constexpr all the things! Since the evaluation of a constant expression never results in an erroneous behavior (EB, C++26)! (But use constexpr since C++11)

This was mentioned by many at the conference, not to forget: @DanielaKEngert, Mikhail Svetkin, and others.

@meetingcpp #cpp #cpp26 #cpp11 #meetingcpp #dev #undefined_behavior #ub #erroneous_behavior #eb