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Date: Wed, 23 Mar 2011 11:46:46 -0600
From: Eric Blake <eblake AT redhat DOT com>
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Subject: Re: Broken autoconf mmap test
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On 03/23/2011 11:40 AM, Ken Brown wrote:
>> Usually it shouldn't.  While you can write into a mmaped area beyond
>> EOF up to the end of the last page, it doesn't make a lot of sense.
>> The data will never show up in the mapped file.
>>
>> I have no idea if there are applications out there which rely on this
>> crude behaviour.
>=20
> It doesn't look like there's going to be an autoconf change to resolve
> this:
>=20
>   http://lists.gnu.org/archive/html/autoconf/2011-03/msg00041.html

Unless the right thing to do in autoconf is to separate the test into
two levels; one of whether most mmap works but you can't extend files
(cygwin always passes) and one whether writing beyond EOF works as
required by POSIX (cygwin currently fails on W64, but hopefully fewer
packages rely on this stricter behavior).  Or figure out a way to make
cygwin work around the W64 limitations.

--=20
Eric Blake   eblake AT redhat DOT com    +1-801-349-2682
Libvirt virtualization library http://libvirt.org


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