The PORTING checkers identify code that might rely on specific implementation details in different compilers. The PORTING.OPTS checker detects situations in which a compiler-dependent option is used.
Vulnerability and risk
This checker warns you of options that are compiler-dependent, in case you need to take action. If you use the checker just before the port begins, you can evaluate those parts of your build that are dependent on particular switches being passed to the compiler. This practice allows you to plan for equivalent switches on the new compiler, or rewrite those parts of the system.