[Haskell-cafe] Waiting for async exception (and nothing else)

[Silvio Frischknecht]

> but this seems like a bit of a hack. Waiting on an otherwise-unused MVar
> or doing 'atomically retry' don't work because GHC kills them off
> straight away.

Not that this will help you any but this might actually be a bug.

From:
https://hackage.haskell.org/package/base-4.8.1.0/docs/Control-Concurrent.html

Holding a normal ThreadId reference will prevent the delivery of
BlockedIndefinitely exceptions because the reference could be used as
the target of throwTo at any time, which would unblock the thread.

So this will in fact run forever because threadId is still in scope.

main = do
	threadId  <-forkIO $ do
		var <- newEmptyMVar
		takeMVar var
	forever $ threadDelay maxBound

so wouldn't it make sense to keep this alive

main = do
	var <- newEmptyMVar
	takeMVar var

because a user interrupt may ocure.

Silvio