> I'm trying to write some code that catches unix signals and turns them
> into GHC exceptions, GHC version 6.0, debian linux
>
> Heres my code:
>
> ------
> module Main where
>
> import Control.Concurrent
> import Control.Exception
> import System.Posix
> import IO
>
> catchCtrlC :: IO Handler
> catchCtrlC
> = do main_thread <- myThreadId
> installHandler sigINT (Catch (handler main_thread)) Nothing
> where
> handler :: ThreadId -> IO ()
> handler main_thread = throwTo main_thread
> (ErrorCall "Kaboom")
>
> main :: IO ()
> main = do catchCtrlC
> print (f 1)
>
> f :: Int -> Int
> f x = f (x + 1)
> ------
>
> The function "f" is intentionally bogus, I want it to loop so
> I have enough time to hit cntrl-C.
You've hit a known bug with concurrency, described in the
Control.Concurrent documentation.
The problem is that context switches only happen when some allocation is
going on: in your f function above, the optimiser turns it into a loop
that does no allocation, so no context switches can happen and the
exception is never delivered.
You probably won't run into this bug in a real program ;-)
Cheers,
Simon
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