How to correctly reference a function in an anonymous namespace

Question

Consider this fragment of C++ code:

namespace
{
    void f()
    {
    }

    class A
    {
        void f()
        {
            ::f(); // VC++: error C2039: 'f' : is not a member of '`global namespace''
        }
    };
}

GCC compiles this just fine. Visual C++ 2008 fails to compile spitting out the C2039 error. Which one of these two compilers is correct here? Is there any way to reference that "global" f properly?

Edit: Zack suggested to try and it works with both compilers. Looks a bit weird to me.

namespace
{
    void f()
    {
    }

    class A
    {
        void f();
    };
}

void A::f()
{
    ::f();
}

Answer 1

VC++ 2008 is wrong here. According to the c++03 standard 3.4.3.4:

A name prefixed by the unary scope operator :: (5.1) is looked up in global scope, in the translation unit where it is used. The name shall be declared in global namespace scope or shall be a name whose declaration is visible in global scope because of a using-directive (3.4.3.2). The use of :: allows a global name to be referred to even if its identifier has been hidden (3.3.7).

The important part here is that a using directive in the global namespace will make those symbols accessible with the scope operator.

And according to 7.3.1.1/1, an anonymous namespace is equivalent to:

namespace *unique* { /* empty body */ }
using namespace *unique*;
namespace *unique* { namespace-body }

So between these two sections, the standalone function should be accessible in global namespace.

Answer 2

As academicRobot points out, Visual C++ is wrong. As a workaround, adding an empty unnamed namespace block should resolve the issue (I don't have Visual C++ 2008 to test, but this works in Visual C++ 2010):

// empty unnamed namespace to placate compiler
namespace { }

namespace {
    void f() { }
    struct A {
        void f() { ::f(); }
    };
}

I've reported the issue to the Visual C++ team.