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29a2b744 | 1 | \input texinfo @c -*-texinfo-*- |
5986c8ea | 2 | @c Copyright 1988 1989 1990 1991 1992 1993 1994 Free Software Foundation, Inc. |
18fae2a8 | 3 | @c |
29a2b744 | 4 | @c %**start of header |
18fae2a8 | 5 | @c makeinfo ignores cmds prev to setfilename, so its arg cannot make use |
1d7c3357 | 6 | @c of @set vars. However, you can override filename with makeinfo -o. |
18fae2a8 RP |
7 | @setfilename gdb.info |
8 | @c | |
361daf65 | 9 | @include gdb-cfg.texi |
18fae2a8 RP |
10 | @c |
11 | @ifset GENERIC | |
12 | @settitle Debugging with @value{GDBN} | |
13 | @end ifset | |
14 | @ifclear GENERIC | |
1d7c3357 | 15 | @settitle Debugging with @value{GDBN} (@value{TARGET}) |
18fae2a8 | 16 | @end ifclear |
29a2b744 | 17 | @setchapternewpage odd |
29a2b744 RP |
18 | @c %**end of header |
19 | ||
ed447b95 | 20 | @iftex |
51b65b74 | 21 | @c @smallbook |
fe715d06 | 22 | @c @cropmarks |
ed447b95 RP |
23 | @end iftex |
24 | ||
29a2b744 RP |
25 | @finalout |
26 | @syncodeindex ky cp | |
27 | ||
fe715d06 RP |
28 | @c readline appendices use @vindex |
29 | @syncodeindex vr cp | |
30 | ||
0cb95a9c | 31 | @c !!set GDB manual's edition---not the same as GDB version! |
9a27b06e | 32 | @set EDITION 4.12 |
0cb95a9c RP |
33 | |
34 | @c !!set GDB manual's revision date | |
9a27b06e | 35 | @set DATE January 1994 |
29a2b744 | 36 | |
d24e0922 | 37 | @c GDB CHANGELOG CONSULTED BETWEEN: |
29a2b744 RP |
38 | @c Fri Oct 11 23:27:06 1991 John Gilmore (gnu at cygnus.com) |
39 | @c Sat Dec 22 02:51:40 1990 John Gilmore (gnu at cygint) | |
40 | ||
9c3ad547 | 41 | @c THIS MANUAL REQUIRES TEXINFO-2 macros and info-makers to format properly. |
29a2b744 | 42 | |
b7becc8f | 43 | @ifinfo |
ed447b95 RP |
44 | @c This is a dir.info fragment to support semi-automated addition of |
45 | @c manuals to an info tree. zoo@cygnus.com is developing this facility. | |
b7becc8f RP |
46 | @format |
47 | START-INFO-DIR-ENTRY | |
95cb23dc | 48 | * Gdb: (gdb). The GNU debugger. |
b7becc8f RP |
49 | END-INFO-DIR-ENTRY |
50 | @end format | |
51 | @end ifinfo | |
18fae2a8 | 52 | @c |
70b88761 | 53 | @c |
70b88761 | 54 | @ifinfo |
18fae2a8 | 55 | This file documents the GNU debugger @value{GDBN}. |
70b88761 | 56 | |
0cb95a9c RP |
57 | |
58 | This is Edition @value{EDITION}, @value{DATE}, | |
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59 | of @cite{Debugging with @value{GDBN}: the GNU Source-Level Debugger} |
60 | for GDB Version @value{GDBVN}. | |
29a2b744 | 61 | |
6b51acad | 62 | Copyright (C) 1988, '89, '90, '91, '92, '93 Free Software Foundation, Inc. |
70b88761 RP |
63 | |
64 | Permission is granted to make and distribute verbatim copies of | |
65 | this manual provided the copyright notice and this permission notice | |
66 | are preserved on all copies. | |
67 | ||
68 | @ignore | |
69 | Permission is granted to process this file through TeX and print the | |
70 | results, provided the printed document carries copying permission | |
71 | notice identical to this one except for the removal of this paragraph | |
72 | (this paragraph not being relevant to the printed manual). | |
73 | ||
74 | @end ignore | |
75 | Permission is granted to copy and distribute modified versions of this | |
76 | manual under the conditions for verbatim copying, provided also that the | |
d55320a0 RP |
77 | entire resulting derived work is distributed under the terms of a |
78 | permission notice identical to this one. | |
70b88761 RP |
79 | |
80 | Permission is granted to copy and distribute translations of this manual | |
d55320a0 | 81 | into another language, under the above conditions for modified versions. |
70b88761 | 82 | @end ifinfo |
1041a570 | 83 | |
70b88761 | 84 | @titlepage |
18fae2a8 | 85 | @title Debugging with @value{GDBN} |
95d5ceb9 | 86 | @subtitle The GNU Source-Level Debugger |
18fae2a8 | 87 | @ifclear GENERIC |
a64a6c2b | 88 | @subtitle (@value{TARGET}) |
18fae2a8 | 89 | @end ifclear |
70b88761 | 90 | @sp 1 |
0cb95a9c RP |
91 | @subtitle Edition @value{EDITION}, for @value{GDBN} version @value{GDBVN} |
92 | @subtitle @value{DATE} | |
6b51acad | 93 | @author Richard M. Stallman and Roland H. Pesch |
70b88761 RP |
94 | @page |
95 | @tex | |
96 | {\parskip=0pt | |
18fae2a8 | 97 | \hfill (Send bugs and comments on @value{GDBN} to bug-gdb\@prep.ai.mit.edu.)\par |
ed447b95 | 98 | \hfill {\it Debugging with @value{GDBN}}\par |
70b88761 | 99 | \hfill \TeX{}info \texinfoversion\par |
ed447b95 | 100 | \hfill pesch\@cygnus.com\par |
70b88761 RP |
101 | } |
102 | @end tex | |
103 | ||
104 | @vskip 0pt plus 1filll | |
6b51acad RP |
105 | Copyright @copyright{} 1988, '89, '90, '91, '92, '93 Free Software |
106 | Foundation, Inc. | |
107 | @sp 2 | |
108 | Published by the Free Software Foundation @* | |
109 | 675 Massachusetts Avenue, @* | |
110 | Cambridge, MA 02139 USA @* | |
111 | Printed copies are available for $20 each. @* | |
112 | ISBN 1-882114-11-6 @* | |
70b88761 RP |
113 | |
114 | Permission is granted to make and distribute verbatim copies of | |
115 | this manual provided the copyright notice and this permission notice | |
116 | are preserved on all copies. | |
117 | ||
118 | Permission is granted to copy and distribute modified versions of this | |
119 | manual under the conditions for verbatim copying, provided also that the | |
d55320a0 RP |
120 | entire resulting derived work is distributed under the terms of a |
121 | permission notice identical to this one. | |
70b88761 RP |
122 | |
123 | Permission is granted to copy and distribute translations of this manual | |
d55320a0 | 124 | into another language, under the above conditions for modified versions. |
70b88761 RP |
125 | @end titlepage |
126 | @page | |
127 | ||
70b88761 | 128 | @ifinfo |
4eb4cf57 | 129 | @node Top |
18fae2a8 | 130 | @top Debugging with @value{GDBN} |
29a2b744 | 131 | |
18fae2a8 | 132 | This file describes @value{GDBN}, the GNU symbolic debugger. |
29a2b744 | 133 | |
0cb95a9c | 134 | This is Edition @value{EDITION}, @value{DATE}, for GDB Version @value{GDBVN}. |
70b88761 RP |
135 | |
136 | @menu | |
18fae2a8 RP |
137 | * Summary:: Summary of @value{GDBN} |
138 | @ifset NOVEL | |
c7cb8acb | 139 | * New Features:: New features since GDB version 3.5 |
18fae2a8 RP |
140 | @end ifset |
141 | @ifclear BARETARGET | |
142 | * Sample Session:: A sample @value{GDBN} session | |
143 | @end ifclear | |
b0157555 | 144 | |
18fae2a8 RP |
145 | * Invocation:: Getting in and out of @value{GDBN} |
146 | * Commands:: @value{GDBN} commands | |
147 | * Running:: Running programs under @value{GDBN} | |
29a2b744 RP |
148 | * Stopping:: Stopping and continuing |
149 | * Stack:: Examining the stack | |
150 | * Source:: Examining source files | |
151 | * Data:: Examining data | |
18fae2a8 RP |
152 | @ifclear CONLY |
153 | * Languages:: Using @value{GDBN} with different languages | |
154 | @end ifclear | |
155 | @ifset CONLY | |
1d7c3357 | 156 | * C:: C language support |
18fae2a8 | 157 | @end ifset |
1d7c3357 | 158 | @c remnant makeinfo bug, blank line needed after two end-ifs? |
18fae2a8 | 159 | |
18fae2a8 RP |
160 | * Symbols:: Examining the symbol table |
161 | * Altering:: Altering execution | |
93918348 | 162 | * GDB Files:: @value{GDBN} files |
18fae2a8 RP |
163 | * Targets:: Specifying a debugging target |
164 | * Controlling GDB:: Controlling @value{GDBN} | |
165 | * Sequences:: Canned sequences of commands | |
18fae2a8 | 166 | @ifclear DOSHOST |
18fae2a8 | 167 | * Emacs:: Using @value{GDBN} under GNU Emacs |
18fae2a8 | 168 | @end ifclear |
b0157555 | 169 | |
18fae2a8 | 170 | * GDB Bugs:: Reporting bugs in @value{GDBN} |
da24340c RP |
171 | * Command Line Editing:: Facilities of the readline library |
172 | * Using History Interactively:: | |
18fae2a8 | 173 | @ifset NOVEL |
18fae2a8 | 174 | * Renamed Commands:: |
18fae2a8 | 175 | @end ifset |
1d7c3357 | 176 | @ifclear PRECONFIGURED |
18fae2a8 RP |
177 | * Formatting Documentation:: How to format and print GDB documentation |
178 | * Installing GDB:: Installing GDB | |
18fae2a8 | 179 | @end ifclear |
b0157555 | 180 | |
18fae2a8 RP |
181 | * Index:: Index |
182 | @end menu | |
18fae2a8 | 183 | @end ifinfo |
70b88761 | 184 | |
4eb4cf57 | 185 | @node Summary |
18fae2a8 | 186 | @unnumbered Summary of @value{GDBN} |
70b88761 | 187 | |
18fae2a8 | 188 | The purpose of a debugger such as @value{GDBN} is to allow you to see what is |
70b88761 | 189 | going on ``inside'' another program while it executes---or what another |
1041a570 | 190 | program was doing at the moment it crashed. |
70b88761 | 191 | |
18fae2a8 | 192 | @value{GDBN} can do four main kinds of things (plus other things in support of |
1041a570 | 193 | these) to help you catch bugs in the act: |
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194 | |
195 | @itemize @bullet | |
196 | @item | |
197 | Start your program, specifying anything that might affect its behavior. | |
198 | ||
199 | @item | |
200 | Make your program stop on specified conditions. | |
201 | ||
202 | @item | |
203 | Examine what has happened, when your program has stopped. | |
204 | ||
205 | @item | |
206 | Change things in your program, so you can experiment with correcting the | |
207 | effects of one bug and go on to learn about another. | |
208 | @end itemize | |
209 | ||
18fae2a8 | 210 | @ifclear CONLY |
9934dce8 | 211 | You can use @value{GDBN} to debug programs written in C or C++. |
22b5dba5 RP |
212 | @c "MOD2" used as a "miscellaneous languages" flag here. |
213 | @c This is acceptable while there is no real doc for Chill and Pascal. | |
9934dce8 RP |
214 | @ifclear MOD2 |
215 | For more information, see @ref{Support,,Supported languages}. | |
216 | @end ifclear | |
217 | @ifset MOD2 | |
218 | For more information, see @ref{C,,C and C++}. | |
219 | ||
3f73b7c8 | 220 | Support for Modula-2 and Chill is partial. For information on Modula-2, |
2ae6d007 | 221 | see @ref{Modula-2,,Modula-2}. There is no further documentation on Chill yet. |
3f73b7c8 | 222 | |
b1955f0b | 223 | Debugging Pascal programs which use sets, subranges, file variables, or nested |
22b5dba5 | 224 | functions does not currently work. @value{GDBN} does not support |
b1955f0b | 225 | entering expressions, printing values, or similar features using Pascal syntax. |
09934a2b RP |
226 | @end ifset |
227 | @ifset FORTRAN | |
11e7b867 | 228 | @cindex Fortran |
3ff8a96f | 229 | @value{GDBN} can be used to debug programs written in Fortran, although |
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230 | it does not yet support entering expressions, printing values, or |
231 | similar features using Fortran syntax. It may be necessary to refer to | |
232 | some variables with a trailing underscore. | |
09934a2b | 233 | @end ifset |
18fae2a8 | 234 | @end ifclear |
70b88761 RP |
235 | |
236 | @menu | |
ed447b95 | 237 | * Free Software:: Freely redistributable software |
b80282d5 | 238 | * Contributors:: Contributors to GDB |
70b88761 RP |
239 | @end menu |
240 | ||
4eb4cf57 | 241 | @node Free Software |
93928b60 | 242 | @unnumberedsec Free software |
1041a570 | 243 | |
18fae2a8 | 244 | @value{GDBN} is @dfn{free software}, protected by the GNU General Public License |
1041a570 | 245 | (GPL). The GPL gives you the freedom to copy or adapt a licensed |
70b88761 RP |
246 | program---but every person getting a copy also gets with it the |
247 | freedom to modify that copy (which means that they must get access to | |
248 | the source code), and the freedom to distribute further copies. | |
249 | Typical software companies use copyrights to limit your freedoms; the | |
250 | Free Software Foundation uses the GPL to preserve these freedoms. | |
251 | ||
252 | Fundamentally, the General Public License is a license which says that | |
29a2b744 | 253 | you have these freedoms and that you cannot take these freedoms away |
70b88761 RP |
254 | from anyone else. |
255 | ||
4eb4cf57 | 256 | @node Contributors |
70b88761 RP |
257 | @unnumberedsec Contributors to GDB |
258 | ||
259 | Richard Stallman was the original author of GDB, and of many other GNU | |
260 | programs. Many others have contributed to its development. This | |
261 | section attempts to credit major contributors. One of the virtues of | |
262 | free software is that everyone is free to contribute to it; with | |
263 | regret, we cannot actually acknowledge everyone here. The file | |
264 | @file{ChangeLog} in the GDB distribution approximates a blow-by-blow | |
265 | account. | |
266 | ||
267 | Changes much prior to version 2.0 are lost in the mists of time. | |
268 | ||
269 | @quotation | |
270 | @emph{Plea:} Additions to this section are particularly welcome. If you | |
93918348 | 271 | or your friends (or enemies, to be evenhanded) have been unfairly |
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272 | omitted from this list, we would like to add your names! |
273 | @end quotation | |
274 | ||
275 | So that they may not regard their long labor as thankless, we | |
356bc67b SS |
276 | particularly thank those who shepherded GDB through major releases: |
277 | Fred Fish (releases 4.12, 4.11, 4.10, and 4.9), | |
278 | Stu Grossman and John Gilmore (releases 4.8, 4.7, 4.6, 4.5, and 4.4), | |
279 | John Gilmore (releases 4.3, 4.2, 4.1, 4.0, and 3.9); | |
280 | Jim Kingdon (releases 3.5, 3.4, and 3.3); | |
281 | and Randy Smith (releases 3.2, 3.1, and 3.0). | |
282 | As major maintainer of GDB for some period, each | |
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283 | contributed significantly to the structure, stability, and capabilities |
284 | of the entire debugger. | |
70b88761 | 285 | |
6b51acad | 286 | Richard Stallman, assisted at various times by Peter TerMaat, Chris |
70b88761 RP |
287 | Hanson, and Richard Mlynarik, handled releases through 2.8. |
288 | ||
1d7c3357 | 289 | @ifclear CONLY |
70b88761 RP |
290 | Michael Tiemann is the author of most of the GNU C++ support in GDB, |
291 | with significant additional contributions from Per Bothner. James | |
292 | Clark wrote the GNU C++ demangler. Early work on C++ was by Peter | |
293 | TerMaat (who also did much general update work leading to release 3.0). | |
1d7c3357 | 294 | @end ifclear |
70b88761 | 295 | |
1041a570 RP |
296 | GDB 4 uses the BFD subroutine library to examine multiple |
297 | object-file formats; BFD was a joint project of David V. | |
298 | Henkel-Wallace, Rich Pixley, Steve Chamberlain, and John Gilmore. | |
70b88761 | 299 | |
1041a570 RP |
300 | David Johnson wrote the original COFF support; Pace Willison did |
301 | the original support for encapsulated COFF. | |
70b88761 RP |
302 | |
303 | Adam de Boor and Bradley Davis contributed the ISI Optimum V support. | |
304 | Per Bothner, Noboyuki Hikichi, and Alessandro Forin contributed MIPS | |
1041a570 | 305 | support. |
356bc67b SS |
306 | Jean-Daniel Fekete contributed Sun 386i support. |
307 | Chris Hanson improved the HP9000 support. | |
308 | Noboyuki Hikichi and Tomoyuki Hasei contributed Sony/News OS 3 support. | |
309 | David Johnson contributed Encore Umax support. | |
310 | Jyrki Kuoppala contributed Altos 3068 support. | |
311 | Jeff Law contributed HP PA and SOM support. | |
312 | Keith Packard contributed NS32K support. | |
313 | Doug Rabson contributed Acorn Risc Machine support. | |
314 | Bob Rusk contributed Harris Nighthawk CX-UX support. | |
315 | Chris Smith contributed Convex support (and Fortran debugging). | |
316 | Jonathan Stone contributed Pyramid support. | |
317 | Michael Tiemann contributed SPARC support. | |
318 | Tim Tucker contributed support for the Gould NP1 and Gould Powernode. | |
319 | Pace Willison contributed Intel 386 support. | |
320 | Jay Vosburgh contributed Symmetry support. | |
70b88761 | 321 | |
c338a2fd RP |
322 | Rich Schaefer and Peter Schauer helped with support of SunOS shared |
323 | libraries. | |
70b88761 RP |
324 | |
325 | Jay Fenlason and Roland McGrath ensured that GDB and GAS agree about | |
326 | several machine instruction sets. | |
327 | ||
1041a570 RP |
328 | Patrick Duval, Ted Goldstein, Vikram Koka and Glenn Engel helped |
329 | develop remote debugging. Intel Corporation and Wind River Systems | |
330 | contributed remote debugging modules for their products. | |
70b88761 | 331 | |
1041a570 RP |
332 | Brian Fox is the author of the readline libraries providing |
333 | command-line editing and command history. | |
70b88761 | 334 | |
09934a2b RP |
335 | Andrew Beers of SUNY Buffalo wrote the language-switching code, |
336 | @ifset MOD2 | |
337 | the Modula-2 support, | |
338 | @end ifset | |
339 | and contributed the Languages chapter of this manual. | |
c2bbbb22 | 340 | |
1d7c3357 RP |
341 | Fred Fish wrote most of the support for Unix System Vr4. |
342 | @ifclear CONLY | |
343 | He also enhanced the command-completion support to cover C++ overloaded | |
344 | symbols. | |
345 | @end ifclear | |
346 | ||
a64a6c2b | 347 | Hitachi America, Ltd. sponsored the support for Hitachi microprocessors. |
14d01801 | 348 | |
356bc67b SS |
349 | Kung Hsu, Jeff Law, and Rick Sladkey added support for hardware |
350 | watchpoints. | |
351 | ||
352 | Stu Grossman wrote gdbserver. | |
353 | ||
354 | Jim Kingdon, Peter Schauer, Ian Taylor, and Stu Grossman made | |
355 | nearly innumerable bug fixes and cleanups throughout GDB. | |
356 | ||
18fae2a8 | 357 | @ifset NOVEL |
4eb4cf57 | 358 | @node New Features |
ed447b95 | 359 | @unnumbered New Features since GDB Version 3.5 |
70b88761 RP |
360 | |
361 | @table @emph | |
362 | @item Targets | |
363 | Using the new command @code{target}, you can select at runtime whether | |
364 | you are debugging local files, local processes, standalone systems over | |
b1955f0b | 365 | a serial port, or realtime systems over a TCP/IP connection. The |
b80282d5 | 366 | command @code{load} can download programs into a remote system. Serial |
b21b18e1 RP |
367 | stubs are available for Motorola 680x0, Intel 80386, and Sparc remote |
368 | systems; GDB also supports debugging realtime processes running under | |
b80282d5 | 369 | VxWorks, using SunRPC Remote Procedure Calls over TCP/IP to talk to a |
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370 | debugger stub on the target system. Internally, GDB now uses a function |
371 | vector to mediate access to different targets; if you need to add your | |
372 | own support for a remote protocol, this makes it much easier. | |
70b88761 RP |
373 | |
374 | @item Watchpoints | |
c7cb8acb | 375 | GDB now sports watchpoints as well as breakpoints. You can use a |
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376 | watchpoint to stop execution whenever the value of an expression |
377 | changes, without having to predict a particular place in your program | |
378 | where this may happen. | |
379 | ||
b80282d5 RP |
380 | @item Wide Output |
381 | Commands that issue wide output now insert newlines at places designed | |
382 | to make the output more readable. | |
383 | ||
70b88761 | 384 | @item Object Code Formats |
d55320a0 RP |
385 | GDB uses a new library called the Binary File Descriptor (BFD) Library |
386 | to permit it to switch dynamically, without reconfiguration or | |
3d3ab540 | 387 | recompilation, between different object-file formats. Formats currently |
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388 | supported are COFF, ELF, a.out, Intel 960 b.out, MIPS ECOFF, HPPA SOM |
389 | (with stabs debugging), and S-records; files may be read as .o files, | |
390 | archive libraries, or core dumps. BFD is available as a subroutine | |
391 | library so that other programs may take advantage of it, and the other | |
392 | GNU binary utilities are being converted to use it. | |
70b88761 | 393 | |
b80282d5 | 394 | @item Configuration and Ports |
70b88761 | 395 | Compile-time configuration (to select a particular architecture and |
7463aadd | 396 | operating system) is much easier. The script @code{configure} now |
c7cb8acb RP |
397 | allows you to configure GDB as either a native debugger or a |
398 | cross-debugger. @xref{Installing GDB}, for details on how to | |
6a8cb0e7 | 399 | configure. |
70b88761 RP |
400 | |
401 | @item Interaction | |
93918348 RP |
402 | The user interface to the GDB control variables is simpler, |
403 | and is consolidated in two commands, @code{set} and @code{show}. Output | |
70b88761 RP |
404 | lines are now broken at readable places, rather than overflowing onto |
405 | the next line. You can suppress output of machine-level addresses, | |
406 | displaying only source language information. | |
407 | ||
b80282d5 | 408 | @item C++ |
c7cb8acb | 409 | GDB now supports C++ multiple inheritance (if used with a GCC |
b80282d5 | 410 | version 2 compiler), and also has limited support for C++ exception |
c7cb8acb | 411 | handling, with the commands @code{catch} and @code{info catch}: GDB |
b80282d5 RP |
412 | can break when an exception is raised, before the stack is peeled back |
413 | to the exception handler's context. | |
70b88761 | 414 | |
09934a2b | 415 | @ifset MOD2 |
c2bbbb22 | 416 | @item Modula-2 |
ed447b95 RP |
417 | GDB now has preliminary support for the GNU Modula-2 compiler, currently |
418 | under development at the State University of New York at Buffalo. | |
419 | Coordinated development of both GDB and the GNU Modula-2 compiler will | |
420 | continue. Other Modula-2 compilers are currently not supported, and | |
421 | attempting to debug programs compiled with them will likely result in an | |
422 | error as the symbol table of the executable is read in. | |
09934a2b | 423 | @end ifset |
c2bbbb22 | 424 | |
70b88761 | 425 | @item Command Rationalization |
c7cb8acb | 426 | Many GDB commands have been renamed to make them easier to remember |
70b88761 RP |
427 | and use. In particular, the subcommands of @code{info} and |
428 | @code{show}/@code{set} are grouped to make the former refer to the state | |
c7cb8acb | 429 | of your program, and the latter refer to the state of GDB itself. |
70b88761 RP |
430 | @xref{Renamed Commands}, for details on what commands were renamed. |
431 | ||
70b88761 | 432 | @item Shared Libraries |
77b46d13 JG |
433 | GDB 4 can debug programs and core files that use SunOS, SVR4, or IBM RS/6000 |
434 | shared libraries. | |
b80282d5 | 435 | |
22b5dba5 RP |
436 | @item Threads |
437 | On some systems, GDB 4 has facilities to debug multi-thread programs. | |
438 | ||
b80282d5 | 439 | @item Reference Card |
6f3ec223 | 440 | GDB 4 has a reference card. @xref{Formatting Documentation,,Formatting |
ed447b95 | 441 | the Documentation}, for instructions about how to print it. |
70b88761 | 442 | @end table |
18fae2a8 | 443 | @end ifset |
70b88761 | 444 | |
18fae2a8 | 445 | @ifclear BARETARGET |
4eb4cf57 | 446 | @node Sample Session |
18fae2a8 | 447 | @chapter A Sample @value{GDBN} Session |
70b88761 | 448 | |
18fae2a8 | 449 | You can use this manual at your leisure to read all about @value{GDBN}. |
70b88761 | 450 | However, a handful of commands are enough to get started using the |
ed447b95 | 451 | debugger. This chapter illustrates those commands. |
70b88761 RP |
452 | |
453 | @iftex | |
6ca72cc6 | 454 | In this sample session, we emphasize user input like this: @b{input}, |
70b88761 RP |
455 | to make it easier to pick out from the surrounding output. |
456 | @end iftex | |
457 | ||
458 | @c FIXME: this example may not be appropriate for some configs, where | |
459 | @c FIXME...primary interest is in remote use. | |
18fae2a8 | 460 | |
70b88761 RP |
461 | One of the preliminary versions of GNU @code{m4} (a generic macro |
462 | processor) exhibits the following bug: sometimes, when we change its | |
93918348 RP |
463 | quote strings from the default, the commands used to capture one macro |
464 | definition within another stop working. In the following short @code{m4} | |
70b88761 | 465 | session, we define a macro @code{foo} which expands to @code{0000}; we |
29a2b744 | 466 | then use the @code{m4} built-in @code{defn} to define @code{bar} as the |
70b88761 RP |
467 | same thing. However, when we change the open quote string to |
468 | @code{<QUOTE>} and the close quote string to @code{<UNQUOTE>}, the same | |
469 | procedure fails to define a new synonym @code{baz}: | |
470 | ||
471 | @smallexample | |
6ca72cc6 RP |
472 | $ @b{cd gnu/m4} |
473 | $ @b{./m4} | |
474 | @b{define(foo,0000)} | |
70b88761 | 475 | |
6ca72cc6 | 476 | @b{foo} |
70b88761 | 477 | 0000 |
6ca72cc6 | 478 | @b{define(bar,defn(`foo'))} |
70b88761 | 479 | |
6ca72cc6 | 480 | @b{bar} |
70b88761 | 481 | 0000 |
6ca72cc6 | 482 | @b{changequote(<QUOTE>,<UNQUOTE>)} |
70b88761 | 483 | |
6ca72cc6 RP |
484 | @b{define(baz,defn(<QUOTE>foo<UNQUOTE>))} |
485 | @b{baz} | |
486 | @b{C-d} | |
70b88761 RP |
487 | m4: End of input: 0: fatal error: EOF in string |
488 | @end smallexample | |
489 | ||
490 | @noindent | |
93918348 | 491 | Let us use @value{GDBN} to try to see what is going on. |
70b88761 RP |
492 | |
493 | @smallexample | |
18fae2a8 | 494 | $ @b{@value{GDBP} m4} |
203eea5d RP |
495 | @c FIXME: this falsifies the exact text played out, to permit smallbook |
496 | @c FIXME... format to come out better. | |
497 | GDB is free software and you are welcome to distribute copies | |
498 | of it under certain conditions; type "show copying" to see | |
499 | the conditions. | |
500 | There is absolutely no warranty for GDB; type "show warranty" | |
ed447b95 RP |
501 | for details. |
502 | GDB @value{GDBVN}, Copyright 1993 Free Software Foundation, Inc... | |
18fae2a8 | 503 | (@value{GDBP}) |
70b88761 RP |
504 | @end smallexample |
505 | ||
506 | @noindent | |
9a27b06e RP |
507 | @value{GDBN} reads only enough symbol data to know where to find the |
508 | rest when needed; as a result, the first prompt comes up very quickly. | |
509 | We now tell @value{GDBN} to use a narrower display width than usual, so | |
510 | that examples fit in this manual. | |
70b88761 RP |
511 | |
512 | @smallexample | |
18fae2a8 | 513 | (@value{GDBP}) @b{set width 70} |
70b88761 RP |
514 | @end smallexample |
515 | ||
e251e767 | 516 | @noindent |
93918348 | 517 | We need to see how the @code{m4} built-in @code{changequote} works. |
70b88761 | 518 | Having looked at the source, we know the relevant subroutine is |
93918348 | 519 | @code{m4_changequote}, so we set a breakpoint there with the @value{GDBN} |
70b88761 RP |
520 | @code{break} command. |
521 | ||
522 | @smallexample | |
18fae2a8 | 523 | (@value{GDBP}) @b{break m4_changequote} |
70b88761 RP |
524 | Breakpoint 1 at 0x62f4: file builtin.c, line 879. |
525 | @end smallexample | |
526 | ||
527 | @noindent | |
18fae2a8 | 528 | Using the @code{run} command, we start @code{m4} running under @value{GDBN} |
70b88761 RP |
529 | control; as long as control does not reach the @code{m4_changequote} |
530 | subroutine, the program runs as usual: | |
531 | ||
532 | @smallexample | |
18fae2a8 | 533 | (@value{GDBP}) @b{run} |
e251e767 | 534 | Starting program: /work/Editorial/gdb/gnu/m4/m4 |
6ca72cc6 | 535 | @b{define(foo,0000)} |
70b88761 | 536 | |
6ca72cc6 | 537 | @b{foo} |
70b88761 RP |
538 | 0000 |
539 | @end smallexample | |
540 | ||
541 | @noindent | |
18fae2a8 | 542 | To trigger the breakpoint, we call @code{changequote}. @value{GDBN} |
70b88761 RP |
543 | suspends execution of @code{m4}, displaying information about the |
544 | context where it stops. | |
545 | ||
546 | @smallexample | |
6ca72cc6 | 547 | @b{changequote(<QUOTE>,<UNQUOTE>)} |
70b88761 | 548 | |
203eea5d RP |
549 | Breakpoint 1, m4_changequote (argc=3, argv=0x33c70) |
550 | at builtin.c:879 | |
38962738 | 551 | 879 if (bad_argc(TOKEN_DATA_TEXT(argv[0]),argc,1,3)) |
70b88761 RP |
552 | @end smallexample |
553 | ||
554 | @noindent | |
555 | Now we use the command @code{n} (@code{next}) to advance execution to | |
556 | the next line of the current function. | |
557 | ||
558 | @smallexample | |
18fae2a8 | 559 | (@value{GDBP}) @b{n} |
203eea5d RP |
560 | 882 set_quotes((argc >= 2) ? TOKEN_DATA_TEXT(argv[1])\ |
561 | : nil, | |
70b88761 RP |
562 | @end smallexample |
563 | ||
564 | @noindent | |
565 | @code{set_quotes} looks like a promising subroutine. We can go into it | |
566 | by using the command @code{s} (@code{step}) instead of @code{next}. | |
567 | @code{step} goes to the next line to be executed in @emph{any} | |
e251e767 | 568 | subroutine, so it steps into @code{set_quotes}. |
70b88761 RP |
569 | |
570 | @smallexample | |
18fae2a8 | 571 | (@value{GDBP}) @b{s} |
70b88761 RP |
572 | set_quotes (lq=0x34c78 "<QUOTE>", rq=0x34c88 "<UNQUOTE>") |
573 | at input.c:530 | |
574 | 530 if (lquote != def_lquote) | |
575 | @end smallexample | |
576 | ||
577 | @noindent | |
29a2b744 RP |
578 | The display that shows the subroutine where @code{m4} is now |
579 | suspended (and its arguments) is called a stack frame display. It | |
580 | shows a summary of the stack. We can use the @code{backtrace} | |
581 | command (which can also be spelled @code{bt}), to see where we are | |
582 | in the stack as a whole: the @code{backtrace} command displays a | |
583 | stack frame for each active subroutine. | |
70b88761 RP |
584 | |
585 | @smallexample | |
18fae2a8 | 586 | (@value{GDBP}) @b{bt} |
70b88761 RP |
587 | #0 set_quotes (lq=0x34c78 "<QUOTE>", rq=0x34c88 "<UNQUOTE>") |
588 | at input.c:530 | |
203eea5d RP |
589 | #1 0x6344 in m4_changequote (argc=3, argv=0x33c70) |
590 | at builtin.c:882 | |
70b88761 RP |
591 | #2 0x8174 in expand_macro (sym=0x33320) at macro.c:242 |
592 | #3 0x7a88 in expand_token (obs=0x0, t=209696, td=0xf7fffa30) | |
593 | at macro.c:71 | |
594 | #4 0x79dc in expand_input () at macro.c:40 | |
595 | #5 0x2930 in main (argc=0, argv=0xf7fffb20) at m4.c:195 | |
596 | @end smallexample | |
597 | ||
598 | @noindent | |
9a27b06e | 599 | We step through a few more lines to see what happens. The first two |
70b88761 RP |
600 | times, we can use @samp{s}; the next two times we use @code{n} to avoid |
601 | falling into the @code{xstrdup} subroutine. | |
1041a570 | 602 | |
70b88761 | 603 | @smallexample |
18fae2a8 | 604 | (@value{GDBP}) @b{s} |
70b88761 | 605 | 0x3b5c 532 if (rquote != def_rquote) |
18fae2a8 | 606 | (@value{GDBP}) @b{s} |
203eea5d RP |
607 | 0x3b80 535 lquote = (lq == nil || *lq == '\0') ? \ |
608 | def_lquote : xstrdup(lq); | |
18fae2a8 | 609 | (@value{GDBP}) @b{n} |
203eea5d RP |
610 | 536 rquote = (rq == nil || *rq == '\0') ? def_rquote\ |
611 | : xstrdup(rq); | |
18fae2a8 | 612 | (@value{GDBP}) @b{n} |
70b88761 RP |
613 | 538 len_lquote = strlen(rquote); |
614 | @end smallexample | |
615 | ||
616 | @noindent | |
93918348 | 617 | The last line displayed looks a little odd; we can examine the variables |
70b88761 | 618 | @code{lquote} and @code{rquote} to see if they are in fact the new left |
93918348 | 619 | and right quotes we specified. We use the command @code{p} |
70b88761 RP |
620 | (@code{print}) to see their values. |
621 | ||
622 | @smallexample | |
18fae2a8 | 623 | (@value{GDBP}) @b{p lquote} |
70b88761 | 624 | $1 = 0x35d40 "<QUOTE>" |
18fae2a8 | 625 | (@value{GDBP}) @b{p rquote} |
70b88761 RP |
626 | $2 = 0x35d50 "<UNQUOTE>" |
627 | @end smallexample | |
628 | ||
629 | @noindent | |
630 | @code{lquote} and @code{rquote} are indeed the new left and right quotes. | |
93918348 RP |
631 | To look at some context, we can display ten lines of source |
632 | surrounding the current line with the @code{l} (@code{list}) command. | |
70b88761 RP |
633 | |
634 | @smallexample | |
18fae2a8 | 635 | (@value{GDBP}) @b{l} |
70b88761 | 636 | 533 xfree(rquote); |
e251e767 | 637 | 534 |
203eea5d RP |
638 | 535 lquote = (lq == nil || *lq == '\0') ? def_lquote\ |
639 | : xstrdup (lq); | |
640 | 536 rquote = (rq == nil || *rq == '\0') ? def_rquote\ | |
641 | : xstrdup (rq); | |
e251e767 | 642 | 537 |
70b88761 RP |
643 | 538 len_lquote = strlen(rquote); |
644 | 539 len_rquote = strlen(lquote); | |
645 | 540 @} | |
e251e767 | 646 | 541 |
70b88761 RP |
647 | 542 void |
648 | @end smallexample | |
649 | ||
650 | @noindent | |
93918348 | 651 | Let us step past the two lines that set @code{len_lquote} and |
70b88761 RP |
652 | @code{len_rquote}, and then examine the values of those variables. |
653 | ||
654 | @smallexample | |
18fae2a8 | 655 | (@value{GDBP}) @b{n} |
70b88761 | 656 | 539 len_rquote = strlen(lquote); |
18fae2a8 | 657 | (@value{GDBP}) @b{n} |
70b88761 | 658 | 540 @} |
18fae2a8 | 659 | (@value{GDBP}) @b{p len_lquote} |
70b88761 | 660 | $3 = 9 |
18fae2a8 | 661 | (@value{GDBP}) @b{p len_rquote} |
70b88761 RP |
662 | $4 = 7 |
663 | @end smallexample | |
664 | ||
665 | @noindent | |
666 | That certainly looks wrong, assuming @code{len_lquote} and | |
667 | @code{len_rquote} are meant to be the lengths of @code{lquote} and | |
93918348 RP |
668 | @code{rquote} respectively. We can set them to better values using |
669 | the @code{p} command, since it can print the value of | |
70b88761 | 670 | any expression---and that expression can include subroutine calls and |
e251e767 | 671 | assignments. |
70b88761 RP |
672 | |
673 | @smallexample | |
18fae2a8 | 674 | (@value{GDBP}) @b{p len_lquote=strlen(lquote)} |
70b88761 | 675 | $5 = 7 |
18fae2a8 | 676 | (@value{GDBP}) @b{p len_rquote=strlen(rquote)} |
70b88761 RP |
677 | $6 = 9 |
678 | @end smallexample | |
679 | ||
680 | @noindent | |
93918348 RP |
681 | Is that enough to fix the problem of using the new quotes with the |
682 | @code{m4} built-in @code{defn}? We can allow @code{m4} to continue | |
70b88761 RP |
683 | executing with the @code{c} (@code{continue}) command, and then try the |
684 | example that caused trouble initially: | |
685 | ||
686 | @smallexample | |
18fae2a8 | 687 | (@value{GDBP}) @b{c} |
70b88761 RP |
688 | Continuing. |
689 | ||
6ca72cc6 | 690 | @b{define(baz,defn(<QUOTE>foo<UNQUOTE>))} |
70b88761 RP |
691 | |
692 | baz | |
693 | 0000 | |
694 | @end smallexample | |
695 | ||
696 | @noindent | |
697 | Success! The new quotes now work just as well as the default ones. The | |
698 | problem seems to have been just the two typos defining the wrong | |
93918348 | 699 | lengths. We allow @code{m4} exit by giving it an EOF as input: |
70b88761 RP |
700 | |
701 | @smallexample | |
6ca72cc6 | 702 | @b{C-d} |
70b88761 RP |
703 | Program exited normally. |
704 | @end smallexample | |
705 | ||
e251e767 | 706 | @noindent |
18fae2a8 RP |
707 | The message @samp{Program exited normally.} is from @value{GDBN}; it |
708 | indicates @code{m4} has finished executing. We can end our @value{GDBN} | |
709 | session with the @value{GDBN} @code{quit} command. | |
70b88761 RP |
710 | |
711 | @smallexample | |
18fae2a8 RP |
712 | (@value{GDBP}) @b{quit} |
713 | @end smallexample | |
714 | @end ifclear | |
70b88761 | 715 | |
4eb4cf57 | 716 | @node Invocation |
18fae2a8 | 717 | @chapter Getting In and Out of @value{GDBN} |
70b88761 | 718 | |
18fae2a8 RP |
719 | This chapter discusses how to start @value{GDBN}, and how to get out of it. |
720 | (The essentials: type @samp{@value{GDBP}} to start GDB, and type @kbd{quit} | |
c7cb8acb | 721 | or @kbd{C-d} to exit.) |
29a2b744 | 722 | |
70b88761 | 723 | @menu |
ed447b95 RP |
724 | * Invoking GDB:: How to start @value{GDBN} |
725 | * Quitting GDB:: How to quit @value{GDBN} | |
ed447b95 | 726 | * Shell Commands:: How to use shell commands inside @value{GDBN} |
70b88761 | 727 | @end menu |
18fae2a8 RP |
728 | |
729 | @node Invoking GDB | |
ed447b95 | 730 | @section Invoking @value{GDBN} |
18fae2a8 | 731 | |
a64a6c2b | 732 | @ifset H8EXCLUSIVE |
18fae2a8 | 733 | For details on starting up @value{GDBP} as a |
a64a6c2b RP |
734 | remote debugger attached to a Hitachi microprocessor, see @ref{Hitachi |
735 | Remote,,@value{GDBN} and Hitachi Microprocessors}. | |
18fae2a8 | 736 | @end ifset |
4eb4cf57 | 737 | |
ed447b95 | 738 | Invoke @value{GDBN} by running the program @code{@value{GDBP}}. Once started, |
18fae2a8 | 739 | @value{GDBN} reads commands from the terminal until you tell it to exit. |
70b88761 | 740 | |
18fae2a8 | 741 | You can also run @code{@value{GDBP}} with a variety of arguments and options, |
c7cb8acb RP |
742 | to specify more of your debugging environment at the outset. |
743 | ||
18fae2a8 | 744 | @ifset GENERIC |
c7cb8acb RP |
745 | The command-line options described here are designed |
746 | to cover a variety of situations; in some environments, some of these | |
747 | options may effectively be unavailable. | |
18fae2a8 | 748 | @end ifset |
c7cb8acb | 749 | |
18fae2a8 | 750 | The most usual way to start @value{GDBN} is with one argument, |
4eb4cf57 | 751 | specifying an executable program: |
1041a570 | 752 | |
70b88761 | 753 | @example |
18fae2a8 | 754 | @value{GDBP} @var{program} |
70b88761 | 755 | @end example |
1041a570 | 756 | |
18fae2a8 | 757 | @ifclear BARETARGET |
70b88761 | 758 | @noindent |
29a2b744 RP |
759 | You can also start with both an executable program and a core file |
760 | specified: | |
1041a570 | 761 | |
70b88761 | 762 | @example |
18fae2a8 | 763 | @value{GDBP} @var{program} @var{core} |
70b88761 RP |
764 | @end example |
765 | ||
b80282d5 RP |
766 | You can, instead, specify a process ID as a second argument, if you want |
767 | to debug a running process: | |
1041a570 | 768 | |
b80282d5 | 769 | @example |
18fae2a8 | 770 | @value{GDBP} @var{program} 1234 |
b80282d5 | 771 | @end example |
1041a570 | 772 | |
b80282d5 | 773 | @noindent |
18fae2a8 RP |
774 | would attach @value{GDBN} to process @code{1234} (unless you also have a file |
775 | named @file{1234}; @value{GDBN} does check for a core file first). | |
b80282d5 | 776 | |
c7cb8acb | 777 | Taking advantage of the second command-line argument requires a fairly |
18fae2a8 | 778 | complete operating system; when you use @value{GDBN} as a remote debugger |
c7cb8acb RP |
779 | attached to a bare board, there may not be any notion of ``process'', |
780 | and there is often no way to get a core dump. | |
18fae2a8 | 781 | @end ifclear |
c7cb8acb | 782 | |
70b88761 | 783 | @noindent |
18fae2a8 RP |
784 | You can further control how @value{GDBN} starts up by using command-line |
785 | options. @value{GDBN} itself can remind you of the options available. | |
29a2b744 RP |
786 | |
787 | @noindent | |
788 | Type | |
789 | ||
70b88761 | 790 | @example |
18fae2a8 | 791 | @value{GDBP} -help |
70b88761 | 792 | @end example |
29a2b744 | 793 | |
70b88761 | 794 | @noindent |
29a2b744 | 795 | to display all available options and briefly describe their use |
18fae2a8 | 796 | (@samp{@value{GDBP} -h} is a shorter equivalent). |
70b88761 RP |
797 | |
798 | All options and command line arguments you give are processed | |
799 | in sequential order. The order makes a difference when the | |
e251e767 | 800 | @samp{-x} option is used. |
70b88761 | 801 | |
18fae2a8 | 802 | |
70b88761 | 803 | @menu |
18fae2a8 RP |
804 | @ifclear GENERIC |
805 | @ifset REMOTESTUB | |
806 | * Remote Serial:: @value{GDBN} remote serial protocol | |
807 | @end ifset | |
a64a6c2b | 808 | @ifset I960 |
18fae2a8 RP |
809 | * i960-Nindy Remote:: @value{GDBN} with a remote i960 (Nindy) |
810 | @end ifset | |
a64a6c2b | 811 | @ifset AMD29K |
b1955f0b RP |
812 | * UDI29K Remote:: The UDI protocol for AMD29K |
813 | * EB29K Remote:: The EBMON protocol for AMD29K | |
18fae2a8 RP |
814 | @end ifset |
815 | @ifset VXWORKS | |
816 | * VxWorks Remote:: @value{GDBN} and VxWorks | |
817 | @end ifset | |
a64a6c2b | 818 | @ifset ST2000 |
18fae2a8 RP |
819 | * ST2000 Remote:: @value{GDBN} with a Tandem ST2000 |
820 | @end ifset | |
a64a6c2b RP |
821 | @ifset H8 |
822 | * Hitachi Remote:: @value{GDBN} and Hitachi Microprocessors | |
18fae2a8 | 823 | @end ifset |
34ae25cd RP |
824 | @ifset MIPS |
825 | * MIPS Remote:: @value{GDBN} and MIPS boards | |
826 | @end ifset | |
fe715d06 RP |
827 | @ifset SIMS |
828 | * Simulator:: Simulated CPU target | |
18fae2a8 RP |
829 | @end ifset |
830 | @end ifclear | |
1d7c3357 | 831 | @c remnant makeinfo bug requires this blank line after *two* end-ifblahs: |
18fae2a8 | 832 | |
ed447b95 RP |
833 | * File Options:: Choosing files |
834 | * Mode Options:: Choosing modes | |
18fae2a8 | 835 | @end menu |
18fae2a8 RP |
836 | |
837 | @ifclear GENERIC | |
4af6d502 | 838 | @include remote.texi |
18fae2a8 | 839 | @end ifclear |
4eb4cf57 RP |
840 | |
841 | @node File Options | |
93928b60 | 842 | @subsection Choosing files |
70b88761 | 843 | |
18fae2a8 RP |
844 | @ifclear BARETARGET |
845 | When @value{GDBN} starts, it reads any arguments other than options as | |
29a2b744 RP |
846 | specifying an executable file and core file (or process ID). This is |
847 | the same as if the arguments were specified by the @samp{-se} and | |
18fae2a8 | 848 | @samp{-c} options respectively. (@value{GDBN} reads the first argument |
29a2b744 RP |
849 | that does not have an associated option flag as equivalent to the |
850 | @samp{-se} option followed by that argument; and the second argument | |
851 | that does not have an associated option flag, if any, as equivalent to | |
852 | the @samp{-c} option followed by that argument.) | |
18fae2a8 RP |
853 | @end ifclear |
854 | @ifset BARETARGET | |
855 | When @value{GDBN} starts, it reads any argument other than options as | |
4eb4cf57 RP |
856 | specifying an executable file. This is the same as if the argument was |
857 | specified by the @samp{-se} option. | |
18fae2a8 | 858 | @end ifset |
29a2b744 RP |
859 | |
860 | Many options have both long and short forms; both are shown in the | |
18fae2a8 | 861 | following list. @value{GDBN} also recognizes the long forms if you truncate |
29a2b744 RP |
862 | them, so long as enough of the option is present to be unambiguous. |
863 | (If you prefer, you can flag option arguments with @samp{--} rather | |
864 | than @samp{-}, though we illustrate the more usual convention.) | |
70b88761 RP |
865 | |
866 | @table @code | |
6b51acad | 867 | @item -symbols @var{file} |
70b88761 RP |
868 | @itemx -s @var{file} |
869 | Read symbol table from file @var{file}. | |
870 | ||
6b51acad | 871 | @item -exec @var{file} |
70b88761 RP |
872 | @itemx -e @var{file} |
873 | Use file @var{file} as the executable file to execute when | |
1d7c3357 RP |
874 | @ifset BARETARGET |
875 | appropriate. | |
876 | @end ifset | |
877 | @ifclear BARETARGET | |
70b88761 RP |
878 | appropriate, and for examining pure data in conjunction with a core |
879 | dump. | |
1d7c3357 | 880 | @end ifclear |
70b88761 | 881 | |
6b51acad | 882 | @item -se @var{file} |
70b88761 RP |
883 | Read symbol table from file @var{file} and use it as the executable |
884 | file. | |
885 | ||
18fae2a8 | 886 | @ifclear BARETARGET |
6b51acad | 887 | @item -core @var{file} |
70b88761 RP |
888 | @itemx -c @var{file} |
889 | Use file @var{file} as a core dump to examine. | |
d55320a0 RP |
890 | |
891 | @item -c @var{number} | |
892 | Connect to process ID @var{number}, as with the @code{attach} command | |
893 | (unless there is a file in core-dump format named @var{number}, in which | |
894 | case @samp{-c} specifies that file as a core dump to read). | |
18fae2a8 | 895 | @end ifclear |
70b88761 | 896 | |
6b51acad | 897 | @item -command @var{file} |
70b88761 | 898 | @itemx -x @var{file} |
93928b60 RP |
899 | Execute @value{GDBN} commands from file @var{file}. @xref{Command |
900 | Files,, Command files}. | |
70b88761 | 901 | |
6b51acad | 902 | @item -directory @var{directory} |
70b88761 RP |
903 | @itemx -d @var{directory} |
904 | Add @var{directory} to the path to search for source files. | |
14d01801 | 905 | |
18fae2a8 | 906 | @ifclear BARETARGET |
14d01801 RP |
907 | @item -m |
908 | @itemx -mapped | |
909 | @emph{Warning: this option depends on operating system facilities that are not | |
910 | supported on all systems.}@* | |
77b46d13 JG |
911 | If memory-mapped files are available on your system through the @code{mmap} |
912 | system call, you can use this option | |
18fae2a8 | 913 | to have @value{GDBN} write the symbols from your |
77b46d13 | 914 | program into a reusable file in the current directory. If the program you are debugging is |
9a27b06e RP |
915 | called @file{/tmp/fred}, the mapped symbol file is @file{./fred.syms}. |
916 | Future @value{GDBN} debugging sessions notice the presence of this file, | |
917 | and can quickly map in symbol information from it, rather than reading | |
77b46d13 JG |
918 | the symbol table from the executable program. |
919 | ||
1d7c3357 RP |
920 | @c FIXME! Really host, not target? |
921 | The @file{.syms} file is specific to the host machine where @value{GDBN} | |
922 | is run. It holds an exact image of the internal @value{GDBN} symbol | |
923 | table. It cannot be shared across multiple host platforms. | |
18fae2a8 | 924 | @end ifclear |
77b46d13 JG |
925 | |
926 | @item -r | |
927 | @itemx -readnow | |
928 | Read each symbol file's entire symbol table immediately, rather than | |
929 | the default, which is to read it incrementally as it is needed. | |
930 | This makes startup slower, but makes future operations faster. | |
70b88761 RP |
931 | @end table |
932 | ||
18fae2a8 | 933 | @ifclear BARETARGET |
93918348 RP |
934 | The @code{-mapped} and @code{-readnow} options are typically combined in |
935 | order to build a @file{.syms} file that contains complete symbol | |
93928b60 | 936 | information. (@xref{Files,,Commands to specify files}, for information |
93918348 RP |
937 | on @file{.syms} files.) A simple GDB invocation to do nothing but build |
938 | a @file{.syms} file for future use is: | |
77b46d13 JG |
939 | |
940 | @example | |
941 | gdb -batch -nx -mapped -readnow programname | |
942 | @end example | |
18fae2a8 | 943 | @end ifclear |
77b46d13 | 944 | |
4eb4cf57 | 945 | @node Mode Options |
93928b60 | 946 | @subsection Choosing modes |
1041a570 | 947 | |
18fae2a8 | 948 | You can run @value{GDBN} in various alternative modes---for example, in |
29a2b744 | 949 | batch mode or quiet mode. |
70b88761 RP |
950 | |
951 | @table @code | |
952 | @item -nx | |
953 | @itemx -n | |
d55320a0 RP |
954 | Do not execute commands from any initialization files (normally called |
955 | @file{@value{GDBINIT}}). Normally, the commands in these files are | |
956 | executed after all the command options and arguments have been | |
957 | processed. @xref{Command Files,,Command files}. | |
70b88761 RP |
958 | |
959 | @item -quiet | |
960 | @itemx -q | |
961 | ``Quiet''. Do not print the introductory and copyright messages. These | |
c338a2fd | 962 | messages are also suppressed in batch mode. |
70b88761 RP |
963 | |
964 | @item -batch | |
d55320a0 RP |
965 | Run in batch mode. Exit with status @code{0} after processing all the |
966 | command files specified with @samp{-x} (and all commands from | |
967 | initialization files, if not inhibited with @samp{-n}). Exit with | |
968 | nonzero status if an error occurs in executing the @value{GDBN} commands | |
969 | in the command files. | |
70b88761 | 970 | |
18fae2a8 | 971 | Batch mode may be useful for running @value{GDBN} as a filter, for example to |
70b88761 | 972 | download and run a program on another computer; in order to make this |
e251e767 | 973 | more useful, the message |
1041a570 | 974 | |
70b88761 RP |
975 | @example |
976 | Program exited normally. | |
977 | @end example | |
1041a570 | 978 | |
70b88761 | 979 | @noindent |
18fae2a8 | 980 | (which is ordinarily issued whenever a program running under @value{GDBN} control |
70b88761 RP |
981 | terminates) is not issued when running in batch mode. |
982 | ||
6b51acad | 983 | @item -cd @var{directory} |
18fae2a8 | 984 | Run @value{GDBN} using @var{directory} as its working directory, |
70b88761 RP |
985 | instead of the current directory. |
986 | ||
18fae2a8 | 987 | @ifset LUCID |
45c53080 | 988 | @item -context @var{authentication} |
18fae2a8 | 989 | When the Energize programming system starts up @value{GDBN}, it uses this |
6ca72cc6 | 990 | option to trigger an alternate mode of interaction. |
18fae2a8 | 991 | @var{authentication} is a pair of numeric codes that identify @value{GDBN} |
6ca72cc6 | 992 | as a client in the Energize environment. Avoid this option when you run |
18fae2a8 RP |
993 | @value{GDBN} directly from the command line. See @ref{Energize,,Using |
994 | @value{GDBN} with Energize} for more discussion of using @value{GDBN} with Energize. | |
995 | @end ifset | |
6ca72cc6 | 996 | |
1d7c3357 | 997 | @ifclear DOSHOST |
70b88761 RP |
998 | @item -fullname |
999 | @itemx -f | |
18fae2a8 | 1000 | Emacs sets this option when it runs @value{GDBN} as a subprocess. It tells @value{GDBN} |
70b88761 RP |
1001 | to output the full file name and line number in a standard, |
1002 | recognizable fashion each time a stack frame is displayed (which | |
29a2b744 | 1003 | includes each time your program stops). This recognizable format looks |
70b88761 RP |
1004 | like two @samp{\032} characters, followed by the file name, line number |
1005 | and character position separated by colons, and a newline. The | |
18fae2a8 | 1006 | Emacs-to-@value{GDBN} interface program uses the two @samp{\032} characters as |
70b88761 | 1007 | a signal to display the source code for the frame. |
1d7c3357 | 1008 | @end ifclear |
70b88761 | 1009 | |
18fae2a8 | 1010 | @ifset SERIAL |
70b88761 RP |
1011 | @item -b @var{bps} |
1012 | Set the line speed (baud rate or bits per second) of any serial | |
18fae2a8 | 1013 | interface used by @value{GDBN} for remote debugging. |
70b88761 | 1014 | |
6b51acad | 1015 | @item -tty @var{device} |
70b88761 | 1016 | Run using @var{device} for your program's standard input and output. |
29a2b744 | 1017 | @c FIXME: kingdon thinks there is more to -tty. Investigate. |
18fae2a8 | 1018 | @end ifset |
70b88761 RP |
1019 | @end table |
1020 | ||
ed447b95 RP |
1021 | @node Quitting GDB |
1022 | @section Quitting @value{GDBN} | |
18fae2a8 | 1023 | @cindex exiting @value{GDBN} |
ed447b95 | 1024 | @cindex leaving @value{GDBN} |
1041a570 | 1025 | |
70b88761 RP |
1026 | @table @code |
1027 | @item quit | |
1028 | @kindex quit | |
1029 | @kindex q | |
18fae2a8 | 1030 | To exit @value{GDBN}, use the @code{quit} command (abbreviated @code{q}), or type |
e251e767 | 1031 | an end-of-file character (usually @kbd{C-d}). |
70b88761 RP |
1032 | @end table |
1033 | ||
1034 | @cindex interrupt | |
9a27b06e RP |
1035 | An interrupt (often @kbd{C-c}) does not exit from @value{GDBN}, but rather |
1036 | terminates the action of any @value{GDBN} command that is in progress and | |
1037 | returns to @value{GDBN} command level. It is safe to type the interrupt | |
18fae2a8 | 1038 | character at any time because @value{GDBN} does not allow it to take effect |
70b88761 RP |
1039 | until a time when it is safe. |
1040 | ||
18fae2a8 | 1041 | @ifclear BARETARGET |
ed447b95 RP |
1042 | If you have been using @value{GDBN} to control an attached process or |
1043 | device, you can release it with the @code{detach} command | |
93928b60 | 1044 | (@pxref{Attach, ,Debugging an already-running process}). |
18fae2a8 | 1045 | @end ifclear |
70b88761 | 1046 | |
4eb4cf57 | 1047 | @node Shell Commands |
93928b60 | 1048 | @section Shell commands |
1041a570 | 1049 | |
70b88761 | 1050 | If you need to execute occasional shell commands during your |
18fae2a8 | 1051 | debugging session, there is no need to leave or suspend @value{GDBN}; you can |
70b88761 RP |
1052 | just use the @code{shell} command. |
1053 | ||
1054 | @table @code | |
1055 | @item shell @var{command string} | |
1056 | @kindex shell | |
1057 | @cindex shell escape | |
75f844cc | 1058 | Invoke a the standard shell to execute @var{command string}. |
a1eff6c2 | 1059 | @ifclear DOSHOST |
75f844cc RP |
1060 | If it exists, the environment variable @code{SHELL} determines which |
1061 | shell to run. Otherwise @value{GDBN} uses @code{/bin/sh}. | |
a1eff6c2 | 1062 | @end ifclear |
70b88761 RP |
1063 | @end table |
1064 | ||
1065 | The utility @code{make} is often needed in development environments. | |
a1eff6c2 RP |
1066 | You do not have to use the @code{shell} command for this purpose in |
1067 | @value{GDBN}: | |
70b88761 RP |
1068 | |
1069 | @table @code | |
1070 | @item make @var{make-args} | |
1071 | @kindex make | |
1072 | @cindex calling make | |
a1eff6c2 | 1073 | Execute the @code{make} program with the specified |
70b88761 RP |
1074 | arguments. This is equivalent to @samp{shell make @var{make-args}}. |
1075 | @end table | |
1076 | ||
4eb4cf57 | 1077 | @node Commands |
18fae2a8 | 1078 | @chapter @value{GDBN} Commands |
70b88761 | 1079 | |
18fae2a8 | 1080 | You can abbreviate a @value{GDBN} command to the first few letters of the command |
6f3ec223 | 1081 | name, if that abbreviation is unambiguous; and you can repeat certain |
18fae2a8 RP |
1082 | @value{GDBN} commands by typing just @key{RET}. You can also use the @key{TAB} |
1083 | key to get @value{GDBN} to fill out the rest of a word in a command (or to | |
93918348 | 1084 | show you the alternatives available, if there is more than one possibility). |
29a2b744 | 1085 | |
70b88761 | 1086 | @menu |
ed447b95 RP |
1087 | * Command Syntax:: How to give commands to @value{GDBN} |
1088 | * Completion:: Command completion | |
1089 | * Help:: How to ask @value{GDBN} for help | |
70b88761 RP |
1090 | @end menu |
1091 | ||
4eb4cf57 | 1092 | @node Command Syntax |
93928b60 | 1093 | @section Command syntax |
1041a570 | 1094 | |
fe715d06 RP |
1095 | A @value{GDBN} command is a single line of input. There is no limit on |
1096 | how long it can be. It starts with a command name, which is followed by | |
1097 | arguments whose meaning depends on the command name. For example, the | |
1098 | command @code{step} accepts an argument which is the number of times to | |
1099 | step, as in @samp{step 5}. You can also use the @code{step} command | |
1100 | with no arguments. Some command names do not allow any arguments. | |
70b88761 RP |
1101 | |
1102 | @cindex abbreviation | |
18fae2a8 | 1103 | @value{GDBN} command names may always be truncated if that abbreviation is |
70b88761 RP |
1104 | unambiguous. Other possible command abbreviations are listed in the |
1105 | documentation for individual commands. In some cases, even ambiguous | |
1106 | abbreviations are allowed; for example, @code{s} is specially defined as | |
1107 | equivalent to @code{step} even though there are other commands whose | |
1108 | names start with @code{s}. You can test abbreviations by using them as | |
7463aadd | 1109 | arguments to the @code{help} command. |
70b88761 | 1110 | |
e251e767 | 1111 | @cindex repeating commands |
70b88761 | 1112 | @kindex RET |
18fae2a8 | 1113 | A blank line as input to @value{GDBN} (typing just @key{RET}) means to |
70b88761 | 1114 | repeat the previous command. Certain commands (for example, @code{run}) |
9a27b06e | 1115 | will not repeat this way; these are commands whose unintentional |
70b88761 RP |
1116 | repetition might cause trouble and which you are unlikely to want to |
1117 | repeat. | |
1118 | ||
1119 | The @code{list} and @code{x} commands, when you repeat them with | |
1120 | @key{RET}, construct new arguments rather than repeating | |
1121 | exactly as typed. This permits easy scanning of source or memory. | |
1122 | ||
18fae2a8 | 1123 | @value{GDBN} can also use @key{RET} in another way: to partition lengthy |
b80282d5 | 1124 | output, in a way similar to the common utility @code{more} |
93928b60 RP |
1125 | (@pxref{Screen Size,,Screen size}). Since it is easy to press one |
1126 | @key{RET} too many in this situation, @value{GDBN} disables command | |
1127 | repetition after any command that generates this sort of display. | |
b80282d5 | 1128 | |
70b88761 RP |
1129 | @kindex # |
1130 | @cindex comment | |
fe715d06 RP |
1131 | Any text from a @kbd{#} to the end of the line is a comment; it does |
1132 | nothing. This is useful mainly in command files (@pxref{Command | |
1133 | Files,,Command files}). | |
70b88761 | 1134 | |
4eb4cf57 | 1135 | @node Completion |
93928b60 | 1136 | @section Command completion |
6f3ec223 RP |
1137 | |
1138 | @cindex completion | |
1139 | @cindex word completion | |
93918348 | 1140 | @value{GDBN} can fill in the rest of a word in a command for you, if there is |
6f3ec223 | 1141 | only one possibility; it can also show you what the valid possibilities |
18fae2a8 RP |
1142 | are for the next word in a command, at any time. This works for @value{GDBN} |
1143 | commands, @value{GDBN} subcommands, and the names of symbols in your program. | |
6f3ec223 | 1144 | |
18fae2a8 | 1145 | Press the @key{TAB} key whenever you want @value{GDBN} to fill out the rest |
9a27b06e RP |
1146 | of a word. If there is only one possibility, @value{GDBN} fills in the |
1147 | word, and waits for you to finish the command (or press @key{RET} to | |
6f3ec223 RP |
1148 | enter it). For example, if you type |
1149 | ||
93918348 | 1150 | @c FIXME "@key" does not distinguish its argument sufficiently to permit |
0fdc6e27 RP |
1151 | @c complete accuracy in these examples; space introduced for clarity. |
1152 | @c If texinfo enhancements make it unnecessary, it would be nice to | |
1153 | @c replace " @key" by "@key" in the following... | |
6f3ec223 | 1154 | @example |
18fae2a8 | 1155 | (@value{GDBP}) info bre @key{TAB} |
6f3ec223 RP |
1156 | @end example |
1157 | ||
1158 | @noindent | |
93918348 | 1159 | @value{GDBN} fills in the rest of the word @samp{breakpoints}, since that is |
6f3ec223 RP |
1160 | the only @code{info} subcommand beginning with @samp{bre}: |
1161 | ||
1162 | @example | |
18fae2a8 | 1163 | (@value{GDBP}) info breakpoints |
6f3ec223 RP |
1164 | @end example |
1165 | ||
1166 | @noindent | |
1167 | You can either press @key{RET} at this point, to run the @code{info | |
1168 | breakpoints} command, or backspace and enter something else, if | |
93918348 | 1169 | @samp{breakpoints} does not look like the command you expected. (If you |
6f3ec223 RP |
1170 | were sure you wanted @code{info breakpoints} in the first place, you |
1171 | might as well just type @key{RET} immediately after @samp{info bre}, | |
1172 | to exploit command abbreviations rather than command completion). | |
1173 | ||
1174 | If there is more than one possibility for the next word when you press | |
9a27b06e RP |
1175 | @key{TAB}, @value{GDBN} sounds a bell. You can either supply more |
1176 | characters and try again, or just press @key{TAB} a second time; | |
1177 | @value{GDBN} displays all the possible completions for that word. For | |
6f3ec223 | 1178 | example, you might want to set a breakpoint on a subroutine whose name |
18fae2a8 | 1179 | begins with @samp{make_}, but when you type @kbd{b make_@key{TAB}} @value{GDBN} |
9a27b06e | 1180 | just sounds the bell. Typing @key{TAB} again displays all the |
6f3ec223 RP |
1181 | function names in your program that begin with those characters, for |
1182 | example: | |
1183 | ||
1184 | @example | |
18fae2a8 RP |
1185 | (@value{GDBP}) b make_ @key{TAB} |
1186 | @exdent @value{GDBN} sounds bell; press @key{TAB} again, to see: | |
6f3ec223 RP |
1187 | make_a_section_from_file make_environ |
1188 | make_abs_section make_function_type | |
1189 | make_blockvector make_pointer_type | |
1190 | make_cleanup make_reference_type | |
1191 | make_command make_symbol_completion_list | |
18fae2a8 | 1192 | (@value{GDBP}) b make_ |
6f3ec223 RP |
1193 | @end example |
1194 | ||
1195 | @noindent | |
18fae2a8 | 1196 | After displaying the available possibilities, @value{GDBN} copies your |
b1385986 | 1197 | partial input (@samp{b make_} in the example) so you can finish the |
6f3ec223 RP |
1198 | command. |
1199 | ||
1200 | If you just want to see the list of alternatives in the first place, you | |
b1385986 | 1201 | can press @kbd{M-?} rather than pressing @key{TAB} twice. @kbd{M-?} |
0f153e74 | 1202 | means @kbd{@key{META} ?}. You can type this |
18fae2a8 | 1203 | @ifclear DOSHOST |
0f153e74 | 1204 | either by holding down a |
b1385986 | 1205 | key designated as the @key{META} shift on your keyboard (if there is |
0f153e74 | 1206 | one) while typing @kbd{?}, or |
18fae2a8 | 1207 | @end ifclear |
0f153e74 | 1208 | as @key{ESC} followed by @kbd{?}. |
6f3ec223 RP |
1209 | |
1210 | @cindex quotes in commands | |
1211 | @cindex completion of quoted strings | |
1212 | Sometimes the string you need, while logically a ``word'', may contain | |
18fae2a8 | 1213 | parentheses or other characters that @value{GDBN} normally excludes from its |
6f3ec223 | 1214 | notion of a word. To permit word completion to work in this situation, |
18fae2a8 | 1215 | you may enclose words in @code{'} (single quote marks) in @value{GDBN} commands. |
6f3ec223 | 1216 | |
1d7c3357 | 1217 | @ifclear CONLY |
6f3ec223 RP |
1218 | The most likely situation where you might need this is in typing the |
1219 | name of a C++ function. This is because C++ allows function overloading | |
1220 | (multiple definitions of the same function, distinguished by argument | |
b1385986 RP |
1221 | type). For example, when you want to set a breakpoint you may need to |
1222 | distinguish whether you mean the version of @code{name} that takes an | |
1223 | @code{int} parameter, @code{name(int)}, or the version that takes a | |
1224 | @code{float} parameter, @code{name(float)}. To use the word-completion | |
1225 | facilities in this situation, type a single quote @code{'} at the | |
18fae2a8 | 1226 | beginning of the function name. This alerts @value{GDBN} that it may need to |
b1385986 RP |
1227 | consider more information than usual when you press @key{TAB} or |
1228 | @kbd{M-?} to request word completion: | |
6f3ec223 RP |
1229 | |
1230 | @example | |
18fae2a8 | 1231 | (@value{GDBP}) b 'bubble( @key{M-?} |
0fdc6e27 | 1232 | bubble(double,double) bubble(int,int) |
18fae2a8 | 1233 | (@value{GDBP}) b 'bubble( |
6f3ec223 RP |
1234 | @end example |
1235 | ||
9a27b06e RP |
1236 | In some cases, @value{GDBN} can tell that completing a name requires using |
1237 | quotes. When this happens, @value{GDBN} inserts the quote for you (while | |
0fdc6e27 RP |
1238 | completing as much as it can) if you do not type the quote in the first |
1239 | place: | |
1240 | ||
1241 | @example | |
18fae2a8 RP |
1242 | (@value{GDBP}) b bub @key{TAB} |
1243 | @exdent @value{GDBN} alters your input line to the following, and rings a bell: | |
1244 | (@value{GDBP}) b 'bubble( | |
0fdc6e27 RP |
1245 | @end example |
1246 | ||
1247 | @noindent | |
18fae2a8 | 1248 | In general, @value{GDBN} can tell that a quote is needed (and inserts it) if |
0fdc6e27 RP |
1249 | you have not yet started typing the argument list when you ask for |
1250 | completion on an overloaded symbol. | |
1d7c3357 | 1251 | @end ifclear |
0fdc6e27 RP |
1252 | |
1253 | ||
4eb4cf57 | 1254 | @node Help |
93928b60 | 1255 | @section Getting help |
70b88761 RP |
1256 | @cindex online documentation |
1257 | @kindex help | |
1041a570 | 1258 | |
18fae2a8 | 1259 | You can always ask @value{GDBN} itself for information on its commands, using the |
e251e767 | 1260 | command @code{help}. |
70b88761 RP |
1261 | |
1262 | @table @code | |
1263 | @item help | |
1264 | @itemx h | |
1265 | @kindex h | |
1266 | You can use @code{help} (abbreviated @code{h}) with no arguments to | |
1267 | display a short list of named classes of commands: | |
1041a570 | 1268 | |
70b88761 | 1269 | @smallexample |
18fae2a8 | 1270 | (@value{GDBP}) help |
70b88761 RP |
1271 | List of classes of commands: |
1272 | ||
1273 | running -- Running the program | |
1274 | stack -- Examining the stack | |
1275 | data -- Examining data | |
1276 | breakpoints -- Making program stop at certain points | |
1277 | files -- Specifying and examining files | |
1278 | status -- Status inquiries | |
1279 | support -- Support facilities | |
1280 | user-defined -- User-defined commands | |
1281 | aliases -- Aliases of other commands | |
1282 | obscure -- Obscure features | |
1283 | ||
203eea5d RP |
1284 | Type "help" followed by a class name for a list of |
1285 | commands in that class. | |
1286 | Type "help" followed by command name for full | |
1287 | documentation. | |
70b88761 | 1288 | Command name abbreviations are allowed if unambiguous. |
18fae2a8 | 1289 | (@value{GDBP}) |
70b88761 RP |
1290 | @end smallexample |
1291 | ||
1292 | @item help @var{class} | |
1293 | Using one of the general help classes as an argument, you can get a | |
1294 | list of the individual commands in that class. For example, here is the | |
1295 | help display for the class @code{status}: | |
1041a570 | 1296 | |
70b88761 | 1297 | @smallexample |
18fae2a8 | 1298 | (@value{GDBP}) help status |
70b88761 RP |
1299 | Status inquiries. |
1300 | ||
1301 | List of commands: | |
1302 | ||
8c69096b RP |
1303 | @c Line break in "show" line falsifies real output, but needed |
1304 | @c to fit in smallbook page size. | |
1305 | show -- Generic command for showing things set | |
1306 | with "set" | |
70b88761 RP |
1307 | info -- Generic command for printing status |
1308 | ||
203eea5d RP |
1309 | Type "help" followed by command name for full |
1310 | documentation. | |
70b88761 | 1311 | Command name abbreviations are allowed if unambiguous. |
18fae2a8 | 1312 | (@value{GDBP}) |
70b88761 RP |
1313 | @end smallexample |
1314 | ||
1315 | @item help @var{command} | |
9a27b06e | 1316 | With a command name as @code{help} argument, @value{GDBN} displays a |
e251e767 | 1317 | short paragraph on how to use that command. |
70b88761 RP |
1318 | @end table |
1319 | ||
18fae2a8 | 1320 | In addition to @code{help}, you can use the @value{GDBN} commands @code{info} |
70b88761 | 1321 | and @code{show} to inquire about the state of your program, or the state |
18fae2a8 | 1322 | of @value{GDBN} itself. Each command supports many topics of inquiry; this |
70b88761 RP |
1323 | manual introduces each of them in the appropriate context. The listings |
1324 | under @code{info} and under @code{show} in the Index point to | |
29a2b744 | 1325 | all the sub-commands. @xref{Index}. |
70b88761 RP |
1326 | |
1327 | @c @group | |
1328 | @table @code | |
1329 | @item info | |
1330 | @kindex info | |
1331 | @kindex i | |
1332 | This command (abbreviated @code{i}) is for describing the state of your | |
ed447b95 RP |
1333 | program. For example, you can list the arguments given to your program |
1334 | with @code{info args}, list the registers currently in use with @code{info | |
1335 | registers}, or list the breakpoints you have set with @code{info breakpoints}. | |
70b88761 RP |
1336 | You can get a complete list of the @code{info} sub-commands with |
1337 | @w{@code{help info}}. | |
1338 | ||
1339 | @kindex show | |
1340 | @item show | |
18fae2a8 | 1341 | In contrast, @code{show} is for describing the state of @value{GDBN} itself. |
70b88761 RP |
1342 | You can change most of the things you can @code{show}, by using the |
1343 | related command @code{set}; for example, you can control what number | |
1344 | system is used for displays with @code{set radix}, or simply inquire | |
e251e767 | 1345 | which is currently in use with @code{show radix}. |
70b88761 RP |
1346 | |
1347 | @kindex info set | |
1348 | To display all the settable parameters and their current | |
1349 | values, you can use @code{show} with no arguments; you may also use | |
1350 | @code{info set}. Both commands produce the same display. | |
1351 | @c FIXME: "info set" violates the rule that "info" is for state of | |
1352 | @c FIXME...program. Ck w/ GNU: "info set" to be called something else, | |
1353 | @c FIXME...or change desc of rule---eg "state of prog and debugging session"? | |
1354 | @end table | |
1355 | @c @end group | |
1356 | ||
1357 | Here are three miscellaneous @code{show} subcommands, all of which are | |
1358 | exceptional in lacking corresponding @code{set} commands: | |
1359 | ||
1360 | @table @code | |
1361 | @kindex show version | |
3d3ab540 | 1362 | @cindex version number |
70b88761 | 1363 | @item show version |
18fae2a8 RP |
1364 | Show what version of @value{GDBN} is running. You should include this |
1365 | information in @value{GDBN} bug-reports. If multiple versions of @value{GDBN} are in | |
ed447b95 | 1366 | use at your site, you may occasionally want to determine which version |
18fae2a8 | 1367 | of @value{GDBN} you are running; as @value{GDBN} evolves, new commands are introduced, |
1041a570 | 1368 | and old ones may wither away. The version number is also announced |
d55320a0 | 1369 | when you start @value{GDBN}. |
70b88761 RP |
1370 | |
1371 | @kindex show copying | |
1372 | @item show copying | |
18fae2a8 | 1373 | Display information about permission for copying @value{GDBN}. |
70b88761 RP |
1374 | |
1375 | @kindex show warranty | |
1376 | @item show warranty | |
1377 | Display the GNU ``NO WARRANTY'' statement. | |
1378 | @end table | |
1379 | ||
4eb4cf57 | 1380 | @node Running |
18fae2a8 | 1381 | @chapter Running Programs Under @value{GDBN} |
70b88761 | 1382 | |
ed447b95 | 1383 | When you run a program under @value{GDBN}, you must first generate |
1d7c3357 | 1384 | debugging information when you compile it. |
18fae2a8 | 1385 | @ifclear BARETARGET |
1d7c3357 RP |
1386 | You may start it with its arguments, if any, in an environment of your |
1387 | choice. You may redirect your program's input and output, debug an | |
1388 | already running process, or kill a child process. | |
18fae2a8 | 1389 | @end ifclear |
18fae2a8 | 1390 | |
18fae2a8 | 1391 | @menu |
ed447b95 RP |
1392 | * Compilation:: Compiling for debugging |
1393 | * Starting:: Starting your program | |
1d7c3357 | 1394 | @ifclear BARETARGET |
ed447b95 RP |
1395 | * Arguments:: Your program's arguments |
1396 | * Environment:: Your program's environment | |
1397 | * Working Directory:: Your program's working directory | |
1398 | * Input/Output:: Your program's input and output | |
1399 | * Attach:: Debugging an already-running process | |
1400 | * Kill Process:: Killing the child process | |
1401 | * Process Information:: Additional process information | |
0cb95a9c | 1402 | * Threads:: Debugging programs with multiple threads |
18fae2a8 | 1403 | @end ifclear |
18fae2a8 | 1404 | @end menu |
70b88761 | 1405 | |
4eb4cf57 | 1406 | @node Compilation |
93928b60 | 1407 | @section Compiling for debugging |
70b88761 RP |
1408 | |
1409 | In order to debug a program effectively, you need to generate | |
1410 | debugging information when you compile it. This debugging information | |
1411 | is stored in the object file; it describes the data type of each | |
1412 | variable or function and the correspondence between source line numbers | |
1413 | and addresses in the executable code. | |
1414 | ||
1415 | To request debugging information, specify the @samp{-g} option when you run | |
1416 | the compiler. | |
1417 | ||
1418 | Many C compilers are unable to handle the @samp{-g} and @samp{-O} | |
1419 | options together. Using those compilers, you cannot generate optimized | |
1420 | executables containing debugging information. | |
1421 | ||
18fae2a8 | 1422 | @value{NGCC}, the GNU C compiler, supports @samp{-g} with or without |
c7cb8acb RP |
1423 | @samp{-O}, making it possible to debug optimized code. We recommend |
1424 | that you @emph{always} use @samp{-g} whenever you compile a program. | |
1425 | You may think your program is correct, but there is no sense in pushing | |
1426 | your luck. | |
70b88761 | 1427 | |
6ca72cc6 RP |
1428 | @cindex optimized code, debugging |
1429 | @cindex debugging optimized code | |
1430 | When you debug a program compiled with @samp{-g -O}, remember that the | |
9a27b06e | 1431 | optimizer is rearranging your code; the debugger shows you what is |
93918348 | 1432 | really there. Do not be too surprised when the execution path does not |
6ca72cc6 | 1433 | exactly match your source file! An extreme example: if you define a |
9a27b06e | 1434 | variable, but never use it, @value{GDBN} never sees that |
6ca72cc6 RP |
1435 | variable---because the compiler optimizes it out of existence. |
1436 | ||
70b88761 RP |
1437 | Some things do not work as well with @samp{-g -O} as with just |
1438 | @samp{-g}, particularly on machines with instruction scheduling. If in | |
1439 | doubt, recompile with @samp{-g} alone, and if this fixes the problem, | |
1440 | please report it as a bug (including a test case!). | |
1441 | ||
1442 | Older versions of the GNU C compiler permitted a variant option | |
18fae2a8 | 1443 | @w{@samp{-gg}} for debugging information. @value{GDBN} no longer supports this |
70b88761 RP |
1444 | format; if your GNU C compiler has this option, do not use it. |
1445 | ||
d55320a0 | 1446 | @need 2000 |
4eb4cf57 | 1447 | @node Starting |
93928b60 | 1448 | @section Starting your program |
70b88761 RP |
1449 | @cindex starting |
1450 | @cindex running | |
1041a570 | 1451 | |
70b88761 RP |
1452 | @table @code |
1453 | @item run | |
1454 | @itemx r | |
1455 | @kindex run | |
18fae2a8 | 1456 | Use the @code{run} command to start your program under @value{GDBN}. You must |
1041a570 | 1457 | first specify the program name |
18fae2a8 | 1458 | @ifset VXWORKS |
7463aadd | 1459 | (except on VxWorks) |
18fae2a8 | 1460 | @end ifset |
ed447b95 RP |
1461 | with an argument to @value{GDBN} (@pxref{Invocation, ,Getting In and |
1462 | Out of @value{GDBN}}), or by using the @code{file} or @code{exec-file} | |
93928b60 | 1463 | command (@pxref{Files, ,Commands to specify files}). |
1041a570 | 1464 | |
70b88761 RP |
1465 | @end table |
1466 | ||
18fae2a8 | 1467 | @ifclear BARETARGET |
29a2b744 RP |
1468 | If you are running your program in an execution environment that |
1469 | supports processes, @code{run} creates an inferior process and makes | |
1470 | that process run your program. (In environments without processes, | |
1471 | @code{run} jumps to the start of your program.) | |
70b88761 RP |
1472 | |
1473 | The execution of a program is affected by certain information it | |
18fae2a8 | 1474 | receives from its superior. @value{GDBN} provides ways to specify this |
6ca72cc6 | 1475 | information, which you must do @emph{before} starting your program. (You |
9a27b06e | 1476 | can change it after starting your program, but such changes only affect |
29a2b744 | 1477 | your program the next time you start it.) This information may be |
70b88761 RP |
1478 | divided into four categories: |
1479 | ||
1480 | @table @asis | |
6ca72cc6 | 1481 | @item The @emph{arguments.} |
29a2b744 | 1482 | Specify the arguments to give your program as the arguments of the |
1041a570 RP |
1483 | @code{run} command. If a shell is available on your target, the shell |
1484 | is used to pass the arguments, so that you may use normal conventions | |
1485 | (such as wildcard expansion or variable substitution) in describing | |
1486 | the arguments. In Unix systems, you can control which shell is used | |
1487 | with the @code{SHELL} environment variable. @xref{Arguments, ,Your | |
93928b60 | 1488 | program's arguments}. |
70b88761 | 1489 | |
6ca72cc6 | 1490 | @item The @emph{environment.} |
18fae2a8 RP |
1491 | Your program normally inherits its environment from @value{GDBN}, but you can |
1492 | use the @value{GDBN} commands @code{set environment} and @code{unset | |
9a27b06e | 1493 | environment} to change parts of the environment that affect |
93928b60 | 1494 | your program. @xref{Environment, ,Your program's environment}. |
70b88761 | 1495 | |
6ca72cc6 | 1496 | @item The @emph{working directory.} |
18fae2a8 | 1497 | Your program inherits its working directory from @value{GDBN}. You can set |
93918348 | 1498 | the @value{GDBN} working directory with the @code{cd} command in @value{GDBN}. |
93928b60 | 1499 | @xref{Working Directory, ,Your program's working directory}. |
70b88761 | 1500 | |
6ca72cc6 | 1501 | @item The @emph{standard input and output.} |
70b88761 | 1502 | Your program normally uses the same device for standard input and |
18fae2a8 | 1503 | standard output as @value{GDBN} is using. You can redirect input and output |
70b88761 RP |
1504 | in the @code{run} command line, or you can use the @code{tty} command to |
1505 | set a different device for your program. | |
93928b60 | 1506 | @xref{Input/Output, ,Your program's input and output}. |
3d3ab540 RP |
1507 | |
1508 | @cindex pipes | |
29a2b744 RP |
1509 | @emph{Warning:} While input and output redirection work, you cannot use |
1510 | pipes to pass the output of the program you are debugging to another | |
18fae2a8 | 1511 | program; if you attempt this, @value{GDBN} is likely to wind up debugging the |
3d3ab540 | 1512 | wrong program. |
70b88761 | 1513 | @end table |
18fae2a8 | 1514 | @end ifclear |
70b88761 | 1515 | |
1041a570 | 1516 | When you issue the @code{run} command, your program begins to execute |
93928b60 | 1517 | immediately. @xref{Stopping, ,Stopping and continuing}, for discussion |
4eb4cf57 | 1518 | of how to arrange for your program to stop. Once your program has |
6b51acad | 1519 | stopped, you may call functions in your program, using the @code{print} |
4eb4cf57 | 1520 | or @code{call} commands. @xref{Data, ,Examining Data}. |
70b88761 | 1521 | |
9a27b06e RP |
1522 | If the modification time of your symbol file has changed since the last |
1523 | time @value{GDBN} read its symbols, @value{GDBN} discards its symbol | |
1524 | table, and reads it again. When it does this, @value{GDBN} tries to retain | |
1525 | your current breakpoints. | |
70b88761 | 1526 | |
18fae2a8 | 1527 | @ifclear BARETARGET |
4eb4cf57 | 1528 | @node Arguments |
93928b60 | 1529 | @section Your program's arguments |
70b88761 RP |
1530 | |
1531 | @cindex arguments (to your program) | |
1532 | The arguments to your program can be specified by the arguments of the | |
1533 | @code{run} command. They are passed to a shell, which expands wildcard | |
29a2b744 | 1534 | characters and performs redirection of I/O, and thence to your program. |
34ae25cd | 1535 | Your @code{SHELL} environment variable (if it exists) specifies what |
ac74588e JK |
1536 | shell @value{GDBN} uses. If you do not define @code{SHELL}, |
1537 | @value{GDBN} uses @code{/bin/sh}. | |
70b88761 RP |
1538 | |
1539 | @code{run} with no arguments uses the same arguments used by the previous | |
1540 | @code{run}, or those set by the @code{set args} command. | |
1541 | ||
1542 | @kindex set args | |
1543 | @table @code | |
1544 | @item set args | |
1545 | Specify the arguments to be used the next time your program is run. If | |
9a27b06e | 1546 | @code{set args} has no arguments, @code{run} executes your program |
e251e767 | 1547 | with no arguments. Once you have run your program with arguments, |
70b88761 RP |
1548 | using @code{set args} before the next @code{run} is the only way to run |
1549 | it again without arguments. | |
1550 | ||
1551 | @item show args | |
1552 | @kindex show args | |
1553 | Show the arguments to give your program when it is started. | |
1554 | @end table | |
1555 | ||
4eb4cf57 | 1556 | @node Environment |
93928b60 | 1557 | @section Your program's environment |
70b88761 RP |
1558 | |
1559 | @cindex environment (of your program) | |
1560 | The @dfn{environment} consists of a set of environment variables and | |
1561 | their values. Environment variables conventionally record such things as | |
1562 | your user name, your home directory, your terminal type, and your search | |
1563 | path for programs to run. Usually you set up environment variables with | |
1564 | the shell and they are inherited by all the other programs you run. When | |
29a2b744 | 1565 | debugging, it can be useful to try running your program with a modified |
18fae2a8 | 1566 | environment without having to start @value{GDBN} over again. |
70b88761 RP |
1567 | |
1568 | @table @code | |
1569 | @item path @var{directory} | |
1570 | @kindex path | |
1571 | Add @var{directory} to the front of the @code{PATH} environment variable | |
18fae2a8 | 1572 | (the search path for executables), for both @value{GDBN} and your program. |
70b88761 RP |
1573 | You may specify several directory names, separated by @samp{:} or |
1574 | whitespace. If @var{directory} is already in the path, it is moved to | |
9a27b06e | 1575 | the front, so it is searched sooner. |
7463aadd RP |
1576 | |
1577 | You can use the string @samp{$cwd} to refer to whatever is the current | |
d55320a0 RP |
1578 | working directory at the time @value{GDBN} searches the path. If you |
1579 | use @samp{.} instead, it refers to the directory where you executed the | |
1580 | @code{path} command. @value{GDBN} replaces @samp{.} in the | |
1581 | @var{directory} argument (with the current path) before adding | |
1582 | @var{directory} to the search path. | |
29a2b744 | 1583 | @c 'path' is explicitly nonrepeatable, but RMS points out it is silly to |
70b88761 RP |
1584 | @c document that, since repeating it would be a no-op. |
1585 | ||
1586 | @item show paths | |
1587 | @kindex show paths | |
1588 | Display the list of search paths for executables (the @code{PATH} | |
1589 | environment variable). | |
1590 | ||
1591 | @item show environment @r{[}@var{varname}@r{]} | |
1592 | @kindex show environment | |
1593 | Print the value of environment variable @var{varname} to be given to | |
29a2b744 | 1594 | your program when it starts. If you do not supply @var{varname}, |
70b88761 RP |
1595 | print the names and values of all environment variables to be given to |
1596 | your program. You can abbreviate @code{environment} as @code{env}. | |
1597 | ||
7463aadd | 1598 | @item set environment @var{varname} @r{[}=@r{]} @var{value} |
70b88761 | 1599 | @kindex set environment |
ed447b95 | 1600 | Set environment variable @var{varname} to @var{value}. The value |
18fae2a8 | 1601 | changes for your program only, not for @value{GDBN} itself. @var{value} may |
70b88761 RP |
1602 | be any string; the values of environment variables are just strings, and |
1603 | any interpretation is supplied by your program itself. The @var{value} | |
1604 | parameter is optional; if it is eliminated, the variable is set to a | |
1605 | null value. | |
29a2b744 | 1606 | @c "any string" here does not include leading, trailing |
70b88761 RP |
1607 | @c blanks. Gnu asks: does anyone care? |
1608 | ||
1609 | For example, this command: | |
1610 | ||
1611 | @example | |
1612 | set env USER = foo | |
1613 | @end example | |
1614 | ||
1615 | @noindent | |
1616 | tells a Unix program, when subsequently run, that its user is named | |
1617 | @samp{foo}. (The spaces around @samp{=} are used for clarity here; they | |
1618 | are not actually required.) | |
1619 | ||
1620 | @item unset environment @var{varname} | |
1621 | @kindex unset environment | |
1622 | Remove variable @var{varname} from the environment to be passed to your | |
1623 | program. This is different from @samp{set env @var{varname} =}; | |
1624 | @code{unset environment} removes the variable from the environment, | |
e251e767 | 1625 | rather than assigning it an empty value. |
70b88761 RP |
1626 | @end table |
1627 | ||
34ae25cd RP |
1628 | @emph{Warning:} @value{GDBN} runs your program using the shell indicated |
1629 | by your @code{SHELL} environment variable if it exists (or | |
1630 | @code{/bin/sh} if not). If your @code{SHELL} variable names a shell | |
1631 | that runs an initialization file---such as @file{.cshrc} for C-shell, or | |
9a27b06e | 1632 | @file{.bashrc} for BASH---any variables you set in that file affect |
34ae25cd RP |
1633 | your program. You may wish to move setting of environment variables to |
1634 | files that are only run when you sign on, such as @file{.login} or | |
1635 | @file{.profile}. | |
562a18b2 | 1636 | |
4eb4cf57 | 1637 | @node Working Directory |
93928b60 | 1638 | @section Your program's working directory |
70b88761 RP |
1639 | |
1640 | @cindex working directory (of your program) | |
1641 | Each time you start your program with @code{run}, it inherits its | |
93918348 RP |
1642 | working directory from the current working directory of @value{GDBN}. |
1643 | The @value{GDBN} working directory is initially whatever it inherited | |
1644 | from its parent process (typically the shell), but you can specify a new | |
1645 | working directory in @value{GDBN} with the @code{cd} command. | |
70b88761 | 1646 | |
18fae2a8 RP |
1647 | The @value{GDBN} working directory also serves as a default for the commands |
1648 | that specify files for @value{GDBN} to operate on. @xref{Files, ,Commands to | |
93928b60 | 1649 | specify files}. |
70b88761 RP |
1650 | |
1651 | @table @code | |
1652 | @item cd @var{directory} | |
1653 | @kindex cd | |
93918348 | 1654 | Set the @value{GDBN} working directory to @var{directory}. |
70b88761 RP |
1655 | |
1656 | @item pwd | |
1657 | @kindex pwd | |
93918348 | 1658 | Print the @value{GDBN} working directory. |
70b88761 RP |
1659 | @end table |
1660 | ||
4eb4cf57 | 1661 | @node Input/Output |
93928b60 | 1662 | @section Your program's input and output |
70b88761 RP |
1663 | |
1664 | @cindex redirection | |
1665 | @cindex i/o | |
1666 | @cindex terminal | |
18fae2a8 RP |
1667 | By default, the program you run under @value{GDBN} does input and output to |
1668 | the same terminal that @value{GDBN} uses. @value{GDBN} switches the terminal to | |
70b88761 RP |
1669 | its own terminal modes to interact with you, but it records the terminal |
1670 | modes your program was using and switches back to them when you continue | |
1671 | running your program. | |
1672 | ||
1673 | @table @code | |
1674 | @item info terminal | |
1675 | @kindex info terminal | |
93918348 | 1676 | Displays information recorded by @value{GDBN} about the terminal modes your |
70b88761 RP |
1677 | program is using. |
1678 | @end table | |
1679 | ||
29a2b744 | 1680 | You can redirect your program's input and/or output using shell |
70b88761 RP |
1681 | redirection with the @code{run} command. For example, |
1682 | ||
18fae2a8 | 1683 | @example |
70b88761 | 1684 | run > outfile |
18fae2a8 | 1685 | @end example |
70b88761 RP |
1686 | |
1687 | @noindent | |
29a2b744 | 1688 | starts your program, diverting its output to the file @file{outfile}. |
70b88761 RP |
1689 | |
1690 | @kindex tty | |
1691 | @cindex controlling terminal | |
29a2b744 | 1692 | Another way to specify where your program should do input and output is |
70b88761 RP |
1693 | with the @code{tty} command. This command accepts a file name as |
1694 | argument, and causes this file to be the default for future @code{run} | |
1695 | commands. It also resets the controlling terminal for the child | |
1696 | process, for future @code{run} commands. For example, | |
1697 | ||
1698 | @example | |
1699 | tty /dev/ttyb | |
1700 | @end example | |
1701 | ||
1702 | @noindent | |
1703 | directs that processes started with subsequent @code{run} commands | |
1704 | default to do input and output on the terminal @file{/dev/ttyb} and have | |
1705 | that as their controlling terminal. | |
1706 | ||
1707 | An explicit redirection in @code{run} overrides the @code{tty} command's | |
1708 | effect on the input/output device, but not its effect on the controlling | |
1709 | terminal. | |
1710 | ||
1711 | When you use the @code{tty} command or redirect input in the @code{run} | |
1712 | command, only the input @emph{for your program} is affected. The input | |
18fae2a8 | 1713 | for @value{GDBN} still comes from your terminal. |
70b88761 | 1714 | |
4eb4cf57 | 1715 | @node Attach |
93928b60 | 1716 | @section Debugging an already-running process |
70b88761 RP |
1717 | @kindex attach |
1718 | @cindex attach | |
1719 | ||
1720 | @table @code | |
1721 | @item attach @var{process-id} | |
1d7c3357 | 1722 | This command attaches to a running process---one that was started |
9a27b06e | 1723 | outside @value{GDBN}. (@code{info files} shows your active |
1d7c3357 RP |
1724 | targets.) The command takes as argument a process ID. The usual way to |
1725 | find out the process-id of a Unix process is with the @code{ps} utility, | |
1726 | or with the @samp{jobs -l} shell command. | |
70b88761 | 1727 | |
9a27b06e | 1728 | @code{attach} does not repeat if you press @key{RET} a second time after |
70b88761 RP |
1729 | executing the command. |
1730 | @end table | |
1731 | ||
d55320a0 RP |
1732 | To use @code{attach}, your program must be running in an environment |
1733 | which supports processes; for example, @code{attach} does not work for | |
1734 | programs on bare-board targets that lack an operating system. You must | |
1735 | also have permission to send the process a signal. | |
70b88761 RP |
1736 | |
1737 | When using @code{attach}, you should first use the @code{file} command | |
1738 | to specify the program running in the process and load its symbol table. | |
29a2b744 | 1739 | @xref{Files, ,Commands to Specify Files}. |
70b88761 | 1740 | |
18fae2a8 | 1741 | The first thing @value{GDBN} does after arranging to debug the specified |
70b88761 | 1742 | process is to stop it. You can examine and modify an attached process |
18fae2a8 | 1743 | with all the @value{GDBN} commands that are ordinarily available when you start |
70b88761 RP |
1744 | processes with @code{run}. You can insert breakpoints; you can step and |
1745 | continue; you can modify storage. If you would rather the process | |
1746 | continue running, you may use the @code{continue} command after | |
18fae2a8 | 1747 | attaching @value{GDBN} to the process. |
70b88761 RP |
1748 | |
1749 | @table @code | |
1750 | @item detach | |
1751 | @kindex detach | |
1752 | When you have finished debugging the attached process, you can use the | |
93918348 | 1753 | @code{detach} command to release it from @value{GDBN} control. Detaching |
70b88761 | 1754 | the process continues its execution. After the @code{detach} command, |
18fae2a8 | 1755 | that process and @value{GDBN} become completely independent once more, and you |
70b88761 | 1756 | are ready to @code{attach} another process or start one with @code{run}. |
9a27b06e | 1757 | @code{detach} does not repeat if you press @key{RET} again after |
70b88761 RP |
1758 | executing the command. |
1759 | @end table | |
1760 | ||
9a27b06e RP |
1761 | If you exit @value{GDBN} or use the @code{run} command while you have an |
1762 | attached process, you kill that process. By default, @value{GDBN} asks | |
1763 | for confirmation if you try to do either of these things; you can | |
1764 | control whether or not you need to confirm by using the @code{set | |
1765 | confirm} command (@pxref{Messages/Warnings, ,Optional warnings and | |
1766 | messages}). | |
70b88761 | 1767 | |
4eb4cf57 | 1768 | @node Kill Process |
70b88761 | 1769 | @c @group |
93928b60 | 1770 | @section Killing the child process |
70b88761 RP |
1771 | |
1772 | @table @code | |
1773 | @item kill | |
1774 | @kindex kill | |
18fae2a8 | 1775 | Kill the child process in which your program is running under @value{GDBN}. |
70b88761 RP |
1776 | @end table |
1777 | ||
1778 | This command is useful if you wish to debug a core dump instead of a | |
18fae2a8 | 1779 | running process. @value{GDBN} ignores any core dump file while your program |
70b88761 RP |
1780 | is running. |
1781 | @c @end group | |
1782 | ||
18fae2a8 RP |
1783 | On some operating systems, a program cannot be executed outside @value{GDBN} |
1784 | while you have breakpoints set on it inside @value{GDBN}. You can use the | |
29a2b744 | 1785 | @code{kill} command in this situation to permit running your program |
70b88761 RP |
1786 | outside the debugger. |
1787 | ||
1788 | The @code{kill} command is also useful if you wish to recompile and | |
29a2b744 | 1789 | relink your program, since on many systems it is impossible to modify an |
70b88761 | 1790 | executable file while it is running in a process. In this case, when you |
9a27b06e RP |
1791 | next type @code{run}, @value{GDBN} notices that the file has changed, and |
1792 | reads the symbol table again (while trying to preserve your current | |
70b88761 RP |
1793 | breakpoint settings). |
1794 | ||
4eb4cf57 | 1795 | @node Process Information |
93928b60 | 1796 | @section Additional process information |
d24e0922 RP |
1797 | |
1798 | @kindex /proc | |
1799 | @cindex process image | |
1800 | Some operating systems provide a facility called @samp{/proc} that can | |
cc9bc574 | 1801 | be used to examine the image of a running process using file-system |
18fae2a8 | 1802 | subroutines. If @value{GDBN} is configured for an operating system with this |
cc9bc574 RP |
1803 | facility, the command @code{info proc} is available to report on several |
1804 | kinds of information about the process running your program. | |
d24e0922 RP |
1805 | |
1806 | @table @code | |
1807 | @item info proc | |
1808 | @kindex info proc | |
1809 | Summarize available information about the process. | |
1810 | ||
1811 | @item info proc mappings | |
1812 | @kindex info proc mappings | |
1813 | Report on the address ranges accessible in the program, with information | |
1814 | on whether your program may read, write, or execute each range. | |
1815 | ||
1816 | @item info proc times | |
1817 | @kindex info proc times | |
1818 | Starting time, user CPU time, and system CPU time for your program and | |
1819 | its children. | |
1820 | ||
1821 | @item info proc id | |
1822 | @kindex info proc id | |
93918348 RP |
1823 | Report on the process IDs related to your program: its own process ID, |
1824 | the ID of its parent, the process group ID, and the session ID. | |
d24e0922 RP |
1825 | |
1826 | @item info proc status | |
1827 | @kindex info proc status | |
1828 | General information on the state of the process. If the process is | |
1829 | stopped, this report includes the reason for stopping, and any signal | |
1830 | received. | |
cc9bc574 RP |
1831 | |
1832 | @item info proc all | |
1833 | Show all the above information about the process. | |
d24e0922 | 1834 | @end table |
0cb95a9c RP |
1835 | |
1836 | @node Threads | |
1837 | @section Debugging programs with multiple threads | |
1838 | ||
1839 | @cindex threads of execution | |
1840 | @cindex multiple threads | |
1841 | @cindex switching threads | |
1842 | In some operating systems, a single program may have more than one | |
1843 | @dfn{thread} of execution. The precise semantics of threads differ from | |
1844 | one operating system to another, but in general the threads of a single | |
1845 | program are akin to multiple processes---except that they share one | |
1846 | address space (that is, they can all examine and modify the same | |
1847 | variables). On the other hand, each thread has its own registers and | |
1848 | execution stack, and perhaps private memory. | |
1849 | ||
22b5dba5 | 1850 | @value{GDBN} provides these facilities for debugging multi-thread |
0cb95a9c RP |
1851 | programs: |
1852 | ||
1853 | @itemize @bullet | |
1854 | @item automatic notification of new threads | |
1855 | @item @samp{thread @var{threadno}}, a command to switch among threads | |
1856 | @item @samp{info threads}, a command to inquire about existing threads | |
1857 | @item thread-specific breakpoints | |
1858 | @end itemize | |
1859 | ||
1860 | @quotation | |
1861 | @emph{Warning:} These facilities are not yet available on every | |
1862 | @value{GDBN} configuration where the operating system supports threads. | |
1863 | If your @value{GDBN} does not support threads, these commands have no | |
1864 | effect. For example, a system without thread support shows no output | |
1865 | from @samp{info threads}, and always rejects the @code{thread} command, | |
1866 | like this: | |
1867 | ||
1868 | @smallexample | |
1869 | (@value{GDBP}) info threads | |
1870 | (@value{GDBP}) thread 1 | |
1871 | Thread ID 1 not known. Use the "info threads" command to | |
1872 | see the IDs of currently known threads. | |
1873 | @end smallexample | |
1874 | @c FIXME to implementors: how hard would it be to say "sorry, this GDB | |
1875 | @c doesn't support threads"? | |
1876 | @end quotation | |
1877 | ||
1878 | @cindex focus of debugging | |
1879 | @cindex current thread | |
1880 | The @value{GDBN} thread debugging facility allows you to observe all | |
1881 | threads while your program runs---but whenever @value{GDBN} takes | |
1882 | control, one thread in particular is always the focus of debugging. | |
1883 | This thread is called the @dfn{current thread}. Debugging commands show | |
1884 | program information from the perspective of the current thread. | |
1885 | ||
1886 | @kindex New @var{systag} | |
1887 | @cindex thread identifier (system) | |
1888 | @c FIXME-implementors!! It would be more helpful if the [New...] message | |
1889 | @c included GDB's numeric thread handle, so you could just go to that | |
1890 | @c thread without first checking `info threads'. | |
1891 | Whenever @value{GDBN} detects a new thread in your program, it displays | |
22b5dba5 RP |
1892 | the target system's identification for the thread with a message in the |
1893 | form @samp{[New @var{systag}]}. @var{systag} is a thread identifier | |
1894 | whose form varies depending on the particular system. For example, on | |
1895 | LynxOS, you might see | |
0cb95a9c RP |
1896 | |
1897 | @example | |
1898 | [New process 35 thread 27] | |
1899 | @end example | |
1900 | ||
1901 | @noindent | |
1902 | when @value{GDBN} notices a new thread. In contrast, on an SGI system, | |
1903 | the @var{systag} is simply something like @samp{process 368}, with no | |
1904 | further qualifier. | |
1905 | ||
1906 | @c FIXME!! (1) Does the [New...] message appear even for the very first | |
1907 | @c thread of a program, or does it only appear for the | |
1908 | @c second---i.e., when it becomes obvious we have a multithread | |
1909 | @c program? | |
1910 | @c (2) *Is* there necessarily a first thread always? Or do some | |
1911 | @c multithread systems permit starting a program with multiple | |
1912 | @c threads ab initio? | |
1913 | ||
1914 | @cindex thread number | |
1915 | @cindex thread identifier (GDB) | |
1916 | For debugging purposes, @value{GDBN} associates its own thread | |
1917 | number---always a single integer---with each thread in your program. | |
1918 | ||
1919 | @table @code | |
1920 | @item info threads | |
1921 | @kindex info threads | |
1922 | Display a summary of all threads currently in your | |
1923 | program. @value{GDBN} displays for each thread (in this order): | |
1924 | ||
1925 | @enumerate | |
22b5dba5 | 1926 | @item the thread number assigned by @value{GDBN} |
0cb95a9c | 1927 | |
22b5dba5 | 1928 | @item the target system's thread identifier (@var{systag}) |
0cb95a9c RP |
1929 | |
1930 | @item the current stack frame summary for that thread | |
1931 | @end enumerate | |
1932 | ||
1933 | @noindent | |
1934 | An asterisk @samp{*} to the left of the @value{GDBN} thread number | |
1935 | indicates the current thread. | |
1936 | ||
1937 | For example, | |
1938 | @end table | |
1939 | @c end table here to get a little more width for example | |
1940 | ||
1941 | @smallexample | |
1942 | (@value{GDBP}) info threads | |
1943 | 3 process 35 thread 27 0x34e5 in sigpause () | |
1944 | 2 process 35 thread 23 0x34e5 in sigpause () | |
1945 | * 1 process 35 thread 13 main (argc=1, argv=0x7ffffff8) | |
1946 | at threadtest.c:68 | |
1947 | @end smallexample | |
1948 | ||
1949 | @table @code | |
1950 | @item thread @var{threadno} | |
22b5dba5 | 1951 | @kindex thread @var{threadno} |
0cb95a9c RP |
1952 | Make thread number @var{threadno} the current thread. The command |
1953 | argument @var{threadno} is the internal @value{GDBN} thread number, as | |
1954 | shown in the first field of the @samp{info threads} display. | |
1955 | @value{GDBN} responds by displaying the system identifier of the thread | |
1956 | you selected, and its current stack frame summary: | |
1957 | ||
1958 | @smallexample | |
1959 | @c FIXME!! This example made up; find a GDB w/threads and get real one | |
1960 | (@value{GDBP}) thread 2 | |
1961 | [Switching to process 35 thread 23] | |
1962 | 0x34e5 in sigpause () | |
1963 | @end smallexample | |
1964 | ||
1965 | @noindent | |
1966 | As with the @samp{[New @dots{}]} message, the form of the text after | |
1967 | @samp{Switching to} depends on your system's conventions for identifying | |
1968 | threads. | |
1969 | @end table | |
1970 | ||
1971 | @cindex automatic thread selection | |
1972 | @cindex switching threads automatically | |
1973 | @cindex threads, automatic switching | |
1974 | Whenever @value{GDBN} stops your program, due to a breakpoint or a | |
1975 | signal, it automatically selects the thread where that breakpoint or | |
1976 | signal happened. @value{GDBN} alerts you to the context switch with a | |
1977 | message of the form @samp{[Switching to @var{systag}]} to identify the | |
1978 | thread. | |
1979 | ||
1980 | @xref{Thread Stops,,Stopping and starting multi-thread programs}, for | |
1981 | more information about how @value{GDBN} behaves when you stop and start | |
1982 | programs with multiple threads. | |
22b5dba5 RP |
1983 | |
1984 | @xref{Set Watchpoints,,Setting watchpoints}, for information about | |
1985 | watchpoints in programs with multiple threads. | |
18fae2a8 | 1986 | @end ifclear |
d24e0922 | 1987 | |
4eb4cf57 | 1988 | @node Stopping |
70b88761 RP |
1989 | @chapter Stopping and Continuing |
1990 | ||
ed447b95 | 1991 | The principal purposes of using a debugger are so that you can stop your |
29a2b744 | 1992 | program before it terminates; or so that, if your program runs into |
70b88761 RP |
1993 | trouble, you can investigate and find out why. |
1994 | ||
18fae2a8 | 1995 | Inside @value{GDBN}, your program may stop for any of several reasons, such |
1d7c3357 RP |
1996 | as |
1997 | @ifclear BARETARGET | |
1998 | a signal, | |
1999 | @end ifclear | |
2000 | a breakpoint, or reaching a new line after a @value{GDBN} | |
70b88761 RP |
2001 | command such as @code{step}. You may then examine and change |
2002 | variables, set new breakpoints or remove old ones, and then continue | |
18fae2a8 | 2003 | execution. Usually, the messages shown by @value{GDBN} provide ample |
70b88761 RP |
2004 | explanation of the status of your program---but you can also explicitly |
2005 | request this information at any time. | |
2006 | ||
2007 | @table @code | |
2008 | @item info program | |
2009 | @kindex info program | |
2010 | Display information about the status of your program: whether it is | |
1d7c3357 RP |
2011 | running or not, |
2012 | @ifclear BARETARGET | |
2013 | what process it is, | |
2014 | @end ifclear | |
2015 | and why it stopped. | |
70b88761 RP |
2016 | @end table |
2017 | ||
18fae2a8 RP |
2018 | @menu |
2019 | @ifclear CONLY | |
ed447b95 | 2020 | * Breakpoints:: Breakpoints, watchpoints, and exceptions |
18fae2a8 RP |
2021 | @end ifclear |
2022 | @ifset CONLY | |
ed447b95 | 2023 | * Breakpoints:: Breakpoints and watchpoints |
18fae2a8 | 2024 | @end ifset |
1d7c3357 | 2025 | @c Remnant makeinfo bug requires blank line after *successful* end-if in menu: |
18fae2a8 | 2026 | |
ed447b95 | 2027 | * Continuing and Stepping:: Resuming execution |
18fae2a8 | 2028 | @ifset POSIX |
b80282d5 | 2029 | * Signals:: Signals |
18fae2a8 | 2030 | @end ifset |
0cb95a9c RP |
2031 | @ifclear BARETARGET |
2032 | * Thread Stops:: Stopping and starting multi-thread programs | |
2033 | @end ifclear | |
18fae2a8 | 2034 | @end menu |
70b88761 | 2035 | |
1d7c3357 | 2036 | @c makeinfo node-defaulting requires adjacency of @node and sectioning cmds |
18fae2a8 RP |
2037 | @c ...hence distribute @node Breakpoints over two possible @if expansions. |
2038 | @c | |
2039 | @ifclear CONLY | |
4eb4cf57 | 2040 | @node Breakpoints |
93928b60 | 2041 | @section Breakpoints, watchpoints, and exceptions |
18fae2a8 RP |
2042 | @end ifclear |
2043 | @ifset CONLY | |
2044 | @node Breakpoints | |
93928b60 | 2045 | @section Breakpoints and watchpoints |
18fae2a8 | 2046 | @end ifset |
70b88761 RP |
2047 | |
2048 | @cindex breakpoints | |
2049 | A @dfn{breakpoint} makes your program stop whenever a certain point in | |
9a27b06e RP |
2050 | the program is reached. For each breakpoint, you can add |
2051 | conditions to control in finer detail whether your program stops. | |
70b88761 | 2052 | You can set breakpoints with the @code{break} command and its variants |
93928b60 | 2053 | (@pxref{Set Breaks, ,Setting breakpoints}), to specify the place where |
29a2b744 | 2054 | your program should stop by line number, function name or exact address |
0f153e74 | 2055 | in the program. |
18fae2a8 | 2056 | @ifclear CONLY |
0f153e74 | 2057 | In languages with exception handling (such as GNU C++), you can also set |
0cb95a9c RP |
2058 | breakpoints where an exception is raised (@pxref{Exception Handling,, |
2059 | Breakpoints and exceptions}). | |
18fae2a8 | 2060 | @end ifclear |
70b88761 RP |
2061 | |
2062 | @cindex watchpoints | |
6ca72cc6 RP |
2063 | @cindex memory tracing |
2064 | @cindex breakpoint on memory address | |
2065 | @cindex breakpoint on variable modification | |
29a2b744 RP |
2066 | A @dfn{watchpoint} is a special breakpoint that stops your program |
2067 | when the value of an expression changes. You must use a different | |
2068 | command to set watchpoints (@pxref{Set Watchpoints, ,Setting | |
93928b60 | 2069 | watchpoints}), but aside from that, you can manage a watchpoint like |
29a2b744 | 2070 | any other breakpoint: you enable, disable, and delete both breakpoints |
1041a570 | 2071 | and watchpoints using the same commands. |
70b88761 | 2072 | |
fe715d06 | 2073 | You can arrange to have values from your program displayed automatically |
0cb95a9c RP |
2074 | whenever @value{GDBN} stops at a breakpoint. @xref{Auto Display,, |
2075 | Automatic display}. | |
fe715d06 | 2076 | |
6ca72cc6 RP |
2077 | @cindex breakpoint numbers |
2078 | @cindex numbers for breakpoints | |
18fae2a8 | 2079 | @value{GDBN} assigns a number to each breakpoint or watchpoint when you |
6ca72cc6 RP |
2080 | create it; these numbers are successive integers starting with one. In |
2081 | many of the commands for controlling various features of breakpoints you | |
2082 | use the breakpoint number to say which breakpoint you want to change. | |
2083 | Each breakpoint may be @dfn{enabled} or @dfn{disabled}; if disabled, it has | |
29a2b744 | 2084 | no effect on your program until you enable it again. |
70b88761 RP |
2085 | |
2086 | @menu | |
ed447b95 RP |
2087 | * Set Breaks:: Setting breakpoints |
2088 | * Set Watchpoints:: Setting watchpoints | |
1d7c3357 | 2089 | @ifclear CONLY |
ed447b95 | 2090 | * Exception Handling:: Breakpoints and exceptions |
1d7c3357 | 2091 | @end ifclear |
b0157555 | 2092 | |
ed447b95 RP |
2093 | * Delete Breaks:: Deleting breakpoints |
2094 | * Disabling:: Disabling breakpoints | |
2095 | * Conditions:: Break conditions | |
2096 | * Break Commands:: Breakpoint command lists | |
1d7c3357 | 2097 | @ifclear CONLY |
ed447b95 | 2098 | * Breakpoint Menus:: Breakpoint menus |
1d7c3357 RP |
2099 | @end ifclear |
2100 | @ifclear BARETARGET | |
ed447b95 | 2101 | * Error in Breakpoints:: ``Cannot insert breakpoints'' |
1d7c3357 | 2102 | @end ifclear |
70b88761 RP |
2103 | @end menu |
2104 | ||
4eb4cf57 | 2105 | @node Set Breaks |
93928b60 | 2106 | @subsection Setting breakpoints |
70b88761 | 2107 | |
4906534f RP |
2108 | @c FIXME LMB what does GDB do if no code on line of breakpt? |
2109 | @c consider in particular declaration with/without initialization. | |
2110 | @c | |
2111 | @c FIXME 2 is there stuff on this already? break at fun start, already init? | |
2112 | ||
70b88761 RP |
2113 | @kindex break |
2114 | @kindex b | |
6ca72cc6 RP |
2115 | @kindex $bpnum |
2116 | @cindex latest breakpoint | |
2117 | Breakpoints are set with the @code{break} command (abbreviated | |
2118 | @code{b}). The debugger convenience variable @samp{$bpnum} records the | |
2119 | number of the beakpoint you've set most recently; see @ref{Convenience | |
93928b60 | 2120 | Vars,, Convenience variables}, for a discussion of what you can do with |
6ca72cc6 | 2121 | convenience variables. |
70b88761 RP |
2122 | |
2123 | You have several ways to say where the breakpoint should go. | |
2124 | ||
2125 | @table @code | |
2126 | @item break @var{function} | |
0f153e74 | 2127 | Set a breakpoint at entry to function @var{function}. |
18fae2a8 | 2128 | @ifclear CONLY |
0f153e74 RP |
2129 | When using source languages that permit overloading of symbols, such as |
2130 | C++, @var{function} may refer to more than one possible place to break. | |
93928b60 | 2131 | @xref{Breakpoint Menus,,Breakpoint menus}, for a discussion of that situation. |
18fae2a8 | 2132 | @end ifclear |
70b88761 RP |
2133 | |
2134 | @item break +@var{offset} | |
2135 | @itemx break -@var{offset} | |
2136 | Set a breakpoint some number of lines forward or back from the position | |
2137 | at which execution stopped in the currently selected frame. | |
2138 | ||
2139 | @item break @var{linenum} | |
2140 | Set a breakpoint at line @var{linenum} in the current source file. | |
2141 | That file is the last file whose source text was printed. This | |
9a27b06e | 2142 | breakpoint stops your program just before it executes any of the |
70b88761 RP |
2143 | code on that line. |
2144 | ||
2145 | @item break @var{filename}:@var{linenum} | |
2146 | Set a breakpoint at line @var{linenum} in source file @var{filename}. | |
2147 | ||
2148 | @item break @var{filename}:@var{function} | |
2149 | Set a breakpoint at entry to function @var{function} found in file | |
2150 | @var{filename}. Specifying a file name as well as a function name is | |
2151 | superfluous except when multiple files contain similarly named | |
2152 | functions. | |
2153 | ||
2154 | @item break *@var{address} | |
2155 | Set a breakpoint at address @var{address}. You can use this to set | |
29a2b744 | 2156 | breakpoints in parts of your program which do not have debugging |
70b88761 RP |
2157 | information or source files. |
2158 | ||
2159 | @item break | |
29a2b744 RP |
2160 | When called without any arguments, @code{break} sets a breakpoint at |
2161 | the next instruction to be executed in the selected stack frame | |
2162 | (@pxref{Stack, ,Examining the Stack}). In any selected frame but the | |
9a27b06e | 2163 | innermost, this makes your program stop as soon as control |
29a2b744 RP |
2164 | returns to that frame. This is similar to the effect of a |
2165 | @code{finish} command in the frame inside the selected frame---except | |
2166 | that @code{finish} does not leave an active breakpoint. If you use | |
9a27b06e | 2167 | @code{break} without an argument in the innermost frame, @value{GDBN} stops |
1041a570 RP |
2168 | the next time it reaches the current location; this may be useful |
2169 | inside loops. | |
70b88761 | 2170 | |
18fae2a8 | 2171 | @value{GDBN} normally ignores breakpoints when it resumes execution, until at |
70b88761 RP |
2172 | least one instruction has been executed. If it did not do this, you |
2173 | would be unable to proceed past a breakpoint without first disabling the | |
2174 | breakpoint. This rule applies whether or not the breakpoint already | |
29a2b744 | 2175 | existed when your program stopped. |
70b88761 RP |
2176 | |
2177 | @item break @dots{} if @var{cond} | |
2178 | Set a breakpoint with condition @var{cond}; evaluate the expression | |
2179 | @var{cond} each time the breakpoint is reached, and stop only if the | |
3d3ab540 | 2180 | value is nonzero---that is, if @var{cond} evaluates as true. |
1041a570 RP |
2181 | @samp{@dots{}} stands for one of the possible arguments described |
2182 | above (or no argument) specifying where to break. @xref{Conditions, | |
93928b60 | 2183 | ,Break conditions}, for more information on breakpoint conditions. |
70b88761 RP |
2184 | |
2185 | @item tbreak @var{args} | |
2186 | @kindex tbreak | |
2187 | Set a breakpoint enabled only for one stop. @var{args} are the | |
2188 | same as for the @code{break} command, and the breakpoint is set in the same | |
cfcafcba | 2189 | way, but the breakpoint is automatically deleted after the first time your |
93928b60 | 2190 | program stops there. @xref{Disabling, ,Disabling breakpoints}. |
70b88761 RP |
2191 | |
2192 | @item rbreak @var{regex} | |
2193 | @kindex rbreak | |
2194 | @cindex regular expression | |
4906534f | 2195 | @c FIXME what kind of regexp? |
70b88761 | 2196 | Set breakpoints on all functions matching the regular expression |
b80282d5 | 2197 | @var{regex}. This command |
70b88761 | 2198 | sets an unconditional breakpoint on all matches, printing a list of all |
b1955f0b RP |
2199 | breakpoints it set. Once these breakpoints are set, they are treated |
2200 | just like the breakpoints set with the @code{break} command. You can | |
2201 | delete them, disable them, or make them conditional the same way as any | |
2202 | other breakpoint. | |
70b88761 | 2203 | |
18fae2a8 | 2204 | @ifclear CONLY |
b80282d5 RP |
2205 | When debugging C++ programs, @code{rbreak} is useful for setting |
2206 | breakpoints on overloaded functions that are not members of any special | |
2207 | classes. | |
18fae2a8 | 2208 | @end ifclear |
b80282d5 | 2209 | |
70b88761 | 2210 | @kindex info breakpoints |
c338a2fd | 2211 | @cindex @code{$_} and @code{info breakpoints} |
70b88761 | 2212 | @item info breakpoints @r{[}@var{n}@r{]} |
6ca72cc6 RP |
2213 | @itemx info break @r{[}@var{n}@r{]} |
2214 | @itemx info watchpoints @r{[}@var{n}@r{]} | |
2215 | Print a table of all breakpoints and watchpoints set and not | |
2216 | deleted, with the following columns for each breakpoint: | |
2217 | ||
2218 | @table @emph | |
2219 | @item Breakpoint Numbers | |
2220 | @item Type | |
2221 | Breakpoint or watchpoint. | |
2222 | @item Disposition | |
2223 | Whether the breakpoint is marked to be disabled or deleted when hit. | |
2224 | @item Enabled or Disabled | |
d24e0922 | 2225 | Enabled breakpoints are marked with @samp{y}. @samp{n} marks breakpoints |
6ca72cc6 RP |
2226 | that are not enabled. |
2227 | @item Address | |
2228 | Where the breakpoint is in your program, as a memory address | |
2229 | @item What | |
2230 | Where the breakpoint is in the source for your program, as a file and | |
2231 | line number. | |
2232 | @end table | |
2233 | ||
2234 | @noindent | |
d55320a0 RP |
2235 | If a breakpoint is conditional, @code{info break} shows the condition on |
2236 | the line following the affected breakpoint; breakpoint commands, if any, | |
2237 | are listed after that. | |
6ca72cc6 RP |
2238 | |
2239 | @noindent | |
2240 | @code{info break} with a breakpoint | |
29a2b744 RP |
2241 | number @var{n} as argument lists only that breakpoint. The |
2242 | convenience variable @code{$_} and the default examining-address for | |
2243 | the @code{x} command are set to the address of the last breakpoint | |
93928b60 | 2244 | listed (@pxref{Memory, ,Examining memory}). |
1041a570 | 2245 | @end table |
70b88761 | 2246 | |
18fae2a8 | 2247 | @value{GDBN} allows you to set any number of breakpoints at the same place in |
1041a570 RP |
2248 | your program. There is nothing silly or meaningless about this. When |
2249 | the breakpoints are conditional, this is even useful | |
93928b60 | 2250 | (@pxref{Conditions, ,Break conditions}). |
70b88761 | 2251 | |
6ca72cc6 | 2252 | @cindex negative breakpoint numbers |
18fae2a8 RP |
2253 | @cindex internal @value{GDBN} breakpoints |
2254 | @value{GDBN} itself sometimes sets breakpoints in your program for special | |
6ca72cc6 RP |
2255 | purposes, such as proper handling of @code{longjmp} (in C programs). |
2256 | These internal breakpoints are assigned negative numbers, starting with | |
5a2c1d85 | 2257 | @code{-1}; @samp{info breakpoints} does not display them. |
d48da190 | 2258 | |
18fae2a8 | 2259 | You can see these breakpoints with the @value{GDBN} maintenance command |
5a2c1d85 | 2260 | @samp{maint info breakpoints}. |
6ca72cc6 RP |
2261 | |
2262 | @table @code | |
d48da190 RP |
2263 | @kindex maint info breakpoints |
2264 | @item maint info breakpoints | |
6ca72cc6 | 2265 | Using the same format as @samp{info breakpoints}, display both the |
18fae2a8 | 2266 | breakpoints you've set explicitly, and those @value{GDBN} is using for |
6ca72cc6 RP |
2267 | internal purposes. Internal breakpoints are shown with negative |
2268 | breakpoint numbers. The type column identifies what kind of breakpoint | |
2269 | is shown: | |
2270 | ||
2271 | @table @code | |
2272 | @item breakpoint | |
2273 | Normal, explicitly set breakpoint. | |
2274 | ||
2275 | @item watchpoint | |
2276 | Normal, explicitly set watchpoint. | |
2277 | ||
2278 | @item longjmp | |
2279 | Internal breakpoint, used to handle correctly stepping through | |
2280 | @code{longjmp} calls. | |
2281 | ||
2282 | @item longjmp resume | |
2283 | Internal breakpoint at the target of a @code{longjmp}. | |
2284 | ||
2285 | @item until | |
18fae2a8 | 2286 | Temporary internal breakpoint used by the @value{GDBN} @code{until} command. |
6ca72cc6 RP |
2287 | |
2288 | @item finish | |
18fae2a8 | 2289 | Temporary internal breakpoint used by the @value{GDBN} @code{finish} command. |
6ca72cc6 RP |
2290 | @end table |
2291 | ||
2292 | @end table | |
2293 | ||
2294 | ||
4eb4cf57 | 2295 | @node Set Watchpoints |
93928b60 | 2296 | @subsection Setting watchpoints |
70b88761 | 2297 | @cindex setting watchpoints |
1041a570 | 2298 | |
70b88761 | 2299 | You can use a watchpoint to stop execution whenever the value of an |
e251e767 | 2300 | expression changes, without having to predict a particular place |
70b88761 RP |
2301 | where this may happen. |
2302 | ||
2303 | Watchpoints currently execute two orders of magnitude more slowly than | |
6b51acad | 2304 | other breakpoints, but this can be well worth it to catch errors where |
9a27b06e RP |
2305 | you have no clue what part of your program is the culprit. |
2306 | ||
2307 | @ignore | |
2308 | @c this "future releases" promise has been in too long, is getting | |
2309 | @c embarrassing. But... | |
2310 | @c FIXME: in future updates, check whether hardware watchpoints in on any | |
2311 | @c platforms yet. As of 26jan94, they're very close on HPPA running | |
2312 | @c Berkeley and on Irix 4. | |
2313 | Some processors provide special hardware to support watchpoint | |
2314 | evaluation; future releases of @value{GDBN} will use such hardware if it | |
2315 | is available. | |
2316 | @end ignore | |
70b88761 RP |
2317 | |
2318 | @table @code | |
e251e767 | 2319 | @kindex watch |
70b88761 RP |
2320 | @item watch @var{expr} |
2321 | Set a watchpoint for an expression. | |
2322 | ||
2323 | @kindex info watchpoints | |
2324 | @item info watchpoints | |
6ca72cc6 RP |
2325 | This command prints a list of watchpoints and breakpoints; it is the |
2326 | same as @code{info break}. | |
70b88761 RP |
2327 | @end table |
2328 | ||
0cb95a9c RP |
2329 | @ifclear BARETARGET |
2330 | @quotation | |
2331 | @cindex watchpoints and threads | |
2332 | @cindex threads and watchpoints | |
2333 | @emph{Warning:} in multi-thread programs, watchpoints have only limited | |
2334 | usefulness. With the current watchpoint implementation, @value{GDBN} | |
2335 | can only watch the value of an expression @emph{in a single thread}. If | |
2336 | you are confident that the expression can only change due to the current | |
9a27b06e RP |
2337 | thread's activity (and if you are also confident that no other thread |
2338 | can become current), then you can use watchpoints as usual. However, | |
0cb95a9c RP |
2339 | @value{GDBN} may not notice when a non-current thread's activity changes |
2340 | the expression. | |
2341 | @end quotation | |
2342 | @end ifclear | |
2343 | ||
1d7c3357 | 2344 | @ifclear CONLY |
4eb4cf57 | 2345 | @node Exception Handling |
93928b60 | 2346 | @subsection Breakpoints and exceptions |
70b88761 RP |
2347 | @cindex exception handlers |
2348 | ||
b80282d5 | 2349 | Some languages, such as GNU C++, implement exception handling. You can |
18fae2a8 | 2350 | use @value{GDBN} to examine what caused your program to raise an exception, |
29a2b744 | 2351 | and to list the exceptions your program is prepared to handle at a |
70b88761 RP |
2352 | given point in time. |
2353 | ||
2354 | @table @code | |
2355 | @item catch @var{exceptions} | |
2356 | @kindex catch | |
2357 | You can set breakpoints at active exception handlers by using the | |
2358 | @code{catch} command. @var{exceptions} is a list of names of exceptions | |
2359 | to catch. | |
2360 | @end table | |
2361 | ||
29a2b744 | 2362 | You can use @code{info catch} to list active exception handlers. |
93928b60 | 2363 | @xref{Frame Info, ,Information about a frame}. |
70b88761 | 2364 | |
9a27b06e | 2365 | There are currently some limitations to exception handling in @value{GDBN}: |
70b88761 RP |
2366 | |
2367 | @itemize @bullet | |
2368 | @item | |
18fae2a8 | 2369 | If you call a function interactively, @value{GDBN} normally returns |
70b88761 RP |
2370 | control to you when the function has finished executing. If the call |
2371 | raises an exception, however, the call may bypass the mechanism that | |
29a2b744 | 2372 | returns control to you and cause your program to simply continue |
18fae2a8 | 2373 | running until it hits a breakpoint, catches a signal that @value{GDBN} is |
70b88761 | 2374 | listening for, or exits. |
9a27b06e | 2375 | |
70b88761 RP |
2376 | @item |
2377 | You cannot raise an exception interactively. | |
9a27b06e | 2378 | |
70b88761 | 2379 | @item |
9a27b06e | 2380 | You cannot install an exception handler interactively. |
70b88761 RP |
2381 | @end itemize |
2382 | ||
2383 | @cindex raise exceptions | |
2384 | Sometimes @code{catch} is not the best way to debug exception handling: | |
29a2b744 | 2385 | if you need to know exactly where an exception is raised, it is better to |
70b88761 RP |
2386 | stop @emph{before} the exception handler is called, since that way you |
2387 | can see the stack before any unwinding takes place. If you set a | |
2388 | breakpoint in an exception handler instead, it may not be easy to find | |
2389 | out where the exception was raised. | |
2390 | ||
2391 | To stop just before an exception handler is called, you need some | |
b80282d5 | 2392 | knowledge of the implementation. In the case of GNU C++, exceptions are |
70b88761 RP |
2393 | raised by calling a library function named @code{__raise_exception} |
2394 | which has the following ANSI C interface: | |
2395 | ||
2396 | @example | |
b80282d5 | 2397 | /* @var{addr} is where the exception identifier is stored. |
70b88761 RP |
2398 | ID is the exception identifier. */ |
2399 | void __raise_exception (void **@var{addr}, void *@var{id}); | |
2400 | @end example | |
2401 | ||
2402 | @noindent | |
2403 | To make the debugger catch all exceptions before any stack | |
2404 | unwinding takes place, set a breakpoint on @code{__raise_exception} | |
93928b60 | 2405 | (@pxref{Breakpoints, ,Breakpoints; watchpoints; and exceptions}). |
70b88761 | 2406 | |
93928b60 | 2407 | With a conditional breakpoint (@pxref{Conditions, ,Break conditions}) |
29a2b744 RP |
2408 | that depends on the value of @var{id}, you can stop your program when |
2409 | a specific exception is raised. You can use multiple conditional | |
2410 | breakpoints to stop your program when any of a number of exceptions are | |
2411 | raised. | |
1d7c3357 | 2412 | @end ifclear |
70b88761 | 2413 | |
4eb4cf57 | 2414 | @node Delete Breaks |
93928b60 | 2415 | @subsection Deleting breakpoints |
70b88761 RP |
2416 | |
2417 | @cindex clearing breakpoints, watchpoints | |
2418 | @cindex deleting breakpoints, watchpoints | |
2419 | It is often necessary to eliminate a breakpoint or watchpoint once it | |
29a2b744 | 2420 | has done its job and you no longer want your program to stop there. This |
70b88761 RP |
2421 | is called @dfn{deleting} the breakpoint. A breakpoint that has been |
2422 | deleted no longer exists; it is forgotten. | |
2423 | ||
2424 | With the @code{clear} command you can delete breakpoints according to | |
29a2b744 | 2425 | where they are in your program. With the @code{delete} command you can |
70b88761 RP |
2426 | delete individual breakpoints or watchpoints by specifying their |
2427 | breakpoint numbers. | |
2428 | ||
18fae2a8 | 2429 | It is not necessary to delete a breakpoint to proceed past it. @value{GDBN} |
70b88761 RP |
2430 | automatically ignores breakpoints on the first instruction to be executed |
2431 | when you continue execution without changing the execution address. | |
2432 | ||
2433 | @table @code | |
2434 | @item clear | |
2435 | @kindex clear | |
2436 | Delete any breakpoints at the next instruction to be executed in the | |
93928b60 | 2437 | selected stack frame (@pxref{Selection, ,Selecting a frame}). When |
29a2b744 RP |
2438 | the innermost frame is selected, this is a good way to delete a |
2439 | breakpoint where your program just stopped. | |
70b88761 RP |
2440 | |
2441 | @item clear @var{function} | |
2442 | @itemx clear @var{filename}:@var{function} | |
2443 | Delete any breakpoints set at entry to the function @var{function}. | |
2444 | ||
2445 | @item clear @var{linenum} | |
2446 | @itemx clear @var{filename}:@var{linenum} | |
2447 | Delete any breakpoints set at or within the code of the specified line. | |
2448 | ||
2449 | @item delete @r{[}breakpoints@r{]} @r{[}@var{bnums}@dots{}@r{]} | |
2450 | @cindex delete breakpoints | |
2451 | @kindex delete | |
2452 | @kindex d | |
2453 | Delete the breakpoints or watchpoints of the numbers specified as | |
18fae2a8 | 2454 | arguments. If no argument is specified, delete all breakpoints (@value{GDBN} |
1041a570 | 2455 | asks confirmation, unless you have @code{set confirm off}). You |
70b88761 RP |
2456 | can abbreviate this command as @code{d}. |
2457 | @end table | |
2458 | ||
4eb4cf57 | 2459 | @node Disabling |
93928b60 | 2460 | @subsection Disabling breakpoints |
70b88761 RP |
2461 | |
2462 | @cindex disabled breakpoints | |
2463 | @cindex enabled breakpoints | |
2464 | Rather than deleting a breakpoint or watchpoint, you might prefer to | |
2465 | @dfn{disable} it. This makes the breakpoint inoperative as if it had | |
2466 | been deleted, but remembers the information on the breakpoint so that | |
2467 | you can @dfn{enable} it again later. | |
2468 | ||
2469 | You disable and enable breakpoints and watchpoints with the | |
2470 | @code{enable} and @code{disable} commands, optionally specifying one or | |
2471 | more breakpoint numbers as arguments. Use @code{info break} or | |
2472 | @code{info watch} to print a list of breakpoints or watchpoints if you | |
29a2b744 | 2473 | do not know which numbers to use. |
70b88761 RP |
2474 | |
2475 | A breakpoint or watchpoint can have any of four different states of | |
2476 | enablement: | |
2477 | ||
2478 | @itemize @bullet | |
2479 | @item | |
9a27b06e | 2480 | Enabled. The breakpoint stops your program. A breakpoint set |
70b88761 RP |
2481 | with the @code{break} command starts out in this state. |
2482 | @item | |
29a2b744 | 2483 | Disabled. The breakpoint has no effect on your program. |
70b88761 | 2484 | @item |
9a27b06e RP |
2485 | Enabled once. The breakpoint stops your program, but then becomes |
2486 | disabled. A breakpoint set with the @code{tbreak} command starts out in | |
2487 | this state. | |
70b88761 | 2488 | @item |
9a27b06e RP |
2489 | Enabled for deletion. The breakpoint stops your program, but |
2490 | immediately after it does so it is deleted permanently. | |
70b88761 RP |
2491 | @end itemize |
2492 | ||
2493 | You can use the following commands to enable or disable breakpoints and | |
2494 | watchpoints: | |
2495 | ||
2496 | @table @code | |
2497 | @item disable @r{[}breakpoints@r{]} @r{[}@var{bnums}@dots{}@r{]} | |
2498 | @kindex disable breakpoints | |
2499 | @kindex disable | |
2500 | @kindex dis | |
2501 | Disable the specified breakpoints---or all breakpoints, if none are | |
2502 | listed. A disabled breakpoint has no effect but is not forgotten. All | |
2503 | options such as ignore-counts, conditions and commands are remembered in | |
2504 | case the breakpoint is enabled again later. You may abbreviate | |
2505 | @code{disable} as @code{dis}. | |
2506 | ||
2507 | @item enable @r{[}breakpoints@r{]} @r{[}@var{bnums}@dots{}@r{]} | |
2508 | @kindex enable breakpoints | |
2509 | @kindex enable | |
2510 | Enable the specified breakpoints (or all defined breakpoints). They | |
29a2b744 | 2511 | become effective once again in stopping your program. |
70b88761 RP |
2512 | |
2513 | @item enable @r{[}breakpoints@r{]} once @var{bnums}@dots{} | |
9a27b06e RP |
2514 | Enable the specified breakpoints temporarily. @value{GDBN} disables any |
2515 | of these breakpoints immediately after stopping your program. | |
70b88761 RP |
2516 | |
2517 | @item enable @r{[}breakpoints@r{]} delete @var{bnums}@dots{} | |
9a27b06e RP |
2518 | Enable the specified breakpoints to work once, then die. @value{GDBN} |
2519 | deletes any of these breakpoints as soon as your program stops there. | |
70b88761 RP |
2520 | @end table |
2521 | ||
29a2b744 | 2522 | Save for a breakpoint set with @code{tbreak} (@pxref{Set Breaks, |
93928b60 RP |
2523 | ,Setting breakpoints}), breakpoints that you set are initially enabled; |
2524 | subsequently, they become disabled or enabled only when you use one of | |
2525 | the commands above. (The command @code{until} can set and delete a | |
9a27b06e | 2526 | breakpoint of its own, but it does not change the state of your other |
93928b60 RP |
2527 | breakpoints; see @ref{Continuing and Stepping, ,Continuing and |
2528 | stepping}.) | |
70b88761 | 2529 | |
4eb4cf57 | 2530 | @node Conditions |
93928b60 | 2531 | @subsection Break conditions |
70b88761 RP |
2532 | @cindex conditional breakpoints |
2533 | @cindex breakpoint conditions | |
2534 | ||
4906534f RP |
2535 | @c FIXME what is scope of break condition expr? Context where wanted? |
2536 | @c in particular for a watchpoint? | |
29a2b744 | 2537 | The simplest sort of breakpoint breaks every time your program reaches a |
70b88761 RP |
2538 | specified place. You can also specify a @dfn{condition} for a |
2539 | breakpoint. A condition is just a Boolean expression in your | |
1041a570 RP |
2540 | programming language (@pxref{Expressions, ,Expressions}). A breakpoint with |
2541 | a condition evaluates the expression each time your program reaches it, | |
2542 | and your program stops only if the condition is @emph{true}. | |
3d3ab540 RP |
2543 | |
2544 | This is the converse of using assertions for program validation; in that | |
2545 | situation, you want to stop when the assertion is violated---that is, | |
2546 | when the condition is false. In C, if you want to test an assertion expressed | |
e251e767 | 2547 | by the condition @var{assert}, you should set the condition |
3d3ab540 | 2548 | @samp{! @var{assert}} on the appropriate breakpoint. |
70b88761 RP |
2549 | |
2550 | Conditions are also accepted for watchpoints; you may not need them, | |
2551 | since a watchpoint is inspecting the value of an expression anyhow---but | |
2552 | it might be simpler, say, to just set a watchpoint on a variable name, | |
2553 | and specify a condition that tests whether the new value is an interesting | |
e251e767 | 2554 | one. |
70b88761 | 2555 | |
29a2b744 | 2556 | Break conditions can have side effects, and may even call functions in |
70b88761 | 2557 | your program. This can be useful, for example, to activate functions |
29a2b744 RP |
2558 | that log program progress, or to use your own print functions to |
2559 | format special data structures. The effects are completely predictable | |
2560 | unless there is another enabled breakpoint at the same address. (In | |
18fae2a8 | 2561 | that case, @value{GDBN} might see the other breakpoint first and stop your |
29a2b744 RP |
2562 | program without checking the condition of this one.) Note that |
2563 | breakpoint commands are usually more convenient and flexible for the | |
2564 | purpose of performing side effects when a breakpoint is reached | |
93928b60 | 2565 | (@pxref{Break Commands, ,Breakpoint command lists}). |
70b88761 RP |
2566 | |
2567 | Break conditions can be specified when a breakpoint is set, by using | |
29a2b744 | 2568 | @samp{if} in the arguments to the @code{break} command. @xref{Set |
93928b60 | 2569 | Breaks, ,Setting breakpoints}. They can also be changed at any time |
29a2b744 RP |
2570 | with the @code{condition} command. The @code{watch} command does not |
2571 | recognize the @code{if} keyword; @code{condition} is the only way to | |
2572 | impose a further condition on a watchpoint. | |
70b88761 | 2573 | |
e251e767 RP |
2574 | @table @code |
2575 | @item condition @var{bnum} @var{expression} | |
2576 | @kindex condition | |
70b88761 | 2577 | Specify @var{expression} as the break condition for breakpoint or |
9a27b06e RP |
2578 | watchpoint number @var{bnum}. After you set a condition, breakpoint |
2579 | @var{bnum} stops your program only if the value of @var{expression} is | |
2580 | true (nonzero, in C). When you use @code{condition}, @value{GDBN} | |
2581 | checks @var{expression} immediately for syntactic correctness, and to | |
2582 | determine whether symbols in it have referents in the context of your | |
2583 | breakpoint. | |
29a2b744 | 2584 | @c FIXME so what does GDB do if there is no referent? Moreover, what |
4906534f | 2585 | @c about watchpoints? |
18fae2a8 | 2586 | @value{GDBN} does |
70b88761 | 2587 | not actually evaluate @var{expression} at the time the @code{condition} |
1041a570 | 2588 | command is given, however. @xref{Expressions, ,Expressions}. |
70b88761 RP |
2589 | |
2590 | @item condition @var{bnum} | |
2591 | Remove the condition from breakpoint number @var{bnum}. It becomes | |
2592 | an ordinary unconditional breakpoint. | |
2593 | @end table | |
2594 | ||
2595 | @cindex ignore count (of breakpoint) | |
2596 | A special case of a breakpoint condition is to stop only when the | |
2597 | breakpoint has been reached a certain number of times. This is so | |
2598 | useful that there is a special way to do it, using the @dfn{ignore | |
2599 | count} of the breakpoint. Every breakpoint has an ignore count, which | |
2600 | is an integer. Most of the time, the ignore count is zero, and | |
29a2b744 | 2601 | therefore has no effect. But if your program reaches a breakpoint whose |
70b88761 RP |
2602 | ignore count is positive, then instead of stopping, it just decrements |
2603 | the ignore count by one and continues. As a result, if the ignore count | |
9a27b06e RP |
2604 | value is @var{n}, the breakpoint does not stop the next @var{n} times |
2605 | your program reaches it. | |
70b88761 RP |
2606 | |
2607 | @table @code | |
2608 | @item ignore @var{bnum} @var{count} | |
2609 | @kindex ignore | |
2610 | Set the ignore count of breakpoint number @var{bnum} to @var{count}. | |
2611 | The next @var{count} times the breakpoint is reached, your program's | |
9a27b06e | 2612 | execution does not stop; other than to decrement the ignore count, @value{GDBN} |
70b88761 RP |
2613 | takes no action. |
2614 | ||
2615 | To make the breakpoint stop the next time it is reached, specify | |
2616 | a count of zero. | |
2617 | ||
d55320a0 RP |
2618 | When you use @code{continue} to resume execution of your program from a |
2619 | breakpoint, you can specify an ignore count directly as an argument to | |
2620 | @code{continue}, rather than using @code{ignore}. @xref{Continuing and | |
2621 | Stepping,,Continuing and stepping}. | |
70b88761 | 2622 | |
9a27b06e RP |
2623 | If a breakpoint has a positive ignore count and a condition, the |
2624 | condition is not checked. Once the ignore count reaches zero, | |
2625 | @value{GDBN} resumes checking the condition. | |
70b88761 | 2626 | |
29a2b744 | 2627 | You could achieve the effect of the ignore count with a condition such |
18fae2a8 | 2628 | as @w{@samp{$foo-- <= 0}} using a debugger convenience variable that |
1041a570 | 2629 | is decremented each time. @xref{Convenience Vars, ,Convenience |
93928b60 | 2630 | variables}. |
d55320a0 | 2631 | @end table |
70b88761 | 2632 | |
4eb4cf57 | 2633 | @node Break Commands |
93928b60 | 2634 | @subsection Breakpoint command lists |
70b88761 RP |
2635 | |
2636 | @cindex breakpoint commands | |
2637 | You can give any breakpoint (or watchpoint) a series of commands to | |
29a2b744 | 2638 | execute when your program stops due to that breakpoint. For example, you |
70b88761 RP |
2639 | might want to print the values of certain expressions, or enable other |
2640 | breakpoints. | |
2641 | ||
2642 | @table @code | |
2643 | @item commands @r{[}@var{bnum}@r{]} | |
2644 | @itemx @dots{} @var{command-list} @dots{} | |
2645 | @itemx end | |
2646 | @kindex commands | |
2647 | @kindex end | |
2648 | Specify a list of commands for breakpoint number @var{bnum}. The commands | |
2649 | themselves appear on the following lines. Type a line containing just | |
2650 | @code{end} to terminate the commands. | |
2651 | ||
203eea5d RP |
2652 | To remove all commands from a breakpoint, type @code{commands} and |
2653 | follow it immediately with @code{end}; that is, give no commands. | |
70b88761 RP |
2654 | |
2655 | With no @var{bnum} argument, @code{commands} refers to the last | |
2656 | breakpoint or watchpoint set (not to the breakpoint most recently | |
2657 | encountered). | |
2658 | @end table | |
2659 | ||
18fae2a8 | 2660 | Pressing @key{RET} as a means of repeating the last @value{GDBN} command is |
70b88761 RP |
2661 | disabled within a @var{command-list}. |
2662 | ||
29a2b744 | 2663 | You can use breakpoint commands to start your program up again. Simply |
70b88761 | 2664 | use the @code{continue} command, or @code{step}, or any other command |
fe715d06 RP |
2665 | that resumes execution. |
2666 | ||
2667 | Any other commands in the command list, after a command that resumes | |
2668 | execution, are ignored. This is because any time you resume execution | |
2669 | (even with a simple @code{next} or @code{step}), you may encounter | |
2670 | another breakpoint---which could have its own command list, leading to | |
2671 | ambiguities about which list to execute. | |
70b88761 RP |
2672 | |
2673 | @kindex silent | |
fe715d06 RP |
2674 | If the first command you specify in a command list is @code{silent}, the |
2675 | usual message about stopping at a breakpoint is not printed. This may | |
2676 | be desirable for breakpoints that are to print a specific message and | |
2677 | then continue. If none of the remaining commands print anything, you | |
9a27b06e | 2678 | see no sign that the breakpoint was reached. @code{silent} is |
fe715d06 | 2679 | meaningful only at the beginning of a breakpoint command list. |
70b88761 | 2680 | |
d55320a0 RP |
2681 | The commands @code{echo}, @code{output}, and @code{printf} allow you to |
2682 | print precisely controlled output, and are often useful in silent | |
2683 | breakpoints. @xref{Output, ,Commands for controlled output}. | |
70b88761 RP |
2684 | |
2685 | For example, here is how you could use breakpoint commands to print the | |
2686 | value of @code{x} at entry to @code{foo} whenever @code{x} is positive. | |
2687 | ||
18fae2a8 | 2688 | @example |
70b88761 RP |
2689 | break foo if x>0 |
2690 | commands | |
2691 | silent | |
d55320a0 | 2692 | printf "x is %d\n",x |
70b88761 RP |
2693 | cont |
2694 | end | |
18fae2a8 | 2695 | @end example |
70b88761 RP |
2696 | |
2697 | One application for breakpoint commands is to compensate for one bug so | |
2698 | you can test for another. Put a breakpoint just after the erroneous line | |
2699 | of code, give it a condition to detect the case in which something | |
2700 | erroneous has been done, and give it commands to assign correct values | |
2701 | to any variables that need them. End with the @code{continue} command | |
29a2b744 | 2702 | so that your program does not stop, and start with the @code{silent} |
70b88761 RP |
2703 | command so that no output is produced. Here is an example: |
2704 | ||
2705 | @example | |
2706 | break 403 | |
2707 | commands | |
2708 | silent | |
2709 | set x = y + 4 | |
2710 | cont | |
2711 | end | |
2712 | @end example | |
2713 | ||
1d7c3357 | 2714 | @ifclear CONLY |
4eb4cf57 | 2715 | @node Breakpoint Menus |
93928b60 | 2716 | @subsection Breakpoint menus |
b80282d5 | 2717 | @cindex overloading |
e251e767 | 2718 | @cindex symbol overloading |
70b88761 RP |
2719 | |
2720 | Some programming languages (notably C++) permit a single function name | |
2721 | to be defined several times, for application in different contexts. | |
2722 | This is called @dfn{overloading}. When a function name is overloaded, | |
18fae2a8 | 2723 | @samp{break @var{function}} is not enough to tell @value{GDBN} where you want |
9a27b06e | 2724 | a breakpoint. If you realize this is a problem, you can use |
6f3ec223 | 2725 | something like @samp{break @var{function}(@var{types})} to specify which |
18fae2a8 | 2726 | particular version of the function you want. Otherwise, @value{GDBN} offers |
6f3ec223 RP |
2727 | you a menu of numbered choices for different possible breakpoints, and |
2728 | waits for your selection with the prompt @samp{>}. The first two | |
2729 | options are always @samp{[0] cancel} and @samp{[1] all}. Typing @kbd{1} | |
2730 | sets a breakpoint at each definition of @var{function}, and typing | |
2731 | @kbd{0} aborts the @code{break} command without setting any new | |
2732 | breakpoints. | |
70b88761 RP |
2733 | |
2734 | For example, the following session excerpt shows an attempt to set a | |
e251e767 | 2735 | breakpoint at the overloaded symbol @code{String::after}. |
70b88761 RP |
2736 | We choose three particular definitions of that function name: |
2737 | ||
6f3ec223 | 2738 | @c FIXME! This is likely to change to show arg type lists, at least |
d55320a0 | 2739 | @smallexample |
18fae2a8 | 2740 | (@value{GDBP}) b String::after |
70b88761 RP |
2741 | [0] cancel |
2742 | [1] all | |
2743 | [2] file:String.cc; line number:867 | |
2744 | [3] file:String.cc; line number:860 | |
2745 | [4] file:String.cc; line number:875 | |
2746 | [5] file:String.cc; line number:853 | |
2747 | [6] file:String.cc; line number:846 | |
2748 | [7] file:String.cc; line number:735 | |
2749 | > 2 4 6 | |
2750 | Breakpoint 1 at 0xb26c: file String.cc, line 867. | |
2751 | Breakpoint 2 at 0xb344: file String.cc, line 875. | |
2752 | Breakpoint 3 at 0xafcc: file String.cc, line 846. | |
2753 | Multiple breakpoints were set. | |
d55320a0 RP |
2754 | Use the "delete" command to delete unwanted |
2755 | breakpoints. | |
18fae2a8 | 2756 | (@value{GDBP}) |
d55320a0 | 2757 | @end smallexample |
1d7c3357 | 2758 | @end ifclear |
70b88761 | 2759 | |
1d7c3357 | 2760 | @ifclear BARETARGET |
4eb4cf57 | 2761 | @node Error in Breakpoints |
93928b60 | 2762 | @subsection ``Cannot insert breakpoints'' |
70b88761 | 2763 | |
e251e767 | 2764 | @c FIXME: "cannot insert breakpoints" error, v unclear. |
70b88761 | 2765 | @c Q in pending mail to Gilmore. ---pesch@cygnus.com, 26mar91 |
e251e767 | 2766 | @c some light may be shed by looking at instances of |
d24e0922 | 2767 | @c ONE_PROCESS_WRITETEXT. But error message seems possible otherwise |
c338a2fd | 2768 | @c too. pesch, 20sep91 |
70b88761 RP |
2769 | Under some operating systems, breakpoints cannot be used in a program if |
2770 | any other process is running that program. In this situation, | |
18fae2a8 | 2771 | attempting to run or continue a program with a breakpoint causes @value{GDBN} |
70b88761 RP |
2772 | to stop the other process. |
2773 | ||
2774 | When this happens, you have three ways to proceed: | |
2775 | ||
2776 | @enumerate | |
2777 | @item | |
2778 | Remove or disable the breakpoints, then continue. | |
2779 | ||
2780 | @item | |
18fae2a8 RP |
2781 | Suspend @value{GDBN}, and copy the file containing your program to a new name. |
2782 | Resume @value{GDBN} and use the @code{exec-file} command to specify that @value{GDBN} | |
29a2b744 | 2783 | should run your program under that name. Then start your program again. |
70b88761 RP |
2784 | |
2785 | @c FIXME: RMS commented here "Show example". Maybe when someone | |
2786 | @c explains the first FIXME: in this section... | |
2787 | ||
2788 | @item | |
29a2b744 | 2789 | Relink your program so that the text segment is nonsharable, using the |
70b88761 RP |
2790 | linker option @samp{-N}. The operating system limitation may not apply |
2791 | to nonsharable executables. | |
2792 | @end enumerate | |
1d7c3357 | 2793 | @end ifclear |
70b88761 | 2794 | |
4eb4cf57 | 2795 | @node Continuing and Stepping |
93928b60 | 2796 | @section Continuing and stepping |
70b88761 RP |
2797 | |
2798 | @cindex stepping | |
7463aadd RP |
2799 | @cindex continuing |
2800 | @cindex resuming execution | |
3d3ab540 | 2801 | @dfn{Continuing} means resuming program execution until your program |
cedaf8bc RP |
2802 | completes normally. In contrast, @dfn{stepping} means executing just |
2803 | one more ``step'' of your program, where ``step'' may mean either one | |
2804 | line of source code, or one machine instruction (depending on what | |
2805 | particular command you use). Either when continuing | |
4eb4cf57 | 2806 | or when stepping, your program may stop even sooner, due to |
18fae2a8 | 2807 | @ifset BARETARGET |
4eb4cf57 | 2808 | a breakpoint. |
18fae2a8 RP |
2809 | @end ifset |
2810 | @ifclear BARETARGET | |
6b51acad | 2811 | a breakpoint or a signal. (If due to a signal, you may want to use |
4eb4cf57 RP |
2812 | @code{handle}, or use @samp{signal 0} to resume execution. |
2813 | @xref{Signals, ,Signals}.) | |
18fae2a8 | 2814 | @end ifclear |
3d3ab540 RP |
2815 | |
2816 | @table @code | |
6b51acad RP |
2817 | @item continue @r{[}@var{ignore-count}@r{]} |
2818 | @itemx c @r{[}@var{ignore-count}@r{]} | |
2819 | @itemx fg @r{[}@var{ignore-count}@r{]} | |
3d3ab540 | 2820 | @kindex continue |
d55320a0 RP |
2821 | @kindex c |
2822 | @kindex fg | |
6b51acad RP |
2823 | Resume program execution, at the address where your program last stopped; |
2824 | any breakpoints set at that address are bypassed. The optional argument | |
2825 | @var{ignore-count} allows you to specify a further number of times to | |
2826 | ignore a breakpoint at this location; its effect is like that of | |
2827 | @code{ignore} (@pxref{Conditions, ,Break conditions}). | |
2828 | ||
2829 | The argument @var{ignore-count} is meaningful only when your program | |
d55320a0 RP |
2830 | stopped due to a breakpoint. At other times, the argument to |
2831 | @code{continue} is ignored. | |
2832 | ||
2833 | The synonyms @code{c} and @code{fg} are provided purely for convenience, | |
2834 | and have exactly the same behavior as @code{continue}. | |
2835 | @end table | |
2836 | ||
3d3ab540 | 2837 | To resume execution at a different place, you can use @code{return} |
93928b60 | 2838 | (@pxref{Returning, ,Returning from a function}) to go back to the |
29a2b744 | 2839 | calling function; or @code{jump} (@pxref{Jumping, ,Continuing at a |
93928b60 | 2840 | different address}) to go to an arbitrary location in your program. |
7463aadd RP |
2841 | |
2842 | A typical technique for using stepping is to set a breakpoint | |
93928b60 RP |
2843 | @ifclear CONLY |
2844 | (@pxref{Breakpoints, ,Breakpoints; watchpoints; and exceptions}) | |
2845 | @end ifclear | |
2846 | @ifset CONLY | |
2847 | (@pxref{Breakpoints, ,Breakpoints and watchpoints}) | |
2848 | @end ifset | |
2849 | at the | |
29a2b744 RP |
2850 | beginning of the function or the section of your program where a |
2851 | problem is believed to lie, run your program until it stops at that | |
2852 | breakpoint, and then step through the suspect area, examining the | |
2853 | variables that are interesting, until you see the problem happen. | |
70b88761 RP |
2854 | |
2855 | @table @code | |
2856 | @item step | |
2857 | @kindex step | |
2858 | @kindex s | |
29a2b744 | 2859 | Continue running your program until control reaches a different source |
18fae2a8 | 2860 | line, then stop it and return control to @value{GDBN}. This command is |
70b88761 RP |
2861 | abbreviated @code{s}. |
2862 | ||
3d3ab540 | 2863 | @quotation |
068b06f2 JK |
2864 | @c "without debugging information" is imprecise; actually "without line |
2865 | @c numbers in the debugging information". (gcc -g1 has debugging info but | |
2866 | @c not line numbers). But it seems complex to try to make that | |
2867 | @c distinction here. | |
3d3ab540 RP |
2868 | @emph{Warning:} If you use the @code{step} command while control is |
2869 | within a function that was compiled without debugging information, | |
d55320a0 | 2870 | execution proceeds until control reaches a function that does have |
068b06f2 JK |
2871 | debugging information. Likewise, it will not step into a function which |
2872 | is compiled without debugging information. To step through functions | |
2873 | without debugging information, use the @code{stepi} command, described | |
2874 | below. | |
3d3ab540 | 2875 | @end quotation |
70b88761 RP |
2876 | |
2877 | @item step @var{count} | |
2878 | Continue running as in @code{step}, but do so @var{count} times. If a | |
1d7c3357 RP |
2879 | breakpoint is reached, |
2880 | @ifclear BARETARGET | |
2881 | or a signal not related to stepping occurs before @var{count} steps, | |
2882 | @end ifclear | |
2883 | stepping stops right away. | |
70b88761 | 2884 | |
7463aadd | 2885 | @item next @r{[}@var{count}@r{]} |
70b88761 RP |
2886 | @kindex next |
2887 | @kindex n | |
7463aadd RP |
2888 | Continue to the next source line in the current (innermost) stack frame. |
2889 | Similar to @code{step}, but any function calls appearing within the line | |
2890 | of code are executed without stopping. Execution stops when control | |
2891 | reaches a different line of code at the stack level which was executing | |
2892 | when the @code{next} command was given. This command is abbreviated | |
2893 | @code{n}. | |
70b88761 | 2894 | |
7463aadd | 2895 | An argument @var{count} is a repeat count, as for @code{step}. |
70b88761 RP |
2896 | |
2897 | @code{next} within a function that lacks debugging information acts like | |
2898 | @code{step}, but any function calls appearing within the code of the | |
2899 | function are executed without stopping. | |
2900 | ||
2901 | @item finish | |
2902 | @kindex finish | |
7463aadd RP |
2903 | Continue running until just after function in the selected stack frame |
2904 | returns. Print the returned value (if any). | |
70b88761 | 2905 | |
29a2b744 | 2906 | Contrast this with the @code{return} command (@pxref{Returning, |
93928b60 | 2907 | ,Returning from a function}). |
70b88761 RP |
2908 | |
2909 | @item until | |
2910 | @kindex until | |
6b51acad | 2911 | @itemx u |
70b88761 RP |
2912 | @kindex u |
2913 | Continue running until a source line past the current line, in the | |
2914 | current stack frame, is reached. This command is used to avoid single | |
2915 | stepping through a loop more than once. It is like the @code{next} | |
2916 | command, except that when @code{until} encounters a jump, it | |
2917 | automatically continues execution until the program counter is greater | |
2918 | than the address of the jump. | |
2919 | ||
2920 | This means that when you reach the end of a loop after single stepping | |
9a27b06e RP |
2921 | though it, @code{until} makes your program continue execution until it |
2922 | exits the loop. In contrast, a @code{next} command at the end of a loop | |
2923 | simply steps back to the beginning of the loop, which forces you to step | |
2924 | through the next iteration. | |
70b88761 | 2925 | |
29a2b744 | 2926 | @code{until} always stops your program if it attempts to exit the current |
70b88761 RP |
2927 | stack frame. |
2928 | ||
2929 | @code{until} may produce somewhat counterintuitive results if the order | |
7463aadd | 2930 | of machine code does not match the order of the source lines. For |
70b88761 RP |
2931 | example, in the following excerpt from a debugging session, the @code{f} |
2932 | (@code{frame}) command shows that execution is stopped at line | |
2933 | @code{206}; yet when we use @code{until}, we get to line @code{195}: | |
2934 | ||
2935 | @example | |
18fae2a8 | 2936 | (@value{GDBP}) f |
70b88761 | 2937 | #0 main (argc=4, argv=0xf7fffae8) at m4.c:206 |
b80282d5 | 2938 | 206 expand_input(); |
18fae2a8 | 2939 | (@value{GDBP}) until |
b80282d5 | 2940 | 195 for ( ; argc > 0; NEXTARG) @{ |
70b88761 RP |
2941 | @end example |
2942 | ||
7463aadd RP |
2943 | This happened because, for execution efficiency, the compiler had |
2944 | generated code for the loop closure test at the end, rather than the | |
2945 | start, of the loop---even though the test in a C @code{for}-loop is | |
2946 | written before the body of the loop. The @code{until} command appeared | |
2947 | to step back to the beginning of the loop when it advanced to this | |
2948 | expression; however, it has not really gone to an earlier | |
2949 | statement---not in terms of the actual machine code. | |
70b88761 RP |
2950 | |
2951 | @code{until} with no argument works by means of single | |
2952 | instruction stepping, and hence is slower than @code{until} with an | |
2953 | argument. | |
2954 | ||
2955 | @item until @var{location} | |
6b51acad | 2956 | @itemx u @var{location} |
29a2b744 RP |
2957 | Continue running your program until either the specified location is |
2958 | reached, or the current stack frame returns. @var{location} is any of | |
2959 | the forms of argument acceptable to @code{break} (@pxref{Set Breaks, | |
93928b60 | 2960 | ,Setting breakpoints}). This form of the command uses breakpoints, |
1041a570 | 2961 | and hence is quicker than @code{until} without an argument. |
70b88761 RP |
2962 | |
2963 | @item stepi | |
2964 | @itemx si | |
2965 | @kindex stepi | |
2966 | @kindex si | |
2967 | Execute one machine instruction, then stop and return to the debugger. | |
2968 | ||
2969 | It is often useful to do @samp{display/i $pc} when stepping by machine | |
9a27b06e RP |
2970 | instructions. This makes @value{GDBN} automatically display the next |
2971 | instruction to be executed, each time your program stops. @xref{Auto | |
2972 | Display,, Automatic display}. | |
70b88761 RP |
2973 | |
2974 | An argument is a repeat count, as in @code{step}. | |
2975 | ||
ed447b95 | 2976 | @need 750 |
70b88761 RP |
2977 | @item nexti |
2978 | @itemx ni | |
2979 | @kindex nexti | |
2980 | @kindex ni | |
2981 | Execute one machine instruction, but if it is a function call, | |
2982 | proceed until the function returns. | |
2983 | ||
2984 | An argument is a repeat count, as in @code{next}. | |
70b88761 RP |
2985 | @end table |
2986 | ||
18fae2a8 | 2987 | @ifset POSIX |
4eb4cf57 | 2988 | @node Signals |
70b88761 RP |
2989 | @section Signals |
2990 | @cindex signals | |
2991 | ||
2992 | A signal is an asynchronous event that can happen in a program. The | |
2993 | operating system defines the possible kinds of signals, and gives each | |
2994 | kind a name and a number. For example, in Unix @code{SIGINT} is the | |
2995 | signal a program gets when you type an interrupt (often @kbd{C-c}); | |
2996 | @code{SIGSEGV} is the signal a program gets from referencing a place in | |
2997 | memory far away from all the areas in use; @code{SIGALRM} occurs when | |
29a2b744 | 2998 | the alarm clock timer goes off (which happens only if your program has |
70b88761 RP |
2999 | requested an alarm). |
3000 | ||
3001 | @cindex fatal signals | |
3002 | Some signals, including @code{SIGALRM}, are a normal part of the | |
29a2b744 RP |
3003 | functioning of your program. Others, such as @code{SIGSEGV}, indicate |
3004 | errors; these signals are @dfn{fatal} (kill your program immediately) if the | |
70b88761 | 3005 | program has not specified in advance some other way to handle the signal. |
29a2b744 | 3006 | @code{SIGINT} does not indicate an error in your program, but it is normally |
70b88761 RP |
3007 | fatal so it can carry out the purpose of the interrupt: to kill the program. |
3008 | ||
18fae2a8 RP |
3009 | @value{GDBN} has the ability to detect any occurrence of a signal in your |
3010 | program. You can tell @value{GDBN} in advance what to do for each kind of | |
29a2b744 | 3011 | signal. |
70b88761 RP |
3012 | |
3013 | @cindex handling signals | |
18fae2a8 | 3014 | Normally, @value{GDBN} is set up to ignore non-erroneous signals like @code{SIGALRM} |
29a2b744 RP |
3015 | (so as not to interfere with their role in the functioning of your program) |
3016 | but to stop your program immediately whenever an error signal happens. | |
70b88761 RP |
3017 | You can change these settings with the @code{handle} command. |
3018 | ||
3019 | @table @code | |
3020 | @item info signals | |
3021 | @kindex info signals | |
18fae2a8 | 3022 | Print a table of all the kinds of signals and how @value{GDBN} has been told to |
70b88761 RP |
3023 | handle each one. You can use this to see the signal numbers of all |
3024 | the defined types of signals. | |
3025 | ||
3026 | @item handle @var{signal} @var{keywords}@dots{} | |
3027 | @kindex handle | |
18fae2a8 | 3028 | Change the way @value{GDBN} handles signal @var{signal}. @var{signal} can be the |
70b88761 RP |
3029 | number of a signal or its name (with or without the @samp{SIG} at the |
3030 | beginning). The @var{keywords} say what change to make. | |
3031 | @end table | |
3032 | ||
3033 | @c @group | |
3034 | The keywords allowed by the @code{handle} command can be abbreviated. | |
3035 | Their full names are: | |
3036 | ||
3037 | @table @code | |
3038 | @item nostop | |
18fae2a8 | 3039 | @value{GDBN} should not stop your program when this signal happens. It may |
70b88761 RP |
3040 | still print a message telling you that the signal has come in. |
3041 | ||
3042 | @item stop | |
18fae2a8 | 3043 | @value{GDBN} should stop your program when this signal happens. This implies |
70b88761 RP |
3044 | the @code{print} keyword as well. |
3045 | ||
3046 | @item print | |
18fae2a8 | 3047 | @value{GDBN} should print a message when this signal happens. |
70b88761 RP |
3048 | |
3049 | @item noprint | |
18fae2a8 | 3050 | @value{GDBN} should not mention the occurrence of the signal at all. This |
70b88761 RP |
3051 | implies the @code{nostop} keyword as well. |
3052 | ||
3053 | @item pass | |
9a27b06e RP |
3054 | @value{GDBN} should allow your program to see this signal; your program |
3055 | can handle the signal, or else it may terminate if the signal is fatal | |
70b88761 RP |
3056 | and not handled. |
3057 | ||
3058 | @item nopass | |
18fae2a8 | 3059 | @value{GDBN} should not allow your program to see this signal. |
70b88761 RP |
3060 | @end table |
3061 | @c @end group | |
3062 | ||
ed447b95 | 3063 | When a signal stops your program, the signal is not visible until you |
9a27b06e | 3064 | continue. Your program sees the signal then, if @code{pass} is in |
ed447b95 RP |
3065 | effect for the signal in question @emph{at that time}. In other words, |
3066 | after @value{GDBN} reports a signal, you can use the @code{handle} | |
9a27b06e RP |
3067 | command with @code{pass} or @code{nopass} to control whether your |
3068 | program sees that signal when you continue. | |
70b88761 | 3069 | |
29a2b744 | 3070 | You can also use the @code{signal} command to prevent your program from |
70b88761 | 3071 | seeing a signal, or cause it to see a signal it normally would not see, |
29a2b744 | 3072 | or to give it any signal at any time. For example, if your program stopped |
7463aadd RP |
3073 | due to some sort of memory reference error, you might store correct |
3074 | values into the erroneous variables and continue, hoping to see more | |
29a2b744 RP |
3075 | execution; but your program would probably terminate immediately as |
3076 | a result of the fatal signal once it saw the signal. To prevent this, | |
3077 | you can continue with @samp{signal 0}. @xref{Signaling, ,Giving your | |
93928b60 | 3078 | program a signal}. |
18fae2a8 | 3079 | @end ifset |
70b88761 | 3080 | |
0cb95a9c RP |
3081 | @ifclear BARETARGET |
3082 | @node Thread Stops | |
3083 | @section Stopping and starting multi-thread programs | |
3084 | ||
3085 | When your program has multiple threads (@pxref{Threads,, Debugging | |
3086 | programs with multiple threads}), you can choose whether to set | |
3087 | breakpoints on all threads, or on a particular thread. | |
3088 | ||
3089 | @table @code | |
22b5dba5 RP |
3090 | @cindex breakpoints and threads |
3091 | @cindex thread breakpoints | |
0cb95a9c RP |
3092 | @kindex break @dots{} thread @var{threadno} |
3093 | @item break @var{linespec} thread @var{threadno} | |
3094 | @itemx break @var{linespec} thread @var{threadno} if @dots{} | |
3095 | Use the qualifier @samp{thread @var{threadno}} with a breakpoint command | |
3096 | to specify that you only want @value{GDBN} to stop the program when a | |
22b5dba5 RP |
3097 | particular thread reaches this breakpoint. @var{threadno} is one of the |
3098 | numeric thread identifiers assigned by @value{GDBN}, shown in the first | |
3099 | column of the @samp{info threads} display. | |
0cb95a9c RP |
3100 | |
3101 | If you do not specify @samp{thread @var{threadno}} when you set a | |
3102 | breakpoint, the breakpoint applies to @emph{all} threads of your | |
3103 | program. | |
22b5dba5 RP |
3104 | |
3105 | You can use the @code{thread} qualifier on conditional breakpoints as | |
3106 | well; in this case, place @samp{thread @var{threadno}} before the | |
3107 | breakpoint condition, like this: | |
3108 | ||
3109 | @smallexample | |
3110 | (gdb) break frik.c:13 thread 28 if bartab > lim | |
3111 | @end smallexample | |
0cb95a9c RP |
3112 | @end table |
3113 | ||
3114 | @cindex stopped threads | |
3115 | @cindex threads, stopped | |
3116 | Whenever your program stops under @value{GDBN} for any reason, | |
3117 | @emph{all} threads of execution stop, not just the current thread. This | |
3118 | allows you to examine the overall state of the program, including | |
3119 | switching between threads, without worrying that things may change | |
3120 | underfoot. | |
3121 | ||
3122 | @cindex continuing threads | |
3123 | @cindex threads, continuing | |
3124 | Conversely, whenever you restart the program, @emph{all} threads start | |
3125 | executing. @emph{This is true even when single-stepping} with commands | |
3126 | like @code{step} or @code{next}. | |
3127 | ||
3128 | In particular, @value{GDBN} cannot single-step all threads in lockstep. | |
22b5dba5 RP |
3129 | Since thread scheduling is up to your debugging target's operating |
3130 | system (not controlled by @value{GDBN}), other threads may | |
3131 | execute more than one statement while the current thread completes a | |
3132 | single step. Moreover, in general other threads stop in the middle of a | |
3133 | statement, rather than at a clean statement boundary, when the program | |
3134 | stops. | |
0cb95a9c RP |
3135 | |
3136 | You might even find your program stopped in another thread after | |
3137 | continuing or even single-stepping. This happens whenever some other | |
3138 | thread runs into a breakpoint, a signal, or an exception before the | |
3139 | first thread completes whatever you requested. | |
3140 | @end ifclear | |
3141 | ||
4eb4cf57 | 3142 | @node Stack |
70b88761 RP |
3143 | @chapter Examining the Stack |
3144 | ||
3145 | When your program has stopped, the first thing you need to know is where it | |
3146 | stopped and how it got there. | |
3147 | ||
3148 | @cindex call stack | |
3149 | Each time your program performs a function call, the information about | |
29a2b744 | 3150 | where in your program the call was made from is saved in a block of data |
70b88761 RP |
3151 | called a @dfn{stack frame}. The frame also contains the arguments of the |
3152 | call and the local variables of the function that was called. All the | |
3153 | stack frames are allocated in a region of memory called the @dfn{call | |
3154 | stack}. | |
3155 | ||
93928b60 RP |
3156 | When your program stops, the @value{GDBN} commands for examining the |
3157 | stack allow you to see all of this information. | |
70b88761 RP |
3158 | |
3159 | @cindex selected frame | |
93928b60 RP |
3160 | One of the stack frames is @dfn{selected} by @value{GDBN} and many |
3161 | @value{GDBN} commands refer implicitly to the selected frame. In | |
3162 | particular, whenever you ask @value{GDBN} for the value of a variable in | |
3163 | your program, the value is found in the selected frame. There are | |
3164 | special @value{GDBN} commands to select whichever frame you are | |
3165 | interested in. | |
70b88761 | 3166 | |
93928b60 RP |
3167 | When your program stops, @value{GDBN} automatically selects the |
3168 | currently executing frame and describes it briefly as the @code{frame} | |
3169 | command does (@pxref{Frame Info, ,Information about a frame}). | |
70b88761 RP |
3170 | |
3171 | @menu | |
ed447b95 | 3172 | * Frames:: Stack frames |
b80282d5 | 3173 | * Backtrace:: Backtraces |
ed447b95 RP |
3174 | * Selection:: Selecting a frame |
3175 | * Frame Info:: Information on a frame | |
572867a8 RP |
3176 | @ifset MIPS |
3177 | * MIPS Stack:: MIPS machines and the function stack | |
3178 | @end ifset | |
70b88761 RP |
3179 | @end menu |
3180 | ||
4eb4cf57 | 3181 | @node Frames |
93928b60 | 3182 | @section Stack frames |
70b88761 RP |
3183 | |
3184 | @cindex frame | |
3185 | @cindex stack frame | |
3186 | The call stack is divided up into contiguous pieces called @dfn{stack | |
3187 | frames}, or @dfn{frames} for short; each frame is the data associated | |
3188 | with one call to one function. The frame contains the arguments given | |
3189 | to the function, the function's local variables, and the address at | |
3190 | which the function is executing. | |
3191 | ||
3192 | @cindex initial frame | |
3193 | @cindex outermost frame | |
3194 | @cindex innermost frame | |
3195 | When your program is started, the stack has only one frame, that of the | |
3196 | function @code{main}. This is called the @dfn{initial} frame or the | |
3197 | @dfn{outermost} frame. Each time a function is called, a new frame is | |
3198 | made. Each time a function returns, the frame for that function invocation | |
3199 | is eliminated. If a function is recursive, there can be many frames for | |
3200 | the same function. The frame for the function in which execution is | |
3201 | actually occurring is called the @dfn{innermost} frame. This is the most | |
3202 | recently created of all the stack frames that still exist. | |
3203 | ||
3204 | @cindex frame pointer | |
3205 | Inside your program, stack frames are identified by their addresses. A | |
3206 | stack frame consists of many bytes, each of which has its own address; each | |
3207 | kind of computer has a convention for choosing one of those bytes whose | |
3208 | address serves as the address of the frame. Usually this address is kept | |
3209 | in a register called the @dfn{frame pointer register} while execution is | |
3210 | going on in that frame. | |
3211 | ||
3212 | @cindex frame number | |
18fae2a8 | 3213 | @value{GDBN} assigns numbers to all existing stack frames, starting with |
70b88761 RP |
3214 | zero for the innermost frame, one for the frame that called it, |
3215 | and so on upward. These numbers do not really exist in your program; | |
18fae2a8 RP |
3216 | they are assigned by @value{GDBN} to give you a way of designating stack |
3217 | frames in @value{GDBN} commands. | |
70b88761 | 3218 | |
6b51acad | 3219 | @c below produces an acceptable overful hbox. --mew 13aug1993 |
70b88761 | 3220 | @cindex frameless execution |
8c69096b | 3221 | Some compilers provide a way to compile functions so that they operate |
18fae2a8 | 3222 | without stack frames. (For example, the @code{@value{GCC}} option |
9a27b06e | 3223 | @samp{-fomit-frame-pointer} generates functions without a frame.) |
70b88761 | 3224 | This is occasionally done with heavily used library functions to save |
8c69096b RP |
3225 | the frame setup time. @value{GDBN} has limited facilities for dealing |
3226 | with these function invocations. If the innermost function invocation | |
9a27b06e | 3227 | has no stack frame, @value{GDBN} nevertheless regards it as though |
8c69096b RP |
3228 | it had a separate frame, which is numbered zero as usual, allowing |
3229 | correct tracing of the function call chain. However, @value{GDBN} has | |
3230 | no provision for frameless functions elsewhere in the stack. | |
70b88761 | 3231 | |
4eb4cf57 | 3232 | @node Backtrace |
70b88761 RP |
3233 | @section Backtraces |
3234 | ||
29a2b744 | 3235 | A backtrace is a summary of how your program got where it is. It shows one |
70b88761 RP |
3236 | line per frame, for many frames, starting with the currently executing |
3237 | frame (frame zero), followed by its caller (frame one), and on up the | |
3238 | stack. | |
3239 | ||
3240 | @table @code | |
3241 | @item backtrace | |
3242 | @itemx bt | |
3243 | @kindex backtrace | |
3244 | @kindex bt | |
3245 | Print a backtrace of the entire stack: one line per frame for all | |
3246 | frames in the stack. | |
3247 | ||
3248 | You can stop the backtrace at any time by typing the system interrupt | |
3249 | character, normally @kbd{C-c}. | |
3250 | ||
3251 | @item backtrace @var{n} | |
3252 | @itemx bt @var{n} | |
3253 | Similar, but print only the innermost @var{n} frames. | |
3254 | ||
3255 | @item backtrace -@var{n} | |
3256 | @itemx bt -@var{n} | |
3257 | Similar, but print only the outermost @var{n} frames. | |
3258 | @end table | |
3259 | ||
3260 | @kindex where | |
3261 | @kindex info stack | |
3262 | @kindex info s | |
3263 | The names @code{where} and @code{info stack} (abbreviated @code{info s}) | |
3264 | are additional aliases for @code{backtrace}. | |
3265 | ||
3266 | Each line in the backtrace shows the frame number and the function name. | |
3267 | The program counter value is also shown---unless you use @code{set | |
3268 | print address off}. The backtrace also shows the source file name and | |
3269 | line number, as well as the arguments to the function. The program | |
3270 | counter value is omitted if it is at the beginning of the code for that | |
3271 | line number. | |
3272 | ||
3273 | Here is an example of a backtrace. It was made with the command | |
3274 | @samp{bt 3}, so it shows the innermost three frames. | |
3275 | ||
3276 | @smallexample | |
3277 | @group | |
203eea5d RP |
3278 | #0 m4_traceon (obs=0x24eb0, argc=1, argv=0x2b8c8) |
3279 | at builtin.c:993 | |
70b88761 RP |
3280 | #1 0x6e38 in expand_macro (sym=0x2b600) at macro.c:242 |
3281 | #2 0x6840 in expand_token (obs=0x0, t=177664, td=0xf7fffb08) | |
3282 | at macro.c:71 | |
3283 | (More stack frames follow...) | |
3284 | @end group | |
3285 | @end smallexample | |
3286 | ||
3287 | @noindent | |
29a2b744 RP |
3288 | The display for frame zero does not begin with a program counter |
3289 | value, indicating that your program has stopped at the beginning of the | |
70b88761 RP |
3290 | code for line @code{993} of @code{builtin.c}. |
3291 | ||
4eb4cf57 | 3292 | @node Selection |
93928b60 | 3293 | @section Selecting a frame |
70b88761 | 3294 | |
29a2b744 | 3295 | Most commands for examining the stack and other data in your program work on |
70b88761 RP |
3296 | whichever stack frame is selected at the moment. Here are the commands for |
3297 | selecting a stack frame; all of them finish by printing a brief description | |
3298 | of the stack frame just selected. | |
3299 | ||
3300 | @table @code | |
3301 | @item frame @var{n} | |
3302 | @itemx f @var{n} | |
3303 | @kindex frame | |
3304 | @kindex f | |
3305 | Select frame number @var{n}. Recall that frame zero is the innermost | |
3306 | (currently executing) frame, frame one is the frame that called the | |
93918348 RP |
3307 | innermost one, and so on. The highest-numbered frame is the one for |
3308 | @code{main}. | |
70b88761 RP |
3309 | |
3310 | @item frame @var{addr} | |
3311 | @itemx f @var{addr} | |
3312 | Select the frame at address @var{addr}. This is useful mainly if the | |
3313 | chaining of stack frames has been damaged by a bug, making it | |
18fae2a8 | 3314 | impossible for @value{GDBN} to assign numbers properly to all frames. In |
29a2b744 | 3315 | addition, this can be useful when your program has multiple stacks and |
70b88761 RP |
3316 | switches between them. |
3317 | ||
7e17041f | 3318 | @ifclear H8EXCLUSIVE |
70b88761 | 3319 | On the SPARC architecture, @code{frame} needs two addresses to |
e251e767 | 3320 | select an arbitrary frame: a frame pointer and a stack pointer. |
7e17041f JK |
3321 | |
3322 | On the MIPS and Alpha architecture, it needs two addresses: a stack | |
3323 | pointer and a program counter. | |
3324 | ||
3325 | On the 29k architecture, it needs three addresses: a register stack | |
3326 | pointer, a program counter, and a memory stack pointer. | |
70b88761 | 3327 | @c note to future updaters: this is conditioned on a flag |
7e17041f JK |
3328 | @c SETUP_ARBITRARY_FRAME in the tm-*.h files. The above is up to date |
3329 | @c as of 27 Jan 1994. | |
3330 | @end ifclear | |
70b88761 RP |
3331 | |
3332 | @item up @var{n} | |
3333 | @kindex up | |
3334 | Move @var{n} frames up the stack. For positive numbers @var{n}, this | |
3335 | advances toward the outermost frame, to higher frame numbers, to frames | |
3336 | that have existed longer. @var{n} defaults to one. | |
3337 | ||
3338 | @item down @var{n} | |
3339 | @kindex down | |
3340 | @kindex do | |
3341 | Move @var{n} frames down the stack. For positive numbers @var{n}, this | |
3342 | advances toward the innermost frame, to lower frame numbers, to frames | |
3343 | that were created more recently. @var{n} defaults to one. You may | |
3344 | abbreviate @code{down} as @code{do}. | |
3345 | @end table | |
3346 | ||
3347 | All of these commands end by printing two lines of output describing the | |
3348 | frame. The first line shows the frame number, the function name, the | |
3349 | arguments, and the source file and line number of execution in that | |
ed447b95 | 3350 | frame. The second line shows the text of that source line. |
70b88761 | 3351 | |
b1955f0b | 3352 | @need 1000 |
ed447b95 | 3353 | For example: |
b1955f0b | 3354 | |
70b88761 | 3355 | @smallexample |
29a2b744 | 3356 | @group |
18fae2a8 | 3357 | (@value{GDBP}) up |
203eea5d RP |
3358 | #1 0x22f0 in main (argc=1, argv=0xf7fffbf4, env=0xf7fffbfc) |
3359 | at env.c:10 | |
70b88761 | 3360 | 10 read_input_file (argv[i]); |
29a2b744 | 3361 | @end group |
70b88761 RP |
3362 | @end smallexample |
3363 | ||
9a27b06e RP |
3364 | After such a printout, the @code{list} command with no arguments |
3365 | prints ten lines centered on the point of execution in the frame. | |
93928b60 | 3366 | @xref{List, ,Printing source lines}. |
70b88761 RP |
3367 | |
3368 | @table @code | |
3369 | @item up-silently @var{n} | |
3370 | @itemx down-silently @var{n} | |
3371 | @kindex down-silently | |
3372 | @kindex up-silently | |
3373 | These two commands are variants of @code{up} and @code{down}, | |
3374 | respectively; they differ in that they do their work silently, without | |
3375 | causing display of the new frame. They are intended primarily for use | |
18fae2a8 | 3376 | in @value{GDBN} command scripts, where the output might be unnecessary and |
e251e767 | 3377 | distracting. |
70b88761 RP |
3378 | @end table |
3379 | ||
4eb4cf57 | 3380 | @node Frame Info |
93928b60 | 3381 | @section Information about a frame |
70b88761 RP |
3382 | |
3383 | There are several other commands to print information about the selected | |
3384 | stack frame. | |
3385 | ||
3386 | @table @code | |
3387 | @item frame | |
3388 | @itemx f | |
29a2b744 RP |
3389 | When used without any argument, this command does not change which |
3390 | frame is selected, but prints a brief description of the currently | |
70b88761 | 3391 | selected stack frame. It can be abbreviated @code{f}. With an |
ed447b95 | 3392 | argument, this command is used to select a stack frame. |
93928b60 | 3393 | @xref{Selection, ,Selecting a frame}. |
70b88761 RP |
3394 | |
3395 | @item info frame | |
70b88761 | 3396 | @itemx info f |
29a2b744 | 3397 | @kindex info frame |
70b88761 RP |
3398 | @kindex info f |
3399 | This command prints a verbose description of the selected stack frame, | |
3400 | including the address of the frame, the addresses of the next frame down | |
c2bbbb22 RP |
3401 | (called by this frame) and the next frame up (caller of this frame), the |
3402 | language that the source code corresponding to this frame was written in, | |
70b88761 RP |
3403 | the address of the frame's arguments, the program counter saved in it |
3404 | (the address of execution in the caller frame), and which registers | |
3405 | were saved in the frame. The verbose description is useful when | |
3406 | something has gone wrong that has made the stack format fail to fit | |
3407 | the usual conventions. | |
3408 | ||
3409 | @item info frame @var{addr} | |
3410 | @itemx info f @var{addr} | |
7e17041f JK |
3411 | Print a verbose description of the frame at address @var{addr}, without |
3412 | selecting that frame. The selected frame remains unchanged by this | |
3413 | command. This requires the same kind of address (more than one for some | |
3414 | architectures) that you specify in the @code{frame} command. | |
3415 | @xref{Selection, ,Selecting a frame}. | |
70b88761 RP |
3416 | |
3417 | @item info args | |
3418 | @kindex info args | |
3419 | Print the arguments of the selected frame, each on a separate line. | |
3420 | ||
3421 | @item info locals | |
3422 | @kindex info locals | |
3423 | Print the local variables of the selected frame, each on a separate | |
ed447b95 RP |
3424 | line. These are all variables (declared either static or automatic) |
3425 | accessible at the point of execution of the selected frame. | |
70b88761 | 3426 | |
1d7c3357 | 3427 | @ifclear CONLY |
70b88761 RP |
3428 | @item info catch |
3429 | @kindex info catch | |
3430 | @cindex catch exceptions | |
3431 | @cindex exception handlers | |
3432 | Print a list of all the exception handlers that are active in the | |
3433 | current stack frame at the current point of execution. To see other | |
3434 | exception handlers, visit the associated frame (using the @code{up}, | |
3435 | @code{down}, or @code{frame} commands); then type @code{info catch}. | |
93928b60 | 3436 | @xref{Exception Handling, ,Breakpoints and exceptions}. |
1d7c3357 | 3437 | @end ifclear |
70b88761 RP |
3438 | @end table |
3439 | ||
572867a8 RP |
3440 | @ifset MIPS |
3441 | @node MIPS Stack | |
3442 | @section MIPS machines and the function stack | |
3443 | ||
3444 | @cindex stack on MIPS | |
3445 | @cindex MIPS stack | |
3446 | MIPS based computers use an unusual stack frame, which sometimes | |
3447 | requires @value{GDBN} to search backward in the object code to find the | |
3448 | beginning of a function. | |
3449 | ||
3450 | @cindex response time, MIPS debugging | |
3451 | To improve response time (especially for embedded applications, where | |
3452 | @value{GDBN} may be restricted to a slow serial line for this search) | |
3453 | you may want to limit the size of this search, using one of these | |
3454 | commands: | |
3455 | @c FIXME! So what happens when GDB does *not* find the beginning of a | |
3456 | @c function? | |
3457 | ||
3458 | @cindex @code{heuristic-fence-post} (MIPS) | |
3459 | @table @code | |
3460 | @item set heuristic-fence-post @var{limit} | |
c79890ee | 3461 | Restrict @value{GDBN} to examining at most @var{limit} bytes in its search |
572867a8 RP |
3462 | for the beginning of a function. A value of @code{0} (the default) |
3463 | means there is no limit. | |
3464 | ||
3465 | @item show heuristic-fence-post | |
3466 | Display the current limit. | |
3467 | @end table | |
3468 | ||
3469 | @noindent | |
3470 | These commands are available @emph{only} when @value{GDBN} is configured | |
3471 | for debugging programs on MIPS processors. | |
3472 | @end ifset | |
3473 | ||
4eb4cf57 | 3474 | @node Source |
70b88761 RP |
3475 | @chapter Examining Source Files |
3476 | ||
18fae2a8 | 3477 | @value{GDBN} can print parts of your program's source, since the debugging |
ed447b95 | 3478 | information recorded in the program tells @value{GDBN} what source files were |
18fae2a8 | 3479 | used to build it. When your program stops, @value{GDBN} spontaneously prints |
1041a570 | 3480 | the line where it stopped. Likewise, when you select a stack frame |
93928b60 | 3481 | (@pxref{Selection, ,Selecting a frame}), @value{GDBN} prints the line where |
1041a570 RP |
3482 | execution in that frame has stopped. You can print other portions of |
3483 | source files by explicit command. | |
70b88761 | 3484 | |
18fae2a8 RP |
3485 | @ifclear DOSHOST |
3486 | If you use @value{GDBN} through its GNU Emacs interface, you may prefer to use | |
3487 | Emacs facilities to view source; @pxref{Emacs, ,Using @value{GDBN} under GNU | |
1041a570 | 3488 | Emacs}. |
18fae2a8 | 3489 | @end ifclear |
70b88761 RP |
3490 | |
3491 | @menu | |
ed447b95 | 3492 | * List:: Printing source lines |
18fae2a8 | 3493 | @ifclear DOSHOST |
ed447b95 | 3494 | * Search:: Searching source files |
18fae2a8 | 3495 | @end ifclear |
b0157555 | 3496 | |
ed447b95 RP |
3497 | * Source Path:: Specifying source directories |
3498 | * Machine Code:: Source and machine code | |
70b88761 RP |
3499 | @end menu |
3500 | ||
4eb4cf57 | 3501 | @node List |
93928b60 | 3502 | @section Printing source lines |
70b88761 RP |
3503 | |
3504 | @kindex list | |
3505 | @kindex l | |
3506 | To print lines from a source file, use the @code{list} command | |
3507 | (abbreviated @code{l}). There are several ways to specify what part | |
3508 | of the file you want to print. | |
3509 | ||
3510 | Here are the forms of the @code{list} command most commonly used: | |
3511 | ||
3512 | @table @code | |
3513 | @item list @var{linenum} | |
c338a2fd | 3514 | Print lines centered around line number @var{linenum} in the |
70b88761 RP |
3515 | current source file. |
3516 | ||
3517 | @item list @var{function} | |
c338a2fd | 3518 | Print lines centered around the beginning of function |
70b88761 RP |
3519 | @var{function}. |
3520 | ||
3521 | @item list | |
c338a2fd RP |
3522 | Print more lines. If the last lines printed were printed with a |
3523 | @code{list} command, this prints lines following the last lines | |
70b88761 | 3524 | printed; however, if the last line printed was a solitary line printed |
29a2b744 | 3525 | as part of displaying a stack frame (@pxref{Stack, ,Examining the |
1041a570 | 3526 | Stack}), this prints lines centered around that line. |
70b88761 RP |
3527 | |
3528 | @item list - | |
c338a2fd RP |
3529 | Print lines just before the lines last printed. |
3530 | @end table | |
3531 | ||
18fae2a8 | 3532 | By default, @value{GDBN} prints ten source lines with any of these forms of |
c338a2fd RP |
3533 | the @code{list} command. You can change this using @code{set listsize}: |
3534 | ||
3535 | @table @code | |
3536 | @item set listsize @var{count} | |
3537 | @kindex set listsize | |
3538 | Make the @code{list} command display @var{count} source lines (unless | |
3539 | the @code{list} argument explicitly specifies some other number). | |
3540 | ||
3541 | @item show listsize | |
3542 | @kindex show listsize | |
9a27b06e | 3543 | Display the number of lines that @code{list} prints. |
70b88761 RP |
3544 | @end table |
3545 | ||
3546 | Repeating a @code{list} command with @key{RET} discards the argument, | |
3547 | so it is equivalent to typing just @code{list}. This is more useful | |
3548 | than listing the same lines again. An exception is made for an | |
3549 | argument of @samp{-}; that argument is preserved in repetition so that | |
3550 | each repetition moves up in the source file. | |
3551 | ||
3552 | @cindex linespec | |
3553 | In general, the @code{list} command expects you to supply zero, one or two | |
3554 | @dfn{linespecs}. Linespecs specify source lines; there are several ways | |
3555 | of writing them but the effect is always to specify some source line. | |
3556 | Here is a complete description of the possible arguments for @code{list}: | |
3557 | ||
3558 | @table @code | |
3559 | @item list @var{linespec} | |
c338a2fd | 3560 | Print lines centered around the line specified by @var{linespec}. |
70b88761 RP |
3561 | |
3562 | @item list @var{first},@var{last} | |
3563 | Print lines from @var{first} to @var{last}. Both arguments are | |
3564 | linespecs. | |
3565 | ||
3566 | @item list ,@var{last} | |
c338a2fd | 3567 | Print lines ending with @var{last}. |
70b88761 RP |
3568 | |
3569 | @item list @var{first}, | |
c338a2fd | 3570 | Print lines starting with @var{first}. |
70b88761 RP |
3571 | |
3572 | @item list + | |
c338a2fd | 3573 | Print lines just after the lines last printed. |
70b88761 RP |
3574 | |
3575 | @item list - | |
c338a2fd | 3576 | Print lines just before the lines last printed. |
70b88761 RP |
3577 | |
3578 | @item list | |
3579 | As described in the preceding table. | |
3580 | @end table | |
3581 | ||
3582 | Here are the ways of specifying a single source line---all the | |
3583 | kinds of linespec. | |
3584 | ||
3585 | @table @code | |
3586 | @item @var{number} | |
3587 | Specifies line @var{number} of the current source file. | |
3588 | When a @code{list} command has two linespecs, this refers to | |
3589 | the same source file as the first linespec. | |
3590 | ||
3591 | @item +@var{offset} | |
3592 | Specifies the line @var{offset} lines after the last line printed. | |
3593 | When used as the second linespec in a @code{list} command that has | |
3594 | two, this specifies the line @var{offset} lines down from the | |
3595 | first linespec. | |
3596 | ||
3597 | @item -@var{offset} | |
3598 | Specifies the line @var{offset} lines before the last line printed. | |
3599 | ||
3600 | @item @var{filename}:@var{number} | |
3601 | Specifies line @var{number} in the source file @var{filename}. | |
3602 | ||
3603 | @item @var{function} | |
3604 | @c FIXME: "of the open-brace" is C-centric. When we add other langs... | |
3605 | Specifies the line of the open-brace that begins the body of the | |
3606 | function @var{function}. | |
3607 | ||
3608 | @item @var{filename}:@var{function} | |
3609 | Specifies the line of the open-brace that begins the body of the | |
3610 | function @var{function} in the file @var{filename}. You only need the | |
3611 | file name with a function name to avoid ambiguity when there are | |
3612 | identically named functions in different source files. | |
3613 | ||
3614 | @item *@var{address} | |
3615 | Specifies the line containing the program address @var{address}. | |
3616 | @var{address} may be any expression. | |
3617 | @end table | |
3618 | ||
18fae2a8 | 3619 | @ifclear DOSHOST |
4eb4cf57 | 3620 | @node Search |
93928b60 | 3621 | @section Searching source files |
70b88761 RP |
3622 | @cindex searching |
3623 | @kindex reverse-search | |
3624 | ||
3625 | There are two commands for searching through the current source file for a | |
3626 | regular expression. | |
3627 | ||
3628 | @table @code | |
3629 | @item forward-search @var{regexp} | |
3630 | @itemx search @var{regexp} | |
3631 | @kindex search | |
3632 | @kindex forward-search | |
1041a570 RP |
3633 | The command @samp{forward-search @var{regexp}} checks each line, |
3634 | starting with the one following the last line listed, for a match for | |
3635 | @var{regexp}. It lists the line that is found. You can use | |
3636 | synonym @samp{search @var{regexp}} or abbreviate the command name as | |
3637 | @code{fo}. | |
70b88761 RP |
3638 | |
3639 | @item reverse-search @var{regexp} | |
3640 | The command @samp{reverse-search @var{regexp}} checks each line, starting | |
3641 | with the one before the last line listed and going backward, for a match | |
3642 | for @var{regexp}. It lists the line that is found. You can abbreviate | |
3643 | this command as @code{rev}. | |
3644 | @end table | |
18fae2a8 | 3645 | @end ifclear |
70b88761 | 3646 | |
4eb4cf57 | 3647 | @node Source Path |
93928b60 | 3648 | @section Specifying source directories |
70b88761 RP |
3649 | |
3650 | @cindex source path | |
3651 | @cindex directories for source files | |
3652 | Executable programs sometimes do not record the directories of the source | |
3653 | files from which they were compiled, just the names. Even when they do, | |
3654 | the directories could be moved between the compilation and your debugging | |
18fae2a8 RP |
3655 | session. @value{GDBN} has a list of directories to search for source files; |
3656 | this is called the @dfn{source path}. Each time @value{GDBN} wants a source file, | |
70b88761 RP |
3657 | it tries all the directories in the list, in the order they are present |
3658 | in the list, until it finds a file with the desired name. Note that | |
3659 | the executable search path is @emph{not} used for this purpose. Neither is | |
3660 | the current working directory, unless it happens to be in the source | |
3661 | path. | |
3662 | ||
9a27b06e RP |
3663 | If @value{GDBN} cannot find a source file in the source path, and the |
3664 | object program records a directory, @value{GDBN} tries that directory | |
3665 | too. If the source path is empty, and there is no record of the | |
3666 | compilation directory, @value{GDBN} looks in the current directory as a | |
3667 | last resort. | |
70b88761 | 3668 | |
9a27b06e | 3669 | Whenever you reset or rearrange the source path, @value{GDBN} clears out |
b1955f0b RP |
3670 | any information it has cached about where source files are found and where |
3671 | each line is in the file. | |
70b88761 RP |
3672 | |
3673 | @kindex directory | |
18fae2a8 | 3674 | When you start @value{GDBN}, its source path is empty. |
70b88761 RP |
3675 | To add other directories, use the @code{directory} command. |
3676 | ||
3677 | @table @code | |
3678 | @item directory @var{dirname} @dots{} | |
3679 | Add directory @var{dirname} to the front of the source path. Several | |
3680 | directory names may be given to this command, separated by @samp{:} or | |
3681 | whitespace. You may specify a directory that is already in the source | |
9a27b06e | 3682 | path; this moves it forward, so @value{GDBN} searches it sooner. |
7463aadd | 3683 | |
fa6df1a7 RP |
3684 | @kindex cdir |
3685 | @kindex cwd | |
a88ec213 RP |
3686 | @kindex $cdir |
3687 | @kindex $cwd | |
fa6df1a7 RP |
3688 | @cindex compilation directory |
3689 | @cindex current directory | |
3690 | @cindex working directory | |
3691 | @cindex directory, current | |
3692 | @cindex directory, compilation | |
7463aadd RP |
3693 | You can use the string @samp{$cdir} to refer to the compilation |
3694 | directory (if one is recorded), and @samp{$cwd} to refer to the current | |
3695 | working directory. @samp{$cwd} is not the same as @samp{.}---the former | |
18fae2a8 | 3696 | tracks the current working directory as it changes during your @value{GDBN} |
7463aadd RP |
3697 | session, while the latter is immediately expanded to the current |
3698 | directory at the time you add an entry to the source path. | |
70b88761 RP |
3699 | |
3700 | @item directory | |
3701 | Reset the source path to empty again. This requires confirmation. | |
3702 | ||
3703 | @c RET-repeat for @code{directory} is explicitly disabled, but since | |
29a2b744 | 3704 | @c repeating it would be a no-op we do not say that. (thanks to RMS) |
70b88761 RP |
3705 | |
3706 | @item show directories | |
3707 | @kindex show directories | |
3708 | Print the source path: show which directories it contains. | |
3709 | @end table | |
3710 | ||
3711 | If your source path is cluttered with directories that are no longer of | |
18fae2a8 | 3712 | interest, @value{GDBN} may sometimes cause confusion by finding the wrong |
70b88761 RP |
3713 | versions of source. You can correct the situation as follows: |
3714 | ||
3715 | @enumerate | |
3716 | @item | |
3717 | Use @code{directory} with no argument to reset the source path to empty. | |
3718 | ||
3719 | @item | |
3720 | Use @code{directory} with suitable arguments to reinstall the | |
3721 | directories you want in the source path. You can add all the | |
3722 | directories in one command. | |
3723 | @end enumerate | |
3724 | ||
4eb4cf57 | 3725 | @node Machine Code |
93928b60 | 3726 | @section Source and machine code |
1041a570 | 3727 | |
70b88761 | 3728 | You can use the command @code{info line} to map source lines to program |
ed447b95 | 3729 | addresses (and vice versa), and the command @code{disassemble} to display |
70b88761 RP |
3730 | a range of addresses as machine instructions. |
3731 | ||
3732 | @table @code | |
3733 | @item info line @var{linespec} | |
3734 | @kindex info line | |
3735 | Print the starting and ending addresses of the compiled code for | |
1041a570 RP |
3736 | source line @var{linespec}. You can specify source lines in any of |
3737 | the ways understood by the @code{list} command (@pxref{List, ,Printing | |
93928b60 | 3738 | source lines}). |
70b88761 RP |
3739 | @end table |
3740 | ||
1041a570 RP |
3741 | For example, we can use @code{info line} to discover the location of |
3742 | the object code for the first line of function | |
3743 | @code{m4_changequote}: | |
3744 | ||
70b88761 | 3745 | @smallexample |
18fae2a8 | 3746 | (@value{GDBP}) info line m4_changecom |
70b88761 RP |
3747 | Line 895 of "builtin.c" starts at pc 0x634c and ends at 0x6350. |
3748 | @end smallexample | |
3749 | ||
3750 | @noindent | |
3751 | We can also inquire (using @code{*@var{addr}} as the form for | |
3752 | @var{linespec}) what source line covers a particular address: | |
3753 | @smallexample | |
18fae2a8 | 3754 | (@value{GDBP}) info line *0x63ff |
70b88761 RP |
3755 | Line 926 of "builtin.c" starts at pc 0x63e4 and ends at 0x6404. |
3756 | @end smallexample | |
3757 | ||
c338a2fd | 3758 | @cindex @code{$_} and @code{info line} |
29a2b744 RP |
3759 | After @code{info line}, the default address for the @code{x} command |
3760 | is changed to the starting address of the line, so that @samp{x/i} is | |
3761 | sufficient to begin examining the machine code (@pxref{Memory, | |
93928b60 | 3762 | ,Examining memory}). Also, this address is saved as the value of the |
29a2b744 | 3763 | convenience variable @code{$_} (@pxref{Convenience Vars, ,Convenience |
93928b60 | 3764 | variables}). |
70b88761 RP |
3765 | |
3766 | @table @code | |
3767 | @kindex disassemble | |
3768 | @item disassemble | |
c5f69ff8 RP |
3769 | @cindex assembly instructions |
3770 | @cindex instructions, assembly | |
3771 | @cindex machine instructions | |
3772 | @cindex listing machine instructions | |
e94b4a2b RP |
3773 | This specialized command dumps a range of memory as machine |
3774 | instructions. The default memory range is the function surrounding the | |
3775 | program counter of the selected frame. A single argument to this | |
9a27b06e RP |
3776 | command is a program counter value; @value{GDBN} dumps the function |
3777 | surrounding this value. Two arguments specify a range of addresses | |
3778 | (first inclusive, second exclusive) to dump. | |
70b88761 RP |
3779 | @end table |
3780 | ||
a64a6c2b | 3781 | @ifclear H8EXCLUSIVE |
70b88761 | 3782 | We can use @code{disassemble} to inspect the object code |
4eb4cf57 RP |
3783 | range shown in the last @code{info line} example (the example |
3784 | shows SPARC machine instructions): | |
70b88761 | 3785 | |
18fae2a8 | 3786 | |
70b88761 | 3787 | @smallexample |
18fae2a8 | 3788 | (@value{GDBP}) disas 0x63e4 0x6404 |
70b88761 | 3789 | Dump of assembler code from 0x63e4 to 0x6404: |
b80282d5 RP |
3790 | 0x63e4 <builtin_init+5340>: ble 0x63f8 <builtin_init+5360> |
3791 | 0x63e8 <builtin_init+5344>: sethi %hi(0x4c00), %o0 | |
3792 | 0x63ec <builtin_init+5348>: ld [%i1+4], %o0 | |
3793 | 0x63f0 <builtin_init+5352>: b 0x63fc <builtin_init+5364> | |
3794 | 0x63f4 <builtin_init+5356>: ld [%o0+4], %o0 | |
3795 | 0x63f8 <builtin_init+5360>: or %o0, 0x1a4, %o0 | |
3796 | 0x63fc <builtin_init+5364>: call 0x9288 <path_search> | |
e251e767 | 3797 | 0x6400 <builtin_init+5368>: nop |
70b88761 | 3798 | End of assembler dump. |
70b88761 | 3799 | @end smallexample |
18fae2a8 | 3800 | @end ifclear |
4eb4cf57 | 3801 | |
a64a6c2b | 3802 | @ifset H8EXCLUSIVE |
4eb4cf57 RP |
3803 | For example, here is the beginning of the output for the |
3804 | disassembly of a function @code{fact}: | |
70b88761 | 3805 | |
18fae2a8 | 3806 | |
4eb4cf57 | 3807 | @smallexample |
18fae2a8 | 3808 | (@value{GDBP}) disas fact |
4eb4cf57 RP |
3809 | Dump of assembler code for function fact: |
3810 | to 0x808c: | |
3811 | 0x802c <fact>: 6d f2 mov.w r2,@@-r7 | |
3812 | 0x802e <fact+2>: 6d f3 mov.w r3,@@-r7 | |
3813 | 0x8030 <fact+4>: 6d f6 mov.w r6,@@-r7 | |
3814 | 0x8032 <fact+6>: 0d 76 mov.w r7,r6 | |
3815 | 0x8034 <fact+8>: 6f 70 00 08 mov.w @@(0x8,r7),r0 | |
3816 | 0x8038 <fact+12> 19 11 sub.w r1,r1 | |
3817 | . | |
3818 | . | |
3819 | . | |
3820 | @end smallexample | |
18fae2a8 | 3821 | @end ifset |
4eb4cf57 RP |
3822 | |
3823 | @node Data | |
70b88761 RP |
3824 | @chapter Examining Data |
3825 | ||
3826 | @cindex printing data | |
3827 | @cindex examining data | |
3828 | @kindex print | |
3829 | @kindex inspect | |
1041a570 | 3830 | @c "inspect" is not quite a synonym if you are using Epoch, which we do not |
29a2b744 | 3831 | @c document because it is nonstandard... Under Epoch it displays in a |
70b88761 RP |
3832 | @c different window or something like that. |
3833 | The usual way to examine data in your program is with the @code{print} | |
4eb4cf57 | 3834 | command (abbreviated @code{p}), or its synonym @code{inspect}. |
18fae2a8 | 3835 | @ifclear CONLY |
4eb4cf57 | 3836 | It evaluates and prints the value of an expression of the language your |
18fae2a8 | 3837 | program is written in (@pxref{Languages, ,Using @value{GDBN} with Different |
4eb4cf57 | 3838 | Languages}). |
18fae2a8 | 3839 | @end ifclear |
70b88761 | 3840 | |
e0dacfd1 RP |
3841 | @table @code |
3842 | @item print @var{exp} | |
3843 | @itemx print /@var{f} @var{exp} | |
93928b60 RP |
3844 | @var{exp} is an expression (in the source language). By default the |
3845 | value of @var{exp} is printed in a format appropriate to its data type; | |
3846 | you can choose a different format by specifying @samp{/@var{f}}, where | |
3847 | @var{f} is a letter specifying the format; @pxref{Output Formats,,Output | |
3848 | formats}. | |
e0dacfd1 RP |
3849 | |
3850 | @item print | |
3851 | @itemx print /@var{f} | |
18fae2a8 | 3852 | If you omit @var{exp}, @value{GDBN} displays the last value again (from the |
93928b60 | 3853 | @dfn{value history}; @pxref{Value History, ,Value history}). This allows you to |
e0dacfd1 RP |
3854 | conveniently inspect the same value in an alternative format. |
3855 | @end table | |
70b88761 RP |
3856 | |
3857 | A more low-level way of examining data is with the @code{x} command. | |
3858 | It examines data in memory at a specified address and prints it in a | |
93928b60 | 3859 | specified format. @xref{Memory, ,Examining memory}. |
70b88761 | 3860 | |
29a2b744 | 3861 | If you are interested in information about types, or about how the fields |
1d7c3357 RP |
3862 | of a struct |
3863 | @ifclear CONLY | |
3864 | or class | |
18fae2a8 | 3865 | @end ifclear |
1d7c3357 RP |
3866 | are declared, use the @code{ptype @var{exp}} |
3867 | command rather than @code{print}. @xref{Symbols, ,Examining the Symbol Table}. | |
18fae2a8 | 3868 | |
70b88761 | 3869 | @menu |
b80282d5 | 3870 | * Expressions:: Expressions |
ed447b95 RP |
3871 | * Variables:: Program variables |
3872 | * Arrays:: Artificial arrays | |
eb7faec1 | 3873 | * Output Formats:: Output formats |
ed447b95 RP |
3874 | * Memory:: Examining memory |
3875 | * Auto Display:: Automatic display | |
3876 | * Print Settings:: Print settings | |
3877 | * Value History:: Value history | |
3878 | * Convenience Vars:: Convenience variables | |
b80282d5 | 3879 | * Registers:: Registers |
a64a6c2b | 3880 | @ifclear HAVE-FLOAT |
ed447b95 | 3881 | * Floating Point Hardware:: Floating point hardware |
18fae2a8 | 3882 | @end ifclear |
18fae2a8 | 3883 | @end menu |
70b88761 | 3884 | |
4eb4cf57 | 3885 | @node Expressions |
70b88761 RP |
3886 | @section Expressions |
3887 | ||
3888 | @cindex expressions | |
18fae2a8 | 3889 | @code{print} and many other @value{GDBN} commands accept an expression and |
70b88761 | 3890 | compute its value. Any kind of constant, variable or operator defined |
fe715d06 | 3891 | by the programming language you are using is valid in an expression in |
18fae2a8 | 3892 | @value{GDBN}. This includes conditional expressions, function calls, casts |
70b88761 | 3893 | and string constants. It unfortunately does not include symbols defined |
b80282d5 | 3894 | by preprocessor @code{#define} commands. |
70b88761 | 3895 | |
18fae2a8 | 3896 | @ifclear CONLY |
c2bbbb22 | 3897 | Because C is so widespread, most of the expressions shown in examples in |
18fae2a8 | 3898 | this manual are in C. @xref{Languages, , Using @value{GDBN} with Different |
c2bbbb22 | 3899 | Languages}, for information on how to use expressions in other |
e251e767 | 3900 | languages. |
c2bbbb22 | 3901 | |
18fae2a8 | 3902 | In this section, we discuss operators that you can use in @value{GDBN} |
e251e767 | 3903 | expressions regardless of your programming language. |
c2bbbb22 | 3904 | |
70b88761 RP |
3905 | Casts are supported in all languages, not just in C, because it is so |
3906 | useful to cast a number into a pointer so as to examine a structure | |
3907 | at that address in memory. | |
c2bbbb22 | 3908 | @c FIXME: casts supported---Mod2 true? |
18fae2a8 | 3909 | @end ifclear |
70b88761 | 3910 | |
18fae2a8 | 3911 | @value{GDBN} supports these operators in addition to those of programming |
70b88761 RP |
3912 | languages: |
3913 | ||
3914 | @table @code | |
3915 | @item @@ | |
3916 | @samp{@@} is a binary operator for treating parts of memory as arrays. | |
93928b60 | 3917 | @xref{Arrays, ,Artificial arrays}, for more information. |
70b88761 RP |
3918 | |
3919 | @item :: | |
3920 | @samp{::} allows you to specify a variable in terms of the file or | |
93928b60 | 3921 | function where it is defined. @xref{Variables, ,Program variables}. |
70b88761 RP |
3922 | |
3923 | @item @{@var{type}@} @var{addr} | |
fe715d06 RP |
3924 | @cindex @{@var{type}@} |
3925 | @cindex type casting memory | |
3926 | @cindex memory, viewing as typed object | |
3927 | @cindex casts, to view memory | |
70b88761 RP |
3928 | Refers to an object of type @var{type} stored at address @var{addr} in |
3929 | memory. @var{addr} may be any expression whose value is an integer or | |
3930 | pointer (but parentheses are required around binary operators, just as in | |
3931 | a cast). This construct is allowed regardless of what kind of data is | |
1041a570 | 3932 | normally supposed to reside at @var{addr}. |
70b88761 RP |
3933 | @end table |
3934 | ||
4eb4cf57 | 3935 | @node Variables |
93928b60 | 3936 | @section Program variables |
70b88761 RP |
3937 | |
3938 | The most common kind of expression to use is the name of a variable | |
3939 | in your program. | |
3940 | ||
3941 | Variables in expressions are understood in the selected stack frame | |
93928b60 | 3942 | (@pxref{Selection, ,Selecting a frame}); they must either be global |
29a2b744 RP |
3943 | (or static) or be visible according to the scope rules of the |
3944 | programming language from the point of execution in that frame. This | |
3945 | means that in the function | |
70b88761 RP |
3946 | |
3947 | @example | |
3948 | foo (a) | |
3949 | int a; | |
3950 | @{ | |
3951 | bar (a); | |
3952 | @{ | |
3953 | int b = test (); | |
3954 | bar (b); | |
3955 | @} | |
3956 | @} | |
3957 | @end example | |
3958 | ||
3959 | @noindent | |
ed447b95 RP |
3960 | you can examine and use the variable @code{a} whenever your program is |
3961 | executing within the function @code{foo}, but you can only use or | |
3962 | examine the variable @code{b} while your program is executing inside | |
3963 | the block where @code{b} is declared. | |
70b88761 RP |
3964 | |
3965 | @cindex variable name conflict | |
3966 | There is an exception: you can refer to a variable or function whose | |
3967 | scope is a single source file even if the current execution point is not | |
3968 | in this file. But it is possible to have more than one such variable or | |
6ca72cc6 RP |
3969 | function with the same name (in different source files). If that |
3970 | happens, referring to that name has unpredictable effects. If you wish, | |
3971 | you can specify a static variable in a particular function or file, | |
3972 | using the colon-colon notation: | |
70b88761 RP |
3973 | |
3974 | @cindex colon-colon | |
a6d0b6d3 | 3975 | @iftex |
29a2b744 | 3976 | @c info cannot cope with a :: index entry, but why deprive hard copy readers? |
70b88761 | 3977 | @kindex :: |
a6d0b6d3 | 3978 | @end iftex |
70b88761 RP |
3979 | @example |
3980 | @var{file}::@var{variable} | |
6ca72cc6 | 3981 | @var{function}::@var{variable} |
70b88761 RP |
3982 | @end example |
3983 | ||
3984 | @noindent | |
6ca72cc6 | 3985 | Here @var{file} or @var{function} is the name of the context for the |
6c380b13 | 3986 | static @var{variable}. In the case of file names, you can use quotes to |
18fae2a8 | 3987 | make sure @value{GDBN} parses the file name as a single word---for example, |
6c380b13 RP |
3988 | to print a global value of @code{x} defined in @file{f2.c}: |
3989 | ||
3990 | @example | |
18fae2a8 | 3991 | (@value{GDBP}) p 'f2.c'::x |
6c380b13 | 3992 | @end example |
70b88761 | 3993 | |
18fae2a8 | 3994 | @ifclear CONLY |
c2bbbb22 | 3995 | @cindex C++ scope resolution |
70b88761 | 3996 | This use of @samp{::} is very rarely in conflict with the very similar |
18fae2a8 RP |
3997 | use of the same notation in C++. @value{GDBN} also supports use of the C++ |
3998 | scope resolution operator in @value{GDBN} expressions. | |
ed447b95 RP |
3999 | @c FIXME: Um, so what happens in one of those rare cases where it's in |
4000 | @c conflict?? --mew | |
18fae2a8 | 4001 | @end ifclear |
70b88761 | 4002 | |
3d3ab540 RP |
4003 | @cindex wrong values |
4004 | @cindex variable values, wrong | |
4005 | @quotation | |
4006 | @emph{Warning:} Occasionally, a local variable may appear to have the | |
b0157555 RP |
4007 | wrong value at certain points in a function---just after entry to a new |
4008 | scope, and just before exit. | |
3d3ab540 | 4009 | @end quotation |
b0157555 RP |
4010 | You may see this problem when you are stepping by machine instructions. |
4011 | This is because on most machines, it takes more than one instruction to | |
4012 | set up a stack frame (including local variable definitions); if you are | |
4013 | stepping by machine instructions, variables may appear to have the wrong | |
4014 | values until the stack frame is completely built. On exit, it usually | |
4015 | also takes more than one machine instruction to destroy a stack frame; | |
4016 | after you begin stepping through that group of instructions, local | |
4017 | variable definitions may be gone. | |
3d3ab540 | 4018 | |
4eb4cf57 | 4019 | @node Arrays |
93928b60 | 4020 | @section Artificial arrays |
70b88761 RP |
4021 | |
4022 | @cindex artificial array | |
4023 | @kindex @@ | |
4024 | It is often useful to print out several successive objects of the | |
4025 | same type in memory; a section of an array, or an array of | |
4026 | dynamically determined size for which only a pointer exists in the | |
4027 | program. | |
4028 | ||
fe715d06 RP |
4029 | You can do this by referring to a contiguous span of memory as an |
4030 | @dfn{artificial array}, using the binary operator @samp{@@}. The left | |
4031 | operand of @samp{@@} should be the first element of the desired array, | |
4032 | as an individual object. The right operand should be the desired length | |
4033 | of the array. The result is an array value whose elements are all of | |
4034 | the type of the left argument. The first element is actually the left | |
4035 | argument; the second element comes from bytes of memory immediately | |
4036 | following those that hold the first element, and so on. Here is an | |
4037 | example. If a program says | |
70b88761 RP |
4038 | |
4039 | @example | |
4040 | int *array = (int *) malloc (len * sizeof (int)); | |
4041 | @end example | |
4042 | ||
4043 | @noindent | |
4044 | you can print the contents of @code{array} with | |
4045 | ||
4046 | @example | |
4047 | p *array@@len | |
4048 | @end example | |
4049 | ||
4050 | The left operand of @samp{@@} must reside in memory. Array values made | |
4051 | with @samp{@@} in this way behave just like other arrays in terms of | |
4052 | subscripting, and are coerced to pointers when used in expressions. | |
4053 | Artificial arrays most often appear in expressions via the value history | |
7640fe71 | 4054 | (@pxref{Value History, ,Value history}), after printing one out. |
70b88761 | 4055 | |
1041a570 | 4056 | Sometimes the artificial array mechanism is not quite enough; in |
3d3ab540 | 4057 | moderately complex data structures, the elements of interest may not |
1041a570 RP |
4058 | actually be adjacent---for example, if you are interested in the values |
4059 | of pointers in an array. One useful work-around in this situation is | |
4060 | to use a convenience variable (@pxref{Convenience Vars, ,Convenience | |
93928b60 | 4061 | variables}) as a counter in an expression that prints the first |
1041a570 RP |
4062 | interesting value, and then repeat that expression via @key{RET}. For |
4063 | instance, suppose you have an array @code{dtab} of pointers to | |
4064 | structures, and you are interested in the values of a field @code{fv} | |
4065 | in each structure. Here is an example of what you might type: | |
4066 | ||
3d3ab540 RP |
4067 | @example |
4068 | set $i = 0 | |
4069 | p dtab[$i++]->fv | |
4070 | @key{RET} | |
4071 | @key{RET} | |
4072 | @dots{} | |
4073 | @end example | |
4074 | ||
ed447b95 | 4075 | @node Output Formats |
70b88761 RP |
4076 | @section Output formats |
4077 | ||
4078 | @cindex formatted output | |
4079 | @cindex output formats | |
18fae2a8 | 4080 | By default, @value{GDBN} prints a value according to its data type. Sometimes |
70b88761 RP |
4081 | this is not what you want. For example, you might want to print a number |
4082 | in hex, or a pointer in decimal. Or you might want to view data in memory | |
4083 | at a certain address as a character string or as an instruction. To do | |
4084 | these things, specify an @dfn{output format} when you print a value. | |
4085 | ||
4086 | The simplest use of output formats is to say how to print a value | |
4087 | already computed. This is done by starting the arguments of the | |
4088 | @code{print} command with a slash and a format letter. The format | |
4089 | letters supported are: | |
4090 | ||
4091 | @table @code | |
4092 | @item x | |
4093 | Regard the bits of the value as an integer, and print the integer in | |
4094 | hexadecimal. | |
4095 | ||
4096 | @item d | |
4097 | Print as integer in signed decimal. | |
4098 | ||
4099 | @item u | |
4100 | Print as integer in unsigned decimal. | |
4101 | ||
4102 | @item o | |
4103 | Print as integer in octal. | |
4104 | ||
4105 | @item t | |
4106 | Print as integer in binary. The letter @samp{t} stands for ``two''. | |
fe715d06 RP |
4107 | @footnote{@samp{b} cannot be used because these format letters are also |
4108 | used with the @code{x} command, where @samp{b} stands for ``byte''; | |
4109 | @pxref{Memory,,Examining memory}.} | |
70b88761 RP |
4110 | |
4111 | @item a | |
9a27b06e RP |
4112 | @cindex unknown address, locating |
4113 | Print as an address, both absolute in hexadecimal and as an offset from | |
4114 | the nearest preceding symbol. You can use this format used to discover | |
4115 | where (in what function) an unknown address is located: | |
1041a570 | 4116 | |
70b88761 | 4117 | @example |
18fae2a8 RP |
4118 | (@value{GDBP}) p/a 0x54320 |
4119 | $3 = 0x54320 <_initialize_vx+396> | |
70b88761 RP |
4120 | @end example |
4121 | ||
70b88761 RP |
4122 | @item c |
4123 | Regard as an integer and print it as a character constant. | |
4124 | ||
4125 | @item f | |
4126 | Regard the bits of the value as a floating point number and print | |
4127 | using typical floating point syntax. | |
4128 | @end table | |
4129 | ||
4130 | For example, to print the program counter in hex (@pxref{Registers}), type | |
4131 | ||
4132 | @example | |
4133 | p/x $pc | |
4134 | @end example | |
4135 | ||
4136 | @noindent | |
4137 | Note that no space is required before the slash; this is because command | |
18fae2a8 | 4138 | names in @value{GDBN} cannot contain a slash. |
70b88761 RP |
4139 | |
4140 | To reprint the last value in the value history with a different format, | |
4141 | you can use the @code{print} command with just a format and no | |
4142 | expression. For example, @samp{p/x} reprints the last value in hex. | |
4143 | ||
4eb4cf57 | 4144 | @node Memory |
93928b60 | 4145 | @section Examining memory |
70b88761 | 4146 | |
1041a570 RP |
4147 | You can use the command @code{x} (for ``examine'') to examine memory in |
4148 | any of several formats, independently of your program's data types. | |
4149 | ||
70b88761 RP |
4150 | @cindex examining memory |
4151 | @table @code | |
4152 | @kindex x | |
cedaf8bc RP |
4153 | @item x/@var{nfu} @var{addr} |
4154 | @itemx x @var{addr} | |
4155 | @itemx x | |
ed447b95 | 4156 | Use the @code{x} command to examine memory. |
1041a570 RP |
4157 | @end table |
4158 | ||
4159 | @var{n}, @var{f}, and @var{u} are all optional parameters that specify how | |
4160 | much memory to display and how to format it; @var{addr} is an | |
cedaf8bc RP |
4161 | expression giving the address where you want to start displaying memory. |
4162 | If you use defaults for @var{nfu}, you need not type the slash @samp{/}. | |
4163 | Several commands set convenient defaults for @var{addr}. | |
70b88761 | 4164 | |
1041a570 RP |
4165 | @table @r |
4166 | @item @var{n}, the repeat count | |
4167 | The repeat count is a decimal integer; the default is 1. It specifies | |
4168 | how much memory (counting by units @var{u}) to display. | |
cedaf8bc RP |
4169 | @c This really is **decimal**; unaffected by 'set radix' as of GDB |
4170 | @c 4.1.2. | |
70b88761 | 4171 | |
1041a570 RP |
4172 | @item @var{f}, the display format |
4173 | The display format is one of the formats used by @code{print}, | |
cedaf8bc RP |
4174 | or @samp{s} (null-terminated string) or @samp{i} (machine instruction). |
4175 | The default is @samp{x} (hexadecimal) initially, or the format from the | |
4176 | last time you used either @code{x} or @code{print}. | |
70b88761 | 4177 | |
1041a570 RP |
4178 | @item @var{u}, the unit size |
4179 | The unit size is any of | |
ed447b95 | 4180 | |
70b88761 RP |
4181 | @table @code |
4182 | @item b | |
cedaf8bc | 4183 | Bytes. |
70b88761 | 4184 | @item h |
cedaf8bc | 4185 | Halfwords (two bytes). |
70b88761 | 4186 | @item w |
cedaf8bc | 4187 | Words (four bytes). This is the initial default. |
70b88761 | 4188 | @item g |
cedaf8bc | 4189 | Giant words (eight bytes). |
70b88761 RP |
4190 | @end table |
4191 | ||
cedaf8bc RP |
4192 | Each time you specify a unit size with @code{x}, that size becomes the |
4193 | default unit the next time you use @code{x}. (For the @samp{s} and | |
4194 | @samp{i} formats, the unit size is ignored and is normally not written.) | |
4195 | ||
1041a570 | 4196 | @item @var{addr}, starting display address |
18fae2a8 | 4197 | @var{addr} is the address where you want @value{GDBN} to begin displaying |
cedaf8bc RP |
4198 | memory. The expression need not have a pointer value (though it may); |
4199 | it is always interpreted as an integer address of a byte of memory. | |
1041a570 | 4200 | @xref{Expressions, ,Expressions}, for more information on expressions. The default for |
cedaf8bc RP |
4201 | @var{addr} is usually just after the last address examined---but several |
4202 | other commands also set the default address: @code{info breakpoints} (to | |
4203 | the address of the last breakpoint listed), @code{info line} (to the | |
4204 | starting address of a line), and @code{print} (if you use it to display | |
4205 | a value from memory). | |
1041a570 | 4206 | @end table |
70b88761 | 4207 | |
cedaf8bc RP |
4208 | For example, @samp{x/3uh 0x54320} is a request to display three halfwords |
4209 | (@code{h}) of memory, formatted as unsigned decimal integers (@samp{u}), | |
4210 | starting at address @code{0x54320}. @samp{x/4xw $sp} prints the four | |
4211 | words (@samp{w}) of memory above the stack pointer (here, @samp{$sp}; | |
4212 | @pxref{Registers}) in hexadecimal (@samp{x}). | |
70b88761 | 4213 | |
cedaf8bc | 4214 | Since the letters indicating unit sizes are all distinct from the |
29a2b744 | 4215 | letters specifying output formats, you do not have to remember whether |
9a27b06e | 4216 | unit size or format comes first; either order works. The output |
cedaf8bc | 4217 | specifications @samp{4xw} and @samp{4wx} mean exactly the same thing. |
9a27b06e | 4218 | (However, the count @var{n} must come first; @samp{wx4} does not work.) |
cedaf8bc RP |
4219 | |
4220 | Even though the unit size @var{u} is ignored for the formats @samp{s} | |
4221 | and @samp{i}, you might still want to use a count @var{n}; for example, | |
4222 | @samp{3i} specifies that you want to see three machine instructions, | |
4223 | including any operands. The command @code{disassemble} gives an | |
4224 | alternative way of inspecting machine instructions; @pxref{Machine | |
93928b60 | 4225 | Code,,Source and machine code}. |
cedaf8bc RP |
4226 | |
4227 | All the defaults for the arguments to @code{x} are designed to make it | |
4228 | easy to continue scanning memory with minimal specifications each time | |
1041a570 | 4229 | you use @code{x}. For example, after you have inspected three machine |
cedaf8bc RP |
4230 | instructions with @samp{x/3i @var{addr}}, you can inspect the next seven |
4231 | with just @samp{x/7}. If you use @key{RET} to repeat the @code{x} command, | |
4232 | the repeat count @var{n} is used again; the other arguments default as | |
4233 | for successive uses of @code{x}. | |
70b88761 | 4234 | |
c338a2fd | 4235 | @cindex @code{$_}, @code{$__}, and value history |
cedaf8bc | 4236 | The addresses and contents printed by the @code{x} command are not saved |
70b88761 | 4237 | in the value history because there is often too much of them and they |
18fae2a8 | 4238 | would get in the way. Instead, @value{GDBN} makes these values available for |
70b88761 RP |
4239 | subsequent use in expressions as values of the convenience variables |
4240 | @code{$_} and @code{$__}. After an @code{x} command, the last address | |
4241 | examined is available for use in expressions in the convenience variable | |
4242 | @code{$_}. The contents of that address, as examined, are available in | |
4243 | the convenience variable @code{$__}. | |
4244 | ||
4245 | If the @code{x} command has a repeat count, the address and contents saved | |
4246 | are from the last memory unit printed; this is not the same as the last | |
4247 | address printed if several units were printed on the last line of output. | |
4248 | ||
4eb4cf57 | 4249 | @node Auto Display |
93928b60 | 4250 | @section Automatic display |
70b88761 RP |
4251 | @cindex automatic display |
4252 | @cindex display of expressions | |
4253 | ||
4254 | If you find that you want to print the value of an expression frequently | |
4255 | (to see how it changes), you might want to add it to the @dfn{automatic | |
9a27b06e | 4256 | display list} so that @value{GDBN} prints its value each time your program stops. |
70b88761 RP |
4257 | Each expression added to the list is given a number to identify it; |
4258 | to remove an expression from the list, you specify that number. | |
4259 | The automatic display looks like this: | |
4260 | ||
4261 | @example | |
4262 | 2: foo = 38 | |
4263 | 3: bar[5] = (struct hack *) 0x3804 | |
4264 | @end example | |
4265 | ||
4266 | @noindent | |
ed447b95 | 4267 | This display shows item numbers, expressions and their current values. As with |
70b88761 RP |
4268 | displays you request manually using @code{x} or @code{print}, you can |
4269 | specify the output format you prefer; in fact, @code{display} decides | |
4270 | whether to use @code{print} or @code{x} depending on how elaborate your | |
4271 | format specification is---it uses @code{x} if you specify a unit size, | |
4272 | or one of the two formats (@samp{i} and @samp{s}) that are only | |
4273 | supported by @code{x}; otherwise it uses @code{print}. | |
4274 | ||
4275 | @table @code | |
4276 | @item display @var{exp} | |
4277 | @kindex display | |
4278 | Add the expression @var{exp} to the list of expressions to display | |
1041a570 | 4279 | each time your program stops. @xref{Expressions, ,Expressions}. |
70b88761 | 4280 | |
9a27b06e | 4281 | @code{display} does not repeat if you press @key{RET} again after using it. |
70b88761 RP |
4282 | |
4283 | @item display/@var{fmt} @var{exp} | |
4284 | For @var{fmt} specifying only a display format and not a size or | |
4285 | count, add the expression @var{exp} to the auto-display list but | |
7640fe71 | 4286 | arrange to display it each time in the specified format @var{fmt}. |
ed447b95 | 4287 | @xref{Output Formats,,Output formats}. |
70b88761 RP |
4288 | |
4289 | @item display/@var{fmt} @var{addr} | |
4290 | For @var{fmt} @samp{i} or @samp{s}, or including a unit-size or a | |
4291 | number of units, add the expression @var{addr} as a memory address to | |
29a2b744 | 4292 | be examined each time your program stops. Examining means in effect |
93928b60 | 4293 | doing @samp{x/@var{fmt} @var{addr}}. @xref{Memory, ,Examining memory}. |
70b88761 RP |
4294 | @end table |
4295 | ||
4296 | For example, @samp{display/i $pc} can be helpful, to see the machine | |
4297 | instruction about to be executed each time execution stops (@samp{$pc} | |
4298 | is a common name for the program counter; @pxref{Registers}). | |
4299 | ||
4300 | @table @code | |
4301 | @item undisplay @var{dnums}@dots{} | |
4302 | @itemx delete display @var{dnums}@dots{} | |
4303 | @kindex delete display | |
4304 | @kindex undisplay | |
4305 | Remove item numbers @var{dnums} from the list of expressions to display. | |
4306 | ||
9a27b06e | 4307 | @code{undisplay} does not repeat if you press @key{RET} after using it. |
70b88761 RP |
4308 | (Otherwise you would just get the error @samp{No display number @dots{}}.) |
4309 | ||
4310 | @item disable display @var{dnums}@dots{} | |
4311 | @kindex disable display | |
4312 | Disable the display of item numbers @var{dnums}. A disabled display | |
4313 | item is not printed automatically, but is not forgotten. It may be | |
4314 | enabled again later. | |
4315 | ||
4316 | @item enable display @var{dnums}@dots{} | |
4317 | @kindex enable display | |
4318 | Enable display of item numbers @var{dnums}. It becomes effective once | |
4319 | again in auto display of its expression, until you specify otherwise. | |
4320 | ||
4321 | @item display | |
4322 | Display the current values of the expressions on the list, just as is | |
29a2b744 | 4323 | done when your program stops. |
70b88761 RP |
4324 | |
4325 | @item info display | |
4326 | @kindex info display | |
4327 | Print the list of expressions previously set up to display | |
4328 | automatically, each one with its item number, but without showing the | |
4329 | values. This includes disabled expressions, which are marked as such. | |
4330 | It also includes expressions which would not be displayed right now | |
4331 | because they refer to automatic variables not currently available. | |
4332 | @end table | |
4333 | ||
4334 | If a display expression refers to local variables, then it does not make | |
4335 | sense outside the lexical context for which it was set up. Such an | |
4336 | expression is disabled when execution enters a context where one of its | |
4337 | variables is not defined. For example, if you give the command | |
4338 | @code{display last_char} while inside a function with an argument | |
9a27b06e | 4339 | @code{last_char}, @value{GDBN} displays this argument while your program |
70b88761 | 4340 | continues to stop inside that function. When it stops elsewhere---where |
9a27b06e RP |
4341 | there is no variable @code{last_char}---the display is disabled |
4342 | automatically. The next time your program stops where @code{last_char} | |
4343 | is meaningful, you can enable the display expression once again. | |
70b88761 | 4344 | |
4eb4cf57 | 4345 | @node Print Settings |
93928b60 | 4346 | @section Print settings |
70b88761 RP |
4347 | |
4348 | @cindex format options | |
4349 | @cindex print settings | |
18fae2a8 | 4350 | @value{GDBN} provides the following ways to control how arrays, structures, |
e251e767 | 4351 | and symbols are printed. |
70b88761 RP |
4352 | |
4353 | @noindent | |
4354 | These settings are useful for debugging programs in any language: | |
4355 | ||
4356 | @table @code | |
4357 | @item set print address | |
6b51acad | 4358 | @itemx set print address on |
70b88761 | 4359 | @kindex set print address |
9a27b06e | 4360 | @value{GDBN} prints memory addresses showing the location of stack |
70b88761 RP |
4361 | traces, structure values, pointer values, breakpoints, and so forth, |
4362 | even when it also displays the contents of those addresses. The default | |
9a27b06e | 4363 | is @code{on}. For example, this is what a stack frame display looks like, with |
70b88761 | 4364 | @code{set print address on}: |
1041a570 | 4365 | |
70b88761 | 4366 | @smallexample |
1041a570 | 4367 | @group |
18fae2a8 | 4368 | (@value{GDBP}) f |
e251e767 | 4369 | #0 set_quotes (lq=0x34c78 "<<", rq=0x34c88 ">>") |
70b88761 | 4370 | at input.c:530 |
b80282d5 | 4371 | 530 if (lquote != def_lquote) |
1041a570 | 4372 | @end group |
70b88761 RP |
4373 | @end smallexample |
4374 | ||
4375 | @item set print address off | |
4376 | Do not print addresses when displaying their contents. For example, | |
4377 | this is the same stack frame displayed with @code{set print address off}: | |
1041a570 | 4378 | |
d55320a0 | 4379 | @smallexample |
1041a570 | 4380 | @group |
18fae2a8 RP |
4381 | (@value{GDBP}) set print addr off |
4382 | (@value{GDBP}) f | |
70b88761 | 4383 | #0 set_quotes (lq="<<", rq=">>") at input.c:530 |
b80282d5 | 4384 | 530 if (lquote != def_lquote) |
1041a570 | 4385 | @end group |
d55320a0 | 4386 | @end smallexample |
70b88761 | 4387 | |
fe715d06 RP |
4388 | You can use @samp{set print address off} to eliminate all machine |
4389 | dependent displays from the @value{GDBN} interface. For example, with | |
4390 | @code{print address off}, you should get the same text for backtraces on | |
4391 | all machines---whether or not they involve pointer arguments. | |
4392 | ||
70b88761 RP |
4393 | @item show print address |
4394 | @kindex show print address | |
4395 | Show whether or not addresses are to be printed. | |
14621224 JK |
4396 | @end table |
4397 | ||
4398 | When @value{GDBN} prints a symbolic address, it normally prints the | |
4399 | closest earlier symbol plus an offset. If that symbol does not uniquely | |
4400 | identify the address (for example, it is a name whose scope is a single | |
4401 | source file), you may need to disambiguate. One way to do this is with | |
9a27b06e | 4402 | @code{info line}, for example @samp{info line *0x4537}. Alternately, |
14621224 JK |
4403 | you can set @value{GDBN} to print the source file and line number when |
4404 | it prints a symbolic address: | |
4405 | ||
4406 | @table @code | |
4407 | @item set print symbol-filename on | |
4408 | @kindex set print symbol-filename | |
4409 | Tell @value{GDBN} to print the source file name and line number of a | |
4410 | symbol in the symbolic form of an address. | |
4411 | ||
4412 | @item set print symbol-filename off | |
4413 | Do not print source file name and line number of a symbol. This is the | |
4414 | default. | |
4415 | ||
4416 | @item show print symbol-filename | |
4417 | @kindex show print symbol-filename | |
4418 | Show whether or not @value{GDBN} will print the source file name and | |
4419 | line number of a symbol in the symbolic form of an address. | |
4420 | @end table | |
4421 | ||
9a27b06e RP |
4422 | Another situation where it is helpful to show symbol filenames and line |
4423 | numbers is when disassembling code; @value{GDBN} shows you the line | |
5986c8ea JG |
4424 | number and source file that corresponds to each instruction. |
4425 | ||
14621224 JK |
4426 | Also, you may wish to see the symbolic form only if the address being |
4427 | printed is reasonably close to the closest earlier symbol: | |
4428 | ||
4429 | @table @code | |
4430 | @item set print max-symbolic-offset @var{max-offset} | |
4431 | @kindex set print max-symbolic-offset | |
4432 | Tell @value{GDBN} to only display the symbolic form of an address if the | |
4433 | offset between the closest earlier symbol and the address is less than | |
4434 | @var{max-offset}. The default is 0, which means to always print the | |
4435 | symbolic form of an address, if any symbol precedes it. | |
4436 | ||
4437 | @item show print max-symbolic-offset | |
4438 | @kindex show print max-symbolic-offset | |
9a27b06e | 4439 | Ask how large the maximum offset is that @value{GDBN} prints in a |
14621224 JK |
4440 | symbolic address. |
4441 | @end table | |
70b88761 | 4442 | |
9a27b06e RP |
4443 | @cindex wild pointer, interpreting |
4444 | @cindex pointer, finding referent | |
4445 | If you have a pointer and you are not sure where it points, try | |
ec35141c JK |
4446 | @samp{set print symbol-filename on}. Then you can determine the name |
4447 | and source file location of the variable where it points, using | |
4448 | @samp{p/a @var{pointer}}. This interprets the address in symbolic form. | |
4449 | For example, here @value{GDBN} shows that a variable @code{ptt} points | |
4450 | at another variable @code{t}, defined in @file{hi2.c}: | |
9a27b06e RP |
4451 | |
4452 | @example | |
9a27b06e RP |
4453 | (@value{GDBP}) set print symbol-filename on |
4454 | (@value{GDBP}) p/a ptt | |
4455 | $4 = 0xe008 <t in hi2.c> | |
4456 | @end example | |
4457 | ||
4458 | @quotation | |
4459 | @emph{Warning:} For pointers that point to a local variable, @samp{p/a} | |
4460 | does not show the symbol name and filename of the referent, even with | |
4461 | the appropriate @code{set print} options turned on. | |
4462 | @end quotation | |
4463 | ||
5986c8ea JG |
4464 | Other settings control how different kinds of objects are printed: |
4465 | ||
14621224 | 4466 | @table @code |
70b88761 RP |
4467 | @item set print array |
4468 | @itemx set print array on | |
4469 | @kindex set print array | |
9a27b06e | 4470 | Pretty-print arrays. This format is more convenient to read, |
70b88761 RP |
4471 | but uses more space. The default is off. |
4472 | ||
fe715d06 | 4473 | @item set print array off |
70b88761 RP |
4474 | Return to compressed format for arrays. |
4475 | ||
4476 | @item show print array | |
4477 | @kindex show print array | |
4478 | Show whether compressed or pretty format is selected for displaying | |
e251e767 | 4479 | arrays. |
70b88761 RP |
4480 | |
4481 | @item set print elements @var{number-of-elements} | |
4482 | @kindex set print elements | |
9a27b06e | 4483 | If @value{GDBN} is printing a large array, it stops printing after it has |
70b88761 RP |
4484 | printed the number of elements set by the @code{set print elements} command. |
4485 | This limit also applies to the display of strings. | |
6edfa487 | 4486 | Setting the number of elements to zero means that the printing is unlimited. |
70b88761 RP |
4487 | |
4488 | @item show print elements | |
4489 | @kindex show print elements | |
9a27b06e | 4490 | Display the number of elements of a large array that @value{GDBN} prints |
70b88761 RP |
4491 | before losing patience. |
4492 | ||
4493 | @item set print pretty on | |
4494 | @kindex set print pretty | |
18fae2a8 | 4495 | Cause @value{GDBN} to print structures in an indented format with one member per |
70b88761 RP |
4496 | line, like this: |
4497 | ||
d55320a0 | 4498 | @smallexample |
1041a570 | 4499 | @group |
70b88761 RP |
4500 | $1 = @{ |
4501 | next = 0x0, | |
4502 | flags = @{ | |
4503 | sweet = 1, | |
4504 | sour = 1 | |
4505 | @}, | |
4506 | meat = 0x54 "Pork" | |
4507 | @} | |
1041a570 | 4508 | @end group |
d55320a0 | 4509 | @end smallexample |
70b88761 RP |
4510 | |
4511 | @item set print pretty off | |
18fae2a8 | 4512 | Cause @value{GDBN} to print structures in a compact format, like this: |
70b88761 RP |
4513 | |
4514 | @smallexample | |
1041a570 | 4515 | @group |
38962738 RP |
4516 | $1 = @{next = 0x0, flags = @{sweet = 1, sour = 1@}, \ |
4517 | meat = 0x54 "Pork"@} | |
1041a570 | 4518 | @end group |
70b88761 RP |
4519 | @end smallexample |
4520 | ||
4521 | @noindent | |
4522 | This is the default format. | |
4523 | ||
4524 | @item show print pretty | |
4525 | @kindex show print pretty | |
9a27b06e | 4526 | Show which format @value{GDBN} is using to print structures. |
70b88761 RP |
4527 | |
4528 | @item set print sevenbit-strings on | |
f2857bd9 | 4529 | @kindex set print sevenbit-strings |
e251e767 | 4530 | Print using only seven-bit characters; if this option is set, |
9a27b06e RP |
4531 | @value{GDBN} displays any eight-bit characters (in strings or |
4532 | character values) using the notation @code{\}@var{nnn}. This setting is | |
4533 | best if you are working in English (@sc{ascii}) and you use the | |
4534 | high-order bit of characters as a marker or ``meta'' bit. | |
70b88761 RP |
4535 | |
4536 | @item set print sevenbit-strings off | |
9a27b06e RP |
4537 | Print full eight-bit characters. This allows the use of more |
4538 | international character sets, and is the default. | |
70b88761 RP |
4539 | |
4540 | @item show print sevenbit-strings | |
f2857bd9 | 4541 | @kindex show print sevenbit-strings |
9a27b06e | 4542 | Show whether or not @value{GDBN} is printing only seven-bit characters. |
70b88761 RP |
4543 | |
4544 | @item set print union on | |
4545 | @kindex set print union | |
18fae2a8 | 4546 | Tell @value{GDBN} to print unions which are contained in structures. This is the |
70b88761 RP |
4547 | default setting. |
4548 | ||
4549 | @item set print union off | |
18fae2a8 | 4550 | Tell @value{GDBN} not to print unions which are contained in structures. |
70b88761 RP |
4551 | |
4552 | @item show print union | |
4553 | @kindex show print union | |
18fae2a8 | 4554 | Ask @value{GDBN} whether or not it will print unions which are contained in |
e251e767 | 4555 | structures. |
70b88761 RP |
4556 | |
4557 | For example, given the declarations | |
4558 | ||
4559 | @smallexample | |
4560 | typedef enum @{Tree, Bug@} Species; | |
4561 | typedef enum @{Big_tree, Acorn, Seedling@} Tree_forms; | |
203eea5d RP |
4562 | typedef enum @{Caterpillar, Cocoon, Butterfly@} |
4563 | Bug_forms; | |
70b88761 RP |
4564 | |
4565 | struct thing @{ | |
4566 | Species it; | |
4567 | union @{ | |
4568 | Tree_forms tree; | |
4569 | Bug_forms bug; | |
4570 | @} form; | |
4571 | @}; | |
4572 | ||
4573 | struct thing foo = @{Tree, @{Acorn@}@}; | |
4574 | @end smallexample | |
4575 | ||
4576 | @noindent | |
4577 | with @code{set print union on} in effect @samp{p foo} would print | |
4578 | ||
4579 | @smallexample | |
4580 | $1 = @{it = Tree, form = @{tree = Acorn, bug = Cocoon@}@} | |
4581 | @end smallexample | |
4582 | ||
4583 | @noindent | |
4584 | and with @code{set print union off} in effect it would print | |
4585 | ||
4586 | @smallexample | |
4587 | $1 = @{it = Tree, form = @{...@}@} | |
4588 | @end smallexample | |
4589 | @end table | |
4590 | ||
1d7c3357 | 4591 | @ifclear CONLY |
d55320a0 | 4592 | @need 1000 |
70b88761 RP |
4593 | @noindent |
4594 | These settings are of interest when debugging C++ programs: | |
4595 | ||
4596 | @table @code | |
e251e767 RP |
4597 | @item set print demangle |
4598 | @itemx set print demangle on | |
70b88761 | 4599 | @kindex set print demangle |
fe715d06 RP |
4600 | Print C++ names in their source form rather than in the encoded |
4601 | (``mangled'') form passed to the assembler and linker for type-safe | |
4602 | linkage. The default is @samp{on}. | |
70b88761 RP |
4603 | |
4604 | @item show print demangle | |
4605 | @kindex show print demangle | |
9a27b06e | 4606 | Show whether C++ names are printed in mangled or demangled form. |
70b88761 | 4607 | |
e251e767 RP |
4608 | @item set print asm-demangle |
4609 | @itemx set print asm-demangle on | |
70b88761 RP |
4610 | @kindex set print asm-demangle |
4611 | Print C++ names in their source form rather than their mangled form, even | |
4612 | in assembler code printouts such as instruction disassemblies. | |
4613 | The default is off. | |
4614 | ||
4615 | @item show print asm-demangle | |
4616 | @kindex show print asm-demangle | |
9a27b06e | 4617 | Show whether C++ names in assembly listings are printed in mangled |
70b88761 RP |
4618 | or demangled form. |
4619 | ||
fe715d06 RP |
4620 | @item set demangle-style @var{style} |
4621 | @kindex set demangle-style | |
4622 | @cindex C++ symbol decoding style | |
4623 | @cindex symbol decoding style, C++ | |
4624 | Choose among several encoding schemes used by different compilers to | |
4625 | represent C++ names. The choices for @var{style} are currently: | |
4626 | ||
4627 | @table @code | |
4628 | @item auto | |
4629 | Allow @value{GDBN} to choose a decoding style by inspecting your program. | |
4630 | ||
4631 | @item gnu | |
4632 | Decode based on the GNU C++ compiler (@code{g++}) encoding algorithm. | |
4633 | ||
4634 | @item lucid | |
4635 | Decode based on the Lucid C++ compiler (@code{lcc}) encoding algorithm. | |
4636 | ||
a1eff6c2 | 4637 | @item arm |
fe715d06 | 4638 | Decode using the algorithm in the @cite{C++ Annotated Reference Manual}. |
a1eff6c2 RP |
4639 | @strong{Warning:} this setting alone is not sufficient to allow |
4640 | debugging @code{cfront}-generated executables. @value{GDBN} would | |
4641 | require further enhancement to permit that. | |
fe715d06 RP |
4642 | @end table |
4643 | ||
4644 | @item show demangle-style | |
4645 | @kindex show demangle-style | |
4646 | Display the encoding style currently in use for decoding C++ symbols. | |
4647 | ||
70b88761 RP |
4648 | @item set print object |
4649 | @itemx set print object on | |
4650 | @kindex set print object | |
4651 | When displaying a pointer to an object, identify the @emph{actual} | |
4652 | (derived) type of the object rather than the @emph{declared} type, using | |
4653 | the virtual function table. | |
4654 | ||
4655 | @item set print object off | |
4656 | Display only the declared type of objects, without reference to the | |
4657 | virtual function table. This is the default setting. | |
4658 | ||
4659 | @item show print object | |
4660 | @kindex show print object | |
9a27b06e | 4661 | Show whether actual, or declared, object types are displayed. |
70b88761 | 4662 | |
e251e767 RP |
4663 | @item set print vtbl |
4664 | @itemx set print vtbl on | |
70b88761 RP |
4665 | @kindex set print vtbl |
4666 | Pretty print C++ virtual function tables. The default is off. | |
4667 | ||
4668 | @item set print vtbl off | |
4669 | Do not pretty print C++ virtual function tables. | |
4670 | ||
4671 | @item show print vtbl | |
4672 | @kindex show print vtbl | |
4673 | Show whether C++ virtual function tables are pretty printed, or not. | |
70b88761 | 4674 | @end table |
1d7c3357 | 4675 | @end ifclear |
70b88761 | 4676 | |
4eb4cf57 | 4677 | @node Value History |
93928b60 | 4678 | @section Value history |
70b88761 RP |
4679 | |
4680 | @cindex value history | |
93918348 | 4681 | Values printed by the @code{print} command are saved in the @value{GDBN} @dfn{value |
70b88761 RP |
4682 | history} so that you can refer to them in other expressions. Values are |
4683 | kept until the symbol table is re-read or discarded (for example with | |
4684 | the @code{file} or @code{symbol-file} commands). When the symbol table | |
4685 | changes, the value history is discarded, since the values may contain | |
4686 | pointers back to the types defined in the symbol table. | |
4687 | ||
4688 | @cindex @code{$} | |
4689 | @cindex @code{$$} | |
4690 | @cindex history number | |
6b51acad RP |
4691 | The values printed are given @dfn{history numbers} by which you can |
4692 | refer to them. These are successive integers starting with one. | |
4693 | @code{print} shows you the history number assigned to a value by | |
4694 | printing @samp{$@var{num} = } before the value; here @var{num} is the | |
4695 | history number. | |
70b88761 RP |
4696 | |
4697 | To refer to any previous value, use @samp{$} followed by the value's | |
4698 | history number. The way @code{print} labels its output is designed to | |
4699 | remind you of this. Just @code{$} refers to the most recent value in | |
4700 | the history, and @code{$$} refers to the value before that. | |
4701 | @code{$$@var{n}} refers to the @var{n}th value from the end; @code{$$2} | |
4702 | is the value just prior to @code{$$}, @code{$$1} is equivalent to | |
4703 | @code{$$}, and @code{$$0} is equivalent to @code{$}. | |
4704 | ||
4705 | For example, suppose you have just printed a pointer to a structure and | |
4706 | want to see the contents of the structure. It suffices to type | |
4707 | ||
4708 | @example | |
4709 | p *$ | |
4710 | @end example | |
4711 | ||
4712 | If you have a chain of structures where the component @code{next} points | |
4713 | to the next one, you can print the contents of the next one with this: | |
4714 | ||
4715 | @example | |
4716 | p *$.next | |
4717 | @end example | |
4718 | ||
4719 | @noindent | |
4720 | You can print successive links in the chain by repeating this | |
4721 | command---which you can do by just typing @key{RET}. | |
4722 | ||
4723 | Note that the history records values, not expressions. If the value of | |
4724 | @code{x} is 4 and you type these commands: | |
4725 | ||
4726 | @example | |
4727 | print x | |
4728 | set x=5 | |
4729 | @end example | |
4730 | ||
4731 | @noindent | |
4732 | then the value recorded in the value history by the @code{print} command | |
4733 | remains 4 even though the value of @code{x} has changed. | |
4734 | ||
4735 | @table @code | |
4736 | @kindex show values | |
4737 | @item show values | |
4738 | Print the last ten values in the value history, with their item numbers. | |
4739 | This is like @samp{p@ $$9} repeated ten times, except that @code{show | |
4740 | values} does not change the history. | |
4741 | ||
4742 | @item show values @var{n} | |
4743 | Print ten history values centered on history item number @var{n}. | |
4744 | ||
4745 | @item show values + | |
4746 | Print ten history values just after the values last printed. If no more | |
4747 | values are available, produces no display. | |
4748 | @end table | |
4749 | ||
4750 | Pressing @key{RET} to repeat @code{show values @var{n}} has exactly the | |
e251e767 | 4751 | same effect as @samp{show values +}. |
70b88761 | 4752 | |
4eb4cf57 | 4753 | @node Convenience Vars |
93928b60 | 4754 | @section Convenience variables |
70b88761 RP |
4755 | |
4756 | @cindex convenience variables | |
18fae2a8 RP |
4757 | @value{GDBN} provides @dfn{convenience variables} that you can use within |
4758 | @value{GDBN} to hold on to a value and refer to it later. These variables | |
4759 | exist entirely within @value{GDBN}; they are not part of your program, and | |
70b88761 | 4760 | setting a convenience variable has no direct effect on further execution |
1041a570 | 4761 | of your program. That is why you can use them freely. |
70b88761 RP |
4762 | |
4763 | Convenience variables are prefixed with @samp{$}. Any name preceded by | |
4764 | @samp{$} can be used for a convenience variable, unless it is one of | |
4765 | the predefined machine-specific register names (@pxref{Registers}). | |
4766 | (Value history references, in contrast, are @emph{numbers} preceded | |
93928b60 | 4767 | by @samp{$}. @xref{Value History, ,Value history}.) |
70b88761 RP |
4768 | |
4769 | You can save a value in a convenience variable with an assignment | |
ed447b95 RP |
4770 | expression, just as you would set a variable in your program. |
4771 | For example: | |
70b88761 RP |
4772 | |
4773 | @example | |
4774 | set $foo = *object_ptr | |
4775 | @end example | |
4776 | ||
4777 | @noindent | |
4778 | would save in @code{$foo} the value contained in the object pointed to by | |
4779 | @code{object_ptr}. | |
4780 | ||
6b51acad RP |
4781 | Using a convenience variable for the first time creates it, but its |
4782 | value is @code{void} until you assign a new value. You can alter the | |
4783 | value with another assignment at any time. | |
70b88761 RP |
4784 | |
4785 | Convenience variables have no fixed types. You can assign a convenience | |
4786 | variable any type of value, including structures and arrays, even if | |
4787 | that variable already has a value of a different type. The convenience | |
4788 | variable, when used as an expression, has the type of its current value. | |
4789 | ||
4790 | @table @code | |
4791 | @item show convenience | |
4792 | @kindex show convenience | |
4793 | Print a list of convenience variables used so far, and their values. | |
4794 | Abbreviated @code{show con}. | |
4795 | @end table | |
4796 | ||
4797 | One of the ways to use a convenience variable is as a counter to be | |
4798 | incremented or a pointer to be advanced. For example, to print | |
4799 | a field from successive elements of an array of structures: | |
4800 | ||
18fae2a8 | 4801 | @example |
70b88761 RP |
4802 | set $i = 0 |
4803 | print bar[$i++]->contents | |
4804 | @i{@dots{} repeat that command by typing @key{RET}.} | |
18fae2a8 | 4805 | @end example |
70b88761 | 4806 | |
18fae2a8 | 4807 | Some convenience variables are created automatically by @value{GDBN} and given |
70b88761 RP |
4808 | values likely to be useful. |
4809 | ||
4810 | @table @code | |
4811 | @item $_ | |
c338a2fd | 4812 | @kindex $_ |
70b88761 | 4813 | The variable @code{$_} is automatically set by the @code{x} command to |
93928b60 | 4814 | the last address examined (@pxref{Memory, ,Examining memory}). Other |
29a2b744 RP |
4815 | commands which provide a default address for @code{x} to examine also |
4816 | set @code{$_} to that address; these commands include @code{info line} | |
4817 | and @code{info breakpoint}. The type of @code{$_} is @code{void *} | |
4818 | except when set by the @code{x} command, in which case it is a pointer | |
4819 | to the type of @code{$__}. | |
70b88761 RP |
4820 | |
4821 | @item $__ | |
c338a2fd | 4822 | @kindex $__ |
70b88761 | 4823 | The variable @code{$__} is automatically set by the @code{x} command |
c2bbbb22 RP |
4824 | to the value found in the last address examined. Its type is chosen |
4825 | to match the format in which the data was printed. | |
70b88761 RP |
4826 | @end table |
4827 | ||
4eb4cf57 | 4828 | @node Registers |
70b88761 RP |
4829 | @section Registers |
4830 | ||
4831 | @cindex registers | |
b80282d5 | 4832 | You can refer to machine register contents, in expressions, as variables |
70b88761 RP |
4833 | with names starting with @samp{$}. The names of registers are different |
4834 | for each machine; use @code{info registers} to see the names used on | |
e251e767 | 4835 | your machine. |
70b88761 RP |
4836 | |
4837 | @table @code | |
4838 | @item info registers | |
4839 | @kindex info registers | |
b80282d5 RP |
4840 | Print the names and values of all registers except floating-point |
4841 | registers (in the selected stack frame). | |
4842 | ||
4843 | @item info all-registers | |
4844 | @kindex info all-registers | |
4845 | @cindex floating point registers | |
4846 | Print the names and values of all registers, including floating-point | |
4847 | registers. | |
70b88761 | 4848 | |
4eb4cf57 | 4849 | @item info registers @var{regname} @dots{} |
0d1cd01e JG |
4850 | Print the relativized value of each specified register @var{regname}. |
4851 | @var{regname} may be any register name valid on the machine you are using, with | |
70b88761 RP |
4852 | or without the initial @samp{$}. |
4853 | @end table | |
4854 | ||
18fae2a8 | 4855 | @value{GDBN} has four ``standard'' register names that are available (in |
29a2b744 | 4856 | expressions) on most machines---whenever they do not conflict with an |
09267865 RP |
4857 | architecture's canonical mnemonics for registers. The register names |
4858 | @code{$pc} and @code{$sp} are used for the program counter register and | |
4859 | the stack pointer. @code{$fp} is used for a register that contains a | |
4860 | pointer to the current stack frame, and @code{$ps} is used for a | |
4861 | register that contains the processor status. For example, | |
70b88761 | 4862 | you could print the program counter in hex with |
1041a570 | 4863 | |
70b88761 RP |
4864 | @example |
4865 | p/x $pc | |
4866 | @end example | |
4867 | ||
4868 | @noindent | |
4869 | or print the instruction to be executed next with | |
1041a570 | 4870 | |
70b88761 RP |
4871 | @example |
4872 | x/i $pc | |
4873 | @end example | |
4874 | ||
4875 | @noindent | |
ed447b95 | 4876 | or add four to the stack pointer@footnote{This is a way of removing |
29a2b744 RP |
4877 | one word from the stack, on machines where stacks grow downward in |
4878 | memory (most machines, nowadays). This assumes that the innermost | |
4879 | stack frame is selected; setting @code{$sp} is not allowed when other | |
4880 | stack frames are selected. To pop entire frames off the stack, | |
4881 | regardless of machine architecture, use @code{return}; | |
93928b60 | 4882 | @pxref{Returning, ,Returning from a function}.} with |
1041a570 | 4883 | |
70b88761 RP |
4884 | @example |
4885 | set $sp += 4 | |
4886 | @end example | |
4887 | ||
09267865 RP |
4888 | Whenever possible, these four standard register names are available on |
4889 | your machine even though the machine has different canonical mnemonics, | |
4890 | so long as there is no conflict. The @code{info registers} command | |
4891 | shows the canonical names. For example, on the SPARC, @code{info | |
70b88761 RP |
4892 | registers} displays the processor status register as @code{$psr} but you |
4893 | can also refer to it as @code{$ps}. | |
4894 | ||
18fae2a8 | 4895 | @value{GDBN} always considers the contents of an ordinary register as an |
70b88761 RP |
4896 | integer when the register is examined in this way. Some machines have |
4897 | special registers which can hold nothing but floating point; these | |
4898 | registers are considered to have floating point values. There is no way | |
4899 | to refer to the contents of an ordinary register as floating point value | |
4900 | (although you can @emph{print} it as a floating point value with | |
4901 | @samp{print/f $@var{regname}}). | |
4902 | ||
4903 | Some registers have distinct ``raw'' and ``virtual'' data formats. This | |
4904 | means that the data format in which the register contents are saved by | |
4905 | the operating system is not the same one that your program normally | |
4906 | sees. For example, the registers of the 68881 floating point | |
4907 | coprocessor are always saved in ``extended'' (raw) format, but all C | |
4908 | programs expect to work with ``double'' (virtual) format. In such | |
18fae2a8 | 4909 | cases, @value{GDBN} normally works with the virtual format only (the format that |
70b88761 RP |
4910 | makes sense for your program), but the @code{info registers} command |
4911 | prints the data in both formats. | |
4912 | ||
4913 | Normally, register values are relative to the selected stack frame | |
93928b60 | 4914 | (@pxref{Selection, ,Selecting a frame}). This means that you get the |
29a2b744 RP |
4915 | value that the register would contain if all stack frames farther in |
4916 | were exited and their saved registers restored. In order to see the | |
4917 | true contents of hardware registers, you must select the innermost | |
4918 | frame (with @samp{frame 0}). | |
70b88761 | 4919 | |
18fae2a8 | 4920 | However, @value{GDBN} must deduce where registers are saved, from the machine |
70b88761 | 4921 | code generated by your compiler. If some registers are not saved, or if |
18fae2a8 | 4922 | @value{GDBN} is unable to locate the saved registers, the selected stack |
9a27b06e | 4923 | frame makes no difference. |
70b88761 | 4924 | |
a64a6c2b | 4925 | @ifset AMD29K |
03a77779 | 4926 | @table @code |
d8a68b28 JG |
4927 | @item set rstack_high_address @var{address} |
4928 | @kindex set rstack_high_address | |
03a77779 RP |
4929 | @cindex AMD 29K register stack |
4930 | @cindex register stack, AMD29K | |
4931 | On AMD 29000 family processors, registers are saved in a separate | |
18fae2a8 RP |
4932 | ``register stack''. There is no way for @value{GDBN} to determine the extent |
4933 | of this stack. Normally, @value{GDBN} just assumes that the stack is ``large | |
4934 | enough''. This may result in @value{GDBN} referencing memory locations that | |
93918348 | 4935 | do not exist. If necessary, you can get around this problem by |
03a77779 RP |
4936 | specifying the ending address of the register stack with the @code{set |
4937 | rstack_high_address} command. The argument should be an address, which | |
9a27b06e | 4938 | you probably want to precede with @samp{0x} to specify in |
03a77779 | 4939 | hexadecimal. |
d8a68b28 JG |
4940 | |
4941 | @item show rstack_high_address | |
4942 | @kindex show rstack_high_address | |
03a77779 RP |
4943 | Display the current limit of the register stack, on AMD 29000 family |
4944 | processors. | |
4945 | @end table | |
18fae2a8 | 4946 | @end ifset |
d8a68b28 | 4947 | |
a64a6c2b | 4948 | @ifclear HAVE-FLOAT |
4eb4cf57 | 4949 | @node Floating Point Hardware |
93928b60 | 4950 | @section Floating point hardware |
70b88761 | 4951 | @cindex floating point |
1041a570 | 4952 | |
1d7c3357 | 4953 | @c FIXME! Really host, not target? |
18fae2a8 | 4954 | Depending on the host machine architecture, @value{GDBN} may be able to give |
70b88761 RP |
4955 | you more information about the status of the floating point hardware. |
4956 | ||
4957 | @table @code | |
4958 | @item info float | |
4959 | @kindex info float | |
8c69096b | 4960 | Display hardware-dependent information about the floating |
70b88761 | 4961 | point unit. The exact contents and layout vary depending on the |
8c69096b RP |
4962 | floating point chip; on some platforms, @samp{info float} is not |
4963 | available at all. | |
70b88761 RP |
4964 | @end table |
4965 | @c FIXME: this is a cop-out. Try to get examples, explanations. Only | |
e251e767 RP |
4966 | @c FIXME...supported currently on arm's and 386's. Mark properly with |
4967 | @c FIXME... m4 macros to isolate general statements from hardware-dep, | |
70b88761 | 4968 | @c FIXME... at that point. |
18fae2a8 | 4969 | @end ifclear |
70b88761 | 4970 | |
18fae2a8 | 4971 | @ifclear CONLY |
4eb4cf57 | 4972 | @node Languages |
18fae2a8 | 4973 | @chapter Using @value{GDBN} with Different Languages |
c2bbbb22 RP |
4974 | @cindex languages |
4975 | ||
09934a2b | 4976 | @ifset MOD2 |
c2bbbb22 RP |
4977 | Although programming languages generally have common aspects, they are |
4978 | rarely expressed in the same manner. For instance, in ANSI C, | |
4979 | dereferencing a pointer @code{p} is accomplished by @code{*p}, but in | |
4980 | Modula-2, it is accomplished by @code{p^}. Values can also be | |
4981 | represented (and displayed) differently. Hex numbers in C are written | |
4982 | like @samp{0x1ae}, while in Modula-2 they appear as @samp{1AEH}. | |
09934a2b | 4983 | @end ifset |
c2bbbb22 RP |
4984 | |
4985 | @cindex working language | |
18fae2a8 | 4986 | Language-specific information is built into @value{GDBN} for some languages, |
29a2b744 | 4987 | allowing you to express operations like the above in your program's |
18fae2a8 | 4988 | native language, and allowing @value{GDBN} to output values in a manner |
29a2b744 | 4989 | consistent with the syntax of your program's native language. The |
c2bbbb22 | 4990 | language you use to build expressions, called the @dfn{working |
18fae2a8 | 4991 | language}, can be selected manually, or @value{GDBN} can set it |
c2bbbb22 RP |
4992 | automatically. |
4993 | ||
4994 | @menu | |
4995 | * Setting:: Switching between source languages | |
4996 | * Show:: Displaying the language | |
09934a2b | 4997 | @ifset MOD2 |
ed447b95 | 4998 | * Checks:: Type and range checks |
09934a2b | 4999 | @end ifset |
da374d80 | 5000 | |
c2bbbb22 RP |
5001 | * Support:: Supported languages |
5002 | @end menu | |
5003 | ||
4eb4cf57 | 5004 | @node Setting |
c2bbbb22 RP |
5005 | @section Switching between source languages |
5006 | ||
18fae2a8 | 5007 | There are two ways to control the working language---either have @value{GDBN} |
c2bbbb22 | 5008 | set it automatically, or select it manually yourself. You can use the |
18fae2a8 | 5009 | @code{set language} command for either purpose. On startup, @value{GDBN} |
c2bbbb22 RP |
5010 | defaults to setting the language automatically. |
5011 | ||
5012 | @menu | |
5013 | * Manually:: Setting the working language manually | |
18fae2a8 | 5014 | * Automatically:: Having @value{GDBN} infer the source language |
c2bbbb22 RP |
5015 | @end menu |
5016 | ||
4eb4cf57 | 5017 | @node Manually |
c2bbbb22 RP |
5018 | @subsection Setting the working language |
5019 | ||
ed447b95 RP |
5020 | If you allow @value{GDBN} to set the language automatically, |
5021 | expressions are interpreted the same way in your debugging session and | |
5022 | your program. | |
5023 | ||
c2bbbb22 | 5024 | @kindex set language |
ed447b95 RP |
5025 | If you wish, you may set the language manually. To do this, issue the |
5026 | command @samp{set language @var{lang}}, where @var{lang} is the name of | |
09934a2b RP |
5027 | a language, such as |
5028 | @ifclear MOD2 | |
5029 | @code{c}. | |
5030 | @end ifclear | |
5031 | @ifset MOD2 | |
5032 | @code{c} or @code{modula-2}. | |
5033 | @end ifset | |
5034 | For a list of the supported languages, type @samp{set language}. | |
ed447b95 | 5035 | @c FIXME: rms: eventually this command should be "help set language". |
c2bbbb22 | 5036 | |
09934a2b | 5037 | @ifset MOD2 |
18fae2a8 | 5038 | Setting the language manually prevents @value{GDBN} from updating the working |
c2bbbb22 RP |
5039 | language automatically. This can lead to confusion if you try |
5040 | to debug a program when the working language is not the same as the | |
5041 | source language, when an expression is acceptable to both | |
5042 | languages---but means different things. For instance, if the current | |
18fae2a8 | 5043 | source file were written in C, and @value{GDBN} was parsing Modula-2, a |
c2bbbb22 RP |
5044 | command such as: |
5045 | ||
5046 | @example | |
5047 | print a = b + c | |
5048 | @end example | |
5049 | ||
5050 | @noindent | |
5051 | might not have the effect you intended. In C, this means to add | |
5052 | @code{b} and @code{c} and place the result in @code{a}. The result | |
5053 | printed would be the value of @code{a}. In Modula-2, this means to compare | |
5054 | @code{a} to the result of @code{b+c}, yielding a @code{BOOLEAN} value. | |
09934a2b | 5055 | @end ifset |
c2bbbb22 | 5056 | |
4eb4cf57 | 5057 | @node Automatically |
18fae2a8 | 5058 | @subsection Having @value{GDBN} infer the source language |
c2bbbb22 | 5059 | |
18fae2a8 RP |
5060 | To have @value{GDBN} set the working language automatically, use @samp{set |
5061 | language local} or @samp{set language auto}. @value{GDBN} then infers the | |
c2bbbb22 RP |
5062 | language that a program was written in by looking at the name of its |
5063 | source files, and examining their extensions: | |
5064 | ||
5065 | @table @file | |
09934a2b | 5066 | @ifset MOD2 |
c2bbbb22 RP |
5067 | @item *.mod |
5068 | Modula-2 source file | |
09934a2b | 5069 | @end ifset |
c2bbbb22 RP |
5070 | |
5071 | @item *.c | |
5a2c1d85 RP |
5072 | C source file |
5073 | ||
5074 | @item *.C | |
c2bbbb22 | 5075 | @itemx *.cc |
5a2c1d85 | 5076 | C++ source file |
c2bbbb22 RP |
5077 | @end table |
5078 | ||
5079 | This information is recorded for each function or procedure in a source | |
5080 | file. When your program stops in a frame (usually by encountering a | |
18fae2a8 | 5081 | breakpoint), @value{GDBN} sets the working language to the language recorded |
c2bbbb22 RP |
5082 | for the function in that frame. If the language for a frame is unknown |
5083 | (that is, if the function or block corresponding to the frame was | |
5084 | defined in a source file that does not have a recognized extension), the | |
18fae2a8 | 5085 | current working language is not changed, and @value{GDBN} issues a warning. |
c2bbbb22 RP |
5086 | |
5087 | This may not seem necessary for most programs, which are written | |
5088 | entirely in one source language. However, program modules and libraries | |
5089 | written in one source language can be used by a main program written in | |
5090 | a different source language. Using @samp{set language auto} in this | |
5091 | case frees you from having to set the working language manually. | |
5092 | ||
4eb4cf57 | 5093 | @node Show |
c2bbbb22 RP |
5094 | @section Displaying the language |
5095 | ||
9a27b06e | 5096 | The following commands help you find out which language is the |
c2bbbb22 RP |
5097 | working language, and also what language source files were written in. |
5098 | ||
5099 | @kindex show language | |
5100 | @kindex info frame | |
5101 | @kindex info source | |
5102 | @table @code | |
5103 | @item show language | |
5104 | Display the current working language. This is the | |
5105 | language you can use with commands such as @code{print} to | |
29a2b744 | 5106 | build and compute expressions that may involve variables in your program. |
c2bbbb22 RP |
5107 | |
5108 | @item info frame | |
1041a570 | 5109 | Among the other information listed here (@pxref{Frame Info, ,Information |
9a27b06e RP |
5110 | about a frame}) is the source language for this frame. This |
5111 | language becomes the working language if you use an | |
5112 | identifier from this frame. | |
c2bbbb22 RP |
5113 | |
5114 | @item info source | |
1041a570 | 5115 | Among the other information listed here (@pxref{Symbols, ,Examining the |
c2bbbb22 | 5116 | Symbol Table}) is the source language of this source file. |
c2bbbb22 RP |
5117 | @end table |
5118 | ||
09934a2b | 5119 | @ifset MOD2 |
4eb4cf57 | 5120 | @node Checks |
93928b60 | 5121 | @section Type and range checking |
c2bbbb22 RP |
5122 | |
5123 | @quotation | |
18fae2a8 | 5124 | @emph{Warning:} In this release, the @value{GDBN} commands for type and range |
c2bbbb22 RP |
5125 | checking are included, but they do not yet have any effect. This |
5126 | section documents the intended facilities. | |
5127 | @end quotation | |
5128 | @c FIXME remove warning when type/range code added | |
5129 | ||
5130 | Some languages are designed to guard you against making seemingly common | |
5131 | errors through a series of compile- and run-time checks. These include | |
5132 | checking the type of arguments to functions and operators, and making | |
5133 | sure mathematical overflows are caught at run time. Checks such as | |
5134 | these help to ensure a program's correctness once it has been compiled | |
5135 | by eliminating type mismatches, and providing active checks for range | |
29a2b744 | 5136 | errors when your program is running. |
c2bbbb22 | 5137 | |
18fae2a8 | 5138 | @value{GDBN} can check for conditions like the above if you wish. |
9a27b06e | 5139 | Although @value{GDBN} does not check the statements in your program, it |
18fae2a8 | 5140 | can check expressions entered directly into @value{GDBN} for evaluation via |
1041a570 | 5141 | the @code{print} command, for example. As with the working language, |
18fae2a8 | 5142 | @value{GDBN} can also decide whether or not to check automatically based on |
93928b60 | 5143 | your program's source language. @xref{Support, ,Supported languages}, |
1041a570 | 5144 | for the default settings of supported languages. |
c2bbbb22 RP |
5145 | |
5146 | @menu | |
5147 | * Type Checking:: An overview of type checking | |
5148 | * Range Checking:: An overview of range checking | |
5149 | @end menu | |
5150 | ||
5151 | @cindex type checking | |
5152 | @cindex checks, type | |
4eb4cf57 | 5153 | @node Type Checking |
c2bbbb22 RP |
5154 | @subsection An overview of type checking |
5155 | ||
5156 | Some languages, such as Modula-2, are strongly typed, meaning that the | |
5157 | arguments to operators and functions have to be of the correct type, | |
5158 | otherwise an error occurs. These checks prevent type mismatch | |
5159 | errors from ever causing any run-time problems. For example, | |
5160 | ||
5161 | @example | |
5162 | 1 + 2 @result{} 3 | |
1041a570 | 5163 | @exdent but |
c2bbbb22 RP |
5164 | @error{} 1 + 2.3 |
5165 | @end example | |
5166 | ||
5167 | The second example fails because the @code{CARDINAL} 1 is not | |
5168 | type-compatible with the @code{REAL} 2.3. | |
5169 | ||
18fae2a8 | 5170 | For expressions you use in @value{GDBN} commands, you can tell the @value{GDBN} |
c2bbbb22 RP |
5171 | type checker to skip checking; to treat any mismatches as errors and |
5172 | abandon the expression; or only issue warnings when type mismatches | |
5173 | occur, but evaluate the expression anyway. When you choose the last of | |
18fae2a8 | 5174 | these, @value{GDBN} evaluates expressions like the second example above, but |
c2bbbb22 RP |
5175 | also issues a warning. |
5176 | ||
5177 | Even though you may turn type checking off, other type-based reasons may | |
18fae2a8 | 5178 | prevent @value{GDBN} from evaluating an expression. For instance, @value{GDBN} does not |
c2bbbb22 RP |
5179 | know how to add an @code{int} and a @code{struct foo}. These particular |
5180 | type errors have nothing to do with the language in use, and usually | |
5181 | arise from expressions, such as the one described above, which make | |
5182 | little sense to evaluate anyway. | |
5183 | ||
5184 | Each language defines to what degree it is strict about type. For | |
5185 | instance, both Modula-2 and C require the arguments to arithmetical | |
5186 | operators to be numbers. In C, enumerated types and pointers can be | |
5187 | represented as numbers, so that they are valid arguments to mathematical | |
93928b60 | 5188 | operators. @xref{Support, ,Supported languages}, for further |
c2bbbb22 RP |
5189 | details on specific languages. |
5190 | ||
18fae2a8 | 5191 | @value{GDBN} provides some additional commands for controlling the type checker: |
c2bbbb22 RP |
5192 | |
5193 | @kindex set check | |
5194 | @kindex set check type | |
5195 | @kindex show check type | |
5196 | @table @code | |
5197 | @item set check type auto | |
e251e767 | 5198 | Set type checking on or off based on the current working language. |
93928b60 | 5199 | @xref{Support, ,Supported languages}, for the default settings for |
c2bbbb22 RP |
5200 | each language. |
5201 | ||
5202 | @item set check type on | |
5203 | @itemx set check type off | |
5204 | Set type checking on or off, overriding the default setting for the | |
5205 | current working language. Issue a warning if the setting does not | |
93918348 | 5206 | match the language default. If any type mismatches occur in |
18fae2a8 | 5207 | evaluating an expression while typechecking is on, @value{GDBN} prints a |
c2bbbb22 RP |
5208 | message and aborts evaluation of the expression. |
5209 | ||
5210 | @item set check type warn | |
5211 | Cause the type checker to issue warnings, but to always attempt to | |
5212 | evaluate the expression. Evaluating the expression may still | |
18fae2a8 | 5213 | be impossible for other reasons. For example, @value{GDBN} cannot add |
c2bbbb22 RP |
5214 | numbers and structures. |
5215 | ||
5216 | @item show type | |
18fae2a8 | 5217 | Show the current setting of the type checker, and whether or not @value{GDBN} is |
c2bbbb22 RP |
5218 | setting it automatically. |
5219 | @end table | |
5220 | ||
5221 | @cindex range checking | |
5222 | @cindex checks, range | |
4eb4cf57 | 5223 | @node Range Checking |
ed447b95 | 5224 | @subsection An overview of range checking |
c2bbbb22 RP |
5225 | |
5226 | In some languages (such as Modula-2), it is an error to exceed the | |
5227 | bounds of a type; this is enforced with run-time checks. Such range | |
5228 | checking is meant to ensure program correctness by making sure | |
5229 | computations do not overflow, or indices on an array element access do | |
5230 | not exceed the bounds of the array. | |
5231 | ||
ed447b95 RP |
5232 | For expressions you use in @value{GDBN} commands, you can tell |
5233 | @value{GDBN} to treat range errors in one of three ways: ignore them, | |
5234 | always treat them as errors and abandon the expression, or issue | |
5235 | warnings but evaluate the expression anyway. | |
c2bbbb22 RP |
5236 | |
5237 | A range error can result from numerical overflow, from exceeding an | |
ed447b95 | 5238 | array index bound, or when you type a constant that is not a member |
c2bbbb22 RP |
5239 | of any type. Some languages, however, do not treat overflows as an |
5240 | error. In many implementations of C, mathematical overflow causes the | |
5241 | result to ``wrap around'' to lower values---for example, if @var{m} is | |
5242 | the largest integer value, and @var{s} is the smallest, then | |
1041a570 | 5243 | |
c2bbbb22 RP |
5244 | @example |
5245 | @var{m} + 1 @result{} @var{s} | |
5246 | @end example | |
5247 | ||
5248 | This, too, is specific to individual languages, and in some cases | |
1041a570 | 5249 | specific to individual compilers or machines. @xref{Support, , |
93928b60 | 5250 | Supported languages}, for further details on specific languages. |
c2bbbb22 | 5251 | |
18fae2a8 | 5252 | @value{GDBN} provides some additional commands for controlling the range checker: |
c2bbbb22 RP |
5253 | |
5254 | @kindex set check | |
5255 | @kindex set check range | |
5256 | @kindex show check range | |
5257 | @table @code | |
5258 | @item set check range auto | |
e251e767 | 5259 | Set range checking on or off based on the current working language. |
93928b60 | 5260 | @xref{Support, ,Supported languages}, for the default settings for |
c2bbbb22 RP |
5261 | each language. |
5262 | ||
5263 | @item set check range on | |
5264 | @itemx set check range off | |
5265 | Set range checking on or off, overriding the default setting for the | |
5266 | current working language. A warning is issued if the setting does not | |
93918348 | 5267 | match the language default. If a range error occurs, then a message |
c2bbbb22 RP |
5268 | is printed and evaluation of the expression is aborted. |
5269 | ||
5270 | @item set check range warn | |
18fae2a8 | 5271 | Output messages when the @value{GDBN} range checker detects a range error, |
c2bbbb22 RP |
5272 | but attempt to evaluate the expression anyway. Evaluating the |
5273 | expression may still be impossible for other reasons, such as accessing | |
6b51acad | 5274 | memory that the process does not own (a typical example from many Unix |
c2bbbb22 RP |
5275 | systems). |
5276 | ||
5277 | @item show range | |
e251e767 | 5278 | Show the current setting of the range checker, and whether or not it is |
18fae2a8 | 5279 | being set automatically by @value{GDBN}. |
c2bbbb22 | 5280 | @end table |
09934a2b | 5281 | @end ifset |
c2bbbb22 | 5282 | |
4eb4cf57 | 5283 | @node Support |
93928b60 | 5284 | @section Supported languages |
c2bbbb22 | 5285 | |
09934a2b RP |
5286 | @ifset MOD2 |
5287 | @value{GDBN} 4 supports C, C++, and Modula-2. | |
5288 | @end ifset | |
5289 | @ifclear MOD2 | |
5290 | @value{GDBN} 4 supports C, and C++. | |
5291 | @end ifclear | |
5292 | Some @value{GDBN} features may be used in expressions regardless of the | |
5293 | language you use: the @value{GDBN} @code{@@} and @code{::} operators, | |
5294 | and the @samp{@{type@}addr} construct (@pxref{Expressions, | |
5295 | ,Expressions}) can be used with the constructs of any supported | |
5296 | language. | |
5297 | ||
5298 | The following sections detail to what degree each source language is | |
5299 | supported by @value{GDBN}. These sections are not meant to be language | |
5300 | tutorials or references, but serve only as a reference guide to what the | |
9a27b06e | 5301 | @value{GDBN} expression parser accepts, and what input and output |
09934a2b RP |
5302 | formats should look like for different languages. There are many good |
5303 | books written on each of these languages; please look to these for a | |
5304 | language reference or tutorial. | |
5305 | ||
5306 | @ifset MOD2 | |
c2bbbb22 RP |
5307 | @menu |
5308 | * C:: C and C++ | |
5309 | * Modula-2:: Modula-2 | |
5310 | @end menu | |
5311 | ||
4eb4cf57 | 5312 | @node C |
c2bbbb22 RP |
5313 | @subsection C and C++ |
5314 | @cindex C and C++ | |
c2bbbb22 | 5315 | @cindex expressions in C or C++ |
0f153e74 | 5316 | |
18fae2a8 | 5317 | Since C and C++ are so closely related, many features of @value{GDBN} apply |
5a2c1d85 RP |
5318 | to both languages. Whenever this is the case, we discuss both languages |
5319 | together. | |
09934a2b RP |
5320 | @end ifset |
5321 | @ifclear MOD2 | |
5322 | @c Cancel this below, under same condition, at end of this chapter! | |
6370267a | 5323 | @raisesections |
09934a2b | 5324 | @end ifclear |
b80282d5 RP |
5325 | |
5326 | @cindex C++ | |
5327 | @kindex g++ | |
5328 | @cindex GNU C++ | |
c2bbbb22 | 5329 | The C++ debugging facilities are jointly implemented by the GNU C++ |
22b5dba5 RP |
5330 | compiler and @value{GDBN}. Therefore, to debug your C++ code |
5331 | effectively, you must compile your C++ programs with the GNU C++ | |
5332 | compiler, @code{g++}. | |
5333 | ||
5334 | For best results when debugging C++ programs, use the stabs debugging | |
5335 | format. You can select that format explicitly with the @code{g++} | |
5336 | command-line options @samp{-gstabs} or @samp{-gstabs+}. See | |
5337 | @ref{Debugging Options,,Options for Debugging Your Program or GNU CC, | |
5338 | gcc.info, Using GNU CC}, for more information. | |
18fae2a8 RP |
5339 | @end ifclear |
5340 | @ifset CONLY | |
0f153e74 RP |
5341 | @node C |
5342 | @chapter C Language Support | |
5343 | @cindex C language | |
5344 | @cindex expressions in C | |
5345 | ||
18fae2a8 RP |
5346 | Information specific to the C language is built into @value{GDBN} so that you |
5347 | can use C expressions while degugging. This also permits @value{GDBN} to | |
0f153e74 | 5348 | output values in a manner consistent with C conventions. |
c2bbbb22 | 5349 | |
0f153e74 | 5350 | @menu |
ed447b95 RP |
5351 | * C Operators:: C operators |
5352 | * C Constants:: C constants | |
18fae2a8 | 5353 | * Debugging C:: @value{GDBN} and C |
0f153e74 | 5354 | @end menu |
18fae2a8 RP |
5355 | @end ifset |
5356 | @ifclear CONLY | |
b80282d5 | 5357 | @menu |
ed447b95 RP |
5358 | * C Operators:: C and C++ operators |
5359 | * C Constants:: C and C++ constants | |
5360 | * Cplus expressions:: C++ expressions | |
c2bbbb22 | 5361 | * C Defaults:: Default settings for C and C++ |
09934a2b | 5362 | @ifset MOD2 |
ed447b95 | 5363 | * C Checks:: C and C++ type and range checks |
09934a2b | 5364 | @end ifset |
da374d80 | 5365 | |
18fae2a8 | 5366 | * Debugging C:: @value{GDBN} and C |
c2bbbb22 | 5367 | * Debugging C plus plus:: Special features for C++ |
b80282d5 | 5368 | @end menu |
18fae2a8 | 5369 | @end ifclear |
b80282d5 | 5370 | |
18fae2a8 | 5371 | @ifclear CONLY |
c2bbbb22 | 5372 | @cindex C and C++ operators |
4eb4cf57 | 5373 | @node C Operators |
93928b60 | 5374 | @subsubsection C and C++ operators |
18fae2a8 RP |
5375 | @end ifclear |
5376 | @ifset CONLY | |
0f153e74 RP |
5377 | @cindex C operators |
5378 | @node C Operators | |
93928b60 | 5379 | @section C operators |
18fae2a8 | 5380 | @end ifset |
c2bbbb22 RP |
5381 | |
5382 | Operators must be defined on values of specific types. For instance, | |
5383 | @code{+} is defined on numbers, but not on structures. Operators are | |
0f153e74 RP |
5384 | often defined on groups of types. |
5385 | ||
18fae2a8 | 5386 | @ifclear CONLY |
0f153e74 | 5387 | For the purposes of C and C++, the following definitions hold: |
18fae2a8 | 5388 | @end ifclear |
c2bbbb22 RP |
5389 | |
5390 | @itemize @bullet | |
e251e767 | 5391 | @item |
c2bbbb22 | 5392 | @emph{Integral types} include @code{int} with any of its storage-class |
9aa964da | 5393 | specifiers; @code{char}; and @code{enum}. |
c2bbbb22 RP |
5394 | |
5395 | @item | |
5396 | @emph{Floating-point types} include @code{float} and @code{double}. | |
5397 | ||
5398 | @item | |
5399 | @emph{Pointer types} include all types defined as @code{(@var{type} | |
5400 | *)}. | |
5401 | ||
e251e767 | 5402 | @item |
c2bbbb22 | 5403 | @emph{Scalar types} include all of the above. |
c2bbbb22 RP |
5404 | @end itemize |
5405 | ||
5406 | @noindent | |
5407 | The following operators are supported. They are listed here | |
5408 | in order of increasing precedence: | |
5409 | ||
5410 | @table @code | |
18fae2a8 | 5411 | @item , |
c2bbbb22 RP |
5412 | The comma or sequencing operator. Expressions in a comma-separated list |
5413 | are evaluated from left to right, with the result of the entire | |
5414 | expression being the last expression evaluated. | |
5415 | ||
5416 | @item = | |
5417 | Assignment. The value of an assignment expression is the value | |
5418 | assigned. Defined on scalar types. | |
5419 | ||
5420 | @item @var{op}= | |
1041a570 RP |
5421 | Used in an expression of the form @w{@code{@var{a} @var{op}= @var{b}}}, |
5422 | and translated to @w{@code{@var{a} = @var{a op b}}}. | |
5423 | @w{@code{@var{op}=}} and @code{=} have the same precendence. | |
5424 | @var{op} is any one of the operators @code{|}, @code{^}, @code{&}, | |
5425 | @code{<<}, @code{>>}, @code{+}, @code{-}, @code{*}, @code{/}, @code{%}. | |
c2bbbb22 RP |
5426 | |
5427 | @item ?: | |
5428 | The ternary operator. @code{@var{a} ? @var{b} : @var{c}} can be thought | |
5429 | of as: if @var{a} then @var{b} else @var{c}. @var{a} should be of an | |
5430 | integral type. | |
5431 | ||
5432 | @item || | |
1041a570 | 5433 | Logical @sc{or}. Defined on integral types. |
c2bbbb22 RP |
5434 | |
5435 | @item && | |
1041a570 | 5436 | Logical @sc{and}. Defined on integral types. |
c2bbbb22 RP |
5437 | |
5438 | @item | | |
1041a570 | 5439 | Bitwise @sc{or}. Defined on integral types. |
c2bbbb22 RP |
5440 | |
5441 | @item ^ | |
1041a570 | 5442 | Bitwise exclusive-@sc{or}. Defined on integral types. |
c2bbbb22 RP |
5443 | |
5444 | @item & | |
1041a570 | 5445 | Bitwise @sc{and}. Defined on integral types. |
c2bbbb22 RP |
5446 | |
5447 | @item ==@r{, }!= | |
5448 | Equality and inequality. Defined on scalar types. The value of these | |
5449 | expressions is 0 for false and non-zero for true. | |
5450 | ||
5451 | @item <@r{, }>@r{, }<=@r{, }>= | |
5452 | Less than, greater than, less than or equal, greater than or equal. | |
5453 | Defined on scalar types. The value of these expressions is 0 for false | |
5454 | and non-zero for true. | |
5455 | ||
5456 | @item <<@r{, }>> | |
18fae2a8 | 5457 | left shift, and right shift. Defined on integral types. |
c2bbbb22 | 5458 | |
e251e767 | 5459 | @item @@ |
18fae2a8 | 5460 | The @value{GDBN} ``artificial array'' operator (@pxref{Expressions, ,Expressions}). |
c2bbbb22 RP |
5461 | |
5462 | @item +@r{, }- | |
5463 | Addition and subtraction. Defined on integral types, floating-point types and | |
e251e767 | 5464 | pointer types. |
c2bbbb22 RP |
5465 | |
5466 | @item *@r{, }/@r{, }% | |
5467 | Multiplication, division, and modulus. Multiplication and division are | |
5468 | defined on integral and floating-point types. Modulus is defined on | |
5469 | integral types. | |
5470 | ||
5471 | @item ++@r{, }-- | |
5472 | Increment and decrement. When appearing before a variable, the | |
5473 | operation is performed before the variable is used in an expression; | |
5474 | when appearing after it, the variable's value is used before the | |
5475 | operation takes place. | |
5476 | ||
5477 | @item * | |
5478 | Pointer dereferencing. Defined on pointer types. Same precedence as | |
5479 | @code{++}. | |
5480 | ||
5481 | @item & | |
5482 | Address operator. Defined on variables. Same precedence as @code{++}. | |
5483 | ||
18fae2a8 | 5484 | @ifclear CONLY |
93918348 | 5485 | For debugging C++, @value{GDBN} implements a use of @samp{&} beyond what is |
6ca72cc6 | 5486 | allowed in the C++ language itself: you can use @samp{&(&@var{ref})} |
7640fe71 | 5487 | (or, if you prefer, simply @samp{&&@var{ref}}) to examine the address |
6ca72cc6 RP |
5488 | where a C++ reference variable (declared with @samp{&@var{ref}}) is |
5489 | stored. | |
18fae2a8 | 5490 | @end ifclear |
6ca72cc6 | 5491 | |
c2bbbb22 RP |
5492 | @item - |
5493 | Negative. Defined on integral and floating-point types. Same | |
5494 | precedence as @code{++}. | |
5495 | ||
5496 | @item ! | |
5497 | Logical negation. Defined on integral types. Same precedence as | |
5498 | @code{++}. | |
5499 | ||
5500 | @item ~ | |
5501 | Bitwise complement operator. Defined on integral types. Same precedence as | |
5502 | @code{++}. | |
5503 | ||
18fae2a8 | 5504 | |
c2bbbb22 RP |
5505 | @item .@r{, }-> |
5506 | Structure member, and pointer-to-structure member. For convenience, | |
18fae2a8 | 5507 | @value{GDBN} regards the two as equivalent, choosing whether to dereference a |
e251e767 | 5508 | pointer based on the stored type information. |
9aa964da | 5509 | Defined on @code{struct} and @code{union} data. |
c2bbbb22 RP |
5510 | |
5511 | @item [] | |
5512 | Array indexing. @code{@var{a}[@var{i}]} is defined as | |
5513 | @code{*(@var{a}+@var{i})}. Same precedence as @code{->}. | |
5514 | ||
5515 | @item () | |
18fae2a8 | 5516 | Function parameter list. Same precedence as @code{->}. |
c2bbbb22 | 5517 | |
18fae2a8 | 5518 | @ifclear CONLY |
c2bbbb22 RP |
5519 | @item :: |
5520 | C++ scope resolution operator. Defined on | |
5521 | @code{struct}, @code{union}, and @code{class} types. | |
18fae2a8 | 5522 | @end ifclear |
c2bbbb22 RP |
5523 | |
5524 | @item :: | |
ed447b95 RP |
5525 | Doubled colons |
5526 | @ifclear CONLY | |
5527 | also | |
5528 | @end ifclear | |
5529 | represent the @value{GDBN} scope operator (@pxref{Expressions, | |
5530 | ,Expressions}). | |
18fae2a8 | 5531 | @ifclear CONLY |
0f153e74 | 5532 | Same precedence as @code{::}, above. |
18fae2a8 | 5533 | @end ifclear |
c2bbbb22 RP |
5534 | @end table |
5535 | ||
18fae2a8 | 5536 | @ifclear CONLY |
c2bbbb22 | 5537 | @cindex C and C++ constants |
4eb4cf57 | 5538 | @node C Constants |
93928b60 | 5539 | @subsubsection C and C++ constants |
0f153e74 | 5540 | |
18fae2a8 | 5541 | @value{GDBN} allows you to express the constants of C and C++ in the |
0f153e74 | 5542 | following ways: |
18fae2a8 RP |
5543 | @end ifclear |
5544 | @ifset CONLY | |
0f153e74 RP |
5545 | @cindex C constants |
5546 | @node C Constants | |
93928b60 | 5547 | @section C constants |
c2bbbb22 | 5548 | |
18fae2a8 | 5549 | @value{GDBN} allows you to express the constants of C in the |
c2bbbb22 | 5550 | following ways: |
18fae2a8 | 5551 | @end ifset |
c2bbbb22 RP |
5552 | |
5553 | @itemize @bullet | |
c2bbbb22 RP |
5554 | @item |
5555 | Integer constants are a sequence of digits. Octal constants are | |
5556 | specified by a leading @samp{0} (ie. zero), and hexadecimal constants by | |
1041a570 | 5557 | a leading @samp{0x} or @samp{0X}. Constants may also end with a letter |
c2bbbb22 RP |
5558 | @samp{l}, specifying that the constant should be treated as a |
5559 | @code{long} value. | |
5560 | ||
5561 | @item | |
5562 | Floating point constants are a sequence of digits, followed by a decimal | |
5563 | point, followed by a sequence of digits, and optionally followed by an | |
5564 | exponent. An exponent is of the form: | |
5565 | @samp{@w{e@r{[[}+@r{]|}-@r{]}@var{nnn}}}, where @var{nnn} is another | |
5566 | sequence of digits. The @samp{+} is optional for positive exponents. | |
5567 | ||
5568 | @item | |
5569 | Enumerated constants consist of enumerated identifiers, or their | |
5570 | integral equivalents. | |
5571 | ||
5572 | @item | |
5573 | Character constants are a single character surrounded by single quotes | |
5574 | (@code{'}), or a number---the ordinal value of the corresponding character | |
5575 | (usually its @sc{ASCII} value). Within quotes, the single character may | |
5576 | be represented by a letter or by @dfn{escape sequences}, which are of | |
5577 | the form @samp{\@var{nnn}}, where @var{nnn} is the octal representation | |
5578 | of the character's ordinal value; or of the form @samp{\@var{x}}, where | |
5579 | @samp{@var{x}} is a predefined special character---for example, | |
5580 | @samp{\n} for newline. | |
5581 | ||
5582 | @item | |
5583 | String constants are a sequence of character constants surrounded | |
5584 | by double quotes (@code{"}). | |
5585 | ||
5586 | @item | |
fe715d06 RP |
5587 | Pointer constants are an integral value. You can also write pointers |
5588 | to constants using the C operator @samp{&}. | |
5589 | ||
5590 | @item | |
5591 | Array constants are comma-separated lists surrounded by braces @samp{@{} | |
5592 | and @samp{@}}; for example, @samp{@{1,2,3@}} is a three-element array of | |
5593 | integers, @samp{@{@{1,2@}, @{3,4@}, @{5,6@}@}} is a three-by-two array, | |
5594 | and @samp{@{&"hi", &"there", &"fred"@}} is a three-element array of pointers. | |
c2bbbb22 RP |
5595 | @end itemize |
5596 | ||
18fae2a8 | 5597 | @ifclear CONLY |
ed447b95 | 5598 | @node Cplus expressions |
93928b60 | 5599 | @subsubsection C++ expressions |
b80282d5 RP |
5600 | |
5601 | @cindex expressions in C++ | |
93918348 | 5602 | @value{GDBN} expression handling has a number of extensions to |
b1385986 RP |
5603 | interpret a significant subset of C++ expressions. |
5604 | ||
5605 | @cindex C++ support, not in @sc{coff} | |
5606 | @cindex @sc{coff} versus C++ | |
5607 | @cindex C++ and object formats | |
5608 | @cindex object formats and C++ | |
5609 | @cindex a.out and C++ | |
5610 | @cindex @sc{ecoff} and C++ | |
5611 | @cindex @sc{xcoff} and C++ | |
5612 | @cindex @sc{elf}/stabs and C++ | |
5613 | @cindex @sc{elf}/@sc{dwarf} and C++ | |
9a27b06e RP |
5614 | @c FIXME!! GDB may eventually be able to debug C++ using DWARF; check |
5615 | @c periodically whether this has happened... | |
b1385986 | 5616 | @quotation |
9a27b06e RP |
5617 | @emph{Warning:} @value{GDBN} can only debug C++ code if you compile with |
5618 | the GNU C++ compiler. Moreover, C++ debugging depends on the use of | |
5619 | additional debugging information in the symbol table, and thus requires | |
5620 | special support. @value{GDBN} has this support @emph{only} with the | |
5621 | stabs debug format. In particular, if your compiler generates a.out, | |
5622 | MIPS @sc{ecoff}, RS/6000 @sc{xcoff}, or @sc{elf} with stabs extensions | |
5623 | to the symbol table, these facilities are all available. (With GNU CC, | |
5624 | you can use the @samp{-gstabs} option to request stabs debugging | |
5625 | extensions explicitly.) Where the object code format is standard | |
5626 | @sc{coff} or @sc{dwarf} in @sc{elf}, on the other hand, most of the C++ | |
5627 | support in @value{GDBN} does @emph{not} work. | |
b1385986 | 5628 | @end quotation |
b80282d5 RP |
5629 | |
5630 | @enumerate | |
5631 | ||
5632 | @cindex member functions | |
e251e767 | 5633 | @item |
b80282d5 | 5634 | Member function calls are allowed; you can use expressions like |
1041a570 | 5635 | |
b80282d5 RP |
5636 | @example |
5637 | count = aml->GetOriginal(x, y) | |
5638 | @end example | |
5639 | ||
5640 | @kindex this | |
5641 | @cindex namespace in C++ | |
e251e767 | 5642 | @item |
b80282d5 RP |
5643 | While a member function is active (in the selected stack frame), your |
5644 | expressions have the same namespace available as the member function; | |
18fae2a8 | 5645 | that is, @value{GDBN} allows implicit references to the class instance |
b80282d5 RP |
5646 | pointer @code{this} following the same rules as C++. |
5647 | ||
5648 | @cindex call overloaded functions | |
5649 | @cindex type conversions in C++ | |
e251e767 | 5650 | @item |
9a27b06e | 5651 | You can call overloaded functions; @value{GDBN} resolves the function |
b80282d5 RP |
5652 | call to the right definition, with one restriction---you must use |
5653 | arguments of the type required by the function that you want to call. | |
9a27b06e | 5654 | @value{GDBN} does not perform conversions requiring constructors or |
b80282d5 RP |
5655 | user-defined type operators. |
5656 | ||
5657 | @cindex reference declarations | |
5658 | @item | |
18fae2a8 | 5659 | @value{GDBN} understands variables declared as C++ references; you can use them in |
b80282d5 | 5660 | expressions just as you do in C++ source---they are automatically |
e251e767 | 5661 | dereferenced. |
b80282d5 | 5662 | |
18fae2a8 | 5663 | In the parameter list shown when @value{GDBN} displays a frame, the values of |
b80282d5 RP |
5664 | reference variables are not displayed (unlike other variables); this |
5665 | avoids clutter, since references are often used for large structures. | |
5666 | The @emph{address} of a reference variable is always shown, unless | |
1041a570 | 5667 | you have specified @samp{set print address off}. |
b80282d5 RP |
5668 | |
5669 | @item | |
18fae2a8 | 5670 | @value{GDBN} supports the C++ name resolution operator @code{::}---your |
c2bbbb22 RP |
5671 | expressions can use it just as expressions in your program do. Since |
5672 | one scope may be defined in another, you can use @code{::} repeatedly if | |
5673 | necessary, for example in an expression like | |
18fae2a8 | 5674 | @samp{@var{scope1}::@var{scope2}::@var{name}}. @value{GDBN} also allows |
c2bbbb22 | 5675 | resolving name scope by reference to source files, in both C and C++ |
93928b60 | 5676 | debugging (@pxref{Variables, ,Program variables}). |
b80282d5 RP |
5677 | @end enumerate |
5678 | ||
4eb4cf57 | 5679 | @node C Defaults |
93928b60 | 5680 | @subsubsection C and C++ defaults |
c2bbbb22 RP |
5681 | @cindex C and C++ defaults |
5682 | ||
18fae2a8 | 5683 | If you allow @value{GDBN} to set type and range checking automatically, they |
e251e767 | 5684 | both default to @code{off} whenever the working language changes to |
18fae2a8 | 5685 | C or C++. This happens regardless of whether you, or @value{GDBN}, |
c2bbbb22 RP |
5686 | selected the working language. |
5687 | ||
18fae2a8 | 5688 | If you allow @value{GDBN} to set the language automatically, it sets the |
5a2c1d85 RP |
5689 | working language to C or C++ on entering code compiled from a source file |
5690 | whose name ends with @file{.c}, @file{.C}, or @file{.cc}. | |
18fae2a8 | 5691 | @xref{Automatically, ,Having @value{GDBN} infer the source language}, for |
c2bbbb22 RP |
5692 | further details. |
5693 | ||
09934a2b RP |
5694 | @ifset MOD2 |
5695 | @c Type checking is (a) primarily motivated by Modula-2, and (b) | |
5696 | @c unimplemented. If (b) changes, it might make sense to let this node | |
5697 | @c appear even if Mod-2 does not, but meanwhile ignore it. pesch 16jul93. | |
4eb4cf57 | 5698 | @node C Checks |
93928b60 | 5699 | @subsubsection C and C++ type and range checks |
c2bbbb22 RP |
5700 | @cindex C and C++ checks |
5701 | ||
18fae2a8 | 5702 | By default, when @value{GDBN} parses C or C++ expressions, type checking |
9a27b06e RP |
5703 | is not used. However, if you turn type checking on, @value{GDBN} |
5704 | considers two variables type equivalent if: | |
c2bbbb22 RP |
5705 | |
5706 | @itemize @bullet | |
5707 | @item | |
5708 | The two variables are structured and have the same structure, union, or | |
5709 | enumerated tag. | |
5710 | ||
e251e767 | 5711 | @item |
c2bbbb22 RP |
5712 | Two two variables have the same type name, or types that have been |
5713 | declared equivalent through @code{typedef}. | |
5714 | ||
5715 | @ignore | |
5716 | @c leaving this out because neither J Gilmore nor R Pesch understand it. | |
5717 | @c FIXME--beers? | |
5718 | @item | |
5719 | The two @code{struct}, @code{union}, or @code{enum} variables are | |
5720 | declared in the same declaration. (Note: this may not be true for all C | |
5721 | compilers.) | |
5722 | @end ignore | |
c2bbbb22 RP |
5723 | @end itemize |
5724 | ||
5725 | Range checking, if turned on, is done on mathematical operations. Array | |
5726 | indices are not checked, since they are often used to index a pointer | |
5727 | that is not itself an array. | |
09934a2b | 5728 | @end ifset |
18fae2a8 | 5729 | @end ifclear |
c2bbbb22 | 5730 | |
18fae2a8 | 5731 | @ifclear CONLY |
4eb4cf57 | 5732 | @node Debugging C |
18fae2a8 RP |
5733 | @subsubsection @value{GDBN} and C |
5734 | @end ifclear | |
5735 | @ifset CONLY | |
5736 | @node Debugging C | |
5737 | @section @value{GDBN} and C | |
5738 | @end ifset | |
c2bbbb22 RP |
5739 | |
5740 | The @code{set print union} and @code{show print union} commands apply to | |
5741 | the @code{union} type. When set to @samp{on}, any @code{union} that is | |
1d7c3357 RP |
5742 | inside a @code{struct} |
5743 | @ifclear CONLY | |
5744 | or @code{class} | |
5745 | @end ifclear | |
9a27b06e RP |
5746 | is also printed. |
5747 | Otherwise, it appears as @samp{@{...@}}. | |
c2bbbb22 RP |
5748 | |
5749 | The @code{@@} operator aids in the debugging of dynamic arrays, formed | |
ed447b95 RP |
5750 | with pointers and a memory allocation function. @xref{Expressions, |
5751 | ,Expressions}. | |
c2bbbb22 | 5752 | |
18fae2a8 | 5753 | @ifclear CONLY |
4eb4cf57 | 5754 | @node Debugging C plus plus |
93928b60 | 5755 | @subsubsection @value{GDBN} features for C++ |
b80282d5 RP |
5756 | |
5757 | @cindex commands for C++ | |
18fae2a8 | 5758 | Some @value{GDBN} commands are particularly useful with C++, and some are |
b80282d5 RP |
5759 | designed specifically for use with C++. Here is a summary: |
5760 | ||
5761 | @table @code | |
5762 | @cindex break in overloaded functions | |
5763 | @item @r{breakpoint menus} | |
5764 | When you want a breakpoint in a function whose name is overloaded, | |
93918348 | 5765 | @value{GDBN} breakpoint menus help you specify which function definition |
93928b60 | 5766 | you want. @xref{Breakpoint Menus,,Breakpoint menus}. |
b80282d5 RP |
5767 | |
5768 | @cindex overloading in C++ | |
5769 | @item rbreak @var{regex} | |
5770 | Setting breakpoints using regular expressions is helpful for setting | |
5771 | breakpoints on overloaded functions that are not members of any special | |
e251e767 | 5772 | classes. |
93928b60 | 5773 | @xref{Set Breaks, ,Setting breakpoints}. |
b80282d5 RP |
5774 | |
5775 | @cindex C++ exception handling | |
5776 | @item catch @var{exceptions} | |
5777 | @itemx info catch | |
29a2b744 | 5778 | Debug C++ exception handling using these commands. @xref{Exception |
93928b60 | 5779 | Handling, ,Breakpoints and exceptions}. |
b80282d5 | 5780 | |
e251e767 | 5781 | @cindex inheritance |
b80282d5 RP |
5782 | @item ptype @var{typename} |
5783 | Print inheritance relationships as well as other information for type | |
e251e767 | 5784 | @var{typename}. |
1041a570 | 5785 | @xref{Symbols, ,Examining the Symbol Table}. |
b80282d5 RP |
5786 | |
5787 | @cindex C++ symbol display | |
5788 | @item set print demangle | |
5789 | @itemx show print demangle | |
5790 | @itemx set print asm-demangle | |
5791 | @itemx show print asm-demangle | |
5792 | Control whether C++ symbols display in their source form, both when | |
5793 | displaying code as C++ source and when displaying disassemblies. | |
93928b60 | 5794 | @xref{Print Settings, ,Print settings}. |
b80282d5 RP |
5795 | |
5796 | @item set print object | |
5797 | @itemx show print object | |
e251e767 | 5798 | Choose whether to print derived (actual) or declared types of objects. |
93928b60 | 5799 | @xref{Print Settings, ,Print settings}. |
b80282d5 RP |
5800 | |
5801 | @item set print vtbl | |
5802 | @itemx show print vtbl | |
5803 | Control the format for printing virtual function tables. | |
93928b60 | 5804 | @xref{Print Settings, ,Print settings}. |
6f3ec223 RP |
5805 | |
5806 | @item @r{Overloaded symbol names} | |
5807 | You can specify a particular definition of an overloaded symbol, using | |
93918348 | 5808 | the same notation that is used to declare such symbols in C++: type |
6f3ec223 | 5809 | @code{@var{symbol}(@var{types})} rather than just @var{symbol}. You can |
93918348 | 5810 | also use the @value{GDBN} command-line word completion facilities to list the |
6f3ec223 | 5811 | available choices, or to finish the type list for you. |
93928b60 | 5812 | @xref{Completion,, Command completion}, for details on how to do this. |
b80282d5 | 5813 | @end table |
09934a2b | 5814 | @ifclear MOD2 |
6370267a RP |
5815 | @c cancels "raisesections" under same conditions near bgn of chapter |
5816 | @lowersections | |
09934a2b | 5817 | @end ifclear |
b80282d5 | 5818 | |
09934a2b | 5819 | @ifset MOD2 |
4eb4cf57 | 5820 | @node Modula-2 |
c2bbbb22 RP |
5821 | @subsection Modula-2 |
5822 | @cindex Modula-2 | |
5823 | ||
ed447b95 RP |
5824 | The extensions made to @value{GDBN} to support Modula-2 only support |
5825 | output from the GNU Modula-2 compiler (which is currently being | |
5826 | developed). Other Modula-2 compilers are not currently supported, and | |
9a27b06e RP |
5827 | attempting to debug executables produced by them is most likely |
5828 | to give an error as @value{GDBN} reads in the executable's symbol | |
ed447b95 | 5829 | table. |
c2bbbb22 RP |
5830 | |
5831 | @cindex expressions in Modula-2 | |
5832 | @menu | |
5833 | * M2 Operators:: Built-in operators | |
ed447b95 RP |
5834 | * Built-In Func/Proc:: Built-in functions and procedures |
5835 | * M2 Constants:: Modula-2 constants | |
c2bbbb22 RP |
5836 | * M2 Defaults:: Default settings for Modula-2 |
5837 | * Deviations:: Deviations from standard Modula-2 | |
ed447b95 | 5838 | * M2 Checks:: Modula-2 type and range checks |
c2bbbb22 | 5839 | * M2 Scope:: The scope operators @code{::} and @code{.} |
18fae2a8 | 5840 | * GDB/M2:: @value{GDBN} and Modula-2 |
c2bbbb22 RP |
5841 | @end menu |
5842 | ||
4eb4cf57 | 5843 | @node M2 Operators |
c2bbbb22 RP |
5844 | @subsubsection Operators |
5845 | @cindex Modula-2 operators | |
5846 | ||
5847 | Operators must be defined on values of specific types. For instance, | |
5848 | @code{+} is defined on numbers, but not on structures. Operators are | |
5849 | often defined on groups of types. For the purposes of Modula-2, the | |
5850 | following definitions hold: | |
5851 | ||
5852 | @itemize @bullet | |
5853 | ||
5854 | @item | |
5855 | @emph{Integral types} consist of @code{INTEGER}, @code{CARDINAL}, and | |
5856 | their subranges. | |
5857 | ||
5858 | @item | |
5859 | @emph{Character types} consist of @code{CHAR} and its subranges. | |
5860 | ||
5861 | @item | |
5862 | @emph{Floating-point types} consist of @code{REAL}. | |
5863 | ||
5864 | @item | |
5865 | @emph{Pointer types} consist of anything declared as @code{POINTER TO | |
5866 | @var{type}}. | |
5867 | ||
5868 | @item | |
5869 | @emph{Scalar types} consist of all of the above. | |
5870 | ||
5871 | @item | |
9aa964da | 5872 | @emph{Set types} consist of @code{SET} and @code{BITSET} types. |
c2bbbb22 RP |
5873 | |
5874 | @item | |
5875 | @emph{Boolean types} consist of @code{BOOLEAN}. | |
c2bbbb22 RP |
5876 | @end itemize |
5877 | ||
5878 | @noindent | |
5879 | The following operators are supported, and appear in order of | |
5880 | increasing precedence: | |
5881 | ||
5882 | @table @code | |
c2bbbb22 RP |
5883 | @item , |
5884 | Function argument or array index separator. | |
18fae2a8 | 5885 | |
c2bbbb22 RP |
5886 | @item := |
5887 | Assignment. The value of @var{var} @code{:=} @var{value} is | |
5888 | @var{value}. | |
5889 | ||
5890 | @item <@r{, }> | |
5891 | Less than, greater than on integral, floating-point, or enumerated | |
5892 | types. | |
5893 | ||
5894 | @item <=@r{, }>= | |
5895 | Less than, greater than, less than or equal to, greater than or equal to | |
5896 | on integral, floating-point and enumerated types, or set inclusion on | |
5897 | set types. Same precedence as @code{<}. | |
5898 | ||
5899 | @item =@r{, }<>@r{, }# | |
5900 | Equality and two ways of expressing inequality, valid on scalar types. | |
18fae2a8 | 5901 | Same precedence as @code{<}. In @value{GDBN} scripts, only @code{<>} is |
c2bbbb22 RP |
5902 | available for inequality, since @code{#} conflicts with the script |
5903 | comment character. | |
5904 | ||
5905 | @item IN | |
5906 | Set membership. Defined on set types and the types of their members. | |
5907 | Same precedence as @code{<}. | |
5908 | ||
5909 | @item OR | |
5910 | Boolean disjunction. Defined on boolean types. | |
5911 | ||
5912 | @item AND@r{, }& | |
5913 | Boolean conjuction. Defined on boolean types. | |
5914 | ||
5915 | @item @@ | |
18fae2a8 | 5916 | The @value{GDBN} ``artificial array'' operator (@pxref{Expressions, ,Expressions}). |
c2bbbb22 RP |
5917 | |
5918 | @item +@r{, }- | |
5919 | Addition and subtraction on integral and floating-point types, or union | |
5920 | and difference on set types. | |
5921 | ||
5922 | @item * | |
5923 | Multiplication on integral and floating-point types, or set intersection | |
5924 | on set types. | |
5925 | ||
5926 | @item / | |
5927 | Division on floating-point types, or symmetric set difference on set | |
5928 | types. Same precedence as @code{*}. | |
5929 | ||
5930 | @item DIV@r{, }MOD | |
5931 | Integer division and remainder. Defined on integral types. Same | |
5932 | precedence as @code{*}. | |
5933 | ||
5934 | @item - | |
9aa964da | 5935 | Negative. Defined on @code{INTEGER} and @code{REAL} data. |
c2bbbb22 RP |
5936 | |
5937 | @item ^ | |
e251e767 | 5938 | Pointer dereferencing. Defined on pointer types. |
c2bbbb22 RP |
5939 | |
5940 | @item NOT | |
5941 | Boolean negation. Defined on boolean types. Same precedence as | |
5942 | @code{^}. | |
5943 | ||
5944 | @item . | |
9aa964da | 5945 | @code{RECORD} field selector. Defined on @code{RECORD} data. Same |
c2bbbb22 RP |
5946 | precedence as @code{^}. |
5947 | ||
5948 | @item [] | |
9aa964da | 5949 | Array indexing. Defined on @code{ARRAY} data. Same precedence as @code{^}. |
c2bbbb22 RP |
5950 | |
5951 | @item () | |
9aa964da | 5952 | Procedure argument list. Defined on @code{PROCEDURE} objects. Same precedence |
c2bbbb22 RP |
5953 | as @code{^}. |
5954 | ||
5955 | @item ::@r{, }. | |
18fae2a8 | 5956 | @value{GDBN} and Modula-2 scope operators. |
c2bbbb22 RP |
5957 | @end table |
5958 | ||
5959 | @quotation | |
18fae2a8 | 5960 | @emph{Warning:} Sets and their operations are not yet supported, so @value{GDBN} |
9a27b06e | 5961 | treats the use of the operator @code{IN}, or the use of operators |
c2bbbb22 RP |
5962 | @code{+}, @code{-}, @code{*}, @code{/}, @code{=}, , @code{<>}, @code{#}, |
5963 | @code{<=}, and @code{>=} on sets as an error. | |
5964 | @end quotation | |
18fae2a8 | 5965 | |
29a2b744 | 5966 | @cindex Modula-2 built-ins |
4eb4cf57 | 5967 | @node Built-In Func/Proc |
93928b60 | 5968 | @subsubsection Built-in functions and procedures |
c2bbbb22 RP |
5969 | |
5970 | Modula-2 also makes available several built-in procedures and functions. | |
5971 | In describing these, the following metavariables are used: | |
5972 | ||
5973 | @table @var | |
5974 | ||
5975 | @item a | |
5976 | represents an @code{ARRAY} variable. | |
5977 | ||
5978 | @item c | |
5979 | represents a @code{CHAR} constant or variable. | |
5980 | ||
5981 | @item i | |
5982 | represents a variable or constant of integral type. | |
5983 | ||
5984 | @item m | |
5985 | represents an identifier that belongs to a set. Generally used in the | |
5986 | same function with the metavariable @var{s}. The type of @var{s} should | |
6b51acad | 5987 | be @code{SET OF @var{mtype}} (where @var{mtype} is the type of @var{m}). |
c2bbbb22 RP |
5988 | |
5989 | @item n | |
5990 | represents a variable or constant of integral or floating-point type. | |
5991 | ||
5992 | @item r | |
5993 | represents a variable or constant of floating-point type. | |
5994 | ||
5995 | @item t | |
5996 | represents a type. | |
5997 | ||
5998 | @item v | |
5999 | represents a variable. | |
6000 | ||
6001 | @item x | |
6002 | represents a variable or constant of one of many types. See the | |
6003 | explanation of the function for details. | |
c2bbbb22 RP |
6004 | @end table |
6005 | ||
6006 | All Modula-2 built-in procedures also return a result, described below. | |
6007 | ||
6008 | @table @code | |
6009 | @item ABS(@var{n}) | |
6010 | Returns the absolute value of @var{n}. | |
6011 | ||
6012 | @item CAP(@var{c}) | |
6013 | If @var{c} is a lower case letter, it returns its upper case | |
6014 | equivalent, otherwise it returns its argument | |
6015 | ||
6016 | @item CHR(@var{i}) | |
6017 | Returns the character whose ordinal value is @var{i}. | |
6018 | ||
6019 | @item DEC(@var{v}) | |
6020 | Decrements the value in the variable @var{v}. Returns the new value. | |
6021 | ||
6022 | @item DEC(@var{v},@var{i}) | |
6023 | Decrements the value in the variable @var{v} by @var{i}. Returns the | |
6024 | new value. | |
6025 | ||
6026 | @item EXCL(@var{m},@var{s}) | |
6027 | Removes the element @var{m} from the set @var{s}. Returns the new | |
6028 | set. | |
6029 | ||
6030 | @item FLOAT(@var{i}) | |
6031 | Returns the floating point equivalent of the integer @var{i}. | |
6032 | ||
6033 | @item HIGH(@var{a}) | |
6034 | Returns the index of the last member of @var{a}. | |
6035 | ||
6036 | @item INC(@var{v}) | |
6037 | Increments the value in the variable @var{v}. Returns the new value. | |
6038 | ||
6039 | @item INC(@var{v},@var{i}) | |
6040 | Increments the value in the variable @var{v} by @var{i}. Returns the | |
6041 | new value. | |
6042 | ||
6043 | @item INCL(@var{m},@var{s}) | |
6044 | Adds the element @var{m} to the set @var{s} if it is not already | |
6045 | there. Returns the new set. | |
6046 | ||
6047 | @item MAX(@var{t}) | |
6048 | Returns the maximum value of the type @var{t}. | |
6049 | ||
6050 | @item MIN(@var{t}) | |
6051 | Returns the minimum value of the type @var{t}. | |
6052 | ||
6053 | @item ODD(@var{i}) | |
6054 | Returns boolean TRUE if @var{i} is an odd number. | |
6055 | ||
6056 | @item ORD(@var{x}) | |
6057 | Returns the ordinal value of its argument. For example, the ordinal | |
6058 | value of a character is its ASCII value (on machines supporting the | |
6059 | ASCII character set). @var{x} must be of an ordered type, which include | |
6060 | integral, character and enumerated types. | |
6061 | ||
6062 | @item SIZE(@var{x}) | |
6063 | Returns the size of its argument. @var{x} can be a variable or a type. | |
6064 | ||
6065 | @item TRUNC(@var{r}) | |
6066 | Returns the integral part of @var{r}. | |
6067 | ||
6068 | @item VAL(@var{t},@var{i}) | |
6069 | Returns the member of the type @var{t} whose ordinal value is @var{i}. | |
6070 | @end table | |
6071 | ||
6072 | @quotation | |
6073 | @emph{Warning:} Sets and their operations are not yet supported, so | |
9a27b06e | 6074 | @value{GDBN} treats the use of procedures @code{INCL} and @code{EXCL} as |
c2bbbb22 RP |
6075 | an error. |
6076 | @end quotation | |
6077 | ||
6078 | @cindex Modula-2 constants | |
4eb4cf57 | 6079 | @node M2 Constants |
c2bbbb22 RP |
6080 | @subsubsection Constants |
6081 | ||
18fae2a8 | 6082 | @value{GDBN} allows you to express the constants of Modula-2 in the following |
c2bbbb22 RP |
6083 | ways: |
6084 | ||
6085 | @itemize @bullet | |
6086 | ||
6087 | @item | |
6088 | Integer constants are simply a sequence of digits. When used in an | |
6089 | expression, a constant is interpreted to be type-compatible with the | |
6090 | rest of the expression. Hexadecimal integers are specified by a | |
6091 | trailing @samp{H}, and octal integers by a trailing @samp{B}. | |
6092 | ||
6093 | @item | |
6094 | Floating point constants appear as a sequence of digits, followed by a | |
6095 | decimal point and another sequence of digits. An optional exponent can | |
6096 | then be specified, in the form @samp{E@r{[}+@r{|}-@r{]}@var{nnn}}, where | |
6097 | @samp{@r{[}+@r{|}-@r{]}@var{nnn}} is the desired exponent. All of the | |
6098 | digits of the floating point constant must be valid decimal (base 10) | |
6099 | digits. | |
6100 | ||
6101 | @item | |
6102 | Character constants consist of a single character enclosed by a pair of | |
6103 | like quotes, either single (@code{'}) or double (@code{"}). They may | |
6104 | also be expressed by their ordinal value (their ASCII value, usually) | |
6105 | followed by a @samp{C}. | |
6106 | ||
6107 | @item | |
1041a570 RP |
6108 | String constants consist of a sequence of characters enclosed by a |
6109 | pair of like quotes, either single (@code{'}) or double (@code{"}). | |
6110 | Escape sequences in the style of C are also allowed. @xref{C | |
93928b60 | 6111 | Constants, ,C and C++ constants}, for a brief explanation of escape |
1041a570 | 6112 | sequences. |
c2bbbb22 RP |
6113 | |
6114 | @item | |
6115 | Enumerated constants consist of an enumerated identifier. | |
6116 | ||
6117 | @item | |
6118 | Boolean constants consist of the identifiers @code{TRUE} and | |
6119 | @code{FALSE}. | |
6120 | ||
6121 | @item | |
6122 | Pointer constants consist of integral values only. | |
6123 | ||
6124 | @item | |
6125 | Set constants are not yet supported. | |
c2bbbb22 RP |
6126 | @end itemize |
6127 | ||
4eb4cf57 | 6128 | @node M2 Defaults |
93928b60 | 6129 | @subsubsection Modula-2 defaults |
c2bbbb22 RP |
6130 | @cindex Modula-2 defaults |
6131 | ||
18fae2a8 | 6132 | If type and range checking are set automatically by @value{GDBN}, they |
e251e767 | 6133 | both default to @code{on} whenever the working language changes to |
18fae2a8 | 6134 | Modula-2. This happens regardless of whether you, or @value{GDBN}, |
c2bbbb22 RP |
6135 | selected the working language. |
6136 | ||
18fae2a8 | 6137 | If you allow @value{GDBN} to set the language automatically, then entering |
9a27b06e | 6138 | code compiled from a file whose name ends with @file{.mod} sets the |
18fae2a8 | 6139 | working language to Modula-2. @xref{Automatically, ,Having @value{GDBN} set |
c2bbbb22 RP |
6140 | the language automatically}, for further details. |
6141 | ||
4eb4cf57 | 6142 | @node Deviations |
93928b60 | 6143 | @subsubsection Deviations from standard Modula-2 |
c2bbbb22 RP |
6144 | @cindex Modula-2, deviations from |
6145 | ||
6146 | A few changes have been made to make Modula-2 programs easier to debug. | |
6147 | This is done primarily via loosening its type strictness: | |
6148 | ||
6149 | @itemize @bullet | |
e251e767 | 6150 | @item |
c2bbbb22 RP |
6151 | Unlike in standard Modula-2, pointer constants can be formed by |
6152 | integers. This allows you to modify pointer variables during | |
6153 | debugging. (In standard Modula-2, the actual address contained in a | |
6154 | pointer variable is hidden from you; it can only be modified | |
6155 | through direct assignment to another pointer variable or expression that | |
6156 | returned a pointer.) | |
6157 | ||
e251e767 | 6158 | @item |
c2bbbb22 | 6159 | C escape sequences can be used in strings and characters to represent |
9a27b06e | 6160 | non-printable characters. @value{GDBN} prints out strings with these |
c2bbbb22 RP |
6161 | escape sequences embedded. Single non-printable characters are |
6162 | printed using the @samp{CHR(@var{nnn})} format. | |
6163 | ||
6164 | @item | |
6165 | The assignment operator (@code{:=}) returns the value of its right-hand | |
6166 | argument. | |
6167 | ||
6168 | @item | |
29a2b744 | 6169 | All built-in procedures both modify @emph{and} return their argument. |
e251e767 | 6170 | @end itemize |
c2bbbb22 | 6171 | |
4eb4cf57 | 6172 | @node M2 Checks |
93928b60 | 6173 | @subsubsection Modula-2 type and range checks |
c2bbbb22 RP |
6174 | @cindex Modula-2 checks |
6175 | ||
6176 | @quotation | |
18fae2a8 | 6177 | @emph{Warning:} in this release, @value{GDBN} does not yet perform type or |
c2bbbb22 RP |
6178 | range checking. |
6179 | @end quotation | |
6180 | @c FIXME remove warning when type/range checks added | |
6181 | ||
18fae2a8 | 6182 | @value{GDBN} considers two Modula-2 variables type equivalent if: |
c2bbbb22 RP |
6183 | |
6184 | @itemize @bullet | |
6185 | @item | |
6186 | They are of types that have been declared equivalent via a @code{TYPE | |
6187 | @var{t1} = @var{t2}} statement | |
6188 | ||
6189 | @item | |
6190 | They have been declared on the same line. (Note: This is true of the | |
6191 | GNU Modula-2 compiler, but it may not be true of other compilers.) | |
c2bbbb22 RP |
6192 | @end itemize |
6193 | ||
6194 | As long as type checking is enabled, any attempt to combine variables | |
6195 | whose types are not equivalent is an error. | |
6196 | ||
6197 | Range checking is done on all mathematical operations, assignment, array | |
29a2b744 | 6198 | index bounds, and all built-in functions and procedures. |
c2bbbb22 | 6199 | |
4eb4cf57 | 6200 | @node M2 Scope |
c2bbbb22 RP |
6201 | @subsubsection The scope operators @code{::} and @code{.} |
6202 | @cindex scope | |
6203 | @kindex . | |
e94b4a2b | 6204 | @cindex colon, doubled as scope operator |
1041a570 RP |
6205 | @ifinfo |
6206 | @kindex colon-colon | |
ed447b95 | 6207 | @c Info cannot handle :: but TeX can. |
1041a570 RP |
6208 | @end ifinfo |
6209 | @iftex | |
c2bbbb22 | 6210 | @kindex :: |
1041a570 | 6211 | @end iftex |
c2bbbb22 RP |
6212 | |
6213 | There are a few subtle differences between the Modula-2 scope operator | |
18fae2a8 | 6214 | (@code{.}) and the @value{GDBN} scope operator (@code{::}). The two have |
c2bbbb22 RP |
6215 | similar syntax: |
6216 | ||
6217 | @example | |
6218 | ||
6219 | @var{module} . @var{id} | |
6220 | @var{scope} :: @var{id} | |
c2bbbb22 RP |
6221 | @end example |
6222 | ||
6223 | @noindent | |
6224 | where @var{scope} is the name of a module or a procedure, | |
29a2b744 RP |
6225 | @var{module} the name of a module, and @var{id} is any declared |
6226 | identifier within your program, except another module. | |
c2bbbb22 | 6227 | |
18fae2a8 | 6228 | Using the @code{::} operator makes @value{GDBN} search the scope |
c2bbbb22 | 6229 | specified by @var{scope} for the identifier @var{id}. If it is not |
9a27b06e | 6230 | found in the specified scope, then @value{GDBN} searches all scopes |
c2bbbb22 RP |
6231 | enclosing the one specified by @var{scope}. |
6232 | ||
18fae2a8 | 6233 | Using the @code{.} operator makes @value{GDBN} search the current scope for |
c2bbbb22 RP |
6234 | the identifier specified by @var{id} that was imported from the |
6235 | definition module specified by @var{module}. With this operator, it is | |
6236 | an error if the identifier @var{id} was not imported from definition | |
6237 | module @var{module}, or if @var{id} is not an identifier in | |
6238 | @var{module}. | |
6239 | ||
4eb4cf57 | 6240 | @node GDB/M2 |
18fae2a8 | 6241 | @subsubsection @value{GDBN} and Modula-2 |
c2bbbb22 | 6242 | |
18fae2a8 | 6243 | Some @value{GDBN} commands have little use when debugging Modula-2 programs. |
c2bbbb22 RP |
6244 | Five subcommands of @code{set print} and @code{show print} apply |
6245 | specifically to C and C++: @samp{vtbl}, @samp{demangle}, | |
6246 | @samp{asm-demangle}, @samp{object}, and @samp{union}. The first four | |
93918348 | 6247 | apply to C++, and the last to the C @code{union} type, which has no direct |
c2bbbb22 RP |
6248 | analogue in Modula-2. |
6249 | ||
1041a570 | 6250 | The @code{@@} operator (@pxref{Expressions, ,Expressions}), while available |
c2bbbb22 RP |
6251 | while using any language, is not useful with Modula-2. Its |
6252 | intent is to aid the debugging of @dfn{dynamic arrays}, which cannot be | |
6253 | created in Modula-2 as they can in C or C++. However, because an | |
6254 | address can be specified by an integral constant, the construct | |
1041a570 | 6255 | @samp{@{@var{type}@}@var{adrexp}} is still useful. (@pxref{Expressions, ,Expressions}) |
18fae2a8 | 6256 | |
c2bbbb22 | 6257 | @cindex @code{#} in Modula-2 |
18fae2a8 | 6258 | In @value{GDBN} scripts, the Modula-2 inequality operator @code{#} is |
c2bbbb22 | 6259 | interpreted as the beginning of a comment. Use @code{<>} instead. |
18fae2a8 | 6260 | |
09934a2b | 6261 | @end ifset |
da374d80 | 6262 | @end ifclear |
4eb4cf57 RP |
6263 | |
6264 | @node Symbols | |
70b88761 RP |
6265 | @chapter Examining the Symbol Table |
6266 | ||
6267 | The commands described in this section allow you to inquire about the | |
6268 | symbols (names of variables, functions and types) defined in your | |
6269 | program. This information is inherent in the text of your program and | |
18fae2a8 RP |
6270 | does not change as your program executes. @value{GDBN} finds it in your |
6271 | program's symbol table, in the file indicated when you started @value{GDBN} | |
93928b60 RP |
6272 | (@pxref{File Options, ,Choosing files}), or by one of the |
6273 | file-management commands (@pxref{Files, ,Commands to specify files}). | |
70b88761 | 6274 | |
6c380b13 RP |
6275 | @c FIXME! This might be intentionally specific to C and C++; if so, move |
6276 | @c to someplace in C section of lang chapter. | |
6277 | @cindex symbol names | |
6278 | @cindex names of symbols | |
6279 | @cindex quoting names | |
6280 | Occasionally, you may need to refer to symbols that contain unusual | |
18fae2a8 | 6281 | characters, which @value{GDBN} ordinarily treats as word delimiters. The |
6c380b13 | 6282 | most frequent case is in referring to static variables in other |
93928b60 | 6283 | source files (@pxref{Variables,,Program variables}). File names |
18fae2a8 | 6284 | are recorded in object files as debugging symbols, but @value{GDBN} would |
6c380b13 | 6285 | ordinarily parse a typical file name, like @file{foo.c}, as the three words |
18fae2a8 | 6286 | @samp{foo} @samp{.} @samp{c}. To allow @value{GDBN} to recognize |
6c380b13 RP |
6287 | @samp{foo.c} as a single symbol, enclose it in single quotes; for example, |
6288 | ||
6289 | @example | |
6290 | p 'foo.c'::x | |
6291 | @end example | |
6292 | ||
6293 | @noindent | |
6294 | looks up the value of @code{x} in the scope of the file @file{foo.c}. | |
6295 | ||
70b88761 RP |
6296 | @table @code |
6297 | @item info address @var{symbol} | |
6298 | @kindex info address | |
6299 | Describe where the data for @var{symbol} is stored. For a register | |
6300 | variable, this says which register it is kept in. For a non-register | |
6301 | local variable, this prints the stack-frame offset at which the variable | |
6302 | is always stored. | |
6303 | ||
6304 | Note the contrast with @samp{print &@var{symbol}}, which does not work | |
6b51acad | 6305 | at all for a register variable, and for a stack local variable prints |
70b88761 RP |
6306 | the exact address of the current instantiation of the variable. |
6307 | ||
6308 | @item whatis @var{exp} | |
6309 | @kindex whatis | |
6310 | Print the data type of expression @var{exp}. @var{exp} is not | |
6311 | actually evaluated, and any side-effecting operations (such as | |
6312 | assignments or function calls) inside it do not take place. | |
1041a570 | 6313 | @xref{Expressions, ,Expressions}. |
70b88761 RP |
6314 | |
6315 | @item whatis | |
6316 | Print the data type of @code{$}, the last value in the value history. | |
6317 | ||
6318 | @item ptype @var{typename} | |
6319 | @kindex ptype | |
6320 | Print a description of data type @var{typename}. @var{typename} may be | |
6321 | the name of a type, or for C code it may have the form | |
25f9d853 JK |
6322 | @ifclear CONLY |
6323 | @samp{class @var{class-name}}, | |
6324 | @end ifclear | |
70b88761 | 6325 | @samp{struct @var{struct-tag}}, @samp{union @var{union-tag}} or |
1041a570 | 6326 | @samp{enum @var{enum-tag}}. |
70b88761 RP |
6327 | |
6328 | @item ptype @var{exp} | |
e0dacfd1 | 6329 | @itemx ptype |
70b88761 | 6330 | Print a description of the type of expression @var{exp}. @code{ptype} |
1041a570 | 6331 | differs from @code{whatis} by printing a detailed description, instead |
ed447b95 RP |
6332 | of just the name of the type. |
6333 | ||
6334 | For example, for this variable declaration: | |
1041a570 | 6335 | |
70b88761 RP |
6336 | @example |
6337 | struct complex @{double real; double imag;@} v; | |
6338 | @end example | |
1041a570 | 6339 | |
70b88761 | 6340 | @noindent |
ed447b95 | 6341 | the two commands give this output: |
1041a570 | 6342 | |
70b88761 | 6343 | @example |
1041a570 | 6344 | @group |
18fae2a8 | 6345 | (@value{GDBP}) whatis v |
70b88761 | 6346 | type = struct complex |
18fae2a8 | 6347 | (@value{GDBP}) ptype v |
70b88761 RP |
6348 | type = struct complex @{ |
6349 | double real; | |
6350 | double imag; | |
6351 | @} | |
1041a570 | 6352 | @end group |
70b88761 | 6353 | @end example |
1041a570 | 6354 | |
e0dacfd1 RP |
6355 | @noindent |
6356 | As with @code{whatis}, using @code{ptype} without an argument refers to | |
6357 | the type of @code{$}, the last value in the value history. | |
70b88761 RP |
6358 | |
6359 | @item info types @var{regexp} | |
6360 | @itemx info types | |
e251e767 | 6361 | @kindex info types |
70b88761 RP |
6362 | Print a brief description of all types whose name matches @var{regexp} |
6363 | (or all types in your program, if you supply no argument). Each | |
6364 | complete typename is matched as though it were a complete line; thus, | |
6365 | @samp{i type value} gives information on all types in your program whose | |
6366 | name includes the string @code{value}, but @samp{i type ^value$} gives | |
6367 | information only on types whose complete name is @code{value}. | |
6368 | ||
6369 | This command differs from @code{ptype} in two ways: first, like | |
6370 | @code{whatis}, it does not print a detailed description; second, it | |
6371 | lists all source files where a type is defined. | |
6372 | ||
6373 | @item info source | |
6374 | @kindex info source | |
6375 | Show the name of the current source file---that is, the source file for | |
c2bbbb22 RP |
6376 | the function containing the current point of execution---and the language |
6377 | it was written in. | |
70b88761 RP |
6378 | |
6379 | @item info sources | |
6380 | @kindex info sources | |
29a2b744 | 6381 | Print the names of all source files in your program for which there is |
b80282d5 RP |
6382 | debugging information, organized into two lists: files whose symbols |
6383 | have already been read, and files whose symbols will be read when needed. | |
70b88761 RP |
6384 | |
6385 | @item info functions | |
6386 | @kindex info functions | |
6387 | Print the names and data types of all defined functions. | |
6388 | ||
6389 | @item info functions @var{regexp} | |
6390 | Print the names and data types of all defined functions | |
6391 | whose names contain a match for regular expression @var{regexp}. | |
6392 | Thus, @samp{info fun step} finds all functions whose names | |
6393 | include @code{step}; @samp{info fun ^step} finds those whose names | |
6394 | start with @code{step}. | |
6395 | ||
6396 | @item info variables | |
6397 | @kindex info variables | |
6398 | Print the names and data types of all variables that are declared | |
6399 | outside of functions (i.e., excluding local variables). | |
6400 | ||
6401 | @item info variables @var{regexp} | |
6402 | Print the names and data types of all variables (except for local | |
6403 | variables) whose names contain a match for regular expression | |
6404 | @var{regexp}. | |
6405 | ||
70b88761 RP |
6406 | @ignore |
6407 | This was never implemented. | |
6408 | @item info methods | |
6409 | @itemx info methods @var{regexp} | |
6410 | @kindex info methods | |
6411 | The @code{info methods} command permits the user to examine all defined | |
6412 | methods within C++ program, or (with the @var{regexp} argument) a | |
6413 | specific set of methods found in the various C++ classes. Many | |
6414 | C++ classes provide a large number of methods. Thus, the output | |
6415 | from the @code{ptype} command can be overwhelming and hard to use. The | |
6416 | @code{info-methods} command filters the methods, printing only those | |
6417 | which match the regular-expression @var{regexp}. | |
6418 | @end ignore | |
6419 | ||
d48da190 RP |
6420 | @item maint print symbols @var{filename} |
6421 | @itemx maint print psymbols @var{filename} | |
6422 | @itemx maint print msymbols @var{filename} | |
6423 | @kindex maint print symbols | |
440d9834 | 6424 | @cindex symbol dump |
d48da190 | 6425 | @kindex maint print psymbols |
440d9834 RP |
6426 | @cindex partial symbol dump |
6427 | Write a dump of debugging symbol data into the file @var{filename}. | |
18fae2a8 | 6428 | These commands are used to debug the @value{GDBN} symbol-reading code. Only |
d48da190 | 6429 | symbols with debugging data are included. If you use @samp{maint print |
18fae2a8 | 6430 | symbols}, @value{GDBN} includes all the symbols for which it has already |
d48da190 | 6431 | collected full details: that is, @var{filename} reflects symbols for |
18fae2a8 | 6432 | only those files whose symbols @value{GDBN} has read. You can use the |
d48da190 RP |
6433 | command @code{info sources} to find out which files these are. If you |
6434 | use @samp{maint print psymbols} instead, the dump shows information about | |
18fae2a8 RP |
6435 | symbols that @value{GDBN} only knows partially---that is, symbols defined in |
6436 | files that @value{GDBN} has skimmed, but not yet read completely. Finally, | |
d48da190 | 6437 | @samp{maint print msymbols} dumps just the minimal symbol information |
18fae2a8 | 6438 | required for each object file from which @value{GDBN} has read some symbols. |
d55320a0 RP |
6439 | @xref{Files, ,Commands to specify files}, for a discussion of how |
6440 | @value{GDBN} reads symbols (in the description of @code{symbol-file}). | |
70b88761 RP |
6441 | @end table |
6442 | ||
4eb4cf57 | 6443 | @node Altering |
70b88761 RP |
6444 | @chapter Altering Execution |
6445 | ||
29a2b744 | 6446 | Once you think you have found an error in your program, you might want to |
70b88761 RP |
6447 | find out for certain whether correcting the apparent error would lead to |
6448 | correct results in the rest of the run. You can find the answer by | |
18fae2a8 | 6449 | experiment, using the @value{GDBN} features for altering execution of the |
70b88761 RP |
6450 | program. |
6451 | ||
6452 | For example, you can store new values into variables or memory | |
1d7c3357 | 6453 | locations, |
18fae2a8 | 6454 | @ifclear BARETARGET |
1d7c3357 | 6455 | give your program a signal, restart it |
18fae2a8 | 6456 | @end ifclear |
1d7c3357 RP |
6457 | @ifset BARETARGET |
6458 | restart your program | |
6459 | @end ifset | |
6460 | at a different address, or even return prematurely from a function to | |
6461 | its caller. | |
18fae2a8 | 6462 | |
18fae2a8 | 6463 | @menu |
ed447b95 RP |
6464 | * Assignment:: Assignment to variables |
6465 | * Jumping:: Continuing at a different address | |
1d7c3357 | 6466 | @ifclear BARETARGET |
ed447b95 | 6467 | * Signaling:: Giving your program a signal |
18fae2a8 | 6468 | @end ifclear |
b0157555 | 6469 | |
ed447b95 RP |
6470 | * Returning:: Returning from a function |
6471 | * Calling:: Calling your program's functions | |
6472 | * Patching:: Patching your program | |
18fae2a8 | 6473 | @end menu |
70b88761 | 6474 | |
4eb4cf57 | 6475 | @node Assignment |
93928b60 | 6476 | @section Assignment to variables |
70b88761 RP |
6477 | |
6478 | @cindex assignment | |
6479 | @cindex setting variables | |
6480 | To alter the value of a variable, evaluate an assignment expression. | |
1041a570 | 6481 | @xref{Expressions, ,Expressions}. For example, |
70b88761 RP |
6482 | |
6483 | @example | |
6484 | print x=4 | |
6485 | @end example | |
6486 | ||
6487 | @noindent | |
1041a570 | 6488 | stores the value 4 into the variable @code{x}, and then prints the |
4eb4cf57 | 6489 | value of the assignment expression (which is 4). |
18fae2a8 RP |
6490 | @ifclear CONLY |
6491 | @xref{Languages, ,Using @value{GDBN} with Different Languages}, for more | |
4eb4cf57 | 6492 | information on operators in supported languages. |
18fae2a8 | 6493 | @end ifclear |
70b88761 | 6494 | |
70b88761 RP |
6495 | @kindex set variable |
6496 | @cindex variables, setting | |
6497 | If you are not interested in seeing the value of the assignment, use the | |
6498 | @code{set} command instead of the @code{print} command. @code{set} is | |
93928b60 RP |
6499 | really the same as @code{print} except that the expression's value is |
6500 | not printed and is not put in the value history (@pxref{Value History, | |
6501 | ,Value history}). The expression is evaluated only for its effects. | |
70b88761 RP |
6502 | |
6503 | If the beginning of the argument string of the @code{set} command | |
6504 | appears identical to a @code{set} subcommand, use the @code{set | |
6505 | variable} command instead of just @code{set}. This command is identical | |
ed447b95 RP |
6506 | to @code{set} except for its lack of subcommands. For example, if |
6507 | your program has a variable @code{width}, you get | |
6508 | an error if you try to set a new value with just @samp{set width=13}, | |
6509 | because @value{GDBN} has the command @code{set width}: | |
1041a570 | 6510 | |
70b88761 | 6511 | @example |
18fae2a8 | 6512 | (@value{GDBP}) whatis width |
70b88761 | 6513 | type = double |
18fae2a8 | 6514 | (@value{GDBP}) p width |
70b88761 | 6515 | $4 = 13 |
18fae2a8 | 6516 | (@value{GDBP}) set width=47 |
70b88761 RP |
6517 | Invalid syntax in expression. |
6518 | @end example | |
1041a570 | 6519 | |
70b88761 | 6520 | @noindent |
ed447b95 RP |
6521 | The invalid expression, of course, is @samp{=47}. In |
6522 | order to actually set the program's variable @code{width}, use | |
1041a570 | 6523 | |
70b88761 | 6524 | @example |
18fae2a8 | 6525 | (@value{GDBP}) set var width=47 |
70b88761 RP |
6526 | @end example |
6527 | ||
18fae2a8 | 6528 | @value{GDBN} allows more implicit conversions in assignments than C; you can |
1041a570 | 6529 | freely store an integer value into a pointer variable or vice versa, |
ed447b95 | 6530 | and you can convert any structure to any other structure that is the |
1041a570 | 6531 | same length or shorter. |
e251e767 | 6532 | @comment FIXME: how do structs align/pad in these conversions? |
70b88761 RP |
6533 | @comment /pesch@cygnus.com 18dec1990 |
6534 | ||
6535 | To store values into arbitrary places in memory, use the @samp{@{@dots{}@}} | |
6536 | construct to generate a value of specified type at a specified address | |
1041a570 | 6537 | (@pxref{Expressions, ,Expressions}). For example, @code{@{int@}0x83040} refers |
70b88761 RP |
6538 | to memory location @code{0x83040} as an integer (which implies a certain size |
6539 | and representation in memory), and | |
6540 | ||
6541 | @example | |
6542 | set @{int@}0x83040 = 4 | |
6543 | @end example | |
6544 | ||
6545 | @noindent | |
6546 | stores the value 4 into that memory location. | |
6547 | ||
4eb4cf57 | 6548 | @node Jumping |
93928b60 | 6549 | @section Continuing at a different address |
70b88761 | 6550 | |
29a2b744 | 6551 | Ordinarily, when you continue your program, you do so at the place where |
70b88761 RP |
6552 | it stopped, with the @code{continue} command. You can instead continue at |
6553 | an address of your own choosing, with the following commands: | |
6554 | ||
6555 | @table @code | |
6556 | @item jump @var{linespec} | |
6557 | @kindex jump | |
9a27b06e | 6558 | Resume execution at line @var{linespec}. Execution stops again |
29a2b744 | 6559 | immediately if there is a breakpoint there. @xref{List, ,Printing |
93928b60 | 6560 | source lines}, for a description of the different forms of |
29a2b744 | 6561 | @var{linespec}. |
70b88761 RP |
6562 | |
6563 | The @code{jump} command does not change the current stack frame, or | |
6564 | the stack pointer, or the contents of any memory location or any | |
6565 | register other than the program counter. If line @var{linespec} is in | |
6566 | a different function from the one currently executing, the results may | |
6567 | be bizarre if the two functions expect different patterns of arguments or | |
6568 | of local variables. For this reason, the @code{jump} command requests | |
6569 | confirmation if the specified line is not in the function currently | |
6570 | executing. However, even bizarre results are predictable if you are | |
29a2b744 | 6571 | well acquainted with the machine-language code of your program. |
70b88761 RP |
6572 | |
6573 | @item jump *@var{address} | |
6574 | Resume execution at the instruction at address @var{address}. | |
6575 | @end table | |
6576 | ||
6577 | You can get much the same effect as the @code{jump} command by storing a | |
6578 | new value into the register @code{$pc}. The difference is that this | |
29a2b744 | 6579 | does not start your program running; it only changes the address where it |
9a27b06e | 6580 | @emph{will} run when you continue. For example, |
70b88761 RP |
6581 | |
6582 | @example | |
6583 | set $pc = 0x485 | |
6584 | @end example | |
6585 | ||
6586 | @noindent | |
9a27b06e | 6587 | makes the next @code{continue} command or stepping command execute at |
1041a570 | 6588 | address @code{0x485}, rather than at the address where your program stopped. |
93928b60 | 6589 | @xref{Continuing and Stepping, ,Continuing and stepping}. |
70b88761 RP |
6590 | |
6591 | The most common occasion to use the @code{jump} command is to back up, | |
6592 | perhaps with more breakpoints set, over a portion of a program that has | |
6593 | already executed, in order to examine its execution in more detail. | |
6594 | ||
18fae2a8 | 6595 | @ifclear BARETARGET |
70b88761 | 6596 | @c @group |
ed447b95 RP |
6597 | @node Signaling |
6598 | @section Giving your program a signal | |
70b88761 RP |
6599 | |
6600 | @table @code | |
fd32a1dd | 6601 | @item signal @var{signal} |
70b88761 | 6602 | @kindex signal |
6b51acad | 6603 | Resume execution where your program stopped, but immediately give it the |
fd32a1dd JK |
6604 | signal @var{signal}. @var{signal} can be the name or the number of a |
6605 | signal. For example, on many systems @code{signal 2} and @code{signal | |
6606 | SIGINT} are both ways of sending an interrupt signal. | |
70b88761 | 6607 | |
fd32a1dd | 6608 | Alternatively, if @var{signal} is zero, continue execution without |
29a2b744 | 6609 | giving a signal. This is useful when your program stopped on account of |
70b88761 RP |
6610 | a signal and would ordinary see the signal when resumed with the |
6611 | @code{continue} command; @samp{signal 0} causes it to resume without a | |
6612 | signal. | |
6613 | ||
6614 | @code{signal} does not repeat when you press @key{RET} a second time | |
6615 | after executing the command. | |
6616 | @end table | |
6617 | @c @end group | |
fd32a1dd JK |
6618 | |
6619 | Invoking the @code{signal} command is not the same as invoking the | |
6620 | @code{kill} utility from the shell. Sending a signal with @code{kill} | |
6621 | causes @value{GDBN} to decide what to do with the signal depending on | |
6622 | the signal handling tables (@pxref{Signals}). The @code{signal} command | |
6623 | passes the signal directly to your program. | |
6624 | ||
18fae2a8 | 6625 | @end ifclear |
70b88761 | 6626 | |
4eb4cf57 | 6627 | @node Returning |
93928b60 | 6628 | @section Returning from a function |
70b88761 RP |
6629 | |
6630 | @table @code | |
6631 | @item return | |
6632 | @itemx return @var{expression} | |
6633 | @cindex returning from a function | |
6634 | @kindex return | |
6635 | You can cancel execution of a function call with the @code{return} | |
6636 | command. If you give an | |
6637 | @var{expression} argument, its value is used as the function's return | |
e251e767 | 6638 | value. |
70b88761 RP |
6639 | @end table |
6640 | ||
18fae2a8 | 6641 | When you use @code{return}, @value{GDBN} discards the selected stack frame |
70b88761 RP |
6642 | (and all frames within it). You can think of this as making the |
6643 | discarded frame return prematurely. If you wish to specify a value to | |
6644 | be returned, give that value as the argument to @code{return}. | |
6645 | ||
29a2b744 | 6646 | This pops the selected stack frame (@pxref{Selection, ,Selecting a |
93928b60 | 6647 | frame}), and any other frames inside of it, leaving its caller as the |
29a2b744 RP |
6648 | innermost remaining frame. That frame becomes selected. The |
6649 | specified value is stored in the registers used for returning values | |
6650 | of functions. | |
70b88761 RP |
6651 | |
6652 | The @code{return} command does not resume execution; it leaves the | |
6653 | program stopped in the state that would exist if the function had just | |
1041a570 | 6654 | returned. In contrast, the @code{finish} command (@pxref{Continuing |
93928b60 | 6655 | and Stepping, ,Continuing and stepping}) resumes execution until the |
1041a570 | 6656 | selected stack frame returns naturally. |
70b88761 | 6657 | |
4eb4cf57 | 6658 | @node Calling |
ed447b95 | 6659 | @section Calling program functions |
70b88761 RP |
6660 | |
6661 | @cindex calling functions | |
6662 | @kindex call | |
6663 | @table @code | |
6664 | @item call @var{expr} | |
6665 | Evaluate the expression @var{expr} without displaying @code{void} | |
6666 | returned values. | |
6667 | @end table | |
6668 | ||
6669 | You can use this variant of the @code{print} command if you want to | |
6670 | execute a function from your program, but without cluttering the output | |
6671 | with @code{void} returned values. The result is printed and saved in | |
6672 | the value history, if it is not void. | |
6673 | ||
4eb4cf57 | 6674 | @node Patching |
ed447b95 | 6675 | @section Patching programs |
c338a2fd RP |
6676 | @cindex patching binaries |
6677 | @cindex writing into executables | |
1d7c3357 | 6678 | @ifclear BARETARGET |
c338a2fd | 6679 | @cindex writing into corefiles |
1d7c3357 | 6680 | @end ifclear |
1041a570 | 6681 | |
18fae2a8 | 6682 | By default, @value{GDBN} opens the file containing your program's executable |
1d7c3357 RP |
6683 | code |
6684 | @ifclear BARETARGET | |
6685 | (or the corefile) | |
6686 | @end ifclear | |
6687 | read-only. This prevents accidental alterations | |
c338a2fd RP |
6688 | to machine code; but it also prevents you from intentionally patching |
6689 | your program's binary. | |
6690 | ||
6691 | If you'd like to be able to patch the binary, you can specify that | |
6692 | explicitly with the @code{set write} command. For example, you might | |
6693 | want to turn on internal debugging flags, or even to make emergency | |
e251e767 | 6694 | repairs. |
c338a2fd RP |
6695 | |
6696 | @table @code | |
6697 | @item set write on | |
6698 | @itemx set write off | |
6699 | @kindex set write | |
9a27b06e | 6700 | If you specify @samp{set write on}, @value{GDBN} opens executable |
18fae2a8 | 6701 | @ifclear BARETARGET |
0f153e74 | 6702 | and core |
18fae2a8 | 6703 | @end ifclear |
0f153e74 | 6704 | files for both reading and writing; if you specify @samp{set write |
9a27b06e | 6705 | off} (the default), @value{GDBN} opens them read-only. |
c338a2fd | 6706 | |
1d7c3357 RP |
6707 | If you have already loaded a file, you must load it again (using the |
6708 | @code{exec-file} | |
6709 | @ifclear BARETARGET | |
6710 | or @code{core-file} | |
6711 | @end ifclear | |
6712 | command) after changing @code{set write}, for your new setting to take | |
6713 | effect. | |
c338a2fd RP |
6714 | |
6715 | @item show write | |
7d7ff5f6 | 6716 | @kindex show write |
0f153e74 | 6717 | Display whether executable files |
18fae2a8 | 6718 | @ifclear BARETARGET |
0f153e74 | 6719 | and core files |
18fae2a8 | 6720 | @end ifclear |
9a27b06e | 6721 | are opened for writing as well as reading. |
c338a2fd RP |
6722 | @end table |
6723 | ||
18fae2a8 | 6724 | @node GDB Files |
93918348 | 6725 | @chapter @value{GDBN} Files |
70b88761 | 6726 | |
18fae2a8 | 6727 | @value{GDBN} needs to know the file name of the program to be debugged, both in |
4eb4cf57 | 6728 | order to read its symbol table and in order to start your program. |
18fae2a8 | 6729 | @ifclear BARETARGET |
93918348 RP |
6730 | To debug a core dump of a previous run, you must also tell @value{GDBN} |
6731 | the name of the core dump file. | |
18fae2a8 | 6732 | @end ifclear |
1041a570 | 6733 | |
70b88761 | 6734 | @menu |
ed447b95 RP |
6735 | * Files:: Commands to specify files |
6736 | * Symbol Errors:: Errors reading symbol files | |
70b88761 RP |
6737 | @end menu |
6738 | ||
4eb4cf57 | 6739 | @node Files |
93928b60 | 6740 | @section Commands to specify files |
70b88761 | 6741 | @cindex symbol table |
70b88761 | 6742 | |
18fae2a8 | 6743 | @ifclear BARETARGET |
0f153e74 | 6744 | @cindex core dump file |
1041a570 | 6745 | The usual way to specify executable and core dump file names is with |
ed447b95 | 6746 | the command arguments given when you start @value{GDBN} (@pxref{Invocation, |
18fae2a8 RP |
6747 | ,Getting In and Out of @value{GDBN}}. |
6748 | @end ifclear | |
6749 | @ifset BARETARGET | |
4eb4cf57 | 6750 | The usual way to specify an executable file name is with |
18fae2a8 RP |
6751 | the command argument given when you start @value{GDBN}, (@pxref{Invocation, |
6752 | ,Getting In and Out of @value{GDBN}}. | |
6753 | @end ifset | |
70b88761 RP |
6754 | |
6755 | Occasionally it is necessary to change to a different file during a | |
93918348 RP |
6756 | @value{GDBN} session. Or you may run @value{GDBN} and forget to specify |
6757 | a file you want to use. In these situations the @value{GDBN} commands | |
6758 | to specify new files are useful. | |
70b88761 RP |
6759 | |
6760 | @table @code | |
6761 | @item file @var{filename} | |
6762 | @cindex executable file | |
6763 | @kindex file | |
6764 | Use @var{filename} as the program to be debugged. It is read for its | |
6765 | symbols and for the contents of pure memory. It is also the program | |
6766 | executed when you use the @code{run} command. If you do not specify a | |
93918348 | 6767 | directory and the file is not found in the @value{GDBN} working directory, @value{GDBN} |
1041a570 RP |
6768 | uses the environment variable @code{PATH} as a list of directories to |
6769 | search, just as the shell does when looking for a program to run. You | |
18fae2a8 | 6770 | can change the value of this variable, for both @value{GDBN} and your program, |
1041a570 | 6771 | using the @code{path} command. |
70b88761 | 6772 | |
9a27b06e RP |
6773 | On systems with memory-mapped files, an auxiliary file |
6774 | @file{@var{filename}.syms} may hold symbol table information for | |
6775 | @var{filename}. If so, @value{GDBN} maps in the symbol table from | |
14d01801 | 6776 | @file{@var{filename}.syms}, starting up more quickly. See the |
9a27b06e RP |
6777 | descriptions of the options @samp{-mapped} and @samp{-readnow} |
6778 | (available on the command line, and with the commands @code{file}, | |
6779 | @code{symbol-file}, or @code{add-symbol-file}), for more information. | |
14d01801 | 6780 | |
e0dacfd1 | 6781 | @item file |
18fae2a8 | 6782 | @code{file} with no argument makes @value{GDBN} discard any information it |
70b88761 RP |
6783 | has on both executable file and the symbol table. |
6784 | ||
e0dacfd1 | 6785 | @item exec-file @r{[} @var{filename} @r{]} |
70b88761 RP |
6786 | @kindex exec-file |
6787 | Specify that the program to be run (but not the symbol table) is found | |
9a27b06e | 6788 | in @var{filename}. @value{GDBN} searches the environment variable @code{PATH} |
29a2b744 | 6789 | if necessary to locate your program. Omitting @var{filename} means to |
e0dacfd1 | 6790 | discard information on the executable file. |
70b88761 | 6791 | |
e0dacfd1 | 6792 | @item symbol-file @r{[} @var{filename} @r{]} |
70b88761 RP |
6793 | @kindex symbol-file |
6794 | Read symbol table information from file @var{filename}. @code{PATH} is | |
6795 | searched when necessary. Use the @code{file} command to get both symbol | |
6796 | table and program to run from the same file. | |
6797 | ||
93918348 | 6798 | @code{symbol-file} with no argument clears out @value{GDBN} information on your |
70b88761 RP |
6799 | program's symbol table. |
6800 | ||
18fae2a8 | 6801 | The @code{symbol-file} command causes @value{GDBN} to forget the contents of its |
70b88761 RP |
6802 | convenience variables, the value history, and all breakpoints and |
6803 | auto-display expressions. This is because they may contain pointers to | |
6804 | the internal data recording symbols and data types, which are part of | |
18fae2a8 | 6805 | the old symbol table data being discarded inside @value{GDBN}. |
70b88761 | 6806 | |
9a27b06e | 6807 | @code{symbol-file} does not repeat if you press @key{RET} again after |
70b88761 RP |
6808 | executing it once. |
6809 | ||
9a27b06e RP |
6810 | When @value{GDBN} is configured for a particular environment, it |
6811 | understands debugging information in whatever format is the standard | |
14d01801 RP |
6812 | generated for that environment; you may use either a GNU compiler, or |
6813 | other compilers that adhere to the local conventions. Best results are | |
18fae2a8 | 6814 | usually obtained from GNU compilers; for example, using @code{@value{GCC}} |
14d01801 RP |
6815 | you can generate debugging information for optimized code. |
6816 | ||
70b88761 | 6817 | On some kinds of object files, the @code{symbol-file} command does not |
14d01801 | 6818 | normally read the symbol table in full right away. Instead, it scans |
70b88761 RP |
6819 | the symbol table quickly to find which source files and which symbols |
6820 | are present. The details are read later, one source file at a time, | |
1041a570 | 6821 | as they are needed. |
70b88761 | 6822 | |
18fae2a8 | 6823 | The purpose of this two-stage reading strategy is to make @value{GDBN} start up |
1041a570 RP |
6824 | faster. For the most part, it is invisible except for occasional |
6825 | pauses while the symbol table details for a particular source file are | |
6826 | being read. (The @code{set verbose} command can turn these pauses | |
93928b60 RP |
6827 | into messages if desired. @xref{Messages/Warnings, ,Optional warnings |
6828 | and messages}.) | |
70b88761 | 6829 | |
8c69096b RP |
6830 | We have not implemented the two-stage strategy for COFF yet. When the |
6831 | symbol table is stored in COFF format, @code{symbol-file} reads the | |
6832 | symbol table data in full right away. | |
70b88761 | 6833 | |
95d5ceb9 RP |
6834 | @item symbol-file @var{filename} @r{[} -readnow @r{]} @r{[} -mapped @r{]} |
6835 | @itemx file @var{filename} @r{[} -readnow @r{]} @r{[} -mapped @r{]} | |
14d01801 RP |
6836 | @kindex readnow |
6837 | @cindex reading symbols immediately | |
6838 | @cindex symbols, reading immediately | |
6839 | @kindex mapped | |
6840 | @cindex memory-mapped symbol file | |
38962738 | 6841 | @cindex saving symbol table |
18fae2a8 | 6842 | You can override the @value{GDBN} two-stage strategy for reading symbol |
95d5ceb9 | 6843 | tables by using the @samp{-readnow} option with any of the commands that |
18fae2a8 | 6844 | load symbol table information, if you want to be sure @value{GDBN} has the |
14d01801 RP |
6845 | entire symbol table available. |
6846 | ||
18fae2a8 | 6847 | @ifclear BARETARGET |
14d01801 | 6848 | If memory-mapped files are available on your system through the |
95d5ceb9 | 6849 | @code{mmap} system call, you can use another option, @samp{-mapped}, to |
18fae2a8 | 6850 | cause @value{GDBN} to write the symbols for your program into a reusable |
9a27b06e | 6851 | file. Future @value{GDBN} debugging sessions map in symbol information |
93918348 | 6852 | from this auxiliary symbol file (if the program has not changed), rather |
77b46d13 JG |
6853 | than spending time reading the symbol table from the executable |
6854 | program. Using the @samp{-mapped} option has the same effect as | |
18fae2a8 | 6855 | starting @value{GDBN} with the @samp{-mapped} command-line option. |
14d01801 | 6856 | |
95d5ceb9 | 6857 | You can use both options together, to make sure the auxiliary symbol |
14d01801 RP |
6858 | file has all the symbol information for your program. |
6859 | ||
6860 | The auxiliary symbol file for a program called @var{myprog} is called | |
6861 | @samp{@var{myprog}.syms}. Once this file exists (so long as it is newer | |
9a27b06e | 6862 | than the corresponding executable), @value{GDBN} always attempts to use |
14d01801 RP |
6863 | it when you debug @var{myprog}; no special options or commands are |
6864 | needed. | |
93918348 RP |
6865 | |
6866 | The @file{.syms} file is specific to the host machine where you run | |
34ae25cd | 6867 | @value{GDBN}. It holds an exact image of the internal @value{GDBN} |
93918348 RP |
6868 | symbol table. It cannot be shared across multiple host platforms. |
6869 | ||
14d01801 RP |
6870 | @c FIXME: for now no mention of directories, since this seems to be in |
6871 | @c flux. 13mar1992 status is that in theory GDB would look either in | |
6872 | @c current dir or in same dir as myprog; but issues like competing | |
6873 | @c GDB's, or clutter in system dirs, mean that in practice right now | |
6874 | @c only current dir is used. FFish says maybe a special GDB hierarchy | |
6875 | @c (eg rooted in val of env var GDBSYMS) could exist for mappable symbol | |
6876 | @c files. | |
70b88761 | 6877 | |
e0dacfd1 | 6878 | @item core-file @r{[} @var{filename} @r{]} |
70b88761 RP |
6879 | @kindex core |
6880 | @kindex core-file | |
6881 | Specify the whereabouts of a core dump file to be used as the ``contents | |
6882 | of memory''. Traditionally, core files contain only some parts of the | |
18fae2a8 | 6883 | address space of the process that generated them; @value{GDBN} can access the |
70b88761 RP |
6884 | executable file itself for other parts. |
6885 | ||
6886 | @code{core-file} with no argument specifies that no core file is | |
6887 | to be used. | |
6888 | ||
6889 | Note that the core file is ignored when your program is actually running | |
18fae2a8 | 6890 | under @value{GDBN}. So, if you have been running your program and you wish to |
70b88761 RP |
6891 | debug a core file instead, you must kill the subprocess in which the |
6892 | program is running. To do this, use the @code{kill} command | |
93928b60 | 6893 | (@pxref{Kill Process, ,Killing the child process}). |
18fae2a8 | 6894 | @end ifclear |
70b88761 RP |
6895 | |
6896 | @item load @var{filename} | |
6897 | @kindex load | |
18fae2a8 | 6898 | @ifset GENERIC |
70b88761 | 6899 | Depending on what remote debugging facilities are configured into |
18fae2a8 | 6900 | @value{GDBN}, the @code{load} command may be available. Where it exists, it |
70b88761 RP |
6901 | is meant to make @var{filename} (an executable) available for debugging |
6902 | on the remote system---by downloading, or dynamic linking, for example. | |
93918348 | 6903 | @code{load} also records the @var{filename} symbol table in @value{GDBN}, like |
70b88761 RP |
6904 | the @code{add-symbol-file} command. |
6905 | ||
ed447b95 RP |
6906 | If your @value{GDBN} does not have a @code{load} command, attempting to |
6907 | execute it gets the error message ``@code{You can't do that when your | |
6908 | target is @dots{}}'' | |
18fae2a8 | 6909 | @end ifset |
70b88761 | 6910 | |
99d1da6a | 6911 | The file is loaded at whatever address is specified in the executable. |
22b5dba5 RP |
6912 | For some object file formats, you can specify the load address when you |
6913 | link the program; for other formats, like a.out, the object file format | |
6914 | specifies a fixed address. | |
6915 | @c FIXME! This would be a good place for an xref to the GNU linker doc. | |
99d1da6a | 6916 | |
18fae2a8 | 6917 | @ifset VXWORKS |
9a27b06e | 6918 | On VxWorks, @code{load} links @var{filename} dynamically on the |
18fae2a8 RP |
6919 | current target system as well as adding its symbols in @value{GDBN}. |
6920 | @end ifset | |
70b88761 | 6921 | |
a64a6c2b | 6922 | @ifset I960 |
70b88761 | 6923 | @cindex download to Nindy-960 |
9a27b06e RP |
6924 | With the Nindy interface to an Intel 960 board, @code{load} |
6925 | downloads @var{filename} to the 960 as well as adding its symbols in | |
18fae2a8 RP |
6926 | @value{GDBN}. |
6927 | @end ifset | |
70b88761 | 6928 | |
a64a6c2b | 6929 | @ifset H8 |
1d7c3357 RP |
6930 | @cindex download to H8/300 or H8/500 |
6931 | @cindex H8/300 or H8/500 download | |
a64a6c2b RP |
6932 | @cindex download to Hitachi SH |
6933 | @cindex Hitachi SH download | |
72545cc6 | 6934 | When you select remote debugging to a Hitachi SH, H8/300, or H8/500 board |
a64a6c2b | 6935 | (@pxref{Hitachi Remote,,@value{GDBN} and Hitachi Microprocessors}), |
1d7c3357 RP |
6936 | the @code{load} command downloads your program to the Hitachi board and also |
6937 | opens it as the current executable target for @value{GDBN} on your host | |
6938 | (like the @code{file} command). | |
18fae2a8 | 6939 | @end ifset |
c7cb8acb | 6940 | |
9a27b06e | 6941 | @code{load} does not repeat if you press @key{RET} again after using it. |
70b88761 | 6942 | |
18fae2a8 | 6943 | @ifclear BARETARGET |
70b88761 | 6944 | @item add-symbol-file @var{filename} @var{address} |
95d5ceb9 | 6945 | @itemx add-symbol-file @var{filename} @var{address} @r{[} -readnow @r{]} @r{[} -mapped @r{]} |
70b88761 RP |
6946 | @kindex add-symbol-file |
6947 | @cindex dynamic linking | |
6948 | The @code{add-symbol-file} command reads additional symbol table information | |
b80282d5 | 6949 | from the file @var{filename}. You would use this command when @var{filename} |
70b88761 RP |
6950 | has been dynamically loaded (by some other means) into the program that |
6951 | is running. @var{address} should be the memory address at which the | |
18fae2a8 | 6952 | file has been loaded; @value{GDBN} cannot figure this out for itself. |
d55320a0 | 6953 | You can specify @var{address} as an expression. |
70b88761 RP |
6954 | |
6955 | The symbol table of the file @var{filename} is added to the symbol table | |
6956 | originally read with the @code{symbol-file} command. You can use the | |
6957 | @code{add-symbol-file} command any number of times; the new symbol data thus | |
6958 | read keeps adding to the old. To discard all old symbol data instead, | |
e251e767 | 6959 | use the @code{symbol-file} command. |
70b88761 | 6960 | |
9a27b06e | 6961 | @code{add-symbol-file} does not repeat if you press @key{RET} after using it. |
70b88761 | 6962 | |
95d5ceb9 | 6963 | You can use the @samp{-mapped} and @samp{-readnow} options just as with |
18fae2a8 | 6964 | the @code{symbol-file} command, to change how @value{GDBN} manages the symbol |
0f153e74 | 6965 | table information for @var{filename}. |
18fae2a8 | 6966 | @end ifclear |
95d5ceb9 | 6967 | |
70b88761 RP |
6968 | @item info files |
6969 | @itemx info target | |
6970 | @kindex info files | |
6971 | @kindex info target | |
1041a570 | 6972 | @code{info files} and @code{info target} are synonymous; both print |
1d7c3357 RP |
6973 | the current target (@pxref{Targets, ,Specifying a Debugging Target}), |
6974 | including the | |
6975 | @ifclear BARETARGET | |
6976 | names of the executable and core dump files | |
6977 | @end ifclear | |
6978 | @ifset BARETARGET | |
6979 | name of the executable file | |
6980 | @end ifset | |
6981 | currently in use by @value{GDBN}, and the files from which symbols were | |
a4ae3702 | 6982 | loaded. The command @code{help target} lists all possible targets |
1d7c3357 | 6983 | rather than current ones. |
70b88761 RP |
6984 | @end table |
6985 | ||
6986 | All file-specifying commands allow both absolute and relative file names | |
b550c03a | 6987 | as arguments. @value{GDBN} always converts the file name to an absolute file |
70b88761 RP |
6988 | name and remembers it that way. |
6989 | ||
18fae2a8 | 6990 | @ifclear BARETARGET |
70b88761 | 6991 | @cindex shared libraries |
9a27b06e | 6992 | @value{GDBN} supports SunOS, SVr4, Irix 5, and IBM RS/6000 shared libraries. |
18fae2a8 | 6993 | @value{GDBN} automatically loads symbol definitions from shared libraries |
77b46d13 | 6994 | when you use the @code{run} command, or when you examine a core file. |
9a27b06e | 6995 | (Before you issue the @code{run} command, @value{GDBN} does not understand |
77b46d13 JG |
6996 | references to a function in a shared library, however---unless you are |
6997 | debugging a core file). | |
9a27b06e RP |
6998 | @c FIXME: some @value{GDBN} release may permit some refs to undef |
6999 | @c FIXME...symbols---eg in a break cmd---assuming they are from a shared | |
7000 | @c FIXME...lib; check this from time to time when updating manual | |
70b88761 RP |
7001 | |
7002 | @table @code | |
70b88761 RP |
7003 | @item info share |
7004 | @itemx info sharedlibrary | |
7005 | @kindex info sharedlibrary | |
7006 | @kindex info share | |
c338a2fd | 7007 | Print the names of the shared libraries which are currently loaded. |
70b88761 | 7008 | |
c338a2fd RP |
7009 | @item sharedlibrary @var{regex} |
7010 | @itemx share @var{regex} | |
7011 | @kindex sharedlibrary | |
7012 | @kindex share | |
6b51acad RP |
7013 | This is an obsolescent command; you can use it to explicitly load shared |
7014 | object library symbols for files matching a Unix regular expression, but | |
9a27b06e | 7015 | as with files loaded automatically, it only loads shared libraries |
6b51acad RP |
7016 | required by your program for a core file or after typing @code{run}. If |
7017 | @var{regex} is omitted all shared libraries required by your program are | |
7018 | loaded. | |
c338a2fd | 7019 | @end table |
18fae2a8 | 7020 | @end ifclear |
70b88761 | 7021 | |
4eb4cf57 | 7022 | @node Symbol Errors |
93928b60 | 7023 | @section Errors reading symbol files |
1041a570 | 7024 | |
9a27b06e | 7025 | While reading a symbol file, @value{GDBN} occasionally encounters problems, |
1041a570 | 7026 | such as symbol types it does not recognize, or known bugs in compiler |
18fae2a8 | 7027 | output. By default, @value{GDBN} does not notify you of such problems, since |
1041a570 RP |
7028 | they are relatively common and primarily of interest to people |
7029 | debugging compilers. If you are interested in seeing information | |
18fae2a8 | 7030 | about ill-constructed symbol tables, you can either ask @value{GDBN} to print |
b80282d5 | 7031 | only one message about each such type of problem, no matter how many |
18fae2a8 | 7032 | times the problem occurs; or you can ask @value{GDBN} to print more messages, |
1041a570 | 7033 | to see how many times the problems occur, with the @code{set |
93928b60 RP |
7034 | complaints} command (@pxref{Messages/Warnings, ,Optional warnings and |
7035 | messages}). | |
70b88761 | 7036 | |
d55320a0 | 7037 | The messages currently printed, and their meanings, include: |
70b88761 RP |
7038 | |
7039 | @table @code | |
7040 | @item inner block not inside outer block in @var{symbol} | |
7041 | ||
7042 | The symbol information shows where symbol scopes begin and end | |
7043 | (such as at the start of a function or a block of statements). This | |
7044 | error indicates that an inner scope block is not fully contained | |
e251e767 | 7045 | in its outer scope blocks. |
70b88761 | 7046 | |
18fae2a8 | 7047 | @value{GDBN} circumvents the problem by treating the inner block as if it had |
70b88761 RP |
7048 | the same scope as the outer block. In the error message, @var{symbol} |
7049 | may be shown as ``@code{(don't know)}'' if the outer block is not a | |
7050 | function. | |
7051 | ||
7052 | @item block at @var{address} out of order | |
7053 | ||
e251e767 | 7054 | The symbol information for symbol scope blocks should occur in |
70b88761 | 7055 | order of increasing addresses. This error indicates that it does not |
e251e767 | 7056 | do so. |
70b88761 | 7057 | |
9a27b06e | 7058 | @value{GDBN} does not circumvent this problem, and has trouble |
ed447b95 RP |
7059 | locating symbols in the source file whose symbols it is reading. (You |
7060 | can often determine what source file is affected by specifying | |
93928b60 RP |
7061 | @code{set verbose on}. @xref{Messages/Warnings, ,Optional warnings and |
7062 | messages}.) | |
70b88761 RP |
7063 | |
7064 | @item bad block start address patched | |
7065 | ||
7066 | The symbol information for a symbol scope block has a start address | |
7067 | smaller than the address of the preceding source line. This is known | |
e251e767 | 7068 | to occur in the SunOS 4.1.1 (and earlier) C compiler. |
70b88761 | 7069 | |
18fae2a8 | 7070 | @value{GDBN} circumvents the problem by treating the symbol scope block as |
70b88761 RP |
7071 | starting on the previous source line. |
7072 | ||
70b88761 RP |
7073 | @item bad string table offset in symbol @var{n} |
7074 | ||
7075 | @cindex foo | |
7076 | Symbol number @var{n} contains a pointer into the string table which is | |
e251e767 | 7077 | larger than the size of the string table. |
70b88761 | 7078 | |
18fae2a8 | 7079 | @value{GDBN} circumvents the problem by considering the symbol to have the |
70b88761 RP |
7080 | name @code{foo}, which may cause other problems if many symbols end up |
7081 | with this name. | |
7082 | ||
7083 | @item unknown symbol type @code{0x@var{nn}} | |
7084 | ||
18fae2a8 | 7085 | The symbol information contains new data types that @value{GDBN} does not yet |
70b88761 | 7086 | know how to read. @code{0x@var{nn}} is the symbol type of the misunderstood |
e251e767 | 7087 | information, in hexadecimal. |
70b88761 | 7088 | |
18fae2a8 | 7089 | @value{GDBN} circumvents the error by ignoring this symbol information. This |
9a27b06e RP |
7090 | usually allows you to debug your program, though certain symbols |
7091 | are not accessible. If you encounter such a problem and feel like | |
18fae2a8 | 7092 | debugging it, you can debug @code{@value{GDBP}} with itself, breakpoint on |
70b88761 RP |
7093 | @code{complain}, then go up to the function @code{read_dbx_symtab} and |
7094 | examine @code{*bufp} to see the symbol. | |
7095 | ||
7096 | @item stub type has NULL name | |
1d7c3357 RP |
7097 | @value{GDBN} could not find the full definition for |
7098 | @ifclear CONLY | |
7099 | a struct or class. | |
7100 | @end ifclear | |
7101 | @ifset CONLY | |
7102 | a struct. | |
7103 | @end ifset | |
70b88761 | 7104 | |
1d7c3357 | 7105 | @ifclear CONLY |
440d9834 | 7106 | @item const/volatile indicator missing (ok if using g++ v1.x), got@dots{} |
70b88761 RP |
7107 | |
7108 | The symbol information for a C++ member function is missing some | |
440d9834 RP |
7109 | information that recent versions of the compiler should have output |
7110 | for it. | |
1d7c3357 | 7111 | @end ifclear |
70b88761 | 7112 | |
440d9834 | 7113 | @item info mismatch between compiler and debugger |
70b88761 | 7114 | |
18fae2a8 | 7115 | @value{GDBN} could not parse a type specification output by the compiler. |
70b88761 RP |
7116 | @end table |
7117 | ||
4eb4cf57 | 7118 | @node Targets |
e251e767 | 7119 | @chapter Specifying a Debugging Target |
70b88761 RP |
7120 | @cindex debugging target |
7121 | @kindex target | |
1041a570 | 7122 | |
cedaf8bc | 7123 | A @dfn{target} is the execution environment occupied by your program. |
18fae2a8 RP |
7124 | @ifclear BARETARGET |
7125 | Often, @value{GDBN} runs in the same host environment as your program; in | |
1041a570 RP |
7126 | that case, the debugging target is specified as a side effect when you |
7127 | use the @code{file} or @code{core} commands. When you need more | |
18fae2a8 | 7128 | flexibility---for example, running @value{GDBN} on a physically separate |
1041a570 | 7129 | host, or controlling a standalone system over a serial port or a |
0f153e74 | 7130 | realtime system over a TCP/IP connection---you |
18fae2a8 RP |
7131 | @end ifclear |
7132 | @ifset BARETARGET | |
0f153e74 | 7133 | You |
18fae2a8 | 7134 | @end ifset |
0f153e74 | 7135 | can use the @code{target} command to specify one of the target types |
93928b60 RP |
7136 | configured for @value{GDBN} (@pxref{Target Commands, ,Commands for managing |
7137 | targets}). | |
70b88761 RP |
7138 | |
7139 | @menu | |
ed447b95 RP |
7140 | * Active Targets:: Active targets |
7141 | * Target Commands:: Commands for managing targets | |
7142 | * Remote:: Remote debugging | |
70b88761 RP |
7143 | @end menu |
7144 | ||
4eb4cf57 | 7145 | @node Active Targets |
93928b60 | 7146 | @section Active targets |
70b88761 RP |
7147 | @cindex stacking targets |
7148 | @cindex active targets | |
7149 | @cindex multiple targets | |
7150 | ||
18fae2a8 | 7151 | @ifclear BARETARGET |
cedaf8bc | 7152 | There are three classes of targets: processes, core files, and |
18fae2a8 | 7153 | executable files. @value{GDBN} can work concurrently on up to three active |
cedaf8bc RP |
7154 | targets, one in each class. This allows you to (for example) start a |
7155 | process and inspect its activity without abandoning your work on a core | |
7156 | file. | |
70b88761 | 7157 | |
ed447b95 | 7158 | For example, if you execute @samp{gdb a.out}, then the executable file |
cedaf8bc RP |
7159 | @code{a.out} is the only active target. If you designate a core file as |
7160 | well---presumably from a prior run that crashed and coredumped---then | |
9a27b06e | 7161 | @value{GDBN} has two active targets and uses them in tandem, looking |
cedaf8bc RP |
7162 | first in the corefile target, then in the executable file, to satisfy |
7163 | requests for memory addresses. (Typically, these two classes of target | |
29a2b744 | 7164 | are complementary, since core files contain only a program's |
cedaf8bc RP |
7165 | read-write memory---variables and so on---plus machine status, while |
7166 | executable files contain only the program text and initialized data.) | |
18fae2a8 | 7167 | @end ifclear |
cedaf8bc RP |
7168 | |
7169 | When you type @code{run}, your executable file becomes an active process | |
18fae2a8 | 7170 | target as well. When a process target is active, all @value{GDBN} commands |
0f153e74 | 7171 | requesting memory addresses refer to that target; addresses in an |
18fae2a8 | 7172 | @ifclear BARETARGET |
0f153e74 | 7173 | active core file or |
18fae2a8 | 7174 | @end ifclear |
0f153e74 | 7175 | executable file target are obscured while the process |
cedaf8bc RP |
7176 | target is active. |
7177 | ||
18fae2a8 | 7178 | @ifset BARETARGET |
4eb4cf57 | 7179 | Use the @code{exec-file} command to select a |
93928b60 RP |
7180 | new executable target (@pxref{Files, ,Commands to specify |
7181 | files}). | |
18fae2a8 RP |
7182 | @end ifset |
7183 | @ifclear BARETARGET | |
1041a570 | 7184 | Use the @code{core-file} and @code{exec-file} commands to select a |
93928b60 RP |
7185 | new core file or executable target (@pxref{Files, ,Commands to specify |
7186 | files}). To specify as a target a process that is already running, use | |
1041a570 | 7187 | the @code{attach} command (@pxref{Attach, ,Debugging an |
93928b60 | 7188 | already-running process}). |
18fae2a8 | 7189 | @end ifclear |
70b88761 | 7190 | |
4eb4cf57 | 7191 | @node Target Commands |
93928b60 | 7192 | @section Commands for managing targets |
70b88761 RP |
7193 | |
7194 | @table @code | |
7195 | @item target @var{type} @var{parameters} | |
1d7c3357 RP |
7196 | Connects the @value{GDBN} host environment to a target |
7197 | @ifset BARETARGET | |
7198 | machine. | |
7199 | @end ifset | |
7200 | @ifclear BARETARGET | |
7201 | machine or process. A target is typically a protocol for talking to | |
7202 | debugging facilities. You use the argument @var{type} to specify the | |
7203 | type or protocol of the target machine. | |
70b88761 RP |
7204 | |
7205 | Further @var{parameters} are interpreted by the target protocol, but | |
7206 | typically include things like device names or host names to connect | |
e251e767 | 7207 | with, process numbers, and baud rates. |
1d7c3357 | 7208 | @end ifclear |
70b88761 | 7209 | |
9a27b06e | 7210 | The @code{target} command does not repeat if you press @key{RET} again |
70b88761 RP |
7211 | after executing the command. |
7212 | ||
7213 | @item help target | |
7214 | @kindex help target | |
7215 | Displays the names of all targets available. To display targets | |
7216 | currently selected, use either @code{info target} or @code{info files} | |
93928b60 | 7217 | (@pxref{Files, ,Commands to specify files}). |
70b88761 RP |
7218 | |
7219 | @item help target @var{name} | |
7220 | Describe a particular target, including any parameters necessary to | |
7221 | select it. | |
7222 | @end table | |
7223 | ||
c7cb8acb | 7224 | Here are some common targets (available, or not, depending on the GDB |
70b88761 RP |
7225 | configuration): |
7226 | ||
7227 | @table @code | |
fe715d06 | 7228 | @item target exec @var{program} |
70b88761 | 7229 | @kindex target exec |
fe715d06 RP |
7230 | An executable file. @samp{target exec @var{program}} is the same as |
7231 | @samp{exec-file @var{program}}. | |
70b88761 | 7232 | |
1d7c3357 | 7233 | @ifclear BARETARGET |
70b88761 RP |
7234 | @item target core @var{filename} |
7235 | @kindex target core | |
7236 | A core dump file. @samp{target core @var{filename}} is the same as | |
7237 | @samp{core-file @var{filename}}. | |
1d7c3357 | 7238 | @end ifclear |
70b88761 | 7239 | |
18fae2a8 | 7240 | @ifset REMOTESTUB |
70b88761 RP |
7241 | @item target remote @var{dev} |
7242 | @kindex target remote | |
c7cb8acb | 7243 | Remote serial target in GDB-specific protocol. The argument @var{dev} |
70b88761 | 7244 | specifies what serial device to use for the connection (e.g. |
93928b60 | 7245 | @file{/dev/ttya}). @xref{Remote, ,Remote debugging}. |
18fae2a8 | 7246 | @end ifset |
70b88761 | 7247 | |
fe715d06 RP |
7248 | @ifset SIMS |
7249 | @item target sim | |
7250 | @kindex target sim | |
7251 | CPU simulator. @xref{Simulator,,Simulated CPU Target}. | |
7252 | @end ifset | |
7253 | ||
a64a6c2b | 7254 | @ifset AMD29K |
fe715d06 RP |
7255 | @item target udi @var{keyword} |
7256 | @kindex target udi | |
7257 | Remote AMD29K target, using the AMD UDI protocol. The @var{keyword} | |
7258 | argument specifies which 29K board or simulator to use. @xref{UDI29K | |
b1955f0b | 7259 | Remote,,The UDI protocol for AMD29K}. |
fe715d06 | 7260 | |
70b88761 RP |
7261 | @item target amd-eb @var{dev} @var{speed} @var{PROG} |
7262 | @kindex target amd-eb | |
7263 | @cindex AMD EB29K | |
7264 | Remote PC-resident AMD EB29K board, attached over serial lines. | |
7265 | @var{dev} is the serial device, as for @code{target remote}; | |
7266 | @var{speed} allows you to specify the linespeed; and @var{PROG} is the | |
7267 | name of the program to be debugged, as it appears to DOS on the PC. | |
b1955f0b | 7268 | @xref{EB29K Remote, ,The EBMON protocol for AMD29K}. |
77fe5411 | 7269 | |
18fae2a8 | 7270 | @end ifset |
a64a6c2b | 7271 | @ifset H8 |
c7cb8acb RP |
7272 | @item target hms |
7273 | @kindex target hms | |
72545cc6 | 7274 | A Hitachi SH, H8/300, or H8/500 board, attached via serial line to your host. |
a64a6c2b RP |
7275 | @ifclear H8EXCLUSIVE |
7276 | @c Unix only, not currently of interest for H8-only manual | |
7277 | Use special commands @code{device} and @code{speed} to control the serial | |
7278 | line and the communications speed used. | |
7279 | @end ifclear | |
7280 | @xref{Hitachi Remote,,@value{GDBN} and Hitachi Microprocessors}. | |
c7cb8acb | 7281 | |
18fae2a8 | 7282 | @end ifset |
a64a6c2b | 7283 | @ifset I960 |
70b88761 RP |
7284 | @item target nindy @var{devicename} |
7285 | @kindex target nindy | |
7286 | An Intel 960 board controlled by a Nindy Monitor. @var{devicename} is | |
7287 | the name of the serial device to use for the connection, e.g. | |
ed447b95 | 7288 | @file{/dev/ttya}. @xref{i960-Nindy Remote, ,@value{GDBN} with a remote i960 (Nindy)}. |
70b88761 | 7289 | |
18fae2a8 | 7290 | @end ifset |
a64a6c2b | 7291 | @ifset ST2000 |
77fe5411 RP |
7292 | @item target st2000 @var{dev} @var{speed} |
7293 | @kindex target st2000 | |
7294 | A Tandem ST2000 phone switch, running Tandem's STDBUG protocol. @var{dev} | |
7295 | is the name of the device attached to the ST2000 serial line; | |
7296 | @var{speed} is the communication line speed. The arguments are not used | |
18fae2a8 RP |
7297 | if @value{GDBN} is configured to connect to the ST2000 using TCP or Telnet. |
7298 | @xref{ST2000 Remote,,@value{GDBN} with a Tandem ST2000}. | |
77fe5411 | 7299 | |
18fae2a8 RP |
7300 | @end ifset |
7301 | @ifset VXWORKS | |
70b88761 RP |
7302 | @item target vxworks @var{machinename} |
7303 | @kindex target vxworks | |
7304 | A VxWorks system, attached via TCP/IP. The argument @var{machinename} | |
7305 | is the target system's machine name or IP address. | |
18fae2a8 RP |
7306 | @xref{VxWorks Remote, ,@value{GDBN} and VxWorks}. |
7307 | @end ifset | |
70b88761 RP |
7308 | @end table |
7309 | ||
18fae2a8 RP |
7310 | @ifset GENERIC |
7311 | Different targets are available on different configurations of @value{GDBN}; your | |
70b88761 | 7312 | configuration may have more or fewer targets. |
18fae2a8 | 7313 | @end ifset |
70b88761 | 7314 | |
4eb4cf57 | 7315 | @node Remote |
93928b60 | 7316 | @section Remote debugging |
70b88761 RP |
7317 | @cindex remote debugging |
7318 | ||
29a2b744 | 7319 | If you are trying to debug a program running on a machine that cannot run |
c7cb8acb | 7320 | GDB in the usual way, it is often useful to use remote debugging. For |
70b88761 RP |
7321 | example, you might use remote debugging on an operating system kernel, or on |
7322 | a small system which does not have a general purpose operating system | |
e251e767 | 7323 | powerful enough to run a full-featured debugger. |
70b88761 | 7324 | |
c7cb8acb | 7325 | Some configurations of GDB have special serial or TCP/IP interfaces |
70b88761 | 7326 | to make this work with particular debugging targets. In addition, |
c7cb8acb | 7327 | GDB comes with a generic serial protocol (specific to GDB, but |
70b88761 | 7328 | not specific to any particular target system) which you can use if you |
9a27b06e | 7329 | write the remote stubs---the code that runs on the remote system to |
c7cb8acb | 7330 | communicate with GDB. |
70b88761 | 7331 | |
70b88761 | 7332 | Other remote targets may be available in your |
a4ae3702 | 7333 | configuration of GDB; use @code{help target} to list them. |
70b88761 | 7334 | |
18fae2a8 RP |
7335 | @ifset GENERIC |
7336 | @c Text on starting up GDB in various specific cases; it goes up front | |
7337 | @c in manuals configured for any of those particular situations, here | |
7338 | @c otherwise. | |
18fae2a8 RP |
7339 | @menu |
7340 | @ifset REMOTESTUB | |
7341 | * Remote Serial:: @value{GDBN} remote serial protocol | |
7342 | @end ifset | |
a64a6c2b | 7343 | @ifset I960 |
18fae2a8 RP |
7344 | * i960-Nindy Remote:: @value{GDBN} with a remote i960 (Nindy) |
7345 | @end ifset | |
a64a6c2b | 7346 | @ifset AMD29K |
b1955f0b RP |
7347 | * UDI29K Remote:: The UDI protocol for AMD29K |
7348 | * EB29K Remote:: The EBMON protocol for AMD29K | |
18fae2a8 RP |
7349 | @end ifset |
7350 | @ifset VXWORKS | |
7351 | * VxWorks Remote:: @value{GDBN} and VxWorks | |
7352 | @end ifset | |
a64a6c2b | 7353 | @ifset ST2000 |
18fae2a8 RP |
7354 | * ST2000 Remote:: @value{GDBN} with a Tandem ST2000 |
7355 | @end ifset | |
a64a6c2b RP |
7356 | @ifset H8 |
7357 | * Hitachi Remote:: @value{GDBN} and Hitachi Microprocessors | |
18fae2a8 | 7358 | @end ifset |
34ae25cd RP |
7359 | @ifset MIPS |
7360 | * MIPS Remote:: @value{GDBN} and MIPS boards | |
7361 | @end ifset | |
fe715d06 RP |
7362 | @ifset SIMS |
7363 | * Simulator:: Simulated CPU target | |
18fae2a8 RP |
7364 | @end ifset |
7365 | @end menu | |
70b88761 | 7366 | |
4af6d502 | 7367 | @include remote.texi |
18fae2a8 RP |
7368 | @end ifset |
7369 | ||
7370 | @node Controlling GDB | |
7371 | @chapter Controlling @value{GDBN} | |
70b88761 | 7372 | |
93918348 | 7373 | You can alter the way @value{GDBN} interacts with you by using |
18fae2a8 | 7374 | the @code{set} command. For commands controlling how @value{GDBN} displays |
93928b60 | 7375 | data, @pxref{Print Settings, ,Print settings}; other settings are described here. |
70b88761 RP |
7376 | |
7377 | @menu | |
b80282d5 | 7378 | * Prompt:: Prompt |
ed447b95 RP |
7379 | * Editing:: Command editing |
7380 | * History:: Command history | |
7381 | * Screen Size:: Screen size | |
b80282d5 | 7382 | * Numbers:: Numbers |
ed447b95 | 7383 | * Messages/Warnings:: Optional warnings and messages |
70b88761 RP |
7384 | @end menu |
7385 | ||
4eb4cf57 | 7386 | @node Prompt |
70b88761 RP |
7387 | @section Prompt |
7388 | @cindex prompt | |
1041a570 | 7389 | |
18fae2a8 RP |
7390 | @value{GDBN} indicates its readiness to read a command by printing a string |
7391 | called the @dfn{prompt}. This string is normally @samp{(@value{GDBP})}. You | |
70b88761 | 7392 | can change the prompt string with the @code{set prompt} command. For |
18fae2a8 | 7393 | instance, when debugging @value{GDBN} with @value{GDBN}, it is useful to change |
9aa964da | 7394 | the prompt in one of the @value{GDBN} sessions so that you can always tell which |
70b88761 RP |
7395 | one you are talking to. |
7396 | ||
7397 | @table @code | |
7398 | @item set prompt @var{newprompt} | |
7399 | @kindex set prompt | |
18fae2a8 | 7400 | Directs @value{GDBN} to use @var{newprompt} as its prompt string henceforth. |
70b88761 RP |
7401 | @kindex show prompt |
7402 | @item show prompt | |
7403 | Prints a line of the form: @samp{Gdb's prompt is: @var{your-prompt}} | |
7404 | @end table | |
7405 | ||
4eb4cf57 | 7406 | @node Editing |
93928b60 | 7407 | @section Command editing |
70b88761 RP |
7408 | @cindex readline |
7409 | @cindex command line editing | |
1041a570 | 7410 | |
18fae2a8 | 7411 | @value{GDBN} reads its input commands via the @dfn{readline} interface. This |
70b88761 RP |
7412 | GNU library provides consistent behavior for programs which provide a |
7413 | command line interface to the user. Advantages are @code{emacs}-style | |
7414 | or @code{vi}-style inline editing of commands, @code{csh}-like history | |
7415 | substitution, and a storage and recall of command history across | |
7416 | debugging sessions. | |
7417 | ||
18fae2a8 | 7418 | You may control the behavior of command line editing in @value{GDBN} with the |
e251e767 | 7419 | command @code{set}. |
70b88761 RP |
7420 | |
7421 | @table @code | |
7422 | @kindex set editing | |
7423 | @cindex editing | |
7424 | @item set editing | |
7425 | @itemx set editing on | |
7426 | Enable command line editing (enabled by default). | |
7427 | ||
7428 | @item set editing off | |
7429 | Disable command line editing. | |
7430 | ||
7431 | @kindex show editing | |
7432 | @item show editing | |
7433 | Show whether command line editing is enabled. | |
7434 | @end table | |
7435 | ||
4eb4cf57 | 7436 | @node History |
ed447b95 RP |
7437 | @section Command history |
7438 | ||
7439 | @value{GDBN} can keep track of the commands you type during your | |
7440 | debugging sessions, so that you can be certain of precisely what | |
7441 | happened. Use these commands to manage the @value{GDBN} command | |
7442 | history facility. | |
1041a570 | 7443 | |
70b88761 RP |
7444 | @table @code |
7445 | @cindex history substitution | |
7446 | @cindex history file | |
7447 | @kindex set history filename | |
9a27b06e | 7448 | @kindex GDBHISTFILE |
70b88761 | 7449 | @item set history filename @var{fname} |
9a27b06e RP |
7450 | Set the name of the @value{GDBN} command history file to @var{fname}. |
7451 | This is the file where @value{GDBN} reads an initial command history | |
7452 | list, and where it writes the command history from this session when it | |
7453 | exits. You can access this list through history expansion or through | |
7454 | the history command editing characters listed below. This file defaults | |
7455 | to the value of the environment variable @code{GDBHISTFILE}, or to | |
70b88761 RP |
7456 | @file{./.gdb_history} if this variable is not set. |
7457 | ||
7458 | @cindex history save | |
7459 | @kindex set history save | |
7460 | @item set history save | |
7461 | @itemx set history save on | |
7462 | Record command history in a file, whose name may be specified with the | |
7463 | @code{set history filename} command. By default, this option is disabled. | |
7464 | ||
7465 | @item set history save off | |
7466 | Stop recording command history in a file. | |
7467 | ||
7468 | @cindex history size | |
7469 | @kindex set history size | |
7470 | @item set history size @var{size} | |
9a27b06e | 7471 | Set the number of commands which @value{GDBN} keeps in its history list. |
70b88761 RP |
7472 | This defaults to the value of the environment variable |
7473 | @code{HISTSIZE}, or to 256 if this variable is not set. | |
7474 | @end table | |
7475 | ||
7476 | @cindex history expansion | |
7477 | History expansion assigns special meaning to the character @kbd{!}. | |
ed447b95 | 7478 | @ifset have-readline-appendices |
1041a570 | 7479 | @xref{Event Designators}. |
ed447b95 RP |
7480 | @end ifset |
7481 | ||
70b88761 RP |
7482 | Since @kbd{!} is also the logical not operator in C, history expansion |
7483 | is off by default. If you decide to enable history expansion with the | |
7484 | @code{set history expansion on} command, you may sometimes need to | |
7485 | follow @kbd{!} (when it is used as logical not, in an expression) with | |
7486 | a space or a tab to prevent it from being expanded. The readline | |
9a27b06e | 7487 | history facilities do not attempt substitution on the strings |
70b88761 RP |
7488 | @kbd{!=} and @kbd{!(}, even when history expansion is enabled. |
7489 | ||
7490 | The commands to control history expansion are: | |
7491 | ||
7492 | @table @code | |
7493 | ||
7494 | @kindex set history expansion | |
7495 | @item set history expansion on | |
7496 | @itemx set history expansion | |
7497 | Enable history expansion. History expansion is off by default. | |
7498 | ||
7499 | @item set history expansion off | |
7500 | Disable history expansion. | |
7501 | ||
7502 | The readline code comes with more complete documentation of | |
7503 | editing and history expansion features. Users unfamiliar with @code{emacs} | |
e251e767 | 7504 | or @code{vi} may wish to read it. |
ed447b95 | 7505 | @ifset have-readline-appendices |
70b88761 | 7506 | @xref{Command Line Editing}. |
ed447b95 | 7507 | @end ifset |
70b88761 RP |
7508 | |
7509 | @c @group | |
7510 | @kindex show history | |
7511 | @item show history | |
7512 | @itemx show history filename | |
7513 | @itemx show history save | |
7514 | @itemx show history size | |
7515 | @itemx show history expansion | |
18fae2a8 | 7516 | These commands display the state of the @value{GDBN} history parameters. |
70b88761 RP |
7517 | @code{show history} by itself displays all four states. |
7518 | @c @end group | |
70b88761 RP |
7519 | @end table |
7520 | ||
7521 | @table @code | |
7522 | @kindex show commands | |
7523 | @item show commands | |
7524 | Display the last ten commands in the command history. | |
7525 | ||
7526 | @item show commands @var{n} | |
7527 | Print ten commands centered on command number @var{n}. | |
7528 | ||
7529 | @item show commands + | |
7530 | Print ten commands just after the commands last printed. | |
70b88761 RP |
7531 | @end table |
7532 | ||
4eb4cf57 | 7533 | @node Screen Size |
93928b60 | 7534 | @section Screen size |
70b88761 RP |
7535 | @cindex size of screen |
7536 | @cindex pauses in output | |
1041a570 | 7537 | |
a1eff6c2 RP |
7538 | Certain commands to @value{GDBN} may produce large amounts of |
7539 | information output to the screen. To help you read all of it, | |
7540 | @value{GDBN} pauses and asks you for input at the end of each page of | |
7541 | output. Type @key{RET} when you want to continue the output, or @kbd{q} | |
34ae25cd RP |
7542 | to discard the remaining output. Also, the screen width setting |
7543 | determines when to wrap lines of output. Depending on what is being | |
7544 | printed, @value{GDBN} tries to break the line at a readable place, | |
70b88761 RP |
7545 | rather than simply letting it overflow onto the following line. |
7546 | ||
18fae2a8 | 7547 | Normally @value{GDBN} knows the size of the screen from the termcap data base |
70b88761 RP |
7548 | together with the value of the @code{TERM} environment variable and the |
7549 | @code{stty rows} and @code{stty cols} settings. If this is not correct, | |
7550 | you can override it with the @code{set height} and @code{set | |
7551 | width} commands: | |
7552 | ||
7553 | @table @code | |
7554 | @item set height @var{lpp} | |
7555 | @itemx show height | |
7556 | @itemx set width @var{cpl} | |
7557 | @itemx show width | |
7558 | @kindex set height | |
7559 | @kindex set width | |
7560 | @kindex show width | |
7561 | @kindex show height | |
7562 | These @code{set} commands specify a screen height of @var{lpp} lines and | |
7563 | a screen width of @var{cpl} characters. The associated @code{show} | |
7564 | commands display the current settings. | |
7565 | ||
9a27b06e | 7566 | If you specify a height of zero lines, @value{GDBN} does not pause during output |
70b88761 RP |
7567 | no matter how long the output is. This is useful if output is to a file |
7568 | or to an editor buffer. | |
d55320a0 RP |
7569 | |
7570 | Likewise, you can specify @samp{set width 0} to prevent @value{GDBN} | |
7571 | from wrapping its output. | |
70b88761 RP |
7572 | @end table |
7573 | ||
4eb4cf57 | 7574 | @node Numbers |
70b88761 RP |
7575 | @section Numbers |
7576 | @cindex number representation | |
7577 | @cindex entering numbers | |
1041a570 | 7578 | |
18fae2a8 | 7579 | You can always enter numbers in octal, decimal, or hexadecimal in @value{GDBN} by |
70b88761 RP |
7580 | the usual conventions: octal numbers begin with @samp{0}, decimal |
7581 | numbers end with @samp{.}, and hexadecimal numbers begin with @samp{0x}. | |
7582 | Numbers that begin with none of these are, by default, entered in base | |
7583 | 10; likewise, the default display for numbers---when no particular | |
7584 | format is specified---is base 10. You can change the default base for | |
7585 | both input and output with the @code{set radix} command. | |
7586 | ||
7587 | @table @code | |
7588 | @kindex set radix | |
7589 | @item set radix @var{base} | |
7590 | Set the default base for numeric input and display. Supported choices | |
d55320a0 | 7591 | for @var{base} are decimal 8, 10, or 16. @var{base} must itself be |
70b88761 RP |
7592 | specified either unambiguously or using the current default radix; for |
7593 | example, any of | |
7594 | ||
7595 | @example | |
7596 | set radix 012 | |
7597 | set radix 10. | |
7598 | set radix 0xa | |
7599 | @end example | |
7600 | ||
7601 | @noindent | |
9a27b06e RP |
7602 | sets the base to decimal. On the other hand, @samp{set radix 10} |
7603 | leaves the radix unchanged no matter what it was. | |
70b88761 RP |
7604 | |
7605 | @kindex show radix | |
7606 | @item show radix | |
7607 | Display the current default base for numeric input and display. | |
70b88761 RP |
7608 | @end table |
7609 | ||
4eb4cf57 | 7610 | @node Messages/Warnings |
93928b60 | 7611 | @section Optional warnings and messages |
1041a570 | 7612 | |
18fae2a8 | 7613 | By default, @value{GDBN} is silent about its inner workings. If you are running |
70b88761 | 7614 | on a slow machine, you may want to use the @code{set verbose} command. |
9a27b06e | 7615 | It makes @value{GDBN} tell you when it does a lengthy internal operation, so |
1041a570 | 7616 | you will not think it has crashed. |
70b88761 | 7617 | |
1041a570 | 7618 | Currently, the messages controlled by @code{set verbose} are those |
d48da190 | 7619 | which announce that the symbol table for a source file is being read; |
93928b60 | 7620 | see @code{symbol-file} in @ref{Files, ,Commands to specify files}. |
70b88761 RP |
7621 | |
7622 | @table @code | |
7623 | @kindex set verbose | |
7624 | @item set verbose on | |
93918348 | 7625 | Enables @value{GDBN} output of certain informational messages. |
70b88761 RP |
7626 | |
7627 | @item set verbose off | |
93918348 | 7628 | Disables @value{GDBN} output of certain informational messages. |
70b88761 RP |
7629 | |
7630 | @kindex show verbose | |
7631 | @item show verbose | |
7632 | Displays whether @code{set verbose} is on or off. | |
7633 | @end table | |
7634 | ||
18fae2a8 | 7635 | By default, if @value{GDBN} encounters bugs in the symbol table of an object |
b80282d5 | 7636 | file, it is silent; but if you are debugging a compiler, you may find |
93928b60 | 7637 | this information useful (@pxref{Symbol Errors, ,Errors reading symbol files}). |
70b88761 RP |
7638 | |
7639 | @table @code | |
7640 | @kindex set complaints | |
7641 | @item set complaints @var{limit} | |
18fae2a8 | 7642 | Permits @value{GDBN} to output @var{limit} complaints about each type of unusual |
70b88761 RP |
7643 | symbols before becoming silent about the problem. Set @var{limit} to |
7644 | zero to suppress all complaints; set it to a large number to prevent | |
7645 | complaints from being suppressed. | |
7646 | ||
7647 | @kindex show complaints | |
7648 | @item show complaints | |
18fae2a8 | 7649 | Displays how many symbol complaints @value{GDBN} is permitted to produce. |
70b88761 RP |
7650 | @end table |
7651 | ||
18fae2a8 | 7652 | By default, @value{GDBN} is cautious, and asks what sometimes seems to be a |
70b88761 RP |
7653 | lot of stupid questions to confirm certain commands. For example, if |
7654 | you try to run a program which is already running: | |
1041a570 | 7655 | |
70b88761 | 7656 | @example |
18fae2a8 | 7657 | (@value{GDBP}) run |
70b88761 | 7658 | The program being debugged has been started already. |
e251e767 | 7659 | Start it from the beginning? (y or n) |
70b88761 RP |
7660 | @end example |
7661 | ||
29a2b744 | 7662 | If you are willing to unflinchingly face the consequences of your own |
70b88761 RP |
7663 | commands, you can disable this ``feature'': |
7664 | ||
7665 | @table @code | |
7666 | @kindex set confirm | |
7667 | @cindex flinching | |
7668 | @cindex confirmation | |
7669 | @cindex stupid questions | |
7670 | @item set confirm off | |
7671 | Disables confirmation requests. | |
7672 | ||
7673 | @item set confirm on | |
7674 | Enables confirmation requests (the default). | |
7675 | ||
7676 | @item show confirm | |
7677 | @kindex show confirm | |
7678 | Displays state of confirmation requests. | |
7679 | @end table | |
7680 | ||
29a2b744 | 7681 | @c FIXME this does not really belong here. But where *does* it belong? |
b80282d5 RP |
7682 | @cindex reloading symbols |
7683 | Some systems allow individual object files that make up your program to | |
7684 | be replaced without stopping and restarting your program. | |
18fae2a8 | 7685 | @ifset VXWORKS |
b80282d5 RP |
7686 | For example, in VxWorks you can simply recompile a defective object file |
7687 | and keep on running. | |
18fae2a8 RP |
7688 | @end ifset |
7689 | If you are running on one of these systems, you can allow @value{GDBN} to | |
1041a570 RP |
7690 | reload the symbols for automatically relinked modules: |
7691 | ||
b80282d5 RP |
7692 | @table @code |
7693 | @kindex set symbol-reloading | |
7694 | @item set symbol-reloading on | |
7695 | Replace symbol definitions for the corresponding source file when an | |
7696 | object file with a particular name is seen again. | |
7697 | ||
7698 | @item set symbol-reloading off | |
1041a570 | 7699 | Do not replace symbol definitions when re-encountering object files of |
29a2b744 | 7700 | the same name. This is the default state; if you are not running on a |
b80282d5 | 7701 | system that permits automatically relinking modules, you should leave |
18fae2a8 | 7702 | @code{symbol-reloading} off, since otherwise @value{GDBN} may discard symbols |
b80282d5 RP |
7703 | when linking large programs, that may contain several modules (from |
7704 | different directories or libraries) with the same name. | |
7705 | ||
7706 | @item show symbol-reloading | |
7707 | Show the current @code{on} or @code{off} setting. | |
7708 | @end table | |
7709 | ||
4eb4cf57 | 7710 | @node Sequences |
70b88761 RP |
7711 | @chapter Canned Sequences of Commands |
7712 | ||
29a2b744 | 7713 | Aside from breakpoint commands (@pxref{Break Commands, ,Breakpoint |
93928b60 | 7714 | command lists}), @value{GDBN} provides two ways to store sequences of commands |
1041a570 | 7715 | for execution as a unit: user-defined commands and command files. |
70b88761 RP |
7716 | |
7717 | @menu | |
ed447b95 RP |
7718 | * Define:: User-defined commands |
7719 | * Hooks:: User-defined command hooks | |
7720 | * Command Files:: Command files | |
7721 | * Output:: Commands for controlled output | |
70b88761 RP |
7722 | @end menu |
7723 | ||
4eb4cf57 | 7724 | @node Define |
ed447b95 | 7725 | @section User-defined commands |
70b88761 RP |
7726 | |
7727 | @cindex user-defined command | |
18fae2a8 | 7728 | A @dfn{user-defined command} is a sequence of @value{GDBN} commands to which you |
70b88761 RP |
7729 | assign a new name as a command. This is done with the @code{define} |
7730 | command. | |
7731 | ||
7732 | @table @code | |
7733 | @item define @var{commandname} | |
7734 | @kindex define | |
7735 | Define a command named @var{commandname}. If there is already a command | |
7736 | by that name, you are asked to confirm that you want to redefine it. | |
7737 | ||
18fae2a8 | 7738 | The definition of the command is made up of other @value{GDBN} command lines, |
70b88761 RP |
7739 | which are given following the @code{define} command. The end of these |
7740 | commands is marked by a line containing @code{end}. | |
7741 | ||
7742 | @item document @var{commandname} | |
7743 | @kindex document | |
7744 | Give documentation to the user-defined command @var{commandname}. The | |
7745 | command @var{commandname} must already be defined. This command reads | |
7746 | lines of documentation just as @code{define} reads the lines of the | |
7747 | command definition, ending with @code{end}. After the @code{document} | |
9a27b06e | 7748 | command is finished, @code{help} on command @var{commandname} displays |
70b88761 RP |
7749 | the documentation you have specified. |
7750 | ||
7751 | You may use the @code{document} command again to change the | |
7752 | documentation of a command. Redefining the command with @code{define} | |
7753 | does not change the documentation. | |
7754 | ||
7755 | @item help user-defined | |
7756 | @kindex help user-defined | |
7757 | List all user-defined commands, with the first line of the documentation | |
7758 | (if any) for each. | |
7759 | ||
4768ba62 JG |
7760 | @item show user |
7761 | @itemx show user @var{commandname} | |
7762 | @kindex show user | |
18fae2a8 | 7763 | Display the @value{GDBN} commands used to define @var{commandname} (but not its |
70b88761 RP |
7764 | documentation). If no @var{commandname} is given, display the |
7765 | definitions for all user-defined commands. | |
7766 | @end table | |
7767 | ||
7768 | User-defined commands do not take arguments. When they are executed, the | |
7769 | commands of the definition are not printed. An error in any command | |
7770 | stops execution of the user-defined command. | |
7771 | ||
7772 | Commands that would ask for confirmation if used interactively proceed | |
18fae2a8 | 7773 | without asking when used inside a user-defined command. Many @value{GDBN} commands |
70b88761 RP |
7774 | that normally print messages to say what they are doing omit the messages |
7775 | when used in a user-defined command. | |
7776 | ||
35a15d60 | 7777 | @node Hooks |
93928b60 | 7778 | @section User-defined command hooks |
35a15d60 JG |
7779 | @cindex command files |
7780 | ||
7781 | You may define @emph{hooks}, which are a special kind of user-defined | |
7782 | command. Whenever you run the command @samp{foo}, if the user-defined | |
7783 | command @samp{hook-foo} exists, it is executed (with no arguments) | |
7784 | before that command. | |
7785 | ||
1d7c3357 RP |
7786 | In addition, a pseudo-command, @samp{stop} exists. Defining |
7787 | (@samp{hook-stop}) makes the associated commands execute every time | |
7788 | execution stops in your program: before breakpoint commands are run, | |
7789 | displays are printed, or the stack frame is printed. | |
35a15d60 | 7790 | |
1d7c3357 RP |
7791 | @ifclear BARETARGET |
7792 | For example, to ignore @code{SIGALRM} signals while | |
7793 | single-stepping, but treat them normally during normal execution, | |
7794 | you could define: | |
35a15d60 JG |
7795 | |
7796 | @example | |
7797 | define hook-stop | |
7798 | handle SIGALRM nopass | |
7799 | end | |
7800 | ||
7801 | define hook-run | |
7802 | handle SIGALRM pass | |
7803 | end | |
7804 | ||
7805 | define hook-continue | |
7806 | handle SIGLARM pass | |
7807 | end | |
7808 | @end example | |
1d7c3357 | 7809 | @end ifclear |
35a15d60 | 7810 | |
1d7c3357 RP |
7811 | You can define a hook for any single-word command in @value{GDBN}, but |
7812 | not for command aliases; you should define a hook for the basic command | |
7813 | name, e.g. @code{backtrace} rather than @code{bt}. | |
7814 | @c FIXME! So how does Joe User discover whether a command is an alias | |
7815 | @c or not? | |
7816 | If an error occurs during the execution of your hook, execution of | |
7817 | @value{GDBN} commands stops and @value{GDBN} issues a prompt | |
7818 | (before the command that you actually typed had a chance to run). | |
35a15d60 | 7819 | |
93918348 | 7820 | If you try to define a hook which does not match any known command, you |
9a27b06e | 7821 | get a warning from the @code{define} command. |
35a15d60 | 7822 | |
4eb4cf57 | 7823 | @node Command Files |
93928b60 | 7824 | @section Command files |
70b88761 RP |
7825 | |
7826 | @cindex command files | |
18fae2a8 | 7827 | A command file for @value{GDBN} is a file of lines that are @value{GDBN} commands. Comments |
70b88761 RP |
7828 | (lines starting with @kbd{#}) may also be included. An empty line in a |
7829 | command file does nothing; it does not mean to repeat the last command, as | |
7830 | it would from the terminal. | |
7831 | ||
7832 | @cindex init file | |
18fae2a8 RP |
7833 | @cindex @file{@value{GDBINIT}} |
7834 | When you start @value{GDBN}, it automatically executes commands from its | |
64a01450 JK |
7835 | @dfn{init files}. These are files named @file{@value{GDBINIT}}. |
7836 | @value{GDBN} reads the init file (if any) in your home directory, then | |
7837 | processes command line options and operands, and then reads the init | |
7838 | file (if any) in the current working directory. This is so the init | |
7839 | file in your home directory can set options (such as @code{set | |
8d43be62 | 7840 | complaints}) which affect the processing of the command line options and |
64a01450 JK |
7841 | operands. The init files are not executed if you use the @samp{-nx} |
7842 | option; @pxref{Mode Options, ,Choosing modes}. | |
51b65b74 RP |
7843 | |
7844 | @ifset GENERIC | |
7845 | @cindex init file name | |
7846 | On some configurations of @value{GDBN}, the init file is known by a | |
7847 | different name (these are typically environments where a specialized | |
7848 | form of GDB may need to coexist with other forms, hence a different name | |
7849 | for the specialized version's init file). These are the environments | |
7850 | with special init file names: | |
7851 | ||
7852 | @itemize @bullet | |
7853 | @kindex .vxgdbinit | |
7854 | @item | |
7855 | VxWorks (Wind River Systems real-time OS): @samp{.vxgdbinit} | |
7856 | ||
7857 | @kindex .os68gdbinit | |
7858 | @item | |
7859 | OS68K (Enea Data Systems real-time OS): @samp{.os68gdbinit} | |
7860 | ||
7861 | @kindex .esgdbinit | |
7862 | @item | |
7863 | ES-1800 (Ericsson Telecom AB M68000 emulator): @samp{.esgdbinit} | |
7864 | @end itemize | |
7865 | @end ifset | |
7866 | ||
7867 | You can also request the execution of a command file with the | |
7868 | @code{source} command: | |
70b88761 RP |
7869 | |
7870 | @table @code | |
7871 | @item source @var{filename} | |
7872 | @kindex source | |
7873 | Execute the command file @var{filename}. | |
7874 | @end table | |
7875 | ||
7876 | The lines in a command file are executed sequentially. They are not | |
7877 | printed as they are executed. An error in any command terminates execution | |
7878 | of the command file. | |
7879 | ||
7880 | Commands that would ask for confirmation if used interactively proceed | |
18fae2a8 | 7881 | without asking when used in a command file. Many @value{GDBN} commands that |
70b88761 RP |
7882 | normally print messages to say what they are doing omit the messages |
7883 | when called from command files. | |
7884 | ||
4eb4cf57 | 7885 | @node Output |
93928b60 | 7886 | @section Commands for controlled output |
70b88761 RP |
7887 | |
7888 | During the execution of a command file or a user-defined command, normal | |
18fae2a8 | 7889 | @value{GDBN} output is suppressed; the only output that appears is what is |
70b88761 RP |
7890 | explicitly printed by the commands in the definition. This section |
7891 | describes three commands useful for generating exactly the output you | |
7892 | want. | |
7893 | ||
7894 | @table @code | |
7895 | @item echo @var{text} | |
7896 | @kindex echo | |
29a2b744 RP |
7897 | @c I do not consider backslash-space a standard C escape sequence |
7898 | @c because it is not in ANSI. | |
1041a570 RP |
7899 | Print @var{text}. Nonprinting characters can be included in |
7900 | @var{text} using C escape sequences, such as @samp{\n} to print a | |
9a27b06e | 7901 | newline. @strong{No newline is printed unless you specify one.} |
1041a570 | 7902 | In addition to the standard C escape sequences, a backslash followed |
ed447b95 | 7903 | by a space stands for a space. This is useful for displaying a |
1041a570 RP |
7904 | string with spaces at the beginning or the end, since leading and |
7905 | trailing spaces are otherwise trimmed from all arguments. | |
7906 | To print @samp{@w{ }and foo =@w{ }}, use the command | |
7907 | @samp{echo \@w{ }and foo = \@w{ }}. | |
70b88761 RP |
7908 | |
7909 | A backslash at the end of @var{text} can be used, as in C, to continue | |
7910 | the command onto subsequent lines. For example, | |
7911 | ||
7912 | @example | |
7913 | echo This is some text\n\ | |
7914 | which is continued\n\ | |
7915 | onto several lines.\n | |
7916 | @end example | |
7917 | ||
7918 | produces the same output as | |
7919 | ||
7920 | @example | |
7921 | echo This is some text\n | |
7922 | echo which is continued\n | |
7923 | echo onto several lines.\n | |
7924 | @end example | |
7925 | ||
7926 | @item output @var{expression} | |
7927 | @kindex output | |
7928 | Print the value of @var{expression} and nothing but that value: no | |
7929 | newlines, no @samp{$@var{nn} = }. The value is not entered in the | |
1041a570 | 7930 | value history either. @xref{Expressions, ,Expressions}, for more information on |
e251e767 | 7931 | expressions. |
70b88761 RP |
7932 | |
7933 | @item output/@var{fmt} @var{expression} | |
7934 | Print the value of @var{expression} in format @var{fmt}. You can use | |
ed447b95 RP |
7935 | the same formats as for @code{print}. @xref{Output Formats,,Output |
7936 | formats}, for more information. | |
70b88761 RP |
7937 | |
7938 | @item printf @var{string}, @var{expressions}@dots{} | |
7939 | @kindex printf | |
7940 | Print the values of the @var{expressions} under the control of | |
d55320a0 RP |
7941 | @var{string}. The @var{expressions} are separated by commas and may be |
7942 | either numbers or pointers. Their values are printed as specified by | |
7943 | @var{string}, exactly as if your program were to execute the C | |
7944 | subroutine | |
70b88761 RP |
7945 | |
7946 | @example | |
7947 | printf (@var{string}, @var{expressions}@dots{}); | |
7948 | @end example | |
7949 | ||
7950 | For example, you can print two values in hex like this: | |
7951 | ||
0fd24984 | 7952 | @smallexample |
70b88761 | 7953 | printf "foo, bar-foo = 0x%x, 0x%x\n", foo, bar-foo |
0fd24984 | 7954 | @end smallexample |
70b88761 RP |
7955 | |
7956 | The only backslash-escape sequences that you can use in the format | |
7957 | string are the simple ones that consist of backslash followed by a | |
7958 | letter. | |
7959 | @end table | |
7960 | ||
18fae2a8 | 7961 | @ifclear DOSHOST |
4eb4cf57 | 7962 | @node Emacs |
18fae2a8 | 7963 | @chapter Using @value{GDBN} under GNU Emacs |
70b88761 RP |
7964 | |
7965 | @cindex emacs | |
7966 | A special interface allows you to use GNU Emacs to view (and | |
7967 | edit) the source files for the program you are debugging with | |
18fae2a8 | 7968 | @value{GDBN}. |
70b88761 RP |
7969 | |
7970 | To use this interface, use the command @kbd{M-x gdb} in Emacs. Give the | |
7971 | executable file you want to debug as an argument. This command starts | |
18fae2a8 | 7972 | @value{GDBN} as a subprocess of Emacs, with input and output through a newly |
70b88761 RP |
7973 | created Emacs buffer. |
7974 | ||
18fae2a8 | 7975 | Using @value{GDBN} under Emacs is just like using @value{GDBN} normally except for two |
70b88761 RP |
7976 | things: |
7977 | ||
7978 | @itemize @bullet | |
7979 | @item | |
e251e767 | 7980 | All ``terminal'' input and output goes through the Emacs buffer. |
70b88761 RP |
7981 | @end itemize |
7982 | ||
18fae2a8 | 7983 | This applies both to @value{GDBN} commands and their output, and to the input |
70b88761 RP |
7984 | and output done by the program you are debugging. |
7985 | ||
7986 | This is useful because it means that you can copy the text of previous | |
7987 | commands and input them again; you can even use parts of the output | |
7988 | in this way. | |
7989 | ||
3d3ab540 RP |
7990 | All the facilities of Emacs' Shell mode are available for interacting |
7991 | with your program. In particular, you can send signals the usual | |
7992 | way---for example, @kbd{C-c C-c} for an interrupt, @kbd{C-c C-z} for a | |
7993 | stop. | |
70b88761 RP |
7994 | |
7995 | @itemize @bullet | |
7996 | @item | |
18fae2a8 | 7997 | @value{GDBN} displays source code through Emacs. |
70b88761 RP |
7998 | @end itemize |
7999 | ||
18fae2a8 RP |
8000 | Each time @value{GDBN} displays a stack frame, Emacs automatically finds the |
8001 | source file for that frame and puts an arrow (@samp{=>}) at the | |
70b88761 | 8002 | left margin of the current line. Emacs uses a separate buffer for |
fe715d06 | 8003 | source display, and splits the screen to show both your @value{GDBN} session |
70b88761 RP |
8004 | and the source. |
8005 | ||
18fae2a8 | 8006 | Explicit @value{GDBN} @code{list} or search commands still produce output as |
9a27b06e | 8007 | usual, but you probably have no reason to use them from Emacs. |
70b88761 RP |
8008 | |
8009 | @quotation | |
8010 | @emph{Warning:} If the directory where your program resides is not your | |
8011 | current directory, it can be easy to confuse Emacs about the location of | |
9a27b06e | 8012 | the source files, in which case the auxiliary display buffer does not |
18fae2a8 RP |
8013 | appear to show your source. @value{GDBN} can find programs by searching your |
8014 | environment's @code{PATH} variable, so the @value{GDBN} input and output | |
9a27b06e | 8015 | session proceeds normally; but Emacs does not get enough information |
18fae2a8 RP |
8016 | back from @value{GDBN} to locate the source files in this situation. To |
8017 | avoid this problem, either start @value{GDBN} mode from the directory where | |
b550c03a | 8018 | your program resides, or specify an absolute file name when prompted for the |
70b88761 RP |
8019 | @kbd{M-x gdb} argument. |
8020 | ||
18fae2a8 | 8021 | A similar confusion can result if you use the @value{GDBN} @code{file} command to |
70b88761 | 8022 | switch to debugging a program in some other location, from an existing |
18fae2a8 | 8023 | @value{GDBN} buffer in Emacs. |
70b88761 RP |
8024 | @end quotation |
8025 | ||
8026 | By default, @kbd{M-x gdb} calls the program called @file{gdb}. If | |
18fae2a8 | 8027 | you need to call @value{GDBN} by a different name (for example, if you keep |
70b88761 RP |
8028 | several configurations around, with different names) you can set the |
8029 | Emacs variable @code{gdb-command-name}; for example, | |
1041a570 | 8030 | |
70b88761 RP |
8031 | @example |
8032 | (setq gdb-command-name "mygdb") | |
8033 | @end example | |
1041a570 | 8034 | |
70b88761 RP |
8035 | @noindent |
8036 | (preceded by @kbd{ESC ESC}, or typed in the @code{*scratch*} buffer, or | |
9a27b06e | 8037 | in your @file{.emacs} file) makes Emacs call the program named |
70b88761 RP |
8038 | ``@code{mygdb}'' instead. |
8039 | ||
18fae2a8 | 8040 | In the @value{GDBN} I/O buffer, you can use these special Emacs commands in |
70b88761 RP |
8041 | addition to the standard Shell mode commands: |
8042 | ||
8043 | @table @kbd | |
8044 | @item C-h m | |
18fae2a8 | 8045 | Describe the features of Emacs' @value{GDBN} Mode. |
70b88761 RP |
8046 | |
8047 | @item M-s | |
18fae2a8 | 8048 | Execute to another source line, like the @value{GDBN} @code{step} command; also |
70b88761 RP |
8049 | update the display window to show the current file and location. |
8050 | ||
8051 | @item M-n | |
8052 | Execute to next source line in this function, skipping all function | |
18fae2a8 | 8053 | calls, like the @value{GDBN} @code{next} command. Then update the display window |
70b88761 RP |
8054 | to show the current file and location. |
8055 | ||
8056 | @item M-i | |
18fae2a8 | 8057 | Execute one instruction, like the @value{GDBN} @code{stepi} command; update |
70b88761 RP |
8058 | display window accordingly. |
8059 | ||
8060 | @item M-x gdb-nexti | |
18fae2a8 | 8061 | Execute to next instruction, using the @value{GDBN} @code{nexti} command; update |
70b88761 RP |
8062 | display window accordingly. |
8063 | ||
8064 | @item C-c C-f | |
18fae2a8 | 8065 | Execute until exit from the selected stack frame, like the @value{GDBN} |
70b88761 RP |
8066 | @code{finish} command. |
8067 | ||
8068 | @item M-c | |
18fae2a8 | 8069 | Continue execution of your program, like the @value{GDBN} @code{continue} |
1041a570 | 8070 | command. |
203eea5d RP |
8071 | |
8072 | @emph{Warning:} In Emacs v19, this command is @kbd{C-c C-p}. | |
70b88761 RP |
8073 | |
8074 | @item M-u | |
8075 | Go up the number of frames indicated by the numeric argument | |
8076 | (@pxref{Arguments, , Numeric Arguments, emacs, The GNU Emacs Manual}), | |
18fae2a8 | 8077 | like the @value{GDBN} @code{up} command. |
203eea5d | 8078 | |
1041a570 | 8079 | @emph{Warning:} In Emacs v19, this command is @kbd{C-c C-u}. |
70b88761 RP |
8080 | |
8081 | @item M-d | |
8082 | Go down the number of frames indicated by the numeric argument, like the | |
18fae2a8 | 8083 | @value{GDBN} @code{down} command. |
203eea5d RP |
8084 | |
8085 | @emph{Warning:} In Emacs v19, this command is @kbd{C-c C-d}. | |
70b88761 RP |
8086 | |
8087 | @item C-x & | |
8088 | Read the number where the cursor is positioned, and insert it at the end | |
18fae2a8 | 8089 | of the @value{GDBN} I/O buffer. For example, if you wish to disassemble code |
70b88761 RP |
8090 | around an address that was displayed earlier, type @kbd{disassemble}; |
8091 | then move the cursor to the address display, and pick up the | |
e251e767 | 8092 | argument for @code{disassemble} by typing @kbd{C-x &}. |
70b88761 | 8093 | |
ed447b95 | 8094 | You can customize this further by defining elements of the list |
70b88761 RP |
8095 | @code{gdb-print-command}; once it is defined, you can format or |
8096 | otherwise process numbers picked up by @kbd{C-x &} before they are | |
9a27b06e RP |
8097 | inserted. A numeric argument to @kbd{C-x &} indicates that you |
8098 | wish special formatting, and also acts as an index to pick an element of the | |
70b88761 RP |
8099 | list. If the list element is a string, the number to be inserted is |
8100 | formatted using the Emacs function @code{format}; otherwise the number | |
8101 | is passed as an argument to the corresponding list element. | |
70b88761 RP |
8102 | @end table |
8103 | ||
8104 | In any source file, the Emacs command @kbd{C-x SPC} (@code{gdb-break}) | |
18fae2a8 | 8105 | tells @value{GDBN} to set a breakpoint on the source line point is on. |
70b88761 RP |
8106 | |
8107 | If you accidentally delete the source-display buffer, an easy way to get | |
18fae2a8 | 8108 | it back is to type the command @code{f} in the @value{GDBN} buffer, to |
9a27b06e | 8109 | request a frame display; when you run under Emacs, this recreates |
70b88761 RP |
8110 | the source buffer if necessary to show you the context of the current |
8111 | frame. | |
8112 | ||
8113 | The source files displayed in Emacs are in ordinary Emacs buffers | |
8114 | which are visiting the source files in the usual way. You can edit | |
18fae2a8 | 8115 | the files with these buffers if you wish; but keep in mind that @value{GDBN} |
70b88761 | 8116 | communicates with Emacs in terms of line numbers. If you add or |
9a27b06e | 8117 | delete lines from the text, the line numbers that @value{GDBN} knows cease |
ed447b95 | 8118 | to correspond properly with the code. |
70b88761 RP |
8119 | |
8120 | @c The following dropped because Epoch is nonstandard. Reactivate | |
8121 | @c if/when v19 does something similar. ---pesch@cygnus.com 19dec1990 | |
8122 | @ignore | |
e251e767 | 8123 | @kindex emacs epoch environment |
70b88761 RP |
8124 | @kindex epoch |
8125 | @kindex inspect | |
8126 | ||
8127 | Version 18 of Emacs has a built-in window system called the @code{epoch} | |
8128 | environment. Users of this environment can use a new command, | |
8129 | @code{inspect} which performs identically to @code{print} except that | |
8130 | each value is printed in its own window. | |
8131 | @end ignore | |
18fae2a8 | 8132 | @end ifclear |
70b88761 | 8133 | |
18fae2a8 | 8134 | @ifset LUCID |
4eb4cf57 | 8135 | @node Energize |
18fae2a8 | 8136 | @chapter Using @value{GDBN} with Energize |
6ca72cc6 RP |
8137 | |
8138 | @cindex Energize | |
8139 | The Energize Programming System is an integrated development environment | |
8140 | that includes a point-and-click interface to many programming tools. | |
18fae2a8 RP |
8141 | When you use @value{GDBN} in this environment, you can use the standard |
8142 | Energize graphical interface to drive @value{GDBN}; you can also, if you | |
8143 | choose, type @value{GDBN} commands as usual in a debugging window. Even if | |
6ca72cc6 | 8144 | you use the graphical interface, the debugging window (which uses Emacs, |
18fae2a8 | 8145 | and resembles the standard Emacs interface to @value{GDBN}) displays the |
6ca72cc6 RP |
8146 | equivalent commands, so that the history of your debugging session is |
8147 | properly reflected. | |
8148 | ||
18fae2a8 | 8149 | When Energize starts up a @value{GDBN} session, it uses one of the |
6ca72cc6 RP |
8150 | command-line options @samp{-energize} or @samp{-cadillac} (``cadillac'' |
8151 | is the name of the communications protocol used by the Energize system). | |
18fae2a8 | 8152 | This option makes @value{GDBN} run as one of the tools in the Energize Tool |
6ca72cc6 RP |
8153 | Set: it sends all output to the Energize kernel, and accept input from |
8154 | it as well. | |
8155 | ||
8156 | See the user manual for the Energize Programming System for | |
8157 | information on how to use the Energize graphical interface and the other | |
18fae2a8 | 8158 | development tools that Energize integrates with @value{GDBN}. |
6ca72cc6 | 8159 | |
18fae2a8 | 8160 | @end ifset |
4eb4cf57 | 8161 | |
18fae2a8 RP |
8162 | @node GDB Bugs |
8163 | @chapter Reporting Bugs in @value{GDBN} | |
ed447b95 RP |
8164 | @cindex bugs in @value{GDBN} |
8165 | @cindex reporting bugs in @value{GDBN} | |
70b88761 | 8166 | |
18fae2a8 | 8167 | Your bug reports play an essential role in making @value{GDBN} reliable. |
70b88761 RP |
8168 | |
8169 | Reporting a bug may help you by bringing a solution to your problem, or it | |
8170 | may not. But in any case the principal function of a bug report is to help | |
18fae2a8 RP |
8171 | the entire community by making the next version of @value{GDBN} work better. Bug |
8172 | reports are your contribution to the maintenance of @value{GDBN}. | |
70b88761 RP |
8173 | |
8174 | In order for a bug report to serve its purpose, you must include the | |
8175 | information that enables us to fix the bug. | |
8176 | ||
8177 | @menu | |
ed447b95 RP |
8178 | * Bug Criteria:: Have you found a bug? |
8179 | * Bug Reporting:: How to report bugs | |
70b88761 RP |
8180 | @end menu |
8181 | ||
4eb4cf57 | 8182 | @node Bug Criteria |
93928b60 | 8183 | @section Have you found a bug? |
ed447b95 | 8184 | @cindex bug criteria |
70b88761 RP |
8185 | |
8186 | If you are not sure whether you have found a bug, here are some guidelines: | |
8187 | ||
8188 | @itemize @bullet | |
8189 | @item | |
0f153e74 | 8190 | @cindex fatal signal |
1d7c3357 RP |
8191 | @cindex debugger crash |
8192 | @cindex crash of debugger | |
70b88761 | 8193 | If the debugger gets a fatal signal, for any input whatever, that is a |
18fae2a8 | 8194 | @value{GDBN} bug. Reliable debuggers never crash. |
70b88761 RP |
8195 | |
8196 | @item | |
0f153e74 | 8197 | @cindex error on valid input |
18fae2a8 | 8198 | If @value{GDBN} produces an error message for valid input, that is a bug. |
70b88761 RP |
8199 | |
8200 | @item | |
ed447b95 | 8201 | @cindex invalid input |
18fae2a8 | 8202 | If @value{GDBN} does not produce an error message for invalid input, |
70b88761 RP |
8203 | that is a bug. However, you should note that your idea of |
8204 | ``invalid input'' might be our idea of ``an extension'' or ``support | |
8205 | for traditional practice''. | |
8206 | ||
8207 | @item | |
8208 | If you are an experienced user of debugging tools, your suggestions | |
18fae2a8 | 8209 | for improvement of @value{GDBN} are welcome in any case. |
70b88761 RP |
8210 | @end itemize |
8211 | ||
4eb4cf57 | 8212 | @node Bug Reporting |
93928b60 | 8213 | @section How to report bugs |
0f153e74 | 8214 | @cindex bug reports |
18fae2a8 | 8215 | @cindex @value{GDBN} bugs, reporting |
70b88761 RP |
8216 | |
8217 | A number of companies and individuals offer support for GNU products. | |
18fae2a8 | 8218 | If you obtained @value{GDBN} from a support organization, we recommend you |
e251e767 | 8219 | contact that organization first. |
70b88761 | 8220 | |
ed447b95 RP |
8221 | You can find contact information for many support companies and |
8222 | individuals in the file @file{etc/SERVICE} in the GNU Emacs | |
8223 | distribution. | |
70b88761 | 8224 | |
18fae2a8 | 8225 | In any event, we also recommend that you send bug reports for @value{GDBN} to one |
70b88761 RP |
8226 | of these addresses: |
8227 | ||
8228 | @example | |
8229 | bug-gdb@@prep.ai.mit.edu | |
8230 | @{ucbvax|mit-eddie|uunet@}!prep.ai.mit.edu!bug-gdb | |
8231 | @end example | |
8232 | ||
8233 | @strong{Do not send bug reports to @samp{info-gdb}, or to | |
18fae2a8 | 8234 | @samp{help-gdb}, or to any newsgroups.} Most users of @value{GDBN} do not want to |
70b88761 RP |
8235 | receive bug reports. Those that do, have arranged to receive @samp{bug-gdb}. |
8236 | ||
3d3ab540 RP |
8237 | The mailing list @samp{bug-gdb} has a newsgroup @samp{gnu.gdb.bug} which |
8238 | serves as a repeater. The mailing list and the newsgroup carry exactly | |
8239 | the same messages. Often people think of posting bug reports to the | |
8240 | newsgroup instead of mailing them. This appears to work, but it has one | |
8241 | problem which can be crucial: a newsgroup posting often lacks a mail | |
8242 | path back to the sender. Thus, if we need to ask for more information, | |
8243 | we may be unable to reach you. For this reason, it is better to send | |
8244 | bug reports to the mailing list. | |
70b88761 RP |
8245 | |
8246 | As a last resort, send bug reports on paper to: | |
8247 | ||
8248 | @example | |
8249 | GNU Debugger Bugs | |
3d3ab540 | 8250 | Free Software Foundation |
70b88761 RP |
8251 | 545 Tech Square |
8252 | Cambridge, MA 02139 | |
8253 | @end example | |
8254 | ||
8255 | The fundamental principle of reporting bugs usefully is this: | |
8256 | @strong{report all the facts}. If you are not sure whether to state a | |
8257 | fact or leave it out, state it! | |
8258 | ||
8259 | Often people omit facts because they think they know what causes the | |
29a2b744 | 8260 | problem and assume that some details do not matter. Thus, you might |
70b88761 | 8261 | assume that the name of the variable you use in an example does not matter. |
29a2b744 | 8262 | Well, probably it does not, but one cannot be sure. Perhaps the bug is a |
70b88761 RP |
8263 | stray memory reference which happens to fetch from the location where that |
8264 | name is stored in memory; perhaps, if the name were different, the contents | |
8265 | of that location would fool the debugger into doing the right thing despite | |
8266 | the bug. Play it safe and give a specific, complete example. That is the | |
8267 | easiest thing for you to do, and the most helpful. | |
8268 | ||
8269 | Keep in mind that the purpose of a bug report is to enable us to fix | |
1041a570 | 8270 | the bug if it is new to us. It is not as important as what happens if |
70b88761 RP |
8271 | the bug is already known. Therefore, always write your bug reports on |
8272 | the assumption that the bug has not been reported previously. | |
8273 | ||
8274 | Sometimes people give a few sketchy facts and ask, ``Does this ring a | |
8275 | bell?'' Those bug reports are useless, and we urge everyone to | |
8276 | @emph{refuse to respond to them} except to chide the sender to report | |
8277 | bugs properly. | |
8278 | ||
8279 | To enable us to fix the bug, you should include all these things: | |
8280 | ||
8281 | @itemize @bullet | |
8282 | @item | |
18fae2a8 | 8283 | The version of @value{GDBN}. @value{GDBN} announces it if you start with no |
70b88761 RP |
8284 | arguments; you can also print it at any time using @code{show version}. |
8285 | ||
1041a570 | 8286 | Without this, we will not know whether there is any point in looking for |
18fae2a8 | 8287 | the bug in the current version of @value{GDBN}. |
70b88761 RP |
8288 | |
8289 | @item | |
ddf21240 JG |
8290 | The type of machine you are using, and the operating system name and |
8291 | version number. | |
70b88761 RP |
8292 | |
8293 | @item | |
18fae2a8 RP |
8294 | What compiler (and its version) was used to compile @value{GDBN}---e.g. |
8295 | ``@value{GCC}--2.0''. | |
70b88761 | 8296 | |
ddf21240 JG |
8297 | @item |
8298 | What compiler (and its version) was used to compile the program you | |
18fae2a8 | 8299 | are debugging---e.g. ``@value{GCC}--2.0''. |
ddf21240 | 8300 | |
70b88761 RP |
8301 | @item |
8302 | The command arguments you gave the compiler to compile your example and | |
8303 | observe the bug. For example, did you use @samp{-O}? To guarantee | |
1041a570 | 8304 | you will not omit something important, list them all. A copy of the |
ddf21240 | 8305 | Makefile (or the output from make) is sufficient. |
70b88761 RP |
8306 | |
8307 | If we were to try to guess the arguments, we would probably guess wrong | |
8308 | and then we might not encounter the bug. | |
8309 | ||
8310 | @item | |
ddf21240 JG |
8311 | A complete input script, and all necessary source files, that will |
8312 | reproduce the bug. | |
70b88761 RP |
8313 | |
8314 | @item | |
8315 | A description of what behavior you observe that you believe is | |
8316 | incorrect. For example, ``It gets a fatal signal.'' | |
8317 | ||
18fae2a8 | 8318 | Of course, if the bug is that @value{GDBN} gets a fatal signal, then we will |
70b88761 RP |
8319 | certainly notice it. But if the bug is incorrect output, we might not |
8320 | notice unless it is glaringly wrong. We are human, after all. You | |
8321 | might as well not give us a chance to make a mistake. | |
8322 | ||
8323 | Even if the problem you experience is a fatal signal, you should still | |
8324 | say so explicitly. Suppose something strange is going on, such as, | |
18fae2a8 | 8325 | your copy of @value{GDBN} is out of synch, or you have encountered a |
70b88761 RP |
8326 | bug in the C library on your system. (This has happened!) Your copy |
8327 | might crash and ours would not. If you told us to expect a crash, | |
8328 | then when ours fails to crash, we would know that the bug was not | |
8329 | happening for us. If you had not told us to expect a crash, then we | |
8330 | would not be able to draw any conclusion from our observations. | |
8331 | ||
8332 | @item | |
18fae2a8 RP |
8333 | If you wish to suggest changes to the @value{GDBN} source, send us context |
8334 | diffs. If you even discuss something in the @value{GDBN} source, refer to | |
70b88761 RP |
8335 | it by context, not by line number. |
8336 | ||
1041a570 | 8337 | The line numbers in our development sources will not match those in your |
70b88761 | 8338 | sources. Your line numbers would convey no useful information to us. |
70b88761 RP |
8339 | @end itemize |
8340 | ||
8341 | Here are some things that are not necessary: | |
8342 | ||
8343 | @itemize @bullet | |
8344 | @item | |
8345 | A description of the envelope of the bug. | |
8346 | ||
8347 | Often people who encounter a bug spend a lot of time investigating | |
8348 | which changes to the input file will make the bug go away and which | |
8349 | changes will not affect it. | |
8350 | ||
8351 | This is often time consuming and not very useful, because the way we | |
8352 | will find the bug is by running a single example under the debugger | |
8353 | with breakpoints, not by pure deduction from a series of examples. | |
8354 | We recommend that you save your time for something else. | |
8355 | ||
8356 | Of course, if you can find a simpler example to report @emph{instead} | |
8357 | of the original one, that is a convenience for us. Errors in the | |
8358 | output will be easier to spot, running under the debugger will take | |
b1955f0b | 8359 | less time, and so on. |
70b88761 | 8360 | |
29a2b744 | 8361 | However, simplification is not vital; if you do not want to do this, |
70b88761 RP |
8362 | report the bug anyway and send us the entire test case you used. |
8363 | ||
8364 | @item | |
8365 | A patch for the bug. | |
8366 | ||
29a2b744 | 8367 | A patch for the bug does help us if it is a good one. But do not omit |
70b88761 RP |
8368 | the necessary information, such as the test case, on the assumption that |
8369 | a patch is all we need. We might see problems with your patch and decide | |
8370 | to fix the problem another way, or we might not understand it at all. | |
8371 | ||
18fae2a8 | 8372 | Sometimes with a program as complicated as @value{GDBN} it is very hard to |
70b88761 | 8373 | construct an example that will make the program follow a certain path |
1041a570 RP |
8374 | through the code. If you do not send us the example, we will not be able |
8375 | to construct one, so we will not be able to verify that the bug is fixed. | |
70b88761 | 8376 | |
29a2b744 | 8377 | And if we cannot understand what bug you are trying to fix, or why your |
1041a570 | 8378 | patch should be an improvement, we will not install it. A test case will |
70b88761 RP |
8379 | help us to understand. |
8380 | ||
8381 | @item | |
8382 | A guess about what the bug is or what it depends on. | |
8383 | ||
29a2b744 | 8384 | Such guesses are usually wrong. Even we cannot guess right about such |
70b88761 RP |
8385 | things without first using the debugger to find the facts. |
8386 | @end itemize | |
8387 | ||
da24340c RP |
8388 | @c The readline documentation is distributed with the readline code |
8389 | @c and consists of the two following files: | |
8390 | @c rluser.texinfo | |
8391 | @c inc-hist.texi | |
8392 | @c Use -I with makeinfo to point to the appropriate directory, | |
8393 | @c environment var TEXINPUTS with TeX. | |
cacf5942 RP |
8394 | @include rluser.texinfo |
8395 | @include inc-hist.texi | |
70b88761 | 8396 | |
18fae2a8 | 8397 | @ifset NOVEL |
4eb4cf57 | 8398 | @node Renamed Commands |
70b88761 RP |
8399 | @appendix Renamed Commands |
8400 | ||
c7cb8acb | 8401 | The following commands were renamed in GDB 4, in order to make the |
70b88761 RP |
8402 | command set as a whole more consistent and easier to use and remember: |
8403 | ||
e251e767 RP |
8404 | @kindex add-syms |
8405 | @kindex delete environment | |
8406 | @kindex info copying | |
8407 | @kindex info convenience | |
8408 | @kindex info directories | |
8409 | @kindex info editing | |
8410 | @kindex info history | |
8411 | @kindex info targets | |
8412 | @kindex info values | |
8413 | @kindex info version | |
8414 | @kindex info warranty | |
8415 | @kindex set addressprint | |
8416 | @kindex set arrayprint | |
8417 | @kindex set prettyprint | |
8418 | @kindex set screen-height | |
8419 | @kindex set screen-width | |
8420 | @kindex set unionprint | |
8421 | @kindex set vtblprint | |
8422 | @kindex set demangle | |
8423 | @kindex set asm-demangle | |
8424 | @kindex set sevenbit-strings | |
8425 | @kindex set array-max | |
8426 | @kindex set caution | |
8427 | @kindex set history write | |
8428 | @kindex show addressprint | |
8429 | @kindex show arrayprint | |
8430 | @kindex show prettyprint | |
8431 | @kindex show screen-height | |
8432 | @kindex show screen-width | |
8433 | @kindex show unionprint | |
8434 | @kindex show vtblprint | |
8435 | @kindex show demangle | |
8436 | @kindex show asm-demangle | |
8437 | @kindex show sevenbit-strings | |
8438 | @kindex show array-max | |
8439 | @kindex show caution | |
8440 | @kindex show history write | |
8441 | @kindex unset | |
70b88761 | 8442 | |
92b73793 | 8443 | @c TEXI2ROFF-KILL |
70b88761 | 8444 | @ifinfo |
92b73793 | 8445 | @c END TEXI2ROFF-KILL |
cf496415 RP |
8446 | @example |
8447 | OLD COMMAND NEW COMMAND | |
92b73793 | 8448 | @c TEXI2ROFF-KILL |
cf496415 | 8449 | --------------- ------------------------------- |
92b73793 | 8450 | @c END TEXI2ROFF-KILL |
cf496415 RP |
8451 | add-syms add-symbol-file |
8452 | delete environment unset environment | |
8453 | info convenience show convenience | |
8454 | info copying show copying | |
e251e767 | 8455 | info directories show directories |
cf496415 RP |
8456 | info editing show commands |
8457 | info history show values | |
8458 | info targets help target | |
8459 | info values show values | |
8460 | info version show version | |
8461 | info warranty show warranty | |
8462 | set/show addressprint set/show print address | |
8463 | set/show array-max set/show print elements | |
8464 | set/show arrayprint set/show print array | |
8465 | set/show asm-demangle set/show print asm-demangle | |
8466 | set/show caution set/show confirm | |
8467 | set/show demangle set/show print demangle | |
8468 | set/show history write set/show history save | |
8469 | set/show prettyprint set/show print pretty | |
8470 | set/show screen-height set/show height | |
8471 | set/show screen-width set/show width | |
8472 | set/show sevenbit-strings set/show print sevenbit-strings | |
8473 | set/show unionprint set/show print union | |
8474 | set/show vtblprint set/show print vtbl | |
8475 | ||
8476 | unset [No longer an alias for delete] | |
8477 | @end example | |
92b73793 | 8478 | @c TEXI2ROFF-KILL |
70b88761 RP |
8479 | @end ifinfo |
8480 | ||
8481 | @tex | |
8482 | \vskip \parskip\vskip \baselineskip | |
8483 | \halign{\tt #\hfil &\qquad#&\tt #\hfil\cr | |
8484 | {\bf Old Command} &&{\bf New Command}\cr | |
8485 | add-syms &&add-symbol-file\cr | |
8486 | delete environment &&unset environment\cr | |
8487 | info convenience &&show convenience\cr | |
8488 | info copying &&show copying\cr | |
8489 | info directories &&show directories \cr | |
8490 | info editing &&show commands\cr | |
8491 | info history &&show values\cr | |
8492 | info targets &&help target\cr | |
8493 | info values &&show values\cr | |
8494 | info version &&show version\cr | |
8495 | info warranty &&show warranty\cr | |
8496 | set{\rm / }show addressprint &&set{\rm / }show print address\cr | |
8497 | set{\rm / }show array-max &&set{\rm / }show print elements\cr | |
8498 | set{\rm / }show arrayprint &&set{\rm / }show print array\cr | |
8499 | set{\rm / }show asm-demangle &&set{\rm / }show print asm-demangle\cr | |
8500 | set{\rm / }show caution &&set{\rm / }show confirm\cr | |
8501 | set{\rm / }show demangle &&set{\rm / }show print demangle\cr | |
8502 | set{\rm / }show history write &&set{\rm / }show history save\cr | |
8503 | set{\rm / }show prettyprint &&set{\rm / }show print pretty\cr | |
8504 | set{\rm / }show screen-height &&set{\rm / }show height\cr | |
8505 | set{\rm / }show screen-width &&set{\rm / }show width\cr | |
8506 | set{\rm / }show sevenbit-strings &&set{\rm / }show print sevenbit-strings\cr | |
8507 | set{\rm / }show unionprint &&set{\rm / }show print union\cr | |
8508 | set{\rm / }show vtblprint &&set{\rm / }show print vtbl\cr | |
8509 | \cr | |
8510 | unset &&\rm(No longer an alias for delete)\cr | |
8511 | } | |
8512 | @end tex | |
92b73793 | 8513 | @c END TEXI2ROFF-KILL |
18fae2a8 | 8514 | @end ifset |
70b88761 | 8515 | |
18fae2a8 | 8516 | @ifclear PRECONFIGURED |
4eb4cf57 | 8517 | @node Formatting Documentation |
fe715d06 | 8518 | @appendix Formatting Documentation |
77b46d13 JG |
8519 | |
8520 | @cindex GDB reference card | |
8521 | @cindex reference card | |
8522 | The GDB 4 release includes an already-formatted reference card, ready | |
d241c8c8 | 8523 | for printing with PostScript or Ghostscript, in the @file{gdb} |
ed447b95 RP |
8524 | subdirectory of the main source directory@footnote{In |
8525 | @file{gdb-@value{GDBVN}/gdb/refcard.ps} of the version @value{GDBVN} | |
d241c8c8 | 8526 | release.}. If you can use PostScript or Ghostscript with your printer, |
ed447b95 | 8527 | you can print the reference card immediately with @file{refcard.ps}. |
77b46d13 JG |
8528 | |
8529 | The release also includes the source for the reference card. You | |
8530 | can format it, using @TeX{}, by typing: | |
8531 | ||
8532 | @example | |
8533 | make refcard.dvi | |
8534 | @end example | |
8535 | ||
8536 | The GDB reference card is designed to print in landscape mode on US | |
8537 | ``letter'' size paper; that is, on a sheet 11 inches wide by 8.5 inches | |
8538 | high. You will need to specify this form of printing as an option to | |
8539 | your @sc{dvi} output program. | |
8540 | ||
8541 | @cindex documentation | |
8542 | ||
8543 | All the documentation for GDB comes as part of the machine-readable | |
8544 | distribution. The documentation is written in Texinfo format, which is | |
8545 | a documentation system that uses a single source file to produce both | |
8546 | on-line information and a printed manual. You can use one of the Info | |
8547 | formatting commands to create the on-line version of the documentation | |
8548 | and @TeX{} (or @code{texi2roff}) to typeset the printed version. | |
8549 | ||
8550 | GDB includes an already formatted copy of the on-line Info version of | |
8551 | this manual in the @file{gdb} subdirectory. The main Info file is | |
8552 | @file{gdb-@var{version-number}/gdb/gdb.info}, and it refers to | |
a89f94c2 RP |
8553 | subordinate files matching @samp{gdb.info*} in the same directory. If |
8554 | necessary, you can print out these files, or read them with any editor; | |
8555 | but they are easier to read using the @code{info} subsystem in GNU Emacs | |
8556 | or the standalone @code{info} program, available as part of the GNU | |
8557 | Texinfo distribution. | |
77b46d13 JG |
8558 | |
8559 | If you want to format these Info files yourself, you need one of the | |
8560 | Info formatting programs, such as @code{texinfo-format-buffer} or | |
8561 | @code{makeinfo}. | |
8562 | ||
8563 | If you have @code{makeinfo} installed, and are in the top level GDB | |
18fae2a8 | 8564 | source directory (@file{gdb-@value{GDBVN}}, in the case of version @value{GDBVN}), you can |
77b46d13 JG |
8565 | make the Info file by typing: |
8566 | ||
8567 | @example | |
8568 | cd gdb | |
8569 | make gdb.info | |
8570 | @end example | |
8571 | ||
fe715d06 RP |
8572 | If you want to typeset and print copies of this manual, you need @TeX{}, |
8573 | a program to print its @sc{dvi} output files, and @file{texinfo.tex}, the | |
8574 | Texinfo definitions file. | |
77b46d13 | 8575 | |
83bfcbae | 8576 | @TeX{} is a typesetting program; it does not print files directly, but |
77b46d13 JG |
8577 | produces output files called @sc{dvi} files. To print a typeset |
8578 | document, you need a program to print @sc{dvi} files. If your system | |
8579 | has @TeX{} installed, chances are it has such a program. The precise | |
8580 | command to use depends on your system; @kbd{lpr -d} is common; another | |
fe715d06 RP |
8581 | (for PostScript devices) is @kbd{dvips}. The @sc{dvi} print command may |
8582 | require a file name without any extension or a @samp{.dvi} extension. | |
77b46d13 JG |
8583 | |
8584 | @TeX{} also requires a macro definitions file called | |
8585 | @file{texinfo.tex}. This file tells @TeX{} how to typeset a document | |
8586 | written in Texinfo format. On its own, @TeX{} cannot read, much less | |
8587 | typeset a Texinfo file. @file{texinfo.tex} is distributed with GDB | |
8588 | and is located in the @file{gdb-@var{version-number}/texinfo} | |
8589 | directory. | |
8590 | ||
8591 | If you have @TeX{} and a @sc{dvi} printer program installed, you can | |
8592 | typeset and print this manual. First switch to the the @file{gdb} | |
8593 | subdirectory of the main source directory (for example, to | |
18fae2a8 | 8594 | @file{gdb-@value{GDBVN}/gdb}) and then type: |
77b46d13 JG |
8595 | |
8596 | @example | |
8597 | make gdb.dvi | |
8598 | @end example | |
8599 | ||
4eb4cf57 | 8600 | @node Installing GDB |
c7cb8acb RP |
8601 | @appendix Installing GDB |
8602 | @cindex configuring GDB | |
70b88761 RP |
8603 | @cindex installation |
8604 | ||
ed447b95 RP |
8605 | GDB comes with a @code{configure} script that automates the process |
8606 | of preparing GDB for installation; you can then use @code{make} to | |
8607 | build the @code{gdb} program. | |
f672bb7f RP |
8608 | @iftex |
8609 | @c irrelevant in info file; it's as current as the code it lives with. | |
ed447b95 RP |
8610 | @footnote{If you have a more recent version of GDB than @value{GDBVN}, |
8611 | look at the @file{README} file in the sources; we may have improved the | |
8612 | installation procedures since publishing this manual.} | |
f672bb7f RP |
8613 | @end iftex |
8614 | ||
c7cb8acb | 8615 | The GDB distribution includes all the source code you need for GDB in |
1041a570 RP |
8616 | a single directory, whose name is usually composed by appending the |
8617 | version number to @samp{gdb}. | |
8618 | ||
ed447b95 RP |
8619 | For example, the GDB version @value{GDBVN} distribution is in the |
8620 | @file{gdb-@value{GDBVN}} directory. That directory contains: | |
b80282d5 | 8621 | |
3d3ab540 | 8622 | @table @code |
18fae2a8 | 8623 | @item gdb-@value{GDBVN}/configure @r{(and supporting files)} |
c7cb8acb | 8624 | script for configuring GDB and all its supporting libraries. |
b80282d5 | 8625 | |
18fae2a8 | 8626 | @item gdb-@value{GDBVN}/gdb |
c7cb8acb | 8627 | the source specific to GDB itself |
3d3ab540 | 8628 | |
18fae2a8 | 8629 | @item gdb-@value{GDBVN}/bfd |
77b46d13 | 8630 | source for the Binary File Descriptor library |
3d3ab540 | 8631 | |
18fae2a8 | 8632 | @item gdb-@value{GDBVN}/include |
b80282d5 | 8633 | GNU include files |
3d3ab540 | 8634 | |
18fae2a8 | 8635 | @item gdb-@value{GDBVN}/libiberty |
3d3ab540 RP |
8636 | source for the @samp{-liberty} free software library |
8637 | ||
18fae2a8 | 8638 | @item gdb-@value{GDBVN}/opcodes |
3214c51c JG |
8639 | source for the library of opcode tables and disassemblers |
8640 | ||
18fae2a8 | 8641 | @item gdb-@value{GDBVN}/readline |
b80282d5 | 8642 | source for the GNU command-line interface |
77b46d13 | 8643 | |
18fae2a8 | 8644 | @item gdb-@value{GDBVN}/glob |
77b46d13 JG |
8645 | source for the GNU filename pattern-matching subroutine |
8646 | ||
18fae2a8 | 8647 | @item gdb-@value{GDBVN}/mmalloc |
77b46d13 | 8648 | source for the GNU memory-mapped malloc package |
3d3ab540 | 8649 | @end table |
1041a570 | 8650 | |
c7cb8acb | 8651 | The simplest way to configure and build GDB is to run @code{configure} |
1041a570 | 8652 | from the @file{gdb-@var{version-number}} source directory, which in |
18fae2a8 | 8653 | this example is the @file{gdb-@value{GDBVN}} directory. |
1041a570 RP |
8654 | |
8655 | First switch to the @file{gdb-@var{version-number}} source directory | |
8656 | if you are not already in it; then run @code{configure}. Pass the | |
c7cb8acb | 8657 | identifier for the platform on which GDB will run as an |
1041a570 RP |
8658 | argument. |
8659 | ||
8660 | For example: | |
8661 | ||
7463aadd | 8662 | @example |
18fae2a8 | 8663 | cd gdb-@value{GDBVN} |
3d3ab540 | 8664 | ./configure @var{host} |
7463aadd RP |
8665 | make |
8666 | @end example | |
1041a570 | 8667 | |
7463aadd | 8668 | @noindent |
1041a570 | 8669 | where @var{host} is an identifier such as @samp{sun4} or |
c7cb8acb | 8670 | @samp{decstation}, that identifies the platform where GDB will run. |
d55320a0 RP |
8671 | (You can often leave off @var{host}; @code{configure} tries to guess the |
8672 | correct value by examining your system.) | |
1041a570 | 8673 | |
8c69096b | 8674 | Running @samp{configure @var{host}} and then running @code{make} builds the |
38962738 RP |
8675 | @file{bfd}, @file{readline}, @file{mmalloc}, and @file{libiberty} |
8676 | libraries, then @code{gdb} itself. The configured source files, and the | |
8677 | binaries, are left in the corresponding source directories. | |
3d3ab540 | 8678 | |
e251e767 | 8679 | @code{configure} is a Bourne-shell (@code{/bin/sh}) script; if your |
29a2b744 | 8680 | system does not recognize this automatically when you run a different |
1041a570 RP |
8681 | shell, you may need to run @code{sh} on it explicitly: |
8682 | ||
8683 | @example | |
8684 | sh configure @var{host} | |
8685 | @end example | |
e251e767 | 8686 | |
f672bb7f RP |
8687 | If you run @code{configure} from a directory that contains source |
8688 | directories for multiple libraries or programs, such as the | |
18fae2a8 | 8689 | @file{gdb-@value{GDBVN}} source directory for version @value{GDBVN}, @code{configure} |
f672bb7f | 8690 | creates configuration files for every directory level underneath (unless |
98349959 | 8691 | you tell it not to, with the @samp{--norecursion} option). |
f672bb7f RP |
8692 | |
8693 | You can run the @code{configure} script from any of the | |
d55320a0 RP |
8694 | subordinate directories in the GDB distribution if you only want to |
8695 | configure that subdirectory, but be sure to specify a path to it. | |
1041a570 | 8696 | |
18fae2a8 | 8697 | For example, with version @value{GDBVN}, type the following to configure only |
1041a570 RP |
8698 | the @code{bfd} subdirectory: |
8699 | ||
e251e767 | 8700 | @example |
203eea5d | 8701 | @group |
18fae2a8 | 8702 | cd gdb-@value{GDBVN}/bfd |
e251e767 | 8703 | ../configure @var{host} |
203eea5d | 8704 | @end group |
e251e767 RP |
8705 | @end example |
8706 | ||
18fae2a8 | 8707 | You can install @code{@value{GDBP}} anywhere; it has no hardwired paths. |
1041a570 RP |
8708 | However, you should make sure that the shell on your path (named by |
8709 | the @samp{SHELL} environment variable) is publicly readable. Remember | |
c7cb8acb RP |
8710 | that GDB uses the shell to start your program---some systems refuse to |
8711 | let GDB debug child processes whose programs are not readable. | |
3d3ab540 RP |
8712 | |
8713 | @menu | |
c7cb8acb | 8714 | * Separate Objdir:: Compiling GDB in another directory |
b80282d5 RP |
8715 | * Config Names:: Specifying names for hosts and targets |
8716 | * configure Options:: Summary of options for configure | |
3d3ab540 RP |
8717 | @end menu |
8718 | ||
4eb4cf57 | 8719 | @node Separate Objdir |
93928b60 | 8720 | @section Compiling GDB in another directory |
1041a570 | 8721 | |
c7cb8acb | 8722 | If you want to run GDB versions for several host or target machines, |
ed447b95 | 8723 | you need a different @code{gdb} compiled for each combination of |
1041a570 | 8724 | host and target. @code{configure} is designed to make this easy by |
f672bb7f RP |
8725 | allowing you to generate each configuration in a separate subdirectory, |
8726 | rather than in the source directory. If your @code{make} program | |
8727 | handles the @samp{VPATH} feature (GNU @code{make} does), running | |
ed447b95 | 8728 | @code{make} in each of these directories builds the @code{gdb} |
f672bb7f | 8729 | program specified there. |
b80282d5 | 8730 | |
c7cb8acb | 8731 | To build @code{gdb} in a separate directory, run @code{configure} |
f672bb7f | 8732 | with the @samp{--srcdir} option to specify where to find the source. |
93918348 | 8733 | (You also need to specify a path to find @code{configure} |
77b46d13 JG |
8734 | itself from your working directory. If the path to @code{configure} |
8735 | would be the same as the argument to @samp{--srcdir}, you can leave out | |
9a27b06e | 8736 | the @samp{--srcdir} option; it is assumed.) |
1041a570 | 8737 | |
18fae2a8 | 8738 | For example, with version @value{GDBVN}, you can build GDB in a separate |
f672bb7f | 8739 | directory for a Sun 4 like this: |
70b88761 RP |
8740 | |
8741 | @example | |
3d3ab540 | 8742 | @group |
18fae2a8 | 8743 | cd gdb-@value{GDBVN} |
f672bb7f RP |
8744 | mkdir ../gdb-sun4 |
8745 | cd ../gdb-sun4 | |
18fae2a8 | 8746 | ../gdb-@value{GDBVN}/configure sun4 |
70b88761 | 8747 | make |
3d3ab540 | 8748 | @end group |
70b88761 RP |
8749 | @end example |
8750 | ||
f672bb7f RP |
8751 | When @code{configure} builds a configuration using a remote source |
8752 | directory, it creates a tree for the binaries with the same structure | |
8753 | (and using the same names) as the tree under the source directory. In | |
8754 | the example, you'd find the Sun 4 library @file{libiberty.a} in the | |
c7cb8acb | 8755 | directory @file{gdb-sun4/libiberty}, and GDB itself in |
f672bb7f | 8756 | @file{gdb-sun4/gdb}. |
1041a570 | 8757 | |
38962738 | 8758 | One popular reason to build several GDB configurations in separate |
c7cb8acb | 8759 | directories is to configure GDB for cross-compiling (where GDB |
f672bb7f RP |
8760 | runs on one machine---the host---while debugging programs that run on |
8761 | another machine---the target). You specify a cross-debugging target by | |
8762 | giving the @samp{--target=@var{target}} option to @code{configure}. | |
c7637ea6 | 8763 | |
1041a570 | 8764 | When you run @code{make} to build a program or library, you must run |
f672bb7f RP |
8765 | it in a configured directory---whatever directory you were in when you |
8766 | called @code{configure} (or one of its subdirectories). | |
c7637ea6 | 8767 | |
fe715d06 | 8768 | The @code{Makefile} that @code{configure} generates in each source |
f672bb7f | 8769 | directory also runs recursively. If you type @code{make} in a source |
18fae2a8 | 8770 | directory such as @file{gdb-@value{GDBVN}} (or in a separate configured |
b550c03a | 8771 | directory configured with @samp{--srcdir=@var{dirname}/gdb-@value{GDBVN}}), you |
ed447b95 | 8772 | will build all the required libraries, and then build GDB. |
3d3ab540 | 8773 | |
f672bb7f RP |
8774 | When you have multiple hosts or targets configured in separate |
8775 | directories, you can run @code{make} on them in parallel (for example, | |
8776 | if they are NFS-mounted on each of the hosts); they will not interfere | |
8777 | with each other. | |
3d3ab540 | 8778 | |
4eb4cf57 | 8779 | @node Config Names |
93928b60 | 8780 | @section Specifying names for hosts and targets |
b80282d5 RP |
8781 | |
8782 | The specifications used for hosts and targets in the @code{configure} | |
8783 | script are based on a three-part naming scheme, but some short predefined | |
8784 | aliases are also supported. The full naming scheme encodes three pieces | |
e251e767 | 8785 | of information in the following pattern: |
1041a570 | 8786 | |
b80282d5 RP |
8787 | @example |
8788 | @var{architecture}-@var{vendor}-@var{os} | |
8789 | @end example | |
8790 | ||
8c69096b RP |
8791 | For example, you can use the alias @code{sun4} as a @var{host} argument, |
8792 | or as the value for @var{target} in a @code{--target=@var{target}} | |
8793 | option. The equivalent full name is @samp{sparc-sun-sunos4}. | |
b80282d5 | 8794 | |
c7cb8acb | 8795 | The @code{configure} script accompanying GDB does not provide |
b80282d5 RP |
8796 | any query facility to list all supported host and target names or |
8797 | aliases. @code{configure} calls the Bourne shell script | |
8798 | @code{config.sub} to map abbreviations to full names; you can read the | |
8799 | script, if you wish, or you can use it to test your guesses on | |
8800 | abbreviations---for example: | |
1041a570 | 8801 | |
b1385986 | 8802 | @smallexample |
b80282d5 | 8803 | % sh config.sub sun4 |
d55320a0 | 8804 | sparc-sun-sunos4.1.1 |
b80282d5 | 8805 | % sh config.sub sun3 |
d55320a0 | 8806 | m68k-sun-sunos4.1.1 |
b80282d5 | 8807 | % sh config.sub decstation |
d55320a0 | 8808 | mips-dec-ultrix4.2 |
b80282d5 RP |
8809 | % sh config.sub hp300bsd |
8810 | m68k-hp-bsd | |
8811 | % sh config.sub i386v | |
6a8cb0e7 | 8812 | i386-unknown-sysv |
e94b4a2b | 8813 | % sh config.sub i786v |
6a8cb0e7 | 8814 | Invalid configuration `i786v': machine `i786v' not recognized |
b1385986 | 8815 | @end smallexample |
1041a570 | 8816 | |
c7637ea6 | 8817 | @noindent |
1041a570 | 8818 | @code{config.sub} is also distributed in the GDB source |
18fae2a8 | 8819 | directory (@file{gdb-@value{GDBVN}}, for version @value{GDBVN}). |
b80282d5 | 8820 | |
4eb4cf57 | 8821 | @node configure Options |
93928b60 | 8822 | @section @code{configure} options |
7463aadd | 8823 | |
d48da190 | 8824 | Here is a summary of the @code{configure} options and arguments that |
18fae2a8 | 8825 | are most often useful for building @value{GDBN}. @code{configure} also has |
d48da190 RP |
8826 | several other options not listed here. @inforef{What Configure |
8827 | Does,,configure.info}, for a full explanation of @code{configure}. | |
8828 | @c FIXME: Would this be more, or less, useful as an xref (ref to printed | |
8829 | @c manual in the printed manual, ref to info file only from the info file)? | |
7463aadd RP |
8830 | |
8831 | @example | |
d48da190 RP |
8832 | configure @r{[}--help@r{]} |
8833 | @r{[}--prefix=@var{dir}@r{]} | |
b550c03a | 8834 | @r{[}--srcdir=@var{dirname}@r{]} |
f672bb7f RP |
8835 | @r{[}--norecursion@r{]} @r{[}--rm@r{]} |
8836 | @r{[}--target=@var{target}@r{]} @var{host} | |
7463aadd | 8837 | @end example |
1041a570 | 8838 | |
3d3ab540 | 8839 | @noindent |
f672bb7f RP |
8840 | You may introduce options with a single @samp{-} rather than |
8841 | @samp{--} if you prefer; but you may abbreviate option names if you use | |
8842 | @samp{--}. | |
70b88761 RP |
8843 | |
8844 | @table @code | |
d48da190 RP |
8845 | @item --help |
8846 | Display a quick summary of how to invoke @code{configure}. | |
8847 | ||
8848 | @item -prefix=@var{dir} | |
8849 | Configure the source to install programs and files under directory | |
8850 | @file{@var{dir}}. | |
8851 | ||
b1955f0b RP |
8852 | @c avoid splitting the warning from the explanation: |
8853 | @need 2000 | |
b550c03a | 8854 | @item --srcdir=@var{dirname} |
6ca72cc6 RP |
8855 | @strong{Warning: using this option requires GNU @code{make}, or another |
8856 | @code{make} that implements the @code{VPATH} feature.}@* | |
f672bb7f | 8857 | Use this option to make configurations in directories separate from the |
c7cb8acb | 8858 | GDB source directories. Among other things, you can use this to |
f672bb7f RP |
8859 | build (or maintain) several configurations simultaneously, in separate |
8860 | directories. @code{configure} writes configuration specific files in | |
8861 | the current directory, but arranges for them to use the source in the | |
b550c03a | 8862 | directory @var{dirname}. @code{configure} creates directories under |
f672bb7f | 8863 | the working directory in parallel to the source directories below |
b550c03a | 8864 | @var{dirname}. |
f672bb7f RP |
8865 | |
8866 | @item --norecursion | |
8867 | Configure only the directory level where @code{configure} is executed; do not | |
7463aadd RP |
8868 | propagate configuration to subdirectories. |
8869 | ||
f672bb7f | 8870 | @item --rm |
d55320a0 | 8871 | @emph{Remove} files otherwise built during configuration. |
7463aadd | 8872 | |
29a2b744 | 8873 | @c This does not work (yet if ever). FIXME. |
f672bb7f | 8874 | @c @item --parse=@var{lang} @dots{} |
c7cb8acb RP |
8875 | @c Configure the GDB expression parser to parse the listed languages. |
8876 | @c @samp{all} configures GDB for all supported languages. To get a | |
d7b569d5 | 8877 | @c list of all supported languages, omit the argument. Without this |
c7cb8acb | 8878 | @c option, GDB is configured to parse all supported languages. |
c2bbbb22 | 8879 | |
f672bb7f | 8880 | @item --target=@var{target} |
c7cb8acb RP |
8881 | Configure GDB for cross-debugging programs running on the specified |
8882 | @var{target}. Without this option, GDB is configured to debug | |
8883 | programs that run on the same machine (@var{host}) as GDB itself. | |
b80282d5 RP |
8884 | |
8885 | There is no convenient way to generate a list of all available targets. | |
7463aadd RP |
8886 | |
8887 | @item @var{host} @dots{} | |
c7cb8acb | 8888 | Configure GDB to run on the specified @var{host}. |
b80282d5 RP |
8889 | |
8890 | There is no convenient way to generate a list of all available hosts. | |
70b88761 RP |
8891 | @end table |
8892 | ||
3d3ab540 RP |
8893 | @noindent |
8894 | @code{configure} accepts other options, for compatibility with | |
b80282d5 | 8895 | configuring other GNU tools recursively; but these are the only |
c7cb8acb | 8896 | options that affect GDB or its supporting libraries. |
18fae2a8 | 8897 | @end ifclear |
3d3ab540 | 8898 | |
4eb4cf57 | 8899 | @node Index |
d2e08421 | 8900 | @unnumbered Index |
e91b87a3 | 8901 | |
8902 | @printindex cp | |
8903 | ||
fe3f5fc8 RP |
8904 | @tex |
8905 | % I think something like @colophon should be in texinfo. In the | |
8906 | % meantime: | |
8907 | \long\def\colophon{\hbox to0pt{}\vfill | |
8908 | \centerline{The body of this manual is set in} | |
8909 | \centerline{\fontname\tenrm,} | |
8910 | \centerline{with headings in {\bf\fontname\tenbf}} | |
8911 | \centerline{and examples in {\tt\fontname\tentt}.} | |
a6d0b6d3 RP |
8912 | \centerline{{\it\fontname\tenit\/},} |
8913 | \centerline{{\bf\fontname\tenbf}, and} | |
fe3f5fc8 RP |
8914 | \centerline{{\sl\fontname\tensl\/}} |
8915 | \centerline{are used for emphasis.}\vfill} | |
8916 | \page\colophon | |
a6d0b6d3 | 8917 | % Blame: pesch@cygnus.com, 1991. |
fe3f5fc8 RP |
8918 | @end tex |
8919 | ||
e91b87a3 | 8920 | @contents |
8921 | @bye |