UglyError1

#include <iostream>

struct Base
{
    Base()
    {}
    virtual void show()
    {};
    ~Base()
    {}
};

class Derived : public Base
{
    int a;
    Base* hidden;
public:
    Derived()
    : a(10)
    {
        hidden = new Base;
    }
    virtual void show()
    {
        std::cout << a << std::endl;
    }
    ~Derived()
    {
        delete hidden;
    }
};

void g(Base* b)
{
    b->show();
}

Base* f()
{
    Base* d = new Derived;
    return d;
}

int main (void)
{
    Base* d = f();
    g(d);
    delete d;
}