#include <mutex>
#include <thread>
#include <atomic>

int main() {
    std::atomic< bool > kill{ false };
    std::mutex mtx;
    int x = 0;
    std::thread t( [&] {
        while ( !kill ) {
            std::lock_guard< std::mutex > lock( mtx );
            x = x % 2 + 1;
        } // unlock
    } );
    {
        std::lock_guard< std::mutex > lock( mtx );
        while ( x != 0 )
        { }
    } // unlock
    kill = true;
    t.join();
}