[Bug c++/86491] bogus and unsuppressible warning: 'YYY' has a base 'ZZZ' whose type uses the anonymous namespace

[jason.vas.dias at gmail dot com]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=86491

--- Comment #3 from Jason Vas Dias <jason.vas.dias at gmail dot com> ---
Of course, these lines of t2.h from Comment #1 :
<quote>
template < class _C_, _C_ *_C_OBJ_, void (_C_::*_M_)() >
  class NT
  { static constexpr _C_ *c_ = _C_OBJ_;
 public:
    NT()
    { (c_->*_M_)();
</quote>

could be replaced by:
<quote>
template < class _C_, _C_ *_C_OBJ_, void (_C_::*_M_)() >
  class NT
  { static constexpr _C_ *c_ = _C_OBJ_;
 public:
    NT()
    { (c_->*_M_)();
</quote>

and the same problem would occur (-Wsubobject-linkage warning) .

(the existence of the 'c_' static const copy of '_C_' is irrelevant.

It is simply that any occurrence of, in file A:
    namespace N {
      template <class C, C *, (retval (C::*M())()>  
        class T { ... /* something that uses C */}
    }
and in file B :
    namespace N {
    namespace X { 
      class Y  { ... };
      Y y;
    }
    class C : T< Y, &y, retval (&Y::a_Y_method) (,..) >
    {...};
    } // end namespace N

will trigger this bug.

I am trying to figure out why, and how it can be avoided.

I do not want to trigger C++'s special 'anonymous namespace object'
processing in any way here, and I do not see why it is being triggered.