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import Control.Concurrent
import Control.Exception
-- test blocking & unblocking of async exceptions.
-- the first exception "foo" should be caught by the "caught1" handler,
-- since async exceptions are blocked outside this handler.
-- the second exception "bar" should be caught by the outer "caught2" handler,
-- (i.e. this tests that async exceptions are properly unblocked after
-- being blocked).
main = do
main_thread <- myThreadId
print =<< blocked -- False
m <- newEmptyMVar
m2 <- newEmptyMVar
forkIO (do takeMVar m
throwTo main_thread (ErrorCall "foo")
throwTo main_thread (ErrorCall "bar")
putMVar m2 ()
)
( do
block (do
putMVar m ()
print =<< blocked -- True
sum [1..1] `seq` -- give 'foo' a chance to be raised
(unblock $ myDelay 500000)
`Control.Exception.catch`
\e -> putStrLn ("caught1: " ++ show (e::SomeException))
)
threadDelay 10000
takeMVar m2
)
`Control.Exception.catch`
\e -> do print =<< blocked
putStrLn ("caught2: " ++ show (e::SomeException))
-- compensate for the fact that threadDelay is non-interruptible
-- on Windows with the threaded RTS in 6.6.
myDelay usec = do
m <- newEmptyMVar
forkIO $ do threadDelay usec; putMVar m ()
takeMVar m
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