Date: Thu, 30 Mar 2006 23:59:58 +0200
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From: Bernhard Loos <bernloos AT web DOT de>
To: cygwin AT cygwin DOT com
Subject: Re: dlopen() bug (new testcase)
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-----Ursprüngliche Nachricht-----
Von: Eric Blake 
Gesendet: Thu, 30 Mar 2006 15:04:27 +0000 (UTC)
>Bernhard Loos <bernloos <at> web.de> writes:
>>
>> >You'll have to read the archives.  Eric Blake has talked about this very
>> >recently.
>> 
>> Sorry, but I'm unable to locate it. The last post mentioning IsBad*Ptr 
>occoured
>> arround March 2005 -  not very recently.
>
>http://cygwin.com/ml/cygwin/2006-03/msg00455.html
>
>The gist of it is that IsBad*Ptr is a syscall, and a relatively
>dangerous one at that - Microsoft documents that it is not threadsafe,
>and that calling IsBadWritePtr on a stack guard page will disable
>the ability to grow that stack, meaning that the next time you
>write to the guard page your process will just quit (no popup
>box, no exception, nothing - just quit).  On the other hand, an
>exception handler is faster in the normal case of good pointers,
>does not corrupt system state of whether the stack guard page can
>grow, and does not cause data races with other threads.
>
>-- 
>Eric Blake

Thank you very much for explaining this in detail. I have read the other
message bevor, but it doesn't really explain the problems with IsBadReadPtr.

I was able to track the problem down, inserting a call to
_my_tls.init_exception_handler (_cygtls::handle_exceptions);
in the function dll::init() solves it. But I'm unsure, whether it introduce
other bugs. If somebody has checked this, I could submit a patch, if necessary.

                     Bernhard Loos
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