虚函数相关的题目笔记

#include <iostream>

class A {

public:
  virtual void fun() {
    std::cout << "A" << std::endl;
  }
  int i;
};

class B : public A {
public:
  virtual void fun() {
    std::cout << "B" << std::endl;
  }
  int j;
};

class C : public A {
public:
  virtual void fun() {
    std::cout << "C" << std::endl;
  }
  virtual void fun2() {
    std::cout << "C2" << std::endl;
  }
  int k;
};

int main() {
  A a;
  B b;
  C c;
  return 0;
}

上面的例子主要是想知道B，C是否会有自己的虚表指针，结果我用gdb -g test.cpp进行调试，发现：

p a -> {_vptr.A = 0x400c28 <vtable for A+16>, i = 4197277}

p b -> {<A> = {_vptr.A = 0x400c10 <vtable for B+16>, i = 0}, j = 0}

p c -> {<A> = {_vptr.A = 0x400bf0 <vtable for C+16>, i = 4196496}, k = 0}

a,b,c都是只有一个虚表指针，并且指向的是不同的虚表。