任务
阅读下面代码，修复代码中存在的bug
#include <iostream>
using namespace std;
class A
{
public:
virtual void function(void) = 0;
};
class B:public A
{
public:
void show(void)
{
cout << "B::show()" << endl;
}
};
int main(void)
{
B obj;
obj.show();
return 0;
}