https://gcc.gnu.org/bugzilla/show_bug.cgi?id=94454
--- Comment #11 from Iain Sandoe <iains at gcc dot gnu.org> --- (In reply to Nathan Sidwell from comment #10) > I cannot reproduce it, it is frustratingly difficult to do so. > but looking at the gist referenced in comment #1 I > see that the complaint is about two instances of the same instantiation of > struct std::integral_constant<bool, and_v<__is_constructible(Ts)...> > > > One of which has __attribute__ ((__abi_tag__ ("cxx11"))) attached to it. > That seems to be the error -- how did that abi_tag get there? it's not on > the original declaration. > > I can't see how those could have become attached. AFAICT we don't propagate > attributes from the arguments of an instantiation, to the instantiation > itself (and that wouldn't explain it here, as 'and_v' and __is_constructible > are unattributed. this does not seem to be reproducible, possibly a result of some other bug that's since been fixed. - I don't think it's the smoking gun (but could be that the relevant field contains something random).