Changes approved by kev@cygnus.com, ezannoni@cygnus.com, eliz@is.elta.co.il.
[deliverable/binutils-gdb.git] / gdb / doc / gdb.texinfo
1 \input texinfo @c -*-texinfo-*-
2 @c Copyright 1988, 1989, 1990, 1991, 1992, 1993, 1994, 1995, 1996, 1998,
3 @c 1999, 2000, 2001
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
25 @c readline appendices use @vindex, @findex and @ftable,
26 @c annotate.texi and gdbmi use @findex.
27 @syncodeindex vr cp
28 @syncodeindex fn cp
29
30 @c !!set GDB manual's edition---not the same as GDB version!
31 @set EDITION Ninth
32
33 @c !!set GDB manual's revision date
34 @set DATE April 2001
35
36 @c THIS MANUAL REQUIRES TEXINFO 3.12 OR LATER.
37
38 @c This is a dir.info fragment to support semi-automated addition of
39 @c manuals to an info tree.
40 @dircategory Programming & development tools.
41 @direntry
42 * Gdb: (gdb). The @sc{gnu} debugger.
43 @end direntry
44
45 @ifinfo
46 This file documents the @sc{gnu} debugger @value{GDBN}.
47
48
49 This is the @value{EDITION} Edition, @value{DATE},
50 of @cite{Debugging with @value{GDBN}: the @sc{gnu} Source-Level Debugger}
51 for @value{GDBN} Version @value{GDBVN}.
52
53 Copyright (C) 1988,1989,1990,1991,1992,1993,1994,1995,1996,1998,1999,2000,2001
54 Free Software Foundation, Inc.
55
56 Permission is granted to copy, distribute and/or modify this document
57 under the terms of the GNU Free Documentation License, Version 1.1 or
58 any later version published by the Free Software Foundation; with the
59 Invariant Sections being ``A Sample GDB Session'' and ``Free
60 Software'', with the Front-Cover texts being ``A GNU Manual,'' and
61 with the Back-Cover Texts as in (a) below.
62
63 (a) The FSF's Back-Cover Text is: ``You have freedom to copy and modify
64 this GNU Manual, like GNU software. Copies published by the Free
65 Software Foundation raise funds for GNU development.''
66 @end ifinfo
67
68 @titlepage
69 @title Debugging with @value{GDBN}
70 @subtitle The @sc{gnu} Source-Level Debugger
71 @sp 1
72 @subtitle @value{EDITION} Edition, for @value{GDBN} version @value{GDBVN}
73 @subtitle @value{DATE}
74 @author Richard Stallman, Roland Pesch, Stan Shebs, et al.
75 @page
76 @tex
77 {\parskip=0pt
78 \hfill (Send bugs and comments on @value{GDBN} to bug-gdb\@gnu.org.)\par
79 \hfill {\it Debugging with @value{GDBN}}\par
80 \hfill \TeX{}info \texinfoversion\par
81 }
82 @end tex
83
84 @vskip 0pt plus 1filll
85 Copyright @copyright{} 1988,1989,1990,1991,1992,1993,1994,1995,1996,1998,1999,2000,2001
86 Free Software Foundation, Inc.
87 @sp 2
88 Published by the Free Software Foundation @*
89 59 Temple Place - Suite 330, @*
90 Boston, MA 02111-1307 USA @*
91 ISBN 1-882114-77-9 @*
92
93 Permission is granted to copy, distribute and/or modify this document
94 under the terms of the GNU Free Documentation License, Version 1.1 or
95 any later version published by the Free Software Foundation; with the
96 Invariant Sections being ``A Sample GDB Session'' and ``Free
97 Software'', with the Front-Cover texts being ``A GNU Manual,'' and
98 with the Back-Cover Texts as in (a) below.
99
100 (a) The FSF's Back-Cover Text is: ``You have freedom to copy and modify
101 this GNU Manual, like GNU software. Copies published by the Free
102 Software Foundation raise funds for GNU development.''
103 @end titlepage
104 @page
105
106 @ifinfo
107 @node Top, Summary, (dir), (dir)
108
109 @top Debugging with @value{GDBN}
110
111 This file describes @value{GDBN}, the @sc{gnu} symbolic debugger.
112
113 This is the @value{EDITION} Edition, @value{DATE}, for @value{GDBN} Version
114 @value{GDBVN}.
115
116 Copyright (C) 1988-2001 Free Software Foundation, Inc.
117
118 @menu
119 * Summary:: Summary of @value{GDBN}
120 * Sample Session:: A sample @value{GDBN} session
121
122 * Invocation:: Getting in and out of @value{GDBN}
123 * Commands:: @value{GDBN} commands
124 * Running:: Running programs under @value{GDBN}
125 * Stopping:: Stopping and continuing
126 * Stack:: Examining the stack
127 * Source:: Examining source files
128 * Data:: Examining data
129 * Tracepoints:: Debugging remote targets non-intrusively
130
131 * Languages:: Using @value{GDBN} with different languages
132
133 * Symbols:: Examining the symbol table
134 * Altering:: Altering execution
135 * GDB Files:: @value{GDBN} files
136 * Targets:: Specifying a debugging target
137 * Configurations:: Configuration-specific information
138 * Controlling GDB:: Controlling @value{GDBN}
139 * Sequences:: Canned sequences of commands
140 * TUI:: @value{GDBN} Text User Interface
141 * Emacs:: Using @value{GDBN} under @sc{gnu} Emacs
142 * Annotations:: @value{GDBN}'s annotation interface.
143 * GDB/MI:: @value{GDBN}'s Machine Interface.
144
145 * GDB Bugs:: Reporting bugs in @value{GDBN}
146 * Formatting Documentation:: How to format and print @value{GDBN} documentation
147
148 * Command Line Editing:: Command Line Editing
149 * Using History Interactively:: Using History Interactively
150 * Installing GDB:: Installing GDB
151 * Index:: Index
152 @end menu
153
154 @end ifinfo
155
156 @c the replication sucks, but this avoids a texinfo 3.12 lameness
157
158 @ifhtml
159 @node Top
160
161 @top Debugging with @value{GDBN}
162
163 This file describes @value{GDBN}, the @sc{gnu} symbolic debugger.
164
165 This is the @value{EDITION} Edition, @value{DATE}, for @value{GDBN} Version
166 @value{GDBVN}.
167
168 Copyright (C) 1988-2000 Free Software Foundation, Inc.
169
170 @menu
171 * Summary:: Summary of @value{GDBN}
172 * Sample Session:: A sample @value{GDBN} session
173
174 * Invocation:: Getting in and out of @value{GDBN}
175 * Commands:: @value{GDBN} commands
176 * Running:: Running programs under @value{GDBN}
177 * Stopping:: Stopping and continuing
178 * Stack:: Examining the stack
179 * Source:: Examining source files
180 * Data:: Examining data
181 * Tracepoints:: Debugging remote targets non-intrusively
182
183 * Languages:: Using @value{GDBN} with different languages
184
185 * Symbols:: Examining the symbol table
186 * Altering:: Altering execution
187 * GDB Files:: @value{GDBN} files
188 * Targets:: Specifying a debugging target
189 * Configurations:: Configuration-specific information
190 * Controlling GDB:: Controlling @value{GDBN}
191 * Sequences:: Canned sequences of commands
192 * TUI:: @value{GDBN} Text User Interface
193 * Emacs:: Using @value{GDBN} under @sc{gnu} Emacs
194 * Annotations:: @value{GDBN}'s annotation interface.
195 * GDB/MI:: @value{GDBN}'s Machine Interface.
196
197 * GDB Bugs:: Reporting bugs in @value{GDBN}
198 * Formatting Documentation:: How to format and print @value{GDBN} documentation
199
200 * Command Line Editing:: Command Line Editing
201 * Using History Interactively:: Using History Interactively
202 * Installing GDB:: Installing GDB
203 * Index:: Index
204 @end menu
205
206 @end ifhtml
207
208 @c TeX can handle the contents at the start but makeinfo 3.12 can not
209 @iftex
210 @contents
211 @end iftex
212
213 @node Summary
214 @unnumbered Summary of @value{GDBN}
215
216 The purpose of a debugger such as @value{GDBN} is to allow you to see what is
217 going on ``inside'' another program while it executes---or what another
218 program was doing at the moment it crashed.
219
220 @value{GDBN} can do four main kinds of things (plus other things in support of
221 these) to help you catch bugs in the act:
222
223 @itemize @bullet
224 @item
225 Start your program, specifying anything that might affect its behavior.
226
227 @item
228 Make your program stop on specified conditions.
229
230 @item
231 Examine what has happened, when your program has stopped.
232
233 @item
234 Change things in your program, so you can experiment with correcting the
235 effects of one bug and go on to learn about another.
236 @end itemize
237
238 You can use @value{GDBN} to debug programs written in C and C++.
239 For more information, see @ref{Support,,Supported languages}.
240 For more information, see @ref{C,,C and C++}.
241
242 @cindex Chill
243 @cindex Modula-2
244 Support for Modula-2 and Chill is partial. For information on Modula-2,
245 see @ref{Modula-2,,Modula-2}. For information on Chill, see @ref{Chill}.
246
247 @cindex Pascal
248 Debugging Pascal programs which use sets, subranges, file variables, or
249 nested functions does not currently work. @value{GDBN} does not support
250 entering expressions, printing values, or similar features using Pascal
251 syntax.
252
253 @cindex Fortran
254 @value{GDBN} can be used to debug programs written in Fortran, although
255 it may be necessary to refer to some variables with a trailing
256 underscore.
257
258 @menu
259 * Free Software:: Freely redistributable software
260 * Contributors:: Contributors to GDB
261 @end menu
262
263 @node Free Software
264 @unnumberedsec Free software
265
266 @value{GDBN} is @dfn{free software}, protected by the @sc{gnu}
267 General Public License
268 (GPL). The GPL gives you the freedom to copy or adapt a licensed
269 program---but every person getting a copy also gets with it the
270 freedom to modify that copy (which means that they must get access to
271 the source code), and the freedom to distribute further copies.
272 Typical software companies use copyrights to limit your freedoms; the
273 Free Software Foundation uses the GPL to preserve these freedoms.
274
275 Fundamentally, the General Public License is a license which says that
276 you have these freedoms and that you cannot take these freedoms away
277 from anyone else.
278
279 @node Contributors
280 @unnumberedsec Contributors to @value{GDBN}
281
282 Richard Stallman was the original author of @value{GDBN}, and of many
283 other @sc{gnu} programs. Many others have contributed to its
284 development. This section attempts to credit major contributors. One
285 of the virtues of free software is that everyone is free to contribute
286 to it; with regret, we cannot actually acknowledge everyone here. The
287 file @file{ChangeLog} in the @value{GDBN} distribution approximates a
288 blow-by-blow account.
289
290 Changes much prior to version 2.0 are lost in the mists of time.
291
292 @quotation
293 @emph{Plea:} Additions to this section are particularly welcome. If you
294 or your friends (or enemies, to be evenhanded) have been unfairly
295 omitted from this list, we would like to add your names!
296 @end quotation
297
298 So that they may not regard their many labors as thankless, we
299 particularly thank those who shepherded @value{GDBN} through major
300 releases:
301 Andrew Cagney (releases 5.0 and 5.1);
302 Jim Blandy (release 4.18);
303 Jason Molenda (release 4.17);
304 Stan Shebs (release 4.14);
305 Fred Fish (releases 4.16, 4.15, 4.13, 4.12, 4.11, 4.10, and 4.9);
306 Stu Grossman and John Gilmore (releases 4.8, 4.7, 4.6, 4.5, and 4.4);
307 John Gilmore (releases 4.3, 4.2, 4.1, 4.0, and 3.9);
308 Jim Kingdon (releases 3.5, 3.4, and 3.3);
309 and Randy Smith (releases 3.2, 3.1, and 3.0).
310
311 Richard Stallman, assisted at various times by Peter TerMaat, Chris
312 Hanson, and Richard Mlynarik, handled releases through 2.8.
313
314 Michael Tiemann is the author of most of the @sc{gnu} C@t{++} support
315 in @value{GDBN}, with significant additional contributions from Per
316 Bothner and Daniel Berlin. James Clark wrote the @sc{gnu} C@t{++}
317 demangler. Early work on C@t{++} was by Peter TerMaat (who also did
318 much general update work leading to release 3.0).
319
320 @value{GDBN} uses the BFD subroutine library to examine multiple
321 object-file formats; BFD was a joint project of David V.
322 Henkel-Wallace, Rich Pixley, Steve Chamberlain, and John Gilmore.
323
324 David Johnson wrote the original COFF support; Pace Willison did
325 the original support for encapsulated COFF.
326
327 Brent Benson of Harris Computer Systems contributed DWARF2 support.
328
329 Adam de Boor and Bradley Davis contributed the ISI Optimum V support.
330 Per Bothner, Noboyuki Hikichi, and Alessandro Forin contributed MIPS
331 support.
332 Jean-Daniel Fekete contributed Sun 386i support.
333 Chris Hanson improved the HP9000 support.
334 Noboyuki Hikichi and Tomoyuki Hasei contributed Sony/News OS 3 support.
335 David Johnson contributed Encore Umax support.
336 Jyrki Kuoppala contributed Altos 3068 support.
337 Jeff Law contributed HP PA and SOM support.
338 Keith Packard contributed NS32K support.
339 Doug Rabson contributed Acorn Risc Machine support.
340 Bob Rusk contributed Harris Nighthawk CX-UX support.
341 Chris Smith contributed Convex support (and Fortran debugging).
342 Jonathan Stone contributed Pyramid support.
343 Michael Tiemann contributed SPARC support.
344 Tim Tucker contributed support for the Gould NP1 and Gould Powernode.
345 Pace Willison contributed Intel 386 support.
346 Jay Vosburgh contributed Symmetry support.
347
348 Andreas Schwab contributed M68K Linux support.
349
350 Rich Schaefer and Peter Schauer helped with support of SunOS shared
351 libraries.
352
353 Jay Fenlason and Roland McGrath ensured that @value{GDBN} and GAS agree
354 about several machine instruction sets.
355
356 Patrick Duval, Ted Goldstein, Vikram Koka and Glenn Engel helped develop
357 remote debugging. Intel Corporation, Wind River Systems, AMD, and ARM
358 contributed remote debugging modules for the i960, VxWorks, A29K UDI,
359 and RDI targets, respectively.
360
361 Brian Fox is the author of the readline libraries providing
362 command-line editing and command history.
363
364 Andrew Beers of SUNY Buffalo wrote the language-switching code, the
365 Modula-2 support, and contributed the Languages chapter of this manual.
366
367 Fred Fish wrote most of the support for Unix System Vr4.
368 He also enhanced the command-completion support to cover C@t{++} overloaded
369 symbols.
370
371 Hitachi America, Ltd. sponsored the support for H8/300, H8/500, and
372 Super-H processors.
373
374 NEC sponsored the support for the v850, Vr4xxx, and Vr5xxx processors.
375
376 Mitsubishi sponsored the support for D10V, D30V, and M32R/D processors.
377
378 Toshiba sponsored the support for the TX39 Mips processor.
379
380 Matsushita sponsored the support for the MN10200 and MN10300 processors.
381
382 Fujitsu sponsored the support for SPARClite and FR30 processors.
383
384 Kung Hsu, Jeff Law, and Rick Sladkey added support for hardware
385 watchpoints.
386
387 Michael Snyder added support for tracepoints.
388
389 Stu Grossman wrote gdbserver.
390
391 Jim Kingdon, Peter Schauer, Ian Taylor, and Stu Grossman made
392 nearly innumerable bug fixes and cleanups throughout @value{GDBN}.
393
394 The following people at the Hewlett-Packard Company contributed
395 support for the PA-RISC 2.0 architecture, HP-UX 10.20, 10.30, and 11.0
396 (narrow mode), HP's implementation of kernel threads, HP's aC@t{++}
397 compiler, and the terminal user interface: Ben Krepp, Richard Title,
398 John Bishop, Susan Macchia, Kathy Mann, Satish Pai, India Paul, Steve
399 Rehrauer, and Elena Zannoni. Kim Haase provided HP-specific
400 information in this manual.
401
402 DJ Delorie ported @value{GDBN} to MS-DOS, for the DJGPP project.
403 Robert Hoehne made significant contributions to the DJGPP port.
404
405 Cygnus Solutions has sponsored @value{GDBN} maintenance and much of its
406 development since 1991. Cygnus engineers who have worked on @value{GDBN}
407 fulltime include Mark Alexander, Jim Blandy, Per Bothner, Kevin
408 Buettner, Edith Epstein, Chris Faylor, Fred Fish, Martin Hunt, Jim
409 Ingham, John Gilmore, Stu Grossman, Kung Hsu, Jim Kingdon, John Metzler,
410 Fernando Nasser, Geoffrey Noer, Dawn Perchik, Rich Pixley, Zdenek
411 Radouch, Keith Seitz, Stan Shebs, David Taylor, and Elena Zannoni. In
412 addition, Dave Brolley, Ian Carmichael, Steve Chamberlain, Nick Clifton,
413 JT Conklin, Stan Cox, DJ Delorie, Ulrich Drepper, Frank Eigler, Doug
414 Evans, Sean Fagan, David Henkel-Wallace, Richard Henderson, Jeff
415 Holcomb, Jeff Law, Jim Lemke, Tom Lord, Bob Manson, Michael Meissner,
416 Jason Merrill, Catherine Moore, Drew Moseley, Ken Raeburn, Gavin
417 Romig-Koch, Rob Savoye, Jamie Smith, Mike Stump, Ian Taylor, Angela
418 Thomas, Michael Tiemann, Tom Tromey, Ron Unrau, Jim Wilson, and David
419 Zuhn have made contributions both large and small.
420
421
422 @node Sample Session
423 @chapter A Sample @value{GDBN} Session
424
425 You can use this manual at your leisure to read all about @value{GDBN}.
426 However, a handful of commands are enough to get started using the
427 debugger. This chapter illustrates those commands.
428
429 @iftex
430 In this sample session, we emphasize user input like this: @b{input},
431 to make it easier to pick out from the surrounding output.
432 @end iftex
433
434 @c FIXME: this example may not be appropriate for some configs, where
435 @c FIXME...primary interest is in remote use.
436
437 One of the preliminary versions of @sc{gnu} @code{m4} (a generic macro
438 processor) exhibits the following bug: sometimes, when we change its
439 quote strings from the default, the commands used to capture one macro
440 definition within another stop working. In the following short @code{m4}
441 session, we define a macro @code{foo} which expands to @code{0000}; we
442 then use the @code{m4} built-in @code{defn} to define @code{bar} as the
443 same thing. However, when we change the open quote string to
444 @code{<QUOTE>} and the close quote string to @code{<UNQUOTE>}, the same
445 procedure fails to define a new synonym @code{baz}:
446
447 @smallexample
448 $ @b{cd gnu/m4}
449 $ @b{./m4}
450 @b{define(foo,0000)}
451
452 @b{foo}
453 0000
454 @b{define(bar,defn(`foo'))}
455
456 @b{bar}
457 0000
458 @b{changequote(<QUOTE>,<UNQUOTE>)}
459
460 @b{define(baz,defn(<QUOTE>foo<UNQUOTE>))}
461 @b{baz}
462 @b{C-d}
463 m4: End of input: 0: fatal error: EOF in string
464 @end smallexample
465
466 @noindent
467 Let us use @value{GDBN} to try to see what is going on.
468
469 @smallexample
470 $ @b{@value{GDBP} m4}
471 @c FIXME: this falsifies the exact text played out, to permit smallbook
472 @c FIXME... format to come out better.
473 @value{GDBN} is free software and you are welcome to distribute copies
474 of it under certain conditions; type "show copying" to see
475 the conditions.
476 There is absolutely no warranty for @value{GDBN}; type "show warranty"
477 for details.
478
479 @value{GDBN} @value{GDBVN}, Copyright 1999 Free Software Foundation, Inc...
480 (@value{GDBP})
481 @end smallexample
482
483 @noindent
484 @value{GDBN} reads only enough symbol data to know where to find the
485 rest when needed; as a result, the first prompt comes up very quickly.
486 We now tell @value{GDBN} to use a narrower display width than usual, so
487 that examples fit in this manual.
488
489 @smallexample
490 (@value{GDBP}) @b{set width 70}
491 @end smallexample
492
493 @noindent
494 We need to see how the @code{m4} built-in @code{changequote} works.
495 Having looked at the source, we know the relevant subroutine is
496 @code{m4_changequote}, so we set a breakpoint there with the @value{GDBN}
497 @code{break} command.
498
499 @smallexample
500 (@value{GDBP}) @b{break m4_changequote}
501 Breakpoint 1 at 0x62f4: file builtin.c, line 879.
502 @end smallexample
503
504 @noindent
505 Using the @code{run} command, we start @code{m4} running under @value{GDBN}
506 control; as long as control does not reach the @code{m4_changequote}
507 subroutine, the program runs as usual:
508
509 @smallexample
510 (@value{GDBP}) @b{run}
511 Starting program: /work/Editorial/gdb/gnu/m4/m4
512 @b{define(foo,0000)}
513
514 @b{foo}
515 0000
516 @end smallexample
517
518 @noindent
519 To trigger the breakpoint, we call @code{changequote}. @value{GDBN}
520 suspends execution of @code{m4}, displaying information about the
521 context where it stops.
522
523 @smallexample
524 @b{changequote(<QUOTE>,<UNQUOTE>)}
525
526 Breakpoint 1, m4_changequote (argc=3, argv=0x33c70)
527 at builtin.c:879
528 879 if (bad_argc(TOKEN_DATA_TEXT(argv[0]),argc,1,3))
529 @end smallexample
530
531 @noindent
532 Now we use the command @code{n} (@code{next}) to advance execution to
533 the next line of the current function.
534
535 @smallexample
536 (@value{GDBP}) @b{n}
537 882 set_quotes((argc >= 2) ? TOKEN_DATA_TEXT(argv[1])\
538 : nil,
539 @end smallexample
540
541 @noindent
542 @code{set_quotes} looks like a promising subroutine. We can go into it
543 by using the command @code{s} (@code{step}) instead of @code{next}.
544 @code{step} goes to the next line to be executed in @emph{any}
545 subroutine, so it steps into @code{set_quotes}.
546
547 @smallexample
548 (@value{GDBP}) @b{s}
549 set_quotes (lq=0x34c78 "<QUOTE>", rq=0x34c88 "<UNQUOTE>")
550 at input.c:530
551 530 if (lquote != def_lquote)
552 @end smallexample
553
554 @noindent
555 The display that shows the subroutine where @code{m4} is now
556 suspended (and its arguments) is called a stack frame display. It
557 shows a summary of the stack. We can use the @code{backtrace}
558 command (which can also be spelled @code{bt}), to see where we are
559 in the stack as a whole: the @code{backtrace} command displays a
560 stack frame for each active subroutine.
561
562 @smallexample
563 (@value{GDBP}) @b{bt}
564 #0 set_quotes (lq=0x34c78 "<QUOTE>", rq=0x34c88 "<UNQUOTE>")
565 at input.c:530
566 #1 0x6344 in m4_changequote (argc=3, argv=0x33c70)
567 at builtin.c:882
568 #2 0x8174 in expand_macro (sym=0x33320) at macro.c:242
569 #3 0x7a88 in expand_token (obs=0x0, t=209696, td=0xf7fffa30)
570 at macro.c:71
571 #4 0x79dc in expand_input () at macro.c:40
572 #5 0x2930 in main (argc=0, argv=0xf7fffb20) at m4.c:195
573 @end smallexample
574
575 @noindent
576 We step through a few more lines to see what happens. The first two
577 times, we can use @samp{s}; the next two times we use @code{n} to avoid
578 falling into the @code{xstrdup} subroutine.
579
580 @smallexample
581 (@value{GDBP}) @b{s}
582 0x3b5c 532 if (rquote != def_rquote)
583 (@value{GDBP}) @b{s}
584 0x3b80 535 lquote = (lq == nil || *lq == '\0') ? \
585 def_lquote : xstrdup(lq);
586 (@value{GDBP}) @b{n}
587 536 rquote = (rq == nil || *rq == '\0') ? def_rquote\
588 : xstrdup(rq);
589 (@value{GDBP}) @b{n}
590 538 len_lquote = strlen(rquote);
591 @end smallexample
592
593 @noindent
594 The last line displayed looks a little odd; we can examine the variables
595 @code{lquote} and @code{rquote} to see if they are in fact the new left
596 and right quotes we specified. We use the command @code{p}
597 (@code{print}) to see their values.
598
599 @smallexample
600 (@value{GDBP}) @b{p lquote}
601 $1 = 0x35d40 "<QUOTE>"
602 (@value{GDBP}) @b{p rquote}
603 $2 = 0x35d50 "<UNQUOTE>"
604 @end smallexample
605
606 @noindent
607 @code{lquote} and @code{rquote} are indeed the new left and right quotes.
608 To look at some context, we can display ten lines of source
609 surrounding the current line with the @code{l} (@code{list}) command.
610
611 @smallexample
612 (@value{GDBP}) @b{l}
613 533 xfree(rquote);
614 534
615 535 lquote = (lq == nil || *lq == '\0') ? def_lquote\
616 : xstrdup (lq);
617 536 rquote = (rq == nil || *rq == '\0') ? def_rquote\
618 : xstrdup (rq);
619 537
620 538 len_lquote = strlen(rquote);
621 539 len_rquote = strlen(lquote);
622 540 @}
623 541
624 542 void
625 @end smallexample
626
627 @noindent
628 Let us step past the two lines that set @code{len_lquote} and
629 @code{len_rquote}, and then examine the values of those variables.
630
631 @smallexample
632 (@value{GDBP}) @b{n}
633 539 len_rquote = strlen(lquote);
634 (@value{GDBP}) @b{n}
635 540 @}
636 (@value{GDBP}) @b{p len_lquote}
637 $3 = 9
638 (@value{GDBP}) @b{p len_rquote}
639 $4 = 7
640 @end smallexample
641
642 @noindent
643 That certainly looks wrong, assuming @code{len_lquote} and
644 @code{len_rquote} are meant to be the lengths of @code{lquote} and
645 @code{rquote} respectively. We can set them to better values using
646 the @code{p} command, since it can print the value of
647 any expression---and that expression can include subroutine calls and
648 assignments.
649
650 @smallexample
651 (@value{GDBP}) @b{p len_lquote=strlen(lquote)}
652 $5 = 7
653 (@value{GDBP}) @b{p len_rquote=strlen(rquote)}
654 $6 = 9
655 @end smallexample
656
657 @noindent
658 Is that enough to fix the problem of using the new quotes with the
659 @code{m4} built-in @code{defn}? We can allow @code{m4} to continue
660 executing with the @code{c} (@code{continue}) command, and then try the
661 example that caused trouble initially:
662
663 @smallexample
664 (@value{GDBP}) @b{c}
665 Continuing.
666
667 @b{define(baz,defn(<QUOTE>foo<UNQUOTE>))}
668
669 baz
670 0000
671 @end smallexample
672
673 @noindent
674 Success! The new quotes now work just as well as the default ones. The
675 problem seems to have been just the two typos defining the wrong
676 lengths. We allow @code{m4} exit by giving it an EOF as input:
677
678 @smallexample
679 @b{C-d}
680 Program exited normally.
681 @end smallexample
682
683 @noindent
684 The message @samp{Program exited normally.} is from @value{GDBN}; it
685 indicates @code{m4} has finished executing. We can end our @value{GDBN}
686 session with the @value{GDBN} @code{quit} command.
687
688 @smallexample
689 (@value{GDBP}) @b{quit}
690 @end smallexample
691
692 @node Invocation
693 @chapter Getting In and Out of @value{GDBN}
694
695 This chapter discusses how to start @value{GDBN}, and how to get out of it.
696 The essentials are:
697 @itemize @bullet
698 @item
699 type @samp{@value{GDBP}} to start @value{GDBN}.
700 @item
701 type @kbd{quit} or @kbd{C-d} to exit.
702 @end itemize
703
704 @menu
705 * Invoking GDB:: How to start @value{GDBN}
706 * Quitting GDB:: How to quit @value{GDBN}
707 * Shell Commands:: How to use shell commands inside @value{GDBN}
708 @end menu
709
710 @node Invoking GDB
711 @section Invoking @value{GDBN}
712
713 Invoke @value{GDBN} by running the program @code{@value{GDBP}}. Once started,
714 @value{GDBN} reads commands from the terminal until you tell it to exit.
715
716 You can also run @code{@value{GDBP}} with a variety of arguments and options,
717 to specify more of your debugging environment at the outset.
718
719 The command-line options described here are designed
720 to cover a variety of situations; in some environments, some of these
721 options may effectively be unavailable.
722
723 The most usual way to start @value{GDBN} is with one argument,
724 specifying an executable program:
725
726 @example
727 @value{GDBP} @var{program}
728 @end example
729
730 @noindent
731 You can also start with both an executable program and a core file
732 specified:
733
734 @example
735 @value{GDBP} @var{program} @var{core}
736 @end example
737
738 You can, instead, specify a process ID as a second argument, if you want
739 to debug a running process:
740
741 @example
742 @value{GDBP} @var{program} 1234
743 @end example
744
745 @noindent
746 would attach @value{GDBN} to process @code{1234} (unless you also have a file
747 named @file{1234}; @value{GDBN} does check for a core file first).
748
749 Taking advantage of the second command-line argument requires a fairly
750 complete operating system; when you use @value{GDBN} as a remote
751 debugger attached to a bare board, there may not be any notion of
752 ``process'', and there is often no way to get a core dump. @value{GDBN}
753 will warn you if it is unable to attach or to read core dumps.
754
755 You can run @code{@value{GDBP}} without printing the front material, which describes
756 @value{GDBN}'s non-warranty, by specifying @code{-silent}:
757
758 @smallexample
759 @value{GDBP} -silent
760 @end smallexample
761
762 @noindent
763 You can further control how @value{GDBN} starts up by using command-line
764 options. @value{GDBN} itself can remind you of the options available.
765
766 @noindent
767 Type
768
769 @example
770 @value{GDBP} -help
771 @end example
772
773 @noindent
774 to display all available options and briefly describe their use
775 (@samp{@value{GDBP} -h} is a shorter equivalent).
776
777 All options and command line arguments you give are processed
778 in sequential order. The order makes a difference when the
779 @samp{-x} option is used.
780
781
782 @menu
783 * File Options:: Choosing files
784 * Mode Options:: Choosing modes
785 @end menu
786
787 @node File Options
788 @subsection Choosing files
789
790 When @value{GDBN} starts, it reads any arguments other than options as
791 specifying an executable file and core file (or process ID). This is
792 the same as if the arguments were specified by the @samp{-se} and
793 @samp{-c} options respectively. (@value{GDBN} reads the first argument
794 that does not have an associated option flag as equivalent to the
795 @samp{-se} option followed by that argument; and the second argument
796 that does not have an associated option flag, if any, as equivalent to
797 the @samp{-c} option followed by that argument.)
798
799 If @value{GDBN} has not been configured to included core file support,
800 such as for most embedded targets, then it will complain about a second
801 argument and ignore it.
802
803 Many options have both long and short forms; both are shown in the
804 following list. @value{GDBN} also recognizes the long forms if you truncate
805 them, so long as enough of the option is present to be unambiguous.
806 (If you prefer, you can flag option arguments with @samp{--} rather
807 than @samp{-}, though we illustrate the more usual convention.)
808
809 @c NOTE: the @cindex entries here use double dashes ON PURPOSE. This
810 @c way, both those who look for -foo and --foo in the index, will find
811 @c it.
812
813 @table @code
814 @item -symbols @var{file}
815 @itemx -s @var{file}
816 @cindex @code{--symbols}
817 @cindex @code{-s}
818 Read symbol table from file @var{file}.
819
820 @item -exec @var{file}
821 @itemx -e @var{file}
822 @cindex @code{--exec}
823 @cindex @code{-e}
824 Use file @var{file} as the executable file to execute when appropriate,
825 and for examining pure data in conjunction with a core dump.
826
827 @item -se @var{file}
828 @cindex @code{--se}
829 Read symbol table from file @var{file} and use it as the executable
830 file.
831
832 @item -core @var{file}
833 @itemx -c @var{file}
834 @cindex @code{--core}
835 @cindex @code{-c}
836 Use file @var{file} as a core dump to examine.
837
838 @item -c @var{number}
839 Connect to process ID @var{number}, as with the @code{attach} command
840 (unless there is a file in core-dump format named @var{number}, in which
841 case @samp{-c} specifies that file as a core dump to read).
842
843 @item -command @var{file}
844 @itemx -x @var{file}
845 @cindex @code{--command}
846 @cindex @code{-x}
847 Execute @value{GDBN} commands from file @var{file}. @xref{Command
848 Files,, Command files}.
849
850 @item -directory @var{directory}
851 @itemx -d @var{directory}
852 @cindex @code{--directory}
853 @cindex @code{-d}
854 Add @var{directory} to the path to search for source files.
855
856 @item -m
857 @itemx -mapped
858 @cindex @code{--mapped}
859 @cindex @code{-m}
860 @emph{Warning: this option depends on operating system facilities that are not
861 supported on all systems.}@*
862 If memory-mapped files are available on your system through the @code{mmap}
863 system call, you can use this option
864 to have @value{GDBN} write the symbols from your
865 program into a reusable file in the current directory. If the program you are debugging is
866 called @file{/tmp/fred}, the mapped symbol file is @file{/tmp/fred.syms}.
867 Future @value{GDBN} debugging sessions notice the presence of this file,
868 and can quickly map in symbol information from it, rather than reading
869 the symbol table from the executable program.
870
871 The @file{.syms} file is specific to the host machine where @value{GDBN}
872 is run. It holds an exact image of the internal @value{GDBN} symbol
873 table. It cannot be shared across multiple host platforms.
874
875 @item -r
876 @itemx -readnow
877 @cindex @code{--readnow}
878 @cindex @code{-r}
879 Read each symbol file's entire symbol table immediately, rather than
880 the default, which is to read it incrementally as it is needed.
881 This makes startup slower, but makes future operations faster.
882
883 @end table
884
885 You typically combine the @code{-mapped} and @code{-readnow} options in
886 order to build a @file{.syms} file that contains complete symbol
887 information. (@xref{Files,,Commands to specify files}, for information
888 on @file{.syms} files.) A simple @value{GDBN} invocation to do nothing
889 but build a @file{.syms} file for future use is:
890
891 @example
892 gdb -batch -nx -mapped -readnow programname
893 @end example
894
895 @node Mode Options
896 @subsection Choosing modes
897
898 You can run @value{GDBN} in various alternative modes---for example, in
899 batch mode or quiet mode.
900
901 @table @code
902 @item -nx
903 @itemx -n
904 @cindex @code{--nx}
905 @cindex @code{-n}
906 Do not execute commands found in any initialization files (normally
907 called @file{.gdbinit}, or @file{gdb.ini} on PCs). Normally,
908 @value{GDBN} executes the commands in these files after all the command
909 options and arguments have been processed. @xref{Command Files,,Command
910 files}.
911
912 @item -quiet
913 @itemx -silent
914 @itemx -q
915 @cindex @code{--quiet}
916 @cindex @code{--silent}
917 @cindex @code{-q}
918 ``Quiet''. Do not print the introductory and copyright messages. These
919 messages are also suppressed in batch mode.
920
921 @item -batch
922 @cindex @code{--batch}
923 Run in batch mode. Exit with status @code{0} after processing all the
924 command files specified with @samp{-x} (and all commands from
925 initialization files, if not inhibited with @samp{-n}). Exit with
926 nonzero status if an error occurs in executing the @value{GDBN} commands
927 in the command files.
928
929 Batch mode may be useful for running @value{GDBN} as a filter, for
930 example to download and run a program on another computer; in order to
931 make this more useful, the message
932
933 @example
934 Program exited normally.
935 @end example
936
937 @noindent
938 (which is ordinarily issued whenever a program running under
939 @value{GDBN} control terminates) is not issued when running in batch
940 mode.
941
942 @item -nowindows
943 @itemx -nw
944 @cindex @code{--nowindows}
945 @cindex @code{-nw}
946 ``No windows''. If @value{GDBN} comes with a graphical user interface
947 (GUI) built in, then this option tells @value{GDBN} to only use the command-line
948 interface. If no GUI is available, this option has no effect.
949
950 @item -windows
951 @itemx -w
952 @cindex @code{--windows}
953 @cindex @code{-w}
954 If @value{GDBN} includes a GUI, then this option requires it to be
955 used if possible.
956
957 @item -cd @var{directory}
958 @cindex @code{--cd}
959 Run @value{GDBN} using @var{directory} as its working directory,
960 instead of the current directory.
961
962 @item -fullname
963 @itemx -f
964 @cindex @code{--fullname}
965 @cindex @code{-f}
966 @sc{gnu} Emacs sets this option when it runs @value{GDBN} as a
967 subprocess. It tells @value{GDBN} to output the full file name and line
968 number in a standard, recognizable fashion each time a stack frame is
969 displayed (which includes each time your program stops). This
970 recognizable format looks like two @samp{\032} characters, followed by
971 the file name, line number and character position separated by colons,
972 and a newline. The Emacs-to-@value{GDBN} interface program uses the two
973 @samp{\032} characters as a signal to display the source code for the
974 frame.
975
976 @item -epoch
977 @cindex @code{--epoch}
978 The Epoch Emacs-@value{GDBN} interface sets this option when it runs
979 @value{GDBN} as a subprocess. It tells @value{GDBN} to modify its print
980 routines so as to allow Epoch to display values of expressions in a
981 separate window.
982
983 @item -annotate @var{level}
984 @cindex @code{--annotate}
985 This option sets the @dfn{annotation level} inside @value{GDBN}. Its
986 effect is identical to using @samp{set annotate @var{level}}
987 (@pxref{Annotations}).
988 Annotation level controls how much information does @value{GDBN} print
989 together with its prompt, values of expressions, source lines, and other
990 types of output. Level 0 is the normal, level 1 is for use when
991 @value{GDBN} is run as a subprocess of @sc{gnu} Emacs, level 2 is the
992 maximum annotation suitable for programs that control @value{GDBN}.
993
994 @item -async
995 @cindex @code{--async}
996 Use the asynchronous event loop for the command-line interface.
997 @value{GDBN} processes all events, such as user keyboard input, via a
998 special event loop. This allows @value{GDBN} to accept and process user
999 commands in parallel with the debugged process being
1000 run@footnote{@value{GDBN} built with @sc{djgpp} tools for
1001 MS-DOS/MS-Windows supports this mode of operation, but the event loop is
1002 suspended when the debuggee runs.}, so you don't need to wait for
1003 control to return to @value{GDBN} before you type the next command.
1004 (@emph{Note:} as of version 5.1, the target side of the asynchronous
1005 operation is not yet in place, so @samp{-async} does not work fully
1006 yet.)
1007 @c FIXME: when the target side of the event loop is done, the above NOTE
1008 @c should be removed.
1009
1010 When the standard input is connected to a terminal device, @value{GDBN}
1011 uses the asynchronous event loop by default, unless disabled by the
1012 @samp{-noasync} option.
1013
1014 @item -noasync
1015 @cindex @code{--noasync}
1016 Disable the asynchronous event loop for the command-line interface.
1017
1018 @item -baud @var{bps}
1019 @itemx -b @var{bps}
1020 @cindex @code{--baud}
1021 @cindex @code{-b}
1022 Set the line speed (baud rate or bits per second) of any serial
1023 interface used by @value{GDBN} for remote debugging.
1024
1025 @item -tty @var{device}
1026 @itemx -t @var{device}
1027 @cindex @code{--tty}
1028 @cindex @code{-t}
1029 Run using @var{device} for your program's standard input and output.
1030 @c FIXME: kingdon thinks there is more to -tty. Investigate.
1031
1032 @c resolve the situation of these eventually
1033 @item -tui
1034 @cindex @code{--tui}
1035 Activate the Terminal User Interface when starting.
1036 The Terminal User Interface manages several text windows on the terminal,
1037 showing source, assembly, registers and @value{GDBN} command outputs
1038 (@pxref{TUI, ,@value{GDBN} Text User Interface}).
1039 Do not use this option if you run @value{GDBN} from Emacs
1040 (@pxref{Emacs, ,Using @value{GDBN} under @sc{gnu} Emacs}).
1041
1042 @c @item -xdb
1043 @c @cindex @code{--xdb}
1044 @c Run in XDB compatibility mode, allowing the use of certain XDB commands.
1045 @c For information, see the file @file{xdb_trans.html}, which is usually
1046 @c installed in the directory @code{/opt/langtools/wdb/doc} on HP-UX
1047 @c systems.
1048
1049 @item -interpreter @var{interp}
1050 @cindex @code{--interpreter}
1051 Use the interpreter @var{interp} for interface with the controlling
1052 program or device. This option is meant to be set by programs which
1053 communicate with @value{GDBN} using it as a back end.
1054
1055 @samp{--interpreter=mi} (or @samp{--interpreter=mi1}) causes
1056 @value{GDBN} to use the @dfn{gdb/mi interface} (@pxref{GDB/MI, , The
1057 @sc{gdb/mi} Interface}). The older @sc{gdb/mi} interface, included in
1058 @value{GDBN} version 5.0 can be selected with @samp{--interpreter=mi0}.
1059
1060 @item -write
1061 @cindex @code{--write}
1062 Open the executable and core files for both reading and writing. This
1063 is equivalent to the @samp{set write on} command inside @value{GDBN}
1064 (@pxref{Patching}).
1065
1066 @item -statistics
1067 @cindex @code{--statistics}
1068 This option causes @value{GDBN} to print statistics about time and
1069 memory usage after it completes each command and returns to the prompt.
1070
1071 @item -version
1072 @cindex @code{--version}
1073 This option causes @value{GDBN} to print its version number and
1074 no-warranty blurb, and exit.
1075
1076 @end table
1077
1078 @node Quitting GDB
1079 @section Quitting @value{GDBN}
1080 @cindex exiting @value{GDBN}
1081 @cindex leaving @value{GDBN}
1082
1083 @table @code
1084 @kindex quit @r{[}@var{expression}@r{]}
1085 @kindex q @r{(@code{quit})}
1086 @item quit @r{[}@var{expression}@r{]}
1087 @itemx q
1088 To exit @value{GDBN}, use the @code{quit} command (abbreviated
1089 @code{q}), or type an end-of-file character (usually @kbd{C-d}). If you
1090 do not supply @var{expression}, @value{GDBN} will terminate normally;
1091 otherwise it will terminate using the result of @var{expression} as the
1092 error code.
1093 @end table
1094
1095 @cindex interrupt
1096 An interrupt (often @kbd{C-c}) does not exit from @value{GDBN}, but rather
1097 terminates the action of any @value{GDBN} command that is in progress and
1098 returns to @value{GDBN} command level. It is safe to type the interrupt
1099 character at any time because @value{GDBN} does not allow it to take effect
1100 until a time when it is safe.
1101
1102 If you have been using @value{GDBN} to control an attached process or
1103 device, you can release it with the @code{detach} command
1104 (@pxref{Attach, ,Debugging an already-running process}).
1105
1106 @node Shell Commands
1107 @section Shell commands
1108
1109 If you need to execute occasional shell commands during your
1110 debugging session, there is no need to leave or suspend @value{GDBN}; you can
1111 just use the @code{shell} command.
1112
1113 @table @code
1114 @kindex shell
1115 @cindex shell escape
1116 @item shell @var{command string}
1117 Invoke a standard shell to execute @var{command string}.
1118 If it exists, the environment variable @code{SHELL} determines which
1119 shell to run. Otherwise @value{GDBN} uses the default shell
1120 (@file{/bin/sh} on Unix systems, @file{COMMAND.COM} on MS-DOS, etc.).
1121 @end table
1122
1123 The utility @code{make} is often needed in development environments.
1124 You do not have to use the @code{shell} command for this purpose in
1125 @value{GDBN}:
1126
1127 @table @code
1128 @kindex make
1129 @cindex calling make
1130 @item make @var{make-args}
1131 Execute the @code{make} program with the specified
1132 arguments. This is equivalent to @samp{shell make @var{make-args}}.
1133 @end table
1134
1135 @node Commands
1136 @chapter @value{GDBN} Commands
1137
1138 You can abbreviate a @value{GDBN} command to the first few letters of the command
1139 name, if that abbreviation is unambiguous; and you can repeat certain
1140 @value{GDBN} commands by typing just @key{RET}. You can also use the @key{TAB}
1141 key to get @value{GDBN} to fill out the rest of a word in a command (or to
1142 show you the alternatives available, if there is more than one possibility).
1143
1144 @menu
1145 * Command Syntax:: How to give commands to @value{GDBN}
1146 * Completion:: Command completion
1147 * Help:: How to ask @value{GDBN} for help
1148 @end menu
1149
1150 @node Command Syntax
1151 @section Command syntax
1152
1153 A @value{GDBN} command is a single line of input. There is no limit on
1154 how long it can be. It starts with a command name, which is followed by
1155 arguments whose meaning depends on the command name. For example, the
1156 command @code{step} accepts an argument which is the number of times to
1157 step, as in @samp{step 5}. You can also use the @code{step} command
1158 with no arguments. Some commands do not allow any arguments.
1159
1160 @cindex abbreviation
1161 @value{GDBN} command names may always be truncated if that abbreviation is
1162 unambiguous. Other possible command abbreviations are listed in the
1163 documentation for individual commands. In some cases, even ambiguous
1164 abbreviations are allowed; for example, @code{s} is specially defined as
1165 equivalent to @code{step} even though there are other commands whose
1166 names start with @code{s}. You can test abbreviations by using them as
1167 arguments to the @code{help} command.
1168
1169 @cindex repeating commands
1170 @kindex RET @r{(repeat last command)}
1171 A blank line as input to @value{GDBN} (typing just @key{RET}) means to
1172 repeat the previous command. Certain commands (for example, @code{run})
1173 will not repeat this way; these are commands whose unintentional
1174 repetition might cause trouble and which you are unlikely to want to
1175 repeat.
1176
1177 The @code{list} and @code{x} commands, when you repeat them with
1178 @key{RET}, construct new arguments rather than repeating
1179 exactly as typed. This permits easy scanning of source or memory.
1180
1181 @value{GDBN} can also use @key{RET} in another way: to partition lengthy
1182 output, in a way similar to the common utility @code{more}
1183 (@pxref{Screen Size,,Screen size}). Since it is easy to press one
1184 @key{RET} too many in this situation, @value{GDBN} disables command
1185 repetition after any command that generates this sort of display.
1186
1187 @kindex # @r{(a comment)}
1188 @cindex comment
1189 Any text from a @kbd{#} to the end of the line is a comment; it does
1190 nothing. This is useful mainly in command files (@pxref{Command
1191 Files,,Command files}).
1192
1193 @node Completion
1194 @section Command completion
1195
1196 @cindex completion
1197 @cindex word completion
1198 @value{GDBN} can fill in the rest of a word in a command for you, if there is
1199 only one possibility; it can also show you what the valid possibilities
1200 are for the next word in a command, at any time. This works for @value{GDBN}
1201 commands, @value{GDBN} subcommands, and the names of symbols in your program.
1202
1203 Press the @key{TAB} key whenever you want @value{GDBN} to fill out the rest
1204 of a word. If there is only one possibility, @value{GDBN} fills in the
1205 word, and waits for you to finish the command (or press @key{RET} to
1206 enter it). For example, if you type
1207
1208 @c FIXME "@key" does not distinguish its argument sufficiently to permit
1209 @c complete accuracy in these examples; space introduced for clarity.
1210 @c If texinfo enhancements make it unnecessary, it would be nice to
1211 @c replace " @key" by "@key" in the following...
1212 @example
1213 (@value{GDBP}) info bre @key{TAB}
1214 @end example
1215
1216 @noindent
1217 @value{GDBN} fills in the rest of the word @samp{breakpoints}, since that is
1218 the only @code{info} subcommand beginning with @samp{bre}:
1219
1220 @example
1221 (@value{GDBP}) info breakpoints
1222 @end example
1223
1224 @noindent
1225 You can either press @key{RET} at this point, to run the @code{info
1226 breakpoints} command, or backspace and enter something else, if
1227 @samp{breakpoints} does not look like the command you expected. (If you
1228 were sure you wanted @code{info breakpoints} in the first place, you
1229 might as well just type @key{RET} immediately after @samp{info bre},
1230 to exploit command abbreviations rather than command completion).
1231
1232 If there is more than one possibility for the next word when you press
1233 @key{TAB}, @value{GDBN} sounds a bell. You can either supply more
1234 characters and try again, or just press @key{TAB} a second time;
1235 @value{GDBN} displays all the possible completions for that word. For
1236 example, you might want to set a breakpoint on a subroutine whose name
1237 begins with @samp{make_}, but when you type @kbd{b make_@key{TAB}} @value{GDBN}
1238 just sounds the bell. Typing @key{TAB} again displays all the
1239 function names in your program that begin with those characters, for
1240 example:
1241
1242 @example
1243 (@value{GDBP}) b make_ @key{TAB}
1244 @exdent @value{GDBN} sounds bell; press @key{TAB} again, to see:
1245 make_a_section_from_file make_environ
1246 make_abs_section make_function_type
1247 make_blockvector make_pointer_type
1248 make_cleanup make_reference_type
1249 make_command make_symbol_completion_list
1250 (@value{GDBP}) b make_
1251 @end example
1252
1253 @noindent
1254 After displaying the available possibilities, @value{GDBN} copies your
1255 partial input (@samp{b make_} in the example) so you can finish the
1256 command.
1257
1258 If you just want to see the list of alternatives in the first place, you
1259 can press @kbd{M-?} rather than pressing @key{TAB} twice. @kbd{M-?}
1260 means @kbd{@key{META} ?}. You can type this either by holding down a
1261 key designated as the @key{META} shift on your keyboard (if there is
1262 one) while typing @kbd{?}, or as @key{ESC} followed by @kbd{?}.
1263
1264 @cindex quotes in commands
1265 @cindex completion of quoted strings
1266 Sometimes the string you need, while logically a ``word'', may contain
1267 parentheses or other characters that @value{GDBN} normally excludes from
1268 its notion of a word. To permit word completion to work in this
1269 situation, you may enclose words in @code{'} (single quote marks) in
1270 @value{GDBN} commands.
1271
1272 The most likely situation where you might need this is in typing the
1273 name of a C@t{++} function. This is because C@t{++} allows function
1274 overloading (multiple definitions of the same function, distinguished
1275 by argument type). For example, when you want to set a breakpoint you
1276 may need to distinguish whether you mean the version of @code{name}
1277 that takes an @code{int} parameter, @code{name(int)}, or the version
1278 that takes a @code{float} parameter, @code{name(float)}. To use the
1279 word-completion facilities in this situation, type a single quote
1280 @code{'} at the beginning of the function name. This alerts
1281 @value{GDBN} that it may need to consider more information than usual
1282 when you press @key{TAB} or @kbd{M-?} to request word completion:
1283
1284 @example
1285 (@value{GDBP}) b 'bubble( @kbd{M-?}
1286 bubble(double,double) bubble(int,int)
1287 (@value{GDBP}) b 'bubble(
1288 @end example
1289
1290 In some cases, @value{GDBN} can tell that completing a name requires using
1291 quotes. When this happens, @value{GDBN} inserts the quote for you (while
1292 completing as much as it can) if you do not type the quote in the first
1293 place:
1294
1295 @example
1296 (@value{GDBP}) b bub @key{TAB}
1297 @exdent @value{GDBN} alters your input line to the following, and rings a bell:
1298 (@value{GDBP}) b 'bubble(
1299 @end example
1300
1301 @noindent
1302 In general, @value{GDBN} can tell that a quote is needed (and inserts it) if
1303 you have not yet started typing the argument list when you ask for
1304 completion on an overloaded symbol.
1305
1306 For more information about overloaded functions, see @ref{C plus plus
1307 expressions, ,C@t{++} expressions}. You can use the command @code{set
1308 overload-resolution off} to disable overload resolution;
1309 see @ref{Debugging C plus plus, ,@value{GDBN} features for C@t{++}}.
1310
1311
1312 @node Help
1313 @section Getting help
1314 @cindex online documentation
1315 @kindex help
1316
1317 You can always ask @value{GDBN} itself for information on its commands,
1318 using the command @code{help}.
1319
1320 @table @code
1321 @kindex h @r{(@code{help})}
1322 @item help
1323 @itemx h
1324 You can use @code{help} (abbreviated @code{h}) with no arguments to
1325 display a short list of named classes of commands:
1326
1327 @smallexample
1328 (@value{GDBP}) help
1329 List of classes of commands:
1330
1331 aliases -- Aliases of other commands
1332 breakpoints -- Making program stop at certain points
1333 data -- Examining data
1334 files -- Specifying and examining files
1335 internals -- Maintenance commands
1336 obscure -- Obscure features
1337 running -- Running the program
1338 stack -- Examining the stack
1339 status -- Status inquiries
1340 support -- Support facilities
1341 tracepoints -- Tracing of program execution without@*
1342 stopping the program
1343 user-defined -- User-defined commands
1344
1345 Type "help" followed by a class name for a list of
1346 commands in that class.
1347 Type "help" followed by command name for full
1348 documentation.
1349 Command name abbreviations are allowed if unambiguous.
1350 (@value{GDBP})
1351 @end smallexample
1352 @c the above line break eliminates huge line overfull...
1353
1354 @item help @var{class}
1355 Using one of the general help classes as an argument, you can get a
1356 list of the individual commands in that class. For example, here is the
1357 help display for the class @code{status}:
1358
1359 @smallexample
1360 (@value{GDBP}) help status
1361 Status inquiries.
1362
1363 List of commands:
1364
1365 @c Line break in "show" line falsifies real output, but needed
1366 @c to fit in smallbook page size.
1367 info -- Generic command for showing things
1368 about the program being debugged
1369 show -- Generic command for showing things
1370 about the debugger
1371
1372 Type "help" followed by command name for full
1373 documentation.
1374 Command name abbreviations are allowed if unambiguous.
1375 (@value{GDBP})
1376 @end smallexample
1377
1378 @item help @var{command}
1379 With a command name as @code{help} argument, @value{GDBN} displays a
1380 short paragraph on how to use that command.
1381
1382 @kindex apropos
1383 @item apropos @var{args}
1384 The @code{apropos @var{args}} command searches through all of the @value{GDBN}
1385 commands, and their documentation, for the regular expression specified in
1386 @var{args}. It prints out all matches found. For example:
1387
1388 @smallexample
1389 apropos reload
1390 @end smallexample
1391
1392 @noindent
1393 results in:
1394
1395 @smallexample
1396 @c @group
1397 set symbol-reloading -- Set dynamic symbol table reloading
1398 multiple times in one run
1399 show symbol-reloading -- Show dynamic symbol table reloading
1400 multiple times in one run
1401 @c @end group
1402 @end smallexample
1403
1404 @kindex complete
1405 @item complete @var{args}
1406 The @code{complete @var{args}} command lists all the possible completions
1407 for the beginning of a command. Use @var{args} to specify the beginning of the
1408 command you want completed. For example:
1409
1410 @smallexample
1411 complete i
1412 @end smallexample
1413
1414 @noindent results in:
1415
1416 @smallexample
1417 @group
1418 if
1419 ignore
1420 info
1421 inspect
1422 @end group
1423 @end smallexample
1424
1425 @noindent This is intended for use by @sc{gnu} Emacs.
1426 @end table
1427
1428 In addition to @code{help}, you can use the @value{GDBN} commands @code{info}
1429 and @code{show} to inquire about the state of your program, or the state
1430 of @value{GDBN} itself. Each command supports many topics of inquiry; this
1431 manual introduces each of them in the appropriate context. The listings
1432 under @code{info} and under @code{show} in the Index point to
1433 all the sub-commands. @xref{Index}.
1434
1435 @c @group
1436 @table @code
1437 @kindex info
1438 @kindex i @r{(@code{info})}
1439 @item info
1440 This command (abbreviated @code{i}) is for describing the state of your
1441 program. For example, you can list the arguments given to your program
1442 with @code{info args}, list the registers currently in use with @code{info
1443 registers}, or list the breakpoints you have set with @code{info breakpoints}.
1444 You can get a complete list of the @code{info} sub-commands with
1445 @w{@code{help info}}.
1446
1447 @kindex set
1448 @item set
1449 You can assign the result of an expression to an environment variable with
1450 @code{set}. For example, you can set the @value{GDBN} prompt to a $-sign with
1451 @code{set prompt $}.
1452
1453 @kindex show
1454 @item show
1455 In contrast to @code{info}, @code{show} is for describing the state of
1456 @value{GDBN} itself.
1457 You can change most of the things you can @code{show}, by using the
1458 related command @code{set}; for example, you can control what number
1459 system is used for displays with @code{set radix}, or simply inquire
1460 which is currently in use with @code{show radix}.
1461
1462 @kindex info set
1463 To display all the settable parameters and their current
1464 values, you can use @code{show} with no arguments; you may also use
1465 @code{info set}. Both commands produce the same display.
1466 @c FIXME: "info set" violates the rule that "info" is for state of
1467 @c FIXME...program. Ck w/ GNU: "info set" to be called something else,
1468 @c FIXME...or change desc of rule---eg "state of prog and debugging session"?
1469 @end table
1470 @c @end group
1471
1472 Here are three miscellaneous @code{show} subcommands, all of which are
1473 exceptional in lacking corresponding @code{set} commands:
1474
1475 @table @code
1476 @kindex show version
1477 @cindex version number
1478 @item show version
1479 Show what version of @value{GDBN} is running. You should include this
1480 information in @value{GDBN} bug-reports. If multiple versions of
1481 @value{GDBN} are in use at your site, you may need to determine which
1482 version of @value{GDBN} you are running; as @value{GDBN} evolves, new
1483 commands are introduced, and old ones may wither away. Also, many
1484 system vendors ship variant versions of @value{GDBN}, and there are
1485 variant versions of @value{GDBN} in @sc{gnu}/Linux distributions as well.
1486 The version number is the same as the one announced when you start
1487 @value{GDBN}.
1488
1489 @kindex show copying
1490 @item show copying
1491 Display information about permission for copying @value{GDBN}.
1492
1493 @kindex show warranty
1494 @item show warranty
1495 Display the @sc{gnu} ``NO WARRANTY'' statement, or a warranty,
1496 if your version of @value{GDBN} comes with one.
1497
1498 @end table
1499
1500 @node Running
1501 @chapter Running Programs Under @value{GDBN}
1502
1503 When you run a program under @value{GDBN}, you must first generate
1504 debugging information when you compile it.
1505
1506 You may start @value{GDBN} with its arguments, if any, in an environment
1507 of your choice. If you are doing native debugging, you may redirect
1508 your program's input and output, debug an already running process, or
1509 kill a child process.
1510
1511 @menu
1512 * Compilation:: Compiling for debugging
1513 * Starting:: Starting your program
1514 * Arguments:: Your program's arguments
1515 * Environment:: Your program's environment
1516
1517 * Working Directory:: Your program's working directory
1518 * Input/Output:: Your program's input and output
1519 * Attach:: Debugging an already-running process
1520 * Kill Process:: Killing the child process
1521
1522 * Threads:: Debugging programs with multiple threads
1523 * Processes:: Debugging programs with multiple processes
1524 @end menu
1525
1526 @node Compilation
1527 @section Compiling for debugging
1528
1529 In order to debug a program effectively, you need to generate
1530 debugging information when you compile it. This debugging information
1531 is stored in the object file; it describes the data type of each
1532 variable or function and the correspondence between source line numbers
1533 and addresses in the executable code.
1534
1535 To request debugging information, specify the @samp{-g} option when you run
1536 the compiler.
1537
1538 Many C compilers are unable to handle the @samp{-g} and @samp{-O}
1539 options together. Using those compilers, you cannot generate optimized
1540 executables containing debugging information.
1541
1542 @value{NGCC}, the @sc{gnu} C compiler, supports @samp{-g} with or
1543 without @samp{-O}, making it possible to debug optimized code. We
1544 recommend that you @emph{always} use @samp{-g} whenever you compile a
1545 program. You may think your program is correct, but there is no sense
1546 in pushing your luck.
1547
1548 @cindex optimized code, debugging
1549 @cindex debugging optimized code
1550 When you debug a program compiled with @samp{-g -O}, remember that the
1551 optimizer is rearranging your code; the debugger shows you what is
1552 really there. Do not be too surprised when the execution path does not
1553 exactly match your source file! An extreme example: if you define a
1554 variable, but never use it, @value{GDBN} never sees that
1555 variable---because the compiler optimizes it out of existence.
1556
1557 Some things do not work as well with @samp{-g -O} as with just
1558 @samp{-g}, particularly on machines with instruction scheduling. If in
1559 doubt, recompile with @samp{-g} alone, and if this fixes the problem,
1560 please report it to us as a bug (including a test case!).
1561
1562 Older versions of the @sc{gnu} C compiler permitted a variant option
1563 @w{@samp{-gg}} for debugging information. @value{GDBN} no longer supports this
1564 format; if your @sc{gnu} C compiler has this option, do not use it.
1565
1566 @need 2000
1567 @node Starting
1568 @section Starting your program
1569 @cindex starting
1570 @cindex running
1571
1572 @table @code
1573 @kindex run
1574 @kindex r @r{(@code{run})}
1575 @item run
1576 @itemx r
1577 Use the @code{run} command to start your program under @value{GDBN}.
1578 You must first specify the program name (except on VxWorks) with an
1579 argument to @value{GDBN} (@pxref{Invocation, ,Getting In and Out of
1580 @value{GDBN}}), or by using the @code{file} or @code{exec-file} command
1581 (@pxref{Files, ,Commands to specify files}).
1582
1583 @end table
1584
1585 If you are running your program in an execution environment that
1586 supports processes, @code{run} creates an inferior process and makes
1587 that process run your program. (In environments without processes,
1588 @code{run} jumps to the start of your program.)
1589
1590 The execution of a program is affected by certain information it
1591 receives from its superior. @value{GDBN} provides ways to specify this
1592 information, which you must do @emph{before} starting your program. (You
1593 can change it after starting your program, but such changes only affect
1594 your program the next time you start it.) This information may be
1595 divided into four categories:
1596
1597 @table @asis
1598 @item The @emph{arguments.}
1599 Specify the arguments to give your program as the arguments of the
1600 @code{run} command. If a shell is available on your target, the shell
1601 is used to pass the arguments, so that you may use normal conventions
1602 (such as wildcard expansion or variable substitution) in describing
1603 the arguments.
1604 In Unix systems, you can control which shell is used with the
1605 @code{SHELL} environment variable.
1606 @xref{Arguments, ,Your program's arguments}.
1607
1608 @item The @emph{environment.}
1609 Your program normally inherits its environment from @value{GDBN}, but you can
1610 use the @value{GDBN} commands @code{set environment} and @code{unset
1611 environment} to change parts of the environment that affect
1612 your program. @xref{Environment, ,Your program's environment}.
1613
1614 @item The @emph{working directory.}
1615 Your program inherits its working directory from @value{GDBN}. You can set
1616 the @value{GDBN} working directory with the @code{cd} command in @value{GDBN}.
1617 @xref{Working Directory, ,Your program's working directory}.
1618
1619 @item The @emph{standard input and output.}
1620 Your program normally uses the same device for standard input and
1621 standard output as @value{GDBN} is using. You can redirect input and output
1622 in the @code{run} command line, or you can use the @code{tty} command to
1623 set a different device for your program.
1624 @xref{Input/Output, ,Your program's input and output}.
1625
1626 @cindex pipes
1627 @emph{Warning:} While input and output redirection work, you cannot use
1628 pipes to pass the output of the program you are debugging to another
1629 program; if you attempt this, @value{GDBN} is likely to wind up debugging the
1630 wrong program.
1631 @end table
1632
1633 When you issue the @code{run} command, your program begins to execute
1634 immediately. @xref{Stopping, ,Stopping and continuing}, for discussion
1635 of how to arrange for your program to stop. Once your program has
1636 stopped, you may call functions in your program, using the @code{print}
1637 or @code{call} commands. @xref{Data, ,Examining Data}.
1638
1639 If the modification time of your symbol file has changed since the last
1640 time @value{GDBN} read its symbols, @value{GDBN} discards its symbol
1641 table, and reads it again. When it does this, @value{GDBN} tries to retain
1642 your current breakpoints.
1643
1644 @node Arguments
1645 @section Your program's arguments
1646
1647 @cindex arguments (to your program)
1648 The arguments to your program can be specified by the arguments of the
1649 @code{run} command.
1650 They are passed to a shell, which expands wildcard characters and
1651 performs redirection of I/O, and thence to your program. Your
1652 @code{SHELL} environment variable (if it exists) specifies what shell
1653 @value{GDBN} uses. If you do not define @code{SHELL}, @value{GDBN} uses
1654 the default shell (@file{/bin/sh} on Unix).
1655
1656 On non-Unix systems, the program is usually invoked directly by
1657 @value{GDBN}, which emulates I/O redirection via the appropriate system
1658 calls, and the wildcard characters are expanded by the startup code of
1659 the program, not by the shell.
1660
1661 @code{run} with no arguments uses the same arguments used by the previous
1662 @code{run}, or those set by the @code{set args} command.
1663
1664 @table @code
1665 @kindex set args
1666 @item set args
1667 Specify the arguments to be used the next time your program is run. If
1668 @code{set args} has no arguments, @code{run} executes your program
1669 with no arguments. Once you have run your program with arguments,
1670 using @code{set args} before the next @code{run} is the only way to run
1671 it again without arguments.
1672
1673 @kindex show args
1674 @item show args
1675 Show the arguments to give your program when it is started.
1676 @end table
1677
1678 @node Environment
1679 @section Your program's environment
1680
1681 @cindex environment (of your program)
1682 The @dfn{environment} consists of a set of environment variables and
1683 their values. Environment variables conventionally record such things as
1684 your user name, your home directory, your terminal type, and your search
1685 path for programs to run. Usually you set up environment variables with
1686 the shell and they are inherited by all the other programs you run. When
1687 debugging, it can be useful to try running your program with a modified
1688 environment without having to start @value{GDBN} over again.
1689
1690 @table @code
1691 @kindex path
1692 @item path @var{directory}
1693 Add @var{directory} to the front of the @code{PATH} environment variable
1694 (the search path for executables) that will be passed to your program.
1695 The value of @code{PATH} used by @value{GDBN} does not change.
1696 You may specify several directory names, separated by whitespace or by a
1697 system-dependent separator character (@samp{:} on Unix, @samp{;} on
1698 MS-DOS and MS-Windows). If @var{directory} is already in the path, it
1699 is moved to the front, so it is searched sooner.
1700
1701 You can use the string @samp{$cwd} to refer to whatever is the current
1702 working directory at the time @value{GDBN} searches the path. If you
1703 use @samp{.} instead, it refers to the directory where you executed the
1704 @code{path} command. @value{GDBN} replaces @samp{.} in the
1705 @var{directory} argument (with the current path) before adding
1706 @var{directory} to the search path.
1707 @c 'path' is explicitly nonrepeatable, but RMS points out it is silly to
1708 @c document that, since repeating it would be a no-op.
1709
1710 @kindex show paths
1711 @item show paths
1712 Display the list of search paths for executables (the @code{PATH}
1713 environment variable).
1714
1715 @kindex show environment
1716 @item show environment @r{[}@var{varname}@r{]}
1717 Print the value of environment variable @var{varname} to be given to
1718 your program when it starts. If you do not supply @var{varname},
1719 print the names and values of all environment variables to be given to
1720 your program. You can abbreviate @code{environment} as @code{env}.
1721
1722 @kindex set environment
1723 @item set environment @var{varname} @r{[}=@var{value}@r{]}
1724 Set environment variable @var{varname} to @var{value}. The value
1725 changes for your program only, not for @value{GDBN} itself. @var{value} may
1726 be any string; the values of environment variables are just strings, and
1727 any interpretation is supplied by your program itself. The @var{value}
1728 parameter is optional; if it is eliminated, the variable is set to a
1729 null value.
1730 @c "any string" here does not include leading, trailing
1731 @c blanks. Gnu asks: does anyone care?
1732
1733 For example, this command:
1734
1735 @example
1736 set env USER = foo
1737 @end example
1738
1739 @noindent
1740 tells the debugged program, when subsequently run, that its user is named
1741 @samp{foo}. (The spaces around @samp{=} are used for clarity here; they
1742 are not actually required.)
1743
1744 @kindex unset environment
1745 @item unset environment @var{varname}
1746 Remove variable @var{varname} from the environment to be passed to your
1747 program. This is different from @samp{set env @var{varname} =};
1748 @code{unset environment} removes the variable from the environment,
1749 rather than assigning it an empty value.
1750 @end table
1751
1752 @emph{Warning:} On Unix systems, @value{GDBN} runs your program using
1753 the shell indicated
1754 by your @code{SHELL} environment variable if it exists (or
1755 @code{/bin/sh} if not). If your @code{SHELL} variable names a shell
1756 that runs an initialization file---such as @file{.cshrc} for C-shell, or
1757 @file{.bashrc} for BASH---any variables you set in that file affect
1758 your program. You may wish to move setting of environment variables to
1759 files that are only run when you sign on, such as @file{.login} or
1760 @file{.profile}.
1761
1762 @node Working Directory
1763 @section Your program's working directory
1764
1765 @cindex working directory (of your program)
1766 Each time you start your program with @code{run}, it inherits its
1767 working directory from the current working directory of @value{GDBN}.
1768 The @value{GDBN} working directory is initially whatever it inherited
1769 from its parent process (typically the shell), but you can specify a new
1770 working directory in @value{GDBN} with the @code{cd} command.
1771
1772 The @value{GDBN} working directory also serves as a default for the commands
1773 that specify files for @value{GDBN} to operate on. @xref{Files, ,Commands to
1774 specify files}.
1775
1776 @table @code
1777 @kindex cd
1778 @item cd @var{directory}
1779 Set the @value{GDBN} working directory to @var{directory}.
1780
1781 @kindex pwd
1782 @item pwd
1783 Print the @value{GDBN} working directory.
1784 @end table
1785
1786 @node Input/Output
1787 @section Your program's input and output
1788
1789 @cindex redirection
1790 @cindex i/o
1791 @cindex terminal
1792 By default, the program you run under @value{GDBN} does input and output to
1793 the same terminal that @value{GDBN} uses. @value{GDBN} switches the terminal
1794 to its own terminal modes to interact with you, but it records the terminal
1795 modes your program was using and switches back to them when you continue
1796 running your program.
1797
1798 @table @code
1799 @kindex info terminal
1800 @item info terminal
1801 Displays information recorded by @value{GDBN} about the terminal modes your
1802 program is using.
1803 @end table
1804
1805 You can redirect your program's input and/or output using shell
1806 redirection with the @code{run} command. For example,
1807
1808 @example
1809 run > outfile
1810 @end example
1811
1812 @noindent
1813 starts your program, diverting its output to the file @file{outfile}.
1814
1815 @kindex tty
1816 @cindex controlling terminal
1817 Another way to specify where your program should do input and output is
1818 with the @code{tty} command. This command accepts a file name as
1819 argument, and causes this file to be the default for future @code{run}
1820 commands. It also resets the controlling terminal for the child
1821 process, for future @code{run} commands. For example,
1822
1823 @example
1824 tty /dev/ttyb
1825 @end example
1826
1827 @noindent
1828 directs that processes started with subsequent @code{run} commands
1829 default to do input and output on the terminal @file{/dev/ttyb} and have
1830 that as their controlling terminal.
1831
1832 An explicit redirection in @code{run} overrides the @code{tty} command's
1833 effect on the input/output device, but not its effect on the controlling
1834 terminal.
1835
1836 When you use the @code{tty} command or redirect input in the @code{run}
1837 command, only the input @emph{for your program} is affected. The input
1838 for @value{GDBN} still comes from your terminal.
1839
1840 @node Attach
1841 @section Debugging an already-running process
1842 @kindex attach
1843 @cindex attach
1844
1845 @table @code
1846 @item attach @var{process-id}
1847 This command attaches to a running process---one that was started
1848 outside @value{GDBN}. (@code{info files} shows your active
1849 targets.) The command takes as argument a process ID. The usual way to
1850 find out the process-id of a Unix process is with the @code{ps} utility,
1851 or with the @samp{jobs -l} shell command.
1852
1853 @code{attach} does not repeat if you press @key{RET} a second time after
1854 executing the command.
1855 @end table
1856
1857 To use @code{attach}, your program must be running in an environment
1858 which supports processes; for example, @code{attach} does not work for
1859 programs on bare-board targets that lack an operating system. You must
1860 also have permission to send the process a signal.
1861
1862 When you use @code{attach}, the debugger finds the program running in
1863 the process first by looking in the current working directory, then (if
1864 the program is not found) by using the source file search path
1865 (@pxref{Source Path, ,Specifying source directories}). You can also use
1866 the @code{file} command to load the program. @xref{Files, ,Commands to
1867 Specify Files}.
1868
1869 The first thing @value{GDBN} does after arranging to debug the specified
1870 process is to stop it. You can examine and modify an attached process
1871 with all the @value{GDBN} commands that are ordinarily available when
1872 you start processes with @code{run}. You can insert breakpoints; you
1873 can step and continue; you can modify storage. If you would rather the
1874 process continue running, you may use the @code{continue} command after
1875 attaching @value{GDBN} to the process.
1876
1877 @table @code
1878 @kindex detach
1879 @item detach
1880 When you have finished debugging the attached process, you can use the
1881 @code{detach} command to release it from @value{GDBN} control. Detaching
1882 the process continues its execution. After the @code{detach} command,
1883 that process and @value{GDBN} become completely independent once more, and you
1884 are ready to @code{attach} another process or start one with @code{run}.
1885 @code{detach} does not repeat if you press @key{RET} again after
1886 executing the command.
1887 @end table
1888
1889 If you exit @value{GDBN} or use the @code{run} command while you have an
1890 attached process, you kill that process. By default, @value{GDBN} asks
1891 for confirmation if you try to do either of these things; you can
1892 control whether or not you need to confirm by using the @code{set
1893 confirm} command (@pxref{Messages/Warnings, ,Optional warnings and
1894 messages}).
1895
1896 @node Kill Process
1897 @section Killing the child process
1898
1899 @table @code
1900 @kindex kill
1901 @item kill
1902 Kill the child process in which your program is running under @value{GDBN}.
1903 @end table
1904
1905 This command is useful if you wish to debug a core dump instead of a
1906 running process. @value{GDBN} ignores any core dump file while your program
1907 is running.
1908
1909 On some operating systems, a program cannot be executed outside @value{GDBN}
1910 while you have breakpoints set on it inside @value{GDBN}. You can use the
1911 @code{kill} command in this situation to permit running your program
1912 outside the debugger.
1913
1914 The @code{kill} command is also useful if you wish to recompile and
1915 relink your program, since on many systems it is impossible to modify an
1916 executable file while it is running in a process. In this case, when you
1917 next type @code{run}, @value{GDBN} notices that the file has changed, and
1918 reads the symbol table again (while trying to preserve your current
1919 breakpoint settings).
1920
1921 @node Threads
1922 @section Debugging programs with multiple threads
1923
1924 @cindex threads of execution
1925 @cindex multiple threads
1926 @cindex switching threads
1927 In some operating systems, such as HP-UX and Solaris, a single program
1928 may have more than one @dfn{thread} of execution. The precise semantics
1929 of threads differ from one operating system to another, but in general
1930 the threads of a single program are akin to multiple processes---except
1931 that they share one address space (that is, they can all examine and
1932 modify the same variables). On the other hand, each thread has its own
1933 registers and execution stack, and perhaps private memory.
1934
1935 @value{GDBN} provides these facilities for debugging multi-thread
1936 programs:
1937
1938 @itemize @bullet
1939 @item automatic notification of new threads
1940 @item @samp{thread @var{threadno}}, a command to switch among threads
1941 @item @samp{info threads}, a command to inquire about existing threads
1942 @item @samp{thread apply [@var{threadno}] [@var{all}] @var{args}},
1943 a command to apply a command to a list of threads
1944 @item thread-specific breakpoints
1945 @end itemize
1946
1947 @quotation
1948 @emph{Warning:} These facilities are not yet available on every
1949 @value{GDBN} configuration where the operating system supports threads.
1950 If your @value{GDBN} does not support threads, these commands have no
1951 effect. For example, a system without thread support shows no output
1952 from @samp{info threads}, and always rejects the @code{thread} command,
1953 like this:
1954
1955 @smallexample
1956 (@value{GDBP}) info threads
1957 (@value{GDBP}) thread 1
1958 Thread ID 1 not known. Use the "info threads" command to
1959 see the IDs of currently known threads.
1960 @end smallexample
1961 @c FIXME to implementors: how hard would it be to say "sorry, this GDB
1962 @c doesn't support threads"?
1963 @end quotation
1964
1965 @cindex focus of debugging
1966 @cindex current thread
1967 The @value{GDBN} thread debugging facility allows you to observe all
1968 threads while your program runs---but whenever @value{GDBN} takes
1969 control, one thread in particular is always the focus of debugging.
1970 This thread is called the @dfn{current thread}. Debugging commands show
1971 program information from the perspective of the current thread.
1972
1973 @cindex @code{New} @var{systag} message
1974 @cindex thread identifier (system)
1975 @c FIXME-implementors!! It would be more helpful if the [New...] message
1976 @c included GDB's numeric thread handle, so you could just go to that
1977 @c thread without first checking `info threads'.
1978 Whenever @value{GDBN} detects a new thread in your program, it displays
1979 the target system's identification for the thread with a message in the
1980 form @samp{[New @var{systag}]}. @var{systag} is a thread identifier
1981 whose form varies depending on the particular system. For example, on
1982 LynxOS, you might see
1983
1984 @example
1985 [New process 35 thread 27]
1986 @end example
1987
1988 @noindent
1989 when @value{GDBN} notices a new thread. In contrast, on an SGI system,
1990 the @var{systag} is simply something like @samp{process 368}, with no
1991 further qualifier.
1992
1993 @c FIXME!! (1) Does the [New...] message appear even for the very first
1994 @c thread of a program, or does it only appear for the
1995 @c second---i.e., when it becomes obvious we have a multithread
1996 @c program?
1997 @c (2) *Is* there necessarily a first thread always? Or do some
1998 @c multithread systems permit starting a program with multiple
1999 @c threads ab initio?
2000
2001 @cindex thread number
2002 @cindex thread identifier (GDB)
2003 For debugging purposes, @value{GDBN} associates its own thread
2004 number---always a single integer---with each thread in your program.
2005
2006 @table @code
2007 @kindex info threads
2008 @item info threads
2009 Display a summary of all threads currently in your
2010 program. @value{GDBN} displays for each thread (in this order):
2011
2012 @enumerate
2013 @item the thread number assigned by @value{GDBN}
2014
2015 @item the target system's thread identifier (@var{systag})
2016
2017 @item the current stack frame summary for that thread
2018 @end enumerate
2019
2020 @noindent
2021 An asterisk @samp{*} to the left of the @value{GDBN} thread number
2022 indicates the current thread.
2023
2024 For example,
2025 @end table
2026 @c end table here to get a little more width for example
2027
2028 @smallexample
2029 (@value{GDBP}) info threads
2030 3 process 35 thread 27 0x34e5 in sigpause ()
2031 2 process 35 thread 23 0x34e5 in sigpause ()
2032 * 1 process 35 thread 13 main (argc=1, argv=0x7ffffff8)
2033 at threadtest.c:68
2034 @end smallexample
2035
2036 On HP-UX systems:
2037
2038 @cindex thread number
2039 @cindex thread identifier (GDB)
2040 For debugging purposes, @value{GDBN} associates its own thread
2041 number---a small integer assigned in thread-creation order---with each
2042 thread in your program.
2043
2044 @cindex @code{New} @var{systag} message, on HP-UX
2045 @cindex thread identifier (system), on HP-UX
2046 @c FIXME-implementors!! It would be more helpful if the [New...] message
2047 @c included GDB's numeric thread handle, so you could just go to that
2048 @c thread without first checking `info threads'.
2049 Whenever @value{GDBN} detects a new thread in your program, it displays
2050 both @value{GDBN}'s thread number and the target system's identification for the thread with a message in the
2051 form @samp{[New @var{systag}]}. @var{systag} is a thread identifier
2052 whose form varies depending on the particular system. For example, on
2053 HP-UX, you see
2054
2055 @example
2056 [New thread 2 (system thread 26594)]
2057 @end example
2058
2059 @noindent
2060 when @value{GDBN} notices a new thread.
2061
2062 @table @code
2063 @kindex info threads
2064 @item info threads
2065 Display a summary of all threads currently in your
2066 program. @value{GDBN} displays for each thread (in this order):
2067
2068 @enumerate
2069 @item the thread number assigned by @value{GDBN}
2070
2071 @item the target system's thread identifier (@var{systag})
2072
2073 @item the current stack frame summary for that thread
2074 @end enumerate
2075
2076 @noindent
2077 An asterisk @samp{*} to the left of the @value{GDBN} thread number
2078 indicates the current thread.
2079
2080 For example,
2081 @end table
2082 @c end table here to get a little more width for example
2083
2084 @example
2085 (@value{GDBP}) info threads
2086 * 3 system thread 26607 worker (wptr=0x7b09c318 "@@") \@*
2087 at quicksort.c:137
2088 2 system thread 26606 0x7b0030d8 in __ksleep () \@*
2089 from /usr/lib/libc.2
2090 1 system thread 27905 0x7b003498 in _brk () \@*
2091 from /usr/lib/libc.2
2092 @end example
2093
2094 @table @code
2095 @kindex thread @var{threadno}
2096 @item thread @var{threadno}
2097 Make thread number @var{threadno} the current thread. The command
2098 argument @var{threadno} is the internal @value{GDBN} thread number, as
2099 shown in the first field of the @samp{info threads} display.
2100 @value{GDBN} responds by displaying the system identifier of the thread
2101 you selected, and its current stack frame summary:
2102
2103 @smallexample
2104 @c FIXME!! This example made up; find a @value{GDBN} w/threads and get real one
2105 (@value{GDBP}) thread 2
2106 [Switching to process 35 thread 23]
2107 0x34e5 in sigpause ()
2108 @end smallexample
2109
2110 @noindent
2111 As with the @samp{[New @dots{}]} message, the form of the text after
2112 @samp{Switching to} depends on your system's conventions for identifying
2113 threads.
2114
2115 @kindex thread apply
2116 @item thread apply [@var{threadno}] [@var{all}] @var{args}
2117 The @code{thread apply} command allows you to apply a command to one or
2118 more threads. Specify the numbers of the threads that you want affected
2119 with the command argument @var{threadno}. @var{threadno} is the internal
2120 @value{GDBN} thread number, as shown in the first field of the @samp{info
2121 threads} display. To apply a command to all threads, use
2122 @code{thread apply all} @var{args}.
2123 @end table
2124
2125 @cindex automatic thread selection
2126 @cindex switching threads automatically
2127 @cindex threads, automatic switching
2128 Whenever @value{GDBN} stops your program, due to a breakpoint or a
2129 signal, it automatically selects the thread where that breakpoint or
2130 signal happened. @value{GDBN} alerts you to the context switch with a
2131 message of the form @samp{[Switching to @var{systag}]} to identify the
2132 thread.
2133
2134 @xref{Thread Stops,,Stopping and starting multi-thread programs}, for
2135 more information about how @value{GDBN} behaves when you stop and start
2136 programs with multiple threads.
2137
2138 @xref{Set Watchpoints,,Setting watchpoints}, for information about
2139 watchpoints in programs with multiple threads.
2140
2141 @node Processes
2142 @section Debugging programs with multiple processes
2143
2144 @cindex fork, debugging programs which call
2145 @cindex multiple processes
2146 @cindex processes, multiple
2147 On most systems, @value{GDBN} has no special support for debugging
2148 programs which create additional processes using the @code{fork}
2149 function. When a program forks, @value{GDBN} will continue to debug the
2150 parent process and the child process will run unimpeded. If you have
2151 set a breakpoint in any code which the child then executes, the child
2152 will get a @code{SIGTRAP} signal which (unless it catches the signal)
2153 will cause it to terminate.
2154
2155 However, if you want to debug the child process there is a workaround
2156 which isn't too painful. Put a call to @code{sleep} in the code which
2157 the child process executes after the fork. It may be useful to sleep
2158 only if a certain environment variable is set, or a certain file exists,
2159 so that the delay need not occur when you don't want to run @value{GDBN}
2160 on the child. While the child is sleeping, use the @code{ps} program to
2161 get its process ID. Then tell @value{GDBN} (a new invocation of
2162 @value{GDBN} if you are also debugging the parent process) to attach to
2163 the child process (@pxref{Attach}). From that point on you can debug
2164 the child process just like any other process which you attached to.
2165
2166 On HP-UX (11.x and later only?), @value{GDBN} provides support for
2167 debugging programs that create additional processes using the
2168 @code{fork} or @code{vfork} function.
2169
2170 By default, when a program forks, @value{GDBN} will continue to debug
2171 the parent process and the child process will run unimpeded.
2172
2173 If you want to follow the child process instead of the parent process,
2174 use the command @w{@code{set follow-fork-mode}}.
2175
2176 @table @code
2177 @kindex set follow-fork-mode
2178 @item set follow-fork-mode @var{mode}
2179 Set the debugger response to a program call of @code{fork} or
2180 @code{vfork}. A call to @code{fork} or @code{vfork} creates a new
2181 process. The @var{mode} can be:
2182
2183 @table @code
2184 @item parent
2185 The original process is debugged after a fork. The child process runs
2186 unimpeded. This is the default.
2187
2188 @item child
2189 The new process is debugged after a fork. The parent process runs
2190 unimpeded.
2191
2192 @item ask
2193 The debugger will ask for one of the above choices.
2194 @end table
2195
2196 @item show follow-fork-mode
2197 Display the current debugger response to a @code{fork} or @code{vfork} call.
2198 @end table
2199
2200 If you ask to debug a child process and a @code{vfork} is followed by an
2201 @code{exec}, @value{GDBN} executes the new target up to the first
2202 breakpoint in the new target. If you have a breakpoint set on
2203 @code{main} in your original program, the breakpoint will also be set on
2204 the child process's @code{main}.
2205
2206 When a child process is spawned by @code{vfork}, you cannot debug the
2207 child or parent until an @code{exec} call completes.
2208
2209 If you issue a @code{run} command to @value{GDBN} after an @code{exec}
2210 call executes, the new target restarts. To restart the parent process,
2211 use the @code{file} command with the parent executable name as its
2212 argument.
2213
2214 You can use the @code{catch} command to make @value{GDBN} stop whenever
2215 a @code{fork}, @code{vfork}, or @code{exec} call is made. @xref{Set
2216 Catchpoints, ,Setting catchpoints}.
2217
2218 @node Stopping
2219 @chapter Stopping and Continuing
2220
2221 The principal purposes of using a debugger are so that you can stop your
2222 program before it terminates; or so that, if your program runs into
2223 trouble, you can investigate and find out why.
2224
2225 Inside @value{GDBN}, your program may stop for any of several reasons,
2226 such as a signal, a breakpoint, or reaching a new line after a
2227 @value{GDBN} command such as @code{step}. You may then examine and
2228 change variables, set new breakpoints or remove old ones, and then
2229 continue execution. Usually, the messages shown by @value{GDBN} provide
2230 ample explanation of the status of your program---but you can also
2231 explicitly request this information at any time.
2232
2233 @table @code
2234 @kindex info program
2235 @item info program
2236 Display information about the status of your program: whether it is
2237 running or not, what process it is, and why it stopped.
2238 @end table
2239
2240 @menu
2241 * Breakpoints:: Breakpoints, watchpoints, and catchpoints
2242 * Continuing and Stepping:: Resuming execution
2243 * Signals:: Signals
2244 * Thread Stops:: Stopping and starting multi-thread programs
2245 @end menu
2246
2247 @node Breakpoints
2248 @section Breakpoints, watchpoints, and catchpoints
2249
2250 @cindex breakpoints
2251 A @dfn{breakpoint} makes your program stop whenever a certain point in
2252 the program is reached. For each breakpoint, you can add conditions to
2253 control in finer detail whether your program stops. You can set
2254 breakpoints with the @code{break} command and its variants (@pxref{Set
2255 Breaks, ,Setting breakpoints}), to specify the place where your program
2256 should stop by line number, function name or exact address in the
2257 program.
2258
2259 In HP-UX, SunOS 4.x, SVR4, and Alpha OSF/1 configurations, you can set
2260 breakpoints in shared libraries before the executable is run. There is
2261 a minor limitation on HP-UX systems: you must wait until the executable
2262 is run in order to set breakpoints in shared library routines that are
2263 not called directly by the program (for example, routines that are
2264 arguments in a @code{pthread_create} call).
2265
2266 @cindex watchpoints
2267 @cindex memory tracing
2268 @cindex breakpoint on memory address
2269 @cindex breakpoint on variable modification
2270 A @dfn{watchpoint} is a special breakpoint that stops your program
2271 when the value of an expression changes. You must use a different
2272 command to set watchpoints (@pxref{Set Watchpoints, ,Setting
2273 watchpoints}), but aside from that, you can manage a watchpoint like
2274 any other breakpoint: you enable, disable, and delete both breakpoints
2275 and watchpoints using the same commands.
2276
2277 You can arrange to have values from your program displayed automatically
2278 whenever @value{GDBN} stops at a breakpoint. @xref{Auto Display,,
2279 Automatic display}.
2280
2281 @cindex catchpoints
2282 @cindex breakpoint on events
2283 A @dfn{catchpoint} is another special breakpoint that stops your program
2284 when a certain kind of event occurs, such as the throwing of a C@t{++}
2285 exception or the loading of a library. As with watchpoints, you use a
2286 different command to set a catchpoint (@pxref{Set Catchpoints, ,Setting
2287 catchpoints}), but aside from that, you can manage a catchpoint like any
2288 other breakpoint. (To stop when your program receives a signal, use the
2289 @code{handle} command; see @ref{Signals, ,Signals}.)
2290
2291 @cindex breakpoint numbers
2292 @cindex numbers for breakpoints
2293 @value{GDBN} assigns a number to each breakpoint, watchpoint, or
2294 catchpoint when you create it; these numbers are successive integers
2295 starting with one. In many of the commands for controlling various
2296 features of breakpoints you use the breakpoint number to say which
2297 breakpoint you want to change. Each breakpoint may be @dfn{enabled} or
2298 @dfn{disabled}; if disabled, it has no effect on your program until you
2299 enable it again.
2300
2301 @cindex breakpoint ranges
2302 @cindex ranges of breakpoints
2303 Some @value{GDBN} commands accept a range of breakpoints on which to
2304 operate. A breakpoint range is either a single breakpoint number, like
2305 @samp{5}, or two such numbers, in increasing order, separated by a
2306 hyphen, like @samp{5-7}. When a breakpoint range is given to a command,
2307 all breakpoint in that range are operated on.
2308
2309 @menu
2310 * Set Breaks:: Setting breakpoints
2311 * Set Watchpoints:: Setting watchpoints
2312 * Set Catchpoints:: Setting catchpoints
2313 * Delete Breaks:: Deleting breakpoints
2314 * Disabling:: Disabling breakpoints
2315 * Conditions:: Break conditions
2316 * Break Commands:: Breakpoint command lists
2317 * Breakpoint Menus:: Breakpoint menus
2318 * Error in Breakpoints:: ``Cannot insert breakpoints''
2319 @end menu
2320
2321 @node Set Breaks
2322 @subsection Setting breakpoints
2323
2324 @c FIXME LMB what does GDB do if no code on line of breakpt?
2325 @c consider in particular declaration with/without initialization.
2326 @c
2327 @c FIXME 2 is there stuff on this already? break at fun start, already init?
2328
2329 @kindex break
2330 @kindex b @r{(@code{break})}
2331 @vindex $bpnum@r{, convenience variable}
2332 @cindex latest breakpoint
2333 Breakpoints are set with the @code{break} command (abbreviated
2334 @code{b}). The debugger convenience variable @samp{$bpnum} records the
2335 number of the breakpoint you've set most recently; see @ref{Convenience
2336 Vars,, Convenience variables}, for a discussion of what you can do with
2337 convenience variables.
2338
2339 You have several ways to say where the breakpoint should go.
2340
2341 @table @code
2342 @item break @var{function}
2343 Set a breakpoint at entry to function @var{function}.
2344 When using source languages that permit overloading of symbols, such as
2345 C@t{++}, @var{function} may refer to more than one possible place to break.
2346 @xref{Breakpoint Menus,,Breakpoint menus}, for a discussion of that situation.
2347
2348 @item break +@var{offset}
2349 @itemx break -@var{offset}
2350 Set a breakpoint some number of lines forward or back from the position
2351 at which execution stopped in the currently selected @dfn{stack frame}.
2352 (@xref{Frames, ,Frames}, for a description of stack frames.)
2353
2354 @item break @var{linenum}
2355 Set a breakpoint at line @var{linenum} in the current source file.
2356 The current source file is the last file whose source text was printed.
2357 The breakpoint will stop your program just before it executes any of the
2358 code on that line.
2359
2360 @item break @var{filename}:@var{linenum}
2361 Set a breakpoint at line @var{linenum} in source file @var{filename}.
2362
2363 @item break @var{filename}:@var{function}
2364 Set a breakpoint at entry to function @var{function} found in file
2365 @var{filename}. Specifying a file name as well as a function name is
2366 superfluous except when multiple files contain similarly named
2367 functions.
2368
2369 @item break *@var{address}
2370 Set a breakpoint at address @var{address}. You can use this to set
2371 breakpoints in parts of your program which do not have debugging
2372 information or source files.
2373
2374 @item break
2375 When called without any arguments, @code{break} sets a breakpoint at
2376 the next instruction to be executed in the selected stack frame
2377 (@pxref{Stack, ,Examining the Stack}). In any selected frame but the
2378 innermost, this makes your program stop as soon as control
2379 returns to that frame. This is similar to the effect of a
2380 @code{finish} command in the frame inside the selected frame---except
2381 that @code{finish} does not leave an active breakpoint. If you use
2382 @code{break} without an argument in the innermost frame, @value{GDBN} stops
2383 the next time it reaches the current location; this may be useful
2384 inside loops.
2385
2386 @value{GDBN} normally ignores breakpoints when it resumes execution, until at
2387 least one instruction has been executed. If it did not do this, you
2388 would be unable to proceed past a breakpoint without first disabling the
2389 breakpoint. This rule applies whether or not the breakpoint already
2390 existed when your program stopped.
2391
2392 @item break @dots{} if @var{cond}
2393 Set a breakpoint with condition @var{cond}; evaluate the expression
2394 @var{cond} each time the breakpoint is reached, and stop only if the
2395 value is nonzero---that is, if @var{cond} evaluates as true.
2396 @samp{@dots{}} stands for one of the possible arguments described
2397 above (or no argument) specifying where to break. @xref{Conditions,
2398 ,Break conditions}, for more information on breakpoint conditions.
2399
2400 @kindex tbreak
2401 @item tbreak @var{args}
2402 Set a breakpoint enabled only for one stop. @var{args} are the
2403 same as for the @code{break} command, and the breakpoint is set in the same
2404 way, but the breakpoint is automatically deleted after the first time your
2405 program stops there. @xref{Disabling, ,Disabling breakpoints}.
2406
2407 @kindex hbreak
2408 @item hbreak @var{args}
2409 Set a hardware-assisted breakpoint. @var{args} are the same as for the
2410 @code{break} command and the breakpoint is set in the same way, but the
2411 breakpoint requires hardware support and some target hardware may not
2412 have this support. The main purpose of this is EPROM/ROM code
2413 debugging, so you can set a breakpoint at an instruction without
2414 changing the instruction. This can be used with the new trap-generation
2415 provided by SPARClite DSU and some x86-based targets. These targets
2416 will generate traps when a program accesses some data or instruction
2417 address that is assigned to the debug registers. However the hardware
2418 breakpoint registers can take a limited number of breakpoints. For
2419 example, on the DSU, only two data breakpoints can be set at a time, and
2420 @value{GDBN} will reject this command if more than two are used. Delete
2421 or disable unused hardware breakpoints before setting new ones
2422 (@pxref{Disabling, ,Disabling}). @xref{Conditions, ,Break conditions}.
2423
2424 @kindex thbreak
2425 @item thbreak @var{args}
2426 Set a hardware-assisted breakpoint enabled only for one stop. @var{args}
2427 are the same as for the @code{hbreak} command and the breakpoint is set in
2428 the same way. However, like the @code{tbreak} command,
2429 the breakpoint is automatically deleted after the
2430 first time your program stops there. Also, like the @code{hbreak}
2431 command, the breakpoint requires hardware support and some target hardware
2432 may not have this support. @xref{Disabling, ,Disabling breakpoints}.
2433 See also @ref{Conditions, ,Break conditions}.
2434
2435 @kindex rbreak
2436 @cindex regular expression
2437 @item rbreak @var{regex}
2438 Set breakpoints on all functions matching the regular expression
2439 @var{regex}. This command sets an unconditional breakpoint on all
2440 matches, printing a list of all breakpoints it set. Once these
2441 breakpoints are set, they are treated just like the breakpoints set with
2442 the @code{break} command. You can delete them, disable them, or make
2443 them conditional the same way as any other breakpoint.
2444
2445 The syntax of the regular expression is the standard one used with tools
2446 like @file{grep}. Note that this is different from the syntax used by
2447 shells, so for instance @code{foo*} matches all functions that include
2448 an @code{fo} followed by zero or more @code{o}s. There is an implicit
2449 @code{.*} leading and trailing the regular expression you supply, so to
2450 match only functions that begin with @code{foo}, use @code{^foo}.
2451
2452 When debugging C@t{++} programs, @code{rbreak} is useful for setting
2453 breakpoints on overloaded functions that are not members of any special
2454 classes.
2455
2456 @kindex info breakpoints
2457 @cindex @code{$_} and @code{info breakpoints}
2458 @item info breakpoints @r{[}@var{n}@r{]}
2459 @itemx info break @r{[}@var{n}@r{]}
2460 @itemx info watchpoints @r{[}@var{n}@r{]}
2461 Print a table of all breakpoints, watchpoints, and catchpoints set and
2462 not deleted, with the following columns for each breakpoint:
2463
2464 @table @emph
2465 @item Breakpoint Numbers
2466 @item Type
2467 Breakpoint, watchpoint, or catchpoint.
2468 @item Disposition
2469 Whether the breakpoint is marked to be disabled or deleted when hit.
2470 @item Enabled or Disabled
2471 Enabled breakpoints are marked with @samp{y}. @samp{n} marks breakpoints
2472 that are not enabled.
2473 @item Address
2474 Where the breakpoint is in your program, as a memory address.
2475 @item What
2476 Where the breakpoint is in the source for your program, as a file and
2477 line number.
2478 @end table
2479
2480 @noindent
2481 If a breakpoint is conditional, @code{info break} shows the condition on
2482 the line following the affected breakpoint; breakpoint commands, if any,
2483 are listed after that.
2484
2485 @noindent
2486 @code{info break} with a breakpoint
2487 number @var{n} as argument lists only that breakpoint. The
2488 convenience variable @code{$_} and the default examining-address for
2489 the @code{x} command are set to the address of the last breakpoint
2490 listed (@pxref{Memory, ,Examining memory}).
2491
2492 @noindent
2493 @code{info break} displays a count of the number of times the breakpoint
2494 has been hit. This is especially useful in conjunction with the
2495 @code{ignore} command. You can ignore a large number of breakpoint
2496 hits, look at the breakpoint info to see how many times the breakpoint
2497 was hit, and then run again, ignoring one less than that number. This
2498 will get you quickly to the last hit of that breakpoint.
2499 @end table
2500
2501 @value{GDBN} allows you to set any number of breakpoints at the same place in
2502 your program. There is nothing silly or meaningless about this. When
2503 the breakpoints are conditional, this is even useful
2504 (@pxref{Conditions, ,Break conditions}).
2505
2506 @cindex negative breakpoint numbers
2507 @cindex internal @value{GDBN} breakpoints
2508 @value{GDBN} itself sometimes sets breakpoints in your program for special
2509 purposes, such as proper handling of @code{longjmp} (in C programs).
2510 These internal breakpoints are assigned negative numbers, starting with
2511 @code{-1}; @samp{info breakpoints} does not display them.
2512
2513 You can see these breakpoints with the @value{GDBN} maintenance command
2514 @samp{maint info breakpoints}.
2515
2516 @table @code
2517 @kindex maint info breakpoints
2518 @item maint info breakpoints
2519 Using the same format as @samp{info breakpoints}, display both the
2520 breakpoints you've set explicitly, and those @value{GDBN} is using for
2521 internal purposes. Internal breakpoints are shown with negative
2522 breakpoint numbers. The type column identifies what kind of breakpoint
2523 is shown:
2524
2525 @table @code
2526 @item breakpoint
2527 Normal, explicitly set breakpoint.
2528
2529 @item watchpoint
2530 Normal, explicitly set watchpoint.
2531
2532 @item longjmp
2533 Internal breakpoint, used to handle correctly stepping through
2534 @code{longjmp} calls.
2535
2536 @item longjmp resume
2537 Internal breakpoint at the target of a @code{longjmp}.
2538
2539 @item until
2540 Temporary internal breakpoint used by the @value{GDBN} @code{until} command.
2541
2542 @item finish
2543 Temporary internal breakpoint used by the @value{GDBN} @code{finish} command.
2544
2545 @item shlib events
2546 Shared library events.
2547
2548 @end table
2549
2550 @end table
2551
2552
2553 @node Set Watchpoints
2554 @subsection Setting watchpoints
2555
2556 @cindex setting watchpoints
2557 @cindex software watchpoints
2558 @cindex hardware watchpoints
2559 You can use a watchpoint to stop execution whenever the value of an
2560 expression changes, without having to predict a particular place where
2561 this may happen.
2562
2563 Depending on your system, watchpoints may be implemented in software or
2564 hardware. @value{GDBN} does software watchpointing by single-stepping your
2565 program and testing the variable's value each time, which is hundreds of
2566 times slower than normal execution. (But this may still be worth it, to
2567 catch errors where you have no clue what part of your program is the
2568 culprit.)
2569
2570 On some systems, such as HP-UX, Linux and some other x86-based targets,
2571 @value{GDBN} includes support for
2572 hardware watchpoints, which do not slow down the running of your
2573 program.
2574
2575 @table @code
2576 @kindex watch
2577 @item watch @var{expr}
2578 Set a watchpoint for an expression. @value{GDBN} will break when @var{expr}
2579 is written into by the program and its value changes.
2580
2581 @kindex rwatch
2582 @item rwatch @var{expr}
2583 Set a watchpoint that will break when watch @var{expr} is read by the program.
2584
2585 @kindex awatch
2586 @item awatch @var{expr}
2587 Set a watchpoint that will break when @var{expr} is either read or written into
2588 by the program.
2589
2590 @kindex info watchpoints
2591 @item info watchpoints
2592 This command prints a list of watchpoints, breakpoints, and catchpoints;
2593 it is the same as @code{info break}.
2594 @end table
2595
2596 @value{GDBN} sets a @dfn{hardware watchpoint} if possible. Hardware
2597 watchpoints execute very quickly, and the debugger reports a change in
2598 value at the exact instruction where the change occurs. If @value{GDBN}
2599 cannot set a hardware watchpoint, it sets a software watchpoint, which
2600 executes more slowly and reports the change in value at the next
2601 statement, not the instruction, after the change occurs.
2602
2603 When you issue the @code{watch} command, @value{GDBN} reports
2604
2605 @example
2606 Hardware watchpoint @var{num}: @var{expr}
2607 @end example
2608
2609 @noindent
2610 if it was able to set a hardware watchpoint.
2611
2612 Currently, the @code{awatch} and @code{rwatch} commands can only set
2613 hardware watchpoints, because accesses to data that don't change the
2614 value of the watched expression cannot be detected without examining
2615 every instruction as it is being executed, and @value{GDBN} does not do
2616 that currently. If @value{GDBN} finds that it is unable to set a
2617 hardware breakpoint with the @code{awatch} or @code{rwatch} command, it
2618 will print a message like this:
2619
2620 @smallexample
2621 Expression cannot be implemented with read/access watchpoint.
2622 @end smallexample
2623
2624 Sometimes, @value{GDBN} cannot set a hardware watchpoint because the
2625 data type of the watched expression is wider than what a hardware
2626 watchpoint on the target machine can handle. For example, some systems
2627 can only watch regions that are up to 4 bytes wide; on such systems you
2628 cannot set hardware watchpoints for an expression that yields a
2629 double-precision floating-point number (which is typically 8 bytes
2630 wide). As a work-around, it might be possible to break the large region
2631 into a series of smaller ones and watch them with separate watchpoints.
2632
2633 If you set too many hardware watchpoints, @value{GDBN} might be unable
2634 to insert all of them when you resume the execution of your program.
2635 Since the precise number of active watchpoints is unknown until such
2636 time as the program is about to be resumed, @value{GDBN} might not be
2637 able to warn you about this when you set the watchpoints, and the
2638 warning will be printed only when the program is resumed:
2639
2640 @smallexample
2641 Hardware watchpoint @var{num}: Could not insert watchpoint
2642 @end smallexample
2643
2644 @noindent
2645 If this happens, delete or disable some of the watchpoints.
2646
2647 The SPARClite DSU will generate traps when a program accesses some data
2648 or instruction address that is assigned to the debug registers. For the
2649 data addresses, DSU facilitates the @code{watch} command. However the
2650 hardware breakpoint registers can only take two data watchpoints, and
2651 both watchpoints must be the same kind. For example, you can set two
2652 watchpoints with @code{watch} commands, two with @code{rwatch} commands,
2653 @strong{or} two with @code{awatch} commands, but you cannot set one
2654 watchpoint with one command and the other with a different command.
2655 @value{GDBN} will reject the command if you try to mix watchpoints.
2656 Delete or disable unused watchpoint commands before setting new ones.
2657
2658 If you call a function interactively using @code{print} or @code{call},
2659 any watchpoints you have set will be inactive until @value{GDBN} reaches another
2660 kind of breakpoint or the call completes.
2661
2662 @value{GDBN} automatically deletes watchpoints that watch local
2663 (automatic) variables, or expressions that involve such variables, when
2664 they go out of scope, that is, when the execution leaves the block in
2665 which these variables were defined. In particular, when the program
2666 being debugged terminates, @emph{all} local variables go out of scope,
2667 and so only watchpoints that watch global variables remain set. If you
2668 rerun the program, you will need to set all such watchpoints again. One
2669 way of doing that would be to set a code breakpoint at the entry to the
2670 @code{main} function and when it breaks, set all the watchpoints.
2671
2672 @quotation
2673 @cindex watchpoints and threads
2674 @cindex threads and watchpoints
2675 @emph{Warning:} In multi-thread programs, watchpoints have only limited
2676 usefulness. With the current watchpoint implementation, @value{GDBN}
2677 can only watch the value of an expression @emph{in a single thread}. If
2678 you are confident that the expression can only change due to the current
2679 thread's activity (and if you are also confident that no other thread
2680 can become current), then you can use watchpoints as usual. However,
2681 @value{GDBN} may not notice when a non-current thread's activity changes
2682 the expression.
2683
2684 @c FIXME: this is almost identical to the previous paragraph.
2685 @emph{HP-UX Warning:} In multi-thread programs, software watchpoints
2686 have only limited usefulness. If @value{GDBN} creates a software
2687 watchpoint, it can only watch the value of an expression @emph{in a
2688 single thread}. If you are confident that the expression can only
2689 change due to the current thread's activity (and if you are also
2690 confident that no other thread can become current), then you can use
2691 software watchpoints as usual. However, @value{GDBN} may not notice
2692 when a non-current thread's activity changes the expression. (Hardware
2693 watchpoints, in contrast, watch an expression in all threads.)
2694 @end quotation
2695
2696 @node Set Catchpoints
2697 @subsection Setting catchpoints
2698 @cindex catchpoints, setting
2699 @cindex exception handlers
2700 @cindex event handling
2701
2702 You can use @dfn{catchpoints} to cause the debugger to stop for certain
2703 kinds of program events, such as C@t{++} exceptions or the loading of a
2704 shared library. Use the @code{catch} command to set a catchpoint.
2705
2706 @table @code
2707 @kindex catch
2708 @item catch @var{event}
2709 Stop when @var{event} occurs. @var{event} can be any of the following:
2710 @table @code
2711 @item throw
2712 @kindex catch throw
2713 The throwing of a C@t{++} exception.
2714
2715 @item catch
2716 @kindex catch catch
2717 The catching of a C@t{++} exception.
2718
2719 @item exec
2720 @kindex catch exec
2721 A call to @code{exec}. This is currently only available for HP-UX.
2722
2723 @item fork
2724 @kindex catch fork
2725 A call to @code{fork}. This is currently only available for HP-UX.
2726
2727 @item vfork
2728 @kindex catch vfork
2729 A call to @code{vfork}. This is currently only available for HP-UX.
2730
2731 @item load
2732 @itemx load @var{libname}
2733 @kindex catch load
2734 The dynamic loading of any shared library, or the loading of the library
2735 @var{libname}. This is currently only available for HP-UX.
2736
2737 @item unload
2738 @itemx unload @var{libname}
2739 @kindex catch unload
2740 The unloading of any dynamically loaded shared library, or the unloading
2741 of the library @var{libname}. This is currently only available for HP-UX.
2742 @end table
2743
2744 @item tcatch @var{event}
2745 Set a catchpoint that is enabled only for one stop. The catchpoint is
2746 automatically deleted after the first time the event is caught.
2747
2748 @end table
2749
2750 Use the @code{info break} command to list the current catchpoints.
2751
2752 There are currently some limitations to C@t{++} exception handling
2753 (@code{catch throw} and @code{catch catch}) in @value{GDBN}:
2754
2755 @itemize @bullet
2756 @item
2757 If you call a function interactively, @value{GDBN} normally returns
2758 control to you when the function has finished executing. If the call
2759 raises an exception, however, the call may bypass the mechanism that
2760 returns control to you and cause your program either to abort or to
2761 simply continue running until it hits a breakpoint, catches a signal
2762 that @value{GDBN} is listening for, or exits. This is the case even if
2763 you set a catchpoint for the exception; catchpoints on exceptions are
2764 disabled within interactive calls.
2765
2766 @item
2767 You cannot raise an exception interactively.
2768
2769 @item
2770 You cannot install an exception handler interactively.
2771 @end itemize
2772
2773 @cindex raise exceptions
2774 Sometimes @code{catch} is not the best way to debug exception handling:
2775 if you need to know exactly where an exception is raised, it is better to
2776 stop @emph{before} the exception handler is called, since that way you
2777 can see the stack before any unwinding takes place. If you set a
2778 breakpoint in an exception handler instead, it may not be easy to find
2779 out where the exception was raised.
2780
2781 To stop just before an exception handler is called, you need some
2782 knowledge of the implementation. In the case of @sc{gnu} C@t{++}, exceptions are
2783 raised by calling a library function named @code{__raise_exception}
2784 which has the following ANSI C interface:
2785
2786 @example
2787 /* @var{addr} is where the exception identifier is stored.
2788 @var{id} is the exception identifier. */
2789 void __raise_exception (void **addr, void *id);
2790 @end example
2791
2792 @noindent
2793 To make the debugger catch all exceptions before any stack
2794 unwinding takes place, set a breakpoint on @code{__raise_exception}
2795 (@pxref{Breakpoints, ,Breakpoints; watchpoints; and exceptions}).
2796
2797 With a conditional breakpoint (@pxref{Conditions, ,Break conditions})
2798 that depends on the value of @var{id}, you can stop your program when
2799 a specific exception is raised. You can use multiple conditional
2800 breakpoints to stop your program when any of a number of exceptions are
2801 raised.
2802
2803
2804 @node Delete Breaks
2805 @subsection Deleting breakpoints
2806
2807 @cindex clearing breakpoints, watchpoints, catchpoints
2808 @cindex deleting breakpoints, watchpoints, catchpoints
2809 It is often necessary to eliminate a breakpoint, watchpoint, or
2810 catchpoint once it has done its job and you no longer want your program
2811 to stop there. This is called @dfn{deleting} the breakpoint. A
2812 breakpoint that has been deleted no longer exists; it is forgotten.
2813
2814 With the @code{clear} command you can delete breakpoints according to
2815 where they are in your program. With the @code{delete} command you can
2816 delete individual breakpoints, watchpoints, or catchpoints by specifying
2817 their breakpoint numbers.
2818
2819 It is not necessary to delete a breakpoint to proceed past it. @value{GDBN}
2820 automatically ignores breakpoints on the first instruction to be executed
2821 when you continue execution without changing the execution address.
2822
2823 @table @code
2824 @kindex clear
2825 @item clear
2826 Delete any breakpoints at the next instruction to be executed in the
2827 selected stack frame (@pxref{Selection, ,Selecting a frame}). When
2828 the innermost frame is selected, this is a good way to delete a
2829 breakpoint where your program just stopped.
2830
2831 @item clear @var{function}
2832 @itemx clear @var{filename}:@var{function}
2833 Delete any breakpoints set at entry to the function @var{function}.
2834
2835 @item clear @var{linenum}
2836 @itemx clear @var{filename}:@var{linenum}
2837 Delete any breakpoints set at or within the code of the specified line.
2838
2839 @cindex delete breakpoints
2840 @kindex delete
2841 @kindex d @r{(@code{delete})}
2842 @item delete @r{[}breakpoints@r{]} @r{[}@var{range}@dots{}@r{]}
2843 Delete the breakpoints, watchpoints, or catchpoints of the breakpoint
2844 ranges specified as arguments. If no argument is specified, delete all
2845 breakpoints (@value{GDBN} asks confirmation, unless you have @code{set
2846 confirm off}). You can abbreviate this command as @code{d}.
2847 @end table
2848
2849 @node Disabling
2850 @subsection Disabling breakpoints
2851
2852 @kindex disable breakpoints
2853 @kindex enable breakpoints
2854 Rather than deleting a breakpoint, watchpoint, or catchpoint, you might
2855 prefer to @dfn{disable} it. This makes the breakpoint inoperative as if
2856 it had been deleted, but remembers the information on the breakpoint so
2857 that you can @dfn{enable} it again later.
2858
2859 You disable and enable breakpoints, watchpoints, and catchpoints with
2860 the @code{enable} and @code{disable} commands, optionally specifying one
2861 or more breakpoint numbers as arguments. Use @code{info break} or
2862 @code{info watch} to print a list of breakpoints, watchpoints, and
2863 catchpoints if you do not know which numbers to use.
2864
2865 A breakpoint, watchpoint, or catchpoint can have any of four different
2866 states of enablement:
2867
2868 @itemize @bullet
2869 @item
2870 Enabled. The breakpoint stops your program. A breakpoint set
2871 with the @code{break} command starts out in this state.
2872 @item
2873 Disabled. The breakpoint has no effect on your program.
2874 @item
2875 Enabled once. The breakpoint stops your program, but then becomes
2876 disabled.
2877 @item
2878 Enabled for deletion. The breakpoint stops your program, but
2879 immediately after it does so it is deleted permanently. A breakpoint
2880 set with the @code{tbreak} command starts out in this state.
2881 @end itemize
2882
2883 You can use the following commands to enable or disable breakpoints,
2884 watchpoints, and catchpoints:
2885
2886 @table @code
2887 @kindex disable breakpoints
2888 @kindex disable
2889 @kindex dis @r{(@code{disable})}
2890 @item disable @r{[}breakpoints@r{]} @r{[}@var{range}@dots{}@r{]}
2891 Disable the specified breakpoints---or all breakpoints, if none are
2892 listed. A disabled breakpoint has no effect but is not forgotten. All
2893 options such as ignore-counts, conditions and commands are remembered in
2894 case the breakpoint is enabled again later. You may abbreviate
2895 @code{disable} as @code{dis}.
2896
2897 @kindex enable breakpoints
2898 @kindex enable
2899 @item enable @r{[}breakpoints@r{]} @r{[}@var{range}@dots{}@r{]}
2900 Enable the specified breakpoints (or all defined breakpoints). They
2901 become effective once again in stopping your program.
2902
2903 @item enable @r{[}breakpoints@r{]} once @var{range}@dots{}
2904 Enable the specified breakpoints temporarily. @value{GDBN} disables any
2905 of these breakpoints immediately after stopping your program.
2906
2907 @item enable @r{[}breakpoints@r{]} delete @var{range}@dots{}
2908 Enable the specified breakpoints to work once, then die. @value{GDBN}
2909 deletes any of these breakpoints as soon as your program stops there.
2910 @end table
2911
2912 @c FIXME: I think the following ``Except for [...] @code{tbreak}'' is
2913 @c confusing: tbreak is also initially enabled.
2914 Except for a breakpoint set with @code{tbreak} (@pxref{Set Breaks,
2915 ,Setting breakpoints}), breakpoints that you set are initially enabled;
2916 subsequently, they become disabled or enabled only when you use one of
2917 the commands above. (The command @code{until} can set and delete a
2918 breakpoint of its own, but it does not change the state of your other
2919 breakpoints; see @ref{Continuing and Stepping, ,Continuing and
2920 stepping}.)
2921
2922 @node Conditions
2923 @subsection Break conditions
2924 @cindex conditional breakpoints
2925 @cindex breakpoint conditions
2926
2927 @c FIXME what is scope of break condition expr? Context where wanted?
2928 @c in particular for a watchpoint?
2929 The simplest sort of breakpoint breaks every time your program reaches a
2930 specified place. You can also specify a @dfn{condition} for a
2931 breakpoint. A condition is just a Boolean expression in your
2932 programming language (@pxref{Expressions, ,Expressions}). A breakpoint with
2933 a condition evaluates the expression each time your program reaches it,
2934 and your program stops only if the condition is @emph{true}.
2935
2936 This is the converse of using assertions for program validation; in that
2937 situation, you want to stop when the assertion is violated---that is,
2938 when the condition is false. In C, if you want to test an assertion expressed
2939 by the condition @var{assert}, you should set the condition
2940 @samp{! @var{assert}} on the appropriate breakpoint.
2941
2942 Conditions are also accepted for watchpoints; you may not need them,
2943 since a watchpoint is inspecting the value of an expression anyhow---but
2944 it might be simpler, say, to just set a watchpoint on a variable name,
2945 and specify a condition that tests whether the new value is an interesting
2946 one.
2947
2948 Break conditions can have side effects, and may even call functions in
2949 your program. This can be useful, for example, to activate functions
2950 that log program progress, or to use your own print functions to
2951 format special data structures. The effects are completely predictable
2952 unless there is another enabled breakpoint at the same address. (In
2953 that case, @value{GDBN} might see the other breakpoint first and stop your
2954 program without checking the condition of this one.) Note that
2955 breakpoint commands are usually more convenient and flexible than break
2956 conditions for the
2957 purpose of performing side effects when a breakpoint is reached
2958 (@pxref{Break Commands, ,Breakpoint command lists}).
2959
2960 Break conditions can be specified when a breakpoint is set, by using
2961 @samp{if} in the arguments to the @code{break} command. @xref{Set
2962 Breaks, ,Setting breakpoints}. They can also be changed at any time
2963 with the @code{condition} command.
2964
2965 You can also use the @code{if} keyword with the @code{watch} command.
2966 The @code{catch} command does not recognize the @code{if} keyword;
2967 @code{condition} is the only way to impose a further condition on a
2968 catchpoint.
2969
2970 @table @code
2971 @kindex condition
2972 @item condition @var{bnum} @var{expression}
2973 Specify @var{expression} as the break condition for breakpoint,
2974 watchpoint, or catchpoint number @var{bnum}. After you set a condition,
2975 breakpoint @var{bnum} stops your program only if the value of
2976 @var{expression} is true (nonzero, in C). When you use
2977 @code{condition}, @value{GDBN} checks @var{expression} immediately for
2978 syntactic correctness, and to determine whether symbols in it have
2979 referents in the context of your breakpoint. If @var{expression} uses
2980 symbols not referenced in the context of the breakpoint, @value{GDBN}
2981 prints an error message:
2982
2983 @example
2984 No symbol "foo" in current context.
2985 @end example
2986
2987 @noindent
2988 @value{GDBN} does
2989 not actually evaluate @var{expression} at the time the @code{condition}
2990 command (or a command that sets a breakpoint with a condition, like
2991 @code{break if @dots{}}) is given, however. @xref{Expressions, ,Expressions}.
2992
2993 @item condition @var{bnum}
2994 Remove the condition from breakpoint number @var{bnum}. It becomes
2995 an ordinary unconditional breakpoint.
2996 @end table
2997
2998 @cindex ignore count (of breakpoint)
2999 A special case of a breakpoint condition is to stop only when the
3000 breakpoint has been reached a certain number of times. This is so
3001 useful that there is a special way to do it, using the @dfn{ignore
3002 count} of the breakpoint. Every breakpoint has an ignore count, which
3003 is an integer. Most of the time, the ignore count is zero, and
3004 therefore has no effect. But if your program reaches a breakpoint whose
3005 ignore count is positive, then instead of stopping, it just decrements
3006 the ignore count by one and continues. As a result, if the ignore count
3007 value is @var{n}, the breakpoint does not stop the next @var{n} times
3008 your program reaches it.
3009
3010 @table @code
3011 @kindex ignore
3012 @item ignore @var{bnum} @var{count}
3013 Set the ignore count of breakpoint number @var{bnum} to @var{count}.
3014 The next @var{count} times the breakpoint is reached, your program's
3015 execution does not stop; other than to decrement the ignore count, @value{GDBN}
3016 takes no action.
3017
3018 To make the breakpoint stop the next time it is reached, specify
3019 a count of zero.
3020
3021 When you use @code{continue} to resume execution of your program from a
3022 breakpoint, you can specify an ignore count directly as an argument to
3023 @code{continue}, rather than using @code{ignore}. @xref{Continuing and
3024 Stepping,,Continuing and stepping}.
3025
3026 If a breakpoint has a positive ignore count and a condition, the
3027 condition is not checked. Once the ignore count reaches zero,
3028 @value{GDBN} resumes checking the condition.
3029
3030 You could achieve the effect of the ignore count with a condition such
3031 as @w{@samp{$foo-- <= 0}} using a debugger convenience variable that
3032 is decremented each time. @xref{Convenience Vars, ,Convenience
3033 variables}.
3034 @end table
3035
3036 Ignore counts apply to breakpoints, watchpoints, and catchpoints.
3037
3038
3039 @node Break Commands
3040 @subsection Breakpoint command lists
3041
3042 @cindex breakpoint commands
3043 You can give any breakpoint (or watchpoint or catchpoint) a series of
3044 commands to execute when your program stops due to that breakpoint. For
3045 example, you might want to print the values of certain expressions, or
3046 enable other breakpoints.
3047
3048 @table @code
3049 @kindex commands
3050 @kindex end
3051 @item commands @r{[}@var{bnum}@r{]}
3052 @itemx @dots{} @var{command-list} @dots{}
3053 @itemx end
3054 Specify a list of commands for breakpoint number @var{bnum}. The commands
3055 themselves appear on the following lines. Type a line containing just
3056 @code{end} to terminate the commands.
3057
3058 To remove all commands from a breakpoint, type @code{commands} and
3059 follow it immediately with @code{end}; that is, give no commands.
3060
3061 With no @var{bnum} argument, @code{commands} refers to the last
3062 breakpoint, watchpoint, or catchpoint set (not to the breakpoint most
3063 recently encountered).
3064 @end table
3065
3066 Pressing @key{RET} as a means of repeating the last @value{GDBN} command is
3067 disabled within a @var{command-list}.
3068
3069 You can use breakpoint commands to start your program up again. Simply
3070 use the @code{continue} command, or @code{step}, or any other command
3071 that resumes execution.
3072
3073 Any other commands in the command list, after a command that resumes
3074 execution, are ignored. This is because any time you resume execution
3075 (even with a simple @code{next} or @code{step}), you may encounter
3076 another breakpoint---which could have its own command list, leading to
3077 ambiguities about which list to execute.
3078
3079 @kindex silent
3080 If the first command you specify in a command list is @code{silent}, the
3081 usual message about stopping at a breakpoint is not printed. This may
3082 be desirable for breakpoints that are to print a specific message and
3083 then continue. If none of the remaining commands print anything, you
3084 see no sign that the breakpoint was reached. @code{silent} is
3085 meaningful only at the beginning of a breakpoint command list.
3086
3087 The commands @code{echo}, @code{output}, and @code{printf} allow you to
3088 print precisely controlled output, and are often useful in silent
3089 breakpoints. @xref{Output, ,Commands for controlled output}.
3090
3091 For example, here is how you could use breakpoint commands to print the
3092 value of @code{x} at entry to @code{foo} whenever @code{x} is positive.
3093
3094 @example
3095 break foo if x>0
3096 commands
3097 silent
3098 printf "x is %d\n",x
3099 cont
3100 end
3101 @end example
3102
3103 One application for breakpoint commands is to compensate for one bug so
3104 you can test for another. Put a breakpoint just after the erroneous line
3105 of code, give it a condition to detect the case in which something
3106 erroneous has been done, and give it commands to assign correct values
3107 to any variables that need them. End with the @code{continue} command
3108 so that your program does not stop, and start with the @code{silent}
3109 command so that no output is produced. Here is an example:
3110
3111 @example
3112 break 403
3113 commands
3114 silent
3115 set x = y + 4
3116 cont
3117 end
3118 @end example
3119
3120 @node Breakpoint Menus
3121 @subsection Breakpoint menus
3122 @cindex overloading
3123 @cindex symbol overloading
3124
3125 Some programming languages (notably C@t{++}) permit a single function name
3126 to be defined several times, for application in different contexts.
3127 This is called @dfn{overloading}. When a function name is overloaded,
3128 @samp{break @var{function}} is not enough to tell @value{GDBN} where you want
3129 a breakpoint. If you realize this is a problem, you can use
3130 something like @samp{break @var{function}(@var{types})} to specify which
3131 particular version of the function you want. Otherwise, @value{GDBN} offers
3132 you a menu of numbered choices for different possible breakpoints, and
3133 waits for your selection with the prompt @samp{>}. The first two
3134 options are always @samp{[0] cancel} and @samp{[1] all}. Typing @kbd{1}
3135 sets a breakpoint at each definition of @var{function}, and typing
3136 @kbd{0} aborts the @code{break} command without setting any new
3137 breakpoints.
3138
3139 For example, the following session excerpt shows an attempt to set a
3140 breakpoint at the overloaded symbol @code{String::after}.
3141 We choose three particular definitions of that function name:
3142
3143 @c FIXME! This is likely to change to show arg type lists, at least
3144 @smallexample
3145 @group
3146 (@value{GDBP}) b String::after
3147 [0] cancel
3148 [1] all
3149 [2] file:String.cc; line number:867
3150 [3] file:String.cc; line number:860
3151 [4] file:String.cc; line number:875
3152 [5] file:String.cc; line number:853
3153 [6] file:String.cc; line number:846
3154 [7] file:String.cc; line number:735
3155 > 2 4 6
3156 Breakpoint 1 at 0xb26c: file String.cc, line 867.
3157 Breakpoint 2 at 0xb344: file String.cc, line 875.
3158 Breakpoint 3 at 0xafcc: file String.cc, line 846.
3159 Multiple breakpoints were set.
3160 Use the "delete" command to delete unwanted
3161 breakpoints.
3162 (@value{GDBP})
3163 @end group
3164 @end smallexample
3165
3166 @c @ifclear BARETARGET
3167 @node Error in Breakpoints
3168 @subsection ``Cannot insert breakpoints''
3169 @c
3170 @c FIXME!! 14/6/95 Is there a real example of this? Let's use it.
3171 @c
3172 Under some operating systems, breakpoints cannot be used in a program if
3173 any other process is running that program. In this situation,
3174 attempting to run or continue a program with a breakpoint causes
3175 @value{GDBN} to print an error message:
3176
3177 @example
3178 Cannot insert breakpoints.
3179 The same program may be running in another process.
3180 @end example
3181
3182 When this happens, you have three ways to proceed:
3183
3184 @enumerate
3185 @item
3186 Remove or disable the breakpoints, then continue.
3187
3188 @item
3189 Suspend @value{GDBN}, and copy the file containing your program to a new
3190 name. Resume @value{GDBN} and use the @code{exec-file} command to specify
3191 that @value{GDBN} should run your program under that name.
3192 Then start your program again.
3193
3194 @item
3195 Relink your program so that the text segment is nonsharable, using the
3196 linker option @samp{-N}. The operating system limitation may not apply
3197 to nonsharable executables.
3198 @end enumerate
3199 @c @end ifclear
3200
3201 A similar message can be printed if you request too many active
3202 hardware-assisted breakpoints and watchpoints:
3203
3204 @c FIXME: the precise wording of this message may change; the relevant
3205 @c source change is not committed yet (Sep 3, 1999).
3206 @smallexample
3207 Stopped; cannot insert breakpoints.
3208 You may have requested too many hardware breakpoints and watchpoints.
3209 @end smallexample
3210
3211 @noindent
3212 This message is printed when you attempt to resume the program, since
3213 only then @value{GDBN} knows exactly how many hardware breakpoints and
3214 watchpoints it needs to insert.
3215
3216 When this message is printed, you need to disable or remove some of the
3217 hardware-assisted breakpoints and watchpoints, and then continue.
3218
3219
3220 @node Continuing and Stepping
3221 @section Continuing and stepping
3222
3223 @cindex stepping
3224 @cindex continuing
3225 @cindex resuming execution
3226 @dfn{Continuing} means resuming program execution until your program
3227 completes normally. In contrast, @dfn{stepping} means executing just
3228 one more ``step'' of your program, where ``step'' may mean either one
3229 line of source code, or one machine instruction (depending on what
3230 particular command you use). Either when continuing or when stepping,
3231 your program may stop even sooner, due to a breakpoint or a signal. (If
3232 it stops due to a signal, you may want to use @code{handle}, or use
3233 @samp{signal 0} to resume execution. @xref{Signals, ,Signals}.)
3234
3235 @table @code
3236 @kindex continue
3237 @kindex c @r{(@code{continue})}
3238 @kindex fg @r{(resume foreground execution)}
3239 @item continue @r{[}@var{ignore-count}@r{]}
3240 @itemx c @r{[}@var{ignore-count}@r{]}
3241 @itemx fg @r{[}@var{ignore-count}@r{]}
3242 Resume program execution, at the address where your program last stopped;
3243 any breakpoints set at that address are bypassed. The optional argument
3244 @var{ignore-count} allows you to specify a further number of times to
3245 ignore a breakpoint at this location; its effect is like that of
3246 @code{ignore} (@pxref{Conditions, ,Break conditions}).
3247
3248 The argument @var{ignore-count} is meaningful only when your program
3249 stopped due to a breakpoint. At other times, the argument to
3250 @code{continue} is ignored.
3251
3252 The synonyms @code{c} and @code{fg} (for @dfn{foreground}, as the
3253 debugged program is deemed to be the foreground program) are provided
3254 purely for convenience, and have exactly the same behavior as
3255 @code{continue}.
3256 @end table
3257
3258 To resume execution at a different place, you can use @code{return}
3259 (@pxref{Returning, ,Returning from a function}) to go back to the
3260 calling function; or @code{jump} (@pxref{Jumping, ,Continuing at a
3261 different address}) to go to an arbitrary location in your program.
3262
3263 A typical technique for using stepping is to set a breakpoint
3264 (@pxref{Breakpoints, ,Breakpoints; watchpoints; and catchpoints}) at the
3265 beginning of the function or the section of your program where a problem
3266 is believed to lie, run your program until it stops at that breakpoint,
3267 and then step through the suspect area, examining the variables that are
3268 interesting, until you see the problem happen.
3269
3270 @table @code
3271 @kindex step
3272 @kindex s @r{(@code{step})}
3273 @item step
3274 Continue running your program until control reaches a different source
3275 line, then stop it and return control to @value{GDBN}. This command is
3276 abbreviated @code{s}.
3277
3278 @quotation
3279 @c "without debugging information" is imprecise; actually "without line
3280 @c numbers in the debugging information". (gcc -g1 has debugging info but
3281 @c not line numbers). But it seems complex to try to make that
3282 @c distinction here.
3283 @emph{Warning:} If you use the @code{step} command while control is
3284 within a function that was compiled without debugging information,
3285 execution proceeds until control reaches a function that does have
3286 debugging information. Likewise, it will not step into a function which
3287 is compiled without debugging information. To step through functions
3288 without debugging information, use the @code{stepi} command, described
3289 below.
3290 @end quotation
3291
3292 The @code{step} command only stops at the first instruction of a source
3293 line. This prevents the multiple stops that could otherwise occur in
3294 @code{switch} statements, @code{for} loops, etc. @code{step} continues
3295 to stop if a function that has debugging information is called within
3296 the line. In other words, @code{step} @emph{steps inside} any functions
3297 called within the line.
3298
3299 Also, the @code{step} command only enters a function if there is line
3300 number information for the function. Otherwise it acts like the
3301 @code{next} command. This avoids problems when using @code{cc -gl}
3302 on MIPS machines. Previously, @code{step} entered subroutines if there
3303 was any debugging information about the routine.
3304
3305 @item step @var{count}
3306 Continue running as in @code{step}, but do so @var{count} times. If a
3307 breakpoint is reached, or a signal not related to stepping occurs before
3308 @var{count} steps, stepping stops right away.
3309
3310 @kindex next
3311 @kindex n @r{(@code{next})}
3312 @item next @r{[}@var{count}@r{]}
3313 Continue to the next source line in the current (innermost) stack frame.
3314 This is similar to @code{step}, but function calls that appear within
3315 the line of code are executed without stopping. Execution stops when
3316 control reaches a different line of code at the original stack level
3317 that was executing when you gave the @code{next} command. This command
3318 is abbreviated @code{n}.
3319
3320 An argument @var{count} is a repeat count, as for @code{step}.
3321
3322
3323 @c FIX ME!! Do we delete this, or is there a way it fits in with
3324 @c the following paragraph? --- Vctoria
3325 @c
3326 @c @code{next} within a function that lacks debugging information acts like
3327 @c @code{step}, but any function calls appearing within the code of the
3328 @c function are executed without stopping.
3329
3330 The @code{next} command only stops at the first instruction of a
3331 source line. This prevents multiple stops that could otherwise occur in
3332 @code{switch} statements, @code{for} loops, etc.
3333
3334 @kindex set step-mode
3335 @item set step-mode
3336 @cindex functions without line info, and stepping
3337 @cindex stepping into functions with no line info
3338 @itemx set step-mode on
3339 The @code{set step-mode on} command causes the @code{step} command to
3340 stop at the first instruction of a function which contains no debug line
3341 information rather than stepping over it.
3342
3343 This is useful in cases where you may be interested in inspecting the
3344 machine instructions of a function which has no symbolic info and do not
3345 want @value{GDBN} to automatically skip over this function.
3346
3347 @item set step-mode off
3348 Causes the @code{step} command to step over any functions which contains no
3349 debug information. This is the default.
3350
3351 @kindex finish
3352 @item finish
3353 Continue running until just after function in the selected stack frame
3354 returns. Print the returned value (if any).
3355
3356 Contrast this with the @code{return} command (@pxref{Returning,
3357 ,Returning from a function}).
3358
3359 @kindex until
3360 @kindex u @r{(@code{until})}
3361 @item until
3362 @itemx u
3363 Continue running until a source line past the current line, in the
3364 current stack frame, is reached. This command is used to avoid single
3365 stepping through a loop more than once. It is like the @code{next}
3366 command, except that when @code{until} encounters a jump, it
3367 automatically continues execution until the program counter is greater
3368 than the address of the jump.
3369
3370 This means that when you reach the end of a loop after single stepping
3371 though it, @code{until} makes your program continue execution until it
3372 exits the loop. In contrast, a @code{next} command at the end of a loop
3373 simply steps back to the beginning of the loop, which forces you to step
3374 through the next iteration.
3375
3376 @code{until} always stops your program if it attempts to exit the current
3377 stack frame.
3378
3379 @code{until} may produce somewhat counterintuitive results if the order
3380 of machine code does not match the order of the source lines. For
3381 example, in the following excerpt from a debugging session, the @code{f}
3382 (@code{frame}) command shows that execution is stopped at line
3383 @code{206}; yet when we use @code{until}, we get to line @code{195}:
3384
3385 @example
3386 (@value{GDBP}) f
3387 #0 main (argc=4, argv=0xf7fffae8) at m4.c:206
3388 206 expand_input();
3389 (@value{GDBP}) until
3390 195 for ( ; argc > 0; NEXTARG) @{
3391 @end example
3392
3393 This happened because, for execution efficiency, the compiler had
3394 generated code for the loop closure test at the end, rather than the
3395 start, of the loop---even though the test in a C @code{for}-loop is
3396 written before the body of the loop. The @code{until} command appeared
3397 to step back to the beginning of the loop when it advanced to this
3398 expression; however, it has not really gone to an earlier
3399 statement---not in terms of the actual machine code.
3400
3401 @code{until} with no argument works by means of single
3402 instruction stepping, and hence is slower than @code{until} with an
3403 argument.
3404
3405 @item until @var{location}
3406 @itemx u @var{location}
3407 Continue running your program until either the specified location is
3408 reached, or the current stack frame returns. @var{location} is any of
3409 the forms of argument acceptable to @code{break} (@pxref{Set Breaks,
3410 ,Setting breakpoints}). This form of the command uses breakpoints,
3411 and hence is quicker than @code{until} without an argument.
3412
3413 @kindex stepi
3414 @kindex si @r{(@code{stepi})}
3415 @item stepi
3416 @itemx stepi @var{arg}
3417 @itemx si
3418 Execute one machine instruction, then stop and return to the debugger.
3419
3420 It is often useful to do @samp{display/i $pc} when stepping by machine
3421 instructions. This makes @value{GDBN} automatically display the next
3422 instruction to be executed, each time your program stops. @xref{Auto
3423 Display,, Automatic display}.
3424
3425 An argument is a repeat count, as in @code{step}.
3426
3427 @need 750
3428 @kindex nexti
3429 @kindex ni @r{(@code{nexti})}
3430 @item nexti
3431 @itemx nexti @var{arg}
3432 @itemx ni
3433 Execute one machine instruction, but if it is a function call,
3434 proceed until the function returns.
3435
3436 An argument is a repeat count, as in @code{next}.
3437 @end table
3438
3439 @node Signals
3440 @section Signals
3441 @cindex signals
3442
3443 A signal is an asynchronous event that can happen in a program. The
3444 operating system defines the possible kinds of signals, and gives each
3445 kind a name and a number. For example, in Unix @code{SIGINT} is the
3446 signal a program gets when you type an interrupt character (often @kbd{C-c});
3447 @code{SIGSEGV} is the signal a program gets from referencing a place in
3448 memory far away from all the areas in use; @code{SIGALRM} occurs when
3449 the alarm clock timer goes off (which happens only if your program has
3450 requested an alarm).
3451
3452 @cindex fatal signals
3453 Some signals, including @code{SIGALRM}, are a normal part of the
3454 functioning of your program. Others, such as @code{SIGSEGV}, indicate
3455 errors; these signals are @dfn{fatal} (they kill your program immediately) if the
3456 program has not specified in advance some other way to handle the signal.
3457 @code{SIGINT} does not indicate an error in your program, but it is normally
3458 fatal so it can carry out the purpose of the interrupt: to kill the program.
3459
3460 @value{GDBN} has the ability to detect any occurrence of a signal in your
3461 program. You can tell @value{GDBN} in advance what to do for each kind of
3462 signal.
3463
3464 @cindex handling signals
3465 Normally, @value{GDBN} is set up to let the non-erroneous signals like
3466 @code{SIGALRM} be silently passed to your program
3467 (so as not to interfere with their role in the program's functioning)
3468 but to stop your program immediately whenever an error signal happens.
3469 You can change these settings with the @code{handle} command.
3470
3471 @table @code
3472 @kindex info signals
3473 @item info signals
3474 @itemx info handle
3475 Print a table of all the kinds of signals and how @value{GDBN} has been told to
3476 handle each one. You can use this to see the signal numbers of all
3477 the defined types of signals.
3478
3479 @code{info handle} is an alias for @code{info signals}.
3480
3481 @kindex handle
3482 @item handle @var{signal} @var{keywords}@dots{}
3483 Change the way @value{GDBN} handles signal @var{signal}. @var{signal}
3484 can be the number of a signal or its name (with or without the
3485 @samp{SIG} at the beginning); a list of signal numbers of the form
3486 @samp{@var{low}-@var{high}}; or the word @samp{all}, meaning all the
3487 known signals. The @var{keywords} say what change to make.
3488 @end table
3489
3490 @c @group
3491 The keywords allowed by the @code{handle} command can be abbreviated.
3492 Their full names are:
3493
3494 @table @code
3495 @item nostop
3496 @value{GDBN} should not stop your program when this signal happens. It may
3497 still print a message telling you that the signal has come in.
3498
3499 @item stop
3500 @value{GDBN} should stop your program when this signal happens. This implies
3501 the @code{print} keyword as well.
3502
3503 @item print
3504 @value{GDBN} should print a message when this signal happens.
3505
3506 @item noprint
3507 @value{GDBN} should not mention the occurrence of the signal at all. This
3508 implies the @code{nostop} keyword as well.
3509
3510 @item pass
3511 @itemx noignore
3512 @value{GDBN} should allow your program to see this signal; your program
3513 can handle the signal, or else it may terminate if the signal is fatal
3514 and not handled. @code{pass} and @code{noignore} are synonyms.
3515
3516 @item nopass
3517 @itemx ignore
3518 @value{GDBN} should not allow your program to see this signal.
3519 @code{nopass} and @code{ignore} are synonyms.
3520 @end table
3521 @c @end group
3522
3523 When a signal stops your program, the signal is not visible to the
3524 program until you
3525 continue. Your program sees the signal then, if @code{pass} is in
3526 effect for the signal in question @emph{at that time}. In other words,
3527 after @value{GDBN} reports a signal, you can use the @code{handle}
3528 command with @code{pass} or @code{nopass} to control whether your
3529 program sees that signal when you continue.
3530
3531 The default is set to @code{nostop}, @code{noprint}, @code{pass} for
3532 non-erroneous signals such as @code{SIGALRM}, @code{SIGWINCH} and
3533 @code{SIGCHLD}, and to @code{stop}, @code{print}, @code{pass} for the
3534 erroneous signals.
3535
3536 You can also use the @code{signal} command to prevent your program from
3537 seeing a signal, or cause it to see a signal it normally would not see,
3538 or to give it any signal at any time. For example, if your program stopped
3539 due to some sort of memory reference error, you might store correct
3540 values into the erroneous variables and continue, hoping to see more
3541 execution; but your program would probably terminate immediately as
3542 a result of the fatal signal once it saw the signal. To prevent this,
3543 you can continue with @samp{signal 0}. @xref{Signaling, ,Giving your
3544 program a signal}.
3545
3546 @node Thread Stops
3547 @section Stopping and starting multi-thread programs
3548
3549 When your program has multiple threads (@pxref{Threads,, Debugging
3550 programs with multiple threads}), you can choose whether to set
3551 breakpoints on all threads, or on a particular thread.
3552
3553 @table @code
3554 @cindex breakpoints and threads
3555 @cindex thread breakpoints
3556 @kindex break @dots{} thread @var{threadno}
3557 @item break @var{linespec} thread @var{threadno}
3558 @itemx break @var{linespec} thread @var{threadno} if @dots{}
3559 @var{linespec} specifies source lines; there are several ways of
3560 writing them, but the effect is always to specify some source line.
3561
3562 Use the qualifier @samp{thread @var{threadno}} with a breakpoint command
3563 to specify that you only want @value{GDBN} to stop the program when a
3564 particular thread reaches this breakpoint. @var{threadno} is one of the
3565 numeric thread identifiers assigned by @value{GDBN}, shown in the first
3566 column of the @samp{info threads} display.
3567
3568 If you do not specify @samp{thread @var{threadno}} when you set a
3569 breakpoint, the breakpoint applies to @emph{all} threads of your
3570 program.
3571
3572 You can use the @code{thread} qualifier on conditional breakpoints as
3573 well; in this case, place @samp{thread @var{threadno}} before the
3574 breakpoint condition, like this:
3575
3576 @smallexample
3577 (@value{GDBP}) break frik.c:13 thread 28 if bartab > lim
3578 @end smallexample
3579
3580 @end table
3581
3582 @cindex stopped threads
3583 @cindex threads, stopped
3584 Whenever your program stops under @value{GDBN} for any reason,
3585 @emph{all} threads of execution stop, not just the current thread. This
3586 allows you to examine the overall state of the program, including
3587 switching between threads, without worrying that things may change
3588 underfoot.
3589
3590 @cindex continuing threads
3591 @cindex threads, continuing
3592 Conversely, whenever you restart the program, @emph{all} threads start
3593 executing. @emph{This is true even when single-stepping} with commands
3594 like @code{step} or @code{next}.
3595
3596 In particular, @value{GDBN} cannot single-step all threads in lockstep.
3597 Since thread scheduling is up to your debugging target's operating
3598 system (not controlled by @value{GDBN}), other threads may
3599 execute more than one statement while the current thread completes a
3600 single step. Moreover, in general other threads stop in the middle of a
3601 statement, rather than at a clean statement boundary, when the program
3602 stops.
3603
3604 You might even find your program stopped in another thread after
3605 continuing or even single-stepping. This happens whenever some other
3606 thread runs into a breakpoint, a signal, or an exception before the
3607 first thread completes whatever you requested.
3608
3609 On some OSes, you can lock the OS scheduler and thus allow only a single
3610 thread to run.
3611
3612 @table @code
3613 @item set scheduler-locking @var{mode}
3614 Set the scheduler locking mode. If it is @code{off}, then there is no
3615 locking and any thread may run at any time. If @code{on}, then only the
3616 current thread may run when the inferior is resumed. The @code{step}
3617 mode optimizes for single-stepping. It stops other threads from
3618 ``seizing the prompt'' by preempting the current thread while you are
3619 stepping. Other threads will only rarely (or never) get a chance to run
3620 when you step. They are more likely to run when you @samp{next} over a
3621 function call, and they are completely free to run when you use commands
3622 like @samp{continue}, @samp{until}, or @samp{finish}. However, unless another
3623 thread hits a breakpoint during its timeslice, they will never steal the
3624 @value{GDBN} prompt away from the thread that you are debugging.
3625
3626 @item show scheduler-locking
3627 Display the current scheduler locking mode.
3628 @end table
3629
3630
3631 @node Stack
3632 @chapter Examining the Stack
3633
3634 When your program has stopped, the first thing you need to know is where it
3635 stopped and how it got there.
3636
3637 @cindex call stack
3638 Each time your program performs a function call, information about the call
3639 is generated.
3640 That information includes the location of the call in your program,
3641 the arguments of the call,
3642 and the local variables of the function being called.
3643 The information is saved in a block of data called a @dfn{stack frame}.
3644 The stack frames are allocated in a region of memory called the @dfn{call
3645 stack}.
3646
3647 When your program stops, the @value{GDBN} commands for examining the
3648 stack allow you to see all of this information.
3649
3650 @cindex selected frame
3651 One of the stack frames is @dfn{selected} by @value{GDBN} and many
3652 @value{GDBN} commands refer implicitly to the selected frame. In
3653 particular, whenever you ask @value{GDBN} for the value of a variable in
3654 your program, the value is found in the selected frame. There are
3655 special @value{GDBN} commands to select whichever frame you are
3656 interested in. @xref{Selection, ,Selecting a frame}.
3657
3658 When your program stops, @value{GDBN} automatically selects the
3659 currently executing frame and describes it briefly, similar to the
3660 @code{frame} command (@pxref{Frame Info, ,Information about a frame}).
3661
3662 @menu
3663 * Frames:: Stack frames
3664 * Backtrace:: Backtraces
3665 * Selection:: Selecting a frame
3666 * Frame Info:: Information on a frame
3667
3668 @end menu
3669
3670 @node Frames
3671 @section Stack frames
3672
3673 @cindex frame, definition
3674 @cindex stack frame
3675 The call stack is divided up into contiguous pieces called @dfn{stack
3676 frames}, or @dfn{frames} for short; each frame is the data associated
3677 with one call to one function. The frame contains the arguments given
3678 to the function, the function's local variables, and the address at
3679 which the function is executing.
3680
3681 @cindex initial frame
3682 @cindex outermost frame
3683 @cindex innermost frame
3684 When your program is started, the stack has only one frame, that of the
3685 function @code{main}. This is called the @dfn{initial} frame or the
3686 @dfn{outermost} frame. Each time a function is called, a new frame is
3687 made. Each time a function returns, the frame for that function invocation
3688 is eliminated. If a function is recursive, there can be many frames for
3689 the same function. The frame for the function in which execution is
3690 actually occurring is called the @dfn{innermost} frame. This is the most
3691 recently created of all the stack frames that still exist.
3692
3693 @cindex frame pointer
3694 Inside your program, stack frames are identified by their addresses. A
3695 stack frame consists of many bytes, each of which has its own address; each
3696 kind of computer has a convention for choosing one byte whose
3697 address serves as the address of the frame. Usually this address is kept
3698 in a register called the @dfn{frame pointer register} while execution is
3699 going on in that frame.
3700
3701 @cindex frame number
3702 @value{GDBN} assigns numbers to all existing stack frames, starting with
3703 zero for the innermost frame, one for the frame that called it,
3704 and so on upward. These numbers do not really exist in your program;
3705 they are assigned by @value{GDBN} to give you a way of designating stack
3706 frames in @value{GDBN} commands.
3707
3708 @c The -fomit-frame-pointer below perennially causes hbox overflow
3709 @c underflow problems.
3710 @cindex frameless execution
3711 Some compilers provide a way to compile functions so that they operate
3712 without stack frames. (For example, the @value{GCC} option
3713 @example
3714 @samp{-fomit-frame-pointer}
3715 @end example
3716 generates functions without a frame.)
3717 This is occasionally done with heavily used library functions to save
3718 the frame setup time. @value{GDBN} has limited facilities for dealing
3719 with these function invocations. If the innermost function invocation
3720 has no stack frame, @value{GDBN} nevertheless regards it as though
3721 it had a separate frame, which is numbered zero as usual, allowing
3722 correct tracing of the function call chain. However, @value{GDBN} has
3723 no provision for frameless functions elsewhere in the stack.
3724
3725 @table @code
3726 @kindex frame@r{, command}
3727 @cindex current stack frame
3728 @item frame @var{args}
3729 The @code{frame} command allows you to move from one stack frame to another,
3730 and to print the stack frame you select. @var{args} may be either the
3731 address of the frame or the stack frame number. Without an argument,
3732 @code{frame} prints the current stack frame.
3733
3734 @kindex select-frame
3735 @cindex selecting frame silently
3736 @item select-frame
3737 The @code{select-frame} command allows you to move from one stack frame
3738 to another without printing the frame. This is the silent version of
3739 @code{frame}.
3740 @end table
3741
3742 @node Backtrace
3743 @section Backtraces
3744
3745 @cindex backtraces
3746 @cindex tracebacks
3747 @cindex stack traces
3748 A backtrace is a summary of how your program got where it is. It shows one
3749 line per frame, for many frames, starting with the currently executing
3750 frame (frame zero), followed by its caller (frame one), and on up the
3751 stack.
3752
3753 @table @code
3754 @kindex backtrace
3755 @kindex bt @r{(@code{backtrace})}
3756 @item backtrace
3757 @itemx bt
3758 Print a backtrace of the entire stack: one line per frame for all
3759 frames in the stack.
3760
3761 You can stop the backtrace at any time by typing the system interrupt
3762 character, normally @kbd{C-c}.
3763
3764 @item backtrace @var{n}
3765 @itemx bt @var{n}
3766 Similar, but print only the innermost @var{n} frames.
3767
3768 @item backtrace -@var{n}
3769 @itemx bt -@var{n}
3770 Similar, but print only the outermost @var{n} frames.
3771 @end table
3772
3773 @kindex where
3774 @kindex info stack
3775 @kindex info s @r{(@code{info stack})}
3776 The names @code{where} and @code{info stack} (abbreviated @code{info s})
3777 are additional aliases for @code{backtrace}.
3778
3779 Each line in the backtrace shows the frame number and the function name.
3780 The program counter value is also shown---unless you use @code{set
3781 print address off}. The backtrace also shows the source file name and
3782 line number, as well as the arguments to the function. The program
3783 counter value is omitted if it is at the beginning of the code for that
3784 line number.
3785
3786 Here is an example of a backtrace. It was made with the command
3787 @samp{bt 3}, so it shows the innermost three frames.
3788
3789 @smallexample
3790 @group
3791 #0 m4_traceon (obs=0x24eb0, argc=1, argv=0x2b8c8)
3792 at builtin.c:993
3793 #1 0x6e38 in expand_macro (sym=0x2b600) at macro.c:242
3794 #2 0x6840 in expand_token (obs=0x0, t=177664, td=0xf7fffb08)
3795 at macro.c:71
3796 (More stack frames follow...)
3797 @end group
3798 @end smallexample
3799
3800 @noindent
3801 The display for frame zero does not begin with a program counter
3802 value, indicating that your program has stopped at the beginning of the
3803 code for line @code{993} of @code{builtin.c}.
3804
3805 @node Selection
3806 @section Selecting a frame
3807
3808 Most commands for examining the stack and other data in your program work on
3809 whichever stack frame is selected at the moment. Here are the commands for
3810 selecting a stack frame; all of them finish by printing a brief description
3811 of the stack frame just selected.
3812
3813 @table @code
3814 @kindex frame@r{, selecting}
3815 @kindex f @r{(@code{frame})}
3816 @item frame @var{n}
3817 @itemx f @var{n}
3818 Select frame number @var{n}. Recall that frame zero is the innermost
3819 (currently executing) frame, frame one is the frame that called the
3820 innermost one, and so on. The highest-numbered frame is the one for
3821 @code{main}.
3822
3823 @item frame @var{addr}
3824 @itemx f @var{addr}
3825 Select the frame at address @var{addr}. This is useful mainly if the
3826 chaining of stack frames has been damaged by a bug, making it
3827 impossible for @value{GDBN} to assign numbers properly to all frames. In
3828 addition, this can be useful when your program has multiple stacks and
3829 switches between them.
3830
3831 On the SPARC architecture, @code{frame} needs two addresses to
3832 select an arbitrary frame: a frame pointer and a stack pointer.
3833
3834 On the MIPS and Alpha architecture, it needs two addresses: a stack
3835 pointer and a program counter.
3836
3837 On the 29k architecture, it needs three addresses: a register stack
3838 pointer, a program counter, and a memory stack pointer.
3839 @c note to future updaters: this is conditioned on a flag
3840 @c SETUP_ARBITRARY_FRAME in the tm-*.h files. The above is up to date
3841 @c as of 27 Jan 1994.
3842
3843 @kindex up
3844 @item up @var{n}
3845 Move @var{n} frames up the stack. For positive numbers @var{n}, this
3846 advances toward the outermost frame, to higher frame numbers, to frames
3847 that have existed longer. @var{n} defaults to one.
3848
3849 @kindex down
3850 @kindex do @r{(@code{down})}
3851 @item down @var{n}
3852 Move @var{n} frames down the stack. For positive numbers @var{n}, this
3853 advances toward the innermost frame, to lower frame numbers, to frames
3854 that were created more recently. @var{n} defaults to one. You may
3855 abbreviate @code{down} as @code{do}.
3856 @end table
3857
3858 All of these commands end by printing two lines of output describing the
3859 frame. The first line shows the frame number, the function name, the
3860 arguments, and the source file and line number of execution in that
3861 frame. The second line shows the text of that source line.
3862
3863 @need 1000
3864 For example:
3865
3866 @smallexample
3867 @group
3868 (@value{GDBP}) up
3869 #1 0x22f0 in main (argc=1, argv=0xf7fffbf4, env=0xf7fffbfc)
3870 at env.c:10
3871 10 read_input_file (argv[i]);
3872 @end group
3873 @end smallexample
3874
3875 After such a printout, the @code{list} command with no arguments
3876 prints ten lines centered on the point of execution in the frame.
3877 @xref{List, ,Printing source lines}.
3878
3879 @table @code
3880 @kindex down-silently
3881 @kindex up-silently
3882 @item up-silently @var{n}
3883 @itemx down-silently @var{n}
3884 These two commands are variants of @code{up} and @code{down},
3885 respectively; they differ in that they do their work silently, without
3886 causing display of the new frame. They are intended primarily for use
3887 in @value{GDBN} command scripts, where the output might be unnecessary and
3888 distracting.
3889 @end table
3890
3891 @node Frame Info
3892 @section Information about a frame
3893
3894 There are several other commands to print information about the selected
3895 stack frame.
3896
3897 @table @code
3898 @item frame
3899 @itemx f
3900 When used without any argument, this command does not change which
3901 frame is selected, but prints a brief description of the currently
3902 selected stack frame. It can be abbreviated @code{f}. With an
3903 argument, this command is used to select a stack frame.
3904 @xref{Selection, ,Selecting a frame}.
3905
3906 @kindex info frame
3907 @kindex info f @r{(@code{info frame})}
3908 @item info frame
3909 @itemx info f
3910 This command prints a verbose description of the selected stack frame,
3911 including:
3912
3913 @itemize @bullet
3914 @item
3915 the address of the frame
3916 @item
3917 the address of the next frame down (called by this frame)
3918 @item
3919 the address of the next frame up (caller of this frame)
3920 @item
3921 the language in which the source code corresponding to this frame is written
3922 @item
3923 the address of the frame's arguments
3924 @item
3925 the address of the frame's local variables
3926 @item
3927 the program counter saved in it (the address of execution in the caller frame)
3928 @item
3929 which registers were saved in the frame
3930 @end itemize
3931
3932 @noindent The verbose description is useful when
3933 something has gone wrong that has made the stack format fail to fit
3934 the usual conventions.
3935
3936 @item info frame @var{addr}
3937 @itemx info f @var{addr}
3938 Print a verbose description of the frame at address @var{addr}, without
3939 selecting that frame. The selected frame remains unchanged by this
3940 command. This requires the same kind of address (more than one for some
3941 architectures) that you specify in the @code{frame} command.
3942 @xref{Selection, ,Selecting a frame}.
3943
3944 @kindex info args
3945 @item info args
3946 Print the arguments of the selected frame, each on a separate line.
3947
3948 @item info locals
3949 @kindex info locals
3950 Print the local variables of the selected frame, each on a separate
3951 line. These are all variables (declared either static or automatic)
3952 accessible at the point of execution of the selected frame.
3953
3954 @kindex info catch
3955 @cindex catch exceptions, list active handlers
3956 @cindex exception handlers, how to list
3957 @item info catch
3958 Print a list of all the exception handlers that are active in the
3959 current stack frame at the current point of execution. To see other
3960 exception handlers, visit the associated frame (using the @code{up},
3961 @code{down}, or @code{frame} commands); then type @code{info catch}.
3962 @xref{Set Catchpoints, , Setting catchpoints}.
3963
3964 @end table
3965
3966
3967 @node Source
3968 @chapter Examining Source Files
3969
3970 @value{GDBN} can print parts of your program's source, since the debugging
3971 information recorded in the program tells @value{GDBN} what source files were
3972 used to build it. When your program stops, @value{GDBN} spontaneously prints
3973 the line where it stopped. Likewise, when you select a stack frame
3974 (@pxref{Selection, ,Selecting a frame}), @value{GDBN} prints the line where
3975 execution in that frame has stopped. You can print other portions of
3976 source files by explicit command.
3977
3978 If you use @value{GDBN} through its @sc{gnu} Emacs interface, you may
3979 prefer to use Emacs facilities to view source; see @ref{Emacs, ,Using
3980 @value{GDBN} under @sc{gnu} Emacs}.
3981
3982 @menu
3983 * List:: Printing source lines
3984 * Search:: Searching source files
3985 * Source Path:: Specifying source directories
3986 * Machine Code:: Source and machine code
3987 @end menu
3988
3989 @node List
3990 @section Printing source lines
3991
3992 @kindex list
3993 @kindex l @r{(@code{list})}
3994 To print lines from a source file, use the @code{list} command
3995 (abbreviated @code{l}). By default, ten lines are printed.
3996 There are several ways to specify what part of the file you want to print.
3997
3998 Here are the forms of the @code{list} command most commonly used:
3999
4000 @table @code
4001 @item list @var{linenum}
4002 Print lines centered around line number @var{linenum} in the
4003 current source file.
4004
4005 @item list @var{function}
4006 Print lines centered around the beginning of function
4007 @var{function}.
4008
4009 @item list
4010 Print more lines. If the last lines printed were printed with a
4011 @code{list} command, this prints lines following the last lines
4012 printed; however, if the last line printed was a solitary line printed
4013 as part of displaying a stack frame (@pxref{Stack, ,Examining the
4014 Stack}), this prints lines centered around that line.
4015
4016 @item list -
4017 Print lines just before the lines last printed.
4018 @end table
4019
4020 By default, @value{GDBN} prints ten source lines with any of these forms of
4021 the @code{list} command. You can change this using @code{set listsize}:
4022
4023 @table @code
4024 @kindex set listsize
4025 @item set listsize @var{count}
4026 Make the @code{list} command display @var{count} source lines (unless
4027 the @code{list} argument explicitly specifies some other number).
4028
4029 @kindex show listsize
4030 @item show listsize
4031 Display the number of lines that @code{list} prints.
4032 @end table
4033
4034 Repeating a @code{list} command with @key{RET} discards the argument,
4035 so it is equivalent to typing just @code{list}. This is more useful
4036 than listing the same lines again. An exception is made for an
4037 argument of @samp{-}; that argument is preserved in repetition so that
4038 each repetition moves up in the source file.
4039
4040 @cindex linespec
4041 In general, the @code{list} command expects you to supply zero, one or two
4042 @dfn{linespecs}. Linespecs specify source lines; there are several ways
4043 of writing them, but the effect is always to specify some source line.
4044 Here is a complete description of the possible arguments for @code{list}:
4045
4046 @table @code
4047 @item list @var{linespec}
4048 Print lines centered around the line specified by @var{linespec}.
4049
4050 @item list @var{first},@var{last}
4051 Print lines from @var{first} to @var{last}. Both arguments are
4052 linespecs.
4053
4054 @item list ,@var{last}
4055 Print lines ending with @var{last}.
4056
4057 @item list @var{first},
4058 Print lines starting with @var{first}.
4059
4060 @item list +
4061 Print lines just after the lines last printed.
4062
4063 @item list -
4064 Print lines just before the lines last printed.
4065
4066 @item list
4067 As described in the preceding table.
4068 @end table
4069
4070 Here are the ways of specifying a single source line---all the
4071 kinds of linespec.
4072
4073 @table @code
4074 @item @var{number}
4075 Specifies line @var{number} of the current source file.
4076 When a @code{list} command has two linespecs, this refers to
4077 the same source file as the first linespec.
4078
4079 @item +@var{offset}
4080 Specifies the line @var{offset} lines after the last line printed.
4081 When used as the second linespec in a @code{list} command that has
4082 two, this specifies the line @var{offset} lines down from the
4083 first linespec.
4084
4085 @item -@var{offset}
4086 Specifies the line @var{offset} lines before the last line printed.
4087
4088 @item @var{filename}:@var{number}
4089 Specifies line @var{number} in the source file @var{filename}.
4090
4091 @item @var{function}
4092 Specifies the line that begins the body of the function @var{function}.
4093 For example: in C, this is the line with the open brace.
4094
4095 @item @var{filename}:@var{function}
4096 Specifies the line of the open-brace that begins the body of the
4097 function @var{function} in the file @var{filename}. You only need the
4098 file name with a function name to avoid ambiguity when there are
4099 identically named functions in different source files.
4100
4101 @item *@var{address}
4102 Specifies the line containing the program address @var{address}.
4103 @var{address} may be any expression.
4104 @end table
4105
4106 @node Search
4107 @section Searching source files
4108 @cindex searching
4109 @kindex reverse-search
4110
4111 There are two commands for searching through the current source file for a
4112 regular expression.
4113
4114 @table @code
4115 @kindex search
4116 @kindex forward-search
4117 @item forward-search @var{regexp}
4118 @itemx search @var{regexp}
4119 The command @samp{forward-search @var{regexp}} checks each line,
4120 starting with the one following the last line listed, for a match for
4121 @var{regexp}. It lists the line that is found. You can use the
4122 synonym @samp{search @var{regexp}} or abbreviate the command name as
4123 @code{fo}.
4124
4125 @item reverse-search @var{regexp}
4126 The command @samp{reverse-search @var{regexp}} checks each line, starting
4127 with the one before the last line listed and going backward, for a match
4128 for @var{regexp}. It lists the line that is found. You can abbreviate
4129 this command as @code{rev}.
4130 @end table
4131
4132 @node Source Path
4133 @section Specifying source directories
4134
4135 @cindex source path
4136 @cindex directories for source files
4137 Executable programs sometimes do not record the directories of the source
4138 files from which they were compiled, just the names. Even when they do,
4139 the directories could be moved between the compilation and your debugging
4140 session. @value{GDBN} has a list of directories to search for source files;
4141 this is called the @dfn{source path}. Each time @value{GDBN} wants a source file,
4142 it tries all the directories in the list, in the order they are present
4143 in the list, until it finds a file with the desired name. Note that
4144 the executable search path is @emph{not} used for this purpose. Neither is
4145 the current working directory, unless it happens to be in the source
4146 path.
4147
4148 If @value{GDBN} cannot find a source file in the source path, and the
4149 object program records a directory, @value{GDBN} tries that directory
4150 too. If the source path is empty, and there is no record of the
4151 compilation directory, @value{GDBN} looks in the current directory as a
4152 last resort.
4153
4154 Whenever you reset or rearrange the source path, @value{GDBN} clears out
4155 any information it has cached about where source files are found and where
4156 each line is in the file.
4157
4158 @kindex directory
4159 @kindex dir
4160 When you start @value{GDBN}, its source path includes only @samp{cdir}
4161 and @samp{cwd}, in that order.
4162 To add other directories, use the @code{directory} command.
4163
4164 @table @code
4165 @item directory @var{dirname} @dots{}
4166 @item dir @var{dirname} @dots{}
4167 Add directory @var{dirname} to the front of the source path. Several
4168 directory names may be given to this command, separated by @samp{:}
4169 (@samp{;} on MS-DOS and MS-Windows, where @samp{:} usually appears as
4170 part of absolute file names) or
4171 whitespace. You may specify a directory that is already in the source
4172 path; this moves it forward, so @value{GDBN} searches it sooner.
4173
4174 @kindex cdir
4175 @kindex cwd
4176 @vindex $cdir@r{, convenience variable}
4177 @vindex $cwdr@r{, convenience variable}
4178 @cindex compilation directory
4179 @cindex current directory
4180 @cindex working directory
4181 @cindex directory, current
4182 @cindex directory, compilation
4183 You can use the string @samp{$cdir} to refer to the compilation
4184 directory (if one is recorded), and @samp{$cwd} to refer to the current
4185 working directory. @samp{$cwd} is not the same as @samp{.}---the former
4186 tracks the current working directory as it changes during your @value{GDBN}
4187 session, while the latter is immediately expanded to the current
4188 directory at the time you add an entry to the source path.
4189
4190 @item directory
4191 Reset the source path to empty again. This requires confirmation.
4192
4193 @c RET-repeat for @code{directory} is explicitly disabled, but since
4194 @c repeating it would be a no-op we do not say that. (thanks to RMS)
4195
4196 @item show directories
4197 @kindex show directories
4198 Print the source path: show which directories it contains.
4199 @end table
4200
4201 If your source path is cluttered with directories that are no longer of
4202 interest, @value{GDBN} may sometimes cause confusion by finding the wrong
4203 versions of source. You can correct the situation as follows:
4204
4205 @enumerate
4206 @item
4207 Use @code{directory} with no argument to reset the source path to empty.
4208
4209 @item
4210 Use @code{directory} with suitable arguments to reinstall the
4211 directories you want in the source path. You can add all the
4212 directories in one command.
4213 @end enumerate
4214
4215 @node Machine Code
4216 @section Source and machine code
4217
4218 You can use the command @code{info line} to map source lines to program
4219 addresses (and vice versa), and the command @code{disassemble} to display
4220 a range of addresses as machine instructions. When run under @sc{gnu} Emacs
4221 mode, the @code{info line} command causes the arrow to point to the
4222 line specified. Also, @code{info line} prints addresses in symbolic form as
4223 well as hex.
4224
4225 @table @code
4226 @kindex info line
4227 @item info line @var{linespec}
4228 Print the starting and ending addresses of the compiled code for
4229 source line @var{linespec}. You can specify source lines in any of
4230 the ways understood by the @code{list} command (@pxref{List, ,Printing
4231 source lines}).
4232 @end table
4233
4234 For example, we can use @code{info line} to discover the location of
4235 the object code for the first line of function
4236 @code{m4_changequote}:
4237
4238 @c FIXME: I think this example should also show the addresses in
4239 @c symbolic form, as they usually would be displayed.
4240 @smallexample
4241 (@value{GDBP}) info line m4_changequote
4242 Line 895 of "builtin.c" starts at pc 0x634c and ends at 0x6350.
4243 @end smallexample
4244
4245 @noindent
4246 We can also inquire (using @code{*@var{addr}} as the form for
4247 @var{linespec}) what source line covers a particular address:
4248 @smallexample
4249 (@value{GDBP}) info line *0x63ff
4250 Line 926 of "builtin.c" starts at pc 0x63e4 and ends at 0x6404.
4251 @end smallexample
4252
4253 @cindex @code{$_} and @code{info line}
4254 @kindex x@r{(examine), and} info line
4255 After @code{info line}, the default address for the @code{x} command
4256 is changed to the starting address of the line, so that @samp{x/i} is
4257 sufficient to begin examining the machine code (@pxref{Memory,
4258 ,Examining memory}). Also, this address is saved as the value of the
4259 convenience variable @code{$_} (@pxref{Convenience Vars, ,Convenience
4260 variables}).
4261
4262 @table @code
4263 @kindex disassemble
4264 @cindex assembly instructions
4265 @cindex instructions, assembly
4266 @cindex machine instructions
4267 @cindex listing machine instructions
4268 @item disassemble
4269 This specialized command dumps a range of memory as machine
4270 instructions. The default memory range is the function surrounding the
4271 program counter of the selected frame. A single argument to this
4272 command is a program counter value; @value{GDBN} dumps the function
4273 surrounding this value. Two arguments specify a range of addresses
4274 (first inclusive, second exclusive) to dump.
4275 @end table
4276
4277 The following example shows the disassembly of a range of addresses of
4278 HP PA-RISC 2.0 code:
4279
4280 @smallexample
4281 (@value{GDBP}) disas 0x32c4 0x32e4
4282 Dump of assembler code from 0x32c4 to 0x32e4:
4283 0x32c4 <main+204>: addil 0,dp
4284 0x32c8 <main+208>: ldw 0x22c(sr0,r1),r26
4285 0x32cc <main+212>: ldil 0x3000,r31
4286 0x32d0 <main+216>: ble 0x3f8(sr4,r31)
4287 0x32d4 <main+220>: ldo 0(r31),rp
4288 0x32d8 <main+224>: addil -0x800,dp
4289 0x32dc <main+228>: ldo 0x588(r1),r26
4290 0x32e0 <main+232>: ldil 0x3000,r31
4291 End of assembler dump.
4292 @end smallexample
4293
4294 Some architectures have more than one commonly-used set of instruction
4295 mnemonics or other syntax.
4296
4297 @table @code
4298 @kindex set disassembly-flavor
4299 @cindex assembly instructions
4300 @cindex instructions, assembly
4301 @cindex machine instructions
4302 @cindex listing machine instructions
4303 @cindex Intel disassembly flavor
4304 @cindex AT&T disassembly flavor
4305 @item set disassembly-flavor @var{instruction-set}
4306 Select the instruction set to use when disassembling the
4307 program via the @code{disassemble} or @code{x/i} commands.
4308
4309 Currently this command is only defined for the Intel x86 family. You
4310 can set @var{instruction-set} to either @code{intel} or @code{att}.
4311 The default is @code{att}, the AT&T flavor used by default by Unix
4312 assemblers for x86-based targets.
4313 @end table
4314
4315
4316 @node Data
4317 @chapter Examining Data
4318
4319 @cindex printing data
4320 @cindex examining data
4321 @kindex print
4322 @kindex inspect
4323 @c "inspect" is not quite a synonym if you are using Epoch, which we do not
4324 @c document because it is nonstandard... Under Epoch it displays in a
4325 @c different window or something like that.
4326 The usual way to examine data in your program is with the @code{print}
4327 command (abbreviated @code{p}), or its synonym @code{inspect}. It
4328 evaluates and prints the value of an expression of the language your
4329 program is written in (@pxref{Languages, ,Using @value{GDBN} with
4330 Different Languages}).
4331
4332 @table @code
4333 @item print @var{expr}
4334 @itemx print /@var{f} @var{expr}
4335 @var{expr} is an expression (in the source language). By default the
4336 value of @var{expr} is printed in a format appropriate to its data type;
4337 you can choose a different format by specifying @samp{/@var{f}}, where
4338 @var{f} is a letter specifying the format; see @ref{Output Formats,,Output
4339 formats}.
4340
4341 @item print
4342 @itemx print /@var{f}
4343 If you omit @var{expr}, @value{GDBN} displays the last value again (from the
4344 @dfn{value history}; @pxref{Value History, ,Value history}). This allows you to
4345 conveniently inspect the same value in an alternative format.
4346 @end table
4347
4348 A more low-level way of examining data is with the @code{x} command.
4349 It examines data in memory at a specified address and prints it in a
4350 specified format. @xref{Memory, ,Examining memory}.
4351
4352 If you are interested in information about types, or about how the
4353 fields of a struct or a class are declared, use the @code{ptype @var{exp}}
4354 command rather than @code{print}. @xref{Symbols, ,Examining the Symbol
4355 Table}.
4356
4357 @menu
4358 * Expressions:: Expressions
4359 * Variables:: Program variables
4360 * Arrays:: Artificial arrays
4361 * Output Formats:: Output formats
4362 * Memory:: Examining memory
4363 * Auto Display:: Automatic display
4364 * Print Settings:: Print settings
4365 * Value History:: Value history
4366 * Convenience Vars:: Convenience variables
4367 * Registers:: Registers
4368 * Floating Point Hardware:: Floating point hardware
4369 * Memory Region Attributes:: Memory region attributes
4370 @end menu
4371
4372 @node Expressions
4373 @section Expressions
4374
4375 @cindex expressions
4376 @code{print} and many other @value{GDBN} commands accept an expression and
4377 compute its value. Any kind of constant, variable or operator defined
4378 by the programming language you are using is valid in an expression in
4379 @value{GDBN}. This includes conditional expressions, function calls, casts
4380 and string constants. It unfortunately does not include symbols defined
4381 by preprocessor @code{#define} commands.
4382
4383 @value{GDBN} supports array constants in expressions input by
4384 the user. The syntax is @{@var{element}, @var{element}@dots{}@}. For example,
4385 you can use the command @code{print @{1, 2, 3@}} to build up an array in
4386 memory that is @code{malloc}ed in the target program.
4387
4388 Because C is so widespread, most of the expressions shown in examples in
4389 this manual are in C. @xref{Languages, , Using @value{GDBN} with Different
4390 Languages}, for information on how to use expressions in other
4391 languages.
4392
4393 In this section, we discuss operators that you can use in @value{GDBN}
4394 expressions regardless of your programming language.
4395
4396 Casts are supported in all languages, not just in C, because it is so
4397 useful to cast a number into a pointer in order to examine a structure
4398 at that address in memory.
4399 @c FIXME: casts supported---Mod2 true?
4400
4401 @value{GDBN} supports these operators, in addition to those common
4402 to programming languages:
4403
4404 @table @code
4405 @item @@
4406 @samp{@@} is a binary operator for treating parts of memory as arrays.
4407 @xref{Arrays, ,Artificial arrays}, for more information.
4408
4409 @item ::
4410 @samp{::} allows you to specify a variable in terms of the file or
4411 function where it is defined. @xref{Variables, ,Program variables}.
4412
4413 @cindex @{@var{type}@}
4414 @cindex type casting memory
4415 @cindex memory, viewing as typed object
4416 @cindex casts, to view memory
4417 @item @{@var{type}@} @var{addr}
4418 Refers to an object of type @var{type} stored at address @var{addr} in
4419 memory. @var{addr} may be any expression whose value is an integer or
4420 pointer (but parentheses are required around binary operators, just as in
4421 a cast). This construct is allowed regardless of what kind of data is
4422 normally supposed to reside at @var{addr}.
4423 @end table
4424
4425 @node Variables
4426 @section Program variables
4427
4428 The most common kind of expression to use is the name of a variable
4429 in your program.
4430
4431 Variables in expressions are understood in the selected stack frame
4432 (@pxref{Selection, ,Selecting a frame}); they must be either:
4433
4434 @itemize @bullet
4435 @item
4436 global (or file-static)
4437 @end itemize
4438
4439 @noindent or
4440
4441 @itemize @bullet
4442 @item
4443 visible according to the scope rules of the
4444 programming language from the point of execution in that frame
4445 @end itemize
4446
4447 @noindent This means that in the function
4448
4449 @example
4450 foo (a)
4451 int a;
4452 @{
4453 bar (a);
4454 @{
4455 int b = test ();
4456 bar (b);
4457 @}
4458 @}
4459 @end example
4460
4461 @noindent
4462 you can examine and use the variable @code{a} whenever your program is
4463 executing within the function @code{foo}, but you can only use or
4464 examine the variable @code{b} while your program is executing inside
4465 the block where @code{b} is declared.
4466
4467 @cindex variable name conflict
4468 There is an exception: you can refer to a variable or function whose
4469 scope is a single source file even if the current execution point is not
4470 in this file. But it is possible to have more than one such variable or
4471 function with the same name (in different source files). If that
4472 happens, referring to that name has unpredictable effects. If you wish,
4473 you can specify a static variable in a particular function or file,
4474 using the colon-colon notation:
4475
4476 @cindex colon-colon, context for variables/functions
4477 @iftex
4478 @c info cannot cope with a :: index entry, but why deprive hard copy readers?
4479 @cindex @code{::}, context for variables/functions
4480 @end iftex
4481 @example
4482 @var{file}::@var{variable}
4483 @var{function}::@var{variable}
4484 @end example
4485
4486 @noindent
4487 Here @var{file} or @var{function} is the name of the context for the
4488 static @var{variable}. In the case of file names, you can use quotes to
4489 make sure @value{GDBN} parses the file name as a single word---for example,
4490 to print a global value of @code{x} defined in @file{f2.c}:
4491
4492 @example
4493 (@value{GDBP}) p 'f2.c'::x
4494 @end example
4495
4496 @cindex C@t{++} scope resolution
4497 This use of @samp{::} is very rarely in conflict with the very similar
4498 use of the same notation in C@t{++}. @value{GDBN} also supports use of the C@t{++}
4499 scope resolution operator in @value{GDBN} expressions.
4500 @c FIXME: Um, so what happens in one of those rare cases where it's in
4501 @c conflict?? --mew
4502
4503 @cindex wrong values
4504 @cindex variable values, wrong
4505 @quotation
4506 @emph{Warning:} Occasionally, a local variable may appear to have the
4507 wrong value at certain points in a function---just after entry to a new
4508 scope, and just before exit.
4509 @end quotation
4510 You may see this problem when you are stepping by machine instructions.
4511 This is because, on most machines, it takes more than one instruction to
4512 set up a stack frame (including local variable definitions); if you are
4513 stepping by machine instructions, variables may appear to have the wrong
4514 values until the stack frame is completely built. On exit, it usually
4515 also takes more than one machine instruction to destroy a stack frame;
4516 after you begin stepping through that group of instructions, local
4517 variable definitions may be gone.
4518
4519 This may also happen when the compiler does significant optimizations.
4520 To be sure of always seeing accurate values, turn off all optimization
4521 when compiling.
4522
4523 @cindex ``No symbol "foo" in current context''
4524 Another possible effect of compiler optimizations is to optimize
4525 unused variables out of existence, or assign variables to registers (as
4526 opposed to memory addresses). Depending on the support for such cases
4527 offered by the debug info format used by the compiler, @value{GDBN}
4528 might not be able to display values for such local variables. If that
4529 happens, @value{GDBN} will print a message like this:
4530
4531 @example
4532 No symbol "foo" in current context.
4533 @end example
4534
4535 To solve such problems, either recompile without optimizations, or use a
4536 different debug info format, if the compiler supports several such
4537 formats. For example, @value{NGCC}, the @sc{gnu} C/C@t{++} compiler usually
4538 supports the @samp{-gstabs} option. @samp{-gstabs} produces debug info
4539 in a format that is superior to formats such as COFF. You may be able
4540 to use DWARF2 (@samp{-gdwarf-2}), which is also an effective form for
4541 debug info. See @ref{Debugging Options,,Options for Debugging Your
4542 Program or @sc{gnu} CC, gcc.info, Using @sc{gnu} CC}, for more
4543 information.
4544
4545
4546 @node Arrays
4547 @section Artificial arrays
4548
4549 @cindex artificial array
4550 @kindex @@@r{, referencing memory as an array}
4551 It is often useful to print out several successive objects of the
4552 same type in memory; a section of an array, or an array of
4553 dynamically determined size for which only a pointer exists in the
4554 program.
4555
4556 You can do this by referring to a contiguous span of memory as an
4557 @dfn{artificial array}, using the binary operator @samp{@@}. The left
4558 operand of @samp{@@} should be the first element of the desired array
4559 and be an individual object. The right operand should be the desired length
4560 of the array. The result is an array value whose elements are all of
4561 the type of the left argument. The first element is actually the left
4562 argument; the second element comes from bytes of memory immediately
4563 following those that hold the first element, and so on. Here is an
4564 example. If a program says
4565
4566 @example
4567 int *array = (int *) malloc (len * sizeof (int));
4568 @end example
4569
4570 @noindent
4571 you can print the contents of @code{array} with
4572
4573 @example
4574 p *array@@len
4575 @end example
4576
4577 The left operand of @samp{@@} must reside in memory. Array values made
4578 with @samp{@@} in this way behave just like other arrays in terms of
4579 subscripting, and are coerced to pointers when used in expressions.
4580 Artificial arrays most often appear in expressions via the value history
4581 (@pxref{Value History, ,Value history}), after printing one out.
4582
4583 Another way to create an artificial array is to use a cast.
4584 This re-interprets a value as if it were an array.
4585 The value need not be in memory:
4586 @example
4587 (@value{GDBP}) p/x (short[2])0x12345678
4588 $1 = @{0x1234, 0x5678@}
4589 @end example
4590
4591 As a convenience, if you leave the array length out (as in
4592 @samp{(@var{type}[])@var{value}}) @value{GDBN} calculates the size to fill
4593 the value (as @samp{sizeof(@var{value})/sizeof(@var{type})}:
4594 @example
4595 (@value{GDBP}) p/x (short[])0x12345678
4596 $2 = @{0x1234, 0x5678@}
4597 @end example
4598
4599 Sometimes the artificial array mechanism is not quite enough; in
4600 moderately complex data structures, the elements of interest may not
4601 actually be adjacent---for example, if you are interested in the values
4602 of pointers in an array. One useful work-around in this situation is
4603 to use a convenience variable (@pxref{Convenience Vars, ,Convenience
4604 variables}) as a counter in an expression that prints the first
4605 interesting value, and then repeat that expression via @key{RET}. For
4606 instance, suppose you have an array @code{dtab} of pointers to
4607 structures, and you are interested in the values of a field @code{fv}
4608 in each structure. Here is an example of what you might type:
4609
4610 @example
4611 set $i = 0
4612 p dtab[$i++]->fv
4613 @key{RET}
4614 @key{RET}
4615 @dots{}
4616 @end example
4617
4618 @node Output Formats
4619 @section Output formats
4620
4621 @cindex formatted output
4622 @cindex output formats
4623 By default, @value{GDBN} prints a value according to its data type. Sometimes
4624 this is not what you want. For example, you might want to print a number
4625 in hex, or a pointer in decimal. Or you might want to view data in memory
4626 at a certain address as a character string or as an instruction. To do
4627 these things, specify an @dfn{output format} when you print a value.
4628
4629 The simplest use of output formats is to say how to print a value
4630 already computed. This is done by starting the arguments of the
4631 @code{print} command with a slash and a format letter. The format
4632 letters supported are:
4633
4634 @table @code
4635 @item x
4636 Regard the bits of the value as an integer, and print the integer in
4637 hexadecimal.
4638
4639 @item d
4640 Print as integer in signed decimal.
4641
4642 @item u
4643 Print as integer in unsigned decimal.
4644
4645 @item o
4646 Print as integer in octal.
4647
4648 @item t
4649 Print as integer in binary. The letter @samp{t} stands for ``two''.
4650 @footnote{@samp{b} cannot be used because these format letters are also
4651 used with the @code{x} command, where @samp{b} stands for ``byte'';
4652 see @ref{Memory,,Examining memory}.}
4653
4654 @item a
4655 @cindex unknown address, locating
4656 @cindex locate address
4657 Print as an address, both absolute in hexadecimal and as an offset from
4658 the nearest preceding symbol. You can use this format used to discover
4659 where (in what function) an unknown address is located:
4660
4661 @example
4662 (@value{GDBP}) p/a 0x54320
4663 $3 = 0x54320 <_initialize_vx+396>
4664 @end example
4665
4666 @noindent
4667 The command @code{info symbol 0x54320} yields similar results.
4668 @xref{Symbols, info symbol}.
4669
4670 @item c
4671 Regard as an integer and print it as a character constant.
4672
4673 @item f
4674 Regard the bits of the value as a floating point number and print
4675 using typical floating point syntax.
4676 @end table
4677
4678 For example, to print the program counter in hex (@pxref{Registers}), type
4679
4680 @example
4681 p/x $pc
4682 @end example
4683
4684 @noindent
4685 Note that no space is required before the slash; this is because command
4686 names in @value{GDBN} cannot contain a slash.
4687
4688 To reprint the last value in the value history with a different format,
4689 you can use the @code{print} command with just a format and no
4690 expression. For example, @samp{p/x} reprints the last value in hex.
4691
4692 @node Memory
4693 @section Examining memory
4694
4695 You can use the command @code{x} (for ``examine'') to examine memory in
4696 any of several formats, independently of your program's data types.
4697
4698 @cindex examining memory
4699 @table @code
4700 @kindex x @r{(examine memory)}
4701 @item x/@var{nfu} @var{addr}
4702 @itemx x @var{addr}
4703 @itemx x
4704 Use the @code{x} command to examine memory.
4705 @end table
4706
4707 @var{n}, @var{f}, and @var{u} are all optional parameters that specify how
4708 much memory to display and how to format it; @var{addr} is an
4709 expression giving the address where you want to start displaying memory.
4710 If you use defaults for @var{nfu}, you need not type the slash @samp{/}.
4711 Several commands set convenient defaults for @var{addr}.
4712
4713 @table @r
4714 @item @var{n}, the repeat count
4715 The repeat count is a decimal integer; the default is 1. It specifies
4716 how much memory (counting by units @var{u}) to display.
4717 @c This really is **decimal**; unaffected by 'set radix' as of GDB
4718 @c 4.1.2.
4719
4720 @item @var{f}, the display format
4721 The display format is one of the formats used by @code{print},
4722 @samp{s} (null-terminated string), or @samp{i} (machine instruction).
4723 The default is @samp{x} (hexadecimal) initially.
4724 The default changes each time you use either @code{x} or @code{print}.
4725
4726 @item @var{u}, the unit size
4727 The unit size is any of
4728
4729 @table @code
4730 @item b
4731 Bytes.
4732 @item h
4733 Halfwords (two bytes).
4734 @item w
4735 Words (four bytes). This is the initial default.
4736 @item g
4737 Giant words (eight bytes).
4738 @end table
4739
4740 Each time you specify a unit size with @code{x}, that size becomes the
4741 default unit the next time you use @code{x}. (For the @samp{s} and
4742 @samp{i} formats, the unit size is ignored and is normally not written.)
4743
4744 @item @var{addr}, starting display address
4745 @var{addr} is the address where you want @value{GDBN} to begin displaying
4746 memory. The expression need not have a pointer value (though it may);
4747 it is always interpreted as an integer address of a byte of memory.
4748 @xref{Expressions, ,Expressions}, for more information on expressions. The default for
4749 @var{addr} is usually just after the last address examined---but several
4750 other commands also set the default address: @code{info breakpoints} (to
4751 the address of the last breakpoint listed), @code{info line} (to the
4752 starting address of a line), and @code{print} (if you use it to display
4753 a value from memory).
4754 @end table
4755
4756 For example, @samp{x/3uh 0x54320} is a request to display three halfwords
4757 (@code{h}) of memory, formatted as unsigned decimal integers (@samp{u}),
4758 starting at address @code{0x54320}. @samp{x/4xw $sp} prints the four
4759 words (@samp{w}) of memory above the stack pointer (here, @samp{$sp};
4760 @pxref{Registers, ,Registers}) in hexadecimal (@samp{x}).
4761
4762 Since the letters indicating unit sizes are all distinct from the
4763 letters specifying output formats, you do not have to remember whether
4764 unit size or format comes first; either order works. The output
4765 specifications @samp{4xw} and @samp{4wx} mean exactly the same thing.
4766 (However, the count @var{n} must come first; @samp{wx4} does not work.)
4767
4768 Even though the unit size @var{u} is ignored for the formats @samp{s}
4769 and @samp{i}, you might still want to use a count @var{n}; for example,
4770 @samp{3i} specifies that you want to see three machine instructions,
4771 including any operands. The command @code{disassemble} gives an
4772 alternative way of inspecting machine instructions; see @ref{Machine
4773 Code,,Source and machine code}.
4774
4775 All the defaults for the arguments to @code{x} are designed to make it
4776 easy to continue scanning memory with minimal specifications each time
4777 you use @code{x}. For example, after you have inspected three machine
4778 instructions with @samp{x/3i @var{addr}}, you can inspect the next seven
4779 with just @samp{x/7}. If you use @key{RET} to repeat the @code{x} command,
4780 the repeat count @var{n} is used again; the other arguments default as
4781 for successive uses of @code{x}.
4782
4783 @cindex @code{$_}, @code{$__}, and value history
4784 The addresses and contents printed by the @code{x} command are not saved
4785 in the value history because there is often too much of them and they
4786 would get in the way. Instead, @value{GDBN} makes these values available for
4787 subsequent use in expressions as values of the convenience variables
4788 @code{$_} and @code{$__}. After an @code{x} command, the last address
4789 examined is available for use in expressions in the convenience variable
4790 @code{$_}. The contents of that address, as examined, are available in
4791 the convenience variable @code{$__}.
4792
4793 If the @code{x} command has a repeat count, the address and contents saved
4794 are from the last memory unit printed; this is not the same as the last
4795 address printed if several units were printed on the last line of output.
4796
4797 @node Auto Display
4798 @section Automatic display
4799 @cindex automatic display
4800 @cindex display of expressions
4801
4802 If you find that you want to print the value of an expression frequently
4803 (to see how it changes), you might want to add it to the @dfn{automatic
4804 display list} so that @value{GDBN} prints its value each time your program stops.
4805 Each expression added to the list is given a number to identify it;
4806 to remove an expression from the list, you specify that number.
4807 The automatic display looks like this:
4808
4809 @example
4810 2: foo = 38
4811 3: bar[5] = (struct hack *) 0x3804
4812 @end example
4813
4814 @noindent
4815 This display shows item numbers, expressions and their current values. As with
4816 displays you request manually using @code{x} or @code{print}, you can
4817 specify the output format you prefer; in fact, @code{display} decides
4818 whether to use @code{print} or @code{x} depending on how elaborate your
4819 format specification is---it uses @code{x} if you specify a unit size,
4820 or one of the two formats (@samp{i} and @samp{s}) that are only
4821 supported by @code{x}; otherwise it uses @code{print}.
4822
4823 @table @code
4824 @kindex display
4825 @item display @var{expr}
4826 Add the expression @var{expr} to the list of expressions to display
4827 each time your program stops. @xref{Expressions, ,Expressions}.
4828
4829 @code{display} does not repeat if you press @key{RET} again after using it.
4830
4831 @item display/@var{fmt} @var{expr}
4832 For @var{fmt} specifying only a display format and not a size or
4833 count, add the expression @var{expr} to the auto-display list but
4834 arrange to display it each time in the specified format @var{fmt}.
4835 @xref{Output Formats,,Output formats}.
4836
4837 @item display/@var{fmt} @var{addr}
4838 For @var{fmt} @samp{i} or @samp{s}, or including a unit-size or a
4839 number of units, add the expression @var{addr} as a memory address to
4840 be examined each time your program stops. Examining means in effect
4841 doing @samp{x/@var{fmt} @var{addr}}. @xref{Memory, ,Examining memory}.
4842 @end table
4843
4844 For example, @samp{display/i $pc} can be helpful, to see the machine
4845 instruction about to be executed each time execution stops (@samp{$pc}
4846 is a common name for the program counter; @pxref{Registers, ,Registers}).
4847
4848 @table @code
4849 @kindex delete display
4850 @kindex undisplay
4851 @item undisplay @var{dnums}@dots{}
4852 @itemx delete display @var{dnums}@dots{}
4853 Remove item numbers @var{dnums} from the list of expressions to display.
4854
4855 @code{undisplay} does not repeat if you press @key{RET} after using it.
4856 (Otherwise you would just get the error @samp{No display number @dots{}}.)
4857
4858 @kindex disable display
4859 @item disable display @var{dnums}@dots{}
4860 Disable the display of item numbers @var{dnums}. A disabled display
4861 item is not printed automatically, but is not forgotten. It may be
4862 enabled again later.
4863
4864 @kindex enable display
4865 @item enable display @var{dnums}@dots{}
4866 Enable display of item numbers @var{dnums}. It becomes effective once
4867 again in auto display of its expression, until you specify otherwise.
4868
4869 @item display
4870 Display the current values of the expressions on the list, just as is
4871 done when your program stops.
4872
4873 @kindex info display
4874 @item info display
4875 Print the list of expressions previously set up to display
4876 automatically, each one with its item number, but without showing the
4877 values. This includes disabled expressions, which are marked as such.
4878 It also includes expressions which would not be displayed right now
4879 because they refer to automatic variables not currently available.
4880 @end table
4881
4882 If a display expression refers to local variables, then it does not make
4883 sense outside the lexical context for which it was set up. Such an
4884 expression is disabled when execution enters a context where one of its
4885 variables is not defined. For example, if you give the command
4886 @code{display last_char} while inside a function with an argument
4887 @code{last_char}, @value{GDBN} displays this argument while your program
4888 continues to stop inside that function. When it stops elsewhere---where
4889 there is no variable @code{last_char}---the display is disabled
4890 automatically. The next time your program stops where @code{last_char}
4891 is meaningful, you can enable the display expression once again.
4892
4893 @node Print Settings
4894 @section Print settings
4895
4896 @cindex format options
4897 @cindex print settings
4898 @value{GDBN} provides the following ways to control how arrays, structures,
4899 and symbols are printed.
4900
4901 @noindent
4902 These settings are useful for debugging programs in any language:
4903
4904 @table @code
4905 @kindex set print address
4906 @item set print address
4907 @itemx set print address on
4908 @value{GDBN} prints memory addresses showing the location of stack
4909 traces, structure values, pointer values, breakpoints, and so forth,
4910 even when it also displays the contents of those addresses. The default
4911 is @code{on}. For example, this is what a stack frame display looks like with
4912 @code{set print address on}:
4913
4914 @smallexample
4915 @group
4916 (@value{GDBP}) f
4917 #0 set_quotes (lq=0x34c78 "<<", rq=0x34c88 ">>")
4918 at input.c:530
4919 530 if (lquote != def_lquote)
4920 @end group
4921 @end smallexample
4922
4923 @item set print address off
4924 Do not print addresses when displaying their contents. For example,
4925 this is the same stack frame displayed with @code{set print address off}:
4926
4927 @smallexample
4928 @group
4929 (@value{GDBP}) set print addr off
4930 (@value{GDBP}) f
4931 #0 set_quotes (lq="<<", rq=">>") at input.c:530
4932 530 if (lquote != def_lquote)
4933 @end group
4934 @end smallexample
4935
4936 You can use @samp{set print address off} to eliminate all machine
4937 dependent displays from the @value{GDBN} interface. For example, with
4938 @code{print address off}, you should get the same text for backtraces on
4939 all machines---whether or not they involve pointer arguments.
4940
4941 @kindex show print address
4942 @item show print address
4943 Show whether or not addresses are to be printed.
4944 @end table
4945
4946 When @value{GDBN} prints a symbolic address, it normally prints the
4947 closest earlier symbol plus an offset. If that symbol does not uniquely
4948 identify the address (for example, it is a name whose scope is a single
4949 source file), you may need to clarify. One way to do this is with
4950 @code{info line}, for example @samp{info line *0x4537}. Alternately,
4951 you can set @value{GDBN} to print the source file and line number when
4952 it prints a symbolic address:
4953
4954 @table @code
4955 @kindex set print symbol-filename
4956 @item set print symbol-filename on
4957 Tell @value{GDBN} to print the source file name and line number of a
4958 symbol in the symbolic form of an address.
4959
4960 @item set print symbol-filename off
4961 Do not print source file name and line number of a symbol. This is the
4962 default.
4963
4964 @kindex show print symbol-filename
4965 @item show print symbol-filename
4966 Show whether or not @value{GDBN} will print the source file name and
4967 line number of a symbol in the symbolic form of an address.
4968 @end table
4969
4970 Another situation where it is helpful to show symbol filenames and line
4971 numbers is when disassembling code; @value{GDBN} shows you the line
4972 number and source file that corresponds to each instruction.
4973
4974 Also, you may wish to see the symbolic form only if the address being
4975 printed is reasonably close to the closest earlier symbol:
4976
4977 @table @code
4978 @kindex set print max-symbolic-offset
4979 @item set print max-symbolic-offset @var{max-offset}
4980 Tell @value{GDBN} to only display the symbolic form of an address if the
4981 offset between the closest earlier symbol and the address is less than
4982 @var{max-offset}. The default is 0, which tells @value{GDBN}
4983 to always print the symbolic form of an address if any symbol precedes it.
4984
4985 @kindex show print max-symbolic-offset
4986 @item show print max-symbolic-offset
4987 Ask how large the maximum offset is that @value{GDBN} prints in a
4988 symbolic address.
4989 @end table
4990
4991 @cindex wild pointer, interpreting
4992 @cindex pointer, finding referent
4993 If you have a pointer and you are not sure where it points, try
4994 @samp{set print symbol-filename on}. Then you can determine the name
4995 and source file location of the variable where it points, using
4996 @samp{p/a @var{pointer}}. This interprets the address in symbolic form.
4997 For example, here @value{GDBN} shows that a variable @code{ptt} points
4998 at another variable @code{t}, defined in @file{hi2.c}:
4999
5000 @example
5001 (@value{GDBP}) set print symbol-filename on
5002 (@value{GDBP}) p/a ptt
5003 $4 = 0xe008 <t in hi2.c>
5004 @end example
5005
5006 @quotation
5007 @emph{Warning:} For pointers that point to a local variable, @samp{p/a}
5008 does not show the symbol name and filename of the referent, even with
5009 the appropriate @code{set print} options turned on.
5010 @end quotation
5011
5012 Other settings control how different kinds of objects are printed:
5013
5014 @table @code
5015 @kindex set print array
5016 @item set print array
5017 @itemx set print array on
5018 Pretty print arrays. This format is more convenient to read,
5019 but uses more space. The default is off.
5020
5021 @item set print array off
5022 Return to compressed format for arrays.
5023
5024 @kindex show print array
5025 @item show print array
5026 Show whether compressed or pretty format is selected for displaying
5027 arrays.
5028
5029 @kindex set print elements
5030 @item set print elements @var{number-of-elements}
5031 Set a limit on how many elements of an array @value{GDBN} will print.
5032 If @value{GDBN} is printing a large array, it stops printing after it has
5033 printed the number of elements set by the @code{set print elements} command.
5034 This limit also applies to the display of strings.
5035 When @value{GDBN} starts, this limit is set to 200.
5036 Setting @var{number-of-elements} to zero means that the printing is unlimited.
5037
5038 @kindex show print elements
5039 @item show print elements
5040 Display the number of elements of a large array that @value{GDBN} will print.
5041 If the number is 0, then the printing is unlimited.
5042
5043 @kindex set print null-stop
5044 @item set print null-stop
5045 Cause @value{GDBN} to stop printing the characters of an array when the first
5046 @sc{null} is encountered. This is useful when large arrays actually
5047 contain only short strings.
5048 The default is off.
5049
5050 @kindex set print pretty
5051 @item set print pretty on
5052 Cause @value{GDBN} to print structures in an indented format with one member
5053 per line, like this:
5054
5055 @smallexample
5056 @group
5057 $1 = @{
5058 next = 0x0,
5059 flags = @{
5060 sweet = 1,
5061 sour = 1
5062 @},
5063 meat = 0x54 "Pork"
5064 @}
5065 @end group
5066 @end smallexample
5067
5068 @item set print pretty off
5069 Cause @value{GDBN} to print structures in a compact format, like this:
5070
5071 @smallexample
5072 @group
5073 $1 = @{next = 0x0, flags = @{sweet = 1, sour = 1@}, \
5074 meat = 0x54 "Pork"@}
5075 @end group
5076 @end smallexample
5077
5078 @noindent
5079 This is the default format.
5080
5081 @kindex show print pretty
5082 @item show print pretty
5083 Show which format @value{GDBN} is using to print structures.
5084
5085 @kindex set print sevenbit-strings
5086 @item set print sevenbit-strings on
5087 Print using only seven-bit characters; if this option is set,
5088 @value{GDBN} displays any eight-bit characters (in strings or
5089 character values) using the notation @code{\}@var{nnn}. This setting is
5090 best if you are working in English (@sc{ascii}) and you use the
5091 high-order bit of characters as a marker or ``meta'' bit.
5092
5093 @item set print sevenbit-strings off
5094 Print full eight-bit characters. This allows the use of more
5095 international character sets, and is the default.
5096
5097 @kindex show print sevenbit-strings
5098 @item show print sevenbit-strings
5099 Show whether or not @value{GDBN} is printing only seven-bit characters.
5100
5101 @kindex set print union
5102 @item set print union on
5103 Tell @value{GDBN} to print unions which are contained in structures. This
5104 is the default setting.
5105
5106 @item set print union off
5107 Tell @value{GDBN} not to print unions which are contained in structures.
5108
5109 @kindex show print union
5110 @item show print union
5111 Ask @value{GDBN} whether or not it will print unions which are contained in
5112 structures.
5113
5114 For example, given the declarations
5115
5116 @smallexample
5117 typedef enum @{Tree, Bug@} Species;
5118 typedef enum @{Big_tree, Acorn, Seedling@} Tree_forms;
5119 typedef enum @{Caterpillar, Cocoon, Butterfly@}
5120 Bug_forms;
5121
5122 struct thing @{
5123 Species it;
5124 union @{
5125 Tree_forms tree;
5126 Bug_forms bug;
5127 @} form;
5128 @};
5129
5130 struct thing foo = @{Tree, @{Acorn@}@};
5131 @end smallexample
5132
5133 @noindent
5134 with @code{set print union on} in effect @samp{p foo} would print
5135
5136 @smallexample
5137 $1 = @{it = Tree, form = @{tree = Acorn, bug = Cocoon@}@}
5138 @end smallexample
5139
5140 @noindent
5141 and with @code{set print union off} in effect it would print
5142
5143 @smallexample
5144 $1 = @{it = Tree, form = @{...@}@}
5145 @end smallexample
5146 @end table
5147
5148 @need 1000
5149 @noindent
5150 These settings are of interest when debugging C@t{++} programs:
5151
5152 @table @code
5153 @cindex demangling
5154 @kindex set print demangle
5155 @item set print demangle
5156 @itemx set print demangle on
5157 Print C@t{++} names in their source form rather than in the encoded
5158 (``mangled'') form passed to the assembler and linker for type-safe
5159 linkage. The default is on.
5160
5161 @kindex show print demangle
5162 @item show print demangle
5163 Show whether C@t{++} names are printed in mangled or demangled form.
5164
5165 @kindex set print asm-demangle
5166 @item set print asm-demangle
5167 @itemx set print asm-demangle on
5168 Print C@t{++} names in their source form rather than their mangled form, even
5169 in assembler code printouts such as instruction disassemblies.
5170 The default is off.
5171
5172 @kindex show print asm-demangle
5173 @item show print asm-demangle
5174 Show whether C@t{++} names in assembly listings are printed in mangled
5175 or demangled form.
5176
5177 @kindex set demangle-style
5178 @cindex C@t{++} symbol decoding style
5179 @cindex symbol decoding style, C@t{++}
5180 @item set demangle-style @var{style}
5181 Choose among several encoding schemes used by different compilers to
5182 represent C@t{++} names. The choices for @var{style} are currently:
5183
5184 @table @code
5185 @item auto
5186 Allow @value{GDBN} to choose a decoding style by inspecting your program.
5187
5188 @item gnu
5189 Decode based on the @sc{gnu} C@t{++} compiler (@code{g++}) encoding algorithm.
5190 This is the default.
5191
5192 @item hp
5193 Decode based on the HP ANSI C@t{++} (@code{aCC}) encoding algorithm.
5194
5195 @item lucid
5196 Decode based on the Lucid C@t{++} compiler (@code{lcc}) encoding algorithm.
5197
5198 @item arm
5199 Decode using the algorithm in the @cite{C@t{++} Annotated Reference Manual}.
5200 @strong{Warning:} this setting alone is not sufficient to allow
5201 debugging @code{cfront}-generated executables. @value{GDBN} would
5202 require further enhancement to permit that.
5203
5204 @end table
5205 If you omit @var{style}, you will see a list of possible formats.
5206
5207 @kindex show demangle-style
5208 @item show demangle-style
5209 Display the encoding style currently in use for decoding C@t{++} symbols.
5210
5211 @kindex set print object
5212 @item set print object
5213 @itemx set print object on
5214 When displaying a pointer to an object, identify the @emph{actual}
5215 (derived) type of the object rather than the @emph{declared} type, using
5216 the virtual function table.
5217
5218 @item set print object off
5219 Display only the declared type of objects, without reference to the
5220 virtual function table. This is the default setting.
5221
5222 @kindex show print object
5223 @item show print object
5224 Show whether actual, or declared, object types are displayed.
5225
5226 @kindex set print static-members
5227 @item set print static-members
5228 @itemx set print static-members on
5229 Print static members when displaying a C@t{++} object. The default is on.
5230
5231 @item set print static-members off
5232 Do not print static members when displaying a C@t{++} object.
5233
5234 @kindex show print static-members
5235 @item show print static-members
5236 Show whether C@t{++} static members are printed, or not.
5237
5238 @c These don't work with HP ANSI C++ yet.
5239 @kindex set print vtbl
5240 @item set print vtbl
5241 @itemx set print vtbl on
5242 Pretty print C@t{++} virtual function tables. The default is off.
5243 (The @code{vtbl} commands do not work on programs compiled with the HP
5244 ANSI C@t{++} compiler (@code{aCC}).)
5245
5246 @item set print vtbl off
5247 Do not pretty print C@t{++} virtual function tables.
5248
5249 @kindex show print vtbl
5250 @item show print vtbl
5251 Show whether C@t{++} virtual function tables are pretty printed, or not.
5252 @end table
5253
5254 @node Value History
5255 @section Value history
5256
5257 @cindex value history
5258 Values printed by the @code{print} command are saved in the @value{GDBN}
5259 @dfn{value history}. This allows you to refer to them in other expressions.
5260 Values are kept until the symbol table is re-read or discarded
5261 (for example with the @code{file} or @code{symbol-file} commands).
5262 When the symbol table changes, the value history is discarded,
5263 since the values may contain pointers back to the types defined in the
5264 symbol table.
5265
5266 @cindex @code{$}
5267 @cindex @code{$$}
5268 @cindex history number
5269 The values printed are given @dfn{history numbers} by which you can
5270 refer to them. These are successive integers starting with one.
5271 @code{print} shows you the history number assigned to a value by
5272 printing @samp{$@var{num} = } before the value; here @var{num} is the
5273 history number.
5274
5275 To refer to any previous value, use @samp{$} followed by the value's
5276 history number. The way @code{print} labels its output is designed to
5277 remind you of this. Just @code{$} refers to the most recent value in
5278 the history, and @code{$$} refers to the value before that.
5279 @code{$$@var{n}} refers to the @var{n}th value from the end; @code{$$2}
5280 is the value just prior to @code{$$}, @code{$$1} is equivalent to
5281 @code{$$}, and @code{$$0} is equivalent to @code{$}.
5282
5283 For example, suppose you have just printed a pointer to a structure and
5284 want to see the contents of the structure. It suffices to type
5285
5286 @example
5287 p *$
5288 @end example
5289
5290 If you have a chain of structures where the component @code{next} points
5291 to the next one, you can print the contents of the next one with this:
5292
5293 @example
5294 p *$.next
5295 @end example
5296
5297 @noindent
5298 You can print successive links in the chain by repeating this
5299 command---which you can do by just typing @key{RET}.
5300
5301 Note that the history records values, not expressions. If the value of
5302 @code{x} is 4 and you type these commands:
5303
5304 @example
5305 print x
5306 set x=5
5307 @end example
5308
5309 @noindent
5310 then the value recorded in the value history by the @code{print} command
5311 remains 4 even though the value of @code{x} has changed.
5312
5313 @table @code
5314 @kindex show values
5315 @item show values
5316 Print the last ten values in the value history, with their item numbers.
5317 This is like @samp{p@ $$9} repeated ten times, except that @code{show
5318 values} does not change the history.
5319
5320 @item show values @var{n}
5321 Print ten history values centered on history item number @var{n}.
5322
5323 @item show values +
5324 Print ten history values just after the values last printed. If no more
5325 values are available, @code{show values +} produces no display.
5326 @end table
5327
5328 Pressing @key{RET} to repeat @code{show values @var{n}} has exactly the
5329 same effect as @samp{show values +}.
5330
5331 @node Convenience Vars
5332 @section Convenience variables
5333
5334 @cindex convenience variables
5335 @value{GDBN} provides @dfn{convenience variables} that you can use within
5336 @value{GDBN} to hold on to a value and refer to it later. These variables
5337 exist entirely within @value{GDBN}; they are not part of your program, and
5338 setting a convenience variable has no direct effect on further execution
5339 of your program. That is why you can use them freely.
5340
5341 Convenience variables are prefixed with @samp{$}. Any name preceded by
5342 @samp{$} can be used for a convenience variable, unless it is one of
5343 the predefined machine-specific register names (@pxref{Registers, ,Registers}).
5344 (Value history references, in contrast, are @emph{numbers} preceded
5345 by @samp{$}. @xref{Value History, ,Value history}.)
5346
5347 You can save a value in a convenience variable with an assignment
5348 expression, just as you would set a variable in your program.
5349 For example:
5350
5351 @example
5352 set $foo = *object_ptr
5353 @end example
5354
5355 @noindent
5356 would save in @code{$foo} the value contained in the object pointed to by
5357 @code{object_ptr}.
5358
5359 Using a convenience variable for the first time creates it, but its
5360 value is @code{void} until you assign a new value. You can alter the
5361 value with another assignment at any time.
5362
5363 Convenience variables have no fixed types. You can assign a convenience
5364 variable any type of value, including structures and arrays, even if
5365 that variable already has a value of a different type. The convenience
5366 variable, when used as an expression, has the type of its current value.
5367
5368 @table @code
5369 @kindex show convenience
5370 @item show convenience
5371 Print a list of convenience variables used so far, and their values.
5372 Abbreviated @code{show conv}.
5373 @end table
5374
5375 One of the ways to use a convenience variable is as a counter to be
5376 incremented or a pointer to be advanced. For example, to print
5377 a field from successive elements of an array of structures:
5378
5379 @example
5380 set $i = 0
5381 print bar[$i++]->contents
5382 @end example
5383
5384 @noindent
5385 Repeat that command by typing @key{RET}.
5386
5387 Some convenience variables are created automatically by @value{GDBN} and given
5388 values likely to be useful.
5389
5390 @table @code
5391 @vindex $_@r{, convenience variable}
5392 @item $_
5393 The variable @code{$_} is automatically set by the @code{x} command to
5394 the last address examined (@pxref{Memory, ,Examining memory}). Other
5395 commands which provide a default address for @code{x} to examine also
5396 set @code{$_} to that address; these commands include @code{info line}
5397 and @code{info breakpoint}. The type of @code{$_} is @code{void *}
5398 except when set by the @code{x} command, in which case it is a pointer
5399 to the type of @code{$__}.
5400
5401 @vindex $__@r{, convenience variable}
5402 @item $__
5403 The variable @code{$__} is automatically set by the @code{x} command
5404 to the value found in the last address examined. Its type is chosen
5405 to match the format in which the data was printed.
5406
5407 @item $_exitcode
5408 @vindex $_exitcode@r{, convenience variable}
5409 The variable @code{$_exitcode} is automatically set to the exit code when
5410 the program being debugged terminates.
5411 @end table
5412
5413 On HP-UX systems, if you refer to a function or variable name that
5414 begins with a dollar sign, @value{GDBN} searches for a user or system
5415 name first, before it searches for a convenience variable.
5416
5417 @node Registers
5418 @section Registers
5419
5420 @cindex registers
5421 You can refer to machine register contents, in expressions, as variables
5422 with names starting with @samp{$}. The names of registers are different
5423 for each machine; use @code{info registers} to see the names used on
5424 your machine.
5425
5426 @table @code
5427 @kindex info registers
5428 @item info registers
5429 Print the names and values of all registers except floating-point
5430 registers (in the selected stack frame).
5431
5432 @kindex info all-registers
5433 @cindex floating point registers
5434 @item info all-registers
5435 Print the names and values of all registers, including floating-point
5436 registers.
5437
5438 @item info registers @var{regname} @dots{}
5439 Print the @dfn{relativized} value of each specified register @var{regname}.
5440 As discussed in detail below, register values are normally relative to
5441 the selected stack frame. @var{regname} may be any register name valid on
5442 the machine you are using, with or without the initial @samp{$}.
5443 @end table
5444
5445 @value{GDBN} has four ``standard'' register names that are available (in
5446 expressions) on most machines---whenever they do not conflict with an
5447 architecture's canonical mnemonics for registers. The register names
5448 @code{$pc} and @code{$sp} are used for the program counter register and
5449 the stack pointer. @code{$fp} is used for a register that contains a
5450 pointer to the current stack frame, and @code{$ps} is used for a
5451 register that contains the processor status. For example,
5452 you could print the program counter in hex with
5453
5454 @example
5455 p/x $pc
5456 @end example
5457
5458 @noindent
5459 or print the instruction to be executed next with
5460
5461 @example
5462 x/i $pc
5463 @end example
5464
5465 @noindent
5466 or add four to the stack pointer@footnote{This is a way of removing
5467 one word from the stack, on machines where stacks grow downward in
5468 memory (most machines, nowadays). This assumes that the innermost
5469 stack frame is selected; setting @code{$sp} is not allowed when other
5470 stack frames are selected. To pop entire frames off the stack,
5471 regardless of machine architecture, use @code{return};
5472 see @ref{Returning, ,Returning from a function}.} with
5473
5474 @example
5475 set $sp += 4
5476 @end example
5477
5478 Whenever possible, these four standard register names are available on
5479 your machine even though the machine has different canonical mnemonics,
5480 so long as there is no conflict. The @code{info registers} command
5481 shows the canonical names. For example, on the SPARC, @code{info
5482 registers} displays the processor status register as @code{$psr} but you
5483 can also refer to it as @code{$ps}; and on x86-based machines @code{$ps}
5484 is an alias for the @sc{eflags} register.
5485
5486 @value{GDBN} always considers the contents of an ordinary register as an
5487 integer when the register is examined in this way. Some machines have
5488 special registers which can hold nothing but floating point; these
5489 registers are considered to have floating point values. There is no way
5490 to refer to the contents of an ordinary register as floating point value
5491 (although you can @emph{print} it as a floating point value with
5492 @samp{print/f $@var{regname}}).
5493
5494 Some registers have distinct ``raw'' and ``virtual'' data formats. This
5495 means that the data format in which the register contents are saved by
5496 the operating system is not the same one that your program normally
5497 sees. For example, the registers of the 68881 floating point
5498 coprocessor are always saved in ``extended'' (raw) format, but all C
5499 programs expect to work with ``double'' (virtual) format. In such
5500 cases, @value{GDBN} normally works with the virtual format only (the format
5501 that makes sense for your program), but the @code{info registers} command
5502 prints the data in both formats.
5503
5504 Normally, register values are relative to the selected stack frame
5505 (@pxref{Selection, ,Selecting a frame}). This means that you get the
5506 value that the register would contain if all stack frames farther in
5507 were exited and their saved registers restored. In order to see the
5508 true contents of hardware registers, you must select the innermost
5509 frame (with @samp{frame 0}).
5510
5511 However, @value{GDBN} must deduce where registers are saved, from the machine
5512 code generated by your compiler. If some registers are not saved, or if
5513 @value{GDBN} is unable to locate the saved registers, the selected stack
5514 frame makes no difference.
5515
5516 @node Floating Point Hardware
5517 @section Floating point hardware
5518 @cindex floating point
5519
5520 Depending on the configuration, @value{GDBN} may be able to give
5521 you more information about the status of the floating point hardware.
5522
5523 @table @code
5524 @kindex info float
5525 @item info float
5526 Display hardware-dependent information about the floating
5527 point unit. The exact contents and layout vary depending on the
5528 floating point chip. Currently, @samp{info float} is supported on
5529 the ARM and x86 machines.
5530 @end table
5531
5532 @node Memory Region Attributes
5533 @section Memory Region Attributes
5534 @cindex memory region attributes
5535
5536 @dfn{Memory region attributes} allow you to describe special handling
5537 required by regions of your target's memory. @value{GDBN} uses attributes
5538 to determine whether to allow certain types of memory accesses; whether to
5539 use specific width accesses; and whether to cache target memory.
5540
5541 Defined memory regions can be individually enabled and disabled. When a
5542 memory region is disabled, @value{GDBN} uses the default attributes when
5543 accessing memory in that region. Similarly, if no memory regions have
5544 been defined, @value{GDBN} uses the default attributes when accessing
5545 all memory.
5546
5547 When a memory region is defined, it is given a number to identify it;
5548 to enable, disable, or remove a memory region, you specify that number.
5549
5550 @table @code
5551 @kindex mem
5552 @item mem @var{address1} @var{address1} @var{attributes}@dots{}
5553 Define memory region bounded by @var{address1} and @var{address2}
5554 with attributes @var{attributes}@dots{}.
5555
5556 @kindex delete mem
5557 @item delete mem @var{nums}@dots{}
5558 Remove memory region numbers @var{nums}.
5559
5560 @kindex disable mem
5561 @item disable mem @var{nums}@dots{}
5562 Disable memory region numbers @var{nums}.
5563 A disabled memory region is not forgotten.
5564 It may be enabled again later.
5565
5566 @kindex enable mem
5567 @item enable mem @var{nums}@dots{}
5568 Enable memory region numbers @var{nums}.
5569
5570 @kindex info mem
5571 @item info mem
5572 Print a table of all defined memory regions, with the following columns
5573 for each region.
5574
5575 @table @emph
5576 @item Memory Region Number
5577 @item Enabled or Disabled.
5578 Enabled memory regions are marked with @samp{y}.
5579 Disabled memory regions are marked with @samp{n}.
5580
5581 @item Lo Address
5582 The address defining the inclusive lower bound of the memory region.
5583
5584 @item Hi Address
5585 The address defining the exclusive upper bound of the memory region.
5586
5587 @item Attributes
5588 The list of attributes set for this memory region.
5589 @end table
5590 @end table
5591
5592
5593 @subsection Attributes
5594
5595 @subsubsection Memory Access Mode
5596 The access mode attributes set whether @value{GDBN} may make read or
5597 write accesses to a memory region.
5598
5599 While these attributes prevent @value{GDBN} from performing invalid
5600 memory accesses, they do nothing to prevent the target system, I/O DMA,
5601 etc. from accessing memory.
5602
5603 @table @code
5604 @item ro
5605 Memory is read only.
5606 @item wo
5607 Memory is write only.
5608 @item rw
5609 Memory is read/write (default).
5610 @end table
5611
5612 @subsubsection Memory Access Size
5613 The acccess size attributes tells @value{GDBN} to use specific sized
5614 accesses in the memory region. Often memory mapped device registers
5615 require specific sized accesses. If no access size attribute is
5616 specified, @value{GDBN} may use accesses of any size.
5617
5618 @table @code
5619 @item 8
5620 Use 8 bit memory accesses.
5621 @item 16
5622 Use 16 bit memory accesses.
5623 @item 32
5624 Use 32 bit memory accesses.
5625 @item 64
5626 Use 64 bit memory accesses.
5627 @end table
5628
5629 @c @subsubsection Hardware/Software Breakpoints
5630 @c The hardware/software breakpoint attributes set whether @value{GDBN}
5631 @c will use hardware or software breakpoints for the internal breakpoints
5632 @c used by the step, next, finish, until, etc. commands.
5633 @c
5634 @c @table @code
5635 @c @item hwbreak
5636 @c Always use hardware breakpoints
5637 @c @item swbreak (default)
5638 @c @end table
5639
5640 @subsubsection Data Cache
5641 The data cache attributes set whether @value{GDBN} will cache target
5642 memory. While this generally improves performance by reducing debug
5643 protocol overhead, it can lead to incorrect results because @value{GDBN}
5644 does not know about volatile variables or memory mapped device
5645 registers.
5646
5647 @table @code
5648 @item cache
5649 Enable @value{GDBN} to cache target memory.
5650 @item nocache (default)
5651 Disable @value{GDBN} from caching target memory.
5652 @end table
5653
5654 @c @subsubsection Memory Write Verification
5655 @c The memory write verification attributes set whether @value{GDBN}
5656 @c will re-reads data after each write to verify the write was successful.
5657 @c
5658 @c @table @code
5659 @c @item verify
5660 @c @item noverify (default)
5661 @c @end table
5662
5663 @node Tracepoints
5664 @chapter Tracepoints
5665 @c This chapter is based on the documentation written by Michael
5666 @c Snyder, David Taylor, Jim Blandy, and Elena Zannoni.
5667
5668 @cindex tracepoints
5669 In some applications, it is not feasible for the debugger to interrupt
5670 the program's execution long enough for the developer to learn
5671 anything helpful about its behavior. If the program's correctness
5672 depends on its real-time behavior, delays introduced by a debugger
5673 might cause the program to change its behavior drastically, or perhaps
5674 fail, even when the code itself is correct. It is useful to be able
5675 to observe the program's behavior without interrupting it.
5676
5677 Using @value{GDBN}'s @code{trace} and @code{collect} commands, you can
5678 specify locations in the program, called @dfn{tracepoints}, and
5679 arbitrary expressions to evaluate when those tracepoints are reached.
5680 Later, using the @code{tfind} command, you can examine the values
5681 those expressions had when the program hit the tracepoints. The
5682 expressions may also denote objects in memory---structures or arrays,
5683 for example---whose values @value{GDBN} should record; while visiting
5684 a particular tracepoint, you may inspect those objects as if they were
5685 in memory at that moment. However, because @value{GDBN} records these
5686 values without interacting with you, it can do so quickly and
5687 unobtrusively, hopefully not disturbing the program's behavior.
5688
5689 The tracepoint facility is currently available only for remote
5690 targets. @xref{Targets}.
5691
5692 This chapter describes the tracepoint commands and features.
5693
5694 @menu
5695 * Set Tracepoints::
5696 * Analyze Collected Data::
5697 * Tracepoint Variables::
5698 @end menu
5699
5700 @node Set Tracepoints
5701 @section Commands to Set Tracepoints
5702
5703 Before running such a @dfn{trace experiment}, an arbitrary number of
5704 tracepoints can be set. Like a breakpoint (@pxref{Set Breaks}), a
5705 tracepoint has a number assigned to it by @value{GDBN}. Like with
5706 breakpoints, tracepoint numbers are successive integers starting from
5707 one. Many of the commands associated with tracepoints take the
5708 tracepoint number as their argument, to identify which tracepoint to
5709 work on.
5710
5711 For each tracepoint, you can specify, in advance, some arbitrary set
5712 of data that you want the target to collect in the trace buffer when
5713 it hits that tracepoint. The collected data can include registers,
5714 local variables, or global data. Later, you can use @value{GDBN}
5715 commands to examine the values these data had at the time the
5716 tracepoint was hit.
5717
5718 This section describes commands to set tracepoints and associated
5719 conditions and actions.
5720
5721 @menu
5722 * Create and Delete Tracepoints::
5723 * Enable and Disable Tracepoints::
5724 * Tracepoint Passcounts::
5725 * Tracepoint Actions::
5726 * Listing Tracepoints::
5727 * Starting and Stopping Trace Experiment::
5728 @end menu
5729
5730 @node Create and Delete Tracepoints
5731 @subsection Create and Delete Tracepoints
5732
5733 @table @code
5734 @cindex set tracepoint
5735 @kindex trace
5736 @item trace
5737 The @code{trace} command is very similar to the @code{break} command.
5738 Its argument can be a source line, a function name, or an address in
5739 the target program. @xref{Set Breaks}. The @code{trace} command
5740 defines a tracepoint, which is a point in the target program where the
5741 debugger will briefly stop, collect some data, and then allow the
5742 program to continue. Setting a tracepoint or changing its commands
5743 doesn't take effect until the next @code{tstart} command; thus, you
5744 cannot change the tracepoint attributes once a trace experiment is
5745 running.
5746
5747 Here are some examples of using the @code{trace} command:
5748
5749 @smallexample
5750 (@value{GDBP}) @b{trace foo.c:121} // a source file and line number
5751
5752 (@value{GDBP}) @b{trace +2} // 2 lines forward
5753
5754 (@value{GDBP}) @b{trace my_function} // first source line of function
5755
5756 (@value{GDBP}) @b{trace *my_function} // EXACT start address of function
5757
5758 (@value{GDBP}) @b{trace *0x2117c4} // an address
5759 @end smallexample
5760
5761 @noindent
5762 You can abbreviate @code{trace} as @code{tr}.
5763
5764 @vindex $tpnum
5765 @cindex last tracepoint number
5766 @cindex recent tracepoint number
5767 @cindex tracepoint number
5768 The convenience variable @code{$tpnum} records the tracepoint number
5769 of the most recently set tracepoint.
5770
5771 @kindex delete tracepoint
5772 @cindex tracepoint deletion
5773 @item delete tracepoint @r{[}@var{num}@r{]}
5774 Permanently delete one or more tracepoints. With no argument, the
5775 default is to delete all tracepoints.
5776
5777 Examples:
5778
5779 @smallexample
5780 (@value{GDBP}) @b{delete trace 1 2 3} // remove three tracepoints
5781
5782 (@value{GDBP}) @b{delete trace} // remove all tracepoints
5783 @end smallexample
5784
5785 @noindent
5786 You can abbreviate this command as @code{del tr}.
5787 @end table
5788
5789 @node Enable and Disable Tracepoints
5790 @subsection Enable and Disable Tracepoints
5791
5792 @table @code
5793 @kindex disable tracepoint
5794 @item disable tracepoint @r{[}@var{num}@r{]}
5795 Disable tracepoint @var{num}, or all tracepoints if no argument
5796 @var{num} is given. A disabled tracepoint will have no effect during
5797 the next trace experiment, but it is not forgotten. You can re-enable
5798 a disabled tracepoint using the @code{enable tracepoint} command.
5799
5800 @kindex enable tracepoint
5801 @item enable tracepoint @r{[}@var{num}@r{]}
5802 Enable tracepoint @var{num}, or all tracepoints. The enabled
5803 tracepoints will become effective the next time a trace experiment is
5804 run.
5805 @end table
5806
5807 @node Tracepoint Passcounts
5808 @subsection Tracepoint Passcounts
5809
5810 @table @code
5811 @kindex passcount
5812 @cindex tracepoint pass count
5813 @item passcount @r{[}@var{n} @r{[}@var{num}@r{]]}
5814 Set the @dfn{passcount} of a tracepoint. The passcount is a way to
5815 automatically stop a trace experiment. If a tracepoint's passcount is
5816 @var{n}, then the trace experiment will be automatically stopped on
5817 the @var{n}'th time that tracepoint is hit. If the tracepoint number
5818 @var{num} is not specified, the @code{passcount} command sets the
5819 passcount of the most recently defined tracepoint. If no passcount is
5820 given, the trace experiment will run until stopped explicitly by the
5821 user.
5822
5823 Examples:
5824
5825 @smallexample
5826 (@value{GDBP}) @b{passcount 5 2} // Stop on the 5th execution of tracepoint 2
5827
5828 (@value{GDBP}) @b{passcount 12} // Stop on the 12th execution of the
5829 // most recently defined tracepoint.
5830 (@value{GDBP}) @b{trace foo}
5831 (@value{GDBP}) @b{pass 3}
5832 (@value{GDBP}) @b{trace bar}
5833 (@value{GDBP}) @b{pass 2}
5834 (@value{GDBP}) @b{trace baz}
5835 (@value{GDBP}) @b{pass 1} // Stop tracing when foo has been
5836 // executed 3 times OR when bar has
5837 // been executed 2 times
5838 // OR when baz has been executed 1 time.
5839 @end smallexample
5840 @end table
5841
5842 @node Tracepoint Actions
5843 @subsection Tracepoint Action Lists
5844
5845 @table @code
5846 @kindex actions
5847 @cindex tracepoint actions
5848 @item actions @r{[}@var{num}@r{]}
5849 This command will prompt for a list of actions to be taken when the
5850 tracepoint is hit. If the tracepoint number @var{num} is not
5851 specified, this command sets the actions for the one that was most
5852 recently defined (so that you can define a tracepoint and then say
5853 @code{actions} without bothering about its number). You specify the
5854 actions themselves on the following lines, one action at a time, and
5855 terminate the actions list with a line containing just @code{end}. So
5856 far, the only defined actions are @code{collect} and
5857 @code{while-stepping}.
5858
5859 @cindex remove actions from a tracepoint
5860 To remove all actions from a tracepoint, type @samp{actions @var{num}}
5861 and follow it immediately with @samp{end}.
5862
5863 @smallexample
5864 (@value{GDBP}) @b{collect @var{data}} // collect some data
5865
5866 (@value{GDBP}) @b{while-stepping 5} // single-step 5 times and collect data
5867
5868 (@value{GDBP}) @b{end} // signals the end of actions.
5869 @end smallexample
5870
5871 In the following example, the action list begins with @code{collect}
5872 commands indicating the things to be collected when the tracepoint is
5873 hit. Then, in order to single-step and collect additional data
5874 following the tracepoint, a @code{while-stepping} command is used,
5875 followed by the list of things to be collected while stepping. The
5876 @code{while-stepping} command is terminated by its own separate
5877 @code{end} command. Lastly, the action list is terminated by an
5878 @code{end} command.
5879
5880 @smallexample
5881 (@value{GDBP}) @b{trace foo}
5882 (@value{GDBP}) @b{actions}
5883 Enter actions for tracepoint 1, one per line:
5884 > collect bar,baz
5885 > collect $regs
5886 > while-stepping 12
5887 > collect $fp, $sp
5888 > end
5889 end
5890 @end smallexample
5891
5892 @kindex collect @r{(tracepoints)}
5893 @item collect @var{expr1}, @var{expr2}, @dots{}
5894 Collect values of the given expressions when the tracepoint is hit.
5895 This command accepts a comma-separated list of any valid expressions.
5896 In addition to global, static, or local variables, the following
5897 special arguments are supported:
5898
5899 @table @code
5900 @item $regs
5901 collect all registers
5902
5903 @item $args
5904 collect all function arguments
5905
5906 @item $locals
5907 collect all local variables.
5908 @end table
5909
5910 You can give several consecutive @code{collect} commands, each one
5911 with a single argument, or one @code{collect} command with several
5912 arguments separated by commas: the effect is the same.
5913
5914 The command @code{info scope} (@pxref{Symbols, info scope}) is
5915 particularly useful for figuring out what data to collect.
5916
5917 @kindex while-stepping @r{(tracepoints)}
5918 @item while-stepping @var{n}
5919 Perform @var{n} single-step traces after the tracepoint, collecting
5920 new data at each step. The @code{while-stepping} command is
5921 followed by the list of what to collect while stepping (followed by
5922 its own @code{end} command):
5923
5924 @smallexample
5925 > while-stepping 12
5926 > collect $regs, myglobal
5927 > end
5928 >
5929 @end smallexample
5930
5931 @noindent
5932 You may abbreviate @code{while-stepping} as @code{ws} or
5933 @code{stepping}.
5934 @end table
5935
5936 @node Listing Tracepoints
5937 @subsection Listing Tracepoints
5938
5939 @table @code
5940 @kindex info tracepoints
5941 @cindex information about tracepoints
5942 @item info tracepoints @r{[}@var{num}@r{]}
5943 Display information the tracepoint @var{num}. If you don't specify a
5944 tracepoint number displays information about all the tracepoints
5945 defined so far. For each tracepoint, the following information is
5946 shown:
5947
5948 @itemize @bullet
5949 @item
5950 its number
5951 @item
5952 whether it is enabled or disabled
5953 @item
5954 its address
5955 @item
5956 its passcount as given by the @code{passcount @var{n}} command
5957 @item
5958 its step count as given by the @code{while-stepping @var{n}} command
5959 @item
5960 where in the source files is the tracepoint set
5961 @item
5962 its action list as given by the @code{actions} command
5963 @end itemize
5964
5965 @smallexample
5966 (@value{GDBP}) @b{info trace}
5967 Num Enb Address PassC StepC What
5968 1 y 0x002117c4 0 0 <gdb_asm>
5969 2 y 0x0020dc64 0 0 in gdb_test at gdb_test.c:375
5970 3 y 0x0020b1f4 0 0 in collect_data at ../foo.c:1741
5971 (@value{GDBP})
5972 @end smallexample
5973
5974 @noindent
5975 This command can be abbreviated @code{info tp}.
5976 @end table
5977
5978 @node Starting and Stopping Trace Experiment
5979 @subsection Starting and Stopping Trace Experiment
5980
5981 @table @code
5982 @kindex tstart
5983 @cindex start a new trace experiment
5984 @cindex collected data discarded
5985 @item tstart
5986 This command takes no arguments. It starts the trace experiment, and
5987 begins collecting data. This has the side effect of discarding all
5988 the data collected in the trace buffer during the previous trace
5989 experiment.
5990
5991 @kindex tstop
5992 @cindex stop a running trace experiment
5993 @item tstop
5994 This command takes no arguments. It ends the trace experiment, and
5995 stops collecting data.
5996
5997 @strong{Note:} a trace experiment and data collection may stop
5998 automatically if any tracepoint's passcount is reached
5999 (@pxref{Tracepoint Passcounts}), or if the trace buffer becomes full.
6000
6001 @kindex tstatus
6002 @cindex status of trace data collection
6003 @cindex trace experiment, status of
6004 @item tstatus
6005 This command displays the status of the current trace data
6006 collection.
6007 @end table
6008
6009 Here is an example of the commands we described so far:
6010
6011 @smallexample
6012 (@value{GDBP}) @b{trace gdb_c_test}
6013 (@value{GDBP}) @b{actions}
6014 Enter actions for tracepoint #1, one per line.
6015 > collect $regs,$locals,$args
6016 > while-stepping 11
6017 > collect $regs
6018 > end
6019 > end
6020 (@value{GDBP}) @b{tstart}
6021 [time passes @dots{}]
6022 (@value{GDBP}) @b{tstop}
6023 @end smallexample
6024
6025
6026 @node Analyze Collected Data
6027 @section Using the collected data
6028
6029 After the tracepoint experiment ends, you use @value{GDBN} commands
6030 for examining the trace data. The basic idea is that each tracepoint
6031 collects a trace @dfn{snapshot} every time it is hit and another
6032 snapshot every time it single-steps. All these snapshots are
6033 consecutively numbered from zero and go into a buffer, and you can
6034 examine them later. The way you examine them is to @dfn{focus} on a
6035 specific trace snapshot. When the remote stub is focused on a trace
6036 snapshot, it will respond to all @value{GDBN} requests for memory and
6037 registers by reading from the buffer which belongs to that snapshot,
6038 rather than from @emph{real} memory or registers of the program being
6039 debugged. This means that @strong{all} @value{GDBN} commands
6040 (@code{print}, @code{info registers}, @code{backtrace}, etc.) will
6041 behave as if we were currently debugging the program state as it was
6042 when the tracepoint occurred. Any requests for data that are not in
6043 the buffer will fail.
6044
6045 @menu
6046 * tfind:: How to select a trace snapshot
6047 * tdump:: How to display all data for a snapshot
6048 * save-tracepoints:: How to save tracepoints for a future run
6049 @end menu
6050
6051 @node tfind
6052 @subsection @code{tfind @var{n}}
6053
6054 @kindex tfind
6055 @cindex select trace snapshot
6056 @cindex find trace snapshot
6057 The basic command for selecting a trace snapshot from the buffer is
6058 @code{tfind @var{n}}, which finds trace snapshot number @var{n},
6059 counting from zero. If no argument @var{n} is given, the next
6060 snapshot is selected.
6061
6062 Here are the various forms of using the @code{tfind} command.
6063
6064 @table @code
6065 @item tfind start
6066 Find the first snapshot in the buffer. This is a synonym for
6067 @code{tfind 0} (since 0 is the number of the first snapshot).
6068
6069 @item tfind none
6070 Stop debugging trace snapshots, resume @emph{live} debugging.
6071
6072 @item tfind end
6073 Same as @samp{tfind none}.
6074
6075 @item tfind
6076 No argument means find the next trace snapshot.
6077
6078 @item tfind -
6079 Find the previous trace snapshot before the current one. This permits
6080 retracing earlier steps.
6081
6082 @item tfind tracepoint @var{num}
6083 Find the next snapshot associated with tracepoint @var{num}. Search
6084 proceeds forward from the last examined trace snapshot. If no
6085 argument @var{num} is given, it means find the next snapshot collected
6086 for the same tracepoint as the current snapshot.
6087
6088 @item tfind pc @var{addr}
6089 Find the next snapshot associated with the value @var{addr} of the
6090 program counter. Search proceeds forward from the last examined trace
6091 snapshot. If no argument @var{addr} is given, it means find the next
6092 snapshot with the same value of PC as the current snapshot.
6093
6094 @item tfind outside @var{addr1}, @var{addr2}
6095 Find the next snapshot whose PC is outside the given range of
6096 addresses.
6097
6098 @item tfind range @var{addr1}, @var{addr2}
6099 Find the next snapshot whose PC is between @var{addr1} and
6100 @var{addr2}. @c FIXME: Is the range inclusive or exclusive?
6101
6102 @item tfind line @r{[}@var{file}:@r{]}@var{n}
6103 Find the next snapshot associated with the source line @var{n}. If
6104 the optional argument @var{file} is given, refer to line @var{n} in
6105 that source file. Search proceeds forward from the last examined
6106 trace snapshot. If no argument @var{n} is given, it means find the
6107 next line other than the one currently being examined; thus saying
6108 @code{tfind line} repeatedly can appear to have the same effect as
6109 stepping from line to line in a @emph{live} debugging session.
6110 @end table
6111
6112 The default arguments for the @code{tfind} commands are specifically
6113 designed to make it easy to scan through the trace buffer. For
6114 instance, @code{tfind} with no argument selects the next trace
6115 snapshot, and @code{tfind -} with no argument selects the previous
6116 trace snapshot. So, by giving one @code{tfind} command, and then
6117 simply hitting @key{RET} repeatedly you can examine all the trace
6118 snapshots in order. Or, by saying @code{tfind -} and then hitting
6119 @key{RET} repeatedly you can examine the snapshots in reverse order.
6120 The @code{tfind line} command with no argument selects the snapshot
6121 for the next source line executed. The @code{tfind pc} command with
6122 no argument selects the next snapshot with the same program counter
6123 (PC) as the current frame. The @code{tfind tracepoint} command with
6124 no argument selects the next trace snapshot collected by the same
6125 tracepoint as the current one.
6126
6127 In addition to letting you scan through the trace buffer manually,
6128 these commands make it easy to construct @value{GDBN} scripts that
6129 scan through the trace buffer and print out whatever collected data
6130 you are interested in. Thus, if we want to examine the PC, FP, and SP
6131 registers from each trace frame in the buffer, we can say this:
6132
6133 @smallexample
6134 (@value{GDBP}) @b{tfind start}
6135 (@value{GDBP}) @b{while ($trace_frame != -1)}
6136 > printf "Frame %d, PC = %08X, SP = %08X, FP = %08X\n", \
6137 $trace_frame, $pc, $sp, $fp
6138 > tfind
6139 > end
6140
6141 Frame 0, PC = 0020DC64, SP = 0030BF3C, FP = 0030BF44
6142 Frame 1, PC = 0020DC6C, SP = 0030BF38, FP = 0030BF44
6143 Frame 2, PC = 0020DC70, SP = 0030BF34, FP = 0030BF44
6144 Frame 3, PC = 0020DC74, SP = 0030BF30, FP = 0030BF44
6145 Frame 4, PC = 0020DC78, SP = 0030BF2C, FP = 0030BF44
6146 Frame 5, PC = 0020DC7C, SP = 0030BF28, FP = 0030BF44
6147 Frame 6, PC = 0020DC80, SP = 0030BF24, FP = 0030BF44
6148 Frame 7, PC = 0020DC84, SP = 0030BF20, FP = 0030BF44
6149 Frame 8, PC = 0020DC88, SP = 0030BF1C, FP = 0030BF44
6150 Frame 9, PC = 0020DC8E, SP = 0030BF18, FP = 0030BF44
6151 Frame 10, PC = 00203F6C, SP = 0030BE3C, FP = 0030BF14
6152 @end smallexample
6153
6154 Or, if we want to examine the variable @code{X} at each source line in
6155 the buffer:
6156
6157 @smallexample
6158 (@value{GDBP}) @b{tfind start}
6159 (@value{GDBP}) @b{while ($trace_frame != -1)}
6160 > printf "Frame %d, X == %d\n", $trace_frame, X
6161 > tfind line
6162 > end
6163
6164 Frame 0, X = 1
6165 Frame 7, X = 2
6166 Frame 13, X = 255
6167 @end smallexample
6168
6169 @node tdump
6170 @subsection @code{tdump}
6171 @kindex tdump
6172 @cindex dump all data collected at tracepoint
6173 @cindex tracepoint data, display
6174
6175 This command takes no arguments. It prints all the data collected at
6176 the current trace snapshot.
6177
6178 @smallexample
6179 (@value{GDBP}) @b{trace 444}
6180 (@value{GDBP}) @b{actions}
6181 Enter actions for tracepoint #2, one per line:
6182 > collect $regs, $locals, $args, gdb_long_test
6183 > end
6184
6185 (@value{GDBP}) @b{tstart}
6186
6187 (@value{GDBP}) @b{tfind line 444}
6188 #0 gdb_test (p1=0x11, p2=0x22, p3=0x33, p4=0x44, p5=0x55, p6=0x66)
6189 at gdb_test.c:444
6190 444 printp( "%s: arguments = 0x%X 0x%X 0x%X 0x%X 0x%X 0x%X\n", )
6191
6192 (@value{GDBP}) @b{tdump}
6193 Data collected at tracepoint 2, trace frame 1:
6194 d0 0xc4aa0085 -995491707
6195 d1 0x18 24
6196 d2 0x80 128
6197 d3 0x33 51
6198 d4 0x71aea3d 119204413
6199 d5 0x22 34
6200 d6 0xe0 224
6201 d7 0x380035 3670069
6202 a0 0x19e24a 1696330
6203 a1 0x3000668 50333288
6204 a2 0x100 256
6205 a3 0x322000 3284992
6206 a4 0x3000698 50333336
6207 a5 0x1ad3cc 1758156
6208 fp 0x30bf3c 0x30bf3c
6209 sp 0x30bf34 0x30bf34
6210 ps 0x0 0
6211 pc 0x20b2c8 0x20b2c8
6212 fpcontrol 0x0 0
6213 fpstatus 0x0 0
6214 fpiaddr 0x0 0
6215 p = 0x20e5b4 "gdb-test"
6216 p1 = (void *) 0x11
6217 p2 = (void *) 0x22
6218 p3 = (void *) 0x33
6219 p4 = (void *) 0x44
6220 p5 = (void *) 0x55
6221 p6 = (void *) 0x66
6222 gdb_long_test = 17 '\021'
6223
6224 (@value{GDBP})
6225 @end smallexample
6226
6227 @node save-tracepoints
6228 @subsection @code{save-tracepoints @var{filename}}
6229 @kindex save-tracepoints
6230 @cindex save tracepoints for future sessions
6231
6232 This command saves all current tracepoint definitions together with
6233 their actions and passcounts, into a file @file{@var{filename}}
6234 suitable for use in a later debugging session. To read the saved
6235 tracepoint definitions, use the @code{source} command (@pxref{Command
6236 Files}).
6237
6238 @node Tracepoint Variables
6239 @section Convenience Variables for Tracepoints
6240 @cindex tracepoint variables
6241 @cindex convenience variables for tracepoints
6242
6243 @table @code
6244 @vindex $trace_frame
6245 @item (int) $trace_frame
6246 The current trace snapshot (a.k.a.@: @dfn{frame}) number, or -1 if no
6247 snapshot is selected.
6248
6249 @vindex $tracepoint
6250 @item (int) $tracepoint
6251 The tracepoint for the current trace snapshot.
6252
6253 @vindex $trace_line
6254 @item (int) $trace_line
6255 The line number for the current trace snapshot.
6256
6257 @vindex $trace_file
6258 @item (char []) $trace_file
6259 The source file for the current trace snapshot.
6260
6261 @vindex $trace_func
6262 @item (char []) $trace_func
6263 The name of the function containing @code{$tracepoint}.
6264 @end table
6265
6266 Note: @code{$trace_file} is not suitable for use in @code{printf},
6267 use @code{output} instead.
6268
6269 Here's a simple example of using these convenience variables for
6270 stepping through all the trace snapshots and printing some of their
6271 data.
6272
6273 @smallexample
6274 (@value{GDBP}) @b{tfind start}
6275
6276 (@value{GDBP}) @b{while $trace_frame != -1}
6277 > output $trace_file
6278 > printf ", line %d (tracepoint #%d)\n", $trace_line, $tracepoint
6279 > tfind
6280 > end
6281 @end smallexample
6282
6283 @node Languages
6284 @chapter Using @value{GDBN} with Different Languages
6285 @cindex languages
6286
6287 Although programming languages generally have common aspects, they are
6288 rarely expressed in the same manner. For instance, in ANSI C,
6289 dereferencing a pointer @code{p} is accomplished by @code{*p}, but in
6290 Modula-2, it is accomplished by @code{p^}. Values can also be
6291 represented (and displayed) differently. Hex numbers in C appear as
6292 @samp{0x1ae}, while in Modula-2 they appear as @samp{1AEH}.
6293
6294 @cindex working language
6295 Language-specific information is built into @value{GDBN} for some languages,
6296 allowing you to express operations like the above in your program's
6297 native language, and allowing @value{GDBN} to output values in a manner
6298 consistent with the syntax of your program's native language. The
6299 language you use to build expressions is called the @dfn{working
6300 language}.
6301
6302 @menu
6303 * Setting:: Switching between source languages
6304 * Show:: Displaying the language
6305 * Checks:: Type and range checks
6306 * Support:: Supported languages
6307 @end menu
6308
6309 @node Setting
6310 @section Switching between source languages
6311
6312 There are two ways to control the working language---either have @value{GDBN}
6313 set it automatically, or select it manually yourself. You can use the
6314 @code{set language} command for either purpose. On startup, @value{GDBN}
6315 defaults to setting the language automatically. The working language is
6316 used to determine how expressions you type are interpreted, how values
6317 are printed, etc.
6318
6319 In addition to the working language, every source file that
6320 @value{GDBN} knows about has its own working language. For some object
6321 file formats, the compiler might indicate which language a particular
6322 source file is in. However, most of the time @value{GDBN} infers the
6323 language from the name of the file. The language of a source file
6324 controls whether C@t{++} names are demangled---this way @code{backtrace} can
6325 show each frame appropriately for its own language. There is no way to
6326 set the language of a source file from within @value{GDBN}, but you can
6327 set the language associated with a filename extension. @xref{Show, ,
6328 Displaying the language}.
6329
6330 This is most commonly a problem when you use a program, such
6331 as @code{cfront} or @code{f2c}, that generates C but is written in
6332 another language. In that case, make the
6333 program use @code{#line} directives in its C output; that way
6334 @value{GDBN} will know the correct language of the source code of the original
6335 program, and will display that source code, not the generated C code.
6336
6337 @menu
6338 * Filenames:: Filename extensions and languages.
6339 * Manually:: Setting the working language manually
6340 * Automatically:: Having @value{GDBN} infer the source language
6341 @end menu
6342
6343 @node Filenames
6344 @subsection List of filename extensions and languages
6345
6346 If a source file name ends in one of the following extensions, then
6347 @value{GDBN} infers that its language is the one indicated.
6348
6349 @table @file
6350
6351 @item .c
6352 C source file
6353
6354 @item .C
6355 @itemx .cc
6356 @itemx .cp
6357 @itemx .cpp
6358 @itemx .cxx
6359 @itemx .c++
6360 C@t{++} source file
6361
6362 @item .f
6363 @itemx .F
6364 Fortran source file
6365
6366 @item .ch
6367 @itemx .c186
6368 @itemx .c286
6369 CHILL source file
6370
6371 @item .mod
6372 Modula-2 source file
6373
6374 @item .s
6375 @itemx .S
6376 Assembler source file. This actually behaves almost like C, but
6377 @value{GDBN} does not skip over function prologues when stepping.
6378 @end table
6379
6380 In addition, you may set the language associated with a filename
6381 extension. @xref{Show, , Displaying the language}.
6382
6383 @node Manually
6384 @subsection Setting the working language
6385
6386 If you allow @value{GDBN} to set the language automatically,
6387 expressions are interpreted the same way in your debugging session and
6388 your program.
6389
6390 @kindex set language
6391 If you wish, you may set the language manually. To do this, issue the
6392 command @samp{set language @var{lang}}, where @var{lang} is the name of
6393 a language, such as
6394 @code{c} or @code{modula-2}.
6395 For a list of the supported languages, type @samp{set language}.
6396
6397 Setting the language manually prevents @value{GDBN} from updating the working
6398 language automatically. This can lead to confusion if you try
6399 to debug a program when the working language is not the same as the
6400 source language, when an expression is acceptable to both
6401 languages---but means different things. For instance, if the current
6402 source file were written in C, and @value{GDBN} was parsing Modula-2, a
6403 command such as:
6404
6405 @example
6406 print a = b + c
6407 @end example
6408
6409 @noindent
6410 might not have the effect you intended. In C, this means to add
6411 @code{b} and @code{c} and place the result in @code{a}. The result
6412 printed would be the value of @code{a}. In Modula-2, this means to compare
6413 @code{a} to the result of @code{b+c}, yielding a @code{BOOLEAN} value.
6414
6415 @node Automatically
6416 @subsection Having @value{GDBN} infer the source language
6417
6418 To have @value{GDBN} set the working language automatically, use
6419 @samp{set language local} or @samp{set language auto}. @value{GDBN}
6420 then infers the working language. That is, when your program stops in a
6421 frame (usually by encountering a breakpoint), @value{GDBN} sets the
6422 working language to the language recorded for the function in that
6423 frame. If the language for a frame is unknown (that is, if the function
6424 or block corresponding to the frame was defined in a source file that
6425 does not have a recognized extension), the current working language is
6426 not changed, and @value{GDBN} issues a warning.
6427
6428 This may not seem necessary for most programs, which are written
6429 entirely in one source language. However, program modules and libraries
6430 written in one source language can be used by a main program written in
6431 a different source language. Using @samp{set language auto} in this
6432 case frees you from having to set the working language manually.
6433
6434 @node Show
6435 @section Displaying the language
6436
6437 The following commands help you find out which language is the
6438 working language, and also what language source files were written in.
6439
6440 @kindex show language
6441 @kindex info frame@r{, show the source language}
6442 @kindex info source@r{, show the source language}
6443 @table @code
6444 @item show language
6445 Display the current working language. This is the
6446 language you can use with commands such as @code{print} to
6447 build and compute expressions that may involve variables in your program.
6448
6449 @item info frame
6450 Display the source language for this frame. This language becomes the
6451 working language if you use an identifier from this frame.
6452 @xref{Frame Info, ,Information about a frame}, to identify the other
6453 information listed here.
6454
6455 @item info source
6456 Display the source language of this source file.
6457 @xref{Symbols, ,Examining the Symbol Table}, to identify the other
6458 information listed here.
6459 @end table
6460
6461 In unusual circumstances, you may have source files with extensions
6462 not in the standard list. You can then set the extension associated
6463 with a language explicitly:
6464
6465 @kindex set extension-language
6466 @kindex info extensions
6467 @table @code
6468 @item set extension-language @var{.ext} @var{language}
6469 Set source files with extension @var{.ext} to be assumed to be in
6470 the source language @var{language}.
6471
6472 @item info extensions
6473 List all the filename extensions and the associated languages.
6474 @end table
6475
6476 @node Checks
6477 @section Type and range checking
6478
6479 @quotation
6480 @emph{Warning:} In this release, the @value{GDBN} commands for type and range
6481 checking are included, but they do not yet have any effect. This
6482 section documents the intended facilities.
6483 @end quotation
6484 @c FIXME remove warning when type/range code added
6485
6486 Some languages are designed to guard you against making seemingly common
6487 errors through a series of compile- and run-time checks. These include
6488 checking the type of arguments to functions and operators, and making
6489 sure mathematical overflows are caught at run time. Checks such as
6490 these help to ensure a program's correctness once it has been compiled
6491 by eliminating type mismatches, and providing active checks for range
6492 errors when your program is running.
6493
6494 @value{GDBN} can check for conditions like the above if you wish.
6495 Although @value{GDBN} does not check the statements in your program, it
6496 can check expressions entered directly into @value{GDBN} for evaluation via
6497 the @code{print} command, for example. As with the working language,
6498 @value{GDBN} can also decide whether or not to check automatically based on
6499 your program's source language. @xref{Support, ,Supported languages},
6500 for the default settings of supported languages.
6501
6502 @menu
6503 * Type Checking:: An overview of type checking
6504 * Range Checking:: An overview of range checking
6505 @end menu
6506
6507 @cindex type checking
6508 @cindex checks, type
6509 @node Type Checking
6510 @subsection An overview of type checking
6511
6512 Some languages, such as Modula-2, are strongly typed, meaning that the
6513 arguments to operators and functions have to be of the correct type,
6514 otherwise an error occurs. These checks prevent type mismatch
6515 errors from ever causing any run-time problems. For example,
6516
6517 @smallexample
6518 1 + 2 @result{} 3
6519 @exdent but
6520 @error{} 1 + 2.3
6521 @end smallexample
6522
6523 The second example fails because the @code{CARDINAL} 1 is not
6524 type-compatible with the @code{REAL} 2.3.
6525
6526 For the expressions you use in @value{GDBN} commands, you can tell the
6527 @value{GDBN} type checker to skip checking;
6528 to treat any mismatches as errors and abandon the expression;
6529 or to only issue warnings when type mismatches occur,
6530 but evaluate the expression anyway. When you choose the last of
6531 these, @value{GDBN} evaluates expressions like the second example above, but
6532 also issues a warning.
6533
6534 Even if you turn type checking off, there may be other reasons
6535 related to type that prevent @value{GDBN} from evaluating an expression.
6536 For instance, @value{GDBN} does not know how to add an @code{int} and
6537 a @code{struct foo}. These particular type errors have nothing to do
6538 with the language in use, and usually arise from expressions, such as
6539 the one described above, which make little sense to evaluate anyway.
6540
6541 Each language defines to what degree it is strict about type. For
6542 instance, both Modula-2 and C require the arguments to arithmetical
6543 operators to be numbers. In C, enumerated types and pointers can be
6544 represented as numbers, so that they are valid arguments to mathematical
6545 operators. @xref{Support, ,Supported languages}, for further
6546 details on specific languages.
6547
6548 @value{GDBN} provides some additional commands for controlling the type checker:
6549
6550 @kindex set check@r{, type}
6551 @kindex set check type
6552 @kindex show check type
6553 @table @code
6554 @item set check type auto
6555 Set type checking on or off based on the current working language.
6556 @xref{Support, ,Supported languages}, for the default settings for
6557 each language.
6558
6559 @item set check type on
6560 @itemx set check type off
6561 Set type checking on or off, overriding the default setting for the
6562 current working language. Issue a warning if the setting does not
6563 match the language default. If any type mismatches occur in
6564 evaluating an expression while type checking is on, @value{GDBN} prints a
6565 message and aborts evaluation of the expression.
6566
6567 @item set check type warn
6568 Cause the type checker to issue warnings, but to always attempt to
6569 evaluate the expression. Evaluating the expression may still
6570 be impossible for other reasons. For example, @value{GDBN} cannot add
6571 numbers and structures.
6572
6573 @item show type
6574 Show the current setting of the type checker, and whether or not @value{GDBN}
6575 is setting it automatically.
6576 @end table
6577
6578 @cindex range checking
6579 @cindex checks, range
6580 @node Range Checking
6581 @subsection An overview of range checking
6582
6583 In some languages (such as Modula-2), it is an error to exceed the
6584 bounds of a type; this is enforced with run-time checks. Such range
6585 checking is meant to ensure program correctness by making sure
6586 computations do not overflow, or indices on an array element access do
6587 not exceed the bounds of the array.
6588
6589 For expressions you use in @value{GDBN} commands, you can tell
6590 @value{GDBN} to treat range errors in one of three ways: ignore them,
6591 always treat them as errors and abandon the expression, or issue
6592 warnings but evaluate the expression anyway.
6593
6594 A range error can result from numerical overflow, from exceeding an
6595 array index bound, or when you type a constant that is not a member
6596 of any type. Some languages, however, do not treat overflows as an
6597 error. In many implementations of C, mathematical overflow causes the
6598 result to ``wrap around'' to lower values---for example, if @var{m} is
6599 the largest integer value, and @var{s} is the smallest, then
6600
6601 @example
6602 @var{m} + 1 @result{} @var{s}
6603 @end example
6604
6605 This, too, is specific to individual languages, and in some cases
6606 specific to individual compilers or machines. @xref{Support, ,
6607 Supported languages}, for further details on specific languages.
6608
6609 @value{GDBN} provides some additional commands for controlling the range checker:
6610
6611 @kindex set check@r{, range}
6612 @kindex set check range
6613 @kindex show check range
6614 @table @code
6615 @item set check range auto
6616 Set range checking on or off based on the current working language.
6617 @xref{Support, ,Supported languages}, for the default settings for
6618 each language.
6619
6620 @item set check range on
6621 @itemx set check range off
6622 Set range checking on or off, overriding the default setting for the
6623 current working language. A warning is issued if the setting does not
6624 match the language default. If a range error occurs and range checking is on,
6625 then a message is printed and evaluation of the expression is aborted.
6626
6627 @item set check range warn
6628 Output messages when the @value{GDBN} range checker detects a range error,
6629 but attempt to evaluate the expression anyway. Evaluating the
6630 expression may still be impossible for other reasons, such as accessing
6631 memory that the process does not own (a typical example from many Unix
6632 systems).
6633
6634 @item show range
6635 Show the current setting of the range checker, and whether or not it is
6636 being set automatically by @value{GDBN}.
6637 @end table
6638
6639 @node Support
6640 @section Supported languages
6641
6642 @value{GDBN} supports C, C@t{++}, Fortran, Java, Chill, assembly, and Modula-2.
6643 @c This is false ...
6644 Some @value{GDBN} features may be used in expressions regardless of the
6645 language you use: the @value{GDBN} @code{@@} and @code{::} operators,
6646 and the @samp{@{type@}addr} construct (@pxref{Expressions,
6647 ,Expressions}) can be used with the constructs of any supported
6648 language.
6649
6650 The following sections detail to what degree each source language is
6651 supported by @value{GDBN}. These sections are not meant to be language
6652 tutorials or references, but serve only as a reference guide to what the
6653 @value{GDBN} expression parser accepts, and what input and output
6654 formats should look like for different languages. There are many good
6655 books written on each of these languages; please look to these for a
6656 language reference or tutorial.
6657
6658 @menu
6659 * C:: C and C@t{++}
6660 * Modula-2:: Modula-2
6661 * Chill:: Chill
6662 @end menu
6663
6664 @node C
6665 @subsection C and C@t{++}
6666
6667 @cindex C and C@t{++}
6668 @cindex expressions in C or C@t{++}
6669
6670 Since C and C@t{++} are so closely related, many features of @value{GDBN} apply
6671 to both languages. Whenever this is the case, we discuss those languages
6672 together.
6673
6674 @cindex C@t{++}
6675 @cindex @code{g++}, @sc{gnu} C@t{++} compiler
6676 @cindex @sc{gnu} C@t{++}
6677 The C@t{++} debugging facilities are jointly implemented by the C@t{++}
6678 compiler and @value{GDBN}. Therefore, to debug your C@t{++} code
6679 effectively, you must compile your C@t{++} programs with a supported
6680 C@t{++} compiler, such as @sc{gnu} @code{g++}, or the HP ANSI C@t{++}
6681 compiler (@code{aCC}).
6682
6683 For best results when using @sc{gnu} C@t{++}, use the stabs debugging
6684 format. You can select that format explicitly with the @code{g++}
6685 command-line options @samp{-gstabs} or @samp{-gstabs+}. See
6686 @ref{Debugging Options,,Options for Debugging Your Program or @sc{gnu}
6687 CC, gcc.info, Using @sc{gnu} CC}, for more information.
6688
6689 @menu
6690 * C Operators:: C and C@t{++} operators
6691 * C Constants:: C and C@t{++} constants
6692 * C plus plus expressions:: C@t{++} expressions
6693 * C Defaults:: Default settings for C and C@t{++}
6694 * C Checks:: C and C@t{++} type and range checks
6695 * Debugging C:: @value{GDBN} and C
6696 * Debugging C plus plus:: @value{GDBN} features for C@t{++}
6697 @end menu
6698
6699 @node C Operators
6700 @subsubsection C and C@t{++} operators
6701
6702 @cindex C and C@t{++} operators
6703
6704 Operators must be defined on values of specific types. For instance,
6705 @code{+} is defined on numbers, but not on structures. Operators are
6706 often defined on groups of types.
6707
6708 For the purposes of C and C@t{++}, the following definitions hold:
6709
6710 @itemize @bullet
6711
6712 @item
6713 @emph{Integral types} include @code{int} with any of its storage-class
6714 specifiers; @code{char}; @code{enum}; and, for C@t{++}, @code{bool}.
6715
6716 @item
6717 @emph{Floating-point types} include @code{float}, @code{double}, and
6718 @code{long double} (if supported by the target platform).
6719
6720 @item
6721 @emph{Pointer types} include all types defined as @code{(@var{type} *)}.
6722
6723 @item
6724 @emph{Scalar types} include all of the above.
6725
6726 @end itemize
6727
6728 @noindent
6729 The following operators are supported. They are listed here
6730 in order of increasing precedence:
6731
6732 @table @code
6733 @item ,
6734 The comma or sequencing operator. Expressions in a comma-separated list
6735 are evaluated from left to right, with the result of the entire
6736 expression being the last expression evaluated.
6737
6738 @item =
6739 Assignment. The value of an assignment expression is the value
6740 assigned. Defined on scalar types.
6741
6742 @item @var{op}=
6743 Used in an expression of the form @w{@code{@var{a} @var{op}= @var{b}}},
6744 and translated to @w{@code{@var{a} = @var{a op b}}}.
6745 @w{@code{@var{op}=}} and @code{=} have the same precedence.
6746 @var{op} is any one of the operators @code{|}, @code{^}, @code{&},
6747 @code{<<}, @code{>>}, @code{+}, @code{-}, @code{*}, @code{/}, @code{%}.
6748
6749 @item ?:
6750 The ternary operator. @code{@var{a} ? @var{b} : @var{c}} can be thought
6751 of as: if @var{a} then @var{b} else @var{c}. @var{a} should be of an
6752 integral type.
6753
6754 @item ||
6755 Logical @sc{or}. Defined on integral types.
6756
6757 @item &&
6758 Logical @sc{and}. Defined on integral types.
6759
6760 @item |
6761 Bitwise @sc{or}. Defined on integral types.
6762
6763 @item ^
6764 Bitwise exclusive-@sc{or}. Defined on integral types.
6765
6766 @item &
6767 Bitwise @sc{and}. Defined on integral types.
6768
6769 @item ==@r{, }!=
6770 Equality and inequality. Defined on scalar types. The value of these
6771 expressions is 0 for false and non-zero for true.
6772
6773 @item <@r{, }>@r{, }<=@r{, }>=
6774 Less than, greater than, less than or equal, greater than or equal.
6775 Defined on scalar types. The value of these expressions is 0 for false
6776 and non-zero for true.
6777
6778 @item <<@r{, }>>
6779 left shift, and right shift. Defined on integral types.
6780
6781 @item @@
6782 The @value{GDBN} ``artificial array'' operator (@pxref{Expressions, ,Expressions}).
6783
6784 @item +@r{, }-
6785 Addition and subtraction. Defined on integral types, floating-point types and
6786 pointer types.
6787
6788 @item *@r{, }/@r{, }%
6789 Multiplication, division, and modulus. Multiplication and division are
6790 defined on integral and floating-point types. Modulus is defined on
6791 integral types.
6792
6793 @item ++@r{, }--
6794 Increment and decrement. When appearing before a variable, the
6795 operation is performed before the variable is used in an expression;
6796 when appearing after it, the variable's value is used before the
6797 operation takes place.
6798
6799 @item *
6800 Pointer dereferencing. Defined on pointer types. Same precedence as
6801 @code{++}.
6802
6803 @item &
6804 Address operator. Defined on variables. Same precedence as @code{++}.
6805
6806 For debugging C@t{++}, @value{GDBN} implements a use of @samp{&} beyond what is
6807 allowed in the C@t{++} language itself: you can use @samp{&(&@var{ref})}
6808 (or, if you prefer, simply @samp{&&@var{ref}}) to examine the address
6809 where a C@t{++} reference variable (declared with @samp{&@var{ref}}) is
6810 stored.
6811
6812 @item -
6813 Negative. Defined on integral and floating-point types. Same
6814 precedence as @code{++}.
6815
6816 @item !
6817 Logical negation. Defined on integral types. Same precedence as
6818 @code{++}.
6819
6820 @item ~
6821 Bitwise complement operator. Defined on integral types. Same precedence as
6822 @code{++}.
6823
6824
6825 @item .@r{, }->
6826 Structure member, and pointer-to-structure member. For convenience,
6827 @value{GDBN} regards the two as equivalent, choosing whether to dereference a
6828 pointer based on the stored type information.
6829 Defined on @code{struct} and @code{union} data.
6830
6831 @item .*@r{, }->*
6832 Dereferences of pointers to members.
6833
6834 @item []
6835 Array indexing. @code{@var{a}[@var{i}]} is defined as
6836 @code{*(@var{a}+@var{i})}. Same precedence as @code{->}.
6837
6838 @item ()
6839 Function parameter list. Same precedence as @code{->}.
6840
6841 @item ::
6842 C@t{++} scope resolution operator. Defined on @code{struct}, @code{union},
6843 and @code{class} types.
6844
6845 @item ::
6846 Doubled colons also represent the @value{GDBN} scope operator
6847 (@pxref{Expressions, ,Expressions}). Same precedence as @code{::},
6848 above.
6849 @end table
6850
6851 If an operator is redefined in the user code, @value{GDBN} usually
6852 attempts to invoke the redefined version instead of using the operator's
6853 predefined meaning.
6854
6855 @menu
6856 * C Constants::
6857 @end menu
6858
6859 @node C Constants
6860 @subsubsection C and C@t{++} constants
6861
6862 @cindex C and C@t{++} constants
6863
6864 @value{GDBN} allows you to express the constants of C and C@t{++} in the
6865 following ways:
6866
6867 @itemize @bullet
6868 @item
6869 Integer constants are a sequence of digits. Octal constants are
6870 specified by a leading @samp{0} (i.e. zero), and hexadecimal constants by
6871 a leading @samp{0x} or @samp{0X}. Constants may also end with a letter
6872 @samp{l}, specifying that the constant should be treated as a
6873 @code{long} value.
6874
6875 @item
6876 Floating point constants are a sequence of digits, followed by a decimal
6877 point, followed by a sequence of digits, and optionally followed by an
6878 exponent. An exponent is of the form:
6879 @samp{@w{e@r{[[}+@r{]|}-@r{]}@var{nnn}}}, where @var{nnn} is another
6880 sequence of digits. The @samp{+} is optional for positive exponents.
6881 A floating-point constant may also end with a letter @samp{f} or
6882 @samp{F}, specifying that the constant should be treated as being of
6883 the @code{float} (as opposed to the default @code{double}) type; or with
6884 a letter @samp{l} or @samp{L}, which specifies a @code{long double}
6885 constant.
6886
6887 @item
6888 Enumerated constants consist of enumerated identifiers, or their
6889 integral equivalents.
6890
6891 @item
6892 Character constants are a single character surrounded by single quotes
6893 (@code{'}), or a number---the ordinal value of the corresponding character
6894 (usually its @sc{ascii} value). Within quotes, the single character may
6895 be represented by a letter or by @dfn{escape sequences}, which are of
6896 the form @samp{\@var{nnn}}, where @var{nnn} is the octal representation
6897 of the character's ordinal value; or of the form @samp{\@var{x}}, where
6898 @samp{@var{x}} is a predefined special character---for example,
6899 @samp{\n} for newline.
6900
6901 @item
6902 String constants are a sequence of character constants surrounded by
6903 double quotes (@code{"}). Any valid character constant (as described
6904 above) may appear. Double quotes within the string must be preceded by
6905 a backslash, so for instance @samp{"a\"b'c"} is a string of five
6906 characters.
6907
6908 @item
6909 Pointer constants are an integral value. You can also write pointers
6910 to constants using the C operator @samp{&}.
6911
6912 @item
6913 Array constants are comma-separated lists surrounded by braces @samp{@{}
6914 and @samp{@}}; for example, @samp{@{1,2,3@}} is a three-element array of
6915 integers, @samp{@{@{1,2@}, @{3,4@}, @{5,6@}@}} is a three-by-two array,
6916 and @samp{@{&"hi", &"there", &"fred"@}} is a three-element array of pointers.
6917 @end itemize
6918
6919 @menu
6920 * C plus plus expressions::
6921 * C Defaults::
6922 * C Checks::
6923
6924 * Debugging C::
6925 @end menu
6926
6927 @node C plus plus expressions
6928 @subsubsection C@t{++} expressions
6929
6930 @cindex expressions in C@t{++}
6931 @value{GDBN} expression handling can interpret most C@t{++} expressions.
6932
6933 @cindex C@t{++} support, not in @sc{coff}
6934 @cindex @sc{coff} versus C@t{++}
6935 @cindex C@t{++} and object formats
6936 @cindex object formats and C@t{++}
6937 @cindex a.out and C@t{++}
6938 @cindex @sc{ecoff} and C@t{++}
6939 @cindex @sc{xcoff} and C@t{++}
6940 @cindex @sc{elf}/stabs and C@t{++}
6941 @cindex @sc{elf}/@sc{dwarf} and C@t{++}
6942 @c FIXME!! GDB may eventually be able to debug C++ using DWARF; check
6943 @c periodically whether this has happened...
6944 @quotation
6945 @emph{Warning:} @value{GDBN} can only debug C@t{++} code if you use the
6946 proper compiler. Typically, C@t{++} debugging depends on the use of
6947 additional debugging information in the symbol table, and thus requires
6948 special support. In particular, if your compiler generates a.out, MIPS
6949 @sc{ecoff}, RS/6000 @sc{xcoff}, or @sc{elf} with stabs extensions to the
6950 symbol table, these facilities are all available. (With @sc{gnu} CC,
6951 you can use the @samp{-gstabs} option to request stabs debugging
6952 extensions explicitly.) Where the object code format is standard
6953 @sc{coff} or @sc{dwarf} in @sc{elf}, on the other hand, most of the C@t{++}
6954 support in @value{GDBN} does @emph{not} work.
6955 @end quotation
6956
6957 @enumerate
6958
6959 @cindex member functions
6960 @item
6961 Member function calls are allowed; you can use expressions like
6962
6963 @example
6964 count = aml->GetOriginal(x, y)
6965 @end example
6966
6967 @vindex this@r{, inside C@t{++} member functions}
6968 @cindex namespace in C@t{++}
6969 @item
6970 While a member function is active (in the selected stack frame), your
6971 expressions have the same namespace available as the member function;
6972 that is, @value{GDBN} allows implicit references to the class instance
6973 pointer @code{this} following the same rules as C@t{++}.
6974
6975 @cindex call overloaded functions
6976 @cindex overloaded functions, calling
6977 @cindex type conversions in C@t{++}
6978 @item
6979 You can call overloaded functions; @value{GDBN} resolves the function
6980 call to the right definition, with some restrictions. @value{GDBN} does not
6981 perform overload resolution involving user-defined type conversions,
6982 calls to constructors, or instantiations of templates that do not exist
6983 in the program. It also cannot handle ellipsis argument lists or
6984 default arguments.
6985
6986 It does perform integral conversions and promotions, floating-point
6987 promotions, arithmetic conversions, pointer conversions, conversions of
6988 class objects to base classes, and standard conversions such as those of
6989 functions or arrays to pointers; it requires an exact match on the
6990 number of function arguments.
6991
6992 Overload resolution is always performed, unless you have specified
6993 @code{set overload-resolution off}. @xref{Debugging C plus plus,
6994 ,@value{GDBN} features for C@t{++}}.
6995
6996 You must specify @code{set overload-resolution off} in order to use an
6997 explicit function signature to call an overloaded function, as in
6998 @smallexample
6999 p 'foo(char,int)'('x', 13)
7000 @end smallexample
7001
7002 The @value{GDBN} command-completion facility can simplify this;
7003 see @ref{Completion, ,Command completion}.
7004
7005 @cindex reference declarations
7006 @item
7007 @value{GDBN} understands variables declared as C@t{++} references; you can use
7008 them in expressions just as you do in C@t{++} source---they are automatically
7009 dereferenced.
7010
7011 In the parameter list shown when @value{GDBN} displays a frame, the values of
7012 reference variables are not displayed (unlike other variables); this
7013 avoids clutter, since references are often used for large structures.
7014 The @emph{address} of a reference variable is always shown, unless
7015 you have specified @samp{set print address off}.
7016
7017 @item
7018 @value{GDBN} supports the C@t{++} name resolution operator @code{::}---your
7019 expressions can use it just as expressions in your program do. Since
7020 one scope may be defined in another, you can use @code{::} repeatedly if
7021 necessary, for example in an expression like
7022 @samp{@var{scope1}::@var{scope2}::@var{name}}. @value{GDBN} also allows
7023 resolving name scope by reference to source files, in both C and C@t{++}
7024 debugging (@pxref{Variables, ,Program variables}).
7025 @end enumerate
7026
7027 In addition, when used with HP's C@t{++} compiler, @value{GDBN} supports
7028 calling virtual functions correctly, printing out virtual bases of
7029 objects, calling functions in a base subobject, casting objects, and
7030 invoking user-defined operators.
7031
7032 @node C Defaults
7033 @subsubsection C and C@t{++} defaults
7034
7035 @cindex C and C@t{++} defaults
7036
7037 If you allow @value{GDBN} to set type and range checking automatically, they
7038 both default to @code{off} whenever the working language changes to
7039 C or C@t{++}. This happens regardless of whether you or @value{GDBN}
7040 selects the working language.
7041
7042 If you allow @value{GDBN} to set the language automatically, it
7043 recognizes source files whose names end with @file{.c}, @file{.C}, or
7044 @file{.cc}, etc, and when @value{GDBN} enters code compiled from one of
7045 these files, it sets the working language to C or C@t{++}.
7046 @xref{Automatically, ,Having @value{GDBN} infer the source language},
7047 for further details.
7048
7049 @c Type checking is (a) primarily motivated by Modula-2, and (b)
7050 @c unimplemented. If (b) changes, it might make sense to let this node
7051 @c appear even if Mod-2 does not, but meanwhile ignore it. roland 16jul93.
7052
7053 @node C Checks
7054 @subsubsection C and C@t{++} type and range checks
7055
7056 @cindex C and C@t{++} checks
7057
7058 By default, when @value{GDBN} parses C or C@t{++} expressions, type checking
7059 is not used. However, if you turn type checking on, @value{GDBN}
7060 considers two variables type equivalent if:
7061
7062 @itemize @bullet
7063 @item
7064 The two variables are structured and have the same structure, union, or
7065 enumerated tag.
7066
7067 @item
7068 The two variables have the same type name, or types that have been
7069 declared equivalent through @code{typedef}.
7070
7071 @ignore
7072 @c leaving this out because neither J Gilmore nor R Pesch understand it.
7073 @c FIXME--beers?
7074 @item
7075 The two @code{struct}, @code{union}, or @code{enum} variables are
7076 declared in the same declaration. (Note: this may not be true for all C
7077 compilers.)
7078 @end ignore
7079 @end itemize
7080
7081 Range checking, if turned on, is done on mathematical operations. Array
7082 indices are not checked, since they are often used to index a pointer
7083 that is not itself an array.
7084
7085 @node Debugging C
7086 @subsubsection @value{GDBN} and C
7087
7088 The @code{set print union} and @code{show print union} commands apply to
7089 the @code{union} type. When set to @samp{on}, any @code{union} that is
7090 inside a @code{struct} or @code{class} is also printed. Otherwise, it
7091 appears as @samp{@{...@}}.
7092
7093 The @code{@@} operator aids in the debugging of dynamic arrays, formed
7094 with pointers and a memory allocation function. @xref{Expressions,
7095 ,Expressions}.
7096
7097 @menu
7098 * Debugging C plus plus::
7099 @end menu
7100
7101 @node Debugging C plus plus
7102 @subsubsection @value{GDBN} features for C@t{++}
7103
7104 @cindex commands for C@t{++}
7105
7106 Some @value{GDBN} commands are particularly useful with C@t{++}, and some are
7107 designed specifically for use with C@t{++}. Here is a summary:
7108
7109 @table @code
7110 @cindex break in overloaded functions
7111 @item @r{breakpoint menus}
7112 When you want a breakpoint in a function whose name is overloaded,
7113 @value{GDBN} breakpoint menus help you specify which function definition
7114 you want. @xref{Breakpoint Menus,,Breakpoint menus}.
7115
7116 @cindex overloading in C@t{++}
7117 @item rbreak @var{regex}
7118 Setting breakpoints using regular expressions is helpful for setting
7119 breakpoints on overloaded functions that are not members of any special
7120 classes.
7121 @xref{Set Breaks, ,Setting breakpoints}.
7122
7123 @cindex C@t{++} exception handling
7124 @item catch throw
7125 @itemx catch catch
7126 Debug C@t{++} exception handling using these commands. @xref{Set
7127 Catchpoints, , Setting catchpoints}.
7128
7129 @cindex inheritance
7130 @item ptype @var{typename}
7131 Print inheritance relationships as well as other information for type
7132 @var{typename}.
7133 @xref{Symbols, ,Examining the Symbol Table}.
7134
7135 @cindex C@t{++} symbol display
7136 @item set print demangle
7137 @itemx show print demangle
7138 @itemx set print asm-demangle
7139 @itemx show print asm-demangle
7140 Control whether C@t{++} symbols display in their source form, both when
7141 displaying code as C@t{++} source and when displaying disassemblies.
7142 @xref{Print Settings, ,Print settings}.
7143
7144 @item set print object
7145 @itemx show print object
7146 Choose whether to print derived (actual) or declared types of objects.
7147 @xref{Print Settings, ,Print settings}.
7148
7149 @item set print vtbl
7150 @itemx show print vtbl
7151 Control the format for printing virtual function tables.
7152 @xref{Print Settings, ,Print settings}.
7153 (The @code{vtbl} commands do not work on programs compiled with the HP
7154 ANSI C@t{++} compiler (@code{aCC}).)
7155
7156 @kindex set overload-resolution
7157 @cindex overloaded functions, overload resolution
7158 @item set overload-resolution on
7159 Enable overload resolution for C@t{++} expression evaluation. The default
7160 is on. For overloaded functions, @value{GDBN} evaluates the arguments
7161 and searches for a function whose signature matches the argument types,
7162 using the standard C@t{++} conversion rules (see @ref{C plus plus expressions, ,C@t{++}
7163 expressions}, for details). If it cannot find a match, it emits a
7164 message.
7165
7166 @item set overload-resolution off
7167 Disable overload resolution for C@t{++} expression evaluation. For
7168 overloaded functions that are not class member functions, @value{GDBN}
7169 chooses the first function of the specified name that it finds in the
7170 symbol table, whether or not its arguments are of the correct type. For
7171 overloaded functions that are class member functions, @value{GDBN}
7172 searches for a function whose signature @emph{exactly} matches the
7173 argument types.
7174
7175 @item @r{Overloaded symbol names}
7176 You can specify a particular definition of an overloaded symbol, using
7177 the same notation that is used to declare such symbols in C@t{++}: type
7178 @code{@var{symbol}(@var{types})} rather than just @var{symbol}. You can
7179 also use the @value{GDBN} command-line word completion facilities to list the
7180 available choices, or to finish the type list for you.
7181 @xref{Completion,, Command completion}, for details on how to do this.
7182 @end table
7183
7184 @node Modula-2
7185 @subsection Modula-2
7186
7187 @cindex Modula-2, @value{GDBN} support
7188
7189 The extensions made to @value{GDBN} to support Modula-2 only support
7190 output from the @sc{gnu} Modula-2 compiler (which is currently being
7191 developed). Other Modula-2 compilers are not currently supported, and
7192 attempting to debug executables produced by them is most likely
7193 to give an error as @value{GDBN} reads in the executable's symbol
7194 table.
7195
7196 @cindex expressions in Modula-2
7197 @menu
7198 * M2 Operators:: Built-in operators
7199 * Built-In Func/Proc:: Built-in functions and procedures
7200 * M2 Constants:: Modula-2 constants
7201 * M2 Defaults:: Default settings for Modula-2
7202 * Deviations:: Deviations from standard Modula-2
7203 * M2 Checks:: Modula-2 type and range checks
7204 * M2 Scope:: The scope operators @code{::} and @code{.}
7205 * GDB/M2:: @value{GDBN} and Modula-2
7206 @end menu
7207
7208 @node M2 Operators
7209 @subsubsection Operators
7210 @cindex Modula-2 operators
7211
7212 Operators must be defined on values of specific types. For instance,
7213 @code{+} is defined on numbers, but not on structures. Operators are
7214 often defined on groups of types. For the purposes of Modula-2, the
7215 following definitions hold:
7216
7217 @itemize @bullet
7218
7219 @item
7220 @emph{Integral types} consist of @code{INTEGER}, @code{CARDINAL}, and
7221 their subranges.
7222
7223 @item
7224 @emph{Character types} consist of @code{CHAR} and its subranges.
7225
7226 @item
7227 @emph{Floating-point types} consist of @code{REAL}.
7228
7229 @item
7230 @emph{Pointer types} consist of anything declared as @code{POINTER TO
7231 @var{type}}.
7232
7233 @item
7234 @emph{Scalar types} consist of all of the above.
7235
7236 @item
7237 @emph{Set types} consist of @code{SET} and @code{BITSET} types.
7238
7239 @item
7240 @emph{Boolean types} consist of @code{BOOLEAN}.
7241 @end itemize
7242
7243 @noindent
7244 The following operators are supported, and appear in order of
7245 increasing precedence:
7246
7247 @table @code
7248 @item ,
7249 Function argument or array index separator.
7250
7251 @item :=
7252 Assignment. The value of @var{var} @code{:=} @var{value} is
7253 @var{value}.
7254
7255 @item <@r{, }>
7256 Less than, greater than on integral, floating-point, or enumerated
7257 types.
7258
7259 @item <=@r{, }>=
7260 Less than or equal to, greater than or equal to
7261 on integral, floating-point and enumerated types, or set inclusion on
7262 set types. Same precedence as @code{<}.
7263
7264 @item =@r{, }<>@r{, }#
7265 Equality and two ways of expressing inequality, valid on scalar types.
7266 Same precedence as @code{<}. In @value{GDBN} scripts, only @code{<>} is
7267 available for inequality, since @code{#} conflicts with the script
7268 comment character.
7269
7270 @item IN
7271 Set membership. Defined on set types and the types of their members.
7272 Same precedence as @code{<}.
7273
7274 @item OR
7275 Boolean disjunction. Defined on boolean types.
7276
7277 @item AND@r{, }&
7278 Boolean conjunction. Defined on boolean types.
7279
7280 @item @@
7281 The @value{GDBN} ``artificial array'' operator (@pxref{Expressions, ,Expressions}).
7282
7283 @item +@r{, }-
7284 Addition and subtraction on integral and floating-point types, or union
7285 and difference on set types.
7286
7287 @item *
7288 Multiplication on integral and floating-point types, or set intersection
7289 on set types.
7290
7291 @item /
7292 Division on floating-point types, or symmetric set difference on set
7293 types. Same precedence as @code{*}.
7294
7295 @item DIV@r{, }MOD
7296 Integer division and remainder. Defined on integral types. Same
7297 precedence as @code{*}.
7298
7299 @item -
7300 Negative. Defined on @code{INTEGER} and @code{REAL} data.
7301
7302 @item ^
7303 Pointer dereferencing. Defined on pointer types.
7304
7305 @item NOT
7306 Boolean negation. Defined on boolean types. Same precedence as
7307 @code{^}.
7308
7309 @item .
7310 @code{RECORD} field selector. Defined on @code{RECORD} data. Same
7311 precedence as @code{^}.
7312
7313 @item []
7314 Array indexing. Defined on @code{ARRAY} data. Same precedence as @code{^}.
7315
7316 @item ()
7317 Procedure argument list. Defined on @code{PROCEDURE} objects. Same precedence
7318 as @code{^}.
7319
7320 @item ::@r{, }.
7321 @value{GDBN} and Modula-2 scope operators.
7322 @end table
7323
7324 @quotation
7325 @emph{Warning:} Sets and their operations are not yet supported, so @value{GDBN}
7326 treats the use of the operator @code{IN}, or the use of operators
7327 @code{+}, @code{-}, @code{*}, @code{/}, @code{=}, , @code{<>}, @code{#},
7328 @code{<=}, and @code{>=} on sets as an error.
7329 @end quotation
7330
7331
7332 @node Built-In Func/Proc
7333 @subsubsection Built-in functions and procedures
7334 @cindex Modula-2 built-ins
7335
7336 Modula-2 also makes available several built-in procedures and functions.
7337 In describing these, the following metavariables are used:
7338
7339 @table @var
7340
7341 @item a
7342 represents an @code{ARRAY} variable.
7343
7344 @item c
7345 represents a @code{CHAR} constant or variable.
7346
7347 @item i
7348 represents a variable or constant of integral type.
7349
7350 @item m
7351 represents an identifier that belongs to a set. Generally used in the
7352 same function with the metavariable @var{s}. The type of @var{s} should
7353 be @code{SET OF @var{mtype}} (where @var{mtype} is the type of @var{m}).
7354
7355 @item n
7356 represents a variable or constant of integral or floating-point type.
7357
7358 @item r
7359 represents a variable or constant of floating-point type.
7360
7361 @item t
7362 represents a type.
7363
7364 @item v
7365 represents a variable.
7366
7367 @item x
7368 represents a variable or constant of one of many types. See the
7369 explanation of the function for details.
7370 @end table
7371
7372 All Modula-2 built-in procedures also return a result, described below.
7373
7374 @table @code
7375 @item ABS(@var{n})
7376 Returns the absolute value of @var{n}.
7377
7378 @item CAP(@var{c})
7379 If @var{c} is a lower case letter, it returns its upper case
7380 equivalent, otherwise it returns its argument.
7381
7382 @item CHR(@var{i})
7383 Returns the character whose ordinal value is @var{i}.
7384
7385 @item DEC(@var{v})
7386 Decrements the value in the variable @var{v} by one. Returns the new value.
7387
7388 @item DEC(@var{v},@var{i})
7389 Decrements the value in the variable @var{v} by @var{i}. Returns the
7390 new value.
7391
7392 @item EXCL(@var{m},@var{s})
7393 Removes the element @var{m} from the set @var{s}. Returns the new
7394 set.
7395
7396 @item FLOAT(@var{i})
7397 Returns the floating point equivalent of the integer @var{i}.
7398
7399 @item HIGH(@var{a})
7400 Returns the index of the last member of @var{a}.
7401
7402 @item INC(@var{v})
7403 Increments the value in the variable @var{v} by one. Returns the new value.
7404
7405 @item INC(@var{v},@var{i})
7406 Increments the value in the variable @var{v} by @var{i}. Returns the
7407 new value.
7408
7409 @item INCL(@var{m},@var{s})
7410 Adds the element @var{m} to the set @var{s} if it is not already
7411 there. Returns the new set.
7412
7413 @item MAX(@var{t})
7414 Returns the maximum value of the type @var{t}.
7415
7416 @item MIN(@var{t})
7417 Returns the minimum value of the type @var{t}.
7418
7419 @item ODD(@var{i})
7420 Returns boolean TRUE if @var{i} is an odd number.
7421
7422 @item ORD(@var{x})
7423 Returns the ordinal value of its argument. For example, the ordinal
7424 value of a character is its @sc{ascii} value (on machines supporting the
7425 @sc{ascii} character set). @var{x} must be of an ordered type, which include
7426 integral, character and enumerated types.
7427
7428 @item SIZE(@var{x})
7429 Returns the size of its argument. @var{x} can be a variable or a type.
7430
7431 @item TRUNC(@var{r})
7432 Returns the integral part of @var{r}.
7433
7434 @item VAL(@var{t},@var{i})
7435 Returns the member of the type @var{t} whose ordinal value is @var{i}.
7436 @end table
7437
7438 @quotation
7439 @emph{Warning:} Sets and their operations are not yet supported, so
7440 @value{GDBN} treats the use of procedures @code{INCL} and @code{EXCL} as
7441 an error.
7442 @end quotation
7443
7444 @cindex Modula-2 constants
7445 @node M2 Constants
7446 @subsubsection Constants
7447
7448 @value{GDBN} allows you to express the constants of Modula-2 in the following
7449 ways:
7450
7451 @itemize @bullet
7452
7453 @item
7454 Integer constants are simply a sequence of digits. When used in an
7455 expression, a constant is interpreted to be type-compatible with the
7456 rest of the expression. Hexadecimal integers are specified by a
7457 trailing @samp{H}, and octal integers by a trailing @samp{B}.
7458
7459 @item
7460 Floating point constants appear as a sequence of digits, followed by a
7461 decimal point and another sequence of digits. An optional exponent can
7462 then be specified, in the form @samp{E@r{[}+@r{|}-@r{]}@var{nnn}}, where
7463 @samp{@r{[}+@r{|}-@r{]}@var{nnn}} is the desired exponent. All of the
7464 digits of the floating point constant must be valid decimal (base 10)
7465 digits.
7466
7467 @item
7468 Character constants consist of a single character enclosed by a pair of
7469 like quotes, either single (@code{'}) or double (@code{"}). They may
7470 also be expressed by their ordinal value (their @sc{ascii} value, usually)
7471 followed by a @samp{C}.
7472
7473 @item
7474 String constants consist of a sequence of characters enclosed by a
7475 pair of like quotes, either single (@code{'}) or double (@code{"}).
7476 Escape sequences in the style of C are also allowed. @xref{C
7477 Constants, ,C and C@t{++} constants}, for a brief explanation of escape
7478 sequences.
7479
7480 @item
7481 Enumerated constants consist of an enumerated identifier.
7482
7483 @item
7484 Boolean constants consist of the identifiers @code{TRUE} and
7485 @code{FALSE}.
7486
7487 @item
7488 Pointer constants consist of integral values only.
7489
7490 @item
7491 Set constants are not yet supported.
7492 @end itemize
7493
7494 @node M2 Defaults
7495 @subsubsection Modula-2 defaults
7496 @cindex Modula-2 defaults
7497
7498 If type and range checking are set automatically by @value{GDBN}, they
7499 both default to @code{on} whenever the working language changes to
7500 Modula-2. This happens regardless of whether you or @value{GDBN}
7501 selected the working language.
7502
7503 If you allow @value{GDBN} to set the language automatically, then entering
7504 code compiled from a file whose name ends with @file{.mod} sets the
7505 working language to Modula-2. @xref{Automatically, ,Having @value{GDBN} set
7506 the language automatically}, for further details.
7507
7508 @node Deviations
7509 @subsubsection Deviations from standard Modula-2
7510 @cindex Modula-2, deviations from
7511
7512 A few changes have been made to make Modula-2 programs easier to debug.
7513 This is done primarily via loosening its type strictness:
7514
7515 @itemize @bullet
7516 @item
7517 Unlike in standard Modula-2, pointer constants can be formed by
7518 integers. This allows you to modify pointer variables during
7519 debugging. (In standard Modula-2, the actual address contained in a
7520 pointer variable is hidden from you; it can only be modified
7521 through direct assignment to another pointer variable or expression that
7522 returned a pointer.)
7523
7524 @item
7525 C escape sequences can be used in strings and characters to represent
7526 non-printable characters. @value{GDBN} prints out strings with these
7527 escape sequences embedded. Single non-printable characters are
7528 printed using the @samp{CHR(@var{nnn})} format.
7529
7530 @item
7531 The assignment operator (@code{:=}) returns the value of its right-hand
7532 argument.
7533
7534 @item
7535 All built-in procedures both modify @emph{and} return their argument.
7536 @end itemize
7537
7538 @node M2 Checks
7539 @subsubsection Modula-2 type and range checks
7540 @cindex Modula-2 checks
7541
7542 @quotation
7543 @emph{Warning:} in this release, @value{GDBN} does not yet perform type or
7544 range checking.
7545 @end quotation
7546 @c FIXME remove warning when type/range checks added
7547
7548 @value{GDBN} considers two Modula-2 variables type equivalent if:
7549
7550 @itemize @bullet
7551 @item
7552 They are of types that have been declared equivalent via a @code{TYPE
7553 @var{t1} = @var{t2}} statement
7554
7555 @item
7556 They have been declared on the same line. (Note: This is true of the
7557 @sc{gnu} Modula-2 compiler, but it may not be true of other compilers.)
7558 @end itemize
7559
7560 As long as type checking is enabled, any attempt to combine variables
7561 whose types are not equivalent is an error.
7562
7563 Range checking is done on all mathematical operations, assignment, array
7564 index bounds, and all built-in functions and procedures.
7565
7566 @node M2 Scope
7567 @subsubsection The scope operators @code{::} and @code{.}
7568 @cindex scope
7569 @cindex @code{.}, Modula-2 scope operator
7570 @cindex colon, doubled as scope operator
7571 @ifinfo
7572 @vindex colon-colon@r{, in Modula-2}
7573 @c Info cannot handle :: but TeX can.
7574 @end ifinfo
7575 @iftex
7576 @vindex ::@r{, in Modula-2}
7577 @end iftex
7578
7579 There are a few subtle differences between the Modula-2 scope operator
7580 (@code{.}) and the @value{GDBN} scope operator (@code{::}). The two have
7581 similar syntax:
7582
7583 @example
7584
7585 @var{module} . @var{id}
7586 @var{scope} :: @var{id}
7587 @end example
7588
7589 @noindent
7590 where @var{scope} is the name of a module or a procedure,
7591 @var{module} the name of a module, and @var{id} is any declared
7592 identifier within your program, except another module.
7593
7594 Using the @code{::} operator makes @value{GDBN} search the scope
7595 specified by @var{scope} for the identifier @var{id}. If it is not
7596 found in the specified scope, then @value{GDBN} searches all scopes
7597 enclosing the one specified by @var{scope}.
7598
7599 Using the @code{.} operator makes @value{GDBN} search the current scope for
7600 the identifier specified by @var{id} that was imported from the
7601 definition module specified by @var{module}. With this operator, it is
7602 an error if the identifier @var{id} was not imported from definition
7603 module @var{module}, or if @var{id} is not an identifier in
7604 @var{module}.
7605
7606 @node GDB/M2
7607 @subsubsection @value{GDBN} and Modula-2
7608
7609 Some @value{GDBN} commands have little use when debugging Modula-2 programs.
7610 Five subcommands of @code{set print} and @code{show print} apply
7611 specifically to C and C@t{++}: @samp{vtbl}, @samp{demangle},
7612 @samp{asm-demangle}, @samp{object}, and @samp{union}. The first four
7613 apply to C@t{++}, and the last to the C @code{union} type, which has no direct
7614 analogue in Modula-2.
7615
7616 The @code{@@} operator (@pxref{Expressions, ,Expressions}), while available
7617 with any language, is not useful with Modula-2. Its
7618 intent is to aid the debugging of @dfn{dynamic arrays}, which cannot be
7619 created in Modula-2 as they can in C or C@t{++}. However, because an
7620 address can be specified by an integral constant, the construct
7621 @samp{@{@var{type}@}@var{adrexp}} is still useful.
7622
7623 @cindex @code{#} in Modula-2
7624 In @value{GDBN} scripts, the Modula-2 inequality operator @code{#} is
7625 interpreted as the beginning of a comment. Use @code{<>} instead.
7626
7627 @node Chill
7628 @subsection Chill
7629
7630 The extensions made to @value{GDBN} to support Chill only support output
7631 from the @sc{gnu} Chill compiler. Other Chill compilers are not currently
7632 supported, and attempting to debug executables produced by them is most
7633 likely to give an error as @value{GDBN} reads in the executable's symbol
7634 table.
7635
7636 @c This used to say "... following Chill related topics ...", but since
7637 @c menus are not shown in the printed manual, it would look awkward.
7638 This section covers the Chill related topics and the features
7639 of @value{GDBN} which support these topics.
7640
7641 @menu
7642 * How modes are displayed:: How modes are displayed
7643 * Locations:: Locations and their accesses
7644 * Values and their Operations:: Values and their Operations
7645 * Chill type and range checks::
7646 * Chill defaults::
7647 @end menu
7648
7649 @node How modes are displayed
7650 @subsubsection How modes are displayed
7651
7652 The Chill Datatype- (Mode) support of @value{GDBN} is directly related
7653 with the functionality of the @sc{gnu} Chill compiler, and therefore deviates
7654 slightly from the standard specification of the Chill language. The
7655 provided modes are:
7656
7657 @c FIXME: this @table's contents effectively disable @code by using @r
7658 @c on every @item. So why does it need @code?
7659 @table @code
7660 @item @r{@emph{Discrete modes:}}
7661 @itemize @bullet
7662 @item
7663 @emph{Integer Modes} which are predefined by @code{BYTE, UBYTE, INT,
7664 UINT, LONG, ULONG},
7665 @item
7666 @emph{Boolean Mode} which is predefined by @code{BOOL},
7667 @item
7668 @emph{Character Mode} which is predefined by @code{CHAR},
7669 @item
7670 @emph{Set Mode} which is displayed by the keyword @code{SET}.
7671 @smallexample
7672 (@value{GDBP}) ptype x
7673 type = SET (karli = 10, susi = 20, fritzi = 100)
7674 @end smallexample
7675 If the type is an unnumbered set the set element values are omitted.
7676 @item
7677 @emph{Range Mode} which is displayed by
7678 @smallexample
7679 @code{type = <basemode>(<lower bound> : <upper bound>)}
7680 @end smallexample
7681 where @code{<lower bound>, <upper bound>} can be of any discrete literal
7682 expression (e.g. set element names).
7683 @end itemize
7684
7685 @item @r{@emph{Powerset Mode:}}
7686 A Powerset Mode is displayed by the keyword @code{POWERSET} followed by
7687 the member mode of the powerset. The member mode can be any discrete mode.
7688 @smallexample
7689 (@value{GDBP}) ptype x
7690 type = POWERSET SET (egon, hugo, otto)
7691 @end smallexample
7692
7693 @item @r{@emph{Reference Modes:}}
7694 @itemize @bullet
7695 @item
7696 @emph{Bound Reference Mode} which is displayed by the keyword @code{REF}
7697 followed by the mode name to which the reference is bound.
7698 @item
7699 @emph{Free Reference Mode} which is displayed by the keyword @code{PTR}.
7700 @end itemize
7701
7702 @item @r{@emph{Procedure mode}}
7703 The procedure mode is displayed by @code{type = PROC(<parameter list>)
7704 <return mode> EXCEPTIONS (<exception list>)}. The @code{<parameter
7705 list>} is a list of the parameter modes. @code{<return mode>} indicates
7706 the mode of the result of the procedure if any. The exceptionlist lists
7707 all possible exceptions which can be raised by the procedure.
7708
7709 @ignore
7710 @item @r{@emph{Instance mode}}
7711 The instance mode is represented by a structure, which has a static
7712 type, and is therefore not really of interest.
7713 @end ignore
7714
7715 @item @r{@emph{Synchronization Modes:}}
7716 @itemize @bullet
7717 @item
7718 @emph{Event Mode} which is displayed by
7719 @smallexample
7720 @code{EVENT (<event length>)}
7721 @end smallexample
7722 where @code{(<event length>)} is optional.
7723 @item
7724 @emph{Buffer Mode} which is displayed by
7725 @smallexample
7726 @code{BUFFER (<buffer length>)<buffer element mode>}
7727 @end smallexample
7728 where @code{(<buffer length>)} is optional.
7729 @end itemize
7730
7731 @item @r{@emph{Timing Modes:}}
7732 @itemize @bullet
7733 @item
7734 @emph{Duration Mode} which is predefined by @code{DURATION}
7735 @item
7736 @emph{Absolute Time Mode} which is predefined by @code{TIME}
7737 @end itemize
7738
7739 @item @r{@emph{Real Modes:}}
7740 Real Modes are predefined with @code{REAL} and @code{LONG_REAL}.
7741
7742 @item @r{@emph{String Modes:}}
7743 @itemize @bullet
7744 @item
7745 @emph{Character String Mode} which is displayed by
7746 @smallexample
7747 @code{CHARS(<string length>)}
7748 @end smallexample
7749 followed by the keyword @code{VARYING} if the String Mode is a varying
7750 mode
7751 @item
7752 @emph{Bit String Mode} which is displayed by
7753 @smallexample
7754 @code{BOOLS(<string
7755 length>)}
7756 @end smallexample
7757 @end itemize
7758
7759 @item @r{@emph{Array Mode:}}
7760 The Array Mode is displayed by the keyword @code{ARRAY(<range>)}
7761 followed by the element mode (which may in turn be an array mode).
7762 @smallexample
7763 (@value{GDBP}) ptype x
7764 type = ARRAY (1:42)
7765 ARRAY (1:20)
7766 SET (karli = 10, susi = 20, fritzi = 100)
7767 @end smallexample
7768
7769 @item @r{@emph{Structure Mode}}
7770 The Structure mode is displayed by the keyword @code{STRUCT(<field
7771 list>)}. The @code{<field list>} consists of names and modes of fields
7772 of the structure. Variant structures have the keyword @code{CASE <field>
7773 OF <variant fields> ESAC} in their field list. Since the current version
7774 of the GNU Chill compiler doesn't implement tag processing (no runtime
7775 checks of variant fields, and therefore no debugging info), the output
7776 always displays all variant fields.
7777 @smallexample
7778 (@value{GDBP}) ptype str
7779 type = STRUCT (
7780 as x,
7781 bs x,
7782 CASE bs OF
7783 (karli):
7784 cs a
7785 (ott):
7786 ds x
7787 ESAC
7788 )
7789 @end smallexample
7790 @end table
7791
7792 @node Locations
7793 @subsubsection Locations and their accesses
7794
7795 A location in Chill is an object which can contain values.
7796
7797 A value of a location is generally accessed by the (declared) name of
7798 the location. The output conforms to the specification of values in
7799 Chill programs. How values are specified
7800 is the topic of the next section, @ref{Values and their Operations}.
7801
7802 The pseudo-location @code{RESULT} (or @code{result}) can be used to
7803 display or change the result of a currently-active procedure:
7804
7805 @smallexample
7806 set result := EXPR
7807 @end smallexample
7808
7809 @noindent
7810 This does the same as the Chill action @code{RESULT EXPR} (which
7811 is not available in @value{GDBN}).
7812
7813 Values of reference mode locations are printed by @code{PTR(<hex
7814 value>)} in case of a free reference mode, and by @code{(REF <reference
7815 mode>) (<hex-value>)} in case of a bound reference. @code{<hex value>}
7816 represents the address where the reference points to. To access the
7817 value of the location referenced by the pointer, use the dereference
7818 operator @samp{->}.
7819
7820 Values of procedure mode locations are displayed by
7821 @smallexample
7822 @code{@{ PROC
7823 (<argument modes> ) <return mode> @} <address> <name of procedure
7824 location>}
7825 @end smallexample
7826 @code{<argument modes>} is a list of modes according to the parameter
7827 specification of the procedure and @code{<address>} shows the address of
7828 the entry point.
7829
7830 @ignore
7831 Locations of instance modes are displayed just like a structure with two
7832 fields specifying the @emph{process type} and the @emph{copy number} of
7833 the investigated instance location@footnote{This comes from the current
7834 implementation of instances. They are implemented as a structure (no
7835 na). The output should be something like @code{[<name of the process>;
7836 <instance number>]}.}. The field names are @code{__proc_type} and
7837 @code{__proc_copy}.
7838
7839 Locations of synchronization modes are displayed like a structure with
7840 the field name @code{__event_data} in case of a event mode location, and
7841 like a structure with the field @code{__buffer_data} in case of a buffer
7842 mode location (refer to previous paragraph).
7843
7844 Structure Mode locations are printed by @code{[.<field name>: <value>,
7845 ...]}. The @code{<field name>} corresponds to the structure mode
7846 definition and the layout of @code{<value>} varies depending of the mode
7847 of the field. If the investigated structure mode location is of variant
7848 structure mode, the variant parts of the structure are enclosed in curled
7849 braces (@samp{@{@}}). Fields enclosed by @samp{@{,@}} are residing
7850 on the same memory location and represent the current values of the
7851 memory location in their specific modes. Since no tag processing is done
7852 all variants are displayed. A variant field is printed by
7853 @code{(<variant name>) = .<field name>: <value>}. (who implements the
7854 stuff ???)
7855 @smallexample
7856 (@value{GDBP}) print str1 $4 = [.as: 0, .bs: karli, .<TAG>: { (karli) =
7857 [.cs: []], (susi) = [.ds: susi]}]
7858 @end smallexample
7859 @end ignore
7860
7861 Substructures of string mode-, array mode- or structure mode-values
7862 (e.g. array slices, fields of structure locations) are accessed using
7863 certain operations which are described in the next section, @ref{Values
7864 and their Operations}.
7865
7866 A location value may be interpreted as having a different mode using the
7867 location conversion. This mode conversion is written as @code{<mode
7868 name>(<location>)}. The user has to consider that the sizes of the modes
7869 have to be equal otherwise an error occurs. Furthermore, no range
7870 checking of the location against the destination mode is performed, and
7871 therefore the result can be quite confusing.
7872
7873 @smallexample
7874 (@value{GDBP}) print int (s(3 up 4)) XXX TO be filled in !! XXX
7875 @end smallexample
7876
7877 @node Values and their Operations
7878 @subsubsection Values and their Operations
7879
7880 Values are used to alter locations, to investigate complex structures in
7881 more detail or to filter relevant information out of a large amount of
7882 data. There are several (mode dependent) operations defined which enable
7883 such investigations. These operations are not only applicable to
7884 constant values but also to locations, which can become quite useful
7885 when debugging complex structures. During parsing the command line
7886 (e.g. evaluating an expression) @value{GDBN} treats location names as
7887 the values behind these locations.
7888
7889 This section describes how values have to be specified and which
7890 operations are legal to be used with such values.
7891
7892 @table @code
7893 @item Literal Values
7894 Literal values are specified in the same manner as in @sc{gnu} Chill programs.
7895 For detailed specification refer to the @sc{gnu} Chill implementation Manual
7896 chapter 1.5.
7897 @c FIXME: if the Chill Manual is a Texinfo documents, the above should
7898 @c be converted to a @ref.
7899
7900 @ignore
7901 @itemize @bullet
7902 @item
7903 @emph{Integer Literals} are specified in the same manner as in Chill
7904 programs (refer to the Chill Standard z200/88 chpt 5.2.4.2)
7905 @item
7906 @emph{Boolean Literals} are defined by @code{TRUE} and @code{FALSE}.
7907 @item
7908 @emph{Character Literals} are defined by @code{'<character>'}. (e.g.
7909 @code{'M'})
7910 @item
7911 @emph{Set Literals} are defined by a name which was specified in a set
7912 mode. The value delivered by a Set Literal is the set value. This is
7913 comparable to an enumeration in C/C@t{++} language.
7914 @item
7915 @emph{Emptiness Literal} is predefined by @code{NULL}. The value of the
7916 emptiness literal delivers either the empty reference value, the empty
7917 procedure value or the empty instance value.
7918
7919 @item
7920 @emph{Character String Literals} are defined by a sequence of characters
7921 enclosed in single- or double quotes. If a single- or double quote has
7922 to be part of the string literal it has to be stuffed (specified twice).
7923 @item
7924 @emph{Bitstring Literals} are specified in the same manner as in Chill
7925 programs (refer z200/88 chpt 5.2.4.8).
7926 @item
7927 @emph{Floating point literals} are specified in the same manner as in
7928 (gnu-)Chill programs (refer @sc{gnu} Chill implementation Manual chapter 1.5).
7929 @end itemize
7930 @end ignore
7931
7932 @item Tuple Values
7933 A tuple is specified by @code{<mode name>[<tuple>]}, where @code{<mode
7934 name>} can be omitted if the mode of the tuple is unambiguous. This
7935 unambiguity is derived from the context of a evaluated expression.
7936 @code{<tuple>} can be one of the following:
7937
7938 @itemize @bullet
7939 @item @emph{Powerset Tuple}
7940 @item @emph{Array Tuple}
7941 @item @emph{Structure Tuple}
7942 Powerset tuples, array tuples and structure tuples are specified in the
7943 same manner as in Chill programs refer to z200/88 chpt 5.2.5.
7944 @end itemize
7945
7946 @item String Element Value
7947 A string element value is specified by
7948 @smallexample
7949 @code{<string value>(<index>)}
7950 @end smallexample
7951 where @code{<index>} is a integer expression. It delivers a character
7952 value which is equivalent to the character indexed by @code{<index>} in
7953 the string.
7954
7955 @item String Slice Value
7956 A string slice value is specified by @code{<string value>(<slice
7957 spec>)}, where @code{<slice spec>} can be either a range of integer
7958 expressions or specified by @code{<start expr> up <size>}.
7959 @code{<size>} denotes the number of elements which the slice contains.
7960 The delivered value is a string value, which is part of the specified
7961 string.
7962
7963 @item Array Element Values
7964 An array element value is specified by @code{<array value>(<expr>)} and
7965 delivers a array element value of the mode of the specified array.
7966
7967 @item Array Slice Values
7968 An array slice is specified by @code{<array value>(<slice spec>)}, where
7969 @code{<slice spec>} can be either a range specified by expressions or by
7970 @code{<start expr> up <size>}. @code{<size>} denotes the number of
7971 arrayelements the slice contains. The delivered value is an array value
7972 which is part of the specified array.
7973
7974 @item Structure Field Values
7975 A structure field value is derived by @code{<structure value>.<field
7976 name>}, where @code{<field name>} indicates the name of a field specified
7977 in the mode definition of the structure. The mode of the delivered value
7978 corresponds to this mode definition in the structure definition.
7979
7980 @item Procedure Call Value
7981 The procedure call value is derived from the return value of the
7982 procedure@footnote{If a procedure call is used for instance in an
7983 expression, then this procedure is called with all its side
7984 effects. This can lead to confusing results if used carelessly.}.
7985
7986 Values of duration mode locations are represented by @code{ULONG} literals.
7987
7988 Values of time mode locations appear as
7989 @smallexample
7990 @code{TIME(<secs>:<nsecs>)}
7991 @end smallexample
7992
7993
7994 @ignore
7995 This is not implemented yet:
7996 @item Built-in Value
7997 @noindent
7998 The following built in functions are provided:
7999
8000 @table @code
8001 @item @code{ADDR()}
8002 @item @code{NUM()}
8003 @item @code{PRED()}
8004 @item @code{SUCC()}
8005 @item @code{ABS()}
8006 @item @code{CARD()}
8007 @item @code{MAX()}
8008 @item @code{MIN()}
8009 @item @code{SIZE()}
8010 @item @code{UPPER()}
8011 @item @code{LOWER()}
8012 @item @code{LENGTH()}
8013 @item @code{SIN()}
8014 @item @code{COS()}
8015 @item @code{TAN()}
8016 @item @code{ARCSIN()}
8017 @item @code{ARCCOS()}
8018 @item @code{ARCTAN()}
8019 @item @code{EXP()}
8020 @item @code{LN()}
8021 @item @code{LOG()}
8022 @item @code{SQRT()}
8023 @end table
8024
8025 For a detailed description refer to the GNU Chill implementation manual
8026 chapter 1.6.
8027 @end ignore
8028
8029 @item Zero-adic Operator Value
8030 The zero-adic operator value is derived from the instance value for the
8031 current active process.
8032
8033 @item Expression Values
8034 The value delivered by an expression is the result of the evaluation of
8035 the specified expression. If there are error conditions (mode
8036 incompatibility, etc.) the evaluation of expressions is aborted with a
8037 corresponding error message. Expressions may be parenthesised which
8038 causes the evaluation of this expression before any other expression
8039 which uses the result of the parenthesised expression. The following
8040 operators are supported by @value{GDBN}:
8041
8042 @table @code
8043 @item @code{OR, ORIF, XOR}
8044 @itemx @code{AND, ANDIF}
8045 @itemx @code{NOT}
8046 Logical operators defined over operands of boolean mode.
8047
8048 @item @code{=, /=}
8049 Equality and inequality operators defined over all modes.
8050
8051 @item @code{>, >=}
8052 @itemx @code{<, <=}
8053 Relational operators defined over predefined modes.
8054
8055 @item @code{+, -}
8056 @itemx @code{*, /, MOD, REM}
8057 Arithmetic operators defined over predefined modes.
8058
8059 @item @code{-}
8060 Change sign operator.
8061
8062 @item @code{//}
8063 String concatenation operator.
8064
8065 @item @code{()}
8066 String repetition operator.
8067
8068 @item @code{->}
8069 Referenced location operator which can be used either to take the
8070 address of a location (@code{->loc}), or to dereference a reference
8071 location (@code{loc->}).
8072
8073 @item @code{OR, XOR}
8074 @itemx @code{AND}
8075 @itemx @code{NOT}
8076 Powerset and bitstring operators.
8077
8078 @item @code{>, >=}
8079 @itemx @code{<, <=}
8080 Powerset inclusion operators.
8081
8082 @item @code{IN}
8083 Membership operator.
8084 @end table
8085 @end table
8086
8087 @node Chill type and range checks
8088 @subsubsection Chill type and range checks
8089
8090 @value{GDBN} considers two Chill variables mode equivalent if the sizes
8091 of the two modes are equal. This rule applies recursively to more
8092 complex datatypes which means that complex modes are treated
8093 equivalent if all element modes (which also can be complex modes like
8094 structures, arrays, etc.) have the same size.
8095
8096 Range checking is done on all mathematical operations, assignment, array
8097 index bounds and all built in procedures.
8098
8099 Strong type checks are forced using the @value{GDBN} command @code{set
8100 check strong}. This enforces strong type and range checks on all
8101 operations where Chill constructs are used (expressions, built in
8102 functions, etc.) in respect to the semantics as defined in the z.200
8103 language specification.
8104
8105 All checks can be disabled by the @value{GDBN} command @code{set check
8106 off}.
8107
8108 @ignore
8109 @c Deviations from the Chill Standard Z200/88
8110 see last paragraph ?
8111 @end ignore
8112
8113 @node Chill defaults
8114 @subsubsection Chill defaults
8115
8116 If type and range checking are set automatically by @value{GDBN}, they
8117 both default to @code{on} whenever the working language changes to
8118 Chill. This happens regardless of whether you or @value{GDBN}
8119 selected the working language.
8120
8121 If you allow @value{GDBN} to set the language automatically, then entering
8122 code compiled from a file whose name ends with @file{.ch} sets the
8123 working language to Chill. @xref{Automatically, ,Having @value{GDBN} set
8124 the language automatically}, for further details.
8125
8126 @node Symbols
8127 @chapter Examining the Symbol Table
8128
8129 The commands described in this chapter allow you to inquire about the
8130 symbols (names of variables, functions and types) defined in your
8131 program. This information is inherent in the text of your program and
8132 does not change as your program executes. @value{GDBN} finds it in your
8133 program's symbol table, in the file indicated when you started @value{GDBN}
8134 (@pxref{File Options, ,Choosing files}), or by one of the
8135 file-management commands (@pxref{Files, ,Commands to specify files}).
8136
8137 @cindex symbol names
8138 @cindex names of symbols
8139 @cindex quoting names
8140 Occasionally, you may need to refer to symbols that contain unusual
8141 characters, which @value{GDBN} ordinarily treats as word delimiters. The
8142 most frequent case is in referring to static variables in other
8143 source files (@pxref{Variables,,Program variables}). File names
8144 are recorded in object files as debugging symbols, but @value{GDBN} would
8145 ordinarily parse a typical file name, like @file{foo.c}, as the three words
8146 @samp{foo} @samp{.} @samp{c}. To allow @value{GDBN} to recognize
8147 @samp{foo.c} as a single symbol, enclose it in single quotes; for example,
8148
8149 @example
8150 p 'foo.c'::x
8151 @end example
8152
8153 @noindent
8154 looks up the value of @code{x} in the scope of the file @file{foo.c}.
8155
8156 @table @code
8157 @kindex info address
8158 @cindex address of a symbol
8159 @item info address @var{symbol}
8160 Describe where the data for @var{symbol} is stored. For a register
8161 variable, this says which register it is kept in. For a non-register
8162 local variable, this prints the stack-frame offset at which the variable
8163 is always stored.
8164
8165 Note the contrast with @samp{print &@var{symbol}}, which does not work
8166 at all for a register variable, and for a stack local variable prints
8167 the exact address of the current instantiation of the variable.
8168
8169 @kindex info symbol
8170 @cindex symbol from address
8171 @item info symbol @var{addr}
8172 Print the name of a symbol which is stored at the address @var{addr}.
8173 If no symbol is stored exactly at @var{addr}, @value{GDBN} prints the
8174 nearest symbol and an offset from it:
8175
8176 @example
8177 (@value{GDBP}) info symbol 0x54320
8178 _initialize_vx + 396 in section .text
8179 @end example
8180
8181 @noindent
8182 This is the opposite of the @code{info address} command. You can use
8183 it to find out the name of a variable or a function given its address.
8184
8185 @kindex whatis
8186 @item whatis @var{expr}
8187 Print the data type of expression @var{expr}. @var{expr} is not
8188 actually evaluated, and any side-effecting operations (such as
8189 assignments or function calls) inside it do not take place.
8190 @xref{Expressions, ,Expressions}.
8191
8192 @item whatis
8193 Print the data type of @code{$}, the last value in the value history.
8194
8195 @kindex ptype
8196 @item ptype @var{typename}
8197 Print a description of data type @var{typename}. @var{typename} may be
8198 the name of a type, or for C code it may have the form @samp{class
8199 @var{class-name}}, @samp{struct @var{struct-tag}}, @samp{union
8200 @var{union-tag}} or @samp{enum @var{enum-tag}}.
8201
8202 @item ptype @var{expr}
8203 @itemx ptype
8204 Print a description of the type of expression @var{expr}. @code{ptype}
8205 differs from @code{whatis} by printing a detailed description, instead
8206 of just the name of the type.
8207
8208 For example, for this variable declaration:
8209
8210 @example
8211 struct complex @{double real; double imag;@} v;
8212 @end example
8213
8214 @noindent
8215 the two commands give this output:
8216
8217 @example
8218 @group
8219 (@value{GDBP}) whatis v
8220 type = struct complex
8221 (@value{GDBP}) ptype v
8222 type = struct complex @{
8223 double real;
8224 double imag;
8225 @}
8226 @end group
8227 @end example
8228
8229 @noindent
8230 As with @code{whatis}, using @code{ptype} without an argument refers to
8231 the type of @code{$}, the last value in the value history.
8232
8233 @kindex info types
8234 @item info types @var{regexp}
8235 @itemx info types
8236 Print a brief description of all types whose names match @var{regexp}
8237 (or all types in your program, if you supply no argument). Each
8238 complete typename is matched as though it were a complete line; thus,
8239 @samp{i type value} gives information on all types in your program whose
8240 names include the string @code{value}, but @samp{i type ^value$} gives
8241 information only on types whose complete name is @code{value}.
8242
8243 This command differs from @code{ptype} in two ways: first, like
8244 @code{whatis}, it does not print a detailed description; second, it
8245 lists all source files where a type is defined.
8246
8247 @kindex info scope
8248 @cindex local variables
8249 @item info scope @var{addr}
8250 List all the variables local to a particular scope. This command
8251 accepts a location---a function name, a source line, or an address
8252 preceded by a @samp{*}, and prints all the variables local to the
8253 scope defined by that location. For example:
8254
8255 @smallexample
8256 (@value{GDBP}) @b{info scope command_line_handler}
8257 Scope for command_line_handler:
8258 Symbol rl is an argument at stack/frame offset 8, length 4.
8259 Symbol linebuffer is in static storage at address 0x150a18, length 4.
8260 Symbol linelength is in static storage at address 0x150a1c, length 4.
8261 Symbol p is a local variable in register $esi, length 4.
8262 Symbol p1 is a local variable in register $ebx, length 4.
8263 Symbol nline is a local variable in register $edx, length 4.
8264 Symbol repeat is a local variable at frame offset -8, length 4.
8265 @end smallexample
8266
8267 @noindent
8268 This command is especially useful for determining what data to collect
8269 during a @dfn{trace experiment}, see @ref{Tracepoint Actions,
8270 collect}.
8271
8272 @kindex info source
8273 @item info source
8274 Show the name of the current source file---that is, the source file for
8275 the function containing the current point of execution---and the language
8276 it was written in.
8277
8278 @kindex info sources
8279 @item info sources
8280 Print the names of all source files in your program for which there is
8281 debugging information, organized into two lists: files whose symbols
8282 have already been read, and files whose symbols will be read when needed.
8283
8284 @kindex info functions
8285 @item info functions
8286 Print the names and data types of all defined functions.
8287
8288 @item info functions @var{regexp}
8289 Print the names and data types of all defined functions
8290 whose names contain a match for regular expression @var{regexp}.
8291 Thus, @samp{info fun step} finds all functions whose names
8292 include @code{step}; @samp{info fun ^step} finds those whose names
8293 start with @code{step}.
8294
8295 @kindex info variables
8296 @item info variables
8297 Print the names and data types of all variables that are declared
8298 outside of functions (i.e., excluding local variables).
8299
8300 @item info variables @var{regexp}
8301 Print the names and data types of all variables (except for local
8302 variables) whose names contain a match for regular expression
8303 @var{regexp}.
8304
8305 @ignore
8306 This was never implemented.
8307 @kindex info methods
8308 @item info methods
8309 @itemx info methods @var{regexp}
8310 The @code{info methods} command permits the user to examine all defined
8311 methods within C@t{++} program, or (with the @var{regexp} argument) a
8312 specific set of methods found in the various C@t{++} classes. Many
8313 C@t{++} classes provide a large number of methods. Thus, the output
8314 from the @code{ptype} command can be overwhelming and hard to use. The
8315 @code{info-methods} command filters the methods, printing only those
8316 which match the regular-expression @var{regexp}.
8317 @end ignore
8318
8319 @cindex reloading symbols
8320 Some systems allow individual object files that make up your program to
8321 be replaced without stopping and restarting your program. For example,
8322 in VxWorks you can simply recompile a defective object file and keep on
8323 running. If you are running on one of these systems, you can allow
8324 @value{GDBN} to reload the symbols for automatically relinked modules:
8325
8326 @table @code
8327 @kindex set symbol-reloading
8328 @item set symbol-reloading on
8329 Replace symbol definitions for the corresponding source file when an
8330 object file with a particular name is seen again.
8331
8332 @item set symbol-reloading off
8333 Do not replace symbol definitions when encountering object files of the
8334 same name more than once. This is the default state; if you are not
8335 running on a system that permits automatic relinking of modules, you
8336 should leave @code{symbol-reloading} off, since otherwise @value{GDBN}
8337 may discard symbols when linking large programs, that may contain
8338 several modules (from different directories or libraries) with the same
8339 name.
8340
8341 @kindex show symbol-reloading
8342 @item show symbol-reloading
8343 Show the current @code{on} or @code{off} setting.
8344 @end table
8345
8346 @kindex set opaque-type-resolution
8347 @item set opaque-type-resolution on
8348 Tell @value{GDBN} to resolve opaque types. An opaque type is a type
8349 declared as a pointer to a @code{struct}, @code{class}, or
8350 @code{union}---for example, @code{struct MyType *}---that is used in one
8351 source file although the full declaration of @code{struct MyType} is in
8352 another source file. The default is on.
8353
8354 A change in the setting of this subcommand will not take effect until
8355 the next time symbols for a file are loaded.
8356
8357 @item set opaque-type-resolution off
8358 Tell @value{GDBN} not to resolve opaque types. In this case, the type
8359 is printed as follows:
8360 @smallexample
8361 @{<no data fields>@}
8362 @end smallexample
8363
8364 @kindex show opaque-type-resolution
8365 @item show opaque-type-resolution
8366 Show whether opaque types are resolved or not.
8367
8368 @kindex maint print symbols
8369 @cindex symbol dump
8370 @kindex maint print psymbols
8371 @cindex partial symbol dump
8372 @item maint print symbols @var{filename}
8373 @itemx maint print psymbols @var{filename}
8374 @itemx maint print msymbols @var{filename}
8375 Write a dump of debugging symbol data into the file @var{filename}.
8376 These commands are used to debug the @value{GDBN} symbol-reading code. Only
8377 symbols with debugging data are included. If you use @samp{maint print
8378 symbols}, @value{GDBN} includes all the symbols for which it has already
8379 collected full details: that is, @var{filename} reflects symbols for
8380 only those files whose symbols @value{GDBN} has read. You can use the
8381 command @code{info sources} to find out which files these are. If you
8382 use @samp{maint print psymbols} instead, the dump shows information about
8383 symbols that @value{GDBN} only knows partially---that is, symbols defined in
8384 files that @value{GDBN} has skimmed, but not yet read completely. Finally,
8385 @samp{maint print msymbols} dumps just the minimal symbol information
8386 required for each object file from which @value{GDBN} has read some symbols.
8387 @xref{Files, ,Commands to specify files}, for a discussion of how
8388 @value{GDBN} reads symbols (in the description of @code{symbol-file}).
8389 @end table
8390
8391 @node Altering
8392 @chapter Altering Execution
8393
8394 Once you think you have found an error in your program, you might want to
8395 find out for certain whether correcting the apparent error would lead to
8396 correct results in the rest of the run. You can find the answer by
8397 experiment, using the @value{GDBN} features for altering execution of the
8398 program.
8399
8400 For example, you can store new values into variables or memory
8401 locations, give your program a signal, restart it at a different
8402 address, or even return prematurely from a function.
8403
8404 @menu
8405 * Assignment:: Assignment to variables
8406 * Jumping:: Continuing at a different address
8407 * Signaling:: Giving your program a signal
8408 * Returning:: Returning from a function
8409 * Calling:: Calling your program's functions
8410 * Patching:: Patching your program
8411 @end menu
8412
8413 @node Assignment
8414 @section Assignment to variables
8415
8416 @cindex assignment
8417 @cindex setting variables
8418 To alter the value of a variable, evaluate an assignment expression.
8419 @xref{Expressions, ,Expressions}. For example,
8420
8421 @example
8422 print x=4
8423 @end example
8424
8425 @noindent
8426 stores the value 4 into the variable @code{x}, and then prints the
8427 value of the assignment expression (which is 4).
8428 @xref{Languages, ,Using @value{GDBN} with Different Languages}, for more
8429 information on operators in supported languages.
8430
8431 @kindex set variable
8432 @cindex variables, setting
8433 If you are not interested in seeing the value of the assignment, use the
8434 @code{set} command instead of the @code{print} command. @code{set} is
8435 really the same as @code{print} except that the expression's value is
8436 not printed and is not put in the value history (@pxref{Value History,
8437 ,Value history}). The expression is evaluated only for its effects.
8438
8439 If the beginning of the argument string of the @code{set} command
8440 appears identical to a @code{set} subcommand, use the @code{set
8441 variable} command instead of just @code{set}. This command is identical
8442 to @code{set} except for its lack of subcommands. For example, if your
8443 program has a variable @code{width}, you get an error if you try to set
8444 a new value with just @samp{set width=13}, because @value{GDBN} has the
8445 command @code{set width}:
8446
8447 @example
8448 (@value{GDBP}) whatis width
8449 type = double
8450 (@value{GDBP}) p width
8451 $4 = 13
8452 (@value{GDBP}) set width=47
8453 Invalid syntax in expression.
8454 @end example
8455
8456 @noindent
8457 The invalid expression, of course, is @samp{=47}. In
8458 order to actually set the program's variable @code{width}, use
8459
8460 @example
8461 (@value{GDBP}) set var width=47
8462 @end example
8463
8464 Because the @code{set} command has many subcommands that can conflict
8465 with the names of program variables, it is a good idea to use the
8466 @code{set variable} command instead of just @code{set}. For example, if
8467 your program has a variable @code{g}, you run into problems if you try
8468 to set a new value with just @samp{set g=4}, because @value{GDBN} has
8469 the command @code{set gnutarget}, abbreviated @code{set g}:
8470
8471 @example
8472 @group
8473 (@value{GDBP}) whatis g
8474 type = double
8475 (@value{GDBP}) p g
8476 $1 = 1
8477 (@value{GDBP}) set g=4
8478 (@value{GDBP}) p g
8479 $2 = 1
8480 (@value{GDBP}) r
8481 The program being debugged has been started already.
8482 Start it from the beginning? (y or n) y
8483 Starting program: /home/smith/cc_progs/a.out
8484 "/home/smith/cc_progs/a.out": can't open to read symbols:
8485 Invalid bfd target.
8486 (@value{GDBP}) show g
8487 The current BFD target is "=4".
8488 @end group
8489 @end example
8490
8491 @noindent
8492 The program variable @code{g} did not change, and you silently set the
8493 @code{gnutarget} to an invalid value. In order to set the variable
8494 @code{g}, use
8495
8496 @example
8497 (@value{GDBP}) set var g=4
8498 @end example
8499
8500 @value{GDBN} allows more implicit conversions in assignments than C; you can
8501 freely store an integer value into a pointer variable or vice versa,
8502 and you can convert any structure to any other structure that is the
8503 same length or shorter.
8504 @comment FIXME: how do structs align/pad in these conversions?
8505 @comment /doc@cygnus.com 18dec1990
8506
8507 To store values into arbitrary places in memory, use the @samp{@{@dots{}@}}
8508 construct to generate a value of specified type at a specified address
8509 (@pxref{Expressions, ,Expressions}). For example, @code{@{int@}0x83040} refers
8510 to memory location @code{0x83040} as an integer (which implies a certain size
8511 and representation in memory), and
8512
8513 @example
8514 set @{int@}0x83040 = 4
8515 @end example
8516
8517 @noindent
8518 stores the value 4 into that memory location.
8519
8520 @node Jumping
8521 @section Continuing at a different address
8522
8523 Ordinarily, when you continue your program, you do so at the place where
8524 it stopped, with the @code{continue} command. You can instead continue at
8525 an address of your own choosing, with the following commands:
8526
8527 @table @code
8528 @kindex jump
8529 @item jump @var{linespec}
8530 Resume execution at line @var{linespec}. Execution stops again
8531 immediately if there is a breakpoint there. @xref{List, ,Printing
8532 source lines}, for a description of the different forms of
8533 @var{linespec}. It is common practice to use the @code{tbreak} command
8534 in conjunction with @code{jump}. @xref{Set Breaks, ,Setting
8535 breakpoints}.
8536
8537 The @code{jump} command does not change the current stack frame, or
8538 the stack pointer, or the contents of any memory location or any
8539 register other than the program counter. If line @var{linespec} is in
8540 a different function from the one currently executing, the results may
8541 be bizarre if the two functions expect different patterns of arguments or
8542 of local variables. For this reason, the @code{jump} command requests
8543 confirmation if the specified line is not in the function currently
8544 executing. However, even bizarre results are predictable if you are
8545 well acquainted with the machine-language code of your program.
8546
8547 @item jump *@var{address}
8548 Resume execution at the instruction at address @var{address}.
8549 @end table
8550
8551 @c Doesn't work on HP-UX; have to set $pcoqh and $pcoqt.
8552 On many systems, you can get much the same effect as the @code{jump}
8553 command by storing a new value into the register @code{$pc}. The
8554 difference is that this does not start your program running; it only
8555 changes the address of where it @emph{will} run when you continue. For
8556 example,
8557
8558 @example
8559 set $pc = 0x485
8560 @end example
8561
8562 @noindent
8563 makes the next @code{continue} command or stepping command execute at
8564 address @code{0x485}, rather than at the address where your program stopped.
8565 @xref{Continuing and Stepping, ,Continuing and stepping}.
8566
8567 The most common occasion to use the @code{jump} command is to back
8568 up---perhaps with more breakpoints set---over a portion of a program
8569 that has already executed, in order to examine its execution in more
8570 detail.
8571
8572 @c @group
8573 @node Signaling
8574 @section Giving your program a signal
8575
8576 @table @code
8577 @kindex signal
8578 @item signal @var{signal}
8579 Resume execution where your program stopped, but immediately give it the
8580 signal @var{signal}. @var{signal} can be the name or the number of a
8581 signal. For example, on many systems @code{signal 2} and @code{signal
8582 SIGINT} are both ways of sending an interrupt signal.
8583
8584 Alternatively, if @var{signal} is zero, continue execution without
8585 giving a signal. This is useful when your program stopped on account of
8586 a signal and would ordinary see the signal when resumed with the
8587 @code{continue} command; @samp{signal 0} causes it to resume without a
8588 signal.
8589
8590 @code{signal} does not repeat when you press @key{RET} a second time
8591 after executing the command.
8592 @end table
8593 @c @end group
8594
8595 Invoking the @code{signal} command is not the same as invoking the
8596 @code{kill} utility from the shell. Sending a signal with @code{kill}
8597 causes @value{GDBN} to decide what to do with the signal depending on
8598 the signal handling tables (@pxref{Signals}). The @code{signal} command
8599 passes the signal directly to your program.
8600
8601
8602 @node Returning
8603 @section Returning from a function
8604
8605 @table @code
8606 @cindex returning from a function
8607 @kindex return
8608 @item return
8609 @itemx return @var{expression}
8610 You can cancel execution of a function call with the @code{return}
8611 command. If you give an
8612 @var{expression} argument, its value is used as the function's return
8613 value.
8614 @end table
8615
8616 When you use @code{return}, @value{GDBN} discards the selected stack frame
8617 (and all frames within it). You can think of this as making the
8618 discarded frame return prematurely. If you wish to specify a value to
8619 be returned, give that value as the argument to @code{return}.
8620
8621 This pops the selected stack frame (@pxref{Selection, ,Selecting a
8622 frame}), and any other frames inside of it, leaving its caller as the
8623 innermost remaining frame. That frame becomes selected. The
8624 specified value is stored in the registers used for returning values
8625 of functions.
8626
8627 The @code{return} command does not resume execution; it leaves the
8628 program stopped in the state that would exist if the function had just
8629 returned. In contrast, the @code{finish} command (@pxref{Continuing
8630 and Stepping, ,Continuing and stepping}) resumes execution until the
8631 selected stack frame returns naturally.
8632
8633 @node Calling
8634 @section Calling program functions
8635
8636 @cindex calling functions
8637 @kindex call
8638 @table @code
8639 @item call @var{expr}
8640 Evaluate the expression @var{expr} without displaying @code{void}
8641 returned values.
8642 @end table
8643
8644 You can use this variant of the @code{print} command if you want to
8645 execute a function from your program, but without cluttering the output
8646 with @code{void} returned values. If the result is not void, it
8647 is printed and saved in the value history.
8648
8649 For the A29K, a user-controlled variable @code{call_scratch_address},
8650 specifies the location of a scratch area to be used when @value{GDBN}
8651 calls a function in the target. This is necessary because the usual
8652 method of putting the scratch area on the stack does not work in systems
8653 that have separate instruction and data spaces.
8654
8655 @node Patching
8656 @section Patching programs
8657
8658 @cindex patching binaries
8659 @cindex writing into executables
8660 @cindex writing into corefiles
8661
8662 By default, @value{GDBN} opens the file containing your program's
8663 executable code (or the corefile) read-only. This prevents accidental
8664 alterations to machine code; but it also prevents you from intentionally
8665 patching your program's binary.
8666
8667 If you'd like to be able to patch the binary, you can specify that
8668 explicitly with the @code{set write} command. For example, you might
8669 want to turn on internal debugging flags, or even to make emergency
8670 repairs.
8671
8672 @table @code
8673 @kindex set write
8674 @item set write on
8675 @itemx set write off
8676 If you specify @samp{set write on}, @value{GDBN} opens executable and
8677 core files for both reading and writing; if you specify @samp{set write
8678 off} (the default), @value{GDBN} opens them read-only.
8679
8680 If you have already loaded a file, you must load it again (using the
8681 @code{exec-file} or @code{core-file} command) after changing @code{set
8682 write}, for your new setting to take effect.
8683
8684 @item show write
8685 @kindex show write
8686 Display whether executable files and core files are opened for writing
8687 as well as reading.
8688 @end table
8689
8690 @node GDB Files
8691 @chapter @value{GDBN} Files
8692
8693 @value{GDBN} needs to know the file name of the program to be debugged,
8694 both in order to read its symbol table and in order to start your
8695 program. To debug a core dump of a previous run, you must also tell
8696 @value{GDBN} the name of the core dump file.
8697
8698 @menu
8699 * Files:: Commands to specify files
8700 * Symbol Errors:: Errors reading symbol files
8701 @end menu
8702
8703 @node Files
8704 @section Commands to specify files
8705
8706 @cindex symbol table
8707 @cindex core dump file
8708
8709 You may want to specify executable and core dump file names. The usual
8710 way to do this is at start-up time, using the arguments to
8711 @value{GDBN}'s start-up commands (@pxref{Invocation, , Getting In and
8712 Out of @value{GDBN}}).
8713
8714 Occasionally it is necessary to change to a different file during a
8715 @value{GDBN} session. Or you may run @value{GDBN} and forget to specify
8716 a file you want to use. In these situations the @value{GDBN} commands
8717 to specify new files are useful.
8718
8719 @table @code
8720 @cindex executable file
8721 @kindex file
8722 @item file @var{filename}
8723 Use @var{filename} as the program to be debugged. It is read for its
8724 symbols and for the contents of pure memory. It is also the program
8725 executed when you use the @code{run} command. If you do not specify a
8726 directory and the file is not found in the @value{GDBN} working directory,
8727 @value{GDBN} uses the environment variable @code{PATH} as a list of
8728 directories to search, just as the shell does when looking for a program
8729 to run. You can change the value of this variable, for both @value{GDBN}
8730 and your program, using the @code{path} command.
8731
8732 On systems with memory-mapped files, an auxiliary file named
8733 @file{@var{filename}.syms} may hold symbol table information for
8734 @var{filename}. If so, @value{GDBN} maps in the symbol table from
8735 @file{@var{filename}.syms}, starting up more quickly. See the
8736 descriptions of the file options @samp{-mapped} and @samp{-readnow}
8737 (available on the command line, and with the commands @code{file},
8738 @code{symbol-file}, or @code{add-symbol-file}, described below),
8739 for more information.
8740
8741 @item file
8742 @code{file} with no argument makes @value{GDBN} discard any information it
8743 has on both executable file and the symbol table.
8744
8745 @kindex exec-file
8746 @item exec-file @r{[} @var{filename} @r{]}
8747 Specify that the program to be run (but not the symbol table) is found
8748 in @var{filename}. @value{GDBN} searches the environment variable @code{PATH}
8749 if necessary to locate your program. Omitting @var{filename} means to
8750 discard information on the executable file.
8751
8752 @kindex symbol-file
8753 @item symbol-file @r{[} @var{filename} @r{]}
8754 Read symbol table information from file @var{filename}. @code{PATH} is
8755 searched when necessary. Use the @code{file} command to get both symbol
8756 table and program to run from the same file.
8757
8758 @code{symbol-file} with no argument clears out @value{GDBN} information on your
8759 program's symbol table.
8760
8761 The @code{symbol-file} command causes @value{GDBN} to forget the contents
8762 of its convenience variables, the value history, and all breakpoints and
8763 auto-display expressions. This is because they may contain pointers to
8764 the internal data recording symbols and data types, which are part of
8765 the old symbol table data being discarded inside @value{GDBN}.
8766
8767 @code{symbol-file} does not repeat if you press @key{RET} again after
8768 executing it once.
8769
8770 When @value{GDBN} is configured for a particular environment, it
8771 understands debugging information in whatever format is the standard
8772 generated for that environment; you may use either a @sc{gnu} compiler, or
8773 other compilers that adhere to the local conventions.
8774 Best results are usually obtained from @sc{gnu} compilers; for example,
8775 using @code{@value{GCC}} you can generate debugging information for
8776 optimized code.
8777
8778 For most kinds of object files, with the exception of old SVR3 systems
8779 using COFF, the @code{symbol-file} command does not normally read the
8780 symbol table in full right away. Instead, it scans the symbol table
8781 quickly to find which source files and which symbols are present. The
8782 details are read later, one source file at a time, as they are needed.
8783
8784 The purpose of this two-stage reading strategy is to make @value{GDBN}
8785 start up faster. For the most part, it is invisible except for
8786 occasional pauses while the symbol table details for a particular source
8787 file are being read. (The @code{set verbose} command can turn these
8788 pauses into messages if desired. @xref{Messages/Warnings, ,Optional
8789 warnings and messages}.)
8790
8791 We have not implemented the two-stage strategy for COFF yet. When the
8792 symbol table is stored in COFF format, @code{symbol-file} reads the
8793 symbol table data in full right away. Note that ``stabs-in-COFF''
8794 still does the two-stage strategy, since the debug info is actually
8795 in stabs format.
8796
8797 @kindex readnow
8798 @cindex reading symbols immediately
8799 @cindex symbols, reading immediately
8800 @kindex mapped
8801 @cindex memory-mapped symbol file
8802 @cindex saving symbol table
8803 @item symbol-file @var{filename} @r{[} -readnow @r{]} @r{[} -mapped @r{]}
8804 @itemx file @var{filename} @r{[} -readnow @r{]} @r{[} -mapped @r{]}
8805 You can override the @value{GDBN} two-stage strategy for reading symbol
8806 tables by using the @samp{-readnow} option with any of the commands that
8807 load symbol table information, if you want to be sure @value{GDBN} has the
8808 entire symbol table available.
8809
8810 If memory-mapped files are available on your system through the
8811 @code{mmap} system call, you can use another option, @samp{-mapped}, to
8812 cause @value{GDBN} to write the symbols for your program into a reusable
8813 file. Future @value{GDBN} debugging sessions map in symbol information
8814 from this auxiliary symbol file (if the program has not changed), rather
8815 than spending time reading the symbol table from the executable
8816 program. Using the @samp{-mapped} option has the same effect as
8817 starting @value{GDBN} with the @samp{-mapped} command-line option.
8818
8819 You can use both options together, to make sure the auxiliary symbol
8820 file has all the symbol information for your program.
8821
8822 The auxiliary symbol file for a program called @var{myprog} is called
8823 @samp{@var{myprog}.syms}. Once this file exists (so long as it is newer
8824 than the corresponding executable), @value{GDBN} always attempts to use
8825 it when you debug @var{myprog}; no special options or commands are
8826 needed.
8827
8828 The @file{.syms} file is specific to the host machine where you run
8829 @value{GDBN}. It holds an exact image of the internal @value{GDBN}
8830 symbol table. It cannot be shared across multiple host platforms.
8831
8832 @c FIXME: for now no mention of directories, since this seems to be in
8833 @c flux. 13mar1992 status is that in theory GDB would look either in
8834 @c current dir or in same dir as myprog; but issues like competing
8835 @c GDB's, or clutter in system dirs, mean that in practice right now
8836 @c only current dir is used. FFish says maybe a special GDB hierarchy
8837 @c (eg rooted in val of env var GDBSYMS) could exist for mappable symbol
8838 @c files.
8839
8840 @kindex core
8841 @kindex core-file
8842 @item core-file @r{[} @var{filename} @r{]}
8843 Specify the whereabouts of a core dump file to be used as the ``contents
8844 of memory''. Traditionally, core files contain only some parts of the
8845 address space of the process that generated them; @value{GDBN} can access the
8846 executable file itself for other parts.
8847
8848 @code{core-file} with no argument specifies that no core file is
8849 to be used.
8850
8851 Note that the core file is ignored when your program is actually running
8852 under @value{GDBN}. So, if you have been running your program and you
8853 wish to debug a core file instead, you must kill the subprocess in which
8854 the program is running. To do this, use the @code{kill} command
8855 (@pxref{Kill Process, ,Killing the child process}).
8856
8857 @kindex add-symbol-file
8858 @cindex dynamic linking
8859 @item add-symbol-file @var{filename} @var{address}
8860 @itemx add-symbol-file @var{filename} @var{address} @r{[} -readnow @r{]} @r{[} -mapped @r{]}
8861 @itemx add-symbol-file @var{filename} @r{-s}@var{section} @var{address} @dots{}
8862 The @code{add-symbol-file} command reads additional symbol table
8863 information from the file @var{filename}. You would use this command
8864 when @var{filename} has been dynamically loaded (by some other means)
8865 into the program that is running. @var{address} should be the memory
8866 address at which the file has been loaded; @value{GDBN} cannot figure
8867 this out for itself. You can additionally specify an arbitrary number
8868 of @samp{@r{-s}@var{section} @var{address}} pairs, to give an explicit
8869 section name and base address for that section. You can specify any
8870 @var{address} as an expression.
8871
8872 The symbol table of the file @var{filename} is added to the symbol table
8873 originally read with the @code{symbol-file} command. You can use the
8874 @code{add-symbol-file} command any number of times; the new symbol data
8875 thus read keeps adding to the old. To discard all old symbol data
8876 instead, use the @code{symbol-file} command without any arguments.
8877
8878 @cindex relocatable object files, reading symbols from
8879 @cindex object files, relocatable, reading symbols from
8880 @cindex reading symbols from relocatable object files
8881 @cindex symbols, reading from relocatable object files
8882 @cindex @file{.o} files, reading symbols from
8883 Although @var{filename} is typically a shared library file, an
8884 executable file, or some other object file which has been fully
8885 relocated for loading into a process, you can also load symbolic
8886 information from relocatable @file{.o} files, as long as:
8887
8888 @itemize @bullet
8889 @item
8890 the file's symbolic information refers only to linker symbols defined in
8891 that file, not to symbols defined by other object files,
8892 @item
8893 every section the file's symbolic information refers to has actually
8894 been loaded into the inferior, as it appears in the file, and
8895 @item
8896 you can determine the address at which every section was loaded, and
8897 provide these to the @code{add-symbol-file} command.
8898 @end itemize
8899
8900 @noindent
8901 Some embedded operating systems, like Sun Chorus and VxWorks, can load
8902 relocatable files into an already running program; such systems
8903 typically make the requirements above easy to meet. However, it's
8904 important to recognize that many native systems use complex link
8905 procedures (@code{.linkonce} section factoring and C++ constructor table
8906 assembly, for example) that make the requirements difficult to meet. In
8907 general, one cannot assume that using @code{add-symbol-file} to read a
8908 relocatable object file's symbolic information will have the same effect
8909 as linking the relocatable object file into the program in the normal
8910 way.
8911
8912 @code{add-symbol-file} does not repeat if you press @key{RET} after using it.
8913
8914 You can use the @samp{-mapped} and @samp{-readnow} options just as with
8915 the @code{symbol-file} command, to change how @value{GDBN} manages the symbol
8916 table information for @var{filename}.
8917
8918 @kindex add-shared-symbol-file
8919 @item add-shared-symbol-file
8920 The @code{add-shared-symbol-file} command can be used only under Harris' CXUX
8921 operating system for the Motorola 88k. @value{GDBN} automatically looks for
8922 shared libraries, however if @value{GDBN} does not find yours, you can run
8923 @code{add-shared-symbol-file}. It takes no arguments.
8924
8925 @kindex section
8926 @item section
8927 The @code{section} command changes the base address of section SECTION of
8928 the exec file to ADDR. This can be used if the exec file does not contain
8929 section addresses, (such as in the a.out format), or when the addresses
8930 specified in the file itself are wrong. Each section must be changed
8931 separately. The @code{info files} command, described below, lists all
8932 the sections and their addresses.
8933
8934 @kindex info files
8935 @kindex info target
8936 @item info files
8937 @itemx info target
8938 @code{info files} and @code{info target} are synonymous; both print the
8939 current target (@pxref{Targets, ,Specifying a Debugging Target}),
8940 including the names of the executable and core dump files currently in
8941 use by @value{GDBN}, and the files from which symbols were loaded. The
8942 command @code{help target} lists all possible targets rather than
8943 current ones.
8944
8945 @end table
8946
8947 All file-specifying commands allow both absolute and relative file names
8948 as arguments. @value{GDBN} always converts the file name to an absolute file
8949 name and remembers it that way.
8950
8951 @cindex shared libraries
8952 @value{GDBN} supports HP-UX, SunOS, SVr4, Irix 5, and IBM RS/6000 shared
8953 libraries.
8954
8955 @value{GDBN} automatically loads symbol definitions from shared libraries
8956 when you use the @code{run} command, or when you examine a core file.
8957 (Before you issue the @code{run} command, @value{GDBN} does not understand
8958 references to a function in a shared library, however---unless you are
8959 debugging a core file).
8960
8961 On HP-UX, if the program loads a library explicitly, @value{GDBN}
8962 automatically loads the symbols at the time of the @code{shl_load} call.
8963
8964 @c FIXME: some @value{GDBN} release may permit some refs to undef
8965 @c FIXME...symbols---eg in a break cmd---assuming they are from a shared
8966 @c FIXME...lib; check this from time to time when updating manual
8967
8968 There are times, however, when you may wish to not automatically load
8969 symbol definitions from shared libraries, such as when they are
8970 particularly large or there are many of them.
8971
8972 To control the automatic loading of shared library symbols, use the
8973 commands:
8974
8975 @table @code
8976 @kindex set auto-solib-add
8977 @item set auto-solib-add @var{mode}
8978 If @var{mode} is @code{on}, symbols from all shared object libraries
8979 will be loaded automatically when the inferior begins execution, you
8980 attach to an independently started inferior, or when the dynamic linker
8981 informs @value{GDBN} that a new library has been loaded. If @var{mode}
8982 is @code{off}, symbols must be loaded manually, using the
8983 @code{sharedlibrary} command. The default value is @code{on}.
8984
8985 @kindex show auto-solib-add
8986 @item show auto-solib-add
8987 Display the current autoloading mode.
8988 @end table
8989
8990 To explicitly load shared library symbols, use the @code{sharedlibrary}
8991 command:
8992
8993 @table @code
8994 @kindex info sharedlibrary
8995 @kindex info share
8996 @item info share
8997 @itemx info sharedlibrary
8998 Print the names of the shared libraries which are currently loaded.
8999
9000 @kindex sharedlibrary
9001 @kindex share
9002 @item sharedlibrary @var{regex}
9003 @itemx share @var{regex}
9004 Load shared object library symbols for files matching a
9005 Unix regular expression.
9006 As with files loaded automatically, it only loads shared libraries
9007 required by your program for a core file or after typing @code{run}. If
9008 @var{regex} is omitted all shared libraries required by your program are
9009 loaded.
9010 @end table
9011
9012 On some systems, such as HP-UX systems, @value{GDBN} supports
9013 autoloading shared library symbols until a limiting threshold size is
9014 reached. This provides the benefit of allowing autoloading to remain on
9015 by default, but avoids autoloading excessively large shared libraries,
9016 up to a threshold that is initially set, but which you can modify if you
9017 wish.
9018
9019 Beyond that threshold, symbols from shared libraries must be explicitly
9020 loaded. To load these symbols, use the command @code{sharedlibrary
9021 @var{filename}}. The base address of the shared library is determined
9022 automatically by @value{GDBN} and need not be specified.
9023
9024 To display or set the threshold, use the commands:
9025
9026 @table @code
9027 @kindex set auto-solib-limit
9028 @item set auto-solib-limit @var{threshold}
9029 Set the autoloading size threshold, in an integral number of megabytes.
9030 If @var{threshold} is nonzero and shared library autoloading is enabled,
9031 symbols from all shared object libraries will be loaded until the total
9032 size of the loaded shared library symbols exceeds this threshold.
9033 Otherwise, symbols must be loaded manually, using the
9034 @code{sharedlibrary} command. The default threshold is 100 (i.e. 100
9035 Mb).
9036
9037 @kindex show auto-solib-limit
9038 @item show auto-solib-limit
9039 Display the current autoloading size threshold, in megabytes.
9040 @end table
9041
9042 @node Symbol Errors
9043 @section Errors reading symbol files
9044
9045 While reading a symbol file, @value{GDBN} occasionally encounters problems,
9046 such as symbol types it does not recognize, or known bugs in compiler
9047 output. By default, @value{GDBN} does not notify you of such problems, since
9048 they are relatively common and primarily of interest to people
9049 debugging compilers. If you are interested in seeing information
9050 about ill-constructed symbol tables, you can either ask @value{GDBN} to print
9051 only one message about each such type of problem, no matter how many
9052 times the problem occurs; or you can ask @value{GDBN} to print more messages,
9053 to see how many times the problems occur, with the @code{set
9054 complaints} command (@pxref{Messages/Warnings, ,Optional warnings and
9055 messages}).
9056
9057 The messages currently printed, and their meanings, include:
9058
9059 @table @code
9060 @item inner block not inside outer block in @var{symbol}
9061
9062 The symbol information shows where symbol scopes begin and end
9063 (such as at the start of a function or a block of statements). This
9064 error indicates that an inner scope block is not fully contained
9065 in its outer scope blocks.
9066
9067 @value{GDBN} circumvents the problem by treating the inner block as if it had
9068 the same scope as the outer block. In the error message, @var{symbol}
9069 may be shown as ``@code{(don't know)}'' if the outer block is not a
9070 function.
9071
9072 @item block at @var{address} out of order
9073
9074 The symbol information for symbol scope blocks should occur in
9075 order of increasing addresses. This error indicates that it does not
9076 do so.
9077
9078 @value{GDBN} does not circumvent this problem, and has trouble
9079 locating symbols in the source file whose symbols it is reading. (You
9080 can often determine what source file is affected by specifying
9081 @code{set verbose on}. @xref{Messages/Warnings, ,Optional warnings and
9082 messages}.)
9083
9084 @item bad block start address patched
9085
9086 The symbol information for a symbol scope block has a start address
9087 smaller than the address of the preceding source line. This is known
9088 to occur in the SunOS 4.1.1 (and earlier) C compiler.
9089
9090 @value{GDBN} circumvents the problem by treating the symbol scope block as
9091 starting on the previous source line.
9092
9093 @item bad string table offset in symbol @var{n}
9094
9095 @cindex foo
9096 Symbol number @var{n} contains a pointer into the string table which is
9097 larger than the size of the string table.
9098
9099 @value{GDBN} circumvents the problem by considering the symbol to have the
9100 name @code{foo}, which may cause other problems if many symbols end up
9101 with this name.
9102
9103 @item unknown symbol type @code{0x@var{nn}}
9104
9105 The symbol information contains new data types that @value{GDBN} does
9106 not yet know how to read. @code{0x@var{nn}} is the symbol type of the
9107 uncomprehended information, in hexadecimal.
9108
9109 @value{GDBN} circumvents the error by ignoring this symbol information.
9110 This usually allows you to debug your program, though certain symbols
9111 are not accessible. If you encounter such a problem and feel like
9112 debugging it, you can debug @code{@value{GDBP}} with itself, breakpoint
9113 on @code{complain}, then go up to the function @code{read_dbx_symtab}
9114 and examine @code{*bufp} to see the symbol.
9115
9116 @item stub type has NULL name
9117
9118 @value{GDBN} could not find the full definition for a struct or class.
9119
9120 @item const/volatile indicator missing (ok if using g++ v1.x), got@dots{}
9121 The symbol information for a C@t{++} member function is missing some
9122 information that recent versions of the compiler should have output for
9123 it.
9124
9125 @item info mismatch between compiler and debugger
9126
9127 @value{GDBN} could not parse a type specification output by the compiler.
9128
9129 @end table
9130
9131 @node Targets
9132 @chapter Specifying a Debugging Target
9133
9134 @cindex debugging target
9135 @kindex target
9136
9137 A @dfn{target} is the execution environment occupied by your program.
9138
9139 Often, @value{GDBN} runs in the same host environment as your program;
9140 in that case, the debugging target is specified as a side effect when
9141 you use the @code{file} or @code{core} commands. When you need more
9142 flexibility---for example, running @value{GDBN} on a physically separate
9143 host, or controlling a standalone system over a serial port or a
9144 realtime system over a TCP/IP connection---you can use the @code{target}
9145 command to specify one of the target types configured for @value{GDBN}
9146 (@pxref{Target Commands, ,Commands for managing targets}).
9147
9148 @menu
9149 * Active Targets:: Active targets
9150 * Target Commands:: Commands for managing targets
9151 * Byte Order:: Choosing target byte order
9152 * Remote:: Remote debugging
9153 * KOD:: Kernel Object Display
9154
9155 @end menu
9156
9157 @node Active Targets
9158 @section Active targets
9159
9160 @cindex stacking targets
9161 @cindex active targets
9162 @cindex multiple targets
9163
9164 There are three classes of targets: processes, core files, and
9165 executable files. @value{GDBN} can work concurrently on up to three
9166 active targets, one in each class. This allows you to (for example)
9167 start a process and inspect its activity without abandoning your work on
9168 a core file.
9169
9170 For example, if you execute @samp{gdb a.out}, then the executable file
9171 @code{a.out} is the only active target. If you designate a core file as
9172 well---presumably from a prior run that crashed and coredumped---then
9173 @value{GDBN} has two active targets and uses them in tandem, looking
9174 first in the corefile target, then in the executable file, to satisfy
9175 requests for memory addresses. (Typically, these two classes of target
9176 are complementary, since core files contain only a program's
9177 read-write memory---variables and so on---plus machine status, while
9178 executable files contain only the program text and initialized data.)
9179
9180 When you type @code{run}, your executable file becomes an active process
9181 target as well. When a process target is active, all @value{GDBN}
9182 commands requesting memory addresses refer to that target; addresses in
9183 an active core file or executable file target are obscured while the
9184 process target is active.
9185
9186 Use the @code{core-file} and @code{exec-file} commands to select a new
9187 core file or executable target (@pxref{Files, ,Commands to specify
9188 files}). To specify as a target a process that is already running, use
9189 the @code{attach} command (@pxref{Attach, ,Debugging an already-running
9190 process}).
9191
9192 @node Target Commands
9193 @section Commands for managing targets
9194
9195 @table @code
9196 @item target @var{type} @var{parameters}
9197 Connects the @value{GDBN} host environment to a target machine or
9198 process. A target is typically a protocol for talking to debugging
9199 facilities. You use the argument @var{type} to specify the type or
9200 protocol of the target machine.
9201
9202 Further @var{parameters} are interpreted by the target protocol, but
9203 typically include things like device names or host names to connect
9204 with, process numbers, and baud rates.
9205
9206 The @code{target} command does not repeat if you press @key{RET} again
9207 after executing the command.
9208
9209 @kindex help target
9210 @item help target
9211 Displays the names of all targets available. To display targets
9212 currently selected, use either @code{info target} or @code{info files}
9213 (@pxref{Files, ,Commands to specify files}).
9214
9215 @item help target @var{name}
9216 Describe a particular target, including any parameters necessary to
9217 select it.
9218
9219 @kindex set gnutarget
9220 @item set gnutarget @var{args}
9221 @value{GDBN} uses its own library BFD to read your files. @value{GDBN}
9222 knows whether it is reading an @dfn{executable},
9223 a @dfn{core}, or a @dfn{.o} file; however, you can specify the file format
9224 with the @code{set gnutarget} command. Unlike most @code{target} commands,
9225 with @code{gnutarget} the @code{target} refers to a program, not a machine.
9226
9227 @quotation
9228 @emph{Warning:} To specify a file format with @code{set gnutarget},
9229 you must know the actual BFD name.
9230 @end quotation
9231
9232 @noindent
9233 @xref{Files, , Commands to specify files}.
9234
9235 @kindex show gnutarget
9236 @item show gnutarget
9237 Use the @code{show gnutarget} command to display what file format
9238 @code{gnutarget} is set to read. If you have not set @code{gnutarget},
9239 @value{GDBN} will determine the file format for each file automatically,
9240 and @code{show gnutarget} displays @samp{The current BDF target is "auto"}.
9241 @end table
9242
9243 Here are some common targets (available, or not, depending on the GDB
9244 configuration):
9245
9246 @table @code
9247 @kindex target exec
9248 @item target exec @var{program}
9249 An executable file. @samp{target exec @var{program}} is the same as
9250 @samp{exec-file @var{program}}.
9251
9252 @kindex target core
9253 @item target core @var{filename}
9254 A core dump file. @samp{target core @var{filename}} is the same as
9255 @samp{core-file @var{filename}}.
9256
9257 @kindex target remote
9258 @item target remote @var{dev}
9259 Remote serial target in GDB-specific protocol. The argument @var{dev}
9260 specifies what serial device to use for the connection (e.g.
9261 @file{/dev/ttya}). @xref{Remote, ,Remote debugging}. @code{target remote}
9262 supports the @code{load} command. This is only useful if you have
9263 some other way of getting the stub to the target system, and you can put
9264 it somewhere in memory where it won't get clobbered by the download.
9265
9266 @kindex target sim
9267 @item target sim
9268 Builtin CPU simulator. @value{GDBN} includes simulators for most architectures.
9269 In general,
9270 @example
9271 target sim
9272 load
9273 run
9274 @end example
9275 @noindent
9276 works; however, you cannot assume that a specific memory map, device
9277 drivers, or even basic I/O is available, although some simulators do
9278 provide these. For info about any processor-specific simulator details,
9279 see the appropriate section in @ref{Embedded Processors, ,Embedded
9280 Processors}.
9281
9282 @end table
9283
9284 Some configurations may include these targets as well:
9285
9286 @table @code
9287
9288 @kindex target nrom
9289 @item target nrom @var{dev}
9290 NetROM ROM emulator. This target only supports downloading.
9291
9292 @end table
9293
9294 Different targets are available on different configurations of @value{GDBN};
9295 your configuration may have more or fewer targets.
9296
9297 Many remote targets require you to download the executable's code
9298 once you've successfully established a connection.
9299
9300 @table @code
9301
9302 @kindex load @var{filename}
9303 @item load @var{filename}
9304 Depending on what remote debugging facilities are configured into
9305 @value{GDBN}, the @code{load} command may be available. Where it exists, it
9306 is meant to make @var{filename} (an executable) available for debugging
9307 on the remote system---by downloading, or dynamic linking, for example.
9308 @code{load} also records the @var{filename} symbol table in @value{GDBN}, like
9309 the @code{add-symbol-file} command.
9310
9311 If your @value{GDBN} does not have a @code{load} command, attempting to
9312 execute it gets the error message ``@code{You can't do that when your
9313 target is @dots{}}''
9314
9315 The file is loaded at whatever address is specified in the executable.
9316 For some object file formats, you can specify the load address when you
9317 link the program; for other formats, like a.out, the object file format
9318 specifies a fixed address.
9319 @c FIXME! This would be a good place for an xref to the GNU linker doc.
9320
9321 @code{load} does not repeat if you press @key{RET} again after using it.
9322 @end table
9323
9324 @node Byte Order
9325 @section Choosing target byte order
9326
9327 @cindex choosing target byte order
9328 @cindex target byte order
9329
9330 Some types of processors, such as the MIPS, PowerPC, and Hitachi SH,
9331 offer the ability to run either big-endian or little-endian byte
9332 orders. Usually the executable or symbol will include a bit to
9333 designate the endian-ness, and you will not need to worry about
9334 which to use. However, you may still find it useful to adjust
9335 @value{GDBN}'s idea of processor endian-ness manually.
9336
9337 @table @code
9338 @kindex set endian big
9339 @item set endian big
9340 Instruct @value{GDBN} to assume the target is big-endian.
9341
9342 @kindex set endian little
9343 @item set endian little
9344 Instruct @value{GDBN} to assume the target is little-endian.
9345
9346 @kindex set endian auto
9347 @item set endian auto
9348 Instruct @value{GDBN} to use the byte order associated with the
9349 executable.
9350
9351 @item show endian
9352 Display @value{GDBN}'s current idea of the target byte order.
9353
9354 @end table
9355
9356 Note that these commands merely adjust interpretation of symbolic
9357 data on the host, and that they have absolutely no effect on the
9358 target system.
9359
9360 @node Remote
9361 @section Remote debugging
9362 @cindex remote debugging
9363
9364 If you are trying to debug a program running on a machine that cannot run
9365 @value{GDBN} in the usual way, it is often useful to use remote debugging.
9366 For example, you might use remote debugging on an operating system kernel,
9367 or on a small system which does not have a general purpose operating system
9368 powerful enough to run a full-featured debugger.
9369
9370 Some configurations of @value{GDBN} have special serial or TCP/IP interfaces
9371 to make this work with particular debugging targets. In addition,
9372 @value{GDBN} comes with a generic serial protocol (specific to @value{GDBN},
9373 but not specific to any particular target system) which you can use if you
9374 write the remote stubs---the code that runs on the remote system to
9375 communicate with @value{GDBN}.
9376
9377 Other remote targets may be available in your
9378 configuration of @value{GDBN}; use @code{help target} to list them.
9379
9380 @menu
9381 * Remote Serial:: @value{GDBN} remote serial protocol
9382 @end menu
9383
9384 @node Remote Serial
9385 @subsection The @value{GDBN} remote serial protocol
9386
9387 @cindex remote serial debugging, overview
9388 To debug a program running on another machine (the debugging
9389 @dfn{target} machine), you must first arrange for all the usual
9390 prerequisites for the program to run by itself. For example, for a C
9391 program, you need:
9392
9393 @enumerate
9394 @item
9395 A startup routine to set up the C runtime environment; these usually
9396 have a name like @file{crt0}. The startup routine may be supplied by
9397 your hardware supplier, or you may have to write your own.
9398
9399 @item
9400 A C subroutine library to support your program's
9401 subroutine calls, notably managing input and output.
9402
9403 @item
9404 A way of getting your program to the other machine---for example, a
9405 download program. These are often supplied by the hardware
9406 manufacturer, but you may have to write your own from hardware
9407 documentation.
9408 @end enumerate
9409
9410 The next step is to arrange for your program to use a serial port to
9411 communicate with the machine where @value{GDBN} is running (the @dfn{host}
9412 machine). In general terms, the scheme looks like this:
9413
9414 @table @emph
9415 @item On the host,
9416 @value{GDBN} already understands how to use this protocol; when everything
9417 else is set up, you can simply use the @samp{target remote} command
9418 (@pxref{Targets,,Specifying a Debugging Target}).
9419
9420 @item On the target,
9421 you must link with your program a few special-purpose subroutines that
9422 implement the @value{GDBN} remote serial protocol. The file containing these
9423 subroutines is called a @dfn{debugging stub}.
9424
9425 On certain remote targets, you can use an auxiliary program
9426 @code{gdbserver} instead of linking a stub into your program.
9427 @xref{Server,,Using the @code{gdbserver} program}, for details.
9428 @end table
9429
9430 The debugging stub is specific to the architecture of the remote
9431 machine; for example, use @file{sparc-stub.c} to debug programs on
9432 @sc{sparc} boards.
9433
9434 @cindex remote serial stub list
9435 These working remote stubs are distributed with @value{GDBN}:
9436
9437 @table @code
9438
9439 @item i386-stub.c
9440 @cindex @file{i386-stub.c}
9441 @cindex Intel
9442 @cindex i386
9443 For Intel 386 and compatible architectures.
9444
9445 @item m68k-stub.c
9446 @cindex @file{m68k-stub.c}
9447 @cindex Motorola 680x0
9448 @cindex m680x0
9449 For Motorola 680x0 architectures.
9450
9451 @item sh-stub.c
9452 @cindex @file{sh-stub.c}
9453 @cindex Hitachi
9454 @cindex SH
9455 For Hitachi SH architectures.
9456
9457 @item sparc-stub.c
9458 @cindex @file{sparc-stub.c}
9459 @cindex Sparc
9460 For @sc{sparc} architectures.
9461
9462 @item sparcl-stub.c
9463 @cindex @file{sparcl-stub.c}
9464 @cindex Fujitsu
9465 @cindex SparcLite
9466 For Fujitsu @sc{sparclite} architectures.
9467
9468 @end table
9469
9470 The @file{README} file in the @value{GDBN} distribution may list other
9471 recently added stubs.
9472
9473 @menu
9474 * Stub Contents:: What the stub can do for you
9475 * Bootstrapping:: What you must do for the stub
9476 * Debug Session:: Putting it all together
9477 * Protocol:: Definition of the communication protocol
9478 * Server:: Using the `gdbserver' program
9479 * NetWare:: Using the `gdbserve.nlm' program
9480 @end menu
9481
9482 @node Stub Contents
9483 @subsubsection What the stub can do for you
9484
9485 @cindex remote serial stub
9486 The debugging stub for your architecture supplies these three
9487 subroutines:
9488
9489 @table @code
9490 @item set_debug_traps
9491 @kindex set_debug_traps
9492 @cindex remote serial stub, initialization
9493 This routine arranges for @code{handle_exception} to run when your
9494 program stops. You must call this subroutine explicitly near the
9495 beginning of your program.
9496
9497 @item handle_exception
9498 @kindex handle_exception
9499 @cindex remote serial stub, main routine
9500 This is the central workhorse, but your program never calls it
9501 explicitly---the setup code arranges for @code{handle_exception} to
9502 run when a trap is triggered.
9503
9504 @code{handle_exception} takes control when your program stops during
9505 execution (for example, on a breakpoint), and mediates communications
9506 with @value{GDBN} on the host machine. This is where the communications
9507 protocol is implemented; @code{handle_exception} acts as the @value{GDBN}
9508 representative on the target machine. It begins by sending summary
9509 information on the state of your program, then continues to execute,
9510 retrieving and transmitting any information @value{GDBN} needs, until you
9511 execute a @value{GDBN} command that makes your program resume; at that point,
9512 @code{handle_exception} returns control to your own code on the target
9513 machine.
9514
9515 @item breakpoint
9516 @cindex @code{breakpoint} subroutine, remote
9517 Use this auxiliary subroutine to make your program contain a
9518 breakpoint. Depending on the particular situation, this may be the only
9519 way for @value{GDBN} to get control. For instance, if your target
9520 machine has some sort of interrupt button, you won't need to call this;
9521 pressing the interrupt button transfers control to
9522 @code{handle_exception}---in effect, to @value{GDBN}. On some machines,
9523 simply receiving characters on the serial port may also trigger a trap;
9524 again, in that situation, you don't need to call @code{breakpoint} from
9525 your own program---simply running @samp{target remote} from the host
9526 @value{GDBN} session gets control.
9527
9528 Call @code{breakpoint} if none of these is true, or if you simply want
9529 to make certain your program stops at a predetermined point for the
9530 start of your debugging session.
9531 @end table
9532
9533 @node Bootstrapping
9534 @subsubsection What you must do for the stub
9535
9536 @cindex remote stub, support routines
9537 The debugging stubs that come with @value{GDBN} are set up for a particular
9538 chip architecture, but they have no information about the rest of your
9539 debugging target machine.
9540
9541 First of all you need to tell the stub how to communicate with the
9542 serial port.
9543
9544 @table @code
9545 @item int getDebugChar()
9546 @kindex getDebugChar
9547 Write this subroutine to read a single character from the serial port.
9548 It may be identical to @code{getchar} for your target system; a
9549 different name is used to allow you to distinguish the two if you wish.
9550
9551 @item void putDebugChar(int)
9552 @kindex putDebugChar
9553 Write this subroutine to write a single character to the serial port.
9554 It may be identical to @code{putchar} for your target system; a
9555 different name is used to allow you to distinguish the two if you wish.
9556 @end table
9557
9558 @cindex control C, and remote debugging
9559 @cindex interrupting remote targets
9560 If you want @value{GDBN} to be able to stop your program while it is
9561 running, you need to use an interrupt-driven serial driver, and arrange
9562 for it to stop when it receives a @code{^C} (@samp{\003}, the control-C
9563 character). That is the character which @value{GDBN} uses to tell the
9564 remote system to stop.
9565
9566 Getting the debugging target to return the proper status to @value{GDBN}
9567 probably requires changes to the standard stub; one quick and dirty way
9568 is to just execute a breakpoint instruction (the ``dirty'' part is that
9569 @value{GDBN} reports a @code{SIGTRAP} instead of a @code{SIGINT}).
9570
9571 Other routines you need to supply are:
9572
9573 @table @code
9574 @item void exceptionHandler (int @var{exception_number}, void *@var{exception_address})
9575 @kindex exceptionHandler
9576 Write this function to install @var{exception_address} in the exception
9577 handling tables. You need to do this because the stub does not have any
9578 way of knowing what the exception handling tables on your target system
9579 are like (for example, the processor's table might be in @sc{rom},
9580 containing entries which point to a table in @sc{ram}).
9581 @var{exception_number} is the exception number which should be changed;
9582 its meaning is architecture-dependent (for example, different numbers
9583 might represent divide by zero, misaligned access, etc). When this
9584 exception occurs, control should be transferred directly to
9585 @var{exception_address}, and the processor state (stack, registers,
9586 and so on) should be just as it is when a processor exception occurs. So if
9587 you want to use a jump instruction to reach @var{exception_address}, it
9588 should be a simple jump, not a jump to subroutine.
9589
9590 For the 386, @var{exception_address} should be installed as an interrupt
9591 gate so that interrupts are masked while the handler runs. The gate
9592 should be at privilege level 0 (the most privileged level). The
9593 @sc{sparc} and 68k stubs are able to mask interrupts themselves without
9594 help from @code{exceptionHandler}.
9595
9596 @item void flush_i_cache()
9597 @kindex flush_i_cache
9598 On @sc{sparc} and @sc{sparclite} only, write this subroutine to flush the
9599 instruction cache, if any, on your target machine. If there is no
9600 instruction cache, this subroutine may be a no-op.
9601
9602 On target machines that have instruction caches, @value{GDBN} requires this
9603 function to make certain that the state of your program is stable.
9604 @end table
9605
9606 @noindent
9607 You must also make sure this library routine is available:
9608
9609 @table @code
9610 @item void *memset(void *, int, int)
9611 @kindex memset
9612 This is the standard library function @code{memset} that sets an area of
9613 memory to a known value. If you have one of the free versions of
9614 @code{libc.a}, @code{memset} can be found there; otherwise, you must
9615 either obtain it from your hardware manufacturer, or write your own.
9616 @end table
9617
9618 If you do not use the GNU C compiler, you may need other standard
9619 library subroutines as well; this varies from one stub to another,
9620 but in general the stubs are likely to use any of the common library
9621 subroutines which @code{@value{GCC}} generates as inline code.
9622
9623
9624 @node Debug Session
9625 @subsubsection Putting it all together
9626
9627 @cindex remote serial debugging summary
9628 In summary, when your program is ready to debug, you must follow these
9629 steps.
9630
9631 @enumerate
9632 @item
9633 Make sure you have defined the supporting low-level routines
9634 (@pxref{Bootstrapping,,What you must do for the stub}):
9635 @display
9636 @code{getDebugChar}, @code{putDebugChar},
9637 @code{flush_i_cache}, @code{memset}, @code{exceptionHandler}.
9638 @end display
9639
9640 @item
9641 Insert these lines near the top of your program:
9642
9643 @example
9644 set_debug_traps();
9645 breakpoint();
9646 @end example
9647
9648 @item
9649 For the 680x0 stub only, you need to provide a variable called
9650 @code{exceptionHook}. Normally you just use:
9651
9652 @example
9653 void (*exceptionHook)() = 0;
9654 @end example
9655
9656 @noindent
9657 but if before calling @code{set_debug_traps}, you set it to point to a
9658 function in your program, that function is called when
9659 @code{@value{GDBN}} continues after stopping on a trap (for example, bus
9660 error). The function indicated by @code{exceptionHook} is called with
9661 one parameter: an @code{int} which is the exception number.
9662
9663 @item
9664 Compile and link together: your program, the @value{GDBN} debugging stub for
9665 your target architecture, and the supporting subroutines.
9666
9667 @item
9668 Make sure you have a serial connection between your target machine and
9669 the @value{GDBN} host, and identify the serial port on the host.
9670
9671 @item
9672 @c The "remote" target now provides a `load' command, so we should
9673 @c document that. FIXME.
9674 Download your program to your target machine (or get it there by
9675 whatever means the manufacturer provides), and start it.
9676
9677 @item
9678 To start remote debugging, run @value{GDBN} on the host machine, and specify
9679 as an executable file the program that is running in the remote machine.
9680 This tells @value{GDBN} how to find your program's symbols and the contents
9681 of its pure text.
9682
9683 @item
9684 @cindex serial line, @code{target remote}
9685 Establish communication using the @code{target remote} command.
9686 Its argument specifies how to communicate with the target
9687 machine---either via a devicename attached to a direct serial line, or a
9688 TCP port (usually to a terminal server which in turn has a serial line
9689 to the target). For example, to use a serial line connected to the
9690 device named @file{/dev/ttyb}:
9691
9692 @example
9693 target remote /dev/ttyb
9694 @end example
9695
9696 @cindex TCP port, @code{target remote}
9697 To use a TCP connection, use an argument of the form
9698 @code{@var{host}:port}. For example, to connect to port 2828 on a
9699 terminal server named @code{manyfarms}:
9700
9701 @example
9702 target remote manyfarms:2828
9703 @end example
9704
9705 If your remote target is actually running on the same machine as
9706 your debugger session (e.g.@: a simulator of your target running on
9707 the same host), you can omit the hostname. For example, to connect
9708 to port 1234 on your local machine:
9709
9710 @example
9711 target remote :1234
9712 @end example
9713 @noindent
9714
9715 Note that the colon is still required here.
9716 @end enumerate
9717
9718 Now you can use all the usual commands to examine and change data and to
9719 step and continue the remote program.
9720
9721 To resume the remote program and stop debugging it, use the @code{detach}
9722 command.
9723
9724 @cindex interrupting remote programs
9725 @cindex remote programs, interrupting
9726 Whenever @value{GDBN} is waiting for the remote program, if you type the
9727 interrupt character (often @key{C-C}), @value{GDBN} attempts to stop the
9728 program. This may or may not succeed, depending in part on the hardware
9729 and the serial drivers the remote system uses. If you type the
9730 interrupt character once again, @value{GDBN} displays this prompt:
9731
9732 @example
9733 Interrupted while waiting for the program.
9734 Give up (and stop debugging it)? (y or n)
9735 @end example
9736
9737 If you type @kbd{y}, @value{GDBN} abandons the remote debugging session.
9738 (If you decide you want to try again later, you can use @samp{target
9739 remote} again to connect once more.) If you type @kbd{n}, @value{GDBN}
9740 goes back to waiting.
9741
9742 @node Protocol
9743 @subsubsection Communication protocol
9744
9745 @cindex debugging stub, example
9746 @cindex remote stub, example
9747 @cindex stub example, remote debugging
9748 The stub files provided with @value{GDBN} implement the target side of the
9749 communication protocol, and the @value{GDBN} side is implemented in the
9750 @value{GDBN} source file @file{remote.c}. Normally, you can simply allow
9751 these subroutines to communicate, and ignore the details. (If you're
9752 implementing your own stub file, you can still ignore the details: start
9753 with one of the existing stub files. @file{sparc-stub.c} is the best
9754 organized, and therefore the easiest to read.)
9755
9756 However, there may be occasions when you need to know something about
9757 the protocol---for example, if there is only one serial port to your
9758 target machine, you might want your program to do something special if
9759 it recognizes a packet meant for @value{GDBN}.
9760
9761 In the examples below, @samp{<-} and @samp{->} are used to indicate
9762 transmitted and received data respectfully.
9763
9764 @cindex protocol, @value{GDBN} remote serial
9765 @cindex serial protocol, @value{GDBN} remote
9766 @cindex remote serial protocol
9767 All @value{GDBN} commands and responses (other than acknowledgments) are
9768 sent as a @var{packet}. A @var{packet} is introduced with the character
9769 @samp{$}, the actual @var{packet-data}, and the terminating character
9770 @samp{#} followed by a two-digit @var{checksum}:
9771
9772 @example
9773 @code{$}@var{packet-data}@code{#}@var{checksum}
9774 @end example
9775 @noindent
9776
9777 @cindex checksum, for @value{GDBN} remote
9778 @noindent
9779 The two-digit @var{checksum} is computed as the modulo 256 sum of all
9780 characters between the leading @samp{$} and the trailing @samp{#} (an
9781 eight bit unsigned checksum).
9782
9783 Implementors should note that prior to @value{GDBN} 5.0 the protocol
9784 specification also included an optional two-digit @var{sequence-id}:
9785
9786 @example
9787 @code{$}@var{sequence-id}@code{:}@var{packet-data}@code{#}@var{checksum}
9788 @end example
9789
9790 @cindex sequence-id, for @value{GDBN} remote
9791 @noindent
9792 That @var{sequence-id} was appended to the acknowledgment. @value{GDBN}
9793 has never output @var{sequence-id}s. Stubs that handle packets added
9794 since @value{GDBN} 5.0 must not accept @var{sequence-id}.
9795
9796 @cindex acknowledgment, for @value{GDBN} remote
9797 When either the host or the target machine receives a packet, the first
9798 response expected is an acknowledgment: either @samp{+} (to indicate
9799 the package was received correctly) or @samp{-} (to request
9800 retransmission):
9801
9802 @example
9803 <- @code{$}@var{packet-data}@code{#}@var{checksum}
9804 -> @code{+}
9805 @end example
9806 @noindent
9807
9808 The host (@value{GDBN}) sends @var{command}s, and the target (the
9809 debugging stub incorporated in your program) sends a @var{response}. In
9810 the case of step and continue @var{command}s, the response is only sent
9811 when the operation has completed (the target has again stopped).
9812
9813 @var{packet-data} consists of a sequence of characters with the
9814 exception of @samp{#} and @samp{$} (see @samp{X} packet for additional
9815 exceptions).
9816
9817 Fields within the packet should be separated using @samp{,} @samp{;} or
9818 @samp{:}. Except where otherwise noted all numbers are represented in
9819 HEX with leading zeros suppressed.
9820
9821 Implementors should note that prior to @value{GDBN} 5.0, the character
9822 @samp{:} could not appear as the third character in a packet (as it
9823 would potentially conflict with the @var{sequence-id}).
9824
9825 Response @var{data} can be run-length encoded to save space. A @samp{*}
9826 means that the next character is an @sc{ascii} encoding giving a repeat count
9827 which stands for that many repetitions of the character preceding the
9828 @samp{*}. The encoding is @code{n+29}, yielding a printable character
9829 where @code{n >=3} (which is where rle starts to win). The printable
9830 characters @samp{$}, @samp{#}, @samp{+} and @samp{-} or with a numeric
9831 value greater than 126 should not be used.
9832
9833 Some remote systems have used a different run-length encoding mechanism
9834 loosely refered to as the cisco encoding. Following the @samp{*}
9835 character are two hex digits that indicate the size of the packet.
9836
9837 So:
9838 @example
9839 "@code{0* }"
9840 @end example
9841 @noindent
9842 means the same as "0000".
9843
9844 The error response returned for some packets includes a two character
9845 error number. That number is not well defined.
9846
9847 For any @var{command} not supported by the stub, an empty response
9848 (@samp{$#00}) should be returned. That way it is possible to extend the
9849 protocol. A newer @value{GDBN} can tell if a packet is supported based
9850 on that response.
9851
9852 A stub is required to support the @samp{g}, @samp{G}, @samp{m}, @samp{M},
9853 @samp{c}, and @samp{s} @var{command}s. All other @var{command}s are
9854 optional.
9855
9856 Below is a complete list of all currently defined @var{command}s and
9857 their corresponding response @var{data}:
9858 @page
9859 @multitable @columnfractions .30 .30 .40
9860 @item Packet
9861 @tab Request
9862 @tab Description
9863
9864 @item extended mode
9865 @tab @code{!}
9866 @tab
9867 Enable extended mode. In extended mode, the remote server is made
9868 persistent. The @samp{R} packet is used to restart the program being
9869 debugged.
9870 @item
9871 @tab reply @samp{OK}
9872 @tab
9873 The remote target both supports and has enabled extended mode.
9874
9875 @item last signal
9876 @tab @code{?}
9877 @tab
9878 Indicate the reason the target halted. The reply is the same as for step
9879 and continue.
9880 @item
9881 @tab reply
9882 @tab see below
9883
9884
9885 @item reserved
9886 @tab @code{a}
9887 @tab Reserved for future use
9888
9889 @item set program arguments @strong{(reserved)}
9890 @tab @code{A}@var{arglen}@code{,}@var{argnum}@code{,}@var{arg}@code{,...}
9891 @tab
9892 @item
9893 @tab
9894 @tab
9895 Initialized @samp{argv[]} array passed into program. @var{arglen}
9896 specifies the number of bytes in the hex encoded byte stream @var{arg}.
9897 See @file{gdbserver} for more details.
9898 @item
9899 @tab reply @code{OK}
9900 @item
9901 @tab reply @code{E}@var{NN}
9902
9903 @item set baud @strong{(deprecated)}
9904 @tab @code{b}@var{baud}
9905 @tab
9906 Change the serial line speed to @var{baud}. JTC: @emph{When does the
9907 transport layer state change? When it's received, or after the ACK is
9908 transmitted. In either case, there are problems if the command or the
9909 acknowledgment packet is dropped.} Stan: @emph{If people really wanted
9910 to add something like this, and get it working for the first time, they
9911 ought to modify ser-unix.c to send some kind of out-of-band message to a
9912 specially-setup stub and have the switch happen "in between" packets, so
9913 that from remote protocol's point of view, nothing actually
9914 happened.}
9915
9916 @item set breakpoint @strong{(deprecated)}
9917 @tab @code{B}@var{addr},@var{mode}
9918 @tab
9919 Set (@var{mode} is @samp{S}) or clear (@var{mode} is @samp{C}) a
9920 breakpoint at @var{addr}. @emph{This has been replaced by the @samp{Z} and
9921 @samp{z} packets.}
9922
9923 @item continue
9924 @tab @code{c}@var{addr}
9925 @tab
9926 @var{addr} is address to resume. If @var{addr} is omitted, resume at
9927 current address.
9928 @item
9929 @tab reply
9930 @tab see below
9931
9932 @item continue with signal
9933 @tab @code{C}@var{sig}@code{;}@var{addr}
9934 @tab
9935 Continue with signal @var{sig} (hex signal number). If
9936 @code{;}@var{addr} is omitted, resume at same address.
9937 @item
9938 @tab reply
9939 @tab see below
9940
9941 @item toggle debug @strong{(deprecated)}
9942 @tab @code{d}
9943 @tab
9944 toggle debug flag.
9945
9946 @item detach
9947 @tab @code{D}
9948 @tab
9949 Detach @value{GDBN} from the remote system. Sent to the remote target before
9950 @value{GDBN} disconnects.
9951 @item
9952 @tab reply @emph{no response}
9953 @tab
9954 @value{GDBN} does not check for any response after sending this packet.
9955
9956 @item reserved
9957 @tab @code{e}
9958 @tab Reserved for future use
9959
9960 @item reserved
9961 @tab @code{E}
9962 @tab Reserved for future use
9963
9964 @item reserved
9965 @tab @code{f}
9966 @tab Reserved for future use
9967
9968 @item reserved
9969 @tab @code{F}
9970 @tab Reserved for future use
9971
9972 @item read registers
9973 @tab @code{g}
9974 @tab Read general registers.
9975 @item
9976 @tab reply @var{XX...}
9977 @tab
9978 Each byte of register data is described by two hex digits. The bytes
9979 with the register are transmitted in target byte order. The size of
9980 each register and their position within the @samp{g} @var{packet} are
9981 determined by the @value{GDBN} internal macros @var{REGISTER_RAW_SIZE} and
9982 @var{REGISTER_NAME} macros. The specification of several standard
9983 @code{g} packets is specified below.
9984 @item
9985 @tab @code{E}@var{NN}
9986 @tab for an error.
9987
9988 @item write regs
9989 @tab @code{G}@var{XX...}
9990 @tab
9991 See @samp{g} for a description of the @var{XX...} data.
9992 @item
9993 @tab reply @code{OK}
9994 @tab for success
9995 @item
9996 @tab reply @code{E}@var{NN}
9997 @tab for an error
9998
9999 @item reserved
10000 @tab @code{h}
10001 @tab Reserved for future use
10002
10003 @item set thread
10004 @tab @code{H}@var{c}@var{t...}
10005 @tab
10006 Set thread for subsequent operations (@samp{m}, @samp{M}, @samp{g},
10007 @samp{G}, et.al.). @var{c} = @samp{c} for thread used in step and
10008 continue; @var{t...} can be -1 for all threads. @var{c} = @samp{g} for
10009 thread used in other operations. If zero, pick a thread, any thread.
10010 @item
10011 @tab reply @code{OK}
10012 @tab for success
10013 @item
10014 @tab reply @code{E}@var{NN}
10015 @tab for an error
10016
10017 @c FIXME: JTC:
10018 @c 'H': How restrictive (or permissive) is the thread model. If a
10019 @c thread is selected and stopped, are other threads allowed
10020 @c to continue to execute? As I mentioned above, I think the
10021 @c semantics of each command when a thread is selected must be
10022 @c described. For example:
10023 @c
10024 @c 'g': If the stub supports threads and a specific thread is
10025 @c selected, returns the register block from that thread;
10026 @c otherwise returns current registers.
10027 @c
10028 @c 'G' If the stub supports threads and a specific thread is
10029 @c selected, sets the registers of the register block of
10030 @c that thread; otherwise sets current registers.
10031
10032 @item cycle step @strong{(draft)}
10033 @tab @code{i}@var{addr}@code{,}@var{nnn}
10034 @tab
10035 Step the remote target by a single clock cycle. If @code{,}@var{nnn} is
10036 present, cycle step @var{nnn} cycles. If @var{addr} is present, cycle
10037 step starting at that address.
10038
10039 @item signal then cycle step @strong{(reserved)}
10040 @tab @code{I}
10041 @tab
10042 See @samp{i} and @samp{S} for likely syntax and semantics.
10043
10044 @item reserved
10045 @tab @code{j}
10046 @tab Reserved for future use
10047
10048 @item reserved
10049 @tab @code{J}
10050 @tab Reserved for future use
10051
10052 @item kill request
10053 @tab @code{k}
10054 @tab
10055 FIXME: @emph{There is no description of how operate when a specific
10056 thread context has been selected (ie. does 'k' kill only that thread?)}.
10057
10058 @item reserved
10059 @tab @code{l}
10060 @tab Reserved for future use
10061
10062 @item reserved
10063 @tab @code{L}
10064 @tab Reserved for future use
10065
10066 @item read memory
10067 @tab @code{m}@var{addr}@code{,}@var{length}
10068 @tab
10069 Read @var{length} bytes of memory starting at address @var{addr}.
10070 Neither @value{GDBN} nor the stub assume that sized memory transfers are assumed
10071 using word alligned accesses. FIXME: @emph{A word aligned memory
10072 transfer mechanism is needed.}
10073 @item
10074 @tab reply @var{XX...}
10075 @tab
10076 @var{XX...} is mem contents. Can be fewer bytes than requested if able
10077 to read only part of the data. Neither @value{GDBN} nor the stub assume that
10078 sized memory transfers are assumed using word alligned accesses. FIXME:
10079 @emph{A word aligned memory transfer mechanism is needed.}
10080 @item
10081 @tab reply @code{E}@var{NN}
10082 @tab @var{NN} is errno
10083
10084 @item write mem
10085 @tab @code{M}@var{addr},@var{length}@code{:}@var{XX...}
10086 @tab
10087 Write @var{length} bytes of memory starting at address @var{addr}.
10088 @var{XX...} is the data.
10089 @item
10090 @tab reply @code{OK}
10091 @tab for success
10092 @item
10093 @tab reply @code{E}@var{NN}
10094 @tab
10095 for an error (this includes the case where only part of the data was
10096 written).
10097
10098 @item reserved
10099 @tab @code{n}
10100 @tab Reserved for future use
10101
10102 @item reserved
10103 @tab @code{N}
10104 @tab Reserved for future use
10105
10106 @item reserved
10107 @tab @code{o}
10108 @tab Reserved for future use
10109
10110 @item reserved
10111 @tab @code{O}
10112 @tab Reserved for future use
10113
10114 @item read reg @strong{(reserved)}
10115 @tab @code{p}@var{n...}
10116 @tab
10117 See write register.
10118 @item
10119 @tab return @var{r....}
10120 @tab The hex encoded value of the register in target byte order.
10121
10122 @item write reg
10123 @tab @code{P}@var{n...}@code{=}@var{r...}
10124 @tab
10125 Write register @var{n...} with value @var{r...}, which contains two hex
10126 digits for each byte in the register (target byte order).
10127 @item
10128 @tab reply @code{OK}
10129 @tab for success
10130 @item
10131 @tab reply @code{E}@var{NN}
10132 @tab for an error
10133
10134 @item general query
10135 @tab @code{q}@var{query}
10136 @tab
10137 Request info about @var{query}. In general @value{GDBN} queries
10138 have a leading upper case letter. Custom vendor queries should use a
10139 company prefix (in lower case) ex: @samp{qfsf.var}. @var{query} may
10140 optionally be followed by a @samp{,} or @samp{;} separated list. Stubs
10141 must ensure that they match the full @var{query} name.
10142 @item
10143 @tab reply @code{XX...}
10144 @tab Hex encoded data from query. The reply can not be empty.
10145 @item
10146 @tab reply @code{E}@var{NN}
10147 @tab error reply
10148 @item
10149 @tab reply @samp{}
10150 @tab Indicating an unrecognized @var{query}.
10151
10152 @item general set
10153 @tab @code{Q}@var{var}@code{=}@var{val}
10154 @tab
10155 Set value of @var{var} to @var{val}. See @samp{q} for a discussing of
10156 naming conventions.
10157
10158 @item reset @strong{(deprecated)}
10159 @tab @code{r}
10160 @tab
10161 Reset the entire system.
10162
10163 @item remote restart
10164 @tab @code{R}@var{XX}
10165 @tab
10166 Restart the program being debugged. @var{XX}, while needed, is ignored.
10167 This packet is only available in extended mode.
10168 @item
10169 @tab
10170 no reply
10171 @tab
10172 The @samp{R} packet has no reply.
10173
10174 @item step
10175 @tab @code{s}@var{addr}
10176 @tab
10177 @var{addr} is address to resume. If @var{addr} is omitted, resume at
10178 same address.
10179 @item
10180 @tab reply
10181 @tab see below
10182
10183 @item step with signal
10184 @tab @code{S}@var{sig}@code{;}@var{addr}
10185 @tab
10186 Like @samp{C} but step not continue.
10187 @item
10188 @tab reply
10189 @tab see below
10190
10191 @item search
10192 @tab @code{t}@var{addr}@code{:}@var{PP}@code{,}@var{MM}
10193 @tab
10194 Search backwards starting at address @var{addr} for a match with pattern
10195 @var{PP} and mask @var{MM}. @var{PP} and @var{MM} are 4
10196 bytes. @var{addr} must be at least 3 digits.
10197
10198 @item thread alive
10199 @tab @code{T}@var{XX}
10200 @tab Find out if the thread XX is alive.
10201 @item
10202 @tab reply @code{OK}
10203 @tab thread is still alive
10204 @item
10205 @tab reply @code{E}@var{NN}
10206 @tab thread is dead
10207
10208 @item reserved
10209 @tab @code{u}
10210 @tab Reserved for future use
10211
10212 @item reserved
10213 @tab @code{U}
10214 @tab Reserved for future use
10215
10216 @item reserved
10217 @tab @code{v}
10218 @tab Reserved for future use
10219
10220 @item reserved
10221 @tab @code{V}
10222 @tab Reserved for future use
10223
10224 @item reserved
10225 @tab @code{w}
10226 @tab Reserved for future use
10227
10228 @item reserved
10229 @tab @code{W}
10230 @tab Reserved for future use
10231
10232 @item reserved
10233 @tab @code{x}
10234 @tab Reserved for future use
10235
10236 @item write mem (binary)
10237 @tab @code{X}@var{addr}@code{,}@var{length}@var{:}@var{XX...}
10238 @tab
10239 @var{addr} is address, @var{length} is number of bytes, @var{XX...} is
10240 binary data. The characters @code{$}, @code{#}, and @code{0x7d} are
10241 escaped using @code{0x7d}.
10242 @item
10243 @tab reply @code{OK}
10244 @tab for success
10245 @item
10246 @tab reply @code{E}@var{NN}
10247 @tab for an error
10248
10249 @item reserved
10250 @tab @code{y}
10251 @tab Reserved for future use
10252
10253 @item reserved
10254 @tab @code{Y}
10255 @tab Reserved for future use
10256
10257 @item remove break or watchpoint @strong{(draft)}
10258 @tab @code{z}@var{t}@code{,}@var{addr}@code{,}@var{length}
10259 @tab
10260 See @samp{Z}.
10261
10262 @item insert break or watchpoint @strong{(draft)}
10263 @tab @code{Z}@var{t}@code{,}@var{addr}@code{,}@var{length}
10264 @tab
10265 @var{t} is type: @samp{0} - software breakpoint, @samp{1} - hardware
10266 breakpoint, @samp{2} - write watchpoint, @samp{3} - read watchpoint,
10267 @samp{4} - access watchpoint; @var{addr} is address; @var{length} is in
10268 bytes. For a software breakpoint, @var{length} specifies the size of
10269 the instruction to be patched. For hardware breakpoints and watchpoints
10270 @var{length} specifies the memory region to be monitored. To avoid
10271 potential problems with duplicate packets, the operations should be
10272 implemented in an idempotent way.
10273 @item
10274 @tab reply @code{E}@var{NN}
10275 @tab for an error
10276 @item
10277 @tab reply @code{OK}
10278 @tab for success
10279 @item
10280 @tab @samp{}
10281 @tab If not supported.
10282
10283 @item reserved
10284 @tab <other>
10285 @tab Reserved for future use
10286
10287 @end multitable
10288
10289 The @samp{C}, @samp{c}, @samp{S}, @samp{s} and @samp{?} packets can
10290 receive any of the below as a reply. In the case of the @samp{C},
10291 @samp{c}, @samp{S} and @samp{s} packets, that reply is only returned
10292 when the target halts. In the below the exact meaning of @samp{signal
10293 number} is poorly defined. In general one of the UNIX signal numbering
10294 conventions is used.
10295
10296 @multitable @columnfractions .4 .6
10297
10298 @item @code{S}@var{AA}
10299 @tab @var{AA} is the signal number
10300
10301 @item @code{T}@var{AA}@var{n...}@code{:}@var{r...}@code{;}@var{n...}@code{:}@var{r...}@code{;}@var{n...}@code{:}@var{r...}@code{;}
10302 @tab
10303 @var{AA} = two hex digit signal number; @var{n...} = register number
10304 (hex), @var{r...} = target byte ordered register contents, size defined
10305 by @code{REGISTER_RAW_SIZE}; @var{n...} = @samp{thread}, @var{r...} =
10306 thread process ID, this is a hex integer; @var{n...} = other string not
10307 starting with valid hex digit. @value{GDBN} should ignore this
10308 @var{n...}, @var{r...} pair and go on to the next. This way we can
10309 extend the protocol.
10310
10311 @item @code{W}@var{AA}
10312 @tab
10313 The process exited, and @var{AA} is the exit status. This is only
10314 applicable for certains sorts of targets.
10315
10316 @item @code{X}@var{AA}
10317 @tab
10318 The process terminated with signal @var{AA}.
10319
10320 @item @code{N}@var{AA}@code{;}@var{t...}@code{;}@var{d...}@code{;}@var{b...} @strong{(obsolete)}
10321 @tab
10322 @var{AA} = signal number; @var{t...} = address of symbol "_start";
10323 @var{d...} = base of data section; @var{b...} = base of bss section.
10324 @emph{Note: only used by Cisco Systems targets. The difference between
10325 this reply and the "qOffsets" query is that the 'N' packet may arrive
10326 spontaneously whereas the 'qOffsets' is a query initiated by the host
10327 debugger.}
10328
10329 @item @code{O}@var{XX...}
10330 @tab
10331 @var{XX...} is hex encoding of @sc{ascii} data. This can happen at any time
10332 while the program is running and the debugger should continue to wait
10333 for 'W', 'T', etc.
10334
10335 @end multitable
10336
10337 The following set and query packets have already been defined.
10338
10339 @multitable @columnfractions .2 .2 .6
10340
10341 @item current thread
10342 @tab @code{q}@code{C}
10343 @tab Return the current thread id.
10344 @item
10345 @tab reply @code{QC}@var{pid}
10346 @tab
10347 Where @var{pid} is a HEX encoded 16 bit process id.
10348 @item
10349 @tab reply *
10350 @tab Any other reply implies the old pid.
10351
10352 @item all thread ids
10353 @tab @code{q}@code{fThreadInfo}
10354 @item
10355 @tab @code{q}@code{sThreadInfo}
10356 @tab
10357 Obtain a list of active thread ids from the target (OS). Since there
10358 may be too many active threads to fit into one reply packet, this query
10359 works iteratively: it may require more than one query/reply sequence to
10360 obtain the entire list of threads. The first query of the sequence will
10361 be the @code{qf}@code{ThreadInfo} query; subsequent queries in the
10362 sequence will be the @code{qs}@code{ThreadInfo} query.
10363 @item
10364 @tab
10365 @tab NOTE: replaces the @code{qL} query (see below).
10366 @item
10367 @tab reply @code{m}@var{<id>}
10368 @tab A single thread id
10369 @item
10370 @tab reply @code{m}@var{<id>},@var{<id>...}
10371 @tab a comma-separated list of thread ids
10372 @item
10373 @tab reply @code{l}
10374 @tab (lower case 'el') denotes end of list.
10375 @item
10376 @tab
10377 @tab
10378 In response to each query, the target will reply with a list of one
10379 or more thread ids, in big-endian hex, separated by commas. GDB will
10380 respond to each reply with a request for more thread ids (using the
10381 @code{qs} form of the query), until the target responds with @code{l}
10382 (lower-case el, for @code{'last'}).
10383
10384 @item extra thread info
10385 @tab @code{q}@code{ThreadExtraInfo}@code{,}@var{id}
10386 @tab
10387 @item
10388 @tab
10389 @tab
10390 Where @var{<id>} is a thread-id in big-endian hex.
10391 Obtain a printable string description of a thread's attributes from
10392 the target OS. This string may contain anything that the target OS
10393 thinks is interesting for @value{GDBN} to tell the user about the thread.
10394 The string is displayed in @value{GDBN}'s @samp{info threads} display.
10395 Some examples of possible thread extra info strings are "Runnable", or
10396 "Blocked on Mutex".
10397 @item
10398 @tab reply @var{XX...}
10399 @tab
10400 Where @var{XX...} is a hex encoding of @sc{ascii} data, comprising the
10401 printable string containing the extra information about the thread's
10402 attributes.
10403
10404 @item query @var{LIST} or @var{threadLIST} @strong{(deprecated)}
10405 @tab @code{q}@code{L}@var{startflag}@var{threadcount}@var{nextthread}
10406 @tab
10407 @item
10408 @tab
10409 @tab
10410 Obtain thread information from RTOS. Where: @var{startflag} (one hex
10411 digit) is one to indicate the first query and zero to indicate a
10412 subsequent query; @var{threadcount} (two hex digits) is the maximum
10413 number of threads the response packet can contain; and @var{nextthread}
10414 (eight hex digits), for subsequent queries (@var{startflag} is zero), is
10415 returned in the response as @var{argthread}.
10416 @item
10417 @tab
10418 @tab NOTE: this query is replaced by the @code{q}@code{fThreadInfo}
10419 query (see above).
10420 @item
10421 @tab reply @code{q}@code{M}@var{count}@var{done}@var{argthread}@var{thread...}
10422 @tab
10423 @item
10424 @tab
10425 @tab
10426 Where: @var{count} (two hex digits) is the number of threads being
10427 returned; @var{done} (one hex digit) is zero to indicate more threads
10428 and one indicates no further threads; @var{argthreadid} (eight hex
10429 digits) is @var{nextthread} from the request packet; @var{thread...} is
10430 a sequence of thread IDs from the target. @var{threadid} (eight hex
10431 digits). See @code{remote.c:parse_threadlist_response()}.
10432
10433 @item compute CRC of memory block
10434 @tab @code{q}@code{CRC:}@var{addr}@code{,}@var{length}
10435 @tab
10436 @item
10437 @tab reply @code{E}@var{NN}
10438 @tab An error (such as memory fault)
10439 @item
10440 @tab reply @code{C}@var{CRC32}
10441 @tab A 32 bit cyclic redundancy check of the specified memory region.
10442
10443 @item query sect offs
10444 @tab @code{q}@code{Offsets}
10445 @tab
10446 Get section offsets that the target used when re-locating the downloaded
10447 image. @emph{Note: while a @code{Bss} offset is included in the
10448 response, @value{GDBN} ignores this and instead applies the @code{Data}
10449 offset to the @code{Bss} section.}
10450 @item
10451 @tab reply @code{Text=}@var{xxx}@code{;Data=}@var{yyy}@code{;Bss=}@var{zzz}
10452
10453 @item thread info request
10454 @tab @code{q}@code{P}@var{mode}@var{threadid}
10455 @tab
10456 @item
10457 @tab
10458 @tab
10459 Returns information on @var{threadid}. Where: @var{mode} is a hex
10460 encoded 32 bit mode; @var{threadid} is a hex encoded 64 bit thread ID.
10461 @item
10462 @tab reply *
10463 @tab
10464 See @code{remote.c:remote_unpack_thread_info_response()}.
10465
10466 @item remote command
10467 @tab @code{q}@code{Rcmd,}@var{COMMAND}
10468 @tab
10469 @item
10470 @tab
10471 @tab
10472 @var{COMMAND} (hex encoded) is passed to the local interpreter for
10473 execution. Invalid commands should be reported using the output string.
10474 Before the final result packet, the target may also respond with a
10475 number of intermediate @code{O}@var{OUTPUT} console output
10476 packets. @emph{Implementors should note that providing access to a
10477 stubs's interpreter may have security implications}.
10478 @item
10479 @tab reply @code{OK}
10480 @tab
10481 A command response with no output.
10482 @item
10483 @tab reply @var{OUTPUT}
10484 @tab
10485 A command response with the hex encoded output string @var{OUTPUT}.
10486 @item
10487 @tab reply @code{E}@var{NN}
10488 @tab
10489 Indicate a badly formed request.
10490
10491 @item
10492 @tab reply @samp{}
10493 @tab
10494 When @samp{q}@samp{Rcmd} is not recognized.
10495
10496 @item symbol lookup
10497 @tab @code{qSymbol::}
10498 @tab
10499 Notify the target that @value{GDBN} is prepared to serve symbol lookup
10500 requests. Accept requests from the target for the values of symbols.
10501 @item
10502 @tab
10503 @tab
10504 @item
10505 @tab reply @code{OK}
10506 @tab
10507 The target does not need to look up any (more) symbols.
10508 @item
10509 @tab reply @code{qSymbol:}@var{sym_name}
10510 @tab
10511 The target requests the value of symbol @var{sym_name} (hex encoded).
10512 @value{GDBN} may provide the value by using the
10513 @code{qSymbol:}@var{sym_value}:@var{sym_name}
10514 message, described below.
10515
10516 @item symbol value
10517 @tab @code{qSymbol:}@var{sym_value}:@var{sym_name}
10518 @tab
10519 Set the value of SYM_NAME to SYM_VALUE.
10520 @item
10521 @tab
10522 @tab
10523 @var{sym_name} (hex encoded) is the name of a symbol whose value
10524 the target has previously requested.
10525 @item
10526 @tab
10527 @tab
10528 @var{sym_value} (hex) is the value for symbol @var{sym_name}.
10529 If @value{GDBN} cannot supply a value for @var{sym_name}, then this
10530 field will be empty.
10531 @item
10532 @tab reply @code{OK}
10533 @tab
10534 The target does not need to look up any (more) symbols.
10535 @item
10536 @tab reply @code{qSymbol:}@var{sym_name}
10537 @tab
10538 The target requests the value of a new symbol @var{sym_name} (hex encoded).
10539 @value{GDBN} will continue to supply the values of symbols (if available),
10540 until the target ceases to request them.
10541
10542 @end multitable
10543
10544 The following @samp{g}/@samp{G} packets have previously been defined.
10545 In the below, some thirty-two bit registers are transferred as sixty-four
10546 bits. Those registers should be zero/sign extended (which?) to fill the
10547 space allocated. Register bytes are transfered in target byte order.
10548 The two nibbles within a register byte are transfered most-significant -
10549 least-significant.
10550
10551 @multitable @columnfractions .5 .5
10552
10553 @item MIPS32
10554 @tab
10555 All registers are transfered as thirty-two bit quantities in the order:
10556 32 general-purpose; sr; lo; hi; bad; cause; pc; 32 floating-point
10557 registers; fsr; fir; fp.
10558
10559 @item MIPS64
10560 @tab
10561 All registers are transfered as sixty-four bit quantities (including
10562 thirty-two bit registers such as @code{sr}). The ordering is the same
10563 as @code{MIPS32}.
10564
10565 @end multitable
10566
10567 Example sequence of a target being re-started. Notice how the restart
10568 does not get any direct output:
10569
10570 @example
10571 <- @code{R00}
10572 -> @code{+}
10573 @emph{target restarts}
10574 <- @code{?}
10575 -> @code{+}
10576 -> @code{T001:1234123412341234}
10577 <- @code{+}
10578 @end example
10579
10580 Example sequence of a target being stepped by a single instruction:
10581
10582 @example
10583 <- @code{G1445...}
10584 -> @code{+}
10585 <- @code{s}
10586 -> @code{+}
10587 @emph{time passes}
10588 -> @code{T001:1234123412341234}
10589 <- @code{+}
10590 <- @code{g}
10591 -> @code{+}
10592 -> @code{1455...}
10593 <- @code{+}
10594 @end example
10595
10596 @node Server
10597 @subsubsection Using the @code{gdbserver} program
10598
10599 @kindex gdbserver
10600 @cindex remote connection without stubs
10601 @code{gdbserver} is a control program for Unix-like systems, which
10602 allows you to connect your program with a remote @value{GDBN} via
10603 @code{target remote}---but without linking in the usual debugging stub.
10604
10605 @code{gdbserver} is not a complete replacement for the debugging stubs,
10606 because it requires essentially the same operating-system facilities
10607 that @value{GDBN} itself does. In fact, a system that can run
10608 @code{gdbserver} to connect to a remote @value{GDBN} could also run
10609 @value{GDBN} locally! @code{gdbserver} is sometimes useful nevertheless,
10610 because it is a much smaller program than @value{GDBN} itself. It is
10611 also easier to port than all of @value{GDBN}, so you may be able to get
10612 started more quickly on a new system by using @code{gdbserver}.
10613 Finally, if you develop code for real-time systems, you may find that
10614 the tradeoffs involved in real-time operation make it more convenient to
10615 do as much development work as possible on another system, for example
10616 by cross-compiling. You can use @code{gdbserver} to make a similar
10617 choice for debugging.
10618
10619 @value{GDBN} and @code{gdbserver} communicate via either a serial line
10620 or a TCP connection, using the standard @value{GDBN} remote serial
10621 protocol.
10622
10623 @table @emph
10624 @item On the target machine,
10625 you need to have a copy of the program you want to debug.
10626 @code{gdbserver} does not need your program's symbol table, so you can
10627 strip the program if necessary to save space. @value{GDBN} on the host
10628 system does all the symbol handling.
10629
10630 To use the server, you must tell it how to communicate with @value{GDBN};
10631 the name of your program; and the arguments for your program. The
10632 syntax is:
10633
10634 @smallexample
10635 target> gdbserver @var{comm} @var{program} [ @var{args} @dots{} ]
10636 @end smallexample
10637
10638 @var{comm} is either a device name (to use a serial line) or a TCP
10639 hostname and portnumber. For example, to debug Emacs with the argument
10640 @samp{foo.txt} and communicate with @value{GDBN} over the serial port
10641 @file{/dev/com1}:
10642
10643 @smallexample
10644 target> gdbserver /dev/com1 emacs foo.txt
10645 @end smallexample
10646
10647 @code{gdbserver} waits passively for the host @value{GDBN} to communicate
10648 with it.
10649
10650 To use a TCP connection instead of a serial line:
10651
10652 @smallexample
10653 target> gdbserver host:2345 emacs foo.txt
10654 @end smallexample
10655
10656 The only difference from the previous example is the first argument,
10657 specifying that you are communicating with the host @value{GDBN} via
10658 TCP. The @samp{host:2345} argument means that @code{gdbserver} is to
10659 expect a TCP connection from machine @samp{host} to local TCP port 2345.
10660 (Currently, the @samp{host} part is ignored.) You can choose any number
10661 you want for the port number as long as it does not conflict with any
10662 TCP ports already in use on the target system (for example, @code{23} is
10663 reserved for @code{telnet}).@footnote{If you choose a port number that
10664 conflicts with another service, @code{gdbserver} prints an error message
10665 and exits.} You must use the same port number with the host @value{GDBN}
10666 @code{target remote} command.
10667
10668 @item On the @value{GDBN} host machine,
10669 you need an unstripped copy of your program, since @value{GDBN} needs
10670 symbols and debugging information. Start up @value{GDBN} as usual,
10671 using the name of the local copy of your program as the first argument.
10672 (You may also need the @w{@samp{--baud}} option if the serial line is
10673 running at anything other than 9600@dmn{bps}.) After that, use @code{target
10674 remote} to establish communications with @code{gdbserver}. Its argument
10675 is either a device name (usually a serial device, like
10676 @file{/dev/ttyb}), or a TCP port descriptor in the form
10677 @code{@var{host}:@var{PORT}}. For example:
10678
10679 @smallexample
10680 (@value{GDBP}) target remote /dev/ttyb
10681 @end smallexample
10682
10683 @noindent
10684 communicates with the server via serial line @file{/dev/ttyb}, and
10685
10686 @smallexample
10687 (@value{GDBP}) target remote the-target:2345
10688 @end smallexample
10689
10690 @noindent
10691 communicates via a TCP connection to port 2345 on host @w{@file{the-target}}.
10692 For TCP connections, you must start up @code{gdbserver} prior to using
10693 the @code{target remote} command. Otherwise you may get an error whose
10694 text depends on the host system, but which usually looks something like
10695 @samp{Connection refused}.
10696 @end table
10697
10698 @node NetWare
10699 @subsubsection Using the @code{gdbserve.nlm} program
10700
10701 @kindex gdbserve.nlm
10702 @code{gdbserve.nlm} is a control program for NetWare systems, which
10703 allows you to connect your program with a remote @value{GDBN} via
10704 @code{target remote}.
10705
10706 @value{GDBN} and @code{gdbserve.nlm} communicate via a serial line,
10707 using the standard @value{GDBN} remote serial protocol.
10708
10709 @table @emph
10710 @item On the target machine,
10711 you need to have a copy of the program you want to debug.
10712 @code{gdbserve.nlm} does not need your program's symbol table, so you
10713 can strip the program if necessary to save space. @value{GDBN} on the
10714 host system does all the symbol handling.
10715
10716 To use the server, you must tell it how to communicate with
10717 @value{GDBN}; the name of your program; and the arguments for your
10718 program. The syntax is:
10719
10720 @smallexample
10721 load gdbserve [ BOARD=@var{board} ] [ PORT=@var{port} ]
10722 [ BAUD=@var{baud} ] @var{program} [ @var{args} @dots{} ]
10723 @end smallexample
10724
10725 @var{board} and @var{port} specify the serial line; @var{baud} specifies
10726 the baud rate used by the connection. @var{port} and @var{node} default
10727 to 0, @var{baud} defaults to 9600@dmn{bps}.
10728
10729 For example, to debug Emacs with the argument @samp{foo.txt}and
10730 communicate with @value{GDBN} over serial port number 2 or board 1
10731 using a 19200@dmn{bps} connection:
10732
10733 @smallexample
10734 load gdbserve BOARD=1 PORT=2 BAUD=19200 emacs foo.txt
10735 @end smallexample
10736
10737 @item On the @value{GDBN} host machine,
10738 you need an unstripped copy of your program, since @value{GDBN} needs
10739 symbols and debugging information. Start up @value{GDBN} as usual,
10740 using the name of the local copy of your program as the first argument.
10741 (You may also need the @w{@samp{--baud}} option if the serial line is
10742 running at anything other than 9600@dmn{bps}. After that, use @code{target
10743 remote} to establish communications with @code{gdbserve.nlm}. Its
10744 argument is a device name (usually a serial device, like
10745 @file{/dev/ttyb}). For example:
10746
10747 @smallexample
10748 (@value{GDBP}) target remote /dev/ttyb
10749 @end smallexample
10750
10751 @noindent
10752 communications with the server via serial line @file{/dev/ttyb}.
10753 @end table
10754
10755 @node KOD
10756 @section Kernel Object Display
10757
10758 @cindex kernel object display
10759 @cindex kernel object
10760 @cindex KOD
10761
10762 Some targets support kernel object display. Using this facility,
10763 @value{GDBN} communicates specially with the underlying operating system
10764 and can display information about operating system-level objects such as
10765 mutexes and other synchronization objects. Exactly which objects can be
10766 displayed is determined on a per-OS basis.
10767
10768 Use the @code{set os} command to set the operating system. This tells
10769 @value{GDBN} which kernel object display module to initialize:
10770
10771 @example
10772 (@value{GDBP}) set os cisco
10773 @end example
10774
10775 If @code{set os} succeeds, @value{GDBN} will display some information
10776 about the operating system, and will create a new @code{info} command
10777 which can be used to query the target. The @code{info} command is named
10778 after the operating system:
10779
10780 @example
10781 (@value{GDBP}) info cisco
10782 List of Cisco Kernel Objects
10783 Object Description
10784 any Any and all objects
10785 @end example
10786
10787 Further subcommands can be used to query about particular objects known
10788 by the kernel.
10789
10790 There is currently no way to determine whether a given operating system
10791 is supported other than to try it.
10792
10793
10794 @node Configurations
10795 @chapter Configuration-Specific Information
10796
10797 While nearly all @value{GDBN} commands are available for all native and
10798 cross versions of the debugger, there are some exceptions. This chapter
10799 describes things that are only available in certain configurations.
10800
10801 There are three major categories of configurations: native
10802 configurations, where the host and target are the same, embedded
10803 operating system configurations, which are usually the same for several
10804 different processor architectures, and bare embedded processors, which
10805 are quite different from each other.
10806
10807 @menu
10808 * Native::
10809 * Embedded OS::
10810 * Embedded Processors::
10811 * Architectures::
10812 @end menu
10813
10814 @node Native
10815 @section Native
10816
10817 This section describes details specific to particular native
10818 configurations.
10819
10820 @menu
10821 * HP-UX:: HP-UX
10822 * SVR4 Process Information:: SVR4 process information
10823 * DJGPP Native:: Features specific to the DJGPP port
10824 @end menu
10825
10826 @node HP-UX
10827 @subsection HP-UX
10828
10829 On HP-UX systems, if you refer to a function or variable name that
10830 begins with a dollar sign, @value{GDBN} searches for a user or system
10831 name first, before it searches for a convenience variable.
10832
10833 @node SVR4 Process Information
10834 @subsection SVR4 process information
10835
10836 @kindex /proc
10837 @cindex process image
10838
10839 Many versions of SVR4 provide a facility called @samp{/proc} that can be
10840 used to examine the image of a running process using file-system
10841 subroutines. If @value{GDBN} is configured for an operating system with
10842 this facility, the command @code{info proc} is available to report on
10843 several kinds of information about the process running your program.
10844 @code{info proc} works only on SVR4 systems that include the
10845 @code{procfs} code. This includes OSF/1 (Digital Unix), Solaris, Irix,
10846 and Unixware, but not HP-UX or Linux, for example.
10847
10848 @table @code
10849 @kindex info proc
10850 @item info proc
10851 Summarize available information about the process.
10852
10853 @kindex info proc mappings
10854 @item info proc mappings
10855 Report on the address ranges accessible in the program, with information
10856 on whether your program may read, write, or execute each range.
10857
10858 @kindex info proc times
10859 @item info proc times
10860 Starting time, user CPU time, and system CPU time for your program and
10861 its children.
10862
10863 @kindex info proc id
10864 @item info proc id
10865 Report on the process IDs related to your program: its own process ID,
10866 the ID of its parent, the process group ID, and the session ID.
10867
10868 @kindex info proc status
10869 @item info proc status
10870 General information on the state of the process. If the process is
10871 stopped, this report includes the reason for stopping, and any signal
10872 received.
10873
10874 @item info proc all
10875 Show all the above information about the process.
10876 @end table
10877
10878 @node DJGPP Native
10879 @subsection Features for Debugging @sc{djgpp} Programs
10880 @cindex @sc{djgpp} debugging
10881 @cindex native @sc{djgpp} debugging
10882 @cindex MS-DOS-specific commands
10883
10884 @sc{djgpp} is the port of @sc{gnu} development tools to MS-DOS and
10885 MS-Windows. @sc{djgpp} programs are 32-bit protected-mode programs
10886 that use the @dfn{DPMI} (DOS Protected-Mode Interface) API to run on
10887 top of real-mode DOS systems and their emulations.
10888
10889 @value{GDBN} supports native debugging of @sc{djgpp} programs, and
10890 defines a few commands specific to the @sc{djgpp} port. This
10891 subsection describes those commands.
10892
10893 @table @code
10894 @kindex info dos
10895 @item info dos
10896 This is a prefix of @sc{djgpp}-specific commands which print
10897 information about the target system and important OS structures.
10898
10899 @kindex sysinfo
10900 @cindex MS-DOS system info
10901 @cindex free memory information (MS-DOS)
10902 @item info dos sysinfo
10903 This command displays assorted information about the underlying
10904 platform: the CPU type and features, the OS version and flavor, the
10905 DPMI version, and the available conventional and DPMI memory.
10906
10907 @cindex GDT
10908 @cindex LDT
10909 @cindex IDT
10910 @cindex segment descriptor tables
10911 @cindex descriptor tables display
10912 @item info dos gdt
10913 @itemx info dos ldt
10914 @itemx info dos idt
10915 These 3 commands display entries from, respectively, Global, Local,
10916 and Interrupt Descriptor Tables (GDT, LDT, and IDT). The descriptor
10917 tables are data structures which store a descriptor for each segment
10918 that is currently in use. The segment's selector is an index into a
10919 descriptor table; the table entry for that index holds the
10920 descriptor's base address and limit, and its attributes and access
10921 rights.
10922
10923 A typical @sc{djgpp} program uses 3 segments: a code segment, a data
10924 segment (used for both data and the stack), and a DOS segment (which
10925 allows access to DOS/BIOS data structures and absolute addresses in
10926 conventional memory). However, the DPMI host will usually define
10927 additional segments in order to support the DPMI environment.
10928
10929 @cindex garbled pointers
10930 These commands allow to display entries from the descriptor tables.
10931 Without an argument, all entries from the specified table are
10932 displayed. An argument, which should be an integer expression, means
10933 display a single entry whose index is given by the argument. For
10934 example, here's a convenient way to display information about the
10935 debugged program's data segment:
10936
10937 @smallexample
10938 (@value{GDBP}) info dos ldt $ds
10939 0x13f: base=0x11970000 limit=0x0009ffff 32-Bit Data (Read/Write, Exp-up)
10940 @end smallexample
10941
10942 @noindent
10943 This comes in handy when you want to see whether a pointer is outside
10944 the data segment's limit (i.e.@: @dfn{garbled}).
10945
10946 @cindex page tables display (MS-DOS)
10947 @item info dos pde
10948 @itemx info dos pte
10949 These two commands display entries from, respectively, the Page
10950 Directory and the Page Tables. Page Directories and Page Tables are
10951 data structures which control how virtual memory addresses are mapped
10952 into physical addresses. A Page Table includes an entry for every
10953 page of memory that is mapped into the program's address space; there
10954 may be several Page Tables, each one holding up to 4096 entries. A
10955 Page Directory has up to 4096 entries, one each for every Page Table
10956 that is currently in use.
10957
10958 Without an argument, @kbd{info dos pde} displays the entire Page
10959 Directory, and @kbd{info dos pte} displays all the entries in all of
10960 the Page Tables. An argument, an integer expression, given to the
10961 @kbd{info dos pde} command means display only that entry from the Page
10962 Directory table. An argument given to the @kbd{info dos pte} command
10963 means display entries from a single Page Table, the one pointed to by
10964 the specified entry in the Page Directory.
10965
10966 These commands are useful when your program uses @dfn{DMA} (Direct
10967 Memory Access), which needs physical addresses to program the DMA
10968 controller.
10969
10970 These commands are supported only with some DPMI servers.
10971
10972 @cindex physical address from linear address
10973 @item info dos address-pte
10974 This command displays the Page Table entry for a specified linear
10975 address. The argument linear address should already have the
10976 appropriate segment's base address added to it, because this command
10977 accepts addresses which may belong to @emph{any} segment. For
10978 example, here's how to display the Page Table entry for the page where
10979 the variable @code{i} is stored:
10980
10981 @smallexample
10982 (@value{GDBP}) info dos address-pte __djgpp_base_address + (char *)&i
10983 Page Table entry for address 0x11a00d30:
10984 Base=0x02698000 Dirty Acc. Not-Cached Write-Back Usr Read-Write +0xd30
10985 @end smallexample
10986
10987 @noindent
10988 This says that @code{i} is stored at offset @code{0xd30} from the page
10989 whose physical base address is @code{0x02698000}, and prints all the
10990 attributes of that page.
10991
10992 Note that you must cast the addresses of variables to a @code{char *},
10993 since otherwise the value of @code{__djgpp_base_address}, the base
10994 address of all variables and functions in a @sc{djgpp} program, will
10995 be added using the rules of C pointer arithmetics: if @code{i} is
10996 declared an @code{int}, @value{GDBN} will add 4 times the value of
10997 @code{__djgpp_base_address} to the address of @code{i}.
10998
10999 Here's another example, it displays the Page Table entry for the
11000 transfer buffer:
11001
11002 @smallexample
11003 (@value{GDBP}) info dos address-pte *((unsigned *)&_go32_info_block + 3)
11004 Page Table entry for address 0x29110:
11005 Base=0x00029000 Dirty Acc. Not-Cached Write-Back Usr Read-Write +0x110
11006 @end smallexample
11007
11008 @noindent
11009 (The @code{+ 3} offset is because the transfer buffer's address is the
11010 3rd member of the @code{_go32_info_block} structure.) The output of
11011 this command clearly shows that addresses in conventional memory are
11012 mapped 1:1, i.e.@: the physical and linear addresses are identical.
11013
11014 This command is supported only with some DPMI servers.
11015 @end table
11016
11017 @node Embedded OS
11018 @section Embedded Operating Systems
11019
11020 This section describes configurations involving the debugging of
11021 embedded operating systems that are available for several different
11022 architectures.
11023
11024 @menu
11025 * VxWorks:: Using @value{GDBN} with VxWorks
11026 @end menu
11027
11028 @value{GDBN} includes the ability to debug programs running on
11029 various real-time operating systems.
11030
11031 @node VxWorks
11032 @subsection Using @value{GDBN} with VxWorks
11033
11034 @cindex VxWorks
11035
11036 @table @code
11037
11038 @kindex target vxworks
11039 @item target vxworks @var{machinename}
11040 A VxWorks system, attached via TCP/IP. The argument @var{machinename}
11041 is the target system's machine name or IP address.
11042
11043 @end table
11044
11045 On VxWorks, @code{load} links @var{filename} dynamically on the
11046 current target system as well as adding its symbols in @value{GDBN}.
11047
11048 @value{GDBN} enables developers to spawn and debug tasks running on networked
11049 VxWorks targets from a Unix host. Already-running tasks spawned from
11050 the VxWorks shell can also be debugged. @value{GDBN} uses code that runs on
11051 both the Unix host and on the VxWorks target. The program
11052 @code{@value{GDBP}} is installed and executed on the Unix host. (It may be
11053 installed with the name @code{vxgdb}, to distinguish it from a
11054 @value{GDBN} for debugging programs on the host itself.)
11055
11056 @table @code
11057 @item VxWorks-timeout @var{args}
11058 @kindex vxworks-timeout
11059 All VxWorks-based targets now support the option @code{vxworks-timeout}.
11060 This option is set by the user, and @var{args} represents the number of
11061 seconds @value{GDBN} waits for responses to rpc's. You might use this if
11062 your VxWorks target is a slow software simulator or is on the far side
11063 of a thin network line.
11064 @end table
11065
11066 The following information on connecting to VxWorks was current when
11067 this manual was produced; newer releases of VxWorks may use revised
11068 procedures.
11069
11070 @kindex INCLUDE_RDB
11071 To use @value{GDBN} with VxWorks, you must rebuild your VxWorks kernel
11072 to include the remote debugging interface routines in the VxWorks
11073 library @file{rdb.a}. To do this, define @code{INCLUDE_RDB} in the
11074 VxWorks configuration file @file{configAll.h} and rebuild your VxWorks
11075 kernel. The resulting kernel contains @file{rdb.a}, and spawns the
11076 source debugging task @code{tRdbTask} when VxWorks is booted. For more
11077 information on configuring and remaking VxWorks, see the manufacturer's
11078 manual.
11079 @c VxWorks, see the @cite{VxWorks Programmer's Guide}.
11080
11081 Once you have included @file{rdb.a} in your VxWorks system image and set
11082 your Unix execution search path to find @value{GDBN}, you are ready to
11083 run @value{GDBN}. From your Unix host, run @code{@value{GDBP}} (or
11084 @code{vxgdb}, depending on your installation).
11085
11086 @value{GDBN} comes up showing the prompt:
11087
11088 @example
11089 (vxgdb)
11090 @end example
11091
11092 @menu
11093 * VxWorks Connection:: Connecting to VxWorks
11094 * VxWorks Download:: VxWorks download
11095 * VxWorks Attach:: Running tasks
11096 @end menu
11097
11098 @node VxWorks Connection
11099 @subsubsection Connecting to VxWorks
11100
11101 The @value{GDBN} command @code{target} lets you connect to a VxWorks target on the
11102 network. To connect to a target whose host name is ``@code{tt}'', type:
11103
11104 @example
11105 (vxgdb) target vxworks tt
11106 @end example
11107
11108 @need 750
11109 @value{GDBN} displays messages like these:
11110
11111 @smallexample
11112 Attaching remote machine across net...
11113 Connected to tt.
11114 @end smallexample
11115
11116 @need 1000
11117 @value{GDBN} then attempts to read the symbol tables of any object modules
11118 loaded into the VxWorks target since it was last booted. @value{GDBN} locates
11119 these files by searching the directories listed in the command search
11120 path (@pxref{Environment, ,Your program's environment}); if it fails
11121 to find an object file, it displays a message such as:
11122
11123 @example
11124 prog.o: No such file or directory.
11125 @end example
11126
11127 When this happens, add the appropriate directory to the search path with
11128 the @value{GDBN} command @code{path}, and execute the @code{target}
11129 command again.
11130
11131 @node VxWorks Download
11132 @subsubsection VxWorks download
11133
11134 @cindex download to VxWorks
11135 If you have connected to the VxWorks target and you want to debug an
11136 object that has not yet been loaded, you can use the @value{GDBN}
11137 @code{load} command to download a file from Unix to VxWorks
11138 incrementally. The object file given as an argument to the @code{load}
11139 command is actually opened twice: first by the VxWorks target in order
11140 to download the code, then by @value{GDBN} in order to read the symbol
11141 table. This can lead to problems if the current working directories on
11142 the two systems differ. If both systems have NFS mounted the same
11143 filesystems, you can avoid these problems by using absolute paths.
11144 Otherwise, it is simplest to set the working directory on both systems
11145 to the directory in which the object file resides, and then to reference
11146 the file by its name, without any path. For instance, a program
11147 @file{prog.o} may reside in @file{@var{vxpath}/vw/demo/rdb} in VxWorks
11148 and in @file{@var{hostpath}/vw/demo/rdb} on the host. To load this
11149 program, type this on VxWorks:
11150
11151 @example
11152 -> cd "@var{vxpath}/vw/demo/rdb"
11153 @end example
11154
11155 @noindent
11156 Then, in @value{GDBN}, type:
11157
11158 @example
11159 (vxgdb) cd @var{hostpath}/vw/demo/rdb
11160 (vxgdb) load prog.o
11161 @end example
11162
11163 @value{GDBN} displays a response similar to this:
11164
11165 @smallexample
11166 Reading symbol data from wherever/vw/demo/rdb/prog.o... done.
11167 @end smallexample
11168
11169 You can also use the @code{load} command to reload an object module
11170 after editing and recompiling the corresponding source file. Note that
11171 this makes @value{GDBN} delete all currently-defined breakpoints,
11172 auto-displays, and convenience variables, and to clear the value
11173 history. (This is necessary in order to preserve the integrity of
11174 debugger's data structures that reference the target system's symbol
11175 table.)
11176
11177 @node VxWorks Attach
11178 @subsubsection Running tasks
11179
11180 @cindex running VxWorks tasks
11181 You can also attach to an existing task using the @code{attach} command as
11182 follows:
11183
11184 @example
11185 (vxgdb) attach @var{task}
11186 @end example
11187
11188 @noindent
11189 where @var{task} is the VxWorks hexadecimal task ID. The task can be running
11190 or suspended when you attach to it. Running tasks are suspended at
11191 the time of attachment.
11192
11193 @node Embedded Processors
11194 @section Embedded Processors
11195
11196 This section goes into details specific to particular embedded
11197 configurations.
11198
11199 @menu
11200 * A29K Embedded:: AMD A29K Embedded
11201 * ARM:: ARM
11202 * H8/300:: Hitachi H8/300
11203 * H8/500:: Hitachi H8/500
11204 * i960:: Intel i960
11205 * M32R/D:: Mitsubishi M32R/D
11206 * M68K:: Motorola M68K
11207 * M88K:: Motorola M88K
11208 * MIPS Embedded:: MIPS Embedded
11209 * PA:: HP PA Embedded
11210 * PowerPC: PowerPC
11211 * SH:: Hitachi SH
11212 * Sparclet:: Tsqware Sparclet
11213 * Sparclite:: Fujitsu Sparclite
11214 * ST2000:: Tandem ST2000
11215 * Z8000:: Zilog Z8000
11216 @end menu
11217
11218 @node A29K Embedded
11219 @subsection AMD A29K Embedded
11220
11221 @menu
11222 * A29K UDI::
11223 * A29K EB29K::
11224 * Comms (EB29K):: Communications setup
11225 * gdb-EB29K:: EB29K cross-debugging
11226 * Remote Log:: Remote log
11227 @end menu
11228
11229 @table @code
11230
11231 @kindex target adapt
11232 @item target adapt @var{dev}
11233 Adapt monitor for A29K.
11234
11235 @kindex target amd-eb
11236 @item target amd-eb @var{dev} @var{speed} @var{PROG}
11237 @cindex AMD EB29K
11238 Remote PC-resident AMD EB29K board, attached over serial lines.
11239 @var{dev} is the serial device, as for @code{target remote};
11240 @var{speed} allows you to specify the linespeed; and @var{PROG} is the
11241 name of the program to be debugged, as it appears to DOS on the PC.
11242 @xref{A29K EB29K, ,EBMON protocol for AMD29K}.
11243
11244 @end table
11245
11246 @node A29K UDI
11247 @subsubsection A29K UDI
11248
11249 @cindex UDI
11250 @cindex AMD29K via UDI
11251
11252 @value{GDBN} supports AMD's UDI (``Universal Debugger Interface'')
11253 protocol for debugging the a29k processor family. To use this
11254 configuration with AMD targets running the MiniMON monitor, you need the
11255 program @code{MONTIP}, available from AMD at no charge. You can also
11256 use @value{GDBN} with the UDI-conformant a29k simulator program
11257 @code{ISSTIP}, also available from AMD.
11258
11259 @table @code
11260 @item target udi @var{keyword}
11261 @kindex udi
11262 Select the UDI interface to a remote a29k board or simulator, where
11263 @var{keyword} is an entry in the AMD configuration file @file{udi_soc}.
11264 This file contains keyword entries which specify parameters used to
11265 connect to a29k targets. If the @file{udi_soc} file is not in your
11266 working directory, you must set the environment variable @samp{UDICONF}
11267 to its pathname.
11268 @end table
11269
11270 @node A29K EB29K
11271 @subsubsection EBMON protocol for AMD29K
11272
11273 @cindex EB29K board
11274 @cindex running 29K programs
11275
11276 AMD distributes a 29K development board meant to fit in a PC, together
11277 with a DOS-hosted monitor program called @code{EBMON}. As a shorthand
11278 term, this development system is called the ``EB29K''. To use
11279 @value{GDBN} from a Unix system to run programs on the EB29K board, you
11280 must first connect a serial cable between the PC (which hosts the EB29K
11281 board) and a serial port on the Unix system. In the following, we
11282 assume you've hooked the cable between the PC's @file{COM1} port and
11283 @file{/dev/ttya} on the Unix system.
11284
11285 @node Comms (EB29K)
11286 @subsubsection Communications setup
11287
11288 The next step is to set up the PC's port, by doing something like this
11289 in DOS on the PC:
11290
11291 @example
11292 C:\> MODE com1:9600,n,8,1,none
11293 @end example
11294
11295 @noindent
11296 This example---run on an MS DOS 4.0 system---sets the PC port to 9600
11297 bps, no parity, eight data bits, one stop bit, and no ``retry'' action;
11298 you must match the communications parameters when establishing the Unix
11299 end of the connection as well.
11300 @c FIXME: Who knows what this "no retry action" crud from the DOS manual may
11301 @c mean? It's optional; leave it out? ---doc@cygnus.com, 25feb91
11302 @c
11303 @c It's optional, but it's unwise to omit it: who knows what is the
11304 @c default value set when the DOS machines boots? "No retry" means that
11305 @c the DOS serial device driver won't retry the operation if it fails;
11306 @c I understand that this is needed because the GDB serial protocol
11307 @c handles any errors and retransmissions itself. ---Eli Zaretskii, 3sep99
11308
11309 To give control of the PC to the Unix side of the serial line, type
11310 the following at the DOS console:
11311
11312 @example
11313 C:\> CTTY com1
11314 @end example
11315
11316 @noindent
11317 (Later, if you wish to return control to the DOS console, you can use
11318 the command @code{CTTY con}---but you must send it over the device that
11319 had control, in our example over the @file{COM1} serial line.)
11320
11321 From the Unix host, use a communications program such as @code{tip} or
11322 @code{cu} to communicate with the PC; for example,
11323
11324 @example
11325 cu -s 9600 -l /dev/ttya
11326 @end example
11327
11328 @noindent
11329 The @code{cu} options shown specify, respectively, the linespeed and the
11330 serial port to use. If you use @code{tip} instead, your command line
11331 may look something like the following:
11332
11333 @example
11334 tip -9600 /dev/ttya
11335 @end example
11336
11337 @noindent
11338 Your system may require a different name where we show
11339 @file{/dev/ttya} as the argument to @code{tip}. The communications
11340 parameters, including which port to use, are associated with the
11341 @code{tip} argument in the ``remote'' descriptions file---normally the
11342 system table @file{/etc/remote}.
11343 @c FIXME: What if anything needs doing to match the "n,8,1,none" part of
11344 @c the DOS side's comms setup? cu can support -o (odd
11345 @c parity), -e (even parity)---apparently no settings for no parity or
11346 @c for character size. Taken from stty maybe...? John points out tip
11347 @c can set these as internal variables, eg ~s parity=none; man stty
11348 @c suggests that it *might* work to stty these options with stdin or
11349 @c stdout redirected... ---doc@cygnus.com, 25feb91
11350 @c
11351 @c There's nothing to be done for the "none" part of the DOS MODE
11352 @c command. The rest of the parameters should be matched by the
11353 @c baudrate, bits, and parity used by the Unix side. ---Eli Zaretskii, 3Sep99
11354
11355 @kindex EBMON
11356 Using the @code{tip} or @code{cu} connection, change the DOS working
11357 directory to the directory containing a copy of your 29K program, then
11358 start the PC program @code{EBMON} (an EB29K control program supplied
11359 with your board by AMD). You should see an initial display from
11360 @code{EBMON} similar to the one that follows, ending with the
11361 @code{EBMON} prompt @samp{#}---
11362
11363 @example
11364 C:\> G:
11365
11366 G:\> CD \usr\joe\work29k
11367
11368 G:\USR\JOE\WORK29K> EBMON
11369 Am29000 PC Coprocessor Board Monitor, version 3.0-18
11370 Copyright 1990 Advanced Micro Devices, Inc.
11371 Written by Gibbons and Associates, Inc.
11372
11373 Enter '?' or 'H' for help
11374
11375 PC Coprocessor Type = EB29K
11376 I/O Base = 0x208
11377 Memory Base = 0xd0000
11378
11379 Data Memory Size = 2048KB
11380 Available I-RAM Range = 0x8000 to 0x1fffff
11381 Available D-RAM Range = 0x80002000 to 0x801fffff
11382
11383 PageSize = 0x400
11384 Register Stack Size = 0x800
11385 Memory Stack Size = 0x1800
11386
11387 CPU PRL = 0x3
11388 Am29027 Available = No
11389 Byte Write Available = Yes
11390
11391 # ~.
11392 @end example
11393
11394 Then exit the @code{cu} or @code{tip} program (done in the example by
11395 typing @code{~.} at the @code{EBMON} prompt). @code{EBMON} keeps
11396 running, ready for @value{GDBN} to take over.
11397
11398 For this example, we've assumed what is probably the most convenient
11399 way to make sure the same 29K program is on both the PC and the Unix
11400 system: a PC/NFS connection that establishes ``drive @file{G:}'' on the
11401 PC as a file system on the Unix host. If you do not have PC/NFS or
11402 something similar connecting the two systems, you must arrange some
11403 other way---perhaps floppy-disk transfer---of getting the 29K program
11404 from the Unix system to the PC; @value{GDBN} does @emph{not} download it over the
11405 serial line.
11406
11407 @node gdb-EB29K
11408 @subsubsection EB29K cross-debugging
11409
11410 Finally, @code{cd} to the directory containing an image of your 29K
11411 program on the Unix system, and start @value{GDBN}---specifying as argument the
11412 name of your 29K program:
11413
11414 @example
11415 cd /usr/joe/work29k
11416 @value{GDBP} myfoo
11417 @end example
11418
11419 @need 500
11420 Now you can use the @code{target} command:
11421
11422 @example
11423 target amd-eb /dev/ttya 9600 MYFOO
11424 @c FIXME: test above 'target amd-eb' as spelled, with caps! caps are meant to
11425 @c emphasize that this is the name as seen by DOS (since I think DOS is
11426 @c single-minded about case of letters). ---doc@cygnus.com, 25feb91
11427 @end example
11428
11429 @noindent
11430 In this example, we've assumed your program is in a file called
11431 @file{myfoo}. Note that the filename given as the last argument to
11432 @code{target amd-eb} should be the name of the program as it appears to DOS.
11433 In our example this is simply @code{MYFOO}, but in general it can include
11434 a DOS path, and depending on your transfer mechanism may not resemble
11435 the name on the Unix side.
11436
11437 At this point, you can set any breakpoints you wish; when you are ready
11438 to see your program run on the 29K board, use the @value{GDBN} command
11439 @code{run}.
11440
11441 To stop debugging the remote program, use the @value{GDBN} @code{detach}
11442 command.
11443
11444 To return control of the PC to its console, use @code{tip} or @code{cu}
11445 once again, after your @value{GDBN} session has concluded, to attach to
11446 @code{EBMON}. You can then type the command @code{q} to shut down
11447 @code{EBMON}, returning control to the DOS command-line interpreter.
11448 Type @kbd{CTTY con} to return command input to the main DOS console,
11449 and type @kbd{~.} to leave @code{tip} or @code{cu}.
11450
11451 @node Remote Log
11452 @subsubsection Remote log
11453 @cindex @file{eb.log}, a log file for EB29K
11454 @cindex log file for EB29K
11455
11456 The @code{target amd-eb} command creates a file @file{eb.log} in the
11457 current working directory, to help debug problems with the connection.
11458 @file{eb.log} records all the output from @code{EBMON}, including echoes
11459 of the commands sent to it. Running @samp{tail -f} on this file in
11460 another window often helps to understand trouble with @code{EBMON}, or
11461 unexpected events on the PC side of the connection.
11462
11463 @node ARM
11464 @subsection ARM
11465
11466 @table @code
11467
11468 @kindex target rdi
11469 @item target rdi @var{dev}
11470 ARM Angel monitor, via RDI library interface to ADP protocol. You may
11471 use this target to communicate with both boards running the Angel
11472 monitor, or with the EmbeddedICE JTAG debug device.
11473
11474 @kindex target rdp
11475 @item target rdp @var{dev}
11476 ARM Demon monitor.
11477
11478 @end table
11479
11480 @node H8/300
11481 @subsection Hitachi H8/300
11482
11483 @table @code
11484
11485 @kindex target hms@r{, with H8/300}
11486 @item target hms @var{dev}
11487 A Hitachi SH, H8/300, or H8/500 board, attached via serial line to your host.
11488 Use special commands @code{device} and @code{speed} to control the serial
11489 line and the communications speed used.
11490
11491 @kindex target e7000@r{, with H8/300}
11492 @item target e7000 @var{dev}
11493 E7000 emulator for Hitachi H8 and SH.
11494
11495 @kindex target sh3@r{, with H8/300}
11496 @kindex target sh3e@r{, with H8/300}
11497 @item target sh3 @var{dev}
11498 @itemx target sh3e @var{dev}
11499 Hitachi SH-3 and SH-3E target systems.
11500
11501 @end table
11502
11503 @cindex download to H8/300 or H8/500
11504 @cindex H8/300 or H8/500 download
11505 @cindex download to Hitachi SH
11506 @cindex Hitachi SH download
11507 When you select remote debugging to a Hitachi SH, H8/300, or H8/500
11508 board, the @code{load} command downloads your program to the Hitachi
11509 board and also opens it as the current executable target for
11510 @value{GDBN} on your host (like the @code{file} command).
11511
11512 @value{GDBN} needs to know these things to talk to your
11513 Hitachi SH, H8/300, or H8/500:
11514
11515 @enumerate
11516 @item
11517 that you want to use @samp{target hms}, the remote debugging interface
11518 for Hitachi microprocessors, or @samp{target e7000}, the in-circuit
11519 emulator for the Hitachi SH and the Hitachi 300H. (@samp{target hms} is
11520 the default when @value{GDBN} is configured specifically for the Hitachi SH,
11521 H8/300, or H8/500.)
11522
11523 @item
11524 what serial device connects your host to your Hitachi board (the first
11525 serial device available on your host is the default).
11526
11527 @item
11528 what speed to use over the serial device.
11529 @end enumerate
11530
11531 @menu
11532 * Hitachi Boards:: Connecting to Hitachi boards.
11533 * Hitachi ICE:: Using the E7000 In-Circuit Emulator.
11534 * Hitachi Special:: Special @value{GDBN} commands for Hitachi micros.
11535 @end menu
11536
11537 @node Hitachi Boards
11538 @subsubsection Connecting to Hitachi boards
11539
11540 @c only for Unix hosts
11541 @kindex device
11542 @cindex serial device, Hitachi micros
11543 Use the special @code{@value{GDBN}} command @samp{device @var{port}} if you
11544 need to explicitly set the serial device. The default @var{port} is the
11545 first available port on your host. This is only necessary on Unix
11546 hosts, where it is typically something like @file{/dev/ttya}.
11547
11548 @kindex speed
11549 @cindex serial line speed, Hitachi micros
11550 @code{@value{GDBN}} has another special command to set the communications
11551 speed: @samp{speed @var{bps}}. This command also is only used from Unix
11552 hosts; on DOS hosts, set the line speed as usual from outside @value{GDBN} with
11553 the DOS @code{mode} command (for instance,
11554 @w{@kbd{mode com2:9600,n,8,1,p}} for a 9600@dmn{bps} connection).
11555
11556 The @samp{device} and @samp{speed} commands are available only when you
11557 use a Unix host to debug your Hitachi microprocessor programs. If you
11558 use a DOS host,
11559 @value{GDBN} depends on an auxiliary terminate-and-stay-resident program
11560 called @code{asynctsr} to communicate with the development board
11561 through a PC serial port. You must also use the DOS @code{mode} command
11562 to set up the serial port on the DOS side.
11563
11564 The following sample session illustrates the steps needed to start a
11565 program under @value{GDBN} control on an H8/300. The example uses a
11566 sample H8/300 program called @file{t.x}. The procedure is the same for
11567 the Hitachi SH and the H8/500.
11568
11569 First hook up your development board. In this example, we use a
11570 board attached to serial port @code{COM2}; if you use a different serial
11571 port, substitute its name in the argument of the @code{mode} command.
11572 When you call @code{asynctsr}, the auxiliary comms program used by the
11573 debugger, you give it just the numeric part of the serial port's name;
11574 for example, @samp{asyncstr 2} below runs @code{asyncstr} on
11575 @code{COM2}.
11576
11577 @example
11578 C:\H8300\TEST> asynctsr 2
11579 C:\H8300\TEST> mode com2:9600,n,8,1,p
11580
11581 Resident portion of MODE loaded
11582
11583 COM2: 9600, n, 8, 1, p
11584
11585 @end example
11586
11587 @quotation
11588 @emph{Warning:} We have noticed a bug in PC-NFS that conflicts with
11589 @code{asynctsr}. If you also run PC-NFS on your DOS host, you may need to
11590 disable it, or even boot without it, to use @code{asynctsr} to control
11591 your development board.
11592 @end quotation
11593
11594 @kindex target hms@r{, and serial protocol}
11595 Now that serial communications are set up, and the development board is
11596 connected, you can start up @value{GDBN}. Call @code{@value{GDBP}} with
11597 the name of your program as the argument. @code{@value{GDBN}} prompts
11598 you, as usual, with the prompt @samp{(@value{GDBP})}. Use two special
11599 commands to begin your debugging session: @samp{target hms} to specify
11600 cross-debugging to the Hitachi board, and the @code{load} command to
11601 download your program to the board. @code{load} displays the names of
11602 the program's sections, and a @samp{*} for each 2K of data downloaded.
11603 (If you want to refresh @value{GDBN} data on symbols or on the
11604 executable file without downloading, use the @value{GDBN} commands
11605 @code{file} or @code{symbol-file}. These commands, and @code{load}
11606 itself, are described in @ref{Files,,Commands to specify files}.)
11607
11608 @smallexample
11609 (eg-C:\H8300\TEST) @value{GDBP} t.x
11610 @value{GDBN} is free software and you are welcome to distribute copies
11611 of it under certain conditions; type "show copying" to see
11612 the conditions.
11613 There is absolutely no warranty for @value{GDBN}; type "show warranty"
11614 for details.
11615 @value{GDBN} @value{GDBVN}, Copyright 1992 Free Software Foundation, Inc...
11616 (@value{GDBP}) target hms
11617 Connected to remote H8/300 HMS system.
11618 (@value{GDBP}) load t.x
11619 .text : 0x8000 .. 0xabde ***********
11620 .data : 0xabde .. 0xad30 *
11621 .stack : 0xf000 .. 0xf014 *
11622 @end smallexample
11623
11624 At this point, you're ready to run or debug your program. From here on,
11625 you can use all the usual @value{GDBN} commands. The @code{break} command
11626 sets breakpoints; the @code{run} command starts your program;
11627 @code{print} or @code{x} display data; the @code{continue} command
11628 resumes execution after stopping at a breakpoint. You can use the
11629 @code{help} command at any time to find out more about @value{GDBN} commands.
11630
11631 Remember, however, that @emph{operating system} facilities aren't
11632 available on your development board; for example, if your program hangs,
11633 you can't send an interrupt---but you can press the @sc{reset} switch!
11634
11635 Use the @sc{reset} button on the development board
11636 @itemize @bullet
11637 @item
11638 to interrupt your program (don't use @kbd{ctl-C} on the DOS host---it has
11639 no way to pass an interrupt signal to the development board); and
11640
11641 @item
11642 to return to the @value{GDBN} command prompt after your program finishes
11643 normally. The communications protocol provides no other way for @value{GDBN}
11644 to detect program completion.
11645 @end itemize
11646
11647 In either case, @value{GDBN} sees the effect of a @sc{reset} on the
11648 development board as a ``normal exit'' of your program.
11649
11650 @node Hitachi ICE
11651 @subsubsection Using the E7000 in-circuit emulator
11652
11653 @kindex target e7000@r{, with Hitachi ICE}
11654 You can use the E7000 in-circuit emulator to develop code for either the
11655 Hitachi SH or the H8/300H. Use one of these forms of the @samp{target
11656 e7000} command to connect @value{GDBN} to your E7000:
11657
11658 @table @code
11659 @item target e7000 @var{port} @var{speed}
11660 Use this form if your E7000 is connected to a serial port. The
11661 @var{port} argument identifies what serial port to use (for example,
11662 @samp{com2}). The third argument is the line speed in bits per second
11663 (for example, @samp{9600}).
11664
11665 @item target e7000 @var{hostname}
11666 If your E7000 is installed as a host on a TCP/IP network, you can just
11667 specify its hostname; @value{GDBN} uses @code{telnet} to connect.
11668 @end table
11669
11670 @node Hitachi Special
11671 @subsubsection Special @value{GDBN} commands for Hitachi micros
11672
11673 Some @value{GDBN} commands are available only for the H8/300:
11674
11675 @table @code
11676
11677 @kindex set machine
11678 @kindex show machine
11679 @item set machine h8300
11680 @itemx set machine h8300h
11681 Condition @value{GDBN} for one of the two variants of the H8/300
11682 architecture with @samp{set machine}. You can use @samp{show machine}
11683 to check which variant is currently in effect.
11684
11685 @end table
11686
11687 @node H8/500
11688 @subsection H8/500
11689
11690 @table @code
11691
11692 @kindex set memory @var{mod}
11693 @cindex memory models, H8/500
11694 @item set memory @var{mod}
11695 @itemx show memory
11696 Specify which H8/500 memory model (@var{mod}) you are using with
11697 @samp{set memory}; check which memory model is in effect with @samp{show
11698 memory}. The accepted values for @var{mod} are @code{small},
11699 @code{big}, @code{medium}, and @code{compact}.
11700
11701 @end table
11702
11703 @node i960
11704 @subsection Intel i960
11705
11706 @table @code
11707
11708 @kindex target mon960
11709 @item target mon960 @var{dev}
11710 MON960 monitor for Intel i960.
11711
11712 @kindex target nindy
11713 @item target nindy @var{devicename}
11714 An Intel 960 board controlled by a Nindy Monitor. @var{devicename} is
11715 the name of the serial device to use for the connection, e.g.
11716 @file{/dev/ttya}.
11717
11718 @end table
11719
11720 @cindex Nindy
11721 @cindex i960
11722 @dfn{Nindy} is a ROM Monitor program for Intel 960 target systems. When
11723 @value{GDBN} is configured to control a remote Intel 960 using Nindy, you can
11724 tell @value{GDBN} how to connect to the 960 in several ways:
11725
11726 @itemize @bullet
11727 @item
11728 Through command line options specifying serial port, version of the
11729 Nindy protocol, and communications speed;
11730
11731 @item
11732 By responding to a prompt on startup;
11733
11734 @item
11735 By using the @code{target} command at any point during your @value{GDBN}
11736 session. @xref{Target Commands, ,Commands for managing targets}.
11737
11738 @end itemize
11739
11740 @cindex download to Nindy-960
11741 With the Nindy interface to an Intel 960 board, @code{load}
11742 downloads @var{filename} to the 960 as well as adding its symbols in
11743 @value{GDBN}.
11744
11745 @menu
11746 * Nindy Startup:: Startup with Nindy
11747 * Nindy Options:: Options for Nindy
11748 * Nindy Reset:: Nindy reset command
11749 @end menu
11750
11751 @node Nindy Startup
11752 @subsubsection Startup with Nindy
11753
11754 If you simply start @code{@value{GDBP}} without using any command-line
11755 options, you are prompted for what serial port to use, @emph{before} you
11756 reach the ordinary @value{GDBN} prompt:
11757
11758 @example
11759 Attach /dev/ttyNN -- specify NN, or "quit" to quit:
11760 @end example
11761
11762 @noindent
11763 Respond to the prompt with whatever suffix (after @samp{/dev/tty})
11764 identifies the serial port you want to use. You can, if you choose,
11765 simply start up with no Nindy connection by responding to the prompt
11766 with an empty line. If you do this and later wish to attach to Nindy,
11767 use @code{target} (@pxref{Target Commands, ,Commands for managing targets}).
11768
11769 @node Nindy Options
11770 @subsubsection Options for Nindy
11771
11772 These are the startup options for beginning your @value{GDBN} session with a
11773 Nindy-960 board attached:
11774
11775 @table @code
11776 @item -r @var{port}
11777 Specify the serial port name of a serial interface to be used to connect
11778 to the target system. This option is only available when @value{GDBN} is
11779 configured for the Intel 960 target architecture. You may specify
11780 @var{port} as any of: a full pathname (e.g. @samp{-r /dev/ttya}), a
11781 device name in @file{/dev} (e.g. @samp{-r ttya}), or simply the unique
11782 suffix for a specific @code{tty} (e.g. @samp{-r a}).
11783
11784 @item -O
11785 (An uppercase letter ``O'', not a zero.) Specify that @value{GDBN} should use
11786 the ``old'' Nindy monitor protocol to connect to the target system.
11787 This option is only available when @value{GDBN} is configured for the Intel 960
11788 target architecture.
11789
11790 @quotation
11791 @emph{Warning:} if you specify @samp{-O}, but are actually trying to
11792 connect to a target system that expects the newer protocol, the connection
11793 fails, appearing to be a speed mismatch. @value{GDBN} repeatedly
11794 attempts to reconnect at several different line speeds. You can abort
11795 this process with an interrupt.
11796 @end quotation
11797
11798 @item -brk
11799 Specify that @value{GDBN} should first send a @code{BREAK} signal to the target
11800 system, in an attempt to reset it, before connecting to a Nindy target.
11801
11802 @quotation
11803 @emph{Warning:} Many target systems do not have the hardware that this
11804 requires; it only works with a few boards.
11805 @end quotation
11806 @end table
11807
11808 The standard @samp{-b} option controls the line speed used on the serial
11809 port.
11810
11811 @c @group
11812 @node Nindy Reset
11813 @subsubsection Nindy reset command
11814
11815 @table @code
11816 @item reset
11817 @kindex reset
11818 For a Nindy target, this command sends a ``break'' to the remote target
11819 system; this is only useful if the target has been equipped with a
11820 circuit to perform a hard reset (or some other interesting action) when
11821 a break is detected.
11822 @end table
11823 @c @end group
11824
11825 @node M32R/D
11826 @subsection Mitsubishi M32R/D
11827
11828 @table @code
11829
11830 @kindex target m32r
11831 @item target m32r @var{dev}
11832 Mitsubishi M32R/D ROM monitor.
11833
11834 @end table
11835
11836 @node M68K
11837 @subsection M68k
11838
11839 The Motorola m68k configuration includes ColdFire support, and
11840 target command for the following ROM monitors.
11841
11842 @table @code
11843
11844 @kindex target abug
11845 @item target abug @var{dev}
11846 ABug ROM monitor for M68K.
11847
11848 @kindex target cpu32bug
11849 @item target cpu32bug @var{dev}
11850 CPU32BUG monitor, running on a CPU32 (M68K) board.
11851
11852 @kindex target dbug
11853 @item target dbug @var{dev}
11854 dBUG ROM monitor for Motorola ColdFire.
11855
11856 @kindex target est
11857 @item target est @var{dev}
11858 EST-300 ICE monitor, running on a CPU32 (M68K) board.
11859
11860 @kindex target rom68k
11861 @item target rom68k @var{dev}
11862 ROM 68K monitor, running on an M68K IDP board.
11863
11864 @end table
11865
11866 If @value{GDBN} is configured with @code{m68*-ericsson-*}, it will
11867 instead have only a single special target command:
11868
11869 @table @code
11870
11871 @kindex target es1800
11872 @item target es1800 @var{dev}
11873 ES-1800 emulator for M68K.
11874
11875 @end table
11876
11877 [context?]
11878
11879 @table @code
11880
11881 @kindex target rombug
11882 @item target rombug @var{dev}
11883 ROMBUG ROM monitor for OS/9000.
11884
11885 @end table
11886
11887 @node M88K
11888 @subsection M88K
11889
11890 @table @code
11891
11892 @kindex target bug
11893 @item target bug @var{dev}
11894 BUG monitor, running on a MVME187 (m88k) board.
11895
11896 @end table
11897
11898 @node MIPS Embedded
11899 @subsection MIPS Embedded
11900
11901 @cindex MIPS boards
11902 @value{GDBN} can use the MIPS remote debugging protocol to talk to a
11903 MIPS board attached to a serial line. This is available when
11904 you configure @value{GDBN} with @samp{--target=mips-idt-ecoff}.
11905
11906 @need 1000
11907 Use these @value{GDBN} commands to specify the connection to your target board:
11908
11909 @table @code
11910 @item target mips @var{port}
11911 @kindex target mips @var{port}
11912 To run a program on the board, start up @code{@value{GDBP}} with the
11913 name of your program as the argument. To connect to the board, use the
11914 command @samp{target mips @var{port}}, where @var{port} is the name of
11915 the serial port connected to the board. If the program has not already
11916 been downloaded to the board, you may use the @code{load} command to
11917 download it. You can then use all the usual @value{GDBN} commands.
11918
11919 For example, this sequence connects to the target board through a serial
11920 port, and loads and runs a program called @var{prog} through the
11921 debugger:
11922
11923 @example
11924 host$ @value{GDBP} @var{prog}
11925 @value{GDBN} is free software and @dots{}
11926 (@value{GDBP}) target mips /dev/ttyb
11927 (@value{GDBP}) load @var{prog}
11928 (@value{GDBP}) run
11929 @end example
11930
11931 @item target mips @var{hostname}:@var{portnumber}
11932 On some @value{GDBN} host configurations, you can specify a TCP
11933 connection (for instance, to a serial line managed by a terminal
11934 concentrator) instead of a serial port, using the syntax
11935 @samp{@var{hostname}:@var{portnumber}}.
11936
11937 @item target pmon @var{port}
11938 @kindex target pmon @var{port}
11939 PMON ROM monitor.
11940
11941 @item target ddb @var{port}
11942 @kindex target ddb @var{port}
11943 NEC's DDB variant of PMON for Vr4300.
11944
11945 @item target lsi @var{port}
11946 @kindex target lsi @var{port}
11947 LSI variant of PMON.
11948
11949 @kindex target r3900
11950 @item target r3900 @var{dev}
11951 Densan DVE-R3900 ROM monitor for Toshiba R3900 Mips.
11952
11953 @kindex target array
11954 @item target array @var{dev}
11955 Array Tech LSI33K RAID controller board.
11956
11957 @end table
11958
11959
11960 @noindent
11961 @value{GDBN} also supports these special commands for MIPS targets:
11962
11963 @table @code
11964 @item set processor @var{args}
11965 @itemx show processor
11966 @kindex set processor @var{args}
11967 @kindex show processor
11968 Use the @code{set processor} command to set the type of MIPS
11969 processor when you want to access processor-type-specific registers.
11970 For example, @code{set processor @var{r3041}} tells @value{GDBN}
11971 to use the CPU registers appropriate for the 3041 chip.
11972 Use the @code{show processor} command to see what MIPS processor @value{GDBN}
11973 is using. Use the @code{info reg} command to see what registers
11974 @value{GDBN} is using.
11975
11976 @item set mipsfpu double
11977 @itemx set mipsfpu single
11978 @itemx set mipsfpu none
11979 @itemx show mipsfpu
11980 @kindex set mipsfpu
11981 @kindex show mipsfpu
11982 @cindex MIPS remote floating point
11983 @cindex floating point, MIPS remote
11984 If your target board does not support the MIPS floating point
11985 coprocessor, you should use the command @samp{set mipsfpu none} (if you
11986 need this, you may wish to put the command in your @value{GDBN} init
11987 file). This tells @value{GDBN} how to find the return value of
11988 functions which return floating point values. It also allows
11989 @value{GDBN} to avoid saving the floating point registers when calling
11990 functions on the board. If you are using a floating point coprocessor
11991 with only single precision floating point support, as on the @sc{r4650}
11992 processor, use the command @samp{set mipsfpu single}. The default
11993 double precision floating point coprocessor may be selected using
11994 @samp{set mipsfpu double}.
11995
11996 In previous versions the only choices were double precision or no
11997 floating point, so @samp{set mipsfpu on} will select double precision
11998 and @samp{set mipsfpu off} will select no floating point.
11999
12000 As usual, you can inquire about the @code{mipsfpu} variable with
12001 @samp{show mipsfpu}.
12002
12003 @item set remotedebug @var{n}
12004 @itemx show remotedebug
12005 @kindex set remotedebug@r{, MIPS protocol}
12006 @kindex show remotedebug@r{, MIPS protocol}
12007 @cindex @code{remotedebug}, MIPS protocol
12008 @cindex MIPS @code{remotedebug} protocol
12009 @c FIXME! For this to be useful, you must know something about the MIPS
12010 @c FIXME...protocol. Where is it described?
12011 You can see some debugging information about communications with the board
12012 by setting the @code{remotedebug} variable. If you set it to @code{1} using
12013 @samp{set remotedebug 1}, every packet is displayed. If you set it
12014 to @code{2}, every character is displayed. You can check the current value
12015 at any time with the command @samp{show remotedebug}.
12016
12017 @item set timeout @var{seconds}
12018 @itemx set retransmit-timeout @var{seconds}
12019 @itemx show timeout
12020 @itemx show retransmit-timeout
12021 @cindex @code{timeout}, MIPS protocol
12022 @cindex @code{retransmit-timeout}, MIPS protocol
12023 @kindex set timeout
12024 @kindex show timeout
12025 @kindex set retransmit-timeout
12026 @kindex show retransmit-timeout
12027 You can control the timeout used while waiting for a packet, in the MIPS
12028 remote protocol, with the @code{set timeout @var{seconds}} command. The
12029 default is 5 seconds. Similarly, you can control the timeout used while
12030 waiting for an acknowledgement of a packet with the @code{set
12031 retransmit-timeout @var{seconds}} command. The default is 3 seconds.
12032 You can inspect both values with @code{show timeout} and @code{show
12033 retransmit-timeout}. (These commands are @emph{only} available when
12034 @value{GDBN} is configured for @samp{--target=mips-idt-ecoff}.)
12035
12036 The timeout set by @code{set timeout} does not apply when @value{GDBN}
12037 is waiting for your program to stop. In that case, @value{GDBN} waits
12038 forever because it has no way of knowing how long the program is going
12039 to run before stopping.
12040 @end table
12041
12042 @node PowerPC
12043 @subsection PowerPC
12044
12045 @table @code
12046
12047 @kindex target dink32
12048 @item target dink32 @var{dev}
12049 DINK32 ROM monitor.
12050
12051 @kindex target ppcbug
12052 @item target ppcbug @var{dev}
12053 @kindex target ppcbug1
12054 @item target ppcbug1 @var{dev}
12055 PPCBUG ROM monitor for PowerPC.
12056
12057 @kindex target sds
12058 @item target sds @var{dev}
12059 SDS monitor, running on a PowerPC board (such as Motorola's ADS).
12060
12061 @end table
12062
12063 @node PA
12064 @subsection HP PA Embedded
12065
12066 @table @code
12067
12068 @kindex target op50n
12069 @item target op50n @var{dev}
12070 OP50N monitor, running on an OKI HPPA board.
12071
12072 @kindex target w89k
12073 @item target w89k @var{dev}
12074 W89K monitor, running on a Winbond HPPA board.
12075
12076 @end table
12077
12078 @node SH
12079 @subsection Hitachi SH
12080
12081 @table @code
12082
12083 @kindex target hms@r{, with Hitachi SH}
12084 @item target hms @var{dev}
12085 A Hitachi SH board attached via serial line to your host. Use special
12086 commands @code{device} and @code{speed} to control the serial line and
12087 the communications speed used.
12088
12089 @kindex target e7000@r{, with Hitachi SH}
12090 @item target e7000 @var{dev}
12091 E7000 emulator for Hitachi SH.
12092
12093 @kindex target sh3@r{, with SH}
12094 @kindex target sh3e@r{, with SH}
12095 @item target sh3 @var{dev}
12096 @item target sh3e @var{dev}
12097 Hitachi SH-3 and SH-3E target systems.
12098
12099 @end table
12100
12101 @node Sparclet
12102 @subsection Tsqware Sparclet
12103
12104 @cindex Sparclet
12105
12106 @value{GDBN} enables developers to debug tasks running on
12107 Sparclet targets from a Unix host.
12108 @value{GDBN} uses code that runs on
12109 both the Unix host and on the Sparclet target. The program
12110 @code{@value{GDBP}} is installed and executed on the Unix host.
12111
12112 @table @code
12113 @item remotetimeout @var{args}
12114 @kindex remotetimeout
12115 @value{GDBN} supports the option @code{remotetimeout}.
12116 This option is set by the user, and @var{args} represents the number of
12117 seconds @value{GDBN} waits for responses.
12118 @end table
12119
12120 @cindex compiling, on Sparclet
12121 When compiling for debugging, include the options @samp{-g} to get debug
12122 information and @samp{-Ttext} to relocate the program to where you wish to
12123 load it on the target. You may also want to add the options @samp{-n} or
12124 @samp{-N} in order to reduce the size of the sections. Example:
12125
12126 @example
12127 sparclet-aout-gcc prog.c -Ttext 0x12010000 -g -o prog -N
12128 @end example
12129
12130 You can use @code{objdump} to verify that the addresses are what you intended:
12131
12132 @example
12133 sparclet-aout-objdump --headers --syms prog
12134 @end example
12135
12136 @cindex running, on Sparclet
12137 Once you have set
12138 your Unix execution search path to find @value{GDBN}, you are ready to
12139 run @value{GDBN}. From your Unix host, run @code{@value{GDBP}}
12140 (or @code{sparclet-aout-gdb}, depending on your installation).
12141
12142 @value{GDBN} comes up showing the prompt:
12143
12144 @example
12145 (gdbslet)
12146 @end example
12147
12148 @menu
12149 * Sparclet File:: Setting the file to debug
12150 * Sparclet Connection:: Connecting to Sparclet
12151 * Sparclet Download:: Sparclet download
12152 * Sparclet Execution:: Running and debugging
12153 @end menu
12154
12155 @node Sparclet File
12156 @subsubsection Setting file to debug
12157
12158 The @value{GDBN} command @code{file} lets you choose with program to debug.
12159
12160 @example
12161 (gdbslet) file prog
12162 @end example
12163
12164 @need 1000
12165 @value{GDBN} then attempts to read the symbol table of @file{prog}.
12166 @value{GDBN} locates
12167 the file by searching the directories listed in the command search
12168 path.
12169 If the file was compiled with debug information (option "-g"), source
12170 files will be searched as well.
12171 @value{GDBN} locates
12172 the source files by searching the directories listed in the directory search
12173 path (@pxref{Environment, ,Your program's environment}).
12174 If it fails
12175 to find a file, it displays a message such as:
12176
12177 @example
12178 prog: No such file or directory.
12179 @end example
12180
12181 When this happens, add the appropriate directories to the search paths with
12182 the @value{GDBN} commands @code{path} and @code{dir}, and execute the
12183 @code{target} command again.
12184
12185 @node Sparclet Connection
12186 @subsubsection Connecting to Sparclet
12187
12188 The @value{GDBN} command @code{target} lets you connect to a Sparclet target.
12189 To connect to a target on serial port ``@code{ttya}'', type:
12190
12191 @example
12192 (gdbslet) target sparclet /dev/ttya
12193 Remote target sparclet connected to /dev/ttya
12194 main () at ../prog.c:3
12195 @end example
12196
12197 @need 750
12198 @value{GDBN} displays messages like these:
12199
12200 @example
12201 Connected to ttya.
12202 @end example
12203
12204 @node Sparclet Download
12205 @subsubsection Sparclet download
12206
12207 @cindex download to Sparclet
12208 Once connected to the Sparclet target,
12209 you can use the @value{GDBN}
12210 @code{load} command to download the file from the host to the target.
12211 The file name and load offset should be given as arguments to the @code{load}
12212 command.
12213 Since the file format is aout, the program must be loaded to the starting
12214 address. You can use @code{objdump} to find out what this value is. The load
12215 offset is an offset which is added to the VMA (virtual memory address)
12216 of each of the file's sections.
12217 For instance, if the program
12218 @file{prog} was linked to text address 0x1201000, with data at 0x12010160
12219 and bss at 0x12010170, in @value{GDBN}, type:
12220
12221 @example
12222 (gdbslet) load prog 0x12010000
12223 Loading section .text, size 0xdb0 vma 0x12010000
12224 @end example
12225
12226 If the code is loaded at a different address then what the program was linked
12227 to, you may need to use the @code{section} and @code{add-symbol-file} commands
12228 to tell @value{GDBN} where to map the symbol table.
12229
12230 @node Sparclet Execution
12231 @subsubsection Running and debugging
12232
12233 @cindex running and debugging Sparclet programs
12234 You can now begin debugging the task using @value{GDBN}'s execution control
12235 commands, @code{b}, @code{step}, @code{run}, etc. See the @value{GDBN}
12236 manual for the list of commands.
12237
12238 @example
12239 (gdbslet) b main
12240 Breakpoint 1 at 0x12010000: file prog.c, line 3.
12241 (gdbslet) run
12242 Starting program: prog
12243 Breakpoint 1, main (argc=1, argv=0xeffff21c) at prog.c:3
12244 3 char *symarg = 0;
12245 (gdbslet) step
12246 4 char *execarg = "hello!";
12247 (gdbslet)
12248 @end example
12249
12250 @node Sparclite
12251 @subsection Fujitsu Sparclite
12252
12253 @table @code
12254
12255 @kindex target sparclite
12256 @item target sparclite @var{dev}
12257 Fujitsu sparclite boards, used only for the purpose of loading.
12258 You must use an additional command to debug the program.
12259 For example: target remote @var{dev} using @value{GDBN} standard
12260 remote protocol.
12261
12262 @end table
12263
12264 @node ST2000
12265 @subsection Tandem ST2000
12266
12267 @value{GDBN} may be used with a Tandem ST2000 phone switch, running Tandem's
12268 STDBUG protocol.
12269
12270 To connect your ST2000 to the host system, see the manufacturer's
12271 manual. Once the ST2000 is physically attached, you can run:
12272
12273 @example
12274 target st2000 @var{dev} @var{speed}
12275 @end example
12276
12277 @noindent
12278 to establish it as your debugging environment. @var{dev} is normally
12279 the name of a serial device, such as @file{/dev/ttya}, connected to the
12280 ST2000 via a serial line. You can instead specify @var{dev} as a TCP
12281 connection (for example, to a serial line attached via a terminal
12282 concentrator) using the syntax @code{@var{hostname}:@var{portnumber}}.
12283
12284 The @code{load} and @code{attach} commands are @emph{not} defined for
12285 this target; you must load your program into the ST2000 as you normally
12286 would for standalone operation. @value{GDBN} reads debugging information
12287 (such as symbols) from a separate, debugging version of the program
12288 available on your host computer.
12289 @c FIXME!! This is terribly vague; what little content is here is
12290 @c basically hearsay.
12291
12292 @cindex ST2000 auxiliary commands
12293 These auxiliary @value{GDBN} commands are available to help you with the ST2000
12294 environment:
12295
12296 @table @code
12297 @item st2000 @var{command}
12298 @kindex st2000 @var{cmd}
12299 @cindex STDBUG commands (ST2000)
12300 @cindex commands to STDBUG (ST2000)
12301 Send a @var{command} to the STDBUG monitor. See the manufacturer's
12302 manual for available commands.
12303
12304 @item connect
12305 @cindex connect (to STDBUG)
12306 Connect the controlling terminal to the STDBUG command monitor. When
12307 you are done interacting with STDBUG, typing either of two character
12308 sequences gets you back to the @value{GDBN} command prompt:
12309 @kbd{@key{RET}~.} (Return, followed by tilde and period) or
12310 @kbd{@key{RET}~@key{C-d}} (Return, followed by tilde and control-D).
12311 @end table
12312
12313 @node Z8000
12314 @subsection Zilog Z8000
12315
12316 @cindex Z8000
12317 @cindex simulator, Z8000
12318 @cindex Zilog Z8000 simulator
12319
12320 When configured for debugging Zilog Z8000 targets, @value{GDBN} includes
12321 a Z8000 simulator.
12322
12323 For the Z8000 family, @samp{target sim} simulates either the Z8002 (the
12324 unsegmented variant of the Z8000 architecture) or the Z8001 (the
12325 segmented variant). The simulator recognizes which architecture is
12326 appropriate by inspecting the object code.
12327
12328 @table @code
12329 @item target sim @var{args}
12330 @kindex sim
12331 @kindex target sim@r{, with Z8000}
12332 Debug programs on a simulated CPU. If the simulator supports setup
12333 options, specify them via @var{args}.
12334 @end table
12335
12336 @noindent
12337 After specifying this target, you can debug programs for the simulated
12338 CPU in the same style as programs for your host computer; use the
12339 @code{file} command to load a new program image, the @code{run} command
12340 to run your program, and so on.
12341
12342 As well as making available all the usual machine registers
12343 (@pxref{Registers, ,Registers}), the Z8000 simulator provides three
12344 additional items of information as specially named registers:
12345
12346 @table @code
12347
12348 @item cycles
12349 Counts clock-ticks in the simulator.
12350
12351 @item insts
12352 Counts instructions run in the simulator.
12353
12354 @item time
12355 Execution time in 60ths of a second.
12356
12357 @end table
12358
12359 You can refer to these values in @value{GDBN} expressions with the usual
12360 conventions; for example, @w{@samp{b fputc if $cycles>5000}} sets a
12361 conditional breakpoint that suspends only after at least 5000
12362 simulated clock ticks.
12363
12364 @node Architectures
12365 @section Architectures
12366
12367 This section describes characteristics of architectures that affect
12368 all uses of @value{GDBN} with the architecture, both native and cross.
12369
12370 @menu
12371 * A29K::
12372 * Alpha::
12373 * MIPS::
12374 @end menu
12375
12376 @node A29K
12377 @subsection A29K
12378
12379 @table @code
12380
12381 @kindex set rstack_high_address
12382 @cindex AMD 29K register stack
12383 @cindex register stack, AMD29K
12384 @item set rstack_high_address @var{address}
12385 On AMD 29000 family processors, registers are saved in a separate
12386 @dfn{register stack}. There is no way for @value{GDBN} to determine the
12387 extent of this stack. Normally, @value{GDBN} just assumes that the
12388 stack is ``large enough''. This may result in @value{GDBN} referencing
12389 memory locations that do not exist. If necessary, you can get around
12390 this problem by specifying the ending address of the register stack with
12391 the @code{set rstack_high_address} command. The argument should be an
12392 address, which you probably want to precede with @samp{0x} to specify in
12393 hexadecimal.
12394
12395 @kindex show rstack_high_address
12396 @item show rstack_high_address
12397 Display the current limit of the register stack, on AMD 29000 family
12398 processors.
12399
12400 @end table
12401
12402 @node Alpha
12403 @subsection Alpha
12404
12405 See the following section.
12406
12407 @node MIPS
12408 @subsection MIPS
12409
12410 @cindex stack on Alpha
12411 @cindex stack on MIPS
12412 @cindex Alpha stack
12413 @cindex MIPS stack
12414 Alpha- and MIPS-based computers use an unusual stack frame, which
12415 sometimes requires @value{GDBN} to search backward in the object code to
12416 find the beginning of a function.
12417
12418 @cindex response time, MIPS debugging
12419 To improve response time (especially for embedded applications, where
12420 @value{GDBN} may be restricted to a slow serial line for this search)
12421 you may want to limit the size of this search, using one of these
12422 commands:
12423
12424 @table @code
12425 @cindex @code{heuristic-fence-post} (Alpha, MIPS)
12426 @item set heuristic-fence-post @var{limit}
12427 Restrict @value{GDBN} to examining at most @var{limit} bytes in its
12428 search for the beginning of a function. A value of @var{0} (the
12429 default) means there is no limit. However, except for @var{0}, the
12430 larger the limit the more bytes @code{heuristic-fence-post} must search
12431 and therefore the longer it takes to run.
12432
12433 @item show heuristic-fence-post
12434 Display the current limit.
12435 @end table
12436
12437 @noindent
12438 These commands are available @emph{only} when @value{GDBN} is configured
12439 for debugging programs on Alpha or MIPS processors.
12440
12441
12442 @node Controlling GDB
12443 @chapter Controlling @value{GDBN}
12444
12445 You can alter the way @value{GDBN} interacts with you by using the
12446 @code{set} command. For commands controlling how @value{GDBN} displays
12447 data, see @ref{Print Settings, ,Print settings}. Other settings are
12448 described here.
12449
12450 @menu
12451 * Prompt:: Prompt
12452 * Editing:: Command editing
12453 * History:: Command history
12454 * Screen Size:: Screen size
12455 * Numbers:: Numbers
12456 * Messages/Warnings:: Optional warnings and messages
12457 * Debugging Output:: Optional messages about internal happenings
12458 @end menu
12459
12460 @node Prompt
12461 @section Prompt
12462
12463 @cindex prompt
12464
12465 @value{GDBN} indicates its readiness to read a command by printing a string
12466 called the @dfn{prompt}. This string is normally @samp{(@value{GDBP})}. You
12467 can change the prompt string with the @code{set prompt} command. For
12468 instance, when debugging @value{GDBN} with @value{GDBN}, it is useful to change
12469 the prompt in one of the @value{GDBN} sessions so that you can always tell
12470 which one you are talking to.
12471
12472 @emph{Note:} @code{set prompt} does not add a space for you after the
12473 prompt you set. This allows you to set a prompt which ends in a space
12474 or a prompt that does not.
12475
12476 @table @code
12477 @kindex set prompt
12478 @item set prompt @var{newprompt}
12479 Directs @value{GDBN} to use @var{newprompt} as its prompt string henceforth.
12480
12481 @kindex show prompt
12482 @item show prompt
12483 Prints a line of the form: @samp{Gdb's prompt is: @var{your-prompt}}
12484 @end table
12485
12486 @node Editing
12487 @section Command editing
12488 @cindex readline
12489 @cindex command line editing
12490
12491 @value{GDBN} reads its input commands via the @dfn{readline} interface. This
12492 @sc{gnu} library provides consistent behavior for programs which provide a
12493 command line interface to the user. Advantages are @sc{gnu} Emacs-style
12494 or @dfn{vi}-style inline editing of commands, @code{csh}-like history
12495 substitution, and a storage and recall of command history across
12496 debugging sessions.
12497
12498 You may control the behavior of command line editing in @value{GDBN} with the
12499 command @code{set}.
12500
12501 @table @code
12502 @kindex set editing
12503 @cindex editing
12504 @item set editing
12505 @itemx set editing on
12506 Enable command line editing (enabled by default).
12507
12508 @item set editing off
12509 Disable command line editing.
12510
12511 @kindex show editing
12512 @item show editing
12513 Show whether command line editing is enabled.
12514 @end table
12515
12516 @node History
12517 @section Command history
12518
12519 @value{GDBN} can keep track of the commands you type during your
12520 debugging sessions, so that you can be certain of precisely what
12521 happened. Use these commands to manage the @value{GDBN} command
12522 history facility.
12523
12524 @table @code
12525 @cindex history substitution
12526 @cindex history file
12527 @kindex set history filename
12528 @kindex GDBHISTFILE
12529 @item set history filename @var{fname}
12530 Set the name of the @value{GDBN} command history file to @var{fname}.
12531 This is the file where @value{GDBN} reads an initial command history
12532 list, and where it writes the command history from this session when it
12533 exits. You can access this list through history expansion or through
12534 the history command editing characters listed below. This file defaults
12535 to the value of the environment variable @code{GDBHISTFILE}, or to
12536 @file{./.gdb_history} (@file{./_gdb_history} on MS-DOS) if this variable
12537 is not set.
12538
12539 @cindex history save
12540 @kindex set history save
12541 @item set history save
12542 @itemx set history save on
12543 Record command history in a file, whose name may be specified with the
12544 @code{set history filename} command. By default, this option is disabled.
12545
12546 @item set history save off
12547 Stop recording command history in a file.
12548
12549 @cindex history size
12550 @kindex set history size
12551 @item set history size @var{size}
12552 Set the number of commands which @value{GDBN} keeps in its history list.
12553 This defaults to the value of the environment variable
12554 @code{HISTSIZE}, or to 256 if this variable is not set.
12555 @end table
12556
12557 @cindex history expansion
12558 History expansion assigns special meaning to the character @kbd{!}.
12559 @ifset have-readline-appendices
12560 @xref{Event Designators}.
12561 @end ifset
12562
12563 Since @kbd{!} is also the logical not operator in C, history expansion
12564 is off by default. If you decide to enable history expansion with the
12565 @code{set history expansion on} command, you may sometimes need to
12566 follow @kbd{!} (when it is used as logical not, in an expression) with
12567 a space or a tab to prevent it from being expanded. The readline
12568 history facilities do not attempt substitution on the strings
12569 @kbd{!=} and @kbd{!(}, even when history expansion is enabled.
12570
12571 The commands to control history expansion are:
12572
12573 @table @code
12574 @kindex set history expansion
12575 @item set history expansion on
12576 @itemx set history expansion
12577 Enable history expansion. History expansion is off by default.
12578
12579 @item set history expansion off
12580 Disable history expansion.
12581
12582 The readline code comes with more complete documentation of
12583 editing and history expansion features. Users unfamiliar with @sc{gnu} Emacs
12584 or @code{vi} may wish to read it.
12585 @ifset have-readline-appendices
12586 @xref{Command Line Editing}.
12587 @end ifset
12588
12589 @c @group
12590 @kindex show history
12591 @item show history
12592 @itemx show history filename
12593 @itemx show history save
12594 @itemx show history size
12595 @itemx show history expansion
12596 These commands display the state of the @value{GDBN} history parameters.
12597 @code{show history} by itself displays all four states.
12598 @c @end group
12599 @end table
12600
12601 @table @code
12602 @kindex shows
12603 @item show commands
12604 Display the last ten commands in the command history.
12605
12606 @item show commands @var{n}
12607 Print ten commands centered on command number @var{n}.
12608
12609 @item show commands +
12610 Print ten commands just after the commands last printed.
12611 @end table
12612
12613 @node Screen Size
12614 @section Screen size
12615 @cindex size of screen
12616 @cindex pauses in output
12617
12618 Certain commands to @value{GDBN} may produce large amounts of
12619 information output to the screen. To help you read all of it,
12620 @value{GDBN} pauses and asks you for input at the end of each page of
12621 output. Type @key{RET} when you want to continue the output, or @kbd{q}
12622 to discard the remaining output. Also, the screen width setting
12623 determines when to wrap lines of output. Depending on what is being
12624 printed, @value{GDBN} tries to break the line at a readable place,
12625 rather than simply letting it overflow onto the following line.
12626
12627 Normally @value{GDBN} knows the size of the screen from the terminal
12628 driver software. For example, on Unix @value{GDBN} uses the termcap data base
12629 together with the value of the @code{TERM} environment variable and the
12630 @code{stty rows} and @code{stty cols} settings. If this is not correct,
12631 you can override it with the @code{set height} and @code{set
12632 width} commands:
12633
12634 @table @code
12635 @kindex set height
12636 @kindex set width
12637 @kindex show width
12638 @kindex show height
12639 @item set height @var{lpp}
12640 @itemx show height
12641 @itemx set width @var{cpl}
12642 @itemx show width
12643 These @code{set} commands specify a screen height of @var{lpp} lines and
12644 a screen width of @var{cpl} characters. The associated @code{show}
12645 commands display the current settings.
12646
12647 If you specify a height of zero lines, @value{GDBN} does not pause during
12648 output no matter how long the output is. This is useful if output is to a
12649 file or to an editor buffer.
12650
12651 Likewise, you can specify @samp{set width 0} to prevent @value{GDBN}
12652 from wrapping its output.
12653 @end table
12654
12655 @node Numbers
12656 @section Numbers
12657 @cindex number representation
12658 @cindex entering numbers
12659
12660 You can always enter numbers in octal, decimal, or hexadecimal in
12661 @value{GDBN} by the usual conventions: octal numbers begin with
12662 @samp{0}, decimal numbers end with @samp{.}, and hexadecimal numbers
12663 begin with @samp{0x}. Numbers that begin with none of these are, by
12664 default, entered in base 10; likewise, the default display for
12665 numbers---when no particular format is specified---is base 10. You can
12666 change the default base for both input and output with the @code{set
12667 radix} command.
12668
12669 @table @code
12670 @kindex set input-radix
12671 @item set input-radix @var{base}
12672 Set the default base for numeric input. Supported choices
12673 for @var{base} are decimal 8, 10, or 16. @var{base} must itself be
12674 specified either unambiguously or using the current default radix; for
12675 example, any of
12676
12677 @smallexample
12678 set radix 012
12679 set radix 10.
12680 set radix 0xa
12681 @end smallexample
12682
12683 @noindent
12684 sets the base to decimal. On the other hand, @samp{set radix 10}
12685 leaves the radix unchanged no matter what it was.
12686
12687 @kindex set output-radix
12688 @item set output-radix @var{base}
12689 Set the default base for numeric display. Supported choices
12690 for @var{base} are decimal 8, 10, or 16. @var{base} must itself be
12691 specified either unambiguously or using the current default radix.
12692
12693 @kindex show input-radix
12694 @item show input-radix
12695 Display the current default base for numeric input.
12696
12697 @kindex show output-radix
12698 @item show output-radix
12699 Display the current default base for numeric display.
12700 @end table
12701
12702 @node Messages/Warnings
12703 @section Optional warnings and messages
12704
12705 By default, @value{GDBN} is silent about its inner workings. If you are
12706 running on a slow machine, you may want to use the @code{set verbose}
12707 command. This makes @value{GDBN} tell you when it does a lengthy
12708 internal operation, so you will not think it has crashed.
12709
12710 Currently, the messages controlled by @code{set verbose} are those
12711 which announce that the symbol table for a source file is being read;
12712 see @code{symbol-file} in @ref{Files, ,Commands to specify files}.
12713
12714 @table @code
12715 @kindex set verbose
12716 @item set verbose on
12717 Enables @value{GDBN} output of certain informational messages.
12718
12719 @item set verbose off
12720 Disables @value{GDBN} output of certain informational messages.
12721
12722 @kindex show verbose
12723 @item show verbose
12724 Displays whether @code{set verbose} is on or off.
12725 @end table
12726
12727 By default, if @value{GDBN} encounters bugs in the symbol table of an
12728 object file, it is silent; but if you are debugging a compiler, you may
12729 find this information useful (@pxref{Symbol Errors, ,Errors reading
12730 symbol files}).
12731
12732 @table @code
12733
12734 @kindex set complaints
12735 @item set complaints @var{limit}
12736 Permits @value{GDBN} to output @var{limit} complaints about each type of
12737 unusual symbols before becoming silent about the problem. Set
12738 @var{limit} to zero to suppress all complaints; set it to a large number
12739 to prevent complaints from being suppressed.
12740
12741 @kindex show complaints
12742 @item show complaints
12743 Displays how many symbol complaints @value{GDBN} is permitted to produce.
12744
12745 @end table
12746
12747 By default, @value{GDBN} is cautious, and asks what sometimes seems to be a
12748 lot of stupid questions to confirm certain commands. For example, if
12749 you try to run a program which is already running:
12750
12751 @example
12752 (@value{GDBP}) run
12753 The program being debugged has been started already.
12754 Start it from the beginning? (y or n)
12755 @end example
12756
12757 If you are willing to unflinchingly face the consequences of your own
12758 commands, you can disable this ``feature'':
12759
12760 @table @code
12761
12762 @kindex set confirm
12763 @cindex flinching
12764 @cindex confirmation
12765 @cindex stupid questions
12766 @item set confirm off
12767 Disables confirmation requests.
12768
12769 @item set confirm on
12770 Enables confirmation requests (the default).
12771
12772 @kindex show confirm
12773 @item show confirm
12774 Displays state of confirmation requests.
12775
12776 @end table
12777
12778 @node Debugging Output
12779 @section Optional messages about internal happenings
12780 @table @code
12781 @kindex set debug arch
12782 @item set debug arch
12783 Turns on or off display of gdbarch debugging info. The default is off
12784 @kindex show debug arch
12785 @item show debug arch
12786 Displays the current state of displaying gdbarch debugging info.
12787 @kindex set debug event
12788 @item set debug event
12789 Turns on or off display of @value{GDBN} event debugging info. The
12790 default is off.
12791 @kindex show debug event
12792 @item show debug event
12793 Displays the current state of displaying @value{GDBN} event debugging
12794 info.
12795 @kindex set debug expression
12796 @item set debug expression
12797 Turns on or off display of @value{GDBN} expression debugging info. The
12798 default is off.
12799 @kindex show debug expression
12800 @item show debug expression
12801 Displays the current state of displaying @value{GDBN} expression
12802 debugging info.
12803 @kindex set debug overload
12804 @item set debug overload
12805 Turns on or off display of @value{GDBN} C@t{++} overload debugging
12806 info. This includes info such as ranking of functions, etc. The default
12807 is off.
12808 @kindex show debug overload
12809 @item show debug overload
12810 Displays the current state of displaying @value{GDBN} C@t{++} overload
12811 debugging info.
12812 @kindex set debug remote
12813 @cindex packets, reporting on stdout
12814 @cindex serial connections, debugging
12815 @item set debug remote
12816 Turns on or off display of reports on all packets sent back and forth across
12817 the serial line to the remote machine. The info is printed on the
12818 @value{GDBN} standard output stream. The default is off.
12819 @kindex show debug remote
12820 @item show debug remote
12821 Displays the state of display of remote packets.
12822 @kindex set debug serial
12823 @item set debug serial
12824 Turns on or off display of @value{GDBN} serial debugging info. The
12825 default is off.
12826 @kindex show debug serial
12827 @item show debug serial
12828 Displays the current state of displaying @value{GDBN} serial debugging
12829 info.
12830 @kindex set debug target
12831 @item set debug target
12832 Turns on or off display of @value{GDBN} target debugging info. This info
12833 includes what is going on at the target level of GDB, as it happens. The
12834 default is off.
12835 @kindex show debug target
12836 @item show debug target
12837 Displays the current state of displaying @value{GDBN} target debugging
12838 info.
12839 @kindex set debug varobj
12840 @item set debug varobj
12841 Turns on or off display of @value{GDBN} variable object debugging
12842 info. The default is off.
12843 @kindex show debug varobj
12844 @item show debug varobj
12845 Displays the current state of displaying @value{GDBN} variable object
12846 debugging info.
12847 @end table
12848
12849 @node Sequences
12850 @chapter Canned Sequences of Commands
12851
12852 Aside from breakpoint commands (@pxref{Break Commands, ,Breakpoint
12853 command lists}), @value{GDBN} provides two ways to store sequences of
12854 commands for execution as a unit: user-defined commands and command
12855 files.
12856
12857 @menu
12858 * Define:: User-defined commands
12859 * Hooks:: User-defined command hooks
12860 * Command Files:: Command files
12861 * Output:: Commands for controlled output
12862 @end menu
12863
12864 @node Define
12865 @section User-defined commands
12866
12867 @cindex user-defined command
12868 A @dfn{user-defined command} is a sequence of @value{GDBN} commands to
12869 which you assign a new name as a command. This is done with the
12870 @code{define} command. User commands may accept up to 10 arguments
12871 separated by whitespace. Arguments are accessed within the user command
12872 via @var{$arg0@dots{}$arg9}. A trivial example:
12873
12874 @smallexample
12875 define adder
12876 print $arg0 + $arg1 + $arg2
12877 @end smallexample
12878
12879 @noindent
12880 To execute the command use:
12881
12882 @smallexample
12883 adder 1 2 3
12884 @end smallexample
12885
12886 @noindent
12887 This defines the command @code{adder}, which prints the sum of
12888 its three arguments. Note the arguments are text substitutions, so they may
12889 reference variables, use complex expressions, or even perform inferior
12890 functions calls.
12891
12892 @table @code
12893
12894 @kindex define
12895 @item define @var{commandname}
12896 Define a command named @var{commandname}. If there is already a command
12897 by that name, you are asked to confirm that you want to redefine it.
12898
12899 The definition of the command is made up of other @value{GDBN} command lines,
12900 which are given following the @code{define} command. The end of these
12901 commands is marked by a line containing @code{end}.
12902
12903 @kindex if
12904 @kindex else
12905 @item if
12906 Takes a single argument, which is an expression to evaluate.
12907 It is followed by a series of commands that are executed
12908 only if the expression is true (nonzero).
12909 There can then optionally be a line @code{else}, followed
12910 by a series of commands that are only executed if the expression
12911 was false. The end of the list is marked by a line containing @code{end}.
12912
12913 @kindex while
12914 @item while
12915 The syntax is similar to @code{if}: the command takes a single argument,
12916 which is an expression to evaluate, and must be followed by the commands to
12917 execute, one per line, terminated by an @code{end}.
12918 The commands are executed repeatedly as long as the expression
12919 evaluates to true.
12920
12921 @kindex document
12922 @item document @var{commandname}
12923 Document the user-defined command @var{commandname}, so that it can be
12924 accessed by @code{help}. The command @var{commandname} must already be
12925 defined. This command reads lines of documentation just as @code{define}
12926 reads the lines of the command definition, ending with @code{end}.
12927 After the @code{document} command is finished, @code{help} on command
12928 @var{commandname} displays the documentation you have written.
12929
12930 You may use the @code{document} command again to change the
12931 documentation of a command. Redefining the command with @code{define}
12932 does not change the documentation.
12933
12934 @kindex help user-defined
12935 @item help user-defined
12936 List all user-defined commands, with the first line of the documentation
12937 (if any) for each.
12938
12939 @kindex show user
12940 @item show user
12941 @itemx show user @var{commandname}
12942 Display the @value{GDBN} commands used to define @var{commandname} (but
12943 not its documentation). If no @var{commandname} is given, display the
12944 definitions for all user-defined commands.
12945
12946 @end table
12947
12948 When user-defined commands are executed, the
12949 commands of the definition are not printed. An error in any command
12950 stops execution of the user-defined command.
12951
12952 If used interactively, commands that would ask for confirmation proceed
12953 without asking when used inside a user-defined command. Many @value{GDBN}
12954 commands that normally print messages to say what they are doing omit the
12955 messages when used in a user-defined command.
12956
12957 @node Hooks
12958 @section User-defined command hooks
12959 @cindex command hooks
12960 @cindex hooks, for commands
12961 @cindex hooks, pre-command
12962
12963 @kindex hook
12964 @kindex hook-
12965 You may define @dfn{hooks}, which are a special kind of user-defined
12966 command. Whenever you run the command @samp{foo}, if the user-defined
12967 command @samp{hook-foo} exists, it is executed (with no arguments)
12968 before that command.
12969
12970 @cindex hooks, post-command
12971 @kindex hookpost
12972 @kindex hookpost-
12973 A hook may also be defined which is run after the command you executed.
12974 Whenever you run the command @samp{foo}, if the user-defined command
12975 @samp{hookpost-foo} exists, it is executed (with no arguments) after
12976 that command. Post-execution hooks may exist simultaneously with
12977 pre-execution hooks, for the same command.
12978
12979 It is valid for a hook to call the command which it hooks. If this
12980 occurs, the hook is not re-executed, thereby avoiding infinte recursion.
12981
12982 @c It would be nice if hookpost could be passed a parameter indicating
12983 @c if the command it hooks executed properly or not. FIXME!
12984
12985 @kindex stop@r{, a pseudo-command}
12986 In addition, a pseudo-command, @samp{stop} exists. Defining
12987 (@samp{hook-stop}) makes the associated commands execute every time
12988 execution stops in your program: before breakpoint commands are run,
12989 displays are printed, or the stack frame is printed.
12990
12991 For example, to ignore @code{SIGALRM} signals while
12992 single-stepping, but treat them normally during normal execution,
12993 you could define:
12994
12995 @example
12996 define hook-stop
12997 handle SIGALRM nopass
12998 end
12999
13000 define hook-run
13001 handle SIGALRM pass
13002 end
13003
13004 define hook-continue
13005 handle SIGLARM pass
13006 end
13007 @end example
13008
13009 As a further example, to hook at the begining and end of the @code{echo}
13010 command, and to add extra text to the beginning and end of the message,
13011 you could define:
13012
13013 @example
13014 define hook-echo
13015 echo <<<---
13016 end
13017
13018 define hookpost-echo
13019 echo --->>>\n
13020 end
13021
13022 (@value{GDBP}) echo Hello World
13023 <<<---Hello World--->>>
13024 (@value{GDBP})
13025
13026 @end example
13027
13028 You can define a hook for any single-word command in @value{GDBN}, but
13029 not for command aliases; you should define a hook for the basic command
13030 name, e.g. @code{backtrace} rather than @code{bt}.
13031 @c FIXME! So how does Joe User discover whether a command is an alias
13032 @c or not?
13033 If an error occurs during the execution of your hook, execution of
13034 @value{GDBN} commands stops and @value{GDBN} issues a prompt
13035 (before the command that you actually typed had a chance to run).
13036
13037 If you try to define a hook which does not match any known command, you
13038 get a warning from the @code{define} command.
13039
13040 @node Command Files
13041 @section Command files
13042
13043 @cindex command files
13044 A command file for @value{GDBN} is a file of lines that are @value{GDBN}
13045 commands. Comments (lines starting with @kbd{#}) may also be included.
13046 An empty line in a command file does nothing; it does not mean to repeat
13047 the last command, as it would from the terminal.
13048
13049 @cindex init file
13050 @cindex @file{.gdbinit}
13051 @cindex @file{gdb.ini}
13052 When you start @value{GDBN}, it automatically executes commands from its
13053 @dfn{init files}. These are files named @file{.gdbinit} on Unix and
13054 @file{gdb.ini} on DOS/Windows. During startup, @value{GDBN} does the
13055 following:
13056
13057 @enumerate
13058 @item
13059 Reads the init file (if any) in your home directory@footnote{On
13060 DOS/Windows systems, the home directory is the one pointed to by the
13061 @code{HOME} environment variable.}.
13062
13063 @item
13064 Processes command line options and operands.
13065
13066 @item
13067 Reads the init file (if any) in the current working directory.
13068
13069 @item
13070 Reads command files specified by the @samp{-x} option.
13071 @end enumerate
13072
13073 The init file in your home directory can set options (such as @samp{set
13074 complaints}) that affect subsequent processing of command line options
13075 and operands. Init files are not executed if you use the @samp{-nx}
13076 option (@pxref{Mode Options, ,Choosing modes}).
13077
13078 @cindex init file name
13079 On some configurations of @value{GDBN}, the init file is known by a
13080 different name (these are typically environments where a specialized
13081 form of @value{GDBN} may need to coexist with other forms, hence a
13082 different name for the specialized version's init file). These are the
13083 environments with special init file names:
13084
13085 @cindex @file{.vxgdbinit}
13086 @itemize @bullet
13087 @item
13088 VxWorks (Wind River Systems real-time OS): @file{.vxgdbinit}
13089
13090 @cindex @file{.os68gdbinit}
13091 @item
13092 OS68K (Enea Data Systems real-time OS): @file{.os68gdbinit}
13093
13094 @cindex @file{.esgdbinit}
13095 @item
13096 ES-1800 (Ericsson Telecom AB M68000 emulator): @file{.esgdbinit}
13097 @end itemize
13098
13099 You can also request the execution of a command file with the
13100 @code{source} command:
13101
13102 @table @code
13103 @kindex source
13104 @item source @var{filename}
13105 Execute the command file @var{filename}.
13106 @end table
13107
13108 The lines in a command file are executed sequentially. They are not
13109 printed as they are executed. An error in any command terminates execution
13110 of the command file.
13111
13112 Commands that would ask for confirmation if used interactively proceed
13113 without asking when used in a command file. Many @value{GDBN} commands that
13114 normally print messages to say what they are doing omit the messages
13115 when called from command files.
13116
13117 @node Output
13118 @section Commands for controlled output
13119
13120 During the execution of a command file or a user-defined command, normal
13121 @value{GDBN} output is suppressed; the only output that appears is what is
13122 explicitly printed by the commands in the definition. This section
13123 describes three commands useful for generating exactly the output you
13124 want.
13125
13126 @table @code
13127 @kindex echo
13128 @item echo @var{text}
13129 @c I do not consider backslash-space a standard C escape sequence
13130 @c because it is not in ANSI.
13131 Print @var{text}. Nonprinting characters can be included in
13132 @var{text} using C escape sequences, such as @samp{\n} to print a
13133 newline. @strong{No newline is printed unless you specify one.}
13134 In addition to the standard C escape sequences, a backslash followed
13135 by a space stands for a space. This is useful for displaying a
13136 string with spaces at the beginning or the end, since leading and
13137 trailing spaces are otherwise trimmed from all arguments.
13138 To print @samp{@w{ }and foo =@w{ }}, use the command
13139 @samp{echo \@w{ }and foo = \@w{ }}.
13140
13141 A backslash at the end of @var{text} can be used, as in C, to continue
13142 the command onto subsequent lines. For example,
13143
13144 @example
13145 echo This is some text\n\
13146 which is continued\n\
13147 onto several lines.\n
13148 @end example
13149
13150 produces the same output as
13151
13152 @example
13153 echo This is some text\n
13154 echo which is continued\n
13155 echo onto several lines.\n
13156 @end example
13157
13158 @kindex output
13159 @item output @var{expression}
13160 Print the value of @var{expression} and nothing but that value: no
13161 newlines, no @samp{$@var{nn} = }. The value is not entered in the
13162 value history either. @xref{Expressions, ,Expressions}, for more information
13163 on expressions.
13164
13165 @item output/@var{fmt} @var{expression}
13166 Print the value of @var{expression} in format @var{fmt}. You can use
13167 the same formats as for @code{print}. @xref{Output Formats,,Output
13168 formats}, for more information.
13169
13170 @kindex printf
13171 @item printf @var{string}, @var{expressions}@dots{}
13172 Print the values of the @var{expressions} under the control of
13173 @var{string}. The @var{expressions} are separated by commas and may be
13174 either numbers or pointers. Their values are printed as specified by
13175 @var{string}, exactly as if your program were to execute the C
13176 subroutine
13177 @c FIXME: the above implies that at least all ANSI C formats are
13178 @c supported, but it isn't true: %E and %G don't work (or so it seems).
13179 @c Either this is a bug, or the manual should document what formats are
13180 @c supported.
13181
13182 @example
13183 printf (@var{string}, @var{expressions}@dots{});
13184 @end example
13185
13186 For example, you can print two values in hex like this:
13187
13188 @smallexample
13189 printf "foo, bar-foo = 0x%x, 0x%x\n", foo, bar-foo
13190 @end smallexample
13191
13192 The only backslash-escape sequences that you can use in the format
13193 string are the simple ones that consist of backslash followed by a
13194 letter.
13195 @end table
13196
13197 @node TUI
13198 @chapter @value{GDBN} Text User Interface
13199 @cindex TUI
13200
13201 @menu
13202 * TUI Overview:: TUI overview
13203 * TUI Keys:: TUI key bindings
13204 * TUI Commands:: TUI specific commands
13205 * TUI Configuration:: TUI configuration variables
13206 @end menu
13207
13208 The @value{GDBN} Text User Interface, TUI in short,
13209 is a terminal interface which uses the @code{curses} library
13210 to show the source file, the assembly output, the program registers
13211 and @value{GDBN} commands in separate text windows.
13212 The TUI is available only when @value{GDBN} is configured
13213 with the @code{--enable-tui} configure option (@pxref{Configure Options}).
13214
13215 @node TUI Overview
13216 @section TUI overview
13217
13218 The TUI has two display modes that can be switched while
13219 @value{GDBN} runs:
13220
13221 @itemize @bullet
13222 @item
13223 A curses (or TUI) mode in which it displays several text
13224 windows on the terminal.
13225
13226 @item
13227 A standard mode which corresponds to the @value{GDBN} configured without
13228 the TUI.
13229 @end itemize
13230
13231 In the TUI mode, @value{GDBN} can display several text window
13232 on the terminal:
13233
13234 @table @emph
13235 @item command
13236 This window is the @value{GDBN} command window with the @value{GDBN}
13237 prompt and the @value{GDBN} outputs. The @value{GDBN} input is still
13238 managed using readline but through the TUI. The @emph{command}
13239 window is always visible.
13240
13241 @item source
13242 The source window shows the source file of the program. The current
13243 line as well as active breakpoints are displayed in this window.
13244 The current program position is shown with the @samp{>} marker and
13245 active breakpoints are shown with @samp{*} markers.
13246
13247 @item assembly
13248 The assembly window shows the disassembly output of the program.
13249
13250 @item register
13251 This window shows the processor registers. It detects when
13252 a register is changed and when this is the case, registers that have
13253 changed are highlighted.
13254
13255 @end table
13256
13257 The source, assembly and register windows are attached to the thread
13258 and the frame position. They are updated when the current thread
13259 changes, when the frame changes or when the program counter changes.
13260 These three windows are arranged by the TUI according to several
13261 layouts. The layout defines which of these three windows are visible.
13262 The following layouts are available:
13263
13264 @itemize @bullet
13265 @item
13266 source
13267
13268 @item
13269 assembly
13270
13271 @item
13272 source and assembly
13273
13274 @item
13275 source and registers
13276
13277 @item
13278 assembly and registers
13279
13280 @end itemize
13281
13282 @node TUI Keys
13283 @section TUI Key Bindings
13284 @cindex TUI key bindings
13285
13286 The TUI installs several key bindings in the readline keymaps
13287 (@pxref{Command Line Editing}).
13288 They allow to leave or enter in the TUI mode or they operate
13289 directly on the TUI layout and windows. The following key bindings
13290 are installed for both TUI mode and the @value{GDBN} standard mode.
13291
13292 @table @kbd
13293 @kindex C-x C-a
13294 @item C-x C-a
13295 @kindex C-x a
13296 @itemx C-x a
13297 @kindex C-x A
13298 @itemx C-x A
13299 Enter or leave the TUI mode. When the TUI mode is left,
13300 the curses window management is left and @value{GDBN} operates using
13301 its standard mode writing on the terminal directly. When the TUI
13302 mode is entered, the control is given back to the curses windows.
13303 The screen is then refreshed.
13304
13305 @kindex C-x 1
13306 @item C-x 1
13307 Use a TUI layout with only one window. The layout will
13308 either be @samp{source} or @samp{assembly}. When the TUI mode
13309 is not active, it will switch to the TUI mode.
13310
13311 Think of this key binding as the Emacs @kbd{C-x 1} binding.
13312
13313 @kindex C-x 2
13314 @item C-x 2
13315 Use a TUI layout with at least two windows. When the current
13316 layout shows already two windows, a next layout with two windows is used.
13317 When a new layout is chosen, one window will always be common to the
13318 previous layout and the new one.
13319
13320 Think of it as the Emacs @kbd{C-x 2} binding.
13321
13322 @end table
13323
13324 The following key bindings are handled only by the TUI mode:
13325
13326 @table @key
13327 @kindex PgUp
13328 @item PgUp
13329 Scroll the active window one page up.
13330
13331 @kindex PgDn
13332 @item PgDn
13333 Scroll the active window one page down.
13334
13335 @kindex Up
13336 @item Up
13337 Scroll the active window one line up.
13338
13339 @kindex Down
13340 @item Down
13341 Scroll the active window one line down.
13342
13343 @kindex Left
13344 @item Left
13345 Scroll the active window one column left.
13346
13347 @kindex Right
13348 @item Right
13349 Scroll the active window one column right.
13350
13351 @kindex C-L
13352 @item C-L
13353 Refresh the screen.
13354
13355 @end table
13356
13357 In the TUI mode, the arrow keys are used by the active window
13358 for scrolling. This means they are not available for readline. It is
13359 necessary to use other readline key bindings such as @key{C-p}, @key{C-n},
13360 @key{C-b} and @key{C-f}.
13361
13362 @node TUI Commands
13363 @section TUI specific commands
13364 @cindex TUI commands
13365
13366 The TUI has specific commands to control the text windows.
13367 These commands are always available, that is they do not depend on
13368 the current terminal mode in which @value{GDBN} runs. When @value{GDBN}
13369 is in the standard mode, using these commands will automatically switch
13370 in the TUI mode.
13371
13372 @table @code
13373 @item layout next
13374 @kindex layout next
13375 Display the next layout.
13376
13377 @item layout prev
13378 @kindex layout prev
13379 Display the previous layout.
13380
13381 @item layout src
13382 @kindex layout src
13383 Display the source window only.
13384
13385 @item layout asm
13386 @kindex layout asm
13387 Display the assembly window only.
13388
13389 @item layout split
13390 @kindex layout split
13391 Display the source and assembly window.
13392
13393 @item layout regs
13394 @kindex layout regs
13395 Display the register window together with the source or assembly window.
13396
13397 @item focus next | prev | src | asm | regs | split
13398 @kindex focus
13399 Set the focus to the named window.
13400 This command allows to change the active window so that scrolling keys
13401 can be affected to another window.
13402
13403 @item refresh
13404 @kindex refresh
13405 Refresh the screen. This is similar to using @key{C-L} key.
13406
13407 @item update
13408 @kindex update
13409 Update the source window and the current execution point.
13410
13411 @item winheight @var{name} +@var{count}
13412 @itemx winheight @var{name} -@var{count}
13413 @kindex winheight
13414 Change the height of the window @var{name} by @var{count}
13415 lines. Positive counts increase the height, while negative counts
13416 decrease it.
13417
13418 @end table
13419
13420 @node TUI Configuration
13421 @section TUI configuration variables
13422 @cindex TUI configuration variables
13423
13424 The TUI has several configuration variables that control the
13425 appearance of windows on the terminal.
13426
13427 @table @code
13428 @item set tui border-kind @var{kind}
13429 @kindex set tui border-kind
13430 Select the border appearance for the source, assembly and register windows.
13431 The possible values are the following:
13432 @table @code
13433 @item space
13434 Use a space character to draw the border.
13435
13436 @item ascii
13437 Use ascii characters + - and | to draw the border.
13438
13439 @item acs
13440 Use the Alternate Character Set to draw the border. The border is
13441 drawn using character line graphics if the terminal supports them.
13442
13443 @end table
13444
13445 @item set tui active-border-mode @var{mode}
13446 @kindex set tui active-border-mode
13447 Select the attributes to display the border of the active window.
13448 The possible values are @code{normal}, @code{standout}, @code{reverse},
13449 @code{half}, @code{half-standout}, @code{bold} and @code{bold-standout}.
13450
13451 @item set tui border-mode @var{mode}
13452 @kindex set tui border-mode
13453 Select the attributes to display the border of other windows.
13454 The @var{mode} can be one of the following:
13455 @table @code
13456 @item normal
13457 Use normal attributes to display the border.
13458
13459 @item standout
13460 Use standout mode.
13461
13462 @item reverse
13463 Use reverse video mode.
13464
13465 @item half
13466 Use half bright mode.
13467
13468 @item half-standout
13469 Use half bright and standout mode.
13470
13471 @item bold
13472 Use extra bright or bold mode.
13473
13474 @item bold-standout
13475 Use extra bright or bold and standout mode.
13476
13477 @end table
13478
13479 @end table
13480
13481 @node Emacs
13482 @chapter Using @value{GDBN} under @sc{gnu} Emacs
13483
13484 @cindex Emacs
13485 @cindex @sc{gnu} Emacs
13486 A special interface allows you to use @sc{gnu} Emacs to view (and
13487 edit) the source files for the program you are debugging with
13488 @value{GDBN}.
13489
13490 To use this interface, use the command @kbd{M-x gdb} in Emacs. Give the
13491 executable file you want to debug as an argument. This command starts
13492 @value{GDBN} as a subprocess of Emacs, with input and output through a newly
13493 created Emacs buffer.
13494 @c (Do not use the @code{-tui} option to run @value{GDBN} from Emacs.)
13495
13496 Using @value{GDBN} under Emacs is just like using @value{GDBN} normally except for two
13497 things:
13498
13499 @itemize @bullet
13500 @item
13501 All ``terminal'' input and output goes through the Emacs buffer.
13502 @end itemize
13503
13504 This applies both to @value{GDBN} commands and their output, and to the input
13505 and output done by the program you are debugging.
13506
13507 This is useful because it means that you can copy the text of previous
13508 commands and input them again; you can even use parts of the output
13509 in this way.
13510
13511 All the facilities of Emacs' Shell mode are available for interacting
13512 with your program. In particular, you can send signals the usual
13513 way---for example, @kbd{C-c C-c} for an interrupt, @kbd{C-c C-z} for a
13514 stop.
13515
13516 @itemize @bullet
13517 @item
13518 @value{GDBN} displays source code through Emacs.
13519 @end itemize
13520
13521 Each time @value{GDBN} displays a stack frame, Emacs automatically finds the
13522 source file for that frame and puts an arrow (@samp{=>}) at the
13523 left margin of the current line. Emacs uses a separate buffer for
13524 source display, and splits the screen to show both your @value{GDBN} session
13525 and the source.
13526
13527 Explicit @value{GDBN} @code{list} or search commands still produce output as
13528 usual, but you probably have no reason to use them from Emacs.
13529
13530 @quotation
13531 @emph{Warning:} If the directory where your program resides is not your
13532 current directory, it can be easy to confuse Emacs about the location of
13533 the source files, in which case the auxiliary display buffer does not
13534 appear to show your source. @value{GDBN} can find programs by searching your
13535 environment's @code{PATH} variable, so the @value{GDBN} input and output
13536 session proceeds normally; but Emacs does not get enough information
13537 back from @value{GDBN} to locate the source files in this situation. To
13538 avoid this problem, either start @value{GDBN} mode from the directory where
13539 your program resides, or specify an absolute file name when prompted for the
13540 @kbd{M-x gdb} argument.
13541
13542 A similar confusion can result if you use the @value{GDBN} @code{file} command to
13543 switch to debugging a program in some other location, from an existing
13544 @value{GDBN} buffer in Emacs.
13545 @end quotation
13546
13547 By default, @kbd{M-x gdb} calls the program called @file{gdb}. If
13548 you need to call @value{GDBN} by a different name (for example, if you keep
13549 several configurations around, with different names) you can set the
13550 Emacs variable @code{gdb-command-name}; for example,
13551
13552 @example
13553 (setq gdb-command-name "mygdb")
13554 @end example
13555
13556 @noindent
13557 (preceded by @kbd{M-:} or @kbd{ESC :}, or typed in the @code{*scratch*} buffer, or
13558 in your @file{.emacs} file) makes Emacs call the program named
13559 ``@code{mygdb}'' instead.
13560
13561 In the @value{GDBN} I/O buffer, you can use these special Emacs commands in
13562 addition to the standard Shell mode commands:
13563
13564 @table @kbd
13565 @item C-h m
13566 Describe the features of Emacs' @value{GDBN} Mode.
13567
13568 @item M-s
13569 Execute to another source line, like the @value{GDBN} @code{step} command; also
13570 update the display window to show the current file and location.
13571
13572 @item M-n
13573 Execute to next source line in this function, skipping all function
13574 calls, like the @value{GDBN} @code{next} command. Then update the display window
13575 to show the current file and location.
13576
13577 @item M-i
13578 Execute one instruction, like the @value{GDBN} @code{stepi} command; update
13579 display window accordingly.
13580
13581 @item M-x gdb-nexti
13582 Execute to next instruction, using the @value{GDBN} @code{nexti} command; update
13583 display window accordingly.
13584
13585 @item C-c C-f
13586 Execute until exit from the selected stack frame, like the @value{GDBN}
13587 @code{finish} command.
13588
13589 @item M-c
13590 Continue execution of your program, like the @value{GDBN} @code{continue}
13591 command.
13592
13593 @emph{Warning:} In Emacs v19, this command is @kbd{C-c C-p}.
13594
13595 @item M-u
13596 Go up the number of frames indicated by the numeric argument
13597 (@pxref{Arguments, , Numeric Arguments, Emacs, The @sc{gnu} Emacs Manual}),
13598 like the @value{GDBN} @code{up} command.
13599
13600 @emph{Warning:} In Emacs v19, this command is @kbd{C-c C-u}.
13601
13602 @item M-d
13603 Go down the number of frames indicated by the numeric argument, like the
13604 @value{GDBN} @code{down} command.
13605
13606 @emph{Warning:} In Emacs v19, this command is @kbd{C-c C-d}.
13607
13608 @item C-x &
13609 Read the number where the cursor is positioned, and insert it at the end
13610 of the @value{GDBN} I/O buffer. For example, if you wish to disassemble code
13611 around an address that was displayed earlier, type @kbd{disassemble};
13612 then move the cursor to the address display, and pick up the
13613 argument for @code{disassemble} by typing @kbd{C-x &}.
13614
13615 You can customize this further by defining elements of the list
13616 @code{gdb-print-command}; once it is defined, you can format or
13617 otherwise process numbers picked up by @kbd{C-x &} before they are
13618 inserted. A numeric argument to @kbd{C-x &} indicates that you
13619 wish special formatting, and also acts as an index to pick an element of the
13620 list. If the list element is a string, the number to be inserted is
13621 formatted using the Emacs function @code{format}; otherwise the number
13622 is passed as an argument to the corresponding list element.
13623 @end table
13624
13625 In any source file, the Emacs command @kbd{C-x SPC} (@code{gdb-break})
13626 tells @value{GDBN} to set a breakpoint on the source line point is on.
13627
13628 If you accidentally delete the source-display buffer, an easy way to get
13629 it back is to type the command @code{f} in the @value{GDBN} buffer, to
13630 request a frame display; when you run under Emacs, this recreates
13631 the source buffer if necessary to show you the context of the current
13632 frame.
13633
13634 The source files displayed in Emacs are in ordinary Emacs buffers
13635 which are visiting the source files in the usual way. You can edit
13636 the files with these buffers if you wish; but keep in mind that @value{GDBN}
13637 communicates with Emacs in terms of line numbers. If you add or
13638 delete lines from the text, the line numbers that @value{GDBN} knows cease
13639 to correspond properly with the code.
13640
13641 @c The following dropped because Epoch is nonstandard. Reactivate
13642 @c if/when v19 does something similar. ---doc@cygnus.com 19dec1990
13643 @ignore
13644 @kindex Emacs Epoch environment
13645 @kindex Epoch
13646 @kindex inspect
13647
13648 Version 18 of @sc{gnu} Emacs has a built-in window system
13649 called the @code{epoch}
13650 environment. Users of this environment can use a new command,
13651 @code{inspect} which performs identically to @code{print} except that
13652 each value is printed in its own window.
13653 @end ignore
13654
13655 @include annotate.texi
13656 @include gdbmi.texinfo
13657
13658 @node GDB Bugs
13659 @chapter Reporting Bugs in @value{GDBN}
13660 @cindex bugs in @value{GDBN}
13661 @cindex reporting bugs in @value{GDBN}
13662
13663 Your bug reports play an essential role in making @value{GDBN} reliable.
13664
13665 Reporting a bug may help you by bringing a solution to your problem, or it
13666 may not. But in any case the principal function of a bug report is to help
13667 the entire community by making the next version of @value{GDBN} work better. Bug
13668 reports are your contribution to the maintenance of @value{GDBN}.
13669
13670 In order for a bug report to serve its purpose, you must include the
13671 information that enables us to fix the bug.
13672
13673 @menu
13674 * Bug Criteria:: Have you found a bug?
13675 * Bug Reporting:: How to report bugs
13676 @end menu
13677
13678 @node Bug Criteria
13679 @section Have you found a bug?
13680 @cindex bug criteria
13681
13682 If you are not sure whether you have found a bug, here are some guidelines:
13683
13684 @itemize @bullet
13685 @cindex fatal signal
13686 @cindex debugger crash
13687 @cindex crash of debugger
13688 @item
13689 If the debugger gets a fatal signal, for any input whatever, that is a
13690 @value{GDBN} bug. Reliable debuggers never crash.
13691
13692 @cindex error on valid input
13693 @item
13694 If @value{GDBN} produces an error message for valid input, that is a
13695 bug. (Note that if you're cross debugging, the problem may also be
13696 somewhere in the connection to the target.)
13697
13698 @cindex invalid input
13699 @item
13700 If @value{GDBN} does not produce an error message for invalid input,
13701 that is a bug. However, you should note that your idea of
13702 ``invalid input'' might be our idea of ``an extension'' or ``support
13703 for traditional practice''.
13704
13705 @item
13706 If you are an experienced user of debugging tools, your suggestions
13707 for improvement of @value{GDBN} are welcome in any case.
13708 @end itemize
13709
13710 @node Bug Reporting
13711 @section How to report bugs
13712 @cindex bug reports
13713 @cindex @value{GDBN} bugs, reporting
13714
13715 A number of companies and individuals offer support for @sc{gnu} products.
13716 If you obtained @value{GDBN} from a support organization, we recommend you
13717 contact that organization first.
13718
13719 You can find contact information for many support companies and
13720 individuals in the file @file{etc/SERVICE} in the @sc{gnu} Emacs
13721 distribution.
13722 @c should add a web page ref...
13723
13724 In any event, we also recommend that you send bug reports for
13725 @value{GDBN} to this addresses:
13726
13727 @example
13728 bug-gdb@@gnu.org
13729 @end example
13730
13731 @strong{Do not send bug reports to @samp{info-gdb}, or to
13732 @samp{help-gdb}, or to any newsgroups.} Most users of @value{GDBN} do
13733 not want to receive bug reports. Those that do have arranged to receive
13734 @samp{bug-gdb}.
13735
13736 The mailing list @samp{bug-gdb} has a newsgroup @samp{gnu.gdb.bug} which
13737 serves as a repeater. The mailing list and the newsgroup carry exactly
13738 the same messages. Often people think of posting bug reports to the
13739 newsgroup instead of mailing them. This appears to work, but it has one
13740 problem which can be crucial: a newsgroup posting often lacks a mail
13741 path back to the sender. Thus, if we need to ask for more information,
13742 we may be unable to reach you. For this reason, it is better to send
13743 bug reports to the mailing list.
13744
13745 As a last resort, send bug reports on paper to:
13746
13747 @example
13748 @sc{gnu} Debugger Bugs
13749 Free Software Foundation Inc.
13750 59 Temple Place - Suite 330
13751 Boston, MA 02111-1307
13752 USA
13753 @end example
13754
13755 The fundamental principle of reporting bugs usefully is this:
13756 @strong{report all the facts}. If you are not sure whether to state a
13757 fact or leave it out, state it!
13758
13759 Often people omit facts because they think they know what causes the
13760 problem and assume that some details do not matter. Thus, you might
13761 assume that the name of the variable you use in an example does not matter.
13762 Well, probably it does not, but one cannot be sure. Perhaps the bug is a
13763 stray memory reference which happens to fetch from the location where that
13764 name is stored in memory; perhaps, if the name were different, the contents
13765 of that location would fool the debugger into doing the right thing despite
13766 the bug. Play it safe and give a specific, complete example. That is the
13767 easiest thing for you to do, and the most helpful.
13768
13769 Keep in mind that the purpose of a bug report is to enable us to fix the
13770 bug. It may be that the bug has been reported previously, but neither
13771 you nor we can know that unless your bug report is complete and
13772 self-contained.
13773
13774 Sometimes people give a few sketchy facts and ask, ``Does this ring a
13775 bell?'' Those bug reports are useless, and we urge everyone to
13776 @emph{refuse to respond to them} except to chide the sender to report
13777 bugs properly.
13778
13779 To enable us to fix the bug, you should include all these things:
13780
13781 @itemize @bullet
13782 @item
13783 The version of @value{GDBN}. @value{GDBN} announces it if you start
13784 with no arguments; you can also print it at any time using @code{show
13785 version}.
13786
13787 Without this, we will not know whether there is any point in looking for
13788 the bug in the current version of @value{GDBN}.
13789
13790 @item
13791 The type of machine you are using, and the operating system name and
13792 version number.
13793
13794 @item
13795 What compiler (and its version) was used to compile @value{GDBN}---e.g.
13796 ``@value{GCC}--2.8.1''.
13797
13798 @item
13799 What compiler (and its version) was used to compile the program you are
13800 debugging---e.g. ``@value{GCC}--2.8.1'', or ``HP92453-01 A.10.32.03 HP
13801 C Compiler''. For GCC, you can say @code{gcc --version} to get this
13802 information; for other compilers, see the documentation for those
13803 compilers.
13804
13805 @item
13806 The command arguments you gave the compiler to compile your example and
13807 observe the bug. For example, did you use @samp{-O}? To guarantee
13808 you will not omit something important, list them all. A copy of the
13809 Makefile (or the output from make) is sufficient.
13810
13811 If we were to try to guess the arguments, we would probably guess wrong
13812 and then we might not encounter the bug.
13813
13814 @item
13815 A complete input script, and all necessary source files, that will
13816 reproduce the bug.
13817
13818 @item
13819 A description of what behavior you observe that you believe is
13820 incorrect. For example, ``It gets a fatal signal.''
13821
13822 Of course, if the bug is that @value{GDBN} gets a fatal signal, then we
13823 will certainly notice it. But if the bug is incorrect output, we might
13824 not notice unless it is glaringly wrong. You might as well not give us
13825 a chance to make a mistake.
13826
13827 Even if the problem you experience is a fatal signal, you should still
13828 say so explicitly. Suppose something strange is going on, such as, your
13829 copy of @value{GDBN} is out of synch, or you have encountered a bug in
13830 the C library on your system. (This has happened!) Your copy might
13831 crash and ours would not. If you told us to expect a crash, then when
13832 ours fails to crash, we would know that the bug was not happening for
13833 us. If you had not told us to expect a crash, then we would not be able
13834 to draw any conclusion from our observations.
13835
13836 @item
13837 If you wish to suggest changes to the @value{GDBN} source, send us context
13838 diffs. If you even discuss something in the @value{GDBN} source, refer to
13839 it by context, not by line number.
13840
13841 The line numbers in our development sources will not match those in your
13842 sources. Your line numbers would convey no useful information to us.
13843
13844 @end itemize
13845
13846 Here are some things that are not necessary:
13847
13848 @itemize @bullet
13849 @item
13850 A description of the envelope of the bug.
13851
13852 Often people who encounter a bug spend a lot of time investigating
13853 which changes to the input file will make the bug go away and which
13854 changes will not affect it.
13855
13856 This is often time consuming and not very useful, because the way we
13857 will find the bug is by running a single example under the debugger
13858 with breakpoints, not by pure deduction from a series of examples.
13859 We recommend that you save your time for something else.
13860
13861 Of course, if you can find a simpler example to report @emph{instead}
13862 of the original one, that is a convenience for us. Errors in the
13863 output will be easier to spot, running under the debugger will take
13864 less time, and so on.
13865
13866 However, simplification is not vital; if you do not want to do this,
13867 report the bug anyway and send us the entire test case you used.
13868
13869 @item
13870 A patch for the bug.
13871
13872 A patch for the bug does help us if it is a good one. But do not omit
13873 the necessary information, such as the test case, on the assumption that
13874 a patch is all we need. We might see problems with your patch and decide
13875 to fix the problem another way, or we might not understand it at all.
13876
13877 Sometimes with a program as complicated as @value{GDBN} it is very hard to
13878 construct an example that will make the program follow a certain path
13879 through the code. If you do not send us the example, we will not be able
13880 to construct one, so we will not be able to verify that the bug is fixed.
13881
13882 And if we cannot understand what bug you are trying to fix, or why your
13883 patch should be an improvement, we will not install it. A test case will
13884 help us to understand.
13885
13886 @item
13887 A guess about what the bug is or what it depends on.
13888
13889 Such guesses are usually wrong. Even we cannot guess right about such
13890 things without first using the debugger to find the facts.
13891 @end itemize
13892
13893 @c The readline documentation is distributed with the readline code
13894 @c and consists of the two following files:
13895 @c rluser.texinfo
13896 @c inc-hist.texinfo
13897 @c Use -I with makeinfo to point to the appropriate directory,
13898 @c environment var TEXINPUTS with TeX.
13899 @include rluser.texinfo
13900 @include inc-hist.texinfo
13901
13902
13903 @node Formatting Documentation
13904 @appendix Formatting Documentation
13905
13906 @cindex @value{GDBN} reference card
13907 @cindex reference card
13908 The @value{GDBN} 4 release includes an already-formatted reference card, ready
13909 for printing with PostScript or Ghostscript, in the @file{gdb}
13910 subdirectory of the main source directory@footnote{In
13911 @file{gdb-@value{GDBVN}/gdb/refcard.ps} of the version @value{GDBVN}
13912 release.}. If you can use PostScript or Ghostscript with your printer,
13913 you can print the reference card immediately with @file{refcard.ps}.
13914
13915 The release also includes the source for the reference card. You
13916 can format it, using @TeX{}, by typing:
13917
13918 @example
13919 make refcard.dvi
13920 @end example
13921
13922 The @value{GDBN} reference card is designed to print in @dfn{landscape}
13923 mode on US ``letter'' size paper;
13924 that is, on a sheet 11 inches wide by 8.5 inches
13925 high. You will need to specify this form of printing as an option to
13926 your @sc{dvi} output program.
13927
13928 @cindex documentation
13929
13930 All the documentation for @value{GDBN} comes as part of the machine-readable
13931 distribution. The documentation is written in Texinfo format, which is
13932 a documentation system that uses a single source file to produce both
13933 on-line information and a printed manual. You can use one of the Info
13934 formatting commands to create the on-line version of the documentation
13935 and @TeX{} (or @code{texi2roff}) to typeset the printed version.
13936
13937 @value{GDBN} includes an already formatted copy of the on-line Info
13938 version of this manual in the @file{gdb} subdirectory. The main Info
13939 file is @file{gdb-@value{GDBVN}/gdb/gdb.info}, and it refers to
13940 subordinate files matching @samp{gdb.info*} in the same directory. If
13941 necessary, you can print out these files, or read them with any editor;
13942 but they are easier to read using the @code{info} subsystem in @sc{gnu}
13943 Emacs or the standalone @code{info} program, available as part of the
13944 @sc{gnu} Texinfo distribution.
13945
13946 If you want to format these Info files yourself, you need one of the
13947 Info formatting programs, such as @code{texinfo-format-buffer} or
13948 @code{makeinfo}.
13949
13950 If you have @code{makeinfo} installed, and are in the top level
13951 @value{GDBN} source directory (@file{gdb-@value{GDBVN}}, in the case of
13952 version @value{GDBVN}), you can make the Info file by typing:
13953
13954 @example
13955 cd gdb
13956 make gdb.info
13957 @end example
13958
13959 If you want to typeset and print copies of this manual, you need @TeX{},
13960 a program to print its @sc{dvi} output files, and @file{texinfo.tex}, the
13961 Texinfo definitions file.
13962
13963 @TeX{} is a typesetting program; it does not print files directly, but
13964 produces output files called @sc{dvi} files. To print a typeset
13965 document, you need a program to print @sc{dvi} files. If your system
13966 has @TeX{} installed, chances are it has such a program. The precise
13967 command to use depends on your system; @kbd{lpr -d} is common; another
13968 (for PostScript devices) is @kbd{dvips}. The @sc{dvi} print command may
13969 require a file name without any extension or a @samp{.dvi} extension.
13970
13971 @TeX{} also requires a macro definitions file called
13972 @file{texinfo.tex}. This file tells @TeX{} how to typeset a document
13973 written in Texinfo format. On its own, @TeX{} cannot either read or
13974 typeset a Texinfo file. @file{texinfo.tex} is distributed with GDB
13975 and is located in the @file{gdb-@var{version-number}/texinfo}
13976 directory.
13977
13978 If you have @TeX{} and a @sc{dvi} printer program installed, you can
13979 typeset and print this manual. First switch to the the @file{gdb}
13980 subdirectory of the main source directory (for example, to
13981 @file{gdb-@value{GDBVN}/gdb}) and type:
13982
13983 @example
13984 make gdb.dvi
13985 @end example
13986
13987 Then give @file{gdb.dvi} to your @sc{dvi} printing program.
13988
13989 @node Installing GDB
13990 @appendix Installing @value{GDBN}
13991 @cindex configuring @value{GDBN}
13992 @cindex installation
13993
13994 @value{GDBN} comes with a @code{configure} script that automates the process
13995 of preparing @value{GDBN} for installation; you can then use @code{make} to
13996 build the @code{gdb} program.
13997 @iftex
13998 @c irrelevant in info file; it's as current as the code it lives with.
13999 @footnote{If you have a more recent version of @value{GDBN} than @value{GDBVN},
14000 look at the @file{README} file in the sources; we may have improved the
14001 installation procedures since publishing this manual.}
14002 @end iftex
14003
14004 The @value{GDBN} distribution includes all the source code you need for
14005 @value{GDBN} in a single directory, whose name is usually composed by
14006 appending the version number to @samp{gdb}.
14007
14008 For example, the @value{GDBN} version @value{GDBVN} distribution is in the
14009 @file{gdb-@value{GDBVN}} directory. That directory contains:
14010
14011 @table @code
14012 @item gdb-@value{GDBVN}/configure @r{(and supporting files)}
14013 script for configuring @value{GDBN} and all its supporting libraries
14014
14015 @item gdb-@value{GDBVN}/gdb
14016 the source specific to @value{GDBN} itself
14017
14018 @item gdb-@value{GDBVN}/bfd
14019 source for the Binary File Descriptor library
14020
14021 @item gdb-@value{GDBVN}/include
14022 @sc{gnu} include files
14023
14024 @item gdb-@value{GDBVN}/libiberty
14025 source for the @samp{-liberty} free software library
14026
14027 @item gdb-@value{GDBVN}/opcodes
14028 source for the library of opcode tables and disassemblers
14029
14030 @item gdb-@value{GDBVN}/readline
14031 source for the @sc{gnu} command-line interface
14032
14033 @item gdb-@value{GDBVN}/glob
14034 source for the @sc{gnu} filename pattern-matching subroutine
14035
14036 @item gdb-@value{GDBVN}/mmalloc
14037 source for the @sc{gnu} memory-mapped malloc package
14038 @end table
14039
14040 The simplest way to configure and build @value{GDBN} is to run @code{configure}
14041 from the @file{gdb-@var{version-number}} source directory, which in
14042 this example is the @file{gdb-@value{GDBVN}} directory.
14043
14044 First switch to the @file{gdb-@var{version-number}} source directory
14045 if you are not already in it; then run @code{configure}. Pass the
14046 identifier for the platform on which @value{GDBN} will run as an
14047 argument.
14048
14049 For example:
14050
14051 @example
14052 cd gdb-@value{GDBVN}
14053 ./configure @var{host}
14054 make
14055 @end example
14056
14057 @noindent
14058 where @var{host} is an identifier such as @samp{sun4} or
14059 @samp{decstation}, that identifies the platform where @value{GDBN} will run.
14060 (You can often leave off @var{host}; @code{configure} tries to guess the
14061 correct value by examining your system.)
14062
14063 Running @samp{configure @var{host}} and then running @code{make} builds the
14064 @file{bfd}, @file{readline}, @file{mmalloc}, and @file{libiberty}
14065 libraries, then @code{gdb} itself. The configured source files, and the
14066 binaries, are left in the corresponding source directories.
14067
14068 @need 750
14069 @code{configure} is a Bourne-shell (@code{/bin/sh}) script; if your
14070 system does not recognize this automatically when you run a different
14071 shell, you may need to run @code{sh} on it explicitly:
14072
14073 @example
14074 sh configure @var{host}
14075 @end example
14076
14077 If you run @code{configure} from a directory that contains source
14078 directories for multiple libraries or programs, such as the
14079 @file{gdb-@value{GDBVN}} source directory for version @value{GDBVN}, @code{configure}
14080 creates configuration files for every directory level underneath (unless
14081 you tell it not to, with the @samp{--norecursion} option).
14082
14083 You can run the @code{configure} script from any of the
14084 subordinate directories in the @value{GDBN} distribution if you only want to
14085 configure that subdirectory, but be sure to specify a path to it.
14086
14087 For example, with version @value{GDBVN}, type the following to configure only
14088 the @code{bfd} subdirectory:
14089
14090 @example
14091 @group
14092 cd gdb-@value{GDBVN}/bfd
14093 ../configure @var{host}
14094 @end group
14095 @end example
14096
14097 You can install @code{@value{GDBP}} anywhere; it has no hardwired paths.
14098 However, you should make sure that the shell on your path (named by
14099 the @samp{SHELL} environment variable) is publicly readable. Remember
14100 that @value{GDBN} uses the shell to start your program---some systems refuse to
14101 let @value{GDBN} debug child processes whose programs are not readable.
14102
14103 @menu
14104 * Separate Objdir:: Compiling @value{GDBN} in another directory
14105 * Config Names:: Specifying names for hosts and targets
14106 * Configure Options:: Summary of options for configure
14107 @end menu
14108
14109 @node Separate Objdir
14110 @section Compiling @value{GDBN} in another directory
14111
14112 If you want to run @value{GDBN} versions for several host or target machines,
14113 you need a different @code{gdb} compiled for each combination of
14114 host and target. @code{configure} is designed to make this easy by
14115 allowing you to generate each configuration in a separate subdirectory,
14116 rather than in the source directory. If your @code{make} program
14117 handles the @samp{VPATH} feature (@sc{gnu} @code{make} does), running
14118 @code{make} in each of these directories builds the @code{gdb}
14119 program specified there.
14120
14121 To build @code{gdb} in a separate directory, run @code{configure}
14122 with the @samp{--srcdir} option to specify where to find the source.
14123 (You also need to specify a path to find @code{configure}
14124 itself from your working directory. If the path to @code{configure}
14125 would be the same as the argument to @samp{--srcdir}, you can leave out
14126 the @samp{--srcdir} option; it is assumed.)
14127
14128 For example, with version @value{GDBVN}, you can build @value{GDBN} in a
14129 separate directory for a Sun 4 like this:
14130
14131 @example
14132 @group
14133 cd gdb-@value{GDBVN}
14134 mkdir ../gdb-sun4
14135 cd ../gdb-sun4
14136 ../gdb-@value{GDBVN}/configure sun4
14137 make
14138 @end group
14139 @end example
14140
14141 When @code{configure} builds a configuration using a remote source
14142 directory, it creates a tree for the binaries with the same structure
14143 (and using the same names) as the tree under the source directory. In
14144 the example, you'd find the Sun 4 library @file{libiberty.a} in the
14145 directory @file{gdb-sun4/libiberty}, and @value{GDBN} itself in
14146 @file{gdb-sun4/gdb}.
14147
14148 One popular reason to build several @value{GDBN} configurations in separate
14149 directories is to configure @value{GDBN} for cross-compiling (where
14150 @value{GDBN} runs on one machine---the @dfn{host}---while debugging
14151 programs that run on another machine---the @dfn{target}).
14152 You specify a cross-debugging target by
14153 giving the @samp{--target=@var{target}} option to @code{configure}.
14154
14155 When you run @code{make} to build a program or library, you must run
14156 it in a configured directory---whatever directory you were in when you
14157 called @code{configure} (or one of its subdirectories).
14158
14159 The @code{Makefile} that @code{configure} generates in each source
14160 directory also runs recursively. If you type @code{make} in a source
14161 directory such as @file{gdb-@value{GDBVN}} (or in a separate configured
14162 directory configured with @samp{--srcdir=@var{dirname}/gdb-@value{GDBVN}}), you
14163 will build all the required libraries, and then build GDB.
14164
14165 When you have multiple hosts or targets configured in separate
14166 directories, you can run @code{make} on them in parallel (for example,
14167 if they are NFS-mounted on each of the hosts); they will not interfere
14168 with each other.
14169
14170 @node Config Names
14171 @section Specifying names for hosts and targets
14172
14173 The specifications used for hosts and targets in the @code{configure}
14174 script are based on a three-part naming scheme, but some short predefined
14175 aliases are also supported. The full naming scheme encodes three pieces
14176 of information in the following pattern:
14177
14178 @example
14179 @var{architecture}-@var{vendor}-@var{os}
14180 @end example
14181
14182 For example, you can use the alias @code{sun4} as a @var{host} argument,
14183 or as the value for @var{target} in a @code{--target=@var{target}}
14184 option. The equivalent full name is @samp{sparc-sun-sunos4}.
14185
14186 The @code{configure} script accompanying @value{GDBN} does not provide
14187 any query facility to list all supported host and target names or
14188 aliases. @code{configure} calls the Bourne shell script
14189 @code{config.sub} to map abbreviations to full names; you can read the
14190 script, if you wish, or you can use it to test your guesses on
14191 abbreviations---for example:
14192
14193 @smallexample
14194 % sh config.sub i386-linux
14195 i386-pc-linux-gnu
14196 % sh config.sub alpha-linux
14197 alpha-unknown-linux-gnu
14198 % sh config.sub hp9k700
14199 hppa1.1-hp-hpux
14200 % sh config.sub sun4
14201 sparc-sun-sunos4.1.1
14202 % sh config.sub sun3
14203 m68k-sun-sunos4.1.1
14204 % sh config.sub i986v
14205 Invalid configuration `i986v': machine `i986v' not recognized
14206 @end smallexample
14207
14208 @noindent
14209 @code{config.sub} is also distributed in the @value{GDBN} source
14210 directory (@file{gdb-@value{GDBVN}}, for version @value{GDBVN}).
14211
14212 @node Configure Options
14213 @section @code{configure} options
14214
14215 Here is a summary of the @code{configure} options and arguments that
14216 are most often useful for building @value{GDBN}. @code{configure} also has
14217 several other options not listed here. @inforef{What Configure
14218 Does,,configure.info}, for a full explanation of @code{configure}.
14219
14220 @example
14221 configure @r{[}--help@r{]}
14222 @r{[}--prefix=@var{dir}@r{]}
14223 @r{[}--exec-prefix=@var{dir}@r{]}
14224 @r{[}--srcdir=@var{dirname}@r{]}
14225 @r{[}--norecursion@r{]} @r{[}--rm@r{]}
14226 @r{[}--target=@var{target}@r{]}
14227 @var{host}
14228 @end example
14229
14230 @noindent
14231 You may introduce options with a single @samp{-} rather than
14232 @samp{--} if you prefer; but you may abbreviate option names if you use
14233 @samp{--}.
14234
14235 @table @code
14236 @item --help
14237 Display a quick summary of how to invoke @code{configure}.
14238
14239 @item --prefix=@var{dir}
14240 Configure the source to install programs and files under directory
14241 @file{@var{dir}}.
14242
14243 @item --exec-prefix=@var{dir}
14244 Configure the source to install programs under directory
14245 @file{@var{dir}}.
14246
14247 @c avoid splitting the warning from the explanation:
14248 @need 2000
14249 @item --srcdir=@var{dirname}
14250 @strong{Warning: using this option requires @sc{gnu} @code{make}, or another
14251 @code{make} that implements the @code{VPATH} feature.}@*
14252 Use this option to make configurations in directories separate from the
14253 @value{GDBN} source directories. Among other things, you can use this to
14254 build (or maintain) several configurations simultaneously, in separate
14255 directories. @code{configure} writes configuration specific files in
14256 the current directory, but arranges for them to use the source in the
14257 directory @var{dirname}. @code{configure} creates directories under
14258 the working directory in parallel to the source directories below
14259 @var{dirname}.
14260
14261 @item --norecursion
14262 Configure only the directory level where @code{configure} is executed; do not
14263 propagate configuration to subdirectories.
14264
14265 @item --target=@var{target}
14266 Configure @value{GDBN} for cross-debugging programs running on the specified
14267 @var{target}. Without this option, @value{GDBN} is configured to debug
14268 programs that run on the same machine (@var{host}) as @value{GDBN} itself.
14269
14270 There is no convenient way to generate a list of all available targets.
14271
14272 @item @var{host} @dots{}
14273 Configure @value{GDBN} to run on the specified @var{host}.
14274
14275 There is no convenient way to generate a list of all available hosts.
14276 @end table
14277
14278 There are many other options available as well, but they are generally
14279 needed for special purposes only.
14280
14281 @node Index
14282 @unnumbered Index
14283
14284 @printindex cp
14285
14286 @tex
14287 % I think something like @colophon should be in texinfo. In the
14288 % meantime:
14289 \long\def\colophon{\hbox to0pt{}\vfill
14290 \centerline{The body of this manual is set in}
14291 \centerline{\fontname\tenrm,}
14292 \centerline{with headings in {\bf\fontname\tenbf}}
14293 \centerline{and examples in {\tt\fontname\tentt}.}
14294 \centerline{{\it\fontname\tenit\/},}
14295 \centerline{{\bf\fontname\tenbf}, and}
14296 \centerline{{\sl\fontname\tensl\/}}
14297 \centerline{are used for emphasis.}\vfill}
14298 \page\colophon
14299 % Blame: doc@cygnus.com, 1991.
14300 @end tex
14301
14302 @c TeX can handle the contents at the start but makeinfo 3.12 can not
14303 @ifinfo
14304 @contents
14305 @end ifinfo
14306 @ifhtml
14307 @contents
14308 @end ifhtml
14309
14310 @bye
This page took 0.355811 seconds and 4 git commands to generate.