On Mon, Feb 03, 2003 at 09:20:03PM +1100, m v wrote:
I do not understand the rational of the type of:
newForeignPtr :: Ptr a -> FunPtr (Ptr a -> IO ()) -> IO (ForeignPtr a)
suppose I have a c function
foreign import ccall fooalloc :: Ptr Foo
and another
foreign import ccall foofree :: Ptr Foo -> IO ()
now I want to combine fooalloc and foofree to create a Foreign pointer without wrapping foofree again, as in:
foreign import "wrapper" mkfoofree :: FunPtr (Ptr Foo -> IO ())
which I think counter productive - why should I import a function only to have to re-export it again !
You don't need to wrap it -- you can import its address with foreign import ccall "&foofree" foofreeptr :: FunPtr (Ptr a -> IO ())
previouse proposals did not require this - or am I missing something ?
why should the finaliser be a foreign function ?
It's a long story, but it turned out that Haskell side finalizers are hard to implement correctly in conventional single-threaded implementations. After a long discussion on this list in October last year, SimonM came up with a killer example: http://www.haskell.org/pipermail/ffi/2002-October/000866.html http://www.haskell.org/pipermail/ffi/2002-October/000910.html For a summary of the discussion, see http://cvs.haskell.org/cgi-bin/cvsweb.cgi/haskell-report/ffi/finalizers.txt However, only Hugs implements this part of the spec at the moment.