https://gcc.gnu.org/bugzilla/show_bug.cgi?id=82417
--- Comment #3 from Marc Glisse <glisse at gcc dot gnu.org> --- (In reply to Jonathan Wakely from comment #2) > Thinking about this further, I think we must not include <complex.h> at all > for strict -std=c++1* modes, Yes. Can we get a #warning in that case which explains that including <complex.h> in strict C++11+ mode makes no sense? Actually, <ccomplex> could also do with a #warning explaining that it never makes sense to include it.