#if ((!defined __STRICT_ANSI__ || (_XOPEN_SOURCE - 0) >= 500) && \
     !defined _POSIX_SOURCE && !defined _POSIX_C_SOURCE)
# define _POSIX_SOURCE	1
# if defined _XOPEN_SOURCE && (_XOPEN_SOURCE - 0) < 500
#  define _POSIX_C_SOURCE	2
# elif defined _XOPEN_SOURCE && (_XOPEN_SOURCE - 0) < 600
#  define _POSIX_C_SOURCE	199506L
# else
#  define _POSIX_C_SOURCE	200112L
# endif
#endif