Re: Adding doubly linked list type which stores the number of items in the list

Hi hackers,

> I will take another look at v3 tomorrow and probably mark it RfC.

I very much like the patch. While on it:

```
+static inline bool
+dclist_is_empty(dclist_head *head)
+{
+    Assert(dlist_is_empty(&head->dlist) == (head->count == 0));
+    return (head->count == 0);
+}
```

Should we consider const'ifying the arguments of the dlist_*/dclist_*
functions that don't change the arguments?

Additionally it doesn't seem that we have any unit tests for dlist /
dclist. Should we consider adding unit tests for them to
src/test/regress?

To clarify, IMO both questions are out of scope of this specific patch
and should be submitted separately.

-- 
Best regards,
Aleksander Alekseev