process.c:1274
static VALUE
p_sys_seteuid(obj, id)
    VALUE obj, id;
{
#if defined HAVE_SETEUID
    rb_secure(2);
    if (under_uid_switch) {
	rb_raise(rb_eRuntimeError, "can't handle UID during evaluating the block given to the Process::UID.switch method");
    }
    if (seteuid(NUM2INT(id)) != 0) rb_sys_fail(0);
#else
    rb_notimplement();
#endif
    return Qnil;
}
