Re: Calling ghc dll's with MSVC++ code

31 Jan 2003

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"Sigbjorn" == Sigbjorn Finne  writes:
Sigbjorn> That's the system trap interrupt (i.e., transition to
    Sigbjorn> ring 0 / kernel mode to perform a system call/service.)

Thanks!  I've learned more about Windows and DLLs in a few days than I
ever expected or wanted to.  The problem appears to be related to

http://support.microsoft.com/default.aspx?scid=kb%3ben-us%3b153867

and

http://support.microsoft.com/default.aspx?scid=kb%3bEN-US%3b142243

int 0x2e is (presumably) an attempt to attach to the (my) DLL.
DllMain is (by design) not reentrant.  An attempt to create a thread
from DllMain would attach to the DLL, calling DllMain with a reason of
DLL_THREAD_ATTACH.  This latter call will hang until the original call
returns (which will never happen, now).  timeSetEvent creates a new
thread; and the callback is in the same DLL as the call to
startupHaskell.

The workaround appears to be to not put code that might possibly
create a new thread (that needs the DLL) in DllMain; instead such code
should go in an initialization function that is called after DllMain
returns.

I'll test it out and post code that corrects the example from the
User's Guide.
-- 
Kevin S. Millikin      Architecture Technology Corporation
Research Scientist     Specialists in Computer Architecture
(952)829-5864 x. 162   http://www.atcorp.com