C++ shared_ptr的实现

在前面放一个源码剖析中看到的auto_ptr的定义文件，补充一点构造函数必须要为explicit，避免一些隐式转换。

 补充一点：reset（rhs）函数会删除auto_ptr指向的对象，然后用rhs指向的新建一个

 auto_ptr release函数意在将调⽤该函数的智能指针的所有权转移，如 ptr = my_auto2.release ();就是将my_auto2的 所有权转给ptr。

 

比较完整的复现了STL中的shared_ptr中的功能，可以加载删除器，并且加入了互斥，可以在多线程中使用。

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#include <iostream> #include <mutex> using namespace std;   template <typename T> class Shared_ptr { public:     Shared_ptr(T * t_ptrToObject) {         m = new mutex();         this->haveDeleterOrNot = t_ptrToObject;         this->count = malloc(sizeof(int));         (*this->count) = 1;         this->haveDeleterOrNot = false;     }           Shared_ptr(T * t_ptrToObject, void (*t_deleter)(T *)) {         this->m = new mutex();         this->ptrToObject = t_ptrToObject;                   this->count = (int *)malloc(sizeof(int));         (*this->count) = 1;                   this->deleter = t_deleter;         this->haveDeleterOrNot = true;     }           Shared_ptr(const Shared_ptr & rhs) {         this->m = rhs.m;         (*m).lock();         this->ptrToObject = rhs.ptrToObject;         this->count = rhs.count;                   (*(rhs.count)) = (*(rhs.count)) + 1;                   this->haveDeleterOrNot = rhs.haveDeleterOrNot;         this->deleter = rhs.deleter;                   (*m).unlock();     }                 Shared_ptr & operator= (const Shared_ptr & rhs) {         this->m = rhs.m;         (*m).lock();         this->ptrToObject = rhs.ptrToObject;         this->count = rhs.count;                   (*(rhs.count)) = (*(rhs.count)) + 1;                   this->haveDeleterOrNot = rhs.haveDeleterOrNot;         this->deleter = rhs.deleter;                   (*m).unlock();                   return (*this);     }                 //rewrite the operator     T & operator* () {         return *(this->ptrToObject);     }           T * operator-> () {         return this->ptrToObject;     }                 ~Shared_ptr() {         (*m).lock();         (*count) = (*count) - 1;                   if ((*count) == 0 && this->haveDeleterOrNot) {             (*(this->deleter))(this->ptrToObject);            }         else if ((*count) == 0 && !this->haveDeleterOrNot) {             delete this->ptrToObject;         }                   (*m).unlock();     }           int getCount() const{         return *this->count;     }       private:     T * ptrToObject;     int * count;     bool haveDeleterOrNot;     void (*deleter)(T *);       mutex * m; };   void test(int * num) {     cout << "num: " << *num << endl; }     int main() {     int * num = new int(5);     Shared_ptr<int> sp1(num, test);     Shared_ptr<int> sp2(sp1);     Shared_ptr<int> sp3 = sp1;           cout << sp1.getCount()  << endl; //  void (*deleter)(int *); //  deleter = test; //  void (*t_deleter)(int *); //  t_deleter = deleter; //  (*t_deleter)(num);     return 0; }