp{--recurse} option
31459 and the recursion depth. Presently, only recursion depth of 1 is
31460 permitted. If this option is present, then every reported thread group
31461 will also include its children, either as @samp{group} or
31462 @samp{threads} field.
31464 In general, any combination of option and parameters is permitted, with
31465 the following caveats:
31469 When a single thread group is passed, the output will typically
31470 be the @samp{threads} result. Because threads may not contain
31471 anything, the @samp{recurse} option will be ignored.
31474 When the @samp{--available} option is passed, limited information may
31475 be available. In particular, the list of threads of a process might
31476 be inaccessible. Further, specifying specific thread groups might
31477 not give any performance advantage over listing all thread groups.
31478 The frontend should assume that @samp{-list-thread-groups --available}
31479 is always an expensive operation and cache the results.
31483 The @samp{groups} result is a list of tuples, where each tuple may
31484 have the following fields:
31488 Identifier of the thread group. This field is always present.
31489 The identifier is an opaque string; frontends should not try to
31490 convert it to an integer, even though it might look like one.
31493 The type of the thread group. At present, only @samp{process} is a
31497 The target-specific process identifier. This field is only present
31498 for thread groups of type @samp{process} and only if the process exists.
31501 The number of children this thread group has. This field may be
31502 absent for an available thread group.
31505 This field has a list of tuples as value, each tuple describing a
31506 thread. It may be present if the @samp{--recurse} option is
31507 specified, and it's actually possible to obtain the threads.
31510 This field is a list of integers, each identifying a core that one
31511 thread of the group is running on. This field may be absent if
31512 such information is not available.
31515 The name of the executable file that corresponds to this thread group.
31516 The field is only present for thread groups of type @samp{process},
31517 and only if there is a corresponding executable file.
31521 @subheading Example
31525 -list-thread-groups
31526 ^done,groups=[@{id="17",type="process",pid="yyy",num_children="2"@}]
31527 -list-thread-groups 17
31528 ^done,threads=[@{id="2",target-id="Thread 0xb7e14b90 (LWP 21257)",
31529 frame=@{level="0",addr="0xffffe410",func="__kernel_vsyscall",args=[]@},state="running"@},
31530 @{id="1",target-id="Thread 0xb7e156b0 (LWP 21254)",
31531 frame=@{level="0",addr="0x0804891f",func="foo",args=[@{name="i",value="10"@}],
31532 file="/tmp/a.c",fullname="/tmp/a.c",line="158"@},state="running"@}]]
31533 -list-thread-groups --available
31534 ^done,groups=[@{id="17",type="process",pid="yyy",num_children="2",cores=[1,2]@}]
31535 -list-thread-groups --available --recurse 1
31536 ^done,groups=[@{id="17", types="process",pid="yyy",num_children="2",cores=[1,2],
31537 threads=[@{id="1",target-id="Thread 0xb7e14b90",cores=[1]@},
31538 @{id="2",target-id="Thread 0xb7e14b90",cores=[2]@}]@},..]
31539 -list-thread-groups --available --recurse 1 17 18
31540 ^done,groups=[@{id="17", types="process",pid="yyy",num_children="2",cores=[1,2],
31541 threads=[@{id="1",target-id="Thread 0xb7e14b90",cores=[1]@},
31542 @{id="2",target-id="Thread 0xb7e14b90",cores=[2]@}]@},...]
31546 @subheading The @code{-add-inferior} Command
31547 @findex -add-inferior
31549 @subheading Synopsis
31555 Creates a new inferior (@pxref{Inferiors and Programs}). The created
31556 inferior is not associated with any executable. Such association may
31557 be established with the @samp{-file-exec-and-symbols} command
31558 (@pxref{GDB/MI File Commands}). The command response has a single
31559 field, @samp{thread-group}, whose value is the identifier of the
31560 thread group corresponding to the new inferior.
31562 @subheading Example
31567 ^done,thread-group="i3"
31570 @subheading The @code{-interpreter-exec} Command
31571 @findex -interpreter-exec
31573 @subheading Synopsis
31576 -interpreter-exec @var{interpreter} @var{command}
31578 @anchor{-interpreter-exec}
31580 Execute the specified @var{command} in the given @var{interpreter}.
31582 @subheading @value{GDBN} Command
31584 The corresponding @value{GDBN} command is @samp{interpreter-exec}.
31586 @subheading Example
31590 -interpreter-exec console "break main"
31591 &"During symbol reading, couldn't parse type; debugger out of date?.\n"
31592 &"During symbol reading, bad structure-type format.\n"
31593 ~"Breakpoint 1 at 0x8074fc6: file ../../src/gdb/main.c, line 743.\n"
31598 @subheading The @code{-inferior-tty-set} Command
31599 @findex -inferior-tty-set
31601 @subheading Synopsis
31604 -inferior-tty-set /dev/pts/1
31607 Set terminal for future runs of the program being debugged.
31609 @subheading @value{GDBN} Command
31611 The corresponding @value{GDBN} command is @samp{set inferior-tty} /dev/pts/1.
31613 @subheading Example
31617 -inferior-tty-set /dev/pts/1
31622 @subheading The @code{-inferior-tty-show} Command
31623 @findex -inferior-tty-show
31625 @subheading Synopsis
31631 Show terminal for future runs of program being debugged.
31633 @subheading @value{GDBN} Command
31635 The corresponding @value{GDBN} command is @samp{show inferior-tty}.
31637 @subheading Example
31641 -inferior-tty-set /dev/pts/1
31645 ^done,inferior_tty_terminal="/dev/pts/1"
31649 @subheading The @code{-enable-timings} Command
31650 @findex -enable-timings
31652 @subheading Synopsis
31655 -enable-timings [yes | no]
31658 Toggle the printing of the wallclock, user and system times for an MI
31659 command as a field in its output. This command is to help frontend
31660 developers optimize the performance of their code. No argument is
31661 equivalent to @samp{yes}.
31663 @subheading @value{GDBN} Command
31667 @subheading Example
31675 ^done,bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
31676 addr="0x080484ed",func="main",file="myprog.c",
31677 fullname="/home/nickrob/myprog.c",line="73",times="0"@},
31678 time=@{wallclock="0.05185",user="0.00800",system="0.00000"@}
31686 *stopped,reason="breakpoint-hit",disp="keep",bkptno="1",thread-id="0",
31687 frame=@{addr="0x080484ed",func="main",args=[@{name="argc",value="1"@},
31688 @{name="argv",value="0xbfb60364"@}],file="myprog.c",
31689 fullname="/home/nickrob/myprog.c",line="73"@}
31694 @chapter @value{GDBN} Annotations
31696 This chapter describes annotations in @value{GDBN}. Annotations were
31697 designed to interface @value{GDBN} to graphical user interfaces or other
31698 similar programs which want to interact with @value{GDBN} at a
31699 relatively high level.
31701 The annotation mechanism has largely been superseded by @sc{gdb/mi}
31705 This is Edition @value{EDITION}, @value{DATE}.
31709 * Annotations Overview:: What annotations are; the general syntax.
31710 * Server Prefix:: Issuing a command without affecting user state.
31711 * Prompting:: Annotations marking @value{GDBN}'s need for input.
31712 * Errors:: Annotations for error messages.
31713 * Invalidation:: Some annotations describe things now invalid.
31714 * Annotations for Running::
31715 Whether the program is running, how it stopped, etc.
31716 * Source Annotations:: Annotations describing source code.
31719 @node Annotations Overview
31720 @section What is an Annotation?
31721 @cindex annotations
31723 Annotations start with a newline character, two @samp{control-z}
31724 characters, and the name of the annotation. If there is no additional
31725 information associated with this annotation, the name of the annotation
31726 is followed immediately by a newline. If there is additional
31727 information, the name of the annotation is followed by a space, the
31728 additional information, and a newline. The additional information
31729 cannot contain newline characters.
31731 Any output not beginning with a newline and two @samp{control-z}
31732 characters denotes literal output from @value{GDBN}. Currently there is
31733 no need for @value{GDBN} to output a newline followed by two
31734 @samp{control-z} characters, but if there was such a need, the
31735 annotations could be extended with an @samp{escape} annotation which
31736 means those three characters as output.
31738 The annotation @var{level}, which is specified using the
31739 @option{--annotate} command line option (@pxref{Mode Options}), controls
31740 how much information @value{GDBN} prints together with its prompt,
31741 values of expressions, source lines, and other types of output. Level 0
31742 is for no annotations, level 1 is for use when @value{GDBN} is run as a
31743 subprocess of @sc{gnu} Emacs, level 3 is the maximum annotation suitable
31744 for programs that control @value{GDBN}, and level 2 annotations have
31745 been made obsolete (@pxref{Limitations, , Limitations of the Annotation
31746 Interface, annotate, GDB's Obsolete Annotations}).
31749 @kindex set annotate
31750 @item set annotate @var{level}
31751 The @value{GDBN} command @code{set annotate} sets the level of
31752 annotations to the specified @var{level}.
31754 @item show annotate
31755 @kindex show annotate
31756 Show the current annotation level.
31759 This chapter describes level 3 annotations.
31761 A simple example of starting up @value{GDBN} with annotations is:
31764 $ @kbd{gdb --annotate=3}
31766 Copyright 2003 Free Software Foundation, Inc.
31767 GDB is free software, covered by the GNU General Public License,
31768 and you are welcome to change it and/or distribute copies of it
31769 under certain conditions.
31770 Type "show copying" to see the conditions.
31771 There is absolutely no warranty for GDB. Type "show warranty"
31773 This GDB was configured as "i386-pc-linux-gnu"
31784 Here @samp{quit} is input to @value{GDBN}; the rest is output from
31785 @value{GDBN}. The three lines beginning @samp{^Z^Z} (where @samp{^Z}
31786 denotes a @samp{control-z} character) are annotations; the rest is
31787 output from @value{GDBN}.
31789 @node Server Prefix
31790 @section The Server Prefix
31791 @cindex server prefix
31793 If you prefix a command with @samp{server } then it will not affect
31794 the command history, nor will it affect @value{GDBN}'s notion of which
31795 command to repeat if @key{RET} is pressed on a line by itself. This
31796 means that commands can be run behind a user's back by a front-end in
31797 a transparent manner.
31799 The @code{server } prefix does not affect the recording of values into
31800 the value history; to print a value without recording it into the
31801 value history, use the @code{output} command instead of the
31802 @code{print} command.
31804 Using this prefix also disables confirmation requests
31805 (@pxref{confirmation requests}).
31808 @section Annotation for @value{GDBN} Input
31810 @cindex annotations for prompts
31811 When @value{GDBN} prompts for input, it annotates this fact so it is possible
31812 to know when to send output, when the output from a given command is
31815 Different kinds of input each have a different @dfn{input type}. Each
31816 input type has three annotations: a @code{pre-} annotation, which
31817 denotes the beginning of any prompt which is being output, a plain
31818 annotation, which denotes the end of the prompt, and then a @code{post-}
31819 annotation which denotes the end of any echo which may (or may not) be
31820 associated with the input. For example, the @code{prompt} input type
31821 features the following annotations:
31829 The input types are
31832 @findex pre-prompt annotation
31833 @findex prompt annotation
31834 @findex post-prompt annotation
31836 When @value{GDBN} is prompting for a command (the main @value{GDBN} prompt).
31838 @findex pre-commands annotation
31839 @findex commands annotation
31840 @findex post-commands annotation
31842 When @value{GDBN} prompts for a set of commands, like in the @code{commands}
31843 command. The annotations are repeated for each command which is input.
31845 @findex pre-overload-choice annotation
31846 @findex overload-choice annotation
31847 @findex post-overload-choice annotation
31848 @item overload-choice
31849 When @value{GDBN} wants the user to select between various overloaded functions.
31851 @findex pre-query annotation
31852 @findex query annotation
31853 @findex post-query annotation
31855 When @value{GDBN} wants the user to confirm a potentially dangerous operation.
31857 @findex pre-prompt-for-continue annotation
31858 @findex prompt-for-continue annotation
31859 @findex post-prompt-for-continue annotation
31860 @item prompt-for-continue
31861 When @value{GDBN} is asking the user to press return to continue. Note: Don't
31862 expect this to work well; instead use @code{set height 0} to disable
31863 prompting. This is because the counting of lines is buggy in the
31864 presence of annotations.
31869 @cindex annotations for errors, warnings and interrupts
31871 @findex quit annotation
31876 This annotation occurs right before @value{GDBN} responds to an interrupt.
31878 @findex error annotation
31883 This annotation occurs right before @value{GDBN} responds to an error.
31885 Quit and error annotations indicate that any annotations which @value{GDBN} was
31886 in the middle of may end abruptly. For example, if a
31887 @code{value-history-begin} annotation is followed by a @code{error}, one
31888 cannot expect to receive the matching @code{value-history-end}. One
31889 cannot expect not to receive it either, however; an error annotation
31890 does not necessarily mean that @value{GDBN} is immediately returning all the way
31893 @findex error-begin annotation
31894 A quit or error annotation may be preceded by
31900 Any output between that and the quit or error annotation is the error
31903 Warning messages are not yet annotated.
31904 @c If we want to change that, need to fix warning(), type_error(),
31905 @c range_error(), and possibly other places.
31908 @section Invalidation Notices
31910 @cindex annotations for invalidation messages
31911 The following annotations say that certain pieces of state may have
31915 @findex frames-invalid annotation
31916 @item ^Z^Zframes-invalid
31918 The frames (for example, output from the @code{backtrace} command) may
31921 @findex breakpoints-invalid annotation
31922 @item ^Z^Zbreakpoints-invalid
31924 The breakpoints may have changed. For example, the user just added or
31925 deleted a breakpoint.
31928 @node Annotations for Running
31929 @section Running the Program
31930 @cindex annotations for running programs
31932 @findex starting annotation
31933 @findex stopping annotation
31934 When the program starts executing due to a @value{GDBN} command such as
31935 @code{step} or @code{continue},
31941 is output. When the program stops,
31947 is output. Before the @code{stopped} annotation, a variety of
31948 annotations describe how the program stopped.
31951 @findex exited annotation
31952 @item ^Z^Zexited @var{exit-status}
31953 The program exited, and @var{exit-status} is the exit status (zero for
31954 successful exit, otherwise nonzero).
31956 @findex signalled annotation
31957 @findex signal-name annotation
31958 @findex signal-name-end annotation
31959 @findex signal-string annotation
31960 @findex signal-string-end annotation
31961 @item ^Z^Zsignalled
31962 The program exited with a signal. After the @code{^Z^Zsignalled}, the
31963 annotation continues:
31969 ^Z^Zsignal-name-end
31973 ^Z^Zsignal-string-end
31978 where @var{name} is the name of the signal, such as @code{SIGILL} or
31979 @code{SIGSEGV}, and @var{string} is the explanation of the signal, such
31980 as @code{Illegal Instruction} or @code{Segmentation fault}.
31981 @var{intro-text}, @var{middle-text}, and @var{end-text} are for the
31982 user's benefit and have no particular format.
31984 @findex signal annotation
31986 The syntax of this annotation is just like @code{signalled}, but @value{GDBN} is
31987 just saying that the program received the signal, not that it was
31988 terminated with it.
31990 @findex breakpoint annotation
31991 @item ^Z^Zbreakpoint @var{number}
31992 The program hit breakpoint number @var{number}.
31994 @findex watchpoint annotation
31995 @item ^Z^Zwatchpoint @var{number}
31996 The program hit watchpoint number @var{number}.
31999 @node Source Annotations
32000 @section Displaying Source
32001 @cindex annotations for source display
32003 @findex source annotation
32004 The following annotation is used instead of displaying source code:
32007 ^Z^Zsource @var{filename}:@var{line}:@var{character}:@var{middle}:@var{addr}
32010 where @var{filename} is an absolute file name indicating which source
32011 file, @var{line} is the line number within that file (where 1 is the
32012 first line in the file), @var{character} is the character position
32013 within the file (where 0 is the first character in the file) (for most
32014 debug formats this will necessarily point to the beginning of a line),
32015 @var{middle} is @samp{middle} if @var{addr} is in the middle of the
32016 line, or @samp{beg} if @var{addr} is at the beginning of the line, and
32017 @var{addr} is the address in the target program associated with the
32018 source which is being displayed. @var{addr} is in the form @samp{0x}
32019 followed by one or more lowercase hex digits (note that this does not
32020 depend on the language).
32022 @node JIT Interface
32023 @chapter JIT Compilation Interface
32024 @cindex just-in-time compilation
32025 @cindex JIT compilation interface
32027 This chapter documents @value{GDBN}'s @dfn{just-in-time} (JIT) compilation
32028 interface. A JIT compiler is a program or library that generates native
32029 executable code at runtime and executes it, usually in order to achieve good
32030 performance while maintaining platform independence.
32032 Programs that use JIT compilation are normally difficult to debug because
32033 portions of their code are generated at runtime, instead of being loaded from
32034 object files, which is where @value{GDBN} normally finds the program's symbols
32035 and debug information. In order to debug programs that use JIT compilation,
32036 @value{GDBN} has an interface that allows the program to register in-memory
32037 symbol files with @value{GDBN} at runtime.
32039 If you are using @value{GDBN} to debug a program that uses this interface, then
32040 it should work transparently so long as you have not stripped the binary. If
32041 you are developing a JIT compiler, then the interface is documented in the rest
32042 of this chapter. At this time, the only known client of this interface is the
32045 Broadly speaking, the JIT interface mirrors the dynamic loader interface. The
32046 JIT compiler communicates with @value{GDBN} by writing data into a global
32047 variable and calling a fuction at a well-known symbol. When @value{GDBN}
32048 attaches, it reads a linked list of symbol files from the global variable to
32049 find existing code, and puts a breakpoint in the function so that it can find
32050 out about additional code.
32053 * Declarations:: Relevant C struct declarations
32054 * Registering Code:: Steps to register code
32055 * Unregistering Code:: Steps to unregister code
32056 * Custom Debug Info:: Emit debug information in a custom format
32060 @section JIT Declarations
32062 These are the relevant struct declarations that a C program should include to
32063 implement the interface:
32073 struct jit_code_entry
32075 struct jit_code_entry *next_entry;
32076 struct jit_code_entry *prev_entry;
32077 const char *symfile_addr;
32078 uint64_t symfile_size;
32081 struct jit_descriptor
32084 /* This type should be jit_actions_t, but we use uint32_t
32085 to be explicit about the bitwidth. */
32086 uint32_t action_flag;
32087 struct jit_code_entry *relevant_entry;
32088 struct jit_code_entry *first_entry;
32091 /* GDB puts a breakpoint in this function. */
32092 void __attribute__((noinline)) __jit_debug_register_code() @{ @};
32094 /* Make sure to specify the version statically, because the
32095 debugger may check the version before we can set it. */
32096 struct jit_descriptor __jit_debug_descriptor = @{ 1, 0, 0, 0 @};
32099 If the JIT is multi-threaded, then it is important that the JIT synchronize any
32100 modifications to this global data properly, which can easily be done by putting
32101 a global mutex around modifications to these structures.
32103 @node Registering Code
32104 @section Registering Code
32106 To register code with @value{GDBN}, the JIT should follow this protocol:
32110 Generate an object file in memory with symbols and other desired debug
32111 information. The file must include the virtual addresses of the sections.
32114 Create a code entry for the file, which gives the start and size of the symbol
32118 Add it to the linked list in the JIT descriptor.
32121 Point the relevant_entry field of the descriptor at the entry.
32124 Set @code{action_flag} to @code{JIT_REGISTER} and call
32125 @code{__jit_debug_register_code}.
32128 When @value{GDBN} is attached and the breakpoint fires, @value{GDBN} uses the
32129 @code{relevant_entry} pointer so it doesn't have to walk the list looking for
32130 new code. However, the linked list must still be maintained in order to allow
32131 @value{GDBN} to attach to a running process and still find the symbol files.
32133 @node Unregistering Code
32134 @section Unregistering Code
32136 If code is freed, then the JIT should use the following protocol:
32140 Remove the code entry corresponding to the code from the linked list.
32143 Point the @code{relevant_entry} field of the descriptor at the code entry.
32146 Set @code{action_flag} to @code{JIT_UNREGISTER} and call
32147 @code{__jit_debug_register_code}.
32150 If the JIT frees or recompiles code without unregistering it, then @value{GDBN}
32151 and the JIT will leak the memory used for the associated symbol files.
32153 @node Custom Debug Info
32154 @section Custom Debug Info
32155 @cindex custom JIT debug info
32156 @cindex JIT debug info reader
32158 Generating debug information in platform-native file formats (like ELF
32159 or COFF) may be an overkill for JIT compilers; especially if all the
32160 debug info is used for is displaying a meaningful backtrace. The
32161 issue can be resolved by having the JIT writers decide on a debug info
32162 format and also provide a reader that parses the debug info generated
32163 by the JIT compiler. This section gives a brief overview on writing
32164 such a parser. More specific details can be found in the source file
32165 @file{gdb/jit-reader.in}, which is also installed as a header at
32166 @file{@var{includedir}/gdb/jit-reader.h} for easy inclusion.
32168 The reader is implemented as a shared object (so this functionality is
32169 not available on platforms which don't allow loading shared objects at
32170 runtime). Two @value{GDBN} commands, @code{jit-reader-load} and
32171 @code{jit-reader-unload} are provided, to be used to load and unload
32172 the readers from a preconfigured directory. Once loaded, the shared
32173 object is used the parse the debug information emitted by the JIT
32177 * Using JIT Debug Info Readers:: How to use supplied readers correctly
32178 * Writing JIT Debug Info Readers:: Creating a debug-info reader
32181 @node Using JIT Debug Info Readers
32182 @subsection Using JIT Debug Info Readers
32183 @kindex jit-reader-load
32184 @kindex jit-reader-unload
32186 Readers can be loaded and unloaded using the @code{jit-reader-load}
32187 and @code{jit-reader-unload} commands.
32190 @item jit-reader-load @var{reader-name}
32191 Load the JIT reader named @var{reader-name}. On a UNIX system, this
32192 will usually load @file{@var{libdir}/gdb/@var{reader-name}}, where
32193 @var{libdir} is the system library directory, usually
32194 @file{/usr/local/lib}. Only one reader can be active at a time;
32195 trying to load a second reader when one is already loaded will result
32196 in @value{GDBN} reporting an error. A new JIT reader can be loaded by
32197 first unloading the current one using @code{jit-reader-load} and then
32198 invoking @code{jit-reader-load}.
32200 @item jit-reader-unload
32201 Unload the currently loaded JIT reader.
32205 @node Writing JIT Debug Info Readers
32206 @subsection Writing JIT Debug Info Readers
32207 @cindex writing JIT debug info readers
32209 As mentioned, a reader is essentially a shared object conforming to a
32210 certain ABI. This ABI is described in @file{jit-reader.h}.
32212 @file{jit-reader.h} defines the structures, macros and functions
32213 required to write a reader. It is installed (along with
32214 @value{GDBN}), in @file{@var{includedir}/gdb} where @var{includedir} is
32215 the system include directory.
32217 Readers need to be released under a GPL compatible license. A reader
32218 can be declared as released under such a license by placing the macro
32219 @code{GDB_DECLARE_GPL_COMPATIBLE_READER} in a source file.
32221 The entry point for readers is the symbol @code{gdb_init_reader},
32222 which is expected to be a function with the prototype
32224 @findex gdb_init_reader
32226 extern struct gdb_reader_funcs *gdb_init_reader (void);
32229 @cindex @code{struct gdb_reader_funcs}
32231 @code{struct gdb_reader_funcs} contains a set of pointers to callback
32232 functions. These functions are executed to read the debug info
32233 generated by the JIT compiler (@code{read}), to unwind stack frames
32234 (@code{unwind}) and to create canonical frame IDs
32235 (@code{get_Frame_id}). It also has a callback that is called when the
32236 reader is being unloaded (@code{destroy}). The struct looks like this
32239 struct gdb_reader_funcs
32241 /* Must be set to GDB_READER_INTERFACE_VERSION. */
32242 int reader_version;
32244 /* For use by the reader. */
32247 gdb_read_debug_info *read;
32248 gdb_unwind_frame *unwind;
32249 gdb_get_frame_id *get_frame_id;
32250 gdb_destroy_reader *destroy;
32254 @cindex @code{struct gdb_symbol_callbacks}
32255 @cindex @code{struct gdb_unwind_callbacks}
32257 The callbacks are provided with another set of callbacks by
32258 @value{GDBN} to do their job. For @code{read}, these callbacks are
32259 passed in a @code{struct gdb_symbol_callbacks} and for @code{unwind}
32260 and @code{get_frame_id}, in a @code{struct gdb_unwind_callbacks}.
32261 @code{struct gdb_symbol_callbacks} has callbacks to create new object
32262 files and new symbol tables inside those object files. @code{struct
32263 gdb_unwind_callbacks} has callbacks to read registers off the current
32264 frame and to write out the values of the registers in the previous
32265 frame. Both have a callback (@code{target_read}) to read bytes off the
32266 target's address space.
32268 @node In-Process Agent
32269 @chapter In-Process Agent
32270 @cindex debugging agent
32271 The traditional debugging model is conceptually low-speed, but works fine,
32272 because most bugs can be reproduced in debugging-mode execution. However,
32273 as multi-core or many-core processors are becoming mainstream, and
32274 multi-threaded programs become more and more popular, there should be more
32275 and more bugs that only manifest themselves at normal-mode execution, for
32276 example, thread races, because debugger's interference with the program's
32277 timing may conceal the bugs. On the other hand, in some applications,
32278 it is not feasible for the debugger to interrupt the program's execution
32279 long enough for the developer to learn anything helpful about its behavior.
32280 If the program's correctness depends on its real-time behavior, delays
32281 introduced by a debugger might cause the program to fail, even when the
32282 code itself is correct. It is useful to be able to observe the program's
32283 behavior without interrupting it.
32285 Therefore, traditional debugging model is too intrusive to reproduce
32286 some bugs. In order to reduce the interference with the program, we can
32287 reduce the number of operations performed by debugger. The
32288 @dfn{In-Process Agent}, a shared library, is running within the same
32289 process with inferior, and is able to perform some debugging operations
32290 itself. As a result, debugger is only involved when necessary, and
32291 performance of debugging can be improved accordingly. Note that
32292 interference with program can be reduced but can't be removed completely,
32293 because the in-process agent will still stop or slow down the program.
32295 The in-process agent can interpret and execute Agent Expressions
32296 (@pxref{Agent Expressions}) during performing debugging operations. The
32297 agent expressions can be used for different purposes, such as collecting
32298 data in tracepoints, and condition evaluation in breakpoints.
32300 @anchor{Control Agent}
32301 You can control whether the in-process agent is used as an aid for
32302 debugging with the following commands:
32305 @kindex set agent on
32307 Causes the in-process agent to perform some operations on behalf of the
32308 debugger. Just which operations requested by the user will be done
32309 by the in-process agent depends on the its capabilities. For example,
32310 if you request to evaluate breakpoint conditions in the in-process agent,
32311 and the in-process agent has such capability as well, then breakpoint
32312 conditions will be evaluated in the in-process agent.
32314 @kindex set agent off
32315 @item set agent off
32316 Disables execution of debugging operations by the in-process agent. All
32317 of the operations will be performed by @value{GDBN}.
32321 Display the current setting of execution of debugging operations by
32322 the in-process agent.
32326 @chapter Reporting Bugs in @value{GDBN}
32327 @cindex bugs in @value{GDBN}
32328 @cindex reporting bugs in @value{GDBN}
32330 Your bug reports play an essential role in making @value{GDBN} reliable.
32332 Reporting a bug may help you by bringing a solution to your problem, or it
32333 may not. But in any case the principal function of a bug report is to help
32334 the entire community by making the next version of @value{GDBN} work better. Bug
32335 reports are your contribution to the maintenance of @value{GDBN}.
32337 In order for a bug report to serve its purpose, you must include the
32338 information that enables us to fix the bug.
32341 * Bug Criteria:: Have you found a bug?
32342 * Bug Reporting:: How to report bugs
32346 @section Have You Found a Bug?
32347 @cindex bug criteria
32349 If you are not sure whether you have found a bug, here are some guidelines:
32352 @cindex fatal signal
32353 @cindex debugger crash
32354 @cindex crash of debugger
32356 If the debugger gets a fatal signal, for any input whatever, that is a
32357 @value{GDBN} bug. Reliable debuggers never crash.
32359 @cindex error on valid input
32361 If @value{GDBN} produces an error message for valid input, that is a
32362 bug. (Note that if you're cross debugging, the problem may also be
32363 somewhere in the connection to the target.)
32365 @cindex invalid input
32367 If @value{GDBN} does not produce an error message for invalid input,
32368 that is a bug. However, you should note that your idea of
32369 ``invalid input'' might be our idea of ``an extension'' or ``support
32370 for traditional practice''.
32373 If you are an experienced user of debugging tools, your suggestions
32374 for improvement of @value{GDBN} are welcome in any case.
32377 @node Bug Reporting
32378 @section How to Report Bugs
32379 @cindex bug reports
32380 @cindex @value{GDBN} bugs, reporting
32382 A number of companies and individuals offer support for @sc{gnu} products.
32383 If you obtained @value{GDBN} from a support organization, we recommend you
32384 contact that organization first.
32386 You can find contact information for many support companies and
32387 individuals in the file @file{etc/SERVICE} in the @sc{gnu} Emacs
32389 @c should add a web page ref...
32392 @ifset BUGURL_DEFAULT
32393 In any event, we also recommend that you submit bug reports for
32394 @value{GDBN}. The preferred method is to submit them directly using
32395 @uref{http://www.gnu.org/software/gdb/bugs/, @value{GDBN}'s Bugs web
32396 page}. Alternatively, the @email{bug-gdb@@gnu.org, e-mail gateway} can
32399 @strong{Do not send bug reports to @samp{info-gdb}, or to
32400 @samp{help-gdb}, or to any newsgroups.} Most users of @value{GDBN} do
32401 not want to receive bug reports. Those that do have arranged to receive
32404 The mailing list @samp{bug-gdb} has a newsgroup @samp{gnu.gdb.bug} which
32405 serves as a repeater. The mailing list and the newsgroup carry exactly
32406 the same messages. Often people think of posting bug reports to the
32407 newsgroup instead of mailing them. This appears to work, but it has one
32408 problem which can be crucial: a newsgroup posting often lacks a mail
32409 path back to the sender. Thus, if we need to ask for more information,
32410 we may be unable to reach you. For this reason, it is better to send
32411 bug reports to the mailing list.
32413 @ifclear BUGURL_DEFAULT
32414 In any event, we also recommend that you submit bug reports for
32415 @value{GDBN} to @value{BUGURL}.
32419 The fundamental principle of reporting bugs usefully is this:
32420 @strong{report all the facts}. If you are not sure whether to state a
32421 fact or leave it out, state it!
32423 Often people omit facts because they think they know what causes the
32424 problem and assume that some details do not matter. Thus, you might
32425 assume that the name of the variable you use in an example does not matter.
32426 Well, probably it does not, but one cannot be sure. Perhaps the bug is a
32427 stray memory reference which happens to fetch from the location where that
32428 name is stored in memory; perhaps, if the name were different, the contents
32429 of that location would fool the debugger into doing the right thing despite
32430 the bug. Play it safe and give a specific, complete example. That is the
32431 easiest thing for you to do, and the most helpful.
32433 Keep in mind that the purpose of a bug report is to enable us to fix the
32434 bug. It may be that the bug has been reported previously, but neither
32435 you nor we can know that unless your bug report is complete and
32438 Sometimes people give a few sketchy facts and ask, ``Does this ring a
32439 bell?'' Those bug reports are useless, and we urge everyone to
32440 @emph{refuse to respond to them} except to chide the sender to report
32443 To enable us to fix the bug, you should include all these things:
32447 The version of @value{GDBN}. @value{GDBN} announces it if you start
32448 with no arguments; you can also print it at any time using @code{show
32451 Without this, we will not know whether there is any point in looking for
32452 the bug in the current version of @value{GDBN}.
32455 The type of machine you are using, and the operating system name and
32459 What compiler (and its version) was used to compile @value{GDBN}---e.g.@:
32460 ``@value{GCC}--2.8.1''.
32463 What compiler (and its version) was used to compile the program you are
32464 debugging---e.g.@: ``@value{GCC}--2.8.1'', or ``HP92453-01 A.10.32.03 HP
32465 C Compiler''. For @value{NGCC}, you can say @kbd{@value{GCC} --version}
32466 to get this information; for other compilers, see the documentation for
32470 The command arguments you gave the compiler to compile your example and
32471 observe the bug. For example, did you use @samp{-O}? To guarantee
32472 you will not omit something important, list them all. A copy of the
32473 Makefile (or the output from make) is sufficient.
32475 If we were to try to guess the arguments, we would probably guess wrong
32476 and then we might not encounter the bug.
32479 A complete input script, and all necessary source files, that will
32483 A description of what behavior you observe that you believe is
32484 incorrect. For example, ``It gets a fatal signal.''
32486 Of course, if the bug is that @value{GDBN} gets a fatal signal, then we
32487 will certainly notice it. But if the bug is incorrect output, we might
32488 not notice unless it is glaringly wrong. You might as well not give us
32489 a chance to make a mistake.
32491 Even if the problem you experience is a fatal signal, you should still
32492 say so explicitly. Suppose something strange is going on, such as, your
32493 copy of @value{GDBN} is out of synch, or you have encountered a bug in
32494 the C library on your system. (This has happened!) Your copy might
32495 crash and ours would not. If you told us to expect a crash, then when
32496 ours fails to crash, we would know that the bug was not happening for
32497 us. If you had not told us to expect a crash, then we would not be able
32498 to draw any conclusion from our observations.
32501 @cindex recording a session script
32502 To collect all this information, you can use a session recording program
32503 such as @command{script}, which is available on many Unix systems.
32504 Just run your @value{GDBN} session inside @command{script} and then
32505 include the @file{typescript} file with your bug report.
32507 Another way to record a @value{GDBN} session is to run @value{GDBN}
32508 inside Emacs and then save the entire buffer to a file.
32511 If you wish to suggest changes to the @value{GDBN} source, send us context
32512 diffs. If you even discuss something in the @value{GDBN} source, refer to
32513 it by context, not by line number.
32515 The line numbers in our development sources will not match those in your
32516 sources. Your line numbers would convey no useful information to us.
32520 Here are some things that are not necessary:
32524 A description of the envelope of the bug.
32526 Often people who encounter a bug spend a lot of time investigating
32527 which changes to the input file will make the bug go away and which
32528 changes will not affect it.
32530 This is often time consuming and not very useful, because the way we
32531 will find the bug is by running a single example under the debugger
32532 with breakpoints, not by pure deduction from a series of examples.
32533 We recommend that you save your time for something else.
32535 Of course, if you can find a simpler example to report @emph{instead}
32536 of the original one, that is a convenience for us. Errors in the
32537 output will be easier to spot, running under the debugger will take
32538 less time, and so on.
32540 However, simplification is not vital; if you do not want to do this,
32541 report the bug anyway and send us the entire test case you used.
32544 A patch for the bug.
32546 A patch for the bug does help us if it is a good one. But do not omit
32547 the necessary information, such as the test case, on the assumption that
32548 a patch is all we need. We might see problems with your patch and decide
32549 to fix the problem another way, or we might not understand it at all.
32551 Sometimes with a program as complicated as @value{GDBN} it is very hard to
32552 construct an example that will make the program follow a certain path
32553 through the code. If you do not send us the example, we will not be able
32554 to construct one, so we will not be able to verify that the bug is fixed.
32556 And if we cannot understand what bug you are trying to fix, or why your
32557 patch should be an improvement, we will not install it. A test case will
32558 help us to understand.
32561 A guess about what the bug is or what it depends on.
32563 Such guesses are usually wrong. Even we cannot guess right about such
32564 things without first using the debugger to find the facts.
32567 @c The readline documentation is distributed with the readline code
32568 @c and consists of the two following files:
32571 @c Use -I with makeinfo to point to the appropriate directory,
32572 @c environment var TEXINPUTS with TeX.
32573 @ifclear SYSTEM_READLINE
32574 @include rluser.texi
32575 @include hsuser.texi
32579 @appendix In Memoriam
32581 The @value{GDBN} project mourns the loss of the following long-time
32586 Fred was a long-standing contributor to @value{GDBN} (1991-2006), and
32587 to Free Software in general. Outside of @value{GDBN}, he was known in
32588 the Amiga world for his series of Fish Disks, and the GeekGadget project.
32590 @item Michael Snyder
32591 Michael was one of the Global Maintainers of the @value{GDBN} project,
32592 with contributions recorded as early as 1996, until 2011. In addition
32593 to his day to day participation, he was a large driving force behind
32594 adding Reverse Debugging to @value{GDBN}.
32597 Beyond their technical contributions to the project, they were also
32598 enjoyable members of the Free Software Community. We will miss them.
32600 @node Formatting Documentation
32601 @appendix Formatting Documentation
32603 @cindex @value{GDBN} reference card
32604 @cindex reference card
32605 The @value{GDBN} 4 release includes an already-formatted reference card, ready
32606 for printing with PostScript or Ghostscript, in the @file{gdb}
32607 subdirectory of the main source directory@footnote{In
32608 @file{gdb-@value{GDBVN}/gdb/refcard.ps} of the version @value{GDBVN}
32609 release.}. If you can use PostScript or Ghostscript with your printer,
32610 you can print the reference card immediately with @file{refcard.ps}.
32612 The release also includes the source for the reference card. You
32613 can format it, using @TeX{}, by typing:
32619 The @value{GDBN} reference card is designed to print in @dfn{landscape}
32620 mode on US ``letter'' size paper;
32621 that is, on a sheet 11 inches wide by 8.5 inches
32622 high. You will need to specify this form of printing as an option to
32623 your @sc{dvi} output program.
32625 @cindex documentation
32627 All the documentation for @value{GDBN} comes as part of the machine-readable
32628 distribution. The documentation is written in Texinfo format, which is
32629 a documentation system that uses a single source file to produce both
32630 on-line information and a printed manual. You can use one of the Info
32631 formatting commands to create the on-line version of the documentation
32632 and @TeX{} (or @code{texi2roff}) to typeset the printed version.
32634 @value{GDBN} includes an already formatted copy of the on-line Info
32635 version of this manual in the @file{gdb} subdirectory. The main Info
32636 file is @file{gdb-@value{GDBVN}/gdb/gdb.info}, and it refers to
32637 subordinate files matching @samp{gdb.info*} in the same directory. If
32638 necessary, you can print out these files, or read them with any editor;
32639 but they are easier to read using the @code{info} subsystem in @sc{gnu}
32640 Emacs or the standalone @code{info} program, available as part of the
32641 @sc{gnu} Texinfo distribution.
32643 If you want to format these Info files yourself, you need one of the
32644 Info formatting programs, such as @code{texinfo-format-buffer} or
32647 If you have @code{makeinfo} installed, and are in the top level
32648 @value{GDBN} source directory (@file{gdb-@value{GDBVN}}, in the case of
32649 version @value{GDBVN}), you can make the Info file by typing:
32656 If you want to typeset and print copies of this manual, you need @TeX{},
32657 a program to print its @sc{dvi} output files, and @file{texinfo.tex}, the
32658 Texinfo definitions file.
32660 @TeX{} is a typesetting program; it does not print files directly, but
32661 produces output files called @sc{dvi} files. To print a typeset
32662 document, you need a program to print @sc{dvi} files. If your system
32663 has @TeX{} installed, chances are it has such a program. The precise
32664 command to use depends on your system; @kbd{lpr -d} is common; another
32665 (for PostScript devices) is @kbd{dvips}. The @sc{dvi} print command may
32666 require a file name without any extension or a @samp{.dvi} extension.
32668 @TeX{} also requires a macro definitions file called
32669 @file{texinfo.tex}. This file tells @TeX{} how to typeset a document
32670 written in Texinfo format. On its own, @TeX{} cannot either read or
32671 typeset a Texinfo file. @file{texinfo.tex} is distributed with GDB
32672 and is located in the @file{gdb-@var{version-number}/texinfo}
32675 If you have @TeX{} and a @sc{dvi} printer program installed, you can
32676 typeset and print this manual. First switch to the @file{gdb}
32677 subdirectory of the main source directory (for example, to
32678 @file{gdb-@value{GDBVN}/gdb}) and type:
32684 Then give @file{gdb.dvi} to your @sc{dvi} printing program.
32686 @node Installing GDB
32687 @appendix Installing @value{GDBN}
32688 @cindex installation
32691 * Requirements:: Requirements for building @value{GDBN}
32692 * Running Configure:: Invoking the @value{GDBN} @file{configure} script
32693 * Separate Objdir:: Compiling @value{GDBN} in another directory
32694 * Config Names:: Specifying names for hosts and targets
32695 * Configure Options:: Summary of options for configure
32696 * System-wide configuration:: Having a system-wide init file
32700 @section Requirements for Building @value{GDBN}
32701 @cindex building @value{GDBN}, requirements for
32703 Building @value{GDBN} requires various tools and packages to be available.
32704 Other packages will be used only if they are found.
32706 @heading Tools/Packages Necessary for Building @value{GDBN}
32708 @item ISO C90 compiler
32709 @value{GDBN} is written in ISO C90. It should be buildable with any
32710 working C90 compiler, e.g.@: GCC.
32714 @heading Tools/Packages Optional for Building @value{GDBN}
32718 @value{GDBN} can use the Expat XML parsing library. This library may be
32719 included with your operating system distribution; if it is not, you
32720 can get the latest version from @url{http://expat.sourceforge.net}.
32721 The @file{configure} script will search for this library in several
32722 standard locations; if it is installed in an unusual path, you can
32723 use the @option{--with-libexpat-prefix} option to specify its location.
32729 Remote protocol memory maps (@pxref{Memory Map Format})
32731 Target descriptions (@pxref{Target Descriptions})
32733 Remote shared library lists (@xref{Library List Format},
32734 or alternatively @pxref{Library List Format for SVR4 Targets})
32736 MS-Windows shared libraries (@pxref{Shared Libraries})
32738 Traceframe info (@pxref{Traceframe Info Format})
32742 @cindex compressed debug sections
32743 @value{GDBN} will use the @samp{zlib} library, if available, to read
32744 compressed debug sections. Some linkers, such as GNU gold, are capable
32745 of producing binaries with compressed debug sections. If @value{GDBN}
32746 is compiled with @samp{zlib}, it will be able to read the debug
32747 information in such binaries.
32749 The @samp{zlib} library is likely included with your operating system
32750 distribution; if it is not, you can get the latest version from
32751 @url{http://zlib.net}.
32754 @value{GDBN}'s features related to character sets (@pxref{Character
32755 Sets}) require a functioning @code{iconv} implementation. If you are
32756 on a GNU system, then this is provided by the GNU C Library. Some
32757 other systems also provide a working @code{iconv}.
32759 If @value{GDBN} is using the @code{iconv} program which is installed
32760 in a non-standard place, you will need to tell @value{GDBN} where to find it.
32761 This is done with @option{--with-iconv-bin} which specifies the
32762 directory that contains the @code{iconv} program.
32764 On systems without @code{iconv}, you can install GNU Libiconv. If you
32765 have previously installed Libiconv, you can use the
32766 @option{--with-libiconv-prefix} option to configure.
32768 @value{GDBN}'s top-level @file{configure} and @file{Makefile} will
32769 arrange to build Libiconv if a directory named @file{libiconv} appears
32770 in the top-most source directory. If Libiconv is built this way, and
32771 if the operating system does not provide a suitable @code{iconv}
32772 implementation, then the just-built library will automatically be used
32773 by @value{GDBN}. One easy way to set this up is to download GNU
32774 Libiconv, unpack it, and then rename the directory holding the
32775 Libiconv source code to @samp{libiconv}.
32778 @node Running Configure
32779 @section Invoking the @value{GDBN} @file{configure} Script
32780 @cindex configuring @value{GDBN}
32781 @value{GDBN} comes with a @file{configure} script that automates the process
32782 of preparing @value{GDBN} for installation; you can then use @code{make} to
32783 build the @code{gdb} program.
32785 @c irrelevant in info file; it's as current as the code it lives with.
32786 @footnote{If you have a more recent version of @value{GDBN} than @value{GDBVN},
32787 look at the @file{README} file in the sources; we may have improved the
32788 installation procedures since publishing this manual.}
32791 The @value{GDBN} distribution includes all the source code you need for
32792 @value{GDBN} in a single directory, whose name is usually composed by
32793 appending the version number to @samp{gdb}.
32795 For example, the @value{GDBN} version @value{GDBVN} distribution is in the
32796 @file{gdb-@value{GDBVN}} directory. That directory contains:
32799 @item gdb-@value{GDBVN}/configure @r{(and supporting files)}
32800 script for configuring @value{GDBN} and all its supporting libraries
32802 @item gdb-@value{GDBVN}/gdb
32803 the source specific to @value{GDBN} itself
32805 @item gdb-@value{GDBVN}/bfd
32806 source for the Binary File Descriptor library
32808 @item gdb-@value{GDBVN}/include
32809 @sc{gnu} include files
32811 @item gdb-@value{GDBVN}/libiberty
32812 source for the @samp{-liberty} free software library
32814 @item gdb-@value{GDBVN}/opcodes
32815 source for the library of opcode tables and disassemblers
32817 @item gdb-@value{GDBVN}/readline
32818 source for the @sc{gnu} command-line interface
32820 @item gdb-@value{GDBVN}/glob
32821 source for the @sc{gnu} filename pattern-matching subroutine
32823 @item gdb-@value{GDBVN}/mmalloc
32824 source for the @sc{gnu} memory-mapped malloc package
32827 The simplest way to configure and build @value{GDBN} is to run @file{configure}
32828 from the @file{gdb-@var{version-number}} source directory, which in
32829 this example is the @file{gdb-@value{GDBVN}} directory.
32831 First switch to the @file{gdb-@var{version-number}} source directory
32832 if you are not already in it; then run @file{configure}. Pass the
32833 identifier for the platform on which @value{GDBN} will run as an
32839 cd gdb-@value{GDBVN}
32840 ./configure @var{host}
32845 where @var{host} is an identifier such as @samp{sun4} or
32846 @samp{decstation}, that identifies the platform where @value{GDBN} will run.
32847 (You can often leave off @var{host}; @file{configure} tries to guess the
32848 correct value by examining your system.)
32850 Running @samp{configure @var{host}} and then running @code{make} builds the
32851 @file{bfd}, @file{readline}, @file{mmalloc}, and @file{libiberty}
32852 libraries, then @code{gdb} itself. The configured source files, and the
32853 binaries, are left in the corresponding source directories.
32856 @file{configure} is a Bourne-shell (@code{/bin/sh}) script; if your
32857 system does not recognize this automatically when you run a different
32858 shell, you may need to run @code{sh} on it explicitly:
32861 sh configure @var{host}
32864 If you run @file{configure} from a directory that contains source
32865 directories for multiple libraries or programs, such as the
32866 @file{gdb-@value{GDBVN}} source directory for version @value{GDBVN},
32868 creates configuration files for every directory level underneath (unless
32869 you tell it not to, with the @samp{--norecursion} option).
32871 You should run the @file{configure} script from the top directory in the
32872 source tree, the @file{gdb-@var{version-number}} directory. If you run
32873 @file{configure} from one of the subdirectories, you will configure only
32874 that subdirectory. That is usually not what you want. In particular,
32875 if you run the first @file{configure} from the @file{gdb} subdirectory
32876 of the @file{gdb-@var{version-number}} directory, you will omit the
32877 configuration of @file{bfd}, @file{readline}, and other sibling
32878 directories of the @file{gdb} subdirectory. This leads to build errors
32879 about missing include files such as @file{bfd/bfd.h}.
32881 You can install @code{@value{GDBP}} anywhere; it has no hardwired paths.
32882 However, you should make sure that the shell on your path (named by
32883 the @samp{SHELL} environment variable) is publicly readable. Remember
32884 that @value{GDBN} uses the shell to start your program---some systems refuse to
32885 let @value{GDBN} debug child processes whose programs are not readable.
32887 @node Separate Objdir
32888 @section Compiling @value{GDBN} in Another Directory
32890 If you want to run @value{GDBN} versions for several host or target machines,
32891 you need a different @code{gdb} compiled for each combination of
32892 host and target. @file{configure} is designed to make this easy by
32893 allowing you to generate each configuration in a separate subdirectory,
32894 rather than in the source directory. If your @code{make} program
32895 handles the @samp{VPATH} feature (@sc{gnu} @code{make} does), running
32896 @code{make} in each of these directories builds the @code{gdb}
32897 program specified there.
32899 To build @code{gdb} in a separate directory, run @file{configure}
32900 with the @samp{--srcdir} option to specify where to find the source.
32901 (You also need to specify a path to find @file{configure}
32902 itself from your working directory. If the path to @file{configure}
32903 would be the same as the argument to @samp{--srcdir}, you can leave out
32904 the @samp{--srcdir} option; it is assumed.)
32906 For example, with version @value{GDBVN}, you can build @value{GDBN} in a
32907 separate directory for a Sun 4 like this:
32911 cd gdb-@value{GDBVN}
32914 ../gdb-@value{GDBVN}/configure sun4
32919 When @file{configure} builds a configuration using a remote source
32920 directory, it creates a tree for the binaries with the same structure
32921 (and using the same names) as the tree under the source directory. In
32922 the example, you'd find the Sun 4 library @file{libiberty.a} in the
32923 directory @file{gdb-sun4/libiberty}, and @value{GDBN} itself in
32924 @file{gdb-sun4/gdb}.
32926 Make sure that your path to the @file{configure} script has just one
32927 instance of @file{gdb} in it. If your path to @file{configure} looks
32928 like @file{../gdb-@value{GDBVN}/gdb/configure}, you are configuring only
32929 one subdirectory of @value{GDBN}, not the whole package. This leads to
32930 build errors about missing include files such as @file{bfd/bfd.h}.
32932 One popular reason to build several @value{GDBN} configurations in separate
32933 directories is to configure @value{GDBN} for cross-compiling (where
32934 @value{GDBN} runs on one machine---the @dfn{host}---while debugging
32935 programs that run on another machine---the @dfn{target}).
32936 You specify a cross-debugging target by
32937 giving the @samp{--target=@var{target}} option to @file{configure}.
32939 When you run @code{make} to build a program or library, you must run
32940 it in a configured directory---whatever directory you were in when you
32941 called @file{configure} (or one of its subdirectories).
32943 The @code{Makefile} that @file{configure} generates in each source
32944 directory also runs recursively. If you type @code{make} in a source
32945 directory such as @file{gdb-@value{GDBVN}} (or in a separate configured
32946 directory configured with @samp{--srcdir=@var{dirname}/gdb-@value{GDBVN}}), you
32947 will build all the required libraries, and then build GDB.
32949 When you have multiple hosts or targets configured in separate
32950 directories, you can run @code{make} on them in parallel (for example,
32951 if they are NFS-mounted on each of the hosts); they will not interfere
32955 @section Specifying Names for Hosts and Targets
32957 The specifications used for hosts and targets in the @file{configure}
32958 script are based on a three-part naming scheme, but some short predefined
32959 aliases are also supported. The full naming scheme encodes three pieces
32960 of information in the following pattern:
32963 @var{architecture}-@var{vendor}-@var{os}
32966 For example, you can use the alias @code{sun4} as a @var{host} argument,
32967 or as the value for @var{target} in a @code{--target=@var{target}}
32968 option. The equivalent full name is @samp{sparc-sun-sunos4}.
32970 The @file{configure} script accompanying @value{GDBN} does not provide
32971 any query facility to list all supported host and target names or
32972 aliases. @file{configure} calls the Bourne shell script
32973 @code{config.sub} to map abbreviations to full names; you can read the
32974 script, if you wish, or you can use it to test your guesses on
32975 abbreviations---for example:
32978 % sh config.sub i386-linux
32980 % sh config.sub alpha-linux
32981 alpha-unknown-linux-gnu
32982 % sh config.sub hp9k700
32984 % sh config.sub sun4
32985 sparc-sun-sunos4.1.1
32986 % sh config.sub sun3
32987 m68k-sun-sunos4.1.1
32988 % sh config.sub i986v
32989 Invalid configuration `i986v': machine `i986v' not recognized
32993 @code{config.sub} is also distributed in the @value{GDBN} source
32994 directory (@file{gdb-@value{GDBVN}}, for version @value{GDBVN}).
32996 @node Configure Options
32997 @section @file{configure} Options
32999 Here is a summary of the @file{configure} options and arguments that
33000 are most often useful for building @value{GDBN}. @file{configure} also has
33001 several other options not listed here. @inforef{What Configure
33002 Does,,configure.info}, for a full explanation of @file{configure}.
33005 configure @r{[}--help@r{]}
33006 @r{[}--prefix=@var{dir}@r{]}
33007 @r{[}--exec-prefix=@var{dir}@r{]}
33008 @r{[}--srcdir=@var{dirname}@r{]}
33009 @r{[}--norecursion@r{]} @r{[}--rm@r{]}
33010 @r{[}--target=@var{target}@r{]}
33015 You may introduce options with a single @samp{-} rather than
33016 @samp{--} if you prefer; but you may abbreviate option names if you use
33021 Display a quick summary of how to invoke @file{configure}.
33023 @item --prefix=@var{dir}
33024 Configure the source to install programs and files under directory
33027 @item --exec-prefix=@var{dir}
33028 Configure the source to install programs under directory
33031 @c avoid splitting the warning from the explanation:
33033 @item --srcdir=@var{dirname}
33034 @strong{Warning: using this option requires @sc{gnu} @code{make}, or another
33035 @code{make} that implements the @code{VPATH} feature.}@*
33036 Use this option to make configurations in directories separate from the
33037 @value{GDBN} source directories. Among other things, you can use this to
33038 build (or maintain) several configurations simultaneously, in separate
33039 directories. @file{configure} writes configuration-specific files in
33040 the current directory, but arranges for them to use the source in the
33041 directory @var{dirname}. @file{configure} creates directories under
33042 the working directory in parallel to the source directories below
33045 @item --norecursion
33046 Configure only the directory level where @file{configure} is executed; do not
33047 propagate configuration to subdirectories.
33049 @item --target=@var{target}
33050 Configure @value{GDBN} for cross-debugging programs running on the specified
33051 @var{target}. Without this option, @value{GDBN} is configured to debug
33052 programs that run on the same machine (@var{host}) as @value{GDBN} itself.
33054 There is no convenient way to generate a list of all available targets.
33056 @item @var{host} @dots{}
33057 Configure @value{GDBN} to run on the specified @var{host}.
33059 There is no convenient way to generate a list of all available hosts.
33062 There are many other options available as well, but they are generally
33063 needed for special purposes only.
33065 @node System-wide configuration
33066 @section System-wide configuration and settings
33067 @cindex system-wide init file
33069 @value{GDBN} can be configured to have a system-wide init file;
33070 this file will be read and executed at startup (@pxref{Startup, , What
33071 @value{GDBN} does during startup}).
33073 Here is the corresponding configure option:
33076 @item --with-system-gdbinit=@var{file}
33077 Specify that the default location of the system-wide init file is
33081 If @value{GDBN} has been configured with the option @option{--prefix=$prefix},
33082 it may be subject to relocation. Two possible cases:
33086 If the default location of this init file contains @file{$prefix},
33087 it will be subject to relocation. Suppose that the configure options
33088 are @option{--prefix=$prefix --with-system-gdbinit=$prefix/etc/gdbinit};
33089 if @value{GDBN} is moved from @file{$prefix} to @file{$install}, the system
33090 init file is looked for as @file{$install/etc/gdbinit} instead of
33091 @file{$prefix/etc/gdbinit}.
33094 By contrast, if the default location does not contain the prefix,
33095 it will not be relocated. E.g.@: if @value{GDBN} has been configured with
33096 @option{--prefix=/usr/local --with-system-gdbinit=/usr/share/gdb/gdbinit},
33097 then @value{GDBN} will always look for @file{/usr/share/gdb/gdbinit},
33098 wherever @value{GDBN} is installed.
33101 @node Maintenance Commands
33102 @appendix Maintenance Commands
33103 @cindex maintenance commands
33104 @cindex internal commands
33106 In addition to commands intended for @value{GDBN} users, @value{GDBN}
33107 includes a number of commands intended for @value{GDBN} developers,
33108 that are not documented elsewhere in this manual. These commands are
33109 provided here for reference. (For commands that turn on debugging
33110 messages, see @ref{Debugging Output}.)
33113 @kindex maint agent
33114 @kindex maint agent-eval
33115 @item maint agent @var{expression}
33116 @itemx maint agent-eval @var{expression}
33117 Translate the given @var{expression} into remote agent bytecodes.
33118 This command is useful for debugging the Agent Expression mechanism
33119 (@pxref{Agent Expressions}). The @samp{agent} version produces an
33120 expression useful for data collection, such as by tracepoints, while
33121 @samp{maint agent-eval} produces an expression that evaluates directly
33122 to a result. For instance, a collection expression for @code{globa +
33123 globb} will include bytecodes to record four bytes of memory at each
33124 of the addresses of @code{globa} and @code{globb}, while discarding
33125 the result of the addition, while an evaluation expression will do the
33126 addition and return the sum.
33128 @kindex maint info breakpoints
33129 @item @anchor{maint info breakpoints}maint info breakpoints
33130 Using the same format as @samp{info breakpoints}, display both the
33131 breakpoints you've set explicitly, and those @value{GDBN} is using for
33132 internal purposes. Internal breakpoints are shown with negative
33133 breakpoint numbers. The type column identifies what kind of breakpoint
33138 Normal, explicitly set breakpoint.
33141 Normal, explicitly set watchpoint.
33144 Internal breakpoint, used to handle correctly stepping through
33145 @code{longjmp} calls.
33147 @item longjmp resume
33148 Internal breakpoint at the target of a @code{longjmp}.
33151 Temporary internal breakpoint used by the @value{GDBN} @code{until} command.
33154 Temporary internal breakpoint used by the @value{GDBN} @code{finish} command.
33157 Shared library events.
33161 @kindex set displaced-stepping
33162 @kindex show displaced-stepping
33163 @cindex displaced stepping support
33164 @cindex out-of-line single-stepping
33165 @item set displaced-stepping
33166 @itemx show displaced-stepping
33167 Control whether or not @value{GDBN} will do @dfn{displaced stepping}
33168 if the target supports it. Displaced stepping is a way to single-step
33169 over breakpoints without removing them from the inferior, by executing
33170 an out-of-line copy of the instruction that was originally at the
33171 breakpoint location. It is also known as out-of-line single-stepping.
33174 @item set displaced-stepping on
33175 If the target architecture supports it, @value{GDBN} will use
33176 displaced stepping to step over breakpoints.
33178 @item set displaced-stepping off
33179 @value{GDBN} will not use displaced stepping to step over breakpoints,
33180 even if such is supported by the target architecture.
33182 @cindex non-stop mode, and @samp{set displaced-stepping}
33183 @item set displaced-stepping auto
33184 This is the default mode. @value{GDBN} will use displaced stepping
33185 only if non-stop mode is active (@pxref{Non-Stop Mode}) and the target
33186 architecture supports displaced stepping.
33189 @kindex maint check-symtabs
33190 @item maint check-symtabs
33191 Check the consistency of psymtabs and symtabs.
33193 @kindex maint cplus first_component
33194 @item maint cplus first_component @var{name}
33195 Print the first C@t{++} class/namespace component of @var{name}.
33197 @kindex maint cplus namespace
33198 @item maint cplus namespace
33199 Print the list of possible C@t{++} namespaces.
33201 @kindex maint demangle
33202 @item maint demangle @var{name}
33203 Demangle a C@t{++} or Objective-C mangled @var{name}.
33205 @kindex maint deprecate
33206 @kindex maint undeprecate
33207 @cindex deprecated commands
33208 @item maint deprecate @var{command} @r{[}@var{replacement}@r{]}
33209 @itemx maint undeprecate @var{command}
33210 Deprecate or undeprecate the named @var{command}. Deprecated commands
33211 cause @value{GDBN} to issue a warning when you use them. The optional
33212 argument @var{replacement} says which newer command should be used in
33213 favor of the deprecated one; if it is given, @value{GDBN} will mention
33214 the replacement as part of the warning.
33216 @kindex maint dump-me
33217 @item maint dump-me
33218 @cindex @code{SIGQUIT} signal, dump core of @value{GDBN}
33219 Cause a fatal signal in the debugger and force it to dump its core.
33220 This is supported only on systems which support aborting a program
33221 with the @code{SIGQUIT} signal.
33223 @kindex maint internal-error
33224 @kindex maint internal-warning
33225 @item maint internal-error @r{[}@var{message-text}@r{]}
33226 @itemx maint internal-warning @r{[}@var{message-text}@r{]}
33227 Cause @value{GDBN} to call the internal function @code{internal_error}
33228 or @code{internal_warning} and hence behave as though an internal error
33229 or internal warning has been detected. In addition to reporting the
33230 internal problem, these functions give the user the opportunity to
33231 either quit @value{GDBN} or create a core file of the current
33232 @value{GDBN} session.
33234 These commands take an optional parameter @var{message-text} that is
33235 used as the text of the error or warning message.
33237 Here's an example of using @code{internal-error}:
33240 (@value{GDBP}) @kbd{maint internal-error testing, 1, 2}
33241 @dots{}/maint.c:121: internal-error: testing, 1, 2
33242 A problem internal to GDB has been detected. Further
33243 debugging may prove unreliable.
33244 Quit this debugging session? (y or n) @kbd{n}
33245 Create a core file? (y or n) @kbd{n}
33249 @cindex @value{GDBN} internal error
33250 @cindex internal errors, control of @value{GDBN} behavior
33252 @kindex maint set internal-error
33253 @kindex maint show internal-error
33254 @kindex maint set internal-warning
33255 @kindex maint show internal-warning
33256 @item maint set internal-error @var{action} [ask|yes|no]
33257 @itemx maint show internal-error @var{action}
33258 @itemx maint set internal-warning @var{action} [ask|yes|no]
33259 @itemx maint show internal-warning @var{action}
33260 When @value{GDBN} reports an internal problem (error or warning) it
33261 gives the user the opportunity to both quit @value{GDBN} and create a
33262 core file of the current @value{GDBN} session. These commands let you
33263 override the default behaviour for each particular @var{action},
33264 described in the table below.
33268 You can specify that @value{GDBN} should always (yes) or never (no)
33269 quit. The default is to ask the user what to do.
33272 You can specify that @value{GDBN} should always (yes) or never (no)
33273 create a core file. The default is to ask the user what to do.
33276 @kindex maint packet
33277 @item maint packet @var{text}
33278 If @value{GDBN} is talking to an inferior via the serial protocol,
33279 then this command sends the string @var{text} to the inferior, and
33280 displays the response packet. @value{GDBN} supplies the initial
33281 @samp{$} character, the terminating @samp{#} character, and the
33284 @kindex maint print architecture
33285 @item maint print architecture @r{[}@var{file}@r{]}
33286 Print the entire architecture configuration. The optional argument
33287 @var{file} names the file where the output goes.
33289 @kindex maint print c-tdesc
33290 @item maint print c-tdesc
33291 Print the current target description (@pxref{Target Descriptions}) as
33292 a C source file. The created source file can be used in @value{GDBN}
33293 when an XML parser is not available to parse the description.
33295 @kindex maint print dummy-frames
33296 @item maint print dummy-frames
33297 Prints the contents of @value{GDBN}'s internal dummy-frame stack.
33300 (@value{GDBP}) @kbd{b add}
33302 (@value{GDBP}) @kbd{print add(2,3)}
33303 Breakpoint 2, add (a=2, b=3) at @dots{}
33305 The program being debugged stopped while in a function called from GDB.
33307 (@value{GDBP}) @kbd{maint print dummy-frames}
33308 0x1a57c80: pc=0x01014068 fp=0x0200bddc sp=0x0200bdd6
33309 top=0x0200bdd4 id=@{stack=0x200bddc,code=0x101405c@}
33310 call_lo=0x01014000 call_hi=0x01014001
33314 Takes an optional file parameter.
33316 @kindex maint print registers
33317 @kindex maint print raw-registers
33318 @kindex maint print cooked-registers
33319 @kindex maint print register-groups
33320 @kindex maint print remote-registers
33321 @item maint print registers @r{[}@var{file}@r{]}
33322 @itemx maint print raw-registers @r{[}@var{file}@r{]}
33323 @itemx maint print cooked-registers @r{[}@var{file}@r{]}
33324 @itemx maint print register-groups @r{[}@var{file}@r{]}
33325 @itemx maint print remote-registers @r{[}@var{file}@r{]}
33326 Print @value{GDBN}'s internal register data structures.
33328 The command @code{maint print raw-registers} includes the contents of
33329 the raw register cache; the command @code{maint print
33330 cooked-registers} includes the (cooked) value of all registers,
33331 including registers which aren't available on the target nor visible
33332 to user; the command @code{maint print register-groups} includes the
33333 groups that each register is a member of; and the command @code{maint
33334 print remote-registers} includes the remote target's register numbers
33335 and offsets in the `G' packets. @xref{Registers,, Registers, gdbint,
33336 @value{GDBN} Internals}.
33338 These commands take an optional parameter, a file name to which to
33339 write the information.
33341 @kindex maint print reggroups
33342 @item maint print reggroups @r{[}@var{file}@r{]}
33343 Print @value{GDBN}'s internal register group data structures. The
33344 optional argument @var{file} tells to what file to write the
33347 The register groups info looks like this:
33350 (@value{GDBP}) @kbd{maint print reggroups}
33363 This command forces @value{GDBN} to flush its internal register cache.
33365 @kindex maint print objfiles
33366 @cindex info for known object files
33367 @item maint print objfiles
33368 Print a dump of all known object files. For each object file, this
33369 command prints its name, address in memory, and all of its psymtabs
33372 @kindex maint print section-scripts
33373 @cindex info for known .debug_gdb_scripts-loaded scripts
33374 @item maint print section-scripts [@var{regexp}]
33375 Print a dump of scripts specified in the @code{.debug_gdb_section} section.
33376 If @var{regexp} is specified, only print scripts loaded by object files
33377 matching @var{regexp}.
33378 For each script, this command prints its name as specified in the objfile,
33379 and the full path if known.
33380 @xref{.debug_gdb_scripts section}.
33382 @kindex maint print statistics
33383 @cindex bcache statistics
33384 @item maint print statistics
33385 This command prints, for each object file in the program, various data
33386 about that object file followed by the byte cache (@dfn{bcache})
33387 statistics for the object file. The objfile data includes the number
33388 of minimal, partial, full, and stabs symbols, the number of types
33389 defined by the objfile, the number of as yet unexpanded psym tables,
33390 the number of line tables and string tables, and the amount of memory
33391 used by the various tables. The bcache statistics include the counts,
33392 sizes, and counts of duplicates of all and unique objects, max,
33393 average, and median entry size, total memory used and its overhead and
33394 savings, and various measures of the hash table size and chain
33397 @kindex maint print target-stack
33398 @cindex target stack description
33399 @item maint print target-stack
33400 A @dfn{target} is an interface between the debugger and a particular
33401 kind of file or process. Targets can be stacked in @dfn{strata},
33402 so that more than one target can potentially respond to a request.
33403 In particular, memory accesses will walk down the stack of targets
33404 until they find a target that is interested in handling that particular
33407 This command prints a short description of each layer that was pushed on
33408 the @dfn{target stack}, starting from the top layer down to the bottom one.
33410 @kindex maint print type
33411 @cindex type chain of a data type
33412 @item maint print type @var{expr}
33413 Print the type chain for a type specified by @var{expr}. The argument
33414 can be either a type name or a symbol. If it is a symbol, the type of
33415 that symbol is described. The type chain produced by this command is
33416 a recursive definition of the data type as stored in @value{GDBN}'s
33417 data structures, including its flags and contained types.
33419 @kindex maint set dwarf2 always-disassemble
33420 @kindex maint show dwarf2 always-disassemble
33421 @item maint set dwarf2 always-disassemble
33422 @item maint show dwarf2 always-disassemble
33423 Control the behavior of @code{info address} when using DWARF debugging
33426 The default is @code{off}, which means that @value{GDBN} should try to
33427 describe a variable's location in an easily readable format. When
33428 @code{on}, @value{GDBN} will instead display the DWARF location
33429 expression in an assembly-like format. Note that some locations are
33430 too complex for @value{GDBN} to describe simply; in this case you will
33431 always see the disassembly form.
33433 Here is an example of the resulting disassembly:
33436 (gdb) info addr argc
33437 Symbol "argc" is a complex DWARF expression:
33441 For more information on these expressions, see
33442 @uref{http://www.dwarfstd.org/, the DWARF standard}.
33444 @kindex maint set dwarf2 max-cache-age
33445 @kindex maint show dwarf2 max-cache-age
33446 @item maint set dwarf2 max-cache-age
33447 @itemx maint show dwarf2 max-cache-age
33448 Control the DWARF 2 compilation unit cache.
33450 @cindex DWARF 2 compilation units cache
33451 In object files with inter-compilation-unit references, such as those
33452 produced by the GCC option @samp{-feliminate-dwarf2-dups}, the DWARF 2
33453 reader needs to frequently refer to previously read compilation units.
33454 This setting controls how long a compilation unit will remain in the
33455 cache if it is not referenced. A higher limit means that cached
33456 compilation units will be stored in memory longer, and more total
33457 memory will be used. Setting it to zero disables caching, which will
33458 slow down @value{GDBN} startup, but reduce memory consumption.
33460 @kindex maint set profile
33461 @kindex maint show profile
33462 @cindex profiling GDB
33463 @item maint set profile
33464 @itemx maint show profile
33465 Control profiling of @value{GDBN}.
33467 Profiling will be disabled until you use the @samp{maint set profile}
33468 command to enable it. When you enable profiling, the system will begin
33469 collecting timing and execution count data; when you disable profiling or
33470 exit @value{GDBN}, the results will be written to a log file. Remember that
33471 if you use profiling, @value{GDBN} will overwrite the profiling log file
33472 (often called @file{gmon.out}). If you have a record of important profiling
33473 data in a @file{gmon.out} file, be sure to move it to a safe location.
33475 Configuring with @samp{--enable-profiling} arranges for @value{GDBN} to be
33476 compiled with the @samp{-pg} compiler option.
33478 @kindex maint set show-debug-regs
33479 @kindex maint show show-debug-regs
33480 @cindex hardware debug registers
33481 @item maint set show-debug-regs
33482 @itemx maint show show-debug-regs
33483 Control whether to show variables that mirror the hardware debug
33484 registers. Use @code{ON} to enable, @code{OFF} to disable. If
33485 enabled, the debug registers values are shown when @value{GDBN} inserts or
33486 removes a hardware breakpoint or watchpoint, and when the inferior
33487 triggers a hardware-assisted breakpoint or watchpoint.
33489 @kindex maint set show-all-tib
33490 @kindex maint show show-all-tib
33491 @item maint set show-all-tib
33492 @itemx maint show show-all-tib
33493 Control whether to show all non zero areas within a 1k block starting
33494 at thread local base, when using the @samp{info w32 thread-information-block}
33497 @kindex maint space
33498 @cindex memory used by commands
33500 Control whether to display memory usage for each command. If set to a
33501 nonzero value, @value{GDBN} will display how much memory each command
33502 took, following the command's own output. This can also be requested
33503 by invoking @value{GDBN} with the @option{--statistics} command-line
33504 switch (@pxref{Mode Options}).
33507 @cindex time of command execution
33509 Control whether to display the execution time of @value{GDBN} for each command.
33510 If set to a nonzero value, @value{GDBN} will display how much time it
33511 took to execute each command, following the command's own output.
33512 Both CPU time and wallclock time are printed.
33513 Printing both is useful when trying to determine whether the cost is
33514 CPU or, e.g., disk/network, latency.
33515 Note that the CPU time printed is for @value{GDBN} only, it does not include
33516 the execution time of the inferior because there's no mechanism currently
33517 to compute how much time was spent by @value{GDBN} and how much time was
33518 spent by the program been debugged.
33519 This can also be requested by invoking @value{GDBN} with the
33520 @option{--statistics} command-line switch (@pxref{Mode Options}).
33522 @kindex maint translate-address
33523 @item maint translate-address @r{[}@var{section}@r{]} @var{addr}
33524 Find the symbol stored at the location specified by the address
33525 @var{addr} and an optional section name @var{section}. If found,
33526 @value{GDBN} prints the name of the closest symbol and an offset from
33527 the symbol's location to the specified address. This is similar to
33528 the @code{info address} command (@pxref{Symbols}), except that this
33529 command also allows to find symbols in other sections.
33531 If section was not specified, the section in which the symbol was found
33532 is also printed. For dynamically linked executables, the name of
33533 executable or shared library containing the symbol is printed as well.
33537 The following command is useful for non-interactive invocations of
33538 @value{GDBN}, such as in the test suite.
33541 @item set watchdog @var{nsec}
33542 @kindex set watchdog
33543 @cindex watchdog timer
33544 @cindex timeout for commands
33545 Set the maximum number of seconds @value{GDBN} will wait for the
33546 target operation to finish. If this time expires, @value{GDBN}
33547 reports and error and the command is aborted.
33549 @item show watchdog
33550 Show the current setting of the target wait timeout.
33553 @node Remote Protocol
33554 @appendix @value{GDBN} Remote Serial Protocol
33559 * Stop Reply Packets::
33560 * General Query Packets::
33561 * Architecture-Specific Protocol Details::
33562 * Tracepoint Packets::
33563 * Host I/O Packets::
33565 * Notification Packets::
33566 * Remote Non-Stop::
33567 * Packet Acknowledgment::
33569 * File-I/O Remote Protocol Extension::
33570 * Library List Format::
33571 * Library List Format for SVR4 Targets::
33572 * Memory Map Format::
33573 * Thread List Format::
33574 * Traceframe Info Format::
33580 There may be occasions when you need to know something about the
33581 protocol---for example, if there is only one serial port to your target
33582 machine, you might want your program to do something special if it
33583 recognizes a packet meant for @value{GDBN}.
33585 In the examples below, @samp{->} and @samp{<-} are used to indicate
33586 transmitted and received data, respectively.
33588 @cindex protocol, @value{GDBN} remote serial
33589 @cindex serial protocol, @value{GDBN} remote
33590 @cindex remote serial protocol
33591 All @value{GDBN} commands and responses (other than acknowledgments
33592 and notifications, see @ref{Notification Packets}) are sent as a
33593 @var{packet}. A @var{packet} is introduced with the character
33594 @samp{$}, the actual @var{packet-data}, and the terminating character
33595 @samp{#} followed by a two-digit @var{checksum}:
33598 @code{$}@var{packet-data}@code{#}@var{checksum}
33602 @cindex checksum, for @value{GDBN} remote
33604 The two-digit @var{checksum} is computed as the modulo 256 sum of all
33605 characters between the leading @samp{$} and the trailing @samp{#} (an
33606 eight bit unsigned checksum).
33608 Implementors should note that prior to @value{GDBN} 5.0 the protocol
33609 specification also included an optional two-digit @var{sequence-id}:
33612 @code{$}@var{sequence-id}@code{:}@var{packet-data}@code{#}@var{checksum}
33615 @cindex sequence-id, for @value{GDBN} remote
33617 That @var{sequence-id} was appended to the acknowledgment. @value{GDBN}
33618 has never output @var{sequence-id}s. Stubs that handle packets added
33619 since @value{GDBN} 5.0 must not accept @var{sequence-id}.
33621 When either the host or the target machine receives a packet, the first
33622 response expected is an acknowledgment: either @samp{+} (to indicate
33623 the package was received correctly) or @samp{-} (to request
33627 -> @code{$}@var{packet-data}@code{#}@var{checksum}
33632 The @samp{+}/@samp{-} acknowledgments can be disabled
33633 once a connection is established.
33634 @xref{Packet Acknowledgment}, for details.
33636 The host (@value{GDBN}) sends @var{command}s, and the target (the
33637 debugging stub incorporated in your program) sends a @var{response}. In
33638 the case of step and continue @var{command}s, the response is only sent
33639 when the operation has completed, and the target has again stopped all
33640 threads in all attached processes. This is the default all-stop mode
33641 behavior, but the remote protocol also supports @value{GDBN}'s non-stop
33642 execution mode; see @ref{Remote Non-Stop}, for details.
33644 @var{packet-data} consists of a sequence of characters with the
33645 exception of @samp{#} and @samp{$} (see @samp{X} packet for additional
33648 @cindex remote protocol, field separator
33649 Fields within the packet should be separated using @samp{,} @samp{;} or
33650 @samp{:}. Except where otherwise noted all numbers are represented in
33651 @sc{hex} with leading zeros suppressed.
33653 Implementors should note that prior to @value{GDBN} 5.0, the character
33654 @samp{:} could not appear as the third character in a packet (as it
33655 would potentially conflict with the @var{sequence-id}).
33657 @cindex remote protocol, binary data
33658 @anchor{Binary Data}
33659 Binary data in most packets is encoded either as two hexadecimal
33660 digits per byte of binary data. This allowed the traditional remote
33661 protocol to work over connections which were only seven-bit clean.
33662 Some packets designed more recently assume an eight-bit clean
33663 connection, and use a more efficient encoding to send and receive
33666 The binary data representation uses @code{7d} (@sc{ascii} @samp{@}})
33667 as an escape character. Any escaped byte is transmitted as the escape
33668 character followed by the original character XORed with @code{0x20}.
33669 For example, the byte @code{0x7d} would be transmitted as the two
33670 bytes @code{0x7d 0x5d}. The bytes @code{0x23} (@sc{ascii} @samp{#}),
33671 @code{0x24} (@sc{ascii} @samp{$}), and @code{0x7d} (@sc{ascii}
33672 @samp{@}}) must always be escaped. Responses sent by the stub
33673 must also escape @code{0x2a} (@sc{ascii} @samp{*}), so that it
33674 is not interpreted as the start of a run-length encoded sequence
33677 Response @var{data} can be run-length encoded to save space.
33678 Run-length encoding replaces runs of identical characters with one
33679 instance of the repeated character, followed by a @samp{*} and a
33680 repeat count. The repeat count is itself sent encoded, to avoid
33681 binary characters in @var{data}: a value of @var{n} is sent as
33682 @code{@var{n}+29}. For a repeat count greater or equal to 3, this
33683 produces a printable @sc{ascii} character, e.g.@: a space (@sc{ascii}
33684 code 32) for a repeat count of 3. (This is because run-length
33685 encoding starts to win for counts 3 or more.) Thus, for example,
33686 @samp{0* } is a run-length encoding of ``0000'': the space character
33687 after @samp{*} means repeat the leading @code{0} @w{@code{32 - 29 =
33690 The printable characters @samp{#} and @samp{$} or with a numeric value
33691 greater than 126 must not be used. Runs of six repeats (@samp{#}) or
33692 seven repeats (@samp{$}) can be expanded using a repeat count of only
33693 five (@samp{"}). For example, @samp{00000000} can be encoded as
33696 The error response returned for some packets includes a two character
33697 error number. That number is not well defined.
33699 @cindex empty response, for unsupported packets
33700 For any @var{command} not supported by the stub, an empty response
33701 (@samp{$#00}) should be returned. That way it is possible to extend the
33702 protocol. A newer @value{GDBN} can tell if a packet is supported based
33705 At a minimum, a stub is required to support the @samp{g} and @samp{G}
33706 commands for register access, and the @samp{m} and @samp{M} commands
33707 for memory access. Stubs that only control single-threaded targets
33708 can implement run control with the @samp{c} (continue), and @samp{s}
33709 (step) commands. Stubs that support multi-threading targets should
33710 support the @samp{vCont} command. All other commands are optional.
33715 The following table provides a complete list of all currently defined
33716 @var{command}s and their corresponding response @var{data}.
33717 @xref{File-I/O Remote Protocol Extension}, for details about the File
33718 I/O extension of the remote protocol.
33720 Each packet's description has a template showing the packet's overall
33721 syntax, followed by an explanation of the packet's meaning. We
33722 include spaces in some of the templates for clarity; these are not
33723 part of the packet's syntax. No @value{GDBN} packet uses spaces to
33724 separate its components. For example, a template like @samp{foo
33725 @var{bar} @var{baz}} describes a packet beginning with the three ASCII
33726 bytes @samp{foo}, followed by a @var{bar}, followed directly by a
33727 @var{baz}. @value{GDBN} does not transmit a space character between the
33728 @samp{foo} and the @var{bar}, or between the @var{bar} and the
33731 @cindex @var{thread-id}, in remote protocol
33732 @anchor{thread-id syntax}
33733 Several packets and replies include a @var{thread-id} field to identify
33734 a thread. Normally these are positive numbers with a target-specific
33735 interpretation, formatted as big-endian hex strings. A @var{thread-id}
33736 can also be a literal @samp{-1} to indicate all threads, or @samp{0} to
33739 In addition, the remote protocol supports a multiprocess feature in
33740 which the @var{thread-id} syntax is extended to optionally include both
33741 process and thread ID fields, as @samp{p@var{pid}.@var{tid}}.
33742 The @var{pid} (process) and @var{tid} (thread) components each have the
33743 format described above: a positive number with target-specific
33744 interpretation formatted as a big-endian hex string, literal @samp{-1}
33745 to indicate all processes or threads (respectively), or @samp{0} to
33746 indicate an arbitrary process or thread. Specifying just a process, as
33747 @samp{p@var{pid}}, is equivalent to @samp{p@var{pid}.-1}. It is an
33748 error to specify all processes but a specific thread, such as
33749 @samp{p-1.@var{tid}}. Note that the @samp{p} prefix is @emph{not} used
33750 for those packets and replies explicitly documented to include a process
33751 ID, rather than a @var{thread-id}.
33753 The multiprocess @var{thread-id} syntax extensions are only used if both
33754 @value{GDBN} and the stub report support for the @samp{multiprocess}
33755 feature using @samp{qSupported}. @xref{multiprocess extensions}, for
33758 Note that all packet forms beginning with an upper- or lower-case
33759 letter, other than those described here, are reserved for future use.
33761 Here are the packet descriptions.
33766 @cindex @samp{!} packet
33767 @anchor{extended mode}
33768 Enable extended mode. In extended mode, the remote server is made
33769 persistent. The @samp{R} packet is used to restart the program being
33775 The remote target both supports and has enabled extended mode.
33779 @cindex @samp{?} packet
33780 Indicate the reason the target halted. The reply is the same as for
33781 step and continue. This packet has a special interpretation when the
33782 target is in non-stop mode; see @ref{Remote Non-Stop}.
33785 @xref{Stop Reply Packets}, for the reply specifications.
33787 @item A @var{arglen},@var{argnum},@var{arg},@dots{}
33788 @cindex @samp{A} packet
33789 Initialized @code{argv[]} array passed into program. @var{arglen}
33790 specifies the number of bytes in the hex encoded byte stream
33791 @var{arg}. See @code{gdbserver} for more details.
33796 The arguments were set.
33802 @cindex @samp{b} packet
33803 (Don't use this packet; its behavior is not well-defined.)
33804 Change the serial line speed to @var{baud}.
33806 JTC: @emph{When does the transport layer state change? When it's
33807 received, or after the ACK is transmitted. In either case, there are
33808 problems if the command or the acknowledgment packet is dropped.}
33810 Stan: @emph{If people really wanted to add something like this, and get
33811 it working for the first time, they ought to modify ser-unix.c to send
33812 some kind of out-of-band message to a specially-setup stub and have the
33813 switch happen "in between" packets, so that from remote protocol's point
33814 of view, nothing actually happened.}
33816 @item B @var{addr},@var{mode}
33817 @cindex @samp{B} packet
33818 Set (@var{mode} is @samp{S}) or clear (@var{mode} is @samp{C}) a
33819 breakpoint at @var{addr}.
33821 Don't use this packet. Use the @samp{Z} and @samp{z} packets instead
33822 (@pxref{insert breakpoint or watchpoint packet}).
33824 @cindex @samp{bc} packet
33827 Backward continue. Execute the target system in reverse. No parameter.
33828 @xref{Reverse Execution}, for more information.
33831 @xref{Stop Reply Packets}, for the reply specifications.
33833 @cindex @samp{bs} packet
33836 Backward single step. Execute one instruction in reverse. No parameter.
33837 @xref{Reverse Execution}, for more information.
33840 @xref{Stop Reply Packets}, for the reply specifications.
33842 @item c @r{[}@var{addr}@r{]}
33843 @cindex @samp{c} packet
33844 Continue. @var{addr} is address to resume. If @var{addr} is omitted,
33845 resume at current address.
33847 This packet is deprecated for multi-threading support. @xref{vCont
33851 @xref{Stop Reply Packets}, for the reply specifications.
33853 @item C @var{sig}@r{[};@var{addr}@r{]}
33854 @cindex @samp{C} packet
33855 Continue with signal @var{sig} (hex signal number). If
33856 @samp{;@var{addr}} is omitted, resume at same address.
33858 This packet is deprecated for multi-threading support. @xref{vCont
33862 @xref{Stop Reply Packets}, for the reply specifications.
33865 @cindex @samp{d} packet
33868 Don't use this packet; instead, define a general set packet
33869 (@pxref{General Query Packets}).
33873 @cindex @samp{D} packet
33874 The first form of the packet is used to detach @value{GDBN} from the
33875 remote system. It is sent to the remote target
33876 before @value{GDBN} disconnects via the @code{detach} command.
33878 The second form, including a process ID, is used when multiprocess
33879 protocol extensions are enabled (@pxref{multiprocess extensions}), to
33880 detach only a specific process. The @var{pid} is specified as a
33881 big-endian hex string.
33891 @item F @var{RC},@var{EE},@var{CF};@var{XX}
33892 @cindex @samp{F} packet
33893 A reply from @value{GDBN} to an @samp{F} packet sent by the target.
33894 This is part of the File-I/O protocol extension. @xref{File-I/O
33895 Remote Protocol Extension}, for the specification.
33898 @anchor{read registers packet}
33899 @cindex @samp{g} packet
33900 Read general registers.
33904 @item @var{XX@dots{}}
33905 Each byte of register data is described by two hex digits. The bytes
33906 with the register are transmitted in target byte order. The size of
33907 each register and their position within the @samp{g} packet are
33908 determined by the @value{GDBN} internal gdbarch functions
33909 @code{DEPRECATED_REGISTER_RAW_SIZE} and @code{gdbarch_register_name}. The
33910 specification of several standard @samp{g} packets is specified below.
33912 When reading registers from a trace frame (@pxref{Analyze Collected
33913 Data,,Using the Collected Data}), the stub may also return a string of
33914 literal @samp{x}'s in place of the register data digits, to indicate
33915 that the corresponding register has not been collected, thus its value
33916 is unavailable. For example, for an architecture with 4 registers of
33917 4 bytes each, the following reply indicates to @value{GDBN} that
33918 registers 0 and 2 have not been collected, while registers 1 and 3
33919 have been collected, and both have zero value:
33923 <- @code{xxxxxxxx00000000xxxxxxxx00000000}
33930 @item G @var{XX@dots{}}
33931 @cindex @samp{G} packet
33932 Write general registers. @xref{read registers packet}, for a
33933 description of the @var{XX@dots{}} data.
33943 @item H @var{op} @var{thread-id}
33944 @cindex @samp{H} packet
33945 Set thread for subsequent operations (@samp{m}, @samp{M}, @samp{g},
33946 @samp{G}, et.al.). @var{op} depends on the operation to be performed:
33947 it should be @samp{c} for step and continue operations (note that this
33948 is deprecated, supporting the @samp{vCont} command is a better
33949 option), @samp{g} for other operations. The thread designator
33950 @var{thread-id} has the format and interpretation described in
33951 @ref{thread-id syntax}.
33962 @c 'H': How restrictive (or permissive) is the thread model. If a
33963 @c thread is selected and stopped, are other threads allowed
33964 @c to continue to execute? As I mentioned above, I think the
33965 @c semantics of each command when a thread is selected must be
33966 @c described. For example:
33968 @c 'g': If the stub supports threads and a specific thread is
33969 @c selected, returns the register block from that thread;
33970 @c otherwise returns current registers.
33972 @c 'G' If the stub supports threads and a specific thread is
33973 @c selected, sets the registers of the register block of
33974 @c that thread; otherwise sets current registers.
33976 @item i @r{[}@var{addr}@r{[},@var{nnn}@r{]]}
33977 @anchor{cycle step packet}
33978 @cindex @samp{i} packet
33979 Step the remote target by a single clock cycle. If @samp{,@var{nnn}} is
33980 present, cycle step @var{nnn} cycles. If @var{addr} is present, cycle
33981 step starting at that address.
33984 @cindex @samp{I} packet
33985 Signal, then cycle step. @xref{step with signal packet}. @xref{cycle
33989 @cindex @samp{k} packet
33992 FIXME: @emph{There is no description of how to operate when a specific
33993 thread context has been selected (i.e.@: does 'k' kill only that
33996 @item m @var{addr},@var{length}
33997 @cindex @samp{m} packet
33998 Read @var{length} bytes of memory starting at address @var{addr}.
33999 Note that @var{addr} may not be aligned to any particular boundary.
34001 The stub need not use any particular size or alignment when gathering
34002 data from memory for the response; even if @var{addr} is word-aligned
34003 and @var{length} is a multiple of the word size, the stub is free to
34004 use byte accesses, or not. For this reason, this packet may not be
34005 suitable for accessing memory-mapped I/O devices.
34006 @cindex alignment of remote memory accesses
34007 @cindex size of remote memory accesses
34008 @cindex memory, alignment and size of remote accesses
34012 @item @var{XX@dots{}}
34013 Memory contents; each byte is transmitted as a two-digit hexadecimal
34014 number. The reply may contain fewer bytes than requested if the
34015 server was able to read only part of the region of memory.
34020 @item M @var{addr},@var{length}:@var{XX@dots{}}
34021 @cindex @samp{M} packet
34022 Write @var{length} bytes of memory starting at address @var{addr}.
34023 @var{XX@dots{}} is the data; each byte is transmitted as a two-digit
34024 hexadecimal number.
34031 for an error (this includes the case where only part of the data was
34036 @cindex @samp{p} packet
34037 Read the value of register @var{n}; @var{n} is in hex.
34038 @xref{read registers packet}, for a description of how the returned
34039 register value is encoded.
34043 @item @var{XX@dots{}}
34044 the register's value
34048 Indicating an unrecognized @var{query}.
34051 @item P @var{n@dots{}}=@var{r@dots{}}
34052 @anchor{write register packet}
34053 @cindex @samp{P} packet
34054 Write register @var{n@dots{}} with value @var{r@dots{}}. The register
34055 number @var{n} is in hexadecimal, and @var{r@dots{}} contains two hex
34056 digits for each byte in the register (target byte order).
34066 @item q @var{name} @var{params}@dots{}
34067 @itemx Q @var{name} @var{params}@dots{}
34068 @cindex @samp{q} packet
34069 @cindex @samp{Q} packet
34070 General query (@samp{q}) and set (@samp{Q}). These packets are
34071 described fully in @ref{General Query Packets}.
34074 @cindex @samp{r} packet
34075 Reset the entire system.
34077 Don't use this packet; use the @samp{R} packet instead.
34080 @cindex @samp{R} packet
34081 Restart the program being debugged. @var{XX}, while needed, is ignored.
34082 This packet is only available in extended mode (@pxref{extended mode}).
34084 The @samp{R} packet has no reply.
34086 @item s @r{[}@var{addr}@r{]}
34087 @cindex @samp{s} packet
34088 Single step. @var{addr} is the address at which to resume. If
34089 @var{addr} is omitted, resume at same address.
34091 This packet is deprecated for multi-threading support. @xref{vCont
34095 @xref{Stop Reply Packets}, for the reply specifications.
34097 @item S @var{sig}@r{[};@var{addr}@r{]}
34098 @anchor{step with signal packet}
34099 @cindex @samp{S} packet
34100 Step with signal. This is analogous to the @samp{C} packet, but
34101 requests a single-step, rather than a normal resumption of execution.
34103 This packet is deprecated for multi-threading support. @xref{vCont
34107 @xref{Stop Reply Packets}, for the reply specifications.
34109 @item t @var{addr}:@var{PP},@var{MM}
34110 @cindex @samp{t} packet
34111 Search backwards starting at address @var{addr} for a match with pattern
34112 @var{PP} and mask @var{MM}. @var{PP} and @var{MM} are 4 bytes.
34113 @var{addr} must be at least 3 digits.
34115 @item T @var{thread-id}
34116 @cindex @samp{T} packet
34117 Find out if the thread @var{thread-id} is alive. @xref{thread-id syntax}.
34122 thread is still alive
34128 Packets starting with @samp{v} are identified by a multi-letter name,
34129 up to the first @samp{;} or @samp{?} (or the end of the packet).
34131 @item vAttach;@var{pid}
34132 @cindex @samp{vAttach} packet
34133 Attach to a new process with the specified process ID @var{pid}.
34134 The process ID is a
34135 hexadecimal integer identifying the process. In all-stop mode, all
34136 threads in the attached process are stopped; in non-stop mode, it may be
34137 attached without being stopped if that is supported by the target.
34139 @c In non-stop mode, on a successful vAttach, the stub should set the
34140 @c current thread to a thread of the newly-attached process. After
34141 @c attaching, GDB queries for the attached process's thread ID with qC.
34142 @c Also note that, from a user perspective, whether or not the
34143 @c target is stopped on attach in non-stop mode depends on whether you
34144 @c use the foreground or background version of the attach command, not
34145 @c on what vAttach does; GDB does the right thing with respect to either
34146 @c stopping or restarting threads.
34148 This packet is only available in extended mode (@pxref{extended mode}).
34154 @item @r{Any stop packet}
34155 for success in all-stop mode (@pxref{Stop Reply Packets})
34157 for success in non-stop mode (@pxref{Remote Non-Stop})
34160 @item vCont@r{[};@var{action}@r{[}:@var{thread-id}@r{]]}@dots{}
34161 @cindex @samp{vCont} packet
34162 @anchor{vCont packet}
34163 Resume the inferior, specifying different actions for each thread.
34164 If an action is specified with no @var{thread-id}, then it is applied to any
34165 threads that don't have a specific action specified; if no default action is
34166 specified then other threads should remain stopped in all-stop mode and
34167 in their current state in non-stop mode.
34168 Specifying multiple
34169 default actions is an error; specifying no actions is also an error.
34170 Thread IDs are specified using the syntax described in @ref{thread-id syntax}.
34172 Currently supported actions are:
34178 Continue with signal @var{sig}. The signal @var{sig} should be two hex digits.
34182 Step with signal @var{sig}. The signal @var{sig} should be two hex digits.
34187 The optional argument @var{addr} normally associated with the
34188 @samp{c}, @samp{C}, @samp{s}, and @samp{S} packets is
34189 not supported in @samp{vCont}.
34191 The @samp{t} action is only relevant in non-stop mode
34192 (@pxref{Remote Non-Stop}) and may be ignored by the stub otherwise.
34193 A stop reply should be generated for any affected thread not already stopped.
34194 When a thread is stopped by means of a @samp{t} action,
34195 the corresponding stop reply should indicate that the thread has stopped with
34196 signal @samp{0}, regardless of whether the target uses some other signal
34197 as an implementation detail.
34199 The stub must support @samp{vCont} if it reports support for
34200 multiprocess extensions (@pxref{multiprocess extensions}). Note that in
34201 this case @samp{vCont} actions can be specified to apply to all threads
34202 in a process by using the @samp{p@var{pid}.-1} form of the
34206 @xref{Stop Reply Packets}, for the reply specifications.
34209 @cindex @samp{vCont?} packet
34210 Request a list of actions supported by the @samp{vCont} packet.
34214 @item vCont@r{[};@var{action}@dots{}@r{]}
34215 The @samp{vCont} packet is supported. Each @var{action} is a supported
34216 command in the @samp{vCont} packet.
34218 The @samp{vCont} packet is not supported.
34221 @item vFile:@var{operation}:@var{parameter}@dots{}
34222 @cindex @samp{vFile} packet
34223 Perform a file operation on the target system. For details,
34224 see @ref{Host I/O Packets}.
34226 @item vFlashErase:@var{addr},@var{length}
34227 @cindex @samp{vFlashErase} packet
34228 Direct the stub to erase @var{length} bytes of flash starting at
34229 @var{addr}. The region may enclose any number of flash blocks, but
34230 its start and end must fall on block boundaries, as indicated by the
34231 flash block size appearing in the memory map (@pxref{Memory Map
34232 Format}). @value{GDBN} groups flash memory programming operations
34233 together, and sends a @samp{vFlashDone} request after each group; the
34234 stub is allowed to delay erase operation until the @samp{vFlashDone}
34235 packet is received.
34245 @item vFlashWrite:@var{addr}:@var{XX@dots{}}
34246 @cindex @samp{vFlashWrite} packet
34247 Direct the stub to write data to flash address @var{addr}. The data
34248 is passed in binary form using the same encoding as for the @samp{X}
34249 packet (@pxref{Binary Data}). The memory ranges specified by
34250 @samp{vFlashWrite} packets preceding a @samp{vFlashDone} packet must
34251 not overlap, and must appear in order of increasing addresses
34252 (although @samp{vFlashErase} packets for higher addresses may already
34253 have been received; the ordering is guaranteed only between
34254 @samp{vFlashWrite} packets). If a packet writes to an address that was
34255 neither erased by a preceding @samp{vFlashErase} packet nor by some other
34256 target-specific method, the results are unpredictable.
34264 for vFlashWrite addressing non-flash memory
34270 @cindex @samp{vFlashDone} packet
34271 Indicate to the stub that flash programming operation is finished.
34272 The stub is permitted to delay or batch the effects of a group of
34273 @samp{vFlashErase} and @samp{vFlashWrite} packets until a
34274 @samp{vFlashDone} packet is received. The contents of the affected
34275 regions of flash memory are unpredictable until the @samp{vFlashDone}
34276 request is completed.
34278 @item vKill;@var{pid}
34279 @cindex @samp{vKill} packet
34280 Kill the process with the specified process ID. @var{pid} is a
34281 hexadecimal integer identifying the process. This packet is used in
34282 preference to @samp{k} when multiprocess protocol extensions are
34283 supported; see @ref{multiprocess extensions}.
34293 @item vRun;@var{filename}@r{[};@var{argument}@r{]}@dots{}
34294 @cindex @samp{vRun} packet
34295 Run the program @var{filename}, passing it each @var{argument} on its
34296 command line. The file and arguments are hex-encoded strings. If
34297 @var{filename} is an empty string, the stub may use a default program
34298 (e.g.@: the last program run). The program is created in the stopped
34301 @c FIXME: What about non-stop mode?
34303 This packet is only available in extended mode (@pxref{extended mode}).
34309 @item @r{Any stop packet}
34310 for success (@pxref{Stop Reply Packets})
34314 @anchor{vStopped packet}
34315 @cindex @samp{vStopped} packet
34317 In non-stop mode (@pxref{Remote Non-Stop}), acknowledge a previous stop
34318 reply and prompt for the stub to report another one.
34322 @item @r{Any stop packet}
34323 if there is another unreported stop event (@pxref{Stop Reply Packets})
34325 if there are no unreported stop events
34328 @item X @var{addr},@var{length}:@var{XX@dots{}}
34330 @cindex @samp{X} packet
34331 Write data to memory, where the data is transmitted in binary.
34332 @var{addr} is address, @var{length} is number of bytes,
34333 @samp{@var{XX}@dots{}} is binary data (@pxref{Binary Data}).
34343 @item z @var{type},@var{addr},@var{kind}
34344 @itemx Z @var{type},@var{addr},@var{kind}
34345 @anchor{insert breakpoint or watchpoint packet}
34346 @cindex @samp{z} packet
34347 @cindex @samp{Z} packets
34348 Insert (@samp{Z}) or remove (@samp{z}) a @var{type} breakpoint or
34349 watchpoint starting at address @var{address} of kind @var{kind}.
34351 Each breakpoint and watchpoint packet @var{type} is documented
34354 @emph{Implementation notes: A remote target shall return an empty string
34355 for an unrecognized breakpoint or watchpoint packet @var{type}. A
34356 remote target shall support either both or neither of a given
34357 @samp{Z@var{type}@dots{}} and @samp{z@var{type}@dots{}} packet pair. To
34358 avoid potential problems with duplicate packets, the operations should
34359 be implemented in an idempotent way.}
34361 @item z0,@var{addr},@var{kind}
34362 @itemx Z0,@var{addr},@var{kind}@r{[};@var{cond_list}@dots{}@r{]}
34363 @cindex @samp{z0} packet
34364 @cindex @samp{Z0} packet
34365 Insert (@samp{Z0}) or remove (@samp{z0}) a memory breakpoint at address
34366 @var{addr} of type @var{kind}.
34368 A memory breakpoint is implemented by replacing the instruction at
34369 @var{addr} with a software breakpoint or trap instruction. The
34370 @var{kind} is target-specific and typically indicates the size of
34371 the breakpoint in bytes that should be inserted. E.g., the @sc{arm}
34372 and @sc{mips} can insert either a 2 or 4 byte breakpoint. Some
34373 architectures have additional meanings for @var{kind};
34374 @var{cond_list} is an optional list of conditional expressions in bytecode
34375 form that should be evaluated on the target's side. These are the
34376 conditions that should be taken into consideration when deciding if
34377 the breakpoint trigger should be reported back to @var{GDBN}.
34379 The @var{cond_list} parameter is comprised of a series of expressions,
34380 concatenated without separators. Each expression has the following form:
34384 @item X @var{len},@var{expr}
34385 @var{len} is the length of the bytecode expression and @var{expr} is the
34386 actual conditional expression in bytecode form.
34390 see @ref{Architecture-Specific Protocol Details}.
34392 @emph{Implementation note: It is possible for a target to copy or move
34393 code that contains memory breakpoints (e.g., when implementing
34394 overlays). The behavior of this packet, in the presence of such a
34395 target, is not defined.}
34407 @item z1,@var{addr},@var{kind}
34408 @itemx Z1,@var{addr},@var{kind}@r{[};@var{cond_list}@dots{}@r{]}
34409 @cindex @samp{z1} packet
34410 @cindex @samp{Z1} packet
34411 Insert (@samp{Z1}) or remove (@samp{z1}) a hardware breakpoint at
34412 address @var{addr}.
34414 A hardware breakpoint is implemented using a mechanism that is not
34415 dependant on being able to modify the target's memory. @var{kind}
34416 and @var{cond_list} have the same meaning as in @samp{Z0} packets.
34418 @emph{Implementation note: A hardware breakpoint is not affected by code
34431 @item z2,@var{addr},@var{kind}
34432 @itemx Z2,@var{addr},@var{kind}
34433 @cindex @samp{z2} packet
34434 @cindex @samp{Z2} packet
34435 Insert (@samp{Z2}) or remove (@samp{z2}) a write watchpoint at @var{addr}.
34436 @var{kind} is interpreted as the number of bytes to watch.
34448 @item z3,@var{addr},@var{kind}
34449 @itemx Z3,@var{addr},@var{kind}
34450 @cindex @samp{z3} packet
34451 @cindex @samp{Z3} packet
34452 Insert (@samp{Z3}) or remove (@samp{z3}) a read watchpoint at @var{addr}.
34453 @var{kind} is interpreted as the number of bytes to watch.
34465 @item z4,@var{addr},@var{kind}
34466 @itemx Z4,@var{addr},@var{kind}
34467 @cindex @samp{z4} packet
34468 @cindex @samp{Z4} packet
34469 Insert (@samp{Z4}) or remove (@samp{z4}) an access watchpoint at @var{addr}.
34470 @var{kind} is interpreted as the number of bytes to watch.
34484 @node Stop Reply Packets
34485 @section Stop Reply Packets
34486 @cindex stop reply packets
34488 The @samp{C}, @samp{c}, @samp{S}, @samp{s}, @samp{vCont},
34489 @samp{vAttach}, @samp{vRun}, @samp{vStopped}, and @samp{?} packets can
34490 receive any of the below as a reply. Except for @samp{?}
34491 and @samp{vStopped}, that reply is only returned
34492 when the target halts. In the below the exact meaning of @dfn{signal
34493 number} is defined by the header @file{include/gdb/signals.h} in the
34494 @value{GDBN} source code.
34496 As in the description of request packets, we include spaces in the
34497 reply templates for clarity; these are not part of the reply packet's
34498 syntax. No @value{GDBN} stop reply packet uses spaces to separate its
34504 The program received signal number @var{AA} (a two-digit hexadecimal
34505 number). This is equivalent to a @samp{T} response with no
34506 @var{n}:@var{r} pairs.
34508 @item T @var{AA} @var{n1}:@var{r1};@var{n2}:@var{r2};@dots{}
34509 @cindex @samp{T} packet reply
34510 The program received signal number @var{AA} (a two-digit hexadecimal
34511 number). This is equivalent to an @samp{S} response, except that the
34512 @samp{@var{n}:@var{r}} pairs can carry values of important registers
34513 and other information directly in the stop reply packet, reducing
34514 round-trip latency. Single-step and breakpoint traps are reported
34515 this way. Each @samp{@var{n}:@var{r}} pair is interpreted as follows:
34519 If @var{n} is a hexadecimal number, it is a register number, and the
34520 corresponding @var{r} gives that register's value. @var{r} is a
34521 series of bytes in target byte order, with each byte given by a
34522 two-digit hex number.
34525 If @var{n} is @samp{thread}, then @var{r} is the @var{thread-id} of
34526 the stopped thread, as specified in @ref{thread-id syntax}.
34529 If @var{n} is @samp{core}, then @var{r} is the hexadecimal number of
34530 the core on which the stop event was detected.
34533 If @var{n} is a recognized @dfn{stop reason}, it describes a more
34534 specific event that stopped the target. The currently defined stop
34535 reasons are listed below. @var{aa} should be @samp{05}, the trap
34536 signal. At most one stop reason should be present.
34539 Otherwise, @value{GDBN} should ignore this @samp{@var{n}:@var{r}} pair
34540 and go on to the next; this allows us to extend the protocol in the
34544 The currently defined stop reasons are:
34550 The packet indicates a watchpoint hit, and @var{r} is the data address, in
34553 @cindex shared library events, remote reply
34555 The packet indicates that the loaded libraries have changed.
34556 @value{GDBN} should use @samp{qXfer:libraries:read} to fetch a new
34557 list of loaded libraries. @var{r} is ignored.
34559 @cindex replay log events, remote reply
34561 The packet indicates that the target cannot continue replaying
34562 logged execution events, because it has reached the end (or the
34563 beginning when executing backward) of the log. The value of @var{r}
34564 will be either @samp{begin} or @samp{end}. @xref{Reverse Execution},
34565 for more information.
34569 @itemx W @var{AA} ; process:@var{pid}
34570 The process exited, and @var{AA} is the exit status. This is only
34571 applicable to certain targets.
34573 The second form of the response, including the process ID of the exited
34574 process, can be used only when @value{GDBN} has reported support for
34575 multiprocess protocol extensions; see @ref{multiprocess extensions}.
34576 The @var{pid} is formatted as a big-endian hex string.
34579 @itemx X @var{AA} ; process:@var{pid}
34580 The process terminated with signal @var{AA}.
34582 The second form of the response, including the process ID of the
34583 terminated process, can be used only when @value{GDBN} has reported
34584 support for multiprocess protocol extensions; see @ref{multiprocess
34585 extensions}. The @var{pid} is formatted as a big-endian hex string.
34587 @item O @var{XX}@dots{}
34588 @samp{@var{XX}@dots{}} is hex encoding of @sc{ascii} data, to be
34589 written as the program's console output. This can happen at any time
34590 while the program is running and the debugger should continue to wait
34591 for @samp{W}, @samp{T}, etc. This reply is not permitted in non-stop mode.
34593 @item F @var{call-id},@var{parameter}@dots{}
34594 @var{call-id} is the identifier which says which host system call should
34595 be called. This is just the name of the function. Translation into the
34596 correct system call is only applicable as it's defined in @value{GDBN}.
34597 @xref{File-I/O Remote Protocol Extension}, for a list of implemented
34600 @samp{@var{parameter}@dots{}} is a list of parameters as defined for
34601 this very system call.
34603 The target replies with this packet when it expects @value{GDBN} to
34604 call a host system call on behalf of the target. @value{GDBN} replies
34605 with an appropriate @samp{F} packet and keeps up waiting for the next
34606 reply packet from the target. The latest @samp{C}, @samp{c}, @samp{S}
34607 or @samp{s} action is expected to be continued. @xref{File-I/O Remote
34608 Protocol Extension}, for more details.
34612 @node General Query Packets
34613 @section General Query Packets
34614 @cindex remote query requests
34616 Packets starting with @samp{q} are @dfn{general query packets};
34617 packets starting with @samp{Q} are @dfn{general set packets}. General
34618 query and set packets are a semi-unified form for retrieving and
34619 sending information to and from the stub.
34621 The initial letter of a query or set packet is followed by a name
34622 indicating what sort of thing the packet applies to. For example,
34623 @value{GDBN} may use a @samp{qSymbol} packet to exchange symbol
34624 definitions with the stub. These packet names follow some
34629 The name must not contain commas, colons or semicolons.
34631 Most @value{GDBN} query and set packets have a leading upper case
34634 The names of custom vendor packets should use a company prefix, in
34635 lower case, followed by a period. For example, packets designed at
34636 the Acme Corporation might begin with @samp{qacme.foo} (for querying
34637 foos) or @samp{Qacme.bar} (for setting bars).
34640 The name of a query or set packet should be separated from any
34641 parameters by a @samp{:}; the parameters themselves should be
34642 separated by @samp{,} or @samp{;}. Stubs must be careful to match the
34643 full packet name, and check for a separator or the end of the packet,
34644 in case two packet names share a common prefix. New packets should not begin
34645 with @samp{qC}, @samp{qP}, or @samp{qL}@footnote{The @samp{qP} and @samp{qL}
34646 packets predate these conventions, and have arguments without any terminator
34647 for the packet name; we suspect they are in widespread use in places that
34648 are difficult to upgrade. The @samp{qC} packet has no arguments, but some
34649 existing stubs (e.g.@: RedBoot) are known to not check for the end of the
34652 Like the descriptions of the other packets, each description here
34653 has a template showing the packet's overall syntax, followed by an
34654 explanation of the packet's meaning. We include spaces in some of the
34655 templates for clarity; these are not part of the packet's syntax. No
34656 @value{GDBN} packet uses spaces to separate its components.
34658 Here are the currently defined query and set packets:
34664 Turn on or off the agent as a helper to perform some debugging operations
34665 delegated from @value{GDBN} (@pxref{Control Agent}).
34667 @item QAllow:@var{op}:@var{val}@dots{}
34668 @cindex @samp{QAllow} packet
34669 Specify which operations @value{GDBN} expects to request of the
34670 target, as a semicolon-separated list of operation name and value
34671 pairs. Possible values for @var{op} include @samp{WriteReg},
34672 @samp{WriteMem}, @samp{InsertBreak}, @samp{InsertTrace},
34673 @samp{InsertFastTrace}, and @samp{Stop}. @var{val} is either 0,
34674 indicating that @value{GDBN} will not request the operation, or 1,
34675 indicating that it may. (The target can then use this to set up its
34676 own internals optimally, for instance if the debugger never expects to
34677 insert breakpoints, it may not need to install its own trap handler.)
34680 @cindex current thread, remote request
34681 @cindex @samp{qC} packet
34682 Return the current thread ID.
34686 @item QC @var{thread-id}
34687 Where @var{thread-id} is a thread ID as documented in
34688 @ref{thread-id syntax}.
34689 @item @r{(anything else)}
34690 Any other reply implies the old thread ID.
34693 @item qCRC:@var{addr},@var{length}
34694 @cindex CRC of memory block, remote request
34695 @cindex @samp{qCRC} packet
34696 Compute the CRC checksum of a block of memory using CRC-32 defined in
34697 IEEE 802.3. The CRC is computed byte at a time, taking the most
34698 significant bit of each byte first. The initial pattern code
34699 @code{0xffffffff} is used to ensure leading zeros affect the CRC.
34701 @emph{Note:} This is the same CRC used in validating separate debug
34702 files (@pxref{Separate Debug Files, , Debugging Information in Separate
34703 Files}). However the algorithm is slightly different. When validating
34704 separate debug files, the CRC is computed taking the @emph{least}
34705 significant bit of each byte first, and the final result is inverted to
34706 detect trailing zeros.
34711 An error (such as memory fault)
34712 @item C @var{crc32}
34713 The specified memory region's checksum is @var{crc32}.
34716 @item QDisableRandomization:@var{value}
34717 @cindex disable address space randomization, remote request
34718 @cindex @samp{QDisableRandomization} packet
34719 Some target operating systems will randomize the virtual address space
34720 of the inferior process as a security feature, but provide a feature
34721 to disable such randomization, e.g.@: to allow for a more deterministic
34722 debugging experience. On such systems, this packet with a @var{value}
34723 of 1 directs the target to disable address space randomization for
34724 processes subsequently started via @samp{vRun} packets, while a packet
34725 with a @var{value} of 0 tells the target to enable address space
34728 This packet is only available in extended mode (@pxref{extended mode}).
34733 The request succeeded.
34736 An error occurred. @var{nn} are hex digits.
34739 An empty reply indicates that @samp{QDisableRandomization} is not supported
34743 This packet is not probed by default; the remote stub must request it,
34744 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
34745 This should only be done on targets that actually support disabling
34746 address space randomization.
34749 @itemx qsThreadInfo
34750 @cindex list active threads, remote request
34751 @cindex @samp{qfThreadInfo} packet
34752 @cindex @samp{qsThreadInfo} packet
34753 Obtain a list of all active thread IDs from the target (OS). Since there
34754 may be too many active threads to fit into one reply packet, this query
34755 works iteratively: it may require more than one query/reply sequence to
34756 obtain the entire list of threads. The first query of the sequence will
34757 be the @samp{qfThreadInfo} query; subsequent queries in the
34758 sequence will be the @samp{qsThreadInfo} query.
34760 NOTE: This packet replaces the @samp{qL} query (see below).
34764 @item m @var{thread-id}
34766 @item m @var{thread-id},@var{thread-id}@dots{}
34767 a comma-separated list of thread IDs
34769 (lower case letter @samp{L}) denotes end of list.
34772 In response to each query, the target will reply with a list of one or
34773 more thread IDs, separated by commas.
34774 @value{GDBN} will respond to each reply with a request for more thread
34775 ids (using the @samp{qs} form of the query), until the target responds
34776 with @samp{l} (lower-case ell, for @dfn{last}).
34777 Refer to @ref{thread-id syntax}, for the format of the @var{thread-id}
34780 @item qGetTLSAddr:@var{thread-id},@var{offset},@var{lm}
34781 @cindex get thread-local storage address, remote request
34782 @cindex @samp{qGetTLSAddr} packet
34783 Fetch the address associated with thread local storage specified
34784 by @var{thread-id}, @var{offset}, and @var{lm}.
34786 @var{thread-id} is the thread ID associated with the
34787 thread for which to fetch the TLS address. @xref{thread-id syntax}.
34789 @var{offset} is the (big endian, hex encoded) offset associated with the
34790 thread local variable. (This offset is obtained from the debug
34791 information associated with the variable.)
34793 @var{lm} is the (big endian, hex encoded) OS/ABI-specific encoding of the
34794 load module associated with the thread local storage. For example,
34795 a @sc{gnu}/Linux system will pass the link map address of the shared
34796 object associated with the thread local storage under consideration.
34797 Other operating environments may choose to represent the load module
34798 differently, so the precise meaning of this parameter will vary.
34802 @item @var{XX}@dots{}
34803 Hex encoded (big endian) bytes representing the address of the thread
34804 local storage requested.
34807 An error occurred. @var{nn} are hex digits.
34810 An empty reply indicates that @samp{qGetTLSAddr} is not supported by the stub.
34813 @item qGetTIBAddr:@var{thread-id}
34814 @cindex get thread information block address
34815 @cindex @samp{qGetTIBAddr} packet
34816 Fetch address of the Windows OS specific Thread Information Block.
34818 @var{thread-id} is the thread ID associated with the thread.
34822 @item @var{XX}@dots{}
34823 Hex encoded (big endian) bytes representing the linear address of the
34824 thread information block.
34827 An error occured. This means that either the thread was not found, or the
34828 address could not be retrieved.
34831 An empty reply indicates that @samp{qGetTIBAddr} is not supported by the stub.
34834 @item qL @var{startflag} @var{threadcount} @var{nextthread}
34835 Obtain thread information from RTOS. Where: @var{startflag} (one hex
34836 digit) is one to indicate the first query and zero to indicate a
34837 subsequent query; @var{threadcount} (two hex digits) is the maximum
34838 number of threads the response packet can contain; and @var{nextthread}
34839 (eight hex digits), for subsequent queries (@var{startflag} is zero), is
34840 returned in the response as @var{argthread}.
34842 Don't use this packet; use the @samp{qfThreadInfo} query instead (see above).
34846 @item qM @var{count} @var{done} @var{argthread} @var{thread}@dots{}
34847 Where: @var{count} (two hex digits) is the number of threads being
34848 returned; @var{done} (one hex digit) is zero to indicate more threads
34849 and one indicates no further threads; @var{argthreadid} (eight hex
34850 digits) is @var{nextthread} from the request packet; @var{thread}@dots{}
34851 is a sequence of thread IDs from the target. @var{threadid} (eight hex
34852 digits). See @code{remote.c:parse_threadlist_response()}.
34856 @cindex section offsets, remote request
34857 @cindex @samp{qOffsets} packet
34858 Get section offsets that the target used when relocating the downloaded
34863 @item Text=@var{xxx};Data=@var{yyy}@r{[};Bss=@var{zzz}@r{]}
34864 Relocate the @code{Text} section by @var{xxx} from its original address.
34865 Relocate the @code{Data} section by @var{yyy} from its original address.
34866 If the object file format provides segment information (e.g.@: @sc{elf}
34867 @samp{PT_LOAD} program headers), @value{GDBN} will relocate entire
34868 segments by the supplied offsets.
34870 @emph{Note: while a @code{Bss} offset may be included in the response,
34871 @value{GDBN} ignores this and instead applies the @code{Data} offset
34872 to the @code{Bss} section.}
34874 @item TextSeg=@var{xxx}@r{[};DataSeg=@var{yyy}@r{]}
34875 Relocate the first segment of the object file, which conventionally
34876 contains program code, to a starting address of @var{xxx}. If
34877 @samp{DataSeg} is specified, relocate the second segment, which
34878 conventionally contains modifiable data, to a starting address of
34879 @var{yyy}. @value{GDBN} will report an error if the object file
34880 does not contain segment information, or does not contain at least
34881 as many segments as mentioned in the reply. Extra segments are
34882 kept at fixed offsets relative to the last relocated segment.
34885 @item qP @var{mode} @var{thread-id}
34886 @cindex thread information, remote request
34887 @cindex @samp{qP} packet
34888 Returns information on @var{thread-id}. Where: @var{mode} is a hex
34889 encoded 32 bit mode; @var{thread-id} is a thread ID
34890 (@pxref{thread-id syntax}).
34892 Don't use this packet; use the @samp{qThreadExtraInfo} query instead
34895 Reply: see @code{remote.c:remote_unpack_thread_info_response()}.
34899 @cindex non-stop mode, remote request
34900 @cindex @samp{QNonStop} packet
34902 Enter non-stop (@samp{QNonStop:1}) or all-stop (@samp{QNonStop:0}) mode.
34903 @xref{Remote Non-Stop}, for more information.
34908 The request succeeded.
34911 An error occurred. @var{nn} are hex digits.
34914 An empty reply indicates that @samp{QNonStop} is not supported by
34918 This packet is not probed by default; the remote stub must request it,
34919 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
34920 Use of this packet is controlled by the @code{set non-stop} command;
34921 @pxref{Non-Stop Mode}.
34923 @item QPassSignals: @var{signal} @r{[};@var{signal}@r{]}@dots{}
34924 @cindex pass signals to inferior, remote request
34925 @cindex @samp{QPassSignals} packet
34926 @anchor{QPassSignals}
34927 Each listed @var{signal} should be passed directly to the inferior process.
34928 Signals are numbered identically to continue packets and stop replies
34929 (@pxref{Stop Reply Packets}). Each @var{signal} list item should be
34930 strictly greater than the previous item. These signals do not need to stop
34931 the inferior, or be reported to @value{GDBN}. All other signals should be
34932 reported to @value{GDBN}. Multiple @samp{QPassSignals} packets do not
34933 combine; any earlier @samp{QPassSignals} list is completely replaced by the
34934 new list. This packet improves performance when using @samp{handle
34935 @var{signal} nostop noprint pass}.
34940 The request succeeded.
34943 An error occurred. @var{nn} are hex digits.
34946 An empty reply indicates that @samp{QPassSignals} is not supported by
34950 Use of this packet is controlled by the @code{set remote pass-signals}
34951 command (@pxref{Remote Configuration, set remote pass-signals}).
34952 This packet is not probed by default; the remote stub must request it,
34953 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
34955 @item QProgramSignals: @var{signal} @r{[};@var{signal}@r{]}@dots{}
34956 @cindex signals the inferior may see, remote request
34957 @cindex @samp{QProgramSignals} packet
34958 @anchor{QProgramSignals}
34959 Each listed @var{signal} may be delivered to the inferior process.
34960 Others should be silently discarded.
34962 In some cases, the remote stub may need to decide whether to deliver a
34963 signal to the program or not without @value{GDBN} involvement. One
34964 example of that is while detaching --- the program's threads may have
34965 stopped for signals that haven't yet had a chance of being reported to
34966 @value{GDBN}, and so the remote stub can use the signal list specified
34967 by this packet to know whether to deliver or ignore those pending
34970 This does not influence whether to deliver a signal as requested by a
34971 resumption packet (@pxref{vCont packet}).
34973 Signals are numbered identically to continue packets and stop replies
34974 (@pxref{Stop Reply Packets}). Each @var{signal} list item should be
34975 strictly greater than the previous item. Multiple
34976 @samp{QProgramSignals} packets do not combine; any earlier
34977 @samp{QProgramSignals} list is completely replaced by the new list.
34982 The request succeeded.
34985 An error occurred. @var{nn} are hex digits.
34988 An empty reply indicates that @samp{QProgramSignals} is not supported
34992 Use of this packet is controlled by the @code{set remote program-signals}
34993 command (@pxref{Remote Configuration, set remote program-signals}).
34994 This packet is not probed by default; the remote stub must request it,
34995 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
34997 @item qRcmd,@var{command}
34998 @cindex execute remote command, remote request
34999 @cindex @samp{qRcmd} packet
35000 @var{command} (hex encoded) is passed to the local interpreter for
35001 execution. Invalid commands should be reported using the output
35002 string. Before the final result packet, the target may also respond
35003 with a number of intermediate @samp{O@var{output}} console output
35004 packets. @emph{Implementors should note that providing access to a
35005 stubs's interpreter may have security implications}.
35010 A command response with no output.
35012 A command response with the hex encoded output string @var{OUTPUT}.
35014 Indicate a badly formed request.
35016 An empty reply indicates that @samp{qRcmd} is not recognized.
35019 (Note that the @code{qRcmd} packet's name is separated from the
35020 command by a @samp{,}, not a @samp{:}, contrary to the naming
35021 conventions above. Please don't use this packet as a model for new
35024 @item qSearch:memory:@var{address};@var{length};@var{search-pattern}
35025 @cindex searching memory, in remote debugging
35026 @cindex @samp{qSearch:memory} packet
35027 @anchor{qSearch memory}
35028 Search @var{length} bytes at @var{address} for @var{search-pattern}.
35029 @var{address} and @var{length} are encoded in hex.
35030 @var{search-pattern} is a sequence of bytes, hex encoded.
35035 The pattern was not found.
35037 The pattern was found at @var{address}.
35039 A badly formed request or an error was encountered while searching memory.
35041 An empty reply indicates that @samp{qSearch:memory} is not recognized.
35044 @item QStartNoAckMode
35045 @cindex @samp{QStartNoAckMode} packet
35046 @anchor{QStartNoAckMode}
35047 Request that the remote stub disable the normal @samp{+}/@samp{-}
35048 protocol acknowledgments (@pxref{Packet Acknowledgment}).
35053 The stub has switched to no-acknowledgment mode.
35054 @value{GDBN} acknowledges this reponse,
35055 but neither the stub nor @value{GDBN} shall send or expect further
35056 @samp{+}/@samp{-} acknowledgments in the current connection.
35058 An empty reply indicates that the stub does not support no-acknowledgment mode.
35061 @item qSupported @r{[}:@var{gdbfeature} @r{[};@var{gdbfeature}@r{]}@dots{} @r{]}
35062 @cindex supported packets, remote query
35063 @cindex features of the remote protocol
35064 @cindex @samp{qSupported} packet
35065 @anchor{qSupported}
35066 Tell the remote stub about features supported by @value{GDBN}, and
35067 query the stub for features it supports. This packet allows
35068 @value{GDBN} and the remote stub to take advantage of each others'
35069 features. @samp{qSupported} also consolidates multiple feature probes
35070 at startup, to improve @value{GDBN} performance---a single larger
35071 packet performs better than multiple smaller probe packets on
35072 high-latency links. Some features may enable behavior which must not
35073 be on by default, e.g.@: because it would confuse older clients or
35074 stubs. Other features may describe packets which could be
35075 automatically probed for, but are not. These features must be
35076 reported before @value{GDBN} will use them. This ``default
35077 unsupported'' behavior is not appropriate for all packets, but it
35078 helps to keep the initial connection time under control with new
35079 versions of @value{GDBN} which support increasing numbers of packets.
35083 @item @var{stubfeature} @r{[};@var{stubfeature}@r{]}@dots{}
35084 The stub supports or does not support each returned @var{stubfeature},
35085 depending on the form of each @var{stubfeature} (see below for the
35088 An empty reply indicates that @samp{qSupported} is not recognized,
35089 or that no features needed to be reported to @value{GDBN}.
35092 The allowed forms for each feature (either a @var{gdbfeature} in the
35093 @samp{qSupported} packet, or a @var{stubfeature} in the response)
35097 @item @var{name}=@var{value}
35098 The remote protocol feature @var{name} is supported, and associated
35099 with the specified @var{value}. The format of @var{value} depends
35100 on the feature, but it must not include a semicolon.
35102 The remote protocol feature @var{name} is supported, and does not
35103 need an associated value.
35105 The remote protocol feature @var{name} is not supported.
35107 The remote protocol feature @var{name} may be supported, and
35108 @value{GDBN} should auto-detect support in some other way when it is
35109 needed. This form will not be used for @var{gdbfeature} notifications,
35110 but may be used for @var{stubfeature} responses.
35113 Whenever the stub receives a @samp{qSupported} request, the
35114 supplied set of @value{GDBN} features should override any previous
35115 request. This allows @value{GDBN} to put the stub in a known
35116 state, even if the stub had previously been communicating with
35117 a different version of @value{GDBN}.
35119 The following values of @var{gdbfeature} (for the packet sent by @value{GDBN})
35124 This feature indicates whether @value{GDBN} supports multiprocess
35125 extensions to the remote protocol. @value{GDBN} does not use such
35126 extensions unless the stub also reports that it supports them by
35127 including @samp{multiprocess+} in its @samp{qSupported} reply.
35128 @xref{multiprocess extensions}, for details.
35131 This feature indicates that @value{GDBN} supports the XML target
35132 description. If the stub sees @samp{xmlRegisters=} with target
35133 specific strings separated by a comma, it will report register
35137 This feature indicates whether @value{GDBN} supports the
35138 @samp{qRelocInsn} packet (@pxref{Tracepoint Packets,,Relocate
35139 instruction reply packet}).
35142 Stubs should ignore any unknown values for
35143 @var{gdbfeature}. Any @value{GDBN} which sends a @samp{qSupported}
35144 packet supports receiving packets of unlimited length (earlier
35145 versions of @value{GDBN} may reject overly long responses). Additional values
35146 for @var{gdbfeature} may be defined in the future to let the stub take
35147 advantage of new features in @value{GDBN}, e.g.@: incompatible
35148 improvements in the remote protocol---the @samp{multiprocess} feature is
35149 an example of such a feature. The stub's reply should be independent
35150 of the @var{gdbfeature} entries sent by @value{GDBN}; first @value{GDBN}
35151 describes all the features it supports, and then the stub replies with
35152 all the features it supports.
35154 Similarly, @value{GDBN} will silently ignore unrecognized stub feature
35155 responses, as long as each response uses one of the standard forms.
35157 Some features are flags. A stub which supports a flag feature
35158 should respond with a @samp{+} form response. Other features
35159 require values, and the stub should respond with an @samp{=}
35162 Each feature has a default value, which @value{GDBN} will use if
35163 @samp{qSupported} is not available or if the feature is not mentioned
35164 in the @samp{qSupported} response. The default values are fixed; a
35165 stub is free to omit any feature responses that match the defaults.
35167 Not all features can be probed, but for those which can, the probing
35168 mechanism is useful: in some cases, a stub's internal
35169 architecture may not allow the protocol layer to know some information
35170 about the underlying target in advance. This is especially common in
35171 stubs which may be configured for multiple targets.
35173 These are the currently defined stub features and their properties:
35175 @multitable @columnfractions 0.35 0.2 0.12 0.2
35176 @c NOTE: The first row should be @headitem, but we do not yet require
35177 @c a new enough version of Texinfo (4.7) to use @headitem.
35179 @tab Value Required
35183 @item @samp{PacketSize}
35188 @item @samp{qXfer:auxv:read}
35193 @item @samp{qXfer:features:read}
35198 @item @samp{qXfer:libraries:read}
35203 @item @samp{qXfer:memory-map:read}
35208 @item @samp{qXfer:sdata:read}
35213 @item @samp{qXfer:spu:read}
35218 @item @samp{qXfer:spu:write}
35223 @item @samp{qXfer:siginfo:read}
35228 @item @samp{qXfer:siginfo:write}
35233 @item @samp{qXfer:threads:read}
35238 @item @samp{qXfer:traceframe-info:read}
35243 @item @samp{qXfer:uib:read}
35248 @item @samp{qXfer:fdpic:read}
35253 @item @samp{QNonStop}
35258 @item @samp{QPassSignals}
35263 @item @samp{QStartNoAckMode}
35268 @item @samp{multiprocess}
35273 @item @samp{ConditionalBreakpoints}
35278 @item @samp{ConditionalTracepoints}
35283 @item @samp{ReverseContinue}
35288 @item @samp{ReverseStep}
35293 @item @samp{TracepointSource}
35298 @item @samp{QAgent}
35303 @item @samp{QAllow}
35308 @item @samp{QDisableRandomization}
35313 @item @samp{EnableDisableTracepoints}
35318 @item @samp{tracenz}
35325 These are the currently defined stub features, in more detail:
35328 @cindex packet size, remote protocol
35329 @item PacketSize=@var{bytes}
35330 The remote stub can accept packets up to at least @var{bytes} in
35331 length. @value{GDBN} will send packets up to this size for bulk
35332 transfers, and will never send larger packets. This is a limit on the
35333 data characters in the packet, including the frame and checksum.
35334 There is no trailing NUL byte in a remote protocol packet; if the stub
35335 stores packets in a NUL-terminated format, it should allow an extra
35336 byte in its buffer for the NUL. If this stub feature is not supported,
35337 @value{GDBN} guesses based on the size of the @samp{g} packet response.
35339 @item qXfer:auxv:read
35340 The remote stub understands the @samp{qXfer:auxv:read} packet
35341 (@pxref{qXfer auxiliary vector read}).
35343 @item qXfer:features:read
35344 The remote stub understands the @samp{qXfer:features:read} packet
35345 (@pxref{qXfer target description read}).
35347 @item qXfer:libraries:read
35348 The remote stub understands the @samp{qXfer:libraries:read} packet
35349 (@pxref{qXfer library list read}).
35351 @item qXfer:libraries-svr4:read
35352 The remote stub understands the @samp{qXfer:libraries-svr4:read} packet
35353 (@pxref{qXfer svr4 library list read}).
35355 @item qXfer:memory-map:read
35356 The remote stub understands the @samp{qXfer:memory-map:read} packet
35357 (@pxref{qXfer memory map read}).
35359 @item qXfer:sdata:read
35360 The remote stub understands the @samp{qXfer:sdata:read} packet
35361 (@pxref{qXfer sdata read}).
35363 @item qXfer:spu:read
35364 The remote stub understands the @samp{qXfer:spu:read} packet
35365 (@pxref{qXfer spu read}).
35367 @item qXfer:spu:write
35368 The remote stub understands the @samp{qXfer:spu:write} packet
35369 (@pxref{qXfer spu write}).
35371 @item qXfer:siginfo:read
35372 The remote stub understands the @samp{qXfer:siginfo:read} packet
35373 (@pxref{qXfer siginfo read}).
35375 @item qXfer:siginfo:write
35376 The remote stub understands the @samp{qXfer:siginfo:write} packet
35377 (@pxref{qXfer siginfo write}).
35379 @item qXfer:threads:read
35380 The remote stub understands the @samp{qXfer:threads:read} packet
35381 (@pxref{qXfer threads read}).
35383 @item qXfer:traceframe-info:read
35384 The remote stub understands the @samp{qXfer:traceframe-info:read}
35385 packet (@pxref{qXfer traceframe info read}).
35387 @item qXfer:uib:read
35388 The remote stub understands the @samp{qXfer:uib:read}
35389 packet (@pxref{qXfer unwind info block}).
35391 @item qXfer:fdpic:read
35392 The remote stub understands the @samp{qXfer:fdpic:read}
35393 packet (@pxref{qXfer fdpic loadmap read}).
35396 The remote stub understands the @samp{QNonStop} packet
35397 (@pxref{QNonStop}).
35400 The remote stub understands the @samp{QPassSignals} packet
35401 (@pxref{QPassSignals}).
35403 @item QStartNoAckMode
35404 The remote stub understands the @samp{QStartNoAckMode} packet and
35405 prefers to operate in no-acknowledgment mode. @xref{Packet Acknowledgment}.
35408 @anchor{multiprocess extensions}
35409 @cindex multiprocess extensions, in remote protocol
35410 The remote stub understands the multiprocess extensions to the remote
35411 protocol syntax. The multiprocess extensions affect the syntax of
35412 thread IDs in both packets and replies (@pxref{thread-id syntax}), and
35413 add process IDs to the @samp{D} packet and @samp{W} and @samp{X}
35414 replies. Note that reporting this feature indicates support for the
35415 syntactic extensions only, not that the stub necessarily supports
35416 debugging of more than one process at a time. The stub must not use
35417 multiprocess extensions in packet replies unless @value{GDBN} has also
35418 indicated it supports them in its @samp{qSupported} request.
35420 @item qXfer:osdata:read
35421 The remote stub understands the @samp{qXfer:osdata:read} packet
35422 ((@pxref{qXfer osdata read}).
35424 @item ConditionalBreakpoints
35425 The target accepts and implements evaluation of conditional expressions
35426 defined for breakpoints. The target will only report breakpoint triggers
35427 when such conditions are true (@pxref{Conditions, ,Break Conditions}).
35429 @item ConditionalTracepoints
35430 The remote stub accepts and implements conditional expressions defined
35431 for tracepoints (@pxref{Tracepoint Conditions}).
35433 @item ReverseContinue
35434 The remote stub accepts and implements the reverse continue packet
35438 The remote stub accepts and implements the reverse step packet
35441 @item TracepointSource
35442 The remote stub understands the @samp{QTDPsrc} packet that supplies
35443 the source form of tracepoint definitions.
35446 The remote stub understands the @samp{QAgent} packet.
35449 The remote stub understands the @samp{QAllow} packet.
35451 @item QDisableRandomization
35452 The remote stub understands the @samp{QDisableRandomization} packet.
35454 @item StaticTracepoint
35455 @cindex static tracepoints, in remote protocol
35456 The remote stub supports static tracepoints.
35458 @item InstallInTrace
35459 @anchor{install tracepoint in tracing}
35460 The remote stub supports installing tracepoint in tracing.
35462 @item EnableDisableTracepoints
35463 The remote stub supports the @samp{QTEnable} (@pxref{QTEnable}) and
35464 @samp{QTDisable} (@pxref{QTDisable}) packets that allow tracepoints
35465 to be enabled and disabled while a trace experiment is running.
35468 @cindex string tracing, in remote protocol
35469 The remote stub supports the @samp{tracenz} bytecode for collecting strings.
35470 See @ref{Bytecode Descriptions} for details about the bytecode.
35475 @cindex symbol lookup, remote request
35476 @cindex @samp{qSymbol} packet
35477 Notify the target that @value{GDBN} is prepared to serve symbol lookup
35478 requests. Accept requests from the target for the values of symbols.
35483 The target does not need to look up any (more) symbols.
35484 @item qSymbol:@var{sym_name}
35485 The target requests the value of symbol @var{sym_name} (hex encoded).
35486 @value{GDBN} may provide the value by using the
35487 @samp{qSymbol:@var{sym_value}:@var{sym_name}} message, described
35491 @item qSymbol:@var{sym_value}:@var{sym_name}
35492 Set the value of @var{sym_name} to @var{sym_value}.
35494 @var{sym_name} (hex encoded) is the name of a symbol whose value the
35495 target has previously requested.
35497 @var{sym_value} (hex) is the value for symbol @var{sym_name}. If
35498 @value{GDBN} cannot supply a value for @var{sym_name}, then this field
35504 The target does not need to look up any (more) symbols.
35505 @item qSymbol:@var{sym_name}
35506 The target requests the value of a new symbol @var{sym_name} (hex
35507 encoded). @value{GDBN} will continue to supply the values of symbols
35508 (if available), until the target ceases to request them.
35513 @item QTDisconnected
35520 @itemx qTMinFTPILen
35522 @xref{Tracepoint Packets}.
35524 @item qThreadExtraInfo,@var{thread-id}
35525 @cindex thread attributes info, remote request
35526 @cindex @samp{qThreadExtraInfo} packet
35527 Obtain a printable string description of a thread's attributes from
35528 the target OS. @var{thread-id} is a thread ID;
35529 see @ref{thread-id syntax}. This
35530 string may contain anything that the target OS thinks is interesting
35531 for @value{GDBN} to tell the user about the thread. The string is
35532 displayed in @value{GDBN}'s @code{info threads} display. Some
35533 examples of possible thread extra info strings are @samp{Runnable}, or
35534 @samp{Blocked on Mutex}.
35538 @item @var{XX}@dots{}
35539 Where @samp{@var{XX}@dots{}} is a hex encoding of @sc{ascii} data,
35540 comprising the printable string containing the extra information about
35541 the thread's attributes.
35544 (Note that the @code{qThreadExtraInfo} packet's name is separated from
35545 the command by a @samp{,}, not a @samp{:}, contrary to the naming
35546 conventions above. Please don't use this packet as a model for new
35565 @xref{Tracepoint Packets}.
35567 @item qXfer:@var{object}:read:@var{annex}:@var{offset},@var{length}
35568 @cindex read special object, remote request
35569 @cindex @samp{qXfer} packet
35570 @anchor{qXfer read}
35571 Read uninterpreted bytes from the target's special data area
35572 identified by the keyword @var{object}. Request @var{length} bytes
35573 starting at @var{offset} bytes into the data. The content and
35574 encoding of @var{annex} is specific to @var{object}; it can supply
35575 additional details about what data to access.
35577 Here are the specific requests of this form defined so far. All
35578 @samp{qXfer:@var{object}:read:@dots{}} requests use the same reply
35579 formats, listed below.
35582 @item qXfer:auxv:read::@var{offset},@var{length}
35583 @anchor{qXfer auxiliary vector read}
35584 Access the target's @dfn{auxiliary vector}. @xref{OS Information,
35585 auxiliary vector}. Note @var{annex} must be empty.
35587 This packet is not probed by default; the remote stub must request it,
35588 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
35590 @item qXfer:features:read:@var{annex}:@var{offset},@var{length}
35591 @anchor{qXfer target description read}
35592 Access the @dfn{target description}. @xref{Target Descriptions}. The
35593 annex specifies which XML document to access. The main description is
35594 always loaded from the @samp{target.xml} annex.
35596 This packet is not probed by default; the remote stub must request it,
35597 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
35599 @item qXfer:libraries:read:@var{annex}:@var{offset},@var{length}
35600 @anchor{qXfer library list read}
35601 Access the target's list of loaded libraries. @xref{Library List Format}.
35602 The annex part of the generic @samp{qXfer} packet must be empty
35603 (@pxref{qXfer read}).
35605 Targets which maintain a list of libraries in the program's memory do
35606 not need to implement this packet; it is designed for platforms where
35607 the operating system manages the list of loaded libraries.
35609 This packet is not probed by default; the remote stub must request it,
35610 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
35612 @item qXfer:libraries-svr4:read:@var{annex}:@var{offset},@var{length}
35613 @anchor{qXfer svr4 library list read}
35614 Access the target's list of loaded libraries when the target is an SVR4
35615 platform. @xref{Library List Format for SVR4 Targets}. The annex part
35616 of the generic @samp{qXfer} packet must be empty (@pxref{qXfer read}).
35618 This packet is optional for better performance on SVR4 targets.
35619 @value{GDBN} uses memory read packets to read the SVR4 library list otherwise.
35621 This packet is not probed by default; the remote stub must request it,
35622 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
35624 @item qXfer:memory-map:read::@var{offset},@var{length}
35625 @anchor{qXfer memory map read}
35626 Access the target's @dfn{memory-map}. @xref{Memory Map Format}. The
35627 annex part of the generic @samp{qXfer} packet must be empty
35628 (@pxref{qXfer read}).
35630 This packet is not probed by default; the remote stub must request it,
35631 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
35633 @item qXfer:sdata:read::@var{offset},@var{length}
35634 @anchor{qXfer sdata read}
35636 Read contents of the extra collected static tracepoint marker
35637 information. The annex part of the generic @samp{qXfer} packet must
35638 be empty (@pxref{qXfer read}). @xref{Tracepoint Actions,,Tracepoint
35641 This packet is not probed by default; the remote stub must request it,
35642 by supplying an appropriate @samp{qSupported} response
35643 (@pxref{qSupported}).
35645 @item qXfer:siginfo:read::@var{offset},@var{length}
35646 @anchor{qXfer siginfo read}
35647 Read contents of the extra signal information on the target
35648 system. The annex part of the generic @samp{qXfer} packet must be
35649 empty (@pxref{qXfer read}).
35651 This packet is not probed by default; the remote stub must request it,
35652 by supplying an appropriate @samp{qSupported} response
35653 (@pxref{qSupported}).
35655 @item qXfer:spu:read:@var{annex}:@var{offset},@var{length}
35656 @anchor{qXfer spu read}
35657 Read contents of an @code{spufs} file on the target system. The
35658 annex specifies which file to read; it must be of the form
35659 @file{@var{id}/@var{name}}, where @var{id} specifies an SPU context ID
35660 in the target process, and @var{name} identifes the @code{spufs} file
35661 in that context to be accessed.
35663 This packet is not probed by default; the remote stub must request it,
35664 by supplying an appropriate @samp{qSupported} response
35665 (@pxref{qSupported}).
35667 @item qXfer:threads:read::@var{offset},@var{length}
35668 @anchor{qXfer threads read}
35669 Access the list of threads on target. @xref{Thread List Format}. The
35670 annex part of the generic @samp{qXfer} packet must be empty
35671 (@pxref{qXfer read}).
35673 This packet is not probed by default; the remote stub must request it,
35674 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
35676 @item qXfer:traceframe-info:read::@var{offset},@var{length}
35677 @anchor{qXfer traceframe info read}
35679 Return a description of the current traceframe's contents.
35680 @xref{Traceframe Info Format}. The annex part of the generic
35681 @samp{qXfer} packet must be empty (@pxref{qXfer read}).
35683 This packet is not probed by default; the remote stub must request it,
35684 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
35686 @item qXfer:uib:read:@var{pc}:@var{offset},@var{length}
35687 @anchor{qXfer unwind info block}
35689 Return the unwind information block for @var{pc}. This packet is used
35690 on OpenVMS/ia64 to ask the kernel unwind information.
35692 This packet is not probed by default.
35694 @item qXfer:fdpic:read:@var{annex}:@var{offset},@var{length}
35695 @anchor{qXfer fdpic loadmap read}
35696 Read contents of @code{loadmap}s on the target system. The
35697 annex, either @samp{exec} or @samp{interp}, specifies which @code{loadmap},
35698 executable @code{loadmap} or interpreter @code{loadmap} to read.
35700 This packet is not probed by default; the remote stub must request it,
35701 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
35703 @item qXfer:osdata:read::@var{offset},@var{length}
35704 @anchor{qXfer osdata read}
35705 Access the target's @dfn{operating system information}.
35706 @xref{Operating System Information}.
35713 Data @var{data} (@pxref{Binary Data}) has been read from the
35714 target. There may be more data at a higher address (although
35715 it is permitted to return @samp{m} even for the last valid
35716 block of data, as long as at least one byte of data was read).
35717 @var{data} may have fewer bytes than the @var{length} in the
35721 Data @var{data} (@pxref{Binary Data}) has been read from the target.
35722 There is no more data to be read. @var{data} may have fewer bytes
35723 than the @var{length} in the request.
35726 The @var{offset} in the request is at the end of the data.
35727 There is no more data to be read.
35730 The request was malformed, or @var{annex} was invalid.
35733 The offset was invalid, or there was an error encountered reading the data.
35734 @var{nn} is a hex-encoded @code{errno} value.
35737 An empty reply indicates the @var{object} string was not recognized by
35738 the stub, or that the object does not support reading.
35741 @item qXfer:@var{object}:write:@var{annex}:@var{offset}:@var{data}@dots{}
35742 @cindex write data into object, remote request
35743 @anchor{qXfer write}
35744 Write uninterpreted bytes into the target's special data area
35745 identified by the keyword @var{object}, starting at @var{offset} bytes
35746 into the data. @var{data}@dots{} is the binary-encoded data
35747 (@pxref{Binary Data}) to be written. The content and encoding of @var{annex}
35748 is specific to @var{object}; it can supply additional details about what data
35751 Here are the specific requests of this form defined so far. All
35752 @samp{qXfer:@var{object}:write:@dots{}} requests use the same reply
35753 formats, listed below.
35756 @item qXfer:siginfo:write::@var{offset}:@var{data}@dots{}
35757 @anchor{qXfer siginfo write}
35758 Write @var{data} to the extra signal information on the target system.
35759 The annex part of the generic @samp{qXfer} packet must be
35760 empty (@pxref{qXfer write}).
35762 This packet is not probed by default; the remote stub must request it,
35763 by supplying an appropriate @samp{qSupported} response
35764 (@pxref{qSupported}).
35766 @item qXfer:spu:write:@var{annex}:@var{offset}:@var{data}@dots{}
35767 @anchor{qXfer spu write}
35768 Write @var{data} to an @code{spufs} file on the target system. The
35769 annex specifies which file to write; it must be of the form
35770 @file{@var{id}/@var{name}}, where @var{id} specifies an SPU context ID
35771 in the target process, and @var{name} identifes the @code{spufs} file
35772 in that context to be accessed.
35774 This packet is not probed by default; the remote stub must request it,
35775 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
35781 @var{nn} (hex encoded) is the number of bytes written.
35782 This may be fewer bytes than supplied in the request.
35785 The request was malformed, or @var{annex} was invalid.
35788 The offset was invalid, or there was an error encountered writing the data.
35789 @var{nn} is a hex-encoded @code{errno} value.
35792 An empty reply indicates the @var{object} string was not
35793 recognized by the stub, or that the object does not support writing.
35796 @item qXfer:@var{object}:@var{operation}:@dots{}
35797 Requests of this form may be added in the future. When a stub does
35798 not recognize the @var{object} keyword, or its support for
35799 @var{object} does not recognize the @var{operation} keyword, the stub
35800 must respond with an empty packet.
35802 @item qAttached:@var{pid}
35803 @cindex query attached, remote request
35804 @cindex @samp{qAttached} packet
35805 Return an indication of whether the remote server attached to an
35806 existing process or created a new process. When the multiprocess
35807 protocol extensions are supported (@pxref{multiprocess extensions}),
35808 @var{pid} is an integer in hexadecimal format identifying the target
35809 process. Otherwise, @value{GDBN} will omit the @var{pid} field and
35810 the query packet will be simplified as @samp{qAttached}.
35812 This query is used, for example, to know whether the remote process
35813 should be detached or killed when a @value{GDBN} session is ended with
35814 the @code{quit} command.
35819 The remote server attached to an existing process.
35821 The remote server created a new process.
35823 A badly formed request or an error was encountered.
35828 @node Architecture-Specific Protocol Details
35829 @section Architecture-Specific Protocol Details
35831 This section describes how the remote protocol is applied to specific
35832 target architectures. Also see @ref{Standard Target Features}, for
35833 details of XML target descriptions for each architecture.
35837 @subsubsection Breakpoint Kinds
35839 These breakpoint kinds are defined for the @samp{Z0} and @samp{Z1} packets.
35844 16-bit Thumb mode breakpoint.
35847 32-bit Thumb mode (Thumb-2) breakpoint.
35850 32-bit ARM mode breakpoint.
35856 @subsubsection Register Packet Format
35858 The following @code{g}/@code{G} packets have previously been defined.
35859 In the below, some thirty-two bit registers are transferred as
35860 sixty-four bits. Those registers should be zero/sign extended (which?)
35861 to fill the space allocated. Register bytes are transferred in target
35862 byte order. The two nibbles within a register byte are transferred
35863 most-significant - least-significant.
35869 All registers are transferred as thirty-two bit quantities in the order:
35870 32 general-purpose; sr; lo; hi; bad; cause; pc; 32 floating-point
35871 registers; fsr; fir; fp.
35875 All registers are transferred as sixty-four bit quantities (including
35876 thirty-two bit registers such as @code{sr}). The ordering is the same
35881 @node Tracepoint Packets
35882 @section Tracepoint Packets
35883 @cindex tracepoint packets
35884 @cindex packets, tracepoint
35886 Here we describe the packets @value{GDBN} uses to implement
35887 tracepoints (@pxref{Tracepoints}).
35891 @item QTDP:@var{n}:@var{addr}:@var{ena}:@var{step}:@var{pass}[:F@var{flen}][:X@var{len},@var{bytes}]@r{[}-@r{]}
35892 Create a new tracepoint, number @var{n}, at @var{addr}. If @var{ena}
35893 is @samp{E}, then the tracepoint is enabled; if it is @samp{D}, then
35894 the tracepoint is disabled. @var{step} is the tracepoint's step
35895 count, and @var{pass} is its pass count. If an @samp{F} is present,
35896 then the tracepoint is to be a fast tracepoint, and the @var{flen} is
35897 the number of bytes that the target should copy elsewhere to make room
35898 for the tracepoint. If an @samp{X} is present, it introduces a
35899 tracepoint condition, which consists of a hexadecimal length, followed
35900 by a comma and hex-encoded bytes, in a manner similar to action
35901 encodings as described below. If the trailing @samp{-} is present,
35902 further @samp{QTDP} packets will follow to specify this tracepoint's
35908 The packet was understood and carried out.
35910 @xref{Tracepoint Packets,,Relocate instruction reply packet}.
35912 The packet was not recognized.
35915 @item QTDP:-@var{n}:@var{addr}:@r{[}S@r{]}@var{action}@dots{}@r{[}-@r{]}
35916 Define actions to be taken when a tracepoint is hit. @var{n} and
35917 @var{addr} must be the same as in the initial @samp{QTDP} packet for
35918 this tracepoint. This packet may only be sent immediately after
35919 another @samp{QTDP} packet that ended with a @samp{-}. If the
35920 trailing @samp{-} is present, further @samp{QTDP} packets will follow,
35921 specifying more actions for this tracepoint.
35923 In the series of action packets for a given tracepoint, at most one
35924 can have an @samp{S} before its first @var{action}. If such a packet
35925 is sent, it and the following packets define ``while-stepping''
35926 actions. Any prior packets define ordinary actions --- that is, those
35927 taken when the tracepoint is first hit. If no action packet has an
35928 @samp{S}, then all the packets in the series specify ordinary
35929 tracepoint actions.
35931 The @samp{@var{action}@dots{}} portion of the packet is a series of
35932 actions, concatenated without separators. Each action has one of the
35938 Collect the registers whose bits are set in @var{mask}. @var{mask} is
35939 a hexadecimal number whose @var{i}'th bit is set if register number
35940 @var{i} should be collected. (The least significant bit is numbered
35941 zero.) Note that @var{mask} may be any number of digits long; it may
35942 not fit in a 32-bit word.
35944 @item M @var{basereg},@var{offset},@var{len}
35945 Collect @var{len} bytes of memory starting at the address in register
35946 number @var{basereg}, plus @var{offset}. If @var{basereg} is
35947 @samp{-1}, then the range has a fixed address: @var{offset} is the
35948 address of the lowest byte to collect. The @var{basereg},
35949 @var{offset}, and @var{len} parameters are all unsigned hexadecimal
35950 values (the @samp{-1} value for @var{basereg} is a special case).
35952 @item X @var{len},@var{expr}
35953 Evaluate @var{expr}, whose length is @var{len}, and collect memory as
35954 it directs. @var{expr} is an agent expression, as described in
35955 @ref{Agent Expressions}. Each byte of the expression is encoded as a
35956 two-digit hex number in the packet; @var{len} is the number of bytes
35957 in the expression (and thus one-half the number of hex digits in the
35962 Any number of actions may be packed together in a single @samp{QTDP}
35963 packet, as long as the packet does not exceed the maximum packet
35964 length (400 bytes, for many stubs). There may be only one @samp{R}
35965 action per tracepoint, and it must precede any @samp{M} or @samp{X}
35966 actions. Any registers referred to by @samp{M} and @samp{X} actions
35967 must be collected by a preceding @samp{R} action. (The
35968 ``while-stepping'' actions are treated as if they were attached to a
35969 separate tracepoint, as far as these restrictions are concerned.)
35974 The packet was understood and carried out.
35976 @xref{Tracepoint Packets,,Relocate instruction reply packet}.
35978 The packet was not recognized.
35981 @item QTDPsrc:@var{n}:@var{addr}:@var{type}:@var{start}:@var{slen}:@var{bytes}
35982 @cindex @samp{QTDPsrc} packet
35983 Specify a source string of tracepoint @var{n} at address @var{addr}.
35984 This is useful to get accurate reproduction of the tracepoints
35985 originally downloaded at the beginning of the trace run. @var{type}
35986 is the name of the tracepoint part, such as @samp{cond} for the
35987 tracepoint's conditional expression (see below for a list of types), while
35988 @var{bytes} is the string, encoded in hexadecimal.
35990 @var{start} is the offset of the @var{bytes} within the overall source
35991 string, while @var{slen} is the total length of the source string.
35992 This is intended for handling source strings that are longer than will
35993 fit in a single packet.
35994 @c Add detailed example when this info is moved into a dedicated
35995 @c tracepoint descriptions section.
35997 The available string types are @samp{at} for the location,
35998 @samp{cond} for the conditional, and @samp{cmd} for an action command.
35999 @value{GDBN} sends a separate packet for each command in the action
36000 list, in the same order in which the commands are stored in the list.
36002 The target does not need to do anything with source strings except
36003 report them back as part of the replies to the @samp{qTfP}/@samp{qTsP}
36006 Although this packet is optional, and @value{GDBN} will only send it
36007 if the target replies with @samp{TracepointSource} @xref{General
36008 Query Packets}, it makes both disconnected tracing and trace files
36009 much easier to use. Otherwise the user must be careful that the
36010 tracepoints in effect while looking at trace frames are identical to
36011 the ones in effect during the trace run; even a small discrepancy
36012 could cause @samp{tdump} not to work, or a particular trace frame not
36015 @item QTDV:@var{n}:@var{value}
36016 @cindex define trace state variable, remote request
36017 @cindex @samp{QTDV} packet
36018 Create a new trace state variable, number @var{n}, with an initial
36019 value of @var{value}, which is a 64-bit signed integer. Both @var{n}
36020 and @var{value} are encoded as hexadecimal values. @value{GDBN} has
36021 the option of not using this packet for initial values of zero; the
36022 target should simply create the trace state variables as they are
36023 mentioned in expressions.
36025 @item QTFrame:@var{n}
36026 Select the @var{n}'th tracepoint frame from the buffer, and use the
36027 register and memory contents recorded there to answer subsequent
36028 request packets from @value{GDBN}.
36030 A successful reply from the stub indicates that the stub has found the
36031 requested frame. The response is a series of parts, concatenated
36032 without separators, describing the frame we selected. Each part has
36033 one of the following forms:
36037 The selected frame is number @var{n} in the trace frame buffer;
36038 @var{f} is a hexadecimal number. If @var{f} is @samp{-1}, then there
36039 was no frame matching the criteria in the request packet.
36042 The selected trace frame records a hit of tracepoint number @var{t};
36043 @var{t} is a hexadecimal number.
36047 @item QTFrame:pc:@var{addr}
36048 Like @samp{QTFrame:@var{n}}, but select the first tracepoint frame after the
36049 currently selected frame whose PC is @var{addr};
36050 @var{addr} is a hexadecimal number.
36052 @item QTFrame:tdp:@var{t}
36053 Like @samp{QTFrame:@var{n}}, but select the first tracepoint frame after the
36054 currently selected frame that is a hit of tracepoint @var{t}; @var{t}
36055 is a hexadecimal number.
36057 @item QTFrame:range:@var{start}:@var{end}
36058 Like @samp{QTFrame:@var{n}}, but select the first tracepoint frame after the
36059 currently selected frame whose PC is between @var{start} (inclusive)
36060 and @var{end} (inclusive); @var{start} and @var{end} are hexadecimal
36063 @item QTFrame:outside:@var{start}:@var{end}
36064 Like @samp{QTFrame:range:@var{start}:@var{end}}, but select the first
36065 frame @emph{outside} the given range of addresses (exclusive).
36068 This packet requests the minimum length of instruction at which a fast
36069 tracepoint (@pxref{Set Tracepoints}) may be placed. For instance, on
36070 the 32-bit x86 architecture, it is possible to use a 4-byte jump, but
36071 it depends on the target system being able to create trampolines in
36072 the first 64K of memory, which might or might not be possible for that
36073 system. So the reply to this packet will be 4 if it is able to
36080 The minimum instruction length is currently unknown.
36082 The minimum instruction length is @var{length}, where @var{length} is greater
36083 or equal to 1. @var{length} is a hexadecimal number. A reply of 1 means
36084 that a fast tracepoint may be placed on any instruction regardless of size.
36086 An error has occurred.
36088 An empty reply indicates that the request is not supported by the stub.
36092 Begin the tracepoint experiment. Begin collecting data from
36093 tracepoint hits in the trace frame buffer. This packet supports the
36094 @samp{qRelocInsn} reply (@pxref{Tracepoint Packets,,Relocate
36095 instruction reply packet}).
36098 End the tracepoint experiment. Stop collecting trace frames.
36100 @item QTEnable:@var{n}:@var{addr}
36102 Enable tracepoint @var{n} at address @var{addr} in a started tracepoint
36103 experiment. If the tracepoint was previously disabled, then collection
36104 of data from it will resume.
36106 @item QTDisable:@var{n}:@var{addr}
36108 Disable tracepoint @var{n} at address @var{addr} in a started tracepoint
36109 experiment. No more data will be collected from the tracepoint unless
36110 @samp{QTEnable:@var{n}:@var{addr}} is subsequently issued.
36113 Clear the table of tracepoints, and empty the trace frame buffer.
36115 @item QTro:@var{start1},@var{end1}:@var{start2},@var{end2}:@dots{}
36116 Establish the given ranges of memory as ``transparent''. The stub
36117 will answer requests for these ranges from memory's current contents,
36118 if they were not collected as part of the tracepoint hit.
36120 @value{GDBN} uses this to mark read-only regions of memory, like those
36121 containing program code. Since these areas never change, they should
36122 still have the same contents they did when the tracepoint was hit, so
36123 there's no reason for the stub to refuse to provide their contents.
36125 @item QTDisconnected:@var{value}
36126 Set the choice to what to do with the tracing run when @value{GDBN}
36127 disconnects from the target. A @var{value} of 1 directs the target to
36128 continue the tracing run, while 0 tells the target to stop tracing if
36129 @value{GDBN} is no longer in the picture.
36132 Ask the stub if there is a trace experiment running right now.
36134 The reply has the form:
36138 @item T@var{running}@r{[};@var{field}@r{]}@dots{}
36139 @var{running} is a single digit @code{1} if the trace is presently
36140 running, or @code{0} if not. It is followed by semicolon-separated
36141 optional fields that an agent may use to report additional status.
36145 If the trace is not running, the agent may report any of several
36146 explanations as one of the optional fields:
36151 No trace has been run yet.
36153 @item tstop[:@var{text}]:0
36154 The trace was stopped by a user-originated stop command. The optional
36155 @var{text} field is a user-supplied string supplied as part of the
36156 stop command (for instance, an explanation of why the trace was
36157 stopped manually). It is hex-encoded.
36160 The trace stopped because the trace buffer filled up.
36162 @item tdisconnected:0
36163 The trace stopped because @value{GDBN} disconnected from the target.
36165 @item tpasscount:@var{tpnum}
36166 The trace stopped because tracepoint @var{tpnum} exceeded its pass count.
36168 @item terror:@var{text}:@var{tpnum}
36169 The trace stopped because tracepoint @var{tpnum} had an error. The
36170 string @var{text} is available to describe the nature of the error
36171 (for instance, a divide by zero in the condition expression).
36172 @var{text} is hex encoded.
36175 The trace stopped for some other reason.
36179 Additional optional fields supply statistical and other information.
36180 Although not required, they are extremely useful for users monitoring
36181 the progress of a trace run. If a trace has stopped, and these
36182 numbers are reported, they must reflect the state of the just-stopped
36187 @item tframes:@var{n}
36188 The number of trace frames in the buffer.
36190 @item tcreated:@var{n}
36191 The total number of trace frames created during the run. This may
36192 be larger than the trace frame count, if the buffer is circular.
36194 @item tsize:@var{n}
36195 The total size of the trace buffer, in bytes.
36197 @item tfree:@var{n}
36198 The number of bytes still unused in the buffer.
36200 @item circular:@var{n}
36201 The value of the circular trace buffer flag. @code{1} means that the
36202 trace buffer is circular and old trace frames will be discarded if
36203 necessary to make room, @code{0} means that the trace buffer is linear
36206 @item disconn:@var{n}
36207 The value of the disconnected tracing flag. @code{1} means that
36208 tracing will continue after @value{GDBN} disconnects, @code{0} means
36209 that the trace run will stop.
36213 @item qTP:@var{tp}:@var{addr}
36214 @cindex tracepoint status, remote request
36215 @cindex @samp{qTP} packet
36216 Ask the stub for the current state of tracepoint number @var{tp} at
36217 address @var{addr}.
36221 @item V@var{hits}:@var{usage}
36222 The tracepoint has been hit @var{hits} times so far during the trace
36223 run, and accounts for @var{usage} in the trace buffer. Note that
36224 @code{while-stepping} steps are not counted as separate hits, but the
36225 steps' space consumption is added into the usage number.
36229 @item qTV:@var{var}
36230 @cindex trace state variable value, remote request
36231 @cindex @samp{qTV} packet
36232 Ask the stub for the value of the trace state variable number @var{var}.
36237 The value of the variable is @var{value}. This will be the current
36238 value of the variable if the user is examining a running target, or a
36239 saved value if the variable was collected in the trace frame that the
36240 user is looking at. Note that multiple requests may result in
36241 different reply values, such as when requesting values while the
36242 program is running.
36245 The value of the variable is unknown. This would occur, for example,
36246 if the user is examining a trace frame in which the requested variable
36252 These packets request data about tracepoints that are being used by
36253 the target. @value{GDBN} sends @code{qTfP} to get the first piece
36254 of data, and multiple @code{qTsP} to get additional pieces. Replies
36255 to these packets generally take the form of the @code{QTDP} packets
36256 that define tracepoints. (FIXME add detailed syntax)
36260 These packets request data about trace state variables that are on the
36261 target. @value{GDBN} sends @code{qTfV} to get the first vari of data,
36262 and multiple @code{qTsV} to get additional variables. Replies to
36263 these packets follow the syntax of the @code{QTDV} packets that define
36264 trace state variables.
36268 These packets request data about static tracepoint markers that exist
36269 in the target program. @value{GDBN} sends @code{qTfSTM} to get the
36270 first piece of data, and multiple @code{qTsSTM} to get additional
36271 pieces. Replies to these packets take the following form:
36275 @item m @var{address}:@var{id}:@var{extra}
36277 @item m @var{address}:@var{id}:@var{extra},@var{address}:@var{id}:@var{extra}@dots{}
36278 a comma-separated list of markers
36280 (lower case letter @samp{L}) denotes end of list.
36282 An error occurred. @var{nn} are hex digits.
36284 An empty reply indicates that the request is not supported by the
36288 @var{address} is encoded in hex.
36289 @var{id} and @var{extra} are strings encoded in hex.
36291 In response to each query, the target will reply with a list of one or
36292 more markers, separated by commas. @value{GDBN} will respond to each
36293 reply with a request for more markers (using the @samp{qs} form of the
36294 query), until the target responds with @samp{l} (lower-case ell, for
36297 @item qTSTMat:@var{address}
36298 This packets requests data about static tracepoint markers in the
36299 target program at @var{address}. Replies to this packet follow the
36300 syntax of the @samp{qTfSTM} and @code{qTsSTM} packets that list static
36301 tracepoint markers.
36303 @item QTSave:@var{filename}
36304 This packet directs the target to save trace data to the file name
36305 @var{filename} in the target's filesystem. @var{filename} is encoded
36306 as a hex string; the interpretation of the file name (relative vs
36307 absolute, wild cards, etc) is up to the target.
36309 @item qTBuffer:@var{offset},@var{len}
36310 Return up to @var{len} bytes of the current contents of trace buffer,
36311 starting at @var{offset}. The trace buffer is treated as if it were
36312 a contiguous collection of traceframes, as per the trace file format.
36313 The reply consists as many hex-encoded bytes as the target can deliver
36314 in a packet; it is not an error to return fewer than were asked for.
36315 A reply consisting of just @code{l} indicates that no bytes are
36318 @item QTBuffer:circular:@var{value}
36319 This packet directs the target to use a circular trace buffer if
36320 @var{value} is 1, or a linear buffer if the value is 0.
36322 @item QTNotes:@r{[}@var{type}:@var{text}@r{]}@r{[};@var{type}:@var{text}@r{]}@dots{}
36323 This packet adds optional textual notes to the trace run. Allowable
36324 types include @code{user}, @code{notes}, and @code{tstop}, the
36325 @var{text} fields are arbitrary strings, hex-encoded.
36329 @subsection Relocate instruction reply packet
36330 When installing fast tracepoints in memory, the target may need to
36331 relocate the instruction currently at the tracepoint address to a
36332 different address in memory. For most instructions, a simple copy is
36333 enough, but, for example, call instructions that implicitly push the
36334 return address on the stack, and relative branches or other
36335 PC-relative instructions require offset adjustment, so that the effect
36336 of executing the instruction at a different address is the same as if
36337 it had executed in the original location.
36339 In response to several of the tracepoint packets, the target may also
36340 respond with a number of intermediate @samp{qRelocInsn} request
36341 packets before the final result packet, to have @value{GDBN} handle
36342 this relocation operation. If a packet supports this mechanism, its
36343 documentation will explicitly say so. See for example the above
36344 descriptions for the @samp{QTStart} and @samp{QTDP} packets. The
36345 format of the request is:
36348 @item qRelocInsn:@var{from};@var{to}
36350 This requests @value{GDBN} to copy instruction at address @var{from}
36351 to address @var{to}, possibly adjusted so that executing the
36352 instruction at @var{to} has the same effect as executing it at
36353 @var{from}. @value{GDBN} writes the adjusted instruction to target
36354 memory starting at @var{to}.
36359 @item qRelocInsn:@var{adjusted_size}
36360 Informs the stub the relocation is complete. @var{adjusted_size} is
36361 the length in bytes of resulting relocated instruction sequence.
36363 A badly formed request was detected, or an error was encountered while
36364 relocating the instruction.
36367 @node Host I/O Packets
36368 @section Host I/O Packets
36369 @cindex Host I/O, remote protocol
36370 @cindex file transfer, remote protocol
36372 The @dfn{Host I/O} packets allow @value{GDBN} to perform I/O
36373 operations on the far side of a remote link. For example, Host I/O is
36374 used to upload and download files to a remote target with its own
36375 filesystem. Host I/O uses the same constant values and data structure
36376 layout as the target-initiated File-I/O protocol. However, the
36377 Host I/O packets are structured differently. The target-initiated
36378 protocol relies on target memory to store parameters and buffers.
36379 Host I/O requests are initiated by @value{GDBN}, and the
36380 target's memory is not involved. @xref{File-I/O Remote Protocol
36381 Extension}, for more details on the target-initiated protocol.
36383 The Host I/O request packets all encode a single operation along with
36384 its arguments. They have this format:
36388 @item vFile:@var{operation}: @var{parameter}@dots{}
36389 @var{operation} is the name of the particular request; the target
36390 should compare the entire packet name up to the second colon when checking
36391 for a supported operation. The format of @var{parameter} depends on
36392 the operation. Numbers are always passed in hexadecimal. Negative
36393 numbers have an explicit minus sign (i.e.@: two's complement is not
36394 used). Strings (e.g.@: filenames) are encoded as a series of
36395 hexadecimal bytes. The last argument to a system call may be a
36396 buffer of escaped binary data (@pxref{Binary Data}).
36400 The valid responses to Host I/O packets are:
36404 @item F @var{result} [, @var{errno}] [; @var{attachment}]
36405 @var{result} is the integer value returned by this operation, usually
36406 non-negative for success and -1 for errors. If an error has occured,
36407 @var{errno} will be included in the result. @var{errno} will have a
36408 value defined by the File-I/O protocol (@pxref{Errno Values}). For
36409 operations which return data, @var{attachment} supplies the data as a
36410 binary buffer. Binary buffers in response packets are escaped in the
36411 normal way (@pxref{Binary Data}). See the individual packet
36412 documentation for the interpretation of @var{result} and
36416 An empty response indicates that this operation is not recognized.
36420 These are the supported Host I/O operations:
36423 @item vFile:open: @var{pathname}, @var{flags}, @var{mode}
36424 Open a file at @var{pathname} and return a file descriptor for it, or
36425 return -1 if an error occurs. @var{pathname} is a string,
36426 @var{flags} is an integer indicating a mask of open flags
36427 (@pxref{Open Flags}), and @var{mode} is an integer indicating a mask
36428 of mode bits to use if the file is created (@pxref{mode_t Values}).
36429 @xref{open}, for details of the open flags and mode values.
36431 @item vFile:close: @var{fd}
36432 Close the open file corresponding to @var{fd} and return 0, or
36433 -1 if an error occurs.
36435 @item vFile:pread: @var{fd}, @var{count}, @var{offset}
36436 Read data from the open file corresponding to @var{fd}. Up to
36437 @var{count} bytes will be read from the file, starting at @var{offset}
36438 relative to the start of the file. The target may read fewer bytes;
36439 common reasons include packet size limits and an end-of-file
36440 condition. The number of bytes read is returned. Zero should only be
36441 returned for a successful read at the end of the file, or if
36442 @var{count} was zero.
36444 The data read should be returned as a binary attachment on success.
36445 If zero bytes were read, the response should include an empty binary
36446 attachment (i.e.@: a trailing semicolon). The return value is the
36447 number of target bytes read; the binary attachment may be longer if
36448 some characters were escaped.
36450 @item vFile:pwrite: @var{fd}, @var{offset}, @var{data}
36451 Write @var{data} (a binary buffer) to the open file corresponding
36452 to @var{fd}. Start the write at @var{offset} from the start of the
36453 file. Unlike many @code{write} system calls, there is no
36454 separate @var{count} argument; the length of @var{data} in the
36455 packet is used. @samp{vFile:write} returns the number of bytes written,
36456 which may be shorter than the length of @var{data}, or -1 if an
36459 @item vFile:unlink: @var{pathname}
36460 Delete the file at @var{pathname} on the target. Return 0,
36461 or -1 if an error occurs. @var{pathname} is a string.
36463 @item vFile:readlink: @var{filename}
36464 Read value of symbolic link @var{filename} on the target. Return
36465 the number of bytes read, or -1 if an error occurs.
36467 The data read should be returned as a binary attachment on success.
36468 If zero bytes were read, the response should include an empty binary
36469 attachment (i.e.@: a trailing semicolon). The return value is the
36470 number of target bytes read; the binary attachment may be longer if
36471 some characters were escaped.
36476 @section Interrupts
36477 @cindex interrupts (remote protocol)
36479 When a program on the remote target is running, @value{GDBN} may
36480 attempt to interrupt it by sending a @samp{Ctrl-C}, @code{BREAK} or
36481 a @code{BREAK} followed by @code{g},
36482 control of which is specified via @value{GDBN}'s @samp{interrupt-sequence}.
36484 The precise meaning of @code{BREAK} is defined by the transport
36485 mechanism and may, in fact, be undefined. @value{GDBN} does not
36486 currently define a @code{BREAK} mechanism for any of the network
36487 interfaces except for TCP, in which case @value{GDBN} sends the
36488 @code{telnet} BREAK sequence.
36490 @samp{Ctrl-C}, on the other hand, is defined and implemented for all
36491 transport mechanisms. It is represented by sending the single byte
36492 @code{0x03} without any of the usual packet overhead described in
36493 the Overview section (@pxref{Overview}). When a @code{0x03} byte is
36494 transmitted as part of a packet, it is considered to be packet data
36495 and does @emph{not} represent an interrupt. E.g., an @samp{X} packet
36496 (@pxref{X packet}), used for binary downloads, may include an unescaped
36497 @code{0x03} as part of its packet.
36499 @code{BREAK} followed by @code{g} is also known as Magic SysRq g.
36500 When Linux kernel receives this sequence from serial port,
36501 it stops execution and connects to gdb.
36503 Stubs are not required to recognize these interrupt mechanisms and the
36504 precise meaning associated with receipt of the interrupt is
36505 implementation defined. If the target supports debugging of multiple
36506 threads and/or processes, it should attempt to interrupt all
36507 currently-executing threads and processes.
36508 If the stub is successful at interrupting the
36509 running program, it should send one of the stop
36510 reply packets (@pxref{Stop Reply Packets}) to @value{GDBN} as a result
36511 of successfully stopping the program in all-stop mode, and a stop reply
36512 for each stopped thread in non-stop mode.
36513 Interrupts received while the
36514 program is stopped are discarded.
36516 @node Notification Packets
36517 @section Notification Packets
36518 @cindex notification packets
36519 @cindex packets, notification
36521 The @value{GDBN} remote serial protocol includes @dfn{notifications},
36522 packets that require no acknowledgment. Both the GDB and the stub
36523 may send notifications (although the only notifications defined at
36524 present are sent by the stub). Notifications carry information
36525 without incurring the round-trip latency of an acknowledgment, and so
36526 are useful for low-impact communications where occasional packet loss
36529 A notification packet has the form @samp{% @var{data} #
36530 @var{checksum}}, where @var{data} is the content of the notification,
36531 and @var{checksum} is a checksum of @var{data}, computed and formatted
36532 as for ordinary @value{GDBN} packets. A notification's @var{data}
36533 never contains @samp{$}, @samp{%} or @samp{#} characters. Upon
36534 receiving a notification, the recipient sends no @samp{+} or @samp{-}
36535 to acknowledge the notification's receipt or to report its corruption.
36537 Every notification's @var{data} begins with a name, which contains no
36538 colon characters, followed by a colon character.
36540 Recipients should silently ignore corrupted notifications and
36541 notifications they do not understand. Recipients should restart
36542 timeout periods on receipt of a well-formed notification, whether or
36543 not they understand it.
36545 Senders should only send the notifications described here when this
36546 protocol description specifies that they are permitted. In the
36547 future, we may extend the protocol to permit existing notifications in
36548 new contexts; this rule helps older senders avoid confusing newer
36551 (Older versions of @value{GDBN} ignore bytes received until they see
36552 the @samp{$} byte that begins an ordinary packet, so new stubs may
36553 transmit notifications without fear of confusing older clients. There
36554 are no notifications defined for @value{GDBN} to send at the moment, but we
36555 assume that most older stubs would ignore them, as well.)
36557 The following notification packets from the stub to @value{GDBN} are
36561 @item Stop: @var{reply}
36562 Report an asynchronous stop event in non-stop mode.
36563 The @var{reply} has the form of a stop reply, as
36564 described in @ref{Stop Reply Packets}. Refer to @ref{Remote Non-Stop},
36565 for information on how these notifications are acknowledged by
36569 @node Remote Non-Stop
36570 @section Remote Protocol Support for Non-Stop Mode
36572 @value{GDBN}'s remote protocol supports non-stop debugging of
36573 multi-threaded programs, as described in @ref{Non-Stop Mode}. If the stub
36574 supports non-stop mode, it should report that to @value{GDBN} by including
36575 @samp{QNonStop+} in its @samp{qSupported} response (@pxref{qSupported}).
36577 @value{GDBN} typically sends a @samp{QNonStop} packet only when
36578 establishing a new connection with the stub. Entering non-stop mode
36579 does not alter the state of any currently-running threads, but targets
36580 must stop all threads in any already-attached processes when entering
36581 all-stop mode. @value{GDBN} uses the @samp{?} packet as necessary to
36582 probe the target state after a mode change.
36584 In non-stop mode, when an attached process encounters an event that
36585 would otherwise be reported with a stop reply, it uses the
36586 asynchronous notification mechanism (@pxref{Notification Packets}) to
36587 inform @value{GDBN}. In contrast to all-stop mode, where all threads
36588 in all processes are stopped when a stop reply is sent, in non-stop
36589 mode only the thread reporting the stop event is stopped. That is,
36590 when reporting a @samp{S} or @samp{T} response to indicate completion
36591 of a step operation, hitting a breakpoint, or a fault, only the
36592 affected thread is stopped; any other still-running threads continue
36593 to run. When reporting a @samp{W} or @samp{X} response, all running
36594 threads belonging to other attached processes continue to run.
36596 Only one stop reply notification at a time may be pending; if
36597 additional stop events occur before @value{GDBN} has acknowledged the
36598 previous notification, they must be queued by the stub for later
36599 synchronous transmission in response to @samp{vStopped} packets from
36600 @value{GDBN}. Because the notification mechanism is unreliable,
36601 the stub is permitted to resend a stop reply notification
36602 if it believes @value{GDBN} may not have received it. @value{GDBN}
36603 ignores additional stop reply notifications received before it has
36604 finished processing a previous notification and the stub has completed
36605 sending any queued stop events.
36607 Otherwise, @value{GDBN} must be prepared to receive a stop reply
36608 notification at any time. Specifically, they may appear when
36609 @value{GDBN} is not otherwise reading input from the stub, or when
36610 @value{GDBN} is expecting to read a normal synchronous response or a
36611 @samp{+}/@samp{-} acknowledgment to a packet it has sent.
36612 Notification packets are distinct from any other communication from
36613 the stub so there is no ambiguity.
36615 After receiving a stop reply notification, @value{GDBN} shall
36616 acknowledge it by sending a @samp{vStopped} packet (@pxref{vStopped packet})
36617 as a regular, synchronous request to the stub. Such acknowledgment
36618 is not required to happen immediately, as @value{GDBN} is permitted to
36619 send other, unrelated packets to the stub first, which the stub should
36622 Upon receiving a @samp{vStopped} packet, if the stub has other queued
36623 stop events to report to @value{GDBN}, it shall respond by sending a
36624 normal stop reply response. @value{GDBN} shall then send another
36625 @samp{vStopped} packet to solicit further responses; again, it is
36626 permitted to send other, unrelated packets as well which the stub
36627 should process normally.
36629 If the stub receives a @samp{vStopped} packet and there are no
36630 additional stop events to report, the stub shall return an @samp{OK}
36631 response. At this point, if further stop events occur, the stub shall
36632 send a new stop reply notification, @value{GDBN} shall accept the
36633 notification, and the process shall be repeated.
36635 In non-stop mode, the target shall respond to the @samp{?} packet as
36636 follows. First, any incomplete stop reply notification/@samp{vStopped}
36637 sequence in progress is abandoned. The target must begin a new
36638 sequence reporting stop events for all stopped threads, whether or not
36639 it has previously reported those events to @value{GDBN}. The first
36640 stop reply is sent as a synchronous reply to the @samp{?} packet, and
36641 subsequent stop replies are sent as responses to @samp{vStopped} packets
36642 using the mechanism described above. The target must not send
36643 asynchronous stop reply notifications until the sequence is complete.
36644 If all threads are running when the target receives the @samp{?} packet,
36645 or if the target is not attached to any process, it shall respond
36648 @node Packet Acknowledgment
36649 @section Packet Acknowledgment
36651 @cindex acknowledgment, for @value{GDBN} remote
36652 @cindex packet acknowledgment, for @value{GDBN} remote
36653 By default, when either the host or the target machine receives a packet,
36654 the first response expected is an acknowledgment: either @samp{+} (to indicate
36655 the package was received correctly) or @samp{-} (to request retransmission).
36656 This mechanism allows the @value{GDBN} remote protocol to operate over
36657 unreliable transport mechanisms, such as a serial line.
36659 In cases where the transport mechanism is itself reliable (such as a pipe or
36660 TCP connection), the @samp{+}/@samp{-} acknowledgments are redundant.
36661 It may be desirable to disable them in that case to reduce communication
36662 overhead, or for other reasons. This can be accomplished by means of the
36663 @samp{QStartNoAckMode} packet; @pxref{QStartNoAckMode}.
36665 When in no-acknowledgment mode, neither the stub nor @value{GDBN} shall send or
36666 expect @samp{+}/@samp{-} protocol acknowledgments. The packet
36667 and response format still includes the normal checksum, as described in
36668 @ref{Overview}, but the checksum may be ignored by the receiver.
36670 If the stub supports @samp{QStartNoAckMode} and prefers to operate in
36671 no-acknowledgment mode, it should report that to @value{GDBN}
36672 by including @samp{QStartNoAckMode+} in its response to @samp{qSupported};
36673 @pxref{qSupported}.
36674 If @value{GDBN} also supports @samp{QStartNoAckMode} and it has not been
36675 disabled via the @code{set remote noack-packet off} command
36676 (@pxref{Remote Configuration}),
36677 @value{GDBN} may then send a @samp{QStartNoAckMode} packet to the stub.
36678 Only then may the stub actually turn off packet acknowledgments.
36679 @value{GDBN} sends a final @samp{+} acknowledgment of the stub's @samp{OK}
36680 response, which can be safely ignored by the stub.
36682 Note that @code{set remote noack-packet} command only affects negotiation
36683 between @value{GDBN} and the stub when subsequent connections are made;
36684 it does not affect the protocol acknowledgment state for any current
36686 Since @samp{+}/@samp{-} acknowledgments are enabled by default when a
36687 new connection is established,
36688 there is also no protocol request to re-enable the acknowledgments
36689 for the current connection, once disabled.
36694 Example sequence of a target being re-started. Notice how the restart
36695 does not get any direct output:
36700 @emph{target restarts}
36703 <- @code{T001:1234123412341234}
36707 Example sequence of a target being stepped by a single instruction:
36710 -> @code{G1445@dots{}}
36715 <- @code{T001:1234123412341234}
36719 <- @code{1455@dots{}}
36723 @node File-I/O Remote Protocol Extension
36724 @section File-I/O Remote Protocol Extension
36725 @cindex File-I/O remote protocol extension
36728 * File-I/O Overview::
36729 * Protocol Basics::
36730 * The F Request Packet::
36731 * The F Reply Packet::
36732 * The Ctrl-C Message::
36734 * List of Supported Calls::
36735 * Protocol-specific Representation of Datatypes::
36737 * File-I/O Examples::
36740 @node File-I/O Overview
36741 @subsection File-I/O Overview
36742 @cindex file-i/o overview
36744 The @dfn{File I/O remote protocol extension} (short: File-I/O) allows the
36745 target to use the host's file system and console I/O to perform various
36746 system calls. System calls on the target system are translated into a
36747 remote protocol packet to the host system, which then performs the needed
36748 actions and returns a response packet to the target system.
36749 This simulates file system operations even on targets that lack file systems.
36751 The protocol is defined to be independent of both the host and target systems.
36752 It uses its own internal representation of datatypes and values. Both
36753 @value{GDBN} and the target's @value{GDBN} stub are responsible for
36754 translating the system-dependent value representations into the internal
36755 protocol representations when data is transmitted.
36757 The communication is synchronous. A system call is possible only when
36758 @value{GDBN} is waiting for a response from the @samp{C}, @samp{c}, @samp{S}
36759 or @samp{s} packets. While @value{GDBN} handles the request for a system call,
36760 the target is stopped to allow deterministic access to the target's
36761 memory. Therefore File-I/O is not interruptible by target signals. On
36762 the other hand, it is possible to interrupt File-I/O by a user interrupt
36763 (@samp{Ctrl-C}) within @value{GDBN}.
36765 The target's request to perform a host system call does not finish
36766 the latest @samp{C}, @samp{c}, @samp{S} or @samp{s} action. That means,
36767 after finishing the system call, the target returns to continuing the
36768 previous activity (continue, step). No additional continue or step
36769 request from @value{GDBN} is required.
36772 (@value{GDBP}) continue
36773 <- target requests 'system call X'
36774 target is stopped, @value{GDBN} executes system call
36775 -> @value{GDBN} returns result
36776 ... target continues, @value{GDBN} returns to wait for the target
36777 <- target hits breakpoint and sends a Txx packet
36780 The protocol only supports I/O on the console and to regular files on
36781 the host file system. Character or block special devices, pipes,
36782 named pipes, sockets or any other communication method on the host
36783 system are not supported by this protocol.
36785 File I/O is not supported in non-stop mode.
36787 @node Protocol Basics
36788 @subsection Protocol Basics
36789 @cindex protocol basics, file-i/o
36791 The File-I/O protocol uses the @code{F} packet as the request as well
36792 as reply packet. Since a File-I/O system call can only occur when
36793 @value{GDBN} is waiting for a response from the continuing or stepping target,
36794 the File-I/O request is a reply that @value{GDBN} has to expect as a result
36795 of a previous @samp{C}, @samp{c}, @samp{S} or @samp{s} packet.
36796 This @code{F} packet contains all information needed to allow @value{GDBN}
36797 to call the appropriate host system call:
36801 A unique identifier for the requested system call.
36804 All parameters to the system call. Pointers are given as addresses
36805 in the target memory address space. Pointers to strings are given as
36806 pointer/length pair. Numerical values are given as they are.
36807 Numerical control flags are given in a protocol-specific representation.
36811 At this point, @value{GDBN} has to perform the following actions.
36815 If the parameters include pointer values to data needed as input to a
36816 system call, @value{GDBN} requests this data from the target with a
36817 standard @code{m} packet request. This additional communication has to be
36818 expected by the target implementation and is handled as any other @code{m}
36822 @value{GDBN} translates all value from protocol representation to host
36823 representation as needed. Datatypes are coerced into the host types.
36826 @value{GDBN} calls the system call.
36829 It then coerces datatypes back to protocol representation.
36832 If the system call is expected to return data in buffer space specified
36833 by pointer parameters to the call, the data is transmitted to the
36834 target using a @code{M} or @code{X} packet. This packet has to be expected
36835 by the target implementation and is handled as any other @code{M} or @code{X}
36840 Eventually @value{GDBN} replies with another @code{F} packet which contains all
36841 necessary information for the target to continue. This at least contains
36848 @code{errno}, if has been changed by the system call.
36855 After having done the needed type and value coercion, the target continues
36856 the latest continue or step action.
36858 @node The F Request Packet
36859 @subsection The @code{F} Request Packet
36860 @cindex file-i/o request packet
36861 @cindex @code{F} request packet
36863 The @code{F} request packet has the following format:
36866 @item F@var{call-id},@var{parameter@dots{}}
36868 @var{call-id} is the identifier to indicate the host system call to be called.
36869 This is just the name of the function.
36871 @var{parameter@dots{}} are the parameters to the system call.
36872 Parameters are hexadecimal integer values, either the actual values in case
36873 of scalar datatypes, pointers to target buffer space in case of compound
36874 datatypes and unspecified memory areas, or pointer/length pairs in case
36875 of string parameters. These are appended to the @var{call-id} as a
36876 comma-delimited list. All values are transmitted in ASCII
36877 string representation, pointer/length pairs separated by a slash.
36883 @node The F Reply Packet
36884 @subsection The @code{F} Reply Packet
36885 @cindex file-i/o reply packet
36886 @cindex @code{F} reply packet
36888 The @code{F} reply packet has the following format:
36892 @item F@var{retcode},@var{errno},@var{Ctrl-C flag};@var{call-specific attachment}
36894 @var{retcode} is the return code of the system call as hexadecimal value.
36896 @var{errno} is the @code{errno} set by the call, in protocol-specific
36898 This parameter can be omitted if the call was successful.
36900 @var{Ctrl-C flag} is only sent if the user requested a break. In this
36901 case, @var{errno} must be sent as well, even if the call was successful.
36902 The @var{Ctrl-C flag} itself consists of the character @samp{C}:
36909 or, if the call was interrupted before the host call has been performed:
36916 assuming 4 is the protocol-specific representation of @code{EINTR}.
36921 @node The Ctrl-C Message
36922 @subsection The @samp{Ctrl-C} Message
36923 @cindex ctrl-c message, in file-i/o protocol
36925 If the @samp{Ctrl-C} flag is set in the @value{GDBN}
36926 reply packet (@pxref{The F Reply Packet}),
36927 the target should behave as if it had
36928 gotten a break message. The meaning for the target is ``system call
36929 interrupted by @code{SIGINT}''. Consequentially, the target should actually stop
36930 (as with a break message) and return to @value{GDBN} with a @code{T02}
36933 It's important for the target to know in which
36934 state the system call was interrupted. There are two possible cases:
36938 The system call hasn't been performed on the host yet.
36941 The system call on the host has been finished.
36945 These two states can be distinguished by the target by the value of the
36946 returned @code{errno}. If it's the protocol representation of @code{EINTR}, the system
36947 call hasn't been performed. This is equivalent to the @code{EINTR} handling
36948 on POSIX systems. In any other case, the target may presume that the
36949 system call has been finished --- successfully or not --- and should behave
36950 as if the break message arrived right after the system call.
36952 @value{GDBN} must behave reliably. If the system call has not been called
36953 yet, @value{GDBN} may send the @code{F} reply immediately, setting @code{EINTR} as
36954 @code{errno} in the packet. If the system call on the host has been finished
36955 before the user requests a break, the full action must be finished by
36956 @value{GDBN}. This requires sending @code{M} or @code{X} packets as necessary.
36957 The @code{F} packet may only be sent when either nothing has happened
36958 or the full action has been completed.
36961 @subsection Console I/O
36962 @cindex console i/o as part of file-i/o
36964 By default and if not explicitly closed by the target system, the file
36965 descriptors 0, 1 and 2 are connected to the @value{GDBN} console. Output
36966 on the @value{GDBN} console is handled as any other file output operation
36967 (@code{write(1, @dots{})} or @code{write(2, @dots{})}). Console input is handled
36968 by @value{GDBN} so that after the target read request from file descriptor
36969 0 all following typing is buffered until either one of the following
36974 The user types @kbd{Ctrl-c}. The behaviour is as explained above, and the
36976 system call is treated as finished.
36979 The user presses @key{RET}. This is treated as end of input with a trailing
36983 The user types @kbd{Ctrl-d}. This is treated as end of input. No trailing
36984 character (neither newline nor @samp{Ctrl-D}) is appended to the input.
36988 If the user has typed more characters than fit in the buffer given to
36989 the @code{read} call, the trailing characters are buffered in @value{GDBN} until
36990 either another @code{read(0, @dots{})} is requested by the target, or debugging
36991 is stopped at the user's request.
36994 @node List of Supported Calls
36995 @subsection List of Supported Calls
36996 @cindex list of supported file-i/o calls
37013 @unnumberedsubsubsec open
37014 @cindex open, file-i/o system call
37019 int open(const char *pathname, int flags);
37020 int open(const char *pathname, int flags, mode_t mode);
37024 @samp{Fopen,@var{pathptr}/@var{len},@var{flags},@var{mode}}
37027 @var{flags} is the bitwise @code{OR} of the following values:
37031 If the file does not exist it will be created. The host
37032 rules apply as far as file ownership and time stamps
37036 When used with @code{O_CREAT}, if the file already exists it is
37037 an error and open() fails.
37040 If the file already exists and the open mode allows
37041 writing (@code{O_RDWR} or @code{O_WRONLY} is given) it will be
37042 truncated to zero length.
37045 The file is opened in append mode.
37048 The file is opened for reading only.
37051 The file is opened for writing only.
37054 The file is opened for reading and writing.
37058 Other bits are silently ignored.
37062 @var{mode} is the bitwise @code{OR} of the following values:
37066 User has read permission.
37069 User has write permission.
37072 Group has read permission.
37075 Group has write permission.
37078 Others have read permission.
37081 Others have write permission.
37085 Other bits are silently ignored.
37088 @item Return value:
37089 @code{open} returns the new file descriptor or -1 if an error
37096 @var{pathname} already exists and @code{O_CREAT} and @code{O_EXCL} were used.
37099 @var{pathname} refers to a directory.
37102 The requested access is not allowed.
37105 @var{pathname} was too long.
37108 A directory component in @var{pathname} does not exist.
37111 @var{pathname} refers to a device, pipe, named pipe or socket.
37114 @var{pathname} refers to a file on a read-only filesystem and
37115 write access was requested.
37118 @var{pathname} is an invalid pointer value.
37121 No space on device to create the file.
37124 The process already has the maximum number of files open.
37127 The limit on the total number of files open on the system
37131 The call was interrupted by the user.
37137 @unnumberedsubsubsec close
37138 @cindex close, file-i/o system call
37147 @samp{Fclose,@var{fd}}
37149 @item Return value:
37150 @code{close} returns zero on success, or -1 if an error occurred.
37156 @var{fd} isn't a valid open file descriptor.
37159 The call was interrupted by the user.
37165 @unnumberedsubsubsec read
37166 @cindex read, file-i/o system call
37171 int read(int fd, void *buf, unsigned int count);
37175 @samp{Fread,@var{fd},@var{bufptr},@var{count}}
37177 @item Return value:
37178 On success, the number of bytes read is returned.
37179 Zero indicates end of file. If count is zero, read
37180 returns zero as well. On error, -1 is returned.
37186 @var{fd} is not a valid file descriptor or is not open for
37190 @var{bufptr} is an invalid pointer value.
37193 The call was interrupted by the user.
37199 @unnumberedsubsubsec write
37200 @cindex write, file-i/o system call
37205 int write(int fd, const void *buf, unsigned int count);
37209 @samp{Fwrite,@var{fd},@var{bufptr},@var{count}}
37211 @item Return value:
37212 On success, the number of bytes written are returned.
37213 Zero indicates nothing was written. On error, -1
37220 @var{fd} is not a valid file descriptor or is not open for
37224 @var{bufptr} is an invalid pointer value.
37227 An attempt was made to write a file that exceeds the
37228 host-specific maximum file size allowed.
37231 No space on device to write the data.
37234 The call was interrupted by the user.
37240 @unnumberedsubsubsec lseek
37241 @cindex lseek, file-i/o system call
37246 long lseek (int fd, long offset, int flag);
37250 @samp{Flseek,@var{fd},@var{offset},@var{flag}}
37252 @var{flag} is one of:
37256 The offset is set to @var{offset} bytes.
37259 The offset is set to its current location plus @var{offset}
37263 The offset is set to the size of the file plus @var{offset}
37267 @item Return value:
37268 On success, the resulting unsigned offset in bytes from
37269 the beginning of the file is returned. Otherwise, a
37270 value of -1 is returned.
37276 @var{fd} is not a valid open file descriptor.
37279 @var{fd} is associated with the @value{GDBN} console.
37282 @var{flag} is not a proper value.
37285 The call was interrupted by the user.
37291 @unnumberedsubsubsec rename
37292 @cindex rename, file-i/o system call
37297 int rename(const char *oldpath, const char *newpath);
37301 @samp{Frename,@var{oldpathptr}/@var{len},@var{newpathptr}/@var{len}}
37303 @item Return value:
37304 On success, zero is returned. On error, -1 is returned.
37310 @var{newpath} is an existing directory, but @var{oldpath} is not a
37314 @var{newpath} is a non-empty directory.
37317 @var{oldpath} or @var{newpath} is a directory that is in use by some
37321 An attempt was made to make a directory a subdirectory
37325 A component used as a directory in @var{oldpath} or new
37326 path is not a directory. Or @var{oldpath} is a directory
37327 and @var{newpath} exists but is not a directory.
37330 @var{oldpathptr} or @var{newpathptr} are invalid pointer values.
37333 No access to the file or the path of the file.
37337 @var{oldpath} or @var{newpath} was too long.
37340 A directory component in @var{oldpath} or @var{newpath} does not exist.
37343 The file is on a read-only filesystem.
37346 The device containing the file has no room for the new
37350 The call was interrupted by the user.
37356 @unnumberedsubsubsec unlink
37357 @cindex unlink, file-i/o system call
37362 int unlink(const char *pathname);
37366 @samp{Funlink,@var{pathnameptr}/@var{len}}
37368 @item Return value:
37369 On success, zero is returned. On error, -1 is returned.
37375 No access to the file or the path of the file.
37378 The system does not allow unlinking of directories.
37381 The file @var{pathname} cannot be unlinked because it's
37382 being used by another process.
37385 @var{pathnameptr} is an invalid pointer value.
37388 @var{pathname} was too long.
37391 A directory component in @var{pathname} does not exist.
37394 A component of the path is not a directory.
37397 The file is on a read-only filesystem.
37400 The call was interrupted by the user.
37406 @unnumberedsubsubsec stat/fstat
37407 @cindex fstat, file-i/o system call
37408 @cindex stat, file-i/o system call
37413 int stat(const char *pathname, struct stat *buf);
37414 int fstat(int fd, struct stat *buf);
37418 @samp{Fstat,@var{pathnameptr}/@var{len},@var{bufptr}}@*
37419 @samp{Ffstat,@var{fd},@var{bufptr}}
37421 @item Return value:
37422 On success, zero is returned. On error, -1 is returned.
37428 @var{fd} is not a valid open file.
37431 A directory component in @var{pathname} does not exist or the
37432 path is an empty string.
37435 A component of the path is not a directory.
37438 @var{pathnameptr} is an invalid pointer value.
37441 No access to the file or the path of the file.
37444 @var{pathname} was too long.
37447 The call was interrupted by the user.
37453 @unnumberedsubsubsec gettimeofday
37454 @cindex gettimeofday, file-i/o system call
37459 int gettimeofday(struct timeval *tv, void *tz);
37463 @samp{Fgettimeofday,@var{tvptr},@var{tzptr}}
37465 @item Return value:
37466 On success, 0 is returned, -1 otherwise.
37472 @var{tz} is a non-NULL pointer.
37475 @var{tvptr} and/or @var{tzptr} is an invalid pointer value.
37481 @unnumberedsubsubsec isatty
37482 @cindex isatty, file-i/o system call
37487 int isatty(int fd);
37491 @samp{Fisatty,@var{fd}}
37493 @item Return value:
37494 Returns 1 if @var{fd} refers to the @value{GDBN} console, 0 otherwise.
37500 The call was interrupted by the user.
37505 Note that the @code{isatty} call is treated as a special case: it returns
37506 1 to the target if the file descriptor is attached
37507 to the @value{GDBN} console, 0 otherwise. Implementing through system calls
37508 would require implementing @code{ioctl} and would be more complex than
37513 @unnumberedsubsubsec system
37514 @cindex system, file-i/o system call
37519 int system(const char *command);
37523 @samp{Fsystem,@var{commandptr}/@var{len}}
37525 @item Return value:
37526 If @var{len} is zero, the return value indicates whether a shell is
37527 available. A zero return value indicates a shell is not available.
37528 For non-zero @var{len}, the value returned is -1 on error and the
37529 return status of the command otherwise. Only the exit status of the
37530 command is returned, which is extracted from the host's @code{system}
37531 return value by calling @code{WEXITSTATUS(retval)}. In case
37532 @file{/bin/sh} could not be executed, 127 is returned.
37538 The call was interrupted by the user.
37543 @value{GDBN} takes over the full task of calling the necessary host calls
37544 to perform the @code{system} call. The return value of @code{system} on
37545 the host is simplified before it's returned
37546 to the target. Any termination signal information from the child process
37547 is discarded, and the return value consists
37548 entirely of the exit status of the called command.
37550 Due to security concerns, the @code{system} call is by default refused
37551 by @value{GDBN}. The user has to allow this call explicitly with the
37552 @code{set remote system-call-allowed 1} command.
37555 @item set remote system-call-allowed
37556 @kindex set remote system-call-allowed
37557 Control whether to allow the @code{system} calls in the File I/O
37558 protocol for the remote target. The default is zero (disabled).
37560 @item show remote system-call-allowed
37561 @kindex show remote system-call-allowed
37562 Show whether the @code{system} calls are allowed in the File I/O
37566 @node Protocol-specific Representation of Datatypes
37567 @subsection Protocol-specific Representation of Datatypes
37568 @cindex protocol-specific representation of datatypes, in file-i/o protocol
37571 * Integral Datatypes::
37573 * Memory Transfer::
37578 @node Integral Datatypes
37579 @unnumberedsubsubsec Integral Datatypes
37580 @cindex integral datatypes, in file-i/o protocol
37582 The integral datatypes used in the system calls are @code{int},
37583 @code{unsigned int}, @code{long}, @code{unsigned long},
37584 @code{mode_t}, and @code{time_t}.
37586 @code{int}, @code{unsigned int}, @code{mode_t} and @code{time_t} are
37587 implemented as 32 bit values in this protocol.
37589 @code{long} and @code{unsigned long} are implemented as 64 bit types.
37591 @xref{Limits}, for corresponding MIN and MAX values (similar to those
37592 in @file{limits.h}) to allow range checking on host and target.
37594 @code{time_t} datatypes are defined as seconds since the Epoch.
37596 All integral datatypes transferred as part of a memory read or write of a
37597 structured datatype e.g.@: a @code{struct stat} have to be given in big endian
37600 @node Pointer Values
37601 @unnumberedsubsubsec Pointer Values
37602 @cindex pointer values, in file-i/o protocol
37604 Pointers to target data are transmitted as they are. An exception
37605 is made for pointers to buffers for which the length isn't
37606 transmitted as part of the function call, namely strings. Strings
37607 are transmitted as a pointer/length pair, both as hex values, e.g.@:
37614 which is a pointer to data of length 18 bytes at position 0x1aaf.
37615 The length is defined as the full string length in bytes, including
37616 the trailing null byte. For example, the string @code{"hello world"}
37617 at address 0x123456 is transmitted as
37623 @node Memory Transfer
37624 @unnumberedsubsubsec Memory Transfer
37625 @cindex memory transfer, in file-i/o protocol
37627 Structured data which is transferred using a memory read or write (for
37628 example, a @code{struct stat}) is expected to be in a protocol-specific format
37629 with all scalar multibyte datatypes being big endian. Translation to
37630 this representation needs to be done both by the target before the @code{F}
37631 packet is sent, and by @value{GDBN} before
37632 it transfers memory to the target. Transferred pointers to structured
37633 data should point to the already-coerced data at any time.
37637 @unnumberedsubsubsec struct stat
37638 @cindex struct stat, in file-i/o protocol
37640 The buffer of type @code{struct stat} used by the target and @value{GDBN}
37641 is defined as follows:
37645 unsigned int st_dev; /* device */
37646 unsigned int st_ino; /* inode */
37647 mode_t st_mode; /* protection */
37648 unsigned int st_nlink; /* number of hard links */
37649 unsigned int st_uid; /* user ID of owner */
37650 unsigned int st_gid; /* group ID of owner */
37651 unsigned int st_rdev; /* device type (if inode device) */
37652 unsigned long st_size; /* total size, in bytes */
37653 unsigned long st_blksize; /* blocksize for filesystem I/O */
37654 unsigned long st_blocks; /* number of blocks allocated */
37655 time_t st_atime; /* time of last access */
37656 time_t st_mtime; /* time of last modification */
37657 time_t st_ctime; /* time of last change */
37661 The integral datatypes conform to the definitions given in the
37662 appropriate section (see @ref{Integral Datatypes}, for details) so this
37663 structure is of size 64 bytes.
37665 The values of several fields have a restricted meaning and/or
37671 A value of 0 represents a file, 1 the console.
37674 No valid meaning for the target. Transmitted unchanged.
37677 Valid mode bits are described in @ref{Constants}. Any other
37678 bits have currently no meaning for the target.
37683 No valid meaning for the target. Transmitted unchanged.
37688 These values have a host and file system dependent
37689 accuracy. Especially on Windows hosts, the file system may not
37690 support exact timing values.
37693 The target gets a @code{struct stat} of the above representation and is
37694 responsible for coercing it to the target representation before
37697 Note that due to size differences between the host, target, and protocol
37698 representations of @code{struct stat} members, these members could eventually
37699 get truncated on the target.
37701 @node struct timeval
37702 @unnumberedsubsubsec struct timeval
37703 @cindex struct timeval, in file-i/o protocol
37705 The buffer of type @code{struct timeval} used by the File-I/O protocol
37706 is defined as follows:
37710 time_t tv_sec; /* second */
37711 long tv_usec; /* microsecond */
37715 The integral datatypes conform to the definitions given in the
37716 appropriate section (see @ref{Integral Datatypes}, for details) so this
37717 structure is of size 8 bytes.
37720 @subsection Constants
37721 @cindex constants, in file-i/o protocol
37723 The following values are used for the constants inside of the
37724 protocol. @value{GDBN} and target are responsible for translating these
37725 values before and after the call as needed.
37736 @unnumberedsubsubsec Open Flags
37737 @cindex open flags, in file-i/o protocol
37739 All values are given in hexadecimal representation.
37751 @node mode_t Values
37752 @unnumberedsubsubsec mode_t Values
37753 @cindex mode_t values, in file-i/o protocol
37755 All values are given in octal representation.
37772 @unnumberedsubsubsec Errno Values
37773 @cindex errno values, in file-i/o protocol
37775 All values are given in decimal representation.
37800 @code{EUNKNOWN} is used as a fallback error value if a host system returns
37801 any error value not in the list of supported error numbers.
37804 @unnumberedsubsubsec Lseek Flags
37805 @cindex lseek flags, in file-i/o protocol
37814 @unnumberedsubsubsec Limits
37815 @cindex limits, in file-i/o protocol
37817 All values are given in decimal representation.
37820 INT_MIN -2147483648
37822 UINT_MAX 4294967295
37823 LONG_MIN -9223372036854775808
37824 LONG_MAX 9223372036854775807
37825 ULONG_MAX 18446744073709551615
37828 @node File-I/O Examples
37829 @subsection File-I/O Examples
37830 @cindex file-i/o examples
37832 Example sequence of a write call, file descriptor 3, buffer is at target
37833 address 0x1234, 6 bytes should be written:
37836 <- @code{Fwrite,3,1234,6}
37837 @emph{request memory read from target}
37840 @emph{return "6 bytes written"}
37844 Example sequence of a read call, file descriptor 3, buffer is at target
37845 address 0x1234, 6 bytes should be read:
37848 <- @code{Fread,3,1234,6}
37849 @emph{request memory write to target}
37850 -> @code{X1234,6:XXXXXX}
37851 @emph{return "6 bytes read"}
37855 Example sequence of a read call, call fails on the host due to invalid
37856 file descriptor (@code{EBADF}):
37859 <- @code{Fread,3,1234,6}
37863 Example sequence of a read call, user presses @kbd{Ctrl-c} before syscall on
37867 <- @code{Fread,3,1234,6}
37872 Example sequence of a read call, user presses @kbd{Ctrl-c} after syscall on
37876 <- @code{Fread,3,1234,6}
37877 -> @code{X1234,6:XXXXXX}
37881 @node Library List Format
37882 @section Library List Format
37883 @cindex library list format, remote protocol
37885 On some platforms, a dynamic loader (e.g.@: @file{ld.so}) runs in the
37886 same process as your application to manage libraries. In this case,
37887 @value{GDBN} can use the loader's symbol table and normal memory
37888 operations to maintain a list of shared libraries. On other
37889 platforms, the operating system manages loaded libraries.
37890 @value{GDBN} can not retrieve the list of currently loaded libraries
37891 through memory operations, so it uses the @samp{qXfer:libraries:read}
37892 packet (@pxref{qXfer library list read}) instead. The remote stub
37893 queries the target's operating system and reports which libraries
37896 The @samp{qXfer:libraries:read} packet returns an XML document which
37897 lists loaded libraries and their offsets. Each library has an
37898 associated name and one or more segment or section base addresses,
37899 which report where the library was loaded in memory.
37901 For the common case of libraries that are fully linked binaries, the
37902 library should have a list of segments. If the target supports
37903 dynamic linking of a relocatable object file, its library XML element
37904 should instead include a list of allocated sections. The segment or
37905 section bases are start addresses, not relocation offsets; they do not
37906 depend on the library's link-time base addresses.
37908 @value{GDBN} must be linked with the Expat library to support XML
37909 library lists. @xref{Expat}.
37911 A simple memory map, with one loaded library relocated by a single
37912 offset, looks like this:
37916 <library name="/lib/libc.so.6">
37917 <segment address="0x10000000"/>
37922 Another simple memory map, with one loaded library with three
37923 allocated sections (.text, .data, .bss), looks like this:
37927 <library name="sharedlib.o">
37928 <section address="0x10000000"/>
37929 <section address="0x20000000"/>
37930 <section address="0x30000000"/>
37935 The format of a library list is described by this DTD:
37938 <!-- library-list: Root element with versioning -->
37939 <!ELEMENT library-list (library)*>
37940 <!ATTLIST library-list version CDATA #FIXED "1.0">
37941 <!ELEMENT library (segment*, section*)>
37942 <!ATTLIST library name CDATA #REQUIRED>
37943 <!ELEMENT segment EMPTY>
37944 <!ATTLIST segment address CDATA #REQUIRED>
37945 <!ELEMENT section EMPTY>
37946 <!ATTLIST section address CDATA #REQUIRED>
37949 In addition, segments and section descriptors cannot be mixed within a
37950 single library element, and you must supply at least one segment or
37951 section for each library.
37953 @node Library List Format for SVR4 Targets
37954 @section Library List Format for SVR4 Targets
37955 @cindex library list format, remote protocol
37957 On SVR4 platforms @value{GDBN} can use the symbol table of a dynamic loader
37958 (e.g.@: @file{ld.so}) and normal memory operations to maintain a list of
37959 shared libraries. Still a special library list provided by this packet is
37960 more efficient for the @value{GDBN} remote protocol.
37962 The @samp{qXfer:libraries-svr4:read} packet returns an XML document which lists
37963 loaded libraries and their SVR4 linker parameters. For each library on SVR4
37964 target, the following parameters are reported:
37968 @code{name}, the absolute file name from the @code{l_name} field of
37969 @code{struct link_map}.
37971 @code{lm} with address of @code{struct link_map} used for TLS
37972 (Thread Local Storage) access.
37974 @code{l_addr}, the displacement as read from the field @code{l_addr} of
37975 @code{struct link_map}. For prelinked libraries this is not an absolute
37976 memory address. It is a displacement of absolute memory address against
37977 address the file was prelinked to during the library load.
37979 @code{l_ld}, which is memory address of the @code{PT_DYNAMIC} segment
37982 Additionally the single @code{main-lm} attribute specifies address of
37983 @code{struct link_map} used for the main executable. This parameter is used
37984 for TLS access and its presence is optional.
37986 @value{GDBN} must be linked with the Expat library to support XML
37987 SVR4 library lists. @xref{Expat}.
37989 A simple memory map, with two loaded libraries (which do not use prelink),
37993 <library-list-svr4 version="1.0" main-lm="0xe4f8f8">
37994 <library name="/lib/ld-linux.so.2" lm="0xe4f51c" l_addr="0xe2d000"
37996 <library name="/lib/libc.so.6" lm="0xe4fbe8" l_addr="0x154000"
37998 </library-list-svr>
38001 The format of an SVR4 library list is described by this DTD:
38004 <!-- library-list-svr4: Root element with versioning -->
38005 <!ELEMENT library-list-svr4 (library)*>
38006 <!ATTLIST library-list-svr4 version CDATA #FIXED "1.0">
38007 <!ATTLIST library-list-svr4 main-lm CDATA #IMPLIED>
38008 <!ELEMENT library EMPTY>
38009 <!ATTLIST library name CDATA #REQUIRED>
38010 <!ATTLIST library lm CDATA #REQUIRED>
38011 <!ATTLIST library l_addr CDATA #REQUIRED>
38012 <!ATTLIST library l_ld CDATA #REQUIRED>
38015 @node Memory Map Format
38016 @section Memory Map Format
38017 @cindex memory map format
38019 To be able to write into flash memory, @value{GDBN} needs to obtain a
38020 memory map from the target. This section describes the format of the
38023 The memory map is obtained using the @samp{qXfer:memory-map:read}
38024 (@pxref{qXfer memory map read}) packet and is an XML document that
38025 lists memory regions.
38027 @value{GDBN} must be linked with the Expat library to support XML
38028 memory maps. @xref{Expat}.
38030 The top-level structure of the document is shown below:
38033 <?xml version="1.0"?>
38034 <!DOCTYPE memory-map
38035 PUBLIC "+//IDN gnu.org//DTD GDB Memory Map V1.0//EN"
38036 "http://sourceware.org/gdb/gdb-memory-map.dtd">
38042 Each region can be either:
38047 A region of RAM starting at @var{addr} and extending for @var{length}
38051 <memory type="ram" start="@var{addr}" length="@var{length}"/>
38056 A region of read-only memory:
38059 <memory type="rom" start="@var{addr}" length="@var{length}"/>
38064 A region of flash memory, with erasure blocks @var{blocksize}
38068 <memory type="flash" start="@var{addr}" length="@var{length}">
38069 <property name="blocksize">@var{blocksize}</property>
38075 Regions must not overlap. @value{GDBN} assumes that areas of memory not covered
38076 by the memory map are RAM, and uses the ordinary @samp{M} and @samp{X}
38077 packets to write to addresses in such ranges.
38079 The formal DTD for memory map format is given below:
38082 <!-- ................................................... -->
38083 <!-- Memory Map XML DTD ................................ -->
38084 <!-- File: memory-map.dtd .............................. -->
38085 <!-- .................................... .............. -->
38086 <!-- memory-map.dtd -->
38087 <!-- memory-map: Root element with versioning -->
38088 <!ELEMENT memory-map (memory | property)>
38089 <!ATTLIST memory-map version CDATA #FIXED "1.0.0">
38090 <!ELEMENT memory (property)>
38091 <!-- memory: Specifies a memory region,
38092 and its type, or device. -->
38093 <!ATTLIST memory type CDATA #REQUIRED
38094 start CDATA #REQUIRED
38095 length CDATA #REQUIRED
38096 device CDATA #IMPLIED>
38097 <!-- property: Generic attribute tag -->
38098 <!ELEMENT property (#PCDATA | property)*>
38099 <!ATTLIST property name CDATA #REQUIRED>
38102 @node Thread List Format
38103 @section Thread List Format
38104 @cindex thread list format
38106 To efficiently update the list of threads and their attributes,
38107 @value{GDBN} issues the @samp{qXfer:threads:read} packet
38108 (@pxref{qXfer threads read}) and obtains the XML document with
38109 the following structure:
38112 <?xml version="1.0"?>
38114 <thread id="id" core="0">
38115 ... description ...
38120 Each @samp{thread} element must have the @samp{id} attribute that
38121 identifies the thread (@pxref{thread-id syntax}). The
38122 @samp{core} attribute, if present, specifies which processor core
38123 the thread was last executing on. The content of the of @samp{thread}
38124 element is interpreted as human-readable auxilliary information.
38126 @node Traceframe Info Format
38127 @section Traceframe Info Format
38128 @cindex traceframe info format
38130 To be able to know which objects in the inferior can be examined when
38131 inspecting a tracepoint hit, @value{GDBN} needs to obtain the list of
38132 memory ranges, registers and trace state variables that have been
38133 collected in a traceframe.
38135 This list is obtained using the @samp{qXfer:traceframe-info:read}
38136 (@pxref{qXfer traceframe info read}) packet and is an XML document.
38138 @value{GDBN} must be linked with the Expat library to support XML
38139 traceframe info discovery. @xref{Expat}.
38141 The top-level structure of the document is shown below:
38144 <?xml version="1.0"?>
38145 <!DOCTYPE traceframe-info
38146 PUBLIC "+//IDN gnu.org//DTD GDB Memory Map V1.0//EN"
38147 "http://sourceware.org/gdb/gdb-traceframe-info.dtd">
38153 Each traceframe block can be either:
38158 A region of collected memory starting at @var{addr} and extending for
38159 @var{length} bytes from there:
38162 <memory start="@var{addr}" length="@var{length}"/>
38167 The formal DTD for the traceframe info format is given below:
38170 <!ELEMENT traceframe-info (memory)* >
38171 <!ATTLIST traceframe-info version CDATA #FIXED "1.0">
38173 <!ELEMENT memory EMPTY>
38174 <!ATTLIST memory start CDATA #REQUIRED
38175 length CDATA #REQUIRED>
38178 @include agentexpr.texi
38180 @node Target Descriptions
38181 @appendix Target Descriptions
38182 @cindex target descriptions
38184 One of the challenges of using @value{GDBN} to debug embedded systems
38185 is that there are so many minor variants of each processor
38186 architecture in use. It is common practice for vendors to start with
38187 a standard processor core --- ARM, PowerPC, or MIPS, for example ---
38188 and then make changes to adapt it to a particular market niche. Some
38189 architectures have hundreds of variants, available from dozens of
38190 vendors. This leads to a number of problems:
38194 With so many different customized processors, it is difficult for
38195 the @value{GDBN} maintainers to keep up with the changes.
38197 Since individual variants may have short lifetimes or limited
38198 audiences, it may not be worthwhile to carry information about every
38199 variant in the @value{GDBN} source tree.
38201 When @value{GDBN} does support the architecture of the embedded system
38202 at hand, the task of finding the correct architecture name to give the
38203 @command{set architecture} command can be error-prone.
38206 To address these problems, the @value{GDBN} remote protocol allows a
38207 target system to not only identify itself to @value{GDBN}, but to
38208 actually describe its own features. This lets @value{GDBN} support
38209 processor variants it has never seen before --- to the extent that the
38210 descriptions are accurate, and that @value{GDBN} understands them.
38212 @value{GDBN} must be linked with the Expat library to support XML
38213 target descriptions. @xref{Expat}.
38216 * Retrieving Descriptions:: How descriptions are fetched from a target.
38217 * Target Description Format:: The contents of a target description.
38218 * Predefined Target Types:: Standard types available for target
38220 * Standard Target Features:: Features @value{GDBN} knows about.
38223 @node Retrieving Descriptions
38224 @section Retrieving Descriptions
38226 Target descriptions can be read from the target automatically, or
38227 specified by the user manually. The default behavior is to read the
38228 description from the target. @value{GDBN} retrieves it via the remote
38229 protocol using @samp{qXfer} requests (@pxref{General Query Packets,
38230 qXfer}). The @var{annex} in the @samp{qXfer} packet will be
38231 @samp{target.xml}. The contents of the @samp{target.xml} annex are an
38232 XML document, of the form described in @ref{Target Description
38235 Alternatively, you can specify a file to read for the target description.
38236 If a file is set, the target will not be queried. The commands to
38237 specify a file are:
38240 @cindex set tdesc filename
38241 @item set tdesc filename @var{path}
38242 Read the target description from @var{path}.
38244 @cindex unset tdesc filename
38245 @item unset tdesc filename
38246 Do not read the XML target description from a file. @value{GDBN}
38247 will use the description supplied by the current target.
38249 @cindex show tdesc filename
38250 @item show tdesc filename
38251 Show the filename to read for a target description, if any.
38255 @node Target Description Format
38256 @section Target Description Format
38257 @cindex target descriptions, XML format
38259 A target description annex is an @uref{http://www.w3.org/XML/, XML}
38260 document which complies with the Document Type Definition provided in
38261 the @value{GDBN} sources in @file{gdb/features/gdb-target.dtd}. This
38262 means you can use generally available tools like @command{xmllint} to
38263 check that your feature descriptions are well-formed and valid.
38264 However, to help people unfamiliar with XML write descriptions for
38265 their targets, we also describe the grammar here.
38267 Target descriptions can identify the architecture of the remote target
38268 and (for some architectures) provide information about custom register
38269 sets. They can also identify the OS ABI of the remote target.
38270 @value{GDBN} can use this information to autoconfigure for your
38271 target, or to warn you if you connect to an unsupported target.
38273 Here is a simple target description:
38276 <target version="1.0">
38277 <architecture>i386:x86-64</architecture>
38282 This minimal description only says that the target uses
38283 the x86-64 architecture.
38285 A target description has the following overall form, with [ ] marking
38286 optional elements and @dots{} marking repeatable elements. The elements
38287 are explained further below.
38290 <?xml version="1.0"?>
38291 <!DOCTYPE target SYSTEM "gdb-target.dtd">
38292 <target version="1.0">
38293 @r{[}@var{architecture}@r{]}
38294 @r{[}@var{osabi}@r{]}
38295 @r{[}@var{compatible}@r{]}
38296 @r{[}@var{feature}@dots{}@r{]}
38301 The description is generally insensitive to whitespace and line
38302 breaks, under the usual common-sense rules. The XML version
38303 declaration and document type declaration can generally be omitted
38304 (@value{GDBN} does not require them), but specifying them may be
38305 useful for XML validation tools. The @samp{version} attribute for
38306 @samp{<target>} may also be omitted, but we recommend
38307 including it; if future versions of @value{GDBN} use an incompatible
38308 revision of @file{gdb-target.dtd}, they will detect and report
38309 the version mismatch.
38311 @subsection Inclusion
38312 @cindex target descriptions, inclusion
38315 @cindex <xi:include>
38318 It can sometimes be valuable to split a target description up into
38319 several different annexes, either for organizational purposes, or to
38320 share files between different possible target descriptions. You can
38321 divide a description into multiple files by replacing any element of
38322 the target description with an inclusion directive of the form:
38325 <xi:include href="@var{document}"/>
38329 When @value{GDBN} encounters an element of this form, it will retrieve
38330 the named XML @var{document}, and replace the inclusion directive with
38331 the contents of that document. If the current description was read
38332 using @samp{qXfer}, then so will be the included document;
38333 @var{document} will be interpreted as the name of an annex. If the
38334 current description was read from a file, @value{GDBN} will look for
38335 @var{document} as a file in the same directory where it found the
38336 original description.
38338 @subsection Architecture
38339 @cindex <architecture>
38341 An @samp{<architecture>} element has this form:
38344 <architecture>@var{arch}</architecture>
38347 @var{arch} is one of the architectures from the set accepted by
38348 @code{set architecture} (@pxref{Targets, ,Specifying a Debugging Target}).
38351 @cindex @code{<osabi>}
38353 This optional field was introduced in @value{GDBN} version 7.0.
38354 Previous versions of @value{GDBN} ignore it.
38356 An @samp{<osabi>} element has this form:
38359 <osabi>@var{abi-name}</osabi>
38362 @var{abi-name} is an OS ABI name from the same selection accepted by
38363 @w{@code{set osabi}} (@pxref{ABI, ,Configuring the Current ABI}).
38365 @subsection Compatible Architecture
38366 @cindex @code{<compatible>}
38368 This optional field was introduced in @value{GDBN} version 7.0.
38369 Previous versions of @value{GDBN} ignore it.
38371 A @samp{<compatible>} element has this form:
38374 <compatible>@var{arch}</compatible>
38377 @var{arch} is one of the architectures from the set accepted by
38378 @code{set architecture} (@pxref{Targets, ,Specifying a Debugging Target}).
38380 A @samp{<compatible>} element is used to specify that the target
38381 is able to run binaries in some other than the main target architecture
38382 given by the @samp{<architecture>} element. For example, on the
38383 Cell Broadband Engine, the main architecture is @code{powerpc:common}
38384 or @code{powerpc:common64}, but the system is able to run binaries
38385 in the @code{spu} architecture as well. The way to describe this
38386 capability with @samp{<compatible>} is as follows:
38389 <architecture>powerpc:common</architecture>
38390 <compatible>spu</compatible>
38393 @subsection Features
38396 Each @samp{<feature>} describes some logical portion of the target
38397 system. Features are currently used to describe available CPU
38398 registers and the types of their contents. A @samp{<feature>} element
38402 <feature name="@var{name}">
38403 @r{[}@var{type}@dots{}@r{]}
38409 Each feature's name should be unique within the description. The name
38410 of a feature does not matter unless @value{GDBN} has some special
38411 knowledge of the contents of that feature; if it does, the feature
38412 should have its standard name. @xref{Standard Target Features}.
38416 Any register's value is a collection of bits which @value{GDBN} must
38417 interpret. The default interpretation is a two's complement integer,
38418 but other types can be requested by name in the register description.
38419 Some predefined types are provided by @value{GDBN} (@pxref{Predefined
38420 Target Types}), and the description can define additional composite types.
38422 Each type element must have an @samp{id} attribute, which gives
38423 a unique (within the containing @samp{<feature>}) name to the type.
38424 Types must be defined before they are used.
38427 Some targets offer vector registers, which can be treated as arrays
38428 of scalar elements. These types are written as @samp{<vector>} elements,
38429 specifying the array element type, @var{type}, and the number of elements,
38433 <vector id="@var{id}" type="@var{type}" count="@var{count}"/>
38437 If a register's value is usefully viewed in multiple ways, define it
38438 with a union type containing the useful representations. The
38439 @samp{<union>} element contains one or more @samp{<field>} elements,
38440 each of which has a @var{name} and a @var{type}:
38443 <union id="@var{id}">
38444 <field name="@var{name}" type="@var{type}"/>
38450 If a register's value is composed from several separate values, define
38451 it with a structure type. There are two forms of the @samp{<struct>}
38452 element; a @samp{<struct>} element must either contain only bitfields
38453 or contain no bitfields. If the structure contains only bitfields,
38454 its total size in bytes must be specified, each bitfield must have an
38455 explicit start and end, and bitfields are automatically assigned an
38456 integer type. The field's @var{start} should be less than or
38457 equal to its @var{end}, and zero represents the least significant bit.
38460 <struct id="@var{id}" size="@var{size}">
38461 <field name="@var{name}" start="@var{start}" end="@var{end}"/>
38466 If the structure contains no bitfields, then each field has an
38467 explicit type, and no implicit padding is added.
38470 <struct id="@var{id}">
38471 <field name="@var{name}" type="@var{type}"/>
38477 If a register's value is a series of single-bit flags, define it with
38478 a flags type. The @samp{<flags>} element has an explicit @var{size}
38479 and contains one or more @samp{<field>} elements. Each field has a
38480 @var{name}, a @var{start}, and an @var{end}. Only single-bit flags
38484 <flags id="@var{id}" size="@var{size}">
38485 <field name="@var{name}" start="@var{start}" end="@var{end}"/>
38490 @subsection Registers
38493 Each register is represented as an element with this form:
38496 <reg name="@var{name}"
38497 bitsize="@var{size}"
38498 @r{[}regnum="@var{num}"@r{]}
38499 @r{[}save-restore="@var{save-restore}"@r{]}
38500 @r{[}type="@var{type}"@r{]}
38501 @r{[}group="@var{group}"@r{]}/>
38505 The components are as follows:
38510 The register's name; it must be unique within the target description.
38513 The register's size, in bits.
38516 The register's number. If omitted, a register's number is one greater
38517 than that of the previous register (either in the current feature or in
38518 a preceding feature); the first register in the target description
38519 defaults to zero. This register number is used to read or write
38520 the register; e.g.@: it is used in the remote @code{p} and @code{P}
38521 packets, and registers appear in the @code{g} and @code{G} packets
38522 in order of increasing register number.
38525 Whether the register should be preserved across inferior function
38526 calls; this must be either @code{yes} or @code{no}. The default is
38527 @code{yes}, which is appropriate for most registers except for
38528 some system control registers; this is not related to the target's
38532 The type of the register. @var{type} may be a predefined type, a type
38533 defined in the current feature, or one of the special types @code{int}
38534 and @code{float}. @code{int} is an integer type of the correct size
38535 for @var{bitsize}, and @code{float} is a floating point type (in the
38536 architecture's normal floating point format) of the correct size for
38537 @var{bitsize}. The default is @code{int}.
38540 The register group to which this register belongs. @var{group} must
38541 be either @code{general}, @code{float}, or @code{vector}. If no
38542 @var{group} is specified, @value{GDBN} will not display the register
38543 in @code{info registers}.
38547 @node Predefined Target Types
38548 @section Predefined Target Types
38549 @cindex target descriptions, predefined types
38551 Type definitions in the self-description can build up composite types
38552 from basic building blocks, but can not define fundamental types. Instead,
38553 standard identifiers are provided by @value{GDBN} for the fundamental
38554 types. The currently supported types are:
38563 Signed integer types holding the specified number of bits.
38570 Unsigned integer types holding the specified number of bits.
38574 Pointers to unspecified code and data. The program counter and
38575 any dedicated return address register may be marked as code
38576 pointers; printing a code pointer converts it into a symbolic
38577 address. The stack pointer and any dedicated address registers
38578 may be marked as data pointers.
38581 Single precision IEEE floating point.
38584 Double precision IEEE floating point.
38587 The 12-byte extended precision format used by ARM FPA registers.
38590 The 10-byte extended precision format used by x87 registers.
38593 32bit @sc{eflags} register used by x86.
38596 32bit @sc{mxcsr} register used by x86.
38600 @node Standard Target Features
38601 @section Standard Target Features
38602 @cindex target descriptions, standard features
38604 A target description must contain either no registers or all the
38605 target's registers. If the description contains no registers, then
38606 @value{GDBN} will assume a default register layout, selected based on
38607 the architecture. If the description contains any registers, the
38608 default layout will not be used; the standard registers must be
38609 described in the target description, in such a way that @value{GDBN}
38610 can recognize them.
38612 This is accomplished by giving specific names to feature elements
38613 which contain standard registers. @value{GDBN} will look for features
38614 with those names and verify that they contain the expected registers;
38615 if any known feature is missing required registers, or if any required
38616 feature is missing, @value{GDBN} will reject the target
38617 description. You can add additional registers to any of the
38618 standard features --- @value{GDBN} will display them just as if
38619 they were added to an unrecognized feature.
38621 This section lists the known features and their expected contents.
38622 Sample XML documents for these features are included in the
38623 @value{GDBN} source tree, in the directory @file{gdb/features}.
38625 Names recognized by @value{GDBN} should include the name of the
38626 company or organization which selected the name, and the overall
38627 architecture to which the feature applies; so e.g.@: the feature
38628 containing ARM core registers is named @samp{org.gnu.gdb.arm.core}.
38630 The names of registers are not case sensitive for the purpose
38631 of recognizing standard features, but @value{GDBN} will only display
38632 registers using the capitalization used in the description.
38639 * PowerPC Features::
38645 @subsection ARM Features
38646 @cindex target descriptions, ARM features
38648 The @samp{org.gnu.gdb.arm.core} feature is required for non-M-profile
38650 It should contain registers @samp{r0} through @samp{r13}, @samp{sp},
38651 @samp{lr}, @samp{pc}, and @samp{cpsr}.
38653 For M-profile targets (e.g. Cortex-M3), the @samp{org.gnu.gdb.arm.core}
38654 feature is replaced by @samp{org.gnu.gdb.arm.m-profile}. It should contain
38655 registers @samp{r0} through @samp{r13}, @samp{sp}, @samp{lr}, @samp{pc},
38658 The @samp{org.gnu.gdb.arm.fpa} feature is optional. If present, it
38659 should contain registers @samp{f0} through @samp{f7} and @samp{fps}.
38661 The @samp{org.gnu.gdb.xscale.iwmmxt} feature is optional. If present,
38662 it should contain at least registers @samp{wR0} through @samp{wR15} and
38663 @samp{wCGR0} through @samp{wCGR3}. The @samp{wCID}, @samp{wCon},
38664 @samp{wCSSF}, and @samp{wCASF} registers are optional.
38666 The @samp{org.gnu.gdb.arm.vfp} feature is optional. If present, it
38667 should contain at least registers @samp{d0} through @samp{d15}. If
38668 they are present, @samp{d16} through @samp{d31} should also be included.
38669 @value{GDBN} will synthesize the single-precision registers from
38670 halves of the double-precision registers.
38672 The @samp{org.gnu.gdb.arm.neon} feature is optional. It does not
38673 need to contain registers; it instructs @value{GDBN} to display the
38674 VFP double-precision registers as vectors and to synthesize the
38675 quad-precision registers from pairs of double-precision registers.
38676 If this feature is present, @samp{org.gnu.gdb.arm.vfp} must also
38677 be present and include 32 double-precision registers.
38679 @node i386 Features
38680 @subsection i386 Features
38681 @cindex target descriptions, i386 features
38683 The @samp{org.gnu.gdb.i386.core} feature is required for i386/amd64
38684 targets. It should describe the following registers:
38688 @samp{eax} through @samp{edi} plus @samp{eip} for i386
38690 @samp{rax} through @samp{r15} plus @samp{rip} for amd64
38692 @samp{eflags}, @samp{cs}, @samp{ss}, @samp{ds}, @samp{es},
38693 @samp{fs}, @samp{gs}
38695 @samp{st0} through @samp{st7}
38697 @samp{fctrl}, @samp{fstat}, @samp{ftag}, @samp{fiseg}, @samp{fioff},
38698 @samp{foseg}, @samp{fooff} and @samp{fop}
38701 The register sets may be different, depending on the target.
38703 The @samp{org.gnu.gdb.i386.sse} feature is optional. It should
38704 describe registers:
38708 @samp{xmm0} through @samp{xmm7} for i386
38710 @samp{xmm0} through @samp{xmm15} for amd64
38715 The @samp{org.gnu.gdb.i386.avx} feature is optional and requires the
38716 @samp{org.gnu.gdb.i386.sse} feature. It should
38717 describe the upper 128 bits of @sc{ymm} registers:
38721 @samp{ymm0h} through @samp{ymm7h} for i386
38723 @samp{ymm0h} through @samp{ymm15h} for amd64
38726 The @samp{org.gnu.gdb.i386.linux} feature is optional. It should
38727 describe a single register, @samp{orig_eax}.
38729 @node MIPS Features
38730 @subsection MIPS Features
38731 @cindex target descriptions, MIPS features
38733 The @samp{org.gnu.gdb.mips.cpu} feature is required for MIPS targets.
38734 It should contain registers @samp{r0} through @samp{r31}, @samp{lo},
38735 @samp{hi}, and @samp{pc}. They may be 32-bit or 64-bit depending
38738 The @samp{org.gnu.gdb.mips.cp0} feature is also required. It should
38739 contain at least the @samp{status}, @samp{badvaddr}, and @samp{cause}
38740 registers. They may be 32-bit or 64-bit depending on the target.
38742 The @samp{org.gnu.gdb.mips.fpu} feature is currently required, though
38743 it may be optional in a future version of @value{GDBN}. It should
38744 contain registers @samp{f0} through @samp{f31}, @samp{fcsr}, and
38745 @samp{fir}. They may be 32-bit or 64-bit depending on the target.
38747 The @samp{org.gnu.gdb.mips.dsp} feature is optional. It should
38748 contain registers @samp{hi1} through @samp{hi3}, @samp{lo1} through
38749 @samp{lo3}, and @samp{dspctl}. The @samp{dspctl} register should
38750 be 32-bit and the rest may be 32-bit or 64-bit depending on the target.
38752 The @samp{org.gnu.gdb.mips.linux} feature is optional. It should
38753 contain a single register, @samp{restart}, which is used by the
38754 Linux kernel to control restartable syscalls.
38756 @node M68K Features
38757 @subsection M68K Features
38758 @cindex target descriptions, M68K features
38761 @item @samp{org.gnu.gdb.m68k.core}
38762 @itemx @samp{org.gnu.gdb.coldfire.core}
38763 @itemx @samp{org.gnu.gdb.fido.core}
38764 One of those features must be always present.
38765 The feature that is present determines which flavor of m68k is
38766 used. The feature that is present should contain registers
38767 @samp{d0} through @samp{d7}, @samp{a0} through @samp{a5}, @samp{fp},
38768 @samp{sp}, @samp{ps} and @samp{pc}.
38770 @item @samp{org.gnu.gdb.coldfire.fp}
38771 This feature is optional. If present, it should contain registers
38772 @samp{fp0} through @samp{fp7}, @samp{fpcontrol}, @samp{fpstatus} and
38776 @node PowerPC Features
38777 @subsection PowerPC Features
38778 @cindex target descriptions, PowerPC features
38780 The @samp{org.gnu.gdb.power.core} feature is required for PowerPC
38781 targets. It should contain registers @samp{r0} through @samp{r31},
38782 @samp{pc}, @samp{msr}, @samp{cr}, @samp{lr}, @samp{ctr}, and
38783 @samp{xer}. They may be 32-bit or 64-bit depending on the target.
38785 The @samp{org.gnu.gdb.power.fpu} feature is optional. It should
38786 contain registers @samp{f0} through @samp{f31} and @samp{fpscr}.
38788 The @samp{org.gnu.gdb.power.altivec} feature is optional. It should
38789 contain registers @samp{vr0} through @samp{vr31}, @samp{vscr},
38792 The @samp{org.gnu.gdb.power.vsx} feature is optional. It should
38793 contain registers @samp{vs0h} through @samp{vs31h}. @value{GDBN}
38794 will combine these registers with the floating point registers
38795 (@samp{f0} through @samp{f31}) and the altivec registers (@samp{vr0}
38796 through @samp{vr31}) to present the 128-bit wide registers @samp{vs0}
38797 through @samp{vs63}, the set of vector registers for POWER7.
38799 The @samp{org.gnu.gdb.power.spe} feature is optional. It should
38800 contain registers @samp{ev0h} through @samp{ev31h}, @samp{acc}, and
38801 @samp{spefscr}. SPE targets should provide 32-bit registers in
38802 @samp{org.gnu.gdb.power.core} and provide the upper halves in
38803 @samp{ev0h} through @samp{ev31h}. @value{GDBN} will combine
38804 these to present registers @samp{ev0} through @samp{ev31} to the
38807 @node TIC6x Features
38808 @subsection TMS320C6x Features
38809 @cindex target descriptions, TIC6x features
38810 @cindex target descriptions, TMS320C6x features
38811 The @samp{org.gnu.gdb.tic6x.core} feature is required for TMS320C6x
38812 targets. It should contain registers @samp{A0} through @samp{A15},
38813 registers @samp{B0} through @samp{B15}, @samp{CSR} and @samp{PC}.
38815 The @samp{org.gnu.gdb.tic6x.gp} feature is optional. It should
38816 contain registers @samp{A16} through @samp{A31} and @samp{B16}
38817 through @samp{B31}.
38819 The @samp{org.gnu.gdb.tic6x.c6xp} feature is optional. It should
38820 contain registers @samp{TSR}, @samp{ILC} and @samp{RILC}.
38822 @node Operating System Information
38823 @appendix Operating System Information
38824 @cindex operating system information
38830 Users of @value{GDBN} often wish to obtain information about the state of
38831 the operating system running on the target---for example the list of
38832 processes, or the list of open files. This section describes the
38833 mechanism that makes it possible. This mechanism is similar to the
38834 target features mechanism (@pxref{Target Descriptions}), but focuses
38835 on a different aspect of target.
38837 Operating system information is retrived from the target via the
38838 remote protocol, using @samp{qXfer} requests (@pxref{qXfer osdata
38839 read}). The object name in the request should be @samp{osdata}, and
38840 the @var{annex} identifies the data to be fetched.
38843 @appendixsection Process list
38844 @cindex operating system information, process list
38846 When requesting the process list, the @var{annex} field in the
38847 @samp{qXfer} request should be @samp{processes}. The returned data is
38848 an XML document. The formal syntax of this document is defined in
38849 @file{gdb/features/osdata.dtd}.
38851 An example document is:
38854 <?xml version="1.0"?>
38855 <!DOCTYPE target SYSTEM "osdata.dtd">
38856 <osdata type="processes">
38858 <column name="pid">1</column>
38859 <column name="user">root</column>
38860 <column name="command">/sbin/init</column>
38861 <column name="cores">1,2,3</column>
38866 Each item should include a column whose name is @samp{pid}. The value
38867 of that column should identify the process on the target. The
38868 @samp{user} and @samp{command} columns are optional, and will be
38869 displayed by @value{GDBN}. The @samp{cores} column, if present,
38870 should contain a comma-separated list of cores that this process
38871 is running on. Target may provide additional columns,
38872 which @value{GDBN} currently ignores.
38874 @node Trace File Format
38875 @appendix Trace File Format
38876 @cindex trace file format
38878 The trace file comes in three parts: a header, a textual description
38879 section, and a trace frame section with binary data.
38881 The header has the form @code{\x7fTRACE0\n}. The first byte is
38882 @code{0x7f} so as to indicate that the file contains binary data,
38883 while the @code{0} is a version number that may have different values
38886 The description section consists of multiple lines of @sc{ascii} text
38887 separated by newline characters (@code{0xa}). The lines may include a
38888 variety of optional descriptive or context-setting information, such
38889 as tracepoint definitions or register set size. @value{GDBN} will
38890 ignore any line that it does not recognize. An empty line marks the end
38893 @c FIXME add some specific types of data
38895 The trace frame section consists of a number of consecutive frames.
38896 Each frame begins with a two-byte tracepoint number, followed by a
38897 four-byte size giving the amount of data in the frame. The data in
38898 the frame consists of a number of blocks, each introduced by a
38899 character indicating its type (at least register, memory, and trace
38900 state variable). The data in this section is raw binary, not a
38901 hexadecimal or other encoding; its endianness matches the target's
38904 @c FIXME bi-arch may require endianness/arch info in description section
38907 @item R @var{bytes}
38908 Register block. The number and ordering of bytes matches that of a
38909 @code{g} packet in the remote protocol. Note that these are the
38910 actual bytes, in target order and @value{GDBN} register order, not a
38911 hexadecimal encoding.
38913 @item M @var{address} @var{length} @var{bytes}...
38914 Memory block. This is a contiguous block of memory, at the 8-byte
38915 address @var{address}, with a 2-byte length @var{length}, followed by
38916 @var{length} bytes.
38918 @item V @var{number} @var{value}
38919 Trace state variable block. This records the 8-byte signed value
38920 @var{value} of trace state variable numbered @var{number}.
38924 Future enhancements of the trace file format may include additional types
38927 @node Index Section Format
38928 @appendix @code{.gdb_index} section format
38929 @cindex .gdb_index section format
38930 @cindex index section format
38932 This section documents the index section that is created by @code{save
38933 gdb-index} (@pxref{Index Files}). The index section is
38934 DWARF-specific; some knowledge of DWARF is assumed in this
38937 The mapped index file format is designed to be directly
38938 @code{mmap}able on any architecture. In most cases, a datum is
38939 represented using a little-endian 32-bit integer value, called an
38940 @code{offset_type}. Big endian machines must byte-swap the values
38941 before using them. Exceptions to this rule are noted. The data is
38942 laid out such that alignment is always respected.
38944 A mapped index consists of several areas, laid out in order.
38948 The file header. This is a sequence of values, of @code{offset_type}
38949 unless otherwise noted:
38953 The version number, currently 5. Versions 1, 2 and 3 are obsolete.
38954 Version 4 differs by its hashing function.
38957 The offset, from the start of the file, of the CU list.
38960 The offset, from the start of the file, of the types CU list. Note
38961 that this area can be empty, in which case this offset will be equal
38962 to the next offset.
38965 The offset, from the start of the file, of the address area.
38968 The offset, from the start of the file, of the symbol table.
38971 The offset, from the start of the file, of the constant pool.
38975 The CU list. This is a sequence of pairs of 64-bit little-endian
38976 values, sorted by the CU offset. The first element in each pair is
38977 the offset of a CU in the @code{.debug_info} section. The second
38978 element in each pair is the length of that CU. References to a CU
38979 elsewhere in the map are done using a CU index, which is just the
38980 0-based index into this table. Note that if there are type CUs, then
38981 conceptually CUs and type CUs form a single list for the purposes of
38985 The types CU list. This is a sequence of triplets of 64-bit
38986 little-endian values. In a triplet, the first value is the CU offset,
38987 the second value is the type offset in the CU, and the third value is
38988 the type signature. The types CU list is not sorted.
38991 The address area. The address area consists of a sequence of address
38992 entries. Each address entry has three elements:
38996 The low address. This is a 64-bit little-endian value.
38999 The high address. This is a 64-bit little-endian value. Like
39000 @code{DW_AT_high_pc}, the value is one byte beyond the end.
39003 The CU index. This is an @code{offset_type} value.
39007 The symbol table. This is an open-addressed hash table. The size of
39008 the hash table is always a power of 2.
39010 Each slot in the hash table consists of a pair of @code{offset_type}
39011 values. The first value is the offset of the symbol's name in the
39012 constant pool. The second value is the offset of the CU vector in the
39015 If both values are 0, then this slot in the hash table is empty. This
39016 is ok because while 0 is a valid constant pool index, it cannot be a
39017 valid index for both a string and a CU vector.
39019 The hash value for a table entry is computed by applying an
39020 iterative hash function to the symbol's name. Starting with an
39021 initial value of @code{r = 0}, each (unsigned) character @samp{c} in
39022 the string is incorporated into the hash using the formula depending on the
39027 The formula is @code{r = r * 67 + c - 113}.
39030 The formula is @code{r = r * 67 + tolower (c) - 113}.
39033 The terminating @samp{\0} is not incorporated into the hash.
39035 The step size used in the hash table is computed via
39036 @code{((hash * 17) & (size - 1)) | 1}, where @samp{hash} is the hash
39037 value, and @samp{size} is the size of the hash table. The step size
39038 is used to find the next candidate slot when handling a hash
39041 The names of C@t{++} symbols in the hash table are canonicalized. We
39042 don't currently have a simple description of the canonicalization
39043 algorithm; if you intend to create new index sections, you must read
39047 The constant pool. This is simply a bunch of bytes. It is organized
39048 so that alignment is correct: CU vectors are stored first, followed by
39051 A CU vector in the constant pool is a sequence of @code{offset_type}
39052 values. The first value is the number of CU indices in the vector.
39053 Each subsequent value is the index of a CU in the CU list. This
39054 element in the hash table is used to indicate which CUs define the
39057 A string in the constant pool is zero-terminated.
39062 @node GNU Free Documentation License
39063 @appendix GNU Free Documentation License
39072 % I think something like @colophon should be in texinfo. In the
39074 \long\def\colophon{\hbox to0pt{}\vfill
39075 \centerline{The body of this manual is set in}
39076 \centerline{\fontname\tenrm,}
39077 \centerline{with headings in {\bf\fontname\tenbf}}
39078 \centerline{and examples in {\tt\fontname\tentt}.}
39079 \centerline{{\it\fontname\tenit\/},}
39080 \centerline{{\bf\fontname\tenbf}, and}
39081 \centerline{{\sl\fontname\tensl\/}}
39082 \centerline{are used for emphasis.}\vfill}
39084 % Blame: doc@cygnus.com, 1991.