-----------------------------------------------------------------------------
module System.Exit
- (
+ (
ExitCode(ExitSuccess,ExitFailure)
, exitWith -- :: ExitCode -> IO a
, exitFailure -- :: IO a
+ , exitSuccess -- :: IO a
) where
import Prelude
#ifdef __GLASGOW_HASKELL__
-import GHC.IOBase
+import GHC.IO
+import GHC.IO.Exception
#endif
#ifdef __HUGS__
-import Hugs.Prelude
-import Hugs.Exception
+import Hugs.Prelude (ExitCode(..))
+import Control.Exception.Base
#endif
#ifdef __NHC__
-- ---------------------------------------------------------------------------
-- exitWith
--- | Computation 'exitWith' @code@ throws 'ExitException' @code@.
+-- | Computation 'exitWith' @code@ throws 'ExitCode' @code@.
-- Normally this terminates the program, returning @code@ to the
--- program's caller. Before the program terminates, any open or
--- semi-closed handles are first closed.
+-- program's caller.
+--
+-- On program termination, the standard 'Handle's 'stdout' and
+-- 'stderr' are flushed automatically; any other buffered 'Handle's
+-- need to be flushed manually, otherwise the buffered data will be
+-- discarded.
--
-- A program that fails in any other way is treated as if it had
-- called 'exitFailure'.
-- A program that terminates successfully without calling 'exitWith'
-- explicitly is treated as it it had called 'exitWith' 'ExitSuccess'.
--
--- As an 'ExitException' is not an 'IOError', 'exitWith' bypasses
+-- As an 'ExitCode' is not an 'IOError', 'exitWith' bypasses
-- the error handling in the 'IO' monad and cannot be intercepted by
--- 'catch' from the "Prelude". However it is an 'Exception', and can
+-- 'catch' from the "Prelude". However it is a 'SomeException', and can
-- be caught using the functions of "Control.Exception". This means
-- that cleanup computations added with 'Control.Exception.bracket'
-- (from "Control.Exception") are also executed properly on 'exitWith'.
-
+--
+-- Note: in GHC, 'exitWith' should be called from the main program
+-- thread in order to exit the process. When called from another
+-- thread, 'exitWith' will throw an 'ExitException' as normal, but the
+-- exception will not cause the process itself to exit.
+--
#ifndef __NHC__
exitWith :: ExitCode -> IO a
-exitWith ExitSuccess = throwIO (ExitException ExitSuccess)
+exitWith ExitSuccess = throwIO ExitSuccess
exitWith code@(ExitFailure n)
- | n /= 0 = throwIO (ExitException code)
+ | n /= 0 = throwIO code
#ifdef __GLASGOW_HASKELL__
- | otherwise = ioError (IOError Nothing InvalidArgument "exitWith" "ExitFailure 0" Nothing)
+ | otherwise = ioError (IOError Nothing InvalidArgument "exitWith" "ExitFailure 0" Nothing Nothing)
#endif
#endif /* ! __NHC__ */
-- where /exitfail/ is implementation-dependent.
exitFailure :: IO a
exitFailure = exitWith (ExitFailure 1)
+
+-- | The computation 'exitSuccess' is equivalent to
+-- 'exitWith' 'ExitSuccess', It terminates the program
+-- successfully.
+exitSuccess :: IO a
+exitSuccess = exitWith ExitSuccess