From e4e74ba3520adeefc0a7e59b7834a23a0cf7eec1 Mon Sep 17 00:00:00 2001
From: Ed Schouten <ed@FreeBSD.org>
Date: Fri, 31 Aug 2012 22:22:14 +0000
Subject: [PATCH] Properly enable Clang-style atomics when available.

In addition to testing against cxx_atomic, we must check c_atomic. The
former is only set when building C++ code. Also use __has_extension
instead of __has_feature. This allows us to use the atomics outside of
C11.

Reported by:	Ariane van der Steldt <ariane stack nl>
PR:		threads/170073
---
 include/stdatomic.h | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/include/stdatomic.h b/include/stdatomic.h
index 35469e31456..b9f520432c1 100644
--- a/include/stdatomic.h
+++ b/include/stdatomic.h
@@ -33,7 +33,7 @@
 #include <sys/cdefs.h>
 #include <sys/_types.h>
 
-#if __has_feature(cxx_atomic)
+#if __has_extension(c_atomic) || __has_extension(cxx_atomic)
 #define	__CLANG_ATOMICS
 #elif __GNUC_PREREQ__(4, 7)
 #define	__GNUC_ATOMICS