ChrisK wrote:
A safer gimmick...
Ben Franksen wrote:
tickWhileDoing :: String -> IO a -> IO a tickWhileDoing msg act = do hPutStr stderr msg >> hPutChar stderr ' ' >> hFlush stderr start_time <- getCPUTime tickerId <- forkIO ticker ... an async exception here will leave the ticker runnning.... res <- act `finally` killThread tickerId
The best way to make this safe that I know of is:
res <- block $ do tickerId <- forkIO ticker unblock act `finally` killThread tickerId
...but with a change that Simon M just checked in to GHC head, this will now spawn 'ticker' in blocked state, so you won't be able to kill it. You would therefore want unblock $ forkIO ticker or forkIO $ unblock ticker I'm not sure if there is a strong reason to prefer one over the other. Jules