[Bug c++/95677] undefined reference to `(anonymous namespace)::xx'

[nathan at gcc dot gnu.org]

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.