Re: [Haskell-cafe] semantics of concurrent program depends on -O level, -f[no-]omit-yields

Quoting Johannes Waldmann (2018-11-30 05:50:03)

Given that, it now feels strange that the following *does* work:

main = do forkIO $ do threadDelay 1000000 ; putStrLn "foo" forever $ putStr ""

I am seeing the "foo" output. I expect the last line to be non-allocating. But it does still yield? Why?

putStr has to acquire a lock on stdout, so that's probably enough to allow the scheduler to run.