[Haskell-beginners] How to initialize a C struct with FFI

Marco De Oliveira deolivem at gmail.com
Sat Feb 6 06:28:31 EST 2010


I try to initialize a C struct using the FFI API and ghc stays blocked when
I execute my code (and I got sometimes the error "out of memory").
I do not understand, I do not find any mistake in my code:

{-# OPTIONS -XTypeSynonymInstances #-}

import Foreign.C.Types
import Foreign.Marshal.Alloc
import Foreign.Ptr
import Foreign.Storable

type CStruct = (CULong, CULong)

instance Storable CStruct where
  sizeOf _ = 2*sizeOf (undefined::CULong)
  alignment _ = alignment (undefined::CULong)

test = alloca (\pStruct -> do
         poke pStruct ( (fromIntegral 1)::CULong, (fromIntegral 1)::CULong )

Thanks for your help.

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