[C++] Weffc++/Wnon-virtual-dtor confusion

[Markus Trippelsdorf]

On 2014.04.04 at 18:04 +0100, Nathan Sidwell wrote:
> On 04/04/14 17:54, Markus Trippelsdorf wrote:
> 
> > markus@x4 tmp % g++ -Wnon-virtual-dtor -std=c++11 -c test.ii
> > test.ii: In instantiation of ‘class A<>’:
> > test.ii:12:16:   required from here
> > test.ii:9:26: warning: base class ‘class opt_storage<0>’ has accessible non-virtual destructor [-Wnon-virtual-dtor]
> >   template <int = 0> class A : Option, opt_storage<0>
> 
> ah, you've hit on the one case I was unsure about -- IMHO Scott's rule about 
> bases is incomplete.  The rule should be for publicly accessible bases only -- 
> opt_storage is private.
> 
> The aim of the rule is to make sure that random code doing:
> 
>    A_Base_type *ptr = ptr_to_derived; // implicit base cast
>    ...
>    delete ptr;
> 
> behaved as one might expect and invoke the final polymorphic dtor.  Such an 
> implicit cast to a private base can't happen outside of the class.  Inside the 
> class one's expected to know what one's doing.
> 
> I'm fine with adding a TREE_PUBLIC (base_binfo) check into the loop in c_b_a_m. 
>   Would that work for you?

Yes. Thanks.

-- 
Markus