std::unique_ptr of base class holding reference of derived class does not show warning in gcc compiler while naked pointer shows it. Why?

Question

I have a hierarchy of base class and derived class. Base class has one virtual function which is overridden by derived class.

class Base {   public:       ~Base();         virtual void other_functionality() = 0;   };  class Derived : public Base {   public:       ~Derived ();         void other_functionality() {//some code};   }; 

Now if i do like this:

int main() { Base * P = new Derived (); delete p; return 0; } 

It gives error:
deleting object of polymorphic class type which has non-virtual destructor.

But with unique_ptr it passes without warning.

int main() {  std::unique_ptr<Base> p;  p.reset(new Derived ());  return 0; } 

I know if I use virtual destructor. Warning with naked pointer will be solved. But question remains - why absence of virtual destructor shows problem with naked pointer and not with unique_ptr.

Answer 1

Well, first of all, deleting a derived object through a base pointer when the base class does not have a virtual destructor is undefined behavior. Compilers are not required to diagnose undefined behavior…

That being said, the reason why this warning does not appear when using std::unique_ptr is most likely due to the fact that GCC does not report warnings that would appear in system headers.