C++经典面试题 | 带引用计数的智能指针循环交叉引用问题

1. 强智能指针shared_ptr循环引用所带来的问题：

class B;
class A
{
   
   
public:
	A() {
   
    cout << "A()" << endl; }
	~A() {
   
    cout << "~A()" << endl; }
	shared_ptr<B> _ptrb;
};

class B
{
   
   
public:
	B() {
   
    cout << "B()" << endl; }
	~B() {
   
    cout << "~B()" <<