What happens to an unnamed-namespace variable defined in a header included by three trans…

What happens to an unnamed-namespace variable defined in a header included by three translation units?

1. Each translation unit gets its own internal-linkage entity.
2. The linker automatically merges all three into one object.
3. The variable becomes a member of the global namespace with external linkage.
4. The program is ill-formed solely because the header was included more than once.