2 {-# OPTIONS_GHC -XNoImplicitPrelude #-}
3 {-# OPTIONS_HADDOCK hide #-}
4 -----------------------------------------------------------------------------
6 -- Module : GHC.TopHandler
7 -- Copyright : (c) The University of Glasgow, 2001-2002
8 -- License : see libraries/base/LICENSE
10 -- Maintainer : cvs-ghc@haskell.org
11 -- Stability : internal
12 -- Portability : non-portable (GHC Extensions)
14 -- Support for catching exceptions raised during top-level computations
15 -- (e.g. @Main.main@, 'Control.Concurrent.forkIO', and foreign exports)
17 -----------------------------------------------------------------------------
20 module GHC.TopHandler (
21 runMainIO, runIO, runIOFastExit, runNonIO,
22 topHandler, topHandlerFastExit,
23 reportStackOverflow, reportError,
26 #include "HsBaseConfig.h"
28 import Control.Exception
34 import GHC.Conc hiding (throwTo)
41 #if defined(mingw32_HOST_OS)
42 import GHC.ConsoleHandler
45 -- | 'runMainIO' is wrapped around 'Main.main' (or whatever main is
46 -- called in the program). It catches otherwise uncaught exceptions,
47 -- and also flushes stdout\/stderr before exiting.
48 runMainIO :: IO a -> IO a
51 main_thread_id <- myThreadId
52 weak_tid <- mkWeakThreadId main_thread_id
53 install_interrupt_handler $ do
54 m <- deRefWeak weak_tid
57 Just tid -> throwTo tid (toException UserInterrupt)
64 install_interrupt_handler :: IO () -> IO ()
65 #ifdef mingw32_HOST_OS
66 install_interrupt_handler handler = do
67 GHC.ConsoleHandler.installHandler $
77 -- specialised version of System.Posix.Signals.installHandler, which
78 -- isn't available here.
79 install_interrupt_handler handler = do
80 let sig = CONST_SIGINT :: CInt
81 withSignalHandlerLock $
83 sptr <- newStablePtr handler
85 stg_sig_install sig STG_SIG_RST p_sp nullPtr
88 withSignalHandlerLock :: IO () -> IO ()
89 withSignalHandlerLock io
91 takeMVar signalHandlerLock
92 catchAny (unblock io) (\e -> do putMVar signalHandlerLock (); throw e)
93 putMVar signalHandlerLock ()
95 foreign import ccall unsafe
98 -> CInt -- action code (STG_SIG_HAN etc.)
99 -> Ptr (StablePtr (IO ())) -- (in, out) Haskell handler
100 -> Ptr () -- (in, out) blocked
101 -> IO CInt -- (ret) action code
104 -- make a weak pointer to a ThreadId: holding the weak pointer doesn't
105 -- keep the thread alive and prevent it from being identified as
106 -- deadlocked. Vitally important for the main thread.
107 mkWeakThreadId :: ThreadId -> IO (Weak ThreadId)
108 mkWeakThreadId t@(ThreadId t#) = IO $ \s ->
109 case mkWeak# t# t (unsafeCoerce# 0#) s of
110 (# s1, w #) -> (# s1, Weak w #)
112 -- | 'runIO' is wrapped around every @foreign export@ and @foreign
113 -- import \"wrapper\"@ to mop up any uncaught exceptions. Thus, the
114 -- result of running 'System.Exit.exitWith' in a foreign-exported
115 -- function is the same as in the main thread: it terminates the
118 runIO :: IO a -> IO a
119 runIO main = catch main topHandler
121 -- | Like 'runIO', but in the event of an exception that causes an exit,
122 -- we don't shut down the system cleanly, we just exit. This is
123 -- useful in some cases, because the safe exit version will give other
124 -- threads a chance to clean up first, which might shut down the
125 -- system in a different way. For example, try
127 -- main = forkIO (runIO (exitWith (ExitFailure 1))) >> threadDelay 10000
129 -- This will sometimes exit with "interrupted" and code 0, because the
130 -- main thread is given a chance to shut down when the child thread calls
131 -- safeExit. There is a race to shut down between the main and child threads.
133 runIOFastExit :: IO a -> IO a
134 runIOFastExit main = catch main topHandlerFastExit
135 -- NB. this is used by the testsuite driver
137 -- | The same as 'runIO', but for non-IO computations. Used for
138 -- wrapping @foreign export@ and @foreign import \"wrapper\"@ when these
139 -- are used to export Haskell functions with non-IO types.
141 runNonIO :: a -> IO a
142 runNonIO a = catch (a `seq` return a) topHandler
144 topHandler :: SomeException -> IO a
145 topHandler err = catch (real_handler safeExit err) topHandler
147 topHandlerFastExit :: SomeException -> IO a
148 topHandlerFastExit err =
149 catchException (real_handler fastExit err) topHandlerFastExit
151 -- Make sure we handle errors while reporting the error!
152 -- (e.g. evaluating the string passed to 'error' might generate
153 -- another error, etc.)
155 real_handler :: (Int -> IO a) -> SomeException -> IO a
156 real_handler exit se@(SomeException exn) =
159 Just StackOverflow -> do
163 Just UserInterrupt -> exitInterrupted
165 _ -> case cast exn of
166 -- only the main thread gets ExitException exceptions
167 Just ExitSuccess -> exit 0
168 Just (ExitFailure n) -> exit n
170 _ -> do reportError se
174 -- try to flush stdout/stderr, but don't worry if we fail
175 -- (these handles might have errors, and we don't want to go into
176 -- an infinite loop).
179 hFlush stdout `catchAny` \_ -> return ()
180 hFlush stderr `catchAny` \_ -> return ()
182 cleanUpAndExit :: Int -> IO a
183 cleanUpAndExit r = do cleanUp; safeExit r
185 -- we have to use unsafeCoerce# to get the 'IO a' result type, since the
186 -- compiler doesn't let us declare that as the result type of a foreign export.
187 safeExit :: Int -> IO a
188 safeExit r = unsafeCoerce# (shutdownHaskellAndExit $ fromIntegral r)
190 exitInterrupted :: IO a
192 #ifdef mingw32_HOST_OS
195 -- we must exit via the default action for SIGINT, so that the
196 -- parent of this process can take appropriate action (see #2301)
197 unsafeCoerce# (shutdownHaskellAndSignal CONST_SIGINT)
199 foreign import ccall "shutdownHaskellAndSignal"
200 shutdownHaskellAndSignal :: CInt -> IO ()
203 -- NOTE: shutdownHaskellAndExit must be called "safe", because it *can*
204 -- re-enter Haskell land through finalizers.
205 foreign import ccall "Rts.h shutdownHaskellAndExit"
206 shutdownHaskellAndExit :: CInt -> IO ()
208 fastExit :: Int -> IO a
209 fastExit r = unsafeCoerce# (stg_exit (fromIntegral r))
211 foreign import ccall "Rts.h stg_exit"
212 stg_exit :: CInt -> IO ()