rb_fd_isset       233 include/ruby/intern.h #define rb_fd_isset(n, f)	rb_w32_fdisset(n, (f)->fdset)
rb_fd_isset       245 include/ruby/intern.h #define rb_fd_isset(n, f) FD_ISSET(n, f)
rb_fd_isset      2206 thread.c       rb_fd_isset(int n, const rb_fdset_t *fds)