benchmark.cpp

class A {
  std::vector<std::string> _values;
public:
  void addValue(const std::string &val) {
    // some logic
    _values.emplace_back(val);
  }
  
  void addValue(std::string &&val) { // r-value ref overload
    // some logic
    _values.emplace_back(std::move(val)); // We know that is a r-value
  }
};

class B {
  std::vector<std::string> _values;
public:
  void addValue(const std::string &val) {
    // some logic
    _values.emplace_back(val);
  }
};

std::string f() {
  return std::string("a long enough string that will better show our results in our awesome benchmark");
}

static void AddValueCopy(benchmark::State& state) {
  // Code inside this loop is measured repeatedly
  for (auto _ : state) {
    B b;
    for(int i = 0; i < 10; ++i) {
      auto v = f();
      b.addValue(v);
    }
    benchmark::DoNotOptimize(b);
  }
}
// Register the function as a benchmark
BENCHMARK(AddValueCopy);

static void AddValueMove(benchmark::State& state) {
  // Code before the loop is not measured
  for (auto _ : state) {
    A a;
    for(int i = 0; i < 10; ++i) {
      a.addValue(f());
    }
    benchmark::DoNotOptimize(a);
  }
}
BENCHMARK(AddValueMove);