gcc: how best to handle warning about (unreachable) end of function after switch?

When I compile the following code at c++11 standard, it works fine with clang, and also with gcc, but gcc (all versions that I tested 4.8.2, 4.9.2, 5.1.0) gives a warning:

#include <iostream>

enum class FOO { A, B, C };

const char * bar(FOO f) {
  switch (f) {
    case FOO::A:
      return "A";
    case FOO::B:
      return "B";
    case FOO::C:
      return "C";
  }
}

int main() {
  unsigned int x;
  std::cin >> x;

  FOO f = static_cast<FOO>(x % 3);
  std::cout << bar(f) << std::endl;
}

The warning is -Wreturn-type:

main.cpp: In function ‘const char* bar(FOO)’:
main.cpp:14:1: error: control reaches end of non-void function [-Werror=return-type]
 }
 ^
cc1plus: all warnings being treated as errors

I still get the warning even with -O2 or -O3 optimizations -- does this mean that even at high optimization levels, gcc cannot dead-code eliminate the 'end' of the function?

Notably, it doesn't give me the warning about unhandled switch cases.

Is there a good way to suppress this warning locally within such a function, or is the only way to suppress this to disable the warning generally?