From: "Michael Marte" <marte@pms.informatik.uni-muenchen.de> To: "Andreas Marth" <Andreas-Haskell@gmx.net> Cc: <haskell@haskell.org> Sent: Wednesday, September 06, 2006 6:04 PM Subject: Re: [Haskell] How to generate a dll?

Andreas,

I am using a DLL generated by ghc 6.4.2 in combination with Visual C++ 2005. Some useful links:

http://www.willus.com/mingw/yongweiwu_stdcall.html

http://en.wikipedia.org/wiki/Name_mangling

http://www.mingw.org/mingwfaq.shtml#faq-msvcdll

What do you mean by "the resulting dll was not stable"?

Michael

I meant that the dll crashed Excel wenn I stopped the debugging mode and also if I used it in a VB-projekt it crahed that when stopped. This happend with DLLs which had a Bool or Int as return or were only a sub. If I tried to return a String (marshalled to CString) the dll just plain crashed when called. Thank you for the links. I am working through them and hope it will get better. Do I understand it right that I will get a dll that can be incorporated into VB but is not a com-dll or is it a com dll just by being able to be called from VB? Thanks, Andreas

Hi!

Hi, Andreas! Try adding these lines to your DllMain:

if (reason == DLL_PROCESS_DETACH) { shutdownHaskell(); return TRUE; }

This worked great. (At least with Excel. I didn't test it with the VB-Project yet.)

...

If I tried to return a String (marshalled to CString) the dll just plain crashed when called. How exactly is it marshalled?

At the moment the test program is: module Calculate where import Foreign.C.String foreign export stdcall calculate :: CString -> IO (CString) calculate :: CString -> IO (CString) calculate cs = do s <- peekCString cs newCString (reverse s) So the newCString does the marshalling. (At least I think so.) But if I call this in VBA it crashes Excel VBA code: Dim helper As String Private Declare Function calculate Lib "Calculate.dll" (ByVal x as String) As String Sub test () helper = calculate("Test") Debug.Print helper End Sub All really basic. Does anybody know why that does not work? Thanks for all the answers up to now. Andreas

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