c++ - 为什么不调用成员类的拷贝构造函数？

Question

class member
{
public:
    member()
    {
       cout<<"Calling member constr"<<'\n';
    }
    member(const member&)
    {
        cout<<"Calling member copy constr"<<'\n';
    }
};

class fred
{
public:
    fred()
    {
        cout<<"calling fred constr"<<'\n';
    }
    fred(const fred &)
    {
        cout<<"Calling fred copy constr"<<'\n';
    }
protected:
    member member_;
};

int main()
{
    fred a;
    fred b=a;
}

Output:
Calling member constr
calling fred constr
**Calling member constr**
Calling fred copy constr

Answer 1

因为你没有调用member的拷贝构造函数。如果覆盖 fred 的默认复制构造函数，则需要显式复制成员。

fred(const fred& other) : member_(other.member_) {
    cout<<"Calling fred copy constr"<<'\n';
}