@c This is part of the GNU Emacs Lisp Reference Manual.
@c Copyright (C) 1990-1993, 1998-1999, 2001-2012 Free Software Foundation, Inc.
@c See the file elisp.texi for copying conditions.
-@node GNU Emacs Internals, Standard Errors, Tips, Top
-@comment node-name, next, previous, up
+@node GNU Emacs Internals
@appendix GNU Emacs Internals
This chapter describes how the runnable Emacs executable is dumped with
(such as by loading a library), that data is placed in normal storage.
If normal storage runs low, then Emacs asks the operating system to
allocate more memory. Different types of Lisp objects, such as
-symbols, cons cells, markers, etc., are segregated in distinct blocks
-in memory. (Vectors, long strings, buffers and certain other editing
-types, which are fairly large, are allocated in individual blocks, one
-per object, while small strings are packed into blocks of 8k bytes.)
+symbols, cons cells, small vectors, markers, etc., are segregated in
+distinct blocks in memory. (Large vectors, long strings, buffers and
+certain other editing types, which are fairly large, are allocated in
+individual blocks, one per object; small strings are packed into blocks
+of 8k bytes, and small vectors are packed into blocks of 4k bytes).
+
+@cindex vector-like objects, storage
+@cindex storage of vector-like Lisp objects
+ Beyond the basic vector, a lot of objects like window, buffer, and
+frame are managed as if they were vectors. The corresponding C data
+structures include the @code{struct vectorlike_header} field whose
+@code{next} field points to the next object in the chain:
+@code{header.next.buffer} points to the next buffer (which could be
+a killed buffer), and @code{header.next.vector} points to the next
+vector in a free list. If a vector is small (smaller than or equal to
+@code{VBLOCK_BYTES_MAX} bytes, see @file{alloc.c}), then
+@code{header.next.nbytes} contains the vector size in bytes.
@cindex garbage collection
It is quite common to use some storage for a while, then release it
The sweep phase puts unused cons cells onto a @dfn{free list}
for future allocation; likewise for symbols and markers. It compacts
the accessible strings so they occupy fewer 8k blocks; then it frees the
-other 8k blocks. Vectors, buffers, windows, and other large objects are
-individually allocated and freed using @code{malloc} and @code{free}.
+other 8k blocks. Unreachable vectors from vector blocks are coalesced
+to create largest possible free areas; if a free area spans a complete
+4k block, that block is freed. Otherwise, the free area is recorded
+in a free list array, where each entry corresponds to a free list
+of areas of the same size. Large vectors, buffers, and other large
+objects are allocated and freed individually.
@cindex CL note---allocate more storage
@quotation
If there was overflow in pure space (@pxref{Pure Storage}),
@code{garbage-collect} returns @code{nil}, because a real garbage
-collection can not be done in this situation.
+collection cannot be done.
@end deffn
@defopt garbage-collection-messages
@defvar string-chars-consed
The total number of string characters that have been allocated so far
-in this Emacs session.
+in this session.
@end defvar
@defvar misc-objects-consed
The total number of miscellaneous objects that have been allocated so
-far in this Emacs session. These include markers and overlays, plus
+far in this session. These include markers and overlays, plus
certain objects not visible to users.
@end defvar
indicating a special form that receives unevaluated arguments, or
@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 eight.
+macros. If @var{max} is a number, it must be more than @var{min} but
+less than 8.
@item interactive
This is an interactive specification, a string such as might be used as
message in the process buffer.
@item pty_flag
-Non-@code{nil} if communication with the subprocess uses a @acronym{PTY};
+Non-@code{nil} if communication with the subprocess uses a pty;
@code{nil} if it uses a pipe.
@item infd
HCoop / bpt / emacs.git / blobdiff