[Bug c/65040] [5 Regression] gcc-5 -Wformat broken

[rguenth at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=65040

--- Comment #18 from Richard Biener <rguenth at gcc dot gnu.org> ---
And it was just mentioned that the diagnostic should print

 [-Wformat-signedness]

not

 [-Wformat=]

(or both)