Question

With the below function is based on the 0MQ Haskell bindings. I get an error at runtime. The error says getIntOpt: interrupted (Interrupted system call) and the program stops.

It probably has to do something with command line options that I use and then discard because of criterion?

Edit: found out that I get the error also when I leave my own code with cmdArgs away.
There is actually a much more interesting problem behind. See last paragraph here. But I have still no clue how to deal with it effectively.

    sendReceive :: B.ByteString -> IO ()
    sendReceive datastring = withContext 1 $ \context -> do
         withSocket context Req $ \requester -> do
            --putStrLn "Connecting ..."
            connect requester "tcp://192.168.35.84:5559"
            let tryOnePing (!c, !f) i = do
                send requester datastring []
                --putStrLn "Sent ..."
                r <- receive requester []
                --putStrLn "Received ..."
                return $ case B.unpack r of
                   datastring -> (c+1, f)
                   _ -> (c, f+1)
            (c,f) <- foldM tryOnePing (0,0) [1 .. 1000]
            -- c and f are not used in this example
            return ()

main = do
     n <- cmdArgsRun strlen
     let datastring  = B.pack (take (byte n) $ randomRs ('a','z') (mkStdGen 3))
     putStrLn "Starting..."
     withArgs [] $ defaultMain [bench "sendReceive" $ whnfIO (sendReceive datastring)]

Answer 1

The bindings use the FFI helper function throwErrnoIfMinus1_, which throws an error from errno if the wrapped function returns -1. The new zeromq library expects the caller to properly handler EINTR, which isn’t happening here.

You could ask the library maintainer to use throwErrnoIfMinus1Retry_, which retries the wrapped function automatically if it returns -1 and errno is set to EINTR.

It looks like you can catch the IOException, but I don’t know how to get at the value of errno, even though it is stored within it (unless you want to import GHC.IO.Exception, which seems a it shady to me).