How can I generate UUID in c++, without using boost library?

This will do, if you’re using modern C++.

#include <random>
#include <sstream>

namespace uuid {
    static std::random_device              rd;
    static std::mt19937                    gen(rd());
    static std::uniform_int_distribution<> dis(0, 15);
    static std::uniform_int_distribution<> dis2(8, 11);

    std::string generate_uuid_v4() {
        std::stringstream ss;
        int i;
        ss << std::hex;
        for (i = 0; i < 8; i++) {
            ss << dis(gen);
        }
        ss << "-";
        for (i = 0; i < 4; i++) {
            ss << dis(gen);
        }
        ss << "-4";
        for (i = 0; i < 3; i++) {
            ss << dis(gen);
        }
        ss << "-";
        ss << dis2(gen);
        for (i = 0; i < 3; i++) {
            ss << dis(gen);
        }
        ss << "-";
        for (i = 0; i < 12; i++) {
            ss << dis(gen);
        };
        return ss.str();
    }
}