[ 2020-06-08 Nina Dinka Ranns comments and provides alternative wording ]

The revised wording draft also resolves LWG 2289, LWG 2829, and LWG 3215.

This wording is relative to N4861.

1. 1. Modify [constexpr.functions] as indicated:

   -1- This document explicitly requires that certain standard library functions are constexpr ([dcl.constexpr]). An implementation shall not declare any standard library function signature as constexpr except for those where it is explicitly required. Within any header that provides any non-defining declarations of constexpr functions or constructors an implementation shall provide corresponding definitions.

   -?- Let F denote a standard library function template or member function of a class template. If the specification of F declares it to be constexpr, unless otherwise specified, then F can be used in a constant expression if and only if all the expressions that are evaluated as specified in the description of F's semantics can be used in a constant expression.

2. 2. - 10. […] // Remainder of Nina's update