CppCoreGuidelines C.149 new 对象的时候，用 unique_ptr 或 shared_ptr，避免忘记删除对象

void use(int i)
{
    auto p = new int {7};           // bad: initialize local pointers with new
    auto q = make_unique<int>(9);   // ok: guarantee the release of the memory-allocated for 9
    if (0 < i) return;              // maybe return and leak
    delete p;                       // too late
}

class Flower {
  public:
    Flower(int id):m_id{id} { cout << "new flower " << m_id << "\n"; }
    ~Flower() { cout << "delete flower " << m_id << "\n"; }
  private:
    int m_id{0};
};

void use(int i)
{
    auto p = new Flower {7};
    // bad: initialize local pointers with new
    auto q = make_unique<Flower>(9);
    // ok: guarantee the release of the memory-allocated for 9
    if (0 < i) return;              // maybe return and leak
    delete p;                       // too late
}

int main()
{
    use(0);
    use(42);
}