sys/_select.h

This is called from sys/select.h and sys/time.h for the common prototype of select(). Setting _DARWIN_C_SOURCE or _DARWIN_UNLIMITED_SELECT uses the version of select() that does not place a limit on the first argument (nfds). In the UNIX conformance case, values of nfds greater than FD_SETSIZE will return an error of EINVAL.

__DARWIN_EXTSN_C(select) __DARWIN_1050(select)
int select(
	int,
	fd_set * __restrict,
	fd_set * __restrict,
	fd_set * __restrict,
	struct timeval * __restrict
)