虚继承中的内存布局

Posted 2020-09-21 Key_Ky

直接看例子就好：

#include "qdatetime.h"

class Person {
public:
    Person(QString name, QDate birthdate)
    QObject(name.ascii()),
    m_Birthdate(birthdate) {}

    Person(const Person& p) : QObject(p),
    m_Birthdate(p.m_Birthdate) {}

private:
    QDate m_Birthdate;
};

class Student : virtual public Person {       1
    // other class members
};

class Teacher : virtual public Person {       2
    // other class members
}


class GraduateTeachingFellow :
    public Student, public Teacher {          3
public:
    GraduateTeachingFellow(const Person& p,
                           const Student& s, const Teacher& t):
    Person(p), Students(s), Teacher(t) {}     4

	Note keyword virtual here.
	virtual inheritance.
	virtual not needed here.
	It is necessary to initialize all virtual base classes explicitly in multiply-derived classes, to resolve ambiguity about how they should be initialized.

Each instance of a class that virtually inherits from another has a pointer (or a variable offset) to its virtual base class subobject. 看来这里每个虚继承类的实例代表的是Student和Teacher都会有一个指针指向虚基类的 virtual base class subobject。具体这里怎么翻译还得查查