Proposed resolution:

This wording is relative to N4600.

1. Edit [numeric.ops.gcd] as indicated:

   template<class M, class N>
     constexpr common_type_t<M, N> gcd(M m, N n);
   

   -2- Requires: |m| shall be representable as a value of type M and |n| shall be representable as a value of type N|m| and |n| shall be representable as a value of common_type_t<M, N>. [Note: These requirements ensure, for example, that gcd(m, m) = |m| is representable as a value of type M. — end note]

2. Edit [numeric.ops.lcm] as indicated:

   template<class M, class N>
     constexpr common_type_t<M, N> lcm(M m, N n);
   

   -2- Requires: |m| shall be representable as a value of type M and |n| shall be representable as a value of type N|m| and |n| shall be representable as a value of common_type_t<M, N>. The least common multiple of |m| and |n| shall be representable as a value of type common_type_t<M, N>.