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import Control.Concurrent
import Control.Exception
import System.Mem ( performGC )
import System.Mem.Weak ( addFinalizer )
data P = P (MVar Bool)
-- Bug reported by Manuel Chakravarty, namely that we weren't checking
-- for runnable finalizers before declaring that the program is
-- deadlocked.
main = do
-- gcThread -- with this thread enabled, no error
mv <- newEmptyMVar
let p = P mv
addFinalizer p (set p)
takeMVar mv >>= print
putStrLn "End."
where
set (P mv) = putMVar mv True
--
-- this is just to demonstrate that it is only about the GC timing
--
gcThread = forkIO $ let gc = do
putStrLn "delay"
threadDelay 100000
putStrLn "gc"
performGC
gc
in gc
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