为什么派生类无法访问受保护的基类成员？

Question

I have a base class (VectorRaw) and a derived class (Vector).

I use operator new in the constructor of the base class to create a memory buffer and then placement new in the constructor of the derived class to place elements therein.

The base class has its virtual destructor which cleans up if something in the constructor of the derived class goes wrong.

When I try to compile it, there is an error: all of the base class' members ( begin, end, end_of_reserved ) are out of scope in all derived classes' functions.

What am I doing wrong?

Here's my code:

template <typename T>
class VectorRaw {
protected:
    T * begin;
    T * end;
    T * end_of_reserved;

    VectorRaw(const size_t size) {
        begin = (T*) operator new (2 * size * sizeof(T));
        end = begin;
        end_of_reserved = begin + 2 * size;
    }
    virtual ~VectorRaw<T> () throw() {
        for (T * iter = begin; iter != end; ++iter) {
            iter->~T();
        }
        operator delete (begin);
        end_of_reserved = end = begin;
    }
};

template <typename T>
class Vector : public VectorRaw<T> {
public: 
    Vector(const size_t size, const T& value) : VectorRaw<T>(size) {
        for (end = begin; end != begin + size; ++end)
            {   
            new (end) T (value);
        }
    }
    bool Empty() const throw() {
        return (begin == end);
    }
};

Answer 1

Since your base class is a template class, you need to access the members through the this pointer:

template <typename T>
class Vector : public VectorRaw<T> {
public: 
    Vector(const size_t size, const T& value) : VectorRaw<T>(size) {
        for (this->end = begin; this->end != this->begin + size; ++this->end)
            {   
            new (this->end) T (value);
        }
    }
    bool Empty() const {
        return (this->begin == this->end);
    }

};

This is necessary to defer the lookup of these names until the template parameter is known. It makes them dependent names . See this answer for more details.