--- -----------------------------------------------------------------------------
--- $Id: TopHandler.lhs,v 1.4 2002/02/05 17:32:27 simonmar Exp $
---
--- (c) The University of Glasgow, 2001
+\begin{code}
+{-# LANGUAGE CPP
+ , NoImplicitPrelude
+ , ForeignFunctionInterface
+ , MagicHash
+ , UnboxedTuples
+ , PatternGuards
+ #-}
+{-# OPTIONS_GHC -fno-warn-unused-imports #-}
+{-# OPTIONS_HADDOCK hide #-}
+
+-----------------------------------------------------------------------------
+-- |
+-- 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,
+ topHandler, topHandlerFastExit,
+ reportStackOverflow, reportError,
) where
-import Prelude
-
-import System.IO
+#include "HsBaseConfig.h"
+
+import Control.Exception
+import Data.Maybe
+import Data.Dynamic (toDyn)
+
+import Foreign
+import Foreign.C
+import GHC.Base
+import GHC.Conc hiding (throwTo)
+import GHC.Num
+import GHC.Real
+import GHC.MVar
+import GHC.IO
+import GHC.IO.Handle.FD
+import GHC.IO.Handle
+import GHC.IO.Exception
+import GHC.Weak
+import Data.Typeable
+#if defined(mingw32_HOST_OS)
+import GHC.ConsoleHandler
+#endif
-import Foreign.C.String
-import Foreign.Ptr
-import GHC.IOBase
-import GHC.Exception
+-- | '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
+ main_thread_id <- myThreadId
+ weak_tid <- mkWeakThreadId main_thread_id
+ install_interrupt_handler $ do
+ m <- deRefWeak weak_tid
+ case m of
+ Nothing -> return ()
+ Just tid -> throwTo tid (toException UserInterrupt)
+ a <- main
+ cleanUp
+ return a
+ `catch`
+ topHandler
+
+install_interrupt_handler :: IO () -> IO ()
+#ifdef mingw32_HOST_OS
+install_interrupt_handler handler = do
+ _ <- GHC.ConsoleHandler.installHandler $
+ Catch $ \event ->
+ case event of
+ ControlC -> handler
+ Break -> handler
+ Close -> handler
+ _ -> return ()
+ return ()
+#else
+#include "rts/Signals.h"
+-- specialised version of System.Posix.Signals.installHandler, which
+-- isn't available here.
+install_interrupt_handler handler = do
+ let sig = CONST_SIGINT :: CInt
+ _ <- setHandler sig (Just (const handler, toDyn handler))
+ _ <- stg_sig_install sig STG_SIG_RST nullPtr
+ -- STG_SIG_RST: the second ^C kills us for real, just in case the
+ -- RTS or program is unresponsive.
+ return ()
+
+foreign import ccall unsafe
+ stg_sig_install
+ :: CInt -- sig no.
+ -> CInt -- action code (STG_SIG_HAN etc.)
+ -> Ptr () -- (in, out) blocked
+ -> IO CInt -- (ret) old action code
+#endif
-topHandler :: Exception -> IO ()
-topHandler err = catchException (real_handler err) topHandler
+-- make a weak pointer to a ThreadId: holding the weak pointer doesn't
+-- keep the thread alive and prevent it from being identified as
+-- deadlocked. Vitally important for the main thread.
+mkWeakThreadId :: ThreadId -> IO (Weak ThreadId)
+mkWeakThreadId t@(ThreadId t#) = IO $ \s ->
+ case mkWeak# t# t (unsafeCoerce# 0#) s of
+ (# s1, w #) -> (# s1, Weak w #)
+
+-- | '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 = catch 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 = catch main topHandlerFastExit
+ -- NB. this is used by the testsuite driver
-real_handler :: Exception -> IO ()
-real_handler ex =
- case ex of
- AsyncException StackOverflow -> reportStackOverflow True
+-- | 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 = catch (a `seq` return a) topHandler
- -- only the main thread gets ExitException exceptions
- ExitException ExitSuccess -> shutdownHaskellAndExit 0
- ExitException (ExitFailure n) -> shutdownHaskellAndExit n
+topHandler :: SomeException -> IO a
+topHandler err = catch (real_handler safeExit err) topHandler
- Deadlock -> reportError True
- "no threads to run: infinite loop or deadlock?"
-
- ErrorCall s -> reportError True s
- other -> reportError True (showsPrec 0 other "\n")
+topHandlerFastExit :: SomeException -> IO a
+topHandlerFastExit err =
+ catchException (real_handler fastExit err) topHandlerFastExit
--- 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 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 ()
+-- 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) -> SomeException -> IO a
+real_handler exit se@(SomeException exn) =
+ cleanUp >>
+ case cast exn of
+ Just StackOverflow -> do
+ reportStackOverflow
+ exit 2
+
+ Just UserInterrupt -> exitInterrupted
+
+ _ -> case cast exn of
+ -- only the main thread gets ExitException exceptions
+ Just ExitSuccess -> exit 0
+ Just (ExitFailure n) -> exit n
+
+ -- EPIPE errors received for stdout are ignored (#2699)
+ _ -> case cast exn of
+ Just IOError{ ioe_type = ResourceVanished,
+ ioe_errno = Just ioe,
+ ioe_handle = Just hdl }
+ | Errno ioe == ePIPE, hdl == stdout -> exit 0
+ _ -> do reportError se
+ exit 1
+
+
+-- 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 `catchAny` \_ -> return ()
+ hFlush stderr `catchAny` \_ -> return ()
+
+-- 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 $ fromIntegral r)
+
+exitInterrupted :: IO a
+exitInterrupted =
+#ifdef mingw32_HOST_OS
+ safeExit 252
#else
-foreign import "ErrorHdrHook" errorHdrHook :: Ptr ()
+ -- we must exit via the default action for SIGINT, so that the
+ -- parent of this process can take appropriate action (see #2301)
+ unsafeCoerce# (shutdownHaskellAndSignal CONST_SIGINT)
+
+foreign import ccall "shutdownHaskellAndSignal"
+ shutdownHaskellAndSignal :: CInt -> IO ()
#endif
-foreign import ccall "writeErrString__" unsafe
- writeErrString :: Ptr () -> CString -> Int -> IO ()
+-- NOTE: shutdownHaskellAndExit must be called "safe", because it *can*
+-- re-enter Haskell land through finalizers.
+foreign import ccall "Rts.h shutdownHaskellAndExit"
+ shutdownHaskellAndExit :: CInt -> IO ()
--- SUP: Are the hooks allowed to re-enter Haskell land? If so, remove
--- the unsafe below.
-foreign import ccall "stackOverflow" unsafe
- callStackOverflowHook :: IO ()
+fastExit :: Int -> IO a
+fastExit r = unsafeCoerce# (stg_exit (fromIntegral r))
-foreign import ccall "stg_exit" unsafe
- stg_exit :: Int -> IO ()
+foreign import ccall "Rts.h stg_exit"
+ stg_exit :: CInt -> IO ()
\end{code}
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