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Date:	Fri, 7 Sep 2001 13:19:21 +0200
From:	Corinna Vinschen <vinschen AT redhat DOT com>
To:	cygwin-developers AT cygwin DOT com
Subject:	Re: Figured out how to reproduce vfork/rsync bug! (proposed fix)
Message-ID:	<20010907131921.C17245@cygbert.vinschen.de>
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In-Reply-To:	<20010906210458.A8242@redhat.com>; from cgf@redhat.com on Thu, Sep 06, 2001 at 09:04:58PM -0400

On Thu, Sep 06, 2001 at 09:04:58PM -0400, Christopher Faylor wrote:
> On Thu, Sep 06, 2001 at 04:13:43PM -0400, Christopher Faylor wrote:
> >On Thu, Sep 06, 2001 at 02:53:26PM -0400, Jonathan Kamens wrote:
> >>I think I'll try the patch that cgf just sent out and see if it makes
> >>this problem go away.
> >>
> >>It will be very amusing if we discover that the bug I'm encountering
> >>is the same as Egor's.
> >
> >Try this.
> 
> I think this is the actual fix.  I noticed this about four hours ago but
> concluded that there just HAD to be something wrong with the cygheap
> stuff since that is what I had previously been working on.
> 
> I believe that cygheap was not the problem in this case.  What is actually
> happening is that the it is assumed prot_info_ptr is a zero filled array --
> that is not the case when you set that long environment variable.  The
> environment variable space was freed and then reused by the cmalloc
> in fhandler_socket::fhandler_socket.  So, when you look at the buffer
> it actually contains the contents of the environment variable.  That is
> acceptable behavior for cmalloc, of course but it looks like the
> subsequent code in fhandler_socket.cc needs assumes that this buffer
> is zeroed.
> 
> Anyway, I checked in the fix below.  It seems to resolve the problems.
> On further investigation, my previous fix was bogus.  It just resulted
> in never freeing space for the cygwin environment, which is incorrect.
> 
> Jonathan, Corinna, could you try the CVS version of cygwin and see
> if it fixes the problem?

It seems to fix it.  I'm mildly surprised, though.  prot_info_ptr is
used twice, first in `fixup_before_fork_exec' where it's getting
it's content and then in `fixup_after_fork' where it's content is
used to create the new socket handle.

If it's actually _used_ before being _set_ that would mean,
`fixup_after_fork' has been called w/o calling `fixup_before_fork_exec'
first.  But that would be simply wrong.

So the only other explanation would be that `WSADuplicateSocketA'
needs a zero filled buffer on input?!?

Corinna

-- 
Corinna Vinschen                  Please, send mails regarding Cygwin to
Cygwin Developer                                mailto:cygwin AT cygwin DOT com
Red Hat, Inc.

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