RE: Running a "final" finaliser

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