https://gcc.gnu.org/bugzilla/show_bug.cgi?id=95677
--- Comment #3 from Nathan Sidwell <nathan at gcc dot gnu.org> --- I think the testcase is should be formed. it was ok in C++98, but that changed when anonymous namespaces gave their contents internal linkage (rather than external but with unpronounceable symbols). [basic.link]/6 does not anticipate this issue.