https://gcc.gnu.org/bugzilla/show_bug.cgi?id=82172
--- Comment #14 from Jonathan Wakely <redi at gcc dot gnu.org> --- I have no idea what PREVAILING_DEF_IRONLY means, but a web search found https://sourceware.org/bugzilla/show_bug.cgi?id=12370 -- I can't tell if that's relevant.