On 07/07/2012 05:06, Favonia wrote:
Hi all,
Recently I am tuning one of our incomplete libraries that uses FFI.
After dumping the interface file I realized strictness/demand analysis
failed for imported foreign functions---that is, they are not inferred
to be strict in their arguments. In my naive understanding all
imported foreign functions are strict! Here's a minimum example (with
GHC 7.4.2):
{-# LANGUAGE ForeignFunctionInterface #-}
module Main where
import Foreign.C
foreign import ccall unsafe "sin" sin' :: CDouble -> CDouble
where in the interface file the function sin' will have strictness
U(L) (meaning Unpackable(Lazy)).
This is fine - it means the CDouble is unpacked into its unboxed Double#
component. An unboxed value is always represented by L in strictness
signatures.
Cheers,
Simon
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