FD_ZERO          3559 thread.c       #undef FD_ZERO
FD_ZERO          3564 thread.c       #define FD_ZERO(f)	rb_fd_zero(f)
FD_ZERO          3612 thread.c       #undef FD_ZERO
FD_ZERO          3617 thread.c       #define FD_ZERO(f)	rb_fd_zero(f)