I am not sure that these directives affect "speed" at all. And in any case, if you spend even one minute of your time puzzling-out a bug that use of these directives could have pointed-out to you, you've burned up 60 million microseconds, and it will be a very long time before you recover that one minute through faster execution speeds . . . In the grand scheme of things, the computer's time is free – yours is not. You should take advantage of every bug-finding tool that every language offers you.