C++智能指针

智能指针介绍

C++在堆上申请的内存，需要程序员自己去手动释放，这个内存很容易忘记释放或者在释放之前遭遇了异常，造成内存泄露。
堆内存的多次释放，会造成程序崩溃，同样，访问已经释放的内存也会造成不可预期的错误，而这些问题，都可以用智能指针来解决。
智能指针，主要用于堆内存的管理，在堆上生成的对象，可由智能指针进行管理，程序员无需手动释放，堆上的内存。

智能指针简易代码实现

···c/c++

include

template < typename T > class SmartPointer {
public:
SmartPointer(T * p):ptr_(p) {
std::cout << "create smart pointer" << std::endl;
user_count_ = new int (1);

}
SmartPointer(const SmartPointer & s_ptr) {
std::cout << "copy constructor is called" << std::endl;
ptr_ = s_ptr.ptr_;
user_count_ = s_ptr.user_count_;
++(*user_count_);
}

SmartPointer & operator=(const SmartPointer & s_ptr) {
std::cout << "Assignment constructor is called" << std::endl;
if (this == &s_ptr) {
    return *this;
}

--(*user_count_);
if (!(*user_count_)) {
    delete ptr_;
    ptr_ = nullptr;
    delete user_count_;
    user_count_ = nullptr;
    std::cout << "left side object is called" << std::endl;
}

ptr_ = s_ptr.ptr_;
user_count_ = s_ptr.user_count_;
++(*user_count_);
}

~SmartPointer() {
std::cout << "Destructor is called" << std::endl;
--(*user_count_);
if (!(*user_count_)) {
    delete ptr_;
    ptr_ = nullptr;
    delete user_count_;
    user_count_ = nullptr;
}

}

private:
T * ptr_;
int *user_count_;
};

int main()
{
SmartPointer < int >ptr1(new int (10));
ptr1 = ptr1;
SmartPointer < int >ptr2(ptr1);
SmartPointer < int >ptr3(new int (20));
ptr3 = ptr1;
}

···

来源：https://www.cnblogs.com/wanshuafe/p/11645266.html