-#if __GNUC__ || __IBMC__ || __IBMCPP__ || 0x5110 <= __SUNPRO_C
-# define _Alignas(a) __attribute__ ((__aligned__ (a)))
-#elif 1300 <= _MSC_VER
-# define _Alignas(a) __declspec (align (a))
+#if !defined __STDC_VERSION__ || __STDC_VERSION__ < 201112
+# if defined __cplusplus && 201103 <= __cplusplus
+# define _Alignas(a) alignas (a)
+# elif (__GNUC__ || __HP_cc || __HP_aCC || __IBMC__ || __IBMCPP__ \
+ || __ICC || 0x5110 <= __SUNPRO_C)
+# define _Alignas(a) __attribute__ ((__aligned__ (a)))
+# elif 1300 <= _MSC_VER
+# define _Alignas(a) __declspec (align (a))
+# endif