rule of three-five-zero

参考

The rule of three/five/zero

rule of three

class rule_of_three
{
    char* cstring; // raw pointer used as a handle to a dynamically-allocated memory block
 
    void init(const char* s)
    {
        std::size_t n = std::strlen(s) + 1;
        cstring = new char[n];
        std::memcpy(cstring, s, n); // populate
    }
 public:
    rule_of_three(const char* s = "") { init(s); }
 
    ~rule_of_three()
    {
        delete[] cstring;  // deallocate
    }
 
    rule_of_three(const rule_of_three& other) // copy constructor
    { 
        init(other.cstring);
    }
 
    rule_of_three& operator=(const rule_of_three& other) // copy assignment
    {
        if(this != &other) {
            delete[] cstring;  // deallocate
            init(other.cstring);
        }
        return *this;
    }
};

析构函数，拷贝构造函数，赋值拷贝运算符函数，如果用户实现了其中一个，则应该实现所有的三个。主要针对类内成员作为指针指向对象或者是句柄，而导致的释放关闭问题。

• 如果只实现了析构函数，系统默认拷贝构造函数是浅拷贝，后面涉及多次析构同一地址
• 如果只实现了拷贝构造函数，析构

ending