命名空间“std”中的“bad\u cast”未命名类型错误[已关闭]

给出下一个代码:

#include <iostream>
using std::cout;
using std::endl;
using std::cerr;

class A {
public:
    virtual ~A() {
    }
};

class B: public A {
public:

};

int main() {
    int n = 4;
    A a;
    A& base = a;
    B* ptr = dynamic_cast<B*>(&base);
    if (ptr == NULL) {
        cerr << "base is not a B";
    }
    try {
        B& derived = dynamic_cast<B&>(base);
        derived = *ptr;
    } catch (std::bad_cast&) { // ERROR
        cerr << "base is not a B";
    }
    if (n == 3) {
    }
    return 0;
}

我收到此消息错误,我不明白原因是什么,如何修复它?

命名空间“std”中的“bad\u cast”未命名类型