166 lines
6.5 KiB
Text
Executable file
166 lines
6.5 KiB
Text
Executable file
_dnl__ -*- Texinfo -*-
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_dnl__ Copyright (c) 1988 1989 1990 1991 Free Software Foundation, Inc.
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_dnl__ This file is part of the source for the GDB manual.
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@c M4 FRAGMENT: $Id$
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@node Emacs, _GDBN__ Bugs, Sequences, Top
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@chapter Using _GDBN__ under GNU Emacs
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@cindex emacs
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A special interface allows you to use GNU Emacs to view (and
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edit) the source files for the program you are debugging with
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_GDBN__.
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To use this interface, use the command @kbd{M-x gdb} in Emacs. Give the
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executable file you want to debug as an argument. This command starts
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_GDBN__ as a subprocess of Emacs, with input and output through a newly
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created Emacs buffer.
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Using _GDBN__ under Emacs is just like using _GDBN__ normally except for two
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things:
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@itemize @bullet
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@item
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All ``terminal'' input and output goes through the Emacs buffer.
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@end itemize
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This applies both to _GDBN__ commands and their output, and to the input
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and output done by the program you are debugging.
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This is useful because it means that you can copy the text of previous
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commands and input them again; you can even use parts of the output
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in this way.
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All the facilities of Emacs' Shell mode are available for this purpose.
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@itemize @bullet
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@item
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_GDBN__ displays source code through Emacs.
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@end itemize
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Each time _GDBN__ displays a stack frame, Emacs automatically finds the
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source file for that frame and puts an arrow (_0__@samp{=>}_1__) at the
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left margin of the current line. Emacs uses a separate buffer for
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source display, and splits the window to show both your _GDBN__ session
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and the source.
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Explicit _GDBN__ @code{list} or search commands still produce output as
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usual, but you probably will have no reason to use them.
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@quotation
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@emph{Warning:} If the directory where your program resides is not your
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current directory, it can be easy to confuse Emacs about the location of
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the source files, in which case the auxiliary display buffer will not
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appear to show your source. _GDBN__ can find programs by searching your
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environment's @code{PATH} variable, so the _GDBN__ input and output
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session will proceed normally; but Emacs doesn't get enough information
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back from _GDBN__ to locate the source files in this situation. To
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avoid this problem, either start _GDBN__ mode from the directory where
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your program resides, or specify a full path name when prompted for the
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@kbd{M-x gdb} argument.
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A similar confusion can result if you use the _GDBN__ @code{file} command to
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switch to debugging a program in some other location, from an existing
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_GDBN__ buffer in Emacs.
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@end quotation
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By default, @kbd{M-x gdb} calls the program called @file{gdb}. If
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you need to call _GDBN__ by a different name (for example, if you keep
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several configurations around, with different names) you can set the
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Emacs variable @code{gdb-command-name}; for example,
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@example
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(setq gdb-command-name "mygdb")
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@end example
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@noindent
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(preceded by @kbd{ESC ESC}, or typed in the @code{*scratch*} buffer, or
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in your @file{.emacs} file) will make Emacs call the program named
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``@code{mygdb}'' instead.
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In the _GDBN__ I/O buffer, you can use these special Emacs commands in
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addition to the standard Shell mode commands:
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@table @kbd
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@item C-h m
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Describe the features of Emacs' _GDBN__ Mode.
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@item M-s
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Execute to another source line, like the _GDBN__ @code{step} command; also
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update the display window to show the current file and location.
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@item M-n
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Execute to next source line in this function, skipping all function
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calls, like the _GDBN__ @code{next} command. Then update the display window
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to show the current file and location.
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@item M-i
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Execute one instruction, like the _GDBN__ @code{stepi} command; update
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display window accordingly.
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@item M-x gdb-nexti
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Execute to next instruction, using the _GDBN__ @code{nexti} command; update
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display window accordingly.
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@item C-c C-f
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Execute until exit from the selected stack frame, like the _GDBN__
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@code{finish} command.
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@item M-c
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Continue execution of the program, like the _GDBN__ @code{continue}
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command. @emph{Warning:} In Emacs v19, this command is @kbd{C-c C-p}.
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@item M-u
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Go up the number of frames indicated by the numeric argument
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(@pxref{Arguments, , Numeric Arguments, emacs, The GNU Emacs Manual}),
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like the _GDBN__ @code{up} command. @emph{Warning:} In Emacs v19, this
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command is @kbd{C-c C-u}.@refill
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@item M-d
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Go down the number of frames indicated by the numeric argument, like the
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_GDBN__ @code{down} command. @emph{Warning:} In Emacs v19, this command
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is @kbd{C-c C-d}.
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@item C-x &
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Read the number where the cursor is positioned, and insert it at the end
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of the _GDBN__ I/O buffer. For example, if you wish to disassemble code
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around an address that was displayed earlier, type @kbd{disassemble};
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then move the cursor to the address display, and pick up the
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argument for @code{disassemble} by typing @kbd{C-x &}.
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You can customize this further on the fly by defining elements of the list
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@code{gdb-print-command}; once it is defined, you can format or
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otherwise process numbers picked up by @kbd{C-x &} before they are
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inserted. A numeric argument to @kbd{C-x &} will both flag that you
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wish special formatting, and act as an index to pick an element of the
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list. If the list element is a string, the number to be inserted is
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formatted using the Emacs function @code{format}; otherwise the number
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is passed as an argument to the corresponding list element.
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@end table
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In any source file, the Emacs command @kbd{C-x SPC} (@code{gdb-break})
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tells _GDBN__ to set a breakpoint on the source line point is on.
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If you accidentally delete the source-display buffer, an easy way to get
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it back is to type the command @code{f} in the _GDBN__ buffer, to
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request a frame display; when you run under Emacs, this will recreate
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the source buffer if necessary to show you the context of the current
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frame.
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The source files displayed in Emacs are in ordinary Emacs buffers
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which are visiting the source files in the usual way. You can edit
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the files with these buffers if you wish; but keep in mind that _GDBN__
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communicates with Emacs in terms of line numbers. If you add or
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delete lines from the text, the line numbers that _GDBN__ knows will cease
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to correspond properly to the code.
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@c The following dropped because Epoch is nonstandard. Reactivate
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@c if/when v19 does something similar. ---pesch@cygnus.com 19dec1990
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@ignore
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@kindex emacs epoch environment
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@kindex epoch
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@kindex inspect
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Version 18 of Emacs has a built-in window system called the @code{epoch}
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environment. Users of this environment can use a new command,
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@code{inspect} which performs identically to @code{print} except that
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each value is printed in its own window.
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@end ignore
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