#if defined(_STDC_C99) && (defined(__XOPEN_OR_POSIX) && !defined(_XPG6))
#error "Compiler or options invalid for pre-UNIX 03 X/Open applications \
	and pre-2001 POSIX applications"
#elif !defined(_STDC_C99) && \
	(defined(__XOPEN_OR_POSIX) && defined(_XPG6))
#error "Compiler or options invalid; UNIX 03 and POSIX.1-2001 applications \
	require the use of c99"
#endif