#include<iostream>
using namespace std;
struct Base1 {int x;};   //结构体Base1定义
struct Base2 {float y;};   //结构体Base2定义
struct Derived:Base1,Base2{};   //派生类结构体Derived，基类为Base1,Base2，默认继承方式为公有继承
int main(){     //主函数
    Derived *pd=new Derived;
    pd->x=1;pd->y=2.0f;
    void *pv=pd;
    Base2*pd=static_cast<Base2*>(pv);
    cout<<pd->y<<" "<<pb->y<<endl;
    delete pb;
    return 0;
}

两个变量重名吧

给我对每一行进行注释和修改一下嘛！

    Base2*pd2=static_cast<Base2*>(pv);
    cout<<pd->y<<" "<<pd2->y<<endl;
    delete pd;
    delete pd2;

还是搞不清楚

就是两个变量用了同一个名字