https://gcc.gnu.org/bugzilla/show_bug.cgi?id=117577
--- Comment #5 from Jakub Jelinek <jakub at gcc dot gnu.org> --- The [] part is just a hint what option is related to it and how it can be controlled. The error: vs. warning: keyword is what is the most important part. And, as I wrote above, printing there [-Werror=incompatible-pointer-types] would be even more confusing, this isn't error because user used -Werror=incompatible-pointer-types or the compiler defaulted to that. And -Wno-error=incompatible-pointer-types affects the behavior, but so does -Wno-incompatible-pointer-types (and in a different way).