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
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