X-Git-Url: http://git.megacz.com/?a=blobdiff_plain;f=GHC%2FTopHandler.lhs;h=b1ac1b83c2b0e6b0899ddce5caeb8f9cab9f58c6;hb=8f298c3539c4786f48ae89d8ca754115210106cf;hp=344a856038059090f99157665ab013e2faeb3745;hpb=3d39b8130899c46c9c96b941fddb4e4784e860dc;p=ghc-base.git

diff --git a/GHC/TopHandler.lhs b/GHC/TopHandler.lhs
index 344a856..b1ac1b8 100644
--- a/GHC/TopHandler.lhs
+++ b/GHC/TopHandler.lhs
@@ -1,88 +1,111 @@
--- -----------------------------------------------------------------------------
--- $Id: TopHandler.lhs,v 1.3 2001/08/17 12:50:34 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, 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#)
+
+-- | '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
+
+-- | 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 ()
+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 =
+  cleanUp >>
   case ex of
-	AsyncException StackOverflow -> reportStackOverflow True
+	AsyncException StackOverflow -> do
+	   reportStackOverflow
+	   safeExit 2
 
 	-- only the main thread gets ExitException exceptions
-	ExitException ExitSuccess     -> shutdownHaskellAndExit 0
-	ExitException (ExitFailure n) -> shutdownHaskellAndExit n
+	ExitException ExitSuccess     -> safeExit 0
+	ExitException (ExitFailure n) -> safeExit n
 
-	ErrorCall s -> reportError True s
-	other       -> reportError True (showsPrec 0 other "\n")
+	other -> do
+	   reportError other
+	   safeExit 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 errorHdrHook cstr len
-     if bombOut 
-	then stg_exit 1
-        else return ()
-
-#ifndef ILX
-foreign label "ErrorHdrHook" errorHdrHook :: Ptr ()
-#else
-foreign import "ErrorHdrHook" errorHdrHook :: Ptr ()
-#endif
-
-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 "shutdownHaskellAndExit" 
+  shutdownHaskellAndExit :: Int -> IO ()
 \end{code}