#include<iostream>
using namespace std;
class A
{
public:
char a;
int b;
};
/**
* @brief 此时B按照顺序:
* char a
* int b
* short a
* long b
* 根据字节对齐4+4=8+8+8=24
*/
class B : A
{
public:
short a;
long b;
};
class C
{
A a;
char c;
};
class A1
{
virtual void fun(){}
};
class C1:public A1
{
};
int main()
{
cout << sizeof(A) << endl; // 8
cout << sizeof(B) << endl; // 24
cout << sizeof(C) << endl; // 12
/**
* @brief 对于虚单函数继承,派生类也继承了基类的vptr,所以是8字节
*/
cout << sizeof(C1) << endl; // 8
return 0;
}
虚继承, 继承基类的vptr。
#include<iostream>
using namespace std;
class A
{
virtual void fun() {}
};
class B
{
virtual void fun2() {}
};
class C : virtual public A, virtual public B
{
public:
virtual void fun3() {}
};
int main()
{
/**
* @brief 8 8 16 派生类虚继承多个虚函数,会继承所有虚函数的vptr
*/
cout<<sizeof(A)<<" "<<sizeof(B)<<" "<<sizeof(C);
return 0;
}