Turn on all warnings.
Turn warnings into errors. Note that this option alone 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 warning.
Turn off warning.
Turn on warning and treat it as an error (this implies -W<warning>).
Don’t treat this particular warning as an error. This doesn’t turn off the warning itself.

re2c has the following warnings: