2 {-# OPTIONS_GHC -XNoImplicitPrelude #-}
3 {-# OPTIONS_GHC -fno-warn-unused-imports #-}
4 {-# OPTIONS_HADDOCK hide #-}
5 -----------------------------------------------------------------------------
7 -- Module : GHC.TopHandler
8 -- Copyright : (c) The University of Glasgow, 2001-2002
9 -- License : see libraries/base/LICENSE
11 -- Maintainer : cvs-ghc@haskell.org
12 -- Stability : internal
13 -- Portability : non-portable (GHC Extensions)
15 -- Support for catching exceptions raised during top-level computations
16 -- (e.g. @Main.main@, 'Control.Concurrent.forkIO', and foreign exports)
18 -----------------------------------------------------------------------------
21 module GHC.TopHandler (
22 runMainIO, runIO, runIOFastExit, runNonIO,
23 topHandler, topHandlerFastExit,
24 reportStackOverflow, reportError,
27 #include "HsBaseConfig.h"
29 import Control.Exception
35 import GHC.Conc hiding (throwTo)
42 #if defined(mingw32_HOST_OS)
43 import GHC.ConsoleHandler
46 -- | 'runMainIO' is wrapped around 'Main.main' (or whatever main is
47 -- called in the program). It catches otherwise uncaught exceptions,
48 -- and also flushes stdout\/stderr before exiting.
49 runMainIO :: IO a -> IO a
52 main_thread_id <- myThreadId
53 weak_tid <- mkWeakThreadId main_thread_id
54 install_interrupt_handler $ do
55 m <- deRefWeak weak_tid
58 Just tid -> throwTo tid (toException UserInterrupt)
65 install_interrupt_handler :: IO () -> IO ()
66 #ifdef mingw32_HOST_OS
67 install_interrupt_handler handler = do
68 GHC.ConsoleHandler.installHandler $
78 -- specialised version of System.Posix.Signals.installHandler, which
79 -- isn't available here.
80 install_interrupt_handler handler = do
81 let sig = CONST_SIGINT :: CInt
82 withSignalHandlerLock $
84 sptr <- newStablePtr handler
86 stg_sig_install sig STG_SIG_RST p_sp nullPtr
89 withSignalHandlerLock :: IO () -> IO ()
90 withSignalHandlerLock io
92 takeMVar signalHandlerLock
93 catchAny (unblock io) (\e -> do putMVar signalHandlerLock (); throw e)
94 putMVar signalHandlerLock ()
96 foreign import ccall unsafe
99 -> CInt -- action code (STG_SIG_HAN etc.)
100 -> Ptr (StablePtr (IO ())) -- (in, out) Haskell handler
101 -> Ptr () -- (in, out) blocked
102 -> IO CInt -- (ret) action code
105 -- make a weak pointer to a ThreadId: holding the weak pointer doesn't
106 -- keep the thread alive and prevent it from being identified as
107 -- deadlocked. Vitally important for the main thread.
108 mkWeakThreadId :: ThreadId -> IO (Weak ThreadId)
109 mkWeakThreadId t@(ThreadId t#) = IO $ \s ->
110 case mkWeak# t# t (unsafeCoerce# 0#) s of
111 (# s1, w #) -> (# s1, Weak w #)
113 -- | 'runIO' is wrapped around every @foreign export@ and @foreign
114 -- import \"wrapper\"@ to mop up any uncaught exceptions. Thus, the
115 -- result of running 'System.Exit.exitWith' in a foreign-exported
116 -- function is the same as in the main thread: it terminates the
119 runIO :: IO a -> IO a
120 runIO main = catch main topHandler
122 -- | Like 'runIO', but in the event of an exception that causes an exit,
123 -- we don't shut down the system cleanly, we just exit. This is
124 -- useful in some cases, because the safe exit version will give other
125 -- threads a chance to clean up first, which might shut down the
126 -- system in a different way. For example, try
128 -- main = forkIO (runIO (exitWith (ExitFailure 1))) >> threadDelay 10000
130 -- This will sometimes exit with "interrupted" and code 0, because the
131 -- main thread is given a chance to shut down when the child thread calls
132 -- safeExit. There is a race to shut down between the main and child threads.
134 runIOFastExit :: IO a -> IO a
135 runIOFastExit main = catch main topHandlerFastExit
136 -- NB. this is used by the testsuite driver
138 -- | The same as 'runIO', but for non-IO computations. Used for
139 -- wrapping @foreign export@ and @foreign import \"wrapper\"@ when these
140 -- are used to export Haskell functions with non-IO types.
142 runNonIO :: a -> IO a
143 runNonIO a = catch (a `seq` return a) topHandler
145 topHandler :: SomeException -> IO a
146 topHandler err = catch (real_handler safeExit err) topHandler
148 topHandlerFastExit :: SomeException -> IO a
149 topHandlerFastExit err =
150 catchException (real_handler fastExit err) topHandlerFastExit
152 -- Make sure we handle errors while reporting the error!
153 -- (e.g. evaluating the string passed to 'error' might generate
154 -- another error, etc.)
156 real_handler :: (Int -> IO a) -> SomeException -> IO a
157 real_handler exit se@(SomeException exn) =
160 Just StackOverflow -> do
164 Just UserInterrupt -> exitInterrupted
166 _ -> case cast exn of
167 -- only the main thread gets ExitException exceptions
168 Just ExitSuccess -> exit 0
169 Just (ExitFailure n) -> exit n
171 _ -> do reportError se
175 -- try to flush stdout/stderr, but don't worry if we fail
176 -- (these handles might have errors, and we don't want to go into
177 -- an infinite loop).
180 hFlush stdout `catchAny` \_ -> return ()
181 hFlush stderr `catchAny` \_ -> return ()
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 ()