使用初始化列表初始化父类的指针

Question

我有一个类字符串：

    class strings
    {
    protected:
    string *ptr;
    int size;
public:
    strings() {
        ptr = NULL;
        size = -1;
    }
    strings(int size) {
        this->size = size;
        ptr = new string[size];
    }
    string* retPtr() {
        return ptr;
    }
    void setPtr(int size)
    {
        ptr = new string[size];
        this->size = size;
    }
    strings(const strings& obj) {
        this->size = obj.size;
        for (int i = 0;i < size;++i)
            this->ptr[i] = obj.ptr[i];
    }
    friend istream& operator>>(istream& input, strings& obj) {
        cin.ignore();
        cout << "Enter " << obj.size << " string one by one:\n";
        for (int i = 0;i < obj.size;++i)
        {
            getline(input, obj.ptr[i]);
        }
        return input;
    }
    friend ostream& operator<<(ostream& output, const strings& obj) {
        cout << "Strings are:\n";
        for (int i = 0;i < obj.size;++i)
            output << obj.ptr[i] << "\n";
        return output;
    }
    void operator =(const strings& obj)
    {
        this->size = obj.size;
        for (int i = 0;i < size;++i)
            ptr[i] = obj.ptr[i];
    }
    ~strings()
    {
        delete[]ptr;
    }
};

另一个类stringsFromNumbers：

class stringsFromNumbers:public strings
{
    int numbers;
public:
    stringsFromNumbers(){
        numbers = -1;
    }
    stringsFromNumbers(int size, int numbers):strings(size){
        this->numbers = numbers;
    }
    stringsFromNumbers(const stringsFromNumbers& obj)
    {
        this->numbers = obj.numbers;
        this->size = obj.size;
        for (int i = 0;i < size;++i)
            this->ptr[i] = obj.ptr[i];
    }
    friend istream& operator>>(istream& input, stringsFromNumbers& obj) {
        cin.ignore();
        cout << "Enter " << obj.size << " string one by one:\n";
        for (int i = 0;i < obj.size;++i)
        {
            getline(cin, obj.ptr[i]);
        }
        return input;
    }
    friend ostream& operator<<(ostream& output, const stringsFromNumbers& obj) {
        cout << "Numbers are: " << obj.numbers;
        cout << "\nStrings are:\n";
        for (int i = 0;i < obj.size;++i)
            output << obj.ptr[i] << "\n";
        return output;
    }
    void operator =(const stringsFromNumbers& obj)
    {
        this->numbers = obj.numbers;
        this->size = obj.size;
        for (int i = 0;i < size;++i)
            this->ptr[i] = obj.ptr[i];
    }
    ~stringsFromNumbers()
    {
        delete[] ptr;
    }
};

每当我尝试执行这行代码时：

stringsFromNumbers obj2(N, P);

其中 N 和 P 是有效整数，我收到“访问读取冲突”，您是否发现代码中有问题？ 我已经坚持了将近2个小时。我已经尝试调试和修复它，我还尝试了多种其他方法。异常将我带到这个函数：

inline void _Container_base12::_Orphan_all() noexcept {
#if _ITERATOR_DEBUG_LEVEL == 2
    if (_Myproxy) { // proxy allocated, drain it
        _Lockit _Lock(_LOCK_DEBUG);

        for (auto _Pnext = &_Myproxy->_Myfirstiter; *_Pnext; *_Pnext = (*_Pnext)->_Mynextiter) {
            (*_Pnext)->_Myproxy = nullptr;
        }

        _Myproxy->_Myfirstiter = nullptr;
    }
#endif // _ITERATOR_DEBUG_LEVEL == 2
}

这个问题很可能出在这个功能上，但是如何解决呢？

stringsFromNumbers(int size, int numbers):strings(size){
    this->numbers = numbers;
}

Answer 1

stringsFromNumbers::~stringsFromNumbers 和strings::strings 都在ptr 上调用delete[]，因此尝试释放数组两次；第二次出现问题。

这些类中只有一个应该负责管理ptr 的生命周期。从stringsFromNumbers::~stringsFromNumbers 中删除delete[]。

如果在其他情况下您有正当理由在子类的析构函数中释放数组，请确保父类析构函数能够处理新状态（例如，通过将 ptr 设置为 @987654329 @ 删除后），但一般情况下，您应该避免让两个类共同负责释放内存的复杂性。