with @code{setq-default}.
@strong{Warning:} When a variable has buffer-local values in one or
-more buffers, you can get Emacs very confused by binding the variable
-with @code{let}, changing to a different current buffer in which a
-different binding is in effect, and then exiting the @code{let}. This
-can scramble the values of the buffer-local and default bindings.
+more buffers, binding the variable with @code{let} and changing to a
+different current buffer in which a different binding is in
+effect, and then exiting the @code{let}, the variable may not be
+restored to the value it had before the @code{let}.
To preserve your sanity, avoid using a variable in that way. If you
use @code{save-excursion} around each piece of code that changes to a
@example
@group
-(setq foo 'b)
+(setq foo 'g)
(set-buffer "a")
(make-local-variable 'foo)
@end group
(setq foo 'a)
(let ((foo 'temp))
+ ;; foo @result{} 'temp ; @r{let binding in buffer @samp{a}}
(set-buffer "b")
+ ;; foo @result{} 'g ; @r{the global value since foo is not local in @samp{b}}
@var{body}@dots{})
@group
-foo @result{} 'a ; @r{The old buffer-local value from buffer @samp{a}}
- ; @r{is now the default value.}
+foo @result{} 'a ; @r{we are still in buffer @samp{b}, but exiting the let}
+ ; @r{restored the local value in buffer @samp{a}}
@end group
@group
-(set-buffer "a")
-foo @result{} 'temp ; @r{The local @code{let} value that should be gone}
- ; @r{is now the buffer-local value in buffer @samp{a}.}
+(set-buffer "a") ; @r{This can be seen here:}
+foo @result{} 'a ; @r{we are back to the local value in buffer @samp{a}}
@end group
@end example
to keep the old name as an @emph{alias} of the new one for
compatibility. You can do this with @code{defvaralias}.
-@defmac defvaralias alias-var base-var
+@defun defvaralias alias-var base-var [docstring]
This function defines the symbol @var{alias-var} as a variable alias
-for symbol @var{base-var}. This means that retrieving the value of
+for symbol @var{base-var}. This means that retrieving the value of
@var{alias-var} returns the value of @var{base-var}, and changing the
value of @var{alias-var} changes the value of @var{base-var}.
-@end defmac
+
+If the @var{docstring} argument is present, it specifies the documentation for
+@var{alias-var}; otherwise, it has the same documentation as @var{base-var},
+if any.
+@end defun
@defun indirect-variable variable
This function returns the variable at the end of the chain of aliases
visiting a file could take over your Emacs. To prevent this, Emacs
takes care not to allow local variable lists to set such variables.
- For one thing, any variable whose name ends in @samp{-function},
-@samp{-functions}, @samp{-hook}, @samp{-hooks}, @samp{-form},
-@samp{-forms}, @samp{-program}, @samp{-command} or @samp{-predicate}
-cannot be set in a local variable list. In general, you should use such
-a name whenever it is appropriate for the variable's meaning.
+ For one thing, any variable whose name ends in @samp{-command},
+@samp{-frame-alist}, @samp{-function}, @samp{-functions},
+@samp{-hook}, @samp{-hooks}, @samp{-form}, @samp{-forms}, @samp{-map},
+@samp{-map-alist}, @samp{-mode-alist}, @samp{-program}, or
+@samp{-predicate} cannot be set in a local variable list. In general,
+you should use such a name whenever it is appropriate for the
+variable's meaning. The variables @samp{font-lock-keywords},
+@samp{font-lock-keywords-[0-9]}, and
+@samp{font-lock-syntactic-keywords} cannot be set in a local variable
+list, either.
In addition, any variable whose name has a non-@code{nil}
-@code{risky-local-variable} property is also ignored. So are
-all variables listed in @code{ignored-local-variables}:
+@code{risky-local-variable} property is also ignored. So are all
+variables listed in @code{ignored-local-variables}:
@defvar ignored-local-variables
This variable holds a list of variables that should not be
for one of these variables is ignored.
@end defvar
+@defun risky-local-variable-p sym
+Returns non-nil if @var{sym} is risky for any of the reasons stated above.
+@end defun
+
The @samp{Eval:} ``variable'' is also a potential loophole, so Emacs
normally asks for confirmation before handling it.