-- |
-- Module : System.Exit
-- Copyright : (c) The University of Glasgow 2001
--- License : BSD-style (see the file libraries/core/LICENSE)
+-- License : BSD-style (see the file libraries/base/LICENSE)
--
-- Maintainer : libraries@haskell.org
-- Stability : provisional
import GHC.IOBase
#endif
+#ifdef __HUGS__
+import Hugs.Prelude
+import Hugs.Exception
+#endif
+
+#ifdef __NHC__
+import System
+ ( ExitCode(..)
+ , exitWith
+ )
+#endif
+
-- ---------------------------------------------------------------------------
-- exitWith
--- `exitWith code' terminates the program, returning `code' to the
--- program's caller. Before it terminates, any open or semi-closed
--- handles are first closed.
+-- | Computation 'exitWith' @code@ throws 'ExitException' @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.
+--
+-- 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
+-- the error handling in the 'IO' monad and cannot be intercepted by
+-- 'catch' from the "Prelude". However it is an 'Exception', 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'.
+#ifndef __NHC__
exitWith :: ExitCode -> IO a
-exitWith ExitSuccess = throw (ExitException ExitSuccess)
-exitWith code@(ExitFailure n)
- | n == 0 = ioException (IOError Nothing InvalidArgument "exitWith" "ExitFailure 0" Nothing)
- | otherwise = throw (ExitException code)
+exitWith ExitSuccess = throwIO (ExitException ExitSuccess)
+exitWith code@(ExitFailure n)
+ | n /= 0 = throwIO (ExitException code)
+#ifdef __GLASGOW_HASKELL__
+ | otherwise = ioError (IOError Nothing InvalidArgument "exitWith" "ExitFailure 0" Nothing)
+#endif
+#endif /* ! __NHC__ */
+-- | The computation 'exitFailure' is equivalent to
+-- 'exitWith' @(@'ExitFailure' /exitfail/@)@,
+-- where /exitfail/ is implementation-dependent.
exitFailure :: IO a
exitFailure = exitWith (ExitFailure 1)