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)
38 import {-# SOURCE #-} GHC.Handle
43 -- | 'runMainIO' is wrapped around 'Main.main' (or whatever main is
44 -- called in the program). It catches otherwise uncaught exceptions,
45 -- and also flushes stdout\/stderr before exiting.
46 runMainIO :: IO a -> IO a
49 main_thread_id <- myThreadId
50 weak_tid <- mkWeakThreadId main_thread_id
51 install_interrupt_handler $ do
52 m <- deRefWeak weak_tid
55 Just tid -> throwTo tid (toException UserInterrupt)
62 install_interrupt_handler :: IO () -> IO ()
63 #ifdef mingw32_HOST_OS
64 install_interrupt_handler handler = do
65 GHC.ConsoleHandler.installHandler $
75 -- specialised version of System.Posix.Signals.installHandler, which
76 -- isn't available here.
77 install_interrupt_handler handler = do
78 let sig = CONST_SIGINT :: CInt
79 withSignalHandlerLock $
81 sptr <- newStablePtr handler
83 stg_sig_install sig STG_SIG_RST p_sp nullPtr
86 withSignalHandlerLock :: IO () -> IO ()
87 withSignalHandlerLock io
89 takeMVar signalHandlerLock
90 catchAny (unblock io) (\e -> do putMVar signalHandlerLock (); throw e)
91 putMVar signalHandlerLock ()
93 foreign import ccall unsafe
96 -> CInt -- action code (STG_SIG_HAN etc.)
97 -> Ptr (StablePtr (IO ())) -- (in, out) Haskell handler
98 -> Ptr () -- (in, out) blocked
99 -> IO CInt -- (ret) action code
102 -- make a weak pointer to a ThreadId: holding the weak pointer doesn't
103 -- keep the thread alive and prevent it from being identified as
104 -- deadlocked. Vitally important for the main thread.
105 mkWeakThreadId :: ThreadId -> IO (Weak ThreadId)
106 mkWeakThreadId t@(ThreadId t#) = IO $ \s ->
107 case mkWeak# t# t (unsafeCoerce# 0#) s of
108 (# s1, w #) -> (# s1, Weak w #)
110 -- | 'runIO' is wrapped around every @foreign export@ and @foreign
111 -- import \"wrapper\"@ to mop up any uncaught exceptions. Thus, the
112 -- result of running 'System.Exit.exitWith' in a foreign-exported
113 -- function is the same as in the main thread: it terminates the
116 runIO :: IO a -> IO a
117 runIO main = catch main topHandler
119 -- | Like 'runIO', but in the event of an exception that causes an exit,
120 -- we don't shut down the system cleanly, we just exit. This is
121 -- useful in some cases, because the safe exit version will give other
122 -- threads a chance to clean up first, which might shut down the
123 -- system in a different way. For example, try
125 -- main = forkIO (runIO (exitWith (ExitFailure 1))) >> threadDelay 10000
127 -- This will sometimes exit with "interrupted" and code 0, because the
128 -- main thread is given a chance to shut down when the child thread calls
129 -- safeExit. There is a race to shut down between the main and child threads.
131 runIOFastExit :: IO a -> IO a
132 runIOFastExit main = catch main topHandlerFastExit
133 -- NB. this is used by the testsuite driver
135 -- | The same as 'runIO', but for non-IO computations. Used for
136 -- wrapping @foreign export@ and @foreign import \"wrapper\"@ when these
137 -- are used to export Haskell functions with non-IO types.
139 runNonIO :: a -> IO a
140 runNonIO a = catch (a `seq` return a) topHandler
142 topHandler :: SomeException -> IO a
143 topHandler err = catch (real_handler safeExit err) topHandler
145 topHandlerFastExit :: SomeException -> IO a
146 topHandlerFastExit err =
147 catchException (real_handler fastExit err) topHandlerFastExit
149 -- Make sure we handle errors while reporting the error!
150 -- (e.g. evaluating the string passed to 'error' might generate
151 -- another error, etc.)
153 real_handler :: (Int -> IO a) -> SomeException -> IO a
154 real_handler exit se@(SomeException exn) =
157 Just StackOverflow -> do
161 Just UserInterrupt -> exitInterrupted
163 _ -> case cast exn of
164 -- only the main thread gets ExitException exceptions
165 Just ExitSuccess -> exit 0
166 Just (ExitFailure n) -> exit n
168 _ -> do reportError se
172 -- try to flush stdout/stderr, but don't worry if we fail
173 -- (these handles might have errors, and we don't want to go into
174 -- an infinite loop).
177 hFlush stdout `catchAny` \_ -> return ()
178 hFlush stderr `catchAny` \_ -> return ()
180 cleanUpAndExit :: Int -> IO a
181 cleanUpAndExit r = do cleanUp; safeExit r
183 -- we have to use unsafeCoerce# to get the 'IO a' result type, since the
184 -- compiler doesn't let us declare that as the result type of a foreign export.
185 safeExit :: Int -> IO a
186 safeExit r = unsafeCoerce# (shutdownHaskellAndExit $ fromIntegral r)
188 exitInterrupted :: IO a
190 #ifdef mingw32_HOST_OS
193 -- we must exit via the default action for SIGINT, so that the
194 -- parent of this process can take appropriate action (see #2301)
195 unsafeCoerce# (shutdownHaskellAndSignal CONST_SIGINT)
197 foreign import ccall "shutdownHaskellAndSignal"
198 shutdownHaskellAndSignal :: CInt -> IO ()
201 -- NOTE: shutdownHaskellAndExit must be called "safe", because it *can*
202 -- re-enter Haskell land through finalizers.
203 foreign import ccall "Rts.h shutdownHaskellAndExit"
204 shutdownHaskellAndExit :: CInt -> IO ()
206 fastExit :: Int -> IO a
207 fastExit r = unsafeCoerce# (stg_exit (fromIntegral r))
209 foreign import ccall "Rts.h stg_exit"
210 stg_exit :: CInt -> IO ()