bug#2790: emacs 22.1.1 cannot open 5GB file on 64GB 64-bit GNU/Linux box

[Mike Coleman]

I'm not quite sure I'm following this.  Are you running your
experiments with a 64-bit emacs, or a 32-bit one?



On Fri, Mar 27, 2009 at 9:12 PM, Stefan Monnier
<monnier@iro.umontreal.ca> wrote:
>> Okay, tried it (emacs-23.0.91), but no luck.  Looks very nice, but
>> finding that large file produced the same error.  The value of
>> 'most-positive-fixnum' prints correctly, though (which is different).
>
> There was an incorrect check that limited the size to INT_MAX/4
> (i.e. 512MB for systems where ints are 32bit).  I've removed this check
> in the CVS code (see patch below).  I am now able to open an 800MB file
> with this check removed.  OTOH with a 2GB file, I got some unjustified
> "memory exhausted" error, but I haven't tracked it down yet.  Note also
> that when you open large files, it's worthwhile to use
> find-file-literally to be sure it's opened in unibyte mode; otherwise
> it gets decoded which takes ages.  Also if the file has many lines (my
> 800MB file was made up by copying a C file many times, so it had
> millions of lines), turning off line-number-mode is is needed to recover
> responsiveness when navigating near the end of the buffer.
>
>
>        Stefan
>
>
> Index: src/fileio.c
> ===================================================================
> RCS file: /sources/emacs/emacs/src/fileio.c,v
> retrieving revision 1.651
> retrieving revision 1.652
> diff -u -r1.651 -r1.652
> --- src/fileio.c        24 Mar 2009 14:14:54 -0000      1.651
> +++ src/fileio.c        28 Mar 2009 02:06:08 -0000      1.652
> @@ -3300,7 +3300,11 @@
>             overflow.  The calculations below double the file size
>             twice, so check that it can be multiplied by 4 safely.  */
>          if (XINT (end) != st.st_size
> -             || st.st_size > INT_MAX / 4)
> +             /* Actually, it should test either INT_MAX or LONG_MAX
> +                depending on which one is used for EMACS_INT.  But in
> +                any case, in practice, this test is redundant with the
> +                one above.
> +                || st.st_size > INT_MAX / 4 */)
>            error ("Maximum buffer size exceeded");
>
>          /* The file size returned from stat may be zero, but data
>