C++ 中的指针构造函数

Question

I'm asked to write a SmartPointer class. One of the constructors takes a pointer variable, and I assume that I should simply copy the pointer to the relevant variable. But when I try, I get a segmentation error. Here is the content of the header file and my implementation of Pointer Constructor .

class ReferenceCount {
public:
    size_t AddRef() {
        return ++count;
    }

    size_t Release() {
        return --count;
    }

    size_t getCount() const {
        return count;
    }

private:
    size_t count = 0; // Reference count
};



template<typename T>
class SmartPointer {

private:
    void free();
    // pointer to actual data
    T *dataPointer;
    // Reference count
    ReferenceCount *referenceCount;

public:
    //Constructor
    SmartPointer();

    // Copy constructor
    SmartPointer(const SmartPointer<T> &sp);

    explicit SmartPointer(T *pValue);

    // Assignment operator
    SmartPointer<T> &operator=(const SmartPointer<T> &sp);

    SmartPointer<T> &operator=(T *pValue);

    // Destructor
    ~SmartPointer();

    T &operator*() const;

    T *operator->() const;

    T *get() const;

    ReferenceCount *getReferenceCount() const;

};

The constructor:

template<typename T>
SmartPointer<T>::SmartPointer(T *pValue) {
    dataPointer = pValue;
    referenceCount = nullptr;
}

Answer 1

You appear to be writing something similar to shared_ptr<T> .

For a shared_ptr -like smart pointer, each smart pointer has both a pointer-to-object and a pointer-to-control-block.

When you are constructed with a pointer-to-object, you are responsible to create the control block.

In your case, your control block name is ReferenceCount .

So add a new ReferenceCount to that constructor. Probably start it off with a count of 1.