rb_w32_fdisset    338 include/ruby/intern.h #define rb_fd_isset(n, f)	rb_w32_fdisset((n), (f)->fdset)
rb_w32_fdisset    246 include/ruby/win32.h extern int    rb_w32_fdisset(int, fd_set*);
rb_w32_fdisset    613 include/ruby/win32.h #define FD_ISSET(f, s)		rb_w32_fdisset(f, s)