C++派生类和赋值运算符

如果基类重载了赋值运算符=而派生类没有，那么在派生类对象之间赋值，或用派生类对象对基类对象进行赋值时，其中基类部分的赋值操作是调用被基类重载的=完成的。例如下面的程序：

#include <iostream>
using namespace std;
class CBase
{
public:
    CBase() {}
    CBase(CBase & c) { cout << "CBase::copy constructor called" << endl; }
    CBase & operator = (const CBase & b)
    {
        cout << "CBase::opeartor = called" << endl;
        return *this;
    }
};
class CDerived : public CBase {};
int main()
{
    CDerived d1, d2;
    CDerived d3(d1);  //d3初始化过程中会调用CBase类的复制构造函数
    d2 = d1;  //会调用CBase类重载的“=”运算符
    return 0;
}

程序的输出结果是：
CBase::copy constructor called
CBase::opeartor = called