C++虚函数引发的~

最新推荐文章于 2025-08-14 22:07:01 发布

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最新推荐文章于 2025-08-14 22:07:01 发布

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分类专栏： C++ 文章标签： c++ class c system

本文链接：https://blog.youkuaiyun.com/jeiwt/article/details/5903880

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6 篇文章

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首先转摘一篇高人文章，介绍C++的虚函数表

http://blog.youkuaiyun.com/haoel/archive/2007/12/18/1948051.aspx

其次

看如下打印结果

#include <stdio.h> #include <stdlib.h> class BaseA { public: void f(){printf("A:f()/n");} }; class BaseB { public: virtual void f2(){printf("B:f2()/n");} }; class C : public BaseA, public BaseB { public: void f(){printf("C:f()/n");} }; int main() { printf("sizeof(BaseA) = %d/n", sizeof(BaseA)); printf("sizeof(C) = %d/n", sizeof(C)); C c; BaseA *a = &c; a->f(); c.f(); system("pause"); return 0; }

输出结果为：

sizeof(BaseA) = 1
sizeof(C) = 4
A:f()
C:f()

再看如果class BaseA的f()方法变为virtual之后

#include <stdio.h> #include <stdlib.h> class BaseA { public: virtual void f(){printf("A:f()/n");} }; class BaseB { public: virtual void f2(){printf("B:f2()/n");} }; class C : public BaseA, public BaseB { public: void f(){printf("C:f()/n");} }; int main() { printf("sizeof(BaseA) = %d/n", sizeof(BaseA)); printf("sizeof(C) = %d/n", sizeof(C)); C c; BaseA *a = &c; a->f(); c.f(); system("pause"); return 0; }

输出结果为：

sizeof(BaseA) = 4
sizeof(C) = 8
C:f()
C:f()

在C++中，空类（无非静态的成员变量的）大小为1