string move vs string copy

const_string_vs_value_string.cpp

#include <iostream>
#include <ctime>
#include <string>

void function_a(const std::string& str) {
    return;
}

void function_b(std::string str) {
    return;
}

int main() {
    std::string str = "a really not so long string";
    clock_t start, end;

    start = clock();
        for (int i = 0; i < 1e6; ++i) {
            function_a(str);
        }
    end = clock();

    std::cout << "function_a: " << float(end - start) / CLOCKS_PER_SEC * 1000.f << "ms" << std::endl;

    start = clock();
        for (int i = 0; i < 1e6; ++i) {
            function_b(str);
        }
    end = clock();

    std::cout << "function_b: " << float(end - start) / CLOCKS_PER_SEC * 1000.f << "ms" << std::endl;

    start = clock();
        for (int i = 0; i < 1e6; ++i) {
            function_b(std::move(str));
        }
    end = clock();

    std::cout << "function_b-move: " << float(end - start) / CLOCKS_PER_SEC * 1000.f << "ms" << std::endl;
}