_POSIX_C_SOURCE
#if defined(_POSIX_C_SOURCE) && (_POSIX_C_SOURCE - 0) == 1
#undef _POSIX_C_SOURCE /* Probably illegal, but beyond caring now. */
#define _POSIX_C_SOURCE 199009
#if defined(_POSIX_C_SOURCE) && (_POSIX_C_SOURCE - 0) == 2
#undef _POSIX_C_SOURCE
#define _POSIX_C_SOURCE 199209
#undef _POSIX_C_SOURCE
#define _POSIX_C_SOURCE 200809
#undef _POSIX_C_SOURCE
#define _POSIX_C_SOURCE 200112
#undef _POSIX_C_SOURCE
#define _POSIX_C_SOURCE 199506
#if defined(_POSIX_SOURCE) && !defined(_POSIX_C_SOURCE)
#define _POSIX_C_SOURCE 198808
#ifdef _POSIX_C_SOURCE
#if (_POSIX_C_SOURCE - 0) >= 200809
#elif (_POSIX_C_SOURCE - 0) >= 200112
#elif (_POSIX_C_SOURCE - 0) >= 199506
#elif (_POSIX_C_SOURCE - 0) >= 199309
#elif (_POSIX_C_SOURCE - 0) >= 199209
#elif (_POSIX_C_SOURCE - 0) >= 199009