Bug ID: 86491
           Summary: bogus and unsuppressible warning: 'YYY' has a base
                    'ZZZ' whose type uses the anonymous namespace
           Product: gcc
           Version: unknown
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: c++
          Assignee: unassigned at gcc dot
          Reporter: jason.vas.dias at gmail dot com
  Target Milestone: ---

Created attachment 44383
test code demonstrating problem as described above.

This could be a duplicate of (now closed) bug #57317 , 
or a demonstration that the fix for that bug is not complete.

It occurs with all versions of GCC on Linux x86_64 - tested:
 o RHEL7 system compiler: 4.8.5 (rpm: 4.8.5-28.el7_5.1.x86_64)
My own builds of:
 o gcc 5.4.0
 o gcc 6.4.1 (from gcc-6-branch r260630)
 o gcc 7.3.1 (r260631)
 o gcc 8.1.0 (r261026) 

The following test code triggers a -Wsubobject-linkage warning,
with all the above compilers :

./t2.H:14:9: warning: 'N::D' has a base 'N::NT<N::NA::C, (& N::NA::c_),\  
             &N::NA::C::m> whose type uses the anonymous namespace \
             [enabled by default]
  class D : public NT<NA::C,&NA::c_,&NA::C::m>

I have constructed the following test code,
which triggers the same -Wsubobject-linkage warning
I am seeing in a large more complex real-world example.

I am not intentionally using the anonymous namespace
in any of this code, and I cannot for the life of me
see how any part of it uses the anonymous namespace:

Test Code :

File t1.H:
// t1.H :
namespace N
  template < class _C_, _C_ *_C_OBJ_, void (_C_::*_M_)() >
  class NT
  { static constexpr _C_ *c_ = _C_OBJ_;
    { (c_->*_M_)();

File t2.H:
// t2.H :
#include <t1.H>
namespace N
  namespace NA
    class C
    { public:
      void m()
    static C c_;

  class D : public NT<NA::C,&NA::c_,&NA::C::m>
    typedef NT<NA::C,&NA::c_,&NA::C::m> NT_t;
    D(): NT_t()
file tM.C (main program):

#include <t2.H>

extern int main()
{ N::D d;
  return 0;


The above files are included in the attached 
'Wsubobject-linkage-anon-base-bug.tar' file, which includes a make file:

$ tar -xpf Wsubobject-linkage-anon-base-bug.tar
$ cd Wsubobject-linkage-anon-base-bug
$ make
g++ -std=gnu++14 -I. -Wall -Wextra -Werror -o tM tM.C
In file included from tM.C:1:0:
./t2.H:14:9: error: 'N::D' has a base 'N::NT<N::NA::C, (& N::NA::c_),
&N::NA::C::m>' whose type uses the anonymous namespace [-Werror]
   class D : public NT<NA::C,&NA::c_,&NA::C::m>
cc1plus: all warnings being treated as errors
make: *** [Makefile:4: tM] Error 1

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