Proposed change to ForeignPtr

[Alastair Reid]

Since requiring ForeignPtr.newForeignPtr would require preemptive
concurrency (see previosu discussion), I propose the following changes:

1) Add these functions:

  makeForeignPtr :: Ptr a -> FunPtr (Ptr a -> IO ()) -> IO ForeignObj
  attachForeignPtrFinalizer :: ForeignPtr a -> FunPtr (Ptr a -> IO ()) -> IO ()

2) Remove newForeignPtr and addForeignPtrFinalizer


Two variants on this proposal:

1) Reuse the old function names instead of inventing new ones.

   I don't care much either way.  

2) Instead of removing the old functions, rename them and mark them
   as an optional extra.  

   I think this would be a mistake - the GHC documentation is the
   right place to mention extensions which are not available on all
   ffi implementations.


I have implemented makeForeignPtr in Hugs (I didn't do
attachForeignPtrFinalizer yet because it'll take a bit longer to add
that functionality and we can compile most (all?) of the hierarchial
libs without it.

-- 
Alastair Reid                 alastair at reid-consulting-uk.ltd.uk  
Reid Consulting (UK) Limited  http://www.reid-consulting-uk.ltd.uk/alastair/