[Bug c++/68300] Bogus -Wnon-virtual-dtor warning with protected base class constructor

[trippels at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=68300

--- Comment #1 from Markus Trippelsdorf <trippels at gcc dot gnu.org> ---
From class.c:

1629 /* Return true, iff class T has a non-virtual destructor that is
1630    accessible from outside the class heirarchy (i.e. is public, or
1631    there's a suitable friend.  */
1632
1633 static bool
1634 accessible_nvdtor_p (tree t)
1635 {
1636   tree dtor = CLASSTYPE_DESTRUCTORS (t);
1637
1638   /* An implicitly declared destructor is always public.  And,
1639      if it were virtual, we would have created it by now.  */
1640   if (!dtor)
1641     return true;
1642
1643   if (DECL_VINDEX (dtor))
1644     return false; /* Virtual */
1645
1646   if (!TREE_PRIVATE (dtor) && !TREE_PROTECTED (dtor))
1647     return true;  /* Public */
1648
1649   if (CLASSTYPE_FRIEND_CLASSES (t)
1650       || DECL_FRIENDLIST (TYPE_MAIN_DECL (t)))
1651     return true;   /* Has friends */
1652
1653   return false;
1654 }

Removing the friends check would fix the issue.
Thoughts?