vector 加入结构体问题

struct A
{
    A()
    {
        x = 0;
        y = 0;
        b = null;
    }
    ~A()
    {
        delete b;
    }
    int x;
    int y;
    B* b;
};

vector<A*> vec;
A* a = new A;
a->b = new B;
a->x = 10;
a->y = 10;

vec.push_back(a); //这里报错。。。求答案