保存变量并且在程序结束时候还原的方法

template
  class Save
      {
      protected:
          Type &_var;
          Type _save_value;
      public:
          Save(Type &elem):_var(elem),_save_value(elem){}
          ~Save(){_var = _save_value;}
     };

void start(int &x)
    {
        Save<int> temp(x);
        x=3;
        std::cout<<"start x:"<std::endl;
    }

int main()
    {
        int x=2;
        start(x);
        std::cout<<"main x:"<std::end;
    }