Merge branch 'nested-bracket' (see haskell#590)

Network/Socket/Shutdown.hs

@@ -1,4 +1,5 @@
 {-# LANGUAGE CPP #-}
+{-# LANGUAGE ScopedTypeVariables #-}
 
 #include "HsNetDef.h"
 
@@ -59,7 +60,8 @@ gracefulClose s tmout0 = sendRecvFIN `E.finally` close s
         -- Sending TCP FIN.
         ex <- E.try $ shutdown s ShutdownSend
         case ex of
-          Left (E.SomeException _) -> return ()
+          -- Don't catch asynchronous exceptions
+          Left (_ :: E.IOException) -> return ()
           Right () -> do
               -- Giving CPU time to other threads hoping that
               -- FIN arrives meanwhile.
@@ -93,29 +95,26 @@ recvEOFevent :: Socket -> Int -> Ptr Word8 -> IO ()
 recvEOFevent s tmout0 buf = do
     tmmgr <- Ev.getSystemTimerManager
     tvar <- newTVarIO False
-    E.bracket (setup tmmgr tvar) teardown $ \(wait, _) -> do
-        waitRes <- wait
-        case waitRes of
-          TimeoutTripped -> return ()
-          -- We don't check the (positive) length.
-          -- In normal case, it's 0. That is, only FIN is received.
-          -- In error cases, data is available. But there is no
-          -- application which can read it. So, let's stop receiving
-          -- to prevent attacks.
-          MoreData       -> void $ recvBufNoWait s buf bufSize
+    E.bracket (setupTimeout tmmgr tvar) (cancelTimeout tmmgr) $ \_ -> do
+        E.bracket (setupRead s) cancelRead $ \(rxWait,_) -> do
+            let toWait = readTVar tvar >>= check
+                wait = atomically ((toWait >> return TimeoutTripped)
+                               <|> (rxWait >> return MoreData))
+            waitRes <- wait
+            case waitRes of
+              TimeoutTripped -> return ()
+              -- We don't check the (positive) length.
+              -- In normal case, it's 0. That is, only FIN is received.
+              -- In error cases, data is available. But there is no
+              -- application which can read it. So, let's stop receiving
+              -- to prevent attacks.
+              MoreData       -> void $ recvBufNoWait s buf bufSize
   where
-    setup tmmgr tvar = do
-        -- millisecond to microsecond
-        key <- Ev.registerTimeout tmmgr (tmout0 * 1000) $
-            atomically $ writeTVar tvar True
-        (evWait, evCancel) <- waitAndCancelReadSocketSTM s
-        let toWait = do
-                tmout <- readTVar tvar
-                check tmout
-            toCancel = Ev.unregisterTimeout tmmgr key
-            wait = atomically ((toWait >> return TimeoutTripped)
-                           <|> (evWait >> return MoreData))
-            cancel = evCancel >> toCancel
-        return (wait, cancel)
-    teardown (_, cancel) = cancel
+    -- millisecond to microsecond
+    tmout = tmout0 * 1000
+    setupTimeout tmmgr tvar =
+        Ev.registerTimeout tmmgr tmout $ atomically $ writeTVar tvar True
+    cancelTimeout = Ev.unregisterTimeout
+    setupRead = waitAndCancelReadSocketSTM
+    cancelRead (_,cancel) = cancel
 #endif