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\begin{code}
-----------------------------------------------------------------------------
-- |
-- Module : GHC.TopHandler
-- Copyright : (c) The University of Glasgow, 2001-2002
-- License : see libraries/base/LICENSE
--
-- Maintainer : cvs-ghc@haskell.org
-- Stability : internal
-- Portability : non-portable (GHC Extensions)
--
-- Support for catching exceptions raised during top-level computations
-- (e.g. @Main.main@, 'Control.Concurrent.forkIO', and foreign exports)
--
-----------------------------------------------------------------------------
module GHC.TopHandler (
runIO, runNonIO, reportStackOverflow, reportError
) where
import Prelude
import System.IO
import Control.Exception
import Foreign.C.String
import Foreign.Ptr
import GHC.IOBase
import GHC.Exception
import GHC.Prim (unsafeCoerce#)
-- | 'runIO' is wrapped around @Main.main@ by @TcModule@. It is also wrapped
-- around every @foreign export@ and @foreign import \"wrapper\"@ to mop up
-- any uncaught exceptions. Thus, the result of running
-- 'System.Exit.exitWith' in a foreign-exported function is the same as
-- in the main thread: it terminates the program.
--
runIO :: IO a -> IO a
runIO main = catchException main topHandler
-- | The same as 'runIO', but for non-IO computations. Used for
-- wrapping @foreign export@ and @foreign import \"wrapper\"@ when these
-- are used to export Haskell functions with non-IO types.
--
runNonIO :: a -> IO a
runNonIO a = catchException (a `seq` return a) topHandler
topHandler :: Exception -> IO a
topHandler err = catchException (real_handler err) topHandler
-- Make sure we handle errors while reporting the error!
-- (e.g. evaluating the string passed to 'error' might generate
-- another error, etc.)
--
real_handler :: Exception -> IO a
real_handler ex =
case ex of
AsyncException StackOverflow -> reportStackOverflow True
-- only the main thread gets ExitException exceptions
ExitException ExitSuccess -> safe_exit 0
ExitException (ExitFailure n) -> safe_exit n
other -> reportError True other
reportStackOverflow :: Bool -> IO a
reportStackOverflow bombOut = do
(hFlush stdout) `catchException` (\ _ -> return ())
callStackOverflowHook
if bombOut
then exit 2
else return undefined
reportError :: Bool -> Exception -> IO a
reportError bombOut ex = do
handler <- getUncaughtExceptionHandler
handler ex
if bombOut
then exit 1
else return undefined
-- SUP: Are the hooks allowed to re-enter Haskell land? If so, remove
-- the unsafe below.
foreign import ccall unsafe "stackOverflow"
callStackOverflowHook :: IO ()
foreign import ccall unsafe "stg_exit"
stg_exit :: Int -> IO ()
exit :: Int -> IO a
exit r = unsafeCoerce# (stg_exit r)
-- NOTE: shutdownHaskellAndExit must be called "safe", because it *can*
-- re-enter Haskell land through finalizers.
foreign import ccall "shutdownHaskellAndExit"
shutdownHaskellAndExit :: Int -> IO ()
-- we have to use unsafeCoerce# to get the 'IO a' result type, since the
-- compiler doesn't let us declare that as the result type of a foreign export.
safe_exit :: Int -> IO a
safe_exit r = unsafeCoerce# (shutdownHaskellAndExit r)
\end{code}
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