how to use reinterpret_cast to cast to a derived class pointer in c++

Question

Here is my test example:

struct base {
    virtual ~base(){}
    int x;
};

struct derived: public virtual base {
    base * clone() {
        return new derived;
    }
    derived(): s("a") {}
    std::string s;
};

int main () {
    derived d;
    base * b = d.clone();
    derived * t = reinterpret_cast<derived*>(b);
    std::cout << t->s << std::endl;
    return 0;
}

It crashes at the line where I print s. Since "b" is a pointer to the derived class, reinterpret_cast should just work. I wonder why it crashes. At the same time, if I replace reinterpret_cast with dynamic_cast, then it works.