[Bug c++/56641] New: [4.7/4.8 regression] Bogus warning: 'A' has a field 'A::e' whose type uses the anonymous namespace

[Bug c++/56641] New: [4.7/4.8 regression] Bogus warning: 'A' has a field 'A::e' whose type uses the anonymous namespace

[ppluzhnikov at google dot com]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=56641

             Bug #: 56641
           Summary: [4.7/4.8 regression] Bogus warning: 'A' has a field
                    'A::e' whose type uses the anonymous namespace
    Classification: Unclassified
           Product: gcc
           Version: unknown
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: c++
        AssignedTo: unassigned@gcc.gnu.org
        ReportedBy: ppluzhnikov@google.com


This one is recent regression of gcc-4_7 branch.
Confirmed with current trunk r196749.


namespace {
#1 "foo.cc"
enum E { };
}

struct A
{
    enum E e;
};


g++ -c foo.ii
foo.cc:4:8: warning: ‘A’ has a field ‘A::e’ whose type uses the anonymous
namespace [enabled by default]

Deleting the '#1 "foo.cc"' line makes the warning go away.

[Bug c++/56641] [4.7/4.8 regression] Bogus warning: 'A' has a field 'A::e' whose type uses the anonymous namespace

[jason at gcc dot gnu.org]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=56641

Jason Merrill <jason at gcc dot gnu.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
                 CC|                            |jason at gcc dot gnu.org

--- Comment #1 from Jason Merrill <jason at gcc dot gnu.org> 2013-03-17 19:24:45 UTC ---
The compiler is working as intended; the warning is there because if E and A
are included in multiple translation units, the A type changes between
translation units, creating an ODR violation.  Without the #1 line, the
compiler doesn't warn because the types are being defined in the main input
file rather than an #included file.

[Bug c++/56641] [4.7/4.8 regression] Bogus warning: 'A' has a field 'A::e' whose type uses the anonymous namespace

[ppluzhnikov at google dot com]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=56641

Paul Pluzhnikov <ppluzhnikov at google dot com> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|UNCONFIRMED                 |RESOLVED
         Resolution|                            |INVALID

--- Comment #2 from Paul Pluzhnikov <ppluzhnikov at google dot com> 2013-03-17 19:42:28 UTC ---
Thanks for the explanation.

The actual use case looks like this:

// test-skeleton.cc
namespace { enum E { }; }
struct A { E e; };
//... other common test skeleton code ...

// foo-test.cc
#include "test-skeleton.cc"
//... specific foo tests


The workaround is to either make 'enum E' global, or name the namespace.