On 15/06/18 16:46 +0100, Jonathan Wakely wrote:
This macro should not be defined unconditionally.The macro isn't official (it was proposed in P0426R1 but doesn't appear in SD-6 or the drafts, or the C++2a working paper) so I haven't added any tests. Ideally we would have negative tests for each feature test macro, to make sure they aren't defined when the feature isn't available. I've done a review and this seems to be the only problem. * include/bits/char_traits.h (__cpp_lib_constexpr_char_traits): Only define for C++17 and above.
I'm going to backport this to gcc-7-branch and gcc-8-branch too, because a feature test macro that lies is worse than no feature test macro at all.
