gistfile1.cpp

#define NONIUS_RUNNER
#include <nonius.h++>

#include <string>
#include <vector>

std::string f(std::string const& s) {
    return s + "some text";
}
void f(std::string const& s, std::string& result) {
    result = s + "some text";
}

void f2(std::string const& s, std::string& result) {
    result.clear();
    result += s;
    result += "some text";
}

void byval(std::string const& s) {
    for(int i = 0; i < 10; ++i) {
        volatile std::string x = f(s);
        (void)x;
    }
}

void byref(std::string const& s) {
    std::string x;
    for(int i = 0; i < 10; ++i) {
        f(s, x);
    }
}

void byref2(std::string const& s) {
    std::string x;
    for(int i = 0; i < 10; ++i) {
        f2(s, x);
    }
}

NONIUS_BENCHMARK("return by value", [](nonius::chronometer meter) {
    std::string x = "It was big. Really, really big. No, bigger than that. Even bigger. Keep going. More. No, more. Look, we're talking krakens and dreadnoughts for jewelry. It was big!";
    meter.measure([&]{ byval(x); });
})

NONIUS_BENCHMARK("return by ref", [](nonius::chronometer meter) {
    std::string x = "It was big. Really, really big. No, bigger than that. Even bigger. Keep going. More. No, more. Look, we're talking krakens and dreadnoughts for jewelry. It was big!";
    meter.measure([&]{ byref(x); });
})

NONIUS_BENCHMARK("return by ref [optimised]", [](nonius::chronometer meter) {
    std::string x = "It was big. Really, really big. No, bigger than that. Even bigger. Keep going. More. No, more. Look, we're talking krakens and dreadnoughts for jewelry. It was big!";
    meter.measure([&]{ byref2(x); });
})