类的虚函数\虚继承所占的空间
本文地址: http://blog.csdn.net/caroline_wendy/article/details/24236469
char占用一个字节, 但不满足4的倍数时, 会进行数据对齐, 使用4的倍数的字节(byte).
无论是虚函数还是虚继承, 都需要将指针存储在虚函数表(virtual function table), 占用4个字节.
继承会继承基类的数据, 和虚函数表, 即继承基类的空间.
代码:
/*
* test.cpp
*
* Created on: 2014.04.20
* Author: Spike
*/
/*eclipse cdt, gcc 4.8.1*/
#include <iostream>
using namespace std;
class A {
char k[5];
public:
virtual void aa() {};
};
class B : virtual public A {
char j[6];
public:
virtual void bb() {};
};
class C : virtual public B {
char i[7];
public:
virtual void cc() {};
};
int main() {
std::cout << "sizeof(A) = " << sizeof(A) << std::endl;
std::cout << "sizeof(B) = " << sizeof(B) << std::endl;
std::cout << "sizeof(C) = " << sizeof(C) << std::endl;
return 0;
}
输出:
sizeof(A) = 12 sizeof(B) = 24 sizeof(C) = 36