process.c:1586
static VALUE
p_sys_issetugid(obj)
    VALUE obj;
{
#if defined HAVE_ISSETUGID
    if (issetugid()) {
	return Qtrue;
    } else {
	return Qfalse;
    }
#else
    rb_notimplement();
    return Qnil;		/* not reached */
#endif
}
