1 @c This is part of the Emacs manual.
2 @c Copyright (C) 1985,86,87,93,94,95,97,2000,2001 Free Software Foundation, Inc.
3 @c See file emacs.texi for copying conditions.
4 @node Building, Maintaining, Programs, Top
5 @chapter Compiling and Testing Programs
6 @cindex building programs
7 @cindex program building
8 @cindex running Lisp functions
10 The previous chapter discusses the Emacs commands that are useful for
11 making changes in programs. This chapter deals with commands that assist
12 in the larger process of developing and maintaining programs.
15 * Compilation:: Compiling programs in languages other
16 than Lisp (C, Pascal, etc.).
17 * Grep Searching:: Running grep as if it were a compiler.
18 * Compilation Mode:: The mode for visiting compiler errors.
19 * Compilation Shell:: Customizing your shell properly
20 for use in the compilation buffer.
21 * Debuggers:: Running symbolic debuggers for non-Lisp programs.
22 * Executing Lisp:: Various modes for editing Lisp programs,
23 with different facilities for running
25 * Libraries: Lisp Libraries. Creating Lisp programs to run in Emacs.
26 * Eval: Lisp Eval. Executing a single Lisp expression in Emacs.
27 * Interaction: Lisp Interaction. Executing Lisp in an Emacs buffer.
28 * External Lisp:: Communicating through Emacs with a separate Lisp.
32 @section Running Compilations under Emacs
33 @cindex inferior process
35 @cindex compilation errors
38 Emacs can run compilers for noninteractive languages such as C and
39 Fortran as inferior processes, feeding the error log into an Emacs buffer.
40 It can also parse the error messages and show you the source lines where
41 compilation errors occurred.
45 Run a compiler asynchronously under Emacs, with error messages going to
46 the @samp{*compilation*} buffer.
48 Invoke a compiler with the same command as in the last invocation of
51 Run @code{grep} asynchronously under Emacs, with matching lines
52 listed in the buffer named @samp{*grep*}.
54 Run @code{grep} via @code{find}, with user-specified arguments, and
55 collect output in the buffer named @samp{*grep*}.
56 @item M-x kill-compilation
58 Kill the running compilation or @code{grep} subprocess.
62 To run @code{make} or another compilation command, do @kbd{M-x
63 compile}. This command reads a shell command line using the minibuffer,
64 and then executes the command in an inferior shell, putting output in
65 the buffer named @samp{*compilation*}. The current buffer's default
66 directory is used as the working directory for the execution of the
67 command; normally, therefore, the compilation happens in this
70 @vindex compile-command
71 When the shell command line is read, the minibuffer appears
72 containing a default command line, which is the command you used the
73 last time you did @kbd{M-x compile}. If you type just @key{RET}, the
74 same command line is used again. For the first @kbd{M-x compile}, the
75 default is @samp{make -k}, which is correct most of the time for
76 nontrivial programs. (@xref{Top,, Make, make, GNU Make Manual}.)
77 The default compilation command comes from the variable
78 @code{compile-command}; if the appropriate compilation command for a
79 file is something other than @samp{make -k}, it can be useful for the
80 file to specify a local value for @code{compile-command} (@pxref{File
83 Starting a compilation displays the buffer @samp{*compilation*} in
84 another window but does not select it. The buffer's mode line tells you
85 whether compilation is finished, with the word @samp{run} or @samp{exit}
86 inside the parentheses. You do not have to keep this buffer visible;
87 compilation continues in any case. While a compilation is going on, the
88 string @samp{Compiling} appears in the mode lines of all windows. When
89 this string disappears, the compilation is finished.
91 If you want to watch the compilation transcript as it appears, switch
92 to the @samp{*compilation*} buffer and move point to the end of the
93 buffer. When point is at the end, new compilation output is inserted
94 above point, which remains at the end. If point is not at the end of
95 the buffer, it remains fixed while more compilation output is added at
96 the end of the buffer.
98 @cindex compilation buffer, keeping current position at the end
99 @vindex compilation-scroll-output
100 If you set the variable @code{compilation-scroll-output} to a
101 non-@code{nil} value, then the compilation buffer always scrolls to
102 follow output as it comes in.
104 @findex kill-compilation
105 When the compiler process terminates, for whatever reason, the mode
106 line of the @samp{*compilation*} buffer changes to say @samp{signal}
107 instead of @samp{run}. Starting a new compilation also kills any
108 running compilation, as only one can exist at any time. However,
109 @kbd{M-x compile} asks for confirmation before actually killing a
110 compilation that is running. You can also kill the compilation
111 process with @kbd{M-x kill-compilation}.
114 To rerun the last compilation with the same command, type @kbd{M-x
115 recompile}. This automatically reuses the compilation command from the
116 last invocation of @kbd{M-x compile}.
118 Emacs does not expect a compiler process to launch asynchronous
119 subprocesses; if it does, and they keep running after the main
120 compiler process has terminated, Emacs may kill them or their output
121 may not arrive in Emacs. To avoid this problem, make the main process
122 wait for its subprocesses to finish. In a shell script, you can do this
123 using @samp{$!} and @samp{wait}, like this:
126 (sleep 10; echo 2nd)& pid=$! # @r{Record pid of subprocess}
128 wait $pid # @r{Wait for subprocess}
131 If the background process does not output to the compilation buffer,
132 so you only need to prevent it from being killed when the main
133 compilation process terminates, this is sufficient:
136 nohup @var{command}; sleep 1
139 @vindex compilation-environment
140 You can control the environment passed to the compilation command
141 with the variable @code{compilation-environment}. Its value is a list
142 of environment variable settings; each element should be a string of
143 the form @code{"@var{envvarname}=@var{value}"}. These environment
144 variable settings override the usual ones.
147 @section Searching with Grep under Emacs
150 Just as you can run a compiler from Emacs and then visit the lines
151 where there were compilation errors, you can also run @code{grep} and
152 then visit the lines on which matches were found. This works by
153 treating the matches reported by @code{grep} as if they were ``errors.''
155 To do this, type @kbd{M-x grep}, then enter a command line that
156 specifies how to run @code{grep}. Use the same arguments you would give
157 @code{grep} when running it normally: a @code{grep}-style regexp
158 (usually in single-quotes to quote the shell's special characters)
159 followed by file names, which may use wildcards. The output from
160 @code{grep} goes in the @samp{*grep*} buffer. You can find the
161 corresponding lines in the original files using @kbd{C-x `} and
162 @key{RET}, as with compilation errors.
164 If you specify a prefix argument for @kbd{M-x grep}, it figures out
165 the tag (@pxref{Tags}) around point, and puts that into the default
169 The command @kbd{M-x grep-find} is similar to @kbd{M-x grep}, but it
170 supplies a different initial default for the command---one that runs
171 both @code{find} and @code{grep}, so as to search every file in a
172 directory tree. See also the @code{find-grep-dired} command,
173 in @ref{Dired and Find}.
175 @node Compilation Mode
176 @section Compilation Mode
178 @findex compile-goto-error
179 @cindex Compilation mode
180 @cindex mode, Compilation
181 The @samp{*compilation*} buffer uses a special major mode, Compilation
182 mode, whose main feature is to provide a convenient way to look at the
183 source line where the error happened.
185 If you set the variable @code{compilation-scroll-output} to a
186 non-@code{nil} value, then the compilation buffer always scrolls to
187 follow output as it comes in.
191 Visit the locus of the next compiler error message or @code{grep} match.
193 Visit the locus of the error message that point is on.
194 This command is used in the compilation buffer.
196 Visit the locus of the error message that you click on.
201 You can visit the source for any particular error message by moving
202 point in the @samp{*compilation*} buffer to that error message and
203 typing @key{RET} (@code{compile-goto-error}). Alternatively, you can
204 click @kbd{Mouse-2} on the error message; you need not switch to the
205 @samp{*compilation*} buffer first.
207 To parse the compiler error messages sequentially, type @kbd{C-x `}
208 (@code{next-error}). The character following the @kbd{C-x} is the
209 backquote or ``grave accent,'' not the single-quote. This command is
210 available in all buffers, not just in @samp{*compilation*}; it displays
211 the next error message at the top of one window and source location of
212 the error in another window.
214 The first time @kbd{C-x `} is used after the start of a compilation,
215 it moves to the first error's location. Subsequent uses of @kbd{C-x `}
216 advance down to subsequent errors. If you visit a specific error
217 message with @key{RET} or @kbd{Mouse-2}, subsequent @kbd{C-x `}
218 commands advance from there. When @kbd{C-x `} gets to the end of the
219 buffer and finds no more error messages to visit, it fails and signals
222 You don't have to be in the compilation buffer in order to use
223 @code{next-error}. If one window on the selected frame can be the
224 target of the @code{next-error} call, it is used. Else, if a buffer
225 previously had @code{next-error} called on it, it is used. Else,
226 if the current buffer can be the target of @code{next-error}, it is
227 used. Else, all the buffers Emacs manages are tried for
228 @code{next-error} support.
230 @kbd{C-u C-x `} starts scanning from the beginning of the compilation
231 buffer. This is one way to process the same set of errors again.
233 @vindex compilation-error-regexp-alist
234 @vindex grep-regexp-alist
235 To parse messages from the compiler, Compilation mode uses the
236 variable @code{compilation-error-regexp-alist} which lists various
237 formats of error messages and tells Emacs how to extract the source file
238 and the line number from the text of a message. If your compiler isn't
239 supported, you can tailor Compilation mode to it by adding elements to
240 that list. A similar variable @code{grep-regexp-alist} tells Emacs how
241 to parse output of a @code{grep} command.
243 Compilation mode also redefines the keys @key{SPC} and @key{DEL} to
244 scroll by screenfuls, and @kbd{M-n} and @kbd{M-p} to move to the next or
245 previous error message. You can also use @kbd{M-@{} and @kbd{M-@}} to
246 move up or down to an error message for a different source file.
248 The features of Compilation mode are also available in a minor mode
249 called Compilation Minor mode. This lets you parse error messages in
250 any buffer, not just a normal compilation output buffer. Type @kbd{M-x
251 compilation-minor-mode} to enable the minor mode. This defines the keys
252 @key{RET} and @kbd{Mouse-2}, as in the Compilation major mode.
254 Compilation minor mode works in any buffer, as long as the contents
255 are in a format that it understands. In an Rlogin buffer (@pxref{Remote
256 Host}), Compilation minor mode automatically accesses remote source
257 files by FTP (@pxref{File Names}).
259 @node Compilation Shell
260 @section Subshells for Compilation
262 Emacs uses a shell to run the compilation command, but specifies
263 the option for a noninteractive shell. This means, in particular, that
264 the shell should start with no prompt. If you find your usual shell
265 prompt making an unsightly appearance in the @samp{*compilation*}
266 buffer, it means you have made a mistake in your shell's init file by
267 setting the prompt unconditionally. (This init file's name may be
268 @file{.bashrc}, @file{.profile}, @file{.cshrc}, @file{.shrc}, or various
269 other things, depending on the shell you use.) The shell init file
270 should set the prompt only if there already is a prompt. In csh, here
274 if ($?prompt) set prompt = @dots{}
278 And here's how to do it in bash:
281 if [ "$@{PS1+set@}" = set ]
286 There may well be other things that your shell's init file
287 ought to do only for an interactive shell. You can use the same
288 method to conditionalize them.
290 The MS-DOS ``operating system'' does not support asynchronous
291 subprocesses; to work around this lack, @kbd{M-x compile} runs the
292 compilation command synchronously on MS-DOS. As a consequence, you must
293 wait until the command finishes before you can do anything else in
294 Emacs. @xref{MS-DOS}.
297 @section Running Debuggers Under Emacs
308 @c Do you believe in GUD?
309 The GUD (Grand Unified Debugger) library provides an interface to
310 various symbolic debuggers from within Emacs. We recommend the debugger
311 GDB, which is free software, but you can also run DBX, SDB or XDB if you
312 have them. GUD can also serve as an interface to Perl's debugging
313 mode, the Python debugger PDB, and to JDB, the Java Debugger.
314 @xref{Debugging,, The Lisp Debugger, elisp, the Emacs Lisp Reference Manual},
315 for information on debugging Emacs Lisp programs.
318 * Starting GUD:: How to start a debugger subprocess.
319 * Debugger Operation:: Connection between the debugger and source buffers.
320 * Commands of GUD:: Key bindings for common commands.
321 * GUD Customization:: Defining your own commands for GUD.
322 * GUD Tooltips:: Showing variable values by pointing with the mouse.
323 * GDB Graphical Interface:: An enhanced mode that uses GDB features to
324 implement a graphical debugging environment through
329 @subsection Starting GUD
331 There are several commands for starting a debugger, each corresponding
332 to a particular debugger program.
335 @item M-x gdb @key{RET} @var{file} @key{RET}
337 Run GDB as a subprocess of Emacs. If the variable
338 @code{gud-gdb-command-name} is ``gdb --annotate=3'' (the default
339 value) then GDB starts as for @kbd{M-x gdba} below. If you want to
340 GDB to start as in Emacs 21.3 and earlier then set
341 @code{gud-gdb-command-name} to ``gdb --fullname''. In this case, the
342 command creates a buffer for input and output to GDB, and switches to
343 it. If a GDB buffer already exists, it just switches to that buffer.
345 @item M-x gdba @key{RET} @var{file} @key{RET}
346 Run GDB as a subprocess of Emacs, providing a graphical interface
347 to GDB features through Emacs. @xref{GDB Graphical Interface}.
349 @item M-x dbx @key{RET} @var{file} @key{RET}
351 Similar, but run DBX instead of GDB.
353 @item M-x xdb @key{RET} @var{file} @key{RET}
355 @vindex gud-xdb-directories
356 Similar, but run XDB instead of GDB. Use the variable
357 @code{gud-xdb-directories} to specify directories to search for source
360 @item M-x sdb @key{RET} @var{file} @key{RET}
362 Similar, but run SDB instead of GDB.
364 Some versions of SDB do not mention source file names in their
365 messages. When you use them, you need to have a valid tags table
366 (@pxref{Tags}) in order for GUD to find functions in the source code.
367 If you have not visited a tags table or the tags table doesn't list one
368 of the functions, you get a message saying @samp{The sdb support
369 requires a valid tags table to work}. If this happens, generate a valid
370 tags table in the working directory and try again.
372 @item M-x perldb @key{RET} @var{file} @key{RET}
374 Run the Perl interpreter in debug mode to debug @var{file}, a Perl program.
376 @item M-x jdb @key{RET} @var{file} @key{RET}
378 Run the Java debugger to debug @var{file}.
380 @item M-x pdb @key{RET} @var{file} @key{RET}
382 Run the Python debugger to debug @var{file}.
385 Each of these commands takes one argument: a command line to invoke
386 the debugger. In the simplest case, specify just the name of the
387 executable file you want to debug. You may also use options that the
388 debugger supports. However, shell wildcards and variables are not
389 allowed. GUD assumes that the first argument not starting with a
390 @samp{-} is the executable file name.
392 Emacs can only run one debugger process at a time.
394 @node Debugger Operation
395 @subsection Debugger Operation
397 @cindex fringes, and current execution line in GUD
398 When you run a debugger with GUD, the debugger uses an Emacs buffer
399 for its ordinary input and output. This is called the GUD buffer. The
400 debugger displays the source files of the program by visiting them in
401 Emacs buffers. An arrow (@samp{=>}) in one of these buffers indicates
402 the current execution line.@footnote{Under a window system, the arrow
403 appears in the left fringe of the Emacs window.} Moving point in this
404 buffer does not move the arrow.
406 You can start editing these source files at any time in the buffers
407 that display them. The arrow is not part of the file's
408 text; it appears only on the screen. If you do modify a source file,
409 keep in mind that inserting or deleting lines will throw off the arrow's
410 positioning; GUD has no way of figuring out which line corresponded
411 before your changes to the line number in a debugger message. Also,
412 you'll typically have to recompile and restart the program for your
413 changes to be reflected in the debugger's tables.
415 If you wish, you can control your debugger process entirely through the
416 debugger buffer, which uses a variant of Shell mode. All the usual
417 commands for your debugger are available, and you can use the Shell mode
418 history commands to repeat them. @xref{Shell Mode}.
420 @node Commands of GUD
421 @subsection Commands of GUD
423 The GUD interaction buffer uses a variant of Shell mode, so the
424 commands of Shell mode are available (@pxref{Shell Mode}). GUD mode
425 also provides commands for setting and clearing breakpoints, for
426 selecting stack frames, and for stepping through the program. These
427 commands are available both in the GUD buffer and globally, but with
428 different key bindings. It also has its own toolbar from which you
429 can invoke the more common commands by clicking on the appropriate
430 icon. This is particularly useful for repetitive commands like
431 gud-next and gud-step and allows the user to hide the GUD buffer.
433 The breakpoint commands are normally used in source file buffers,
434 because that is the easiest way to specify where to set or clear the
435 breakpoint. Here's the global command to set a breakpoint:
440 Set a breakpoint on the source line that point is on.
443 @kindex C-x C-a @r{(GUD)}
444 Here are the other special commands provided by GUD. The keys
445 starting with @kbd{C-c} are available only in the GUD interaction
446 buffer. The key bindings that start with @kbd{C-x C-a} are available in
447 the GUD interaction buffer and also in source files.
451 @kindex C-c C-l @r{(GUD)}
454 Display in another window the last line referred to in the GUD
455 buffer (that is, the line indicated in the last location message).
456 This runs the command @code{gud-refresh}.
459 @kindex C-c C-s @r{(GUD)}
462 Execute a single line of code (@code{gud-step}). If the line contains
463 a function call, execution stops after entering the called function.
466 @kindex C-c C-n @r{(GUD)}
469 Execute a single line of code, stepping across entire function calls
470 at full speed (@code{gud-next}).
473 @kindex C-c C-i @r{(GUD)}
476 Execute a single machine instruction (@code{gud-stepi}).
480 @kindex C-c C-r @r{(GUD)}
483 Continue execution without specifying any stopping point. The program
484 will run until it hits a breakpoint, terminates, or gets a signal that
485 the debugger is checking for (@code{gud-cont}).
489 @kindex C-c C-d @r{(GUD)}
492 Delete the breakpoint(s) on the current source line, if any
493 (@code{gud-remove}). If you use this command in the GUD interaction
494 buffer, it applies to the line where the program last stopped.
497 @kindex C-c C-t @r{(GUD)}
500 Set a temporary breakpoint on the current source line, if any.
501 If you use this command in the GUD interaction buffer,
502 it applies to the line where the program last stopped.
505 The above commands are common to all supported debuggers. If you are
506 using GDB or (some versions of) DBX, these additional commands are available:
510 @kindex C-c < @r{(GUD)}
513 Select the next enclosing stack frame (@code{gud-up}). This is
514 equivalent to the @samp{up} command.
517 @kindex C-c > @r{(GUD)}
520 Select the next inner stack frame (@code{gud-down}). This is
521 equivalent to the @samp{down} command.
524 If you are using GDB, these additional key bindings are available:
528 @kindex C-c C-r @r{(GUD)}
531 Start execution of the program (@code{gud-run}).
534 @kindex C-c C-u @r{(GUD)}
537 Continue execution to the current line. The program will run until
538 it hits a breakpoint, terminates, gets a signal that the debugger is
539 checking for, or reaches the line on which the cursor currently sits
543 @kindex TAB @r{(GUD)}
544 @findex gud-gdb-complete-command
545 With GDB, complete a symbol name (@code{gud-gdb-complete-command}).
546 This key is available only in the GUD interaction buffer, and requires
547 GDB versions 4.13 and later.
550 @kindex C-c C-f @r{(GUD)}
553 Run the program until the selected stack frame returns (or until it
554 stops for some other reason).
557 @kindex C-x C-a C-j @r{(GUD)}
559 Only useful in a source buffer, (@code{gud-jump}) transfers the
560 program's execution point to the current line. In other words, the
561 next line that the program executes will be the one where you gave the
562 command. If the new execution line is in a different function from
563 the previously one, GDB prompts for confirmation since the results may
564 be bizarre. See the GDB manual entry regarding @code{jump} for
568 If you started GDB with the command @code{gdba}, you can click
569 @kbd{Mouse-1} on a line of the source buffer, in the fringe or display
570 margin, to set a breakpoint there. If a breakpoint already exists on
571 that line, this action will remove it.
572 (@code{gdb-mouse-toggle-breakpoint}).
574 These commands interpret a numeric argument as a repeat count, when
577 Because @key{TAB} serves as a completion command, you can't use it to
578 enter a tab as input to the program you are debugging with GDB.
579 Instead, type @kbd{C-q @key{TAB}} to enter a tab.
581 @node GUD Customization
582 @subsection GUD Customization
584 @vindex gdb-mode-hook
585 @vindex dbx-mode-hook
586 @vindex sdb-mode-hook
587 @vindex xdb-mode-hook
588 @vindex perldb-mode-hook
589 @vindex pdb-mode-hook
590 @vindex jdb-mode-hook
591 On startup, GUD runs one of the following hooks: @code{gdb-mode-hook},
592 if you are using GDB; @code{dbx-mode-hook}, if you are using DBX;
593 @code{sdb-mode-hook}, if you are using SDB; @code{xdb-mode-hook}, if you
594 are using XDB; @code{perldb-mode-hook}, for Perl debugging mode;
595 @code{pdb-mode-hook}, for PDB; @code{jdb-mode-hook}, for JDB. You can
596 use these hooks to define custom key bindings for the debugger
597 interaction buffer. @xref{Hooks}.
599 Here is a convenient way to define a command that sends a particular
600 command string to the debugger, and set up a key binding for it in the
601 debugger interaction buffer:
605 (gud-def @var{function} @var{cmdstring} @var{binding} @var{docstring})
608 This defines a command named @var{function} which sends
609 @var{cmdstring} to the debugger process, and gives it the documentation
610 string @var{docstring}. You can then use the command @var{function} in any
611 buffer. If @var{binding} is non-@code{nil}, @code{gud-def} also binds
612 the command to @kbd{C-c @var{binding}} in the GUD buffer's mode and to
613 @kbd{C-x C-a @var{binding}} generally.
615 The command string @var{cmdstring} may contain certain
616 @samp{%}-sequences that stand for data to be filled in at the time
617 @var{function} is called:
621 The name of the current source file. If the current buffer is the GUD
622 buffer, then the ``current source file'' is the file that the program
624 @c This said, ``the name of the file the program counter was in at the last breakpoint.''
625 @c But I suspect it is really the last stop file.
628 The number of the current source line. If the current buffer is the GUD
629 buffer, then the ``current source line'' is the line that the program
633 The text of the C lvalue or function-call expression at or adjacent to point.
636 The text of the hexadecimal address at or adjacent to point.
639 The numeric argument of the called function, as a decimal number. If
640 the command is used without a numeric argument, @samp{%p} stands for the
643 If you don't use @samp{%p} in the command string, the command you define
644 ignores any numeric argument.
648 @subsection GUD Tooltips
650 @cindex tooltips with GUD
651 The Tooltip facility (@pxref{Tooltips}) provides support for GUD@. If
652 GUD support is activated by customizing the @code{tooltip} group,
653 variable values can be displayed in tooltips by pointing at them with
654 the mouse in the GUD buffer or in source buffers with major modes in the
655 customizable list @code{tooltip-gud-modes}.
657 @node GDB Graphical Interface
658 @subsection GDB Graphical Interface
661 The command @code{gdba} starts GDB using a graphical interface where
662 you view and control the program's data using Emacs windows. You can
663 still interact with GDB through the GUD buffer, but the point of this
664 mode is that you can do it through menus and clicks, without needing
665 to know GDB commands.
668 * Layout:: Control the number of displayed buffers.
669 * Breakpoints Buffer:: A breakpoint control panel.
670 * Stack Buffer:: Select a frame from the call stack.
671 * Watch Expressions:: Monitor variable values in the speedbar.
672 * Other Buffers:: Input/output, locals, registers and assembler buffers.
676 @subsubsection Layout
677 @cindex GDB User Interface layout
679 @findex gdb-many-windows
680 @vindex gdb-many-windows
682 If the variable @code{gdb-many-windows} is @code{nil} (the default
683 value) then gdb just pops up the GUD buffer unless the variable
684 @code{gdb-show-main} is non-@code{nil}. In this case it starts with
685 two windows: one displaying the GUD buffer and the other with the
686 source file with the main routine of the inferior.
688 If @code{gdb-many-windows} is non-@code{nil}, regardless of the value of
689 @code{gdb-show-main}, the layout below will appear unless
690 @code{gdb-use-inferior-io-buffer} is @code{nil}. In this case the
691 source buffer occupies the full width of the frame.
693 @multitable @columnfractions .5 .5
694 @item GUD buffer (I/O of GDB)
699 @tab Input/Output (of inferior) buffer
703 @tab Breakpoints buffer
706 To toggle this layout, do @kbd{M-x gdb-many-windows}.
708 @findex gdb-restore-windows
709 If you change the window layout, for example, while editing and
710 re-compiling your program, then you can restore it with the command
711 @code{gdb-restore-windows}.
713 You may also choose which additional buffers you want to display,
714 either in the same frame or a different one. Select GDB-windows or
715 GDB-Frames from the menu-bar under the heading GUD. If the menu-bar
716 is unavailable, type @code{M-x
717 gdb-display-@var{buffertype}-buffer} or @code{M-x
718 gdb-frame-@var{buffertype}-buffer} respectively, where @var{buffertype}
719 is the relevant buffer type e.g breakpoints.
721 @node Breakpoints Buffer
722 @subsubsection Breakpoints Buffer
724 The breakpoints buffer shows the existing breakpoints and watchpoints
725 (@pxref{Breakpoints,,, gdb, The GNU debugger}). It has three special
730 @kindex SPC @r{(GDB breakpoints buffer)}
731 @findex gdb-toggle-breakpoint
732 Enable/disable the breakpoint at the current line
733 (@code{gdb-toggle-breakpoint}). On a graphical display, this changes
734 the color of a bullet in the margin of the source buffer at the
735 relevant line. This is red when the breakpoint is enabled and grey
736 when it is disabled. Text-only terminals correspondingly display
737 a @samp{B} or @samp{b}.
740 @kindex d @r{(GDB breakpoints buffer)}
741 @findex gdb-delete-breakpoint
742 Delete the breakpoint at the current line (@code{gdb-delete-breakpoint}).
745 @kindex RET @r{(GDB breakpoints buffer)}
746 @findex gdb-goto-breakpoint
747 Display the file in the source buffer at the breakpoint specified at
748 the current line (@code{gdb-goto-breakpoint}). Alternatively, click @kbd{Mouse-2} on the breakpoint that you wish to visit.
752 @subsubsection Stack Buffer
754 The stack buffer displays a @dfn{call stack}, with one line for each
755 of the nested subroutine calls (@dfn{stack frames}) now active in the
756 program. @xref{Backtrace,,info stack, gdb, The GNU debugger}.
758 Move point to any frame in the stack and type @key{RET} to make it
759 become the current frame (@code{gdb-frames-select}) and display the
760 associated source in the source buffer. Alternatively, click
761 @kbd{Mouse-2} to make the selected frame become the current one. If the
762 locals buffer is displayed then its contents update to display the
763 variables that are local to the new frame.
765 @node Watch Expressions
766 @subsubsection Watch Expressions
767 @cindex Watching expressions in GDB
769 If you want to see how a variable changes each time your program stops
770 then place the cursor over the variable name and click on the watch
771 icon in the toolbar (@code{gud-watch}).
773 Each watch expression is displayed in the speedbar. Complex data
774 types, such as arrays, structures and unions are represented in a tree
775 format. To expand or contract a complex data type, click @kbd{Mouse-2}
776 on the tag to the left of the expression.
778 @kindex RET @r{(GDB speedbar)}
779 @findex gdb-var-delete
780 With the cursor over the root expression of a complex data type, type
781 @kbd{D} to delete it from the speedbar
782 (@code{gdb-var-delete}).
784 @findex gdb-edit-value
785 With the cursor over a simple data type or an element of a complex
786 data type which holds a value, type @key{RET} or click @kbd{Mouse-2} to edit
787 its value. A prompt for a new value appears in the mini-buffer
788 (@code{gdb-edit-value}).
790 If you set the variable @code{gdb-show-changed-values} to
791 non-@code{nil} (the default value), then Emacs will use
792 font-lock-warning-face to display values that have recently changed in
795 If you set the variable @code{gdb-use-colon-colon-notation} to a
796 non-@code{nil} value, then, in C, Emacs will use the
797 FUNCTION::VARIABLE format to display variables in the speedbar.
798 Since this does not work for variables defined in compound statements,
799 the default value is @code{nil}.
802 @subsubsection Other Buffers
805 @item Input/Output Buffer
806 If the variable @code{gdb-use-inferior-io-buffer} is non-@code{nil},
807 the executable program that is being debugged takes its input and
808 displays its output here. Some of the commands from shell mode are
809 available here. @xref{Shell Mode}.
812 The locals buffer displays the values of local variables of the
813 current frame for simple data types (@pxref{Frame Info,,, gdb, The GNU
816 Arrays and structures display their type only. You must display them
817 separately to examine their values. @ref{Watch Expressions}.
819 @item Registers Buffer
820 The registers buffer displays the values held by the registers
821 (@pxref{Registers,,, gdb, The GNU debugger}).
823 @item Assembler Buffer
824 The assembler buffer displays the current frame as machine code. An
825 overlay arrow points to the current instruction and you can set and
826 remove breakpoints as with the source buffer. Breakpoints also
827 appear in the margin.
831 The threads buffer displays a summary of all threads currently in your
832 program.(@pxref{Threads,,, gdb, The GNU debugger}). Move point to
833 any thread in the list and type @key{RET} to make it become the
834 current thread (@code{gdb-threads-select}) and display the associated
835 source in the source buffer. Alternatively, click @kbd{Mouse-2} to
836 make the selected thread become the current one.
841 @section Executing Lisp Expressions
843 Emacs has several different major modes for Lisp and Scheme. They are
844 the same in terms of editing commands, but differ in the commands for
845 executing Lisp expressions. Each mode has its own purpose.
848 @item Emacs-Lisp mode
849 The mode for editing source files of programs to run in Emacs Lisp.
850 This mode defines @kbd{C-M-x} to evaluate the current defun.
851 @xref{Lisp Libraries}.
852 @item Lisp Interaction mode
853 The mode for an interactive session with Emacs Lisp. It defines
854 @kbd{C-j} to evaluate the sexp before point and insert its value in the
855 buffer. @xref{Lisp Interaction}.
857 The mode for editing source files of programs that run in Lisps other
858 than Emacs Lisp. This mode defines @kbd{C-M-x} to send the current defun
859 to an inferior Lisp process. @xref{External Lisp}.
860 @item Inferior Lisp mode
861 The mode for an interactive session with an inferior Lisp process.
862 This mode combines the special features of Lisp mode and Shell mode
863 (@pxref{Shell Mode}).
865 Like Lisp mode but for Scheme programs.
866 @item Inferior Scheme mode
867 The mode for an interactive session with an inferior Scheme process.
870 Most editing commands for working with Lisp programs are in fact
871 available globally. @xref{Programs}.
874 @section Libraries of Lisp Code for Emacs
876 @cindex loading Lisp code
878 Lisp code for Emacs editing commands is stored in files whose names
879 conventionally end in @file{.el}. This ending tells Emacs to edit them in
880 Emacs-Lisp mode (@pxref{Executing Lisp}).
883 To execute a file of Emacs Lisp code, use @kbd{M-x load-file}. This
884 command reads a file name using the minibuffer and then executes the
885 contents of that file as Lisp code. It is not necessary to visit the
886 file first; in any case, this command reads the file as found on disk,
887 not text in an Emacs buffer.
891 Once a file of Lisp code is installed in the Emacs Lisp library
892 directories, users can load it using @kbd{M-x load-library}. Programs can
893 load it by calling @code{load-library}, or with @code{load}, a more primitive
894 function that is similar but accepts some additional arguments.
896 @kbd{M-x load-library} differs from @kbd{M-x load-file} in that it
897 searches a sequence of directories and tries three file names in each
898 directory. Suppose your argument is @var{lib}; the three names are
899 @file{@var{lib}.elc}, @file{@var{lib}.el}, and lastly just
900 @file{@var{lib}}. If @file{@var{lib}.elc} exists, it is by convention
901 the result of compiling @file{@var{lib}.el}; it is better to load the
902 compiled file, since it will load and run faster.
904 If @code{load-library} finds that @file{@var{lib}.el} is newer than
905 @file{@var{lib}.elc} file, it issues a warning, because it's likely that
906 somebody made changes to the @file{.el} file and forgot to recompile
909 Because the argument to @code{load-library} is usually not in itself
910 a valid file name, file name completion is not available. Indeed, when
911 using this command, you usually do not know exactly what file name
915 The sequence of directories searched by @kbd{M-x load-library} is
916 specified by the variable @code{load-path}, a list of strings that are
917 directory names. The default value of the list contains the directory where
918 the Lisp code for Emacs itself is stored. If you have libraries of
919 your own, put them in a single directory and add that directory
920 to @code{load-path}. @code{nil} in this list stands for the current default
921 directory, but it is probably not a good idea to put @code{nil} in the
922 list. If you find yourself wishing that @code{nil} were in the list,
923 most likely what you really want to do is use @kbd{M-x load-file}
927 Often you do not have to give any command to load a library, because
928 the commands defined in the library are set up to @dfn{autoload} that
929 library. Trying to run any of those commands calls @code{load} to load
930 the library; this replaces the autoload definitions with the real ones
934 Emacs Lisp code can be compiled into byte-code which loads faster,
935 takes up less space when loaded, and executes faster. @xref{Byte
936 Compilation,, Byte Compilation, elisp, the Emacs Lisp Reference Manual}.
937 By convention, the compiled code for a library goes in a separate file
938 whose name consists of the library source file with @samp{c} appended.
939 Thus, the compiled code for @file{foo.el} goes in @file{foo.elc}.
940 That's why @code{load-library} searches for @samp{.elc} files first.
942 @vindex load-dangerous-libraries
943 @cindex Lisp files byte-compiled by XEmacs
944 By default, Emacs refuses to load compiled Lisp files which were
945 compiled with XEmacs, a modified versions of Emacs---they can cause
946 Emacs to crash. Set the variable @code{load-dangerous-libraries} to
947 @code{t} if you want to try loading them.
950 @section Evaluating Emacs-Lisp Expressions
951 @cindex Emacs-Lisp mode
952 @cindex mode, Emacs-Lisp
954 @findex emacs-lisp-mode
955 Lisp programs intended to be run in Emacs should be edited in
956 Emacs-Lisp mode; this happens automatically for file names ending in
957 @file{.el}. By contrast, Lisp mode itself is used for editing Lisp
958 programs intended for other Lisp systems. To switch to Emacs-Lisp mode
959 explicitly, use the command @kbd{M-x emacs-lisp-mode}.
961 For testing of Lisp programs to run in Emacs, it is often useful to
962 evaluate part of the program as it is found in the Emacs buffer. For
963 example, after changing the text of a Lisp function definition,
964 evaluating the definition installs the change for future calls to the
965 function. Evaluation of Lisp expressions is also useful in any kind of
966 editing, for invoking noninteractive functions (functions that are
971 Read a single Lisp expression in the minibuffer, evaluate it, and print
972 the value in the echo area (@code{eval-expression}).
974 Evaluate the Lisp expression before point, and print the value in the
975 echo area (@code{eval-last-sexp}).
977 Evaluate the defun containing or after point, and print the value in
978 the echo area (@code{eval-defun}).
979 @item M-x eval-region
980 Evaluate all the Lisp expressions in the region.
981 @item M-x eval-current-buffer
982 Evaluate all the Lisp expressions in the buffer.
986 @c This uses ``colon'' instead of a literal `:' because Info cannot
987 @c cope with a `:' in a menu
988 @kindex M-@key{colon}
993 @findex eval-expression
994 @kbd{M-:} (@code{eval-expression}) is the most basic command for evaluating
995 a Lisp expression interactively. It reads the expression using the
996 minibuffer, so you can execute any expression on a buffer regardless of
997 what the buffer contains. When the expression is evaluated, the current
998 buffer is once again the buffer that was current when @kbd{M-:} was
1001 @kindex C-M-x @r{(Emacs-Lisp mode)}
1003 In Emacs-Lisp mode, the key @kbd{C-M-x} is bound to the command
1004 @code{eval-defun}, which parses the defun containing or following point
1005 as a Lisp expression and evaluates it. The value is printed in the echo
1006 area. This command is convenient for installing in the Lisp environment
1007 changes that you have just made in the text of a function definition.
1009 @kbd{C-M-x} treats @code{defvar} expressions specially. Normally,
1010 evaluating a @code{defvar} expression does nothing if the variable it
1011 defines already has a value. But @kbd{C-M-x} unconditionally resets the
1012 variable to the initial value specified in the @code{defvar} expression.
1013 @code{defcustom} expressions are treated similarly.
1014 This special feature is convenient for debugging Lisp programs.
1015 Typing @kbd{C-M-x} on a @code{defface} expression reinitializes
1016 the face according to the @code{defface} specification.
1019 @findex eval-last-sexp
1020 The command @kbd{C-x C-e} (@code{eval-last-sexp}) evaluates the Lisp
1021 expression preceding point in the buffer, and displays the value in the
1022 echo area. It is available in all major modes, not just Emacs-Lisp
1023 mode. It does not treat @code{defvar} specially.
1025 If @kbd{C-M-x}, @kbd{C-x C-e}, or @kbd{M-:} is given a numeric
1026 argument, it inserts the value into the current buffer at point, rather
1027 than displaying it in the echo area. The argument's value does not
1031 @findex eval-current-buffer
1032 The most general command for evaluating Lisp expressions from a buffer
1033 is @code{eval-region}. @kbd{M-x eval-region} parses the text of the
1034 region as one or more Lisp expressions, evaluating them one by one.
1035 @kbd{M-x eval-current-buffer} is similar but evaluates the entire
1036 buffer. This is a reasonable way to install the contents of a file of
1037 Lisp code that you are ready to test. Later, as you find bugs and
1038 change individual functions, use @kbd{C-M-x} on each function that you
1039 change. This keeps the Lisp world in step with the source file.
1041 @vindex eval-expression-print-level
1042 @vindex eval-expression-print-length
1043 @vindex eval-expression-debug-on-error
1044 The customizable variables @code{eval-expression-print-level} and
1045 @code{eval-expression-print-length} control the maximum depth and length
1046 of lists to print in the result of the evaluation commands before
1047 abbreviating them. @code{eval-expression-debug-on-error} controls
1048 whether evaluation errors invoke the debugger when these commands are
1051 @node Lisp Interaction
1052 @section Lisp Interaction Buffers
1054 The buffer @samp{*scratch*} which is selected when Emacs starts up is
1055 provided for evaluating Lisp expressions interactively inside Emacs.
1057 The simplest way to use the @samp{*scratch*} buffer is to insert Lisp
1058 expressions and type @kbd{C-j} after each expression. This command
1059 reads the Lisp expression before point, evaluates it, and inserts the
1060 value in printed representation before point. The result is a complete
1061 typescript of the expressions you have evaluated and their values.
1063 The @samp{*scratch*} buffer's major mode is Lisp Interaction mode, which
1064 is the same as Emacs-Lisp mode except for the binding of @kbd{C-j}.
1066 @findex lisp-interaction-mode
1067 The rationale for this feature is that Emacs must have a buffer when
1068 it starts up, but that buffer is not useful for editing files since a
1069 new buffer is made for every file that you visit. The Lisp interpreter
1070 typescript is the most useful thing I can think of for the initial
1071 buffer to do. Type @kbd{M-x lisp-interaction-mode} to put the current
1072 buffer in Lisp Interaction mode.
1075 An alternative way of evaluating Emacs Lisp expressions interactively
1076 is to use Inferior Emacs-Lisp mode, which provides an interface rather
1077 like Shell mode (@pxref{Shell Mode}) for evaluating Emacs Lisp
1078 expressions. Type @kbd{M-x ielm} to create an @samp{*ielm*} buffer
1079 which uses this mode.
1082 @section Running an External Lisp
1084 Emacs has facilities for running programs in other Lisp systems. You can
1085 run a Lisp process as an inferior of Emacs, and pass expressions to it to
1086 be evaluated. You can also pass changed function definitions directly from
1087 the Emacs buffers in which you edit the Lisp programs to the inferior Lisp
1091 @vindex inferior-lisp-program
1093 To run an inferior Lisp process, type @kbd{M-x run-lisp}. This runs
1094 the program named @code{lisp}, the same program you would run by typing
1095 @code{lisp} as a shell command, with both input and output going through
1096 an Emacs buffer named @samp{*lisp*}. That is to say, any ``terminal
1097 output'' from Lisp will go into the buffer, advancing point, and any
1098 ``terminal input'' for Lisp comes from text in the buffer. (You can
1099 change the name of the Lisp executable file by setting the variable
1100 @code{inferior-lisp-program}.)
1102 To give input to Lisp, go to the end of the buffer and type the input,
1103 terminated by @key{RET}. The @samp{*lisp*} buffer is in Inferior Lisp
1104 mode, which combines the special characteristics of Lisp mode with most
1105 of the features of Shell mode (@pxref{Shell Mode}). The definition of
1106 @key{RET} to send a line to a subprocess is one of the features of Shell
1110 For the source files of programs to run in external Lisps, use Lisp
1111 mode. This mode can be selected with @kbd{M-x lisp-mode}, and is used
1112 automatically for files whose names end in @file{.l}, @file{.lsp}, or
1113 @file{.lisp}, as most Lisp systems usually expect.
1115 @kindex C-M-x @r{(Lisp mode)}
1116 @findex lisp-eval-defun
1117 When you edit a function in a Lisp program you are running, the easiest
1118 way to send the changed definition to the inferior Lisp process is the key
1119 @kbd{C-M-x}. In Lisp mode, this runs the function @code{lisp-eval-defun},
1120 which finds the defun around or following point and sends it as input to
1121 the Lisp process. (Emacs can send input to any inferior process regardless
1122 of what buffer is current.)
1124 Contrast the meanings of @kbd{C-M-x} in Lisp mode (for editing programs
1125 to be run in another Lisp system) and Emacs-Lisp mode (for editing Lisp
1126 programs to be run in Emacs): in both modes it has the effect of installing
1127 the function definition that point is in, but the way of doing so is
1128 different according to where the relevant Lisp environment is found.
1129 @xref{Executing Lisp}.
1132 arch-tag: 9c3c2f71-b332-4144-8500-3ff9945a50ed