Re: Proposal: System.Timeout module for base

28 Jan 2007

      On 26.01 23:48, Peter Simons wrote:
...
timeout :: Int -> IO a -> IO (Maybe a)
timeout n f
    | n <  0    = fmap Just f
    | n == 0    = return Nothing
    | otherwise = do
        pid <- myThreadId
        ex  <- fmap Timeout newUnique
        handleJust (\e -> dynExceptions e >>= fromDynamic >>= guard . (ex ==))
                   (\_ -> return Nothing)
                   (bracket (forkIO (threadDelay n >> throwDynTo pid ex))
                            (killThread)
                            (\_ -> fmap Just f))
This seems broken on GHC with FFI.

The thread gets blocked on a FFI call that blocks forever and thus the
timeout exception is not delivered - if I remember things correctly.

- Einar Karttunen