Pure storage removal: Remove documentation
As pure storage is now gone, it no longer needs to be documented. * doc/lispref/elisp.texi (Top): * doc/lispref/internals.texi (GNU Emacs Internals): Remove "Pure Storage" section. (Building Emacs, Garbage Collection, Writing Emacs Primitives): * doc/lispref/symbols.texi (Standard Properties): Remove references to pure storage. * src/alloc.c (Fgarbage_collect): Remove docstring text referring to pure storage.
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Pip Cet
Stefan Kangas
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4 changed files with 1 additions and 80 deletions
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@ -1651,7 +1651,6 @@ Tips and Conventions
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GNU Emacs Internals
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* Building Emacs:: How the dumped Emacs is made.
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* Pure Storage:: Kludge to make preloaded Lisp functions shareable.
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* Garbage Collection:: Reclaiming space for Lisp objects no longer used.
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* Stack-allocated Objects:: Temporary conses and strings on C stack.
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* Memory Usage:: Info about total size of Lisp objects made so far.
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@ -12,7 +12,6 @@ internal aspects of GNU Emacs that may be of interest to C programmers.
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@menu
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* Building Emacs:: How the dumped Emacs is made.
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* Pure Storage:: Kludge to make preloaded Lisp functions shareable.
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* Garbage Collection:: Reclaiming space for Lisp objects no longer used.
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* Stack-allocated Objects:: Temporary conses and strings on C stack.
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* Memory Usage:: Info about total size of Lisp objects made so far.
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@ -251,71 +250,6 @@ If the current session was not restored from a dump file, the
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value is @code{nil}.
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@end defun
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@node Pure Storage
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@section Pure Storage
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@cindex pure storage
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Emacs Lisp uses two kinds of storage for user-created Lisp objects:
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@dfn{normal storage} and @dfn{pure storage}. Normal storage is where
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all the new data created during an Emacs session are kept
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(@pxref{Garbage Collection}). Pure storage is used for certain data
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in the preloaded standard Lisp files---data that should never change
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during actual use of Emacs.
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Pure storage is allocated only while @command{temacs} is loading the
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standard preloaded Lisp libraries. In the file @file{emacs}, it is
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marked as read-only (on operating systems that permit this), so that
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the memory space can be shared by all the Emacs jobs running on the
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machine at once. Pure storage is not expandable; a fixed amount is
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allocated when Emacs is compiled, and if that is not sufficient for
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the preloaded libraries, @file{temacs} allocates dynamic memory for
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the part that didn't fit. If Emacs will be dumped using the
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@code{pdump} method (@pxref{Building Emacs}), the pure-space overflow
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is of no special importance (it just means some of the preloaded stuff
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cannot be shared with other Emacs jobs). However, if Emacs will be
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dumped using the now obsolete @code{unexec} method, the resulting
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image will work, but garbage collection (@pxref{Garbage Collection})
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is disabled in this situation, causing a memory leak. Such an
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overflow normally won't happen unless you try to preload additional
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libraries or add features to the standard ones. Emacs will display a
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warning about the overflow when it starts, if it was dumped using
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@code{unexec}. If this happens, you should increase the compilation
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parameter @code{SYSTEM_PURESIZE_EXTRA} in the file
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@file{src/puresize.h} and rebuild Emacs.
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@defun purecopy object
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This function makes a copy in pure storage of @var{object}, and returns
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it. It copies a string by simply making a new string with the same
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characters, but without text properties, in pure storage. It
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recursively copies the contents of vectors and cons cells. It does
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not make copies of other objects such as symbols, but just returns
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them unchanged. It signals an error if asked to copy markers.
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This function is a no-op except while Emacs is being built and dumped;
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it is usually called only in preloaded Lisp files.
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@end defun
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@defvar pure-bytes-used
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The value of this variable is the number of bytes of pure storage
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allocated so far. Typically, in a dumped Emacs, this number is very
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close to the total amount of pure storage available---if it were not,
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we would preallocate less.
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@end defvar
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@defvar purify-flag
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This variable determines whether @code{defun} should make a copy of the
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function definition in pure storage. If it is non-@code{nil}, then the
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function definition is copied into pure storage.
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This flag is @code{t} while loading all of the basic functions for
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building Emacs initially (allowing those functions to be shareable and
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non-collectible). Dumping Emacs as an executable always writes
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@code{nil} in this variable, regardless of the value it actually has
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before and after dumping.
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You should not change this flag in a running Emacs.
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@end defvar
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@node Garbage Collection
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@section Garbage Collection
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@ -526,12 +460,6 @@ Total heap size, in @var{unit-size} units.
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@item free-size
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Heap space which is not currently used, in @var{unit-size} units.
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@end table
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If there was overflow in pure space (@pxref{Pure Storage}), and Emacs
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was dumped using the (now obsolete) @code{unexec} method
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(@pxref{Building Emacs}), then @code{garbage-collect} returns
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@code{nil}, because a real garbage collection cannot be done in that
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case.
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@end deffn
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@defopt garbage-collection-messages
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@ -967,7 +895,6 @@ improves user experience.
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the variables are never written once Emacs is dumped. These variables
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with initializers are allocated in an area of memory that becomes
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read-only (on certain operating systems) as a result of dumping Emacs.
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@xref{Pure Storage}.
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@cindex @code{defsubr}, Lisp symbol for a primitive
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Defining the C function is not enough to make a Lisp primitive
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@ -593,8 +593,7 @@ modes. @xref{Setting Hooks}.
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If the value is non-@code{nil}, the named function is considered to be
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pure (@pxref{What Is a Function}). Calls with constant arguments can
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be evaluated at compile time. This may shift run time errors to
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compile time. Not to be confused with pure storage (@pxref{Pure
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Storage}).
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compile time.
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@item risky-local-variable
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If the value is non-@code{nil}, the named variable is considered risky
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@ -6296,10 +6296,6 @@ where each entry has the form (NAME SIZE USED FREE), where:
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keeps around for future allocations (maybe because it does not know how
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to return them to the OS).
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However, if there was overflow in pure space, and Emacs was dumped
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using the \"unexec\" method, `garbage-collect' returns nil, because
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real GC can't be done.
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Note that calling this function does not guarantee that absolutely all
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unreachable objects will be garbage-collected. Emacs uses a
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mark-and-sweep garbage collector, but is conservative when it comes to
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