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Date:	Wed, 27 Jun 2001 02:42:03 -0400
From:	Christopher Faylor <cgf AT redhat DOT com>
To:	cygwin AT cygwin DOT com
Subject:	Re: pthreads works, sorta
Message-ID:	<20010627024203.A20077@redhat.com>
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In-Reply-To:	<20010627023128.R19058@redhat.com>; from cgf@redhat.com on Wed, Jun 27, 2001 at 02:31:28AM -0400

On Wed, Jun 27, 2001 at 02:31:28AM -0400, Christopher Faylor wrote:
>On Wed, Jun 27, 2001 at 02:51:13PM +0800, Dmitry Timoshkov wrote:
>>"Robert Collins" <robert DOT collins AT itdomain DOT com DOT au> wrote:
>>
>>[skipped]
>>
>>> What does all this mean? We need to catch invalid memroy access, and
>>> ValidQuery was supplied by Chris as a tool to do that.
>>
>>In a multithreaded environment VirtualQuery, IsBad* and similar approaches
>>are wrong. It can't be guaranteed that after a successful test that memory
>>will be still accessable.
>
>They are not necessarily wrong if they are controlled by appropriate mutexes.
>The file handling code should be protected this way.   I don't know about
>the thread code, though.

Actually, this is wrong.  I was assuming that access to an object X would
only be by well-behaved manipulators of object X.  It's possible for a rogue
thread to do something odd with a wild pointer and still screw up memory.

So SEH is the only safe way to handle this.  However, I don't think that SEH
will actually work in the Cygwin DLL.

cgf

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