* string begins with a '+'.
*/
if (posixly_correct == -1 || optreset) {
-#ifdef _WIN32
+#if (defined(__STDC_LIB_EXT1__) && defined(__STDC_WANT_LIB_EXT1__)) || (defined(__STDC_SECURE_LIB__) && defined(__STDC_WANT_SECURE_LIB__))
size_t requiredSize;
getenv_s(&requiredSize, NULL, 0, "POSIXLY_CORRECT");
posixly_correct = requiredSize != 0;