From 1c9b440bf6768c1053101c4a473f5fc9757f52a5 Mon Sep 17 00:00:00 2001
From: Jason Merrill <jason@redhat.com>
Date: Tue, 1 Oct 2024 10:58:35 -0400
Subject: [PATCH] c++: don't advertise C++20 concepts in C++14

There have been various problems with -std=c++14 -fconcepts; let's stop
defining the feature test macro in that case.

gcc/c-family/ChangeLog:

	* c-cppbuiltin.cc (c_cpp_builtins): Don't define __cpp_concepts
	before C++17.
---
 gcc/c-family/c-cppbuiltin.cc | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/gcc/c-family/c-cppbuiltin.cc b/gcc/c-family/c-cppbuiltin.cc
index 73a07055a86..b37a4c09792 100644
--- a/gcc/c-family/c-cppbuiltin.cc
+++ b/gcc/c-family/c-cppbuiltin.cc
@@ -1102,7 +1102,7 @@ c_cpp_builtins (cpp_reader *pfile)
 	  cpp_define (pfile, "__cpp_deleted_function=202403L");
 	  cpp_define (pfile, "__cpp_variadic_friend=202403L");
 	}
-      if (flag_concepts)
+      if (flag_concepts && cxx_dialect > cxx14)
 	cpp_define (pfile, "__cpp_concepts=202002L");
       if (flag_contracts)
 	{