[project @ 2001-05-18 16:54:04 by simonmar]

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

diff --git a/ghc/lib/std/PrelMain.lhs b/ghc/lib/std/PrelMain.lhs
index ca298ee..6674dc3 100644 (file)
--- a/ghc/lib/std/PrelMain.lhs
+++ b/ghc/lib/std/PrelMain.lhs
@@ -1,5 +1,5 @@
 % ------------------------------------------------------------------------------
-% $Id: PrelMain.lhs,v 1.7 2000/06/30 13:39:36 simonmar Exp $
+% $Id: PrelMain.lhs,v 1.8 2001/05/18 16:54:05 simonmar Exp $
 %
 % (c) The University of Glasgow, 1994-2000
 %
@@ -7,19 +7,69 @@
 \section[PrelMain]{Module @PrelMain@}
 
 \begin{code}
-module PrelMain( mainIO ) where
+module PrelMain( mainIO, reportStackOverflow, reportError ) where
 
 import Prelude
 import {-# SOURCE #-} qualified Main   -- for type of "Main.main"
 
+import IO
+import PrelCString
+import PrelPtr
 import PrelException
-import PrelHandle ( topHandler )
-
 \end{code}
 
 \begin{code}
 mainIO :: IO ()                -- It must be of type (IO t) because that's what
                        -- the RTS expects.  GHC doesn't check this, so
                        -- make sure this type signature stays!
-mainIO = catchException Main.main (topHandler True)
+mainIO = catchException Main.main topHandler
+
+-- '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.)
+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}