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Date: Tue, 15 Mar 2011 20:50:55 +0000
From: Jon TURNEY <jon DOT turney AT dronecode DOT org DOT uk>
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Subject: Re: Calling sem_wait() in DllMain( DLL_THREAD_DETACH) crashes
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On 15/03/2011 20:28, Christopher Faylor wrote:
> On Tue, Mar 15, 2011 at 04:01:35PM -0400, Charles Wilson wrote:
>> On 3/15/2011 3:07 PM, Christopher Faylor wrote:
>>> On Tue, Mar 15, 2011 at 06:34:27PM +0000, Jon TURNEY wrote:
>>>>
>>>> I've come across a problem whilst trying to run the twisted test suite, where
>>>> some tests just cause python to segfault.  It seems to be the same issue with
>>>> libcrypto as reported in [2],[3]
>>
>>> Actually you aren't supposed to be able to call anything you like here
>>> and it isn't clear why a POSIX/UNIX/Linux program would be relying on
>>> DllMain.

Thanks for the clarification.

>> There are cases where cygwin-ish code does win32-ish things, like
>> login.exe, or the PyWin32 extensions for Python-on-Windows(and cygwin).
>> Maybe twisty uses PyWin32?
> 
> The python Twisted stuff works on UNIX systems so there should be no
> reason to use Windows-isms in Cygwin code - especially when the
> Windows-ism *calls* UNIX code.  The ability to get into trouble when you
> mix Windows stuff like DllMain with Cygwin stuff is very high.

Absolutely.

I did read through the UG looking for a statement like that, but the only
thing I found was the caveat about mixing POSIX and Win32 calls to set cwd.
Perhaps I overlooked something, or maybe it would be good if that was more
clearly documented.

>> However, it does seem that python (or one of its extensions) is doing
>> something it shouldn't.

Given the above clarification about cygwin, this is a bug in libcrypto from
OpenSSL (which tries to be portable to more than just POSIX, and has a
DllMain() which is built for both cygwin and Win32), and a patch like that at
[1] (or perhaps one which avoids DllMain on cygwin entirely) should be applied.

Sorry that I didn't make it more clear that the underlying issue is in
libcrypto rather than twisted or python.

[1] http://www.mail-archive.com/openssl-dev AT openssl DOT org/msg24599.html

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