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{-# language GADTSyntax #-}
{-# language KindSignatures #-}
{-# language UnliftedFFITypes #-}
{-# language ForeignFunctionInterface #-}
{-# language MagicHash #-}
{-# language UnboxedTuples #-}
-- Test for shims when passing a ByteArray# to a foreign function.
-- The bad behavior here was initially observed in the MR
-- https://gitlab.haskell.org/ghc/ghc/merge_requests/939,
-- but this test has been named after issue #16650 since it
-- is closely related to the unexpected behavior there.
import GHC.Exts
import GHC.Word
import GHC.IO
import Data.Kind (Type)
main :: IO ()
main = do
mb0 <- luckySingleton
print =<< readByteArray mb0 0
case box mb0 of
Box x -> print =<< c_head_bytearray (unsafeCoerce# x)
foreign import ccall unsafe "head_bytearray"
c_head_bytearray :: MutableByteArray# RealWorld -> IO Word8
data Box :: Type where
Box :: (Any :: TYPE 'UnliftedRep) -> Box
data MutableByteArray :: Type where
MutableByteArray :: MutableByteArray# RealWorld -> MutableByteArray
box :: MutableByteArray -> Box
{-# noinline box #-}
box (MutableByteArray x) = Box (unsafeCoerce# x)
luckySingleton :: IO MutableByteArray
luckySingleton = IO $ \s0 -> case newByteArray# 1# s0 of
(# s1, marr# #) -> case writeWord8Array# marr# 0# fortyTwo s1 of
s2 -> (# s2, MutableByteArray marr# #)
where W8# fortyTwo = 42
readByteArray :: MutableByteArray -> Int -> IO Word8
readByteArray (MutableByteArray b#) (I# i#) = IO $ \s0 ->
case readWord8Array# b# i# s0 of
(# s1, w #) -> (# s1, W8# w #)
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