--- Libc/Libc-320/include/iso646.h
+++ Libc/Libc-583/include/iso646.h
@@ -29,6 +29,11 @@
 #ifndef _ISO646_H_
 #define	_ISO646_H_
 
+#include <sys/cdefs.h>
+
+#if !defined(_POSIX_C_SOURCE) || defined(_DARWIN_C_SOURCE)
+
+#ifndef __cplusplus
 #define	and	&&
 #define	and_eq	&=
 #define	bitand	&
@@ -40,5 +45,8 @@
 #define	or_eq	|=
 #define	xor	^
 #define	xor_eq	^=
+#endif /* ! __cplusplus */
+
+#endif /* (!_POSIX_C_SOURCE || _DARWIN_C_SOURCE) */
 
 #endif /* !_ISO646_H_ */