https://gcc.gnu.org/bugzilla/show_bug.cgi?id=97876
--- Comment #2 from Jonathan Wakely <redi at gcc dot gnu.org> --- Changing the _Stop_state_ref default constructor to: _Stop_state_ref() noexcept {} allows it to compile. It shouldn't be needed, but I suppose since the constructor is already non-trivial (due to the default member initializer that is the cause of the error) we could do that.