Like it or not, there are already tons of lint-like warnings in GCC [1] and clang [2]. Many (uh, most?) of them are not required by the C/C++ standards (which by the way have their own requirements for diagnostic messages).

[1] https://gcc.gnu.org/onlinedocs/gcc/Warning-Options.html

[2] https://clang.llvm.org/docs/DiagnosticsReference.html