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Date: Tue, 28 Nov 2000 22:52:59 -0500
From: Christopher Faylor <cgf AT redhat DOT com>
To: "cygwin AT cygwin DOT com" <cygwin AT cygwin DOT com>
Cc: zackw AT stanford DOT edu
Subject: Re: [PATCH] Problems with Cygwin mmap/munmap (mmap.cc)
Message-ID: <20001128225259.B11647@redhat.com>
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	zackw AT stanford DOT edu
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In-Reply-To: <20001128114558.R2285@wolery.stanford.edu>; from zackw@Stanford.EDU on Tue, Nov 28, 2000 at 11:45:58AM -0800

On Tue, Nov 28, 2000 at 11:45:58AM -0800, Zack Weinberg wrote:
>I might point out that we only want these things for mmap of anonymous
>memory.  If Cygwin used VirtualAlloc instead of CreateFileMapping with
>an invalid handle to implement anonymous mmap, then both behaviors
>would be implementable easily.  (I don't know if this would interfere
>with cygwin's brk() implementation, though.)

I think that I raised this specter before but, on reflection, this
implementation detail should matter.  We'd have the same issue with
VirtualAlloc or CreateFileMapping.

I think that you (Zack) noted that using VirtualAlloc actually might
save us some precious upper memory in the Windows 9x "OS"'s.

The problem, I think, is that VirtualAlloc space is not inherited.  We
could kludge around this, like we do with fork, by copying the regions
but that could slow down things a lot.

The Microsoft docs sometimes seem to imply that you can mark a
VirtualAlloc'ed region as shareable but I've never been able to get that
to work.

cgf

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