--- -----------------------------------------------------------------------------
--- $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}
module GHC.TopHandler (
- topHandler, reportStackOverflow, reportError
+ runIO, runNonIO, reportStackOverflow, reportError
) where
import Prelude
import Foreign.Ptr
import GHC.IOBase
import GHC.Exception
+import GHC.Prim (unsafeCoerce#)
-topHandler :: Exception -> IO ()
+-- | '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
-real_handler :: Exception -> IO ()
+-- 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 -> shutdownHaskellAndExit 0
- ExitException (ExitFailure n) -> shutdownHaskellAndExit n
+ ExitException ExitSuccess -> safe_exit 0
+ ExitException (ExitFailure n) -> safe_exit n
+ Deadlock -> reportError True
+ "no threads to run: infinite loop or deadlock?"
+
ErrorCall s -> reportError True s
other -> reportError True (showsPrec 0 other "\n")
--- NOTE: shutdownHaskellAndExit must be called "safe", because it *can*
--- re-enter Haskell land through finalizers.
-foreign import ccall "shutdownHaskellAndExit"
- shutdownHaskellAndExit :: Int -> IO ()
-
-reportStackOverflow :: Bool -> IO ()
+reportStackOverflow :: Bool -> IO a
reportStackOverflow bombOut = do
(hFlush stdout) `catchException` (\ _ -> return ())
callStackOverflowHook
- if bombOut then
- stg_exit 2
- else
- return ()
+ if bombOut
+ then exit 2
+ else return undefined
-reportError :: Bool -> String -> IO ()
+reportError :: Bool -> String -> IO a
reportError bombOut str = do
(hFlush stdout) `catchException` (\ _ -> return ())
withCStringLen str $ \(cstr,len) -> do
- writeErrString addrOf_ErrorHdrHook cstr len
+ writeErrString errorHdrHook cstr len
if bombOut
- then stg_exit 1
- else return ()
+ then exit 1
+ else return undefined
-foreign import ccall "addrOf_ErrorHdrHook" unsafe
- addrOf_ErrorHdrHook :: Ptr ()
+#ifndef ILX
+foreign import ccall "&ErrorHdrHook" errorHdrHook :: Ptr ()
+#else
+foreign import ccall "ErrorHdrHook" errorHdrHook :: Ptr ()
+#endif
-foreign import ccall "writeErrString__" unsafe
+foreign import ccall unsafe "writeErrString__"
writeErrString :: Ptr () -> CString -> Int -> IO ()
-- 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
+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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