It is recommended that Technical Specifications include the wording below. "yyyymm" indicates the year and month of the date of the TS.
1.x Feature-testing recommendations (Informative) [intro.features]
An implementation that provides support for this Technical Specification should define the feature test macro(s) in table X.
Table X -- Feature Test Macro(s)
Name Value Header __cpp_[name] yyyymm header name or predeclared