Turn on all warnings.
Turn warnings into errors. Note that this option along doesn’t turn on any warnings, it only affects those warnings that have been turned on so far or will be turned on later.
Turn on individual warning.
Turn off individual warning.
Turn on individual warning and treat it as error (this implies -W<warning>).
Don’t treat this particular warning as error. This doesn’t turn off the warning itself.

re2c has the following warnings: