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bug#8884: closed (Re: bug#8884: wide-int crash)

From: Eli Zaretskii
Subject: bug#8884: closed (Re: bug#8884: wide-int crash)
Date: Tue, 18 Oct 2011 06:55:09 -0400

> From: Peter Dyballa <address@hidden>
> Date: Tue, 18 Oct 2011 11:14:10 +0200
> Cc: address@hidden
> > (A 32-bit machine can't access more than 4 GiB of memory.
> It rather looks that *I* am missing some understanding... I thought that the 
> use of wide ints on a 32-bit architecture was meant to give it the ability to 
> handle larger files.

It was, and it does.  See below.

> What is the intention of their introduction then? Increasing the size of the 
> binary?


>       ** There is a new configure option --with-wide-int.
>       With it, Emacs integers typically have 62 bits, even on 32-bit machines.

Perhaps the NEWS entry could be improved.

> From buffers.texi this text is derived:
>          A buffer's size cannot be larger than some maximum, which is defined
>       by the largest buffer position representable by the "Emacs integer"
>       data type.  This is because Emacs tracks buffer positions using that
>       data type.  For 32-bit machines, the largest buffer size is 256
>       megabytes.
> 4 GiB is 16 times that value, quite a bit more. Maths with large numbers, 
> greater than 2**28, works. 

Exactly.  So with this option, you can:

  . visit files or have buffers up to 4GB

  . use integer arithmetics up to 62-bit values

None of these is possible without this option.  The first of these two
advantages is the more important one: Emacs can now access the largest
files supported by the OS, instead of having a more-or-less arbitrary
limit below that.

Sounds better now?

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