I am looking at using ResourceT to manage the acquisiition and
deallocation of network sockets.  In comparing resourceT's `allocate`
with `bracket` I was somewhat perplexed to find that `allocate` in
Control.Monad.Trans.Resource seems to not mask exceptions during
allocation (see "No mask" comment I inserted):

        allocateRIO :: IO a -> (a -> IO ()) -> ResourceT IO (ReleaseKey, a)
        allocateRIO acquire rel = ResourceT $ \istate -> liftIO $ E.mask $ \restore -> do
            a <- restore acquire
            --   ^^^ No mask ^^^
            key <- register' istate $ rel a
            return (key, a)

        allocate :: MonadResource m
                 => IO a -- ^ allocate
                 -> (a -> IO ()) -- ^ free resource
                 -> m (ReleaseKey, a)
        allocate a = liftResourceT . allocateRIO a

By contrast in Exception.Base we see that `bracket` masks
the initialization action:

        bracket before after thing =
          mask $ \restore -> do
            a <- before
            --   ^^^ masked! ^^^
            r <- restore (thing a) `onException` after a
            _ <- after a
            return r

This seems to suggest that ResourceT is more exposes to resource
leaks via asynchronous exceptions.  Say if a file descriptor is a
allocated, but an exception interrupts "allocate" before it can
register the resource.

Perhaps I am missing something, or there are good reasons for
the difference in approach.  Can anyone shed some light on the
reason why ResourceT differs (seemingly) from bracket in this
regard.

--
        Viktor.
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