Regression in vector Primitive/Unboxed.Mutable move operations

[dfordivam]

This issue was discovered with the following test failure of the vector package. The tests work fine with ghcjs 8.6.5.

  Data.Vector.Primitive.Mutable (Move):          FAIL
    *** Failed! Falsified (after 4 tests):
    [1,0,-2]
    Move: ([1,0,-2],2,0,1)
    Use --quickcheck-replay=430678 to reproduce.
  Data.Vector.Unboxed.Mutable (Move):            FAIL
    *** Failed! Falsified (after 6 tests):
    [0,2,-3,-5]
    Move: ([0,2,-3,-5],0,3,1)
    Use --quickcheck-replay=189345 to reproduce.

And could be easily reproduced as done here. (Here I am using an older haskell.nix because the latest ghcjs has a different bug #809 )

git clone https://github.com/dfordivam/try-haskell-nix.git
cd try-haskell-nix
nix-build vector-ghcjs-issue/default.nix -A projectCross.ghcjs.hsPkgs.hello-world.components.exes.hello-world

[dfordivam]

On further digging I could figure out that this is a primitive pkg issue

import Data.Primitive.ByteArray
import Data.Primitive.Types

main :: IO ()
main = do
  let src = byteArrayFromList [0, 1, 2 :: Int]
  print src
  a <- unsafeThawByteArray src
  let srcLoc = 0
      dstLoc = 1
      sz = (sizeOf (undefined :: Int))
      len = 2
  moveByteArray a (srcLoc * sz) a (dstLoc * sz) (len * sz)
  b <- unsafeFreezeByteArray a
  print b
  if b == byteArrayFromList [0, 1, 2 :: Int]
    then putStrLn "Fail"
    else putStrLn "Pass"

[luite]

thanks for the good testcase. I think 929e11f fixes this.

[dfordivam]

@luite Thanks for looking into the issue. I am afraid that this commit only fixes part of the issue. The below test shows the problematic case. I have a fix here #814

test4 = do
  let srcLoc = 1
      dstLoc = 0
      sz = (sizeOf (undefined :: Word8))
      len = 2
      src = [0, 1, 2, 3 :: Word8]
  print (byteArrayFromList src)
  a <- newByteArray (length src * sz)
  copyByteArray a 0 (byteArrayFromList src) 0 (length src * sz)
  moveByteArray a (dstLoc * sz) a (srcLoc * sz) (len * sz)
  b <- unsafeFreezeByteArray a
  print b
  if b /= byteArrayFromList [1, 2, 2, 3 :: Word8]
    then putStrLn "Fail"
    else putStrLn "Pass"

[dfordivam]

fix has been merged