Hello world without -O2 -Werror? I've done several compiler toolchain updates on larger code bases and every new version of Clang, GCC or glibc will trip up new compiler warnings. Worse, occasionally taking advantage of some UB laying around leading to runtime bugs.

I'm not complaining, the new stricter warnings are usually for the better, what I'm saying is that the bedrock of that world isn't as stable as it's sometimes portraited.

If you go into mainframes, you'll compile code that was written 50 years ago without issue. In fact, you'll run code that was compiled 50 years ago and all that'll happen is that it'll finish much sooner than it did on the old 360 it originally ran on.