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The following hangs on the current ghc-STABLE snapshot, and shouldn't.

module Main where

import Control.Concurrent
import qualified Data.ByteString.Lazy.Char8 as B
import System.IO
import System.Process

launch :: B.ByteString -> IO B.ByteString
launch i = do (hin,hout,herr,ph) <- runInteractiveProcess "cat" [] Nothing Nothing
              -- forkIO $ collect ph  -- This doesn't seem to be relevant to the problem.
              forkIO $ do B.hPut hin i
                          hClose hin
              B.hGetContents hout

collect :: ProcessHandle -> IO ()
collect ph = do waitForProcess ph
                return ()

main :: IO ()
main = let i = B.pack "foo" in
       do o <- foldl (>>=) (return i) (take 5 (repeat launch))
          B.putStrLn o

See also #1936 (closed).

Trac metadata

Trac field	Value
Version	6.8.2
Type	Bug
TypeOfFailure	OtherFailure
Priority	normal
Resolution	Unresolved
Component	Compiler
Test case
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Architecture