--- -----------------------------------------------------------------------------
--- $Id: TopHandler.lhs,v 1.1 2001/06/28 14:15:03 simonmar Exp $
---
--- (c) The University of Glasgow, 2001
+\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)
--
--- GHC.TopHandler
+-- Support for catching exceptions raised during top-level computations
+-- (e.g. @Main.main@, 'Control.Concurrent.forkIO', and foreign exports)
--
--- 'Top-level' IO actions want to catch exceptions (e.g., forkIO and
--- GHC.Main.mainIO) and report them - topHandler is the exception
--- handler they should use for this:
+-----------------------------------------------------------------------------
--- make sure we handle errors while reporting the error!
--- (e.g. evaluating the string passed to 'error' might generate
--- another error, etc.)
-
--- These functions can't go in GHC.Main, because GHC.Main isn't
--- included in HSstd.o (because GHC.Main depends on Main, which
--- doesn't exist yet...).
-
-\begin{code}
+-- #hide
module GHC.TopHandler (
- topHandler, 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#)
+
+-- | '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 -> IO a
+runNonIO a = catchException (a `seq` return a) topHandler
+
+topHandler :: Exception -> IO a
+topHandler err = catchException (real_handler safeExit err) topHandler
-topHandler :: Exception -> IO ()
-topHandler err = catchException (real_handler err) topHandler
+topHandlerFastExit :: Exception -> IO a
+topHandlerFastExit err =
+ catchException (real_handler fastExit err) topHandlerFastExit
-real_handler :: Exception -> IO ()
-real_handler ex =
- case ex of
- AsyncException StackOverflow -> reportStackOverflow True
+-- Make sure we handle errors while reporting the error!
+-- (e.g. evaluating the string passed to 'error' might generate
+-- another error, etc.)
+--
+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 -> shutdownHaskellAndExit 0
- ExitException (ExitFailure n) -> shutdownHaskellAndExit n
+ ExitException ExitSuccess -> exit 0
+ ExitException (ExitFailure n) -> exit n
- ErrorCall s -> reportError True s
- other -> reportError True (showsPrec 0 other "\n")
+ other -> do
+ reportError other
+ exit 1
+
--- NOTE: shutdownHaskellAndExit must be called "safe", because it *can*
--- re-enter Haskell land through finalizers.
-foreign import ccall "shutdownHaskellAndExit"
- shutdownHaskellAndExit :: Int -> IO ()
+reportStackOverflow :: IO a
+reportStackOverflow = do callStackOverflowHook; return undefined
-reportStackOverflow :: Bool -> IO ()
-reportStackOverflow bombOut = do
- (hFlush stdout) `catchException` (\ _ -> return ())
- callStackOverflowHook
- if bombOut then
- stg_exit 2
- else
- return ()
-
-reportError :: Bool -> String -> IO ()
-reportError bombOut str = do
- (hFlush stdout) `catchException` (\ _ -> return ())
- withCStringLen str $ \(cstr,len) -> do
- writeErrString addrOf_ErrorHdrHook cstr len
- if bombOut
- then stg_exit 1
- else return ()
-
-foreign import ccall "addrOf_ErrorHdrHook" unsafe
- addrOf_ErrorHdrHook :: Ptr ()
-
-foreign import ccall "writeErrString__" unsafe
- writeErrString :: Ptr () -> CString -> Int -> IO ()
+reportError :: Exception -> IO a
+reportError ex = do
+ handler <- getUncaughtExceptionHandler
+ handler ex
+ return undefined
-- SUP: Are the hooks allowed to re-enter Haskell land? If so, remove
-- the unsafe below.
-foreign import ccall "stackOverflow" unsafe
+foreign import ccall unsafe "stackOverflow"
callStackOverflowHook :: IO ()
-foreign import ccall "stg_exit" unsafe
- 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 ()
+
+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 "Rts.h shutdownHaskellAndExit"
+ shutdownHaskellAndExit :: Int -> IO ()
+
+fastExit :: Int -> IO a
+fastExit r = unsafeCoerce# (stg_exit (fromIntegral r))
+
+foreign import ccall "Rts.h stg_exit"
+ stg_exit :: CInt -> IO ()
\end{code}
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