Hello Maurнcio, Tuesday, February 10, 2009, 11:56:40 PM, you wrote: 1. haskell compiler should check that your haskell imports match C function prototypes. ghc does it in -fvia-C mode if you declare .h file where the function prototype may be found: foreign import ccall unsafe "Environment.h UpdateCRC" c_UpdateCRC :: Ptr CChar -> CUInt -> CUInt -> IO CUInt but who now uses -fvia-C mode? 2. there is correspondence between C and Haskell types. haskell equivalents for C tpes are defined in FFI addendum. C equivalents for GHC haskell types are defined in ghc .h files, these are things like HsInt and so on if you use, for example, Int type on haskell side and int on C side, they may turn out to be the same or not. if you don't use -fvia-C and .h file, you will not get even a warning - program will just stop working i think that we may propose changing FFI addendum so that haskell compilers guarantees correspondence between Int16 and int16_t and so on disclaimer: i don't used ghc versions after 6.6, so things may be worse or better now :)
Yes, I can. Thanks. Just forget my idea, with this I can provide all those types in a library.
I'm confused. When is it possible to use a type as a parameter to a foreign function call? My first guess was that I had to provide an instance for class Storable, but after I tried writing a complex-like type that way GHC told me my type was unaceptable. So I thought only types allowed by the compiler (including forall a. Ptr a) could be used that way.
What is the rule? I've read all of FFI report and found nothing. Did I miss something? How can I make a type of mine acceptable? Why are Data.Int acceptable, and how could I know that?
Thanks, Maurнcio
I think you can use Data.Word and Data.Int types for this, that is. (...)
After reading an ISO draft for standard C, I found a few types that could be usefull when binding to libraries (these are from
): int8_t, uint8_t, int16_t, uint16_t, int32_t, uint32_t, int64_t, uint64_t
(...)
_______________________________________________ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
-- Best regards, Bulat mailto:Bulat.Ziganshin@gmail.com