实现c++智能指针

改造一下标准库里的share指针

// 需要一个结构体保存计数器和裸指针
template 
struct Conptr {
    T * ptr;
    unsigned int Counter;
};
 
template 
class shared_ptr {
    public:
      Conptr * ptr;

      // 允许通过 （） 或者 = 传入指针
      shared_ptr(T *aptr){
        ptr = new Conptr;
        ptr->ptr = aptr;
        ptr->Counter = 1;
      }
      // 允许复制构造
      shared_ptr(const shared_ptr & aptr){
        ptr = aptr->ptr;
        ptr->Counter ++;
      }
      ~shared_ptr(){
        ptr->Counter --;
        if(ptr->Counter == 0){
            delete ptr->ptr;
            delete ptr;
        }
      }
 
      T * const operator -> (){
          return ptr->ptr;
      }
      // 禁止循环构造
      shared_ptr & operator = (shared_ptr & aptr) = delete;
      // 禁止生成裸指针
      shared_ptr() = delete;
      // 通过get()得到值，而不是指针
      T & get(){
        return * (ptr->ptr);
      }

};

class test{
public:
  test(){std::cout<<"create an obj of the test class";}
  ~test(){std::cout<<"delete the obj";}

};

int main(){
  shared_ptr ptr = new int;
  ptr.get() = 10;
  std::cout << ptr.get();
  shared_ptr ptr2 = ptr;

  {
    shared_ptr tp = new test;
  }

  auto test_for_function [&](const shared_ptr & p){
    share_ptr t = p;
    return t;
  }

  shared_ptr tp2 = test_for_function();

  ptr2 = ptr; // error
  shared_ptr ptr3; // error
}