Merge pull request #205 from osa1/close_dev_handle

withDev: Close the FD on exception

Crypto/Random/Entropy/Unix.hs

@@ -58,7 +58,7 @@ withDev :: String -> (H -> IO a) -> IO a
 withDev filepath f = openDev filepath >>= \h ->
     case h of
         Nothing -> error ("device " ++ filepath ++ " cannot be grabbed")
-        Just fd -> f fd >>= \r -> (closeDev fd >> return r)
+        Just fd -> f fd `E.finally` closeDev fd
 
 closeDev :: H -> IO ()
 closeDev h = hClose h