[Phyx]

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

[mid-kid]

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

[Phyx]

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.