RE: [Haskell-cafe] Re: Are handles garbage-collected?

On 26 October 2004 10:42, Malcolm Wallace wrote:

"Simon Marlow" writes:

...

I didn't mean fully synchronous, just "more synchronous". For example, the finalization routine could be run directly after garbage collection. Hugs & nhc98 already do this, because they don't support Haskell finalizers.

Actually, nhc98 supports both C and Haskell finalisers, with the same signatures as in ghc:

newForeignPtr :: FinalizerPtr a -> Ptr a -> IO (ForeignPtr a) newConcForeignPtr :: IO () -> Ptr a -> IO (ForeignPtr a)

C finalisers are run during garbage collection, Haskell finalisers are run immediately afterwards. In fact, you cannot run a Haskell finaliser during GC, because you don't have a valid heap to run it in.

But don't you run into problems in the implementation of newConcForeignPtr, when the Haskell finalizer needs the value of a thunk that was already under evaluation when the GC happened? ie. the need for concurrency that stopped this from becoming part of the official FFI. Cheers, Simon