gcc/testsuite/g++.dg/cpp2a/concepts-feature-macro.C - gcc - Git at Google

 // { dg-do compile { target c++2a } }

 #ifndef __cpp_concepts
 #error __cpp_concepts not defined
 #endif
	// { dg-do compile { target c++2a } }

	#ifndef __cpp_concepts
	#error __cpp_concepts not defined
	#endif