Hi Kyra! First thanks for your repeated responses. I tried to use SysAllocString as suggested by you and Esa Ilari Vuokko. Unfortuntly I get an error: "fake: undefined reference to `SysAllocString@4`" from the linker if I use "stdcall" (wich I think I should use) or fake: undefined reference to `SysAllocString`" if I use ccall. I solved this with adding C:\WINNT\system32\oleaut32.dll to the files the linker shold link. Was that correct? Because this dll crashes Excel instantly. I used the code suggested by Esa Ilari Vuokko: newtype BSTR = BSTR CWString foreign import stdcall "oleauto.h SysAllocString" c_SysAllocString :: CWString -> IO BSTR sysAllocString :: String -> IO BSTR sysAllocString s = withCWString s c_SysAllocString >>= return Added my function: testL :: Int -> CString -> IO BSTR8 testL n cs = do s <- peekCString cs sysAllocString $ concat $ take n $ repeat s foreign export stdcall testL :: Int -> CString -> IO BSTR8
Use SysAllocString... family. Also, remember they (by convention) have to be released from the client side.
Cheers, Kyra
Regarding the release from the client side: If I call a Haskell DLL from Excel shall I release the BSTR within the Haskell DLL? That would mean before the value is returned? Thanks a lot, Andreas