@c -*-texinfo-*-
@c This is part of the GNU Emacs Lisp Reference Manual.
-@c Copyright (C) 1990, 1991, 1992, 1993, 1994, 1995, 1998, 1999, 2000
-@c Free Software Foundation, Inc.
+@c Copyright (C) 1990, 1991, 1992, 1993, 1994, 1995, 1998, 1999, 2000,
+@c 2001, 2002, 2003, 2004, 2005, 2006, 2007 Free Software Foundation, Inc.
@c See the file elisp.texi for copying conditions.
@setfilename ../info/variables
@node Variables, Functions, Control Structures, Top
* Buffer-Local Variables:: Variable values in effect only in one buffer.
* Frame-Local Variables:: Variable values in effect only in one frame.
* Future Local Variables:: New kinds of local values we might add some day.
-* Variable Aliases:: Variables that are aliases for other variables.
* File Local Variables:: Handling local variable lists in files.
+* Variable Aliases:: Variables that are aliases for other variables.
+* Variables with Restricted Values:: Non-constant variables whose value can
+ @emph{not} be an arbitrary Lisp object.
@end menu
@node Global Variables
@node Constant Variables
@section Variables that Never Change
-@vindex nil
-@vindex t
@kindex setting-constant
@cindex keyword symbol
+@cindex variable with constant value
+@cindex constant variables
+@cindex symbol that evaluates to itself
+@cindex symbol with constant value
In Emacs Lisp, certain symbols normally evaluate to themselves. These
include @code{nil} and @code{t}, as well as any symbol whose name starts
@end example
@defun keywordp object
-@tindex keywordp
function returns @code{t} if @var{object} is a symbol whose name
starts with @samp{:}, interned in the standard obarray, and returns
@code{nil} otherwise.
All of the @var{value-form}s in @var{bindings} are evaluated in the
order they appear and @emph{before} binding any of the symbols to them.
-Here is an example of this: @code{Z} is bound to the old value of
-@code{Y}, which is 2, not the new value of @code{Y}, which is 1.
+Here is an example of this: @code{z} is bound to the old value of
+@code{y}, which is 2, not the new value of @code{y}, which is 1.
@example
@group
-(setq Y 2)
+(setq y 2)
@result{} 2
@end group
@group
-(let ((Y 1)
- (Z Y))
- (list Y Z))
+(let ((y 1)
+ (z y))
+ (list y z))
@result{} (1 2)
@end group
@end example
@example
@group
-(setq Y 2)
+(setq y 2)
@result{} 2
@end group
@group
-(let* ((Y 1)
- (Z Y)) ; @r{Use the just-established value of @code{Y}.}
- (list Y Z))
+(let* ((y 1)
+ (z y)) ; @r{Use the just-established value of @code{y}.}
+ (list y z))
@result{} (1 1)
@end group
@end example
localized in time.
@defvar max-specpdl-size
+@anchor{Definition of max-specpdl-size}
@cindex variable limit error
@cindex evaluation error
@cindex infinite recursion
This variable defines the limit on the total number of local variable
-bindings and @code{unwind-protect} cleanups (@pxref{Nonlocal Exits})
-that are allowed before signaling an error (with data @code{"Variable
-binding depth exceeds max-specpdl-size"}).
+bindings and @code{unwind-protect} cleanups (@pxref{Cleanups,,
+Cleaning Up from Nonlocal Exits}) that are allowed before signaling an
+error (with data @code{"Variable binding depth exceeds
+max-specpdl-size"}).
This limit, with the associated error when it is exceeded, is one way
that Lisp avoids infinite recursion on an ill-defined function.
@code{max-lisp-eval-depth} provides another limit on depth of nesting.
-@xref{Eval}.
+@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
at top level in a file where its value does not matter.
@end defspec
-@defspec defconst symbol [value [doc-string]]
+@defspec defconst symbol value [doc-string]
This special form defines @var{symbol} as a value and initializes it.
It informs a person reading your code that @var{symbol} has a standard
global value, established here, that should not be changed by the user
symbol to be defined must appear explicitly in the @code{defconst}.
@code{defconst} always evaluates @var{value}, and sets the value of
-@var{symbol} to the result if @var{value} is given. If @var{symbol}
-does have a buffer-local binding in the current buffer, @code{defconst}
-sets the default value, not the buffer-local value. (But you should not
-be making buffer-local bindings for a symbol that is defined with
+@var{symbol} to the result. If @var{symbol} does have a buffer-local
+binding in the current buffer, @code{defconst} sets the default value,
+not the buffer-local value. (But you should not be making
+buffer-local bindings for a symbol that is defined with
@code{defconst}.)
Here, @code{pi} is a constant that presumably ought not to be changed
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
(@pxref{Customization}).
@strong{Warning:} If the @code{defconst} and @code{defvar} special
-forms are used while the variable has a local binding, they set the
-local binding's value; the global binding is not changed. This is not
-what you usually want. To prevent it, use these special forms at top
-level in a file, where normally no local binding is in effect, and make
-sure to load the file before making a local binding for the variable.
+forms are used while the variable has a local binding (made with
+@code{let}, or a function argument), they set the local-binding's
+value; the top-level binding is not changed. This is not what you
+usually want. To prevent it, use these special forms at top level in
+a file, where normally no local binding is in effect, and make sure to
+load the file before making a local binding for the variable.
@node Tips for Defining
@section Tips for Defining Variables Robustly
@item @dots{}-command
The value is a whole shell command.
-@item @samp{}-switches
+@item @dots{}-switches
The value specifies options for a command.
@end table
@end group
@group
-;; @r{Here the value of @code{abracadabra},}
+;; @r{Here, the value of @code{abracadabra},}
;; @r{which is @code{foo},}
;; @r{is the symbol whose value is examined.}
(let ((abracadabra 'foo))
x ; @r{@code{x} now has a global value.}
@result{} 3
@group
-(let ((x 5))
+(let ((x 5))
(setq x 6) ; @r{The local binding of @code{x} is set.}
x)
@result{} 6
@group
(setq x 10 ; @r{Notice that @code{x} is set before}
y (1+ x)) ; @r{the value of @code{y} is computed.}
- @result{} 11
+ @result{} 11
@end group
@end example
@end defspec
@end quotation
@end defun
- One other function for setting a variable is designed to add
-an element to a list if it is not already present in the list.
-
-@defun add-to-list symbol element
-This function sets the variable @var{symbol} by consing @var{element}
-onto the old value, if @var{element} is not already a member of that
-value. It returns the resulting list, whether updated or not. The
-value of @var{symbol} had better be a list already before the call.
-
-The argument @var{symbol} is not implicitly quoted; @code{add-to-list}
-is an ordinary function, like @code{set} and unlike @code{setq}. Quote
-the argument yourself if that is what you want.
-@end defun
-
-Here's a scenario showing how to use @code{add-to-list}:
-
-@example
-(setq foo '(a b))
- @result{} (a b)
-
-(add-to-list 'foo 'c) ;; @r{Add @code{c}.}
- @result{} (c a b)
-
-(add-to-list 'foo 'b) ;; @r{No effect.}
- @result{} (c a b)
-
-foo ;; @r{@code{foo} was changed.}
- @result{} (c a b)
-@end example
-
- An equivalent expression for @code{(add-to-list '@var{var}
-@var{value})} is this:
-
-@example
-(or (member @var{value} @var{var})
- (setq @var{var} (cons @var{value} @var{var})))
-@end example
-
@node Variable Scoping
@section Scoping Rules for Variable Bindings
@cindex scope
@cindex extent
@cindex dynamic scoping
+@cindex lexical scoping
Local bindings in Emacs Lisp have @dfn{indefinite scope} and
@dfn{dynamic extent}. @dfn{Scope} refers to @emph{where} textually in
the source code the binding can be accessed. ``Indefinite scope'' means
@end example
@cindex closures not available
- Some Lisp dialects have ``closures'', objects that are like functions
+ Some Lisp dialects have ``closures,'' objects that are like functions
but record additional variable bindings. Emacs Lisp does not have
closures.
@node Buffer-Local Variables
@section Buffer-Local Variables
-@cindex variables, buffer-local
+@cindex variable, buffer-local
@cindex buffer-local variables
Global and local variable bindings are found in most programming
be changed with @code{setq} in any buffer; the only way to change it is
with @code{setq-default}.
- @strong{Warning:} When a variable has buffer-local values in one or
-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
-different current buffer, you will not have this problem
-(@pxref{Excursions}). Here is an example of what to avoid:
+ @strong{Warning:} When a variable has buffer-local or frame-local
+bindings in one or more buffers, @code{let} rebinds the binding that's
+currently in effect. For instance, if the current buffer has a
+buffer-local value, @code{let} temporarily rebinds that. If no
+buffer-local or frame-local bindings are in effect, @code{let} rebinds
+the default value. If inside the @code{let} you then change to a
+different current buffer in which a different binding is in effect,
+you won't see the @code{let} binding any more. And if you exit the
+@code{let} while still in the other buffer, you won't see the
+unbinding occur (though it will occur properly). Here is an example
+to illustrate:
@example
@group
;; foo @result{} 'g ; @r{the global value since foo is not local in @samp{b}}
@var{body}@dots{})
@group
-foo @result{} 'a ; @r{we are still in buffer @samp{b}, but exiting the let}
- ; @r{restored the local value in buffer @samp{a}}
+foo @result{} 'g ; @r{exiting restored the local value in buffer @samp{a},}
+ ; @r{but we don't see that in buffer @samp{b}}
@end group
@group
-(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
-
-@noindent
-But @code{save-excursion} as shown here avoids the problem:
-
-@example
-@group
-(let ((foo 'temp))
- (save-excursion
- (set-buffer "b")
- @var{body}@dots{}))
+(set-buffer "a") ; @r{verify the local value was restored}
+foo @result{} 'a
@end group
@end example
variables cannot have buffer-local bindings as well. @xref{Multiple
Displays}.
-@strong{Note:} Do not use @code{make-local-variable} for a hook
-variable. The hook variables are automatically made buffer-local
-as needed if you use the @var{local} argument to @code{add-hook} or
+@strong{Warning:} do not use @code{make-local-variable} for a hook
+variable. The hook variables are automatically made buffer-local as
+needed if you use the @var{local} argument to @code{add-hook} or
@code{remove-hook}.
@end deffn
A peculiar wrinkle of this feature is that binding the variable (with
@code{let} or other binding constructs) does not create a buffer-local
binding for it. Only setting the variable (with @code{set} or
-@code{setq}) does so.
+@code{setq}), while the variable does not have a @code{let}-style
+binding that was made in the current buffer, does so.
+
+If @var{variable} does not have a default value, then calling this
+command will give it a default value of @code{nil}. If @var{variable}
+already has a default value, that value remains unchanged.
+Subsequently calling @code{makunbound} on @var{variable} will result
+in a void buffer-local value and leave the default value unaffected.
The value returned is @var{variable}.
@code{nil}.
@end defun
+@defun local-variable-if-set-p variable &optional buffer
+This returns @code{t} if @var{variable} will become buffer-local in
+buffer @var{buffer} (which defaults to the current buffer) if it is
+set there.
+@end defun
+
+@defun buffer-local-value variable buffer
+This function returns the buffer-local binding of @var{variable} (a
+symbol) in buffer @var{buffer}. If @var{variable} does not have a
+buffer-local binding in buffer @var{buffer}, it returns the default
+value (@pxref{Default Value}) of @var{variable} instead.
+@end defun
+
@defun buffer-local-variables &optional buffer
This function returns a list describing the buffer-local variables in
buffer @var{buffer}. (If @var{buffer} is omitted, the current buffer is
(mode-name . "Fundamental")
@dots{}
@group
- ;; @r{Next, non-built-in buffer-local variables.}
+ ;; @r{Next, non-built-in buffer-local variables.}
;; @r{This one is buffer-local and void:}
foobar
;; @r{This one is buffer-local and nonvoid:}
list does @emph{not} change the buffer-local values of the variables.
@end defun
-@defun buffer-local-value variable buffer
-This function returns the buffer-local binding of @var{variable} (a
-symbol) in buffer @var{buffer}. If @var{variable} does not have a
-buffer-local binding in buffer @var{buffer}, it returns the default
-value (@pxref{Default Value}) of @var{variable} instead.
-@end defun
-
@deffn Command kill-local-variable variable
This function deletes the buffer-local binding (if any) for
@var{variable} (a symbol) in the current buffer. As a result, the
@defun kill-all-local-variables
This function eliminates all the buffer-local variable bindings of the
-current buffer except for variables marked as ``permanent''. As a
+current buffer except for variables marked as ``permanent.'' As a
result, the buffer will see the default values of most variables.
This function also resets certain other information pertaining to the
The function @code{kill-all-local-variables} runs this normal hook
before it does anything else. This gives major modes a way to arrange
for something special to be done if the user switches to a different
-major mode. For best results, make this variable buffer-local, so that
-it will disappear after doing its job and will not interfere with the
+major mode. It is also useful for buffer-specific minor modes
+that should be forgotten if the user changes the major mode.
+
+For best results, make this variable buffer-local, so that it will
+disappear after doing its job and will not interfere with the
subsequent major mode. @xref{Hooks}.
@end defvar
@node Frame-Local Variables
@section Frame-Local Variables
+@cindex frame-local variables
Just as variables can have buffer-local bindings, they can also have
frame-local bindings. These bindings belong to one frame, and are in
if some frame already has a value for @var{variable} as a frame
parameter, that value automatically becomes a frame-local binding.
+If @var{variable} does not have a default value, then calling this
+command will give it a default value of @code{nil}. If @var{variable}
+already has a default value, that value remains unchanged.
+
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
Buffer-local bindings take precedence over frame-local bindings. Thus,
If sufficient application is found for either of these two kinds of
local bindings, we will provide it in a subsequent Emacs version.
+@node File Local Variables
+@section File Local Variables
+@cindex file local variables
+
+ A file can specify local variable values; Emacs uses these to create
+buffer-local bindings for those variables in the buffer visiting that
+file. @xref{File variables, , Local Variables in Files, emacs, The
+GNU Emacs Manual}, for basic information about file local variables.
+This section describes the functions and variables that affect
+processing of file local variables.
+
+@defopt enable-local-variables
+This variable controls whether to process file local variables.
+The possible values are:
+
+@table @asis
+@item @code{t} (the default)
+Set the safe variables, and query (once) about any unsafe variables.
+@item @code{:safe}
+Set only the safe variables and do not query.
+@item @code{:all}
+Set all the variables and do not query.
+@item @code{nil}
+Don't set any variables.
+@item anything else
+Query (once) about all the variables.
+@end table
+@end defopt
+
+@defun hack-local-variables &optional mode-only
+This function parses, and binds or evaluates as appropriate, any local
+variables specified by the contents of the current buffer. The variable
+@code{enable-local-variables} has its effect here. However, this
+function does not look for the @samp{mode:} local variable in the
+@w{@samp{-*-}} line. @code{set-auto-mode} does that, also taking
+@code{enable-local-variables} into account (@pxref{Auto Major Mode}).
+
+If the optional argument @var{mode-only} is non-@code{nil}, then all
+this function does is return @code{t} if the @w{@samp{-*-}} line or
+the local variables list specifies a mode and @code{nil} otherwise.
+It does not set the mode nor any other file local variable.
+@end defun
+
+ 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. 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. Lambda expressions should
+be quoted so that @code{describe-variable} can display the predicate.
+
+@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
+
+@c @cindex risky local variable Duplicates 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} 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
+completely ignored.
+@end defvar
+
+ The @samp{Eval:} ``variable'' is also a potential loophole, so Emacs
+normally asks for confirmation before handling it.
+
+@defopt enable-local-eval
+This variable controls processing of @samp{Eval:} in @samp{-*-} lines
+or local variables
+lists in files being visited. 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{maybe}.
+@end defopt
+
+@defopt safe-local-eval-forms
+This variable holds a list of expressions that are safe to
+evaluate when found in the @samp{Eval:} ``variable'' in a file
+local variables list.
+@end defopt
+
+ If the expression is a function call and the function has a
+@code{safe-local-eval-function} property, the property value
+determines whether the expression is safe to evaluate. The property
+value can be a predicate to call to test the expression, a list of
+such predicates (it's safe if any predicate succeeds), or @code{t}
+(always safe provided the arguments are constant).
+
+ Text properties are also potential loopholes, since their values
+could include functions to call. So Emacs discards all text
+properties from string values specified for file local variables.
+
@node Variable Aliases
@section Variable Aliases
+@cindex variable aliases
It is sometimes useful to make two variables synonyms, so that both
variables always have the same value, and changing either one also
to keep the old name as an @emph{alias} of the new one for
compatibility. You can do this with @code{defvaralias}.
-@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
-@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}.
+@defun defvaralias new-alias base-variable &optional docstring
+This function defines the symbol @var{new-alias} as a variable alias
+for symbol @var{base-variable}. This means that retrieving the value
+of @var{new-alias} returns the value of @var{base-variable}, and
+changing the value of @var{new-alias} changes the value of
+@var{base-variable}. The two aliased variable names always share the
+same value and the same bindings.
+
+If the @var{docstring} argument is non-@code{nil}, it specifies the
+documentation for @var{new-alias}; otherwise, the alias gets the same
+documentation as @var{base-variable} has, if any, unless
+@var{base-variable} is itself an alias, in which case @var{new-alias} gets
+the documentation of the variable at the end of the chain of aliases.
+
+This function returns @var{base-variable}.
+@end defun
-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.
+ Variable aliases are convenient for replacing an old name for a
+variable with a new name. @code{make-obsolete-variable} declares that
+the old name is obsolete and therefore that it may be removed at some
+stage in the future.
+
+@defun make-obsolete-variable obsolete-name current-name &optional when
+This function makes the byte-compiler warn that the variable
+@var{obsolete-name} is obsolete. If @var{current-name} is a symbol, it is
+the variable's new name; then the warning message says to use
+@var{current-name} instead of @var{obsolete-name}. If @var{current-name}
+is a string, this is the message and there is no replacement variable.
+
+If provided, @var{when} should be a string indicating when the
+variable was first made obsolete---for example, a date or a release
+number.
@end defun
+ You can make two variables synonyms and declare one obsolete at the
+same time using the macro @code{define-obsolete-variable-alias}.
+
+@defmac define-obsolete-variable-alias obsolete-name current-name &optional when docstring
+This macro marks the variable @var{obsolete-name} as obsolete and also
+makes it an alias for the variable @var{current-name}. It is
+equivalent to the following:
+
+@example
+(defvaralias @var{obsolete-name} @var{current-name} @var{docstring})
+(make-obsolete-variable @var{obsolete-name} @var{current-name} @var{when})
+@end example
+@end defmac
+
@defun indirect-variable variable
This function returns the variable at the end of the chain of aliases
of @var{variable}. If @var{variable} is not a symbol, or if @var{variable} is
not defined as an alias, the function returns @var{variable}.
+
+This function signals a @code{cyclic-variable-indirection} error if
+there is a loop in the chain of symbols.
@end defun
@example
(setq bar 2)
bar
@result{} 2
+@group
foo
@result{} 2
+@end group
(setq foo 0)
bar
@result{} 0
@result{} 0
@end example
-@node File Local Variables
-@section File Local Variables
+@node Variables with Restricted Values
+@section Variables with Restricted Values
- This section describes the functions and variables that affect
-processing of local variables lists in files.
+ Ordinary Lisp variables can be assigned any value that is a valid
+Lisp object. However, certain Lisp variables are not defined in Lisp,
+but in C. Most of these variables are defined in the C code using
+@code{DEFVAR_LISP}. Like variables defined in Lisp, these can take on
+any value. However, some variables are defined using
+@code{DEFVAR_INT} or @code{DEFVAR_BOOL}. @xref{Defining Lisp
+variables in C,, Writing Emacs Primitives}, in particular the
+description of functions of the type @code{syms_of_@var{filename}},
+for a brief discussion of the C implementation.
-@defopt enable-local-variables
-This variable controls whether to process file local variables lists. A
-value of @code{t} means process the local variables lists
-unconditionally; @code{nil} means ignore them; anything else means ask
-the user what to do for each file. The default value is @code{t}.
-@end defopt
+ Variables of type @code{DEFVAR_BOOL} can only take on the values
+@code{nil} or @code{t}. Attempting to assign them any other value
+will set them to @code{t}:
-@defun hack-local-variables &optional force
-This function parses, and binds or evaluates as appropriate, any local
-variables specified by the contents of the current buffer. The variable
-@code{enable-local-variables} has its effect here.
-
-The argument @var{force} usually comes from the argument @var{find-file}
-given to @code{normal-mode}.
-@end defun
-
- If a file local variable list could specify the a function that will
-be called later, or an expression that will be executed later, simply
-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.
-
- 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}:
+@example
+(let ((display-hourglass 5))
+ display-hourglass)
+ @result{} t
+@end example
-@defvar ignored-local-variables
-This variable holds a list of variables that should not be
-set by a file's local variables list. Any value specified
-for one of these variables is ignored.
+@defvar byte-boolean-vars
+This variable holds a list of all variables of type @code{DEFVAR_BOOL}.
@end defvar
- The @samp{Eval:} ``variable'' is also a potential loophole, so Emacs
-normally asks for confirmation before handling it.
+ Variables of type @code{DEFVAR_INT} can only take on integer values.
+Attempting to assign them any other value will result in an error:
-@defopt enable-local-eval
-This variable controls processing of @samp{Eval:} in local variables
-lists in files being visited. 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{maybe}.
-@end defopt
+@example
+(setq window-min-height 5.0)
+@error{} Wrong type argument: integerp, 5.0
+@end example
+
+@ignore
+ arch-tag: 5ff62c44-2b51-47bb-99d4-fea5aeec5d3e
+@end ignore