for (auto dummy : state) {
    sum = *(o.Get<Callable>(String("f")))->Call<Integer>(sum, Integer(i));
    i++;
  }
}

// Add numbers in a loop by calling a raw C++ function with a function
// pointer.
void CallFunctionsBase(::testing::benchmark::State& state) {
  int64_t sum = 0;
  typedef int64_t (*Func)(int64_t a, int64_t b);
  volatile Func f_raw = AddRaw;
  Func f = f_raw;
  size_t i = 0;
  for (auto dummy : state) {