C++11 weak_ptr智能指针

#include<iostream>
using namespace std;
class test {
public:
  test() {
    cout << "调用构造函数" << endl;
  }
  ~test() {
    cout << "调用析构函数" << endl;
  }
  void func() {
    cout << "void func()" << endl;
  }
};
int main(void) {
  shared_ptr<test>sp(new test());
  shared_ptr<test>sp2(new test());
  //weak_ptr<test>wp(new test());//报错
  weak_ptr<test>wp;
  wp = sp;//使用共享赋值构造
  weak_ptr<test>wp2(sp2);//使用共享构造
  //使用weak_ptr 不会导致 shared_ptr计数增加
  cout << "weak_ptr wp:" << wp.use_count() << endl;//1
  cout << "shared_ptr:" << sp.use_count() << endl;//1
  //weak_ptr不支持 *和->对指针进行访问
  sp->func();
  // wp->func();//报错
  //必要时使用 lock()可将weak_ptr转为shared_ptr
  shared_ptr<test>sp3;
  sp3 = wp.lock();
  cout << "---sp3 = wp.lock()---" << endl;
  cout<<"shared_ptr sp3:" << sp3.use_count() << endl;
  system("pause");
  return 0;
}