Remove SHM_QUEUE

Prior patches got rid of all the uses of SHM_QUEUE. ilist.h style lists are
more widely used and have an easier to use interface. As there are no users
left, remove SHM_QUEUE.

Reviewed-by: Thomas Munro <thomas.munro@gmail.com> (in an older version)
Discussion: https://postgr.es/m/20221120055930.t6kl3tyivzhlrzu2@awork3.anarazel.de
Discussion: https://postgr.es/m/20200211042229.msv23badgqljrdg2@alap3.anarazel.de

src/backend/storage/ipc/Makefile

@@ -21,7 +21,6 @@ OBJS = \
 	shm_mq.o \
 	shm_toc.o \
 	shmem.o \
-	shmqueue.o \
 	signalfuncs.o \
 	sinval.o \
 	sinvaladt.o \

src/backend/storage/ipc/meson.build

@@ -13,7 +13,6 @@ backend_sources += files(
   'shm_mq.c',
   'shm_toc.c',
   'shmem.c',
-  'shmqueue.c',
   'signalfuncs.c',
   'sinval.c',
   'sinvaladt.c',

src/backend/storage/ipc/shmqueue.c

@@ -1,190 +0,0 @@
-/*-------------------------------------------------------------------------
- *
- * shmqueue.c
- *	  shared memory linked lists
- *
- * Portions Copyright (c) 1996-2023, PostgreSQL Global Development Group
- * Portions Copyright (c) 1994, Regents of the University of California
- *
- *
- * IDENTIFICATION
- *	  src/backend/storage/ipc/shmqueue.c
- *
- * NOTES
- *
- * Package for managing doubly-linked lists in shared memory.
- * The only tricky thing is that SHM_QUEUE will usually be a field
- * in a larger record.  SHMQueueNext has to return a pointer
- * to the record itself instead of a pointer to the SHMQueue field
- * of the record.  It takes an extra parameter and does some extra
- * pointer arithmetic to do this correctly.
- *
- * NOTE: These are set up so they can be turned into macros some day.
- *
- *-------------------------------------------------------------------------
- */
-#include "postgres.h"
-
-#include "storage/shmem.h"
-
-
-/*
- * ShmemQueueInit -- make the head of a new queue point
- *		to itself
- */
-void
-SHMQueueInit(SHM_QUEUE *queue)
-{
-	Assert(ShmemAddrIsValid(queue));
-	queue->prev = queue->next = queue;
-}
-
-/*
- * SHMQueueIsDetached -- true if element is not currently
- *		in a queue.
- */
-bool
-SHMQueueIsDetached(const SHM_QUEUE *queue)
-{
-	Assert(ShmemAddrIsValid(queue));
-	return (queue->prev == NULL);
-}
-
-/*
- * SHMQueueElemInit -- clear an element's links
- */
-void
-SHMQueueElemInit(SHM_QUEUE *queue)
-{
-	Assert(ShmemAddrIsValid(queue));
-	queue->prev = queue->next = NULL;
-}
-
-/*
- * SHMQueueDelete -- remove an element from the queue and
- *		close the links
- */
-void
-SHMQueueDelete(SHM_QUEUE *queue)
-{
-	SHM_QUEUE  *nextElem = queue->next;
-	SHM_QUEUE  *prevElem = queue->prev;
-
-	Assert(ShmemAddrIsValid(queue));
-	Assert(ShmemAddrIsValid(nextElem));
-	Assert(ShmemAddrIsValid(prevElem));
-
-	prevElem->next = queue->next;
-	nextElem->prev = queue->prev;
-
-	queue->prev = queue->next = NULL;
-}
-
-/*
- * SHMQueueInsertBefore -- put elem in queue before the given queue
- *		element.  Inserting "before" the queue head puts the elem
- *		at the tail of the queue.
- */
-void
-SHMQueueInsertBefore(SHM_QUEUE *queue, SHM_QUEUE *elem)
-{
-	SHM_QUEUE  *prevPtr = queue->prev;
-
-	Assert(ShmemAddrIsValid(queue));
-	Assert(ShmemAddrIsValid(elem));
-
-	elem->next = prevPtr->next;
-	elem->prev = queue->prev;
-	queue->prev = elem;
-	prevPtr->next = elem;
-}
-
-/*
- * SHMQueueInsertAfter -- put elem in queue after the given queue
- *		element.  Inserting "after" the queue head puts the elem
- *		at the head of the queue.
- */
-void
-SHMQueueInsertAfter(SHM_QUEUE *queue, SHM_QUEUE *elem)
-{
-	SHM_QUEUE  *nextPtr = queue->next;
-
-	Assert(ShmemAddrIsValid(queue));
-	Assert(ShmemAddrIsValid(elem));
-
-	elem->prev = nextPtr->prev;
-	elem->next = queue->next;
-	queue->next = elem;
-	nextPtr->prev = elem;
-}
-
-/*--------------------
- * SHMQueueNext -- Get the next element from a queue
- *
- * To start the iteration, pass the queue head as both queue and curElem.
- * Returns NULL if no more elements.
- *
- * Next element is at curElem->next.  If SHMQueue is part of
- * a larger structure, we want to return a pointer to the
- * whole structure rather than a pointer to its SHMQueue field.
- * For example,
- * struct {
- *		int				stuff;
- *		SHMQueue		elem;
- * } ELEMType;
- * When this element is in a queue, prevElem->next points at struct.elem.
- * We subtract linkOffset to get the correct start address of the structure.
- *
- * calls to SHMQueueNext should take these parameters:
- *	 &(queueHead), &(queueHead), offsetof(ELEMType, elem)
- * or
- *	 &(queueHead), &(curElem->elem), offsetof(ELEMType, elem)
- *--------------------
- */
-Pointer
-SHMQueueNext(const SHM_QUEUE *queue, const SHM_QUEUE *curElem, Size linkOffset)
-{
-	SHM_QUEUE  *elemPtr = curElem->next;
-
-	Assert(ShmemAddrIsValid(curElem));
-
-	if (elemPtr == queue)		/* back to the queue head? */
-		return NULL;
-
-	return (Pointer) (((char *) elemPtr) - linkOffset);
-}
-
-/*--------------------
- * SHMQueuePrev -- Get the previous element from a queue
- *
- * Same as SHMQueueNext, just starting at tail and moving towards head.
- * All other comments and usage applies.
- */
-Pointer
-SHMQueuePrev(const SHM_QUEUE *queue, const SHM_QUEUE *curElem, Size linkOffset)
-{
-	SHM_QUEUE  *elemPtr = curElem->prev;
-
-	Assert(ShmemAddrIsValid(curElem));
-
-	if (elemPtr == queue)		/* back to the queue head? */
-		return NULL;
-
-	return (Pointer) (((char *) elemPtr) - linkOffset);
-}
-
-/*
- * SHMQueueEmpty -- true if queue head is only element, false otherwise
- */
-bool
-SHMQueueEmpty(const SHM_QUEUE *queue)
-{
-	Assert(ShmemAddrIsValid(queue));
-
-	if (queue->prev == queue)
-	{
-		Assert(queue->next == queue);
-		return true;
-	}
-	return false;
-}

src/include/storage/shmem.h

@@ -24,13 +24,6 @@
 #include "utils/hsearch.h"
 
 
-/* shmqueue.c */
-typedef struct SHM_QUEUE
-{
-	struct SHM_QUEUE *prev;
-	struct SHM_QUEUE *next;
-} SHM_QUEUE;
-
 /* shmem.c */
 extern void InitShmemAccess(void *seghdr);
 extern void InitShmemAllocation(void);
@@ -63,19 +56,4 @@ typedef struct
 	Size		allocated_size; /* # bytes actually allocated */
 } ShmemIndexEnt;
 
-/*
- * prototypes for functions in shmqueue.c
- */
-extern void SHMQueueInit(SHM_QUEUE *queue);
-extern void SHMQueueElemInit(SHM_QUEUE *queue);
-extern void SHMQueueDelete(SHM_QUEUE *queue);
-extern void SHMQueueInsertBefore(SHM_QUEUE *queue, SHM_QUEUE *elem);
-extern void SHMQueueInsertAfter(SHM_QUEUE *queue, SHM_QUEUE *elem);
-extern Pointer SHMQueueNext(const SHM_QUEUE *queue, const SHM_QUEUE *curElem,
-							Size linkOffset);
-extern Pointer SHMQueuePrev(const SHM_QUEUE *queue, const SHM_QUEUE *curElem,
-							Size linkOffset);
-extern bool SHMQueueEmpty(const SHM_QUEUE *queue);
-extern bool SHMQueueIsDetached(const SHM_QUEUE *queue);
-
 #endif							/* SHMEM_H */

src/tools/pgindent/typedefs.list

@@ -2377,7 +2377,6 @@ SERIALIZABLEXIDTAG
 SERVICE_STATUS
 SERVICE_STATUS_HANDLE
 SERVICE_TABLE_ENTRY
-SHM_QUEUE
 SID_AND_ATTRIBUTES
 SID_IDENTIFIER_AUTHORITY
 SID_NAME_USE