@c -*-texinfo-*-
@c This is part of the GNU Emacs Lisp Reference Manual.
-@c Copyright (C) 1990, 1991, 1992, 1993, 1994, 1995, 1998, 1999,
-@c 2000, 2003, 2004
-@c Free Software Foundation, Inc.
+@c Copyright (C) 1990, 1991, 1992, 1993, 1994, 1995, 1998, 1999, 2000, 2002,
+@c 2003, 2004, 2005, 2006 Free Software Foundation, Inc.
@c See the file elisp.texi for copying conditions.
@setfilename ../info/variables
@node Variables, Functions, Control Structures, Top
@code{max-lisp-eval-depth} provides another limit on depth of nesting.
@xref{Definition of max-lisp-eval-depth,, Eval}.
-The default value is 600. Entry to the Lisp debugger increases the
+The default value is 1000. Entry to the Lisp debugger increases the
value, if there is little room left, to make sure the debugger itself
has room to execute.
@end defvar
declared equivalently in @file{cus-start.el}.} or by the first character
of their @code{variable-documentation} property. If the property exists
and is a string, and its first character is @samp{*}, then the variable
-is a user option.
+is a user option. Aliases of user options are also user options.
@end defun
@kindex variable-interactive
position specified by @var{order}. If @var{element} is already a
member of the list, its position in the list is adjusted according
to @var{order}. Membership is tested using @code{eq}.
-The valued returned is the resulting list, whether updated or not.
+This function returns the resulting list, whether updated or not.
-The @var{order} is a number, and the elements on list are sorted in
-increasing numerical order. Elements without a numeric list order are
-placed at the end of @var{symbol}.
+The @var{order} is typically a number (integer or float), and the
+elements of the list are sorted in non-decreasing numerical order.
+
+@var{order} may also be omitted or @code{nil}. Then the numeric order
+of @var{element} stays unchanged if it already has one; otherwise,
+@var{element} has no numeric order. Elements without a numeric list
+order are placed at the end of the list, in no particular order.
+
+Any other value for @var{order} removes the numeric order of @var{element}
+if it already has one; otherwise, it is equivalent to @code{nil}.
The argument @var{symbol} is not implicitly quoted;
@code{add-to-ordered-list} is an ordinary function, like @code{set}
and unlike @code{setq}. Quote the argument yourself if that is what
you want.
-The ordering information is stored in an alist on @var{symbol}'s
+The ordering information is stored in a hash table on @var{symbol}'s
@code{list-order} property.
@end defun
(add-to-ordered-list 'foo 'd) ;; @r{Append @code{d}.}
@result{} (a c b d)
-(add-to-ordered-list 'foo 'b 2) ;; @r{Move @code{b}.}
- @result{} (a b c d)
+(add-to-ordered-list 'foo 'e) ;; @r{Add @code{e}}.
+ @result{} (a c b e d)
foo ;; @r{@code{foo} was changed.}
- @result{} (a b c d)
+ @result{} (a c b e d)
@end example
@node Variable Scoping
If the variable is terminal-local, this function signals an error,
because such variables cannot have frame-local bindings as well.
@xref{Multiple Displays}. A few variables that are implemented
-specially in Emacs can be (and usually are) buffer-local, but can never
-be frame-local.
+specially in Emacs can be buffer-local, but can never be frame-local.
This command returns @var{variable}.
@end deffn
@defopt enable-local-variables
This variable controls whether to process file local variables. A
-value of @code{t} means process them unconditionally; @code{nil} means
-ignore them; anything else means ask the user what to do for each
-file. The default value is @code{t}.
+value of @code{t} means to process them, querying the user if unsafe
+variables are encountered; @code{nil} means ignore them; anything else
+means to query the user for each file. The default value is @code{t}.
@end defopt
@defun hack-local-variables &optional mode-only
If a file local variable could specify a function that would
be called later, or an expression that would be executed later, simply
-visiting a file could take over your Emacs. To prevent this, Emacs
-takes care not to allow to set such file local variables.
+visiting a file could take over your Emacs. Emacs takes several
+measures to prevent this.
+
+@cindex safe local variable
+ You can specify safe values for a variable with a
+@code{safe-local-variable} property. The property has to be
+a function of one argument; any value is safe if the function
+returns non-@code{nil} given that value. Many commonly encountered
+file variables standardly have @code{safe-local-variable} properties,
+including @code{fill-column}, @code{fill-prefix}, and
+@code{indent-tabs-mode}. For boolean-valued variables that are safe,
+use @code{booleanp} as the property value.
+
+@defopt safe-local-variable-values
+This variable provides another way to mark some variable values as
+safe. It is a list of cons cells @code{(@var{var} . @var{val})},
+where @var{var} is a variable name and @var{val} is a value which is
+safe for that variable.
+
+When Emacs asks the user whether or not to obey a set of file local
+variable specifications, the user can choose to mark them as safe.
+Doing so adds those variable/value pairs to
+@code{safe-local-variable-values}, and saves it to the user's custom
+file.
+@end defopt
+
+@defun safe-local-variable-p sym val
+This function returns non-@code{nil} if it is safe to give @var{sym}
+the value @var{val}, based on the above criteria.
+@end defun
- For one thing, any variable whose name ends in any of
-@samp{-command}, @samp{-frame-alist}, @samp{-function},
+@cindex risky local variable
+ Some variables are considered @dfn{risky}. A variable whose name
+ends in any of @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 given a file local
-value. 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} followed by a
-digit, and @samp{font-lock-syntactic-keywords} cannot be given file
-local values either. These rules can be overridden by giving the
-variable's name a non-@code{nil} @code{safe-local-variable} property.
-If one gives it a @code{safe-local-variable} property of @code{t},
-then one can give the variable any file local value. One can also
-give any symbol, including the above, a @code{safe-local-variable}
-property that is a function taking exactly one argument. In that
-case, giving a variable with that name a file local value is only
-allowed if the function returns non-@code{nil} when called with that
-value as argument.
-
- 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}:
+@samp{-program}, or @samp{-predicate} is considered risky. The
+variables @samp{font-lock-keywords}, @samp{font-lock-keywords}
+followed by a digit, and @samp{font-lock-syntactic-keywords} are also
+considered risky. Finally, any variable whose name has a
+non-@code{nil} @code{risky-local-variable} property is considered
+risky.
+
+@defun risky-local-variable-p sym
+This function returns non-@code{nil} if @var{sym} is a risky variable,
+based on the above criteria.
+@end defun
+
+ If a variable is risky, it will not be entered automatically into
+@code{safe-local-variable-values} as described above. Therefore,
+Emacs will always query before setting a risky variable, unless the
+user explicitly allows the setting by customizing
+@code{safe-local-variable-values} directly.
@defvar ignored-local-variables
This variable holds a list of variables that should not be given local
values by files. Any value specified for one of these variables is
-ignored.
+completely ignored.
@end defvar
-@defun risky-local-variable-p sym &optional val
-If @var{val} is non-@code{nil}, returns non-@code{nil} if giving
-@var{sym} a file local value of @var{val} would be risky, for any of
-the reasons stated above. If @var{val} is @code{nil} or omitted, only
-returns @code{nil} if @var{sym} can be safely assigned any file local
-value whatsoever.
-@end defun
-
The @samp{Eval:} ``variable'' is also a potential loophole, so Emacs
normally asks for confirmation before handling it.