| \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 |
| @settitle Debugging with @value{GDBN} |
| @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 |
| @sp 1 |
| @subtitle @value{EDITION} Edition, for @value{GDBN} version @value{GDBVN} |
| @subtitle @value{DATE} |
| @author Richard M. Stallman and Roland H. Pesch |
| @page |
| @tex |
| {\parskip=0pt |
| \hfill (Send bugs and comments on @value{GDBN} to bug-gdb\@gnu.org.)\par |
| \hfill {\it Debugging with @value{GDBN}}\par |
| \hfill \TeX{}info \texinfoversion\par |
| } |
| @end tex |
| |
| @c ISBN seems to be wrong... |
| |
| @vskip 0pt plus 1filll |
| Copyright @copyright{} 1988-1999 Free Software Foundation, Inc. |
| @sp 2 |
| 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 @* |
| |
| 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 |
| @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} |
| * Sample Session:: A sample @value{GDBN} session |
| |
| * 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 |
| |
| * Languages:: Using @value{GDBN} with different languages |
| |
| * Symbols:: Examining the symbol table |
| * Altering:: Altering execution |
| * GDB Files:: @value{GDBN} files |
| * Targets:: Specifying a debugging target |
| * Configurations:: Configuration-specific information |
| * Controlling GDB:: Controlling @value{GDBN} |
| * Sequences:: Canned sequences of commands |
| * Emacs:: Using @value{GDBN} under @sc{gnu} Emacs |
| |
| * GDB Bugs:: Reporting bugs in @value{GDBN} |
| * Formatting Documentation:: How to format and print @value{GDBN} documentation |
| |
| * Command Line Editing:: Command Line Editing |
| * Using History Interactively:: Using History Interactively |
| * Installing GDB:: Installing GDB |
| * Index:: Index |
| @end menu |
| |
| @end ifinfo |
| |
| @node Summary |
| @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 |
| |
| You can use @value{GDBN} to debug programs written in C and C++. |
| For more information, see @ref{Support,,Supported languages}. |
| For more information, see @ref{C,,C and C++}. |
| |
| @cindex Chill |
| @cindex Modula-2 |
| Support for Modula-2 and Chill is partial. For information on Modula-2, |
| see @ref{Modula-2,,Modula-2}. For information on Chill, see @ref{Chill}. |
| |
| @cindex Pascal |
| 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. |
| |
| @cindex Fortran |
| @value{GDBN} can be used to debug programs written in Fortran, although |
| it may be necessary to refer to some variables with a trailing |
| underscore. |
| |
| @menu |
| * Free Software:: Freely redistributable software |
| * Contributors:: Contributors to GDB |
| @end menu |
| |
| @node Free Software |
| @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 |
| @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. |
| |
| 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). |
| |
| @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, the |
| Modula-2 support, and contributed the Languages chapter of this manual. |
| |
| Fred Fish wrote most of the support for Unix System Vr4. |
| He also enhanced the command-completion support to cover C++ overloaded |
| symbols. |
| |
| 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, Kevin |
| Buettner, 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. |
| |
| |
| @node Sample Session |
| @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. |
| |
| @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 |
| |
| @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 |
| |
| @node Invocation |
| @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 @value{GDBN}. |
| @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 |
| @section Invoking @value{GDBN} |
| |
| 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. |
| |
| 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. |
| |
| The most usual way to start @value{GDBN} is with one argument, |
| specifying an executable program: |
| |
| @example |
| @value{GDBP} @var{program} |
| @end example |
| |
| @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). |
| |
| 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. @value{GDBN} |
| will warn you if it is unable to attach or to read core dumps. |
| |
| 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 |
| * File Options:: Choosing files |
| * Mode Options:: Choosing modes |
| @end menu |
| |
| @node File Options |
| @subsection Choosing files |
| |
| 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.) |
| |
| If @value{GDBN} has not been configured to included core file support, |
| such as for most embedded targets, then it will complain about a second |
| argument and ignore it. |
| |
| 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 appropriate, |
| and for examining pure data in conjunction with a core dump. |
| |
| @item -se @var{file} |
| Read symbol table from file @var{file} and use it as the executable |
| file. |
| |
| @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). |
| |
| @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. |
| |
| @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. |
| |
| @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 table |
| |
| You typically combine the @code{-mapped} and @code{-readnow} options 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 @value{GDBN} invocation to do nothing |
| but build a @file{.syms} file for future use is: |
| |
| @example |
| gdb -batch -nx -mapped -readnow programname |
| @end example |
| |
| @node Mode Options |
| @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 found in any initialization files (normally |
| called @file{.gdbinit}, or @file{gdb.ini} on PCs). Normally, |
| @value{GDBN} executes the commands in these files 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 -nowindows |
| @itemx -nw |
| ``No windows''. If @value{GDBN} comes with a graphical user interface |
| (GUI) built in, then this option tells GDB to only use the command-line |
| interface. If no GUI is available, this option has no effect. |
| |
| @item -windows |
| @itemx -w |
| If @value{GDBN} includes a GUI, then this option requires it to be |
| used if possible. |
| |
| @item -cd @var{directory} |
| Run @value{GDBN} using @var{directory} as its working directory, |
| instead of the current directory. |
| |
| @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. |
| |
| @item -baud @var{bps} |
| @itemx -b @var{bps} |
| Set the line speed (baud rate or bits per second) of any serial |
| interface used by @value{GDBN} for remote debugging. |
| |
| @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. |
| |
| @c resolve the situation of these eventually |
| @c @item -tui |
| @c Use a Terminal User Interface. For information, use your Web browser to |
| @c read the file @file{TUI.html}, which is usually installed in the |
| @c directory @code{/opt/langtools/wdb/doc} on HP-UX systems. Do not use |
| @c this option if you run @value{GDBN} from Emacs (see @pxref{Emacs, ,Using |
| @c @value{GDBN} under @sc{gnu} Emacs}). |
| |
| @c @item -xdb |
| @c Run in XDB compatibility mode, allowing the use of certain XDB commands. |
| @c For information, see the file @file{xdb_trans.html}, which is usually |
| @c installed in the directory @code{/opt/langtools/wdb/doc} on HP-UX |
| @c systems. |
| |
| @end table |
| |
| @node Quitting GDB |
| @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. |
| |
| 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}). |
| |
| @node Shell Commands |
| @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}. |
| If it exists, the environment variable @code{SHELL} determines which |
| shell to run. Otherwise @value{GDBN} uses the default shell |
| (@file{/bin/sh} on Unix systems, @file{COMMAND.COM} on MS-DOS, etc.). |
| @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 |
| @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 |
| @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 |
| @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 either by holding down a |
| key designated as the @key{META} shift on your keyboard (if there is |
| one) while typing @kbd{?}, or 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. |
| |
| 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, see @ref{C plus plus |
| expressions, ,C++ expressions}. You can use the command @code{set |
| overload-resolution off} to disable overload resolution; |
| see @ref{Debugging C plus plus, ,@value{GDBN} features for C++}. |
| |
| |
| @node Help |
| @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: |
| |
| aliases -- Aliases of other commands |
| breakpoints -- Making program stop at certain points |
| data -- Examining data |
| files -- Specifying and examining files |
| internals -- Maintenance commands |
| obscure -- Obscure features |
| running -- Running the program |
| stack -- Examining the stack |
| status -- Status inquiries |
| support -- Support facilities |
| tracepoints -- Tracing of program execution without stopping the program |
| user-defined -- User-defined commands |
| |
| 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. |
| info -- Generic command for showing things |
| about the program being debugged |
| show -- Generic command for showing things |
| about the debugger |
| |
| 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 |
| if |
| ignore |
| info |
| inspect |
| @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 need to determine which |
| version of @value{GDBN} you are running; as @value{GDBN} evolves, new |
| commands are introduced, and old ones may wither away. Also, many |
| system vendors ship variant versions of @value{GDBN}, and there are |
| variant versions of @value{GDBN} in GNU/Linux distributions as well. |
| The version number is the same as the one 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, or a warranty, |
| if your version of @value{GDB} comes with one. |
| |
| @end table |
| |
| @node Running |
| @chapter Running Programs Under @value{GDBN} |
| |
| When you run a program under @value{GDBN}, you must first generate |
| debugging information when you compile it. |
| |
| You may start @value{GDBN} with its arguments, if any, in an environment |
| of your choice. If you are doing native debugging, you may redirect |
| your program's input and output, debug an already running process, or |
| kill a child process. |
| |
| @menu |
| * Compilation:: Compiling for debugging |
| * Starting:: Starting your program |
| * Arguments:: Your program's arguments |
| * Environment:: Your program's environment |
| |
| * 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 |
| |
| * Threads:: Debugging programs with multiple threads |
| * Processes:: Debugging programs with multiple processes |
| @end menu |
| |
| @node Compilation |
| @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. |
| |
| @value{NGCC}, the @sc{gnu} C compiler, supports @samp{-g} with or |
| without @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 |
| @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 (except on VxWorks) 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 |
| |
| 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 |
| |
| 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. |
| |
| @node Arguments |
| @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 |
| the default shell (@file{/bin/sh} on Unix). |
| |
| On non-Unix systems, the program is usually invoked directly by |
| @value{GDBN}, which emulates I/O redirection via the appropriate system |
| calls, and the wildcard characters are expanded by the startup code of |
| the program, not by the shell. |
| |
| @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 |
| @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 whitespace or by a |
| system-dependent separator character (@samp{:} on Unix, @samp{;} on |
| MS-DOS and MS-Windows). 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{[}=@var{value}@r{]} |
| 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 the debugged 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:} On Unix systems, @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 |
| @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 |
| @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 |
| @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 processes with @code{run}. You can insert breakpoints; you |
| can step and 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}). |
| |
| @node Kill Process |
| @section Killing the child process |
| |
| @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). |
| |
| @node Threads |
| @section Debugging programs with multiple threads |
| |
| @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 |
| |
| @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 |
| |
| @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. |
| |
| @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 |
| |
| On HP-UX systems: |
| |
| @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 |
| |
| @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 |
| [Switching to process 35 thread 23] |
| 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. |
| |
| @node Processes |
| @section Debugging programs with multiple processes |
| |
| @cindex fork, debugging programs which call |
| @cindex multiple processes |
| @cindex processes, multiple |
| On most systems, @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 (@pxref{Attach}). From that point on you can debug |
| the child process just like any other process which you attached to. |
| |
| On HP-UX (11.x and later only?), @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. This is the default. |
| |
| @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 @code{fork} or @code{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}. |
| |
| @node Stopping |
| @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 a signal, 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, what process it is, and why it stopped. |
| @end table |
| |
| @menu |
| * Breakpoints:: Breakpoints, watchpoints, and catchpoints |
| * Continuing and Stepping:: Resuming execution |
| * Signals:: Signals |
| * Thread Stops:: Stopping and starting multi-thread programs |
| @end menu |
| |
| @node Breakpoints |
| @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; see @ref{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 |
| * Breakpoint Menus:: Breakpoint menus |
| * Error in Breakpoints:: ``Cannot insert breakpoints'' |
| @end menu |
| |
| @node Set Breaks |
| @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}. |
| 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. |
| |
| @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 @dfn{stack frame}. |
| (@xref{Frames, ,Frames}, for a description of stack frames.) |
| |
| @item break @var{linenum} |
| Set a breakpoint at line @var{linenum} in the current source file. |
| The current source file is the last file whose source text was printed. |
| The breakpoint will stop 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}. |
| |
| @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 and some x86-based targets. These targets |
| 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 take a limited number of breakpoints. For |
| example, on the DSU, only two data breakpoints can be set at a time, and |
| @value{GDBN} will reject this command if more than two are used. Delete |
| or disable unused hardware breakpoints before setting new ones |
| (@pxref{Disabling, ,Disabling}). @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}. |
| See also @ref{Conditions, ,Break conditions}. |
| |
| @kindex rbreak |
| @cindex regular expression |
| @item rbreak @var{regex} |
| 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. |
| |
| The syntax of the regular expression is the standard one used with tools |
| like @file{grep}. Note that this is different from the syntax used by |
| shells, so for instance @code{foo*} matches all functions that include |
| an @code{fo} followed by zero or more @code{o}s. There is an implicit |
| @code{.*} leading and trailing the regular expression you supply, so to |
| match only functions that begin with @code{foo}, use @code{^foo}. |
| |
| When debugging C++ programs, @code{rbreak} is useful for setting |
| breakpoints on overloaded functions that are not members of any special |
| classes. |
| |
| @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. |
| |
| @item shlib events |
| Shared library events. |
| |
| @end table |
| |
| @end table |
| |
| |
| @node Set Watchpoints |
| @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. @value{GDBN} 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, Linux and some other x86-based targets, |
| @value{GDBN} 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. |
| |
| @kindex awatch |
| @item awatch @var{expr} |
| Set a watchpoint that will break when @var{expr} is either read or written into |
| by the program. |
| |
| @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. |
| |
| Currently, the @code{awatch} and @code{rwatch} commands can only set |
| hardware watchpoints, because accesses to data that don't change the |
| value of the watched expression cannot be detected without examining |
| every instruction as it is being executed, and @value{GDBN} does not do |
| that currently. If @value{GDBN} finds that it is unable to set a |
| hardware breakpoint with the @code{awatch} or @code{rwatch} command, it |
| will print a message like this: |
| |
| @smallexample |
| Expression cannot be implemented with read/access watchpoint. |
| @end smallexample |
| |
| Sometimes, @value{GDBN} cannot set a hardware watchpoint because the |
| data type of the watched expression is wider than what a hardware |
| watchpoint on the target machine can handle. For example, some systems |
| can only watch regions that are up to 4 bytes wide; on such systems you |
| cannot set hardware watchpoints for an expression that yields a |
| double-precision floating-point number (which is typically 8 bytes |
| wide). As a work-around, it might be possible to break the large region |
| into a series of smaller ones and watch them with separate watchpoints. |
| |
| If you set too many hardware watchpoints, @value{GDBN} might be unable |
| to insert all of them when you resume the execution of your program. |
| Since the precise number of active watchpoints is unknown until such |
| time as the program is about to be resumed, @value{GDBN} might not be |
| able to warn you about this when you set the watchpoints, and the |
| warning will be printed only when the program is resumed: |
| |
| @smallexample |
| Hardware watchpoint @var{num}: Could not insert watchpoint |
| @end smallexample |
| |
| @noindent |
| If this happens, delete or disable some of the watchpoints. |
| |
| 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 @value{GDBN} reaches another |
| kind of breakpoint or the call completes. |
| |
| @value{GDBN} automatically deletes watchpoints that watch local |
| (automatic) variables, or expressions that involve such variables, when |
| they go out of scope, that is, when the execution leaves the block in |
| which these variables were defined. In particular, when the program |
| being debugged terminates, @emph{all} local variables go out of scope, |
| and so only watchpoints that watch global variables remain set. If you |
| rerun the program, you will need to set all such watchpoints again. One |
| way of doing that would be to set a code breakpoint at the entry to the |
| @code{main} function and when it breaks, set all the watchpoints. |
| |
| @quotation |
| @cindex watchpoints and threads |
| @cindex threads and watchpoints |
| @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. |
| |
| @c FIXME: this is almost identical to the previous paragraph. |
| @emph{HP-UX 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 quotation |
| |
| @node Set Catchpoints |
| @subsection Setting catchpoints |
| @cindex catchpoints, setting |
| @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. |
| @var{id} is the exception identifier. */ |
| void __raise_exception (void **addr, void *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 |
| @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 |
| @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. |
| @item |
| Enabled for deletion. The breakpoint stops your program, but |
| immediately after it does so it is deleted permanently. A breakpoint |
| set with the @code{tbreak} command starts out in this state. |
| @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 |
| |
| @c FIXME: I think the following ``Except for [...] @code{tbreak}'' is |
| @c confusing: tbreak is also initially enabled. |
| 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 |
| @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 than break |
| conditions 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. |
| |
| 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. |
| |
| @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. If @var{expression} uses |
| symbols not referenced in the context of the breakpoint, @value{GDBN} |
| prints an error message: |
| |
| @example |
| No symbol "foo" in current context. |
| @end example |
| |
| @noindent |
| @value{GDBN} does |
| not actually evaluate @var{expression} at the time the @code{condition} |
| command (or a command that sets a breakpoint with a condition, like |
| @code{break if @dots{}}) 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 |
| @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 |
| |
| @node Breakpoint Menus |
| @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 |
| |
| @c @ifclear BARETARGET |
| @node Error in Breakpoints |
| @subsection ``Cannot insert breakpoints'' |
| @c |
| @c FIXME!! 14/6/95 Is there a real example of this? Let's use it. |
| @c |
| Under some operating systems, breakpoints cannot be used in a program if |
| any other process is running that program. In this situation, |
| attempting to run or continue a program with a breakpoint causes |
| @value{GDBN} to print an error message: |
| |
| @example |
| Cannot insert breakpoints. |
| The same program may be running in another process. |
| @end example |
| |
| When this happens, you have three ways to proceed: |
| |
| @enumerate |
| @item |
| Remove or disable the breakpoints, then continue. |
| |
| @item |
| Suspend @value{GDBN}, and copy the file containing your program to a new |
| name. Resume @value{GDBN} and use the @code{exec-file} command to specify |
| that @value{GDBN} should run your program under that name. |
| Then start your program again. |
| |
| @item |
| Relink your program so that the text segment is nonsharable, using the |
| linker option @samp{-N}. The operating system limitation may not apply |
| to nonsharable executables. |
| @end enumerate |
| @c @end ifclear |
| |
| A similar message can be printed if you request too many active |
| hardware-assisted breakpoints and watchpoints: |
| |
| @c FIXME: the precise wording of this message may change; the relevant |
| @c source change is not committed yet (Sep 3, 1999). |
| @smallexample |
| Stopped; cannot insert breakpoints. |
| You may have requested too many hardware breakpoints and watchpoints. |
| @end smallexample |
| |
| @noindent |
| This message is printed when you attempt to resume the program, since |
| only then @value{GDBN} knows exactly how many hardware breakpoints and |
| watchpoints it needs to insert. |
| |
| When this message is printed, you need to disable or remove some of the |
| hardware-assisted breakpoints and watchpoints, and then continue. |
| |
| |
| @node Continuing and Stepping |
| @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 a breakpoint or a signal. (If |
| it stops due to a signal, you may want to use @code{handle}, or use |
| @samp{signal 0} to resume execution. @xref{Signals, ,Signals}.) |
| |
| @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} (for @dfn{foreground}, as the |
| debugged program is deemed to be the foreground program) 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 only stops at the first instruction of a |
| source line. This prevents the multiple stops that could otherwise occur in |
| switch statements, for loops, etc. @code{step} continues to stop if a |
| function that has debugging information is called within the line. |
| In other words, @code{step} @emph{steps inside} any functions called |
| within the line. |
| |
| Also, the @code{step} command only enters a function if there is line |
| number information for the function. 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, or a signal not related to stepping occurs before |
| @var{count} steps, 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 only stops at the first instruction of a |
| source line. This prevents multiple stops that could otherwise 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 |
| |
| @node Signals |
| @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 character (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} (they 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 an 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 to the |
| program 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}. |
| |
| @node Thread Stops |
| @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 |
| (@value{GDBP}) 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 @samp{next} over a |
| function call, and they are completely free to run when you use commands |
| like @samp{continue}, @samp{until}, or @samp{finish}. However, unless another |
| thread hits a breakpoint during its timeslice, they will never steal the |
| @value{GDBN} prompt away from the thread that you are debugging. |
| |
| @item show scheduler-locking |
| Display the current scheduler locking mode. |
| @end table |
| |
| |
| @node Stack |
| @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 |
| |
| @end menu |
| |
| @node Frames |
| @section Stack frames |
| |
| @cindex frame, definition |
| @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@r{, command} |
| @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 |
| @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 |
| @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@r{, selecting} |
| @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. |
| |
| 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. |
| |
| @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 |
| @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 address of the frame's local variables |
| @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. |
| |
| @kindex info catch |
| @cindex catch exceptions, list active handlers |
| @cindex exception handlers, how to list |
| @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 table |
| |
| |
| @node Source |
| @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. |
| |
| If you use @value{GDBN} through its @sc{gnu} Emacs interface, you may |
| prefer to use Emacs facilities to view source; see @ref{Emacs, ,Using |
| @value{GDBN} under @sc{gnu} Emacs}. |
| |
| @menu |
| * List:: Printing source lines |
| * Search:: Searching source files |
| * Source Path:: Specifying source directories |
| * Machine Code:: Source and machine code |
| @end menu |
| |
| @node List |
| @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 |
| |
| @node Search |
| @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 |
| |
| @node Source Path |
| @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 includes only @samp{cdir} |
| and @samp{cwd}, in that order. |
| 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{:} |
| (@samp{;} on MS-DOS and MS-Windows, where @samp{:} usually appears as |
| part of absolute file names) 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 |
| @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 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}: |
| |
| @c FIXME: I think this example should also show the addresses in |
| @c symbolic form, as they usually would be displayed. |
| @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{$_} and @code{info line} |
| @kindex x@r{, and }@code{info line} |
| After @code{info line}, the default address for the @code{x} command |
| is changed to the starting address of the line, so that @samp{x/i} is |
| sufficient to begin examining the machine code (@pxref{Memory, |
| ,Examining memory}). Also, this address is saved as the value of the |
| convenience variable @code{$_} (@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 |
| |
| 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 |
| |
| Some architectures have more than one commonly-used set of instruction |
| mnemonics or other syntax. |
| |
| @table @code |
| @kindex set disassembly-flavor |
| @cindex assembly instructions |
| @cindex instructions, assembly |
| @cindex machine instructions |
| @cindex listing machine instructions |
| @cindex Intel disassembly flavor |
| @cindex AT&T disassembly flavor |
| @item set disassembly-flavor @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{intel} or @code{att}. |
| The default is @code{att}, the AT&T flavor used by default by Unix |
| assemblers for x86-based targets. |
| @end table |
| |
| |
| @node Data |
| @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}. 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}). |
| |
| @table @code |
| @item print @var{expr} |
| @itemx print /@var{f} @var{expr} |
| @var{expr} is an expression (in the source language). By default the |
| value of @var{expr} 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; see @ref{Output Formats,,Output |
| formats}. |
| |
| @item print |
| @itemx print /@var{f} |
| If you omit @var{expr}, @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 or a class 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 |
| * Floating Point Hardware:: Floating point hardware |
| @end menu |
| |
| @node Expressions |
| @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} supports array constants in expressions input by |
| the user. The syntax is @{@var{element}, @var{element}@dots{}@}. For example, |
| you can use the command @code{print @{1, 2, 3@}} to build up an array in |
| memory that is @code{malloc}ed in the target program. |
| |
| 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? |
| |
| @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 |
| @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, context for variables/functions |
| @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 |
| |
| @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 |
| |
| @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. |
| |
| @cindex ``No symbol "foo" in current context'' |
| Another possible effect of compiler optimizations is to optimize |
| unused variables out of existence, or assign variables to registers (as |
| opposed to memory addresses). Depending on the support for such cases |
| offered by the debug info format used by the compiler, @value{GDBN} |
| might not be able to display values for such local variables. If that |
| happens, @value{GDBN} will print a message like this: |
| |
| @example |
| No symbol "foo" in current context. |
| @end example |
| |
| To solve such problems, either recompile without optimizations, or use a |
| different debug info format, if the compiler supports several such |
| formats. For example, @value{NGCC}, the @sc{gnu} C/C++ compiler usually |
| supports the @samp{-gstabs} option. @samp{-gstabs} produces debug info |
| in a format that is superior to formats such as COFF. You may be able |
| to use DWARF-2 (@samp{-gdwarf-2}), which is also an effective form for |
| debug info. See @ref{Debugging Options,,Options for Debugging Your |
| Program or @sc{gnu} CC, gcc.info, Using @sc{gnu} CC}, for more |
| information. |
| |
| |
| @node Arrays |
| @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}}) @value{GDBN} 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 |
| @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''; |
| see @ref{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 |
| @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, ,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; see @ref{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 |
| @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{expr} |
| Add the expression @var{expr} 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{expr} |
| For @var{fmt} specifying only a display format and not a size or |
| count, add the expression @var{expr} 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, ,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 |
| @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. |
| When @value{GDBN} starts, this limit is set to 200. |
| 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. |
| The default is off. |
| |
| @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 |
| |
| @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 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. |
| This is the default. |
| |
| @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. |
| (The @code{vtbl} commands do not work on programs compiled with the HP |
| ANSI C++ compiler (@code{aCC}).) |
| |
| @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 |
| |
| @node Value History |
| @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 |
| @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, ,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 conv}. |
| @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 |
| |
| On HP-UX systems, 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. |
| |
| @node Registers |
| @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}; |
| see @ref{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{$ps}; and on x86-based machines @code{$ps} |
| is an alias for the @sc{eflags} register. |
| |
| @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. |
| |
| @node Floating Point Hardware |
| @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 |
| |
| @node Languages |
| @chapter Using @value{GDBN} with Different Languages |
| @cindex languages |
| |
| 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}. |
| |
| @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 |
| * Checks:: Type and range checks |
| * Support:: Supported languages |
| @end menu |
| |
| @node Setting |
| @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}, but you can |
| set the language associated with a filename extension. @xref{Show, , |
| Displaying the language}. |
| |
| 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 |
| @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 |
| |
| @item .ch |
| @itemx .c186 |
| @itemx .c286 |
| CHILL source file. |
| |
| @item .mod |
| Modula-2 source file |
| |
| @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 |
| @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 |
| @code{c} or @code{modula-2}. |
| For a list of the supported languages, type @samp{set language}. |
| |
| 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. |
| |
| @node Automatically |
| @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. |
| |
| @node Show |
| @section Displaying the language |
| |
| 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@r{, show the source language} |
| @kindex info source@r{, show the source language} |
| @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 |
| |
| @node Checks |
| @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 |
| @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@r{, type} |
| @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 type checking 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 |
| @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@r{, range} |
| @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 and range checking is on, |
| 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 |
| |
| @node Support |
| @section Supported languages |
| |
| @value{GDBN} supports C, C++, Fortran, Java, Chill, assembly, and Modula-2. |
| @c This is false ... |
| 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. |
| |
| @menu |
| * C:: C and C++ |
| * Modula-2:: Modula-2 |
| * Chill:: Chill |
| @end menu |
| |
| @node C |
| @subsection C and C++ |
| |
| @cindex C and C++ |
| @cindex expressions in C or C++ |
| |
| 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. |
| |
| @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. |
| |
| @menu |
| * C Operators:: C and C++ operators |
| * C Constants:: C and C++ constants |
| * C plus plus expressions:: C++ expressions |
| * C Defaults:: Default settings for C and C++ |
| * C Checks:: C and C++ type and range checks |
| * Debugging C:: @value{GDBN} and C |
| * Debugging C plus plus:: @value{GDBN} features for C++ |
| @end menu |
| |
| @node C Operators |
| @subsubsection C and C++ operators |
| |
| @cindex C and C++ 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 C and C++, the following definitions hold: |
| |
| @itemize @bullet |
| |
| @item |
| @emph{Integral types} include @code{int} with any of its storage-class |
| specifiers; @code{char}; @code{enum}; and, for C++, @code{bool}. |
| |
| @item |
| @emph{Floating-point types} include @code{float}, @code{double}, and |
| @code{long double} (if supported by the target platform). |
| |
| @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 precedence. |
| @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{++}. |
| |
| 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. |
| |
| @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. |
| |
| @item .*@r{, }->* |
| Dereferences of pointers to members. |
| |
| @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{->}. |
| |
| @item :: |
| C++ scope resolution operator. Defined on @code{struct}, @code{union}, |
| and @code{class} types. |
| |
| @item :: |
| Doubled colons also represent the @value{GDBN} scope operator |
| (@pxref{Expressions, ,Expressions}). Same precedence as @code{::}, |
| above. |
| @end table |
| |
| 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. |
| |
| @menu |
| * C Constants:: |
| @end menu |
| |
| @node C Constants |
| @subsubsection C and C++ constants |
| |
| @cindex C and C++ constants |
| |
| @value{GDBN} allows you to express the constants of C and C++ in the |
| following ways: |
| |
| @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. |
| A floating-point constant may also end with a letter @samp{f} or |
| @samp{F}, specifying that the constant should be treated as being of |
| the @code{float} (as opposed to the default @code{double}) type; or with |
| a letter @samp{l} or @samp{L}, which specifies a @code{long double} |
| constant. |
| |
| @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 |
| |
| @menu |
| * C plus plus expressions:: |
| * C Defaults:: |
| * C Checks:: |
| |
| * Debugging C:: |
| @end menu |
| |
| @node C plus plus expressions |
| @subsubsection C++ expressions |
| |
| @cindex expressions in C++ |
| @value{GDBN} expression handling can interpret most C++ expressions. |
| |
| @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 |
| |
| @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++. |
| |
| @cindex call overloaded functions |
| @cindex overloaded functions, calling |
| @cindex type conversions in C++ |
| @item |
| You can call overloaded functions; @value{GDBN} resolves the function |
| call to the right definition, with some restrictions. @value{GDBN} 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; |
| see @ref{Completion, ,Command completion}. |
| |
| @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 |
| |
| In addition, when used with HP's C++ compiler, @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. |
| |
| @node C Defaults |
| @subsubsection C and C++ defaults |
| |
| @cindex C and C++ defaults |
| |
| 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. |
| |
| 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. |
| |
| @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 |
| @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. |
| |
| @node Debugging C |
| @subsubsection @value{GDBN} and C |
| |
| 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} or @code{class} 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}. |
| |
| @menu |
| * Debugging C plus plus:: |
| @end menu |
| |
| @node Debugging C plus plus |
| @subsubsection @value{GDBN} features for C++ |
| |
| @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}. |
| (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, overload resolution |
| @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 (see @ref{C plus plus 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. |
| |
| @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 |
| |
| @node Modula-2 |
| @subsection Modula-2 |
| |
| @cindex Modula-2, @value{GDBN} support |
| |
| 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 |
| @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 conjunction. 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 |
| @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} by one. 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} by one. 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 @sc{ascii} value (on machines supporting the |
| @sc{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 |
| @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 @sc{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 |
| @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 |
| @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 |
| @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 |
| @subsubsection The scope operators @code{::} and @code{.} |
| @cindex scope |
| @kindex . |
| @cindex colon, doubled as scope operator |
| @ifinfo |
| @kindex colon-colon@r{, in Modula-2} |
| @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 |
| @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 |
| with 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. |
| |
| @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. |
| |
| @node Chill |
| @subsection Chill |
| |
| The extensions made to @value{GDBN} to support Chill only support output |
| from the @sc{gnu} Chill compiler. Other Chill 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. |
| |
| @c This used to say "... following Chill related topics ...", but since |
| @c menus are not shown in the printed manual, it would look awkward. |
| This section covers the Chill related topics and the features |
| of @value{GDBN} which support these topics. |
| |
| @menu |
| * How modes are displayed:: How modes are displayed |
| * Locations:: Locations and their accesses |
| * Values and their Operations:: Values and their Operations |
| * Chill type and range checks:: |
| * Chill defaults:: |
| @end menu |
| |
| @node How modes are displayed |
| @subsubsection How modes are displayed |
| |
| The Chill Datatype- (Mode) support of @value{GDBN} is directly related |
| with the functionality of the @sc{gnu} Chill compiler, and therefore deviates |
| slightly from the standard specification of the Chill language. The |
| provided modes are: |
| |
| @c FIXME: this @table's contents effectively disable @code by using @r |
| @c on every @item. So why does it need @code? |
| @table @code |
| @item @r{@emph{Discrete modes:}} |
| @itemize @bullet |
| @item |
| @emph{Integer Modes} which are predefined by @code{BYTE, UBYTE, INT, |
| UINT, LONG, ULONG}, |
| @item |
| @emph{Boolean Mode} which is predefined by @code{BOOL}, |
| @item |
| @emph{Character Mode} which is predefined by @code{CHAR}, |
| @item |
| @emph{Set Mode} which is displayed by the keyword @code{SET}. |
| @smallexample |
| (@value{GDBP}) ptype x |
| type = SET (karli = 10, susi = 20, fritzi = 100) |
| @end smallexample |
| If the type is an unnumbered set the set element values are omitted. |
| @item |
| @emph{Range Mode} which is displayed by @code{type = <basemode> |
| (<lower bound> : <upper bound>)}, where @code{<lower bound>, <upper |
| bound>} can be of any discrete literal expression (e.g. set element |
| names). |
| @end itemize |
| |
| @item @r{@emph{Powerset Mode:}} |
| A Powerset Mode is displayed by the keyword @code{POWERSET} followed by |
| the member mode of the powerset. The member mode can be any discrete mode. |
| @smallexample |
| (@value{GDBP}) ptype x |
| type = POWERSET SET (egon, hugo, otto) |
| @end smallexample |
| |
| @item @r{@emph{Reference Modes:}} |
| @itemize @bullet |
| @item |
| @emph{Bound Reference Mode} which is displayed by the keyword @code{REF} |
| followed by the mode name to which the reference is bound. |
| @item |
| @emph{Free Reference Mode} which is displayed by the keyword @code{PTR}. |
| @end itemize |
| |
| @item @r{@emph{Procedure mode}} |
| The procedure mode is displayed by @code{type = PROC(<parameter list>) |
| <return mode> EXCEPTIONS (<exception list>)}. The @code{<parameter |
| list>} is a list of the parameter modes. @code{<return mode>} indicates |
| the mode of the result of the procedure if any. The exceptionlist lists |
| all possible exceptions which can be raised by the procedure. |
| |
| @ignore |
| @item @r{@emph{Instance mode}} |
| The instance mode is represented by a structure, which has a static |
| type, and is therefore not really of interest. |
| @end ignore |
| |
| @item @r{@emph{Synchronization Modes:}} |
| @itemize @bullet |
| @item |
| @emph{Event Mode} which is displayed by @code{EVENT (<event length>)}, |
| where @code{(<event length>)} is optional. |
| @item |
| @emph{Buffer Mode} which is displayed by @code{BUFFER (<buffer length>) |
| <buffer element mode>}, where @code{(<buffer length>)} is optional. |
| @end itemize |
| |
| @item @r{@emph{Timing Modes:}} |
| @itemize @bullet |
| @item |
| @emph{Duration Mode} which is predefined by @code{DURATION} |
| @item |
| @emph{Absolute Time Mode} which is predefined by @code{TIME} |
| @end itemize |
| |
| @item @r{@emph{Real Modes:}} |
| Real Modes are predefined with @code{REAL} and @code{LONG_REAL}. |
| |
| @item @r{@emph{String Modes:}} |
| @itemize @bullet |
| @item |
| @emph{Character String Mode} which is displayed by @code{CHARS(<string |
| length>)}, followed by the keyword @code{VARYING} if the String Mode is |
| a varying mode |
| @item |
| @emph{Bit String Mode} which is displayed by @code{BOOLS(<string |
| length>)}. |
| @end itemize |
| |
| @item @r{@emph{Array Mode:}} |
| The Array Mode is displayed by the keyword @code{ARRAY(<range>)} |
| followed by the element mode (which may in turn be an array mode). |
| @smallexample |
| (@value{GDBP}) ptype x |
| type = ARRAY (1:42) |
| ARRAY (1:20) |
| SET (karli = 10, susi = 20, fritzi = 100) |
| @end smallexample |
| |
| @item @r{@emph{Structure Mode}} |
| The Structure mode is displayed by the keyword @code{STRUCT(<field |
| list>)}. The @code{<field list>} consists of names and modes of fields |
| of the structure. Variant structures have the keyword @code{CASE <field> |
| OF <variant fields> ESAC} in their field list. Since the current version |
| of the GNU Chill compiler doesn't implement tag processing (no runtime |
| checks of variant fields, and therefore no debugging info), the output |
| always displays all variant fields. |
| @smallexample |
| (@value{GDBP}) ptype str |
| type = STRUCT ( |
| as x, |
| bs x, |
| CASE bs OF |
| (karli): |
| cs a |
| (ott): |
| ds x |
| ESAC |
| ) |
| @end smallexample |
| @end table |
| |
| @node Locations |
| @subsubsection Locations and their accesses |
| |
| A location in Chill is an object which can contain values. |
| |
| A value of a location is generally accessed by the (declared) name of |
| the location. The output conforms to the specification of values in |
| Chill programs. How values are specified |
| is the topic of the next section, @ref{Values and their Operations}. |
| |
| The pseudo-location @code{RESULT} (or @code{result}) can be used to |
| display or change the result of a currently-active procedure: |
| |
| @smallexample |
| set result := EXPR |
| @end smallexample |
| |
| @noindent |
| This does the same as the Chill action @code{RESULT EXPR} (which |
| is not available in @value{GDBN}). |
| |
| Values of reference mode locations are printed by @code{PTR(<hex |
| value>)} in case of a free reference mode, and by @code{(REF <reference |
| mode>) (<hex-value>)} in case of a bound reference. @code{<hex value>} |
| represents the address where the reference points to. To access the |
| value of the location referenced by the pointer, use the dereference |
| operator @samp{->}. |
| |
| Values of procedure mode locations are displayed by @code{@{ PROC |
| (<argument modes> ) <return mode> @} <address> <name of procedure |
| location>}. @code{<argument modes>} is a list of modes according to the |
| parameter specification of the procedure and @code{<address>} shows the |
| address of the entry point. |
| |
| @ignore |
| Locations of instance modes are displayed just like a structure with two |
| fields specifying the @emph{process type} and the @emph{copy number} of |
| the investigated instance location@footnote{This comes from the current |
| implementation of instances. They are implemented as a structure (no |
| na). The output should be something like @code{[<name of the process>; |
| <instance number>]}.}. The field names are @code{__proc_type} and |
| @code{__proc_copy}. |
| |
| Locations of synchronization modes are displayed like a structure with |
| the field name @code{__event_data} in case of a event mode location, and |
| like a structure with the field @code{__buffer_data} in case of a buffer |
| mode location (refer to previous paragraph). |
| |
| Structure Mode locations are printed by @code{[.<field name>: <value>, |
| ...]}. The @code{<field name>} corresponds to the structure mode |
| definition and the layout of @code{<value>} varies depending of the mode |
| of the field. If the investigated structure mode location is of variant |
| structure mode, the variant parts of the structure are enclosed in curled |
| braces (@samp{@{@}}). Fields enclosed by @samp{@{,@}} are residing |
| on the same memory location and represent the current values of the |
| memory location in their specific modes. Since no tag processing is done |
| all variants are displayed. A variant field is printed by |
| @code{(<variant name>) = .<field name>: <value>}. (who implements the |
| stuff ???) |
| @smallexample |
| (@value{GDBP}) print str1 $4 = [.as: 0, .bs: karli, .<TAG>: { (karli) = |
| [.cs: []], (susi) = [.ds: susi]}] |
| @end smallexample |
| @end ignore |
| |
| Substructures of string mode-, array mode- or structure mode-values |
| (e.g. array slices, fields of structure locations) are accessed using |
| certain operations which are described in the next section, @ref{Values |
| and their Operations}. |
| |
| A location value may be interpreted as having a different mode using the |
| location conversion. This mode conversion is written as @code{<mode |
| name>(<location>)}. The user has to consider that the sizes of the modes |
| have to be equal otherwise an error occurs. Furthermore, no range |
| checking of the location against the destination mode is performed, and |
| therefore the result can be quite confusing. |
| |
| @smallexample |
| (@value{GDBP}) print int (s(3 up 4)) XXX TO be filled in !! XXX |
| @end smallexample |
| |
| @node Values and their Operations |
| @subsubsection Values and their Operations |
| |
| Values are used to alter locations, to investigate complex structures in |
| more detail or to filter relevant information out of a large amount of |
| data. There are several (mode dependent) operations defined which enable |
| such investigations. These operations are not only applicable to |
| constant values but also to locations, which can become quite useful |
| when debugging complex structures. During parsing the command line |
| (e.g. evaluating an expression) @value{GDBN} treats location names as |
| the values behind these locations. |
| |
| This section describes how values have to be specified and which |
| operations are legal to be used with such values. |
| |
| @table @code |
| @item Literal Values |
| Literal values are specified in the same manner as in @sc{gnu} Chill programs. |
| For detailed specification refer to the @sc{gnu} Chill implementation Manual |
| chapter 1.5. |
| @c FIXME: if the Chill Manual is a Texinfo documents, the above should |
| @c be converted to a @ref. |
| |
| @ignore |
| @itemize @bullet |
| @item |
| @emph{Integer Literals} are specified in the same manner as in Chill |
| programs (refer to the Chill Standard z200/88 chpt 5.2.4.2) |
| @item |
| @emph{Boolean Literals} are defined by @code{TRUE} and @code{FALSE}. |
| @item |
| @emph{Character Literals} are defined by @code{'<character>'}. (e.g. |
| @code{'M'}) |
| @item |
| @emph{Set Literals} are defined by a name which was specified in a set |
| mode. The value delivered by a Set Literal is the set value. This is |
| comparable to an enumeration in C/C++ language. |
| @item |
| @emph{Emptiness Literal} is predefined by @code{NULL}. The value of the |
| emptiness literal delivers either the empty reference value, the empty |
| procedure value or the empty instance value. |
| |
| @item |
| @emph{Character String Literals} are defined by a sequence of characters |
| enclosed in single- or double quotes. If a single- or double quote has |
| to be part of the string literal it has to be stuffed (specified twice). |
| @item |
| @emph{Bitstring Literals} are specified in the same manner as in Chill |
| programs (refer z200/88 chpt 5.2.4.8). |
| @item |
| @emph{Floating point literals} are specified in the same manner as in |
| (gnu-)Chill programs (refer @sc{gnu} Chill implementation Manual chapter 1.5). |
| @end itemize |
| @end ignore |
| |
| @item Tuple Values |
| A tuple is specified by @code{<mode name>[<tuple>]}, where @code{<mode |
| name>} can be omitted if the mode of the tuple is unambiguous. This |
| unambiguity is derived from the context of a evaluated expression. |
| @code{<tuple>} can be one of the following: |
| |
| @itemize @bullet |
| @item @emph{Powerset Tuple} |
| @item @emph{Array Tuple} |
| @item @emph{Structure Tuple} |
| Powerset tuples, array tuples and structure tuples are specified in the |
| same manner as in Chill programs refer to z200/88 chpt 5.2.5. |
| @end itemize |
| |
| @item String Element Value |
| A string element value is specified by @code{<string value>(<index>)}, |
| where @code{<index>} is a integer expression. It delivers a character |
| value which is equivalent to the character indexed by @code{<index>} in |
| the string. |
| |
| @item String Slice Value |
| A string slice value is specified by @code{<string value>(<slice |
| spec>)}, where @code{<slice spec>} can be either a range of integer |
| expressions or specified by @code{<start expr> up <size>}. |
| @code{<size>} denotes the number of elements which the slice contains. |
| The delivered value is a string value, which is part of the specified |
| string. |
| |
| @item Array Element Values |
| An array element value is specified by @code{<array value>(<expr>)} and |
| delivers a array element value of the mode of the specified array. |
| |
| @item Array Slice Values |
| An array slice is specified by @code{<array value>(<slice spec>)}, where |
| @code{<slice spec>} can be either a range specified by expressions or by |
| @code{<start expr> up <size>}. @code{<size>} denotes the number of |
| arrayelements the slice contains. The delivered value is an array value |
| which is part of the specified array. |
| |
| @item Structure Field Values |
| A structure field value is derived by @code{<structure value>.<field |
| name>}, where @code{<field name>} indicates the name of a field specified |
| in the mode definition of the structure. The mode of the delivered value |
| corresponds to this mode definition in the structure definition. |
| |
| @item Procedure Call Value |
| The procedure call value is derived from the return value of the |
| procedure@footnote{If a procedure call is used for instance in an |
| expression, then this procedure is called with all its side |
| effects. This can lead to confusing results if used carelessly.}. |
| |
| Values of duration mode locations are represented by @code{ULONG} literals. |
| |
| Values of time mode locations are represented by @code{TIME(<secs>:<nsecs>)}. |
| |
| @ignore |
| This is not implemented yet: |
| @item Built-in Value |
| @noindent |
| The following built in functions are provided: |
| |
| @table @code |
| @item @code{ADDR()} |
| @item @code{NUM()} |
| @item @code{PRED()} |
| @item @code{SUCC()} |
| @item @code{ABS()} |
| @item @code{CARD()} |
| @item @code{MAX()} |
| @item @code{MIN()} |
| @item @code{SIZE()} |
| @item @code{UPPER()} |
| @item @code{LOWER()} |
| @item @code{LENGTH()} |
| @item @code{SIN()} |
| @item @code{COS()} |
| @item @code{TAN()} |
| @item @code{ARCSIN()} |
| @item @code{ARCCOS()} |
| @item @code{ARCTAN()} |
| @item @code{EXP()} |
| @item @code{LN()} |
| @item @code{LOG()} |
| @item @code{SQRT()} |
| @end table |
| |
| For a detailed description refer to the GNU Chill implementation manual |
| chapter 1.6. |
| @end ignore |
| |
| @item Zero-adic Operator Value |
| The zero-adic operator value is derived from the instance value for the |
| current active process. |
| |
| @item Expression Values |
| The value delivered by an expression is the result of the evaluation of |
| the specified expression. If there are error conditions (mode |
| incompatibility, etc.) the evaluation of expressions is aborted with a |
| corresponding error message. Expressions may be parenthesised which |
| causes the evaluation of this expression before any other expression |
| which uses the result of the parenthesised expression. The following |
| operators are supported by @value{GDBN}: |
| |
| @table @code |
| @item @code{OR, ORIF, XOR} |
| @itemx @code{AND, ANDIF} |
| @itemx @code{NOT} |
| Logical operators defined over operands of boolean mode. |
| |
| @item @code{=, /=} |
| Equality and inequality operators defined over all modes. |
| |
| @item @code{>, >=} |
| @itemx @code{<, <=} |
| Relational operators defined over predefined modes. |
| |
| @item @code{+, -} |
| @itemx @code{*, /, MOD, REM} |
| Arithmetic operators defined over predefined modes. |
| |
| @item @code{-} |
| Change sign operator. |
| |
| @item @code{//} |
| String concatenation operator. |
| |
| @item @code{()} |
| String repetition operator. |
| |
| @item @code{->} |
| Referenced location operator which can be used either to take the |
| address of a location (@code{->loc}), or to dereference a reference |
| location (@code{loc->}). |
| |
| @item @code{OR, XOR} |
| @itemx @code{AND} |
| @itemx @code{NOT} |
| Powerset and bitstring operators. |
| |
| @item @code{>, >=} |
| @itemx @code{<, <=} |
| Powerset inclusion operators. |
| |
| @item @code{IN} |
| Membership operator. |
| @end table |
| @end table |
| |
| @node Chill type and range checks |
| @subsubsection Chill type and range checks |
| |
| @value{GDBN} considers two Chill variables mode equivalent if the sizes |
| of the two modes are equal. This rule applies recursively to more |
| complex datatypes which means that complex modes are treated |
| equivalent if all element modes (which also can be complex modes like |
| structures, arrays, etc.) have the same size. |
| |
| Range checking is done on all mathematical operations, assignment, array |
| index bounds and all built in procedures. |
| |
| Strong type checks are forced using the @value{GDBN} command @code{set |
| check strong}. This enforces strong type and range checks on all |
| operations where Chill constructs are used (expressions, built in |
| functions, etc.) in respect to the semantics as defined in the z.200 |
| language specification. |
| |
| All checks can be disabled by the @value{GDBN} command @code{set check |
| off}. |
| |
| @ignore |
| @c Deviations from the Chill Standard Z200/88 |
| see last paragraph ? |
| @end ignore |
| |
| @node Chill defaults |
| @subsubsection Chill defaults |
| |
| If type and range checking are set automatically by @value{GDBN}, they |
| both default to @code{on} whenever the working language changes to |
| Chill. 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{.ch} sets the |
| working language to Chill. @xref{Automatically, ,Having @value{GDBN} set |
| the language automatically}, for further details. |
| |
| @node Symbols |
| @chapter Examining the Symbol Table |
| |
| The commands described in this chapter 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{expr} |
| Print the data type of expression @var{expr}. @var{expr} 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 @samp{class |
| @var{class-name}}, @samp{struct @var{struct-tag}}, @samp{union |
| @var{union-tag}} or @samp{enum @var{enum-tag}}. |
| |
| @item ptype @var{expr} |
| @itemx ptype |
| Print a description of the type of expression @var{expr}. @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{$}, the last value in the value history. |
| |
| @kindex info types |
| @item info types @var{regexp} |
| @itemx info types |
| Print a brief description of all types whose names match @var{regexp} |
| (or all types in your program, if you supply no argument). Each |
| complete typename is matched as though it were a complete line; thus, |
| @samp{i type value} gives information on all types in your program whose |
| names include the string @code{value}, but @samp{i type ^value$} 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 |
| |
| @cindex reloading symbols |
| Some systems allow individual object files that make up your program to |
| be replaced without stopping and restarting your program. For example, |
| in VxWorks you can simply recompile a defective object file and keep on |
| running. 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 |
| |
| @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. |
| |
| @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 |
| @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, give your program a signal, restart it at a different |
| address, or even return prematurely from a function. |
| |
| @menu |
| * Assignment:: Assignment to variables |
| * Jumping:: Continuing at a different address |
| * Signaling:: Giving your program a signal |
| * Returning:: Returning from a function |
| * Calling:: Calling your program's functions |
| * Patching:: Patching your program |
| @end menu |
| |
| @node Assignment |
| @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). |
| @xref{Languages, ,Using @value{GDBN} with Different Languages}, for more |
| information on operators in supported languages. |
| |
| @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. |
| |
| 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 |
| |
| 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 |
| (@value{GDBP}) 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 |
| |
| @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 |
| @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 |
| |
| @c Doesn't work on HP-UX; have to set $pcoqh and $pcoqt. |
| On many systems, you can get much the same effect as the @code{jump} |
| command by storing a new value into the register @code{$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}. |
| |
| 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. |
| |
| @c @group |
| @node Signaling |
| @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. |
| |
| |
| @node Returning |
| @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 |
| @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. |
| |
| 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. |
| |
| @node Patching |
| @section Patching programs |
| |
| @cindex patching binaries |
| @cindex writing into executables |
| @cindex writing into corefiles |
| |
| By default, @value{GDBN} opens the file containing your program's |
| executable code (or the corefile) 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 and |
| core 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} or @code{core-file} command) after changing @code{set |
| write}, for your new setting to take effect. |
| |
| @item show write |
| @kindex show write |
| Display whether executable files and core files are opened for writing |
| as well as reading. |
| @end table |
| |
| @node GDB Files |
| @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. To debug a core dump of a previous run, you must also tell |
| @value{GDBN} the name of the core dump file. |
| |
| @menu |
| * Files:: Commands to specify files |
| * Symbol Errors:: Errors reading symbol files |
| @end menu |
| |
| @node Files |
| @section Commands to specify files |
| |
| @cindex symbol table |
| @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}}). |
| |
| 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. |
| |
| 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. |
| |
| @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. |
| Best results are usually obtained from @sc{gnu} compilers; for example, |
| using @code{@value{GCC}} you can generate debugging information for |
| optimized code. |
| |
| 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}.) |
| |
| 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. |
| |
| 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. |
| |
| @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}). |
| |
| @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{]} |
| @itemx add-symbol-file @var{filename} @var{address} @var{data_address} @var{bss_address} |
| @itemx add-symbol-file @var{filename} @r{-T}@var{section} @var{address} |
| 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 up to three addresses, in which case they are taken to be |
| the addresses of the text, data, and bss segments respectively. |
| For complicated cases, you can specify an arbitrary number of @r{-T}@var{section} @var{address} |
| pairs, to give an explicit section name and base address for that section. |
| You can specify any @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. |
| |
| @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 @code{info files} command, described below, lists all |
| the sections and their addresses. |
| |
| @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 names of the executable and core dump files 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. |
| |
| @cindex shared libraries |
| @value{GDBN} supports HP-UX, SunOS, SVr4, Irix 5, and IBM RS/6000 shared |
| libraries. |
| |
| @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). |
| |
| On HP-UX, if the program loads a library explicitly, @value{GDBN} |
| automatically loads the symbols at the time of the @code{shl_load} call. |
| |
| @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 |
| |
| On HP-UX systems, @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 |
| |
| @node Symbol Errors |
| @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 |
| uncomprehended 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 a struct or class. |
| |
| @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. |
| |
| @item info mismatch between compiler and debugger |
| |
| @value{GDBN} could not parse a type specification output by the compiler. |
| |
| @end table |
| |
| @node Targets |
| @chapter Specifying a Debugging Target |
| |
| @cindex debugging target |
| @kindex target |
| |
| A @dfn{target} is the execution environment occupied by your program. |
| |
| 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 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 |
| * Byte Order:: Choosing target byte order |
| * Remote:: Remote debugging |
| * KOD:: Kernel Object Display |
| |
| @end menu |
| |
| @node Active Targets |
| @section Active targets |
| |
| @cindex stacking targets |
| @cindex active targets |
| @cindex multiple targets |
| |
| 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.) |
| |
| 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 active core file or executable file target are obscured while the |
| process target is active. |
| |
| 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}). |
| |
| @node Target Commands |
| @section Commands for managing targets |
| |
| @table @code |
| @item target @var{type} @var{parameters} |
| Connects the @value{GDBN} host environment to a target 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. |
| |
| 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. |
| |
| @quotation |
| @emph{Warning:} To specify a file format with @code{set gnutarget}, |
| you must know the actual BFD name. |
| @end quotation |
| |
| @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 |
| |
| Here are some common targets (available, or not, depending on the GDB |
| configuration): |
| |
| @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}}. |
| |
| @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}}. |
| |
| @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} |
| 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. |
| |
| @kindex target sim |
| @item target sim |
| Builtin CPU simulator. @value{GDBN} includes simulators for most architectures. |
| In general, |
| @example |
| target sim |
| load |
| run |
| @end example |
| @noindent |
| works; however, you cannot assume that a specific memory map, device |
| drivers, or even basic I/O is available, although some simulators do |
| provide these. For info about any processor-specific simulator details, |
| see the appropriate section in @ref{Embedded Processors, ,Embedded |
| Processors}. |
| |
| @end table |
| |
| Some configurations may include these targets as well: |
| |
| @table @code |
| |
| @kindex target nrom |
| @item target nrom @var{dev} |
| NetROM ROM emulator. This target only supports downloading. |
| |
| @end table |
| |
| Different targets are available on different configurations of @value{GDBN}; |
| your configuration may have more or fewer targets. |
| |
| 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} |
| 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{}}'' |
| |
| 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. |
| |
| @code{load} does not repeat if you press @key{RET} again after using it. |
| @end table |
| |
| @node Byte Order |
| @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 |
| @value{GDBN}'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 |
| @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. |
| |
| @menu |
| * Remote Serial:: @value{GDBN} remote serial protocol |
| @end menu |
| |
| @node Remote Serial |
| @subsection The @value{GDBN} remote serial protocol |
| |
| @cindex remote serial debugging, overview |
| To debug a program running on another machine (the debugging |
| @dfn{target} machine), you must first arrange for all the usual |
| prerequisites for the program to run by itself. For example, for a C |
| program, you need: |
| |
| @enumerate |
| @item |
| A startup routine to set up the C runtime environment; these usually |
| have a name like @file{crt0}. The startup routine may be supplied by |
| your hardware supplier, or you may have to write your own. |
| |
| @item |
| A C subroutine library to support your program's |
| subroutine calls, notably managing input and output. |
| |
| @item |
| A way of getting your program to the other machine---for example, a |
| download program. These are often supplied by the hardware |
| manufacturer, but you may have to write your own from hardware |
| documentation. |
| @end enumerate |
| |
| The next step is to arrange for your program to use a serial port to |
| communicate with the machine where @value{GDBN} is running (the @dfn{host} |
| machine). In general terms, the scheme looks like this: |
| |
| @table @emph |
| @item On the host, |
| @value{GDBN} already understands how to use this protocol; when everything |
| else is set up, you can simply use the @samp{target remote} command |
| (@pxref{Targets,,Specifying a Debugging Target}). |
| |
| @item On the target, |
| you must link with your program a few special-purpose subroutines that |
| implement the @value{GDBN} remote serial protocol. The file containing these |
| subroutines is called a @dfn{debugging stub}. |
| |
| On certain remote targets, you can use an auxiliary program |
| @code{gdbserver} instead of linking a stub into your program. |
| @xref{Server,,Using the @code{gdbserver} program}, for details. |
| @end table |
| |
| The debugging stub is specific to the architecture of the remote |
| machine; for example, use @file{sparc-stub.c} to debug programs on |
| @sc{sparc} boards. |
| |
| @cindex remote serial stub list |
| These working remote stubs are distributed with @value{GDBN}: |
| |
| @table @code |
| |
| @item i386-stub.c |
| @kindex i386-stub.c |
| @cindex Intel |
| @cindex i386 |
| For Intel 386 and compatible architectures. |
| |
| @item m68k-stub.c |
| @kindex m68k-stub.c |
| @cindex Motorola 680x0 |
| @cindex m680x0 |
| For Motorola 680x0 architectures. |
| |
| @item sh-stub.c |
| @kindex sh-stub.c |
| @cindex Hitachi |
| @cindex SH |
| For Hitachi SH architectures. |
| |
| @item sparc-stub.c |
| @kindex sparc-stub.c |
| @cindex Sparc |
| For @sc{sparc} architectures. |
| |
| @item sparcl-stub.c |
| @kindex sparcl-stub.c |
| @cindex Fujitsu |
| @cindex SparcLite |
| For Fujitsu @sc{sparclite} architectures. |
| |
| @end table |
| |
| The @file{README} file in the @value{GDBN} distribution may list other |
| recently added stubs. |
| |
| @menu |
| * Stub Contents:: What the stub can do for you |
| * Bootstrapping:: What you must do for the stub |
| * Debug Session:: Putting it all together |
| * Protocol:: Definition of the communication protocol |
| * Server:: Using the `gdbserver' program |
| * NetWare:: Using the `gdbserve.nlm' program |
| @end menu |
| |
| @node Stub Contents |
| @subsubsection What the stub can do for you |
| |
| @cindex remote serial stub |
| The debugging stub for your architecture supplies these three |
| subroutines: |
| |
| @table @code |
| @item set_debug_traps |
| @kindex set_debug_traps |
| @cindex remote serial stub, initialization |
| This routine arranges for @code{handle_exception} to run when your |
| program stops. You must call this subroutine explicitly near the |
| beginning of your program. |
| |
| @item handle_exception |
| @kindex handle_exception |
| @cindex remote serial stub, main routine |
| This is the central workhorse, but your program never calls it |
| explicitly---the setup code arranges for @code{handle_exception} to |
| run when a trap is triggered. |
| |
| @code{handle_exception} takes control when your program stops during |
| execution (for example, on a breakpoint), and mediates communications |
| with @value{GDBN} on the host machine. This is where the communications |
| protocol is implemented; @code{handle_exception} acts as the @value{GDBN} |
| representative on the target machine. It begins by sending summary |
| information on the state of your program, then continues to execute, |
| retrieving and transmitting any information @value{GDBN} needs, until you |
| execute a @value{GDBN} command that makes your program resume; at that point, |
| @code{handle_exception} returns control to your own code on the target |
| machine. |
| |
| @item breakpoint |
| @cindex @code{breakpoint} subroutine, remote |
| Use this auxiliary subroutine to make your program contain a |
| breakpoint. Depending on the particular situation, this may be the only |
| way for @value{GDBN} to get control. For instance, if your target |
| machine has some sort of interrupt button, you won't need to call this; |
| pressing the interrupt button transfers control to |
| @code{handle_exception}---in effect, to @value{GDBN}. On some machines, |
| simply receiving characters on the serial port may also trigger a trap; |
| again, in that situation, you don't need to call @code{breakpoint} from |
| your own program---simply running @samp{target remote} from the host |
| @value{GDBN} session gets control. |
| |
| Call @code{breakpoint} if none of these is true, or if you simply want |
| to make certain your program stops at a predetermined point for the |
| start of your debugging session. |
| @end table |
| |
| @node Bootstrapping |
| @subsubsection What you must do for the stub |
| |
| @cindex remote stub, support routines |
| The debugging stubs that come with @value{GDBN} are set up for a particular |
| chip architecture, but they have no information about the rest of your |
| debugging target machine. |
| |
| First of all you need to tell the stub how to communicate with the |
| serial port. |
| |
| @table @code |
| @item int getDebugChar() |
| @kindex getDebugChar |
| Write this subroutine to read a single character from the serial port. |
| It may be identical to @code{getchar} for your target system; a |
| different name is used to allow you to distinguish the two if you wish. |
| |
| @item void putDebugChar(int) |
| @kindex putDebugChar |
| Write this subroutine to write a single character to the serial port. |
| It may be identical to @code{putchar} for your target system; a |
| different name is used to allow you to distinguish the two if you wish. |
| @end table |
| |
| @cindex control C, and remote debugging |
| @cindex interrupting remote targets |
| If you want @value{GDBN} to be able to stop your program while it is |
| running, you need to use an interrupt-driven serial driver, and arrange |
| for it to stop when it receives a @code{^C} (@samp{\003}, the control-C |
| character). That is the character which @value{GDBN} uses to tell the |
| remote system to stop. |
| |
| Getting the debugging target to return the proper status to @value{GDBN} |
| probably requires changes to the standard stub; one quick and dirty way |
| is to just execute a breakpoint instruction (the ``dirty'' part is that |
| @value{GDBN} reports a @code{SIGTRAP} instead of a @code{SIGINT}). |
| |
| Other routines you need to supply are: |
| |
| @table @code |
| @item void exceptionHandler (int @var{exception_number}, void *@var{exception_address}) |
| @kindex exceptionHandler |
| Write this function to install @var{exception_address} in the exception |
| handling tables. You need to do this because the stub does not have any |
| way of knowing what the exception handling tables on your target system |
| are like (for example, the processor's table might be in @sc{rom}, |
| containing entries which point to a table in @sc{ram}). |
| @var{exception_number} is the exception number which should be changed; |
| its meaning is architecture-dependent (for example, different numbers |
| might represent divide by zero, misaligned access, etc). When this |
| exception occurs, control should be transferred directly to |
| @var{exception_address}, and the processor state (stack, registers, |
| and so on) should be just as it is when a processor exception occurs. So if |
| you want to use a jump instruction to reach @var{exception_address}, it |
| should be a simple jump, not a jump to subroutine. |
| |
| For the 386, @var{exception_address} should be installed as an interrupt |
| gate so that interrupts are masked while the handler runs. The gate |
| should be at privilege level 0 (the most privileged level). The |
| @sc{sparc} and 68k stubs are able to mask interrupts themselves without |
| help from @code{exceptionHandler}. |
| |
| @item void flush_i_cache() |
| @kindex flush_i_cache |
| On @sc{sparc} and @sc{sparclite} only, write this subroutine to flush the |
| instruction cache, if any, on your target machine. If there is no |
| instruction cache, this subroutine may be a no-op. |
| |
| On target machines that have instruction caches, @value{GDBN} requires this |
| function to make certain that the state of your program is stable. |
| @end table |
| |
| @noindent |
| You must also make sure this library routine is available: |
| |
| @table @code |
| @item void *memset(void *, int, int) |
| @kindex memset |
| This is the standard library function @code{memset} that sets an area of |
| memory to a known value. If you have one of the free versions of |
| @code{libc.a}, @code{memset} can be found there; otherwise, you must |
| either obtain it from your hardware manufacturer, or write your own. |
| @end table |
| |
| If you do not use the GNU C compiler, you may need other standard |
| library subroutines as well; this varies from one stub to another, |
| but in general the stubs are likely to use any of the common library |
| subroutines which @code{@value{GCC}} generates as inline code. |
| |
| |
| @node Debug Session |
| @subsubsection Putting it all together |
| |
| @cindex remote serial debugging summary |
| In summary, when your program is ready to debug, you must follow these |
| steps. |
| |
| @enumerate |
| @item |
| Make sure you have the supporting low-level routines |
| (@pxref{Bootstrapping,,What you must do for the stub}): |
| @display |
| @code{getDebugChar}, @code{putDebugChar}, |
| @code{flush_i_cache}, @code{memset}, @code{exceptionHandler}. |
| @end display |
| |
| @item |
| Insert these lines near the top of your program: |
| |
| @example |
| set_debug_traps(); |
| breakpoint(); |
| @end example |
| |
| @item |
| For the 680x0 stub only, you need to provide a variable called |
| @code{exceptionHook}. Normally you just use: |
| |
| @example |
| void (*exceptionHook)() = 0; |
| @end example |
| |
| @noindent |
| but if before calling @code{set_debug_traps}, you set it to point to a |
| function in your program; that function is called when |
| @code{@value{GDBN}} continues after stopping on a trap (for example, bus |
| error). The function indicated by @code{exceptionHook} is called with |
| one parameter: an @code{int} which is the exception number. |
| |
| @item |
| Compile and link together: your program, the @value{GDBN} debugging stub for |
| your target architecture, and the supporting subroutines. |
| |
| @item |
| Make sure you have a serial connection between your target machine and |
| the @value{GDBN} host, and identify the serial port on the host. |
| |
| @item |
| @c The "remote" target now provides a `load' command, so we should |
| @c document that. FIXME. |
| Download your program to your target machine (or get it there by |
| whatever means the manufacturer provides), and start it. |
| |
| @item |
| To start remote debugging, run @value{GDBN} on the host machine, and specify |
| as an executable file the program that is running in the remote machine. |
| This tells @value{GDBN} how to find your program's symbols and the contents |
| of its pure text. |
| |
| @item |
| @cindex serial line, @code{target remote} |
| Establish communication using the @code{target remote} command. |
| Its argument specifies how to communicate with the target |
| machine---either via a devicename attached to a direct serial line, or a |
| TCP port (usually to a terminal server which in turn has a serial line |
| to the target). For example, to use a serial line connected to the |
| device named @file{/dev/ttyb}: |
| |
| @example |
| target remote /dev/ttyb |
| @end example |
| |
| @cindex TCP port, @code{target remote} |
| To use a TCP connection, use an argument of the form |
| @code{@var{host}:port}. For example, to connect to port 2828 on a |
| terminal server named @code{manyfarms}: |
| |
| @example |
| target remote manyfarms:2828 |
| @end example |
| @end enumerate |
| |
| Now you can use all the usual commands to examine and change data and to |
| step and continue the remote program. |
| |
| To resume the remote program and stop debugging it, use the @code{detach} |
| command. |
| |
| @cindex interrupting remote programs |
| @cindex remote programs, interrupting |
| Whenever @value{GDBN} is waiting for the remote program, if you type the |
| interrupt character (often @key{C-C}), @value{GDBN} attempts to stop the |
| program. This may or may not succeed, depending in part on the hardware |
| and the serial drivers the remote system uses. If you type the |
| interrupt character once again, @value{GDBN} displays this prompt: |
| |
| @example |
| Interrupted while waiting for the program. |
| Give up (and stop debugging it)? (y or n) |
| @end example |
| |
| If you type @kbd{y}, @value{GDBN} abandons the remote debugging session. |
| (If you decide you want to try again later, you can use @samp{target |
| remote} again to connect once more.) If you type @kbd{n}, @value{GDBN} |
| goes back to waiting. |
| |
| @node Protocol |
| @subsubsection Communication protocol |
| |
| @cindex debugging stub, example |
| @cindex remote stub, example |
| @cindex stub example, remote debugging |
| The stub files provided with @value{GDBN} implement the target side of the |
| communication protocol, and the @value{GDBN} side is implemented in the |
| @value{GDBN} source file @file{remote.c}. Normally, you can simply allow |
| these subroutines to communicate, and ignore the details. (If you're |
| implementing your own stub file, you can still ignore the details: start |
| with one of the existing stub files. @file{sparc-stub.c} is the best |
| organized, and therefore the easiest to read.) |
| |
| However, there may be occasions when you need to know something about |
| the protocol---for example, if there is only one serial port to your |
| target machine, you might want your program to do something special if |
| it recognizes a packet meant for @value{GDBN}. |
| |
| In the examples below, @samp{<-} and @samp{->} are used to indicate |
| transmitted and received data respectfully. |
| |
| @cindex protocol, @value{GDBN} remote serial |
| @cindex serial protocol, @value{GDBN} remote |
| @cindex remote serial protocol |
| All @value{GDBN} commands and responses (other than acknowledgments) |
| are sent as a @var{packet}. A @var{packet} is introduced with the |
| character @samp{$}, this is followed by an optional two-digit |
| @var{sequence-id} and the character @samp{:}, the actual |
| @var{packet-data}, and the terminating character @samp{#} followed by a |
| two-digit @var{checksum}: |
| |
| @example |
| @code{$}@var{packet-data}@code{#}@var{checksum} |
| @end example |
| @noindent |
| or, with the optional @var{sequence-id}: |
| @example |
| @code{$}@var{sequence-id}@code{:}@var{packet-data}@code{#}@var{checksum} |
| @end example |
| |
| @cindex checksum, for @value{GDBN} remote |
| @noindent |
| The two-digit @var{checksum} is computed as the modulo 256 sum of all |
| characters between the leading @samp{$} and the trailing @samp{#} (that |
| consisting of both the optional @var{sequence-id}@code{:} and the actual |
| @var{packet-data}) (an eight bit unsigned checksum). |
| |
| @cindex sequence-id, for @value{GDBN} remote |
| @noindent |
| The two-digit @var{sequence-id}, when present, is returned with the |
| acknowledgment. Beyond that its meaning is poorly defined. |
| @value{GDBN} is not known to output @var{sequence-id}s. |
| |
| When either the host or the target machine receives a packet, the first |
| response expected is an acknowledgment: either @samp{+} (to indicate |
| the package was received correctly) or @samp{-} (to request |
| retransmission): |
| |
| @example |
| <- @code{$}@var{packet-data}@code{#}@var{checksum} |
| -> @code{+} |
| @end example |
| @noindent |
| If the received packet included a @var{sequence-id} than that is |
| appended to a positive acknowledgment: |
| |
| @example |
| <- @code{$}@var{sequence-id}@code{:}@var{packet-data}@code{#}@var{checksum} |
| -> @code{+}@var{sequence-id} |
| @end example |
| |
| The host (@value{GDBN}) sends @var{command}s, and the target (the |
| debugging stub incorporated in your program) sends a @var{response}. In |
| the case of step and continue @var{command}s, the response is only sent |
| when the operation has completed (the target has again stopped). |
| |
| @var{packet-data} consists of a sequence of characters with the |
| exception of @samp{#} and @samp{$} (see @samp{X} packet for an |
| exception). @samp{:} can not appear as the third character in a packet. |
| Fields within the packet should be separated using @samp{,} and @samp{;} |
| (unfortunately some packets chose to use @samp{:}). Except where |
| otherwise noted all numbers are represented in HEX with leading zeros |
| suppressed. |
| |
| Response @var{data} can be run-length encoded to save space. A @samp{*} |
| means that the next character is an @sc{ascii} encoding giving a repeat count |
| which stands for that many repetitions of the character preceding the |
| @samp{*}. The encoding is @code{n+29}, yielding a printable character |
| where @code{n >=3} (which is where rle starts to win). The printable |
| characters @samp{$}, @samp{#}, @samp{+} and @samp{-} or with a numeric |
| value greater than 126 should not be used. |
| |
| Some remote systems have used a different run-length encoding mechanism |
| loosely refered to as the cisco encoding. Following the @samp{*} |
| character are two hex digits that indicate the size of the packet. |
| |
| So: |
| @example |
| "@code{0* }" |
| @end example |
| @noindent |
| means the same as "0000". |
| |
| The error response, returned for some packets includes a two character |
| error number. That number is not well defined. |
| |
| For any @var{command} not supported by the stub, an empty response |
| (@samp{$#00}) should be returned. That way it is possible to extend the |
| protocol. A newer @value{GDBN} can tell if a packet is supported based |
| on that response. |
| |
| Below is a complete list of all currently defined @var{command}s and |
| their corresponding response @var{data}: |
| |
| @multitable @columnfractions .30 .30 .40 |
| @item Packet |
| @tab Request |
| @tab Description |
| |
| @item extended ops @emph{(optional)} |
| @tab @code{!} |
| @tab |
| Use the extended remote protocol. Sticky---only needs to be set once. |
| The extended remote protocol support the @samp{R} packet. |
| @item |
| @tab reply @samp{} |
| @tab |
| Stubs that support the extended remote protocol return @samp{} which, |
| unfortunately, is identical to the response returned by stubs that do not |
| support protocol extensions. |
| |
| @item last signal |
| @tab @code{?} |
| @tab |
| Indicate the reason the target halted. The reply is the same as for step |
| and continue. |
| @item |
| @tab reply |
| @tab see below |
| |
| |
| @item reserved |
| @tab @code{a} |
| @tab Reserved for future use |
| |
| @item set program arguments @strong{(reserved)} @emph{(optional)} |
| @tab @code{A}@var{arglen}@code{,}@var{argnum}@code{,}@var{arg}@code{,...} |
| @tab |
| Initialized @samp{argv[]} array passed into program. @var{arglen} |
| specifies the number of bytes in the hex encoded byte stream @var{arg}. |
| See @file{gdbserver} for more details. |
| @item |
| @tab reply @code{OK} |
| @item |
| @tab reply @code{E}@var{NN} |
| |
| @item set baud @strong{(deprecated)} |
| @tab @code{b}@var{baud} |
| @tab |
| Change the serial line speed to @var{baud}. JTC: @emph{When does the |
| transport layer state change? When it's received, or after the ACK is |
| transmitted. In either case, there are problems if the command or the |
| acknowledgment packet is dropped.} Stan: @emph{If people really wanted |
| to add something like this, and get it working for the first time, they |
| ought to modify ser-unix.c to send some kind of out-of-band message to a |
| specially-setup stub and have the switch happen "in between" packets, so |
| that from remote protocol's point of view, nothing actually |
| happened.} |
| |
| @item set breakpoint @strong{(deprecated)} |
| @tab @code{B}@var{addr},@var{mode} |
| @tab |
| Set (@var{mode} is @samp{S}) or clear (@var{mode} is @samp{C}) a |
| breakpoint at @var{addr}. @emph{This has been replaced by the @samp{Z} and |
| @samp{z} packets.} |
| |
| @item continue |
| @tab @code{c}@var{addr} |
| @tab |
| @var{addr} is address to resume. If @var{addr} is omitted, resume at |
| current address. |
| @item |
| @tab reply |
| @tab see below |
| |
| @item continue with signal @emph{(optional)} |
| @tab @code{C}@var{sig}@code{;}@var{addr} |
| @tab |
| Continue with signal @var{sig} (hex signal number). If |
| @code{;}@var{addr} is omitted, resume at same address. |
| @item |
| @tab reply |
| @tab see below |
| |
| @item toggle debug @emph{(deprecated)} |
| @tab @code{d} |
| @tab |
| toggle debug flag. |
| |
| @item detach @emph{(optional)} |
| @tab @code{D} |
| @tab |
| Detach @value{GDBN} from the remote system. Sent to the remote target before |
| @value{GDBN} disconnects. |
| @item |
| @tab reply @emph{no response} |
| @tab |
| @value{GDBN} does not check for any response after sending this packet |
| |
| @item reserved |
| @tab @code{e} |
| @tab Reserved for future use |
| |
| @item reserved |
| @tab @code{E} |
| @tab Reserved for future use |
| |
| @item reserved |
| @tab @code{f} |
| @tab Reserved for future use |
| |
| @item reserved |
| @tab @code{F} |
| @tab Reserved for future use |
| |
| @item read registers |
| @tab @code{g} |
| @tab Read general registers. |
| @item |
| @tab reply @var{XX...} |
| @tab |
| Each byte of register data is described by two hex digits. The bytes |
| with the register are transmitted in target byte order. The size of |
| each register and their position within the @samp{g} @var{packet} are |
| determined by the @value{GDBN} internal macros @var{REGISTER_RAW_SIZE} and |
| @var{REGISTER_NAME} macros. The specification of several standard |
| @code{g} packets is specified below. |
| @item |
| @tab @code{E}@var{NN} |
| @tab for an error. |
| |
| @item write regs |
| @tab @code{G}@var{XX...} |
| @tab |
| See @samp{g} for a description of the @var{XX...} data. |
| @item |
| @tab reply @code{OK} |
| @tab for success |
| @item |
| @tab reply @code{E}@var{NN} |
| @tab for an error |
| |
| @item reserved |
| @tab @code{h} |
| @tab Reserved for future use |
| |
| @item set thread @emph{(optional)} |
| @tab @code{H}@var{c}@var{t...} |
| @tab |
| Set thread for subsequent operations (@samp{m}, @samp{M}, @samp{g}, |
| @samp{G}, et.al.). @var{c} = @samp{c} for thread used in step and |
| continue; @var{t...} can be -1 for all threads. @var{c} = @samp{g} for |
| thread used in other operations. If zero, pick a thread, any thread. |
| @item |
| @tab reply @code{OK} |
| @tab for success |
| @item |
| @tab reply @code{E}@var{NN} |
| @tab for an error |
| |
| @c FIXME: JTC: |
| @c 'H': How restrictive (or permissive) is the thread model. If a |
| @c thread is selected and stopped, are other threads allowed |
| @c to continue to execute? As I mentioned above, I think the |
| @c semantics of each command when a thread is selected must be |
| @c described. For example: |
| @c |
| @c 'g': If the stub supports threads and a specific thread is |
| @c selected, returns the register block from that thread; |
| @c otherwise returns current registers. |
| @c |
| @c 'G' If the stub supports threads and a specific thread is |
| @c selected, sets the registers of the register block of |
| @c that thread; otherwise sets current registers. |
| |
| @item cycle step @strong{(draft)} @emph{(optional)} |
| @tab @code{i}@var{addr}@code{,}@var{nnn} |
| @tab |
| Step the remote target by a single clock cycle. If @code{,}@var{nnn} is |
| present, cycle step @var{nnn} cycles. If @var{addr} is present, cycle |
| step starting at that address. |
| |
| @item signal then cycle step @strong{(reserved)} @emph{(optional)} |
| @tab @code{I} |
| @tab |
| See @samp{i} and @samp{S} for likely syntax and semantics. |
| |
| @item reserved |
| @tab @code{j} |
| @tab Reserved for future use |
| |
| @item reserved |
| @tab @code{J} |
| @tab Reserved for future use |
| |
| @item kill request @emph{(optional)} |
| @tab @code{k} |
| @tab |
| FIXME: @emph{There is no description of how operate when a specific |
| thread context has been selected (ie. does 'k' kill only that thread?)}. |
| |
| @item reserved |
| @tab @code{l} |
| @tab Reserved for future use |
| |
| @item reserved |
| @tab @code{L} |
| @tab Reserved for future use |
| |
| @item read memory |
| @tab @code{m}@var{addr}@code{,}@var{length} |
| @tab |
| Read @var{length} bytes of memory starting at address @var{addr}. |
| Neither @value{GDBN} nor the stub assume that sized memory transfers are assumed |
| using word alligned accesses. FIXME: @emph{A word aligned memory |
| transfer mechanism is needed.} |
| @item |
| @tab reply @var{XX...} |
| @tab |
| @var{XX...} is mem contents. Can be fewer bytes than requested if able |
| to read only part of the data. Neither @value{GDBN} nor the stub assume that |
| sized memory transfers are assumed using word alligned accesses. FIXME: |
| @emph{A word aligned memory transfer mechanism is needed.} |
| @item |
| @tab reply @code{E}@var{NN} |
| @tab @var{NN} is errno |
| |
| @item write mem |
| @tab @code{M}@var{addr},@var{length}@code{:}@var{XX...} |
| @tab |
| Write @var{length} bytes of memory starting at address @var{addr}. |
| @var{XX...} is the data. |
| @item |
| @tab reply @code{OK} |
| @tab for success |
| @item |
| @tab reply @code{E}@var{NN} |
| @tab |
| for an error (this includes the case where only part of the data was |
| written). |
| |
| @item reserved |
| @tab @code{n} |
| @tab Reserved for future use |
| |
| @item reserved |
| @tab @code{N} |
| @tab Reserved for future use |
| |
| @item reserved |
| @tab @code{o} |
| @tab Reserved for future use |
| |
| @item reserved |
| @tab @code{O} |
| @tab Reserved for future use |
| |
| @item read reg @strong{(reserved)} |
| @tab @code{p}@var{n...} |
| @tab |
| See write register. |
| @item |
| @tab return @var{r....} |
| @tab The hex encoded value of the register in target byte order. |
| |
| @item write reg @emph{(optional)} |
| @tab @code{P}@var{n...}@code{=}@var{r...} |
| @tab |
| Write register @var{n...} with value @var{r...}, which contains two hex |
| digits for each byte in the register (target byte order). |
| @item |
| @tab reply @code{OK} |
| @tab for success |
| @item |
| @tab reply @code{E}@var{NN} |
| @tab for an error |
| |
| @item general query @emph{(optional)} |
| @tab @code{q}@var{query} |
| @tab |
| Request info about @var{query}. In general @value{GDBN} @var{query}'s |
| have a leading upper case letter. Custom vendor queries should use a |
| company prefix (in lower case) ex: @samp{qfsf.var}. @var{query} may |
| optionally be followed by a @samp{,} or @samp{;} separated list. Stubs |
| must ensure that they match the full @var{query} name. |
| @item |
| @tab reply @code{XX...} |
| @tab Hex encoded data from query. The reply can not be empty. |
| @item |
| @tab reply @code{E}@var{NN} |
| @tab error reply |
| @item |
| @tab reply @samp{} |
| @tab Indicating an unrecognized @var{query}. |
| |
| @item general set @emph{(optional)} |
| @tab @code{Q}@var{var}@code{=}@var{val} |
| @tab |
| Set value of @var{var} to @var{val}. See @samp{q} for a discussing of |
| naming conventions. |
| |
| @item reset @emph{(deprecated)} |
| @tab @code{r} |
| @tab |
| Reset the entire system. |
| |
| @item remote restart @emph{(optional)} |
| @tab @code{R}@var{XX} |
| @tab |
| Restart the remote server. @var{XX} while needed has no clear |
| definition. FIXME: @emph{An example interaction explaining how this |
| packet is used in extended-remote mode is needed}. |
| |
| @item step @emph{(optional)} |
| @tab @code{s}@var{addr} |
| @tab |
| @var{addr} is address to resume. If @var{addr} is omitted, resume at |
| same address. |
| @item |
| @tab reply |
| @tab see below |
| |
| @item step with signal @emph{(optional)} |
| @tab @code{S}@var{sig}@code{;}@var{addr} |
| @tab |
| Like @samp{C} but step not continue. |
| @item |
| @tab reply |
| @tab see below |
| |
| @item search @emph{(optional)} |
| @tab @code{t}@var{addr}@code{:}@var{PP}@code{,}@var{MM} |
| @tab |
| Search backwards starting at address @var{addr} for a match with pattern |
| @var{PP} and mask @var{MM}. @var{PP} and @var{MM} are 4 |
| bytes. @var{addr} must be at least 3 digits. |
| |
| @item thread alive @emph{(optional)} |
| @tab @code{T}@var{XX} |
| @tab Find out if the thread XX is alive. |
| @item |
| @tab reply @code{OK} |
| @tab thread is still alive |
| @item |
| @tab reply @code{E}@var{NN} |
| @tab thread is dead |
| |
| @item reserved |
| @tab @code{u} |
| @tab Reserved for future use |
| |
| @item reserved |
| @tab @code{U} |
| @tab Reserved for future use |
| |
| @item reserved |
| @tab @code{v} |
| @tab Reserved for future use |
| |
| @item reserved |
| @tab @code{V} |
| @tab Reserved for future use |
| |
| @item reserved |
| @tab @code{w} |
| @tab Reserved for future use |
| |
| @item reserved |
| @tab @code{W} |
| @tab Reserved for future use |
| |
| @item reserved |
| @tab @code{x} |
| @tab Reserved for future use |
| |
| @item write mem (binary) @emph{(optional)} |
| @tab @code{X}@var{addr}@code{,}@var{length}@var{:}@var{XX...} |
| @tab |
| @var{addr} is address, @var{length} is number of bytes, @var{XX...} is |
| binary data. The characters @code{$}, @code{#}, and @code{0x7d} are |
| escaped using @code{0x7d}. |
| @item |
| @tab reply @code{OK} |
| @tab for success |
| @item |
| @tab reply @code{E}@var{NN} |
| @tab for an error |
| |
| @item reserved |
| @tab @code{y} |
| @tab Reserved for future use |
| |
| @item reserved |
| @tab @code{Y} |
| @tab Reserved for future use |
| |
| @item remove break or watchpoint @strong{(draft)} @emph{(optional)} |
| @tab @code{z}@var{t}@code{,}@var{addr}@code{,}@var{length} |
| @tab |
| See @samp{Z}. |
| |
| @item insert break or watchpoint @strong{(draft)} @emph{(optional)} |
| @tab @code{Z}@var{t}@code{,}@var{addr}@code{,}@var{length} |
| @tab |
| @var{t} is type: @samp{0} - software breakpoint, @samp{1} - hardware |
| breakpoint, @samp{2} - write watchpoint, @samp{3} - read watchpoint, |
| @samp{4} - access watchpoint; @var{addr} is address; @var{length} is in |
| bytes. For a software breakpoint, @var{length} specifies the size of |
| the instruction to be patched. For hardware breakpoints and watchpoints |
| @var{length} specifies the memory region to be monitored. To avoid |
| potential problems with duplicate packets, the operations should be |
| implemented in an ident-potentent way. |
| @item |
| @tab reply @code{E}@var{NN} |
| @tab for an error |
| @item |
| @tab reply @code{OK} |
| @tab for success |
| @item |
| @tab @samp{} |
| @tab If not supported. |
| |
| @item reserved |
| @tab <other> |
| @tab Reserved for future use |
| |
| @end multitable |
| |
| The @samp{C}, @samp{c}, @samp{S}, @samp{s} and @samp{?} packets can |
| receive any of the below as a reply. In the case of the @samp{C}, |
| @samp{c}, @samp{S} and @samp{s} packets, that reply is only returned |
| when the target halts. In the below the exact meaning of @samp{signal |
| number} is poorly defined. In general one of the UNIX signal numbering |
| conventions is used. |
| |
| @multitable @columnfractions .4 .6 |
| |
| @item @code{S}@var{AA} |
| @tab @var{AA} is the signal number |
| |
| @item @code{T}@var{AA}@var{n...}@code{:}@var{r...}@code{;}@var{n...}@code{:}@var{r...}@code{;}@var{n...}@code{:}@var{r...}@code{;} |
| @tab |
| @var{AA} = two hex digit signal number; @var{n...} = register number |
| (hex), @var{r...} = target byte ordered register contents, size defined |
| by @code{REGISTER_RAW_SIZE}; @var{n...} = @samp{thread}, @var{r...} = |
| thread process ID, this is a hex integer; @var{n...} = other string not |
| starting with valid hex digit. @value{GDBN} should ignore this |
| @var{n...}, @var{r...} pair and go on to the next. This way we can |
| extend the protocol. |
| |
| @item @code{W}@var{AA} |
| @tab |
| The process exited, and @var{AA} is the exit status. This is only |
| applicable for certains sorts of targets. |
| |
| @item @code{X}@var{AA} |
| @tab |
| The process terminated with signal @var{AA}. |
| |
| @item @code{N}@var{AA}@code{;}@var{tttttttt}@code{;}@var{dddddddd}@code{;}@var{bbbbbbbb} @strong{(obsolete)} |
| @tab |
| @var{AA} = signal number; @var{tttttttt} = address of symbol "_start"; |
| @var{dddddddd} = base of data section; @var{bbbbbbbb} = base of bss |
| section. @emph{Note: only used by Cisco Systems targets. The difference |
| between this reply and the "qOffsets" query is that the 'N' packet may |
| arrive spontaneously whereas the 'qOffsets' is a query initiated by the |
| host debugger.} |
| |
| @item @code{O}@var{XX...} |
| @tab |
| @var{XX...} is hex encoding of @sc{ascii} data. This can happen at any time |
| while the program is running and the debugger should continue to wait |
| for 'W', 'T', etc. |
| |
| @end multitable |
| |
| The following set and query packets have already been defined. |
| |
| @multitable @columnfractions .2 .2 .6 |
| |
| @item current thread |
| @tab @code{q}@code{C} |
| @tab Return the current thread id. |
| @item |
| @tab reply @code{QC}@var{pid} |
| @tab |
| Where @var{pid} is a HEX encoded 16 bit process id. |
| @item |
| @tab reply * |
| @tab Any other reply implies the old pid. |
| |
| @item compute CRC of memory block |
| @tab @code{q}@code{CRC:}@var{addr}@code{,}@var{length} |
| @tab |
| @item |
| @tab reply @code{E}@var{NN} |
| @tab An error (such as memory fault) |
| @item |
| @tab reply @code{C}@var{CRC32} |
| @tab A 32 bit cyclic redundancy check of the specified memory region. |
| |
| @item query @var{LIST} or @var{threadLIST} @strong{(deprecated)} |
| @tab @code{q}@code{L}@var{startflag}@var{threadcount}@var{nextthread} |
| @tab |
| Obtain thread information from RTOS. Where: @var{startflag} (one hex |
| digit) is one to indicate the first query and zero to indicate a |
| subsequent query; @var{threadcount} (two hex digits) is the maximum |
| number of threads the response packet can contain; and @var{nextthread} |
| (eight hex digits), for subsequent queries (@var{startflag} is zero), is |
| returned in the response as @var{argthread}. |
| @item |
| @tab reply @code{q}@code{M}@var{count}@var{done}@var{argthread}@var{thread...} |
| @tab |
| Where: @var{count} (two hex digits) is the number of threads being |
| returned; @var{done} (one hex digit) is zero to indicate more threads |
| and one indicates no further threads; @var{argthreadid} (eight hex |
| digits) is @var{nextthread} from the request packet; @var{thread...} is |
| a sequence of thread IDs from the target. @var{threadid} (eight hex |
| digits). See @code{remote.c:parse_threadlist_response()}. |
| |
| @item query sect offs |
| @tab @code{q}@code{Offsets} |
| @tab |
| Get section offsets that the target used when re-locating the downloaded |
| image. @emph{Note: while a @code{Bss} offset is included in the |
| response, @value{GDBN} ignores this and instead applies the @code{Data} |
| offset to the @code{Bss} section.} |
| @item |
| @tab reply @code{Text=}@var{xxx}@code{;Data=}@var{yyy}@code{;Bss=}@var{zzz} |
| |
| @item thread info request |
| @tab @code{q}@code{P}@var{mode}@var{threadid} |
| @tab |
| Returns information on @var{threadid}. Where: @var{mode} is a hex |
| encoded 32 bit mode; @var{threadid} is a hex encoded 64 bit thread ID. |
| @item |
| @tab reply * |
| @tab |
| See @code{remote.c:remote_unpack_thread_info_response()}. |
| |
| @item remote command |
| @tab @code{q}@code{Rcmd,}@var{COMMAND} |
| @tab |
| @var{COMMAND} (hex encoded) is passed to the local interpreter for |
| execution. Invalid commands should be reported using the output string. |
| Before the final result packet, the target may also respond with a |
| number of intermediate @code{O}@var{OUTPUT} console output |
| packets. @emph{Implementors should note that providing access to a |
| stubs's interpreter may have security implications}. |
| @item |
| @tab reply @code{OK} |
| @tab |
| A command response with no output. |
| @item |
| @tab reply @var{OUTPUT} |
| @tab |
| A command response with the hex encoded output string @var{OUTPUT}. |
| @item |
| @tab reply @code{E}@var{NN} |
| @tab |
| Indicate a badly formed request. |
| |
| @item |
| @tab reply @samp{} |
| @tab |
| When @samp{q}@samp{Rcmd} is not recognized. |
| |
| @end multitable |
| |
| The following @samp{g}/@samp{G} packets have previously been defined. |
| In the below, some thirty-two bit registers are transferred as sixty-four |
| bits. Those registers should be zero/sign extended (which?) to fill the |
| space allocated. Register bytes are transfered in target byte order. |
| The two nibbles within a register byte are transfered most-significant - |
| least-significant. |
| |
| @multitable @columnfractions .5 .5 |
| |
| @item MIPS32 |
| @tab |
| All registers are transfered as thirty-two bit quantities in the order: |
| 32 general-purpose; sr; lo; hi; bad; cause; pc; 32 floating-point |
| registers; fsr; fir; fp. |
| |
| @item MIPS64 |
| @tab |
| All registers are transfered as sixty-four bit quantities (including |
| thirty-two bit registers such as @code{sr}). The ordering is the same |
| as @code{MIPS32}. |
| |
| @end multitable |
| |
| Example sequence of a target being re-started. Notice how the restart |
| does not get any direct output: |
| |
| @example |
| <- @code{R00} |
| -> @code{+} |
| @emph{target restarts} |
| <- @code{?} |
| -> @code{+} |
| -> @code{T001:1234123412341234} |
| <- @code{+} |
| @end example |
| |
| Example sequence of a target being stepped by a single instruction: |
| |
| @example |
| <- @code{G1445...} |
| -> @code{+} |
| <- @code{s} |
| -> @code{+} |
| @emph{time passes} |
| -> @code{T001:1234123412341234} |
| <- @code{+} |
| <- @code{g} |
| -> @code{+} |
| -> @code{1455...} |
| <- @code{+} |
| @end example |
| |
| @kindex set remotedebug@r{, serial protocol} |
| @kindex show remotedebug@r{, serial protocol} |
| @cindex packets, reporting on stdout |
| @cindex serial connections, debugging |
| If you have trouble with the serial connection, you can use the command |
| @code{set remotedebug}. This makes @value{GDBN} report on all packets sent |
| back and forth across the serial line to the remote machine. The |
| packet-debugging information is printed on the @value{GDBN} standard output |
| stream. @code{set remotedebug off} turns it off, and @code{show |
| remotedebug} shows you its current state. |
| |
| @node Server |
| @subsubsection Using the @code{gdbserver} program |
| |
| @kindex gdbserver |
| @cindex remote connection without stubs |
| @code{gdbserver} is a control program for Unix-like systems, which |
| allows you to connect your program with a remote @value{GDBN} via |
| @code{target remote}---but without linking in the usual debugging stub. |
| |
| @code{gdbserver} is not a complete replacement for the debugging stubs, |
| because it requires essentially the same operating-system facilities |
| that @value{GDBN} itself does. In fact, a system that can run |
| @code{gdbserver} to connect to a remote @value{GDBN} could also run |
| @value{GDBN} locally! @code{gdbserver} is sometimes useful nevertheless, |
| because it is a much smaller program than @value{GDBN} itself. It is |
| also easier to port than all of @value{GDBN}, so you may be able to get |
| started more quickly on a new system by using @code{gdbserver}. |
| Finally, if you develop code for real-time systems, you may find that |
| the tradeoffs involved in real-time operation make it more convenient to |
| do as much development work as possible on another system, for example |
| by cross-compiling. You can use @code{gdbserver} to make a similar |
| choice for debugging. |
| |
| @value{GDBN} and @code{gdbserver} communicate via either a serial line |
| or a TCP connection, using the standard @value{GDBN} remote serial |
| protocol. |
| |
| @table @emph |
| @item On the target machine, |
| you need to have a copy of the program you want to debug. |
| @code{gdbserver} does not need your program's symbol table, so you can |
| strip the program if necessary to save space. @value{GDBN} on the host |
| system does all the symbol handling. |
| |
| To use the server, you must tell it how to communicate with @value{GDBN}; |
| the name of your program; and the arguments for your program. The |
| syntax is: |
| |
| @smallexample |
| target> gdbserver @var{comm} @var{program} [ @var{args} @dots{} ] |
| @end smallexample |
| |
| @var{comm} is either a device name (to use a serial line) or a TCP |
| hostname and portnumber. For example, to debug Emacs with the argument |
| @samp{foo.txt} and communicate with @value{GDBN} over the serial port |
| @file{/dev/com1}: |
| |
| @smallexample |
| target> gdbserver /dev/com1 emacs foo.txt |
| @end smallexample |
| |
| @code{gdbserver} waits passively for the host @value{GDBN} to communicate |
| with it. |
| |
| To use a TCP connection instead of a serial line: |
| |
| @smallexample |
| target> gdbserver host:2345 emacs foo.txt |
| @end smallexample |
| |
| The only difference from the previous example is the first argument, |
| specifying that you are communicating with the host @value{GDBN} via |
| TCP. The @samp{host:2345} argument means that @code{gdbserver} is to |
| expect a TCP connection from machine @samp{host} to local TCP port 2345. |
| (Currently, the @samp{host} part is ignored.) You can choose any number |
| you want for the port number as long as it does not conflict with any |
| TCP ports already in use on the target system (for example, @code{23} is |
| reserved for @code{telnet}).@footnote{If you choose a port number that |
| conflicts with another service, @code{gdbserver} prints an error message |
| and exits.} You must use the same port number with the host @value{GDBN} |
| @code{target remote} command. |
| |
| @item On the @value{GDBN} host machine, |
| you need an unstripped copy of your program, since @value{GDBN} needs |
| symbols and debugging information. Start up @value{GDBN} as usual, |
| using the name of the local copy of your program as the first argument. |
| (You may also need the @w{@samp{--baud}} option if the serial line is |
| running at anything other than 9600@dmn{bps}.) After that, use @code{target |
| remote} to establish communications with @code{gdbserver}. Its argument |
| is either a device name (usually a serial device, like |
| @file{/dev/ttyb}), or a TCP port descriptor in the form |
| @code{@var{host}:@var{PORT}}. For example: |
| |
| @smallexample |
| (@value{GDBP}) target remote /dev/ttyb |
| @end smallexample |
| |
| @noindent |
| communicates with the server via serial line @file{/dev/ttyb}, and |
| |
| @smallexample |
| (@value{GDBP}) target remote the-target:2345 |
| @end smallexample |
| |
| @noindent |
| communicates via a TCP connection to port 2345 on host @w{@file{the-target}}. |
| For TCP connections, you must start up @code{gdbserver} prior to using |
| the @code{target remote} command. Otherwise you may get an error whose |
| text depends on the host system, but which usually looks something like |
| @samp{Connection refused}. |
| @end table |
| |
| @node NetWare |
| @subsubsection Using the @code{gdbserve.nlm} program |
| |
| @kindex gdbserve.nlm |
| @code{gdbserve.nlm} is a control program for NetWare systems, which |
| allows you to connect your program with a remote @value{GDBN} via |
| @code{target remote}. |
| |
| @value{GDBN} and @code{gdbserve.nlm} communicate via a serial line, |
| using the standard @value{GDBN} remote serial protocol. |
| |
| @table @emph |
| @item On the target machine, |
| you need to have a copy of the program you want to debug. |
| @code{gdbserve.nlm} does not need your program's symbol table, so you |
| can strip the program if necessary to save space. @value{GDBN} on the |
| host system does all the symbol handling. |
| |
| To use the server, you must tell it how to communicate with |
| @value{GDBN}; the name of your program; and the arguments for your |
| program. The syntax is: |
| |
| @smallexample |
| load gdbserve [ BOARD=@var{board} ] [ PORT=@var{port} ] |
| [ BAUD=@var{baud} ] @var{program} [ @var{args} @dots{} ] |
| @end smallexample |
| |
| @var{board} and @var{port} specify the serial line; @var{baud} specifies |
| the baud rate used by the connection. @var{port} and @var{node} default |
| to 0, @var{baud} defaults to 9600@dmn{bps}. |
| |
| For example, to debug Emacs with the argument @samp{foo.txt}and |
| communicate with @value{GDBN} over serial port number 2 or board 1 |
| using a 19200@dmn{bps} connection: |
| |
| @smallexample |
| load gdbserve BOARD=1 PORT=2 BAUD=19200 emacs foo.txt |
| @end smallexample |
| |
| @item On the @value{GDBN} host machine, |
| you need an unstripped copy of your program, since @value{GDBN} needs |
| symbols and debugging information. Start up @value{GDBN} as usual, |
| using the name of the local copy of your program as the first argument. |
| (You may also need the @w{@samp{--baud}} option if the serial line is |
| running at anything other than 9600@dmn{bps}. After that, use @code{target |
| remote} to establish communications with @code{gdbserve.nlm}. Its |
| argument is a device name (usually a serial device, like |
| @file{/dev/ttyb}). For example: |
| |
| @smallexample |
| (@value{GDBP}) target remote /dev/ttyb |
| @end smallexample |
| |
| @noindent |
| communications with the server via serial line @file{/dev/ttyb}. |
| @end table |
| |
| @node KOD |
| @section Kernel Object Display |
| |
| @cindex kernel object display |
| @cindex kernel object |
| @cindex KOD |
| |
| Some targets support kernel object display. Using this facility, |
| @value{GDBN} communicates specially with the underlying operating system |
| and can display information about operating system-level objects such as |
| mutexes and other synchronization objects. Exactly which objects can be |
| displayed is determined on a per-OS basis. |
| |
| Use the @code{set os} command to set the operating system. This tells |
| @value{GDBN} which kernel object display module to initialize: |
| |
| @example |
| (@value{GDBP}) set os cisco |
| @end example |
| |
| If @code{set os} succeeds, @value{GDBN} will display some information |
| about the operating system, and will create a new @code{info} command |
| which can be used to query the target. The @code{info} command is named |
| after the operating system: |
| |
| @example |
| (@value{GDBP}) info cisco |
| List of Cisco Kernel Objects |
| Object Description |
| any Any and all objects |
| @end example |
| |
| Further subcommands can be used to query about particular objects known |
| by the kernel. |
| |
| There is currently no way to determine whether a given operating system |
| is supported other than to try it. |
| |
| |
| @node Configurations |
| @chapter Configuration-Specific Information |
| |
| While nearly all @value{GDBN} commands are available for all native and |
| cross versions of the debugger, there are some exceptions. This chapter |
| describes things that are only available in certain configurations. |
| |
| There are three major categories of configurations: native |
| configurations, where the host and target are the same, embedded |
| operating system configurations, which are usually the same for several |
| different processor architectures, and bare embedded processors, which |
| are quite different from each other. |
| |
| @menu |
| * Native:: |
| * Embedded OS:: |
| * Embedded Processors:: |
| * Architectures:: |
| @end menu |
| |
| @node Native |
| @section Native |
| |
| This section describes details specific to particular native |
| configurations. |
| |
| @menu |
| * HP-UX:: HP-UX |
| * SVR4 Process Information:: SVR4 process information |
| @end menu |
| |
| @node HP-UX |
| @subsection HP-UX |
| |
| On HP-UX systems, 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. |
| |
| @node SVR4 Process Information |
| @subsection SVR4 process information |
| |
| @kindex /proc |
| @cindex process image |
| |
| Many versions of SVR4 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 include the |
| @code{procfs} code. This includes OSF/1 (Digital Unix), Solaris, Irix, |
| and Unixware, but not HP-UX or Linux, for example. |
| |
| @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 |
| |
| @node Embedded OS |
| @section Embedded Operating Systems |
| |
| This section describes configurations involving the debugging of |
| embedded operating systems that are available for several different |
| architectures. |
| |
| @menu |
| * VxWorks:: Using @value{GDBN} with VxWorks |
| @end menu |
| |
| @value{GDBN} includes the ability to debug programs running on |
| various real-time operating systems. |
| |
| @node VxWorks |
| @subsection Using @value{GDBN} with VxWorks |
| |
| @cindex VxWorks |
| |
| @table @code |
| |
| @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. |
| |
| @end table |
| |
| On VxWorks, @code{load} links @var{filename} dynamically on the |
| current target system as well as adding its symbols in @value{GDBN}. |
| |
| @value{GDBN} enables developers to spawn and debug tasks running on networked |
| VxWorks targets from a Unix host. Already-running tasks spawned from |
| the VxWorks shell can also be debugged. @value{GDBN} uses code that runs on |
| both the Unix host and on the VxWorks target. The program |
| @code{@value{GDBP}} is installed and executed on the Unix host. (It may be |
| installed with the name @code{vxgdb}, to distinguish it from a |
| @value{GDB} for debugging programs on the host itself.) |
| |
| @table @code |
| @item VxWorks-timeout @var{args} |
| @kindex vxworks-timeout |
| All VxWorks-based targets now support the option @code{vxworks-timeout}. |
| This option is set by the user, and @var{args} represents the number of |
| seconds @value{GDBN} waits for responses to rpc's. You might use this if |
| your VxWorks target is a slow software simulator or is on the far side |
| of a thin network line. |
| @end table |
| |
| The following information on connecting to VxWorks was current when |
| this manual was produced; newer releases of VxWorks may use revised |
| procedures. |
| |
| @kindex INCLUDE_RDB |
| To use @value{GDBN} with VxWorks, you must rebuild your VxWorks kernel |
| to include the remote debugging interface routines in the VxWorks |
| library @file{rdb.a}. To do this, define @code{INCLUDE_RDB} in the |
| VxWorks configuration file @file{configAll.h} and rebuild your VxWorks |
| kernel. The resulting kernel contains @file{rdb.a}, and spawns the |
| source debugging task @code{tRdbTask} when VxWorks is booted. For more |
| information on configuring and remaking VxWorks, see the manufacturer's |
| manual. |
| @c VxWorks, see the @cite{VxWorks Programmer's Guide}. |
| |
| Once you have included @file{rdb.a} in your VxWorks system image and set |
| your Unix execution search path to find @value{GDBN}, you are ready to |
| run @value{GDBN}. From your Unix host, run @code{@value{GDBP}} (or @code{vxgdb}, |
| depending on your installation). |
| |
| @value{GDBN} comes up showing the prompt: |
| |
| @example |
| (vxgdb) |
| @end example |
| |
| @menu |
| * VxWorks Connection:: Connecting to VxWorks |
| * VxWorks Download:: VxWorks download |
| * VxWorks Attach:: Running tasks |
| @end menu |
| |
| @node VxWorks Connection |
| @subsubsection Connecting to VxWorks |
| |
| The @value{GDBN} command @code{target} lets you connect to a VxWorks target on the |
| network. To connect to a target whose host name is ``@code{tt}'', type: |
| |
| @example |
| (vxgdb) target vxworks tt |
| @end example |
| |
| @need 750 |
| @value{GDBN} displays messages like these: |
| |
| @smallexample |
| Attaching remote machine across net... |
| Connected to tt. |
| @end smallexample |
| |
| @need 1000 |
| @value{GDBN} then attempts to read the symbol tables of any object modules |
| loaded into the VxWorks target since it was last booted. @value{GDBN} locates |
| these files by searching the directories listed in the command search |
| path (@pxref{Environment, ,Your program's environment}); if it fails |
| to find an object file, it displays a message such as: |
| |
| @example |
| prog.o: No such file or directory. |
| @end example |
| |
| When this happens, add the appropriate directory to the search path with |
| the @value{GDBN} command @code{path}, and execute the @code{target} |
| command again. |
| |
| @node VxWorks Download |
| @subsubsection VxWorks download |
| |
| @cindex download to VxWorks |
| If you have connected to the VxWorks target and you want to debug an |
| object that has not yet been loaded, you can use the @value{GDBN} |
| @code{load} command to download a file from Unix to VxWorks |
| incrementally. The object file given as an argument to the @code{load} |
| command is actually opened twice: first by the VxWorks target in order |
| to download the code, then by @value{GDBN} in order to read the symbol |
| table. This can lead to problems if the current working directories on |
| the two systems differ. If both systems have NFS mounted the same |
| filesystems, you can avoid these problems by using absolute paths. |
| Otherwise, it is simplest to set the working directory on both systems |
| to the directory in which the object file resides, and then to reference |
| the file by its name, without any path. For instance, a program |
| @file{prog.o} may reside in @file{@var{vxpath}/vw/demo/rdb} in VxWorks |
| and in @file{@var{hostpath}/vw/demo/rdb} on the host. To load this |
| program, type this on VxWorks: |
| |
| @example |
| -> cd "@var{vxpath}/vw/demo/rdb" |
| @end example |
| |
| @noindent |
| Then, in @value{GDBN}, type: |
| |
| @example |
| (vxgdb) cd @var{hostpath}/vw/demo/rdb |
| (vxgdb) load prog.o |
| @end example |
| |
| @value{GDBN} displays a response similar to this: |
| |
| @smallexample |
| Reading symbol data from wherever/vw/demo/rdb/prog.o... done. |
| @end smallexample |
| |
| You can also use the @code{load} command to reload an object module |
| after editing and recompiling the corresponding source file. Note that |
| this makes @value{GDBN} delete all currently-defined breakpoints, |
| auto-displays, and convenience variables, and to clear the value |
| history. (This is necessary in order to preserve the integrity of |
| debugger's data structures that reference the target system's symbol |
| table.) |
| |
| @node VxWorks Attach |
| @subsubsection Running tasks |
| |
| @cindex running VxWorks tasks |
| You can also attach to an existing task using the @code{attach} command as |
| follows: |
| |
| @example |
| (vxgdb) attach @var{task} |
| @end example |
| |
| @noindent |
| where @var{task} is the VxWorks hexadecimal task ID. The task can be running |
| or suspended when you attach to it. Running tasks are suspended at |
| the time of attachment. |
| |
| @node Embedded Processors |
| @section Embedded Processors |
| |
| This section goes into details specific to particular embedded |
| configurations. |
| |
| @menu |
| * A29K Embedded:: AMD A29K Embedded |
| * ARM:: ARM |
| * H8/300:: Hitachi H8/300 |
| * H8/500:: Hitachi H8/500 |
| * i960:: Intel i960 |
| * M32R/D:: Mitsubishi M32R/D |
| * M68K:: Motorola M68K |
| * M88K:: Motorola M88K |
| * MIPS Embedded:: MIPS Embedded |
| * PA:: HP PA Embedded |
| * PowerPC: PowerPC |
| * SH:: Hitachi SH |
| * Sparclet:: Tsqware Sparclet |
| * Sparclite:: Fujitsu Sparclite |
| * ST2000:: Tandem ST2000 |
| * Z8000:: Zilog Z8000 |
| @end menu |
| |
| @node A29K Embedded |
| @subsection AMD A29K Embedded |
| |
| @menu |
| * A29K UDI:: |
| * A29K EB29K:: |
| * Comms (EB29K):: Communications setup |
| * gdb-EB29K:: EB29K cross-debugging |
| * Remote Log:: Remote log |
| @end menu |
| |
| @table @code |
| |
| @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{A29K EB29K, ,EBMON protocol for AMD29K}. |
| |
| @end table |
| |
| @node A29K UDI |
| @subsubsection A29K UDI |
| |
| @cindex UDI |
| @cindex AMD29K via UDI |
| |
| @value{GDBN} supports AMD's UDI (``Universal Debugger Interface'') |
| protocol for debugging the a29k processor family. To use this |
| configuration with AMD targets running the MiniMON monitor, you need the |
| program @code{MONTIP}, available from AMD at no charge. You can also |
| use @value{GDBN} with the UDI-conformant a29k simulator program |
| @code{ISSTIP}, also available from AMD. |
| |
| @table @code |
| @item target udi @var{keyword} |
| @kindex udi |
| Select the UDI interface to a remote a29k board or simulator, where |
| @var{keyword} is an entry in the AMD configuration file @file{udi_soc}. |
| This file contains keyword entries which specify parameters used to |
| connect to a29k targets. If the @file{udi_soc} file is not in your |
| working directory, you must set the environment variable @samp{UDICONF} |
| to its pathname. |
| @end table |
| |
| @node A29K EB29K |
| @subsubsection EBMON protocol for AMD29K |
| |
| @cindex EB29K board |
| @cindex running 29K programs |
| |
| AMD distributes a 29K development board meant to fit in a PC, together |
| with a DOS-hosted monitor program called @code{EBMON}. As a shorthand |
| term, this development system is called the ``EB29K''. To use |
| @value{GDBN} from a Unix system to run programs on the EB29K board, you |
| must first connect a serial cable between the PC (which hosts the EB29K |
| board) and a serial port on the Unix system. In the following, we |
| assume you've hooked the cable between the PC's @file{COM1} port and |
| @file{/dev/ttya} on the Unix system. |
| |
| @node Comms (EB29K) |
| @subsubsection Communications setup |
| |
| The next step is to set up the PC's port, by doing something like this |
| in DOS on the PC: |
| |
| @example |
| C:\> MODE com1:9600,n,8,1,none |
| @end example |
| |
| @noindent |
| This example---run on an MS DOS 4.0 system---sets the PC port to 9600 |
| bps, no parity, eight data bits, one stop bit, and no ``retry'' action; |
| you must match the communications parameters when establishing the Unix |
| end of the connection as well. |
| @c FIXME: Who knows what this "no retry action" crud from the DOS manual may |
| @c mean? It's optional; leave it out? ---doc@cygnus.com, 25feb91 |
| @c |
| @c It's optional, but it's unwise to omit it: who knows what is the |
| @c default value set when the DOS machines boots? "No retry" means that |
| @c the DOS serial device driver won't retry the operation if it fails; |
| @c I understand that this is needed because the GDB serial protocol |
| @c handles any errors and retransmissions itself. ---Eli Zaretskii, 3sep99 |
| |
| To give control of the PC to the Unix side of the serial line, type |
| the following at the DOS console: |
| |
| @example |
| C:\> CTTY com1 |
| @end example |
| |
| @noindent |
| (Later, if you wish to return control to the DOS console, you can use |
| the command @code{CTTY con}---but you must send it over the device that |
| had control, in our example over the @file{COM1} serial line). |
| |
| From the Unix host, use a communications program such as @code{tip} or |
| @code{cu} to communicate with the PC; for example, |
| |
| @example |
| cu -s 9600 -l /dev/ttya |
| @end example |
| |
| @noindent |
| The @code{cu} options shown specify, respectively, the linespeed and the |
| serial port to use. If you use @code{tip} instead, your command line |
| may look something like the following: |
| |
| @example |
| tip -9600 /dev/ttya |
| @end example |
| |
| @noindent |
| Your system may require a different name where we show |
| @file{/dev/ttya} as the argument to @code{tip}. The communications |
| parameters, including which port to use, are associated with the |
| @code{tip} argument in the ``remote'' descriptions file---normally the |
| system table @file{/etc/remote}. |
| @c FIXME: What if anything needs doing to match the "n,8,1,none" part of |
| @c the DOS side's comms setup? cu can support -o (odd |
| @c parity), -e (even parity)---apparently no settings for no parity or |
| @c for character size. Taken from stty maybe...? John points out tip |
| @c can set these as internal variables, eg ~s parity=none; man stty |
| @c suggests that it *might* work to stty these options with stdin or |
| @c stdout redirected... ---doc@cygnus.com, 25feb91 |
| @c |
| @c There's nothing to be done for the "none" part of the DOS MODE |
| @c command. The rest of the parameters should be matched by the |
| @c baudrate, bits, and parity used by the Unix side. ---Eli Zaretskii, 3Sep99 |
| |
| @kindex EBMON |
| Using the @code{tip} or @code{cu} connection, change the DOS working |
| directory to the directory containing a copy of your 29K program, then |
| start the PC program @code{EBMON} (an EB29K control program supplied |
| with your board by AMD). You should see an initial display from |
| @code{EBMON} similar to the one that follows, ending with the |
| @code{EBMON} prompt @samp{#}--- |
| |
| @example |
| C:\> G: |
| |
| G:\> CD \usr\joe\work29k |
| |
| G:\USR\JOE\WORK29K> EBMON |
| Am29000 PC Coprocessor Board Monitor, version 3.0-18 |
| Copyright 1990 Advanced Micro Devices, Inc. |
| Written by Gibbons and Associates, Inc. |
| |
| Enter '?' or 'H' for help |
| |
| PC Coprocessor Type = EB29K |
| I/O Base = 0x208 |
| Memory Base = 0xd0000 |
| |
| Data Memory Size = 2048KB |
| Available I-RAM Range = 0x8000 to 0x1fffff |
| Available D-RAM Range = 0x80002000 to 0x801fffff |
| |
| PageSize = 0x400 |
| Register Stack Size = 0x800 |
| Memory Stack Size = 0x1800 |
| |
| CPU PRL = 0x3 |
| Am29027 Available = No |
| Byte Write Available = Yes |
| |
| # ~. |
| @end example |
| |
| Then exit the @code{cu} or @code{tip} program (done in the example by |
| typing @code{~.} at the @code{EBMON} prompt). @code{EBMON} keeps |
| running, ready for @value{GDBN} to take over. |
| |
| For this example, we've assumed what is probably the most convenient |
| way to make sure the same 29K program is on both the PC and the Unix |
| system: a PC/NFS connection that establishes ``drive @file{G:}'' on the |
| PC as a file system on the Unix host. If you do not have PC/NFS or |
| something similar connecting the two systems, you must arrange some |
| other way---perhaps floppy-disk transfer---of getting the 29K program |
| from the Unix system to the PC; @value{GDBN} does @emph{not} download it over the |
| serial line. |
| |
| @node gdb-EB29K |
| @subsubsection EB29K cross-debugging |
| |
| Finally, @code{cd} to the directory containing an image of your 29K |
| program on the Unix system, and start @value{GDBN}---specifying as argument the |
| name of your 29K program: |
| |
| @example |
| cd /usr/joe/work29k |
| @value{GDBP} myfoo |
| @end example |
| |
| @need 500 |
| Now you can use the @code{target} command: |
| |
| @example |
| target amd-eb /dev/ttya 9600 MYFOO |
| @c FIXME: test above 'target amd-eb' as spelled, with caps! caps are meant to |
| @c emphasize that this is the name as seen by DOS (since I think DOS is |
| @c single-minded about case of letters). ---doc@cygnus.com, 25feb91 |
| @end example |
| |
| @noindent |
| In this example, we've assumed your program is in a file called |
| @file{myfoo}. Note that the filename given as the last argument to |
| @code{target amd-eb} should be the name of the program as it appears to DOS. |
| In our example this is simply @code{MYFOO}, but in general it can include |
| a DOS path, and depending on your transfer mechanism may not resemble |
| the name on the Unix side. |
| |
| At this point, you can set any breakpoints you wish; when you are ready |
| to see your program run on the 29K board, use the @value{GDBN} command |
| @code{run}. |
| |
| To stop debugging the remote program, use the @value{GDBN} @code{detach} |
| command. |
| |
| To return control of the PC to its console, use @code{tip} or @code{cu} |
| once again, after your @value{GDBN} session has concluded, to attach to |
| @code{EBMON}. You can then type the command @code{q} to shut down |
| @code{EBMON}, returning control to the DOS command-line interpreter. |
| Type @kbd{CTTY con} to return command input to the main DOS console, |
| and type @kbd{~.} to leave @code{tip} or @code{cu}. |
| |
| @node Remote Log |
| @subsubsection Remote log |
| @kindex eb.log |
| @cindex log file for EB29K |
| |
| The @code{target amd-eb} command creates a file @file{eb.log} in the |
| current working directory, to help debug problems with the connection. |
| @file{eb.log} records all the output from @code{EBMON}, including echoes |
| of the commands sent to it. Running @samp{tail -f} on this file in |
| another window often helps to understand trouble with @code{EBMON}, or |
| unexpected events on the PC side of the connection. |
| |
| @node ARM |
| @subsection ARM |
| |
| @table @code |
| |
| @kindex target rdi |
| @item target rdi @var{dev} |
| ARM Angel monitor, via RDI library interface to ADP protocol. You may |
| use this target to communicate with both boards running the Angel |
| monitor, or with the EmbeddedICE JTAG debug device. |
| |
| @kindex target rdp |
| @item target rdp @var{dev} |
| ARM Demon monitor. |
| |
| @end table |
| |
| @node H8/300 |
| @subsection Hitachi H8/300 |
| |
| @table @code |
| |
| @kindex target hms@r{, with H8/300} |
| @item target hms @var{dev} |
| A Hitachi SH, H8/300, or H8/500 board, attached via serial line to your host. |
| Use special commands @code{device} and @code{speed} to control the serial |
| line and the communications speed used. |
| |
| @kindex target e7000@r{, with H8/300} |
| @item target e7000 @var{dev} |
| E7000 emulator for Hitachi H8 and SH. |
| |
| @kindex target sh3@r{, with H8/300} |
| @kindex target sh3e@r{, with H8/300} |
| @item target sh3 @var{dev} |
| @item target sh3e @var{dev} |
| Hitachi SH-3 and SH-3E target systems. |
| |
| @end table |
| |
| @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, 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). |
| |
| @value{GDBN} needs to know these things to talk to your |
| Hitachi SH, H8/300, or H8/500: |
| |
| @enumerate |
| @item |
| that you want to use @samp{target hms}, the remote debugging interface |
| for Hitachi microprocessors, or @samp{target e7000}, the in-circuit |
| emulator for the Hitachi SH and the Hitachi 300H. (@samp{target hms} is |
| the default when @value{GDBN} is configured specifically for the Hitachi SH, |
| H8/300, or H8/500.) |
| |
| @item |
| what serial device connects your host to your Hitachi board (the first |
| serial device available on your host is the default). |
| |
| @item |
| what speed to use over the serial device. |
| @end enumerate |
| |
| @menu |
| * Hitachi Boards:: Connecting to Hitachi boards. |
| * Hitachi ICE:: Using the E7000 In-Circuit Emulator. |
| * Hitachi Special:: Special @value{GDBN} commands for Hitachi micros. |
| @end menu |
| |
| @node Hitachi Boards |
| @subsubsection Connecting to Hitachi boards |
| |
| @c only for Unix hosts |
| @kindex device |
| @cindex serial device, Hitachi micros |
| Use the special @code{@value{GDBP}} command @samp{device @var{port}} if you |
| need to explicitly set the serial device. The default @var{port} is the |
| first available port on your host. This is only necessary on Unix |
| hosts, where it is typically something like @file{/dev/ttya}. |
| |
| @kindex speed |
| @cindex serial line speed, Hitachi micros |
| @code{@value{GDBP}} has another special command to set the communications |
| speed: @samp{speed @var{bps}}. This command also is only used from Unix |
| hosts; on DOS hosts, set the line speed as usual from outside @value{GDBN} with |
| the DOS @code{mode} command (for instance, |
| @w{@kbd{mode com2:9600,n,8,1,p}} for a 9600@dmn{bps} connection). |
| |
| The @samp{device} and @samp{speed} commands are available only when you |
| use a Unix host to debug your Hitachi microprocessor programs. If you |
| use a DOS host, |
| @value{GDBN} depends on an auxiliary terminate-and-stay-resident program |
| called @code{asynctsr} to communicate with the development board |
| through a PC serial port. You must also use the DOS @code{mode} command |
| to set up the serial port on the DOS side. |
| |
| The following sample session illustrates the steps needed to start a |
| program under @value{GDBN} control on an H8/300. The example uses a |
| sample H8/300 program called @file{t.x}. The procedure is the same for |
| the Hitachi SH and the H8/500. |
| |
| First hook up your development board. In this example, we use a |
| board attached to serial port @code{COM2}; if you use a different serial |
| port, substitute its name in the argument of the @code{mode} command. |
| When you call @code{asynctsr}, the auxiliary comms program used by the |
| debugger, you give it just the numeric part of the serial port's name; |
| for example, @samp{asyncstr 2} below runs @code{asyncstr} on |
| @code{COM2}. |
| |
| @example |
| C:\H8300\TEST> asynctsr 2 |
| C:\H8300\TEST> mode com2:9600,n,8,1,p |
| |
| Resident portion of MODE loaded |
| |
| COM2: 9600, n, 8, 1, p |
| |
| @end example |
| |
| @quotation |
| @emph{Warning:} We have noticed a bug in PC-NFS that conflicts with |
| @code{asynctsr}. If you also run PC-NFS on your DOS host, you may need to |
| disable it, or even boot without it, to use @code{asynctsr} to control |
| your development board. |
| @end quotation |
| |
| @kindex target hms@r{, and serial protocol} |
| Now that serial communications are set up, and the development board is |
| connected, you can start up @value{GDBN}. Call @code{@value{GDBP}} with |
| the name of your program as the argument. @code{@value{GDBP}} prompts |
| you, as usual, with the prompt @samp{(@value{GDBP})}. Use two special |
| commands to begin your debugging session: @samp{target hms} to specify |
| cross-debugging to the Hitachi board, and the @code{load} command to |
| download your program to the board. @code{load} displays the names of |
| the program's sections, and a @samp{*} for each 2K of data downloaded. |
| (If you want to refresh @value{GDBN} data on symbols or on the |
| executable file without downloading, use the @value{GDBN} commands |
| @code{file} or @code{symbol-file}. These commands, and @code{load} |
| itself, are described in @ref{Files,,Commands to specify files}.) |
| |
| @smallexample |
| (eg-C:\H8300\TEST) @value{GDBP} t.x |
| @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 1992 Free Software Foundation, Inc... |
| (@value{GDBP}) target hms |
| Connected to remote H8/300 HMS system. |
| (@value{GDBP}) load t.x |
| .text : 0x8000 .. 0xabde *********** |
| .data : 0xabde .. 0xad30 * |
| .stack : 0xf000 .. 0xf014 * |
| @end smallexample |
| |
| At this point, you're ready to run or debug your program. From here on, |
| you can use all the usual @value{GDBN} commands. The @code{break} command |
| sets breakpoints; the @code{run} command starts your program; |
| @code{print} or @code{x} display data; the @code{continue} command |
| resumes execution after stopping at a breakpoint. You can use the |
| @code{help} command at any time to find out more about @value{GDBN} commands. |
| |
| Remember, however, that @emph{operating system} facilities aren't |
| available on your development board; for example, if your program hangs, |
| you can't send an interrupt---but you can press the @sc{reset} switch! |
| |
| Use the @sc{reset} button on the development board |
| @itemize @bullet |
| @item |
| to interrupt your program (don't use @kbd{ctl-C} on the DOS host---it has |
| no way to pass an interrupt signal to the development board); and |
| |
| @item |
| to return to the @value{GDBN} command prompt after your program finishes |
| normally. The communications protocol provides no other way for @value{GDBN} |
| to detect program completion. |
| @end itemize |
| |
| In either case, @value{GDBN} sees the effect of a @sc{reset} on the |
| development board as a ``normal exit'' of your program. |
| |
| @node Hitachi ICE |
| @subsubsection Using the E7000 in-circuit emulator |
| |
| @kindex target e7000@r{, with Hitachi ICE} |
| You can use the E7000 in-circuit emulator to develop code for either the |
| Hitachi SH or the H8/300H. Use one of these forms of the @samp{target |
| e7000} command to connect @value{GDBN} to your E7000: |
| |
| @table @code |
| @item target e7000 @var{port} @var{speed} |
| Use this form if your E7000 is connected to a serial port. The |
| @var{port} argument identifies what serial port to use (for example, |
| @samp{com2}). The third argument is the line speed in bits per second |
| (for example, @samp{9600}). |
| |
| @item target e7000 @var{hostname} |
| If your E7000 is installed as a host on a TCP/IP network, you can just |
| specify its hostname; @value{GDBN} uses @code{telnet} to connect. |
| @end table |
| |
| @node Hitachi Special |
| @subsubsection Special @value{GDBN} commands for Hitachi micros |
| |
| Some @value{GDBN} commands are available only for the H8/300: |
| |
| @table @code |
| |
| @kindex set machine |
| @kindex show machine |
| @item set machine h8300 |
| @itemx set machine h8300h |
| Condition @value{GDBN} for one of the two variants of the H8/300 |
| architecture with @samp{set machine}. You can use @samp{show machine} |
| to check which variant is currently in effect. |
| |
| @end table |
| |
| @node H8/500 |
| @subsection H8/500 |
| |
| @table @code |
| |
| @kindex set memory @var{mod} |
| @cindex memory models, H8/500 |
| @item set memory @var{mod} |
| @itemx show memory |
| Specify which H8/500 memory model (@var{mod}) you are using with |
| @samp{set memory}; check which memory model is in effect with @samp{show |
| memory}. The accepted values for @var{mod} are @code{small}, |
| @code{big}, @code{medium}, and @code{compact}. |
| |
| @end table |
| |
| @node i960 |
| @subsection Intel i960 |
| |
| @table @code |
| |
| @kindex target mon960 |
| @item target mon960 @var{dev} |
| MON960 monitor for Intel i960. |
| |
| @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}. |
| |
| @end table |
| |
| @cindex Nindy |
| @cindex i960 |
| @dfn{Nindy} is a ROM Monitor program for Intel 960 target systems. When |
| @value{GDBN} is configured to control a remote Intel 960 using Nindy, you can |
| tell @value{GDBN} how to connect to the 960 in several ways: |
| |
| @itemize @bullet |
| @item |
| Through command line options specifying serial port, version of the |
| Nindy protocol, and communications speed; |
| |
| @item |
| By responding to a prompt on startup; |
| |
| @item |
| By using the @code{target} command at any point during your @value{GDBN} |
| session. @xref{Target Commands, ,Commands for managing targets}. |
| |
| @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}. |
| |
| @end itemize |
| |
| @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}. |
| |
| @menu |
| * Nindy Startup:: Startup with Nindy |
| * Nindy Options:: Options for Nindy |
| * Nindy Reset:: Nindy reset command |
| @end menu |
| |
| @node Nindy Startup |
| @subsubsection Startup with Nindy |
| |
| If you simply start @code{@value{GDBP}} without using any command-line |
| options, you are prompted for what serial port to use, @emph{before} you |
| reach the ordinary @value{GDBN} prompt: |
| |
| @example |
| Attach /dev/ttyNN -- specify NN, or "quit" to quit: |
| @end example |
| |
| @noindent |
| Respond to the prompt with whatever suffix (after @samp{/dev/tty}) |
| identifies the serial port you want to use. You can, if you choose, |
| simply start up with no Nindy connection by responding to the prompt |
| with an empty line. If you do this and later wish to attach to Nindy, |
| use @code{target} (@pxref{Target Commands, ,Commands for managing targets}). |
| |
| @node Nindy Options |
| @subsubsection Options for Nindy |
| |
| These are the startup options for beginning your @value{GDBN} session with a |
| Nindy-960 board attached: |
| |
| @table @code |
| @item -r @var{port} |
| Specify the serial port name of a serial interface to be used to connect |
| to the target system. This option is only available when @value{GDBN} is |
| configured for the Intel 960 target architecture. You may specify |
| @var{port} as any of: a full pathname (e.g. @samp{-r /dev/ttya}), a |
| device name in @file{/dev} (e.g. @samp{-r ttya}), or simply the unique |
| suffix for a specific @code{tty} (e.g. @samp{-r a}). |
| |
| @item -O |
| (An uppercase letter ``O'', not a zero.) Specify that @value{GDBN} should use |
| the ``old'' Nindy monitor protocol to connect to the target system. |
| This option is only available when @value{GDBN} is configured for the Intel 960 |
| target architecture. |
| |
| @quotation |
| @emph{Warning:} if you specify @samp{-O}, but are actually trying to |
| connect to a target system that expects the newer protocol, the connection |
| fails, appearing to be a speed mismatch. @value{GDBN} repeatedly |
| attempts to reconnect at several different line speeds. You can abort |
| this process with an interrupt. |
| @end quotation |
| |
| @item -brk |
| Specify that @value{GDBN} should first send a @code{BREAK} signal to the target |
| system, in an attempt to reset it, before connecting to a Nindy target. |
| |
| @quotation |
| @emph{Warning:} Many target systems do not have the hardware that this |
| requires; it only works with a few boards. |
| @end quotation |
| @end table |
| |
| The standard @samp{-b} option controls the line speed used on the serial |
| port. |
| |
| @c @group |
| @node Nindy Reset |
| @subsubsection Nindy reset command |
| |
| @table @code |
| @item reset |
| @kindex reset |
| For a Nindy target, this command sends a ``break'' to the remote target |
| system; this is only useful if the target has been equipped with a |
| circuit to perform a hard reset (or some other interesting action) when |
| a break is detected. |
| @end table |
| @c @end group |
| |
| @node M32R/D |
| @subsection Mitsubishi M32R/D |
| |
| @table @code |
| |
| @kindex target m32r |
| @item target m32r @var{dev} |
| Mitsubishi M32R/D ROM monitor. |
| |
| @end table |
| |
| @node M68K |
| @subsection M68k |
| |
| The Motorola m68k configuration includes ColdFire support, and |
| target command for the following ROM monitors. |
| |
| @table @code |
| |
| @kindex target abug |
| @item target abug @var{dev} |
| ABug ROM monitor for M68K. |
| |
| @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 est |
| @item target est @var{dev} |
| EST-300 ICE monitor, running on a CPU32 (M68K) board. |
| |
| @kindex target rom68k |
| @item target rom68k @var{dev} |
| ROM 68K monitor, running on an M68K IDP board. |
| |
| @end table |
| |
| If @value{GDBN} is configured with @code{m68*-ericsson-*}, it will |
| instead have only a single special target command: |
| |
| @table @code |
| |
| @kindex target es1800 |
| @item target es1800 @var{dev} |
| ES-1800 emulator for M68K. |
| |
| @end table |
| |
| [context?] |
| |
| @table @code |
| |
| @kindex target rombug |
| @item target rombug @var{dev} |
| ROMBUG ROM monitor for OS/9000. |
| |
| @end table |
| |
| @node M88K |
| @subsection M88K |
| |
| @table @code |
| |
| @kindex target bug |
| @item target bug @var{dev} |
| BUG monitor, running on a MVME187 (m88k) board. |
| |
| @end table |
| |
| @node MIPS Embedded |
| @subsection MIPS Embedded |
| |
| @cindex MIPS boards |
| @value{GDBN} can use the MIPS remote debugging protocol to talk to a |
| MIPS board attached to a serial line. This is available when |
| you configure @value{GDBN} with @samp{--target=mips-idt-ecoff}. |
| |
| @need 1000 |
| Use these @value{GDBN} commands to specify the connection to your target board: |
| |
| @table @code |
| @item target mips @var{port} |
| @kindex target mips @var{port} |
| To run a program on the board, start up @code{@value{GDBP}} with the |
| name of your program as the argument. To connect to the board, use the |
| command @samp{target mips @var{port}}, where @var{port} is the name of |
| the serial port connected to the board. If the program has not already |
| been downloaded to the board, you may use the @code{load} command to |
| download it. You can then use all the usual @value{GDBN} commands. |
| |
| For example, this sequence connects to the target board through a serial |
| port, and loads and runs a program called @var{prog} through the |
| debugger: |
| |
| @example |
| host$ @value{GDBP} @var{prog} |
| @value{GDBN} is free software and @dots{} |
| (@value{GDBP}) target mips /dev/ttyb |
| (@value{GDBP}) load @var{prog} |
| (@value{GDBP}) run |
| @end example |
| |
| @item target mips @var{hostname}:@var{portnumber} |
| On some @value{GDBN} host configurations, you can specify a TCP |
| connection (for instance, to a serial line managed by a terminal |
| concentrator) instead of a serial port, using the syntax |
| @samp{@var{hostname}:@var{portnumber}}. |
| |
| @item target pmon @var{port} |
| @kindex target pmon @var{port} |
| PMON ROM monitor. |
| |
| @item target ddb @var{port} |
| @kindex target ddb @var{port} |
| NEC's DDB variant of PMON for Vr4300. |
| |
| @item target lsi @var{port} |
| @kindex target lsi @var{port} |
| LSI variant of PMON. |
| |
| @kindex target r3900 |
| @item target r3900 @var{dev} |
| Densan DVE-R3900 ROM monitor for Toshiba R3900 Mips. |
| |
| @kindex target array |
| @item target array @var{dev} |
| Array Tech LSI33K RAID controller board. |
| |
| @end table |
| |
| |
| @noindent |
| @value{GDBN} also supports these special commands for MIPS targets: |
| |
| @table @code |
| @item set processor @var{args} |
| @itemx show processor |
| @kindex set processor @var{args} |
| @kindex show processor |
| Use the @code{set processor} command to set the type of MIPS |
| processor when you want to access processor-type-specific registers. |
| For example, @code{set processor @var{r3041}} tells @value{GDBN} |
| to use the CPO registers appropriate for the 3041 chip. |
| Use the @code{show processor} command to see what MIPS processor @value{GDBN} |
| is using. Use the @code{info reg} command to see what registers |
| @value{GDBN} is using. |
| |
| @item set mipsfpu double |
| @itemx set mipsfpu single |
| @itemx set mipsfpu none |
| @itemx show mipsfpu |
| @kindex set mipsfpu |
| @kindex show mipsfpu |
| @cindex MIPS remote floating point |
| @cindex floating point, MIPS remote |
| If your target board does not support the MIPS floating point |
| coprocessor, you should use the command @samp{set mipsfpu none} (if you |
| need this, you may wish to put the command in your @value{GDBINIT} |
| file). This tells @value{GDBN} how to find the return value of |
| functions which return floating point values. It also allows |
| @value{GDBN} to avoid saving the floating point registers when calling |
| functions on the board. If you are using a floating point coprocessor |
| with only single precision floating point support, as on the @sc{r4650} |
| processor, use the command @samp{set mipsfpu single}. The default |
| double precision floating point coprocessor may be selected using |
| @samp{set mipsfpu double}. |
| |
| In previous versions the only choices were double precision or no |
| floating point, so @samp{set mipsfpu on} will select double precision |
| and @samp{set mipsfpu off} will select no floating point. |
| |
| As usual, you can inquire about the @code{mipsfpu} variable with |
| @samp{show mipsfpu}. |
| |
| @item set remotedebug @var{n} |
| @itemx show remotedebug |
| @kindex set remotedebug@r{, MIPS protocol} |
| @kindex show remotedebug@r{, MIPS protocol} |
| @cindex @code{remotedebug}, MIPS protocol |
| @cindex MIPS @code{remotedebug} protocol |
| @c FIXME! For this to be useful, you must know something about the MIPS |
| @c FIXME...protocol. Where is it described? |
| You can see some debugging information about communications with the board |
| by setting the @code{remotedebug} variable. If you set it to @code{1} using |
| @samp{set remotedebug 1}, every packet is displayed. If you set it |
| to @code{2}, every character is displayed. You can check the current value |
| at any time with the command @samp{show remotedebug}. |
| |
| @item set timeout @var{seconds} |
| @itemx set retransmit-timeout @var{seconds} |
| @itemx show timeout |
| @itemx show retransmit-timeout |
| @cindex @code{timeout}, MIPS protocol |
| @cindex @code{retransmit-timeout}, MIPS protocol |
| @kindex set timeout |
| @kindex show timeout |
| @kindex set retransmit-timeout |
| @kindex show retransmit-timeout |
| You can control the timeout used while waiting for a packet, in the MIPS |
| remote protocol, with the @code{set timeout @var{seconds}} command. The |
| default is 5 seconds. Similarly, you can control the timeout used while |
| waiting for an acknowledgement of a packet with the @code{set |
| retransmit-timeout @var{seconds}} command. The default is 3 seconds. |
| You can inspect both values with @code{show timeout} and @code{show |
| retransmit-timeout}. (These commands are @emph{only} available when |
| @value{GDBN} is configured for @samp{--target=mips-idt-ecoff}.) |
| |
| The timeout set by @code{set timeout} does not apply when @value{GDBN} |
| is waiting for your program to stop. In that case, @value{GDBN} waits |
| forever because it has no way of knowing how long the program is going |
| to run before stopping. |
| @end table |
| |
| @node PowerPC |
| @subsection PowerPC |
| |
| @table @code |
| |
| @kindex target dink32 |
| @item target dink32 @var{dev} |
| DINK32 ROM monitor. |
| |
| @kindex target ppcbug |
| @item target ppcbug @var{dev} |
| @kindex target ppcbug1 |
| @item target ppcbug1 @var{dev} |
| PPCBUG ROM monitor for PowerPC. |
| |
| @kindex target sds |
| @item target sds @var{dev} |
| SDS monitor, running on a PowerPC board (such as Motorola's ADS). |
| |
| @end table |
| |
| @node PA |
| @subsection HP PA Embedded |
| |
| @table @code |
| |
| @kindex target op50n |
| @item target op50n @var{dev} |
| OP50N monitor, running on an OKI HPPA board. |
| |
| @kindex target w89k |
| @item target w89k @var{dev} |
| W89K monitor, running on a Winbond HPPA board. |
| |
| @end table |
| |
| @node SH |
| @subsection Hitachi SH |
| |
| @table @code |
| |
| @kindex target hms@r{, with Hitachi SH} |
| @item target hms @var{dev} |
| A Hitachi SH board attached via serial line to your host. Use special |
| commands @code{device} and @code{speed} to control the serial line and |
| the communications speed used. |
| |
| @kindex target e7000@r{, with Hitachi SH} |
| @item target e7000 @var{dev} |
| E7000 emulator for Hitachi SH. |
| |
| @kindex target sh3@r{, with SH} |
| @kindex target sh3e@r{, with SH} |
| @item target sh3 @var{dev} |
| @item target sh3e @var{dev} |
| Hitachi SH-3 and SH-3E target systems. |
| |
| @end table |
| |
| @node Sparclet |
| @subsection Tsqware Sparclet |
| |
| @cindex Sparclet |
| |
| @value{GDBN} enables developers to debug tasks running on |
| Sparclet targets from a Unix host. |
| @value{GDBN} uses code that runs on |
| both the Unix host and on the Sparclet target. The program |
| @code{@value{GDBP}} is installed and executed on the Unix host. |
| |
| @table @code |
| @item timeout @var{args} |
| @kindex remotetimeout |
| @value{GDBN} supports the option @code{remotetimeout}. |
| This option is set by the user, and @var{args} represents the number of |
| seconds @value{GDBN} waits for responses. |
| @end table |
| |
| @kindex Compiling |
| When compiling for debugging, include the options @samp{-g} to get debug |
| information and @samp{-Ttext} to relocate the program to where you wish to |
| load it on the target. You may also want to add the options @samp{-n} or |
| @samp{-N} in order to reduce the size of the sections. Example: |
| |
| @example |
| sparclet-aout-gcc prog.c -Ttext 0x12010000 -g -o prog -N |
| @end example |
| |
| You can use @code{objdump} to verify that the addresses are what you intended: |
| |
| @example |
| sparclet-aout-objdump --headers --syms prog |
| @end example |
| |
| @kindex Running |
| Once you have set |
| your Unix execution search path to find @value{GDBN}, you are ready to |
| run @value{GDBN}. From your Unix host, run @code{@value{GDBP}} |
| (or @code{sparclet-aout-gdb}, depending on your installation). |
| |
| @value{GDBN} comes up showing the prompt: |
| |
| @example |
| (gdbslet) |
| @end example |
| |
| @menu |
| * Sparclet File:: Setting the file to debug |
| * Sparclet Connection:: Connecting to Sparclet |
| * Sparclet Download:: Sparclet download |
| * Sparclet Execution:: Running and debugging |
| @end menu |
| |
| @node Sparclet File |
| @subsubsection Setting file to debug |
| |
| The @value{GDBN} command @code{file} lets you choose with program to debug. |
| |
| @example |
| (gdbslet) file prog |
| @end example |
| |
| @need 1000 |
| @value{GDBN} then attempts to read the symbol table of @file{prog}. |
| @value{GDBN} locates |
| the file by searching the directories listed in the command search |
| path. |
| If the file was compiled with debug information (option "-g"), source |
| files will be searched as well. |
| @value{GDBN} locates |
| the source files by searching the directories listed in the directory search |
| path (@pxref{Environment, ,Your program's environment}). |
| If it fails |
| to find a file, it displays a message such as: |
| |
| @example |
| prog: No such file or directory. |
| @end example |
| |
| When this happens, add the appropriate directories to the search paths with |
| the @value{GDBN} commands @code{path} and @code{dir}, and execute the |
| @code{target} command again. |
| |
| @node Sparclet Connection |
| @subsubsection Connecting to Sparclet |
| |
| The @value{GDBN} command @code{target} lets you connect to a Sparclet target. |
| To connect to a target on serial port ``@code{ttya}'', type: |
| |
| @example |
| (gdbslet) target sparclet /dev/ttya |
| Remote target sparclet connected to /dev/ttya |
| main () at ../prog.c:3 |
| @end example |
| |
| @need 750 |
| @value{GDBN} displays messages like these: |
| |
| @example |
| Connected to ttya. |
| @end example |
| |
| @node Sparclet Download |
| @subsubsection Sparclet download |
| |
| @cindex download to Sparclet |
| Once connected to the Sparclet target, |
| you can use the @value{GDBN} |
| @code{load} command to download the file from the host to the target. |
| The file name and load offset should be given as arguments to the @code{load} |
| command. |
| Since the file format is aout, the program must be loaded to the starting |
| address. You can use @code{objdump} to find out what this value is. The load |
| offset is an offset which is added to the VMA (virtual memory address) |
| of each of the file's sections. |
| For instance, if the program |
| @file{prog} was linked to text address 0x1201000, with data at 0x12010160 |
| and bss at 0x12010170, in @value{GDBN}, type: |
| |
| @example |
| (gdbslet) load prog 0x12010000 |
| Loading section .text, size 0xdb0 vma 0x12010000 |
| @end example |
| |
| If the code is loaded at a different address then what the program was linked |
| to, you may need to use the @code{section} and @code{add-symbol-file} commands |
| to tell @value{GDBN} where to map the symbol table. |
| |
| @node Sparclet Execution |
| @subsubsection Running and debugging |
| |
| @cindex running and debugging Sparclet programs |
| You can now begin debugging the task using @value{GDBN}'s execution control |
| commands, @code{b}, @code{step}, @code{run}, etc. See the @value{GDBN} |
| manual for the list of commands. |
| |
| @example |
| (gdbslet) b main |
| Breakpoint 1 at 0x12010000: file prog.c, line 3. |
| (gdbslet) run |
| Starting program: prog |
| Breakpoint 1, main (argc=1, argv=0xeffff21c) at prog.c:3 |
| 3 char *symarg = 0; |
| (gdbslet) step |
| 4 char *execarg = "hello!"; |
| (gdbslet) |
| @end example |
| |
| @node Sparclite |
| @subsection Fujitsu Sparclite |
| |
| @table @code |
| |
| @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. |
| |
| @end table |
| |
| @node ST2000 |
| @subsection Tandem ST2000 |
| |
| @value{GDBN} may be used with a Tandem ST2000 phone switch, running Tandem's |
| STDBUG protocol. |
| |
| To connect your ST2000 to the host system, see the manufacturer's |
| manual. Once the ST2000 is physically attached, you can run: |
| |
| @example |
| target st2000 @var{dev} @var{speed} |
| @end example |
| |
| @noindent |
| to establish it as your debugging environment. @var{dev} is normally |
| the name of a serial device, such as @file{/dev/ttya}, connected to the |
| ST2000 via a serial line. You can instead specify @var{dev} as a TCP |
| connection (for example, to a serial line attached via a terminal |
| concentrator) using the syntax @code{@var{hostname}:@var{portnumber}}. |
| |
| The @code{load} and @code{attach} commands are @emph{not} defined for |
| this target; you must load your program into the ST2000 as you normally |
| would for standalone operation. @value{GDBN} reads debugging information |
| (such as symbols) from a separate, debugging version of the program |
| available on your host computer. |
| @c FIXME!! This is terribly vague; what little content is here is |
| @c basically hearsay. |
| |
| @cindex ST2000 auxiliary commands |
| These auxiliary @value{GDBN} commands are available to help you with the ST2000 |
| environment: |
| |
| @table @code |
| @item st2000 @var{command} |
| @kindex st2000 @var{cmd} |
| @cindex STDBUG commands (ST2000) |
| @cindex commands to STDBUG (ST2000) |
| Send a @var{command} to the STDBUG monitor. See the manufacturer's |
| manual for available commands. |
| |
| @item connect |
| @cindex connect (to STDBUG) |
| Connect the controlling terminal to the STDBUG command monitor. When |
| you are done interacting with STDBUG, typing either of two character |
| sequences gets you back to the @value{GDBN} command prompt: |
| @kbd{@key{RET}~.} (Return, followed by tilde and period) or |
| @kbd{@key{RET}~@key{C-d}} (Return, followed by tilde and control-D). |
| @end table |
| |
| @node Z8000 |
| @subsection Zilog Z8000 |
| |
| @cindex Z8000 |
| @cindex simulator, Z8000 |
| @cindex Zilog Z8000 simulator |
| |
| When configured for debugging Zilog Z8000 targets, @value{GDBN} includes |
| a Z8000 simulator. |
| |
| For the Z8000 family, @samp{target sim} simulates either the Z8002 (the |
| unsegmented variant of the Z8000 architecture) or the Z8001 (the |
| segmented variant). The simulator recognizes which architecture is |
| appropriate by inspecting the object code. |
| |
| @table @code |
| @item target sim @var{args} |
| @kindex sim |
| @kindex target sim@r{, with Z8000} |
| Debug programs on a simulated CPU. If the simulator supports setup |
| options, specify them via @var{args}. |
| @end table |
| |
| @noindent |
| After specifying this target, you can debug programs for the simulated |
| CPU in the same style as programs for your host computer; use the |
| @code{file} command to load a new program image, the @code{run} command |
| to run your program, and so on. |
| |
| As well as making available all the usual machine registers |
| (@pxref{Registers, ,Registers}), the Z8000 simulator provides three |
| additional items of information as specially named registers: |
| |
| @table @code |
| |
| @item cycles |
| Counts clock-ticks in the simulator. |
| |
| @item insts |
| Counts instructions run in the simulator. |
| |
| @item time |
| Execution time in 60ths of a second. |
| |
| @end table |
| |
| You can refer to these values in @value{GDBN} expressions with the usual |
| conventions; for example, @w{@samp{b fputc if $cycles>5000}} sets a |
| conditional breakpoint that suspends only after at least 5000 |
| simulated clock ticks. |
| |
| @node Architectures |
| @section Architectures |
| |
| This section describes characteristics of architectures that affect |
| all uses of @value{GDBN} with the architecture, both native and cross. |
| |
| @menu |
| * A29K:: |
| * Alpha:: |
| * MIPS:: |
| @end menu |
| |
| @node A29K |
| @subsection A29K |
| |
| @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 |
| @dfn{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 |
| |
| @node Alpha |
| @subsection Alpha |
| |
| See the following section. |
| |
| @node MIPS |
| @subsection MIPS |
| |
| @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 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, see @ref{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 |
| @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} does not add 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 |
| @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 |
| @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} (@file{./_gdb_history} on MS-DOS) 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 |
| @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 terminal |
| driver software. For example, on Unix @value{GDBN} uses 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 |
| @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 |
| @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 |
| @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 |
| @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 |
| @section User-defined command hooks |
| @cindex command hooks |
| @cindex hooks, for commands |
| |
| 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. |
| |
| @kindex stop@r{, a pseudo-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. |
| |
| 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 |
| |
| 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 |
| @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} |
| @cindex @file{gdb.ini} |
| 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@footnote{On DOS/Windows systems, the home |
| directory is the one pointed to by the @code{HOME} environment |
| variable.}, 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}. |
| |
| @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 |
| |
| 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 |
| @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 |
| @c FIXME: the above implies that at least all ANSI C formats are |
| @c supported, but it isn't true: %E and %G don't work (or so it seems). |
| @c Either this is a bug, or the manual should document what formats are |
| @c supported. |
| |
| @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 |
| |
| @node Emacs |
| @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. |
| @c (Do not use the @code{-tui} option to run @value{GDBN} from Emacs.) |
| |
| 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{M-:} or @kbd{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 |
| |
| @node GDB Bugs |
| @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 |
| @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 |
| @section How to report bugs |
| @cindex bug reports |
| @cindex @value{GDBN} bugs, reporting |
| |
| 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@@gnu.org |
| @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 |
| |
| 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. |
| |
| @item |
| What compiler (and its version) was used to compile @value{GDBN}---e.g. |
| ``@value{GCC}--2.8.1''. |
| |
| @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. |
| |
| @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 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.texinfo |
| @c Use -I with makeinfo to point to the appropriate directory, |
| @c environment var TEXINPUTS with TeX. |
| @include rluser.texinfo |
| @include inc-hist.texinfo |
| |
| |
| @node Formatting Documentation |
| @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. |
| |
| @node Installing GDB |
| @appendix Installing @value{GDBN} |
| @cindex configuring @value{GDBN} |
| @cindex installation |
| |
| @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 |
| @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 |
| @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 |
| @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. |
| |
| @node Index |
| @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 |