Thread inside class with class function

#include <iostream>
#include <thread>
#include <chrono>
#include <ctime>


class tmp {
private:
    bool ativo;
    int n;
    void print_n() {
        while(true) {
            if(!ativo)
                return;

            std::clock_t start = std::clock();


            while(std::clock() - start < 1000) {
                if(!ativo)
                    return;
            }

            std::cout << n << std::endl;

            //std::this_thread::sleep_for(std::chrono::seconds(1));
        }
    }
public:
    tmp() {
        ativo = true;
    }
    void setativo(bool set) {
        ativo = set;
        return;
    }
    void set(int v) {
        n = v;
        return;
    }

    void print() {
        //print_n(n);
        std::thread(&tmp::print_n, this).detach();
        return;
    }
};


tmp TMP;

int main()
{

    TMP.set(5);

    TMP.print();

    while(true) {
        int get;
        std::cin >> get;
        if(get == 0) {
            TMP.setativo(false);
            break;
        }
        TMP.set(get);
    }

    return 0;
}