--
-----------------------------------------------------------------------------
+-- #hide
module GHC.TopHandler (
- runIO, runNonIO, reportStackOverflow, reportError
+ runMainIO, runIO, runIOFastExit, runNonIO, reportStackOverflow, reportError
) where
import Prelude
import System.IO
import Control.Exception
-import Foreign.C.String
-import Foreign.Ptr
+import Foreign.C ( CInt )
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.
+-- | 'runMainIO' is wrapped around 'Main.main' (or whatever main is
+-- called in the program). It catches otherwise uncaught exceptions,
+-- and also flushes stdout\/stderr before exiting.
+runMainIO :: IO a -> IO a
+runMainIO main = (do a <- main; cleanUp; return a) `catchException` topHandler
+
+-- | 'runIO' is 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
+-- | Like 'runIO', but in the event of an exception that causes an exit,
+-- we don't shut down the system cleanly, we just exit. This is
+-- useful in some cases, because the safe exit version will give other
+-- threads a chance to clean up first, which might shut down the
+-- system in a different way. For example, try
+--
+-- main = forkIO (runIO (exitWith (ExitFailure 1))) >> threadDelay 10000
+--
+-- This will sometimes exit with "interrupted" and code 0, because the
+-- main thread is given a chance to shut down when the child thread calls
+-- safeExit. There is a race to shut down between the main and child threads.
+--
+runIOFastExit :: IO a -> IO a
+runIOFastExit main = catchException main topHandlerFastExit
+ -- NB. this is used by the testsuite driver
+
-- | 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 = catchException (a `seq` return a) topHandler
topHandler :: Exception -> IO a
-topHandler err = catchException (real_handler err) topHandler
+topHandler err = catchException (real_handler safeExit err) topHandler
+
+topHandlerFastExit :: Exception -> IO a
+topHandlerFastExit err =
+ catchException (real_handler fastExit err) topHandlerFastExit
-- 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
+real_handler :: (Int -> IO a) -> Exception -> IO a
+real_handler exit exn =
+ cleanUp >>
+ case exn of
+ AsyncException StackOverflow -> do
+ reportStackOverflow
+ exit 2
-- only the main thread gets ExitException exceptions
- ExitException ExitSuccess -> safe_exit 0
- ExitException (ExitFailure n) -> safe_exit n
+ ExitException ExitSuccess -> exit 0
+ ExitException (ExitFailure n) -> exit n
- other -> reportError True other
+ other -> do
+ reportError other
+ exit 1
-reportStackOverflow :: Bool -> IO a
-reportStackOverflow bombOut = do
- (hFlush stdout) `catchException` (\ _ -> return ())
- callStackOverflowHook
- if bombOut
- then exit 2
- else return undefined
+reportStackOverflow :: IO a
+reportStackOverflow = do callStackOverflowHook; return undefined
-reportError :: Bool -> Exception -> IO a
-reportError bombOut ex = do
+reportError :: Exception -> IO a
+reportError ex = do
handler <- getUncaughtExceptionHandler
handler ex
- if bombOut
- then exit 1
- else return undefined
+ 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 ()
+-- try to flush stdout/stderr, but don't worry if we fail
+-- (these handles might have errors, and we don't want to go into
+-- an infinite loop).
+cleanUp :: IO ()
+cleanUp = do
+ hFlush stdout `catchException` \_ -> return ()
+ hFlush stderr `catchException` \_ -> return ()
-exit :: Int -> IO a
-exit r = unsafeCoerce# (stg_exit r)
+cleanUpAndExit :: Int -> IO a
+cleanUpAndExit r = do cleanUp; safeExit r
+
+-- 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.
+safeExit :: Int -> IO a
+safeExit r = unsafeCoerce# (shutdownHaskellAndExit r)
-- NOTE: shutdownHaskellAndExit must be called "safe", because it *can*
-- re-enter Haskell land through finalizers.
-foreign import ccall "shutdownHaskellAndExit"
+foreign import ccall "Rts.h 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)
+fastExit :: Int -> IO a
+fastExit r = unsafeCoerce# (stg_exit (fromIntegral r))
+
+foreign import ccall "Rts.h stg_exit"
+ stg_exit :: CInt -> IO ()
\end{code}
projects / haskell-directory.git / blobdiff