* gdb.texinfo (Python): Fix long line.
[deliverable/binutils-gdb.git] / gdb / doc / gdb.texinfo
1 \input texinfo @c -*-texinfo-*-
2 @c Copyright (C) 1988, 1989, 1990, 1991, 1992, 1993, 1994, 1995, 1996, 1998,
3 @c 1999, 2000, 2001, 2002, 2003, 2004, 2005, 2006, 2007, 2008, 2009, 2010
4 @c Free Software Foundation, Inc.
5 @c
6 @c %**start of header
7 @c makeinfo ignores cmds prev to setfilename, so its arg cannot make use
8 @c of @set vars. However, you can override filename with makeinfo -o.
9 @setfilename gdb.info
10 @c
11 @include gdb-cfg.texi
12 @c
13 @settitle Debugging with @value{GDBN}
14 @setchapternewpage odd
15 @c %**end of header
16
17 @iftex
18 @c @smallbook
19 @c @cropmarks
20 @end iftex
21
22 @finalout
23 @syncodeindex ky cp
24 @syncodeindex tp cp
25
26 @c readline appendices use @vindex, @findex and @ftable,
27 @c annotate.texi and gdbmi use @findex.
28 @syncodeindex vr cp
29 @syncodeindex fn cp
30
31 @c !!set GDB manual's edition---not the same as GDB version!
32 @c This is updated by GNU Press.
33 @set EDITION Ninth
34
35 @c !!set GDB edit command default editor
36 @set EDITOR /bin/ex
37
38 @c THIS MANUAL REQUIRES TEXINFO 4.0 OR LATER.
39
40 @c This is a dir.info fragment to support semi-automated addition of
41 @c manuals to an info tree.
42 @dircategory Software development
43 @direntry
44 * Gdb: (gdb). The GNU debugger.
45 @end direntry
46
47 @copying
48 Copyright @copyright{} 1988, 1989, 1990, 1991, 1992, 1993, 1994, 1995, 1996,
49 1998, 1999, 2000, 2001, 2002, 2003, 2004, 2005, 2006, 2007, 2008, 2009, 2010
50 Free Software Foundation, Inc.
51
52 Permission is granted to copy, distribute and/or modify this document
53 under the terms of the GNU Free Documentation License, Version 1.3 or
54 any later version published by the Free Software Foundation; with the
55 Invariant Sections being ``Free Software'' and ``Free Software Needs
56 Free Documentation'', with the Front-Cover Texts being ``A GNU Manual,''
57 and with the Back-Cover Texts as in (a) below.
58
59 (a) The FSF's Back-Cover Text is: ``You are free to copy and modify
60 this GNU Manual. Buying copies from GNU Press supports the FSF in
61 developing GNU and promoting software freedom.''
62 @end copying
63
64 @ifnottex
65 This file documents the @sc{gnu} debugger @value{GDBN}.
66
67 This is the @value{EDITION} Edition, of @cite{Debugging with
68 @value{GDBN}: the @sc{gnu} Source-Level Debugger} for @value{GDBN}
69 @ifset VERSION_PACKAGE
70 @value{VERSION_PACKAGE}
71 @end ifset
72 Version @value{GDBVN}.
73
74 @insertcopying
75 @end ifnottex
76
77 @titlepage
78 @title Debugging with @value{GDBN}
79 @subtitle The @sc{gnu} Source-Level Debugger
80 @sp 1
81 @subtitle @value{EDITION} Edition, for @value{GDBN} version @value{GDBVN}
82 @ifset VERSION_PACKAGE
83 @sp 1
84 @subtitle @value{VERSION_PACKAGE}
85 @end ifset
86 @author Richard Stallman, Roland Pesch, Stan Shebs, et al.
87 @page
88 @tex
89 {\parskip=0pt
90 \hfill (Send bugs and comments on @value{GDBN} to @value{BUGURL}.)\par
91 \hfill {\it Debugging with @value{GDBN}}\par
92 \hfill \TeX{}info \texinfoversion\par
93 }
94 @end tex
95
96 @vskip 0pt plus 1filll
97 Published by the Free Software Foundation @*
98 51 Franklin Street, Fifth Floor,
99 Boston, MA 02110-1301, USA@*
100 ISBN 1-882114-77-9 @*
101
102 @insertcopying
103 @page
104 This edition of the GDB manual is dedicated to the memory of Fred
105 Fish. Fred was a long-standing contributor to GDB and to Free
106 software in general. We will miss him.
107 @end titlepage
108 @page
109
110 @ifnottex
111 @node Top, Summary, (dir), (dir)
112
113 @top Debugging with @value{GDBN}
114
115 This file describes @value{GDBN}, the @sc{gnu} symbolic debugger.
116
117 This is the @value{EDITION} Edition, for @value{GDBN}
118 @ifset VERSION_PACKAGE
119 @value{VERSION_PACKAGE}
120 @end ifset
121 Version @value{GDBVN}.
122
123 Copyright (C) 1988-2010 Free Software Foundation, Inc.
124
125 This edition of the GDB manual is dedicated to the memory of Fred
126 Fish. Fred was a long-standing contributor to GDB and to Free
127 software in general. We will miss him.
128
129 @menu
130 * Summary:: Summary of @value{GDBN}
131 * Sample Session:: A sample @value{GDBN} session
132
133 * Invocation:: Getting in and out of @value{GDBN}
134 * Commands:: @value{GDBN} commands
135 * Running:: Running programs under @value{GDBN}
136 * Stopping:: Stopping and continuing
137 * Reverse Execution:: Running programs backward
138 * Process Record and Replay:: Recording inferior's execution and replaying it
139 * Stack:: Examining the stack
140 * Source:: Examining source files
141 * Data:: Examining data
142 * Optimized Code:: Debugging optimized code
143 * Macros:: Preprocessor Macros
144 * Tracepoints:: Debugging remote targets non-intrusively
145 * Overlays:: Debugging programs that use overlays
146
147 * Languages:: Using @value{GDBN} with different languages
148
149 * Symbols:: Examining the symbol table
150 * Altering:: Altering execution
151 * GDB Files:: @value{GDBN} files
152 * Targets:: Specifying a debugging target
153 * Remote Debugging:: Debugging remote programs
154 * Configurations:: Configuration-specific information
155 * Controlling GDB:: Controlling @value{GDBN}
156 * Extending GDB:: Extending @value{GDBN}
157 * Interpreters:: Command Interpreters
158 * TUI:: @value{GDBN} Text User Interface
159 * Emacs:: Using @value{GDBN} under @sc{gnu} Emacs
160 * GDB/MI:: @value{GDBN}'s Machine Interface.
161 * Annotations:: @value{GDBN}'s annotation interface.
162 * JIT Interface:: Using the JIT debugging interface.
163
164 * GDB Bugs:: Reporting bugs in @value{GDBN}
165
166 * Command Line Editing:: Command Line Editing
167 * Using History Interactively:: Using History Interactively
168 * Formatting Documentation:: How to format and print @value{GDBN} documentation
169 * Installing GDB:: Installing GDB
170 * Maintenance Commands:: Maintenance Commands
171 * Remote Protocol:: GDB Remote Serial Protocol
172 * Agent Expressions:: The GDB Agent Expression Mechanism
173 * Target Descriptions:: How targets can describe themselves to
174 @value{GDBN}
175 * Operating System Information:: Getting additional information from
176 the operating system
177 * Trace File Format:: GDB trace file format
178 * Copying:: GNU General Public License says
179 how you can copy and share GDB
180 * GNU Free Documentation License:: The license for this documentation
181 * Index:: Index
182 @end menu
183
184 @end ifnottex
185
186 @contents
187
188 @node Summary
189 @unnumbered Summary of @value{GDBN}
190
191 The purpose of a debugger such as @value{GDBN} is to allow you to see what is
192 going on ``inside'' another program while it executes---or what another
193 program was doing at the moment it crashed.
194
195 @value{GDBN} can do four main kinds of things (plus other things in support of
196 these) to help you catch bugs in the act:
197
198 @itemize @bullet
199 @item
200 Start your program, specifying anything that might affect its behavior.
201
202 @item
203 Make your program stop on specified conditions.
204
205 @item
206 Examine what has happened, when your program has stopped.
207
208 @item
209 Change things in your program, so you can experiment with correcting the
210 effects of one bug and go on to learn about another.
211 @end itemize
212
213 You can use @value{GDBN} to debug programs written in C and C@t{++}.
214 For more information, see @ref{Supported Languages,,Supported Languages}.
215 For more information, see @ref{C,,C and C++}.
216
217 Support for D is partial. For information on D, see
218 @ref{D,,D}.
219
220 @cindex Modula-2
221 Support for Modula-2 is partial. For information on Modula-2, see
222 @ref{Modula-2,,Modula-2}.
223
224 @cindex Pascal
225 Debugging Pascal programs which use sets, subranges, file variables, or
226 nested functions does not currently work. @value{GDBN} does not support
227 entering expressions, printing values, or similar features using Pascal
228 syntax.
229
230 @cindex Fortran
231 @value{GDBN} can be used to debug programs written in Fortran, although
232 it may be necessary to refer to some variables with a trailing
233 underscore.
234
235 @value{GDBN} can be used to debug programs written in Objective-C,
236 using either the Apple/NeXT or the GNU Objective-C runtime.
237
238 @menu
239 * Free Software:: Freely redistributable software
240 * Contributors:: Contributors to GDB
241 @end menu
242
243 @node Free Software
244 @unnumberedsec Free Software
245
246 @value{GDBN} is @dfn{free software}, protected by the @sc{gnu}
247 General Public License
248 (GPL). The GPL gives you the freedom to copy or adapt a licensed
249 program---but every person getting a copy also gets with it the
250 freedom to modify that copy (which means that they must get access to
251 the source code), and the freedom to distribute further copies.
252 Typical software companies use copyrights to limit your freedoms; the
253 Free Software Foundation uses the GPL to preserve these freedoms.
254
255 Fundamentally, the General Public License is a license which says that
256 you have these freedoms and that you cannot take these freedoms away
257 from anyone else.
258
259 @unnumberedsec Free Software Needs Free Documentation
260
261 The biggest deficiency in the free software community today is not in
262 the software---it is the lack of good free documentation that we can
263 include with the free software. Many of our most important
264 programs do not come with free reference manuals and free introductory
265 texts. Documentation is an essential part of any software package;
266 when an important free software package does not come with a free
267 manual and a free tutorial, that is a major gap. We have many such
268 gaps today.
269
270 Consider Perl, for instance. The tutorial manuals that people
271 normally use are non-free. How did this come about? Because the
272 authors of those manuals published them with restrictive terms---no
273 copying, no modification, source files not available---which exclude
274 them from the free software world.
275
276 That wasn't the first time this sort of thing happened, and it was far
277 from the last. Many times we have heard a GNU user eagerly describe a
278 manual that he is writing, his intended contribution to the community,
279 only to learn that he had ruined everything by signing a publication
280 contract to make it non-free.
281
282 Free documentation, like free software, is a matter of freedom, not
283 price. The problem with the non-free manual is not that publishers
284 charge a price for printed copies---that in itself is fine. (The Free
285 Software Foundation sells printed copies of manuals, too.) The
286 problem is the restrictions on the use of the manual. Free manuals
287 are available in source code form, and give you permission to copy and
288 modify. Non-free manuals do not allow this.
289
290 The criteria of freedom for a free manual are roughly the same as for
291 free software. Redistribution (including the normal kinds of
292 commercial redistribution) must be permitted, so that the manual can
293 accompany every copy of the program, both on-line and on paper.
294
295 Permission for modification of the technical content is crucial too.
296 When people modify the software, adding or changing features, if they
297 are conscientious they will change the manual too---so they can
298 provide accurate and clear documentation for the modified program. A
299 manual that leaves you no choice but to write a new manual to document
300 a changed version of the program is not really available to our
301 community.
302
303 Some kinds of limits on the way modification is handled are
304 acceptable. For example, requirements to preserve the original
305 author's copyright notice, the distribution terms, or the list of
306 authors, are ok. It is also no problem to require modified versions
307 to include notice that they were modified. Even entire sections that
308 may not be deleted or changed are acceptable, as long as they deal
309 with nontechnical topics (like this one). These kinds of restrictions
310 are acceptable because they don't obstruct the community's normal use
311 of the manual.
312
313 However, it must be possible to modify all the @emph{technical}
314 content of the manual, and then distribute the result in all the usual
315 media, through all the usual channels. Otherwise, the restrictions
316 obstruct the use of the manual, it is not free, and we need another
317 manual to replace it.
318
319 Please spread the word about this issue. Our community continues to
320 lose manuals to proprietary publishing. If we spread the word that
321 free software needs free reference manuals and free tutorials, perhaps
322 the next person who wants to contribute by writing documentation will
323 realize, before it is too late, that only free manuals contribute to
324 the free software community.
325
326 If you are writing documentation, please insist on publishing it under
327 the GNU Free Documentation License or another free documentation
328 license. Remember that this decision requires your approval---you
329 don't have to let the publisher decide. Some commercial publishers
330 will use a free license if you insist, but they will not propose the
331 option; it is up to you to raise the issue and say firmly that this is
332 what you want. If the publisher you are dealing with refuses, please
333 try other publishers. If you're not sure whether a proposed license
334 is free, write to @email{licensing@@gnu.org}.
335
336 You can encourage commercial publishers to sell more free, copylefted
337 manuals and tutorials by buying them, and particularly by buying
338 copies from the publishers that paid for their writing or for major
339 improvements. Meanwhile, try to avoid buying non-free documentation
340 at all. Check the distribution terms of a manual before you buy it,
341 and insist that whoever seeks your business must respect your freedom.
342 Check the history of the book, and try to reward the publishers that
343 have paid or pay the authors to work on it.
344
345 The Free Software Foundation maintains a list of free documentation
346 published by other publishers, at
347 @url{http://www.fsf.org/doc/other-free-books.html}.
348
349 @node Contributors
350 @unnumberedsec Contributors to @value{GDBN}
351
352 Richard Stallman was the original author of @value{GDBN}, and of many
353 other @sc{gnu} programs. Many others have contributed to its
354 development. This section attempts to credit major contributors. One
355 of the virtues of free software is that everyone is free to contribute
356 to it; with regret, we cannot actually acknowledge everyone here. The
357 file @file{ChangeLog} in the @value{GDBN} distribution approximates a
358 blow-by-blow account.
359
360 Changes much prior to version 2.0 are lost in the mists of time.
361
362 @quotation
363 @emph{Plea:} Additions to this section are particularly welcome. If you
364 or your friends (or enemies, to be evenhanded) have been unfairly
365 omitted from this list, we would like to add your names!
366 @end quotation
367
368 So that they may not regard their many labors as thankless, we
369 particularly thank those who shepherded @value{GDBN} through major
370 releases:
371 Andrew Cagney (releases 6.3, 6.2, 6.1, 6.0, 5.3, 5.2, 5.1 and 5.0);
372 Jim Blandy (release 4.18);
373 Jason Molenda (release 4.17);
374 Stan Shebs (release 4.14);
375 Fred Fish (releases 4.16, 4.15, 4.13, 4.12, 4.11, 4.10, and 4.9);
376 Stu Grossman and John Gilmore (releases 4.8, 4.7, 4.6, 4.5, and 4.4);
377 John Gilmore (releases 4.3, 4.2, 4.1, 4.0, and 3.9);
378 Jim Kingdon (releases 3.5, 3.4, and 3.3);
379 and Randy Smith (releases 3.2, 3.1, and 3.0).
380
381 Richard Stallman, assisted at various times by Peter TerMaat, Chris
382 Hanson, and Richard Mlynarik, handled releases through 2.8.
383
384 Michael Tiemann is the author of most of the @sc{gnu} C@t{++} support
385 in @value{GDBN}, with significant additional contributions from Per
386 Bothner and Daniel Berlin. James Clark wrote the @sc{gnu} C@t{++}
387 demangler. Early work on C@t{++} was by Peter TerMaat (who also did
388 much general update work leading to release 3.0).
389
390 @value{GDBN} uses the BFD subroutine library to examine multiple
391 object-file formats; BFD was a joint project of David V.
392 Henkel-Wallace, Rich Pixley, Steve Chamberlain, and John Gilmore.
393
394 David Johnson wrote the original COFF support; Pace Willison did
395 the original support for encapsulated COFF.
396
397 Brent Benson of Harris Computer Systems contributed DWARF 2 support.
398
399 Adam de Boor and Bradley Davis contributed the ISI Optimum V support.
400 Per Bothner, Noboyuki Hikichi, and Alessandro Forin contributed MIPS
401 support.
402 Jean-Daniel Fekete contributed Sun 386i support.
403 Chris Hanson improved the HP9000 support.
404 Noboyuki Hikichi and Tomoyuki Hasei contributed Sony/News OS 3 support.
405 David Johnson contributed Encore Umax support.
406 Jyrki Kuoppala contributed Altos 3068 support.
407 Jeff Law contributed HP PA and SOM support.
408 Keith Packard contributed NS32K support.
409 Doug Rabson contributed Acorn Risc Machine support.
410 Bob Rusk contributed Harris Nighthawk CX-UX support.
411 Chris Smith contributed Convex support (and Fortran debugging).
412 Jonathan Stone contributed Pyramid support.
413 Michael Tiemann contributed SPARC support.
414 Tim Tucker contributed support for the Gould NP1 and Gould Powernode.
415 Pace Willison contributed Intel 386 support.
416 Jay Vosburgh contributed Symmetry support.
417 Marko Mlinar contributed OpenRISC 1000 support.
418
419 Andreas Schwab contributed M68K @sc{gnu}/Linux support.
420
421 Rich Schaefer and Peter Schauer helped with support of SunOS shared
422 libraries.
423
424 Jay Fenlason and Roland McGrath ensured that @value{GDBN} and GAS agree
425 about several machine instruction sets.
426
427 Patrick Duval, Ted Goldstein, Vikram Koka and Glenn Engel helped develop
428 remote debugging. Intel Corporation, Wind River Systems, AMD, and ARM
429 contributed remote debugging modules for the i960, VxWorks, A29K UDI,
430 and RDI targets, respectively.
431
432 Brian Fox is the author of the readline libraries providing
433 command-line editing and command history.
434
435 Andrew Beers of SUNY Buffalo wrote the language-switching code, the
436 Modula-2 support, and contributed the Languages chapter of this manual.
437
438 Fred Fish wrote most of the support for Unix System Vr4.
439 He also enhanced the command-completion support to cover C@t{++} overloaded
440 symbols.
441
442 Hitachi America (now Renesas America), Ltd. sponsored the support for
443 H8/300, H8/500, and Super-H processors.
444
445 NEC sponsored the support for the v850, Vr4xxx, and Vr5xxx processors.
446
447 Mitsubishi (now Renesas) sponsored the support for D10V, D30V, and M32R/D
448 processors.
449
450 Toshiba sponsored the support for the TX39 Mips processor.
451
452 Matsushita sponsored the support for the MN10200 and MN10300 processors.
453
454 Fujitsu sponsored the support for SPARClite and FR30 processors.
455
456 Kung Hsu, Jeff Law, and Rick Sladkey added support for hardware
457 watchpoints.
458
459 Michael Snyder added support for tracepoints.
460
461 Stu Grossman wrote gdbserver.
462
463 Jim Kingdon, Peter Schauer, Ian Taylor, and Stu Grossman made
464 nearly innumerable bug fixes and cleanups throughout @value{GDBN}.
465
466 The following people at the Hewlett-Packard Company contributed
467 support for the PA-RISC 2.0 architecture, HP-UX 10.20, 10.30, and 11.0
468 (narrow mode), HP's implementation of kernel threads, HP's aC@t{++}
469 compiler, and the Text User Interface (nee Terminal User Interface):
470 Ben Krepp, Richard Title, John Bishop, Susan Macchia, Kathy Mann,
471 Satish Pai, India Paul, Steve Rehrauer, and Elena Zannoni. Kim Haase
472 provided HP-specific information in this manual.
473
474 DJ Delorie ported @value{GDBN} to MS-DOS, for the DJGPP project.
475 Robert Hoehne made significant contributions to the DJGPP port.
476
477 Cygnus Solutions has sponsored @value{GDBN} maintenance and much of its
478 development since 1991. Cygnus engineers who have worked on @value{GDBN}
479 fulltime include Mark Alexander, Jim Blandy, Per Bothner, Kevin
480 Buettner, Edith Epstein, Chris Faylor, Fred Fish, Martin Hunt, Jim
481 Ingham, John Gilmore, Stu Grossman, Kung Hsu, Jim Kingdon, John Metzler,
482 Fernando Nasser, Geoffrey Noer, Dawn Perchik, Rich Pixley, Zdenek
483 Radouch, Keith Seitz, Stan Shebs, David Taylor, and Elena Zannoni. In
484 addition, Dave Brolley, Ian Carmichael, Steve Chamberlain, Nick Clifton,
485 JT Conklin, Stan Cox, DJ Delorie, Ulrich Drepper, Frank Eigler, Doug
486 Evans, Sean Fagan, David Henkel-Wallace, Richard Henderson, Jeff
487 Holcomb, Jeff Law, Jim Lemke, Tom Lord, Bob Manson, Michael Meissner,
488 Jason Merrill, Catherine Moore, Drew Moseley, Ken Raeburn, Gavin
489 Romig-Koch, Rob Savoye, Jamie Smith, Mike Stump, Ian Taylor, Angela
490 Thomas, Michael Tiemann, Tom Tromey, Ron Unrau, Jim Wilson, and David
491 Zuhn have made contributions both large and small.
492
493 Andrew Cagney, Fernando Nasser, and Elena Zannoni, while working for
494 Cygnus Solutions, implemented the original @sc{gdb/mi} interface.
495
496 Jim Blandy added support for preprocessor macros, while working for Red
497 Hat.
498
499 Andrew Cagney designed @value{GDBN}'s architecture vector. Many
500 people including Andrew Cagney, Stephane Carrez, Randolph Chung, Nick
501 Duffek, Richard Henderson, Mark Kettenis, Grace Sainsbury, Kei
502 Sakamoto, Yoshinori Sato, Michael Snyder, Andreas Schwab, Jason
503 Thorpe, Corinna Vinschen, Ulrich Weigand, and Elena Zannoni, helped
504 with the migration of old architectures to this new framework.
505
506 Andrew Cagney completely re-designed and re-implemented @value{GDBN}'s
507 unwinder framework, this consisting of a fresh new design featuring
508 frame IDs, independent frame sniffers, and the sentinel frame. Mark
509 Kettenis implemented the @sc{dwarf 2} unwinder, Jeff Johnston the
510 libunwind unwinder, and Andrew Cagney the dummy, sentinel, tramp, and
511 trad unwinders. The architecture-specific changes, each involving a
512 complete rewrite of the architecture's frame code, were carried out by
513 Jim Blandy, Joel Brobecker, Kevin Buettner, Andrew Cagney, Stephane
514 Carrez, Randolph Chung, Orjan Friberg, Richard Henderson, Daniel
515 Jacobowitz, Jeff Johnston, Mark Kettenis, Theodore A. Roth, Kei
516 Sakamoto, Yoshinori Sato, Michael Snyder, Corinna Vinschen, and Ulrich
517 Weigand.
518
519 Christian Zankel, Ross Morley, Bob Wilson, and Maxim Grigoriev from
520 Tensilica, Inc.@: contributed support for Xtensa processors. Others
521 who have worked on the Xtensa port of @value{GDBN} in the past include
522 Steve Tjiang, John Newlin, and Scott Foehner.
523
524 Michael Eager and staff of Xilinx, Inc., contributed support for the
525 Xilinx MicroBlaze architecture.
526
527 @node Sample Session
528 @chapter A Sample @value{GDBN} Session
529
530 You can use this manual at your leisure to read all about @value{GDBN}.
531 However, a handful of commands are enough to get started using the
532 debugger. This chapter illustrates those commands.
533
534 @iftex
535 In this sample session, we emphasize user input like this: @b{input},
536 to make it easier to pick out from the surrounding output.
537 @end iftex
538
539 @c FIXME: this example may not be appropriate for some configs, where
540 @c FIXME...primary interest is in remote use.
541
542 One of the preliminary versions of @sc{gnu} @code{m4} (a generic macro
543 processor) exhibits the following bug: sometimes, when we change its
544 quote strings from the default, the commands used to capture one macro
545 definition within another stop working. In the following short @code{m4}
546 session, we define a macro @code{foo} which expands to @code{0000}; we
547 then use the @code{m4} built-in @code{defn} to define @code{bar} as the
548 same thing. However, when we change the open quote string to
549 @code{<QUOTE>} and the close quote string to @code{<UNQUOTE>}, the same
550 procedure fails to define a new synonym @code{baz}:
551
552 @smallexample
553 $ @b{cd gnu/m4}
554 $ @b{./m4}
555 @b{define(foo,0000)}
556
557 @b{foo}
558 0000
559 @b{define(bar,defn(`foo'))}
560
561 @b{bar}
562 0000
563 @b{changequote(<QUOTE>,<UNQUOTE>)}
564
565 @b{define(baz,defn(<QUOTE>foo<UNQUOTE>))}
566 @b{baz}
567 @b{Ctrl-d}
568 m4: End of input: 0: fatal error: EOF in string
569 @end smallexample
570
571 @noindent
572 Let us use @value{GDBN} to try to see what is going on.
573
574 @smallexample
575 $ @b{@value{GDBP} m4}
576 @c FIXME: this falsifies the exact text played out, to permit smallbook
577 @c FIXME... format to come out better.
578 @value{GDBN} is free software and you are welcome to distribute copies
579 of it under certain conditions; type "show copying" to see
580 the conditions.
581 There is absolutely no warranty for @value{GDBN}; type "show warranty"
582 for details.
583
584 @value{GDBN} @value{GDBVN}, Copyright 1999 Free Software Foundation, Inc...
585 (@value{GDBP})
586 @end smallexample
587
588 @noindent
589 @value{GDBN} reads only enough symbol data to know where to find the
590 rest when needed; as a result, the first prompt comes up very quickly.
591 We now tell @value{GDBN} to use a narrower display width than usual, so
592 that examples fit in this manual.
593
594 @smallexample
595 (@value{GDBP}) @b{set width 70}
596 @end smallexample
597
598 @noindent
599 We need to see how the @code{m4} built-in @code{changequote} works.
600 Having looked at the source, we know the relevant subroutine is
601 @code{m4_changequote}, so we set a breakpoint there with the @value{GDBN}
602 @code{break} command.
603
604 @smallexample
605 (@value{GDBP}) @b{break m4_changequote}
606 Breakpoint 1 at 0x62f4: file builtin.c, line 879.
607 @end smallexample
608
609 @noindent
610 Using the @code{run} command, we start @code{m4} running under @value{GDBN}
611 control; as long as control does not reach the @code{m4_changequote}
612 subroutine, the program runs as usual:
613
614 @smallexample
615 (@value{GDBP}) @b{run}
616 Starting program: /work/Editorial/gdb/gnu/m4/m4
617 @b{define(foo,0000)}
618
619 @b{foo}
620 0000
621 @end smallexample
622
623 @noindent
624 To trigger the breakpoint, we call @code{changequote}. @value{GDBN}
625 suspends execution of @code{m4}, displaying information about the
626 context where it stops.
627
628 @smallexample
629 @b{changequote(<QUOTE>,<UNQUOTE>)}
630
631 Breakpoint 1, m4_changequote (argc=3, argv=0x33c70)
632 at builtin.c:879
633 879 if (bad_argc(TOKEN_DATA_TEXT(argv[0]),argc,1,3))
634 @end smallexample
635
636 @noindent
637 Now we use the command @code{n} (@code{next}) to advance execution to
638 the next line of the current function.
639
640 @smallexample
641 (@value{GDBP}) @b{n}
642 882 set_quotes((argc >= 2) ? TOKEN_DATA_TEXT(argv[1])\
643 : nil,
644 @end smallexample
645
646 @noindent
647 @code{set_quotes} looks like a promising subroutine. We can go into it
648 by using the command @code{s} (@code{step}) instead of @code{next}.
649 @code{step} goes to the next line to be executed in @emph{any}
650 subroutine, so it steps into @code{set_quotes}.
651
652 @smallexample
653 (@value{GDBP}) @b{s}
654 set_quotes (lq=0x34c78 "<QUOTE>", rq=0x34c88 "<UNQUOTE>")
655 at input.c:530
656 530 if (lquote != def_lquote)
657 @end smallexample
658
659 @noindent
660 The display that shows the subroutine where @code{m4} is now
661 suspended (and its arguments) is called a stack frame display. It
662 shows a summary of the stack. We can use the @code{backtrace}
663 command (which can also be spelled @code{bt}), to see where we are
664 in the stack as a whole: the @code{backtrace} command displays a
665 stack frame for each active subroutine.
666
667 @smallexample
668 (@value{GDBP}) @b{bt}
669 #0 set_quotes (lq=0x34c78 "<QUOTE>", rq=0x34c88 "<UNQUOTE>")
670 at input.c:530
671 #1 0x6344 in m4_changequote (argc=3, argv=0x33c70)
672 at builtin.c:882
673 #2 0x8174 in expand_macro (sym=0x33320) at macro.c:242
674 #3 0x7a88 in expand_token (obs=0x0, t=209696, td=0xf7fffa30)
675 at macro.c:71
676 #4 0x79dc in expand_input () at macro.c:40
677 #5 0x2930 in main (argc=0, argv=0xf7fffb20) at m4.c:195
678 @end smallexample
679
680 @noindent
681 We step through a few more lines to see what happens. The first two
682 times, we can use @samp{s}; the next two times we use @code{n} to avoid
683 falling into the @code{xstrdup} subroutine.
684
685 @smallexample
686 (@value{GDBP}) @b{s}
687 0x3b5c 532 if (rquote != def_rquote)
688 (@value{GDBP}) @b{s}
689 0x3b80 535 lquote = (lq == nil || *lq == '\0') ? \
690 def_lquote : xstrdup(lq);
691 (@value{GDBP}) @b{n}
692 536 rquote = (rq == nil || *rq == '\0') ? def_rquote\
693 : xstrdup(rq);
694 (@value{GDBP}) @b{n}
695 538 len_lquote = strlen(rquote);
696 @end smallexample
697
698 @noindent
699 The last line displayed looks a little odd; we can examine the variables
700 @code{lquote} and @code{rquote} to see if they are in fact the new left
701 and right quotes we specified. We use the command @code{p}
702 (@code{print}) to see their values.
703
704 @smallexample
705 (@value{GDBP}) @b{p lquote}
706 $1 = 0x35d40 "<QUOTE>"
707 (@value{GDBP}) @b{p rquote}
708 $2 = 0x35d50 "<UNQUOTE>"
709 @end smallexample
710
711 @noindent
712 @code{lquote} and @code{rquote} are indeed the new left and right quotes.
713 To look at some context, we can display ten lines of source
714 surrounding the current line with the @code{l} (@code{list}) command.
715
716 @smallexample
717 (@value{GDBP}) @b{l}
718 533 xfree(rquote);
719 534
720 535 lquote = (lq == nil || *lq == '\0') ? def_lquote\
721 : xstrdup (lq);
722 536 rquote = (rq == nil || *rq == '\0') ? def_rquote\
723 : xstrdup (rq);
724 537
725 538 len_lquote = strlen(rquote);
726 539 len_rquote = strlen(lquote);
727 540 @}
728 541
729 542 void
730 @end smallexample
731
732 @noindent
733 Let us step past the two lines that set @code{len_lquote} and
734 @code{len_rquote}, and then examine the values of those variables.
735
736 @smallexample
737 (@value{GDBP}) @b{n}
738 539 len_rquote = strlen(lquote);
739 (@value{GDBP}) @b{n}
740 540 @}
741 (@value{GDBP}) @b{p len_lquote}
742 $3 = 9
743 (@value{GDBP}) @b{p len_rquote}
744 $4 = 7
745 @end smallexample
746
747 @noindent
748 That certainly looks wrong, assuming @code{len_lquote} and
749 @code{len_rquote} are meant to be the lengths of @code{lquote} and
750 @code{rquote} respectively. We can set them to better values using
751 the @code{p} command, since it can print the value of
752 any expression---and that expression can include subroutine calls and
753 assignments.
754
755 @smallexample
756 (@value{GDBP}) @b{p len_lquote=strlen(lquote)}
757 $5 = 7
758 (@value{GDBP}) @b{p len_rquote=strlen(rquote)}
759 $6 = 9
760 @end smallexample
761
762 @noindent
763 Is that enough to fix the problem of using the new quotes with the
764 @code{m4} built-in @code{defn}? We can allow @code{m4} to continue
765 executing with the @code{c} (@code{continue}) command, and then try the
766 example that caused trouble initially:
767
768 @smallexample
769 (@value{GDBP}) @b{c}
770 Continuing.
771
772 @b{define(baz,defn(<QUOTE>foo<UNQUOTE>))}
773
774 baz
775 0000
776 @end smallexample
777
778 @noindent
779 Success! The new quotes now work just as well as the default ones. The
780 problem seems to have been just the two typos defining the wrong
781 lengths. We allow @code{m4} exit by giving it an EOF as input:
782
783 @smallexample
784 @b{Ctrl-d}
785 Program exited normally.
786 @end smallexample
787
788 @noindent
789 The message @samp{Program exited normally.} is from @value{GDBN}; it
790 indicates @code{m4} has finished executing. We can end our @value{GDBN}
791 session with the @value{GDBN} @code{quit} command.
792
793 @smallexample
794 (@value{GDBP}) @b{quit}
795 @end smallexample
796
797 @node Invocation
798 @chapter Getting In and Out of @value{GDBN}
799
800 This chapter discusses how to start @value{GDBN}, and how to get out of it.
801 The essentials are:
802 @itemize @bullet
803 @item
804 type @samp{@value{GDBP}} to start @value{GDBN}.
805 @item
806 type @kbd{quit} or @kbd{Ctrl-d} to exit.
807 @end itemize
808
809 @menu
810 * Invoking GDB:: How to start @value{GDBN}
811 * Quitting GDB:: How to quit @value{GDBN}
812 * Shell Commands:: How to use shell commands inside @value{GDBN}
813 * Logging Output:: How to log @value{GDBN}'s output to a file
814 @end menu
815
816 @node Invoking GDB
817 @section Invoking @value{GDBN}
818
819 Invoke @value{GDBN} by running the program @code{@value{GDBP}}. Once started,
820 @value{GDBN} reads commands from the terminal until you tell it to exit.
821
822 You can also run @code{@value{GDBP}} with a variety of arguments and options,
823 to specify more of your debugging environment at the outset.
824
825 The command-line options described here are designed
826 to cover a variety of situations; in some environments, some of these
827 options may effectively be unavailable.
828
829 The most usual way to start @value{GDBN} is with one argument,
830 specifying an executable program:
831
832 @smallexample
833 @value{GDBP} @var{program}
834 @end smallexample
835
836 @noindent
837 You can also start with both an executable program and a core file
838 specified:
839
840 @smallexample
841 @value{GDBP} @var{program} @var{core}
842 @end smallexample
843
844 You can, instead, specify a process ID as a second argument, if you want
845 to debug a running process:
846
847 @smallexample
848 @value{GDBP} @var{program} 1234
849 @end smallexample
850
851 @noindent
852 would attach @value{GDBN} to process @code{1234} (unless you also have a file
853 named @file{1234}; @value{GDBN} does check for a core file first).
854
855 Taking advantage of the second command-line argument requires a fairly
856 complete operating system; when you use @value{GDBN} as a remote
857 debugger attached to a bare board, there may not be any notion of
858 ``process'', and there is often no way to get a core dump. @value{GDBN}
859 will warn you if it is unable to attach or to read core dumps.
860
861 You can optionally have @code{@value{GDBP}} pass any arguments after the
862 executable file to the inferior using @code{--args}. This option stops
863 option processing.
864 @smallexample
865 @value{GDBP} --args gcc -O2 -c foo.c
866 @end smallexample
867 This will cause @code{@value{GDBP}} to debug @code{gcc}, and to set
868 @code{gcc}'s command-line arguments (@pxref{Arguments}) to @samp{-O2 -c foo.c}.
869
870 You can run @code{@value{GDBP}} without printing the front material, which describes
871 @value{GDBN}'s non-warranty, by specifying @code{-silent}:
872
873 @smallexample
874 @value{GDBP} -silent
875 @end smallexample
876
877 @noindent
878 You can further control how @value{GDBN} starts up by using command-line
879 options. @value{GDBN} itself can remind you of the options available.
880
881 @noindent
882 Type
883
884 @smallexample
885 @value{GDBP} -help
886 @end smallexample
887
888 @noindent
889 to display all available options and briefly describe their use
890 (@samp{@value{GDBP} -h} is a shorter equivalent).
891
892 All options and command line arguments you give are processed
893 in sequential order. The order makes a difference when the
894 @samp{-x} option is used.
895
896
897 @menu
898 * File Options:: Choosing files
899 * Mode Options:: Choosing modes
900 * Startup:: What @value{GDBN} does during startup
901 @end menu
902
903 @node File Options
904 @subsection Choosing Files
905
906 When @value{GDBN} starts, it reads any arguments other than options as
907 specifying an executable file and core file (or process ID). This is
908 the same as if the arguments were specified by the @samp{-se} and
909 @samp{-c} (or @samp{-p}) options respectively. (@value{GDBN} reads the
910 first argument that does not have an associated option flag as
911 equivalent to the @samp{-se} option followed by that argument; and the
912 second argument that does not have an associated option flag, if any, as
913 equivalent to the @samp{-c}/@samp{-p} option followed by that argument.)
914 If the second argument begins with a decimal digit, @value{GDBN} will
915 first attempt to attach to it as a process, and if that fails, attempt
916 to open it as a corefile. If you have a corefile whose name begins with
917 a digit, you can prevent @value{GDBN} from treating it as a pid by
918 prefixing it with @file{./}, e.g.@: @file{./12345}.
919
920 If @value{GDBN} has not been configured to included core file support,
921 such as for most embedded targets, then it will complain about a second
922 argument and ignore it.
923
924 Many options have both long and short forms; both are shown in the
925 following list. @value{GDBN} also recognizes the long forms if you truncate
926 them, so long as enough of the option is present to be unambiguous.
927 (If you prefer, you can flag option arguments with @samp{--} rather
928 than @samp{-}, though we illustrate the more usual convention.)
929
930 @c NOTE: the @cindex entries here use double dashes ON PURPOSE. This
931 @c way, both those who look for -foo and --foo in the index, will find
932 @c it.
933
934 @table @code
935 @item -symbols @var{file}
936 @itemx -s @var{file}
937 @cindex @code{--symbols}
938 @cindex @code{-s}
939 Read symbol table from file @var{file}.
940
941 @item -exec @var{file}
942 @itemx -e @var{file}
943 @cindex @code{--exec}
944 @cindex @code{-e}
945 Use file @var{file} as the executable file to execute when appropriate,
946 and for examining pure data in conjunction with a core dump.
947
948 @item -se @var{file}
949 @cindex @code{--se}
950 Read symbol table from file @var{file} and use it as the executable
951 file.
952
953 @item -core @var{file}
954 @itemx -c @var{file}
955 @cindex @code{--core}
956 @cindex @code{-c}
957 Use file @var{file} as a core dump to examine.
958
959 @item -pid @var{number}
960 @itemx -p @var{number}
961 @cindex @code{--pid}
962 @cindex @code{-p}
963 Connect to process ID @var{number}, as with the @code{attach} command.
964
965 @item -command @var{file}
966 @itemx -x @var{file}
967 @cindex @code{--command}
968 @cindex @code{-x}
969 Execute commands from file @var{file}. The contents of this file is
970 evaluated exactly as the @code{source} command would.
971 @xref{Command Files,, Command files}.
972
973 @item -eval-command @var{command}
974 @itemx -ex @var{command}
975 @cindex @code{--eval-command}
976 @cindex @code{-ex}
977 Execute a single @value{GDBN} command.
978
979 This option may be used multiple times to call multiple commands. It may
980 also be interleaved with @samp{-command} as required.
981
982 @smallexample
983 @value{GDBP} -ex 'target sim' -ex 'load' \
984 -x setbreakpoints -ex 'run' a.out
985 @end smallexample
986
987 @item -directory @var{directory}
988 @itemx -d @var{directory}
989 @cindex @code{--directory}
990 @cindex @code{-d}
991 Add @var{directory} to the path to search for source and script files.
992
993 @item -r
994 @itemx -readnow
995 @cindex @code{--readnow}
996 @cindex @code{-r}
997 Read each symbol file's entire symbol table immediately, rather than
998 the default, which is to read it incrementally as it is needed.
999 This makes startup slower, but makes future operations faster.
1000
1001 @end table
1002
1003 @node Mode Options
1004 @subsection Choosing Modes
1005
1006 You can run @value{GDBN} in various alternative modes---for example, in
1007 batch mode or quiet mode.
1008
1009 @table @code
1010 @item -nx
1011 @itemx -n
1012 @cindex @code{--nx}
1013 @cindex @code{-n}
1014 Do not execute commands found in any initialization files. Normally,
1015 @value{GDBN} executes the commands in these files after all the command
1016 options and arguments have been processed. @xref{Command Files,,Command
1017 Files}.
1018
1019 @item -quiet
1020 @itemx -silent
1021 @itemx -q
1022 @cindex @code{--quiet}
1023 @cindex @code{--silent}
1024 @cindex @code{-q}
1025 ``Quiet''. Do not print the introductory and copyright messages. These
1026 messages are also suppressed in batch mode.
1027
1028 @item -batch
1029 @cindex @code{--batch}
1030 Run in batch mode. Exit with status @code{0} after processing all the
1031 command files specified with @samp{-x} (and all commands from
1032 initialization files, if not inhibited with @samp{-n}). Exit with
1033 nonzero status if an error occurs in executing the @value{GDBN} commands
1034 in the command files. Batch mode also disables pagination, sets unlimited
1035 terminal width and height @pxref{Screen Size}, and acts as if @kbd{set confirm
1036 off} were in effect (@pxref{Messages/Warnings}).
1037
1038 Batch mode may be useful for running @value{GDBN} as a filter, for
1039 example to download and run a program on another computer; in order to
1040 make this more useful, the message
1041
1042 @smallexample
1043 Program exited normally.
1044 @end smallexample
1045
1046 @noindent
1047 (which is ordinarily issued whenever a program running under
1048 @value{GDBN} control terminates) is not issued when running in batch
1049 mode.
1050
1051 @item -batch-silent
1052 @cindex @code{--batch-silent}
1053 Run in batch mode exactly like @samp{-batch}, but totally silently. All
1054 @value{GDBN} output to @code{stdout} is prevented (@code{stderr} is
1055 unaffected). This is much quieter than @samp{-silent} and would be useless
1056 for an interactive session.
1057
1058 This is particularly useful when using targets that give @samp{Loading section}
1059 messages, for example.
1060
1061 Note that targets that give their output via @value{GDBN}, as opposed to
1062 writing directly to @code{stdout}, will also be made silent.
1063
1064 @item -return-child-result
1065 @cindex @code{--return-child-result}
1066 The return code from @value{GDBN} will be the return code from the child
1067 process (the process being debugged), with the following exceptions:
1068
1069 @itemize @bullet
1070 @item
1071 @value{GDBN} exits abnormally. E.g., due to an incorrect argument or an
1072 internal error. In this case the exit code is the same as it would have been
1073 without @samp{-return-child-result}.
1074 @item
1075 The user quits with an explicit value. E.g., @samp{quit 1}.
1076 @item
1077 The child process never runs, or is not allowed to terminate, in which case
1078 the exit code will be -1.
1079 @end itemize
1080
1081 This option is useful in conjunction with @samp{-batch} or @samp{-batch-silent},
1082 when @value{GDBN} is being used as a remote program loader or simulator
1083 interface.
1084
1085 @item -nowindows
1086 @itemx -nw
1087 @cindex @code{--nowindows}
1088 @cindex @code{-nw}
1089 ``No windows''. If @value{GDBN} comes with a graphical user interface
1090 (GUI) built in, then this option tells @value{GDBN} to only use the command-line
1091 interface. If no GUI is available, this option has no effect.
1092
1093 @item -windows
1094 @itemx -w
1095 @cindex @code{--windows}
1096 @cindex @code{-w}
1097 If @value{GDBN} includes a GUI, then this option requires it to be
1098 used if possible.
1099
1100 @item -cd @var{directory}
1101 @cindex @code{--cd}
1102 Run @value{GDBN} using @var{directory} as its working directory,
1103 instead of the current directory.
1104
1105 @item -fullname
1106 @itemx -f
1107 @cindex @code{--fullname}
1108 @cindex @code{-f}
1109 @sc{gnu} Emacs sets this option when it runs @value{GDBN} as a
1110 subprocess. It tells @value{GDBN} to output the full file name and line
1111 number in a standard, recognizable fashion each time a stack frame is
1112 displayed (which includes each time your program stops). This
1113 recognizable format looks like two @samp{\032} characters, followed by
1114 the file name, line number and character position separated by colons,
1115 and a newline. The Emacs-to-@value{GDBN} interface program uses the two
1116 @samp{\032} characters as a signal to display the source code for the
1117 frame.
1118
1119 @item -epoch
1120 @cindex @code{--epoch}
1121 The Epoch Emacs-@value{GDBN} interface sets this option when it runs
1122 @value{GDBN} as a subprocess. It tells @value{GDBN} to modify its print
1123 routines so as to allow Epoch to display values of expressions in a
1124 separate window.
1125
1126 @item -annotate @var{level}
1127 @cindex @code{--annotate}
1128 This option sets the @dfn{annotation level} inside @value{GDBN}. Its
1129 effect is identical to using @samp{set annotate @var{level}}
1130 (@pxref{Annotations}). The annotation @var{level} controls how much
1131 information @value{GDBN} prints together with its prompt, values of
1132 expressions, source lines, and other types of output. Level 0 is the
1133 normal, level 1 is for use when @value{GDBN} is run as a subprocess of
1134 @sc{gnu} Emacs, level 3 is the maximum annotation suitable for programs
1135 that control @value{GDBN}, and level 2 has been deprecated.
1136
1137 The annotation mechanism has largely been superseded by @sc{gdb/mi}
1138 (@pxref{GDB/MI}).
1139
1140 @item --args
1141 @cindex @code{--args}
1142 Change interpretation of command line so that arguments following the
1143 executable file are passed as command line arguments to the inferior.
1144 This option stops option processing.
1145
1146 @item -baud @var{bps}
1147 @itemx -b @var{bps}
1148 @cindex @code{--baud}
1149 @cindex @code{-b}
1150 Set the line speed (baud rate or bits per second) of any serial
1151 interface used by @value{GDBN} for remote debugging.
1152
1153 @item -l @var{timeout}
1154 @cindex @code{-l}
1155 Set the timeout (in seconds) of any communication used by @value{GDBN}
1156 for remote debugging.
1157
1158 @item -tty @var{device}
1159 @itemx -t @var{device}
1160 @cindex @code{--tty}
1161 @cindex @code{-t}
1162 Run using @var{device} for your program's standard input and output.
1163 @c FIXME: kingdon thinks there is more to -tty. Investigate.
1164
1165 @c resolve the situation of these eventually
1166 @item -tui
1167 @cindex @code{--tui}
1168 Activate the @dfn{Text User Interface} when starting. The Text User
1169 Interface manages several text windows on the terminal, showing
1170 source, assembly, registers and @value{GDBN} command outputs
1171 (@pxref{TUI, ,@value{GDBN} Text User Interface}). Alternatively, the
1172 Text User Interface can be enabled by invoking the program
1173 @samp{@value{GDBTUI}}. Do not use this option if you run @value{GDBN} from
1174 Emacs (@pxref{Emacs, ,Using @value{GDBN} under @sc{gnu} Emacs}).
1175
1176 @c @item -xdb
1177 @c @cindex @code{--xdb}
1178 @c Run in XDB compatibility mode, allowing the use of certain XDB commands.
1179 @c For information, see the file @file{xdb_trans.html}, which is usually
1180 @c installed in the directory @code{/opt/langtools/wdb/doc} on HP-UX
1181 @c systems.
1182
1183 @item -interpreter @var{interp}
1184 @cindex @code{--interpreter}
1185 Use the interpreter @var{interp} for interface with the controlling
1186 program or device. This option is meant to be set by programs which
1187 communicate with @value{GDBN} using it as a back end.
1188 @xref{Interpreters, , Command Interpreters}.
1189
1190 @samp{--interpreter=mi} (or @samp{--interpreter=mi2}) causes
1191 @value{GDBN} to use the @dfn{@sc{gdb/mi} interface} (@pxref{GDB/MI, ,
1192 The @sc{gdb/mi} Interface}) included since @value{GDBN} version 6.0. The
1193 previous @sc{gdb/mi} interface, included in @value{GDBN} version 5.3 and
1194 selected with @samp{--interpreter=mi1}, is deprecated. Earlier
1195 @sc{gdb/mi} interfaces are no longer supported.
1196
1197 @item -write
1198 @cindex @code{--write}
1199 Open the executable and core files for both reading and writing. This
1200 is equivalent to the @samp{set write on} command inside @value{GDBN}
1201 (@pxref{Patching}).
1202
1203 @item -statistics
1204 @cindex @code{--statistics}
1205 This option causes @value{GDBN} to print statistics about time and
1206 memory usage after it completes each command and returns to the prompt.
1207
1208 @item -version
1209 @cindex @code{--version}
1210 This option causes @value{GDBN} to print its version number and
1211 no-warranty blurb, and exit.
1212
1213 @end table
1214
1215 @node Startup
1216 @subsection What @value{GDBN} Does During Startup
1217 @cindex @value{GDBN} startup
1218
1219 Here's the description of what @value{GDBN} does during session startup:
1220
1221 @enumerate
1222 @item
1223 Sets up the command interpreter as specified by the command line
1224 (@pxref{Mode Options, interpreter}).
1225
1226 @item
1227 @cindex init file
1228 Reads the system-wide @dfn{init file} (if @option{--with-system-gdbinit} was
1229 used when building @value{GDBN}; @pxref{System-wide configuration,
1230 ,System-wide configuration and settings}) and executes all the commands in
1231 that file.
1232
1233 @item
1234 Reads the init file (if any) in your home directory@footnote{On
1235 DOS/Windows systems, the home directory is the one pointed to by the
1236 @code{HOME} environment variable.} and executes all the commands in
1237 that file.
1238
1239 @item
1240 Processes command line options and operands.
1241
1242 @item
1243 Reads and executes the commands from init file (if any) in the current
1244 working directory. This is only done if the current directory is
1245 different from your home directory. Thus, you can have more than one
1246 init file, one generic in your home directory, and another, specific
1247 to the program you are debugging, in the directory where you invoke
1248 @value{GDBN}.
1249
1250 @item
1251 Reads command files specified by the @samp{-x} option. @xref{Command
1252 Files}, for more details about @value{GDBN} command files.
1253
1254 @item
1255 Reads the command history recorded in the @dfn{history file}.
1256 @xref{Command History}, for more details about the command history and the
1257 files where @value{GDBN} records it.
1258 @end enumerate
1259
1260 Init files use the same syntax as @dfn{command files} (@pxref{Command
1261 Files}) and are processed by @value{GDBN} in the same way. The init
1262 file in your home directory can set options (such as @samp{set
1263 complaints}) that affect subsequent processing of command line options
1264 and operands. Init files are not executed if you use the @samp{-nx}
1265 option (@pxref{Mode Options, ,Choosing Modes}).
1266
1267 To display the list of init files loaded by gdb at startup, you
1268 can use @kbd{gdb --help}.
1269
1270 @cindex init file name
1271 @cindex @file{.gdbinit}
1272 @cindex @file{gdb.ini}
1273 The @value{GDBN} init files are normally called @file{.gdbinit}.
1274 The DJGPP port of @value{GDBN} uses the name @file{gdb.ini}, due to
1275 the limitations of file names imposed by DOS filesystems. The Windows
1276 ports of @value{GDBN} use the standard name, but if they find a
1277 @file{gdb.ini} file, they warn you about that and suggest to rename
1278 the file to the standard name.
1279
1280
1281 @node Quitting GDB
1282 @section Quitting @value{GDBN}
1283 @cindex exiting @value{GDBN}
1284 @cindex leaving @value{GDBN}
1285
1286 @table @code
1287 @kindex quit @r{[}@var{expression}@r{]}
1288 @kindex q @r{(@code{quit})}
1289 @item quit @r{[}@var{expression}@r{]}
1290 @itemx q
1291 To exit @value{GDBN}, use the @code{quit} command (abbreviated
1292 @code{q}), or type an end-of-file character (usually @kbd{Ctrl-d}). If you
1293 do not supply @var{expression}, @value{GDBN} will terminate normally;
1294 otherwise it will terminate using the result of @var{expression} as the
1295 error code.
1296 @end table
1297
1298 @cindex interrupt
1299 An interrupt (often @kbd{Ctrl-c}) does not exit from @value{GDBN}, but rather
1300 terminates the action of any @value{GDBN} command that is in progress and
1301 returns to @value{GDBN} command level. It is safe to type the interrupt
1302 character at any time because @value{GDBN} does not allow it to take effect
1303 until a time when it is safe.
1304
1305 If you have been using @value{GDBN} to control an attached process or
1306 device, you can release it with the @code{detach} command
1307 (@pxref{Attach, ,Debugging an Already-running Process}).
1308
1309 @node Shell Commands
1310 @section Shell Commands
1311
1312 If you need to execute occasional shell commands during your
1313 debugging session, there is no need to leave or suspend @value{GDBN}; you can
1314 just use the @code{shell} command.
1315
1316 @table @code
1317 @kindex shell
1318 @cindex shell escape
1319 @item shell @var{command string}
1320 Invoke a standard shell to execute @var{command string}.
1321 If it exists, the environment variable @code{SHELL} determines which
1322 shell to run. Otherwise @value{GDBN} uses the default shell
1323 (@file{/bin/sh} on Unix systems, @file{COMMAND.COM} on MS-DOS, etc.).
1324 @end table
1325
1326 The utility @code{make} is often needed in development environments.
1327 You do not have to use the @code{shell} command for this purpose in
1328 @value{GDBN}:
1329
1330 @table @code
1331 @kindex make
1332 @cindex calling make
1333 @item make @var{make-args}
1334 Execute the @code{make} program with the specified
1335 arguments. This is equivalent to @samp{shell make @var{make-args}}.
1336 @end table
1337
1338 @node Logging Output
1339 @section Logging Output
1340 @cindex logging @value{GDBN} output
1341 @cindex save @value{GDBN} output to a file
1342
1343 You may want to save the output of @value{GDBN} commands to a file.
1344 There are several commands to control @value{GDBN}'s logging.
1345
1346 @table @code
1347 @kindex set logging
1348 @item set logging on
1349 Enable logging.
1350 @item set logging off
1351 Disable logging.
1352 @cindex logging file name
1353 @item set logging file @var{file}
1354 Change the name of the current logfile. The default logfile is @file{gdb.txt}.
1355 @item set logging overwrite [on|off]
1356 By default, @value{GDBN} will append to the logfile. Set @code{overwrite} if
1357 you want @code{set logging on} to overwrite the logfile instead.
1358 @item set logging redirect [on|off]
1359 By default, @value{GDBN} output will go to both the terminal and the logfile.
1360 Set @code{redirect} if you want output to go only to the log file.
1361 @kindex show logging
1362 @item show logging
1363 Show the current values of the logging settings.
1364 @end table
1365
1366 @node Commands
1367 @chapter @value{GDBN} Commands
1368
1369 You can abbreviate a @value{GDBN} command to the first few letters of the command
1370 name, if that abbreviation is unambiguous; and you can repeat certain
1371 @value{GDBN} commands by typing just @key{RET}. You can also use the @key{TAB}
1372 key to get @value{GDBN} to fill out the rest of a word in a command (or to
1373 show you the alternatives available, if there is more than one possibility).
1374
1375 @menu
1376 * Command Syntax:: How to give commands to @value{GDBN}
1377 * Completion:: Command completion
1378 * Help:: How to ask @value{GDBN} for help
1379 @end menu
1380
1381 @node Command Syntax
1382 @section Command Syntax
1383
1384 A @value{GDBN} command is a single line of input. There is no limit on
1385 how long it can be. It starts with a command name, which is followed by
1386 arguments whose meaning depends on the command name. For example, the
1387 command @code{step} accepts an argument which is the number of times to
1388 step, as in @samp{step 5}. You can also use the @code{step} command
1389 with no arguments. Some commands do not allow any arguments.
1390
1391 @cindex abbreviation
1392 @value{GDBN} command names may always be truncated if that abbreviation is
1393 unambiguous. Other possible command abbreviations are listed in the
1394 documentation for individual commands. In some cases, even ambiguous
1395 abbreviations are allowed; for example, @code{s} is specially defined as
1396 equivalent to @code{step} even though there are other commands whose
1397 names start with @code{s}. You can test abbreviations by using them as
1398 arguments to the @code{help} command.
1399
1400 @cindex repeating commands
1401 @kindex RET @r{(repeat last command)}
1402 A blank line as input to @value{GDBN} (typing just @key{RET}) means to
1403 repeat the previous command. Certain commands (for example, @code{run})
1404 will not repeat this way; these are commands whose unintentional
1405 repetition might cause trouble and which you are unlikely to want to
1406 repeat. User-defined commands can disable this feature; see
1407 @ref{Define, dont-repeat}.
1408
1409 The @code{list} and @code{x} commands, when you repeat them with
1410 @key{RET}, construct new arguments rather than repeating
1411 exactly as typed. This permits easy scanning of source or memory.
1412
1413 @value{GDBN} can also use @key{RET} in another way: to partition lengthy
1414 output, in a way similar to the common utility @code{more}
1415 (@pxref{Screen Size,,Screen Size}). Since it is easy to press one
1416 @key{RET} too many in this situation, @value{GDBN} disables command
1417 repetition after any command that generates this sort of display.
1418
1419 @kindex # @r{(a comment)}
1420 @cindex comment
1421 Any text from a @kbd{#} to the end of the line is a comment; it does
1422 nothing. This is useful mainly in command files (@pxref{Command
1423 Files,,Command Files}).
1424
1425 @cindex repeating command sequences
1426 @kindex Ctrl-o @r{(operate-and-get-next)}
1427 The @kbd{Ctrl-o} binding is useful for repeating a complex sequence of
1428 commands. This command accepts the current line, like @key{RET}, and
1429 then fetches the next line relative to the current line from the history
1430 for editing.
1431
1432 @node Completion
1433 @section Command Completion
1434
1435 @cindex completion
1436 @cindex word completion
1437 @value{GDBN} can fill in the rest of a word in a command for you, if there is
1438 only one possibility; it can also show you what the valid possibilities
1439 are for the next word in a command, at any time. This works for @value{GDBN}
1440 commands, @value{GDBN} subcommands, and the names of symbols in your program.
1441
1442 Press the @key{TAB} key whenever you want @value{GDBN} to fill out the rest
1443 of a word. If there is only one possibility, @value{GDBN} fills in the
1444 word, and waits for you to finish the command (or press @key{RET} to
1445 enter it). For example, if you type
1446
1447 @c FIXME "@key" does not distinguish its argument sufficiently to permit
1448 @c complete accuracy in these examples; space introduced for clarity.
1449 @c If texinfo enhancements make it unnecessary, it would be nice to
1450 @c replace " @key" by "@key" in the following...
1451 @smallexample
1452 (@value{GDBP}) info bre @key{TAB}
1453 @end smallexample
1454
1455 @noindent
1456 @value{GDBN} fills in the rest of the word @samp{breakpoints}, since that is
1457 the only @code{info} subcommand beginning with @samp{bre}:
1458
1459 @smallexample
1460 (@value{GDBP}) info breakpoints
1461 @end smallexample
1462
1463 @noindent
1464 You can either press @key{RET} at this point, to run the @code{info
1465 breakpoints} command, or backspace and enter something else, if
1466 @samp{breakpoints} does not look like the command you expected. (If you
1467 were sure you wanted @code{info breakpoints} in the first place, you
1468 might as well just type @key{RET} immediately after @samp{info bre},
1469 to exploit command abbreviations rather than command completion).
1470
1471 If there is more than one possibility for the next word when you press
1472 @key{TAB}, @value{GDBN} sounds a bell. You can either supply more
1473 characters and try again, or just press @key{TAB} a second time;
1474 @value{GDBN} displays all the possible completions for that word. For
1475 example, you might want to set a breakpoint on a subroutine whose name
1476 begins with @samp{make_}, but when you type @kbd{b make_@key{TAB}} @value{GDBN}
1477 just sounds the bell. Typing @key{TAB} again displays all the
1478 function names in your program that begin with those characters, for
1479 example:
1480
1481 @smallexample
1482 (@value{GDBP}) b make_ @key{TAB}
1483 @exdent @value{GDBN} sounds bell; press @key{TAB} again, to see:
1484 make_a_section_from_file make_environ
1485 make_abs_section make_function_type
1486 make_blockvector make_pointer_type
1487 make_cleanup make_reference_type
1488 make_command make_symbol_completion_list
1489 (@value{GDBP}) b make_
1490 @end smallexample
1491
1492 @noindent
1493 After displaying the available possibilities, @value{GDBN} copies your
1494 partial input (@samp{b make_} in the example) so you can finish the
1495 command.
1496
1497 If you just want to see the list of alternatives in the first place, you
1498 can press @kbd{M-?} rather than pressing @key{TAB} twice. @kbd{M-?}
1499 means @kbd{@key{META} ?}. You can type this either by holding down a
1500 key designated as the @key{META} shift on your keyboard (if there is
1501 one) while typing @kbd{?}, or as @key{ESC} followed by @kbd{?}.
1502
1503 @cindex quotes in commands
1504 @cindex completion of quoted strings
1505 Sometimes the string you need, while logically a ``word'', may contain
1506 parentheses or other characters that @value{GDBN} normally excludes from
1507 its notion of a word. To permit word completion to work in this
1508 situation, you may enclose words in @code{'} (single quote marks) in
1509 @value{GDBN} commands.
1510
1511 The most likely situation where you might need this is in typing the
1512 name of a C@t{++} function. This is because C@t{++} allows function
1513 overloading (multiple definitions of the same function, distinguished
1514 by argument type). For example, when you want to set a breakpoint you
1515 may need to distinguish whether you mean the version of @code{name}
1516 that takes an @code{int} parameter, @code{name(int)}, or the version
1517 that takes a @code{float} parameter, @code{name(float)}. To use the
1518 word-completion facilities in this situation, type a single quote
1519 @code{'} at the beginning of the function name. This alerts
1520 @value{GDBN} that it may need to consider more information than usual
1521 when you press @key{TAB} or @kbd{M-?} to request word completion:
1522
1523 @smallexample
1524 (@value{GDBP}) b 'bubble( @kbd{M-?}
1525 bubble(double,double) bubble(int,int)
1526 (@value{GDBP}) b 'bubble(
1527 @end smallexample
1528
1529 In some cases, @value{GDBN} can tell that completing a name requires using
1530 quotes. When this happens, @value{GDBN} inserts the quote for you (while
1531 completing as much as it can) if you do not type the quote in the first
1532 place:
1533
1534 @smallexample
1535 (@value{GDBP}) b bub @key{TAB}
1536 @exdent @value{GDBN} alters your input line to the following, and rings a bell:
1537 (@value{GDBP}) b 'bubble(
1538 @end smallexample
1539
1540 @noindent
1541 In general, @value{GDBN} can tell that a quote is needed (and inserts it) if
1542 you have not yet started typing the argument list when you ask for
1543 completion on an overloaded symbol.
1544
1545 For more information about overloaded functions, see @ref{C Plus Plus
1546 Expressions, ,C@t{++} Expressions}. You can use the command @code{set
1547 overload-resolution off} to disable overload resolution;
1548 see @ref{Debugging C Plus Plus, ,@value{GDBN} Features for C@t{++}}.
1549
1550 @cindex completion of structure field names
1551 @cindex structure field name completion
1552 @cindex completion of union field names
1553 @cindex union field name completion
1554 When completing in an expression which looks up a field in a
1555 structure, @value{GDBN} also tries@footnote{The completer can be
1556 confused by certain kinds of invalid expressions. Also, it only
1557 examines the static type of the expression, not the dynamic type.} to
1558 limit completions to the field names available in the type of the
1559 left-hand-side:
1560
1561 @smallexample
1562 (@value{GDBP}) p gdb_stdout.@kbd{M-?}
1563 magic to_delete to_fputs to_put to_rewind
1564 to_data to_flush to_isatty to_read to_write
1565 @end smallexample
1566
1567 @noindent
1568 This is because the @code{gdb_stdout} is a variable of the type
1569 @code{struct ui_file} that is defined in @value{GDBN} sources as
1570 follows:
1571
1572 @smallexample
1573 struct ui_file
1574 @{
1575 int *magic;
1576 ui_file_flush_ftype *to_flush;
1577 ui_file_write_ftype *to_write;
1578 ui_file_fputs_ftype *to_fputs;
1579 ui_file_read_ftype *to_read;
1580 ui_file_delete_ftype *to_delete;
1581 ui_file_isatty_ftype *to_isatty;
1582 ui_file_rewind_ftype *to_rewind;
1583 ui_file_put_ftype *to_put;
1584 void *to_data;
1585 @}
1586 @end smallexample
1587
1588
1589 @node Help
1590 @section Getting Help
1591 @cindex online documentation
1592 @kindex help
1593
1594 You can always ask @value{GDBN} itself for information on its commands,
1595 using the command @code{help}.
1596
1597 @table @code
1598 @kindex h @r{(@code{help})}
1599 @item help
1600 @itemx h
1601 You can use @code{help} (abbreviated @code{h}) with no arguments to
1602 display a short list of named classes of commands:
1603
1604 @smallexample
1605 (@value{GDBP}) help
1606 List of classes of commands:
1607
1608 aliases -- Aliases of other commands
1609 breakpoints -- Making program stop at certain points
1610 data -- Examining data
1611 files -- Specifying and examining files
1612 internals -- Maintenance commands
1613 obscure -- Obscure features
1614 running -- Running the program
1615 stack -- Examining the stack
1616 status -- Status inquiries
1617 support -- Support facilities
1618 tracepoints -- Tracing of program execution without
1619 stopping the program
1620 user-defined -- User-defined commands
1621
1622 Type "help" followed by a class name for a list of
1623 commands in that class.
1624 Type "help" followed by command name for full
1625 documentation.
1626 Command name abbreviations are allowed if unambiguous.
1627 (@value{GDBP})
1628 @end smallexample
1629 @c the above line break eliminates huge line overfull...
1630
1631 @item help @var{class}
1632 Using one of the general help classes as an argument, you can get a
1633 list of the individual commands in that class. For example, here is the
1634 help display for the class @code{status}:
1635
1636 @smallexample
1637 (@value{GDBP}) help status
1638 Status inquiries.
1639
1640 List of commands:
1641
1642 @c Line break in "show" line falsifies real output, but needed
1643 @c to fit in smallbook page size.
1644 info -- Generic command for showing things
1645 about the program being debugged
1646 show -- Generic command for showing things
1647 about the debugger
1648
1649 Type "help" followed by command name for full
1650 documentation.
1651 Command name abbreviations are allowed if unambiguous.
1652 (@value{GDBP})
1653 @end smallexample
1654
1655 @item help @var{command}
1656 With a command name as @code{help} argument, @value{GDBN} displays a
1657 short paragraph on how to use that command.
1658
1659 @kindex apropos
1660 @item apropos @var{args}
1661 The @code{apropos} command searches through all of the @value{GDBN}
1662 commands, and their documentation, for the regular expression specified in
1663 @var{args}. It prints out all matches found. For example:
1664
1665 @smallexample
1666 apropos reload
1667 @end smallexample
1668
1669 @noindent
1670 results in:
1671
1672 @smallexample
1673 @c @group
1674 set symbol-reloading -- Set dynamic symbol table reloading
1675 multiple times in one run
1676 show symbol-reloading -- Show dynamic symbol table reloading
1677 multiple times in one run
1678 @c @end group
1679 @end smallexample
1680
1681 @kindex complete
1682 @item complete @var{args}
1683 The @code{complete @var{args}} command lists all the possible completions
1684 for the beginning of a command. Use @var{args} to specify the beginning of the
1685 command you want completed. For example:
1686
1687 @smallexample
1688 complete i
1689 @end smallexample
1690
1691 @noindent results in:
1692
1693 @smallexample
1694 @group
1695 if
1696 ignore
1697 info
1698 inspect
1699 @end group
1700 @end smallexample
1701
1702 @noindent This is intended for use by @sc{gnu} Emacs.
1703 @end table
1704
1705 In addition to @code{help}, you can use the @value{GDBN} commands @code{info}
1706 and @code{show} to inquire about the state of your program, or the state
1707 of @value{GDBN} itself. Each command supports many topics of inquiry; this
1708 manual introduces each of them in the appropriate context. The listings
1709 under @code{info} and under @code{show} in the Index point to
1710 all the sub-commands. @xref{Index}.
1711
1712 @c @group
1713 @table @code
1714 @kindex info
1715 @kindex i @r{(@code{info})}
1716 @item info
1717 This command (abbreviated @code{i}) is for describing the state of your
1718 program. For example, you can show the arguments passed to a function
1719 with @code{info args}, list the registers currently in use with @code{info
1720 registers}, or list the breakpoints you have set with @code{info breakpoints}.
1721 You can get a complete list of the @code{info} sub-commands with
1722 @w{@code{help info}}.
1723
1724 @kindex set
1725 @item set
1726 You can assign the result of an expression to an environment variable with
1727 @code{set}. For example, you can set the @value{GDBN} prompt to a $-sign with
1728 @code{set prompt $}.
1729
1730 @kindex show
1731 @item show
1732 In contrast to @code{info}, @code{show} is for describing the state of
1733 @value{GDBN} itself.
1734 You can change most of the things you can @code{show}, by using the
1735 related command @code{set}; for example, you can control what number
1736 system is used for displays with @code{set radix}, or simply inquire
1737 which is currently in use with @code{show radix}.
1738
1739 @kindex info set
1740 To display all the settable parameters and their current
1741 values, you can use @code{show} with no arguments; you may also use
1742 @code{info set}. Both commands produce the same display.
1743 @c FIXME: "info set" violates the rule that "info" is for state of
1744 @c FIXME...program. Ck w/ GNU: "info set" to be called something else,
1745 @c FIXME...or change desc of rule---eg "state of prog and debugging session"?
1746 @end table
1747 @c @end group
1748
1749 Here are three miscellaneous @code{show} subcommands, all of which are
1750 exceptional in lacking corresponding @code{set} commands:
1751
1752 @table @code
1753 @kindex show version
1754 @cindex @value{GDBN} version number
1755 @item show version
1756 Show what version of @value{GDBN} is running. You should include this
1757 information in @value{GDBN} bug-reports. If multiple versions of
1758 @value{GDBN} are in use at your site, you may need to determine which
1759 version of @value{GDBN} you are running; as @value{GDBN} evolves, new
1760 commands are introduced, and old ones may wither away. Also, many
1761 system vendors ship variant versions of @value{GDBN}, and there are
1762 variant versions of @value{GDBN} in @sc{gnu}/Linux distributions as well.
1763 The version number is the same as the one announced when you start
1764 @value{GDBN}.
1765
1766 @kindex show copying
1767 @kindex info copying
1768 @cindex display @value{GDBN} copyright
1769 @item show copying
1770 @itemx info copying
1771 Display information about permission for copying @value{GDBN}.
1772
1773 @kindex show warranty
1774 @kindex info warranty
1775 @item show warranty
1776 @itemx info warranty
1777 Display the @sc{gnu} ``NO WARRANTY'' statement, or a warranty,
1778 if your version of @value{GDBN} comes with one.
1779
1780 @end table
1781
1782 @node Running
1783 @chapter Running Programs Under @value{GDBN}
1784
1785 When you run a program under @value{GDBN}, you must first generate
1786 debugging information when you compile it.
1787
1788 You may start @value{GDBN} with its arguments, if any, in an environment
1789 of your choice. If you are doing native debugging, you may redirect
1790 your program's input and output, debug an already running process, or
1791 kill a child process.
1792
1793 @menu
1794 * Compilation:: Compiling for debugging
1795 * Starting:: Starting your program
1796 * Arguments:: Your program's arguments
1797 * Environment:: Your program's environment
1798
1799 * Working Directory:: Your program's working directory
1800 * Input/Output:: Your program's input and output
1801 * Attach:: Debugging an already-running process
1802 * Kill Process:: Killing the child process
1803
1804 * Inferiors and Programs:: Debugging multiple inferiors and programs
1805 * Threads:: Debugging programs with multiple threads
1806 * Forks:: Debugging forks
1807 * Checkpoint/Restart:: Setting a @emph{bookmark} to return to later
1808 @end menu
1809
1810 @node Compilation
1811 @section Compiling for Debugging
1812
1813 In order to debug a program effectively, you need to generate
1814 debugging information when you compile it. This debugging information
1815 is stored in the object file; it describes the data type of each
1816 variable or function and the correspondence between source line numbers
1817 and addresses in the executable code.
1818
1819 To request debugging information, specify the @samp{-g} option when you run
1820 the compiler.
1821
1822 Programs that are to be shipped to your customers are compiled with
1823 optimizations, using the @samp{-O} compiler option. However, some
1824 compilers are unable to handle the @samp{-g} and @samp{-O} options
1825 together. Using those compilers, you cannot generate optimized
1826 executables containing debugging information.
1827
1828 @value{NGCC}, the @sc{gnu} C/C@t{++} compiler, supports @samp{-g} with or
1829 without @samp{-O}, making it possible to debug optimized code. We
1830 recommend that you @emph{always} use @samp{-g} whenever you compile a
1831 program. You may think your program is correct, but there is no sense
1832 in pushing your luck. For more information, see @ref{Optimized Code}.
1833
1834 Older versions of the @sc{gnu} C compiler permitted a variant option
1835 @w{@samp{-gg}} for debugging information. @value{GDBN} no longer supports this
1836 format; if your @sc{gnu} C compiler has this option, do not use it.
1837
1838 @value{GDBN} knows about preprocessor macros and can show you their
1839 expansion (@pxref{Macros}). Most compilers do not include information
1840 about preprocessor macros in the debugging information if you specify
1841 the @option{-g} flag alone, because this information is rather large.
1842 Version 3.1 and later of @value{NGCC}, the @sc{gnu} C compiler,
1843 provides macro information if you specify the options
1844 @option{-gdwarf-2} and @option{-g3}; the former option requests
1845 debugging information in the Dwarf 2 format, and the latter requests
1846 ``extra information''. In the future, we hope to find more compact
1847 ways to represent macro information, so that it can be included with
1848 @option{-g} alone.
1849
1850 @need 2000
1851 @node Starting
1852 @section Starting your Program
1853 @cindex starting
1854 @cindex running
1855
1856 @table @code
1857 @kindex run
1858 @kindex r @r{(@code{run})}
1859 @item run
1860 @itemx r
1861 Use the @code{run} command to start your program under @value{GDBN}.
1862 You must first specify the program name (except on VxWorks) with an
1863 argument to @value{GDBN} (@pxref{Invocation, ,Getting In and Out of
1864 @value{GDBN}}), or by using the @code{file} or @code{exec-file} command
1865 (@pxref{Files, ,Commands to Specify Files}).
1866
1867 @end table
1868
1869 If you are running your program in an execution environment that
1870 supports processes, @code{run} creates an inferior process and makes
1871 that process run your program. In some environments without processes,
1872 @code{run} jumps to the start of your program. Other targets,
1873 like @samp{remote}, are always running. If you get an error
1874 message like this one:
1875
1876 @smallexample
1877 The "remote" target does not support "run".
1878 Try "help target" or "continue".
1879 @end smallexample
1880
1881 @noindent
1882 then use @code{continue} to run your program. You may need @code{load}
1883 first (@pxref{load}).
1884
1885 The execution of a program is affected by certain information it
1886 receives from its superior. @value{GDBN} provides ways to specify this
1887 information, which you must do @emph{before} starting your program. (You
1888 can change it after starting your program, but such changes only affect
1889 your program the next time you start it.) This information may be
1890 divided into four categories:
1891
1892 @table @asis
1893 @item The @emph{arguments.}
1894 Specify the arguments to give your program as the arguments of the
1895 @code{run} command. If a shell is available on your target, the shell
1896 is used to pass the arguments, so that you may use normal conventions
1897 (such as wildcard expansion or variable substitution) in describing
1898 the arguments.
1899 In Unix systems, you can control which shell is used with the
1900 @code{SHELL} environment variable.
1901 @xref{Arguments, ,Your Program's Arguments}.
1902
1903 @item The @emph{environment.}
1904 Your program normally inherits its environment from @value{GDBN}, but you can
1905 use the @value{GDBN} commands @code{set environment} and @code{unset
1906 environment} to change parts of the environment that affect
1907 your program. @xref{Environment, ,Your Program's Environment}.
1908
1909 @item The @emph{working directory.}
1910 Your program inherits its working directory from @value{GDBN}. You can set
1911 the @value{GDBN} working directory with the @code{cd} command in @value{GDBN}.
1912 @xref{Working Directory, ,Your Program's Working Directory}.
1913
1914 @item The @emph{standard input and output.}
1915 Your program normally uses the same device for standard input and
1916 standard output as @value{GDBN} is using. You can redirect input and output
1917 in the @code{run} command line, or you can use the @code{tty} command to
1918 set a different device for your program.
1919 @xref{Input/Output, ,Your Program's Input and Output}.
1920
1921 @cindex pipes
1922 @emph{Warning:} While input and output redirection work, you cannot use
1923 pipes to pass the output of the program you are debugging to another
1924 program; if you attempt this, @value{GDBN} is likely to wind up debugging the
1925 wrong program.
1926 @end table
1927
1928 When you issue the @code{run} command, your program begins to execute
1929 immediately. @xref{Stopping, ,Stopping and Continuing}, for discussion
1930 of how to arrange for your program to stop. Once your program has
1931 stopped, you may call functions in your program, using the @code{print}
1932 or @code{call} commands. @xref{Data, ,Examining Data}.
1933
1934 If the modification time of your symbol file has changed since the last
1935 time @value{GDBN} read its symbols, @value{GDBN} discards its symbol
1936 table, and reads it again. When it does this, @value{GDBN} tries to retain
1937 your current breakpoints.
1938
1939 @table @code
1940 @kindex start
1941 @item start
1942 @cindex run to main procedure
1943 The name of the main procedure can vary from language to language.
1944 With C or C@t{++}, the main procedure name is always @code{main}, but
1945 other languages such as Ada do not require a specific name for their
1946 main procedure. The debugger provides a convenient way to start the
1947 execution of the program and to stop at the beginning of the main
1948 procedure, depending on the language used.
1949
1950 The @samp{start} command does the equivalent of setting a temporary
1951 breakpoint at the beginning of the main procedure and then invoking
1952 the @samp{run} command.
1953
1954 @cindex elaboration phase
1955 Some programs contain an @dfn{elaboration} phase where some startup code is
1956 executed before the main procedure is called. This depends on the
1957 languages used to write your program. In C@t{++}, for instance,
1958 constructors for static and global objects are executed before
1959 @code{main} is called. It is therefore possible that the debugger stops
1960 before reaching the main procedure. However, the temporary breakpoint
1961 will remain to halt execution.
1962
1963 Specify the arguments to give to your program as arguments to the
1964 @samp{start} command. These arguments will be given verbatim to the
1965 underlying @samp{run} command. Note that the same arguments will be
1966 reused if no argument is provided during subsequent calls to
1967 @samp{start} or @samp{run}.
1968
1969 It is sometimes necessary to debug the program during elaboration. In
1970 these cases, using the @code{start} command would stop the execution of
1971 your program too late, as the program would have already completed the
1972 elaboration phase. Under these circumstances, insert breakpoints in your
1973 elaboration code before running your program.
1974
1975 @kindex set exec-wrapper
1976 @item set exec-wrapper @var{wrapper}
1977 @itemx show exec-wrapper
1978 @itemx unset exec-wrapper
1979 When @samp{exec-wrapper} is set, the specified wrapper is used to
1980 launch programs for debugging. @value{GDBN} starts your program
1981 with a shell command of the form @kbd{exec @var{wrapper}
1982 @var{program}}. Quoting is added to @var{program} and its
1983 arguments, but not to @var{wrapper}, so you should add quotes if
1984 appropriate for your shell. The wrapper runs until it executes
1985 your program, and then @value{GDBN} takes control.
1986
1987 You can use any program that eventually calls @code{execve} with
1988 its arguments as a wrapper. Several standard Unix utilities do
1989 this, e.g.@: @code{env} and @code{nohup}. Any Unix shell script ending
1990 with @code{exec "$@@"} will also work.
1991
1992 For example, you can use @code{env} to pass an environment variable to
1993 the debugged program, without setting the variable in your shell's
1994 environment:
1995
1996 @smallexample
1997 (@value{GDBP}) set exec-wrapper env 'LD_PRELOAD=libtest.so'
1998 (@value{GDBP}) run
1999 @end smallexample
2000
2001 This command is available when debugging locally on most targets, excluding
2002 @sc{djgpp}, Cygwin, MS Windows, and QNX Neutrino.
2003
2004 @kindex set disable-randomization
2005 @item set disable-randomization
2006 @itemx set disable-randomization on
2007 This option (enabled by default in @value{GDBN}) will turn off the native
2008 randomization of the virtual address space of the started program. This option
2009 is useful for multiple debugging sessions to make the execution better
2010 reproducible and memory addresses reusable across debugging sessions.
2011
2012 This feature is implemented only on @sc{gnu}/Linux. You can get the same
2013 behavior using
2014
2015 @smallexample
2016 (@value{GDBP}) set exec-wrapper setarch `uname -m` -R
2017 @end smallexample
2018
2019 @item set disable-randomization off
2020 Leave the behavior of the started executable unchanged. Some bugs rear their
2021 ugly heads only when the program is loaded at certain addresses. If your bug
2022 disappears when you run the program under @value{GDBN}, that might be because
2023 @value{GDBN} by default disables the address randomization on platforms, such
2024 as @sc{gnu}/Linux, which do that for stand-alone programs. Use @kbd{set
2025 disable-randomization off} to try to reproduce such elusive bugs.
2026
2027 The virtual address space randomization is implemented only on @sc{gnu}/Linux.
2028 It protects the programs against some kinds of security attacks. In these
2029 cases the attacker needs to know the exact location of a concrete executable
2030 code. Randomizing its location makes it impossible to inject jumps misusing
2031 a code at its expected addresses.
2032
2033 Prelinking shared libraries provides a startup performance advantage but it
2034 makes addresses in these libraries predictable for privileged processes by
2035 having just unprivileged access at the target system. Reading the shared
2036 library binary gives enough information for assembling the malicious code
2037 misusing it. Still even a prelinked shared library can get loaded at a new
2038 random address just requiring the regular relocation process during the
2039 startup. Shared libraries not already prelinked are always loaded at
2040 a randomly chosen address.
2041
2042 Position independent executables (PIE) contain position independent code
2043 similar to the shared libraries and therefore such executables get loaded at
2044 a randomly chosen address upon startup. PIE executables always load even
2045 already prelinked shared libraries at a random address. You can build such
2046 executable using @command{gcc -fPIE -pie}.
2047
2048 Heap (malloc storage), stack and custom mmap areas are always placed randomly
2049 (as long as the randomization is enabled).
2050
2051 @item show disable-randomization
2052 Show the current setting of the explicit disable of the native randomization of
2053 the virtual address space of the started program.
2054
2055 @end table
2056
2057 @node Arguments
2058 @section Your Program's Arguments
2059
2060 @cindex arguments (to your program)
2061 The arguments to your program can be specified by the arguments of the
2062 @code{run} command.
2063 They are passed to a shell, which expands wildcard characters and
2064 performs redirection of I/O, and thence to your program. Your
2065 @code{SHELL} environment variable (if it exists) specifies what shell
2066 @value{GDBN} uses. If you do not define @code{SHELL}, @value{GDBN} uses
2067 the default shell (@file{/bin/sh} on Unix).
2068
2069 On non-Unix systems, the program is usually invoked directly by
2070 @value{GDBN}, which emulates I/O redirection via the appropriate system
2071 calls, and the wildcard characters are expanded by the startup code of
2072 the program, not by the shell.
2073
2074 @code{run} with no arguments uses the same arguments used by the previous
2075 @code{run}, or those set by the @code{set args} command.
2076
2077 @table @code
2078 @kindex set args
2079 @item set args
2080 Specify the arguments to be used the next time your program is run. If
2081 @code{set args} has no arguments, @code{run} executes your program
2082 with no arguments. Once you have run your program with arguments,
2083 using @code{set args} before the next @code{run} is the only way to run
2084 it again without arguments.
2085
2086 @kindex show args
2087 @item show args
2088 Show the arguments to give your program when it is started.
2089 @end table
2090
2091 @node Environment
2092 @section Your Program's Environment
2093
2094 @cindex environment (of your program)
2095 The @dfn{environment} consists of a set of environment variables and
2096 their values. Environment variables conventionally record such things as
2097 your user name, your home directory, your terminal type, and your search
2098 path for programs to run. Usually you set up environment variables with
2099 the shell and they are inherited by all the other programs you run. When
2100 debugging, it can be useful to try running your program with a modified
2101 environment without having to start @value{GDBN} over again.
2102
2103 @table @code
2104 @kindex path
2105 @item path @var{directory}
2106 Add @var{directory} to the front of the @code{PATH} environment variable
2107 (the search path for executables) that will be passed to your program.
2108 The value of @code{PATH} used by @value{GDBN} does not change.
2109 You may specify several directory names, separated by whitespace or by a
2110 system-dependent separator character (@samp{:} on Unix, @samp{;} on
2111 MS-DOS and MS-Windows). If @var{directory} is already in the path, it
2112 is moved to the front, so it is searched sooner.
2113
2114 You can use the string @samp{$cwd} to refer to whatever is the current
2115 working directory at the time @value{GDBN} searches the path. If you
2116 use @samp{.} instead, it refers to the directory where you executed the
2117 @code{path} command. @value{GDBN} replaces @samp{.} in the
2118 @var{directory} argument (with the current path) before adding
2119 @var{directory} to the search path.
2120 @c 'path' is explicitly nonrepeatable, but RMS points out it is silly to
2121 @c document that, since repeating it would be a no-op.
2122
2123 @kindex show paths
2124 @item show paths
2125 Display the list of search paths for executables (the @code{PATH}
2126 environment variable).
2127
2128 @kindex show environment
2129 @item show environment @r{[}@var{varname}@r{]}
2130 Print the value of environment variable @var{varname} to be given to
2131 your program when it starts. If you do not supply @var{varname},
2132 print the names and values of all environment variables to be given to
2133 your program. You can abbreviate @code{environment} as @code{env}.
2134
2135 @kindex set environment
2136 @item set environment @var{varname} @r{[}=@var{value}@r{]}
2137 Set environment variable @var{varname} to @var{value}. The value
2138 changes for your program only, not for @value{GDBN} itself. @var{value} may
2139 be any string; the values of environment variables are just strings, and
2140 any interpretation is supplied by your program itself. The @var{value}
2141 parameter is optional; if it is eliminated, the variable is set to a
2142 null value.
2143 @c "any string" here does not include leading, trailing
2144 @c blanks. Gnu asks: does anyone care?
2145
2146 For example, this command:
2147
2148 @smallexample
2149 set env USER = foo
2150 @end smallexample
2151
2152 @noindent
2153 tells the debugged program, when subsequently run, that its user is named
2154 @samp{foo}. (The spaces around @samp{=} are used for clarity here; they
2155 are not actually required.)
2156
2157 @kindex unset environment
2158 @item unset environment @var{varname}
2159 Remove variable @var{varname} from the environment to be passed to your
2160 program. This is different from @samp{set env @var{varname} =};
2161 @code{unset environment} removes the variable from the environment,
2162 rather than assigning it an empty value.
2163 @end table
2164
2165 @emph{Warning:} On Unix systems, @value{GDBN} runs your program using
2166 the shell indicated
2167 by your @code{SHELL} environment variable if it exists (or
2168 @code{/bin/sh} if not). If your @code{SHELL} variable names a shell
2169 that runs an initialization file---such as @file{.cshrc} for C-shell, or
2170 @file{.bashrc} for BASH---any variables you set in that file affect
2171 your program. You may wish to move setting of environment variables to
2172 files that are only run when you sign on, such as @file{.login} or
2173 @file{.profile}.
2174
2175 @node Working Directory
2176 @section Your Program's Working Directory
2177
2178 @cindex working directory (of your program)
2179 Each time you start your program with @code{run}, it inherits its
2180 working directory from the current working directory of @value{GDBN}.
2181 The @value{GDBN} working directory is initially whatever it inherited
2182 from its parent process (typically the shell), but you can specify a new
2183 working directory in @value{GDBN} with the @code{cd} command.
2184
2185 The @value{GDBN} working directory also serves as a default for the commands
2186 that specify files for @value{GDBN} to operate on. @xref{Files, ,Commands to
2187 Specify Files}.
2188
2189 @table @code
2190 @kindex cd
2191 @cindex change working directory
2192 @item cd @var{directory}
2193 Set the @value{GDBN} working directory to @var{directory}.
2194
2195 @kindex pwd
2196 @item pwd
2197 Print the @value{GDBN} working directory.
2198 @end table
2199
2200 It is generally impossible to find the current working directory of
2201 the process being debugged (since a program can change its directory
2202 during its run). If you work on a system where @value{GDBN} is
2203 configured with the @file{/proc} support, you can use the @code{info
2204 proc} command (@pxref{SVR4 Process Information}) to find out the
2205 current working directory of the debuggee.
2206
2207 @node Input/Output
2208 @section Your Program's Input and Output
2209
2210 @cindex redirection
2211 @cindex i/o
2212 @cindex terminal
2213 By default, the program you run under @value{GDBN} does input and output to
2214 the same terminal that @value{GDBN} uses. @value{GDBN} switches the terminal
2215 to its own terminal modes to interact with you, but it records the terminal
2216 modes your program was using and switches back to them when you continue
2217 running your program.
2218
2219 @table @code
2220 @kindex info terminal
2221 @item info terminal
2222 Displays information recorded by @value{GDBN} about the terminal modes your
2223 program is using.
2224 @end table
2225
2226 You can redirect your program's input and/or output using shell
2227 redirection with the @code{run} command. For example,
2228
2229 @smallexample
2230 run > outfile
2231 @end smallexample
2232
2233 @noindent
2234 starts your program, diverting its output to the file @file{outfile}.
2235
2236 @kindex tty
2237 @cindex controlling terminal
2238 Another way to specify where your program should do input and output is
2239 with the @code{tty} command. This command accepts a file name as
2240 argument, and causes this file to be the default for future @code{run}
2241 commands. It also resets the controlling terminal for the child
2242 process, for future @code{run} commands. For example,
2243
2244 @smallexample
2245 tty /dev/ttyb
2246 @end smallexample
2247
2248 @noindent
2249 directs that processes started with subsequent @code{run} commands
2250 default to do input and output on the terminal @file{/dev/ttyb} and have
2251 that as their controlling terminal.
2252
2253 An explicit redirection in @code{run} overrides the @code{tty} command's
2254 effect on the input/output device, but not its effect on the controlling
2255 terminal.
2256
2257 When you use the @code{tty} command or redirect input in the @code{run}
2258 command, only the input @emph{for your program} is affected. The input
2259 for @value{GDBN} still comes from your terminal. @code{tty} is an alias
2260 for @code{set inferior-tty}.
2261
2262 @cindex inferior tty
2263 @cindex set inferior controlling terminal
2264 You can use the @code{show inferior-tty} command to tell @value{GDBN} to
2265 display the name of the terminal that will be used for future runs of your
2266 program.
2267
2268 @table @code
2269 @item set inferior-tty /dev/ttyb
2270 @kindex set inferior-tty
2271 Set the tty for the program being debugged to /dev/ttyb.
2272
2273 @item show inferior-tty
2274 @kindex show inferior-tty
2275 Show the current tty for the program being debugged.
2276 @end table
2277
2278 @node Attach
2279 @section Debugging an Already-running Process
2280 @kindex attach
2281 @cindex attach
2282
2283 @table @code
2284 @item attach @var{process-id}
2285 This command attaches to a running process---one that was started
2286 outside @value{GDBN}. (@code{info files} shows your active
2287 targets.) The command takes as argument a process ID. The usual way to
2288 find out the @var{process-id} of a Unix process is with the @code{ps} utility,
2289 or with the @samp{jobs -l} shell command.
2290
2291 @code{attach} does not repeat if you press @key{RET} a second time after
2292 executing the command.
2293 @end table
2294
2295 To use @code{attach}, your program must be running in an environment
2296 which supports processes; for example, @code{attach} does not work for
2297 programs on bare-board targets that lack an operating system. You must
2298 also have permission to send the process a signal.
2299
2300 When you use @code{attach}, the debugger finds the program running in
2301 the process first by looking in the current working directory, then (if
2302 the program is not found) by using the source file search path
2303 (@pxref{Source Path, ,Specifying Source Directories}). You can also use
2304 the @code{file} command to load the program. @xref{Files, ,Commands to
2305 Specify Files}.
2306
2307 The first thing @value{GDBN} does after arranging to debug the specified
2308 process is to stop it. You can examine and modify an attached process
2309 with all the @value{GDBN} commands that are ordinarily available when
2310 you start processes with @code{run}. You can insert breakpoints; you
2311 can step and continue; you can modify storage. If you would rather the
2312 process continue running, you may use the @code{continue} command after
2313 attaching @value{GDBN} to the process.
2314
2315 @table @code
2316 @kindex detach
2317 @item detach
2318 When you have finished debugging the attached process, you can use the
2319 @code{detach} command to release it from @value{GDBN} control. Detaching
2320 the process continues its execution. After the @code{detach} command,
2321 that process and @value{GDBN} become completely independent once more, and you
2322 are ready to @code{attach} another process or start one with @code{run}.
2323 @code{detach} does not repeat if you press @key{RET} again after
2324 executing the command.
2325 @end table
2326
2327 If you exit @value{GDBN} while you have an attached process, you detach
2328 that process. If you use the @code{run} command, you kill that process.
2329 By default, @value{GDBN} asks for confirmation if you try to do either of these
2330 things; you can control whether or not you need to confirm by using the
2331 @code{set confirm} command (@pxref{Messages/Warnings, ,Optional Warnings and
2332 Messages}).
2333
2334 @node Kill Process
2335 @section Killing the Child Process
2336
2337 @table @code
2338 @kindex kill
2339 @item kill
2340 Kill the child process in which your program is running under @value{GDBN}.
2341 @end table
2342
2343 This command is useful if you wish to debug a core dump instead of a
2344 running process. @value{GDBN} ignores any core dump file while your program
2345 is running.
2346
2347 On some operating systems, a program cannot be executed outside @value{GDBN}
2348 while you have breakpoints set on it inside @value{GDBN}. You can use the
2349 @code{kill} command in this situation to permit running your program
2350 outside the debugger.
2351
2352 The @code{kill} command is also useful if you wish to recompile and
2353 relink your program, since on many systems it is impossible to modify an
2354 executable file while it is running in a process. In this case, when you
2355 next type @code{run}, @value{GDBN} notices that the file has changed, and
2356 reads the symbol table again (while trying to preserve your current
2357 breakpoint settings).
2358
2359 @node Inferiors and Programs
2360 @section Debugging Multiple Inferiors and Programs
2361
2362 @value{GDBN} lets you run and debug multiple programs in a single
2363 session. In addition, @value{GDBN} on some systems may let you run
2364 several programs simultaneously (otherwise you have to exit from one
2365 before starting another). In the most general case, you can have
2366 multiple threads of execution in each of multiple processes, launched
2367 from multiple executables.
2368
2369 @cindex inferior
2370 @value{GDBN} represents the state of each program execution with an
2371 object called an @dfn{inferior}. An inferior typically corresponds to
2372 a process, but is more general and applies also to targets that do not
2373 have processes. Inferiors may be created before a process runs, and
2374 may be retained after a process exits. Inferiors have unique
2375 identifiers that are different from process ids. Usually each
2376 inferior will also have its own distinct address space, although some
2377 embedded targets may have several inferiors running in different parts
2378 of a single address space. Each inferior may in turn have multiple
2379 threads running in it.
2380
2381 To find out what inferiors exist at any moment, use @w{@code{info
2382 inferiors}}:
2383
2384 @table @code
2385 @kindex info inferiors
2386 @item info inferiors
2387 Print a list of all inferiors currently being managed by @value{GDBN}.
2388
2389 @value{GDBN} displays for each inferior (in this order):
2390
2391 @enumerate
2392 @item
2393 the inferior number assigned by @value{GDBN}
2394
2395 @item
2396 the target system's inferior identifier
2397
2398 @item
2399 the name of the executable the inferior is running.
2400
2401 @end enumerate
2402
2403 @noindent
2404 An asterisk @samp{*} preceding the @value{GDBN} inferior number
2405 indicates the current inferior.
2406
2407 For example,
2408 @end table
2409 @c end table here to get a little more width for example
2410
2411 @smallexample
2412 (@value{GDBP}) info inferiors
2413 Num Description Executable
2414 2 process 2307 hello
2415 * 1 process 3401 goodbye
2416 @end smallexample
2417
2418 To switch focus between inferiors, use the @code{inferior} command:
2419
2420 @table @code
2421 @kindex inferior @var{infno}
2422 @item inferior @var{infno}
2423 Make inferior number @var{infno} the current inferior. The argument
2424 @var{infno} is the inferior number assigned by @value{GDBN}, as shown
2425 in the first field of the @samp{info inferiors} display.
2426 @end table
2427
2428
2429 You can get multiple executables into a debugging session via the
2430 @code{add-inferior} and @w{@code{clone-inferior}} commands. On some
2431 systems @value{GDBN} can add inferiors to the debug session
2432 automatically by following calls to @code{fork} and @code{exec}. To
2433 remove inferiors from the debugging session use the
2434 @w{@code{remove-inferior}} command.
2435
2436 @table @code
2437 @kindex add-inferior
2438 @item add-inferior [ -copies @var{n} ] [ -exec @var{executable} ]
2439 Adds @var{n} inferiors to be run using @var{executable} as the
2440 executable. @var{n} defaults to 1. If no executable is specified,
2441 the inferiors begins empty, with no program. You can still assign or
2442 change the program assigned to the inferior at any time by using the
2443 @code{file} command with the executable name as its argument.
2444
2445 @kindex clone-inferior
2446 @item clone-inferior [ -copies @var{n} ] [ @var{infno} ]
2447 Adds @var{n} inferiors ready to execute the same program as inferior
2448 @var{infno}. @var{n} defaults to 1. @var{infno} defaults to the
2449 number of the current inferior. This is a convenient command when you
2450 want to run another instance of the inferior you are debugging.
2451
2452 @smallexample
2453 (@value{GDBP}) info inferiors
2454 Num Description Executable
2455 * 1 process 29964 helloworld
2456 (@value{GDBP}) clone-inferior
2457 Added inferior 2.
2458 1 inferiors added.
2459 (@value{GDBP}) info inferiors
2460 Num Description Executable
2461 2 <null> helloworld
2462 * 1 process 29964 helloworld
2463 @end smallexample
2464
2465 You can now simply switch focus to inferior 2 and run it.
2466
2467 @kindex remove-inferior
2468 @item remove-inferior @var{infno}
2469 Removes the inferior @var{infno}. It is not possible to remove an
2470 inferior that is running with this command. For those, use the
2471 @code{kill} or @code{detach} command first.
2472
2473 @end table
2474
2475 To quit debugging one of the running inferiors that is not the current
2476 inferior, you can either detach from it by using the @w{@code{detach
2477 inferior}} command (allowing it to run independently), or kill it
2478 using the @w{@code{kill inferior}} command:
2479
2480 @table @code
2481 @kindex detach inferior @var{infno}
2482 @item detach inferior @var{infno}
2483 Detach from the inferior identified by @value{GDBN} inferior number
2484 @var{infno}. Note that the inferior's entry still stays on the list
2485 of inferiors shown by @code{info inferiors}, but its Description will
2486 show @samp{<null>}.
2487
2488 @kindex kill inferior @var{infno}
2489 @item kill inferior @var{infno}
2490 Kill the inferior identified by @value{GDBN} inferior number
2491 @var{infno}. Note that the inferior's entry still stays on the list
2492 of inferiors shown by @code{info inferiors}, but its Description will
2493 show @samp{<null>}.
2494 @end table
2495
2496 After the successful completion of a command such as @code{detach},
2497 @code{detach inferior}, @code{kill} or @code{kill inferior}, or after
2498 a normal process exit, the inferior is still valid and listed with
2499 @code{info inferiors}, ready to be restarted.
2500
2501
2502 To be notified when inferiors are started or exit under @value{GDBN}'s
2503 control use @w{@code{set print inferior-events}}:
2504
2505 @table @code
2506 @kindex set print inferior-events
2507 @cindex print messages on inferior start and exit
2508 @item set print inferior-events
2509 @itemx set print inferior-events on
2510 @itemx set print inferior-events off
2511 The @code{set print inferior-events} command allows you to enable or
2512 disable printing of messages when @value{GDBN} notices that new
2513 inferiors have started or that inferiors have exited or have been
2514 detached. By default, these messages will not be printed.
2515
2516 @kindex show print inferior-events
2517 @item show print inferior-events
2518 Show whether messages will be printed when @value{GDBN} detects that
2519 inferiors have started, exited or have been detached.
2520 @end table
2521
2522 Many commands will work the same with multiple programs as with a
2523 single program: e.g., @code{print myglobal} will simply display the
2524 value of @code{myglobal} in the current inferior.
2525
2526
2527 Occasionaly, when debugging @value{GDBN} itself, it may be useful to
2528 get more info about the relationship of inferiors, programs, address
2529 spaces in a debug session. You can do that with the @w{@code{maint
2530 info program-spaces}} command.
2531
2532 @table @code
2533 @kindex maint info program-spaces
2534 @item maint info program-spaces
2535 Print a list of all program spaces currently being managed by
2536 @value{GDBN}.
2537
2538 @value{GDBN} displays for each program space (in this order):
2539
2540 @enumerate
2541 @item
2542 the program space number assigned by @value{GDBN}
2543
2544 @item
2545 the name of the executable loaded into the program space, with e.g.,
2546 the @code{file} command.
2547
2548 @end enumerate
2549
2550 @noindent
2551 An asterisk @samp{*} preceding the @value{GDBN} program space number
2552 indicates the current program space.
2553
2554 In addition, below each program space line, @value{GDBN} prints extra
2555 information that isn't suitable to display in tabular form. For
2556 example, the list of inferiors bound to the program space.
2557
2558 @smallexample
2559 (@value{GDBP}) maint info program-spaces
2560 Id Executable
2561 2 goodbye
2562 Bound inferiors: ID 1 (process 21561)
2563 * 1 hello
2564 @end smallexample
2565
2566 Here we can see that no inferior is running the program @code{hello},
2567 while @code{process 21561} is running the program @code{goodbye}. On
2568 some targets, it is possible that multiple inferiors are bound to the
2569 same program space. The most common example is that of debugging both
2570 the parent and child processes of a @code{vfork} call. For example,
2571
2572 @smallexample
2573 (@value{GDBP}) maint info program-spaces
2574 Id Executable
2575 * 1 vfork-test
2576 Bound inferiors: ID 2 (process 18050), ID 1 (process 18045)
2577 @end smallexample
2578
2579 Here, both inferior 2 and inferior 1 are running in the same program
2580 space as a result of inferior 1 having executed a @code{vfork} call.
2581 @end table
2582
2583 @node Threads
2584 @section Debugging Programs with Multiple Threads
2585
2586 @cindex threads of execution
2587 @cindex multiple threads
2588 @cindex switching threads
2589 In some operating systems, such as HP-UX and Solaris, a single program
2590 may have more than one @dfn{thread} of execution. The precise semantics
2591 of threads differ from one operating system to another, but in general
2592 the threads of a single program are akin to multiple processes---except
2593 that they share one address space (that is, they can all examine and
2594 modify the same variables). On the other hand, each thread has its own
2595 registers and execution stack, and perhaps private memory.
2596
2597 @value{GDBN} provides these facilities for debugging multi-thread
2598 programs:
2599
2600 @itemize @bullet
2601 @item automatic notification of new threads
2602 @item @samp{thread @var{threadno}}, a command to switch among threads
2603 @item @samp{info threads}, a command to inquire about existing threads
2604 @item @samp{thread apply [@var{threadno}] [@var{all}] @var{args}},
2605 a command to apply a command to a list of threads
2606 @item thread-specific breakpoints
2607 @item @samp{set print thread-events}, which controls printing of
2608 messages on thread start and exit.
2609 @item @samp{set libthread-db-search-path @var{path}}, which lets
2610 the user specify which @code{libthread_db} to use if the default choice
2611 isn't compatible with the program.
2612 @end itemize
2613
2614 @quotation
2615 @emph{Warning:} These facilities are not yet available on every
2616 @value{GDBN} configuration where the operating system supports threads.
2617 If your @value{GDBN} does not support threads, these commands have no
2618 effect. For example, a system without thread support shows no output
2619 from @samp{info threads}, and always rejects the @code{thread} command,
2620 like this:
2621
2622 @smallexample
2623 (@value{GDBP}) info threads
2624 (@value{GDBP}) thread 1
2625 Thread ID 1 not known. Use the "info threads" command to
2626 see the IDs of currently known threads.
2627 @end smallexample
2628 @c FIXME to implementors: how hard would it be to say "sorry, this GDB
2629 @c doesn't support threads"?
2630 @end quotation
2631
2632 @cindex focus of debugging
2633 @cindex current thread
2634 The @value{GDBN} thread debugging facility allows you to observe all
2635 threads while your program runs---but whenever @value{GDBN} takes
2636 control, one thread in particular is always the focus of debugging.
2637 This thread is called the @dfn{current thread}. Debugging commands show
2638 program information from the perspective of the current thread.
2639
2640 @cindex @code{New} @var{systag} message
2641 @cindex thread identifier (system)
2642 @c FIXME-implementors!! It would be more helpful if the [New...] message
2643 @c included GDB's numeric thread handle, so you could just go to that
2644 @c thread without first checking `info threads'.
2645 Whenever @value{GDBN} detects a new thread in your program, it displays
2646 the target system's identification for the thread with a message in the
2647 form @samp{[New @var{systag}]}. @var{systag} is a thread identifier
2648 whose form varies depending on the particular system. For example, on
2649 @sc{gnu}/Linux, you might see
2650
2651 @smallexample
2652 [New Thread 46912507313328 (LWP 25582)]
2653 @end smallexample
2654
2655 @noindent
2656 when @value{GDBN} notices a new thread. In contrast, on an SGI system,
2657 the @var{systag} is simply something like @samp{process 368}, with no
2658 further qualifier.
2659
2660 @c FIXME!! (1) Does the [New...] message appear even for the very first
2661 @c thread of a program, or does it only appear for the
2662 @c second---i.e.@: when it becomes obvious we have a multithread
2663 @c program?
2664 @c (2) *Is* there necessarily a first thread always? Or do some
2665 @c multithread systems permit starting a program with multiple
2666 @c threads ab initio?
2667
2668 @cindex thread number
2669 @cindex thread identifier (GDB)
2670 For debugging purposes, @value{GDBN} associates its own thread
2671 number---always a single integer---with each thread in your program.
2672
2673 @table @code
2674 @kindex info threads
2675 @item info threads
2676 Display a summary of all threads currently in your
2677 program. @value{GDBN} displays for each thread (in this order):
2678
2679 @enumerate
2680 @item
2681 the thread number assigned by @value{GDBN}
2682
2683 @item
2684 the target system's thread identifier (@var{systag})
2685
2686 @item
2687 the current stack frame summary for that thread
2688 @end enumerate
2689
2690 @noindent
2691 An asterisk @samp{*} to the left of the @value{GDBN} thread number
2692 indicates the current thread.
2693
2694 For example,
2695 @end table
2696 @c end table here to get a little more width for example
2697
2698 @smallexample
2699 (@value{GDBP}) info threads
2700 3 process 35 thread 27 0x34e5 in sigpause ()
2701 2 process 35 thread 23 0x34e5 in sigpause ()
2702 * 1 process 35 thread 13 main (argc=1, argv=0x7ffffff8)
2703 at threadtest.c:68
2704 @end smallexample
2705
2706 On HP-UX systems:
2707
2708 @cindex debugging multithreaded programs (on HP-UX)
2709 @cindex thread identifier (GDB), on HP-UX
2710 For debugging purposes, @value{GDBN} associates its own thread
2711 number---a small integer assigned in thread-creation order---with each
2712 thread in your program.
2713
2714 @cindex @code{New} @var{systag} message, on HP-UX
2715 @cindex thread identifier (system), on HP-UX
2716 @c FIXME-implementors!! It would be more helpful if the [New...] message
2717 @c included GDB's numeric thread handle, so you could just go to that
2718 @c thread without first checking `info threads'.
2719 Whenever @value{GDBN} detects a new thread in your program, it displays
2720 both @value{GDBN}'s thread number and the target system's identification for the thread with a message in the
2721 form @samp{[New @var{systag}]}. @var{systag} is a thread identifier
2722 whose form varies depending on the particular system. For example, on
2723 HP-UX, you see
2724
2725 @smallexample
2726 [New thread 2 (system thread 26594)]
2727 @end smallexample
2728
2729 @noindent
2730 when @value{GDBN} notices a new thread.
2731
2732 @table @code
2733 @kindex info threads (HP-UX)
2734 @item info threads
2735 Display a summary of all threads currently in your
2736 program. @value{GDBN} displays for each thread (in this order):
2737
2738 @enumerate
2739 @item the thread number assigned by @value{GDBN}
2740
2741 @item the target system's thread identifier (@var{systag})
2742
2743 @item the current stack frame summary for that thread
2744 @end enumerate
2745
2746 @noindent
2747 An asterisk @samp{*} to the left of the @value{GDBN} thread number
2748 indicates the current thread.
2749
2750 For example,
2751 @end table
2752 @c end table here to get a little more width for example
2753
2754 @smallexample
2755 (@value{GDBP}) info threads
2756 * 3 system thread 26607 worker (wptr=0x7b09c318 "@@") \@*
2757 at quicksort.c:137
2758 2 system thread 26606 0x7b0030d8 in __ksleep () \@*
2759 from /usr/lib/libc.2
2760 1 system thread 27905 0x7b003498 in _brk () \@*
2761 from /usr/lib/libc.2
2762 @end smallexample
2763
2764 On Solaris, you can display more information about user threads with a
2765 Solaris-specific command:
2766
2767 @table @code
2768 @item maint info sol-threads
2769 @kindex maint info sol-threads
2770 @cindex thread info (Solaris)
2771 Display info on Solaris user threads.
2772 @end table
2773
2774 @table @code
2775 @kindex thread @var{threadno}
2776 @item thread @var{threadno}
2777 Make thread number @var{threadno} the current thread. The command
2778 argument @var{threadno} is the internal @value{GDBN} thread number, as
2779 shown in the first field of the @samp{info threads} display.
2780 @value{GDBN} responds by displaying the system identifier of the thread
2781 you selected, and its current stack frame summary:
2782
2783 @smallexample
2784 @c FIXME!! This example made up; find a @value{GDBN} w/threads and get real one
2785 (@value{GDBP}) thread 2
2786 [Switching to process 35 thread 23]
2787 0x34e5 in sigpause ()
2788 @end smallexample
2789
2790 @noindent
2791 As with the @samp{[New @dots{}]} message, the form of the text after
2792 @samp{Switching to} depends on your system's conventions for identifying
2793 threads.
2794
2795 @vindex $_thread@r{, convenience variable}
2796 The debugger convenience variable @samp{$_thread} contains the number
2797 of the current thread. You may find this useful in writing breakpoint
2798 conditional expressions, command scripts, and so forth. See
2799 @xref{Convenience Vars,, Convenience Variables}, for general
2800 information on convenience variables.
2801
2802 @kindex thread apply
2803 @cindex apply command to several threads
2804 @item thread apply [@var{threadno}] [@var{all}] @var{command}
2805 The @code{thread apply} command allows you to apply the named
2806 @var{command} to one or more threads. Specify the numbers of the
2807 threads that you want affected with the command argument
2808 @var{threadno}. It can be a single thread number, one of the numbers
2809 shown in the first field of the @samp{info threads} display; or it
2810 could be a range of thread numbers, as in @code{2-4}. To apply a
2811 command to all threads, type @kbd{thread apply all @var{command}}.
2812
2813 @kindex set print thread-events
2814 @cindex print messages on thread start and exit
2815 @item set print thread-events
2816 @itemx set print thread-events on
2817 @itemx set print thread-events off
2818 The @code{set print thread-events} command allows you to enable or
2819 disable printing of messages when @value{GDBN} notices that new threads have
2820 started or that threads have exited. By default, these messages will
2821 be printed if detection of these events is supported by the target.
2822 Note that these messages cannot be disabled on all targets.
2823
2824 @kindex show print thread-events
2825 @item show print thread-events
2826 Show whether messages will be printed when @value{GDBN} detects that threads
2827 have started and exited.
2828 @end table
2829
2830 @xref{Thread Stops,,Stopping and Starting Multi-thread Programs}, for
2831 more information about how @value{GDBN} behaves when you stop and start
2832 programs with multiple threads.
2833
2834 @xref{Set Watchpoints,,Setting Watchpoints}, for information about
2835 watchpoints in programs with multiple threads.
2836
2837 @table @code
2838 @kindex set libthread-db-search-path
2839 @cindex search path for @code{libthread_db}
2840 @item set libthread-db-search-path @r{[}@var{path}@r{]}
2841 If this variable is set, @var{path} is a colon-separated list of
2842 directories @value{GDBN} will use to search for @code{libthread_db}.
2843 If you omit @var{path}, @samp{libthread-db-search-path} will be reset to
2844 an empty list.
2845
2846 On @sc{gnu}/Linux and Solaris systems, @value{GDBN} uses a ``helper''
2847 @code{libthread_db} library to obtain information about threads in the
2848 inferior process. @value{GDBN} will use @samp{libthread-db-search-path}
2849 to find @code{libthread_db}. If that fails, @value{GDBN} will continue
2850 with default system shared library directories, and finally the directory
2851 from which @code{libpthread} was loaded in the inferior process.
2852
2853 For any @code{libthread_db} library @value{GDBN} finds in above directories,
2854 @value{GDBN} attempts to initialize it with the current inferior process.
2855 If this initialization fails (which could happen because of a version
2856 mismatch between @code{libthread_db} and @code{libpthread}), @value{GDBN}
2857 will unload @code{libthread_db}, and continue with the next directory.
2858 If none of @code{libthread_db} libraries initialize successfully,
2859 @value{GDBN} will issue a warning and thread debugging will be disabled.
2860
2861 Setting @code{libthread-db-search-path} is currently implemented
2862 only on some platforms.
2863
2864 @kindex show libthread-db-search-path
2865 @item show libthread-db-search-path
2866 Display current libthread_db search path.
2867
2868 @kindex set debug libthread-db
2869 @kindex show debug libthread-db
2870 @cindex debugging @code{libthread_db}
2871 @item set debug libthread-db
2872 @itemx show debug libthread-db
2873 Turns on or off display of @code{libthread_db}-related events.
2874 Use @code{1} to enable, @code{0} to disable.
2875 @end table
2876
2877 @node Forks
2878 @section Debugging Forks
2879
2880 @cindex fork, debugging programs which call
2881 @cindex multiple processes
2882 @cindex processes, multiple
2883 On most systems, @value{GDBN} has no special support for debugging
2884 programs which create additional processes using the @code{fork}
2885 function. When a program forks, @value{GDBN} will continue to debug the
2886 parent process and the child process will run unimpeded. If you have
2887 set a breakpoint in any code which the child then executes, the child
2888 will get a @code{SIGTRAP} signal which (unless it catches the signal)
2889 will cause it to terminate.
2890
2891 However, if you want to debug the child process there is a workaround
2892 which isn't too painful. Put a call to @code{sleep} in the code which
2893 the child process executes after the fork. It may be useful to sleep
2894 only if a certain environment variable is set, or a certain file exists,
2895 so that the delay need not occur when you don't want to run @value{GDBN}
2896 on the child. While the child is sleeping, use the @code{ps} program to
2897 get its process ID. Then tell @value{GDBN} (a new invocation of
2898 @value{GDBN} if you are also debugging the parent process) to attach to
2899 the child process (@pxref{Attach}). From that point on you can debug
2900 the child process just like any other process which you attached to.
2901
2902 On some systems, @value{GDBN} provides support for debugging programs that
2903 create additional processes using the @code{fork} or @code{vfork} functions.
2904 Currently, the only platforms with this feature are HP-UX (11.x and later
2905 only?) and @sc{gnu}/Linux (kernel version 2.5.60 and later).
2906
2907 By default, when a program forks, @value{GDBN} will continue to debug
2908 the parent process and the child process will run unimpeded.
2909
2910 If you want to follow the child process instead of the parent process,
2911 use the command @w{@code{set follow-fork-mode}}.
2912
2913 @table @code
2914 @kindex set follow-fork-mode
2915 @item set follow-fork-mode @var{mode}
2916 Set the debugger response to a program call of @code{fork} or
2917 @code{vfork}. A call to @code{fork} or @code{vfork} creates a new
2918 process. The @var{mode} argument can be:
2919
2920 @table @code
2921 @item parent
2922 The original process is debugged after a fork. The child process runs
2923 unimpeded. This is the default.
2924
2925 @item child
2926 The new process is debugged after a fork. The parent process runs
2927 unimpeded.
2928
2929 @end table
2930
2931 @kindex show follow-fork-mode
2932 @item show follow-fork-mode
2933 Display the current debugger response to a @code{fork} or @code{vfork} call.
2934 @end table
2935
2936 @cindex debugging multiple processes
2937 On Linux, if you want to debug both the parent and child processes, use the
2938 command @w{@code{set detach-on-fork}}.
2939
2940 @table @code
2941 @kindex set detach-on-fork
2942 @item set detach-on-fork @var{mode}
2943 Tells gdb whether to detach one of the processes after a fork, or
2944 retain debugger control over them both.
2945
2946 @table @code
2947 @item on
2948 The child process (or parent process, depending on the value of
2949 @code{follow-fork-mode}) will be detached and allowed to run
2950 independently. This is the default.
2951
2952 @item off
2953 Both processes will be held under the control of @value{GDBN}.
2954 One process (child or parent, depending on the value of
2955 @code{follow-fork-mode}) is debugged as usual, while the other
2956 is held suspended.
2957
2958 @end table
2959
2960 @kindex show detach-on-fork
2961 @item show detach-on-fork
2962 Show whether detach-on-fork mode is on/off.
2963 @end table
2964
2965 If you choose to set @samp{detach-on-fork} mode off, then @value{GDBN}
2966 will retain control of all forked processes (including nested forks).
2967 You can list the forked processes under the control of @value{GDBN} by
2968 using the @w{@code{info inferiors}} command, and switch from one fork
2969 to another by using the @code{inferior} command (@pxref{Inferiors and
2970 Programs, ,Debugging Multiple Inferiors and Programs}).
2971
2972 To quit debugging one of the forked processes, you can either detach
2973 from it by using the @w{@code{detach inferior}} command (allowing it
2974 to run independently), or kill it using the @w{@code{kill inferior}}
2975 command. @xref{Inferiors and Programs, ,Debugging Multiple Inferiors
2976 and Programs}.
2977
2978 If you ask to debug a child process and a @code{vfork} is followed by an
2979 @code{exec}, @value{GDBN} executes the new target up to the first
2980 breakpoint in the new target. If you have a breakpoint set on
2981 @code{main} in your original program, the breakpoint will also be set on
2982 the child process's @code{main}.
2983
2984 On some systems, when a child process is spawned by @code{vfork}, you
2985 cannot debug the child or parent until an @code{exec} call completes.
2986
2987 If you issue a @code{run} command to @value{GDBN} after an @code{exec}
2988 call executes, the new target restarts. To restart the parent
2989 process, use the @code{file} command with the parent executable name
2990 as its argument. By default, after an @code{exec} call executes,
2991 @value{GDBN} discards the symbols of the previous executable image.
2992 You can change this behaviour with the @w{@code{set follow-exec-mode}}
2993 command.
2994
2995 @table @code
2996 @kindex set follow-exec-mode
2997 @item set follow-exec-mode @var{mode}
2998
2999 Set debugger response to a program call of @code{exec}. An
3000 @code{exec} call replaces the program image of a process.
3001
3002 @code{follow-exec-mode} can be:
3003
3004 @table @code
3005 @item new
3006 @value{GDBN} creates a new inferior and rebinds the process to this
3007 new inferior. The program the process was running before the
3008 @code{exec} call can be restarted afterwards by restarting the
3009 original inferior.
3010
3011 For example:
3012
3013 @smallexample
3014 (@value{GDBP}) info inferiors
3015 (gdb) info inferior
3016 Id Description Executable
3017 * 1 <null> prog1
3018 (@value{GDBP}) run
3019 process 12020 is executing new program: prog2
3020 Program exited normally.
3021 (@value{GDBP}) info inferiors
3022 Id Description Executable
3023 * 2 <null> prog2
3024 1 <null> prog1
3025 @end smallexample
3026
3027 @item same
3028 @value{GDBN} keeps the process bound to the same inferior. The new
3029 executable image replaces the previous executable loaded in the
3030 inferior. Restarting the inferior after the @code{exec} call, with
3031 e.g., the @code{run} command, restarts the executable the process was
3032 running after the @code{exec} call. This is the default mode.
3033
3034 For example:
3035
3036 @smallexample
3037 (@value{GDBP}) info inferiors
3038 Id Description Executable
3039 * 1 <null> prog1
3040 (@value{GDBP}) run
3041 process 12020 is executing new program: prog2
3042 Program exited normally.
3043 (@value{GDBP}) info inferiors
3044 Id Description Executable
3045 * 1 <null> prog2
3046 @end smallexample
3047
3048 @end table
3049 @end table
3050
3051 You can use the @code{catch} command to make @value{GDBN} stop whenever
3052 a @code{fork}, @code{vfork}, or @code{exec} call is made. @xref{Set
3053 Catchpoints, ,Setting Catchpoints}.
3054
3055 @node Checkpoint/Restart
3056 @section Setting a @emph{Bookmark} to Return to Later
3057
3058 @cindex checkpoint
3059 @cindex restart
3060 @cindex bookmark
3061 @cindex snapshot of a process
3062 @cindex rewind program state
3063
3064 On certain operating systems@footnote{Currently, only
3065 @sc{gnu}/Linux.}, @value{GDBN} is able to save a @dfn{snapshot} of a
3066 program's state, called a @dfn{checkpoint}, and come back to it
3067 later.
3068
3069 Returning to a checkpoint effectively undoes everything that has
3070 happened in the program since the @code{checkpoint} was saved. This
3071 includes changes in memory, registers, and even (within some limits)
3072 system state. Effectively, it is like going back in time to the
3073 moment when the checkpoint was saved.
3074
3075 Thus, if you're stepping thru a program and you think you're
3076 getting close to the point where things go wrong, you can save
3077 a checkpoint. Then, if you accidentally go too far and miss
3078 the critical statement, instead of having to restart your program
3079 from the beginning, you can just go back to the checkpoint and
3080 start again from there.
3081
3082 This can be especially useful if it takes a lot of time or
3083 steps to reach the point where you think the bug occurs.
3084
3085 To use the @code{checkpoint}/@code{restart} method of debugging:
3086
3087 @table @code
3088 @kindex checkpoint
3089 @item checkpoint
3090 Save a snapshot of the debugged program's current execution state.
3091 The @code{checkpoint} command takes no arguments, but each checkpoint
3092 is assigned a small integer id, similar to a breakpoint id.
3093
3094 @kindex info checkpoints
3095 @item info checkpoints
3096 List the checkpoints that have been saved in the current debugging
3097 session. For each checkpoint, the following information will be
3098 listed:
3099
3100 @table @code
3101 @item Checkpoint ID
3102 @item Process ID
3103 @item Code Address
3104 @item Source line, or label
3105 @end table
3106
3107 @kindex restart @var{checkpoint-id}
3108 @item restart @var{checkpoint-id}
3109 Restore the program state that was saved as checkpoint number
3110 @var{checkpoint-id}. All program variables, registers, stack frames
3111 etc.@: will be returned to the values that they had when the checkpoint
3112 was saved. In essence, gdb will ``wind back the clock'' to the point
3113 in time when the checkpoint was saved.
3114
3115 Note that breakpoints, @value{GDBN} variables, command history etc.
3116 are not affected by restoring a checkpoint. In general, a checkpoint
3117 only restores things that reside in the program being debugged, not in
3118 the debugger.
3119
3120 @kindex delete checkpoint @var{checkpoint-id}
3121 @item delete checkpoint @var{checkpoint-id}
3122 Delete the previously-saved checkpoint identified by @var{checkpoint-id}.
3123
3124 @end table
3125
3126 Returning to a previously saved checkpoint will restore the user state
3127 of the program being debugged, plus a significant subset of the system
3128 (OS) state, including file pointers. It won't ``un-write'' data from
3129 a file, but it will rewind the file pointer to the previous location,
3130 so that the previously written data can be overwritten. For files
3131 opened in read mode, the pointer will also be restored so that the
3132 previously read data can be read again.
3133
3134 Of course, characters that have been sent to a printer (or other
3135 external device) cannot be ``snatched back'', and characters received
3136 from eg.@: a serial device can be removed from internal program buffers,
3137 but they cannot be ``pushed back'' into the serial pipeline, ready to
3138 be received again. Similarly, the actual contents of files that have
3139 been changed cannot be restored (at this time).
3140
3141 However, within those constraints, you actually can ``rewind'' your
3142 program to a previously saved point in time, and begin debugging it
3143 again --- and you can change the course of events so as to debug a
3144 different execution path this time.
3145
3146 @cindex checkpoints and process id
3147 Finally, there is one bit of internal program state that will be
3148 different when you return to a checkpoint --- the program's process
3149 id. Each checkpoint will have a unique process id (or @var{pid}),
3150 and each will be different from the program's original @var{pid}.
3151 If your program has saved a local copy of its process id, this could
3152 potentially pose a problem.
3153
3154 @subsection A Non-obvious Benefit of Using Checkpoints
3155
3156 On some systems such as @sc{gnu}/Linux, address space randomization
3157 is performed on new processes for security reasons. This makes it
3158 difficult or impossible to set a breakpoint, or watchpoint, on an
3159 absolute address if you have to restart the program, since the
3160 absolute location of a symbol will change from one execution to the
3161 next.
3162
3163 A checkpoint, however, is an @emph{identical} copy of a process.
3164 Therefore if you create a checkpoint at (eg.@:) the start of main,
3165 and simply return to that checkpoint instead of restarting the
3166 process, you can avoid the effects of address randomization and
3167 your symbols will all stay in the same place.
3168
3169 @node Stopping
3170 @chapter Stopping and Continuing
3171
3172 The principal purposes of using a debugger are so that you can stop your
3173 program before it terminates; or so that, if your program runs into
3174 trouble, you can investigate and find out why.
3175
3176 Inside @value{GDBN}, your program may stop for any of several reasons,
3177 such as a signal, a breakpoint, or reaching a new line after a
3178 @value{GDBN} command such as @code{step}. You may then examine and
3179 change variables, set new breakpoints or remove old ones, and then
3180 continue execution. Usually, the messages shown by @value{GDBN} provide
3181 ample explanation of the status of your program---but you can also
3182 explicitly request this information at any time.
3183
3184 @table @code
3185 @kindex info program
3186 @item info program
3187 Display information about the status of your program: whether it is
3188 running or not, what process it is, and why it stopped.
3189 @end table
3190
3191 @menu
3192 * Breakpoints:: Breakpoints, watchpoints, and catchpoints
3193 * Continuing and Stepping:: Resuming execution
3194 * Signals:: Signals
3195 * Thread Stops:: Stopping and starting multi-thread programs
3196 @end menu
3197
3198 @node Breakpoints
3199 @section Breakpoints, Watchpoints, and Catchpoints
3200
3201 @cindex breakpoints
3202 A @dfn{breakpoint} makes your program stop whenever a certain point in
3203 the program is reached. For each breakpoint, you can add conditions to
3204 control in finer detail whether your program stops. You can set
3205 breakpoints with the @code{break} command and its variants (@pxref{Set
3206 Breaks, ,Setting Breakpoints}), to specify the place where your program
3207 should stop by line number, function name or exact address in the
3208 program.
3209
3210 On some systems, you can set breakpoints in shared libraries before
3211 the executable is run. There is a minor limitation on HP-UX systems:
3212 you must wait until the executable is run in order to set breakpoints
3213 in shared library routines that are not called directly by the program
3214 (for example, routines that are arguments in a @code{pthread_create}
3215 call).
3216
3217 @cindex watchpoints
3218 @cindex data breakpoints
3219 @cindex memory tracing
3220 @cindex breakpoint on memory address
3221 @cindex breakpoint on variable modification
3222 A @dfn{watchpoint} is a special breakpoint that stops your program
3223 when the value of an expression changes. The expression may be a value
3224 of a variable, or it could involve values of one or more variables
3225 combined by operators, such as @samp{a + b}. This is sometimes called
3226 @dfn{data breakpoints}. You must use a different command to set
3227 watchpoints (@pxref{Set Watchpoints, ,Setting Watchpoints}), but aside
3228 from that, you can manage a watchpoint like any other breakpoint: you
3229 enable, disable, and delete both breakpoints and watchpoints using the
3230 same commands.
3231
3232 You can arrange to have values from your program displayed automatically
3233 whenever @value{GDBN} stops at a breakpoint. @xref{Auto Display,,
3234 Automatic Display}.
3235
3236 @cindex catchpoints
3237 @cindex breakpoint on events
3238 A @dfn{catchpoint} is another special breakpoint that stops your program
3239 when a certain kind of event occurs, such as the throwing of a C@t{++}
3240 exception or the loading of a library. As with watchpoints, you use a
3241 different command to set a catchpoint (@pxref{Set Catchpoints, ,Setting
3242 Catchpoints}), but aside from that, you can manage a catchpoint like any
3243 other breakpoint. (To stop when your program receives a signal, use the
3244 @code{handle} command; see @ref{Signals, ,Signals}.)
3245
3246 @cindex breakpoint numbers
3247 @cindex numbers for breakpoints
3248 @value{GDBN} assigns a number to each breakpoint, watchpoint, or
3249 catchpoint when you create it; these numbers are successive integers
3250 starting with one. In many of the commands for controlling various
3251 features of breakpoints you use the breakpoint number to say which
3252 breakpoint you want to change. Each breakpoint may be @dfn{enabled} or
3253 @dfn{disabled}; if disabled, it has no effect on your program until you
3254 enable it again.
3255
3256 @cindex breakpoint ranges
3257 @cindex ranges of breakpoints
3258 Some @value{GDBN} commands accept a range of breakpoints on which to
3259 operate. A breakpoint range is either a single breakpoint number, like
3260 @samp{5}, or two such numbers, in increasing order, separated by a
3261 hyphen, like @samp{5-7}. When a breakpoint range is given to a command,
3262 all breakpoints in that range are operated on.
3263
3264 @menu
3265 * Set Breaks:: Setting breakpoints
3266 * Set Watchpoints:: Setting watchpoints
3267 * Set Catchpoints:: Setting catchpoints
3268 * Delete Breaks:: Deleting breakpoints
3269 * Disabling:: Disabling breakpoints
3270 * Conditions:: Break conditions
3271 * Break Commands:: Breakpoint command lists
3272 * Save Breakpoints:: How to save breakpoints in a file
3273 * Error in Breakpoints:: ``Cannot insert breakpoints''
3274 * Breakpoint-related Warnings:: ``Breakpoint address adjusted...''
3275 @end menu
3276
3277 @node Set Breaks
3278 @subsection Setting Breakpoints
3279
3280 @c FIXME LMB what does GDB do if no code on line of breakpt?
3281 @c consider in particular declaration with/without initialization.
3282 @c
3283 @c FIXME 2 is there stuff on this already? break at fun start, already init?
3284
3285 @kindex break
3286 @kindex b @r{(@code{break})}
3287 @vindex $bpnum@r{, convenience variable}
3288 @cindex latest breakpoint
3289 Breakpoints are set with the @code{break} command (abbreviated
3290 @code{b}). The debugger convenience variable @samp{$bpnum} records the
3291 number of the breakpoint you've set most recently; see @ref{Convenience
3292 Vars,, Convenience Variables}, for a discussion of what you can do with
3293 convenience variables.
3294
3295 @table @code
3296 @item break @var{location}
3297 Set a breakpoint at the given @var{location}, which can specify a
3298 function name, a line number, or an address of an instruction.
3299 (@xref{Specify Location}, for a list of all the possible ways to
3300 specify a @var{location}.) The breakpoint will stop your program just
3301 before it executes any of the code in the specified @var{location}.
3302
3303 When using source languages that permit overloading of symbols, such as
3304 C@t{++}, a function name may refer to more than one possible place to break.
3305 @xref{Ambiguous Expressions,,Ambiguous Expressions}, for a discussion of
3306 that situation.
3307
3308 It is also possible to insert a breakpoint that will stop the program
3309 only if a specific thread (@pxref{Thread-Specific Breakpoints})
3310 or a specific task (@pxref{Ada Tasks}) hits that breakpoint.
3311
3312 @item break
3313 When called without any arguments, @code{break} sets a breakpoint at
3314 the next instruction to be executed in the selected stack frame
3315 (@pxref{Stack, ,Examining the Stack}). In any selected frame but the
3316 innermost, this makes your program stop as soon as control
3317 returns to that frame. This is similar to the effect of a
3318 @code{finish} command in the frame inside the selected frame---except
3319 that @code{finish} does not leave an active breakpoint. If you use
3320 @code{break} without an argument in the innermost frame, @value{GDBN} stops
3321 the next time it reaches the current location; this may be useful
3322 inside loops.
3323
3324 @value{GDBN} normally ignores breakpoints when it resumes execution, until at
3325 least one instruction has been executed. If it did not do this, you
3326 would be unable to proceed past a breakpoint without first disabling the
3327 breakpoint. This rule applies whether or not the breakpoint already
3328 existed when your program stopped.
3329
3330 @item break @dots{} if @var{cond}
3331 Set a breakpoint with condition @var{cond}; evaluate the expression
3332 @var{cond} each time the breakpoint is reached, and stop only if the
3333 value is nonzero---that is, if @var{cond} evaluates as true.
3334 @samp{@dots{}} stands for one of the possible arguments described
3335 above (or no argument) specifying where to break. @xref{Conditions,
3336 ,Break Conditions}, for more information on breakpoint conditions.
3337
3338 @kindex tbreak
3339 @item tbreak @var{args}
3340 Set a breakpoint enabled only for one stop. @var{args} are the
3341 same as for the @code{break} command, and the breakpoint is set in the same
3342 way, but the breakpoint is automatically deleted after the first time your
3343 program stops there. @xref{Disabling, ,Disabling Breakpoints}.
3344
3345 @kindex hbreak
3346 @cindex hardware breakpoints
3347 @item hbreak @var{args}
3348 Set a hardware-assisted breakpoint. @var{args} are the same as for the
3349 @code{break} command and the breakpoint is set in the same way, but the
3350 breakpoint requires hardware support and some target hardware may not
3351 have this support. The main purpose of this is EPROM/ROM code
3352 debugging, so you can set a breakpoint at an instruction without
3353 changing the instruction. This can be used with the new trap-generation
3354 provided by SPARClite DSU and most x86-based targets. These targets
3355 will generate traps when a program accesses some data or instruction
3356 address that is assigned to the debug registers. However the hardware
3357 breakpoint registers can take a limited number of breakpoints. For
3358 example, on the DSU, only two data breakpoints can be set at a time, and
3359 @value{GDBN} will reject this command if more than two are used. Delete
3360 or disable unused hardware breakpoints before setting new ones
3361 (@pxref{Disabling, ,Disabling Breakpoints}).
3362 @xref{Conditions, ,Break Conditions}.
3363 For remote targets, you can restrict the number of hardware
3364 breakpoints @value{GDBN} will use, see @ref{set remote
3365 hardware-breakpoint-limit}.
3366
3367 @kindex thbreak
3368 @item thbreak @var{args}
3369 Set a hardware-assisted breakpoint enabled only for one stop. @var{args}
3370 are the same as for the @code{hbreak} command and the breakpoint is set in
3371 the same way. However, like the @code{tbreak} command,
3372 the breakpoint is automatically deleted after the
3373 first time your program stops there. Also, like the @code{hbreak}
3374 command, the breakpoint requires hardware support and some target hardware
3375 may not have this support. @xref{Disabling, ,Disabling Breakpoints}.
3376 See also @ref{Conditions, ,Break Conditions}.
3377
3378 @kindex rbreak
3379 @cindex regular expression
3380 @cindex breakpoints at functions matching a regexp
3381 @cindex set breakpoints in many functions
3382 @item rbreak @var{regex}
3383 Set breakpoints on all functions matching the regular expression
3384 @var{regex}. This command sets an unconditional breakpoint on all
3385 matches, printing a list of all breakpoints it set. Once these
3386 breakpoints are set, they are treated just like the breakpoints set with
3387 the @code{break} command. You can delete them, disable them, or make
3388 them conditional the same way as any other breakpoint.
3389
3390 The syntax of the regular expression is the standard one used with tools
3391 like @file{grep}. Note that this is different from the syntax used by
3392 shells, so for instance @code{foo*} matches all functions that include
3393 an @code{fo} followed by zero or more @code{o}s. There is an implicit
3394 @code{.*} leading and trailing the regular expression you supply, so to
3395 match only functions that begin with @code{foo}, use @code{^foo}.
3396
3397 @cindex non-member C@t{++} functions, set breakpoint in
3398 When debugging C@t{++} programs, @code{rbreak} is useful for setting
3399 breakpoints on overloaded functions that are not members of any special
3400 classes.
3401
3402 @cindex set breakpoints on all functions
3403 The @code{rbreak} command can be used to set breakpoints in
3404 @strong{all} the functions in a program, like this:
3405
3406 @smallexample
3407 (@value{GDBP}) rbreak .
3408 @end smallexample
3409
3410 @item rbreak @var{file}:@var{regex}
3411 If @code{rbreak} is called with a filename qualification, it limits
3412 the search for functions matching the given regular expression to the
3413 specified @var{file}. This can be used, for example, to set breakpoints on
3414 every function in a given file:
3415
3416 @smallexample
3417 (@value{GDBP}) rbreak file.c:.
3418 @end smallexample
3419
3420 The colon separating the filename qualifier from the regex may
3421 optionally be surrounded by spaces.
3422
3423 @kindex info breakpoints
3424 @cindex @code{$_} and @code{info breakpoints}
3425 @item info breakpoints @r{[}@var{n}@r{]}
3426 @itemx info break @r{[}@var{n}@r{]}
3427 Print a table of all breakpoints, watchpoints, and catchpoints set and
3428 not deleted. Optional argument @var{n} means print information only
3429 about the specified breakpoint (or watchpoint or catchpoint). For
3430 each breakpoint, following columns are printed:
3431
3432 @table @emph
3433 @item Breakpoint Numbers
3434 @item Type
3435 Breakpoint, watchpoint, or catchpoint.
3436 @item Disposition
3437 Whether the breakpoint is marked to be disabled or deleted when hit.
3438 @item Enabled or Disabled
3439 Enabled breakpoints are marked with @samp{y}. @samp{n} marks breakpoints
3440 that are not enabled.
3441 @item Address
3442 Where the breakpoint is in your program, as a memory address. For a
3443 pending breakpoint whose address is not yet known, this field will
3444 contain @samp{<PENDING>}. Such breakpoint won't fire until a shared
3445 library that has the symbol or line referred by breakpoint is loaded.
3446 See below for details. A breakpoint with several locations will
3447 have @samp{<MULTIPLE>} in this field---see below for details.
3448 @item What
3449 Where the breakpoint is in the source for your program, as a file and
3450 line number. For a pending breakpoint, the original string passed to
3451 the breakpoint command will be listed as it cannot be resolved until
3452 the appropriate shared library is loaded in the future.
3453 @end table
3454
3455 @noindent
3456 If a breakpoint is conditional, @code{info break} shows the condition on
3457 the line following the affected breakpoint; breakpoint commands, if any,
3458 are listed after that. A pending breakpoint is allowed to have a condition
3459 specified for it. The condition is not parsed for validity until a shared
3460 library is loaded that allows the pending breakpoint to resolve to a
3461 valid location.
3462
3463 @noindent
3464 @code{info break} with a breakpoint
3465 number @var{n} as argument lists only that breakpoint. The
3466 convenience variable @code{$_} and the default examining-address for
3467 the @code{x} command are set to the address of the last breakpoint
3468 listed (@pxref{Memory, ,Examining Memory}).
3469
3470 @noindent
3471 @code{info break} displays a count of the number of times the breakpoint
3472 has been hit. This is especially useful in conjunction with the
3473 @code{ignore} command. You can ignore a large number of breakpoint
3474 hits, look at the breakpoint info to see how many times the breakpoint
3475 was hit, and then run again, ignoring one less than that number. This
3476 will get you quickly to the last hit of that breakpoint.
3477 @end table
3478
3479 @value{GDBN} allows you to set any number of breakpoints at the same place in
3480 your program. There is nothing silly or meaningless about this. When
3481 the breakpoints are conditional, this is even useful
3482 (@pxref{Conditions, ,Break Conditions}).
3483
3484 @cindex multiple locations, breakpoints
3485 @cindex breakpoints, multiple locations
3486 It is possible that a breakpoint corresponds to several locations
3487 in your program. Examples of this situation are:
3488
3489 @itemize @bullet
3490 @item
3491 For a C@t{++} constructor, the @value{NGCC} compiler generates several
3492 instances of the function body, used in different cases.
3493
3494 @item
3495 For a C@t{++} template function, a given line in the function can
3496 correspond to any number of instantiations.
3497
3498 @item
3499 For an inlined function, a given source line can correspond to
3500 several places where that function is inlined.
3501 @end itemize
3502
3503 In all those cases, @value{GDBN} will insert a breakpoint at all
3504 the relevant locations@footnote{
3505 As of this writing, multiple-location breakpoints work only if there's
3506 line number information for all the locations. This means that they
3507 will generally not work in system libraries, unless you have debug
3508 info with line numbers for them.}.
3509
3510 A breakpoint with multiple locations is displayed in the breakpoint
3511 table using several rows---one header row, followed by one row for
3512 each breakpoint location. The header row has @samp{<MULTIPLE>} in the
3513 address column. The rows for individual locations contain the actual
3514 addresses for locations, and show the functions to which those
3515 locations belong. The number column for a location is of the form
3516 @var{breakpoint-number}.@var{location-number}.
3517
3518 For example:
3519
3520 @smallexample
3521 Num Type Disp Enb Address What
3522 1 breakpoint keep y <MULTIPLE>
3523 stop only if i==1
3524 breakpoint already hit 1 time
3525 1.1 y 0x080486a2 in void foo<int>() at t.cc:8
3526 1.2 y 0x080486ca in void foo<double>() at t.cc:8
3527 @end smallexample
3528
3529 Each location can be individually enabled or disabled by passing
3530 @var{breakpoint-number}.@var{location-number} as argument to the
3531 @code{enable} and @code{disable} commands. Note that you cannot
3532 delete the individual locations from the list, you can only delete the
3533 entire list of locations that belong to their parent breakpoint (with
3534 the @kbd{delete @var{num}} command, where @var{num} is the number of
3535 the parent breakpoint, 1 in the above example). Disabling or enabling
3536 the parent breakpoint (@pxref{Disabling}) affects all of the locations
3537 that belong to that breakpoint.
3538
3539 @cindex pending breakpoints
3540 It's quite common to have a breakpoint inside a shared library.
3541 Shared libraries can be loaded and unloaded explicitly,
3542 and possibly repeatedly, as the program is executed. To support
3543 this use case, @value{GDBN} updates breakpoint locations whenever
3544 any shared library is loaded or unloaded. Typically, you would
3545 set a breakpoint in a shared library at the beginning of your
3546 debugging session, when the library is not loaded, and when the
3547 symbols from the library are not available. When you try to set
3548 breakpoint, @value{GDBN} will ask you if you want to set
3549 a so called @dfn{pending breakpoint}---breakpoint whose address
3550 is not yet resolved.
3551
3552 After the program is run, whenever a new shared library is loaded,
3553 @value{GDBN} reevaluates all the breakpoints. When a newly loaded
3554 shared library contains the symbol or line referred to by some
3555 pending breakpoint, that breakpoint is resolved and becomes an
3556 ordinary breakpoint. When a library is unloaded, all breakpoints
3557 that refer to its symbols or source lines become pending again.
3558
3559 This logic works for breakpoints with multiple locations, too. For
3560 example, if you have a breakpoint in a C@t{++} template function, and
3561 a newly loaded shared library has an instantiation of that template,
3562 a new location is added to the list of locations for the breakpoint.
3563
3564 Except for having unresolved address, pending breakpoints do not
3565 differ from regular breakpoints. You can set conditions or commands,
3566 enable and disable them and perform other breakpoint operations.
3567
3568 @value{GDBN} provides some additional commands for controlling what
3569 happens when the @samp{break} command cannot resolve breakpoint
3570 address specification to an address:
3571
3572 @kindex set breakpoint pending
3573 @kindex show breakpoint pending
3574 @table @code
3575 @item set breakpoint pending auto
3576 This is the default behavior. When @value{GDBN} cannot find the breakpoint
3577 location, it queries you whether a pending breakpoint should be created.
3578
3579 @item set breakpoint pending on
3580 This indicates that an unrecognized breakpoint location should automatically
3581 result in a pending breakpoint being created.
3582
3583 @item set breakpoint pending off
3584 This indicates that pending breakpoints are not to be created. Any
3585 unrecognized breakpoint location results in an error. This setting does
3586 not affect any pending breakpoints previously created.
3587
3588 @item show breakpoint pending
3589 Show the current behavior setting for creating pending breakpoints.
3590 @end table
3591
3592 The settings above only affect the @code{break} command and its
3593 variants. Once breakpoint is set, it will be automatically updated
3594 as shared libraries are loaded and unloaded.
3595
3596 @cindex automatic hardware breakpoints
3597 For some targets, @value{GDBN} can automatically decide if hardware or
3598 software breakpoints should be used, depending on whether the
3599 breakpoint address is read-only or read-write. This applies to
3600 breakpoints set with the @code{break} command as well as to internal
3601 breakpoints set by commands like @code{next} and @code{finish}. For
3602 breakpoints set with @code{hbreak}, @value{GDBN} will always use hardware
3603 breakpoints.
3604
3605 You can control this automatic behaviour with the following commands::
3606
3607 @kindex set breakpoint auto-hw
3608 @kindex show breakpoint auto-hw
3609 @table @code
3610 @item set breakpoint auto-hw on
3611 This is the default behavior. When @value{GDBN} sets a breakpoint, it
3612 will try to use the target memory map to decide if software or hardware
3613 breakpoint must be used.
3614
3615 @item set breakpoint auto-hw off
3616 This indicates @value{GDBN} should not automatically select breakpoint
3617 type. If the target provides a memory map, @value{GDBN} will warn when
3618 trying to set software breakpoint at a read-only address.
3619 @end table
3620
3621 @value{GDBN} normally implements breakpoints by replacing the program code
3622 at the breakpoint address with a special instruction, which, when
3623 executed, given control to the debugger. By default, the program
3624 code is so modified only when the program is resumed. As soon as
3625 the program stops, @value{GDBN} restores the original instructions. This
3626 behaviour guards against leaving breakpoints inserted in the
3627 target should gdb abrubptly disconnect. However, with slow remote
3628 targets, inserting and removing breakpoint can reduce the performance.
3629 This behavior can be controlled with the following commands::
3630
3631 @kindex set breakpoint always-inserted
3632 @kindex show breakpoint always-inserted
3633 @table @code
3634 @item set breakpoint always-inserted off
3635 All breakpoints, including newly added by the user, are inserted in
3636 the target only when the target is resumed. All breakpoints are
3637 removed from the target when it stops.
3638
3639 @item set breakpoint always-inserted on
3640 Causes all breakpoints to be inserted in the target at all times. If
3641 the user adds a new breakpoint, or changes an existing breakpoint, the
3642 breakpoints in the target are updated immediately. A breakpoint is
3643 removed from the target only when breakpoint itself is removed.
3644
3645 @cindex non-stop mode, and @code{breakpoint always-inserted}
3646 @item set breakpoint always-inserted auto
3647 This is the default mode. If @value{GDBN} is controlling the inferior
3648 in non-stop mode (@pxref{Non-Stop Mode}), gdb behaves as if
3649 @code{breakpoint always-inserted} mode is on. If @value{GDBN} is
3650 controlling the inferior in all-stop mode, @value{GDBN} behaves as if
3651 @code{breakpoint always-inserted} mode is off.
3652 @end table
3653
3654 @cindex negative breakpoint numbers
3655 @cindex internal @value{GDBN} breakpoints
3656 @value{GDBN} itself sometimes sets breakpoints in your program for
3657 special purposes, such as proper handling of @code{longjmp} (in C
3658 programs). These internal breakpoints are assigned negative numbers,
3659 starting with @code{-1}; @samp{info breakpoints} does not display them.
3660 You can see these breakpoints with the @value{GDBN} maintenance command
3661 @samp{maint info breakpoints} (@pxref{maint info breakpoints}).
3662
3663
3664 @node Set Watchpoints
3665 @subsection Setting Watchpoints
3666
3667 @cindex setting watchpoints
3668 You can use a watchpoint to stop execution whenever the value of an
3669 expression changes, without having to predict a particular place where
3670 this may happen. (This is sometimes called a @dfn{data breakpoint}.)
3671 The expression may be as simple as the value of a single variable, or
3672 as complex as many variables combined by operators. Examples include:
3673
3674 @itemize @bullet
3675 @item
3676 A reference to the value of a single variable.
3677
3678 @item
3679 An address cast to an appropriate data type. For example,
3680 @samp{*(int *)0x12345678} will watch a 4-byte region at the specified
3681 address (assuming an @code{int} occupies 4 bytes).
3682
3683 @item
3684 An arbitrarily complex expression, such as @samp{a*b + c/d}. The
3685 expression can use any operators valid in the program's native
3686 language (@pxref{Languages}).
3687 @end itemize
3688
3689 You can set a watchpoint on an expression even if the expression can
3690 not be evaluated yet. For instance, you can set a watchpoint on
3691 @samp{*global_ptr} before @samp{global_ptr} is initialized.
3692 @value{GDBN} will stop when your program sets @samp{global_ptr} and
3693 the expression produces a valid value. If the expression becomes
3694 valid in some other way than changing a variable (e.g.@: if the memory
3695 pointed to by @samp{*global_ptr} becomes readable as the result of a
3696 @code{malloc} call), @value{GDBN} may not stop until the next time
3697 the expression changes.
3698
3699 @cindex software watchpoints
3700 @cindex hardware watchpoints
3701 Depending on your system, watchpoints may be implemented in software or
3702 hardware. @value{GDBN} does software watchpointing by single-stepping your
3703 program and testing the variable's value each time, which is hundreds of
3704 times slower than normal execution. (But this may still be worth it, to
3705 catch errors where you have no clue what part of your program is the
3706 culprit.)
3707
3708 On some systems, such as HP-UX, PowerPC, @sc{gnu}/Linux and most other
3709 x86-based targets, @value{GDBN} includes support for hardware
3710 watchpoints, which do not slow down the running of your program.
3711
3712 @table @code
3713 @kindex watch
3714 @item watch @r{[}-l@r{|}-location@r{]} @var{expr} @r{[}thread @var{threadnum}@r{]}
3715 Set a watchpoint for an expression. @value{GDBN} will break when the
3716 expression @var{expr} is written into by the program and its value
3717 changes. The simplest (and the most popular) use of this command is
3718 to watch the value of a single variable:
3719
3720 @smallexample
3721 (@value{GDBP}) watch foo
3722 @end smallexample
3723
3724 If the command includes a @code{@r{[}thread @var{threadnum}@r{]}}
3725 clause, @value{GDBN} breaks only when the thread identified by
3726 @var{threadnum} changes the value of @var{expr}. If any other threads
3727 change the value of @var{expr}, @value{GDBN} will not break. Note
3728 that watchpoints restricted to a single thread in this way only work
3729 with Hardware Watchpoints.
3730
3731 Ordinarily a watchpoint respects the scope of variables in @var{expr}
3732 (see below). The @code{-location} argument tells @value{GDBN} to
3733 instead watch the memory referred to by @var{expr}. In this case,
3734 @value{GDBN} will evaluate @var{expr}, take the address of the result,
3735 and watch the memory at that address. The type of the result is used
3736 to determine the size of the watched memory. If the expression's
3737 result does not have an address, then @value{GDBN} will print an
3738 error.
3739
3740 @kindex rwatch
3741 @item rwatch @r{[}-l@r{|}-location@r{]} @var{expr} @r{[}thread @var{threadnum}@r{]}
3742 Set a watchpoint that will break when the value of @var{expr} is read
3743 by the program.
3744
3745 @kindex awatch
3746 @item awatch @r{[}-l@r{|}-location@r{]} @var{expr} @r{[}thread @var{threadnum}@r{]}
3747 Set a watchpoint that will break when @var{expr} is either read from
3748 or written into by the program.
3749
3750 @kindex info watchpoints @r{[}@var{n}@r{]}
3751 @item info watchpoints
3752 This command prints a list of watchpoints, using the same format as
3753 @code{info break} (@pxref{Set Breaks}).
3754 @end table
3755
3756 If you watch for a change in a numerically entered address you need to
3757 dereference it, as the address itself is just a constant number which will
3758 never change. @value{GDBN} refuses to create a watchpoint that watches
3759 a never-changing value:
3760
3761 @smallexample
3762 (@value{GDBP}) watch 0x600850
3763 Cannot watch constant value 0x600850.
3764 (@value{GDBP}) watch *(int *) 0x600850
3765 Watchpoint 1: *(int *) 6293584
3766 @end smallexample
3767
3768 @value{GDBN} sets a @dfn{hardware watchpoint} if possible. Hardware
3769 watchpoints execute very quickly, and the debugger reports a change in
3770 value at the exact instruction where the change occurs. If @value{GDBN}
3771 cannot set a hardware watchpoint, it sets a software watchpoint, which
3772 executes more slowly and reports the change in value at the next
3773 @emph{statement}, not the instruction, after the change occurs.
3774
3775 @cindex use only software watchpoints
3776 You can force @value{GDBN} to use only software watchpoints with the
3777 @kbd{set can-use-hw-watchpoints 0} command. With this variable set to
3778 zero, @value{GDBN} will never try to use hardware watchpoints, even if
3779 the underlying system supports them. (Note that hardware-assisted
3780 watchpoints that were set @emph{before} setting
3781 @code{can-use-hw-watchpoints} to zero will still use the hardware
3782 mechanism of watching expression values.)
3783
3784 @table @code
3785 @item set can-use-hw-watchpoints
3786 @kindex set can-use-hw-watchpoints
3787 Set whether or not to use hardware watchpoints.
3788
3789 @item show can-use-hw-watchpoints
3790 @kindex show can-use-hw-watchpoints
3791 Show the current mode of using hardware watchpoints.
3792 @end table
3793
3794 For remote targets, you can restrict the number of hardware
3795 watchpoints @value{GDBN} will use, see @ref{set remote
3796 hardware-breakpoint-limit}.
3797
3798 When you issue the @code{watch} command, @value{GDBN} reports
3799
3800 @smallexample
3801 Hardware watchpoint @var{num}: @var{expr}
3802 @end smallexample
3803
3804 @noindent
3805 if it was able to set a hardware watchpoint.
3806
3807 Currently, the @code{awatch} and @code{rwatch} commands can only set
3808 hardware watchpoints, because accesses to data that don't change the
3809 value of the watched expression cannot be detected without examining
3810 every instruction as it is being executed, and @value{GDBN} does not do
3811 that currently. If @value{GDBN} finds that it is unable to set a
3812 hardware breakpoint with the @code{awatch} or @code{rwatch} command, it
3813 will print a message like this:
3814
3815 @smallexample
3816 Expression cannot be implemented with read/access watchpoint.
3817 @end smallexample
3818
3819 Sometimes, @value{GDBN} cannot set a hardware watchpoint because the
3820 data type of the watched expression is wider than what a hardware
3821 watchpoint on the target machine can handle. For example, some systems
3822 can only watch regions that are up to 4 bytes wide; on such systems you
3823 cannot set hardware watchpoints for an expression that yields a
3824 double-precision floating-point number (which is typically 8 bytes
3825 wide). As a work-around, it might be possible to break the large region
3826 into a series of smaller ones and watch them with separate watchpoints.
3827
3828 If you set too many hardware watchpoints, @value{GDBN} might be unable
3829 to insert all of them when you resume the execution of your program.
3830 Since the precise number of active watchpoints is unknown until such
3831 time as the program is about to be resumed, @value{GDBN} might not be
3832 able to warn you about this when you set the watchpoints, and the
3833 warning will be printed only when the program is resumed:
3834
3835 @smallexample
3836 Hardware watchpoint @var{num}: Could not insert watchpoint
3837 @end smallexample
3838
3839 @noindent
3840 If this happens, delete or disable some of the watchpoints.
3841
3842 Watching complex expressions that reference many variables can also
3843 exhaust the resources available for hardware-assisted watchpoints.
3844 That's because @value{GDBN} needs to watch every variable in the
3845 expression with separately allocated resources.
3846
3847 If you call a function interactively using @code{print} or @code{call},
3848 any watchpoints you have set will be inactive until @value{GDBN} reaches another
3849 kind of breakpoint or the call completes.
3850
3851 @value{GDBN} automatically deletes watchpoints that watch local
3852 (automatic) variables, or expressions that involve such variables, when
3853 they go out of scope, that is, when the execution leaves the block in
3854 which these variables were defined. In particular, when the program
3855 being debugged terminates, @emph{all} local variables go out of scope,
3856 and so only watchpoints that watch global variables remain set. If you
3857 rerun the program, you will need to set all such watchpoints again. One
3858 way of doing that would be to set a code breakpoint at the entry to the
3859 @code{main} function and when it breaks, set all the watchpoints.
3860
3861 @cindex watchpoints and threads
3862 @cindex threads and watchpoints
3863 In multi-threaded programs, watchpoints will detect changes to the
3864 watched expression from every thread.
3865
3866 @quotation
3867 @emph{Warning:} In multi-threaded programs, software watchpoints
3868 have only limited usefulness. If @value{GDBN} creates a software
3869 watchpoint, it can only watch the value of an expression @emph{in a
3870 single thread}. If you are confident that the expression can only
3871 change due to the current thread's activity (and if you are also
3872 confident that no other thread can become current), then you can use
3873 software watchpoints as usual. However, @value{GDBN} may not notice
3874 when a non-current thread's activity changes the expression. (Hardware
3875 watchpoints, in contrast, watch an expression in all threads.)
3876 @end quotation
3877
3878 @xref{set remote hardware-watchpoint-limit}.
3879
3880 @node Set Catchpoints
3881 @subsection Setting Catchpoints
3882 @cindex catchpoints, setting
3883 @cindex exception handlers
3884 @cindex event handling
3885
3886 You can use @dfn{catchpoints} to cause the debugger to stop for certain
3887 kinds of program events, such as C@t{++} exceptions or the loading of a
3888 shared library. Use the @code{catch} command to set a catchpoint.
3889
3890 @table @code
3891 @kindex catch
3892 @item catch @var{event}
3893 Stop when @var{event} occurs. @var{event} can be any of the following:
3894 @table @code
3895 @item throw
3896 @cindex stop on C@t{++} exceptions
3897 The throwing of a C@t{++} exception.
3898
3899 @item catch
3900 The catching of a C@t{++} exception.
3901
3902 @item exception
3903 @cindex Ada exception catching
3904 @cindex catch Ada exceptions
3905 An Ada exception being raised. If an exception name is specified
3906 at the end of the command (eg @code{catch exception Program_Error}),
3907 the debugger will stop only when this specific exception is raised.
3908 Otherwise, the debugger stops execution when any Ada exception is raised.
3909
3910 When inserting an exception catchpoint on a user-defined exception whose
3911 name is identical to one of the exceptions defined by the language, the
3912 fully qualified name must be used as the exception name. Otherwise,
3913 @value{GDBN} will assume that it should stop on the pre-defined exception
3914 rather than the user-defined one. For instance, assuming an exception
3915 called @code{Constraint_Error} is defined in package @code{Pck}, then
3916 the command to use to catch such exceptions is @kbd{catch exception
3917 Pck.Constraint_Error}.
3918
3919 @item exception unhandled
3920 An exception that was raised but is not handled by the program.
3921
3922 @item assert
3923 A failed Ada assertion.
3924
3925 @item exec
3926 @cindex break on fork/exec
3927 A call to @code{exec}. This is currently only available for HP-UX
3928 and @sc{gnu}/Linux.
3929
3930 @item syscall
3931 @itemx syscall @r{[}@var{name} @r{|} @var{number}@r{]} @dots{}
3932 @cindex break on a system call.
3933 A call to or return from a system call, a.k.a.@: @dfn{syscall}. A
3934 syscall is a mechanism for application programs to request a service
3935 from the operating system (OS) or one of the OS system services.
3936 @value{GDBN} can catch some or all of the syscalls issued by the
3937 debuggee, and show the related information for each syscall. If no
3938 argument is specified, calls to and returns from all system calls
3939 will be caught.
3940
3941 @var{name} can be any system call name that is valid for the
3942 underlying OS. Just what syscalls are valid depends on the OS. On
3943 GNU and Unix systems, you can find the full list of valid syscall
3944 names on @file{/usr/include/asm/unistd.h}.
3945
3946 @c For MS-Windows, the syscall names and the corresponding numbers
3947 @c can be found, e.g., on this URL:
3948 @c http://www.metasploit.com/users/opcode/syscalls.html
3949 @c but we don't support Windows syscalls yet.
3950
3951 Normally, @value{GDBN} knows in advance which syscalls are valid for
3952 each OS, so you can use the @value{GDBN} command-line completion
3953 facilities (@pxref{Completion,, command completion}) to list the
3954 available choices.
3955
3956 You may also specify the system call numerically. A syscall's
3957 number is the value passed to the OS's syscall dispatcher to
3958 identify the requested service. When you specify the syscall by its
3959 name, @value{GDBN} uses its database of syscalls to convert the name
3960 into the corresponding numeric code, but using the number directly
3961 may be useful if @value{GDBN}'s database does not have the complete
3962 list of syscalls on your system (e.g., because @value{GDBN} lags
3963 behind the OS upgrades).
3964
3965 The example below illustrates how this command works if you don't provide
3966 arguments to it:
3967
3968 @smallexample
3969 (@value{GDBP}) catch syscall
3970 Catchpoint 1 (syscall)
3971 (@value{GDBP}) r
3972 Starting program: /tmp/catch-syscall
3973
3974 Catchpoint 1 (call to syscall 'close'), \
3975 0xffffe424 in __kernel_vsyscall ()
3976 (@value{GDBP}) c
3977 Continuing.
3978
3979 Catchpoint 1 (returned from syscall 'close'), \
3980 0xffffe424 in __kernel_vsyscall ()
3981 (@value{GDBP})
3982 @end smallexample
3983
3984 Here is an example of catching a system call by name:
3985
3986 @smallexample
3987 (@value{GDBP}) catch syscall chroot
3988 Catchpoint 1 (syscall 'chroot' [61])
3989 (@value{GDBP}) r
3990 Starting program: /tmp/catch-syscall
3991
3992 Catchpoint 1 (call to syscall 'chroot'), \
3993 0xffffe424 in __kernel_vsyscall ()
3994 (@value{GDBP}) c
3995 Continuing.
3996
3997 Catchpoint 1 (returned from syscall 'chroot'), \
3998 0xffffe424 in __kernel_vsyscall ()
3999 (@value{GDBP})
4000 @end smallexample
4001
4002 An example of specifying a system call numerically. In the case
4003 below, the syscall number has a corresponding entry in the XML
4004 file, so @value{GDBN} finds its name and prints it:
4005
4006 @smallexample
4007 (@value{GDBP}) catch syscall 252
4008 Catchpoint 1 (syscall(s) 'exit_group')
4009 (@value{GDBP}) r
4010 Starting program: /tmp/catch-syscall
4011
4012 Catchpoint 1 (call to syscall 'exit_group'), \
4013 0xffffe424 in __kernel_vsyscall ()
4014 (@value{GDBP}) c
4015 Continuing.
4016
4017 Program exited normally.
4018 (@value{GDBP})
4019 @end smallexample
4020
4021 However, there can be situations when there is no corresponding name
4022 in XML file for that syscall number. In this case, @value{GDBN} prints
4023 a warning message saying that it was not able to find the syscall name,
4024 but the catchpoint will be set anyway. See the example below:
4025
4026 @smallexample
4027 (@value{GDBP}) catch syscall 764
4028 warning: The number '764' does not represent a known syscall.
4029 Catchpoint 2 (syscall 764)
4030 (@value{GDBP})
4031 @end smallexample
4032
4033 If you configure @value{GDBN} using the @samp{--without-expat} option,
4034 it will not be able to display syscall names. Also, if your
4035 architecture does not have an XML file describing its system calls,
4036 you will not be able to see the syscall names. It is important to
4037 notice that these two features are used for accessing the syscall
4038 name database. In either case, you will see a warning like this:
4039
4040 @smallexample
4041 (@value{GDBP}) catch syscall
4042 warning: Could not open "syscalls/i386-linux.xml"
4043 warning: Could not load the syscall XML file 'syscalls/i386-linux.xml'.
4044 GDB will not be able to display syscall names.
4045 Catchpoint 1 (syscall)
4046 (@value{GDBP})
4047 @end smallexample
4048
4049 Of course, the file name will change depending on your architecture and system.
4050
4051 Still using the example above, you can also try to catch a syscall by its
4052 number. In this case, you would see something like:
4053
4054 @smallexample
4055 (@value{GDBP}) catch syscall 252
4056 Catchpoint 1 (syscall(s) 252)
4057 @end smallexample
4058
4059 Again, in this case @value{GDBN} would not be able to display syscall's names.
4060
4061 @item fork
4062 A call to @code{fork}. This is currently only available for HP-UX
4063 and @sc{gnu}/Linux.
4064
4065 @item vfork
4066 A call to @code{vfork}. This is currently only available for HP-UX
4067 and @sc{gnu}/Linux.
4068
4069 @end table
4070
4071 @item tcatch @var{event}
4072 Set a catchpoint that is enabled only for one stop. The catchpoint is
4073 automatically deleted after the first time the event is caught.
4074
4075 @end table
4076
4077 Use the @code{info break} command to list the current catchpoints.
4078
4079 There are currently some limitations to C@t{++} exception handling
4080 (@code{catch throw} and @code{catch catch}) in @value{GDBN}:
4081
4082 @itemize @bullet
4083 @item
4084 If you call a function interactively, @value{GDBN} normally returns
4085 control to you when the function has finished executing. If the call
4086 raises an exception, however, the call may bypass the mechanism that
4087 returns control to you and cause your program either to abort or to
4088 simply continue running until it hits a breakpoint, catches a signal
4089 that @value{GDBN} is listening for, or exits. This is the case even if
4090 you set a catchpoint for the exception; catchpoints on exceptions are
4091 disabled within interactive calls.
4092
4093 @item
4094 You cannot raise an exception interactively.
4095
4096 @item
4097 You cannot install an exception handler interactively.
4098 @end itemize
4099
4100 @cindex raise exceptions
4101 Sometimes @code{catch} is not the best way to debug exception handling:
4102 if you need to know exactly where an exception is raised, it is better to
4103 stop @emph{before} the exception handler is called, since that way you
4104 can see the stack before any unwinding takes place. If you set a
4105 breakpoint in an exception handler instead, it may not be easy to find
4106 out where the exception was raised.
4107
4108 To stop just before an exception handler is called, you need some
4109 knowledge of the implementation. In the case of @sc{gnu} C@t{++}, exceptions are
4110 raised by calling a library function named @code{__raise_exception}
4111 which has the following ANSI C interface:
4112
4113 @smallexample
4114 /* @var{addr} is where the exception identifier is stored.
4115 @var{id} is the exception identifier. */
4116 void __raise_exception (void **addr, void *id);
4117 @end smallexample
4118
4119 @noindent
4120 To make the debugger catch all exceptions before any stack
4121 unwinding takes place, set a breakpoint on @code{__raise_exception}
4122 (@pxref{Breakpoints, ,Breakpoints; Watchpoints; and Exceptions}).
4123
4124 With a conditional breakpoint (@pxref{Conditions, ,Break Conditions})
4125 that depends on the value of @var{id}, you can stop your program when
4126 a specific exception is raised. You can use multiple conditional
4127 breakpoints to stop your program when any of a number of exceptions are
4128 raised.
4129
4130
4131 @node Delete Breaks
4132 @subsection Deleting Breakpoints
4133
4134 @cindex clearing breakpoints, watchpoints, catchpoints
4135 @cindex deleting breakpoints, watchpoints, catchpoints
4136 It is often necessary to eliminate a breakpoint, watchpoint, or
4137 catchpoint once it has done its job and you no longer want your program
4138 to stop there. This is called @dfn{deleting} the breakpoint. A
4139 breakpoint that has been deleted no longer exists; it is forgotten.
4140
4141 With the @code{clear} command you can delete breakpoints according to
4142 where they are in your program. With the @code{delete} command you can
4143 delete individual breakpoints, watchpoints, or catchpoints by specifying
4144 their breakpoint numbers.
4145
4146 It is not necessary to delete a breakpoint to proceed past it. @value{GDBN}
4147 automatically ignores breakpoints on the first instruction to be executed
4148 when you continue execution without changing the execution address.
4149
4150 @table @code
4151 @kindex clear
4152 @item clear
4153 Delete any breakpoints at the next instruction to be executed in the
4154 selected stack frame (@pxref{Selection, ,Selecting a Frame}). When
4155 the innermost frame is selected, this is a good way to delete a
4156 breakpoint where your program just stopped.
4157
4158 @item clear @var{location}
4159 Delete any breakpoints set at the specified @var{location}.
4160 @xref{Specify Location}, for the various forms of @var{location}; the
4161 most useful ones are listed below:
4162
4163 @table @code
4164 @item clear @var{function}
4165 @itemx clear @var{filename}:@var{function}
4166 Delete any breakpoints set at entry to the named @var{function}.
4167
4168 @item clear @var{linenum}
4169 @itemx clear @var{filename}:@var{linenum}
4170 Delete any breakpoints set at or within the code of the specified
4171 @var{linenum} of the specified @var{filename}.
4172 @end table
4173
4174 @cindex delete breakpoints
4175 @kindex delete
4176 @kindex d @r{(@code{delete})}
4177 @item delete @r{[}breakpoints@r{]} @r{[}@var{range}@dots{}@r{]}
4178 Delete the breakpoints, watchpoints, or catchpoints of the breakpoint
4179 ranges specified as arguments. If no argument is specified, delete all
4180 breakpoints (@value{GDBN} asks confirmation, unless you have @code{set
4181 confirm off}). You can abbreviate this command as @code{d}.
4182 @end table
4183
4184 @node Disabling
4185 @subsection Disabling Breakpoints
4186
4187 @cindex enable/disable a breakpoint
4188 Rather than deleting a breakpoint, watchpoint, or catchpoint, you might
4189 prefer to @dfn{disable} it. This makes the breakpoint inoperative as if
4190 it had been deleted, but remembers the information on the breakpoint so
4191 that you can @dfn{enable} it again later.
4192
4193 You disable and enable breakpoints, watchpoints, and catchpoints with
4194 the @code{enable} and @code{disable} commands, optionally specifying
4195 one or more breakpoint numbers as arguments. Use @code{info break} to
4196 print a list of all breakpoints, watchpoints, and catchpoints if you
4197 do not know which numbers to use.
4198
4199 Disabling and enabling a breakpoint that has multiple locations
4200 affects all of its locations.
4201
4202 A breakpoint, watchpoint, or catchpoint can have any of four different
4203 states of enablement:
4204
4205 @itemize @bullet
4206 @item
4207 Enabled. The breakpoint stops your program. A breakpoint set
4208 with the @code{break} command starts out in this state.
4209 @item
4210 Disabled. The breakpoint has no effect on your program.
4211 @item
4212 Enabled once. The breakpoint stops your program, but then becomes
4213 disabled.
4214 @item
4215 Enabled for deletion. The breakpoint stops your program, but
4216 immediately after it does so it is deleted permanently. A breakpoint
4217 set with the @code{tbreak} command starts out in this state.
4218 @end itemize
4219
4220 You can use the following commands to enable or disable breakpoints,
4221 watchpoints, and catchpoints:
4222
4223 @table @code
4224 @kindex disable
4225 @kindex dis @r{(@code{disable})}
4226 @item disable @r{[}breakpoints@r{]} @r{[}@var{range}@dots{}@r{]}
4227 Disable the specified breakpoints---or all breakpoints, if none are
4228 listed. A disabled breakpoint has no effect but is not forgotten. All
4229 options such as ignore-counts, conditions and commands are remembered in
4230 case the breakpoint is enabled again later. You may abbreviate
4231 @code{disable} as @code{dis}.
4232
4233 @kindex enable
4234 @item enable @r{[}breakpoints@r{]} @r{[}@var{range}@dots{}@r{]}
4235 Enable the specified breakpoints (or all defined breakpoints). They
4236 become effective once again in stopping your program.
4237
4238 @item enable @r{[}breakpoints@r{]} once @var{range}@dots{}
4239 Enable the specified breakpoints temporarily. @value{GDBN} disables any
4240 of these breakpoints immediately after stopping your program.
4241
4242 @item enable @r{[}breakpoints@r{]} delete @var{range}@dots{}
4243 Enable the specified breakpoints to work once, then die. @value{GDBN}
4244 deletes any of these breakpoints as soon as your program stops there.
4245 Breakpoints set by the @code{tbreak} command start out in this state.
4246 @end table
4247
4248 @c FIXME: I think the following ``Except for [...] @code{tbreak}'' is
4249 @c confusing: tbreak is also initially enabled.
4250 Except for a breakpoint set with @code{tbreak} (@pxref{Set Breaks,
4251 ,Setting Breakpoints}), breakpoints that you set are initially enabled;
4252 subsequently, they become disabled or enabled only when you use one of
4253 the commands above. (The command @code{until} can set and delete a
4254 breakpoint of its own, but it does not change the state of your other
4255 breakpoints; see @ref{Continuing and Stepping, ,Continuing and
4256 Stepping}.)
4257
4258 @node Conditions
4259 @subsection Break Conditions
4260 @cindex conditional breakpoints
4261 @cindex breakpoint conditions
4262
4263 @c FIXME what is scope of break condition expr? Context where wanted?
4264 @c in particular for a watchpoint?
4265 The simplest sort of breakpoint breaks every time your program reaches a
4266 specified place. You can also specify a @dfn{condition} for a
4267 breakpoint. A condition is just a Boolean expression in your
4268 programming language (@pxref{Expressions, ,Expressions}). A breakpoint with
4269 a condition evaluates the expression each time your program reaches it,
4270 and your program stops only if the condition is @emph{true}.
4271
4272 This is the converse of using assertions for program validation; in that
4273 situation, you want to stop when the assertion is violated---that is,
4274 when the condition is false. In C, if you want to test an assertion expressed
4275 by the condition @var{assert}, you should set the condition
4276 @samp{! @var{assert}} on the appropriate breakpoint.
4277
4278 Conditions are also accepted for watchpoints; you may not need them,
4279 since a watchpoint is inspecting the value of an expression anyhow---but
4280 it might be simpler, say, to just set a watchpoint on a variable name,
4281 and specify a condition that tests whether the new value is an interesting
4282 one.
4283
4284 Break conditions can have side effects, and may even call functions in
4285 your program. This can be useful, for example, to activate functions
4286 that log program progress, or to use your own print functions to
4287 format special data structures. The effects are completely predictable
4288 unless there is another enabled breakpoint at the same address. (In
4289 that case, @value{GDBN} might see the other breakpoint first and stop your
4290 program without checking the condition of this one.) Note that
4291 breakpoint commands are usually more convenient and flexible than break
4292 conditions for the
4293 purpose of performing side effects when a breakpoint is reached
4294 (@pxref{Break Commands, ,Breakpoint Command Lists}).
4295
4296 Break conditions can be specified when a breakpoint is set, by using
4297 @samp{if} in the arguments to the @code{break} command. @xref{Set
4298 Breaks, ,Setting Breakpoints}. They can also be changed at any time
4299 with the @code{condition} command.
4300
4301 You can also use the @code{if} keyword with the @code{watch} command.
4302 The @code{catch} command does not recognize the @code{if} keyword;
4303 @code{condition} is the only way to impose a further condition on a
4304 catchpoint.
4305
4306 @table @code
4307 @kindex condition
4308 @item condition @var{bnum} @var{expression}
4309 Specify @var{expression} as the break condition for breakpoint,
4310 watchpoint, or catchpoint number @var{bnum}. After you set a condition,
4311 breakpoint @var{bnum} stops your program only if the value of
4312 @var{expression} is true (nonzero, in C). When you use
4313 @code{condition}, @value{GDBN} checks @var{expression} immediately for
4314 syntactic correctness, and to determine whether symbols in it have
4315 referents in the context of your breakpoint. If @var{expression} uses
4316 symbols not referenced in the context of the breakpoint, @value{GDBN}
4317 prints an error message:
4318
4319 @smallexample
4320 No symbol "foo" in current context.
4321 @end smallexample
4322
4323 @noindent
4324 @value{GDBN} does
4325 not actually evaluate @var{expression} at the time the @code{condition}
4326 command (or a command that sets a breakpoint with a condition, like
4327 @code{break if @dots{}}) is given, however. @xref{Expressions, ,Expressions}.
4328
4329 @item condition @var{bnum}
4330 Remove the condition from breakpoint number @var{bnum}. It becomes
4331 an ordinary unconditional breakpoint.
4332 @end table
4333
4334 @cindex ignore count (of breakpoint)
4335 A special case of a breakpoint condition is to stop only when the
4336 breakpoint has been reached a certain number of times. This is so
4337 useful that there is a special way to do it, using the @dfn{ignore
4338 count} of the breakpoint. Every breakpoint has an ignore count, which
4339 is an integer. Most of the time, the ignore count is zero, and
4340 therefore has no effect. But if your program reaches a breakpoint whose
4341 ignore count is positive, then instead of stopping, it just decrements
4342 the ignore count by one and continues. As a result, if the ignore count
4343 value is @var{n}, the breakpoint does not stop the next @var{n} times
4344 your program reaches it.
4345
4346 @table @code
4347 @kindex ignore
4348 @item ignore @var{bnum} @var{count}
4349 Set the ignore count of breakpoint number @var{bnum} to @var{count}.
4350 The next @var{count} times the breakpoint is reached, your program's
4351 execution does not stop; other than to decrement the ignore count, @value{GDBN}
4352 takes no action.
4353
4354 To make the breakpoint stop the next time it is reached, specify
4355 a count of zero.
4356
4357 When you use @code{continue} to resume execution of your program from a
4358 breakpoint, you can specify an ignore count directly as an argument to
4359 @code{continue}, rather than using @code{ignore}. @xref{Continuing and
4360 Stepping,,Continuing and Stepping}.
4361
4362 If a breakpoint has a positive ignore count and a condition, the
4363 condition is not checked. Once the ignore count reaches zero,
4364 @value{GDBN} resumes checking the condition.
4365
4366 You could achieve the effect of the ignore count with a condition such
4367 as @w{@samp{$foo-- <= 0}} using a debugger convenience variable that
4368 is decremented each time. @xref{Convenience Vars, ,Convenience
4369 Variables}.
4370 @end table
4371
4372 Ignore counts apply to breakpoints, watchpoints, and catchpoints.
4373
4374
4375 @node Break Commands
4376 @subsection Breakpoint Command Lists
4377
4378 @cindex breakpoint commands
4379 You can give any breakpoint (or watchpoint or catchpoint) a series of
4380 commands to execute when your program stops due to that breakpoint. For
4381 example, you might want to print the values of certain expressions, or
4382 enable other breakpoints.
4383
4384 @table @code
4385 @kindex commands
4386 @kindex end@r{ (breakpoint commands)}
4387 @item commands @r{[}@var{range}@dots{}@r{]}
4388 @itemx @dots{} @var{command-list} @dots{}
4389 @itemx end
4390 Specify a list of commands for the given breakpoints. The commands
4391 themselves appear on the following lines. Type a line containing just
4392 @code{end} to terminate the commands.
4393
4394 To remove all commands from a breakpoint, type @code{commands} and
4395 follow it immediately with @code{end}; that is, give no commands.
4396
4397 With no argument, @code{commands} refers to the last breakpoint,
4398 watchpoint, or catchpoint set (not to the breakpoint most recently
4399 encountered). If the most recent breakpoints were set with a single
4400 command, then the @code{commands} will apply to all the breakpoints
4401 set by that command. This applies to breakpoints set by
4402 @code{rbreak}, and also applies when a single @code{break} command
4403 creates multiple breakpoints (@pxref{Ambiguous Expressions,,Ambiguous
4404 Expressions}).
4405 @end table
4406
4407 Pressing @key{RET} as a means of repeating the last @value{GDBN} command is
4408 disabled within a @var{command-list}.
4409
4410 You can use breakpoint commands to start your program up again. Simply
4411 use the @code{continue} command, or @code{step}, or any other command
4412 that resumes execution.
4413
4414 Any other commands in the command list, after a command that resumes
4415 execution, are ignored. This is because any time you resume execution
4416 (even with a simple @code{next} or @code{step}), you may encounter
4417 another breakpoint---which could have its own command list, leading to
4418 ambiguities about which list to execute.
4419
4420 @kindex silent
4421 If the first command you specify in a command list is @code{silent}, the
4422 usual message about stopping at a breakpoint is not printed. This may
4423 be desirable for breakpoints that are to print a specific message and
4424 then continue. If none of the remaining commands print anything, you
4425 see no sign that the breakpoint was reached. @code{silent} is
4426 meaningful only at the beginning of a breakpoint command list.
4427
4428 The commands @code{echo}, @code{output}, and @code{printf} allow you to
4429 print precisely controlled output, and are often useful in silent
4430 breakpoints. @xref{Output, ,Commands for Controlled Output}.
4431
4432 For example, here is how you could use breakpoint commands to print the
4433 value of @code{x} at entry to @code{foo} whenever @code{x} is positive.
4434
4435 @smallexample
4436 break foo if x>0
4437 commands
4438 silent
4439 printf "x is %d\n",x
4440 cont
4441 end
4442 @end smallexample
4443
4444 One application for breakpoint commands is to compensate for one bug so
4445 you can test for another. Put a breakpoint just after the erroneous line
4446 of code, give it a condition to detect the case in which something
4447 erroneous has been done, and give it commands to assign correct values
4448 to any variables that need them. End with the @code{continue} command
4449 so that your program does not stop, and start with the @code{silent}
4450 command so that no output is produced. Here is an example:
4451
4452 @smallexample
4453 break 403
4454 commands
4455 silent
4456 set x = y + 4
4457 cont
4458 end
4459 @end smallexample
4460
4461 @node Save Breakpoints
4462 @subsection How to save breakpoints to a file
4463
4464 To save breakpoint definitions to a file use the @w{@code{save
4465 breakpoints}} command.
4466
4467 @table @code
4468 @kindex save breakpoints
4469 @cindex save breakpoints to a file for future sessions
4470 @item save breakpoints [@var{filename}]
4471 This command saves all current breakpoint definitions together with
4472 their commands and ignore counts, into a file @file{@var{filename}}
4473 suitable for use in a later debugging session. This includes all
4474 types of breakpoints (breakpoints, watchpoints, catchpoints,
4475 tracepoints). To read the saved breakpoint definitions, use the
4476 @code{source} command (@pxref{Command Files}). Note that watchpoints
4477 with expressions involving local variables may fail to be recreated
4478 because it may not be possible to access the context where the
4479 watchpoint is valid anymore. Because the saved breakpoint definitions
4480 are simply a sequence of @value{GDBN} commands that recreate the
4481 breakpoints, you can edit the file in your favorite editing program,
4482 and remove the breakpoint definitions you're not interested in, or
4483 that can no longer be recreated.
4484 @end table
4485
4486 @c @ifclear BARETARGET
4487 @node Error in Breakpoints
4488 @subsection ``Cannot insert breakpoints''
4489
4490 If you request too many active hardware-assisted breakpoints and
4491 watchpoints, you will see this error message:
4492
4493 @c FIXME: the precise wording of this message may change; the relevant
4494 @c source change is not committed yet (Sep 3, 1999).
4495 @smallexample
4496 Stopped; cannot insert breakpoints.
4497 You may have requested too many hardware breakpoints and watchpoints.
4498 @end smallexample
4499
4500 @noindent
4501 This message is printed when you attempt to resume the program, since
4502 only then @value{GDBN} knows exactly how many hardware breakpoints and
4503 watchpoints it needs to insert.
4504
4505 When this message is printed, you need to disable or remove some of the
4506 hardware-assisted breakpoints and watchpoints, and then continue.
4507
4508 @node Breakpoint-related Warnings
4509 @subsection ``Breakpoint address adjusted...''
4510 @cindex breakpoint address adjusted
4511
4512 Some processor architectures place constraints on the addresses at
4513 which breakpoints may be placed. For architectures thus constrained,
4514 @value{GDBN} will attempt to adjust the breakpoint's address to comply
4515 with the constraints dictated by the architecture.
4516
4517 One example of such an architecture is the Fujitsu FR-V. The FR-V is
4518 a VLIW architecture in which a number of RISC-like instructions may be
4519 bundled together for parallel execution. The FR-V architecture
4520 constrains the location of a breakpoint instruction within such a
4521 bundle to the instruction with the lowest address. @value{GDBN}
4522 honors this constraint by adjusting a breakpoint's address to the
4523 first in the bundle.
4524
4525 It is not uncommon for optimized code to have bundles which contain
4526 instructions from different source statements, thus it may happen that
4527 a breakpoint's address will be adjusted from one source statement to
4528 another. Since this adjustment may significantly alter @value{GDBN}'s
4529 breakpoint related behavior from what the user expects, a warning is
4530 printed when the breakpoint is first set and also when the breakpoint
4531 is hit.
4532
4533 A warning like the one below is printed when setting a breakpoint
4534 that's been subject to address adjustment:
4535
4536 @smallexample
4537 warning: Breakpoint address adjusted from 0x00010414 to 0x00010410.
4538 @end smallexample
4539
4540 Such warnings are printed both for user settable and @value{GDBN}'s
4541 internal breakpoints. If you see one of these warnings, you should
4542 verify that a breakpoint set at the adjusted address will have the
4543 desired affect. If not, the breakpoint in question may be removed and
4544 other breakpoints may be set which will have the desired behavior.
4545 E.g., it may be sufficient to place the breakpoint at a later
4546 instruction. A conditional breakpoint may also be useful in some
4547 cases to prevent the breakpoint from triggering too often.
4548
4549 @value{GDBN} will also issue a warning when stopping at one of these
4550 adjusted breakpoints:
4551
4552 @smallexample
4553 warning: Breakpoint 1 address previously adjusted from 0x00010414
4554 to 0x00010410.
4555 @end smallexample
4556
4557 When this warning is encountered, it may be too late to take remedial
4558 action except in cases where the breakpoint is hit earlier or more
4559 frequently than expected.
4560
4561 @node Continuing and Stepping
4562 @section Continuing and Stepping
4563
4564 @cindex stepping
4565 @cindex continuing
4566 @cindex resuming execution
4567 @dfn{Continuing} means resuming program execution until your program
4568 completes normally. In contrast, @dfn{stepping} means executing just
4569 one more ``step'' of your program, where ``step'' may mean either one
4570 line of source code, or one machine instruction (depending on what
4571 particular command you use). Either when continuing or when stepping,
4572 your program may stop even sooner, due to a breakpoint or a signal. (If
4573 it stops due to a signal, you may want to use @code{handle}, or use
4574 @samp{signal 0} to resume execution. @xref{Signals, ,Signals}.)
4575
4576 @table @code
4577 @kindex continue
4578 @kindex c @r{(@code{continue})}
4579 @kindex fg @r{(resume foreground execution)}
4580 @item continue @r{[}@var{ignore-count}@r{]}
4581 @itemx c @r{[}@var{ignore-count}@r{]}
4582 @itemx fg @r{[}@var{ignore-count}@r{]}
4583 Resume program execution, at the address where your program last stopped;
4584 any breakpoints set at that address are bypassed. The optional argument
4585 @var{ignore-count} allows you to specify a further number of times to
4586 ignore a breakpoint at this location; its effect is like that of
4587 @code{ignore} (@pxref{Conditions, ,Break Conditions}).
4588
4589 The argument @var{ignore-count} is meaningful only when your program
4590 stopped due to a breakpoint. At other times, the argument to
4591 @code{continue} is ignored.
4592
4593 The synonyms @code{c} and @code{fg} (for @dfn{foreground}, as the
4594 debugged program is deemed to be the foreground program) are provided
4595 purely for convenience, and have exactly the same behavior as
4596 @code{continue}.
4597 @end table
4598
4599 To resume execution at a different place, you can use @code{return}
4600 (@pxref{Returning, ,Returning from a Function}) to go back to the
4601 calling function; or @code{jump} (@pxref{Jumping, ,Continuing at a
4602 Different Address}) to go to an arbitrary location in your program.
4603
4604 A typical technique for using stepping is to set a breakpoint
4605 (@pxref{Breakpoints, ,Breakpoints; Watchpoints; and Catchpoints}) at the
4606 beginning of the function or the section of your program where a problem
4607 is believed to lie, run your program until it stops at that breakpoint,
4608 and then step through the suspect area, examining the variables that are
4609 interesting, until you see the problem happen.
4610
4611 @table @code
4612 @kindex step
4613 @kindex s @r{(@code{step})}
4614 @item step
4615 Continue running your program until control reaches a different source
4616 line, then stop it and return control to @value{GDBN}. This command is
4617 abbreviated @code{s}.
4618
4619 @quotation
4620 @c "without debugging information" is imprecise; actually "without line
4621 @c numbers in the debugging information". (gcc -g1 has debugging info but
4622 @c not line numbers). But it seems complex to try to make that
4623 @c distinction here.
4624 @emph{Warning:} If you use the @code{step} command while control is
4625 within a function that was compiled without debugging information,
4626 execution proceeds until control reaches a function that does have
4627 debugging information. Likewise, it will not step into a function which
4628 is compiled without debugging information. To step through functions
4629 without debugging information, use the @code{stepi} command, described
4630 below.
4631 @end quotation
4632
4633 The @code{step} command only stops at the first instruction of a source
4634 line. This prevents the multiple stops that could otherwise occur in
4635 @code{switch} statements, @code{for} loops, etc. @code{step} continues
4636 to stop if a function that has debugging information is called within
4637 the line. In other words, @code{step} @emph{steps inside} any functions
4638 called within the line.
4639
4640 Also, the @code{step} command only enters a function if there is line
4641 number information for the function. Otherwise it acts like the
4642 @code{next} command. This avoids problems when using @code{cc -gl}
4643 on MIPS machines. Previously, @code{step} entered subroutines if there
4644 was any debugging information about the routine.
4645
4646 @item step @var{count}
4647 Continue running as in @code{step}, but do so @var{count} times. If a
4648 breakpoint is reached, or a signal not related to stepping occurs before
4649 @var{count} steps, stepping stops right away.
4650
4651 @kindex next
4652 @kindex n @r{(@code{next})}
4653 @item next @r{[}@var{count}@r{]}
4654 Continue to the next source line in the current (innermost) stack frame.
4655 This is similar to @code{step}, but function calls that appear within
4656 the line of code are executed without stopping. Execution stops when
4657 control reaches a different line of code at the original stack level
4658 that was executing when you gave the @code{next} command. This command
4659 is abbreviated @code{n}.
4660
4661 An argument @var{count} is a repeat count, as for @code{step}.
4662
4663
4664 @c FIX ME!! Do we delete this, or is there a way it fits in with
4665 @c the following paragraph? --- Vctoria
4666 @c
4667 @c @code{next} within a function that lacks debugging information acts like
4668 @c @code{step}, but any function calls appearing within the code of the
4669 @c function are executed without stopping.
4670
4671 The @code{next} command only stops at the first instruction of a
4672 source line. This prevents multiple stops that could otherwise occur in
4673 @code{switch} statements, @code{for} loops, etc.
4674
4675 @kindex set step-mode
4676 @item set step-mode
4677 @cindex functions without line info, and stepping
4678 @cindex stepping into functions with no line info
4679 @itemx set step-mode on
4680 The @code{set step-mode on} command causes the @code{step} command to
4681 stop at the first instruction of a function which contains no debug line
4682 information rather than stepping over it.
4683
4684 This is useful in cases where you may be interested in inspecting the
4685 machine instructions of a function which has no symbolic info and do not
4686 want @value{GDBN} to automatically skip over this function.
4687
4688 @item set step-mode off
4689 Causes the @code{step} command to step over any functions which contains no
4690 debug information. This is the default.
4691
4692 @item show step-mode
4693 Show whether @value{GDBN} will stop in or step over functions without
4694 source line debug information.
4695
4696 @kindex finish
4697 @kindex fin @r{(@code{finish})}
4698 @item finish
4699 Continue running until just after function in the selected stack frame
4700 returns. Print the returned value (if any). This command can be
4701 abbreviated as @code{fin}.
4702
4703 Contrast this with the @code{return} command (@pxref{Returning,
4704 ,Returning from a Function}).
4705
4706 @kindex until
4707 @kindex u @r{(@code{until})}
4708 @cindex run until specified location
4709 @item until
4710 @itemx u
4711 Continue running until a source line past the current line, in the
4712 current stack frame, is reached. This command is used to avoid single
4713 stepping through a loop more than once. It is like the @code{next}
4714 command, except that when @code{until} encounters a jump, it
4715 automatically continues execution until the program counter is greater
4716 than the address of the jump.
4717
4718 This means that when you reach the end of a loop after single stepping
4719 though it, @code{until} makes your program continue execution until it
4720 exits the loop. In contrast, a @code{next} command at the end of a loop
4721 simply steps back to the beginning of the loop, which forces you to step
4722 through the next iteration.
4723
4724 @code{until} always stops your program if it attempts to exit the current
4725 stack frame.
4726
4727 @code{until} may produce somewhat counterintuitive results if the order
4728 of machine code does not match the order of the source lines. For
4729 example, in the following excerpt from a debugging session, the @code{f}
4730 (@code{frame}) command shows that execution is stopped at line
4731 @code{206}; yet when we use @code{until}, we get to line @code{195}:
4732
4733 @smallexample
4734 (@value{GDBP}) f
4735 #0 main (argc=4, argv=0xf7fffae8) at m4.c:206
4736 206 expand_input();
4737 (@value{GDBP}) until
4738 195 for ( ; argc > 0; NEXTARG) @{
4739 @end smallexample
4740
4741 This happened because, for execution efficiency, the compiler had
4742 generated code for the loop closure test at the end, rather than the
4743 start, of the loop---even though the test in a C @code{for}-loop is
4744 written before the body of the loop. The @code{until} command appeared
4745 to step back to the beginning of the loop when it advanced to this
4746 expression; however, it has not really gone to an earlier
4747 statement---not in terms of the actual machine code.
4748
4749 @code{until} with no argument works by means of single
4750 instruction stepping, and hence is slower than @code{until} with an
4751 argument.
4752
4753 @item until @var{location}
4754 @itemx u @var{location}
4755 Continue running your program until either the specified location is
4756 reached, or the current stack frame returns. @var{location} is any of
4757 the forms described in @ref{Specify Location}.
4758 This form of the command uses temporary breakpoints, and
4759 hence is quicker than @code{until} without an argument. The specified
4760 location is actually reached only if it is in the current frame. This
4761 implies that @code{until} can be used to skip over recursive function
4762 invocations. For instance in the code below, if the current location is
4763 line @code{96}, issuing @code{until 99} will execute the program up to
4764 line @code{99} in the same invocation of factorial, i.e., after the inner
4765 invocations have returned.
4766
4767 @smallexample
4768 94 int factorial (int value)
4769 95 @{
4770 96 if (value > 1) @{
4771 97 value *= factorial (value - 1);
4772 98 @}
4773 99 return (value);
4774 100 @}
4775 @end smallexample
4776
4777
4778 @kindex advance @var{location}
4779 @itemx advance @var{location}
4780 Continue running the program up to the given @var{location}. An argument is
4781 required, which should be of one of the forms described in
4782 @ref{Specify Location}.
4783 Execution will also stop upon exit from the current stack
4784 frame. This command is similar to @code{until}, but @code{advance} will
4785 not skip over recursive function calls, and the target location doesn't
4786 have to be in the same frame as the current one.
4787
4788
4789 @kindex stepi
4790 @kindex si @r{(@code{stepi})}
4791 @item stepi
4792 @itemx stepi @var{arg}
4793 @itemx si
4794 Execute one machine instruction, then stop and return to the debugger.
4795
4796 It is often useful to do @samp{display/i $pc} when stepping by machine
4797 instructions. This makes @value{GDBN} automatically display the next
4798 instruction to be executed, each time your program stops. @xref{Auto
4799 Display,, Automatic Display}.
4800
4801 An argument is a repeat count, as in @code{step}.
4802
4803 @need 750
4804 @kindex nexti
4805 @kindex ni @r{(@code{nexti})}
4806 @item nexti
4807 @itemx nexti @var{arg}
4808 @itemx ni
4809 Execute one machine instruction, but if it is a function call,
4810 proceed until the function returns.
4811
4812 An argument is a repeat count, as in @code{next}.
4813 @end table
4814
4815 @node Signals
4816 @section Signals
4817 @cindex signals
4818
4819 A signal is an asynchronous event that can happen in a program. The
4820 operating system defines the possible kinds of signals, and gives each
4821 kind a name and a number. For example, in Unix @code{SIGINT} is the
4822 signal a program gets when you type an interrupt character (often @kbd{Ctrl-c});
4823 @code{SIGSEGV} is the signal a program gets from referencing a place in
4824 memory far away from all the areas in use; @code{SIGALRM} occurs when
4825 the alarm clock timer goes off (which happens only if your program has
4826 requested an alarm).
4827
4828 @cindex fatal signals
4829 Some signals, including @code{SIGALRM}, are a normal part of the
4830 functioning of your program. Others, such as @code{SIGSEGV}, indicate
4831 errors; these signals are @dfn{fatal} (they kill your program immediately) if the
4832 program has not specified in advance some other way to handle the signal.
4833 @code{SIGINT} does not indicate an error in your program, but it is normally
4834 fatal so it can carry out the purpose of the interrupt: to kill the program.
4835
4836 @value{GDBN} has the ability to detect any occurrence of a signal in your
4837 program. You can tell @value{GDBN} in advance what to do for each kind of
4838 signal.
4839
4840 @cindex handling signals
4841 Normally, @value{GDBN} is set up to let the non-erroneous signals like
4842 @code{SIGALRM} be silently passed to your program
4843 (so as not to interfere with their role in the program's functioning)
4844 but to stop your program immediately whenever an error signal happens.
4845 You can change these settings with the @code{handle} command.
4846
4847 @table @code
4848 @kindex info signals
4849 @kindex info handle
4850 @item info signals
4851 @itemx info handle
4852 Print a table of all the kinds of signals and how @value{GDBN} has been told to
4853 handle each one. You can use this to see the signal numbers of all
4854 the defined types of signals.
4855
4856 @item info signals @var{sig}
4857 Similar, but print information only about the specified signal number.
4858
4859 @code{info handle} is an alias for @code{info signals}.
4860
4861 @kindex handle
4862 @item handle @var{signal} @r{[}@var{keywords}@dots{}@r{]}
4863 Change the way @value{GDBN} handles signal @var{signal}. @var{signal}
4864 can be the number of a signal or its name (with or without the
4865 @samp{SIG} at the beginning); a list of signal numbers of the form
4866 @samp{@var{low}-@var{high}}; or the word @samp{all}, meaning all the
4867 known signals. Optional arguments @var{keywords}, described below,
4868 say what change to make.
4869 @end table
4870
4871 @c @group
4872 The keywords allowed by the @code{handle} command can be abbreviated.
4873 Their full names are:
4874
4875 @table @code
4876 @item nostop
4877 @value{GDBN} should not stop your program when this signal happens. It may
4878 still print a message telling you that the signal has come in.
4879
4880 @item stop
4881 @value{GDBN} should stop your program when this signal happens. This implies
4882 the @code{print} keyword as well.
4883
4884 @item print
4885 @value{GDBN} should print a message when this signal happens.
4886
4887 @item noprint
4888 @value{GDBN} should not mention the occurrence of the signal at all. This
4889 implies the @code{nostop} keyword as well.
4890
4891 @item pass
4892 @itemx noignore
4893 @value{GDBN} should allow your program to see this signal; your program
4894 can handle the signal, or else it may terminate if the signal is fatal
4895 and not handled. @code{pass} and @code{noignore} are synonyms.
4896
4897 @item nopass
4898 @itemx ignore
4899 @value{GDBN} should not allow your program to see this signal.
4900 @code{nopass} and @code{ignore} are synonyms.
4901 @end table
4902 @c @end group
4903
4904 When a signal stops your program, the signal is not visible to the
4905 program until you
4906 continue. Your program sees the signal then, if @code{pass} is in
4907 effect for the signal in question @emph{at that time}. In other words,
4908 after @value{GDBN} reports a signal, you can use the @code{handle}
4909 command with @code{pass} or @code{nopass} to control whether your
4910 program sees that signal when you continue.
4911
4912 The default is set to @code{nostop}, @code{noprint}, @code{pass} for
4913 non-erroneous signals such as @code{SIGALRM}, @code{SIGWINCH} and
4914 @code{SIGCHLD}, and to @code{stop}, @code{print}, @code{pass} for the
4915 erroneous signals.
4916
4917 You can also use the @code{signal} command to prevent your program from
4918 seeing a signal, or cause it to see a signal it normally would not see,
4919 or to give it any signal at any time. For example, if your program stopped
4920 due to some sort of memory reference error, you might store correct
4921 values into the erroneous variables and continue, hoping to see more
4922 execution; but your program would probably terminate immediately as
4923 a result of the fatal signal once it saw the signal. To prevent this,
4924 you can continue with @samp{signal 0}. @xref{Signaling, ,Giving your
4925 Program a Signal}.
4926
4927 @cindex extra signal information
4928 @anchor{extra signal information}
4929
4930 On some targets, @value{GDBN} can inspect extra signal information
4931 associated with the intercepted signal, before it is actually
4932 delivered to the program being debugged. This information is exported
4933 by the convenience variable @code{$_siginfo}, and consists of data
4934 that is passed by the kernel to the signal handler at the time of the
4935 receipt of a signal. The data type of the information itself is
4936 target dependent. You can see the data type using the @code{ptype
4937 $_siginfo} command. On Unix systems, it typically corresponds to the
4938 standard @code{siginfo_t} type, as defined in the @file{signal.h}
4939 system header.
4940
4941 Here's an example, on a @sc{gnu}/Linux system, printing the stray
4942 referenced address that raised a segmentation fault.
4943
4944 @smallexample
4945 @group
4946 (@value{GDBP}) continue
4947 Program received signal SIGSEGV, Segmentation fault.
4948 0x0000000000400766 in main ()
4949 69 *(int *)p = 0;
4950 (@value{GDBP}) ptype $_siginfo
4951 type = struct @{
4952 int si_signo;
4953 int si_errno;
4954 int si_code;
4955 union @{
4956 int _pad[28];
4957 struct @{...@} _kill;
4958 struct @{...@} _timer;
4959 struct @{...@} _rt;
4960 struct @{...@} _sigchld;
4961 struct @{...@} _sigfault;
4962 struct @{...@} _sigpoll;
4963 @} _sifields;
4964 @}
4965 (@value{GDBP}) ptype $_siginfo._sifields._sigfault
4966 type = struct @{
4967 void *si_addr;
4968 @}
4969 (@value{GDBP}) p $_siginfo._sifields._sigfault.si_addr
4970 $1 = (void *) 0x7ffff7ff7000
4971 @end group
4972 @end smallexample
4973
4974 Depending on target support, @code{$_siginfo} may also be writable.
4975
4976 @node Thread Stops
4977 @section Stopping and Starting Multi-thread Programs
4978
4979 @cindex stopped threads
4980 @cindex threads, stopped
4981
4982 @cindex continuing threads
4983 @cindex threads, continuing
4984
4985 @value{GDBN} supports debugging programs with multiple threads
4986 (@pxref{Threads,, Debugging Programs with Multiple Threads}). There
4987 are two modes of controlling execution of your program within the
4988 debugger. In the default mode, referred to as @dfn{all-stop mode},
4989 when any thread in your program stops (for example, at a breakpoint
4990 or while being stepped), all other threads in the program are also stopped by
4991 @value{GDBN}. On some targets, @value{GDBN} also supports
4992 @dfn{non-stop mode}, in which other threads can continue to run freely while
4993 you examine the stopped thread in the debugger.
4994
4995 @menu
4996 * All-Stop Mode:: All threads stop when GDB takes control
4997 * Non-Stop Mode:: Other threads continue to execute
4998 * Background Execution:: Running your program asynchronously
4999 * Thread-Specific Breakpoints:: Controlling breakpoints
5000 * Interrupted System Calls:: GDB may interfere with system calls
5001 * Observer Mode:: GDB does not alter program behavior
5002 @end menu
5003
5004 @node All-Stop Mode
5005 @subsection All-Stop Mode
5006
5007 @cindex all-stop mode
5008
5009 In all-stop mode, whenever your program stops under @value{GDBN} for any reason,
5010 @emph{all} threads of execution stop, not just the current thread. This
5011 allows you to examine the overall state of the program, including
5012 switching between threads, without worrying that things may change
5013 underfoot.
5014
5015 Conversely, whenever you restart the program, @emph{all} threads start
5016 executing. @emph{This is true even when single-stepping} with commands
5017 like @code{step} or @code{next}.
5018
5019 In particular, @value{GDBN} cannot single-step all threads in lockstep.
5020 Since thread scheduling is up to your debugging target's operating
5021 system (not controlled by @value{GDBN}), other threads may
5022 execute more than one statement while the current thread completes a
5023 single step. Moreover, in general other threads stop in the middle of a
5024 statement, rather than at a clean statement boundary, when the program
5025 stops.
5026
5027 You might even find your program stopped in another thread after
5028 continuing or even single-stepping. This happens whenever some other
5029 thread runs into a breakpoint, a signal, or an exception before the
5030 first thread completes whatever you requested.
5031
5032 @cindex automatic thread selection
5033 @cindex switching threads automatically
5034 @cindex threads, automatic switching
5035 Whenever @value{GDBN} stops your program, due to a breakpoint or a
5036 signal, it automatically selects the thread where that breakpoint or
5037 signal happened. @value{GDBN} alerts you to the context switch with a
5038 message such as @samp{[Switching to Thread @var{n}]} to identify the
5039 thread.
5040
5041 On some OSes, you can modify @value{GDBN}'s default behavior by
5042 locking the OS scheduler to allow only a single thread to run.
5043
5044 @table @code
5045 @item set scheduler-locking @var{mode}
5046 @cindex scheduler locking mode
5047 @cindex lock scheduler
5048 Set the scheduler locking mode. If it is @code{off}, then there is no
5049 locking and any thread may run at any time. If @code{on}, then only the
5050 current thread may run when the inferior is resumed. The @code{step}
5051 mode optimizes for single-stepping; it prevents other threads
5052 from preempting the current thread while you are stepping, so that
5053 the focus of debugging does not change unexpectedly.
5054 Other threads only rarely (or never) get a chance to run
5055 when you step. They are more likely to run when you @samp{next} over a
5056 function call, and they are completely free to run when you use commands
5057 like @samp{continue}, @samp{until}, or @samp{finish}. However, unless another
5058 thread hits a breakpoint during its timeslice, @value{GDBN} does not change
5059 the current thread away from the thread that you are debugging.
5060
5061 @item show scheduler-locking
5062 Display the current scheduler locking mode.
5063 @end table
5064
5065 @cindex resume threads of multiple processes simultaneously
5066 By default, when you issue one of the execution commands such as
5067 @code{continue}, @code{next} or @code{step}, @value{GDBN} allows only
5068 threads of the current inferior to run. For example, if @value{GDBN}
5069 is attached to two inferiors, each with two threads, the
5070 @code{continue} command resumes only the two threads of the current
5071 inferior. This is useful, for example, when you debug a program that
5072 forks and you want to hold the parent stopped (so that, for instance,
5073 it doesn't run to exit), while you debug the child. In other
5074 situations, you may not be interested in inspecting the current state
5075 of any of the processes @value{GDBN} is attached to, and you may want
5076 to resume them all until some breakpoint is hit. In the latter case,
5077 you can instruct @value{GDBN} to allow all threads of all the
5078 inferiors to run with the @w{@code{set schedule-multiple}} command.
5079
5080 @table @code
5081 @kindex set schedule-multiple
5082 @item set schedule-multiple
5083 Set the mode for allowing threads of multiple processes to be resumed
5084 when an execution command is issued. When @code{on}, all threads of
5085 all processes are allowed to run. When @code{off}, only the threads
5086 of the current process are resumed. The default is @code{off}. The
5087 @code{scheduler-locking} mode takes precedence when set to @code{on},
5088 or while you are stepping and set to @code{step}.
5089
5090 @item show schedule-multiple
5091 Display the current mode for resuming the execution of threads of
5092 multiple processes.
5093 @end table
5094
5095 @node Non-Stop Mode
5096 @subsection Non-Stop Mode
5097
5098 @cindex non-stop mode
5099
5100 @c This section is really only a place-holder, and needs to be expanded
5101 @c with more details.
5102
5103 For some multi-threaded targets, @value{GDBN} supports an optional
5104 mode of operation in which you can examine stopped program threads in
5105 the debugger while other threads continue to execute freely. This
5106 minimizes intrusion when debugging live systems, such as programs
5107 where some threads have real-time constraints or must continue to
5108 respond to external events. This is referred to as @dfn{non-stop} mode.
5109
5110 In non-stop mode, when a thread stops to report a debugging event,
5111 @emph{only} that thread is stopped; @value{GDBN} does not stop other
5112 threads as well, in contrast to the all-stop mode behavior. Additionally,
5113 execution commands such as @code{continue} and @code{step} apply by default
5114 only to the current thread in non-stop mode, rather than all threads as
5115 in all-stop mode. This allows you to control threads explicitly in
5116 ways that are not possible in all-stop mode --- for example, stepping
5117 one thread while allowing others to run freely, stepping
5118 one thread while holding all others stopped, or stepping several threads
5119 independently and simultaneously.
5120
5121 To enter non-stop mode, use this sequence of commands before you run
5122 or attach to your program:
5123
5124 @smallexample
5125 # Enable the async interface.
5126 set target-async 1
5127
5128 # If using the CLI, pagination breaks non-stop.
5129 set pagination off
5130
5131 # Finally, turn it on!
5132 set non-stop on
5133 @end smallexample
5134
5135 You can use these commands to manipulate the non-stop mode setting:
5136
5137 @table @code
5138 @kindex set non-stop
5139 @item set non-stop on
5140 Enable selection of non-stop mode.
5141 @item set non-stop off
5142 Disable selection of non-stop mode.
5143 @kindex show non-stop
5144 @item show non-stop
5145 Show the current non-stop enablement setting.
5146 @end table
5147
5148 Note these commands only reflect whether non-stop mode is enabled,
5149 not whether the currently-executing program is being run in non-stop mode.
5150 In particular, the @code{set non-stop} preference is only consulted when
5151 @value{GDBN} starts or connects to the target program, and it is generally
5152 not possible to switch modes once debugging has started. Furthermore,
5153 since not all targets support non-stop mode, even when you have enabled
5154 non-stop mode, @value{GDBN} may still fall back to all-stop operation by
5155 default.
5156
5157 In non-stop mode, all execution commands apply only to the current thread
5158 by default. That is, @code{continue} only continues one thread.
5159 To continue all threads, issue @code{continue -a} or @code{c -a}.
5160
5161 You can use @value{GDBN}'s background execution commands
5162 (@pxref{Background Execution}) to run some threads in the background
5163 while you continue to examine or step others from @value{GDBN}.
5164 The MI execution commands (@pxref{GDB/MI Program Execution}) are
5165 always executed asynchronously in non-stop mode.
5166
5167 Suspending execution is done with the @code{interrupt} command when
5168 running in the background, or @kbd{Ctrl-c} during foreground execution.
5169 In all-stop mode, this stops the whole process;
5170 but in non-stop mode the interrupt applies only to the current thread.
5171 To stop the whole program, use @code{interrupt -a}.
5172
5173 Other execution commands do not currently support the @code{-a} option.
5174
5175 In non-stop mode, when a thread stops, @value{GDBN} doesn't automatically make
5176 that thread current, as it does in all-stop mode. This is because the
5177 thread stop notifications are asynchronous with respect to @value{GDBN}'s
5178 command interpreter, and it would be confusing if @value{GDBN} unexpectedly
5179 changed to a different thread just as you entered a command to operate on the
5180 previously current thread.
5181
5182 @node Background Execution
5183 @subsection Background Execution
5184
5185 @cindex foreground execution
5186 @cindex background execution
5187 @cindex asynchronous execution
5188 @cindex execution, foreground, background and asynchronous
5189
5190 @value{GDBN}'s execution commands have two variants: the normal
5191 foreground (synchronous) behavior, and a background
5192 (asynchronous) behavior. In foreground execution, @value{GDBN} waits for
5193 the program to report that some thread has stopped before prompting for
5194 another command. In background execution, @value{GDBN} immediately gives
5195 a command prompt so that you can issue other commands while your program runs.
5196
5197 You need to explicitly enable asynchronous mode before you can use
5198 background execution commands. You can use these commands to
5199 manipulate the asynchronous mode setting:
5200
5201 @table @code
5202 @kindex set target-async
5203 @item set target-async on
5204 Enable asynchronous mode.
5205 @item set target-async off
5206 Disable asynchronous mode.
5207 @kindex show target-async
5208 @item show target-async
5209 Show the current target-async setting.
5210 @end table
5211
5212 If the target doesn't support async mode, @value{GDBN} issues an error
5213 message if you attempt to use the background execution commands.
5214
5215 To specify background execution, add a @code{&} to the command. For example,
5216 the background form of the @code{continue} command is @code{continue&}, or
5217 just @code{c&}. The execution commands that accept background execution
5218 are:
5219
5220 @table @code
5221 @kindex run&
5222 @item run
5223 @xref{Starting, , Starting your Program}.
5224
5225 @item attach
5226 @kindex attach&
5227 @xref{Attach, , Debugging an Already-running Process}.
5228
5229 @item step
5230 @kindex step&
5231 @xref{Continuing and Stepping, step}.
5232
5233 @item stepi
5234 @kindex stepi&
5235 @xref{Continuing and Stepping, stepi}.
5236
5237 @item next
5238 @kindex next&
5239 @xref{Continuing and Stepping, next}.
5240
5241 @item nexti
5242 @kindex nexti&
5243 @xref{Continuing and Stepping, nexti}.
5244
5245 @item continue
5246 @kindex continue&
5247 @xref{Continuing and Stepping, continue}.
5248
5249 @item finish
5250 @kindex finish&
5251 @xref{Continuing and Stepping, finish}.
5252
5253 @item until
5254 @kindex until&
5255 @xref{Continuing and Stepping, until}.
5256
5257 @end table
5258
5259 Background execution is especially useful in conjunction with non-stop
5260 mode for debugging programs with multiple threads; see @ref{Non-Stop Mode}.
5261 However, you can also use these commands in the normal all-stop mode with
5262 the restriction that you cannot issue another execution command until the
5263 previous one finishes. Examples of commands that are valid in all-stop
5264 mode while the program is running include @code{help} and @code{info break}.
5265
5266 You can interrupt your program while it is running in the background by
5267 using the @code{interrupt} command.
5268
5269 @table @code
5270 @kindex interrupt
5271 @item interrupt
5272 @itemx interrupt -a
5273
5274 Suspend execution of the running program. In all-stop mode,
5275 @code{interrupt} stops the whole process, but in non-stop mode, it stops
5276 only the current thread. To stop the whole program in non-stop mode,
5277 use @code{interrupt -a}.
5278 @end table
5279
5280 @node Thread-Specific Breakpoints
5281 @subsection Thread-Specific Breakpoints
5282
5283 When your program has multiple threads (@pxref{Threads,, Debugging
5284 Programs with Multiple Threads}), you can choose whether to set
5285 breakpoints on all threads, or on a particular thread.
5286
5287 @table @code
5288 @cindex breakpoints and threads
5289 @cindex thread breakpoints
5290 @kindex break @dots{} thread @var{threadno}
5291 @item break @var{linespec} thread @var{threadno}
5292 @itemx break @var{linespec} thread @var{threadno} if @dots{}
5293 @var{linespec} specifies source lines; there are several ways of
5294 writing them (@pxref{Specify Location}), but the effect is always to
5295 specify some source line.
5296
5297 Use the qualifier @samp{thread @var{threadno}} with a breakpoint command
5298 to specify that you only want @value{GDBN} to stop the program when a
5299 particular thread reaches this breakpoint. @var{threadno} is one of the
5300 numeric thread identifiers assigned by @value{GDBN}, shown in the first
5301 column of the @samp{info threads} display.
5302
5303 If you do not specify @samp{thread @var{threadno}} when you set a
5304 breakpoint, the breakpoint applies to @emph{all} threads of your
5305 program.
5306
5307 You can use the @code{thread} qualifier on conditional breakpoints as
5308 well; in this case, place @samp{thread @var{threadno}} before or
5309 after the breakpoint condition, like this:
5310
5311 @smallexample
5312 (@value{GDBP}) break frik.c:13 thread 28 if bartab > lim
5313 @end smallexample
5314
5315 @end table
5316
5317 @node Interrupted System Calls
5318 @subsection Interrupted System Calls
5319
5320 @cindex thread breakpoints and system calls
5321 @cindex system calls and thread breakpoints
5322 @cindex premature return from system calls
5323 There is an unfortunate side effect when using @value{GDBN} to debug
5324 multi-threaded programs. If one thread stops for a
5325 breakpoint, or for some other reason, and another thread is blocked in a
5326 system call, then the system call may return prematurely. This is a
5327 consequence of the interaction between multiple threads and the signals
5328 that @value{GDBN} uses to implement breakpoints and other events that
5329 stop execution.
5330
5331 To handle this problem, your program should check the return value of
5332 each system call and react appropriately. This is good programming
5333 style anyways.
5334
5335 For example, do not write code like this:
5336
5337 @smallexample
5338 sleep (10);
5339 @end smallexample
5340
5341 The call to @code{sleep} will return early if a different thread stops
5342 at a breakpoint or for some other reason.
5343
5344 Instead, write this:
5345
5346 @smallexample
5347 int unslept = 10;
5348 while (unslept > 0)
5349 unslept = sleep (unslept);
5350 @end smallexample
5351
5352 A system call is allowed to return early, so the system is still
5353 conforming to its specification. But @value{GDBN} does cause your
5354 multi-threaded program to behave differently than it would without
5355 @value{GDBN}.
5356
5357 Also, @value{GDBN} uses internal breakpoints in the thread library to
5358 monitor certain events such as thread creation and thread destruction.
5359 When such an event happens, a system call in another thread may return
5360 prematurely, even though your program does not appear to stop.
5361
5362 @node Observer Mode
5363 @subsection Observer Mode
5364
5365 If you want to build on non-stop mode and observe program behavior
5366 without any chance of disruption by @value{GDBN}, you can set
5367 variables to disable all of the debugger's attempts to modify state,
5368 whether by writing memory, inserting breakpoints, etc. These operate
5369 at a low level, intercepting operations from all commands.
5370
5371 When all of these are set to @code{off}, then @value{GDBN} is said to
5372 be @dfn{observer mode}. As a convenience, the variable
5373 @code{observer} can be set to disable these, plus enable non-stop
5374 mode.
5375
5376 Note that @value{GDBN} will not prevent you from making nonsensical
5377 combinations of these settings. For instance, if you have enabled
5378 @code{may-insert-breakpoints} but disabled @code{may-write-memory},
5379 then breakpoints that work by writing trap instructions into the code
5380 stream will still not be able to be placed.
5381
5382 @table @code
5383
5384 @kindex observer
5385 @item set observer on
5386 @itemx set observer off
5387 When set to @code{on}, this disables all the permission variables
5388 below (except for @code{insert-fast-tracepoints}), plus enables
5389 non-stop debugging. Setting this to @code{off} switches back to
5390 normal debugging, though remaining in non-stop mode.
5391
5392 @item show observer
5393 Show whether observer mode is on or off.
5394
5395 @kindex may-write-registers
5396 @item set may-write-registers on
5397 @itemx set may-write-registers off
5398 This controls whether @value{GDBN} will attempt to alter the values of
5399 registers, such as with assignment expressions in @code{print}, or the
5400 @code{jump} command. It defaults to @code{on}.
5401
5402 @item show may-write-registers
5403 Show the current permission to write registers.
5404
5405 @kindex may-write-memory
5406 @item set may-write-memory on
5407 @itemx set may-write-memory off
5408 This controls whether @value{GDBN} will attempt to alter the contents
5409 of memory, such as with assignment expressions in @code{print}. It
5410 defaults to @code{on}.
5411
5412 @item show may-write-memory
5413 Show the current permission to write memory.
5414
5415 @kindex may-insert-breakpoints
5416 @item set may-insert-breakpoints on
5417 @itemx set may-insert-breakpoints off
5418 This controls whether @value{GDBN} will attempt to insert breakpoints.
5419 This affects all breakpoints, including internal breakpoints defined
5420 by @value{GDBN}. It defaults to @code{on}.
5421
5422 @item show may-insert-breakpoints
5423 Show the current permission to insert breakpoints.
5424
5425 @kindex may-insert-tracepoints
5426 @item set may-insert-tracepoints on
5427 @itemx set may-insert-tracepoints off
5428 This controls whether @value{GDBN} will attempt to insert (regular)
5429 tracepoints at the beginning of a tracing experiment. It affects only
5430 non-fast tracepoints, fast tracepoints being under the control of
5431 @code{may-insert-fast-tracepoints}. It defaults to @code{on}.
5432
5433 @item show may-insert-tracepoints
5434 Show the current permission to insert tracepoints.
5435
5436 @kindex may-insert-fast-tracepoints
5437 @item set may-insert-fast-tracepoints on
5438 @itemx set may-insert-fast-tracepoints off
5439 This controls whether @value{GDBN} will attempt to insert fast
5440 tracepoints at the beginning of a tracing experiment. It affects only
5441 fast tracepoints, regular (non-fast) tracepoints being under the
5442 control of @code{may-insert-tracepoints}. It defaults to @code{on}.
5443
5444 @item show may-insert-fast-tracepoints
5445 Show the current permission to insert fast tracepoints.
5446
5447 @kindex may-interrupt
5448 @item set may-interrupt on
5449 @itemx set may-interrupt off
5450 This controls whether @value{GDBN} will attempt to interrupt or stop
5451 program execution. When this variable is @code{off}, the
5452 @code{interrupt} command will have no effect, nor will
5453 @kbd{Ctrl-c}. It defaults to @code{on}.
5454
5455 @item show may-interrupt
5456 Show the current permission to interrupt or stop the program.
5457
5458 @end table
5459
5460 @node Reverse Execution
5461 @chapter Running programs backward
5462 @cindex reverse execution
5463 @cindex running programs backward
5464
5465 When you are debugging a program, it is not unusual to realize that
5466 you have gone too far, and some event of interest has already happened.
5467 If the target environment supports it, @value{GDBN} can allow you to
5468 ``rewind'' the program by running it backward.
5469
5470 A target environment that supports reverse execution should be able
5471 to ``undo'' the changes in machine state that have taken place as the
5472 program was executing normally. Variables, registers etc.@: should
5473 revert to their previous values. Obviously this requires a great
5474 deal of sophistication on the part of the target environment; not
5475 all target environments can support reverse execution.
5476
5477 When a program is executed in reverse, the instructions that
5478 have most recently been executed are ``un-executed'', in reverse
5479 order. The program counter runs backward, following the previous
5480 thread of execution in reverse. As each instruction is ``un-executed'',
5481 the values of memory and/or registers that were changed by that
5482 instruction are reverted to their previous states. After executing
5483 a piece of source code in reverse, all side effects of that code
5484 should be ``undone'', and all variables should be returned to their
5485 prior values@footnote{
5486 Note that some side effects are easier to undo than others. For instance,
5487 memory and registers are relatively easy, but device I/O is hard. Some
5488 targets may be able undo things like device I/O, and some may not.
5489
5490 The contract between @value{GDBN} and the reverse executing target
5491 requires only that the target do something reasonable when
5492 @value{GDBN} tells it to execute backwards, and then report the
5493 results back to @value{GDBN}. Whatever the target reports back to
5494 @value{GDBN}, @value{GDBN} will report back to the user. @value{GDBN}
5495 assumes that the memory and registers that the target reports are in a
5496 consistant state, but @value{GDBN} accepts whatever it is given.
5497 }.
5498
5499 If you are debugging in a target environment that supports
5500 reverse execution, @value{GDBN} provides the following commands.
5501
5502 @table @code
5503 @kindex reverse-continue
5504 @kindex rc @r{(@code{reverse-continue})}
5505 @item reverse-continue @r{[}@var{ignore-count}@r{]}
5506 @itemx rc @r{[}@var{ignore-count}@r{]}
5507 Beginning at the point where your program last stopped, start executing
5508 in reverse. Reverse execution will stop for breakpoints and synchronous
5509 exceptions (signals), just like normal execution. Behavior of
5510 asynchronous signals depends on the target environment.
5511
5512 @kindex reverse-step
5513 @kindex rs @r{(@code{step})}
5514 @item reverse-step @r{[}@var{count}@r{]}
5515 Run the program backward until control reaches the start of a
5516 different source line; then stop it, and return control to @value{GDBN}.
5517
5518 Like the @code{step} command, @code{reverse-step} will only stop
5519 at the beginning of a source line. It ``un-executes'' the previously
5520 executed source line. If the previous source line included calls to
5521 debuggable functions, @code{reverse-step} will step (backward) into
5522 the called function, stopping at the beginning of the @emph{last}
5523 statement in the called function (typically a return statement).
5524
5525 Also, as with the @code{step} command, if non-debuggable functions are
5526 called, @code{reverse-step} will run thru them backward without stopping.
5527
5528 @kindex reverse-stepi
5529 @kindex rsi @r{(@code{reverse-stepi})}
5530 @item reverse-stepi @r{[}@var{count}@r{]}
5531 Reverse-execute one machine instruction. Note that the instruction
5532 to be reverse-executed is @emph{not} the one pointed to by the program
5533 counter, but the instruction executed prior to that one. For instance,
5534 if the last instruction was a jump, @code{reverse-stepi} will take you
5535 back from the destination of the jump to the jump instruction itself.
5536
5537 @kindex reverse-next
5538 @kindex rn @r{(@code{reverse-next})}
5539 @item reverse-next @r{[}@var{count}@r{]}
5540 Run backward to the beginning of the previous line executed in
5541 the current (innermost) stack frame. If the line contains function
5542 calls, they will be ``un-executed'' without stopping. Starting from
5543 the first line of a function, @code{reverse-next} will take you back
5544 to the caller of that function, @emph{before} the function was called,
5545 just as the normal @code{next} command would take you from the last
5546 line of a function back to its return to its caller
5547 @footnote{Unless the code is too heavily optimized.}.
5548
5549 @kindex reverse-nexti
5550 @kindex rni @r{(@code{reverse-nexti})}
5551 @item reverse-nexti @r{[}@var{count}@r{]}
5552 Like @code{nexti}, @code{reverse-nexti} executes a single instruction
5553 in reverse, except that called functions are ``un-executed'' atomically.
5554 That is, if the previously executed instruction was a return from
5555 another function, @code{reverse-nexti} will continue to execute
5556 in reverse until the call to that function (from the current stack
5557 frame) is reached.
5558
5559 @kindex reverse-finish
5560 @item reverse-finish
5561 Just as the @code{finish} command takes you to the point where the
5562 current function returns, @code{reverse-finish} takes you to the point
5563 where it was called. Instead of ending up at the end of the current
5564 function invocation, you end up at the beginning.
5565
5566 @kindex set exec-direction
5567 @item set exec-direction
5568 Set the direction of target execution.
5569 @itemx set exec-direction reverse
5570 @cindex execute forward or backward in time
5571 @value{GDBN} will perform all execution commands in reverse, until the
5572 exec-direction mode is changed to ``forward''. Affected commands include
5573 @code{step, stepi, next, nexti, continue, and finish}. The @code{return}
5574 command cannot be used in reverse mode.
5575 @item set exec-direction forward
5576 @value{GDBN} will perform all execution commands in the normal fashion.
5577 This is the default.
5578 @end table
5579
5580
5581 @node Process Record and Replay
5582 @chapter Recording Inferior's Execution and Replaying It
5583 @cindex process record and replay
5584 @cindex recording inferior's execution and replaying it
5585
5586 On some platforms, @value{GDBN} provides a special @dfn{process record
5587 and replay} target that can record a log of the process execution, and
5588 replay it later with both forward and reverse execution commands.
5589
5590 @cindex replay mode
5591 When this target is in use, if the execution log includes the record
5592 for the next instruction, @value{GDBN} will debug in @dfn{replay
5593 mode}. In the replay mode, the inferior does not really execute code
5594 instructions. Instead, all the events that normally happen during
5595 code execution are taken from the execution log. While code is not
5596 really executed in replay mode, the values of registers (including the
5597 program counter register) and the memory of the inferior are still
5598 changed as they normally would. Their contents are taken from the
5599 execution log.
5600
5601 @cindex record mode
5602 If the record for the next instruction is not in the execution log,
5603 @value{GDBN} will debug in @dfn{record mode}. In this mode, the
5604 inferior executes normally, and @value{GDBN} records the execution log
5605 for future replay.
5606
5607 The process record and replay target supports reverse execution
5608 (@pxref{Reverse Execution}), even if the platform on which the
5609 inferior runs does not. However, the reverse execution is limited in
5610 this case by the range of the instructions recorded in the execution
5611 log. In other words, reverse execution on platforms that don't
5612 support it directly can only be done in the replay mode.
5613
5614 When debugging in the reverse direction, @value{GDBN} will work in
5615 replay mode as long as the execution log includes the record for the
5616 previous instruction; otherwise, it will work in record mode, if the
5617 platform supports reverse execution, or stop if not.
5618
5619 For architecture environments that support process record and replay,
5620 @value{GDBN} provides the following commands:
5621
5622 @table @code
5623 @kindex target record
5624 @kindex record
5625 @kindex rec
5626 @item target record
5627 This command starts the process record and replay target. The process
5628 record and replay target can only debug a process that is already
5629 running. Therefore, you need first to start the process with the
5630 @kbd{run} or @kbd{start} commands, and then start the recording with
5631 the @kbd{target record} command.
5632
5633 Both @code{record} and @code{rec} are aliases of @code{target record}.
5634
5635 @cindex displaced stepping, and process record and replay
5636 Displaced stepping (@pxref{Maintenance Commands,, displaced stepping})
5637 will be automatically disabled when process record and replay target
5638 is started. That's because the process record and replay target
5639 doesn't support displaced stepping.
5640
5641 @cindex non-stop mode, and process record and replay
5642 @cindex asynchronous execution, and process record and replay
5643 If the inferior is in the non-stop mode (@pxref{Non-Stop Mode}) or in
5644 the asynchronous execution mode (@pxref{Background Execution}), the
5645 process record and replay target cannot be started because it doesn't
5646 support these two modes.
5647
5648 @kindex record stop
5649 @kindex rec s
5650 @item record stop
5651 Stop the process record and replay target. When process record and
5652 replay target stops, the entire execution log will be deleted and the
5653 inferior will either be terminated, or will remain in its final state.
5654
5655 When you stop the process record and replay target in record mode (at
5656 the end of the execution log), the inferior will be stopped at the
5657 next instruction that would have been recorded. In other words, if
5658 you record for a while and then stop recording, the inferior process
5659 will be left in the same state as if the recording never happened.
5660
5661 On the other hand, if the process record and replay target is stopped
5662 while in replay mode (that is, not at the end of the execution log,
5663 but at some earlier point), the inferior process will become ``live''
5664 at that earlier state, and it will then be possible to continue the
5665 usual ``live'' debugging of the process from that state.
5666
5667 When the inferior process exits, or @value{GDBN} detaches from it,
5668 process record and replay target will automatically stop itself.
5669
5670 @kindex record save
5671 @item record save @var{filename}
5672 Save the execution log to a file @file{@var{filename}}.
5673 Default filename is @file{gdb_record.@var{process_id}}, where
5674 @var{process_id} is the process ID of the inferior.
5675
5676 @kindex record restore
5677 @item record restore @var{filename}
5678 Restore the execution log from a file @file{@var{filename}}.
5679 File must have been created with @code{record save}.
5680
5681 @kindex set record insn-number-max
5682 @item set record insn-number-max @var{limit}
5683 Set the limit of instructions to be recorded. Default value is 200000.
5684
5685 If @var{limit} is a positive number, then @value{GDBN} will start
5686 deleting instructions from the log once the number of the record
5687 instructions becomes greater than @var{limit}. For every new recorded
5688 instruction, @value{GDBN} will delete the earliest recorded
5689 instruction to keep the number of recorded instructions at the limit.
5690 (Since deleting recorded instructions loses information, @value{GDBN}
5691 lets you control what happens when the limit is reached, by means of
5692 the @code{stop-at-limit} option, described below.)
5693
5694 If @var{limit} is zero, @value{GDBN} will never delete recorded
5695 instructions from the execution log. The number of recorded
5696 instructions is unlimited in this case.
5697
5698 @kindex show record insn-number-max
5699 @item show record insn-number-max
5700 Show the limit of instructions to be recorded.
5701
5702 @kindex set record stop-at-limit
5703 @item set record stop-at-limit
5704 Control the behavior when the number of recorded instructions reaches
5705 the limit. If ON (the default), @value{GDBN} will stop when the limit
5706 is reached for the first time and ask you whether you want to stop the
5707 inferior or continue running it and recording the execution log. If
5708 you decide to continue recording, each new recorded instruction will
5709 cause the oldest one to be deleted.
5710
5711 If this option is OFF, @value{GDBN} will automatically delete the
5712 oldest record to make room for each new one, without asking.
5713
5714 @kindex show record stop-at-limit
5715 @item show record stop-at-limit
5716 Show the current setting of @code{stop-at-limit}.
5717
5718 @kindex set record memory-query
5719 @item set record memory-query
5720 Control the behavior when @value{GDBN} is unable to record memory
5721 changes caused by an instruction. If ON, @value{GDBN} will query
5722 whether to stop the inferior in that case.
5723
5724 If this option is OFF (the default), @value{GDBN} will automatically
5725 ignore the effect of such instructions on memory. Later, when
5726 @value{GDBN} replays this execution log, it will mark the log of this
5727 instruction as not accessible, and it will not affect the replay
5728 results.
5729
5730 @kindex show record memory-query
5731 @item show record memory-query
5732 Show the current setting of @code{memory-query}.
5733
5734 @kindex info record
5735 @item info record
5736 Show various statistics about the state of process record and its
5737 in-memory execution log buffer, including:
5738
5739 @itemize @bullet
5740 @item
5741 Whether in record mode or replay mode.
5742 @item
5743 Lowest recorded instruction number (counting from when the current execution log started recording instructions).
5744 @item
5745 Highest recorded instruction number.
5746 @item
5747 Current instruction about to be replayed (if in replay mode).
5748 @item
5749 Number of instructions contained in the execution log.
5750 @item
5751 Maximum number of instructions that may be contained in the execution log.
5752 @end itemize
5753
5754 @kindex record delete
5755 @kindex rec del
5756 @item record delete
5757 When record target runs in replay mode (``in the past''), delete the
5758 subsequent execution log and begin to record a new execution log starting
5759 from the current address. This means you will abandon the previously
5760 recorded ``future'' and begin recording a new ``future''.
5761 @end table
5762
5763
5764 @node Stack
5765 @chapter Examining the Stack
5766
5767 When your program has stopped, the first thing you need to know is where it
5768 stopped and how it got there.
5769
5770 @cindex call stack
5771 Each time your program performs a function call, information about the call
5772 is generated.
5773 That information includes the location of the call in your program,
5774 the arguments of the call,
5775 and the local variables of the function being called.
5776 The information is saved in a block of data called a @dfn{stack frame}.
5777 The stack frames are allocated in a region of memory called the @dfn{call
5778 stack}.
5779
5780 When your program stops, the @value{GDBN} commands for examining the
5781 stack allow you to see all of this information.
5782
5783 @cindex selected frame
5784 One of the stack frames is @dfn{selected} by @value{GDBN} and many
5785 @value{GDBN} commands refer implicitly to the selected frame. In
5786 particular, whenever you ask @value{GDBN} for the value of a variable in
5787 your program, the value is found in the selected frame. There are
5788 special @value{GDBN} commands to select whichever frame you are
5789 interested in. @xref{Selection, ,Selecting a Frame}.
5790
5791 When your program stops, @value{GDBN} automatically selects the
5792 currently executing frame and describes it briefly, similar to the
5793 @code{frame} command (@pxref{Frame Info, ,Information about a Frame}).
5794
5795 @menu
5796 * Frames:: Stack frames
5797 * Backtrace:: Backtraces
5798 * Selection:: Selecting a frame
5799 * Frame Info:: Information on a frame
5800
5801 @end menu
5802
5803 @node Frames
5804 @section Stack Frames
5805
5806 @cindex frame, definition
5807 @cindex stack frame
5808 The call stack is divided up into contiguous pieces called @dfn{stack
5809 frames}, or @dfn{frames} for short; each frame is the data associated
5810 with one call to one function. The frame contains the arguments given
5811 to the function, the function's local variables, and the address at
5812 which the function is executing.
5813
5814 @cindex initial frame
5815 @cindex outermost frame
5816 @cindex innermost frame
5817 When your program is started, the stack has only one frame, that of the
5818 function @code{main}. This is called the @dfn{initial} frame or the
5819 @dfn{outermost} frame. Each time a function is called, a new frame is
5820 made. Each time a function returns, the frame for that function invocation
5821 is eliminated. If a function is recursive, there can be many frames for
5822 the same function. The frame for the function in which execution is
5823 actually occurring is called the @dfn{innermost} frame. This is the most
5824 recently created of all the stack frames that still exist.
5825
5826 @cindex frame pointer
5827 Inside your program, stack frames are identified by their addresses. A
5828 stack frame consists of many bytes, each of which has its own address; each
5829 kind of computer has a convention for choosing one byte whose
5830 address serves as the address of the frame. Usually this address is kept
5831 in a register called the @dfn{frame pointer register}
5832 (@pxref{Registers, $fp}) while execution is going on in that frame.
5833
5834 @cindex frame number
5835 @value{GDBN} assigns numbers to all existing stack frames, starting with
5836 zero for the innermost frame, one for the frame that called it,
5837 and so on upward. These numbers do not really exist in your program;
5838 they are assigned by @value{GDBN} to give you a way of designating stack
5839 frames in @value{GDBN} commands.
5840
5841 @c The -fomit-frame-pointer below perennially causes hbox overflow
5842 @c underflow problems.
5843 @cindex frameless execution
5844 Some compilers provide a way to compile functions so that they operate
5845 without stack frames. (For example, the @value{NGCC} option
5846 @smallexample
5847 @samp{-fomit-frame-pointer}
5848 @end smallexample
5849 generates functions without a frame.)
5850 This is occasionally done with heavily used library functions to save
5851 the frame setup time. @value{GDBN} has limited facilities for dealing
5852 with these function invocations. If the innermost function invocation
5853 has no stack frame, @value{GDBN} nevertheless regards it as though
5854 it had a separate frame, which is numbered zero as usual, allowing
5855 correct tracing of the function call chain. However, @value{GDBN} has
5856 no provision for frameless functions elsewhere in the stack.
5857
5858 @table @code
5859 @kindex frame@r{, command}
5860 @cindex current stack frame
5861 @item frame @var{args}
5862 The @code{frame} command allows you to move from one stack frame to another,
5863 and to print the stack frame you select. @var{args} may be either the
5864 address of the frame or the stack frame number. Without an argument,
5865 @code{frame} prints the current stack frame.
5866
5867 @kindex select-frame
5868 @cindex selecting frame silently
5869 @item select-frame
5870 The @code{select-frame} command allows you to move from one stack frame
5871 to another without printing the frame. This is the silent version of
5872 @code{frame}.
5873 @end table
5874
5875 @node Backtrace
5876 @section Backtraces
5877
5878 @cindex traceback
5879 @cindex call stack traces
5880 A backtrace is a summary of how your program got where it is. It shows one
5881 line per frame, for many frames, starting with the currently executing
5882 frame (frame zero), followed by its caller (frame one), and on up the
5883 stack.
5884
5885 @table @code
5886 @kindex backtrace
5887 @kindex bt @r{(@code{backtrace})}
5888 @item backtrace
5889 @itemx bt
5890 Print a backtrace of the entire stack: one line per frame for all
5891 frames in the stack.
5892
5893 You can stop the backtrace at any time by typing the system interrupt
5894 character, normally @kbd{Ctrl-c}.
5895
5896 @item backtrace @var{n}
5897 @itemx bt @var{n}
5898 Similar, but print only the innermost @var{n} frames.
5899
5900 @item backtrace -@var{n}
5901 @itemx bt -@var{n}
5902 Similar, but print only the outermost @var{n} frames.
5903
5904 @item backtrace full
5905 @itemx bt full
5906 @itemx bt full @var{n}
5907 @itemx bt full -@var{n}
5908 Print the values of the local variables also. @var{n} specifies the
5909 number of frames to print, as described above.
5910 @end table
5911
5912 @kindex where
5913 @kindex info stack
5914 The names @code{where} and @code{info stack} (abbreviated @code{info s})
5915 are additional aliases for @code{backtrace}.
5916
5917 @cindex multiple threads, backtrace
5918 In a multi-threaded program, @value{GDBN} by default shows the
5919 backtrace only for the current thread. To display the backtrace for
5920 several or all of the threads, use the command @code{thread apply}
5921 (@pxref{Threads, thread apply}). For example, if you type @kbd{thread
5922 apply all backtrace}, @value{GDBN} will display the backtrace for all
5923 the threads; this is handy when you debug a core dump of a
5924 multi-threaded program.
5925
5926 Each line in the backtrace shows the frame number and the function name.
5927 The program counter value is also shown---unless you use @code{set
5928 print address off}. The backtrace also shows the source file name and
5929 line number, as well as the arguments to the function. The program
5930 counter value is omitted if it is at the beginning of the code for that
5931 line number.
5932
5933 Here is an example of a backtrace. It was made with the command
5934 @samp{bt 3}, so it shows the innermost three frames.
5935
5936 @smallexample
5937 @group
5938 #0 m4_traceon (obs=0x24eb0, argc=1, argv=0x2b8c8)
5939 at builtin.c:993
5940 #1 0x6e38 in expand_macro (sym=0x2b600, data=...) at macro.c:242
5941 #2 0x6840 in expand_token (obs=0x0, t=177664, td=0xf7fffb08)
5942 at macro.c:71
5943 (More stack frames follow...)
5944 @end group
5945 @end smallexample
5946
5947 @noindent
5948 The display for frame zero does not begin with a program counter
5949 value, indicating that your program has stopped at the beginning of the
5950 code for line @code{993} of @code{builtin.c}.
5951
5952 @noindent
5953 The value of parameter @code{data} in frame 1 has been replaced by
5954 @code{@dots{}}. By default, @value{GDBN} prints the value of a parameter
5955 only if it is a scalar (integer, pointer, enumeration, etc). See command
5956 @kbd{set print frame-arguments} in @ref{Print Settings} for more details
5957 on how to configure the way function parameter values are printed.
5958
5959 @cindex value optimized out, in backtrace
5960 @cindex function call arguments, optimized out
5961 If your program was compiled with optimizations, some compilers will
5962 optimize away arguments passed to functions if those arguments are
5963 never used after the call. Such optimizations generate code that
5964 passes arguments through registers, but doesn't store those arguments
5965 in the stack frame. @value{GDBN} has no way of displaying such
5966 arguments in stack frames other than the innermost one. Here's what
5967 such a backtrace might look like:
5968
5969 @smallexample
5970 @group
5971 #0 m4_traceon (obs=0x24eb0, argc=1, argv=0x2b8c8)
5972 at builtin.c:993
5973 #1 0x6e38 in expand_macro (sym=<value optimized out>) at macro.c:242
5974 #2 0x6840 in expand_token (obs=0x0, t=<value optimized out>, td=0xf7fffb08)
5975 at macro.c:71
5976 (More stack frames follow...)
5977 @end group
5978 @end smallexample
5979
5980 @noindent
5981 The values of arguments that were not saved in their stack frames are
5982 shown as @samp{<value optimized out>}.
5983
5984 If you need to display the values of such optimized-out arguments,
5985 either deduce that from other variables whose values depend on the one
5986 you are interested in, or recompile without optimizations.
5987
5988 @cindex backtrace beyond @code{main} function
5989 @cindex program entry point
5990 @cindex startup code, and backtrace
5991 Most programs have a standard user entry point---a place where system
5992 libraries and startup code transition into user code. For C this is
5993 @code{main}@footnote{
5994 Note that embedded programs (the so-called ``free-standing''
5995 environment) are not required to have a @code{main} function as the
5996 entry point. They could even have multiple entry points.}.
5997 When @value{GDBN} finds the entry function in a backtrace
5998 it will terminate the backtrace, to avoid tracing into highly
5999 system-specific (and generally uninteresting) code.
6000
6001 If you need to examine the startup code, or limit the number of levels
6002 in a backtrace, you can change this behavior:
6003
6004 @table @code
6005 @item set backtrace past-main
6006 @itemx set backtrace past-main on
6007 @kindex set backtrace
6008 Backtraces will continue past the user entry point.
6009
6010 @item set backtrace past-main off
6011 Backtraces will stop when they encounter the user entry point. This is the
6012 default.
6013
6014 @item show backtrace past-main
6015 @kindex show backtrace
6016 Display the current user entry point backtrace policy.
6017
6018 @item set backtrace past-entry
6019 @itemx set backtrace past-entry on
6020 Backtraces will continue past the internal entry point of an application.
6021 This entry point is encoded by the linker when the application is built,
6022 and is likely before the user entry point @code{main} (or equivalent) is called.
6023
6024 @item set backtrace past-entry off
6025 Backtraces will stop when they encounter the internal entry point of an
6026 application. This is the default.
6027
6028 @item show backtrace past-entry
6029 Display the current internal entry point backtrace policy.
6030
6031 @item set backtrace limit @var{n}
6032 @itemx set backtrace limit 0
6033 @cindex backtrace limit
6034 Limit the backtrace to @var{n} levels. A value of zero means
6035 unlimited.
6036
6037 @item show backtrace limit
6038 Display the current limit on backtrace levels.
6039 @end table
6040
6041 @node Selection
6042 @section Selecting a Frame
6043
6044 Most commands for examining the stack and other data in your program work on
6045 whichever stack frame is selected at the moment. Here are the commands for
6046 selecting a stack frame; all of them finish by printing a brief description
6047 of the stack frame just selected.
6048
6049 @table @code
6050 @kindex frame@r{, selecting}
6051 @kindex f @r{(@code{frame})}
6052 @item frame @var{n}
6053 @itemx f @var{n}
6054 Select frame number @var{n}. Recall that frame zero is the innermost
6055 (currently executing) frame, frame one is the frame that called the
6056 innermost one, and so on. The highest-numbered frame is the one for
6057 @code{main}.
6058
6059 @item frame @var{addr}
6060 @itemx f @var{addr}
6061 Select the frame at address @var{addr}. This is useful mainly if the
6062 chaining of stack frames has been damaged by a bug, making it
6063 impossible for @value{GDBN} to assign numbers properly to all frames. In
6064 addition, this can be useful when your program has multiple stacks and
6065 switches between them.
6066
6067 On the SPARC architecture, @code{frame} needs two addresses to
6068 select an arbitrary frame: a frame pointer and a stack pointer.
6069
6070 On the MIPS and Alpha architecture, it needs two addresses: a stack
6071 pointer and a program counter.
6072
6073 On the 29k architecture, it needs three addresses: a register stack
6074 pointer, a program counter, and a memory stack pointer.
6075
6076 @kindex up
6077 @item up @var{n}
6078 Move @var{n} frames up the stack. For positive numbers @var{n}, this
6079 advances toward the outermost frame, to higher frame numbers, to frames
6080 that have existed longer. @var{n} defaults to one.
6081
6082 @kindex down
6083 @kindex do @r{(@code{down})}
6084 @item down @var{n}
6085 Move @var{n} frames down the stack. For positive numbers @var{n}, this
6086 advances toward the innermost frame, to lower frame numbers, to frames
6087 that were created more recently. @var{n} defaults to one. You may
6088 abbreviate @code{down} as @code{do}.
6089 @end table
6090
6091 All of these commands end by printing two lines of output describing the
6092 frame. The first line shows the frame number, the function name, the
6093 arguments, and the source file and line number of execution in that
6094 frame. The second line shows the text of that source line.
6095
6096 @need 1000
6097 For example:
6098
6099 @smallexample
6100 @group
6101 (@value{GDBP}) up
6102 #1 0x22f0 in main (argc=1, argv=0xf7fffbf4, env=0xf7fffbfc)
6103 at env.c:10
6104 10 read_input_file (argv[i]);
6105 @end group
6106 @end smallexample
6107
6108 After such a printout, the @code{list} command with no arguments
6109 prints ten lines centered on the point of execution in the frame.
6110 You can also edit the program at the point of execution with your favorite
6111 editing program by typing @code{edit}.
6112 @xref{List, ,Printing Source Lines},
6113 for details.
6114
6115 @table @code
6116 @kindex down-silently
6117 @kindex up-silently
6118 @item up-silently @var{n}
6119 @itemx down-silently @var{n}
6120 These two commands are variants of @code{up} and @code{down},
6121 respectively; they differ in that they do their work silently, without
6122 causing display of the new frame. They are intended primarily for use
6123 in @value{GDBN} command scripts, where the output might be unnecessary and
6124 distracting.
6125 @end table
6126
6127 @node Frame Info
6128 @section Information About a Frame
6129
6130 There are several other commands to print information about the selected
6131 stack frame.
6132
6133 @table @code
6134 @item frame
6135 @itemx f
6136 When used without any argument, this command does not change which
6137 frame is selected, but prints a brief description of the currently
6138 selected stack frame. It can be abbreviated @code{f}. With an
6139 argument, this command is used to select a stack frame.
6140 @xref{Selection, ,Selecting a Frame}.
6141
6142 @kindex info frame
6143 @kindex info f @r{(@code{info frame})}
6144 @item info frame
6145 @itemx info f
6146 This command prints a verbose description of the selected stack frame,
6147 including:
6148
6149 @itemize @bullet
6150 @item
6151 the address of the frame
6152 @item
6153 the address of the next frame down (called by this frame)
6154 @item
6155 the address of the next frame up (caller of this frame)
6156 @item
6157 the language in which the source code corresponding to this frame is written
6158 @item
6159 the address of the frame's arguments
6160 @item
6161 the address of the frame's local variables
6162 @item
6163 the program counter saved in it (the address of execution in the caller frame)
6164 @item
6165 which registers were saved in the frame
6166 @end itemize
6167
6168 @noindent The verbose description is useful when
6169 something has gone wrong that has made the stack format fail to fit
6170 the usual conventions.
6171
6172 @item info frame @var{addr}
6173 @itemx info f @var{addr}
6174 Print a verbose description of the frame at address @var{addr}, without
6175 selecting that frame. The selected frame remains unchanged by this
6176 command. This requires the same kind of address (more than one for some
6177 architectures) that you specify in the @code{frame} command.
6178 @xref{Selection, ,Selecting a Frame}.
6179
6180 @kindex info args
6181 @item info args
6182 Print the arguments of the selected frame, each on a separate line.
6183
6184 @item info locals
6185 @kindex info locals
6186 Print the local variables of the selected frame, each on a separate
6187 line. These are all variables (declared either static or automatic)
6188 accessible at the point of execution of the selected frame.
6189
6190 @kindex info catch
6191 @cindex catch exceptions, list active handlers
6192 @cindex exception handlers, how to list
6193 @item info catch
6194 Print a list of all the exception handlers that are active in the
6195 current stack frame at the current point of execution. To see other
6196 exception handlers, visit the associated frame (using the @code{up},
6197 @code{down}, or @code{frame} commands); then type @code{info catch}.
6198 @xref{Set Catchpoints, , Setting Catchpoints}.
6199
6200 @end table
6201
6202
6203 @node Source
6204 @chapter Examining Source Files
6205
6206 @value{GDBN} can print parts of your program's source, since the debugging
6207 information recorded in the program tells @value{GDBN} what source files were
6208 used to build it. When your program stops, @value{GDBN} spontaneously prints
6209 the line where it stopped. Likewise, when you select a stack frame
6210 (@pxref{Selection, ,Selecting a Frame}), @value{GDBN} prints the line where
6211 execution in that frame has stopped. You can print other portions of
6212 source files by explicit command.
6213
6214 If you use @value{GDBN} through its @sc{gnu} Emacs interface, you may
6215 prefer to use Emacs facilities to view source; see @ref{Emacs, ,Using
6216 @value{GDBN} under @sc{gnu} Emacs}.
6217
6218 @menu
6219 * List:: Printing source lines
6220 * Specify Location:: How to specify code locations
6221 * Edit:: Editing source files
6222 * Search:: Searching source files
6223 * Source Path:: Specifying source directories
6224 * Machine Code:: Source and machine code
6225 @end menu
6226
6227 @node List
6228 @section Printing Source Lines
6229
6230 @kindex list
6231 @kindex l @r{(@code{list})}
6232 To print lines from a source file, use the @code{list} command
6233 (abbreviated @code{l}). By default, ten lines are printed.
6234 There are several ways to specify what part of the file you want to
6235 print; see @ref{Specify Location}, for the full list.
6236
6237 Here are the forms of the @code{list} command most commonly used:
6238
6239 @table @code
6240 @item list @var{linenum}
6241 Print lines centered around line number @var{linenum} in the
6242 current source file.
6243
6244 @item list @var{function}
6245 Print lines centered around the beginning of function
6246 @var{function}.
6247
6248 @item list
6249 Print more lines. If the last lines printed were printed with a
6250 @code{list} command, this prints lines following the last lines
6251 printed; however, if the last line printed was a solitary line printed
6252 as part of displaying a stack frame (@pxref{Stack, ,Examining the
6253 Stack}), this prints lines centered around that line.
6254
6255 @item list -
6256 Print lines just before the lines last printed.
6257 @end table
6258
6259 @cindex @code{list}, how many lines to display
6260 By default, @value{GDBN} prints ten source lines with any of these forms of
6261 the @code{list} command. You can change this using @code{set listsize}:
6262
6263 @table @code
6264 @kindex set listsize
6265 @item set listsize @var{count}
6266 Make the @code{list} command display @var{count} source lines (unless
6267 the @code{list} argument explicitly specifies some other number).
6268
6269 @kindex show listsize
6270 @item show listsize
6271 Display the number of lines that @code{list} prints.
6272 @end table
6273
6274 Repeating a @code{list} command with @key{RET} discards the argument,
6275 so it is equivalent to typing just @code{list}. This is more useful
6276 than listing the same lines again. An exception is made for an
6277 argument of @samp{-}; that argument is preserved in repetition so that
6278 each repetition moves up in the source file.
6279
6280 In general, the @code{list} command expects you to supply zero, one or two
6281 @dfn{linespecs}. Linespecs specify source lines; there are several ways
6282 of writing them (@pxref{Specify Location}), but the effect is always
6283 to specify some source line.
6284
6285 Here is a complete description of the possible arguments for @code{list}:
6286
6287 @table @code
6288 @item list @var{linespec}
6289 Print lines centered around the line specified by @var{linespec}.
6290
6291 @item list @var{first},@var{last}
6292 Print lines from @var{first} to @var{last}. Both arguments are
6293 linespecs. When a @code{list} command has two linespecs, and the
6294 source file of the second linespec is omitted, this refers to
6295 the same source file as the first linespec.
6296
6297 @item list ,@var{last}
6298 Print lines ending with @var{last}.
6299
6300 @item list @var{first},
6301 Print lines starting with @var{first}.
6302
6303 @item list +
6304 Print lines just after the lines last printed.
6305
6306 @item list -
6307 Print lines just before the lines last printed.
6308
6309 @item list
6310 As described in the preceding table.
6311 @end table
6312
6313 @node Specify Location
6314 @section Specifying a Location
6315 @cindex specifying location
6316 @cindex linespec
6317
6318 Several @value{GDBN} commands accept arguments that specify a location
6319 of your program's code. Since @value{GDBN} is a source-level
6320 debugger, a location usually specifies some line in the source code;
6321 for that reason, locations are also known as @dfn{linespecs}.
6322
6323 Here are all the different ways of specifying a code location that
6324 @value{GDBN} understands:
6325
6326 @table @code
6327 @item @var{linenum}
6328 Specifies the line number @var{linenum} of the current source file.
6329
6330 @item -@var{offset}
6331 @itemx +@var{offset}
6332 Specifies the line @var{offset} lines before or after the @dfn{current
6333 line}. For the @code{list} command, the current line is the last one
6334 printed; for the breakpoint commands, this is the line at which
6335 execution stopped in the currently selected @dfn{stack frame}
6336 (@pxref{Frames, ,Frames}, for a description of stack frames.) When
6337 used as the second of the two linespecs in a @code{list} command,
6338 this specifies the line @var{offset} lines up or down from the first
6339 linespec.
6340
6341 @item @var{filename}:@var{linenum}
6342 Specifies the line @var{linenum} in the source file @var{filename}.
6343
6344 @item @var{function}
6345 Specifies the line that begins the body of the function @var{function}.
6346 For example, in C, this is the line with the open brace.
6347
6348 @item @var{filename}:@var{function}
6349 Specifies the line that begins the body of the function @var{function}
6350 in the file @var{filename}. You only need the file name with a
6351 function name to avoid ambiguity when there are identically named
6352 functions in different source files.
6353
6354 @item @var{label}
6355 Specifies the line at which the label named @var{label} appears.
6356 @value{GDBN} searches for the label in the function corresponding to
6357 the currently selected stack frame. If there is no current selected
6358 stack frame (for instance, if the inferior is not running), then
6359 @value{GDBN} will not search for a label.
6360
6361 @item *@var{address}
6362 Specifies the program address @var{address}. For line-oriented
6363 commands, such as @code{list} and @code{edit}, this specifies a source
6364 line that contains @var{address}. For @code{break} and other
6365 breakpoint oriented commands, this can be used to set breakpoints in
6366 parts of your program which do not have debugging information or
6367 source files.
6368
6369 Here @var{address} may be any expression valid in the current working
6370 language (@pxref{Languages, working language}) that specifies a code
6371 address. In addition, as a convenience, @value{GDBN} extends the
6372 semantics of expressions used in locations to cover the situations
6373 that frequently happen during debugging. Here are the various forms
6374 of @var{address}:
6375
6376 @table @code
6377 @item @var{expression}
6378 Any expression valid in the current working language.
6379
6380 @item @var{funcaddr}
6381 An address of a function or procedure derived from its name. In C,
6382 C@t{++}, Java, Objective-C, Fortran, minimal, and assembly, this is
6383 simply the function's name @var{function} (and actually a special case
6384 of a valid expression). In Pascal and Modula-2, this is
6385 @code{&@var{function}}. In Ada, this is @code{@var{function}'Address}
6386 (although the Pascal form also works).
6387
6388 This form specifies the address of the function's first instruction,
6389 before the stack frame and arguments have been set up.
6390
6391 @item '@var{filename}'::@var{funcaddr}
6392 Like @var{funcaddr} above, but also specifies the name of the source
6393 file explicitly. This is useful if the name of the function does not
6394 specify the function unambiguously, e.g., if there are several
6395 functions with identical names in different source files.
6396 @end table
6397
6398 @end table
6399
6400
6401 @node Edit
6402 @section Editing Source Files
6403 @cindex editing source files
6404
6405 @kindex edit
6406 @kindex e @r{(@code{edit})}
6407 To edit the lines in a source file, use the @code{edit} command.
6408 The editing program of your choice
6409 is invoked with the current line set to
6410 the active line in the program.
6411 Alternatively, there are several ways to specify what part of the file you
6412 want to print if you want to see other parts of the program:
6413
6414 @table @code
6415 @item edit @var{location}
6416 Edit the source file specified by @code{location}. Editing starts at
6417 that @var{location}, e.g., at the specified source line of the
6418 specified file. @xref{Specify Location}, for all the possible forms
6419 of the @var{location} argument; here are the forms of the @code{edit}
6420 command most commonly used:
6421
6422 @table @code
6423 @item edit @var{number}
6424 Edit the current source file with @var{number} as the active line number.
6425
6426 @item edit @var{function}
6427 Edit the file containing @var{function} at the beginning of its definition.
6428 @end table
6429
6430 @end table
6431
6432 @subsection Choosing your Editor
6433 You can customize @value{GDBN} to use any editor you want
6434 @footnote{
6435 The only restriction is that your editor (say @code{ex}), recognizes the
6436 following command-line syntax:
6437 @smallexample
6438 ex +@var{number} file
6439 @end smallexample
6440 The optional numeric value +@var{number} specifies the number of the line in
6441 the file where to start editing.}.
6442 By default, it is @file{@value{EDITOR}}, but you can change this
6443 by setting the environment variable @code{EDITOR} before using
6444 @value{GDBN}. For example, to configure @value{GDBN} to use the
6445 @code{vi} editor, you could use these commands with the @code{sh} shell:
6446 @smallexample
6447 EDITOR=/usr/bin/vi
6448 export EDITOR
6449 gdb @dots{}
6450 @end smallexample
6451 or in the @code{csh} shell,
6452 @smallexample
6453 setenv EDITOR /usr/bin/vi
6454 gdb @dots{}
6455 @end smallexample
6456
6457 @node Search
6458 @section Searching Source Files
6459 @cindex searching source files
6460
6461 There are two commands for searching through the current source file for a
6462 regular expression.
6463
6464 @table @code
6465 @kindex search
6466 @kindex forward-search
6467 @item forward-search @var{regexp}
6468 @itemx search @var{regexp}
6469 The command @samp{forward-search @var{regexp}} checks each line,
6470 starting with the one following the last line listed, for a match for
6471 @var{regexp}. It lists the line that is found. You can use the
6472 synonym @samp{search @var{regexp}} or abbreviate the command name as
6473 @code{fo}.
6474
6475 @kindex reverse-search
6476 @item reverse-search @var{regexp}
6477 The command @samp{reverse-search @var{regexp}} checks each line, starting
6478 with the one before the last line listed and going backward, for a match
6479 for @var{regexp}. It lists the line that is found. You can abbreviate
6480 this command as @code{rev}.
6481 @end table
6482
6483 @node Source Path
6484 @section Specifying Source Directories
6485
6486 @cindex source path
6487 @cindex directories for source files
6488 Executable programs sometimes do not record the directories of the source
6489 files from which they were compiled, just the names. Even when they do,
6490 the directories could be moved between the compilation and your debugging
6491 session. @value{GDBN} has a list of directories to search for source files;
6492 this is called the @dfn{source path}. Each time @value{GDBN} wants a source file,
6493 it tries all the directories in the list, in the order they are present
6494 in the list, until it finds a file with the desired name.
6495
6496 For example, suppose an executable references the file
6497 @file{/usr/src/foo-1.0/lib/foo.c}, and our source path is
6498 @file{/mnt/cross}. The file is first looked up literally; if this
6499 fails, @file{/mnt/cross/usr/src/foo-1.0/lib/foo.c} is tried; if this
6500 fails, @file{/mnt/cross/foo.c} is opened; if this fails, an error
6501 message is printed. @value{GDBN} does not look up the parts of the
6502 source file name, such as @file{/mnt/cross/src/foo-1.0/lib/foo.c}.
6503 Likewise, the subdirectories of the source path are not searched: if
6504 the source path is @file{/mnt/cross}, and the binary refers to
6505 @file{foo.c}, @value{GDBN} would not find it under
6506 @file{/mnt/cross/usr/src/foo-1.0/lib}.
6507
6508 Plain file names, relative file names with leading directories, file
6509 names containing dots, etc.@: are all treated as described above; for
6510 instance, if the source path is @file{/mnt/cross}, and the source file
6511 is recorded as @file{../lib/foo.c}, @value{GDBN} would first try
6512 @file{../lib/foo.c}, then @file{/mnt/cross/../lib/foo.c}, and after
6513 that---@file{/mnt/cross/foo.c}.
6514
6515 Note that the executable search path is @emph{not} used to locate the
6516 source files.
6517
6518 Whenever you reset or rearrange the source path, @value{GDBN} clears out
6519 any information it has cached about where source files are found and where
6520 each line is in the file.
6521
6522 @kindex directory
6523 @kindex dir
6524 When you start @value{GDBN}, its source path includes only @samp{cdir}
6525 and @samp{cwd}, in that order.
6526 To add other directories, use the @code{directory} command.
6527
6528 The search path is used to find both program source files and @value{GDBN}
6529 script files (read using the @samp{-command} option and @samp{source} command).
6530
6531 In addition to the source path, @value{GDBN} provides a set of commands
6532 that manage a list of source path substitution rules. A @dfn{substitution
6533 rule} specifies how to rewrite source directories stored in the program's
6534 debug information in case the sources were moved to a different
6535 directory between compilation and debugging. A rule is made of
6536 two strings, the first specifying what needs to be rewritten in
6537 the path, and the second specifying how it should be rewritten.
6538 In @ref{set substitute-path}, we name these two parts @var{from} and
6539 @var{to} respectively. @value{GDBN} does a simple string replacement
6540 of @var{from} with @var{to} at the start of the directory part of the
6541 source file name, and uses that result instead of the original file
6542 name to look up the sources.
6543
6544 Using the previous example, suppose the @file{foo-1.0} tree has been
6545 moved from @file{/usr/src} to @file{/mnt/cross}, then you can tell
6546 @value{GDBN} to replace @file{/usr/src} in all source path names with
6547 @file{/mnt/cross}. The first lookup will then be
6548 @file{/mnt/cross/foo-1.0/lib/foo.c} in place of the original location
6549 of @file{/usr/src/foo-1.0/lib/foo.c}. To define a source path
6550 substitution rule, use the @code{set substitute-path} command
6551 (@pxref{set substitute-path}).
6552
6553 To avoid unexpected substitution results, a rule is applied only if the
6554 @var{from} part of the directory name ends at a directory separator.
6555 For instance, a rule substituting @file{/usr/source} into
6556 @file{/mnt/cross} will be applied to @file{/usr/source/foo-1.0} but
6557 not to @file{/usr/sourceware/foo-2.0}. And because the substitution
6558 is applied only at the beginning of the directory name, this rule will
6559 not be applied to @file{/root/usr/source/baz.c} either.
6560
6561 In many cases, you can achieve the same result using the @code{directory}
6562 command. However, @code{set substitute-path} can be more efficient in
6563 the case where the sources are organized in a complex tree with multiple
6564 subdirectories. With the @code{directory} command, you need to add each
6565 subdirectory of your project. If you moved the entire tree while
6566 preserving its internal organization, then @code{set substitute-path}
6567 allows you to direct the debugger to all the sources with one single
6568 command.
6569
6570 @code{set substitute-path} is also more than just a shortcut command.
6571 The source path is only used if the file at the original location no
6572 longer exists. On the other hand, @code{set substitute-path} modifies
6573 the debugger behavior to look at the rewritten location instead. So, if
6574 for any reason a source file that is not relevant to your executable is
6575 located at the original location, a substitution rule is the only
6576 method available to point @value{GDBN} at the new location.
6577
6578 @cindex @samp{--with-relocated-sources}
6579 @cindex default source path substitution
6580 You can configure a default source path substitution rule by
6581 configuring @value{GDBN} with the
6582 @samp{--with-relocated-sources=@var{dir}} option. The @var{dir}
6583 should be the name of a directory under @value{GDBN}'s configured
6584 prefix (set with @samp{--prefix} or @samp{--exec-prefix}), and
6585 directory names in debug information under @var{dir} will be adjusted
6586 automatically if the installed @value{GDBN} is moved to a new
6587 location. This is useful if @value{GDBN}, libraries or executables
6588 with debug information and corresponding source code are being moved
6589 together.
6590
6591 @table @code
6592 @item directory @var{dirname} @dots{}
6593 @item dir @var{dirname} @dots{}
6594 Add directory @var{dirname} to the front of the source path. Several
6595 directory names may be given to this command, separated by @samp{:}
6596 (@samp{;} on MS-DOS and MS-Windows, where @samp{:} usually appears as
6597 part of absolute file names) or
6598 whitespace. You may specify a directory that is already in the source
6599 path; this moves it forward, so @value{GDBN} searches it sooner.
6600
6601 @kindex cdir
6602 @kindex cwd
6603 @vindex $cdir@r{, convenience variable}
6604 @vindex $cwd@r{, convenience variable}
6605 @cindex compilation directory
6606 @cindex current directory
6607 @cindex working directory
6608 @cindex directory, current
6609 @cindex directory, compilation
6610 You can use the string @samp{$cdir} to refer to the compilation
6611 directory (if one is recorded), and @samp{$cwd} to refer to the current
6612 working directory. @samp{$cwd} is not the same as @samp{.}---the former
6613 tracks the current working directory as it changes during your @value{GDBN}
6614 session, while the latter is immediately expanded to the current
6615 directory at the time you add an entry to the source path.
6616
6617 @item directory
6618 Reset the source path to its default value (@samp{$cdir:$cwd} on Unix systems). This requires confirmation.
6619
6620 @c RET-repeat for @code{directory} is explicitly disabled, but since
6621 @c repeating it would be a no-op we do not say that. (thanks to RMS)
6622
6623 @item show directories
6624 @kindex show directories
6625 Print the source path: show which directories it contains.
6626
6627 @anchor{set substitute-path}
6628 @item set substitute-path @var{from} @var{to}
6629 @kindex set substitute-path
6630 Define a source path substitution rule, and add it at the end of the
6631 current list of existing substitution rules. If a rule with the same
6632 @var{from} was already defined, then the old rule is also deleted.
6633
6634 For example, if the file @file{/foo/bar/baz.c} was moved to
6635 @file{/mnt/cross/baz.c}, then the command
6636
6637 @smallexample
6638 (@value{GDBP}) set substitute-path /usr/src /mnt/cross
6639 @end smallexample
6640
6641 @noindent
6642 will tell @value{GDBN} to replace @samp{/usr/src} with
6643 @samp{/mnt/cross}, which will allow @value{GDBN} to find the file
6644 @file{baz.c} even though it was moved.
6645
6646 In the case when more than one substitution rule have been defined,
6647 the rules are evaluated one by one in the order where they have been
6648 defined. The first one matching, if any, is selected to perform
6649 the substitution.
6650
6651 For instance, if we had entered the following commands:
6652
6653 @smallexample
6654 (@value{GDBP}) set substitute-path /usr/src/include /mnt/include
6655 (@value{GDBP}) set substitute-path /usr/src /mnt/src
6656 @end smallexample
6657
6658 @noindent
6659 @value{GDBN} would then rewrite @file{/usr/src/include/defs.h} into
6660 @file{/mnt/include/defs.h} by using the first rule. However, it would
6661 use the second rule to rewrite @file{/usr/src/lib/foo.c} into
6662 @file{/mnt/src/lib/foo.c}.
6663
6664
6665 @item unset substitute-path [path]
6666 @kindex unset substitute-path
6667 If a path is specified, search the current list of substitution rules
6668 for a rule that would rewrite that path. Delete that rule if found.
6669 A warning is emitted by the debugger if no rule could be found.
6670
6671 If no path is specified, then all substitution rules are deleted.
6672
6673 @item show substitute-path [path]
6674 @kindex show substitute-path
6675 If a path is specified, then print the source path substitution rule
6676 which would rewrite that path, if any.
6677
6678 If no path is specified, then print all existing source path substitution
6679 rules.
6680
6681 @end table
6682
6683 If your source path is cluttered with directories that are no longer of
6684 interest, @value{GDBN} may sometimes cause confusion by finding the wrong
6685 versions of source. You can correct the situation as follows:
6686
6687 @enumerate
6688 @item
6689 Use @code{directory} with no argument to reset the source path to its default value.
6690
6691 @item
6692 Use @code{directory} with suitable arguments to reinstall the
6693 directories you want in the source path. You can add all the
6694 directories in one command.
6695 @end enumerate
6696
6697 @node Machine Code
6698 @section Source and Machine Code
6699 @cindex source line and its code address
6700
6701 You can use the command @code{info line} to map source lines to program
6702 addresses (and vice versa), and the command @code{disassemble} to display
6703 a range of addresses as machine instructions. You can use the command
6704 @code{set disassemble-next-line} to set whether to disassemble next
6705 source line when execution stops. When run under @sc{gnu} Emacs
6706 mode, the @code{info line} command causes the arrow to point to the
6707 line specified. Also, @code{info line} prints addresses in symbolic form as
6708 well as hex.
6709
6710 @table @code
6711 @kindex info line
6712 @item info line @var{linespec}
6713 Print the starting and ending addresses of the compiled code for
6714 source line @var{linespec}. You can specify source lines in any of
6715 the ways documented in @ref{Specify Location}.
6716 @end table
6717
6718 For example, we can use @code{info line} to discover the location of
6719 the object code for the first line of function
6720 @code{m4_changequote}:
6721
6722 @c FIXME: I think this example should also show the addresses in
6723 @c symbolic form, as they usually would be displayed.
6724 @smallexample
6725 (@value{GDBP}) info line m4_changequote
6726 Line 895 of "builtin.c" starts at pc 0x634c and ends at 0x6350.
6727 @end smallexample
6728
6729 @noindent
6730 @cindex code address and its source line
6731 We can also inquire (using @code{*@var{addr}} as the form for
6732 @var{linespec}) what source line covers a particular address:
6733 @smallexample
6734 (@value{GDBP}) info line *0x63ff
6735 Line 926 of "builtin.c" starts at pc 0x63e4 and ends at 0x6404.
6736 @end smallexample
6737
6738 @cindex @code{$_} and @code{info line}
6739 @cindex @code{x} command, default address
6740 @kindex x@r{(examine), and} info line
6741 After @code{info line}, the default address for the @code{x} command
6742 is changed to the starting address of the line, so that @samp{x/i} is
6743 sufficient to begin examining the machine code (@pxref{Memory,
6744 ,Examining Memory}). Also, this address is saved as the value of the
6745 convenience variable @code{$_} (@pxref{Convenience Vars, ,Convenience
6746 Variables}).
6747
6748 @table @code
6749 @kindex disassemble
6750 @cindex assembly instructions
6751 @cindex instructions, assembly
6752 @cindex machine instructions
6753 @cindex listing machine instructions
6754 @item disassemble
6755 @itemx disassemble /m
6756 @itemx disassemble /r
6757 This specialized command dumps a range of memory as machine
6758 instructions. It can also print mixed source+disassembly by specifying
6759 the @code{/m} modifier and print the raw instructions in hex as well as
6760 in symbolic form by specifying the @code{/r}.
6761 The default memory range is the function surrounding the
6762 program counter of the selected frame. A single argument to this
6763 command is a program counter value; @value{GDBN} dumps the function
6764 surrounding this value. When two arguments are given, they should
6765 be separated by a comma, possibly surrounded by whitespace. The
6766 arguments specify a range of addresses to dump, in one of two forms:
6767
6768 @table @code
6769 @item @var{start},@var{end}
6770 the addresses from @var{start} (inclusive) to @var{end} (exclusive)
6771 @item @var{start},+@var{length}
6772 the addresses from @var{start} (inclusive) to
6773 @code{@var{start}+@var{length}} (exclusive).
6774 @end table
6775
6776 @noindent
6777 When 2 arguments are specified, the name of the function is also
6778 printed (since there could be several functions in the given range).
6779
6780 The argument(s) can be any expression yielding a numeric value, such as
6781 @samp{0x32c4}, @samp{&main+10} or @samp{$pc - 8}.
6782
6783 If the range of memory being disassembled contains current program counter,
6784 the instruction at that location is shown with a @code{=>} marker.
6785 @end table
6786
6787 The following example shows the disassembly of a range of addresses of
6788 HP PA-RISC 2.0 code:
6789
6790 @smallexample
6791 (@value{GDBP}) disas 0x32c4, 0x32e4
6792 Dump of assembler code from 0x32c4 to 0x32e4:
6793 0x32c4 <main+204>: addil 0,dp
6794 0x32c8 <main+208>: ldw 0x22c(sr0,r1),r26
6795 0x32cc <main+212>: ldil 0x3000,r31
6796 0x32d0 <main+216>: ble 0x3f8(sr4,r31)
6797 0x32d4 <main+220>: ldo 0(r31),rp
6798 0x32d8 <main+224>: addil -0x800,dp
6799 0x32dc <main+228>: ldo 0x588(r1),r26
6800 0x32e0 <main+232>: ldil 0x3000,r31
6801 End of assembler dump.
6802 @end smallexample
6803
6804 Here is an example showing mixed source+assembly for Intel x86, when the
6805 program is stopped just after function prologue:
6806
6807 @smallexample
6808 (@value{GDBP}) disas /m main
6809 Dump of assembler code for function main:
6810 5 @{
6811 0x08048330 <+0>: push %ebp
6812 0x08048331 <+1>: mov %esp,%ebp
6813 0x08048333 <+3>: sub $0x8,%esp
6814 0x08048336 <+6>: and $0xfffffff0,%esp
6815 0x08048339 <+9>: sub $0x10,%esp
6816
6817 6 printf ("Hello.\n");
6818 => 0x0804833c <+12>: movl $0x8048440,(%esp)
6819 0x08048343 <+19>: call 0x8048284 <puts@@plt>
6820
6821 7 return 0;
6822 8 @}
6823 0x08048348 <+24>: mov $0x0,%eax
6824 0x0804834d <+29>: leave
6825 0x0804834e <+30>: ret
6826
6827 End of assembler dump.
6828 @end smallexample
6829
6830 Here is another example showing raw instructions in hex for AMD x86-64,
6831
6832 @smallexample
6833 (gdb) disas /r 0x400281,+10
6834 Dump of assembler code from 0x400281 to 0x40028b:
6835 0x0000000000400281: 38 36 cmp %dh,(%rsi)
6836 0x0000000000400283: 2d 36 34 2e 73 sub $0x732e3436,%eax
6837 0x0000000000400288: 6f outsl %ds:(%rsi),(%dx)
6838 0x0000000000400289: 2e 32 00 xor %cs:(%rax),%al
6839 End of assembler dump.
6840 @end smallexample
6841
6842 Some architectures have more than one commonly-used set of instruction
6843 mnemonics or other syntax.
6844
6845 For programs that were dynamically linked and use shared libraries,
6846 instructions that call functions or branch to locations in the shared
6847 libraries might show a seemingly bogus location---it's actually a
6848 location of the relocation table. On some architectures, @value{GDBN}
6849 might be able to resolve these to actual function names.
6850
6851 @table @code
6852 @kindex set disassembly-flavor
6853 @cindex Intel disassembly flavor
6854 @cindex AT&T disassembly flavor
6855 @item set disassembly-flavor @var{instruction-set}
6856 Select the instruction set to use when disassembling the
6857 program via the @code{disassemble} or @code{x/i} commands.
6858
6859 Currently this command is only defined for the Intel x86 family. You
6860 can set @var{instruction-set} to either @code{intel} or @code{att}.
6861 The default is @code{att}, the AT&T flavor used by default by Unix
6862 assemblers for x86-based targets.
6863
6864 @kindex show disassembly-flavor
6865 @item show disassembly-flavor
6866 Show the current setting of the disassembly flavor.
6867 @end table
6868
6869 @table @code
6870 @kindex set disassemble-next-line
6871 @kindex show disassemble-next-line
6872 @item set disassemble-next-line
6873 @itemx show disassemble-next-line
6874 Control whether or not @value{GDBN} will disassemble the next source
6875 line or instruction when execution stops. If ON, @value{GDBN} will
6876 display disassembly of the next source line when execution of the
6877 program being debugged stops. This is @emph{in addition} to
6878 displaying the source line itself, which @value{GDBN} always does if
6879 possible. If the next source line cannot be displayed for some reason
6880 (e.g., if @value{GDBN} cannot find the source file, or there's no line
6881 info in the debug info), @value{GDBN} will display disassembly of the
6882 next @emph{instruction} instead of showing the next source line. If
6883 AUTO, @value{GDBN} will display disassembly of next instruction only
6884 if the source line cannot be displayed. This setting causes
6885 @value{GDBN} to display some feedback when you step through a function
6886 with no line info or whose source file is unavailable. The default is
6887 OFF, which means never display the disassembly of the next line or
6888 instruction.
6889 @end table
6890
6891
6892 @node Data
6893 @chapter Examining Data
6894
6895 @cindex printing data
6896 @cindex examining data
6897 @kindex print
6898 @kindex inspect
6899 @c "inspect" is not quite a synonym if you are using Epoch, which we do not
6900 @c document because it is nonstandard... Under Epoch it displays in a
6901 @c different window or something like that.
6902 The usual way to examine data in your program is with the @code{print}
6903 command (abbreviated @code{p}), or its synonym @code{inspect}. It
6904 evaluates and prints the value of an expression of the language your
6905 program is written in (@pxref{Languages, ,Using @value{GDBN} with
6906 Different Languages}). It may also print the expression using a
6907 Python-based pretty-printer (@pxref{Pretty Printing}).
6908
6909 @table @code
6910 @item print @var{expr}
6911 @itemx print /@var{f} @var{expr}
6912 @var{expr} is an expression (in the source language). By default the
6913 value of @var{expr} is printed in a format appropriate to its data type;
6914 you can choose a different format by specifying @samp{/@var{f}}, where
6915 @var{f} is a letter specifying the format; see @ref{Output Formats,,Output
6916 Formats}.
6917
6918 @item print
6919 @itemx print /@var{f}
6920 @cindex reprint the last value
6921 If you omit @var{expr}, @value{GDBN} displays the last value again (from the
6922 @dfn{value history}; @pxref{Value History, ,Value History}). This allows you to
6923 conveniently inspect the same value in an alternative format.
6924 @end table
6925
6926 A more low-level way of examining data is with the @code{x} command.
6927 It examines data in memory at a specified address and prints it in a
6928 specified format. @xref{Memory, ,Examining Memory}.
6929
6930 If you are interested in information about types, or about how the
6931 fields of a struct or a class are declared, use the @code{ptype @var{exp}}
6932 command rather than @code{print}. @xref{Symbols, ,Examining the Symbol
6933 Table}.
6934
6935 @menu
6936 * Expressions:: Expressions
6937 * Ambiguous Expressions:: Ambiguous Expressions
6938 * Variables:: Program variables
6939 * Arrays:: Artificial arrays
6940 * Output Formats:: Output formats
6941 * Memory:: Examining memory
6942 * Auto Display:: Automatic display
6943 * Print Settings:: Print settings
6944 * Pretty Printing:: Python pretty printing
6945 * Value History:: Value history
6946 * Convenience Vars:: Convenience variables
6947 * Registers:: Registers
6948 * Floating Point Hardware:: Floating point hardware
6949 * Vector Unit:: Vector Unit
6950 * OS Information:: Auxiliary data provided by operating system
6951 * Memory Region Attributes:: Memory region attributes
6952 * Dump/Restore Files:: Copy between memory and a file
6953 * Core File Generation:: Cause a program dump its core
6954 * Character Sets:: Debugging programs that use a different
6955 character set than GDB does
6956 * Caching Remote Data:: Data caching for remote targets
6957 * Searching Memory:: Searching memory for a sequence of bytes
6958 @end menu
6959
6960 @node Expressions
6961 @section Expressions
6962
6963 @cindex expressions
6964 @code{print} and many other @value{GDBN} commands accept an expression and
6965 compute its value. Any kind of constant, variable or operator defined
6966 by the programming language you are using is valid in an expression in
6967 @value{GDBN}. This includes conditional expressions, function calls,
6968 casts, and string constants. It also includes preprocessor macros, if
6969 you compiled your program to include this information; see
6970 @ref{Compilation}.
6971
6972 @cindex arrays in expressions
6973 @value{GDBN} supports array constants in expressions input by
6974 the user. The syntax is @{@var{element}, @var{element}@dots{}@}. For example,
6975 you can use the command @code{print @{1, 2, 3@}} to create an array
6976 of three integers. If you pass an array to a function or assign it
6977 to a program variable, @value{GDBN} copies the array to memory that
6978 is @code{malloc}ed in the target program.
6979
6980 Because C is so widespread, most of the expressions shown in examples in
6981 this manual are in C. @xref{Languages, , Using @value{GDBN} with Different
6982 Languages}, for information on how to use expressions in other
6983 languages.
6984
6985 In this section, we discuss operators that you can use in @value{GDBN}
6986 expressions regardless of your programming language.
6987
6988 @cindex casts, in expressions
6989 Casts are supported in all languages, not just in C, because it is so
6990 useful to cast a number into a pointer in order to examine a structure
6991 at that address in memory.
6992 @c FIXME: casts supported---Mod2 true?
6993
6994 @value{GDBN} supports these operators, in addition to those common
6995 to programming languages:
6996
6997 @table @code
6998 @item @@
6999 @samp{@@} is a binary operator for treating parts of memory as arrays.
7000 @xref{Arrays, ,Artificial Arrays}, for more information.
7001
7002 @item ::
7003 @samp{::} allows you to specify a variable in terms of the file or
7004 function where it is defined. @xref{Variables, ,Program Variables}.
7005
7006 @cindex @{@var{type}@}
7007 @cindex type casting memory
7008 @cindex memory, viewing as typed object
7009 @cindex casts, to view memory
7010 @item @{@var{type}@} @var{addr}
7011 Refers to an object of type @var{type} stored at address @var{addr} in
7012 memory. @var{addr} may be any expression whose value is an integer or
7013 pointer (but parentheses are required around binary operators, just as in
7014 a cast). This construct is allowed regardless of what kind of data is
7015 normally supposed to reside at @var{addr}.
7016 @end table
7017
7018 @node Ambiguous Expressions
7019 @section Ambiguous Expressions
7020 @cindex ambiguous expressions
7021
7022 Expressions can sometimes contain some ambiguous elements. For instance,
7023 some programming languages (notably Ada, C@t{++} and Objective-C) permit
7024 a single function name to be defined several times, for application in
7025 different contexts. This is called @dfn{overloading}. Another example
7026 involving Ada is generics. A @dfn{generic package} is similar to C@t{++}
7027 templates and is typically instantiated several times, resulting in
7028 the same function name being defined in different contexts.
7029
7030 In some cases and depending on the language, it is possible to adjust
7031 the expression to remove the ambiguity. For instance in C@t{++}, you
7032 can specify the signature of the function you want to break on, as in
7033 @kbd{break @var{function}(@var{types})}. In Ada, using the fully
7034 qualified name of your function often makes the expression unambiguous
7035 as well.
7036
7037 When an ambiguity that needs to be resolved is detected, the debugger
7038 has the capability to display a menu of numbered choices for each
7039 possibility, and then waits for the selection with the prompt @samp{>}.
7040 The first option is always @samp{[0] cancel}, and typing @kbd{0 @key{RET}}
7041 aborts the current command. If the command in which the expression was
7042 used allows more than one choice to be selected, the next option in the
7043 menu is @samp{[1] all}, and typing @kbd{1 @key{RET}} selects all possible
7044 choices.
7045
7046 For example, the following session excerpt shows an attempt to set a
7047 breakpoint at the overloaded symbol @code{String::after}.
7048 We choose three particular definitions of that function name:
7049
7050 @c FIXME! This is likely to change to show arg type lists, at least
7051 @smallexample
7052 @group
7053 (@value{GDBP}) b String::after
7054 [0] cancel
7055 [1] all
7056 [2] file:String.cc; line number:867
7057 [3] file:String.cc; line number:860
7058 [4] file:String.cc; line number:875
7059 [5] file:String.cc; line number:853
7060 [6] file:String.cc; line number:846
7061 [7] file:String.cc; line number:735
7062 > 2 4 6
7063 Breakpoint 1 at 0xb26c: file String.cc, line 867.
7064 Breakpoint 2 at 0xb344: file String.cc, line 875.
7065 Breakpoint 3 at 0xafcc: file String.cc, line 846.
7066 Multiple breakpoints were set.
7067 Use the "delete" command to delete unwanted
7068 breakpoints.
7069 (@value{GDBP})
7070 @end group
7071 @end smallexample
7072
7073 @table @code
7074 @kindex set multiple-symbols
7075 @item set multiple-symbols @var{mode}
7076 @cindex multiple-symbols menu
7077
7078 This option allows you to adjust the debugger behavior when an expression
7079 is ambiguous.
7080
7081 By default, @var{mode} is set to @code{all}. If the command with which
7082 the expression is used allows more than one choice, then @value{GDBN}
7083 automatically selects all possible choices. For instance, inserting
7084 a breakpoint on a function using an ambiguous name results in a breakpoint
7085 inserted on each possible match. However, if a unique choice must be made,
7086 then @value{GDBN} uses the menu to help you disambiguate the expression.
7087 For instance, printing the address of an overloaded function will result
7088 in the use of the menu.
7089
7090 When @var{mode} is set to @code{ask}, the debugger always uses the menu
7091 when an ambiguity is detected.
7092
7093 Finally, when @var{mode} is set to @code{cancel}, the debugger reports
7094 an error due to the ambiguity and the command is aborted.
7095
7096 @kindex show multiple-symbols
7097 @item show multiple-symbols
7098 Show the current value of the @code{multiple-symbols} setting.
7099 @end table
7100
7101 @node Variables
7102 @section Program Variables
7103
7104 The most common kind of expression to use is the name of a variable
7105 in your program.
7106
7107 Variables in expressions are understood in the selected stack frame
7108 (@pxref{Selection, ,Selecting a Frame}); they must be either:
7109
7110 @itemize @bullet
7111 @item
7112 global (or file-static)
7113 @end itemize
7114
7115 @noindent or
7116
7117 @itemize @bullet
7118 @item
7119 visible according to the scope rules of the
7120 programming language from the point of execution in that frame
7121 @end itemize
7122
7123 @noindent This means that in the function
7124
7125 @smallexample
7126 foo (a)
7127 int a;
7128 @{
7129 bar (a);
7130 @{
7131 int b = test ();
7132 bar (b);
7133 @}
7134 @}
7135 @end smallexample
7136
7137 @noindent
7138 you can examine and use the variable @code{a} whenever your program is
7139 executing within the function @code{foo}, but you can only use or
7140 examine the variable @code{b} while your program is executing inside
7141 the block where @code{b} is declared.
7142
7143 @cindex variable name conflict
7144 There is an exception: you can refer to a variable or function whose
7145 scope is a single source file even if the current execution point is not
7146 in this file. But it is possible to have more than one such variable or
7147 function with the same name (in different source files). If that
7148 happens, referring to that name has unpredictable effects. If you wish,
7149 you can specify a static variable in a particular function or file,
7150 using the colon-colon (@code{::}) notation:
7151
7152 @cindex colon-colon, context for variables/functions
7153 @ifnotinfo
7154 @c info cannot cope with a :: index entry, but why deprive hard copy readers?
7155 @cindex @code{::}, context for variables/functions
7156 @end ifnotinfo
7157 @smallexample
7158 @var{file}::@var{variable}
7159 @var{function}::@var{variable}
7160 @end smallexample
7161
7162 @noindent
7163 Here @var{file} or @var{function} is the name of the context for the
7164 static @var{variable}. In the case of file names, you can use quotes to
7165 make sure @value{GDBN} parses the file name as a single word---for example,
7166 to print a global value of @code{x} defined in @file{f2.c}:
7167
7168 @smallexample
7169 (@value{GDBP}) p 'f2.c'::x
7170 @end smallexample
7171
7172 @cindex C@t{++} scope resolution
7173 This use of @samp{::} is very rarely in conflict with the very similar
7174 use of the same notation in C@t{++}. @value{GDBN} also supports use of the C@t{++}
7175 scope resolution operator in @value{GDBN} expressions.
7176 @c FIXME: Um, so what happens in one of those rare cases where it's in
7177 @c conflict?? --mew
7178
7179 @cindex wrong values
7180 @cindex variable values, wrong
7181 @cindex function entry/exit, wrong values of variables
7182 @cindex optimized code, wrong values of variables
7183 @quotation
7184 @emph{Warning:} Occasionally, a local variable may appear to have the
7185 wrong value at certain points in a function---just after entry to a new
7186 scope, and just before exit.
7187 @end quotation
7188 You may see this problem when you are stepping by machine instructions.
7189 This is because, on most machines, it takes more than one instruction to
7190 set up a stack frame (including local variable definitions); if you are
7191 stepping by machine instructions, variables may appear to have the wrong
7192 values until the stack frame is completely built. On exit, it usually
7193 also takes more than one machine instruction to destroy a stack frame;
7194 after you begin stepping through that group of instructions, local
7195 variable definitions may be gone.
7196
7197 This may also happen when the compiler does significant optimizations.
7198 To be sure of always seeing accurate values, turn off all optimization
7199 when compiling.
7200
7201 @cindex ``No symbol "foo" in current context''
7202 Another possible effect of compiler optimizations is to optimize
7203 unused variables out of existence, or assign variables to registers (as
7204 opposed to memory addresses). Depending on the support for such cases
7205 offered by the debug info format used by the compiler, @value{GDBN}
7206 might not be able to display values for such local variables. If that
7207 happens, @value{GDBN} will print a message like this:
7208
7209 @smallexample
7210 No symbol "foo" in current context.
7211 @end smallexample
7212
7213 To solve such problems, either recompile without optimizations, or use a
7214 different debug info format, if the compiler supports several such
7215 formats. For example, @value{NGCC}, the @sc{gnu} C/C@t{++} compiler,
7216 usually supports the @option{-gstabs+} option. @option{-gstabs+}
7217 produces debug info in a format that is superior to formats such as
7218 COFF. You may be able to use DWARF 2 (@option{-gdwarf-2}), which is also
7219 an effective form for debug info. @xref{Debugging Options,,Options
7220 for Debugging Your Program or GCC, gcc.info, Using the @sc{gnu}
7221 Compiler Collection (GCC)}.
7222 @xref{C, ,C and C@t{++}}, for more information about debug info formats
7223 that are best suited to C@t{++} programs.
7224
7225 If you ask to print an object whose contents are unknown to
7226 @value{GDBN}, e.g., because its data type is not completely specified
7227 by the debug information, @value{GDBN} will say @samp{<incomplete
7228 type>}. @xref{Symbols, incomplete type}, for more about this.
7229
7230 Strings are identified as arrays of @code{char} values without specified
7231 signedness. Arrays of either @code{signed char} or @code{unsigned char} get
7232 printed as arrays of 1 byte sized integers. @code{-fsigned-char} or
7233 @code{-funsigned-char} @value{NGCC} options have no effect as @value{GDBN}
7234 defines literal string type @code{"char"} as @code{char} without a sign.
7235 For program code
7236
7237 @smallexample
7238 char var0[] = "A";
7239 signed char var1[] = "A";
7240 @end smallexample
7241
7242 You get during debugging
7243 @smallexample
7244 (gdb) print var0
7245 $1 = "A"
7246 (gdb) print var1
7247 $2 = @{65 'A', 0 '\0'@}
7248 @end smallexample
7249
7250 @node Arrays
7251 @section Artificial Arrays
7252
7253 @cindex artificial array
7254 @cindex arrays
7255 @kindex @@@r{, referencing memory as an array}
7256 It is often useful to print out several successive objects of the
7257 same type in memory; a section of an array, or an array of
7258 dynamically determined size for which only a pointer exists in the
7259 program.
7260
7261 You can do this by referring to a contiguous span of memory as an
7262 @dfn{artificial array}, using the binary operator @samp{@@}. The left
7263 operand of @samp{@@} should be the first element of the desired array
7264 and be an individual object. The right operand should be the desired length
7265 of the array. The result is an array value whose elements are all of
7266 the type of the left argument. The first element is actually the left
7267 argument; the second element comes from bytes of memory immediately
7268 following those that hold the first element, and so on. Here is an
7269 example. If a program says
7270
7271 @smallexample
7272 int *array = (int *) malloc (len * sizeof (int));
7273 @end smallexample
7274
7275 @noindent
7276 you can print the contents of @code{array} with
7277
7278 @smallexample
7279 p *array@@len
7280 @end smallexample
7281
7282 The left operand of @samp{@@} must reside in memory. Array values made
7283 with @samp{@@} in this way behave just like other arrays in terms of
7284 subscripting, and are coerced to pointers when used in expressions.
7285 Artificial arrays most often appear in expressions via the value history
7286 (@pxref{Value History, ,Value History}), after printing one out.
7287
7288 Another way to create an artificial array is to use a cast.
7289 This re-interprets a value as if it were an array.
7290 The value need not be in memory:
7291 @smallexample
7292 (@value{GDBP}) p/x (short[2])0x12345678
7293 $1 = @{0x1234, 0x5678@}
7294 @end smallexample
7295
7296 As a convenience, if you leave the array length out (as in
7297 @samp{(@var{type}[])@var{value}}) @value{GDBN} calculates the size to fill
7298 the value (as @samp{sizeof(@var{value})/sizeof(@var{type})}:
7299 @smallexample
7300 (@value{GDBP}) p/x (short[])0x12345678
7301 $2 = @{0x1234, 0x5678@}
7302 @end smallexample
7303
7304 Sometimes the artificial array mechanism is not quite enough; in
7305 moderately complex data structures, the elements of interest may not
7306 actually be adjacent---for example, if you are interested in the values
7307 of pointers in an array. One useful work-around in this situation is
7308 to use a convenience variable (@pxref{Convenience Vars, ,Convenience
7309 Variables}) as a counter in an expression that prints the first
7310 interesting value, and then repeat that expression via @key{RET}. For
7311 instance, suppose you have an array @code{dtab} of pointers to
7312 structures, and you are interested in the values of a field @code{fv}
7313 in each structure. Here is an example of what you might type:
7314
7315 @smallexample
7316 set $i = 0
7317 p dtab[$i++]->fv
7318 @key{RET}
7319 @key{RET}
7320 @dots{}
7321 @end smallexample
7322
7323 @node Output Formats
7324 @section Output Formats
7325
7326 @cindex formatted output
7327 @cindex output formats
7328 By default, @value{GDBN} prints a value according to its data type. Sometimes
7329 this is not what you want. For example, you might want to print a number
7330 in hex, or a pointer in decimal. Or you might want to view data in memory
7331 at a certain address as a character string or as an instruction. To do
7332 these things, specify an @dfn{output format} when you print a value.
7333
7334 The simplest use of output formats is to say how to print a value
7335 already computed. This is done by starting the arguments of the
7336 @code{print} command with a slash and a format letter. The format
7337 letters supported are:
7338
7339 @table @code
7340 @item x
7341 Regard the bits of the value as an integer, and print the integer in
7342 hexadecimal.
7343
7344 @item d
7345 Print as integer in signed decimal.
7346
7347 @item u
7348 Print as integer in unsigned decimal.
7349
7350 @item o
7351 Print as integer in octal.
7352
7353 @item t
7354 Print as integer in binary. The letter @samp{t} stands for ``two''.
7355 @footnote{@samp{b} cannot be used because these format letters are also
7356 used with the @code{x} command, where @samp{b} stands for ``byte'';
7357 see @ref{Memory,,Examining Memory}.}
7358
7359 @item a
7360 @cindex unknown address, locating
7361 @cindex locate address
7362 Print as an address, both absolute in hexadecimal and as an offset from
7363 the nearest preceding symbol. You can use this format used to discover
7364 where (in what function) an unknown address is located:
7365
7366 @smallexample
7367 (@value{GDBP}) p/a 0x54320
7368 $3 = 0x54320 <_initialize_vx+396>
7369 @end smallexample
7370
7371 @noindent
7372 The command @code{info symbol 0x54320} yields similar results.
7373 @xref{Symbols, info symbol}.
7374
7375 @item c
7376 Regard as an integer and print it as a character constant. This
7377 prints both the numerical value and its character representation. The
7378 character representation is replaced with the octal escape @samp{\nnn}
7379 for characters outside the 7-bit @sc{ascii} range.
7380
7381 Without this format, @value{GDBN} displays @code{char},
7382 @w{@code{unsigned char}}, and @w{@code{signed char}} data as character
7383 constants. Single-byte members of vectors are displayed as integer
7384 data.
7385
7386 @item f
7387 Regard the bits of the value as a floating point number and print
7388 using typical floating point syntax.
7389
7390 @item s
7391 @cindex printing strings
7392 @cindex printing byte arrays
7393 Regard as a string, if possible. With this format, pointers to single-byte
7394 data are displayed as null-terminated strings and arrays of single-byte data
7395 are displayed as fixed-length strings. Other values are displayed in their
7396 natural types.
7397
7398 Without this format, @value{GDBN} displays pointers to and arrays of
7399 @code{char}, @w{@code{unsigned char}}, and @w{@code{signed char}} as
7400 strings. Single-byte members of a vector are displayed as an integer
7401 array.
7402
7403 @item r
7404 @cindex raw printing
7405 Print using the @samp{raw} formatting. By default, @value{GDBN} will
7406 use a Python-based pretty-printer, if one is available (@pxref{Pretty
7407 Printing}). This typically results in a higher-level display of the
7408 value's contents. The @samp{r} format bypasses any Python
7409 pretty-printer which might exist.
7410 @end table
7411
7412 For example, to print the program counter in hex (@pxref{Registers}), type
7413
7414 @smallexample
7415 p/x $pc
7416 @end smallexample
7417
7418 @noindent
7419 Note that no space is required before the slash; this is because command
7420 names in @value{GDBN} cannot contain a slash.
7421
7422 To reprint the last value in the value history with a different format,
7423 you can use the @code{print} command with just a format and no
7424 expression. For example, @samp{p/x} reprints the last value in hex.
7425
7426 @node Memory
7427 @section Examining Memory
7428
7429 You can use the command @code{x} (for ``examine'') to examine memory in
7430 any of several formats, independently of your program's data types.
7431
7432 @cindex examining memory
7433 @table @code
7434 @kindex x @r{(examine memory)}
7435 @item x/@var{nfu} @var{addr}
7436 @itemx x @var{addr}
7437 @itemx x
7438 Use the @code{x} command to examine memory.
7439 @end table
7440
7441 @var{n}, @var{f}, and @var{u} are all optional parameters that specify how
7442 much memory to display and how to format it; @var{addr} is an
7443 expression giving the address where you want to start displaying memory.
7444 If you use defaults for @var{nfu}, you need not type the slash @samp{/}.
7445 Several commands set convenient defaults for @var{addr}.
7446
7447 @table @r
7448 @item @var{n}, the repeat count
7449 The repeat count is a decimal integer; the default is 1. It specifies
7450 how much memory (counting by units @var{u}) to display.
7451 @c This really is **decimal**; unaffected by 'set radix' as of GDB
7452 @c 4.1.2.
7453
7454 @item @var{f}, the display format
7455 The display format is one of the formats used by @code{print}
7456 (@samp{x}, @samp{d}, @samp{u}, @samp{o}, @samp{t}, @samp{a}, @samp{c},
7457 @samp{f}, @samp{s}), and in addition @samp{i} (for machine instructions).
7458 The default is @samp{x} (hexadecimal) initially. The default changes
7459 each time you use either @code{x} or @code{print}.
7460
7461 @item @var{u}, the unit size
7462 The unit size is any of
7463
7464 @table @code
7465 @item b
7466 Bytes.
7467 @item h
7468 Halfwords (two bytes).
7469 @item w
7470 Words (four bytes). This is the initial default.
7471 @item g
7472 Giant words (eight bytes).
7473 @end table
7474
7475 Each time you specify a unit size with @code{x}, that size becomes the
7476 default unit the next time you use @code{x}. For the @samp{i} format,
7477 the unit size is ignored and is normally not written. For the @samp{s} format,
7478 the unit size defaults to @samp{b}, unless it is explicitly given.
7479 Use @kbd{x /hs} to display 16-bit char strings and @kbd{x /ws} to display
7480 32-bit strings. The next use of @kbd{x /s} will again display 8-bit strings.
7481 Note that the results depend on the programming language of the
7482 current compilation unit. If the language is C, the @samp{s}
7483 modifier will use the UTF-16 encoding while @samp{w} will use
7484 UTF-32. The encoding is set by the programming language and cannot
7485 be altered.
7486
7487 @item @var{addr}, starting display address
7488 @var{addr} is the address where you want @value{GDBN} to begin displaying
7489 memory. The expression need not have a pointer value (though it may);
7490 it is always interpreted as an integer address of a byte of memory.
7491 @xref{Expressions, ,Expressions}, for more information on expressions. The default for
7492 @var{addr} is usually just after the last address examined---but several
7493 other commands also set the default address: @code{info breakpoints} (to
7494 the address of the last breakpoint listed), @code{info line} (to the
7495 starting address of a line), and @code{print} (if you use it to display
7496 a value from memory).
7497 @end table
7498
7499 For example, @samp{x/3uh 0x54320} is a request to display three halfwords
7500 (@code{h}) of memory, formatted as unsigned decimal integers (@samp{u}),
7501 starting at address @code{0x54320}. @samp{x/4xw $sp} prints the four
7502 words (@samp{w}) of memory above the stack pointer (here, @samp{$sp};
7503 @pxref{Registers, ,Registers}) in hexadecimal (@samp{x}).
7504
7505 Since the letters indicating unit sizes are all distinct from the
7506 letters specifying output formats, you do not have to remember whether
7507 unit size or format comes first; either order works. The output
7508 specifications @samp{4xw} and @samp{4wx} mean exactly the same thing.
7509 (However, the count @var{n} must come first; @samp{wx4} does not work.)
7510
7511 Even though the unit size @var{u} is ignored for the formats @samp{s}
7512 and @samp{i}, you might still want to use a count @var{n}; for example,
7513 @samp{3i} specifies that you want to see three machine instructions,
7514 including any operands. For convenience, especially when used with
7515 the @code{display} command, the @samp{i} format also prints branch delay
7516 slot instructions, if any, beyond the count specified, which immediately
7517 follow the last instruction that is within the count. The command
7518 @code{disassemble} gives an alternative way of inspecting machine
7519 instructions; see @ref{Machine Code,,Source and Machine Code}.
7520
7521 All the defaults for the arguments to @code{x} are designed to make it
7522 easy to continue scanning memory with minimal specifications each time
7523 you use @code{x}. For example, after you have inspected three machine
7524 instructions with @samp{x/3i @var{addr}}, you can inspect the next seven
7525 with just @samp{x/7}. If you use @key{RET} to repeat the @code{x} command,
7526 the repeat count @var{n} is used again; the other arguments default as
7527 for successive uses of @code{x}.
7528
7529 When examining machine instructions, the instruction at current program
7530 counter is shown with a @code{=>} marker. For example:
7531
7532 @smallexample
7533 (@value{GDBP}) x/5i $pc-6
7534 0x804837f <main+11>: mov %esp,%ebp
7535 0x8048381 <main+13>: push %ecx
7536 0x8048382 <main+14>: sub $0x4,%esp
7537 => 0x8048385 <main+17>: movl $0x8048460,(%esp)
7538 0x804838c <main+24>: call 0x80482d4 <puts@@plt>
7539 @end smallexample
7540
7541 @cindex @code{$_}, @code{$__}, and value history
7542 The addresses and contents printed by the @code{x} command are not saved
7543 in the value history because there is often too much of them and they
7544 would get in the way. Instead, @value{GDBN} makes these values available for
7545 subsequent use in expressions as values of the convenience variables
7546 @code{$_} and @code{$__}. After an @code{x} command, the last address
7547 examined is available for use in expressions in the convenience variable
7548 @code{$_}. The contents of that address, as examined, are available in
7549 the convenience variable @code{$__}.
7550
7551 If the @code{x} command has a repeat count, the address and contents saved
7552 are from the last memory unit printed; this is not the same as the last
7553 address printed if several units were printed on the last line of output.
7554
7555 @cindex remote memory comparison
7556 @cindex verify remote memory image
7557 When you are debugging a program running on a remote target machine
7558 (@pxref{Remote Debugging}), you may wish to verify the program's image in the
7559 remote machine's memory against the executable file you downloaded to
7560 the target. The @code{compare-sections} command is provided for such
7561 situations.
7562
7563 @table @code
7564 @kindex compare-sections
7565 @item compare-sections @r{[}@var{section-name}@r{]}
7566 Compare the data of a loadable section @var{section-name} in the
7567 executable file of the program being debugged with the same section in
7568 the remote machine's memory, and report any mismatches. With no
7569 arguments, compares all loadable sections. This command's
7570 availability depends on the target's support for the @code{"qCRC"}
7571 remote request.
7572 @end table
7573
7574 @node Auto Display
7575 @section Automatic Display
7576 @cindex automatic display
7577 @cindex display of expressions
7578
7579 If you find that you want to print the value of an expression frequently
7580 (to see how it changes), you might want to add it to the @dfn{automatic
7581 display list} so that @value{GDBN} prints its value each time your program stops.
7582 Each expression added to the list is given a number to identify it;
7583 to remove an expression from the list, you specify that number.
7584 The automatic display looks like this:
7585
7586 @smallexample
7587 2: foo = 38
7588 3: bar[5] = (struct hack *) 0x3804
7589 @end smallexample
7590
7591 @noindent
7592 This display shows item numbers, expressions and their current values. As with
7593 displays you request manually using @code{x} or @code{print}, you can
7594 specify the output format you prefer; in fact, @code{display} decides
7595 whether to use @code{print} or @code{x} depending your format
7596 specification---it uses @code{x} if you specify either the @samp{i}
7597 or @samp{s} format, or a unit size; otherwise it uses @code{print}.
7598
7599 @table @code
7600 @kindex display
7601 @item display @var{expr}
7602 Add the expression @var{expr} to the list of expressions to display
7603 each time your program stops. @xref{Expressions, ,Expressions}.
7604
7605 @code{display} does not repeat if you press @key{RET} again after using it.
7606
7607 @item display/@var{fmt} @var{expr}
7608 For @var{fmt} specifying only a display format and not a size or
7609 count, add the expression @var{expr} to the auto-display list but
7610 arrange to display it each time in the specified format @var{fmt}.
7611 @xref{Output Formats,,Output Formats}.
7612
7613 @item display/@var{fmt} @var{addr}
7614 For @var{fmt} @samp{i} or @samp{s}, or including a unit-size or a
7615 number of units, add the expression @var{addr} as a memory address to
7616 be examined each time your program stops. Examining means in effect
7617 doing @samp{x/@var{fmt} @var{addr}}. @xref{Memory, ,Examining Memory}.
7618 @end table
7619
7620 For example, @samp{display/i $pc} can be helpful, to see the machine
7621 instruction about to be executed each time execution stops (@samp{$pc}
7622 is a common name for the program counter; @pxref{Registers, ,Registers}).
7623
7624 @table @code
7625 @kindex delete display
7626 @kindex undisplay
7627 @item undisplay @var{dnums}@dots{}
7628 @itemx delete display @var{dnums}@dots{}
7629 Remove item numbers @var{dnums} from the list of expressions to display.
7630
7631 @code{undisplay} does not repeat if you press @key{RET} after using it.
7632 (Otherwise you would just get the error @samp{No display number @dots{}}.)
7633
7634 @kindex disable display
7635 @item disable display @var{dnums}@dots{}
7636 Disable the display of item numbers @var{dnums}. A disabled display
7637 item is not printed automatically, but is not forgotten. It may be
7638 enabled again later.
7639
7640 @kindex enable display
7641 @item enable display @var{dnums}@dots{}
7642 Enable display of item numbers @var{dnums}. It becomes effective once
7643 again in auto display of its expression, until you specify otherwise.
7644
7645 @item display
7646 Display the current values of the expressions on the list, just as is
7647 done when your program stops.
7648
7649 @kindex info display
7650 @item info display
7651 Print the list of expressions previously set up to display
7652 automatically, each one with its item number, but without showing the
7653 values. This includes disabled expressions, which are marked as such.
7654 It also includes expressions which would not be displayed right now
7655 because they refer to automatic variables not currently available.
7656 @end table
7657
7658 @cindex display disabled out of scope
7659 If a display expression refers to local variables, then it does not make
7660 sense outside the lexical context for which it was set up. Such an
7661 expression is disabled when execution enters a context where one of its
7662 variables is not defined. For example, if you give the command
7663 @code{display last_char} while inside a function with an argument
7664 @code{last_char}, @value{GDBN} displays this argument while your program
7665 continues to stop inside that function. When it stops elsewhere---where
7666 there is no variable @code{last_char}---the display is disabled
7667 automatically. The next time your program stops where @code{last_char}
7668 is meaningful, you can enable the display expression once again.
7669
7670 @node Print Settings
7671 @section Print Settings
7672
7673 @cindex format options
7674 @cindex print settings
7675 @value{GDBN} provides the following ways to control how arrays, structures,
7676 and symbols are printed.
7677
7678 @noindent
7679 These settings are useful for debugging programs in any language:
7680
7681 @table @code
7682 @kindex set print
7683 @item set print address
7684 @itemx set print address on
7685 @cindex print/don't print memory addresses
7686 @value{GDBN} prints memory addresses showing the location of stack
7687 traces, structure values, pointer values, breakpoints, and so forth,
7688 even when it also displays the contents of those addresses. The default
7689 is @code{on}. For example, this is what a stack frame display looks like with
7690 @code{set print address on}:
7691
7692 @smallexample
7693 @group
7694 (@value{GDBP}) f
7695 #0 set_quotes (lq=0x34c78 "<<", rq=0x34c88 ">>")
7696 at input.c:530
7697 530 if (lquote != def_lquote)
7698 @end group
7699 @end smallexample
7700
7701 @item set print address off
7702 Do not print addresses when displaying their contents. For example,
7703 this is the same stack frame displayed with @code{set print address off}:
7704
7705 @smallexample
7706 @group
7707 (@value{GDBP}) set print addr off
7708 (@value{GDBP}) f
7709 #0 set_quotes (lq="<<", rq=">>") at input.c:530
7710 530 if (lquote != def_lquote)
7711 @end group
7712 @end smallexample
7713
7714 You can use @samp{set print address off} to eliminate all machine
7715 dependent displays from the @value{GDBN} interface. For example, with
7716 @code{print address off}, you should get the same text for backtraces on
7717 all machines---whether or not they involve pointer arguments.
7718
7719 @kindex show print
7720 @item show print address
7721 Show whether or not addresses are to be printed.
7722 @end table
7723
7724 When @value{GDBN} prints a symbolic address, it normally prints the
7725 closest earlier symbol plus an offset. If that symbol does not uniquely
7726 identify the address (for example, it is a name whose scope is a single
7727 source file), you may need to clarify. One way to do this is with
7728 @code{info line}, for example @samp{info line *0x4537}. Alternately,
7729 you can set @value{GDBN} to print the source file and line number when
7730 it prints a symbolic address:
7731
7732 @table @code
7733 @item set print symbol-filename on
7734 @cindex source file and line of a symbol
7735 @cindex symbol, source file and line
7736 Tell @value{GDBN} to print the source file name and line number of a
7737 symbol in the symbolic form of an address.
7738
7739 @item set print symbol-filename off
7740 Do not print source file name and line number of a symbol. This is the
7741 default.
7742
7743 @item show print symbol-filename
7744 Show whether or not @value{GDBN} will print the source file name and
7745 line number of a symbol in the symbolic form of an address.
7746 @end table
7747
7748 Another situation where it is helpful to show symbol filenames and line
7749 numbers is when disassembling code; @value{GDBN} shows you the line
7750 number and source file that corresponds to each instruction.
7751
7752 Also, you may wish to see the symbolic form only if the address being
7753 printed is reasonably close to the closest earlier symbol:
7754
7755 @table @code
7756 @item set print max-symbolic-offset @var{max-offset}
7757 @cindex maximum value for offset of closest symbol
7758 Tell @value{GDBN} to only display the symbolic form of an address if the
7759 offset between the closest earlier symbol and the address is less than
7760 @var{max-offset}. The default is 0, which tells @value{GDBN}
7761 to always print the symbolic form of an address if any symbol precedes it.
7762
7763 @item show print max-symbolic-offset
7764 Ask how large the maximum offset is that @value{GDBN} prints in a
7765 symbolic address.
7766 @end table
7767
7768 @cindex wild pointer, interpreting
7769 @cindex pointer, finding referent
7770 If you have a pointer and you are not sure where it points, try
7771 @samp{set print symbol-filename on}. Then you can determine the name
7772 and source file location of the variable where it points, using
7773 @samp{p/a @var{pointer}}. This interprets the address in symbolic form.
7774 For example, here @value{GDBN} shows that a variable @code{ptt} points
7775 at another variable @code{t}, defined in @file{hi2.c}:
7776
7777 @smallexample
7778 (@value{GDBP}) set print symbol-filename on
7779 (@value{GDBP}) p/a ptt
7780 $4 = 0xe008 <t in hi2.c>
7781 @end smallexample
7782
7783 @quotation
7784 @emph{Warning:} For pointers that point to a local variable, @samp{p/a}
7785 does not show the symbol name and filename of the referent, even with
7786 the appropriate @code{set print} options turned on.
7787 @end quotation
7788
7789 Other settings control how different kinds of objects are printed:
7790
7791 @table @code
7792 @item set print array
7793 @itemx set print array on
7794 @cindex pretty print arrays
7795 Pretty print arrays. This format is more convenient to read,
7796 but uses more space. The default is off.
7797
7798 @item set print array off
7799 Return to compressed format for arrays.
7800
7801 @item show print array
7802 Show whether compressed or pretty format is selected for displaying
7803 arrays.
7804
7805 @cindex print array indexes
7806 @item set print array-indexes
7807 @itemx set print array-indexes on
7808 Print the index of each element when displaying arrays. May be more
7809 convenient to locate a given element in the array or quickly find the
7810 index of a given element in that printed array. The default is off.
7811
7812 @item set print array-indexes off
7813 Stop printing element indexes when displaying arrays.
7814
7815 @item show print array-indexes
7816 Show whether the index of each element is printed when displaying
7817 arrays.
7818
7819 @item set print elements @var{number-of-elements}
7820 @cindex number of array elements to print
7821 @cindex limit on number of printed array elements
7822 Set a limit on how many elements of an array @value{GDBN} will print.
7823 If @value{GDBN} is printing a large array, it stops printing after it has
7824 printed the number of elements set by the @code{set print elements} command.
7825 This limit also applies to the display of strings.
7826 When @value{GDBN} starts, this limit is set to 200.
7827 Setting @var{number-of-elements} to zero means that the printing is unlimited.
7828
7829 @item show print elements
7830 Display the number of elements of a large array that @value{GDBN} will print.
7831 If the number is 0, then the printing is unlimited.
7832
7833 @item set print frame-arguments @var{value}
7834 @kindex set print frame-arguments
7835 @cindex printing frame argument values
7836 @cindex print all frame argument values
7837 @cindex print frame argument values for scalars only
7838 @cindex do not print frame argument values
7839 This command allows to control how the values of arguments are printed
7840 when the debugger prints a frame (@pxref{Frames}). The possible
7841 values are:
7842
7843 @table @code
7844 @item all
7845 The values of all arguments are printed.
7846
7847 @item scalars
7848 Print the value of an argument only if it is a scalar. The value of more
7849 complex arguments such as arrays, structures, unions, etc, is replaced
7850 by @code{@dots{}}. This is the default. Here is an example where
7851 only scalar arguments are shown:
7852
7853 @smallexample
7854 #1 0x08048361 in call_me (i=3, s=@dots{}, ss=0xbf8d508c, u=@dots{}, e=green)
7855 at frame-args.c:23
7856 @end smallexample
7857
7858 @item none
7859 None of the argument values are printed. Instead, the value of each argument
7860 is replaced by @code{@dots{}}. In this case, the example above now becomes:
7861
7862 @smallexample
7863 #1 0x08048361 in call_me (i=@dots{}, s=@dots{}, ss=@dots{}, u=@dots{}, e=@dots{})
7864 at frame-args.c:23
7865 @end smallexample
7866 @end table
7867
7868 By default, only scalar arguments are printed. This command can be used
7869 to configure the debugger to print the value of all arguments, regardless
7870 of their type. However, it is often advantageous to not print the value
7871 of more complex parameters. For instance, it reduces the amount of
7872 information printed in each frame, making the backtrace more readable.
7873 Also, it improves performance when displaying Ada frames, because
7874 the computation of large arguments can sometimes be CPU-intensive,
7875 especially in large applications. Setting @code{print frame-arguments}
7876 to @code{scalars} (the default) or @code{none} avoids this computation,
7877 thus speeding up the display of each Ada frame.
7878
7879 @item show print frame-arguments
7880 Show how the value of arguments should be displayed when printing a frame.
7881
7882 @item set print repeats
7883 @cindex repeated array elements
7884 Set the threshold for suppressing display of repeated array
7885 elements. When the number of consecutive identical elements of an
7886 array exceeds the threshold, @value{GDBN} prints the string
7887 @code{"<repeats @var{n} times>"}, where @var{n} is the number of
7888 identical repetitions, instead of displaying the identical elements
7889 themselves. Setting the threshold to zero will cause all elements to
7890 be individually printed. The default threshold is 10.
7891
7892 @item show print repeats
7893 Display the current threshold for printing repeated identical
7894 elements.
7895
7896 @item set print null-stop
7897 @cindex @sc{null} elements in arrays
7898 Cause @value{GDBN} to stop printing the characters of an array when the first
7899 @sc{null} is encountered. This is useful when large arrays actually
7900 contain only short strings.
7901 The default is off.
7902
7903 @item show print null-stop
7904 Show whether @value{GDBN} stops printing an array on the first
7905 @sc{null} character.
7906
7907 @item set print pretty on
7908 @cindex print structures in indented form
7909 @cindex indentation in structure display
7910 Cause @value{GDBN} to print structures in an indented format with one member
7911 per line, like this:
7912
7913 @smallexample
7914 @group
7915 $1 = @{
7916 next = 0x0,
7917 flags = @{
7918 sweet = 1,
7919 sour = 1
7920 @},
7921 meat = 0x54 "Pork"
7922 @}
7923 @end group
7924 @end smallexample
7925
7926 @item set print pretty off
7927 Cause @value{GDBN} to print structures in a compact format, like this:
7928
7929 @smallexample
7930 @group
7931 $1 = @{next = 0x0, flags = @{sweet = 1, sour = 1@}, \
7932 meat = 0x54 "Pork"@}
7933 @end group
7934 @end smallexample
7935
7936 @noindent
7937 This is the default format.
7938
7939 @item show print pretty
7940 Show which format @value{GDBN} is using to print structures.
7941
7942 @item set print sevenbit-strings on
7943 @cindex eight-bit characters in strings
7944 @cindex octal escapes in strings
7945 Print using only seven-bit characters; if this option is set,
7946 @value{GDBN} displays any eight-bit characters (in strings or
7947 character values) using the notation @code{\}@var{nnn}. This setting is
7948 best if you are working in English (@sc{ascii}) and you use the
7949 high-order bit of characters as a marker or ``meta'' bit.
7950
7951 @item set print sevenbit-strings off
7952 Print full eight-bit characters. This allows the use of more
7953 international character sets, and is the default.
7954
7955 @item show print sevenbit-strings
7956 Show whether or not @value{GDBN} is printing only seven-bit characters.
7957
7958 @item set print union on
7959 @cindex unions in structures, printing
7960 Tell @value{GDBN} to print unions which are contained in structures
7961 and other unions. This is the default setting.
7962
7963 @item set print union off
7964 Tell @value{GDBN} not to print unions which are contained in
7965 structures and other unions. @value{GDBN} will print @code{"@{...@}"}
7966 instead.
7967
7968 @item show print union
7969 Ask @value{GDBN} whether or not it will print unions which are contained in
7970 structures and other unions.
7971
7972 For example, given the declarations
7973
7974 @smallexample
7975 typedef enum @{Tree, Bug@} Species;
7976 typedef enum @{Big_tree, Acorn, Seedling@} Tree_forms;
7977 typedef enum @{Caterpillar, Cocoon, Butterfly@}
7978 Bug_forms;
7979
7980 struct thing @{
7981 Species it;
7982 union @{
7983 Tree_forms tree;
7984 Bug_forms bug;
7985 @} form;
7986 @};
7987
7988 struct thing foo = @{Tree, @{Acorn@}@};
7989 @end smallexample
7990
7991 @noindent
7992 with @code{set print union on} in effect @samp{p foo} would print
7993
7994 @smallexample
7995 $1 = @{it = Tree, form = @{tree = Acorn, bug = Cocoon@}@}
7996 @end smallexample
7997
7998 @noindent
7999 and with @code{set print union off} in effect it would print
8000
8001 @smallexample
8002 $1 = @{it = Tree, form = @{...@}@}
8003 @end smallexample
8004
8005 @noindent
8006 @code{set print union} affects programs written in C-like languages
8007 and in Pascal.
8008 @end table
8009
8010 @need 1000
8011 @noindent
8012 These settings are of interest when debugging C@t{++} programs:
8013
8014 @table @code
8015 @cindex demangling C@t{++} names
8016 @item set print demangle
8017 @itemx set print demangle on
8018 Print C@t{++} names in their source form rather than in the encoded
8019 (``mangled'') form passed to the assembler and linker for type-safe
8020 linkage. The default is on.
8021
8022 @item show print demangle
8023 Show whether C@t{++} names are printed in mangled or demangled form.
8024
8025 @item set print asm-demangle
8026 @itemx set print asm-demangle on
8027 Print C@t{++} names in their source form rather than their mangled form, even
8028 in assembler code printouts such as instruction disassemblies.
8029 The default is off.
8030
8031 @item show print asm-demangle
8032 Show whether C@t{++} names in assembly listings are printed in mangled
8033 or demangled form.
8034
8035 @cindex C@t{++} symbol decoding style
8036 @cindex symbol decoding style, C@t{++}
8037 @kindex set demangle-style
8038 @item set demangle-style @var{style}
8039 Choose among several encoding schemes used by different compilers to
8040 represent C@t{++} names. The choices for @var{style} are currently:
8041
8042 @table @code
8043 @item auto
8044 Allow @value{GDBN} to choose a decoding style by inspecting your program.
8045
8046 @item gnu
8047 Decode based on the @sc{gnu} C@t{++} compiler (@code{g++}) encoding algorithm.
8048 This is the default.
8049
8050 @item hp
8051 Decode based on the HP ANSI C@t{++} (@code{aCC}) encoding algorithm.
8052
8053 @item lucid
8054 Decode based on the Lucid C@t{++} compiler (@code{lcc}) encoding algorithm.
8055
8056 @item arm
8057 Decode using the algorithm in the @cite{C@t{++} Annotated Reference Manual}.
8058 @strong{Warning:} this setting alone is not sufficient to allow
8059 debugging @code{cfront}-generated executables. @value{GDBN} would
8060 require further enhancement to permit that.
8061
8062 @end table
8063 If you omit @var{style}, you will see a list of possible formats.
8064
8065 @item show demangle-style
8066 Display the encoding style currently in use for decoding C@t{++} symbols.
8067
8068 @item set print object
8069 @itemx set print object on
8070 @cindex derived type of an object, printing
8071 @cindex display derived types
8072 When displaying a pointer to an object, identify the @emph{actual}
8073 (derived) type of the object rather than the @emph{declared} type, using
8074 the virtual function table.
8075
8076 @item set print object off
8077 Display only the declared type of objects, without reference to the
8078 virtual function table. This is the default setting.
8079
8080 @item show print object
8081 Show whether actual, or declared, object types are displayed.
8082
8083 @item set print static-members
8084 @itemx set print static-members on
8085 @cindex static members of C@t{++} objects
8086 Print static members when displaying a C@t{++} object. The default is on.
8087
8088 @item set print static-members off
8089 Do not print static members when displaying a C@t{++} object.
8090
8091 @item show print static-members
8092 Show whether C@t{++} static members are printed or not.
8093
8094 @item set print pascal_static-members
8095 @itemx set print pascal_static-members on
8096 @cindex static members of Pascal objects
8097 @cindex Pascal objects, static members display
8098 Print static members when displaying a Pascal object. The default is on.
8099
8100 @item set print pascal_static-members off
8101 Do not print static members when displaying a Pascal object.
8102
8103 @item show print pascal_static-members
8104 Show whether Pascal static members are printed or not.
8105
8106 @c These don't work with HP ANSI C++ yet.
8107 @item set print vtbl
8108 @itemx set print vtbl on
8109 @cindex pretty print C@t{++} virtual function tables
8110 @cindex virtual functions (C@t{++}) display
8111 @cindex VTBL display
8112 Pretty print C@t{++} virtual function tables. The default is off.
8113 (The @code{vtbl} commands do not work on programs compiled with the HP
8114 ANSI C@t{++} compiler (@code{aCC}).)
8115
8116 @item set print vtbl off
8117 Do not pretty print C@t{++} virtual function tables.
8118
8119 @item show print vtbl
8120 Show whether C@t{++} virtual function tables are pretty printed, or not.
8121 @end table
8122
8123 @node Pretty Printing
8124 @section Pretty Printing
8125
8126 @value{GDBN} provides a mechanism to allow pretty-printing of values using
8127 Python code. It greatly simplifies the display of complex objects. This
8128 mechanism works for both MI and the CLI.
8129
8130 For example, here is how a C@t{++} @code{std::string} looks without a
8131 pretty-printer:
8132
8133 @smallexample
8134 (@value{GDBP}) print s
8135 $1 = @{
8136 static npos = 4294967295,
8137 _M_dataplus = @{
8138 <std::allocator<char>> = @{
8139 <__gnu_cxx::new_allocator<char>> = @{
8140 <No data fields>@}, <No data fields>
8141 @},
8142 members of std::basic_string<char, std::char_traits<char>,
8143 std::allocator<char> >::_Alloc_hider:
8144 _M_p = 0x804a014 "abcd"
8145 @}
8146 @}
8147 @end smallexample
8148
8149 With a pretty-printer for @code{std::string} only the contents are printed:
8150
8151 @smallexample
8152 (@value{GDBP}) print s
8153 $2 = "abcd"
8154 @end smallexample
8155
8156 For implementing pretty printers for new types you should read the Python API
8157 details (@pxref{Pretty Printing API}).
8158
8159 @node Value History
8160 @section Value History
8161
8162 @cindex value history
8163 @cindex history of values printed by @value{GDBN}
8164 Values printed by the @code{print} command are saved in the @value{GDBN}
8165 @dfn{value history}. This allows you to refer to them in other expressions.
8166 Values are kept until the symbol table is re-read or discarded
8167 (for example with the @code{file} or @code{symbol-file} commands).
8168 When the symbol table changes, the value history is discarded,
8169 since the values may contain pointers back to the types defined in the
8170 symbol table.
8171
8172 @cindex @code{$}
8173 @cindex @code{$$}
8174 @cindex history number
8175 The values printed are given @dfn{history numbers} by which you can
8176 refer to them. These are successive integers starting with one.
8177 @code{print} shows you the history number assigned to a value by
8178 printing @samp{$@var{num} = } before the value; here @var{num} is the
8179 history number.
8180
8181 To refer to any previous value, use @samp{$} followed by the value's
8182 history number. The way @code{print} labels its output is designed to
8183 remind you of this. Just @code{$} refers to the most recent value in
8184 the history, and @code{$$} refers to the value before that.
8185 @code{$$@var{n}} refers to the @var{n}th value from the end; @code{$$2}
8186 is the value just prior to @code{$$}, @code{$$1} is equivalent to
8187 @code{$$}, and @code{$$0} is equivalent to @code{$}.
8188
8189 For example, suppose you have just printed a pointer to a structure and
8190 want to see the contents of the structure. It suffices to type
8191
8192 @smallexample
8193 p *$
8194 @end smallexample
8195
8196 If you have a chain of structures where the component @code{next} points
8197 to the next one, you can print the contents of the next one with this:
8198
8199 @smallexample
8200 p *$.next
8201 @end smallexample
8202
8203 @noindent
8204 You can print successive links in the chain by repeating this
8205 command---which you can do by just typing @key{RET}.
8206
8207 Note that the history records values, not expressions. If the value of
8208 @code{x} is 4 and you type these commands:
8209
8210 @smallexample
8211 print x
8212 set x=5
8213 @end smallexample
8214
8215 @noindent
8216 then the value recorded in the value history by the @code{print} command
8217 remains 4 even though the value of @code{x} has changed.
8218
8219 @table @code
8220 @kindex show values
8221 @item show values
8222 Print the last ten values in the value history, with their item numbers.
8223 This is like @samp{p@ $$9} repeated ten times, except that @code{show
8224 values} does not change the history.
8225
8226 @item show values @var{n}
8227 Print ten history values centered on history item number @var{n}.
8228
8229 @item show values +
8230 Print ten history values just after the values last printed. If no more
8231 values are available, @code{show values +} produces no display.
8232 @end table
8233
8234 Pressing @key{RET} to repeat @code{show values @var{n}} has exactly the
8235 same effect as @samp{show values +}.
8236
8237 @node Convenience Vars
8238 @section Convenience Variables
8239
8240 @cindex convenience variables
8241 @cindex user-defined variables
8242 @value{GDBN} provides @dfn{convenience variables} that you can use within
8243 @value{GDBN} to hold on to a value and refer to it later. These variables
8244 exist entirely within @value{GDBN}; they are not part of your program, and
8245 setting a convenience variable has no direct effect on further execution
8246 of your program. That is why you can use them freely.
8247
8248 Convenience variables are prefixed with @samp{$}. Any name preceded by
8249 @samp{$} can be used for a convenience variable, unless it is one of
8250 the predefined machine-specific register names (@pxref{Registers, ,Registers}).
8251 (Value history references, in contrast, are @emph{numbers} preceded
8252 by @samp{$}. @xref{Value History, ,Value History}.)
8253
8254 You can save a value in a convenience variable with an assignment
8255 expression, just as you would set a variable in your program.
8256 For example:
8257
8258 @smallexample
8259 set $foo = *object_ptr
8260 @end smallexample
8261
8262 @noindent
8263 would save in @code{$foo} the value contained in the object pointed to by
8264 @code{object_ptr}.
8265
8266 Using a convenience variable for the first time creates it, but its
8267 value is @code{void} until you assign a new value. You can alter the
8268 value with another assignment at any time.
8269
8270 Convenience variables have no fixed types. You can assign a convenience
8271 variable any type of value, including structures and arrays, even if
8272 that variable already has a value of a different type. The convenience
8273 variable, when used as an expression, has the type of its current value.
8274
8275 @table @code
8276 @kindex show convenience
8277 @cindex show all user variables
8278 @item show convenience
8279 Print a list of convenience variables used so far, and their values.
8280 Abbreviated @code{show conv}.
8281
8282 @kindex init-if-undefined
8283 @cindex convenience variables, initializing
8284 @item init-if-undefined $@var{variable} = @var{expression}
8285 Set a convenience variable if it has not already been set. This is useful
8286 for user-defined commands that keep some state. It is similar, in concept,
8287 to using local static variables with initializers in C (except that
8288 convenience variables are global). It can also be used to allow users to
8289 override default values used in a command script.
8290
8291 If the variable is already defined then the expression is not evaluated so
8292 any side-effects do not occur.
8293 @end table
8294
8295 One of the ways to use a convenience variable is as a counter to be
8296 incremented or a pointer to be advanced. For example, to print
8297 a field from successive elements of an array of structures:
8298
8299 @smallexample
8300 set $i = 0
8301 print bar[$i++]->contents
8302 @end smallexample
8303
8304 @noindent
8305 Repeat that command by typing @key{RET}.
8306
8307 Some convenience variables are created automatically by @value{GDBN} and given
8308 values likely to be useful.
8309
8310 @table @code
8311 @vindex $_@r{, convenience variable}
8312 @item $_
8313 The variable @code{$_} is automatically set by the @code{x} command to
8314 the last address examined (@pxref{Memory, ,Examining Memory}). Other
8315 commands which provide a default address for @code{x} to examine also
8316 set @code{$_} to that address; these commands include @code{info line}
8317 and @code{info breakpoint}. The type of @code{$_} is @code{void *}
8318 except when set by the @code{x} command, in which case it is a pointer
8319 to the type of @code{$__}.
8320
8321 @vindex $__@r{, convenience variable}
8322 @item $__
8323 The variable @code{$__} is automatically set by the @code{x} command
8324 to the value found in the last address examined. Its type is chosen
8325 to match the format in which the data was printed.
8326
8327 @item $_exitcode
8328 @vindex $_exitcode@r{, convenience variable}
8329 The variable @code{$_exitcode} is automatically set to the exit code when
8330 the program being debugged terminates.
8331
8332 @item $_sdata
8333 @vindex $_sdata@r{, inspect, convenience variable}
8334 The variable @code{$_sdata} contains extra collected static tracepoint
8335 data. @xref{Tracepoint Actions,,Tracepoint Action Lists}. Note that
8336 @code{$_sdata} could be empty, if not inspecting a trace buffer, or
8337 if extra static tracepoint data has not been collected.
8338
8339 @item $_siginfo
8340 @vindex $_siginfo@r{, convenience variable}
8341 The variable @code{$_siginfo} contains extra signal information
8342 (@pxref{extra signal information}). Note that @code{$_siginfo}
8343 could be empty, if the application has not yet received any signals.
8344 For example, it will be empty before you execute the @code{run} command.
8345
8346 @item $_tlb
8347 @vindex $_tlb@r{, convenience variable}
8348 The variable @code{$_tlb} is automatically set when debugging
8349 applications running on MS-Windows in native mode or connected to
8350 gdbserver that supports the @code{qGetTIBAddr} request.
8351 @xref{General Query Packets}.
8352 This variable contains the address of the thread information block.
8353
8354 @end table
8355
8356 On HP-UX systems, if you refer to a function or variable name that
8357 begins with a dollar sign, @value{GDBN} searches for a user or system
8358 name first, before it searches for a convenience variable.
8359
8360 @cindex convenience functions
8361 @value{GDBN} also supplies some @dfn{convenience functions}. These
8362 have a syntax similar to convenience variables. A convenience
8363 function can be used in an expression just like an ordinary function;
8364 however, a convenience function is implemented internally to
8365 @value{GDBN}.
8366
8367 @table @code
8368 @item help function
8369 @kindex help function
8370 @cindex show all convenience functions
8371 Print a list of all convenience functions.
8372 @end table
8373
8374 @node Registers
8375 @section Registers
8376
8377 @cindex registers
8378 You can refer to machine register contents, in expressions, as variables
8379 with names starting with @samp{$}. The names of registers are different
8380 for each machine; use @code{info registers} to see the names used on
8381 your machine.
8382
8383 @table @code
8384 @kindex info registers
8385 @item info registers
8386 Print the names and values of all registers except floating-point
8387 and vector registers (in the selected stack frame).
8388
8389 @kindex info all-registers
8390 @cindex floating point registers
8391 @item info all-registers
8392 Print the names and values of all registers, including floating-point
8393 and vector registers (in the selected stack frame).
8394
8395 @item info registers @var{regname} @dots{}
8396 Print the @dfn{relativized} value of each specified register @var{regname}.
8397 As discussed in detail below, register values are normally relative to
8398 the selected stack frame. @var{regname} may be any register name valid on
8399 the machine you are using, with or without the initial @samp{$}.
8400 @end table
8401
8402 @cindex stack pointer register
8403 @cindex program counter register
8404 @cindex process status register
8405 @cindex frame pointer register
8406 @cindex standard registers
8407 @value{GDBN} has four ``standard'' register names that are available (in
8408 expressions) on most machines---whenever they do not conflict with an
8409 architecture's canonical mnemonics for registers. The register names
8410 @code{$pc} and @code{$sp} are used for the program counter register and
8411 the stack pointer. @code{$fp} is used for a register that contains a
8412 pointer to the current stack frame, and @code{$ps} is used for a
8413 register that contains the processor status. For example,
8414 you could print the program counter in hex with
8415
8416 @smallexample
8417 p/x $pc
8418 @end smallexample
8419
8420 @noindent
8421 or print the instruction to be executed next with
8422
8423 @smallexample
8424 x/i $pc
8425 @end smallexample
8426
8427 @noindent
8428 or add four to the stack pointer@footnote{This is a way of removing
8429 one word from the stack, on machines where stacks grow downward in
8430 memory (most machines, nowadays). This assumes that the innermost
8431 stack frame is selected; setting @code{$sp} is not allowed when other
8432 stack frames are selected. To pop entire frames off the stack,
8433 regardless of machine architecture, use @code{return};
8434 see @ref{Returning, ,Returning from a Function}.} with
8435
8436 @smallexample
8437 set $sp += 4
8438 @end smallexample
8439
8440 Whenever possible, these four standard register names are available on
8441 your machine even though the machine has different canonical mnemonics,
8442 so long as there is no conflict. The @code{info registers} command
8443 shows the canonical names. For example, on the SPARC, @code{info
8444 registers} displays the processor status register as @code{$psr} but you
8445 can also refer to it as @code{$ps}; and on x86-based machines @code{$ps}
8446 is an alias for the @sc{eflags} register.
8447
8448 @value{GDBN} always considers the contents of an ordinary register as an
8449 integer when the register is examined in this way. Some machines have
8450 special registers which can hold nothing but floating point; these
8451 registers are considered to have floating point values. There is no way
8452 to refer to the contents of an ordinary register as floating point value
8453 (although you can @emph{print} it as a floating point value with
8454 @samp{print/f $@var{regname}}).
8455
8456 Some registers have distinct ``raw'' and ``virtual'' data formats. This
8457 means that the data format in which the register contents are saved by
8458 the operating system is not the same one that your program normally
8459 sees. For example, the registers of the 68881 floating point
8460 coprocessor are always saved in ``extended'' (raw) format, but all C
8461 programs expect to work with ``double'' (virtual) format. In such
8462 cases, @value{GDBN} normally works with the virtual format only (the format
8463 that makes sense for your program), but the @code{info registers} command
8464 prints the data in both formats.
8465
8466 @cindex SSE registers (x86)
8467 @cindex MMX registers (x86)
8468 Some machines have special registers whose contents can be interpreted
8469 in several different ways. For example, modern x86-based machines
8470 have SSE and MMX registers that can hold several values packed
8471 together in several different formats. @value{GDBN} refers to such
8472 registers in @code{struct} notation:
8473
8474 @smallexample
8475 (@value{GDBP}) print $xmm1
8476 $1 = @{
8477 v4_float = @{0, 3.43859137e-038, 1.54142831e-044, 1.821688e-044@},
8478 v2_double = @{9.92129282474342e-303, 2.7585945287983262e-313@},
8479 v16_int8 = "\000\000\000\000\3706;\001\v\000\000\000\r\000\000",
8480 v8_int16 = @{0, 0, 14072, 315, 11, 0, 13, 0@},
8481 v4_int32 = @{0, 20657912, 11, 13@},
8482 v2_int64 = @{88725056443645952, 55834574859@},
8483 uint128 = 0x0000000d0000000b013b36f800000000
8484 @}
8485 @end smallexample
8486
8487 @noindent
8488 To set values of such registers, you need to tell @value{GDBN} which
8489 view of the register you wish to change, as if you were assigning
8490 value to a @code{struct} member:
8491
8492 @smallexample
8493 (@value{GDBP}) set $xmm1.uint128 = 0x000000000000000000000000FFFFFFFF
8494 @end smallexample
8495
8496 Normally, register values are relative to the selected stack frame
8497 (@pxref{Selection, ,Selecting a Frame}). This means that you get the
8498 value that the register would contain if all stack frames farther in
8499 were exited and their saved registers restored. In order to see the
8500 true contents of hardware registers, you must select the innermost
8501 frame (with @samp{frame 0}).
8502
8503 However, @value{GDBN} must deduce where registers are saved, from the machine
8504 code generated by your compiler. If some registers are not saved, or if
8505 @value{GDBN} is unable to locate the saved registers, the selected stack
8506 frame makes no difference.
8507
8508 @node Floating Point Hardware
8509 @section Floating Point Hardware
8510 @cindex floating point
8511
8512 Depending on the configuration, @value{GDBN} may be able to give
8513 you more information about the status of the floating point hardware.
8514
8515 @table @code
8516 @kindex info float
8517 @item info float
8518 Display hardware-dependent information about the floating
8519 point unit. The exact contents and layout vary depending on the
8520 floating point chip. Currently, @samp{info float} is supported on
8521 the ARM and x86 machines.
8522 @end table
8523
8524 @node Vector Unit
8525 @section Vector Unit
8526 @cindex vector unit
8527
8528 Depending on the configuration, @value{GDBN} may be able to give you
8529 more information about the status of the vector unit.
8530
8531 @table @code
8532 @kindex info vector
8533 @item info vector
8534 Display information about the vector unit. The exact contents and
8535 layout vary depending on the hardware.
8536 @end table
8537
8538 @node OS Information
8539 @section Operating System Auxiliary Information
8540 @cindex OS information
8541
8542 @value{GDBN} provides interfaces to useful OS facilities that can help
8543 you debug your program.
8544
8545 @cindex @code{ptrace} system call
8546 @cindex @code{struct user} contents
8547 When @value{GDBN} runs on a @dfn{Posix system} (such as GNU or Unix
8548 machines), it interfaces with the inferior via the @code{ptrace}
8549 system call. The operating system creates a special sata structure,
8550 called @code{struct user}, for this interface. You can use the
8551 command @code{info udot} to display the contents of this data
8552 structure.
8553
8554 @table @code
8555 @item info udot
8556 @kindex info udot
8557 Display the contents of the @code{struct user} maintained by the OS
8558 kernel for the program being debugged. @value{GDBN} displays the
8559 contents of @code{struct user} as a list of hex numbers, similar to
8560 the @code{examine} command.
8561 @end table
8562
8563 @cindex auxiliary vector
8564 @cindex vector, auxiliary
8565 Some operating systems supply an @dfn{auxiliary vector} to programs at
8566 startup. This is akin to the arguments and environment that you
8567 specify for a program, but contains a system-dependent variety of
8568 binary values that tell system libraries important details about the
8569 hardware, operating system, and process. Each value's purpose is
8570 identified by an integer tag; the meanings are well-known but system-specific.
8571 Depending on the configuration and operating system facilities,
8572 @value{GDBN} may be able to show you this information. For remote
8573 targets, this functionality may further depend on the remote stub's
8574 support of the @samp{qXfer:auxv:read} packet, see
8575 @ref{qXfer auxiliary vector read}.
8576
8577 @table @code
8578 @kindex info auxv
8579 @item info auxv
8580 Display the auxiliary vector of the inferior, which can be either a
8581 live process or a core dump file. @value{GDBN} prints each tag value
8582 numerically, and also shows names and text descriptions for recognized
8583 tags. Some values in the vector are numbers, some bit masks, and some
8584 pointers to strings or other data. @value{GDBN} displays each value in the
8585 most appropriate form for a recognized tag, and in hexadecimal for
8586 an unrecognized tag.
8587 @end table
8588
8589 On some targets, @value{GDBN} can access operating-system-specific information
8590 and display it to user, without interpretation. For remote targets,
8591 this functionality depends on the remote stub's support of the
8592 @samp{qXfer:osdata:read} packet, see @ref{qXfer osdata read}.
8593
8594 @table @code
8595 @kindex info os
8596 @item info os
8597 List the types of OS information available for the target. If the
8598 target does not return a list of possible types, this command will
8599 report an error.
8600
8601 @kindex info os processes
8602 @item info os processes
8603 Display the list of processes on the target. For each process,
8604 @value{GDBN} prints the process identifier, the name of the user, and
8605 the command corresponding to the process.
8606 @end table
8607
8608 @node Memory Region Attributes
8609 @section Memory Region Attributes
8610 @cindex memory region attributes
8611
8612 @dfn{Memory region attributes} allow you to describe special handling
8613 required by regions of your target's memory. @value{GDBN} uses
8614 attributes to determine whether to allow certain types of memory
8615 accesses; whether to use specific width accesses; and whether to cache
8616 target memory. By default the description of memory regions is
8617 fetched from the target (if the current target supports this), but the
8618 user can override the fetched regions.
8619
8620 Defined memory regions can be individually enabled and disabled. When a
8621 memory region is disabled, @value{GDBN} uses the default attributes when
8622 accessing memory in that region. Similarly, if no memory regions have
8623 been defined, @value{GDBN} uses the default attributes when accessing
8624 all memory.
8625
8626 When a memory region is defined, it is given a number to identify it;
8627 to enable, disable, or remove a memory region, you specify that number.
8628
8629 @table @code
8630 @kindex mem
8631 @item mem @var{lower} @var{upper} @var{attributes}@dots{}
8632 Define a memory region bounded by @var{lower} and @var{upper} with
8633 attributes @var{attributes}@dots{}, and add it to the list of regions
8634 monitored by @value{GDBN}. Note that @var{upper} == 0 is a special
8635 case: it is treated as the target's maximum memory address.
8636 (0xffff on 16 bit targets, 0xffffffff on 32 bit targets, etc.)
8637
8638 @item mem auto
8639 Discard any user changes to the memory regions and use target-supplied
8640 regions, if available, or no regions if the target does not support.
8641
8642 @kindex delete mem
8643 @item delete mem @var{nums}@dots{}
8644 Remove memory regions @var{nums}@dots{} from the list of regions
8645 monitored by @value{GDBN}.
8646
8647 @kindex disable mem
8648 @item disable mem @var{nums}@dots{}
8649 Disable monitoring of memory regions @var{nums}@dots{}.
8650 A disabled memory region is not forgotten.
8651 It may be enabled again later.
8652
8653 @kindex enable mem
8654 @item enable mem @var{nums}@dots{}
8655 Enable monitoring of memory regions @var{nums}@dots{}.
8656
8657 @kindex info mem
8658 @item info mem
8659 Print a table of all defined memory regions, with the following columns
8660 for each region:
8661
8662 @table @emph
8663 @item Memory Region Number
8664 @item Enabled or Disabled.
8665 Enabled memory regions are marked with @samp{y}.
8666 Disabled memory regions are marked with @samp{n}.
8667
8668 @item Lo Address
8669 The address defining the inclusive lower bound of the memory region.
8670
8671 @item Hi Address
8672 The address defining the exclusive upper bound of the memory region.
8673
8674 @item Attributes
8675 The list of attributes set for this memory region.
8676 @end table
8677 @end table
8678
8679
8680 @subsection Attributes
8681
8682 @subsubsection Memory Access Mode
8683 The access mode attributes set whether @value{GDBN} may make read or
8684 write accesses to a memory region.
8685
8686 While these attributes prevent @value{GDBN} from performing invalid
8687 memory accesses, they do nothing to prevent the target system, I/O DMA,
8688 etc.@: from accessing memory.
8689
8690 @table @code
8691 @item ro
8692 Memory is read only.
8693 @item wo
8694 Memory is write only.
8695 @item rw
8696 Memory is read/write. This is the default.
8697 @end table
8698
8699 @subsubsection Memory Access Size
8700 The access size attribute tells @value{GDBN} to use specific sized
8701 accesses in the memory region. Often memory mapped device registers
8702 require specific sized accesses. If no access size attribute is
8703 specified, @value{GDBN} may use accesses of any size.
8704
8705 @table @code
8706 @item 8
8707 Use 8 bit memory accesses.
8708 @item 16
8709 Use 16 bit memory accesses.
8710 @item 32
8711 Use 32 bit memory accesses.
8712 @item 64
8713 Use 64 bit memory accesses.
8714 @end table
8715
8716 @c @subsubsection Hardware/Software Breakpoints
8717 @c The hardware/software breakpoint attributes set whether @value{GDBN}
8718 @c will use hardware or software breakpoints for the internal breakpoints
8719 @c used by the step, next, finish, until, etc. commands.
8720 @c
8721 @c @table @code
8722 @c @item hwbreak
8723 @c Always use hardware breakpoints
8724 @c @item swbreak (default)
8725 @c @end table
8726
8727 @subsubsection Data Cache
8728 The data cache attributes set whether @value{GDBN} will cache target
8729 memory. While this generally improves performance by reducing debug
8730 protocol overhead, it can lead to incorrect results because @value{GDBN}
8731 does not know about volatile variables or memory mapped device
8732 registers.
8733
8734 @table @code
8735 @item cache
8736 Enable @value{GDBN} to cache target memory.
8737 @item nocache
8738 Disable @value{GDBN} from caching target memory. This is the default.
8739 @end table
8740
8741 @subsection Memory Access Checking
8742 @value{GDBN} can be instructed to refuse accesses to memory that is
8743 not explicitly described. This can be useful if accessing such
8744 regions has undesired effects for a specific target, or to provide
8745 better error checking. The following commands control this behaviour.
8746
8747 @table @code
8748 @kindex set mem inaccessible-by-default
8749 @item set mem inaccessible-by-default [on|off]
8750 If @code{on} is specified, make @value{GDBN} treat memory not
8751 explicitly described by the memory ranges as non-existent and refuse accesses
8752 to such memory. The checks are only performed if there's at least one
8753 memory range defined. If @code{off} is specified, make @value{GDBN}
8754 treat the memory not explicitly described by the memory ranges as RAM.
8755 The default value is @code{on}.
8756 @kindex show mem inaccessible-by-default
8757 @item show mem inaccessible-by-default
8758 Show the current handling of accesses to unknown memory.
8759 @end table
8760
8761
8762 @c @subsubsection Memory Write Verification
8763 @c The memory write verification attributes set whether @value{GDBN}
8764 @c will re-reads data after each write to verify the write was successful.
8765 @c
8766 @c @table @code
8767 @c @item verify
8768 @c @item noverify (default)
8769 @c @end table
8770
8771 @node Dump/Restore Files
8772 @section Copy Between Memory and a File
8773 @cindex dump/restore files
8774 @cindex append data to a file
8775 @cindex dump data to a file
8776 @cindex restore data from a file
8777
8778 You can use the commands @code{dump}, @code{append}, and
8779 @code{restore} to copy data between target memory and a file. The
8780 @code{dump} and @code{append} commands write data to a file, and the
8781 @code{restore} command reads data from a file back into the inferior's
8782 memory. Files may be in binary, Motorola S-record, Intel hex, or
8783 Tektronix Hex format; however, @value{GDBN} can only append to binary
8784 files.
8785
8786 @table @code
8787
8788 @kindex dump
8789 @item dump @r{[}@var{format}@r{]} memory @var{filename} @var{start_addr} @var{end_addr}
8790 @itemx dump @r{[}@var{format}@r{]} value @var{filename} @var{expr}
8791 Dump the contents of memory from @var{start_addr} to @var{end_addr},
8792 or the value of @var{expr}, to @var{filename} in the given format.
8793
8794 The @var{format} parameter may be any one of:
8795 @table @code
8796 @item binary
8797 Raw binary form.
8798 @item ihex
8799 Intel hex format.
8800 @item srec
8801 Motorola S-record format.
8802 @item tekhex
8803 Tektronix Hex format.
8804 @end table
8805
8806 @value{GDBN} uses the same definitions of these formats as the
8807 @sc{gnu} binary utilities, like @samp{objdump} and @samp{objcopy}. If
8808 @var{format} is omitted, @value{GDBN} dumps the data in raw binary
8809 form.
8810
8811 @kindex append
8812 @item append @r{[}binary@r{]} memory @var{filename} @var{start_addr} @var{end_addr}
8813 @itemx append @r{[}binary@r{]} value @var{filename} @var{expr}
8814 Append the contents of memory from @var{start_addr} to @var{end_addr},
8815 or the value of @var{expr}, to the file @var{filename}, in raw binary form.
8816 (@value{GDBN} can only append data to files in raw binary form.)
8817
8818 @kindex restore
8819 @item restore @var{filename} @r{[}binary@r{]} @var{bias} @var{start} @var{end}
8820 Restore the contents of file @var{filename} into memory. The
8821 @code{restore} command can automatically recognize any known @sc{bfd}
8822 file format, except for raw binary. To restore a raw binary file you
8823 must specify the optional keyword @code{binary} after the filename.
8824
8825 If @var{bias} is non-zero, its value will be added to the addresses
8826 contained in the file. Binary files always start at address zero, so
8827 they will be restored at address @var{bias}. Other bfd files have
8828 a built-in location; they will be restored at offset @var{bias}
8829 from that location.
8830
8831 If @var{start} and/or @var{end} are non-zero, then only data between
8832 file offset @var{start} and file offset @var{end} will be restored.
8833 These offsets are relative to the addresses in the file, before
8834 the @var{bias} argument is applied.
8835
8836 @end table
8837
8838 @node Core File Generation
8839 @section How to Produce a Core File from Your Program
8840 @cindex dump core from inferior
8841
8842 A @dfn{core file} or @dfn{core dump} is a file that records the memory
8843 image of a running process and its process status (register values
8844 etc.). Its primary use is post-mortem debugging of a program that
8845 crashed while it ran outside a debugger. A program that crashes
8846 automatically produces a core file, unless this feature is disabled by
8847 the user. @xref{Files}, for information on invoking @value{GDBN} in
8848 the post-mortem debugging mode.
8849
8850 Occasionally, you may wish to produce a core file of the program you
8851 are debugging in order to preserve a snapshot of its state.
8852 @value{GDBN} has a special command for that.
8853
8854 @table @code
8855 @kindex gcore
8856 @kindex generate-core-file
8857 @item generate-core-file [@var{file}]
8858 @itemx gcore [@var{file}]
8859 Produce a core dump of the inferior process. The optional argument
8860 @var{file} specifies the file name where to put the core dump. If not
8861 specified, the file name defaults to @file{core.@var{pid}}, where
8862 @var{pid} is the inferior process ID.
8863
8864 Note that this command is implemented only for some systems (as of
8865 this writing, @sc{gnu}/Linux, FreeBSD, Solaris, Unixware, and S390).
8866 @end table
8867
8868 @node Character Sets
8869 @section Character Sets
8870 @cindex character sets
8871 @cindex charset
8872 @cindex translating between character sets
8873 @cindex host character set
8874 @cindex target character set
8875
8876 If the program you are debugging uses a different character set to
8877 represent characters and strings than the one @value{GDBN} uses itself,
8878 @value{GDBN} can automatically translate between the character sets for
8879 you. The character set @value{GDBN} uses we call the @dfn{host
8880 character set}; the one the inferior program uses we call the
8881 @dfn{target character set}.
8882
8883 For example, if you are running @value{GDBN} on a @sc{gnu}/Linux system, which
8884 uses the ISO Latin 1 character set, but you are using @value{GDBN}'s
8885 remote protocol (@pxref{Remote Debugging}) to debug a program
8886 running on an IBM mainframe, which uses the @sc{ebcdic} character set,
8887 then the host character set is Latin-1, and the target character set is
8888 @sc{ebcdic}. If you give @value{GDBN} the command @code{set
8889 target-charset EBCDIC-US}, then @value{GDBN} translates between
8890 @sc{ebcdic} and Latin 1 as you print character or string values, or use
8891 character and string literals in expressions.
8892
8893 @value{GDBN} has no way to automatically recognize which character set
8894 the inferior program uses; you must tell it, using the @code{set
8895 target-charset} command, described below.
8896
8897 Here are the commands for controlling @value{GDBN}'s character set
8898 support:
8899
8900 @table @code
8901 @item set target-charset @var{charset}
8902 @kindex set target-charset
8903 Set the current target character set to @var{charset}. To display the
8904 list of supported target character sets, type
8905 @kbd{@w{set target-charset @key{TAB}@key{TAB}}}.
8906
8907 @item set host-charset @var{charset}
8908 @kindex set host-charset
8909 Set the current host character set to @var{charset}.
8910
8911 By default, @value{GDBN} uses a host character set appropriate to the
8912 system it is running on; you can override that default using the
8913 @code{set host-charset} command. On some systems, @value{GDBN} cannot
8914 automatically determine the appropriate host character set. In this
8915 case, @value{GDBN} uses @samp{UTF-8}.
8916
8917 @value{GDBN} can only use certain character sets as its host character
8918 set. If you type @kbd{@w{set host-charset @key{TAB}@key{TAB}}},
8919 @value{GDBN} will list the host character sets it supports.
8920
8921 @item set charset @var{charset}
8922 @kindex set charset
8923 Set the current host and target character sets to @var{charset}. As
8924 above, if you type @kbd{@w{set charset @key{TAB}@key{TAB}}},
8925 @value{GDBN} will list the names of the character sets that can be used
8926 for both host and target.
8927
8928 @item show charset
8929 @kindex show charset
8930 Show the names of the current host and target character sets.
8931
8932 @item show host-charset
8933 @kindex show host-charset
8934 Show the name of the current host character set.
8935
8936 @item show target-charset
8937 @kindex show target-charset
8938 Show the name of the current target character set.
8939
8940 @item set target-wide-charset @var{charset}
8941 @kindex set target-wide-charset
8942 Set the current target's wide character set to @var{charset}. This is
8943 the character set used by the target's @code{wchar_t} type. To
8944 display the list of supported wide character sets, type
8945 @kbd{@w{set target-wide-charset @key{TAB}@key{TAB}}}.
8946
8947 @item show target-wide-charset
8948 @kindex show target-wide-charset
8949 Show the name of the current target's wide character set.
8950 @end table
8951
8952 Here is an example of @value{GDBN}'s character set support in action.
8953 Assume that the following source code has been placed in the file
8954 @file{charset-test.c}:
8955
8956 @smallexample
8957 #include <stdio.h>
8958
8959 char ascii_hello[]
8960 = @{72, 101, 108, 108, 111, 44, 32, 119,
8961 111, 114, 108, 100, 33, 10, 0@};
8962 char ibm1047_hello[]
8963 = @{200, 133, 147, 147, 150, 107, 64, 166,
8964 150, 153, 147, 132, 90, 37, 0@};
8965
8966 main ()
8967 @{
8968 printf ("Hello, world!\n");
8969 @}
8970 @end smallexample
8971
8972 In this program, @code{ascii_hello} and @code{ibm1047_hello} are arrays
8973 containing the string @samp{Hello, world!} followed by a newline,
8974 encoded in the @sc{ascii} and @sc{ibm1047} character sets.
8975
8976 We compile the program, and invoke the debugger on it:
8977
8978 @smallexample
8979 $ gcc -g charset-test.c -o charset-test
8980 $ gdb -nw charset-test
8981 GNU gdb 2001-12-19-cvs
8982 Copyright 2001 Free Software Foundation, Inc.
8983 @dots{}
8984 (@value{GDBP})
8985 @end smallexample
8986
8987 We can use the @code{show charset} command to see what character sets
8988 @value{GDBN} is currently using to interpret and display characters and
8989 strings:
8990
8991 @smallexample
8992 (@value{GDBP}) show charset
8993 The current host and target character set is `ISO-8859-1'.
8994 (@value{GDBP})
8995 @end smallexample
8996
8997 For the sake of printing this manual, let's use @sc{ascii} as our
8998 initial character set:
8999 @smallexample
9000 (@value{GDBP}) set charset ASCII
9001 (@value{GDBP}) show charset
9002 The current host and target character set is `ASCII'.
9003 (@value{GDBP})
9004 @end smallexample
9005
9006 Let's assume that @sc{ascii} is indeed the correct character set for our
9007 host system --- in other words, let's assume that if @value{GDBN} prints
9008 characters using the @sc{ascii} character set, our terminal will display
9009 them properly. Since our current target character set is also
9010 @sc{ascii}, the contents of @code{ascii_hello} print legibly:
9011
9012 @smallexample
9013 (@value{GDBP}) print ascii_hello
9014 $1 = 0x401698 "Hello, world!\n"
9015 (@value{GDBP}) print ascii_hello[0]
9016 $2 = 72 'H'
9017 (@value{GDBP})
9018 @end smallexample
9019
9020 @value{GDBN} uses the target character set for character and string
9021 literals you use in expressions:
9022
9023 @smallexample
9024 (@value{GDBP}) print '+'
9025 $3 = 43 '+'
9026 (@value{GDBP})
9027 @end smallexample
9028
9029 The @sc{ascii} character set uses the number 43 to encode the @samp{+}
9030 character.
9031
9032 @value{GDBN} relies on the user to tell it which character set the
9033 target program uses. If we print @code{ibm1047_hello} while our target
9034 character set is still @sc{ascii}, we get jibberish:
9035
9036 @smallexample
9037 (@value{GDBP}) print ibm1047_hello
9038 $4 = 0x4016a8 "\310\205\223\223\226k@@\246\226\231\223\204Z%"
9039 (@value{GDBP}) print ibm1047_hello[0]
9040 $5 = 200 '\310'
9041 (@value{GDBP})
9042 @end smallexample
9043
9044 If we invoke the @code{set target-charset} followed by @key{TAB}@key{TAB},
9045 @value{GDBN} tells us the character sets it supports:
9046
9047 @smallexample
9048 (@value{GDBP}) set target-charset
9049 ASCII EBCDIC-US IBM1047 ISO-8859-1
9050 (@value{GDBP}) set target-charset
9051 @end smallexample
9052
9053 We can select @sc{ibm1047} as our target character set, and examine the
9054 program's strings again. Now the @sc{ascii} string is wrong, but
9055 @value{GDBN} translates the contents of @code{ibm1047_hello} from the
9056 target character set, @sc{ibm1047}, to the host character set,
9057 @sc{ascii}, and they display correctly:
9058
9059 @smallexample
9060 (@value{GDBP}) set target-charset IBM1047
9061 (@value{GDBP}) show charset
9062 The current host character set is `ASCII'.
9063 The current target character set is `IBM1047'.
9064 (@value{GDBP}) print ascii_hello
9065 $6 = 0x401698 "\110\145%%?\054\040\167?\162%\144\041\012"
9066 (@value{GDBP}) print ascii_hello[0]
9067 $7 = 72 '\110'
9068 (@value{GDBP}) print ibm1047_hello
9069 $8 = 0x4016a8 "Hello, world!\n"
9070 (@value{GDBP}) print ibm1047_hello[0]
9071 $9 = 200 'H'
9072 (@value{GDBP})
9073 @end smallexample
9074
9075 As above, @value{GDBN} uses the target character set for character and
9076 string literals you use in expressions:
9077
9078 @smallexample
9079 (@value{GDBP}) print '+'
9080 $10 = 78 '+'
9081 (@value{GDBP})
9082 @end smallexample
9083
9084 The @sc{ibm1047} character set uses the number 78 to encode the @samp{+}
9085 character.
9086
9087 @node Caching Remote Data
9088 @section Caching Data of Remote Targets
9089 @cindex caching data of remote targets
9090
9091 @value{GDBN} caches data exchanged between the debugger and a
9092 remote target (@pxref{Remote Debugging}). Such caching generally improves
9093 performance, because it reduces the overhead of the remote protocol by
9094 bundling memory reads and writes into large chunks. Unfortunately, simply
9095 caching everything would lead to incorrect results, since @value{GDBN}
9096 does not necessarily know anything about volatile values, memory-mapped I/O
9097 addresses, etc. Furthermore, in non-stop mode (@pxref{Non-Stop Mode})
9098 memory can be changed @emph{while} a gdb command is executing.
9099 Therefore, by default, @value{GDBN} only caches data
9100 known to be on the stack@footnote{In non-stop mode, it is moderately
9101 rare for a running thread to modify the stack of a stopped thread
9102 in a way that would interfere with a backtrace, and caching of
9103 stack reads provides a significant speed up of remote backtraces.}.
9104 Other regions of memory can be explicitly marked as
9105 cacheable; see @pxref{Memory Region Attributes}.
9106
9107 @table @code
9108 @kindex set remotecache
9109 @item set remotecache on
9110 @itemx set remotecache off
9111 This option no longer does anything; it exists for compatibility
9112 with old scripts.
9113
9114 @kindex show remotecache
9115 @item show remotecache
9116 Show the current state of the obsolete remotecache flag.
9117
9118 @kindex set stack-cache
9119 @item set stack-cache on
9120 @itemx set stack-cache off
9121 Enable or disable caching of stack accesses. When @code{ON}, use
9122 caching. By default, this option is @code{ON}.
9123
9124 @kindex show stack-cache
9125 @item show stack-cache
9126 Show the current state of data caching for memory accesses.
9127
9128 @kindex info dcache
9129 @item info dcache @r{[}line@r{]}
9130 Print the information about the data cache performance. The
9131 information displayed includes the dcache width and depth, and for
9132 each cache line, its number, address, and how many times it was
9133 referenced. This command is useful for debugging the data cache
9134 operation.
9135
9136 If a line number is specified, the contents of that line will be
9137 printed in hex.
9138 @end table
9139
9140 @node Searching Memory
9141 @section Search Memory
9142 @cindex searching memory
9143
9144 Memory can be searched for a particular sequence of bytes with the
9145 @code{find} command.
9146
9147 @table @code
9148 @kindex find
9149 @item find @r{[}/@var{sn}@r{]} @var{start_addr}, +@var{len}, @var{val1} @r{[}, @var{val2}, @dots{}@r{]}
9150 @itemx find @r{[}/@var{sn}@r{]} @var{start_addr}, @var{end_addr}, @var{val1} @r{[}, @var{val2}, @dots{}@r{]}
9151 Search memory for the sequence of bytes specified by @var{val1}, @var{val2},
9152 etc. The search begins at address @var{start_addr} and continues for either
9153 @var{len} bytes or through to @var{end_addr} inclusive.
9154 @end table
9155
9156 @var{s} and @var{n} are optional parameters.
9157 They may be specified in either order, apart or together.
9158
9159 @table @r
9160 @item @var{s}, search query size
9161 The size of each search query value.
9162
9163 @table @code
9164 @item b
9165 bytes
9166 @item h
9167 halfwords (two bytes)
9168 @item w
9169 words (four bytes)
9170 @item g
9171 giant words (eight bytes)
9172 @end table
9173
9174 All values are interpreted in the current language.
9175 This means, for example, that if the current source language is C/C@t{++}
9176 then searching for the string ``hello'' includes the trailing '\0'.
9177
9178 If the value size is not specified, it is taken from the
9179 value's type in the current language.
9180 This is useful when one wants to specify the search
9181 pattern as a mixture of types.
9182 Note that this means, for example, that in the case of C-like languages
9183 a search for an untyped 0x42 will search for @samp{(int) 0x42}
9184 which is typically four bytes.
9185
9186 @item @var{n}, maximum number of finds
9187 The maximum number of matches to print. The default is to print all finds.
9188 @end table
9189
9190 You can use strings as search values. Quote them with double-quotes
9191 (@code{"}).
9192 The string value is copied into the search pattern byte by byte,
9193 regardless of the endianness of the target and the size specification.
9194
9195 The address of each match found is printed as well as a count of the
9196 number of matches found.
9197
9198 The address of the last value found is stored in convenience variable
9199 @samp{$_}.
9200 A count of the number of matches is stored in @samp{$numfound}.
9201
9202 For example, if stopped at the @code{printf} in this function:
9203
9204 @smallexample
9205 void
9206 hello ()
9207 @{
9208 static char hello[] = "hello-hello";
9209 static struct @{ char c; short s; int i; @}
9210 __attribute__ ((packed)) mixed
9211 = @{ 'c', 0x1234, 0x87654321 @};
9212 printf ("%s\n", hello);
9213 @}
9214 @end smallexample
9215
9216 @noindent
9217 you get during debugging:
9218
9219 @smallexample
9220 (gdb) find &hello[0], +sizeof(hello), "hello"
9221 0x804956d <hello.1620+6>
9222 1 pattern found
9223 (gdb) find &hello[0], +sizeof(hello), 'h', 'e', 'l', 'l', 'o'
9224 0x8049567 <hello.1620>
9225 0x804956d <hello.1620+6>
9226 2 patterns found
9227 (gdb) find /b1 &hello[0], +sizeof(hello), 'h', 0x65, 'l'
9228 0x8049567 <hello.1620>
9229 1 pattern found
9230 (gdb) find &mixed, +sizeof(mixed), (char) 'c', (short) 0x1234, (int) 0x87654321
9231 0x8049560 <mixed.1625>
9232 1 pattern found
9233 (gdb) print $numfound
9234 $1 = 1
9235 (gdb) print $_
9236 $2 = (void *) 0x8049560
9237 @end smallexample
9238
9239 @node Optimized Code
9240 @chapter Debugging Optimized Code
9241 @cindex optimized code, debugging
9242 @cindex debugging optimized code
9243
9244 Almost all compilers support optimization. With optimization
9245 disabled, the compiler generates assembly code that corresponds
9246 directly to your source code, in a simplistic way. As the compiler
9247 applies more powerful optimizations, the generated assembly code
9248 diverges from your original source code. With help from debugging
9249 information generated by the compiler, @value{GDBN} can map from
9250 the running program back to constructs from your original source.
9251
9252 @value{GDBN} is more accurate with optimization disabled. If you
9253 can recompile without optimization, it is easier to follow the
9254 progress of your program during debugging. But, there are many cases
9255 where you may need to debug an optimized version.
9256
9257 When you debug a program compiled with @samp{-g -O}, remember that the
9258 optimizer has rearranged your code; the debugger shows you what is
9259 really there. Do not be too surprised when the execution path does not
9260 exactly match your source file! An extreme example: if you define a
9261 variable, but never use it, @value{GDBN} never sees that
9262 variable---because the compiler optimizes it out of existence.
9263
9264 Some things do not work as well with @samp{-g -O} as with just
9265 @samp{-g}, particularly on machines with instruction scheduling. If in
9266 doubt, recompile with @samp{-g} alone, and if this fixes the problem,
9267 please report it to us as a bug (including a test case!).
9268 @xref{Variables}, for more information about debugging optimized code.
9269
9270 @menu
9271 * Inline Functions:: How @value{GDBN} presents inlining
9272 @end menu
9273
9274 @node Inline Functions
9275 @section Inline Functions
9276 @cindex inline functions, debugging
9277
9278 @dfn{Inlining} is an optimization that inserts a copy of the function
9279 body directly at each call site, instead of jumping to a shared
9280 routine. @value{GDBN} displays inlined functions just like
9281 non-inlined functions. They appear in backtraces. You can view their
9282 arguments and local variables, step into them with @code{step}, skip
9283 them with @code{next}, and escape from them with @code{finish}.
9284 You can check whether a function was inlined by using the
9285 @code{info frame} command.
9286
9287 For @value{GDBN} to support inlined functions, the compiler must
9288 record information about inlining in the debug information ---
9289 @value{NGCC} using the @sc{dwarf 2} format does this, and several
9290 other compilers do also. @value{GDBN} only supports inlined functions
9291 when using @sc{dwarf 2}. Versions of @value{NGCC} before 4.1
9292 do not emit two required attributes (@samp{DW_AT_call_file} and
9293 @samp{DW_AT_call_line}); @value{GDBN} does not display inlined
9294 function calls with earlier versions of @value{NGCC}. It instead
9295 displays the arguments and local variables of inlined functions as
9296 local variables in the caller.
9297
9298 The body of an inlined function is directly included at its call site;
9299 unlike a non-inlined function, there are no instructions devoted to
9300 the call. @value{GDBN} still pretends that the call site and the
9301 start of the inlined function are different instructions. Stepping to
9302 the call site shows the call site, and then stepping again shows
9303 the first line of the inlined function, even though no additional
9304 instructions are executed.
9305
9306 This makes source-level debugging much clearer; you can see both the
9307 context of the call and then the effect of the call. Only stepping by
9308 a single instruction using @code{stepi} or @code{nexti} does not do
9309 this; single instruction steps always show the inlined body.
9310
9311 There are some ways that @value{GDBN} does not pretend that inlined
9312 function calls are the same as normal calls:
9313
9314 @itemize @bullet
9315 @item
9316 You cannot set breakpoints on inlined functions. @value{GDBN}
9317 either reports that there is no symbol with that name, or else sets the
9318 breakpoint only on non-inlined copies of the function. This limitation
9319 will be removed in a future version of @value{GDBN}; until then,
9320 set a breakpoint by line number on the first line of the inlined
9321 function instead.
9322
9323 @item
9324 Setting breakpoints at the call site of an inlined function may not
9325 work, because the call site does not contain any code. @value{GDBN}
9326 may incorrectly move the breakpoint to the next line of the enclosing
9327 function, after the call. This limitation will be removed in a future
9328 version of @value{GDBN}; until then, set a breakpoint on an earlier line
9329 or inside the inlined function instead.
9330
9331 @item
9332 @value{GDBN} cannot locate the return value of inlined calls after
9333 using the @code{finish} command. This is a limitation of compiler-generated
9334 debugging information; after @code{finish}, you can step to the next line
9335 and print a variable where your program stored the return value.
9336
9337 @end itemize
9338
9339
9340 @node Macros
9341 @chapter C Preprocessor Macros
9342
9343 Some languages, such as C and C@t{++}, provide a way to define and invoke
9344 ``preprocessor macros'' which expand into strings of tokens.
9345 @value{GDBN} can evaluate expressions containing macro invocations, show
9346 the result of macro expansion, and show a macro's definition, including
9347 where it was defined.
9348
9349 You may need to compile your program specially to provide @value{GDBN}
9350 with information about preprocessor macros. Most compilers do not
9351 include macros in their debugging information, even when you compile
9352 with the @option{-g} flag. @xref{Compilation}.
9353
9354 A program may define a macro at one point, remove that definition later,
9355 and then provide a different definition after that. Thus, at different
9356 points in the program, a macro may have different definitions, or have
9357 no definition at all. If there is a current stack frame, @value{GDBN}
9358 uses the macros in scope at that frame's source code line. Otherwise,
9359 @value{GDBN} uses the macros in scope at the current listing location;
9360 see @ref{List}.
9361
9362 Whenever @value{GDBN} evaluates an expression, it always expands any
9363 macro invocations present in the expression. @value{GDBN} also provides
9364 the following commands for working with macros explicitly.
9365
9366 @table @code
9367
9368 @kindex macro expand
9369 @cindex macro expansion, showing the results of preprocessor
9370 @cindex preprocessor macro expansion, showing the results of
9371 @cindex expanding preprocessor macros
9372 @item macro expand @var{expression}
9373 @itemx macro exp @var{expression}
9374 Show the results of expanding all preprocessor macro invocations in
9375 @var{expression}. Since @value{GDBN} simply expands macros, but does
9376 not parse the result, @var{expression} need not be a valid expression;
9377 it can be any string of tokens.
9378
9379 @kindex macro exp1
9380 @item macro expand-once @var{expression}
9381 @itemx macro exp1 @var{expression}
9382 @cindex expand macro once
9383 @i{(This command is not yet implemented.)} Show the results of
9384 expanding those preprocessor macro invocations that appear explicitly in
9385 @var{expression}. Macro invocations appearing in that expansion are
9386 left unchanged. This command allows you to see the effect of a
9387 particular macro more clearly, without being confused by further
9388 expansions. Since @value{GDBN} simply expands macros, but does not
9389 parse the result, @var{expression} need not be a valid expression; it
9390 can be any string of tokens.
9391
9392 @kindex info macro
9393 @cindex macro definition, showing
9394 @cindex definition, showing a macro's
9395 @item info macro @var{macro}
9396 Show the definition of the macro named @var{macro}, and describe the
9397 source location or compiler command-line where that definition was established.
9398
9399 @kindex macro define
9400 @cindex user-defined macros
9401 @cindex defining macros interactively
9402 @cindex macros, user-defined
9403 @item macro define @var{macro} @var{replacement-list}
9404 @itemx macro define @var{macro}(@var{arglist}) @var{replacement-list}
9405 Introduce a definition for a preprocessor macro named @var{macro},
9406 invocations of which are replaced by the tokens given in
9407 @var{replacement-list}. The first form of this command defines an
9408 ``object-like'' macro, which takes no arguments; the second form
9409 defines a ``function-like'' macro, which takes the arguments given in
9410 @var{arglist}.
9411
9412 A definition introduced by this command is in scope in every
9413 expression evaluated in @value{GDBN}, until it is removed with the
9414 @code{macro undef} command, described below. The definition overrides
9415 all definitions for @var{macro} present in the program being debugged,
9416 as well as any previous user-supplied definition.
9417
9418 @kindex macro undef
9419 @item macro undef @var{macro}
9420 Remove any user-supplied definition for the macro named @var{macro}.
9421 This command only affects definitions provided with the @code{macro
9422 define} command, described above; it cannot remove definitions present
9423 in the program being debugged.
9424
9425 @kindex macro list
9426 @item macro list
9427 List all the macros defined using the @code{macro define} command.
9428 @end table
9429
9430 @cindex macros, example of debugging with
9431 Here is a transcript showing the above commands in action. First, we
9432 show our source files:
9433
9434 @smallexample
9435 $ cat sample.c
9436 #include <stdio.h>
9437 #include "sample.h"
9438
9439 #define M 42
9440 #define ADD(x) (M + x)
9441
9442 main ()
9443 @{
9444 #define N 28
9445 printf ("Hello, world!\n");
9446 #undef N
9447 printf ("We're so creative.\n");
9448 #define N 1729
9449 printf ("Goodbye, world!\n");
9450 @}
9451 $ cat sample.h
9452 #define Q <
9453 $
9454 @end smallexample
9455
9456 Now, we compile the program using the @sc{gnu} C compiler, @value{NGCC}.
9457 We pass the @option{-gdwarf-2} and @option{-g3} flags to ensure the
9458 compiler includes information about preprocessor macros in the debugging
9459 information.
9460
9461 @smallexample
9462 $ gcc -gdwarf-2 -g3 sample.c -o sample
9463 $
9464 @end smallexample
9465
9466 Now, we start @value{GDBN} on our sample program:
9467
9468 @smallexample
9469 $ gdb -nw sample
9470 GNU gdb 2002-05-06-cvs
9471 Copyright 2002 Free Software Foundation, Inc.
9472 GDB is free software, @dots{}
9473 (@value{GDBP})
9474 @end smallexample
9475
9476 We can expand macros and examine their definitions, even when the
9477 program is not running. @value{GDBN} uses the current listing position
9478 to decide which macro definitions are in scope:
9479
9480 @smallexample
9481 (@value{GDBP}) list main
9482 3
9483 4 #define M 42
9484 5 #define ADD(x) (M + x)
9485 6
9486 7 main ()
9487 8 @{
9488 9 #define N 28
9489 10 printf ("Hello, world!\n");
9490 11 #undef N
9491 12 printf ("We're so creative.\n");
9492 (@value{GDBP}) info macro ADD
9493 Defined at /home/jimb/gdb/macros/play/sample.c:5
9494 #define ADD(x) (M + x)
9495 (@value{GDBP}) info macro Q
9496 Defined at /home/jimb/gdb/macros/play/sample.h:1
9497 included at /home/jimb/gdb/macros/play/sample.c:2
9498 #define Q <
9499 (@value{GDBP}) macro expand ADD(1)
9500 expands to: (42 + 1)
9501 (@value{GDBP}) macro expand-once ADD(1)
9502 expands to: once (M + 1)
9503 (@value{GDBP})
9504 @end smallexample
9505
9506 In the example above, note that @code{macro expand-once} expands only
9507 the macro invocation explicit in the original text --- the invocation of
9508 @code{ADD} --- but does not expand the invocation of the macro @code{M},
9509 which was introduced by @code{ADD}.
9510
9511 Once the program is running, @value{GDBN} uses the macro definitions in
9512 force at the source line of the current stack frame:
9513
9514 @smallexample
9515 (@value{GDBP}) break main
9516 Breakpoint 1 at 0x8048370: file sample.c, line 10.
9517 (@value{GDBP}) run
9518 Starting program: /home/jimb/gdb/macros/play/sample
9519
9520 Breakpoint 1, main () at sample.c:10
9521 10 printf ("Hello, world!\n");
9522 (@value{GDBP})
9523 @end smallexample
9524
9525 At line 10, the definition of the macro @code{N} at line 9 is in force:
9526
9527 @smallexample
9528 (@value{GDBP}) info macro N
9529 Defined at /home/jimb/gdb/macros/play/sample.c:9
9530 #define N 28
9531 (@value{GDBP}) macro expand N Q M
9532 expands to: 28 < 42
9533 (@value{GDBP}) print N Q M
9534 $1 = 1
9535 (@value{GDBP})
9536 @end smallexample
9537
9538 As we step over directives that remove @code{N}'s definition, and then
9539 give it a new definition, @value{GDBN} finds the definition (or lack
9540 thereof) in force at each point:
9541
9542 @smallexample
9543 (@value{GDBP}) next
9544 Hello, world!
9545 12 printf ("We're so creative.\n");
9546 (@value{GDBP}) info macro N
9547 The symbol `N' has no definition as a C/C++ preprocessor macro
9548 at /home/jimb/gdb/macros/play/sample.c:12
9549 (@value{GDBP}) next
9550 We're so creative.
9551 14 printf ("Goodbye, world!\n");
9552 (@value{GDBP}) info macro N
9553 Defined at /home/jimb/gdb/macros/play/sample.c:13
9554 #define N 1729
9555 (@value{GDBP}) macro expand N Q M
9556 expands to: 1729 < 42
9557 (@value{GDBP}) print N Q M
9558 $2 = 0
9559 (@value{GDBP})
9560 @end smallexample
9561
9562 In addition to source files, macros can be defined on the compilation command
9563 line using the @option{-D@var{name}=@var{value}} syntax. For macros defined in
9564 such a way, @value{GDBN} displays the location of their definition as line zero
9565 of the source file submitted to the compiler.
9566
9567 @smallexample
9568 (@value{GDBP}) info macro __STDC__
9569 Defined at /home/jimb/gdb/macros/play/sample.c:0
9570 -D__STDC__=1
9571 (@value{GDBP})
9572 @end smallexample
9573
9574
9575 @node Tracepoints
9576 @chapter Tracepoints
9577 @c This chapter is based on the documentation written by Michael
9578 @c Snyder, David Taylor, Jim Blandy, and Elena Zannoni.
9579
9580 @cindex tracepoints
9581 In some applications, it is not feasible for the debugger to interrupt
9582 the program's execution long enough for the developer to learn
9583 anything helpful about its behavior. If the program's correctness
9584 depends on its real-time behavior, delays introduced by a debugger
9585 might cause the program to change its behavior drastically, or perhaps
9586 fail, even when the code itself is correct. It is useful to be able
9587 to observe the program's behavior without interrupting it.
9588
9589 Using @value{GDBN}'s @code{trace} and @code{collect} commands, you can
9590 specify locations in the program, called @dfn{tracepoints}, and
9591 arbitrary expressions to evaluate when those tracepoints are reached.
9592 Later, using the @code{tfind} command, you can examine the values
9593 those expressions had when the program hit the tracepoints. The
9594 expressions may also denote objects in memory---structures or arrays,
9595 for example---whose values @value{GDBN} should record; while visiting
9596 a particular tracepoint, you may inspect those objects as if they were
9597 in memory at that moment. However, because @value{GDBN} records these
9598 values without interacting with you, it can do so quickly and
9599 unobtrusively, hopefully not disturbing the program's behavior.
9600
9601 The tracepoint facility is currently available only for remote
9602 targets. @xref{Targets}. In addition, your remote target must know
9603 how to collect trace data. This functionality is implemented in the
9604 remote stub; however, none of the stubs distributed with @value{GDBN}
9605 support tracepoints as of this writing. The format of the remote
9606 packets used to implement tracepoints are described in @ref{Tracepoint
9607 Packets}.
9608
9609 It is also possible to get trace data from a file, in a manner reminiscent
9610 of corefiles; you specify the filename, and use @code{tfind} to search
9611 through the file. @xref{Trace Files}, for more details.
9612
9613 This chapter describes the tracepoint commands and features.
9614
9615 @menu
9616 * Set Tracepoints::
9617 * Analyze Collected Data::
9618 * Tracepoint Variables::
9619 * Trace Files::
9620 @end menu
9621
9622 @node Set Tracepoints
9623 @section Commands to Set Tracepoints
9624
9625 Before running such a @dfn{trace experiment}, an arbitrary number of
9626 tracepoints can be set. A tracepoint is actually a special type of
9627 breakpoint (@pxref{Set Breaks}), so you can manipulate it using
9628 standard breakpoint commands. For instance, as with breakpoints,
9629 tracepoint numbers are successive integers starting from one, and many
9630 of the commands associated with tracepoints take the tracepoint number
9631 as their argument, to identify which tracepoint to work on.
9632
9633 For each tracepoint, you can specify, in advance, some arbitrary set
9634 of data that you want the target to collect in the trace buffer when
9635 it hits that tracepoint. The collected data can include registers,
9636 local variables, or global data. Later, you can use @value{GDBN}
9637 commands to examine the values these data had at the time the
9638 tracepoint was hit.
9639
9640 Tracepoints do not support every breakpoint feature. Ignore counts on
9641 tracepoints have no effect, and tracepoints cannot run @value{GDBN}
9642 commands when they are hit. Tracepoints may not be thread-specific
9643 either.
9644
9645 @cindex fast tracepoints
9646 Some targets may support @dfn{fast tracepoints}, which are inserted in
9647 a different way (such as with a jump instead of a trap), that is
9648 faster but possibly restricted in where they may be installed.
9649
9650 @cindex static tracepoints
9651 @cindex markers, static tracepoints
9652 @cindex probing markers, static tracepoints
9653 Regular and fast tracepoints are dynamic tracing facilities, meaning
9654 that they can be used to insert tracepoints at (almost) any location
9655 in the target. Some targets may also support controlling @dfn{static
9656 tracepoints} from @value{GDBN}. With static tracing, a set of
9657 instrumentation points, also known as @dfn{markers}, are embedded in
9658 the target program, and can be activated or deactivated by name or
9659 address. These are usually placed at locations which facilitate
9660 investigating what the target is actually doing. @value{GDBN}'s
9661 support for static tracing includes being able to list instrumentation
9662 points, and attach them with @value{GDBN} defined high level
9663 tracepoints that expose the whole range of convenience of
9664 @value{GDBN}'s tracepoints support. Namelly, support for collecting
9665 registers values and values of global or local (to the instrumentation
9666 point) variables; tracepoint conditions and trace state variables.
9667 The act of installing a @value{GDBN} static tracepoint on an
9668 instrumentation point, or marker, is referred to as @dfn{probing} a
9669 static tracepoint marker.
9670
9671 @code{gdbserver} supports tracepoints on some target systems.
9672 @xref{Server,,Tracepoints support in @code{gdbserver}}.
9673
9674 This section describes commands to set tracepoints and associated
9675 conditions and actions.
9676
9677 @menu
9678 * Create and Delete Tracepoints::
9679 * Enable and Disable Tracepoints::
9680 * Tracepoint Passcounts::
9681 * Tracepoint Conditions::
9682 * Trace State Variables::
9683 * Tracepoint Actions::
9684 * Listing Tracepoints::
9685 * Listing Static Tracepoint Markers::
9686 * Starting and Stopping Trace Experiments::
9687 * Tracepoint Restrictions::
9688 @end menu
9689
9690 @node Create and Delete Tracepoints
9691 @subsection Create and Delete Tracepoints
9692
9693 @table @code
9694 @cindex set tracepoint
9695 @kindex trace
9696 @item trace @var{location}
9697 The @code{trace} command is very similar to the @code{break} command.
9698 Its argument @var{location} can be a source line, a function name, or
9699 an address in the target program. @xref{Specify Location}. The
9700 @code{trace} command defines a tracepoint, which is a point in the
9701 target program where the debugger will briefly stop, collect some
9702 data, and then allow the program to continue. Setting a tracepoint or
9703 changing its actions doesn't take effect until the next @code{tstart}
9704 command, and once a trace experiment is running, further changes will
9705 not have any effect until the next trace experiment starts.
9706
9707 Here are some examples of using the @code{trace} command:
9708
9709 @smallexample
9710 (@value{GDBP}) @b{trace foo.c:121} // a source file and line number
9711
9712 (@value{GDBP}) @b{trace +2} // 2 lines forward
9713
9714 (@value{GDBP}) @b{trace my_function} // first source line of function
9715
9716 (@value{GDBP}) @b{trace *my_function} // EXACT start address of function
9717
9718 (@value{GDBP}) @b{trace *0x2117c4} // an address
9719 @end smallexample
9720
9721 @noindent
9722 You can abbreviate @code{trace} as @code{tr}.
9723
9724 @item trace @var{location} if @var{cond}
9725 Set a tracepoint with condition @var{cond}; evaluate the expression
9726 @var{cond} each time the tracepoint is reached, and collect data only
9727 if the value is nonzero---that is, if @var{cond} evaluates as true.
9728 @xref{Tracepoint Conditions, ,Tracepoint Conditions}, for more
9729 information on tracepoint conditions.
9730
9731 @item ftrace @var{location} [ if @var{cond} ]
9732 @cindex set fast tracepoint
9733 @cindex fast tracepoints, setting
9734 @kindex ftrace
9735 The @code{ftrace} command sets a fast tracepoint. For targets that
9736 support them, fast tracepoints will use a more efficient but possibly
9737 less general technique to trigger data collection, such as a jump
9738 instruction instead of a trap, or some sort of hardware support. It
9739 may not be possible to create a fast tracepoint at the desired
9740 location, in which case the command will exit with an explanatory
9741 message.
9742
9743 @value{GDBN} handles arguments to @code{ftrace} exactly as for
9744 @code{trace}.
9745
9746 @item strace @var{location} [ if @var{cond} ]
9747 @cindex set static tracepoint
9748 @cindex static tracepoints, setting
9749 @cindex probe static tracepoint marker
9750 @kindex strace
9751 The @code{strace} command sets a static tracepoint. For targets that
9752 support it, setting a static tracepoint probes a static
9753 instrumentation point, or marker, found at @var{location}. It may not
9754 be possible to set a static tracepoint at the desired location, in
9755 which case the command will exit with an explanatory message.
9756
9757 @value{GDBN} handles arguments to @code{strace} exactly as for
9758 @code{trace}, with the addition that the user can also specify
9759 @code{-m @var{marker}} as @var{location}. This probes the marker
9760 identified by the @var{marker} string identifier. This identifier
9761 depends on the static tracepoint backend library your program is
9762 using. You can find all the marker identifiers in the @samp{ID} field
9763 of the @code{info static-tracepoint-markers} command output.
9764 @xref{Listing Static Tracepoint Markers,,Listing Static Tracepoint
9765 Markers}. For example, in the following small program using the UST
9766 tracing engine:
9767
9768 @smallexample
9769 main ()
9770 @{
9771 trace_mark(ust, bar33, "str %s", "FOOBAZ");
9772 @}
9773 @end smallexample
9774
9775 @noindent
9776 the marker id is composed of joining the first two arguments to the
9777 @code{trace_mark} call with a slash, which translates to:
9778
9779 @smallexample
9780 (@value{GDBP}) info static-tracepoint-markers
9781 Cnt Enb ID Address What
9782 1 n ust/bar33 0x0000000000400ddc in main at stexample.c:22
9783 Data: "str %s"
9784 [etc...]
9785 @end smallexample
9786
9787 @noindent
9788 so you may probe the marker above with:
9789
9790 @smallexample
9791 (@value{GDBP}) strace -m ust/bar33
9792 @end smallexample
9793
9794 Static tracepoints accept an extra collect action --- @code{collect
9795 $_sdata}. This collects arbitrary user data passed in the probe point
9796 call to the tracing library. In the UST example above, you'll see
9797 that the third argument to @code{trace_mark} is a printf-like format
9798 string. The user data is then the result of running that formating
9799 string against the following arguments. Note that @code{info
9800 static-tracepoint-markers} command output lists that format string in
9801 the @samp{Data:} field.
9802
9803 You can inspect this data when analyzing the trace buffer, by printing
9804 the $_sdata variable like any other variable available to
9805 @value{GDBN}. @xref{Tracepoint Actions,,Tracepoint Action Lists}.
9806
9807 @vindex $tpnum
9808 @cindex last tracepoint number
9809 @cindex recent tracepoint number
9810 @cindex tracepoint number
9811 The convenience variable @code{$tpnum} records the tracepoint number
9812 of the most recently set tracepoint.
9813
9814 @kindex delete tracepoint
9815 @cindex tracepoint deletion
9816 @item delete tracepoint @r{[}@var{num}@r{]}
9817 Permanently delete one or more tracepoints. With no argument, the
9818 default is to delete all tracepoints. Note that the regular
9819 @code{delete} command can remove tracepoints also.
9820
9821 Examples:
9822
9823 @smallexample
9824 (@value{GDBP}) @b{delete trace 1 2 3} // remove three tracepoints
9825
9826 (@value{GDBP}) @b{delete trace} // remove all tracepoints
9827 @end smallexample
9828
9829 @noindent
9830 You can abbreviate this command as @code{del tr}.
9831 @end table
9832
9833 @node Enable and Disable Tracepoints
9834 @subsection Enable and Disable Tracepoints
9835
9836 These commands are deprecated; they are equivalent to plain @code{disable} and @code{enable}.
9837
9838 @table @code
9839 @kindex disable tracepoint
9840 @item disable tracepoint @r{[}@var{num}@r{]}
9841 Disable tracepoint @var{num}, or all tracepoints if no argument
9842 @var{num} is given. A disabled tracepoint will have no effect during
9843 the next trace experiment, but it is not forgotten. You can re-enable
9844 a disabled tracepoint using the @code{enable tracepoint} command.
9845
9846 @kindex enable tracepoint
9847 @item enable tracepoint @r{[}@var{num}@r{]}
9848 Enable tracepoint @var{num}, or all tracepoints. The enabled
9849 tracepoints will become effective the next time a trace experiment is
9850 run.
9851 @end table
9852
9853 @node Tracepoint Passcounts
9854 @subsection Tracepoint Passcounts
9855
9856 @table @code
9857 @kindex passcount
9858 @cindex tracepoint pass count
9859 @item passcount @r{[}@var{n} @r{[}@var{num}@r{]]}
9860 Set the @dfn{passcount} of a tracepoint. The passcount is a way to
9861 automatically stop a trace experiment. If a tracepoint's passcount is
9862 @var{n}, then the trace experiment will be automatically stopped on
9863 the @var{n}'th time that tracepoint is hit. If the tracepoint number
9864 @var{num} is not specified, the @code{passcount} command sets the
9865 passcount of the most recently defined tracepoint. If no passcount is
9866 given, the trace experiment will run until stopped explicitly by the
9867 user.
9868
9869 Examples:
9870
9871 @smallexample
9872 (@value{GDBP}) @b{passcount 5 2} // Stop on the 5th execution of
9873 @exdent @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @code{// tracepoint 2}
9874
9875 (@value{GDBP}) @b{passcount 12} // Stop on the 12th execution of the
9876 @exdent @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @code{// most recently defined tracepoint.}
9877 (@value{GDBP}) @b{trace foo}
9878 (@value{GDBP}) @b{pass 3}
9879 (@value{GDBP}) @b{trace bar}
9880 (@value{GDBP}) @b{pass 2}
9881 (@value{GDBP}) @b{trace baz}
9882 (@value{GDBP}) @b{pass 1} // Stop tracing when foo has been
9883 @exdent @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @code{// executed 3 times OR when bar has}
9884 @exdent @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @code{// been executed 2 times}
9885 @exdent @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @code{// OR when baz has been executed 1 time.}
9886 @end smallexample
9887 @end table
9888
9889 @node Tracepoint Conditions
9890 @subsection Tracepoint Conditions
9891 @cindex conditional tracepoints
9892 @cindex tracepoint conditions
9893
9894 The simplest sort of tracepoint collects data every time your program
9895 reaches a specified place. You can also specify a @dfn{condition} for
9896 a tracepoint. A condition is just a Boolean expression in your
9897 programming language (@pxref{Expressions, ,Expressions}). A
9898 tracepoint with a condition evaluates the expression each time your
9899 program reaches it, and data collection happens only if the condition
9900 is true.
9901
9902 Tracepoint conditions can be specified when a tracepoint is set, by
9903 using @samp{if} in the arguments to the @code{trace} command.
9904 @xref{Create and Delete Tracepoints, ,Setting Tracepoints}. They can
9905 also be set or changed at any time with the @code{condition} command,
9906 just as with breakpoints.
9907
9908 Unlike breakpoint conditions, @value{GDBN} does not actually evaluate
9909 the conditional expression itself. Instead, @value{GDBN} encodes the
9910 expression into an agent expression (@pxref{Agent Expressions}
9911 suitable for execution on the target, independently of @value{GDBN}.
9912 Global variables become raw memory locations, locals become stack
9913 accesses, and so forth.
9914
9915 For instance, suppose you have a function that is usually called
9916 frequently, but should not be called after an error has occurred. You
9917 could use the following tracepoint command to collect data about calls
9918 of that function that happen while the error code is propagating
9919 through the program; an unconditional tracepoint could end up
9920 collecting thousands of useless trace frames that you would have to
9921 search through.
9922
9923 @smallexample
9924 (@value{GDBP}) @kbd{trace normal_operation if errcode > 0}
9925 @end smallexample
9926
9927 @node Trace State Variables
9928 @subsection Trace State Variables
9929 @cindex trace state variables
9930
9931 A @dfn{trace state variable} is a special type of variable that is
9932 created and managed by target-side code. The syntax is the same as
9933 that for GDB's convenience variables (a string prefixed with ``$''),
9934 but they are stored on the target. They must be created explicitly,
9935 using a @code{tvariable} command. They are always 64-bit signed
9936 integers.
9937
9938 Trace state variables are remembered by @value{GDBN}, and downloaded
9939 to the target along with tracepoint information when the trace
9940 experiment starts. There are no intrinsic limits on the number of
9941 trace state variables, beyond memory limitations of the target.
9942
9943 @cindex convenience variables, and trace state variables
9944 Although trace state variables are managed by the target, you can use
9945 them in print commands and expressions as if they were convenience
9946 variables; @value{GDBN} will get the current value from the target
9947 while the trace experiment is running. Trace state variables share
9948 the same namespace as other ``$'' variables, which means that you
9949 cannot have trace state variables with names like @code{$23} or
9950 @code{$pc}, nor can you have a trace state variable and a convenience
9951 variable with the same name.
9952
9953 @table @code
9954
9955 @item tvariable $@var{name} [ = @var{expression} ]
9956 @kindex tvariable
9957 The @code{tvariable} command creates a new trace state variable named
9958 @code{$@var{name}}, and optionally gives it an initial value of
9959 @var{expression}. @var{expression} is evaluated when this command is
9960 entered; the result will be converted to an integer if possible,
9961 otherwise @value{GDBN} will report an error. A subsequent
9962 @code{tvariable} command specifying the same name does not create a
9963 variable, but instead assigns the supplied initial value to the
9964 existing variable of that name, overwriting any previous initial
9965 value. The default initial value is 0.
9966
9967 @item info tvariables
9968 @kindex info tvariables
9969 List all the trace state variables along with their initial values.
9970 Their current values may also be displayed, if the trace experiment is
9971 currently running.
9972
9973 @item delete tvariable @r{[} $@var{name} @dots{} @r{]}
9974 @kindex delete tvariable
9975 Delete the given trace state variables, or all of them if no arguments
9976 are specified.
9977
9978 @end table
9979
9980 @node Tracepoint Actions
9981 @subsection Tracepoint Action Lists
9982
9983 @table @code
9984 @kindex actions
9985 @cindex tracepoint actions
9986 @item actions @r{[}@var{num}@r{]}
9987 This command will prompt for a list of actions to be taken when the
9988 tracepoint is hit. If the tracepoint number @var{num} is not
9989 specified, this command sets the actions for the one that was most
9990 recently defined (so that you can define a tracepoint and then say
9991 @code{actions} without bothering about its number). You specify the
9992 actions themselves on the following lines, one action at a time, and
9993 terminate the actions list with a line containing just @code{end}. So
9994 far, the only defined actions are @code{collect}, @code{teval}, and
9995 @code{while-stepping}.
9996
9997 @code{actions} is actually equivalent to @code{commands} (@pxref{Break
9998 Commands, ,Breakpoint Command Lists}), except that only the defined
9999 actions are allowed; any other @value{GDBN} command is rejected.
10000
10001 @cindex remove actions from a tracepoint
10002 To remove all actions from a tracepoint, type @samp{actions @var{num}}
10003 and follow it immediately with @samp{end}.
10004
10005 @smallexample
10006 (@value{GDBP}) @b{collect @var{data}} // collect some data
10007
10008 (@value{GDBP}) @b{while-stepping 5} // single-step 5 times, collect data
10009
10010 (@value{GDBP}) @b{end} // signals the end of actions.
10011 @end smallexample
10012
10013 In the following example, the action list begins with @code{collect}
10014 commands indicating the things to be collected when the tracepoint is
10015 hit. Then, in order to single-step and collect additional data
10016 following the tracepoint, a @code{while-stepping} command is used,
10017 followed by the list of things to be collected after each step in a
10018 sequence of single steps. The @code{while-stepping} command is
10019 terminated by its own separate @code{end} command. Lastly, the action
10020 list is terminated by an @code{end} command.
10021
10022 @smallexample
10023 (@value{GDBP}) @b{trace foo}
10024 (@value{GDBP}) @b{actions}
10025 Enter actions for tracepoint 1, one per line:
10026 > collect bar,baz
10027 > collect $regs
10028 > while-stepping 12
10029 > collect $pc, arr[i]
10030 > end
10031 end
10032 @end smallexample
10033
10034 @kindex collect @r{(tracepoints)}
10035 @item collect @var{expr1}, @var{expr2}, @dots{}
10036 Collect values of the given expressions when the tracepoint is hit.
10037 This command accepts a comma-separated list of any valid expressions.
10038 In addition to global, static, or local variables, the following
10039 special arguments are supported:
10040
10041 @table @code
10042 @item $regs
10043 Collect all registers.
10044
10045 @item $args
10046 Collect all function arguments.
10047
10048 @item $locals
10049 Collect all local variables.
10050
10051 @item $_sdata
10052 @vindex $_sdata@r{, collect}
10053 Collect static tracepoint marker specific data. Only available for
10054 static tracepoints. @xref{Tracepoint Actions,,Tracepoint Action
10055 Lists}. On the UST static tracepoints library backend, an
10056 instrumentation point resembles a @code{printf} function call. The
10057 tracing library is able to collect user specified data formatted to a
10058 character string using the format provided by the programmer that
10059 instrumented the program. Other backends have similar mechanisms.
10060 Here's an example of a UST marker call:
10061
10062 @smallexample
10063 const char master_name[] = "$your_name";
10064 trace_mark(channel1, marker1, "hello %s", master_name)
10065 @end smallexample
10066
10067 In this case, collecting @code{$_sdata} collects the string
10068 @samp{hello $yourname}. When analyzing the trace buffer, you can
10069 inspect @samp{$_sdata} like any other variable available to
10070 @value{GDBN}.
10071 @end table
10072
10073 You can give several consecutive @code{collect} commands, each one
10074 with a single argument, or one @code{collect} command with several
10075 arguments separated by commas; the effect is the same.
10076
10077 The command @code{info scope} (@pxref{Symbols, info scope}) is
10078 particularly useful for figuring out what data to collect.
10079
10080 @kindex teval @r{(tracepoints)}
10081 @item teval @var{expr1}, @var{expr2}, @dots{}
10082 Evaluate the given expressions when the tracepoint is hit. This
10083 command accepts a comma-separated list of expressions. The results
10084 are discarded, so this is mainly useful for assigning values to trace
10085 state variables (@pxref{Trace State Variables}) without adding those
10086 values to the trace buffer, as would be the case if the @code{collect}
10087 action were used.
10088
10089 @kindex while-stepping @r{(tracepoints)}
10090 @item while-stepping @var{n}
10091 Perform @var{n} single-step instruction traces after the tracepoint,
10092 collecting new data after each step. The @code{while-stepping}
10093 command is followed by the list of what to collect while stepping
10094 (followed by its own @code{end} command):
10095
10096 @smallexample
10097 > while-stepping 12
10098 > collect $regs, myglobal
10099 > end
10100 >
10101 @end smallexample
10102
10103 @noindent
10104 Note that @code{$pc} is not automatically collected by
10105 @code{while-stepping}; you need to explicitly collect that register if
10106 you need it. You may abbreviate @code{while-stepping} as @code{ws} or
10107 @code{stepping}.
10108
10109 @item set default-collect @var{expr1}, @var{expr2}, @dots{}
10110 @kindex set default-collect
10111 @cindex default collection action
10112 This variable is a list of expressions to collect at each tracepoint
10113 hit. It is effectively an additional @code{collect} action prepended
10114 to every tracepoint action list. The expressions are parsed
10115 individually for each tracepoint, so for instance a variable named
10116 @code{xyz} may be interpreted as a global for one tracepoint, and a
10117 local for another, as appropriate to the tracepoint's location.
10118
10119 @item show default-collect
10120 @kindex show default-collect
10121 Show the list of expressions that are collected by default at each
10122 tracepoint hit.
10123
10124 @end table
10125
10126 @node Listing Tracepoints
10127 @subsection Listing Tracepoints
10128
10129 @table @code
10130 @kindex info tracepoints
10131 @kindex info tp
10132 @cindex information about tracepoints
10133 @item info tracepoints @r{[}@var{num}@r{]}
10134 Display information about the tracepoint @var{num}. If you don't
10135 specify a tracepoint number, displays information about all the
10136 tracepoints defined so far. The format is similar to that used for
10137 @code{info breakpoints}; in fact, @code{info tracepoints} is the same
10138 command, simply restricting itself to tracepoints.
10139
10140 A tracepoint's listing may include additional information specific to
10141 tracing:
10142
10143 @itemize @bullet
10144 @item
10145 its passcount as given by the @code{passcount @var{n}} command
10146 @end itemize
10147
10148 @smallexample
10149 (@value{GDBP}) @b{info trace}
10150 Num Type Disp Enb Address What
10151 1 tracepoint keep y 0x0804ab57 in foo() at main.cxx:7
10152 while-stepping 20
10153 collect globfoo, $regs
10154 end
10155 collect globfoo2
10156 end
10157 pass count 1200
10158 (@value{GDBP})
10159 @end smallexample
10160
10161 @noindent
10162 This command can be abbreviated @code{info tp}.
10163 @end table
10164
10165 @node Listing Static Tracepoint Markers
10166 @subsection Listing Static Tracepoint Markers
10167
10168 @table @code
10169 @kindex info static-tracepoint-markers
10170 @cindex information about static tracepoint markers
10171 @item info static-tracepoint-markers
10172 Display information about all static tracepoint markers defined in the
10173 program.
10174
10175 For each marker, the following columns are printed:
10176
10177 @table @emph
10178 @item Count
10179 An incrementing counter, output to help readability. This is not a
10180 stable identifier.
10181 @item ID
10182 The marker ID, as reported by the target.
10183 @item Enabled or Disabled
10184 Probed markers are tagged with @samp{y}. @samp{n} identifies marks
10185 that are not enabled.
10186 @item Address
10187 Where the marker is in your program, as a memory address.
10188 @item What
10189 Where the marker is in the source for your program, as a file and line
10190 number. If the debug information included in the program does not
10191 allow @value{GDBN} to locate the source of the marker, this column
10192 will be left blank.
10193 @end table
10194
10195 @noindent
10196 In addition, the following information may be printed for each marker:
10197
10198 @table @emph
10199 @item Data
10200 User data passed to the tracing library by the marker call. In the
10201 UST backend, this is the format string passed as argument to the
10202 marker call.
10203 @item Static tracepoints probing the marker
10204 The list of static tracepoints attached to the marker.
10205 @end table
10206
10207 @smallexample
10208 (@value{GDBP}) info static-tracepoint-markers
10209 Cnt ID Enb Address What
10210 1 ust/bar2 y 0x0000000000400e1a in main at stexample.c:25
10211 Data: number1 %d number2 %d
10212 Probed by static tracepoints: #2
10213 2 ust/bar33 n 0x0000000000400c87 in main at stexample.c:24
10214 Data: str %s
10215 (@value{GDBP})
10216 @end smallexample
10217 @end table
10218
10219 @node Starting and Stopping Trace Experiments
10220 @subsection Starting and Stopping Trace Experiments
10221
10222 @table @code
10223 @kindex tstart
10224 @cindex start a new trace experiment
10225 @cindex collected data discarded
10226 @item tstart
10227 This command takes no arguments. It starts the trace experiment, and
10228 begins collecting data. This has the side effect of discarding all
10229 the data collected in the trace buffer during the previous trace
10230 experiment.
10231
10232 @kindex tstop
10233 @cindex stop a running trace experiment
10234 @item tstop
10235 This command takes no arguments. It ends the trace experiment, and
10236 stops collecting data.
10237
10238 @strong{Note}: a trace experiment and data collection may stop
10239 automatically if any tracepoint's passcount is reached
10240 (@pxref{Tracepoint Passcounts}), or if the trace buffer becomes full.
10241
10242 @kindex tstatus
10243 @cindex status of trace data collection
10244 @cindex trace experiment, status of
10245 @item tstatus
10246 This command displays the status of the current trace data
10247 collection.
10248 @end table
10249
10250 Here is an example of the commands we described so far:
10251
10252 @smallexample
10253 (@value{GDBP}) @b{trace gdb_c_test}
10254 (@value{GDBP}) @b{actions}
10255 Enter actions for tracepoint #1, one per line.
10256 > collect $regs,$locals,$args
10257 > while-stepping 11
10258 > collect $regs
10259 > end
10260 > end
10261 (@value{GDBP}) @b{tstart}
10262 [time passes @dots{}]
10263 (@value{GDBP}) @b{tstop}
10264 @end smallexample
10265
10266 @cindex disconnected tracing
10267 You can choose to continue running the trace experiment even if
10268 @value{GDBN} disconnects from the target, voluntarily or
10269 involuntarily. For commands such as @code{detach}, the debugger will
10270 ask what you want to do with the trace. But for unexpected
10271 terminations (@value{GDBN} crash, network outage), it would be
10272 unfortunate to lose hard-won trace data, so the variable
10273 @code{disconnected-tracing} lets you decide whether the trace should
10274 continue running without @value{GDBN}.
10275
10276 @table @code
10277 @item set disconnected-tracing on
10278 @itemx set disconnected-tracing off
10279 @kindex set disconnected-tracing
10280 Choose whether a tracing run should continue to run if @value{GDBN}
10281 has disconnected from the target. Note that @code{detach} or
10282 @code{quit} will ask you directly what to do about a running trace no
10283 matter what this variable's setting, so the variable is mainly useful
10284 for handling unexpected situations, such as loss of the network.
10285
10286 @item show disconnected-tracing
10287 @kindex show disconnected-tracing
10288 Show the current choice for disconnected tracing.
10289
10290 @end table
10291
10292 When you reconnect to the target, the trace experiment may or may not
10293 still be running; it might have filled the trace buffer in the
10294 meantime, or stopped for one of the other reasons. If it is running,
10295 it will continue after reconnection.
10296
10297 Upon reconnection, the target will upload information about the
10298 tracepoints in effect. @value{GDBN} will then compare that
10299 information to the set of tracepoints currently defined, and attempt
10300 to match them up, allowing for the possibility that the numbers may
10301 have changed due to creation and deletion in the meantime. If one of
10302 the target's tracepoints does not match any in @value{GDBN}, the
10303 debugger will create a new tracepoint, so that you have a number with
10304 which to specify that tracepoint. This matching-up process is
10305 necessarily heuristic, and it may result in useless tracepoints being
10306 created; you may simply delete them if they are of no use.
10307
10308 @cindex circular trace buffer
10309 If your target agent supports a @dfn{circular trace buffer}, then you
10310 can run a trace experiment indefinitely without filling the trace
10311 buffer; when space runs out, the agent deletes already-collected trace
10312 frames, oldest first, until there is enough room to continue
10313 collecting. This is especially useful if your tracepoints are being
10314 hit too often, and your trace gets terminated prematurely because the
10315 buffer is full. To ask for a circular trace buffer, simply set
10316 @samp{circular_trace_buffer} to on. You can set this at any time,
10317 including during tracing; if the agent can do it, it will change
10318 buffer handling on the fly, otherwise it will not take effect until
10319 the next run.
10320
10321 @table @code
10322 @item set circular-trace-buffer on
10323 @itemx set circular-trace-buffer off
10324 @kindex set circular-trace-buffer
10325 Choose whether a tracing run should use a linear or circular buffer
10326 for trace data. A linear buffer will not lose any trace data, but may
10327 fill up prematurely, while a circular buffer will discard old trace
10328 data, but it will have always room for the latest tracepoint hits.
10329
10330 @item show circular-trace-buffer
10331 @kindex show circular-trace-buffer
10332 Show the current choice for the trace buffer. Note that this may not
10333 match the agent's current buffer handling, nor is it guaranteed to
10334 match the setting that might have been in effect during a past run,
10335 for instance if you are looking at frames from a trace file.
10336
10337 @end table
10338
10339 @node Tracepoint Restrictions
10340 @subsection Tracepoint Restrictions
10341
10342 @cindex tracepoint restrictions
10343 There are a number of restrictions on the use of tracepoints. As
10344 described above, tracepoint data gathering occurs on the target
10345 without interaction from @value{GDBN}. Thus the full capabilities of
10346 the debugger are not available during data gathering, and then at data
10347 examination time, you will be limited by only having what was
10348 collected. The following items describe some common problems, but it
10349 is not exhaustive, and you may run into additional difficulties not
10350 mentioned here.
10351
10352 @itemize @bullet
10353
10354 @item
10355 Tracepoint expressions are intended to gather objects (lvalues). Thus
10356 the full flexibility of GDB's expression evaluator is not available.
10357 You cannot call functions, cast objects to aggregate types, access
10358 convenience variables or modify values (except by assignment to trace
10359 state variables). Some language features may implicitly call
10360 functions (for instance Objective-C fields with accessors), and therefore
10361 cannot be collected either.
10362
10363 @item
10364 Collection of local variables, either individually or in bulk with
10365 @code{$locals} or @code{$args}, during @code{while-stepping} may
10366 behave erratically. The stepping action may enter a new scope (for
10367 instance by stepping into a function), or the location of the variable
10368 may change (for instance it is loaded into a register). The
10369 tracepoint data recorded uses the location information for the
10370 variables that is correct for the tracepoint location. When the
10371 tracepoint is created, it is not possible, in general, to determine
10372 where the steps of a @code{while-stepping} sequence will advance the
10373 program---particularly if a conditional branch is stepped.
10374
10375 @item
10376 Collection of an incompletely-initialized or partially-destroyed object
10377 may result in something that @value{GDBN} cannot display, or displays
10378 in a misleading way.
10379
10380 @item
10381 When @value{GDBN} displays a pointer to character it automatically
10382 dereferences the pointer to also display characters of the string
10383 being pointed to. However, collecting the pointer during tracing does
10384 not automatically collect the string. You need to explicitly
10385 dereference the pointer and provide size information if you want to
10386 collect not only the pointer, but the memory pointed to. For example,
10387 @code{*ptr@@50} can be used to collect the 50 element array pointed to
10388 by @code{ptr}.
10389
10390 @item
10391 It is not possible to collect a complete stack backtrace at a
10392 tracepoint. Instead, you may collect the registers and a few hundred
10393 bytes from the stack pointer with something like @code{*$esp@@300}
10394 (adjust to use the name of the actual stack pointer register on your
10395 target architecture, and the amount of stack you wish to capture).
10396 Then the @code{backtrace} command will show a partial backtrace when
10397 using a trace frame. The number of stack frames that can be examined
10398 depends on the sizes of the frames in the collected stack. Note that
10399 if you ask for a block so large that it goes past the bottom of the
10400 stack, the target agent may report an error trying to read from an
10401 invalid address.
10402
10403 @item
10404 If you do not collect registers at a tracepoint, @value{GDBN} can
10405 infer that the value of @code{$pc} must be the same as the address of
10406 the tracepoint and use that when you are looking at a trace frame
10407 for that tracepoint. However, this cannot work if the tracepoint has
10408 multiple locations (for instance if it was set in a function that was
10409 inlined), or if it has a @code{while-stepping} loop. In those cases
10410 @value{GDBN} will warn you that it can't infer @code{$pc}, and default
10411 it to zero.
10412
10413 @end itemize
10414
10415 @node Analyze Collected Data
10416 @section Using the Collected Data
10417
10418 After the tracepoint experiment ends, you use @value{GDBN} commands
10419 for examining the trace data. The basic idea is that each tracepoint
10420 collects a trace @dfn{snapshot} every time it is hit and another
10421 snapshot every time it single-steps. All these snapshots are
10422 consecutively numbered from zero and go into a buffer, and you can
10423 examine them later. The way you examine them is to @dfn{focus} on a
10424 specific trace snapshot. When the remote stub is focused on a trace
10425 snapshot, it will respond to all @value{GDBN} requests for memory and
10426 registers by reading from the buffer which belongs to that snapshot,
10427 rather than from @emph{real} memory or registers of the program being
10428 debugged. This means that @strong{all} @value{GDBN} commands
10429 (@code{print}, @code{info registers}, @code{backtrace}, etc.) will
10430 behave as if we were currently debugging the program state as it was
10431 when the tracepoint occurred. Any requests for data that are not in
10432 the buffer will fail.
10433
10434 @menu
10435 * tfind:: How to select a trace snapshot
10436 * tdump:: How to display all data for a snapshot
10437 * save tracepoints:: How to save tracepoints for a future run
10438 @end menu
10439
10440 @node tfind
10441 @subsection @code{tfind @var{n}}
10442
10443 @kindex tfind
10444 @cindex select trace snapshot
10445 @cindex find trace snapshot
10446 The basic command for selecting a trace snapshot from the buffer is
10447 @code{tfind @var{n}}, which finds trace snapshot number @var{n},
10448 counting from zero. If no argument @var{n} is given, the next
10449 snapshot is selected.
10450
10451 Here are the various forms of using the @code{tfind} command.
10452
10453 @table @code
10454 @item tfind start
10455 Find the first snapshot in the buffer. This is a synonym for
10456 @code{tfind 0} (since 0 is the number of the first snapshot).
10457
10458 @item tfind none
10459 Stop debugging trace snapshots, resume @emph{live} debugging.
10460
10461 @item tfind end
10462 Same as @samp{tfind none}.
10463
10464 @item tfind
10465 No argument means find the next trace snapshot.
10466
10467 @item tfind -
10468 Find the previous trace snapshot before the current one. This permits
10469 retracing earlier steps.
10470
10471 @item tfind tracepoint @var{num}
10472 Find the next snapshot associated with tracepoint @var{num}. Search
10473 proceeds forward from the last examined trace snapshot. If no
10474 argument @var{num} is given, it means find the next snapshot collected
10475 for the same tracepoint as the current snapshot.
10476
10477 @item tfind pc @var{addr}
10478 Find the next snapshot associated with the value @var{addr} of the
10479 program counter. Search proceeds forward from the last examined trace
10480 snapshot. If no argument @var{addr} is given, it means find the next
10481 snapshot with the same value of PC as the current snapshot.
10482
10483 @item tfind outside @var{addr1}, @var{addr2}
10484 Find the next snapshot whose PC is outside the given range of
10485 addresses (exclusive).
10486
10487 @item tfind range @var{addr1}, @var{addr2}
10488 Find the next snapshot whose PC is between @var{addr1} and
10489 @var{addr2} (inclusive).
10490
10491 @item tfind line @r{[}@var{file}:@r{]}@var{n}
10492 Find the next snapshot associated with the source line @var{n}. If
10493 the optional argument @var{file} is given, refer to line @var{n} in
10494 that source file. Search proceeds forward from the last examined
10495 trace snapshot. If no argument @var{n} is given, it means find the
10496 next line other than the one currently being examined; thus saying
10497 @code{tfind line} repeatedly can appear to have the same effect as
10498 stepping from line to line in a @emph{live} debugging session.
10499 @end table
10500
10501 The default arguments for the @code{tfind} commands are specifically
10502 designed to make it easy to scan through the trace buffer. For
10503 instance, @code{tfind} with no argument selects the next trace
10504 snapshot, and @code{tfind -} with no argument selects the previous
10505 trace snapshot. So, by giving one @code{tfind} command, and then
10506 simply hitting @key{RET} repeatedly you can examine all the trace
10507 snapshots in order. Or, by saying @code{tfind -} and then hitting
10508 @key{RET} repeatedly you can examine the snapshots in reverse order.
10509 The @code{tfind line} command with no argument selects the snapshot
10510 for the next source line executed. The @code{tfind pc} command with
10511 no argument selects the next snapshot with the same program counter
10512 (PC) as the current frame. The @code{tfind tracepoint} command with
10513 no argument selects the next trace snapshot collected by the same
10514 tracepoint as the current one.
10515
10516 In addition to letting you scan through the trace buffer manually,
10517 these commands make it easy to construct @value{GDBN} scripts that
10518 scan through the trace buffer and print out whatever collected data
10519 you are interested in. Thus, if we want to examine the PC, FP, and SP
10520 registers from each trace frame in the buffer, we can say this:
10521
10522 @smallexample
10523 (@value{GDBP}) @b{tfind start}
10524 (@value{GDBP}) @b{while ($trace_frame != -1)}
10525 > printf "Frame %d, PC = %08X, SP = %08X, FP = %08X\n", \
10526 $trace_frame, $pc, $sp, $fp
10527 > tfind
10528 > end
10529
10530 Frame 0, PC = 0020DC64, SP = 0030BF3C, FP = 0030BF44
10531 Frame 1, PC = 0020DC6C, SP = 0030BF38, FP = 0030BF44
10532 Frame 2, PC = 0020DC70, SP = 0030BF34, FP = 0030BF44
10533 Frame 3, PC = 0020DC74, SP = 0030BF30, FP = 0030BF44
10534 Frame 4, PC = 0020DC78, SP = 0030BF2C, FP = 0030BF44
10535 Frame 5, PC = 0020DC7C, SP = 0030BF28, FP = 0030BF44
10536 Frame 6, PC = 0020DC80, SP = 0030BF24, FP = 0030BF44
10537 Frame 7, PC = 0020DC84, SP = 0030BF20, FP = 0030BF44
10538 Frame 8, PC = 0020DC88, SP = 0030BF1C, FP = 0030BF44
10539 Frame 9, PC = 0020DC8E, SP = 0030BF18, FP = 0030BF44
10540 Frame 10, PC = 00203F6C, SP = 0030BE3C, FP = 0030BF14
10541 @end smallexample
10542
10543 Or, if we want to examine the variable @code{X} at each source line in
10544 the buffer:
10545
10546 @smallexample
10547 (@value{GDBP}) @b{tfind start}
10548 (@value{GDBP}) @b{while ($trace_frame != -1)}
10549 > printf "Frame %d, X == %d\n", $trace_frame, X
10550 > tfind line
10551 > end
10552
10553 Frame 0, X = 1
10554 Frame 7, X = 2
10555 Frame 13, X = 255
10556 @end smallexample
10557
10558 @node tdump
10559 @subsection @code{tdump}
10560 @kindex tdump
10561 @cindex dump all data collected at tracepoint
10562 @cindex tracepoint data, display
10563
10564 This command takes no arguments. It prints all the data collected at
10565 the current trace snapshot.
10566
10567 @smallexample
10568 (@value{GDBP}) @b{trace 444}
10569 (@value{GDBP}) @b{actions}
10570 Enter actions for tracepoint #2, one per line:
10571 > collect $regs, $locals, $args, gdb_long_test
10572 > end
10573
10574 (@value{GDBP}) @b{tstart}
10575
10576 (@value{GDBP}) @b{tfind line 444}
10577 #0 gdb_test (p1=0x11, p2=0x22, p3=0x33, p4=0x44, p5=0x55, p6=0x66)
10578 at gdb_test.c:444
10579 444 printp( "%s: arguments = 0x%X 0x%X 0x%X 0x%X 0x%X 0x%X\n", )
10580
10581 (@value{GDBP}) @b{tdump}
10582 Data collected at tracepoint 2, trace frame 1:
10583 d0 0xc4aa0085 -995491707
10584 d1 0x18 24
10585 d2 0x80 128
10586 d3 0x33 51
10587 d4 0x71aea3d 119204413
10588 d5 0x22 34
10589 d6 0xe0 224
10590 d7 0x380035 3670069
10591 a0 0x19e24a 1696330
10592 a1 0x3000668 50333288
10593 a2 0x100 256
10594 a3 0x322000 3284992
10595 a4 0x3000698 50333336
10596 a5 0x1ad3cc 1758156
10597 fp 0x30bf3c 0x30bf3c
10598 sp 0x30bf34 0x30bf34
10599 ps 0x0 0
10600 pc 0x20b2c8 0x20b2c8
10601 fpcontrol 0x0 0
10602 fpstatus 0x0 0
10603 fpiaddr 0x0 0
10604 p = 0x20e5b4 "gdb-test"
10605 p1 = (void *) 0x11
10606 p2 = (void *) 0x22
10607 p3 = (void *) 0x33
10608 p4 = (void *) 0x44
10609 p5 = (void *) 0x55
10610 p6 = (void *) 0x66
10611 gdb_long_test = 17 '\021'
10612
10613 (@value{GDBP})
10614 @end smallexample
10615
10616 @code{tdump} works by scanning the tracepoint's current collection
10617 actions and printing the value of each expression listed. So
10618 @code{tdump} can fail, if after a run, you change the tracepoint's
10619 actions to mention variables that were not collected during the run.
10620
10621 Also, for tracepoints with @code{while-stepping} loops, @code{tdump}
10622 uses the collected value of @code{$pc} to distinguish between trace
10623 frames that were collected at the tracepoint hit, and frames that were
10624 collected while stepping. This allows it to correctly choose whether
10625 to display the basic list of collections, or the collections from the
10626 body of the while-stepping loop. However, if @code{$pc} was not collected,
10627 then @code{tdump} will always attempt to dump using the basic collection
10628 list, and may fail if a while-stepping frame does not include all the
10629 same data that is collected at the tracepoint hit.
10630 @c This is getting pretty arcane, example would be good.
10631
10632 @node save tracepoints
10633 @subsection @code{save tracepoints @var{filename}}
10634 @kindex save tracepoints
10635 @kindex save-tracepoints
10636 @cindex save tracepoints for future sessions
10637
10638 This command saves all current tracepoint definitions together with
10639 their actions and passcounts, into a file @file{@var{filename}}
10640 suitable for use in a later debugging session. To read the saved
10641 tracepoint definitions, use the @code{source} command (@pxref{Command
10642 Files}). The @w{@code{save-tracepoints}} command is a deprecated
10643 alias for @w{@code{save tracepoints}}
10644
10645 @node Tracepoint Variables
10646 @section Convenience Variables for Tracepoints
10647 @cindex tracepoint variables
10648 @cindex convenience variables for tracepoints
10649
10650 @table @code
10651 @vindex $trace_frame
10652 @item (int) $trace_frame
10653 The current trace snapshot (a.k.a.@: @dfn{frame}) number, or -1 if no
10654 snapshot is selected.
10655
10656 @vindex $tracepoint
10657 @item (int) $tracepoint
10658 The tracepoint for the current trace snapshot.
10659
10660 @vindex $trace_line
10661 @item (int) $trace_line
10662 The line number for the current trace snapshot.
10663
10664 @vindex $trace_file
10665 @item (char []) $trace_file
10666 The source file for the current trace snapshot.
10667
10668 @vindex $trace_func
10669 @item (char []) $trace_func
10670 The name of the function containing @code{$tracepoint}.
10671 @end table
10672
10673 Note: @code{$trace_file} is not suitable for use in @code{printf},
10674 use @code{output} instead.
10675
10676 Here's a simple example of using these convenience variables for
10677 stepping through all the trace snapshots and printing some of their
10678 data. Note that these are not the same as trace state variables,
10679 which are managed by the target.
10680
10681 @smallexample
10682 (@value{GDBP}) @b{tfind start}
10683
10684 (@value{GDBP}) @b{while $trace_frame != -1}
10685 > output $trace_file
10686 > printf ", line %d (tracepoint #%d)\n", $trace_line, $tracepoint
10687 > tfind
10688 > end
10689 @end smallexample
10690
10691 @node Trace Files
10692 @section Using Trace Files
10693 @cindex trace files
10694
10695 In some situations, the target running a trace experiment may no
10696 longer be available; perhaps it crashed, or the hardware was needed
10697 for a different activity. To handle these cases, you can arrange to
10698 dump the trace data into a file, and later use that file as a source
10699 of trace data, via the @code{target tfile} command.
10700
10701 @table @code
10702
10703 @kindex tsave
10704 @item tsave [ -r ] @var{filename}
10705 Save the trace data to @var{filename}. By default, this command
10706 assumes that @var{filename} refers to the host filesystem, so if
10707 necessary @value{GDBN} will copy raw trace data up from the target and
10708 then save it. If the target supports it, you can also supply the
10709 optional argument @code{-r} (``remote'') to direct the target to save
10710 the data directly into @var{filename} in its own filesystem, which may be
10711 more efficient if the trace buffer is very large. (Note, however, that
10712 @code{target tfile} can only read from files accessible to the host.)
10713
10714 @kindex target tfile
10715 @kindex tfile
10716 @item target tfile @var{filename}
10717 Use the file named @var{filename} as a source of trace data. Commands
10718 that examine data work as they do with a live target, but it is not
10719 possible to run any new trace experiments. @code{tstatus} will report
10720 the state of the trace run at the moment the data was saved, as well
10721 as the current trace frame you are examining. @var{filename} must be
10722 on a filesystem accessible to the host.
10723
10724 @end table
10725
10726 @node Overlays
10727 @chapter Debugging Programs That Use Overlays
10728 @cindex overlays
10729
10730 If your program is too large to fit completely in your target system's
10731 memory, you can sometimes use @dfn{overlays} to work around this
10732 problem. @value{GDBN} provides some support for debugging programs that
10733 use overlays.
10734
10735 @menu
10736 * How Overlays Work:: A general explanation of overlays.
10737 * Overlay Commands:: Managing overlays in @value{GDBN}.
10738 * Automatic Overlay Debugging:: @value{GDBN} can find out which overlays are
10739 mapped by asking the inferior.
10740 * Overlay Sample Program:: A sample program using overlays.
10741 @end menu
10742
10743 @node How Overlays Work
10744 @section How Overlays Work
10745 @cindex mapped overlays
10746 @cindex unmapped overlays
10747 @cindex load address, overlay's
10748 @cindex mapped address
10749 @cindex overlay area
10750
10751 Suppose you have a computer whose instruction address space is only 64
10752 kilobytes long, but which has much more memory which can be accessed by
10753 other means: special instructions, segment registers, or memory
10754 management hardware, for example. Suppose further that you want to
10755 adapt a program which is larger than 64 kilobytes to run on this system.
10756
10757 One solution is to identify modules of your program which are relatively
10758 independent, and need not call each other directly; call these modules
10759 @dfn{overlays}. Separate the overlays from the main program, and place
10760 their machine code in the larger memory. Place your main program in
10761 instruction memory, but leave at least enough space there to hold the
10762 largest overlay as well.
10763
10764 Now, to call a function located in an overlay, you must first copy that
10765 overlay's machine code from the large memory into the space set aside
10766 for it in the instruction memory, and then jump to its entry point
10767 there.
10768
10769 @c NB: In the below the mapped area's size is greater or equal to the
10770 @c size of all overlays. This is intentional to remind the developer
10771 @c that overlays don't necessarily need to be the same size.
10772
10773 @smallexample
10774 @group
10775 Data Instruction Larger
10776 Address Space Address Space Address Space
10777 +-----------+ +-----------+ +-----------+
10778 | | | | | |
10779 +-----------+ +-----------+ +-----------+<-- overlay 1
10780 | program | | main | .----| overlay 1 | load address
10781 | variables | | program | | +-----------+
10782 | and heap | | | | | |
10783 +-----------+ | | | +-----------+<-- overlay 2
10784 | | +-----------+ | | | load address
10785 +-----------+ | | | .-| overlay 2 |
10786 | | | | | |
10787 mapped --->+-----------+ | | +-----------+
10788 address | | | | | |
10789 | overlay | <-' | | |
10790 | area | <---' +-----------+<-- overlay 3
10791 | | <---. | | load address
10792 +-----------+ `--| overlay 3 |
10793 | | | |
10794 +-----------+ | |
10795 +-----------+
10796 | |
10797 +-----------+
10798
10799 @anchor{A code overlay}A code overlay
10800 @end group
10801 @end smallexample
10802
10803 The diagram (@pxref{A code overlay}) shows a system with separate data
10804 and instruction address spaces. To map an overlay, the program copies
10805 its code from the larger address space to the instruction address space.
10806 Since the overlays shown here all use the same mapped address, only one
10807 may be mapped at a time. For a system with a single address space for
10808 data and instructions, the diagram would be similar, except that the
10809 program variables and heap would share an address space with the main
10810 program and the overlay area.
10811
10812 An overlay loaded into instruction memory and ready for use is called a
10813 @dfn{mapped} overlay; its @dfn{mapped address} is its address in the
10814 instruction memory. An overlay not present (or only partially present)
10815 in instruction memory is called @dfn{unmapped}; its @dfn{load address}
10816 is its address in the larger memory. The mapped address is also called
10817 the @dfn{virtual memory address}, or @dfn{VMA}; the load address is also
10818 called the @dfn{load memory address}, or @dfn{LMA}.
10819
10820 Unfortunately, overlays are not a completely transparent way to adapt a
10821 program to limited instruction memory. They introduce a new set of
10822 global constraints you must keep in mind as you design your program:
10823
10824 @itemize @bullet
10825
10826 @item
10827 Before calling or returning to a function in an overlay, your program
10828 must make sure that overlay is actually mapped. Otherwise, the call or
10829 return will transfer control to the right address, but in the wrong
10830 overlay, and your program will probably crash.
10831
10832 @item
10833 If the process of mapping an overlay is expensive on your system, you
10834 will need to choose your overlays carefully to minimize their effect on
10835 your program's performance.
10836
10837 @item
10838 The executable file you load onto your system must contain each
10839 overlay's instructions, appearing at the overlay's load address, not its
10840 mapped address. However, each overlay's instructions must be relocated
10841 and its symbols defined as if the overlay were at its mapped address.
10842 You can use GNU linker scripts to specify different load and relocation
10843 addresses for pieces of your program; see @ref{Overlay Description,,,
10844 ld.info, Using ld: the GNU linker}.
10845
10846 @item
10847 The procedure for loading executable files onto your system must be able
10848 to load their contents into the larger address space as well as the
10849 instruction and data spaces.
10850
10851 @end itemize
10852
10853 The overlay system described above is rather simple, and could be
10854 improved in many ways:
10855
10856 @itemize @bullet
10857
10858 @item
10859 If your system has suitable bank switch registers or memory management
10860 hardware, you could use those facilities to make an overlay's load area
10861 contents simply appear at their mapped address in instruction space.
10862 This would probably be faster than copying the overlay to its mapped
10863 area in the usual way.
10864
10865 @item
10866 If your overlays are small enough, you could set aside more than one
10867 overlay area, and have more than one overlay mapped at a time.
10868
10869 @item
10870 You can use overlays to manage data, as well as instructions. In
10871 general, data overlays are even less transparent to your design than
10872 code overlays: whereas code overlays only require care when you call or
10873 return to functions, data overlays require care every time you access
10874 the data. Also, if you change the contents of a data overlay, you
10875 must copy its contents back out to its load address before you can copy a
10876 different data overlay into the same mapped area.
10877
10878 @end itemize
10879
10880
10881 @node Overlay Commands
10882 @section Overlay Commands
10883
10884 To use @value{GDBN}'s overlay support, each overlay in your program must
10885 correspond to a separate section of the executable file. The section's
10886 virtual memory address and load memory address must be the overlay's
10887 mapped and load addresses. Identifying overlays with sections allows
10888 @value{GDBN} to determine the appropriate address of a function or
10889 variable, depending on whether the overlay is mapped or not.
10890
10891 @value{GDBN}'s overlay commands all start with the word @code{overlay};
10892 you can abbreviate this as @code{ov} or @code{ovly}. The commands are:
10893
10894 @table @code
10895 @item overlay off
10896 @kindex overlay
10897 Disable @value{GDBN}'s overlay support. When overlay support is
10898 disabled, @value{GDBN} assumes that all functions and variables are
10899 always present at their mapped addresses. By default, @value{GDBN}'s
10900 overlay support is disabled.
10901
10902 @item overlay manual
10903 @cindex manual overlay debugging
10904 Enable @dfn{manual} overlay debugging. In this mode, @value{GDBN}
10905 relies on you to tell it which overlays are mapped, and which are not,
10906 using the @code{overlay map-overlay} and @code{overlay unmap-overlay}
10907 commands described below.
10908
10909 @item overlay map-overlay @var{overlay}
10910 @itemx overlay map @var{overlay}
10911 @cindex map an overlay
10912 Tell @value{GDBN} that @var{overlay} is now mapped; @var{overlay} must
10913 be the name of the object file section containing the overlay. When an
10914 overlay is mapped, @value{GDBN} assumes it can find the overlay's
10915 functions and variables at their mapped addresses. @value{GDBN} assumes
10916 that any other overlays whose mapped ranges overlap that of
10917 @var{overlay} are now unmapped.
10918
10919 @item overlay unmap-overlay @var{overlay}
10920 @itemx overlay unmap @var{overlay}
10921 @cindex unmap an overlay
10922 Tell @value{GDBN} that @var{overlay} is no longer mapped; @var{overlay}
10923 must be the name of the object file section containing the overlay.
10924 When an overlay is unmapped, @value{GDBN} assumes it can find the
10925 overlay's functions and variables at their load addresses.
10926
10927 @item overlay auto
10928 Enable @dfn{automatic} overlay debugging. In this mode, @value{GDBN}
10929 consults a data structure the overlay manager maintains in the inferior
10930 to see which overlays are mapped. For details, see @ref{Automatic
10931 Overlay Debugging}.
10932
10933 @item overlay load-target
10934 @itemx overlay load
10935 @cindex reloading the overlay table
10936 Re-read the overlay table from the inferior. Normally, @value{GDBN}
10937 re-reads the table @value{GDBN} automatically each time the inferior
10938 stops, so this command should only be necessary if you have changed the
10939 overlay mapping yourself using @value{GDBN}. This command is only
10940 useful when using automatic overlay debugging.
10941
10942 @item overlay list-overlays
10943 @itemx overlay list
10944 @cindex listing mapped overlays
10945 Display a list of the overlays currently mapped, along with their mapped
10946 addresses, load addresses, and sizes.
10947
10948 @end table
10949
10950 Normally, when @value{GDBN} prints a code address, it includes the name
10951 of the function the address falls in:
10952
10953 @smallexample
10954 (@value{GDBP}) print main
10955 $3 = @{int ()@} 0x11a0 <main>
10956 @end smallexample
10957 @noindent
10958 When overlay debugging is enabled, @value{GDBN} recognizes code in
10959 unmapped overlays, and prints the names of unmapped functions with
10960 asterisks around them. For example, if @code{foo} is a function in an
10961 unmapped overlay, @value{GDBN} prints it this way:
10962
10963 @smallexample
10964 (@value{GDBP}) overlay list
10965 No sections are mapped.
10966 (@value{GDBP}) print foo
10967 $5 = @{int (int)@} 0x100000 <*foo*>
10968 @end smallexample
10969 @noindent
10970 When @code{foo}'s overlay is mapped, @value{GDBN} prints the function's
10971 name normally:
10972
10973 @smallexample
10974 (@value{GDBP}) overlay list
10975 Section .ov.foo.text, loaded at 0x100000 - 0x100034,
10976 mapped at 0x1016 - 0x104a
10977 (@value{GDBP}) print foo
10978 $6 = @{int (int)@} 0x1016 <foo>
10979 @end smallexample
10980
10981 When overlay debugging is enabled, @value{GDBN} can find the correct
10982 address for functions and variables in an overlay, whether or not the
10983 overlay is mapped. This allows most @value{GDBN} commands, like
10984 @code{break} and @code{disassemble}, to work normally, even on unmapped
10985 code. However, @value{GDBN}'s breakpoint support has some limitations:
10986
10987 @itemize @bullet
10988 @item
10989 @cindex breakpoints in overlays
10990 @cindex overlays, setting breakpoints in
10991 You can set breakpoints in functions in unmapped overlays, as long as
10992 @value{GDBN} can write to the overlay at its load address.
10993 @item
10994 @value{GDBN} can not set hardware or simulator-based breakpoints in
10995 unmapped overlays. However, if you set a breakpoint at the end of your
10996 overlay manager (and tell @value{GDBN} which overlays are now mapped, if
10997 you are using manual overlay management), @value{GDBN} will re-set its
10998 breakpoints properly.
10999 @end itemize
11000
11001
11002 @node Automatic Overlay Debugging
11003 @section Automatic Overlay Debugging
11004 @cindex automatic overlay debugging
11005
11006 @value{GDBN} can automatically track which overlays are mapped and which
11007 are not, given some simple co-operation from the overlay manager in the
11008 inferior. If you enable automatic overlay debugging with the
11009 @code{overlay auto} command (@pxref{Overlay Commands}), @value{GDBN}
11010 looks in the inferior's memory for certain variables describing the
11011 current state of the overlays.
11012
11013 Here are the variables your overlay manager must define to support
11014 @value{GDBN}'s automatic overlay debugging:
11015
11016 @table @asis
11017
11018 @item @code{_ovly_table}:
11019 This variable must be an array of the following structures:
11020
11021 @smallexample
11022 struct
11023 @{
11024 /* The overlay's mapped address. */
11025 unsigned long vma;
11026
11027 /* The size of the overlay, in bytes. */
11028 unsigned long size;
11029
11030 /* The overlay's load address. */
11031 unsigned long lma;
11032
11033 /* Non-zero if the overlay is currently mapped;
11034 zero otherwise. */
11035 unsigned long mapped;
11036 @}
11037 @end smallexample
11038
11039 @item @code{_novlys}:
11040 This variable must be a four-byte signed integer, holding the total
11041 number of elements in @code{_ovly_table}.
11042
11043 @end table
11044
11045 To decide whether a particular overlay is mapped or not, @value{GDBN}
11046 looks for an entry in @w{@code{_ovly_table}} whose @code{vma} and
11047 @code{lma} members equal the VMA and LMA of the overlay's section in the
11048 executable file. When @value{GDBN} finds a matching entry, it consults
11049 the entry's @code{mapped} member to determine whether the overlay is
11050 currently mapped.
11051
11052 In addition, your overlay manager may define a function called
11053 @code{_ovly_debug_event}. If this function is defined, @value{GDBN}
11054 will silently set a breakpoint there. If the overlay manager then
11055 calls this function whenever it has changed the overlay table, this
11056 will enable @value{GDBN} to accurately keep track of which overlays
11057 are in program memory, and update any breakpoints that may be set
11058 in overlays. This will allow breakpoints to work even if the
11059 overlays are kept in ROM or other non-writable memory while they
11060 are not being executed.
11061
11062 @node Overlay Sample Program
11063 @section Overlay Sample Program
11064 @cindex overlay example program
11065
11066 When linking a program which uses overlays, you must place the overlays
11067 at their load addresses, while relocating them to run at their mapped
11068 addresses. To do this, you must write a linker script (@pxref{Overlay
11069 Description,,, ld.info, Using ld: the GNU linker}). Unfortunately,
11070 since linker scripts are specific to a particular host system, target
11071 architecture, and target memory layout, this manual cannot provide
11072 portable sample code demonstrating @value{GDBN}'s overlay support.
11073
11074 However, the @value{GDBN} source distribution does contain an overlaid
11075 program, with linker scripts for a few systems, as part of its test
11076 suite. The program consists of the following files from
11077 @file{gdb/testsuite/gdb.base}:
11078
11079 @table @file
11080 @item overlays.c
11081 The main program file.
11082 @item ovlymgr.c
11083 A simple overlay manager, used by @file{overlays.c}.
11084 @item foo.c
11085 @itemx bar.c
11086 @itemx baz.c
11087 @itemx grbx.c
11088 Overlay modules, loaded and used by @file{overlays.c}.
11089 @item d10v.ld
11090 @itemx m32r.ld
11091 Linker scripts for linking the test program on the @code{d10v-elf}
11092 and @code{m32r-elf} targets.
11093 @end table
11094
11095 You can build the test program using the @code{d10v-elf} GCC
11096 cross-compiler like this:
11097
11098 @smallexample
11099 $ d10v-elf-gcc -g -c overlays.c
11100 $ d10v-elf-gcc -g -c ovlymgr.c
11101 $ d10v-elf-gcc -g -c foo.c
11102 $ d10v-elf-gcc -g -c bar.c
11103 $ d10v-elf-gcc -g -c baz.c
11104 $ d10v-elf-gcc -g -c grbx.c
11105 $ d10v-elf-gcc -g overlays.o ovlymgr.o foo.o bar.o \
11106 baz.o grbx.o -Wl,-Td10v.ld -o overlays
11107 @end smallexample
11108
11109 The build process is identical for any other architecture, except that
11110 you must substitute the appropriate compiler and linker script for the
11111 target system for @code{d10v-elf-gcc} and @code{d10v.ld}.
11112
11113
11114 @node Languages
11115 @chapter Using @value{GDBN} with Different Languages
11116 @cindex languages
11117
11118 Although programming languages generally have common aspects, they are
11119 rarely expressed in the same manner. For instance, in ANSI C,
11120 dereferencing a pointer @code{p} is accomplished by @code{*p}, but in
11121 Modula-2, it is accomplished by @code{p^}. Values can also be
11122 represented (and displayed) differently. Hex numbers in C appear as
11123 @samp{0x1ae}, while in Modula-2 they appear as @samp{1AEH}.
11124
11125 @cindex working language
11126 Language-specific information is built into @value{GDBN} for some languages,
11127 allowing you to express operations like the above in your program's
11128 native language, and allowing @value{GDBN} to output values in a manner
11129 consistent with the syntax of your program's native language. The
11130 language you use to build expressions is called the @dfn{working
11131 language}.
11132
11133 @menu
11134 * Setting:: Switching between source languages
11135 * Show:: Displaying the language
11136 * Checks:: Type and range checks
11137 * Supported Languages:: Supported languages
11138 * Unsupported Languages:: Unsupported languages
11139 @end menu
11140
11141 @node Setting
11142 @section Switching Between Source Languages
11143
11144 There are two ways to control the working language---either have @value{GDBN}
11145 set it automatically, or select it manually yourself. You can use the
11146 @code{set language} command for either purpose. On startup, @value{GDBN}
11147 defaults to setting the language automatically. The working language is
11148 used to determine how expressions you type are interpreted, how values
11149 are printed, etc.
11150
11151 In addition to the working language, every source file that
11152 @value{GDBN} knows about has its own working language. For some object
11153 file formats, the compiler might indicate which language a particular
11154 source file is in. However, most of the time @value{GDBN} infers the
11155 language from the name of the file. The language of a source file
11156 controls whether C@t{++} names are demangled---this way @code{backtrace} can
11157 show each frame appropriately for its own language. There is no way to
11158 set the language of a source file from within @value{GDBN}, but you can
11159 set the language associated with a filename extension. @xref{Show, ,
11160 Displaying the Language}.
11161
11162 This is most commonly a problem when you use a program, such
11163 as @code{cfront} or @code{f2c}, that generates C but is written in
11164 another language. In that case, make the
11165 program use @code{#line} directives in its C output; that way
11166 @value{GDBN} will know the correct language of the source code of the original
11167 program, and will display that source code, not the generated C code.
11168
11169 @menu
11170 * Filenames:: Filename extensions and languages.
11171 * Manually:: Setting the working language manually
11172 * Automatically:: Having @value{GDBN} infer the source language
11173 @end menu
11174
11175 @node Filenames
11176 @subsection List of Filename Extensions and Languages
11177
11178 If a source file name ends in one of the following extensions, then
11179 @value{GDBN} infers that its language is the one indicated.
11180
11181 @table @file
11182 @item .ada
11183 @itemx .ads
11184 @itemx .adb
11185 @itemx .a
11186 Ada source file.
11187
11188 @item .c
11189 C source file
11190
11191 @item .C
11192 @itemx .cc
11193 @itemx .cp
11194 @itemx .cpp
11195 @itemx .cxx
11196 @itemx .c++
11197 C@t{++} source file
11198
11199 @item .d
11200 D source file
11201
11202 @item .m
11203 Objective-C source file
11204
11205 @item .f
11206 @itemx .F
11207 Fortran source file
11208
11209 @item .mod
11210 Modula-2 source file
11211
11212 @item .s
11213 @itemx .S
11214 Assembler source file. This actually behaves almost like C, but
11215 @value{GDBN} does not skip over function prologues when stepping.
11216 @end table
11217
11218 In addition, you may set the language associated with a filename
11219 extension. @xref{Show, , Displaying the Language}.
11220
11221 @node Manually
11222 @subsection Setting the Working Language
11223
11224 If you allow @value{GDBN} to set the language automatically,
11225 expressions are interpreted the same way in your debugging session and
11226 your program.
11227
11228 @kindex set language
11229 If you wish, you may set the language manually. To do this, issue the
11230 command @samp{set language @var{lang}}, where @var{lang} is the name of
11231 a language, such as
11232 @code{c} or @code{modula-2}.
11233 For a list of the supported languages, type @samp{set language}.
11234
11235 Setting the language manually prevents @value{GDBN} from updating the working
11236 language automatically. This can lead to confusion if you try
11237 to debug a program when the working language is not the same as the
11238 source language, when an expression is acceptable to both
11239 languages---but means different things. For instance, if the current
11240 source file were written in C, and @value{GDBN} was parsing Modula-2, a
11241 command such as:
11242
11243 @smallexample
11244 print a = b + c
11245 @end smallexample
11246
11247 @noindent
11248 might not have the effect you intended. In C, this means to add
11249 @code{b} and @code{c} and place the result in @code{a}. The result
11250 printed would be the value of @code{a}. In Modula-2, this means to compare
11251 @code{a} to the result of @code{b+c}, yielding a @code{BOOLEAN} value.
11252
11253 @node Automatically
11254 @subsection Having @value{GDBN} Infer the Source Language
11255
11256 To have @value{GDBN} set the working language automatically, use
11257 @samp{set language local} or @samp{set language auto}. @value{GDBN}
11258 then infers the working language. That is, when your program stops in a
11259 frame (usually by encountering a breakpoint), @value{GDBN} sets the
11260 working language to the language recorded for the function in that
11261 frame. If the language for a frame is unknown (that is, if the function
11262 or block corresponding to the frame was defined in a source file that
11263 does not have a recognized extension), the current working language is
11264 not changed, and @value{GDBN} issues a warning.
11265
11266 This may not seem necessary for most programs, which are written
11267 entirely in one source language. However, program modules and libraries
11268 written in one source language can be used by a main program written in
11269 a different source language. Using @samp{set language auto} in this
11270 case frees you from having to set the working language manually.
11271
11272 @node Show
11273 @section Displaying the Language
11274
11275 The following commands help you find out which language is the
11276 working language, and also what language source files were written in.
11277
11278 @table @code
11279 @item show language
11280 @kindex show language
11281 Display the current working language. This is the
11282 language you can use with commands such as @code{print} to
11283 build and compute expressions that may involve variables in your program.
11284
11285 @item info frame
11286 @kindex info frame@r{, show the source language}
11287 Display the source language for this frame. This language becomes the
11288 working language if you use an identifier from this frame.
11289 @xref{Frame Info, ,Information about a Frame}, to identify the other
11290 information listed here.
11291
11292 @item info source
11293 @kindex info source@r{, show the source language}
11294 Display the source language of this source file.
11295 @xref{Symbols, ,Examining the Symbol Table}, to identify the other
11296 information listed here.
11297 @end table
11298
11299 In unusual circumstances, you may have source files with extensions
11300 not in the standard list. You can then set the extension associated
11301 with a language explicitly:
11302
11303 @table @code
11304 @item set extension-language @var{ext} @var{language}
11305 @kindex set extension-language
11306 Tell @value{GDBN} that source files with extension @var{ext} are to be
11307 assumed as written in the source language @var{language}.
11308
11309 @item info extensions
11310 @kindex info extensions
11311 List all the filename extensions and the associated languages.
11312 @end table
11313
11314 @node Checks
11315 @section Type and Range Checking
11316
11317 @quotation
11318 @emph{Warning:} In this release, the @value{GDBN} commands for type and range
11319 checking are included, but they do not yet have any effect. This
11320 section documents the intended facilities.
11321 @end quotation
11322 @c FIXME remove warning when type/range code added
11323
11324 Some languages are designed to guard you against making seemingly common
11325 errors through a series of compile- and run-time checks. These include
11326 checking the type of arguments to functions and operators, and making
11327 sure mathematical overflows are caught at run time. Checks such as
11328 these help to ensure a program's correctness once it has been compiled
11329 by eliminating type mismatches, and providing active checks for range
11330 errors when your program is running.
11331
11332 @value{GDBN} can check for conditions like the above if you wish.
11333 Although @value{GDBN} does not check the statements in your program,
11334 it can check expressions entered directly into @value{GDBN} for
11335 evaluation via the @code{print} command, for example. As with the
11336 working language, @value{GDBN} can also decide whether or not to check
11337 automatically based on your program's source language.
11338 @xref{Supported Languages, ,Supported Languages}, for the default
11339 settings of supported languages.
11340
11341 @menu
11342 * Type Checking:: An overview of type checking
11343 * Range Checking:: An overview of range checking
11344 @end menu
11345
11346 @cindex type checking
11347 @cindex checks, type
11348 @node Type Checking
11349 @subsection An Overview of Type Checking
11350
11351 Some languages, such as Modula-2, are strongly typed, meaning that the
11352 arguments to operators and functions have to be of the correct type,
11353 otherwise an error occurs. These checks prevent type mismatch
11354 errors from ever causing any run-time problems. For example,
11355
11356 @smallexample
11357 1 + 2 @result{} 3
11358 @exdent but
11359 @error{} 1 + 2.3
11360 @end smallexample
11361
11362 The second example fails because the @code{CARDINAL} 1 is not
11363 type-compatible with the @code{REAL} 2.3.
11364
11365 For the expressions you use in @value{GDBN} commands, you can tell the
11366 @value{GDBN} type checker to skip checking;
11367 to treat any mismatches as errors and abandon the expression;
11368 or to only issue warnings when type mismatches occur,
11369 but evaluate the expression anyway. When you choose the last of
11370 these, @value{GDBN} evaluates expressions like the second example above, but
11371 also issues a warning.
11372
11373 Even if you turn type checking off, there may be other reasons
11374 related to type that prevent @value{GDBN} from evaluating an expression.
11375 For instance, @value{GDBN} does not know how to add an @code{int} and
11376 a @code{struct foo}. These particular type errors have nothing to do
11377 with the language in use, and usually arise from expressions, such as
11378 the one described above, which make little sense to evaluate anyway.
11379
11380 Each language defines to what degree it is strict about type. For
11381 instance, both Modula-2 and C require the arguments to arithmetical
11382 operators to be numbers. In C, enumerated types and pointers can be
11383 represented as numbers, so that they are valid arguments to mathematical
11384 operators. @xref{Supported Languages, ,Supported Languages}, for further
11385 details on specific languages.
11386
11387 @value{GDBN} provides some additional commands for controlling the type checker:
11388
11389 @kindex set check type
11390 @kindex show check type
11391 @table @code
11392 @item set check type auto
11393 Set type checking on or off based on the current working language.
11394 @xref{Supported Languages, ,Supported Languages}, for the default settings for
11395 each language.
11396
11397 @item set check type on
11398 @itemx set check type off
11399 Set type checking on or off, overriding the default setting for the
11400 current working language. Issue a warning if the setting does not
11401 match the language default. If any type mismatches occur in
11402 evaluating an expression while type checking is on, @value{GDBN} prints a
11403 message and aborts evaluation of the expression.
11404
11405 @item set check type warn
11406 Cause the type checker to issue warnings, but to always attempt to
11407 evaluate the expression. Evaluating the expression may still
11408 be impossible for other reasons. For example, @value{GDBN} cannot add
11409 numbers and structures.
11410
11411 @item show type
11412 Show the current setting of the type checker, and whether or not @value{GDBN}
11413 is setting it automatically.
11414 @end table
11415
11416 @cindex range checking
11417 @cindex checks, range
11418 @node Range Checking
11419 @subsection An Overview of Range Checking
11420
11421 In some languages (such as Modula-2), it is an error to exceed the
11422 bounds of a type; this is enforced with run-time checks. Such range
11423 checking is meant to ensure program correctness by making sure
11424 computations do not overflow, or indices on an array element access do
11425 not exceed the bounds of the array.
11426
11427 For expressions you use in @value{GDBN} commands, you can tell
11428 @value{GDBN} to treat range errors in one of three ways: ignore them,
11429 always treat them as errors and abandon the expression, or issue
11430 warnings but evaluate the expression anyway.
11431
11432 A range error can result from numerical overflow, from exceeding an
11433 array index bound, or when you type a constant that is not a member
11434 of any type. Some languages, however, do not treat overflows as an
11435 error. In many implementations of C, mathematical overflow causes the
11436 result to ``wrap around'' to lower values---for example, if @var{m} is
11437 the largest integer value, and @var{s} is the smallest, then
11438
11439 @smallexample
11440 @var{m} + 1 @result{} @var{s}
11441 @end smallexample
11442
11443 This, too, is specific to individual languages, and in some cases
11444 specific to individual compilers or machines. @xref{Supported Languages, ,
11445 Supported Languages}, for further details on specific languages.
11446
11447 @value{GDBN} provides some additional commands for controlling the range checker:
11448
11449 @kindex set check range
11450 @kindex show check range
11451 @table @code
11452 @item set check range auto
11453 Set range checking on or off based on the current working language.
11454 @xref{Supported Languages, ,Supported Languages}, for the default settings for
11455 each language.
11456
11457 @item set check range on
11458 @itemx set check range off
11459 Set range checking on or off, overriding the default setting for the
11460 current working language. A warning is issued if the setting does not
11461 match the language default. If a range error occurs and range checking is on,
11462 then a message is printed and evaluation of the expression is aborted.
11463
11464 @item set check range warn
11465 Output messages when the @value{GDBN} range checker detects a range error,
11466 but attempt to evaluate the expression anyway. Evaluating the
11467 expression may still be impossible for other reasons, such as accessing
11468 memory that the process does not own (a typical example from many Unix
11469 systems).
11470
11471 @item show range
11472 Show the current setting of the range checker, and whether or not it is
11473 being set automatically by @value{GDBN}.
11474 @end table
11475
11476 @node Supported Languages
11477 @section Supported Languages
11478
11479 @value{GDBN} supports C, C@t{++}, D, Objective-C, Fortran, Java, Pascal,
11480 assembly, Modula-2, and Ada.
11481 @c This is false ...
11482 Some @value{GDBN} features may be used in expressions regardless of the
11483 language you use: the @value{GDBN} @code{@@} and @code{::} operators,
11484 and the @samp{@{type@}addr} construct (@pxref{Expressions,
11485 ,Expressions}) can be used with the constructs of any supported
11486 language.
11487
11488 The following sections detail to what degree each source language is
11489 supported by @value{GDBN}. These sections are not meant to be language
11490 tutorials or references, but serve only as a reference guide to what the
11491 @value{GDBN} expression parser accepts, and what input and output
11492 formats should look like for different languages. There are many good
11493 books written on each of these languages; please look to these for a
11494 language reference or tutorial.
11495
11496 @menu
11497 * C:: C and C@t{++}
11498 * D:: D
11499 * Objective-C:: Objective-C
11500 * Fortran:: Fortran
11501 * Pascal:: Pascal
11502 * Modula-2:: Modula-2
11503 * Ada:: Ada
11504 @end menu
11505
11506 @node C
11507 @subsection C and C@t{++}
11508
11509 @cindex C and C@t{++}
11510 @cindex expressions in C or C@t{++}
11511
11512 Since C and C@t{++} are so closely related, many features of @value{GDBN} apply
11513 to both languages. Whenever this is the case, we discuss those languages
11514 together.
11515
11516 @cindex C@t{++}
11517 @cindex @code{g++}, @sc{gnu} C@t{++} compiler
11518 @cindex @sc{gnu} C@t{++}
11519 The C@t{++} debugging facilities are jointly implemented by the C@t{++}
11520 compiler and @value{GDBN}. Therefore, to debug your C@t{++} code
11521 effectively, you must compile your C@t{++} programs with a supported
11522 C@t{++} compiler, such as @sc{gnu} @code{g++}, or the HP ANSI C@t{++}
11523 compiler (@code{aCC}).
11524
11525 For best results when using @sc{gnu} C@t{++}, use the DWARF 2 debugging
11526 format; if it doesn't work on your system, try the stabs+ debugging
11527 format. You can select those formats explicitly with the @code{g++}
11528 command-line options @option{-gdwarf-2} and @option{-gstabs+}.
11529 @xref{Debugging Options,,Options for Debugging Your Program or GCC,
11530 gcc.info, Using the @sc{gnu} Compiler Collection (GCC)}.
11531
11532 @menu
11533 * C Operators:: C and C@t{++} operators
11534 * C Constants:: C and C@t{++} constants
11535 * C Plus Plus Expressions:: C@t{++} expressions
11536 * C Defaults:: Default settings for C and C@t{++}
11537 * C Checks:: C and C@t{++} type and range checks
11538 * Debugging C:: @value{GDBN} and C
11539 * Debugging C Plus Plus:: @value{GDBN} features for C@t{++}
11540 * Decimal Floating Point:: Numbers in Decimal Floating Point format
11541 @end menu
11542
11543 @node C Operators
11544 @subsubsection C and C@t{++} Operators
11545
11546 @cindex C and C@t{++} operators
11547
11548 Operators must be defined on values of specific types. For instance,
11549 @code{+} is defined on numbers, but not on structures. Operators are
11550 often defined on groups of types.
11551
11552 For the purposes of C and C@t{++}, the following definitions hold:
11553
11554 @itemize @bullet
11555
11556 @item
11557 @emph{Integral types} include @code{int} with any of its storage-class
11558 specifiers; @code{char}; @code{enum}; and, for C@t{++}, @code{bool}.
11559
11560 @item
11561 @emph{Floating-point types} include @code{float}, @code{double}, and
11562 @code{long double} (if supported by the target platform).
11563
11564 @item
11565 @emph{Pointer types} include all types defined as @code{(@var{type} *)}.
11566
11567 @item
11568 @emph{Scalar types} include all of the above.
11569
11570 @end itemize
11571
11572 @noindent
11573 The following operators are supported. They are listed here
11574 in order of increasing precedence:
11575
11576 @table @code
11577 @item ,
11578 The comma or sequencing operator. Expressions in a comma-separated list
11579 are evaluated from left to right, with the result of the entire
11580 expression being the last expression evaluated.
11581
11582 @item =
11583 Assignment. The value of an assignment expression is the value
11584 assigned. Defined on scalar types.
11585
11586 @item @var{op}=
11587 Used in an expression of the form @w{@code{@var{a} @var{op}= @var{b}}},
11588 and translated to @w{@code{@var{a} = @var{a op b}}}.
11589 @w{@code{@var{op}=}} and @code{=} have the same precedence.
11590 @var{op} is any one of the operators @code{|}, @code{^}, @code{&},
11591 @code{<<}, @code{>>}, @code{+}, @code{-}, @code{*}, @code{/}, @code{%}.
11592
11593 @item ?:
11594 The ternary operator. @code{@var{a} ? @var{b} : @var{c}} can be thought
11595 of as: if @var{a} then @var{b} else @var{c}. @var{a} should be of an
11596 integral type.
11597
11598 @item ||
11599 Logical @sc{or}. Defined on integral types.
11600
11601 @item &&
11602 Logical @sc{and}. Defined on integral types.
11603
11604 @item |
11605 Bitwise @sc{or}. Defined on integral types.
11606
11607 @item ^
11608 Bitwise exclusive-@sc{or}. Defined on integral types.
11609
11610 @item &
11611 Bitwise @sc{and}. Defined on integral types.
11612
11613 @item ==@r{, }!=
11614 Equality and inequality. Defined on scalar types. The value of these
11615 expressions is 0 for false and non-zero for true.
11616
11617 @item <@r{, }>@r{, }<=@r{, }>=
11618 Less than, greater than, less than or equal, greater than or equal.
11619 Defined on scalar types. The value of these expressions is 0 for false
11620 and non-zero for true.
11621
11622 @item <<@r{, }>>
11623 left shift, and right shift. Defined on integral types.
11624
11625 @item @@
11626 The @value{GDBN} ``artificial array'' operator (@pxref{Expressions, ,Expressions}).
11627
11628 @item +@r{, }-
11629 Addition and subtraction. Defined on integral types, floating-point types and
11630 pointer types.
11631
11632 @item *@r{, }/@r{, }%
11633 Multiplication, division, and modulus. Multiplication and division are
11634 defined on integral and floating-point types. Modulus is defined on
11635 integral types.
11636
11637 @item ++@r{, }--
11638 Increment and decrement. When appearing before a variable, the
11639 operation is performed before the variable is used in an expression;
11640 when appearing after it, the variable's value is used before the
11641 operation takes place.
11642
11643 @item *
11644 Pointer dereferencing. Defined on pointer types. Same precedence as
11645 @code{++}.
11646
11647 @item &
11648 Address operator. Defined on variables. Same precedence as @code{++}.
11649
11650 For debugging C@t{++}, @value{GDBN} implements a use of @samp{&} beyond what is
11651 allowed in the C@t{++} language itself: you can use @samp{&(&@var{ref})}
11652 to examine the address
11653 where a C@t{++} reference variable (declared with @samp{&@var{ref}}) is
11654 stored.
11655
11656 @item -
11657 Negative. Defined on integral and floating-point types. Same
11658 precedence as @code{++}.
11659
11660 @item !
11661 Logical negation. Defined on integral types. Same precedence as
11662 @code{++}.
11663
11664 @item ~
11665 Bitwise complement operator. Defined on integral types. Same precedence as
11666 @code{++}.
11667
11668
11669 @item .@r{, }->
11670 Structure member, and pointer-to-structure member. For convenience,
11671 @value{GDBN} regards the two as equivalent, choosing whether to dereference a
11672 pointer based on the stored type information.
11673 Defined on @code{struct} and @code{union} data.
11674
11675 @item .*@r{, }->*
11676 Dereferences of pointers to members.
11677
11678 @item []
11679 Array indexing. @code{@var{a}[@var{i}]} is defined as
11680 @code{*(@var{a}+@var{i})}. Same precedence as @code{->}.
11681
11682 @item ()
11683 Function parameter list. Same precedence as @code{->}.
11684
11685 @item ::
11686 C@t{++} scope resolution operator. Defined on @code{struct}, @code{union},
11687 and @code{class} types.
11688
11689 @item ::
11690 Doubled colons also represent the @value{GDBN} scope operator
11691 (@pxref{Expressions, ,Expressions}). Same precedence as @code{::},
11692 above.
11693 @end table
11694
11695 If an operator is redefined in the user code, @value{GDBN} usually
11696 attempts to invoke the redefined version instead of using the operator's
11697 predefined meaning.
11698
11699 @node C Constants
11700 @subsubsection C and C@t{++} Constants
11701
11702 @cindex C and C@t{++} constants
11703
11704 @value{GDBN} allows you to express the constants of C and C@t{++} in the
11705 following ways:
11706
11707 @itemize @bullet
11708 @item
11709 Integer constants are a sequence of digits. Octal constants are
11710 specified by a leading @samp{0} (i.e.@: zero), and hexadecimal constants
11711 by a leading @samp{0x} or @samp{0X}. Constants may also end with a letter
11712 @samp{l}, specifying that the constant should be treated as a
11713 @code{long} value.
11714
11715 @item
11716 Floating point constants are a sequence of digits, followed by a decimal
11717 point, followed by a sequence of digits, and optionally followed by an
11718 exponent. An exponent is of the form:
11719 @samp{@w{e@r{[[}+@r{]|}-@r{]}@var{nnn}}}, where @var{nnn} is another
11720 sequence of digits. The @samp{+} is optional for positive exponents.
11721 A floating-point constant may also end with a letter @samp{f} or
11722 @samp{F}, specifying that the constant should be treated as being of
11723 the @code{float} (as opposed to the default @code{double}) type; or with
11724 a letter @samp{l} or @samp{L}, which specifies a @code{long double}
11725 constant.
11726
11727 @item
11728 Enumerated constants consist of enumerated identifiers, or their
11729 integral equivalents.
11730
11731 @item
11732 Character constants are a single character surrounded by single quotes
11733 (@code{'}), or a number---the ordinal value of the corresponding character
11734 (usually its @sc{ascii} value). Within quotes, the single character may
11735 be represented by a letter or by @dfn{escape sequences}, which are of
11736 the form @samp{\@var{nnn}}, where @var{nnn} is the octal representation
11737 of the character's ordinal value; or of the form @samp{\@var{x}}, where
11738 @samp{@var{x}} is a predefined special character---for example,
11739 @samp{\n} for newline.
11740
11741 @item
11742 String constants are a sequence of character constants surrounded by
11743 double quotes (@code{"}). Any valid character constant (as described
11744 above) may appear. Double quotes within the string must be preceded by
11745 a backslash, so for instance @samp{"a\"b'c"} is a string of five
11746 characters.
11747
11748 @item
11749 Pointer constants are an integral value. You can also write pointers
11750 to constants using the C operator @samp{&}.
11751
11752 @item
11753 Array constants are comma-separated lists surrounded by braces @samp{@{}
11754 and @samp{@}}; for example, @samp{@{1,2,3@}} is a three-element array of
11755 integers, @samp{@{@{1,2@}, @{3,4@}, @{5,6@}@}} is a three-by-two array,
11756 and @samp{@{&"hi", &"there", &"fred"@}} is a three-element array of pointers.
11757 @end itemize
11758
11759 @node C Plus Plus Expressions
11760 @subsubsection C@t{++} Expressions
11761
11762 @cindex expressions in C@t{++}
11763 @value{GDBN} expression handling can interpret most C@t{++} expressions.
11764
11765 @cindex debugging C@t{++} programs
11766 @cindex C@t{++} compilers
11767 @cindex debug formats and C@t{++}
11768 @cindex @value{NGCC} and C@t{++}
11769 @quotation
11770 @emph{Warning:} @value{GDBN} can only debug C@t{++} code if you use the
11771 proper compiler and the proper debug format. Currently, @value{GDBN}
11772 works best when debugging C@t{++} code that is compiled with
11773 @value{NGCC} 2.95.3 or with @value{NGCC} 3.1 or newer, using the options
11774 @option{-gdwarf-2} or @option{-gstabs+}. DWARF 2 is preferred over
11775 stabs+. Most configurations of @value{NGCC} emit either DWARF 2 or
11776 stabs+ as their default debug format, so you usually don't need to
11777 specify a debug format explicitly. Other compilers and/or debug formats
11778 are likely to work badly or not at all when using @value{GDBN} to debug
11779 C@t{++} code.
11780 @end quotation
11781
11782 @enumerate
11783
11784 @cindex member functions
11785 @item
11786 Member function calls are allowed; you can use expressions like
11787
11788 @smallexample
11789 count = aml->GetOriginal(x, y)
11790 @end smallexample
11791
11792 @vindex this@r{, inside C@t{++} member functions}
11793 @cindex namespace in C@t{++}
11794 @item
11795 While a member function is active (in the selected stack frame), your
11796 expressions have the same namespace available as the member function;
11797 that is, @value{GDBN} allows implicit references to the class instance
11798 pointer @code{this} following the same rules as C@t{++}.
11799
11800 @cindex call overloaded functions
11801 @cindex overloaded functions, calling
11802 @cindex type conversions in C@t{++}
11803 @item
11804 You can call overloaded functions; @value{GDBN} resolves the function
11805 call to the right definition, with some restrictions. @value{GDBN} does not
11806 perform overload resolution involving user-defined type conversions,
11807 calls to constructors, or instantiations of templates that do not exist
11808 in the program. It also cannot handle ellipsis argument lists or
11809 default arguments.
11810
11811 It does perform integral conversions and promotions, floating-point
11812 promotions, arithmetic conversions, pointer conversions, conversions of
11813 class objects to base classes, and standard conversions such as those of
11814 functions or arrays to pointers; it requires an exact match on the
11815 number of function arguments.
11816
11817 Overload resolution is always performed, unless you have specified
11818 @code{set overload-resolution off}. @xref{Debugging C Plus Plus,
11819 ,@value{GDBN} Features for C@t{++}}.
11820
11821 You must specify @code{set overload-resolution off} in order to use an
11822 explicit function signature to call an overloaded function, as in
11823 @smallexample
11824 p 'foo(char,int)'('x', 13)
11825 @end smallexample
11826
11827 The @value{GDBN} command-completion facility can simplify this;
11828 see @ref{Completion, ,Command Completion}.
11829
11830 @cindex reference declarations
11831 @item
11832 @value{GDBN} understands variables declared as C@t{++} references; you can use
11833 them in expressions just as you do in C@t{++} source---they are automatically
11834 dereferenced.
11835
11836 In the parameter list shown when @value{GDBN} displays a frame, the values of
11837 reference variables are not displayed (unlike other variables); this
11838 avoids clutter, since references are often used for large structures.
11839 The @emph{address} of a reference variable is always shown, unless
11840 you have specified @samp{set print address off}.
11841
11842 @item
11843 @value{GDBN} supports the C@t{++} name resolution operator @code{::}---your
11844 expressions can use it just as expressions in your program do. Since
11845 one scope may be defined in another, you can use @code{::} repeatedly if
11846 necessary, for example in an expression like
11847 @samp{@var{scope1}::@var{scope2}::@var{name}}. @value{GDBN} also allows
11848 resolving name scope by reference to source files, in both C and C@t{++}
11849 debugging (@pxref{Variables, ,Program Variables}).
11850 @end enumerate
11851
11852 In addition, when used with HP's C@t{++} compiler, @value{GDBN} supports
11853 calling virtual functions correctly, printing out virtual bases of
11854 objects, calling functions in a base subobject, casting objects, and
11855 invoking user-defined operators.
11856
11857 @node C Defaults
11858 @subsubsection C and C@t{++} Defaults
11859
11860 @cindex C and C@t{++} defaults
11861
11862 If you allow @value{GDBN} to set type and range checking automatically, they
11863 both default to @code{off} whenever the working language changes to
11864 C or C@t{++}. This happens regardless of whether you or @value{GDBN}
11865 selects the working language.
11866
11867 If you allow @value{GDBN} to set the language automatically, it
11868 recognizes source files whose names end with @file{.c}, @file{.C}, or
11869 @file{.cc}, etc, and when @value{GDBN} enters code compiled from one of
11870 these files, it sets the working language to C or C@t{++}.
11871 @xref{Automatically, ,Having @value{GDBN} Infer the Source Language},
11872 for further details.
11873
11874 @c Type checking is (a) primarily motivated by Modula-2, and (b)
11875 @c unimplemented. If (b) changes, it might make sense to let this node
11876 @c appear even if Mod-2 does not, but meanwhile ignore it. roland 16jul93.
11877
11878 @node C Checks
11879 @subsubsection C and C@t{++} Type and Range Checks
11880
11881 @cindex C and C@t{++} checks
11882
11883 By default, when @value{GDBN} parses C or C@t{++} expressions, type checking
11884 is not used. However, if you turn type checking on, @value{GDBN}
11885 considers two variables type equivalent if:
11886
11887 @itemize @bullet
11888 @item
11889 The two variables are structured and have the same structure, union, or
11890 enumerated tag.
11891
11892 @item
11893 The two variables have the same type name, or types that have been
11894 declared equivalent through @code{typedef}.
11895
11896 @ignore
11897 @c leaving this out because neither J Gilmore nor R Pesch understand it.
11898 @c FIXME--beers?
11899 @item
11900 The two @code{struct}, @code{union}, or @code{enum} variables are
11901 declared in the same declaration. (Note: this may not be true for all C
11902 compilers.)
11903 @end ignore
11904 @end itemize
11905
11906 Range checking, if turned on, is done on mathematical operations. Array
11907 indices are not checked, since they are often used to index a pointer
11908 that is not itself an array.
11909
11910 @node Debugging C
11911 @subsubsection @value{GDBN} and C
11912
11913 The @code{set print union} and @code{show print union} commands apply to
11914 the @code{union} type. When set to @samp{on}, any @code{union} that is
11915 inside a @code{struct} or @code{class} is also printed. Otherwise, it
11916 appears as @samp{@{...@}}.
11917
11918 The @code{@@} operator aids in the debugging of dynamic arrays, formed
11919 with pointers and a memory allocation function. @xref{Expressions,
11920 ,Expressions}.
11921
11922 @node Debugging C Plus Plus
11923 @subsubsection @value{GDBN} Features for C@t{++}
11924
11925 @cindex commands for C@t{++}
11926
11927 Some @value{GDBN} commands are particularly useful with C@t{++}, and some are
11928 designed specifically for use with C@t{++}. Here is a summary:
11929
11930 @table @code
11931 @cindex break in overloaded functions
11932 @item @r{breakpoint menus}
11933 When you want a breakpoint in a function whose name is overloaded,
11934 @value{GDBN} has the capability to display a menu of possible breakpoint
11935 locations to help you specify which function definition you want.
11936 @xref{Ambiguous Expressions,,Ambiguous Expressions}.
11937
11938 @cindex overloading in C@t{++}
11939 @item rbreak @var{regex}
11940 Setting breakpoints using regular expressions is helpful for setting
11941 breakpoints on overloaded functions that are not members of any special
11942 classes.
11943 @xref{Set Breaks, ,Setting Breakpoints}.
11944
11945 @cindex C@t{++} exception handling
11946 @item catch throw
11947 @itemx catch catch
11948 Debug C@t{++} exception handling using these commands. @xref{Set
11949 Catchpoints, , Setting Catchpoints}.
11950
11951 @cindex inheritance
11952 @item ptype @var{typename}
11953 Print inheritance relationships as well as other information for type
11954 @var{typename}.
11955 @xref{Symbols, ,Examining the Symbol Table}.
11956
11957 @cindex C@t{++} symbol display
11958 @item set print demangle
11959 @itemx show print demangle
11960 @itemx set print asm-demangle
11961 @itemx show print asm-demangle
11962 Control whether C@t{++} symbols display in their source form, both when
11963 displaying code as C@t{++} source and when displaying disassemblies.
11964 @xref{Print Settings, ,Print Settings}.
11965
11966 @item set print object
11967 @itemx show print object
11968 Choose whether to print derived (actual) or declared types of objects.
11969 @xref{Print Settings, ,Print Settings}.
11970
11971 @item set print vtbl
11972 @itemx show print vtbl
11973 Control the format for printing virtual function tables.
11974 @xref{Print Settings, ,Print Settings}.
11975 (The @code{vtbl} commands do not work on programs compiled with the HP
11976 ANSI C@t{++} compiler (@code{aCC}).)
11977
11978 @kindex set overload-resolution
11979 @cindex overloaded functions, overload resolution
11980 @item set overload-resolution on
11981 Enable overload resolution for C@t{++} expression evaluation. The default
11982 is on. For overloaded functions, @value{GDBN} evaluates the arguments
11983 and searches for a function whose signature matches the argument types,
11984 using the standard C@t{++} conversion rules (see @ref{C Plus Plus
11985 Expressions, ,C@t{++} Expressions}, for details).
11986 If it cannot find a match, it emits a message.
11987
11988 @item set overload-resolution off
11989 Disable overload resolution for C@t{++} expression evaluation. For
11990 overloaded functions that are not class member functions, @value{GDBN}
11991 chooses the first function of the specified name that it finds in the
11992 symbol table, whether or not its arguments are of the correct type. For
11993 overloaded functions that are class member functions, @value{GDBN}
11994 searches for a function whose signature @emph{exactly} matches the
11995 argument types.
11996
11997 @kindex show overload-resolution
11998 @item show overload-resolution
11999 Show the current setting of overload resolution.
12000
12001 @item @r{Overloaded symbol names}
12002 You can specify a particular definition of an overloaded symbol, using
12003 the same notation that is used to declare such symbols in C@t{++}: type
12004 @code{@var{symbol}(@var{types})} rather than just @var{symbol}. You can
12005 also use the @value{GDBN} command-line word completion facilities to list the
12006 available choices, or to finish the type list for you.
12007 @xref{Completion,, Command Completion}, for details on how to do this.
12008 @end table
12009
12010 @node Decimal Floating Point
12011 @subsubsection Decimal Floating Point format
12012 @cindex decimal floating point format
12013
12014 @value{GDBN} can examine, set and perform computations with numbers in
12015 decimal floating point format, which in the C language correspond to the
12016 @code{_Decimal32}, @code{_Decimal64} and @code{_Decimal128} types as
12017 specified by the extension to support decimal floating-point arithmetic.
12018
12019 There are two encodings in use, depending on the architecture: BID (Binary
12020 Integer Decimal) for x86 and x86-64, and DPD (Densely Packed Decimal) for
12021 PowerPC. @value{GDBN} will use the appropriate encoding for the configured
12022 target.
12023
12024 Because of a limitation in @file{libdecnumber}, the library used by @value{GDBN}
12025 to manipulate decimal floating point numbers, it is not possible to convert
12026 (using a cast, for example) integers wider than 32-bit to decimal float.
12027
12028 In addition, in order to imitate @value{GDBN}'s behaviour with binary floating
12029 point computations, error checking in decimal float operations ignores
12030 underflow, overflow and divide by zero exceptions.
12031
12032 In the PowerPC architecture, @value{GDBN} provides a set of pseudo-registers
12033 to inspect @code{_Decimal128} values stored in floating point registers.
12034 See @ref{PowerPC,,PowerPC} for more details.
12035
12036 @node D
12037 @subsection D
12038
12039 @cindex D
12040 @value{GDBN} can be used to debug programs written in D and compiled with
12041 GDC, LDC or DMD compilers. Currently @value{GDBN} supports only one D
12042 specific feature --- dynamic arrays.
12043
12044 @node Objective-C
12045 @subsection Objective-C
12046
12047 @cindex Objective-C
12048 This section provides information about some commands and command
12049 options that are useful for debugging Objective-C code. See also
12050 @ref{Symbols, info classes}, and @ref{Symbols, info selectors}, for a
12051 few more commands specific to Objective-C support.
12052
12053 @menu
12054 * Method Names in Commands::
12055 * The Print Command with Objective-C::
12056 @end menu
12057
12058 @node Method Names in Commands
12059 @subsubsection Method Names in Commands
12060
12061 The following commands have been extended to accept Objective-C method
12062 names as line specifications:
12063
12064 @kindex clear@r{, and Objective-C}
12065 @kindex break@r{, and Objective-C}
12066 @kindex info line@r{, and Objective-C}
12067 @kindex jump@r{, and Objective-C}
12068 @kindex list@r{, and Objective-C}
12069 @itemize
12070 @item @code{clear}
12071 @item @code{break}
12072 @item @code{info line}
12073 @item @code{jump}
12074 @item @code{list}
12075 @end itemize
12076
12077 A fully qualified Objective-C method name is specified as
12078
12079 @smallexample
12080 -[@var{Class} @var{methodName}]
12081 @end smallexample
12082
12083 where the minus sign is used to indicate an instance method and a
12084 plus sign (not shown) is used to indicate a class method. The class
12085 name @var{Class} and method name @var{methodName} are enclosed in
12086 brackets, similar to the way messages are specified in Objective-C
12087 source code. For example, to set a breakpoint at the @code{create}
12088 instance method of class @code{Fruit} in the program currently being
12089 debugged, enter:
12090
12091 @smallexample
12092 break -[Fruit create]
12093 @end smallexample
12094
12095 To list ten program lines around the @code{initialize} class method,
12096 enter:
12097
12098 @smallexample
12099 list +[NSText initialize]
12100 @end smallexample
12101
12102 In the current version of @value{GDBN}, the plus or minus sign is
12103 required. In future versions of @value{GDBN}, the plus or minus
12104 sign will be optional, but you can use it to narrow the search. It
12105 is also possible to specify just a method name:
12106
12107 @smallexample
12108 break create
12109 @end smallexample
12110
12111 You must specify the complete method name, including any colons. If
12112 your program's source files contain more than one @code{create} method,
12113 you'll be presented with a numbered list of classes that implement that
12114 method. Indicate your choice by number, or type @samp{0} to exit if
12115 none apply.
12116
12117 As another example, to clear a breakpoint established at the
12118 @code{makeKeyAndOrderFront:} method of the @code{NSWindow} class, enter:
12119
12120 @smallexample
12121 clear -[NSWindow makeKeyAndOrderFront:]
12122 @end smallexample
12123
12124 @node The Print Command with Objective-C
12125 @subsubsection The Print Command With Objective-C
12126 @cindex Objective-C, print objects
12127 @kindex print-object
12128 @kindex po @r{(@code{print-object})}
12129
12130 The print command has also been extended to accept methods. For example:
12131
12132 @smallexample
12133 print -[@var{object} hash]
12134 @end smallexample
12135
12136 @cindex print an Objective-C object description
12137 @cindex @code{_NSPrintForDebugger}, and printing Objective-C objects
12138 @noindent
12139 will tell @value{GDBN} to send the @code{hash} message to @var{object}
12140 and print the result. Also, an additional command has been added,
12141 @code{print-object} or @code{po} for short, which is meant to print
12142 the description of an object. However, this command may only work
12143 with certain Objective-C libraries that have a particular hook
12144 function, @code{_NSPrintForDebugger}, defined.
12145
12146 @node Fortran
12147 @subsection Fortran
12148 @cindex Fortran-specific support in @value{GDBN}
12149
12150 @value{GDBN} can be used to debug programs written in Fortran, but it
12151 currently supports only the features of Fortran 77 language.
12152
12153 @cindex trailing underscore, in Fortran symbols
12154 Some Fortran compilers (@sc{gnu} Fortran 77 and Fortran 95 compilers
12155 among them) append an underscore to the names of variables and
12156 functions. When you debug programs compiled by those compilers, you
12157 will need to refer to variables and functions with a trailing
12158 underscore.
12159
12160 @menu
12161 * Fortran Operators:: Fortran operators and expressions
12162 * Fortran Defaults:: Default settings for Fortran
12163 * Special Fortran Commands:: Special @value{GDBN} commands for Fortran
12164 @end menu
12165
12166 @node Fortran Operators
12167 @subsubsection Fortran Operators and Expressions
12168
12169 @cindex Fortran operators and expressions
12170
12171 Operators must be defined on values of specific types. For instance,
12172 @code{+} is defined on numbers, but not on characters or other non-
12173 arithmetic types. Operators are often defined on groups of types.
12174
12175 @table @code
12176 @item **
12177 The exponentiation operator. It raises the first operand to the power
12178 of the second one.
12179
12180 @item :
12181 The range operator. Normally used in the form of array(low:high) to
12182 represent a section of array.
12183
12184 @item %
12185 The access component operator. Normally used to access elements in derived
12186 types. Also suitable for unions. As unions aren't part of regular Fortran,
12187 this can only happen when accessing a register that uses a gdbarch-defined
12188 union type.
12189 @end table
12190
12191 @node Fortran Defaults
12192 @subsubsection Fortran Defaults
12193
12194 @cindex Fortran Defaults
12195
12196 Fortran symbols are usually case-insensitive, so @value{GDBN} by
12197 default uses case-insensitive matches for Fortran symbols. You can
12198 change that with the @samp{set case-insensitive} command, see
12199 @ref{Symbols}, for the details.
12200
12201 @node Special Fortran Commands
12202 @subsubsection Special Fortran Commands
12203
12204 @cindex Special Fortran commands
12205
12206 @value{GDBN} has some commands to support Fortran-specific features,
12207 such as displaying common blocks.
12208
12209 @table @code
12210 @cindex @code{COMMON} blocks, Fortran
12211 @kindex info common
12212 @item info common @r{[}@var{common-name}@r{]}
12213 This command prints the values contained in the Fortran @code{COMMON}
12214 block whose name is @var{common-name}. With no argument, the names of
12215 all @code{COMMON} blocks visible at the current program location are
12216 printed.
12217 @end table
12218
12219 @node Pascal
12220 @subsection Pascal
12221
12222 @cindex Pascal support in @value{GDBN}, limitations
12223 Debugging Pascal programs which use sets, subranges, file variables, or
12224 nested functions does not currently work. @value{GDBN} does not support
12225 entering expressions, printing values, or similar features using Pascal
12226 syntax.
12227
12228 The Pascal-specific command @code{set print pascal_static-members}
12229 controls whether static members of Pascal objects are displayed.
12230 @xref{Print Settings, pascal_static-members}.
12231
12232 @node Modula-2
12233 @subsection Modula-2
12234
12235 @cindex Modula-2, @value{GDBN} support
12236
12237 The extensions made to @value{GDBN} to support Modula-2 only support
12238 output from the @sc{gnu} Modula-2 compiler (which is currently being
12239 developed). Other Modula-2 compilers are not currently supported, and
12240 attempting to debug executables produced by them is most likely
12241 to give an error as @value{GDBN} reads in the executable's symbol
12242 table.
12243
12244 @cindex expressions in Modula-2
12245 @menu
12246 * M2 Operators:: Built-in operators
12247 * Built-In Func/Proc:: Built-in functions and procedures
12248 * M2 Constants:: Modula-2 constants
12249 * M2 Types:: Modula-2 types
12250 * M2 Defaults:: Default settings for Modula-2
12251 * Deviations:: Deviations from standard Modula-2
12252 * M2 Checks:: Modula-2 type and range checks
12253 * M2 Scope:: The scope operators @code{::} and @code{.}
12254 * GDB/M2:: @value{GDBN} and Modula-2
12255 @end menu
12256
12257 @node M2 Operators
12258 @subsubsection Operators
12259 @cindex Modula-2 operators
12260
12261 Operators must be defined on values of specific types. For instance,
12262 @code{+} is defined on numbers, but not on structures. Operators are
12263 often defined on groups of types. For the purposes of Modula-2, the
12264 following definitions hold:
12265
12266 @itemize @bullet
12267
12268 @item
12269 @emph{Integral types} consist of @code{INTEGER}, @code{CARDINAL}, and
12270 their subranges.
12271
12272 @item
12273 @emph{Character types} consist of @code{CHAR} and its subranges.
12274
12275 @item
12276 @emph{Floating-point types} consist of @code{REAL}.
12277
12278 @item
12279 @emph{Pointer types} consist of anything declared as @code{POINTER TO
12280 @var{type}}.
12281
12282 @item
12283 @emph{Scalar types} consist of all of the above.
12284
12285 @item
12286 @emph{Set types} consist of @code{SET} and @code{BITSET} types.
12287
12288 @item
12289 @emph{Boolean types} consist of @code{BOOLEAN}.
12290 @end itemize
12291
12292 @noindent
12293 The following operators are supported, and appear in order of
12294 increasing precedence:
12295
12296 @table @code
12297 @item ,
12298 Function argument or array index separator.
12299
12300 @item :=
12301 Assignment. The value of @var{var} @code{:=} @var{value} is
12302 @var{value}.
12303
12304 @item <@r{, }>
12305 Less than, greater than on integral, floating-point, or enumerated
12306 types.
12307
12308 @item <=@r{, }>=
12309 Less than or equal to, greater than or equal to
12310 on integral, floating-point and enumerated types, or set inclusion on
12311 set types. Same precedence as @code{<}.
12312
12313 @item =@r{, }<>@r{, }#
12314 Equality and two ways of expressing inequality, valid on scalar types.
12315 Same precedence as @code{<}. In @value{GDBN} scripts, only @code{<>} is
12316 available for inequality, since @code{#} conflicts with the script
12317 comment character.
12318
12319 @item IN
12320 Set membership. Defined on set types and the types of their members.
12321 Same precedence as @code{<}.
12322
12323 @item OR
12324 Boolean disjunction. Defined on boolean types.
12325
12326 @item AND@r{, }&
12327 Boolean conjunction. Defined on boolean types.
12328
12329 @item @@
12330 The @value{GDBN} ``artificial array'' operator (@pxref{Expressions, ,Expressions}).
12331
12332 @item +@r{, }-
12333 Addition and subtraction on integral and floating-point types, or union
12334 and difference on set types.
12335
12336 @item *
12337 Multiplication on integral and floating-point types, or set intersection
12338 on set types.
12339
12340 @item /
12341 Division on floating-point types, or symmetric set difference on set
12342 types. Same precedence as @code{*}.
12343
12344 @item DIV@r{, }MOD
12345 Integer division and remainder. Defined on integral types. Same
12346 precedence as @code{*}.
12347
12348 @item -
12349 Negative. Defined on @code{INTEGER} and @code{REAL} data.
12350
12351 @item ^
12352 Pointer dereferencing. Defined on pointer types.
12353
12354 @item NOT
12355 Boolean negation. Defined on boolean types. Same precedence as
12356 @code{^}.
12357
12358 @item .
12359 @code{RECORD} field selector. Defined on @code{RECORD} data. Same
12360 precedence as @code{^}.
12361
12362 @item []
12363 Array indexing. Defined on @code{ARRAY} data. Same precedence as @code{^}.
12364
12365 @item ()
12366 Procedure argument list. Defined on @code{PROCEDURE} objects. Same precedence
12367 as @code{^}.
12368
12369 @item ::@r{, }.
12370 @value{GDBN} and Modula-2 scope operators.
12371 @end table
12372
12373 @quotation
12374 @emph{Warning:} Set expressions and their operations are not yet supported, so @value{GDBN}
12375 treats the use of the operator @code{IN}, or the use of operators
12376 @code{+}, @code{-}, @code{*}, @code{/}, @code{=}, , @code{<>}, @code{#},
12377 @code{<=}, and @code{>=} on sets as an error.
12378 @end quotation
12379
12380
12381 @node Built-In Func/Proc
12382 @subsubsection Built-in Functions and Procedures
12383 @cindex Modula-2 built-ins
12384
12385 Modula-2 also makes available several built-in procedures and functions.
12386 In describing these, the following metavariables are used:
12387
12388 @table @var
12389
12390 @item a
12391 represents an @code{ARRAY} variable.
12392
12393 @item c
12394 represents a @code{CHAR} constant or variable.
12395
12396 @item i
12397 represents a variable or constant of integral type.
12398
12399 @item m
12400 represents an identifier that belongs to a set. Generally used in the
12401 same function with the metavariable @var{s}. The type of @var{s} should
12402 be @code{SET OF @var{mtype}} (where @var{mtype} is the type of @var{m}).
12403
12404 @item n
12405 represents a variable or constant of integral or floating-point type.
12406
12407 @item r
12408 represents a variable or constant of floating-point type.
12409
12410 @item t
12411 represents a type.
12412
12413 @item v
12414 represents a variable.
12415
12416 @item x
12417 represents a variable or constant of one of many types. See the
12418 explanation of the function for details.
12419 @end table
12420
12421 All Modula-2 built-in procedures also return a result, described below.
12422
12423 @table @code
12424 @item ABS(@var{n})
12425 Returns the absolute value of @var{n}.
12426
12427 @item CAP(@var{c})
12428 If @var{c} is a lower case letter, it returns its upper case
12429 equivalent, otherwise it returns its argument.
12430
12431 @item CHR(@var{i})
12432 Returns the character whose ordinal value is @var{i}.
12433
12434 @item DEC(@var{v})
12435 Decrements the value in the variable @var{v} by one. Returns the new value.
12436
12437 @item DEC(@var{v},@var{i})
12438 Decrements the value in the variable @var{v} by @var{i}. Returns the
12439 new value.
12440
12441 @item EXCL(@var{m},@var{s})
12442 Removes the element @var{m} from the set @var{s}. Returns the new
12443 set.
12444
12445 @item FLOAT(@var{i})
12446 Returns the floating point equivalent of the integer @var{i}.
12447
12448 @item HIGH(@var{a})
12449 Returns the index of the last member of @var{a}.
12450
12451 @item INC(@var{v})
12452 Increments the value in the variable @var{v} by one. Returns the new value.
12453
12454 @item INC(@var{v},@var{i})
12455 Increments the value in the variable @var{v} by @var{i}. Returns the
12456 new value.
12457
12458 @item INCL(@var{m},@var{s})
12459 Adds the element @var{m} to the set @var{s} if it is not already
12460 there. Returns the new set.
12461
12462 @item MAX(@var{t})
12463 Returns the maximum value of the type @var{t}.
12464
12465 @item MIN(@var{t})
12466 Returns the minimum value of the type @var{t}.
12467
12468 @item ODD(@var{i})
12469 Returns boolean TRUE if @var{i} is an odd number.
12470
12471 @item ORD(@var{x})
12472 Returns the ordinal value of its argument. For example, the ordinal
12473 value of a character is its @sc{ascii} value (on machines supporting the
12474 @sc{ascii} character set). @var{x} must be of an ordered type, which include
12475 integral, character and enumerated types.
12476
12477 @item SIZE(@var{x})
12478 Returns the size of its argument. @var{x} can be a variable or a type.
12479
12480 @item TRUNC(@var{r})
12481 Returns the integral part of @var{r}.
12482
12483 @item TSIZE(@var{x})
12484 Returns the size of its argument. @var{x} can be a variable or a type.
12485
12486 @item VAL(@var{t},@var{i})
12487 Returns the member of the type @var{t} whose ordinal value is @var{i}.
12488 @end table
12489
12490 @quotation
12491 @emph{Warning:} Sets and their operations are not yet supported, so
12492 @value{GDBN} treats the use of procedures @code{INCL} and @code{EXCL} as
12493 an error.
12494 @end quotation
12495
12496 @cindex Modula-2 constants
12497 @node M2 Constants
12498 @subsubsection Constants
12499
12500 @value{GDBN} allows you to express the constants of Modula-2 in the following
12501 ways:
12502
12503 @itemize @bullet
12504
12505 @item
12506 Integer constants are simply a sequence of digits. When used in an
12507 expression, a constant is interpreted to be type-compatible with the
12508 rest of the expression. Hexadecimal integers are specified by a
12509 trailing @samp{H}, and octal integers by a trailing @samp{B}.
12510
12511 @item
12512 Floating point constants appear as a sequence of digits, followed by a
12513 decimal point and another sequence of digits. An optional exponent can
12514 then be specified, in the form @samp{E@r{[}+@r{|}-@r{]}@var{nnn}}, where
12515 @samp{@r{[}+@r{|}-@r{]}@var{nnn}} is the desired exponent. All of the
12516 digits of the floating point constant must be valid decimal (base 10)
12517 digits.
12518
12519 @item
12520 Character constants consist of a single character enclosed by a pair of
12521 like quotes, either single (@code{'}) or double (@code{"}). They may
12522 also be expressed by their ordinal value (their @sc{ascii} value, usually)
12523 followed by a @samp{C}.
12524
12525 @item
12526 String constants consist of a sequence of characters enclosed by a
12527 pair of like quotes, either single (@code{'}) or double (@code{"}).
12528 Escape sequences in the style of C are also allowed. @xref{C
12529 Constants, ,C and C@t{++} Constants}, for a brief explanation of escape
12530 sequences.
12531
12532 @item
12533 Enumerated constants consist of an enumerated identifier.
12534
12535 @item
12536 Boolean constants consist of the identifiers @code{TRUE} and
12537 @code{FALSE}.
12538
12539 @item
12540 Pointer constants consist of integral values only.
12541
12542 @item
12543 Set constants are not yet supported.
12544 @end itemize
12545
12546 @node M2 Types
12547 @subsubsection Modula-2 Types
12548 @cindex Modula-2 types
12549
12550 Currently @value{GDBN} can print the following data types in Modula-2
12551 syntax: array types, record types, set types, pointer types, procedure
12552 types, enumerated types, subrange types and base types. You can also
12553 print the contents of variables declared using these type.
12554 This section gives a number of simple source code examples together with
12555 sample @value{GDBN} sessions.
12556
12557 The first example contains the following section of code:
12558
12559 @smallexample
12560 VAR
12561 s: SET OF CHAR ;
12562 r: [20..40] ;
12563 @end smallexample
12564
12565 @noindent
12566 and you can request @value{GDBN} to interrogate the type and value of
12567 @code{r} and @code{s}.
12568
12569 @smallexample
12570 (@value{GDBP}) print s
12571 @{'A'..'C', 'Z'@}
12572 (@value{GDBP}) ptype s
12573 SET OF CHAR
12574 (@value{GDBP}) print r
12575 21
12576 (@value{GDBP}) ptype r
12577 [20..40]
12578 @end smallexample
12579
12580 @noindent
12581 Likewise if your source code declares @code{s} as:
12582
12583 @smallexample
12584 VAR
12585 s: SET ['A'..'Z'] ;
12586 @end smallexample
12587
12588 @noindent
12589 then you may query the type of @code{s} by:
12590
12591 @smallexample
12592 (@value{GDBP}) ptype s
12593 type = SET ['A'..'Z']
12594 @end smallexample
12595
12596 @noindent
12597 Note that at present you cannot interactively manipulate set
12598 expressions using the debugger.
12599
12600 The following example shows how you might declare an array in Modula-2
12601 and how you can interact with @value{GDBN} to print its type and contents:
12602
12603 @smallexample
12604 VAR
12605 s: ARRAY [-10..10] OF CHAR ;
12606 @end smallexample
12607
12608 @smallexample
12609 (@value{GDBP}) ptype s
12610 ARRAY [-10..10] OF CHAR
12611 @end smallexample
12612
12613 Note that the array handling is not yet complete and although the type
12614 is printed correctly, expression handling still assumes that all
12615 arrays have a lower bound of zero and not @code{-10} as in the example
12616 above.
12617
12618 Here are some more type related Modula-2 examples:
12619
12620 @smallexample
12621 TYPE
12622 colour = (blue, red, yellow, green) ;
12623 t = [blue..yellow] ;
12624 VAR
12625 s: t ;
12626 BEGIN
12627 s := blue ;
12628 @end smallexample
12629
12630 @noindent
12631 The @value{GDBN} interaction shows how you can query the data type
12632 and value of a variable.
12633
12634 @smallexample
12635 (@value{GDBP}) print s
12636 $1 = blue
12637 (@value{GDBP}) ptype t
12638 type = [blue..yellow]
12639 @end smallexample
12640
12641 @noindent
12642 In this example a Modula-2 array is declared and its contents
12643 displayed. Observe that the contents are written in the same way as
12644 their @code{C} counterparts.
12645
12646 @smallexample
12647 VAR
12648 s: ARRAY [1..5] OF CARDINAL ;
12649 BEGIN
12650 s[1] := 1 ;
12651 @end smallexample
12652
12653 @smallexample
12654 (@value{GDBP}) print s
12655 $1 = @{1, 0, 0, 0, 0@}
12656 (@value{GDBP}) ptype s
12657 type = ARRAY [1..5] OF CARDINAL
12658 @end smallexample
12659
12660 The Modula-2 language interface to @value{GDBN} also understands
12661 pointer types as shown in this example:
12662
12663 @smallexample
12664 VAR
12665 s: POINTER TO ARRAY [1..5] OF CARDINAL ;
12666 BEGIN
12667 NEW(s) ;
12668 s^[1] := 1 ;
12669 @end smallexample
12670
12671 @noindent
12672 and you can request that @value{GDBN} describes the type of @code{s}.
12673
12674 @smallexample
12675 (@value{GDBP}) ptype s
12676 type = POINTER TO ARRAY [1..5] OF CARDINAL
12677 @end smallexample
12678
12679 @value{GDBN} handles compound types as we can see in this example.
12680 Here we combine array types, record types, pointer types and subrange
12681 types:
12682
12683 @smallexample
12684 TYPE
12685 foo = RECORD
12686 f1: CARDINAL ;
12687 f2: CHAR ;
12688 f3: myarray ;
12689 END ;
12690
12691 myarray = ARRAY myrange OF CARDINAL ;
12692 myrange = [-2..2] ;
12693 VAR
12694 s: POINTER TO ARRAY myrange OF foo ;
12695 @end smallexample
12696
12697 @noindent
12698 and you can ask @value{GDBN} to describe the type of @code{s} as shown
12699 below.
12700
12701 @smallexample
12702 (@value{GDBP}) ptype s
12703 type = POINTER TO ARRAY [-2..2] OF foo = RECORD
12704 f1 : CARDINAL;
12705 f2 : CHAR;
12706 f3 : ARRAY [-2..2] OF CARDINAL;
12707 END
12708 @end smallexample
12709
12710 @node M2 Defaults
12711 @subsubsection Modula-2 Defaults
12712 @cindex Modula-2 defaults
12713
12714 If type and range checking are set automatically by @value{GDBN}, they
12715 both default to @code{on} whenever the working language changes to
12716 Modula-2. This happens regardless of whether you or @value{GDBN}
12717 selected the working language.
12718
12719 If you allow @value{GDBN} to set the language automatically, then entering
12720 code compiled from a file whose name ends with @file{.mod} sets the
12721 working language to Modula-2. @xref{Automatically, ,Having @value{GDBN}
12722 Infer the Source Language}, for further details.
12723
12724 @node Deviations
12725 @subsubsection Deviations from Standard Modula-2
12726 @cindex Modula-2, deviations from
12727
12728 A few changes have been made to make Modula-2 programs easier to debug.
12729 This is done primarily via loosening its type strictness:
12730
12731 @itemize @bullet
12732 @item
12733 Unlike in standard Modula-2, pointer constants can be formed by
12734 integers. This allows you to modify pointer variables during
12735 debugging. (In standard Modula-2, the actual address contained in a
12736 pointer variable is hidden from you; it can only be modified
12737 through direct assignment to another pointer variable or expression that
12738 returned a pointer.)
12739
12740 @item
12741 C escape sequences can be used in strings and characters to represent
12742 non-printable characters. @value{GDBN} prints out strings with these
12743 escape sequences embedded. Single non-printable characters are
12744 printed using the @samp{CHR(@var{nnn})} format.
12745
12746 @item
12747 The assignment operator (@code{:=}) returns the value of its right-hand
12748 argument.
12749
12750 @item
12751 All built-in procedures both modify @emph{and} return their argument.
12752 @end itemize
12753
12754 @node M2 Checks
12755 @subsubsection Modula-2 Type and Range Checks
12756 @cindex Modula-2 checks
12757
12758 @quotation
12759 @emph{Warning:} in this release, @value{GDBN} does not yet perform type or
12760 range checking.
12761 @end quotation
12762 @c FIXME remove warning when type/range checks added
12763
12764 @value{GDBN} considers two Modula-2 variables type equivalent if:
12765
12766 @itemize @bullet
12767 @item
12768 They are of types that have been declared equivalent via a @code{TYPE
12769 @var{t1} = @var{t2}} statement
12770
12771 @item
12772 They have been declared on the same line. (Note: This is true of the
12773 @sc{gnu} Modula-2 compiler, but it may not be true of other compilers.)
12774 @end itemize
12775
12776 As long as type checking is enabled, any attempt to combine variables
12777 whose types are not equivalent is an error.
12778
12779 Range checking is done on all mathematical operations, assignment, array
12780 index bounds, and all built-in functions and procedures.
12781
12782 @node M2 Scope
12783 @subsubsection The Scope Operators @code{::} and @code{.}
12784 @cindex scope
12785 @cindex @code{.}, Modula-2 scope operator
12786 @cindex colon, doubled as scope operator
12787 @ifinfo
12788 @vindex colon-colon@r{, in Modula-2}
12789 @c Info cannot handle :: but TeX can.
12790 @end ifinfo
12791 @ifnotinfo
12792 @vindex ::@r{, in Modula-2}
12793 @end ifnotinfo
12794
12795 There are a few subtle differences between the Modula-2 scope operator
12796 (@code{.}) and the @value{GDBN} scope operator (@code{::}). The two have
12797 similar syntax:
12798
12799 @smallexample
12800
12801 @var{module} . @var{id}
12802 @var{scope} :: @var{id}
12803 @end smallexample
12804
12805 @noindent
12806 where @var{scope} is the name of a module or a procedure,
12807 @var{module} the name of a module, and @var{id} is any declared
12808 identifier within your program, except another module.
12809
12810 Using the @code{::} operator makes @value{GDBN} search the scope
12811 specified by @var{scope} for the identifier @var{id}. If it is not
12812 found in the specified scope, then @value{GDBN} searches all scopes
12813 enclosing the one specified by @var{scope}.
12814
12815 Using the @code{.} operator makes @value{GDBN} search the current scope for
12816 the identifier specified by @var{id} that was imported from the
12817 definition module specified by @var{module}. With this operator, it is
12818 an error if the identifier @var{id} was not imported from definition
12819 module @var{module}, or if @var{id} is not an identifier in
12820 @var{module}.
12821
12822 @node GDB/M2
12823 @subsubsection @value{GDBN} and Modula-2
12824
12825 Some @value{GDBN} commands have little use when debugging Modula-2 programs.
12826 Five subcommands of @code{set print} and @code{show print} apply
12827 specifically to C and C@t{++}: @samp{vtbl}, @samp{demangle},
12828 @samp{asm-demangle}, @samp{object}, and @samp{union}. The first four
12829 apply to C@t{++}, and the last to the C @code{union} type, which has no direct
12830 analogue in Modula-2.
12831
12832 The @code{@@} operator (@pxref{Expressions, ,Expressions}), while available
12833 with any language, is not useful with Modula-2. Its
12834 intent is to aid the debugging of @dfn{dynamic arrays}, which cannot be
12835 created in Modula-2 as they can in C or C@t{++}. However, because an
12836 address can be specified by an integral constant, the construct
12837 @samp{@{@var{type}@}@var{adrexp}} is still useful.
12838
12839 @cindex @code{#} in Modula-2
12840 In @value{GDBN} scripts, the Modula-2 inequality operator @code{#} is
12841 interpreted as the beginning of a comment. Use @code{<>} instead.
12842
12843 @node Ada
12844 @subsection Ada
12845 @cindex Ada
12846
12847 The extensions made to @value{GDBN} for Ada only support
12848 output from the @sc{gnu} Ada (GNAT) compiler.
12849 Other Ada compilers are not currently supported, and
12850 attempting to debug executables produced by them is most likely
12851 to be difficult.
12852
12853
12854 @cindex expressions in Ada
12855 @menu
12856 * Ada Mode Intro:: General remarks on the Ada syntax
12857 and semantics supported by Ada mode
12858 in @value{GDBN}.
12859 * Omissions from Ada:: Restrictions on the Ada expression syntax.
12860 * Additions to Ada:: Extensions of the Ada expression syntax.
12861 * Stopping Before Main Program:: Debugging the program during elaboration.
12862 * Ada Tasks:: Listing and setting breakpoints in tasks.
12863 * Ada Tasks and Core Files:: Tasking Support when Debugging Core Files
12864 * Ravenscar Profile:: Tasking Support when using the Ravenscar
12865 Profile
12866 * Ada Glitches:: Known peculiarities of Ada mode.
12867 @end menu
12868
12869 @node Ada Mode Intro
12870 @subsubsection Introduction
12871 @cindex Ada mode, general
12872
12873 The Ada mode of @value{GDBN} supports a fairly large subset of Ada expression
12874 syntax, with some extensions.
12875 The philosophy behind the design of this subset is
12876
12877 @itemize @bullet
12878 @item
12879 That @value{GDBN} should provide basic literals and access to operations for
12880 arithmetic, dereferencing, field selection, indexing, and subprogram calls,
12881 leaving more sophisticated computations to subprograms written into the
12882 program (which therefore may be called from @value{GDBN}).
12883
12884 @item
12885 That type safety and strict adherence to Ada language restrictions
12886 are not particularly important to the @value{GDBN} user.
12887
12888 @item
12889 That brevity is important to the @value{GDBN} user.
12890 @end itemize
12891
12892 Thus, for brevity, the debugger acts as if all names declared in
12893 user-written packages are directly visible, even if they are not visible
12894 according to Ada rules, thus making it unnecessary to fully qualify most
12895 names with their packages, regardless of context. Where this causes
12896 ambiguity, @value{GDBN} asks the user's intent.
12897
12898 The debugger will start in Ada mode if it detects an Ada main program.
12899 As for other languages, it will enter Ada mode when stopped in a program that
12900 was translated from an Ada source file.
12901
12902 While in Ada mode, you may use `@t{--}' for comments. This is useful
12903 mostly for documenting command files. The standard @value{GDBN} comment
12904 (@samp{#}) still works at the beginning of a line in Ada mode, but not in the
12905 middle (to allow based literals).
12906
12907 The debugger supports limited overloading. Given a subprogram call in which
12908 the function symbol has multiple definitions, it will use the number of
12909 actual parameters and some information about their types to attempt to narrow
12910 the set of definitions. It also makes very limited use of context, preferring
12911 procedures to functions in the context of the @code{call} command, and
12912 functions to procedures elsewhere.
12913
12914 @node Omissions from Ada
12915 @subsubsection Omissions from Ada
12916 @cindex Ada, omissions from
12917
12918 Here are the notable omissions from the subset:
12919
12920 @itemize @bullet
12921 @item
12922 Only a subset of the attributes are supported:
12923
12924 @itemize @minus
12925 @item
12926 @t{'First}, @t{'Last}, and @t{'Length}
12927 on array objects (not on types and subtypes).
12928
12929 @item
12930 @t{'Min} and @t{'Max}.
12931
12932 @item
12933 @t{'Pos} and @t{'Val}.
12934
12935 @item
12936 @t{'Tag}.
12937
12938 @item
12939 @t{'Range} on array objects (not subtypes), but only as the right
12940 operand of the membership (@code{in}) operator.
12941
12942 @item
12943 @t{'Access}, @t{'Unchecked_Access}, and
12944 @t{'Unrestricted_Access} (a GNAT extension).
12945
12946 @item
12947 @t{'Address}.
12948 @end itemize
12949
12950 @item
12951 The names in
12952 @code{Characters.Latin_1} are not available and
12953 concatenation is not implemented. Thus, escape characters in strings are
12954 not currently available.
12955
12956 @item
12957 Equality tests (@samp{=} and @samp{/=}) on arrays test for bitwise
12958 equality of representations. They will generally work correctly
12959 for strings and arrays whose elements have integer or enumeration types.
12960 They may not work correctly for arrays whose element
12961 types have user-defined equality, for arrays of real values
12962 (in particular, IEEE-conformant floating point, because of negative
12963 zeroes and NaNs), and for arrays whose elements contain unused bits with
12964 indeterminate values.
12965
12966 @item
12967 The other component-by-component array operations (@code{and}, @code{or},
12968 @code{xor}, @code{not}, and relational tests other than equality)
12969 are not implemented.
12970
12971 @item
12972 @cindex array aggregates (Ada)
12973 @cindex record aggregates (Ada)
12974 @cindex aggregates (Ada)
12975 There is limited support for array and record aggregates. They are
12976 permitted only on the right sides of assignments, as in these examples:
12977
12978 @smallexample
12979 (@value{GDBP}) set An_Array := (1, 2, 3, 4, 5, 6)
12980 (@value{GDBP}) set An_Array := (1, others => 0)
12981 (@value{GDBP}) set An_Array := (0|4 => 1, 1..3 => 2, 5 => 6)
12982 (@value{GDBP}) set A_2D_Array := ((1, 2, 3), (4, 5, 6), (7, 8, 9))
12983 (@value{GDBP}) set A_Record := (1, "Peter", True);
12984 (@value{GDBP}) set A_Record := (Name => "Peter", Id => 1, Alive => True)
12985 @end smallexample
12986
12987 Changing a
12988 discriminant's value by assigning an aggregate has an
12989 undefined effect if that discriminant is used within the record.
12990 However, you can first modify discriminants by directly assigning to
12991 them (which normally would not be allowed in Ada), and then performing an
12992 aggregate assignment. For example, given a variable @code{A_Rec}
12993 declared to have a type such as:
12994
12995 @smallexample
12996 type Rec (Len : Small_Integer := 0) is record
12997 Id : Integer;
12998 Vals : IntArray (1 .. Len);
12999 end record;
13000 @end smallexample
13001
13002 you can assign a value with a different size of @code{Vals} with two
13003 assignments:
13004
13005 @smallexample
13006 (@value{GDBP}) set A_Rec.Len := 4
13007 (@value{GDBP}) set A_Rec := (Id => 42, Vals => (1, 2, 3, 4))
13008 @end smallexample
13009
13010 As this example also illustrates, @value{GDBN} is very loose about the usual
13011 rules concerning aggregates. You may leave out some of the
13012 components of an array or record aggregate (such as the @code{Len}
13013 component in the assignment to @code{A_Rec} above); they will retain their
13014 original values upon assignment. You may freely use dynamic values as
13015 indices in component associations. You may even use overlapping or
13016 redundant component associations, although which component values are
13017 assigned in such cases is not defined.
13018
13019 @item
13020 Calls to dispatching subprograms are not implemented.
13021
13022 @item
13023 The overloading algorithm is much more limited (i.e., less selective)
13024 than that of real Ada. It makes only limited use of the context in
13025 which a subexpression appears to resolve its meaning, and it is much
13026 looser in its rules for allowing type matches. As a result, some
13027 function calls will be ambiguous, and the user will be asked to choose
13028 the proper resolution.
13029
13030 @item
13031 The @code{new} operator is not implemented.
13032
13033 @item
13034 Entry calls are not implemented.
13035
13036 @item
13037 Aside from printing, arithmetic operations on the native VAX floating-point
13038 formats are not supported.
13039
13040 @item
13041 It is not possible to slice a packed array.
13042
13043 @item
13044 The names @code{True} and @code{False}, when not part of a qualified name,
13045 are interpreted as if implicitly prefixed by @code{Standard}, regardless of
13046 context.
13047 Should your program
13048 redefine these names in a package or procedure (at best a dubious practice),
13049 you will have to use fully qualified names to access their new definitions.
13050 @end itemize
13051
13052 @node Additions to Ada
13053 @subsubsection Additions to Ada
13054 @cindex Ada, deviations from
13055
13056 As it does for other languages, @value{GDBN} makes certain generic
13057 extensions to Ada (@pxref{Expressions}):
13058
13059 @itemize @bullet
13060 @item
13061 If the expression @var{E} is a variable residing in memory (typically
13062 a local variable or array element) and @var{N} is a positive integer,
13063 then @code{@var{E}@@@var{N}} displays the values of @var{E} and the
13064 @var{N}-1 adjacent variables following it in memory as an array. In
13065 Ada, this operator is generally not necessary, since its prime use is
13066 in displaying parts of an array, and slicing will usually do this in
13067 Ada. However, there are occasional uses when debugging programs in
13068 which certain debugging information has been optimized away.
13069
13070 @item
13071 @code{@var{B}::@var{var}} means ``the variable named @var{var} that
13072 appears in function or file @var{B}.'' When @var{B} is a file name,
13073 you must typically surround it in single quotes.
13074
13075 @item
13076 The expression @code{@{@var{type}@} @var{addr}} means ``the variable of type
13077 @var{type} that appears at address @var{addr}.''
13078
13079 @item
13080 A name starting with @samp{$} is a convenience variable
13081 (@pxref{Convenience Vars}) or a machine register (@pxref{Registers}).
13082 @end itemize
13083
13084 In addition, @value{GDBN} provides a few other shortcuts and outright
13085 additions specific to Ada:
13086
13087 @itemize @bullet
13088 @item
13089 The assignment statement is allowed as an expression, returning
13090 its right-hand operand as its value. Thus, you may enter
13091
13092 @smallexample
13093 (@value{GDBP}) set x := y + 3
13094 (@value{GDBP}) print A(tmp := y + 1)
13095 @end smallexample
13096
13097 @item
13098 The semicolon is allowed as an ``operator,'' returning as its value
13099 the value of its right-hand operand.
13100 This allows, for example,
13101 complex conditional breaks:
13102
13103 @smallexample
13104 (@value{GDBP}) break f
13105 (@value{GDBP}) condition 1 (report(i); k += 1; A(k) > 100)
13106 @end smallexample
13107
13108 @item
13109 Rather than use catenation and symbolic character names to introduce special
13110 characters into strings, one may instead use a special bracket notation,
13111 which is also used to print strings. A sequence of characters of the form
13112 @samp{["@var{XX}"]} within a string or character literal denotes the
13113 (single) character whose numeric encoding is @var{XX} in hexadecimal. The
13114 sequence of characters @samp{["""]} also denotes a single quotation mark
13115 in strings. For example,
13116 @smallexample
13117 "One line.["0a"]Next line.["0a"]"
13118 @end smallexample
13119 @noindent
13120 contains an ASCII newline character (@code{Ada.Characters.Latin_1.LF})
13121 after each period.
13122
13123 @item
13124 The subtype used as a prefix for the attributes @t{'Pos}, @t{'Min}, and
13125 @t{'Max} is optional (and is ignored in any case). For example, it is valid
13126 to write
13127
13128 @smallexample
13129 (@value{GDBP}) print 'max(x, y)
13130 @end smallexample
13131
13132 @item
13133 When printing arrays, @value{GDBN} uses positional notation when the
13134 array has a lower bound of 1, and uses a modified named notation otherwise.
13135 For example, a one-dimensional array of three integers with a lower bound
13136 of 3 might print as
13137
13138 @smallexample
13139 (3 => 10, 17, 1)
13140 @end smallexample
13141
13142 @noindent
13143 That is, in contrast to valid Ada, only the first component has a @code{=>}
13144 clause.
13145
13146 @item
13147 You may abbreviate attributes in expressions with any unique,
13148 multi-character subsequence of
13149 their names (an exact match gets preference).
13150 For example, you may use @t{a'len}, @t{a'gth}, or @t{a'lh}
13151 in place of @t{a'length}.
13152
13153 @item
13154 @cindex quoting Ada internal identifiers
13155 Since Ada is case-insensitive, the debugger normally maps identifiers you type
13156 to lower case. The GNAT compiler uses upper-case characters for
13157 some of its internal identifiers, which are normally of no interest to users.
13158 For the rare occasions when you actually have to look at them,
13159 enclose them in angle brackets to avoid the lower-case mapping.
13160 For example,
13161 @smallexample
13162 (@value{GDBP}) print <JMPBUF_SAVE>[0]
13163 @end smallexample
13164
13165 @item
13166 Printing an object of class-wide type or dereferencing an
13167 access-to-class-wide value will display all the components of the object's
13168 specific type (as indicated by its run-time tag). Likewise, component
13169 selection on such a value will operate on the specific type of the
13170 object.
13171
13172 @end itemize
13173
13174 @node Stopping Before Main Program
13175 @subsubsection Stopping at the Very Beginning
13176
13177 @cindex breakpointing Ada elaboration code
13178 It is sometimes necessary to debug the program during elaboration, and
13179 before reaching the main procedure.
13180 As defined in the Ada Reference
13181 Manual, the elaboration code is invoked from a procedure called
13182 @code{adainit}. To run your program up to the beginning of
13183 elaboration, simply use the following two commands:
13184 @code{tbreak adainit} and @code{run}.
13185
13186 @node Ada Tasks
13187 @subsubsection Extensions for Ada Tasks
13188 @cindex Ada, tasking
13189
13190 Support for Ada tasks is analogous to that for threads (@pxref{Threads}).
13191 @value{GDBN} provides the following task-related commands:
13192
13193 @table @code
13194 @kindex info tasks
13195 @item info tasks
13196 This command shows a list of current Ada tasks, as in the following example:
13197
13198
13199 @smallexample
13200 @iftex
13201 @leftskip=0.5cm
13202 @end iftex
13203 (@value{GDBP}) info tasks
13204 ID TID P-ID Pri State Name
13205 1 8088000 0 15 Child Activation Wait main_task
13206 2 80a4000 1 15 Accept Statement b
13207 3 809a800 1 15 Child Activation Wait a
13208 * 4 80ae800 3 15 Runnable c
13209
13210 @end smallexample
13211
13212 @noindent
13213 In this listing, the asterisk before the last task indicates it to be the
13214 task currently being inspected.
13215
13216 @table @asis
13217 @item ID
13218 Represents @value{GDBN}'s internal task number.
13219
13220 @item TID
13221 The Ada task ID.
13222
13223 @item P-ID
13224 The parent's task ID (@value{GDBN}'s internal task number).
13225
13226 @item Pri
13227 The base priority of the task.
13228
13229 @item State
13230 Current state of the task.
13231
13232 @table @code
13233 @item Unactivated
13234 The task has been created but has not been activated. It cannot be
13235 executing.
13236
13237 @item Runnable
13238 The task is not blocked for any reason known to Ada. (It may be waiting
13239 for a mutex, though.) It is conceptually "executing" in normal mode.
13240
13241 @item Terminated
13242 The task is terminated, in the sense of ARM 9.3 (5). Any dependents
13243 that were waiting on terminate alternatives have been awakened and have
13244 terminated themselves.
13245
13246 @item Child Activation Wait
13247 The task is waiting for created tasks to complete activation.
13248
13249 @item Accept Statement
13250 The task is waiting on an accept or selective wait statement.
13251
13252 @item Waiting on entry call
13253 The task is waiting on an entry call.
13254
13255 @item Async Select Wait
13256 The task is waiting to start the abortable part of an asynchronous
13257 select statement.
13258
13259 @item Delay Sleep
13260 The task is waiting on a select statement with only a delay
13261 alternative open.
13262
13263 @item Child Termination Wait
13264 The task is sleeping having completed a master within itself, and is
13265 waiting for the tasks dependent on that master to become terminated or
13266 waiting on a terminate Phase.
13267
13268 @item Wait Child in Term Alt
13269 The task is sleeping waiting for tasks on terminate alternatives to
13270 finish terminating.
13271
13272 @item Accepting RV with @var{taskno}
13273 The task is accepting a rendez-vous with the task @var{taskno}.
13274 @end table
13275
13276 @item Name
13277 Name of the task in the program.
13278
13279 @end table
13280
13281 @kindex info task @var{taskno}
13282 @item info task @var{taskno}
13283 This command shows detailled informations on the specified task, as in
13284 the following example:
13285 @smallexample
13286 @iftex
13287 @leftskip=0.5cm
13288 @end iftex
13289 (@value{GDBP}) info tasks
13290 ID TID P-ID Pri State Name
13291 1 8077880 0 15 Child Activation Wait main_task
13292 * 2 807c468 1 15 Runnable task_1
13293 (@value{GDBP}) info task 2
13294 Ada Task: 0x807c468
13295 Name: task_1
13296 Thread: 0x807f378
13297 Parent: 1 (main_task)
13298 Base Priority: 15
13299 State: Runnable
13300 @end smallexample
13301
13302 @item task
13303 @kindex task@r{ (Ada)}
13304 @cindex current Ada task ID
13305 This command prints the ID of the current task.
13306
13307 @smallexample
13308 @iftex
13309 @leftskip=0.5cm
13310 @end iftex
13311 (@value{GDBP}) info tasks
13312 ID TID P-ID Pri State Name
13313 1 8077870 0 15 Child Activation Wait main_task
13314 * 2 807c458 1 15 Runnable t
13315 (@value{GDBP}) task
13316 [Current task is 2]
13317 @end smallexample
13318
13319 @item task @var{taskno}
13320 @cindex Ada task switching
13321 This command is like the @code{thread @var{threadno}}
13322 command (@pxref{Threads}). It switches the context of debugging
13323 from the current task to the given task.
13324
13325 @smallexample
13326 @iftex
13327 @leftskip=0.5cm
13328 @end iftex
13329 (@value{GDBP}) info tasks
13330 ID TID P-ID Pri State Name
13331 1 8077870 0 15 Child Activation Wait main_task
13332 * 2 807c458 1 15 Runnable t
13333 (@value{GDBP}) task 1
13334 [Switching to task 1]
13335 #0 0x8067726 in pthread_cond_wait ()
13336 (@value{GDBP}) bt
13337 #0 0x8067726 in pthread_cond_wait ()
13338 #1 0x8056714 in system.os_interface.pthread_cond_wait ()
13339 #2 0x805cb63 in system.task_primitives.operations.sleep ()
13340 #3 0x806153e in system.tasking.stages.activate_tasks ()
13341 #4 0x804aacc in un () at un.adb:5
13342 @end smallexample
13343
13344 @item break @var{linespec} task @var{taskno}
13345 @itemx break @var{linespec} task @var{taskno} if @dots{}
13346 @cindex breakpoints and tasks, in Ada
13347 @cindex task breakpoints, in Ada
13348 @kindex break @dots{} task @var{taskno}@r{ (Ada)}
13349 These commands are like the @code{break @dots{} thread @dots{}}
13350 command (@pxref{Thread Stops}).
13351 @var{linespec} specifies source lines, as described
13352 in @ref{Specify Location}.
13353
13354 Use the qualifier @samp{task @var{taskno}} with a breakpoint command
13355 to specify that you only want @value{GDBN} to stop the program when a
13356 particular Ada task reaches this breakpoint. @var{taskno} is one of the
13357 numeric task identifiers assigned by @value{GDBN}, shown in the first
13358 column of the @samp{info tasks} display.
13359
13360 If you do not specify @samp{task @var{taskno}} when you set a
13361 breakpoint, the breakpoint applies to @emph{all} tasks of your
13362 program.
13363
13364 You can use the @code{task} qualifier on conditional breakpoints as
13365 well; in this case, place @samp{task @var{taskno}} before the
13366 breakpoint condition (before the @code{if}).
13367
13368 For example,
13369
13370 @smallexample
13371 @iftex
13372 @leftskip=0.5cm
13373 @end iftex
13374 (@value{GDBP}) info tasks
13375 ID TID P-ID Pri State Name
13376 1 140022020 0 15 Child Activation Wait main_task
13377 2 140045060 1 15 Accept/Select Wait t2
13378 3 140044840 1 15 Runnable t1
13379 * 4 140056040 1 15 Runnable t3
13380 (@value{GDBP}) b 15 task 2
13381 Breakpoint 5 at 0x120044cb0: file test_task_debug.adb, line 15.
13382 (@value{GDBP}) cont
13383 Continuing.
13384 task # 1 running
13385 task # 2 running
13386
13387 Breakpoint 5, test_task_debug () at test_task_debug.adb:15
13388 15 flush;
13389 (@value{GDBP}) info tasks
13390 ID TID P-ID Pri State Name
13391 1 140022020 0 15 Child Activation Wait main_task
13392 * 2 140045060 1 15 Runnable t2
13393 3 140044840 1 15 Runnable t1
13394 4 140056040 1 15 Delay Sleep t3
13395 @end smallexample
13396 @end table
13397
13398 @node Ada Tasks and Core Files
13399 @subsubsection Tasking Support when Debugging Core Files
13400 @cindex Ada tasking and core file debugging
13401
13402 When inspecting a core file, as opposed to debugging a live program,
13403 tasking support may be limited or even unavailable, depending on
13404 the platform being used.
13405 For instance, on x86-linux, the list of tasks is available, but task
13406 switching is not supported. On Tru64, however, task switching will work
13407 as usual.
13408
13409 On certain platforms, including Tru64, the debugger needs to perform some
13410 memory writes in order to provide Ada tasking support. When inspecting
13411 a core file, this means that the core file must be opened with read-write
13412 privileges, using the command @samp{"set write on"} (@pxref{Patching}).
13413 Under these circumstances, you should make a backup copy of the core
13414 file before inspecting it with @value{GDBN}.
13415
13416 @node Ravenscar Profile
13417 @subsubsection Tasking Support when using the Ravenscar Profile
13418 @cindex Ravenscar Profile
13419
13420 The @dfn{Ravenscar Profile} is a subset of the Ada tasking features,
13421 specifically designed for systems with safety-critical real-time
13422 requirements.
13423
13424 @table @code
13425 @kindex set ravenscar task-switching on
13426 @cindex task switching with program using Ravenscar Profile
13427 @item set ravenscar task-switching on
13428 Allows task switching when debugging a program that uses the Ravenscar
13429 Profile. This is the default.
13430
13431 @kindex set ravenscar task-switching off
13432 @item set ravenscar task-switching off
13433 Turn off task switching when debugging a program that uses the Ravenscar
13434 Profile. This is mostly intended to disable the code that adds support
13435 for the Ravenscar Profile, in case a bug in either @value{GDBN} or in
13436 the Ravenscar runtime is preventing @value{GDBN} from working properly.
13437 To be effective, this command should be run before the program is started.
13438
13439 @kindex show ravenscar task-switching
13440 @item show ravenscar task-switching
13441 Show whether it is possible to switch from task to task in a program
13442 using the Ravenscar Profile.
13443
13444 @end table
13445
13446 @node Ada Glitches
13447 @subsubsection Known Peculiarities of Ada Mode
13448 @cindex Ada, problems
13449
13450 Besides the omissions listed previously (@pxref{Omissions from Ada}),
13451 we know of several problems with and limitations of Ada mode in
13452 @value{GDBN},
13453 some of which will be fixed with planned future releases of the debugger
13454 and the GNU Ada compiler.
13455
13456 @itemize @bullet
13457 @item
13458 Currently, the debugger
13459 has insufficient information to determine whether certain pointers represent
13460 pointers to objects or the objects themselves.
13461 Thus, the user may have to tack an extra @code{.all} after an expression
13462 to get it printed properly.
13463
13464 @item
13465 Static constants that the compiler chooses not to materialize as objects in
13466 storage are invisible to the debugger.
13467
13468 @item
13469 Named parameter associations in function argument lists are ignored (the
13470 argument lists are treated as positional).
13471
13472 @item
13473 Many useful library packages are currently invisible to the debugger.
13474
13475 @item
13476 Fixed-point arithmetic, conversions, input, and output is carried out using
13477 floating-point arithmetic, and may give results that only approximate those on
13478 the host machine.
13479
13480 @item
13481 The GNAT compiler never generates the prefix @code{Standard} for any of
13482 the standard symbols defined by the Ada language. @value{GDBN} knows about
13483 this: it will strip the prefix from names when you use it, and will never
13484 look for a name you have so qualified among local symbols, nor match against
13485 symbols in other packages or subprograms. If you have
13486 defined entities anywhere in your program other than parameters and
13487 local variables whose simple names match names in @code{Standard},
13488 GNAT's lack of qualification here can cause confusion. When this happens,
13489 you can usually resolve the confusion
13490 by qualifying the problematic names with package
13491 @code{Standard} explicitly.
13492 @end itemize
13493
13494 Older versions of the compiler sometimes generate erroneous debugging
13495 information, resulting in the debugger incorrectly printing the value
13496 of affected entities. In some cases, the debugger is able to work
13497 around an issue automatically. In other cases, the debugger is able
13498 to work around the issue, but the work-around has to be specifically
13499 enabled.
13500
13501 @kindex set ada trust-PAD-over-XVS
13502 @kindex show ada trust-PAD-over-XVS
13503 @table @code
13504
13505 @item set ada trust-PAD-over-XVS on
13506 Configure GDB to strictly follow the GNAT encoding when computing the
13507 value of Ada entities, particularly when @code{PAD} and @code{PAD___XVS}
13508 types are involved (see @code{ada/exp_dbug.ads} in the GCC sources for
13509 a complete description of the encoding used by the GNAT compiler).
13510 This is the default.
13511
13512 @item set ada trust-PAD-over-XVS off
13513 This is related to the encoding using by the GNAT compiler. If @value{GDBN}
13514 sometimes prints the wrong value for certain entities, changing @code{ada
13515 trust-PAD-over-XVS} to @code{off} activates a work-around which may fix
13516 the issue. It is always safe to set @code{ada trust-PAD-over-XVS} to
13517 @code{off}, but this incurs a slight performance penalty, so it is
13518 recommended to leave this setting to @code{on} unless necessary.
13519
13520 @end table
13521
13522 @node Unsupported Languages
13523 @section Unsupported Languages
13524
13525 @cindex unsupported languages
13526 @cindex minimal language
13527 In addition to the other fully-supported programming languages,
13528 @value{GDBN} also provides a pseudo-language, called @code{minimal}.
13529 It does not represent a real programming language, but provides a set
13530 of capabilities close to what the C or assembly languages provide.
13531 This should allow most simple operations to be performed while debugging
13532 an application that uses a language currently not supported by @value{GDBN}.
13533
13534 If the language is set to @code{auto}, @value{GDBN} will automatically
13535 select this language if the current frame corresponds to an unsupported
13536 language.
13537
13538 @node Symbols
13539 @chapter Examining the Symbol Table
13540
13541 The commands described in this chapter allow you to inquire about the
13542 symbols (names of variables, functions and types) defined in your
13543 program. This information is inherent in the text of your program and
13544 does not change as your program executes. @value{GDBN} finds it in your
13545 program's symbol table, in the file indicated when you started @value{GDBN}
13546 (@pxref{File Options, ,Choosing Files}), or by one of the
13547 file-management commands (@pxref{Files, ,Commands to Specify Files}).
13548
13549 @cindex symbol names
13550 @cindex names of symbols
13551 @cindex quoting names
13552 Occasionally, you may need to refer to symbols that contain unusual
13553 characters, which @value{GDBN} ordinarily treats as word delimiters. The
13554 most frequent case is in referring to static variables in other
13555 source files (@pxref{Variables,,Program Variables}). File names
13556 are recorded in object files as debugging symbols, but @value{GDBN} would
13557 ordinarily parse a typical file name, like @file{foo.c}, as the three words
13558 @samp{foo} @samp{.} @samp{c}. To allow @value{GDBN} to recognize
13559 @samp{foo.c} as a single symbol, enclose it in single quotes; for example,
13560
13561 @smallexample
13562 p 'foo.c'::x
13563 @end smallexample
13564
13565 @noindent
13566 looks up the value of @code{x} in the scope of the file @file{foo.c}.
13567
13568 @table @code
13569 @cindex case-insensitive symbol names
13570 @cindex case sensitivity in symbol names
13571 @kindex set case-sensitive
13572 @item set case-sensitive on
13573 @itemx set case-sensitive off
13574 @itemx set case-sensitive auto
13575 Normally, when @value{GDBN} looks up symbols, it matches their names
13576 with case sensitivity determined by the current source language.
13577 Occasionally, you may wish to control that. The command @code{set
13578 case-sensitive} lets you do that by specifying @code{on} for
13579 case-sensitive matches or @code{off} for case-insensitive ones. If
13580 you specify @code{auto}, case sensitivity is reset to the default
13581 suitable for the source language. The default is case-sensitive
13582 matches for all languages except for Fortran, for which the default is
13583 case-insensitive matches.
13584
13585 @kindex show case-sensitive
13586 @item show case-sensitive
13587 This command shows the current setting of case sensitivity for symbols
13588 lookups.
13589
13590 @kindex info address
13591 @cindex address of a symbol
13592 @item info address @var{symbol}
13593 Describe where the data for @var{symbol} is stored. For a register
13594 variable, this says which register it is kept in. For a non-register
13595 local variable, this prints the stack-frame offset at which the variable
13596 is always stored.
13597
13598 Note the contrast with @samp{print &@var{symbol}}, which does not work
13599 at all for a register variable, and for a stack local variable prints
13600 the exact address of the current instantiation of the variable.
13601
13602 @kindex info symbol
13603 @cindex symbol from address
13604 @cindex closest symbol and offset for an address
13605 @item info symbol @var{addr}
13606 Print the name of a symbol which is stored at the address @var{addr}.
13607 If no symbol is stored exactly at @var{addr}, @value{GDBN} prints the
13608 nearest symbol and an offset from it:
13609
13610 @smallexample
13611 (@value{GDBP}) info symbol 0x54320
13612 _initialize_vx + 396 in section .text
13613 @end smallexample
13614
13615 @noindent
13616 This is the opposite of the @code{info address} command. You can use
13617 it to find out the name of a variable or a function given its address.
13618
13619 For dynamically linked executables, the name of executable or shared
13620 library containing the symbol is also printed:
13621
13622 @smallexample
13623 (@value{GDBP}) info symbol 0x400225
13624 _start + 5 in section .text of /tmp/a.out
13625 (@value{GDBP}) info symbol 0x2aaaac2811cf
13626 __read_nocancel + 6 in section .text of /usr/lib64/libc.so.6
13627 @end smallexample
13628
13629 @kindex whatis
13630 @item whatis [@var{arg}]
13631 Print the data type of @var{arg}, which can be either an expression or
13632 a data type. With no argument, print the data type of @code{$}, the
13633 last value in the value history. If @var{arg} is an expression, it is
13634 not actually evaluated, and any side-effecting operations (such as
13635 assignments or function calls) inside it do not take place. If
13636 @var{arg} is a type name, it may be the name of a type or typedef, or
13637 for C code it may have the form @samp{class @var{class-name}},
13638 @samp{struct @var{struct-tag}}, @samp{union @var{union-tag}} or
13639 @samp{enum @var{enum-tag}}.
13640 @xref{Expressions, ,Expressions}.
13641
13642 @kindex ptype
13643 @item ptype [@var{arg}]
13644 @code{ptype} accepts the same arguments as @code{whatis}, but prints a
13645 detailed description of the type, instead of just the name of the type.
13646 @xref{Expressions, ,Expressions}.
13647
13648 For example, for this variable declaration:
13649
13650 @smallexample
13651 struct complex @{double real; double imag;@} v;
13652 @end smallexample
13653
13654 @noindent
13655 the two commands give this output:
13656
13657 @smallexample
13658 @group
13659 (@value{GDBP}) whatis v
13660 type = struct complex
13661 (@value{GDBP}) ptype v
13662 type = struct complex @{
13663 double real;
13664 double imag;
13665 @}
13666 @end group
13667 @end smallexample
13668
13669 @noindent
13670 As with @code{whatis}, using @code{ptype} without an argument refers to
13671 the type of @code{$}, the last value in the value history.
13672
13673 @cindex incomplete type
13674 Sometimes, programs use opaque data types or incomplete specifications
13675 of complex data structure. If the debug information included in the
13676 program does not allow @value{GDBN} to display a full declaration of
13677 the data type, it will say @samp{<incomplete type>}. For example,
13678 given these declarations:
13679
13680 @smallexample
13681 struct foo;
13682 struct foo *fooptr;
13683 @end smallexample
13684
13685 @noindent
13686 but no definition for @code{struct foo} itself, @value{GDBN} will say:
13687
13688 @smallexample
13689 (@value{GDBP}) ptype foo
13690 $1 = <incomplete type>
13691 @end smallexample
13692
13693 @noindent
13694 ``Incomplete type'' is C terminology for data types that are not
13695 completely specified.
13696
13697 @kindex info types
13698 @item info types @var{regexp}
13699 @itemx info types
13700 Print a brief description of all types whose names match the regular
13701 expression @var{regexp} (or all types in your program, if you supply
13702 no argument). Each complete typename is matched as though it were a
13703 complete line; thus, @samp{i type value} gives information on all
13704 types in your program whose names include the string @code{value}, but
13705 @samp{i type ^value$} gives information only on types whose complete
13706 name is @code{value}.
13707
13708 This command differs from @code{ptype} in two ways: first, like
13709 @code{whatis}, it does not print a detailed description; second, it
13710 lists all source files where a type is defined.
13711
13712 @kindex info scope
13713 @cindex local variables
13714 @item info scope @var{location}
13715 List all the variables local to a particular scope. This command
13716 accepts a @var{location} argument---a function name, a source line, or
13717 an address preceded by a @samp{*}, and prints all the variables local
13718 to the scope defined by that location. (@xref{Specify Location}, for
13719 details about supported forms of @var{location}.) For example:
13720
13721 @smallexample
13722 (@value{GDBP}) @b{info scope command_line_handler}
13723 Scope for command_line_handler:
13724 Symbol rl is an argument at stack/frame offset 8, length 4.
13725 Symbol linebuffer is in static storage at address 0x150a18, length 4.
13726 Symbol linelength is in static storage at address 0x150a1c, length 4.
13727 Symbol p is a local variable in register $esi, length 4.
13728 Symbol p1 is a local variable in register $ebx, length 4.
13729 Symbol nline is a local variable in register $edx, length 4.
13730 Symbol repeat is a local variable at frame offset -8, length 4.
13731 @end smallexample
13732
13733 @noindent
13734 This command is especially useful for determining what data to collect
13735 during a @dfn{trace experiment}, see @ref{Tracepoint Actions,
13736 collect}.
13737
13738 @kindex info source
13739 @item info source
13740 Show information about the current source file---that is, the source file for
13741 the function containing the current point of execution:
13742 @itemize @bullet
13743 @item
13744 the name of the source file, and the directory containing it,
13745 @item
13746 the directory it was compiled in,
13747 @item
13748 its length, in lines,
13749 @item
13750 which programming language it is written in,
13751 @item
13752 whether the executable includes debugging information for that file, and
13753 if so, what format the information is in (e.g., STABS, Dwarf 2, etc.), and
13754 @item
13755 whether the debugging information includes information about
13756 preprocessor macros.
13757 @end itemize
13758
13759
13760 @kindex info sources
13761 @item info sources
13762 Print the names of all source files in your program for which there is
13763 debugging information, organized into two lists: files whose symbols
13764 have already been read, and files whose symbols will be read when needed.
13765
13766 @kindex info functions
13767 @item info functions
13768 Print the names and data types of all defined functions.
13769
13770 @item info functions @var{regexp}
13771 Print the names and data types of all defined functions
13772 whose names contain a match for regular expression @var{regexp}.
13773 Thus, @samp{info fun step} finds all functions whose names
13774 include @code{step}; @samp{info fun ^step} finds those whose names
13775 start with @code{step}. If a function name contains characters
13776 that conflict with the regular expression language (e.g.@:
13777 @samp{operator*()}), they may be quoted with a backslash.
13778
13779 @kindex info variables
13780 @item info variables
13781 Print the names and data types of all variables that are defined
13782 outside of functions (i.e.@: excluding local variables).
13783
13784 @item info variables @var{regexp}
13785 Print the names and data types of all variables (except for local
13786 variables) whose names contain a match for regular expression
13787 @var{regexp}.
13788
13789 @kindex info classes
13790 @cindex Objective-C, classes and selectors
13791 @item info classes
13792 @itemx info classes @var{regexp}
13793 Display all Objective-C classes in your program, or
13794 (with the @var{regexp} argument) all those matching a particular regular
13795 expression.
13796
13797 @kindex info selectors
13798 @item info selectors
13799 @itemx info selectors @var{regexp}
13800 Display all Objective-C selectors in your program, or
13801 (with the @var{regexp} argument) all those matching a particular regular
13802 expression.
13803
13804 @ignore
13805 This was never implemented.
13806 @kindex info methods
13807 @item info methods
13808 @itemx info methods @var{regexp}
13809 The @code{info methods} command permits the user to examine all defined
13810 methods within C@t{++} program, or (with the @var{regexp} argument) a
13811 specific set of methods found in the various C@t{++} classes. Many
13812 C@t{++} classes provide a large number of methods. Thus, the output
13813 from the @code{ptype} command can be overwhelming and hard to use. The
13814 @code{info-methods} command filters the methods, printing only those
13815 which match the regular-expression @var{regexp}.
13816 @end ignore
13817
13818 @cindex reloading symbols
13819 Some systems allow individual object files that make up your program to
13820 be replaced without stopping and restarting your program. For example,
13821 in VxWorks you can simply recompile a defective object file and keep on
13822 running. If you are running on one of these systems, you can allow
13823 @value{GDBN} to reload the symbols for automatically relinked modules:
13824
13825 @table @code
13826 @kindex set symbol-reloading
13827 @item set symbol-reloading on
13828 Replace symbol definitions for the corresponding source file when an
13829 object file with a particular name is seen again.
13830
13831 @item set symbol-reloading off
13832 Do not replace symbol definitions when encountering object files of the
13833 same name more than once. This is the default state; if you are not
13834 running on a system that permits automatic relinking of modules, you
13835 should leave @code{symbol-reloading} off, since otherwise @value{GDBN}
13836 may discard symbols when linking large programs, that may contain
13837 several modules (from different directories or libraries) with the same
13838 name.
13839
13840 @kindex show symbol-reloading
13841 @item show symbol-reloading
13842 Show the current @code{on} or @code{off} setting.
13843 @end table
13844
13845 @cindex opaque data types
13846 @kindex set opaque-type-resolution
13847 @item set opaque-type-resolution on
13848 Tell @value{GDBN} to resolve opaque types. An opaque type is a type
13849 declared as a pointer to a @code{struct}, @code{class}, or
13850 @code{union}---for example, @code{struct MyType *}---that is used in one
13851 source file although the full declaration of @code{struct MyType} is in
13852 another source file. The default is on.
13853
13854 A change in the setting of this subcommand will not take effect until
13855 the next time symbols for a file are loaded.
13856
13857 @item set opaque-type-resolution off
13858 Tell @value{GDBN} not to resolve opaque types. In this case, the type
13859 is printed as follows:
13860 @smallexample
13861 @{<no data fields>@}
13862 @end smallexample
13863
13864 @kindex show opaque-type-resolution
13865 @item show opaque-type-resolution
13866 Show whether opaque types are resolved or not.
13867
13868 @kindex maint print symbols
13869 @cindex symbol dump
13870 @kindex maint print psymbols
13871 @cindex partial symbol dump
13872 @item maint print symbols @var{filename}
13873 @itemx maint print psymbols @var{filename}
13874 @itemx maint print msymbols @var{filename}
13875 Write a dump of debugging symbol data into the file @var{filename}.
13876 These commands are used to debug the @value{GDBN} symbol-reading code. Only
13877 symbols with debugging data are included. If you use @samp{maint print
13878 symbols}, @value{GDBN} includes all the symbols for which it has already
13879 collected full details: that is, @var{filename} reflects symbols for
13880 only those files whose symbols @value{GDBN} has read. You can use the
13881 command @code{info sources} to find out which files these are. If you
13882 use @samp{maint print psymbols} instead, the dump shows information about
13883 symbols that @value{GDBN} only knows partially---that is, symbols defined in
13884 files that @value{GDBN} has skimmed, but not yet read completely. Finally,
13885 @samp{maint print msymbols} dumps just the minimal symbol information
13886 required for each object file from which @value{GDBN} has read some symbols.
13887 @xref{Files, ,Commands to Specify Files}, for a discussion of how
13888 @value{GDBN} reads symbols (in the description of @code{symbol-file}).
13889
13890 @kindex maint info symtabs
13891 @kindex maint info psymtabs
13892 @cindex listing @value{GDBN}'s internal symbol tables
13893 @cindex symbol tables, listing @value{GDBN}'s internal
13894 @cindex full symbol tables, listing @value{GDBN}'s internal
13895 @cindex partial symbol tables, listing @value{GDBN}'s internal
13896 @item maint info symtabs @r{[} @var{regexp} @r{]}
13897 @itemx maint info psymtabs @r{[} @var{regexp} @r{]}
13898
13899 List the @code{struct symtab} or @code{struct partial_symtab}
13900 structures whose names match @var{regexp}. If @var{regexp} is not
13901 given, list them all. The output includes expressions which you can
13902 copy into a @value{GDBN} debugging this one to examine a particular
13903 structure in more detail. For example:
13904
13905 @smallexample
13906 (@value{GDBP}) maint info psymtabs dwarf2read
13907 @{ objfile /home/gnu/build/gdb/gdb
13908 ((struct objfile *) 0x82e69d0)
13909 @{ psymtab /home/gnu/src/gdb/dwarf2read.c
13910 ((struct partial_symtab *) 0x8474b10)
13911 readin no
13912 fullname (null)
13913 text addresses 0x814d3c8 -- 0x8158074
13914 globals (* (struct partial_symbol **) 0x8507a08 @@ 9)
13915 statics (* (struct partial_symbol **) 0x40e95b78 @@ 2882)
13916 dependencies (none)
13917 @}
13918 @}
13919 (@value{GDBP}) maint info symtabs
13920 (@value{GDBP})
13921 @end smallexample
13922 @noindent
13923 We see that there is one partial symbol table whose filename contains
13924 the string @samp{dwarf2read}, belonging to the @samp{gdb} executable;
13925 and we see that @value{GDBN} has not read in any symtabs yet at all.
13926 If we set a breakpoint on a function, that will cause @value{GDBN} to
13927 read the symtab for the compilation unit containing that function:
13928
13929 @smallexample
13930 (@value{GDBP}) break dwarf2_psymtab_to_symtab
13931 Breakpoint 1 at 0x814e5da: file /home/gnu/src/gdb/dwarf2read.c,
13932 line 1574.
13933 (@value{GDBP}) maint info symtabs
13934 @{ objfile /home/gnu/build/gdb/gdb
13935 ((struct objfile *) 0x82e69d0)
13936 @{ symtab /home/gnu/src/gdb/dwarf2read.c
13937 ((struct symtab *) 0x86c1f38)
13938 dirname (null)
13939 fullname (null)
13940 blockvector ((struct blockvector *) 0x86c1bd0) (primary)
13941 linetable ((struct linetable *) 0x8370fa0)
13942 debugformat DWARF 2
13943 @}
13944 @}
13945 (@value{GDBP})
13946 @end smallexample
13947 @end table
13948
13949
13950 @node Altering
13951 @chapter Altering Execution
13952
13953 Once you think you have found an error in your program, you might want to
13954 find out for certain whether correcting the apparent error would lead to
13955 correct results in the rest of the run. You can find the answer by
13956 experiment, using the @value{GDBN} features for altering execution of the
13957 program.
13958
13959 For example, you can store new values into variables or memory
13960 locations, give your program a signal, restart it at a different
13961 address, or even return prematurely from a function.
13962
13963 @menu
13964 * Assignment:: Assignment to variables
13965 * Jumping:: Continuing at a different address
13966 * Signaling:: Giving your program a signal
13967 * Returning:: Returning from a function
13968 * Calling:: Calling your program's functions
13969 * Patching:: Patching your program
13970 @end menu
13971
13972 @node Assignment
13973 @section Assignment to Variables
13974
13975 @cindex assignment
13976 @cindex setting variables
13977 To alter the value of a variable, evaluate an assignment expression.
13978 @xref{Expressions, ,Expressions}. For example,
13979
13980 @smallexample
13981 print x=4
13982 @end smallexample
13983
13984 @noindent
13985 stores the value 4 into the variable @code{x}, and then prints the
13986 value of the assignment expression (which is 4).
13987 @xref{Languages, ,Using @value{GDBN} with Different Languages}, for more
13988 information on operators in supported languages.
13989
13990 @kindex set variable
13991 @cindex variables, setting
13992 If you are not interested in seeing the value of the assignment, use the
13993 @code{set} command instead of the @code{print} command. @code{set} is
13994 really the same as @code{print} except that the expression's value is
13995 not printed and is not put in the value history (@pxref{Value History,
13996 ,Value History}). The expression is evaluated only for its effects.
13997
13998 If the beginning of the argument string of the @code{set} command
13999 appears identical to a @code{set} subcommand, use the @code{set
14000 variable} command instead of just @code{set}. This command is identical
14001 to @code{set} except for its lack of subcommands. For example, if your
14002 program has a variable @code{width}, you get an error if you try to set
14003 a new value with just @samp{set width=13}, because @value{GDBN} has the
14004 command @code{set width}:
14005
14006 @smallexample
14007 (@value{GDBP}) whatis width
14008 type = double
14009 (@value{GDBP}) p width
14010 $4 = 13
14011 (@value{GDBP}) set width=47
14012 Invalid syntax in expression.
14013 @end smallexample
14014
14015 @noindent
14016 The invalid expression, of course, is @samp{=47}. In
14017 order to actually set the program's variable @code{width}, use
14018
14019 @smallexample
14020 (@value{GDBP}) set var width=47
14021 @end smallexample
14022
14023 Because the @code{set} command has many subcommands that can conflict
14024 with the names of program variables, it is a good idea to use the
14025 @code{set variable} command instead of just @code{set}. For example, if
14026 your program has a variable @code{g}, you run into problems if you try
14027 to set a new value with just @samp{set g=4}, because @value{GDBN} has
14028 the command @code{set gnutarget}, abbreviated @code{set g}:
14029
14030 @smallexample
14031 @group
14032 (@value{GDBP}) whatis g
14033 type = double
14034 (@value{GDBP}) p g
14035 $1 = 1
14036 (@value{GDBP}) set g=4
14037 (@value{GDBP}) p g
14038 $2 = 1
14039 (@value{GDBP}) r
14040 The program being debugged has been started already.
14041 Start it from the beginning? (y or n) y
14042 Starting program: /home/smith/cc_progs/a.out
14043 "/home/smith/cc_progs/a.out": can't open to read symbols:
14044 Invalid bfd target.
14045 (@value{GDBP}) show g
14046 The current BFD target is "=4".
14047 @end group
14048 @end smallexample
14049
14050 @noindent
14051 The program variable @code{g} did not change, and you silently set the
14052 @code{gnutarget} to an invalid value. In order to set the variable
14053 @code{g}, use
14054
14055 @smallexample
14056 (@value{GDBP}) set var g=4
14057 @end smallexample
14058
14059 @value{GDBN} allows more implicit conversions in assignments than C; you can
14060 freely store an integer value into a pointer variable or vice versa,
14061 and you can convert any structure to any other structure that is the
14062 same length or shorter.
14063 @comment FIXME: how do structs align/pad in these conversions?
14064 @comment /doc@cygnus.com 18dec1990
14065
14066 To store values into arbitrary places in memory, use the @samp{@{@dots{}@}}
14067 construct to generate a value of specified type at a specified address
14068 (@pxref{Expressions, ,Expressions}). For example, @code{@{int@}0x83040} refers
14069 to memory location @code{0x83040} as an integer (which implies a certain size
14070 and representation in memory), and
14071
14072 @smallexample
14073 set @{int@}0x83040 = 4
14074 @end smallexample
14075
14076 @noindent
14077 stores the value 4 into that memory location.
14078
14079 @node Jumping
14080 @section Continuing at a Different Address
14081
14082 Ordinarily, when you continue your program, you do so at the place where
14083 it stopped, with the @code{continue} command. You can instead continue at
14084 an address of your own choosing, with the following commands:
14085
14086 @table @code
14087 @kindex jump
14088 @item jump @var{linespec}
14089 @itemx jump @var{location}
14090 Resume execution at line @var{linespec} or at address given by
14091 @var{location}. Execution stops again immediately if there is a
14092 breakpoint there. @xref{Specify Location}, for a description of the
14093 different forms of @var{linespec} and @var{location}. It is common
14094 practice to use the @code{tbreak} command in conjunction with
14095 @code{jump}. @xref{Set Breaks, ,Setting Breakpoints}.
14096
14097 The @code{jump} command does not change the current stack frame, or
14098 the stack pointer, or the contents of any memory location or any
14099 register other than the program counter. If line @var{linespec} is in
14100 a different function from the one currently executing, the results may
14101 be bizarre if the two functions expect different patterns of arguments or
14102 of local variables. For this reason, the @code{jump} command requests
14103 confirmation if the specified line is not in the function currently
14104 executing. However, even bizarre results are predictable if you are
14105 well acquainted with the machine-language code of your program.
14106 @end table
14107
14108 @c Doesn't work on HP-UX; have to set $pcoqh and $pcoqt.
14109 On many systems, you can get much the same effect as the @code{jump}
14110 command by storing a new value into the register @code{$pc}. The
14111 difference is that this does not start your program running; it only
14112 changes the address of where it @emph{will} run when you continue. For
14113 example,
14114
14115 @smallexample
14116 set $pc = 0x485
14117 @end smallexample
14118
14119 @noindent
14120 makes the next @code{continue} command or stepping command execute at
14121 address @code{0x485}, rather than at the address where your program stopped.
14122 @xref{Continuing and Stepping, ,Continuing and Stepping}.
14123
14124 The most common occasion to use the @code{jump} command is to back
14125 up---perhaps with more breakpoints set---over a portion of a program
14126 that has already executed, in order to examine its execution in more
14127 detail.
14128
14129 @c @group
14130 @node Signaling
14131 @section Giving your Program a Signal
14132 @cindex deliver a signal to a program
14133
14134 @table @code
14135 @kindex signal
14136 @item signal @var{signal}
14137 Resume execution where your program stopped, but immediately give it the
14138 signal @var{signal}. @var{signal} can be the name or the number of a
14139 signal. For example, on many systems @code{signal 2} and @code{signal
14140 SIGINT} are both ways of sending an interrupt signal.
14141
14142 Alternatively, if @var{signal} is zero, continue execution without
14143 giving a signal. This is useful when your program stopped on account of
14144 a signal and would ordinary see the signal when resumed with the
14145 @code{continue} command; @samp{signal 0} causes it to resume without a
14146 signal.
14147
14148 @code{signal} does not repeat when you press @key{RET} a second time
14149 after executing the command.
14150 @end table
14151 @c @end group
14152
14153 Invoking the @code{signal} command is not the same as invoking the
14154 @code{kill} utility from the shell. Sending a signal with @code{kill}
14155 causes @value{GDBN} to decide what to do with the signal depending on
14156 the signal handling tables (@pxref{Signals}). The @code{signal} command
14157 passes the signal directly to your program.
14158
14159
14160 @node Returning
14161 @section Returning from a Function
14162
14163 @table @code
14164 @cindex returning from a function
14165 @kindex return
14166 @item return
14167 @itemx return @var{expression}
14168 You can cancel execution of a function call with the @code{return}
14169 command. If you give an
14170 @var{expression} argument, its value is used as the function's return
14171 value.
14172 @end table
14173
14174 When you use @code{return}, @value{GDBN} discards the selected stack frame
14175 (and all frames within it). You can think of this as making the
14176 discarded frame return prematurely. If you wish to specify a value to
14177 be returned, give that value as the argument to @code{return}.
14178
14179 This pops the selected stack frame (@pxref{Selection, ,Selecting a
14180 Frame}), and any other frames inside of it, leaving its caller as the
14181 innermost remaining frame. That frame becomes selected. The
14182 specified value is stored in the registers used for returning values
14183 of functions.
14184
14185 The @code{return} command does not resume execution; it leaves the
14186 program stopped in the state that would exist if the function had just
14187 returned. In contrast, the @code{finish} command (@pxref{Continuing
14188 and Stepping, ,Continuing and Stepping}) resumes execution until the
14189 selected stack frame returns naturally.
14190
14191 @value{GDBN} needs to know how the @var{expression} argument should be set for
14192 the inferior. The concrete registers assignment depends on the OS ABI and the
14193 type being returned by the selected stack frame. For example it is common for
14194 OS ABI to return floating point values in FPU registers while integer values in
14195 CPU registers. Still some ABIs return even floating point values in CPU
14196 registers. Larger integer widths (such as @code{long long int}) also have
14197 specific placement rules. @value{GDBN} already knows the OS ABI from its
14198 current target so it needs to find out also the type being returned to make the
14199 assignment into the right register(s).
14200
14201 Normally, the selected stack frame has debug info. @value{GDBN} will always
14202 use the debug info instead of the implicit type of @var{expression} when the
14203 debug info is available. For example, if you type @kbd{return -1}, and the
14204 function in the current stack frame is declared to return a @code{long long
14205 int}, @value{GDBN} transparently converts the implicit @code{int} value of -1
14206 into a @code{long long int}:
14207
14208 @smallexample
14209 Breakpoint 1, func () at gdb.base/return-nodebug.c:29
14210 29 return 31;
14211 (@value{GDBP}) return -1
14212 Make func return now? (y or n) y
14213 #0 0x004004f6 in main () at gdb.base/return-nodebug.c:43
14214 43 printf ("result=%lld\n", func ());
14215 (@value{GDBP})
14216 @end smallexample
14217
14218 However, if the selected stack frame does not have a debug info, e.g., if the
14219 function was compiled without debug info, @value{GDBN} has to find out the type
14220 to return from user. Specifying a different type by mistake may set the value
14221 in different inferior registers than the caller code expects. For example,
14222 typing @kbd{return -1} with its implicit type @code{int} would set only a part
14223 of a @code{long long int} result for a debug info less function (on 32-bit
14224 architectures). Therefore the user is required to specify the return type by
14225 an appropriate cast explicitly:
14226
14227 @smallexample
14228 Breakpoint 2, 0x0040050b in func ()
14229 (@value{GDBP}) return -1
14230 Return value type not available for selected stack frame.
14231 Please use an explicit cast of the value to return.
14232 (@value{GDBP}) return (long long int) -1
14233 Make selected stack frame return now? (y or n) y
14234 #0 0x00400526 in main ()
14235 (@value{GDBP})
14236 @end smallexample
14237
14238 @node Calling
14239 @section Calling Program Functions
14240
14241 @table @code
14242 @cindex calling functions
14243 @cindex inferior functions, calling
14244 @item print @var{expr}
14245 Evaluate the expression @var{expr} and display the resulting value.
14246 @var{expr} may include calls to functions in the program being
14247 debugged.
14248
14249 @kindex call
14250 @item call @var{expr}
14251 Evaluate the expression @var{expr} without displaying @code{void}
14252 returned values.
14253
14254 You can use this variant of the @code{print} command if you want to
14255 execute a function from your program that does not return anything
14256 (a.k.a.@: @dfn{a void function}), but without cluttering the output
14257 with @code{void} returned values that @value{GDBN} will otherwise
14258 print. If the result is not void, it is printed and saved in the
14259 value history.
14260 @end table
14261
14262 It is possible for the function you call via the @code{print} or
14263 @code{call} command to generate a signal (e.g., if there's a bug in
14264 the function, or if you passed it incorrect arguments). What happens
14265 in that case is controlled by the @code{set unwindonsignal} command.
14266
14267 Similarly, with a C@t{++} program it is possible for the function you
14268 call via the @code{print} or @code{call} command to generate an
14269 exception that is not handled due to the constraints of the dummy
14270 frame. In this case, any exception that is raised in the frame, but has
14271 an out-of-frame exception handler will not be found. GDB builds a
14272 dummy-frame for the inferior function call, and the unwinder cannot
14273 seek for exception handlers outside of this dummy-frame. What happens
14274 in that case is controlled by the
14275 @code{set unwind-on-terminating-exception} command.
14276
14277 @table @code
14278 @item set unwindonsignal
14279 @kindex set unwindonsignal
14280 @cindex unwind stack in called functions
14281 @cindex call dummy stack unwinding
14282 Set unwinding of the stack if a signal is received while in a function
14283 that @value{GDBN} called in the program being debugged. If set to on,
14284 @value{GDBN} unwinds the stack it created for the call and restores
14285 the context to what it was before the call. If set to off (the
14286 default), @value{GDBN} stops in the frame where the signal was
14287 received.
14288
14289 @item show unwindonsignal
14290 @kindex show unwindonsignal
14291 Show the current setting of stack unwinding in the functions called by
14292 @value{GDBN}.
14293
14294 @item set unwind-on-terminating-exception
14295 @kindex set unwind-on-terminating-exception
14296 @cindex unwind stack in called functions with unhandled exceptions
14297 @cindex call dummy stack unwinding on unhandled exception.
14298 Set unwinding of the stack if a C@t{++} exception is raised, but left
14299 unhandled while in a function that @value{GDBN} called in the program being
14300 debugged. If set to on (the default), @value{GDBN} unwinds the stack
14301 it created for the call and restores the context to what it was before
14302 the call. If set to off, @value{GDBN} the exception is delivered to
14303 the default C@t{++} exception handler and the inferior terminated.
14304
14305 @item show unwind-on-terminating-exception
14306 @kindex show unwind-on-terminating-exception
14307 Show the current setting of stack unwinding in the functions called by
14308 @value{GDBN}.
14309
14310 @end table
14311
14312 @cindex weak alias functions
14313 Sometimes, a function you wish to call is actually a @dfn{weak alias}
14314 for another function. In such case, @value{GDBN} might not pick up
14315 the type information, including the types of the function arguments,
14316 which causes @value{GDBN} to call the inferior function incorrectly.
14317 As a result, the called function will function erroneously and may
14318 even crash. A solution to that is to use the name of the aliased
14319 function instead.
14320
14321 @node Patching
14322 @section Patching Programs
14323
14324 @cindex patching binaries
14325 @cindex writing into executables
14326 @cindex writing into corefiles
14327
14328 By default, @value{GDBN} opens the file containing your program's
14329 executable code (or the corefile) read-only. This prevents accidental
14330 alterations to machine code; but it also prevents you from intentionally
14331 patching your program's binary.
14332
14333 If you'd like to be able to patch the binary, you can specify that
14334 explicitly with the @code{set write} command. For example, you might
14335 want to turn on internal debugging flags, or even to make emergency
14336 repairs.
14337
14338 @table @code
14339 @kindex set write
14340 @item set write on
14341 @itemx set write off
14342 If you specify @samp{set write on}, @value{GDBN} opens executable and
14343 core files for both reading and writing; if you specify @kbd{set write
14344 off} (the default), @value{GDBN} opens them read-only.
14345
14346 If you have already loaded a file, you must load it again (using the
14347 @code{exec-file} or @code{core-file} command) after changing @code{set
14348 write}, for your new setting to take effect.
14349
14350 @item show write
14351 @kindex show write
14352 Display whether executable files and core files are opened for writing
14353 as well as reading.
14354 @end table
14355
14356 @node GDB Files
14357 @chapter @value{GDBN} Files
14358
14359 @value{GDBN} needs to know the file name of the program to be debugged,
14360 both in order to read its symbol table and in order to start your
14361 program. To debug a core dump of a previous run, you must also tell
14362 @value{GDBN} the name of the core dump file.
14363
14364 @menu
14365 * Files:: Commands to specify files
14366 * Separate Debug Files:: Debugging information in separate files
14367 * Index Files:: Index files speed up GDB
14368 * Symbol Errors:: Errors reading symbol files
14369 * Data Files:: GDB data files
14370 @end menu
14371
14372 @node Files
14373 @section Commands to Specify Files
14374
14375 @cindex symbol table
14376 @cindex core dump file
14377
14378 You may want to specify executable and core dump file names. The usual
14379 way to do this is at start-up time, using the arguments to
14380 @value{GDBN}'s start-up commands (@pxref{Invocation, , Getting In and
14381 Out of @value{GDBN}}).
14382
14383 Occasionally it is necessary to change to a different file during a
14384 @value{GDBN} session. Or you may run @value{GDBN} and forget to
14385 specify a file you want to use. Or you are debugging a remote target
14386 via @code{gdbserver} (@pxref{Server, file, Using the @code{gdbserver}
14387 Program}). In these situations the @value{GDBN} commands to specify
14388 new files are useful.
14389
14390 @table @code
14391 @cindex executable file
14392 @kindex file
14393 @item file @var{filename}
14394 Use @var{filename} as the program to be debugged. It is read for its
14395 symbols and for the contents of pure memory. It is also the program
14396 executed when you use the @code{run} command. If you do not specify a
14397 directory and the file is not found in the @value{GDBN} working directory,
14398 @value{GDBN} uses the environment variable @code{PATH} as a list of
14399 directories to search, just as the shell does when looking for a program
14400 to run. You can change the value of this variable, for both @value{GDBN}
14401 and your program, using the @code{path} command.
14402
14403 @cindex unlinked object files
14404 @cindex patching object files
14405 You can load unlinked object @file{.o} files into @value{GDBN} using
14406 the @code{file} command. You will not be able to ``run'' an object
14407 file, but you can disassemble functions and inspect variables. Also,
14408 if the underlying BFD functionality supports it, you could use
14409 @kbd{gdb -write} to patch object files using this technique. Note
14410 that @value{GDBN} can neither interpret nor modify relocations in this
14411 case, so branches and some initialized variables will appear to go to
14412 the wrong place. But this feature is still handy from time to time.
14413
14414 @item file
14415 @code{file} with no argument makes @value{GDBN} discard any information it
14416 has on both executable file and the symbol table.
14417
14418 @kindex exec-file
14419 @item exec-file @r{[} @var{filename} @r{]}
14420 Specify that the program to be run (but not the symbol table) is found
14421 in @var{filename}. @value{GDBN} searches the environment variable @code{PATH}
14422 if necessary to locate your program. Omitting @var{filename} means to
14423 discard information on the executable file.
14424
14425 @kindex symbol-file
14426 @item symbol-file @r{[} @var{filename} @r{]}
14427 Read symbol table information from file @var{filename}. @code{PATH} is
14428 searched when necessary. Use the @code{file} command to get both symbol
14429 table and program to run from the same file.
14430
14431 @code{symbol-file} with no argument clears out @value{GDBN} information on your
14432 program's symbol table.
14433
14434 The @code{symbol-file} command causes @value{GDBN} to forget the contents of
14435 some breakpoints and auto-display expressions. This is because they may
14436 contain pointers to the internal data recording symbols and data types,
14437 which are part of the old symbol table data being discarded inside
14438 @value{GDBN}.
14439
14440 @code{symbol-file} does not repeat if you press @key{RET} again after
14441 executing it once.
14442
14443 When @value{GDBN} is configured for a particular environment, it
14444 understands debugging information in whatever format is the standard
14445 generated for that environment; you may use either a @sc{gnu} compiler, or
14446 other compilers that adhere to the local conventions.
14447 Best results are usually obtained from @sc{gnu} compilers; for example,
14448 using @code{@value{NGCC}} you can generate debugging information for
14449 optimized code.
14450
14451 For most kinds of object files, with the exception of old SVR3 systems
14452 using COFF, the @code{symbol-file} command does not normally read the
14453 symbol table in full right away. Instead, it scans the symbol table
14454 quickly to find which source files and which symbols are present. The
14455 details are read later, one source file at a time, as they are needed.
14456
14457 The purpose of this two-stage reading strategy is to make @value{GDBN}
14458 start up faster. For the most part, it is invisible except for
14459 occasional pauses while the symbol table details for a particular source
14460 file are being read. (The @code{set verbose} command can turn these
14461 pauses into messages if desired. @xref{Messages/Warnings, ,Optional
14462 Warnings and Messages}.)
14463
14464 We have not implemented the two-stage strategy for COFF yet. When the
14465 symbol table is stored in COFF format, @code{symbol-file} reads the
14466 symbol table data in full right away. Note that ``stabs-in-COFF''
14467 still does the two-stage strategy, since the debug info is actually
14468 in stabs format.
14469
14470 @kindex readnow
14471 @cindex reading symbols immediately
14472 @cindex symbols, reading immediately
14473 @item symbol-file @r{[} -readnow @r{]} @var{filename}
14474 @itemx file @r{[} -readnow @r{]} @var{filename}
14475 You can override the @value{GDBN} two-stage strategy for reading symbol
14476 tables by using the @samp{-readnow} option with any of the commands that
14477 load symbol table information, if you want to be sure @value{GDBN} has the
14478 entire symbol table available.
14479
14480 @c FIXME: for now no mention of directories, since this seems to be in
14481 @c flux. 13mar1992 status is that in theory GDB would look either in
14482 @c current dir or in same dir as myprog; but issues like competing
14483 @c GDB's, or clutter in system dirs, mean that in practice right now
14484 @c only current dir is used. FFish says maybe a special GDB hierarchy
14485 @c (eg rooted in val of env var GDBSYMS) could exist for mappable symbol
14486 @c files.
14487
14488 @kindex core-file
14489 @item core-file @r{[}@var{filename}@r{]}
14490 @itemx core
14491 Specify the whereabouts of a core dump file to be used as the ``contents
14492 of memory''. Traditionally, core files contain only some parts of the
14493 address space of the process that generated them; @value{GDBN} can access the
14494 executable file itself for other parts.
14495
14496 @code{core-file} with no argument specifies that no core file is
14497 to be used.
14498
14499 Note that the core file is ignored when your program is actually running
14500 under @value{GDBN}. So, if you have been running your program and you
14501 wish to debug a core file instead, you must kill the subprocess in which
14502 the program is running. To do this, use the @code{kill} command
14503 (@pxref{Kill Process, ,Killing the Child Process}).
14504
14505 @kindex add-symbol-file
14506 @cindex dynamic linking
14507 @item add-symbol-file @var{filename} @var{address}
14508 @itemx add-symbol-file @var{filename} @var{address} @r{[} -readnow @r{]}
14509 @itemx add-symbol-file @var{filename} @r{-s}@var{section} @var{address} @dots{}
14510 The @code{add-symbol-file} command reads additional symbol table
14511 information from the file @var{filename}. You would use this command
14512 when @var{filename} has been dynamically loaded (by some other means)
14513 into the program that is running. @var{address} should be the memory
14514 address at which the file has been loaded; @value{GDBN} cannot figure
14515 this out for itself. You can additionally specify an arbitrary number
14516 of @samp{@r{-s}@var{section} @var{address}} pairs, to give an explicit
14517 section name and base address for that section. You can specify any
14518 @var{address} as an expression.
14519
14520 The symbol table of the file @var{filename} is added to the symbol table
14521 originally read with the @code{symbol-file} command. You can use the
14522 @code{add-symbol-file} command any number of times; the new symbol data
14523 thus read keeps adding to the old. To discard all old symbol data
14524 instead, use the @code{symbol-file} command without any arguments.
14525
14526 @cindex relocatable object files, reading symbols from
14527 @cindex object files, relocatable, reading symbols from
14528 @cindex reading symbols from relocatable object files
14529 @cindex symbols, reading from relocatable object files
14530 @cindex @file{.o} files, reading symbols from
14531 Although @var{filename} is typically a shared library file, an
14532 executable file, or some other object file which has been fully
14533 relocated for loading into a process, you can also load symbolic
14534 information from relocatable @file{.o} files, as long as:
14535
14536 @itemize @bullet
14537 @item
14538 the file's symbolic information refers only to linker symbols defined in
14539 that file, not to symbols defined by other object files,
14540 @item
14541 every section the file's symbolic information refers to has actually
14542 been loaded into the inferior, as it appears in the file, and
14543 @item
14544 you can determine the address at which every section was loaded, and
14545 provide these to the @code{add-symbol-file} command.
14546 @end itemize
14547
14548 @noindent
14549 Some embedded operating systems, like Sun Chorus and VxWorks, can load
14550 relocatable files into an already running program; such systems
14551 typically make the requirements above easy to meet. However, it's
14552 important to recognize that many native systems use complex link
14553 procedures (@code{.linkonce} section factoring and C@t{++} constructor table
14554 assembly, for example) that make the requirements difficult to meet. In
14555 general, one cannot assume that using @code{add-symbol-file} to read a
14556 relocatable object file's symbolic information will have the same effect
14557 as linking the relocatable object file into the program in the normal
14558 way.
14559
14560 @code{add-symbol-file} does not repeat if you press @key{RET} after using it.
14561
14562 @kindex add-symbol-file-from-memory
14563 @cindex @code{syscall DSO}
14564 @cindex load symbols from memory
14565 @item add-symbol-file-from-memory @var{address}
14566 Load symbols from the given @var{address} in a dynamically loaded
14567 object file whose image is mapped directly into the inferior's memory.
14568 For example, the Linux kernel maps a @code{syscall DSO} into each
14569 process's address space; this DSO provides kernel-specific code for
14570 some system calls. The argument can be any expression whose
14571 evaluation yields the address of the file's shared object file header.
14572 For this command to work, you must have used @code{symbol-file} or
14573 @code{exec-file} commands in advance.
14574
14575 @kindex add-shared-symbol-files
14576 @kindex assf
14577 @item add-shared-symbol-files @var{library-file}
14578 @itemx assf @var{library-file}
14579 The @code{add-shared-symbol-files} command can currently be used only
14580 in the Cygwin build of @value{GDBN} on MS-Windows OS, where it is an
14581 alias for the @code{dll-symbols} command (@pxref{Cygwin Native}).
14582 @value{GDBN} automatically looks for shared libraries, however if
14583 @value{GDBN} does not find yours, you can invoke
14584 @code{add-shared-symbol-files}. It takes one argument: the shared
14585 library's file name. @code{assf} is a shorthand alias for
14586 @code{add-shared-symbol-files}.
14587
14588 @kindex section
14589 @item section @var{section} @var{addr}
14590 The @code{section} command changes the base address of the named
14591 @var{section} of the exec file to @var{addr}. This can be used if the
14592 exec file does not contain section addresses, (such as in the
14593 @code{a.out} format), or when the addresses specified in the file
14594 itself are wrong. Each section must be changed separately. The
14595 @code{info files} command, described below, lists all the sections and
14596 their addresses.
14597
14598 @kindex info files
14599 @kindex info target
14600 @item info files
14601 @itemx info target
14602 @code{info files} and @code{info target} are synonymous; both print the
14603 current target (@pxref{Targets, ,Specifying a Debugging Target}),
14604 including the names of the executable and core dump files currently in
14605 use by @value{GDBN}, and the files from which symbols were loaded. The
14606 command @code{help target} lists all possible targets rather than
14607 current ones.
14608
14609 @kindex maint info sections
14610 @item maint info sections
14611 Another command that can give you extra information about program sections
14612 is @code{maint info sections}. In addition to the section information
14613 displayed by @code{info files}, this command displays the flags and file
14614 offset of each section in the executable and core dump files. In addition,
14615 @code{maint info sections} provides the following command options (which
14616 may be arbitrarily combined):
14617
14618 @table @code
14619 @item ALLOBJ
14620 Display sections for all loaded object files, including shared libraries.
14621 @item @var{sections}
14622 Display info only for named @var{sections}.
14623 @item @var{section-flags}
14624 Display info only for sections for which @var{section-flags} are true.
14625 The section flags that @value{GDBN} currently knows about are:
14626 @table @code
14627 @item ALLOC
14628 Section will have space allocated in the process when loaded.
14629 Set for all sections except those containing debug information.
14630 @item LOAD
14631 Section will be loaded from the file into the child process memory.
14632 Set for pre-initialized code and data, clear for @code{.bss} sections.
14633 @item RELOC
14634 Section needs to be relocated before loading.
14635 @item READONLY
14636 Section cannot be modified by the child process.
14637 @item CODE
14638 Section contains executable code only.
14639 @item DATA
14640 Section contains data only (no executable code).
14641 @item ROM
14642 Section will reside in ROM.
14643 @item CONSTRUCTOR
14644 Section contains data for constructor/destructor lists.
14645 @item HAS_CONTENTS
14646 Section is not empty.
14647 @item NEVER_LOAD
14648 An instruction to the linker to not output the section.
14649 @item COFF_SHARED_LIBRARY
14650 A notification to the linker that the section contains
14651 COFF shared library information.
14652 @item IS_COMMON
14653 Section contains common symbols.
14654 @end table
14655 @end table
14656 @kindex set trust-readonly-sections
14657 @cindex read-only sections
14658 @item set trust-readonly-sections on
14659 Tell @value{GDBN} that readonly sections in your object file
14660 really are read-only (i.e.@: that their contents will not change).
14661 In that case, @value{GDBN} can fetch values from these sections
14662 out of the object file, rather than from the target program.
14663 For some targets (notably embedded ones), this can be a significant
14664 enhancement to debugging performance.
14665
14666 The default is off.
14667
14668 @item set trust-readonly-sections off
14669 Tell @value{GDBN} not to trust readonly sections. This means that
14670 the contents of the section might change while the program is running,
14671 and must therefore be fetched from the target when needed.
14672
14673 @item show trust-readonly-sections
14674 Show the current setting of trusting readonly sections.
14675 @end table
14676
14677 All file-specifying commands allow both absolute and relative file names
14678 as arguments. @value{GDBN} always converts the file name to an absolute file
14679 name and remembers it that way.
14680
14681 @cindex shared libraries
14682 @anchor{Shared Libraries}
14683 @value{GDBN} supports @sc{gnu}/Linux, MS-Windows, HP-UX, SunOS, SVr4, Irix,
14684 and IBM RS/6000 AIX shared libraries.
14685
14686 On MS-Windows @value{GDBN} must be linked with the Expat library to support
14687 shared libraries. @xref{Expat}.
14688
14689 @value{GDBN} automatically loads symbol definitions from shared libraries
14690 when you use the @code{run} command, or when you examine a core file.
14691 (Before you issue the @code{run} command, @value{GDBN} does not understand
14692 references to a function in a shared library, however---unless you are
14693 debugging a core file).
14694
14695 On HP-UX, if the program loads a library explicitly, @value{GDBN}
14696 automatically loads the symbols at the time of the @code{shl_load} call.
14697
14698 @c FIXME: some @value{GDBN} release may permit some refs to undef
14699 @c FIXME...symbols---eg in a break cmd---assuming they are from a shared
14700 @c FIXME...lib; check this from time to time when updating manual
14701
14702 There are times, however, when you may wish to not automatically load
14703 symbol definitions from shared libraries, such as when they are
14704 particularly large or there are many of them.
14705
14706 To control the automatic loading of shared library symbols, use the
14707 commands:
14708
14709 @table @code
14710 @kindex set auto-solib-add
14711 @item set auto-solib-add @var{mode}
14712 If @var{mode} is @code{on}, symbols from all shared object libraries
14713 will be loaded automatically when the inferior begins execution, you
14714 attach to an independently started inferior, or when the dynamic linker
14715 informs @value{GDBN} that a new library has been loaded. If @var{mode}
14716 is @code{off}, symbols must be loaded manually, using the
14717 @code{sharedlibrary} command. The default value is @code{on}.
14718
14719 @cindex memory used for symbol tables
14720 If your program uses lots of shared libraries with debug info that
14721 takes large amounts of memory, you can decrease the @value{GDBN}
14722 memory footprint by preventing it from automatically loading the
14723 symbols from shared libraries. To that end, type @kbd{set
14724 auto-solib-add off} before running the inferior, then load each
14725 library whose debug symbols you do need with @kbd{sharedlibrary
14726 @var{regexp}}, where @var{regexp} is a regular expression that matches
14727 the libraries whose symbols you want to be loaded.
14728
14729 @kindex show auto-solib-add
14730 @item show auto-solib-add
14731 Display the current autoloading mode.
14732 @end table
14733
14734 @cindex load shared library
14735 To explicitly load shared library symbols, use the @code{sharedlibrary}
14736 command:
14737
14738 @table @code
14739 @kindex info sharedlibrary
14740 @kindex info share
14741 @item info share @var{regex}
14742 @itemx info sharedlibrary @var{regex}
14743 Print the names of the shared libraries which are currently loaded
14744 that match @var{regex}. If @var{regex} is omitted then print
14745 all shared libraries that are loaded.
14746
14747 @kindex sharedlibrary
14748 @kindex share
14749 @item sharedlibrary @var{regex}
14750 @itemx share @var{regex}
14751 Load shared object library symbols for files matching a
14752 Unix regular expression.
14753 As with files loaded automatically, it only loads shared libraries
14754 required by your program for a core file or after typing @code{run}. If
14755 @var{regex} is omitted all shared libraries required by your program are
14756 loaded.
14757
14758 @item nosharedlibrary
14759 @kindex nosharedlibrary
14760 @cindex unload symbols from shared libraries
14761 Unload all shared object library symbols. This discards all symbols
14762 that have been loaded from all shared libraries. Symbols from shared
14763 libraries that were loaded by explicit user requests are not
14764 discarded.
14765 @end table
14766
14767 Sometimes you may wish that @value{GDBN} stops and gives you control
14768 when any of shared library events happen. Use the @code{set
14769 stop-on-solib-events} command for this:
14770
14771 @table @code
14772 @item set stop-on-solib-events
14773 @kindex set stop-on-solib-events
14774 This command controls whether @value{GDBN} should give you control
14775 when the dynamic linker notifies it about some shared library event.
14776 The most common event of interest is loading or unloading of a new
14777 shared library.
14778
14779 @item show stop-on-solib-events
14780 @kindex show stop-on-solib-events
14781 Show whether @value{GDBN} stops and gives you control when shared
14782 library events happen.
14783 @end table
14784
14785 Shared libraries are also supported in many cross or remote debugging
14786 configurations. @value{GDBN} needs to have access to the target's libraries;
14787 this can be accomplished either by providing copies of the libraries
14788 on the host system, or by asking @value{GDBN} to automatically retrieve the
14789 libraries from the target. If copies of the target libraries are
14790 provided, they need to be the same as the target libraries, although the
14791 copies on the target can be stripped as long as the copies on the host are
14792 not.
14793
14794 @cindex where to look for shared libraries
14795 For remote debugging, you need to tell @value{GDBN} where the target
14796 libraries are, so that it can load the correct copies---otherwise, it
14797 may try to load the host's libraries. @value{GDBN} has two variables
14798 to specify the search directories for target libraries.
14799
14800 @table @code
14801 @cindex prefix for shared library file names
14802 @cindex system root, alternate
14803 @kindex set solib-absolute-prefix
14804 @kindex set sysroot
14805 @item set sysroot @var{path}
14806 Use @var{path} as the system root for the program being debugged. Any
14807 absolute shared library paths will be prefixed with @var{path}; many
14808 runtime loaders store the absolute paths to the shared library in the
14809 target program's memory. If you use @code{set sysroot} to find shared
14810 libraries, they need to be laid out in the same way that they are on
14811 the target, with e.g.@: a @file{/lib} and @file{/usr/lib} hierarchy
14812 under @var{path}.
14813
14814 If @var{path} starts with the sequence @file{remote:}, @value{GDBN} will
14815 retrieve the target libraries from the remote system. This is only
14816 supported when using a remote target that supports the @code{remote get}
14817 command (@pxref{File Transfer,,Sending files to a remote system}).
14818 The part of @var{path} following the initial @file{remote:}
14819 (if present) is used as system root prefix on the remote file system.
14820 @footnote{If you want to specify a local system root using a directory
14821 that happens to be named @file{remote:}, you need to use some equivalent
14822 variant of the name like @file{./remote:}.}
14823
14824 For targets with an MS-DOS based filesystem, such as MS-Windows and
14825 SymbianOS, @value{GDBN} tries prefixing a few variants of the target
14826 absolute file name with @var{path}. But first, on Unix hosts,
14827 @value{GDBN} converts all backslash directory separators into forward
14828 slashes, because the backslash is not a directory separator on Unix:
14829
14830 @smallexample
14831 c:\foo\bar.dll @result{} c:/foo/bar.dll
14832 @end smallexample
14833
14834 Then, @value{GDBN} attempts prefixing the target file name with
14835 @var{path}, and looks for the resulting file name in the host file
14836 system:
14837
14838 @smallexample
14839 c:/foo/bar.dll @result{} /path/to/sysroot/c:/foo/bar.dll
14840 @end smallexample
14841
14842 If that does not find the shared library, @value{GDBN} tries removing
14843 the @samp{:} character from the drive spec, both for convenience, and,
14844 for the case of the host file system not supporting file names with
14845 colons:
14846
14847 @smallexample
14848 c:/foo/bar.dll @result{} /path/to/sysroot/c/foo/bar.dll
14849 @end smallexample
14850
14851 This makes it possible to have a system root that mirrors a target
14852 with more than one drive. E.g., you may want to setup your local
14853 copies of the target system shared libraries like so (note @samp{c} vs
14854 @samp{z}):
14855
14856 @smallexample
14857 @file{/path/to/sysroot/c/sys/bin/foo.dll}
14858 @file{/path/to/sysroot/c/sys/bin/bar.dll}
14859 @file{/path/to/sysroot/z/sys/bin/bar.dll}
14860 @end smallexample
14861
14862 @noindent
14863 and point the system root at @file{/path/to/sysroot}, so that
14864 @value{GDBN} can find the correct copies of both
14865 @file{c:\sys\bin\foo.dll}, and @file{z:\sys\bin\bar.dll}.
14866
14867 If that still does not find the shared library, @value{GDBN} tries
14868 removing the whole drive spec from the target file name:
14869
14870 @smallexample
14871 c:/foo/bar.dll @result{} /path/to/sysroot/foo/bar.dll
14872 @end smallexample
14873
14874 This last lookup makes it possible to not care about the drive name,
14875 if you don't want or need to.
14876
14877 The @code{set solib-absolute-prefix} command is an alias for @code{set
14878 sysroot}.
14879
14880 @cindex default system root
14881 @cindex @samp{--with-sysroot}
14882 You can set the default system root by using the configure-time
14883 @samp{--with-sysroot} option. If the system root is inside
14884 @value{GDBN}'s configured binary prefix (set with @samp{--prefix} or
14885 @samp{--exec-prefix}), then the default system root will be updated
14886 automatically if the installed @value{GDBN} is moved to a new
14887 location.
14888
14889 @kindex show sysroot
14890 @item show sysroot
14891 Display the current shared library prefix.
14892
14893 @kindex set solib-search-path
14894 @item set solib-search-path @var{path}
14895 If this variable is set, @var{path} is a colon-separated list of
14896 directories to search for shared libraries. @samp{solib-search-path}
14897 is used after @samp{sysroot} fails to locate the library, or if the
14898 path to the library is relative instead of absolute. If you want to
14899 use @samp{solib-search-path} instead of @samp{sysroot}, be sure to set
14900 @samp{sysroot} to a nonexistent directory to prevent @value{GDBN} from
14901 finding your host's libraries. @samp{sysroot} is preferred; setting
14902 it to a nonexistent directory may interfere with automatic loading
14903 of shared library symbols.
14904
14905 @kindex show solib-search-path
14906 @item show solib-search-path
14907 Display the current shared library search path.
14908
14909 @cindex DOS file-name semantics of file names.
14910 @kindex set target-file-system-kind (unix|dos-based|auto)
14911 @kindex show target-file-system-kind
14912 @item set target-file-system-kind @var{kind}
14913 Set assumed file system kind for target reported file names.
14914
14915 Shared library file names as reported by the target system may not
14916 make sense as is on the system @value{GDBN} is running on. For
14917 example, when remote debugging a target that has MS-DOS based file
14918 system semantics, from a Unix host, the target may be reporting to
14919 @value{GDBN} a list of loaded shared libraries with file names such as
14920 @file{c:\Windows\kernel32.dll}. On Unix hosts, there's no concept of
14921 drive letters, so the @samp{c:\} prefix is not normally understood as
14922 indicating an absolute file name, and neither is the backslash
14923 normally considered a directory separator character. In that case,
14924 the native file system would interpret this whole absolute file name
14925 as a relative file name with no directory components. This would make
14926 it impossible to point @value{GDBN} at a copy of the remote target's
14927 shared libraries on the host using @code{set sysroot}, and impractical
14928 with @code{set solib-search-path}. Setting
14929 @code{target-file-system-kind} to @code{dos-based} tells @value{GDBN}
14930 to interpret such file names similarly to how the target would, and to
14931 map them to file names valid on @value{GDBN}'s native file system
14932 semantics. The value of @var{kind} can be @code{"auto"}, in addition
14933 to one of the supported file system kinds. In that case, @value{GDBN}
14934 tries to determine the appropriate file system variant based on the
14935 current target's operating system (@pxref{ABI, ,Configuring the
14936 Current ABI}). The supported file system settings are:
14937
14938 @table @code
14939 @item unix
14940 Instruct @value{GDBN} to assume the target file system is of Unix
14941 kind. Only file names starting the forward slash (@samp{/}) character
14942 are considered absolute, and the directory separator character is also
14943 the forward slash.
14944
14945 @item dos-based
14946 Instruct @value{GDBN} to assume the target file system is DOS based.
14947 File names starting with either a forward slash, or a drive letter
14948 followed by a colon (e.g., @samp{c:}), are considered absolute, and
14949 both the slash (@samp{/}) and the backslash (@samp{\\}) characters are
14950 considered directory separators.
14951
14952 @item auto
14953 Instruct @value{GDBN} to use the file system kind associated with the
14954 target operating system (@pxref{ABI, ,Configuring the Current ABI}).
14955 This is the default.
14956 @end table
14957 @end table
14958
14959
14960 @node Separate Debug Files
14961 @section Debugging Information in Separate Files
14962 @cindex separate debugging information files
14963 @cindex debugging information in separate files
14964 @cindex @file{.debug} subdirectories
14965 @cindex debugging information directory, global
14966 @cindex global debugging information directory
14967 @cindex build ID, and separate debugging files
14968 @cindex @file{.build-id} directory
14969
14970 @value{GDBN} allows you to put a program's debugging information in a
14971 file separate from the executable itself, in a way that allows
14972 @value{GDBN} to find and load the debugging information automatically.
14973 Since debugging information can be very large---sometimes larger
14974 than the executable code itself---some systems distribute debugging
14975 information for their executables in separate files, which users can
14976 install only when they need to debug a problem.
14977
14978 @value{GDBN} supports two ways of specifying the separate debug info
14979 file:
14980
14981 @itemize @bullet
14982 @item
14983 The executable contains a @dfn{debug link} that specifies the name of
14984 the separate debug info file. The separate debug file's name is
14985 usually @file{@var{executable}.debug}, where @var{executable} is the
14986 name of the corresponding executable file without leading directories
14987 (e.g., @file{ls.debug} for @file{/usr/bin/ls}). In addition, the
14988 debug link specifies a 32-bit @dfn{Cyclic Redundancy Check} (CRC)
14989 checksum for the debug file, which @value{GDBN} uses to validate that
14990 the executable and the debug file came from the same build.
14991
14992 @item
14993 The executable contains a @dfn{build ID}, a unique bit string that is
14994 also present in the corresponding debug info file. (This is supported
14995 only on some operating systems, notably those which use the ELF format
14996 for binary files and the @sc{gnu} Binutils.) For more details about
14997 this feature, see the description of the @option{--build-id}
14998 command-line option in @ref{Options, , Command Line Options, ld.info,
14999 The GNU Linker}. The debug info file's name is not specified
15000 explicitly by the build ID, but can be computed from the build ID, see
15001 below.
15002 @end itemize
15003
15004 Depending on the way the debug info file is specified, @value{GDBN}
15005 uses two different methods of looking for the debug file:
15006
15007 @itemize @bullet
15008 @item
15009 For the ``debug link'' method, @value{GDBN} looks up the named file in
15010 the directory of the executable file, then in a subdirectory of that
15011 directory named @file{.debug}, and finally under the global debug
15012 directory, in a subdirectory whose name is identical to the leading
15013 directories of the executable's absolute file name.
15014
15015 @item
15016 For the ``build ID'' method, @value{GDBN} looks in the
15017 @file{.build-id} subdirectory of the global debug directory for a file
15018 named @file{@var{nn}/@var{nnnnnnnn}.debug}, where @var{nn} are the
15019 first 2 hex characters of the build ID bit string, and @var{nnnnnnnn}
15020 are the rest of the bit string. (Real build ID strings are 32 or more
15021 hex characters, not 10.)
15022 @end itemize
15023
15024 So, for example, suppose you ask @value{GDBN} to debug
15025 @file{/usr/bin/ls}, which has a debug link that specifies the
15026 file @file{ls.debug}, and a build ID whose value in hex is
15027 @code{abcdef1234}. If the global debug directory is
15028 @file{/usr/lib/debug}, then @value{GDBN} will look for the following
15029 debug information files, in the indicated order:
15030
15031 @itemize @minus
15032 @item
15033 @file{/usr/lib/debug/.build-id/ab/cdef1234.debug}
15034 @item
15035 @file{/usr/bin/ls.debug}
15036 @item
15037 @file{/usr/bin/.debug/ls.debug}
15038 @item
15039 @file{/usr/lib/debug/usr/bin/ls.debug}.
15040 @end itemize
15041
15042 You can set the global debugging info directory's name, and view the
15043 name @value{GDBN} is currently using.
15044
15045 @table @code
15046
15047 @kindex set debug-file-directory
15048 @item set debug-file-directory @var{directories}
15049 Set the directories which @value{GDBN} searches for separate debugging
15050 information files to @var{directory}. Multiple directory components can be set
15051 concatenating them by a directory separator.
15052
15053 @kindex show debug-file-directory
15054 @item show debug-file-directory
15055 Show the directories @value{GDBN} searches for separate debugging
15056 information files.
15057
15058 @end table
15059
15060 @cindex @code{.gnu_debuglink} sections
15061 @cindex debug link sections
15062 A debug link is a special section of the executable file named
15063 @code{.gnu_debuglink}. The section must contain:
15064
15065 @itemize
15066 @item
15067 A filename, with any leading directory components removed, followed by
15068 a zero byte,
15069 @item
15070 zero to three bytes of padding, as needed to reach the next four-byte
15071 boundary within the section, and
15072 @item
15073 a four-byte CRC checksum, stored in the same endianness used for the
15074 executable file itself. The checksum is computed on the debugging
15075 information file's full contents by the function given below, passing
15076 zero as the @var{crc} argument.
15077 @end itemize
15078
15079 Any executable file format can carry a debug link, as long as it can
15080 contain a section named @code{.gnu_debuglink} with the contents
15081 described above.
15082
15083 @cindex @code{.note.gnu.build-id} sections
15084 @cindex build ID sections
15085 The build ID is a special section in the executable file (and in other
15086 ELF binary files that @value{GDBN} may consider). This section is
15087 often named @code{.note.gnu.build-id}, but that name is not mandatory.
15088 It contains unique identification for the built files---the ID remains
15089 the same across multiple builds of the same build tree. The default
15090 algorithm SHA1 produces 160 bits (40 hexadecimal characters) of the
15091 content for the build ID string. The same section with an identical
15092 value is present in the original built binary with symbols, in its
15093 stripped variant, and in the separate debugging information file.
15094
15095 The debugging information file itself should be an ordinary
15096 executable, containing a full set of linker symbols, sections, and
15097 debugging information. The sections of the debugging information file
15098 should have the same names, addresses, and sizes as the original file,
15099 but they need not contain any data---much like a @code{.bss} section
15100 in an ordinary executable.
15101
15102 The @sc{gnu} binary utilities (Binutils) package includes the
15103 @samp{objcopy} utility that can produce
15104 the separated executable / debugging information file pairs using the
15105 following commands:
15106
15107 @smallexample
15108 @kbd{objcopy --only-keep-debug foo foo.debug}
15109 @kbd{strip -g foo}
15110 @end smallexample
15111
15112 @noindent
15113 These commands remove the debugging
15114 information from the executable file @file{foo} and place it in the file
15115 @file{foo.debug}. You can use the first, second or both methods to link the
15116 two files:
15117
15118 @itemize @bullet
15119 @item
15120 The debug link method needs the following additional command to also leave
15121 behind a debug link in @file{foo}:
15122
15123 @smallexample
15124 @kbd{objcopy --add-gnu-debuglink=foo.debug foo}
15125 @end smallexample
15126
15127 Ulrich Drepper's @file{elfutils} package, starting with version 0.53, contains
15128 a version of the @code{strip} command such that the command @kbd{strip foo -f
15129 foo.debug} has the same functionality as the two @code{objcopy} commands and
15130 the @code{ln -s} command above, together.
15131
15132 @item
15133 Build ID gets embedded into the main executable using @code{ld --build-id} or
15134 the @value{NGCC} counterpart @code{gcc -Wl,--build-id}. Build ID support plus
15135 compatibility fixes for debug files separation are present in @sc{gnu} binary
15136 utilities (Binutils) package since version 2.18.
15137 @end itemize
15138
15139 @noindent
15140
15141 @cindex CRC algorithm definition
15142 The CRC used in @code{.gnu_debuglink} is the CRC-32 defined in
15143 IEEE 802.3 using the polynomial:
15144
15145 @c TexInfo requires naked braces for multi-digit exponents for Tex
15146 @c output, but this causes HTML output to barf. HTML has to be set using
15147 @c raw commands. So we end up having to specify this equation in 2
15148 @c different ways!
15149 @ifhtml
15150 @display
15151 @html
15152 <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>
15153 + <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
15154 @end html
15155 @end display
15156 @end ifhtml
15157 @ifnothtml
15158 @display
15159 @math{x^{32} + x^{26} + x^{23} + x^{22} + x^{16} + x^{12} + x^{11}}
15160 @math{+ x^{10} + x^8 + x^7 + x^5 + x^4 + x^2 + x + 1}
15161 @end display
15162 @end ifnothtml
15163
15164 The function is computed byte at a time, taking the least
15165 significant bit of each byte first. The initial pattern
15166 @code{0xffffffff} is used, to ensure leading zeros affect the CRC and
15167 the final result is inverted to ensure trailing zeros also affect the
15168 CRC.
15169
15170 @emph{Note:} This is the same CRC polynomial as used in handling the
15171 @dfn{Remote Serial Protocol} @code{qCRC} packet (@pxref{Remote Protocol,
15172 , @value{GDBN} Remote Serial Protocol}). However in the
15173 case of the Remote Serial Protocol, the CRC is computed @emph{most}
15174 significant bit first, and the result is not inverted, so trailing
15175 zeros have no effect on the CRC value.
15176
15177 To complete the description, we show below the code of the function
15178 which produces the CRC used in @code{.gnu_debuglink}. Inverting the
15179 initially supplied @code{crc} argument means that an initial call to
15180 this function passing in zero will start computing the CRC using
15181 @code{0xffffffff}.
15182
15183 @kindex gnu_debuglink_crc32
15184 @smallexample
15185 unsigned long
15186 gnu_debuglink_crc32 (unsigned long crc,
15187 unsigned char *buf, size_t len)
15188 @{
15189 static const unsigned long crc32_table[256] =
15190 @{
15191 0x00000000, 0x77073096, 0xee0e612c, 0x990951ba, 0x076dc419,
15192 0x706af48f, 0xe963a535, 0x9e6495a3, 0x0edb8832, 0x79dcb8a4,
15193 0xe0d5e91e, 0x97d2d988, 0x09b64c2b, 0x7eb17cbd, 0xe7b82d07,
15194 0x90bf1d91, 0x1db71064, 0x6ab020f2, 0xf3b97148, 0x84be41de,
15195 0x1adad47d, 0x6ddde4eb, 0xf4d4b551, 0x83d385c7, 0x136c9856,
15196 0x646ba8c0, 0xfd62f97a, 0x8a65c9ec, 0x14015c4f, 0x63066cd9,
15197 0xfa0f3d63, 0x8d080df5, 0x3b6e20c8, 0x4c69105e, 0xd56041e4,
15198 0xa2677172, 0x3c03e4d1, 0x4b04d447, 0xd20d85fd, 0xa50ab56b,
15199 0x35b5a8fa, 0x42b2986c, 0xdbbbc9d6, 0xacbcf940, 0x32d86ce3,
15200 0x45df5c75, 0xdcd60dcf, 0xabd13d59, 0x26d930ac, 0x51de003a,
15201 0xc8d75180, 0xbfd06116, 0x21b4f4b5, 0x56b3c423, 0xcfba9599,
15202 0xb8bda50f, 0x2802b89e, 0x5f058808, 0xc60cd9b2, 0xb10be924,
15203 0x2f6f7c87, 0x58684c11, 0xc1611dab, 0xb6662d3d, 0x76dc4190,
15204 0x01db7106, 0x98d220bc, 0xefd5102a, 0x71b18589, 0x06b6b51f,
15205 0x9fbfe4a5, 0xe8b8d433, 0x7807c9a2, 0x0f00f934, 0x9609a88e,
15206 0xe10e9818, 0x7f6a0dbb, 0x086d3d2d, 0x91646c97, 0xe6635c01,
15207 0x6b6b51f4, 0x1c6c6162, 0x856530d8, 0xf262004e, 0x6c0695ed,
15208 0x1b01a57b, 0x8208f4c1, 0xf50fc457, 0x65b0d9c6, 0x12b7e950,
15209 0x8bbeb8ea, 0xfcb9887c, 0x62dd1ddf, 0x15da2d49, 0x8cd37cf3,
15210 0xfbd44c65, 0x4db26158, 0x3ab551ce, 0xa3bc0074, 0xd4bb30e2,
15211 0x4adfa541, 0x3dd895d7, 0xa4d1c46d, 0xd3d6f4fb, 0x4369e96a,
15212 0x346ed9fc, 0xad678846, 0xda60b8d0, 0x44042d73, 0x33031de5,
15213 0xaa0a4c5f, 0xdd0d7cc9, 0x5005713c, 0x270241aa, 0xbe0b1010,
15214 0xc90c2086, 0x5768b525, 0x206f85b3, 0xb966d409, 0xce61e49f,
15215 0x5edef90e, 0x29d9c998, 0xb0d09822, 0xc7d7a8b4, 0x59b33d17,
15216 0x2eb40d81, 0xb7bd5c3b, 0xc0ba6cad, 0xedb88320, 0x9abfb3b6,
15217 0x03b6e20c, 0x74b1d29a, 0xead54739, 0x9dd277af, 0x04db2615,
15218 0x73dc1683, 0xe3630b12, 0x94643b84, 0x0d6d6a3e, 0x7a6a5aa8,
15219 0xe40ecf0b, 0x9309ff9d, 0x0a00ae27, 0x7d079eb1, 0xf00f9344,
15220 0x8708a3d2, 0x1e01f268, 0x6906c2fe, 0xf762575d, 0x806567cb,
15221 0x196c3671, 0x6e6b06e7, 0xfed41b76, 0x89d32be0, 0x10da7a5a,
15222 0x67dd4acc, 0xf9b9df6f, 0x8ebeeff9, 0x17b7be43, 0x60b08ed5,
15223 0xd6d6a3e8, 0xa1d1937e, 0x38d8c2c4, 0x4fdff252, 0xd1bb67f1,
15224 0xa6bc5767, 0x3fb506dd, 0x48b2364b, 0xd80d2bda, 0xaf0a1b4c,
15225 0x36034af6, 0x41047a60, 0xdf60efc3, 0xa867df55, 0x316e8eef,
15226 0x4669be79, 0xcb61b38c, 0xbc66831a, 0x256fd2a0, 0x5268e236,
15227 0xcc0c7795, 0xbb0b4703, 0x220216b9, 0x5505262f, 0xc5ba3bbe,
15228 0xb2bd0b28, 0x2bb45a92, 0x5cb36a04, 0xc2d7ffa7, 0xb5d0cf31,
15229 0x2cd99e8b, 0x5bdeae1d, 0x9b64c2b0, 0xec63f226, 0x756aa39c,
15230 0x026d930a, 0x9c0906a9, 0xeb0e363f, 0x72076785, 0x05005713,
15231 0x95bf4a82, 0xe2b87a14, 0x7bb12bae, 0x0cb61b38, 0x92d28e9b,
15232 0xe5d5be0d, 0x7cdcefb7, 0x0bdbdf21, 0x86d3d2d4, 0xf1d4e242,
15233 0x68ddb3f8, 0x1fda836e, 0x81be16cd, 0xf6b9265b, 0x6fb077e1,
15234 0x18b74777, 0x88085ae6, 0xff0f6a70, 0x66063bca, 0x11010b5c,
15235 0x8f659eff, 0xf862ae69, 0x616bffd3, 0x166ccf45, 0xa00ae278,
15236 0xd70dd2ee, 0x4e048354, 0x3903b3c2, 0xa7672661, 0xd06016f7,
15237 0x4969474d, 0x3e6e77db, 0xaed16a4a, 0xd9d65adc, 0x40df0b66,
15238 0x37d83bf0, 0xa9bcae53, 0xdebb9ec5, 0x47b2cf7f, 0x30b5ffe9,
15239 0xbdbdf21c, 0xcabac28a, 0x53b39330, 0x24b4a3a6, 0xbad03605,
15240 0xcdd70693, 0x54de5729, 0x23d967bf, 0xb3667a2e, 0xc4614ab8,
15241 0x5d681b02, 0x2a6f2b94, 0xb40bbe37, 0xc30c8ea1, 0x5a05df1b,
15242 0x2d02ef8d
15243 @};
15244 unsigned char *end;
15245
15246 crc = ~crc & 0xffffffff;
15247 for (end = buf + len; buf < end; ++buf)
15248 crc = crc32_table[(crc ^ *buf) & 0xff] ^ (crc >> 8);
15249 return ~crc & 0xffffffff;
15250 @}
15251 @end smallexample
15252
15253 @noindent
15254 This computation does not apply to the ``build ID'' method.
15255
15256
15257 @node Index Files
15258 @section Index Files Speed Up @value{GDBN}
15259 @cindex index files
15260 @cindex @samp{.gdb_index} section
15261
15262 When @value{GDBN} finds a symbol file, it scans the symbols in the
15263 file in order to construct an internal symbol table. This lets most
15264 @value{GDBN} operations work quickly---at the cost of a delay early
15265 on. For large programs, this delay can be quite lengthy, so
15266 @value{GDBN} provides a way to build an index, which speeds up
15267 startup.
15268
15269 The index is stored as a section in the symbol file. @value{GDBN} can
15270 write the index to a file, then you can put it into the symbol file
15271 using @command{objcopy}.
15272
15273 To create an index file, use the @code{save gdb-index} command:
15274
15275 @table @code
15276 @item save gdb-index @var{directory}
15277 @kindex save gdb-index
15278 Create an index file for each symbol file currently known by
15279 @value{GDBN}. Each file is named after its corresponding symbol file,
15280 with @samp{.gdb-index} appended, and is written into the given
15281 @var{directory}.
15282 @end table
15283
15284 Once you have created an index file you can merge it into your symbol
15285 file, here named @file{symfile}, using @command{objcopy}:
15286
15287 @smallexample
15288 $ objcopy --add-section .gdb_index=symfile.gdb-index \
15289 --set-section-flags .gdb_index=readonly symfile symfile
15290 @end smallexample
15291
15292 There are currently some limitation on indices. They only work when
15293 for DWARF debugging information, not stabs. And, they do not
15294 currently work for programs using Ada.
15295
15296 @node Symbol Errors
15297 @section Errors Reading Symbol Files
15298
15299 While reading a symbol file, @value{GDBN} occasionally encounters problems,
15300 such as symbol types it does not recognize, or known bugs in compiler
15301 output. By default, @value{GDBN} does not notify you of such problems, since
15302 they are relatively common and primarily of interest to people
15303 debugging compilers. If you are interested in seeing information
15304 about ill-constructed symbol tables, you can either ask @value{GDBN} to print
15305 only one message about each such type of problem, no matter how many
15306 times the problem occurs; or you can ask @value{GDBN} to print more messages,
15307 to see how many times the problems occur, with the @code{set
15308 complaints} command (@pxref{Messages/Warnings, ,Optional Warnings and
15309 Messages}).
15310
15311 The messages currently printed, and their meanings, include:
15312
15313 @table @code
15314 @item inner block not inside outer block in @var{symbol}
15315
15316 The symbol information shows where symbol scopes begin and end
15317 (such as at the start of a function or a block of statements). This
15318 error indicates that an inner scope block is not fully contained
15319 in its outer scope blocks.
15320
15321 @value{GDBN} circumvents the problem by treating the inner block as if it had
15322 the same scope as the outer block. In the error message, @var{symbol}
15323 may be shown as ``@code{(don't know)}'' if the outer block is not a
15324 function.
15325
15326 @item block at @var{address} out of order
15327
15328 The symbol information for symbol scope blocks should occur in
15329 order of increasing addresses. This error indicates that it does not
15330 do so.
15331
15332 @value{GDBN} does not circumvent this problem, and has trouble
15333 locating symbols in the source file whose symbols it is reading. (You
15334 can often determine what source file is affected by specifying
15335 @code{set verbose on}. @xref{Messages/Warnings, ,Optional Warnings and
15336 Messages}.)
15337
15338 @item bad block start address patched
15339
15340 The symbol information for a symbol scope block has a start address
15341 smaller than the address of the preceding source line. This is known
15342 to occur in the SunOS 4.1.1 (and earlier) C compiler.
15343
15344 @value{GDBN} circumvents the problem by treating the symbol scope block as
15345 starting on the previous source line.
15346
15347 @item bad string table offset in symbol @var{n}
15348
15349 @cindex foo
15350 Symbol number @var{n} contains a pointer into the string table which is
15351 larger than the size of the string table.
15352
15353 @value{GDBN} circumvents the problem by considering the symbol to have the
15354 name @code{foo}, which may cause other problems if many symbols end up
15355 with this name.
15356
15357 @item unknown symbol type @code{0x@var{nn}}
15358
15359 The symbol information contains new data types that @value{GDBN} does
15360 not yet know how to read. @code{0x@var{nn}} is the symbol type of the
15361 uncomprehended information, in hexadecimal.
15362
15363 @value{GDBN} circumvents the error by ignoring this symbol information.
15364 This usually allows you to debug your program, though certain symbols
15365 are not accessible. If you encounter such a problem and feel like
15366 debugging it, you can debug @code{@value{GDBP}} with itself, breakpoint
15367 on @code{complain}, then go up to the function @code{read_dbx_symtab}
15368 and examine @code{*bufp} to see the symbol.
15369
15370 @item stub type has NULL name
15371
15372 @value{GDBN} could not find the full definition for a struct or class.
15373
15374 @item const/volatile indicator missing (ok if using g++ v1.x), got@dots{}
15375 The symbol information for a C@t{++} member function is missing some
15376 information that recent versions of the compiler should have output for
15377 it.
15378
15379 @item info mismatch between compiler and debugger
15380
15381 @value{GDBN} could not parse a type specification output by the compiler.
15382
15383 @end table
15384
15385 @node Data Files
15386 @section GDB Data Files
15387
15388 @cindex prefix for data files
15389 @value{GDBN} will sometimes read an auxiliary data file. These files
15390 are kept in a directory known as the @dfn{data directory}.
15391
15392 You can set the data directory's name, and view the name @value{GDBN}
15393 is currently using.
15394
15395 @table @code
15396 @kindex set data-directory
15397 @item set data-directory @var{directory}
15398 Set the directory which @value{GDBN} searches for auxiliary data files
15399 to @var{directory}.
15400
15401 @kindex show data-directory
15402 @item show data-directory
15403 Show the directory @value{GDBN} searches for auxiliary data files.
15404 @end table
15405
15406 @cindex default data directory
15407 @cindex @samp{--with-gdb-datadir}
15408 You can set the default data directory by using the configure-time
15409 @samp{--with-gdb-datadir} option. If the data directory is inside
15410 @value{GDBN}'s configured binary prefix (set with @samp{--prefix} or
15411 @samp{--exec-prefix}), then the default data directory will be updated
15412 automatically if the installed @value{GDBN} is moved to a new
15413 location.
15414
15415 @node Targets
15416 @chapter Specifying a Debugging Target
15417
15418 @cindex debugging target
15419 A @dfn{target} is the execution environment occupied by your program.
15420
15421 Often, @value{GDBN} runs in the same host environment as your program;
15422 in that case, the debugging target is specified as a side effect when
15423 you use the @code{file} or @code{core} commands. When you need more
15424 flexibility---for example, running @value{GDBN} on a physically separate
15425 host, or controlling a standalone system over a serial port or a
15426 realtime system over a TCP/IP connection---you can use the @code{target}
15427 command to specify one of the target types configured for @value{GDBN}
15428 (@pxref{Target Commands, ,Commands for Managing Targets}).
15429
15430 @cindex target architecture
15431 It is possible to build @value{GDBN} for several different @dfn{target
15432 architectures}. When @value{GDBN} is built like that, you can choose
15433 one of the available architectures with the @kbd{set architecture}
15434 command.
15435
15436 @table @code
15437 @kindex set architecture
15438 @kindex show architecture
15439 @item set architecture @var{arch}
15440 This command sets the current target architecture to @var{arch}. The
15441 value of @var{arch} can be @code{"auto"}, in addition to one of the
15442 supported architectures.
15443
15444 @item show architecture
15445 Show the current target architecture.
15446
15447 @item set processor
15448 @itemx processor
15449 @kindex set processor
15450 @kindex show processor
15451 These are alias commands for, respectively, @code{set architecture}
15452 and @code{show architecture}.
15453 @end table
15454
15455 @menu
15456 * Active Targets:: Active targets
15457 * Target Commands:: Commands for managing targets
15458 * Byte Order:: Choosing target byte order
15459 @end menu
15460
15461 @node Active Targets
15462 @section Active Targets
15463
15464 @cindex stacking targets
15465 @cindex active targets
15466 @cindex multiple targets
15467
15468 There are multiple classes of targets such as: processes, executable files or
15469 recording sessions. Core files belong to the process class, making core file
15470 and process mutually exclusive. Otherwise, @value{GDBN} can work concurrently
15471 on multiple active targets, one in each class. This allows you to (for
15472 example) start a process and inspect its activity, while still having access to
15473 the executable file after the process finishes. Or if you start process
15474 recording (@pxref{Reverse Execution}) and @code{reverse-step} there, you are
15475 presented a virtual layer of the recording target, while the process target
15476 remains stopped at the chronologically last point of the process execution.
15477
15478 Use the @code{core-file} and @code{exec-file} commands to select a new core
15479 file or executable target (@pxref{Files, ,Commands to Specify Files}). To
15480 specify as a target a process that is already running, use the @code{attach}
15481 command (@pxref{Attach, ,Debugging an Already-running Process}).
15482
15483 @node Target Commands
15484 @section Commands for Managing Targets
15485
15486 @table @code
15487 @item target @var{type} @var{parameters}
15488 Connects the @value{GDBN} host environment to a target machine or
15489 process. A target is typically a protocol for talking to debugging
15490 facilities. You use the argument @var{type} to specify the type or
15491 protocol of the target machine.
15492
15493 Further @var{parameters} are interpreted by the target protocol, but
15494 typically include things like device names or host names to connect
15495 with, process numbers, and baud rates.
15496
15497 The @code{target} command does not repeat if you press @key{RET} again
15498 after executing the command.
15499
15500 @kindex help target
15501 @item help target
15502 Displays the names of all targets available. To display targets
15503 currently selected, use either @code{info target} or @code{info files}
15504 (@pxref{Files, ,Commands to Specify Files}).
15505
15506 @item help target @var{name}
15507 Describe a particular target, including any parameters necessary to
15508 select it.
15509
15510 @kindex set gnutarget
15511 @item set gnutarget @var{args}
15512 @value{GDBN} uses its own library BFD to read your files. @value{GDBN}
15513 knows whether it is reading an @dfn{executable},
15514 a @dfn{core}, or a @dfn{.o} file; however, you can specify the file format
15515 with the @code{set gnutarget} command. Unlike most @code{target} commands,
15516 with @code{gnutarget} the @code{target} refers to a program, not a machine.
15517
15518 @quotation
15519 @emph{Warning:} To specify a file format with @code{set gnutarget},
15520 you must know the actual BFD name.
15521 @end quotation
15522
15523 @noindent
15524 @xref{Files, , Commands to Specify Files}.
15525
15526 @kindex show gnutarget
15527 @item show gnutarget
15528 Use the @code{show gnutarget} command to display what file format
15529 @code{gnutarget} is set to read. If you have not set @code{gnutarget},
15530 @value{GDBN} will determine the file format for each file automatically,
15531 and @code{show gnutarget} displays @samp{The current BDF target is "auto"}.
15532 @end table
15533
15534 @cindex common targets
15535 Here are some common targets (available, or not, depending on the GDB
15536 configuration):
15537
15538 @table @code
15539 @kindex target
15540 @item target exec @var{program}
15541 @cindex executable file target
15542 An executable file. @samp{target exec @var{program}} is the same as
15543 @samp{exec-file @var{program}}.
15544
15545 @item target core @var{filename}
15546 @cindex core dump file target
15547 A core dump file. @samp{target core @var{filename}} is the same as
15548 @samp{core-file @var{filename}}.
15549
15550 @item target remote @var{medium}
15551 @cindex remote target
15552 A remote system connected to @value{GDBN} via a serial line or network
15553 connection. This command tells @value{GDBN} to use its own remote
15554 protocol over @var{medium} for debugging. @xref{Remote Debugging}.
15555
15556 For example, if you have a board connected to @file{/dev/ttya} on the
15557 machine running @value{GDBN}, you could say:
15558
15559 @smallexample
15560 target remote /dev/ttya
15561 @end smallexample
15562
15563 @code{target remote} supports the @code{load} command. This is only
15564 useful if you have some other way of getting the stub to the target
15565 system, and you can put it somewhere in memory where it won't get
15566 clobbered by the download.
15567
15568 @item target sim @r{[}@var{simargs}@r{]} @dots{}
15569 @cindex built-in simulator target
15570 Builtin CPU simulator. @value{GDBN} includes simulators for most architectures.
15571 In general,
15572 @smallexample
15573 target sim
15574 load
15575 run
15576 @end smallexample
15577 @noindent
15578 works; however, you cannot assume that a specific memory map, device
15579 drivers, or even basic I/O is available, although some simulators do
15580 provide these. For info about any processor-specific simulator details,
15581 see the appropriate section in @ref{Embedded Processors, ,Embedded
15582 Processors}.
15583
15584 @end table
15585
15586 Some configurations may include these targets as well:
15587
15588 @table @code
15589
15590 @item target nrom @var{dev}
15591 @cindex NetROM ROM emulator target
15592 NetROM ROM emulator. This target only supports downloading.
15593
15594 @end table
15595
15596 Different targets are available on different configurations of @value{GDBN};
15597 your configuration may have more or fewer targets.
15598
15599 Many remote targets require you to download the executable's code once
15600 you've successfully established a connection. You may wish to control
15601 various aspects of this process.
15602
15603 @table @code
15604
15605 @item set hash
15606 @kindex set hash@r{, for remote monitors}
15607 @cindex hash mark while downloading
15608 This command controls whether a hash mark @samp{#} is displayed while
15609 downloading a file to the remote monitor. If on, a hash mark is
15610 displayed after each S-record is successfully downloaded to the
15611 monitor.
15612
15613 @item show hash
15614 @kindex show hash@r{, for remote monitors}
15615 Show the current status of displaying the hash mark.
15616
15617 @item set debug monitor
15618 @kindex set debug monitor
15619 @cindex display remote monitor communications
15620 Enable or disable display of communications messages between
15621 @value{GDBN} and the remote monitor.
15622
15623 @item show debug monitor
15624 @kindex show debug monitor
15625 Show the current status of displaying communications between
15626 @value{GDBN} and the remote monitor.
15627 @end table
15628
15629 @table @code
15630
15631 @kindex load @var{filename}
15632 @item load @var{filename}
15633 @anchor{load}
15634 Depending on what remote debugging facilities are configured into
15635 @value{GDBN}, the @code{load} command may be available. Where it exists, it
15636 is meant to make @var{filename} (an executable) available for debugging
15637 on the remote system---by downloading, or dynamic linking, for example.
15638 @code{load} also records the @var{filename} symbol table in @value{GDBN}, like
15639 the @code{add-symbol-file} command.
15640
15641 If your @value{GDBN} does not have a @code{load} command, attempting to
15642 execute it gets the error message ``@code{You can't do that when your
15643 target is @dots{}}''
15644
15645 The file is loaded at whatever address is specified in the executable.
15646 For some object file formats, you can specify the load address when you
15647 link the program; for other formats, like a.out, the object file format
15648 specifies a fixed address.
15649 @c FIXME! This would be a good place for an xref to the GNU linker doc.
15650
15651 Depending on the remote side capabilities, @value{GDBN} may be able to
15652 load programs into flash memory.
15653
15654 @code{load} does not repeat if you press @key{RET} again after using it.
15655 @end table
15656
15657 @node Byte Order
15658 @section Choosing Target Byte Order
15659
15660 @cindex choosing target byte order
15661 @cindex target byte order
15662
15663 Some types of processors, such as the MIPS, PowerPC, and Renesas SH,
15664 offer the ability to run either big-endian or little-endian byte
15665 orders. Usually the executable or symbol will include a bit to
15666 designate the endian-ness, and you will not need to worry about
15667 which to use. However, you may still find it useful to adjust
15668 @value{GDBN}'s idea of processor endian-ness manually.
15669
15670 @table @code
15671 @kindex set endian
15672 @item set endian big
15673 Instruct @value{GDBN} to assume the target is big-endian.
15674
15675 @item set endian little
15676 Instruct @value{GDBN} to assume the target is little-endian.
15677
15678 @item set endian auto
15679 Instruct @value{GDBN} to use the byte order associated with the
15680 executable.
15681
15682 @item show endian
15683 Display @value{GDBN}'s current idea of the target byte order.
15684
15685 @end table
15686
15687 Note that these commands merely adjust interpretation of symbolic
15688 data on the host, and that they have absolutely no effect on the
15689 target system.
15690
15691
15692 @node Remote Debugging
15693 @chapter Debugging Remote Programs
15694 @cindex remote debugging
15695
15696 If you are trying to debug a program running on a machine that cannot run
15697 @value{GDBN} in the usual way, it is often useful to use remote debugging.
15698 For example, you might use remote debugging on an operating system kernel,
15699 or on a small system which does not have a general purpose operating system
15700 powerful enough to run a full-featured debugger.
15701
15702 Some configurations of @value{GDBN} have special serial or TCP/IP interfaces
15703 to make this work with particular debugging targets. In addition,
15704 @value{GDBN} comes with a generic serial protocol (specific to @value{GDBN},
15705 but not specific to any particular target system) which you can use if you
15706 write the remote stubs---the code that runs on the remote system to
15707 communicate with @value{GDBN}.
15708
15709 Other remote targets may be available in your
15710 configuration of @value{GDBN}; use @code{help target} to list them.
15711
15712 @menu
15713 * Connecting:: Connecting to a remote target
15714 * File Transfer:: Sending files to a remote system
15715 * Server:: Using the gdbserver program
15716 * Remote Configuration:: Remote configuration
15717 * Remote Stub:: Implementing a remote stub
15718 @end menu
15719
15720 @node Connecting
15721 @section Connecting to a Remote Target
15722
15723 On the @value{GDBN} host machine, you will need an unstripped copy of
15724 your program, since @value{GDBN} needs symbol and debugging information.
15725 Start up @value{GDBN} as usual, using the name of the local copy of your
15726 program as the first argument.
15727
15728 @cindex @code{target remote}
15729 @value{GDBN} can communicate with the target over a serial line, or
15730 over an @acronym{IP} network using @acronym{TCP} or @acronym{UDP}. In
15731 each case, @value{GDBN} uses the same protocol for debugging your
15732 program; only the medium carrying the debugging packets varies. The
15733 @code{target remote} command establishes a connection to the target.
15734 Its arguments indicate which medium to use:
15735
15736 @table @code
15737
15738 @item target remote @var{serial-device}
15739 @cindex serial line, @code{target remote}
15740 Use @var{serial-device} to communicate with the target. For example,
15741 to use a serial line connected to the device named @file{/dev/ttyb}:
15742
15743 @smallexample
15744 target remote /dev/ttyb
15745 @end smallexample
15746
15747 If you're using a serial line, you may want to give @value{GDBN} the
15748 @w{@samp{--baud}} option, or use the @code{set remotebaud} command
15749 (@pxref{Remote Configuration, set remotebaud}) before the
15750 @code{target} command.
15751
15752 @item target remote @code{@var{host}:@var{port}}
15753 @itemx target remote @code{tcp:@var{host}:@var{port}}
15754 @cindex @acronym{TCP} port, @code{target remote}
15755 Debug using a @acronym{TCP} connection to @var{port} on @var{host}.
15756 The @var{host} may be either a host name or a numeric @acronym{IP}
15757 address; @var{port} must be a decimal number. The @var{host} could be
15758 the target machine itself, if it is directly connected to the net, or
15759 it might be a terminal server which in turn has a serial line to the
15760 target.
15761
15762 For example, to connect to port 2828 on a terminal server named
15763 @code{manyfarms}:
15764
15765 @smallexample
15766 target remote manyfarms:2828
15767 @end smallexample
15768
15769 If your remote target is actually running on the same machine as your
15770 debugger session (e.g.@: a simulator for your target running on the
15771 same host), you can omit the hostname. For example, to connect to
15772 port 1234 on your local machine:
15773
15774 @smallexample
15775 target remote :1234
15776 @end smallexample
15777 @noindent
15778
15779 Note that the colon is still required here.
15780
15781 @item target remote @code{udp:@var{host}:@var{port}}
15782 @cindex @acronym{UDP} port, @code{target remote}
15783 Debug using @acronym{UDP} packets to @var{port} on @var{host}. For example, to
15784 connect to @acronym{UDP} port 2828 on a terminal server named @code{manyfarms}:
15785
15786 @smallexample
15787 target remote udp:manyfarms:2828
15788 @end smallexample
15789
15790 When using a @acronym{UDP} connection for remote debugging, you should
15791 keep in mind that the `U' stands for ``Unreliable''. @acronym{UDP}
15792 can silently drop packets on busy or unreliable networks, which will
15793 cause havoc with your debugging session.
15794
15795 @item target remote | @var{command}
15796 @cindex pipe, @code{target remote} to
15797 Run @var{command} in the background and communicate with it using a
15798 pipe. The @var{command} is a shell command, to be parsed and expanded
15799 by the system's command shell, @code{/bin/sh}; it should expect remote
15800 protocol packets on its standard input, and send replies on its
15801 standard output. You could use this to run a stand-alone simulator
15802 that speaks the remote debugging protocol, to make net connections
15803 using programs like @code{ssh}, or for other similar tricks.
15804
15805 If @var{command} closes its standard output (perhaps by exiting),
15806 @value{GDBN} will try to send it a @code{SIGTERM} signal. (If the
15807 program has already exited, this will have no effect.)
15808
15809 @end table
15810
15811 Once the connection has been established, you can use all the usual
15812 commands to examine and change data. The remote program is already
15813 running; you can use @kbd{step} and @kbd{continue}, and you do not
15814 need to use @kbd{run}.
15815
15816 @cindex interrupting remote programs
15817 @cindex remote programs, interrupting
15818 Whenever @value{GDBN} is waiting for the remote program, if you type the
15819 interrupt character (often @kbd{Ctrl-c}), @value{GDBN} attempts to stop the
15820 program. This may or may not succeed, depending in part on the hardware
15821 and the serial drivers the remote system uses. If you type the
15822 interrupt character once again, @value{GDBN} displays this prompt:
15823
15824 @smallexample
15825 Interrupted while waiting for the program.
15826 Give up (and stop debugging it)? (y or n)
15827 @end smallexample
15828
15829 If you type @kbd{y}, @value{GDBN} abandons the remote debugging session.
15830 (If you decide you want to try again later, you can use @samp{target
15831 remote} again to connect once more.) If you type @kbd{n}, @value{GDBN}
15832 goes back to waiting.
15833
15834 @table @code
15835 @kindex detach (remote)
15836 @item detach
15837 When you have finished debugging the remote program, you can use the
15838 @code{detach} command to release it from @value{GDBN} control.
15839 Detaching from the target normally resumes its execution, but the results
15840 will depend on your particular remote stub. After the @code{detach}
15841 command, @value{GDBN} is free to connect to another target.
15842
15843 @kindex disconnect
15844 @item disconnect
15845 The @code{disconnect} command behaves like @code{detach}, except that
15846 the target is generally not resumed. It will wait for @value{GDBN}
15847 (this instance or another one) to connect and continue debugging. After
15848 the @code{disconnect} command, @value{GDBN} is again free to connect to
15849 another target.
15850
15851 @cindex send command to remote monitor
15852 @cindex extend @value{GDBN} for remote targets
15853 @cindex add new commands for external monitor
15854 @kindex monitor
15855 @item monitor @var{cmd}
15856 This command allows you to send arbitrary commands directly to the
15857 remote monitor. Since @value{GDBN} doesn't care about the commands it
15858 sends like this, this command is the way to extend @value{GDBN}---you
15859 can add new commands that only the external monitor will understand
15860 and implement.
15861 @end table
15862
15863 @node File Transfer
15864 @section Sending files to a remote system
15865 @cindex remote target, file transfer
15866 @cindex file transfer
15867 @cindex sending files to remote systems
15868
15869 Some remote targets offer the ability to transfer files over the same
15870 connection used to communicate with @value{GDBN}. This is convenient
15871 for targets accessible through other means, e.g.@: @sc{gnu}/Linux systems
15872 running @code{gdbserver} over a network interface. For other targets,
15873 e.g.@: embedded devices with only a single serial port, this may be
15874 the only way to upload or download files.
15875
15876 Not all remote targets support these commands.
15877
15878 @table @code
15879 @kindex remote put
15880 @item remote put @var{hostfile} @var{targetfile}
15881 Copy file @var{hostfile} from the host system (the machine running
15882 @value{GDBN}) to @var{targetfile} on the target system.
15883
15884 @kindex remote get
15885 @item remote get @var{targetfile} @var{hostfile}
15886 Copy file @var{targetfile} from the target system to @var{hostfile}
15887 on the host system.
15888
15889 @kindex remote delete
15890 @item remote delete @var{targetfile}
15891 Delete @var{targetfile} from the target system.
15892
15893 @end table
15894
15895 @node Server
15896 @section Using the @code{gdbserver} Program
15897
15898 @kindex gdbserver
15899 @cindex remote connection without stubs
15900 @code{gdbserver} is a control program for Unix-like systems, which
15901 allows you to connect your program with a remote @value{GDBN} via
15902 @code{target remote}---but without linking in the usual debugging stub.
15903
15904 @code{gdbserver} is not a complete replacement for the debugging stubs,
15905 because it requires essentially the same operating-system facilities
15906 that @value{GDBN} itself does. In fact, a system that can run
15907 @code{gdbserver} to connect to a remote @value{GDBN} could also run
15908 @value{GDBN} locally! @code{gdbserver} is sometimes useful nevertheless,
15909 because it is a much smaller program than @value{GDBN} itself. It is
15910 also easier to port than all of @value{GDBN}, so you may be able to get
15911 started more quickly on a new system by using @code{gdbserver}.
15912 Finally, if you develop code for real-time systems, you may find that
15913 the tradeoffs involved in real-time operation make it more convenient to
15914 do as much development work as possible on another system, for example
15915 by cross-compiling. You can use @code{gdbserver} to make a similar
15916 choice for debugging.
15917
15918 @value{GDBN} and @code{gdbserver} communicate via either a serial line
15919 or a TCP connection, using the standard @value{GDBN} remote serial
15920 protocol.
15921
15922 @quotation
15923 @emph{Warning:} @code{gdbserver} does not have any built-in security.
15924 Do not run @code{gdbserver} connected to any public network; a
15925 @value{GDBN} connection to @code{gdbserver} provides access to the
15926 target system with the same privileges as the user running
15927 @code{gdbserver}.
15928 @end quotation
15929
15930 @subsection Running @code{gdbserver}
15931 @cindex arguments, to @code{gdbserver}
15932
15933 Run @code{gdbserver} on the target system. You need a copy of the
15934 program you want to debug, including any libraries it requires.
15935 @code{gdbserver} does not need your program's symbol table, so you can
15936 strip the program if necessary to save space. @value{GDBN} on the host
15937 system does all the symbol handling.
15938
15939 To use the server, you must tell it how to communicate with @value{GDBN};
15940 the name of your program; and the arguments for your program. The usual
15941 syntax is:
15942
15943 @smallexample
15944 target> gdbserver @var{comm} @var{program} [ @var{args} @dots{} ]
15945 @end smallexample
15946
15947 @var{comm} is either a device name (to use a serial line) or a TCP
15948 hostname and portnumber. For example, to debug Emacs with the argument
15949 @samp{foo.txt} and communicate with @value{GDBN} over the serial port
15950 @file{/dev/com1}:
15951
15952 @smallexample
15953 target> gdbserver /dev/com1 emacs foo.txt
15954 @end smallexample
15955
15956 @code{gdbserver} waits passively for the host @value{GDBN} to communicate
15957 with it.
15958
15959 To use a TCP connection instead of a serial line:
15960
15961 @smallexample
15962 target> gdbserver host:2345 emacs foo.txt
15963 @end smallexample
15964
15965 The only difference from the previous example is the first argument,
15966 specifying that you are communicating with the host @value{GDBN} via
15967 TCP. The @samp{host:2345} argument means that @code{gdbserver} is to
15968 expect a TCP connection from machine @samp{host} to local TCP port 2345.
15969 (Currently, the @samp{host} part is ignored.) You can choose any number
15970 you want for the port number as long as it does not conflict with any
15971 TCP ports already in use on the target system (for example, @code{23} is
15972 reserved for @code{telnet}).@footnote{If you choose a port number that
15973 conflicts with another service, @code{gdbserver} prints an error message
15974 and exits.} You must use the same port number with the host @value{GDBN}
15975 @code{target remote} command.
15976
15977 @subsubsection Attaching to a Running Program
15978
15979 On some targets, @code{gdbserver} can also attach to running programs.
15980 This is accomplished via the @code{--attach} argument. The syntax is:
15981
15982 @smallexample
15983 target> gdbserver --attach @var{comm} @var{pid}
15984 @end smallexample
15985
15986 @var{pid} is the process ID of a currently running process. It isn't necessary
15987 to point @code{gdbserver} at a binary for the running process.
15988
15989 @pindex pidof
15990 @cindex attach to a program by name
15991 You can debug processes by name instead of process ID if your target has the
15992 @code{pidof} utility:
15993
15994 @smallexample
15995 target> gdbserver --attach @var{comm} `pidof @var{program}`
15996 @end smallexample
15997
15998 In case more than one copy of @var{program} is running, or @var{program}
15999 has multiple threads, most versions of @code{pidof} support the
16000 @code{-s} option to only return the first process ID.
16001
16002 @subsubsection Multi-Process Mode for @code{gdbserver}
16003 @cindex gdbserver, multiple processes
16004 @cindex multiple processes with gdbserver
16005
16006 When you connect to @code{gdbserver} using @code{target remote},
16007 @code{gdbserver} debugs the specified program only once. When the
16008 program exits, or you detach from it, @value{GDBN} closes the connection
16009 and @code{gdbserver} exits.
16010
16011 If you connect using @kbd{target extended-remote}, @code{gdbserver}
16012 enters multi-process mode. When the debugged program exits, or you
16013 detach from it, @value{GDBN} stays connected to @code{gdbserver} even
16014 though no program is running. The @code{run} and @code{attach}
16015 commands instruct @code{gdbserver} to run or attach to a new program.
16016 The @code{run} command uses @code{set remote exec-file} (@pxref{set
16017 remote exec-file}) to select the program to run. Command line
16018 arguments are supported, except for wildcard expansion and I/O
16019 redirection (@pxref{Arguments}).
16020
16021 To start @code{gdbserver} without supplying an initial command to run
16022 or process ID to attach, use the @option{--multi} command line option.
16023 Then you can connect using @kbd{target extended-remote} and start
16024 the program you want to debug.
16025
16026 @code{gdbserver} does not automatically exit in multi-process mode.
16027 You can terminate it by using @code{monitor exit}
16028 (@pxref{Monitor Commands for gdbserver}).
16029
16030 @subsubsection Other Command-Line Arguments for @code{gdbserver}
16031
16032 The @option{--debug} option tells @code{gdbserver} to display extra
16033 status information about the debugging process. The
16034 @option{--remote-debug} option tells @code{gdbserver} to display
16035 remote protocol debug output. These options are intended for
16036 @code{gdbserver} development and for bug reports to the developers.
16037
16038 The @option{--wrapper} option specifies a wrapper to launch programs
16039 for debugging. The option should be followed by the name of the
16040 wrapper, then any command-line arguments to pass to the wrapper, then
16041 @kbd{--} indicating the end of the wrapper arguments.
16042
16043 @code{gdbserver} runs the specified wrapper program with a combined
16044 command line including the wrapper arguments, then the name of the
16045 program to debug, then any arguments to the program. The wrapper
16046 runs until it executes your program, and then @value{GDBN} gains control.
16047
16048 You can use any program that eventually calls @code{execve} with
16049 its arguments as a wrapper. Several standard Unix utilities do
16050 this, e.g.@: @code{env} and @code{nohup}. Any Unix shell script ending
16051 with @code{exec "$@@"} will also work.
16052
16053 For example, you can use @code{env} to pass an environment variable to
16054 the debugged program, without setting the variable in @code{gdbserver}'s
16055 environment:
16056
16057 @smallexample
16058 $ gdbserver --wrapper env LD_PRELOAD=libtest.so -- :2222 ./testprog
16059 @end smallexample
16060
16061 @subsection Connecting to @code{gdbserver}
16062
16063 Run @value{GDBN} on the host system.
16064
16065 First make sure you have the necessary symbol files. Load symbols for
16066 your application using the @code{file} command before you connect. Use
16067 @code{set sysroot} to locate target libraries (unless your @value{GDBN}
16068 was compiled with the correct sysroot using @code{--with-sysroot}).
16069
16070 The symbol file and target libraries must exactly match the executable
16071 and libraries on the target, with one exception: the files on the host
16072 system should not be stripped, even if the files on the target system
16073 are. Mismatched or missing files will lead to confusing results
16074 during debugging. On @sc{gnu}/Linux targets, mismatched or missing
16075 files may also prevent @code{gdbserver} from debugging multi-threaded
16076 programs.
16077
16078 Connect to your target (@pxref{Connecting,,Connecting to a Remote Target}).
16079 For TCP connections, you must start up @code{gdbserver} prior to using
16080 the @code{target remote} command. Otherwise you may get an error whose
16081 text depends on the host system, but which usually looks something like
16082 @samp{Connection refused}. Don't use the @code{load}
16083 command in @value{GDBN} when using @code{gdbserver}, since the program is
16084 already on the target.
16085
16086 @subsection Monitor Commands for @code{gdbserver}
16087 @cindex monitor commands, for @code{gdbserver}
16088 @anchor{Monitor Commands for gdbserver}
16089
16090 During a @value{GDBN} session using @code{gdbserver}, you can use the
16091 @code{monitor} command to send special requests to @code{gdbserver}.
16092 Here are the available commands.
16093
16094 @table @code
16095 @item monitor help
16096 List the available monitor commands.
16097
16098 @item monitor set debug 0
16099 @itemx monitor set debug 1
16100 Disable or enable general debugging messages.
16101
16102 @item monitor set remote-debug 0
16103 @itemx monitor set remote-debug 1
16104 Disable or enable specific debugging messages associated with the remote
16105 protocol (@pxref{Remote Protocol}).
16106
16107 @item monitor set libthread-db-search-path [PATH]
16108 @cindex gdbserver, search path for @code{libthread_db}
16109 When this command is issued, @var{path} is a colon-separated list of
16110 directories to search for @code{libthread_db} (@pxref{Threads,,set
16111 libthread-db-search-path}). If you omit @var{path},
16112 @samp{libthread-db-search-path} will be reset to an empty list.
16113
16114 @item monitor exit
16115 Tell gdbserver to exit immediately. This command should be followed by
16116 @code{disconnect} to close the debugging session. @code{gdbserver} will
16117 detach from any attached processes and kill any processes it created.
16118 Use @code{monitor exit} to terminate @code{gdbserver} at the end
16119 of a multi-process mode debug session.
16120
16121 @end table
16122
16123 @subsection Tracepoints support in @code{gdbserver}
16124 @cindex tracepoints support in @code{gdbserver}
16125
16126 On some targets, @code{gdbserver} supports tracepoints, fast
16127 tracepoints and static tracepoints.
16128
16129 For fast or static tracepoints to work, a special library called the
16130 @dfn{in-process agent} (IPA), must be loaded in the inferior process.
16131 This library is built and distributed as an integral part of
16132 @code{gdbserver}. In addition, support for static tracepoints
16133 requires building the in-process agent library with static tracepoints
16134 support. At present, the UST (LTTng Userspace Tracer,
16135 @url{http://lttng.org/ust}) tracing engine is supported. This support
16136 is automatically available if UST development headers are found in the
16137 standard include path when @code{gdbserver} is built, or if
16138 @code{gdbserver} was explicitly configured using @option{--with-ust}
16139 to point at such headers. You can explicitly disable the support
16140 using @option{--with-ust=no}.
16141
16142 There are several ways to load the in-process agent in your program:
16143
16144 @table @code
16145 @item Specifying it as dependency at link time
16146
16147 You can link your program dynamically with the in-process agent
16148 library. On most systems, this is accomplished by adding
16149 @code{-linproctrace} to the link command.
16150
16151 @item Using the system's preloading mechanisms
16152
16153 You can force loading the in-process agent at startup time by using
16154 your system's support for preloading shared libraries. Many Unixes
16155 support the concept of preloading user defined libraries. In most
16156 cases, you do that by specifying @code{LD_PRELOAD=libinproctrace.so}
16157 in the environment. See also the description of @code{gdbserver}'s
16158 @option{--wrapper} command line option.
16159
16160 @item Using @value{GDBN} to force loading the agent at run time
16161
16162 On some systems, you can force the inferior to load a shared library,
16163 by calling a dynamic loader function in the inferior that takes care
16164 of dynamically looking up and loading a shared library. On most Unix
16165 systems, the function is @code{dlopen}. You'll use the @code{call}
16166 command for that. For example:
16167
16168 @smallexample
16169 (@value{GDBP}) call dlopen ("libinproctrace.so", ...)
16170 @end smallexample
16171
16172 Note that on most Unix systems, for the @code{dlopen} function to be
16173 available, the program needs to be linked with @code{-ldl}.
16174 @end table
16175
16176 On systems that have a userspace dynamic loader, like most Unix
16177 systems, when you connect to @code{gdbserver} using @code{target
16178 remote}, you'll find that the program is stopped at the dynamic
16179 loader's entry point, and no shared library has been loaded in the
16180 program's address space yet, including the in-process agent. In that
16181 case, before being able to use any of the fast or static tracepoints
16182 features, you need to let the loader run and load the shared
16183 libraries. The simplest way to do that is to run the program to the
16184 main procedure. E.g., if debugging a C or C@t{++} program, start
16185 @code{gdbserver} like so:
16186
16187 @smallexample
16188 $ gdbserver :9999 myprogram
16189 @end smallexample
16190
16191 Start GDB and connect to @code{gdbserver} like so, and run to main:
16192
16193 @smallexample
16194 $ gdb myprogram
16195 (@value{GDBP}) target remote myhost:9999
16196 0x00007f215893ba60 in ?? () from /lib64/ld-linux-x86-64.so.2
16197 (@value{GDBP}) b main
16198 (@value{GDBP}) continue
16199 @end smallexample
16200
16201 The in-process tracing agent library should now be loaded into the
16202 process; you can confirm it with the @code{info sharedlibrary}
16203 command, which will list @file{libinproctrace.so} as loaded in the
16204 process. You are now ready to install fast tracepoints, list static
16205 tracepoint markers, probe static tracepoints markers, and start
16206 tracing.
16207
16208 @node Remote Configuration
16209 @section Remote Configuration
16210
16211 @kindex set remote
16212 @kindex show remote
16213 This section documents the configuration options available when
16214 debugging remote programs. For the options related to the File I/O
16215 extensions of the remote protocol, see @ref{system,
16216 system-call-allowed}.
16217
16218 @table @code
16219 @item set remoteaddresssize @var{bits}
16220 @cindex address size for remote targets
16221 @cindex bits in remote address
16222 Set the maximum size of address in a memory packet to the specified
16223 number of bits. @value{GDBN} will mask off the address bits above
16224 that number, when it passes addresses to the remote target. The
16225 default value is the number of bits in the target's address.
16226
16227 @item show remoteaddresssize
16228 Show the current value of remote address size in bits.
16229
16230 @item set remotebaud @var{n}
16231 @cindex baud rate for remote targets
16232 Set the baud rate for the remote serial I/O to @var{n} baud. The
16233 value is used to set the speed of the serial port used for debugging
16234 remote targets.
16235
16236 @item show remotebaud
16237 Show the current speed of the remote connection.
16238
16239 @item set remotebreak
16240 @cindex interrupt remote programs
16241 @cindex BREAK signal instead of Ctrl-C
16242 @anchor{set remotebreak}
16243 If set to on, @value{GDBN} sends a @code{BREAK} signal to the remote
16244 when you type @kbd{Ctrl-c} to interrupt the program running
16245 on the remote. If set to off, @value{GDBN} sends the @samp{Ctrl-C}
16246 character instead. The default is off, since most remote systems
16247 expect to see @samp{Ctrl-C} as the interrupt signal.
16248
16249 @item show remotebreak
16250 Show whether @value{GDBN} sends @code{BREAK} or @samp{Ctrl-C} to
16251 interrupt the remote program.
16252
16253 @item set remoteflow on
16254 @itemx set remoteflow off
16255 @kindex set remoteflow
16256 Enable or disable hardware flow control (@code{RTS}/@code{CTS})
16257 on the serial port used to communicate to the remote target.
16258
16259 @item show remoteflow
16260 @kindex show remoteflow
16261 Show the current setting of hardware flow control.
16262
16263 @item set remotelogbase @var{base}
16264 Set the base (a.k.a.@: radix) of logging serial protocol
16265 communications to @var{base}. Supported values of @var{base} are:
16266 @code{ascii}, @code{octal}, and @code{hex}. The default is
16267 @code{ascii}.
16268
16269 @item show remotelogbase
16270 Show the current setting of the radix for logging remote serial
16271 protocol.
16272
16273 @item set remotelogfile @var{file}
16274 @cindex record serial communications on file
16275 Record remote serial communications on the named @var{file}. The
16276 default is not to record at all.
16277
16278 @item show remotelogfile.
16279 Show the current setting of the file name on which to record the
16280 serial communications.
16281
16282 @item set remotetimeout @var{num}
16283 @cindex timeout for serial communications
16284 @cindex remote timeout
16285 Set the timeout limit to wait for the remote target to respond to
16286 @var{num} seconds. The default is 2 seconds.
16287
16288 @item show remotetimeout
16289 Show the current number of seconds to wait for the remote target
16290 responses.
16291
16292 @cindex limit hardware breakpoints and watchpoints
16293 @cindex remote target, limit break- and watchpoints
16294 @anchor{set remote hardware-watchpoint-limit}
16295 @anchor{set remote hardware-breakpoint-limit}
16296 @item set remote hardware-watchpoint-limit @var{limit}
16297 @itemx set remote hardware-breakpoint-limit @var{limit}
16298 Restrict @value{GDBN} to using @var{limit} remote hardware breakpoint or
16299 watchpoints. A limit of -1, the default, is treated as unlimited.
16300
16301 @item set remote exec-file @var{filename}
16302 @itemx show remote exec-file
16303 @anchor{set remote exec-file}
16304 @cindex executable file, for remote target
16305 Select the file used for @code{run} with @code{target
16306 extended-remote}. This should be set to a filename valid on the
16307 target system. If it is not set, the target will use a default
16308 filename (e.g.@: the last program run).
16309
16310 @item set remote interrupt-sequence
16311 @cindex interrupt remote programs
16312 @cindex select Ctrl-C, BREAK or BREAK-g
16313 Allow the user to select one of @samp{Ctrl-C}, a @code{BREAK} or
16314 @samp{BREAK-g} as the
16315 sequence to the remote target in order to interrupt the execution.
16316 @samp{Ctrl-C} is a default. Some system prefers @code{BREAK} which
16317 is high level of serial line for some certain time.
16318 Linux kernel prefers @samp{BREAK-g}, a.k.a Magic SysRq g.
16319 It is @code{BREAK} signal followed by character @code{g}.
16320
16321 @item show interrupt-sequence
16322 Show which of @samp{Ctrl-C}, @code{BREAK} or @code{BREAK-g}
16323 is sent by @value{GDBN} to interrupt the remote program.
16324 @code{BREAK-g} is BREAK signal followed by @code{g} and
16325 also known as Magic SysRq g.
16326
16327 @item set remote interrupt-on-connect
16328 @cindex send interrupt-sequence on start
16329 Specify whether interrupt-sequence is sent to remote target when
16330 @value{GDBN} connects to it. This is mostly needed when you debug
16331 Linux kernel. Linux kernel expects @code{BREAK} followed by @code{g}
16332 which is known as Magic SysRq g in order to connect @value{GDBN}.
16333
16334 @item show interrupt-on-connect
16335 Show whether interrupt-sequence is sent
16336 to remote target when @value{GDBN} connects to it.
16337
16338 @kindex set tcp
16339 @kindex show tcp
16340 @item set tcp auto-retry on
16341 @cindex auto-retry, for remote TCP target
16342 Enable auto-retry for remote TCP connections. This is useful if the remote
16343 debugging agent is launched in parallel with @value{GDBN}; there is a race
16344 condition because the agent may not become ready to accept the connection
16345 before @value{GDBN} attempts to connect. When auto-retry is
16346 enabled, if the initial attempt to connect fails, @value{GDBN} reattempts
16347 to establish the connection using the timeout specified by
16348 @code{set tcp connect-timeout}.
16349
16350 @item set tcp auto-retry off
16351 Do not auto-retry failed TCP connections.
16352
16353 @item show tcp auto-retry
16354 Show the current auto-retry setting.
16355
16356 @item set tcp connect-timeout @var{seconds}
16357 @cindex connection timeout, for remote TCP target
16358 @cindex timeout, for remote target connection
16359 Set the timeout for establishing a TCP connection to the remote target to
16360 @var{seconds}. The timeout affects both polling to retry failed connections
16361 (enabled by @code{set tcp auto-retry on}) and waiting for connections
16362 that are merely slow to complete, and represents an approximate cumulative
16363 value.
16364
16365 @item show tcp connect-timeout
16366 Show the current connection timeout setting.
16367 @end table
16368
16369 @cindex remote packets, enabling and disabling
16370 The @value{GDBN} remote protocol autodetects the packets supported by
16371 your debugging stub. If you need to override the autodetection, you
16372 can use these commands to enable or disable individual packets. Each
16373 packet can be set to @samp{on} (the remote target supports this
16374 packet), @samp{off} (the remote target does not support this packet),
16375 or @samp{auto} (detect remote target support for this packet). They
16376 all default to @samp{auto}. For more information about each packet,
16377 see @ref{Remote Protocol}.
16378
16379 During normal use, you should not have to use any of these commands.
16380 If you do, that may be a bug in your remote debugging stub, or a bug
16381 in @value{GDBN}. You may want to report the problem to the
16382 @value{GDBN} developers.
16383
16384 For each packet @var{name}, the command to enable or disable the
16385 packet is @code{set remote @var{name}-packet}. The available settings
16386 are:
16387
16388 @multitable @columnfractions 0.28 0.32 0.25
16389 @item Command Name
16390 @tab Remote Packet
16391 @tab Related Features
16392
16393 @item @code{fetch-register}
16394 @tab @code{p}
16395 @tab @code{info registers}
16396
16397 @item @code{set-register}
16398 @tab @code{P}
16399 @tab @code{set}
16400
16401 @item @code{binary-download}
16402 @tab @code{X}
16403 @tab @code{load}, @code{set}
16404
16405 @item @code{read-aux-vector}
16406 @tab @code{qXfer:auxv:read}
16407 @tab @code{info auxv}
16408
16409 @item @code{symbol-lookup}
16410 @tab @code{qSymbol}
16411 @tab Detecting multiple threads
16412
16413 @item @code{attach}
16414 @tab @code{vAttach}
16415 @tab @code{attach}
16416
16417 @item @code{verbose-resume}
16418 @tab @code{vCont}
16419 @tab Stepping or resuming multiple threads
16420
16421 @item @code{run}
16422 @tab @code{vRun}
16423 @tab @code{run}
16424
16425 @item @code{software-breakpoint}
16426 @tab @code{Z0}
16427 @tab @code{break}
16428
16429 @item @code{hardware-breakpoint}
16430 @tab @code{Z1}
16431 @tab @code{hbreak}
16432
16433 @item @code{write-watchpoint}
16434 @tab @code{Z2}
16435 @tab @code{watch}
16436
16437 @item @code{read-watchpoint}
16438 @tab @code{Z3}
16439 @tab @code{rwatch}
16440
16441 @item @code{access-watchpoint}
16442 @tab @code{Z4}
16443 @tab @code{awatch}
16444
16445 @item @code{target-features}
16446 @tab @code{qXfer:features:read}
16447 @tab @code{set architecture}
16448
16449 @item @code{library-info}
16450 @tab @code{qXfer:libraries:read}
16451 @tab @code{info sharedlibrary}
16452
16453 @item @code{memory-map}
16454 @tab @code{qXfer:memory-map:read}
16455 @tab @code{info mem}
16456
16457 @item @code{read-sdata-object}
16458 @tab @code{qXfer:sdata:read}
16459 @tab @code{print $_sdata}
16460
16461 @item @code{read-spu-object}
16462 @tab @code{qXfer:spu:read}
16463 @tab @code{info spu}
16464
16465 @item @code{write-spu-object}
16466 @tab @code{qXfer:spu:write}
16467 @tab @code{info spu}
16468
16469 @item @code{read-siginfo-object}
16470 @tab @code{qXfer:siginfo:read}
16471 @tab @code{print $_siginfo}
16472
16473 @item @code{write-siginfo-object}
16474 @tab @code{qXfer:siginfo:write}
16475 @tab @code{set $_siginfo}
16476
16477 @item @code{threads}
16478 @tab @code{qXfer:threads:read}
16479 @tab @code{info threads}
16480
16481 @item @code{get-thread-local-@*storage-address}
16482 @tab @code{qGetTLSAddr}
16483 @tab Displaying @code{__thread} variables
16484
16485 @item @code{get-thread-information-block-address}
16486 @tab @code{qGetTIBAddr}
16487 @tab Display MS-Windows Thread Information Block.
16488
16489 @item @code{search-memory}
16490 @tab @code{qSearch:memory}
16491 @tab @code{find}
16492
16493 @item @code{supported-packets}
16494 @tab @code{qSupported}
16495 @tab Remote communications parameters
16496
16497 @item @code{pass-signals}
16498 @tab @code{QPassSignals}
16499 @tab @code{handle @var{signal}}
16500
16501 @item @code{hostio-close-packet}
16502 @tab @code{vFile:close}
16503 @tab @code{remote get}, @code{remote put}
16504
16505 @item @code{hostio-open-packet}
16506 @tab @code{vFile:open}
16507 @tab @code{remote get}, @code{remote put}
16508
16509 @item @code{hostio-pread-packet}
16510 @tab @code{vFile:pread}
16511 @tab @code{remote get}, @code{remote put}
16512
16513 @item @code{hostio-pwrite-packet}
16514 @tab @code{vFile:pwrite}
16515 @tab @code{remote get}, @code{remote put}
16516
16517 @item @code{hostio-unlink-packet}
16518 @tab @code{vFile:unlink}
16519 @tab @code{remote delete}
16520
16521 @item @code{noack-packet}
16522 @tab @code{QStartNoAckMode}
16523 @tab Packet acknowledgment
16524
16525 @item @code{osdata}
16526 @tab @code{qXfer:osdata:read}
16527 @tab @code{info os}
16528
16529 @item @code{query-attached}
16530 @tab @code{qAttached}
16531 @tab Querying remote process attach state.
16532 @end multitable
16533
16534 @node Remote Stub
16535 @section Implementing a Remote Stub
16536
16537 @cindex debugging stub, example
16538 @cindex remote stub, example
16539 @cindex stub example, remote debugging
16540 The stub files provided with @value{GDBN} implement the target side of the
16541 communication protocol, and the @value{GDBN} side is implemented in the
16542 @value{GDBN} source file @file{remote.c}. Normally, you can simply allow
16543 these subroutines to communicate, and ignore the details. (If you're
16544 implementing your own stub file, you can still ignore the details: start
16545 with one of the existing stub files. @file{sparc-stub.c} is the best
16546 organized, and therefore the easiest to read.)
16547
16548 @cindex remote serial debugging, overview
16549 To debug a program running on another machine (the debugging
16550 @dfn{target} machine), you must first arrange for all the usual
16551 prerequisites for the program to run by itself. For example, for a C
16552 program, you need:
16553
16554 @enumerate
16555 @item
16556 A startup routine to set up the C runtime environment; these usually
16557 have a name like @file{crt0}. The startup routine may be supplied by
16558 your hardware supplier, or you may have to write your own.
16559
16560 @item
16561 A C subroutine library to support your program's
16562 subroutine calls, notably managing input and output.
16563
16564 @item
16565 A way of getting your program to the other machine---for example, a
16566 download program. These are often supplied by the hardware
16567 manufacturer, but you may have to write your own from hardware
16568 documentation.
16569 @end enumerate
16570
16571 The next step is to arrange for your program to use a serial port to
16572 communicate with the machine where @value{GDBN} is running (the @dfn{host}
16573 machine). In general terms, the scheme looks like this:
16574
16575 @table @emph
16576 @item On the host,
16577 @value{GDBN} already understands how to use this protocol; when everything
16578 else is set up, you can simply use the @samp{target remote} command
16579 (@pxref{Targets,,Specifying a Debugging Target}).
16580
16581 @item On the target,
16582 you must link with your program a few special-purpose subroutines that
16583 implement the @value{GDBN} remote serial protocol. The file containing these
16584 subroutines is called a @dfn{debugging stub}.
16585
16586 On certain remote targets, you can use an auxiliary program
16587 @code{gdbserver} instead of linking a stub into your program.
16588 @xref{Server,,Using the @code{gdbserver} Program}, for details.
16589 @end table
16590
16591 The debugging stub is specific to the architecture of the remote
16592 machine; for example, use @file{sparc-stub.c} to debug programs on
16593 @sc{sparc} boards.
16594
16595 @cindex remote serial stub list
16596 These working remote stubs are distributed with @value{GDBN}:
16597
16598 @table @code
16599
16600 @item i386-stub.c
16601 @cindex @file{i386-stub.c}
16602 @cindex Intel
16603 @cindex i386
16604 For Intel 386 and compatible architectures.
16605
16606 @item m68k-stub.c
16607 @cindex @file{m68k-stub.c}
16608 @cindex Motorola 680x0
16609 @cindex m680x0
16610 For Motorola 680x0 architectures.
16611
16612 @item sh-stub.c
16613 @cindex @file{sh-stub.c}
16614 @cindex Renesas
16615 @cindex SH
16616 For Renesas SH architectures.
16617
16618 @item sparc-stub.c
16619 @cindex @file{sparc-stub.c}
16620 @cindex Sparc
16621 For @sc{sparc} architectures.
16622
16623 @item sparcl-stub.c
16624 @cindex @file{sparcl-stub.c}
16625 @cindex Fujitsu
16626 @cindex SparcLite
16627 For Fujitsu @sc{sparclite} architectures.
16628
16629 @end table
16630
16631 The @file{README} file in the @value{GDBN} distribution may list other
16632 recently added stubs.
16633
16634 @menu
16635 * Stub Contents:: What the stub can do for you
16636 * Bootstrapping:: What you must do for the stub
16637 * Debug Session:: Putting it all together
16638 @end menu
16639
16640 @node Stub Contents
16641 @subsection What the Stub Can Do for You
16642
16643 @cindex remote serial stub
16644 The debugging stub for your architecture supplies these three
16645 subroutines:
16646
16647 @table @code
16648 @item set_debug_traps
16649 @findex set_debug_traps
16650 @cindex remote serial stub, initialization
16651 This routine arranges for @code{handle_exception} to run when your
16652 program stops. You must call this subroutine explicitly near the
16653 beginning of your program.
16654
16655 @item handle_exception
16656 @findex handle_exception
16657 @cindex remote serial stub, main routine
16658 This is the central workhorse, but your program never calls it
16659 explicitly---the setup code arranges for @code{handle_exception} to
16660 run when a trap is triggered.
16661
16662 @code{handle_exception} takes control when your program stops during
16663 execution (for example, on a breakpoint), and mediates communications
16664 with @value{GDBN} on the host machine. This is where the communications
16665 protocol is implemented; @code{handle_exception} acts as the @value{GDBN}
16666 representative on the target machine. It begins by sending summary
16667 information on the state of your program, then continues to execute,
16668 retrieving and transmitting any information @value{GDBN} needs, until you
16669 execute a @value{GDBN} command that makes your program resume; at that point,
16670 @code{handle_exception} returns control to your own code on the target
16671 machine.
16672
16673 @item breakpoint
16674 @cindex @code{breakpoint} subroutine, remote
16675 Use this auxiliary subroutine to make your program contain a
16676 breakpoint. Depending on the particular situation, this may be the only
16677 way for @value{GDBN} to get control. For instance, if your target
16678 machine has some sort of interrupt button, you won't need to call this;
16679 pressing the interrupt button transfers control to
16680 @code{handle_exception}---in effect, to @value{GDBN}. On some machines,
16681 simply receiving characters on the serial port may also trigger a trap;
16682 again, in that situation, you don't need to call @code{breakpoint} from
16683 your own program---simply running @samp{target remote} from the host
16684 @value{GDBN} session gets control.
16685
16686 Call @code{breakpoint} if none of these is true, or if you simply want
16687 to make certain your program stops at a predetermined point for the
16688 start of your debugging session.
16689 @end table
16690
16691 @node Bootstrapping
16692 @subsection What You Must Do for the Stub
16693
16694 @cindex remote stub, support routines
16695 The debugging stubs that come with @value{GDBN} are set up for a particular
16696 chip architecture, but they have no information about the rest of your
16697 debugging target machine.
16698
16699 First of all you need to tell the stub how to communicate with the
16700 serial port.
16701
16702 @table @code
16703 @item int getDebugChar()
16704 @findex getDebugChar
16705 Write this subroutine to read a single character from the serial port.
16706 It may be identical to @code{getchar} for your target system; a
16707 different name is used to allow you to distinguish the two if you wish.
16708
16709 @item void putDebugChar(int)
16710 @findex putDebugChar
16711 Write this subroutine to write a single character to the serial port.
16712 It may be identical to @code{putchar} for your target system; a
16713 different name is used to allow you to distinguish the two if you wish.
16714 @end table
16715
16716 @cindex control C, and remote debugging
16717 @cindex interrupting remote targets
16718 If you want @value{GDBN} to be able to stop your program while it is
16719 running, you need to use an interrupt-driven serial driver, and arrange
16720 for it to stop when it receives a @code{^C} (@samp{\003}, the control-C
16721 character). That is the character which @value{GDBN} uses to tell the
16722 remote system to stop.
16723
16724 Getting the debugging target to return the proper status to @value{GDBN}
16725 probably requires changes to the standard stub; one quick and dirty way
16726 is to just execute a breakpoint instruction (the ``dirty'' part is that
16727 @value{GDBN} reports a @code{SIGTRAP} instead of a @code{SIGINT}).
16728
16729 Other routines you need to supply are:
16730
16731 @table @code
16732 @item void exceptionHandler (int @var{exception_number}, void *@var{exception_address})
16733 @findex exceptionHandler
16734 Write this function to install @var{exception_address} in the exception
16735 handling tables. You need to do this because the stub does not have any
16736 way of knowing what the exception handling tables on your target system
16737 are like (for example, the processor's table might be in @sc{rom},
16738 containing entries which point to a table in @sc{ram}).
16739 @var{exception_number} is the exception number which should be changed;
16740 its meaning is architecture-dependent (for example, different numbers
16741 might represent divide by zero, misaligned access, etc). When this
16742 exception occurs, control should be transferred directly to
16743 @var{exception_address}, and the processor state (stack, registers,
16744 and so on) should be just as it is when a processor exception occurs. So if
16745 you want to use a jump instruction to reach @var{exception_address}, it
16746 should be a simple jump, not a jump to subroutine.
16747
16748 For the 386, @var{exception_address} should be installed as an interrupt
16749 gate so that interrupts are masked while the handler runs. The gate
16750 should be at privilege level 0 (the most privileged level). The
16751 @sc{sparc} and 68k stubs are able to mask interrupts themselves without
16752 help from @code{exceptionHandler}.
16753
16754 @item void flush_i_cache()
16755 @findex flush_i_cache
16756 On @sc{sparc} and @sc{sparclite} only, write this subroutine to flush the
16757 instruction cache, if any, on your target machine. If there is no
16758 instruction cache, this subroutine may be a no-op.
16759
16760 On target machines that have instruction caches, @value{GDBN} requires this
16761 function to make certain that the state of your program is stable.
16762 @end table
16763
16764 @noindent
16765 You must also make sure this library routine is available:
16766
16767 @table @code
16768 @item void *memset(void *, int, int)
16769 @findex memset
16770 This is the standard library function @code{memset} that sets an area of
16771 memory to a known value. If you have one of the free versions of
16772 @code{libc.a}, @code{memset} can be found there; otherwise, you must
16773 either obtain it from your hardware manufacturer, or write your own.
16774 @end table
16775
16776 If you do not use the GNU C compiler, you may need other standard
16777 library subroutines as well; this varies from one stub to another,
16778 but in general the stubs are likely to use any of the common library
16779 subroutines which @code{@value{NGCC}} generates as inline code.
16780
16781
16782 @node Debug Session
16783 @subsection Putting it All Together
16784
16785 @cindex remote serial debugging summary
16786 In summary, when your program is ready to debug, you must follow these
16787 steps.
16788
16789 @enumerate
16790 @item
16791 Make sure you have defined the supporting low-level routines
16792 (@pxref{Bootstrapping,,What You Must Do for the Stub}):
16793 @display
16794 @code{getDebugChar}, @code{putDebugChar},
16795 @code{flush_i_cache}, @code{memset}, @code{exceptionHandler}.
16796 @end display
16797
16798 @item
16799 Insert these lines near the top of your program:
16800
16801 @smallexample
16802 set_debug_traps();
16803 breakpoint();
16804 @end smallexample
16805
16806 @item
16807 For the 680x0 stub only, you need to provide a variable called
16808 @code{exceptionHook}. Normally you just use:
16809
16810 @smallexample
16811 void (*exceptionHook)() = 0;
16812 @end smallexample
16813
16814 @noindent
16815 but if before calling @code{set_debug_traps}, you set it to point to a
16816 function in your program, that function is called when
16817 @code{@value{GDBN}} continues after stopping on a trap (for example, bus
16818 error). The function indicated by @code{exceptionHook} is called with
16819 one parameter: an @code{int} which is the exception number.
16820
16821 @item
16822 Compile and link together: your program, the @value{GDBN} debugging stub for
16823 your target architecture, and the supporting subroutines.
16824
16825 @item
16826 Make sure you have a serial connection between your target machine and
16827 the @value{GDBN} host, and identify the serial port on the host.
16828
16829 @item
16830 @c The "remote" target now provides a `load' command, so we should
16831 @c document that. FIXME.
16832 Download your program to your target machine (or get it there by
16833 whatever means the manufacturer provides), and start it.
16834
16835 @item
16836 Start @value{GDBN} on the host, and connect to the target
16837 (@pxref{Connecting,,Connecting to a Remote Target}).
16838
16839 @end enumerate
16840
16841 @node Configurations
16842 @chapter Configuration-Specific Information
16843
16844 While nearly all @value{GDBN} commands are available for all native and
16845 cross versions of the debugger, there are some exceptions. This chapter
16846 describes things that are only available in certain configurations.
16847
16848 There are three major categories of configurations: native
16849 configurations, where the host and target are the same, embedded
16850 operating system configurations, which are usually the same for several
16851 different processor architectures, and bare embedded processors, which
16852 are quite different from each other.
16853
16854 @menu
16855 * Native::
16856 * Embedded OS::
16857 * Embedded Processors::
16858 * Architectures::
16859 @end menu
16860
16861 @node Native
16862 @section Native
16863
16864 This section describes details specific to particular native
16865 configurations.
16866
16867 @menu
16868 * HP-UX:: HP-UX
16869 * BSD libkvm Interface:: Debugging BSD kernel memory images
16870 * SVR4 Process Information:: SVR4 process information
16871 * DJGPP Native:: Features specific to the DJGPP port
16872 * Cygwin Native:: Features specific to the Cygwin port
16873 * Hurd Native:: Features specific to @sc{gnu} Hurd
16874 * Neutrino:: Features specific to QNX Neutrino
16875 * Darwin:: Features specific to Darwin
16876 @end menu
16877
16878 @node HP-UX
16879 @subsection HP-UX
16880
16881 On HP-UX systems, if you refer to a function or variable name that
16882 begins with a dollar sign, @value{GDBN} searches for a user or system
16883 name first, before it searches for a convenience variable.
16884
16885
16886 @node BSD libkvm Interface
16887 @subsection BSD libkvm Interface
16888
16889 @cindex libkvm
16890 @cindex kernel memory image
16891 @cindex kernel crash dump
16892
16893 BSD-derived systems (FreeBSD/NetBSD/OpenBSD) have a kernel memory
16894 interface that provides a uniform interface for accessing kernel virtual
16895 memory images, including live systems and crash dumps. @value{GDBN}
16896 uses this interface to allow you to debug live kernels and kernel crash
16897 dumps on many native BSD configurations. This is implemented as a
16898 special @code{kvm} debugging target. For debugging a live system, load
16899 the currently running kernel into @value{GDBN} and connect to the
16900 @code{kvm} target:
16901
16902 @smallexample
16903 (@value{GDBP}) @b{target kvm}
16904 @end smallexample
16905
16906 For debugging crash dumps, provide the file name of the crash dump as an
16907 argument:
16908
16909 @smallexample
16910 (@value{GDBP}) @b{target kvm /var/crash/bsd.0}
16911 @end smallexample
16912
16913 Once connected to the @code{kvm} target, the following commands are
16914 available:
16915
16916 @table @code
16917 @kindex kvm
16918 @item kvm pcb
16919 Set current context from the @dfn{Process Control Block} (PCB) address.
16920
16921 @item kvm proc
16922 Set current context from proc address. This command isn't available on
16923 modern FreeBSD systems.
16924 @end table
16925
16926 @node SVR4 Process Information
16927 @subsection SVR4 Process Information
16928 @cindex /proc
16929 @cindex examine process image
16930 @cindex process info via @file{/proc}
16931
16932 Many versions of SVR4 and compatible systems provide a facility called
16933 @samp{/proc} that can be used to examine the image of a running
16934 process using file-system subroutines. If @value{GDBN} is configured
16935 for an operating system with this facility, the command @code{info
16936 proc} is available to report information about the process running
16937 your program, or about any process running on your system. @code{info
16938 proc} works only on SVR4 systems that include the @code{procfs} code.
16939 This includes, as of this writing, @sc{gnu}/Linux, OSF/1 (Digital
16940 Unix), Solaris, Irix, and Unixware, but not HP-UX, for example.
16941
16942 @table @code
16943 @kindex info proc
16944 @cindex process ID
16945 @item info proc
16946 @itemx info proc @var{process-id}
16947 Summarize available information about any running process. If a
16948 process ID is specified by @var{process-id}, display information about
16949 that process; otherwise display information about the program being
16950 debugged. The summary includes the debugged process ID, the command
16951 line used to invoke it, its current working directory, and its
16952 executable file's absolute file name.
16953
16954 On some systems, @var{process-id} can be of the form
16955 @samp{[@var{pid}]/@var{tid}} which specifies a certain thread ID
16956 within a process. If the optional @var{pid} part is missing, it means
16957 a thread from the process being debugged (the leading @samp{/} still
16958 needs to be present, or else @value{GDBN} will interpret the number as
16959 a process ID rather than a thread ID).
16960
16961 @item info proc mappings
16962 @cindex memory address space mappings
16963 Report the memory address space ranges accessible in the program, with
16964 information on whether the process has read, write, or execute access
16965 rights to each range. On @sc{gnu}/Linux systems, each memory range
16966 includes the object file which is mapped to that range, instead of the
16967 memory access rights to that range.
16968
16969 @item info proc stat
16970 @itemx info proc status
16971 @cindex process detailed status information
16972 These subcommands are specific to @sc{gnu}/Linux systems. They show
16973 the process-related information, including the user ID and group ID;
16974 how many threads are there in the process; its virtual memory usage;
16975 the signals that are pending, blocked, and ignored; its TTY; its
16976 consumption of system and user time; its stack size; its @samp{nice}
16977 value; etc. For more information, see the @samp{proc} man page
16978 (type @kbd{man 5 proc} from your shell prompt).
16979
16980 @item info proc all
16981 Show all the information about the process described under all of the
16982 above @code{info proc} subcommands.
16983
16984 @ignore
16985 @comment These sub-options of 'info proc' were not included when
16986 @comment procfs.c was re-written. Keep their descriptions around
16987 @comment against the day when someone finds the time to put them back in.
16988 @kindex info proc times
16989 @item info proc times
16990 Starting time, user CPU time, and system CPU time for your program and
16991 its children.
16992
16993 @kindex info proc id
16994 @item info proc id
16995 Report on the process IDs related to your program: its own process ID,
16996 the ID of its parent, the process group ID, and the session ID.
16997 @end ignore
16998
16999 @item set procfs-trace
17000 @kindex set procfs-trace
17001 @cindex @code{procfs} API calls
17002 This command enables and disables tracing of @code{procfs} API calls.
17003
17004 @item show procfs-trace
17005 @kindex show procfs-trace
17006 Show the current state of @code{procfs} API call tracing.
17007
17008 @item set procfs-file @var{file}
17009 @kindex set procfs-file
17010 Tell @value{GDBN} to write @code{procfs} API trace to the named
17011 @var{file}. @value{GDBN} appends the trace info to the previous
17012 contents of the file. The default is to display the trace on the
17013 standard output.
17014
17015 @item show procfs-file
17016 @kindex show procfs-file
17017 Show the file to which @code{procfs} API trace is written.
17018
17019 @item proc-trace-entry
17020 @itemx proc-trace-exit
17021 @itemx proc-untrace-entry
17022 @itemx proc-untrace-exit
17023 @kindex proc-trace-entry
17024 @kindex proc-trace-exit
17025 @kindex proc-untrace-entry
17026 @kindex proc-untrace-exit
17027 These commands enable and disable tracing of entries into and exits
17028 from the @code{syscall} interface.
17029
17030 @item info pidlist
17031 @kindex info pidlist
17032 @cindex process list, QNX Neutrino
17033 For QNX Neutrino only, this command displays the list of all the
17034 processes and all the threads within each process.
17035
17036 @item info meminfo
17037 @kindex info meminfo
17038 @cindex mapinfo list, QNX Neutrino
17039 For QNX Neutrino only, this command displays the list of all mapinfos.
17040 @end table
17041
17042 @node DJGPP Native
17043 @subsection Features for Debugging @sc{djgpp} Programs
17044 @cindex @sc{djgpp} debugging
17045 @cindex native @sc{djgpp} debugging
17046 @cindex MS-DOS-specific commands
17047
17048 @cindex DPMI
17049 @sc{djgpp} is a port of the @sc{gnu} development tools to MS-DOS and
17050 MS-Windows. @sc{djgpp} programs are 32-bit protected-mode programs
17051 that use the @dfn{DPMI} (DOS Protected-Mode Interface) API to run on
17052 top of real-mode DOS systems and their emulations.
17053
17054 @value{GDBN} supports native debugging of @sc{djgpp} programs, and
17055 defines a few commands specific to the @sc{djgpp} port. This
17056 subsection describes those commands.
17057
17058 @table @code
17059 @kindex info dos
17060 @item info dos
17061 This is a prefix of @sc{djgpp}-specific commands which print
17062 information about the target system and important OS structures.
17063
17064 @kindex sysinfo
17065 @cindex MS-DOS system info
17066 @cindex free memory information (MS-DOS)
17067 @item info dos sysinfo
17068 This command displays assorted information about the underlying
17069 platform: the CPU type and features, the OS version and flavor, the
17070 DPMI version, and the available conventional and DPMI memory.
17071
17072 @cindex GDT
17073 @cindex LDT
17074 @cindex IDT
17075 @cindex segment descriptor tables
17076 @cindex descriptor tables display
17077 @item info dos gdt
17078 @itemx info dos ldt
17079 @itemx info dos idt
17080 These 3 commands display entries from, respectively, Global, Local,
17081 and Interrupt Descriptor Tables (GDT, LDT, and IDT). The descriptor
17082 tables are data structures which store a descriptor for each segment
17083 that is currently in use. The segment's selector is an index into a
17084 descriptor table; the table entry for that index holds the
17085 descriptor's base address and limit, and its attributes and access
17086 rights.
17087
17088 A typical @sc{djgpp} program uses 3 segments: a code segment, a data
17089 segment (used for both data and the stack), and a DOS segment (which
17090 allows access to DOS/BIOS data structures and absolute addresses in
17091 conventional memory). However, the DPMI host will usually define
17092 additional segments in order to support the DPMI environment.
17093
17094 @cindex garbled pointers
17095 These commands allow to display entries from the descriptor tables.
17096 Without an argument, all entries from the specified table are
17097 displayed. An argument, which should be an integer expression, means
17098 display a single entry whose index is given by the argument. For
17099 example, here's a convenient way to display information about the
17100 debugged program's data segment:
17101
17102 @smallexample
17103 @exdent @code{(@value{GDBP}) info dos ldt $ds}
17104 @exdent @code{0x13f: base=0x11970000 limit=0x0009ffff 32-Bit Data (Read/Write, Exp-up)}
17105 @end smallexample
17106
17107 @noindent
17108 This comes in handy when you want to see whether a pointer is outside
17109 the data segment's limit (i.e.@: @dfn{garbled}).
17110
17111 @cindex page tables display (MS-DOS)
17112 @item info dos pde
17113 @itemx info dos pte
17114 These two commands display entries from, respectively, the Page
17115 Directory and the Page Tables. Page Directories and Page Tables are
17116 data structures which control how virtual memory addresses are mapped
17117 into physical addresses. A Page Table includes an entry for every
17118 page of memory that is mapped into the program's address space; there
17119 may be several Page Tables, each one holding up to 4096 entries. A
17120 Page Directory has up to 4096 entries, one each for every Page Table
17121 that is currently in use.
17122
17123 Without an argument, @kbd{info dos pde} displays the entire Page
17124 Directory, and @kbd{info dos pte} displays all the entries in all of
17125 the Page Tables. An argument, an integer expression, given to the
17126 @kbd{info dos pde} command means display only that entry from the Page
17127 Directory table. An argument given to the @kbd{info dos pte} command
17128 means display entries from a single Page Table, the one pointed to by
17129 the specified entry in the Page Directory.
17130
17131 @cindex direct memory access (DMA) on MS-DOS
17132 These commands are useful when your program uses @dfn{DMA} (Direct
17133 Memory Access), which needs physical addresses to program the DMA
17134 controller.
17135
17136 These commands are supported only with some DPMI servers.
17137
17138 @cindex physical address from linear address
17139 @item info dos address-pte @var{addr}
17140 This command displays the Page Table entry for a specified linear
17141 address. The argument @var{addr} is a linear address which should
17142 already have the appropriate segment's base address added to it,
17143 because this command accepts addresses which may belong to @emph{any}
17144 segment. For example, here's how to display the Page Table entry for
17145 the page where a variable @code{i} is stored:
17146
17147 @smallexample
17148 @exdent @code{(@value{GDBP}) info dos address-pte __djgpp_base_address + (char *)&i}
17149 @exdent @code{Page Table entry for address 0x11a00d30:}
17150 @exdent @code{Base=0x02698000 Dirty Acc. Not-Cached Write-Back Usr Read-Write +0xd30}
17151 @end smallexample
17152
17153 @noindent
17154 This says that @code{i} is stored at offset @code{0xd30} from the page
17155 whose physical base address is @code{0x02698000}, and shows all the
17156 attributes of that page.
17157
17158 Note that you must cast the addresses of variables to a @code{char *},
17159 since otherwise the value of @code{__djgpp_base_address}, the base
17160 address of all variables and functions in a @sc{djgpp} program, will
17161 be added using the rules of C pointer arithmetics: if @code{i} is
17162 declared an @code{int}, @value{GDBN} will add 4 times the value of
17163 @code{__djgpp_base_address} to the address of @code{i}.
17164
17165 Here's another example, it displays the Page Table entry for the
17166 transfer buffer:
17167
17168 @smallexample
17169 @exdent @code{(@value{GDBP}) info dos address-pte *((unsigned *)&_go32_info_block + 3)}
17170 @exdent @code{Page Table entry for address 0x29110:}
17171 @exdent @code{Base=0x00029000 Dirty Acc. Not-Cached Write-Back Usr Read-Write +0x110}
17172 @end smallexample
17173
17174 @noindent
17175 (The @code{+ 3} offset is because the transfer buffer's address is the
17176 3rd member of the @code{_go32_info_block} structure.) The output
17177 clearly shows that this DPMI server maps the addresses in conventional
17178 memory 1:1, i.e.@: the physical (@code{0x00029000} + @code{0x110}) and
17179 linear (@code{0x29110}) addresses are identical.
17180
17181 This command is supported only with some DPMI servers.
17182 @end table
17183
17184 @cindex DOS serial data link, remote debugging
17185 In addition to native debugging, the DJGPP port supports remote
17186 debugging via a serial data link. The following commands are specific
17187 to remote serial debugging in the DJGPP port of @value{GDBN}.
17188
17189 @table @code
17190 @kindex set com1base
17191 @kindex set com1irq
17192 @kindex set com2base
17193 @kindex set com2irq
17194 @kindex set com3base
17195 @kindex set com3irq
17196 @kindex set com4base
17197 @kindex set com4irq
17198 @item set com1base @var{addr}
17199 This command sets the base I/O port address of the @file{COM1} serial
17200 port.
17201
17202 @item set com1irq @var{irq}
17203 This command sets the @dfn{Interrupt Request} (@code{IRQ}) line to use
17204 for the @file{COM1} serial port.
17205
17206 There are similar commands @samp{set com2base}, @samp{set com3irq},
17207 etc.@: for setting the port address and the @code{IRQ} lines for the
17208 other 3 COM ports.
17209
17210 @kindex show com1base
17211 @kindex show com1irq
17212 @kindex show com2base
17213 @kindex show com2irq
17214 @kindex show com3base
17215 @kindex show com3irq
17216 @kindex show com4base
17217 @kindex show com4irq
17218 The related commands @samp{show com1base}, @samp{show com1irq} etc.@:
17219 display the current settings of the base address and the @code{IRQ}
17220 lines used by the COM ports.
17221
17222 @item info serial
17223 @kindex info serial
17224 @cindex DOS serial port status
17225 This command prints the status of the 4 DOS serial ports. For each
17226 port, it prints whether it's active or not, its I/O base address and
17227 IRQ number, whether it uses a 16550-style FIFO, its baudrate, and the
17228 counts of various errors encountered so far.
17229 @end table
17230
17231
17232 @node Cygwin Native
17233 @subsection Features for Debugging MS Windows PE Executables
17234 @cindex MS Windows debugging
17235 @cindex native Cygwin debugging
17236 @cindex Cygwin-specific commands
17237
17238 @value{GDBN} supports native debugging of MS Windows programs, including
17239 DLLs with and without symbolic debugging information.
17240
17241 @cindex Ctrl-BREAK, MS-Windows
17242 @cindex interrupt debuggee on MS-Windows
17243 MS-Windows programs that call @code{SetConsoleMode} to switch off the
17244 special meaning of the @samp{Ctrl-C} keystroke cannot be interrupted
17245 by typing @kbd{C-c}. For this reason, @value{GDBN} on MS-Windows
17246 supports @kbd{C-@key{BREAK}} as an alternative interrupt key
17247 sequence, which can be used to interrupt the debuggee even if it
17248 ignores @kbd{C-c}.
17249
17250 There are various additional Cygwin-specific commands, described in
17251 this section. Working with DLLs that have no debugging symbols is
17252 described in @ref{Non-debug DLL Symbols}.
17253
17254 @table @code
17255 @kindex info w32
17256 @item info w32
17257 This is a prefix of MS Windows-specific commands which print
17258 information about the target system and important OS structures.
17259
17260 @item info w32 selector
17261 This command displays information returned by
17262 the Win32 API @code{GetThreadSelectorEntry} function.
17263 It takes an optional argument that is evaluated to
17264 a long value to give the information about this given selector.
17265 Without argument, this command displays information
17266 about the six segment registers.
17267
17268 @item info w32 thread-information-block
17269 This command displays thread specific information stored in the
17270 Thread Information Block (readable on the X86 CPU family using @code{$fs}
17271 selector for 32-bit programs and @code{$gs} for 64-bit programs).
17272
17273 @kindex info dll
17274 @item info dll
17275 This is a Cygwin-specific alias of @code{info shared}.
17276
17277 @kindex dll-symbols
17278 @item dll-symbols
17279 This command loads symbols from a dll similarly to
17280 add-sym command but without the need to specify a base address.
17281
17282 @kindex set cygwin-exceptions
17283 @cindex debugging the Cygwin DLL
17284 @cindex Cygwin DLL, debugging
17285 @item set cygwin-exceptions @var{mode}
17286 If @var{mode} is @code{on}, @value{GDBN} will break on exceptions that
17287 happen inside the Cygwin DLL. If @var{mode} is @code{off},
17288 @value{GDBN} will delay recognition of exceptions, and may ignore some
17289 exceptions which seem to be caused by internal Cygwin DLL
17290 ``bookkeeping''. This option is meant primarily for debugging the
17291 Cygwin DLL itself; the default value is @code{off} to avoid annoying
17292 @value{GDBN} users with false @code{SIGSEGV} signals.
17293
17294 @kindex show cygwin-exceptions
17295 @item show cygwin-exceptions
17296 Displays whether @value{GDBN} will break on exceptions that happen
17297 inside the Cygwin DLL itself.
17298
17299 @kindex set new-console
17300 @item set new-console @var{mode}
17301 If @var{mode} is @code{on} the debuggee will
17302 be started in a new console on next start.
17303 If @var{mode} is @code{off}, the debuggee will
17304 be started in the same console as the debugger.
17305
17306 @kindex show new-console
17307 @item show new-console
17308 Displays whether a new console is used
17309 when the debuggee is started.
17310
17311 @kindex set new-group
17312 @item set new-group @var{mode}
17313 This boolean value controls whether the debuggee should
17314 start a new group or stay in the same group as the debugger.
17315 This affects the way the Windows OS handles
17316 @samp{Ctrl-C}.
17317
17318 @kindex show new-group
17319 @item show new-group
17320 Displays current value of new-group boolean.
17321
17322 @kindex set debugevents
17323 @item set debugevents
17324 This boolean value adds debug output concerning kernel events related
17325 to the debuggee seen by the debugger. This includes events that
17326 signal thread and process creation and exit, DLL loading and
17327 unloading, console interrupts, and debugging messages produced by the
17328 Windows @code{OutputDebugString} API call.
17329
17330 @kindex set debugexec
17331 @item set debugexec
17332 This boolean value adds debug output concerning execute events
17333 (such as resume thread) seen by the debugger.
17334
17335 @kindex set debugexceptions
17336 @item set debugexceptions
17337 This boolean value adds debug output concerning exceptions in the
17338 debuggee seen by the debugger.
17339
17340 @kindex set debugmemory
17341 @item set debugmemory
17342 This boolean value adds debug output concerning debuggee memory reads
17343 and writes by the debugger.
17344
17345 @kindex set shell
17346 @item set shell
17347 This boolean values specifies whether the debuggee is called
17348 via a shell or directly (default value is on).
17349
17350 @kindex show shell
17351 @item show shell
17352 Displays if the debuggee will be started with a shell.
17353
17354 @end table
17355
17356 @menu
17357 * Non-debug DLL Symbols:: Support for DLLs without debugging symbols
17358 @end menu
17359
17360 @node Non-debug DLL Symbols
17361 @subsubsection Support for DLLs without Debugging Symbols
17362 @cindex DLLs with no debugging symbols
17363 @cindex Minimal symbols and DLLs
17364
17365 Very often on windows, some of the DLLs that your program relies on do
17366 not include symbolic debugging information (for example,
17367 @file{kernel32.dll}). When @value{GDBN} doesn't recognize any debugging
17368 symbols in a DLL, it relies on the minimal amount of symbolic
17369 information contained in the DLL's export table. This section
17370 describes working with such symbols, known internally to @value{GDBN} as
17371 ``minimal symbols''.
17372
17373 Note that before the debugged program has started execution, no DLLs
17374 will have been loaded. The easiest way around this problem is simply to
17375 start the program --- either by setting a breakpoint or letting the
17376 program run once to completion. It is also possible to force
17377 @value{GDBN} to load a particular DLL before starting the executable ---
17378 see the shared library information in @ref{Files}, or the
17379 @code{dll-symbols} command in @ref{Cygwin Native}. Currently,
17380 explicitly loading symbols from a DLL with no debugging information will
17381 cause the symbol names to be duplicated in @value{GDBN}'s lookup table,
17382 which may adversely affect symbol lookup performance.
17383
17384 @subsubsection DLL Name Prefixes
17385
17386 In keeping with the naming conventions used by the Microsoft debugging
17387 tools, DLL export symbols are made available with a prefix based on the
17388 DLL name, for instance @code{KERNEL32!CreateFileA}. The plain name is
17389 also entered into the symbol table, so @code{CreateFileA} is often
17390 sufficient. In some cases there will be name clashes within a program
17391 (particularly if the executable itself includes full debugging symbols)
17392 necessitating the use of the fully qualified name when referring to the
17393 contents of the DLL. Use single-quotes around the name to avoid the
17394 exclamation mark (``!'') being interpreted as a language operator.
17395
17396 Note that the internal name of the DLL may be all upper-case, even
17397 though the file name of the DLL is lower-case, or vice-versa. Since
17398 symbols within @value{GDBN} are @emph{case-sensitive} this may cause
17399 some confusion. If in doubt, try the @code{info functions} and
17400 @code{info variables} commands or even @code{maint print msymbols}
17401 (@pxref{Symbols}). Here's an example:
17402
17403 @smallexample
17404 (@value{GDBP}) info function CreateFileA
17405 All functions matching regular expression "CreateFileA":
17406
17407 Non-debugging symbols:
17408 0x77e885f4 CreateFileA
17409 0x77e885f4 KERNEL32!CreateFileA
17410 @end smallexample
17411
17412 @smallexample
17413 (@value{GDBP}) info function !
17414 All functions matching regular expression "!":
17415
17416 Non-debugging symbols:
17417 0x6100114c cygwin1!__assert
17418 0x61004034 cygwin1!_dll_crt0@@0
17419 0x61004240 cygwin1!dll_crt0(per_process *)
17420 [etc...]
17421 @end smallexample
17422
17423 @subsubsection Working with Minimal Symbols
17424
17425 Symbols extracted from a DLL's export table do not contain very much
17426 type information. All that @value{GDBN} can do is guess whether a symbol
17427 refers to a function or variable depending on the linker section that
17428 contains the symbol. Also note that the actual contents of the memory
17429 contained in a DLL are not available unless the program is running. This
17430 means that you cannot examine the contents of a variable or disassemble
17431 a function within a DLL without a running program.
17432
17433 Variables are generally treated as pointers and dereferenced
17434 automatically. For this reason, it is often necessary to prefix a
17435 variable name with the address-of operator (``&'') and provide explicit
17436 type information in the command. Here's an example of the type of
17437 problem:
17438
17439 @smallexample
17440 (@value{GDBP}) print 'cygwin1!__argv'
17441 $1 = 268572168
17442 @end smallexample
17443
17444 @smallexample
17445 (@value{GDBP}) x 'cygwin1!__argv'
17446 0x10021610: "\230y\""
17447 @end smallexample
17448
17449 And two possible solutions:
17450
17451 @smallexample
17452 (@value{GDBP}) print ((char **)'cygwin1!__argv')[0]
17453 $2 = 0x22fd98 "/cygdrive/c/mydirectory/myprogram"
17454 @end smallexample
17455
17456 @smallexample
17457 (@value{GDBP}) x/2x &'cygwin1!__argv'
17458 0x610c0aa8 <cygwin1!__argv>: 0x10021608 0x00000000
17459 (@value{GDBP}) x/x 0x10021608
17460 0x10021608: 0x0022fd98
17461 (@value{GDBP}) x/s 0x0022fd98
17462 0x22fd98: "/cygdrive/c/mydirectory/myprogram"
17463 @end smallexample
17464
17465 Setting a break point within a DLL is possible even before the program
17466 starts execution. However, under these circumstances, @value{GDBN} can't
17467 examine the initial instructions of the function in order to skip the
17468 function's frame set-up code. You can work around this by using ``*&''
17469 to set the breakpoint at a raw memory address:
17470
17471 @smallexample
17472 (@value{GDBP}) break *&'python22!PyOS_Readline'
17473 Breakpoint 1 at 0x1e04eff0
17474 @end smallexample
17475
17476 The author of these extensions is not entirely convinced that setting a
17477 break point within a shared DLL like @file{kernel32.dll} is completely
17478 safe.
17479
17480 @node Hurd Native
17481 @subsection Commands Specific to @sc{gnu} Hurd Systems
17482 @cindex @sc{gnu} Hurd debugging
17483
17484 This subsection describes @value{GDBN} commands specific to the
17485 @sc{gnu} Hurd native debugging.
17486
17487 @table @code
17488 @item set signals
17489 @itemx set sigs
17490 @kindex set signals@r{, Hurd command}
17491 @kindex set sigs@r{, Hurd command}
17492 This command toggles the state of inferior signal interception by
17493 @value{GDBN}. Mach exceptions, such as breakpoint traps, are not
17494 affected by this command. @code{sigs} is a shorthand alias for
17495 @code{signals}.
17496
17497 @item show signals
17498 @itemx show sigs
17499 @kindex show signals@r{, Hurd command}
17500 @kindex show sigs@r{, Hurd command}
17501 Show the current state of intercepting inferior's signals.
17502
17503 @item set signal-thread
17504 @itemx set sigthread
17505 @kindex set signal-thread
17506 @kindex set sigthread
17507 This command tells @value{GDBN} which thread is the @code{libc} signal
17508 thread. That thread is run when a signal is delivered to a running
17509 process. @code{set sigthread} is the shorthand alias of @code{set
17510 signal-thread}.
17511
17512 @item show signal-thread
17513 @itemx show sigthread
17514 @kindex show signal-thread
17515 @kindex show sigthread
17516 These two commands show which thread will run when the inferior is
17517 delivered a signal.
17518
17519 @item set stopped
17520 @kindex set stopped@r{, Hurd command}
17521 This commands tells @value{GDBN} that the inferior process is stopped,
17522 as with the @code{SIGSTOP} signal. The stopped process can be
17523 continued by delivering a signal to it.
17524
17525 @item show stopped
17526 @kindex show stopped@r{, Hurd command}
17527 This command shows whether @value{GDBN} thinks the debuggee is
17528 stopped.
17529
17530 @item set exceptions
17531 @kindex set exceptions@r{, Hurd command}
17532 Use this command to turn off trapping of exceptions in the inferior.
17533 When exception trapping is off, neither breakpoints nor
17534 single-stepping will work. To restore the default, set exception
17535 trapping on.
17536
17537 @item show exceptions
17538 @kindex show exceptions@r{, Hurd command}
17539 Show the current state of trapping exceptions in the inferior.
17540
17541 @item set task pause
17542 @kindex set task@r{, Hurd commands}
17543 @cindex task attributes (@sc{gnu} Hurd)
17544 @cindex pause current task (@sc{gnu} Hurd)
17545 This command toggles task suspension when @value{GDBN} has control.
17546 Setting it to on takes effect immediately, and the task is suspended
17547 whenever @value{GDBN} gets control. Setting it to off will take
17548 effect the next time the inferior is continued. If this option is set
17549 to off, you can use @code{set thread default pause on} or @code{set
17550 thread pause on} (see below) to pause individual threads.
17551
17552 @item show task pause
17553 @kindex show task@r{, Hurd commands}
17554 Show the current state of task suspension.
17555
17556 @item set task detach-suspend-count
17557 @cindex task suspend count
17558 @cindex detach from task, @sc{gnu} Hurd
17559 This command sets the suspend count the task will be left with when
17560 @value{GDBN} detaches from it.
17561
17562 @item show task detach-suspend-count
17563 Show the suspend count the task will be left with when detaching.
17564
17565 @item set task exception-port
17566 @itemx set task excp
17567 @cindex task exception port, @sc{gnu} Hurd
17568 This command sets the task exception port to which @value{GDBN} will
17569 forward exceptions. The argument should be the value of the @dfn{send
17570 rights} of the task. @code{set task excp} is a shorthand alias.
17571
17572 @item set noninvasive
17573 @cindex noninvasive task options
17574 This command switches @value{GDBN} to a mode that is the least
17575 invasive as far as interfering with the inferior is concerned. This
17576 is the same as using @code{set task pause}, @code{set exceptions}, and
17577 @code{set signals} to values opposite to the defaults.
17578
17579 @item info send-rights
17580 @itemx info receive-rights
17581 @itemx info port-rights
17582 @itemx info port-sets
17583 @itemx info dead-names
17584 @itemx info ports
17585 @itemx info psets
17586 @cindex send rights, @sc{gnu} Hurd
17587 @cindex receive rights, @sc{gnu} Hurd
17588 @cindex port rights, @sc{gnu} Hurd
17589 @cindex port sets, @sc{gnu} Hurd
17590 @cindex dead names, @sc{gnu} Hurd
17591 These commands display information about, respectively, send rights,
17592 receive rights, port rights, port sets, and dead names of a task.
17593 There are also shorthand aliases: @code{info ports} for @code{info
17594 port-rights} and @code{info psets} for @code{info port-sets}.
17595
17596 @item set thread pause
17597 @kindex set thread@r{, Hurd command}
17598 @cindex thread properties, @sc{gnu} Hurd
17599 @cindex pause current thread (@sc{gnu} Hurd)
17600 This command toggles current thread suspension when @value{GDBN} has
17601 control. Setting it to on takes effect immediately, and the current
17602 thread is suspended whenever @value{GDBN} gets control. Setting it to
17603 off will take effect the next time the inferior is continued.
17604 Normally, this command has no effect, since when @value{GDBN} has
17605 control, the whole task is suspended. However, if you used @code{set
17606 task pause off} (see above), this command comes in handy to suspend
17607 only the current thread.
17608
17609 @item show thread pause
17610 @kindex show thread@r{, Hurd command}
17611 This command shows the state of current thread suspension.
17612
17613 @item set thread run
17614 This command sets whether the current thread is allowed to run.
17615
17616 @item show thread run
17617 Show whether the current thread is allowed to run.
17618
17619 @item set thread detach-suspend-count
17620 @cindex thread suspend count, @sc{gnu} Hurd
17621 @cindex detach from thread, @sc{gnu} Hurd
17622 This command sets the suspend count @value{GDBN} will leave on a
17623 thread when detaching. This number is relative to the suspend count
17624 found by @value{GDBN} when it notices the thread; use @code{set thread
17625 takeover-suspend-count} to force it to an absolute value.
17626
17627 @item show thread detach-suspend-count
17628 Show the suspend count @value{GDBN} will leave on the thread when
17629 detaching.
17630
17631 @item set thread exception-port
17632 @itemx set thread excp
17633 Set the thread exception port to which to forward exceptions. This
17634 overrides the port set by @code{set task exception-port} (see above).
17635 @code{set thread excp} is the shorthand alias.
17636
17637 @item set thread takeover-suspend-count
17638 Normally, @value{GDBN}'s thread suspend counts are relative to the
17639 value @value{GDBN} finds when it notices each thread. This command
17640 changes the suspend counts to be absolute instead.
17641
17642 @item set thread default
17643 @itemx show thread default
17644 @cindex thread default settings, @sc{gnu} Hurd
17645 Each of the above @code{set thread} commands has a @code{set thread
17646 default} counterpart (e.g., @code{set thread default pause}, @code{set
17647 thread default exception-port}, etc.). The @code{thread default}
17648 variety of commands sets the default thread properties for all
17649 threads; you can then change the properties of individual threads with
17650 the non-default commands.
17651 @end table
17652
17653
17654 @node Neutrino
17655 @subsection QNX Neutrino
17656 @cindex QNX Neutrino
17657
17658 @value{GDBN} provides the following commands specific to the QNX
17659 Neutrino target:
17660
17661 @table @code
17662 @item set debug nto-debug
17663 @kindex set debug nto-debug
17664 When set to on, enables debugging messages specific to the QNX
17665 Neutrino support.
17666
17667 @item show debug nto-debug
17668 @kindex show debug nto-debug
17669 Show the current state of QNX Neutrino messages.
17670 @end table
17671
17672 @node Darwin
17673 @subsection Darwin
17674 @cindex Darwin
17675
17676 @value{GDBN} provides the following commands specific to the Darwin target:
17677
17678 @table @code
17679 @item set debug darwin @var{num}
17680 @kindex set debug darwin
17681 When set to a non zero value, enables debugging messages specific to
17682 the Darwin support. Higher values produce more verbose output.
17683
17684 @item show debug darwin
17685 @kindex show debug darwin
17686 Show the current state of Darwin messages.
17687
17688 @item set debug mach-o @var{num}
17689 @kindex set debug mach-o
17690 When set to a non zero value, enables debugging messages while
17691 @value{GDBN} is reading Darwin object files. (@dfn{Mach-O} is the
17692 file format used on Darwin for object and executable files.) Higher
17693 values produce more verbose output. This is a command to diagnose
17694 problems internal to @value{GDBN} and should not be needed in normal
17695 usage.
17696
17697 @item show debug mach-o
17698 @kindex show debug mach-o
17699 Show the current state of Mach-O file messages.
17700
17701 @item set mach-exceptions on
17702 @itemx set mach-exceptions off
17703 @kindex set mach-exceptions
17704 On Darwin, faults are first reported as a Mach exception and are then
17705 mapped to a Posix signal. Use this command to turn on trapping of
17706 Mach exceptions in the inferior. This might be sometimes useful to
17707 better understand the cause of a fault. The default is off.
17708
17709 @item show mach-exceptions
17710 @kindex show mach-exceptions
17711 Show the current state of exceptions trapping.
17712 @end table
17713
17714
17715 @node Embedded OS
17716 @section Embedded Operating Systems
17717
17718 This section describes configurations involving the debugging of
17719 embedded operating systems that are available for several different
17720 architectures.
17721
17722 @menu
17723 * VxWorks:: Using @value{GDBN} with VxWorks
17724 @end menu
17725
17726 @value{GDBN} includes the ability to debug programs running on
17727 various real-time operating systems.
17728
17729 @node VxWorks
17730 @subsection Using @value{GDBN} with VxWorks
17731
17732 @cindex VxWorks
17733
17734 @table @code
17735
17736 @kindex target vxworks
17737 @item target vxworks @var{machinename}
17738 A VxWorks system, attached via TCP/IP. The argument @var{machinename}
17739 is the target system's machine name or IP address.
17740
17741 @end table
17742
17743 On VxWorks, @code{load} links @var{filename} dynamically on the
17744 current target system as well as adding its symbols in @value{GDBN}.
17745
17746 @value{GDBN} enables developers to spawn and debug tasks running on networked
17747 VxWorks targets from a Unix host. Already-running tasks spawned from
17748 the VxWorks shell can also be debugged. @value{GDBN} uses code that runs on
17749 both the Unix host and on the VxWorks target. The program
17750 @code{@value{GDBP}} is installed and executed on the Unix host. (It may be
17751 installed with the name @code{vxgdb}, to distinguish it from a
17752 @value{GDBN} for debugging programs on the host itself.)
17753
17754 @table @code
17755 @item VxWorks-timeout @var{args}
17756 @kindex vxworks-timeout
17757 All VxWorks-based targets now support the option @code{vxworks-timeout}.
17758 This option is set by the user, and @var{args} represents the number of
17759 seconds @value{GDBN} waits for responses to rpc's. You might use this if
17760 your VxWorks target is a slow software simulator or is on the far side
17761 of a thin network line.
17762 @end table
17763
17764 The following information on connecting to VxWorks was current when
17765 this manual was produced; newer releases of VxWorks may use revised
17766 procedures.
17767
17768 @findex INCLUDE_RDB
17769 To use @value{GDBN} with VxWorks, you must rebuild your VxWorks kernel
17770 to include the remote debugging interface routines in the VxWorks
17771 library @file{rdb.a}. To do this, define @code{INCLUDE_RDB} in the
17772 VxWorks configuration file @file{configAll.h} and rebuild your VxWorks
17773 kernel. The resulting kernel contains @file{rdb.a}, and spawns the
17774 source debugging task @code{tRdbTask} when VxWorks is booted. For more
17775 information on configuring and remaking VxWorks, see the manufacturer's
17776 manual.
17777 @c VxWorks, see the @cite{VxWorks Programmer's Guide}.
17778
17779 Once you have included @file{rdb.a} in your VxWorks system image and set
17780 your Unix execution search path to find @value{GDBN}, you are ready to
17781 run @value{GDBN}. From your Unix host, run @code{@value{GDBP}} (or
17782 @code{vxgdb}, depending on your installation).
17783
17784 @value{GDBN} comes up showing the prompt:
17785
17786 @smallexample
17787 (vxgdb)
17788 @end smallexample
17789
17790 @menu
17791 * VxWorks Connection:: Connecting to VxWorks
17792 * VxWorks Download:: VxWorks download
17793 * VxWorks Attach:: Running tasks
17794 @end menu
17795
17796 @node VxWorks Connection
17797 @subsubsection Connecting to VxWorks
17798
17799 The @value{GDBN} command @code{target} lets you connect to a VxWorks target on the
17800 network. To connect to a target whose host name is ``@code{tt}'', type:
17801
17802 @smallexample
17803 (vxgdb) target vxworks tt
17804 @end smallexample
17805
17806 @need 750
17807 @value{GDBN} displays messages like these:
17808
17809 @smallexample
17810 Attaching remote machine across net...
17811 Connected to tt.
17812 @end smallexample
17813
17814 @need 1000
17815 @value{GDBN} then attempts to read the symbol tables of any object modules
17816 loaded into the VxWorks target since it was last booted. @value{GDBN} locates
17817 these files by searching the directories listed in the command search
17818 path (@pxref{Environment, ,Your Program's Environment}); if it fails
17819 to find an object file, it displays a message such as:
17820
17821 @smallexample
17822 prog.o: No such file or directory.
17823 @end smallexample
17824
17825 When this happens, add the appropriate directory to the search path with
17826 the @value{GDBN} command @code{path}, and execute the @code{target}
17827 command again.
17828
17829 @node VxWorks Download
17830 @subsubsection VxWorks Download
17831
17832 @cindex download to VxWorks
17833 If you have connected to the VxWorks target and you want to debug an
17834 object that has not yet been loaded, you can use the @value{GDBN}
17835 @code{load} command to download a file from Unix to VxWorks
17836 incrementally. The object file given as an argument to the @code{load}
17837 command is actually opened twice: first by the VxWorks target in order
17838 to download the code, then by @value{GDBN} in order to read the symbol
17839 table. This can lead to problems if the current working directories on
17840 the two systems differ. If both systems have NFS mounted the same
17841 filesystems, you can avoid these problems by using absolute paths.
17842 Otherwise, it is simplest to set the working directory on both systems
17843 to the directory in which the object file resides, and then to reference
17844 the file by its name, without any path. For instance, a program
17845 @file{prog.o} may reside in @file{@var{vxpath}/vw/demo/rdb} in VxWorks
17846 and in @file{@var{hostpath}/vw/demo/rdb} on the host. To load this
17847 program, type this on VxWorks:
17848
17849 @smallexample
17850 -> cd "@var{vxpath}/vw/demo/rdb"
17851 @end smallexample
17852
17853 @noindent
17854 Then, in @value{GDBN}, type:
17855
17856 @smallexample
17857 (vxgdb) cd @var{hostpath}/vw/demo/rdb
17858 (vxgdb) load prog.o
17859 @end smallexample
17860
17861 @value{GDBN} displays a response similar to this:
17862
17863 @smallexample
17864 Reading symbol data from wherever/vw/demo/rdb/prog.o... done.
17865 @end smallexample
17866
17867 You can also use the @code{load} command to reload an object module
17868 after editing and recompiling the corresponding source file. Note that
17869 this makes @value{GDBN} delete all currently-defined breakpoints,
17870 auto-displays, and convenience variables, and to clear the value
17871 history. (This is necessary in order to preserve the integrity of
17872 debugger's data structures that reference the target system's symbol
17873 table.)
17874
17875 @node VxWorks Attach
17876 @subsubsection Running Tasks
17877
17878 @cindex running VxWorks tasks
17879 You can also attach to an existing task using the @code{attach} command as
17880 follows:
17881
17882 @smallexample
17883 (vxgdb) attach @var{task}
17884 @end smallexample
17885
17886 @noindent
17887 where @var{task} is the VxWorks hexadecimal task ID. The task can be running
17888 or suspended when you attach to it. Running tasks are suspended at
17889 the time of attachment.
17890
17891 @node Embedded Processors
17892 @section Embedded Processors
17893
17894 This section goes into details specific to particular embedded
17895 configurations.
17896
17897 @cindex send command to simulator
17898 Whenever a specific embedded processor has a simulator, @value{GDBN}
17899 allows to send an arbitrary command to the simulator.
17900
17901 @table @code
17902 @item sim @var{command}
17903 @kindex sim@r{, a command}
17904 Send an arbitrary @var{command} string to the simulator. Consult the
17905 documentation for the specific simulator in use for information about
17906 acceptable commands.
17907 @end table
17908
17909
17910 @menu
17911 * ARM:: ARM RDI
17912 * M32R/D:: Renesas M32R/D
17913 * M68K:: Motorola M68K
17914 * MicroBlaze:: Xilinx MicroBlaze
17915 * MIPS Embedded:: MIPS Embedded
17916 * OpenRISC 1000:: OpenRisc 1000
17917 * PA:: HP PA Embedded
17918 * PowerPC Embedded:: PowerPC Embedded
17919 * Sparclet:: Tsqware Sparclet
17920 * Sparclite:: Fujitsu Sparclite
17921 * Z8000:: Zilog Z8000
17922 * AVR:: Atmel AVR
17923 * CRIS:: CRIS
17924 * Super-H:: Renesas Super-H
17925 @end menu
17926
17927 @node ARM
17928 @subsection ARM
17929 @cindex ARM RDI
17930
17931 @table @code
17932 @kindex target rdi
17933 @item target rdi @var{dev}
17934 ARM Angel monitor, via RDI library interface to ADP protocol. You may
17935 use this target to communicate with both boards running the Angel
17936 monitor, or with the EmbeddedICE JTAG debug device.
17937
17938 @kindex target rdp
17939 @item target rdp @var{dev}
17940 ARM Demon monitor.
17941
17942 @end table
17943
17944 @value{GDBN} provides the following ARM-specific commands:
17945
17946 @table @code
17947 @item set arm disassembler
17948 @kindex set arm
17949 This commands selects from a list of disassembly styles. The
17950 @code{"std"} style is the standard style.
17951
17952 @item show arm disassembler
17953 @kindex show arm
17954 Show the current disassembly style.
17955
17956 @item set arm apcs32
17957 @cindex ARM 32-bit mode
17958 This command toggles ARM operation mode between 32-bit and 26-bit.
17959
17960 @item show arm apcs32
17961 Display the current usage of the ARM 32-bit mode.
17962
17963 @item set arm fpu @var{fputype}
17964 This command sets the ARM floating-point unit (FPU) type. The
17965 argument @var{fputype} can be one of these:
17966
17967 @table @code
17968 @item auto
17969 Determine the FPU type by querying the OS ABI.
17970 @item softfpa
17971 Software FPU, with mixed-endian doubles on little-endian ARM
17972 processors.
17973 @item fpa
17974 GCC-compiled FPA co-processor.
17975 @item softvfp
17976 Software FPU with pure-endian doubles.
17977 @item vfp
17978 VFP co-processor.
17979 @end table
17980
17981 @item show arm fpu
17982 Show the current type of the FPU.
17983
17984 @item set arm abi
17985 This command forces @value{GDBN} to use the specified ABI.
17986
17987 @item show arm abi
17988 Show the currently used ABI.
17989
17990 @item set arm fallback-mode (arm|thumb|auto)
17991 @value{GDBN} uses the symbol table, when available, to determine
17992 whether instructions are ARM or Thumb. This command controls
17993 @value{GDBN}'s default behavior when the symbol table is not
17994 available. The default is @samp{auto}, which causes @value{GDBN} to
17995 use the current execution mode (from the @code{T} bit in the @code{CPSR}
17996 register).
17997
17998 @item show arm fallback-mode
17999 Show the current fallback instruction mode.
18000
18001 @item set arm force-mode (arm|thumb|auto)
18002 This command overrides use of the symbol table to determine whether
18003 instructions are ARM or Thumb. The default is @samp{auto}, which
18004 causes @value{GDBN} to use the symbol table and then the setting
18005 of @samp{set arm fallback-mode}.
18006
18007 @item show arm force-mode
18008 Show the current forced instruction mode.
18009
18010 @item set debug arm
18011 Toggle whether to display ARM-specific debugging messages from the ARM
18012 target support subsystem.
18013
18014 @item show debug arm
18015 Show whether ARM-specific debugging messages are enabled.
18016 @end table
18017
18018 The following commands are available when an ARM target is debugged
18019 using the RDI interface:
18020
18021 @table @code
18022 @item rdilogfile @r{[}@var{file}@r{]}
18023 @kindex rdilogfile
18024 @cindex ADP (Angel Debugger Protocol) logging
18025 Set the filename for the ADP (Angel Debugger Protocol) packet log.
18026 With an argument, sets the log file to the specified @var{file}. With
18027 no argument, show the current log file name. The default log file is
18028 @file{rdi.log}.
18029
18030 @item rdilogenable @r{[}@var{arg}@r{]}
18031 @kindex rdilogenable
18032 Control logging of ADP packets. With an argument of 1 or @code{"yes"}
18033 enables logging, with an argument 0 or @code{"no"} disables it. With
18034 no arguments displays the current setting. When logging is enabled,
18035 ADP packets exchanged between @value{GDBN} and the RDI target device
18036 are logged to a file.
18037
18038 @item set rdiromatzero
18039 @kindex set rdiromatzero
18040 @cindex ROM at zero address, RDI
18041 Tell @value{GDBN} whether the target has ROM at address 0. If on,
18042 vector catching is disabled, so that zero address can be used. If off
18043 (the default), vector catching is enabled. For this command to take
18044 effect, it needs to be invoked prior to the @code{target rdi} command.
18045
18046 @item show rdiromatzero
18047 @kindex show rdiromatzero
18048 Show the current setting of ROM at zero address.
18049
18050 @item set rdiheartbeat
18051 @kindex set rdiheartbeat
18052 @cindex RDI heartbeat
18053 Enable or disable RDI heartbeat packets. It is not recommended to
18054 turn on this option, since it confuses ARM and EPI JTAG interface, as
18055 well as the Angel monitor.
18056
18057 @item show rdiheartbeat
18058 @kindex show rdiheartbeat
18059 Show the setting of RDI heartbeat packets.
18060 @end table
18061
18062 @table @code
18063 @item target sim @r{[}@var{simargs}@r{]} @dots{}
18064 The @value{GDBN} ARM simulator accepts the following optional arguments.
18065
18066 @table @code
18067 @item --swi-support=@var{type}
18068 Tell the simulator which SWI interfaces to support.
18069 @var{type} may be a comma separated list of the following values.
18070 The default value is @code{all}.
18071
18072 @table @code
18073 @item none
18074 @item demon
18075 @item angel
18076 @item redboot
18077 @item all
18078 @end table
18079 @end table
18080 @end table
18081
18082 @node M32R/D
18083 @subsection Renesas M32R/D and M32R/SDI
18084
18085 @table @code
18086 @kindex target m32r
18087 @item target m32r @var{dev}
18088 Renesas M32R/D ROM monitor.
18089
18090 @kindex target m32rsdi
18091 @item target m32rsdi @var{dev}
18092 Renesas M32R SDI server, connected via parallel port to the board.
18093 @end table
18094
18095 The following @value{GDBN} commands are specific to the M32R monitor:
18096
18097 @table @code
18098 @item set download-path @var{path}
18099 @kindex set download-path
18100 @cindex find downloadable @sc{srec} files (M32R)
18101 Set the default path for finding downloadable @sc{srec} files.
18102
18103 @item show download-path
18104 @kindex show download-path
18105 Show the default path for downloadable @sc{srec} files.
18106
18107 @item set board-address @var{addr}
18108 @kindex set board-address
18109 @cindex M32-EVA target board address
18110 Set the IP address for the M32R-EVA target board.
18111
18112 @item show board-address
18113 @kindex show board-address
18114 Show the current IP address of the target board.
18115
18116 @item set server-address @var{addr}
18117 @kindex set server-address
18118 @cindex download server address (M32R)
18119 Set the IP address for the download server, which is the @value{GDBN}'s
18120 host machine.
18121
18122 @item show server-address
18123 @kindex show server-address
18124 Display the IP address of the download server.
18125
18126 @item upload @r{[}@var{file}@r{]}
18127 @kindex upload@r{, M32R}
18128 Upload the specified @sc{srec} @var{file} via the monitor's Ethernet
18129 upload capability. If no @var{file} argument is given, the current
18130 executable file is uploaded.
18131
18132 @item tload @r{[}@var{file}@r{]}
18133 @kindex tload@r{, M32R}
18134 Test the @code{upload} command.
18135 @end table
18136
18137 The following commands are available for M32R/SDI:
18138
18139 @table @code
18140 @item sdireset
18141 @kindex sdireset
18142 @cindex reset SDI connection, M32R
18143 This command resets the SDI connection.
18144
18145 @item sdistatus
18146 @kindex sdistatus
18147 This command shows the SDI connection status.
18148
18149 @item debug_chaos
18150 @kindex debug_chaos
18151 @cindex M32R/Chaos debugging
18152 Instructs the remote that M32R/Chaos debugging is to be used.
18153
18154 @item use_debug_dma
18155 @kindex use_debug_dma
18156 Instructs the remote to use the DEBUG_DMA method of accessing memory.
18157
18158 @item use_mon_code
18159 @kindex use_mon_code
18160 Instructs the remote to use the MON_CODE method of accessing memory.
18161
18162 @item use_ib_break
18163 @kindex use_ib_break
18164 Instructs the remote to set breakpoints by IB break.
18165
18166 @item use_dbt_break
18167 @kindex use_dbt_break
18168 Instructs the remote to set breakpoints by DBT.
18169 @end table
18170
18171 @node M68K
18172 @subsection M68k
18173
18174 The Motorola m68k configuration includes ColdFire support, and a
18175 target command for the following ROM monitor.
18176
18177 @table @code
18178
18179 @kindex target dbug
18180 @item target dbug @var{dev}
18181 dBUG ROM monitor for Motorola ColdFire.
18182
18183 @end table
18184
18185 @node MicroBlaze
18186 @subsection MicroBlaze
18187 @cindex Xilinx MicroBlaze
18188 @cindex XMD, Xilinx Microprocessor Debugger
18189
18190 The MicroBlaze is a soft-core processor supported on various Xilinx
18191 FPGAs, such as Spartan or Virtex series. Boards with these processors
18192 usually have JTAG ports which connect to a host system running the Xilinx
18193 Embedded Development Kit (EDK) or Software Development Kit (SDK).
18194 This host system is used to download the configuration bitstream to
18195 the target FPGA. The Xilinx Microprocessor Debugger (XMD) program
18196 communicates with the target board using the JTAG interface and
18197 presents a @code{gdbserver} interface to the board. By default
18198 @code{xmd} uses port @code{1234}. (While it is possible to change
18199 this default port, it requires the use of undocumented @code{xmd}
18200 commands. Contact Xilinx support if you need to do this.)
18201
18202 Use these GDB commands to connect to the MicroBlaze target processor.
18203
18204 @table @code
18205 @item target remote :1234
18206 Use this command to connect to the target if you are running @value{GDBN}
18207 on the same system as @code{xmd}.
18208
18209 @item target remote @var{xmd-host}:1234
18210 Use this command to connect to the target if it is connected to @code{xmd}
18211 running on a different system named @var{xmd-host}.
18212
18213 @item load
18214 Use this command to download a program to the MicroBlaze target.
18215
18216 @item set debug microblaze @var{n}
18217 Enable MicroBlaze-specific debugging messages if non-zero.
18218
18219 @item show debug microblaze @var{n}
18220 Show MicroBlaze-specific debugging level.
18221 @end table
18222
18223 @node MIPS Embedded
18224 @subsection MIPS Embedded
18225
18226 @cindex MIPS boards
18227 @value{GDBN} can use the MIPS remote debugging protocol to talk to a
18228 MIPS board attached to a serial line. This is available when
18229 you configure @value{GDBN} with @samp{--target=mips-idt-ecoff}.
18230
18231 @need 1000
18232 Use these @value{GDBN} commands to specify the connection to your target board:
18233
18234 @table @code
18235 @item target mips @var{port}
18236 @kindex target mips @var{port}
18237 To run a program on the board, start up @code{@value{GDBP}} with the
18238 name of your program as the argument. To connect to the board, use the
18239 command @samp{target mips @var{port}}, where @var{port} is the name of
18240 the serial port connected to the board. If the program has not already
18241 been downloaded to the board, you may use the @code{load} command to
18242 download it. You can then use all the usual @value{GDBN} commands.
18243
18244 For example, this sequence connects to the target board through a serial
18245 port, and loads and runs a program called @var{prog} through the
18246 debugger:
18247
18248 @smallexample
18249 host$ @value{GDBP} @var{prog}
18250 @value{GDBN} is free software and @dots{}
18251 (@value{GDBP}) target mips /dev/ttyb
18252 (@value{GDBP}) load @var{prog}
18253 (@value{GDBP}) run
18254 @end smallexample
18255
18256 @item target mips @var{hostname}:@var{portnumber}
18257 On some @value{GDBN} host configurations, you can specify a TCP
18258 connection (for instance, to a serial line managed by a terminal
18259 concentrator) instead of a serial port, using the syntax
18260 @samp{@var{hostname}:@var{portnumber}}.
18261
18262 @item target pmon @var{port}
18263 @kindex target pmon @var{port}
18264 PMON ROM monitor.
18265
18266 @item target ddb @var{port}
18267 @kindex target ddb @var{port}
18268 NEC's DDB variant of PMON for Vr4300.
18269
18270 @item target lsi @var{port}
18271 @kindex target lsi @var{port}
18272 LSI variant of PMON.
18273
18274 @kindex target r3900
18275 @item target r3900 @var{dev}
18276 Densan DVE-R3900 ROM monitor for Toshiba R3900 Mips.
18277
18278 @kindex target array
18279 @item target array @var{dev}
18280 Array Tech LSI33K RAID controller board.
18281
18282 @end table
18283
18284
18285 @noindent
18286 @value{GDBN} also supports these special commands for MIPS targets:
18287
18288 @table @code
18289 @item set mipsfpu double
18290 @itemx set mipsfpu single
18291 @itemx set mipsfpu none
18292 @itemx set mipsfpu auto
18293 @itemx show mipsfpu
18294 @kindex set mipsfpu
18295 @kindex show mipsfpu
18296 @cindex MIPS remote floating point
18297 @cindex floating point, MIPS remote
18298 If your target board does not support the MIPS floating point
18299 coprocessor, you should use the command @samp{set mipsfpu none} (if you
18300 need this, you may wish to put the command in your @value{GDBN} init
18301 file). This tells @value{GDBN} how to find the return value of
18302 functions which return floating point values. It also allows
18303 @value{GDBN} to avoid saving the floating point registers when calling
18304 functions on the board. If you are using a floating point coprocessor
18305 with only single precision floating point support, as on the @sc{r4650}
18306 processor, use the command @samp{set mipsfpu single}. The default
18307 double precision floating point coprocessor may be selected using
18308 @samp{set mipsfpu double}.
18309
18310 In previous versions the only choices were double precision or no
18311 floating point, so @samp{set mipsfpu on} will select double precision
18312 and @samp{set mipsfpu off} will select no floating point.
18313
18314 As usual, you can inquire about the @code{mipsfpu} variable with
18315 @samp{show mipsfpu}.
18316
18317 @item set timeout @var{seconds}
18318 @itemx set retransmit-timeout @var{seconds}
18319 @itemx show timeout
18320 @itemx show retransmit-timeout
18321 @cindex @code{timeout}, MIPS protocol
18322 @cindex @code{retransmit-timeout}, MIPS protocol
18323 @kindex set timeout
18324 @kindex show timeout
18325 @kindex set retransmit-timeout
18326 @kindex show retransmit-timeout
18327 You can control the timeout used while waiting for a packet, in the MIPS
18328 remote protocol, with the @code{set timeout @var{seconds}} command. The
18329 default is 5 seconds. Similarly, you can control the timeout used while
18330 waiting for an acknowledgment of a packet with the @code{set
18331 retransmit-timeout @var{seconds}} command. The default is 3 seconds.
18332 You can inspect both values with @code{show timeout} and @code{show
18333 retransmit-timeout}. (These commands are @emph{only} available when
18334 @value{GDBN} is configured for @samp{--target=mips-idt-ecoff}.)
18335
18336 The timeout set by @code{set timeout} does not apply when @value{GDBN}
18337 is waiting for your program to stop. In that case, @value{GDBN} waits
18338 forever because it has no way of knowing how long the program is going
18339 to run before stopping.
18340
18341 @item set syn-garbage-limit @var{num}
18342 @kindex set syn-garbage-limit@r{, MIPS remote}
18343 @cindex synchronize with remote MIPS target
18344 Limit the maximum number of characters @value{GDBN} should ignore when
18345 it tries to synchronize with the remote target. The default is 10
18346 characters. Setting the limit to -1 means there's no limit.
18347
18348 @item show syn-garbage-limit
18349 @kindex show syn-garbage-limit@r{, MIPS remote}
18350 Show the current limit on the number of characters to ignore when
18351 trying to synchronize with the remote system.
18352
18353 @item set monitor-prompt @var{prompt}
18354 @kindex set monitor-prompt@r{, MIPS remote}
18355 @cindex remote monitor prompt
18356 Tell @value{GDBN} to expect the specified @var{prompt} string from the
18357 remote monitor. The default depends on the target:
18358 @table @asis
18359 @item pmon target
18360 @samp{PMON}
18361 @item ddb target
18362 @samp{NEC010}
18363 @item lsi target
18364 @samp{PMON>}
18365 @end table
18366
18367 @item show monitor-prompt
18368 @kindex show monitor-prompt@r{, MIPS remote}
18369 Show the current strings @value{GDBN} expects as the prompt from the
18370 remote monitor.
18371
18372 @item set monitor-warnings
18373 @kindex set monitor-warnings@r{, MIPS remote}
18374 Enable or disable monitor warnings about hardware breakpoints. This
18375 has effect only for the @code{lsi} target. When on, @value{GDBN} will
18376 display warning messages whose codes are returned by the @code{lsi}
18377 PMON monitor for breakpoint commands.
18378
18379 @item show monitor-warnings
18380 @kindex show monitor-warnings@r{, MIPS remote}
18381 Show the current setting of printing monitor warnings.
18382
18383 @item pmon @var{command}
18384 @kindex pmon@r{, MIPS remote}
18385 @cindex send PMON command
18386 This command allows sending an arbitrary @var{command} string to the
18387 monitor. The monitor must be in debug mode for this to work.
18388 @end table
18389
18390 @node OpenRISC 1000
18391 @subsection OpenRISC 1000
18392 @cindex OpenRISC 1000
18393
18394 @cindex or1k boards
18395 See OR1k Architecture document (@uref{www.opencores.org}) for more information
18396 about platform and commands.
18397
18398 @table @code
18399
18400 @kindex target jtag
18401 @item target jtag jtag://@var{host}:@var{port}
18402
18403 Connects to remote JTAG server.
18404 JTAG remote server can be either an or1ksim or JTAG server,
18405 connected via parallel port to the board.
18406
18407 Example: @code{target jtag jtag://localhost:9999}
18408
18409 @kindex or1ksim
18410 @item or1ksim @var{command}
18411 If connected to @code{or1ksim} OpenRISC 1000 Architectural
18412 Simulator, proprietary commands can be executed.
18413
18414 @kindex info or1k spr
18415 @item info or1k spr
18416 Displays spr groups.
18417
18418 @item info or1k spr @var{group}
18419 @itemx info or1k spr @var{groupno}
18420 Displays register names in selected group.
18421
18422 @item info or1k spr @var{group} @var{register}
18423 @itemx info or1k spr @var{register}
18424 @itemx info or1k spr @var{groupno} @var{registerno}
18425 @itemx info or1k spr @var{registerno}
18426 Shows information about specified spr register.
18427
18428 @kindex spr
18429 @item spr @var{group} @var{register} @var{value}
18430 @itemx spr @var{register @var{value}}
18431 @itemx spr @var{groupno} @var{registerno @var{value}}
18432 @itemx spr @var{registerno @var{value}}
18433 Writes @var{value} to specified spr register.
18434 @end table
18435
18436 Some implementations of OpenRISC 1000 Architecture also have hardware trace.
18437 It is very similar to @value{GDBN} trace, except it does not interfere with normal
18438 program execution and is thus much faster. Hardware breakpoints/watchpoint
18439 triggers can be set using:
18440 @table @code
18441 @item $LEA/$LDATA
18442 Load effective address/data
18443 @item $SEA/$SDATA
18444 Store effective address/data
18445 @item $AEA/$ADATA
18446 Access effective address ($SEA or $LEA) or data ($SDATA/$LDATA)
18447 @item $FETCH
18448 Fetch data
18449 @end table
18450
18451 When triggered, it can capture low level data, like: @code{PC}, @code{LSEA},
18452 @code{LDATA}, @code{SDATA}, @code{READSPR}, @code{WRITESPR}, @code{INSTR}.
18453
18454 @code{htrace} commands:
18455 @cindex OpenRISC 1000 htrace
18456 @table @code
18457 @kindex hwatch
18458 @item hwatch @var{conditional}
18459 Set hardware watchpoint on combination of Load/Store Effective Address(es)
18460 or Data. For example:
18461
18462 @code{hwatch ($LEA == my_var) && ($LDATA < 50) || ($SEA == my_var) && ($SDATA >= 50)}
18463
18464 @code{hwatch ($LEA == my_var) && ($LDATA < 50) || ($SEA == my_var) && ($SDATA >= 50)}
18465
18466 @kindex htrace
18467 @item htrace info
18468 Display information about current HW trace configuration.
18469
18470 @item htrace trigger @var{conditional}
18471 Set starting criteria for HW trace.
18472
18473 @item htrace qualifier @var{conditional}
18474 Set acquisition qualifier for HW trace.
18475
18476 @item htrace stop @var{conditional}
18477 Set HW trace stopping criteria.
18478
18479 @item htrace record [@var{data}]*
18480 Selects the data to be recorded, when qualifier is met and HW trace was
18481 triggered.
18482
18483 @item htrace enable
18484 @itemx htrace disable
18485 Enables/disables the HW trace.
18486
18487 @item htrace rewind [@var{filename}]
18488 Clears currently recorded trace data.
18489
18490 If filename is specified, new trace file is made and any newly collected data
18491 will be written there.
18492
18493 @item htrace print [@var{start} [@var{len}]]
18494 Prints trace buffer, using current record configuration.
18495
18496 @item htrace mode continuous
18497 Set continuous trace mode.
18498
18499 @item htrace mode suspend
18500 Set suspend trace mode.
18501
18502 @end table
18503
18504 @node PowerPC Embedded
18505 @subsection PowerPC Embedded
18506
18507 @cindex DVC register
18508 @value{GDBN} supports using the DVC (Data Value Compare) register to
18509 implement in hardware simple hardware watchpoint conditions of the form:
18510
18511 @smallexample
18512 (@value{GDBP}) watch @var{ADDRESS|VARIABLE} \
18513 if @var{ADDRESS|VARIABLE} == @var{CONSTANT EXPRESSION}
18514 @end smallexample
18515
18516 The DVC register will be automatically used whenever @value{GDBN} detects
18517 such pattern in a condition expression. This feature is available in native
18518 @value{GDBN} running on a Linux kernel version 2.6.34 or newer.
18519
18520 @value{GDBN} provides the following PowerPC-specific commands:
18521
18522 @table @code
18523 @kindex set powerpc
18524 @item set powerpc soft-float
18525 @itemx show powerpc soft-float
18526 Force @value{GDBN} to use (or not use) a software floating point calling
18527 convention. By default, @value{GDBN} selects the calling convention based
18528 on the selected architecture and the provided executable file.
18529
18530 @item set powerpc vector-abi
18531 @itemx show powerpc vector-abi
18532 Force @value{GDBN} to use the specified calling convention for vector
18533 arguments and return values. The valid options are @samp{auto};
18534 @samp{generic}, to avoid vector registers even if they are present;
18535 @samp{altivec}, to use AltiVec registers; and @samp{spe} to use SPE
18536 registers. By default, @value{GDBN} selects the calling convention
18537 based on the selected architecture and the provided executable file.
18538
18539 @kindex target dink32
18540 @item target dink32 @var{dev}
18541 DINK32 ROM monitor.
18542
18543 @kindex target ppcbug
18544 @item target ppcbug @var{dev}
18545 @kindex target ppcbug1
18546 @item target ppcbug1 @var{dev}
18547 PPCBUG ROM monitor for PowerPC.
18548
18549 @kindex target sds
18550 @item target sds @var{dev}
18551 SDS monitor, running on a PowerPC board (such as Motorola's ADS).
18552 @end table
18553
18554 @cindex SDS protocol
18555 The following commands specific to the SDS protocol are supported
18556 by @value{GDBN}:
18557
18558 @table @code
18559 @item set sdstimeout @var{nsec}
18560 @kindex set sdstimeout
18561 Set the timeout for SDS protocol reads to be @var{nsec} seconds. The
18562 default is 2 seconds.
18563
18564 @item show sdstimeout
18565 @kindex show sdstimeout
18566 Show the current value of the SDS timeout.
18567
18568 @item sds @var{command}
18569 @kindex sds@r{, a command}
18570 Send the specified @var{command} string to the SDS monitor.
18571 @end table
18572
18573
18574 @node PA
18575 @subsection HP PA Embedded
18576
18577 @table @code
18578
18579 @kindex target op50n
18580 @item target op50n @var{dev}
18581 OP50N monitor, running on an OKI HPPA board.
18582
18583 @kindex target w89k
18584 @item target w89k @var{dev}
18585 W89K monitor, running on a Winbond HPPA board.
18586
18587 @end table
18588
18589 @node Sparclet
18590 @subsection Tsqware Sparclet
18591
18592 @cindex Sparclet
18593
18594 @value{GDBN} enables developers to debug tasks running on
18595 Sparclet targets from a Unix host.
18596 @value{GDBN} uses code that runs on
18597 both the Unix host and on the Sparclet target. The program
18598 @code{@value{GDBP}} is installed and executed on the Unix host.
18599
18600 @table @code
18601 @item remotetimeout @var{args}
18602 @kindex remotetimeout
18603 @value{GDBN} supports the option @code{remotetimeout}.
18604 This option is set by the user, and @var{args} represents the number of
18605 seconds @value{GDBN} waits for responses.
18606 @end table
18607
18608 @cindex compiling, on Sparclet
18609 When compiling for debugging, include the options @samp{-g} to get debug
18610 information and @samp{-Ttext} to relocate the program to where you wish to
18611 load it on the target. You may also want to add the options @samp{-n} or
18612 @samp{-N} in order to reduce the size of the sections. Example:
18613
18614 @smallexample
18615 sparclet-aout-gcc prog.c -Ttext 0x12010000 -g -o prog -N
18616 @end smallexample
18617
18618 You can use @code{objdump} to verify that the addresses are what you intended:
18619
18620 @smallexample
18621 sparclet-aout-objdump --headers --syms prog
18622 @end smallexample
18623
18624 @cindex running, on Sparclet
18625 Once you have set
18626 your Unix execution search path to find @value{GDBN}, you are ready to
18627 run @value{GDBN}. From your Unix host, run @code{@value{GDBP}}
18628 (or @code{sparclet-aout-gdb}, depending on your installation).
18629
18630 @value{GDBN} comes up showing the prompt:
18631
18632 @smallexample
18633 (gdbslet)
18634 @end smallexample
18635
18636 @menu
18637 * Sparclet File:: Setting the file to debug
18638 * Sparclet Connection:: Connecting to Sparclet
18639 * Sparclet Download:: Sparclet download
18640 * Sparclet Execution:: Running and debugging
18641 @end menu
18642
18643 @node Sparclet File
18644 @subsubsection Setting File to Debug
18645
18646 The @value{GDBN} command @code{file} lets you choose with program to debug.
18647
18648 @smallexample
18649 (gdbslet) file prog
18650 @end smallexample
18651
18652 @need 1000
18653 @value{GDBN} then attempts to read the symbol table of @file{prog}.
18654 @value{GDBN} locates
18655 the file by searching the directories listed in the command search
18656 path.
18657 If the file was compiled with debug information (option @samp{-g}), source
18658 files will be searched as well.
18659 @value{GDBN} locates
18660 the source files by searching the directories listed in the directory search
18661 path (@pxref{Environment, ,Your Program's Environment}).
18662 If it fails
18663 to find a file, it displays a message such as:
18664
18665 @smallexample
18666 prog: No such file or directory.
18667 @end smallexample
18668
18669 When this happens, add the appropriate directories to the search paths with
18670 the @value{GDBN} commands @code{path} and @code{dir}, and execute the
18671 @code{target} command again.
18672
18673 @node Sparclet Connection
18674 @subsubsection Connecting to Sparclet
18675
18676 The @value{GDBN} command @code{target} lets you connect to a Sparclet target.
18677 To connect to a target on serial port ``@code{ttya}'', type:
18678
18679 @smallexample
18680 (gdbslet) target sparclet /dev/ttya
18681 Remote target sparclet connected to /dev/ttya
18682 main () at ../prog.c:3
18683 @end smallexample
18684
18685 @need 750
18686 @value{GDBN} displays messages like these:
18687
18688 @smallexample
18689 Connected to ttya.
18690 @end smallexample
18691
18692 @node Sparclet Download
18693 @subsubsection Sparclet Download
18694
18695 @cindex download to Sparclet
18696 Once connected to the Sparclet target,
18697 you can use the @value{GDBN}
18698 @code{load} command to download the file from the host to the target.
18699 The file name and load offset should be given as arguments to the @code{load}
18700 command.
18701 Since the file format is aout, the program must be loaded to the starting
18702 address. You can use @code{objdump} to find out what this value is. The load
18703 offset is an offset which is added to the VMA (virtual memory address)
18704 of each of the file's sections.
18705 For instance, if the program
18706 @file{prog} was linked to text address 0x1201000, with data at 0x12010160
18707 and bss at 0x12010170, in @value{GDBN}, type:
18708
18709 @smallexample
18710 (gdbslet) load prog 0x12010000
18711 Loading section .text, size 0xdb0 vma 0x12010000
18712 @end smallexample
18713
18714 If the code is loaded at a different address then what the program was linked
18715 to, you may need to use the @code{section} and @code{add-symbol-file} commands
18716 to tell @value{GDBN} where to map the symbol table.
18717
18718 @node Sparclet Execution
18719 @subsubsection Running and Debugging
18720
18721 @cindex running and debugging Sparclet programs
18722 You can now begin debugging the task using @value{GDBN}'s execution control
18723 commands, @code{b}, @code{step}, @code{run}, etc. See the @value{GDBN}
18724 manual for the list of commands.
18725
18726 @smallexample
18727 (gdbslet) b main
18728 Breakpoint 1 at 0x12010000: file prog.c, line 3.
18729 (gdbslet) run
18730 Starting program: prog
18731 Breakpoint 1, main (argc=1, argv=0xeffff21c) at prog.c:3
18732 3 char *symarg = 0;
18733 (gdbslet) step
18734 4 char *execarg = "hello!";
18735 (gdbslet)
18736 @end smallexample
18737
18738 @node Sparclite
18739 @subsection Fujitsu Sparclite
18740
18741 @table @code
18742
18743 @kindex target sparclite
18744 @item target sparclite @var{dev}
18745 Fujitsu sparclite boards, used only for the purpose of loading.
18746 You must use an additional command to debug the program.
18747 For example: target remote @var{dev} using @value{GDBN} standard
18748 remote protocol.
18749
18750 @end table
18751
18752 @node Z8000
18753 @subsection Zilog Z8000
18754
18755 @cindex Z8000
18756 @cindex simulator, Z8000
18757 @cindex Zilog Z8000 simulator
18758
18759 When configured for debugging Zilog Z8000 targets, @value{GDBN} includes
18760 a Z8000 simulator.
18761
18762 For the Z8000 family, @samp{target sim} simulates either the Z8002 (the
18763 unsegmented variant of the Z8000 architecture) or the Z8001 (the
18764 segmented variant). The simulator recognizes which architecture is
18765 appropriate by inspecting the object code.
18766
18767 @table @code
18768 @item target sim @var{args}
18769 @kindex sim
18770 @kindex target sim@r{, with Z8000}
18771 Debug programs on a simulated CPU. If the simulator supports setup
18772 options, specify them via @var{args}.
18773 @end table
18774
18775 @noindent
18776 After specifying this target, you can debug programs for the simulated
18777 CPU in the same style as programs for your host computer; use the
18778 @code{file} command to load a new program image, the @code{run} command
18779 to run your program, and so on.
18780
18781 As well as making available all the usual machine registers
18782 (@pxref{Registers, ,Registers}), the Z8000 simulator provides three
18783 additional items of information as specially named registers:
18784
18785 @table @code
18786
18787 @item cycles
18788 Counts clock-ticks in the simulator.
18789
18790 @item insts
18791 Counts instructions run in the simulator.
18792
18793 @item time
18794 Execution time in 60ths of a second.
18795
18796 @end table
18797
18798 You can refer to these values in @value{GDBN} expressions with the usual
18799 conventions; for example, @w{@samp{b fputc if $cycles>5000}} sets a
18800 conditional breakpoint that suspends only after at least 5000
18801 simulated clock ticks.
18802
18803 @node AVR
18804 @subsection Atmel AVR
18805 @cindex AVR
18806
18807 When configured for debugging the Atmel AVR, @value{GDBN} supports the
18808 following AVR-specific commands:
18809
18810 @table @code
18811 @item info io_registers
18812 @kindex info io_registers@r{, AVR}
18813 @cindex I/O registers (Atmel AVR)
18814 This command displays information about the AVR I/O registers. For
18815 each register, @value{GDBN} prints its number and value.
18816 @end table
18817
18818 @node CRIS
18819 @subsection CRIS
18820 @cindex CRIS
18821
18822 When configured for debugging CRIS, @value{GDBN} provides the
18823 following CRIS-specific commands:
18824
18825 @table @code
18826 @item set cris-version @var{ver}
18827 @cindex CRIS version
18828 Set the current CRIS version to @var{ver}, either @samp{10} or @samp{32}.
18829 The CRIS version affects register names and sizes. This command is useful in
18830 case autodetection of the CRIS version fails.
18831
18832 @item show cris-version
18833 Show the current CRIS version.
18834
18835 @item set cris-dwarf2-cfi
18836 @cindex DWARF-2 CFI and CRIS
18837 Set the usage of DWARF-2 CFI for CRIS debugging. The default is @samp{on}.
18838 Change to @samp{off} when using @code{gcc-cris} whose version is below
18839 @code{R59}.
18840
18841 @item show cris-dwarf2-cfi
18842 Show the current state of using DWARF-2 CFI.
18843
18844 @item set cris-mode @var{mode}
18845 @cindex CRIS mode
18846 Set the current CRIS mode to @var{mode}. It should only be changed when
18847 debugging in guru mode, in which case it should be set to
18848 @samp{guru} (the default is @samp{normal}).
18849
18850 @item show cris-mode
18851 Show the current CRIS mode.
18852 @end table
18853
18854 @node Super-H
18855 @subsection Renesas Super-H
18856 @cindex Super-H
18857
18858 For the Renesas Super-H processor, @value{GDBN} provides these
18859 commands:
18860
18861 @table @code
18862 @item regs
18863 @kindex regs@r{, Super-H}
18864 Show the values of all Super-H registers.
18865
18866 @item set sh calling-convention @var{convention}
18867 @kindex set sh calling-convention
18868 Set the calling-convention used when calling functions from @value{GDBN}.
18869 Allowed values are @samp{gcc}, which is the default setting, and @samp{renesas}.
18870 With the @samp{gcc} setting, functions are called using the @value{NGCC} calling
18871 convention. If the DWARF-2 information of the called function specifies
18872 that the function follows the Renesas calling convention, the function
18873 is called using the Renesas calling convention. If the calling convention
18874 is set to @samp{renesas}, the Renesas calling convention is always used,
18875 regardless of the DWARF-2 information. This can be used to override the
18876 default of @samp{gcc} if debug information is missing, or the compiler
18877 does not emit the DWARF-2 calling convention entry for a function.
18878
18879 @item show sh calling-convention
18880 @kindex show sh calling-convention
18881 Show the current calling convention setting.
18882
18883 @end table
18884
18885
18886 @node Architectures
18887 @section Architectures
18888
18889 This section describes characteristics of architectures that affect
18890 all uses of @value{GDBN} with the architecture, both native and cross.
18891
18892 @menu
18893 * i386::
18894 * A29K::
18895 * Alpha::
18896 * MIPS::
18897 * HPPA:: HP PA architecture
18898 * SPU:: Cell Broadband Engine SPU architecture
18899 * PowerPC::
18900 @end menu
18901
18902 @node i386
18903 @subsection x86 Architecture-specific Issues
18904
18905 @table @code
18906 @item set struct-convention @var{mode}
18907 @kindex set struct-convention
18908 @cindex struct return convention
18909 @cindex struct/union returned in registers
18910 Set the convention used by the inferior to return @code{struct}s and
18911 @code{union}s from functions to @var{mode}. Possible values of
18912 @var{mode} are @code{"pcc"}, @code{"reg"}, and @code{"default"} (the
18913 default). @code{"default"} or @code{"pcc"} means that @code{struct}s
18914 are returned on the stack, while @code{"reg"} means that a
18915 @code{struct} or a @code{union} whose size is 1, 2, 4, or 8 bytes will
18916 be returned in a register.
18917
18918 @item show struct-convention
18919 @kindex show struct-convention
18920 Show the current setting of the convention to return @code{struct}s
18921 from functions.
18922 @end table
18923
18924 @node A29K
18925 @subsection A29K
18926
18927 @table @code
18928
18929 @kindex set rstack_high_address
18930 @cindex AMD 29K register stack
18931 @cindex register stack, AMD29K
18932 @item set rstack_high_address @var{address}
18933 On AMD 29000 family processors, registers are saved in a separate
18934 @dfn{register stack}. There is no way for @value{GDBN} to determine the
18935 extent of this stack. Normally, @value{GDBN} just assumes that the
18936 stack is ``large enough''. This may result in @value{GDBN} referencing
18937 memory locations that do not exist. If necessary, you can get around
18938 this problem by specifying the ending address of the register stack with
18939 the @code{set rstack_high_address} command. The argument should be an
18940 address, which you probably want to precede with @samp{0x} to specify in
18941 hexadecimal.
18942
18943 @kindex show rstack_high_address
18944 @item show rstack_high_address
18945 Display the current limit of the register stack, on AMD 29000 family
18946 processors.
18947
18948 @end table
18949
18950 @node Alpha
18951 @subsection Alpha
18952
18953 See the following section.
18954
18955 @node MIPS
18956 @subsection MIPS
18957
18958 @cindex stack on Alpha
18959 @cindex stack on MIPS
18960 @cindex Alpha stack
18961 @cindex MIPS stack
18962 Alpha- and MIPS-based computers use an unusual stack frame, which
18963 sometimes requires @value{GDBN} to search backward in the object code to
18964 find the beginning of a function.
18965
18966 @cindex response time, MIPS debugging
18967 To improve response time (especially for embedded applications, where
18968 @value{GDBN} may be restricted to a slow serial line for this search)
18969 you may want to limit the size of this search, using one of these
18970 commands:
18971
18972 @table @code
18973 @cindex @code{heuristic-fence-post} (Alpha, MIPS)
18974 @item set heuristic-fence-post @var{limit}
18975 Restrict @value{GDBN} to examining at most @var{limit} bytes in its
18976 search for the beginning of a function. A value of @var{0} (the
18977 default) means there is no limit. However, except for @var{0}, the
18978 larger the limit the more bytes @code{heuristic-fence-post} must search
18979 and therefore the longer it takes to run. You should only need to use
18980 this command when debugging a stripped executable.
18981
18982 @item show heuristic-fence-post
18983 Display the current limit.
18984 @end table
18985
18986 @noindent
18987 These commands are available @emph{only} when @value{GDBN} is configured
18988 for debugging programs on Alpha or MIPS processors.
18989
18990 Several MIPS-specific commands are available when debugging MIPS
18991 programs:
18992
18993 @table @code
18994 @item set mips abi @var{arg}
18995 @kindex set mips abi
18996 @cindex set ABI for MIPS
18997 Tell @value{GDBN} which MIPS ABI is used by the inferior. Possible
18998 values of @var{arg} are:
18999
19000 @table @samp
19001 @item auto
19002 The default ABI associated with the current binary (this is the
19003 default).
19004 @item o32
19005 @item o64
19006 @item n32
19007 @item n64
19008 @item eabi32
19009 @item eabi64
19010 @item auto
19011 @end table
19012
19013 @item show mips abi
19014 @kindex show mips abi
19015 Show the MIPS ABI used by @value{GDBN} to debug the inferior.
19016
19017 @item set mipsfpu
19018 @itemx show mipsfpu
19019 @xref{MIPS Embedded, set mipsfpu}.
19020
19021 @item set mips mask-address @var{arg}
19022 @kindex set mips mask-address
19023 @cindex MIPS addresses, masking
19024 This command determines whether the most-significant 32 bits of 64-bit
19025 MIPS addresses are masked off. The argument @var{arg} can be
19026 @samp{on}, @samp{off}, or @samp{auto}. The latter is the default
19027 setting, which lets @value{GDBN} determine the correct value.
19028
19029 @item show mips mask-address
19030 @kindex show mips mask-address
19031 Show whether the upper 32 bits of MIPS addresses are masked off or
19032 not.
19033
19034 @item set remote-mips64-transfers-32bit-regs
19035 @kindex set remote-mips64-transfers-32bit-regs
19036 This command controls compatibility with 64-bit MIPS targets that
19037 transfer data in 32-bit quantities. If you have an old MIPS 64 target
19038 that transfers 32 bits for some registers, like @sc{sr} and @sc{fsr},
19039 and 64 bits for other registers, set this option to @samp{on}.
19040
19041 @item show remote-mips64-transfers-32bit-regs
19042 @kindex show remote-mips64-transfers-32bit-regs
19043 Show the current setting of compatibility with older MIPS 64 targets.
19044
19045 @item set debug mips
19046 @kindex set debug mips
19047 This command turns on and off debugging messages for the MIPS-specific
19048 target code in @value{GDBN}.
19049
19050 @item show debug mips
19051 @kindex show debug mips
19052 Show the current setting of MIPS debugging messages.
19053 @end table
19054
19055
19056 @node HPPA
19057 @subsection HPPA
19058 @cindex HPPA support
19059
19060 When @value{GDBN} is debugging the HP PA architecture, it provides the
19061 following special commands:
19062
19063 @table @code
19064 @item set debug hppa
19065 @kindex set debug hppa
19066 This command determines whether HPPA architecture-specific debugging
19067 messages are to be displayed.
19068
19069 @item show debug hppa
19070 Show whether HPPA debugging messages are displayed.
19071
19072 @item maint print unwind @var{address}
19073 @kindex maint print unwind@r{, HPPA}
19074 This command displays the contents of the unwind table entry at the
19075 given @var{address}.
19076
19077 @end table
19078
19079
19080 @node SPU
19081 @subsection Cell Broadband Engine SPU architecture
19082 @cindex Cell Broadband Engine
19083 @cindex SPU
19084
19085 When @value{GDBN} is debugging the Cell Broadband Engine SPU architecture,
19086 it provides the following special commands:
19087
19088 @table @code
19089 @item info spu event
19090 @kindex info spu
19091 Display SPU event facility status. Shows current event mask
19092 and pending event status.
19093
19094 @item info spu signal
19095 Display SPU signal notification facility status. Shows pending
19096 signal-control word and signal notification mode of both signal
19097 notification channels.
19098
19099 @item info spu mailbox
19100 Display SPU mailbox facility status. Shows all pending entries,
19101 in order of processing, in each of the SPU Write Outbound,
19102 SPU Write Outbound Interrupt, and SPU Read Inbound mailboxes.
19103
19104 @item info spu dma
19105 Display MFC DMA status. Shows all pending commands in the MFC
19106 DMA queue. For each entry, opcode, tag, class IDs, effective
19107 and local store addresses and transfer size are shown.
19108
19109 @item info spu proxydma
19110 Display MFC Proxy-DMA status. Shows all pending commands in the MFC
19111 Proxy-DMA queue. For each entry, opcode, tag, class IDs, effective
19112 and local store addresses and transfer size are shown.
19113
19114 @end table
19115
19116 When @value{GDBN} is debugging a combined PowerPC/SPU application
19117 on the Cell Broadband Engine, it provides in addition the following
19118 special commands:
19119
19120 @table @code
19121 @item set spu stop-on-load @var{arg}
19122 @kindex set spu
19123 Set whether to stop for new SPE threads. When set to @code{on}, @value{GDBN}
19124 will give control to the user when a new SPE thread enters its @code{main}
19125 function. The default is @code{off}.
19126
19127 @item show spu stop-on-load
19128 @kindex show spu
19129 Show whether to stop for new SPE threads.
19130
19131 @item set spu auto-flush-cache @var{arg}
19132 Set whether to automatically flush the software-managed cache. When set to
19133 @code{on}, @value{GDBN} will automatically cause the SPE software-managed
19134 cache to be flushed whenever SPE execution stops. This provides a consistent
19135 view of PowerPC memory that is accessed via the cache. If an application
19136 does not use the software-managed cache, this option has no effect.
19137
19138 @item show spu auto-flush-cache
19139 Show whether to automatically flush the software-managed cache.
19140
19141 @end table
19142
19143 @node PowerPC
19144 @subsection PowerPC
19145 @cindex PowerPC architecture
19146
19147 When @value{GDBN} is debugging the PowerPC architecture, it provides a set of
19148 pseudo-registers to enable inspection of 128-bit wide Decimal Floating Point
19149 numbers stored in the floating point registers. These values must be stored
19150 in two consecutive registers, always starting at an even register like
19151 @code{f0} or @code{f2}.
19152
19153 The pseudo-registers go from @code{$dl0} through @code{$dl15}, and are formed
19154 by joining the even/odd register pairs @code{f0} and @code{f1} for @code{$dl0},
19155 @code{f2} and @code{f3} for @code{$dl1} and so on.
19156
19157 For POWER7 processors, @value{GDBN} provides a set of pseudo-registers, the 64-bit
19158 wide Extended Floating Point Registers (@samp{f32} through @samp{f63}).
19159
19160
19161 @node Controlling GDB
19162 @chapter Controlling @value{GDBN}
19163
19164 You can alter the way @value{GDBN} interacts with you by using the
19165 @code{set} command. For commands controlling how @value{GDBN} displays
19166 data, see @ref{Print Settings, ,Print Settings}. Other settings are
19167 described here.
19168
19169 @menu
19170 * Prompt:: Prompt
19171 * Editing:: Command editing
19172 * Command History:: Command history
19173 * Screen Size:: Screen size
19174 * Numbers:: Numbers
19175 * ABI:: Configuring the current ABI
19176 * Messages/Warnings:: Optional warnings and messages
19177 * Debugging Output:: Optional messages about internal happenings
19178 * Other Misc Settings:: Other Miscellaneous Settings
19179 @end menu
19180
19181 @node Prompt
19182 @section Prompt
19183
19184 @cindex prompt
19185
19186 @value{GDBN} indicates its readiness to read a command by printing a string
19187 called the @dfn{prompt}. This string is normally @samp{(@value{GDBP})}. You
19188 can change the prompt string with the @code{set prompt} command. For
19189 instance, when debugging @value{GDBN} with @value{GDBN}, it is useful to change
19190 the prompt in one of the @value{GDBN} sessions so that you can always tell
19191 which one you are talking to.
19192
19193 @emph{Note:} @code{set prompt} does not add a space for you after the
19194 prompt you set. This allows you to set a prompt which ends in a space
19195 or a prompt that does not.
19196
19197 @table @code
19198 @kindex set prompt
19199 @item set prompt @var{newprompt}
19200 Directs @value{GDBN} to use @var{newprompt} as its prompt string henceforth.
19201
19202 @kindex show prompt
19203 @item show prompt
19204 Prints a line of the form: @samp{Gdb's prompt is: @var{your-prompt}}
19205 @end table
19206
19207 @node Editing
19208 @section Command Editing
19209 @cindex readline
19210 @cindex command line editing
19211
19212 @value{GDBN} reads its input commands via the @dfn{Readline} interface. This
19213 @sc{gnu} library provides consistent behavior for programs which provide a
19214 command line interface to the user. Advantages are @sc{gnu} Emacs-style
19215 or @dfn{vi}-style inline editing of commands, @code{csh}-like history
19216 substitution, and a storage and recall of command history across
19217 debugging sessions.
19218
19219 You may control the behavior of command line editing in @value{GDBN} with the
19220 command @code{set}.
19221
19222 @table @code
19223 @kindex set editing
19224 @cindex editing
19225 @item set editing
19226 @itemx set editing on
19227 Enable command line editing (enabled by default).
19228
19229 @item set editing off
19230 Disable command line editing.
19231
19232 @kindex show editing
19233 @item show editing
19234 Show whether command line editing is enabled.
19235 @end table
19236
19237 @xref{Command Line Editing}, for more details about the Readline
19238 interface. Users unfamiliar with @sc{gnu} Emacs or @code{vi} are
19239 encouraged to read that chapter.
19240
19241 @node Command History
19242 @section Command History
19243 @cindex command history
19244
19245 @value{GDBN} can keep track of the commands you type during your
19246 debugging sessions, so that you can be certain of precisely what
19247 happened. Use these commands to manage the @value{GDBN} command
19248 history facility.
19249
19250 @value{GDBN} uses the @sc{gnu} History library, a part of the Readline
19251 package, to provide the history facility. @xref{Using History
19252 Interactively}, for the detailed description of the History library.
19253
19254 To issue a command to @value{GDBN} without affecting certain aspects of
19255 the state which is seen by users, prefix it with @samp{server }
19256 (@pxref{Server Prefix}). This
19257 means that this command will not affect the command history, nor will it
19258 affect @value{GDBN}'s notion of which command to repeat if @key{RET} is
19259 pressed on a line by itself.
19260
19261 @cindex @code{server}, command prefix
19262 The server prefix does not affect the recording of values into the value
19263 history; to print a value without recording it into the value history,
19264 use the @code{output} command instead of the @code{print} command.
19265
19266 Here is the description of @value{GDBN} commands related to command
19267 history.
19268
19269 @table @code
19270 @cindex history substitution
19271 @cindex history file
19272 @kindex set history filename
19273 @cindex @env{GDBHISTFILE}, environment variable
19274 @item set history filename @var{fname}
19275 Set the name of the @value{GDBN} command history file to @var{fname}.
19276 This is the file where @value{GDBN} reads an initial command history
19277 list, and where it writes the command history from this session when it
19278 exits. You can access this list through history expansion or through
19279 the history command editing characters listed below. This file defaults
19280 to the value of the environment variable @code{GDBHISTFILE}, or to
19281 @file{./.gdb_history} (@file{./_gdb_history} on MS-DOS) if this variable
19282 is not set.
19283
19284 @cindex save command history
19285 @kindex set history save
19286 @item set history save
19287 @itemx set history save on
19288 Record command history in a file, whose name may be specified with the
19289 @code{set history filename} command. By default, this option is disabled.
19290
19291 @item set history save off
19292 Stop recording command history in a file.
19293
19294 @cindex history size
19295 @kindex set history size
19296 @cindex @env{HISTSIZE}, environment variable
19297 @item set history size @var{size}
19298 Set the number of commands which @value{GDBN} keeps in its history list.
19299 This defaults to the value of the environment variable
19300 @code{HISTSIZE}, or to 256 if this variable is not set.
19301 @end table
19302
19303 History expansion assigns special meaning to the character @kbd{!}.
19304 @xref{Event Designators}, for more details.
19305
19306 @cindex history expansion, turn on/off
19307 Since @kbd{!} is also the logical not operator in C, history expansion
19308 is off by default. If you decide to enable history expansion with the
19309 @code{set history expansion on} command, you may sometimes need to
19310 follow @kbd{!} (when it is used as logical not, in an expression) with
19311 a space or a tab to prevent it from being expanded. The readline
19312 history facilities do not attempt substitution on the strings
19313 @kbd{!=} and @kbd{!(}, even when history expansion is enabled.
19314
19315 The commands to control history expansion are:
19316
19317 @table @code
19318 @item set history expansion on
19319 @itemx set history expansion
19320 @kindex set history expansion
19321 Enable history expansion. History expansion is off by default.
19322
19323 @item set history expansion off
19324 Disable history expansion.
19325
19326 @c @group
19327 @kindex show history
19328 @item show history
19329 @itemx show history filename
19330 @itemx show history save
19331 @itemx show history size
19332 @itemx show history expansion
19333 These commands display the state of the @value{GDBN} history parameters.
19334 @code{show history} by itself displays all four states.
19335 @c @end group
19336 @end table
19337
19338 @table @code
19339 @kindex show commands
19340 @cindex show last commands
19341 @cindex display command history
19342 @item show commands
19343 Display the last ten commands in the command history.
19344
19345 @item show commands @var{n}
19346 Print ten commands centered on command number @var{n}.
19347
19348 @item show commands +
19349 Print ten commands just after the commands last printed.
19350 @end table
19351
19352 @node Screen Size
19353 @section Screen Size
19354 @cindex size of screen
19355 @cindex pauses in output
19356
19357 Certain commands to @value{GDBN} may produce large amounts of
19358 information output to the screen. To help you read all of it,
19359 @value{GDBN} pauses and asks you for input at the end of each page of
19360 output. Type @key{RET} when you want to continue the output, or @kbd{q}
19361 to discard the remaining output. Also, the screen width setting
19362 determines when to wrap lines of output. Depending on what is being
19363 printed, @value{GDBN} tries to break the line at a readable place,
19364 rather than simply letting it overflow onto the following line.
19365
19366 Normally @value{GDBN} knows the size of the screen from the terminal
19367 driver software. For example, on Unix @value{GDBN} uses the termcap data base
19368 together with the value of the @code{TERM} environment variable and the
19369 @code{stty rows} and @code{stty cols} settings. If this is not correct,
19370 you can override it with the @code{set height} and @code{set
19371 width} commands:
19372
19373 @table @code
19374 @kindex set height
19375 @kindex set width
19376 @kindex show width
19377 @kindex show height
19378 @item set height @var{lpp}
19379 @itemx show height
19380 @itemx set width @var{cpl}
19381 @itemx show width
19382 These @code{set} commands specify a screen height of @var{lpp} lines and
19383 a screen width of @var{cpl} characters. The associated @code{show}
19384 commands display the current settings.
19385
19386 If you specify a height of zero lines, @value{GDBN} does not pause during
19387 output no matter how long the output is. This is useful if output is to a
19388 file or to an editor buffer.
19389
19390 Likewise, you can specify @samp{set width 0} to prevent @value{GDBN}
19391 from wrapping its output.
19392
19393 @item set pagination on
19394 @itemx set pagination off
19395 @kindex set pagination
19396 Turn the output pagination on or off; the default is on. Turning
19397 pagination off is the alternative to @code{set height 0}. Note that
19398 running @value{GDBN} with the @option{--batch} option (@pxref{Mode
19399 Options, -batch}) also automatically disables pagination.
19400
19401 @item show pagination
19402 @kindex show pagination
19403 Show the current pagination mode.
19404 @end table
19405
19406 @node Numbers
19407 @section Numbers
19408 @cindex number representation
19409 @cindex entering numbers
19410
19411 You can always enter numbers in octal, decimal, or hexadecimal in
19412 @value{GDBN} by the usual conventions: octal numbers begin with
19413 @samp{0}, decimal numbers end with @samp{.}, and hexadecimal numbers
19414 begin with @samp{0x}. Numbers that neither begin with @samp{0} or
19415 @samp{0x}, nor end with a @samp{.} are, by default, entered in base
19416 10; likewise, the default display for numbers---when no particular
19417 format is specified---is base 10. You can change the default base for
19418 both input and output with the commands described below.
19419
19420 @table @code
19421 @kindex set input-radix
19422 @item set input-radix @var{base}
19423 Set the default base for numeric input. Supported choices
19424 for @var{base} are decimal 8, 10, or 16. @var{base} must itself be
19425 specified either unambiguously or using the current input radix; for
19426 example, any of
19427
19428 @smallexample
19429 set input-radix 012
19430 set input-radix 10.
19431 set input-radix 0xa
19432 @end smallexample
19433
19434 @noindent
19435 sets the input base to decimal. On the other hand, @samp{set input-radix 10}
19436 leaves the input radix unchanged, no matter what it was, since
19437 @samp{10}, being without any leading or trailing signs of its base, is
19438 interpreted in the current radix. Thus, if the current radix is 16,
19439 @samp{10} is interpreted in hex, i.e.@: as 16 decimal, which doesn't
19440 change the radix.
19441
19442 @kindex set output-radix
19443 @item set output-radix @var{base}
19444 Set the default base for numeric display. Supported choices
19445 for @var{base} are decimal 8, 10, or 16. @var{base} must itself be
19446 specified either unambiguously or using the current input radix.
19447
19448 @kindex show input-radix
19449 @item show input-radix
19450 Display the current default base for numeric input.
19451
19452 @kindex show output-radix
19453 @item show output-radix
19454 Display the current default base for numeric display.
19455
19456 @item set radix @r{[}@var{base}@r{]}
19457 @itemx show radix
19458 @kindex set radix
19459 @kindex show radix
19460 These commands set and show the default base for both input and output
19461 of numbers. @code{set radix} sets the radix of input and output to
19462 the same base; without an argument, it resets the radix back to its
19463 default value of 10.
19464
19465 @end table
19466
19467 @node ABI
19468 @section Configuring the Current ABI
19469
19470 @value{GDBN} can determine the @dfn{ABI} (Application Binary Interface) of your
19471 application automatically. However, sometimes you need to override its
19472 conclusions. Use these commands to manage @value{GDBN}'s view of the
19473 current ABI.
19474
19475 @cindex OS ABI
19476 @kindex set osabi
19477 @kindex show osabi
19478
19479 One @value{GDBN} configuration can debug binaries for multiple operating
19480 system targets, either via remote debugging or native emulation.
19481 @value{GDBN} will autodetect the @dfn{OS ABI} (Operating System ABI) in use,
19482 but you can override its conclusion using the @code{set osabi} command.
19483 One example where this is useful is in debugging of binaries which use
19484 an alternate C library (e.g.@: @sc{uClibc} for @sc{gnu}/Linux) which does
19485 not have the same identifying marks that the standard C library for your
19486 platform provides.
19487
19488 @table @code
19489 @item show osabi
19490 Show the OS ABI currently in use.
19491
19492 @item set osabi
19493 With no argument, show the list of registered available OS ABI's.
19494
19495 @item set osabi @var{abi}
19496 Set the current OS ABI to @var{abi}.
19497 @end table
19498
19499 @cindex float promotion
19500
19501 Generally, the way that an argument of type @code{float} is passed to a
19502 function depends on whether the function is prototyped. For a prototyped
19503 (i.e.@: ANSI/ISO style) function, @code{float} arguments are passed unchanged,
19504 according to the architecture's convention for @code{float}. For unprototyped
19505 (i.e.@: K&R style) functions, @code{float} arguments are first promoted to type
19506 @code{double} and then passed.
19507
19508 Unfortunately, some forms of debug information do not reliably indicate whether
19509 a function is prototyped. If @value{GDBN} calls a function that is not marked
19510 as prototyped, it consults @kbd{set coerce-float-to-double}.
19511
19512 @table @code
19513 @kindex set coerce-float-to-double
19514 @item set coerce-float-to-double
19515 @itemx set coerce-float-to-double on
19516 Arguments of type @code{float} will be promoted to @code{double} when passed
19517 to an unprototyped function. This is the default setting.
19518
19519 @item set coerce-float-to-double off
19520 Arguments of type @code{float} will be passed directly to unprototyped
19521 functions.
19522
19523 @kindex show coerce-float-to-double
19524 @item show coerce-float-to-double
19525 Show the current setting of promoting @code{float} to @code{double}.
19526 @end table
19527
19528 @kindex set cp-abi
19529 @kindex show cp-abi
19530 @value{GDBN} needs to know the ABI used for your program's C@t{++}
19531 objects. The correct C@t{++} ABI depends on which C@t{++} compiler was
19532 used to build your application. @value{GDBN} only fully supports
19533 programs with a single C@t{++} ABI; if your program contains code using
19534 multiple C@t{++} ABI's or if @value{GDBN} can not identify your
19535 program's ABI correctly, you can tell @value{GDBN} which ABI to use.
19536 Currently supported ABI's include ``gnu-v2'', for @code{g++} versions
19537 before 3.0, ``gnu-v3'', for @code{g++} versions 3.0 and later, and
19538 ``hpaCC'' for the HP ANSI C@t{++} compiler. Other C@t{++} compilers may
19539 use the ``gnu-v2'' or ``gnu-v3'' ABI's as well. The default setting is
19540 ``auto''.
19541
19542 @table @code
19543 @item show cp-abi
19544 Show the C@t{++} ABI currently in use.
19545
19546 @item set cp-abi
19547 With no argument, show the list of supported C@t{++} ABI's.
19548
19549 @item set cp-abi @var{abi}
19550 @itemx set cp-abi auto
19551 Set the current C@t{++} ABI to @var{abi}, or return to automatic detection.
19552 @end table
19553
19554 @node Messages/Warnings
19555 @section Optional Warnings and Messages
19556
19557 @cindex verbose operation
19558 @cindex optional warnings
19559 By default, @value{GDBN} is silent about its inner workings. If you are
19560 running on a slow machine, you may want to use the @code{set verbose}
19561 command. This makes @value{GDBN} tell you when it does a lengthy
19562 internal operation, so you will not think it has crashed.
19563
19564 Currently, the messages controlled by @code{set verbose} are those
19565 which announce that the symbol table for a source file is being read;
19566 see @code{symbol-file} in @ref{Files, ,Commands to Specify Files}.
19567
19568 @table @code
19569 @kindex set verbose
19570 @item set verbose on
19571 Enables @value{GDBN} output of certain informational messages.
19572
19573 @item set verbose off
19574 Disables @value{GDBN} output of certain informational messages.
19575
19576 @kindex show verbose
19577 @item show verbose
19578 Displays whether @code{set verbose} is on or off.
19579 @end table
19580
19581 By default, if @value{GDBN} encounters bugs in the symbol table of an
19582 object file, it is silent; but if you are debugging a compiler, you may
19583 find this information useful (@pxref{Symbol Errors, ,Errors Reading
19584 Symbol Files}).
19585
19586 @table @code
19587
19588 @kindex set complaints
19589 @item set complaints @var{limit}
19590 Permits @value{GDBN} to output @var{limit} complaints about each type of
19591 unusual symbols before becoming silent about the problem. Set
19592 @var{limit} to zero to suppress all complaints; set it to a large number
19593 to prevent complaints from being suppressed.
19594
19595 @kindex show complaints
19596 @item show complaints
19597 Displays how many symbol complaints @value{GDBN} is permitted to produce.
19598
19599 @end table
19600
19601 @anchor{confirmation requests}
19602 By default, @value{GDBN} is cautious, and asks what sometimes seems to be a
19603 lot of stupid questions to confirm certain commands. For example, if
19604 you try to run a program which is already running:
19605
19606 @smallexample
19607 (@value{GDBP}) run
19608 The program being debugged has been started already.
19609 Start it from the beginning? (y or n)
19610 @end smallexample
19611
19612 If you are willing to unflinchingly face the consequences of your own
19613 commands, you can disable this ``feature'':
19614
19615 @table @code
19616
19617 @kindex set confirm
19618 @cindex flinching
19619 @cindex confirmation
19620 @cindex stupid questions
19621 @item set confirm off
19622 Disables confirmation requests. Note that running @value{GDBN} with
19623 the @option{--batch} option (@pxref{Mode Options, -batch}) also
19624 automatically disables confirmation requests.
19625
19626 @item set confirm on
19627 Enables confirmation requests (the default).
19628
19629 @kindex show confirm
19630 @item show confirm
19631 Displays state of confirmation requests.
19632
19633 @end table
19634
19635 @cindex command tracing
19636 If you need to debug user-defined commands or sourced files you may find it
19637 useful to enable @dfn{command tracing}. In this mode each command will be
19638 printed as it is executed, prefixed with one or more @samp{+} symbols, the
19639 quantity denoting the call depth of each command.
19640
19641 @table @code
19642 @kindex set trace-commands
19643 @cindex command scripts, debugging
19644 @item set trace-commands on
19645 Enable command tracing.
19646 @item set trace-commands off
19647 Disable command tracing.
19648 @item show trace-commands
19649 Display the current state of command tracing.
19650 @end table
19651
19652 @node Debugging Output
19653 @section Optional Messages about Internal Happenings
19654 @cindex optional debugging messages
19655
19656 @value{GDBN} has commands that enable optional debugging messages from
19657 various @value{GDBN} subsystems; normally these commands are of
19658 interest to @value{GDBN} maintainers, or when reporting a bug. This
19659 section documents those commands.
19660
19661 @table @code
19662 @kindex set exec-done-display
19663 @item set exec-done-display
19664 Turns on or off the notification of asynchronous commands'
19665 completion. When on, @value{GDBN} will print a message when an
19666 asynchronous command finishes its execution. The default is off.
19667 @kindex show exec-done-display
19668 @item show exec-done-display
19669 Displays the current setting of asynchronous command completion
19670 notification.
19671 @kindex set debug
19672 @cindex gdbarch debugging info
19673 @cindex architecture debugging info
19674 @item set debug arch
19675 Turns on or off display of gdbarch debugging info. The default is off
19676 @kindex show debug
19677 @item show debug arch
19678 Displays the current state of displaying gdbarch debugging info.
19679 @item set debug aix-thread
19680 @cindex AIX threads
19681 Display debugging messages about inner workings of the AIX thread
19682 module.
19683 @item show debug aix-thread
19684 Show the current state of AIX thread debugging info display.
19685 @item set debug dwarf2-die
19686 @cindex DWARF2 DIEs
19687 Dump DWARF2 DIEs after they are read in.
19688 The value is the number of nesting levels to print.
19689 A value of zero turns off the display.
19690 @item show debug dwarf2-die
19691 Show the current state of DWARF2 DIE debugging.
19692 @item set debug displaced
19693 @cindex displaced stepping debugging info
19694 Turns on or off display of @value{GDBN} debugging info for the
19695 displaced stepping support. The default is off.
19696 @item show debug displaced
19697 Displays the current state of displaying @value{GDBN} debugging info
19698 related to displaced stepping.
19699 @item set debug event
19700 @cindex event debugging info
19701 Turns on or off display of @value{GDBN} event debugging info. The
19702 default is off.
19703 @item show debug event
19704 Displays the current state of displaying @value{GDBN} event debugging
19705 info.
19706 @item set debug expression
19707 @cindex expression debugging info
19708 Turns on or off display of debugging info about @value{GDBN}
19709 expression parsing. The default is off.
19710 @item show debug expression
19711 Displays the current state of displaying debugging info about
19712 @value{GDBN} expression parsing.
19713 @item set debug frame
19714 @cindex frame debugging info
19715 Turns on or off display of @value{GDBN} frame debugging info. The
19716 default is off.
19717 @item show debug frame
19718 Displays the current state of displaying @value{GDBN} frame debugging
19719 info.
19720 @item set debug gnu-nat
19721 @cindex @sc{gnu}/Hurd debug messages
19722 Turns on or off debugging messages from the @sc{gnu}/Hurd debug support.
19723 @item show debug gnu-nat
19724 Show the current state of @sc{gnu}/Hurd debugging messages.
19725 @item set debug infrun
19726 @cindex inferior debugging info
19727 Turns on or off display of @value{GDBN} debugging info for running the inferior.
19728 The default is off. @file{infrun.c} contains GDB's runtime state machine used
19729 for implementing operations such as single-stepping the inferior.
19730 @item show debug infrun
19731 Displays the current state of @value{GDBN} inferior debugging.
19732 @item set debug lin-lwp
19733 @cindex @sc{gnu}/Linux LWP debug messages
19734 @cindex Linux lightweight processes
19735 Turns on or off debugging messages from the Linux LWP debug support.
19736 @item show debug lin-lwp
19737 Show the current state of Linux LWP debugging messages.
19738 @item set debug lin-lwp-async
19739 @cindex @sc{gnu}/Linux LWP async debug messages
19740 @cindex Linux lightweight processes
19741 Turns on or off debugging messages from the Linux LWP async debug support.
19742 @item show debug lin-lwp-async
19743 Show the current state of Linux LWP async debugging messages.
19744 @item set debug observer
19745 @cindex observer debugging info
19746 Turns on or off display of @value{GDBN} observer debugging. This
19747 includes info such as the notification of observable events.
19748 @item show debug observer
19749 Displays the current state of observer debugging.
19750 @item set debug overload
19751 @cindex C@t{++} overload debugging info
19752 Turns on or off display of @value{GDBN} C@t{++} overload debugging
19753 info. This includes info such as ranking of functions, etc. The default
19754 is off.
19755 @item show debug overload
19756 Displays the current state of displaying @value{GDBN} C@t{++} overload
19757 debugging info.
19758 @cindex expression parser, debugging info
19759 @cindex debug expression parser
19760 @item set debug parser
19761 Turns on or off the display of expression parser debugging output.
19762 Internally, this sets the @code{yydebug} variable in the expression
19763 parser. @xref{Tracing, , Tracing Your Parser, bison, Bison}, for
19764 details. The default is off.
19765 @item show debug parser
19766 Show the current state of expression parser debugging.
19767 @cindex packets, reporting on stdout
19768 @cindex serial connections, debugging
19769 @cindex debug remote protocol
19770 @cindex remote protocol debugging
19771 @cindex display remote packets
19772 @item set debug remote
19773 Turns on or off display of reports on all packets sent back and forth across
19774 the serial line to the remote machine. The info is printed on the
19775 @value{GDBN} standard output stream. The default is off.
19776 @item show debug remote
19777 Displays the state of display of remote packets.
19778 @item set debug serial
19779 Turns on or off display of @value{GDBN} serial debugging info. The
19780 default is off.
19781 @item show debug serial
19782 Displays the current state of displaying @value{GDBN} serial debugging
19783 info.
19784 @item set debug solib-frv
19785 @cindex FR-V shared-library debugging
19786 Turns on or off debugging messages for FR-V shared-library code.
19787 @item show debug solib-frv
19788 Display the current state of FR-V shared-library code debugging
19789 messages.
19790 @item set debug target
19791 @cindex target debugging info
19792 Turns on or off display of @value{GDBN} target debugging info. This info
19793 includes what is going on at the target level of GDB, as it happens. The
19794 default is 0. Set it to 1 to track events, and to 2 to also track the
19795 value of large memory transfers. Changes to this flag do not take effect
19796 until the next time you connect to a target or use the @code{run} command.
19797 @item show debug target
19798 Displays the current state of displaying @value{GDBN} target debugging
19799 info.
19800 @item set debug timestamp
19801 @cindex timestampping debugging info
19802 Turns on or off display of timestamps with @value{GDBN} debugging info.
19803 When enabled, seconds and microseconds are displayed before each debugging
19804 message.
19805 @item show debug timestamp
19806 Displays the current state of displaying timestamps with @value{GDBN}
19807 debugging info.
19808 @item set debugvarobj
19809 @cindex variable object debugging info
19810 Turns on or off display of @value{GDBN} variable object debugging
19811 info. The default is off.
19812 @item show debugvarobj
19813 Displays the current state of displaying @value{GDBN} variable object
19814 debugging info.
19815 @item set debug xml
19816 @cindex XML parser debugging
19817 Turns on or off debugging messages for built-in XML parsers.
19818 @item show debug xml
19819 Displays the current state of XML debugging messages.
19820 @end table
19821
19822 @node Other Misc Settings
19823 @section Other Miscellaneous Settings
19824 @cindex miscellaneous settings
19825
19826 @table @code
19827 @kindex set interactive-mode
19828 @item set interactive-mode
19829 If @code{on}, forces @value{GDBN} to operate interactively.
19830 If @code{off}, forces @value{GDBN} to operate non-interactively,
19831 If @code{auto} (the default), @value{GDBN} guesses which mode to use,
19832 based on whether the debugger was started in a terminal or not.
19833
19834 In the vast majority of cases, the debugger should be able to guess
19835 correctly which mode should be used. But this setting can be useful
19836 in certain specific cases, such as running a MinGW @value{GDBN}
19837 inside a cygwin window.
19838
19839 @kindex show interactive-mode
19840 @item show interactive-mode
19841 Displays whether the debugger is operating in interactive mode or not.
19842 @end table
19843
19844 @node Extending GDB
19845 @chapter Extending @value{GDBN}
19846 @cindex extending GDB
19847
19848 @value{GDBN} provides two mechanisms for extension. The first is based
19849 on composition of @value{GDBN} commands, and the second is based on the
19850 Python scripting language.
19851
19852 To facilitate the use of these extensions, @value{GDBN} is capable
19853 of evaluating the contents of a file. When doing so, @value{GDBN}
19854 can recognize which scripting language is being used by looking at
19855 the filename extension. Files with an unrecognized filename extension
19856 are always treated as a @value{GDBN} Command Files.
19857 @xref{Command Files,, Command files}.
19858
19859 You can control how @value{GDBN} evaluates these files with the following
19860 setting:
19861
19862 @table @code
19863 @kindex set script-extension
19864 @kindex show script-extension
19865 @item set script-extension off
19866 All scripts are always evaluated as @value{GDBN} Command Files.
19867
19868 @item set script-extension soft
19869 The debugger determines the scripting language based on filename
19870 extension. If this scripting language is supported, @value{GDBN}
19871 evaluates the script using that language. Otherwise, it evaluates
19872 the file as a @value{GDBN} Command File.
19873
19874 @item set script-extension strict
19875 The debugger determines the scripting language based on filename
19876 extension, and evaluates the script using that language. If the
19877 language is not supported, then the evaluation fails.
19878
19879 @item show script-extension
19880 Display the current value of the @code{script-extension} option.
19881
19882 @end table
19883
19884 @menu
19885 * Sequences:: Canned Sequences of Commands
19886 * Python:: Scripting @value{GDBN} using Python
19887 @end menu
19888
19889 @node Sequences
19890 @section Canned Sequences of Commands
19891
19892 Aside from breakpoint commands (@pxref{Break Commands, ,Breakpoint
19893 Command Lists}), @value{GDBN} provides two ways to store sequences of
19894 commands for execution as a unit: user-defined commands and command
19895 files.
19896
19897 @menu
19898 * Define:: How to define your own commands
19899 * Hooks:: Hooks for user-defined commands
19900 * Command Files:: How to write scripts of commands to be stored in a file
19901 * Output:: Commands for controlled output
19902 @end menu
19903
19904 @node Define
19905 @subsection User-defined Commands
19906
19907 @cindex user-defined command
19908 @cindex arguments, to user-defined commands
19909 A @dfn{user-defined command} is a sequence of @value{GDBN} commands to
19910 which you assign a new name as a command. This is done with the
19911 @code{define} command. User commands may accept up to 10 arguments
19912 separated by whitespace. Arguments are accessed within the user command
19913 via @code{$arg0@dots{}$arg9}. A trivial example:
19914
19915 @smallexample
19916 define adder
19917 print $arg0 + $arg1 + $arg2
19918 end
19919 @end smallexample
19920
19921 @noindent
19922 To execute the command use:
19923
19924 @smallexample
19925 adder 1 2 3
19926 @end smallexample
19927
19928 @noindent
19929 This defines the command @code{adder}, which prints the sum of
19930 its three arguments. Note the arguments are text substitutions, so they may
19931 reference variables, use complex expressions, or even perform inferior
19932 functions calls.
19933
19934 @cindex argument count in user-defined commands
19935 @cindex how many arguments (user-defined commands)
19936 In addition, @code{$argc} may be used to find out how many arguments have
19937 been passed. This expands to a number in the range 0@dots{}10.
19938
19939 @smallexample
19940 define adder
19941 if $argc == 2
19942 print $arg0 + $arg1
19943 end
19944 if $argc == 3
19945 print $arg0 + $arg1 + $arg2
19946 end
19947 end
19948 @end smallexample
19949
19950 @table @code
19951
19952 @kindex define
19953 @item define @var{commandname}
19954 Define a command named @var{commandname}. If there is already a command
19955 by that name, you are asked to confirm that you want to redefine it.
19956 @var{commandname} may be a bare command name consisting of letters,
19957 numbers, dashes, and underscores. It may also start with any predefined
19958 prefix command. For example, @samp{define target my-target} creates
19959 a user-defined @samp{target my-target} command.
19960
19961 The definition of the command is made up of other @value{GDBN} command lines,
19962 which are given following the @code{define} command. The end of these
19963 commands is marked by a line containing @code{end}.
19964
19965 @kindex document
19966 @kindex end@r{ (user-defined commands)}
19967 @item document @var{commandname}
19968 Document the user-defined command @var{commandname}, so that it can be
19969 accessed by @code{help}. The command @var{commandname} must already be
19970 defined. This command reads lines of documentation just as @code{define}
19971 reads the lines of the command definition, ending with @code{end}.
19972 After the @code{document} command is finished, @code{help} on command
19973 @var{commandname} displays the documentation you have written.
19974
19975 You may use the @code{document} command again to change the
19976 documentation of a command. Redefining the command with @code{define}
19977 does not change the documentation.
19978
19979 @kindex dont-repeat
19980 @cindex don't repeat command
19981 @item dont-repeat
19982 Used inside a user-defined command, this tells @value{GDBN} that this
19983 command should not be repeated when the user hits @key{RET}
19984 (@pxref{Command Syntax, repeat last command}).
19985
19986 @kindex help user-defined
19987 @item help user-defined
19988 List all user-defined commands, with the first line of the documentation
19989 (if any) for each.
19990
19991 @kindex show user
19992 @item show user
19993 @itemx show user @var{commandname}
19994 Display the @value{GDBN} commands used to define @var{commandname} (but
19995 not its documentation). If no @var{commandname} is given, display the
19996 definitions for all user-defined commands.
19997
19998 @cindex infinite recursion in user-defined commands
19999 @kindex show max-user-call-depth
20000 @kindex set max-user-call-depth
20001 @item show max-user-call-depth
20002 @itemx set max-user-call-depth
20003 The value of @code{max-user-call-depth} controls how many recursion
20004 levels are allowed in user-defined commands before @value{GDBN} suspects an
20005 infinite recursion and aborts the command.
20006 @end table
20007
20008 In addition to the above commands, user-defined commands frequently
20009 use control flow commands, described in @ref{Command Files}.
20010
20011 When user-defined commands are executed, the
20012 commands of the definition are not printed. An error in any command
20013 stops execution of the user-defined command.
20014
20015 If used interactively, commands that would ask for confirmation proceed
20016 without asking when used inside a user-defined command. Many @value{GDBN}
20017 commands that normally print messages to say what they are doing omit the
20018 messages when used in a user-defined command.
20019
20020 @node Hooks
20021 @subsection User-defined Command Hooks
20022 @cindex command hooks
20023 @cindex hooks, for commands
20024 @cindex hooks, pre-command
20025
20026 @kindex hook
20027 You may define @dfn{hooks}, which are a special kind of user-defined
20028 command. Whenever you run the command @samp{foo}, if the user-defined
20029 command @samp{hook-foo} exists, it is executed (with no arguments)
20030 before that command.
20031
20032 @cindex hooks, post-command
20033 @kindex hookpost
20034 A hook may also be defined which is run after the command you executed.
20035 Whenever you run the command @samp{foo}, if the user-defined command
20036 @samp{hookpost-foo} exists, it is executed (with no arguments) after
20037 that command. Post-execution hooks may exist simultaneously with
20038 pre-execution hooks, for the same command.
20039
20040 It is valid for a hook to call the command which it hooks. If this
20041 occurs, the hook is not re-executed, thereby avoiding infinite recursion.
20042
20043 @c It would be nice if hookpost could be passed a parameter indicating
20044 @c if the command it hooks executed properly or not. FIXME!
20045
20046 @kindex stop@r{, a pseudo-command}
20047 In addition, a pseudo-command, @samp{stop} exists. Defining
20048 (@samp{hook-stop}) makes the associated commands execute every time
20049 execution stops in your program: before breakpoint commands are run,
20050 displays are printed, or the stack frame is printed.
20051
20052 For example, to ignore @code{SIGALRM} signals while
20053 single-stepping, but treat them normally during normal execution,
20054 you could define:
20055
20056 @smallexample
20057 define hook-stop
20058 handle SIGALRM nopass
20059 end
20060
20061 define hook-run
20062 handle SIGALRM pass
20063 end
20064
20065 define hook-continue
20066 handle SIGALRM pass
20067 end
20068 @end smallexample
20069
20070 As a further example, to hook at the beginning and end of the @code{echo}
20071 command, and to add extra text to the beginning and end of the message,
20072 you could define:
20073
20074 @smallexample
20075 define hook-echo
20076 echo <<<---
20077 end
20078
20079 define hookpost-echo
20080 echo --->>>\n
20081 end
20082
20083 (@value{GDBP}) echo Hello World
20084 <<<---Hello World--->>>
20085 (@value{GDBP})
20086
20087 @end smallexample
20088
20089 You can define a hook for any single-word command in @value{GDBN}, but
20090 not for command aliases; you should define a hook for the basic command
20091 name, e.g.@: @code{backtrace} rather than @code{bt}.
20092 @c FIXME! So how does Joe User discover whether a command is an alias
20093 @c or not?
20094 You can hook a multi-word command by adding @code{hook-} or
20095 @code{hookpost-} to the last word of the command, e.g.@:
20096 @samp{define target hook-remote} to add a hook to @samp{target remote}.
20097
20098 If an error occurs during the execution of your hook, execution of
20099 @value{GDBN} commands stops and @value{GDBN} issues a prompt
20100 (before the command that you actually typed had a chance to run).
20101
20102 If you try to define a hook which does not match any known command, you
20103 get a warning from the @code{define} command.
20104
20105 @node Command Files
20106 @subsection Command Files
20107
20108 @cindex command files
20109 @cindex scripting commands
20110 A command file for @value{GDBN} is a text file made of lines that are
20111 @value{GDBN} commands. Comments (lines starting with @kbd{#}) may
20112 also be included. An empty line in a command file does nothing; it
20113 does not mean to repeat the last command, as it would from the
20114 terminal.
20115
20116 You can request the execution of a command file with the @code{source}
20117 command. Note that the @code{source} command is also used to evaluate
20118 scripts that are not Command Files. The exact behavior can be configured
20119 using the @code{script-extension} setting.
20120 @xref{Extending GDB,, Extending GDB}.
20121
20122 @table @code
20123 @kindex source
20124 @cindex execute commands from a file
20125 @item source [-s] [-v] @var{filename}
20126 Execute the command file @var{filename}.
20127 @end table
20128
20129 The lines in a command file are generally executed sequentially,
20130 unless the order of execution is changed by one of the
20131 @emph{flow-control commands} described below. The commands are not
20132 printed as they are executed. An error in any command terminates
20133 execution of the command file and control is returned to the console.
20134
20135 @value{GDBN} first searches for @var{filename} in the current directory.
20136 If the file is not found there, and @var{filename} does not specify a
20137 directory, then @value{GDBN} also looks for the file on the source search path
20138 (specified with the @samp{directory} command);
20139 except that @file{$cdir} is not searched because the compilation directory
20140 is not relevant to scripts.
20141
20142 If @code{-s} is specified, then @value{GDBN} searches for @var{filename}
20143 on the search path even if @var{filename} specifies a directory.
20144 The search is done by appending @var{filename} to each element of the
20145 search path. So, for example, if @var{filename} is @file{mylib/myscript}
20146 and the search path contains @file{/home/user} then @value{GDBN} will
20147 look for the script @file{/home/user/mylib/myscript}.
20148 The search is also done if @var{filename} is an absolute path.
20149 For example, if @var{filename} is @file{/tmp/myscript} and
20150 the search path contains @file{/home/user} then @value{GDBN} will
20151 look for the script @file{/home/user/tmp/myscript}.
20152 For DOS-like systems, if @var{filename} contains a drive specification,
20153 it is stripped before concatenation. For example, if @var{filename} is
20154 @file{d:myscript} and the search path contains @file{c:/tmp} then @value{GDBN}
20155 will look for the script @file{c:/tmp/myscript}.
20156
20157 If @code{-v}, for verbose mode, is given then @value{GDBN} displays
20158 each command as it is executed. The option must be given before
20159 @var{filename}, and is interpreted as part of the filename anywhere else.
20160
20161 Commands that would ask for confirmation if used interactively proceed
20162 without asking when used in a command file. Many @value{GDBN} commands that
20163 normally print messages to say what they are doing omit the messages
20164 when called from command files.
20165
20166 @value{GDBN} also accepts command input from standard input. In this
20167 mode, normal output goes to standard output and error output goes to
20168 standard error. Errors in a command file supplied on standard input do
20169 not terminate execution of the command file---execution continues with
20170 the next command.
20171
20172 @smallexample
20173 gdb < cmds > log 2>&1
20174 @end smallexample
20175
20176 (The syntax above will vary depending on the shell used.) This example
20177 will execute commands from the file @file{cmds}. All output and errors
20178 would be directed to @file{log}.
20179
20180 Since commands stored on command files tend to be more general than
20181 commands typed interactively, they frequently need to deal with
20182 complicated situations, such as different or unexpected values of
20183 variables and symbols, changes in how the program being debugged is
20184 built, etc. @value{GDBN} provides a set of flow-control commands to
20185 deal with these complexities. Using these commands, you can write
20186 complex scripts that loop over data structures, execute commands
20187 conditionally, etc.
20188
20189 @table @code
20190 @kindex if
20191 @kindex else
20192 @item if
20193 @itemx else
20194 This command allows to include in your script conditionally executed
20195 commands. The @code{if} command takes a single argument, which is an
20196 expression to evaluate. It is followed by a series of commands that
20197 are executed only if the expression is true (its value is nonzero).
20198 There can then optionally be an @code{else} line, followed by a series
20199 of commands that are only executed if the expression was false. The
20200 end of the list is marked by a line containing @code{end}.
20201
20202 @kindex while
20203 @item while
20204 This command allows to write loops. Its syntax is similar to
20205 @code{if}: the command takes a single argument, which is an expression
20206 to evaluate, and must be followed by the commands to execute, one per
20207 line, terminated by an @code{end}. These commands are called the
20208 @dfn{body} of the loop. The commands in the body of @code{while} are
20209 executed repeatedly as long as the expression evaluates to true.
20210
20211 @kindex loop_break
20212 @item loop_break
20213 This command exits the @code{while} loop in whose body it is included.
20214 Execution of the script continues after that @code{while}s @code{end}
20215 line.
20216
20217 @kindex loop_continue
20218 @item loop_continue
20219 This command skips the execution of the rest of the body of commands
20220 in the @code{while} loop in whose body it is included. Execution
20221 branches to the beginning of the @code{while} loop, where it evaluates
20222 the controlling expression.
20223
20224 @kindex end@r{ (if/else/while commands)}
20225 @item end
20226 Terminate the block of commands that are the body of @code{if},
20227 @code{else}, or @code{while} flow-control commands.
20228 @end table
20229
20230
20231 @node Output
20232 @subsection Commands for Controlled Output
20233
20234 During the execution of a command file or a user-defined command, normal
20235 @value{GDBN} output is suppressed; the only output that appears is what is
20236 explicitly printed by the commands in the definition. This section
20237 describes three commands useful for generating exactly the output you
20238 want.
20239
20240 @table @code
20241 @kindex echo
20242 @item echo @var{text}
20243 @c I do not consider backslash-space a standard C escape sequence
20244 @c because it is not in ANSI.
20245 Print @var{text}. Nonprinting characters can be included in
20246 @var{text} using C escape sequences, such as @samp{\n} to print a
20247 newline. @strong{No newline is printed unless you specify one.}
20248 In addition to the standard C escape sequences, a backslash followed
20249 by a space stands for a space. This is useful for displaying a
20250 string with spaces at the beginning or the end, since leading and
20251 trailing spaces are otherwise trimmed from all arguments.
20252 To print @samp{@w{ }and foo =@w{ }}, use the command
20253 @samp{echo \@w{ }and foo = \@w{ }}.
20254
20255 A backslash at the end of @var{text} can be used, as in C, to continue
20256 the command onto subsequent lines. For example,
20257
20258 @smallexample
20259 echo This is some text\n\
20260 which is continued\n\
20261 onto several lines.\n
20262 @end smallexample
20263
20264 produces the same output as
20265
20266 @smallexample
20267 echo This is some text\n
20268 echo which is continued\n
20269 echo onto several lines.\n
20270 @end smallexample
20271
20272 @kindex output
20273 @item output @var{expression}
20274 Print the value of @var{expression} and nothing but that value: no
20275 newlines, no @samp{$@var{nn} = }. The value is not entered in the
20276 value history either. @xref{Expressions, ,Expressions}, for more information
20277 on expressions.
20278
20279 @item output/@var{fmt} @var{expression}
20280 Print the value of @var{expression} in format @var{fmt}. You can use
20281 the same formats as for @code{print}. @xref{Output Formats,,Output
20282 Formats}, for more information.
20283
20284 @kindex printf
20285 @item printf @var{template}, @var{expressions}@dots{}
20286 Print the values of one or more @var{expressions} under the control of
20287 the string @var{template}. To print several values, make
20288 @var{expressions} be a comma-separated list of individual expressions,
20289 which may be either numbers or pointers. Their values are printed as
20290 specified by @var{template}, exactly as a C program would do by
20291 executing the code below:
20292
20293 @smallexample
20294 printf (@var{template}, @var{expressions}@dots{});
20295 @end smallexample
20296
20297 As in @code{C} @code{printf}, ordinary characters in @var{template}
20298 are printed verbatim, while @dfn{conversion specification} introduced
20299 by the @samp{%} character cause subsequent @var{expressions} to be
20300 evaluated, their values converted and formatted according to type and
20301 style information encoded in the conversion specifications, and then
20302 printed.
20303
20304 For example, you can print two values in hex like this:
20305
20306 @smallexample
20307 printf "foo, bar-foo = 0x%x, 0x%x\n", foo, bar-foo
20308 @end smallexample
20309
20310 @code{printf} supports all the standard @code{C} conversion
20311 specifications, including the flags and modifiers between the @samp{%}
20312 character and the conversion letter, with the following exceptions:
20313
20314 @itemize @bullet
20315 @item
20316 The argument-ordering modifiers, such as @samp{2$}, are not supported.
20317
20318 @item
20319 The modifier @samp{*} is not supported for specifying precision or
20320 width.
20321
20322 @item
20323 The @samp{'} flag (for separation of digits into groups according to
20324 @code{LC_NUMERIC'}) is not supported.
20325
20326 @item
20327 The type modifiers @samp{hh}, @samp{j}, @samp{t}, and @samp{z} are not
20328 supported.
20329
20330 @item
20331 The conversion letter @samp{n} (as in @samp{%n}) is not supported.
20332
20333 @item
20334 The conversion letters @samp{a} and @samp{A} are not supported.
20335 @end itemize
20336
20337 @noindent
20338 Note that the @samp{ll} type modifier is supported only if the
20339 underlying @code{C} implementation used to build @value{GDBN} supports
20340 the @code{long long int} type, and the @samp{L} type modifier is
20341 supported only if @code{long double} type is available.
20342
20343 As in @code{C}, @code{printf} supports simple backslash-escape
20344 sequences, such as @code{\n}, @samp{\t}, @samp{\\}, @samp{\"},
20345 @samp{\a}, and @samp{\f}, that consist of backslash followed by a
20346 single character. Octal and hexadecimal escape sequences are not
20347 supported.
20348
20349 Additionally, @code{printf} supports conversion specifications for DFP
20350 (@dfn{Decimal Floating Point}) types using the following length modifiers
20351 together with a floating point specifier.
20352 letters:
20353
20354 @itemize @bullet
20355 @item
20356 @samp{H} for printing @code{Decimal32} types.
20357
20358 @item
20359 @samp{D} for printing @code{Decimal64} types.
20360
20361 @item
20362 @samp{DD} for printing @code{Decimal128} types.
20363 @end itemize
20364
20365 If the underlying @code{C} implementation used to build @value{GDBN} has
20366 support for the three length modifiers for DFP types, other modifiers
20367 such as width and precision will also be available for @value{GDBN} to use.
20368
20369 In case there is no such @code{C} support, no additional modifiers will be
20370 available and the value will be printed in the standard way.
20371
20372 Here's an example of printing DFP types using the above conversion letters:
20373 @smallexample
20374 printf "D32: %Hf - D64: %Df - D128: %DDf\n",1.2345df,1.2E10dd,1.2E1dl
20375 @end smallexample
20376
20377 @kindex eval
20378 @item eval @var{template}, @var{expressions}@dots{}
20379 Convert the values of one or more @var{expressions} under the control of
20380 the string @var{template} to a command line, and call it.
20381
20382 @end table
20383
20384 @node Python
20385 @section Scripting @value{GDBN} using Python
20386 @cindex python scripting
20387 @cindex scripting with python
20388
20389 You can script @value{GDBN} using the @uref{http://www.python.org/,
20390 Python programming language}. This feature is available only if
20391 @value{GDBN} was configured using @option{--with-python}.
20392
20393 @cindex python directory
20394 Python scripts used by @value{GDBN} should be installed in
20395 @file{@var{data-directory}/python}, where @var{data-directory} is
20396 the data directory as determined at @value{GDBN} startup (@pxref{Data Files}).
20397 This directory, known as the @dfn{python directory},
20398 is automatically added to the Python Search Path in order to allow
20399 the Python interpreter to locate all scripts installed at this location.
20400
20401 @menu
20402 * Python Commands:: Accessing Python from @value{GDBN}.
20403 * Python API:: Accessing @value{GDBN} from Python.
20404 * Auto-loading:: Automatically loading Python code.
20405 * Python modules:: Python modules provided by @value{GDBN}.
20406 @end menu
20407
20408 @node Python Commands
20409 @subsection Python Commands
20410 @cindex python commands
20411 @cindex commands to access python
20412
20413 @value{GDBN} provides one command for accessing the Python interpreter,
20414 and one related setting:
20415
20416 @table @code
20417 @kindex python
20418 @item python @r{[}@var{code}@r{]}
20419 The @code{python} command can be used to evaluate Python code.
20420
20421 If given an argument, the @code{python} command will evaluate the
20422 argument as a Python command. For example:
20423
20424 @smallexample
20425 (@value{GDBP}) python print 23
20426 23
20427 @end smallexample
20428
20429 If you do not provide an argument to @code{python}, it will act as a
20430 multi-line command, like @code{define}. In this case, the Python
20431 script is made up of subsequent command lines, given after the
20432 @code{python} command. This command list is terminated using a line
20433 containing @code{end}. For example:
20434
20435 @smallexample
20436 (@value{GDBP}) python
20437 Type python script
20438 End with a line saying just "end".
20439 >print 23
20440 >end
20441 23
20442 @end smallexample
20443
20444 @kindex maint set python print-stack
20445 @item maint set python print-stack
20446 By default, @value{GDBN} will print a stack trace when an error occurs
20447 in a Python script. This can be controlled using @code{maint set
20448 python print-stack}: if @code{on}, the default, then Python stack
20449 printing is enabled; if @code{off}, then Python stack printing is
20450 disabled.
20451 @end table
20452
20453 It is also possible to execute a Python script from the @value{GDBN}
20454 interpreter:
20455
20456 @table @code
20457 @item source @file{script-name}
20458 The script name must end with @samp{.py} and @value{GDBN} must be configured
20459 to recognize the script language based on filename extension using
20460 the @code{script-extension} setting. @xref{Extending GDB, ,Extending GDB}.
20461
20462 @item python execfile ("script-name")
20463 This method is based on the @code{execfile} Python built-in function,
20464 and thus is always available.
20465 @end table
20466
20467 @node Python API
20468 @subsection Python API
20469 @cindex python api
20470 @cindex programming in python
20471
20472 @cindex python stdout
20473 @cindex python pagination
20474 At startup, @value{GDBN} overrides Python's @code{sys.stdout} and
20475 @code{sys.stderr} to print using @value{GDBN}'s output-paging streams.
20476 A Python program which outputs to one of these streams may have its
20477 output interrupted by the user (@pxref{Screen Size}). In this
20478 situation, a Python @code{KeyboardInterrupt} exception is thrown.
20479
20480 @menu
20481 * Basic Python:: Basic Python Functions.
20482 * Exception Handling::
20483 * Values From Inferior::
20484 * Types In Python:: Python representation of types.
20485 * Pretty Printing API:: Pretty-printing values.
20486 * Selecting Pretty-Printers:: How GDB chooses a pretty-printer.
20487 * Disabling Pretty-Printers:: Disabling broken printers.
20488 * Inferiors In Python:: Python representation of inferiors (processes)
20489 * Threads In Python:: Accessing inferior threads from Python.
20490 * Commands In Python:: Implementing new commands in Python.
20491 * Parameters In Python:: Adding new @value{GDBN} parameters.
20492 * Functions In Python:: Writing new convenience functions.
20493 * Progspaces In Python:: Program spaces.
20494 * Objfiles In Python:: Object files.
20495 * Frames In Python:: Accessing inferior stack frames from Python.
20496 * Blocks In Python:: Accessing frame blocks from Python.
20497 * Symbols In Python:: Python representation of symbols.
20498 * Symbol Tables In Python:: Python representation of symbol tables.
20499 * Lazy Strings In Python:: Python representation of lazy strings.
20500 * Breakpoints In Python:: Manipulating breakpoints using Python.
20501 @end menu
20502
20503 @node Basic Python
20504 @subsubsection Basic Python
20505
20506 @cindex python functions
20507 @cindex python module
20508 @cindex gdb module
20509 @value{GDBN} introduces a new Python module, named @code{gdb}. All
20510 methods and classes added by @value{GDBN} are placed in this module.
20511 @value{GDBN} automatically @code{import}s the @code{gdb} module for
20512 use in all scripts evaluated by the @code{python} command.
20513
20514 @findex gdb.PYTHONDIR
20515 @defvar PYTHONDIR
20516 A string containing the python directory (@pxref{Python}).
20517 @end defvar
20518
20519 @findex gdb.execute
20520 @defun execute command [from_tty] [to_string]
20521 Evaluate @var{command}, a string, as a @value{GDBN} CLI command.
20522 If a GDB exception happens while @var{command} runs, it is
20523 translated as described in @ref{Exception Handling,,Exception Handling}.
20524
20525 @var{from_tty} specifies whether @value{GDBN} ought to consider this
20526 command as having originated from the user invoking it interactively.
20527 It must be a boolean value. If omitted, it defaults to @code{False}.
20528
20529 By default, any output produced by @var{command} is sent to
20530 @value{GDBN}'s standard output. If the @var{to_string} parameter is
20531 @code{True}, then output will be collected by @code{gdb.execute} and
20532 returned as a string. The default is @code{False}, in which case the
20533 return value is @code{None}. If @var{to_string} is @code{True}, the
20534 @value{GDBN} virtual terminal will be temporarily set to unlimited width
20535 and height, and its pagination will be disabled; @pxref{Screen Size}.
20536 @end defun
20537
20538 @findex gdb.breakpoints
20539 @defun breakpoints
20540 Return a sequence holding all of @value{GDBN}'s breakpoints.
20541 @xref{Breakpoints In Python}, for more information.
20542 @end defun
20543
20544 @findex gdb.parameter
20545 @defun parameter parameter
20546 Return the value of a @value{GDBN} parameter. @var{parameter} is a
20547 string naming the parameter to look up; @var{parameter} may contain
20548 spaces if the parameter has a multi-part name. For example,
20549 @samp{print object} is a valid parameter name.
20550
20551 If the named parameter does not exist, this function throws a
20552 @code{RuntimeError}. Otherwise, the parameter's value is converted to
20553 a Python value of the appropriate type, and returned.
20554 @end defun
20555
20556 @findex gdb.history
20557 @defun history number
20558 Return a value from @value{GDBN}'s value history (@pxref{Value
20559 History}). @var{number} indicates which history element to return.
20560 If @var{number} is negative, then @value{GDBN} will take its absolute value
20561 and count backward from the last element (i.e., the most recent element) to
20562 find the value to return. If @var{number} is zero, then @value{GDBN} will
20563 return the most recent element. If the element specified by @var{number}
20564 doesn't exist in the value history, a @code{RuntimeError} exception will be
20565 raised.
20566
20567 If no exception is raised, the return value is always an instance of
20568 @code{gdb.Value} (@pxref{Values From Inferior}).
20569 @end defun
20570
20571 @findex gdb.parse_and_eval
20572 @defun parse_and_eval expression
20573 Parse @var{expression} as an expression in the current language,
20574 evaluate it, and return the result as a @code{gdb.Value}.
20575 @var{expression} must be a string.
20576
20577 This function can be useful when implementing a new command
20578 (@pxref{Commands In Python}), as it provides a way to parse the
20579 command's argument as an expression. It is also useful simply to
20580 compute values, for example, it is the only way to get the value of a
20581 convenience variable (@pxref{Convenience Vars}) as a @code{gdb.Value}.
20582 @end defun
20583
20584 @findex gdb.post_event
20585 @defun post_event event
20586 Put @var{event}, a callable object taking no arguments, into
20587 @value{GDBN}'s internal event queue. This callable will be invoked at
20588 some later point, during @value{GDBN}'s event processing. Events
20589 posted using @code{post_event} will be run in the order in which they
20590 were posted; however, there is no way to know when they will be
20591 processed relative to other events inside @value{GDBN}.
20592
20593 @value{GDBN} is not thread-safe. If your Python program uses multiple
20594 threads, you must be careful to only call @value{GDBN}-specific
20595 functions in the main @value{GDBN} thread. @code{post_event} ensures
20596 this. For example:
20597
20598 @smallexample
20599 (@value{GDBP}) python
20600 >import threading
20601 >
20602 >class Writer():
20603 > def __init__(self, message):
20604 > self.message = message;
20605 > def __call__(self):
20606 > gdb.write(self.message)
20607 >
20608 >class MyThread1 (threading.Thread):
20609 > def run (self):
20610 > gdb.post_event(Writer("Hello "))
20611 >
20612 >class MyThread2 (threading.Thread):
20613 > def run (self):
20614 > gdb.post_event(Writer("World\n"))
20615 >
20616 >MyThread1().start()
20617 >MyThread2().start()
20618 >end
20619 (@value{GDBP}) Hello World
20620 @end smallexample
20621 @end defun
20622
20623 @findex gdb.write
20624 @defun write string
20625 Print a string to @value{GDBN}'s paginated standard output stream.
20626 Writing to @code{sys.stdout} or @code{sys.stderr} will automatically
20627 call this function.
20628 @end defun
20629
20630 @findex gdb.flush
20631 @defun flush
20632 Flush @value{GDBN}'s paginated standard output stream. Flushing
20633 @code{sys.stdout} or @code{sys.stderr} will automatically call this
20634 function.
20635 @end defun
20636
20637 @findex gdb.target_charset
20638 @defun target_charset
20639 Return the name of the current target character set (@pxref{Character
20640 Sets}). This differs from @code{gdb.parameter('target-charset')} in
20641 that @samp{auto} is never returned.
20642 @end defun
20643
20644 @findex gdb.target_wide_charset
20645 @defun target_wide_charset
20646 Return the name of the current target wide character set
20647 (@pxref{Character Sets}). This differs from
20648 @code{gdb.parameter('target-wide-charset')} in that @samp{auto} is
20649 never returned.
20650 @end defun
20651
20652 @findex gdb.solib_name
20653 @defun solib_name address
20654 Return the name of the shared library holding the given @var{address}
20655 as a string, or @code{None}.
20656 @end defun
20657
20658 @findex gdb.decode_line
20659 @defun decode_line @r{[}expression@r{]}
20660 Return locations of the line specified by @var{expression}, or of the
20661 current line if no argument was given. This function returns a Python
20662 tuple containing two elements. The first element contains a string
20663 holding any unparsed section of @var{expression} (or @code{None} if
20664 the expression has been fully parsed). The second element contains
20665 either @code{None} or another tuple that contains all the locations
20666 that match the expression represented as @code{gdb.Symtab_and_line}
20667 objects (@pxref{Symbol Tables In Python}). If @var{expression} is
20668 provided, it is decoded the way that @value{GDBN}'s inbuilt
20669 @code{break} or @code{edit} commands do (@pxref{Specify Location}).
20670 @end defun
20671
20672 @node Exception Handling
20673 @subsubsection Exception Handling
20674 @cindex python exceptions
20675 @cindex exceptions, python
20676
20677 When executing the @code{python} command, Python exceptions
20678 uncaught within the Python code are translated to calls to
20679 @value{GDBN} error-reporting mechanism. If the command that called
20680 @code{python} does not handle the error, @value{GDBN} will
20681 terminate it and print an error message containing the Python
20682 exception name, the associated value, and the Python call stack
20683 backtrace at the point where the exception was raised. Example:
20684
20685 @smallexample
20686 (@value{GDBP}) python print foo
20687 Traceback (most recent call last):
20688 File "<string>", line 1, in <module>
20689 NameError: name 'foo' is not defined
20690 @end smallexample
20691
20692 @value{GDBN} errors that happen in @value{GDBN} commands invoked by Python
20693 code are converted to Python @code{RuntimeError} exceptions. User
20694 interrupt (via @kbd{C-c} or by typing @kbd{q} at a pagination
20695 prompt) is translated to a Python @code{KeyboardInterrupt}
20696 exception. If you catch these exceptions in your Python code, your
20697 exception handler will see @code{RuntimeError} or
20698 @code{KeyboardInterrupt} as the exception type, the @value{GDBN} error
20699 message as its value, and the Python call stack backtrace at the
20700 Python statement closest to where the @value{GDBN} error occured as the
20701 traceback.
20702
20703 @findex gdb.GdbError
20704 When implementing @value{GDBN} commands in Python via @code{gdb.Command},
20705 it is useful to be able to throw an exception that doesn't cause a
20706 traceback to be printed. For example, the user may have invoked the
20707 command incorrectly. Use the @code{gdb.GdbError} exception
20708 to handle this case. Example:
20709
20710 @smallexample
20711 (gdb) python
20712 >class HelloWorld (gdb.Command):
20713 > """Greet the whole world."""
20714 > def __init__ (self):
20715 > super (HelloWorld, self).__init__ ("hello-world", gdb.COMMAND_OBSCURE)
20716 > def invoke (self, args, from_tty):
20717 > argv = gdb.string_to_argv (args)
20718 > if len (argv) != 0:
20719 > raise gdb.GdbError ("hello-world takes no arguments")
20720 > print "Hello, World!"
20721 >HelloWorld ()
20722 >end
20723 (gdb) hello-world 42
20724 hello-world takes no arguments
20725 @end smallexample
20726
20727 @node Values From Inferior
20728 @subsubsection Values From Inferior
20729 @cindex values from inferior, with Python
20730 @cindex python, working with values from inferior
20731
20732 @cindex @code{gdb.Value}
20733 @value{GDBN} provides values it obtains from the inferior program in
20734 an object of type @code{gdb.Value}. @value{GDBN} uses this object
20735 for its internal bookkeeping of the inferior's values, and for
20736 fetching values when necessary.
20737
20738 Inferior values that are simple scalars can be used directly in
20739 Python expressions that are valid for the value's data type. Here's
20740 an example for an integer or floating-point value @code{some_val}:
20741
20742 @smallexample
20743 bar = some_val + 2
20744 @end smallexample
20745
20746 @noindent
20747 As result of this, @code{bar} will also be a @code{gdb.Value} object
20748 whose values are of the same type as those of @code{some_val}.
20749
20750 Inferior values that are structures or instances of some class can
20751 be accessed using the Python @dfn{dictionary syntax}. For example, if
20752 @code{some_val} is a @code{gdb.Value} instance holding a structure, you
20753 can access its @code{foo} element with:
20754
20755 @smallexample
20756 bar = some_val['foo']
20757 @end smallexample
20758
20759 Again, @code{bar} will also be a @code{gdb.Value} object.
20760
20761 A @code{gdb.Value} that represents a function can be executed via
20762 inferior function call. Any arguments provided to the call must match
20763 the function's prototype, and must be provided in the order specified
20764 by that prototype.
20765
20766 For example, @code{some_val} is a @code{gdb.Value} instance
20767 representing a function that takes two integers as arguments. To
20768 execute this function, call it like so:
20769
20770 @smallexample
20771 result = some_val (10,20)
20772 @end smallexample
20773
20774 Any values returned from a function call will be stored as a
20775 @code{gdb.Value}.
20776
20777 The following attributes are provided:
20778
20779 @table @code
20780 @defivar Value address
20781 If this object is addressable, this read-only attribute holds a
20782 @code{gdb.Value} object representing the address. Otherwise,
20783 this attribute holds @code{None}.
20784 @end defivar
20785
20786 @cindex optimized out value in Python
20787 @defivar Value is_optimized_out
20788 This read-only boolean attribute is true if the compiler optimized out
20789 this value, thus it is not available for fetching from the inferior.
20790 @end defivar
20791
20792 @defivar Value type
20793 The type of this @code{gdb.Value}. The value of this attribute is a
20794 @code{gdb.Type} object (@pxref{Types In Python}).
20795 @end defivar
20796
20797 @defivar Value dynamic_type
20798 The dynamic type of this @code{gdb.Value}. This uses C@t{++} run-time
20799 type information (@acronym{RTTI}) to determine the dynamic type of the
20800 value. If this value is of class type, it will return the class in
20801 which the value is embedded, if any. If this value is of pointer or
20802 reference to a class type, it will compute the dynamic type of the
20803 referenced object, and return a pointer or reference to that type,
20804 respectively. In all other cases, it will return the value's static
20805 type.
20806
20807 Note that this feature will only work when debugging a C@t{++} program
20808 that includes @acronym{RTTI} for the object in question. Otherwise,
20809 it will just return the static type of the value as in @kbd{ptype foo}
20810 (@pxref{Symbols, ptype}).
20811 @end defivar
20812 @end table
20813
20814 The following methods are provided:
20815
20816 @table @code
20817 @defmethod Value __init__ @var{val}
20818 Many Python values can be converted directly to a @code{gdb.Value} via
20819 this object initializer. Specifically:
20820
20821 @table @asis
20822 @item Python boolean
20823 A Python boolean is converted to the boolean type from the current
20824 language.
20825
20826 @item Python integer
20827 A Python integer is converted to the C @code{long} type for the
20828 current architecture.
20829
20830 @item Python long
20831 A Python long is converted to the C @code{long long} type for the
20832 current architecture.
20833
20834 @item Python float
20835 A Python float is converted to the C @code{double} type for the
20836 current architecture.
20837
20838 @item Python string
20839 A Python string is converted to a target string, using the current
20840 target encoding.
20841
20842 @item @code{gdb.Value}
20843 If @code{val} is a @code{gdb.Value}, then a copy of the value is made.
20844
20845 @item @code{gdb.LazyString}
20846 If @code{val} is a @code{gdb.LazyString} (@pxref{Lazy Strings In
20847 Python}), then the lazy string's @code{value} method is called, and
20848 its result is used.
20849 @end table
20850 @end defmethod
20851
20852 @defmethod Value cast type
20853 Return a new instance of @code{gdb.Value} that is the result of
20854 casting this instance to the type described by @var{type}, which must
20855 be a @code{gdb.Type} object. If the cast cannot be performed for some
20856 reason, this method throws an exception.
20857 @end defmethod
20858
20859 @defmethod Value dereference
20860 For pointer data types, this method returns a new @code{gdb.Value} object
20861 whose contents is the object pointed to by the pointer. For example, if
20862 @code{foo} is a C pointer to an @code{int}, declared in your C program as
20863
20864 @smallexample
20865 int *foo;
20866 @end smallexample
20867
20868 @noindent
20869 then you can use the corresponding @code{gdb.Value} to access what
20870 @code{foo} points to like this:
20871
20872 @smallexample
20873 bar = foo.dereference ()
20874 @end smallexample
20875
20876 The result @code{bar} will be a @code{gdb.Value} object holding the
20877 value pointed to by @code{foo}.
20878 @end defmethod
20879
20880 @defmethod Value dynamic_cast type
20881 Like @code{Value.cast}, but works as if the C@t{++} @code{dynamic_cast}
20882 operator were used. Consult a C@t{++} reference for details.
20883 @end defmethod
20884
20885 @defmethod Value reinterpret_cast type
20886 Like @code{Value.cast}, but works as if the C@t{++} @code{reinterpret_cast}
20887 operator were used. Consult a C@t{++} reference for details.
20888 @end defmethod
20889
20890 @defmethod Value string @r{[}encoding@r{]} @r{[}errors@r{]} @r{[}length@r{]}
20891 If this @code{gdb.Value} represents a string, then this method
20892 converts the contents to a Python string. Otherwise, this method will
20893 throw an exception.
20894
20895 Strings are recognized in a language-specific way; whether a given
20896 @code{gdb.Value} represents a string is determined by the current
20897 language.
20898
20899 For C-like languages, a value is a string if it is a pointer to or an
20900 array of characters or ints. The string is assumed to be terminated
20901 by a zero of the appropriate width. However if the optional length
20902 argument is given, the string will be converted to that given length,
20903 ignoring any embedded zeros that the string may contain.
20904
20905 If the optional @var{encoding} argument is given, it must be a string
20906 naming the encoding of the string in the @code{gdb.Value}, such as
20907 @code{"ascii"}, @code{"iso-8859-6"} or @code{"utf-8"}. It accepts
20908 the same encodings as the corresponding argument to Python's
20909 @code{string.decode} method, and the Python codec machinery will be used
20910 to convert the string. If @var{encoding} is not given, or if
20911 @var{encoding} is the empty string, then either the @code{target-charset}
20912 (@pxref{Character Sets}) will be used, or a language-specific encoding
20913 will be used, if the current language is able to supply one.
20914
20915 The optional @var{errors} argument is the same as the corresponding
20916 argument to Python's @code{string.decode} method.
20917
20918 If the optional @var{length} argument is given, the string will be
20919 fetched and converted to the given length.
20920 @end defmethod
20921
20922 @defmethod Value lazy_string @r{[}encoding@r{]} @r{[}length@r{]}
20923 If this @code{gdb.Value} represents a string, then this method
20924 converts the contents to a @code{gdb.LazyString} (@pxref{Lazy Strings
20925 In Python}). Otherwise, this method will throw an exception.
20926
20927 If the optional @var{encoding} argument is given, it must be a string
20928 naming the encoding of the @code{gdb.LazyString}. Some examples are:
20929 @samp{ascii}, @samp{iso-8859-6} or @samp{utf-8}. If the
20930 @var{encoding} argument is an encoding that @value{GDBN} does
20931 recognize, @value{GDBN} will raise an error.
20932
20933 When a lazy string is printed, the @value{GDBN} encoding machinery is
20934 used to convert the string during printing. If the optional
20935 @var{encoding} argument is not provided, or is an empty string,
20936 @value{GDBN} will automatically select the encoding most suitable for
20937 the string type. For further information on encoding in @value{GDBN}
20938 please see @ref{Character Sets}.
20939
20940 If the optional @var{length} argument is given, the string will be
20941 fetched and encoded to the length of characters specified. If
20942 the @var{length} argument is not provided, the string will be fetched
20943 and encoded until a null of appropriate width is found.
20944 @end defmethod
20945 @end table
20946
20947 @node Types In Python
20948 @subsubsection Types In Python
20949 @cindex types in Python
20950 @cindex Python, working with types
20951
20952 @tindex gdb.Type
20953 @value{GDBN} represents types from the inferior using the class
20954 @code{gdb.Type}.
20955
20956 The following type-related functions are available in the @code{gdb}
20957 module:
20958
20959 @findex gdb.lookup_type
20960 @defun lookup_type name [block]
20961 This function looks up a type by name. @var{name} is the name of the
20962 type to look up. It must be a string.
20963
20964 If @var{block} is given, then @var{name} is looked up in that scope.
20965 Otherwise, it is searched for globally.
20966
20967 Ordinarily, this function will return an instance of @code{gdb.Type}.
20968 If the named type cannot be found, it will throw an exception.
20969 @end defun
20970
20971 An instance of @code{Type} has the following attributes:
20972
20973 @table @code
20974 @defivar Type code
20975 The type code for this type. The type code will be one of the
20976 @code{TYPE_CODE_} constants defined below.
20977 @end defivar
20978
20979 @defivar Type sizeof
20980 The size of this type, in target @code{char} units. Usually, a
20981 target's @code{char} type will be an 8-bit byte. However, on some
20982 unusual platforms, this type may have a different size.
20983 @end defivar
20984
20985 @defivar Type tag
20986 The tag name for this type. The tag name is the name after
20987 @code{struct}, @code{union}, or @code{enum} in C and C@t{++}; not all
20988 languages have this concept. If this type has no tag name, then
20989 @code{None} is returned.
20990 @end defivar
20991 @end table
20992
20993 The following methods are provided:
20994
20995 @table @code
20996 @defmethod Type fields
20997 For structure and union types, this method returns the fields. Range
20998 types have two fields, the minimum and maximum values. Enum types
20999 have one field per enum constant. Function and method types have one
21000 field per parameter. The base types of C@t{++} classes are also
21001 represented as fields. If the type has no fields, or does not fit
21002 into one of these categories, an empty sequence will be returned.
21003
21004 Each field is an object, with some pre-defined attributes:
21005 @table @code
21006 @item bitpos
21007 This attribute is not available for @code{static} fields (as in
21008 C@t{++} or Java). For non-@code{static} fields, the value is the bit
21009 position of the field.
21010
21011 @item name
21012 The name of the field, or @code{None} for anonymous fields.
21013
21014 @item artificial
21015 This is @code{True} if the field is artificial, usually meaning that
21016 it was provided by the compiler and not the user. This attribute is
21017 always provided, and is @code{False} if the field is not artificial.
21018
21019 @item is_base_class
21020 This is @code{True} if the field represents a base class of a C@t{++}
21021 structure. This attribute is always provided, and is @code{False}
21022 if the field is not a base class of the type that is the argument of
21023 @code{fields}, or if that type was not a C@t{++} class.
21024
21025 @item bitsize
21026 If the field is packed, or is a bitfield, then this will have a
21027 non-zero value, which is the size of the field in bits. Otherwise,
21028 this will be zero; in this case the field's size is given by its type.
21029
21030 @item type
21031 The type of the field. This is usually an instance of @code{Type},
21032 but it can be @code{None} in some situations.
21033 @end table
21034 @end defmethod
21035
21036 @defmethod Type array @var{n1} @r{[}@var{n2}@r{]}
21037 Return a new @code{gdb.Type} object which represents an array of this
21038 type. If one argument is given, it is the inclusive upper bound of
21039 the array; in this case the lower bound is zero. If two arguments are
21040 given, the first argument is the lower bound of the array, and the
21041 second argument is the upper bound of the array. An array's length
21042 must not be negative, but the bounds can be.
21043 @end defmethod
21044
21045 @defmethod Type const
21046 Return a new @code{gdb.Type} object which represents a
21047 @code{const}-qualified variant of this type.
21048 @end defmethod
21049
21050 @defmethod Type volatile
21051 Return a new @code{gdb.Type} object which represents a
21052 @code{volatile}-qualified variant of this type.
21053 @end defmethod
21054
21055 @defmethod Type unqualified
21056 Return a new @code{gdb.Type} object which represents an unqualified
21057 variant of this type. That is, the result is neither @code{const} nor
21058 @code{volatile}.
21059 @end defmethod
21060
21061 @defmethod Type range
21062 Return a Python @code{Tuple} object that contains two elements: the
21063 low bound of the argument type and the high bound of that type. If
21064 the type does not have a range, @value{GDBN} will raise a
21065 @code{RuntimeError} exception.
21066 @end defmethod
21067
21068 @defmethod Type reference
21069 Return a new @code{gdb.Type} object which represents a reference to this
21070 type.
21071 @end defmethod
21072
21073 @defmethod Type pointer
21074 Return a new @code{gdb.Type} object which represents a pointer to this
21075 type.
21076 @end defmethod
21077
21078 @defmethod Type strip_typedefs
21079 Return a new @code{gdb.Type} that represents the real type,
21080 after removing all layers of typedefs.
21081 @end defmethod
21082
21083 @defmethod Type target
21084 Return a new @code{gdb.Type} object which represents the target type
21085 of this type.
21086
21087 For a pointer type, the target type is the type of the pointed-to
21088 object. For an array type (meaning C-like arrays), the target type is
21089 the type of the elements of the array. For a function or method type,
21090 the target type is the type of the return value. For a complex type,
21091 the target type is the type of the elements. For a typedef, the
21092 target type is the aliased type.
21093
21094 If the type does not have a target, this method will throw an
21095 exception.
21096 @end defmethod
21097
21098 @defmethod Type template_argument n [block]
21099 If this @code{gdb.Type} is an instantiation of a template, this will
21100 return a new @code{gdb.Type} which represents the type of the
21101 @var{n}th template argument.
21102
21103 If this @code{gdb.Type} is not a template type, this will throw an
21104 exception. Ordinarily, only C@t{++} code will have template types.
21105
21106 If @var{block} is given, then @var{name} is looked up in that scope.
21107 Otherwise, it is searched for globally.
21108 @end defmethod
21109 @end table
21110
21111
21112 Each type has a code, which indicates what category this type falls
21113 into. The available type categories are represented by constants
21114 defined in the @code{gdb} module:
21115
21116 @table @code
21117 @findex TYPE_CODE_PTR
21118 @findex gdb.TYPE_CODE_PTR
21119 @item TYPE_CODE_PTR
21120 The type is a pointer.
21121
21122 @findex TYPE_CODE_ARRAY
21123 @findex gdb.TYPE_CODE_ARRAY
21124 @item TYPE_CODE_ARRAY
21125 The type is an array.
21126
21127 @findex TYPE_CODE_STRUCT
21128 @findex gdb.TYPE_CODE_STRUCT
21129 @item TYPE_CODE_STRUCT
21130 The type is a structure.
21131
21132 @findex TYPE_CODE_UNION
21133 @findex gdb.TYPE_CODE_UNION
21134 @item TYPE_CODE_UNION
21135 The type is a union.
21136
21137 @findex TYPE_CODE_ENUM
21138 @findex gdb.TYPE_CODE_ENUM
21139 @item TYPE_CODE_ENUM
21140 The type is an enum.
21141
21142 @findex TYPE_CODE_FLAGS
21143 @findex gdb.TYPE_CODE_FLAGS
21144 @item TYPE_CODE_FLAGS
21145 A bit flags type, used for things such as status registers.
21146
21147 @findex TYPE_CODE_FUNC
21148 @findex gdb.TYPE_CODE_FUNC
21149 @item TYPE_CODE_FUNC
21150 The type is a function.
21151
21152 @findex TYPE_CODE_INT
21153 @findex gdb.TYPE_CODE_INT
21154 @item TYPE_CODE_INT
21155 The type is an integer type.
21156
21157 @findex TYPE_CODE_FLT
21158 @findex gdb.TYPE_CODE_FLT
21159 @item TYPE_CODE_FLT
21160 A floating point type.
21161
21162 @findex TYPE_CODE_VOID
21163 @findex gdb.TYPE_CODE_VOID
21164 @item TYPE_CODE_VOID
21165 The special type @code{void}.
21166
21167 @findex TYPE_CODE_SET
21168 @findex gdb.TYPE_CODE_SET
21169 @item TYPE_CODE_SET
21170 A Pascal set type.
21171
21172 @findex TYPE_CODE_RANGE
21173 @findex gdb.TYPE_CODE_RANGE
21174 @item TYPE_CODE_RANGE
21175 A range type, that is, an integer type with bounds.
21176
21177 @findex TYPE_CODE_STRING
21178 @findex gdb.TYPE_CODE_STRING
21179 @item TYPE_CODE_STRING
21180 A string type. Note that this is only used for certain languages with
21181 language-defined string types; C strings are not represented this way.
21182
21183 @findex TYPE_CODE_BITSTRING
21184 @findex gdb.TYPE_CODE_BITSTRING
21185 @item TYPE_CODE_BITSTRING
21186 A string of bits.
21187
21188 @findex TYPE_CODE_ERROR
21189 @findex gdb.TYPE_CODE_ERROR
21190 @item TYPE_CODE_ERROR
21191 An unknown or erroneous type.
21192
21193 @findex TYPE_CODE_METHOD
21194 @findex gdb.TYPE_CODE_METHOD
21195 @item TYPE_CODE_METHOD
21196 A method type, as found in C@t{++} or Java.
21197
21198 @findex TYPE_CODE_METHODPTR
21199 @findex gdb.TYPE_CODE_METHODPTR
21200 @item TYPE_CODE_METHODPTR
21201 A pointer-to-member-function.
21202
21203 @findex TYPE_CODE_MEMBERPTR
21204 @findex gdb.TYPE_CODE_MEMBERPTR
21205 @item TYPE_CODE_MEMBERPTR
21206 A pointer-to-member.
21207
21208 @findex TYPE_CODE_REF
21209 @findex gdb.TYPE_CODE_REF
21210 @item TYPE_CODE_REF
21211 A reference type.
21212
21213 @findex TYPE_CODE_CHAR
21214 @findex gdb.TYPE_CODE_CHAR
21215 @item TYPE_CODE_CHAR
21216 A character type.
21217
21218 @findex TYPE_CODE_BOOL
21219 @findex gdb.TYPE_CODE_BOOL
21220 @item TYPE_CODE_BOOL
21221 A boolean type.
21222
21223 @findex TYPE_CODE_COMPLEX
21224 @findex gdb.TYPE_CODE_COMPLEX
21225 @item TYPE_CODE_COMPLEX
21226 A complex float type.
21227
21228 @findex TYPE_CODE_TYPEDEF
21229 @findex gdb.TYPE_CODE_TYPEDEF
21230 @item TYPE_CODE_TYPEDEF
21231 A typedef to some other type.
21232
21233 @findex TYPE_CODE_NAMESPACE
21234 @findex gdb.TYPE_CODE_NAMESPACE
21235 @item TYPE_CODE_NAMESPACE
21236 A C@t{++} namespace.
21237
21238 @findex TYPE_CODE_DECFLOAT
21239 @findex gdb.TYPE_CODE_DECFLOAT
21240 @item TYPE_CODE_DECFLOAT
21241 A decimal floating point type.
21242
21243 @findex TYPE_CODE_INTERNAL_FUNCTION
21244 @findex gdb.TYPE_CODE_INTERNAL_FUNCTION
21245 @item TYPE_CODE_INTERNAL_FUNCTION
21246 A function internal to @value{GDBN}. This is the type used to represent
21247 convenience functions.
21248 @end table
21249
21250 Further support for types is provided in the @code{gdb.types}
21251 Python module (@pxref{gdb.types}).
21252
21253 @node Pretty Printing API
21254 @subsubsection Pretty Printing API
21255
21256 An example output is provided (@pxref{Pretty Printing}).
21257
21258 A pretty-printer is just an object that holds a value and implements a
21259 specific interface, defined here.
21260
21261 @defop Operation {pretty printer} children (self)
21262 @value{GDBN} will call this method on a pretty-printer to compute the
21263 children of the pretty-printer's value.
21264
21265 This method must return an object conforming to the Python iterator
21266 protocol. Each item returned by the iterator must be a tuple holding
21267 two elements. The first element is the ``name'' of the child; the
21268 second element is the child's value. The value can be any Python
21269 object which is convertible to a @value{GDBN} value.
21270
21271 This method is optional. If it does not exist, @value{GDBN} will act
21272 as though the value has no children.
21273 @end defop
21274
21275 @defop Operation {pretty printer} display_hint (self)
21276 The CLI may call this method and use its result to change the
21277 formatting of a value. The result will also be supplied to an MI
21278 consumer as a @samp{displayhint} attribute of the variable being
21279 printed.
21280
21281 This method is optional. If it does exist, this method must return a
21282 string.
21283
21284 Some display hints are predefined by @value{GDBN}:
21285
21286 @table @samp
21287 @item array
21288 Indicate that the object being printed is ``array-like''. The CLI
21289 uses this to respect parameters such as @code{set print elements} and
21290 @code{set print array}.
21291
21292 @item map
21293 Indicate that the object being printed is ``map-like'', and that the
21294 children of this value can be assumed to alternate between keys and
21295 values.
21296
21297 @item string
21298 Indicate that the object being printed is ``string-like''. If the
21299 printer's @code{to_string} method returns a Python string of some
21300 kind, then @value{GDBN} will call its internal language-specific
21301 string-printing function to format the string. For the CLI this means
21302 adding quotation marks, possibly escaping some characters, respecting
21303 @code{set print elements}, and the like.
21304 @end table
21305 @end defop
21306
21307 @defop Operation {pretty printer} to_string (self)
21308 @value{GDBN} will call this method to display the string
21309 representation of the value passed to the object's constructor.
21310
21311 When printing from the CLI, if the @code{to_string} method exists,
21312 then @value{GDBN} will prepend its result to the values returned by
21313 @code{children}. Exactly how this formatting is done is dependent on
21314 the display hint, and may change as more hints are added. Also,
21315 depending on the print settings (@pxref{Print Settings}), the CLI may
21316 print just the result of @code{to_string} in a stack trace, omitting
21317 the result of @code{children}.
21318
21319 If this method returns a string, it is printed verbatim.
21320
21321 Otherwise, if this method returns an instance of @code{gdb.Value},
21322 then @value{GDBN} prints this value. This may result in a call to
21323 another pretty-printer.
21324
21325 If instead the method returns a Python value which is convertible to a
21326 @code{gdb.Value}, then @value{GDBN} performs the conversion and prints
21327 the resulting value. Again, this may result in a call to another
21328 pretty-printer. Python scalars (integers, floats, and booleans) and
21329 strings are convertible to @code{gdb.Value}; other types are not.
21330
21331 Finally, if this method returns @code{None} then no further operations
21332 are peformed in this method and nothing is printed.
21333
21334 If the result is not one of these types, an exception is raised.
21335 @end defop
21336
21337 @value{GDBN} provides a function which can be used to look up the
21338 default pretty-printer for a @code{gdb.Value}:
21339
21340 @findex gdb.default_visualizer
21341 @defun default_visualizer value
21342 This function takes a @code{gdb.Value} object as an argument. If a
21343 pretty-printer for this value exists, then it is returned. If no such
21344 printer exists, then this returns @code{None}.
21345 @end defun
21346
21347 @node Selecting Pretty-Printers
21348 @subsubsection Selecting Pretty-Printers
21349
21350 The Python list @code{gdb.pretty_printers} contains an array of
21351 functions or callable objects that have been registered via addition
21352 as a pretty-printer.
21353 Each @code{gdb.Progspace} contains a @code{pretty_printers} attribute.
21354 Each @code{gdb.Objfile} also contains a @code{pretty_printers}
21355 attribute.
21356
21357 A function on one of these lists is passed a single @code{gdb.Value}
21358 argument and should return a pretty-printer object conforming to the
21359 interface definition above (@pxref{Pretty Printing API}). If a function
21360 cannot create a pretty-printer for the value, it should return
21361 @code{None}.
21362
21363 @value{GDBN} first checks the @code{pretty_printers} attribute of each
21364 @code{gdb.Objfile} in the current program space and iteratively calls
21365 each enabled function (@pxref{Disabling Pretty-Printers})
21366 in the list for that @code{gdb.Objfile} until it receives
21367 a pretty-printer object.
21368 If no pretty-printer is found in the objfile lists, @value{GDBN} then
21369 searches the pretty-printer list of the current program space,
21370 calling each enabled function until an object is returned.
21371 After these lists have been exhausted, it tries the global
21372 @code{gdb.pretty_printers} list, again calling each enabled function until an
21373 object is returned.
21374
21375 The order in which the objfiles are searched is not specified. For a
21376 given list, functions are always invoked from the head of the list,
21377 and iterated over sequentially until the end of the list, or a printer
21378 object is returned.
21379
21380 Here is an example showing how a @code{std::string} printer might be
21381 written:
21382
21383 @smallexample
21384 class StdStringPrinter:
21385 "Print a std::string"
21386
21387 def __init__ (self, val):
21388 self.val = val
21389
21390 def to_string (self):
21391 return self.val['_M_dataplus']['_M_p']
21392
21393 def display_hint (self):
21394 return 'string'
21395 @end smallexample
21396
21397 And here is an example showing how a lookup function for the printer
21398 example above might be written.
21399
21400 @smallexample
21401 def str_lookup_function (val):
21402
21403 lookup_tag = val.type.tag
21404 regex = re.compile ("^std::basic_string<char,.*>$")
21405 if lookup_tag == None:
21406 return None
21407 if regex.match (lookup_tag):
21408 return StdStringPrinter (val)
21409
21410 return None
21411 @end smallexample
21412
21413 The example lookup function extracts the value's type, and attempts to
21414 match it to a type that it can pretty-print. If it is a type the
21415 printer can pretty-print, it will return a printer object. If not, it
21416 returns @code{None}.
21417
21418 We recommend that you put your core pretty-printers into a Python
21419 package. If your pretty-printers are for use with a library, we
21420 further recommend embedding a version number into the package name.
21421 This practice will enable @value{GDBN} to load multiple versions of
21422 your pretty-printers at the same time, because they will have
21423 different names.
21424
21425 You should write auto-loaded code (@pxref{Auto-loading}) such that it
21426 can be evaluated multiple times without changing its meaning. An
21427 ideal auto-load file will consist solely of @code{import}s of your
21428 printer modules, followed by a call to a register pretty-printers with
21429 the current objfile.
21430
21431 Taken as a whole, this approach will scale nicely to multiple
21432 inferiors, each potentially using a different library version.
21433 Embedding a version number in the Python package name will ensure that
21434 @value{GDBN} is able to load both sets of printers simultaneously.
21435 Then, because the search for pretty-printers is done by objfile, and
21436 because your auto-loaded code took care to register your library's
21437 printers with a specific objfile, @value{GDBN} will find the correct
21438 printers for the specific version of the library used by each
21439 inferior.
21440
21441 To continue the @code{std::string} example (@pxref{Pretty Printing API}),
21442 this code might appear in @code{gdb.libstdcxx.v6}:
21443
21444 @smallexample
21445 def register_printers (objfile):
21446 objfile.pretty_printers.add (str_lookup_function)
21447 @end smallexample
21448
21449 @noindent
21450 And then the corresponding contents of the auto-load file would be:
21451
21452 @smallexample
21453 import gdb.libstdcxx.v6
21454 gdb.libstdcxx.v6.register_printers (gdb.current_objfile ())
21455 @end smallexample
21456
21457 @node Disabling Pretty-Printers
21458 @subsubsection Disabling Pretty-Printers
21459 @cindex disabling pretty-printers
21460
21461 For various reasons a pretty-printer may not work.
21462 For example, the underlying data structure may have changed and
21463 the pretty-printer is out of date.
21464
21465 The consequences of a broken pretty-printer are severe enough that
21466 @value{GDBN} provides support for enabling and disabling individual
21467 printers. For example, if @code{print frame-arguments} is on,
21468 a backtrace can become highly illegible if any argument is printed
21469 with a broken printer.
21470
21471 Pretty-printers are enabled and disabled by attaching an @code{enabled}
21472 attribute to the registered function or callable object. If this attribute
21473 is present and its value is @code{False}, the printer is disabled, otherwise
21474 the printer is enabled.
21475
21476 @node Inferiors In Python
21477 @subsubsection Inferiors In Python
21478 @cindex inferiors in python
21479
21480 @findex gdb.Inferior
21481 Programs which are being run under @value{GDBN} are called inferiors
21482 (@pxref{Inferiors and Programs}). Python scripts can access
21483 information about and manipulate inferiors controlled by @value{GDBN}
21484 via objects of the @code{gdb.Inferior} class.
21485
21486 The following inferior-related functions are available in the @code{gdb}
21487 module:
21488
21489 @defun inferiors
21490 Return a tuple containing all inferior objects.
21491 @end defun
21492
21493 A @code{gdb.Inferior} object has the following attributes:
21494
21495 @table @code
21496 @defivar Inferior num
21497 ID of inferior, as assigned by GDB.
21498 @end defivar
21499
21500 @defivar Inferior pid
21501 Process ID of the inferior, as assigned by the underlying operating
21502 system.
21503 @end defivar
21504
21505 @defivar Inferior was_attached
21506 Boolean signaling whether the inferior was created using `attach', or
21507 started by @value{GDBN} itself.
21508 @end defivar
21509 @end table
21510
21511 A @code{gdb.Inferior} object has the following methods:
21512
21513 @table @code
21514 @defmethod Inferior threads
21515 This method returns a tuple holding all the threads which are valid
21516 when it is called. If there are no valid threads, the method will
21517 return an empty tuple.
21518 @end defmethod
21519
21520 @findex gdb.read_memory
21521 @defmethod Inferior read_memory address length
21522 Read @var{length} bytes of memory from the inferior, starting at
21523 @var{address}. Returns a buffer object, which behaves much like an array
21524 or a string. It can be modified and given to the @code{gdb.write_memory}
21525 function.
21526 @end defmethod
21527
21528 @findex gdb.write_memory
21529 @defmethod Inferior write_memory address buffer @r{[}length@r{]}
21530 Write the contents of @var{buffer} to the inferior, starting at
21531 @var{address}. The @var{buffer} parameter must be a Python object
21532 which supports the buffer protocol, i.e., a string, an array or the
21533 object returned from @code{gdb.read_memory}. If given, @var{length}
21534 determines the number of bytes from @var{buffer} to be written.
21535 @end defmethod
21536
21537 @findex gdb.search_memory
21538 @defmethod Inferior search_memory address length pattern
21539 Search a region of the inferior memory starting at @var{address} with
21540 the given @var{length} using the search pattern supplied in
21541 @var{pattern}. The @var{pattern} parameter must be a Python object
21542 which supports the buffer protocol, i.e., a string, an array or the
21543 object returned from @code{gdb.read_memory}. Returns a Python @code{Long}
21544 containing the address where the pattern was found, or @code{None} if
21545 the pattern could not be found.
21546 @end defmethod
21547 @end table
21548
21549 @node Threads In Python
21550 @subsubsection Threads In Python
21551 @cindex threads in python
21552
21553 @findex gdb.InferiorThread
21554 Python scripts can access information about, and manipulate inferior threads
21555 controlled by @value{GDBN}, via objects of the @code{gdb.InferiorThread} class.
21556
21557 The following thread-related functions are available in the @code{gdb}
21558 module:
21559
21560 @findex gdb.selected_thread
21561 @defun selected_thread
21562 This function returns the thread object for the selected thread. If there
21563 is no selected thread, this will return @code{None}.
21564 @end defun
21565
21566 A @code{gdb.InferiorThread} object has the following attributes:
21567
21568 @table @code
21569 @defivar InferiorThread num
21570 ID of the thread, as assigned by GDB.
21571 @end defivar
21572
21573 @defivar InferiorThread ptid
21574 ID of the thread, as assigned by the operating system. This attribute is a
21575 tuple containing three integers. The first is the Process ID (PID); the second
21576 is the Lightweight Process ID (LWPID), and the third is the Thread ID (TID).
21577 Either the LWPID or TID may be 0, which indicates that the operating system
21578 does not use that identifier.
21579 @end defivar
21580 @end table
21581
21582 A @code{gdb.InferiorThread} object has the following methods:
21583
21584 @table @code
21585 @defmethod InferiorThread switch
21586 This changes @value{GDBN}'s currently selected thread to the one represented
21587 by this object.
21588 @end defmethod
21589
21590 @defmethod InferiorThread is_stopped
21591 Return a Boolean indicating whether the thread is stopped.
21592 @end defmethod
21593
21594 @defmethod InferiorThread is_running
21595 Return a Boolean indicating whether the thread is running.
21596 @end defmethod
21597
21598 @defmethod InferiorThread is_exited
21599 Return a Boolean indicating whether the thread is exited.
21600 @end defmethod
21601 @end table
21602
21603 @node Commands In Python
21604 @subsubsection Commands In Python
21605
21606 @cindex commands in python
21607 @cindex python commands
21608 You can implement new @value{GDBN} CLI commands in Python. A CLI
21609 command is implemented using an instance of the @code{gdb.Command}
21610 class, most commonly using a subclass.
21611
21612 @defmethod Command __init__ name @var{command_class} @r{[}@var{completer_class}@r{]} @r{[}@var{prefix}@r{]}
21613 The object initializer for @code{Command} registers the new command
21614 with @value{GDBN}. This initializer is normally invoked from the
21615 subclass' own @code{__init__} method.
21616
21617 @var{name} is the name of the command. If @var{name} consists of
21618 multiple words, then the initial words are looked for as prefix
21619 commands. In this case, if one of the prefix commands does not exist,
21620 an exception is raised.
21621
21622 There is no support for multi-line commands.
21623
21624 @var{command_class} should be one of the @samp{COMMAND_} constants
21625 defined below. This argument tells @value{GDBN} how to categorize the
21626 new command in the help system.
21627
21628 @var{completer_class} is an optional argument. If given, it should be
21629 one of the @samp{COMPLETE_} constants defined below. This argument
21630 tells @value{GDBN} how to perform completion for this command. If not
21631 given, @value{GDBN} will attempt to complete using the object's
21632 @code{complete} method (see below); if no such method is found, an
21633 error will occur when completion is attempted.
21634
21635 @var{prefix} is an optional argument. If @code{True}, then the new
21636 command is a prefix command; sub-commands of this command may be
21637 registered.
21638
21639 The help text for the new command is taken from the Python
21640 documentation string for the command's class, if there is one. If no
21641 documentation string is provided, the default value ``This command is
21642 not documented.'' is used.
21643 @end defmethod
21644
21645 @cindex don't repeat Python command
21646 @defmethod Command dont_repeat
21647 By default, a @value{GDBN} command is repeated when the user enters a
21648 blank line at the command prompt. A command can suppress this
21649 behavior by invoking the @code{dont_repeat} method. This is similar
21650 to the user command @code{dont-repeat}, see @ref{Define, dont-repeat}.
21651 @end defmethod
21652
21653 @defmethod Command invoke argument from_tty
21654 This method is called by @value{GDBN} when this command is invoked.
21655
21656 @var{argument} is a string. It is the argument to the command, after
21657 leading and trailing whitespace has been stripped.
21658
21659 @var{from_tty} is a boolean argument. When true, this means that the
21660 command was entered by the user at the terminal; when false it means
21661 that the command came from elsewhere.
21662
21663 If this method throws an exception, it is turned into a @value{GDBN}
21664 @code{error} call. Otherwise, the return value is ignored.
21665
21666 @findex gdb.string_to_argv
21667 To break @var{argument} up into an argv-like string use
21668 @code{gdb.string_to_argv}. This function behaves identically to
21669 @value{GDBN}'s internal argument lexer @code{buildargv}.
21670 It is recommended to use this for consistency.
21671 Arguments are separated by spaces and may be quoted.
21672 Example:
21673
21674 @smallexample
21675 print gdb.string_to_argv ("1 2\ \\\"3 '4 \"5' \"6 '7\"")
21676 ['1', '2 "3', '4 "5', "6 '7"]
21677 @end smallexample
21678
21679 @end defmethod
21680
21681 @cindex completion of Python commands
21682 @defmethod Command complete text word
21683 This method is called by @value{GDBN} when the user attempts
21684 completion on this command. All forms of completion are handled by
21685 this method, that is, the @key{TAB} and @key{M-?} key bindings
21686 (@pxref{Completion}), and the @code{complete} command (@pxref{Help,
21687 complete}).
21688
21689 The arguments @var{text} and @var{word} are both strings. @var{text}
21690 holds the complete command line up to the cursor's location.
21691 @var{word} holds the last word of the command line; this is computed
21692 using a word-breaking heuristic.
21693
21694 The @code{complete} method can return several values:
21695 @itemize @bullet
21696 @item
21697 If the return value is a sequence, the contents of the sequence are
21698 used as the completions. It is up to @code{complete} to ensure that the
21699 contents actually do complete the word. A zero-length sequence is
21700 allowed, it means that there were no completions available. Only
21701 string elements of the sequence are used; other elements in the
21702 sequence are ignored.
21703
21704 @item
21705 If the return value is one of the @samp{COMPLETE_} constants defined
21706 below, then the corresponding @value{GDBN}-internal completion
21707 function is invoked, and its result is used.
21708
21709 @item
21710 All other results are treated as though there were no available
21711 completions.
21712 @end itemize
21713 @end defmethod
21714
21715 When a new command is registered, it must be declared as a member of
21716 some general class of commands. This is used to classify top-level
21717 commands in the on-line help system; note that prefix commands are not
21718 listed under their own category but rather that of their top-level
21719 command. The available classifications are represented by constants
21720 defined in the @code{gdb} module:
21721
21722 @table @code
21723 @findex COMMAND_NONE
21724 @findex gdb.COMMAND_NONE
21725 @item COMMAND_NONE
21726 The command does not belong to any particular class. A command in
21727 this category will not be displayed in any of the help categories.
21728
21729 @findex COMMAND_RUNNING
21730 @findex gdb.COMMAND_RUNNING
21731 @item COMMAND_RUNNING
21732 The command is related to running the inferior. For example,
21733 @code{start}, @code{step}, and @code{continue} are in this category.
21734 Type @kbd{help running} at the @value{GDBN} prompt to see a list of
21735 commands in this category.
21736
21737 @findex COMMAND_DATA
21738 @findex gdb.COMMAND_DATA
21739 @item COMMAND_DATA
21740 The command is related to data or variables. For example,
21741 @code{call}, @code{find}, and @code{print} are in this category. Type
21742 @kbd{help data} at the @value{GDBN} prompt to see a list of commands
21743 in this category.
21744
21745 @findex COMMAND_STACK
21746 @findex gdb.COMMAND_STACK
21747 @item COMMAND_STACK
21748 The command has to do with manipulation of the stack. For example,
21749 @code{backtrace}, @code{frame}, and @code{return} are in this
21750 category. Type @kbd{help stack} at the @value{GDBN} prompt to see a
21751 list of commands in this category.
21752
21753 @findex COMMAND_FILES
21754 @findex gdb.COMMAND_FILES
21755 @item COMMAND_FILES
21756 This class is used for file-related commands. For example,
21757 @code{file}, @code{list} and @code{section} are in this category.
21758 Type @kbd{help files} at the @value{GDBN} prompt to see a list of
21759 commands in this category.
21760
21761 @findex COMMAND_SUPPORT
21762 @findex gdb.COMMAND_SUPPORT
21763 @item COMMAND_SUPPORT
21764 This should be used for ``support facilities'', generally meaning
21765 things that are useful to the user when interacting with @value{GDBN},
21766 but not related to the state of the inferior. For example,
21767 @code{help}, @code{make}, and @code{shell} are in this category. Type
21768 @kbd{help support} at the @value{GDBN} prompt to see a list of
21769 commands in this category.
21770
21771 @findex COMMAND_STATUS
21772 @findex gdb.COMMAND_STATUS
21773 @item COMMAND_STATUS
21774 The command is an @samp{info}-related command, that is, related to the
21775 state of @value{GDBN} itself. For example, @code{info}, @code{macro},
21776 and @code{show} are in this category. Type @kbd{help status} at the
21777 @value{GDBN} prompt to see a list of commands in this category.
21778
21779 @findex COMMAND_BREAKPOINTS
21780 @findex gdb.COMMAND_BREAKPOINTS
21781 @item COMMAND_BREAKPOINTS
21782 The command has to do with breakpoints. For example, @code{break},
21783 @code{clear}, and @code{delete} are in this category. Type @kbd{help
21784 breakpoints} at the @value{GDBN} prompt to see a list of commands in
21785 this category.
21786
21787 @findex COMMAND_TRACEPOINTS
21788 @findex gdb.COMMAND_TRACEPOINTS
21789 @item COMMAND_TRACEPOINTS
21790 The command has to do with tracepoints. For example, @code{trace},
21791 @code{actions}, and @code{tfind} are in this category. Type
21792 @kbd{help tracepoints} at the @value{GDBN} prompt to see a list of
21793 commands in this category.
21794
21795 @findex COMMAND_OBSCURE
21796 @findex gdb.COMMAND_OBSCURE
21797 @item COMMAND_OBSCURE
21798 The command is only used in unusual circumstances, or is not of
21799 general interest to users. For example, @code{checkpoint},
21800 @code{fork}, and @code{stop} are in this category. Type @kbd{help
21801 obscure} at the @value{GDBN} prompt to see a list of commands in this
21802 category.
21803
21804 @findex COMMAND_MAINTENANCE
21805 @findex gdb.COMMAND_MAINTENANCE
21806 @item COMMAND_MAINTENANCE
21807 The command is only useful to @value{GDBN} maintainers. The
21808 @code{maintenance} and @code{flushregs} commands are in this category.
21809 Type @kbd{help internals} at the @value{GDBN} prompt to see a list of
21810 commands in this category.
21811 @end table
21812
21813 A new command can use a predefined completion function, either by
21814 specifying it via an argument at initialization, or by returning it
21815 from the @code{complete} method. These predefined completion
21816 constants are all defined in the @code{gdb} module:
21817
21818 @table @code
21819 @findex COMPLETE_NONE
21820 @findex gdb.COMPLETE_NONE
21821 @item COMPLETE_NONE
21822 This constant means that no completion should be done.
21823
21824 @findex COMPLETE_FILENAME
21825 @findex gdb.COMPLETE_FILENAME
21826 @item COMPLETE_FILENAME
21827 This constant means that filename completion should be performed.
21828
21829 @findex COMPLETE_LOCATION
21830 @findex gdb.COMPLETE_LOCATION
21831 @item COMPLETE_LOCATION
21832 This constant means that location completion should be done.
21833 @xref{Specify Location}.
21834
21835 @findex COMPLETE_COMMAND
21836 @findex gdb.COMPLETE_COMMAND
21837 @item COMPLETE_COMMAND
21838 This constant means that completion should examine @value{GDBN}
21839 command names.
21840
21841 @findex COMPLETE_SYMBOL
21842 @findex gdb.COMPLETE_SYMBOL
21843 @item COMPLETE_SYMBOL
21844 This constant means that completion should be done using symbol names
21845 as the source.
21846 @end table
21847
21848 The following code snippet shows how a trivial CLI command can be
21849 implemented in Python:
21850
21851 @smallexample
21852 class HelloWorld (gdb.Command):
21853 """Greet the whole world."""
21854
21855 def __init__ (self):
21856 super (HelloWorld, self).__init__ ("hello-world", gdb.COMMAND_OBSCURE)
21857
21858 def invoke (self, arg, from_tty):
21859 print "Hello, World!"
21860
21861 HelloWorld ()
21862 @end smallexample
21863
21864 The last line instantiates the class, and is necessary to trigger the
21865 registration of the command with @value{GDBN}. Depending on how the
21866 Python code is read into @value{GDBN}, you may need to import the
21867 @code{gdb} module explicitly.
21868
21869 @node Parameters In Python
21870 @subsubsection Parameters In Python
21871
21872 @cindex parameters in python
21873 @cindex python parameters
21874 @tindex gdb.Parameter
21875 @tindex Parameter
21876 You can implement new @value{GDBN} parameters using Python. A new
21877 parameter is implemented as an instance of the @code{gdb.Parameter}
21878 class.
21879
21880 Parameters are exposed to the user via the @code{set} and
21881 @code{show} commands. @xref{Help}.
21882
21883 There are many parameters that already exist and can be set in
21884 @value{GDBN}. Two examples are: @code{set follow fork} and
21885 @code{set charset}. Setting these parameters influences certain
21886 behavior in @value{GDBN}. Similarly, you can define parameters that
21887 can be used to influence behavior in custom Python scripts and commands.
21888
21889 @defmethod Parameter __init__ name @var{command-class} @var{parameter-class} @r{[}@var{enum-sequence}@r{]}
21890 The object initializer for @code{Parameter} registers the new
21891 parameter with @value{GDBN}. This initializer is normally invoked
21892 from the subclass' own @code{__init__} method.
21893
21894 @var{name} is the name of the new parameter. If @var{name} consists
21895 of multiple words, then the initial words are looked for as prefix
21896 parameters. An example of this can be illustrated with the
21897 @code{set print} set of parameters. If @var{name} is
21898 @code{print foo}, then @code{print} will be searched as the prefix
21899 parameter. In this case the parameter can subsequently be accessed in
21900 @value{GDBN} as @code{set print foo}.
21901
21902 If @var{name} consists of multiple words, and no prefix parameter group
21903 can be found, an exception is raised.
21904
21905 @var{command-class} should be one of the @samp{COMMAND_} constants
21906 (@pxref{Commands In Python}). This argument tells @value{GDBN} how to
21907 categorize the new parameter in the help system.
21908
21909 @var{parameter-class} should be one of the @samp{PARAM_} constants
21910 defined below. This argument tells @value{GDBN} the type of the new
21911 parameter; this information is used for input validation and
21912 completion.
21913
21914 If @var{parameter-class} is @code{PARAM_ENUM}, then
21915 @var{enum-sequence} must be a sequence of strings. These strings
21916 represent the possible values for the parameter.
21917
21918 If @var{parameter-class} is not @code{PARAM_ENUM}, then the presence
21919 of a fourth argument will cause an exception to be thrown.
21920
21921 The help text for the new parameter is taken from the Python
21922 documentation string for the parameter's class, if there is one. If
21923 there is no documentation string, a default value is used.
21924 @end defmethod
21925
21926 @defivar Parameter set_doc
21927 If this attribute exists, and is a string, then its value is used as
21928 the help text for this parameter's @code{set} command. The value is
21929 examined when @code{Parameter.__init__} is invoked; subsequent changes
21930 have no effect.
21931 @end defivar
21932
21933 @defivar Parameter show_doc
21934 If this attribute exists, and is a string, then its value is used as
21935 the help text for this parameter's @code{show} command. The value is
21936 examined when @code{Parameter.__init__} is invoked; subsequent changes
21937 have no effect.
21938 @end defivar
21939
21940 @defivar Parameter value
21941 The @code{value} attribute holds the underlying value of the
21942 parameter. It can be read and assigned to just as any other
21943 attribute. @value{GDBN} does validation when assignments are made.
21944 @end defivar
21945
21946
21947 When a new parameter is defined, its type must be specified. The
21948 available types are represented by constants defined in the @code{gdb}
21949 module:
21950
21951 @table @code
21952 @findex PARAM_BOOLEAN
21953 @findex gdb.PARAM_BOOLEAN
21954 @item PARAM_BOOLEAN
21955 The value is a plain boolean. The Python boolean values, @code{True}
21956 and @code{False} are the only valid values.
21957
21958 @findex PARAM_AUTO_BOOLEAN
21959 @findex gdb.PARAM_AUTO_BOOLEAN
21960 @item PARAM_AUTO_BOOLEAN
21961 The value has three possible states: true, false, and @samp{auto}. In
21962 Python, true and false are represented using boolean constants, and
21963 @samp{auto} is represented using @code{None}.
21964
21965 @findex PARAM_UINTEGER
21966 @findex gdb.PARAM_UINTEGER
21967 @item PARAM_UINTEGER
21968 The value is an unsigned integer. The value of 0 should be
21969 interpreted to mean ``unlimited''.
21970
21971 @findex PARAM_INTEGER
21972 @findex gdb.PARAM_INTEGER
21973 @item PARAM_INTEGER
21974 The value is a signed integer. The value of 0 should be interpreted
21975 to mean ``unlimited''.
21976
21977 @findex PARAM_STRING
21978 @findex gdb.PARAM_STRING
21979 @item PARAM_STRING
21980 The value is a string. When the user modifies the string, any escape
21981 sequences, such as @samp{\t}, @samp{\f}, and octal escapes, are
21982 translated into corresponding characters and encoded into the current
21983 host charset.
21984
21985 @findex PARAM_STRING_NOESCAPE
21986 @findex gdb.PARAM_STRING_NOESCAPE
21987 @item PARAM_STRING_NOESCAPE
21988 The value is a string. When the user modifies the string, escapes are
21989 passed through untranslated.
21990
21991 @findex PARAM_OPTIONAL_FILENAME
21992 @findex gdb.PARAM_OPTIONAL_FILENAME
21993 @item PARAM_OPTIONAL_FILENAME
21994 The value is a either a filename (a string), or @code{None}.
21995
21996 @findex PARAM_FILENAME
21997 @findex gdb.PARAM_FILENAME
21998 @item PARAM_FILENAME
21999 The value is a filename. This is just like
22000 @code{PARAM_STRING_NOESCAPE}, but uses file names for completion.
22001
22002 @findex PARAM_ZINTEGER
22003 @findex gdb.PARAM_ZINTEGER
22004 @item PARAM_ZINTEGER
22005 The value is an integer. This is like @code{PARAM_INTEGER}, except 0
22006 is interpreted as itself.
22007
22008 @findex PARAM_ENUM
22009 @findex gdb.PARAM_ENUM
22010 @item PARAM_ENUM
22011 The value is a string, which must be one of a collection string
22012 constants provided when the parameter is created.
22013 @end table
22014
22015 @node Functions In Python
22016 @subsubsection Writing new convenience functions
22017
22018 @cindex writing convenience functions
22019 @cindex convenience functions in python
22020 @cindex python convenience functions
22021 @tindex gdb.Function
22022 @tindex Function
22023 You can implement new convenience functions (@pxref{Convenience Vars})
22024 in Python. A convenience function is an instance of a subclass of the
22025 class @code{gdb.Function}.
22026
22027 @defmethod Function __init__ name
22028 The initializer for @code{Function} registers the new function with
22029 @value{GDBN}. The argument @var{name} is the name of the function,
22030 a string. The function will be visible to the user as a convenience
22031 variable of type @code{internal function}, whose name is the same as
22032 the given @var{name}.
22033
22034 The documentation for the new function is taken from the documentation
22035 string for the new class.
22036 @end defmethod
22037
22038 @defmethod Function invoke @var{*args}
22039 When a convenience function is evaluated, its arguments are converted
22040 to instances of @code{gdb.Value}, and then the function's
22041 @code{invoke} method is called. Note that @value{GDBN} does not
22042 predetermine the arity of convenience functions. Instead, all
22043 available arguments are passed to @code{invoke}, following the
22044 standard Python calling convention. In particular, a convenience
22045 function can have default values for parameters without ill effect.
22046
22047 The return value of this method is used as its value in the enclosing
22048 expression. If an ordinary Python value is returned, it is converted
22049 to a @code{gdb.Value} following the usual rules.
22050 @end defmethod
22051
22052 The following code snippet shows how a trivial convenience function can
22053 be implemented in Python:
22054
22055 @smallexample
22056 class Greet (gdb.Function):
22057 """Return string to greet someone.
22058 Takes a name as argument."""
22059
22060 def __init__ (self):
22061 super (Greet, self).__init__ ("greet")
22062
22063 def invoke (self, name):
22064 return "Hello, %s!" % name.string ()
22065
22066 Greet ()
22067 @end smallexample
22068
22069 The last line instantiates the class, and is necessary to trigger the
22070 registration of the function with @value{GDBN}. Depending on how the
22071 Python code is read into @value{GDBN}, you may need to import the
22072 @code{gdb} module explicitly.
22073
22074 @node Progspaces In Python
22075 @subsubsection Program Spaces In Python
22076
22077 @cindex progspaces in python
22078 @tindex gdb.Progspace
22079 @tindex Progspace
22080 A program space, or @dfn{progspace}, represents a symbolic view
22081 of an address space.
22082 It consists of all of the objfiles of the program.
22083 @xref{Objfiles In Python}.
22084 @xref{Inferiors and Programs, program spaces}, for more details
22085 about program spaces.
22086
22087 The following progspace-related functions are available in the
22088 @code{gdb} module:
22089
22090 @findex gdb.current_progspace
22091 @defun current_progspace
22092 This function returns the program space of the currently selected inferior.
22093 @xref{Inferiors and Programs}.
22094 @end defun
22095
22096 @findex gdb.progspaces
22097 @defun progspaces
22098 Return a sequence of all the progspaces currently known to @value{GDBN}.
22099 @end defun
22100
22101 Each progspace is represented by an instance of the @code{gdb.Progspace}
22102 class.
22103
22104 @defivar Progspace filename
22105 The file name of the progspace as a string.
22106 @end defivar
22107
22108 @defivar Progspace pretty_printers
22109 The @code{pretty_printers} attribute is a list of functions. It is
22110 used to look up pretty-printers. A @code{Value} is passed to each
22111 function in order; if the function returns @code{None}, then the
22112 search continues. Otherwise, the return value should be an object
22113 which is used to format the value. @xref{Pretty Printing API}, for more
22114 information.
22115 @end defivar
22116
22117 @node Objfiles In Python
22118 @subsubsection Objfiles In Python
22119
22120 @cindex objfiles in python
22121 @tindex gdb.Objfile
22122 @tindex Objfile
22123 @value{GDBN} loads symbols for an inferior from various
22124 symbol-containing files (@pxref{Files}). These include the primary
22125 executable file, any shared libraries used by the inferior, and any
22126 separate debug info files (@pxref{Separate Debug Files}).
22127 @value{GDBN} calls these symbol-containing files @dfn{objfiles}.
22128
22129 The following objfile-related functions are available in the
22130 @code{gdb} module:
22131
22132 @findex gdb.current_objfile
22133 @defun current_objfile
22134 When auto-loading a Python script (@pxref{Auto-loading}), @value{GDBN}
22135 sets the ``current objfile'' to the corresponding objfile. This
22136 function returns the current objfile. If there is no current objfile,
22137 this function returns @code{None}.
22138 @end defun
22139
22140 @findex gdb.objfiles
22141 @defun objfiles
22142 Return a sequence of all the objfiles current known to @value{GDBN}.
22143 @xref{Objfiles In Python}.
22144 @end defun
22145
22146 Each objfile is represented by an instance of the @code{gdb.Objfile}
22147 class.
22148
22149 @defivar Objfile filename
22150 The file name of the objfile as a string.
22151 @end defivar
22152
22153 @defivar Objfile pretty_printers
22154 The @code{pretty_printers} attribute is a list of functions. It is
22155 used to look up pretty-printers. A @code{Value} is passed to each
22156 function in order; if the function returns @code{None}, then the
22157 search continues. Otherwise, the return value should be an object
22158 which is used to format the value. @xref{Pretty Printing API}, for more
22159 information.
22160 @end defivar
22161
22162 @node Frames In Python
22163 @subsubsection Accessing inferior stack frames from Python.
22164
22165 @cindex frames in python
22166 When the debugged program stops, @value{GDBN} is able to analyze its call
22167 stack (@pxref{Frames,,Stack frames}). The @code{gdb.Frame} class
22168 represents a frame in the stack. A @code{gdb.Frame} object is only valid
22169 while its corresponding frame exists in the inferior's stack. If you try
22170 to use an invalid frame object, @value{GDBN} will throw a @code{RuntimeError}
22171 exception.
22172
22173 Two @code{gdb.Frame} objects can be compared for equality with the @code{==}
22174 operator, like:
22175
22176 @smallexample
22177 (@value{GDBP}) python print gdb.newest_frame() == gdb.selected_frame ()
22178 True
22179 @end smallexample
22180
22181 The following frame-related functions are available in the @code{gdb} module:
22182
22183 @findex gdb.selected_frame
22184 @defun selected_frame
22185 Return the selected frame object. (@pxref{Selection,,Selecting a Frame}).
22186 @end defun
22187
22188 @defun frame_stop_reason_string reason
22189 Return a string explaining the reason why @value{GDBN} stopped unwinding
22190 frames, as expressed by the given @var{reason} code (an integer, see the
22191 @code{unwind_stop_reason} method further down in this section).
22192 @end defun
22193
22194 A @code{gdb.Frame} object has the following methods:
22195
22196 @table @code
22197 @defmethod Frame is_valid
22198 Returns true if the @code{gdb.Frame} object is valid, false if not.
22199 A frame object can become invalid if the frame it refers to doesn't
22200 exist anymore in the inferior. All @code{gdb.Frame} methods will throw
22201 an exception if it is invalid at the time the method is called.
22202 @end defmethod
22203
22204 @defmethod Frame name
22205 Returns the function name of the frame, or @code{None} if it can't be
22206 obtained.
22207 @end defmethod
22208
22209 @defmethod Frame type
22210 Returns the type of the frame. The value can be one of
22211 @code{gdb.NORMAL_FRAME}, @code{gdb.DUMMY_FRAME}, @code{gdb.SIGTRAMP_FRAME}
22212 or @code{gdb.SENTINEL_FRAME}.
22213 @end defmethod
22214
22215 @defmethod Frame unwind_stop_reason
22216 Return an integer representing the reason why it's not possible to find
22217 more frames toward the outermost frame. Use
22218 @code{gdb.frame_stop_reason_string} to convert the value returned by this
22219 function to a string.
22220 @end defmethod
22221
22222 @defmethod Frame pc
22223 Returns the frame's resume address.
22224 @end defmethod
22225
22226 @defmethod Frame block
22227 Return the frame's code block. @xref{Blocks In Python}.
22228 @end defmethod
22229
22230 @defmethod Frame function
22231 Return the symbol for the function corresponding to this frame.
22232 @xref{Symbols In Python}.
22233 @end defmethod
22234
22235 @defmethod Frame older
22236 Return the frame that called this frame.
22237 @end defmethod
22238
22239 @defmethod Frame newer
22240 Return the frame called by this frame.
22241 @end defmethod
22242
22243 @defmethod Frame find_sal
22244 Return the frame's symtab and line object.
22245 @xref{Symbol Tables In Python}.
22246 @end defmethod
22247
22248 @defmethod Frame read_var variable @r{[}block@r{]}
22249 Return the value of @var{variable} in this frame. If the optional
22250 argument @var{block} is provided, search for the variable from that
22251 block; otherwise start at the frame's current block (which is
22252 determined by the frame's current program counter). @var{variable}
22253 must be a string or a @code{gdb.Symbol} object. @var{block} must be a
22254 @code{gdb.Block} object.
22255 @end defmethod
22256
22257 @defmethod Frame select
22258 Set this frame to be the selected frame. @xref{Stack, ,Examining the
22259 Stack}.
22260 @end defmethod
22261 @end table
22262
22263 @node Blocks In Python
22264 @subsubsection Accessing frame blocks from Python.
22265
22266 @cindex blocks in python
22267 @tindex gdb.Block
22268
22269 Within each frame, @value{GDBN} maintains information on each block
22270 stored in that frame. These blocks are organized hierarchically, and
22271 are represented individually in Python as a @code{gdb.Block}.
22272 Please see @ref{Frames In Python}, for a more in-depth discussion on
22273 frames. Furthermore, see @ref{Stack, ,Examining the Stack}, for more
22274 detailed technical information on @value{GDBN}'s book-keeping of the
22275 stack.
22276
22277 The following block-related functions are available in the @code{gdb}
22278 module:
22279
22280 @findex gdb.block_for_pc
22281 @defun block_for_pc pc
22282 Return the @code{gdb.Block} containing the given @var{pc} value. If the
22283 block cannot be found for the @var{pc} value specified, the function
22284 will return @code{None}.
22285 @end defun
22286
22287 A @code{gdb.Block} object has the following attributes:
22288
22289 @table @code
22290 @defivar Block start
22291 The start address of the block. This attribute is not writable.
22292 @end defivar
22293
22294 @defivar Block end
22295 The end address of the block. This attribute is not writable.
22296 @end defivar
22297
22298 @defivar Block function
22299 The name of the block represented as a @code{gdb.Symbol}. If the
22300 block is not named, then this attribute holds @code{None}. This
22301 attribute is not writable.
22302 @end defivar
22303
22304 @defivar Block superblock
22305 The block containing this block. If this parent block does not exist,
22306 this attribute holds @code{None}. This attribute is not writable.
22307 @end defivar
22308 @end table
22309
22310 @node Symbols In Python
22311 @subsubsection Python representation of Symbols.
22312
22313 @cindex symbols in python
22314 @tindex gdb.Symbol
22315
22316 @value{GDBN} represents every variable, function and type as an
22317 entry in a symbol table. @xref{Symbols, ,Examining the Symbol Table}.
22318 Similarly, Python represents these symbols in @value{GDBN} with the
22319 @code{gdb.Symbol} object.
22320
22321 The following symbol-related functions are available in the @code{gdb}
22322 module:
22323
22324 @findex gdb.lookup_symbol
22325 @defun lookup_symbol name [block] [domain]
22326 This function searches for a symbol by name. The search scope can be
22327 restricted to the parameters defined in the optional domain and block
22328 arguments.
22329
22330 @var{name} is the name of the symbol. It must be a string. The
22331 optional @var{block} argument restricts the search to symbols visible
22332 in that @var{block}. The @var{block} argument must be a
22333 @code{gdb.Block} object. The optional @var{domain} argument restricts
22334 the search to the domain type. The @var{domain} argument must be a
22335 domain constant defined in the @code{gdb} module and described later
22336 in this chapter.
22337 @end defun
22338
22339 A @code{gdb.Symbol} object has the following attributes:
22340
22341 @table @code
22342 @defivar Symbol symtab
22343 The symbol table in which the symbol appears. This attribute is
22344 represented as a @code{gdb.Symtab} object. @xref{Symbol Tables In
22345 Python}. This attribute is not writable.
22346 @end defivar
22347
22348 @defivar Symbol name
22349 The name of the symbol as a string. This attribute is not writable.
22350 @end defivar
22351
22352 @defivar Symbol linkage_name
22353 The name of the symbol, as used by the linker (i.e., may be mangled).
22354 This attribute is not writable.
22355 @end defivar
22356
22357 @defivar Symbol print_name
22358 The name of the symbol in a form suitable for output. This is either
22359 @code{name} or @code{linkage_name}, depending on whether the user
22360 asked @value{GDBN} to display demangled or mangled names.
22361 @end defivar
22362
22363 @defivar Symbol addr_class
22364 The address class of the symbol. This classifies how to find the value
22365 of a symbol. Each address class is a constant defined in the
22366 @code{gdb} module and described later in this chapter.
22367 @end defivar
22368
22369 @defivar Symbol is_argument
22370 @code{True} if the symbol is an argument of a function.
22371 @end defivar
22372
22373 @defivar Symbol is_constant
22374 @code{True} if the symbol is a constant.
22375 @end defivar
22376
22377 @defivar Symbol is_function
22378 @code{True} if the symbol is a function or a method.
22379 @end defivar
22380
22381 @defivar Symbol is_variable
22382 @code{True} if the symbol is a variable.
22383 @end defivar
22384 @end table
22385
22386 The available domain categories in @code{gdb.Symbol} are represented
22387 as constants in the @code{gdb} module:
22388
22389 @table @code
22390 @findex SYMBOL_UNDEF_DOMAIN
22391 @findex gdb.SYMBOL_UNDEF_DOMAIN
22392 @item SYMBOL_UNDEF_DOMAIN
22393 This is used when a domain has not been discovered or none of the
22394 following domains apply. This usually indicates an error either
22395 in the symbol information or in @value{GDBN}'s handling of symbols.
22396 @findex SYMBOL_VAR_DOMAIN
22397 @findex gdb.SYMBOL_VAR_DOMAIN
22398 @item SYMBOL_VAR_DOMAIN
22399 This domain contains variables, function names, typedef names and enum
22400 type values.
22401 @findex SYMBOL_STRUCT_DOMAIN
22402 @findex gdb.SYMBOL_STRUCT_DOMAIN
22403 @item SYMBOL_STRUCT_DOMAIN
22404 This domain holds struct, union and enum type names.
22405 @findex SYMBOL_LABEL_DOMAIN
22406 @findex gdb.SYMBOL_LABEL_DOMAIN
22407 @item SYMBOL_LABEL_DOMAIN
22408 This domain contains names of labels (for gotos).
22409 @findex SYMBOL_VARIABLES_DOMAIN
22410 @findex gdb.SYMBOL_VARIABLES_DOMAIN
22411 @item SYMBOL_VARIABLES_DOMAIN
22412 This domain holds a subset of the @code{SYMBOLS_VAR_DOMAIN}; it
22413 contains everything minus functions and types.
22414 @findex SYMBOL_FUNCTIONS_DOMAIN
22415 @findex gdb.SYMBOL_FUNCTIONS_DOMAIN
22416 @item SYMBOL_FUNCTION_DOMAIN
22417 This domain contains all functions.
22418 @findex SYMBOL_TYPES_DOMAIN
22419 @findex gdb.SYMBOL_TYPES_DOMAIN
22420 @item SYMBOL_TYPES_DOMAIN
22421 This domain contains all types.
22422 @end table
22423
22424 The available address class categories in @code{gdb.Symbol} are represented
22425 as constants in the @code{gdb} module:
22426
22427 @table @code
22428 @findex SYMBOL_LOC_UNDEF
22429 @findex gdb.SYMBOL_LOC_UNDEF
22430 @item SYMBOL_LOC_UNDEF
22431 If this is returned by address class, it indicates an error either in
22432 the symbol information or in @value{GDBN}'s handling of symbols.
22433 @findex SYMBOL_LOC_CONST
22434 @findex gdb.SYMBOL_LOC_CONST
22435 @item SYMBOL_LOC_CONST
22436 Value is constant int.
22437 @findex SYMBOL_LOC_STATIC
22438 @findex gdb.SYMBOL_LOC_STATIC
22439 @item SYMBOL_LOC_STATIC
22440 Value is at a fixed address.
22441 @findex SYMBOL_LOC_REGISTER
22442 @findex gdb.SYMBOL_LOC_REGISTER
22443 @item SYMBOL_LOC_REGISTER
22444 Value is in a register.
22445 @findex SYMBOL_LOC_ARG
22446 @findex gdb.SYMBOL_LOC_ARG
22447 @item SYMBOL_LOC_ARG
22448 Value is an argument. This value is at the offset stored within the
22449 symbol inside the frame's argument list.
22450 @findex SYMBOL_LOC_REF_ARG
22451 @findex gdb.SYMBOL_LOC_REF_ARG
22452 @item SYMBOL_LOC_REF_ARG
22453 Value address is stored in the frame's argument list. Just like
22454 @code{LOC_ARG} except that the value's address is stored at the
22455 offset, not the value itself.
22456 @findex SYMBOL_LOC_REGPARM_ADDR
22457 @findex gdb.SYMBOL_LOC_REGPARM_ADDR
22458 @item SYMBOL_LOC_REGPARM_ADDR
22459 Value is a specified register. Just like @code{LOC_REGISTER} except
22460 the register holds the address of the argument instead of the argument
22461 itself.
22462 @findex SYMBOL_LOC_LOCAL
22463 @findex gdb.SYMBOL_LOC_LOCAL
22464 @item SYMBOL_LOC_LOCAL
22465 Value is a local variable.
22466 @findex SYMBOL_LOC_TYPEDEF
22467 @findex gdb.SYMBOL_LOC_TYPEDEF
22468 @item SYMBOL_LOC_TYPEDEF
22469 Value not used. Symbols in the domain @code{SYMBOL_STRUCT_DOMAIN} all
22470 have this class.
22471 @findex SYMBOL_LOC_BLOCK
22472 @findex gdb.SYMBOL_LOC_BLOCK
22473 @item SYMBOL_LOC_BLOCK
22474 Value is a block.
22475 @findex SYMBOL_LOC_CONST_BYTES
22476 @findex gdb.SYMBOL_LOC_CONST_BYTES
22477 @item SYMBOL_LOC_CONST_BYTES
22478 Value is a byte-sequence.
22479 @findex SYMBOL_LOC_UNRESOLVED
22480 @findex gdb.SYMBOL_LOC_UNRESOLVED
22481 @item SYMBOL_LOC_UNRESOLVED
22482 Value is at a fixed address, but the address of the variable has to be
22483 determined from the minimal symbol table whenever the variable is
22484 referenced.
22485 @findex SYMBOL_LOC_OPTIMIZED_OUT
22486 @findex gdb.SYMBOL_LOC_OPTIMIZED_OUT
22487 @item SYMBOL_LOC_OPTIMIZED_OUT
22488 The value does not actually exist in the program.
22489 @findex SYMBOL_LOC_COMPUTED
22490 @findex gdb.SYMBOL_LOC_COMPUTED
22491 @item SYMBOL_LOC_COMPUTED
22492 The value's address is a computed location.
22493 @end table
22494
22495 @node Symbol Tables In Python
22496 @subsubsection Symbol table representation in Python.
22497
22498 @cindex symbol tables in python
22499 @tindex gdb.Symtab
22500 @tindex gdb.Symtab_and_line
22501
22502 Access to symbol table data maintained by @value{GDBN} on the inferior
22503 is exposed to Python via two objects: @code{gdb.Symtab_and_line} and
22504 @code{gdb.Symtab}. Symbol table and line data for a frame is returned
22505 from the @code{find_sal} method in @code{gdb.Frame} object.
22506 @xref{Frames In Python}.
22507
22508 For more information on @value{GDBN}'s symbol table management, see
22509 @ref{Symbols, ,Examining the Symbol Table}, for more information.
22510
22511 A @code{gdb.Symtab_and_line} object has the following attributes:
22512
22513 @table @code
22514 @defivar Symtab_and_line symtab
22515 The symbol table object (@code{gdb.Symtab}) for this frame.
22516 This attribute is not writable.
22517 @end defivar
22518
22519 @defivar Symtab_and_line pc
22520 Indicates the current program counter address. This attribute is not
22521 writable.
22522 @end defivar
22523
22524 @defivar Symtab_and_line line
22525 Indicates the current line number for this object. This
22526 attribute is not writable.
22527 @end defivar
22528 @end table
22529
22530 A @code{gdb.Symtab} object has the following attributes:
22531
22532 @table @code
22533 @defivar Symtab filename
22534 The symbol table's source filename. This attribute is not writable.
22535 @end defivar
22536
22537 @defivar Symtab objfile
22538 The symbol table's backing object file. @xref{Objfiles In Python}.
22539 This attribute is not writable.
22540 @end defivar
22541 @end table
22542
22543 The following methods are provided:
22544
22545 @table @code
22546 @defmethod Symtab fullname
22547 Return the symbol table's source absolute file name.
22548 @end defmethod
22549 @end table
22550
22551 @node Breakpoints In Python
22552 @subsubsection Manipulating breakpoints using Python
22553
22554 @cindex breakpoints in python
22555 @tindex gdb.Breakpoint
22556
22557 Python code can manipulate breakpoints via the @code{gdb.Breakpoint}
22558 class.
22559
22560 @defmethod Breakpoint __init__ spec @r{[}type@r{]} @r{[}wp_class@r{]}
22561 Create a new breakpoint. @var{spec} is a string naming the
22562 location of the breakpoint, or an expression that defines a
22563 watchpoint. The contents can be any location recognized by the
22564 @code{break} command, or in the case of a watchpoint, by the @code{watch}
22565 command. The optional @var{type} denotes the breakpoint to create
22566 from the types defined later in this chapter. This argument can be
22567 either: @code{BP_BREAKPOINT} or @code{BP_WATCHPOINT}. @var{type}
22568 defaults to @code{BP_BREAKPOINT}. The optional @var{wp_class}
22569 argument defines the class of watchpoint to create, if @var{type} is
22570 defined as @code{BP_WATCHPOINT}. If a watchpoint class is not
22571 provided, it is assumed to be a @var{WP_WRITE} class.
22572 @end defmethod
22573
22574 The available watchpoint types represented by constants are defined in the
22575 @code{gdb} module:
22576
22577 @table @code
22578 @findex WP_READ
22579 @findex gdb.WP_READ
22580 @item WP_READ
22581 Read only watchpoint.
22582
22583 @findex WP_WRITE
22584 @findex gdb.WP_WRITE
22585 @item WP_WRITE
22586 Write only watchpoint.
22587
22588 @findex WP_ACCESS
22589 @findex gdb.WP_ACCESS
22590 @item WP_ACCESS
22591 Read/Write watchpoint.
22592 @end table
22593
22594 @defmethod Breakpoint is_valid
22595 Return @code{True} if this @code{Breakpoint} object is valid,
22596 @code{False} otherwise. A @code{Breakpoint} object can become invalid
22597 if the user deletes the breakpoint. In this case, the object still
22598 exists, but the underlying breakpoint does not. In the cases of
22599 watchpoint scope, the watchpoint remains valid even if execution of the
22600 inferior leaves the scope of that watchpoint.
22601 @end defmethod
22602
22603 @defivar Breakpoint enabled
22604 This attribute is @code{True} if the breakpoint is enabled, and
22605 @code{False} otherwise. This attribute is writable.
22606 @end defivar
22607
22608 @defivar Breakpoint silent
22609 This attribute is @code{True} if the breakpoint is silent, and
22610 @code{False} otherwise. This attribute is writable.
22611
22612 Note that a breakpoint can also be silent if it has commands and the
22613 first command is @code{silent}. This is not reported by the
22614 @code{silent} attribute.
22615 @end defivar
22616
22617 @defivar Breakpoint thread
22618 If the breakpoint is thread-specific, this attribute holds the thread
22619 id. If the breakpoint is not thread-specific, this attribute is
22620 @code{None}. This attribute is writable.
22621 @end defivar
22622
22623 @defivar Breakpoint task
22624 If the breakpoint is Ada task-specific, this attribute holds the Ada task
22625 id. If the breakpoint is not task-specific (or the underlying
22626 language is not Ada), this attribute is @code{None}. This attribute
22627 is writable.
22628 @end defivar
22629
22630 @defivar Breakpoint ignore_count
22631 This attribute holds the ignore count for the breakpoint, an integer.
22632 This attribute is writable.
22633 @end defivar
22634
22635 @defivar Breakpoint number
22636 This attribute holds the breakpoint's number --- the identifier used by
22637 the user to manipulate the breakpoint. This attribute is not writable.
22638 @end defivar
22639
22640 @defivar Breakpoint type
22641 This attribute holds the breakpoint's type --- the identifier used to
22642 determine the actual breakpoint type or use-case. This attribute is not
22643 writable.
22644 @end defivar
22645
22646 The available types are represented by constants defined in the @code{gdb}
22647 module:
22648
22649 @table @code
22650 @findex BP_BREAKPOINT
22651 @findex gdb.BP_BREAKPOINT
22652 @item BP_BREAKPOINT
22653 Normal code breakpoint.
22654
22655 @findex BP_WATCHPOINT
22656 @findex gdb.BP_WATCHPOINT
22657 @item BP_WATCHPOINT
22658 Watchpoint breakpoint.
22659
22660 @findex BP_HARDWARE_WATCHPOINT
22661 @findex gdb.BP_HARDWARE_WATCHPOINT
22662 @item BP_HARDWARE_WATCHPOINT
22663 Hardware assisted watchpoint.
22664
22665 @findex BP_READ_WATCHPOINT
22666 @findex gdb.BP_READ_WATCHPOINT
22667 @item BP_READ_WATCHPOINT
22668 Hardware assisted read watchpoint.
22669
22670 @findex BP_ACCESS_WATCHPOINT
22671 @findex gdb.BP_ACCESS_WATCHPOINT
22672 @item BP_ACCESS_WATCHPOINT
22673 Hardware assisted access watchpoint.
22674 @end table
22675
22676 @defivar Breakpoint hit_count
22677 This attribute holds the hit count for the breakpoint, an integer.
22678 This attribute is writable, but currently it can only be set to zero.
22679 @end defivar
22680
22681 @defivar Breakpoint location
22682 This attribute holds the location of the breakpoint, as specified by
22683 the user. It is a string. If the breakpoint does not have a location
22684 (that is, it is a watchpoint) the attribute's value is @code{None}. This
22685 attribute is not writable.
22686 @end defivar
22687
22688 @defivar Breakpoint expression
22689 This attribute holds a breakpoint expression, as specified by
22690 the user. It is a string. If the breakpoint does not have an
22691 expression (the breakpoint is not a watchpoint) the attribute's value
22692 is @code{None}. This attribute is not writable.
22693 @end defivar
22694
22695 @defivar Breakpoint condition
22696 This attribute holds the condition of the breakpoint, as specified by
22697 the user. It is a string. If there is no condition, this attribute's
22698 value is @code{None}. This attribute is writable.
22699 @end defivar
22700
22701 @defivar Breakpoint commands
22702 This attribute holds the commands attached to the breakpoint. If
22703 there are commands, this attribute's value is a string holding all the
22704 commands, separated by newlines. If there are no commands, this
22705 attribute is @code{None}. This attribute is not writable.
22706 @end defivar
22707
22708 @node Lazy Strings In Python
22709 @subsubsection Python representation of lazy strings.
22710
22711 @cindex lazy strings in python
22712 @tindex gdb.LazyString
22713
22714 A @dfn{lazy string} is a string whose contents is not retrieved or
22715 encoded until it is needed.
22716
22717 A @code{gdb.LazyString} is represented in @value{GDBN} as an
22718 @code{address} that points to a region of memory, an @code{encoding}
22719 that will be used to encode that region of memory, and a @code{length}
22720 to delimit the region of memory that represents the string. The
22721 difference between a @code{gdb.LazyString} and a string wrapped within
22722 a @code{gdb.Value} is that a @code{gdb.LazyString} will be treated
22723 differently by @value{GDBN} when printing. A @code{gdb.LazyString} is
22724 retrieved and encoded during printing, while a @code{gdb.Value}
22725 wrapping a string is immediately retrieved and encoded on creation.
22726
22727 A @code{gdb.LazyString} object has the following functions:
22728
22729 @defmethod LazyString value
22730 Convert the @code{gdb.LazyString} to a @code{gdb.Value}. This value
22731 will point to the string in memory, but will lose all the delayed
22732 retrieval, encoding and handling that @value{GDBN} applies to a
22733 @code{gdb.LazyString}.
22734 @end defmethod
22735
22736 @defivar LazyString address
22737 This attribute holds the address of the string. This attribute is not
22738 writable.
22739 @end defivar
22740
22741 @defivar LazyString length
22742 This attribute holds the length of the string in characters. If the
22743 length is -1, then the string will be fetched and encoded up to the
22744 first null of appropriate width. This attribute is not writable.
22745 @end defivar
22746
22747 @defivar LazyString encoding
22748 This attribute holds the encoding that will be applied to the string
22749 when the string is printed by @value{GDBN}. If the encoding is not
22750 set, or contains an empty string, then @value{GDBN} will select the
22751 most appropriate encoding when the string is printed. This attribute
22752 is not writable.
22753 @end defivar
22754
22755 @defivar LazyString type
22756 This attribute holds the type that is represented by the lazy string's
22757 type. For a lazy string this will always be a pointer type. To
22758 resolve this to the lazy string's character type, use the type's
22759 @code{target} method. @xref{Types In Python}. This attribute is not
22760 writable.
22761 @end defivar
22762
22763 @node Auto-loading
22764 @subsection Auto-loading
22765 @cindex auto-loading, Python
22766
22767 When a new object file is read (for example, due to the @code{file}
22768 command, or because the inferior has loaded a shared library),
22769 @value{GDBN} will look for Python support scripts in several ways:
22770 @file{@var{objfile}-gdb.py} and @code{.debug_gdb_scripts} section.
22771
22772 @menu
22773 * objfile-gdb.py file:: The @file{@var{objfile}-gdb.py} file
22774 * .debug_gdb_scripts section:: The @code{.debug_gdb_scripts} section
22775 * Which flavor to choose?::
22776 @end menu
22777
22778 The auto-loading feature is useful for supplying application-specific
22779 debugging commands and scripts.
22780
22781 Auto-loading can be enabled or disabled.
22782
22783 @table @code
22784 @kindex maint set python auto-load
22785 @item maint set python auto-load [yes|no]
22786 Enable or disable the Python auto-loading feature.
22787
22788 @kindex maint show python auto-load
22789 @item maint show python auto-load
22790 Show whether Python auto-loading is enabled or disabled.
22791 @end table
22792
22793 When reading an auto-loaded file, @value{GDBN} sets the
22794 @dfn{current objfile}. This is available via the @code{gdb.current_objfile}
22795 function (@pxref{Objfiles In Python}). This can be useful for
22796 registering objfile-specific pretty-printers.
22797
22798 @node objfile-gdb.py file
22799 @subsubsection The @file{@var{objfile}-gdb.py} file
22800 @cindex @file{@var{objfile}-gdb.py}
22801
22802 When a new object file is read, @value{GDBN} looks for
22803 a file named @file{@var{objfile}-gdb.py},
22804 where @var{objfile} is the object file's real name, formed by ensuring
22805 that the file name is absolute, following all symlinks, and resolving
22806 @code{.} and @code{..} components. If this file exists and is
22807 readable, @value{GDBN} will evaluate it as a Python script.
22808
22809 If this file does not exist, and if the parameter
22810 @code{debug-file-directory} is set (@pxref{Separate Debug Files}),
22811 then @value{GDBN} will look for @var{real-name} in all of the
22812 directories mentioned in the value of @code{debug-file-directory}.
22813
22814 Finally, if this file does not exist, then @value{GDBN} will look for
22815 a file named @file{@var{data-directory}/python/auto-load/@var{real-name}}, where
22816 @var{data-directory} is @value{GDBN}'s data directory (available via
22817 @code{show data-directory}, @pxref{Data Files}), and @var{real-name}
22818 is the object file's real name, as described above.
22819
22820 @value{GDBN} does not track which files it has already auto-loaded this way.
22821 @value{GDBN} will load the associated script every time the corresponding
22822 @var{objfile} is opened.
22823 So your @file{-gdb.py} file should be careful to avoid errors if it
22824 is evaluated more than once.
22825
22826 @node .debug_gdb_scripts section
22827 @subsubsection The @code{.debug_gdb_scripts} section
22828 @cindex @code{.debug_gdb_scripts} section
22829
22830 For systems using file formats like ELF and COFF,
22831 when @value{GDBN} loads a new object file
22832 it will look for a special section named @samp{.debug_gdb_scripts}.
22833 If this section exists, its contents is a list of names of scripts to load.
22834
22835 @value{GDBN} will look for each specified script file first in the
22836 current directory and then along the source search path
22837 (@pxref{Source Path, ,Specifying Source Directories}),
22838 except that @file{$cdir} is not searched, since the compilation
22839 directory is not relevant to scripts.
22840
22841 Entries can be placed in section @code{.debug_gdb_scripts} with,
22842 for example, this GCC macro:
22843
22844 @example
22845 /* Note: The "MS" section flags are to remove duplicates. */
22846 #define DEFINE_GDB_SCRIPT(script_name) \
22847 asm("\
22848 .pushsection \".debug_gdb_scripts\", \"MS\",@@progbits,1\n\
22849 .byte 1\n\
22850 .asciz \"" script_name "\"\n\
22851 .popsection \n\
22852 ");
22853 @end example
22854
22855 @noindent
22856 Then one can reference the macro in a header or source file like this:
22857
22858 @example
22859 DEFINE_GDB_SCRIPT ("my-app-scripts.py")
22860 @end example
22861
22862 The script name may include directories if desired.
22863
22864 If the macro is put in a header, any application or library
22865 using this header will get a reference to the specified script.
22866
22867 @node Which flavor to choose?
22868 @subsubsection Which flavor to choose?
22869
22870 Given the multiple ways of auto-loading Python scripts, it might not always
22871 be clear which one to choose. This section provides some guidance.
22872
22873 Benefits of the @file{-gdb.py} way:
22874
22875 @itemize @bullet
22876 @item
22877 Can be used with file formats that don't support multiple sections.
22878
22879 @item
22880 Ease of finding scripts for public libraries.
22881
22882 Scripts specified in the @code{.debug_gdb_scripts} section are searched for
22883 in the source search path.
22884 For publicly installed libraries, e.g., @file{libstdc++}, there typically
22885 isn't a source directory in which to find the script.
22886
22887 @item
22888 Doesn't require source code additions.
22889 @end itemize
22890
22891 Benefits of the @code{.debug_gdb_scripts} way:
22892
22893 @itemize @bullet
22894 @item
22895 Works with static linking.
22896
22897 Scripts for libraries done the @file{-gdb.py} way require an objfile to
22898 trigger their loading. When an application is statically linked the only
22899 objfile available is the executable, and it is cumbersome to attach all the
22900 scripts from all the input libraries to the executable's @file{-gdb.py} script.
22901
22902 @item
22903 Works with classes that are entirely inlined.
22904
22905 Some classes can be entirely inlined, and thus there may not be an associated
22906 shared library to attach a @file{-gdb.py} script to.
22907
22908 @item
22909 Scripts needn't be copied out of the source tree.
22910
22911 In some circumstances, apps can be built out of large collections of internal
22912 libraries, and the build infrastructure necessary to install the
22913 @file{-gdb.py} scripts in a place where @value{GDBN} can find them is
22914 cumbersome. It may be easier to specify the scripts in the
22915 @code{.debug_gdb_scripts} section as relative paths, and add a path to the
22916 top of the source tree to the source search path.
22917 @end itemize
22918
22919 @node Python modules
22920 @subsection Python modules
22921 @cindex python modules
22922
22923 @c It is assumed that at least one more module will be added before
22924 @c the next release of gdb. Thus we use a menu here.
22925 @value{GDBN} comes with a module to assist writing Python code.
22926
22927 @menu
22928 * gdb.types:: Utilities for working with types.
22929 @end menu
22930
22931 @node gdb.types
22932 @subsubsection gdb.types
22933
22934 This module provides a collection of utilities for working with
22935 @code{gdb.Types} objects.
22936
22937 @table @code
22938 @item get_basic_type (@var{type})
22939 Return @var{type} with const and volatile qualifiers stripped,
22940 and with typedefs and C@t{++} references converted to the underlying type.
22941
22942 C@t{++} example:
22943
22944 @smallexample
22945 typedef const int const_int;
22946 const_int foo (3);
22947 const_int& foo_ref (foo);
22948 int main () @{ return 0; @}
22949 @end smallexample
22950
22951 Then in gdb:
22952
22953 @smallexample
22954 (gdb) start
22955 (gdb) python import gdb.types
22956 (gdb) python foo_ref = gdb.parse_and_eval("foo_ref")
22957 (gdb) python print gdb.types.get_basic_type(foo_ref.type)
22958 int
22959 @end smallexample
22960
22961 @item has_field (@var{type}, @var{field})
22962 Return @code{True} if @var{type}, assumed to be a type with fields
22963 (e.g., a structure or union), has field @var{field}.
22964
22965 @item make_enum_dict (@var{enum_type})
22966 Return a Python @code{dictionary} type produced from @var{enum_type}.
22967 @end table
22968
22969 @node Interpreters
22970 @chapter Command Interpreters
22971 @cindex command interpreters
22972
22973 @value{GDBN} supports multiple command interpreters, and some command
22974 infrastructure to allow users or user interface writers to switch
22975 between interpreters or run commands in other interpreters.
22976
22977 @value{GDBN} currently supports two command interpreters, the console
22978 interpreter (sometimes called the command-line interpreter or @sc{cli})
22979 and the machine interface interpreter (or @sc{gdb/mi}). This manual
22980 describes both of these interfaces in great detail.
22981
22982 By default, @value{GDBN} will start with the console interpreter.
22983 However, the user may choose to start @value{GDBN} with another
22984 interpreter by specifying the @option{-i} or @option{--interpreter}
22985 startup options. Defined interpreters include:
22986
22987 @table @code
22988 @item console
22989 @cindex console interpreter
22990 The traditional console or command-line interpreter. This is the most often
22991 used interpreter with @value{GDBN}. With no interpreter specified at runtime,
22992 @value{GDBN} will use this interpreter.
22993
22994 @item mi
22995 @cindex mi interpreter
22996 The newest @sc{gdb/mi} interface (currently @code{mi2}). Used primarily
22997 by programs wishing to use @value{GDBN} as a backend for a debugger GUI
22998 or an IDE. For more information, see @ref{GDB/MI, ,The @sc{gdb/mi}
22999 Interface}.
23000
23001 @item mi2
23002 @cindex mi2 interpreter
23003 The current @sc{gdb/mi} interface.
23004
23005 @item mi1
23006 @cindex mi1 interpreter
23007 The @sc{gdb/mi} interface included in @value{GDBN} 5.1, 5.2, and 5.3.
23008
23009 @end table
23010
23011 @cindex invoke another interpreter
23012 The interpreter being used by @value{GDBN} may not be dynamically
23013 switched at runtime. Although possible, this could lead to a very
23014 precarious situation. Consider an IDE using @sc{gdb/mi}. If a user
23015 enters the command "interpreter-set console" in a console view,
23016 @value{GDBN} would switch to using the console interpreter, rendering
23017 the IDE inoperable!
23018
23019 @kindex interpreter-exec
23020 Although you may only choose a single interpreter at startup, you may execute
23021 commands in any interpreter from the current interpreter using the appropriate
23022 command. If you are running the console interpreter, simply use the
23023 @code{interpreter-exec} command:
23024
23025 @smallexample
23026 interpreter-exec mi "-data-list-register-names"
23027 @end smallexample
23028
23029 @sc{gdb/mi} has a similar command, although it is only available in versions of
23030 @value{GDBN} which support @sc{gdb/mi} version 2 (or greater).
23031
23032 @node TUI
23033 @chapter @value{GDBN} Text User Interface
23034 @cindex TUI
23035 @cindex Text User Interface
23036
23037 @menu
23038 * TUI Overview:: TUI overview
23039 * TUI Keys:: TUI key bindings
23040 * TUI Single Key Mode:: TUI single key mode
23041 * TUI Commands:: TUI-specific commands
23042 * TUI Configuration:: TUI configuration variables
23043 @end menu
23044
23045 The @value{GDBN} Text User Interface (TUI) is a terminal
23046 interface which uses the @code{curses} library to show the source
23047 file, the assembly output, the program registers and @value{GDBN}
23048 commands in separate text windows. The TUI mode is supported only
23049 on platforms where a suitable version of the @code{curses} library
23050 is available.
23051
23052 @pindex @value{GDBTUI}
23053 The TUI mode is enabled by default when you invoke @value{GDBN} as
23054 either @samp{@value{GDBTUI}} or @samp{@value{GDBP} -tui}.
23055 You can also switch in and out of TUI mode while @value{GDBN} runs by
23056 using various TUI commands and key bindings, such as @kbd{C-x C-a}.
23057 @xref{TUI Keys, ,TUI Key Bindings}.
23058
23059 @node TUI Overview
23060 @section TUI Overview
23061
23062 In TUI mode, @value{GDBN} can display several text windows:
23063
23064 @table @emph
23065 @item command
23066 This window is the @value{GDBN} command window with the @value{GDBN}
23067 prompt and the @value{GDBN} output. The @value{GDBN} input is still
23068 managed using readline.
23069
23070 @item source
23071 The source window shows the source file of the program. The current
23072 line and active breakpoints are displayed in this window.
23073
23074 @item assembly
23075 The assembly window shows the disassembly output of the program.
23076
23077 @item register
23078 This window shows the processor registers. Registers are highlighted
23079 when their values change.
23080 @end table
23081
23082 The source and assembly windows show the current program position
23083 by highlighting the current line and marking it with a @samp{>} marker.
23084 Breakpoints are indicated with two markers. The first marker
23085 indicates the breakpoint type:
23086
23087 @table @code
23088 @item B
23089 Breakpoint which was hit at least once.
23090
23091 @item b
23092 Breakpoint which was never hit.
23093
23094 @item H
23095 Hardware breakpoint which was hit at least once.
23096
23097 @item h
23098 Hardware breakpoint which was never hit.
23099 @end table
23100
23101 The second marker indicates whether the breakpoint is enabled or not:
23102
23103 @table @code
23104 @item +
23105 Breakpoint is enabled.
23106
23107 @item -
23108 Breakpoint is disabled.
23109 @end table
23110
23111 The source, assembly and register windows are updated when the current
23112 thread changes, when the frame changes, or when the program counter
23113 changes.
23114
23115 These windows are not all visible at the same time. The command
23116 window is always visible. The others can be arranged in several
23117 layouts:
23118
23119 @itemize @bullet
23120 @item
23121 source only,
23122
23123 @item
23124 assembly only,
23125
23126 @item
23127 source and assembly,
23128
23129 @item
23130 source and registers, or
23131
23132 @item
23133 assembly and registers.
23134 @end itemize
23135
23136 A status line above the command window shows the following information:
23137
23138 @table @emph
23139 @item target
23140 Indicates the current @value{GDBN} target.
23141 (@pxref{Targets, ,Specifying a Debugging Target}).
23142
23143 @item process
23144 Gives the current process or thread number.
23145 When no process is being debugged, this field is set to @code{No process}.
23146
23147 @item function
23148 Gives the current function name for the selected frame.
23149 The name is demangled if demangling is turned on (@pxref{Print Settings}).
23150 When there is no symbol corresponding to the current program counter,
23151 the string @code{??} is displayed.
23152
23153 @item line
23154 Indicates the current line number for the selected frame.
23155 When the current line number is not known, the string @code{??} is displayed.
23156
23157 @item pc
23158 Indicates the current program counter address.
23159 @end table
23160
23161 @node TUI Keys
23162 @section TUI Key Bindings
23163 @cindex TUI key bindings
23164
23165 The TUI installs several key bindings in the readline keymaps
23166 (@pxref{Command Line Editing}). The following key bindings
23167 are installed for both TUI mode and the @value{GDBN} standard mode.
23168
23169 @table @kbd
23170 @kindex C-x C-a
23171 @item C-x C-a
23172 @kindex C-x a
23173 @itemx C-x a
23174 @kindex C-x A
23175 @itemx C-x A
23176 Enter or leave the TUI mode. When leaving the TUI mode,
23177 the curses window management stops and @value{GDBN} operates using
23178 its standard mode, writing on the terminal directly. When reentering
23179 the TUI mode, control is given back to the curses windows.
23180 The screen is then refreshed.
23181
23182 @kindex C-x 1
23183 @item C-x 1
23184 Use a TUI layout with only one window. The layout will
23185 either be @samp{source} or @samp{assembly}. When the TUI mode
23186 is not active, it will switch to the TUI mode.
23187
23188 Think of this key binding as the Emacs @kbd{C-x 1} binding.
23189
23190 @kindex C-x 2
23191 @item C-x 2
23192 Use a TUI layout with at least two windows. When the current
23193 layout already has two windows, the next layout with two windows is used.
23194 When a new layout is chosen, one window will always be common to the
23195 previous layout and the new one.
23196
23197 Think of it as the Emacs @kbd{C-x 2} binding.
23198
23199 @kindex C-x o
23200 @item C-x o
23201 Change the active window. The TUI associates several key bindings
23202 (like scrolling and arrow keys) with the active window. This command
23203 gives the focus to the next TUI window.
23204
23205 Think of it as the Emacs @kbd{C-x o} binding.
23206
23207 @kindex C-x s
23208 @item C-x s
23209 Switch in and out of the TUI SingleKey mode that binds single
23210 keys to @value{GDBN} commands (@pxref{TUI Single Key Mode}).
23211 @end table
23212
23213 The following key bindings only work in the TUI mode:
23214
23215 @table @asis
23216 @kindex PgUp
23217 @item @key{PgUp}
23218 Scroll the active window one page up.
23219
23220 @kindex PgDn
23221 @item @key{PgDn}
23222 Scroll the active window one page down.
23223
23224 @kindex Up
23225 @item @key{Up}
23226 Scroll the active window one line up.
23227
23228 @kindex Down
23229 @item @key{Down}
23230 Scroll the active window one line down.
23231
23232 @kindex Left
23233 @item @key{Left}
23234 Scroll the active window one column left.
23235
23236 @kindex Right
23237 @item @key{Right}
23238 Scroll the active window one column right.
23239
23240 @kindex C-L
23241 @item @kbd{C-L}
23242 Refresh the screen.
23243 @end table
23244
23245 Because the arrow keys scroll the active window in the TUI mode, they
23246 are not available for their normal use by readline unless the command
23247 window has the focus. When another window is active, you must use
23248 other readline key bindings such as @kbd{C-p}, @kbd{C-n}, @kbd{C-b}
23249 and @kbd{C-f} to control the command window.
23250
23251 @node TUI Single Key Mode
23252 @section TUI Single Key Mode
23253 @cindex TUI single key mode
23254
23255 The TUI also provides a @dfn{SingleKey} mode, which binds several
23256 frequently used @value{GDBN} commands to single keys. Type @kbd{C-x s} to
23257 switch into this mode, where the following key bindings are used:
23258
23259 @table @kbd
23260 @kindex c @r{(SingleKey TUI key)}
23261 @item c
23262 continue
23263
23264 @kindex d @r{(SingleKey TUI key)}
23265 @item d
23266 down
23267
23268 @kindex f @r{(SingleKey TUI key)}
23269 @item f
23270 finish
23271
23272 @kindex n @r{(SingleKey TUI key)}
23273 @item n
23274 next
23275
23276 @kindex q @r{(SingleKey TUI key)}
23277 @item q
23278 exit the SingleKey mode.
23279
23280 @kindex r @r{(SingleKey TUI key)}
23281 @item r
23282 run
23283
23284 @kindex s @r{(SingleKey TUI key)}
23285 @item s
23286 step
23287
23288 @kindex u @r{(SingleKey TUI key)}
23289 @item u
23290 up
23291
23292 @kindex v @r{(SingleKey TUI key)}
23293 @item v
23294 info locals
23295
23296 @kindex w @r{(SingleKey TUI key)}
23297 @item w
23298 where
23299 @end table
23300
23301 Other keys temporarily switch to the @value{GDBN} command prompt.
23302 The key that was pressed is inserted in the editing buffer so that
23303 it is possible to type most @value{GDBN} commands without interaction
23304 with the TUI SingleKey mode. Once the command is entered the TUI
23305 SingleKey mode is restored. The only way to permanently leave
23306 this mode is by typing @kbd{q} or @kbd{C-x s}.
23307
23308
23309 @node TUI Commands
23310 @section TUI-specific Commands
23311 @cindex TUI commands
23312
23313 The TUI has specific commands to control the text windows.
23314 These commands are always available, even when @value{GDBN} is not in
23315 the TUI mode. When @value{GDBN} is in the standard mode, most
23316 of these commands will automatically switch to the TUI mode.
23317
23318 Note that if @value{GDBN}'s @code{stdout} is not connected to a
23319 terminal, or @value{GDBN} has been started with the machine interface
23320 interpreter (@pxref{GDB/MI, ,The @sc{gdb/mi} Interface}), most of
23321 these commands will fail with an error, because it would not be
23322 possible or desirable to enable curses window management.
23323
23324 @table @code
23325 @item info win
23326 @kindex info win
23327 List and give the size of all displayed windows.
23328
23329 @item layout next
23330 @kindex layout
23331 Display the next layout.
23332
23333 @item layout prev
23334 Display the previous layout.
23335
23336 @item layout src
23337 Display the source window only.
23338
23339 @item layout asm
23340 Display the assembly window only.
23341
23342 @item layout split
23343 Display the source and assembly window.
23344
23345 @item layout regs
23346 Display the register window together with the source or assembly window.
23347
23348 @item focus next
23349 @kindex focus
23350 Make the next window active for scrolling.
23351
23352 @item focus prev
23353 Make the previous window active for scrolling.
23354
23355 @item focus src
23356 Make the source window active for scrolling.
23357
23358 @item focus asm
23359 Make the assembly window active for scrolling.
23360
23361 @item focus regs
23362 Make the register window active for scrolling.
23363
23364 @item focus cmd
23365 Make the command window active for scrolling.
23366
23367 @item refresh
23368 @kindex refresh
23369 Refresh the screen. This is similar to typing @kbd{C-L}.
23370
23371 @item tui reg float
23372 @kindex tui reg
23373 Show the floating point registers in the register window.
23374
23375 @item tui reg general
23376 Show the general registers in the register window.
23377
23378 @item tui reg next
23379 Show the next register group. The list of register groups as well as
23380 their order is target specific. The predefined register groups are the
23381 following: @code{general}, @code{float}, @code{system}, @code{vector},
23382 @code{all}, @code{save}, @code{restore}.
23383
23384 @item tui reg system
23385 Show the system registers in the register window.
23386
23387 @item update
23388 @kindex update
23389 Update the source window and the current execution point.
23390
23391 @item winheight @var{name} +@var{count}
23392 @itemx winheight @var{name} -@var{count}
23393 @kindex winheight
23394 Change the height of the window @var{name} by @var{count}
23395 lines. Positive counts increase the height, while negative counts
23396 decrease it.
23397
23398 @item tabset @var{nchars}
23399 @kindex tabset
23400 Set the width of tab stops to be @var{nchars} characters.
23401 @end table
23402
23403 @node TUI Configuration
23404 @section TUI Configuration Variables
23405 @cindex TUI configuration variables
23406
23407 Several configuration variables control the appearance of TUI windows.
23408
23409 @table @code
23410 @item set tui border-kind @var{kind}
23411 @kindex set tui border-kind
23412 Select the border appearance for the source, assembly and register windows.
23413 The possible values are the following:
23414 @table @code
23415 @item space
23416 Use a space character to draw the border.
23417
23418 @item ascii
23419 Use @sc{ascii} characters @samp{+}, @samp{-} and @samp{|} to draw the border.
23420
23421 @item acs
23422 Use the Alternate Character Set to draw the border. The border is
23423 drawn using character line graphics if the terminal supports them.
23424 @end table
23425
23426 @item set tui border-mode @var{mode}
23427 @kindex set tui border-mode
23428 @itemx set tui active-border-mode @var{mode}
23429 @kindex set tui active-border-mode
23430 Select the display attributes for the borders of the inactive windows
23431 or the active window. The @var{mode} can be one of the following:
23432 @table @code
23433 @item normal
23434 Use normal attributes to display the border.
23435
23436 @item standout
23437 Use standout mode.
23438
23439 @item reverse
23440 Use reverse video mode.
23441
23442 @item half
23443 Use half bright mode.
23444
23445 @item half-standout
23446 Use half bright and standout mode.
23447
23448 @item bold
23449 Use extra bright or bold mode.
23450
23451 @item bold-standout
23452 Use extra bright or bold and standout mode.
23453 @end table
23454 @end table
23455
23456 @node Emacs
23457 @chapter Using @value{GDBN} under @sc{gnu} Emacs
23458
23459 @cindex Emacs
23460 @cindex @sc{gnu} Emacs
23461 A special interface allows you to use @sc{gnu} Emacs to view (and
23462 edit) the source files for the program you are debugging with
23463 @value{GDBN}.
23464
23465 To use this interface, use the command @kbd{M-x gdb} in Emacs. Give the
23466 executable file you want to debug as an argument. This command starts
23467 @value{GDBN} as a subprocess of Emacs, with input and output through a newly
23468 created Emacs buffer.
23469 @c (Do not use the @code{-tui} option to run @value{GDBN} from Emacs.)
23470
23471 Running @value{GDBN} under Emacs can be just like running @value{GDBN} normally except for two
23472 things:
23473
23474 @itemize @bullet
23475 @item
23476 All ``terminal'' input and output goes through an Emacs buffer, called
23477 the GUD buffer.
23478
23479 This applies both to @value{GDBN} commands and their output, and to the input
23480 and output done by the program you are debugging.
23481
23482 This is useful because it means that you can copy the text of previous
23483 commands and input them again; you can even use parts of the output
23484 in this way.
23485
23486 All the facilities of Emacs' Shell mode are available for interacting
23487 with your program. In particular, you can send signals the usual
23488 way---for example, @kbd{C-c C-c} for an interrupt, @kbd{C-c C-z} for a
23489 stop.
23490
23491 @item
23492 @value{GDBN} displays source code through Emacs.
23493
23494 Each time @value{GDBN} displays a stack frame, Emacs automatically finds the
23495 source file for that frame and puts an arrow (@samp{=>}) at the
23496 left margin of the current line. Emacs uses a separate buffer for
23497 source display, and splits the screen to show both your @value{GDBN} session
23498 and the source.
23499
23500 Explicit @value{GDBN} @code{list} or search commands still produce output as
23501 usual, but you probably have no reason to use them from Emacs.
23502 @end itemize
23503
23504 We call this @dfn{text command mode}. Emacs 22.1, and later, also uses
23505 a graphical mode, enabled by default, which provides further buffers
23506 that can control the execution and describe the state of your program.
23507 @xref{GDB Graphical Interface,,, Emacs, The @sc{gnu} Emacs Manual}.
23508
23509 If you specify an absolute file name when prompted for the @kbd{M-x
23510 gdb} argument, then Emacs sets your current working directory to where
23511 your program resides. If you only specify the file name, then Emacs
23512 sets your current working directory to to the directory associated
23513 with the previous buffer. In this case, @value{GDBN} may find your
23514 program by searching your environment's @code{PATH} variable, but on
23515 some operating systems it might not find the source. So, although the
23516 @value{GDBN} input and output session proceeds normally, the auxiliary
23517 buffer does not display the current source and line of execution.
23518
23519 The initial working directory of @value{GDBN} is printed on the top
23520 line of the GUD buffer and this serves as a default for the commands
23521 that specify files for @value{GDBN} to operate on. @xref{Files,
23522 ,Commands to Specify Files}.
23523
23524 By default, @kbd{M-x gdb} calls the program called @file{gdb}. If you
23525 need to call @value{GDBN} by a different name (for example, if you
23526 keep several configurations around, with different names) you can
23527 customize the Emacs variable @code{gud-gdb-command-name} to run the
23528 one you want.
23529
23530 In the GUD buffer, you can use these special Emacs commands in
23531 addition to the standard Shell mode commands:
23532
23533 @table @kbd
23534 @item C-h m
23535 Describe the features of Emacs' GUD Mode.
23536
23537 @item C-c C-s
23538 Execute to another source line, like the @value{GDBN} @code{step} command; also
23539 update the display window to show the current file and location.
23540
23541 @item C-c C-n
23542 Execute to next source line in this function, skipping all function
23543 calls, like the @value{GDBN} @code{next} command. Then update the display window
23544 to show the current file and location.
23545
23546 @item C-c C-i
23547 Execute one instruction, like the @value{GDBN} @code{stepi} command; update
23548 display window accordingly.
23549
23550 @item C-c C-f
23551 Execute until exit from the selected stack frame, like the @value{GDBN}
23552 @code{finish} command.
23553
23554 @item C-c C-r
23555 Continue execution of your program, like the @value{GDBN} @code{continue}
23556 command.
23557
23558 @item C-c <
23559 Go up the number of frames indicated by the numeric argument
23560 (@pxref{Arguments, , Numeric Arguments, Emacs, The @sc{gnu} Emacs Manual}),
23561 like the @value{GDBN} @code{up} command.
23562
23563 @item C-c >
23564 Go down the number of frames indicated by the numeric argument, like the
23565 @value{GDBN} @code{down} command.
23566 @end table
23567
23568 In any source file, the Emacs command @kbd{C-x @key{SPC}} (@code{gud-break})
23569 tells @value{GDBN} to set a breakpoint on the source line point is on.
23570
23571 In text command mode, if you type @kbd{M-x speedbar}, Emacs displays a
23572 separate frame which shows a backtrace when the GUD buffer is current.
23573 Move point to any frame in the stack and type @key{RET} to make it
23574 become the current frame and display the associated source in the
23575 source buffer. Alternatively, click @kbd{Mouse-2} to make the
23576 selected frame become the current one. In graphical mode, the
23577 speedbar displays watch expressions.
23578
23579 If you accidentally delete the source-display buffer, an easy way to get
23580 it back is to type the command @code{f} in the @value{GDBN} buffer, to
23581 request a frame display; when you run under Emacs, this recreates
23582 the source buffer if necessary to show you the context of the current
23583 frame.
23584
23585 The source files displayed in Emacs are in ordinary Emacs buffers
23586 which are visiting the source files in the usual way. You can edit
23587 the files with these buffers if you wish; but keep in mind that @value{GDBN}
23588 communicates with Emacs in terms of line numbers. If you add or
23589 delete lines from the text, the line numbers that @value{GDBN} knows cease
23590 to correspond properly with the code.
23591
23592 A more detailed description of Emacs' interaction with @value{GDBN} is
23593 given in the Emacs manual (@pxref{Debuggers,,, Emacs, The @sc{gnu}
23594 Emacs Manual}).
23595
23596 @c The following dropped because Epoch is nonstandard. Reactivate
23597 @c if/when v19 does something similar. ---doc@cygnus.com 19dec1990
23598 @ignore
23599 @kindex Emacs Epoch environment
23600 @kindex Epoch
23601 @kindex inspect
23602
23603 Version 18 of @sc{gnu} Emacs has a built-in window system
23604 called the @code{epoch}
23605 environment. Users of this environment can use a new command,
23606 @code{inspect} which performs identically to @code{print} except that
23607 each value is printed in its own window.
23608 @end ignore
23609
23610
23611 @node GDB/MI
23612 @chapter The @sc{gdb/mi} Interface
23613
23614 @unnumberedsec Function and Purpose
23615
23616 @cindex @sc{gdb/mi}, its purpose
23617 @sc{gdb/mi} is a line based machine oriented text interface to
23618 @value{GDBN} and is activated by specifying using the
23619 @option{--interpreter} command line option (@pxref{Mode Options}). It
23620 is specifically intended to support the development of systems which
23621 use the debugger as just one small component of a larger system.
23622
23623 This chapter is a specification of the @sc{gdb/mi} interface. It is written
23624 in the form of a reference manual.
23625
23626 Note that @sc{gdb/mi} is still under construction, so some of the
23627 features described below are incomplete and subject to change
23628 (@pxref{GDB/MI Development and Front Ends, , @sc{gdb/mi} Development and Front Ends}).
23629
23630 @unnumberedsec Notation and Terminology
23631
23632 @cindex notational conventions, for @sc{gdb/mi}
23633 This chapter uses the following notation:
23634
23635 @itemize @bullet
23636 @item
23637 @code{|} separates two alternatives.
23638
23639 @item
23640 @code{[ @var{something} ]} indicates that @var{something} is optional:
23641 it may or may not be given.
23642
23643 @item
23644 @code{( @var{group} )*} means that @var{group} inside the parentheses
23645 may repeat zero or more times.
23646
23647 @item
23648 @code{( @var{group} )+} means that @var{group} inside the parentheses
23649 may repeat one or more times.
23650
23651 @item
23652 @code{"@var{string}"} means a literal @var{string}.
23653 @end itemize
23654
23655 @ignore
23656 @heading Dependencies
23657 @end ignore
23658
23659 @menu
23660 * GDB/MI General Design::
23661 * GDB/MI Command Syntax::
23662 * GDB/MI Compatibility with CLI::
23663 * GDB/MI Development and Front Ends::
23664 * GDB/MI Output Records::
23665 * GDB/MI Simple Examples::
23666 * GDB/MI Command Description Format::
23667 * GDB/MI Breakpoint Commands::
23668 * GDB/MI Program Context::
23669 * GDB/MI Thread Commands::
23670 * GDB/MI Program Execution::
23671 * GDB/MI Stack Manipulation::
23672 * GDB/MI Variable Objects::
23673 * GDB/MI Data Manipulation::
23674 * GDB/MI Tracepoint Commands::
23675 * GDB/MI Symbol Query::
23676 * GDB/MI File Commands::
23677 @ignore
23678 * GDB/MI Kod Commands::
23679 * GDB/MI Memory Overlay Commands::
23680 * GDB/MI Signal Handling Commands::
23681 @end ignore
23682 * GDB/MI Target Manipulation::
23683 * GDB/MI File Transfer Commands::
23684 * GDB/MI Miscellaneous Commands::
23685 @end menu
23686
23687 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
23688 @node GDB/MI General Design
23689 @section @sc{gdb/mi} General Design
23690 @cindex GDB/MI General Design
23691
23692 Interaction of a @sc{GDB/MI} frontend with @value{GDBN} involves three
23693 parts---commands sent to @value{GDBN}, responses to those commands
23694 and notifications. Each command results in exactly one response,
23695 indicating either successful completion of the command, or an error.
23696 For the commands that do not resume the target, the response contains the
23697 requested information. For the commands that resume the target, the
23698 response only indicates whether the target was successfully resumed.
23699 Notifications is the mechanism for reporting changes in the state of the
23700 target, or in @value{GDBN} state, that cannot conveniently be associated with
23701 a command and reported as part of that command response.
23702
23703 The important examples of notifications are:
23704 @itemize @bullet
23705
23706 @item
23707 Exec notifications. These are used to report changes in
23708 target state---when a target is resumed, or stopped. It would not
23709 be feasible to include this information in response of resuming
23710 commands, because one resume commands can result in multiple events in
23711 different threads. Also, quite some time may pass before any event
23712 happens in the target, while a frontend needs to know whether the resuming
23713 command itself was successfully executed.
23714
23715 @item
23716 Console output, and status notifications. Console output
23717 notifications are used to report output of CLI commands, as well as
23718 diagnostics for other commands. Status notifications are used to
23719 report the progress of a long-running operation. Naturally, including
23720 this information in command response would mean no output is produced
23721 until the command is finished, which is undesirable.
23722
23723 @item
23724 General notifications. Commands may have various side effects on
23725 the @value{GDBN} or target state beyond their official purpose. For example,
23726 a command may change the selected thread. Although such changes can
23727 be included in command response, using notification allows for more
23728 orthogonal frontend design.
23729
23730 @end itemize
23731
23732 There's no guarantee that whenever an MI command reports an error,
23733 @value{GDBN} or the target are in any specific state, and especially,
23734 the state is not reverted to the state before the MI command was
23735 processed. Therefore, whenever an MI command results in an error,
23736 we recommend that the frontend refreshes all the information shown in
23737 the user interface.
23738
23739
23740 @menu
23741 * Context management::
23742 * Asynchronous and non-stop modes::
23743 * Thread groups::
23744 @end menu
23745
23746 @node Context management
23747 @subsection Context management
23748
23749 In most cases when @value{GDBN} accesses the target, this access is
23750 done in context of a specific thread and frame (@pxref{Frames}).
23751 Often, even when accessing global data, the target requires that a thread
23752 be specified. The CLI interface maintains the selected thread and frame,
23753 and supplies them to target on each command. This is convenient,
23754 because a command line user would not want to specify that information
23755 explicitly on each command, and because user interacts with
23756 @value{GDBN} via a single terminal, so no confusion is possible as
23757 to what thread and frame are the current ones.
23758
23759 In the case of MI, the concept of selected thread and frame is less
23760 useful. First, a frontend can easily remember this information
23761 itself. Second, a graphical frontend can have more than one window,
23762 each one used for debugging a different thread, and the frontend might
23763 want to access additional threads for internal purposes. This
23764 increases the risk that by relying on implicitly selected thread, the
23765 frontend may be operating on a wrong one. Therefore, each MI command
23766 should explicitly specify which thread and frame to operate on. To
23767 make it possible, each MI command accepts the @samp{--thread} and
23768 @samp{--frame} options, the value to each is @value{GDBN} identifier
23769 for thread and frame to operate on.
23770
23771 Usually, each top-level window in a frontend allows the user to select
23772 a thread and a frame, and remembers the user selection for further
23773 operations. However, in some cases @value{GDBN} may suggest that the
23774 current thread be changed. For example, when stopping on a breakpoint
23775 it is reasonable to switch to the thread where breakpoint is hit. For
23776 another example, if the user issues the CLI @samp{thread} command via
23777 the frontend, it is desirable to change the frontend's selected thread to the
23778 one specified by user. @value{GDBN} communicates the suggestion to
23779 change current thread using the @samp{=thread-selected} notification.
23780 No such notification is available for the selected frame at the moment.
23781
23782 Note that historically, MI shares the selected thread with CLI, so
23783 frontends used the @code{-thread-select} to execute commands in the
23784 right context. However, getting this to work right is cumbersome. The
23785 simplest way is for frontend to emit @code{-thread-select} command
23786 before every command. This doubles the number of commands that need
23787 to be sent. The alternative approach is to suppress @code{-thread-select}
23788 if the selected thread in @value{GDBN} is supposed to be identical to the
23789 thread the frontend wants to operate on. However, getting this
23790 optimization right can be tricky. In particular, if the frontend
23791 sends several commands to @value{GDBN}, and one of the commands changes the
23792 selected thread, then the behaviour of subsequent commands will
23793 change. So, a frontend should either wait for response from such
23794 problematic commands, or explicitly add @code{-thread-select} for
23795 all subsequent commands. No frontend is known to do this exactly
23796 right, so it is suggested to just always pass the @samp{--thread} and
23797 @samp{--frame} options.
23798
23799 @node Asynchronous and non-stop modes
23800 @subsection Asynchronous command execution and non-stop mode
23801
23802 On some targets, @value{GDBN} is capable of processing MI commands
23803 even while the target is running. This is called @dfn{asynchronous
23804 command execution} (@pxref{Background Execution}). The frontend may
23805 specify a preferrence for asynchronous execution using the
23806 @code{-gdb-set target-async 1} command, which should be emitted before
23807 either running the executable or attaching to the target. After the
23808 frontend has started the executable or attached to the target, it can
23809 find if asynchronous execution is enabled using the
23810 @code{-list-target-features} command.
23811
23812 Even if @value{GDBN} can accept a command while target is running,
23813 many commands that access the target do not work when the target is
23814 running. Therefore, asynchronous command execution is most useful
23815 when combined with non-stop mode (@pxref{Non-Stop Mode}). Then,
23816 it is possible to examine the state of one thread, while other threads
23817 are running.
23818
23819 When a given thread is running, MI commands that try to access the
23820 target in the context of that thread may not work, or may work only on
23821 some targets. In particular, commands that try to operate on thread's
23822 stack will not work, on any target. Commands that read memory, or
23823 modify breakpoints, may work or not work, depending on the target. Note
23824 that even commands that operate on global state, such as @code{print},
23825 @code{set}, and breakpoint commands, still access the target in the
23826 context of a specific thread, so frontend should try to find a
23827 stopped thread and perform the operation on that thread (using the
23828 @samp{--thread} option).
23829
23830 Which commands will work in the context of a running thread is
23831 highly target dependent. However, the two commands
23832 @code{-exec-interrupt}, to stop a thread, and @code{-thread-info},
23833 to find the state of a thread, will always work.
23834
23835 @node Thread groups
23836 @subsection Thread groups
23837 @value{GDBN} may be used to debug several processes at the same time.
23838 On some platfroms, @value{GDBN} may support debugging of several
23839 hardware systems, each one having several cores with several different
23840 processes running on each core. This section describes the MI
23841 mechanism to support such debugging scenarios.
23842
23843 The key observation is that regardless of the structure of the
23844 target, MI can have a global list of threads, because most commands that
23845 accept the @samp{--thread} option do not need to know what process that
23846 thread belongs to. Therefore, it is not necessary to introduce
23847 neither additional @samp{--process} option, nor an notion of the
23848 current process in the MI interface. The only strictly new feature
23849 that is required is the ability to find how the threads are grouped
23850 into processes.
23851
23852 To allow the user to discover such grouping, and to support arbitrary
23853 hierarchy of machines/cores/processes, MI introduces the concept of a
23854 @dfn{thread group}. Thread group is a collection of threads and other
23855 thread groups. A thread group always has a string identifier, a type,
23856 and may have additional attributes specific to the type. A new
23857 command, @code{-list-thread-groups}, returns the list of top-level
23858 thread groups, which correspond to processes that @value{GDBN} is
23859 debugging at the moment. By passing an identifier of a thread group
23860 to the @code{-list-thread-groups} command, it is possible to obtain
23861 the members of specific thread group.
23862
23863 To allow the user to easily discover processes, and other objects, he
23864 wishes to debug, a concept of @dfn{available thread group} is
23865 introduced. Available thread group is an thread group that
23866 @value{GDBN} is not debugging, but that can be attached to, using the
23867 @code{-target-attach} command. The list of available top-level thread
23868 groups can be obtained using @samp{-list-thread-groups --available}.
23869 In general, the content of a thread group may be only retrieved only
23870 after attaching to that thread group.
23871
23872 Thread groups are related to inferiors (@pxref{Inferiors and
23873 Programs}). Each inferior corresponds to a thread group of a special
23874 type @samp{process}, and some additional operations are permitted on
23875 such thread groups.
23876
23877 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
23878 @node GDB/MI Command Syntax
23879 @section @sc{gdb/mi} Command Syntax
23880
23881 @menu
23882 * GDB/MI Input Syntax::
23883 * GDB/MI Output Syntax::
23884 @end menu
23885
23886 @node GDB/MI Input Syntax
23887 @subsection @sc{gdb/mi} Input Syntax
23888
23889 @cindex input syntax for @sc{gdb/mi}
23890 @cindex @sc{gdb/mi}, input syntax
23891 @table @code
23892 @item @var{command} @expansion{}
23893 @code{@var{cli-command} | @var{mi-command}}
23894
23895 @item @var{cli-command} @expansion{}
23896 @code{[ @var{token} ] @var{cli-command} @var{nl}}, where
23897 @var{cli-command} is any existing @value{GDBN} CLI command.
23898
23899 @item @var{mi-command} @expansion{}
23900 @code{[ @var{token} ] "-" @var{operation} ( " " @var{option} )*
23901 @code{[} " --" @code{]} ( " " @var{parameter} )* @var{nl}}
23902
23903 @item @var{token} @expansion{}
23904 "any sequence of digits"
23905
23906 @item @var{option} @expansion{}
23907 @code{"-" @var{parameter} [ " " @var{parameter} ]}
23908
23909 @item @var{parameter} @expansion{}
23910 @code{@var{non-blank-sequence} | @var{c-string}}
23911
23912 @item @var{operation} @expansion{}
23913 @emph{any of the operations described in this chapter}
23914
23915 @item @var{non-blank-sequence} @expansion{}
23916 @emph{anything, provided it doesn't contain special characters such as
23917 "-", @var{nl}, """ and of course " "}
23918
23919 @item @var{c-string} @expansion{}
23920 @code{""" @var{seven-bit-iso-c-string-content} """}
23921
23922 @item @var{nl} @expansion{}
23923 @code{CR | CR-LF}
23924 @end table
23925
23926 @noindent
23927 Notes:
23928
23929 @itemize @bullet
23930 @item
23931 The CLI commands are still handled by the @sc{mi} interpreter; their
23932 output is described below.
23933
23934 @item
23935 The @code{@var{token}}, when present, is passed back when the command
23936 finishes.
23937
23938 @item
23939 Some @sc{mi} commands accept optional arguments as part of the parameter
23940 list. Each option is identified by a leading @samp{-} (dash) and may be
23941 followed by an optional argument parameter. Options occur first in the
23942 parameter list and can be delimited from normal parameters using
23943 @samp{--} (this is useful when some parameters begin with a dash).
23944 @end itemize
23945
23946 Pragmatics:
23947
23948 @itemize @bullet
23949 @item
23950 We want easy access to the existing CLI syntax (for debugging).
23951
23952 @item
23953 We want it to be easy to spot a @sc{mi} operation.
23954 @end itemize
23955
23956 @node GDB/MI Output Syntax
23957 @subsection @sc{gdb/mi} Output Syntax
23958
23959 @cindex output syntax of @sc{gdb/mi}
23960 @cindex @sc{gdb/mi}, output syntax
23961 The output from @sc{gdb/mi} consists of zero or more out-of-band records
23962 followed, optionally, by a single result record. This result record
23963 is for the most recent command. The sequence of output records is
23964 terminated by @samp{(gdb)}.
23965
23966 If an input command was prefixed with a @code{@var{token}} then the
23967 corresponding output for that command will also be prefixed by that same
23968 @var{token}.
23969
23970 @table @code
23971 @item @var{output} @expansion{}
23972 @code{( @var{out-of-band-record} )* [ @var{result-record} ] "(gdb)" @var{nl}}
23973
23974 @item @var{result-record} @expansion{}
23975 @code{ [ @var{token} ] "^" @var{result-class} ( "," @var{result} )* @var{nl}}
23976
23977 @item @var{out-of-band-record} @expansion{}
23978 @code{@var{async-record} | @var{stream-record}}
23979
23980 @item @var{async-record} @expansion{}
23981 @code{@var{exec-async-output} | @var{status-async-output} | @var{notify-async-output}}
23982
23983 @item @var{exec-async-output} @expansion{}
23984 @code{[ @var{token} ] "*" @var{async-output}}
23985
23986 @item @var{status-async-output} @expansion{}
23987 @code{[ @var{token} ] "+" @var{async-output}}
23988
23989 @item @var{notify-async-output} @expansion{}
23990 @code{[ @var{token} ] "=" @var{async-output}}
23991
23992 @item @var{async-output} @expansion{}
23993 @code{@var{async-class} ( "," @var{result} )* @var{nl}}
23994
23995 @item @var{result-class} @expansion{}
23996 @code{"done" | "running" | "connected" | "error" | "exit"}
23997
23998 @item @var{async-class} @expansion{}
23999 @code{"stopped" | @var{others}} (where @var{others} will be added
24000 depending on the needs---this is still in development).
24001
24002 @item @var{result} @expansion{}
24003 @code{ @var{variable} "=" @var{value}}
24004
24005 @item @var{variable} @expansion{}
24006 @code{ @var{string} }
24007
24008 @item @var{value} @expansion{}
24009 @code{ @var{const} | @var{tuple} | @var{list} }
24010
24011 @item @var{const} @expansion{}
24012 @code{@var{c-string}}
24013
24014 @item @var{tuple} @expansion{}
24015 @code{ "@{@}" | "@{" @var{result} ( "," @var{result} )* "@}" }
24016
24017 @item @var{list} @expansion{}
24018 @code{ "[]" | "[" @var{value} ( "," @var{value} )* "]" | "["
24019 @var{result} ( "," @var{result} )* "]" }
24020
24021 @item @var{stream-record} @expansion{}
24022 @code{@var{console-stream-output} | @var{target-stream-output} | @var{log-stream-output}}
24023
24024 @item @var{console-stream-output} @expansion{}
24025 @code{"~" @var{c-string}}
24026
24027 @item @var{target-stream-output} @expansion{}
24028 @code{"@@" @var{c-string}}
24029
24030 @item @var{log-stream-output} @expansion{}
24031 @code{"&" @var{c-string}}
24032
24033 @item @var{nl} @expansion{}
24034 @code{CR | CR-LF}
24035
24036 @item @var{token} @expansion{}
24037 @emph{any sequence of digits}.
24038 @end table
24039
24040 @noindent
24041 Notes:
24042
24043 @itemize @bullet
24044 @item
24045 All output sequences end in a single line containing a period.
24046
24047 @item
24048 The @code{@var{token}} is from the corresponding request. Note that
24049 for all async output, while the token is allowed by the grammar and
24050 may be output by future versions of @value{GDBN} for select async
24051 output messages, it is generally omitted. Frontends should treat
24052 all async output as reporting general changes in the state of the
24053 target and there should be no need to associate async output to any
24054 prior command.
24055
24056 @item
24057 @cindex status output in @sc{gdb/mi}
24058 @var{status-async-output} contains on-going status information about the
24059 progress of a slow operation. It can be discarded. All status output is
24060 prefixed by @samp{+}.
24061
24062 @item
24063 @cindex async output in @sc{gdb/mi}
24064 @var{exec-async-output} contains asynchronous state change on the target
24065 (stopped, started, disappeared). All async output is prefixed by
24066 @samp{*}.
24067
24068 @item
24069 @cindex notify output in @sc{gdb/mi}
24070 @var{notify-async-output} contains supplementary information that the
24071 client should handle (e.g., a new breakpoint information). All notify
24072 output is prefixed by @samp{=}.
24073
24074 @item
24075 @cindex console output in @sc{gdb/mi}
24076 @var{console-stream-output} is output that should be displayed as is in the
24077 console. It is the textual response to a CLI command. All the console
24078 output is prefixed by @samp{~}.
24079
24080 @item
24081 @cindex target output in @sc{gdb/mi}
24082 @var{target-stream-output} is the output produced by the target program.
24083 All the target output is prefixed by @samp{@@}.
24084
24085 @item
24086 @cindex log output in @sc{gdb/mi}
24087 @var{log-stream-output} is output text coming from @value{GDBN}'s internals, for
24088 instance messages that should be displayed as part of an error log. All
24089 the log output is prefixed by @samp{&}.
24090
24091 @item
24092 @cindex list output in @sc{gdb/mi}
24093 New @sc{gdb/mi} commands should only output @var{lists} containing
24094 @var{values}.
24095
24096
24097 @end itemize
24098
24099 @xref{GDB/MI Stream Records, , @sc{gdb/mi} Stream Records}, for more
24100 details about the various output records.
24101
24102 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
24103 @node GDB/MI Compatibility with CLI
24104 @section @sc{gdb/mi} Compatibility with CLI
24105
24106 @cindex compatibility, @sc{gdb/mi} and CLI
24107 @cindex @sc{gdb/mi}, compatibility with CLI
24108
24109 For the developers convenience CLI commands can be entered directly,
24110 but there may be some unexpected behaviour. For example, commands
24111 that query the user will behave as if the user replied yes, breakpoint
24112 command lists are not executed and some CLI commands, such as
24113 @code{if}, @code{when} and @code{define}, prompt for further input with
24114 @samp{>}, which is not valid MI output.
24115
24116 This feature may be removed at some stage in the future and it is
24117 recommended that front ends use the @code{-interpreter-exec} command
24118 (@pxref{-interpreter-exec}).
24119
24120 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
24121 @node GDB/MI Development and Front Ends
24122 @section @sc{gdb/mi} Development and Front Ends
24123 @cindex @sc{gdb/mi} development
24124
24125 The application which takes the MI output and presents the state of the
24126 program being debugged to the user is called a @dfn{front end}.
24127
24128 Although @sc{gdb/mi} is still incomplete, it is currently being used
24129 by a variety of front ends to @value{GDBN}. This makes it difficult
24130 to introduce new functionality without breaking existing usage. This
24131 section tries to minimize the problems by describing how the protocol
24132 might change.
24133
24134 Some changes in MI need not break a carefully designed front end, and
24135 for these the MI version will remain unchanged. The following is a
24136 list of changes that may occur within one level, so front ends should
24137 parse MI output in a way that can handle them:
24138
24139 @itemize @bullet
24140 @item
24141 New MI commands may be added.
24142
24143 @item
24144 New fields may be added to the output of any MI command.
24145
24146 @item
24147 The range of values for fields with specified values, e.g.,
24148 @code{in_scope} (@pxref{-var-update}) may be extended.
24149
24150 @c The format of field's content e.g type prefix, may change so parse it
24151 @c at your own risk. Yes, in general?
24152
24153 @c The order of fields may change? Shouldn't really matter but it might
24154 @c resolve inconsistencies.
24155 @end itemize
24156
24157 If the changes are likely to break front ends, the MI version level
24158 will be increased by one. This will allow the front end to parse the
24159 output according to the MI version. Apart from mi0, new versions of
24160 @value{GDBN} will not support old versions of MI and it will be the
24161 responsibility of the front end to work with the new one.
24162
24163 @c Starting with mi3, add a new command -mi-version that prints the MI
24164 @c version?
24165
24166 The best way to avoid unexpected changes in MI that might break your front
24167 end is to make your project known to @value{GDBN} developers and
24168 follow development on @email{gdb@@sourceware.org} and
24169 @email{gdb-patches@@sourceware.org}.
24170 @cindex mailing lists
24171
24172 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
24173 @node GDB/MI Output Records
24174 @section @sc{gdb/mi} Output Records
24175
24176 @menu
24177 * GDB/MI Result Records::
24178 * GDB/MI Stream Records::
24179 * GDB/MI Async Records::
24180 * GDB/MI Frame Information::
24181 * GDB/MI Thread Information::
24182 @end menu
24183
24184 @node GDB/MI Result Records
24185 @subsection @sc{gdb/mi} Result Records
24186
24187 @cindex result records in @sc{gdb/mi}
24188 @cindex @sc{gdb/mi}, result records
24189 In addition to a number of out-of-band notifications, the response to a
24190 @sc{gdb/mi} command includes one of the following result indications:
24191
24192 @table @code
24193 @findex ^done
24194 @item "^done" [ "," @var{results} ]
24195 The synchronous operation was successful, @code{@var{results}} are the return
24196 values.
24197
24198 @item "^running"
24199 @findex ^running
24200 This result record is equivalent to @samp{^done}. Historically, it
24201 was output instead of @samp{^done} if the command has resumed the
24202 target. This behaviour is maintained for backward compatibility, but
24203 all frontends should treat @samp{^done} and @samp{^running}
24204 identically and rely on the @samp{*running} output record to determine
24205 which threads are resumed.
24206
24207 @item "^connected"
24208 @findex ^connected
24209 @value{GDBN} has connected to a remote target.
24210
24211 @item "^error" "," @var{c-string}
24212 @findex ^error
24213 The operation failed. The @code{@var{c-string}} contains the corresponding
24214 error message.
24215
24216 @item "^exit"
24217 @findex ^exit
24218 @value{GDBN} has terminated.
24219
24220 @end table
24221
24222 @node GDB/MI Stream Records
24223 @subsection @sc{gdb/mi} Stream Records
24224
24225 @cindex @sc{gdb/mi}, stream records
24226 @cindex stream records in @sc{gdb/mi}
24227 @value{GDBN} internally maintains a number of output streams: the console, the
24228 target, and the log. The output intended for each of these streams is
24229 funneled through the @sc{gdb/mi} interface using @dfn{stream records}.
24230
24231 Each stream record begins with a unique @dfn{prefix character} which
24232 identifies its stream (@pxref{GDB/MI Output Syntax, , @sc{gdb/mi} Output
24233 Syntax}). In addition to the prefix, each stream record contains a
24234 @code{@var{string-output}}. This is either raw text (with an implicit new
24235 line) or a quoted C string (which does not contain an implicit newline).
24236
24237 @table @code
24238 @item "~" @var{string-output}
24239 The console output stream contains text that should be displayed in the
24240 CLI console window. It contains the textual responses to CLI commands.
24241
24242 @item "@@" @var{string-output}
24243 The target output stream contains any textual output from the running
24244 target. This is only present when GDB's event loop is truly
24245 asynchronous, which is currently only the case for remote targets.
24246
24247 @item "&" @var{string-output}
24248 The log stream contains debugging messages being produced by @value{GDBN}'s
24249 internals.
24250 @end table
24251
24252 @node GDB/MI Async Records
24253 @subsection @sc{gdb/mi} Async Records
24254
24255 @cindex async records in @sc{gdb/mi}
24256 @cindex @sc{gdb/mi}, async records
24257 @dfn{Async} records are used to notify the @sc{gdb/mi} client of
24258 additional changes that have occurred. Those changes can either be a
24259 consequence of @sc{gdb/mi} commands (e.g., a breakpoint modified) or a result of
24260 target activity (e.g., target stopped).
24261
24262 The following is the list of possible async records:
24263
24264 @table @code
24265
24266 @item *running,thread-id="@var{thread}"
24267 The target is now running. The @var{thread} field tells which
24268 specific thread is now running, and can be @samp{all} if all threads
24269 are running. The frontend should assume that no interaction with a
24270 running thread is possible after this notification is produced.
24271 The frontend should not assume that this notification is output
24272 only once for any command. @value{GDBN} may emit this notification
24273 several times, either for different threads, because it cannot resume
24274 all threads together, or even for a single thread, if the thread must
24275 be stepped though some code before letting it run freely.
24276
24277 @item *stopped,reason="@var{reason}",thread-id="@var{id}",stopped-threads="@var{stopped}",core="@var{core}"
24278 The target has stopped. The @var{reason} field can have one of the
24279 following values:
24280
24281 @table @code
24282 @item breakpoint-hit
24283 A breakpoint was reached.
24284 @item watchpoint-trigger
24285 A watchpoint was triggered.
24286 @item read-watchpoint-trigger
24287 A read watchpoint was triggered.
24288 @item access-watchpoint-trigger
24289 An access watchpoint was triggered.
24290 @item function-finished
24291 An -exec-finish or similar CLI command was accomplished.
24292 @item location-reached
24293 An -exec-until or similar CLI command was accomplished.
24294 @item watchpoint-scope
24295 A watchpoint has gone out of scope.
24296 @item end-stepping-range
24297 An -exec-next, -exec-next-instruction, -exec-step, -exec-step-instruction or
24298 similar CLI command was accomplished.
24299 @item exited-signalled
24300 The inferior exited because of a signal.
24301 @item exited
24302 The inferior exited.
24303 @item exited-normally
24304 The inferior exited normally.
24305 @item signal-received
24306 A signal was received by the inferior.
24307 @end table
24308
24309 The @var{id} field identifies the thread that directly caused the stop
24310 -- for example by hitting a breakpoint. Depending on whether all-stop
24311 mode is in effect (@pxref{All-Stop Mode}), @value{GDBN} may either
24312 stop all threads, or only the thread that directly triggered the stop.
24313 If all threads are stopped, the @var{stopped} field will have the
24314 value of @code{"all"}. Otherwise, the value of the @var{stopped}
24315 field will be a list of thread identifiers. Presently, this list will
24316 always include a single thread, but frontend should be prepared to see
24317 several threads in the list. The @var{core} field reports the
24318 processor core on which the stop event has happened. This field may be absent
24319 if such information is not available.
24320
24321 @item =thread-group-added,id="@var{id}"
24322 @itemx =thread-group-removed,id="@var{id}"
24323 A thread group was either added or removed. The @var{id} field
24324 contains the @value{GDBN} identifier of the thread group. When a thread
24325 group is added, it generally might not be associated with a running
24326 process. When a thread group is removed, its id becomes invalid and
24327 cannot be used in any way.
24328
24329 @item =thread-group-started,id="@var{id}",pid="@var{pid}"
24330 A thread group became associated with a running program,
24331 either because the program was just started or the thread group
24332 was attached to a program. The @var{id} field contains the
24333 @value{GDBN} identifier of the thread group. The @var{pid} field
24334 contains process identifier, specific to the operating system.
24335
24336 @itemx =thread-group-exited,id="@var{id}"
24337 A thread group is no longer associated with a running program,
24338 either because the program has exited, or because it was detached
24339 from. The @var{id} field contains the @value{GDBN} identifier of the
24340 thread group.
24341
24342 @item =thread-created,id="@var{id}",group-id="@var{gid}"
24343 @itemx =thread-exited,id="@var{id}",group-id="@var{gid}"
24344 A thread either was created, or has exited. The @var{id} field
24345 contains the @value{GDBN} identifier of the thread. The @var{gid}
24346 field identifies the thread group this thread belongs to.
24347
24348 @item =thread-selected,id="@var{id}"
24349 Informs that the selected thread was changed as result of the last
24350 command. This notification is not emitted as result of @code{-thread-select}
24351 command but is emitted whenever an MI command that is not documented
24352 to change the selected thread actually changes it. In particular,
24353 invoking, directly or indirectly (via user-defined command), the CLI
24354 @code{thread} command, will generate this notification.
24355
24356 We suggest that in response to this notification, front ends
24357 highlight the selected thread and cause subsequent commands to apply to
24358 that thread.
24359
24360 @item =library-loaded,...
24361 Reports that a new library file was loaded by the program. This
24362 notification has 4 fields---@var{id}, @var{target-name},
24363 @var{host-name}, and @var{symbols-loaded}. The @var{id} field is an
24364 opaque identifier of the library. For remote debugging case,
24365 @var{target-name} and @var{host-name} fields give the name of the
24366 library file on the target, and on the host respectively. For native
24367 debugging, both those fields have the same value. The
24368 @var{symbols-loaded} field reports if the debug symbols for this
24369 library are loaded. The @var{thread-group} field, if present,
24370 specifies the id of the thread group in whose context the library was loaded.
24371 If the field is absent, it means the library was loaded in the context
24372 of all present thread groups.
24373
24374 @item =library-unloaded,...
24375 Reports that a library was unloaded by the program. This notification
24376 has 3 fields---@var{id}, @var{target-name} and @var{host-name} with
24377 the same meaning as for the @code{=library-loaded} notification.
24378 The @var{thread-group} field, if present, specifies the id of the
24379 thread group in whose context the library was unloaded. If the field is
24380 absent, it means the library was unloaded in the context of all present
24381 thread groups.
24382
24383 @end table
24384
24385 @node GDB/MI Frame Information
24386 @subsection @sc{gdb/mi} Frame Information
24387
24388 Response from many MI commands includes an information about stack
24389 frame. This information is a tuple that may have the following
24390 fields:
24391
24392 @table @code
24393 @item level
24394 The level of the stack frame. The innermost frame has the level of
24395 zero. This field is always present.
24396
24397 @item func
24398 The name of the function corresponding to the frame. This field may
24399 be absent if @value{GDBN} is unable to determine the function name.
24400
24401 @item addr
24402 The code address for the frame. This field is always present.
24403
24404 @item file
24405 The name of the source files that correspond to the frame's code
24406 address. This field may be absent.
24407
24408 @item line
24409 The source line corresponding to the frames' code address. This field
24410 may be absent.
24411
24412 @item from
24413 The name of the binary file (either executable or shared library) the
24414 corresponds to the frame's code address. This field may be absent.
24415
24416 @end table
24417
24418 @node GDB/MI Thread Information
24419 @subsection @sc{gdb/mi} Thread Information
24420
24421 Whenever @value{GDBN} has to report an information about a thread, it
24422 uses a tuple with the following fields:
24423
24424 @table @code
24425 @item id
24426 The numeric id assigned to the thread by @value{GDBN}. This field is
24427 always present.
24428
24429 @item target-id
24430 Target-specific string identifying the thread. This field is always present.
24431
24432 @item details
24433 Additional information about the thread provided by the target.
24434 It is supposed to be human-readable and not interpreted by the
24435 frontend. This field is optional.
24436
24437 @item state
24438 Either @samp{stopped} or @samp{running}, depending on whether the
24439 thread is presently running. This field is always present.
24440
24441 @item core
24442 The value of this field is an integer number of the processor core the
24443 thread was last seen on. This field is optional.
24444 @end table
24445
24446
24447 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
24448 @node GDB/MI Simple Examples
24449 @section Simple Examples of @sc{gdb/mi} Interaction
24450 @cindex @sc{gdb/mi}, simple examples
24451
24452 This subsection presents several simple examples of interaction using
24453 the @sc{gdb/mi} interface. In these examples, @samp{->} means that the
24454 following line is passed to @sc{gdb/mi} as input, while @samp{<-} means
24455 the output received from @sc{gdb/mi}.
24456
24457 Note the line breaks shown in the examples are here only for
24458 readability, they don't appear in the real output.
24459
24460 @subheading Setting a Breakpoint
24461
24462 Setting a breakpoint generates synchronous output which contains detailed
24463 information of the breakpoint.
24464
24465 @smallexample
24466 -> -break-insert main
24467 <- ^done,bkpt=@{number="1",type="breakpoint",disp="keep",
24468 enabled="y",addr="0x08048564",func="main",file="myprog.c",
24469 fullname="/home/nickrob/myprog.c",line="68",times="0"@}
24470 <- (gdb)
24471 @end smallexample
24472
24473 @subheading Program Execution
24474
24475 Program execution generates asynchronous records and MI gives the
24476 reason that execution stopped.
24477
24478 @smallexample
24479 -> -exec-run
24480 <- ^running
24481 <- (gdb)
24482 <- *stopped,reason="breakpoint-hit",disp="keep",bkptno="1",thread-id="0",
24483 frame=@{addr="0x08048564",func="main",
24484 args=[@{name="argc",value="1"@},@{name="argv",value="0xbfc4d4d4"@}],
24485 file="myprog.c",fullname="/home/nickrob/myprog.c",line="68"@}
24486 <- (gdb)
24487 -> -exec-continue
24488 <- ^running
24489 <- (gdb)
24490 <- *stopped,reason="exited-normally"
24491 <- (gdb)
24492 @end smallexample
24493
24494 @subheading Quitting @value{GDBN}
24495
24496 Quitting @value{GDBN} just prints the result class @samp{^exit}.
24497
24498 @smallexample
24499 -> (gdb)
24500 <- -gdb-exit
24501 <- ^exit
24502 @end smallexample
24503
24504 Please note that @samp{^exit} is printed immediately, but it might
24505 take some time for @value{GDBN} to actually exit. During that time, @value{GDBN}
24506 performs necessary cleanups, including killing programs being debugged
24507 or disconnecting from debug hardware, so the frontend should wait till
24508 @value{GDBN} exits and should only forcibly kill @value{GDBN} if it
24509 fails to exit in reasonable time.
24510
24511 @subheading A Bad Command
24512
24513 Here's what happens if you pass a non-existent command:
24514
24515 @smallexample
24516 -> -rubbish
24517 <- ^error,msg="Undefined MI command: rubbish"
24518 <- (gdb)
24519 @end smallexample
24520
24521
24522 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
24523 @node GDB/MI Command Description Format
24524 @section @sc{gdb/mi} Command Description Format
24525
24526 The remaining sections describe blocks of commands. Each block of
24527 commands is laid out in a fashion similar to this section.
24528
24529 @subheading Motivation
24530
24531 The motivation for this collection of commands.
24532
24533 @subheading Introduction
24534
24535 A brief introduction to this collection of commands as a whole.
24536
24537 @subheading Commands
24538
24539 For each command in the block, the following is described:
24540
24541 @subsubheading Synopsis
24542
24543 @smallexample
24544 -command @var{args}@dots{}
24545 @end smallexample
24546
24547 @subsubheading Result
24548
24549 @subsubheading @value{GDBN} Command
24550
24551 The corresponding @value{GDBN} CLI command(s), if any.
24552
24553 @subsubheading Example
24554
24555 Example(s) formatted for readability. Some of the described commands have
24556 not been implemented yet and these are labeled N.A.@: (not available).
24557
24558
24559 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
24560 @node GDB/MI Breakpoint Commands
24561 @section @sc{gdb/mi} Breakpoint Commands
24562
24563 @cindex breakpoint commands for @sc{gdb/mi}
24564 @cindex @sc{gdb/mi}, breakpoint commands
24565 This section documents @sc{gdb/mi} commands for manipulating
24566 breakpoints.
24567
24568 @subheading The @code{-break-after} Command
24569 @findex -break-after
24570
24571 @subsubheading Synopsis
24572
24573 @smallexample
24574 -break-after @var{number} @var{count}
24575 @end smallexample
24576
24577 The breakpoint number @var{number} is not in effect until it has been
24578 hit @var{count} times. To see how this is reflected in the output of
24579 the @samp{-break-list} command, see the description of the
24580 @samp{-break-list} command below.
24581
24582 @subsubheading @value{GDBN} Command
24583
24584 The corresponding @value{GDBN} command is @samp{ignore}.
24585
24586 @subsubheading Example
24587
24588 @smallexample
24589 (gdb)
24590 -break-insert main
24591 ^done,bkpt=@{number="1",type="breakpoint",disp="keep",
24592 enabled="y",addr="0x000100d0",func="main",file="hello.c",
24593 fullname="/home/foo/hello.c",line="5",times="0"@}
24594 (gdb)
24595 -break-after 1 3
24596 ~
24597 ^done
24598 (gdb)
24599 -break-list
24600 ^done,BreakpointTable=@{nr_rows="1",nr_cols="6",
24601 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
24602 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
24603 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
24604 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
24605 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
24606 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
24607 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
24608 addr="0x000100d0",func="main",file="hello.c",fullname="/home/foo/hello.c",
24609 line="5",times="0",ignore="3"@}]@}
24610 (gdb)
24611 @end smallexample
24612
24613 @ignore
24614 @subheading The @code{-break-catch} Command
24615 @findex -break-catch
24616 @end ignore
24617
24618 @subheading The @code{-break-commands} Command
24619 @findex -break-commands
24620
24621 @subsubheading Synopsis
24622
24623 @smallexample
24624 -break-commands @var{number} [ @var{command1} ... @var{commandN} ]
24625 @end smallexample
24626
24627 Specifies the CLI commands that should be executed when breakpoint
24628 @var{number} is hit. The parameters @var{command1} to @var{commandN}
24629 are the commands. If no command is specified, any previously-set
24630 commands are cleared. @xref{Break Commands}. Typical use of this
24631 functionality is tracing a program, that is, printing of values of
24632 some variables whenever breakpoint is hit and then continuing.
24633
24634 @subsubheading @value{GDBN} Command
24635
24636 The corresponding @value{GDBN} command is @samp{commands}.
24637
24638 @subsubheading Example
24639
24640 @smallexample
24641 (gdb)
24642 -break-insert main
24643 ^done,bkpt=@{number="1",type="breakpoint",disp="keep",
24644 enabled="y",addr="0x000100d0",func="main",file="hello.c",
24645 fullname="/home/foo/hello.c",line="5",times="0"@}
24646 (gdb)
24647 -break-commands 1 "print v" "continue"
24648 ^done
24649 (gdb)
24650 @end smallexample
24651
24652 @subheading The @code{-break-condition} Command
24653 @findex -break-condition
24654
24655 @subsubheading Synopsis
24656
24657 @smallexample
24658 -break-condition @var{number} @var{expr}
24659 @end smallexample
24660
24661 Breakpoint @var{number} will stop the program only if the condition in
24662 @var{expr} is true. The condition becomes part of the
24663 @samp{-break-list} output (see the description of the @samp{-break-list}
24664 command below).
24665
24666 @subsubheading @value{GDBN} Command
24667
24668 The corresponding @value{GDBN} command is @samp{condition}.
24669
24670 @subsubheading Example
24671
24672 @smallexample
24673 (gdb)
24674 -break-condition 1 1
24675 ^done
24676 (gdb)
24677 -break-list
24678 ^done,BreakpointTable=@{nr_rows="1",nr_cols="6",
24679 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
24680 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
24681 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
24682 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
24683 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
24684 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
24685 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
24686 addr="0x000100d0",func="main",file="hello.c",fullname="/home/foo/hello.c",
24687 line="5",cond="1",times="0",ignore="3"@}]@}
24688 (gdb)
24689 @end smallexample
24690
24691 @subheading The @code{-break-delete} Command
24692 @findex -break-delete
24693
24694 @subsubheading Synopsis
24695
24696 @smallexample
24697 -break-delete ( @var{breakpoint} )+
24698 @end smallexample
24699
24700 Delete the breakpoint(s) whose number(s) are specified in the argument
24701 list. This is obviously reflected in the breakpoint list.
24702
24703 @subsubheading @value{GDBN} Command
24704
24705 The corresponding @value{GDBN} command is @samp{delete}.
24706
24707 @subsubheading Example
24708
24709 @smallexample
24710 (gdb)
24711 -break-delete 1
24712 ^done
24713 (gdb)
24714 -break-list
24715 ^done,BreakpointTable=@{nr_rows="0",nr_cols="6",
24716 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
24717 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
24718 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
24719 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
24720 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
24721 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
24722 body=[]@}
24723 (gdb)
24724 @end smallexample
24725
24726 @subheading The @code{-break-disable} Command
24727 @findex -break-disable
24728
24729 @subsubheading Synopsis
24730
24731 @smallexample
24732 -break-disable ( @var{breakpoint} )+
24733 @end smallexample
24734
24735 Disable the named @var{breakpoint}(s). The field @samp{enabled} in the
24736 break list is now set to @samp{n} for the named @var{breakpoint}(s).
24737
24738 @subsubheading @value{GDBN} Command
24739
24740 The corresponding @value{GDBN} command is @samp{disable}.
24741
24742 @subsubheading Example
24743
24744 @smallexample
24745 (gdb)
24746 -break-disable 2
24747 ^done
24748 (gdb)
24749 -break-list
24750 ^done,BreakpointTable=@{nr_rows="1",nr_cols="6",
24751 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
24752 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
24753 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
24754 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
24755 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
24756 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
24757 body=[bkpt=@{number="2",type="breakpoint",disp="keep",enabled="n",
24758 addr="0x000100d0",func="main",file="hello.c",fullname="/home/foo/hello.c",
24759 line="5",times="0"@}]@}
24760 (gdb)
24761 @end smallexample
24762
24763 @subheading The @code{-break-enable} Command
24764 @findex -break-enable
24765
24766 @subsubheading Synopsis
24767
24768 @smallexample
24769 -break-enable ( @var{breakpoint} )+
24770 @end smallexample
24771
24772 Enable (previously disabled) @var{breakpoint}(s).
24773
24774 @subsubheading @value{GDBN} Command
24775
24776 The corresponding @value{GDBN} command is @samp{enable}.
24777
24778 @subsubheading Example
24779
24780 @smallexample
24781 (gdb)
24782 -break-enable 2
24783 ^done
24784 (gdb)
24785 -break-list
24786 ^done,BreakpointTable=@{nr_rows="1",nr_cols="6",
24787 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
24788 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
24789 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
24790 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
24791 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
24792 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
24793 body=[bkpt=@{number="2",type="breakpoint",disp="keep",enabled="y",
24794 addr="0x000100d0",func="main",file="hello.c",fullname="/home/foo/hello.c",
24795 line="5",times="0"@}]@}
24796 (gdb)
24797 @end smallexample
24798
24799 @subheading The @code{-break-info} Command
24800 @findex -break-info
24801
24802 @subsubheading Synopsis
24803
24804 @smallexample
24805 -break-info @var{breakpoint}
24806 @end smallexample
24807
24808 @c REDUNDANT???
24809 Get information about a single breakpoint.
24810
24811 @subsubheading @value{GDBN} Command
24812
24813 The corresponding @value{GDBN} command is @samp{info break @var{breakpoint}}.
24814
24815 @subsubheading Example
24816 N.A.
24817
24818 @subheading The @code{-break-insert} Command
24819 @findex -break-insert
24820
24821 @subsubheading Synopsis
24822
24823 @smallexample
24824 -break-insert [ -t ] [ -h ] [ -f ] [ -d ] [ -a ]
24825 [ -c @var{condition} ] [ -i @var{ignore-count} ]
24826 [ -p @var{thread} ] [ @var{location} ]
24827 @end smallexample
24828
24829 @noindent
24830 If specified, @var{location}, can be one of:
24831
24832 @itemize @bullet
24833 @item function
24834 @c @item +offset
24835 @c @item -offset
24836 @c @item linenum
24837 @item filename:linenum
24838 @item filename:function
24839 @item *address
24840 @end itemize
24841
24842 The possible optional parameters of this command are:
24843
24844 @table @samp
24845 @item -t
24846 Insert a temporary breakpoint.
24847 @item -h
24848 Insert a hardware breakpoint.
24849 @item -c @var{condition}
24850 Make the breakpoint conditional on @var{condition}.
24851 @item -i @var{ignore-count}
24852 Initialize the @var{ignore-count}.
24853 @item -f
24854 If @var{location} cannot be parsed (for example if it
24855 refers to unknown files or functions), create a pending
24856 breakpoint. Without this flag, @value{GDBN} will report
24857 an error, and won't create a breakpoint, if @var{location}
24858 cannot be parsed.
24859 @item -d
24860 Create a disabled breakpoint.
24861 @item -a
24862 Create a tracepoint. @xref{Tracepoints}. When this parameter
24863 is used together with @samp{-h}, a fast tracepoint is created.
24864 @end table
24865
24866 @subsubheading Result
24867
24868 The result is in the form:
24869
24870 @smallexample
24871 ^done,bkpt=@{number="@var{number}",type="@var{type}",disp="del"|"keep",
24872 enabled="y"|"n",addr="@var{hex}",func="@var{funcname}",file="@var{filename}",
24873 fullname="@var{full_filename}",line="@var{lineno}",[thread="@var{threadno},]
24874 times="@var{times}"@}
24875 @end smallexample
24876
24877 @noindent
24878 where @var{number} is the @value{GDBN} number for this breakpoint,
24879 @var{funcname} is the name of the function where the breakpoint was
24880 inserted, @var{filename} is the name of the source file which contains
24881 this function, @var{lineno} is the source line number within that file
24882 and @var{times} the number of times that the breakpoint has been hit
24883 (always 0 for -break-insert but may be greater for -break-info or -break-list
24884 which use the same output).
24885
24886 Note: this format is open to change.
24887 @c An out-of-band breakpoint instead of part of the result?
24888
24889 @subsubheading @value{GDBN} Command
24890
24891 The corresponding @value{GDBN} commands are @samp{break}, @samp{tbreak},
24892 @samp{hbreak}, @samp{thbreak}, and @samp{rbreak}.
24893
24894 @subsubheading Example
24895
24896 @smallexample
24897 (gdb)
24898 -break-insert main
24899 ^done,bkpt=@{number="1",addr="0x0001072c",file="recursive2.c",
24900 fullname="/home/foo/recursive2.c,line="4",times="0"@}
24901 (gdb)
24902 -break-insert -t foo
24903 ^done,bkpt=@{number="2",addr="0x00010774",file="recursive2.c",
24904 fullname="/home/foo/recursive2.c,line="11",times="0"@}
24905 (gdb)
24906 -break-list
24907 ^done,BreakpointTable=@{nr_rows="2",nr_cols="6",
24908 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
24909 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
24910 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
24911 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
24912 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
24913 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
24914 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
24915 addr="0x0001072c", func="main",file="recursive2.c",
24916 fullname="/home/foo/recursive2.c,"line="4",times="0"@},
24917 bkpt=@{number="2",type="breakpoint",disp="del",enabled="y",
24918 addr="0x00010774",func="foo",file="recursive2.c",
24919 fullname="/home/foo/recursive2.c",line="11",times="0"@}]@}
24920 (gdb)
24921 -break-insert -r foo.*
24922 ~int foo(int, int);
24923 ^done,bkpt=@{number="3",addr="0x00010774",file="recursive2.c,
24924 "fullname="/home/foo/recursive2.c",line="11",times="0"@}
24925 (gdb)
24926 @end smallexample
24927
24928 @subheading The @code{-break-list} Command
24929 @findex -break-list
24930
24931 @subsubheading Synopsis
24932
24933 @smallexample
24934 -break-list
24935 @end smallexample
24936
24937 Displays the list of inserted breakpoints, showing the following fields:
24938
24939 @table @samp
24940 @item Number
24941 number of the breakpoint
24942 @item Type
24943 type of the breakpoint: @samp{breakpoint} or @samp{watchpoint}
24944 @item Disposition
24945 should the breakpoint be deleted or disabled when it is hit: @samp{keep}
24946 or @samp{nokeep}
24947 @item Enabled
24948 is the breakpoint enabled or no: @samp{y} or @samp{n}
24949 @item Address
24950 memory location at which the breakpoint is set
24951 @item What
24952 logical location of the breakpoint, expressed by function name, file
24953 name, line number
24954 @item Times
24955 number of times the breakpoint has been hit
24956 @end table
24957
24958 If there are no breakpoints or watchpoints, the @code{BreakpointTable}
24959 @code{body} field is an empty list.
24960
24961 @subsubheading @value{GDBN} Command
24962
24963 The corresponding @value{GDBN} command is @samp{info break}.
24964
24965 @subsubheading Example
24966
24967 @smallexample
24968 (gdb)
24969 -break-list
24970 ^done,BreakpointTable=@{nr_rows="2",nr_cols="6",
24971 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
24972 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
24973 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
24974 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
24975 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
24976 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
24977 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
24978 addr="0x000100d0",func="main",file="hello.c",line="5",times="0"@},
24979 bkpt=@{number="2",type="breakpoint",disp="keep",enabled="y",
24980 addr="0x00010114",func="foo",file="hello.c",fullname="/home/foo/hello.c",
24981 line="13",times="0"@}]@}
24982 (gdb)
24983 @end smallexample
24984
24985 Here's an example of the result when there are no breakpoints:
24986
24987 @smallexample
24988 (gdb)
24989 -break-list
24990 ^done,BreakpointTable=@{nr_rows="0",nr_cols="6",
24991 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
24992 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
24993 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
24994 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
24995 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
24996 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
24997 body=[]@}
24998 (gdb)
24999 @end smallexample
25000
25001 @subheading The @code{-break-passcount} Command
25002 @findex -break-passcount
25003
25004 @subsubheading Synopsis
25005
25006 @smallexample
25007 -break-passcount @var{tracepoint-number} @var{passcount}
25008 @end smallexample
25009
25010 Set the passcount for tracepoint @var{tracepoint-number} to
25011 @var{passcount}. If the breakpoint referred to by @var{tracepoint-number}
25012 is not a tracepoint, error is emitted. This corresponds to CLI
25013 command @samp{passcount}.
25014
25015 @subheading The @code{-break-watch} Command
25016 @findex -break-watch
25017
25018 @subsubheading Synopsis
25019
25020 @smallexample
25021 -break-watch [ -a | -r ]
25022 @end smallexample
25023
25024 Create a watchpoint. With the @samp{-a} option it will create an
25025 @dfn{access} watchpoint, i.e., a watchpoint that triggers either on a
25026 read from or on a write to the memory location. With the @samp{-r}
25027 option, the watchpoint created is a @dfn{read} watchpoint, i.e., it will
25028 trigger only when the memory location is accessed for reading. Without
25029 either of the options, the watchpoint created is a regular watchpoint,
25030 i.e., it will trigger when the memory location is accessed for writing.
25031 @xref{Set Watchpoints, , Setting Watchpoints}.
25032
25033 Note that @samp{-break-list} will report a single list of watchpoints and
25034 breakpoints inserted.
25035
25036 @subsubheading @value{GDBN} Command
25037
25038 The corresponding @value{GDBN} commands are @samp{watch}, @samp{awatch}, and
25039 @samp{rwatch}.
25040
25041 @subsubheading Example
25042
25043 Setting a watchpoint on a variable in the @code{main} function:
25044
25045 @smallexample
25046 (gdb)
25047 -break-watch x
25048 ^done,wpt=@{number="2",exp="x"@}
25049 (gdb)
25050 -exec-continue
25051 ^running
25052 (gdb)
25053 *stopped,reason="watchpoint-trigger",wpt=@{number="2",exp="x"@},
25054 value=@{old="-268439212",new="55"@},
25055 frame=@{func="main",args=[],file="recursive2.c",
25056 fullname="/home/foo/bar/recursive2.c",line="5"@}
25057 (gdb)
25058 @end smallexample
25059
25060 Setting a watchpoint on a variable local to a function. @value{GDBN} will stop
25061 the program execution twice: first for the variable changing value, then
25062 for the watchpoint going out of scope.
25063
25064 @smallexample
25065 (gdb)
25066 -break-watch C
25067 ^done,wpt=@{number="5",exp="C"@}
25068 (gdb)
25069 -exec-continue
25070 ^running
25071 (gdb)
25072 *stopped,reason="watchpoint-trigger",
25073 wpt=@{number="5",exp="C"@},value=@{old="-276895068",new="3"@},
25074 frame=@{func="callee4",args=[],
25075 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
25076 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="13"@}
25077 (gdb)
25078 -exec-continue
25079 ^running
25080 (gdb)
25081 *stopped,reason="watchpoint-scope",wpnum="5",
25082 frame=@{func="callee3",args=[@{name="strarg",
25083 value="0x11940 \"A string argument.\""@}],
25084 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
25085 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="18"@}
25086 (gdb)
25087 @end smallexample
25088
25089 Listing breakpoints and watchpoints, at different points in the program
25090 execution. Note that once the watchpoint goes out of scope, it is
25091 deleted.
25092
25093 @smallexample
25094 (gdb)
25095 -break-watch C
25096 ^done,wpt=@{number="2",exp="C"@}
25097 (gdb)
25098 -break-list
25099 ^done,BreakpointTable=@{nr_rows="2",nr_cols="6",
25100 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
25101 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
25102 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
25103 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
25104 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
25105 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
25106 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
25107 addr="0x00010734",func="callee4",
25108 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
25109 fullname="/home/foo/devo/gdb/testsuite/gdb.mi/basics.c"line="8",times="1"@},
25110 bkpt=@{number="2",type="watchpoint",disp="keep",
25111 enabled="y",addr="",what="C",times="0"@}]@}
25112 (gdb)
25113 -exec-continue
25114 ^running
25115 (gdb)
25116 *stopped,reason="watchpoint-trigger",wpt=@{number="2",exp="C"@},
25117 value=@{old="-276895068",new="3"@},
25118 frame=@{func="callee4",args=[],
25119 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
25120 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="13"@}
25121 (gdb)
25122 -break-list
25123 ^done,BreakpointTable=@{nr_rows="2",nr_cols="6",
25124 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
25125 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
25126 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
25127 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
25128 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
25129 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
25130 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
25131 addr="0x00010734",func="callee4",
25132 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
25133 fullname="/home/foo/devo/gdb/testsuite/gdb.mi/basics.c",line="8",times="1"@},
25134 bkpt=@{number="2",type="watchpoint",disp="keep",
25135 enabled="y",addr="",what="C",times="-5"@}]@}
25136 (gdb)
25137 -exec-continue
25138 ^running
25139 ^done,reason="watchpoint-scope",wpnum="2",
25140 frame=@{func="callee3",args=[@{name="strarg",
25141 value="0x11940 \"A string argument.\""@}],
25142 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
25143 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="18"@}
25144 (gdb)
25145 -break-list
25146 ^done,BreakpointTable=@{nr_rows="1",nr_cols="6",
25147 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
25148 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
25149 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
25150 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
25151 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
25152 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
25153 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
25154 addr="0x00010734",func="callee4",
25155 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
25156 fullname="/home/foo/devo/gdb/testsuite/gdb.mi/basics.c",line="8",
25157 times="1"@}]@}
25158 (gdb)
25159 @end smallexample
25160
25161 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
25162 @node GDB/MI Program Context
25163 @section @sc{gdb/mi} Program Context
25164
25165 @subheading The @code{-exec-arguments} Command
25166 @findex -exec-arguments
25167
25168
25169 @subsubheading Synopsis
25170
25171 @smallexample
25172 -exec-arguments @var{args}
25173 @end smallexample
25174
25175 Set the inferior program arguments, to be used in the next
25176 @samp{-exec-run}.
25177
25178 @subsubheading @value{GDBN} Command
25179
25180 The corresponding @value{GDBN} command is @samp{set args}.
25181
25182 @subsubheading Example
25183
25184 @smallexample
25185 (gdb)
25186 -exec-arguments -v word
25187 ^done
25188 (gdb)
25189 @end smallexample
25190
25191
25192 @ignore
25193 @subheading The @code{-exec-show-arguments} Command
25194 @findex -exec-show-arguments
25195
25196 @subsubheading Synopsis
25197
25198 @smallexample
25199 -exec-show-arguments
25200 @end smallexample
25201
25202 Print the arguments of the program.
25203
25204 @subsubheading @value{GDBN} Command
25205
25206 The corresponding @value{GDBN} command is @samp{show args}.
25207
25208 @subsubheading Example
25209 N.A.
25210 @end ignore
25211
25212
25213 @subheading The @code{-environment-cd} Command
25214 @findex -environment-cd
25215
25216 @subsubheading Synopsis
25217
25218 @smallexample
25219 -environment-cd @var{pathdir}
25220 @end smallexample
25221
25222 Set @value{GDBN}'s working directory.
25223
25224 @subsubheading @value{GDBN} Command
25225
25226 The corresponding @value{GDBN} command is @samp{cd}.
25227
25228 @subsubheading Example
25229
25230 @smallexample
25231 (gdb)
25232 -environment-cd /kwikemart/marge/ezannoni/flathead-dev/devo/gdb
25233 ^done
25234 (gdb)
25235 @end smallexample
25236
25237
25238 @subheading The @code{-environment-directory} Command
25239 @findex -environment-directory
25240
25241 @subsubheading Synopsis
25242
25243 @smallexample
25244 -environment-directory [ -r ] [ @var{pathdir} ]+
25245 @end smallexample
25246
25247 Add directories @var{pathdir} to beginning of search path for source files.
25248 If the @samp{-r} option is used, the search path is reset to the default
25249 search path. If directories @var{pathdir} are supplied in addition to the
25250 @samp{-r} option, the search path is first reset and then addition
25251 occurs as normal.
25252 Multiple directories may be specified, separated by blanks. Specifying
25253 multiple directories in a single command
25254 results in the directories added to the beginning of the
25255 search path in the same order they were presented in the command.
25256 If blanks are needed as
25257 part of a directory name, double-quotes should be used around
25258 the name. In the command output, the path will show up separated
25259 by the system directory-separator character. The directory-separator
25260 character must not be used
25261 in any directory name.
25262 If no directories are specified, the current search path is displayed.
25263
25264 @subsubheading @value{GDBN} Command
25265
25266 The corresponding @value{GDBN} command is @samp{dir}.
25267
25268 @subsubheading Example
25269
25270 @smallexample
25271 (gdb)
25272 -environment-directory /kwikemart/marge/ezannoni/flathead-dev/devo/gdb
25273 ^done,source-path="/kwikemart/marge/ezannoni/flathead-dev/devo/gdb:$cdir:$cwd"
25274 (gdb)
25275 -environment-directory ""
25276 ^done,source-path="/kwikemart/marge/ezannoni/flathead-dev/devo/gdb:$cdir:$cwd"
25277 (gdb)
25278 -environment-directory -r /home/jjohnstn/src/gdb /usr/src
25279 ^done,source-path="/home/jjohnstn/src/gdb:/usr/src:$cdir:$cwd"
25280 (gdb)
25281 -environment-directory -r
25282 ^done,source-path="$cdir:$cwd"
25283 (gdb)
25284 @end smallexample
25285
25286
25287 @subheading The @code{-environment-path} Command
25288 @findex -environment-path
25289
25290 @subsubheading Synopsis
25291
25292 @smallexample
25293 -environment-path [ -r ] [ @var{pathdir} ]+
25294 @end smallexample
25295
25296 Add directories @var{pathdir} to beginning of search path for object files.
25297 If the @samp{-r} option is used, the search path is reset to the original
25298 search path that existed at gdb start-up. If directories @var{pathdir} are
25299 supplied in addition to the
25300 @samp{-r} option, the search path is first reset and then addition
25301 occurs as normal.
25302 Multiple directories may be specified, separated by blanks. Specifying
25303 multiple directories in a single command
25304 results in the directories added to the beginning of the
25305 search path in the same order they were presented in the command.
25306 If blanks are needed as
25307 part of a directory name, double-quotes should be used around
25308 the name. In the command output, the path will show up separated
25309 by the system directory-separator character. The directory-separator
25310 character must not be used
25311 in any directory name.
25312 If no directories are specified, the current path is displayed.
25313
25314
25315 @subsubheading @value{GDBN} Command
25316
25317 The corresponding @value{GDBN} command is @samp{path}.
25318
25319 @subsubheading Example
25320
25321 @smallexample
25322 (gdb)
25323 -environment-path
25324 ^done,path="/usr/bin"
25325 (gdb)
25326 -environment-path /kwikemart/marge/ezannoni/flathead-dev/ppc-eabi/gdb /bin
25327 ^done,path="/kwikemart/marge/ezannoni/flathead-dev/ppc-eabi/gdb:/bin:/usr/bin"
25328 (gdb)
25329 -environment-path -r /usr/local/bin
25330 ^done,path="/usr/local/bin:/usr/bin"
25331 (gdb)
25332 @end smallexample
25333
25334
25335 @subheading The @code{-environment-pwd} Command
25336 @findex -environment-pwd
25337
25338 @subsubheading Synopsis
25339
25340 @smallexample
25341 -environment-pwd
25342 @end smallexample
25343
25344 Show the current working directory.
25345
25346 @subsubheading @value{GDBN} Command
25347
25348 The corresponding @value{GDBN} command is @samp{pwd}.
25349
25350 @subsubheading Example
25351
25352 @smallexample
25353 (gdb)
25354 -environment-pwd
25355 ^done,cwd="/kwikemart/marge/ezannoni/flathead-dev/devo/gdb"
25356 (gdb)
25357 @end smallexample
25358
25359 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
25360 @node GDB/MI Thread Commands
25361 @section @sc{gdb/mi} Thread Commands
25362
25363
25364 @subheading The @code{-thread-info} Command
25365 @findex -thread-info
25366
25367 @subsubheading Synopsis
25368
25369 @smallexample
25370 -thread-info [ @var{thread-id} ]
25371 @end smallexample
25372
25373 Reports information about either a specific thread, if
25374 the @var{thread-id} parameter is present, or about all
25375 threads. When printing information about all threads,
25376 also reports the current thread.
25377
25378 @subsubheading @value{GDBN} Command
25379
25380 The @samp{info thread} command prints the same information
25381 about all threads.
25382
25383 @subsubheading Example
25384
25385 @smallexample
25386 -thread-info
25387 ^done,threads=[
25388 @{id="2",target-id="Thread 0xb7e14b90 (LWP 21257)",
25389 frame=@{level="0",addr="0xffffe410",func="__kernel_vsyscall",args=[]@},state="running"@},
25390 @{id="1",target-id="Thread 0xb7e156b0 (LWP 21254)",
25391 frame=@{level="0",addr="0x0804891f",func="foo",args=[@{name="i",value="10"@}],
25392 file="/tmp/a.c",fullname="/tmp/a.c",line="158"@},state="running"@}],
25393 current-thread-id="1"
25394 (gdb)
25395 @end smallexample
25396
25397 The @samp{state} field may have the following values:
25398
25399 @table @code
25400 @item stopped
25401 The thread is stopped. Frame information is available for stopped
25402 threads.
25403
25404 @item running
25405 The thread is running. There's no frame information for running
25406 threads.
25407
25408 @end table
25409
25410 @subheading The @code{-thread-list-ids} Command
25411 @findex -thread-list-ids
25412
25413 @subsubheading Synopsis
25414
25415 @smallexample
25416 -thread-list-ids
25417 @end smallexample
25418
25419 Produces a list of the currently known @value{GDBN} thread ids. At the
25420 end of the list it also prints the total number of such threads.
25421
25422 This command is retained for historical reasons, the
25423 @code{-thread-info} command should be used instead.
25424
25425 @subsubheading @value{GDBN} Command
25426
25427 Part of @samp{info threads} supplies the same information.
25428
25429 @subsubheading Example
25430
25431 @smallexample
25432 (gdb)
25433 -thread-list-ids
25434 ^done,thread-ids=@{thread-id="3",thread-id="2",thread-id="1"@},
25435 current-thread-id="1",number-of-threads="3"
25436 (gdb)
25437 @end smallexample
25438
25439
25440 @subheading The @code{-thread-select} Command
25441 @findex -thread-select
25442
25443 @subsubheading Synopsis
25444
25445 @smallexample
25446 -thread-select @var{threadnum}
25447 @end smallexample
25448
25449 Make @var{threadnum} the current thread. It prints the number of the new
25450 current thread, and the topmost frame for that thread.
25451
25452 This command is deprecated in favor of explicitly using the
25453 @samp{--thread} option to each command.
25454
25455 @subsubheading @value{GDBN} Command
25456
25457 The corresponding @value{GDBN} command is @samp{thread}.
25458
25459 @subsubheading Example
25460
25461 @smallexample
25462 (gdb)
25463 -exec-next
25464 ^running
25465 (gdb)
25466 *stopped,reason="end-stepping-range",thread-id="2",line="187",
25467 file="../../../devo/gdb/testsuite/gdb.threads/linux-dp.c"
25468 (gdb)
25469 -thread-list-ids
25470 ^done,
25471 thread-ids=@{thread-id="3",thread-id="2",thread-id="1"@},
25472 number-of-threads="3"
25473 (gdb)
25474 -thread-select 3
25475 ^done,new-thread-id="3",
25476 frame=@{level="0",func="vprintf",
25477 args=[@{name="format",value="0x8048e9c \"%*s%c %d %c\\n\""@},
25478 @{name="arg",value="0x2"@}],file="vprintf.c",line="31"@}
25479 (gdb)
25480 @end smallexample
25481
25482 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
25483 @node GDB/MI Program Execution
25484 @section @sc{gdb/mi} Program Execution
25485
25486 These are the asynchronous commands which generate the out-of-band
25487 record @samp{*stopped}. Currently @value{GDBN} only really executes
25488 asynchronously with remote targets and this interaction is mimicked in
25489 other cases.
25490
25491 @subheading The @code{-exec-continue} Command
25492 @findex -exec-continue
25493
25494 @subsubheading Synopsis
25495
25496 @smallexample
25497 -exec-continue [--reverse] [--all|--thread-group N]
25498 @end smallexample
25499
25500 Resumes the execution of the inferior program, which will continue
25501 to execute until it reaches a debugger stop event. If the
25502 @samp{--reverse} option is specified, execution resumes in reverse until
25503 it reaches a stop event. Stop events may include
25504 @itemize @bullet
25505 @item
25506 breakpoints or watchpoints
25507 @item
25508 signals or exceptions
25509 @item
25510 the end of the process (or its beginning under @samp{--reverse})
25511 @item
25512 the end or beginning of a replay log if one is being used.
25513 @end itemize
25514 In all-stop mode (@pxref{All-Stop
25515 Mode}), may resume only one thread, or all threads, depending on the
25516 value of the @samp{scheduler-locking} variable. If @samp{--all} is
25517 specified, all threads (in all inferiors) will be resumed. The @samp{--all} option is
25518 ignored in all-stop mode. If the @samp{--thread-group} options is
25519 specified, then all threads in that thread group are resumed.
25520
25521 @subsubheading @value{GDBN} Command
25522
25523 The corresponding @value{GDBN} corresponding is @samp{continue}.
25524
25525 @subsubheading Example
25526
25527 @smallexample
25528 -exec-continue
25529 ^running
25530 (gdb)
25531 @@Hello world
25532 *stopped,reason="breakpoint-hit",disp="keep",bkptno="2",frame=@{
25533 func="foo",args=[],file="hello.c",fullname="/home/foo/bar/hello.c",
25534 line="13"@}
25535 (gdb)
25536 @end smallexample
25537
25538
25539 @subheading The @code{-exec-finish} Command
25540 @findex -exec-finish
25541
25542 @subsubheading Synopsis
25543
25544 @smallexample
25545 -exec-finish [--reverse]
25546 @end smallexample
25547
25548 Resumes the execution of the inferior program until the current
25549 function is exited. Displays the results returned by the function.
25550 If the @samp{--reverse} option is specified, resumes the reverse
25551 execution of the inferior program until the point where current
25552 function was called.
25553
25554 @subsubheading @value{GDBN} Command
25555
25556 The corresponding @value{GDBN} command is @samp{finish}.
25557
25558 @subsubheading Example
25559
25560 Function returning @code{void}.
25561
25562 @smallexample
25563 -exec-finish
25564 ^running
25565 (gdb)
25566 @@hello from foo
25567 *stopped,reason="function-finished",frame=@{func="main",args=[],
25568 file="hello.c",fullname="/home/foo/bar/hello.c",line="7"@}
25569 (gdb)
25570 @end smallexample
25571
25572 Function returning other than @code{void}. The name of the internal
25573 @value{GDBN} variable storing the result is printed, together with the
25574 value itself.
25575
25576 @smallexample
25577 -exec-finish
25578 ^running
25579 (gdb)
25580 *stopped,reason="function-finished",frame=@{addr="0x000107b0",func="foo",
25581 args=[@{name="a",value="1"],@{name="b",value="9"@}@},
25582 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
25583 gdb-result-var="$1",return-value="0"
25584 (gdb)
25585 @end smallexample
25586
25587
25588 @subheading The @code{-exec-interrupt} Command
25589 @findex -exec-interrupt
25590
25591 @subsubheading Synopsis
25592
25593 @smallexample
25594 -exec-interrupt [--all|--thread-group N]
25595 @end smallexample
25596
25597 Interrupts the background execution of the target. Note how the token
25598 associated with the stop message is the one for the execution command
25599 that has been interrupted. The token for the interrupt itself only
25600 appears in the @samp{^done} output. If the user is trying to
25601 interrupt a non-running program, an error message will be printed.
25602
25603 Note that when asynchronous execution is enabled, this command is
25604 asynchronous just like other execution commands. That is, first the
25605 @samp{^done} response will be printed, and the target stop will be
25606 reported after that using the @samp{*stopped} notification.
25607
25608 In non-stop mode, only the context thread is interrupted by default.
25609 All threads (in all inferiors) will be interrupted if the
25610 @samp{--all} option is specified. If the @samp{--thread-group}
25611 option is specified, all threads in that group will be interrupted.
25612
25613 @subsubheading @value{GDBN} Command
25614
25615 The corresponding @value{GDBN} command is @samp{interrupt}.
25616
25617 @subsubheading Example
25618
25619 @smallexample
25620 (gdb)
25621 111-exec-continue
25622 111^running
25623
25624 (gdb)
25625 222-exec-interrupt
25626 222^done
25627 (gdb)
25628 111*stopped,signal-name="SIGINT",signal-meaning="Interrupt",
25629 frame=@{addr="0x00010140",func="foo",args=[],file="try.c",
25630 fullname="/home/foo/bar/try.c",line="13"@}
25631 (gdb)
25632
25633 (gdb)
25634 -exec-interrupt
25635 ^error,msg="mi_cmd_exec_interrupt: Inferior not executing."
25636 (gdb)
25637 @end smallexample
25638
25639 @subheading The @code{-exec-jump} Command
25640 @findex -exec-jump
25641
25642 @subsubheading Synopsis
25643
25644 @smallexample
25645 -exec-jump @var{location}
25646 @end smallexample
25647
25648 Resumes execution of the inferior program at the location specified by
25649 parameter. @xref{Specify Location}, for a description of the
25650 different forms of @var{location}.
25651
25652 @subsubheading @value{GDBN} Command
25653
25654 The corresponding @value{GDBN} command is @samp{jump}.
25655
25656 @subsubheading Example
25657
25658 @smallexample
25659 -exec-jump foo.c:10
25660 *running,thread-id="all"
25661 ^running
25662 @end smallexample
25663
25664
25665 @subheading The @code{-exec-next} Command
25666 @findex -exec-next
25667
25668 @subsubheading Synopsis
25669
25670 @smallexample
25671 -exec-next [--reverse]
25672 @end smallexample
25673
25674 Resumes execution of the inferior program, stopping when the beginning
25675 of the next source line is reached.
25676
25677 If the @samp{--reverse} option is specified, resumes reverse execution
25678 of the inferior program, stopping at the beginning of the previous
25679 source line. If you issue this command on the first line of a
25680 function, it will take you back to the caller of that function, to the
25681 source line where the function was called.
25682
25683
25684 @subsubheading @value{GDBN} Command
25685
25686 The corresponding @value{GDBN} command is @samp{next}.
25687
25688 @subsubheading Example
25689
25690 @smallexample
25691 -exec-next
25692 ^running
25693 (gdb)
25694 *stopped,reason="end-stepping-range",line="8",file="hello.c"
25695 (gdb)
25696 @end smallexample
25697
25698
25699 @subheading The @code{-exec-next-instruction} Command
25700 @findex -exec-next-instruction
25701
25702 @subsubheading Synopsis
25703
25704 @smallexample
25705 -exec-next-instruction [--reverse]
25706 @end smallexample
25707
25708 Executes one machine instruction. If the instruction is a function
25709 call, continues until the function returns. If the program stops at an
25710 instruction in the middle of a source line, the address will be
25711 printed as well.
25712
25713 If the @samp{--reverse} option is specified, resumes reverse execution
25714 of the inferior program, stopping at the previous instruction. If the
25715 previously executed instruction was a return from another function,
25716 it will continue to execute in reverse until the call to that function
25717 (from the current stack frame) is reached.
25718
25719 @subsubheading @value{GDBN} Command
25720
25721 The corresponding @value{GDBN} command is @samp{nexti}.
25722
25723 @subsubheading Example
25724
25725 @smallexample
25726 (gdb)
25727 -exec-next-instruction
25728 ^running
25729
25730 (gdb)
25731 *stopped,reason="end-stepping-range",
25732 addr="0x000100d4",line="5",file="hello.c"
25733 (gdb)
25734 @end smallexample
25735
25736
25737 @subheading The @code{-exec-return} Command
25738 @findex -exec-return
25739
25740 @subsubheading Synopsis
25741
25742 @smallexample
25743 -exec-return
25744 @end smallexample
25745
25746 Makes current function return immediately. Doesn't execute the inferior.
25747 Displays the new current frame.
25748
25749 @subsubheading @value{GDBN} Command
25750
25751 The corresponding @value{GDBN} command is @samp{return}.
25752
25753 @subsubheading Example
25754
25755 @smallexample
25756 (gdb)
25757 200-break-insert callee4
25758 200^done,bkpt=@{number="1",addr="0x00010734",
25759 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",line="8"@}
25760 (gdb)
25761 000-exec-run
25762 000^running
25763 (gdb)
25764 000*stopped,reason="breakpoint-hit",disp="keep",bkptno="1",
25765 frame=@{func="callee4",args=[],
25766 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
25767 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="8"@}
25768 (gdb)
25769 205-break-delete
25770 205^done
25771 (gdb)
25772 111-exec-return
25773 111^done,frame=@{level="0",func="callee3",
25774 args=[@{name="strarg",
25775 value="0x11940 \"A string argument.\""@}],
25776 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
25777 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="18"@}
25778 (gdb)
25779 @end smallexample
25780
25781
25782 @subheading The @code{-exec-run} Command
25783 @findex -exec-run
25784
25785 @subsubheading Synopsis
25786
25787 @smallexample
25788 -exec-run [--all | --thread-group N]
25789 @end smallexample
25790
25791 Starts execution of the inferior from the beginning. The inferior
25792 executes until either a breakpoint is encountered or the program
25793 exits. In the latter case the output will include an exit code, if
25794 the program has exited exceptionally.
25795
25796 When no option is specified, the current inferior is started. If the
25797 @samp{--thread-group} option is specified, it should refer to a thread
25798 group of type @samp{process}, and that thread group will be started.
25799 If the @samp{--all} option is specified, then all inferiors will be started.
25800
25801 @subsubheading @value{GDBN} Command
25802
25803 The corresponding @value{GDBN} command is @samp{run}.
25804
25805 @subsubheading Examples
25806
25807 @smallexample
25808 (gdb)
25809 -break-insert main
25810 ^done,bkpt=@{number="1",addr="0x0001072c",file="recursive2.c",line="4"@}
25811 (gdb)
25812 -exec-run
25813 ^running
25814 (gdb)
25815 *stopped,reason="breakpoint-hit",disp="keep",bkptno="1",
25816 frame=@{func="main",args=[],file="recursive2.c",
25817 fullname="/home/foo/bar/recursive2.c",line="4"@}
25818 (gdb)
25819 @end smallexample
25820
25821 @noindent
25822 Program exited normally:
25823
25824 @smallexample
25825 (gdb)
25826 -exec-run
25827 ^running
25828 (gdb)
25829 x = 55
25830 *stopped,reason="exited-normally"
25831 (gdb)
25832 @end smallexample
25833
25834 @noindent
25835 Program exited exceptionally:
25836
25837 @smallexample
25838 (gdb)
25839 -exec-run
25840 ^running
25841 (gdb)
25842 x = 55
25843 *stopped,reason="exited",exit-code="01"
25844 (gdb)
25845 @end smallexample
25846
25847 Another way the program can terminate is if it receives a signal such as
25848 @code{SIGINT}. In this case, @sc{gdb/mi} displays this:
25849
25850 @smallexample
25851 (gdb)
25852 *stopped,reason="exited-signalled",signal-name="SIGINT",
25853 signal-meaning="Interrupt"
25854 @end smallexample
25855
25856
25857 @c @subheading -exec-signal
25858
25859
25860 @subheading The @code{-exec-step} Command
25861 @findex -exec-step
25862
25863 @subsubheading Synopsis
25864
25865 @smallexample
25866 -exec-step [--reverse]
25867 @end smallexample
25868
25869 Resumes execution of the inferior program, stopping when the beginning
25870 of the next source line is reached, if the next source line is not a
25871 function call. If it is, stop at the first instruction of the called
25872 function. If the @samp{--reverse} option is specified, resumes reverse
25873 execution of the inferior program, stopping at the beginning of the
25874 previously executed source line.
25875
25876 @subsubheading @value{GDBN} Command
25877
25878 The corresponding @value{GDBN} command is @samp{step}.
25879
25880 @subsubheading Example
25881
25882 Stepping into a function:
25883
25884 @smallexample
25885 -exec-step
25886 ^running
25887 (gdb)
25888 *stopped,reason="end-stepping-range",
25889 frame=@{func="foo",args=[@{name="a",value="10"@},
25890 @{name="b",value="0"@}],file="recursive2.c",
25891 fullname="/home/foo/bar/recursive2.c",line="11"@}
25892 (gdb)
25893 @end smallexample
25894
25895 Regular stepping:
25896
25897 @smallexample
25898 -exec-step
25899 ^running
25900 (gdb)
25901 *stopped,reason="end-stepping-range",line="14",file="recursive2.c"
25902 (gdb)
25903 @end smallexample
25904
25905
25906 @subheading The @code{-exec-step-instruction} Command
25907 @findex -exec-step-instruction
25908
25909 @subsubheading Synopsis
25910
25911 @smallexample
25912 -exec-step-instruction [--reverse]
25913 @end smallexample
25914
25915 Resumes the inferior which executes one machine instruction. If the
25916 @samp{--reverse} option is specified, resumes reverse execution of the
25917 inferior program, stopping at the previously executed instruction.
25918 The output, once @value{GDBN} has stopped, will vary depending on
25919 whether we have stopped in the middle of a source line or not. In the
25920 former case, the address at which the program stopped will be printed
25921 as well.
25922
25923 @subsubheading @value{GDBN} Command
25924
25925 The corresponding @value{GDBN} command is @samp{stepi}.
25926
25927 @subsubheading Example
25928
25929 @smallexample
25930 (gdb)
25931 -exec-step-instruction
25932 ^running
25933
25934 (gdb)
25935 *stopped,reason="end-stepping-range",
25936 frame=@{func="foo",args=[],file="try.c",
25937 fullname="/home/foo/bar/try.c",line="10"@}
25938 (gdb)
25939 -exec-step-instruction
25940 ^running
25941
25942 (gdb)
25943 *stopped,reason="end-stepping-range",
25944 frame=@{addr="0x000100f4",func="foo",args=[],file="try.c",
25945 fullname="/home/foo/bar/try.c",line="10"@}
25946 (gdb)
25947 @end smallexample
25948
25949
25950 @subheading The @code{-exec-until} Command
25951 @findex -exec-until
25952
25953 @subsubheading Synopsis
25954
25955 @smallexample
25956 -exec-until [ @var{location} ]
25957 @end smallexample
25958
25959 Executes the inferior until the @var{location} specified in the
25960 argument is reached. If there is no argument, the inferior executes
25961 until a source line greater than the current one is reached. The
25962 reason for stopping in this case will be @samp{location-reached}.
25963
25964 @subsubheading @value{GDBN} Command
25965
25966 The corresponding @value{GDBN} command is @samp{until}.
25967
25968 @subsubheading Example
25969
25970 @smallexample
25971 (gdb)
25972 -exec-until recursive2.c:6
25973 ^running
25974 (gdb)
25975 x = 55
25976 *stopped,reason="location-reached",frame=@{func="main",args=[],
25977 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="6"@}
25978 (gdb)
25979 @end smallexample
25980
25981 @ignore
25982 @subheading -file-clear
25983 Is this going away????
25984 @end ignore
25985
25986 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
25987 @node GDB/MI Stack Manipulation
25988 @section @sc{gdb/mi} Stack Manipulation Commands
25989
25990
25991 @subheading The @code{-stack-info-frame} Command
25992 @findex -stack-info-frame
25993
25994 @subsubheading Synopsis
25995
25996 @smallexample
25997 -stack-info-frame
25998 @end smallexample
25999
26000 Get info on the selected frame.
26001
26002 @subsubheading @value{GDBN} Command
26003
26004 The corresponding @value{GDBN} command is @samp{info frame} or @samp{frame}
26005 (without arguments).
26006
26007 @subsubheading Example
26008
26009 @smallexample
26010 (gdb)
26011 -stack-info-frame
26012 ^done,frame=@{level="1",addr="0x0001076c",func="callee3",
26013 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
26014 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="17"@}
26015 (gdb)
26016 @end smallexample
26017
26018 @subheading The @code{-stack-info-depth} Command
26019 @findex -stack-info-depth
26020
26021 @subsubheading Synopsis
26022
26023 @smallexample
26024 -stack-info-depth [ @var{max-depth} ]
26025 @end smallexample
26026
26027 Return the depth of the stack. If the integer argument @var{max-depth}
26028 is specified, do not count beyond @var{max-depth} frames.
26029
26030 @subsubheading @value{GDBN} Command
26031
26032 There's no equivalent @value{GDBN} command.
26033
26034 @subsubheading Example
26035
26036 For a stack with frame levels 0 through 11:
26037
26038 @smallexample
26039 (gdb)
26040 -stack-info-depth
26041 ^done,depth="12"
26042 (gdb)
26043 -stack-info-depth 4
26044 ^done,depth="4"
26045 (gdb)
26046 -stack-info-depth 12
26047 ^done,depth="12"
26048 (gdb)
26049 -stack-info-depth 11
26050 ^done,depth="11"
26051 (gdb)
26052 -stack-info-depth 13
26053 ^done,depth="12"
26054 (gdb)
26055 @end smallexample
26056
26057 @subheading The @code{-stack-list-arguments} Command
26058 @findex -stack-list-arguments
26059
26060 @subsubheading Synopsis
26061
26062 @smallexample
26063 -stack-list-arguments @var{print-values}
26064 [ @var{low-frame} @var{high-frame} ]
26065 @end smallexample
26066
26067 Display a list of the arguments for the frames between @var{low-frame}
26068 and @var{high-frame} (inclusive). If @var{low-frame} and
26069 @var{high-frame} are not provided, list the arguments for the whole
26070 call stack. If the two arguments are equal, show the single frame
26071 at the corresponding level. It is an error if @var{low-frame} is
26072 larger than the actual number of frames. On the other hand,
26073 @var{high-frame} may be larger than the actual number of frames, in
26074 which case only existing frames will be returned.
26075
26076 If @var{print-values} is 0 or @code{--no-values}, print only the names of
26077 the variables; if it is 1 or @code{--all-values}, print also their
26078 values; and if it is 2 or @code{--simple-values}, print the name,
26079 type and value for simple data types, and the name and type for arrays,
26080 structures and unions.
26081
26082 Use of this command to obtain arguments in a single frame is
26083 deprecated in favor of the @samp{-stack-list-variables} command.
26084
26085 @subsubheading @value{GDBN} Command
26086
26087 @value{GDBN} does not have an equivalent command. @code{gdbtk} has a
26088 @samp{gdb_get_args} command which partially overlaps with the
26089 functionality of @samp{-stack-list-arguments}.
26090
26091 @subsubheading Example
26092
26093 @smallexample
26094 (gdb)
26095 -stack-list-frames
26096 ^done,
26097 stack=[
26098 frame=@{level="0",addr="0x00010734",func="callee4",
26099 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
26100 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="8"@},
26101 frame=@{level="1",addr="0x0001076c",func="callee3",
26102 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
26103 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="17"@},
26104 frame=@{level="2",addr="0x0001078c",func="callee2",
26105 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
26106 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="22"@},
26107 frame=@{level="3",addr="0x000107b4",func="callee1",
26108 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
26109 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="27"@},
26110 frame=@{level="4",addr="0x000107e0",func="main",
26111 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
26112 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="32"@}]
26113 (gdb)
26114 -stack-list-arguments 0
26115 ^done,
26116 stack-args=[
26117 frame=@{level="0",args=[]@},
26118 frame=@{level="1",args=[name="strarg"]@},
26119 frame=@{level="2",args=[name="intarg",name="strarg"]@},
26120 frame=@{level="3",args=[name="intarg",name="strarg",name="fltarg"]@},
26121 frame=@{level="4",args=[]@}]
26122 (gdb)
26123 -stack-list-arguments 1
26124 ^done,
26125 stack-args=[
26126 frame=@{level="0",args=[]@},
26127 frame=@{level="1",
26128 args=[@{name="strarg",value="0x11940 \"A string argument.\""@}]@},
26129 frame=@{level="2",args=[
26130 @{name="intarg",value="2"@},
26131 @{name="strarg",value="0x11940 \"A string argument.\""@}]@},
26132 @{frame=@{level="3",args=[
26133 @{name="intarg",value="2"@},
26134 @{name="strarg",value="0x11940 \"A string argument.\""@},
26135 @{name="fltarg",value="3.5"@}]@},
26136 frame=@{level="4",args=[]@}]
26137 (gdb)
26138 -stack-list-arguments 0 2 2
26139 ^done,stack-args=[frame=@{level="2",args=[name="intarg",name="strarg"]@}]
26140 (gdb)
26141 -stack-list-arguments 1 2 2
26142 ^done,stack-args=[frame=@{level="2",
26143 args=[@{name="intarg",value="2"@},
26144 @{name="strarg",value="0x11940 \"A string argument.\""@}]@}]
26145 (gdb)
26146 @end smallexample
26147
26148 @c @subheading -stack-list-exception-handlers
26149
26150
26151 @subheading The @code{-stack-list-frames} Command
26152 @findex -stack-list-frames
26153
26154 @subsubheading Synopsis
26155
26156 @smallexample
26157 -stack-list-frames [ @var{low-frame} @var{high-frame} ]
26158 @end smallexample
26159
26160 List the frames currently on the stack. For each frame it displays the
26161 following info:
26162
26163 @table @samp
26164 @item @var{level}
26165 The frame number, 0 being the topmost frame, i.e., the innermost function.
26166 @item @var{addr}
26167 The @code{$pc} value for that frame.
26168 @item @var{func}
26169 Function name.
26170 @item @var{file}
26171 File name of the source file where the function lives.
26172 @item @var{fullname}
26173 The full file name of the source file where the function lives.
26174 @item @var{line}
26175 Line number corresponding to the @code{$pc}.
26176 @item @var{from}
26177 The shared library where this function is defined. This is only given
26178 if the frame's function is not known.
26179 @end table
26180
26181 If invoked without arguments, this command prints a backtrace for the
26182 whole stack. If given two integer arguments, it shows the frames whose
26183 levels are between the two arguments (inclusive). If the two arguments
26184 are equal, it shows the single frame at the corresponding level. It is
26185 an error if @var{low-frame} is larger than the actual number of
26186 frames. On the other hand, @var{high-frame} may be larger than the
26187 actual number of frames, in which case only existing frames will be returned.
26188
26189 @subsubheading @value{GDBN} Command
26190
26191 The corresponding @value{GDBN} commands are @samp{backtrace} and @samp{where}.
26192
26193 @subsubheading Example
26194
26195 Full stack backtrace:
26196
26197 @smallexample
26198 (gdb)
26199 -stack-list-frames
26200 ^done,stack=
26201 [frame=@{level="0",addr="0x0001076c",func="foo",
26202 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="11"@},
26203 frame=@{level="1",addr="0x000107a4",func="foo",
26204 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
26205 frame=@{level="2",addr="0x000107a4",func="foo",
26206 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
26207 frame=@{level="3",addr="0x000107a4",func="foo",
26208 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
26209 frame=@{level="4",addr="0x000107a4",func="foo",
26210 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
26211 frame=@{level="5",addr="0x000107a4",func="foo",
26212 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
26213 frame=@{level="6",addr="0x000107a4",func="foo",
26214 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
26215 frame=@{level="7",addr="0x000107a4",func="foo",
26216 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
26217 frame=@{level="8",addr="0x000107a4",func="foo",
26218 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
26219 frame=@{level="9",addr="0x000107a4",func="foo",
26220 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
26221 frame=@{level="10",addr="0x000107a4",func="foo",
26222 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
26223 frame=@{level="11",addr="0x00010738",func="main",
26224 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="4"@}]
26225 (gdb)
26226 @end smallexample
26227
26228 Show frames between @var{low_frame} and @var{high_frame}:
26229
26230 @smallexample
26231 (gdb)
26232 -stack-list-frames 3 5
26233 ^done,stack=
26234 [frame=@{level="3",addr="0x000107a4",func="foo",
26235 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
26236 frame=@{level="4",addr="0x000107a4",func="foo",
26237 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
26238 frame=@{level="5",addr="0x000107a4",func="foo",
26239 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@}]
26240 (gdb)
26241 @end smallexample
26242
26243 Show a single frame:
26244
26245 @smallexample
26246 (gdb)
26247 -stack-list-frames 3 3
26248 ^done,stack=
26249 [frame=@{level="3",addr="0x000107a4",func="foo",
26250 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@}]
26251 (gdb)
26252 @end smallexample
26253
26254
26255 @subheading The @code{-stack-list-locals} Command
26256 @findex -stack-list-locals
26257
26258 @subsubheading Synopsis
26259
26260 @smallexample
26261 -stack-list-locals @var{print-values}
26262 @end smallexample
26263
26264 Display the local variable names for the selected frame. If
26265 @var{print-values} is 0 or @code{--no-values}, print only the names of
26266 the variables; if it is 1 or @code{--all-values}, print also their
26267 values; and if it is 2 or @code{--simple-values}, print the name,
26268 type and value for simple data types, and the name and type for arrays,
26269 structures and unions. In this last case, a frontend can immediately
26270 display the value of simple data types and create variable objects for
26271 other data types when the user wishes to explore their values in
26272 more detail.
26273
26274 This command is deprecated in favor of the
26275 @samp{-stack-list-variables} command.
26276
26277 @subsubheading @value{GDBN} Command
26278
26279 @samp{info locals} in @value{GDBN}, @samp{gdb_get_locals} in @code{gdbtk}.
26280
26281 @subsubheading Example
26282
26283 @smallexample
26284 (gdb)
26285 -stack-list-locals 0
26286 ^done,locals=[name="A",name="B",name="C"]
26287 (gdb)
26288 -stack-list-locals --all-values
26289 ^done,locals=[@{name="A",value="1"@},@{name="B",value="2"@},
26290 @{name="C",value="@{1, 2, 3@}"@}]
26291 -stack-list-locals --simple-values
26292 ^done,locals=[@{name="A",type="int",value="1"@},
26293 @{name="B",type="int",value="2"@},@{name="C",type="int [3]"@}]
26294 (gdb)
26295 @end smallexample
26296
26297 @subheading The @code{-stack-list-variables} Command
26298 @findex -stack-list-variables
26299
26300 @subsubheading Synopsis
26301
26302 @smallexample
26303 -stack-list-variables @var{print-values}
26304 @end smallexample
26305
26306 Display the names of local variables and function arguments for the selected frame. If
26307 @var{print-values} is 0 or @code{--no-values}, print only the names of
26308 the variables; if it is 1 or @code{--all-values}, print also their
26309 values; and if it is 2 or @code{--simple-values}, print the name,
26310 type and value for simple data types, and the name and type for arrays,
26311 structures and unions.
26312
26313 @subsubheading Example
26314
26315 @smallexample
26316 (gdb)
26317 -stack-list-variables --thread 1 --frame 0 --all-values
26318 ^done,variables=[@{name="x",value="11"@},@{name="s",value="@{a = 1, b = 2@}"@}]
26319 (gdb)
26320 @end smallexample
26321
26322
26323 @subheading The @code{-stack-select-frame} Command
26324 @findex -stack-select-frame
26325
26326 @subsubheading Synopsis
26327
26328 @smallexample
26329 -stack-select-frame @var{framenum}
26330 @end smallexample
26331
26332 Change the selected frame. Select a different frame @var{framenum} on
26333 the stack.
26334
26335 This command in deprecated in favor of passing the @samp{--frame}
26336 option to every command.
26337
26338 @subsubheading @value{GDBN} Command
26339
26340 The corresponding @value{GDBN} commands are @samp{frame}, @samp{up},
26341 @samp{down}, @samp{select-frame}, @samp{up-silent}, and @samp{down-silent}.
26342
26343 @subsubheading Example
26344
26345 @smallexample
26346 (gdb)
26347 -stack-select-frame 2
26348 ^done
26349 (gdb)
26350 @end smallexample
26351
26352 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
26353 @node GDB/MI Variable Objects
26354 @section @sc{gdb/mi} Variable Objects
26355
26356 @ignore
26357
26358 @subheading Motivation for Variable Objects in @sc{gdb/mi}
26359
26360 For the implementation of a variable debugger window (locals, watched
26361 expressions, etc.), we are proposing the adaptation of the existing code
26362 used by @code{Insight}.
26363
26364 The two main reasons for that are:
26365
26366 @enumerate 1
26367 @item
26368 It has been proven in practice (it is already on its second generation).
26369
26370 @item
26371 It will shorten development time (needless to say how important it is
26372 now).
26373 @end enumerate
26374
26375 The original interface was designed to be used by Tcl code, so it was
26376 slightly changed so it could be used through @sc{gdb/mi}. This section
26377 describes the @sc{gdb/mi} operations that will be available and gives some
26378 hints about their use.
26379
26380 @emph{Note}: In addition to the set of operations described here, we
26381 expect the @sc{gui} implementation of a variable window to require, at
26382 least, the following operations:
26383
26384 @itemize @bullet
26385 @item @code{-gdb-show} @code{output-radix}
26386 @item @code{-stack-list-arguments}
26387 @item @code{-stack-list-locals}
26388 @item @code{-stack-select-frame}
26389 @end itemize
26390
26391 @end ignore
26392
26393 @subheading Introduction to Variable Objects
26394
26395 @cindex variable objects in @sc{gdb/mi}
26396
26397 Variable objects are "object-oriented" MI interface for examining and
26398 changing values of expressions. Unlike some other MI interfaces that
26399 work with expressions, variable objects are specifically designed for
26400 simple and efficient presentation in the frontend. A variable object
26401 is identified by string name. When a variable object is created, the
26402 frontend specifies the expression for that variable object. The
26403 expression can be a simple variable, or it can be an arbitrary complex
26404 expression, and can even involve CPU registers. After creating a
26405 variable object, the frontend can invoke other variable object
26406 operations---for example to obtain or change the value of a variable
26407 object, or to change display format.
26408
26409 Variable objects have hierarchical tree structure. Any variable object
26410 that corresponds to a composite type, such as structure in C, has
26411 a number of child variable objects, for example corresponding to each
26412 element of a structure. A child variable object can itself have
26413 children, recursively. Recursion ends when we reach
26414 leaf variable objects, which always have built-in types. Child variable
26415 objects are created only by explicit request, so if a frontend
26416 is not interested in the children of a particular variable object, no
26417 child will be created.
26418
26419 For a leaf variable object it is possible to obtain its value as a
26420 string, or set the value from a string. String value can be also
26421 obtained for a non-leaf variable object, but it's generally a string
26422 that only indicates the type of the object, and does not list its
26423 contents. Assignment to a non-leaf variable object is not allowed.
26424
26425 A frontend does not need to read the values of all variable objects each time
26426 the program stops. Instead, MI provides an update command that lists all
26427 variable objects whose values has changed since the last update
26428 operation. This considerably reduces the amount of data that must
26429 be transferred to the frontend. As noted above, children variable
26430 objects are created on demand, and only leaf variable objects have a
26431 real value. As result, gdb will read target memory only for leaf
26432 variables that frontend has created.
26433
26434 The automatic update is not always desirable. For example, a frontend
26435 might want to keep a value of some expression for future reference,
26436 and never update it. For another example, fetching memory is
26437 relatively slow for embedded targets, so a frontend might want
26438 to disable automatic update for the variables that are either not
26439 visible on the screen, or ``closed''. This is possible using so
26440 called ``frozen variable objects''. Such variable objects are never
26441 implicitly updated.
26442
26443 Variable objects can be either @dfn{fixed} or @dfn{floating}. For the
26444 fixed variable object, the expression is parsed when the variable
26445 object is created, including associating identifiers to specific
26446 variables. The meaning of expression never changes. For a floating
26447 variable object the values of variables whose names appear in the
26448 expressions are re-evaluated every time in the context of the current
26449 frame. Consider this example:
26450
26451 @smallexample
26452 void do_work(...)
26453 @{
26454 struct work_state state;
26455
26456 if (...)
26457 do_work(...);
26458 @}
26459 @end smallexample
26460
26461 If a fixed variable object for the @code{state} variable is created in
26462 this function, and we enter the recursive call, the the variable
26463 object will report the value of @code{state} in the top-level
26464 @code{do_work} invocation. On the other hand, a floating variable
26465 object will report the value of @code{state} in the current frame.
26466
26467 If an expression specified when creating a fixed variable object
26468 refers to a local variable, the variable object becomes bound to the
26469 thread and frame in which the variable object is created. When such
26470 variable object is updated, @value{GDBN} makes sure that the
26471 thread/frame combination the variable object is bound to still exists,
26472 and re-evaluates the variable object in context of that thread/frame.
26473
26474 The following is the complete set of @sc{gdb/mi} operations defined to
26475 access this functionality:
26476
26477 @multitable @columnfractions .4 .6
26478 @item @strong{Operation}
26479 @tab @strong{Description}
26480
26481 @item @code{-enable-pretty-printing}
26482 @tab enable Python-based pretty-printing
26483 @item @code{-var-create}
26484 @tab create a variable object
26485 @item @code{-var-delete}
26486 @tab delete the variable object and/or its children
26487 @item @code{-var-set-format}
26488 @tab set the display format of this variable
26489 @item @code{-var-show-format}
26490 @tab show the display format of this variable
26491 @item @code{-var-info-num-children}
26492 @tab tells how many children this object has
26493 @item @code{-var-list-children}
26494 @tab return a list of the object's children
26495 @item @code{-var-info-type}
26496 @tab show the type of this variable object
26497 @item @code{-var-info-expression}
26498 @tab print parent-relative expression that this variable object represents
26499 @item @code{-var-info-path-expression}
26500 @tab print full expression that this variable object represents
26501 @item @code{-var-show-attributes}
26502 @tab is this variable editable? does it exist here?
26503 @item @code{-var-evaluate-expression}
26504 @tab get the value of this variable
26505 @item @code{-var-assign}
26506 @tab set the value of this variable
26507 @item @code{-var-update}
26508 @tab update the variable and its children
26509 @item @code{-var-set-frozen}
26510 @tab set frozeness attribute
26511 @item @code{-var-set-update-range}
26512 @tab set range of children to display on update
26513 @end multitable
26514
26515 In the next subsection we describe each operation in detail and suggest
26516 how it can be used.
26517
26518 @subheading Description And Use of Operations on Variable Objects
26519
26520 @subheading The @code{-enable-pretty-printing} Command
26521 @findex -enable-pretty-printing
26522
26523 @smallexample
26524 -enable-pretty-printing
26525 @end smallexample
26526
26527 @value{GDBN} allows Python-based visualizers to affect the output of the
26528 MI variable object commands. However, because there was no way to
26529 implement this in a fully backward-compatible way, a front end must
26530 request that this functionality be enabled.
26531
26532 Once enabled, this feature cannot be disabled.
26533
26534 Note that if Python support has not been compiled into @value{GDBN},
26535 this command will still succeed (and do nothing).
26536
26537 This feature is currently (as of @value{GDBN} 7.0) experimental, and
26538 may work differently in future versions of @value{GDBN}.
26539
26540 @subheading The @code{-var-create} Command
26541 @findex -var-create
26542
26543 @subsubheading Synopsis
26544
26545 @smallexample
26546 -var-create @{@var{name} | "-"@}
26547 @{@var{frame-addr} | "*" | "@@"@} @var{expression}
26548 @end smallexample
26549
26550 This operation creates a variable object, which allows the monitoring of
26551 a variable, the result of an expression, a memory cell or a CPU
26552 register.
26553
26554 The @var{name} parameter is the string by which the object can be
26555 referenced. It must be unique. If @samp{-} is specified, the varobj
26556 system will generate a string ``varNNNNNN'' automatically. It will be
26557 unique provided that one does not specify @var{name} of that format.
26558 The command fails if a duplicate name is found.
26559
26560 The frame under which the expression should be evaluated can be
26561 specified by @var{frame-addr}. A @samp{*} indicates that the current
26562 frame should be used. A @samp{@@} indicates that a floating variable
26563 object must be created.
26564
26565 @var{expression} is any expression valid on the current language set (must not
26566 begin with a @samp{*}), or one of the following:
26567
26568 @itemize @bullet
26569 @item
26570 @samp{*@var{addr}}, where @var{addr} is the address of a memory cell
26571
26572 @item
26573 @samp{*@var{addr}-@var{addr}} --- a memory address range (TBD)
26574
26575 @item
26576 @samp{$@var{regname}} --- a CPU register name
26577 @end itemize
26578
26579 @cindex dynamic varobj
26580 A varobj's contents may be provided by a Python-based pretty-printer. In this
26581 case the varobj is known as a @dfn{dynamic varobj}. Dynamic varobjs
26582 have slightly different semantics in some cases. If the
26583 @code{-enable-pretty-printing} command is not sent, then @value{GDBN}
26584 will never create a dynamic varobj. This ensures backward
26585 compatibility for existing clients.
26586
26587 @subsubheading Result
26588
26589 This operation returns attributes of the newly-created varobj. These
26590 are:
26591
26592 @table @samp
26593 @item name
26594 The name of the varobj.
26595
26596 @item numchild
26597 The number of children of the varobj. This number is not necessarily
26598 reliable for a dynamic varobj. Instead, you must examine the
26599 @samp{has_more} attribute.
26600
26601 @item value
26602 The varobj's scalar value. For a varobj whose type is some sort of
26603 aggregate (e.g., a @code{struct}), or for a dynamic varobj, this value
26604 will not be interesting.
26605
26606 @item type
26607 The varobj's type. This is a string representation of the type, as
26608 would be printed by the @value{GDBN} CLI.
26609
26610 @item thread-id
26611 If a variable object is bound to a specific thread, then this is the
26612 thread's identifier.
26613
26614 @item has_more
26615 For a dynamic varobj, this indicates whether there appear to be any
26616 children available. For a non-dynamic varobj, this will be 0.
26617
26618 @item dynamic
26619 This attribute will be present and have the value @samp{1} if the
26620 varobj is a dynamic varobj. If the varobj is not a dynamic varobj,
26621 then this attribute will not be present.
26622
26623 @item displayhint
26624 A dynamic varobj can supply a display hint to the front end. The
26625 value comes directly from the Python pretty-printer object's
26626 @code{display_hint} method. @xref{Pretty Printing API}.
26627 @end table
26628
26629 Typical output will look like this:
26630
26631 @smallexample
26632 name="@var{name}",numchild="@var{N}",type="@var{type}",thread-id="@var{M}",
26633 has_more="@var{has_more}"
26634 @end smallexample
26635
26636
26637 @subheading The @code{-var-delete} Command
26638 @findex -var-delete
26639
26640 @subsubheading Synopsis
26641
26642 @smallexample
26643 -var-delete [ -c ] @var{name}
26644 @end smallexample
26645
26646 Deletes a previously created variable object and all of its children.
26647 With the @samp{-c} option, just deletes the children.
26648
26649 Returns an error if the object @var{name} is not found.
26650
26651
26652 @subheading The @code{-var-set-format} Command
26653 @findex -var-set-format
26654
26655 @subsubheading Synopsis
26656
26657 @smallexample
26658 -var-set-format @var{name} @var{format-spec}
26659 @end smallexample
26660
26661 Sets the output format for the value of the object @var{name} to be
26662 @var{format-spec}.
26663
26664 @anchor{-var-set-format}
26665 The syntax for the @var{format-spec} is as follows:
26666
26667 @smallexample
26668 @var{format-spec} @expansion{}
26669 @{binary | decimal | hexadecimal | octal | natural@}
26670 @end smallexample
26671
26672 The natural format is the default format choosen automatically
26673 based on the variable type (like decimal for an @code{int}, hex
26674 for pointers, etc.).
26675
26676 For a variable with children, the format is set only on the
26677 variable itself, and the children are not affected.
26678
26679 @subheading The @code{-var-show-format} Command
26680 @findex -var-show-format
26681
26682 @subsubheading Synopsis
26683
26684 @smallexample
26685 -var-show-format @var{name}
26686 @end smallexample
26687
26688 Returns the format used to display the value of the object @var{name}.
26689
26690 @smallexample
26691 @var{format} @expansion{}
26692 @var{format-spec}
26693 @end smallexample
26694
26695
26696 @subheading The @code{-var-info-num-children} Command
26697 @findex -var-info-num-children
26698
26699 @subsubheading Synopsis
26700
26701 @smallexample
26702 -var-info-num-children @var{name}
26703 @end smallexample
26704
26705 Returns the number of children of a variable object @var{name}:
26706
26707 @smallexample
26708 numchild=@var{n}
26709 @end smallexample
26710
26711 Note that this number is not completely reliable for a dynamic varobj.
26712 It will return the current number of children, but more children may
26713 be available.
26714
26715
26716 @subheading The @code{-var-list-children} Command
26717 @findex -var-list-children
26718
26719 @subsubheading Synopsis
26720
26721 @smallexample
26722 -var-list-children [@var{print-values}] @var{name} [@var{from} @var{to}]
26723 @end smallexample
26724 @anchor{-var-list-children}
26725
26726 Return a list of the children of the specified variable object and
26727 create variable objects for them, if they do not already exist. With
26728 a single argument or if @var{print-values} has a value of 0 or
26729 @code{--no-values}, print only the names of the variables; if
26730 @var{print-values} is 1 or @code{--all-values}, also print their
26731 values; and if it is 2 or @code{--simple-values} print the name and
26732 value for simple data types and just the name for arrays, structures
26733 and unions.
26734
26735 @var{from} and @var{to}, if specified, indicate the range of children
26736 to report. If @var{from} or @var{to} is less than zero, the range is
26737 reset and all children will be reported. Otherwise, children starting
26738 at @var{from} (zero-based) and up to and excluding @var{to} will be
26739 reported.
26740
26741 If a child range is requested, it will only affect the current call to
26742 @code{-var-list-children}, but not future calls to @code{-var-update}.
26743 For this, you must instead use @code{-var-set-update-range}. The
26744 intent of this approach is to enable a front end to implement any
26745 update approach it likes; for example, scrolling a view may cause the
26746 front end to request more children with @code{-var-list-children}, and
26747 then the front end could call @code{-var-set-update-range} with a
26748 different range to ensure that future updates are restricted to just
26749 the visible items.
26750
26751 For each child the following results are returned:
26752
26753 @table @var
26754
26755 @item name
26756 Name of the variable object created for this child.
26757
26758 @item exp
26759 The expression to be shown to the user by the front end to designate this child.
26760 For example this may be the name of a structure member.
26761
26762 For a dynamic varobj, this value cannot be used to form an
26763 expression. There is no way to do this at all with a dynamic varobj.
26764
26765 For C/C@t{++} structures there are several pseudo children returned to
26766 designate access qualifiers. For these pseudo children @var{exp} is
26767 @samp{public}, @samp{private}, or @samp{protected}. In this case the
26768 type and value are not present.
26769
26770 A dynamic varobj will not report the access qualifying
26771 pseudo-children, regardless of the language. This information is not
26772 available at all with a dynamic varobj.
26773
26774 @item numchild
26775 Number of children this child has. For a dynamic varobj, this will be
26776 0.
26777
26778 @item type
26779 The type of the child.
26780
26781 @item value
26782 If values were requested, this is the value.
26783
26784 @item thread-id
26785 If this variable object is associated with a thread, this is the thread id.
26786 Otherwise this result is not present.
26787
26788 @item frozen
26789 If the variable object is frozen, this variable will be present with a value of 1.
26790 @end table
26791
26792 The result may have its own attributes:
26793
26794 @table @samp
26795 @item displayhint
26796 A dynamic varobj can supply a display hint to the front end. The
26797 value comes directly from the Python pretty-printer object's
26798 @code{display_hint} method. @xref{Pretty Printing API}.
26799
26800 @item has_more
26801 This is an integer attribute which is nonzero if there are children
26802 remaining after the end of the selected range.
26803 @end table
26804
26805 @subsubheading Example
26806
26807 @smallexample
26808 (gdb)
26809 -var-list-children n
26810 ^done,numchild=@var{n},children=[child=@{name=@var{name},exp=@var{exp},
26811 numchild=@var{n},type=@var{type}@},@r{(repeats N times)}]
26812 (gdb)
26813 -var-list-children --all-values n
26814 ^done,numchild=@var{n},children=[child=@{name=@var{name},exp=@var{exp},
26815 numchild=@var{n},value=@var{value},type=@var{type}@},@r{(repeats N times)}]
26816 @end smallexample
26817
26818
26819 @subheading The @code{-var-info-type} Command
26820 @findex -var-info-type
26821
26822 @subsubheading Synopsis
26823
26824 @smallexample
26825 -var-info-type @var{name}
26826 @end smallexample
26827
26828 Returns the type of the specified variable @var{name}. The type is
26829 returned as a string in the same format as it is output by the
26830 @value{GDBN} CLI:
26831
26832 @smallexample
26833 type=@var{typename}
26834 @end smallexample
26835
26836
26837 @subheading The @code{-var-info-expression} Command
26838 @findex -var-info-expression
26839
26840 @subsubheading Synopsis
26841
26842 @smallexample
26843 -var-info-expression @var{name}
26844 @end smallexample
26845
26846 Returns a string that is suitable for presenting this
26847 variable object in user interface. The string is generally
26848 not valid expression in the current language, and cannot be evaluated.
26849
26850 For example, if @code{a} is an array, and variable object
26851 @code{A} was created for @code{a}, then we'll get this output:
26852
26853 @smallexample
26854 (gdb) -var-info-expression A.1
26855 ^done,lang="C",exp="1"
26856 @end smallexample
26857
26858 @noindent
26859 Here, the values of @code{lang} can be @code{@{"C" | "C++" | "Java"@}}.
26860
26861 Note that the output of the @code{-var-list-children} command also
26862 includes those expressions, so the @code{-var-info-expression} command
26863 is of limited use.
26864
26865 @subheading The @code{-var-info-path-expression} Command
26866 @findex -var-info-path-expression
26867
26868 @subsubheading Synopsis
26869
26870 @smallexample
26871 -var-info-path-expression @var{name}
26872 @end smallexample
26873
26874 Returns an expression that can be evaluated in the current
26875 context and will yield the same value that a variable object has.
26876 Compare this with the @code{-var-info-expression} command, which
26877 result can be used only for UI presentation. Typical use of
26878 the @code{-var-info-path-expression} command is creating a
26879 watchpoint from a variable object.
26880
26881 This command is currently not valid for children of a dynamic varobj,
26882 and will give an error when invoked on one.
26883
26884 For example, suppose @code{C} is a C@t{++} class, derived from class
26885 @code{Base}, and that the @code{Base} class has a member called
26886 @code{m_size}. Assume a variable @code{c} is has the type of
26887 @code{C} and a variable object @code{C} was created for variable
26888 @code{c}. Then, we'll get this output:
26889 @smallexample
26890 (gdb) -var-info-path-expression C.Base.public.m_size
26891 ^done,path_expr=((Base)c).m_size)
26892 @end smallexample
26893
26894 @subheading The @code{-var-show-attributes} Command
26895 @findex -var-show-attributes
26896
26897 @subsubheading Synopsis
26898
26899 @smallexample
26900 -var-show-attributes @var{name}
26901 @end smallexample
26902
26903 List attributes of the specified variable object @var{name}:
26904
26905 @smallexample
26906 status=@var{attr} [ ( ,@var{attr} )* ]
26907 @end smallexample
26908
26909 @noindent
26910 where @var{attr} is @code{@{ @{ editable | noneditable @} | TBD @}}.
26911
26912 @subheading The @code{-var-evaluate-expression} Command
26913 @findex -var-evaluate-expression
26914
26915 @subsubheading Synopsis
26916
26917 @smallexample
26918 -var-evaluate-expression [-f @var{format-spec}] @var{name}
26919 @end smallexample
26920
26921 Evaluates the expression that is represented by the specified variable
26922 object and returns its value as a string. The format of the string
26923 can be specified with the @samp{-f} option. The possible values of
26924 this option are the same as for @code{-var-set-format}
26925 (@pxref{-var-set-format}). If the @samp{-f} option is not specified,
26926 the current display format will be used. The current display format
26927 can be changed using the @code{-var-set-format} command.
26928
26929 @smallexample
26930 value=@var{value}
26931 @end smallexample
26932
26933 Note that one must invoke @code{-var-list-children} for a variable
26934 before the value of a child variable can be evaluated.
26935
26936 @subheading The @code{-var-assign} Command
26937 @findex -var-assign
26938
26939 @subsubheading Synopsis
26940
26941 @smallexample
26942 -var-assign @var{name} @var{expression}
26943 @end smallexample
26944
26945 Assigns the value of @var{expression} to the variable object specified
26946 by @var{name}. The object must be @samp{editable}. If the variable's
26947 value is altered by the assign, the variable will show up in any
26948 subsequent @code{-var-update} list.
26949
26950 @subsubheading Example
26951
26952 @smallexample
26953 (gdb)
26954 -var-assign var1 3
26955 ^done,value="3"
26956 (gdb)
26957 -var-update *
26958 ^done,changelist=[@{name="var1",in_scope="true",type_changed="false"@}]
26959 (gdb)
26960 @end smallexample
26961
26962 @subheading The @code{-var-update} Command
26963 @findex -var-update
26964
26965 @subsubheading Synopsis
26966
26967 @smallexample
26968 -var-update [@var{print-values}] @{@var{name} | "*"@}
26969 @end smallexample
26970
26971 Reevaluate the expressions corresponding to the variable object
26972 @var{name} and all its direct and indirect children, and return the
26973 list of variable objects whose values have changed; @var{name} must
26974 be a root variable object. Here, ``changed'' means that the result of
26975 @code{-var-evaluate-expression} before and after the
26976 @code{-var-update} is different. If @samp{*} is used as the variable
26977 object names, all existing variable objects are updated, except
26978 for frozen ones (@pxref{-var-set-frozen}). The option
26979 @var{print-values} determines whether both names and values, or just
26980 names are printed. The possible values of this option are the same
26981 as for @code{-var-list-children} (@pxref{-var-list-children}). It is
26982 recommended to use the @samp{--all-values} option, to reduce the
26983 number of MI commands needed on each program stop.
26984
26985 With the @samp{*} parameter, if a variable object is bound to a
26986 currently running thread, it will not be updated, without any
26987 diagnostic.
26988
26989 If @code{-var-set-update-range} was previously used on a varobj, then
26990 only the selected range of children will be reported.
26991
26992 @code{-var-update} reports all the changed varobjs in a tuple named
26993 @samp{changelist}.
26994
26995 Each item in the change list is itself a tuple holding:
26996
26997 @table @samp
26998 @item name
26999 The name of the varobj.
27000
27001 @item value
27002 If values were requested for this update, then this field will be
27003 present and will hold the value of the varobj.
27004
27005 @item in_scope
27006 @anchor{-var-update}
27007 This field is a string which may take one of three values:
27008
27009 @table @code
27010 @item "true"
27011 The variable object's current value is valid.
27012
27013 @item "false"
27014 The variable object does not currently hold a valid value but it may
27015 hold one in the future if its associated expression comes back into
27016 scope.
27017
27018 @item "invalid"
27019 The variable object no longer holds a valid value.
27020 This can occur when the executable file being debugged has changed,
27021 either through recompilation or by using the @value{GDBN} @code{file}
27022 command. The front end should normally choose to delete these variable
27023 objects.
27024 @end table
27025
27026 In the future new values may be added to this list so the front should
27027 be prepared for this possibility. @xref{GDB/MI Development and Front Ends, ,@sc{GDB/MI} Development and Front Ends}.
27028
27029 @item type_changed
27030 This is only present if the varobj is still valid. If the type
27031 changed, then this will be the string @samp{true}; otherwise it will
27032 be @samp{false}.
27033
27034 @item new_type
27035 If the varobj's type changed, then this field will be present and will
27036 hold the new type.
27037
27038 @item new_num_children
27039 For a dynamic varobj, if the number of children changed, or if the
27040 type changed, this will be the new number of children.
27041
27042 The @samp{numchild} field in other varobj responses is generally not
27043 valid for a dynamic varobj -- it will show the number of children that
27044 @value{GDBN} knows about, but because dynamic varobjs lazily
27045 instantiate their children, this will not reflect the number of
27046 children which may be available.
27047
27048 The @samp{new_num_children} attribute only reports changes to the
27049 number of children known by @value{GDBN}. This is the only way to
27050 detect whether an update has removed children (which necessarily can
27051 only happen at the end of the update range).
27052
27053 @item displayhint
27054 The display hint, if any.
27055
27056 @item has_more
27057 This is an integer value, which will be 1 if there are more children
27058 available outside the varobj's update range.
27059
27060 @item dynamic
27061 This attribute will be present and have the value @samp{1} if the
27062 varobj is a dynamic varobj. If the varobj is not a dynamic varobj,
27063 then this attribute will not be present.
27064
27065 @item new_children
27066 If new children were added to a dynamic varobj within the selected
27067 update range (as set by @code{-var-set-update-range}), then they will
27068 be listed in this attribute.
27069 @end table
27070
27071 @subsubheading Example
27072
27073 @smallexample
27074 (gdb)
27075 -var-assign var1 3
27076 ^done,value="3"
27077 (gdb)
27078 -var-update --all-values var1
27079 ^done,changelist=[@{name="var1",value="3",in_scope="true",
27080 type_changed="false"@}]
27081 (gdb)
27082 @end smallexample
27083
27084 @subheading The @code{-var-set-frozen} Command
27085 @findex -var-set-frozen
27086 @anchor{-var-set-frozen}
27087
27088 @subsubheading Synopsis
27089
27090 @smallexample
27091 -var-set-frozen @var{name} @var{flag}
27092 @end smallexample
27093
27094 Set the frozenness flag on the variable object @var{name}. The
27095 @var{flag} parameter should be either @samp{1} to make the variable
27096 frozen or @samp{0} to make it unfrozen. If a variable object is
27097 frozen, then neither itself, nor any of its children, are
27098 implicitly updated by @code{-var-update} of
27099 a parent variable or by @code{-var-update *}. Only
27100 @code{-var-update} of the variable itself will update its value and
27101 values of its children. After a variable object is unfrozen, it is
27102 implicitly updated by all subsequent @code{-var-update} operations.
27103 Unfreezing a variable does not update it, only subsequent
27104 @code{-var-update} does.
27105
27106 @subsubheading Example
27107
27108 @smallexample
27109 (gdb)
27110 -var-set-frozen V 1
27111 ^done
27112 (gdb)
27113 @end smallexample
27114
27115 @subheading The @code{-var-set-update-range} command
27116 @findex -var-set-update-range
27117 @anchor{-var-set-update-range}
27118
27119 @subsubheading Synopsis
27120
27121 @smallexample
27122 -var-set-update-range @var{name} @var{from} @var{to}
27123 @end smallexample
27124
27125 Set the range of children to be returned by future invocations of
27126 @code{-var-update}.
27127
27128 @var{from} and @var{to} indicate the range of children to report. If
27129 @var{from} or @var{to} is less than zero, the range is reset and all
27130 children will be reported. Otherwise, children starting at @var{from}
27131 (zero-based) and up to and excluding @var{to} will be reported.
27132
27133 @subsubheading Example
27134
27135 @smallexample
27136 (gdb)
27137 -var-set-update-range V 1 2
27138 ^done
27139 @end smallexample
27140
27141 @subheading The @code{-var-set-visualizer} command
27142 @findex -var-set-visualizer
27143 @anchor{-var-set-visualizer}
27144
27145 @subsubheading Synopsis
27146
27147 @smallexample
27148 -var-set-visualizer @var{name} @var{visualizer}
27149 @end smallexample
27150
27151 Set a visualizer for the variable object @var{name}.
27152
27153 @var{visualizer} is the visualizer to use. The special value
27154 @samp{None} means to disable any visualizer in use.
27155
27156 If not @samp{None}, @var{visualizer} must be a Python expression.
27157 This expression must evaluate to a callable object which accepts a
27158 single argument. @value{GDBN} will call this object with the value of
27159 the varobj @var{name} as an argument (this is done so that the same
27160 Python pretty-printing code can be used for both the CLI and MI).
27161 When called, this object must return an object which conforms to the
27162 pretty-printing interface (@pxref{Pretty Printing API}).
27163
27164 The pre-defined function @code{gdb.default_visualizer} may be used to
27165 select a visualizer by following the built-in process
27166 (@pxref{Selecting Pretty-Printers}). This is done automatically when
27167 a varobj is created, and so ordinarily is not needed.
27168
27169 This feature is only available if Python support is enabled. The MI
27170 command @code{-list-features} (@pxref{GDB/MI Miscellaneous Commands})
27171 can be used to check this.
27172
27173 @subsubheading Example
27174
27175 Resetting the visualizer:
27176
27177 @smallexample
27178 (gdb)
27179 -var-set-visualizer V None
27180 ^done
27181 @end smallexample
27182
27183 Reselecting the default (type-based) visualizer:
27184
27185 @smallexample
27186 (gdb)
27187 -var-set-visualizer V gdb.default_visualizer
27188 ^done
27189 @end smallexample
27190
27191 Suppose @code{SomeClass} is a visualizer class. A lambda expression
27192 can be used to instantiate this class for a varobj:
27193
27194 @smallexample
27195 (gdb)
27196 -var-set-visualizer V "lambda val: SomeClass()"
27197 ^done
27198 @end smallexample
27199
27200 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
27201 @node GDB/MI Data Manipulation
27202 @section @sc{gdb/mi} Data Manipulation
27203
27204 @cindex data manipulation, in @sc{gdb/mi}
27205 @cindex @sc{gdb/mi}, data manipulation
27206 This section describes the @sc{gdb/mi} commands that manipulate data:
27207 examine memory and registers, evaluate expressions, etc.
27208
27209 @c REMOVED FROM THE INTERFACE.
27210 @c @subheading -data-assign
27211 @c Change the value of a program variable. Plenty of side effects.
27212 @c @subsubheading GDB Command
27213 @c set variable
27214 @c @subsubheading Example
27215 @c N.A.
27216
27217 @subheading The @code{-data-disassemble} Command
27218 @findex -data-disassemble
27219
27220 @subsubheading Synopsis
27221
27222 @smallexample
27223 -data-disassemble
27224 [ -s @var{start-addr} -e @var{end-addr} ]
27225 | [ -f @var{filename} -l @var{linenum} [ -n @var{lines} ] ]
27226 -- @var{mode}
27227 @end smallexample
27228
27229 @noindent
27230 Where:
27231
27232 @table @samp
27233 @item @var{start-addr}
27234 is the beginning address (or @code{$pc})
27235 @item @var{end-addr}
27236 is the end address
27237 @item @var{filename}
27238 is the name of the file to disassemble
27239 @item @var{linenum}
27240 is the line number to disassemble around
27241 @item @var{lines}
27242 is the number of disassembly lines to be produced. If it is -1,
27243 the whole function will be disassembled, in case no @var{end-addr} is
27244 specified. If @var{end-addr} is specified as a non-zero value, and
27245 @var{lines} is lower than the number of disassembly lines between
27246 @var{start-addr} and @var{end-addr}, only @var{lines} lines are
27247 displayed; if @var{lines} is higher than the number of lines between
27248 @var{start-addr} and @var{end-addr}, only the lines up to @var{end-addr}
27249 are displayed.
27250 @item @var{mode}
27251 is either 0 (meaning only disassembly) or 1 (meaning mixed source and
27252 disassembly).
27253 @end table
27254
27255 @subsubheading Result
27256
27257 The output for each instruction is composed of four fields:
27258
27259 @itemize @bullet
27260 @item Address
27261 @item Func-name
27262 @item Offset
27263 @item Instruction
27264 @end itemize
27265
27266 Note that whatever included in the instruction field, is not manipulated
27267 directly by @sc{gdb/mi}, i.e., it is not possible to adjust its format.
27268
27269 @subsubheading @value{GDBN} Command
27270
27271 There's no direct mapping from this command to the CLI.
27272
27273 @subsubheading Example
27274
27275 Disassemble from the current value of @code{$pc} to @code{$pc + 20}:
27276
27277 @smallexample
27278 (gdb)
27279 -data-disassemble -s $pc -e "$pc + 20" -- 0
27280 ^done,
27281 asm_insns=[
27282 @{address="0x000107c0",func-name="main",offset="4",
27283 inst="mov 2, %o0"@},
27284 @{address="0x000107c4",func-name="main",offset="8",
27285 inst="sethi %hi(0x11800), %o2"@},
27286 @{address="0x000107c8",func-name="main",offset="12",
27287 inst="or %o2, 0x140, %o1\t! 0x11940 <_lib_version+8>"@},
27288 @{address="0x000107cc",func-name="main",offset="16",
27289 inst="sethi %hi(0x11800), %o2"@},
27290 @{address="0x000107d0",func-name="main",offset="20",
27291 inst="or %o2, 0x168, %o4\t! 0x11968 <_lib_version+48>"@}]
27292 (gdb)
27293 @end smallexample
27294
27295 Disassemble the whole @code{main} function. Line 32 is part of
27296 @code{main}.
27297
27298 @smallexample
27299 -data-disassemble -f basics.c -l 32 -- 0
27300 ^done,asm_insns=[
27301 @{address="0x000107bc",func-name="main",offset="0",
27302 inst="save %sp, -112, %sp"@},
27303 @{address="0x000107c0",func-name="main",offset="4",
27304 inst="mov 2, %o0"@},
27305 @{address="0x000107c4",func-name="main",offset="8",
27306 inst="sethi %hi(0x11800), %o2"@},
27307 [@dots{}]
27308 @{address="0x0001081c",func-name="main",offset="96",inst="ret "@},
27309 @{address="0x00010820",func-name="main",offset="100",inst="restore "@}]
27310 (gdb)
27311 @end smallexample
27312
27313 Disassemble 3 instructions from the start of @code{main}:
27314
27315 @smallexample
27316 (gdb)
27317 -data-disassemble -f basics.c -l 32 -n 3 -- 0
27318 ^done,asm_insns=[
27319 @{address="0x000107bc",func-name="main",offset="0",
27320 inst="save %sp, -112, %sp"@},
27321 @{address="0x000107c0",func-name="main",offset="4",
27322 inst="mov 2, %o0"@},
27323 @{address="0x000107c4",func-name="main",offset="8",
27324 inst="sethi %hi(0x11800), %o2"@}]
27325 (gdb)
27326 @end smallexample
27327
27328 Disassemble 3 instructions from the start of @code{main} in mixed mode:
27329
27330 @smallexample
27331 (gdb)
27332 -data-disassemble -f basics.c -l 32 -n 3 -- 1
27333 ^done,asm_insns=[
27334 src_and_asm_line=@{line="31",
27335 file="/kwikemart/marge/ezannoni/flathead-dev/devo/gdb/ \
27336 testsuite/gdb.mi/basics.c",line_asm_insn=[
27337 @{address="0x000107bc",func-name="main",offset="0",
27338 inst="save %sp, -112, %sp"@}]@},
27339 src_and_asm_line=@{line="32",
27340 file="/kwikemart/marge/ezannoni/flathead-dev/devo/gdb/ \
27341 testsuite/gdb.mi/basics.c",line_asm_insn=[
27342 @{address="0x000107c0",func-name="main",offset="4",
27343 inst="mov 2, %o0"@},
27344 @{address="0x000107c4",func-name="main",offset="8",
27345 inst="sethi %hi(0x11800), %o2"@}]@}]
27346 (gdb)
27347 @end smallexample
27348
27349
27350 @subheading The @code{-data-evaluate-expression} Command
27351 @findex -data-evaluate-expression
27352
27353 @subsubheading Synopsis
27354
27355 @smallexample
27356 -data-evaluate-expression @var{expr}
27357 @end smallexample
27358
27359 Evaluate @var{expr} as an expression. The expression could contain an
27360 inferior function call. The function call will execute synchronously.
27361 If the expression contains spaces, it must be enclosed in double quotes.
27362
27363 @subsubheading @value{GDBN} Command
27364
27365 The corresponding @value{GDBN} commands are @samp{print}, @samp{output}, and
27366 @samp{call}. In @code{gdbtk} only, there's a corresponding
27367 @samp{gdb_eval} command.
27368
27369 @subsubheading Example
27370
27371 In the following example, the numbers that precede the commands are the
27372 @dfn{tokens} described in @ref{GDB/MI Command Syntax, ,@sc{gdb/mi}
27373 Command Syntax}. Notice how @sc{gdb/mi} returns the same tokens in its
27374 output.
27375
27376 @smallexample
27377 211-data-evaluate-expression A
27378 211^done,value="1"
27379 (gdb)
27380 311-data-evaluate-expression &A
27381 311^done,value="0xefffeb7c"
27382 (gdb)
27383 411-data-evaluate-expression A+3
27384 411^done,value="4"
27385 (gdb)
27386 511-data-evaluate-expression "A + 3"
27387 511^done,value="4"
27388 (gdb)
27389 @end smallexample
27390
27391
27392 @subheading The @code{-data-list-changed-registers} Command
27393 @findex -data-list-changed-registers
27394
27395 @subsubheading Synopsis
27396
27397 @smallexample
27398 -data-list-changed-registers
27399 @end smallexample
27400
27401 Display a list of the registers that have changed.
27402
27403 @subsubheading @value{GDBN} Command
27404
27405 @value{GDBN} doesn't have a direct analog for this command; @code{gdbtk}
27406 has the corresponding command @samp{gdb_changed_register_list}.
27407
27408 @subsubheading Example
27409
27410 On a PPC MBX board:
27411
27412 @smallexample
27413 (gdb)
27414 -exec-continue
27415 ^running
27416
27417 (gdb)
27418 *stopped,reason="breakpoint-hit",disp="keep",bkptno="1",frame=@{
27419 func="main",args=[],file="try.c",fullname="/home/foo/bar/try.c",
27420 line="5"@}
27421 (gdb)
27422 -data-list-changed-registers
27423 ^done,changed-registers=["0","1","2","4","5","6","7","8","9",
27424 "10","11","13","14","15","16","17","18","19","20","21","22","23",
27425 "24","25","26","27","28","30","31","64","65","66","67","69"]
27426 (gdb)
27427 @end smallexample
27428
27429
27430 @subheading The @code{-data-list-register-names} Command
27431 @findex -data-list-register-names
27432
27433 @subsubheading Synopsis
27434
27435 @smallexample
27436 -data-list-register-names [ ( @var{regno} )+ ]
27437 @end smallexample
27438
27439 Show a list of register names for the current target. If no arguments
27440 are given, it shows a list of the names of all the registers. If
27441 integer numbers are given as arguments, it will print a list of the
27442 names of the registers corresponding to the arguments. To ensure
27443 consistency between a register name and its number, the output list may
27444 include empty register names.
27445
27446 @subsubheading @value{GDBN} Command
27447
27448 @value{GDBN} does not have a command which corresponds to
27449 @samp{-data-list-register-names}. In @code{gdbtk} there is a
27450 corresponding command @samp{gdb_regnames}.
27451
27452 @subsubheading Example
27453
27454 For the PPC MBX board:
27455 @smallexample
27456 (gdb)
27457 -data-list-register-names
27458 ^done,register-names=["r0","r1","r2","r3","r4","r5","r6","r7",
27459 "r8","r9","r10","r11","r12","r13","r14","r15","r16","r17","r18",
27460 "r19","r20","r21","r22","r23","r24","r25","r26","r27","r28","r29",
27461 "r30","r31","f0","f1","f2","f3","f4","f5","f6","f7","f8","f9",
27462 "f10","f11","f12","f13","f14","f15","f16","f17","f18","f19","f20",
27463 "f21","f22","f23","f24","f25","f26","f27","f28","f29","f30","f31",
27464 "", "pc","ps","cr","lr","ctr","xer"]
27465 (gdb)
27466 -data-list-register-names 1 2 3
27467 ^done,register-names=["r1","r2","r3"]
27468 (gdb)
27469 @end smallexample
27470
27471 @subheading The @code{-data-list-register-values} Command
27472 @findex -data-list-register-values
27473
27474 @subsubheading Synopsis
27475
27476 @smallexample
27477 -data-list-register-values @var{fmt} [ ( @var{regno} )*]
27478 @end smallexample
27479
27480 Display the registers' contents. @var{fmt} is the format according to
27481 which the registers' contents are to be returned, followed by an optional
27482 list of numbers specifying the registers to display. A missing list of
27483 numbers indicates that the contents of all the registers must be returned.
27484
27485 Allowed formats for @var{fmt} are:
27486
27487 @table @code
27488 @item x
27489 Hexadecimal
27490 @item o
27491 Octal
27492 @item t
27493 Binary
27494 @item d
27495 Decimal
27496 @item r
27497 Raw
27498 @item N
27499 Natural
27500 @end table
27501
27502 @subsubheading @value{GDBN} Command
27503
27504 The corresponding @value{GDBN} commands are @samp{info reg}, @samp{info
27505 all-reg}, and (in @code{gdbtk}) @samp{gdb_fetch_registers}.
27506
27507 @subsubheading Example
27508
27509 For a PPC MBX board (note: line breaks are for readability only, they
27510 don't appear in the actual output):
27511
27512 @smallexample
27513 (gdb)
27514 -data-list-register-values r 64 65
27515 ^done,register-values=[@{number="64",value="0xfe00a300"@},
27516 @{number="65",value="0x00029002"@}]
27517 (gdb)
27518 -data-list-register-values x
27519 ^done,register-values=[@{number="0",value="0xfe0043c8"@},
27520 @{number="1",value="0x3fff88"@},@{number="2",value="0xfffffffe"@},
27521 @{number="3",value="0x0"@},@{number="4",value="0xa"@},
27522 @{number="5",value="0x3fff68"@},@{number="6",value="0x3fff58"@},
27523 @{number="7",value="0xfe011e98"@},@{number="8",value="0x2"@},
27524 @{number="9",value="0xfa202820"@},@{number="10",value="0xfa202808"@},
27525 @{number="11",value="0x1"@},@{number="12",value="0x0"@},
27526 @{number="13",value="0x4544"@},@{number="14",value="0xffdfffff"@},
27527 @{number="15",value="0xffffffff"@},@{number="16",value="0xfffffeff"@},
27528 @{number="17",value="0xefffffed"@},@{number="18",value="0xfffffffe"@},
27529 @{number="19",value="0xffffffff"@},@{number="20",value="0xffffffff"@},
27530 @{number="21",value="0xffffffff"@},@{number="22",value="0xfffffff7"@},
27531 @{number="23",value="0xffffffff"@},@{number="24",value="0xffffffff"@},
27532 @{number="25",value="0xffffffff"@},@{number="26",value="0xfffffffb"@},
27533 @{number="27",value="0xffffffff"@},@{number="28",value="0xf7bfffff"@},
27534 @{number="29",value="0x0"@},@{number="30",value="0xfe010000"@},
27535 @{number="31",value="0x0"@},@{number="32",value="0x0"@},
27536 @{number="33",value="0x0"@},@{number="34",value="0x0"@},
27537 @{number="35",value="0x0"@},@{number="36",value="0x0"@},
27538 @{number="37",value="0x0"@},@{number="38",value="0x0"@},
27539 @{number="39",value="0x0"@},@{number="40",value="0x0"@},
27540 @{number="41",value="0x0"@},@{number="42",value="0x0"@},
27541 @{number="43",value="0x0"@},@{number="44",value="0x0"@},
27542 @{number="45",value="0x0"@},@{number="46",value="0x0"@},
27543 @{number="47",value="0x0"@},@{number="48",value="0x0"@},
27544 @{number="49",value="0x0"@},@{number="50",value="0x0"@},
27545 @{number="51",value="0x0"@},@{number="52",value="0x0"@},
27546 @{number="53",value="0x0"@},@{number="54",value="0x0"@},
27547 @{number="55",value="0x0"@},@{number="56",value="0x0"@},
27548 @{number="57",value="0x0"@},@{number="58",value="0x0"@},
27549 @{number="59",value="0x0"@},@{number="60",value="0x0"@},
27550 @{number="61",value="0x0"@},@{number="62",value="0x0"@},
27551 @{number="63",value="0x0"@},@{number="64",value="0xfe00a300"@},
27552 @{number="65",value="0x29002"@},@{number="66",value="0x202f04b5"@},
27553 @{number="67",value="0xfe0043b0"@},@{number="68",value="0xfe00b3e4"@},
27554 @{number="69",value="0x20002b03"@}]
27555 (gdb)
27556 @end smallexample
27557
27558
27559 @subheading The @code{-data-read-memory} Command
27560 @findex -data-read-memory
27561
27562 This command is deprecated, use @code{-data-read-memory-bytes} instead.
27563
27564 @subsubheading Synopsis
27565
27566 @smallexample
27567 -data-read-memory [ -o @var{byte-offset} ]
27568 @var{address} @var{word-format} @var{word-size}
27569 @var{nr-rows} @var{nr-cols} [ @var{aschar} ]
27570 @end smallexample
27571
27572 @noindent
27573 where:
27574
27575 @table @samp
27576 @item @var{address}
27577 An expression specifying the address of the first memory word to be
27578 read. Complex expressions containing embedded white space should be
27579 quoted using the C convention.
27580
27581 @item @var{word-format}
27582 The format to be used to print the memory words. The notation is the
27583 same as for @value{GDBN}'s @code{print} command (@pxref{Output Formats,
27584 ,Output Formats}).
27585
27586 @item @var{word-size}
27587 The size of each memory word in bytes.
27588
27589 @item @var{nr-rows}
27590 The number of rows in the output table.
27591
27592 @item @var{nr-cols}
27593 The number of columns in the output table.
27594
27595 @item @var{aschar}
27596 If present, indicates that each row should include an @sc{ascii} dump. The
27597 value of @var{aschar} is used as a padding character when a byte is not a
27598 member of the printable @sc{ascii} character set (printable @sc{ascii}
27599 characters are those whose code is between 32 and 126, inclusively).
27600
27601 @item @var{byte-offset}
27602 An offset to add to the @var{address} before fetching memory.
27603 @end table
27604
27605 This command displays memory contents as a table of @var{nr-rows} by
27606 @var{nr-cols} words, each word being @var{word-size} bytes. In total,
27607 @code{@var{nr-rows} * @var{nr-cols} * @var{word-size}} bytes are read
27608 (returned as @samp{total-bytes}). Should less than the requested number
27609 of bytes be returned by the target, the missing words are identified
27610 using @samp{N/A}. The number of bytes read from the target is returned
27611 in @samp{nr-bytes} and the starting address used to read memory in
27612 @samp{addr}.
27613
27614 The address of the next/previous row or page is available in
27615 @samp{next-row} and @samp{prev-row}, @samp{next-page} and
27616 @samp{prev-page}.
27617
27618 @subsubheading @value{GDBN} Command
27619
27620 The corresponding @value{GDBN} command is @samp{x}. @code{gdbtk} has
27621 @samp{gdb_get_mem} memory read command.
27622
27623 @subsubheading Example
27624
27625 Read six bytes of memory starting at @code{bytes+6} but then offset by
27626 @code{-6} bytes. Format as three rows of two columns. One byte per
27627 word. Display each word in hex.
27628
27629 @smallexample
27630 (gdb)
27631 9-data-read-memory -o -6 -- bytes+6 x 1 3 2
27632 9^done,addr="0x00001390",nr-bytes="6",total-bytes="6",
27633 next-row="0x00001396",prev-row="0x0000138e",next-page="0x00001396",
27634 prev-page="0x0000138a",memory=[
27635 @{addr="0x00001390",data=["0x00","0x01"]@},
27636 @{addr="0x00001392",data=["0x02","0x03"]@},
27637 @{addr="0x00001394",data=["0x04","0x05"]@}]
27638 (gdb)
27639 @end smallexample
27640
27641 Read two bytes of memory starting at address @code{shorts + 64} and
27642 display as a single word formatted in decimal.
27643
27644 @smallexample
27645 (gdb)
27646 5-data-read-memory shorts+64 d 2 1 1
27647 5^done,addr="0x00001510",nr-bytes="2",total-bytes="2",
27648 next-row="0x00001512",prev-row="0x0000150e",
27649 next-page="0x00001512",prev-page="0x0000150e",memory=[
27650 @{addr="0x00001510",data=["128"]@}]
27651 (gdb)
27652 @end smallexample
27653
27654 Read thirty two bytes of memory starting at @code{bytes+16} and format
27655 as eight rows of four columns. Include a string encoding with @samp{x}
27656 used as the non-printable character.
27657
27658 @smallexample
27659 (gdb)
27660 4-data-read-memory bytes+16 x 1 8 4 x
27661 4^done,addr="0x000013a0",nr-bytes="32",total-bytes="32",
27662 next-row="0x000013c0",prev-row="0x0000139c",
27663 next-page="0x000013c0",prev-page="0x00001380",memory=[
27664 @{addr="0x000013a0",data=["0x10","0x11","0x12","0x13"],ascii="xxxx"@},
27665 @{addr="0x000013a4",data=["0x14","0x15","0x16","0x17"],ascii="xxxx"@},
27666 @{addr="0x000013a8",data=["0x18","0x19","0x1a","0x1b"],ascii="xxxx"@},
27667 @{addr="0x000013ac",data=["0x1c","0x1d","0x1e","0x1f"],ascii="xxxx"@},
27668 @{addr="0x000013b0",data=["0x20","0x21","0x22","0x23"],ascii=" !\"#"@},
27669 @{addr="0x000013b4",data=["0x24","0x25","0x26","0x27"],ascii="$%&'"@},
27670 @{addr="0x000013b8",data=["0x28","0x29","0x2a","0x2b"],ascii="()*+"@},
27671 @{addr="0x000013bc",data=["0x2c","0x2d","0x2e","0x2f"],ascii=",-./"@}]
27672 (gdb)
27673 @end smallexample
27674
27675 @subheading The @code{-data-read-memory-bytes} Command
27676 @findex -data-read-memory-bytes
27677
27678 @subsubheading Synopsis
27679
27680 @smallexample
27681 -data-read-memory-bytes [ -o @var{byte-offset} ]
27682 @var{address} @var{count}
27683 @end smallexample
27684
27685 @noindent
27686 where:
27687
27688 @table @samp
27689 @item @var{address}
27690 An expression specifying the address of the first memory word to be
27691 read. Complex expressions containing embedded white space should be
27692 quoted using the C convention.
27693
27694 @item @var{count}
27695 The number of bytes to read. This should be an integer literal.
27696
27697 @item @var{byte-offset}
27698 The offsets in bytes relative to @var{address} at which to start
27699 reading. This should be an integer literal. This option is provided
27700 so that a frontend is not required to first evaluate address and then
27701 perform address arithmetics itself.
27702
27703 @end table
27704
27705 This command attempts to read all accessible memory regions in the
27706 specified range. First, all regions marked as unreadable in the memory
27707 map (if one is defined) will be skipped. @xref{Memory Region
27708 Attributes}. Second, @value{GDBN} will attempt to read the remaining
27709 regions. For each one, if reading full region results in an errors,
27710 @value{GDBN} will try to read a subset of the region.
27711
27712 In general, every single byte in the region may be readable or not,
27713 and the only way to read every readable byte is to try a read at
27714 every address, which is not practical. Therefore, @value{GDBN} will
27715 attempt to read all accessible bytes at either beginning or the end
27716 of the region, using a binary division scheme. This heuristic works
27717 well for reading accross a memory map boundary. Note that if a region
27718 has a readable range that is neither at the beginning or the end,
27719 @value{GDBN} will not read it.
27720
27721 The result record (@pxref{GDB/MI Result Records}) that is output of
27722 the command includes a field named @samp{memory} whose content is a
27723 list of tuples. Each tuple represent a successfully read memory block
27724 and has the following fields:
27725
27726 @table @code
27727 @item begin
27728 The start address of the memory block, as hexadecimal literal.
27729
27730 @item end
27731 The end address of the memory block, as hexadecimal literal.
27732
27733 @item offset
27734 The offset of the memory block, as hexadecimal literal, relative to
27735 the start address passed to @code{-data-read-memory-bytes}.
27736
27737 @item contents
27738 The contents of the memory block, in hex.
27739
27740 @end table
27741
27742
27743
27744 @subsubheading @value{GDBN} Command
27745
27746 The corresponding @value{GDBN} command is @samp{x}.
27747
27748 @subsubheading Example
27749
27750 @smallexample
27751 (gdb)
27752 -data-read-memory-bytes &a 10
27753 ^done,memory=[@{begin="0xbffff154",offset="0x00000000",
27754 end="0xbffff15e",
27755 contents="01000000020000000300"@}]
27756 (gdb)
27757 @end smallexample
27758
27759
27760 @subheading The @code{-data-write-memory-bytes} Command
27761 @findex -data-write-memory-bytes
27762
27763 @subsubheading Synopsis
27764
27765 @smallexample
27766 -data-write-memory-bytes @var{address} @var{contents}
27767 @end smallexample
27768
27769 @noindent
27770 where:
27771
27772 @table @samp
27773 @item @var{address}
27774 An expression specifying the address of the first memory word to be
27775 read. Complex expressions containing embedded white space should be
27776 quoted using the C convention.
27777
27778 @item @var{contents}
27779 The hex-encoded bytes to write.
27780
27781 @end table
27782
27783 @subsubheading @value{GDBN} Command
27784
27785 There's no corresponding @value{GDBN} command.
27786
27787 @subsubheading Example
27788
27789 @smallexample
27790 (gdb)
27791 -data-write-memory-bytes &a "aabbccdd"
27792 ^done
27793 (gdb)
27794 @end smallexample
27795
27796
27797 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
27798 @node GDB/MI Tracepoint Commands
27799 @section @sc{gdb/mi} Tracepoint Commands
27800
27801 The commands defined in this section implement MI support for
27802 tracepoints. For detailed introduction, see @ref{Tracepoints}.
27803
27804 @subheading The @code{-trace-find} Command
27805 @findex -trace-find
27806
27807 @subsubheading Synopsis
27808
27809 @smallexample
27810 -trace-find @var{mode} [@var{parameters}@dots{}]
27811 @end smallexample
27812
27813 Find a trace frame using criteria defined by @var{mode} and
27814 @var{parameters}. The following table lists permissible
27815 modes and their parameters. For details of operation, see @ref{tfind}.
27816
27817 @table @samp
27818
27819 @item none
27820 No parameters are required. Stops examining trace frames.
27821
27822 @item frame-number
27823 An integer is required as parameter. Selects tracepoint frame with
27824 that index.
27825
27826 @item tracepoint-number
27827 An integer is required as parameter. Finds next
27828 trace frame that corresponds to tracepoint with the specified number.
27829
27830 @item pc
27831 An address is required as parameter. Finds
27832 next trace frame that corresponds to any tracepoint at the specified
27833 address.
27834
27835 @item pc-inside-range
27836 Two addresses are required as parameters. Finds next trace
27837 frame that corresponds to a tracepoint at an address inside the
27838 specified range. Both bounds are considered to be inside the range.
27839
27840 @item pc-outside-range
27841 Two addresses are required as parameters. Finds
27842 next trace frame that corresponds to a tracepoint at an address outside
27843 the specified range. Both bounds are considered to be inside the range.
27844
27845 @item line
27846 Line specification is required as parameter. @xref{Specify Location}.
27847 Finds next trace frame that corresponds to a tracepoint at
27848 the specified location.
27849
27850 @end table
27851
27852 If @samp{none} was passed as @var{mode}, the response does not
27853 have fields. Otherwise, the response may have the following fields:
27854
27855 @table @samp
27856 @item found
27857 This field has either @samp{0} or @samp{1} as the value, depending
27858 on whether a matching tracepoint was found.
27859
27860 @item traceframe
27861 The index of the found traceframe. This field is present iff
27862 the @samp{found} field has value of @samp{1}.
27863
27864 @item tracepoint
27865 The index of the found tracepoint. This field is present iff
27866 the @samp{found} field has value of @samp{1}.
27867
27868 @item frame
27869 The information about the frame corresponding to the found trace
27870 frame. This field is present only if a trace frame was found.
27871 @xref{GDB/MI Frame Information}, for description of this field.
27872
27873 @end table
27874
27875 @subsubheading @value{GDBN} Command
27876
27877 The corresponding @value{GDBN} command is @samp{tfind}.
27878
27879 @subheading -trace-define-variable
27880 @findex -trace-define-variable
27881
27882 @subsubheading Synopsis
27883
27884 @smallexample
27885 -trace-define-variable @var{name} [ @var{value} ]
27886 @end smallexample
27887
27888 Create trace variable @var{name} if it does not exist. If
27889 @var{value} is specified, sets the initial value of the specified
27890 trace variable to that value. Note that the @var{name} should start
27891 with the @samp{$} character.
27892
27893 @subsubheading @value{GDBN} Command
27894
27895 The corresponding @value{GDBN} command is @samp{tvariable}.
27896
27897 @subheading -trace-list-variables
27898 @findex -trace-list-variables
27899
27900 @subsubheading Synopsis
27901
27902 @smallexample
27903 -trace-list-variables
27904 @end smallexample
27905
27906 Return a table of all defined trace variables. Each element of the
27907 table has the following fields:
27908
27909 @table @samp
27910 @item name
27911 The name of the trace variable. This field is always present.
27912
27913 @item initial
27914 The initial value. This is a 64-bit signed integer. This
27915 field is always present.
27916
27917 @item current
27918 The value the trace variable has at the moment. This is a 64-bit
27919 signed integer. This field is absent iff current value is
27920 not defined, for example if the trace was never run, or is
27921 presently running.
27922
27923 @end table
27924
27925 @subsubheading @value{GDBN} Command
27926
27927 The corresponding @value{GDBN} command is @samp{tvariables}.
27928
27929 @subsubheading Example
27930
27931 @smallexample
27932 (gdb)
27933 -trace-list-variables
27934 ^done,trace-variables=@{nr_rows="1",nr_cols="3",
27935 hdr=[@{width="15",alignment="-1",col_name="name",colhdr="Name"@},
27936 @{width="11",alignment="-1",col_name="initial",colhdr="Initial"@},
27937 @{width="11",alignment="-1",col_name="current",colhdr="Current"@}],
27938 body=[variable=@{name="$trace_timestamp",initial="0"@}
27939 variable=@{name="$foo",initial="10",current="15"@}]@}
27940 (gdb)
27941 @end smallexample
27942
27943 @subheading -trace-save
27944 @findex -trace-save
27945
27946 @subsubheading Synopsis
27947
27948 @smallexample
27949 -trace-save [-r ] @var{filename}
27950 @end smallexample
27951
27952 Saves the collected trace data to @var{filename}. Without the
27953 @samp{-r} option, the data is downloaded from the target and saved
27954 in a local file. With the @samp{-r} option the target is asked
27955 to perform the save.
27956
27957 @subsubheading @value{GDBN} Command
27958
27959 The corresponding @value{GDBN} command is @samp{tsave}.
27960
27961
27962 @subheading -trace-start
27963 @findex -trace-start
27964
27965 @subsubheading Synopsis
27966
27967 @smallexample
27968 -trace-start
27969 @end smallexample
27970
27971 Starts a tracing experiments. The result of this command does not
27972 have any fields.
27973
27974 @subsubheading @value{GDBN} Command
27975
27976 The corresponding @value{GDBN} command is @samp{tstart}.
27977
27978 @subheading -trace-status
27979 @findex -trace-status
27980
27981 @subsubheading Synopsis
27982
27983 @smallexample
27984 -trace-status
27985 @end smallexample
27986
27987 Obtains the status of a tracing experiment. The result may include
27988 the following fields:
27989
27990 @table @samp
27991
27992 @item supported
27993 May have a value of either @samp{0}, when no tracing operations are
27994 supported, @samp{1}, when all tracing operations are supported, or
27995 @samp{file} when examining trace file. In the latter case, examining
27996 of trace frame is possible but new tracing experiement cannot be
27997 started. This field is always present.
27998
27999 @item running
28000 May have a value of either @samp{0} or @samp{1} depending on whether
28001 tracing experiement is in progress on target. This field is present
28002 if @samp{supported} field is not @samp{0}.
28003
28004 @item stop-reason
28005 Report the reason why the tracing was stopped last time. This field
28006 may be absent iff tracing was never stopped on target yet. The
28007 value of @samp{request} means the tracing was stopped as result of
28008 the @code{-trace-stop} command. The value of @samp{overflow} means
28009 the tracing buffer is full. The value of @samp{disconnection} means
28010 tracing was automatically stopped when @value{GDBN} has disconnected.
28011 The value of @samp{passcount} means tracing was stopped when a
28012 tracepoint was passed a maximal number of times for that tracepoint.
28013 This field is present if @samp{supported} field is not @samp{0}.
28014
28015 @item stopping-tracepoint
28016 The number of tracepoint whose passcount as exceeded. This field is
28017 present iff the @samp{stop-reason} field has the value of
28018 @samp{passcount}.
28019
28020 @item frames
28021 @itemx frames-created
28022 The @samp{frames} field is a count of the total number of trace frames
28023 in the trace buffer, while @samp{frames-created} is the total created
28024 during the run, including ones that were discarded, such as when a
28025 circular trace buffer filled up. Both fields are optional.
28026
28027 @item buffer-size
28028 @itemx buffer-free
28029 These fields tell the current size of the tracing buffer and the
28030 remaining space. These fields are optional.
28031
28032 @item circular
28033 The value of the circular trace buffer flag. @code{1} means that the
28034 trace buffer is circular and old trace frames will be discarded if
28035 necessary to make room, @code{0} means that the trace buffer is linear
28036 and may fill up.
28037
28038 @item disconnected
28039 The value of the disconnected tracing flag. @code{1} means that
28040 tracing will continue after @value{GDBN} disconnects, @code{0} means
28041 that the trace run will stop.
28042
28043 @end table
28044
28045 @subsubheading @value{GDBN} Command
28046
28047 The corresponding @value{GDBN} command is @samp{tstatus}.
28048
28049 @subheading -trace-stop
28050 @findex -trace-stop
28051
28052 @subsubheading Synopsis
28053
28054 @smallexample
28055 -trace-stop
28056 @end smallexample
28057
28058 Stops a tracing experiment. The result of this command has the same
28059 fields as @code{-trace-status}, except that the @samp{supported} and
28060 @samp{running} fields are not output.
28061
28062 @subsubheading @value{GDBN} Command
28063
28064 The corresponding @value{GDBN} command is @samp{tstop}.
28065
28066
28067 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
28068 @node GDB/MI Symbol Query
28069 @section @sc{gdb/mi} Symbol Query Commands
28070
28071
28072 @ignore
28073 @subheading The @code{-symbol-info-address} Command
28074 @findex -symbol-info-address
28075
28076 @subsubheading Synopsis
28077
28078 @smallexample
28079 -symbol-info-address @var{symbol}
28080 @end smallexample
28081
28082 Describe where @var{symbol} is stored.
28083
28084 @subsubheading @value{GDBN} Command
28085
28086 The corresponding @value{GDBN} command is @samp{info address}.
28087
28088 @subsubheading Example
28089 N.A.
28090
28091
28092 @subheading The @code{-symbol-info-file} Command
28093 @findex -symbol-info-file
28094
28095 @subsubheading Synopsis
28096
28097 @smallexample
28098 -symbol-info-file
28099 @end smallexample
28100
28101 Show the file for the symbol.
28102
28103 @subsubheading @value{GDBN} Command
28104
28105 There's no equivalent @value{GDBN} command. @code{gdbtk} has
28106 @samp{gdb_find_file}.
28107
28108 @subsubheading Example
28109 N.A.
28110
28111
28112 @subheading The @code{-symbol-info-function} Command
28113 @findex -symbol-info-function
28114
28115 @subsubheading Synopsis
28116
28117 @smallexample
28118 -symbol-info-function
28119 @end smallexample
28120
28121 Show which function the symbol lives in.
28122
28123 @subsubheading @value{GDBN} Command
28124
28125 @samp{gdb_get_function} in @code{gdbtk}.
28126
28127 @subsubheading Example
28128 N.A.
28129
28130
28131 @subheading The @code{-symbol-info-line} Command
28132 @findex -symbol-info-line
28133
28134 @subsubheading Synopsis
28135
28136 @smallexample
28137 -symbol-info-line
28138 @end smallexample
28139
28140 Show the core addresses of the code for a source line.
28141
28142 @subsubheading @value{GDBN} Command
28143
28144 The corresponding @value{GDBN} command is @samp{info line}.
28145 @code{gdbtk} has the @samp{gdb_get_line} and @samp{gdb_get_file} commands.
28146
28147 @subsubheading Example
28148 N.A.
28149
28150
28151 @subheading The @code{-symbol-info-symbol} Command
28152 @findex -symbol-info-symbol
28153
28154 @subsubheading Synopsis
28155
28156 @smallexample
28157 -symbol-info-symbol @var{addr}
28158 @end smallexample
28159
28160 Describe what symbol is at location @var{addr}.
28161
28162 @subsubheading @value{GDBN} Command
28163
28164 The corresponding @value{GDBN} command is @samp{info symbol}.
28165
28166 @subsubheading Example
28167 N.A.
28168
28169
28170 @subheading The @code{-symbol-list-functions} Command
28171 @findex -symbol-list-functions
28172
28173 @subsubheading Synopsis
28174
28175 @smallexample
28176 -symbol-list-functions
28177 @end smallexample
28178
28179 List the functions in the executable.
28180
28181 @subsubheading @value{GDBN} Command
28182
28183 @samp{info functions} in @value{GDBN}, @samp{gdb_listfunc} and
28184 @samp{gdb_search} in @code{gdbtk}.
28185
28186 @subsubheading Example
28187 N.A.
28188 @end ignore
28189
28190
28191 @subheading The @code{-symbol-list-lines} Command
28192 @findex -symbol-list-lines
28193
28194 @subsubheading Synopsis
28195
28196 @smallexample
28197 -symbol-list-lines @var{filename}
28198 @end smallexample
28199
28200 Print the list of lines that contain code and their associated program
28201 addresses for the given source filename. The entries are sorted in
28202 ascending PC order.
28203
28204 @subsubheading @value{GDBN} Command
28205
28206 There is no corresponding @value{GDBN} command.
28207
28208 @subsubheading Example
28209 @smallexample
28210 (gdb)
28211 -symbol-list-lines basics.c
28212 ^done,lines=[@{pc="0x08048554",line="7"@},@{pc="0x0804855a",line="8"@}]
28213 (gdb)
28214 @end smallexample
28215
28216
28217 @ignore
28218 @subheading The @code{-symbol-list-types} Command
28219 @findex -symbol-list-types
28220
28221 @subsubheading Synopsis
28222
28223 @smallexample
28224 -symbol-list-types
28225 @end smallexample
28226
28227 List all the type names.
28228
28229 @subsubheading @value{GDBN} Command
28230
28231 The corresponding commands are @samp{info types} in @value{GDBN},
28232 @samp{gdb_search} in @code{gdbtk}.
28233
28234 @subsubheading Example
28235 N.A.
28236
28237
28238 @subheading The @code{-symbol-list-variables} Command
28239 @findex -symbol-list-variables
28240
28241 @subsubheading Synopsis
28242
28243 @smallexample
28244 -symbol-list-variables
28245 @end smallexample
28246
28247 List all the global and static variable names.
28248
28249 @subsubheading @value{GDBN} Command
28250
28251 @samp{info variables} in @value{GDBN}, @samp{gdb_search} in @code{gdbtk}.
28252
28253 @subsubheading Example
28254 N.A.
28255
28256
28257 @subheading The @code{-symbol-locate} Command
28258 @findex -symbol-locate
28259
28260 @subsubheading Synopsis
28261
28262 @smallexample
28263 -symbol-locate
28264 @end smallexample
28265
28266 @subsubheading @value{GDBN} Command
28267
28268 @samp{gdb_loc} in @code{gdbtk}.
28269
28270 @subsubheading Example
28271 N.A.
28272
28273
28274 @subheading The @code{-symbol-type} Command
28275 @findex -symbol-type
28276
28277 @subsubheading Synopsis
28278
28279 @smallexample
28280 -symbol-type @var{variable}
28281 @end smallexample
28282
28283 Show type of @var{variable}.
28284
28285 @subsubheading @value{GDBN} Command
28286
28287 The corresponding @value{GDBN} command is @samp{ptype}, @code{gdbtk} has
28288 @samp{gdb_obj_variable}.
28289
28290 @subsubheading Example
28291 N.A.
28292 @end ignore
28293
28294
28295 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
28296 @node GDB/MI File Commands
28297 @section @sc{gdb/mi} File Commands
28298
28299 This section describes the GDB/MI commands to specify executable file names
28300 and to read in and obtain symbol table information.
28301
28302 @subheading The @code{-file-exec-and-symbols} Command
28303 @findex -file-exec-and-symbols
28304
28305 @subsubheading Synopsis
28306
28307 @smallexample
28308 -file-exec-and-symbols @var{file}
28309 @end smallexample
28310
28311 Specify the executable file to be debugged. This file is the one from
28312 which the symbol table is also read. If no file is specified, the
28313 command clears the executable and symbol information. If breakpoints
28314 are set when using this command with no arguments, @value{GDBN} will produce
28315 error messages. Otherwise, no output is produced, except a completion
28316 notification.
28317
28318 @subsubheading @value{GDBN} Command
28319
28320 The corresponding @value{GDBN} command is @samp{file}.
28321
28322 @subsubheading Example
28323
28324 @smallexample
28325 (gdb)
28326 -file-exec-and-symbols /kwikemart/marge/ezannoni/TRUNK/mbx/hello.mbx
28327 ^done
28328 (gdb)
28329 @end smallexample
28330
28331
28332 @subheading The @code{-file-exec-file} Command
28333 @findex -file-exec-file
28334
28335 @subsubheading Synopsis
28336
28337 @smallexample
28338 -file-exec-file @var{file}
28339 @end smallexample
28340
28341 Specify the executable file to be debugged. Unlike
28342 @samp{-file-exec-and-symbols}, the symbol table is @emph{not} read
28343 from this file. If used without argument, @value{GDBN} clears the information
28344 about the executable file. No output is produced, except a completion
28345 notification.
28346
28347 @subsubheading @value{GDBN} Command
28348
28349 The corresponding @value{GDBN} command is @samp{exec-file}.
28350
28351 @subsubheading Example
28352
28353 @smallexample
28354 (gdb)
28355 -file-exec-file /kwikemart/marge/ezannoni/TRUNK/mbx/hello.mbx
28356 ^done
28357 (gdb)
28358 @end smallexample
28359
28360
28361 @ignore
28362 @subheading The @code{-file-list-exec-sections} Command
28363 @findex -file-list-exec-sections
28364
28365 @subsubheading Synopsis
28366
28367 @smallexample
28368 -file-list-exec-sections
28369 @end smallexample
28370
28371 List the sections of the current executable file.
28372
28373 @subsubheading @value{GDBN} Command
28374
28375 The @value{GDBN} command @samp{info file} shows, among the rest, the same
28376 information as this command. @code{gdbtk} has a corresponding command
28377 @samp{gdb_load_info}.
28378
28379 @subsubheading Example
28380 N.A.
28381 @end ignore
28382
28383
28384 @subheading The @code{-file-list-exec-source-file} Command
28385 @findex -file-list-exec-source-file
28386
28387 @subsubheading Synopsis
28388
28389 @smallexample
28390 -file-list-exec-source-file
28391 @end smallexample
28392
28393 List the line number, the current source file, and the absolute path
28394 to the current source file for the current executable. The macro
28395 information field has a value of @samp{1} or @samp{0} depending on
28396 whether or not the file includes preprocessor macro information.
28397
28398 @subsubheading @value{GDBN} Command
28399
28400 The @value{GDBN} equivalent is @samp{info source}
28401
28402 @subsubheading Example
28403
28404 @smallexample
28405 (gdb)
28406 123-file-list-exec-source-file
28407 123^done,line="1",file="foo.c",fullname="/home/bar/foo.c,macro-info="1"
28408 (gdb)
28409 @end smallexample
28410
28411
28412 @subheading The @code{-file-list-exec-source-files} Command
28413 @findex -file-list-exec-source-files
28414
28415 @subsubheading Synopsis
28416
28417 @smallexample
28418 -file-list-exec-source-files
28419 @end smallexample
28420
28421 List the source files for the current executable.
28422
28423 It will always output the filename, but only when @value{GDBN} can find
28424 the absolute file name of a source file, will it output the fullname.
28425
28426 @subsubheading @value{GDBN} Command
28427
28428 The @value{GDBN} equivalent is @samp{info sources}.
28429 @code{gdbtk} has an analogous command @samp{gdb_listfiles}.
28430
28431 @subsubheading Example
28432 @smallexample
28433 (gdb)
28434 -file-list-exec-source-files
28435 ^done,files=[
28436 @{file=foo.c,fullname=/home/foo.c@},
28437 @{file=/home/bar.c,fullname=/home/bar.c@},
28438 @{file=gdb_could_not_find_fullpath.c@}]
28439 (gdb)
28440 @end smallexample
28441
28442 @ignore
28443 @subheading The @code{-file-list-shared-libraries} Command
28444 @findex -file-list-shared-libraries
28445
28446 @subsubheading Synopsis
28447
28448 @smallexample
28449 -file-list-shared-libraries
28450 @end smallexample
28451
28452 List the shared libraries in the program.
28453
28454 @subsubheading @value{GDBN} Command
28455
28456 The corresponding @value{GDBN} command is @samp{info shared}.
28457
28458 @subsubheading Example
28459 N.A.
28460
28461
28462 @subheading The @code{-file-list-symbol-files} Command
28463 @findex -file-list-symbol-files
28464
28465 @subsubheading Synopsis
28466
28467 @smallexample
28468 -file-list-symbol-files
28469 @end smallexample
28470
28471 List symbol files.
28472
28473 @subsubheading @value{GDBN} Command
28474
28475 The corresponding @value{GDBN} command is @samp{info file} (part of it).
28476
28477 @subsubheading Example
28478 N.A.
28479 @end ignore
28480
28481
28482 @subheading The @code{-file-symbol-file} Command
28483 @findex -file-symbol-file
28484
28485 @subsubheading Synopsis
28486
28487 @smallexample
28488 -file-symbol-file @var{file}
28489 @end smallexample
28490
28491 Read symbol table info from the specified @var{file} argument. When
28492 used without arguments, clears @value{GDBN}'s symbol table info. No output is
28493 produced, except for a completion notification.
28494
28495 @subsubheading @value{GDBN} Command
28496
28497 The corresponding @value{GDBN} command is @samp{symbol-file}.
28498
28499 @subsubheading Example
28500
28501 @smallexample
28502 (gdb)
28503 -file-symbol-file /kwikemart/marge/ezannoni/TRUNK/mbx/hello.mbx
28504 ^done
28505 (gdb)
28506 @end smallexample
28507
28508 @ignore
28509 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
28510 @node GDB/MI Memory Overlay Commands
28511 @section @sc{gdb/mi} Memory Overlay Commands
28512
28513 The memory overlay commands are not implemented.
28514
28515 @c @subheading -overlay-auto
28516
28517 @c @subheading -overlay-list-mapping-state
28518
28519 @c @subheading -overlay-list-overlays
28520
28521 @c @subheading -overlay-map
28522
28523 @c @subheading -overlay-off
28524
28525 @c @subheading -overlay-on
28526
28527 @c @subheading -overlay-unmap
28528
28529 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
28530 @node GDB/MI Signal Handling Commands
28531 @section @sc{gdb/mi} Signal Handling Commands
28532
28533 Signal handling commands are not implemented.
28534
28535 @c @subheading -signal-handle
28536
28537 @c @subheading -signal-list-handle-actions
28538
28539 @c @subheading -signal-list-signal-types
28540 @end ignore
28541
28542
28543 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
28544 @node GDB/MI Target Manipulation
28545 @section @sc{gdb/mi} Target Manipulation Commands
28546
28547
28548 @subheading The @code{-target-attach} Command
28549 @findex -target-attach
28550
28551 @subsubheading Synopsis
28552
28553 @smallexample
28554 -target-attach @var{pid} | @var{gid} | @var{file}
28555 @end smallexample
28556
28557 Attach to a process @var{pid} or a file @var{file} outside of
28558 @value{GDBN}, or a thread group @var{gid}. If attaching to a thread
28559 group, the id previously returned by
28560 @samp{-list-thread-groups --available} must be used.
28561
28562 @subsubheading @value{GDBN} Command
28563
28564 The corresponding @value{GDBN} command is @samp{attach}.
28565
28566 @subsubheading Example
28567 @smallexample
28568 (gdb)
28569 -target-attach 34
28570 =thread-created,id="1"
28571 *stopped,thread-id="1",frame=@{addr="0xb7f7e410",func="bar",args=[]@}
28572 ^done
28573 (gdb)
28574 @end smallexample
28575
28576 @ignore
28577 @subheading The @code{-target-compare-sections} Command
28578 @findex -target-compare-sections
28579
28580 @subsubheading Synopsis
28581
28582 @smallexample
28583 -target-compare-sections [ @var{section} ]
28584 @end smallexample
28585
28586 Compare data of section @var{section} on target to the exec file.
28587 Without the argument, all sections are compared.
28588
28589 @subsubheading @value{GDBN} Command
28590
28591 The @value{GDBN} equivalent is @samp{compare-sections}.
28592
28593 @subsubheading Example
28594 N.A.
28595 @end ignore
28596
28597
28598 @subheading The @code{-target-detach} Command
28599 @findex -target-detach
28600
28601 @subsubheading Synopsis
28602
28603 @smallexample
28604 -target-detach [ @var{pid} | @var{gid} ]
28605 @end smallexample
28606
28607 Detach from the remote target which normally resumes its execution.
28608 If either @var{pid} or @var{gid} is specified, detaches from either
28609 the specified process, or specified thread group. There's no output.
28610
28611 @subsubheading @value{GDBN} Command
28612
28613 The corresponding @value{GDBN} command is @samp{detach}.
28614
28615 @subsubheading Example
28616
28617 @smallexample
28618 (gdb)
28619 -target-detach
28620 ^done
28621 (gdb)
28622 @end smallexample
28623
28624
28625 @subheading The @code{-target-disconnect} Command
28626 @findex -target-disconnect
28627
28628 @subsubheading Synopsis
28629
28630 @smallexample
28631 -target-disconnect
28632 @end smallexample
28633
28634 Disconnect from the remote target. There's no output and the target is
28635 generally not resumed.
28636
28637 @subsubheading @value{GDBN} Command
28638
28639 The corresponding @value{GDBN} command is @samp{disconnect}.
28640
28641 @subsubheading Example
28642
28643 @smallexample
28644 (gdb)
28645 -target-disconnect
28646 ^done
28647 (gdb)
28648 @end smallexample
28649
28650
28651 @subheading The @code{-target-download} Command
28652 @findex -target-download
28653
28654 @subsubheading Synopsis
28655
28656 @smallexample
28657 -target-download
28658 @end smallexample
28659
28660 Loads the executable onto the remote target.
28661 It prints out an update message every half second, which includes the fields:
28662
28663 @table @samp
28664 @item section
28665 The name of the section.
28666 @item section-sent
28667 The size of what has been sent so far for that section.
28668 @item section-size
28669 The size of the section.
28670 @item total-sent
28671 The total size of what was sent so far (the current and the previous sections).
28672 @item total-size
28673 The size of the overall executable to download.
28674 @end table
28675
28676 @noindent
28677 Each message is sent as status record (@pxref{GDB/MI Output Syntax, ,
28678 @sc{gdb/mi} Output Syntax}).
28679
28680 In addition, it prints the name and size of the sections, as they are
28681 downloaded. These messages include the following fields:
28682
28683 @table @samp
28684 @item section
28685 The name of the section.
28686 @item section-size
28687 The size of the section.
28688 @item total-size
28689 The size of the overall executable to download.
28690 @end table
28691
28692 @noindent
28693 At the end, a summary is printed.
28694
28695 @subsubheading @value{GDBN} Command
28696
28697 The corresponding @value{GDBN} command is @samp{load}.
28698
28699 @subsubheading Example
28700
28701 Note: each status message appears on a single line. Here the messages
28702 have been broken down so that they can fit onto a page.
28703
28704 @smallexample
28705 (gdb)
28706 -target-download
28707 +download,@{section=".text",section-size="6668",total-size="9880"@}
28708 +download,@{section=".text",section-sent="512",section-size="6668",
28709 total-sent="512",total-size="9880"@}
28710 +download,@{section=".text",section-sent="1024",section-size="6668",
28711 total-sent="1024",total-size="9880"@}
28712 +download,@{section=".text",section-sent="1536",section-size="6668",
28713 total-sent="1536",total-size="9880"@}
28714 +download,@{section=".text",section-sent="2048",section-size="6668",
28715 total-sent="2048",total-size="9880"@}
28716 +download,@{section=".text",section-sent="2560",section-size="6668",
28717 total-sent="2560",total-size="9880"@}
28718 +download,@{section=".text",section-sent="3072",section-size="6668",
28719 total-sent="3072",total-size="9880"@}
28720 +download,@{section=".text",section-sent="3584",section-size="6668",
28721 total-sent="3584",total-size="9880"@}
28722 +download,@{section=".text",section-sent="4096",section-size="6668",
28723 total-sent="4096",total-size="9880"@}
28724 +download,@{section=".text",section-sent="4608",section-size="6668",
28725 total-sent="4608",total-size="9880"@}
28726 +download,@{section=".text",section-sent="5120",section-size="6668",
28727 total-sent="5120",total-size="9880"@}
28728 +download,@{section=".text",section-sent="5632",section-size="6668",
28729 total-sent="5632",total-size="9880"@}
28730 +download,@{section=".text",section-sent="6144",section-size="6668",
28731 total-sent="6144",total-size="9880"@}
28732 +download,@{section=".text",section-sent="6656",section-size="6668",
28733 total-sent="6656",total-size="9880"@}
28734 +download,@{section=".init",section-size="28",total-size="9880"@}
28735 +download,@{section=".fini",section-size="28",total-size="9880"@}
28736 +download,@{section=".data",section-size="3156",total-size="9880"@}
28737 +download,@{section=".data",section-sent="512",section-size="3156",
28738 total-sent="7236",total-size="9880"@}
28739 +download,@{section=".data",section-sent="1024",section-size="3156",
28740 total-sent="7748",total-size="9880"@}
28741 +download,@{section=".data",section-sent="1536",section-size="3156",
28742 total-sent="8260",total-size="9880"@}
28743 +download,@{section=".data",section-sent="2048",section-size="3156",
28744 total-sent="8772",total-size="9880"@}
28745 +download,@{section=".data",section-sent="2560",section-size="3156",
28746 total-sent="9284",total-size="9880"@}
28747 +download,@{section=".data",section-sent="3072",section-size="3156",
28748 total-sent="9796",total-size="9880"@}
28749 ^done,address="0x10004",load-size="9880",transfer-rate="6586",
28750 write-rate="429"
28751 (gdb)
28752 @end smallexample
28753
28754
28755 @ignore
28756 @subheading The @code{-target-exec-status} Command
28757 @findex -target-exec-status
28758
28759 @subsubheading Synopsis
28760
28761 @smallexample
28762 -target-exec-status
28763 @end smallexample
28764
28765 Provide information on the state of the target (whether it is running or
28766 not, for instance).
28767
28768 @subsubheading @value{GDBN} Command
28769
28770 There's no equivalent @value{GDBN} command.
28771
28772 @subsubheading Example
28773 N.A.
28774
28775
28776 @subheading The @code{-target-list-available-targets} Command
28777 @findex -target-list-available-targets
28778
28779 @subsubheading Synopsis
28780
28781 @smallexample
28782 -target-list-available-targets
28783 @end smallexample
28784
28785 List the possible targets to connect to.
28786
28787 @subsubheading @value{GDBN} Command
28788
28789 The corresponding @value{GDBN} command is @samp{help target}.
28790
28791 @subsubheading Example
28792 N.A.
28793
28794
28795 @subheading The @code{-target-list-current-targets} Command
28796 @findex -target-list-current-targets
28797
28798 @subsubheading Synopsis
28799
28800 @smallexample
28801 -target-list-current-targets
28802 @end smallexample
28803
28804 Describe the current target.
28805
28806 @subsubheading @value{GDBN} Command
28807
28808 The corresponding information is printed by @samp{info file} (among
28809 other things).
28810
28811 @subsubheading Example
28812 N.A.
28813
28814
28815 @subheading The @code{-target-list-parameters} Command
28816 @findex -target-list-parameters
28817
28818 @subsubheading Synopsis
28819
28820 @smallexample
28821 -target-list-parameters
28822 @end smallexample
28823
28824 @c ????
28825 @end ignore
28826
28827 @subsubheading @value{GDBN} Command
28828
28829 No equivalent.
28830
28831 @subsubheading Example
28832 N.A.
28833
28834
28835 @subheading The @code{-target-select} Command
28836 @findex -target-select
28837
28838 @subsubheading Synopsis
28839
28840 @smallexample
28841 -target-select @var{type} @var{parameters @dots{}}
28842 @end smallexample
28843
28844 Connect @value{GDBN} to the remote target. This command takes two args:
28845
28846 @table @samp
28847 @item @var{type}
28848 The type of target, for instance @samp{remote}, etc.
28849 @item @var{parameters}
28850 Device names, host names and the like. @xref{Target Commands, ,
28851 Commands for Managing Targets}, for more details.
28852 @end table
28853
28854 The output is a connection notification, followed by the address at
28855 which the target program is, in the following form:
28856
28857 @smallexample
28858 ^connected,addr="@var{address}",func="@var{function name}",
28859 args=[@var{arg list}]
28860 @end smallexample
28861
28862 @subsubheading @value{GDBN} Command
28863
28864 The corresponding @value{GDBN} command is @samp{target}.
28865
28866 @subsubheading Example
28867
28868 @smallexample
28869 (gdb)
28870 -target-select remote /dev/ttya
28871 ^connected,addr="0xfe00a300",func="??",args=[]
28872 (gdb)
28873 @end smallexample
28874
28875 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
28876 @node GDB/MI File Transfer Commands
28877 @section @sc{gdb/mi} File Transfer Commands
28878
28879
28880 @subheading The @code{-target-file-put} Command
28881 @findex -target-file-put
28882
28883 @subsubheading Synopsis
28884
28885 @smallexample
28886 -target-file-put @var{hostfile} @var{targetfile}
28887 @end smallexample
28888
28889 Copy file @var{hostfile} from the host system (the machine running
28890 @value{GDBN}) to @var{targetfile} on the target system.
28891
28892 @subsubheading @value{GDBN} Command
28893
28894 The corresponding @value{GDBN} command is @samp{remote put}.
28895
28896 @subsubheading Example
28897
28898 @smallexample
28899 (gdb)
28900 -target-file-put localfile remotefile
28901 ^done
28902 (gdb)
28903 @end smallexample
28904
28905
28906 @subheading The @code{-target-file-get} Command
28907 @findex -target-file-get
28908
28909 @subsubheading Synopsis
28910
28911 @smallexample
28912 -target-file-get @var{targetfile} @var{hostfile}
28913 @end smallexample
28914
28915 Copy file @var{targetfile} from the target system to @var{hostfile}
28916 on the host system.
28917
28918 @subsubheading @value{GDBN} Command
28919
28920 The corresponding @value{GDBN} command is @samp{remote get}.
28921
28922 @subsubheading Example
28923
28924 @smallexample
28925 (gdb)
28926 -target-file-get remotefile localfile
28927 ^done
28928 (gdb)
28929 @end smallexample
28930
28931
28932 @subheading The @code{-target-file-delete} Command
28933 @findex -target-file-delete
28934
28935 @subsubheading Synopsis
28936
28937 @smallexample
28938 -target-file-delete @var{targetfile}
28939 @end smallexample
28940
28941 Delete @var{targetfile} from the target system.
28942
28943 @subsubheading @value{GDBN} Command
28944
28945 The corresponding @value{GDBN} command is @samp{remote delete}.
28946
28947 @subsubheading Example
28948
28949 @smallexample
28950 (gdb)
28951 -target-file-delete remotefile
28952 ^done
28953 (gdb)
28954 @end smallexample
28955
28956
28957 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
28958 @node GDB/MI Miscellaneous Commands
28959 @section Miscellaneous @sc{gdb/mi} Commands
28960
28961 @c @subheading -gdb-complete
28962
28963 @subheading The @code{-gdb-exit} Command
28964 @findex -gdb-exit
28965
28966 @subsubheading Synopsis
28967
28968 @smallexample
28969 -gdb-exit
28970 @end smallexample
28971
28972 Exit @value{GDBN} immediately.
28973
28974 @subsubheading @value{GDBN} Command
28975
28976 Approximately corresponds to @samp{quit}.
28977
28978 @subsubheading Example
28979
28980 @smallexample
28981 (gdb)
28982 -gdb-exit
28983 ^exit
28984 @end smallexample
28985
28986
28987 @ignore
28988 @subheading The @code{-exec-abort} Command
28989 @findex -exec-abort
28990
28991 @subsubheading Synopsis
28992
28993 @smallexample
28994 -exec-abort
28995 @end smallexample
28996
28997 Kill the inferior running program.
28998
28999 @subsubheading @value{GDBN} Command
29000
29001 The corresponding @value{GDBN} command is @samp{kill}.
29002
29003 @subsubheading Example
29004 N.A.
29005 @end ignore
29006
29007
29008 @subheading The @code{-gdb-set} Command
29009 @findex -gdb-set
29010
29011 @subsubheading Synopsis
29012
29013 @smallexample
29014 -gdb-set
29015 @end smallexample
29016
29017 Set an internal @value{GDBN} variable.
29018 @c IS THIS A DOLLAR VARIABLE? OR SOMETHING LIKE ANNOTATE ?????
29019
29020 @subsubheading @value{GDBN} Command
29021
29022 The corresponding @value{GDBN} command is @samp{set}.
29023
29024 @subsubheading Example
29025
29026 @smallexample
29027 (gdb)
29028 -gdb-set $foo=3
29029 ^done
29030 (gdb)
29031 @end smallexample
29032
29033
29034 @subheading The @code{-gdb-show} Command
29035 @findex -gdb-show
29036
29037 @subsubheading Synopsis
29038
29039 @smallexample
29040 -gdb-show
29041 @end smallexample
29042
29043 Show the current value of a @value{GDBN} variable.
29044
29045 @subsubheading @value{GDBN} Command
29046
29047 The corresponding @value{GDBN} command is @samp{show}.
29048
29049 @subsubheading Example
29050
29051 @smallexample
29052 (gdb)
29053 -gdb-show annotate
29054 ^done,value="0"
29055 (gdb)
29056 @end smallexample
29057
29058 @c @subheading -gdb-source
29059
29060
29061 @subheading The @code{-gdb-version} Command
29062 @findex -gdb-version
29063
29064 @subsubheading Synopsis
29065
29066 @smallexample
29067 -gdb-version
29068 @end smallexample
29069
29070 Show version information for @value{GDBN}. Used mostly in testing.
29071
29072 @subsubheading @value{GDBN} Command
29073
29074 The @value{GDBN} equivalent is @samp{show version}. @value{GDBN} by
29075 default shows this information when you start an interactive session.
29076
29077 @subsubheading Example
29078
29079 @c This example modifies the actual output from GDB to avoid overfull
29080 @c box in TeX.
29081 @smallexample
29082 (gdb)
29083 -gdb-version
29084 ~GNU gdb 5.2.1
29085 ~Copyright 2000 Free Software Foundation, Inc.
29086 ~GDB is free software, covered by the GNU General Public License, and
29087 ~you are welcome to change it and/or distribute copies of it under
29088 ~ certain conditions.
29089 ~Type "show copying" to see the conditions.
29090 ~There is absolutely no warranty for GDB. Type "show warranty" for
29091 ~ details.
29092 ~This GDB was configured as
29093 "--host=sparc-sun-solaris2.5.1 --target=ppc-eabi".
29094 ^done
29095 (gdb)
29096 @end smallexample
29097
29098 @subheading The @code{-list-features} Command
29099 @findex -list-features
29100
29101 Returns a list of particular features of the MI protocol that
29102 this version of gdb implements. A feature can be a command,
29103 or a new field in an output of some command, or even an
29104 important bugfix. While a frontend can sometimes detect presence
29105 of a feature at runtime, it is easier to perform detection at debugger
29106 startup.
29107
29108 The command returns a list of strings, with each string naming an
29109 available feature. Each returned string is just a name, it does not
29110 have any internal structure. The list of possible feature names
29111 is given below.
29112
29113 Example output:
29114
29115 @smallexample
29116 (gdb) -list-features
29117 ^done,result=["feature1","feature2"]
29118 @end smallexample
29119
29120 The current list of features is:
29121
29122 @table @samp
29123 @item frozen-varobjs
29124 Indicates presence of the @code{-var-set-frozen} command, as well
29125 as possible presense of the @code{frozen} field in the output
29126 of @code{-varobj-create}.
29127 @item pending-breakpoints
29128 Indicates presence of the @option{-f} option to the @code{-break-insert} command.
29129 @item python
29130 Indicates presence of Python scripting support, Python-based
29131 pretty-printing commands, and possible presence of the
29132 @samp{display_hint} field in the output of @code{-var-list-children}
29133 @item thread-info
29134 Indicates presence of the @code{-thread-info} command.
29135 @item data-read-memory-bytes
29136 Indicates presense of the @code{-data-read-memory-bytes} and the
29137 @code{-data-write-memory-bytes} commands.
29138
29139 @end table
29140
29141 @subheading The @code{-list-target-features} Command
29142 @findex -list-target-features
29143
29144 Returns a list of particular features that are supported by the
29145 target. Those features affect the permitted MI commands, but
29146 unlike the features reported by the @code{-list-features} command, the
29147 features depend on which target GDB is using at the moment. Whenever
29148 a target can change, due to commands such as @code{-target-select},
29149 @code{-target-attach} or @code{-exec-run}, the list of target features
29150 may change, and the frontend should obtain it again.
29151 Example output:
29152
29153 @smallexample
29154 (gdb) -list-features
29155 ^done,result=["async"]
29156 @end smallexample
29157
29158 The current list of features is:
29159
29160 @table @samp
29161 @item async
29162 Indicates that the target is capable of asynchronous command
29163 execution, which means that @value{GDBN} will accept further commands
29164 while the target is running.
29165
29166 @item reverse
29167 Indicates that the target is capable of reverse execution.
29168 @xref{Reverse Execution}, for more information.
29169
29170 @end table
29171
29172 @subheading The @code{-list-thread-groups} Command
29173 @findex -list-thread-groups
29174
29175 @subheading Synopsis
29176
29177 @smallexample
29178 -list-thread-groups [ --available ] [ --recurse 1 ] [ @var{group} ... ]
29179 @end smallexample
29180
29181 Lists thread groups (@pxref{Thread groups}). When a single thread
29182 group is passed as the argument, lists the children of that group.
29183 When several thread group are passed, lists information about those
29184 thread groups. Without any parameters, lists information about all
29185 top-level thread groups.
29186
29187 Normally, thread groups that are being debugged are reported.
29188 With the @samp{--available} option, @value{GDBN} reports thread groups
29189 available on the target.
29190
29191 The output of this command may have either a @samp{threads} result or
29192 a @samp{groups} result. The @samp{thread} result has a list of tuples
29193 as value, with each tuple describing a thread (@pxref{GDB/MI Thread
29194 Information}). The @samp{groups} result has a list of tuples as value,
29195 each tuple describing a thread group. If top-level groups are
29196 requested (that is, no parameter is passed), or when several groups
29197 are passed, the output always has a @samp{groups} result. The format
29198 of the @samp{group} result is described below.
29199
29200 To reduce the number of roundtrips it's possible to list thread groups
29201 together with their children, by passing the @samp{--recurse} option
29202 and the recursion depth. Presently, only recursion depth of 1 is
29203 permitted. If this option is present, then every reported thread group
29204 will also include its children, either as @samp{group} or
29205 @samp{threads} field.
29206
29207 In general, any combination of option and parameters is permitted, with
29208 the following caveats:
29209
29210 @itemize @bullet
29211 @item
29212 When a single thread group is passed, the output will typically
29213 be the @samp{threads} result. Because threads may not contain
29214 anything, the @samp{recurse} option will be ignored.
29215
29216 @item
29217 When the @samp{--available} option is passed, limited information may
29218 be available. In particular, the list of threads of a process might
29219 be inaccessible. Further, specifying specific thread groups might
29220 not give any performance advantage over listing all thread groups.
29221 The frontend should assume that @samp{-list-thread-groups --available}
29222 is always an expensive operation and cache the results.
29223
29224 @end itemize
29225
29226 The @samp{groups} result is a list of tuples, where each tuple may
29227 have the following fields:
29228
29229 @table @code
29230 @item id
29231 Identifier of the thread group. This field is always present.
29232 The identifier is an opaque string; frontends should not try to
29233 convert it to an integer, even though it might look like one.
29234
29235 @item type
29236 The type of the thread group. At present, only @samp{process} is a
29237 valid type.
29238
29239 @item pid
29240 The target-specific process identifier. This field is only present
29241 for thread groups of type @samp{process} and only if the process exists.
29242
29243 @item num_children
29244 The number of children this thread group has. This field may be
29245 absent for an available thread group.
29246
29247 @item threads
29248 This field has a list of tuples as value, each tuple describing a
29249 thread. It may be present if the @samp{--recurse} option is
29250 specified, and it's actually possible to obtain the threads.
29251
29252 @item cores
29253 This field is a list of integers, each identifying a core that one
29254 thread of the group is running on. This field may be absent if
29255 such information is not available.
29256
29257 @item executable
29258 The name of the executable file that corresponds to this thread group.
29259 The field is only present for thread groups of type @samp{process},
29260 and only if there is a corresponding executable file.
29261
29262 @end table
29263
29264 @subheading Example
29265
29266 @smallexample
29267 @value{GDBP}
29268 -list-thread-groups
29269 ^done,groups=[@{id="17",type="process",pid="yyy",num_children="2"@}]
29270 -list-thread-groups 17
29271 ^done,threads=[@{id="2",target-id="Thread 0xb7e14b90 (LWP 21257)",
29272 frame=@{level="0",addr="0xffffe410",func="__kernel_vsyscall",args=[]@},state="running"@},
29273 @{id="1",target-id="Thread 0xb7e156b0 (LWP 21254)",
29274 frame=@{level="0",addr="0x0804891f",func="foo",args=[@{name="i",value="10"@}],
29275 file="/tmp/a.c",fullname="/tmp/a.c",line="158"@},state="running"@}]]
29276 -list-thread-groups --available
29277 ^done,groups=[@{id="17",type="process",pid="yyy",num_children="2",cores=[1,2]@}]
29278 -list-thread-groups --available --recurse 1
29279 ^done,groups=[@{id="17", types="process",pid="yyy",num_children="2",cores=[1,2],
29280 threads=[@{id="1",target-id="Thread 0xb7e14b90",cores=[1]@},
29281 @{id="2",target-id="Thread 0xb7e14b90",cores=[2]@}]@},..]
29282 -list-thread-groups --available --recurse 1 17 18
29283 ^done,groups=[@{id="17", types="process",pid="yyy",num_children="2",cores=[1,2],
29284 threads=[@{id="1",target-id="Thread 0xb7e14b90",cores=[1]@},
29285 @{id="2",target-id="Thread 0xb7e14b90",cores=[2]@}]@},...]
29286 @end smallexample
29287
29288
29289 @subheading The @code{-add-inferior} Command
29290 @findex -add-inferior
29291
29292 @subheading Synopsis
29293
29294 @smallexample
29295 -add-inferior
29296 @end smallexample
29297
29298 Creates a new inferior (@pxref{Inferiors and Programs}). The created
29299 inferior is not associated with any executable. Such association may
29300 be established with the @samp{-file-exec-and-symbols} command
29301 (@pxref{GDB/MI File Commands}). The command response has a single
29302 field, @samp{thread-group}, whose value is the identifier of the
29303 thread group corresponding to the new inferior.
29304
29305 @subheading Example
29306
29307 @smallexample
29308 @value{GDBP}
29309 -add-inferior
29310 ^done,thread-group="i3"
29311 @end smallexample
29312
29313 @subheading The @code{-interpreter-exec} Command
29314 @findex -interpreter-exec
29315
29316 @subheading Synopsis
29317
29318 @smallexample
29319 -interpreter-exec @var{interpreter} @var{command}
29320 @end smallexample
29321 @anchor{-interpreter-exec}
29322
29323 Execute the specified @var{command} in the given @var{interpreter}.
29324
29325 @subheading @value{GDBN} Command
29326
29327 The corresponding @value{GDBN} command is @samp{interpreter-exec}.
29328
29329 @subheading Example
29330
29331 @smallexample
29332 (gdb)
29333 -interpreter-exec console "break main"
29334 &"During symbol reading, couldn't parse type; debugger out of date?.\n"
29335 &"During symbol reading, bad structure-type format.\n"
29336 ~"Breakpoint 1 at 0x8074fc6: file ../../src/gdb/main.c, line 743.\n"
29337 ^done
29338 (gdb)
29339 @end smallexample
29340
29341 @subheading The @code{-inferior-tty-set} Command
29342 @findex -inferior-tty-set
29343
29344 @subheading Synopsis
29345
29346 @smallexample
29347 -inferior-tty-set /dev/pts/1
29348 @end smallexample
29349
29350 Set terminal for future runs of the program being debugged.
29351
29352 @subheading @value{GDBN} Command
29353
29354 The corresponding @value{GDBN} command is @samp{set inferior-tty} /dev/pts/1.
29355
29356 @subheading Example
29357
29358 @smallexample
29359 (gdb)
29360 -inferior-tty-set /dev/pts/1
29361 ^done
29362 (gdb)
29363 @end smallexample
29364
29365 @subheading The @code{-inferior-tty-show} Command
29366 @findex -inferior-tty-show
29367
29368 @subheading Synopsis
29369
29370 @smallexample
29371 -inferior-tty-show
29372 @end smallexample
29373
29374 Show terminal for future runs of program being debugged.
29375
29376 @subheading @value{GDBN} Command
29377
29378 The corresponding @value{GDBN} command is @samp{show inferior-tty}.
29379
29380 @subheading Example
29381
29382 @smallexample
29383 (gdb)
29384 -inferior-tty-set /dev/pts/1
29385 ^done
29386 (gdb)
29387 -inferior-tty-show
29388 ^done,inferior_tty_terminal="/dev/pts/1"
29389 (gdb)
29390 @end smallexample
29391
29392 @subheading The @code{-enable-timings} Command
29393 @findex -enable-timings
29394
29395 @subheading Synopsis
29396
29397 @smallexample
29398 -enable-timings [yes | no]
29399 @end smallexample
29400
29401 Toggle the printing of the wallclock, user and system times for an MI
29402 command as a field in its output. This command is to help frontend
29403 developers optimize the performance of their code. No argument is
29404 equivalent to @samp{yes}.
29405
29406 @subheading @value{GDBN} Command
29407
29408 No equivalent.
29409
29410 @subheading Example
29411
29412 @smallexample
29413 (gdb)
29414 -enable-timings
29415 ^done
29416 (gdb)
29417 -break-insert main
29418 ^done,bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
29419 addr="0x080484ed",func="main",file="myprog.c",
29420 fullname="/home/nickrob/myprog.c",line="73",times="0"@},
29421 time=@{wallclock="0.05185",user="0.00800",system="0.00000"@}
29422 (gdb)
29423 -enable-timings no
29424 ^done
29425 (gdb)
29426 -exec-run
29427 ^running
29428 (gdb)
29429 *stopped,reason="breakpoint-hit",disp="keep",bkptno="1",thread-id="0",
29430 frame=@{addr="0x080484ed",func="main",args=[@{name="argc",value="1"@},
29431 @{name="argv",value="0xbfb60364"@}],file="myprog.c",
29432 fullname="/home/nickrob/myprog.c",line="73"@}
29433 (gdb)
29434 @end smallexample
29435
29436 @node Annotations
29437 @chapter @value{GDBN} Annotations
29438
29439 This chapter describes annotations in @value{GDBN}. Annotations were
29440 designed to interface @value{GDBN} to graphical user interfaces or other
29441 similar programs which want to interact with @value{GDBN} at a
29442 relatively high level.
29443
29444 The annotation mechanism has largely been superseded by @sc{gdb/mi}
29445 (@pxref{GDB/MI}).
29446
29447 @ignore
29448 This is Edition @value{EDITION}, @value{DATE}.
29449 @end ignore
29450
29451 @menu
29452 * Annotations Overview:: What annotations are; the general syntax.
29453 * Server Prefix:: Issuing a command without affecting user state.
29454 * Prompting:: Annotations marking @value{GDBN}'s need for input.
29455 * Errors:: Annotations for error messages.
29456 * Invalidation:: Some annotations describe things now invalid.
29457 * Annotations for Running::
29458 Whether the program is running, how it stopped, etc.
29459 * Source Annotations:: Annotations describing source code.
29460 @end menu
29461
29462 @node Annotations Overview
29463 @section What is an Annotation?
29464 @cindex annotations
29465
29466 Annotations start with a newline character, two @samp{control-z}
29467 characters, and the name of the annotation. If there is no additional
29468 information associated with this annotation, the name of the annotation
29469 is followed immediately by a newline. If there is additional
29470 information, the name of the annotation is followed by a space, the
29471 additional information, and a newline. The additional information
29472 cannot contain newline characters.
29473
29474 Any output not beginning with a newline and two @samp{control-z}
29475 characters denotes literal output from @value{GDBN}. Currently there is
29476 no need for @value{GDBN} to output a newline followed by two
29477 @samp{control-z} characters, but if there was such a need, the
29478 annotations could be extended with an @samp{escape} annotation which
29479 means those three characters as output.
29480
29481 The annotation @var{level}, which is specified using the
29482 @option{--annotate} command line option (@pxref{Mode Options}), controls
29483 how much information @value{GDBN} prints together with its prompt,
29484 values of expressions, source lines, and other types of output. Level 0
29485 is for no annotations, level 1 is for use when @value{GDBN} is run as a
29486 subprocess of @sc{gnu} Emacs, level 3 is the maximum annotation suitable
29487 for programs that control @value{GDBN}, and level 2 annotations have
29488 been made obsolete (@pxref{Limitations, , Limitations of the Annotation
29489 Interface, annotate, GDB's Obsolete Annotations}).
29490
29491 @table @code
29492 @kindex set annotate
29493 @item set annotate @var{level}
29494 The @value{GDBN} command @code{set annotate} sets the level of
29495 annotations to the specified @var{level}.
29496
29497 @item show annotate
29498 @kindex show annotate
29499 Show the current annotation level.
29500 @end table
29501
29502 This chapter describes level 3 annotations.
29503
29504 A simple example of starting up @value{GDBN} with annotations is:
29505
29506 @smallexample
29507 $ @kbd{gdb --annotate=3}
29508 GNU gdb 6.0
29509 Copyright 2003 Free Software Foundation, Inc.
29510 GDB is free software, covered by the GNU General Public License,
29511 and you are welcome to change it and/or distribute copies of it
29512 under certain conditions.
29513 Type "show copying" to see the conditions.
29514 There is absolutely no warranty for GDB. Type "show warranty"
29515 for details.
29516 This GDB was configured as "i386-pc-linux-gnu"
29517
29518 ^Z^Zpre-prompt
29519 (@value{GDBP})
29520 ^Z^Zprompt
29521 @kbd{quit}
29522
29523 ^Z^Zpost-prompt
29524 $
29525 @end smallexample
29526
29527 Here @samp{quit} is input to @value{GDBN}; the rest is output from
29528 @value{GDBN}. The three lines beginning @samp{^Z^Z} (where @samp{^Z}
29529 denotes a @samp{control-z} character) are annotations; the rest is
29530 output from @value{GDBN}.
29531
29532 @node Server Prefix
29533 @section The Server Prefix
29534 @cindex server prefix
29535
29536 If you prefix a command with @samp{server } then it will not affect
29537 the command history, nor will it affect @value{GDBN}'s notion of which
29538 command to repeat if @key{RET} is pressed on a line by itself. This
29539 means that commands can be run behind a user's back by a front-end in
29540 a transparent manner.
29541
29542 The @code{server } prefix does not affect the recording of values into
29543 the value history; to print a value without recording it into the
29544 value history, use the @code{output} command instead of the
29545 @code{print} command.
29546
29547 Using this prefix also disables confirmation requests
29548 (@pxref{confirmation requests}).
29549
29550 @node Prompting
29551 @section Annotation for @value{GDBN} Input
29552
29553 @cindex annotations for prompts
29554 When @value{GDBN} prompts for input, it annotates this fact so it is possible
29555 to know when to send output, when the output from a given command is
29556 over, etc.
29557
29558 Different kinds of input each have a different @dfn{input type}. Each
29559 input type has three annotations: a @code{pre-} annotation, which
29560 denotes the beginning of any prompt which is being output, a plain
29561 annotation, which denotes the end of the prompt, and then a @code{post-}
29562 annotation which denotes the end of any echo which may (or may not) be
29563 associated with the input. For example, the @code{prompt} input type
29564 features the following annotations:
29565
29566 @smallexample
29567 ^Z^Zpre-prompt
29568 ^Z^Zprompt
29569 ^Z^Zpost-prompt
29570 @end smallexample
29571
29572 The input types are
29573
29574 @table @code
29575 @findex pre-prompt annotation
29576 @findex prompt annotation
29577 @findex post-prompt annotation
29578 @item prompt
29579 When @value{GDBN} is prompting for a command (the main @value{GDBN} prompt).
29580
29581 @findex pre-commands annotation
29582 @findex commands annotation
29583 @findex post-commands annotation
29584 @item commands
29585 When @value{GDBN} prompts for a set of commands, like in the @code{commands}
29586 command. The annotations are repeated for each command which is input.
29587
29588 @findex pre-overload-choice annotation
29589 @findex overload-choice annotation
29590 @findex post-overload-choice annotation
29591 @item overload-choice
29592 When @value{GDBN} wants the user to select between various overloaded functions.
29593
29594 @findex pre-query annotation
29595 @findex query annotation
29596 @findex post-query annotation
29597 @item query
29598 When @value{GDBN} wants the user to confirm a potentially dangerous operation.
29599
29600 @findex pre-prompt-for-continue annotation
29601 @findex prompt-for-continue annotation
29602 @findex post-prompt-for-continue annotation
29603 @item prompt-for-continue
29604 When @value{GDBN} is asking the user to press return to continue. Note: Don't
29605 expect this to work well; instead use @code{set height 0} to disable
29606 prompting. This is because the counting of lines is buggy in the
29607 presence of annotations.
29608 @end table
29609
29610 @node Errors
29611 @section Errors
29612 @cindex annotations for errors, warnings and interrupts
29613
29614 @findex quit annotation
29615 @smallexample
29616 ^Z^Zquit
29617 @end smallexample
29618
29619 This annotation occurs right before @value{GDBN} responds to an interrupt.
29620
29621 @findex error annotation
29622 @smallexample
29623 ^Z^Zerror
29624 @end smallexample
29625
29626 This annotation occurs right before @value{GDBN} responds to an error.
29627
29628 Quit and error annotations indicate that any annotations which @value{GDBN} was
29629 in the middle of may end abruptly. For example, if a
29630 @code{value-history-begin} annotation is followed by a @code{error}, one
29631 cannot expect to receive the matching @code{value-history-end}. One
29632 cannot expect not to receive it either, however; an error annotation
29633 does not necessarily mean that @value{GDBN} is immediately returning all the way
29634 to the top level.
29635
29636 @findex error-begin annotation
29637 A quit or error annotation may be preceded by
29638
29639 @smallexample
29640 ^Z^Zerror-begin
29641 @end smallexample
29642
29643 Any output between that and the quit or error annotation is the error
29644 message.
29645
29646 Warning messages are not yet annotated.
29647 @c If we want to change that, need to fix warning(), type_error(),
29648 @c range_error(), and possibly other places.
29649
29650 @node Invalidation
29651 @section Invalidation Notices
29652
29653 @cindex annotations for invalidation messages
29654 The following annotations say that certain pieces of state may have
29655 changed.
29656
29657 @table @code
29658 @findex frames-invalid annotation
29659 @item ^Z^Zframes-invalid
29660
29661 The frames (for example, output from the @code{backtrace} command) may
29662 have changed.
29663
29664 @findex breakpoints-invalid annotation
29665 @item ^Z^Zbreakpoints-invalid
29666
29667 The breakpoints may have changed. For example, the user just added or
29668 deleted a breakpoint.
29669 @end table
29670
29671 @node Annotations for Running
29672 @section Running the Program
29673 @cindex annotations for running programs
29674
29675 @findex starting annotation
29676 @findex stopping annotation
29677 When the program starts executing due to a @value{GDBN} command such as
29678 @code{step} or @code{continue},
29679
29680 @smallexample
29681 ^Z^Zstarting
29682 @end smallexample
29683
29684 is output. When the program stops,
29685
29686 @smallexample
29687 ^Z^Zstopped
29688 @end smallexample
29689
29690 is output. Before the @code{stopped} annotation, a variety of
29691 annotations describe how the program stopped.
29692
29693 @table @code
29694 @findex exited annotation
29695 @item ^Z^Zexited @var{exit-status}
29696 The program exited, and @var{exit-status} is the exit status (zero for
29697 successful exit, otherwise nonzero).
29698
29699 @findex signalled annotation
29700 @findex signal-name annotation
29701 @findex signal-name-end annotation
29702 @findex signal-string annotation
29703 @findex signal-string-end annotation
29704 @item ^Z^Zsignalled
29705 The program exited with a signal. After the @code{^Z^Zsignalled}, the
29706 annotation continues:
29707
29708 @smallexample
29709 @var{intro-text}
29710 ^Z^Zsignal-name
29711 @var{name}
29712 ^Z^Zsignal-name-end
29713 @var{middle-text}
29714 ^Z^Zsignal-string
29715 @var{string}
29716 ^Z^Zsignal-string-end
29717 @var{end-text}
29718 @end smallexample
29719
29720 @noindent
29721 where @var{name} is the name of the signal, such as @code{SIGILL} or
29722 @code{SIGSEGV}, and @var{string} is the explanation of the signal, such
29723 as @code{Illegal Instruction} or @code{Segmentation fault}.
29724 @var{intro-text}, @var{middle-text}, and @var{end-text} are for the
29725 user's benefit and have no particular format.
29726
29727 @findex signal annotation
29728 @item ^Z^Zsignal
29729 The syntax of this annotation is just like @code{signalled}, but @value{GDBN} is
29730 just saying that the program received the signal, not that it was
29731 terminated with it.
29732
29733 @findex breakpoint annotation
29734 @item ^Z^Zbreakpoint @var{number}
29735 The program hit breakpoint number @var{number}.
29736
29737 @findex watchpoint annotation
29738 @item ^Z^Zwatchpoint @var{number}
29739 The program hit watchpoint number @var{number}.
29740 @end table
29741
29742 @node Source Annotations
29743 @section Displaying Source
29744 @cindex annotations for source display
29745
29746 @findex source annotation
29747 The following annotation is used instead of displaying source code:
29748
29749 @smallexample
29750 ^Z^Zsource @var{filename}:@var{line}:@var{character}:@var{middle}:@var{addr}
29751 @end smallexample
29752
29753 where @var{filename} is an absolute file name indicating which source
29754 file, @var{line} is the line number within that file (where 1 is the
29755 first line in the file), @var{character} is the character position
29756 within the file (where 0 is the first character in the file) (for most
29757 debug formats this will necessarily point to the beginning of a line),
29758 @var{middle} is @samp{middle} if @var{addr} is in the middle of the
29759 line, or @samp{beg} if @var{addr} is at the beginning of the line, and
29760 @var{addr} is the address in the target program associated with the
29761 source which is being displayed. @var{addr} is in the form @samp{0x}
29762 followed by one or more lowercase hex digits (note that this does not
29763 depend on the language).
29764
29765 @node JIT Interface
29766 @chapter JIT Compilation Interface
29767 @cindex just-in-time compilation
29768 @cindex JIT compilation interface
29769
29770 This chapter documents @value{GDBN}'s @dfn{just-in-time} (JIT) compilation
29771 interface. A JIT compiler is a program or library that generates native
29772 executable code at runtime and executes it, usually in order to achieve good
29773 performance while maintaining platform independence.
29774
29775 Programs that use JIT compilation are normally difficult to debug because
29776 portions of their code are generated at runtime, instead of being loaded from
29777 object files, which is where @value{GDBN} normally finds the program's symbols
29778 and debug information. In order to debug programs that use JIT compilation,
29779 @value{GDBN} has an interface that allows the program to register in-memory
29780 symbol files with @value{GDBN} at runtime.
29781
29782 If you are using @value{GDBN} to debug a program that uses this interface, then
29783 it should work transparently so long as you have not stripped the binary. If
29784 you are developing a JIT compiler, then the interface is documented in the rest
29785 of this chapter. At this time, the only known client of this interface is the
29786 LLVM JIT.
29787
29788 Broadly speaking, the JIT interface mirrors the dynamic loader interface. The
29789 JIT compiler communicates with @value{GDBN} by writing data into a global
29790 variable and calling a fuction at a well-known symbol. When @value{GDBN}
29791 attaches, it reads a linked list of symbol files from the global variable to
29792 find existing code, and puts a breakpoint in the function so that it can find
29793 out about additional code.
29794
29795 @menu
29796 * Declarations:: Relevant C struct declarations
29797 * Registering Code:: Steps to register code
29798 * Unregistering Code:: Steps to unregister code
29799 @end menu
29800
29801 @node Declarations
29802 @section JIT Declarations
29803
29804 These are the relevant struct declarations that a C program should include to
29805 implement the interface:
29806
29807 @smallexample
29808 typedef enum
29809 @{
29810 JIT_NOACTION = 0,
29811 JIT_REGISTER_FN,
29812 JIT_UNREGISTER_FN
29813 @} jit_actions_t;
29814
29815 struct jit_code_entry
29816 @{
29817 struct jit_code_entry *next_entry;
29818 struct jit_code_entry *prev_entry;
29819 const char *symfile_addr;
29820 uint64_t symfile_size;
29821 @};
29822
29823 struct jit_descriptor
29824 @{
29825 uint32_t version;
29826 /* This type should be jit_actions_t, but we use uint32_t
29827 to be explicit about the bitwidth. */
29828 uint32_t action_flag;
29829 struct jit_code_entry *relevant_entry;
29830 struct jit_code_entry *first_entry;
29831 @};
29832
29833 /* GDB puts a breakpoint in this function. */
29834 void __attribute__((noinline)) __jit_debug_register_code() @{ @};
29835
29836 /* Make sure to specify the version statically, because the
29837 debugger may check the version before we can set it. */
29838 struct jit_descriptor __jit_debug_descriptor = @{ 1, 0, 0, 0 @};
29839 @end smallexample
29840
29841 If the JIT is multi-threaded, then it is important that the JIT synchronize any
29842 modifications to this global data properly, which can easily be done by putting
29843 a global mutex around modifications to these structures.
29844
29845 @node Registering Code
29846 @section Registering Code
29847
29848 To register code with @value{GDBN}, the JIT should follow this protocol:
29849
29850 @itemize @bullet
29851 @item
29852 Generate an object file in memory with symbols and other desired debug
29853 information. The file must include the virtual addresses of the sections.
29854
29855 @item
29856 Create a code entry for the file, which gives the start and size of the symbol
29857 file.
29858
29859 @item
29860 Add it to the linked list in the JIT descriptor.
29861
29862 @item
29863 Point the relevant_entry field of the descriptor at the entry.
29864
29865 @item
29866 Set @code{action_flag} to @code{JIT_REGISTER} and call
29867 @code{__jit_debug_register_code}.
29868 @end itemize
29869
29870 When @value{GDBN} is attached and the breakpoint fires, @value{GDBN} uses the
29871 @code{relevant_entry} pointer so it doesn't have to walk the list looking for
29872 new code. However, the linked list must still be maintained in order to allow
29873 @value{GDBN} to attach to a running process and still find the symbol files.
29874
29875 @node Unregistering Code
29876 @section Unregistering Code
29877
29878 If code is freed, then the JIT should use the following protocol:
29879
29880 @itemize @bullet
29881 @item
29882 Remove the code entry corresponding to the code from the linked list.
29883
29884 @item
29885 Point the @code{relevant_entry} field of the descriptor at the code entry.
29886
29887 @item
29888 Set @code{action_flag} to @code{JIT_UNREGISTER} and call
29889 @code{__jit_debug_register_code}.
29890 @end itemize
29891
29892 If the JIT frees or recompiles code without unregistering it, then @value{GDBN}
29893 and the JIT will leak the memory used for the associated symbol files.
29894
29895 @node GDB Bugs
29896 @chapter Reporting Bugs in @value{GDBN}
29897 @cindex bugs in @value{GDBN}
29898 @cindex reporting bugs in @value{GDBN}
29899
29900 Your bug reports play an essential role in making @value{GDBN} reliable.
29901
29902 Reporting a bug may help you by bringing a solution to your problem, or it
29903 may not. But in any case the principal function of a bug report is to help
29904 the entire community by making the next version of @value{GDBN} work better. Bug
29905 reports are your contribution to the maintenance of @value{GDBN}.
29906
29907 In order for a bug report to serve its purpose, you must include the
29908 information that enables us to fix the bug.
29909
29910 @menu
29911 * Bug Criteria:: Have you found a bug?
29912 * Bug Reporting:: How to report bugs
29913 @end menu
29914
29915 @node Bug Criteria
29916 @section Have You Found a Bug?
29917 @cindex bug criteria
29918
29919 If you are not sure whether you have found a bug, here are some guidelines:
29920
29921 @itemize @bullet
29922 @cindex fatal signal
29923 @cindex debugger crash
29924 @cindex crash of debugger
29925 @item
29926 If the debugger gets a fatal signal, for any input whatever, that is a
29927 @value{GDBN} bug. Reliable debuggers never crash.
29928
29929 @cindex error on valid input
29930 @item
29931 If @value{GDBN} produces an error message for valid input, that is a
29932 bug. (Note that if you're cross debugging, the problem may also be
29933 somewhere in the connection to the target.)
29934
29935 @cindex invalid input
29936 @item
29937 If @value{GDBN} does not produce an error message for invalid input,
29938 that is a bug. However, you should note that your idea of
29939 ``invalid input'' might be our idea of ``an extension'' or ``support
29940 for traditional practice''.
29941
29942 @item
29943 If you are an experienced user of debugging tools, your suggestions
29944 for improvement of @value{GDBN} are welcome in any case.
29945 @end itemize
29946
29947 @node Bug Reporting
29948 @section How to Report Bugs
29949 @cindex bug reports
29950 @cindex @value{GDBN} bugs, reporting
29951
29952 A number of companies and individuals offer support for @sc{gnu} products.
29953 If you obtained @value{GDBN} from a support organization, we recommend you
29954 contact that organization first.
29955
29956 You can find contact information for many support companies and
29957 individuals in the file @file{etc/SERVICE} in the @sc{gnu} Emacs
29958 distribution.
29959 @c should add a web page ref...
29960
29961 @ifset BUGURL
29962 @ifset BUGURL_DEFAULT
29963 In any event, we also recommend that you submit bug reports for
29964 @value{GDBN}. The preferred method is to submit them directly using
29965 @uref{http://www.gnu.org/software/gdb/bugs/, @value{GDBN}'s Bugs web
29966 page}. Alternatively, the @email{bug-gdb@@gnu.org, e-mail gateway} can
29967 be used.
29968
29969 @strong{Do not send bug reports to @samp{info-gdb}, or to
29970 @samp{help-gdb}, or to any newsgroups.} Most users of @value{GDBN} do
29971 not want to receive bug reports. Those that do have arranged to receive
29972 @samp{bug-gdb}.
29973
29974 The mailing list @samp{bug-gdb} has a newsgroup @samp{gnu.gdb.bug} which
29975 serves as a repeater. The mailing list and the newsgroup carry exactly
29976 the same messages. Often people think of posting bug reports to the
29977 newsgroup instead of mailing them. This appears to work, but it has one
29978 problem which can be crucial: a newsgroup posting often lacks a mail
29979 path back to the sender. Thus, if we need to ask for more information,
29980 we may be unable to reach you. For this reason, it is better to send
29981 bug reports to the mailing list.
29982 @end ifset
29983 @ifclear BUGURL_DEFAULT
29984 In any event, we also recommend that you submit bug reports for
29985 @value{GDBN} to @value{BUGURL}.
29986 @end ifclear
29987 @end ifset
29988
29989 The fundamental principle of reporting bugs usefully is this:
29990 @strong{report all the facts}. If you are not sure whether to state a
29991 fact or leave it out, state it!
29992
29993 Often people omit facts because they think they know what causes the
29994 problem and assume that some details do not matter. Thus, you might
29995 assume that the name of the variable you use in an example does not matter.
29996 Well, probably it does not, but one cannot be sure. Perhaps the bug is a
29997 stray memory reference which happens to fetch from the location where that
29998 name is stored in memory; perhaps, if the name were different, the contents
29999 of that location would fool the debugger into doing the right thing despite
30000 the bug. Play it safe and give a specific, complete example. That is the
30001 easiest thing for you to do, and the most helpful.
30002
30003 Keep in mind that the purpose of a bug report is to enable us to fix the
30004 bug. It may be that the bug has been reported previously, but neither
30005 you nor we can know that unless your bug report is complete and
30006 self-contained.
30007
30008 Sometimes people give a few sketchy facts and ask, ``Does this ring a
30009 bell?'' Those bug reports are useless, and we urge everyone to
30010 @emph{refuse to respond to them} except to chide the sender to report
30011 bugs properly.
30012
30013 To enable us to fix the bug, you should include all these things:
30014
30015 @itemize @bullet
30016 @item
30017 The version of @value{GDBN}. @value{GDBN} announces it if you start
30018 with no arguments; you can also print it at any time using @code{show
30019 version}.
30020
30021 Without this, we will not know whether there is any point in looking for
30022 the bug in the current version of @value{GDBN}.
30023
30024 @item
30025 The type of machine you are using, and the operating system name and
30026 version number.
30027
30028 @item
30029 What compiler (and its version) was used to compile @value{GDBN}---e.g.@:
30030 ``@value{GCC}--2.8.1''.
30031
30032 @item
30033 What compiler (and its version) was used to compile the program you are
30034 debugging---e.g.@: ``@value{GCC}--2.8.1'', or ``HP92453-01 A.10.32.03 HP
30035 C Compiler''. For @value{NGCC}, you can say @kbd{@value{GCC} --version}
30036 to get this information; for other compilers, see the documentation for
30037 those compilers.
30038
30039 @item
30040 The command arguments you gave the compiler to compile your example and
30041 observe the bug. For example, did you use @samp{-O}? To guarantee
30042 you will not omit something important, list them all. A copy of the
30043 Makefile (or the output from make) is sufficient.
30044
30045 If we were to try to guess the arguments, we would probably guess wrong
30046 and then we might not encounter the bug.
30047
30048 @item
30049 A complete input script, and all necessary source files, that will
30050 reproduce the bug.
30051
30052 @item
30053 A description of what behavior you observe that you believe is
30054 incorrect. For example, ``It gets a fatal signal.''
30055
30056 Of course, if the bug is that @value{GDBN} gets a fatal signal, then we
30057 will certainly notice it. But if the bug is incorrect output, we might
30058 not notice unless it is glaringly wrong. You might as well not give us
30059 a chance to make a mistake.
30060
30061 Even if the problem you experience is a fatal signal, you should still
30062 say so explicitly. Suppose something strange is going on, such as, your
30063 copy of @value{GDBN} is out of synch, or you have encountered a bug in
30064 the C library on your system. (This has happened!) Your copy might
30065 crash and ours would not. If you told us to expect a crash, then when
30066 ours fails to crash, we would know that the bug was not happening for
30067 us. If you had not told us to expect a crash, then we would not be able
30068 to draw any conclusion from our observations.
30069
30070 @pindex script
30071 @cindex recording a session script
30072 To collect all this information, you can use a session recording program
30073 such as @command{script}, which is available on many Unix systems.
30074 Just run your @value{GDBN} session inside @command{script} and then
30075 include the @file{typescript} file with your bug report.
30076
30077 Another way to record a @value{GDBN} session is to run @value{GDBN}
30078 inside Emacs and then save the entire buffer to a file.
30079
30080 @item
30081 If you wish to suggest changes to the @value{GDBN} source, send us context
30082 diffs. If you even discuss something in the @value{GDBN} source, refer to
30083 it by context, not by line number.
30084
30085 The line numbers in our development sources will not match those in your
30086 sources. Your line numbers would convey no useful information to us.
30087
30088 @end itemize
30089
30090 Here are some things that are not necessary:
30091
30092 @itemize @bullet
30093 @item
30094 A description of the envelope of the bug.
30095
30096 Often people who encounter a bug spend a lot of time investigating
30097 which changes to the input file will make the bug go away and which
30098 changes will not affect it.
30099
30100 This is often time consuming and not very useful, because the way we
30101 will find the bug is by running a single example under the debugger
30102 with breakpoints, not by pure deduction from a series of examples.
30103 We recommend that you save your time for something else.
30104
30105 Of course, if you can find a simpler example to report @emph{instead}
30106 of the original one, that is a convenience for us. Errors in the
30107 output will be easier to spot, running under the debugger will take
30108 less time, and so on.
30109
30110 However, simplification is not vital; if you do not want to do this,
30111 report the bug anyway and send us the entire test case you used.
30112
30113 @item
30114 A patch for the bug.
30115
30116 A patch for the bug does help us if it is a good one. But do not omit
30117 the necessary information, such as the test case, on the assumption that
30118 a patch is all we need. We might see problems with your patch and decide
30119 to fix the problem another way, or we might not understand it at all.
30120
30121 Sometimes with a program as complicated as @value{GDBN} it is very hard to
30122 construct an example that will make the program follow a certain path
30123 through the code. If you do not send us the example, we will not be able
30124 to construct one, so we will not be able to verify that the bug is fixed.
30125
30126 And if we cannot understand what bug you are trying to fix, or why your
30127 patch should be an improvement, we will not install it. A test case will
30128 help us to understand.
30129
30130 @item
30131 A guess about what the bug is or what it depends on.
30132
30133 Such guesses are usually wrong. Even we cannot guess right about such
30134 things without first using the debugger to find the facts.
30135 @end itemize
30136
30137 @c The readline documentation is distributed with the readline code
30138 @c and consists of the two following files:
30139 @c rluser.texinfo
30140 @c inc-hist.texinfo
30141 @c Use -I with makeinfo to point to the appropriate directory,
30142 @c environment var TEXINPUTS with TeX.
30143 @include rluser.texi
30144 @include inc-hist.texinfo
30145
30146
30147 @node Formatting Documentation
30148 @appendix Formatting Documentation
30149
30150 @cindex @value{GDBN} reference card
30151 @cindex reference card
30152 The @value{GDBN} 4 release includes an already-formatted reference card, ready
30153 for printing with PostScript or Ghostscript, in the @file{gdb}
30154 subdirectory of the main source directory@footnote{In
30155 @file{gdb-@value{GDBVN}/gdb/refcard.ps} of the version @value{GDBVN}
30156 release.}. If you can use PostScript or Ghostscript with your printer,
30157 you can print the reference card immediately with @file{refcard.ps}.
30158
30159 The release also includes the source for the reference card. You
30160 can format it, using @TeX{}, by typing:
30161
30162 @smallexample
30163 make refcard.dvi
30164 @end smallexample
30165
30166 The @value{GDBN} reference card is designed to print in @dfn{landscape}
30167 mode on US ``letter'' size paper;
30168 that is, on a sheet 11 inches wide by 8.5 inches
30169 high. You will need to specify this form of printing as an option to
30170 your @sc{dvi} output program.
30171
30172 @cindex documentation
30173
30174 All the documentation for @value{GDBN} comes as part of the machine-readable
30175 distribution. The documentation is written in Texinfo format, which is
30176 a documentation system that uses a single source file to produce both
30177 on-line information and a printed manual. You can use one of the Info
30178 formatting commands to create the on-line version of the documentation
30179 and @TeX{} (or @code{texi2roff}) to typeset the printed version.
30180
30181 @value{GDBN} includes an already formatted copy of the on-line Info
30182 version of this manual in the @file{gdb} subdirectory. The main Info
30183 file is @file{gdb-@value{GDBVN}/gdb/gdb.info}, and it refers to
30184 subordinate files matching @samp{gdb.info*} in the same directory. If
30185 necessary, you can print out these files, or read them with any editor;
30186 but they are easier to read using the @code{info} subsystem in @sc{gnu}
30187 Emacs or the standalone @code{info} program, available as part of the
30188 @sc{gnu} Texinfo distribution.
30189
30190 If you want to format these Info files yourself, you need one of the
30191 Info formatting programs, such as @code{texinfo-format-buffer} or
30192 @code{makeinfo}.
30193
30194 If you have @code{makeinfo} installed, and are in the top level
30195 @value{GDBN} source directory (@file{gdb-@value{GDBVN}}, in the case of
30196 version @value{GDBVN}), you can make the Info file by typing:
30197
30198 @smallexample
30199 cd gdb
30200 make gdb.info
30201 @end smallexample
30202
30203 If you want to typeset and print copies of this manual, you need @TeX{},
30204 a program to print its @sc{dvi} output files, and @file{texinfo.tex}, the
30205 Texinfo definitions file.
30206
30207 @TeX{} is a typesetting program; it does not print files directly, but
30208 produces output files called @sc{dvi} files. To print a typeset
30209 document, you need a program to print @sc{dvi} files. If your system
30210 has @TeX{} installed, chances are it has such a program. The precise
30211 command to use depends on your system; @kbd{lpr -d} is common; another
30212 (for PostScript devices) is @kbd{dvips}. The @sc{dvi} print command may
30213 require a file name without any extension or a @samp{.dvi} extension.
30214
30215 @TeX{} also requires a macro definitions file called
30216 @file{texinfo.tex}. This file tells @TeX{} how to typeset a document
30217 written in Texinfo format. On its own, @TeX{} cannot either read or
30218 typeset a Texinfo file. @file{texinfo.tex} is distributed with GDB
30219 and is located in the @file{gdb-@var{version-number}/texinfo}
30220 directory.
30221
30222 If you have @TeX{} and a @sc{dvi} printer program installed, you can
30223 typeset and print this manual. First switch to the @file{gdb}
30224 subdirectory of the main source directory (for example, to
30225 @file{gdb-@value{GDBVN}/gdb}) and type:
30226
30227 @smallexample
30228 make gdb.dvi
30229 @end smallexample
30230
30231 Then give @file{gdb.dvi} to your @sc{dvi} printing program.
30232
30233 @node Installing GDB
30234 @appendix Installing @value{GDBN}
30235 @cindex installation
30236
30237 @menu
30238 * Requirements:: Requirements for building @value{GDBN}
30239 * Running Configure:: Invoking the @value{GDBN} @file{configure} script
30240 * Separate Objdir:: Compiling @value{GDBN} in another directory
30241 * Config Names:: Specifying names for hosts and targets
30242 * Configure Options:: Summary of options for configure
30243 * System-wide configuration:: Having a system-wide init file
30244 @end menu
30245
30246 @node Requirements
30247 @section Requirements for Building @value{GDBN}
30248 @cindex building @value{GDBN}, requirements for
30249
30250 Building @value{GDBN} requires various tools and packages to be available.
30251 Other packages will be used only if they are found.
30252
30253 @heading Tools/Packages Necessary for Building @value{GDBN}
30254 @table @asis
30255 @item ISO C90 compiler
30256 @value{GDBN} is written in ISO C90. It should be buildable with any
30257 working C90 compiler, e.g.@: GCC.
30258
30259 @end table
30260
30261 @heading Tools/Packages Optional for Building @value{GDBN}
30262 @table @asis
30263 @item Expat
30264 @anchor{Expat}
30265 @value{GDBN} can use the Expat XML parsing library. This library may be
30266 included with your operating system distribution; if it is not, you
30267 can get the latest version from @url{http://expat.sourceforge.net}.
30268 The @file{configure} script will search for this library in several
30269 standard locations; if it is installed in an unusual path, you can
30270 use the @option{--with-libexpat-prefix} option to specify its location.
30271
30272 Expat is used for:
30273
30274 @itemize @bullet
30275 @item
30276 Remote protocol memory maps (@pxref{Memory Map Format})
30277 @item
30278 Target descriptions (@pxref{Target Descriptions})
30279 @item
30280 Remote shared library lists (@pxref{Library List Format})
30281 @item
30282 MS-Windows shared libraries (@pxref{Shared Libraries})
30283 @end itemize
30284
30285 @item zlib
30286 @cindex compressed debug sections
30287 @value{GDBN} will use the @samp{zlib} library, if available, to read
30288 compressed debug sections. Some linkers, such as GNU gold, are capable
30289 of producing binaries with compressed debug sections. If @value{GDBN}
30290 is compiled with @samp{zlib}, it will be able to read the debug
30291 information in such binaries.
30292
30293 The @samp{zlib} library is likely included with your operating system
30294 distribution; if it is not, you can get the latest version from
30295 @url{http://zlib.net}.
30296
30297 @item iconv
30298 @value{GDBN}'s features related to character sets (@pxref{Character
30299 Sets}) require a functioning @code{iconv} implementation. If you are
30300 on a GNU system, then this is provided by the GNU C Library. Some
30301 other systems also provide a working @code{iconv}.
30302
30303 On systems with @code{iconv}, you can install GNU Libiconv. If you
30304 have previously installed Libiconv, you can use the
30305 @option{--with-libiconv-prefix} option to configure.
30306
30307 @value{GDBN}'s top-level @file{configure} and @file{Makefile} will
30308 arrange to build Libiconv if a directory named @file{libiconv} appears
30309 in the top-most source directory. If Libiconv is built this way, and
30310 if the operating system does not provide a suitable @code{iconv}
30311 implementation, then the just-built library will automatically be used
30312 by @value{GDBN}. One easy way to set this up is to download GNU
30313 Libiconv, unpack it, and then rename the directory holding the
30314 Libiconv source code to @samp{libiconv}.
30315 @end table
30316
30317 @node Running Configure
30318 @section Invoking the @value{GDBN} @file{configure} Script
30319 @cindex configuring @value{GDBN}
30320 @value{GDBN} comes with a @file{configure} script that automates the process
30321 of preparing @value{GDBN} for installation; you can then use @code{make} to
30322 build the @code{gdb} program.
30323 @iftex
30324 @c irrelevant in info file; it's as current as the code it lives with.
30325 @footnote{If you have a more recent version of @value{GDBN} than @value{GDBVN},
30326 look at the @file{README} file in the sources; we may have improved the
30327 installation procedures since publishing this manual.}
30328 @end iftex
30329
30330 The @value{GDBN} distribution includes all the source code you need for
30331 @value{GDBN} in a single directory, whose name is usually composed by
30332 appending the version number to @samp{gdb}.
30333
30334 For example, the @value{GDBN} version @value{GDBVN} distribution is in the
30335 @file{gdb-@value{GDBVN}} directory. That directory contains:
30336
30337 @table @code
30338 @item gdb-@value{GDBVN}/configure @r{(and supporting files)}
30339 script for configuring @value{GDBN} and all its supporting libraries
30340
30341 @item gdb-@value{GDBVN}/gdb
30342 the source specific to @value{GDBN} itself
30343
30344 @item gdb-@value{GDBVN}/bfd
30345 source for the Binary File Descriptor library
30346
30347 @item gdb-@value{GDBVN}/include
30348 @sc{gnu} include files
30349
30350 @item gdb-@value{GDBVN}/libiberty
30351 source for the @samp{-liberty} free software library
30352
30353 @item gdb-@value{GDBVN}/opcodes
30354 source for the library of opcode tables and disassemblers
30355
30356 @item gdb-@value{GDBVN}/readline
30357 source for the @sc{gnu} command-line interface
30358
30359 @item gdb-@value{GDBVN}/glob
30360 source for the @sc{gnu} filename pattern-matching subroutine
30361
30362 @item gdb-@value{GDBVN}/mmalloc
30363 source for the @sc{gnu} memory-mapped malloc package
30364 @end table
30365
30366 The simplest way to configure and build @value{GDBN} is to run @file{configure}
30367 from the @file{gdb-@var{version-number}} source directory, which in
30368 this example is the @file{gdb-@value{GDBVN}} directory.
30369
30370 First switch to the @file{gdb-@var{version-number}} source directory
30371 if you are not already in it; then run @file{configure}. Pass the
30372 identifier for the platform on which @value{GDBN} will run as an
30373 argument.
30374
30375 For example:
30376
30377 @smallexample
30378 cd gdb-@value{GDBVN}
30379 ./configure @var{host}
30380 make
30381 @end smallexample
30382
30383 @noindent
30384 where @var{host} is an identifier such as @samp{sun4} or
30385 @samp{decstation}, that identifies the platform where @value{GDBN} will run.
30386 (You can often leave off @var{host}; @file{configure} tries to guess the
30387 correct value by examining your system.)
30388
30389 Running @samp{configure @var{host}} and then running @code{make} builds the
30390 @file{bfd}, @file{readline}, @file{mmalloc}, and @file{libiberty}
30391 libraries, then @code{gdb} itself. The configured source files, and the
30392 binaries, are left in the corresponding source directories.
30393
30394 @need 750
30395 @file{configure} is a Bourne-shell (@code{/bin/sh}) script; if your
30396 system does not recognize this automatically when you run a different
30397 shell, you may need to run @code{sh} on it explicitly:
30398
30399 @smallexample
30400 sh configure @var{host}
30401 @end smallexample
30402
30403 If you run @file{configure} from a directory that contains source
30404 directories for multiple libraries or programs, such as the
30405 @file{gdb-@value{GDBVN}} source directory for version @value{GDBVN},
30406 @file{configure}
30407 creates configuration files for every directory level underneath (unless
30408 you tell it not to, with the @samp{--norecursion} option).
30409
30410 You should run the @file{configure} script from the top directory in the
30411 source tree, the @file{gdb-@var{version-number}} directory. If you run
30412 @file{configure} from one of the subdirectories, you will configure only
30413 that subdirectory. That is usually not what you want. In particular,
30414 if you run the first @file{configure} from the @file{gdb} subdirectory
30415 of the @file{gdb-@var{version-number}} directory, you will omit the
30416 configuration of @file{bfd}, @file{readline}, and other sibling
30417 directories of the @file{gdb} subdirectory. This leads to build errors
30418 about missing include files such as @file{bfd/bfd.h}.
30419
30420 You can install @code{@value{GDBP}} anywhere; it has no hardwired paths.
30421 However, you should make sure that the shell on your path (named by
30422 the @samp{SHELL} environment variable) is publicly readable. Remember
30423 that @value{GDBN} uses the shell to start your program---some systems refuse to
30424 let @value{GDBN} debug child processes whose programs are not readable.
30425
30426 @node Separate Objdir
30427 @section Compiling @value{GDBN} in Another Directory
30428
30429 If you want to run @value{GDBN} versions for several host or target machines,
30430 you need a different @code{gdb} compiled for each combination of
30431 host and target. @file{configure} is designed to make this easy by
30432 allowing you to generate each configuration in a separate subdirectory,
30433 rather than in the source directory. If your @code{make} program
30434 handles the @samp{VPATH} feature (@sc{gnu} @code{make} does), running
30435 @code{make} in each of these directories builds the @code{gdb}
30436 program specified there.
30437
30438 To build @code{gdb} in a separate directory, run @file{configure}
30439 with the @samp{--srcdir} option to specify where to find the source.
30440 (You also need to specify a path to find @file{configure}
30441 itself from your working directory. If the path to @file{configure}
30442 would be the same as the argument to @samp{--srcdir}, you can leave out
30443 the @samp{--srcdir} option; it is assumed.)
30444
30445 For example, with version @value{GDBVN}, you can build @value{GDBN} in a
30446 separate directory for a Sun 4 like this:
30447
30448 @smallexample
30449 @group
30450 cd gdb-@value{GDBVN}
30451 mkdir ../gdb-sun4
30452 cd ../gdb-sun4
30453 ../gdb-@value{GDBVN}/configure sun4
30454 make
30455 @end group
30456 @end smallexample
30457
30458 When @file{configure} builds a configuration using a remote source
30459 directory, it creates a tree for the binaries with the same structure
30460 (and using the same names) as the tree under the source directory. In
30461 the example, you'd find the Sun 4 library @file{libiberty.a} in the
30462 directory @file{gdb-sun4/libiberty}, and @value{GDBN} itself in
30463 @file{gdb-sun4/gdb}.
30464
30465 Make sure that your path to the @file{configure} script has just one
30466 instance of @file{gdb} in it. If your path to @file{configure} looks
30467 like @file{../gdb-@value{GDBVN}/gdb/configure}, you are configuring only
30468 one subdirectory of @value{GDBN}, not the whole package. This leads to
30469 build errors about missing include files such as @file{bfd/bfd.h}.
30470
30471 One popular reason to build several @value{GDBN} configurations in separate
30472 directories is to configure @value{GDBN} for cross-compiling (where
30473 @value{GDBN} runs on one machine---the @dfn{host}---while debugging
30474 programs that run on another machine---the @dfn{target}).
30475 You specify a cross-debugging target by
30476 giving the @samp{--target=@var{target}} option to @file{configure}.
30477
30478 When you run @code{make} to build a program or library, you must run
30479 it in a configured directory---whatever directory you were in when you
30480 called @file{configure} (or one of its subdirectories).
30481
30482 The @code{Makefile} that @file{configure} generates in each source
30483 directory also runs recursively. If you type @code{make} in a source
30484 directory such as @file{gdb-@value{GDBVN}} (or in a separate configured
30485 directory configured with @samp{--srcdir=@var{dirname}/gdb-@value{GDBVN}}), you
30486 will build all the required libraries, and then build GDB.
30487
30488 When you have multiple hosts or targets configured in separate
30489 directories, you can run @code{make} on them in parallel (for example,
30490 if they are NFS-mounted on each of the hosts); they will not interfere
30491 with each other.
30492
30493 @node Config Names
30494 @section Specifying Names for Hosts and Targets
30495
30496 The specifications used for hosts and targets in the @file{configure}
30497 script are based on a three-part naming scheme, but some short predefined
30498 aliases are also supported. The full naming scheme encodes three pieces
30499 of information in the following pattern:
30500
30501 @smallexample
30502 @var{architecture}-@var{vendor}-@var{os}
30503 @end smallexample
30504
30505 For example, you can use the alias @code{sun4} as a @var{host} argument,
30506 or as the value for @var{target} in a @code{--target=@var{target}}
30507 option. The equivalent full name is @samp{sparc-sun-sunos4}.
30508
30509 The @file{configure} script accompanying @value{GDBN} does not provide
30510 any query facility to list all supported host and target names or
30511 aliases. @file{configure} calls the Bourne shell script
30512 @code{config.sub} to map abbreviations to full names; you can read the
30513 script, if you wish, or you can use it to test your guesses on
30514 abbreviations---for example:
30515
30516 @smallexample
30517 % sh config.sub i386-linux
30518 i386-pc-linux-gnu
30519 % sh config.sub alpha-linux
30520 alpha-unknown-linux-gnu
30521 % sh config.sub hp9k700
30522 hppa1.1-hp-hpux
30523 % sh config.sub sun4
30524 sparc-sun-sunos4.1.1
30525 % sh config.sub sun3
30526 m68k-sun-sunos4.1.1
30527 % sh config.sub i986v
30528 Invalid configuration `i986v': machine `i986v' not recognized
30529 @end smallexample
30530
30531 @noindent
30532 @code{config.sub} is also distributed in the @value{GDBN} source
30533 directory (@file{gdb-@value{GDBVN}}, for version @value{GDBVN}).
30534
30535 @node Configure Options
30536 @section @file{configure} Options
30537
30538 Here is a summary of the @file{configure} options and arguments that
30539 are most often useful for building @value{GDBN}. @file{configure} also has
30540 several other options not listed here. @inforef{What Configure
30541 Does,,configure.info}, for a full explanation of @file{configure}.
30542
30543 @smallexample
30544 configure @r{[}--help@r{]}
30545 @r{[}--prefix=@var{dir}@r{]}
30546 @r{[}--exec-prefix=@var{dir}@r{]}
30547 @r{[}--srcdir=@var{dirname}@r{]}
30548 @r{[}--norecursion@r{]} @r{[}--rm@r{]}
30549 @r{[}--target=@var{target}@r{]}
30550 @var{host}
30551 @end smallexample
30552
30553 @noindent
30554 You may introduce options with a single @samp{-} rather than
30555 @samp{--} if you prefer; but you may abbreviate option names if you use
30556 @samp{--}.
30557
30558 @table @code
30559 @item --help
30560 Display a quick summary of how to invoke @file{configure}.
30561
30562 @item --prefix=@var{dir}
30563 Configure the source to install programs and files under directory
30564 @file{@var{dir}}.
30565
30566 @item --exec-prefix=@var{dir}
30567 Configure the source to install programs under directory
30568 @file{@var{dir}}.
30569
30570 @c avoid splitting the warning from the explanation:
30571 @need 2000
30572 @item --srcdir=@var{dirname}
30573 @strong{Warning: using this option requires @sc{gnu} @code{make}, or another
30574 @code{make} that implements the @code{VPATH} feature.}@*
30575 Use this option to make configurations in directories separate from the
30576 @value{GDBN} source directories. Among other things, you can use this to
30577 build (or maintain) several configurations simultaneously, in separate
30578 directories. @file{configure} writes configuration-specific files in
30579 the current directory, but arranges for them to use the source in the
30580 directory @var{dirname}. @file{configure} creates directories under
30581 the working directory in parallel to the source directories below
30582 @var{dirname}.
30583
30584 @item --norecursion
30585 Configure only the directory level where @file{configure} is executed; do not
30586 propagate configuration to subdirectories.
30587
30588 @item --target=@var{target}
30589 Configure @value{GDBN} for cross-debugging programs running on the specified
30590 @var{target}. Without this option, @value{GDBN} is configured to debug
30591 programs that run on the same machine (@var{host}) as @value{GDBN} itself.
30592
30593 There is no convenient way to generate a list of all available targets.
30594
30595 @item @var{host} @dots{}
30596 Configure @value{GDBN} to run on the specified @var{host}.
30597
30598 There is no convenient way to generate a list of all available hosts.
30599 @end table
30600
30601 There are many other options available as well, but they are generally
30602 needed for special purposes only.
30603
30604 @node System-wide configuration
30605 @section System-wide configuration and settings
30606 @cindex system-wide init file
30607
30608 @value{GDBN} can be configured to have a system-wide init file;
30609 this file will be read and executed at startup (@pxref{Startup, , What
30610 @value{GDBN} does during startup}).
30611
30612 Here is the corresponding configure option:
30613
30614 @table @code
30615 @item --with-system-gdbinit=@var{file}
30616 Specify that the default location of the system-wide init file is
30617 @var{file}.
30618 @end table
30619
30620 If @value{GDBN} has been configured with the option @option{--prefix=$prefix},
30621 it may be subject to relocation. Two possible cases:
30622
30623 @itemize @bullet
30624 @item
30625 If the default location of this init file contains @file{$prefix},
30626 it will be subject to relocation. Suppose that the configure options
30627 are @option{--prefix=$prefix --with-system-gdbinit=$prefix/etc/gdbinit};
30628 if @value{GDBN} is moved from @file{$prefix} to @file{$install}, the system
30629 init file is looked for as @file{$install/etc/gdbinit} instead of
30630 @file{$prefix/etc/gdbinit}.
30631
30632 @item
30633 By contrast, if the default location does not contain the prefix,
30634 it will not be relocated. E.g.@: if @value{GDBN} has been configured with
30635 @option{--prefix=/usr/local --with-system-gdbinit=/usr/share/gdb/gdbinit},
30636 then @value{GDBN} will always look for @file{/usr/share/gdb/gdbinit},
30637 wherever @value{GDBN} is installed.
30638 @end itemize
30639
30640 @node Maintenance Commands
30641 @appendix Maintenance Commands
30642 @cindex maintenance commands
30643 @cindex internal commands
30644
30645 In addition to commands intended for @value{GDBN} users, @value{GDBN}
30646 includes a number of commands intended for @value{GDBN} developers,
30647 that are not documented elsewhere in this manual. These commands are
30648 provided here for reference. (For commands that turn on debugging
30649 messages, see @ref{Debugging Output}.)
30650
30651 @table @code
30652 @kindex maint agent
30653 @kindex maint agent-eval
30654 @item maint agent @var{expression}
30655 @itemx maint agent-eval @var{expression}
30656 Translate the given @var{expression} into remote agent bytecodes.
30657 This command is useful for debugging the Agent Expression mechanism
30658 (@pxref{Agent Expressions}). The @samp{agent} version produces an
30659 expression useful for data collection, such as by tracepoints, while
30660 @samp{maint agent-eval} produces an expression that evaluates directly
30661 to a result. For instance, a collection expression for @code{globa +
30662 globb} will include bytecodes to record four bytes of memory at each
30663 of the addresses of @code{globa} and @code{globb}, while discarding
30664 the result of the addition, while an evaluation expression will do the
30665 addition and return the sum.
30666
30667 @kindex maint info breakpoints
30668 @item @anchor{maint info breakpoints}maint info breakpoints
30669 Using the same format as @samp{info breakpoints}, display both the
30670 breakpoints you've set explicitly, and those @value{GDBN} is using for
30671 internal purposes. Internal breakpoints are shown with negative
30672 breakpoint numbers. The type column identifies what kind of breakpoint
30673 is shown:
30674
30675 @table @code
30676 @item breakpoint
30677 Normal, explicitly set breakpoint.
30678
30679 @item watchpoint
30680 Normal, explicitly set watchpoint.
30681
30682 @item longjmp
30683 Internal breakpoint, used to handle correctly stepping through
30684 @code{longjmp} calls.
30685
30686 @item longjmp resume
30687 Internal breakpoint at the target of a @code{longjmp}.
30688
30689 @item until
30690 Temporary internal breakpoint used by the @value{GDBN} @code{until} command.
30691
30692 @item finish
30693 Temporary internal breakpoint used by the @value{GDBN} @code{finish} command.
30694
30695 @item shlib events
30696 Shared library events.
30697
30698 @end table
30699
30700 @kindex set displaced-stepping
30701 @kindex show displaced-stepping
30702 @cindex displaced stepping support
30703 @cindex out-of-line single-stepping
30704 @item set displaced-stepping
30705 @itemx show displaced-stepping
30706 Control whether or not @value{GDBN} will do @dfn{displaced stepping}
30707 if the target supports it. Displaced stepping is a way to single-step
30708 over breakpoints without removing them from the inferior, by executing
30709 an out-of-line copy of the instruction that was originally at the
30710 breakpoint location. It is also known as out-of-line single-stepping.
30711
30712 @table @code
30713 @item set displaced-stepping on
30714 If the target architecture supports it, @value{GDBN} will use
30715 displaced stepping to step over breakpoints.
30716
30717 @item set displaced-stepping off
30718 @value{GDBN} will not use displaced stepping to step over breakpoints,
30719 even if such is supported by the target architecture.
30720
30721 @cindex non-stop mode, and @samp{set displaced-stepping}
30722 @item set displaced-stepping auto
30723 This is the default mode. @value{GDBN} will use displaced stepping
30724 only if non-stop mode is active (@pxref{Non-Stop Mode}) and the target
30725 architecture supports displaced stepping.
30726 @end table
30727
30728 @kindex maint check-symtabs
30729 @item maint check-symtabs
30730 Check the consistency of psymtabs and symtabs.
30731
30732 @kindex maint cplus first_component
30733 @item maint cplus first_component @var{name}
30734 Print the first C@t{++} class/namespace component of @var{name}.
30735
30736 @kindex maint cplus namespace
30737 @item maint cplus namespace
30738 Print the list of possible C@t{++} namespaces.
30739
30740 @kindex maint demangle
30741 @item maint demangle @var{name}
30742 Demangle a C@t{++} or Objective-C mangled @var{name}.
30743
30744 @kindex maint deprecate
30745 @kindex maint undeprecate
30746 @cindex deprecated commands
30747 @item maint deprecate @var{command} @r{[}@var{replacement}@r{]}
30748 @itemx maint undeprecate @var{command}
30749 Deprecate or undeprecate the named @var{command}. Deprecated commands
30750 cause @value{GDBN} to issue a warning when you use them. The optional
30751 argument @var{replacement} says which newer command should be used in
30752 favor of the deprecated one; if it is given, @value{GDBN} will mention
30753 the replacement as part of the warning.
30754
30755 @kindex maint dump-me
30756 @item maint dump-me
30757 @cindex @code{SIGQUIT} signal, dump core of @value{GDBN}
30758 Cause a fatal signal in the debugger and force it to dump its core.
30759 This is supported only on systems which support aborting a program
30760 with the @code{SIGQUIT} signal.
30761
30762 @kindex maint internal-error
30763 @kindex maint internal-warning
30764 @item maint internal-error @r{[}@var{message-text}@r{]}
30765 @itemx maint internal-warning @r{[}@var{message-text}@r{]}
30766 Cause @value{GDBN} to call the internal function @code{internal_error}
30767 or @code{internal_warning} and hence behave as though an internal error
30768 or internal warning has been detected. In addition to reporting the
30769 internal problem, these functions give the user the opportunity to
30770 either quit @value{GDBN} or create a core file of the current
30771 @value{GDBN} session.
30772
30773 These commands take an optional parameter @var{message-text} that is
30774 used as the text of the error or warning message.
30775
30776 Here's an example of using @code{internal-error}:
30777
30778 @smallexample
30779 (@value{GDBP}) @kbd{maint internal-error testing, 1, 2}
30780 @dots{}/maint.c:121: internal-error: testing, 1, 2
30781 A problem internal to GDB has been detected. Further
30782 debugging may prove unreliable.
30783 Quit this debugging session? (y or n) @kbd{n}
30784 Create a core file? (y or n) @kbd{n}
30785 (@value{GDBP})
30786 @end smallexample
30787
30788 @cindex @value{GDBN} internal error
30789 @cindex internal errors, control of @value{GDBN} behavior
30790
30791 @kindex maint set internal-error
30792 @kindex maint show internal-error
30793 @kindex maint set internal-warning
30794 @kindex maint show internal-warning
30795 @item maint set internal-error @var{action} [ask|yes|no]
30796 @itemx maint show internal-error @var{action}
30797 @itemx maint set internal-warning @var{action} [ask|yes|no]
30798 @itemx maint show internal-warning @var{action}
30799 When @value{GDBN} reports an internal problem (error or warning) it
30800 gives the user the opportunity to both quit @value{GDBN} and create a
30801 core file of the current @value{GDBN} session. These commands let you
30802 override the default behaviour for each particular @var{action},
30803 described in the table below.
30804
30805 @table @samp
30806 @item quit
30807 You can specify that @value{GDBN} should always (yes) or never (no)
30808 quit. The default is to ask the user what to do.
30809
30810 @item corefile
30811 You can specify that @value{GDBN} should always (yes) or never (no)
30812 create a core file. The default is to ask the user what to do.
30813 @end table
30814
30815 @kindex maint packet
30816 @item maint packet @var{text}
30817 If @value{GDBN} is talking to an inferior via the serial protocol,
30818 then this command sends the string @var{text} to the inferior, and
30819 displays the response packet. @value{GDBN} supplies the initial
30820 @samp{$} character, the terminating @samp{#} character, and the
30821 checksum.
30822
30823 @kindex maint print architecture
30824 @item maint print architecture @r{[}@var{file}@r{]}
30825 Print the entire architecture configuration. The optional argument
30826 @var{file} names the file where the output goes.
30827
30828 @kindex maint print c-tdesc
30829 @item maint print c-tdesc
30830 Print the current target description (@pxref{Target Descriptions}) as
30831 a C source file. The created source file can be used in @value{GDBN}
30832 when an XML parser is not available to parse the description.
30833
30834 @kindex maint print dummy-frames
30835 @item maint print dummy-frames
30836 Prints the contents of @value{GDBN}'s internal dummy-frame stack.
30837
30838 @smallexample
30839 (@value{GDBP}) @kbd{b add}
30840 @dots{}
30841 (@value{GDBP}) @kbd{print add(2,3)}
30842 Breakpoint 2, add (a=2, b=3) at @dots{}
30843 58 return (a + b);
30844 The program being debugged stopped while in a function called from GDB.
30845 @dots{}
30846 (@value{GDBP}) @kbd{maint print dummy-frames}
30847 0x1a57c80: pc=0x01014068 fp=0x0200bddc sp=0x0200bdd6
30848 top=0x0200bdd4 id=@{stack=0x200bddc,code=0x101405c@}
30849 call_lo=0x01014000 call_hi=0x01014001
30850 (@value{GDBP})
30851 @end smallexample
30852
30853 Takes an optional file parameter.
30854
30855 @kindex maint print registers
30856 @kindex maint print raw-registers
30857 @kindex maint print cooked-registers
30858 @kindex maint print register-groups
30859 @item maint print registers @r{[}@var{file}@r{]}
30860 @itemx maint print raw-registers @r{[}@var{file}@r{]}
30861 @itemx maint print cooked-registers @r{[}@var{file}@r{]}
30862 @itemx maint print register-groups @r{[}@var{file}@r{]}
30863 Print @value{GDBN}'s internal register data structures.
30864
30865 The command @code{maint print raw-registers} includes the contents of
30866 the raw register cache; the command @code{maint print cooked-registers}
30867 includes the (cooked) value of all registers, including registers which
30868 aren't available on the target nor visible to user; and the
30869 command @code{maint print register-groups} includes the groups that each
30870 register is a member of. @xref{Registers,, Registers, gdbint,
30871 @value{GDBN} Internals}.
30872
30873 These commands take an optional parameter, a file name to which to
30874 write the information.
30875
30876 @kindex maint print reggroups
30877 @item maint print reggroups @r{[}@var{file}@r{]}
30878 Print @value{GDBN}'s internal register group data structures. The
30879 optional argument @var{file} tells to what file to write the
30880 information.
30881
30882 The register groups info looks like this:
30883
30884 @smallexample
30885 (@value{GDBP}) @kbd{maint print reggroups}
30886 Group Type
30887 general user
30888 float user
30889 all user
30890 vector user
30891 system user
30892 save internal
30893 restore internal
30894 @end smallexample
30895
30896 @kindex flushregs
30897 @item flushregs
30898 This command forces @value{GDBN} to flush its internal register cache.
30899
30900 @kindex maint print objfiles
30901 @cindex info for known object files
30902 @item maint print objfiles
30903 Print a dump of all known object files. For each object file, this
30904 command prints its name, address in memory, and all of its psymtabs
30905 and symtabs.
30906
30907 @kindex maint print section-scripts
30908 @cindex info for known .debug_gdb_scripts-loaded scripts
30909 @item maint print section-scripts [@var{regexp}]
30910 Print a dump of scripts specified in the @code{.debug_gdb_section} section.
30911 If @var{regexp} is specified, only print scripts loaded by object files
30912 matching @var{regexp}.
30913 For each script, this command prints its name as specified in the objfile,
30914 and the full path if known.
30915 @xref{.debug_gdb_scripts section}.
30916
30917 @kindex maint print statistics
30918 @cindex bcache statistics
30919 @item maint print statistics
30920 This command prints, for each object file in the program, various data
30921 about that object file followed by the byte cache (@dfn{bcache})
30922 statistics for the object file. The objfile data includes the number
30923 of minimal, partial, full, and stabs symbols, the number of types
30924 defined by the objfile, the number of as yet unexpanded psym tables,
30925 the number of line tables and string tables, and the amount of memory
30926 used by the various tables. The bcache statistics include the counts,
30927 sizes, and counts of duplicates of all and unique objects, max,
30928 average, and median entry size, total memory used and its overhead and
30929 savings, and various measures of the hash table size and chain
30930 lengths.
30931
30932 @kindex maint print target-stack
30933 @cindex target stack description
30934 @item maint print target-stack
30935 A @dfn{target} is an interface between the debugger and a particular
30936 kind of file or process. Targets can be stacked in @dfn{strata},
30937 so that more than one target can potentially respond to a request.
30938 In particular, memory accesses will walk down the stack of targets
30939 until they find a target that is interested in handling that particular
30940 address.
30941
30942 This command prints a short description of each layer that was pushed on
30943 the @dfn{target stack}, starting from the top layer down to the bottom one.
30944
30945 @kindex maint print type
30946 @cindex type chain of a data type
30947 @item maint print type @var{expr}
30948 Print the type chain for a type specified by @var{expr}. The argument
30949 can be either a type name or a symbol. If it is a symbol, the type of
30950 that symbol is described. The type chain produced by this command is
30951 a recursive definition of the data type as stored in @value{GDBN}'s
30952 data structures, including its flags and contained types.
30953
30954 @kindex maint set dwarf2 always-disassemble
30955 @kindex maint show dwarf2 always-disassemble
30956 @item maint set dwarf2 always-disassemble
30957 @item maint show dwarf2 always-disassemble
30958 Control the behavior of @code{info address} when using DWARF debugging
30959 information.
30960
30961 The default is @code{off}, which means that @value{GDBN} should try to
30962 describe a variable's location in an easily readable format. When
30963 @code{on}, @value{GDBN} will instead display the DWARF location
30964 expression in an assembly-like format. Note that some locations are
30965 too complex for @value{GDBN} to describe simply; in this case you will
30966 always see the disassembly form.
30967
30968 Here is an example of the resulting disassembly:
30969
30970 @smallexample
30971 (gdb) info addr argc
30972 Symbol "argc" is a complex DWARF expression:
30973 1: DW_OP_fbreg 0
30974 @end smallexample
30975
30976 For more information on these expressions, see
30977 @uref{http://www.dwarfstd.org/, the DWARF standard}.
30978
30979 @kindex maint set dwarf2 max-cache-age
30980 @kindex maint show dwarf2 max-cache-age
30981 @item maint set dwarf2 max-cache-age
30982 @itemx maint show dwarf2 max-cache-age
30983 Control the DWARF 2 compilation unit cache.
30984
30985 @cindex DWARF 2 compilation units cache
30986 In object files with inter-compilation-unit references, such as those
30987 produced by the GCC option @samp{-feliminate-dwarf2-dups}, the DWARF 2
30988 reader needs to frequently refer to previously read compilation units.
30989 This setting controls how long a compilation unit will remain in the
30990 cache if it is not referenced. A higher limit means that cached
30991 compilation units will be stored in memory longer, and more total
30992 memory will be used. Setting it to zero disables caching, which will
30993 slow down @value{GDBN} startup, but reduce memory consumption.
30994
30995 @kindex maint set profile
30996 @kindex maint show profile
30997 @cindex profiling GDB
30998 @item maint set profile
30999 @itemx maint show profile
31000 Control profiling of @value{GDBN}.
31001
31002 Profiling will be disabled until you use the @samp{maint set profile}
31003 command to enable it. When you enable profiling, the system will begin
31004 collecting timing and execution count data; when you disable profiling or
31005 exit @value{GDBN}, the results will be written to a log file. Remember that
31006 if you use profiling, @value{GDBN} will overwrite the profiling log file
31007 (often called @file{gmon.out}). If you have a record of important profiling
31008 data in a @file{gmon.out} file, be sure to move it to a safe location.
31009
31010 Configuring with @samp{--enable-profiling} arranges for @value{GDBN} to be
31011 compiled with the @samp{-pg} compiler option.
31012
31013 @kindex maint set show-debug-regs
31014 @kindex maint show show-debug-regs
31015 @cindex hardware debug registers
31016 @item maint set show-debug-regs
31017 @itemx maint show show-debug-regs
31018 Control whether to show variables that mirror the hardware debug
31019 registers. Use @code{ON} to enable, @code{OFF} to disable. If
31020 enabled, the debug registers values are shown when @value{GDBN} inserts or
31021 removes a hardware breakpoint or watchpoint, and when the inferior
31022 triggers a hardware-assisted breakpoint or watchpoint.
31023
31024 @kindex maint set show-all-tib
31025 @kindex maint show show-all-tib
31026 @item maint set show-all-tib
31027 @itemx maint show show-all-tib
31028 Control whether to show all non zero areas within a 1k block starting
31029 at thread local base, when using the @samp{info w32 thread-information-block}
31030 command.
31031
31032 @kindex maint space
31033 @cindex memory used by commands
31034 @item maint space
31035 Control whether to display memory usage for each command. If set to a
31036 nonzero value, @value{GDBN} will display how much memory each command
31037 took, following the command's own output. This can also be requested
31038 by invoking @value{GDBN} with the @option{--statistics} command-line
31039 switch (@pxref{Mode Options}).
31040
31041 @kindex maint time
31042 @cindex time of command execution
31043 @item maint time
31044 Control whether to display the execution time for each command. If
31045 set to a nonzero value, @value{GDBN} will display how much time it
31046 took to execute each command, following the command's own output.
31047 The time is not printed for the commands that run the target, since
31048 there's no mechanism currently to compute how much time was spend
31049 by @value{GDBN} and how much time was spend by the program been debugged.
31050 it's not possibly currently
31051 This can also be requested by invoking @value{GDBN} with the
31052 @option{--statistics} command-line switch (@pxref{Mode Options}).
31053
31054 @kindex maint translate-address
31055 @item maint translate-address @r{[}@var{section}@r{]} @var{addr}
31056 Find the symbol stored at the location specified by the address
31057 @var{addr} and an optional section name @var{section}. If found,
31058 @value{GDBN} prints the name of the closest symbol and an offset from
31059 the symbol's location to the specified address. This is similar to
31060 the @code{info address} command (@pxref{Symbols}), except that this
31061 command also allows to find symbols in other sections.
31062
31063 If section was not specified, the section in which the symbol was found
31064 is also printed. For dynamically linked executables, the name of
31065 executable or shared library containing the symbol is printed as well.
31066
31067 @end table
31068
31069 The following command is useful for non-interactive invocations of
31070 @value{GDBN}, such as in the test suite.
31071
31072 @table @code
31073 @item set watchdog @var{nsec}
31074 @kindex set watchdog
31075 @cindex watchdog timer
31076 @cindex timeout for commands
31077 Set the maximum number of seconds @value{GDBN} will wait for the
31078 target operation to finish. If this time expires, @value{GDBN}
31079 reports and error and the command is aborted.
31080
31081 @item show watchdog
31082 Show the current setting of the target wait timeout.
31083 @end table
31084
31085 @node Remote Protocol
31086 @appendix @value{GDBN} Remote Serial Protocol
31087
31088 @menu
31089 * Overview::
31090 * Packets::
31091 * Stop Reply Packets::
31092 * General Query Packets::
31093 * Architecture-Specific Protocol Details::
31094 * Tracepoint Packets::
31095 * Host I/O Packets::
31096 * Interrupts::
31097 * Notification Packets::
31098 * Remote Non-Stop::
31099 * Packet Acknowledgment::
31100 * Examples::
31101 * File-I/O Remote Protocol Extension::
31102 * Library List Format::
31103 * Memory Map Format::
31104 * Thread List Format::
31105 @end menu
31106
31107 @node Overview
31108 @section Overview
31109
31110 There may be occasions when you need to know something about the
31111 protocol---for example, if there is only one serial port to your target
31112 machine, you might want your program to do something special if it
31113 recognizes a packet meant for @value{GDBN}.
31114
31115 In the examples below, @samp{->} and @samp{<-} are used to indicate
31116 transmitted and received data, respectively.
31117
31118 @cindex protocol, @value{GDBN} remote serial
31119 @cindex serial protocol, @value{GDBN} remote
31120 @cindex remote serial protocol
31121 All @value{GDBN} commands and responses (other than acknowledgments
31122 and notifications, see @ref{Notification Packets}) are sent as a
31123 @var{packet}. A @var{packet} is introduced with the character
31124 @samp{$}, the actual @var{packet-data}, and the terminating character
31125 @samp{#} followed by a two-digit @var{checksum}:
31126
31127 @smallexample
31128 @code{$}@var{packet-data}@code{#}@var{checksum}
31129 @end smallexample
31130 @noindent
31131
31132 @cindex checksum, for @value{GDBN} remote
31133 @noindent
31134 The two-digit @var{checksum} is computed as the modulo 256 sum of all
31135 characters between the leading @samp{$} and the trailing @samp{#} (an
31136 eight bit unsigned checksum).
31137
31138 Implementors should note that prior to @value{GDBN} 5.0 the protocol
31139 specification also included an optional two-digit @var{sequence-id}:
31140
31141 @smallexample
31142 @code{$}@var{sequence-id}@code{:}@var{packet-data}@code{#}@var{checksum}
31143 @end smallexample
31144
31145 @cindex sequence-id, for @value{GDBN} remote
31146 @noindent
31147 That @var{sequence-id} was appended to the acknowledgment. @value{GDBN}
31148 has never output @var{sequence-id}s. Stubs that handle packets added
31149 since @value{GDBN} 5.0 must not accept @var{sequence-id}.
31150
31151 When either the host or the target machine receives a packet, the first
31152 response expected is an acknowledgment: either @samp{+} (to indicate
31153 the package was received correctly) or @samp{-} (to request
31154 retransmission):
31155
31156 @smallexample
31157 -> @code{$}@var{packet-data}@code{#}@var{checksum}
31158 <- @code{+}
31159 @end smallexample
31160 @noindent
31161
31162 The @samp{+}/@samp{-} acknowledgments can be disabled
31163 once a connection is established.
31164 @xref{Packet Acknowledgment}, for details.
31165
31166 The host (@value{GDBN}) sends @var{command}s, and the target (the
31167 debugging stub incorporated in your program) sends a @var{response}. In
31168 the case of step and continue @var{command}s, the response is only sent
31169 when the operation has completed, and the target has again stopped all
31170 threads in all attached processes. This is the default all-stop mode
31171 behavior, but the remote protocol also supports @value{GDBN}'s non-stop
31172 execution mode; see @ref{Remote Non-Stop}, for details.
31173
31174 @var{packet-data} consists of a sequence of characters with the
31175 exception of @samp{#} and @samp{$} (see @samp{X} packet for additional
31176 exceptions).
31177
31178 @cindex remote protocol, field separator
31179 Fields within the packet should be separated using @samp{,} @samp{;} or
31180 @samp{:}. Except where otherwise noted all numbers are represented in
31181 @sc{hex} with leading zeros suppressed.
31182
31183 Implementors should note that prior to @value{GDBN} 5.0, the character
31184 @samp{:} could not appear as the third character in a packet (as it
31185 would potentially conflict with the @var{sequence-id}).
31186
31187 @cindex remote protocol, binary data
31188 @anchor{Binary Data}
31189 Binary data in most packets is encoded either as two hexadecimal
31190 digits per byte of binary data. This allowed the traditional remote
31191 protocol to work over connections which were only seven-bit clean.
31192 Some packets designed more recently assume an eight-bit clean
31193 connection, and use a more efficient encoding to send and receive
31194 binary data.
31195
31196 The binary data representation uses @code{7d} (@sc{ascii} @samp{@}})
31197 as an escape character. Any escaped byte is transmitted as the escape
31198 character followed by the original character XORed with @code{0x20}.
31199 For example, the byte @code{0x7d} would be transmitted as the two
31200 bytes @code{0x7d 0x5d}. The bytes @code{0x23} (@sc{ascii} @samp{#}),
31201 @code{0x24} (@sc{ascii} @samp{$}), and @code{0x7d} (@sc{ascii}
31202 @samp{@}}) must always be escaped. Responses sent by the stub
31203 must also escape @code{0x2a} (@sc{ascii} @samp{*}), so that it
31204 is not interpreted as the start of a run-length encoded sequence
31205 (described next).
31206
31207 Response @var{data} can be run-length encoded to save space.
31208 Run-length encoding replaces runs of identical characters with one
31209 instance of the repeated character, followed by a @samp{*} and a
31210 repeat count. The repeat count is itself sent encoded, to avoid
31211 binary characters in @var{data}: a value of @var{n} is sent as
31212 @code{@var{n}+29}. For a repeat count greater or equal to 3, this
31213 produces a printable @sc{ascii} character, e.g.@: a space (@sc{ascii}
31214 code 32) for a repeat count of 3. (This is because run-length
31215 encoding starts to win for counts 3 or more.) Thus, for example,
31216 @samp{0* } is a run-length encoding of ``0000'': the space character
31217 after @samp{*} means repeat the leading @code{0} @w{@code{32 - 29 =
31218 3}} more times.
31219
31220 The printable characters @samp{#} and @samp{$} or with a numeric value
31221 greater than 126 must not be used. Runs of six repeats (@samp{#}) or
31222 seven repeats (@samp{$}) can be expanded using a repeat count of only
31223 five (@samp{"}). For example, @samp{00000000} can be encoded as
31224 @samp{0*"00}.
31225
31226 The error response returned for some packets includes a two character
31227 error number. That number is not well defined.
31228
31229 @cindex empty response, for unsupported packets
31230 For any @var{command} not supported by the stub, an empty response
31231 (@samp{$#00}) should be returned. That way it is possible to extend the
31232 protocol. A newer @value{GDBN} can tell if a packet is supported based
31233 on that response.
31234
31235 A stub is required to support the @samp{g}, @samp{G}, @samp{m}, @samp{M},
31236 @samp{c}, and @samp{s} @var{command}s. All other @var{command}s are
31237 optional.
31238
31239 @node Packets
31240 @section Packets
31241
31242 The following table provides a complete list of all currently defined
31243 @var{command}s and their corresponding response @var{data}.
31244 @xref{File-I/O Remote Protocol Extension}, for details about the File
31245 I/O extension of the remote protocol.
31246
31247 Each packet's description has a template showing the packet's overall
31248 syntax, followed by an explanation of the packet's meaning. We
31249 include spaces in some of the templates for clarity; these are not
31250 part of the packet's syntax. No @value{GDBN} packet uses spaces to
31251 separate its components. For example, a template like @samp{foo
31252 @var{bar} @var{baz}} describes a packet beginning with the three ASCII
31253 bytes @samp{foo}, followed by a @var{bar}, followed directly by a
31254 @var{baz}. @value{GDBN} does not transmit a space character between the
31255 @samp{foo} and the @var{bar}, or between the @var{bar} and the
31256 @var{baz}.
31257
31258 @cindex @var{thread-id}, in remote protocol
31259 @anchor{thread-id syntax}
31260 Several packets and replies include a @var{thread-id} field to identify
31261 a thread. Normally these are positive numbers with a target-specific
31262 interpretation, formatted as big-endian hex strings. A @var{thread-id}
31263 can also be a literal @samp{-1} to indicate all threads, or @samp{0} to
31264 pick any thread.
31265
31266 In addition, the remote protocol supports a multiprocess feature in
31267 which the @var{thread-id} syntax is extended to optionally include both
31268 process and thread ID fields, as @samp{p@var{pid}.@var{tid}}.
31269 The @var{pid} (process) and @var{tid} (thread) components each have the
31270 format described above: a positive number with target-specific
31271 interpretation formatted as a big-endian hex string, literal @samp{-1}
31272 to indicate all processes or threads (respectively), or @samp{0} to
31273 indicate an arbitrary process or thread. Specifying just a process, as
31274 @samp{p@var{pid}}, is equivalent to @samp{p@var{pid}.-1}. It is an
31275 error to specify all processes but a specific thread, such as
31276 @samp{p-1.@var{tid}}. Note that the @samp{p} prefix is @emph{not} used
31277 for those packets and replies explicitly documented to include a process
31278 ID, rather than a @var{thread-id}.
31279
31280 The multiprocess @var{thread-id} syntax extensions are only used if both
31281 @value{GDBN} and the stub report support for the @samp{multiprocess}
31282 feature using @samp{qSupported}. @xref{multiprocess extensions}, for
31283 more information.
31284
31285 Note that all packet forms beginning with an upper- or lower-case
31286 letter, other than those described here, are reserved for future use.
31287
31288 Here are the packet descriptions.
31289
31290 @table @samp
31291
31292 @item !
31293 @cindex @samp{!} packet
31294 @anchor{extended mode}
31295 Enable extended mode. In extended mode, the remote server is made
31296 persistent. The @samp{R} packet is used to restart the program being
31297 debugged.
31298
31299 Reply:
31300 @table @samp
31301 @item OK
31302 The remote target both supports and has enabled extended mode.
31303 @end table
31304
31305 @item ?
31306 @cindex @samp{?} packet
31307 Indicate the reason the target halted. The reply is the same as for
31308 step and continue. This packet has a special interpretation when the
31309 target is in non-stop mode; see @ref{Remote Non-Stop}.
31310
31311 Reply:
31312 @xref{Stop Reply Packets}, for the reply specifications.
31313
31314 @item A @var{arglen},@var{argnum},@var{arg},@dots{}
31315 @cindex @samp{A} packet
31316 Initialized @code{argv[]} array passed into program. @var{arglen}
31317 specifies the number of bytes in the hex encoded byte stream
31318 @var{arg}. See @code{gdbserver} for more details.
31319
31320 Reply:
31321 @table @samp
31322 @item OK
31323 The arguments were set.
31324 @item E @var{NN}
31325 An error occurred.
31326 @end table
31327
31328 @item b @var{baud}
31329 @cindex @samp{b} packet
31330 (Don't use this packet; its behavior is not well-defined.)
31331 Change the serial line speed to @var{baud}.
31332
31333 JTC: @emph{When does the transport layer state change? When it's
31334 received, or after the ACK is transmitted. In either case, there are
31335 problems if the command or the acknowledgment packet is dropped.}
31336
31337 Stan: @emph{If people really wanted to add something like this, and get
31338 it working for the first time, they ought to modify ser-unix.c to send
31339 some kind of out-of-band message to a specially-setup stub and have the
31340 switch happen "in between" packets, so that from remote protocol's point
31341 of view, nothing actually happened.}
31342
31343 @item B @var{addr},@var{mode}
31344 @cindex @samp{B} packet
31345 Set (@var{mode} is @samp{S}) or clear (@var{mode} is @samp{C}) a
31346 breakpoint at @var{addr}.
31347
31348 Don't use this packet. Use the @samp{Z} and @samp{z} packets instead
31349 (@pxref{insert breakpoint or watchpoint packet}).
31350
31351 @cindex @samp{bc} packet
31352 @anchor{bc}
31353 @item bc
31354 Backward continue. Execute the target system in reverse. No parameter.
31355 @xref{Reverse Execution}, for more information.
31356
31357 Reply:
31358 @xref{Stop Reply Packets}, for the reply specifications.
31359
31360 @cindex @samp{bs} packet
31361 @anchor{bs}
31362 @item bs
31363 Backward single step. Execute one instruction in reverse. No parameter.
31364 @xref{Reverse Execution}, for more information.
31365
31366 Reply:
31367 @xref{Stop Reply Packets}, for the reply specifications.
31368
31369 @item c @r{[}@var{addr}@r{]}
31370 @cindex @samp{c} packet
31371 Continue. @var{addr} is address to resume. If @var{addr} is omitted,
31372 resume at current address.
31373
31374 Reply:
31375 @xref{Stop Reply Packets}, for the reply specifications.
31376
31377 @item C @var{sig}@r{[};@var{addr}@r{]}
31378 @cindex @samp{C} packet
31379 Continue with signal @var{sig} (hex signal number). If
31380 @samp{;@var{addr}} is omitted, resume at same address.
31381
31382 Reply:
31383 @xref{Stop Reply Packets}, for the reply specifications.
31384
31385 @item d
31386 @cindex @samp{d} packet
31387 Toggle debug flag.
31388
31389 Don't use this packet; instead, define a general set packet
31390 (@pxref{General Query Packets}).
31391
31392 @item D
31393 @itemx D;@var{pid}
31394 @cindex @samp{D} packet
31395 The first form of the packet is used to detach @value{GDBN} from the
31396 remote system. It is sent to the remote target
31397 before @value{GDBN} disconnects via the @code{detach} command.
31398
31399 The second form, including a process ID, is used when multiprocess
31400 protocol extensions are enabled (@pxref{multiprocess extensions}), to
31401 detach only a specific process. The @var{pid} is specified as a
31402 big-endian hex string.
31403
31404 Reply:
31405 @table @samp
31406 @item OK
31407 for success
31408 @item E @var{NN}
31409 for an error
31410 @end table
31411
31412 @item F @var{RC},@var{EE},@var{CF};@var{XX}
31413 @cindex @samp{F} packet
31414 A reply from @value{GDBN} to an @samp{F} packet sent by the target.
31415 This is part of the File-I/O protocol extension. @xref{File-I/O
31416 Remote Protocol Extension}, for the specification.
31417
31418 @item g
31419 @anchor{read registers packet}
31420 @cindex @samp{g} packet
31421 Read general registers.
31422
31423 Reply:
31424 @table @samp
31425 @item @var{XX@dots{}}
31426 Each byte of register data is described by two hex digits. The bytes
31427 with the register are transmitted in target byte order. The size of
31428 each register and their position within the @samp{g} packet are
31429 determined by the @value{GDBN} internal gdbarch functions
31430 @code{DEPRECATED_REGISTER_RAW_SIZE} and @code{gdbarch_register_name}. The
31431 specification of several standard @samp{g} packets is specified below.
31432 @item E @var{NN}
31433 for an error.
31434 @end table
31435
31436 @item G @var{XX@dots{}}
31437 @cindex @samp{G} packet
31438 Write general registers. @xref{read registers packet}, for a
31439 description of the @var{XX@dots{}} data.
31440
31441 Reply:
31442 @table @samp
31443 @item OK
31444 for success
31445 @item E @var{NN}
31446 for an error
31447 @end table
31448
31449 @item H @var{c} @var{thread-id}
31450 @cindex @samp{H} packet
31451 Set thread for subsequent operations (@samp{m}, @samp{M}, @samp{g},
31452 @samp{G}, et.al.). @var{c} depends on the operation to be performed: it
31453 should be @samp{c} for step and continue operations, @samp{g} for other
31454 operations. The thread designator @var{thread-id} has the format and
31455 interpretation described in @ref{thread-id syntax}.
31456
31457 Reply:
31458 @table @samp
31459 @item OK
31460 for success
31461 @item E @var{NN}
31462 for an error
31463 @end table
31464
31465 @c FIXME: JTC:
31466 @c 'H': How restrictive (or permissive) is the thread model. If a
31467 @c thread is selected and stopped, are other threads allowed
31468 @c to continue to execute? As I mentioned above, I think the
31469 @c semantics of each command when a thread is selected must be
31470 @c described. For example:
31471 @c
31472 @c 'g': If the stub supports threads and a specific thread is
31473 @c selected, returns the register block from that thread;
31474 @c otherwise returns current registers.
31475 @c
31476 @c 'G' If the stub supports threads and a specific thread is
31477 @c selected, sets the registers of the register block of
31478 @c that thread; otherwise sets current registers.
31479
31480 @item i @r{[}@var{addr}@r{[},@var{nnn}@r{]]}
31481 @anchor{cycle step packet}
31482 @cindex @samp{i} packet
31483 Step the remote target by a single clock cycle. If @samp{,@var{nnn}} is
31484 present, cycle step @var{nnn} cycles. If @var{addr} is present, cycle
31485 step starting at that address.
31486
31487 @item I
31488 @cindex @samp{I} packet
31489 Signal, then cycle step. @xref{step with signal packet}. @xref{cycle
31490 step packet}.
31491
31492 @item k
31493 @cindex @samp{k} packet
31494 Kill request.
31495
31496 FIXME: @emph{There is no description of how to operate when a specific
31497 thread context has been selected (i.e.@: does 'k' kill only that
31498 thread?)}.
31499
31500 @item m @var{addr},@var{length}
31501 @cindex @samp{m} packet
31502 Read @var{length} bytes of memory starting at address @var{addr}.
31503 Note that @var{addr} may not be aligned to any particular boundary.
31504
31505 The stub need not use any particular size or alignment when gathering
31506 data from memory for the response; even if @var{addr} is word-aligned
31507 and @var{length} is a multiple of the word size, the stub is free to
31508 use byte accesses, or not. For this reason, this packet may not be
31509 suitable for accessing memory-mapped I/O devices.
31510 @cindex alignment of remote memory accesses
31511 @cindex size of remote memory accesses
31512 @cindex memory, alignment and size of remote accesses
31513
31514 Reply:
31515 @table @samp
31516 @item @var{XX@dots{}}
31517 Memory contents; each byte is transmitted as a two-digit hexadecimal
31518 number. The reply may contain fewer bytes than requested if the
31519 server was able to read only part of the region of memory.
31520 @item E @var{NN}
31521 @var{NN} is errno
31522 @end table
31523
31524 @item M @var{addr},@var{length}:@var{XX@dots{}}
31525 @cindex @samp{M} packet
31526 Write @var{length} bytes of memory starting at address @var{addr}.
31527 @var{XX@dots{}} is the data; each byte is transmitted as a two-digit
31528 hexadecimal number.
31529
31530 Reply:
31531 @table @samp
31532 @item OK
31533 for success
31534 @item E @var{NN}
31535 for an error (this includes the case where only part of the data was
31536 written).
31537 @end table
31538
31539 @item p @var{n}
31540 @cindex @samp{p} packet
31541 Read the value of register @var{n}; @var{n} is in hex.
31542 @xref{read registers packet}, for a description of how the returned
31543 register value is encoded.
31544
31545 Reply:
31546 @table @samp
31547 @item @var{XX@dots{}}
31548 the register's value
31549 @item E @var{NN}
31550 for an error
31551 @item
31552 Indicating an unrecognized @var{query}.
31553 @end table
31554
31555 @item P @var{n@dots{}}=@var{r@dots{}}
31556 @anchor{write register packet}
31557 @cindex @samp{P} packet
31558 Write register @var{n@dots{}} with value @var{r@dots{}}. The register
31559 number @var{n} is in hexadecimal, and @var{r@dots{}} contains two hex
31560 digits for each byte in the register (target byte order).
31561
31562 Reply:
31563 @table @samp
31564 @item OK
31565 for success
31566 @item E @var{NN}
31567 for an error
31568 @end table
31569
31570 @item q @var{name} @var{params}@dots{}
31571 @itemx Q @var{name} @var{params}@dots{}
31572 @cindex @samp{q} packet
31573 @cindex @samp{Q} packet
31574 General query (@samp{q}) and set (@samp{Q}). These packets are
31575 described fully in @ref{General Query Packets}.
31576
31577 @item r
31578 @cindex @samp{r} packet
31579 Reset the entire system.
31580
31581 Don't use this packet; use the @samp{R} packet instead.
31582
31583 @item R @var{XX}
31584 @cindex @samp{R} packet
31585 Restart the program being debugged. @var{XX}, while needed, is ignored.
31586 This packet is only available in extended mode (@pxref{extended mode}).
31587
31588 The @samp{R} packet has no reply.
31589
31590 @item s @r{[}@var{addr}@r{]}
31591 @cindex @samp{s} packet
31592 Single step. @var{addr} is the address at which to resume. If
31593 @var{addr} is omitted, resume at same address.
31594
31595 Reply:
31596 @xref{Stop Reply Packets}, for the reply specifications.
31597
31598 @item S @var{sig}@r{[};@var{addr}@r{]}
31599 @anchor{step with signal packet}
31600 @cindex @samp{S} packet
31601 Step with signal. This is analogous to the @samp{C} packet, but
31602 requests a single-step, rather than a normal resumption of execution.
31603
31604 Reply:
31605 @xref{Stop Reply Packets}, for the reply specifications.
31606
31607 @item t @var{addr}:@var{PP},@var{MM}
31608 @cindex @samp{t} packet
31609 Search backwards starting at address @var{addr} for a match with pattern
31610 @var{PP} and mask @var{MM}. @var{PP} and @var{MM} are 4 bytes.
31611 @var{addr} must be at least 3 digits.
31612
31613 @item T @var{thread-id}
31614 @cindex @samp{T} packet
31615 Find out if the thread @var{thread-id} is alive. @xref{thread-id syntax}.
31616
31617 Reply:
31618 @table @samp
31619 @item OK
31620 thread is still alive
31621 @item E @var{NN}
31622 thread is dead
31623 @end table
31624
31625 @item v
31626 Packets starting with @samp{v} are identified by a multi-letter name,
31627 up to the first @samp{;} or @samp{?} (or the end of the packet).
31628
31629 @item vAttach;@var{pid}
31630 @cindex @samp{vAttach} packet
31631 Attach to a new process with the specified process ID @var{pid}.
31632 The process ID is a
31633 hexadecimal integer identifying the process. In all-stop mode, all
31634 threads in the attached process are stopped; in non-stop mode, it may be
31635 attached without being stopped if that is supported by the target.
31636
31637 @c In non-stop mode, on a successful vAttach, the stub should set the
31638 @c current thread to a thread of the newly-attached process. After
31639 @c attaching, GDB queries for the attached process's thread ID with qC.
31640 @c Also note that, from a user perspective, whether or not the
31641 @c target is stopped on attach in non-stop mode depends on whether you
31642 @c use the foreground or background version of the attach command, not
31643 @c on what vAttach does; GDB does the right thing with respect to either
31644 @c stopping or restarting threads.
31645
31646 This packet is only available in extended mode (@pxref{extended mode}).
31647
31648 Reply:
31649 @table @samp
31650 @item E @var{nn}
31651 for an error
31652 @item @r{Any stop packet}
31653 for success in all-stop mode (@pxref{Stop Reply Packets})
31654 @item OK
31655 for success in non-stop mode (@pxref{Remote Non-Stop})
31656 @end table
31657
31658 @item vCont@r{[};@var{action}@r{[}:@var{thread-id}@r{]]}@dots{}
31659 @cindex @samp{vCont} packet
31660 Resume the inferior, specifying different actions for each thread.
31661 If an action is specified with no @var{thread-id}, then it is applied to any
31662 threads that don't have a specific action specified; if no default action is
31663 specified then other threads should remain stopped in all-stop mode and
31664 in their current state in non-stop mode.
31665 Specifying multiple
31666 default actions is an error; specifying no actions is also an error.
31667 Thread IDs are specified using the syntax described in @ref{thread-id syntax}.
31668
31669 Currently supported actions are:
31670
31671 @table @samp
31672 @item c
31673 Continue.
31674 @item C @var{sig}
31675 Continue with signal @var{sig}. The signal @var{sig} should be two hex digits.
31676 @item s
31677 Step.
31678 @item S @var{sig}
31679 Step with signal @var{sig}. The signal @var{sig} should be two hex digits.
31680 @item t
31681 Stop.
31682 @end table
31683
31684 The optional argument @var{addr} normally associated with the
31685 @samp{c}, @samp{C}, @samp{s}, and @samp{S} packets is
31686 not supported in @samp{vCont}.
31687
31688 The @samp{t} action is only relevant in non-stop mode
31689 (@pxref{Remote Non-Stop}) and may be ignored by the stub otherwise.
31690 A stop reply should be generated for any affected thread not already stopped.
31691 When a thread is stopped by means of a @samp{t} action,
31692 the corresponding stop reply should indicate that the thread has stopped with
31693 signal @samp{0}, regardless of whether the target uses some other signal
31694 as an implementation detail.
31695
31696 Reply:
31697 @xref{Stop Reply Packets}, for the reply specifications.
31698
31699 @item vCont?
31700 @cindex @samp{vCont?} packet
31701 Request a list of actions supported by the @samp{vCont} packet.
31702
31703 Reply:
31704 @table @samp
31705 @item vCont@r{[};@var{action}@dots{}@r{]}
31706 The @samp{vCont} packet is supported. Each @var{action} is a supported
31707 command in the @samp{vCont} packet.
31708 @item
31709 The @samp{vCont} packet is not supported.
31710 @end table
31711
31712 @item vFile:@var{operation}:@var{parameter}@dots{}
31713 @cindex @samp{vFile} packet
31714 Perform a file operation on the target system. For details,
31715 see @ref{Host I/O Packets}.
31716
31717 @item vFlashErase:@var{addr},@var{length}
31718 @cindex @samp{vFlashErase} packet
31719 Direct the stub to erase @var{length} bytes of flash starting at
31720 @var{addr}. The region may enclose any number of flash blocks, but
31721 its start and end must fall on block boundaries, as indicated by the
31722 flash block size appearing in the memory map (@pxref{Memory Map
31723 Format}). @value{GDBN} groups flash memory programming operations
31724 together, and sends a @samp{vFlashDone} request after each group; the
31725 stub is allowed to delay erase operation until the @samp{vFlashDone}
31726 packet is received.
31727
31728 The stub must support @samp{vCont} if it reports support for
31729 multiprocess extensions (@pxref{multiprocess extensions}). Note that in
31730 this case @samp{vCont} actions can be specified to apply to all threads
31731 in a process by using the @samp{p@var{pid}.-1} form of the
31732 @var{thread-id}.
31733
31734 Reply:
31735 @table @samp
31736 @item OK
31737 for success
31738 @item E @var{NN}
31739 for an error
31740 @end table
31741
31742 @item vFlashWrite:@var{addr}:@var{XX@dots{}}
31743 @cindex @samp{vFlashWrite} packet
31744 Direct the stub to write data to flash address @var{addr}. The data
31745 is passed in binary form using the same encoding as for the @samp{X}
31746 packet (@pxref{Binary Data}). The memory ranges specified by
31747 @samp{vFlashWrite} packets preceding a @samp{vFlashDone} packet must
31748 not overlap, and must appear in order of increasing addresses
31749 (although @samp{vFlashErase} packets for higher addresses may already
31750 have been received; the ordering is guaranteed only between
31751 @samp{vFlashWrite} packets). If a packet writes to an address that was
31752 neither erased by a preceding @samp{vFlashErase} packet nor by some other
31753 target-specific method, the results are unpredictable.
31754
31755
31756 Reply:
31757 @table @samp
31758 @item OK
31759 for success
31760 @item E.memtype
31761 for vFlashWrite addressing non-flash memory
31762 @item E @var{NN}
31763 for an error
31764 @end table
31765
31766 @item vFlashDone
31767 @cindex @samp{vFlashDone} packet
31768 Indicate to the stub that flash programming operation is finished.
31769 The stub is permitted to delay or batch the effects of a group of
31770 @samp{vFlashErase} and @samp{vFlashWrite} packets until a
31771 @samp{vFlashDone} packet is received. The contents of the affected
31772 regions of flash memory are unpredictable until the @samp{vFlashDone}
31773 request is completed.
31774
31775 @item vKill;@var{pid}
31776 @cindex @samp{vKill} packet
31777 Kill the process with the specified process ID. @var{pid} is a
31778 hexadecimal integer identifying the process. This packet is used in
31779 preference to @samp{k} when multiprocess protocol extensions are
31780 supported; see @ref{multiprocess extensions}.
31781
31782 Reply:
31783 @table @samp
31784 @item E @var{nn}
31785 for an error
31786 @item OK
31787 for success
31788 @end table
31789
31790 @item vRun;@var{filename}@r{[};@var{argument}@r{]}@dots{}
31791 @cindex @samp{vRun} packet
31792 Run the program @var{filename}, passing it each @var{argument} on its
31793 command line. The file and arguments are hex-encoded strings. If
31794 @var{filename} is an empty string, the stub may use a default program
31795 (e.g.@: the last program run). The program is created in the stopped
31796 state.
31797
31798 @c FIXME: What about non-stop mode?
31799
31800 This packet is only available in extended mode (@pxref{extended mode}).
31801
31802 Reply:
31803 @table @samp
31804 @item E @var{nn}
31805 for an error
31806 @item @r{Any stop packet}
31807 for success (@pxref{Stop Reply Packets})
31808 @end table
31809
31810 @item vStopped
31811 @anchor{vStopped packet}
31812 @cindex @samp{vStopped} packet
31813
31814 In non-stop mode (@pxref{Remote Non-Stop}), acknowledge a previous stop
31815 reply and prompt for the stub to report another one.
31816
31817 Reply:
31818 @table @samp
31819 @item @r{Any stop packet}
31820 if there is another unreported stop event (@pxref{Stop Reply Packets})
31821 @item OK
31822 if there are no unreported stop events
31823 @end table
31824
31825 @item X @var{addr},@var{length}:@var{XX@dots{}}
31826 @anchor{X packet}
31827 @cindex @samp{X} packet
31828 Write data to memory, where the data is transmitted in binary.
31829 @var{addr} is address, @var{length} is number of bytes,
31830 @samp{@var{XX}@dots{}} is binary data (@pxref{Binary Data}).
31831
31832 Reply:
31833 @table @samp
31834 @item OK
31835 for success
31836 @item E @var{NN}
31837 for an error
31838 @end table
31839
31840 @item z @var{type},@var{addr},@var{kind}
31841 @itemx Z @var{type},@var{addr},@var{kind}
31842 @anchor{insert breakpoint or watchpoint packet}
31843 @cindex @samp{z} packet
31844 @cindex @samp{Z} packets
31845 Insert (@samp{Z}) or remove (@samp{z}) a @var{type} breakpoint or
31846 watchpoint starting at address @var{address} of kind @var{kind}.
31847
31848 Each breakpoint and watchpoint packet @var{type} is documented
31849 separately.
31850
31851 @emph{Implementation notes: A remote target shall return an empty string
31852 for an unrecognized breakpoint or watchpoint packet @var{type}. A
31853 remote target shall support either both or neither of a given
31854 @samp{Z@var{type}@dots{}} and @samp{z@var{type}@dots{}} packet pair. To
31855 avoid potential problems with duplicate packets, the operations should
31856 be implemented in an idempotent way.}
31857
31858 @item z0,@var{addr},@var{kind}
31859 @itemx Z0,@var{addr},@var{kind}
31860 @cindex @samp{z0} packet
31861 @cindex @samp{Z0} packet
31862 Insert (@samp{Z0}) or remove (@samp{z0}) a memory breakpoint at address
31863 @var{addr} of type @var{kind}.
31864
31865 A memory breakpoint is implemented by replacing the instruction at
31866 @var{addr} with a software breakpoint or trap instruction. The
31867 @var{kind} is target-specific and typically indicates the size of
31868 the breakpoint in bytes that should be inserted. E.g., the @sc{arm}
31869 and @sc{mips} can insert either a 2 or 4 byte breakpoint. Some
31870 architectures have additional meanings for @var{kind};
31871 see @ref{Architecture-Specific Protocol Details}.
31872
31873 @emph{Implementation note: It is possible for a target to copy or move
31874 code that contains memory breakpoints (e.g., when implementing
31875 overlays). The behavior of this packet, in the presence of such a
31876 target, is not defined.}
31877
31878 Reply:
31879 @table @samp
31880 @item OK
31881 success
31882 @item
31883 not supported
31884 @item E @var{NN}
31885 for an error
31886 @end table
31887
31888 @item z1,@var{addr},@var{kind}
31889 @itemx Z1,@var{addr},@var{kind}
31890 @cindex @samp{z1} packet
31891 @cindex @samp{Z1} packet
31892 Insert (@samp{Z1}) or remove (@samp{z1}) a hardware breakpoint at
31893 address @var{addr}.
31894
31895 A hardware breakpoint is implemented using a mechanism that is not
31896 dependant on being able to modify the target's memory. @var{kind}
31897 has the same meaning as in @samp{Z0} packets.
31898
31899 @emph{Implementation note: A hardware breakpoint is not affected by code
31900 movement.}
31901
31902 Reply:
31903 @table @samp
31904 @item OK
31905 success
31906 @item
31907 not supported
31908 @item E @var{NN}
31909 for an error
31910 @end table
31911
31912 @item z2,@var{addr},@var{kind}
31913 @itemx Z2,@var{addr},@var{kind}
31914 @cindex @samp{z2} packet
31915 @cindex @samp{Z2} packet
31916 Insert (@samp{Z2}) or remove (@samp{z2}) a write watchpoint at @var{addr}.
31917 @var{kind} is interpreted as the number of bytes to watch.
31918
31919 Reply:
31920 @table @samp
31921 @item OK
31922 success
31923 @item
31924 not supported
31925 @item E @var{NN}
31926 for an error
31927 @end table
31928
31929 @item z3,@var{addr},@var{kind}
31930 @itemx Z3,@var{addr},@var{kind}
31931 @cindex @samp{z3} packet
31932 @cindex @samp{Z3} packet
31933 Insert (@samp{Z3}) or remove (@samp{z3}) a read watchpoint at @var{addr}.
31934 @var{kind} is interpreted as the number of bytes to watch.
31935
31936 Reply:
31937 @table @samp
31938 @item OK
31939 success
31940 @item
31941 not supported
31942 @item E @var{NN}
31943 for an error
31944 @end table
31945
31946 @item z4,@var{addr},@var{kind}
31947 @itemx Z4,@var{addr},@var{kind}
31948 @cindex @samp{z4} packet
31949 @cindex @samp{Z4} packet
31950 Insert (@samp{Z4}) or remove (@samp{z4}) an access watchpoint at @var{addr}.
31951 @var{kind} is interpreted as the number of bytes to watch.
31952
31953 Reply:
31954 @table @samp
31955 @item OK
31956 success
31957 @item
31958 not supported
31959 @item E @var{NN}
31960 for an error
31961 @end table
31962
31963 @end table
31964
31965 @node Stop Reply Packets
31966 @section Stop Reply Packets
31967 @cindex stop reply packets
31968
31969 The @samp{C}, @samp{c}, @samp{S}, @samp{s}, @samp{vCont},
31970 @samp{vAttach}, @samp{vRun}, @samp{vStopped}, and @samp{?} packets can
31971 receive any of the below as a reply. Except for @samp{?}
31972 and @samp{vStopped}, that reply is only returned
31973 when the target halts. In the below the exact meaning of @dfn{signal
31974 number} is defined by the header @file{include/gdb/signals.h} in the
31975 @value{GDBN} source code.
31976
31977 As in the description of request packets, we include spaces in the
31978 reply templates for clarity; these are not part of the reply packet's
31979 syntax. No @value{GDBN} stop reply packet uses spaces to separate its
31980 components.
31981
31982 @table @samp
31983
31984 @item S @var{AA}
31985 The program received signal number @var{AA} (a two-digit hexadecimal
31986 number). This is equivalent to a @samp{T} response with no
31987 @var{n}:@var{r} pairs.
31988
31989 @item T @var{AA} @var{n1}:@var{r1};@var{n2}:@var{r2};@dots{}
31990 @cindex @samp{T} packet reply
31991 The program received signal number @var{AA} (a two-digit hexadecimal
31992 number). This is equivalent to an @samp{S} response, except that the
31993 @samp{@var{n}:@var{r}} pairs can carry values of important registers
31994 and other information directly in the stop reply packet, reducing
31995 round-trip latency. Single-step and breakpoint traps are reported
31996 this way. Each @samp{@var{n}:@var{r}} pair is interpreted as follows:
31997
31998 @itemize @bullet
31999 @item
32000 If @var{n} is a hexadecimal number, it is a register number, and the
32001 corresponding @var{r} gives that register's value. @var{r} is a
32002 series of bytes in target byte order, with each byte given by a
32003 two-digit hex number.
32004
32005 @item
32006 If @var{n} is @samp{thread}, then @var{r} is the @var{thread-id} of
32007 the stopped thread, as specified in @ref{thread-id syntax}.
32008
32009 @item
32010 If @var{n} is @samp{core}, then @var{r} is the hexadecimal number of
32011 the core on which the stop event was detected.
32012
32013 @item
32014 If @var{n} is a recognized @dfn{stop reason}, it describes a more
32015 specific event that stopped the target. The currently defined stop
32016 reasons are listed below. @var{aa} should be @samp{05}, the trap
32017 signal. At most one stop reason should be present.
32018
32019 @item
32020 Otherwise, @value{GDBN} should ignore this @samp{@var{n}:@var{r}} pair
32021 and go on to the next; this allows us to extend the protocol in the
32022 future.
32023 @end itemize
32024
32025 The currently defined stop reasons are:
32026
32027 @table @samp
32028 @item watch
32029 @itemx rwatch
32030 @itemx awatch
32031 The packet indicates a watchpoint hit, and @var{r} is the data address, in
32032 hex.
32033
32034 @cindex shared library events, remote reply
32035 @item library
32036 The packet indicates that the loaded libraries have changed.
32037 @value{GDBN} should use @samp{qXfer:libraries:read} to fetch a new
32038 list of loaded libraries. @var{r} is ignored.
32039
32040 @cindex replay log events, remote reply
32041 @item replaylog
32042 The packet indicates that the target cannot continue replaying
32043 logged execution events, because it has reached the end (or the
32044 beginning when executing backward) of the log. The value of @var{r}
32045 will be either @samp{begin} or @samp{end}. @xref{Reverse Execution},
32046 for more information.
32047 @end table
32048
32049 @item W @var{AA}
32050 @itemx W @var{AA} ; process:@var{pid}
32051 The process exited, and @var{AA} is the exit status. This is only
32052 applicable to certain targets.
32053
32054 The second form of the response, including the process ID of the exited
32055 process, can be used only when @value{GDBN} has reported support for
32056 multiprocess protocol extensions; see @ref{multiprocess extensions}.
32057 The @var{pid} is formatted as a big-endian hex string.
32058
32059 @item X @var{AA}
32060 @itemx X @var{AA} ; process:@var{pid}
32061 The process terminated with signal @var{AA}.
32062
32063 The second form of the response, including the process ID of the
32064 terminated process, can be used only when @value{GDBN} has reported
32065 support for multiprocess protocol extensions; see @ref{multiprocess
32066 extensions}. The @var{pid} is formatted as a big-endian hex string.
32067
32068 @item O @var{XX}@dots{}
32069 @samp{@var{XX}@dots{}} is hex encoding of @sc{ascii} data, to be
32070 written as the program's console output. This can happen at any time
32071 while the program is running and the debugger should continue to wait
32072 for @samp{W}, @samp{T}, etc. This reply is not permitted in non-stop mode.
32073
32074 @item F @var{call-id},@var{parameter}@dots{}
32075 @var{call-id} is the identifier which says which host system call should
32076 be called. This is just the name of the function. Translation into the
32077 correct system call is only applicable as it's defined in @value{GDBN}.
32078 @xref{File-I/O Remote Protocol Extension}, for a list of implemented
32079 system calls.
32080
32081 @samp{@var{parameter}@dots{}} is a list of parameters as defined for
32082 this very system call.
32083
32084 The target replies with this packet when it expects @value{GDBN} to
32085 call a host system call on behalf of the target. @value{GDBN} replies
32086 with an appropriate @samp{F} packet and keeps up waiting for the next
32087 reply packet from the target. The latest @samp{C}, @samp{c}, @samp{S}
32088 or @samp{s} action is expected to be continued. @xref{File-I/O Remote
32089 Protocol Extension}, for more details.
32090
32091 @end table
32092
32093 @node General Query Packets
32094 @section General Query Packets
32095 @cindex remote query requests
32096
32097 Packets starting with @samp{q} are @dfn{general query packets};
32098 packets starting with @samp{Q} are @dfn{general set packets}. General
32099 query and set packets are a semi-unified form for retrieving and
32100 sending information to and from the stub.
32101
32102 The initial letter of a query or set packet is followed by a name
32103 indicating what sort of thing the packet applies to. For example,
32104 @value{GDBN} may use a @samp{qSymbol} packet to exchange symbol
32105 definitions with the stub. These packet names follow some
32106 conventions:
32107
32108 @itemize @bullet
32109 @item
32110 The name must not contain commas, colons or semicolons.
32111 @item
32112 Most @value{GDBN} query and set packets have a leading upper case
32113 letter.
32114 @item
32115 The names of custom vendor packets should use a company prefix, in
32116 lower case, followed by a period. For example, packets designed at
32117 the Acme Corporation might begin with @samp{qacme.foo} (for querying
32118 foos) or @samp{Qacme.bar} (for setting bars).
32119 @end itemize
32120
32121 The name of a query or set packet should be separated from any
32122 parameters by a @samp{:}; the parameters themselves should be
32123 separated by @samp{,} or @samp{;}. Stubs must be careful to match the
32124 full packet name, and check for a separator or the end of the packet,
32125 in case two packet names share a common prefix. New packets should not begin
32126 with @samp{qC}, @samp{qP}, or @samp{qL}@footnote{The @samp{qP} and @samp{qL}
32127 packets predate these conventions, and have arguments without any terminator
32128 for the packet name; we suspect they are in widespread use in places that
32129 are difficult to upgrade. The @samp{qC} packet has no arguments, but some
32130 existing stubs (e.g.@: RedBoot) are known to not check for the end of the
32131 packet.}.
32132
32133 Like the descriptions of the other packets, each description here
32134 has a template showing the packet's overall syntax, followed by an
32135 explanation of the packet's meaning. We include spaces in some of the
32136 templates for clarity; these are not part of the packet's syntax. No
32137 @value{GDBN} packet uses spaces to separate its components.
32138
32139 Here are the currently defined query and set packets:
32140
32141 @table @samp
32142
32143 @item QAllow:@var{op}:@var{val}@dots{}
32144 @cindex @samp{QAllow} packet
32145 Specify which operations @value{GDBN} expects to request of the
32146 target, as a semicolon-separated list of operation name and value
32147 pairs. Possible values for @var{op} include @samp{WriteReg},
32148 @samp{WriteMem}, @samp{InsertBreak}, @samp{InsertTrace},
32149 @samp{InsertFastTrace}, and @samp{Stop}. @var{val} is either 0,
32150 indicating that @value{GDBN} will not request the operation, or 1,
32151 indicating that it may. (The target can then use this to set up its
32152 own internals optimally, for instance if the debugger never expects to
32153 insert breakpoints, it may not need to install its own trap handler.)
32154
32155 @item qC
32156 @cindex current thread, remote request
32157 @cindex @samp{qC} packet
32158 Return the current thread ID.
32159
32160 Reply:
32161 @table @samp
32162 @item QC @var{thread-id}
32163 Where @var{thread-id} is a thread ID as documented in
32164 @ref{thread-id syntax}.
32165 @item @r{(anything else)}
32166 Any other reply implies the old thread ID.
32167 @end table
32168
32169 @item qCRC:@var{addr},@var{length}
32170 @cindex CRC of memory block, remote request
32171 @cindex @samp{qCRC} packet
32172 Compute the CRC checksum of a block of memory using CRC-32 defined in
32173 IEEE 802.3. The CRC is computed byte at a time, taking the most
32174 significant bit of each byte first. The initial pattern code
32175 @code{0xffffffff} is used to ensure leading zeros affect the CRC.
32176
32177 @emph{Note:} This is the same CRC used in validating separate debug
32178 files (@pxref{Separate Debug Files, , Debugging Information in Separate
32179 Files}). However the algorithm is slightly different. When validating
32180 separate debug files, the CRC is computed taking the @emph{least}
32181 significant bit of each byte first, and the final result is inverted to
32182 detect trailing zeros.
32183
32184 Reply:
32185 @table @samp
32186 @item E @var{NN}
32187 An error (such as memory fault)
32188 @item C @var{crc32}
32189 The specified memory region's checksum is @var{crc32}.
32190 @end table
32191
32192 @item qfThreadInfo
32193 @itemx qsThreadInfo
32194 @cindex list active threads, remote request
32195 @cindex @samp{qfThreadInfo} packet
32196 @cindex @samp{qsThreadInfo} packet
32197 Obtain a list of all active thread IDs from the target (OS). Since there
32198 may be too many active threads to fit into one reply packet, this query
32199 works iteratively: it may require more than one query/reply sequence to
32200 obtain the entire list of threads. The first query of the sequence will
32201 be the @samp{qfThreadInfo} query; subsequent queries in the
32202 sequence will be the @samp{qsThreadInfo} query.
32203
32204 NOTE: This packet replaces the @samp{qL} query (see below).
32205
32206 Reply:
32207 @table @samp
32208 @item m @var{thread-id}
32209 A single thread ID
32210 @item m @var{thread-id},@var{thread-id}@dots{}
32211 a comma-separated list of thread IDs
32212 @item l
32213 (lower case letter @samp{L}) denotes end of list.
32214 @end table
32215
32216 In response to each query, the target will reply with a list of one or
32217 more thread IDs, separated by commas.
32218 @value{GDBN} will respond to each reply with a request for more thread
32219 ids (using the @samp{qs} form of the query), until the target responds
32220 with @samp{l} (lower-case ell, for @dfn{last}).
32221 Refer to @ref{thread-id syntax}, for the format of the @var{thread-id}
32222 fields.
32223
32224 @item qGetTLSAddr:@var{thread-id},@var{offset},@var{lm}
32225 @cindex get thread-local storage address, remote request
32226 @cindex @samp{qGetTLSAddr} packet
32227 Fetch the address associated with thread local storage specified
32228 by @var{thread-id}, @var{offset}, and @var{lm}.
32229
32230 @var{thread-id} is the thread ID associated with the
32231 thread for which to fetch the TLS address. @xref{thread-id syntax}.
32232
32233 @var{offset} is the (big endian, hex encoded) offset associated with the
32234 thread local variable. (This offset is obtained from the debug
32235 information associated with the variable.)
32236
32237 @var{lm} is the (big endian, hex encoded) OS/ABI-specific encoding of the
32238 the load module associated with the thread local storage. For example,
32239 a @sc{gnu}/Linux system will pass the link map address of the shared
32240 object associated with the thread local storage under consideration.
32241 Other operating environments may choose to represent the load module
32242 differently, so the precise meaning of this parameter will vary.
32243
32244 Reply:
32245 @table @samp
32246 @item @var{XX}@dots{}
32247 Hex encoded (big endian) bytes representing the address of the thread
32248 local storage requested.
32249
32250 @item E @var{nn}
32251 An error occurred. @var{nn} are hex digits.
32252
32253 @item
32254 An empty reply indicates that @samp{qGetTLSAddr} is not supported by the stub.
32255 @end table
32256
32257 @item qGetTIBAddr:@var{thread-id}
32258 @cindex get thread information block address
32259 @cindex @samp{qGetTIBAddr} packet
32260 Fetch address of the Windows OS specific Thread Information Block.
32261
32262 @var{thread-id} is the thread ID associated with the thread.
32263
32264 Reply:
32265 @table @samp
32266 @item @var{XX}@dots{}
32267 Hex encoded (big endian) bytes representing the linear address of the
32268 thread information block.
32269
32270 @item E @var{nn}
32271 An error occured. This means that either the thread was not found, or the
32272 address could not be retrieved.
32273
32274 @item
32275 An empty reply indicates that @samp{qGetTIBAddr} is not supported by the stub.
32276 @end table
32277
32278 @item qL @var{startflag} @var{threadcount} @var{nextthread}
32279 Obtain thread information from RTOS. Where: @var{startflag} (one hex
32280 digit) is one to indicate the first query and zero to indicate a
32281 subsequent query; @var{threadcount} (two hex digits) is the maximum
32282 number of threads the response packet can contain; and @var{nextthread}
32283 (eight hex digits), for subsequent queries (@var{startflag} is zero), is
32284 returned in the response as @var{argthread}.
32285
32286 Don't use this packet; use the @samp{qfThreadInfo} query instead (see above).
32287
32288 Reply:
32289 @table @samp
32290 @item qM @var{count} @var{done} @var{argthread} @var{thread}@dots{}
32291 Where: @var{count} (two hex digits) is the number of threads being
32292 returned; @var{done} (one hex digit) is zero to indicate more threads
32293 and one indicates no further threads; @var{argthreadid} (eight hex
32294 digits) is @var{nextthread} from the request packet; @var{thread}@dots{}
32295 is a sequence of thread IDs from the target. @var{threadid} (eight hex
32296 digits). See @code{remote.c:parse_threadlist_response()}.
32297 @end table
32298
32299 @item qOffsets
32300 @cindex section offsets, remote request
32301 @cindex @samp{qOffsets} packet
32302 Get section offsets that the target used when relocating the downloaded
32303 image.
32304
32305 Reply:
32306 @table @samp
32307 @item Text=@var{xxx};Data=@var{yyy}@r{[};Bss=@var{zzz}@r{]}
32308 Relocate the @code{Text} section by @var{xxx} from its original address.
32309 Relocate the @code{Data} section by @var{yyy} from its original address.
32310 If the object file format provides segment information (e.g.@: @sc{elf}
32311 @samp{PT_LOAD} program headers), @value{GDBN} will relocate entire
32312 segments by the supplied offsets.
32313
32314 @emph{Note: while a @code{Bss} offset may be included in the response,
32315 @value{GDBN} ignores this and instead applies the @code{Data} offset
32316 to the @code{Bss} section.}
32317
32318 @item TextSeg=@var{xxx}@r{[};DataSeg=@var{yyy}@r{]}
32319 Relocate the first segment of the object file, which conventionally
32320 contains program code, to a starting address of @var{xxx}. If
32321 @samp{DataSeg} is specified, relocate the second segment, which
32322 conventionally contains modifiable data, to a starting address of
32323 @var{yyy}. @value{GDBN} will report an error if the object file
32324 does not contain segment information, or does not contain at least
32325 as many segments as mentioned in the reply. Extra segments are
32326 kept at fixed offsets relative to the last relocated segment.
32327 @end table
32328
32329 @item qP @var{mode} @var{thread-id}
32330 @cindex thread information, remote request
32331 @cindex @samp{qP} packet
32332 Returns information on @var{thread-id}. Where: @var{mode} is a hex
32333 encoded 32 bit mode; @var{thread-id} is a thread ID
32334 (@pxref{thread-id syntax}).
32335
32336 Don't use this packet; use the @samp{qThreadExtraInfo} query instead
32337 (see below).
32338
32339 Reply: see @code{remote.c:remote_unpack_thread_info_response()}.
32340
32341 @item QNonStop:1
32342 @item QNonStop:0
32343 @cindex non-stop mode, remote request
32344 @cindex @samp{QNonStop} packet
32345 @anchor{QNonStop}
32346 Enter non-stop (@samp{QNonStop:1}) or all-stop (@samp{QNonStop:0}) mode.
32347 @xref{Remote Non-Stop}, for more information.
32348
32349 Reply:
32350 @table @samp
32351 @item OK
32352 The request succeeded.
32353
32354 @item E @var{nn}
32355 An error occurred. @var{nn} are hex digits.
32356
32357 @item
32358 An empty reply indicates that @samp{QNonStop} is not supported by
32359 the stub.
32360 @end table
32361
32362 This packet is not probed by default; the remote stub must request it,
32363 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
32364 Use of this packet is controlled by the @code{set non-stop} command;
32365 @pxref{Non-Stop Mode}.
32366
32367 @item QPassSignals: @var{signal} @r{[};@var{signal}@r{]}@dots{}
32368 @cindex pass signals to inferior, remote request
32369 @cindex @samp{QPassSignals} packet
32370 @anchor{QPassSignals}
32371 Each listed @var{signal} should be passed directly to the inferior process.
32372 Signals are numbered identically to continue packets and stop replies
32373 (@pxref{Stop Reply Packets}). Each @var{signal} list item should be
32374 strictly greater than the previous item. These signals do not need to stop
32375 the inferior, or be reported to @value{GDBN}. All other signals should be
32376 reported to @value{GDBN}. Multiple @samp{QPassSignals} packets do not
32377 combine; any earlier @samp{QPassSignals} list is completely replaced by the
32378 new list. This packet improves performance when using @samp{handle
32379 @var{signal} nostop noprint pass}.
32380
32381 Reply:
32382 @table @samp
32383 @item OK
32384 The request succeeded.
32385
32386 @item E @var{nn}
32387 An error occurred. @var{nn} are hex digits.
32388
32389 @item
32390 An empty reply indicates that @samp{QPassSignals} is not supported by
32391 the stub.
32392 @end table
32393
32394 Use of this packet is controlled by the @code{set remote pass-signals}
32395 command (@pxref{Remote Configuration, set remote pass-signals}).
32396 This packet is not probed by default; the remote stub must request it,
32397 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
32398
32399 @item qRcmd,@var{command}
32400 @cindex execute remote command, remote request
32401 @cindex @samp{qRcmd} packet
32402 @var{command} (hex encoded) is passed to the local interpreter for
32403 execution. Invalid commands should be reported using the output
32404 string. Before the final result packet, the target may also respond
32405 with a number of intermediate @samp{O@var{output}} console output
32406 packets. @emph{Implementors should note that providing access to a
32407 stubs's interpreter may have security implications}.
32408
32409 Reply:
32410 @table @samp
32411 @item OK
32412 A command response with no output.
32413 @item @var{OUTPUT}
32414 A command response with the hex encoded output string @var{OUTPUT}.
32415 @item E @var{NN}
32416 Indicate a badly formed request.
32417 @item
32418 An empty reply indicates that @samp{qRcmd} is not recognized.
32419 @end table
32420
32421 (Note that the @code{qRcmd} packet's name is separated from the
32422 command by a @samp{,}, not a @samp{:}, contrary to the naming
32423 conventions above. Please don't use this packet as a model for new
32424 packets.)
32425
32426 @item qSearch:memory:@var{address};@var{length};@var{search-pattern}
32427 @cindex searching memory, in remote debugging
32428 @cindex @samp{qSearch:memory} packet
32429 @anchor{qSearch memory}
32430 Search @var{length} bytes at @var{address} for @var{search-pattern}.
32431 @var{address} and @var{length} are encoded in hex.
32432 @var{search-pattern} is a sequence of bytes, hex encoded.
32433
32434 Reply:
32435 @table @samp
32436 @item 0
32437 The pattern was not found.
32438 @item 1,address
32439 The pattern was found at @var{address}.
32440 @item E @var{NN}
32441 A badly formed request or an error was encountered while searching memory.
32442 @item
32443 An empty reply indicates that @samp{qSearch:memory} is not recognized.
32444 @end table
32445
32446 @item QStartNoAckMode
32447 @cindex @samp{QStartNoAckMode} packet
32448 @anchor{QStartNoAckMode}
32449 Request that the remote stub disable the normal @samp{+}/@samp{-}
32450 protocol acknowledgments (@pxref{Packet Acknowledgment}).
32451
32452 Reply:
32453 @table @samp
32454 @item OK
32455 The stub has switched to no-acknowledgment mode.
32456 @value{GDBN} acknowledges this reponse,
32457 but neither the stub nor @value{GDBN} shall send or expect further
32458 @samp{+}/@samp{-} acknowledgments in the current connection.
32459 @item
32460 An empty reply indicates that the stub does not support no-acknowledgment mode.
32461 @end table
32462
32463 @item qSupported @r{[}:@var{gdbfeature} @r{[};@var{gdbfeature}@r{]}@dots{} @r{]}
32464 @cindex supported packets, remote query
32465 @cindex features of the remote protocol
32466 @cindex @samp{qSupported} packet
32467 @anchor{qSupported}
32468 Tell the remote stub about features supported by @value{GDBN}, and
32469 query the stub for features it supports. This packet allows
32470 @value{GDBN} and the remote stub to take advantage of each others'
32471 features. @samp{qSupported} also consolidates multiple feature probes
32472 at startup, to improve @value{GDBN} performance---a single larger
32473 packet performs better than multiple smaller probe packets on
32474 high-latency links. Some features may enable behavior which must not
32475 be on by default, e.g.@: because it would confuse older clients or
32476 stubs. Other features may describe packets which could be
32477 automatically probed for, but are not. These features must be
32478 reported before @value{GDBN} will use them. This ``default
32479 unsupported'' behavior is not appropriate for all packets, but it
32480 helps to keep the initial connection time under control with new
32481 versions of @value{GDBN} which support increasing numbers of packets.
32482
32483 Reply:
32484 @table @samp
32485 @item @var{stubfeature} @r{[};@var{stubfeature}@r{]}@dots{}
32486 The stub supports or does not support each returned @var{stubfeature},
32487 depending on the form of each @var{stubfeature} (see below for the
32488 possible forms).
32489 @item
32490 An empty reply indicates that @samp{qSupported} is not recognized,
32491 or that no features needed to be reported to @value{GDBN}.
32492 @end table
32493
32494 The allowed forms for each feature (either a @var{gdbfeature} in the
32495 @samp{qSupported} packet, or a @var{stubfeature} in the response)
32496 are:
32497
32498 @table @samp
32499 @item @var{name}=@var{value}
32500 The remote protocol feature @var{name} is supported, and associated
32501 with the specified @var{value}. The format of @var{value} depends
32502 on the feature, but it must not include a semicolon.
32503 @item @var{name}+
32504 The remote protocol feature @var{name} is supported, and does not
32505 need an associated value.
32506 @item @var{name}-
32507 The remote protocol feature @var{name} is not supported.
32508 @item @var{name}?
32509 The remote protocol feature @var{name} may be supported, and
32510 @value{GDBN} should auto-detect support in some other way when it is
32511 needed. This form will not be used for @var{gdbfeature} notifications,
32512 but may be used for @var{stubfeature} responses.
32513 @end table
32514
32515 Whenever the stub receives a @samp{qSupported} request, the
32516 supplied set of @value{GDBN} features should override any previous
32517 request. This allows @value{GDBN} to put the stub in a known
32518 state, even if the stub had previously been communicating with
32519 a different version of @value{GDBN}.
32520
32521 The following values of @var{gdbfeature} (for the packet sent by @value{GDBN})
32522 are defined:
32523
32524 @table @samp
32525 @item multiprocess
32526 This feature indicates whether @value{GDBN} supports multiprocess
32527 extensions to the remote protocol. @value{GDBN} does not use such
32528 extensions unless the stub also reports that it supports them by
32529 including @samp{multiprocess+} in its @samp{qSupported} reply.
32530 @xref{multiprocess extensions}, for details.
32531
32532 @item xmlRegisters
32533 This feature indicates that @value{GDBN} supports the XML target
32534 description. If the stub sees @samp{xmlRegisters=} with target
32535 specific strings separated by a comma, it will report register
32536 description.
32537
32538 @item qRelocInsn
32539 This feature indicates whether @value{GDBN} supports the
32540 @samp{qRelocInsn} packet (@pxref{Tracepoint Packets,,Relocate
32541 instruction reply packet}).
32542 @end table
32543
32544 Stubs should ignore any unknown values for
32545 @var{gdbfeature}. Any @value{GDBN} which sends a @samp{qSupported}
32546 packet supports receiving packets of unlimited length (earlier
32547 versions of @value{GDBN} may reject overly long responses). Additional values
32548 for @var{gdbfeature} may be defined in the future to let the stub take
32549 advantage of new features in @value{GDBN}, e.g.@: incompatible
32550 improvements in the remote protocol---the @samp{multiprocess} feature is
32551 an example of such a feature. The stub's reply should be independent
32552 of the @var{gdbfeature} entries sent by @value{GDBN}; first @value{GDBN}
32553 describes all the features it supports, and then the stub replies with
32554 all the features it supports.
32555
32556 Similarly, @value{GDBN} will silently ignore unrecognized stub feature
32557 responses, as long as each response uses one of the standard forms.
32558
32559 Some features are flags. A stub which supports a flag feature
32560 should respond with a @samp{+} form response. Other features
32561 require values, and the stub should respond with an @samp{=}
32562 form response.
32563
32564 Each feature has a default value, which @value{GDBN} will use if
32565 @samp{qSupported} is not available or if the feature is not mentioned
32566 in the @samp{qSupported} response. The default values are fixed; a
32567 stub is free to omit any feature responses that match the defaults.
32568
32569 Not all features can be probed, but for those which can, the probing
32570 mechanism is useful: in some cases, a stub's internal
32571 architecture may not allow the protocol layer to know some information
32572 about the underlying target in advance. This is especially common in
32573 stubs which may be configured for multiple targets.
32574
32575 These are the currently defined stub features and their properties:
32576
32577 @multitable @columnfractions 0.35 0.2 0.12 0.2
32578 @c NOTE: The first row should be @headitem, but we do not yet require
32579 @c a new enough version of Texinfo (4.7) to use @headitem.
32580 @item Feature Name
32581 @tab Value Required
32582 @tab Default
32583 @tab Probe Allowed
32584
32585 @item @samp{PacketSize}
32586 @tab Yes
32587 @tab @samp{-}
32588 @tab No
32589
32590 @item @samp{qXfer:auxv:read}
32591 @tab No
32592 @tab @samp{-}
32593 @tab Yes
32594
32595 @item @samp{qXfer:features:read}
32596 @tab No
32597 @tab @samp{-}
32598 @tab Yes
32599
32600 @item @samp{qXfer:libraries:read}
32601 @tab No
32602 @tab @samp{-}
32603 @tab Yes
32604
32605 @item @samp{qXfer:memory-map:read}
32606 @tab No
32607 @tab @samp{-}
32608 @tab Yes
32609
32610 @item @samp{qXfer:sdata:read}
32611 @tab No
32612 @tab @samp{-}
32613 @tab Yes
32614
32615 @item @samp{qXfer:spu:read}
32616 @tab No
32617 @tab @samp{-}
32618 @tab Yes
32619
32620 @item @samp{qXfer:spu:write}
32621 @tab No
32622 @tab @samp{-}
32623 @tab Yes
32624
32625 @item @samp{qXfer:siginfo:read}
32626 @tab No
32627 @tab @samp{-}
32628 @tab Yes
32629
32630 @item @samp{qXfer:siginfo:write}
32631 @tab No
32632 @tab @samp{-}
32633 @tab Yes
32634
32635 @item @samp{qXfer:threads:read}
32636 @tab No
32637 @tab @samp{-}
32638 @tab Yes
32639
32640
32641 @item @samp{QNonStop}
32642 @tab No
32643 @tab @samp{-}
32644 @tab Yes
32645
32646 @item @samp{QPassSignals}
32647 @tab No
32648 @tab @samp{-}
32649 @tab Yes
32650
32651 @item @samp{QStartNoAckMode}
32652 @tab No
32653 @tab @samp{-}
32654 @tab Yes
32655
32656 @item @samp{multiprocess}
32657 @tab No
32658 @tab @samp{-}
32659 @tab No
32660
32661 @item @samp{ConditionalTracepoints}
32662 @tab No
32663 @tab @samp{-}
32664 @tab No
32665
32666 @item @samp{ReverseContinue}
32667 @tab No
32668 @tab @samp{-}
32669 @tab No
32670
32671 @item @samp{ReverseStep}
32672 @tab No
32673 @tab @samp{-}
32674 @tab No
32675
32676 @item @samp{TracepointSource}
32677 @tab No
32678 @tab @samp{-}
32679 @tab No
32680
32681 @item @samp{QAllow}
32682 @tab No
32683 @tab @samp{-}
32684 @tab No
32685
32686 @end multitable
32687
32688 These are the currently defined stub features, in more detail:
32689
32690 @table @samp
32691 @cindex packet size, remote protocol
32692 @item PacketSize=@var{bytes}
32693 The remote stub can accept packets up to at least @var{bytes} in
32694 length. @value{GDBN} will send packets up to this size for bulk
32695 transfers, and will never send larger packets. This is a limit on the
32696 data characters in the packet, including the frame and checksum.
32697 There is no trailing NUL byte in a remote protocol packet; if the stub
32698 stores packets in a NUL-terminated format, it should allow an extra
32699 byte in its buffer for the NUL. If this stub feature is not supported,
32700 @value{GDBN} guesses based on the size of the @samp{g} packet response.
32701
32702 @item qXfer:auxv:read
32703 The remote stub understands the @samp{qXfer:auxv:read} packet
32704 (@pxref{qXfer auxiliary vector read}).
32705
32706 @item qXfer:features:read
32707 The remote stub understands the @samp{qXfer:features:read} packet
32708 (@pxref{qXfer target description read}).
32709
32710 @item qXfer:libraries:read
32711 The remote stub understands the @samp{qXfer:libraries:read} packet
32712 (@pxref{qXfer library list read}).
32713
32714 @item qXfer:memory-map:read
32715 The remote stub understands the @samp{qXfer:memory-map:read} packet
32716 (@pxref{qXfer memory map read}).
32717
32718 @item qXfer:sdata:read
32719 The remote stub understands the @samp{qXfer:sdata:read} packet
32720 (@pxref{qXfer sdata read}).
32721
32722 @item qXfer:spu:read
32723 The remote stub understands the @samp{qXfer:spu:read} packet
32724 (@pxref{qXfer spu read}).
32725
32726 @item qXfer:spu:write
32727 The remote stub understands the @samp{qXfer:spu:write} packet
32728 (@pxref{qXfer spu write}).
32729
32730 @item qXfer:siginfo:read
32731 The remote stub understands the @samp{qXfer:siginfo:read} packet
32732 (@pxref{qXfer siginfo read}).
32733
32734 @item qXfer:siginfo:write
32735 The remote stub understands the @samp{qXfer:siginfo:write} packet
32736 (@pxref{qXfer siginfo write}).
32737
32738 @item qXfer:threads:read
32739 The remote stub understands the @samp{qXfer:threads:read} packet
32740 (@pxref{qXfer threads read}).
32741
32742 @item QNonStop
32743 The remote stub understands the @samp{QNonStop} packet
32744 (@pxref{QNonStop}).
32745
32746 @item QPassSignals
32747 The remote stub understands the @samp{QPassSignals} packet
32748 (@pxref{QPassSignals}).
32749
32750 @item QStartNoAckMode
32751 The remote stub understands the @samp{QStartNoAckMode} packet and
32752 prefers to operate in no-acknowledgment mode. @xref{Packet Acknowledgment}.
32753
32754 @item multiprocess
32755 @anchor{multiprocess extensions}
32756 @cindex multiprocess extensions, in remote protocol
32757 The remote stub understands the multiprocess extensions to the remote
32758 protocol syntax. The multiprocess extensions affect the syntax of
32759 thread IDs in both packets and replies (@pxref{thread-id syntax}), and
32760 add process IDs to the @samp{D} packet and @samp{W} and @samp{X}
32761 replies. Note that reporting this feature indicates support for the
32762 syntactic extensions only, not that the stub necessarily supports
32763 debugging of more than one process at a time. The stub must not use
32764 multiprocess extensions in packet replies unless @value{GDBN} has also
32765 indicated it supports them in its @samp{qSupported} request.
32766
32767 @item qXfer:osdata:read
32768 The remote stub understands the @samp{qXfer:osdata:read} packet
32769 ((@pxref{qXfer osdata read}).
32770
32771 @item ConditionalTracepoints
32772 The remote stub accepts and implements conditional expressions defined
32773 for tracepoints (@pxref{Tracepoint Conditions}).
32774
32775 @item ReverseContinue
32776 The remote stub accepts and implements the reverse continue packet
32777 (@pxref{bc}).
32778
32779 @item ReverseStep
32780 The remote stub accepts and implements the reverse step packet
32781 (@pxref{bs}).
32782
32783 @item TracepointSource
32784 The remote stub understands the @samp{QTDPsrc} packet that supplies
32785 the source form of tracepoint definitions.
32786
32787 @item QAllow
32788 The remote stub understands the @samp{QAllow} packet.
32789
32790 @item StaticTracepoint
32791 @cindex static tracepoints, in remote protocol
32792 The remote stub supports static tracepoints.
32793
32794 @end table
32795
32796 @item qSymbol::
32797 @cindex symbol lookup, remote request
32798 @cindex @samp{qSymbol} packet
32799 Notify the target that @value{GDBN} is prepared to serve symbol lookup
32800 requests. Accept requests from the target for the values of symbols.
32801
32802 Reply:
32803 @table @samp
32804 @item OK
32805 The target does not need to look up any (more) symbols.
32806 @item qSymbol:@var{sym_name}
32807 The target requests the value of symbol @var{sym_name} (hex encoded).
32808 @value{GDBN} may provide the value by using the
32809 @samp{qSymbol:@var{sym_value}:@var{sym_name}} message, described
32810 below.
32811 @end table
32812
32813 @item qSymbol:@var{sym_value}:@var{sym_name}
32814 Set the value of @var{sym_name} to @var{sym_value}.
32815
32816 @var{sym_name} (hex encoded) is the name of a symbol whose value the
32817 target has previously requested.
32818
32819 @var{sym_value} (hex) is the value for symbol @var{sym_name}. If
32820 @value{GDBN} cannot supply a value for @var{sym_name}, then this field
32821 will be empty.
32822
32823 Reply:
32824 @table @samp
32825 @item OK
32826 The target does not need to look up any (more) symbols.
32827 @item qSymbol:@var{sym_name}
32828 The target requests the value of a new symbol @var{sym_name} (hex
32829 encoded). @value{GDBN} will continue to supply the values of symbols
32830 (if available), until the target ceases to request them.
32831 @end table
32832
32833 @item qTBuffer
32834 @item QTBuffer
32835 @item QTDisconnected
32836 @itemx QTDP
32837 @itemx QTDPsrc
32838 @itemx QTDV
32839 @itemx qTfP
32840 @itemx qTfV
32841 @itemx QTFrame
32842 @xref{Tracepoint Packets}.
32843
32844 @item qThreadExtraInfo,@var{thread-id}
32845 @cindex thread attributes info, remote request
32846 @cindex @samp{qThreadExtraInfo} packet
32847 Obtain a printable string description of a thread's attributes from
32848 the target OS. @var{thread-id} is a thread ID;
32849 see @ref{thread-id syntax}. This
32850 string may contain anything that the target OS thinks is interesting
32851 for @value{GDBN} to tell the user about the thread. The string is
32852 displayed in @value{GDBN}'s @code{info threads} display. Some
32853 examples of possible thread extra info strings are @samp{Runnable}, or
32854 @samp{Blocked on Mutex}.
32855
32856 Reply:
32857 @table @samp
32858 @item @var{XX}@dots{}
32859 Where @samp{@var{XX}@dots{}} is a hex encoding of @sc{ascii} data,
32860 comprising the printable string containing the extra information about
32861 the thread's attributes.
32862 @end table
32863
32864 (Note that the @code{qThreadExtraInfo} packet's name is separated from
32865 the command by a @samp{,}, not a @samp{:}, contrary to the naming
32866 conventions above. Please don't use this packet as a model for new
32867 packets.)
32868
32869 @item QTSave
32870 @item qTsP
32871 @item qTsV
32872 @itemx QTStart
32873 @itemx QTStop
32874 @itemx QTinit
32875 @itemx QTro
32876 @itemx qTStatus
32877 @itemx qTV
32878 @itemx qTfSTM
32879 @itemx qTsSTM
32880 @itemx qTSTMat
32881 @xref{Tracepoint Packets}.
32882
32883 @item qXfer:@var{object}:read:@var{annex}:@var{offset},@var{length}
32884 @cindex read special object, remote request
32885 @cindex @samp{qXfer} packet
32886 @anchor{qXfer read}
32887 Read uninterpreted bytes from the target's special data area
32888 identified by the keyword @var{object}. Request @var{length} bytes
32889 starting at @var{offset} bytes into the data. The content and
32890 encoding of @var{annex} is specific to @var{object}; it can supply
32891 additional details about what data to access.
32892
32893 Here are the specific requests of this form defined so far. All
32894 @samp{qXfer:@var{object}:read:@dots{}} requests use the same reply
32895 formats, listed below.
32896
32897 @table @samp
32898 @item qXfer:auxv:read::@var{offset},@var{length}
32899 @anchor{qXfer auxiliary vector read}
32900 Access the target's @dfn{auxiliary vector}. @xref{OS Information,
32901 auxiliary vector}. Note @var{annex} must be empty.
32902
32903 This packet is not probed by default; the remote stub must request it,
32904 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
32905
32906 @item qXfer:features:read:@var{annex}:@var{offset},@var{length}
32907 @anchor{qXfer target description read}
32908 Access the @dfn{target description}. @xref{Target Descriptions}. The
32909 annex specifies which XML document to access. The main description is
32910 always loaded from the @samp{target.xml} annex.
32911
32912 This packet is not probed by default; the remote stub must request it,
32913 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
32914
32915 @item qXfer:libraries:read:@var{annex}:@var{offset},@var{length}
32916 @anchor{qXfer library list read}
32917 Access the target's list of loaded libraries. @xref{Library List Format}.
32918 The annex part of the generic @samp{qXfer} packet must be empty
32919 (@pxref{qXfer read}).
32920
32921 Targets which maintain a list of libraries in the program's memory do
32922 not need to implement this packet; it is designed for platforms where
32923 the operating system manages the list of loaded libraries.
32924
32925 This packet is not probed by default; the remote stub must request it,
32926 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
32927
32928 @item qXfer:memory-map:read::@var{offset},@var{length}
32929 @anchor{qXfer memory map read}
32930 Access the target's @dfn{memory-map}. @xref{Memory Map Format}. The
32931 annex part of the generic @samp{qXfer} packet must be empty
32932 (@pxref{qXfer read}).
32933
32934 This packet is not probed by default; the remote stub must request it,
32935 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
32936
32937 @item qXfer:sdata:read::@var{offset},@var{length}
32938 @anchor{qXfer sdata read}
32939
32940 Read contents of the extra collected static tracepoint marker
32941 information. The annex part of the generic @samp{qXfer} packet must
32942 be empty (@pxref{qXfer read}). @xref{Tracepoint Actions,,Tracepoint
32943 Action Lists}.
32944
32945 This packet is not probed by default; the remote stub must request it,
32946 by supplying an appropriate @samp{qSupported} response
32947 (@pxref{qSupported}).
32948
32949 @item qXfer:siginfo:read::@var{offset},@var{length}
32950 @anchor{qXfer siginfo read}
32951 Read contents of the extra signal information on the target
32952 system. The annex part of the generic @samp{qXfer} packet must be
32953 empty (@pxref{qXfer read}).
32954
32955 This packet is not probed by default; the remote stub must request it,
32956 by supplying an appropriate @samp{qSupported} response
32957 (@pxref{qSupported}).
32958
32959 @item qXfer:spu:read:@var{annex}:@var{offset},@var{length}
32960 @anchor{qXfer spu read}
32961 Read contents of an @code{spufs} file on the target system. The
32962 annex specifies which file to read; it must be of the form
32963 @file{@var{id}/@var{name}}, where @var{id} specifies an SPU context ID
32964 in the target process, and @var{name} identifes the @code{spufs} file
32965 in that context to be accessed.
32966
32967 This packet is not probed by default; the remote stub must request it,
32968 by supplying an appropriate @samp{qSupported} response
32969 (@pxref{qSupported}).
32970
32971 @item qXfer:threads:read::@var{offset},@var{length}
32972 @anchor{qXfer threads read}
32973 Access the list of threads on target. @xref{Thread List Format}. The
32974 annex part of the generic @samp{qXfer} packet must be empty
32975 (@pxref{qXfer read}).
32976
32977 This packet is not probed by default; the remote stub must request it,
32978 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
32979
32980 @item qXfer:osdata:read::@var{offset},@var{length}
32981 @anchor{qXfer osdata read}
32982 Access the target's @dfn{operating system information}.
32983 @xref{Operating System Information}.
32984
32985 @end table
32986
32987 Reply:
32988 @table @samp
32989 @item m @var{data}
32990 Data @var{data} (@pxref{Binary Data}) has been read from the
32991 target. There may be more data at a higher address (although
32992 it is permitted to return @samp{m} even for the last valid
32993 block of data, as long as at least one byte of data was read).
32994 @var{data} may have fewer bytes than the @var{length} in the
32995 request.
32996
32997 @item l @var{data}
32998 Data @var{data} (@pxref{Binary Data}) has been read from the target.
32999 There is no more data to be read. @var{data} may have fewer bytes
33000 than the @var{length} in the request.
33001
33002 @item l
33003 The @var{offset} in the request is at the end of the data.
33004 There is no more data to be read.
33005
33006 @item E00
33007 The request was malformed, or @var{annex} was invalid.
33008
33009 @item E @var{nn}
33010 The offset was invalid, or there was an error encountered reading the data.
33011 @var{nn} is a hex-encoded @code{errno} value.
33012
33013 @item
33014 An empty reply indicates the @var{object} string was not recognized by
33015 the stub, or that the object does not support reading.
33016 @end table
33017
33018 @item qXfer:@var{object}:write:@var{annex}:@var{offset}:@var{data}@dots{}
33019 @cindex write data into object, remote request
33020 @anchor{qXfer write}
33021 Write uninterpreted bytes into the target's special data area
33022 identified by the keyword @var{object}, starting at @var{offset} bytes
33023 into the data. @var{data}@dots{} is the binary-encoded data
33024 (@pxref{Binary Data}) to be written. The content and encoding of @var{annex}
33025 is specific to @var{object}; it can supply additional details about what data
33026 to access.
33027
33028 Here are the specific requests of this form defined so far. All
33029 @samp{qXfer:@var{object}:write:@dots{}} requests use the same reply
33030 formats, listed below.
33031
33032 @table @samp
33033 @item qXfer:siginfo:write::@var{offset}:@var{data}@dots{}
33034 @anchor{qXfer siginfo write}
33035 Write @var{data} to the extra signal information on the target system.
33036 The annex part of the generic @samp{qXfer} packet must be
33037 empty (@pxref{qXfer write}).
33038
33039 This packet is not probed by default; the remote stub must request it,
33040 by supplying an appropriate @samp{qSupported} response
33041 (@pxref{qSupported}).
33042
33043 @item qXfer:spu:write:@var{annex}:@var{offset}:@var{data}@dots{}
33044 @anchor{qXfer spu write}
33045 Write @var{data} to an @code{spufs} file on the target system. The
33046 annex specifies which file to write; it must be of the form
33047 @file{@var{id}/@var{name}}, where @var{id} specifies an SPU context ID
33048 in the target process, and @var{name} identifes the @code{spufs} file
33049 in that context to be accessed.
33050
33051 This packet is not probed by default; the remote stub must request it,
33052 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
33053 @end table
33054
33055 Reply:
33056 @table @samp
33057 @item @var{nn}
33058 @var{nn} (hex encoded) is the number of bytes written.
33059 This may be fewer bytes than supplied in the request.
33060
33061 @item E00
33062 The request was malformed, or @var{annex} was invalid.
33063
33064 @item E @var{nn}
33065 The offset was invalid, or there was an error encountered writing the data.
33066 @var{nn} is a hex-encoded @code{errno} value.
33067
33068 @item
33069 An empty reply indicates the @var{object} string was not
33070 recognized by the stub, or that the object does not support writing.
33071 @end table
33072
33073 @item qXfer:@var{object}:@var{operation}:@dots{}
33074 Requests of this form may be added in the future. When a stub does
33075 not recognize the @var{object} keyword, or its support for
33076 @var{object} does not recognize the @var{operation} keyword, the stub
33077 must respond with an empty packet.
33078
33079 @item qAttached:@var{pid}
33080 @cindex query attached, remote request
33081 @cindex @samp{qAttached} packet
33082 Return an indication of whether the remote server attached to an
33083 existing process or created a new process. When the multiprocess
33084 protocol extensions are supported (@pxref{multiprocess extensions}),
33085 @var{pid} is an integer in hexadecimal format identifying the target
33086 process. Otherwise, @value{GDBN} will omit the @var{pid} field and
33087 the query packet will be simplified as @samp{qAttached}.
33088
33089 This query is used, for example, to know whether the remote process
33090 should be detached or killed when a @value{GDBN} session is ended with
33091 the @code{quit} command.
33092
33093 Reply:
33094 @table @samp
33095 @item 1
33096 The remote server attached to an existing process.
33097 @item 0
33098 The remote server created a new process.
33099 @item E @var{NN}
33100 A badly formed request or an error was encountered.
33101 @end table
33102
33103 @end table
33104
33105 @node Architecture-Specific Protocol Details
33106 @section Architecture-Specific Protocol Details
33107
33108 This section describes how the remote protocol is applied to specific
33109 target architectures. Also see @ref{Standard Target Features}, for
33110 details of XML target descriptions for each architecture.
33111
33112 @subsection ARM
33113
33114 @subsubsection Breakpoint Kinds
33115
33116 These breakpoint kinds are defined for the @samp{Z0} and @samp{Z1} packets.
33117
33118 @table @r
33119
33120 @item 2
33121 16-bit Thumb mode breakpoint.
33122
33123 @item 3
33124 32-bit Thumb mode (Thumb-2) breakpoint.
33125
33126 @item 4
33127 32-bit ARM mode breakpoint.
33128
33129 @end table
33130
33131 @subsection MIPS
33132
33133 @subsubsection Register Packet Format
33134
33135 The following @code{g}/@code{G} packets have previously been defined.
33136 In the below, some thirty-two bit registers are transferred as
33137 sixty-four bits. Those registers should be zero/sign extended (which?)
33138 to fill the space allocated. Register bytes are transferred in target
33139 byte order. The two nibbles within a register byte are transferred
33140 most-significant - least-significant.
33141
33142 @table @r
33143
33144 @item MIPS32
33145
33146 All registers are transferred as thirty-two bit quantities in the order:
33147 32 general-purpose; sr; lo; hi; bad; cause; pc; 32 floating-point
33148 registers; fsr; fir; fp.
33149
33150 @item MIPS64
33151
33152 All registers are transferred as sixty-four bit quantities (including
33153 thirty-two bit registers such as @code{sr}). The ordering is the same
33154 as @code{MIPS32}.
33155
33156 @end table
33157
33158 @node Tracepoint Packets
33159 @section Tracepoint Packets
33160 @cindex tracepoint packets
33161 @cindex packets, tracepoint
33162
33163 Here we describe the packets @value{GDBN} uses to implement
33164 tracepoints (@pxref{Tracepoints}).
33165
33166 @table @samp
33167
33168 @item QTDP:@var{n}:@var{addr}:@var{ena}:@var{step}:@var{pass}[:F@var{flen}][:X@var{len},@var{bytes}]@r{[}-@r{]}
33169 Create a new tracepoint, number @var{n}, at @var{addr}. If @var{ena}
33170 is @samp{E}, then the tracepoint is enabled; if it is @samp{D}, then
33171 the tracepoint is disabled. @var{step} is the tracepoint's step
33172 count, and @var{pass} is its pass count. If an @samp{F} is present,
33173 then the tracepoint is to be a fast tracepoint, and the @var{flen} is
33174 the number of bytes that the target should copy elsewhere to make room
33175 for the tracepoint. If an @samp{X} is present, it introduces a
33176 tracepoint condition, which consists of a hexadecimal length, followed
33177 by a comma and hex-encoded bytes, in a manner similar to action
33178 encodings as described below. If the trailing @samp{-} is present,
33179 further @samp{QTDP} packets will follow to specify this tracepoint's
33180 actions.
33181
33182 Replies:
33183 @table @samp
33184 @item OK
33185 The packet was understood and carried out.
33186 @item qRelocInsn
33187 @xref{Tracepoint Packets,,Relocate instruction reply packet}.
33188 @item
33189 The packet was not recognized.
33190 @end table
33191
33192 @item QTDP:-@var{n}:@var{addr}:@r{[}S@r{]}@var{action}@dots{}@r{[}-@r{]}
33193 Define actions to be taken when a tracepoint is hit. @var{n} and
33194 @var{addr} must be the same as in the initial @samp{QTDP} packet for
33195 this tracepoint. This packet may only be sent immediately after
33196 another @samp{QTDP} packet that ended with a @samp{-}. If the
33197 trailing @samp{-} is present, further @samp{QTDP} packets will follow,
33198 specifying more actions for this tracepoint.
33199
33200 In the series of action packets for a given tracepoint, at most one
33201 can have an @samp{S} before its first @var{action}. If such a packet
33202 is sent, it and the following packets define ``while-stepping''
33203 actions. Any prior packets define ordinary actions --- that is, those
33204 taken when the tracepoint is first hit. If no action packet has an
33205 @samp{S}, then all the packets in the series specify ordinary
33206 tracepoint actions.
33207
33208 The @samp{@var{action}@dots{}} portion of the packet is a series of
33209 actions, concatenated without separators. Each action has one of the
33210 following forms:
33211
33212 @table @samp
33213
33214 @item R @var{mask}
33215 Collect the registers whose bits are set in @var{mask}. @var{mask} is
33216 a hexadecimal number whose @var{i}'th bit is set if register number
33217 @var{i} should be collected. (The least significant bit is numbered
33218 zero.) Note that @var{mask} may be any number of digits long; it may
33219 not fit in a 32-bit word.
33220
33221 @item M @var{basereg},@var{offset},@var{len}
33222 Collect @var{len} bytes of memory starting at the address in register
33223 number @var{basereg}, plus @var{offset}. If @var{basereg} is
33224 @samp{-1}, then the range has a fixed address: @var{offset} is the
33225 address of the lowest byte to collect. The @var{basereg},
33226 @var{offset}, and @var{len} parameters are all unsigned hexadecimal
33227 values (the @samp{-1} value for @var{basereg} is a special case).
33228
33229 @item X @var{len},@var{expr}
33230 Evaluate @var{expr}, whose length is @var{len}, and collect memory as
33231 it directs. @var{expr} is an agent expression, as described in
33232 @ref{Agent Expressions}. Each byte of the expression is encoded as a
33233 two-digit hex number in the packet; @var{len} is the number of bytes
33234 in the expression (and thus one-half the number of hex digits in the
33235 packet).
33236
33237 @end table
33238
33239 Any number of actions may be packed together in a single @samp{QTDP}
33240 packet, as long as the packet does not exceed the maximum packet
33241 length (400 bytes, for many stubs). There may be only one @samp{R}
33242 action per tracepoint, and it must precede any @samp{M} or @samp{X}
33243 actions. Any registers referred to by @samp{M} and @samp{X} actions
33244 must be collected by a preceding @samp{R} action. (The
33245 ``while-stepping'' actions are treated as if they were attached to a
33246 separate tracepoint, as far as these restrictions are concerned.)
33247
33248 Replies:
33249 @table @samp
33250 @item OK
33251 The packet was understood and carried out.
33252 @item qRelocInsn
33253 @xref{Tracepoint Packets,,Relocate instruction reply packet}.
33254 @item
33255 The packet was not recognized.
33256 @end table
33257
33258 @item QTDPsrc:@var{n}:@var{addr}:@var{type}:@var{start}:@var{slen}:@var{bytes}
33259 @cindex @samp{QTDPsrc} packet
33260 Specify a source string of tracepoint @var{n} at address @var{addr}.
33261 This is useful to get accurate reproduction of the tracepoints
33262 originally downloaded at the beginning of the trace run. @var{type}
33263 is the name of the tracepoint part, such as @samp{cond} for the
33264 tracepoint's conditional expression (see below for a list of types), while
33265 @var{bytes} is the string, encoded in hexadecimal.
33266
33267 @var{start} is the offset of the @var{bytes} within the overall source
33268 string, while @var{slen} is the total length of the source string.
33269 This is intended for handling source strings that are longer than will
33270 fit in a single packet.
33271 @c Add detailed example when this info is moved into a dedicated
33272 @c tracepoint descriptions section.
33273
33274 The available string types are @samp{at} for the location,
33275 @samp{cond} for the conditional, and @samp{cmd} for an action command.
33276 @value{GDBN} sends a separate packet for each command in the action
33277 list, in the same order in which the commands are stored in the list.
33278
33279 The target does not need to do anything with source strings except
33280 report them back as part of the replies to the @samp{qTfP}/@samp{qTsP}
33281 query packets.
33282
33283 Although this packet is optional, and @value{GDBN} will only send it
33284 if the target replies with @samp{TracepointSource} @xref{General
33285 Query Packets}, it makes both disconnected tracing and trace files
33286 much easier to use. Otherwise the user must be careful that the
33287 tracepoints in effect while looking at trace frames are identical to
33288 the ones in effect during the trace run; even a small discrepancy
33289 could cause @samp{tdump} not to work, or a particular trace frame not
33290 be found.
33291
33292 @item QTDV:@var{n}:@var{value}
33293 @cindex define trace state variable, remote request
33294 @cindex @samp{QTDV} packet
33295 Create a new trace state variable, number @var{n}, with an initial
33296 value of @var{value}, which is a 64-bit signed integer. Both @var{n}
33297 and @var{value} are encoded as hexadecimal values. @value{GDBN} has
33298 the option of not using this packet for initial values of zero; the
33299 target should simply create the trace state variables as they are
33300 mentioned in expressions.
33301
33302 @item QTFrame:@var{n}
33303 Select the @var{n}'th tracepoint frame from the buffer, and use the
33304 register and memory contents recorded there to answer subsequent
33305 request packets from @value{GDBN}.
33306
33307 A successful reply from the stub indicates that the stub has found the
33308 requested frame. The response is a series of parts, concatenated
33309 without separators, describing the frame we selected. Each part has
33310 one of the following forms:
33311
33312 @table @samp
33313 @item F @var{f}
33314 The selected frame is number @var{n} in the trace frame buffer;
33315 @var{f} is a hexadecimal number. If @var{f} is @samp{-1}, then there
33316 was no frame matching the criteria in the request packet.
33317
33318 @item T @var{t}
33319 The selected trace frame records a hit of tracepoint number @var{t};
33320 @var{t} is a hexadecimal number.
33321
33322 @end table
33323
33324 @item QTFrame:pc:@var{addr}
33325 Like @samp{QTFrame:@var{n}}, but select the first tracepoint frame after the
33326 currently selected frame whose PC is @var{addr};
33327 @var{addr} is a hexadecimal number.
33328
33329 @item QTFrame:tdp:@var{t}
33330 Like @samp{QTFrame:@var{n}}, but select the first tracepoint frame after the
33331 currently selected frame that is a hit of tracepoint @var{t}; @var{t}
33332 is a hexadecimal number.
33333
33334 @item QTFrame:range:@var{start}:@var{end}
33335 Like @samp{QTFrame:@var{n}}, but select the first tracepoint frame after the
33336 currently selected frame whose PC is between @var{start} (inclusive)
33337 and @var{end} (inclusive); @var{start} and @var{end} are hexadecimal
33338 numbers.
33339
33340 @item QTFrame:outside:@var{start}:@var{end}
33341 Like @samp{QTFrame:range:@var{start}:@var{end}}, but select the first
33342 frame @emph{outside} the given range of addresses (exclusive).
33343
33344 @item QTStart
33345 Begin the tracepoint experiment. Begin collecting data from
33346 tracepoint hits in the trace frame buffer. This packet supports the
33347 @samp{qRelocInsn} reply (@pxref{Tracepoint Packets,,Relocate
33348 instruction reply packet}).
33349
33350 @item QTStop
33351 End the tracepoint experiment. Stop collecting trace frames.
33352
33353 @item QTinit
33354 Clear the table of tracepoints, and empty the trace frame buffer.
33355
33356 @item QTro:@var{start1},@var{end1}:@var{start2},@var{end2}:@dots{}
33357 Establish the given ranges of memory as ``transparent''. The stub
33358 will answer requests for these ranges from memory's current contents,
33359 if they were not collected as part of the tracepoint hit.
33360
33361 @value{GDBN} uses this to mark read-only regions of memory, like those
33362 containing program code. Since these areas never change, they should
33363 still have the same contents they did when the tracepoint was hit, so
33364 there's no reason for the stub to refuse to provide their contents.
33365
33366 @item QTDisconnected:@var{value}
33367 Set the choice to what to do with the tracing run when @value{GDBN}
33368 disconnects from the target. A @var{value} of 1 directs the target to
33369 continue the tracing run, while 0 tells the target to stop tracing if
33370 @value{GDBN} is no longer in the picture.
33371
33372 @item qTStatus
33373 Ask the stub if there is a trace experiment running right now.
33374
33375 The reply has the form:
33376
33377 @table @samp
33378
33379 @item T@var{running}@r{[};@var{field}@r{]}@dots{}
33380 @var{running} is a single digit @code{1} if the trace is presently
33381 running, or @code{0} if not. It is followed by semicolon-separated
33382 optional fields that an agent may use to report additional status.
33383
33384 @end table
33385
33386 If the trace is not running, the agent may report any of several
33387 explanations as one of the optional fields:
33388
33389 @table @samp
33390
33391 @item tnotrun:0
33392 No trace has been run yet.
33393
33394 @item tstop:0
33395 The trace was stopped by a user-originated stop command.
33396
33397 @item tfull:0
33398 The trace stopped because the trace buffer filled up.
33399
33400 @item tdisconnected:0
33401 The trace stopped because @value{GDBN} disconnected from the target.
33402
33403 @item tpasscount:@var{tpnum}
33404 The trace stopped because tracepoint @var{tpnum} exceeded its pass count.
33405
33406 @item terror:@var{text}:@var{tpnum}
33407 The trace stopped because tracepoint @var{tpnum} had an error. The
33408 string @var{text} is available to describe the nature of the error
33409 (for instance, a divide by zero in the condition expression).
33410 @var{text} is hex encoded.
33411
33412 @item tunknown:0
33413 The trace stopped for some other reason.
33414
33415 @end table
33416
33417 Additional optional fields supply statistical and other information.
33418 Although not required, they are extremely useful for users monitoring
33419 the progress of a trace run. If a trace has stopped, and these
33420 numbers are reported, they must reflect the state of the just-stopped
33421 trace.
33422
33423 @table @samp
33424
33425 @item tframes:@var{n}
33426 The number of trace frames in the buffer.
33427
33428 @item tcreated:@var{n}
33429 The total number of trace frames created during the run. This may
33430 be larger than the trace frame count, if the buffer is circular.
33431
33432 @item tsize:@var{n}
33433 The total size of the trace buffer, in bytes.
33434
33435 @item tfree:@var{n}
33436 The number of bytes still unused in the buffer.
33437
33438 @item circular:@var{n}
33439 The value of the circular trace buffer flag. @code{1} means that the
33440 trace buffer is circular and old trace frames will be discarded if
33441 necessary to make room, @code{0} means that the trace buffer is linear
33442 and may fill up.
33443
33444 @item disconn:@var{n}
33445 The value of the disconnected tracing flag. @code{1} means that
33446 tracing will continue after @value{GDBN} disconnects, @code{0} means
33447 that the trace run will stop.
33448
33449 @end table
33450
33451 @item qTV:@var{var}
33452 @cindex trace state variable value, remote request
33453 @cindex @samp{qTV} packet
33454 Ask the stub for the value of the trace state variable number @var{var}.
33455
33456 Replies:
33457 @table @samp
33458 @item V@var{value}
33459 The value of the variable is @var{value}. This will be the current
33460 value of the variable if the user is examining a running target, or a
33461 saved value if the variable was collected in the trace frame that the
33462 user is looking at. Note that multiple requests may result in
33463 different reply values, such as when requesting values while the
33464 program is running.
33465
33466 @item U
33467 The value of the variable is unknown. This would occur, for example,
33468 if the user is examining a trace frame in which the requested variable
33469 was not collected.
33470 @end table
33471
33472 @item qTfP
33473 @itemx qTsP
33474 These packets request data about tracepoints that are being used by
33475 the target. @value{GDBN} sends @code{qTfP} to get the first piece
33476 of data, and multiple @code{qTsP} to get additional pieces. Replies
33477 to these packets generally take the form of the @code{QTDP} packets
33478 that define tracepoints. (FIXME add detailed syntax)
33479
33480 @item qTfV
33481 @itemx qTsV
33482 These packets request data about trace state variables that are on the
33483 target. @value{GDBN} sends @code{qTfV} to get the first vari of data,
33484 and multiple @code{qTsV} to get additional variables. Replies to
33485 these packets follow the syntax of the @code{QTDV} packets that define
33486 trace state variables.
33487
33488 @item qTfSTM
33489 @itemx qTsSTM
33490 These packets request data about static tracepoint markers that exist
33491 in the target program. @value{GDBN} sends @code{qTfSTM} to get the
33492 first piece of data, and multiple @code{qTsSTM} to get additional
33493 pieces. Replies to these packets take the following form:
33494
33495 Reply:
33496 @table @samp
33497 @item m @var{address}:@var{id}:@var{extra}
33498 A single marker
33499 @item m @var{address}:@var{id}:@var{extra},@var{address}:@var{id}:@var{extra}@dots{}
33500 a comma-separated list of markers
33501 @item l
33502 (lower case letter @samp{L}) denotes end of list.
33503 @item E @var{nn}
33504 An error occurred. @var{nn} are hex digits.
33505 @item
33506 An empty reply indicates that the request is not supported by the
33507 stub.
33508 @end table
33509
33510 @var{address} is encoded in hex.
33511 @var{id} and @var{extra} are strings encoded in hex.
33512
33513 In response to each query, the target will reply with a list of one or
33514 more markers, separated by commas. @value{GDBN} will respond to each
33515 reply with a request for more markers (using the @samp{qs} form of the
33516 query), until the target responds with @samp{l} (lower-case ell, for
33517 @dfn{last}).
33518
33519 @item qTSTMat:@var{address}
33520 This packets requests data about static tracepoint markers in the
33521 target program at @var{address}. Replies to this packet follow the
33522 syntax of the @samp{qTfSTM} and @code{qTsSTM} packets that list static
33523 tracepoint markers.
33524
33525 @item QTSave:@var{filename}
33526 This packet directs the target to save trace data to the file name
33527 @var{filename} in the target's filesystem. @var{filename} is encoded
33528 as a hex string; the interpretation of the file name (relative vs
33529 absolute, wild cards, etc) is up to the target.
33530
33531 @item qTBuffer:@var{offset},@var{len}
33532 Return up to @var{len} bytes of the current contents of trace buffer,
33533 starting at @var{offset}. The trace buffer is treated as if it were
33534 a contiguous collection of traceframes, as per the trace file format.
33535 The reply consists as many hex-encoded bytes as the target can deliver
33536 in a packet; it is not an error to return fewer than were asked for.
33537 A reply consisting of just @code{l} indicates that no bytes are
33538 available.
33539
33540 @item QTBuffer:circular:@var{value}
33541 This packet directs the target to use a circular trace buffer if
33542 @var{value} is 1, or a linear buffer if the value is 0.
33543
33544 @end table
33545
33546 @subsection Relocate instruction reply packet
33547 When installing fast tracepoints in memory, the target may need to
33548 relocate the instruction currently at the tracepoint address to a
33549 different address in memory. For most instructions, a simple copy is
33550 enough, but, for example, call instructions that implicitly push the
33551 return address on the stack, and relative branches or other
33552 PC-relative instructions require offset adjustment, so that the effect
33553 of executing the instruction at a different address is the same as if
33554 it had executed in the original location.
33555
33556 In response to several of the tracepoint packets, the target may also
33557 respond with a number of intermediate @samp{qRelocInsn} request
33558 packets before the final result packet, to have @value{GDBN} handle
33559 this relocation operation. If a packet supports this mechanism, its
33560 documentation will explicitly say so. See for example the above
33561 descriptions for the @samp{QTStart} and @samp{QTDP} packets. The
33562 format of the request is:
33563
33564 @table @samp
33565 @item qRelocInsn:@var{from};@var{to}
33566
33567 This requests @value{GDBN} to copy instruction at address @var{from}
33568 to address @var{to}, possibly adjusted so that executing the
33569 instruction at @var{to} has the same effect as executing it at
33570 @var{from}. @value{GDBN} writes the adjusted instruction to target
33571 memory starting at @var{to}.
33572 @end table
33573
33574 Replies:
33575 @table @samp
33576 @item qRelocInsn:@var{adjusted_size}
33577 Informs the stub the relocation is complete. @var{adjusted_size} is
33578 the length in bytes of resulting relocated instruction sequence.
33579 @item E @var{NN}
33580 A badly formed request was detected, or an error was encountered while
33581 relocating the instruction.
33582 @end table
33583
33584 @node Host I/O Packets
33585 @section Host I/O Packets
33586 @cindex Host I/O, remote protocol
33587 @cindex file transfer, remote protocol
33588
33589 The @dfn{Host I/O} packets allow @value{GDBN} to perform I/O
33590 operations on the far side of a remote link. For example, Host I/O is
33591 used to upload and download files to a remote target with its own
33592 filesystem. Host I/O uses the same constant values and data structure
33593 layout as the target-initiated File-I/O protocol. However, the
33594 Host I/O packets are structured differently. The target-initiated
33595 protocol relies on target memory to store parameters and buffers.
33596 Host I/O requests are initiated by @value{GDBN}, and the
33597 target's memory is not involved. @xref{File-I/O Remote Protocol
33598 Extension}, for more details on the target-initiated protocol.
33599
33600 The Host I/O request packets all encode a single operation along with
33601 its arguments. They have this format:
33602
33603 @table @samp
33604
33605 @item vFile:@var{operation}: @var{parameter}@dots{}
33606 @var{operation} is the name of the particular request; the target
33607 should compare the entire packet name up to the second colon when checking
33608 for a supported operation. The format of @var{parameter} depends on
33609 the operation. Numbers are always passed in hexadecimal. Negative
33610 numbers have an explicit minus sign (i.e.@: two's complement is not
33611 used). Strings (e.g.@: filenames) are encoded as a series of
33612 hexadecimal bytes. The last argument to a system call may be a
33613 buffer of escaped binary data (@pxref{Binary Data}).
33614
33615 @end table
33616
33617 The valid responses to Host I/O packets are:
33618
33619 @table @samp
33620
33621 @item F @var{result} [, @var{errno}] [; @var{attachment}]
33622 @var{result} is the integer value returned by this operation, usually
33623 non-negative for success and -1 for errors. If an error has occured,
33624 @var{errno} will be included in the result. @var{errno} will have a
33625 value defined by the File-I/O protocol (@pxref{Errno Values}). For
33626 operations which return data, @var{attachment} supplies the data as a
33627 binary buffer. Binary buffers in response packets are escaped in the
33628 normal way (@pxref{Binary Data}). See the individual packet
33629 documentation for the interpretation of @var{result} and
33630 @var{attachment}.
33631
33632 @item
33633 An empty response indicates that this operation is not recognized.
33634
33635 @end table
33636
33637 These are the supported Host I/O operations:
33638
33639 @table @samp
33640 @item vFile:open: @var{pathname}, @var{flags}, @var{mode}
33641 Open a file at @var{pathname} and return a file descriptor for it, or
33642 return -1 if an error occurs. @var{pathname} is a string,
33643 @var{flags} is an integer indicating a mask of open flags
33644 (@pxref{Open Flags}), and @var{mode} is an integer indicating a mask
33645 of mode bits to use if the file is created (@pxref{mode_t Values}).
33646 @xref{open}, for details of the open flags and mode values.
33647
33648 @item vFile:close: @var{fd}
33649 Close the open file corresponding to @var{fd} and return 0, or
33650 -1 if an error occurs.
33651
33652 @item vFile:pread: @var{fd}, @var{count}, @var{offset}
33653 Read data from the open file corresponding to @var{fd}. Up to
33654 @var{count} bytes will be read from the file, starting at @var{offset}
33655 relative to the start of the file. The target may read fewer bytes;
33656 common reasons include packet size limits and an end-of-file
33657 condition. The number of bytes read is returned. Zero should only be
33658 returned for a successful read at the end of the file, or if
33659 @var{count} was zero.
33660
33661 The data read should be returned as a binary attachment on success.
33662 If zero bytes were read, the response should include an empty binary
33663 attachment (i.e.@: a trailing semicolon). The return value is the
33664 number of target bytes read; the binary attachment may be longer if
33665 some characters were escaped.
33666
33667 @item vFile:pwrite: @var{fd}, @var{offset}, @var{data}
33668 Write @var{data} (a binary buffer) to the open file corresponding
33669 to @var{fd}. Start the write at @var{offset} from the start of the
33670 file. Unlike many @code{write} system calls, there is no
33671 separate @var{count} argument; the length of @var{data} in the
33672 packet is used. @samp{vFile:write} returns the number of bytes written,
33673 which may be shorter than the length of @var{data}, or -1 if an
33674 error occurred.
33675
33676 @item vFile:unlink: @var{pathname}
33677 Delete the file at @var{pathname} on the target. Return 0,
33678 or -1 if an error occurs. @var{pathname} is a string.
33679
33680 @end table
33681
33682 @node Interrupts
33683 @section Interrupts
33684 @cindex interrupts (remote protocol)
33685
33686 When a program on the remote target is running, @value{GDBN} may
33687 attempt to interrupt it by sending a @samp{Ctrl-C}, @code{BREAK} or
33688 a @code{BREAK} followed by @code{g},
33689 control of which is specified via @value{GDBN}'s @samp{interrupt-sequence}.
33690
33691 The precise meaning of @code{BREAK} is defined by the transport
33692 mechanism and may, in fact, be undefined. @value{GDBN} does not
33693 currently define a @code{BREAK} mechanism for any of the network
33694 interfaces except for TCP, in which case @value{GDBN} sends the
33695 @code{telnet} BREAK sequence.
33696
33697 @samp{Ctrl-C}, on the other hand, is defined and implemented for all
33698 transport mechanisms. It is represented by sending the single byte
33699 @code{0x03} without any of the usual packet overhead described in
33700 the Overview section (@pxref{Overview}). When a @code{0x03} byte is
33701 transmitted as part of a packet, it is considered to be packet data
33702 and does @emph{not} represent an interrupt. E.g., an @samp{X} packet
33703 (@pxref{X packet}), used for binary downloads, may include an unescaped
33704 @code{0x03} as part of its packet.
33705
33706 @code{BREAK} followed by @code{g} is also known as Magic SysRq g.
33707 When Linux kernel receives this sequence from serial port,
33708 it stops execution and connects to gdb.
33709
33710 Stubs are not required to recognize these interrupt mechanisms and the
33711 precise meaning associated with receipt of the interrupt is
33712 implementation defined. If the target supports debugging of multiple
33713 threads and/or processes, it should attempt to interrupt all
33714 currently-executing threads and processes.
33715 If the stub is successful at interrupting the
33716 running program, it should send one of the stop
33717 reply packets (@pxref{Stop Reply Packets}) to @value{GDBN} as a result
33718 of successfully stopping the program in all-stop mode, and a stop reply
33719 for each stopped thread in non-stop mode.
33720 Interrupts received while the
33721 program is stopped are discarded.
33722
33723 @node Notification Packets
33724 @section Notification Packets
33725 @cindex notification packets
33726 @cindex packets, notification
33727
33728 The @value{GDBN} remote serial protocol includes @dfn{notifications},
33729 packets that require no acknowledgment. Both the GDB and the stub
33730 may send notifications (although the only notifications defined at
33731 present are sent by the stub). Notifications carry information
33732 without incurring the round-trip latency of an acknowledgment, and so
33733 are useful for low-impact communications where occasional packet loss
33734 is not a problem.
33735
33736 A notification packet has the form @samp{% @var{data} #
33737 @var{checksum}}, where @var{data} is the content of the notification,
33738 and @var{checksum} is a checksum of @var{data}, computed and formatted
33739 as for ordinary @value{GDBN} packets. A notification's @var{data}
33740 never contains @samp{$}, @samp{%} or @samp{#} characters. Upon
33741 receiving a notification, the recipient sends no @samp{+} or @samp{-}
33742 to acknowledge the notification's receipt or to report its corruption.
33743
33744 Every notification's @var{data} begins with a name, which contains no
33745 colon characters, followed by a colon character.
33746
33747 Recipients should silently ignore corrupted notifications and
33748 notifications they do not understand. Recipients should restart
33749 timeout periods on receipt of a well-formed notification, whether or
33750 not they understand it.
33751
33752 Senders should only send the notifications described here when this
33753 protocol description specifies that they are permitted. In the
33754 future, we may extend the protocol to permit existing notifications in
33755 new contexts; this rule helps older senders avoid confusing newer
33756 recipients.
33757
33758 (Older versions of @value{GDBN} ignore bytes received until they see
33759 the @samp{$} byte that begins an ordinary packet, so new stubs may
33760 transmit notifications without fear of confusing older clients. There
33761 are no notifications defined for @value{GDBN} to send at the moment, but we
33762 assume that most older stubs would ignore them, as well.)
33763
33764 The following notification packets from the stub to @value{GDBN} are
33765 defined:
33766
33767 @table @samp
33768 @item Stop: @var{reply}
33769 Report an asynchronous stop event in non-stop mode.
33770 The @var{reply} has the form of a stop reply, as
33771 described in @ref{Stop Reply Packets}. Refer to @ref{Remote Non-Stop},
33772 for information on how these notifications are acknowledged by
33773 @value{GDBN}.
33774 @end table
33775
33776 @node Remote Non-Stop
33777 @section Remote Protocol Support for Non-Stop Mode
33778
33779 @value{GDBN}'s remote protocol supports non-stop debugging of
33780 multi-threaded programs, as described in @ref{Non-Stop Mode}. If the stub
33781 supports non-stop mode, it should report that to @value{GDBN} by including
33782 @samp{QNonStop+} in its @samp{qSupported} response (@pxref{qSupported}).
33783
33784 @value{GDBN} typically sends a @samp{QNonStop} packet only when
33785 establishing a new connection with the stub. Entering non-stop mode
33786 does not alter the state of any currently-running threads, but targets
33787 must stop all threads in any already-attached processes when entering
33788 all-stop mode. @value{GDBN} uses the @samp{?} packet as necessary to
33789 probe the target state after a mode change.
33790
33791 In non-stop mode, when an attached process encounters an event that
33792 would otherwise be reported with a stop reply, it uses the
33793 asynchronous notification mechanism (@pxref{Notification Packets}) to
33794 inform @value{GDBN}. In contrast to all-stop mode, where all threads
33795 in all processes are stopped when a stop reply is sent, in non-stop
33796 mode only the thread reporting the stop event is stopped. That is,
33797 when reporting a @samp{S} or @samp{T} response to indicate completion
33798 of a step operation, hitting a breakpoint, or a fault, only the
33799 affected thread is stopped; any other still-running threads continue
33800 to run. When reporting a @samp{W} or @samp{X} response, all running
33801 threads belonging to other attached processes continue to run.
33802
33803 Only one stop reply notification at a time may be pending; if
33804 additional stop events occur before @value{GDBN} has acknowledged the
33805 previous notification, they must be queued by the stub for later
33806 synchronous transmission in response to @samp{vStopped} packets from
33807 @value{GDBN}. Because the notification mechanism is unreliable,
33808 the stub is permitted to resend a stop reply notification
33809 if it believes @value{GDBN} may not have received it. @value{GDBN}
33810 ignores additional stop reply notifications received before it has
33811 finished processing a previous notification and the stub has completed
33812 sending any queued stop events.
33813
33814 Otherwise, @value{GDBN} must be prepared to receive a stop reply
33815 notification at any time. Specifically, they may appear when
33816 @value{GDBN} is not otherwise reading input from the stub, or when
33817 @value{GDBN} is expecting to read a normal synchronous response or a
33818 @samp{+}/@samp{-} acknowledgment to a packet it has sent.
33819 Notification packets are distinct from any other communication from
33820 the stub so there is no ambiguity.
33821
33822 After receiving a stop reply notification, @value{GDBN} shall
33823 acknowledge it by sending a @samp{vStopped} packet (@pxref{vStopped packet})
33824 as a regular, synchronous request to the stub. Such acknowledgment
33825 is not required to happen immediately, as @value{GDBN} is permitted to
33826 send other, unrelated packets to the stub first, which the stub should
33827 process normally.
33828
33829 Upon receiving a @samp{vStopped} packet, if the stub has other queued
33830 stop events to report to @value{GDBN}, it shall respond by sending a
33831 normal stop reply response. @value{GDBN} shall then send another
33832 @samp{vStopped} packet to solicit further responses; again, it is
33833 permitted to send other, unrelated packets as well which the stub
33834 should process normally.
33835
33836 If the stub receives a @samp{vStopped} packet and there are no
33837 additional stop events to report, the stub shall return an @samp{OK}
33838 response. At this point, if further stop events occur, the stub shall
33839 send a new stop reply notification, @value{GDBN} shall accept the
33840 notification, and the process shall be repeated.
33841
33842 In non-stop mode, the target shall respond to the @samp{?} packet as
33843 follows. First, any incomplete stop reply notification/@samp{vStopped}
33844 sequence in progress is abandoned. The target must begin a new
33845 sequence reporting stop events for all stopped threads, whether or not
33846 it has previously reported those events to @value{GDBN}. The first
33847 stop reply is sent as a synchronous reply to the @samp{?} packet, and
33848 subsequent stop replies are sent as responses to @samp{vStopped} packets
33849 using the mechanism described above. The target must not send
33850 asynchronous stop reply notifications until the sequence is complete.
33851 If all threads are running when the target receives the @samp{?} packet,
33852 or if the target is not attached to any process, it shall respond
33853 @samp{OK}.
33854
33855 @node Packet Acknowledgment
33856 @section Packet Acknowledgment
33857
33858 @cindex acknowledgment, for @value{GDBN} remote
33859 @cindex packet acknowledgment, for @value{GDBN} remote
33860 By default, when either the host or the target machine receives a packet,
33861 the first response expected is an acknowledgment: either @samp{+} (to indicate
33862 the package was received correctly) or @samp{-} (to request retransmission).
33863 This mechanism allows the @value{GDBN} remote protocol to operate over
33864 unreliable transport mechanisms, such as a serial line.
33865
33866 In cases where the transport mechanism is itself reliable (such as a pipe or
33867 TCP connection), the @samp{+}/@samp{-} acknowledgments are redundant.
33868 It may be desirable to disable them in that case to reduce communication
33869 overhead, or for other reasons. This can be accomplished by means of the
33870 @samp{QStartNoAckMode} packet; @pxref{QStartNoAckMode}.
33871
33872 When in no-acknowledgment mode, neither the stub nor @value{GDBN} shall send or
33873 expect @samp{+}/@samp{-} protocol acknowledgments. The packet
33874 and response format still includes the normal checksum, as described in
33875 @ref{Overview}, but the checksum may be ignored by the receiver.
33876
33877 If the stub supports @samp{QStartNoAckMode} and prefers to operate in
33878 no-acknowledgment mode, it should report that to @value{GDBN}
33879 by including @samp{QStartNoAckMode+} in its response to @samp{qSupported};
33880 @pxref{qSupported}.
33881 If @value{GDBN} also supports @samp{QStartNoAckMode} and it has not been
33882 disabled via the @code{set remote noack-packet off} command
33883 (@pxref{Remote Configuration}),
33884 @value{GDBN} may then send a @samp{QStartNoAckMode} packet to the stub.
33885 Only then may the stub actually turn off packet acknowledgments.
33886 @value{GDBN} sends a final @samp{+} acknowledgment of the stub's @samp{OK}
33887 response, which can be safely ignored by the stub.
33888
33889 Note that @code{set remote noack-packet} command only affects negotiation
33890 between @value{GDBN} and the stub when subsequent connections are made;
33891 it does not affect the protocol acknowledgment state for any current
33892 connection.
33893 Since @samp{+}/@samp{-} acknowledgments are enabled by default when a
33894 new connection is established,
33895 there is also no protocol request to re-enable the acknowledgments
33896 for the current connection, once disabled.
33897
33898 @node Examples
33899 @section Examples
33900
33901 Example sequence of a target being re-started. Notice how the restart
33902 does not get any direct output:
33903
33904 @smallexample
33905 -> @code{R00}
33906 <- @code{+}
33907 @emph{target restarts}
33908 -> @code{?}
33909 <- @code{+}
33910 <- @code{T001:1234123412341234}
33911 -> @code{+}
33912 @end smallexample
33913
33914 Example sequence of a target being stepped by a single instruction:
33915
33916 @smallexample
33917 -> @code{G1445@dots{}}
33918 <- @code{+}
33919 -> @code{s}
33920 <- @code{+}
33921 @emph{time passes}
33922 <- @code{T001:1234123412341234}
33923 -> @code{+}
33924 -> @code{g}
33925 <- @code{+}
33926 <- @code{1455@dots{}}
33927 -> @code{+}
33928 @end smallexample
33929
33930 @node File-I/O Remote Protocol Extension
33931 @section File-I/O Remote Protocol Extension
33932 @cindex File-I/O remote protocol extension
33933
33934 @menu
33935 * File-I/O Overview::
33936 * Protocol Basics::
33937 * The F Request Packet::
33938 * The F Reply Packet::
33939 * The Ctrl-C Message::
33940 * Console I/O::
33941 * List of Supported Calls::
33942 * Protocol-specific Representation of Datatypes::
33943 * Constants::
33944 * File-I/O Examples::
33945 @end menu
33946
33947 @node File-I/O Overview
33948 @subsection File-I/O Overview
33949 @cindex file-i/o overview
33950
33951 The @dfn{File I/O remote protocol extension} (short: File-I/O) allows the
33952 target to use the host's file system and console I/O to perform various
33953 system calls. System calls on the target system are translated into a
33954 remote protocol packet to the host system, which then performs the needed
33955 actions and returns a response packet to the target system.
33956 This simulates file system operations even on targets that lack file systems.
33957
33958 The protocol is defined to be independent of both the host and target systems.
33959 It uses its own internal representation of datatypes and values. Both
33960 @value{GDBN} and the target's @value{GDBN} stub are responsible for
33961 translating the system-dependent value representations into the internal
33962 protocol representations when data is transmitted.
33963
33964 The communication is synchronous. A system call is possible only when
33965 @value{GDBN} is waiting for a response from the @samp{C}, @samp{c}, @samp{S}
33966 or @samp{s} packets. While @value{GDBN} handles the request for a system call,
33967 the target is stopped to allow deterministic access to the target's
33968 memory. Therefore File-I/O is not interruptible by target signals. On
33969 the other hand, it is possible to interrupt File-I/O by a user interrupt
33970 (@samp{Ctrl-C}) within @value{GDBN}.
33971
33972 The target's request to perform a host system call does not finish
33973 the latest @samp{C}, @samp{c}, @samp{S} or @samp{s} action. That means,
33974 after finishing the system call, the target returns to continuing the
33975 previous activity (continue, step). No additional continue or step
33976 request from @value{GDBN} is required.
33977
33978 @smallexample
33979 (@value{GDBP}) continue
33980 <- target requests 'system call X'
33981 target is stopped, @value{GDBN} executes system call
33982 -> @value{GDBN} returns result
33983 ... target continues, @value{GDBN} returns to wait for the target
33984 <- target hits breakpoint and sends a Txx packet
33985 @end smallexample
33986
33987 The protocol only supports I/O on the console and to regular files on
33988 the host file system. Character or block special devices, pipes,
33989 named pipes, sockets or any other communication method on the host
33990 system are not supported by this protocol.
33991
33992 File I/O is not supported in non-stop mode.
33993
33994 @node Protocol Basics
33995 @subsection Protocol Basics
33996 @cindex protocol basics, file-i/o
33997
33998 The File-I/O protocol uses the @code{F} packet as the request as well
33999 as reply packet. Since a File-I/O system call can only occur when
34000 @value{GDBN} is waiting for a response from the continuing or stepping target,
34001 the File-I/O request is a reply that @value{GDBN} has to expect as a result
34002 of a previous @samp{C}, @samp{c}, @samp{S} or @samp{s} packet.
34003 This @code{F} packet contains all information needed to allow @value{GDBN}
34004 to call the appropriate host system call:
34005
34006 @itemize @bullet
34007 @item
34008 A unique identifier for the requested system call.
34009
34010 @item
34011 All parameters to the system call. Pointers are given as addresses
34012 in the target memory address space. Pointers to strings are given as
34013 pointer/length pair. Numerical values are given as they are.
34014 Numerical control flags are given in a protocol-specific representation.
34015
34016 @end itemize
34017
34018 At this point, @value{GDBN} has to perform the following actions.
34019
34020 @itemize @bullet
34021 @item
34022 If the parameters include pointer values to data needed as input to a
34023 system call, @value{GDBN} requests this data from the target with a
34024 standard @code{m} packet request. This additional communication has to be
34025 expected by the target implementation and is handled as any other @code{m}
34026 packet.
34027
34028 @item
34029 @value{GDBN} translates all value from protocol representation to host
34030 representation as needed. Datatypes are coerced into the host types.
34031
34032 @item
34033 @value{GDBN} calls the system call.
34034
34035 @item
34036 It then coerces datatypes back to protocol representation.
34037
34038 @item
34039 If the system call is expected to return data in buffer space specified
34040 by pointer parameters to the call, the data is transmitted to the
34041 target using a @code{M} or @code{X} packet. This packet has to be expected
34042 by the target implementation and is handled as any other @code{M} or @code{X}
34043 packet.
34044
34045 @end itemize
34046
34047 Eventually @value{GDBN} replies with another @code{F} packet which contains all
34048 necessary information for the target to continue. This at least contains
34049
34050 @itemize @bullet
34051 @item
34052 Return value.
34053
34054 @item
34055 @code{errno}, if has been changed by the system call.
34056
34057 @item
34058 ``Ctrl-C'' flag.
34059
34060 @end itemize
34061
34062 After having done the needed type and value coercion, the target continues
34063 the latest continue or step action.
34064
34065 @node The F Request Packet
34066 @subsection The @code{F} Request Packet
34067 @cindex file-i/o request packet
34068 @cindex @code{F} request packet
34069
34070 The @code{F} request packet has the following format:
34071
34072 @table @samp
34073 @item F@var{call-id},@var{parameter@dots{}}
34074
34075 @var{call-id} is the identifier to indicate the host system call to be called.
34076 This is just the name of the function.
34077
34078 @var{parameter@dots{}} are the parameters to the system call.
34079 Parameters are hexadecimal integer values, either the actual values in case
34080 of scalar datatypes, pointers to target buffer space in case of compound
34081 datatypes and unspecified memory areas, or pointer/length pairs in case
34082 of string parameters. These are appended to the @var{call-id} as a
34083 comma-delimited list. All values are transmitted in ASCII
34084 string representation, pointer/length pairs separated by a slash.
34085
34086 @end table
34087
34088
34089
34090 @node The F Reply Packet
34091 @subsection The @code{F} Reply Packet
34092 @cindex file-i/o reply packet
34093 @cindex @code{F} reply packet
34094
34095 The @code{F} reply packet has the following format:
34096
34097 @table @samp
34098
34099 @item F@var{retcode},@var{errno},@var{Ctrl-C flag};@var{call-specific attachment}
34100
34101 @var{retcode} is the return code of the system call as hexadecimal value.
34102
34103 @var{errno} is the @code{errno} set by the call, in protocol-specific
34104 representation.
34105 This parameter can be omitted if the call was successful.
34106
34107 @var{Ctrl-C flag} is only sent if the user requested a break. In this
34108 case, @var{errno} must be sent as well, even if the call was successful.
34109 The @var{Ctrl-C flag} itself consists of the character @samp{C}:
34110
34111 @smallexample
34112 F0,0,C
34113 @end smallexample
34114
34115 @noindent
34116 or, if the call was interrupted before the host call has been performed:
34117
34118 @smallexample
34119 F-1,4,C
34120 @end smallexample
34121
34122 @noindent
34123 assuming 4 is the protocol-specific representation of @code{EINTR}.
34124
34125 @end table
34126
34127
34128 @node The Ctrl-C Message
34129 @subsection The @samp{Ctrl-C} Message
34130 @cindex ctrl-c message, in file-i/o protocol
34131
34132 If the @samp{Ctrl-C} flag is set in the @value{GDBN}
34133 reply packet (@pxref{The F Reply Packet}),
34134 the target should behave as if it had
34135 gotten a break message. The meaning for the target is ``system call
34136 interrupted by @code{SIGINT}''. Consequentially, the target should actually stop
34137 (as with a break message) and return to @value{GDBN} with a @code{T02}
34138 packet.
34139
34140 It's important for the target to know in which
34141 state the system call was interrupted. There are two possible cases:
34142
34143 @itemize @bullet
34144 @item
34145 The system call hasn't been performed on the host yet.
34146
34147 @item
34148 The system call on the host has been finished.
34149
34150 @end itemize
34151
34152 These two states can be distinguished by the target by the value of the
34153 returned @code{errno}. If it's the protocol representation of @code{EINTR}, the system
34154 call hasn't been performed. This is equivalent to the @code{EINTR} handling
34155 on POSIX systems. In any other case, the target may presume that the
34156 system call has been finished --- successfully or not --- and should behave
34157 as if the break message arrived right after the system call.
34158
34159 @value{GDBN} must behave reliably. If the system call has not been called
34160 yet, @value{GDBN} may send the @code{F} reply immediately, setting @code{EINTR} as
34161 @code{errno} in the packet. If the system call on the host has been finished
34162 before the user requests a break, the full action must be finished by
34163 @value{GDBN}. This requires sending @code{M} or @code{X} packets as necessary.
34164 The @code{F} packet may only be sent when either nothing has happened
34165 or the full action has been completed.
34166
34167 @node Console I/O
34168 @subsection Console I/O
34169 @cindex console i/o as part of file-i/o
34170
34171 By default and if not explicitly closed by the target system, the file
34172 descriptors 0, 1 and 2 are connected to the @value{GDBN} console. Output
34173 on the @value{GDBN} console is handled as any other file output operation
34174 (@code{write(1, @dots{})} or @code{write(2, @dots{})}). Console input is handled
34175 by @value{GDBN} so that after the target read request from file descriptor
34176 0 all following typing is buffered until either one of the following
34177 conditions is met:
34178
34179 @itemize @bullet
34180 @item
34181 The user types @kbd{Ctrl-c}. The behaviour is as explained above, and the
34182 @code{read}
34183 system call is treated as finished.
34184
34185 @item
34186 The user presses @key{RET}. This is treated as end of input with a trailing
34187 newline.
34188
34189 @item
34190 The user types @kbd{Ctrl-d}. This is treated as end of input. No trailing
34191 character (neither newline nor @samp{Ctrl-D}) is appended to the input.
34192
34193 @end itemize
34194
34195 If the user has typed more characters than fit in the buffer given to
34196 the @code{read} call, the trailing characters are buffered in @value{GDBN} until
34197 either another @code{read(0, @dots{})} is requested by the target, or debugging
34198 is stopped at the user's request.
34199
34200
34201 @node List of Supported Calls
34202 @subsection List of Supported Calls
34203 @cindex list of supported file-i/o calls
34204
34205 @menu
34206 * open::
34207 * close::
34208 * read::
34209 * write::
34210 * lseek::
34211 * rename::
34212 * unlink::
34213 * stat/fstat::
34214 * gettimeofday::
34215 * isatty::
34216 * system::
34217 @end menu
34218
34219 @node open
34220 @unnumberedsubsubsec open
34221 @cindex open, file-i/o system call
34222
34223 @table @asis
34224 @item Synopsis:
34225 @smallexample
34226 int open(const char *pathname, int flags);
34227 int open(const char *pathname, int flags, mode_t mode);
34228 @end smallexample
34229
34230 @item Request:
34231 @samp{Fopen,@var{pathptr}/@var{len},@var{flags},@var{mode}}
34232
34233 @noindent
34234 @var{flags} is the bitwise @code{OR} of the following values:
34235
34236 @table @code
34237 @item O_CREAT
34238 If the file does not exist it will be created. The host
34239 rules apply as far as file ownership and time stamps
34240 are concerned.
34241
34242 @item O_EXCL
34243 When used with @code{O_CREAT}, if the file already exists it is
34244 an error and open() fails.
34245
34246 @item O_TRUNC
34247 If the file already exists and the open mode allows
34248 writing (@code{O_RDWR} or @code{O_WRONLY} is given) it will be
34249 truncated to zero length.
34250
34251 @item O_APPEND
34252 The file is opened in append mode.
34253
34254 @item O_RDONLY
34255 The file is opened for reading only.
34256
34257 @item O_WRONLY
34258 The file is opened for writing only.
34259
34260 @item O_RDWR
34261 The file is opened for reading and writing.
34262 @end table
34263
34264 @noindent
34265 Other bits are silently ignored.
34266
34267
34268 @noindent
34269 @var{mode} is the bitwise @code{OR} of the following values:
34270
34271 @table @code
34272 @item S_IRUSR
34273 User has read permission.
34274
34275 @item S_IWUSR
34276 User has write permission.
34277
34278 @item S_IRGRP
34279 Group has read permission.
34280
34281 @item S_IWGRP
34282 Group has write permission.
34283
34284 @item S_IROTH
34285 Others have read permission.
34286
34287 @item S_IWOTH
34288 Others have write permission.
34289 @end table
34290
34291 @noindent
34292 Other bits are silently ignored.
34293
34294
34295 @item Return value:
34296 @code{open} returns the new file descriptor or -1 if an error
34297 occurred.
34298
34299 @item Errors:
34300
34301 @table @code
34302 @item EEXIST
34303 @var{pathname} already exists and @code{O_CREAT} and @code{O_EXCL} were used.
34304
34305 @item EISDIR
34306 @var{pathname} refers to a directory.
34307
34308 @item EACCES
34309 The requested access is not allowed.
34310
34311 @item ENAMETOOLONG
34312 @var{pathname} was too long.
34313
34314 @item ENOENT
34315 A directory component in @var{pathname} does not exist.
34316
34317 @item ENODEV
34318 @var{pathname} refers to a device, pipe, named pipe or socket.
34319
34320 @item EROFS
34321 @var{pathname} refers to a file on a read-only filesystem and
34322 write access was requested.
34323
34324 @item EFAULT
34325 @var{pathname} is an invalid pointer value.
34326
34327 @item ENOSPC
34328 No space on device to create the file.
34329
34330 @item EMFILE
34331 The process already has the maximum number of files open.
34332
34333 @item ENFILE
34334 The limit on the total number of files open on the system
34335 has been reached.
34336
34337 @item EINTR
34338 The call was interrupted by the user.
34339 @end table
34340
34341 @end table
34342
34343 @node close
34344 @unnumberedsubsubsec close
34345 @cindex close, file-i/o system call
34346
34347 @table @asis
34348 @item Synopsis:
34349 @smallexample
34350 int close(int fd);
34351 @end smallexample
34352
34353 @item Request:
34354 @samp{Fclose,@var{fd}}
34355
34356 @item Return value:
34357 @code{close} returns zero on success, or -1 if an error occurred.
34358
34359 @item Errors:
34360
34361 @table @code
34362 @item EBADF
34363 @var{fd} isn't a valid open file descriptor.
34364
34365 @item EINTR
34366 The call was interrupted by the user.
34367 @end table
34368
34369 @end table
34370
34371 @node read
34372 @unnumberedsubsubsec read
34373 @cindex read, file-i/o system call
34374
34375 @table @asis
34376 @item Synopsis:
34377 @smallexample
34378 int read(int fd, void *buf, unsigned int count);
34379 @end smallexample
34380
34381 @item Request:
34382 @samp{Fread,@var{fd},@var{bufptr},@var{count}}
34383
34384 @item Return value:
34385 On success, the number of bytes read is returned.
34386 Zero indicates end of file. If count is zero, read
34387 returns zero as well. On error, -1 is returned.
34388
34389 @item Errors:
34390
34391 @table @code
34392 @item EBADF
34393 @var{fd} is not a valid file descriptor or is not open for
34394 reading.
34395
34396 @item EFAULT
34397 @var{bufptr} is an invalid pointer value.
34398
34399 @item EINTR
34400 The call was interrupted by the user.
34401 @end table
34402
34403 @end table
34404
34405 @node write
34406 @unnumberedsubsubsec write
34407 @cindex write, file-i/o system call
34408
34409 @table @asis
34410 @item Synopsis:
34411 @smallexample
34412 int write(int fd, const void *buf, unsigned int count);
34413 @end smallexample
34414
34415 @item Request:
34416 @samp{Fwrite,@var{fd},@var{bufptr},@var{count}}
34417
34418 @item Return value:
34419 On success, the number of bytes written are returned.
34420 Zero indicates nothing was written. On error, -1
34421 is returned.
34422
34423 @item Errors:
34424
34425 @table @code
34426 @item EBADF
34427 @var{fd} is not a valid file descriptor or is not open for
34428 writing.
34429
34430 @item EFAULT
34431 @var{bufptr} is an invalid pointer value.
34432
34433 @item EFBIG
34434 An attempt was made to write a file that exceeds the
34435 host-specific maximum file size allowed.
34436
34437 @item ENOSPC
34438 No space on device to write the data.
34439
34440 @item EINTR
34441 The call was interrupted by the user.
34442 @end table
34443
34444 @end table
34445
34446 @node lseek
34447 @unnumberedsubsubsec lseek
34448 @cindex lseek, file-i/o system call
34449
34450 @table @asis
34451 @item Synopsis:
34452 @smallexample
34453 long lseek (int fd, long offset, int flag);
34454 @end smallexample
34455
34456 @item Request:
34457 @samp{Flseek,@var{fd},@var{offset},@var{flag}}
34458
34459 @var{flag} is one of:
34460
34461 @table @code
34462 @item SEEK_SET
34463 The offset is set to @var{offset} bytes.
34464
34465 @item SEEK_CUR
34466 The offset is set to its current location plus @var{offset}
34467 bytes.
34468
34469 @item SEEK_END
34470 The offset is set to the size of the file plus @var{offset}
34471 bytes.
34472 @end table
34473
34474 @item Return value:
34475 On success, the resulting unsigned offset in bytes from
34476 the beginning of the file is returned. Otherwise, a
34477 value of -1 is returned.
34478
34479 @item Errors:
34480
34481 @table @code
34482 @item EBADF
34483 @var{fd} is not a valid open file descriptor.
34484
34485 @item ESPIPE
34486 @var{fd} is associated with the @value{GDBN} console.
34487
34488 @item EINVAL
34489 @var{flag} is not a proper value.
34490
34491 @item EINTR
34492 The call was interrupted by the user.
34493 @end table
34494
34495 @end table
34496
34497 @node rename
34498 @unnumberedsubsubsec rename
34499 @cindex rename, file-i/o system call
34500
34501 @table @asis
34502 @item Synopsis:
34503 @smallexample
34504 int rename(const char *oldpath, const char *newpath);
34505 @end smallexample
34506
34507 @item Request:
34508 @samp{Frename,@var{oldpathptr}/@var{len},@var{newpathptr}/@var{len}}
34509
34510 @item Return value:
34511 On success, zero is returned. On error, -1 is returned.
34512
34513 @item Errors:
34514
34515 @table @code
34516 @item EISDIR
34517 @var{newpath} is an existing directory, but @var{oldpath} is not a
34518 directory.
34519
34520 @item EEXIST
34521 @var{newpath} is a non-empty directory.
34522
34523 @item EBUSY
34524 @var{oldpath} or @var{newpath} is a directory that is in use by some
34525 process.
34526
34527 @item EINVAL
34528 An attempt was made to make a directory a subdirectory
34529 of itself.
34530
34531 @item ENOTDIR
34532 A component used as a directory in @var{oldpath} or new
34533 path is not a directory. Or @var{oldpath} is a directory
34534 and @var{newpath} exists but is not a directory.
34535
34536 @item EFAULT
34537 @var{oldpathptr} or @var{newpathptr} are invalid pointer values.
34538
34539 @item EACCES
34540 No access to the file or the path of the file.
34541
34542 @item ENAMETOOLONG
34543
34544 @var{oldpath} or @var{newpath} was too long.
34545
34546 @item ENOENT
34547 A directory component in @var{oldpath} or @var{newpath} does not exist.
34548
34549 @item EROFS
34550 The file is on a read-only filesystem.
34551
34552 @item ENOSPC
34553 The device containing the file has no room for the new
34554 directory entry.
34555
34556 @item EINTR
34557 The call was interrupted by the user.
34558 @end table
34559
34560 @end table
34561
34562 @node unlink
34563 @unnumberedsubsubsec unlink
34564 @cindex unlink, file-i/o system call
34565
34566 @table @asis
34567 @item Synopsis:
34568 @smallexample
34569 int unlink(const char *pathname);
34570 @end smallexample
34571
34572 @item Request:
34573 @samp{Funlink,@var{pathnameptr}/@var{len}}
34574
34575 @item Return value:
34576 On success, zero is returned. On error, -1 is returned.
34577
34578 @item Errors:
34579
34580 @table @code
34581 @item EACCES
34582 No access to the file or the path of the file.
34583
34584 @item EPERM
34585 The system does not allow unlinking of directories.
34586
34587 @item EBUSY
34588 The file @var{pathname} cannot be unlinked because it's
34589 being used by another process.
34590
34591 @item EFAULT
34592 @var{pathnameptr} is an invalid pointer value.
34593
34594 @item ENAMETOOLONG
34595 @var{pathname} was too long.
34596
34597 @item ENOENT
34598 A directory component in @var{pathname} does not exist.
34599
34600 @item ENOTDIR
34601 A component of the path is not a directory.
34602
34603 @item EROFS
34604 The file is on a read-only filesystem.
34605
34606 @item EINTR
34607 The call was interrupted by the user.
34608 @end table
34609
34610 @end table
34611
34612 @node stat/fstat
34613 @unnumberedsubsubsec stat/fstat
34614 @cindex fstat, file-i/o system call
34615 @cindex stat, file-i/o system call
34616
34617 @table @asis
34618 @item Synopsis:
34619 @smallexample
34620 int stat(const char *pathname, struct stat *buf);
34621 int fstat(int fd, struct stat *buf);
34622 @end smallexample
34623
34624 @item Request:
34625 @samp{Fstat,@var{pathnameptr}/@var{len},@var{bufptr}}@*
34626 @samp{Ffstat,@var{fd},@var{bufptr}}
34627
34628 @item Return value:
34629 On success, zero is returned. On error, -1 is returned.
34630
34631 @item Errors:
34632
34633 @table @code
34634 @item EBADF
34635 @var{fd} is not a valid open file.
34636
34637 @item ENOENT
34638 A directory component in @var{pathname} does not exist or the
34639 path is an empty string.
34640
34641 @item ENOTDIR
34642 A component of the path is not a directory.
34643
34644 @item EFAULT
34645 @var{pathnameptr} is an invalid pointer value.
34646
34647 @item EACCES
34648 No access to the file or the path of the file.
34649
34650 @item ENAMETOOLONG
34651 @var{pathname} was too long.
34652
34653 @item EINTR
34654 The call was interrupted by the user.
34655 @end table
34656
34657 @end table
34658
34659 @node gettimeofday
34660 @unnumberedsubsubsec gettimeofday
34661 @cindex gettimeofday, file-i/o system call
34662
34663 @table @asis
34664 @item Synopsis:
34665 @smallexample
34666 int gettimeofday(struct timeval *tv, void *tz);
34667 @end smallexample
34668
34669 @item Request:
34670 @samp{Fgettimeofday,@var{tvptr},@var{tzptr}}
34671
34672 @item Return value:
34673 On success, 0 is returned, -1 otherwise.
34674
34675 @item Errors:
34676
34677 @table @code
34678 @item EINVAL
34679 @var{tz} is a non-NULL pointer.
34680
34681 @item EFAULT
34682 @var{tvptr} and/or @var{tzptr} is an invalid pointer value.
34683 @end table
34684
34685 @end table
34686
34687 @node isatty
34688 @unnumberedsubsubsec isatty
34689 @cindex isatty, file-i/o system call
34690
34691 @table @asis
34692 @item Synopsis:
34693 @smallexample
34694 int isatty(int fd);
34695 @end smallexample
34696
34697 @item Request:
34698 @samp{Fisatty,@var{fd}}
34699
34700 @item Return value:
34701 Returns 1 if @var{fd} refers to the @value{GDBN} console, 0 otherwise.
34702
34703 @item Errors:
34704
34705 @table @code
34706 @item EINTR
34707 The call was interrupted by the user.
34708 @end table
34709
34710 @end table
34711
34712 Note that the @code{isatty} call is treated as a special case: it returns
34713 1 to the target if the file descriptor is attached
34714 to the @value{GDBN} console, 0 otherwise. Implementing through system calls
34715 would require implementing @code{ioctl} and would be more complex than
34716 needed.
34717
34718
34719 @node system
34720 @unnumberedsubsubsec system
34721 @cindex system, file-i/o system call
34722
34723 @table @asis
34724 @item Synopsis:
34725 @smallexample
34726 int system(const char *command);
34727 @end smallexample
34728
34729 @item Request:
34730 @samp{Fsystem,@var{commandptr}/@var{len}}
34731
34732 @item Return value:
34733 If @var{len} is zero, the return value indicates whether a shell is
34734 available. A zero return value indicates a shell is not available.
34735 For non-zero @var{len}, the value returned is -1 on error and the
34736 return status of the command otherwise. Only the exit status of the
34737 command is returned, which is extracted from the host's @code{system}
34738 return value by calling @code{WEXITSTATUS(retval)}. In case
34739 @file{/bin/sh} could not be executed, 127 is returned.
34740
34741 @item Errors:
34742
34743 @table @code
34744 @item EINTR
34745 The call was interrupted by the user.
34746 @end table
34747
34748 @end table
34749
34750 @value{GDBN} takes over the full task of calling the necessary host calls
34751 to perform the @code{system} call. The return value of @code{system} on
34752 the host is simplified before it's returned
34753 to the target. Any termination signal information from the child process
34754 is discarded, and the return value consists
34755 entirely of the exit status of the called command.
34756
34757 Due to security concerns, the @code{system} call is by default refused
34758 by @value{GDBN}. The user has to allow this call explicitly with the
34759 @code{set remote system-call-allowed 1} command.
34760
34761 @table @code
34762 @item set remote system-call-allowed
34763 @kindex set remote system-call-allowed
34764 Control whether to allow the @code{system} calls in the File I/O
34765 protocol for the remote target. The default is zero (disabled).
34766
34767 @item show remote system-call-allowed
34768 @kindex show remote system-call-allowed
34769 Show whether the @code{system} calls are allowed in the File I/O
34770 protocol.
34771 @end table
34772
34773 @node Protocol-specific Representation of Datatypes
34774 @subsection Protocol-specific Representation of Datatypes
34775 @cindex protocol-specific representation of datatypes, in file-i/o protocol
34776
34777 @menu
34778 * Integral Datatypes::
34779 * Pointer Values::
34780 * Memory Transfer::
34781 * struct stat::
34782 * struct timeval::
34783 @end menu
34784
34785 @node Integral Datatypes
34786 @unnumberedsubsubsec Integral Datatypes
34787 @cindex integral datatypes, in file-i/o protocol
34788
34789 The integral datatypes used in the system calls are @code{int},
34790 @code{unsigned int}, @code{long}, @code{unsigned long},
34791 @code{mode_t}, and @code{time_t}.
34792
34793 @code{int}, @code{unsigned int}, @code{mode_t} and @code{time_t} are
34794 implemented as 32 bit values in this protocol.
34795
34796 @code{long} and @code{unsigned long} are implemented as 64 bit types.
34797
34798 @xref{Limits}, for corresponding MIN and MAX values (similar to those
34799 in @file{limits.h}) to allow range checking on host and target.
34800
34801 @code{time_t} datatypes are defined as seconds since the Epoch.
34802
34803 All integral datatypes transferred as part of a memory read or write of a
34804 structured datatype e.g.@: a @code{struct stat} have to be given in big endian
34805 byte order.
34806
34807 @node Pointer Values
34808 @unnumberedsubsubsec Pointer Values
34809 @cindex pointer values, in file-i/o protocol
34810
34811 Pointers to target data are transmitted as they are. An exception
34812 is made for pointers to buffers for which the length isn't
34813 transmitted as part of the function call, namely strings. Strings
34814 are transmitted as a pointer/length pair, both as hex values, e.g.@:
34815
34816 @smallexample
34817 @code{1aaf/12}
34818 @end smallexample
34819
34820 @noindent
34821 which is a pointer to data of length 18 bytes at position 0x1aaf.
34822 The length is defined as the full string length in bytes, including
34823 the trailing null byte. For example, the string @code{"hello world"}
34824 at address 0x123456 is transmitted as
34825
34826 @smallexample
34827 @code{123456/d}
34828 @end smallexample
34829
34830 @node Memory Transfer
34831 @unnumberedsubsubsec Memory Transfer
34832 @cindex memory transfer, in file-i/o protocol
34833
34834 Structured data which is transferred using a memory read or write (for
34835 example, a @code{struct stat}) is expected to be in a protocol-specific format
34836 with all scalar multibyte datatypes being big endian. Translation to
34837 this representation needs to be done both by the target before the @code{F}
34838 packet is sent, and by @value{GDBN} before
34839 it transfers memory to the target. Transferred pointers to structured
34840 data should point to the already-coerced data at any time.
34841
34842
34843 @node struct stat
34844 @unnumberedsubsubsec struct stat
34845 @cindex struct stat, in file-i/o protocol
34846
34847 The buffer of type @code{struct stat} used by the target and @value{GDBN}
34848 is defined as follows:
34849
34850 @smallexample
34851 struct stat @{
34852 unsigned int st_dev; /* device */
34853 unsigned int st_ino; /* inode */
34854 mode_t st_mode; /* protection */
34855 unsigned int st_nlink; /* number of hard links */
34856 unsigned int st_uid; /* user ID of owner */
34857 unsigned int st_gid; /* group ID of owner */
34858 unsigned int st_rdev; /* device type (if inode device) */
34859 unsigned long st_size; /* total size, in bytes */
34860 unsigned long st_blksize; /* blocksize for filesystem I/O */
34861 unsigned long st_blocks; /* number of blocks allocated */
34862 time_t st_atime; /* time of last access */
34863 time_t st_mtime; /* time of last modification */
34864 time_t st_ctime; /* time of last change */
34865 @};
34866 @end smallexample
34867
34868 The integral datatypes conform to the definitions given in the
34869 appropriate section (see @ref{Integral Datatypes}, for details) so this
34870 structure is of size 64 bytes.
34871
34872 The values of several fields have a restricted meaning and/or
34873 range of values.
34874
34875 @table @code
34876
34877 @item st_dev
34878 A value of 0 represents a file, 1 the console.
34879
34880 @item st_ino
34881 No valid meaning for the target. Transmitted unchanged.
34882
34883 @item st_mode
34884 Valid mode bits are described in @ref{Constants}. Any other
34885 bits have currently no meaning for the target.
34886
34887 @item st_uid
34888 @itemx st_gid
34889 @itemx st_rdev
34890 No valid meaning for the target. Transmitted unchanged.
34891
34892 @item st_atime
34893 @itemx st_mtime
34894 @itemx st_ctime
34895 These values have a host and file system dependent
34896 accuracy. Especially on Windows hosts, the file system may not
34897 support exact timing values.
34898 @end table
34899
34900 The target gets a @code{struct stat} of the above representation and is
34901 responsible for coercing it to the target representation before
34902 continuing.
34903
34904 Note that due to size differences between the host, target, and protocol
34905 representations of @code{struct stat} members, these members could eventually
34906 get truncated on the target.
34907
34908 @node struct timeval
34909 @unnumberedsubsubsec struct timeval
34910 @cindex struct timeval, in file-i/o protocol
34911
34912 The buffer of type @code{struct timeval} used by the File-I/O protocol
34913 is defined as follows:
34914
34915 @smallexample
34916 struct timeval @{
34917 time_t tv_sec; /* second */
34918 long tv_usec; /* microsecond */
34919 @};
34920 @end smallexample
34921
34922 The integral datatypes conform to the definitions given in the
34923 appropriate section (see @ref{Integral Datatypes}, for details) so this
34924 structure is of size 8 bytes.
34925
34926 @node Constants
34927 @subsection Constants
34928 @cindex constants, in file-i/o protocol
34929
34930 The following values are used for the constants inside of the
34931 protocol. @value{GDBN} and target are responsible for translating these
34932 values before and after the call as needed.
34933
34934 @menu
34935 * Open Flags::
34936 * mode_t Values::
34937 * Errno Values::
34938 * Lseek Flags::
34939 * Limits::
34940 @end menu
34941
34942 @node Open Flags
34943 @unnumberedsubsubsec Open Flags
34944 @cindex open flags, in file-i/o protocol
34945
34946 All values are given in hexadecimal representation.
34947
34948 @smallexample
34949 O_RDONLY 0x0
34950 O_WRONLY 0x1
34951 O_RDWR 0x2
34952 O_APPEND 0x8
34953 O_CREAT 0x200
34954 O_TRUNC 0x400
34955 O_EXCL 0x800
34956 @end smallexample
34957
34958 @node mode_t Values
34959 @unnumberedsubsubsec mode_t Values
34960 @cindex mode_t values, in file-i/o protocol
34961
34962 All values are given in octal representation.
34963
34964 @smallexample
34965 S_IFREG 0100000
34966 S_IFDIR 040000
34967 S_IRUSR 0400
34968 S_IWUSR 0200
34969 S_IXUSR 0100
34970 S_IRGRP 040
34971 S_IWGRP 020
34972 S_IXGRP 010
34973 S_IROTH 04
34974 S_IWOTH 02
34975 S_IXOTH 01
34976 @end smallexample
34977
34978 @node Errno Values
34979 @unnumberedsubsubsec Errno Values
34980 @cindex errno values, in file-i/o protocol
34981
34982 All values are given in decimal representation.
34983
34984 @smallexample
34985 EPERM 1
34986 ENOENT 2
34987 EINTR 4
34988 EBADF 9
34989 EACCES 13
34990 EFAULT 14
34991 EBUSY 16
34992 EEXIST 17
34993 ENODEV 19
34994 ENOTDIR 20
34995 EISDIR 21
34996 EINVAL 22
34997 ENFILE 23
34998 EMFILE 24
34999 EFBIG 27
35000 ENOSPC 28
35001 ESPIPE 29
35002 EROFS 30
35003 ENAMETOOLONG 91
35004 EUNKNOWN 9999
35005 @end smallexample
35006
35007 @code{EUNKNOWN} is used as a fallback error value if a host system returns
35008 any error value not in the list of supported error numbers.
35009
35010 @node Lseek Flags
35011 @unnumberedsubsubsec Lseek Flags
35012 @cindex lseek flags, in file-i/o protocol
35013
35014 @smallexample
35015 SEEK_SET 0
35016 SEEK_CUR 1
35017 SEEK_END 2
35018 @end smallexample
35019
35020 @node Limits
35021 @unnumberedsubsubsec Limits
35022 @cindex limits, in file-i/o protocol
35023
35024 All values are given in decimal representation.
35025
35026 @smallexample
35027 INT_MIN -2147483648
35028 INT_MAX 2147483647
35029 UINT_MAX 4294967295
35030 LONG_MIN -9223372036854775808
35031 LONG_MAX 9223372036854775807
35032 ULONG_MAX 18446744073709551615
35033 @end smallexample
35034
35035 @node File-I/O Examples
35036 @subsection File-I/O Examples
35037 @cindex file-i/o examples
35038
35039 Example sequence of a write call, file descriptor 3, buffer is at target
35040 address 0x1234, 6 bytes should be written:
35041
35042 @smallexample
35043 <- @code{Fwrite,3,1234,6}
35044 @emph{request memory read from target}
35045 -> @code{m1234,6}
35046 <- XXXXXX
35047 @emph{return "6 bytes written"}
35048 -> @code{F6}
35049 @end smallexample
35050
35051 Example sequence of a read call, file descriptor 3, buffer is at target
35052 address 0x1234, 6 bytes should be read:
35053
35054 @smallexample
35055 <- @code{Fread,3,1234,6}
35056 @emph{request memory write to target}
35057 -> @code{X1234,6:XXXXXX}
35058 @emph{return "6 bytes read"}
35059 -> @code{F6}
35060 @end smallexample
35061
35062 Example sequence of a read call, call fails on the host due to invalid
35063 file descriptor (@code{EBADF}):
35064
35065 @smallexample
35066 <- @code{Fread,3,1234,6}
35067 -> @code{F-1,9}
35068 @end smallexample
35069
35070 Example sequence of a read call, user presses @kbd{Ctrl-c} before syscall on
35071 host is called:
35072
35073 @smallexample
35074 <- @code{Fread,3,1234,6}
35075 -> @code{F-1,4,C}
35076 <- @code{T02}
35077 @end smallexample
35078
35079 Example sequence of a read call, user presses @kbd{Ctrl-c} after syscall on
35080 host is called:
35081
35082 @smallexample
35083 <- @code{Fread,3,1234,6}
35084 -> @code{X1234,6:XXXXXX}
35085 <- @code{T02}
35086 @end smallexample
35087
35088 @node Library List Format
35089 @section Library List Format
35090 @cindex library list format, remote protocol
35091
35092 On some platforms, a dynamic loader (e.g.@: @file{ld.so}) runs in the
35093 same process as your application to manage libraries. In this case,
35094 @value{GDBN} can use the loader's symbol table and normal memory
35095 operations to maintain a list of shared libraries. On other
35096 platforms, the operating system manages loaded libraries.
35097 @value{GDBN} can not retrieve the list of currently loaded libraries
35098 through memory operations, so it uses the @samp{qXfer:libraries:read}
35099 packet (@pxref{qXfer library list read}) instead. The remote stub
35100 queries the target's operating system and reports which libraries
35101 are loaded.
35102
35103 The @samp{qXfer:libraries:read} packet returns an XML document which
35104 lists loaded libraries and their offsets. Each library has an
35105 associated name and one or more segment or section base addresses,
35106 which report where the library was loaded in memory.
35107
35108 For the common case of libraries that are fully linked binaries, the
35109 library should have a list of segments. If the target supports
35110 dynamic linking of a relocatable object file, its library XML element
35111 should instead include a list of allocated sections. The segment or
35112 section bases are start addresses, not relocation offsets; they do not
35113 depend on the library's link-time base addresses.
35114
35115 @value{GDBN} must be linked with the Expat library to support XML
35116 library lists. @xref{Expat}.
35117
35118 A simple memory map, with one loaded library relocated by a single
35119 offset, looks like this:
35120
35121 @smallexample
35122 <library-list>
35123 <library name="/lib/libc.so.6">
35124 <segment address="0x10000000"/>
35125 </library>
35126 </library-list>
35127 @end smallexample
35128
35129 Another simple memory map, with one loaded library with three
35130 allocated sections (.text, .data, .bss), looks like this:
35131
35132 @smallexample
35133 <library-list>
35134 <library name="sharedlib.o">
35135 <section address="0x10000000"/>
35136 <section address="0x20000000"/>
35137 <section address="0x30000000"/>
35138 </library>
35139 </library-list>
35140 @end smallexample
35141
35142 The format of a library list is described by this DTD:
35143
35144 @smallexample
35145 <!-- library-list: Root element with versioning -->
35146 <!ELEMENT library-list (library)*>
35147 <!ATTLIST library-list version CDATA #FIXED "1.0">
35148 <!ELEMENT library (segment*, section*)>
35149 <!ATTLIST library name CDATA #REQUIRED>
35150 <!ELEMENT segment EMPTY>
35151 <!ATTLIST segment address CDATA #REQUIRED>
35152 <!ELEMENT section EMPTY>
35153 <!ATTLIST section address CDATA #REQUIRED>
35154 @end smallexample
35155
35156 In addition, segments and section descriptors cannot be mixed within a
35157 single library element, and you must supply at least one segment or
35158 section for each library.
35159
35160 @node Memory Map Format
35161 @section Memory Map Format
35162 @cindex memory map format
35163
35164 To be able to write into flash memory, @value{GDBN} needs to obtain a
35165 memory map from the target. This section describes the format of the
35166 memory map.
35167
35168 The memory map is obtained using the @samp{qXfer:memory-map:read}
35169 (@pxref{qXfer memory map read}) packet and is an XML document that
35170 lists memory regions.
35171
35172 @value{GDBN} must be linked with the Expat library to support XML
35173 memory maps. @xref{Expat}.
35174
35175 The top-level structure of the document is shown below:
35176
35177 @smallexample
35178 <?xml version="1.0"?>
35179 <!DOCTYPE memory-map
35180 PUBLIC "+//IDN gnu.org//DTD GDB Memory Map V1.0//EN"
35181 "http://sourceware.org/gdb/gdb-memory-map.dtd">
35182 <memory-map>
35183 region...
35184 </memory-map>
35185 @end smallexample
35186
35187 Each region can be either:
35188
35189 @itemize
35190
35191 @item
35192 A region of RAM starting at @var{addr} and extending for @var{length}
35193 bytes from there:
35194
35195 @smallexample
35196 <memory type="ram" start="@var{addr}" length="@var{length}"/>
35197 @end smallexample
35198
35199
35200 @item
35201 A region of read-only memory:
35202
35203 @smallexample
35204 <memory type="rom" start="@var{addr}" length="@var{length}"/>
35205 @end smallexample
35206
35207
35208 @item
35209 A region of flash memory, with erasure blocks @var{blocksize}
35210 bytes in length:
35211
35212 @smallexample
35213 <memory type="flash" start="@var{addr}" length="@var{length}">
35214 <property name="blocksize">@var{blocksize}</property>
35215 </memory>
35216 @end smallexample
35217
35218 @end itemize
35219
35220 Regions must not overlap. @value{GDBN} assumes that areas of memory not covered
35221 by the memory map are RAM, and uses the ordinary @samp{M} and @samp{X}
35222 packets to write to addresses in such ranges.
35223
35224 The formal DTD for memory map format is given below:
35225
35226 @smallexample
35227 <!-- ................................................... -->
35228 <!-- Memory Map XML DTD ................................ -->
35229 <!-- File: memory-map.dtd .............................. -->
35230 <!-- .................................... .............. -->
35231 <!-- memory-map.dtd -->
35232 <!-- memory-map: Root element with versioning -->
35233 <!ELEMENT memory-map (memory | property)>
35234 <!ATTLIST memory-map version CDATA #FIXED "1.0.0">
35235 <!ELEMENT memory (property)>
35236 <!-- memory: Specifies a memory region,
35237 and its type, or device. -->
35238 <!ATTLIST memory type CDATA #REQUIRED
35239 start CDATA #REQUIRED
35240 length CDATA #REQUIRED
35241 device CDATA #IMPLIED>
35242 <!-- property: Generic attribute tag -->
35243 <!ELEMENT property (#PCDATA | property)*>
35244 <!ATTLIST property name CDATA #REQUIRED>
35245 @end smallexample
35246
35247 @node Thread List Format
35248 @section Thread List Format
35249 @cindex thread list format
35250
35251 To efficiently update the list of threads and their attributes,
35252 @value{GDBN} issues the @samp{qXfer:threads:read} packet
35253 (@pxref{qXfer threads read}) and obtains the XML document with
35254 the following structure:
35255
35256 @smallexample
35257 <?xml version="1.0"?>
35258 <threads>
35259 <thread id="id" core="0">
35260 ... description ...
35261 </thread>
35262 </threads>
35263 @end smallexample
35264
35265 Each @samp{thread} element must have the @samp{id} attribute that
35266 identifies the thread (@pxref{thread-id syntax}). The
35267 @samp{core} attribute, if present, specifies which processor core
35268 the thread was last executing on. The content of the of @samp{thread}
35269 element is interpreted as human-readable auxilliary information.
35270
35271 @include agentexpr.texi
35272
35273 @node Trace File Format
35274 @appendix Trace File Format
35275 @cindex trace file format
35276
35277 The trace file comes in three parts: a header, a textual description
35278 section, and a trace frame section with binary data.
35279
35280 The header has the form @code{\x7fTRACE0\n}. The first byte is
35281 @code{0x7f} so as to indicate that the file contains binary data,
35282 while the @code{0} is a version number that may have different values
35283 in the future.
35284
35285 The description section consists of multiple lines of @sc{ascii} text
35286 separated by newline characters (@code{0xa}). The lines may include a
35287 variety of optional descriptive or context-setting information, such
35288 as tracepoint definitions or register set size. @value{GDBN} will
35289 ignore any line that it does not recognize. An empty line marks the end
35290 of this section.
35291
35292 @c FIXME add some specific types of data
35293
35294 The trace frame section consists of a number of consecutive frames.
35295 Each frame begins with a two-byte tracepoint number, followed by a
35296 four-byte size giving the amount of data in the frame. The data in
35297 the frame consists of a number of blocks, each introduced by a
35298 character indicating its type (at least register, memory, and trace
35299 state variable). The data in this section is raw binary, not a
35300 hexadecimal or other encoding; its endianness matches the target's
35301 endianness.
35302
35303 @c FIXME bi-arch may require endianness/arch info in description section
35304
35305 @table @code
35306 @item R @var{bytes}
35307 Register block. The number and ordering of bytes matches that of a
35308 @code{g} packet in the remote protocol. Note that these are the
35309 actual bytes, in target order and @value{GDBN} register order, not a
35310 hexadecimal encoding.
35311
35312 @item M @var{address} @var{length} @var{bytes}...
35313 Memory block. This is a contiguous block of memory, at the 8-byte
35314 address @var{address}, with a 2-byte length @var{length}, followed by
35315 @var{length} bytes.
35316
35317 @item V @var{number} @var{value}
35318 Trace state variable block. This records the 8-byte signed value
35319 @var{value} of trace state variable numbered @var{number}.
35320
35321 @end table
35322
35323 Future enhancements of the trace file format may include additional types
35324 of blocks.
35325
35326 @node Target Descriptions
35327 @appendix Target Descriptions
35328 @cindex target descriptions
35329
35330 @strong{Warning:} target descriptions are still under active development,
35331 and the contents and format may change between @value{GDBN} releases.
35332 The format is expected to stabilize in the future.
35333
35334 One of the challenges of using @value{GDBN} to debug embedded systems
35335 is that there are so many minor variants of each processor
35336 architecture in use. It is common practice for vendors to start with
35337 a standard processor core --- ARM, PowerPC, or MIPS, for example ---
35338 and then make changes to adapt it to a particular market niche. Some
35339 architectures have hundreds of variants, available from dozens of
35340 vendors. This leads to a number of problems:
35341
35342 @itemize @bullet
35343 @item
35344 With so many different customized processors, it is difficult for
35345 the @value{GDBN} maintainers to keep up with the changes.
35346 @item
35347 Since individual variants may have short lifetimes or limited
35348 audiences, it may not be worthwhile to carry information about every
35349 variant in the @value{GDBN} source tree.
35350 @item
35351 When @value{GDBN} does support the architecture of the embedded system
35352 at hand, the task of finding the correct architecture name to give the
35353 @command{set architecture} command can be error-prone.
35354 @end itemize
35355
35356 To address these problems, the @value{GDBN} remote protocol allows a
35357 target system to not only identify itself to @value{GDBN}, but to
35358 actually describe its own features. This lets @value{GDBN} support
35359 processor variants it has never seen before --- to the extent that the
35360 descriptions are accurate, and that @value{GDBN} understands them.
35361
35362 @value{GDBN} must be linked with the Expat library to support XML
35363 target descriptions. @xref{Expat}.
35364
35365 @menu
35366 * Retrieving Descriptions:: How descriptions are fetched from a target.
35367 * Target Description Format:: The contents of a target description.
35368 * Predefined Target Types:: Standard types available for target
35369 descriptions.
35370 * Standard Target Features:: Features @value{GDBN} knows about.
35371 @end menu
35372
35373 @node Retrieving Descriptions
35374 @section Retrieving Descriptions
35375
35376 Target descriptions can be read from the target automatically, or
35377 specified by the user manually. The default behavior is to read the
35378 description from the target. @value{GDBN} retrieves it via the remote
35379 protocol using @samp{qXfer} requests (@pxref{General Query Packets,
35380 qXfer}). The @var{annex} in the @samp{qXfer} packet will be
35381 @samp{target.xml}. The contents of the @samp{target.xml} annex are an
35382 XML document, of the form described in @ref{Target Description
35383 Format}.
35384
35385 Alternatively, you can specify a file to read for the target description.
35386 If a file is set, the target will not be queried. The commands to
35387 specify a file are:
35388
35389 @table @code
35390 @cindex set tdesc filename
35391 @item set tdesc filename @var{path}
35392 Read the target description from @var{path}.
35393
35394 @cindex unset tdesc filename
35395 @item unset tdesc filename
35396 Do not read the XML target description from a file. @value{GDBN}
35397 will use the description supplied by the current target.
35398
35399 @cindex show tdesc filename
35400 @item show tdesc filename
35401 Show the filename to read for a target description, if any.
35402 @end table
35403
35404
35405 @node Target Description Format
35406 @section Target Description Format
35407 @cindex target descriptions, XML format
35408
35409 A target description annex is an @uref{http://www.w3.org/XML/, XML}
35410 document which complies with the Document Type Definition provided in
35411 the @value{GDBN} sources in @file{gdb/features/gdb-target.dtd}. This
35412 means you can use generally available tools like @command{xmllint} to
35413 check that your feature descriptions are well-formed and valid.
35414 However, to help people unfamiliar with XML write descriptions for
35415 their targets, we also describe the grammar here.
35416
35417 Target descriptions can identify the architecture of the remote target
35418 and (for some architectures) provide information about custom register
35419 sets. They can also identify the OS ABI of the remote target.
35420 @value{GDBN} can use this information to autoconfigure for your
35421 target, or to warn you if you connect to an unsupported target.
35422
35423 Here is a simple target description:
35424
35425 @smallexample
35426 <target version="1.0">
35427 <architecture>i386:x86-64</architecture>
35428 </target>
35429 @end smallexample
35430
35431 @noindent
35432 This minimal description only says that the target uses
35433 the x86-64 architecture.
35434
35435 A target description has the following overall form, with [ ] marking
35436 optional elements and @dots{} marking repeatable elements. The elements
35437 are explained further below.
35438
35439 @smallexample
35440 <?xml version="1.0"?>
35441 <!DOCTYPE target SYSTEM "gdb-target.dtd">
35442 <target version="1.0">
35443 @r{[}@var{architecture}@r{]}
35444 @r{[}@var{osabi}@r{]}
35445 @r{[}@var{compatible}@r{]}
35446 @r{[}@var{feature}@dots{}@r{]}
35447 </target>
35448 @end smallexample
35449
35450 @noindent
35451 The description is generally insensitive to whitespace and line
35452 breaks, under the usual common-sense rules. The XML version
35453 declaration and document type declaration can generally be omitted
35454 (@value{GDBN} does not require them), but specifying them may be
35455 useful for XML validation tools. The @samp{version} attribute for
35456 @samp{<target>} may also be omitted, but we recommend
35457 including it; if future versions of @value{GDBN} use an incompatible
35458 revision of @file{gdb-target.dtd}, they will detect and report
35459 the version mismatch.
35460
35461 @subsection Inclusion
35462 @cindex target descriptions, inclusion
35463 @cindex XInclude
35464 @ifnotinfo
35465 @cindex <xi:include>
35466 @end ifnotinfo
35467
35468 It can sometimes be valuable to split a target description up into
35469 several different annexes, either for organizational purposes, or to
35470 share files between different possible target descriptions. You can
35471 divide a description into multiple files by replacing any element of
35472 the target description with an inclusion directive of the form:
35473
35474 @smallexample
35475 <xi:include href="@var{document}"/>
35476 @end smallexample
35477
35478 @noindent
35479 When @value{GDBN} encounters an element of this form, it will retrieve
35480 the named XML @var{document}, and replace the inclusion directive with
35481 the contents of that document. If the current description was read
35482 using @samp{qXfer}, then so will be the included document;
35483 @var{document} will be interpreted as the name of an annex. If the
35484 current description was read from a file, @value{GDBN} will look for
35485 @var{document} as a file in the same directory where it found the
35486 original description.
35487
35488 @subsection Architecture
35489 @cindex <architecture>
35490
35491 An @samp{<architecture>} element has this form:
35492
35493 @smallexample
35494 <architecture>@var{arch}</architecture>
35495 @end smallexample
35496
35497 @var{arch} is one of the architectures from the set accepted by
35498 @code{set architecture} (@pxref{Targets, ,Specifying a Debugging Target}).
35499
35500 @subsection OS ABI
35501 @cindex @code{<osabi>}
35502
35503 This optional field was introduced in @value{GDBN} version 7.0.
35504 Previous versions of @value{GDBN} ignore it.
35505
35506 An @samp{<osabi>} element has this form:
35507
35508 @smallexample
35509 <osabi>@var{abi-name}</osabi>
35510 @end smallexample
35511
35512 @var{abi-name} is an OS ABI name from the same selection accepted by
35513 @w{@code{set osabi}} (@pxref{ABI, ,Configuring the Current ABI}).
35514
35515 @subsection Compatible Architecture
35516 @cindex @code{<compatible>}
35517
35518 This optional field was introduced in @value{GDBN} version 7.0.
35519 Previous versions of @value{GDBN} ignore it.
35520
35521 A @samp{<compatible>} element has this form:
35522
35523 @smallexample
35524 <compatible>@var{arch}</compatible>
35525 @end smallexample
35526
35527 @var{arch} is one of the architectures from the set accepted by
35528 @code{set architecture} (@pxref{Targets, ,Specifying a Debugging Target}).
35529
35530 A @samp{<compatible>} element is used to specify that the target
35531 is able to run binaries in some other than the main target architecture
35532 given by the @samp{<architecture>} element. For example, on the
35533 Cell Broadband Engine, the main architecture is @code{powerpc:common}
35534 or @code{powerpc:common64}, but the system is able to run binaries
35535 in the @code{spu} architecture as well. The way to describe this
35536 capability with @samp{<compatible>} is as follows:
35537
35538 @smallexample
35539 <architecture>powerpc:common</architecture>
35540 <compatible>spu</compatible>
35541 @end smallexample
35542
35543 @subsection Features
35544 @cindex <feature>
35545
35546 Each @samp{<feature>} describes some logical portion of the target
35547 system. Features are currently used to describe available CPU
35548 registers and the types of their contents. A @samp{<feature>} element
35549 has this form:
35550
35551 @smallexample
35552 <feature name="@var{name}">
35553 @r{[}@var{type}@dots{}@r{]}
35554 @var{reg}@dots{}
35555 </feature>
35556 @end smallexample
35557
35558 @noindent
35559 Each feature's name should be unique within the description. The name
35560 of a feature does not matter unless @value{GDBN} has some special
35561 knowledge of the contents of that feature; if it does, the feature
35562 should have its standard name. @xref{Standard Target Features}.
35563
35564 @subsection Types
35565
35566 Any register's value is a collection of bits which @value{GDBN} must
35567 interpret. The default interpretation is a two's complement integer,
35568 but other types can be requested by name in the register description.
35569 Some predefined types are provided by @value{GDBN} (@pxref{Predefined
35570 Target Types}), and the description can define additional composite types.
35571
35572 Each type element must have an @samp{id} attribute, which gives
35573 a unique (within the containing @samp{<feature>}) name to the type.
35574 Types must be defined before they are used.
35575
35576 @cindex <vector>
35577 Some targets offer vector registers, which can be treated as arrays
35578 of scalar elements. These types are written as @samp{<vector>} elements,
35579 specifying the array element type, @var{type}, and the number of elements,
35580 @var{count}:
35581
35582 @smallexample
35583 <vector id="@var{id}" type="@var{type}" count="@var{count}"/>
35584 @end smallexample
35585
35586 @cindex <union>
35587 If a register's value is usefully viewed in multiple ways, define it
35588 with a union type containing the useful representations. The
35589 @samp{<union>} element contains one or more @samp{<field>} elements,
35590 each of which has a @var{name} and a @var{type}:
35591
35592 @smallexample
35593 <union id="@var{id}">
35594 <field name="@var{name}" type="@var{type}"/>
35595 @dots{}
35596 </union>
35597 @end smallexample
35598
35599 @cindex <struct>
35600 If a register's value is composed from several separate values, define
35601 it with a structure type. There are two forms of the @samp{<struct>}
35602 element; a @samp{<struct>} element must either contain only bitfields
35603 or contain no bitfields. If the structure contains only bitfields,
35604 its total size in bytes must be specified, each bitfield must have an
35605 explicit start and end, and bitfields are automatically assigned an
35606 integer type. The field's @var{start} should be less than or
35607 equal to its @var{end}, and zero represents the least significant bit.
35608
35609 @smallexample
35610 <struct id="@var{id}" size="@var{size}">
35611 <field name="@var{name}" start="@var{start}" end="@var{end}"/>
35612 @dots{}
35613 </struct>
35614 @end smallexample
35615
35616 If the structure contains no bitfields, then each field has an
35617 explicit type, and no implicit padding is added.
35618
35619 @smallexample
35620 <struct id="@var{id}">
35621 <field name="@var{name}" type="@var{type}"/>
35622 @dots{}
35623 </struct>
35624 @end smallexample
35625
35626 @cindex <flags>
35627 If a register's value is a series of single-bit flags, define it with
35628 a flags type. The @samp{<flags>} element has an explicit @var{size}
35629 and contains one or more @samp{<field>} elements. Each field has a
35630 @var{name}, a @var{start}, and an @var{end}. Only single-bit flags
35631 are supported.
35632
35633 @smallexample
35634 <flags id="@var{id}" size="@var{size}">
35635 <field name="@var{name}" start="@var{start}" end="@var{end}"/>
35636 @dots{}
35637 </flags>
35638 @end smallexample
35639
35640 @subsection Registers
35641 @cindex <reg>
35642
35643 Each register is represented as an element with this form:
35644
35645 @smallexample
35646 <reg name="@var{name}"
35647 bitsize="@var{size}"
35648 @r{[}regnum="@var{num}"@r{]}
35649 @r{[}save-restore="@var{save-restore}"@r{]}
35650 @r{[}type="@var{type}"@r{]}
35651 @r{[}group="@var{group}"@r{]}/>
35652 @end smallexample
35653
35654 @noindent
35655 The components are as follows:
35656
35657 @table @var
35658
35659 @item name
35660 The register's name; it must be unique within the target description.
35661
35662 @item bitsize
35663 The register's size, in bits.
35664
35665 @item regnum
35666 The register's number. If omitted, a register's number is one greater
35667 than that of the previous register (either in the current feature or in
35668 a preceeding feature); the first register in the target description
35669 defaults to zero. This register number is used to read or write
35670 the register; e.g.@: it is used in the remote @code{p} and @code{P}
35671 packets, and registers appear in the @code{g} and @code{G} packets
35672 in order of increasing register number.
35673
35674 @item save-restore
35675 Whether the register should be preserved across inferior function
35676 calls; this must be either @code{yes} or @code{no}. The default is
35677 @code{yes}, which is appropriate for most registers except for
35678 some system control registers; this is not related to the target's
35679 ABI.
35680
35681 @item type
35682 The type of the register. @var{type} may be a predefined type, a type
35683 defined in the current feature, or one of the special types @code{int}
35684 and @code{float}. @code{int} is an integer type of the correct size
35685 for @var{bitsize}, and @code{float} is a floating point type (in the
35686 architecture's normal floating point format) of the correct size for
35687 @var{bitsize}. The default is @code{int}.
35688
35689 @item group
35690 The register group to which this register belongs. @var{group} must
35691 be either @code{general}, @code{float}, or @code{vector}. If no
35692 @var{group} is specified, @value{GDBN} will not display the register
35693 in @code{info registers}.
35694
35695 @end table
35696
35697 @node Predefined Target Types
35698 @section Predefined Target Types
35699 @cindex target descriptions, predefined types
35700
35701 Type definitions in the self-description can build up composite types
35702 from basic building blocks, but can not define fundamental types. Instead,
35703 standard identifiers are provided by @value{GDBN} for the fundamental
35704 types. The currently supported types are:
35705
35706 @table @code
35707
35708 @item int8
35709 @itemx int16
35710 @itemx int32
35711 @itemx int64
35712 @itemx int128
35713 Signed integer types holding the specified number of bits.
35714
35715 @item uint8
35716 @itemx uint16
35717 @itemx uint32
35718 @itemx uint64
35719 @itemx uint128
35720 Unsigned integer types holding the specified number of bits.
35721
35722 @item code_ptr
35723 @itemx data_ptr
35724 Pointers to unspecified code and data. The program counter and
35725 any dedicated return address register may be marked as code
35726 pointers; printing a code pointer converts it into a symbolic
35727 address. The stack pointer and any dedicated address registers
35728 may be marked as data pointers.
35729
35730 @item ieee_single
35731 Single precision IEEE floating point.
35732
35733 @item ieee_double
35734 Double precision IEEE floating point.
35735
35736 @item arm_fpa_ext
35737 The 12-byte extended precision format used by ARM FPA registers.
35738
35739 @item i387_ext
35740 The 10-byte extended precision format used by x87 registers.
35741
35742 @item i386_eflags
35743 32bit @sc{eflags} register used by x86.
35744
35745 @item i386_mxcsr
35746 32bit @sc{mxcsr} register used by x86.
35747
35748 @end table
35749
35750 @node Standard Target Features
35751 @section Standard Target Features
35752 @cindex target descriptions, standard features
35753
35754 A target description must contain either no registers or all the
35755 target's registers. If the description contains no registers, then
35756 @value{GDBN} will assume a default register layout, selected based on
35757 the architecture. If the description contains any registers, the
35758 default layout will not be used; the standard registers must be
35759 described in the target description, in such a way that @value{GDBN}
35760 can recognize them.
35761
35762 This is accomplished by giving specific names to feature elements
35763 which contain standard registers. @value{GDBN} will look for features
35764 with those names and verify that they contain the expected registers;
35765 if any known feature is missing required registers, or if any required
35766 feature is missing, @value{GDBN} will reject the target
35767 description. You can add additional registers to any of the
35768 standard features --- @value{GDBN} will display them just as if
35769 they were added to an unrecognized feature.
35770
35771 This section lists the known features and their expected contents.
35772 Sample XML documents for these features are included in the
35773 @value{GDBN} source tree, in the directory @file{gdb/features}.
35774
35775 Names recognized by @value{GDBN} should include the name of the
35776 company or organization which selected the name, and the overall
35777 architecture to which the feature applies; so e.g.@: the feature
35778 containing ARM core registers is named @samp{org.gnu.gdb.arm.core}.
35779
35780 The names of registers are not case sensitive for the purpose
35781 of recognizing standard features, but @value{GDBN} will only display
35782 registers using the capitalization used in the description.
35783
35784 @menu
35785 * ARM Features::
35786 * i386 Features::
35787 * MIPS Features::
35788 * M68K Features::
35789 * PowerPC Features::
35790 @end menu
35791
35792
35793 @node ARM Features
35794 @subsection ARM Features
35795 @cindex target descriptions, ARM features
35796
35797 The @samp{org.gnu.gdb.arm.core} feature is required for non-M-profile
35798 ARM targets.
35799 It should contain registers @samp{r0} through @samp{r13}, @samp{sp},
35800 @samp{lr}, @samp{pc}, and @samp{cpsr}.
35801
35802 For M-profile targets (e.g. Cortex-M3), the @samp{org.gnu.gdb.arm.core}
35803 feature is replaced by @samp{org.gnu.gdb.arm.m-profile}. It should contain
35804 registers @samp{r0} through @samp{r13}, @samp{sp}, @samp{lr}, @samp{pc},
35805 and @samp{xpsr}.
35806
35807 The @samp{org.gnu.gdb.arm.fpa} feature is optional. If present, it
35808 should contain registers @samp{f0} through @samp{f7} and @samp{fps}.
35809
35810 The @samp{org.gnu.gdb.xscale.iwmmxt} feature is optional. If present,
35811 it should contain at least registers @samp{wR0} through @samp{wR15} and
35812 @samp{wCGR0} through @samp{wCGR3}. The @samp{wCID}, @samp{wCon},
35813 @samp{wCSSF}, and @samp{wCASF} registers are optional.
35814
35815 The @samp{org.gnu.gdb.arm.vfp} feature is optional. If present, it
35816 should contain at least registers @samp{d0} through @samp{d15}. If
35817 they are present, @samp{d16} through @samp{d31} should also be included.
35818 @value{GDBN} will synthesize the single-precision registers from
35819 halves of the double-precision registers.
35820
35821 The @samp{org.gnu.gdb.arm.neon} feature is optional. It does not
35822 need to contain registers; it instructs @value{GDBN} to display the
35823 VFP double-precision registers as vectors and to synthesize the
35824 quad-precision registers from pairs of double-precision registers.
35825 If this feature is present, @samp{org.gnu.gdb.arm.vfp} must also
35826 be present and include 32 double-precision registers.
35827
35828 @node i386 Features
35829 @subsection i386 Features
35830 @cindex target descriptions, i386 features
35831
35832 The @samp{org.gnu.gdb.i386.core} feature is required for i386/amd64
35833 targets. It should describe the following registers:
35834
35835 @itemize @minus
35836 @item
35837 @samp{eax} through @samp{edi} plus @samp{eip} for i386
35838 @item
35839 @samp{rax} through @samp{r15} plus @samp{rip} for amd64
35840 @item
35841 @samp{eflags}, @samp{cs}, @samp{ss}, @samp{ds}, @samp{es},
35842 @samp{fs}, @samp{gs}
35843 @item
35844 @samp{st0} through @samp{st7}
35845 @item
35846 @samp{fctrl}, @samp{fstat}, @samp{ftag}, @samp{fiseg}, @samp{fioff},
35847 @samp{foseg}, @samp{fooff} and @samp{fop}
35848 @end itemize
35849
35850 The register sets may be different, depending on the target.
35851
35852 The @samp{org.gnu.gdb.i386.sse} feature is optional. It should
35853 describe registers:
35854
35855 @itemize @minus
35856 @item
35857 @samp{xmm0} through @samp{xmm7} for i386
35858 @item
35859 @samp{xmm0} through @samp{xmm15} for amd64
35860 @item
35861 @samp{mxcsr}
35862 @end itemize
35863
35864 The @samp{org.gnu.gdb.i386.avx} feature is optional and requires the
35865 @samp{org.gnu.gdb.i386.sse} feature. It should
35866 describe the upper 128 bits of @sc{ymm} registers:
35867
35868 @itemize @minus
35869 @item
35870 @samp{ymm0h} through @samp{ymm7h} for i386
35871 @item
35872 @samp{ymm0h} through @samp{ymm15h} for amd64
35873 @end itemize
35874
35875 The @samp{org.gnu.gdb.i386.linux} feature is optional. It should
35876 describe a single register, @samp{orig_eax}.
35877
35878 @node MIPS Features
35879 @subsection MIPS Features
35880 @cindex target descriptions, MIPS features
35881
35882 The @samp{org.gnu.gdb.mips.cpu} feature is required for MIPS targets.
35883 It should contain registers @samp{r0} through @samp{r31}, @samp{lo},
35884 @samp{hi}, and @samp{pc}. They may be 32-bit or 64-bit depending
35885 on the target.
35886
35887 The @samp{org.gnu.gdb.mips.cp0} feature is also required. It should
35888 contain at least the @samp{status}, @samp{badvaddr}, and @samp{cause}
35889 registers. They may be 32-bit or 64-bit depending on the target.
35890
35891 The @samp{org.gnu.gdb.mips.fpu} feature is currently required, though
35892 it may be optional in a future version of @value{GDBN}. It should
35893 contain registers @samp{f0} through @samp{f31}, @samp{fcsr}, and
35894 @samp{fir}. They may be 32-bit or 64-bit depending on the target.
35895
35896 The @samp{org.gnu.gdb.mips.linux} feature is optional. It should
35897 contain a single register, @samp{restart}, which is used by the
35898 Linux kernel to control restartable syscalls.
35899
35900 @node M68K Features
35901 @subsection M68K Features
35902 @cindex target descriptions, M68K features
35903
35904 @table @code
35905 @item @samp{org.gnu.gdb.m68k.core}
35906 @itemx @samp{org.gnu.gdb.coldfire.core}
35907 @itemx @samp{org.gnu.gdb.fido.core}
35908 One of those features must be always present.
35909 The feature that is present determines which flavor of m68k is
35910 used. The feature that is present should contain registers
35911 @samp{d0} through @samp{d7}, @samp{a0} through @samp{a5}, @samp{fp},
35912 @samp{sp}, @samp{ps} and @samp{pc}.
35913
35914 @item @samp{org.gnu.gdb.coldfire.fp}
35915 This feature is optional. If present, it should contain registers
35916 @samp{fp0} through @samp{fp7}, @samp{fpcontrol}, @samp{fpstatus} and
35917 @samp{fpiaddr}.
35918 @end table
35919
35920 @node PowerPC Features
35921 @subsection PowerPC Features
35922 @cindex target descriptions, PowerPC features
35923
35924 The @samp{org.gnu.gdb.power.core} feature is required for PowerPC
35925 targets. It should contain registers @samp{r0} through @samp{r31},
35926 @samp{pc}, @samp{msr}, @samp{cr}, @samp{lr}, @samp{ctr}, and
35927 @samp{xer}. They may be 32-bit or 64-bit depending on the target.
35928
35929 The @samp{org.gnu.gdb.power.fpu} feature is optional. It should
35930 contain registers @samp{f0} through @samp{f31} and @samp{fpscr}.
35931
35932 The @samp{org.gnu.gdb.power.altivec} feature is optional. It should
35933 contain registers @samp{vr0} through @samp{vr31}, @samp{vscr},
35934 and @samp{vrsave}.
35935
35936 The @samp{org.gnu.gdb.power.vsx} feature is optional. It should
35937 contain registers @samp{vs0h} through @samp{vs31h}. @value{GDBN}
35938 will combine these registers with the floating point registers
35939 (@samp{f0} through @samp{f31}) and the altivec registers (@samp{vr0}
35940 through @samp{vr31}) to present the 128-bit wide registers @samp{vs0}
35941 through @samp{vs63}, the set of vector registers for POWER7.
35942
35943 The @samp{org.gnu.gdb.power.spe} feature is optional. It should
35944 contain registers @samp{ev0h} through @samp{ev31h}, @samp{acc}, and
35945 @samp{spefscr}. SPE targets should provide 32-bit registers in
35946 @samp{org.gnu.gdb.power.core} and provide the upper halves in
35947 @samp{ev0h} through @samp{ev31h}. @value{GDBN} will combine
35948 these to present registers @samp{ev0} through @samp{ev31} to the
35949 user.
35950
35951 @node Operating System Information
35952 @appendix Operating System Information
35953 @cindex operating system information
35954
35955 @menu
35956 * Process list::
35957 @end menu
35958
35959 Users of @value{GDBN} often wish to obtain information about the state of
35960 the operating system running on the target---for example the list of
35961 processes, or the list of open files. This section describes the
35962 mechanism that makes it possible. This mechanism is similar to the
35963 target features mechanism (@pxref{Target Descriptions}), but focuses
35964 on a different aspect of target.
35965
35966 Operating system information is retrived from the target via the
35967 remote protocol, using @samp{qXfer} requests (@pxref{qXfer osdata
35968 read}). The object name in the request should be @samp{osdata}, and
35969 the @var{annex} identifies the data to be fetched.
35970
35971 @node Process list
35972 @appendixsection Process list
35973 @cindex operating system information, process list
35974
35975 When requesting the process list, the @var{annex} field in the
35976 @samp{qXfer} request should be @samp{processes}. The returned data is
35977 an XML document. The formal syntax of this document is defined in
35978 @file{gdb/features/osdata.dtd}.
35979
35980 An example document is:
35981
35982 @smallexample
35983 <?xml version="1.0"?>
35984 <!DOCTYPE target SYSTEM "osdata.dtd">
35985 <osdata type="processes">
35986 <item>
35987 <column name="pid">1</column>
35988 <column name="user">root</column>
35989 <column name="command">/sbin/init</column>
35990 <column name="cores">1,2,3</column>
35991 </item>
35992 </osdata>
35993 @end smallexample
35994
35995 Each item should include a column whose name is @samp{pid}. The value
35996 of that column should identify the process on the target. The
35997 @samp{user} and @samp{command} columns are optional, and will be
35998 displayed by @value{GDBN}. The @samp{cores} column, if present,
35999 should contain a comma-separated list of cores that this process
36000 is running on. Target may provide additional columns,
36001 which @value{GDBN} currently ignores.
36002
36003 @include gpl.texi
36004
36005 @node GNU Free Documentation License
36006 @appendix GNU Free Documentation License
36007 @include fdl.texi
36008
36009 @node Index
36010 @unnumbered Index
36011
36012 @printindex cp
36013
36014 @tex
36015 % I think something like @colophon should be in texinfo. In the
36016 % meantime:
36017 \long\def\colophon{\hbox to0pt{}\vfill
36018 \centerline{The body of this manual is set in}
36019 \centerline{\fontname\tenrm,}
36020 \centerline{with headings in {\bf\fontname\tenbf}}
36021 \centerline{and examples in {\tt\fontname\tentt}.}
36022 \centerline{{\it\fontname\tenit\/},}
36023 \centerline{{\bf\fontname\tenbf}, and}
36024 \centerline{{\sl\fontname\tensl\/}}
36025 \centerline{are used for emphasis.}\vfill}
36026 \page\colophon
36027 % Blame: doc@cygnus.com, 1991.
36028 @end tex
36029
36030 @bye
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