https://gcc.gnu.org/bugzilla/show_bug.cgi?id=65641
--- Comment #1 from Jonathan Wakely <redi at gcc dot gnu.org> --- An ABI change is not an option, although an alternative functor could be provided as an optional extension. There was a related thread a year ago starting at https://gcc.gnu.org/ml/libstdc++/2014-03/msg00024.html
