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diff --git a/gdb/doc/gdb.texinfo b/gdb/doc/gdb.texinfo deleted file mode 100644 index fc920bb..0000000 --- a/gdb/doc/gdb.texinfo +++ /dev/null @@ -1,10316 +0,0 @@ -\input texinfo @c -*-texinfo-*- -@c Copyright 1988-1999 -@c Free Software Foundation, Inc. -@c -@c %**start of header -@c makeinfo ignores cmds prev to setfilename, so its arg cannot make use -@c of @set vars. However, you can override filename with makeinfo -o. -@setfilename gdb.info -@c -@include gdb-cfg.texi -@c -@ifset GENERIC -@settitle Debugging with @value{GDBN} -@end ifset -@ifclear GENERIC -@settitle Debugging with @value{GDBN} (@value{TARGET}) -@end ifclear -@setchapternewpage odd -@c %**end of header - -@iftex -@c @smallbook -@c @cropmarks -@end iftex - -@finalout -@syncodeindex ky cp - -@c readline appendices use @vindex -@syncodeindex vr cp - -@c !!set GDB manual's edition---not the same as GDB version! -@set EDITION Seventh - -@c !!set GDB manual's revision date -@set DATE February 1999 - -@c THIS MANUAL REQUIRES TEXINFO-2 macros and info-makers to format properly. - -@ifinfo -@c This is a dir.info fragment to support semi-automated addition of -@c manuals to an info tree. zoo@cygnus.com is developing this facility. -@format -START-INFO-DIR-ENTRY -* Gdb: (gdb). The @sc{gnu} debugger. -END-INFO-DIR-ENTRY -@end format -@end ifinfo -@c -@c -@ifinfo -This file documents the @sc{gnu} debugger @value{GDBN}. - - -This is the @value{EDITION} Edition, @value{DATE}, -of @cite{Debugging with @value{GDBN}: the @sc{gnu} Source-Level Debugger} -for @value{GDBN} Version @value{GDBVN}. - -Copyright (C) 1988-1999 Free Software Foundation, Inc. - -Permission is granted to make and distribute verbatim copies of -this manual provided the copyright notice and this permission notice -are preserved on all copies. - -@ignore -Permission is granted to process this file through TeX and print the -results, provided the printed document carries copying permission -notice identical to this one except for the removal of this paragraph -(this paragraph not being relevant to the printed manual). - -@end ignore -Permission is granted to copy and distribute modified versions of this -manual under the conditions for verbatim copying, provided also that the -entire resulting derived work is distributed under the terms of a -permission notice identical to this one. - -Permission is granted to copy and distribute translations of this manual -into another language, under the above conditions for modified versions. -@end ifinfo - -@titlepage -@title Debugging with @value{GDBN} -@subtitle The @sc{gnu} Source-Level Debugger -@ifclear GENERIC -@subtitle (@value{TARGET}) -@end ifclear -@sp 1 -@ifclear HPPA -@subtitle @value{EDITION} Edition, for @value{GDBN} version @value{GDBVN} -@subtitle @value{DATE} -@author Richard M. Stallman and Roland H. Pesch -@end ifclear -@ifset HPPA -@subtitle Edition @value{EDITION}, for @value{HPVER} (based on @value{GDBN} @value{GDBVN}) -@subtitle @value{DATE} -@author Richard M. Stallman and Roland H. Pesch (modified by HP) -@end ifset -@page -@ifclear HPPA -@tex -{\parskip=0pt -\hfill (Send bugs and comments on @value{GDBN} to bug-gdb\@prep.ai.mit.edu.)\par -\hfill {\it Debugging with @value{GDBN}}\par -\hfill \TeX{}info \texinfoversion\par -} -@end tex -@end ifclear -@ifset HPPA -@tex -{\parskip=0pt -\hfill {\it Debugging with @value{GDBN}}\par -\hfill \TeX{}info \texinfoversion\par -} -@end tex -@end ifset - -@vskip 0pt plus 1filll -Copyright @copyright{} 1988-1999 Free Software Foundation, Inc. -@sp 2 -@ifclear HPPA -Published by the Free Software Foundation @* -59 Temple Place - Suite 330, @* -Boston, MA 02111-1307 USA @* -Printed copies are available for $20 each. @* -ISBN 1-882114-11-6 @* -@end ifclear - -Permission is granted to make and distribute verbatim copies of -this manual provided the copyright notice and this permission notice -are preserved on all copies. - -Permission is granted to copy and distribute modified versions of this -manual under the conditions for verbatim copying, provided also that the -entire resulting derived work is distributed under the terms of a -permission notice identical to this one. - -Permission is granted to copy and distribute translations of this manual -into another language, under the above conditions for modified versions. -@end titlepage -@page - -@ifinfo -@node Top, Summary, (dir), (dir) -@top Debugging with @value{GDBN} - -This file describes @value{GDBN}, the @sc{gnu} symbolic debugger. - -This is the @value{EDITION} Edition, @value{DATE}, for @value{GDBN} Version -@value{GDBVN}. - -Copyright (C) 1988-1999 Free Software Foundation, Inc. -@menu -* Summary:: Summary of @value{GDBN} -@ifclear BARETARGET -* Sample Session:: A sample @value{GDBN} session -@end ifclear - -* Invocation:: Getting in and out of @value{GDBN} -* Commands:: @value{GDBN} commands -* Running:: Running programs under @value{GDBN} -* Stopping:: Stopping and continuing -* Stack:: Examining the stack -* Source:: Examining source files -* Data:: Examining data -@ifclear CONLY -* Languages:: Using @value{GDBN} with different languages -@end ifclear - -@ifset CONLY -* C:: C language support -@end ifset - -* Symbols:: Examining the symbol table -* Altering:: Altering execution -* GDB Files:: @value{GDBN} files -* Targets:: Specifying a debugging target -* Controlling GDB:: Controlling @value{GDBN} -* Sequences:: Canned sequences of commands -@ifclear DOSHOST -* Emacs:: Using @value{GDBN} under @sc{gnu} Emacs -@end ifclear - -* GDB Bugs:: Reporting bugs in @value{GDBN} - -@ifclear PRECONFIGURED -@ifclear HPPA -* Formatting Documentation:: How to format and print @value{GDBN} documentation -@end ifclear - -@end ifclear - -* Command Line Editing:: Command Line Editing -* Using History Interactively:: Using History Interactively -* Installing GDB:: Installing GDB -* Index:: Index - - --- The Detailed Node Listing --- - -Summary of @value{GDBN} - -* Free Software:: Freely redistributable software -* Contributors:: Contributors to GDB - -Getting In and Out of @value{GDBN} - -* Invoking GDB:: How to start @value{GDBN} -* Quitting GDB:: How to quit @value{GDBN} -* Shell Commands:: How to use shell commands inside @value{GDBN} - -Invoking @value{GDBN} - -* File Options:: Choosing files -* Mode Options:: Choosing modes - -@value{GDBN} Commands - -* Command Syntax:: How to give commands to @value{GDBN} -* Completion:: Command completion -* Help:: How to ask @value{GDBN} for help - -Running Programs Under @value{GDBN} - -* Compilation:: Compiling for debugging -* Starting:: Starting your program -@ifclear BARETARGET -* Arguments:: Your program's arguments -* Environment:: Your program's environment -@end ifclear - -* Working Directory:: Your program's working directory -* Input/Output:: Your program's input and output -* Attach:: Debugging an already-running process -* Kill Process:: Killing the child process -@ifclear HPPA -* Process Information:: Additional process information -@end ifclear - -* Threads:: Debugging programs with multiple threads -* Processes:: Debugging programs with multiple processes - -Stopping and Continuing - -* Breakpoints:: Breakpoints, watchpoints, and catchpoints -* Continuing and Stepping:: Resuming execution -@ifset POSIX -* Signals:: Signals -@end ifset -@ifclear BARETARGET -* Thread Stops:: Stopping and starting multi-thread programs -@end ifclear - -Breakpoints and watchpoints - -* Set Breaks:: Setting breakpoints -* Set Watchpoints:: Setting watchpoints -* Set Catchpoints:: Setting catchpoints -* Delete Breaks:: Deleting breakpoints -* Disabling:: Disabling breakpoints -* Conditions:: Break conditions -* Break Commands:: Breakpoint command lists -@ifclear CONLY -* Breakpoint Menus:: Breakpoint menus -@end ifclear - -Examining the Stack - -* Frames:: Stack frames -* Backtrace:: Backtraces -* Selection:: Selecting a frame -* Frame Info:: Information on a frame -* Alpha/MIPS Stack:: Alpha and MIPS machines and the function stack - -Examining Source Files - -* List:: Printing source lines -@ifclear DOSHOST -* Search:: Searching source files -@end ifclear -* Source Path:: Specifying source directories -* Machine Code:: Source and machine code - -Examining Data - -* Expressions:: Expressions -* Variables:: Program variables -* Arrays:: Artificial arrays -* Output Formats:: Output formats -* Memory:: Examining memory -* Auto Display:: Automatic display -* Print Settings:: Print settings -* Value History:: Value history -* Convenience Vars:: Convenience variables -* Registers:: Registers -@ifclear HAVE-FLOAT -* Floating Point Hardware:: Floating point hardware -@end ifclear - -Using @value{GDBN} with Different Languages - -* Setting:: Switching between source languages -* Show:: Displaying the language -@ifset MOD2 -* Checks:: Type and range checks -@end ifset - -* Support:: Supported languages - -Switching between source languages - -* Filenames:: Filename extensions and languages. -* Manually:: Setting the working language manually -* Automatically:: Having @value{GDBN} infer the source language - -@ifset MOD2 -Type and range checking - -* Type Checking:: An overview of type checking -* Range Checking:: An overview of range checking -@end ifset - -Supported languages - -@ifset MOD2 -* C:: C and C++ - -C Language Support - -* C Operators:: C operators - -C Language Support -@end ifset - -* C Operators:: C and C++ operators -* C Constants:: C and C++ constants -* Cplus expressions:: C++ expressions -* C Defaults:: Default settings for C and C++ -@ifset MOD2 -* C Checks:: C and C++ type and range checks -@end ifset -* Debugging C:: @value{GDBN} and C -* Debugging C plus plus:: @value{GDBN} features for C++ - -@ifset MOD2 -Modula-2 - -* M2 Operators:: Built-in operators -* Built-In Func/Proc:: Built-in functions and procedures -* M2 Constants:: Modula-2 constants -* M2 Defaults:: Default settings for Modula-2 -* Deviations:: Deviations from standard Modula-2 -* M2 Checks:: Modula-2 type and range checks -* M2 Scope:: The scope operators @code{::} and @code{.} -* GDB/M2:: @value{GDBN} and Modula-2 -@end ifset - -Altering Execution - -* Assignment:: Assignment to variables -* Jumping:: Continuing at a different address -@ifclear BARETARGET -* Signaling:: Giving your program a signal -@end ifclear -* Returning:: Returning from a function -* Calling:: Calling your program's functions -* Patching:: Patching your program - -@value{GDBN} Files - -* Files:: Commands to specify files -* Symbol Errors:: Errors reading symbol files - -Specifying a Debugging Target - -* Active Targets:: Active targets -* Target Commands:: Commands for managing targets -@ifclear HPPA -* Byte Order:: Choosing target byte order -* Remote:: Remote debugging - -Remote debugging -@end ifclear - -@ifset REMOTESTUB -* Remote Serial:: @value{GDBN} remote serial protocol -@end ifset - -@ifset I960 -* i960-Nindy Remote:: @value{GDBN} with a remote i960 (Nindy) -@end ifset - -@ifset AMD29K -* UDI29K Remote:: The UDI protocol for AMD29K -* EB29K Remote:: The EBMON protocol for AMD29K -@end ifset - -@ifset VXWORKS -* VxWorks Remote:: @value{GDBN} and VxWorks -@end ifset - -@ifset ST2000 -* ST2000 Remote:: @value{GDBN} with a Tandem ST2000 -@end ifset - -@ifset H8 -* Hitachi Remote:: @value{GDBN} and Hitachi Microprocessors -@end ifset - -@ifset MIPS -* MIPS Remote:: @value{GDBN} and MIPS boards -@end ifset - -@ifset SIMS -* Simulator:: Simulated CPU target -@end ifset - -Controlling @value{GDBN} - -* Prompt:: Prompt -* Editing:: Command editing -* History:: Command history -* Screen Size:: Screen size -* Numbers:: Numbers -* Messages/Warnings:: Optional warnings and messages - -Canned Sequences of Commands - -* Define:: User-defined commands -* Hooks:: User-defined command hooks -* Command Files:: Command files -* Output:: Commands for controlled output - -Reporting Bugs in @value{GDBN} - -* Bug Criteria:: Have you found a bug? -* Bug Reporting:: How to report bugs - -Installing @value{GDBN} - -* Separate Objdir:: Compiling @value{GDBN} in another directory -* Config Names:: Specifying names for hosts and targets -* Configure Options:: Summary of options for configure -@end menu - -@end ifinfo - -@node Summary, Sample Session, Top, Top -@unnumbered Summary of @value{GDBN} - -The purpose of a debugger such as @value{GDBN} is to allow you to see what is -going on ``inside'' another program while it executes---or what another -program was doing at the moment it crashed. - -@value{GDBN} can do four main kinds of things (plus other things in support of -these) to help you catch bugs in the act: - -@itemize @bullet -@item -Start your program, specifying anything that might affect its behavior. - -@item -Make your program stop on specified conditions. - -@item -Examine what has happened, when your program has stopped. - -@item -Change things in your program, so you can experiment with correcting the -effects of one bug and go on to learn about another. -@end itemize - -@ifclear CONLY -You can use @value{GDBN} to debug programs written in C or C++. -@c "MOD2" used as a "miscellaneous languages" flag here. -@c This is acceptable while there is no real doc for Chill and Pascal. -@ifclear MOD2 -For more information, see @ref{Support,,Supported languages}. -@end ifclear -@ifset MOD2 -For more information, see @ref{C,,C and C++}. - -Support for Modula-2 and Chill is partial. For information on Modula-2, -see @ref{Modula-2,,Modula-2}. There is no further documentation on Chill yet. - -Debugging Pascal programs which use sets, subranges, file variables, or nested -functions does not currently work. @value{GDBN} does not support -entering expressions, printing values, or similar features using Pascal syntax. -@end ifset - -@ifset FORTRAN -@cindex Fortran -@value{GDBN} can be used to debug programs written in Fortran, although -it does not yet support entering expressions, printing values, or -similar features using Fortran syntax. It may be necessary to refer to -some variables with a trailing underscore. -@end ifset -@end ifclear - -@ifset HPPA -This version of the manual documents HP Wildebeest (WDB) Version 0.75, -implemented on HP 9000 systems running Release 10.20, 10.30, or 11.0 of -the HP-UX operating system. HP WDB 0.75 can be used to debug code -generated by the HP ANSI C and HP ANSI C++ compilers as well as the -@sc{gnu} C and C++ compilers. It does not support the debugging of -Fortran, Modula-2, or Chill programs. -@end ifset - -@menu -* Free Software:: Freely redistributable software -* Contributors:: Contributors to GDB -@end menu - -@node Free Software, Contributors, Summary, Summary -@unnumberedsec Free software - -@value{GDBN} is @dfn{free software}, protected by the @sc{gnu} -General Public License -(GPL). The GPL gives you the freedom to copy or adapt a licensed -program---but every person getting a copy also gets with it the -freedom to modify that copy (which means that they must get access to -the source code), and the freedom to distribute further copies. -Typical software companies use copyrights to limit your freedoms; the -Free Software Foundation uses the GPL to preserve these freedoms. - -Fundamentally, the General Public License is a license which says that -you have these freedoms and that you cannot take these freedoms away -from anyone else. - -@node Contributors, , Free Software, Summary -@unnumberedsec Contributors to GDB - -Richard Stallman was the original author of GDB, and of many other -@sc{gnu} programs. Many others have contributed to its development. -This section attempts to credit major contributors. One of the virtues -of free software is that everyone is free to contribute to it; with -regret, we cannot actually acknowledge everyone here. The file -@file{ChangeLog} in the @value{GDBN} distribution approximates a -blow-by-blow account. - -Changes much prior to version 2.0 are lost in the mists of time. - -@quotation -@emph{Plea:} Additions to this section are particularly welcome. If you -or your friends (or enemies, to be evenhanded) have been unfairly -omitted from this list, we would like to add your names! -@end quotation - -So that they may not regard their many labors as thankless, we -particularly thank those who shepherded @value{GDBN} through major -releases: -Jim Blandy (release 4.18); -Jason Molenda (release 4.17); -Stan Shebs (release 4.14); -Fred Fish (releases 4.16, 4.15, 4.13, 4.12, 4.11, 4.10, and 4.9); -Stu Grossman and John Gilmore (releases 4.8, 4.7, 4.6, 4.5, and 4.4); -John Gilmore (releases 4.3, 4.2, 4.1, 4.0, and 3.9); -Jim Kingdon (releases 3.5, 3.4, and 3.3); -and Randy Smith (releases 3.2, 3.1, and 3.0). - -Richard Stallman, assisted at various times by Peter TerMaat, Chris -Hanson, and Richard Mlynarik, handled releases through 2.8. - -@ifclear CONLY -Michael Tiemann is the author of most of the @sc{gnu} C++ support in GDB, -with significant additional contributions from Per Bothner. James -Clark wrote the @sc{gnu} C++ demangler. Early work on C++ was by Peter -TerMaat (who also did much general update work leading to release 3.0). -@end ifclear - -@value{GDBN} 4 uses the BFD subroutine library to examine multiple -object-file formats; BFD was a joint project of David V. -Henkel-Wallace, Rich Pixley, Steve Chamberlain, and John Gilmore. - -David Johnson wrote the original COFF support; Pace Willison did -the original support for encapsulated COFF. - -Brent Benson of Harris Computer Systems contributed DWARF 2 support. - -Adam de Boor and Bradley Davis contributed the ISI Optimum V support. -Per Bothner, Noboyuki Hikichi, and Alessandro Forin contributed MIPS -support. -Jean-Daniel Fekete contributed Sun 386i support. -Chris Hanson improved the HP9000 support. -Noboyuki Hikichi and Tomoyuki Hasei contributed Sony/News OS 3 support. -David Johnson contributed Encore Umax support. -Jyrki Kuoppala contributed Altos 3068 support. -Jeff Law contributed HP PA and SOM support. -Keith Packard contributed NS32K support. -Doug Rabson contributed Acorn Risc Machine support. -Bob Rusk contributed Harris Nighthawk CX-UX support. -Chris Smith contributed Convex support (and Fortran debugging). -Jonathan Stone contributed Pyramid support. -Michael Tiemann contributed SPARC support. -Tim Tucker contributed support for the Gould NP1 and Gould Powernode. -Pace Willison contributed Intel 386 support. -Jay Vosburgh contributed Symmetry support. - -Andreas Schwab contributed M68K Linux support. - -Rich Schaefer and Peter Schauer helped with support of SunOS shared -libraries. - -Jay Fenlason and Roland McGrath ensured that @value{GDBN} and GAS agree -about several machine instruction sets. - -Patrick Duval, Ted Goldstein, Vikram Koka and Glenn Engel helped develop -remote debugging. Intel Corporation, Wind River Systems, AMD, and ARM -contributed remote debugging modules for the i960, VxWorks, A29K UDI, -and RDI targets, respectively. - -Brian Fox is the author of the readline libraries providing -command-line editing and command history. - -Andrew Beers of SUNY Buffalo wrote the language-switching code, -@ifset MOD2 -the Modula-2 support, -@end ifset -and contributed the Languages chapter of this manual. - -Fred Fish wrote most of the support for Unix System Vr4. -@ifclear CONLY -He also enhanced the command-completion support to cover C++ overloaded -symbols. -@end ifclear - -Hitachi America, Ltd. sponsored the support for H8/300, H8/500, and -Super-H processors. - -NEC sponsored the support for the v850, Vr4xxx, and Vr5xxx processors. - -Mitsubishi sponsored the support for D10V, D30V, and M32R/D processors. - -Toshiba sponsored the support for the TX39 Mips processor. - -Matsushita sponsored the support for the MN10200 and MN10300 processors. - -Fujitsu sponsored the support for SPARClite and FR30 processors - -Kung Hsu, Jeff Law, and Rick Sladkey added support for hardware -watchpoints. - -Michael Snyder added support for tracepoints. - -Stu Grossman wrote gdbserver. - -Jim Kingdon, Peter Schauer, Ian Taylor, and Stu Grossman made -nearly innumerable bug fixes and cleanups throughout GDB. - -The following people at the Hewlett-Packard Company contributed -support for the PA-RISC 2.0 architecture, HP-UX 10.20, 10.30, and 11.0 -(narrow mode), HP's implementation of kernel threads, HP's aC++ -compiler, and the terminal user interface: Ben Krepp, Richard Title, -John Bishop, Susan Macchia, Kathy Mann, Satish Pai, India Paul, Steve -Rehrauer, and Elena Zannoni. Kim Haase provided HP-specific -information in this manual. - -Cygnus Solutions has sponsored GDB maintenance and much of its -development since 1991. Cygnus engineers who have worked on GDB -fulltime include Mark Alexander, Jim Blandy, Per Bothner, Edith Epstein, -Chris Faylor, Fred Fish, Martin Hunt, Jim Ingham, John Gilmore, Stu -Grossman, Kung Hsu, Jim Kingdon, John Metzler, Fernando Nasser, Geoffrey -Noer, Dawn Perchik, Rich Pixley, Zdenek Radouch, Keith Seitz, Stan -Shebs, David Taylor, and Elena Zannoni. In addition, Dave Brolley, Ian -Carmichael, Steve Chamberlain, Nick Clifton, JT Conklin, Stan Cox, DJ -Delorie, Ulrich Drepper, Frank Eigler, Doug Evans, Sean Fagan, David -Henkel-Wallace, Richard Henderson, Jeff Holcomb, Jeff Law, Jim Lemke, -Tom Lord, Bob Manson, Michael Meissner, Jason Merrill, Catherine Moore, -Drew Moseley, Ken Raeburn, Gavin Romig-Koch, Rob Savoye, Jamie Smith, -Mike Stump, Ian Taylor, Angela Thomas, Michael Tiemann, Tom Tromey, Ron -Unrau, Jim Wilson, and David Zuhn have made contributions both large -and small. - - -@ifclear BARETARGET -@node Sample Session, Invocation, Summary, Top -@chapter A Sample @value{GDBN} Session - -You can use this manual at your leisure to read all about @value{GDBN}. -However, a handful of commands are enough to get started using the -debugger. This chapter illustrates those commands. - -@iftex -In this sample session, we emphasize user input like this: @b{input}, -to make it easier to pick out from the surrounding output. -@end iftex - -@c FIXME: this example may not be appropriate for some configs, where -@c FIXME...primary interest is in remote use. - -One of the preliminary versions of @sc{gnu} @code{m4} (a generic macro -processor) exhibits the following bug: sometimes, when we change its -quote strings from the default, the commands used to capture one macro -definition within another stop working. In the following short @code{m4} -session, we define a macro @code{foo} which expands to @code{0000}; we -then use the @code{m4} built-in @code{defn} to define @code{bar} as the -same thing. However, when we change the open quote string to -@code{<QUOTE>} and the close quote string to @code{<UNQUOTE>}, the same -procedure fails to define a new synonym @code{baz}: - -@smallexample -$ @b{cd gnu/m4} -$ @b{./m4} -@b{define(foo,0000)} - -@b{foo} -0000 -@b{define(bar,defn(`foo'))} - -@b{bar} -0000 -@b{changequote(<QUOTE>,<UNQUOTE>)} - -@b{define(baz,defn(<QUOTE>foo<UNQUOTE>))} -@b{baz} -@b{C-d} -m4: End of input: 0: fatal error: EOF in string -@end smallexample - -@noindent -Let us use @value{GDBN} to try to see what is going on. - -@ifclear HPPA -@smallexample -$ @b{@value{GDBP} m4} -@c FIXME: this falsifies the exact text played out, to permit smallbook -@c FIXME... format to come out better. -@value{GDBN} is free software and you are welcome to distribute copies - of it under certain conditions; type "show copying" to see - the conditions. -There is absolutely no warranty for @value{GDBN}; type "show warranty" - for details. - -@value{GDBN} @value{GDBVN}, Copyright 1999 Free Software Foundation, Inc... -(@value{GDBP}) -@end smallexample -@end ifclear -@ifset HPPA -@smallexample -$ @b{@value{GDBP} m4} -Wildebeest is free software and you are welcome to distribute copies of -it under certain conditions; type "show copying" to see the conditions. -There is absolutely no warranty for Wildebeest; type "show warranty" -for details. - -Hewlett-Packard Wildebeest 0.75 (based on GDB 4.16) -(built for PA-RISC 1.1 or 2.0, HP-UX 10.20) -Copyright 1996, 1997 Free Software Foundation, Inc. -(@value{GDBP}) -@end smallexample -@end ifset - -@noindent -@value{GDBN} reads only enough symbol data to know where to find the -rest when needed; as a result, the first prompt comes up very quickly. -We now tell @value{GDBN} to use a narrower display width than usual, so -that examples fit in this manual. - -@smallexample -(@value{GDBP}) @b{set width 70} -@end smallexample - -@noindent -We need to see how the @code{m4} built-in @code{changequote} works. -Having looked at the source, we know the relevant subroutine is -@code{m4_changequote}, so we set a breakpoint there with the @value{GDBN} -@code{break} command. - -@smallexample -(@value{GDBP}) @b{break m4_changequote} -Breakpoint 1 at 0x62f4: file builtin.c, line 879. -@end smallexample - -@noindent -Using the @code{run} command, we start @code{m4} running under @value{GDBN} -control; as long as control does not reach the @code{m4_changequote} -subroutine, the program runs as usual: - -@smallexample -(@value{GDBP}) @b{run} -Starting program: /work/Editorial/gdb/gnu/m4/m4 -@b{define(foo,0000)} - -@b{foo} -0000 -@end smallexample - -@noindent -To trigger the breakpoint, we call @code{changequote}. @value{GDBN} -suspends execution of @code{m4}, displaying information about the -context where it stops. - -@smallexample -@b{changequote(<QUOTE>,<UNQUOTE>)} - -Breakpoint 1, m4_changequote (argc=3, argv=0x33c70) - at builtin.c:879 -879 if (bad_argc(TOKEN_DATA_TEXT(argv[0]),argc,1,3)) -@end smallexample - -@noindent -Now we use the command @code{n} (@code{next}) to advance execution to -the next line of the current function. - -@smallexample -(@value{GDBP}) @b{n} -882 set_quotes((argc >= 2) ? TOKEN_DATA_TEXT(argv[1])\ - : nil, -@end smallexample - -@noindent -@code{set_quotes} looks like a promising subroutine. We can go into it -by using the command @code{s} (@code{step}) instead of @code{next}. -@code{step} goes to the next line to be executed in @emph{any} -subroutine, so it steps into @code{set_quotes}. - -@smallexample -(@value{GDBP}) @b{s} -set_quotes (lq=0x34c78 "<QUOTE>", rq=0x34c88 "<UNQUOTE>") - at input.c:530 -530 if (lquote != def_lquote) -@end smallexample - -@noindent -The display that shows the subroutine where @code{m4} is now -suspended (and its arguments) is called a stack frame display. It -shows a summary of the stack. We can use the @code{backtrace} -command (which can also be spelled @code{bt}), to see where we are -in the stack as a whole: the @code{backtrace} command displays a -stack frame for each active subroutine. - -@smallexample -(@value{GDBP}) @b{bt} -#0 set_quotes (lq=0x34c78 "<QUOTE>", rq=0x34c88 "<UNQUOTE>") - at input.c:530 -#1 0x6344 in m4_changequote (argc=3, argv=0x33c70) - at builtin.c:882 -#2 0x8174 in expand_macro (sym=0x33320) at macro.c:242 -#3 0x7a88 in expand_token (obs=0x0, t=209696, td=0xf7fffa30) - at macro.c:71 -#4 0x79dc in expand_input () at macro.c:40 -#5 0x2930 in main (argc=0, argv=0xf7fffb20) at m4.c:195 -@end smallexample - -@noindent -We step through a few more lines to see what happens. The first two -times, we can use @samp{s}; the next two times we use @code{n} to avoid -falling into the @code{xstrdup} subroutine. - -@smallexample -(@value{GDBP}) @b{s} -0x3b5c 532 if (rquote != def_rquote) -(@value{GDBP}) @b{s} -0x3b80 535 lquote = (lq == nil || *lq == '\0') ? \ -def_lquote : xstrdup(lq); -(@value{GDBP}) @b{n} -536 rquote = (rq == nil || *rq == '\0') ? def_rquote\ - : xstrdup(rq); -(@value{GDBP}) @b{n} -538 len_lquote = strlen(rquote); -@end smallexample - -@noindent -The last line displayed looks a little odd; we can examine the variables -@code{lquote} and @code{rquote} to see if they are in fact the new left -and right quotes we specified. We use the command @code{p} -(@code{print}) to see their values. - -@smallexample -(@value{GDBP}) @b{p lquote} -$1 = 0x35d40 "<QUOTE>" -(@value{GDBP}) @b{p rquote} -$2 = 0x35d50 "<UNQUOTE>" -@end smallexample - -@noindent -@code{lquote} and @code{rquote} are indeed the new left and right quotes. -To look at some context, we can display ten lines of source -surrounding the current line with the @code{l} (@code{list}) command. - -@smallexample -(@value{GDBP}) @b{l} -533 xfree(rquote); -534 -535 lquote = (lq == nil || *lq == '\0') ? def_lquote\ - : xstrdup (lq); -536 rquote = (rq == nil || *rq == '\0') ? def_rquote\ - : xstrdup (rq); -537 -538 len_lquote = strlen(rquote); -539 len_rquote = strlen(lquote); -540 @} -541 -542 void -@end smallexample - -@noindent -Let us step past the two lines that set @code{len_lquote} and -@code{len_rquote}, and then examine the values of those variables. - -@smallexample -(@value{GDBP}) @b{n} -539 len_rquote = strlen(lquote); -(@value{GDBP}) @b{n} -540 @} -(@value{GDBP}) @b{p len_lquote} -$3 = 9 -(@value{GDBP}) @b{p len_rquote} -$4 = 7 -@end smallexample - -@noindent -That certainly looks wrong, assuming @code{len_lquote} and -@code{len_rquote} are meant to be the lengths of @code{lquote} and -@code{rquote} respectively. We can set them to better values using -the @code{p} command, since it can print the value of -any expression---and that expression can include subroutine calls and -assignments. - -@smallexample -(@value{GDBP}) @b{p len_lquote=strlen(lquote)} -$5 = 7 -(@value{GDBP}) @b{p len_rquote=strlen(rquote)} -$6 = 9 -@end smallexample - -@noindent -Is that enough to fix the problem of using the new quotes with the -@code{m4} built-in @code{defn}? We can allow @code{m4} to continue -executing with the @code{c} (@code{continue}) command, and then try the -example that caused trouble initially: - -@smallexample -(@value{GDBP}) @b{c} -Continuing. - -@b{define(baz,defn(<QUOTE>foo<UNQUOTE>))} - -baz -0000 -@end smallexample - -@noindent -Success! The new quotes now work just as well as the default ones. The -problem seems to have been just the two typos defining the wrong -lengths. We allow @code{m4} exit by giving it an EOF as input: - -@smallexample -@b{C-d} -Program exited normally. -@end smallexample - -@noindent -The message @samp{Program exited normally.} is from @value{GDBN}; it -indicates @code{m4} has finished executing. We can end our @value{GDBN} -session with the @value{GDBN} @code{quit} command. - -@smallexample -(@value{GDBP}) @b{quit} -@end smallexample -@end ifclear - -@node Invocation, Commands, Sample Session, Top -@chapter Getting In and Out of @value{GDBN} - -This chapter discusses how to start @value{GDBN}, and how to get out of it. -The essentials are: -@itemize @bullet -@item -type @samp{@value{GDBP}} to start GDB. -@item -type @kbd{quit} or @kbd{C-d} to exit. -@end itemize - -@menu -* Invoking GDB:: How to start @value{GDBN} -* Quitting GDB:: How to quit @value{GDBN} -* Shell Commands:: How to use shell commands inside @value{GDBN} -@end menu - -@node Invoking GDB, Quitting GDB, Invocation, Invocation -@section Invoking @value{GDBN} - -@ifset H8EXCLUSIVE -For details on starting up @value{GDBP} as a -remote debugger attached to a Hitachi microprocessor, see @ref{Hitachi -Remote,,@value{GDBN} and Hitachi Microprocessors}. -@end ifset - -Invoke @value{GDBN} by running the program @code{@value{GDBP}}. Once started, -@value{GDBN} reads commands from the terminal until you tell it to exit. - -You can also run @code{@value{GDBP}} with a variety of arguments and options, -to specify more of your debugging environment at the outset. - -@ifset GENERIC -The command-line options described here are designed -to cover a variety of situations; in some environments, some of these -options may effectively be unavailable. -@end ifset - -The most usual way to start @value{GDBN} is with one argument, -specifying an executable program: - -@example -@value{GDBP} @var{program} -@end example - -@ifclear BARETARGET -@noindent -You can also start with both an executable program and a core file -specified: - -@example -@value{GDBP} @var{program} @var{core} -@end example - -You can, instead, specify a process ID as a second argument, if you want -to debug a running process: - -@example -@value{GDBP} @var{program} 1234 -@end example - -@noindent -would attach @value{GDBN} to process @code{1234} (unless you also have a file -named @file{1234}; @value{GDBN} does check for a core file first). - -@ifclear HPPA -Taking advantage of the second command-line argument requires a fairly -complete operating system; when you use @value{GDBN} as a remote debugger -attached to a bare board, there may not be any notion of ``process'', -and there is often no way to get a core dump. -@end ifclear -@end ifclear - -You can run @code{gdb} without printing the front material, which describes -@value{GDBN}'s non-warranty, by specifying @code{-silent}: - -@smallexample -@value{GDBP} -silent -@end smallexample - -@noindent -You can further control how @value{GDBN} starts up by using command-line -options. @value{GDBN} itself can remind you of the options available. - -@noindent -Type - -@example -@value{GDBP} -help -@end example - -@noindent -to display all available options and briefly describe their use -(@samp{@value{GDBP} -h} is a shorter equivalent). - -All options and command line arguments you give are processed -in sequential order. The order makes a difference when the -@samp{-x} option is used. - - -@menu -@ifclear GENERIC -@ifset REMOTESTUB -* Remote Serial:: @value{GDBN} remote serial protocol -@end ifset -@ifset I960 -* i960-Nindy Remote:: @value{GDBN} with a remote i960 (Nindy) -@end ifset -@ifset AMD29K -* UDI29K Remote:: The UDI protocol for AMD29K -* EB29K Remote:: The EBMON protocol for AMD29K -@end ifset -@ifset VXWORKS -* VxWorks Remote:: @value{GDBN} and VxWorks -@end ifset -@ifset ST2000 -* ST2000 Remote:: @value{GDBN} with a Tandem ST2000 -@end ifset -@ifset H8 -* Hitachi Remote:: @value{GDBN} and Hitachi Microprocessors -@end ifset -@ifset MIPS -* MIPS Remote:: @value{GDBN} and MIPS boards -@end ifset -@ifset SPARCLET -* Sparclet Remote:: @value{GDBN} and Sparclet boards -@end ifset -@ifset SIMS -* Simulator:: Simulated CPU target -@end ifset -@end ifclear -@c remnant makeinfo bug requires this blank line after *two* end-ifblahs: - -* File Options:: Choosing files -* Mode Options:: Choosing modes -@end menu - -@ifclear GENERIC -@ifclear HPPA -@include remote.texi -@end ifclear -@end ifclear - -@node File Options -@subsection Choosing files - -@ifclear BARETARGET -When @value{GDBN} starts, it reads any arguments other than options as -specifying an executable file and core file (or process ID). This is -the same as if the arguments were specified by the @samp{-se} and -@samp{-c} options respectively. (@value{GDBN} reads the first argument -that does not have an associated option flag as equivalent to the -@samp{-se} option followed by that argument; and the second argument -that does not have an associated option flag, if any, as equivalent to -the @samp{-c} option followed by that argument.) -@end ifclear -@ifset BARETARGET -When @value{GDBN} starts, it reads any argument other than options as -specifying an executable file. This is the same as if the argument was -specified by the @samp{-se} option. -@end ifset - -Many options have both long and short forms; both are shown in the -following list. @value{GDBN} also recognizes the long forms if you truncate -them, so long as enough of the option is present to be unambiguous. -(If you prefer, you can flag option arguments with @samp{--} rather -than @samp{-}, though we illustrate the more usual convention.) - -@table @code -@item -symbols @var{file} -@itemx -s @var{file} -Read symbol table from file @var{file}. - -@item -exec @var{file} -@itemx -e @var{file} -Use file @var{file} as the executable file to execute when -@ifset BARETARGET -appropriate. -@end ifset -@ifclear BARETARGET -appropriate, and for examining pure data in conjunction with a core -dump. -@end ifclear - -@item -se @var{file} -Read symbol table from file @var{file} and use it as the executable -file. - -@ifclear BARETARGET -@item -core @var{file} -@itemx -c @var{file} -Use file @var{file} as a core dump to examine. - -@item -c @var{number} -Connect to process ID @var{number}, as with the @code{attach} command -(unless there is a file in core-dump format named @var{number}, in which -case @samp{-c} specifies that file as a core dump to read). -@end ifclear - -@item -command @var{file} -@itemx -x @var{file} -Execute @value{GDBN} commands from file @var{file}. @xref{Command -Files,, Command files}. - -@item -directory @var{directory} -@itemx -d @var{directory} -Add @var{directory} to the path to search for source files. - -@ifclear BARETARGET -@ifclear HPPA -@item -m -@itemx -mapped -@emph{Warning: this option depends on operating system facilities that are not -supported on all systems.}@* -If memory-mapped files are available on your system through the @code{mmap} -system call, you can use this option -to have @value{GDBN} write the symbols from your -program into a reusable file in the current directory. If the program you are debugging is -called @file{/tmp/fred}, the mapped symbol file is @file{./fred.syms}. -Future @value{GDBN} debugging sessions notice the presence of this file, -and can quickly map in symbol information from it, rather than reading -the symbol table from the executable program. - -The @file{.syms} file is specific to the host machine where @value{GDBN} -is run. It holds an exact image of the internal @value{GDBN} symbol -table. It cannot be shared across multiple host platforms. -@end ifclear -@end ifclear - -@ifclear HPPA -@item -r -@itemx -readnow -Read each symbol file's entire symbol table immediately, rather than -the default, which is to read it incrementally as it is needed. -This makes startup slower, but makes future operations faster. -@end ifclear -@end table - -@ifclear BARETARGET -@ifclear HPPA -The @code{-mapped} and @code{-readnow} options are typically combined in -order to build a @file{.syms} file that contains complete symbol -information. (@xref{Files,,Commands to specify files}, for -information on @file{.syms} files.) A simple GDB invocation to do -nothing but build a @file{.syms} file for future use is: - -@example - gdb -batch -nx -mapped -readnow programname -@end example -@end ifclear -@end ifclear - -@node Mode Options, , File Options, Invoking GDB -@subsection Choosing modes - -You can run @value{GDBN} in various alternative modes---for example, in -batch mode or quiet mode. - -@table @code -@item -nx -@itemx -n -Do not execute commands from any initialization files (normally called -@file{.gdbinit}, or @file{gdb.ini} on PCs). Normally, the commands in -these files are executed after all the command options and arguments -have been processed. @xref{Command Files,,Command files}. - -@item -quiet -@itemx -q -``Quiet''. Do not print the introductory and copyright messages. These -messages are also suppressed in batch mode. - -@item -batch -Run in batch mode. Exit with status @code{0} after processing all the -command files specified with @samp{-x} (and all commands from -initialization files, if not inhibited with @samp{-n}). Exit with -nonzero status if an error occurs in executing the @value{GDBN} commands -in the command files. - -Batch mode may be useful for running @value{GDBN} as a filter, for example to -download and run a program on another computer; in order to make this -more useful, the message - -@example -Program exited normally. -@end example - -@noindent -(which is ordinarily issued whenever a program running under @value{GDBN} control -terminates) is not issued when running in batch mode. - -@item -cd @var{directory} -Run @value{GDBN} using @var{directory} as its working directory, -instead of the current directory. - -@ifclear DOSHOST -@item -fullname -@itemx -f -@sc{gnu} Emacs sets this option when it runs @value{GDBN} as a subprocess. It tells @value{GDBN} -to output the full file name and line number in a standard, -recognizable fashion each time a stack frame is displayed (which -includes each time your program stops). This recognizable format looks -like two @samp{\032} characters, followed by the file name, line number -and character position separated by colons, and a newline. The -Emacs-to-@value{GDBN} interface program uses the two @samp{\032} characters as -a signal to display the source code for the frame. -@end ifclear - -@ifset SERIAL -@ifclear HPPA -@item -b @var{bps} -Set the line speed (baud rate or bits per second) of any serial -interface used by @value{GDBN} for remote debugging. -@end ifclear - -@item -tty @var{device} -Run using @var{device} for your program's standard input and output. -@c FIXME: kingdon thinks there is more to -tty. Investigate. -@end ifset - -@ifset HPPA -@item -tui -Use a Terminal User Interface. For information, use your Web browser to -read the file @file{TUI.html}, which is usually installed in the -directory @code{/opt/langtools/wdb/doc} on HP-UX systems. Do not use -this option if you run @value{GDBN} from Emacs (see @pxref{Emacs, ,Using -@value{GDBN} under @sc{gnu} Emacs}). - -@item -xdb -Run in XDB compatibility mode, allowing the use of certain XDB commands. -For information, see the file @file{xdb_trans.html}, which is usually -installed in the directory @code{/opt/langtools/wdb/doc} on HP-UX -systems. -@end ifset -@end table - -@node Quitting GDB, Shell Commands, Invoking GDB, Invocation -@section Quitting @value{GDBN} -@cindex exiting @value{GDBN} -@cindex leaving @value{GDBN} - -@table @code -@kindex quit @r{[}@var{expression}@r{]} -@kindex q -@item quit -To exit @value{GDBN}, use the @code{quit} command (abbreviated @code{q}), or -type an end-of-file character (usually @kbd{C-d}). If you do not supply -@var{expression}, @value{GDBN} will terminate normally; otherwise it will -terminate using the result of @var{expression} as the error code. -@end table - -@cindex interrupt -An interrupt (often @kbd{C-c}) does not exit from @value{GDBN}, but rather -terminates the action of any @value{GDBN} command that is in progress and -returns to @value{GDBN} command level. It is safe to type the interrupt -character at any time because @value{GDBN} does not allow it to take effect -until a time when it is safe. - -@ifclear BARETARGET -If you have been using @value{GDBN} to control an attached process or -device, you can release it with the @code{detach} command -(@pxref{Attach, ,Debugging an already-running process}). -@end ifclear - -@node Shell Commands, , Quitting GDB, Invocation -@section Shell commands - -If you need to execute occasional shell commands during your -debugging session, there is no need to leave or suspend @value{GDBN}; you can -just use the @code{shell} command. - -@table @code -@kindex shell -@cindex shell escape -@item shell @var{command string} -Invoke a standard shell to execute @var{command string}. -@ifclear DOSHOST -If it exists, the environment variable @code{SHELL} determines which -shell to run. Otherwise @value{GDBN} uses @code{/bin/sh}. -@end ifclear -@end table - -The utility @code{make} is often needed in development environments. -You do not have to use the @code{shell} command for this purpose in -@value{GDBN}: - -@table @code -@kindex make -@cindex calling make -@item make @var{make-args} -Execute the @code{make} program with the specified -arguments. This is equivalent to @samp{shell make @var{make-args}}. -@end table - -@node Commands, Running, Invocation, Top -@chapter @value{GDBN} Commands - -You can abbreviate a @value{GDBN} command to the first few letters of the command -name, if that abbreviation is unambiguous; and you can repeat certain -@value{GDBN} commands by typing just @key{RET}. You can also use the @key{TAB} -key to get @value{GDBN} to fill out the rest of a word in a command (or to -show you the alternatives available, if there is more than one possibility). - -@menu -* Command Syntax:: How to give commands to @value{GDBN} -* Completion:: Command completion -* Help:: How to ask @value{GDBN} for help -@end menu - -@node Command Syntax, Completion, Commands, Commands -@section Command syntax - -A @value{GDBN} command is a single line of input. There is no limit on -how long it can be. It starts with a command name, which is followed by -arguments whose meaning depends on the command name. For example, the -command @code{step} accepts an argument which is the number of times to -step, as in @samp{step 5}. You can also use the @code{step} command -with no arguments. Some command names do not allow any arguments. - -@cindex abbreviation -@value{GDBN} command names may always be truncated if that abbreviation is -unambiguous. Other possible command abbreviations are listed in the -documentation for individual commands. In some cases, even ambiguous -abbreviations are allowed; for example, @code{s} is specially defined as -equivalent to @code{step} even though there are other commands whose -names start with @code{s}. You can test abbreviations by using them as -arguments to the @code{help} command. - -@cindex repeating commands -@kindex RET -A blank line as input to @value{GDBN} (typing just @key{RET}) means to -repeat the previous command. Certain commands (for example, @code{run}) -will not repeat this way; these are commands whose unintentional -repetition might cause trouble and which you are unlikely to want to -repeat. - -The @code{list} and @code{x} commands, when you repeat them with -@key{RET}, construct new arguments rather than repeating -exactly as typed. This permits easy scanning of source or memory. - -@value{GDBN} can also use @key{RET} in another way: to partition lengthy -output, in a way similar to the common utility @code{more} -(@pxref{Screen Size,,Screen size}). Since it is easy to press one -@key{RET} too many in this situation, @value{GDBN} disables command -repetition after any command that generates this sort of display. - -@kindex # -@cindex comment -Any text from a @kbd{#} to the end of the line is a comment; it does -nothing. This is useful mainly in command files (@pxref{Command -Files,,Command files}). - -@node Completion, Help, Command Syntax, Commands -@section Command completion - -@cindex completion -@cindex word completion -@value{GDBN} can fill in the rest of a word in a command for you, if there is -only one possibility; it can also show you what the valid possibilities -are for the next word in a command, at any time. This works for @value{GDBN} -commands, @value{GDBN} subcommands, and the names of symbols in your program. - -Press the @key{TAB} key whenever you want @value{GDBN} to fill out the rest -of a word. If there is only one possibility, @value{GDBN} fills in the -word, and waits for you to finish the command (or press @key{RET} to -enter it). For example, if you type - -@c FIXME "@key" does not distinguish its argument sufficiently to permit -@c complete accuracy in these examples; space introduced for clarity. -@c If texinfo enhancements make it unnecessary, it would be nice to -@c replace " @key" by "@key" in the following... -@example -(@value{GDBP}) info bre @key{TAB} -@end example - -@noindent -@value{GDBN} fills in the rest of the word @samp{breakpoints}, since that is -the only @code{info} subcommand beginning with @samp{bre}: - -@example -(@value{GDBP}) info breakpoints -@end example - -@noindent -You can either press @key{RET} at this point, to run the @code{info -breakpoints} command, or backspace and enter something else, if -@samp{breakpoints} does not look like the command you expected. (If you -were sure you wanted @code{info breakpoints} in the first place, you -might as well just type @key{RET} immediately after @samp{info bre}, -to exploit command abbreviations rather than command completion). - -If there is more than one possibility for the next word when you press -@key{TAB}, @value{GDBN} sounds a bell. You can either supply more -characters and try again, or just press @key{TAB} a second time; -@value{GDBN} displays all the possible completions for that word. For -example, you might want to set a breakpoint on a subroutine whose name -begins with @samp{make_}, but when you type @kbd{b make_@key{TAB}} @value{GDBN} -just sounds the bell. Typing @key{TAB} again displays all the -function names in your program that begin with those characters, for -example: - -@example -(@value{GDBP}) b make_ @key{TAB} -@exdent @value{GDBN} sounds bell; press @key{TAB} again, to see: -make_a_section_from_file make_environ -make_abs_section make_function_type -make_blockvector make_pointer_type -make_cleanup make_reference_type -make_command make_symbol_completion_list -(@value{GDBP}) b make_ -@end example - -@noindent -After displaying the available possibilities, @value{GDBN} copies your -partial input (@samp{b make_} in the example) so you can finish the -command. - -If you just want to see the list of alternatives in the first place, you -can press @kbd{M-?} rather than pressing @key{TAB} twice. @kbd{M-?} -means @kbd{@key{META} ?}. You can type this -@ifclear DOSHOST -either by holding down a -key designated as the @key{META} shift on your keyboard (if there is -one) while typing @kbd{?}, or -@end ifclear -as @key{ESC} followed by @kbd{?}. - -@cindex quotes in commands -@cindex completion of quoted strings -Sometimes the string you need, while logically a ``word'', may contain -parentheses or other characters that @value{GDBN} normally excludes from its -notion of a word. To permit word completion to work in this situation, -you may enclose words in @code{'} (single quote marks) in @value{GDBN} commands. - -@ifclear CONLY -The most likely situation where you might need this is in typing the -name of a C++ function. This is because C++ allows function overloading -(multiple definitions of the same function, distinguished by argument -type). For example, when you want to set a breakpoint you may need to -distinguish whether you mean the version of @code{name} that takes an -@code{int} parameter, @code{name(int)}, or the version that takes a -@code{float} parameter, @code{name(float)}. To use the word-completion -facilities in this situation, type a single quote @code{'} at the -beginning of the function name. This alerts @value{GDBN} that it may need to -consider more information than usual when you press @key{TAB} or -@kbd{M-?} to request word completion: - -@example -(@value{GDBP}) b 'bubble( @key{M-?} -bubble(double,double) bubble(int,int) -(@value{GDBP}) b 'bubble( -@end example - -In some cases, @value{GDBN} can tell that completing a name requires using -quotes. When this happens, @value{GDBN} inserts the quote for you (while -completing as much as it can) if you do not type the quote in the first -place: - -@example -(@value{GDBP}) b bub @key{TAB} -@exdent @value{GDBN} alters your input line to the following, and rings a bell: -(@value{GDBP}) b 'bubble( -@end example - -@noindent -In general, @value{GDBN} can tell that a quote is needed (and inserts it) if -you have not yet started typing the argument list when you ask for -completion on an overloaded symbol. - -For more information about overloaded functions, @pxref{Cplus -expressions, ,C++ expressions}. You can use the command @code{set -overload-resolution off} to disable overload resolution; -@pxref{Debugging C plus plus, ,@value{GDBN} features for C++}. -@end ifclear - - -@node Help, , Completion, Commands -@section Getting help -@cindex online documentation -@kindex help - -You can always ask @value{GDBN} itself for information on its commands, -using the command @code{help}. - -@table @code -@kindex h -@item help -@itemx h -You can use @code{help} (abbreviated @code{h}) with no arguments to -display a short list of named classes of commands: - -@smallexample -(@value{GDBP}) help -List of classes of commands: - -running -- Running the program -stack -- Examining the stack -data -- Examining data -breakpoints -- Making program stop at certain points -files -- Specifying and examining files -status -- Status inquiries -support -- Support facilities -user-defined -- User-defined commands -aliases -- Aliases of other commands -obscure -- Obscure features - -Type "help" followed by a class name for a list of -commands in that class. -Type "help" followed by command name for full -documentation. -Command name abbreviations are allowed if unambiguous. -(@value{GDBP}) -@end smallexample - -@item help @var{class} -Using one of the general help classes as an argument, you can get a -list of the individual commands in that class. For example, here is the -help display for the class @code{status}: - -@smallexample -(@value{GDBP}) help status -Status inquiries. - -List of commands: - -@c Line break in "show" line falsifies real output, but needed -@c to fit in smallbook page size. -show -- Generic command for showing things set - with "set" -info -- Generic command for printing status - -Type "help" followed by command name for full -documentation. -Command name abbreviations are allowed if unambiguous. -(@value{GDBP}) -@end smallexample - -@item help @var{command} -With a command name as @code{help} argument, @value{GDBN} displays a -short paragraph on how to use that command. - -@kindex complete -@item complete @var{args} -The @code{complete @var{args}} command lists all the possible completions -for the beginning of a command. Use @var{args} to specify the beginning of the -command you want completed. For example: - -@smallexample -complete i -@end smallexample - -@noindent results in: - -@smallexample -@group -info -inspect -ignore -@end group -@end smallexample - -@noindent This is intended for use by @sc{gnu} Emacs. -@end table - -In addition to @code{help}, you can use the @value{GDBN} commands @code{info} -and @code{show} to inquire about the state of your program, or the state -of @value{GDBN} itself. Each command supports many topics of inquiry; this -manual introduces each of them in the appropriate context. The listings -under @code{info} and under @code{show} in the Index point to -all the sub-commands. @xref{Index}. - -@c @group -@table @code -@kindex info -@kindex i -@item info -This command (abbreviated @code{i}) is for describing the state of your -program. For example, you can list the arguments given to your program -with @code{info args}, list the registers currently in use with @code{info -registers}, or list the breakpoints you have set with @code{info breakpoints}. -You can get a complete list of the @code{info} sub-commands with -@w{@code{help info}}. - -@kindex set -@item set -You can assign the result of an expression to an environment variable with -@code{set}. For example, you can set the @value{GDBN} prompt to a $-sign with -@code{set prompt $}. - -@kindex show -@item show -In contrast to @code{info}, @code{show} is for describing the state of -@value{GDBN} itself. -You can change most of the things you can @code{show}, by using the -related command @code{set}; for example, you can control what number -system is used for displays with @code{set radix}, or simply inquire -which is currently in use with @code{show radix}. - -@kindex info set -To display all the settable parameters and their current -values, you can use @code{show} with no arguments; you may also use -@code{info set}. Both commands produce the same display. -@c FIXME: "info set" violates the rule that "info" is for state of -@c FIXME...program. Ck w/ GNU: "info set" to be called something else, -@c FIXME...or change desc of rule---eg "state of prog and debugging session"? -@end table -@c @end group - -Here are three miscellaneous @code{show} subcommands, all of which are -exceptional in lacking corresponding @code{set} commands: - -@table @code -@kindex show version -@cindex version number -@item show version -Show what version of @value{GDBN} is running. You should include this -information in @value{GDBN} bug-reports. If multiple versions of @value{GDBN} are in -use at your site, you may occasionally want to determine which version -of @value{GDBN} you are running; as @value{GDBN} evolves, new commands are introduced, -and old ones may wither away. The version number is also announced -when you start @value{GDBN}. - -@kindex show copying -@item show copying -Display information about permission for copying @value{GDBN}. - -@kindex show warranty -@item show warranty -Display the @sc{gnu} ``NO WARRANTY'' statement. -@end table - -@node Running, Stopping, Commands, Top -@chapter Running Programs Under @value{GDBN} - -When you run a program under @value{GDBN}, you must first generate -debugging information when you compile it. -@ifclear BARETARGET -You may start @value{GDBN} with its arguments, if any, in an environment -of your choice. You may redirect your program's input and output, debug an -already running process, or kill a child process. -@end ifclear - -@menu -* Compilation:: Compiling for debugging -* Starting:: Starting your program -@ifclear BARETARGET -* Arguments:: Your program's arguments -* Environment:: Your program's environment -@end ifclear - -* Working Directory:: Your program's working directory -* Input/Output:: Your program's input and output -* Attach:: Debugging an already-running process -* Kill Process:: Killing the child process -@ifclear HPPA -* Process Information:: Additional process information -@end ifclear - -* Threads:: Debugging programs with multiple threads -* Processes:: Debugging programs with multiple processes -@end menu - -@node Compilation, Starting, Running, Running -@section Compiling for debugging - -In order to debug a program effectively, you need to generate -debugging information when you compile it. This debugging information -is stored in the object file; it describes the data type of each -variable or function and the correspondence between source line numbers -and addresses in the executable code. - -To request debugging information, specify the @samp{-g} option when you run -the compiler. - -Many C compilers are unable to handle the @samp{-g} and @samp{-O} -options together. Using those compilers, you cannot generate optimized -executables containing debugging information. - -@ifclear HPPA -@value{NGCC}, the @sc{gnu} C compiler, supports @samp{-g} with or without -@end ifclear -@ifset HPPA -The HP ANSI C and C++ compilers, as well as @value{NGCC}, the @sc{gnu} C -compiler, support @samp{-g} with or without -@end ifset -@samp{-O}, making it possible to debug optimized code. We recommend -that you @emph{always} use @samp{-g} whenever you compile a program. -You may think your program is correct, but there is no sense in pushing -your luck. - -@cindex optimized code, debugging -@cindex debugging optimized code -When you debug a program compiled with @samp{-g -O}, remember that the -optimizer is rearranging your code; the debugger shows you what is -really there. Do not be too surprised when the execution path does not -exactly match your source file! An extreme example: if you define a -variable, but never use it, @value{GDBN} never sees that -variable---because the compiler optimizes it out of existence. - -Some things do not work as well with @samp{-g -O} as with just -@samp{-g}, particularly on machines with instruction scheduling. If in -doubt, recompile with @samp{-g} alone, and if this fixes the problem, -please report it to us as a bug (including a test case!). - -Older versions of the @sc{gnu} C compiler permitted a variant option -@w{@samp{-gg}} for debugging information. @value{GDBN} no longer supports this -format; if your @sc{gnu} C compiler has this option, do not use it. - -@need 2000 -@node Starting, Arguments, Compilation, Running -@section Starting your program -@cindex starting -@cindex running - -@table @code -@kindex run -@item run -@itemx r -Use the @code{run} command to start your program under @value{GDBN}. You must -first specify the program name -@ifset VXWORKS -(except on VxWorks) -@end ifset -with an argument to @value{GDBN} (@pxref{Invocation, ,Getting In and -Out of @value{GDBN}}), or by using the @code{file} or @code{exec-file} -command (@pxref{Files, ,Commands to specify files}). - -@end table - -@ifclear BARETARGET -If you are running your program in an execution environment that -supports processes, @code{run} creates an inferior process and makes -that process run your program. (In environments without processes, -@code{run} jumps to the start of your program.) - -The execution of a program is affected by certain information it -receives from its superior. @value{GDBN} provides ways to specify this -information, which you must do @emph{before} starting your program. (You -can change it after starting your program, but such changes only affect -your program the next time you start it.) This information may be -divided into four categories: - -@table @asis -@item The @emph{arguments.} -Specify the arguments to give your program as the arguments of the -@code{run} command. If a shell is available on your target, the shell -is used to pass the arguments, so that you may use normal conventions -(such as wildcard expansion or variable substitution) in describing -the arguments. -In Unix systems, you can control which shell is used with the -@code{SHELL} environment variable. -@xref{Arguments, ,Your program's arguments}. - -@item The @emph{environment.} -Your program normally inherits its environment from @value{GDBN}, but you can -use the @value{GDBN} commands @code{set environment} and @code{unset -environment} to change parts of the environment that affect -your program. @xref{Environment, ,Your program's environment}. - -@item The @emph{working directory.} -Your program inherits its working directory from @value{GDBN}. You can set -the @value{GDBN} working directory with the @code{cd} command in @value{GDBN}. -@xref{Working Directory, ,Your program's working directory}. - -@item The @emph{standard input and output.} -Your program normally uses the same device for standard input and -standard output as @value{GDBN} is using. You can redirect input and output -in the @code{run} command line, or you can use the @code{tty} command to -set a different device for your program. -@xref{Input/Output, ,Your program's input and output}. - -@cindex pipes -@emph{Warning:} While input and output redirection work, you cannot use -pipes to pass the output of the program you are debugging to another -program; if you attempt this, @value{GDBN} is likely to wind up debugging the -wrong program. -@end table -@end ifclear - -When you issue the @code{run} command, your program begins to execute -immediately. @xref{Stopping, ,Stopping and continuing}, for discussion -of how to arrange for your program to stop. Once your program has -stopped, you may call functions in your program, using the @code{print} -or @code{call} commands. @xref{Data, ,Examining Data}. - -If the modification time of your symbol file has changed since the last -time @value{GDBN} read its symbols, @value{GDBN} discards its symbol -table, and reads it again. When it does this, @value{GDBN} tries to retain -your current breakpoints. - -@ifclear BARETARGET -@node Arguments, Environment, Starting, Running -@section Your program's arguments - -@cindex arguments (to your program) -The arguments to your program can be specified by the arguments of the -@code{run} command. -They are passed to a shell, which expands wildcard characters and -performs redirection of I/O, and thence to your program. Your -@code{SHELL} environment variable (if it exists) specifies what shell -@value{GDBN} uses. If you do not define @code{SHELL}, @value{GDBN} uses -@code{/bin/sh}. - -@code{run} with no arguments uses the same arguments used by the previous -@code{run}, or those set by the @code{set args} command. - -@kindex set args -@table @code -@item set args -Specify the arguments to be used the next time your program is run. If -@code{set args} has no arguments, @code{run} executes your program -with no arguments. Once you have run your program with arguments, -using @code{set args} before the next @code{run} is the only way to run -it again without arguments. - -@kindex show args -@item show args -Show the arguments to give your program when it is started. -@end table - -@node Environment, Working Directory, Arguments, Running -@section Your program's environment - -@cindex environment (of your program) -The @dfn{environment} consists of a set of environment variables and -their values. Environment variables conventionally record such things as -your user name, your home directory, your terminal type, and your search -path for programs to run. Usually you set up environment variables with -the shell and they are inherited by all the other programs you run. When -debugging, it can be useful to try running your program with a modified -environment without having to start @value{GDBN} over again. - -@table @code -@kindex path -@item path @var{directory} -Add @var{directory} to the front of the @code{PATH} environment variable -(the search path for executables), for both @value{GDBN} and your program. -You may specify several directory names, separated by @samp{:} or -whitespace. If @var{directory} is already in the path, it is moved to -the front, so it is searched sooner. - -You can use the string @samp{$cwd} to refer to whatever is the current -working directory at the time @value{GDBN} searches the path. If you -use @samp{.} instead, it refers to the directory where you executed the -@code{path} command. @value{GDBN} replaces @samp{.} in the -@var{directory} argument (with the current path) before adding -@var{directory} to the search path. -@c 'path' is explicitly nonrepeatable, but RMS points out it is silly to -@c document that, since repeating it would be a no-op. - -@kindex show paths -@item show paths -Display the list of search paths for executables (the @code{PATH} -environment variable). - -@kindex show environment -@item show environment @r{[}@var{varname}@r{]} -Print the value of environment variable @var{varname} to be given to -your program when it starts. If you do not supply @var{varname}, -print the names and values of all environment variables to be given to -your program. You can abbreviate @code{environment} as @code{env}. - -@kindex set environment -@item set environment @var{varname} @r{[}=@r{]} @var{value} -Set environment variable @var{varname} to @var{value}. The value -changes for your program only, not for @value{GDBN} itself. @var{value} may -be any string; the values of environment variables are just strings, and -any interpretation is supplied by your program itself. The @var{value} -parameter is optional; if it is eliminated, the variable is set to a -null value. -@c "any string" here does not include leading, trailing -@c blanks. Gnu asks: does anyone care? - -For example, this command: - -@example -set env USER = foo -@end example - -@noindent -tells a Unix program, when subsequently run, that its user is named -@samp{foo}. (The spaces around @samp{=} are used for clarity here; they -are not actually required.) - -@kindex unset environment -@item unset environment @var{varname} -Remove variable @var{varname} from the environment to be passed to your -program. This is different from @samp{set env @var{varname} =}; -@code{unset environment} removes the variable from the environment, -rather than assigning it an empty value. -@end table - -@emph{Warning:} @value{GDBN} runs your program using the shell indicated -by your @code{SHELL} environment variable if it exists (or -@code{/bin/sh} if not). If your @code{SHELL} variable names a shell -that runs an initialization file---such as @file{.cshrc} for C-shell, or -@file{.bashrc} for BASH---any variables you set in that file affect -your program. You may wish to move setting of environment variables to -files that are only run when you sign on, such as @file{.login} or -@file{.profile}. - -@node Working Directory, Input/Output, Environment, Running -@section Your program's working directory - -@cindex working directory (of your program) -Each time you start your program with @code{run}, it inherits its -working directory from the current working directory of @value{GDBN}. -The @value{GDBN} working directory is initially whatever it inherited -from its parent process (typically the shell), but you can specify a new -working directory in @value{GDBN} with the @code{cd} command. - -The @value{GDBN} working directory also serves as a default for the commands -that specify files for @value{GDBN} to operate on. @xref{Files, ,Commands to -specify files}. - -@table @code -@kindex cd -@item cd @var{directory} -Set the @value{GDBN} working directory to @var{directory}. - -@kindex pwd -@item pwd -Print the @value{GDBN} working directory. -@end table - -@node Input/Output, Attach, Working Directory, Running -@section Your program's input and output - -@cindex redirection -@cindex i/o -@cindex terminal -By default, the program you run under @value{GDBN} does input and output to -the same terminal that @value{GDBN} uses. @value{GDBN} switches the terminal -to its own terminal modes to interact with you, but it records the terminal -modes your program was using and switches back to them when you continue -running your program. - -@table @code -@kindex info terminal -@item info terminal -Displays information recorded by @value{GDBN} about the terminal modes your -program is using. -@end table - -You can redirect your program's input and/or output using shell -redirection with the @code{run} command. For example, - -@example -run > outfile -@end example - -@noindent -starts your program, diverting its output to the file @file{outfile}. - -@kindex tty -@cindex controlling terminal -Another way to specify where your program should do input and output is -with the @code{tty} command. This command accepts a file name as -argument, and causes this file to be the default for future @code{run} -commands. It also resets the controlling terminal for the child -process, for future @code{run} commands. For example, - -@example -tty /dev/ttyb -@end example - -@noindent -directs that processes started with subsequent @code{run} commands -default to do input and output on the terminal @file{/dev/ttyb} and have -that as their controlling terminal. - -An explicit redirection in @code{run} overrides the @code{tty} command's -effect on the input/output device, but not its effect on the controlling -terminal. - -When you use the @code{tty} command or redirect input in the @code{run} -command, only the input @emph{for your program} is affected. The input -for @value{GDBN} still comes from your terminal. - -@node Attach, Kill Process, Input/Output, Running -@section Debugging an already-running process -@kindex attach -@cindex attach - -@table @code -@item attach @var{process-id} -This command attaches to a running process---one that was started -outside @value{GDBN}. (@code{info files} shows your active -targets.) The command takes as argument a process ID. The usual way to -find out the process-id of a Unix process is with the @code{ps} utility, -or with the @samp{jobs -l} shell command. - -@code{attach} does not repeat if you press @key{RET} a second time after -executing the command. -@end table - -To use @code{attach}, your program must be running in an environment -which supports processes; for example, @code{attach} does not work for -programs on bare-board targets that lack an operating system. You must -also have permission to send the process a signal. - -When you use @code{attach}, the debugger finds the program running in -the process first by looking in the current working directory, then (if -the program is not found) by using the source file search path -(@pxref{Source Path, ,Specifying source directories}). You can also use -the @code{file} command to load the program. @xref{Files, ,Commands to -Specify Files}. - -The first thing @value{GDBN} does after arranging to debug the specified -process is to stop it. You can examine and modify an attached process -with all the @value{GDBN} commands that are ordinarily available when you start -@ifclear HPPA -processes with @code{run}. You can insert breakpoints; you can step and -@end ifclear -@ifset HPPA -processes with @code{run}. You can insert breakpoints (except in shared -libraries); you can step and -@end ifset -continue; you can modify storage. If you would rather the process -continue running, you may use the @code{continue} command after -attaching @value{GDBN} to the process. - -@table @code -@kindex detach -@item detach -When you have finished debugging the attached process, you can use the -@code{detach} command to release it from @value{GDBN} control. Detaching -the process continues its execution. After the @code{detach} command, -that process and @value{GDBN} become completely independent once more, and you -are ready to @code{attach} another process or start one with @code{run}. -@code{detach} does not repeat if you press @key{RET} again after -executing the command. -@end table - -If you exit @value{GDBN} or use the @code{run} command while you have an -attached process, you kill that process. By default, @value{GDBN} asks -for confirmation if you try to do either of these things; you can -control whether or not you need to confirm by using the @code{set -confirm} command (@pxref{Messages/Warnings, ,Optional warnings and -messages}). - -@ifset HPPA -@node Kill Process, Threads, Attach, Running -@section Killing the child process -@end ifset -@ifclear HPPA -@node Kill Process, Process Information, Attach, Running -@section Killing the child process -@end ifclear - -@table @code -@kindex kill -@item kill -Kill the child process in which your program is running under @value{GDBN}. -@end table - -This command is useful if you wish to debug a core dump instead of a -running process. @value{GDBN} ignores any core dump file while your program -is running. - -On some operating systems, a program cannot be executed outside @value{GDBN} -while you have breakpoints set on it inside @value{GDBN}. You can use the -@code{kill} command in this situation to permit running your program -outside the debugger. - -The @code{kill} command is also useful if you wish to recompile and -relink your program, since on many systems it is impossible to modify an -executable file while it is running in a process. In this case, when you -next type @code{run}, @value{GDBN} notices that the file has changed, and -reads the symbol table again (while trying to preserve your current -breakpoint settings). - -@ifclear HPPA -@node Process Information, Threads, Kill Process, Running -@section Additional process information - -@kindex /proc -@cindex process image -Some operating systems provide a facility called @samp{/proc} that can -be used to examine the image of a running process using file-system -subroutines. If @value{GDBN} is configured for an operating system with this -facility, the command @code{info proc} is available to report on several -kinds of information about the process running your program. -@code{info proc} works only on SVR4 systems that support @code{procfs}. - -@table @code -@kindex info proc -@item info proc -Summarize available information about the process. - -@kindex info proc mappings -@item info proc mappings -Report on the address ranges accessible in the program, with information -on whether your program may read, write, or execute each range. - -@kindex info proc times -@item info proc times -Starting time, user CPU time, and system CPU time for your program and -its children. - -@kindex info proc id -@item info proc id -Report on the process IDs related to your program: its own process ID, -the ID of its parent, the process group ID, and the session ID. - -@kindex info proc status -@item info proc status -General information on the state of the process. If the process is -stopped, this report includes the reason for stopping, and any signal -received. - -@item info proc all -Show all the above information about the process. -@end table -@end ifclear - -@ifset HPPA -@node Threads, Processes, Kill Process, Running -@section Debugging programs with multiple threads -@end ifset -@ifclear HPPA -@node Threads, Processes, Process Information, Running -@section Debugging programs with multiple threads -@end ifclear - -@cindex threads of execution -@cindex multiple threads -@cindex switching threads -In some operating systems, such as HP-UX and Solaris, a single program -may have more than one @dfn{thread} of execution. The precise semantics -of threads differ from one operating system to another, but in general -the threads of a single program are akin to multiple processes---except -that they share one address space (that is, they can all examine and -modify the same variables). On the other hand, each thread has its own -registers and execution stack, and perhaps private memory. - -@value{GDBN} provides these facilities for debugging multi-thread -programs: - -@itemize @bullet -@item automatic notification of new threads -@item @samp{thread @var{threadno}}, a command to switch among threads -@item @samp{info threads}, a command to inquire about existing threads -@item @samp{thread apply [@var{threadno}] [@var{all}] @var{args}}, -a command to apply a command to a list of threads -@item thread-specific breakpoints -@end itemize - -@ifclear HPPA -@quotation -@emph{Warning:} These facilities are not yet available on every -@value{GDBN} configuration where the operating system supports threads. -If your @value{GDBN} does not support threads, these commands have no -effect. For example, a system without thread support shows no output -from @samp{info threads}, and always rejects the @code{thread} command, -like this: - -@smallexample -(@value{GDBP}) info threads -(@value{GDBP}) thread 1 -Thread ID 1 not known. Use the "info threads" command to -see the IDs of currently known threads. -@end smallexample -@c FIXME to implementors: how hard would it be to say "sorry, this GDB -@c doesn't support threads"? -@end quotation -@end ifclear - -@cindex focus of debugging -@cindex current thread -The @value{GDBN} thread debugging facility allows you to observe all -threads while your program runs---but whenever @value{GDBN} takes -control, one thread in particular is always the focus of debugging. -This thread is called the @dfn{current thread}. Debugging commands show -program information from the perspective of the current thread. - -@ifclear HPPA -@kindex New @var{systag} -@cindex thread identifier (system) -@c FIXME-implementors!! It would be more helpful if the [New...] message -@c included GDB's numeric thread handle, so you could just go to that -@c thread without first checking `info threads'. -Whenever @value{GDBN} detects a new thread in your program, it displays -the target system's identification for the thread with a message in the -form @samp{[New @var{systag}]}. @var{systag} is a thread identifier -whose form varies depending on the particular system. For example, on -LynxOS, you might see - -@example -[New process 35 thread 27] -@end example - -@noindent -when @value{GDBN} notices a new thread. In contrast, on an SGI system, -the @var{systag} is simply something like @samp{process 368}, with no -further qualifier. - -@c FIXME!! (1) Does the [New...] message appear even for the very first -@c thread of a program, or does it only appear for the -@c second---i.e., when it becomes obvious we have a multithread -@c program? -@c (2) *Is* there necessarily a first thread always? Or do some -@c multithread systems permit starting a program with multiple -@c threads ab initio? - -@cindex thread number -@cindex thread identifier (GDB) -For debugging purposes, @value{GDBN} associates its own thread -number---always a single integer---with each thread in your program. - -@table @code -@kindex info threads -@item info threads -Display a summary of all threads currently in your -program. @value{GDBN} displays for each thread (in this order): - -@enumerate -@item the thread number assigned by @value{GDBN} - -@item the target system's thread identifier (@var{systag}) - -@item the current stack frame summary for that thread -@end enumerate - -@noindent -An asterisk @samp{*} to the left of the @value{GDBN} thread number -indicates the current thread. - -For example, -@end table -@c end table here to get a little more width for example - -@smallexample -(@value{GDBP}) info threads - 3 process 35 thread 27 0x34e5 in sigpause () - 2 process 35 thread 23 0x34e5 in sigpause () -* 1 process 35 thread 13 main (argc=1, argv=0x7ffffff8) - at threadtest.c:68 -@end smallexample -@end ifclear -@ifset HPPA - -@cindex thread number -@cindex thread identifier (GDB) -For debugging purposes, @value{GDBN} associates its own thread -number---a small integer assigned in thread-creation order---with each -thread in your program. - -@kindex New @var{systag} -@cindex thread identifier (system) -@c FIXME-implementors!! It would be more helpful if the [New...] message -@c included GDB's numeric thread handle, so you could just go to that -@c thread without first checking `info threads'. -Whenever @value{GDBN} detects a new thread in your program, it displays -both @value{GDBN}'s thread number and the target system's identification for the thread with a message in the -form @samp{[New @var{systag}]}. @var{systag} is a thread identifier -whose form varies depending on the particular system. For example, on -HP-UX, you see - -@example -[New thread 2 (system thread 26594)] -@end example - -@noindent -when @value{GDBN} notices a new thread. - -@table @code -@kindex info threads -@item info threads -Display a summary of all threads currently in your -program. @value{GDBN} displays for each thread (in this order): - -@enumerate -@item the thread number assigned by @value{GDBN} - -@item the target system's thread identifier (@var{systag}) - -@item the current stack frame summary for that thread -@end enumerate - -@noindent -An asterisk @samp{*} to the left of the @value{GDBN} thread number -indicates the current thread. - -For example, -@end table -@c end table here to get a little more width for example - -@example -(@value{GDBP}) info threads - * 3 system thread 26607 worker (wptr=0x7b09c318 "@@") at quicksort.c:137 - 2 system thread 26606 0x7b0030d8 in __ksleep () from /usr/lib/libc.2 - 1 system thread 27905 0x7b003498 in _brk () from /usr/lib/libc.2 -@end example -@end ifset - -@table @code -@kindex thread @var{threadno} -@item thread @var{threadno} -Make thread number @var{threadno} the current thread. The command -argument @var{threadno} is the internal @value{GDBN} thread number, as -shown in the first field of the @samp{info threads} display. -@value{GDBN} responds by displaying the system identifier of the thread -you selected, and its current stack frame summary: - -@smallexample -@c FIXME!! This example made up; find a @value{GDBN} w/threads and get real one -(@value{GDBP}) thread 2 -@ifclear HPPA -[Switching to process 35 thread 23] -@end ifclear -@ifset HPPA -[Switching to thread 2 (system thread 26594)] -@end ifset -0x34e5 in sigpause () -@end smallexample - -@noindent -As with the @samp{[New @dots{}]} message, the form of the text after -@samp{Switching to} depends on your system's conventions for identifying -threads. - -@kindex thread apply -@item thread apply [@var{threadno}] [@var{all}] @var{args} -The @code{thread apply} command allows you to apply a command to one or -more threads. Specify the numbers of the threads that you want affected -with the command argument @var{threadno}. @var{threadno} is the internal -@value{GDBN} thread number, as shown in the first field of the @samp{info -threads} display. To apply a command to all threads, use -@code{thread apply all} @var{args}. -@end table - -@cindex automatic thread selection -@cindex switching threads automatically -@cindex threads, automatic switching -Whenever @value{GDBN} stops your program, due to a breakpoint or a -signal, it automatically selects the thread where that breakpoint or -signal happened. @value{GDBN} alerts you to the context switch with a -message of the form @samp{[Switching to @var{systag}]} to identify the -thread. - -@xref{Thread Stops,,Stopping and starting multi-thread programs}, for -more information about how @value{GDBN} behaves when you stop and start -programs with multiple threads. - -@xref{Set Watchpoints,,Setting watchpoints}, for information about -watchpoints in programs with multiple threads. -@end ifclear - -@ifclear HPPA -@node Processes, , Threads, Running -@section Debugging programs with multiple processes - -@cindex fork, debugging programs which call -@cindex multiple processes -@cindex processes, multiple -@value{GDBN} has no special support for debugging programs which create -additional processes using the @code{fork} function. When a program -forks, @value{GDBN} will continue to debug the parent process and the -child process will run unimpeded. If you have set a breakpoint in any -code which the child then executes, the child will get a @code{SIGTRAP} -signal which (unless it catches the signal) will cause it to terminate. - -However, if you want to debug the child process there is a workaround -which isn't too painful. Put a call to @code{sleep} in the code which -the child process executes after the fork. It may be useful to sleep -only if a certain environment variable is set, or a certain file exists, -so that the delay need not occur when you don't want to run @value{GDBN} -on the child. While the child is sleeping, use the @code{ps} program to -get its process ID. Then tell @value{GDBN} (a new invocation of -@value{GDBN} if you are also debugging the parent process) to attach to -the child process (see @ref{Attach}). From that point on you can debug -the child process just like any other process which you attached to. -@end ifclear -@ifset HPPA -@node Processes, , Threads, Running -@section Debugging programs with multiple processes - -@cindex fork, debugging programs which call -@cindex multiple processes -@cindex processes, multiple - -@value{GDBN} provides support for debugging programs that create -additional processes using the @code{fork} or @code{vfork} function. - -By default, when a program forks, @value{GDBN} will continue to debug -the parent process and the child process will run unimpeded. - -If you want to follow the child process instead of the parent process, -use the command @w{@code{set follow-fork-mode}}. - -@table @code -@kindex set follow-fork-mode -@item set follow-fork-mode @var{mode} -Set the debugger response to a program call of @code{fork} or -@code{vfork}. A call to @code{fork} or @code{vfork} creates a new -process. The @var{mode} can be: - -@table @code -@item parent -The original process is debugged after a fork. The child process runs -unimpeded. - -@item child -The new process is debugged after a fork. The parent process runs -unimpeded. - -@item ask -The debugger will ask for one of the above choices. -@end table - -@item show follow-fork-mode -Display the current debugger response to a fork or vfork call. -@end table - -If you ask to debug a child process and a @code{vfork} is followed by an -@code{exec}, @value{GDBN} executes the new target up to the first -breakpoint in the new target. If you have a breakpoint set on -@code{main} in your original program, the breakpoint will also be set on -the child process's @code{main}. - -When a child process is spawned by @code{vfork}, you cannot debug the -child or parent until an @code{exec} call completes. - -If you issue a @code{run} command to @value{GDBN} after an @code{exec} -call executes, the new target restarts. To restart the parent process, -use the @code{file} command with the parent executable name as its -argument. - -You can use the @code{catch} command to make @value{GDBN} stop whenever -a @code{fork}, @code{vfork}, or @code{exec} call is made. @xref{Set -Catchpoints, ,Setting catchpoints}. -@end ifset - -@node Stopping, Stack, Running, Top -@chapter Stopping and Continuing - -The principal purposes of using a debugger are so that you can stop your -program before it terminates; or so that, if your program runs into -trouble, you can investigate and find out why. - -Inside @value{GDBN}, your program may stop for any of several reasons, such -as -@ifclear BARETARGET -a signal, -@end ifclear -a breakpoint, or reaching a new line after a @value{GDBN} -command such as @code{step}. You may then examine and change -variables, set new breakpoints or remove old ones, and then continue -execution. Usually, the messages shown by @value{GDBN} provide ample -explanation of the status of your program---but you can also explicitly -request this information at any time. - -@table @code -@kindex info program -@item info program -Display information about the status of your program: whether it is -running or not, -@ifclear BARETARGET -what process it is, -@end ifclear -and why it stopped. -@end table - -@menu -* Breakpoints:: Breakpoints, watchpoints, and catchpoints -* Continuing and Stepping:: Resuming execution -@ifset POSIX -* Signals:: Signals -@end ifset - -@ifclear BARETARGET -* Thread Stops:: Stopping and starting multi-thread programs -@end ifclear - -@end menu - -@node Breakpoints, Continuing and Stepping, Stopping, Stopping -@section Breakpoints, watchpoints, and catchpoints - -@cindex breakpoints -A @dfn{breakpoint} makes your program stop whenever a certain point in -the program is reached. For each breakpoint, you can add conditions to -control in finer detail whether your program stops. You can set -breakpoints with the @code{break} command and its variants (@pxref{Set -Breaks, ,Setting breakpoints}), to specify the place where your program -should stop by line number, function name or exact address in the -program. - -In HP-UX, SunOS 4.x, SVR4, and Alpha OSF/1 configurations, you can set -breakpoints in shared libraries before the executable is run. There is -a minor limitation on HP-UX systems: you must wait until the executable -is run in order to set breakpoints in shared library routines that are -not called directly by the program (for example, routines that are -arguments in a @code{pthread_create} call). - -@cindex watchpoints -@cindex memory tracing -@cindex breakpoint on memory address -@cindex breakpoint on variable modification -A @dfn{watchpoint} is a special breakpoint that stops your program -when the value of an expression changes. You must use a different -command to set watchpoints (@pxref{Set Watchpoints, ,Setting -watchpoints}), but aside from that, you can manage a watchpoint like -any other breakpoint: you enable, disable, and delete both breakpoints -and watchpoints using the same commands. - -You can arrange to have values from your program displayed automatically -whenever @value{GDBN} stops at a breakpoint. @xref{Auto Display,, -Automatic display}. - -@cindex catchpoints -@cindex breakpoint on events -A @dfn{catchpoint} is another special breakpoint that stops your program -when a certain kind of event occurs, such as the throwing of a C++ -exception or the loading of a library. As with watchpoints, you use a -different command to set a catchpoint (@pxref{Set Catchpoints, ,Setting -catchpoints}), but aside from that, you can manage a catchpoint like any -other breakpoint. (To stop when your program receives a signal, use the -@code{handle} command; @pxref{Signals, ,Signals}.) - -@cindex breakpoint numbers -@cindex numbers for breakpoints -@value{GDBN} assigns a number to each breakpoint, watchpoint, or -catchpoint when you create it; these numbers are successive integers -starting with one. In many of the commands for controlling various -features of breakpoints you use the breakpoint number to say which -breakpoint you want to change. Each breakpoint may be @dfn{enabled} or -@dfn{disabled}; if disabled, it has no effect on your program until you -enable it again. - -@menu -* Set Breaks:: Setting breakpoints -* Set Watchpoints:: Setting watchpoints -* Set Catchpoints:: Setting catchpoints -* Delete Breaks:: Deleting breakpoints -* Disabling:: Disabling breakpoints -* Conditions:: Break conditions -* Break Commands:: Breakpoint command lists -@ifclear CONLY -* Breakpoint Menus:: Breakpoint menus -@end ifclear - -@c @ifclear BARETARGET -@c * Error in Breakpoints:: ``Cannot insert breakpoints'' -@c @end ifclear -@end menu - -@node Set Breaks, Set Watchpoints, Breakpoints, Breakpoints -@subsection Setting breakpoints - -@c FIXME LMB what does GDB do if no code on line of breakpt? -@c consider in particular declaration with/without initialization. -@c -@c FIXME 2 is there stuff on this already? break at fun start, already init? - -@kindex break -@kindex b -@kindex $bpnum -@cindex latest breakpoint -Breakpoints are set with the @code{break} command (abbreviated -@code{b}). The debugger convenience variable @samp{$bpnum} records the -number of the breakpoints you've set most recently; see @ref{Convenience -Vars,, Convenience variables}, for a discussion of what you can do with -convenience variables. - -You have several ways to say where the breakpoint should go. - -@table @code -@item break @var{function} -Set a breakpoint at entry to function @var{function}. -@ifclear CONLY -When using source languages that permit overloading of symbols, such as -C++, @var{function} may refer to more than one possible place to break. -@xref{Breakpoint Menus,,Breakpoint menus}, for a discussion of that situation. -@end ifclear - -@item break +@var{offset} -@itemx break -@var{offset} -Set a breakpoint some number of lines forward or back from the position -at which execution stopped in the currently selected frame. - -@item break @var{linenum} -Set a breakpoint at line @var{linenum} in the current source file. -That file is the last file whose source text was printed. This -breakpoint stops your program just before it executes any of the -code on that line. - -@item break @var{filename}:@var{linenum} -Set a breakpoint at line @var{linenum} in source file @var{filename}. - -@item break @var{filename}:@var{function} -Set a breakpoint at entry to function @var{function} found in file -@var{filename}. Specifying a file name as well as a function name is -superfluous except when multiple files contain similarly named -functions. - -@item break *@var{address} -Set a breakpoint at address @var{address}. You can use this to set -breakpoints in parts of your program which do not have debugging -information or source files. - -@item break -When called without any arguments, @code{break} sets a breakpoint at -the next instruction to be executed in the selected stack frame -(@pxref{Stack, ,Examining the Stack}). In any selected frame but the -innermost, this makes your program stop as soon as control -returns to that frame. This is similar to the effect of a -@code{finish} command in the frame inside the selected frame---except -that @code{finish} does not leave an active breakpoint. If you use -@code{break} without an argument in the innermost frame, @value{GDBN} stops -the next time it reaches the current location; this may be useful -inside loops. - -@value{GDBN} normally ignores breakpoints when it resumes execution, until at -least one instruction has been executed. If it did not do this, you -would be unable to proceed past a breakpoint without first disabling the -breakpoint. This rule applies whether or not the breakpoint already -existed when your program stopped. - -@item break @dots{} if @var{cond} -Set a breakpoint with condition @var{cond}; evaluate the expression -@var{cond} each time the breakpoint is reached, and stop only if the -value is nonzero---that is, if @var{cond} evaluates as true. -@samp{@dots{}} stands for one of the possible arguments described -above (or no argument) specifying where to break. @xref{Conditions, -,Break conditions}, for more information on breakpoint conditions. - -@kindex tbreak -@item tbreak @var{args} -Set a breakpoint enabled only for one stop. @var{args} are the -same as for the @code{break} command, and the breakpoint is set in the same -way, but the breakpoint is automatically deleted after the first time your -program stops there. @xref{Disabling, ,Disabling breakpoints}. - -@ifclear HPPA -@kindex hbreak -@item hbreak @var{args} -Set a hardware-assisted breakpoint. @var{args} are the same as for the -@code{break} command and the breakpoint is set in the same way, but the -breakpoint requires hardware support and some target hardware may not -have this support. The main purpose of this is EPROM/ROM code -debugging, so you can set a breakpoint at an instruction without -changing the instruction. This can be used with the new trap-generation -provided by SPARClite DSU. DSU will generate traps when a program accesses -some data or instruction address that is assigned to the debug registers. -However the hardware breakpoint registers can only take two data breakpoints, -and @value{GDBN} will reject this command if more than two are used. -Delete or disable unused hardware breakpoints before setting -new ones. @xref{Conditions, ,Break conditions}. - -@kindex thbreak -@item thbreak @var{args} -Set a hardware-assisted breakpoint enabled only for one stop. @var{args} -are the same as for the @code{hbreak} command and the breakpoint is set in -the same way. However, like the @code{tbreak} command, -the breakpoint is automatically deleted after the -first time your program stops there. Also, like the @code{hbreak} -command, the breakpoint requires hardware support and some target hardware -may not have this support. @xref{Disabling, ,Disabling breakpoints}. -Also @xref{Conditions, ,Break conditions}. -@end ifclear - -@kindex rbreak -@cindex regular expression -@item rbreak @var{regex} -@c FIXME what kind of regexp? -Set breakpoints on all functions matching the regular expression -@var{regex}. This command -sets an unconditional breakpoint on all matches, printing a list of all -breakpoints it set. Once these breakpoints are set, they are treated -just like the breakpoints set with the @code{break} command. You can -delete them, disable them, or make them conditional the same way as any -other breakpoint. - -@ifclear CONLY -When debugging C++ programs, @code{rbreak} is useful for setting -breakpoints on overloaded functions that are not members of any special -classes. -@end ifclear - -@kindex info breakpoints -@cindex @code{$_} and @code{info breakpoints} -@item info breakpoints @r{[}@var{n}@r{]} -@itemx info break @r{[}@var{n}@r{]} -@itemx info watchpoints @r{[}@var{n}@r{]} -Print a table of all breakpoints, watchpoints, and catchpoints set and -not deleted, with the following columns for each breakpoint: - -@table @emph -@item Breakpoint Numbers -@item Type -Breakpoint, watchpoint, or catchpoint. -@item Disposition -Whether the breakpoint is marked to be disabled or deleted when hit. -@item Enabled or Disabled -Enabled breakpoints are marked with @samp{y}. @samp{n} marks breakpoints -that are not enabled. -@item Address -Where the breakpoint is in your program, as a memory address -@item What -Where the breakpoint is in the source for your program, as a file and -line number. -@end table - -@noindent -If a breakpoint is conditional, @code{info break} shows the condition on -the line following the affected breakpoint; breakpoint commands, if any, -are listed after that. - -@noindent -@code{info break} with a breakpoint -number @var{n} as argument lists only that breakpoint. The -convenience variable @code{$_} and the default examining-address for -the @code{x} command are set to the address of the last breakpoint -listed (@pxref{Memory, ,Examining memory}). - -@noindent -@code{info break} displays a count of the number of times the breakpoint -has been hit. This is especially useful in conjunction with the -@code{ignore} command. You can ignore a large number of breakpoint -hits, look at the breakpoint info to see how many times the breakpoint -was hit, and then run again, ignoring one less than that number. This -will get you quickly to the last hit of that breakpoint. -@end table - -@value{GDBN} allows you to set any number of breakpoints at the same place in -your program. There is nothing silly or meaningless about this. When -the breakpoints are conditional, this is even useful -(@pxref{Conditions, ,Break conditions}). - -@cindex negative breakpoint numbers -@cindex internal @value{GDBN} breakpoints -@value{GDBN} itself sometimes sets breakpoints in your program for special -purposes, such as proper handling of @code{longjmp} (in C programs). -These internal breakpoints are assigned negative numbers, starting with -@code{-1}; @samp{info breakpoints} does not display them. - -You can see these breakpoints with the @value{GDBN} maintenance command -@samp{maint info breakpoints}. - -@table @code -@kindex maint info breakpoints -@item maint info breakpoints -Using the same format as @samp{info breakpoints}, display both the -breakpoints you've set explicitly, and those @value{GDBN} is using for -internal purposes. Internal breakpoints are shown with negative -breakpoint numbers. The type column identifies what kind of breakpoint -is shown: - -@table @code -@item breakpoint -Normal, explicitly set breakpoint. - -@item watchpoint -Normal, explicitly set watchpoint. - -@item longjmp -Internal breakpoint, used to handle correctly stepping through -@code{longjmp} calls. - -@item longjmp resume -Internal breakpoint at the target of a @code{longjmp}. - -@item until -Temporary internal breakpoint used by the @value{GDBN} @code{until} command. - -@item finish -Temporary internal breakpoint used by the @value{GDBN} @code{finish} command. - -@ifset HPPA -@item shlib events -Shared library events. -@end ifset -@end table -@end table - - -@node Set Watchpoints, Set Catchpoints, Set Breaks, Breakpoints -@subsection Setting watchpoints - -@cindex setting watchpoints -@cindex software watchpoints -@cindex hardware watchpoints -You can use a watchpoint to stop execution whenever the value of an -expression changes, without having to predict a particular place where -this may happen. - -Depending on your system, watchpoints may be implemented in software or -hardware. GDB does software watchpointing by single-stepping your -program and testing the variable's value each time, which is hundreds of -times slower than normal execution. (But this may still be worth it, to -catch errors where you have no clue what part of your program is the -culprit.) - -On some systems, such as HP-UX and Linux, GDB includes support for -hardware watchpoints, which do not slow down the running of your -program. - -@table @code -@kindex watch -@item watch @var{expr} -Set a watchpoint for an expression. @value{GDBN} will break when @var{expr} -is written into by the program and its value changes. - -@kindex rwatch -@item rwatch @var{expr} -Set a watchpoint that will break when watch @var{expr} is read by the program. -If you use both watchpoints, both must be set with the @code{rwatch} -command. - -@kindex awatch -@item awatch @var{expr} -Set a watchpoint that will break when @var{args} is read and written into -by the program. If you use both watchpoints, both must be set with the -@code{awatch} command. - -@kindex info watchpoints -@item info watchpoints -This command prints a list of watchpoints, breakpoints, and catchpoints; -it is the same as @code{info break}. -@end table - -@value{GDBN} sets a @dfn{hardware watchpoint} if possible. Hardware -watchpoints execute very quickly, and the debugger reports a change in -value at the exact instruction where the change occurs. If @value{GDBN} -cannot set a hardware watchpoint, it sets a software watchpoint, which -executes more slowly and reports the change in value at the next -statement, not the instruction, after the change occurs. - -When you issue the @code{watch} command, @value{GDBN} reports - -@example -Hardware watchpoint @var{num}: @var{expr} -@end example - -@noindent -if it was able to set a hardware watchpoint. - -The SPARClite DSU will generate traps when a program accesses -some data or instruction address that is assigned to the debug registers. -For the data addresses, DSU facilitates the @code{watch} command. -However the hardware breakpoint registers can only take two data watchpoints, -and both watchpoints must be the same kind. For example, you can set two -watchpoints with @code{watch} commands, two with @code{rwatch} -commands, @strong{or} two with @code{awatch} commands, but you cannot set one -watchpoint with one command and the other with a different command. -@value{GDBN} will reject the command if you try to mix watchpoints. -Delete or disable unused watchpoint commands before setting new ones. - -If you call a function interactively using @code{print} or @code{call}, -any watchpoints you have set will be inactive until GDB reaches another -kind of breakpoint or the call completes. - -@ifclear BARETARGET -@quotation -@cindex watchpoints and threads -@cindex threads and watchpoints -@ifclear HPPA -@emph{Warning:} In multi-thread programs, watchpoints have only limited -usefulness. With the current watchpoint implementation, @value{GDBN} -can only watch the value of an expression @emph{in a single thread}. If -you are confident that the expression can only change due to the current -thread's activity (and if you are also confident that no other thread -can become current), then you can use watchpoints as usual. However, -@value{GDBN} may not notice when a non-current thread's activity changes -the expression. -@end ifclear -@ifset HPPA -@emph{Warning:} In multi-thread programs, software watchpoints have only -limited usefulness. If @value{GDBN} creates a software watchpoint, it -can only watch the value of an expression @emph{in a single thread}. If -you are confident that the expression can only change due to the current -thread's activity (and if you are also confident that no other thread -can become current), then you can use software watchpoints as usual. -However, @value{GDBN} may not notice when a non-current thread's -activity changes the expression. (Hardware watchpoints, in contrast, -watch an expression in all threads.) -@end ifset -@end quotation -@end ifclear - -@node Set Catchpoints, Delete Breaks, Set Watchpoints, Breakpoints -@subsection Setting catchpoints -@cindex catchpoints -@cindex exception handlers -@cindex event handling - -You can use @dfn{catchpoints} to cause the debugger to stop for certain -kinds of program events, such as C++ exceptions or the loading of a -shared library. Use the @code{catch} command to set a catchpoint. - -@table @code -@kindex catch -@item catch @var{event} -Stop when @var{event} occurs. @var{event} can be any of the following: -@table @code -@item throw -@kindex catch throw -The throwing of a C++ exception. - -@item catch -@kindex catch catch -The catching of a C++ exception. - -@item exec -@kindex catch exec -A call to @code{exec}. This is currently only available for HP-UX. - -@item fork -@kindex catch fork -A call to @code{fork}. This is currently only available for HP-UX. - -@item vfork -@kindex catch vfork -A call to @code{vfork}. This is currently only available for HP-UX. - -@item load -@itemx load @var{libname} -@kindex catch load -The dynamic loading of any shared library, or the loading of the library -@var{libname}. This is currently only available for HP-UX. - -@item unload -@itemx unload @var{libname} -@kindex catch unload -The unloading of any dynamically loaded shared library, or the unloading -of the library @var{libname}. This is currently only available for HP-UX. -@end table - -@item tcatch @var{event} -Set a catchpoint that is enabled only for one stop. The catchpoint is -automatically deleted after the first time the event is caught. - -@end table - -Use the @code{info break} command to list the current catchpoints. - -There are currently some limitations to C++ exception handling -(@code{catch throw} and @code{catch catch}) in @value{GDBN}: - -@itemize @bullet -@item -If you call a function interactively, @value{GDBN} normally returns -control to you when the function has finished executing. If the call -raises an exception, however, the call may bypass the mechanism that -returns control to you and cause your program either to abort or to -simply continue running until it hits a breakpoint, catches a signal -that @value{GDBN} is listening for, or exits. This is the case even if -you set a catchpoint for the exception; catchpoints on exceptions are -disabled within interactive calls. - -@item -You cannot raise an exception interactively. - -@item -You cannot install an exception handler interactively. -@end itemize - -@cindex raise exceptions -Sometimes @code{catch} is not the best way to debug exception handling: -if you need to know exactly where an exception is raised, it is better to -stop @emph{before} the exception handler is called, since that way you -can see the stack before any unwinding takes place. If you set a -breakpoint in an exception handler instead, it may not be easy to find -out where the exception was raised. - -To stop just before an exception handler is called, you need some -knowledge of the implementation. In the case of @sc{gnu} C++, exceptions are -raised by calling a library function named @code{__raise_exception} -which has the following ANSI C interface: - -@example - /* @var{addr} is where the exception identifier is stored. - ID is the exception identifier. */ - void __raise_exception (void **@var{addr}, void *@var{id}); -@end example - -@noindent -To make the debugger catch all exceptions before any stack -unwinding takes place, set a breakpoint on @code{__raise_exception} -(@pxref{Breakpoints, ,Breakpoints; watchpoints; and exceptions}). - -With a conditional breakpoint (@pxref{Conditions, ,Break conditions}) -that depends on the value of @var{id}, you can stop your program when -a specific exception is raised. You can use multiple conditional -breakpoints to stop your program when any of a number of exceptions are -raised. - - -@node Delete Breaks, Disabling, Set Catchpoints, Breakpoints -@subsection Deleting breakpoints - -@cindex clearing breakpoints, watchpoints, catchpoints -@cindex deleting breakpoints, watchpoints, catchpoints -It is often necessary to eliminate a breakpoint, watchpoint, or -catchpoint once it has done its job and you no longer want your program -to stop there. This is called @dfn{deleting} the breakpoint. A -breakpoint that has been deleted no longer exists; it is forgotten. - -With the @code{clear} command you can delete breakpoints according to -where they are in your program. With the @code{delete} command you can -delete individual breakpoints, watchpoints, or catchpoints by specifying -their breakpoint numbers. - -It is not necessary to delete a breakpoint to proceed past it. @value{GDBN} -automatically ignores breakpoints on the first instruction to be executed -when you continue execution without changing the execution address. - -@table @code -@kindex clear -@item clear -Delete any breakpoints at the next instruction to be executed in the -selected stack frame (@pxref{Selection, ,Selecting a frame}). When -the innermost frame is selected, this is a good way to delete a -breakpoint where your program just stopped. - -@item clear @var{function} -@itemx clear @var{filename}:@var{function} -Delete any breakpoints set at entry to the function @var{function}. - -@item clear @var{linenum} -@itemx clear @var{filename}:@var{linenum} -Delete any breakpoints set at or within the code of the specified line. - -@cindex delete breakpoints -@kindex delete -@kindex d -@item delete @r{[}breakpoints@r{]} @r{[}@var{bnums}@dots{}@r{]} -Delete the breakpoints, watchpoints, or catchpoints of the numbers -specified as arguments. If no argument is specified, delete all -breakpoints (@value{GDBN} asks confirmation, unless you have @code{set -confirm off}). You can abbreviate this command as @code{d}. -@end table - -@node Disabling, Conditions, Delete Breaks, Breakpoints -@subsection Disabling breakpoints - -@kindex disable breakpoints -@kindex enable breakpoints -Rather than deleting a breakpoint, watchpoint, or catchpoint, you might -prefer to @dfn{disable} it. This makes the breakpoint inoperative as if -it had been deleted, but remembers the information on the breakpoint so -that you can @dfn{enable} it again later. - -You disable and enable breakpoints, watchpoints, and catchpoints with -the @code{enable} and @code{disable} commands, optionally specifying one -or more breakpoint numbers as arguments. Use @code{info break} or -@code{info watch} to print a list of breakpoints, watchpoints, and -catchpoints if you do not know which numbers to use. - -A breakpoint, watchpoint, or catchpoint can have any of four different -states of enablement: - -@itemize @bullet -@item -Enabled. The breakpoint stops your program. A breakpoint set -with the @code{break} command starts out in this state. -@item -Disabled. The breakpoint has no effect on your program. -@item -Enabled once. The breakpoint stops your program, but then becomes -disabled. A breakpoint set with the @code{tbreak} command starts out in -this state. -@item -Enabled for deletion. The breakpoint stops your program, but -immediately after it does so it is deleted permanently. -@end itemize - -You can use the following commands to enable or disable breakpoints, -watchpoints, and catchpoints: - -@table @code -@kindex disable breakpoints -@kindex disable -@kindex dis -@item disable @r{[}breakpoints@r{]} @r{[}@var{bnums}@dots{}@r{]} -Disable the specified breakpoints---or all breakpoints, if none are -listed. A disabled breakpoint has no effect but is not forgotten. All -options such as ignore-counts, conditions and commands are remembered in -case the breakpoint is enabled again later. You may abbreviate -@code{disable} as @code{dis}. - -@kindex enable breakpoints -@kindex enable -@item enable @r{[}breakpoints@r{]} @r{[}@var{bnums}@dots{}@r{]} -Enable the specified breakpoints (or all defined breakpoints). They -become effective once again in stopping your program. - -@item enable @r{[}breakpoints@r{]} once @var{bnums}@dots{} -Enable the specified breakpoints temporarily. @value{GDBN} disables any -of these breakpoints immediately after stopping your program. - -@item enable @r{[}breakpoints@r{]} delete @var{bnums}@dots{} -Enable the specified breakpoints to work once, then die. @value{GDBN} -deletes any of these breakpoints as soon as your program stops there. -@end table - -Except for a breakpoint set with @code{tbreak} (@pxref{Set Breaks, -,Setting breakpoints}), breakpoints that you set are initially enabled; -subsequently, they become disabled or enabled only when you use one of -the commands above. (The command @code{until} can set and delete a -breakpoint of its own, but it does not change the state of your other -breakpoints; see @ref{Continuing and Stepping, ,Continuing and -stepping}.) - -@node Conditions, Break Commands, Disabling, Breakpoints -@subsection Break conditions -@cindex conditional breakpoints -@cindex breakpoint conditions - -@c FIXME what is scope of break condition expr? Context where wanted? -@c in particular for a watchpoint? -The simplest sort of breakpoint breaks every time your program reaches a -specified place. You can also specify a @dfn{condition} for a -breakpoint. A condition is just a Boolean expression in your -programming language (@pxref{Expressions, ,Expressions}). A breakpoint with -a condition evaluates the expression each time your program reaches it, -and your program stops only if the condition is @emph{true}. - -This is the converse of using assertions for program validation; in that -situation, you want to stop when the assertion is violated---that is, -when the condition is false. In C, if you want to test an assertion expressed -by the condition @var{assert}, you should set the condition -@samp{! @var{assert}} on the appropriate breakpoint. - -Conditions are also accepted for watchpoints; you may not need them, -since a watchpoint is inspecting the value of an expression anyhow---but -it might be simpler, say, to just set a watchpoint on a variable name, -and specify a condition that tests whether the new value is an interesting -one. - -Break conditions can have side effects, and may even call functions in -your program. This can be useful, for example, to activate functions -that log program progress, or to use your own print functions to -format special data structures. The effects are completely predictable -unless there is another enabled breakpoint at the same address. (In -that case, @value{GDBN} might see the other breakpoint first and stop your -program without checking the condition of this one.) Note that -breakpoint commands are usually more convenient and flexible for the -purpose of performing side effects when a breakpoint is reached -(@pxref{Break Commands, ,Breakpoint command lists}). - -Break conditions can be specified when a breakpoint is set, by using -@samp{if} in the arguments to the @code{break} command. @xref{Set -Breaks, ,Setting breakpoints}. They can also be changed at any time -with the @code{condition} command. -@ifclear HPPA -@c The watch command now seems to recognize the if keyword. -@c catch doesn't, though. -The @code{watch} command does not recognize the @code{if} keyword; -@code{condition} is the only way to impose a further condition on a -watchpoint. -@end ifclear -@ifset HPPA -You can also use the @code{if} keyword with the @code{watch} command. -The @code{catch} command does not recognize the @code{if} keyword; -@code{condition} is the only way to impose a further condition on a -catchpoint. -@end ifset - -@table @code -@kindex condition -@item condition @var{bnum} @var{expression} -Specify @var{expression} as the break condition for breakpoint, -watchpoint, or catchpoint number @var{bnum}. After you set a condition, -breakpoint @var{bnum} stops your program only if the value of -@var{expression} is true (nonzero, in C). When you use -@code{condition}, @value{GDBN} checks @var{expression} immediately for -syntactic correctness, and to determine whether symbols in it have -referents in the context of your breakpoint. -@c FIXME so what does GDB do if there is no referent? Moreover, what -@c about watchpoints? -@value{GDBN} does -not actually evaluate @var{expression} at the time the @code{condition} -command is given, however. @xref{Expressions, ,Expressions}. - -@item condition @var{bnum} -Remove the condition from breakpoint number @var{bnum}. It becomes -an ordinary unconditional breakpoint. -@end table - -@cindex ignore count (of breakpoint) -A special case of a breakpoint condition is to stop only when the -breakpoint has been reached a certain number of times. This is so -useful that there is a special way to do it, using the @dfn{ignore -count} of the breakpoint. Every breakpoint has an ignore count, which -is an integer. Most of the time, the ignore count is zero, and -therefore has no effect. But if your program reaches a breakpoint whose -ignore count is positive, then instead of stopping, it just decrements -the ignore count by one and continues. As a result, if the ignore count -value is @var{n}, the breakpoint does not stop the next @var{n} times -your program reaches it. - -@table @code -@kindex ignore -@item ignore @var{bnum} @var{count} -Set the ignore count of breakpoint number @var{bnum} to @var{count}. -The next @var{count} times the breakpoint is reached, your program's -execution does not stop; other than to decrement the ignore count, @value{GDBN} -takes no action. - -To make the breakpoint stop the next time it is reached, specify -a count of zero. - -When you use @code{continue} to resume execution of your program from a -breakpoint, you can specify an ignore count directly as an argument to -@code{continue}, rather than using @code{ignore}. @xref{Continuing and -Stepping,,Continuing and stepping}. - -If a breakpoint has a positive ignore count and a condition, the -condition is not checked. Once the ignore count reaches zero, -@value{GDBN} resumes checking the condition. - -You could achieve the effect of the ignore count with a condition such -as @w{@samp{$foo-- <= 0}} using a debugger convenience variable that -is decremented each time. @xref{Convenience Vars, ,Convenience -variables}. -@end table - -Ignore counts apply to breakpoints, watchpoints, and catchpoints. - - -@node Break Commands, Breakpoint Menus, Conditions, Breakpoints -@subsection Breakpoint command lists - -@cindex breakpoint commands -You can give any breakpoint (or watchpoint or catchpoint) a series of -commands to execute when your program stops due to that breakpoint. For -example, you might want to print the values of certain expressions, or -enable other breakpoints. - -@table @code -@kindex commands -@kindex end -@item commands @r{[}@var{bnum}@r{]} -@itemx @dots{} @var{command-list} @dots{} -@itemx end -Specify a list of commands for breakpoint number @var{bnum}. The commands -themselves appear on the following lines. Type a line containing just -@code{end} to terminate the commands. - -To remove all commands from a breakpoint, type @code{commands} and -follow it immediately with @code{end}; that is, give no commands. - -With no @var{bnum} argument, @code{commands} refers to the last -breakpoint, watchpoint, or catchpoint set (not to the breakpoint most -recently encountered). -@end table - -Pressing @key{RET} as a means of repeating the last @value{GDBN} command is -disabled within a @var{command-list}. - -You can use breakpoint commands to start your program up again. Simply -use the @code{continue} command, or @code{step}, or any other command -that resumes execution. - -Any other commands in the command list, after a command that resumes -execution, are ignored. This is because any time you resume execution -(even with a simple @code{next} or @code{step}), you may encounter -another breakpoint---which could have its own command list, leading to -ambiguities about which list to execute. - -@kindex silent -If the first command you specify in a command list is @code{silent}, the -usual message about stopping at a breakpoint is not printed. This may -be desirable for breakpoints that are to print a specific message and -then continue. If none of the remaining commands print anything, you -see no sign that the breakpoint was reached. @code{silent} is -meaningful only at the beginning of a breakpoint command list. - -The commands @code{echo}, @code{output}, and @code{printf} allow you to -print precisely controlled output, and are often useful in silent -breakpoints. @xref{Output, ,Commands for controlled output}. - -For example, here is how you could use breakpoint commands to print the -value of @code{x} at entry to @code{foo} whenever @code{x} is positive. - -@example -break foo if x>0 -commands -silent -printf "x is %d\n",x -cont -end -@end example - -One application for breakpoint commands is to compensate for one bug so -you can test for another. Put a breakpoint just after the erroneous line -of code, give it a condition to detect the case in which something -erroneous has been done, and give it commands to assign correct values -to any variables that need them. End with the @code{continue} command -so that your program does not stop, and start with the @code{silent} -command so that no output is produced. Here is an example: - -@example -break 403 -commands -silent -set x = y + 4 -cont -end -@end example - -@ifclear CONLY -@node Breakpoint Menus, , Break Commands, Breakpoints -@subsection Breakpoint menus -@cindex overloading -@cindex symbol overloading - -Some programming languages (notably C++) permit a single function name -to be defined several times, for application in different contexts. -This is called @dfn{overloading}. When a function name is overloaded, -@samp{break @var{function}} is not enough to tell @value{GDBN} where you want -a breakpoint. If you realize this is a problem, you can use -something like @samp{break @var{function}(@var{types})} to specify which -particular version of the function you want. Otherwise, @value{GDBN} offers -you a menu of numbered choices for different possible breakpoints, and -waits for your selection with the prompt @samp{>}. The first two -options are always @samp{[0] cancel} and @samp{[1] all}. Typing @kbd{1} -sets a breakpoint at each definition of @var{function}, and typing -@kbd{0} aborts the @code{break} command without setting any new -breakpoints. - -For example, the following session excerpt shows an attempt to set a -breakpoint at the overloaded symbol @code{String::after}. -We choose three particular definitions of that function name: - -@c FIXME! This is likely to change to show arg type lists, at least -@smallexample -@group -(@value{GDBP}) b String::after -[0] cancel -[1] all -[2] file:String.cc; line number:867 -[3] file:String.cc; line number:860 -[4] file:String.cc; line number:875 -[5] file:String.cc; line number:853 -[6] file:String.cc; line number:846 -[7] file:String.cc; line number:735 -> 2 4 6 -Breakpoint 1 at 0xb26c: file String.cc, line 867. -Breakpoint 2 at 0xb344: file String.cc, line 875. -Breakpoint 3 at 0xafcc: file String.cc, line 846. -Multiple breakpoints were set. -Use the "delete" command to delete unwanted - breakpoints. -(@value{GDBP}) -@end group -@end smallexample -@end ifclear - -@c @ifclear BARETARGET -@c @node Error in Breakpoints -@c @subsection ``Cannot insert breakpoints'' -@c -@c FIXME!! 14/6/95 Is there a real example of this? Let's use it. -@c -@c Under some operating systems, breakpoints cannot be used in a program if -@c any other process is running that program. In this situation, -@c attempting to run or continue a program with a breakpoint causes -@c @value{GDBN} to stop the other process. -@c -@c When this happens, you have three ways to proceed: -@c -@c @enumerate -@c @item -@c Remove or disable the breakpoints, then continue. -@c -@c @item -@c Suspend @value{GDBN}, and copy the file containing your program to a new -@c name. Resume @value{GDBN} and use the @code{exec-file} command to specify -@c that @value{GDBN} should run your program under that name. -@c Then start your program again. -@c -@c @item -@c Relink your program so that the text segment is nonsharable, using the -@c linker option @samp{-N}. The operating system limitation may not apply -@c to nonsharable executables. -@c @end enumerate -@c @end ifclear - -@node Continuing and Stepping, Signals, Breakpoints, Stopping -@section Continuing and stepping - -@cindex stepping -@cindex continuing -@cindex resuming execution -@dfn{Continuing} means resuming program execution until your program -completes normally. In contrast, @dfn{stepping} means executing just -one more ``step'' of your program, where ``step'' may mean either one -line of source code, or one machine instruction (depending on what -particular command you use). Either when continuing -or when stepping, your program may stop even sooner, due to -@ifset BARETARGET -a breakpoint. -@end ifset -@ifclear BARETARGET -a breakpoint or a signal. (If due to a signal, you may want to use -@code{handle}, or use @samp{signal 0} to resume execution. -@xref{Signals, ,Signals}.) -@end ifclear - -@table @code -@kindex continue -@kindex c -@kindex fg -@item continue @r{[}@var{ignore-count}@r{]} -@itemx c @r{[}@var{ignore-count}@r{]} -@itemx fg @r{[}@var{ignore-count}@r{]} -Resume program execution, at the address where your program last stopped; -any breakpoints set at that address are bypassed. The optional argument -@var{ignore-count} allows you to specify a further number of times to -ignore a breakpoint at this location; its effect is like that of -@code{ignore} (@pxref{Conditions, ,Break conditions}). - -The argument @var{ignore-count} is meaningful only when your program -stopped due to a breakpoint. At other times, the argument to -@code{continue} is ignored. - -The synonyms @code{c} and @code{fg} are provided purely for convenience, -and have exactly the same behavior as @code{continue}. -@end table - -To resume execution at a different place, you can use @code{return} -(@pxref{Returning, ,Returning from a function}) to go back to the -calling function; or @code{jump} (@pxref{Jumping, ,Continuing at a -different address}) to go to an arbitrary location in your program. - -A typical technique for using stepping is to set a breakpoint -(@pxref{Breakpoints, ,Breakpoints; watchpoints; and catchpoints}) at the -beginning of the function or the section of your program where a problem -is believed to lie, run your program until it stops at that breakpoint, -and then step through the suspect area, examining the variables that are -interesting, until you see the problem happen. - -@table @code -@kindex step -@kindex s -@item step -Continue running your program until control reaches a different source -line, then stop it and return control to @value{GDBN}. This command is -abbreviated @code{s}. - -@quotation -@c "without debugging information" is imprecise; actually "without line -@c numbers in the debugging information". (gcc -g1 has debugging info but -@c not line numbers). But it seems complex to try to make that -@c distinction here. -@emph{Warning:} If you use the @code{step} command while control is -within a function that was compiled without debugging information, -execution proceeds until control reaches a function that does have -debugging information. Likewise, it will not step into a function which -is compiled without debugging information. To step through functions -without debugging information, use the @code{stepi} command, described -below. -@end quotation - -The @code{step} command now only stops at the first instruction of a -source line. This prevents the multiple stops that used to occur in -switch statements, for loops, etc. @code{step} continues to stop if a -function that has debugging information is called within the line. - -Also, the @code{step} command now only enters a subroutine if there is line -number information for the subroutine. Otherwise it acts like the -@code{next} command. This avoids problems when using @code{cc -gl} -on MIPS machines. Previously, @code{step} entered subroutines if there -was any debugging information about the routine. - -@item step @var{count} -Continue running as in @code{step}, but do so @var{count} times. If a -breakpoint is reached, -@ifclear BARETARGET -or a signal not related to stepping occurs before @var{count} steps, -@end ifclear -stepping stops right away. - -@kindex next -@kindex n -@item next @r{[}@var{count}@r{]} -Continue to the next source line in the current (innermost) stack frame. -This is similar to @code{step}, but function calls that appear within the line -of code are executed without stopping. Execution stops when control -reaches a different line of code at the original stack level that was -executing when you gave the @code{next} command. This command is abbreviated -@code{n}. - -An argument @var{count} is a repeat count, as for @code{step}. - - -@c FIX ME!! Do we delete this, or is there a way it fits in with -@c the following paragraph? --- Vctoria -@c -@c @code{next} within a function that lacks debugging information acts like -@c @code{step}, but any function calls appearing within the code of the -@c function are executed without stopping. - -The @code{next} command now only stops at the first instruction of a -source line. This prevents the multiple stops that used to occur in -switch statements, for loops, etc. - -@kindex finish -@item finish -Continue running until just after function in the selected stack frame -returns. Print the returned value (if any). - -Contrast this with the @code{return} command (@pxref{Returning, -,Returning from a function}). - -@kindex until -@kindex u -@item until -@itemx u -Continue running until a source line past the current line, in the -current stack frame, is reached. This command is used to avoid single -stepping through a loop more than once. It is like the @code{next} -command, except that when @code{until} encounters a jump, it -automatically continues execution until the program counter is greater -than the address of the jump. - -This means that when you reach the end of a loop after single stepping -though it, @code{until} makes your program continue execution until it -exits the loop. In contrast, a @code{next} command at the end of a loop -simply steps back to the beginning of the loop, which forces you to step -through the next iteration. - -@code{until} always stops your program if it attempts to exit the current -stack frame. - -@code{until} may produce somewhat counterintuitive results if the order -of machine code does not match the order of the source lines. For -example, in the following excerpt from a debugging session, the @code{f} -(@code{frame}) command shows that execution is stopped at line -@code{206}; yet when we use @code{until}, we get to line @code{195}: - -@example -(@value{GDBP}) f -#0 main (argc=4, argv=0xf7fffae8) at m4.c:206 -206 expand_input(); -(@value{GDBP}) until -195 for ( ; argc > 0; NEXTARG) @{ -@end example - -This happened because, for execution efficiency, the compiler had -generated code for the loop closure test at the end, rather than the -start, of the loop---even though the test in a C @code{for}-loop is -written before the body of the loop. The @code{until} command appeared -to step back to the beginning of the loop when it advanced to this -expression; however, it has not really gone to an earlier -statement---not in terms of the actual machine code. - -@code{until} with no argument works by means of single -instruction stepping, and hence is slower than @code{until} with an -argument. - -@item until @var{location} -@itemx u @var{location} -Continue running your program until either the specified location is -reached, or the current stack frame returns. @var{location} is any of -the forms of argument acceptable to @code{break} (@pxref{Set Breaks, -,Setting breakpoints}). This form of the command uses breakpoints, -and hence is quicker than @code{until} without an argument. - -@kindex stepi -@kindex si -@item stepi -@itemx si -Execute one machine instruction, then stop and return to the debugger. - -It is often useful to do @samp{display/i $pc} when stepping by machine -instructions. This makes @value{GDBN} automatically display the next -instruction to be executed, each time your program stops. @xref{Auto -Display,, Automatic display}. - -An argument is a repeat count, as in @code{step}. - -@need 750 -@kindex nexti -@kindex ni -@item nexti -@itemx ni -Execute one machine instruction, but if it is a function call, -proceed until the function returns. - -An argument is a repeat count, as in @code{next}. -@end table - -@ifset POSIX -@node Signals, Thread Stops, Continuing and Stepping, Stopping -@section Signals -@cindex signals - -A signal is an asynchronous event that can happen in a program. The -operating system defines the possible kinds of signals, and gives each -kind a name and a number. For example, in Unix @code{SIGINT} is the -signal a program gets when you type an interrupt (often @kbd{C-c}); -@code{SIGSEGV} is the signal a program gets from referencing a place in -memory far away from all the areas in use; @code{SIGALRM} occurs when -the alarm clock timer goes off (which happens only if your program has -requested an alarm). - -@cindex fatal signals -Some signals, including @code{SIGALRM}, are a normal part of the -functioning of your program. Others, such as @code{SIGSEGV}, indicate -errors; these signals are @dfn{fatal} (kill your program immediately) if the -program has not specified in advance some other way to handle the signal. -@code{SIGINT} does not indicate an error in your program, but it is normally -fatal so it can carry out the purpose of the interrupt: to kill the program. - -@value{GDBN} has the ability to detect any occurrence of a signal in your -program. You can tell @value{GDBN} in advance what to do for each kind of -signal. - -@cindex handling signals -Normally, @value{GDBN} is set up to ignore non-erroneous signals like @code{SIGALRM} -(so as not to interfere with their role in the functioning of your program) -but to stop your program immediately whenever an error signal happens. -You can change these settings with the @code{handle} command. - -@table @code -@kindex info signals -@item info signals -Print a table of all the kinds of signals and how @value{GDBN} has been told to -handle each one. You can use this to see the signal numbers of all -the defined types of signals. - -@code{info handle} is the new alias for @code{info signals}. - -@kindex handle -@item handle @var{signal} @var{keywords}@dots{} -Change the way @value{GDBN} handles signal @var{signal}. @var{signal} can -be the number of a signal or its name (with or without the @samp{SIG} at the -beginning). The @var{keywords} say what change to make. -@end table - -@c @group -The keywords allowed by the @code{handle} command can be abbreviated. -Their full names are: - -@table @code -@item nostop -@value{GDBN} should not stop your program when this signal happens. It may -still print a message telling you that the signal has come in. - -@item stop -@value{GDBN} should stop your program when this signal happens. This implies -the @code{print} keyword as well. - -@item print -@value{GDBN} should print a message when this signal happens. - -@item noprint -@value{GDBN} should not mention the occurrence of the signal at all. This -implies the @code{nostop} keyword as well. - -@item pass -@value{GDBN} should allow your program to see this signal; your program -can handle the signal, or else it may terminate if the signal is fatal -and not handled. - -@item nopass -@value{GDBN} should not allow your program to see this signal. -@end table -@c @end group - -When a signal stops your program, the signal is not visible until you -continue. Your program sees the signal then, if @code{pass} is in -effect for the signal in question @emph{at that time}. In other words, -after @value{GDBN} reports a signal, you can use the @code{handle} -command with @code{pass} or @code{nopass} to control whether your -program sees that signal when you continue. - -You can also use the @code{signal} command to prevent your program from -seeing a signal, or cause it to see a signal it normally would not see, -or to give it any signal at any time. For example, if your program stopped -due to some sort of memory reference error, you might store correct -values into the erroneous variables and continue, hoping to see more -execution; but your program would probably terminate immediately as -a result of the fatal signal once it saw the signal. To prevent this, -you can continue with @samp{signal 0}. @xref{Signaling, ,Giving your -program a signal}. -@end ifset - -@ifclear BARETARGET -@node Thread Stops, , Signals, Stopping -@section Stopping and starting multi-thread programs - -When your program has multiple threads (@pxref{Threads,, Debugging -programs with multiple threads}), you can choose whether to set -breakpoints on all threads, or on a particular thread. - -@table @code -@cindex breakpoints and threads -@cindex thread breakpoints -@kindex break @dots{} thread @var{threadno} -@item break @var{linespec} thread @var{threadno} -@itemx break @var{linespec} thread @var{threadno} if @dots{} -@var{linespec} specifies source lines; there are several ways of -writing them, but the effect is always to specify some source line. - -Use the qualifier @samp{thread @var{threadno}} with a breakpoint command -to specify that you only want @value{GDBN} to stop the program when a -particular thread reaches this breakpoint. @var{threadno} is one of the -numeric thread identifiers assigned by @value{GDBN}, shown in the first -column of the @samp{info threads} display. - -If you do not specify @samp{thread @var{threadno}} when you set a -breakpoint, the breakpoint applies to @emph{all} threads of your -program. - -You can use the @code{thread} qualifier on conditional breakpoints as -well; in this case, place @samp{thread @var{threadno}} before the -breakpoint condition, like this: - -@smallexample -(gdb) break frik.c:13 thread 28 if bartab > lim -@end smallexample - -@end table - -@cindex stopped threads -@cindex threads, stopped -Whenever your program stops under @value{GDBN} for any reason, -@emph{all} threads of execution stop, not just the current thread. This -allows you to examine the overall state of the program, including -switching between threads, without worrying that things may change -underfoot. - -@cindex continuing threads -@cindex threads, continuing -Conversely, whenever you restart the program, @emph{all} threads start -executing. @emph{This is true even when single-stepping} with commands -like @code{step} or @code{next}. - -In particular, @value{GDBN} cannot single-step all threads in lockstep. -Since thread scheduling is up to your debugging target's operating -system (not controlled by @value{GDBN}), other threads may -execute more than one statement while the current thread completes a -single step. Moreover, in general other threads stop in the middle of a -statement, rather than at a clean statement boundary, when the program -stops. - -You might even find your program stopped in another thread after -continuing or even single-stepping. This happens whenever some other -thread runs into a breakpoint, a signal, or an exception before the -first thread completes whatever you requested. - -On some OSes, you can lock the OS scheduler and thus allow only a single -thread to run. - -@table @code -@item set scheduler-locking @var{mode} -Set the scheduler locking mode. If it is @code{off}, then there is no -locking and any thread may run at any time. If @code{on}, then only the -current thread may run when the inferior is resumed. The @code{step} -mode optimizes for single-stepping. It stops other threads from -``seizing the prompt'' by preempting the current thread while you are -stepping. Other threads will only rarely (or never) get a chance to run -when you step. They are more likely to run when you ``next'' over a -function call, and they are completely free to run when you use commands -like ``continue'', ``until'', or ``finish''. However, unless another -thread hits a breakpoint during its timeslice, they will never steal the -GDB prompt away from the thread that you are debugging. - -@item show scheduler-locking -Display the current scheduler locking mode. -@end table - -@end ifclear - - -@node Stack, Source, Stopping, Top -@chapter Examining the Stack - -When your program has stopped, the first thing you need to know is where it -stopped and how it got there. - -@cindex call stack -Each time your program performs a function call, information about the call -is generated. -That information includes the location of the call in your program, -the arguments of the call, -and the local variables of the function being called. -The information is saved in a block of data called a @dfn{stack frame}. -The stack frames are allocated in a region of memory called the @dfn{call -stack}. - -When your program stops, the @value{GDBN} commands for examining the -stack allow you to see all of this information. - -@cindex selected frame -One of the stack frames is @dfn{selected} by @value{GDBN} and many -@value{GDBN} commands refer implicitly to the selected frame. In -particular, whenever you ask @value{GDBN} for the value of a variable in -your program, the value is found in the selected frame. There are -special @value{GDBN} commands to select whichever frame you are -interested in. @xref{Selection, ,Selecting a frame}. - -When your program stops, @value{GDBN} automatically selects the -currently executing frame and describes it briefly, similar to the -@code{frame} command (@pxref{Frame Info, ,Information about a frame}). - -@menu -* Frames:: Stack frames -* Backtrace:: Backtraces -* Selection:: Selecting a frame -* Frame Info:: Information on a frame -* Alpha/MIPS Stack:: Alpha and MIPS machines and the function stack - -@end menu - -@node Frames, Backtrace, Stack, Stack -@section Stack frames - -@cindex frame -@cindex stack frame -The call stack is divided up into contiguous pieces called @dfn{stack -frames}, or @dfn{frames} for short; each frame is the data associated -with one call to one function. The frame contains the arguments given -to the function, the function's local variables, and the address at -which the function is executing. - -@cindex initial frame -@cindex outermost frame -@cindex innermost frame -When your program is started, the stack has only one frame, that of the -function @code{main}. This is called the @dfn{initial} frame or the -@dfn{outermost} frame. Each time a function is called, a new frame is -made. Each time a function returns, the frame for that function invocation -is eliminated. If a function is recursive, there can be many frames for -the same function. The frame for the function in which execution is -actually occurring is called the @dfn{innermost} frame. This is the most -recently created of all the stack frames that still exist. - -@cindex frame pointer -Inside your program, stack frames are identified by their addresses. A -stack frame consists of many bytes, each of which has its own address; each -kind of computer has a convention for choosing one byte whose -address serves as the address of the frame. Usually this address is kept -in a register called the @dfn{frame pointer register} while execution is -going on in that frame. - -@cindex frame number -@value{GDBN} assigns numbers to all existing stack frames, starting with -zero for the innermost frame, one for the frame that called it, -and so on upward. These numbers do not really exist in your program; -they are assigned by @value{GDBN} to give you a way of designating stack -frames in @value{GDBN} commands. - -@c below produces an acceptable overful hbox. --mew 13aug1993 -@cindex frameless execution -Some compilers provide a way to compile functions so that they operate -without stack frames. (For example, the @code{@value{GCC}} option -@samp{-fomit-frame-pointer} generates functions without a frame.) -This is occasionally done with heavily used library functions to save -the frame setup time. @value{GDBN} has limited facilities for dealing -with these function invocations. If the innermost function invocation -has no stack frame, @value{GDBN} nevertheless regards it as though -it had a separate frame, which is numbered zero as usual, allowing -correct tracing of the function call chain. However, @value{GDBN} has -no provision for frameless functions elsewhere in the stack. - -@table @code -@kindex frame -@item frame @var{args} -The @code{frame} command allows you to move from one stack frame to another, -and to print the stack frame you select. @var{args} may be either the -address of the frame or the stack frame number. Without an argument, -@code{frame} prints the current stack frame. - -@kindex select-frame -@item select-frame -The @code{select-frame} command allows you to move from one stack frame -to another without printing the frame. This is the silent version of -@code{frame}. -@end table - -@node Backtrace, Selection, Frames, Stack -@section Backtraces - -@cindex backtraces -@cindex tracebacks -@cindex stack traces -A backtrace is a summary of how your program got where it is. It shows one -line per frame, for many frames, starting with the currently executing -frame (frame zero), followed by its caller (frame one), and on up the -stack. - -@table @code -@kindex backtrace -@kindex bt -@item backtrace -@itemx bt -Print a backtrace of the entire stack: one line per frame for all -frames in the stack. - -You can stop the backtrace at any time by typing the system interrupt -character, normally @kbd{C-c}. - -@item backtrace @var{n} -@itemx bt @var{n} -Similar, but print only the innermost @var{n} frames. - -@item backtrace -@var{n} -@itemx bt -@var{n} -Similar, but print only the outermost @var{n} frames. -@end table - -@kindex where -@kindex info stack -@kindex info s -The names @code{where} and @code{info stack} (abbreviated @code{info s}) -are additional aliases for @code{backtrace}. - -Each line in the backtrace shows the frame number and the function name. -The program counter value is also shown---unless you use @code{set -print address off}. The backtrace also shows the source file name and -line number, as well as the arguments to the function. The program -counter value is omitted if it is at the beginning of the code for that -line number. - -Here is an example of a backtrace. It was made with the command -@samp{bt 3}, so it shows the innermost three frames. - -@smallexample -@group -#0 m4_traceon (obs=0x24eb0, argc=1, argv=0x2b8c8) - at builtin.c:993 -#1 0x6e38 in expand_macro (sym=0x2b600) at macro.c:242 -#2 0x6840 in expand_token (obs=0x0, t=177664, td=0xf7fffb08) - at macro.c:71 -(More stack frames follow...) -@end group -@end smallexample - -@noindent -The display for frame zero does not begin with a program counter -value, indicating that your program has stopped at the beginning of the -code for line @code{993} of @code{builtin.c}. - -@node Selection, Frame Info, Backtrace, Stack -@section Selecting a frame - -Most commands for examining the stack and other data in your program work on -whichever stack frame is selected at the moment. Here are the commands for -selecting a stack frame; all of them finish by printing a brief description -of the stack frame just selected. - -@table @code -@kindex frame -@kindex f -@item frame @var{n} -@itemx f @var{n} -Select frame number @var{n}. Recall that frame zero is the innermost -(currently executing) frame, frame one is the frame that called the -innermost one, and so on. The highest-numbered frame is the one for -@code{main}. - -@item frame @var{addr} -@itemx f @var{addr} -Select the frame at address @var{addr}. This is useful mainly if the -chaining of stack frames has been damaged by a bug, making it -impossible for @value{GDBN} to assign numbers properly to all frames. In -addition, this can be useful when your program has multiple stacks and -switches between them. - -@ifclear H8EXCLUSIVE -@ifclear HPPA -On the SPARC architecture, @code{frame} needs two addresses to -select an arbitrary frame: a frame pointer and a stack pointer. - -On the MIPS and Alpha architecture, it needs two addresses: a stack -pointer and a program counter. - -On the 29k architecture, it needs three addresses: a register stack -pointer, a program counter, and a memory stack pointer. -@c note to future updaters: this is conditioned on a flag -@c SETUP_ARBITRARY_FRAME in the tm-*.h files. The above is up to date -@c as of 27 Jan 1994. -@end ifclear -@end ifclear - -@kindex up -@item up @var{n} -Move @var{n} frames up the stack. For positive numbers @var{n}, this -advances toward the outermost frame, to higher frame numbers, to frames -that have existed longer. @var{n} defaults to one. - -@kindex down -@kindex do -@item down @var{n} -Move @var{n} frames down the stack. For positive numbers @var{n}, this -advances toward the innermost frame, to lower frame numbers, to frames -that were created more recently. @var{n} defaults to one. You may -abbreviate @code{down} as @code{do}. -@end table - -All of these commands end by printing two lines of output describing the -frame. The first line shows the frame number, the function name, the -arguments, and the source file and line number of execution in that -frame. The second line shows the text of that source line. - -@need 1000 -For example: - -@smallexample -@group -(@value{GDBP}) up -#1 0x22f0 in main (argc=1, argv=0xf7fffbf4, env=0xf7fffbfc) - at env.c:10 -10 read_input_file (argv[i]); -@end group -@end smallexample - -After such a printout, the @code{list} command with no arguments -prints ten lines centered on the point of execution in the frame. -@xref{List, ,Printing source lines}. - -@table @code -@kindex down-silently -@kindex up-silently -@item up-silently @var{n} -@itemx down-silently @var{n} -These two commands are variants of @code{up} and @code{down}, -respectively; they differ in that they do their work silently, without -causing display of the new frame. They are intended primarily for use -in @value{GDBN} command scripts, where the output might be unnecessary and -distracting. -@end table - -@node Frame Info, Alpha/MIPS Stack, Selection, Stack -@section Information about a frame - -There are several other commands to print information about the selected -stack frame. - -@table @code -@item frame -@itemx f -When used without any argument, this command does not change which -frame is selected, but prints a brief description of the currently -selected stack frame. It can be abbreviated @code{f}. With an -argument, this command is used to select a stack frame. -@xref{Selection, ,Selecting a frame}. - -@kindex info frame -@kindex info f -@item info frame -@itemx info f -This command prints a verbose description of the selected stack frame, -including: - -@itemize @bullet -@item -the address of the frame -@item -the address of the next frame down (called by this frame) -@item -the address of the next frame up (caller of this frame) -@item -the language in which the source code corresponding to this frame is written -@item -the address of the frame's arguments -@item -the program counter saved in it (the address of execution in the caller frame) -@item -which registers were saved in the frame -@end itemize - -@noindent The verbose description is useful when -something has gone wrong that has made the stack format fail to fit -the usual conventions. - -@item info frame @var{addr} -@itemx info f @var{addr} -Print a verbose description of the frame at address @var{addr}, without -selecting that frame. The selected frame remains unchanged by this -command. This requires the same kind of address (more than one for some -architectures) that you specify in the @code{frame} command. -@xref{Selection, ,Selecting a frame}. - -@kindex info args -@item info args -Print the arguments of the selected frame, each on a separate line. - -@item info locals -@kindex info locals -Print the local variables of the selected frame, each on a separate -line. These are all variables (declared either static or automatic) -accessible at the point of execution of the selected frame. - -@ifclear CONLY -@ifclear HPPA -@kindex info catch -@cindex catch exceptions -@cindex exception handlers -@item info catch -Print a list of all the exception handlers that are active in the -current stack frame at the current point of execution. To see other -exception handlers, visit the associated frame (using the @code{up}, -@code{down}, or @code{frame} commands); then type @code{info catch}. -@xref{Set Catchpoints, , Setting catchpoints}. -@end ifclear -@end ifclear -@end table - -@node Alpha/MIPS Stack, , Frame Info, Stack -@section MIPS/Alpha machines and the function stack - -@cindex stack on Alpha -@cindex stack on MIPS -@cindex Alpha stack -@cindex MIPS stack -Alpha- and MIPS-based computers use an unusual stack frame, which -sometimes requires @value{GDBN} to search backward in the object code to -find the beginning of a function. - -@cindex response time, MIPS debugging -To improve response time (especially for embedded applications, where -@value{GDBN} may be restricted to a slow serial line for this search) -you may want to limit the size of this search, using one of these -commands: - -@table @code -@cindex @code{heuristic-fence-post} (Alpha,MIPS) -@item set heuristic-fence-post @var{limit} -Restrict @value{GDBN} to examining at most @var{limit} bytes in its search -for the beginning of a function. A value of @var{0} (the default) -means there is no limit. However, except for @var{0}, the larger the -limit the more bytes @code{heuristic-fence-post} must search and -therefore the longer it takes to run. - -@item show heuristic-fence-post -Display the current limit. -@end table - -@noindent -These commands are available @emph{only} when @value{GDBN} is configured -for debugging programs on Alpha or MIPS processors. - - -@node Source, Data, Stack, Top -@chapter Examining Source Files - -@value{GDBN} can print parts of your program's source, since the debugging -information recorded in the program tells @value{GDBN} what source files were -used to build it. When your program stops, @value{GDBN} spontaneously prints -the line where it stopped. Likewise, when you select a stack frame -(@pxref{Selection, ,Selecting a frame}), @value{GDBN} prints the line where -execution in that frame has stopped. You can print other portions of -source files by explicit command. - -@ifclear DOSHOST -If you use @value{GDBN} through its @sc{gnu} Emacs interface, you may prefer -to use -Emacs facilities to view source; @pxref{Emacs, ,Using @value{GDBN} under @sc{gnu} Emacs}. -@end ifclear - -@menu -* List:: Printing source lines -@ifclear DOSHOST -* Search:: Searching source files -@end ifclear - -* Source Path:: Specifying source directories -* Machine Code:: Source and machine code -@end menu - -@node List, Search, Source, Source -@section Printing source lines - -@kindex list -@kindex l -To print lines from a source file, use the @code{list} command -(abbreviated @code{l}). By default, ten lines are printed. -There are several ways to specify what part of the file you want to print. - -Here are the forms of the @code{list} command most commonly used: - -@table @code -@item list @var{linenum} -Print lines centered around line number @var{linenum} in the -current source file. - -@item list @var{function} -Print lines centered around the beginning of function -@var{function}. - -@item list -Print more lines. If the last lines printed were printed with a -@code{list} command, this prints lines following the last lines -printed; however, if the last line printed was a solitary line printed -as part of displaying a stack frame (@pxref{Stack, ,Examining the -Stack}), this prints lines centered around that line. - -@item list - -Print lines just before the lines last printed. -@end table - -By default, @value{GDBN} prints ten source lines with any of these forms of -the @code{list} command. You can change this using @code{set listsize}: - -@table @code -@kindex set listsize -@item set listsize @var{count} -Make the @code{list} command display @var{count} source lines (unless -the @code{list} argument explicitly specifies some other number). - -@kindex show listsize -@item show listsize -Display the number of lines that @code{list} prints. -@end table - -Repeating a @code{list} command with @key{RET} discards the argument, -so it is equivalent to typing just @code{list}. This is more useful -than listing the same lines again. An exception is made for an -argument of @samp{-}; that argument is preserved in repetition so that -each repetition moves up in the source file. - -@cindex linespec -In general, the @code{list} command expects you to supply zero, one or two -@dfn{linespecs}. Linespecs specify source lines; there are several ways -of writing them but the effect is always to specify some source line. -Here is a complete description of the possible arguments for @code{list}: - -@table @code -@item list @var{linespec} -Print lines centered around the line specified by @var{linespec}. - -@item list @var{first},@var{last} -Print lines from @var{first} to @var{last}. Both arguments are -linespecs. - -@item list ,@var{last} -Print lines ending with @var{last}. - -@item list @var{first}, -Print lines starting with @var{first}. - -@item list + -Print lines just after the lines last printed. - -@item list - -Print lines just before the lines last printed. - -@item list -As described in the preceding table. -@end table - -Here are the ways of specifying a single source line---all the -kinds of linespec. - -@table @code -@item @var{number} -Specifies line @var{number} of the current source file. -When a @code{list} command has two linespecs, this refers to -the same source file as the first linespec. - -@item +@var{offset} -Specifies the line @var{offset} lines after the last line printed. -When used as the second linespec in a @code{list} command that has -two, this specifies the line @var{offset} lines down from the -first linespec. - -@item -@var{offset} -Specifies the line @var{offset} lines before the last line printed. - -@item @var{filename}:@var{number} -Specifies line @var{number} in the source file @var{filename}. - -@item @var{function} -Specifies the line that begins the body of the function @var{function}. -For example: in C, this is the line with the open brace. - -@item @var{filename}:@var{function} -Specifies the line of the open-brace that begins the body of the -function @var{function} in the file @var{filename}. You only need the -file name with a function name to avoid ambiguity when there are -identically named functions in different source files. - -@item *@var{address} -Specifies the line containing the program address @var{address}. -@var{address} may be any expression. -@end table - -@ifclear DOSHOST -@node Search, Source Path, List, Source -@section Searching source files -@cindex searching -@kindex reverse-search - -There are two commands for searching through the current source file for a -regular expression. - -@table @code -@kindex search -@kindex forward-search -@item forward-search @var{regexp} -@itemx search @var{regexp} -The command @samp{forward-search @var{regexp}} checks each line, -starting with the one following the last line listed, for a match for -@var{regexp}. It lists the line that is found. You can use the -synonym @samp{search @var{regexp}} or abbreviate the command name as -@code{fo}. - -@item reverse-search @var{regexp} -The command @samp{reverse-search @var{regexp}} checks each line, starting -with the one before the last line listed and going backward, for a match -for @var{regexp}. It lists the line that is found. You can abbreviate -this command as @code{rev}. -@end table -@end ifclear - -@node Source Path, Machine Code, Search, Source -@section Specifying source directories - -@cindex source path -@cindex directories for source files -Executable programs sometimes do not record the directories of the source -files from which they were compiled, just the names. Even when they do, -the directories could be moved between the compilation and your debugging -session. @value{GDBN} has a list of directories to search for source files; -this is called the @dfn{source path}. Each time @value{GDBN} wants a source file, -it tries all the directories in the list, in the order they are present -in the list, until it finds a file with the desired name. Note that -the executable search path is @emph{not} used for this purpose. Neither is -the current working directory, unless it happens to be in the source -path. - -If @value{GDBN} cannot find a source file in the source path, and the -object program records a directory, @value{GDBN} tries that directory -too. If the source path is empty, and there is no record of the -compilation directory, @value{GDBN} looks in the current directory as a -last resort. - -Whenever you reset or rearrange the source path, @value{GDBN} clears out -any information it has cached about where source files are found and where -each line is in the file. - -@kindex directory -@kindex dir -When you start @value{GDBN}, its source path is empty. -To add other directories, use the @code{directory} command. - -@table @code -@item directory @var{dirname} @dots{} -@item dir @var{dirname} @dots{} -Add directory @var{dirname} to the front of the source path. Several -directory names may be given to this command, separated by @samp{:} or -whitespace. You may specify a directory that is already in the source -path; this moves it forward, so @value{GDBN} searches it sooner. - -@kindex cdir -@kindex cwd -@kindex $cdir -@kindex $cwd -@cindex compilation directory -@cindex current directory -@cindex working directory -@cindex directory, current -@cindex directory, compilation -You can use the string @samp{$cdir} to refer to the compilation -directory (if one is recorded), and @samp{$cwd} to refer to the current -working directory. @samp{$cwd} is not the same as @samp{.}---the former -tracks the current working directory as it changes during your @value{GDBN} -session, while the latter is immediately expanded to the current -directory at the time you add an entry to the source path. - -@item directory -Reset the source path to empty again. This requires confirmation. - -@c RET-repeat for @code{directory} is explicitly disabled, but since -@c repeating it would be a no-op we do not say that. (thanks to RMS) - -@item show directories -@kindex show directories -Print the source path: show which directories it contains. -@end table - -If your source path is cluttered with directories that are no longer of -interest, @value{GDBN} may sometimes cause confusion by finding the wrong -versions of source. You can correct the situation as follows: - -@enumerate -@item -Use @code{directory} with no argument to reset the source path to empty. - -@item -Use @code{directory} with suitable arguments to reinstall the -directories you want in the source path. You can add all the -directories in one command. -@end enumerate - -@node Machine Code, , Source Path, Source -@section Source and machine code - -You can use the command @code{info line} to map source lines to program -addresses (and vice versa), and the command @code{disassemble} to display -a range of addresses as machine instructions. When run under @sc{gnu} Emacs -mode, the @code{info line} command now causes the arrow to point to the -line specified. Also, @code{info line} prints addresses in symbolic form as -well as hex. - -@table @code -@kindex info line -@item info line @var{linespec} -Print the starting and ending addresses of the compiled code for -source line @var{linespec}. You can specify source lines in any of -the ways understood by the @code{list} command (@pxref{List, ,Printing -source lines}). -@end table - -For example, we can use @code{info line} to discover the location of -the object code for the first line of function -@code{m4_changequote}: - -@smallexample -(@value{GDBP}) info line m4_changecom -Line 895 of "builtin.c" starts at pc 0x634c and ends at 0x6350. -@end smallexample - -@noindent -We can also inquire (using @code{*@var{addr}} as the form for -@var{linespec}) what source line covers a particular address: -@smallexample -(@value{GDBP}) info line *0x63ff -Line 926 of "builtin.c" starts at pc 0x63e4 and ends at 0x6404. -@end smallexample - -@cindex @code{$_} and @code{info line} -After @code{info line}, the default address for the @code{x} command -is changed to the starting address of the line, so that @samp{x/i} is -sufficient to begin examining the machine code (@pxref{Memory, -,Examining memory}). Also, this address is saved as the value of the -convenience variable @code{$_} (@pxref{Convenience Vars, ,Convenience -variables}). - -@table @code -@kindex disassemble -@cindex assembly instructions -@cindex instructions, assembly -@cindex machine instructions -@cindex listing machine instructions -@item disassemble -This specialized command dumps a range of memory as machine -instructions. The default memory range is the function surrounding the -program counter of the selected frame. A single argument to this -command is a program counter value; @value{GDBN} dumps the function -surrounding this value. Two arguments specify a range of addresses -(first inclusive, second exclusive) to dump. -@end table - -@ifclear H8EXCLUSIVE -The following example shows the disassembly of a range of addresses of -HP PA-RISC 2.0 code: - -@smallexample -(@value{GDBP}) disas 0x32c4 0x32e4 -Dump of assembler code from 0x32c4 to 0x32e4: -0x32c4 <main+204>: addil 0,dp -0x32c8 <main+208>: ldw 0x22c(sr0,r1),r26 -0x32cc <main+212>: ldil 0x3000,r31 -0x32d0 <main+216>: ble 0x3f8(sr4,r31) -0x32d4 <main+220>: ldo 0(r31),rp -0x32d8 <main+224>: addil -0x800,dp -0x32dc <main+228>: ldo 0x588(r1),r26 -0x32e0 <main+232>: ldil 0x3000,r31 -End of assembler dump. -@end smallexample -@end ifclear - -@ifset H8EXCLUSIVE -For example, here is the beginning of the output for the -disassembly of a function @code{fact}: - - -@smallexample -(@value{GDBP}) disas fact -Dump of assembler code for function fact: -to 0x808c: -0x802c <fact>: 6d f2 mov.w r2,@@-r7 -0x802e <fact+2>: 6d f3 mov.w r3,@@-r7 -0x8030 <fact+4>: 6d f6 mov.w r6,@@-r7 -0x8032 <fact+6>: 0d 76 mov.w r7,r6 -0x8034 <fact+8>: 6f 70 00 08 mov.w @@(0x8,r7),r0 -0x8038 <fact+12> 19 11 sub.w r1,r1 - . - . - . -@end smallexample -@end ifset - -Some architectures have more than one commonly-used set of instruction -mnemonics or other syntax. - -@table @code -@kindex set assembly-language -@cindex assembly instructions -@cindex instructions, assembly -@cindex machine instructions -@cindex listing machine instructions -@item set assembly-language @var{instruction-set} -Select the instruction set to use when disassembling the -program via the @code{disassemble} or @code{x/i} commands. - -Currently this command is only defined for the Intel x86 family. You -can set @var{instruction-set} to either @code{i386} or @code{i8086}. -The default is @code{i386}. -@end table - - -@node Data, Languages, Source, Top -@chapter Examining Data - -@cindex printing data -@cindex examining data -@kindex print -@kindex inspect -@c "inspect" is not quite a synonym if you are using Epoch, which we do not -@c document because it is nonstandard... Under Epoch it displays in a -@c different window or something like that. -The usual way to examine data in your program is with the @code{print} -command (abbreviated @code{p}), or its synonym @code{inspect}. -@ifclear CONLY -It evaluates and prints the value of an expression of the language your -program is written in (@pxref{Languages, ,Using @value{GDBN} with Different -Languages}). -@end ifclear - -@table @code -@item print @var{exp} -@itemx print /@var{f} @var{exp} -@var{exp} is an expression (in the source language). By default the -value of @var{exp} is printed in a format appropriate to its data type; -you can choose a different format by specifying @samp{/@var{f}}, where -@var{f} is a letter specifying the format; @pxref{Output Formats,,Output -formats}. - -@item print -@itemx print /@var{f} -If you omit @var{exp}, @value{GDBN} displays the last value again (from the -@dfn{value history}; @pxref{Value History, ,Value history}). This allows you to -conveniently inspect the same value in an alternative format. -@end table - -A more low-level way of examining data is with the @code{x} command. -It examines data in memory at a specified address and prints it in a -specified format. @xref{Memory, ,Examining memory}. - -If you are interested in information about types, or about how the fields -of a struct -@ifclear CONLY -or class -@end ifclear -are declared, use the @code{ptype @var{exp}} -command rather than @code{print}. @xref{Symbols, ,Examining the Symbol Table}. - -@menu -* Expressions:: Expressions -* Variables:: Program variables -* Arrays:: Artificial arrays -* Output Formats:: Output formats -* Memory:: Examining memory -* Auto Display:: Automatic display -* Print Settings:: Print settings -* Value History:: Value history -* Convenience Vars:: Convenience variables -* Registers:: Registers -@ifclear HAVE-FLOAT -* Floating Point Hardware:: Floating point hardware -@end ifclear - -@end menu - -@node Expressions, Variables, Data, Data -@section Expressions - -@cindex expressions -@code{print} and many other @value{GDBN} commands accept an expression and -compute its value. Any kind of constant, variable or operator defined -by the programming language you are using is valid in an expression in -@value{GDBN}. This includes conditional expressions, function calls, casts -and string constants. It unfortunately does not include symbols defined -by preprocessor @code{#define} commands. - -@value{GDBN} now supports array constants in expressions input by -the user. The syntax is @var{@{element, element@dots{}@}}. For example, -you can now use the command @code{print @{1, 2, 3@}} to build up an array in -memory that is malloc'd in the target program. - -@ifclear CONLY -Because C is so widespread, most of the expressions shown in examples in -this manual are in C. @xref{Languages, , Using @value{GDBN} with Different -Languages}, for information on how to use expressions in other -languages. - -In this section, we discuss operators that you can use in @value{GDBN} -expressions regardless of your programming language. - -Casts are supported in all languages, not just in C, because it is so -useful to cast a number into a pointer in order to examine a structure -at that address in memory. -@c FIXME: casts supported---Mod2 true? -@end ifclear - -@value{GDBN} supports these operators, in addition to those common -to programming languages: - -@table @code -@item @@ -@samp{@@} is a binary operator for treating parts of memory as arrays. -@xref{Arrays, ,Artificial arrays}, for more information. - -@item :: -@samp{::} allows you to specify a variable in terms of the file or -function where it is defined. @xref{Variables, ,Program variables}. - -@cindex @{@var{type}@} -@cindex type casting memory -@cindex memory, viewing as typed object -@cindex casts, to view memory -@item @{@var{type}@} @var{addr} -Refers to an object of type @var{type} stored at address @var{addr} in -memory. @var{addr} may be any expression whose value is an integer or -pointer (but parentheses are required around binary operators, just as in -a cast). This construct is allowed regardless of what kind of data is -normally supposed to reside at @var{addr}. -@end table - -@node Variables, Arrays, Expressions, Data -@section Program variables - -The most common kind of expression to use is the name of a variable -in your program. - -Variables in expressions are understood in the selected stack frame -(@pxref{Selection, ,Selecting a frame}); they must be either: - -@itemize @bullet -@item -global (or file-static) -@end itemize - -@noindent or - -@itemize @bullet -@item -visible according to the scope rules of the -programming language from the point of execution in that frame -@end itemize - -@noindent This means that in the function - -@example -foo (a) - int a; -@{ - bar (a); - @{ - int b = test (); - bar (b); - @} -@} -@end example - -@noindent -you can examine and use the variable @code{a} whenever your program is -executing within the function @code{foo}, but you can only use or -examine the variable @code{b} while your program is executing inside -the block where @code{b} is declared. - -@cindex variable name conflict -There is an exception: you can refer to a variable or function whose -scope is a single source file even if the current execution point is not -in this file. But it is possible to have more than one such variable or -function with the same name (in different source files). If that -happens, referring to that name has unpredictable effects. If you wish, -you can specify a static variable in a particular function or file, -using the colon-colon notation: - -@cindex colon-colon -@iftex -@c info cannot cope with a :: index entry, but why deprive hard copy readers? -@kindex :: -@end iftex -@example -@var{file}::@var{variable} -@var{function}::@var{variable} -@end example - -@noindent -Here @var{file} or @var{function} is the name of the context for the -static @var{variable}. In the case of file names, you can use quotes to -make sure @value{GDBN} parses the file name as a single word---for example, -to print a global value of @code{x} defined in @file{f2.c}: - -@example -(@value{GDBP}) p 'f2.c'::x -@end example - -@ifclear CONLY -@cindex C++ scope resolution -This use of @samp{::} is very rarely in conflict with the very similar -use of the same notation in C++. @value{GDBN} also supports use of the C++ -scope resolution operator in @value{GDBN} expressions. -@c FIXME: Um, so what happens in one of those rare cases where it's in -@c conflict?? --mew -@end ifclear - -@cindex wrong values -@cindex variable values, wrong -@quotation -@emph{Warning:} Occasionally, a local variable may appear to have the -wrong value at certain points in a function---just after entry to a new -scope, and just before exit. -@end quotation -You may see this problem when you are stepping by machine instructions. -This is because, on most machines, it takes more than one instruction to -set up a stack frame (including local variable definitions); if you are -stepping by machine instructions, variables may appear to have the wrong -values until the stack frame is completely built. On exit, it usually -also takes more than one machine instruction to destroy a stack frame; -after you begin stepping through that group of instructions, local -variable definitions may be gone. - -This may also happen when the compiler does significant optimizations. -To be sure of always seeing accurate values, turn off all optimization -when compiling. - -@node Arrays, Output Formats, Variables, Data -@section Artificial arrays - -@cindex artificial array -@kindex @@ -It is often useful to print out several successive objects of the -same type in memory; a section of an array, or an array of -dynamically determined size for which only a pointer exists in the -program. - -You can do this by referring to a contiguous span of memory as an -@dfn{artificial array}, using the binary operator @samp{@@}. The left -operand of @samp{@@} should be the first element of the desired array -and be an individual object. The right operand should be the desired length -of the array. The result is an array value whose elements are all of -the type of the left argument. The first element is actually the left -argument; the second element comes from bytes of memory immediately -following those that hold the first element, and so on. Here is an -example. If a program says - -@example -int *array = (int *) malloc (len * sizeof (int)); -@end example - -@noindent -you can print the contents of @code{array} with - -@example -p *array@@len -@end example - -The left operand of @samp{@@} must reside in memory. Array values made -with @samp{@@} in this way behave just like other arrays in terms of -subscripting, and are coerced to pointers when used in expressions. -Artificial arrays most often appear in expressions via the value history -(@pxref{Value History, ,Value history}), after printing one out. - -Another way to create an artificial array is to use a cast. -This re-interprets a value as if it were an array. -The value need not be in memory: -@example -(@value{GDBP}) p/x (short[2])0x12345678 -$1 = @{0x1234, 0x5678@} -@end example - -As a convenience, if you leave the array length out (as in -@samp{(@var{type})[])@var{value}}) gdb calculates the size to fill -the value (as @samp{sizeof(@var{value})/sizeof(@var{type})}: -@example -(@value{GDBP}) p/x (short[])0x12345678 -$2 = @{0x1234, 0x5678@} -@end example - -Sometimes the artificial array mechanism is not quite enough; in -moderately complex data structures, the elements of interest may not -actually be adjacent---for example, if you are interested in the values -of pointers in an array. One useful work-around in this situation is -to use a convenience variable (@pxref{Convenience Vars, ,Convenience -variables}) as a counter in an expression that prints the first -interesting value, and then repeat that expression via @key{RET}. For -instance, suppose you have an array @code{dtab} of pointers to -structures, and you are interested in the values of a field @code{fv} -in each structure. Here is an example of what you might type: - -@example -set $i = 0 -p dtab[$i++]->fv -@key{RET} -@key{RET} -@dots{} -@end example - -@node Output Formats, Memory, Arrays, Data -@section Output formats - -@cindex formatted output -@cindex output formats -By default, @value{GDBN} prints a value according to its data type. Sometimes -this is not what you want. For example, you might want to print a number -in hex, or a pointer in decimal. Or you might want to view data in memory -at a certain address as a character string or as an instruction. To do -these things, specify an @dfn{output format} when you print a value. - -The simplest use of output formats is to say how to print a value -already computed. This is done by starting the arguments of the -@code{print} command with a slash and a format letter. The format -letters supported are: - -@table @code -@item x -Regard the bits of the value as an integer, and print the integer in -hexadecimal. - -@item d -Print as integer in signed decimal. - -@item u -Print as integer in unsigned decimal. - -@item o -Print as integer in octal. - -@item t -Print as integer in binary. The letter @samp{t} stands for ``two''. -@footnote{@samp{b} cannot be used because these format letters are also -used with the @code{x} command, where @samp{b} stands for ``byte''; -@pxref{Memory,,Examining memory}.} - -@item a -@cindex unknown address, locating -Print as an address, both absolute in hexadecimal and as an offset from -the nearest preceding symbol. You can use this format used to discover -where (in what function) an unknown address is located: - -@example -(@value{GDBP}) p/a 0x54320 -$3 = 0x54320 <_initialize_vx+396> -@end example - -@item c -Regard as an integer and print it as a character constant. - -@item f -Regard the bits of the value as a floating point number and print -using typical floating point syntax. -@end table - -For example, to print the program counter in hex (@pxref{Registers}), type - -@example -p/x $pc -@end example - -@noindent -Note that no space is required before the slash; this is because command -names in @value{GDBN} cannot contain a slash. - -To reprint the last value in the value history with a different format, -you can use the @code{print} command with just a format and no -expression. For example, @samp{p/x} reprints the last value in hex. - -@node Memory, Auto Display, Output Formats, Data -@section Examining memory - -You can use the command @code{x} (for ``examine'') to examine memory in -any of several formats, independently of your program's data types. - -@cindex examining memory -@table @code -@kindex x -@item x/@var{nfu} @var{addr} -@itemx x @var{addr} -@itemx x -Use the @code{x} command to examine memory. -@end table - -@var{n}, @var{f}, and @var{u} are all optional parameters that specify how -much memory to display and how to format it; @var{addr} is an -expression giving the address where you want to start displaying memory. -If you use defaults for @var{nfu}, you need not type the slash @samp{/}. -Several commands set convenient defaults for @var{addr}. - -@table @r -@item @var{n}, the repeat count -The repeat count is a decimal integer; the default is 1. It specifies -how much memory (counting by units @var{u}) to display. -@c This really is **decimal**; unaffected by 'set radix' as of GDB -@c 4.1.2. - -@item @var{f}, the display format -The display format is one of the formats used by @code{print}, -@samp{s} (null-terminated string), or @samp{i} (machine instruction). -The default is @samp{x} (hexadecimal) initially. -The default changes each time you use either @code{x} or @code{print}. - -@item @var{u}, the unit size -The unit size is any of - -@table @code -@item b -Bytes. -@item h -Halfwords (two bytes). -@item w -Words (four bytes). This is the initial default. -@item g -Giant words (eight bytes). -@end table - -Each time you specify a unit size with @code{x}, that size becomes the -default unit the next time you use @code{x}. (For the @samp{s} and -@samp{i} formats, the unit size is ignored and is normally not written.) - -@item @var{addr}, starting display address -@var{addr} is the address where you want @value{GDBN} to begin displaying -memory. The expression need not have a pointer value (though it may); -it is always interpreted as an integer address of a byte of memory. -@xref{Expressions, ,Expressions}, for more information on expressions. The default for -@var{addr} is usually just after the last address examined---but several -other commands also set the default address: @code{info breakpoints} (to -the address of the last breakpoint listed), @code{info line} (to the -starting address of a line), and @code{print} (if you use it to display -a value from memory). -@end table - -For example, @samp{x/3uh 0x54320} is a request to display three halfwords -(@code{h}) of memory, formatted as unsigned decimal integers (@samp{u}), -starting at address @code{0x54320}. @samp{x/4xw $sp} prints the four -words (@samp{w}) of memory above the stack pointer (here, @samp{$sp}; -@pxref{Registers}) in hexadecimal (@samp{x}). - -Since the letters indicating unit sizes are all distinct from the -letters specifying output formats, you do not have to remember whether -unit size or format comes first; either order works. The output -specifications @samp{4xw} and @samp{4wx} mean exactly the same thing. -(However, the count @var{n} must come first; @samp{wx4} does not work.) - -Even though the unit size @var{u} is ignored for the formats @samp{s} -and @samp{i}, you might still want to use a count @var{n}; for example, -@samp{3i} specifies that you want to see three machine instructions, -including any operands. The command @code{disassemble} gives an -alternative way of inspecting machine instructions; @pxref{Machine -Code,,Source and machine code}. - -All the defaults for the arguments to @code{x} are designed to make it -easy to continue scanning memory with minimal specifications each time -you use @code{x}. For example, after you have inspected three machine -instructions with @samp{x/3i @var{addr}}, you can inspect the next seven -with just @samp{x/7}. If you use @key{RET} to repeat the @code{x} command, -the repeat count @var{n} is used again; the other arguments default as -for successive uses of @code{x}. - -@cindex @code{$_}, @code{$__}, and value history -The addresses and contents printed by the @code{x} command are not saved -in the value history because there is often too much of them and they -would get in the way. Instead, @value{GDBN} makes these values available for -subsequent use in expressions as values of the convenience variables -@code{$_} and @code{$__}. After an @code{x} command, the last address -examined is available for use in expressions in the convenience variable -@code{$_}. The contents of that address, as examined, are available in -the convenience variable @code{$__}. - -If the @code{x} command has a repeat count, the address and contents saved -are from the last memory unit printed; this is not the same as the last -address printed if several units were printed on the last line of output. - -@node Auto Display, Print Settings, Memory, Data -@section Automatic display -@cindex automatic display -@cindex display of expressions - -If you find that you want to print the value of an expression frequently -(to see how it changes), you might want to add it to the @dfn{automatic -display list} so that @value{GDBN} prints its value each time your program stops. -Each expression added to the list is given a number to identify it; -to remove an expression from the list, you specify that number. -The automatic display looks like this: - -@example -2: foo = 38 -3: bar[5] = (struct hack *) 0x3804 -@end example - -@noindent -This display shows item numbers, expressions and their current values. As with -displays you request manually using @code{x} or @code{print}, you can -specify the output format you prefer; in fact, @code{display} decides -whether to use @code{print} or @code{x} depending on how elaborate your -format specification is---it uses @code{x} if you specify a unit size, -or one of the two formats (@samp{i} and @samp{s}) that are only -supported by @code{x}; otherwise it uses @code{print}. - -@table @code -@kindex display -@item display @var{exp} -Add the expression @var{exp} to the list of expressions to display -each time your program stops. @xref{Expressions, ,Expressions}. - -@code{display} does not repeat if you press @key{RET} again after using it. - -@item display/@var{fmt} @var{exp} -For @var{fmt} specifying only a display format and not a size or -count, add the expression @var{exp} to the auto-display list but -arrange to display it each time in the specified format @var{fmt}. -@xref{Output Formats,,Output formats}. - -@item display/@var{fmt} @var{addr} -For @var{fmt} @samp{i} or @samp{s}, or including a unit-size or a -number of units, add the expression @var{addr} as a memory address to -be examined each time your program stops. Examining means in effect -doing @samp{x/@var{fmt} @var{addr}}. @xref{Memory, ,Examining memory}. -@end table - -For example, @samp{display/i $pc} can be helpful, to see the machine -instruction about to be executed each time execution stops (@samp{$pc} -is a common name for the program counter; @pxref{Registers}). - -@table @code -@kindex delete display -@kindex undisplay -@item undisplay @var{dnums}@dots{} -@itemx delete display @var{dnums}@dots{} -Remove item numbers @var{dnums} from the list of expressions to display. - -@code{undisplay} does not repeat if you press @key{RET} after using it. -(Otherwise you would just get the error @samp{No display number @dots{}}.) - -@kindex disable display -@item disable display @var{dnums}@dots{} -Disable the display of item numbers @var{dnums}. A disabled display -item is not printed automatically, but is not forgotten. It may be -enabled again later. - -@kindex enable display -@item enable display @var{dnums}@dots{} -Enable display of item numbers @var{dnums}. It becomes effective once -again in auto display of its expression, until you specify otherwise. - -@item display -Display the current values of the expressions on the list, just as is -done when your program stops. - -@kindex info display -@item info display -Print the list of expressions previously set up to display -automatically, each one with its item number, but without showing the -values. This includes disabled expressions, which are marked as such. -It also includes expressions which would not be displayed right now -because they refer to automatic variables not currently available. -@end table - -If a display expression refers to local variables, then it does not make -sense outside the lexical context for which it was set up. Such an -expression is disabled when execution enters a context where one of its -variables is not defined. For example, if you give the command -@code{display last_char} while inside a function with an argument -@code{last_char}, @value{GDBN} displays this argument while your program -continues to stop inside that function. When it stops elsewhere---where -there is no variable @code{last_char}---the display is disabled -automatically. The next time your program stops where @code{last_char} -is meaningful, you can enable the display expression once again. - -@node Print Settings, Value History, Auto Display, Data -@section Print settings - -@cindex format options -@cindex print settings -@value{GDBN} provides the following ways to control how arrays, structures, -and symbols are printed. - -@noindent -These settings are useful for debugging programs in any language: - -@table @code -@kindex set print address -@item set print address -@itemx set print address on -@value{GDBN} prints memory addresses showing the location of stack -traces, structure values, pointer values, breakpoints, and so forth, -even when it also displays the contents of those addresses. The default -is @code{on}. For example, this is what a stack frame display looks like with -@code{set print address on}: - -@smallexample -@group -(@value{GDBP}) f -#0 set_quotes (lq=0x34c78 "<<", rq=0x34c88 ">>") - at input.c:530 -530 if (lquote != def_lquote) -@end group -@end smallexample - -@item set print address off -Do not print addresses when displaying their contents. For example, -this is the same stack frame displayed with @code{set print address off}: - -@smallexample -@group -(@value{GDBP}) set print addr off -(@value{GDBP}) f -#0 set_quotes (lq="<<", rq=">>") at input.c:530 -530 if (lquote != def_lquote) -@end group -@end smallexample - -You can use @samp{set print address off} to eliminate all machine -dependent displays from the @value{GDBN} interface. For example, with -@code{print address off}, you should get the same text for backtraces on -all machines---whether or not they involve pointer arguments. - -@kindex show print address -@item show print address -Show whether or not addresses are to be printed. -@end table - -When @value{GDBN} prints a symbolic address, it normally prints the -closest earlier symbol plus an offset. If that symbol does not uniquely -identify the address (for example, it is a name whose scope is a single -source file), you may need to clarify. One way to do this is with -@code{info line}, for example @samp{info line *0x4537}. Alternately, -you can set @value{GDBN} to print the source file and line number when -it prints a symbolic address: - -@table @code -@kindex set print symbol-filename -@item set print symbol-filename on -Tell @value{GDBN} to print the source file name and line number of a -symbol in the symbolic form of an address. - -@item set print symbol-filename off -Do not print source file name and line number of a symbol. This is the -default. - -@kindex show print symbol-filename -@item show print symbol-filename -Show whether or not @value{GDBN} will print the source file name and -line number of a symbol in the symbolic form of an address. -@end table - -Another situation where it is helpful to show symbol filenames and line -numbers is when disassembling code; @value{GDBN} shows you the line -number and source file that corresponds to each instruction. - -Also, you may wish to see the symbolic form only if the address being -printed is reasonably close to the closest earlier symbol: - -@table @code -@kindex set print max-symbolic-offset -@item set print max-symbolic-offset @var{max-offset} -Tell @value{GDBN} to only display the symbolic form of an address if the -offset between the closest earlier symbol and the address is less than -@var{max-offset}. The default is 0, which tells @value{GDBN} -to always print the symbolic form of an address if any symbol precedes it. - -@kindex show print max-symbolic-offset -@item show print max-symbolic-offset -Ask how large the maximum offset is that @value{GDBN} prints in a -symbolic address. -@end table - -@cindex wild pointer, interpreting -@cindex pointer, finding referent -If you have a pointer and you are not sure where it points, try -@samp{set print symbol-filename on}. Then you can determine the name -and source file location of the variable where it points, using -@samp{p/a @var{pointer}}. This interprets the address in symbolic form. -For example, here @value{GDBN} shows that a variable @code{ptt} points -at another variable @code{t}, defined in @file{hi2.c}: - -@example -(@value{GDBP}) set print symbol-filename on -(@value{GDBP}) p/a ptt -$4 = 0xe008 <t in hi2.c> -@end example - -@quotation -@emph{Warning:} For pointers that point to a local variable, @samp{p/a} -does not show the symbol name and filename of the referent, even with -the appropriate @code{set print} options turned on. -@end quotation - -Other settings control how different kinds of objects are printed: - -@table @code -@kindex set print array -@item set print array -@itemx set print array on -Pretty print arrays. This format is more convenient to read, -but uses more space. The default is off. - -@item set print array off -Return to compressed format for arrays. - -@kindex show print array -@item show print array -Show whether compressed or pretty format is selected for displaying -arrays. - -@kindex set print elements -@item set print elements @var{number-of-elements} -Set a limit on how many elements of an array @value{GDBN} will print. -If @value{GDBN} is printing a large array, it stops printing after it has -printed the number of elements set by the @code{set print elements} command. -This limit also applies to the display of strings. -Setting @var{number-of-elements} to zero means that the printing is unlimited. - -@kindex show print elements -@item show print elements -Display the number of elements of a large array that @value{GDBN} will print. -If the number is 0, then the printing is unlimited. - -@kindex set print null-stop -@item set print null-stop -Cause @value{GDBN} to stop printing the characters of an array when the first -@sc{NULL} is encountered. This is useful when large arrays actually -contain only short strings. - -@kindex set print pretty -@item set print pretty on -Cause @value{GDBN} to print structures in an indented format with one member -per line, like this: - -@smallexample -@group -$1 = @{ - next = 0x0, - flags = @{ - sweet = 1, - sour = 1 - @}, - meat = 0x54 "Pork" -@} -@end group -@end smallexample - -@item set print pretty off -Cause @value{GDBN} to print structures in a compact format, like this: - -@smallexample -@group -$1 = @{next = 0x0, flags = @{sweet = 1, sour = 1@}, \ -meat = 0x54 "Pork"@} -@end group -@end smallexample - -@noindent -This is the default format. - -@kindex show print pretty -@item show print pretty -Show which format @value{GDBN} is using to print structures. - -@kindex set print sevenbit-strings -@item set print sevenbit-strings on -Print using only seven-bit characters; if this option is set, -@value{GDBN} displays any eight-bit characters (in strings or -character values) using the notation @code{\}@var{nnn}. This setting is -best if you are working in English (@sc{ascii}) and you use the -high-order bit of characters as a marker or ``meta'' bit. - -@item set print sevenbit-strings off -Print full eight-bit characters. This allows the use of more -international character sets, and is the default. - -@kindex show print sevenbit-strings -@item show print sevenbit-strings -Show whether or not @value{GDBN} is printing only seven-bit characters. - -@kindex set print union -@item set print union on -Tell @value{GDBN} to print unions which are contained in structures. This -is the default setting. - -@item set print union off -Tell @value{GDBN} not to print unions which are contained in structures. - -@kindex show print union -@item show print union -Ask @value{GDBN} whether or not it will print unions which are contained in -structures. - -For example, given the declarations - -@smallexample -typedef enum @{Tree, Bug@} Species; -typedef enum @{Big_tree, Acorn, Seedling@} Tree_forms; -typedef enum @{Caterpillar, Cocoon, Butterfly@} - Bug_forms; - -struct thing @{ - Species it; - union @{ - Tree_forms tree; - Bug_forms bug; - @} form; -@}; - -struct thing foo = @{Tree, @{Acorn@}@}; -@end smallexample - -@noindent -with @code{set print union on} in effect @samp{p foo} would print - -@smallexample -$1 = @{it = Tree, form = @{tree = Acorn, bug = Cocoon@}@} -@end smallexample - -@noindent -and with @code{set print union off} in effect it would print - -@smallexample -$1 = @{it = Tree, form = @{...@}@} -@end smallexample -@end table - -@ifclear CONLY -@need 1000 -@noindent -These settings are of interest when debugging C++ programs: - -@table @code -@cindex demangling -@kindex set print demangle -@item set print demangle -@itemx set print demangle on -Print C++ names in their source form rather than in the encoded -(``mangled'') form passed to the assembler and linker for type-safe -linkage. The default is @samp{on}. - -@kindex show print demangle -@item show print demangle -Show whether C++ names are printed in mangled or demangled form. - -@kindex set print asm-demangle -@item set print asm-demangle -@itemx set print asm-demangle on -Print C++ names in their source form rather than their mangled form, even -in assembler code printouts such as instruction disassemblies. -The default is off. - -@kindex show print asm-demangle -@item show print asm-demangle -Show whether C++ names in assembly listings are printed in mangled -or demangled form. - -@kindex set demangle-style -@cindex C++ symbol decoding style -@cindex symbol decoding style, C++ -@item set demangle-style @var{style} -Choose among several encoding schemes used by different compilers to -represent C++ names. The choices for @var{style} are currently: - -@table @code -@item auto -Allow @value{GDBN} to choose a decoding style by inspecting your program. - -@item gnu -Decode based on the @sc{gnu} C++ compiler (@code{g++}) encoding algorithm. -@ifclear HPPA -This is the default. -@end ifclear - -@item hp -Decode based on the HP ANSI C++ (@code{aCC}) encoding algorithm. - -@item lucid -Decode based on the Lucid C++ compiler (@code{lcc}) encoding algorithm. - -@item arm -Decode using the algorithm in the @cite{C++ Annotated Reference Manual}. -@strong{Warning:} this setting alone is not sufficient to allow -debugging @code{cfront}-generated executables. @value{GDBN} would -require further enhancement to permit that. - -@end table -If you omit @var{style}, you will see a list of possible formats. - -@kindex show demangle-style -@item show demangle-style -Display the encoding style currently in use for decoding C++ symbols. - -@kindex set print object -@item set print object -@itemx set print object on -When displaying a pointer to an object, identify the @emph{actual} -(derived) type of the object rather than the @emph{declared} type, using -the virtual function table. - -@item set print object off -Display only the declared type of objects, without reference to the -virtual function table. This is the default setting. - -@kindex show print object -@item show print object -Show whether actual, or declared, object types are displayed. - -@kindex set print static-members -@item set print static-members -@itemx set print static-members on -Print static members when displaying a C++ object. The default is on. - -@item set print static-members off -Do not print static members when displaying a C++ object. - -@kindex show print static-members -@item show print static-members -Show whether C++ static members are printed, or not. - -@c These don't work with HP ANSI C++ yet. -@kindex set print vtbl -@item set print vtbl -@itemx set print vtbl on -Pretty print C++ virtual function tables. The default is off. -@ifset HPPA -(The @code{vtbl} commands do not work on programs compiled with the HP -ANSI C++ compiler (@code{aCC}).) -@end ifset - -@item set print vtbl off -Do not pretty print C++ virtual function tables. - -@kindex show print vtbl -@item show print vtbl -Show whether C++ virtual function tables are pretty printed, or not. -@end table -@end ifclear - -@node Value History, Convenience Vars, Print Settings, Data -@section Value history - -@cindex value history -Values printed by the @code{print} command are saved in the @value{GDBN} -@dfn{value history}. This allows you to refer to them in other expressions. -Values are kept until the symbol table is re-read or discarded -(for example with the @code{file} or @code{symbol-file} commands). -When the symbol table changes, the value history is discarded, -since the values may contain pointers back to the types defined in the -symbol table. - -@cindex @code{$} -@cindex @code{$$} -@cindex history number -The values printed are given @dfn{history numbers} by which you can -refer to them. These are successive integers starting with one. -@code{print} shows you the history number assigned to a value by -printing @samp{$@var{num} = } before the value; here @var{num} is the -history number. - -To refer to any previous value, use @samp{$} followed by the value's -history number. The way @code{print} labels its output is designed to -remind you of this. Just @code{$} refers to the most recent value in -the history, and @code{$$} refers to the value before that. -@code{$$@var{n}} refers to the @var{n}th value from the end; @code{$$2} -is the value just prior to @code{$$}, @code{$$1} is equivalent to -@code{$$}, and @code{$$0} is equivalent to @code{$}. - -For example, suppose you have just printed a pointer to a structure and -want to see the contents of the structure. It suffices to type - -@example -p *$ -@end example - -If you have a chain of structures where the component @code{next} points -to the next one, you can print the contents of the next one with this: - -@example -p *$.next -@end example - -@noindent -You can print successive links in the chain by repeating this -command---which you can do by just typing @key{RET}. - -Note that the history records values, not expressions. If the value of -@code{x} is 4 and you type these commands: - -@example -print x -set x=5 -@end example - -@noindent -then the value recorded in the value history by the @code{print} command -remains 4 even though the value of @code{x} has changed. - -@table @code -@kindex show values -@item show values -Print the last ten values in the value history, with their item numbers. -This is like @samp{p@ $$9} repeated ten times, except that @code{show -values} does not change the history. - -@item show values @var{n} -Print ten history values centered on history item number @var{n}. - -@item show values + -Print ten history values just after the values last printed. If no more -values are available, @code{show values +} produces no display. -@end table - -Pressing @key{RET} to repeat @code{show values @var{n}} has exactly the -same effect as @samp{show values +}. - -@node Convenience Vars, Registers, Value History, Data -@section Convenience variables - -@cindex convenience variables -@value{GDBN} provides @dfn{convenience variables} that you can use within -@value{GDBN} to hold on to a value and refer to it later. These variables -exist entirely within @value{GDBN}; they are not part of your program, and -setting a convenience variable has no direct effect on further execution -of your program. That is why you can use them freely. - -Convenience variables are prefixed with @samp{$}. Any name preceded by -@samp{$} can be used for a convenience variable, unless it is one of -the predefined machine-specific register names (@pxref{Registers}). -(Value history references, in contrast, are @emph{numbers} preceded -by @samp{$}. @xref{Value History, ,Value history}.) - -You can save a value in a convenience variable with an assignment -expression, just as you would set a variable in your program. -For example: - -@example -set $foo = *object_ptr -@end example - -@noindent -would save in @code{$foo} the value contained in the object pointed to by -@code{object_ptr}. - -Using a convenience variable for the first time creates it, but its -value is @code{void} until you assign a new value. You can alter the -value with another assignment at any time. - -Convenience variables have no fixed types. You can assign a convenience -variable any type of value, including structures and arrays, even if -that variable already has a value of a different type. The convenience -variable, when used as an expression, has the type of its current value. - -@table @code -@kindex show convenience -@item show convenience -Print a list of convenience variables used so far, and their values. -Abbreviated @code{show con}. -@end table - -One of the ways to use a convenience variable is as a counter to be -incremented or a pointer to be advanced. For example, to print -a field from successive elements of an array of structures: - -@example -set $i = 0 -print bar[$i++]->contents -@end example - -@noindent Repeat that command by typing @key{RET}. - -Some convenience variables are created automatically by @value{GDBN} and given -values likely to be useful. - -@table @code -@kindex $_ -@item $_ -The variable @code{$_} is automatically set by the @code{x} command to -the last address examined (@pxref{Memory, ,Examining memory}). Other -commands which provide a default address for @code{x} to examine also -set @code{$_} to that address; these commands include @code{info line} -and @code{info breakpoint}. The type of @code{$_} is @code{void *} -except when set by the @code{x} command, in which case it is a pointer -to the type of @code{$__}. - -@kindex $__ -@item $__ -The variable @code{$__} is automatically set by the @code{x} command -to the value found in the last address examined. Its type is chosen -to match the format in which the data was printed. - -@item $_exitcode -@kindex $_exitcode -The variable @code{$_exitcode} is automatically set to the exit code when -the program being debugged terminates. -@end table - -@ifset HPPA -If you refer to a function or variable name that begins with a dollar -sign, @value{GDBN} searches for a user or system name first, before it -searches for a convenience variable. -@end ifset - -@node Registers, Floating Point Hardware, Convenience Vars, Data -@section Registers - -@cindex registers -You can refer to machine register contents, in expressions, as variables -with names starting with @samp{$}. The names of registers are different -for each machine; use @code{info registers} to see the names used on -your machine. - -@table @code -@kindex info registers -@item info registers -Print the names and values of all registers except floating-point -registers (in the selected stack frame). - -@kindex info all-registers -@cindex floating point registers -@item info all-registers -Print the names and values of all registers, including floating-point -registers. - -@item info registers @var{regname} @dots{} -Print the @dfn{relativized} value of each specified register @var{regname}. -As discussed in detail below, register values are normally relative to -the selected stack frame. @var{regname} may be any register name valid on -the machine you are using, with or without the initial @samp{$}. -@end table - -@value{GDBN} has four ``standard'' register names that are available (in -expressions) on most machines---whenever they do not conflict with an -architecture's canonical mnemonics for registers. The register names -@code{$pc} and @code{$sp} are used for the program counter register and -the stack pointer. @code{$fp} is used for a register that contains a -pointer to the current stack frame, and @code{$ps} is used for a -register that contains the processor status. For example, -you could print the program counter in hex with - -@example -p/x $pc -@end example - -@noindent -or print the instruction to be executed next with - -@example -x/i $pc -@end example - -@noindent -or add four to the stack pointer@footnote{This is a way of removing -one word from the stack, on machines where stacks grow downward in -memory (most machines, nowadays). This assumes that the innermost -stack frame is selected; setting @code{$sp} is not allowed when other -stack frames are selected. To pop entire frames off the stack, -regardless of machine architecture, use @code{return}; -@pxref{Returning, ,Returning from a function}.} with - -@example -set $sp += 4 -@end example - -Whenever possible, these four standard register names are available on -your machine even though the machine has different canonical mnemonics, -so long as there is no conflict. The @code{info registers} command -shows the canonical names. For example, on the SPARC, @code{info -registers} displays the processor status register as @code{$psr} but you -can also refer to it as @code{$ps}. - -@value{GDBN} always considers the contents of an ordinary register as an -integer when the register is examined in this way. Some machines have -special registers which can hold nothing but floating point; these -registers are considered to have floating point values. There is no way -to refer to the contents of an ordinary register as floating point value -(although you can @emph{print} it as a floating point value with -@samp{print/f $@var{regname}}). - -Some registers have distinct ``raw'' and ``virtual'' data formats. This -means that the data format in which the register contents are saved by -the operating system is not the same one that your program normally -sees. For example, the registers of the 68881 floating point -coprocessor are always saved in ``extended'' (raw) format, but all C -programs expect to work with ``double'' (virtual) format. In such -cases, @value{GDBN} normally works with the virtual format only (the format -that makes sense for your program), but the @code{info registers} command -prints the data in both formats. - -Normally, register values are relative to the selected stack frame -(@pxref{Selection, ,Selecting a frame}). This means that you get the -value that the register would contain if all stack frames farther in -were exited and their saved registers restored. In order to see the -true contents of hardware registers, you must select the innermost -frame (with @samp{frame 0}). - -However, @value{GDBN} must deduce where registers are saved, from the machine -code generated by your compiler. If some registers are not saved, or if -@value{GDBN} is unable to locate the saved registers, the selected stack -frame makes no difference. - -@ifset AMD29K -@table @code -@kindex set rstack_high_address -@cindex AMD 29K register stack -@cindex register stack, AMD29K -@item set rstack_high_address @var{address} -On AMD 29000 family processors, registers are saved in a separate -``register stack''. There is no way for @value{GDBN} to determine the extent -of this stack. Normally, @value{GDBN} just assumes that the stack is ``large -enough''. This may result in @value{GDBN} referencing memory locations that -do not exist. If necessary, you can get around this problem by -specifying the ending address of the register stack with the @code{set -rstack_high_address} command. The argument should be an address, which -you probably want to precede with @samp{0x} to specify in -hexadecimal. - -@kindex show rstack_high_address -@item show rstack_high_address -Display the current limit of the register stack, on AMD 29000 family -processors. -@end table -@end ifset - -@ifclear HAVE-FLOAT -@node Floating Point Hardware, , Registers, Data -@section Floating point hardware -@cindex floating point - -Depending on the configuration, @value{GDBN} may be able to give -you more information about the status of the floating point hardware. - -@table @code -@kindex info float -@item info float -Display hardware-dependent information about the floating -point unit. The exact contents and layout vary depending on the -floating point chip. Currently, @samp{info float} is supported on -the ARM and x86 machines. -@end table -@end ifclear - -@ifclear CONLY -@node Languages, Symbols, Data, Top -@chapter Using @value{GDBN} with Different Languages -@cindex languages - -@ifset MOD2 -Although programming languages generally have common aspects, they are -rarely expressed in the same manner. For instance, in ANSI C, -dereferencing a pointer @code{p} is accomplished by @code{*p}, but in -Modula-2, it is accomplished by @code{p^}. Values can also be -represented (and displayed) differently. Hex numbers in C appear as -@samp{0x1ae}, while in Modula-2 they appear as @samp{1AEH}. -@end ifset - -@cindex working language -Language-specific information is built into @value{GDBN} for some languages, -allowing you to express operations like the above in your program's -native language, and allowing @value{GDBN} to output values in a manner -consistent with the syntax of your program's native language. The -language you use to build expressions is called the @dfn{working -language}. - -@menu -* Setting:: Switching between source languages -* Show:: Displaying the language -@ifset MOD2 -* Checks:: Type and range checks -@end ifset - -* Support:: Supported languages -@end menu - -@node Setting, Show, Languages, Languages -@section Switching between source languages - -There are two ways to control the working language---either have @value{GDBN} -set it automatically, or select it manually yourself. You can use the -@code{set language} command for either purpose. On startup, @value{GDBN} -defaults to setting the language automatically. The working language is -used to determine how expressions you type are interpreted, how values -are printed, etc. - -In addition to the working language, every source file that -@value{GDBN} knows about has its own working language. For some object -file formats, the compiler might indicate which language a particular -source file is in. However, most of the time @value{GDBN} infers the -language from the name of the file. The language of a source file -controls whether C++ names are demangled---this way @code{backtrace} can -show each frame appropriately for its own language. There is no way to -set the language of a source file from within @value{GDBN}. - -This is most commonly a problem when you use a program, such -as @code{cfront} or @code{f2c}, that generates C but is written in -another language. In that case, make the -program use @code{#line} directives in its C output; that way -@value{GDBN} will know the correct language of the source code of the original -program, and will display that source code, not the generated C code. - -@menu -* Filenames:: Filename extensions and languages. -* Manually:: Setting the working language manually -* Automatically:: Having @value{GDBN} infer the source language -@end menu - -@node Filenames, Manually, Setting, Setting -@subsection List of filename extensions and languages - -If a source file name ends in one of the following extensions, then -@value{GDBN} infers that its language is the one indicated. - -@table @file - -@item .c -C source file - -@item .C -@itemx .cc -@itemx .cp -@itemx .cpp -@itemx .cxx -@itemx .c++ -C++ source file - -@item .f -@itemx .F -Fortran source file - -@ifclear HPPA -@item .ch -@itemx .c186 -@itemx .c286 -CHILL source file. -@end ifclear - -@ifset MOD2 -@item .mod -Modula-2 source file -@end ifset - -@item .s -@itemx .S -Assembler source file. This actually behaves almost like C, but -@value{GDBN} does not skip over function prologues when stepping. -@end table - -In addition, you may set the language associated with a filename -extension. @xref{Show, , Displaying the language}. - -@node Manually, Automatically, Filenames, Setting -@subsection Setting the working language - -If you allow @value{GDBN} to set the language automatically, -expressions are interpreted the same way in your debugging session and -your program. - -@kindex set language -If you wish, you may set the language manually. To do this, issue the -command @samp{set language @var{lang}}, where @var{lang} is the name of -a language, such as -@ifclear MOD2 -@code{c}. -@end ifclear -@ifset MOD2 -@code{c} or @code{modula-2}. -@end ifset -For a list of the supported languages, type @samp{set language}. - -@ifclear MOD2 -Setting the language manually prevents @value{GDBN} from updating the -working language automatically. For example, if you used the @code{c} -setting to debug a C++ program, names might not be demangled properly, -overload resolution would not work, user-defined operators might not be -interpreted correctly, and so on. -@end ifclear -@ifset MOD2 -Setting the language manually prevents @value{GDBN} from updating the working -language automatically. This can lead to confusion if you try -to debug a program when the working language is not the same as the -source language, when an expression is acceptable to both -languages---but means different things. For instance, if the current -source file were written in C, and @value{GDBN} was parsing Modula-2, a -command such as: - -@example -print a = b + c -@end example - -@noindent -might not have the effect you intended. In C, this means to add -@code{b} and @code{c} and place the result in @code{a}. The result -printed would be the value of @code{a}. In Modula-2, this means to compare -@code{a} to the result of @code{b+c}, yielding a @code{BOOLEAN} value. -@end ifset - -@node Automatically, , Manually, Setting -@subsection Having @value{GDBN} infer the source language - -To have @value{GDBN} set the working language automatically, use -@samp{set language local} or @samp{set language auto}. @value{GDBN} -then infers the working language. That is, when your program stops in a -frame (usually by encountering a breakpoint), @value{GDBN} sets the -working language to the language recorded for the function in that -frame. If the language for a frame is unknown (that is, if the function -or block corresponding to the frame was defined in a source file that -does not have a recognized extension), the current working language is -not changed, and @value{GDBN} issues a warning. - -This may not seem necessary for most programs, which are written -entirely in one source language. However, program modules and libraries -written in one source language can be used by a main program written in -a different source language. Using @samp{set language auto} in this -case frees you from having to set the working language manually. - -@ifset MOD2 -@node Show, Checks, Setting, Languages -@section Displaying the language -@end ifset -@ifclear MOD2 -@node Show, Support, Setting, Languages -@section Displaying the language -@end ifclear - -The following commands help you find out which language is the -working language, and also what language source files were written in. - -@kindex show language -@kindex info frame -@kindex info source -@table @code -@item show language -Display the current working language. This is the -language you can use with commands such as @code{print} to -build and compute expressions that may involve variables in your program. - -@item info frame -Display the source language for this frame. This language becomes the -working language if you use an identifier from this frame. -@xref{Frame Info, ,Information about a frame}, to identify the other -information listed here. - -@item info source -Display the source language of this source file. -@xref{Symbols, ,Examining the Symbol Table}, to identify the other -information listed here. -@end table - -In unusual circumstances, you may have source files with extensions -not in the standard list. You can then set the extension associated -with a language explicitly: - -@kindex set extension-language -@kindex info extensions -@table @code -@item set extension-language @var{.ext} @var{language} -Set source files with extension @var{.ext} to be assumed to be in -the source language @var{language}. - -@item info extensions -List all the filename extensions and the associated languages. -@end table - -@ifset MOD2 -@node Checks, Support, Show, Languages -@section Type and range checking - -@quotation -@emph{Warning:} In this release, the @value{GDBN} commands for type and range -checking are included, but they do not yet have any effect. This -section documents the intended facilities. -@end quotation -@c FIXME remove warning when type/range code added - -Some languages are designed to guard you against making seemingly common -errors through a series of compile- and run-time checks. These include -checking the type of arguments to functions and operators, and making -sure mathematical overflows are caught at run time. Checks such as -these help to ensure a program's correctness once it has been compiled -by eliminating type mismatches, and providing active checks for range -errors when your program is running. - -@value{GDBN} can check for conditions like the above if you wish. -Although @value{GDBN} does not check the statements in your program, it -can check expressions entered directly into @value{GDBN} for evaluation via -the @code{print} command, for example. As with the working language, -@value{GDBN} can also decide whether or not to check automatically based on -your program's source language. @xref{Support, ,Supported languages}, -for the default settings of supported languages. - -@menu -* Type Checking:: An overview of type checking -* Range Checking:: An overview of range checking -@end menu - -@cindex type checking -@cindex checks, type -@node Type Checking, Range Checking, Checks, Checks -@subsection An overview of type checking - -Some languages, such as Modula-2, are strongly typed, meaning that the -arguments to operators and functions have to be of the correct type, -otherwise an error occurs. These checks prevent type mismatch -errors from ever causing any run-time problems. For example, - -@smallexample -1 + 2 @result{} 3 -@exdent but -@error{} 1 + 2.3 -@end smallexample - -The second example fails because the @code{CARDINAL} 1 is not -type-compatible with the @code{REAL} 2.3. - -For the expressions you use in @value{GDBN} commands, you can tell the -@value{GDBN} type checker to skip checking; -to treat any mismatches as errors and abandon the expression; -or to only issue warnings when type mismatches occur, -but evaluate the expression anyway. When you choose the last of -these, @value{GDBN} evaluates expressions like the second example above, but -also issues a warning. - -Even if you turn type checking off, there may be other reasons -related to type that prevent @value{GDBN} from evaluating an expression. -For instance, @value{GDBN} does not know how to add an @code{int} and -a @code{struct foo}. These particular type errors have nothing to do -with the language in use, and usually arise from expressions, such as -the one described above, which make little sense to evaluate anyway. - -Each language defines to what degree it is strict about type. For -instance, both Modula-2 and C require the arguments to arithmetical -operators to be numbers. In C, enumerated types and pointers can be -represented as numbers, so that they are valid arguments to mathematical -operators. @xref{Support, ,Supported languages}, for further -details on specific languages. - -@value{GDBN} provides some additional commands for controlling the type checker: - -@kindex set check -@kindex set check type -@kindex show check type -@table @code -@item set check type auto -Set type checking on or off based on the current working language. -@xref{Support, ,Supported languages}, for the default settings for -each language. - -@item set check type on -@itemx set check type off -Set type checking on or off, overriding the default setting for the -current working language. Issue a warning if the setting does not -match the language default. If any type mismatches occur in -evaluating an expression while typechecking is on, @value{GDBN} prints a -message and aborts evaluation of the expression. - -@item set check type warn -Cause the type checker to issue warnings, but to always attempt to -evaluate the expression. Evaluating the expression may still -be impossible for other reasons. For example, @value{GDBN} cannot add -numbers and structures. - -@item show type -Show the current setting of the type checker, and whether or not @value{GDBN} -is setting it automatically. -@end table - -@cindex range checking -@cindex checks, range -@node Range Checking, , Type Checking, Checks -@subsection An overview of range checking - -In some languages (such as Modula-2), it is an error to exceed the -bounds of a type; this is enforced with run-time checks. Such range -checking is meant to ensure program correctness by making sure -computations do not overflow, or indices on an array element access do -not exceed the bounds of the array. - -For expressions you use in @value{GDBN} commands, you can tell -@value{GDBN} to treat range errors in one of three ways: ignore them, -always treat them as errors and abandon the expression, or issue -warnings but evaluate the expression anyway. - -A range error can result from numerical overflow, from exceeding an -array index bound, or when you type a constant that is not a member -of any type. Some languages, however, do not treat overflows as an -error. In many implementations of C, mathematical overflow causes the -result to ``wrap around'' to lower values---for example, if @var{m} is -the largest integer value, and @var{s} is the smallest, then - -@example -@var{m} + 1 @result{} @var{s} -@end example - -This, too, is specific to individual languages, and in some cases -specific to individual compilers or machines. @xref{Support, , -Supported languages}, for further details on specific languages. - -@value{GDBN} provides some additional commands for controlling the range checker: - -@kindex set check -@kindex set check range -@kindex show check range -@table @code -@item set check range auto -Set range checking on or off based on the current working language. -@xref{Support, ,Supported languages}, for the default settings for -each language. - -@item set check range on -@itemx set check range off -Set range checking on or off, overriding the default setting for the -current working language. A warning is issued if the setting does not -match the language default. If a range error occurs, then a message -is printed and evaluation of the expression is aborted. - -@item set check range warn -Output messages when the @value{GDBN} range checker detects a range error, -but attempt to evaluate the expression anyway. Evaluating the -expression may still be impossible for other reasons, such as accessing -memory that the process does not own (a typical example from many Unix -systems). - -@item show range -Show the current setting of the range checker, and whether or not it is -being set automatically by @value{GDBN}. -@end table -@end ifset - -@ifset MOD2 -@node Support, , Checks, Languages -@section Supported languages -@end ifset -@ifclear MOD2 -@node Support, , Show, Languages -@section Supported languages -@end ifclear - -@ifset MOD2 -@value{GDBN} supports C, C++, Fortran, Chill, assembly, and Modula-2. -@end ifset -@ifclear MOD2 -@value{GDBN} supports C, C++, Fortran, Chill, and assembly. -@end ifclear -Some @value{GDBN} features may be used in expressions regardless of the -language you use: the @value{GDBN} @code{@@} and @code{::} operators, -and the @samp{@{type@}addr} construct (@pxref{Expressions, -,Expressions}) can be used with the constructs of any supported -language. - -The following sections detail to what degree each source language is -supported by @value{GDBN}. These sections are not meant to be language -tutorials or references, but serve only as a reference guide to what the -@value{GDBN} expression parser accepts, and what input and output -formats should look like for different languages. There are many good -books written on each of these languages; please look to these for a -language reference or tutorial. - -@ifset MOD2 -@menu -* C:: C and C++ -* Modula-2:: Modula-2 -@end menu - -@node C, Modula-2, , Support -@subsection C and C++ -@cindex C and C++ -@cindex expressions in C or C++ -@end ifset - -Since C and C++ are so closely related, many features of @value{GDBN} apply -to both languages. Whenever this is the case, we discuss those languages -together. - -@ifclear MOD2 -@c Cancel this below, under same condition, at end of this chapter! -@raisesections -@end ifclear - -@ifclear HPPA -@cindex C++ -@kindex g++ -@cindex @sc{gnu} C++ -The C++ debugging facilities are jointly implemented by the C++ -compiler and @value{GDBN}. Therefore, to debug your C++ code -effectively, you must compile your C++ programs with a supported -C++ compiler, such as @sc{gnu} @code{g++}, or the HP ANSI C++ -compiler (@code{aCC}). - -For best results when using @sc{gnu} C++, use the stabs debugging -format. You can select that format explicitly with the @code{g++} -command-line options @samp{-gstabs} or @samp{-gstabs+}. See -@ref{Debugging Options,,Options for Debugging Your Program or @sc{gnu} -CC, gcc.info, Using @sc{gnu} CC}, for more information. -@end ifclear -@ifset HPPA -@cindex C++ -@kindex g++ -@cindex @sc{gnu} C++ -You can use @value{GDBN} to debug C programs compiled with either the HP -C compiler (@code{cc}) or the GNU C compiler (@code{gcc}), and to debug -programs compiled with either the HP ANSI C++ compiler (@code{aCC}) or -the @sc{gnu} C++ compiler (@code{g++}). - -If you compile with the @sc{gnu} C++ compiler, use the stabs debugging -format for best results when debugging. You can select that format -explicitly with the @code{g++} command-line options @samp{-gstabs} or -@samp{-gstabs+}. See @ref{Debugging Options,,Options for Debugging Your -Program or @sc{gnu} CC, gcc.info, Using @sc{gnu} CC}, for more -information. -@end ifset -@end ifclear - -@ifset CONLY -@node C, Symbols, Data, Top -@chapter C Language Support -@cindex C language -@cindex expressions in C - -Information specific to the C language is built into @value{GDBN} so that you -can use C expressions while debugging. This also permits @value{GDBN} to -output values in a manner consistent with C conventions. - -@menu -* C Operators:: C operators -@end menu -@end ifset - -@ifclear CONLY -@menu -* C Operators:: C and C++ operators -* C Constants:: C and C++ constants -* Cplus expressions:: C++ expressions -* C Defaults:: Default settings for C and C++ -@ifset MOD2 -* C Checks:: C and C++ type and range checks -@end ifset - -* Debugging C:: @value{GDBN} and C -* Debugging C plus plus:: @value{GDBN} features for C++ -@end menu -@end ifclear - -@ifclear CONLY -@cindex C and C++ operators -@node C Operators, C Constants, , C -@subsubsection C and C++ operators -@end ifclear -@ifset CONLY -@cindex C operators -@node C Operators, C Constants, C, C -@section C operators -@end ifset - -Operators must be defined on values of specific types. For instance, -@code{+} is defined on numbers, but not on structures. Operators are -often defined on groups of types. - -@ifclear CONLY -For the purposes of C and C++, the following definitions hold: -@end ifclear - -@itemize @bullet -@item -@ifclear HPPA -@emph{Integral types} include @code{int} with any of its storage-class -specifiers; @code{char}; and @code{enum}. -@end ifclear -@ifset HPPA -@emph{Integral types} include @code{int} with any of its storage-class -specifiers; @code{char}; @code{enum}; and, for C++, @code{bool}. -@end ifset - -@item -@emph{Floating-point types} include @code{float} and @code{double}. - -@item -@emph{Pointer types} include all types defined as @code{(@var{type} -*)}. - -@item -@emph{Scalar types} include all of the above. -@end itemize - -@noindent -The following operators are supported. They are listed here -in order of increasing precedence: - -@table @code -@item , -The comma or sequencing operator. Expressions in a comma-separated list -are evaluated from left to right, with the result of the entire -expression being the last expression evaluated. - -@item = -Assignment. The value of an assignment expression is the value -assigned. Defined on scalar types. - -@item @var{op}= -Used in an expression of the form @w{@code{@var{a} @var{op}= @var{b}}}, -and translated to @w{@code{@var{a} = @var{a op b}}}. -@w{@code{@var{op}=}} and @code{=} have the same precendence. -@var{op} is any one of the operators @code{|}, @code{^}, @code{&}, -@code{<<}, @code{>>}, @code{+}, @code{-}, @code{*}, @code{/}, @code{%}. - -@item ?: -The ternary operator. @code{@var{a} ? @var{b} : @var{c}} can be thought -of as: if @var{a} then @var{b} else @var{c}. @var{a} should be of an -integral type. - -@item || -Logical @sc{or}. Defined on integral types. - -@item && -Logical @sc{and}. Defined on integral types. - -@item | -Bitwise @sc{or}. Defined on integral types. - -@item ^ -Bitwise exclusive-@sc{or}. Defined on integral types. - -@item & -Bitwise @sc{and}. Defined on integral types. - -@item ==@r{, }!= -Equality and inequality. Defined on scalar types. The value of these -expressions is 0 for false and non-zero for true. - -@item <@r{, }>@r{, }<=@r{, }>= -Less than, greater than, less than or equal, greater than or equal. -Defined on scalar types. The value of these expressions is 0 for false -and non-zero for true. - -@item <<@r{, }>> -left shift, and right shift. Defined on integral types. - -@item @@ -The @value{GDBN} ``artificial array'' operator (@pxref{Expressions, ,Expressions}). - -@item +@r{, }- -Addition and subtraction. Defined on integral types, floating-point types and -pointer types. - -@item *@r{, }/@r{, }% -Multiplication, division, and modulus. Multiplication and division are -defined on integral and floating-point types. Modulus is defined on -integral types. - -@item ++@r{, }-- -Increment and decrement. When appearing before a variable, the -operation is performed before the variable is used in an expression; -when appearing after it, the variable's value is used before the -operation takes place. - -@item * -Pointer dereferencing. Defined on pointer types. Same precedence as -@code{++}. - -@item & -Address operator. Defined on variables. Same precedence as @code{++}. - -@ifclear CONLY -For debugging C++, @value{GDBN} implements a use of @samp{&} beyond what is -allowed in the C++ language itself: you can use @samp{&(&@var{ref})} -(or, if you prefer, simply @samp{&&@var{ref}}) to examine the address -where a C++ reference variable (declared with @samp{&@var{ref}}) is -stored. -@end ifclear - -@item - -Negative. Defined on integral and floating-point types. Same -precedence as @code{++}. - -@item ! -Logical negation. Defined on integral types. Same precedence as -@code{++}. - -@item ~ -Bitwise complement operator. Defined on integral types. Same precedence as -@code{++}. - - -@item .@r{, }-> -Structure member, and pointer-to-structure member. For convenience, -@value{GDBN} regards the two as equivalent, choosing whether to dereference a -pointer based on the stored type information. -Defined on @code{struct} and @code{union} data. - -@ifset HPPA -@item .*@r{, }->* -Dereferences of pointers to members. -@end ifset - -@item [] -Array indexing. @code{@var{a}[@var{i}]} is defined as -@code{*(@var{a}+@var{i})}. Same precedence as @code{->}. - -@item () -Function parameter list. Same precedence as @code{->}. - -@ifclear CONLY -@item :: -C++ scope resolution operator. Defined on -@code{struct}, @code{union}, and @code{class} types. -@end ifclear - -@item :: -Doubled colons -@ifclear CONLY -also -@end ifclear -represent the @value{GDBN} scope operator (@pxref{Expressions, -,Expressions}). -@ifclear CONLY -Same precedence as @code{::}, above. -@end ifclear -@end table - -@ifset HPPA -If an operator is redefined in the user code, @value{GDBN} usually -attempts to invoke the redefined version instead of using the operator's -predefined meaning. -@end ifset - -@ifclear CONLY -@menu -* C Constants:: -@end menu - -@ifset MOD2 -@node C Constants, Cplus expressions, C Operators, C -@subsubsection C and C++ constants -@end ifset -@ifclear MOD2 -@node C Constants, Cplus expressions, C Operators, Support -@subsubsection C and C++ constants -@end ifclear - -@cindex C and C++ constants -@value{GDBN} allows you to express the constants of C and C++ in the -following ways: -@end ifclear -@ifset CONLY -@cindex C constants -@node C Constants, Debugging C, C Operators, C -@section C constants - -@value{GDBN} allows you to express the constants of C in the -following ways: -@end ifset - -@itemize @bullet -@item -Integer constants are a sequence of digits. Octal constants are -specified by a leading @samp{0} (i.e. zero), and hexadecimal constants by -a leading @samp{0x} or @samp{0X}. Constants may also end with a letter -@samp{l}, specifying that the constant should be treated as a -@code{long} value. - -@item -Floating point constants are a sequence of digits, followed by a decimal -point, followed by a sequence of digits, and optionally followed by an -exponent. An exponent is of the form: -@samp{@w{e@r{[[}+@r{]|}-@r{]}@var{nnn}}}, where @var{nnn} is another -sequence of digits. The @samp{+} is optional for positive exponents. - -@item -Enumerated constants consist of enumerated identifiers, or their -integral equivalents. - -@item -Character constants are a single character surrounded by single quotes -(@code{'}), or a number---the ordinal value of the corresponding character -(usually its @sc{ASCII} value). Within quotes, the single character may -be represented by a letter or by @dfn{escape sequences}, which are of -the form @samp{\@var{nnn}}, where @var{nnn} is the octal representation -of the character's ordinal value; or of the form @samp{\@var{x}}, where -@samp{@var{x}} is a predefined special character---for example, -@samp{\n} for newline. - -@item -String constants are a sequence of character constants surrounded -by double quotes (@code{"}). - -@item -Pointer constants are an integral value. You can also write pointers -to constants using the C operator @samp{&}. - -@item -Array constants are comma-separated lists surrounded by braces @samp{@{} -and @samp{@}}; for example, @samp{@{1,2,3@}} is a three-element array of -integers, @samp{@{@{1,2@}, @{3,4@}, @{5,6@}@}} is a three-by-two array, -and @samp{@{&"hi", &"there", &"fred"@}} is a three-element array of pointers. -@end itemize - -@ifclear CONLY -@menu -* Cplus expressions:: -* C Defaults:: -@ifset MOD2 -* C Checks:: -@end ifset - -* Debugging C:: -@end menu - -@ifset MOD2 -@node Cplus expressions, C Defaults, C Constants, C -@subsubsection C++ expressions -@end ifset -@ifclear MOD2 -@node Cplus expressions, C Defaults, C Constants, Support -@subsubsection C++ expressions -@end ifclear - -@cindex expressions in C++ -@value{GDBN} expression handling can interpret most C++ expressions. - -@ifclear HPPA -@cindex C++ support, not in @sc{coff} -@cindex @sc{coff} versus C++ -@cindex C++ and object formats -@cindex object formats and C++ -@cindex a.out and C++ -@cindex @sc{ecoff} and C++ -@cindex @sc{xcoff} and C++ -@cindex @sc{elf}/stabs and C++ -@cindex @sc{elf}/@sc{dwarf} and C++ -@c FIXME!! GDB may eventually be able to debug C++ using DWARF; check -@c periodically whether this has happened... -@quotation -@emph{Warning:} @value{GDBN} can only debug C++ code if you use the -proper compiler. Typically, C++ debugging depends on the use of -additional debugging information in the symbol table, and thus requires -special support. In particular, if your compiler generates a.out, MIPS -@sc{ecoff}, RS/6000 @sc{xcoff}, or @sc{elf} with stabs extensions to the -symbol table, these facilities are all available. (With @sc{gnu} CC, -you can use the @samp{-gstabs} option to request stabs debugging -extensions explicitly.) Where the object code format is standard -@sc{coff} or @sc{dwarf} in @sc{elf}, on the other hand, most of the C++ -support in @value{GDBN} does @emph{not} work. -@end quotation -@end ifclear - -@enumerate - -@cindex member functions -@item -Member function calls are allowed; you can use expressions like - -@example -count = aml->GetOriginal(x, y) -@end example - -@kindex this -@cindex namespace in C++ -@item -While a member function is active (in the selected stack frame), your -expressions have the same namespace available as the member function; -that is, @value{GDBN} allows implicit references to the class instance -pointer @code{this} following the same rules as C++. - -@ifclear HPPA -@cindex call overloaded functions -@cindex type conversions in C++ -@item -You can call overloaded functions; @value{GDBN} resolves the function -call to the right definition, with one restriction---you must use -arguments of the type required by the function that you want to call. -@value{GDBN} does not perform conversions requiring constructors or -user-defined type operators. -@end ifclear -@ifset HPPA -@cindex call overloaded functions -@cindex overloaded functions -@cindex type conversions in C++ -@item -You can call overloaded functions; @value{GDBN} resolves the function -call to the right definition, with some restrictions. GDB does not -perform overload resolution involving user-defined type conversions, -calls to constructors, or instantiations of templates that do not exist -in the program. It also cannot handle ellipsis argument lists or -default arguments. - -It does perform integral conversions and promotions, floating-point -promotions, arithmetic conversions, pointer conversions, conversions of -class objects to base classes, and standard conversions such as those of -functions or arrays to pointers; it requires an exact match on the -number of function arguments. - -Overload resolution is always performed, unless you have specified -@code{set overload-resolution off}. @xref{Debugging C plus plus, -,@value{GDBN} features for C++}. - -You must specify@code{set overload-resolution off} in order to use an -explicit function signature to call an overloaded function, as in -@smallexample -p 'foo(char,int)'('x', 13) -@end smallexample -The @value{GDBN} command-completion facility can simplify this; -@pxref{Completion, ,Command completion}. - -@end ifset - -@cindex reference declarations -@item -@value{GDBN} understands variables declared as C++ references; you can use -them in expressions just as you do in C++ source---they are automatically -dereferenced. - -In the parameter list shown when @value{GDBN} displays a frame, the values of -reference variables are not displayed (unlike other variables); this -avoids clutter, since references are often used for large structures. -The @emph{address} of a reference variable is always shown, unless -you have specified @samp{set print address off}. - -@item -@value{GDBN} supports the C++ name resolution operator @code{::}---your -expressions can use it just as expressions in your program do. Since -one scope may be defined in another, you can use @code{::} repeatedly if -necessary, for example in an expression like -@samp{@var{scope1}::@var{scope2}::@var{name}}. @value{GDBN} also allows -resolving name scope by reference to source files, in both C and C++ -debugging (@pxref{Variables, ,Program variables}). -@end enumerate - -@ifset HPPA -In addition, @value{GDBN} supports calling virtual functions correctly, -printing out virtual bases of objects, calling functions in a base -subobject, casting objects, and invoking user-defined operators. -@end ifset - -@ifset MOD2 -@node C Defaults, C Checks, Cplus expressions, C -@subsubsection C and C++ defaults -@end ifset -@ifclear MOD2 -@node C Defaults, Debugging C, Cplus expressions, Support -@subsubsection C and C++ defaults -@end ifclear -@cindex C and C++ defaults - -@ifclear HPPA -If you allow @value{GDBN} to set type and range checking automatically, they -both default to @code{off} whenever the working language changes to -C or C++. This happens regardless of whether you or @value{GDBN} -selects the working language. -@end ifclear - -If you allow @value{GDBN} to set the language automatically, it -recognizes source files whose names end with @file{.c}, @file{.C}, or -@file{.cc}, etc, and when @value{GDBN} enters code compiled from one of -these files, it sets the working language to C or C++. -@xref{Automatically, ,Having @value{GDBN} infer the source language}, -for further details. - -@ifset MOD2 -@c Type checking is (a) primarily motivated by Modula-2, and (b) -@c unimplemented. If (b) changes, it might make sense to let this node -@c appear even if Mod-2 does not, but meanwhile ignore it. roland 16jul93. -@node C Checks, Debugging C, C Defaults, C Constants -@subsubsection C and C++ type and range checks -@cindex C and C++ checks - -By default, when @value{GDBN} parses C or C++ expressions, type checking -is not used. However, if you turn type checking on, @value{GDBN} -considers two variables type equivalent if: - -@itemize @bullet -@item -The two variables are structured and have the same structure, union, or -enumerated tag. - -@item -The two variables have the same type name, or types that have been -declared equivalent through @code{typedef}. - -@ignore -@c leaving this out because neither J Gilmore nor R Pesch understand it. -@c FIXME--beers? -@item -The two @code{struct}, @code{union}, or @code{enum} variables are -declared in the same declaration. (Note: this may not be true for all C -compilers.) -@end ignore -@end itemize - -Range checking, if turned on, is done on mathematical operations. Array -indices are not checked, since they are often used to index a pointer -that is not itself an array. -@end ifset -@end ifclear - -@ifclear CONLY -@ifset MOD2 -@node Debugging C, Debugging C plus plus, C Checks, C -@subsubsection @value{GDBN} and C -@end ifset -@ifclear MOD2 -@node Debugging C, Debugging C plus plus, C Defaults, Support -@subsubsection @value{GDBN} and C -@end ifclear -@end ifclear -@ifset CONLY -@node Debugging C, , C Constants, C -@section @value{GDBN} and C -@end ifset - -The @code{set print union} and @code{show print union} commands apply to -the @code{union} type. When set to @samp{on}, any @code{union} that is -inside a @code{struct} -@ifclear CONLY -or @code{class} -@end ifclear -is also printed. -Otherwise, it appears as @samp{@{...@}}. - -The @code{@@} operator aids in the debugging of dynamic arrays, formed -with pointers and a memory allocation function. @xref{Expressions, -,Expressions}. - -@ifclear CONLY -@menu -* Debugging C plus plus:: -@end menu - -@ifset MOD2 -@node Debugging C plus plus, , Debugging C, C -@subsubsection @value{GDBN} features for C++ -@end ifset -@ifclear MOD2 -@node Debugging C plus plus, , Debugging C, Support -@subsubsection @value{GDBN} features for C++ -@end ifclear - -@cindex commands for C++ -Some @value{GDBN} commands are particularly useful with C++, and some are -designed specifically for use with C++. Here is a summary: - -@table @code -@cindex break in overloaded functions -@item @r{breakpoint menus} -When you want a breakpoint in a function whose name is overloaded, -@value{GDBN} breakpoint menus help you specify which function definition -you want. @xref{Breakpoint Menus,,Breakpoint menus}. - -@cindex overloading in C++ -@item rbreak @var{regex} -Setting breakpoints using regular expressions is helpful for setting -breakpoints on overloaded functions that are not members of any special -classes. -@xref{Set Breaks, ,Setting breakpoints}. - -@cindex C++ exception handling -@item catch throw -@itemx catch catch -Debug C++ exception handling using these commands. @xref{Set -Catchpoints, , Setting catchpoints}. - -@cindex inheritance -@item ptype @var{typename} -Print inheritance relationships as well as other information for type -@var{typename}. -@xref{Symbols, ,Examining the Symbol Table}. - -@cindex C++ symbol display -@item set print demangle -@itemx show print demangle -@itemx set print asm-demangle -@itemx show print asm-demangle -Control whether C++ symbols display in their source form, both when -displaying code as C++ source and when displaying disassemblies. -@xref{Print Settings, ,Print settings}. - -@item set print object -@itemx show print object -Choose whether to print derived (actual) or declared types of objects. -@xref{Print Settings, ,Print settings}. - -@item set print vtbl -@itemx show print vtbl -Control the format for printing virtual function tables. -@xref{Print Settings, ,Print settings}. -@ifset HPPA -(The @code{vtbl} commands do not work on programs compiled with the HP -ANSI C++ compiler (@code{aCC}).) - -@kindex set overload-resolution -@cindex overloaded functions -@item set overload-resolution on -Enable overload resolution for C++ expression evaluation. The default -is on. For overloaded functions, @value{GDBN} evaluates the arguments -and searches for a function whose signature matches the argument types, -using the standard C++ conversion rules (@pxref{Cplus expressions, ,C++ -expressions} for details). If it cannot find a match, it emits a -message. - -@item set overload-resolution off -Disable overload resolution for C++ expression evaluation. For -overloaded functions that are not class member functions, @value{GDBN} -chooses the first function of the specified name that it finds in the -symbol table, whether or not its arguments are of the correct type. For -overloaded functions that are class member functions, @value{GDBN} -searches for a function whose signature @emph{exactly} matches the -argument types. -@end ifset - -@item @r{Overloaded symbol names} -You can specify a particular definition of an overloaded symbol, using -the same notation that is used to declare such symbols in C++: type -@code{@var{symbol}(@var{types})} rather than just @var{symbol}. You can -also use the @value{GDBN} command-line word completion facilities to list the -available choices, or to finish the type list for you. -@xref{Completion,, Command completion}, for details on how to do this. -@end table -@ifclear MOD2 -@c cancels "raisesections" under same conditions near bgn of chapter -@lowersections -@end ifclear - -@ifset MOD2 -@node Modula-2, ,C , Support -@subsection Modula-2 -@cindex Modula-2 - -The extensions made to @value{GDBN} to support Modula-2 only support -output from the @sc{gnu} Modula-2 compiler (which is currently being -developed). Other Modula-2 compilers are not currently supported, and -attempting to debug executables produced by them is most likely -to give an error as @value{GDBN} reads in the executable's symbol -table. - -@cindex expressions in Modula-2 -@menu -* M2 Operators:: Built-in operators -* Built-In Func/Proc:: Built-in functions and procedures -* M2 Constants:: Modula-2 constants -* M2 Defaults:: Default settings for Modula-2 -* Deviations:: Deviations from standard Modula-2 -* M2 Checks:: Modula-2 type and range checks -* M2 Scope:: The scope operators @code{::} and @code{.} -* GDB/M2:: @value{GDBN} and Modula-2 -@end menu - -@node M2 Operators, Built-In Func/Proc, Modula-2, Modula-2 -@subsubsection Operators -@cindex Modula-2 operators - -Operators must be defined on values of specific types. For instance, -@code{+} is defined on numbers, but not on structures. Operators are -often defined on groups of types. For the purposes of Modula-2, the -following definitions hold: - -@itemize @bullet - -@item -@emph{Integral types} consist of @code{INTEGER}, @code{CARDINAL}, and -their subranges. - -@item -@emph{Character types} consist of @code{CHAR} and its subranges. - -@item -@emph{Floating-point types} consist of @code{REAL}. - -@item -@emph{Pointer types} consist of anything declared as @code{POINTER TO -@var{type}}. - -@item -@emph{Scalar types} consist of all of the above. - -@item -@emph{Set types} consist of @code{SET} and @code{BITSET} types. - -@item -@emph{Boolean types} consist of @code{BOOLEAN}. -@end itemize - -@noindent -The following operators are supported, and appear in order of -increasing precedence: - -@table @code -@item , -Function argument or array index separator. - -@item := -Assignment. The value of @var{var} @code{:=} @var{value} is -@var{value}. - -@item <@r{, }> -Less than, greater than on integral, floating-point, or enumerated -types. - -@item <=@r{, }>= -Less than, greater than, less than or equal to, greater than or equal to -on integral, floating-point and enumerated types, or set inclusion on -set types. Same precedence as @code{<}. - -@item =@r{, }<>@r{, }# -Equality and two ways of expressing inequality, valid on scalar types. -Same precedence as @code{<}. In @value{GDBN} scripts, only @code{<>} is -available for inequality, since @code{#} conflicts with the script -comment character. - -@item IN -Set membership. Defined on set types and the types of their members. -Same precedence as @code{<}. - -@item OR -Boolean disjunction. Defined on boolean types. - -@item AND@r{, }& -Boolean conjuction. Defined on boolean types. - -@item @@ -The @value{GDBN} ``artificial array'' operator (@pxref{Expressions, ,Expressions}). - -@item +@r{, }- -Addition and subtraction on integral and floating-point types, or union -and difference on set types. - -@item * -Multiplication on integral and floating-point types, or set intersection -on set types. - -@item / -Division on floating-point types, or symmetric set difference on set -types. Same precedence as @code{*}. - -@item DIV@r{, }MOD -Integer division and remainder. Defined on integral types. Same -precedence as @code{*}. - -@item - -Negative. Defined on @code{INTEGER} and @code{REAL} data. - -@item ^ -Pointer dereferencing. Defined on pointer types. - -@item NOT -Boolean negation. Defined on boolean types. Same precedence as -@code{^}. - -@item . -@code{RECORD} field selector. Defined on @code{RECORD} data. Same -precedence as @code{^}. - -@item [] -Array indexing. Defined on @code{ARRAY} data. Same precedence as @code{^}. - -@item () -Procedure argument list. Defined on @code{PROCEDURE} objects. Same precedence -as @code{^}. - -@item ::@r{, }. -@value{GDBN} and Modula-2 scope operators. -@end table - -@quotation -@emph{Warning:} Sets and their operations are not yet supported, so @value{GDBN} -treats the use of the operator @code{IN}, or the use of operators -@code{+}, @code{-}, @code{*}, @code{/}, @code{=}, , @code{<>}, @code{#}, -@code{<=}, and @code{>=} on sets as an error. -@end quotation - -@cindex Modula-2 built-ins -@node Built-In Func/Proc, M2 Constants, M2 Operators, Modula-2 -@subsubsection Built-in functions and procedures - -Modula-2 also makes available several built-in procedures and functions. -In describing these, the following metavariables are used: - -@table @var - -@item a -represents an @code{ARRAY} variable. - -@item c -represents a @code{CHAR} constant or variable. - -@item i -represents a variable or constant of integral type. - -@item m -represents an identifier that belongs to a set. Generally used in the -same function with the metavariable @var{s}. The type of @var{s} should -be @code{SET OF @var{mtype}} (where @var{mtype} is the type of @var{m}). - -@item n -represents a variable or constant of integral or floating-point type. - -@item r -represents a variable or constant of floating-point type. - -@item t -represents a type. - -@item v -represents a variable. - -@item x -represents a variable or constant of one of many types. See the -explanation of the function for details. -@end table - -All Modula-2 built-in procedures also return a result, described below. - -@table @code -@item ABS(@var{n}) -Returns the absolute value of @var{n}. - -@item CAP(@var{c}) -If @var{c} is a lower case letter, it returns its upper case -equivalent, otherwise it returns its argument - -@item CHR(@var{i}) -Returns the character whose ordinal value is @var{i}. - -@item DEC(@var{v}) -Decrements the value in the variable @var{v}. Returns the new value. - -@item DEC(@var{v},@var{i}) -Decrements the value in the variable @var{v} by @var{i}. Returns the -new value. - -@item EXCL(@var{m},@var{s}) -Removes the element @var{m} from the set @var{s}. Returns the new -set. - -@item FLOAT(@var{i}) -Returns the floating point equivalent of the integer @var{i}. - -@item HIGH(@var{a}) -Returns the index of the last member of @var{a}. - -@item INC(@var{v}) -Increments the value in the variable @var{v}. Returns the new value. - -@item INC(@var{v},@var{i}) -Increments the value in the variable @var{v} by @var{i}. Returns the -new value. - -@item INCL(@var{m},@var{s}) -Adds the element @var{m} to the set @var{s} if it is not already -there. Returns the new set. - -@item MAX(@var{t}) -Returns the maximum value of the type @var{t}. - -@item MIN(@var{t}) -Returns the minimum value of the type @var{t}. - -@item ODD(@var{i}) -Returns boolean TRUE if @var{i} is an odd number. - -@item ORD(@var{x}) -Returns the ordinal value of its argument. For example, the ordinal -value of a character is its ASCII value (on machines supporting the -ASCII character set). @var{x} must be of an ordered type, which include -integral, character and enumerated types. - -@item SIZE(@var{x}) -Returns the size of its argument. @var{x} can be a variable or a type. - -@item TRUNC(@var{r}) -Returns the integral part of @var{r}. - -@item VAL(@var{t},@var{i}) -Returns the member of the type @var{t} whose ordinal value is @var{i}. -@end table - -@quotation -@emph{Warning:} Sets and their operations are not yet supported, so -@value{GDBN} treats the use of procedures @code{INCL} and @code{EXCL} as -an error. -@end quotation - -@cindex Modula-2 constants -@node M2 Constants, M2 Defaults, Built-In Func/Proc, Modula-2 -@subsubsection Constants - -@value{GDBN} allows you to express the constants of Modula-2 in the following -ways: - -@itemize @bullet - -@item -Integer constants are simply a sequence of digits. When used in an -expression, a constant is interpreted to be type-compatible with the -rest of the expression. Hexadecimal integers are specified by a -trailing @samp{H}, and octal integers by a trailing @samp{B}. - -@item -Floating point constants appear as a sequence of digits, followed by a -decimal point and another sequence of digits. An optional exponent can -then be specified, in the form @samp{E@r{[}+@r{|}-@r{]}@var{nnn}}, where -@samp{@r{[}+@r{|}-@r{]}@var{nnn}} is the desired exponent. All of the -digits of the floating point constant must be valid decimal (base 10) -digits. - -@item -Character constants consist of a single character enclosed by a pair of -like quotes, either single (@code{'}) or double (@code{"}). They may -also be expressed by their ordinal value (their ASCII value, usually) -followed by a @samp{C}. - -@item -String constants consist of a sequence of characters enclosed by a -pair of like quotes, either single (@code{'}) or double (@code{"}). -Escape sequences in the style of C are also allowed. @xref{C -Constants, ,C and C++ constants}, for a brief explanation of escape -sequences. - -@item -Enumerated constants consist of an enumerated identifier. - -@item -Boolean constants consist of the identifiers @code{TRUE} and -@code{FALSE}. - -@item -Pointer constants consist of integral values only. - -@item -Set constants are not yet supported. -@end itemize - -@node M2 Defaults, Deviations, M2 Constants, Modula-2 -@subsubsection Modula-2 defaults -@cindex Modula-2 defaults - -If type and range checking are set automatically by @value{GDBN}, they -both default to @code{on} whenever the working language changes to -Modula-2. This happens regardless of whether you, or @value{GDBN}, -selected the working language. - -If you allow @value{GDBN} to set the language automatically, then entering -code compiled from a file whose name ends with @file{.mod} sets the -working language to Modula-2. @xref{Automatically, ,Having @value{GDBN} set -the language automatically}, for further details. - -@node Deviations, M2 Checks, M2 Defaults, Modula-2 -@subsubsection Deviations from standard Modula-2 -@cindex Modula-2, deviations from - -A few changes have been made to make Modula-2 programs easier to debug. -This is done primarily via loosening its type strictness: - -@itemize @bullet -@item -Unlike in standard Modula-2, pointer constants can be formed by -integers. This allows you to modify pointer variables during -debugging. (In standard Modula-2, the actual address contained in a -pointer variable is hidden from you; it can only be modified -through direct assignment to another pointer variable or expression that -returned a pointer.) - -@item -C escape sequences can be used in strings and characters to represent -non-printable characters. @value{GDBN} prints out strings with these -escape sequences embedded. Single non-printable characters are -printed using the @samp{CHR(@var{nnn})} format. - -@item -The assignment operator (@code{:=}) returns the value of its right-hand -argument. - -@item -All built-in procedures both modify @emph{and} return their argument. -@end itemize - -@node M2 Checks, M2 Scope, Deviations, Modula-2 -@subsubsection Modula-2 type and range checks -@cindex Modula-2 checks - -@quotation -@emph{Warning:} in this release, @value{GDBN} does not yet perform type or -range checking. -@end quotation -@c FIXME remove warning when type/range checks added - -@value{GDBN} considers two Modula-2 variables type equivalent if: - -@itemize @bullet -@item -They are of types that have been declared equivalent via a @code{TYPE -@var{t1} = @var{t2}} statement - -@item -They have been declared on the same line. (Note: This is true of the -@sc{gnu} Modula-2 compiler, but it may not be true of other compilers.) -@end itemize - -As long as type checking is enabled, any attempt to combine variables -whose types are not equivalent is an error. - -Range checking is done on all mathematical operations, assignment, array -index bounds, and all built-in functions and procedures. - -@node M2 Scope, GDB/M2, M2 Checks, Modula-2 -@subsubsection The scope operators @code{::} and @code{.} -@cindex scope -@kindex . -@cindex colon, doubled as scope operator -@ifinfo -@kindex colon-colon -@c Info cannot handle :: but TeX can. -@end ifinfo -@iftex -@kindex :: -@end iftex - -There are a few subtle differences between the Modula-2 scope operator -(@code{.}) and the @value{GDBN} scope operator (@code{::}). The two have -similar syntax: - -@example - -@var{module} . @var{id} -@var{scope} :: @var{id} -@end example - -@noindent -where @var{scope} is the name of a module or a procedure, -@var{module} the name of a module, and @var{id} is any declared -identifier within your program, except another module. - -Using the @code{::} operator makes @value{GDBN} search the scope -specified by @var{scope} for the identifier @var{id}. If it is not -found in the specified scope, then @value{GDBN} searches all scopes -enclosing the one specified by @var{scope}. - -Using the @code{.} operator makes @value{GDBN} search the current scope for -the identifier specified by @var{id} that was imported from the -definition module specified by @var{module}. With this operator, it is -an error if the identifier @var{id} was not imported from definition -module @var{module}, or if @var{id} is not an identifier in -@var{module}. - -@node GDB/M2, , M2 Scope, Modula-2 -@subsubsection @value{GDBN} and Modula-2 - -Some @value{GDBN} commands have little use when debugging Modula-2 programs. -Five subcommands of @code{set print} and @code{show print} apply -specifically to C and C++: @samp{vtbl}, @samp{demangle}, -@samp{asm-demangle}, @samp{object}, and @samp{union}. The first four -apply to C++, and the last to the C @code{union} type, which has no direct -analogue in Modula-2. - -The @code{@@} operator (@pxref{Expressions, ,Expressions}), while available -while using any language, is not useful with Modula-2. Its -intent is to aid the debugging of @dfn{dynamic arrays}, which cannot be -created in Modula-2 as they can in C or C++. However, because an -address can be specified by an integral constant, the construct -@samp{@{@var{type}@}@var{adrexp}} is still useful. (@pxref{Expressions, ,Expressions}) - -@cindex @code{#} in Modula-2 -In @value{GDBN} scripts, the Modula-2 inequality operator @code{#} is -interpreted as the beginning of a comment. Use @code{<>} instead. -@end ifset -@end ifclear - -@node Symbols, Altering, Languages, Top -@chapter Examining the Symbol Table - -The commands described in this section allow you to inquire about the -symbols (names of variables, functions and types) defined in your -program. This information is inherent in the text of your program and -does not change as your program executes. @value{GDBN} finds it in your -program's symbol table, in the file indicated when you started @value{GDBN} -(@pxref{File Options, ,Choosing files}), or by one of the -file-management commands (@pxref{Files, ,Commands to specify files}). - -@cindex symbol names -@cindex names of symbols -@cindex quoting names -Occasionally, you may need to refer to symbols that contain unusual -characters, which @value{GDBN} ordinarily treats as word delimiters. The -most frequent case is in referring to static variables in other -source files (@pxref{Variables,,Program variables}). File names -are recorded in object files as debugging symbols, but @value{GDBN} would -ordinarily parse a typical file name, like @file{foo.c}, as the three words -@samp{foo} @samp{.} @samp{c}. To allow @value{GDBN} to recognize -@samp{foo.c} as a single symbol, enclose it in single quotes; for example, - -@example -p 'foo.c'::x -@end example - -@noindent -looks up the value of @code{x} in the scope of the file @file{foo.c}. - -@table @code -@kindex info address -@item info address @var{symbol} -Describe where the data for @var{symbol} is stored. For a register -variable, this says which register it is kept in. For a non-register -local variable, this prints the stack-frame offset at which the variable -is always stored. - -Note the contrast with @samp{print &@var{symbol}}, which does not work -at all for a register variable, and for a stack local variable prints -the exact address of the current instantiation of the variable. - -@kindex whatis -@item whatis @var{exp} -Print the data type of expression @var{exp}. @var{exp} is not -actually evaluated, and any side-effecting operations (such as -assignments or function calls) inside it do not take place. -@xref{Expressions, ,Expressions}. - -@item whatis -Print the data type of @code{$}, the last value in the value history. - -@kindex ptype -@item ptype @var{typename} -Print a description of data type @var{typename}. @var{typename} may be -the name of a type, or for C code it may have the form -@ifclear CONLY -@samp{class @var{class-name}}, -@end ifclear -@samp{struct @var{struct-tag}}, @samp{union @var{union-tag}} or -@samp{enum @var{enum-tag}}. - -@item ptype @var{exp} -@itemx ptype -Print a description of the type of expression @var{exp}. @code{ptype} -differs from @code{whatis} by printing a detailed description, instead -of just the name of the type. - -For example, for this variable declaration: - -@example -struct complex @{double real; double imag;@} v; -@end example - -@noindent -the two commands give this output: - -@example -@group -(@value{GDBP}) whatis v -type = struct complex -(@value{GDBP}) ptype v -type = struct complex @{ - double real; - double imag; -@} -@end group -@end example - -@noindent -As with @code{whatis}, using @code{ptype} without an argument refers to -the type of @code{$}, the last value in the value history. - -@kindex info types -@item info types @var{regexp} -@itemx info types -Print a brief description of all types whose name matches @var{regexp} -(or all types in your program, if you supply no argument). Each -complete typename is matched as though it were a complete line; thus, -@samp{i type value} gives information on all types in your program whose -name includes the string @code{value}, but @samp{i type ^value$} gives -information only on types whose complete name is @code{value}. - -This command differs from @code{ptype} in two ways: first, like -@code{whatis}, it does not print a detailed description; second, it -lists all source files where a type is defined. - -@kindex info source -@item info source -Show the name of the current source file---that is, the source file for -the function containing the current point of execution---and the language -it was written in. - -@kindex info sources -@item info sources -Print the names of all source files in your program for which there is -debugging information, organized into two lists: files whose symbols -have already been read, and files whose symbols will be read when needed. - -@kindex info functions -@item info functions -Print the names and data types of all defined functions. - -@item info functions @var{regexp} -Print the names and data types of all defined functions -whose names contain a match for regular expression @var{regexp}. -Thus, @samp{info fun step} finds all functions whose names -include @code{step}; @samp{info fun ^step} finds those whose names -start with @code{step}. - -@kindex info variables -@item info variables -Print the names and data types of all variables that are declared -outside of functions (i.e., excluding local variables). - -@item info variables @var{regexp} -Print the names and data types of all variables (except for local -variables) whose names contain a match for regular expression -@var{regexp}. - -@ignore -This was never implemented. -@kindex info methods -@item info methods -@itemx info methods @var{regexp} -The @code{info methods} command permits the user to examine all defined -methods within C++ program, or (with the @var{regexp} argument) a -specific set of methods found in the various C++ classes. Many -C++ classes provide a large number of methods. Thus, the output -from the @code{ptype} command can be overwhelming and hard to use. The -@code{info-methods} command filters the methods, printing only those -which match the regular-expression @var{regexp}. -@end ignore - -@ifclear HPPA -@cindex reloading symbols -Some systems allow individual object files that make up your program to -be replaced without stopping and restarting your program. -@ifset VXWORKS -For example, in VxWorks you can simply recompile a defective object file -and keep on running. -@end ifset -If you are running on one of these systems, you can allow @value{GDBN} to -reload the symbols for automatically relinked modules: - -@table @code -@kindex set symbol-reloading -@item set symbol-reloading on -Replace symbol definitions for the corresponding source file when an -object file with a particular name is seen again. - -@item set symbol-reloading off -Do not replace symbol definitions when re-encountering object files of -the same name. This is the default state; if you are not running on a -system that permits automatically relinking modules, you should leave -@code{symbol-reloading} off, since otherwise @value{GDBN} may discard symbols -when linking large programs, that may contain several modules (from -different directories or libraries) with the same name. - -@kindex show symbol-reloading -@item show symbol-reloading -Show the current @code{on} or @code{off} setting. -@end table -@end ifclear - -@ifset HPPA -@kindex set opaque-type-resolution -@item set opaque-type-resolution on -Tell @value{GDBN} to resolve opaque types. An opaque type is a type -declared as a pointer to a @code{struct}, @code{class}, or -@code{union}---for example, @code{struct MyType *}---that is used in one -source file although the full declaration of @code{struct MyType} is in -another source file. The default is on. - -A change in the setting of this subcommand will not take effect until -the next time symbols for a file are loaded. - -@item set opaque-type-resolution off -Tell @value{GDBN} not to resolve opaque types. In this case, the type -is printed as follows: -@smallexample -@{<no data fields>@} -@end smallexample - -@kindex show opaque-type-resolution -@item show opaque-type-resolution -Show whether opaque types are resolved or not. -@end ifset - -@kindex maint print symbols -@cindex symbol dump -@kindex maint print psymbols -@cindex partial symbol dump -@item maint print symbols @var{filename} -@itemx maint print psymbols @var{filename} -@itemx maint print msymbols @var{filename} -Write a dump of debugging symbol data into the file @var{filename}. -These commands are used to debug the @value{GDBN} symbol-reading code. Only -symbols with debugging data are included. If you use @samp{maint print -symbols}, @value{GDBN} includes all the symbols for which it has already -collected full details: that is, @var{filename} reflects symbols for -only those files whose symbols @value{GDBN} has read. You can use the -command @code{info sources} to find out which files these are. If you -use @samp{maint print psymbols} instead, the dump shows information about -symbols that @value{GDBN} only knows partially---that is, symbols defined in -files that @value{GDBN} has skimmed, but not yet read completely. Finally, -@samp{maint print msymbols} dumps just the minimal symbol information -required for each object file from which @value{GDBN} has read some symbols. -@xref{Files, ,Commands to specify files}, for a discussion of how -@value{GDBN} reads symbols (in the description of @code{symbol-file}). -@end table - -@node Altering, GDB Files, Symbols, Top -@chapter Altering Execution - -Once you think you have found an error in your program, you might want to -find out for certain whether correcting the apparent error would lead to -correct results in the rest of the run. You can find the answer by -experiment, using the @value{GDBN} features for altering execution of the -program. - -For example, you can store new values into variables or memory -locations, -@ifclear BARETARGET -give your program a signal, restart it -@end ifclear -@ifset BARETARGET -restart your program -@end ifset -at a different address, or even return prematurely from a function. - -@menu -* Assignment:: Assignment to variables -* Jumping:: Continuing at a different address -@ifclear BARETARGET -* Signaling:: Giving your program a signal -@end ifclear - -* Returning:: Returning from a function -* Calling:: Calling your program's functions -* Patching:: Patching your program -@end menu - -@node Assignment, Jumping, Altering, Altering -@section Assignment to variables - -@cindex assignment -@cindex setting variables -To alter the value of a variable, evaluate an assignment expression. -@xref{Expressions, ,Expressions}. For example, - -@example -print x=4 -@end example - -@noindent -stores the value 4 into the variable @code{x}, and then prints the -value of the assignment expression (which is 4). -@ifclear CONLY -@xref{Languages, ,Using @value{GDBN} with Different Languages}, for more -information on operators in supported languages. -@end ifclear - -@kindex set variable -@cindex variables, setting -If you are not interested in seeing the value of the assignment, use the -@code{set} command instead of the @code{print} command. @code{set} is -really the same as @code{print} except that the expression's value is -not printed and is not put in the value history (@pxref{Value History, -,Value history}). The expression is evaluated only for its effects. - -@ifclear HPPA -If the beginning of the argument string of the @code{set} command -appears identical to a @code{set} subcommand, use the @code{set -variable} command instead of just @code{set}. This command is identical -to @code{set} except for its lack of subcommands. For example, if your -program has a variable @code{width}, you get an error if you try to set -a new value with just @samp{set width=13}, because @value{GDBN} has the -command @code{set width}: - -@example -(@value{GDBP}) whatis width -type = double -(@value{GDBP}) p width -$4 = 13 -(@value{GDBP}) set width=47 -Invalid syntax in expression. -@end example - -@noindent -The invalid expression, of course, is @samp{=47}. In -order to actually set the program's variable @code{width}, use - -@example -(@value{GDBP}) set var width=47 -@end example -@end ifclear -@ifset HPPA -Because the @code{set} command has many subcommands that can conflict -with the names of program variables, it is a good idea to use the -@code{set variable} command instead of just @code{set}. For example, if -your program has a variable @code{g}, you run into problems if you try -to set a new value with just @samp{set g=4}, because @value{GDBN} has -the command @code{set gnutarget}, abbreviated @code{set g}: - -@example -@group -(@value{GDBP}) whatis g -type = double -(@value{GDBP}) p g -$1 = 1 -(@value{GDBP}) set g=4 -(gdb) p g -$2 = 1 -(@value{GDBP}) r -The program being debugged has been started already. -Start it from the beginning? (y or n) y -Starting program: /home/smith/cc_progs/a.out -"/home/smith/cc_progs/a.out": can't open to read symbols: Invalid bfd target. -(@value{GDBP}) show g -The current BFD target is "=4". -@end group -@end example - -@noindent -The program variable @code{g} did not change, and you silently set the -@code{gnutarget} to an invalid value. In order to set the variable -@code{g}, use - -@example -(@value{GDBP}) set var g=4 -@end example -@end ifset - -@value{GDBN} allows more implicit conversions in assignments than C; you can -freely store an integer value into a pointer variable or vice versa, -and you can convert any structure to any other structure that is the -same length or shorter. -@comment FIXME: how do structs align/pad in these conversions? -@comment /doc@cygnus.com 18dec1990 - -To store values into arbitrary places in memory, use the @samp{@{@dots{}@}} -construct to generate a value of specified type at a specified address -(@pxref{Expressions, ,Expressions}). For example, @code{@{int@}0x83040} refers -to memory location @code{0x83040} as an integer (which implies a certain size -and representation in memory), and - -@example -set @{int@}0x83040 = 4 -@end example - -@noindent -stores the value 4 into that memory location. - -@node Jumping, Signaling, Assignment, Altering -@section Continuing at a different address - -Ordinarily, when you continue your program, you do so at the place where -it stopped, with the @code{continue} command. You can instead continue at -an address of your own choosing, with the following commands: - -@table @code -@kindex jump -@item jump @var{linespec} -Resume execution at line @var{linespec}. Execution stops again -immediately if there is a breakpoint there. @xref{List, ,Printing -source lines}, for a description of the different forms of -@var{linespec}. It is common practice to use the @code{tbreak} command -in conjunction with @code{jump}. @xref{Set Breaks, ,Setting -breakpoints}. - -The @code{jump} command does not change the current stack frame, or -the stack pointer, or the contents of any memory location or any -register other than the program counter. If line @var{linespec} is in -a different function from the one currently executing, the results may -be bizarre if the two functions expect different patterns of arguments or -of local variables. For this reason, the @code{jump} command requests -confirmation if the specified line is not in the function currently -executing. However, even bizarre results are predictable if you are -well acquainted with the machine-language code of your program. - -@item jump *@var{address} -Resume execution at the instruction at address @var{address}. -@end table - -@ifclear HPPA -@c Doesn't work on HP-UX; have to set $pcoqh and $pcoqt. -You can get much the same effect as the @code{jump} command by storing a -new value into the register @code{$pc}. The difference is that this -does not start your program running; it only changes the address of where it -@emph{will} run when you continue. For example, - -@example -set $pc = 0x485 -@end example - -@noindent -makes the next @code{continue} command or stepping command execute at -address @code{0x485}, rather than at the address where your program stopped. -@xref{Continuing and Stepping, ,Continuing and stepping}. -@end ifclear - -The most common occasion to use the @code{jump} command is to back -up---perhaps with more breakpoints set---over a portion of a program -that has already executed, in order to examine its execution in more -detail. - -@ifclear BARETARGET -@c @group -@node Signaling, Returning, Jumping, Altering -@section Giving your program a signal - -@table @code -@kindex signal -@item signal @var{signal} -Resume execution where your program stopped, but immediately give it the -signal @var{signal}. @var{signal} can be the name or the number of a -signal. For example, on many systems @code{signal 2} and @code{signal -SIGINT} are both ways of sending an interrupt signal. - -Alternatively, if @var{signal} is zero, continue execution without -giving a signal. This is useful when your program stopped on account of -a signal and would ordinary see the signal when resumed with the -@code{continue} command; @samp{signal 0} causes it to resume without a -signal. - -@code{signal} does not repeat when you press @key{RET} a second time -after executing the command. -@end table -@c @end group - -Invoking the @code{signal} command is not the same as invoking the -@code{kill} utility from the shell. Sending a signal with @code{kill} -causes @value{GDBN} to decide what to do with the signal depending on -the signal handling tables (@pxref{Signals}). The @code{signal} command -passes the signal directly to your program. - -@end ifclear - -@node Returning, Calling, Signaling, Altering -@section Returning from a function - -@table @code -@cindex returning from a function -@kindex return -@item return -@itemx return @var{expression} -You can cancel execution of a function call with the @code{return} -command. If you give an -@var{expression} argument, its value is used as the function's return -value. -@end table - -When you use @code{return}, @value{GDBN} discards the selected stack frame -(and all frames within it). You can think of this as making the -discarded frame return prematurely. If you wish to specify a value to -be returned, give that value as the argument to @code{return}. - -This pops the selected stack frame (@pxref{Selection, ,Selecting a -frame}), and any other frames inside of it, leaving its caller as the -innermost remaining frame. That frame becomes selected. The -specified value is stored in the registers used for returning values -of functions. - -The @code{return} command does not resume execution; it leaves the -program stopped in the state that would exist if the function had just -returned. In contrast, the @code{finish} command (@pxref{Continuing -and Stepping, ,Continuing and stepping}) resumes execution until the -selected stack frame returns naturally. - -@node Calling, Patching, Returning, Altering -@section Calling program functions - -@cindex calling functions -@kindex call -@table @code -@item call @var{expr} -Evaluate the expression @var{expr} without displaying @code{void} -returned values. -@end table - -You can use this variant of the @code{print} command if you want to -execute a function from your program, but without cluttering the output -with @code{void} returned values. If the result is not void, it -is printed and saved in the value history. - -@ifclear HPPA -For the A29K, a user-controlled variable @code{call_scratch_address}, -specifies the location of a scratch area to be used when @value{GDBN} -calls a function in the target. This is necessary because the usual -method of putting the scratch area on the stack does not work in systems -that have separate instruction and data spaces. -@end ifclear - -@node Patching, , Calling, Altering -@section Patching programs -@cindex patching binaries -@cindex writing into executables -@ifclear BARETARGET -@cindex writing into corefiles -@end ifclear - -By default, @value{GDBN} opens the file containing your program's executable -code -@ifclear BARETARGET -(or the corefile) -@end ifclear -read-only. This prevents accidental alterations -to machine code; but it also prevents you from intentionally patching -your program's binary. - -If you'd like to be able to patch the binary, you can specify that -explicitly with the @code{set write} command. For example, you might -want to turn on internal debugging flags, or even to make emergency -repairs. - -@table @code -@kindex set write -@item set write on -@itemx set write off -If you specify @samp{set write on}, @value{GDBN} opens executable -@ifclear BARETARGET -and core -@end ifclear -files for both reading and writing; if you specify @samp{set write -off} (the default), @value{GDBN} opens them read-only. - -If you have already loaded a file, you must load it again (using the -@code{exec-file} -@ifclear BARETARGET -or @code{core-file} -@end ifclear -command) after changing @code{set write}, for your new setting to take -effect. - -@item show write -@kindex show write -Display whether executable files -@ifclear BARETARGET -and core files -@end ifclear -are opened for writing as well as reading. -@end table - -@node GDB Files, Targets, Altering, Top -@chapter @value{GDBN} Files - -@value{GDBN} needs to know the file name of the program to be debugged, both in -order to read its symbol table and in order to start your program. -@ifclear BARETARGET -To debug a core dump of a previous run, you must also tell @value{GDBN} -the name of the core dump file. -@end ifclear - -@menu -* Files:: Commands to specify files -* Symbol Errors:: Errors reading symbol files -@end menu - -@node Files, Symbol Errors, GDB Files, GDB Files -@section Commands to specify files -@cindex symbol table - -@ifclear BARETARGET -@cindex core dump file -You may want to specify executable and core dump file names. -The usual way to do this is at start-up time, using the arguments to -@value{GDBN}'s start-up commands (@pxref{Invocation, , -Getting In and Out of @value{GDBN}}). -@end ifclear -@ifset BARETARGET -The usual way to specify an executable file name is with -the command argument given when you start @value{GDBN}, (@pxref{Invocation, -,Getting In and Out of @value{GDBN}}. -@end ifset - -Occasionally it is necessary to change to a different file during a -@value{GDBN} session. Or you may run @value{GDBN} and forget to specify -a file you want to use. In these situations the @value{GDBN} commands -to specify new files are useful. - -@table @code -@cindex executable file -@kindex file -@item file @var{filename} -Use @var{filename} as the program to be debugged. It is read for its -symbols and for the contents of pure memory. It is also the program -executed when you use the @code{run} command. If you do not specify a -directory and the file is not found in the @value{GDBN} working directory, -@value{GDBN} uses the environment variable @code{PATH} as a list of -directories to search, just as the shell does when looking for a program -to run. You can change the value of this variable, for both @value{GDBN} -and your program, using the @code{path} command. - -@ifclear HPPA -On systems with memory-mapped files, an auxiliary file -@file{@var{filename}.syms} may hold symbol table information for -@var{filename}. If so, @value{GDBN} maps in the symbol table from -@file{@var{filename}.syms}, starting up more quickly. See the -descriptions of the file options @samp{-mapped} and @samp{-readnow} -(available on the command line, and with the commands @code{file}, -@code{symbol-file}, or @code{add-symbol-file}, described below), -for more information. -@end ifclear - -@item file -@code{file} with no argument makes @value{GDBN} discard any information it -has on both executable file and the symbol table. - -@kindex exec-file -@item exec-file @r{[} @var{filename} @r{]} -Specify that the program to be run (but not the symbol table) is found -in @var{filename}. @value{GDBN} searches the environment variable @code{PATH} -if necessary to locate your program. Omitting @var{filename} means to -discard information on the executable file. - -@kindex symbol-file -@item symbol-file @r{[} @var{filename} @r{]} -Read symbol table information from file @var{filename}. @code{PATH} is -searched when necessary. Use the @code{file} command to get both symbol -table and program to run from the same file. - -@code{symbol-file} with no argument clears out @value{GDBN} information on your -program's symbol table. - -The @code{symbol-file} command causes @value{GDBN} to forget the contents -of its convenience variables, the value history, and all breakpoints and -auto-display expressions. This is because they may contain pointers to -the internal data recording symbols and data types, which are part of -the old symbol table data being discarded inside @value{GDBN}. - -@code{symbol-file} does not repeat if you press @key{RET} again after -executing it once. - -When @value{GDBN} is configured for a particular environment, it -understands debugging information in whatever format is the standard -generated for that environment; you may use either a @sc{gnu} compiler, or -other compilers that adhere to the local conventions. -@ifclear HPPA -Best results are usually obtained from @sc{gnu} compilers; for example, -using @code{@value{GCC}} you can generate debugging information for -optimized code. -@end ifclear - -For most kinds of object files, with the exception of old SVR3 systems -using COFF, the @code{symbol-file} command does not normally read the -symbol table in full right away. Instead, it scans the symbol table -quickly to find which source files and which symbols are present. The -details are read later, one source file at a time, as they are needed. - -The purpose of this two-stage reading strategy is to make @value{GDBN} -start up faster. For the most part, it is invisible except for -occasional pauses while the symbol table details for a particular source -file are being read. (The @code{set verbose} command can turn these -pauses into messages if desired. @xref{Messages/Warnings, ,Optional -warnings and messages}.) - -@ifclear HPPA -We have not implemented the two-stage strategy for COFF yet. When the -symbol table is stored in COFF format, @code{symbol-file} reads the -symbol table data in full right away. Note that ``stabs-in-COFF'' -still does the two-stage strategy, since the debug info is actually -in stabs format. - -@kindex readnow -@cindex reading symbols immediately -@cindex symbols, reading immediately -@kindex mapped -@cindex memory-mapped symbol file -@cindex saving symbol table -@item symbol-file @var{filename} @r{[} -readnow @r{]} @r{[} -mapped @r{]} -@itemx file @var{filename} @r{[} -readnow @r{]} @r{[} -mapped @r{]} -You can override the @value{GDBN} two-stage strategy for reading symbol -tables by using the @samp{-readnow} option with any of the commands that -load symbol table information, if you want to be sure @value{GDBN} has the -entire symbol table available. -@end ifclear - -@ifclear BARETARGET -@ifclear HPPA -If memory-mapped files are available on your system through the -@code{mmap} system call, you can use another option, @samp{-mapped}, to -cause @value{GDBN} to write the symbols for your program into a reusable -file. Future @value{GDBN} debugging sessions map in symbol information -from this auxiliary symbol file (if the program has not changed), rather -than spending time reading the symbol table from the executable -program. Using the @samp{-mapped} option has the same effect as -starting @value{GDBN} with the @samp{-mapped} command-line option. - -You can use both options together, to make sure the auxiliary symbol -file has all the symbol information for your program. - -The auxiliary symbol file for a program called @var{myprog} is called -@samp{@var{myprog}.syms}. Once this file exists (so long as it is newer -than the corresponding executable), @value{GDBN} always attempts to use -it when you debug @var{myprog}; no special options or commands are -needed. - -The @file{.syms} file is specific to the host machine where you run -@value{GDBN}. It holds an exact image of the internal @value{GDBN} -symbol table. It cannot be shared across multiple host platforms. -@end ifclear - -@c FIXME: for now no mention of directories, since this seems to be in -@c flux. 13mar1992 status is that in theory GDB would look either in -@c current dir or in same dir as myprog; but issues like competing -@c GDB's, or clutter in system dirs, mean that in practice right now -@c only current dir is used. FFish says maybe a special GDB hierarchy -@c (eg rooted in val of env var GDBSYMS) could exist for mappable symbol -@c files. - -@kindex core -@kindex core-file -@item core-file @r{[} @var{filename} @r{]} -Specify the whereabouts of a core dump file to be used as the ``contents -of memory''. Traditionally, core files contain only some parts of the -address space of the process that generated them; @value{GDBN} can access the -executable file itself for other parts. - -@code{core-file} with no argument specifies that no core file is -to be used. - -Note that the core file is ignored when your program is actually running -under @value{GDBN}. So, if you have been running your program and you wish to -debug a core file instead, you must kill the subprocess in which the -program is running. To do this, use the @code{kill} command -(@pxref{Kill Process, ,Killing the child process}). -@end ifclear - -@ifclear BARETARGET -@ifclear HPPA -@kindex add-symbol-file -@cindex dynamic linking -@item add-symbol-file @var{filename} @var{address} -@itemx add-symbol-file @var{filename} @var{address} @r{[} -readnow @r{]} @r{[} -mapped @r{]} -The @code{add-symbol-file} command reads additional symbol table information -from the file @var{filename}. You would use this command when @var{filename} -has been dynamically loaded (by some other means) into the program that -is running. @var{address} should be the memory address at which the -file has been loaded; @value{GDBN} cannot figure this out for itself. -You can specify @var{address} as an expression. - -The symbol table of the file @var{filename} is added to the symbol table -originally read with the @code{symbol-file} command. You can use the -@code{add-symbol-file} command any number of times; the new symbol data thus -read keeps adding to the old. To discard all old symbol data instead, -use the @code{symbol-file} command. - -@code{add-symbol-file} does not repeat if you press @key{RET} after using it. - -You can use the @samp{-mapped} and @samp{-readnow} options just as with -the @code{symbol-file} command, to change how @value{GDBN} manages the symbol -table information for @var{filename}. - -@kindex add-shared-symbol-file -@item add-shared-symbol-file -The @code{add-shared-symbol-file} command can be used only under Harris' CXUX -operating system for the Motorola 88k. @value{GDBN} automatically looks for -shared libraries, however if @value{GDBN} does not find yours, you can run -@code{add-shared-symbol-file}. It takes no arguments. -@end ifclear -@end ifclear - -@ifclear HPPA -@kindex section -@item section -The @code{section} command changes the base address of section SECTION of -the exec file to ADDR. This can be used if the exec file does not contain -section addresses, (such as in the a.out format), or when the addresses -specified in the file itself are wrong. Each section must be changed -separately. The ``info files'' command lists all the sections and their -addresses. -@end ifclear - -@kindex info files -@kindex info target -@item info files -@itemx info target -@code{info files} and @code{info target} are synonymous; both print -the current target (@pxref{Targets, ,Specifying a Debugging Target}), -including the -@ifclear BARETARGET -names of the executable and core dump files -@end ifclear -@ifset BARETARGET -name of the executable file -@end ifset -currently in use by @value{GDBN}, and the files from which symbols were -loaded. The command @code{help target} lists all possible targets -rather than current ones. -@end table - -All file-specifying commands allow both absolute and relative file names -as arguments. @value{GDBN} always converts the file name to an absolute file -name and remembers it that way. - -@ifclear BARETARGET -@cindex shared libraries -@ifclear HPPA -@c added HP-UX -- Kim (HP writer) -@value{GDBN} supports HP-UX, SunOS, SVr4, Irix 5, and IBM RS/6000 shared -libraries. -@end ifclear -@ifset HPPA -@value{GDBN} supports HP-UX shared libraries. -@end ifset -@value{GDBN} automatically loads symbol definitions from shared libraries -when you use the @code{run} command, or when you examine a core file. -(Before you issue the @code{run} command, @value{GDBN} does not understand -references to a function in a shared library, however---unless you are -debugging a core file). -@ifset HPPA -If the program loads a library explicitly, @value{GDBN} automatically -loads the symbols at the time of the @code{shl_load} call. -@end ifset -@c FIXME: some @value{GDBN} release may permit some refs to undef -@c FIXME...symbols---eg in a break cmd---assuming they are from a shared -@c FIXME...lib; check this from time to time when updating manual - -@table @code -@kindex info sharedlibrary -@kindex info share -@item info share -@itemx info sharedlibrary -Print the names of the shared libraries which are currently loaded. - -@kindex sharedlibrary -@kindex share -@item sharedlibrary @var{regex} -@itemx share @var{regex} - -Load shared object library symbols for files matching a -Unix regular expression. -As with files loaded automatically, it only loads shared libraries -required by your program for a core file or after typing @code{run}. If -@var{regex} is omitted all shared libraries required by your program are -loaded. -@end table - -@ifset HPPA -@value{GDBN} detects the loading of a shared library and automatically -reads in symbols from the newly loaded library, up to a threshold that -is initially set but that you can modify if you wish. - -Beyond that threshold, symbols from shared libraries must be explicitly -loaded. To load these symbols, use the command @code{sharedlibrary} -@var{filename}. The base address of the shared library is determined -automatically by @value{GDBN} and need not be specified. - -To display or set the threshold, use the commands: - -@table @code -@kindex set auto-solib-add -@item set auto-solib-add @var{threshold} -Set the autoloading size threshold, in megabytes. If @var{threshold} is -nonzero, symbols from all shared object libraries will be loaded -automatically when the inferior begins execution or when the dynamic -linker informs @value{GDBN} that a new library has been loaded, until -the symbol table of the program and libraries exceeds this threshold. -Otherwise, symbols must be loaded manually, using the -@code{sharedlibrary} command. The default threshold is 100 megabytes. - -@kindex show auto-solib-add -@item show auto-solib-add -Display the current autoloading size threshold, in megabytes. -@end table -@end ifset - -@end ifclear - -@node Symbol Errors, , Files, GDB Files -@section Errors reading symbol files - -While reading a symbol file, @value{GDBN} occasionally encounters problems, -such as symbol types it does not recognize, or known bugs in compiler -output. By default, @value{GDBN} does not notify you of such problems, since -they are relatively common and primarily of interest to people -debugging compilers. If you are interested in seeing information -about ill-constructed symbol tables, you can either ask @value{GDBN} to print -only one message about each such type of problem, no matter how many -times the problem occurs; or you can ask @value{GDBN} to print more messages, -to see how many times the problems occur, with the @code{set -complaints} command (@pxref{Messages/Warnings, ,Optional warnings and -messages}). - -The messages currently printed, and their meanings, include: - -@table @code -@item inner block not inside outer block in @var{symbol} - -The symbol information shows where symbol scopes begin and end -(such as at the start of a function or a block of statements). This -error indicates that an inner scope block is not fully contained -in its outer scope blocks. - -@value{GDBN} circumvents the problem by treating the inner block as if it had -the same scope as the outer block. In the error message, @var{symbol} -may be shown as ``@code{(don't know)}'' if the outer block is not a -function. - -@item block at @var{address} out of order - -The symbol information for symbol scope blocks should occur in -order of increasing addresses. This error indicates that it does not -do so. - -@value{GDBN} does not circumvent this problem, and has trouble -locating symbols in the source file whose symbols it is reading. (You -can often determine what source file is affected by specifying -@code{set verbose on}. @xref{Messages/Warnings, ,Optional warnings and -messages}.) - -@item bad block start address patched - -The symbol information for a symbol scope block has a start address -smaller than the address of the preceding source line. This is known -to occur in the SunOS 4.1.1 (and earlier) C compiler. - -@value{GDBN} circumvents the problem by treating the symbol scope block as -starting on the previous source line. - -@item bad string table offset in symbol @var{n} - -@cindex foo -Symbol number @var{n} contains a pointer into the string table which is -larger than the size of the string table. - -@value{GDBN} circumvents the problem by considering the symbol to have the -name @code{foo}, which may cause other problems if many symbols end up -with this name. - -@item unknown symbol type @code{0x@var{nn}} - -The symbol information contains new data types that @value{GDBN} does not yet -know how to read. @code{0x@var{nn}} is the symbol type of the misunderstood -information, in hexadecimal. - -@value{GDBN} circumvents the error by ignoring this symbol information. This -usually allows you to debug your program, though certain symbols -are not accessible. If you encounter such a problem and feel like -debugging it, you can debug @code{@value{GDBP}} with itself, breakpoint on -@code{complain}, then go up to the function @code{read_dbx_symtab} and -examine @code{*bufp} to see the symbol. - -@item stub type has NULL name -@value{GDBN} could not find the full definition for -@ifclear CONLY -a struct or class. -@end ifclear -@ifset CONLY -a struct. -@end ifset - -@ifclear CONLY -@item const/volatile indicator missing (ok if using g++ v1.x), got@dots{} - -The symbol information for a C++ member function is missing some -information that recent versions of the compiler should have output -for it. -@end ifclear - -@item info mismatch between compiler and debugger - -@value{GDBN} could not parse a type specification output by the compiler. -@end table - -@node Targets, Controlling GDB, GDB Files, Top -@chapter Specifying a Debugging Target -@cindex debugging target -@kindex target - -A @dfn{target} is the execution environment occupied by your program. -@ifclear HPPA -@ifclear BARETARGET -Often, @value{GDBN} runs in the same host environment as your program; in -that case, the debugging target is specified as a side effect when you -use the @code{file} or @code{core} commands. When you need more -flexibility---for example, running @value{GDBN} on a physically separate -host, or controlling a standalone system over a serial port or a -realtime system over a TCP/IP connection---you -@end ifclear -@end ifclear -@ifset HPPA -On HP-UX systems, @value{GDBN} has been configured to support debugging -of processes running on the PA-RISC architecture. This means that the -only possible targets are: - -@itemize @bullet -@item -An executable that has been compiled and linked to run on HP-UX - -@item -A live HP-UX process, either started by @value{GDBN} (with the -@code{run} command) or started outside of @value{GDBN} and attached to -(with the @code{attach} command) - -@item -A core file generated by an HP-UX process that previously aborted -execution -@end itemize - -@value{GDBN} on HP-UX has not been configured to support remote -debugging, or to support programs running on other platforms. You -@end ifset -@ifset BARETARGET -You -@end ifset -can use the @code{target} command to specify one of the target types -configured for @value{GDBN} (@pxref{Target Commands, ,Commands for managing -targets}). - -@menu -* Active Targets:: Active targets -* Target Commands:: Commands for managing targets -@ifset REMOTESTUB -* Byte Order:: Choosing target byte order -* Remote:: Remote debugging -@end ifset - -@end menu - -@node Active Targets, Target Commands, Targets, Targets -@section Active targets -@cindex stacking targets -@cindex active targets -@cindex multiple targets - -@ifclear BARETARGET -There are three classes of targets: processes, core files, and -executable files. @value{GDBN} can work concurrently on up to three active -targets, one in each class. This allows you to (for example) start a -process and inspect its activity without abandoning your work on a core -file. - -For example, if you execute @samp{gdb a.out}, then the executable file -@code{a.out} is the only active target. If you designate a core file as -well---presumably from a prior run that crashed and coredumped---then -@value{GDBN} has two active targets and uses them in tandem, looking -first in the corefile target, then in the executable file, to satisfy -requests for memory addresses. (Typically, these two classes of target -are complementary, since core files contain only a program's -read-write memory---variables and so on---plus machine status, while -executable files contain only the program text and initialized data.) -@end ifclear - -When you type @code{run}, your executable file becomes an active process -target as well. When a process target is active, all @value{GDBN} commands -requesting memory addresses refer to that target; addresses in an -@ifclear BARETARGET -active core file or -@end ifclear -executable file target are obscured while the process -target is active. - -@ifset BARETARGET -Use the @code{exec-file} command to select a -new executable target (@pxref{Files, ,Commands to specify -files}). -@end ifset -@ifclear BARETARGET -Use the @code{core-file} and @code{exec-file} commands to select a -new core file or executable target (@pxref{Files, ,Commands to specify -files}). To specify as a target a process that is already running, use -the @code{attach} command (@pxref{Attach, ,Debugging an -already-running process}). -@end ifclear - -@node Target Commands, Byte Order, Active Targets, Targets -@section Commands for managing targets - -@table @code -@item target @var{type} @var{parameters} -Connects the @value{GDBN} host environment to a target -@ifset BARETARGET -machine. -@end ifset -@ifclear BARETARGET -machine or process. A target is typically a protocol for talking to -debugging facilities. You use the argument @var{type} to specify the -type or protocol of the target machine. - -Further @var{parameters} are interpreted by the target protocol, but -typically include things like device names or host names to connect -with, process numbers, and baud rates. -@end ifclear - -The @code{target} command does not repeat if you press @key{RET} again -after executing the command. - -@kindex help target -@item help target -Displays the names of all targets available. To display targets -currently selected, use either @code{info target} or @code{info files} -(@pxref{Files, ,Commands to specify files}). - -@item help target @var{name} -Describe a particular target, including any parameters necessary to -select it. - -@kindex set gnutarget -@item set gnutarget @var{args} -@value{GDBN} uses its own library BFD to read your files. @value{GDBN} -knows whether it is reading an @dfn{executable}, -a @dfn{core}, or a @dfn{.o} file; however, you can specify the file format -with the @code{set gnutarget} command. Unlike most @code{target} commands, -with @code{gnutarget} the @code{target} refers to a program, not a machine. - -@emph{Warning:} To specify a file format with @code{set gnutarget}, -you must know the actual BFD name. - -@noindent @xref{Files, , Commands to specify files}. - -@kindex show gnutarget -@item show gnutarget -Use the @code{show gnutarget} command to display what file format -@code{gnutarget} is set to read. If you have not set @code{gnutarget}, -@value{GDBN} will determine the file format for each file automatically, -and @code{show gnutarget} displays @samp{The current BDF target is "auto"}. -@end table - -@ifclear HPPA -Here are some common targets (available, or not, depending on the GDB -configuration): -@end ifclear -@ifset HPPA -These are the valid targets on HP-UX systems: -@end ifset - -@table @code -@kindex target exec -@item target exec @var{program} -An executable file. @samp{target exec @var{program}} is the same as -@samp{exec-file @var{program}}. - -@ifclear BARETARGET -@kindex target core -@item target core @var{filename} -A core dump file. @samp{target core @var{filename}} is the same as -@samp{core-file @var{filename}}. -@end ifclear - -@kindex target remote -@item target remote @var{dev} -Remote serial target in GDB-specific protocol. The argument @var{dev} -specifies what serial device to use for the connection (e.g. -@file{/dev/ttya}). @xref{Remote, ,Remote debugging}. @code{target remote} -now supports the @code{load} command. This is only useful if you have -some other way of getting the stub to the target system, and you can put -it somewhere in memory where it won't get clobbered by the download. - -@ifclear HPPA -@kindex target sim -@item target sim -CPU simulator. @xref{Simulator,,Simulated CPU Target}. -@end ifclear -@end table - -The following targets are all CPU-specific, and only available for -specific configurations. -@c should organize by CPU - -@table @code - -@kindex target abug -@item target abug @var{dev} -ABug ROM monitor for M68K. - -@kindex target adapt -@item target adapt @var{dev} -Adapt monitor for A29K. - -@kindex target amd-eb -@item target amd-eb @var{dev} @var{speed} @var{PROG} -@cindex AMD EB29K -Remote PC-resident AMD EB29K board, attached over serial lines. -@var{dev} is the serial device, as for @code{target remote}; -@var{speed} allows you to specify the linespeed; and @var{PROG} is the -name of the program to be debugged, as it appears to DOS on the PC. -@xref{EB29K Remote, ,The EBMON protocol for AMD29K}. - -@kindex target array -@item target array @var{dev} -Array Tech LSI33K RAID controller board. - -@kindex target bug -@item target bug @var{dev} -BUG monitor, running on a MVME187 (m88k) board. - -@kindex target cpu32bug -@item target cpu32bug @var{dev} -CPU32BUG monitor, running on a CPU32 (M68K) board. - -@kindex target dbug -@item target dbug @var{dev} -dBUG ROM monitor for Motorola ColdFire. - -@kindex target ddb -@item target ddb @var{dev} -NEC's DDB monitor for Mips Vr4300. - -@kindex target dink32 -@item target dink32 @var{dev} -DINK32 ROM monitor for PowerPC. - -@kindex target e7000 -@item target e7000 @var{dev} -E7000 emulator for Hitachi H8 and SH. - -@kindex target es1800 -@item target es1800 @var{dev} -ES-1800 emulator for M68K. - -@kindex target est -@item target est @var{dev} -EST-300 ICE monitor, running on a CPU32 (M68K) board. - -@kindex target hms -@item target hms @var{dev} -A Hitachi SH, H8/300, or H8/500 board, attached via serial line to your host. -@ifclear H8EXCLUSIVE -Use special commands @code{device} and @code{speed} to control the serial -line and the communications speed used. -@xref{Hitachi Remote,,@value{GDBN} and Hitachi Microprocessors}. - -@kindex target lsi -@item target lsi @var{dev} -LSI ROM monitor for Mips. - -@kindex target m32r -@item target m32r @var{dev} -Mitsubishi M32R/D ROM monitor. - -@kindex target mips -@item target mips @var{dev} -IDT/SIM ROM monitor for Mips. - -@kindex target mon960 -@item target mon960 @var{dev} -MON960 monitor for Intel i960. - -@kindex target nindy -@item target nindy @var{devicename} -An Intel 960 board controlled by a Nindy Monitor. @var{devicename} is -the name of the serial device to use for the connection, e.g. -@file{/dev/ttya}. @xref{i960-Nindy Remote, ,@value{GDBN} with a remote i960 (Nindy)}. - -@kindex target nrom -@item target nrom @var{dev} -NetROM ROM emulator. This target only supports downloading. - -@kindex target op50n -@item target op50n @var{dev} -OP50N monitor, running on an OKI HPPA board. - -@kindex target pmon -@item target pmon @var{dev} -PMON ROM monitor for Mips. - -@kindex target ppcbug -@item target ppcbug @var{dev} -@kindex target ppcbug1 -@item target ppcbug1 @var{dev} -PPCBUG ROM monitor for PowerPC. - -@kindex target r3900 -@item target r3900 @var{dev} -Densan DVE-R3900 ROM monitor for Toshiba R3900 Mips. - -@kindex target rdi -@item target rdi @var{dev} -ARM Angel monitor, via RDI library interface. - -@kindex target rdp -@item target rdp @var{dev} -ARM Demon monitor. - -@kindex target rom68k -@item target rom68k @var{dev} -ROM 68K monitor, running on an M68K IDP board. - -@kindex target rombug -@item target rombug @var{dev} -ROMBUG ROM monitor for OS/9000. - -@kindex target sds -@item target sds @var{dev} -SDS monitor, running on a PowerPC board (such as Motorola's ADS). - -@kindex target sparclite -@item target sparclite @var{dev} -Fujitsu sparclite boards, used only for the purpose of loading. -You must use an additional command to debug the program. -For example: target remote @var{dev} using @value{GDBN} standard -remote protocol. - -@kindex target sh3 -@kindex target sh3e -@item target sh3 @var{dev} -@item target sh3e @var{dev} -Hitachi SH-3 and SH-3E target systems. - -@kindex target st2000 -@item target st2000 @var{dev} @var{speed} -A Tandem ST2000 phone switch, running Tandem's STDBUG protocol. @var{dev} -is the name of the device attached to the ST2000 serial line; -@var{speed} is the communication line speed. The arguments are not used -if @value{GDBN} is configured to connect to the ST2000 using TCP or Telnet. -@xref{ST2000 Remote,,@value{GDBN} with a Tandem ST2000}. - -@kindex target udi -@item target udi @var{keyword} -Remote AMD29K target, using the AMD UDI protocol. The @var{keyword} -argument specifies which 29K board or simulator to use. @xref{UDI29K -Remote,,The UDI protocol for AMD29K}. - -@kindex target vxworks -@item target vxworks @var{machinename} -A VxWorks system, attached via TCP/IP. The argument @var{machinename} -is the target system's machine name or IP address. -@xref{VxWorks Remote, ,@value{GDBN} and VxWorks}. - -@kindex target w89k -@item target w89k @var{dev} -W89K monitor, running on a Winbond HPPA board. - -@end ifclear -@end table - -@ifset GENERIC -Different targets are available on different configurations of @value{GDBN}; -your configuration may have more or fewer targets. -@end ifset - -Many remote targets require you to download the executable's code -once you've successfully established a connection. - -@table @code - -@kindex load @var{filename} -@item load @var{filename} -@ifset GENERIC -Depending on what remote debugging facilities are configured into -@value{GDBN}, the @code{load} command may be available. Where it exists, it -is meant to make @var{filename} (an executable) available for debugging -on the remote system---by downloading, or dynamic linking, for example. -@code{load} also records the @var{filename} symbol table in @value{GDBN}, like -the @code{add-symbol-file} command. - -If your @value{GDBN} does not have a @code{load} command, attempting to -execute it gets the error message ``@code{You can't do that when your -target is @dots{}}'' -@end ifset - -The file is loaded at whatever address is specified in the executable. -For some object file formats, you can specify the load address when you -link the program; for other formats, like a.out, the object file format -specifies a fixed address. -@c FIXME! This would be a good place for an xref to the GNU linker doc. - -@ifset VXWORKS -On VxWorks, @code{load} links @var{filename} dynamically on the -current target system as well as adding its symbols in @value{GDBN}. -@end ifset - -@ifset I960 -@cindex download to Nindy-960 -With the Nindy interface to an Intel 960 board, @code{load} -downloads @var{filename} to the 960 as well as adding its symbols in -@value{GDBN}. -@end ifset - -@ifset H8 -@cindex download to H8/300 or H8/500 -@cindex H8/300 or H8/500 download -@cindex download to Hitachi SH -@cindex Hitachi SH download -When you select remote debugging to a Hitachi SH, H8/300, or H8/500 board -(@pxref{Hitachi Remote,,@value{GDBN} and Hitachi Microprocessors}), -the @code{load} command downloads your program to the Hitachi board and also -opens it as the current executable target for @value{GDBN} on your host -(like the @code{file} command). -@end ifset - -@code{load} does not repeat if you press @key{RET} again after using it. -@end table - -@ifset REMOTESTUB -@node Byte Order, Remote, Target Commands, Targets -@section Choosing target byte order -@cindex choosing target byte order -@cindex target byte order -@kindex set endian big -@kindex set endian little -@kindex set endian auto -@kindex show endian - -Some types of processors, such as the MIPS, PowerPC, and Hitachi SH, -offer the ability to run either big-endian or little-endian byte -orders. Usually the executable or symbol will include a bit to -designate the endian-ness, and you will not need to worry about -which to use. However, you may still find it useful to adjust -GDB's idea of processor endian-ness manually. - -@table @code -@kindex set endian big -@item set endian big -Instruct @value{GDBN} to assume the target is big-endian. - -@kindex set endian little -@item set endian little -Instruct @value{GDBN} to assume the target is little-endian. - -@kindex set endian auto -@item set endian auto -Instruct @value{GDBN} to use the byte order associated with the -executable. - -@item show endian -Display @value{GDBN}'s current idea of the target byte order. - -@end table - -Note that these commands merely adjust interpretation of symbolic -data on the host, and that they have absolutely no effect on the -target system. - -@node Remote, , Byte Order, Targets -@section Remote debugging -@cindex remote debugging - -If you are trying to debug a program running on a machine that cannot run -@value{GDBN} in the usual way, it is often useful to use remote debugging. -For example, you might use remote debugging on an operating system kernel, -or on a small system which does not have a general purpose operating system -powerful enough to run a full-featured debugger. - -Some configurations of @value{GDBN} have special serial or TCP/IP interfaces -to make this work with particular debugging targets. In addition, -@value{GDBN} comes with a generic serial protocol (specific to @value{GDBN}, -but not specific to any particular target system) which you can use if you -write the remote stubs---the code that runs on the remote system to -communicate with @value{GDBN}. - -Other remote targets may be available in your -configuration of @value{GDBN}; use @code{help target} to list them. -@end ifset - -@ifset GENERIC -@c Text on starting up GDB in various specific cases; it goes up front -@c in manuals configured for any of those particular situations, here -@c otherwise. -@menu -@ifset REMOTESTUB -* Remote Serial:: @value{GDBN} remote serial protocol -@end ifset -@ifset I960 -* i960-Nindy Remote:: @value{GDBN} with a remote i960 (Nindy) -@end ifset -@ifset AMD29K -* UDI29K Remote:: The UDI protocol for AMD29K -* EB29K Remote:: The EBMON protocol for AMD29K -@end ifset -@ifset VXWORKS -* VxWorks Remote:: @value{GDBN} and VxWorks -@end ifset -@ifset ST2000 -* ST2000 Remote:: @value{GDBN} with a Tandem ST2000 -@end ifset -@ifset H8 -* Hitachi Remote:: @value{GDBN} and Hitachi Microprocessors -@end ifset -@ifset MIPS -* MIPS Remote:: @value{GDBN} and MIPS boards -@end ifset -@ifset SPARCLET -* Sparclet Remote:: @value{GDBN} and Sparclet boards -@end ifset -@ifset SIMS -* Simulator:: Simulated CPU target -@end ifset -@end menu - -@include remote.texi -@end ifset - -@node Controlling GDB -@chapter Controlling @value{GDBN} - -You can alter the way @value{GDBN} interacts with you by using -the @code{set} command. For commands controlling how @value{GDBN} displays -data, @pxref{Print Settings, ,Print settings}; other settings are described -here. - -@menu -* Prompt:: Prompt -* Editing:: Command editing -* History:: Command history -* Screen Size:: Screen size -* Numbers:: Numbers -* Messages/Warnings:: Optional warnings and messages -@end menu - -@node Prompt, Editing, Controlling GDB, Controlling GDB -@section Prompt - -@cindex prompt - -@value{GDBN} indicates its readiness to read a command by printing a string -called the @dfn{prompt}. This string is normally @samp{(@value{GDBP})}. You -can change the prompt string with the @code{set prompt} command. For -instance, when debugging @value{GDBN} with @value{GDBN}, it is useful to change -the prompt in one of the @value{GDBN} sessions so that you can always tell -which one you are talking to. - -@emph{Note:} @code{set prompt} no longer adds a space for you after the -prompt you set. This allows you to set a prompt which ends in a space -or a prompt that does not. - -@table @code -@kindex set prompt -@item set prompt @var{newprompt} -Directs @value{GDBN} to use @var{newprompt} as its prompt string henceforth. - -@kindex show prompt -@item show prompt -Prints a line of the form: @samp{Gdb's prompt is: @var{your-prompt}} -@end table - -@node Editing, History, Prompt, Controlling GDB -@section Command editing -@cindex readline -@cindex command line editing - -@value{GDBN} reads its input commands via the @dfn{readline} interface. This -@sc{gnu} library provides consistent behavior for programs which provide a -command line interface to the user. Advantages are @sc{gnu} Emacs-style -or @dfn{vi}-style inline editing of commands, @code{csh}-like history -substitution, and a storage and recall of command history across -debugging sessions. - -You may control the behavior of command line editing in @value{GDBN} with the -command @code{set}. - -@table @code -@kindex set editing -@cindex editing -@item set editing -@itemx set editing on -Enable command line editing (enabled by default). - -@item set editing off -Disable command line editing. - -@kindex show editing -@item show editing -Show whether command line editing is enabled. -@end table - -@node History, Screen Size, Editing, Controlling GDB -@section Command history - -@value{GDBN} can keep track of the commands you type during your -debugging sessions, so that you can be certain of precisely what -happened. Use these commands to manage the @value{GDBN} command -history facility. - -@table @code -@cindex history substitution -@cindex history file -@kindex set history filename -@kindex GDBHISTFILE -@item set history filename @var{fname} -Set the name of the @value{GDBN} command history file to @var{fname}. -This is the file where @value{GDBN} reads an initial command history -list, and where it writes the command history from this session when it -exits. You can access this list through history expansion or through -the history command editing characters listed below. This file defaults -to the value of the environment variable @code{GDBHISTFILE}, or to -@file{./.gdb_history} if this variable is not set. - -@cindex history save -@kindex set history save -@item set history save -@itemx set history save on -Record command history in a file, whose name may be specified with the -@code{set history filename} command. By default, this option is disabled. - -@item set history save off -Stop recording command history in a file. - -@cindex history size -@kindex set history size -@item set history size @var{size} -Set the number of commands which @value{GDBN} keeps in its history list. -This defaults to the value of the environment variable -@code{HISTSIZE}, or to 256 if this variable is not set. -@end table - -@cindex history expansion -History expansion assigns special meaning to the character @kbd{!}. -@ifset have-readline-appendices -@xref{Event Designators}. -@end ifset - -Since @kbd{!} is also the logical not operator in C, history expansion -is off by default. If you decide to enable history expansion with the -@code{set history expansion on} command, you may sometimes need to -follow @kbd{!} (when it is used as logical not, in an expression) with -a space or a tab to prevent it from being expanded. The readline -history facilities do not attempt substitution on the strings -@kbd{!=} and @kbd{!(}, even when history expansion is enabled. - -The commands to control history expansion are: - -@table @code -@kindex set history expansion -@item set history expansion on -@itemx set history expansion -Enable history expansion. History expansion is off by default. - -@item set history expansion off -Disable history expansion. - -The readline code comes with more complete documentation of -editing and history expansion features. Users unfamiliar with @sc{gnu} Emacs -or @code{vi} may wish to read it. -@ifset have-readline-appendices -@xref{Command Line Editing}. -@end ifset - -@c @group -@kindex show history -@item show history -@itemx show history filename -@itemx show history save -@itemx show history size -@itemx show history expansion -These commands display the state of the @value{GDBN} history parameters. -@code{show history} by itself displays all four states. -@c @end group -@end table - -@table @code -@kindex show commands -@item show commands -Display the last ten commands in the command history. - -@item show commands @var{n} -Print ten commands centered on command number @var{n}. - -@item show commands + -Print ten commands just after the commands last printed. -@end table - -@node Screen Size, Numbers, History, Controlling GDB -@section Screen size -@cindex size of screen -@cindex pauses in output - -Certain commands to @value{GDBN} may produce large amounts of -information output to the screen. To help you read all of it, -@value{GDBN} pauses and asks you for input at the end of each page of -output. Type @key{RET} when you want to continue the output, or @kbd{q} -to discard the remaining output. Also, the screen width setting -determines when to wrap lines of output. Depending on what is being -printed, @value{GDBN} tries to break the line at a readable place, -rather than simply letting it overflow onto the following line. - -Normally @value{GDBN} knows the size of the screen from the termcap data base -together with the value of the @code{TERM} environment variable and the -@code{stty rows} and @code{stty cols} settings. If this is not correct, -you can override it with the @code{set height} and @code{set -width} commands: - -@table @code -@kindex set height -@kindex set width -@kindex show width -@kindex show height -@item set height @var{lpp} -@itemx show height -@itemx set width @var{cpl} -@itemx show width -These @code{set} commands specify a screen height of @var{lpp} lines and -a screen width of @var{cpl} characters. The associated @code{show} -commands display the current settings. - -If you specify a height of zero lines, @value{GDBN} does not pause during -output no matter how long the output is. This is useful if output is to a -file or to an editor buffer. - -Likewise, you can specify @samp{set width 0} to prevent @value{GDBN} -from wrapping its output. -@end table - -@node Numbers, Messages/Warnings, Screen Size, Controlling GDB -@section Numbers -@cindex number representation -@cindex entering numbers - -You can always enter numbers in octal, decimal, or hexadecimal in @value{GDBN} by -the usual conventions: octal numbers begin with @samp{0}, decimal -numbers end with @samp{.}, and hexadecimal numbers begin with @samp{0x}. -Numbers that begin with none of these are, by default, entered in base -10; likewise, the default display for numbers---when no particular -format is specified---is base 10. You can change the default base for -both input and output with the @code{set radix} command. - -@table @code -@kindex set input-radix -@item set input-radix @var{base} -Set the default base for numeric input. Supported choices -for @var{base} are decimal 8, 10, or 16. @var{base} must itself be -specified either unambiguously or using the current default radix; for -example, any of - -@smallexample -set radix 012 -set radix 10. -set radix 0xa -@end smallexample - -@noindent -sets the base to decimal. On the other hand, @samp{set radix 10} -leaves the radix unchanged no matter what it was. - -@kindex set output-radix -@item set output-radix @var{base} -Set the default base for numeric display. Supported choices -for @var{base} are decimal 8, 10, or 16. @var{base} must itself be -specified either unambiguously or using the current default radix. - -@kindex show input-radix -@item show input-radix -Display the current default base for numeric input. - -@kindex show output-radix -@item show output-radix -Display the current default base for numeric display. -@end table - -@node Messages/Warnings, , Numbers, Controlling GDB -@section Optional warnings and messages - -By default, @value{GDBN} is silent about its inner workings. If you are running -on a slow machine, you may want to use the @code{set verbose} command. -This makes @value{GDBN} tell you when it does a lengthy internal operation, so -you will not think it has crashed. - -Currently, the messages controlled by @code{set verbose} are those -which announce that the symbol table for a source file is being read; -see @code{symbol-file} in @ref{Files, ,Commands to specify files}. - -@table @code -@kindex set verbose -@item set verbose on -Enables @value{GDBN} output of certain informational messages. - -@item set verbose off -Disables @value{GDBN} output of certain informational messages. - -@kindex show verbose -@item show verbose -Displays whether @code{set verbose} is on or off. -@end table - -By default, if @value{GDBN} encounters bugs in the symbol table of an object -file, it is silent; but if you are debugging a compiler, you may find -this information useful (@pxref{Symbol Errors, ,Errors reading symbol files}). - -@table @code -@kindex set complaints -@item set complaints @var{limit} -Permits @value{GDBN} to output @var{limit} complaints about each type of unusual -symbols before becoming silent about the problem. Set @var{limit} to -zero to suppress all complaints; set it to a large number to prevent -complaints from being suppressed. - -@kindex show complaints -@item show complaints -Displays how many symbol complaints @value{GDBN} is permitted to produce. -@end table - -By default, @value{GDBN} is cautious, and asks what sometimes seems to be a -lot of stupid questions to confirm certain commands. For example, if -you try to run a program which is already running: - -@example -(@value{GDBP}) run -The program being debugged has been started already. -Start it from the beginning? (y or n) -@end example - -If you are willing to unflinchingly face the consequences of your own -commands, you can disable this ``feature'': - -@table @code -@kindex set confirm -@cindex flinching -@cindex confirmation -@cindex stupid questions -@item set confirm off -Disables confirmation requests. - -@item set confirm on -Enables confirmation requests (the default). - -@kindex show confirm -@item show confirm -Displays state of confirmation requests. -@end table - -@node Sequences, Emacs, Controlling GDB, Top -@chapter Canned Sequences of Commands - -Aside from breakpoint commands (@pxref{Break Commands, ,Breakpoint -command lists}), @value{GDBN} provides two ways to store sequences of commands -for execution as a unit: user-defined commands and command files. - -@menu -* Define:: User-defined commands -* Hooks:: User-defined command hooks -* Command Files:: Command files -* Output:: Commands for controlled output -@end menu - -@node Define, Hooks, Sequences, Sequences -@section User-defined commands - -@cindex user-defined command -A @dfn{user-defined command} is a sequence of @value{GDBN} commands to which -you assign a new name as a command. This is done with the @code{define} -command. User commands may accept up to 10 arguments separated by whitespace. -Arguments are accessed within the user command via @var{$arg0@dots{}$arg9}. -A trivial example: - -@smallexample -define adder - print $arg0 + $arg1 + $arg2 -@end smallexample - -@noindent To execute the command use: - -@smallexample -adder 1 2 3 -@end smallexample - -@noindent This defines the command @code{adder}, which prints the sum of -its three arguments. Note the arguments are text substitutions, so they may -reference variables, use complex expressions, or even perform inferior -functions calls. - -@table @code -@kindex define -@item define @var{commandname} -Define a command named @var{commandname}. If there is already a command -by that name, you are asked to confirm that you want to redefine it. - -The definition of the command is made up of other @value{GDBN} command lines, -which are given following the @code{define} command. The end of these -commands is marked by a line containing @code{end}. - -@kindex if -@kindex else -@item if -Takes a single argument, which is an expression to evaluate. -It is followed by a series of commands that are executed -only if the expression is true (nonzero). -There can then optionally be a line @code{else}, followed -by a series of commands that are only executed if the expression -was false. The end of the list is marked by a line containing @code{end}. - -@kindex while -@item while -The syntax is similar to @code{if}: the command takes a single argument, -which is an expression to evaluate, and must be followed by the commands to -execute, one per line, terminated by an @code{end}. -The commands are executed repeatedly as long as the expression -evaluates to true. - -@kindex document -@item document @var{commandname} -Document the user-defined command @var{commandname}, so that it can be -accessed by @code{help}. The command @var{commandname} must already be -defined. This command reads lines of documentation just as @code{define} -reads the lines of the command definition, ending with @code{end}. -After the @code{document} command is finished, @code{help} on command -@var{commandname} displays the documentation you have written. - -You may use the @code{document} command again to change the -documentation of a command. Redefining the command with @code{define} -does not change the documentation. - -@kindex help user-defined -@item help user-defined -List all user-defined commands, with the first line of the documentation -(if any) for each. - -@kindex show user -@item show user -@itemx show user @var{commandname} -Display the @value{GDBN} commands used to define @var{commandname} (but not its -documentation). If no @var{commandname} is given, display the -definitions for all user-defined commands. -@end table - -When user-defined commands are executed, the -commands of the definition are not printed. An error in any command -stops execution of the user-defined command. - -If used interactively, commands that would ask for confirmation proceed -without asking when used inside a user-defined command. Many @value{GDBN} -commands that normally print messages to say what they are doing omit the -messages when used in a user-defined command. - -@node Hooks, Command Files, Define, Sequences -@section User-defined command hooks -@cindex command files - -You may define @emph{hooks}, which are a special kind of user-defined -command. Whenever you run the command @samp{foo}, if the user-defined -command @samp{hook-foo} exists, it is executed (with no arguments) -before that command. - -In addition, a pseudo-command, @samp{stop} exists. Defining -(@samp{hook-stop}) makes the associated commands execute every time -execution stops in your program: before breakpoint commands are run, -displays are printed, or the stack frame is printed. - -@ifclear BARETARGET -For example, to ignore @code{SIGALRM} signals while -single-stepping, but treat them normally during normal execution, -you could define: - -@example -define hook-stop -handle SIGALRM nopass -end - -define hook-run -handle SIGALRM pass -end - -define hook-continue -handle SIGLARM pass -end -@end example -@end ifclear - -You can define a hook for any single-word command in @value{GDBN}, but -not for command aliases; you should define a hook for the basic command -name, e.g. @code{backtrace} rather than @code{bt}. -@c FIXME! So how does Joe User discover whether a command is an alias -@c or not? -If an error occurs during the execution of your hook, execution of -@value{GDBN} commands stops and @value{GDBN} issues a prompt -(before the command that you actually typed had a chance to run). - -If you try to define a hook which does not match any known command, you -get a warning from the @code{define} command. - -@node Command Files, Output, Hooks, Sequences -@section Command files - -@cindex command files -A command file for @value{GDBN} is a file of lines that are @value{GDBN} -commands. Comments (lines starting with @kbd{#}) may also be included. -An empty line in a command file does nothing; it does not mean to repeat -the last command, as it would from the terminal. - -@cindex init file -@cindex @file{.gdbinit} -When you start @value{GDBN}, it automatically executes commands from its -@dfn{init files}. These are files named @file{.gdbinit} on Unix, or -@file{gdb.ini} on DOS/Windows. @value{GDBN} reads the init file (if -any) in your home directory, then processes command line options and -operands, and then reads the init file (if any) in the current working -directory. This is so the init file in your home directory can set -options (such as @code{set complaints}) which affect the processing of -the command line options and operands. The init files are not executed -if you use the @samp{-nx} option; @pxref{Mode Options, ,Choosing modes}. - -@ifset GENERIC -@cindex init file name -On some configurations of @value{GDBN}, the init file is known by a -different name (these are typically environments where a specialized -form of @value{GDBN} may need to coexist with other forms, hence a -different name for the specialized version's init file). These are the -environments with special init file names: - -@kindex .vxgdbinit -@itemize @bullet -@item -VxWorks (Wind River Systems real-time OS): @samp{.vxgdbinit} - -@kindex .os68gdbinit -@item -OS68K (Enea Data Systems real-time OS): @samp{.os68gdbinit} - -@kindex .esgdbinit -@item -ES-1800 (Ericsson Telecom AB M68000 emulator): @samp{.esgdbinit} -@end itemize -@end ifset - -You can also request the execution of a command file with the -@code{source} command: - -@table @code -@kindex source -@item source @var{filename} -Execute the command file @var{filename}. -@end table - -The lines in a command file are executed sequentially. They are not -printed as they are executed. An error in any command terminates execution -of the command file. - -Commands that would ask for confirmation if used interactively proceed -without asking when used in a command file. Many @value{GDBN} commands that -normally print messages to say what they are doing omit the messages -when called from command files. - -@node Output, , Command Files, Sequences -@section Commands for controlled output - -During the execution of a command file or a user-defined command, normal -@value{GDBN} output is suppressed; the only output that appears is what is -explicitly printed by the commands in the definition. This section -describes three commands useful for generating exactly the output you -want. - -@table @code -@kindex echo -@item echo @var{text} -@c I do not consider backslash-space a standard C escape sequence -@c because it is not in ANSI. -Print @var{text}. Nonprinting characters can be included in -@var{text} using C escape sequences, such as @samp{\n} to print a -newline. @strong{No newline is printed unless you specify one.} -In addition to the standard C escape sequences, a backslash followed -by a space stands for a space. This is useful for displaying a -string with spaces at the beginning or the end, since leading and -trailing spaces are otherwise trimmed from all arguments. -To print @samp{@w{ }and foo =@w{ }}, use the command -@samp{echo \@w{ }and foo = \@w{ }}. - -A backslash at the end of @var{text} can be used, as in C, to continue -the command onto subsequent lines. For example, - -@example -echo This is some text\n\ -which is continued\n\ -onto several lines.\n -@end example - -produces the same output as - -@example -echo This is some text\n -echo which is continued\n -echo onto several lines.\n -@end example - -@kindex output -@item output @var{expression} -Print the value of @var{expression} and nothing but that value: no -newlines, no @samp{$@var{nn} = }. The value is not entered in the -value history either. @xref{Expressions, ,Expressions}, for more information -on expressions. - -@item output/@var{fmt} @var{expression} -Print the value of @var{expression} in format @var{fmt}. You can use -the same formats as for @code{print}. @xref{Output Formats,,Output -formats}, for more information. - -@kindex printf -@item printf @var{string}, @var{expressions}@dots{} -Print the values of the @var{expressions} under the control of -@var{string}. The @var{expressions} are separated by commas and may be -either numbers or pointers. Their values are printed as specified by -@var{string}, exactly as if your program were to execute the C -subroutine - -@example -printf (@var{string}, @var{expressions}@dots{}); -@end example - -For example, you can print two values in hex like this: - -@smallexample -printf "foo, bar-foo = 0x%x, 0x%x\n", foo, bar-foo -@end smallexample - -The only backslash-escape sequences that you can use in the format -string are the simple ones that consist of backslash followed by a -letter. -@end table - -@ifclear DOSHOST -@node Emacs, GDB Bugs, Sequences, Top -@chapter Using @value{GDBN} under @sc{gnu} Emacs - -@cindex Emacs -@cindex @sc{gnu} Emacs -A special interface allows you to use @sc{gnu} Emacs to view (and -edit) the source files for the program you are debugging with -@value{GDBN}. - -To use this interface, use the command @kbd{M-x gdb} in Emacs. Give the -executable file you want to debug as an argument. This command starts -@value{GDBN} as a subprocess of Emacs, with input and output through a newly -created Emacs buffer. -@ifset HPPA -(Do not use the @code{-tui} option to run @value{GDBN} from Emacs.) -@end ifset - -Using @value{GDBN} under Emacs is just like using @value{GDBN} normally except for two -things: - -@itemize @bullet -@item -All ``terminal'' input and output goes through the Emacs buffer. -@end itemize - -This applies both to @value{GDBN} commands and their output, and to the input -and output done by the program you are debugging. - -This is useful because it means that you can copy the text of previous -commands and input them again; you can even use parts of the output -in this way. - -All the facilities of Emacs' Shell mode are available for interacting -with your program. In particular, you can send signals the usual -way---for example, @kbd{C-c C-c} for an interrupt, @kbd{C-c C-z} for a -stop. - -@itemize @bullet -@item -@value{GDBN} displays source code through Emacs. -@end itemize - -Each time @value{GDBN} displays a stack frame, Emacs automatically finds the -source file for that frame and puts an arrow (@samp{=>}) at the -left margin of the current line. Emacs uses a separate buffer for -source display, and splits the screen to show both your @value{GDBN} session -and the source. - -Explicit @value{GDBN} @code{list} or search commands still produce output as -usual, but you probably have no reason to use them from Emacs. - -@quotation -@emph{Warning:} If the directory where your program resides is not your -current directory, it can be easy to confuse Emacs about the location of -the source files, in which case the auxiliary display buffer does not -appear to show your source. @value{GDBN} can find programs by searching your -environment's @code{PATH} variable, so the @value{GDBN} input and output -session proceeds normally; but Emacs does not get enough information -back from @value{GDBN} to locate the source files in this situation. To -avoid this problem, either start @value{GDBN} mode from the directory where -your program resides, or specify an absolute file name when prompted for the -@kbd{M-x gdb} argument. - -A similar confusion can result if you use the @value{GDBN} @code{file} command to -switch to debugging a program in some other location, from an existing -@value{GDBN} buffer in Emacs. -@end quotation - -By default, @kbd{M-x gdb} calls the program called @file{gdb}. If -you need to call @value{GDBN} by a different name (for example, if you keep -several configurations around, with different names) you can set the -Emacs variable @code{gdb-command-name}; for example, - -@example -(setq gdb-command-name "mygdb") -@end example - -@noindent -(preceded by @kbd{ESC ESC}, or typed in the @code{*scratch*} buffer, or -in your @file{.emacs} file) makes Emacs call the program named -``@code{mygdb}'' instead. - -In the @value{GDBN} I/O buffer, you can use these special Emacs commands in -addition to the standard Shell mode commands: - -@table @kbd -@item C-h m -Describe the features of Emacs' @value{GDBN} Mode. - -@item M-s -Execute to another source line, like the @value{GDBN} @code{step} command; also -update the display window to show the current file and location. - -@item M-n -Execute to next source line in this function, skipping all function -calls, like the @value{GDBN} @code{next} command. Then update the display window -to show the current file and location. - -@item M-i -Execute one instruction, like the @value{GDBN} @code{stepi} command; update -display window accordingly. - -@item M-x gdb-nexti -Execute to next instruction, using the @value{GDBN} @code{nexti} command; update -display window accordingly. - -@item C-c C-f -Execute until exit from the selected stack frame, like the @value{GDBN} -@code{finish} command. - -@item M-c -Continue execution of your program, like the @value{GDBN} @code{continue} -command. - -@emph{Warning:} In Emacs v19, this command is @kbd{C-c C-p}. - -@item M-u -Go up the number of frames indicated by the numeric argument -(@pxref{Arguments, , Numeric Arguments, Emacs, The @sc{gnu} Emacs Manual}), -like the @value{GDBN} @code{up} command. - -@emph{Warning:} In Emacs v19, this command is @kbd{C-c C-u}. - -@item M-d -Go down the number of frames indicated by the numeric argument, like the -@value{GDBN} @code{down} command. - -@emph{Warning:} In Emacs v19, this command is @kbd{C-c C-d}. - -@item C-x & -Read the number where the cursor is positioned, and insert it at the end -of the @value{GDBN} I/O buffer. For example, if you wish to disassemble code -around an address that was displayed earlier, type @kbd{disassemble}; -then move the cursor to the address display, and pick up the -argument for @code{disassemble} by typing @kbd{C-x &}. - -You can customize this further by defining elements of the list -@code{gdb-print-command}; once it is defined, you can format or -otherwise process numbers picked up by @kbd{C-x &} before they are -inserted. A numeric argument to @kbd{C-x &} indicates that you -wish special formatting, and also acts as an index to pick an element of the -list. If the list element is a string, the number to be inserted is -formatted using the Emacs function @code{format}; otherwise the number -is passed as an argument to the corresponding list element. -@end table - -In any source file, the Emacs command @kbd{C-x SPC} (@code{gdb-break}) -tells @value{GDBN} to set a breakpoint on the source line point is on. - -If you accidentally delete the source-display buffer, an easy way to get -it back is to type the command @code{f} in the @value{GDBN} buffer, to -request a frame display; when you run under Emacs, this recreates -the source buffer if necessary to show you the context of the current -frame. - -The source files displayed in Emacs are in ordinary Emacs buffers -which are visiting the source files in the usual way. You can edit -the files with these buffers if you wish; but keep in mind that @value{GDBN} -communicates with Emacs in terms of line numbers. If you add or -delete lines from the text, the line numbers that @value{GDBN} knows cease -to correspond properly with the code. - -@c The following dropped because Epoch is nonstandard. Reactivate -@c if/when v19 does something similar. ---doc@cygnus.com 19dec1990 -@ignore -@kindex Emacs Epoch environment -@kindex Epoch -@kindex inspect - -Version 18 of @sc{gnu} Emacs has a built-in window system -called the @code{epoch} -environment. Users of this environment can use a new command, -@code{inspect} which performs identically to @code{print} except that -each value is printed in its own window. -@end ignore -@end ifclear - -@node GDB Bugs -@c links whacked to pacify makeinfo -@c , Command Line Editing, Emacs, Top -@chapter Reporting Bugs in @value{GDBN} -@cindex bugs in @value{GDBN} -@cindex reporting bugs in @value{GDBN} - -Your bug reports play an essential role in making @value{GDBN} reliable. - -Reporting a bug may help you by bringing a solution to your problem, or it -may not. But in any case the principal function of a bug report is to help -the entire community by making the next version of @value{GDBN} work better. Bug -reports are your contribution to the maintenance of @value{GDBN}. - -In order for a bug report to serve its purpose, you must include the -information that enables us to fix the bug. - -@menu -* Bug Criteria:: Have you found a bug? -* Bug Reporting:: How to report bugs -@end menu - -@node Bug Criteria, Bug Reporting, GDB Bugs, GDB Bugs -@section Have you found a bug? -@cindex bug criteria - -If you are not sure whether you have found a bug, here are some guidelines: - -@itemize @bullet -@cindex fatal signal -@cindex debugger crash -@cindex crash of debugger -@item -If the debugger gets a fatal signal, for any input whatever, that is a -@value{GDBN} bug. Reliable debuggers never crash. - -@cindex error on valid input -@item -If @value{GDBN} produces an error message for valid input, that is a -bug. (Note that if you're cross debugging, the problem may also be -somewhere in the connection to the target.) - -@cindex invalid input -@item -If @value{GDBN} does not produce an error message for invalid input, -that is a bug. However, you should note that your idea of -``invalid input'' might be our idea of ``an extension'' or ``support -for traditional practice''. - -@item -If you are an experienced user of debugging tools, your suggestions -for improvement of @value{GDBN} are welcome in any case. -@end itemize - -@node Bug Reporting, , Bug Criteria, GDB Bugs -@section How to report bugs -@cindex bug reports -@cindex @value{GDBN} bugs, reporting - -@ifclear HPPA -A number of companies and individuals offer support for @sc{gnu} products. -If you obtained @value{GDBN} from a support organization, we recommend you -contact that organization first. - -You can find contact information for many support companies and -individuals in the file @file{etc/SERVICE} in the @sc{gnu} Emacs -distribution. -@c should add a web page ref... - -In any event, we also recommend that you send bug reports for -@value{GDBN} to this addresses: - -@example -bug-gdb@@prep.ai.mit.edu -@end example - -@strong{Do not send bug reports to @samp{info-gdb}, or to -@samp{help-gdb}, or to any newsgroups.} Most users of @value{GDBN} do -not want to receive bug reports. Those that do have arranged to receive -@samp{bug-gdb}. - -The mailing list @samp{bug-gdb} has a newsgroup @samp{gnu.gdb.bug} which -serves as a repeater. The mailing list and the newsgroup carry exactly -the same messages. Often people think of posting bug reports to the -newsgroup instead of mailing them. This appears to work, but it has one -problem which can be crucial: a newsgroup posting often lacks a mail -path back to the sender. Thus, if we need to ask for more information, -we may be unable to reach you. For this reason, it is better to send -bug reports to the mailing list. - -As a last resort, send bug reports on paper to: - -@example -@sc{gnu} Debugger Bugs -Free Software Foundation Inc. -59 Temple Place - Suite 330 -Boston, MA 02111-1307 -USA -@end example -@end ifclear - -@ifset HPPA -If you obtained HP GDB as part of your HP ANSI C or HP ANSI C++ compiler -kit, report problems to your HP Support Representative. - -If you obtained HP GDB from the Hewlett-Packard Web site, report -problems by electronic mail to @code{wdb-www@@ch.hp.com}. -@end ifset - -The fundamental principle of reporting bugs usefully is this: -@strong{report all the facts}. If you are not sure whether to state a -fact or leave it out, state it! - -Often people omit facts because they think they know what causes the -problem and assume that some details do not matter. Thus, you might -assume that the name of the variable you use in an example does not matter. -Well, probably it does not, but one cannot be sure. Perhaps the bug is a -stray memory reference which happens to fetch from the location where that -name is stored in memory; perhaps, if the name were different, the contents -of that location would fool the debugger into doing the right thing despite -the bug. Play it safe and give a specific, complete example. That is the -easiest thing for you to do, and the most helpful. - -Keep in mind that the purpose of a bug report is to enable us to fix the -bug. It may be that the bug has been reported previously, but neither -you nor we can know that unless your bug report is complete and -self-contained. - -Sometimes people give a few sketchy facts and ask, ``Does this ring a -bell?'' Those bug reports are useless, and we urge everyone to -@emph{refuse to respond to them} except to chide the sender to report -bugs properly. - -To enable us to fix the bug, you should include all these things: - -@itemize @bullet -@item -The version of @value{GDBN}. @value{GDBN} announces it if you start -with no arguments; you can also print it at any time using @code{show -version}. - -Without this, we will not know whether there is any point in looking for -the bug in the current version of @value{GDBN}. - -@item -The type of machine you are using, and the operating system name and -version number. - -@ifclear HPPA -@item -What compiler (and its version) was used to compile @value{GDBN}---e.g. -``@value{GCC}--2.8.1''. -@end ifclear - -@item -What compiler (and its version) was used to compile the program you are -debugging---e.g. ``@value{GCC}--2.8.1'', or ``HP92453-01 A.10.32.03 HP -C Compiler''. For GCC, you can say @code{gcc --version} to get this -information; for other compilers, see the documentation for those -compilers. - -@item -The command arguments you gave the compiler to compile your example and -observe the bug. For example, did you use @samp{-O}? To guarantee -you will not omit something important, list them all. A copy of the -Makefile (or the output from make) is sufficient. - -If we were to try to guess the arguments, we would probably guess wrong -and then we might not encounter the bug. - -@item -A complete input script, and all necessary source files, that will -reproduce the bug. - -@item -A description of what behavior you observe that you believe is -incorrect. For example, ``It gets a fatal signal.'' - -Of course, if the bug is that @value{GDBN} gets a fatal signal, then we -will certainly notice it. But if the bug is incorrect output, we might -not notice unless it is glaringly wrong. You might as well not give us -a chance to make a mistake. - -Even if the problem you experience is a fatal signal, you should still -say so explicitly. Suppose something strange is going on, such as, your -copy of @value{GDBN} is out of synch, or you have encountered a bug in -the C library on your system. (This has happened!) Your copy might -crash and ours would not. If you told us to expect a crash, then when -ours fails to crash, we would know that the bug was not happening for -us. If you had not told us to expect a crash, then we would not be able -to draw any conclusion from our observations. - -@ifclear HPPA -@item -If you wish to suggest changes to the @value{GDBN} source, send us context -diffs. If you even discuss something in the @value{GDBN} source, refer to -it by context, not by line number. - -The line numbers in our development sources will not match those in your -sources. Your line numbers would convey no useful information to us. -@end ifclear -@end itemize - -Here are some things that are not necessary: - -@itemize @bullet -@item -A description of the envelope of the bug. - -Often people who encounter a bug spend a lot of time investigating -which changes to the input file will make the bug go away and which -changes will not affect it. - -This is often time consuming and not very useful, because the way we -will find the bug is by running a single example under the debugger -with breakpoints, not by pure deduction from a series of examples. -We recommend that you save your time for something else. - -Of course, if you can find a simpler example to report @emph{instead} -of the original one, that is a convenience for us. Errors in the -output will be easier to spot, running under the debugger will take -less time, and so on. - -However, simplification is not vital; if you do not want to do this, -report the bug anyway and send us the entire test case you used. - -@item -A patch for the bug. - -A patch for the bug does help us if it is a good one. But do not omit -the necessary information, such as the test case, on the assumption that -a patch is all we need. We might see problems with your patch and decide -to fix the problem another way, or we might not understand it at all. - -Sometimes with a program as complicated as @value{GDBN} it is very hard to -construct an example that will make the program follow a certain path -through the code. If you do not send us the example, we will not be able -to construct one, so we will not be able to verify that the bug is fixed. - -And if we cannot understand what bug you are trying to fix, or why your -patch should be an improvement, we will not install it. A test case will -help us to understand. - -@item -A guess about what the bug is or what it depends on. - -Such guesses are usually wrong. Even we cannot guess right about such -things without first using the debugger to find the facts. -@end itemize - -@c The readline documentation is distributed with the readline code -@c and consists of the two following files: -@c rluser.texinfo -@c inc-hist.texi -@c Use -I with makeinfo to point to the appropriate directory, -@c environment var TEXINPUTS with TeX. -@include rluser.texinfo -@include inc-hist.texi - - -@ifclear PRECONFIGURED -@ifclear HPPA -@node Formatting Documentation -@c links whacked to pacify makeinfo -@c , Installing GDB, Renamed Commands, Top -@appendix Formatting Documentation - -@cindex @value{GDBN} reference card -@cindex reference card -The @value{GDBN} 4 release includes an already-formatted reference card, ready -for printing with PostScript or Ghostscript, in the @file{gdb} -subdirectory of the main source directory@footnote{In -@file{gdb-@value{GDBVN}/gdb/refcard.ps} of the version @value{GDBVN} -release.}. If you can use PostScript or Ghostscript with your printer, -you can print the reference card immediately with @file{refcard.ps}. - -The release also includes the source for the reference card. You -can format it, using @TeX{}, by typing: - -@example -make refcard.dvi -@end example - -The @value{GDBN} reference card is designed to print in @dfn{landscape} -mode on US ``letter'' size paper; -that is, on a sheet 11 inches wide by 8.5 inches -high. You will need to specify this form of printing as an option to -your @sc{dvi} output program. - -@cindex documentation - -All the documentation for @value{GDBN} comes as part of the machine-readable -distribution. The documentation is written in Texinfo format, which is -a documentation system that uses a single source file to produce both -on-line information and a printed manual. You can use one of the Info -formatting commands to create the on-line version of the documentation -and @TeX{} (or @code{texi2roff}) to typeset the printed version. - -@value{GDBN} includes an already formatted copy of the on-line Info -version of this manual in the @file{gdb} subdirectory. The main Info -file is @file{gdb-@value{GDBVN}/gdb/gdb.info}, and it refers to -subordinate files matching @samp{gdb.info*} in the same directory. If -necessary, you can print out these files, or read them with any editor; -but they are easier to read using the @code{info} subsystem in @sc{gnu} -Emacs or the standalone @code{info} program, available as part of the -@sc{gnu} Texinfo distribution. - -If you want to format these Info files yourself, you need one of the -Info formatting programs, such as @code{texinfo-format-buffer} or -@code{makeinfo}. - -If you have @code{makeinfo} installed, and are in the top level -@value{GDBN} source directory (@file{gdb-@value{GDBVN}}, in the case of -version @value{GDBVN}), you can make the Info file by typing: - -@example -cd gdb -make gdb.info -@end example - -If you want to typeset and print copies of this manual, you need @TeX{}, -a program to print its @sc{dvi} output files, and @file{texinfo.tex}, the -Texinfo definitions file. - -@TeX{} is a typesetting program; it does not print files directly, but -produces output files called @sc{dvi} files. To print a typeset -document, you need a program to print @sc{dvi} files. If your system -has @TeX{} installed, chances are it has such a program. The precise -command to use depends on your system; @kbd{lpr -d} is common; another -(for PostScript devices) is @kbd{dvips}. The @sc{dvi} print command may -require a file name without any extension or a @samp{.dvi} extension. - -@TeX{} also requires a macro definitions file called -@file{texinfo.tex}. This file tells @TeX{} how to typeset a document -written in Texinfo format. On its own, @TeX{} cannot either read or -typeset a Texinfo file. @file{texinfo.tex} is distributed with GDB -and is located in the @file{gdb-@var{version-number}/texinfo} -directory. - -If you have @TeX{} and a @sc{dvi} printer program installed, you can -typeset and print this manual. First switch to the the @file{gdb} -subdirectory of the main source directory (for example, to -@file{gdb-@value{GDBVN}/gdb}) and type: - -@example -make gdb.dvi -@end example - -Then give @file{gdb.dvi} to your @sc{dvi} printing program. -@end ifclear - -@node Installing GDB, Index, Using History Interactively, Top -@appendix Installing @value{GDBN} -@cindex configuring @value{GDBN} -@cindex installation - -@ifset HPPA -If you obtain @value{GDBN} (HP WDB 0.75) as part of your HP ANSI C or -HP ANSI C++ Developer's Kit at HP-UX Release 11.0, you do not have to -take any special action to build or install @value{GDBN}. - -If you obtain @value{GDBN} (HP WDB 0.75) from an HP web site, you may -download either a @code{swinstall}-able package or a source tree, or -both. - -Most customers will want to install the @value{GDBN} binary that is part -of the @code{swinstall}-able package. To do so, use a command of the -form - -@smallexample -/usr/sbin/swinstall -s @var{package-name} WDB -@end smallexample - -Alternatively, it is possible to build @value{GDBN} from the source -distribution. Sophisticated customers who want to modify the debugger -sources to tailor @value{GDBN} to their their needs may wish to do this. -The source distribution consists of a @code{tar}'ed source tree rooted -at @file{gdb-4.16/...}. The instructions that follow describe how to -build a @file{gdb} executable from this source tree. HP believes that -these instructions apply to the WDB source tree that it distributes. -However, HP does not explicitly support building a @file{gdb} for any -non-HP platform from the WDB source tree. It may work, but HP has not -tested it for any platforms other than those described in the WDB 0.75 -Release Notes. -@end ifset - -@value{GDBN} comes with a @code{configure} script that automates the process -of preparing @value{GDBN} for installation; you can then use @code{make} to -build the @code{gdb} program. -@iftex -@c irrelevant in info file; it's as current as the code it lives with. -@footnote{If you have a more recent version of @value{GDBN} than @value{GDBVN}, -look at the @file{README} file in the sources; we may have improved the -installation procedures since publishing this manual.} -@end iftex - -The @value{GDBN} distribution includes all the source code you need for -@value{GDBN} in a single directory, whose name is usually composed by -appending the version number to @samp{gdb}. - -For example, the @value{GDBN} version @value{GDBVN} distribution is in the -@file{gdb-@value{GDBVN}} directory. That directory contains: - -@table @code -@item gdb-@value{GDBVN}/configure @r{(and supporting files)} -script for configuring @value{GDBN} and all its supporting libraries - -@item gdb-@value{GDBVN}/gdb -the source specific to @value{GDBN} itself - -@item gdb-@value{GDBVN}/bfd -source for the Binary File Descriptor library - -@item gdb-@value{GDBVN}/include -@sc{gnu} include files - -@item gdb-@value{GDBVN}/libiberty -source for the @samp{-liberty} free software library - -@item gdb-@value{GDBVN}/opcodes -source for the library of opcode tables and disassemblers - -@item gdb-@value{GDBVN}/readline -source for the @sc{gnu} command-line interface - -@item gdb-@value{GDBVN}/glob -source for the @sc{gnu} filename pattern-matching subroutine - -@item gdb-@value{GDBVN}/mmalloc -source for the @sc{gnu} memory-mapped malloc package -@end table - -The simplest way to configure and build @value{GDBN} is to run @code{configure} -from the @file{gdb-@var{version-number}} source directory, which in -this example is the @file{gdb-@value{GDBVN}} directory. - -First switch to the @file{gdb-@var{version-number}} source directory -if you are not already in it; then run @code{configure}. Pass the -identifier for the platform on which @value{GDBN} will run as an -argument. - -For example: - -@example -cd gdb-@value{GDBVN} -./configure @var{host} -make -@end example - -@noindent -where @var{host} is an identifier such as @samp{sun4} or -@samp{decstation}, that identifies the platform where @value{GDBN} will run. -(You can often leave off @var{host}; @code{configure} tries to guess the -correct value by examining your system.) - -Running @samp{configure @var{host}} and then running @code{make} builds the -@file{bfd}, @file{readline}, @file{mmalloc}, and @file{libiberty} -libraries, then @code{gdb} itself. The configured source files, and the -binaries, are left in the corresponding source directories. - -@need 750 -@code{configure} is a Bourne-shell (@code{/bin/sh}) script; if your -system does not recognize this automatically when you run a different -shell, you may need to run @code{sh} on it explicitly: - -@example -sh configure @var{host} -@end example - -If you run @code{configure} from a directory that contains source -directories for multiple libraries or programs, such as the -@file{gdb-@value{GDBVN}} source directory for version @value{GDBVN}, @code{configure} -creates configuration files for every directory level underneath (unless -you tell it not to, with the @samp{--norecursion} option). - -You can run the @code{configure} script from any of the -subordinate directories in the @value{GDBN} distribution if you only want to -configure that subdirectory, but be sure to specify a path to it. - -For example, with version @value{GDBVN}, type the following to configure only -the @code{bfd} subdirectory: - -@example -@group -cd gdb-@value{GDBVN}/bfd -../configure @var{host} -@end group -@end example - -You can install @code{@value{GDBP}} anywhere; it has no hardwired paths. -However, you should make sure that the shell on your path (named by -the @samp{SHELL} environment variable) is publicly readable. Remember -that @value{GDBN} uses the shell to start your program---some systems refuse to -let @value{GDBN} debug child processes whose programs are not readable. - -@menu -* Separate Objdir:: Compiling @value{GDBN} in another directory -* Config Names:: Specifying names for hosts and targets -* Configure Options:: Summary of options for configure -@end menu - -@node Separate Objdir, Config Names, Installing GDB, Installing GDB -@section Compiling @value{GDBN} in another directory - -If you want to run @value{GDBN} versions for several host or target machines, -you need a different @code{gdb} compiled for each combination of -host and target. @code{configure} is designed to make this easy by -allowing you to generate each configuration in a separate subdirectory, -rather than in the source directory. If your @code{make} program -handles the @samp{VPATH} feature (@sc{gnu} @code{make} does), running -@code{make} in each of these directories builds the @code{gdb} -program specified there. - -To build @code{gdb} in a separate directory, run @code{configure} -with the @samp{--srcdir} option to specify where to find the source. -(You also need to specify a path to find @code{configure} -itself from your working directory. If the path to @code{configure} -would be the same as the argument to @samp{--srcdir}, you can leave out -the @samp{--srcdir} option; it is assumed.) - -For example, with version @value{GDBVN}, you can build @value{GDBN} in a -separate directory for a Sun 4 like this: - -@example -@group -cd gdb-@value{GDBVN} -mkdir ../gdb-sun4 -cd ../gdb-sun4 -../gdb-@value{GDBVN}/configure sun4 -make -@end group -@end example - -When @code{configure} builds a configuration using a remote source -directory, it creates a tree for the binaries with the same structure -(and using the same names) as the tree under the source directory. In -the example, you'd find the Sun 4 library @file{libiberty.a} in the -directory @file{gdb-sun4/libiberty}, and @value{GDBN} itself in -@file{gdb-sun4/gdb}. - -One popular reason to build several @value{GDBN} configurations in separate -directories is to configure @value{GDBN} for cross-compiling (where -@value{GDBN} runs on one machine---the @dfn{host}---while debugging -programs that run on another machine---the @dfn{target}). -You specify a cross-debugging target by -giving the @samp{--target=@var{target}} option to @code{configure}. - -When you run @code{make} to build a program or library, you must run -it in a configured directory---whatever directory you were in when you -called @code{configure} (or one of its subdirectories). - -The @code{Makefile} that @code{configure} generates in each source -directory also runs recursively. If you type @code{make} in a source -directory such as @file{gdb-@value{GDBVN}} (or in a separate configured -directory configured with @samp{--srcdir=@var{dirname}/gdb-@value{GDBVN}}), you -will build all the required libraries, and then build GDB. - -When you have multiple hosts or targets configured in separate -directories, you can run @code{make} on them in parallel (for example, -if they are NFS-mounted on each of the hosts); they will not interfere -with each other. - -@node Config Names, Configure Options, Separate Objdir, Installing GDB -@section Specifying names for hosts and targets - -The specifications used for hosts and targets in the @code{configure} -script are based on a three-part naming scheme, but some short predefined -aliases are also supported. The full naming scheme encodes three pieces -of information in the following pattern: - -@example -@var{architecture}-@var{vendor}-@var{os} -@end example - -For example, you can use the alias @code{sun4} as a @var{host} argument, -or as the value for @var{target} in a @code{--target=@var{target}} -option. The equivalent full name is @samp{sparc-sun-sunos4}. - -The @code{configure} script accompanying @value{GDBN} does not provide -any query facility to list all supported host and target names or -aliases. @code{configure} calls the Bourne shell script -@code{config.sub} to map abbreviations to full names; you can read the -script, if you wish, or you can use it to test your guesses on -abbreviations---for example: - -@smallexample -% sh config.sub i386-linux -i386-pc-linux-gnu -% sh config.sub alpha-linux -alpha-unknown-linux-gnu -% sh config.sub hp9k700 -hppa1.1-hp-hpux -% sh config.sub sun4 -sparc-sun-sunos4.1.1 -% sh config.sub sun3 -m68k-sun-sunos4.1.1 -% sh config.sub i986v -Invalid configuration `i986v': machine `i986v' not recognized -@end smallexample - -@noindent -@code{config.sub} is also distributed in the @value{GDBN} source -directory (@file{gdb-@value{GDBVN}}, for version @value{GDBVN}). - -@node Configure Options, , Config Names, Installing GDB -@section @code{configure} options - -Here is a summary of the @code{configure} options and arguments that -are most often useful for building @value{GDBN}. @code{configure} also has -several other options not listed here. @inforef{What Configure -Does,,configure.info}, for a full explanation of @code{configure}. - -@example -configure @r{[}--help@r{]} - @r{[}--prefix=@var{dir}@r{]} - @r{[}--exec-prefix=@var{dir}@r{]} - @r{[}--srcdir=@var{dirname}@r{]} - @r{[}--norecursion@r{]} @r{[}--rm@r{]} - @r{[}--target=@var{target}@r{]} - @var{host} -@end example - -@noindent -You may introduce options with a single @samp{-} rather than -@samp{--} if you prefer; but you may abbreviate option names if you use -@samp{--}. - -@table @code -@item --help -Display a quick summary of how to invoke @code{configure}. - -@item --prefix=@var{dir} -Configure the source to install programs and files under directory -@file{@var{dir}}. - -@item --exec-prefix=@var{dir} -Configure the source to install programs under directory -@file{@var{dir}}. - -@c avoid splitting the warning from the explanation: -@need 2000 -@item --srcdir=@var{dirname} -@strong{Warning: using this option requires @sc{gnu} @code{make}, or another -@code{make} that implements the @code{VPATH} feature.}@* -Use this option to make configurations in directories separate from the -@value{GDBN} source directories. Among other things, you can use this to -build (or maintain) several configurations simultaneously, in separate -directories. @code{configure} writes configuration specific files in -the current directory, but arranges for them to use the source in the -directory @var{dirname}. @code{configure} creates directories under -the working directory in parallel to the source directories below -@var{dirname}. - -@item --norecursion -Configure only the directory level where @code{configure} is executed; do not -propagate configuration to subdirectories. - -@item --target=@var{target} -Configure @value{GDBN} for cross-debugging programs running on the specified -@var{target}. Without this option, @value{GDBN} is configured to debug -programs that run on the same machine (@var{host}) as @value{GDBN} itself. - -There is no convenient way to generate a list of all available targets. - -@item @var{host} @dots{} -Configure @value{GDBN} to run on the specified @var{host}. - -There is no convenient way to generate a list of all available hosts. -@end table - -There are many other options available as well, but they are generally -needed for special purposes only. -@end ifclear - - -@node Index, , Installing GDB, Top -@unnumbered Index - -@printindex cp - -@tex -% I think something like @colophon should be in texinfo. In the -% meantime: -\long\def\colophon{\hbox to0pt{}\vfill -\centerline{The body of this manual is set in} -\centerline{\fontname\tenrm,} -\centerline{with headings in {\bf\fontname\tenbf}} -\centerline{and examples in {\tt\fontname\tentt}.} -\centerline{{\it\fontname\tenit\/},} -\centerline{{\bf\fontname\tenbf}, and} -\centerline{{\sl\fontname\tensl\/}} -\centerline{are used for emphasis.}\vfill} -\page\colophon -% Blame: doc@cygnus.com, 1991. -@end tex - -@contents -@bye |