eval.c:10029
static VALUE
thgroup_list(group)
    VALUE group;
{
    struct thgroup *data;
    rb_thread_t th;
    VALUE ary;

    Data_Get_Struct(group, struct thgroup, data);
    ary = rb_ary_new();

    FOREACH_THREAD(th) {
	if (th->thgroup == data->group) {
	    rb_ary_push(ary, th->thread);
	}
    }
    END_FOREACH(th);

    return ary;
}
