_POSIX_C_SOURCE
|| (!defined(__STRICT_ANSI__) && !defined(_POSIX_C_SOURCE))
!(defined _POSIX_SOURCE || defined _POSIX_C_SOURCE || \
!defined _POSIX_SOURCE && !defined _POSIX_C_SOURCE && \
!defined _POSIX_C_SOURCE)
#if defined _POSIX_SOURCE || _POSIX_C_SOURCE >= 1 || defined _XOPEN_SOURCE
#if defined _POSIX_C_SOURCE && _POSIX_C_SOURCE >= 2 || defined _XOPEN_SOURCE
#if (_POSIX_C_SOURCE - 0) >= 199309L
#if (_POSIX_C_SOURCE - 0) >= 199506L