Use explicit language extensions & remove extension fields from base.cabal

[ghc-base.git] / Control / Concurrent / MVar.hs

diff --git a/Control/Concurrent/MVar.hs b/Control/Concurrent/MVar.hs
index d3ff324..9a95b8f 100644 (file)
--- a/Control/Concurrent/MVar.hs
+++ b/Control/Concurrent/MVar.hs
@@ -1,3 +1,5 @@
+{-# LANGUAGE CPP, NoImplicitPrelude #-}
+
 -----------------------------------------------------------------------------
 -- |
 -- Module      :  Control.Concurrent.MVar
@@ -40,13 +42,18 @@ import Hugs.ConcBase ( MVar, newEmptyMVar, newMVar, takeMVar, putMVar,
 #endif
 
 #ifdef __GLASGOW_HASKELL__
-import GHC.Conc ( MVar, newEmptyMVar, newMVar, takeMVar, putMVar,
+import GHC.MVar ( MVar, newEmptyMVar, newMVar, takeMVar, putMVar,
                   tryTakeMVar, tryPutMVar, isEmptyMVar, addMVarFinalizer
                 )
 #endif
 
+#ifdef __GLASGOW_HASKELL__
+import GHC.Base
+#else
 import Prelude
-import Control.Exception as Exception
+#endif
+
+import Control.Exception.Base
 
 {-|
   This is a combination of 'takeMVar' and 'putMVar'; ie. it takes the value
@@ -54,7 +61,7 @@ import Control.Exception as Exception
 -}
 readMVar :: MVar a -> IO a
 readMVar m =
-  block $ do
+  mask_ $ do
     a <- takeMVar m
     putMVar m a
     return a
@@ -67,7 +74,7 @@ readMVar m =
 -}
 swapMVar :: MVar a -> a -> IO a
 swapMVar mvar new =
-  block $ do
+  mask_ $ do
     old <- takeMVar mvar
     putMVar mvar new
     return old
@@ -83,10 +90,9 @@ swapMVar mvar new =
 -- http://www.haskell.org//pipermail/haskell/2006-May/017907.html
 withMVar :: MVar a -> (a -> IO b) -> IO b
 withMVar m io =
-  block $ do
+  mask $ \restore -> do
     a <- takeMVar m
-    b <- Exception.catch (unblock (io a))
-            (\e -> do putMVar m a; throw e)
+    b <- restore (io a) `onException` putMVar m a
     putMVar m a
     return b
 
@@ -98,10 +104,9 @@ withMVar m io =
 {-# INLINE modifyMVar_ #-}
 modifyMVar_ :: MVar a -> (a -> IO a) -> IO ()
 modifyMVar_ m io =
-  block $ do
+  mask $ \restore -> do
     a  <- takeMVar m
-    a' <- Exception.catch (unblock (io a))
-            (\e -> do putMVar m a; throw e)
+    a' <- restore (io a) `onException` putMVar m a
     putMVar m a'
 
 {-|
@@ -111,9 +116,8 @@ modifyMVar_ m io =
 {-# INLINE modifyMVar #-}
 modifyMVar :: MVar a -> (a -> IO (a,b)) -> IO b
 modifyMVar m io =
-  block $ do
+  mask $ \restore -> do
     a      <- takeMVar m
-    (a',b) <- Exception.catch (unblock (io a))
-                (\e -> do putMVar m a; throw e)
+    (a',b) <- restore (io a) `onException` putMVar m a
     putMVar m a'
     return b