Hello, I'm trying to use a C++ class in Haskell through C exports. It works all very well, except that when I call the function that deletes the object, it is still valid, I can still call methods on it. Here is my Haskell code: {-# LANGUAGE ForeignFunctionInterface #-} import Foreign import Foreign.C.Types newtype PKlass = PKlass (Ptr PKlass) foreign import ccall unsafe "Klass_Create" kCreate :: CInt -> CInt -> IO PKlass foreign import ccall unsafe "Klass_Destroy" kDestroy :: PKlass -> IO () foreign import ccall unsafe "Klass_GetX" kGetX :: PKlass -> IO CInt foreign import ccall unsafe "Klass_GetY" kGetY :: PKlass -> IO CInt foreign import ccall unsafe "Klass_AddKlass" kAdd :: PKlass -> PKlass -> IO PKlass main = do k <- kCreate 4 5 kDestroy k *kGetY k >>= print -- This shouldn't work* k' <- kCreate 2 8 k'' <- k `kAdd` k' kDestroy k'' *kGetY k'' >>= print -- This neither* So it is very basic, and I can't understand why the supposedly destroyed objects are still here. Enclosed is all the source code (C++ class, C exportation and the Haskell main hereabove). I compile it this way: ghc --make main.hs *.cpp -lstdc++