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Message-ID: <779F20BCCE5AD31186A50008C75D9979171720@silldn_mail1.sanwaint.com>
From: "Fifer, Eric" <EFifer AT sanwaint DOT com>
To: cygwin AT sourceware DOT cygnus DOT com
Subject: g++ COM problem with function pointers and -O2
Date: Mon, 8 May 2000 14:48:07 +0100 
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I'm use Cygwin, Perl and the Win32::OLE Perl module to interact with
COM objects.  And, of course, the Win32::OLE DLL is compiled with
-fvtable-thunks.  For the most part everything works just fine
(and as of Cygwin 1.1.0, Perl 5.6.0 and Win32::OLE 0.12 build
right out the box).

However, the extra DCOM functions like CoCreateInstanceEx are
implemented in the Win32::OLE Perl module by dynamically looking up
functions, LoadLibrary("OLE32") GetProcAddress("CoCreateInstanceEx"),
and calling through the function pointers.  However, this fails
when Perl is compiled with -O2 or -O.  Note that the Win32::OLE module
is dynamically loaded into Perl and the problem is triggered
when the separate Perl DLL has been built with the optimizer.

There are a couple of work-arounds.  Things are fine if Perl
is built with just -g!  Also, If I change the function pointer
to just a normal function call, it works too.  The failure with
function pointers and -O2 manifests itself as a stack corruption.

I know there are some limitations with COM support, but this
seems particularly strange because it depends on whether the
optimizer is used by a separate DLL.

Any idea what's going on here?

Thanks,

Eric Fifer

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