Have your panic handler call an extern "C" function that doesn't exist, and the linker will complain if there's any calls to that function that weren't optimize

Have your panic handler call an extern "C" function that doesn't exist, and the linker will complain if there's any calls to that function that weren't optimized out. Alternately, you can look for the symbol in the output elf file and fail if it's there, which is a bit more graceful as panicking binaries can still be produced during development.