_Static_assert is a C11ism

git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/trunk@61555 b2dd03c8-39d4-4d8f-98ff-823fe69b080e

internal.h

@@ -79,8 +79,10 @@ extern "C" {
 # define __has_extension __has_feature
 #endif
 
-#if GCC_VERSION_SINCE(4, 6, 0) || __has_extension(c_static_assert)
+#if defined(__STDC_VERSION__) && (__STDC_VERSION__ >= 201112L)
 # define STATIC_ASSERT(name, expr) _Static_assert(expr, #name ": " #expr)
+#elif GCC_VERSION_SINCE(4, 6, 0) || __has_extension(c_static_assert)
+# define STATIC_ASSERT(name, expr) RB_GNUC_EXTENSION _Static_assert(expr, #name ": " #expr)
 #else
 # define STATIC_ASSERT(name, expr) typedef int static_assert_##name##_check[1 - 2*!(expr)]
 #endif