[project @ 2001-05-21 14:07:31 by simonmar]

[ghc-hetmet.git] / ghc / lib / std / PrelTopHandler.lhs

diff --git a/ghc/lib/std/PrelTopHandler.lhs b/ghc/lib/std/PrelTopHandler.lhs
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+-- -----------------------------------------------------------------------------
+-- $Id: PrelTopHandler.lhs,v 1.1 2001/05/21 14:07:31 simonmar Exp $
+--
+-- (c) The University of Glasgow, 2001
+--
+-- PrelTopHandler
+--
+-- 'Top-level' IO actions want to catch exceptions (e.g., forkIO and 
+-- PrelMain.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 PrelMain, because PrelMain isn't
+-- included in HSstd.o (because PrelMain depends on Main, which
+-- doesn't exist yet...).
+
+\begin{code}
+module PrelTopHandler (
+   topHandler, reportStackOverflow, reportError 
+  ) where
+
+import IO
+
+import PrelCString
+import PrelPtr
+import PrelIOBase
+import PrelException
+
+topHandler :: Exception -> IO ()
+topHandler err = catchException (real_handler err) topHandler
+
+real_handler :: Exception -> IO ()
+real_handler ex =
+  case ex of
+       AsyncException StackOverflow -> reportStackOverflow True
+       ErrorCall s -> reportError True s
+       other       -> reportError True (showsPrec 0 other "\n")
+
+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 ()
+
+-- SUP: Are the hooks allowed to re-enter Haskell land?  If so, remove
+-- the unsafe below.
+foreign import ccall "stackOverflow" unsafe
+       callStackOverflowHook :: IO ()
+
+foreign import ccall "stg_exit" unsafe
+       stg_exit :: Int -> IO ()
+\end{code}