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    1 {-# LANGUAGE CPP #-}
    2 module GHCi.Signals (installSignalHandlers) where
    3 
    4 import Prelude -- See note [Why do we import Prelude here?]
    5 import Control.Concurrent
    6 import Control.Exception
    7 import System.Mem.Weak  ( deRefWeak )
    8 
    9 #if !defined(mingw32_HOST_OS)
   10 import System.Posix.Signals
   11 #endif
   12 
   13 #if defined(mingw32_HOST_OS)
   14 import GHC.ConsoleHandler
   15 #endif
   16 
   17 -- | Install standard signal handlers for catching ^C, which just throw an
   18 --   exception in the target thread.  The current target thread is the
   19 --   thread at the head of the list in the MVar passed to
   20 --   installSignalHandlers.
   21 installSignalHandlers :: IO ()
   22 installSignalHandlers = do
   23   main_thread <- myThreadId
   24   wtid <- mkWeakThreadId main_thread
   25 
   26   let interrupt = do
   27         r <- deRefWeak wtid
   28         case r of
   29           Nothing -> return ()
   30           Just t  -> throwTo t UserInterrupt
   31 
   32 #if !defined(mingw32_HOST_OS)
   33   _ <- installHandler sigQUIT  (Catch interrupt) Nothing
   34   _ <- installHandler sigINT   (Catch interrupt) Nothing
   35 #else
   36   -- GHC 6.3+ has support for console events on Windows
   37   -- NOTE: running GHCi under a bash shell for some reason requires
   38   -- you to press Ctrl-Break rather than Ctrl-C to provoke
   39   -- an interrupt.  Ctrl-C is getting blocked somewhere, I don't know
   40   -- why --SDM 17/12/2004
   41   let sig_handler ControlC = interrupt
   42       sig_handler Break    = interrupt
   43       sig_handler _        = return ()
   44 
   45   _ <- installHandler (Catch sig_handler)
   46 #endif
   47   return ()