Lol, whatcha gonna do? Hit us with tarifs?

-std=gnu98 works. ie explicitly telling it your code is not modern C.

The new flags apply regardless of -std value, as does -fno-common

Uhh no they don't, and it's explicitly documented under https://gcc.gnu.org/gcc-14/porting_to.html in "Turning errors back into warnings".

Futher more every warning Explains why the std value affects them.

GCC has among others -fopt-info-vec-missed