https://gcc.gnu.org/bugzilla/show_bug.cgi?id=67114
--- Comment #16 from Jonathan Wakely <redi at gcc dot gnu.org> --- (In reply to Jonathan Wakely from comment #15) > friend bool > operator<(thread::id __x, thread::id __y) noexcept > - { return __x._M_thread < __y._M_thread; } > - > + { return __less<native_handle_type>::_S_less(__x._M_thread, > __y._M_thread); } > +#endif > + > > What's this? Oh, from the earlier patch attached here, which I'd forgotten about! Sorry :)