bug#37818: [PATCH] Various FAQ updates

[Stefan Kangas <stefan@marxist.se>]

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Eli Zaretskii <eliz@gnu.org> writes:

> > +Emacs has an inherent fixed limitation on the size of buffers.
>
> I'd suggest to say that the limitation is more strict that the maximum
> size of objects supported by programs with the same architecture,
> because otherwise this sentence might be misunderstood.

Done.

>
> >                                                                  The
> > +maximum buffer size on 32-bit machines is 512 MBytes beginning with
> > +version 23.2.  If Emacs was built using the @code{--with-wide-int}
> > +flag, the maximum buffer size on 32-bit machines is ***FIXME***
> > +MBytes.
>
> The number here is 2GB.

Fixed.

> > +This limitation imposes a size limit on visiting files, which is
> > +roughly half the buffer limit due to things like decoding of multibyte
> > +characters.  When visiting compressed archives, the file size
> > +limitation will be smaller than that due to decompression.
> > +
> > +Unless you want to visit unusually large files, this should only be an
> > +issue on 32-bit machines.  Emacs compiled on a 64-bit machine can
> > +handle much larger buffers.
>
> The limit value for 64-bit builds is that of most-positive-fixnum.

Fixed.  Please find attached an updated patch.

Best regards,
Stefan Kangas

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From 5bc3d944bf8f22868eecca244240d96dd72812c2 Mon Sep 17 00:00:00 2001
From: Stefan Kangas <stefankangas@gmail.com>
Date: Fri, 18 Oct 2019 22:56:34 +0200
Subject: [PATCH] Update FAQ section on large files (Bug#37818)

* doc/misc/efaq.texi (Problems with very large files): Extend section
and remove information about ancient versions of Emacs.
---
 doc/misc/efaq.texi | 23 ++++++++++++++++-------
 1 file changed, 16 insertions(+), 7 deletions(-)

diff --git a/doc/misc/efaq.texi b/doc/misc/efaq.texi
index 0f2cebe6c3..8bbb4bf3c0 100644
--- a/doc/misc/efaq.texi
+++ b/doc/misc/efaq.texi
@@ -2923,20 +2923,29 @@ Bugs and problems
 @end menu
 
 @node Problems with very large files
-@section Does Emacs have problems with files larger than 8 megabytes?
+@section Does Emacs have problems with large files?
 @cindex Very large files, opening
 @cindex Large files, opening
 @cindex Opening very large files
 @cindex Maximum file size
 @cindex Files, maximum size
 
-Old versions (i.e., anything before 19.29) of Emacs had problems editing
-files larger than 8 megabytes.  In versions 19.29 and later, the maximum
-buffer size is at least @math{2^{27}-1}, or 134,217,727 bytes, or 132 MBytes.
-The maximum buffer size on 32-bit machines increased to 256 MBytes in
-Emacs 22, and again to 512 MBytes in Emacs 23.2.
+Emacs has an inherent fixed limitation on the size of buffers.  This
+limit is stricter than the maximum size of objects supported by other
+programs on the same architecture.
 
-Emacs compiled on a 64-bit machine can handle much larger buffers.
+The maximum buffer size on 32-bit machines is 512 MBytes beginning
+with version 23.2.  If Emacs was built using the
+@code{--with-wide-int} flag, the maximum buffer size on 32-bit
+machines is 2 GB.
+
+Emacs compiled on a 64-bit machine can handle much larger buffers; up
+to @code{most-positive-fixnum} (2.3 exabytes).
+
+Due to things like decoding of multibyte characters, you can only
+visit files with a size that is roughly half the buffer size limit.
+When visiting compressed archives, the file size limit will be
+smaller than that due to decompression.
 
 @node ^M in the shell buffer
 @section How do I get rid of @samp{^M} or echoed commands in my shell buffer?
-- 
2.23.0