https://gcc.gnu.org/bugzilla/show_bug.cgi?id=63329
Jonathan Wakely <redi at gcc dot gnu.org> changed: What |Removed |Added ---------------------------------------------------------------------------- Status|UNCONFIRMED |RESOLVED Resolution|--- |INVALID --- Comment #2 from Jonathan Wakely <redi at gcc dot gnu.org> --- The standard does not require the typedef to be defined (libc++ apparently does it as an extension) See http://www.open-std.org/jtc1/sc22/wg21/docs/papers/2014/n4076.html for a generic replacement for std::not1 that is proposed for a future standard.