[project @ 2005-02-01 00:52:20 by ross]

[ghc-base.git] / GHC / IOBase.lhs

diff --git a/GHC/IOBase.lhs b/GHC/IOBase.lhs
index 07273f9..233148b 100644 (file)
--- a/GHC/IOBase.lhs
+++ b/GHC/IOBase.lhs
@@ -1,5 +1,5 @@
 \begin{code}
-{-# OPTIONS -fno-implicit-prelude #-}
+{-# OPTIONS_GHC -fno-implicit-prelude #-}
 -----------------------------------------------------------------------------
 -- |
 -- Module      :  GHC.IOBase
@@ -266,6 +266,15 @@ instance Eq (MVar a) where
 -- enough information to identify the handle for debugging.  A handle is
 -- equal according to '==' only to itself; no attempt
 -- is made to compare the internal state of different handles for equality.
+--
+-- GHC note: a 'Handle' will be automatically closed when the garbage
+-- collector detects that it has become unreferenced by the program.
+-- However, relying on this behaviour is not generally recommended:
+-- the garbage collector is unpredictable.  If possible, use explicit
+-- an explicit 'hClose' to close 'Handle's when they are no longer
+-- required.  GHC does not currently attempt to free up file
+-- descriptors when they have run out, it is your responsibility to
+-- ensure that this doesn't happen.
 
 data Handle 
   = FileHandle                         -- A normal handle to a file
@@ -559,6 +568,10 @@ data Exception
        -- ^The current thread was executing a call to
        -- 'Control.Concurrent.MVar.takeMVar' that could never return,
        -- because there are no other references to this 'MVar'.
+  | BlockedIndefinitely
+       -- ^The current thread was waiting to retry an atomic memory transaction
+       -- that could never become possible to complete because there are no other
+       -- threads referring to any of teh TVars involved.
   | Deadlock
        -- ^There are no runnable threads, so the program is
        -- deadlocked.  The 'Deadlock' exception is
@@ -696,6 +709,7 @@ instance Show Exception where
   showsPrec _ (DynException _err)        = showString "unknown exception"
   showsPrec _ (AsyncException e)        = shows e
   showsPrec _ (BlockedOnDeadMVar)       = showString "thread blocked indefinitely"
+  showsPrec _ (BlockedIndefinitely)     = showString "thread blocked indefinitely"
   showsPrec _ (NonTermination)           = showString "<<loop>>"
   showsPrec _ (Deadlock)                 = showString "<<deadlock>>"