On 12/07/2010 13:09, John Meacham wrote:
On Mon, Jul 12, 2010 at 11:57:18AM +0100, Simon Marlow wrote:
On 09/07/2010 18:46, John Meacham wrote:
On Fri, Jul 09, 2010 at 12:39:38PM +0100, Simon Marlow wrote:
On 08/07/2010 22:46, John Meacham wrote:
Ack, I just noticed that IntPtr,IntMax, and WordPtr and WordMax were
left out of the report. These are fairly vital for writing portable FFI
code.
Make a proposal to get them into Haskell 2011, I don't imagine it would
be controversial.
That's the thing, They were already accepted as part of H'2010. At least
according to the site:
http://hackage.haskell.org/trac/haskell-prime/wiki/ForeignFunctionInterface
Ok, this is probably an oversight on my part, so sorry about that. I
can treat it as errata and fix the report.
However I'm a bit confused. Currently we have IntPtr and WordPtr
exported by Foreign.Ptr in base, but we don't have IntMax and WordMax
anywhere that I can see, and I don't recall any discussion about where
they should be defined, or what they should be defined to.
Hmm... It appears there was some divergence between my initial proposal,
what jhc implemented, and what ghc implemented. Is there any issue with
declaring that IntPtr and WordPtr marshal to intptr_t and uintptr_t
respectively? If not, then just having those in Foreign.Ptr like ghc
does seems fine. In jhc I export them from Data.Word and Data.Int
respectively, but I will change it to match ghc/the report.
I have added IntPtr and WordPtr to Foreign.Ptr, and added notes that
they are compatible with intptr_t and uintptr_t, respectively.
http://www.haskell.org/onlinereport/haskell2010/haskellch35.html#x43-30600035
Though I'm not sure this is the best solution, because we also have
CIntPtr and CUIntPtr in Foreign.C.Types, which are guaranteed to be
compatible with (u)intptr_t but do not have conversion operations. We
might want to revisit this in the future.
I also followed up with some other changes to the FFI spec that I
overlooked in the Haskell 2010 merge, particularly to do with newtype
marshalling in the definition of foreign type:
http://www.haskell.org/onlinereport/haskell2010/haskellch8.html#x15-1560008.4.2
I do think IntMax and WordMax are quite useful as haskell types and
should be in Data.Int and Data.Word, but if we have CIntMax and CWordMax
then they arn't strictly neccesary from a FFI standpoint.
I've left out IntMax and WordMax for now, as we don't even have them in
GHC. The best way to proceed here is with a library proposal and then a
Haskell 2010 proposal.
Cheers,
Simon
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