20 Oct
2010
20 Oct
'10
4:17 p.m.
and indeed, gethostbyname is famous for being non re-entrant.
it already has a lock in Network.BSD, so I assume it's fine: {-# NOINLINE lock #-} lock :: MVar () lock = unsafePerformIO $ newMVar () withLock :: IO a -> IO a withLock act = withMVar lock (\_ -> act) getHostByName :: HostName -> IO HostEntry getHostByName name = withLock $ do withCString name $ \ name_cstr -> do ent <- throwNoSuchThingIfNull "getHostByName" "no such host entry" $ trySysCall $ c_gethostbyname name_cstr peek ent