https://gcc.gnu.org/bugzilla/show_bug.cgi?id=81078
--- Comment #3 from Arthur O'Dwyer <arthur.j.odwyer at gmail dot com> --- Yes, this is a libstdc++ issue. I'm not 100% sure that "the RTTI [generated by GCC] is correct," because I don't know how to use GCC with libc++; but yeah, there's definitely at least some problem with libstdc++ here. Observe that Clang-with-libstdc++ fails, Clang-with-libc++ succeeds: https://godbolt.org/z/PMq6rW9cE