Hi, please can you help me with following? I'm trying to combine scotty + ffi but it returns 'Segmentation fault/access violation in generated code'. The thing is, that when I run only the ffi setmodulestring function, everything works fine. When I call it from scotty I get the segfault. I have hardcoded the 'param' and 'value' parameters in setmodulestring function just to be sure that the input is correct. scotty code: main = scotty 3000 $ do middleware logStdoutDev post "/setstringtest" $ do let param = "FilePath" let value = "C:/dev/misc/haskell/services/FM" result <- liftIO $ FM.setmodulestring param value text "done" ffi code: setmodulestring :: String -> String -> IO CInt setmodulestring param value = do cParam <- newCString param cValue <- newCString value let cParamLength = fromIntegral $ length param ::CInt cValueLength = fromIntegral $ length value ::CInt setVarInArray = (-1)::CInt result <- c_setmodulestring cParam cParamLength cValue cValueLength setVarInArray return result Any comments/ideas more than appreciated. Cheers, Miro