On Tue, Mar 7, 2023 at 11:14 AM John Maddock via Boost < boost@lists.boost.org> wrote:

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Please see: https://en.cppreference.com/w/cpp/feature_test for language level macros -- look for _cpp_constexpr. I believe you'll discover that every combination you're looking for going back to cxx 2011 is represented -- basically making a boost config macro extraneous. The standard copied this idea from boost.config btw and it's quite powerful for portable libraries. Note that I regret using the boost.config macro for date-time constexpr stuff, because at this point I'd like to make the library available in a stand-alone fashion like boost.math. Not depending on boost.config would be helpful in that endeavor.

I think that would be fairly trivial Jeff: I see nothing in date_time that requires something beyond C++11, so you could probably just check for Boost.Config's presence with __has_include and only include it when available. Otherwise assume a conforming C++11 compiler in standalone mode.

Thanks John. date-time is currently compatible back to 1998 currently.

The constexpr macros from config allow that to happen by removing constexpr when less than c++14 (the limitations of c++11 constexpr were too much to practically support it). But yeah, I agree requiring 14 (and maybe 17 for from_chars support) or above should make standalone date-time relatively easy. I'd actually just like to remove as much of the macro hackery once and for all. Jeff