eval.c:6836
static VALUE
proc_clone(self)
    VALUE self;
{
    struct BLOCK *orig, *data;
    VALUE bind;

    Data_Get_Struct(self, struct BLOCK, orig);
    bind = Data_Make_Struct(rb_obj_class(self),struct BLOCK,blk_mark,blk_free,data);
    CLONESETUP(bind, self);
    MEMCPY(data, orig, struct BLOCK, 1);
    frame_dup(&data->frame);

    if (data->iter) {
	blk_copy_prev(data);
    }
    else {
	data->prev = 0;
    }

    return bind;
}
