I was also wondering a similar thing. I'm writing FFI for a C library. Library has a function like: int pollEvent(EventType* event); Instead of malloc'ing a new EventType in a FFI call for this functions: pollEvent :: IO Event pollEvent = do ev <- malloc ret <- cPollEvent ev -- check if ret is 0 etc. peek ev I was wondering if something like this is also safe: eventObj_ :: Ptr Event eventObj_ = unsafePerformIO malloc pollEvent :: IO Event pollEvent = do ret <- cPollEvent eventObj_ -- check if ret is 0 etc. peek eventObj_ This is one malloc cheaper for every call, and differences are not visible from user side. Still, I did not use this in my FFI bindings because I was not sure how safe is this approach. Any ideas on this? --- Ömer Sinan Ağacan http://osa1.net