@c -*-texinfo-*-
@c This is part of the GNU Emacs Lisp Reference Manual.
-@c Copyright (C) 1990, 1991, 1992, 1993, 1994 Free Software Foundation, Inc.
+@c Copyright (C) 1990, 1991, 1992, 1993, 1994, 2002, 2003, 2004,
+@c 2005 Free Software Foundation, Inc.
@c See the file elisp.texi for copying conditions.
@setfilename ../info/compile
-@node Byte Compilation, Advising, Loading, Top
+@node Byte Compilation, Advising Functions, Loading, Top
@chapter Byte Compilation
@cindex byte-code
@cindex compilation
transportable from machine to machine without recompilation. It is not,
however, as fast as true compiled code.
+ Compiling a Lisp file with the Emacs byte compiler always reads the
+file as multibyte text, even if Emacs was started with @samp{--unibyte},
+unless the file specifies otherwise. This is so that compilation gives
+results compatible with running the same file without compilation.
+@xref{Loading Non-ASCII}.
+
In general, any version of Emacs can run byte-compiled code produced
-by recent earlier versions of Emacs, but the reverse is not true. A
-major incompatible change was introduced in Emacs version 19.29, and
-files compiled with versions since that one will definitely not run
-in earlier versions unless you specify a special option.
-@iftex
-@xref{Docs and Compilation}.
-@end iftex
-In addition, the modifier bits in keyboard characters were renumbered in
-Emacs 19.29; as a result, files compiled in versions before 19.29 will
-not work in subsequent versions if they contain character constants with
-modifier bits.
+by recent earlier versions of Emacs, but the reverse is not true.
+
+@vindex no-byte-compile
+ If you do not want a Lisp file to be compiled, ever, put a file-local
+variable binding for @code{no-byte-compile} into it, like this:
+
+@example
+;; -*-no-byte-compile: t; -*-
+@end example
@xref{Compilation Errors}, for how to investigate errors occurring in
byte compilation.
* Docs and Compilation:: Dynamic loading of documentation strings.
* Dynamic Loading:: Dynamic loading of individual functions.
* Eval During Compile:: Code to be evaluated when you compile.
+* Compiler Errors:: Handling compiler error messages.
* Byte-Code Objects:: The data type used for byte-compiled functions.
* Disassembly:: Disassembling byte-code; how to read byte-code.
@end menu
(defun silly-loop (n)
"Return time before and after N iterations of a loop."
(let ((t1 (current-time-string)))
- (while (> (setq n (1- n))
+ (while (> (setq n (1- n))
0))
(list t1 (current-time-string))))
@result{} silly-loop
Be careful when writing macro calls in files that you may someday
byte-compile. Macro calls are expanded when they are compiled, so the
macros must already be defined for proper compilation. For more
-details, see @ref{Compiling Macros}.
+details, see @ref{Compiling Macros}. If a program does not work the
+same way when compiled as it does when interpreted, erroneous macro
+definitions are one likely cause (@pxref{Problems with Macros}).
+Inline (@code{defsubst}) functions are less troublesome; if you
+compile a call to such a function before its definition is known, the
+call will still work right, it will just run slower.
Normally, compiling a file does not evaluate the file's contents or
load the file. But it does execute any @code{require} calls at top
operand of an instruction. The vector contains all the constants,
variable names and function names used by the function, except for
certain primitives that are coded as special instructions.
+
+If the argument to @code{byte-compile} is a @code{lambda} expression,
+it returns the corresponding compiled code, but does not store
+it anywhere.
@end defun
-@deffn Command compile-defun
+@deffn Command compile-defun &optional arg
This command reads the defun containing point, compiles it, and
evaluates the result. If you use this on a defun that is actually a
function definition, the effect is to install a compiled version of that
function.
+
+@code{compile-defun} normally displays the result of evaluation in the
+echo area, but if @var{arg} is non-@code{nil}, it inserts the result
+in the current buffer after the form it compiled.
@end deffn
-@deffn Command byte-compile-file filename
-This function compiles a file of Lisp code named @var{filename} into
-a file of byte-code. The output file's name is made by appending
-@samp{c} to the end of @var{filename}.
+@deffn Command byte-compile-file filename &optional load
+This function compiles a file of Lisp code named @var{filename} into a
+file of byte-code. The output file's name is made by changing the
+@samp{.el} suffix into @samp{.elc}; if @var{filename} does not end in
+@samp{.el}, it adds @samp{.elc} to the end of @var{filename}.
Compilation works by reading the input file one form at a time. If it
is a definition of a function or macro, the compiled function or macro
executed when the file is read. All comments are discarded when the
input file is read.
-This command returns @code{t}. When called interactively, it prompts
-for the file name.
+This command returns @code{t} if there were no errors and @code{nil}
+otherwise. When called interactively, it prompts for the file name.
+
+If @var{load} is non-@code{nil}, this command loads the compiled file
+after compiling it. Interactively, @var{load} is the prefix argument.
@example
@group
@end example
@end deffn
-@deffn Command byte-recompile-directory directory flag
+@deffn Command byte-recompile-directory directory &optional flag force
@cindex library compilation
-This function recompiles every @samp{.el} file in @var{directory} that
-needs recompilation. A file needs recompilation if a @samp{.elc} file
-exists but is older than the @samp{.el} file.
+This command recompiles every @samp{.el} file in @var{directory} (or
+its subdirectories) that needs recompilation. A file needs
+recompilation if a @samp{.elc} file exists but is older than the
+@samp{.el} file.
+
+When a @samp{.el} file has no corresponding @samp{.elc} file,
+@var{flag} says what to do. If it is @code{nil}, this command ignores
+these files. If @var{flag} is 0, it compiles them. If it is neither
+@code{nil} nor 0, it asks the user whether to compile each such file,
+and asks about each subdirectory as well.
-When a @samp{.el} file has no corresponding @samp{.elc} file, @var{flag}
-says what to do. If it is @code{nil}, these files are ignored. If it
-is non-@code{nil}, the user is asked whether to compile each such file.
+Interactively, @code{byte-recompile-directory} prompts for
+@var{directory} and @var{flag} is the prefix argument.
-The returned value of this command is unpredictable.
+If @var{force} is non-@code{nil}, this command recompiles every
+@samp{.el} file that has a @samp{.elc} file.
+
+The returned value is unpredictable.
@end deffn
-@defun batch-byte-compile
+@defun batch-byte-compile &optional noforce
This function runs @code{byte-compile-file} on files specified on the
command line. This function must be used only in a batch execution of
Emacs, as it kills Emacs on completion. An error in one file does not
generated for it, and the Emacs process will terminate with a nonzero
status code.
+If @var{noforce} is non-@code{nil}, this function does not recompile
+files that have an up-to-date @samp{.elc} file.
+
@example
% emacs -batch -f batch-byte-compile *.el
@end example
@item
If you alter the compiled file (such as by compiling a new version),
-then further access to documentation strings in this file will give
-nonsense results.
+then further access to documentation strings in this file will
+probably give nonsense results.
@end itemize
If your site installs Emacs following the usual procedures, these
occasionally if you edit and recompile Lisp files. When it happens, you
can cure the problem by reloading the file after recompiling it.
- Byte-compiled files made with recent versions of Emacs (since 19.29)
-will not load into older versions because the older versions don't
-support this feature. You can turn off this feature at compile time by
-setting @code{byte-compile-dynamic-docstrings} to @code{nil}; then you
-can compile files that will load into older Emacs versions. You can do
-this globally, or for one source file by specifying a file-local binding
-for the variable. One way to do that is by adding this string to the
-file's first line:
+ You can turn off this feature at compile time by setting
+@code{byte-compile-dynamic-docstrings} to @code{nil}; this is useful
+mainly if you expect to change the file, and you want Emacs processes
+that have already loaded it to keep working when the file changes.
+You can do this globally, or for one source file by specifying a
+file-local binding for the variable. One way to do that is by adding
+this string to the file's first line:
@example
-*-byte-compile-dynamic-docstrings: nil;-*-
@item
If you alter the compiled file (such as by compiling a new version),
-then trying to load any function not already loaded will yield nonsense
-results.
+then trying to load any function not already loaded will usually yield
+nonsense results.
@end itemize
These problems will never happen in normal circumstances with
@end defvar
@defun fetch-bytecode function
-This immediately finishes loading the definition of @var{function} from
-its byte-compiled file, if it is not fully loaded already. The argument
-@var{function} may be a byte-code function object or a function name.
+If @var{function} is a byte-code function object, this immediately
+finishes loading the byte code of @var{function} from its
+byte-compiled file, if it is not fully loaded already. Otherwise,
+it does nothing. It always returns @var{function}.
@end defun
@node Eval During Compile
These features permit you to write code to be evaluated during
compilation of a program.
-@defspec eval-and-compile body
+@defspec eval-and-compile body@dots{}
This form marks @var{body} to be evaluated both when you compile the
containing code and when you run it (whether compiled or not).
preferable when @var{body} is large.
@end defspec
-@defspec eval-when-compile body
+@defspec eval-when-compile body@dots{}
This form marks @var{body} to be evaluated at compile time but not when
the compiled program is loaded. The result of evaluation by the
compiler becomes a constant which appears in the compiled program. If
to what @code{eval-when-compile} does.
@end defspec
+@node Compiler Errors
+@section Compiler Errors
+@cindex compiler errors
+
+ Byte compilation outputs all errors and warnings into the buffer
+@samp{*Compile-Log*}. The messages include file names and line
+numbers that identify the location of the problem. The usual Emacs
+commands for operating on compiler diagnostics work properly on
+these messages.
+
+ However, the warnings about functions that were used but not
+defined are always ``located'' at the end of the file, so these
+commands won't find the places they are really used. To do that,
+you must search for the function names.
+
+ You can suppress the compiler warning for calling an undefined
+function @var{func} by conditionalizing the function call on an
+@code{fboundp} test, like this:
+
+@example
+(if (fboundp '@var{func}) ...(@var{func} ...)...)
+@end example
+
+@noindent
+The call to @var{func} must be in the @var{then-form} of the
+@code{if}, and @var{func} must appear quoted in the call to
+@code{fboundp}. (This feature operates for @code{cond} as well.)
+
+ Likewise, you can suppress a compiler warning for an unbound variable
+@var{variable} by conditionalizing its use on a @code{boundp} test,
+like this:
+
+@example
+(if (boundp '@var{variable}) ...@var{variable}...)
+@end example
+
+@noindent
+The reference to @var{variable} must be in the @var{then-form} of the
+@code{if}, and @var{variable} must appear quoted in the call to
+@code{boundp}.
+
+ You can suppress any compiler warnings using the construct
+@code{with-no-warnings}:
+
+@c This is implemented with a defun, but conceptually it is
+@c a special form.
+
+@defspec with-no-warnings body@dots{}
+In execution, this is equivalent to @code{(progn @var{body}...)},
+but the compiler does not issue warnings for anything that occurs
+inside @var{body}.
+
+We recommend that you use this construct around the smallest
+possible piece of code.
+@end defspec
+
@node Byte-Code Objects
@section Byte-Code Function Objects
@cindex compiled function
ordinary Lisp variables, by transferring values between variables and
the stack.
-@deffn Command disassemble object &optional stream
-This function prints the disassembled code for @var{object}. If
-@var{stream} is supplied, then output goes there. Otherwise, the
-disassembled code is printed to the stream @code{standard-output}. The
-argument @var{object} can be a function name or a lambda expression.
-
-As a special exception, if this function is used interactively,
-it outputs to a buffer named @samp{*Disassemble*}.
+@deffn Command disassemble object &optional buffer-or-name
+This command displays the disassembled code for @var{object}. In
+interactive use, or if @var{buffer-or-name} is @code{nil} or omitted,
+the output goes in a buffer named @samp{*Disassemble*}. If
+@var{buffer-or-name} is non-@code{nil}, it must be a buffer or the
+name of an existing buffer. Then the output goes there, at point, and
+point is left before the output.
+
+The argument @var{object} can be a function name, a lambda expression
+or a byte-code object. If it is a lambda expression, @code{disassemble}
+compiles it and disassembles the resulting compiled code.
@end deffn
Here are two examples of using the @code{disassemble} function. We
@group
0 constant 1 ; @r{Push 1 onto stack.}
-1 varref integer ; @r{Get value of @code{integer}}
+1 varref integer ; @r{Get value of @code{integer}}
; @r{from the environment}
; @r{and push the value}
; @r{onto the stack.}
@group
; @r{Stack now contains:}
; @minus{} @r{decremented value of @code{integer}}
- ; @minus{} @r{@code{factorial}}
+ ; @minus{} @r{@code{factorial}}
; @minus{} @r{value of @code{integer}}
; @minus{} @r{@code{*}}
@end group
(defun silly-loop (n)
"Return time before and after N iterations of a loop."
(let ((t1 (current-time-string)))
- (while (> (setq n (1- n))
+ (while (> (setq n (1- n))
0))
(list t1 (current-time-string))))
@result{} silly-loop
@end group
@group
-19 constant current-time-string ; @r{Push}
+19 constant current-time-string ; @r{Push}
; @r{@code{current-time-string}}
; @r{onto top of stack.}
@end group
@end example
+@ignore
+ arch-tag: f78e3050-2f0a-4dee-be27-d9979a0a2289
+@end ignore