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Warning: this node is a quick draft based on docstrings. There may be inaccuracies, as the docstrings occasionally disagree with each other. This has not been checked yet.
The byte compiler and optimizer are controlled by the following
variables. The byte-compiler-options
macro described below
provides a convenient way to set most of them on a file-by-file basis.
Regexp which matches Emacs Lisp source files.
You may want to redefine byte-compile-dest-file
if you change
this. Default: "\\.el$"
.
Convert an Emacs Lisp source file name to a compiled file name. This
function may be redefined by the user, if necessary, for compatibility
with emacs-lisp-file-regexp
.
When non-nil
, print messages describing progress of
byte-compiler. Default: t
if interactive on a not-too-slow
terminal (see search-slow-speed
), otherwise nil
.
Level of optimization in the byte compiler.
nil
Do no optimization.
t
Do all optimizations.
source
Do optimizations manipulating the source code only.
byte
Do optimizations manipulating the byte code (actually, LAP code) only.
Default: t
.
When non-nil
, the optimizer may delete forms that may signal an
error if that is the only change in the function’s behavior.
This includes variable references and calls to functions such as
car
.
Default: t
.
When non-nil
, the byte-compiler logs optimizations into
*Compile-Log*.
nil
Log no optimization.
t
Log all optimizations.
source
Log optimizations manipulating the source code only.
byte
Log optimizations manipulating the byte code (actually, LAP code) only.
Default: nil
.
When non-nil
, the byte-compiler reports warnings with error
.
Default: nil
.
The warnings used when byte-compile-warnings
is t
. Called
byte-compile-warning-types
in GNU Emacs.
Default: (redefine callargs subr-callargs free-vars unresolved
unused-vars obsolete)
.
List of warnings that the compiler should issue (t
for the
default set). Elements of the list may be:
free-vars
References to variables not in the current lexical scope.
unused-vars
References to non-global variables bound but not referenced.
unresolved
Calls to unknown functions.
callargs
Lambda calls with args that don’t match the definition.
subr-callargs
Calls to subrs with args that don’t match the definition.
redefine
Function cell redefined from a macro to a lambda or vice versa, or redefined to take a different number of arguments.
obsolete
Use of an obsolete function or variable.
pedantic
Warn of use of compatible symbols.
The default set is specified by byte-compile-default-warnings
and
normally encompasses all possible warnings.
See also the macro byte-compiler-options
. Default: t
.
The compiler can generate a call graph, which gives information about which functions call which functions.
When non-nil
, the compiler generates a call graph. This records
functions that were called and from where. If the value is t
,
compilation displays the call graph when it finishes. If the value is
neither t
nor nil
, compilation asks you whether to display
the graph.
The call tree only lists functions called, not macros used. Those
functions which the byte-code interpreter knows about directly
(eq
, cons
, etc.) are not reported.
The call tree also lists those functions which are not known to be called
(that is, to which no calls have been compiled). Functions which can be
invoked interactively are excluded from this list. Default: nil
.
Alist of functions and their call tree, used internally. Each element takes the form
(function callers calls)
where callers is a list of functions that call function, and calls is a list of functions for which calls were generated while compiling function.
When non-nil
, sort the call tree. The values name
,
callers
, calls
, and calls+callers
specify different
fields to sort on.") Default: name
.
byte-compile-overwrite-file
controls treatment of existing
compiled files.
When non-nil
, do not preserve backups of .elcs.
Precisely, if nil
, old .elc files are deleted before the
new one is saved, and .elc files will have the same modes as the
corresponding .el file. Otherwise, existing .elc files
will simply be overwritten, and the existing modes will not be changed.
If this variable is nil
, then an .elc file which is a
symbolic link will be turned into a normal file, instead of the file
which the link points to being overwritten. Default: t
.
Variables controlling recompiling directories are described elsewhere
See Compilation Functions. They are
byte-recompile-directory-ignore-errors-p
and
byte-recompile-directory-recursively
.
The dynamic loading features are described elsewhere. These are
controlled by the variables byte-compile-dynamic
(see Dynamic Loading) and byte-compile-dynamic-docstrings
(see Docs and Compilation).
The byte compiler is a relatively recent development, and has evolved significantly over the period covering Emacs versions 19 and 20. The following variables control use of newer functionality by the byte compiler. These are rarely needed since the release of SXEmacs 22.
Another set of compatibility issues arises between Mule and non-Mule SXEmacsen; there are no known compatibility issues specific to the byte compiler. There are also compatibility issues between SXEmacs and GNU Emacs’s versions of the byte compiler. While almost all of the byte codes are the same, and code compiled by one version often runs perfectly well on the other, this is very dangerous, and can result in crashes or data loss. Always recompile your Lisp when moving between SXEmacs, XEmacs and GNU Emacs.
When non-nil
generate output that can run in Emacs 19.
Default: nil
When non-nil
, the compiler may generate code that creates unique
symbols at run-time. This is achieved by printing uninterned symbols
using the #:
notation, so that they will be read uninterned
when run.
Default: When byte-compile-emacs19-compatibility
is non-nil, this
variable is ignored and considered to be nil
. Otherwise
t
.
This is completely ignored. For backwards compatibility.
Set some compilation-parameters for this file. This will affect only the file in which it appears; this does nothing when evaluated, or when loaded from a .el file.
Each argument to this macro must be a list of a key and a value. (#### Need to check whether the newer variables are settable here.)
Keys: Values: Corresponding variable: verbose t, nil byte-compile-verbose optimize t, nil, source, byte byte-optimize warnings list of warnings byte-compile-warnings file-format emacs19, emacs20 byte-compile-emacs19-compatibility
The value specified with the warnings
option must be a list,
containing some subset of the following flags:
free-vars references to variables not in the current lexical scope. unused-vars references to non-global variables bound but not referenced. unresolved calls to unknown functions. callargs lambda calls with args that don't match the definition. redefine function cell redefined from a macro to a lambda or vice versa, or redefined to take a different number of arguments.
If the first element if the list is +
or ‘ then the
specified elements are added to or removed from the current set of
warnings, instead of the entire set of warnings being overwritten.
(#### Need to check whether the newer warnings are settable here.)
For example, something like this might appear at the top of a source file:
(byte-compiler-options (optimize t) (warnings (- callargs)) ; Don't warn about arglist mismatch (warnings (+ unused-vars)) ; Do warn about unused bindings (file-format emacs19))
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