ANN: H98 FFI Addendum 1.0, Release Candidate 7

[Manuel M T Chakravarty]

Alastair Reid <alastair at reid-consulting-uk.ltd.uk> wrote,

> > RC 7 of the FFI Addendum is now available from
> 
> In adding mallocForeignPtr and friends to Hugs, I found that I needed
> the address of free to pass as a parameter.
> 
> There's no suitable way to generate &free from MarshalAlloc.free (the
> obvious use of a Haskell wrapper would break the whole reason for the
> recent change to ForeignPtrs).
> 
> Could we add &free to the export list of MarshalAlloc?
> 
>   foreign import ccall unsafe "stdlib.h &free" ptr_free :: FunPtr (Ptr a -> IO ())
> 
> I am currently using 'ptr_free' as the Haskell name for this pointer
> but I expect that a better name could be found with little effort.

So far, we never explicitly say (I believe) that `malloc'
corresponds to C's `malloc()'; ie, that C's `free()' (and
hence, `ptr_free') may actually be used to free storage that
has been allocated by `malloc'.

We might define the CAF

  cfree :: FunPtr (Ptr a -> IO ())

as a pointer to a C function that free's storage allocated
with `malloc' from C without entering Haskell land and
explicitly note that this is useful as a finalizer.

The construction still seems pretty awkward to me.  I hope
the change to ForeignPtr doesn't entail any more nasty
suprises like this.

Cheers,
Manuel