Hi All, 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. When I compile this with no optimisations: ghc --make Sig.hs I get the desired behaviour, that is soon after I hit cntrl-C I get: Fail: Kaboom However, when I compile with -O: touch Sig.hs && ghc --make -O Sig.hs Now the exception does not appear to be caught. Indeed the program just keeps on looping. If a give the program a lot of cntrl-Cs then eventually I get this message: a.out: too many pending signals And the program dies. Commenting out the call to "catchCtrlC" from within "main" seems to let GHC's default signal handling mechanism work properly, that is after (strangley 2) cntrl-Cs the program dies (no message). Cheers, Bernie.