http://gcc.gnu.org/bugzilla/show_bug.cgi?id=53646
--- Comment #9 from Jonathan Wakely <redi at gcc dot gnu.org> 2012-06-12 15:57:16 UTC --- Defaulting that move-ctor fixes the issue referred to in comment 1 too. I think we need to find out if that comment is still relevant and fix it if it is, so we can default the move-ctor.