C++实现简易共享指针

#include <iostream>
#include <memory>
using namespace std;
template <typename T>
class SharedPtr{
private:
    T *_ptr;
    int *_pcount;
public:
    SharedPtr(T *ptr= nullptr):_ptr(ptr),_pcount(new int(1)){}//构造函数
    SharedPtr(const SharedPtr &s):_ptr(s._ptr),_pcount(s._pcount){//用另一个共享指针初始化共享指针
        (*_pcount)++;
    }
    SharedPtr<T> &operator=(const SharedPtr &s){//重载=
        if(this != &s)
        {
            if(--(*(this->_pcount))==0)//
            {
                delete this->_ptr;
                delete this->_pcount;
            }
            _ptr=s._ptr;
            _pcount=s._pcount;
            *(_pcount)++;
        }
        return *this;
    }
    T &operator*()//重载*
    {
        return *(this->_ptr);
    }
    T *operator->()//重载->
    {
        return this->_ptr;
    }
    ~SharedPtr()//析构函数
    {
        --(*(this->_pcount));
        if(*(this->_pcount)==0)
        {
            delete _ptr;
            _ptr= nullptr;
            delete _pcount;
            _pcount= nullptr;
        }

    }

};
int main() {
    std::shared_ptr<int> p1(new int(4));
    cout<<"p1: "<<p1<<" *p1 "<<*p1;
    cout<<endl;

    return 0;
}