@c -*-texinfo-*-
@c This is part of the GNU Emacs Lisp Reference Manual.
-@c Copyright (C) 1990, 1991, 1992, 1993, 1998, 1999
-@c Free Software Foundation, Inc.
+@c Copyright (C) 1990, 1991, 1992, 1993, 1998, 1999, 2002, 2003, 2004,
+@c 2005, 2006 Free Software Foundation, Inc.
@c See the file elisp.texi for copying conditions.
@setfilename ../info/internals
@node GNU Emacs Internals, Standard Errors, Tips, Top
internal aspects of GNU Emacs that may be of interest to C programmers.
@menu
-* Building Emacs:: How to the dumped Emacs is made.
+* Building Emacs:: How the dumped Emacs is made.
* Pure Storage:: A kludge to make preloaded Lisp functions sharable.
* Garbage Collection:: Reclaiming space for Lisp objects no longer used.
* Memory Usage:: Info about total size of Lisp objects made so far.
normal features for your site, do it with @file{default.el}, so that
users can override your changes if they wish. @xref{Startup Summary}.
+ In a package that can be preloaded, it is sometimes useful to
+specify a computation to be done when Emacs subsequently starts up.
+For this, use @code{eval-at-startup}:
+
+@defmac eval-at-startup body@dots{}
+This evaluates the @var{body} forms, either immediately if running in
+an Emacs that has already started up, or later when Emacs does start
+up. Since the value of the @var{body} forms is not necessarily
+available when the @code{eval-at-startup} form is run, that form
+always returns @code{nil}.
+@end defmac
+
@defun dump-emacs to-file from-file
@cindex unexec
This function dumps the current state of Emacs into an executable file
marked as read-only (on operating systems that permit this), so that
the memory space can be shared by all the Emacs jobs running on the
machine at once. Pure storage is not expandable; a fixed amount is
-allocated when Emacs is compiled, and if that is not sufficient for the
-preloaded libraries, @file{temacs} crashes. If that happens, you must
-increase the compilation parameter @code{PURESIZE} in the file
-@file{src/puresize.h}. This normally won't happen unless you try to
-preload additional libraries or add features to the standard ones.
+allocated when Emacs is compiled, and if that is not sufficient for
+the preloaded libraries, @file{temacs} allocates dynamic memory for
+the part that didn't fit. If that happens, you should increase the
+compilation parameter @code{PURESIZE} in the file
+@file{src/puresize.h} and rebuild Emacs, even though the resulting
+image will work: garbage collection is disabled in this situation,
+causing a memory leak. Such an overflow normally won't happen unless you
+try to preload additional libraries or add features to the standard
+ones. Emacs will display a warning about the overflow when it
+starts.
@defun purecopy object
This function makes a copy in pure storage of @var{object}, and returns
object consists of a header and the storage for the string text
itself; the latter is only allocated when the string is created.)
@end table
+
+If there was overflow in pure space (see the previous section),
+@code{garbage-collect} returns @code{nil}, because a real garbage
+collection can not be done in this situation.
@end deffn
@defopt garbage-collection-messages
down to 10,000. A value less than 10,000 will remain in effect only
until the subsequent garbage collection, at which time
@code{garbage-collect} will set the threshold back to 10,000.
+@end defopt
+
+@defopt gc-cons-percentage
+The value of this variable specifies the amount of consing before a
+garbage collection occurs, as a fraction of the current heap size.
+This criterion and @code{gc-cons-threshold} apply in parallel, and
+garbage collection occurs only when both criteria are satisfied.
+
+As the heap size increases, the time to perform a garbage collection
+increases. Thus, it can be desirable to do them less frequently in
+proportion.
@end defopt
The value returned by @code{garbage-collect} describes the amount of
memory usage.
@end defun
+@defvar memory-full
+This variable is @code{t} if Emacs is close to out of memory for Lisp
+objects, and @code{nil} otherwise.
+@end defvar
+
@defun memory-use-counts
This returns a list of numbers that count the number of objects
created in this Emacs session. Each of these counters increments for
(args)
Lisp_Object args;
@{
- register Lisp_Object val;
- Lisp_Object args_left;
+ register Lisp_Object val = Qnil;
struct gcpro gcpro1;
@end group
@group
- if (NILP (args))
- return Qnil;
-
- args_left = args;
- GCPRO1 (args_left);
+ GCPRO1 (args);
@end group
@group
- do
+ while (CONSP (args))
@{
- val = Feval (Fcar (args_left));
+ val = Feval (XCAR (args));
if (!NILP (val))
- break;
- args_left = Fcdr (args_left);
+ break;
+ args = XCDR (args);
@}
- while (!NILP (args_left));
@end group
@group
@code{MANY}, indicating an unlimited number of evaluated arguments (the
equivalent of @code{&rest}). Both @code{UNEVALLED} and @code{MANY} are
macros. If @var{max} is a number, it may not be less than @var{min} and
-it may not be greater than seven.
+it may not be greater than eight.
@item interactive
This is an interactive specification, a string such as might be used as
values. They have types @code{int} and @w{@code{Lisp_Object *}}.
Within the function @code{For} itself, note the use of the macros
-@code{GCPRO1} and @code{UNGCPRO}. @code{GCPRO1} is used to ``protect''
-a variable from garbage collection---to inform the garbage collector that
-it must look in that variable and regard its contents as an accessible
-object. This is necessary whenever you call @code{Feval} or anything
-that can directly or indirectly call @code{Feval}. At such a time, any
-Lisp object that you intend to refer to again must be protected somehow.
-@code{UNGCPRO} cancels the protection of the variables that are
-protected in the current function. It is necessary to do this explicitly.
+@code{GCPRO1} and @code{UNGCPRO}. @code{GCPRO1} is used to
+``protect'' a variable from garbage collection---to inform the garbage
+collector that it must look in that variable and regard its contents
+as an accessible object. GC protection is necessary whenever you call
+@code{Feval} or anything that can directly or indirectly call
+@code{Feval}. At such a time, any Lisp object that this function may
+refer to again must be protected somehow.
It suffices to ensure that at least one pointer to each object is
-GC-protected; as long as the object is not recycled, all pointers to
-it remain valid. So if you are sure that a local variable points to
-an object that will be preserved by some other pointer, that local
-variable does not need a @code{GCPRO}. (Formerly, strings were an
-exception to this rule; in older Emacs versions, every pointer to a
-string needed to be marked by GC.)
+GC-protected; that way, the object cannot be recycled, so all pointers
+to it remain valid. Thus, a particular local variable can do without
+protection if it is certain that the object it points to will be
+preserved by some other pointer (such as another local variable which
+has a @code{GCPRO})@footnote{Formerly, strings were a special
+exception; in older Emacs versions, every local variable that might
+point to a string needed a @code{GCPRO}.}. Otherwise, the local
+variable needs a @code{GCPRO}.
The macro @code{GCPRO1} protects just one local variable. If you
-want to protect two, use @code{GCPRO2} instead; repeating
-@code{GCPRO1} will not work. Macros, @code{GCPRO3}, @code{GCPRO4},
-@code{GCPRO5}, and @code{GCPRO6} also exist. These macros implicitly
-use local variables such as @code{gcpro1}; you must declare these
-explicitly, with type @code{struct gcpro}. Thus, if you use
+want to protect two variables, use @code{GCPRO2} instead; repeating
+@code{GCPRO1} will not work. Macros @code{GCPRO3}, @code{GCPRO4},
+@code{GCPRO5}, and @code{GCPRO6} also exist. All these macros
+implicitly use local variables such as @code{gcpro1}; you must declare
+these explicitly, with type @code{struct gcpro}. Thus, if you use
@code{GCPRO2}, you must declare @code{gcpro1} and @code{gcpro2}.
Alas, we can't explain all the tricky details here.
+ @code{UNGCPRO} cancels the protection of the variables that are
+protected in the current function. It is necessary to do this
+explicitly.
+
Built-in functions that take a variable number of arguments actually
accept two arguments at the C level: the number of Lisp arguments, and
a @code{Lisp_Object *} pointer to a C vector containing those Lisp
is @code{nil}, no mode line will be displayed.
@item header_line_format
-This field is analoguous to @code{mode_line_format} for the mode
+This field is analogous to @code{mode_line_format} for the mode
line displayed at the top of windows.
@item keymap
@item file_format
The value of @code{buffer-file-format} in this buffer.
+@item auto_save_file_format
+The value of @code{buffer-auto-save-file-format} in this buffer.
+
@item pt_marker
In an indirect buffer, or a buffer that is the base of an indirect
buffer, this holds a marker that records point for this buffer when the
@item redisplay_end_trigger
If redisplay in this window goes beyond this buffer position, it runs
-run the @code{redisplay-end-trigger-hook}.
+the @code{redisplay-end-trigger-hook}.
@ignore
@item orig_height
The associated buffer of the process.
@item pid
-An integer, the Unix process @acronym{ID}.
+An integer, the operating system's process @acronym{ID}.
@item childp
A flag, non-@code{nil} if this is really a child process.