boost仅运行一次的例程

#include <boost/thread/thread.hpp>#include <boost/thread/once.hpp>#include <iostream>int i = 0;boost::once_flag flag =BOOST_ONCE_INIT;void init(){++i;}void thread(){boost::call_once(&init, flag);}int main(int argc, char* argv[]){boost::thread thrd1(&thread);boost::thread thrd2(&thread);thrd1.join();thrd2.join();std::cout << i << std::endl;return 0;}/*1请按任意键继续. . .*/