摘引传参的疑惑

引用传参的疑惑

C/C++ code

#include "stdafx.h"#include <boost/thread/thread.hpp>#include <boost/bind.hpp>#include <iostream>#include <string>using namespace std;using namespace boost;void One_One(const int a,const int b,int &c){    c=a-b;    cout<<c<<endl;}int main(){    int num=100;//初值    thread thrd1(bind(One_One,2,3,num));    thrd1.join();    cout<<num<<endl;//运行后输出了初值100        getchar();    return 0;}