I do not think i can help you, but my FFi to functions with similar signature looks like this: C definition: PDFLIB_API int PDFLIB_CALL PDF_begin_document(PDF *p, const char *filename, int len, const char *optlist); haskell FFI: c_beginDocument :: Pdf -> String -> String -> IO Int c_beginDocument pdf a2 a3 = withCString a2 $ \a2' -> withCString a3 $ c_beginDocument'_ pdf a2' 0 foreign import ccall safe "Pdflib.chs.h PDF_begin_document" c_beginDocument'_ :: Pdf -> Ptr CChar -> CInt -> Ptr CChar -> IO Int The difference as you see, i'm using withCString to convert from ahskell to C and i'm passing 0 as the string size. On Friday, March 14, 2014 3:24:23 PM UTC-7, Miroslav Karpis wrote:
Hi, please can you help me with following?
I have a call to an external dll (via ffi) which if executed from ghci works fine. If I compile my code with 'ghc -o fm Mycode.hs -L. -lextdll' and run it I get 'Segmentation fault/access violation in generated code'.
main = do let param = "FilePath" let value = "C:/dev/misc/haskell/services/FM" result <- liftIO $ FM.setmodulestring param value return "done"
setmodulestring :: String -> String -> IO CInt setmodulestring param value = do let cParamLength = fromIntegral $ length param ::CInt cValueLength = fromIntegral $ length value ::CInt setVarInArray = (-1)::CInt alloca $ \cParam -> do alloca $ \cValue -> do result <- c_setmodulestring cParam cParamLength cValue cValueLength setVarInArray return result
If I try also with following, the behaviour is the same:
setmodulestring2 :: String -> String -> IO CInt setmodulestring2 param value = do cParam <- newCWString param cValue <- newCWString value let cParamLength = fromIntegral $ length param ::CInt cValueLength = fromIntegral $ length value ::CInt setVarInArray = (-1)::CInt result <- c_setmodulestring cParam cParamLength cValue cValueLength setVarInArray free cParam free cValue return res
Any comments/ideas more than appreciated.
Cheers, Miro