Re: [PATCH] Const'ify the arguments of ilist.c/ilist.h functions

Hi,

On 2022-11-07 12:03:23 +0300, Aleksander Alekseev wrote:
> During the [1] discussion it was suggested to constify the arguments
> of ilist.c/ilist.h functions. Bharath (cc'ed) pointed out that it's
> better to start a new thread in order to attract more hackers that may
> be interested in this change, so I started one.

I needed something similar in https://postgr.es/m/20221120055930.t6kl3tyivzhlrzu2%40awork3.anarazel.de

> @@ -484,7 +484,7 @@ dlist_has_prev(dlist_head *head, dlist_node *node)
> * Return the next node in the list (there must be one).
> */
> static inline dlist_node *
> -dlist_next_node(dlist_head *head, dlist_node *node)
> +dlist_next_node(const dlist_head *head, const dlist_node *node)
> {
> Assert(dlist_has_next(head, node));
> return node->next;
> @@ -494,7 +494,7 @@ dlist_next_node(dlist_head *head, dlist_node *node)
> * Return previous node in the list (there must be one).
> */
> static inline dlist_node *
> -dlist_prev_node(dlist_head *head, dlist_node *node)
> +dlist_prev_node(const dlist_head *head, const dlist_node *node)
> {
> Assert(dlist_has_prev(head, node));
> return node->prev;
> @@ -502,7 +502,7 @@ dlist_prev_node(dlist_head *head, dlist_node *node)
>
> /* internal support function to get address of head element's struct */
> static inline void *
> -dlist_head_element_off(dlist_head *head, size_t off)
> +dlist_head_element_off(const dlist_head *head, size_t off)
> {
> Assert(!dlist_is_empty(head));
> return (char *) head->head.next - off;
> @@ -512,14 +512,14 @@ dlist_head_element_off(dlist_head *head, size_t off)
> * Return the first node in the list (there must be one).
> */
> static inline dlist_node *
> -dlist_head_node(dlist_head *head)
> +dlist_head_node(const dlist_head *head)
> {
> return (dlist_node *) dlist_head_element_off(head, 0);
> }
>
> /* internal support function to get address of tail element's struct */
> static inline void *
> -dlist_tail_element_off(dlist_head *head, size_t off)
> +dlist_tail_element_off(const dlist_head *head, size_t off)
> {
> Assert(!dlist_is_empty(head));
> return (char *) head->head.prev - off;
> @@ -529,7 +529,7 @@ dlist_tail_element_off(dlist_head *head, size_t off)
> * Return the last node in the list (there must be one).
> */
> static inline dlist_node *
> -dlist_tail_node(dlist_head *head)
> +dlist_tail_node(const dlist_head *head)
> {
> return (dlist_node *) dlist_tail_element_off(head, 0);
> }

I don't think it is correct for any of these to add const. The only reason it
works is because of casting etc.

> @@ -801,7 +801,7 @@ dclist_has_prev(dclist_head *head, dlist_node *node)
> * Return the next node in the list (there must be one).
> */
> static inline dlist_node *
> -dclist_next_node(dclist_head *head, dlist_node *node)
> +dclist_next_node(const dclist_head *head, const dlist_node *node)
> {
> Assert(head->count > 0);
>
> @@ -813,7 +813,7 @@ dclist_next_node(dclist_head *head, dlist_node *node)
> * Return the prev node in the list (there must be one).
> */
> static inline dlist_node *
> -dclist_prev_node(dclist_head *head, dlist_node *node)
> +dclist_prev_node(const dclist_head *head, const dlist_node *node)
> {
> Assert(head->count > 0);
>
> @@ -822,7 +822,7 @@ dclist_prev_node(dclist_head *head, dlist_node *node)
>
> /* internal support function to get address of head element's struct */
> static inline void *
> -dclist_head_element_off(dclist_head *head, size_t off)
> +dclist_head_element_off(const dclist_head *head, size_t off)
> {
> Assert(!dclist_is_empty(head));
>
> @@ -834,7 +834,7 @@ dclist_head_element_off(dclist_head *head, size_t off)
> * Return the first node in the list (there must be one).
> */
> static inline dlist_node *
> -dclist_head_node(dclist_head *head)
> +dclist_head_node(const dclist_head *head)
> {
> Assert(head->count > 0);
>
> @@ -843,7 +843,7 @@ dclist_head_node(dclist_head *head)
>
> /* internal support function to get address of tail element's struct */
> static inline void *
> -dclist_tail_element_off(dclist_head *head, size_t off)
> +dclist_tail_element_off(const dclist_head *head, size_t off)
> {
> Assert(!dclist_is_empty(head));
>
> @@ -854,7 +854,7 @@ dclist_tail_element_off(dclist_head *head, size_t off)
> * Return the last node in the list (there must be one).
> */
> static inline dlist_node *
> -dclist_tail_node(dclist_head *head)
> +dclist_tail_node(const dclist_head *head)
> {
> Assert(head->count > 0);
>

Dito.

> @@ -988,7 +988,7 @@ slist_has_next(slist_head *head, slist_node *node)
> * Return the next node in the list (there must be one).
> */
> static inline slist_node *
> -slist_next_node(slist_head *head, slist_node *node)
> +slist_next_node(const slist_head *head, const slist_node *node)
> {
> Assert(slist_has_next(head, node));
> return node->next;
> @@ -996,7 +996,7 @@ slist_next_node(slist_head *head, slist_node *node)
>
> /* internal support function to get address of head element's struct */
> static inline void *
> -slist_head_element_off(slist_head *head, size_t off)
> +slist_head_element_off(const slist_head *head, size_t off)
> {
> Assert(!slist_is_empty(head));
> return (char *) head->head.next - off;
> @@ -1006,7 +1006,7 @@ slist_head_element_off(slist_head *head, size_t off)
> * Return the first node in the list (there must be one).
> */
> static inline slist_node *
> -slist_head_node(slist_head *head)
> +slist_head_node(const slist_head *head)
> {
> return (slist_node *) slist_head_element_off(head, 0);
> }

Dito.

Greetings,

Andres Freund