Control.Concurrent.threadDelay fails in ghci on Mac OS X. Behaviour is correct in compiled code. To reproduce, it is enough to just execute threadDelay at the prompt.

Depending on the architecture, I get different behaviour:

• i386: 7.6.1 and 7.7.20121003: segmentation fault (11)
• x86_64: 7.6.1 and 7.7.20121003: executes without segfault, but there is no actual delay.

This is on Mac OS X 10.7.5 and 10.8.2.

Correct behaviour for ghci-7.6.1-x86_64 on Ubuntu 12.04. Also fine on Mac in the 7.4 series.

Example output:

Nightfall $ ghci
GHCi, version 7.6.1: http://www.haskell.org/ghc/  :? for help
Loading package ghc-prim ... linking ... done.
Loading package integer-gmp ... linking ... done.
Loading package base ... linking ... done.

Prelude > Foreign.Storable.sizeOf (undefined :: Int)
4

Prelude > Control.Concurrent.threadDelay (1000 * 1000)
Segmentation fault: 11

Sample program for the second case:

import Control.Concurrent

count :: Int -> IO ()
count n
  | n <= 0      = return ()
  | otherwise   = do
      putStrLn $ shows n "-ah-ha-ha"
      threadDelay (1000 * 1000) -- 1 second
      count (n-1)

main :: IO ()
main = count 10