Running a "final" finaliser

[Simon Marlow]

> The other complication I can see is that ForeignPtr finalisers can't
> be Haskell. So I have to call the Haskell finalisation from C.
> Is that safe? I'm afraid I still don't fully understand why Haskell
> finalisers are unsafe or why (if) calling Haskell from a C finaliser
> (which then called C land again) would be any safer. 

If you don't mind your code being non-portable, then Foreign.Concurrent
provides Haskell finalisers.  This support will be available only on
Haskell implementations which implement pre-emptive concurrency (i.e.
just GHC for now).

Cheers,
	Simon