Use macro to define the number of enum values

Refactoring in the interest of code consistency, a follow-up to 2e068db56e.

The argument against inserting a special enum value at the end of the enum
definition is that a switch statement might generate a compiler warning unless
it has a default clause.

Aleksander Alekseev, reviewed by Michael Paquier, Dean Rasheed, Peter Eisentraut

Discussion: https://postgr.es/m/CAJ7c6TMsiaV5urU_Pq6zJ2tXPDwk69-NKVh4AMN5XrRiM7N%2BGA%40mail.gmail.com

contrib/pg_stat_statements/pg_stat_statements.c

@@ -126,10 +126,10 @@ typedef enum pgssStoreKind
 	 */
 	PGSS_PLAN = 0,
 	PGSS_EXEC,
-
-	PGSS_NUMKIND				/* Must be last value of this enum */
 } pgssStoreKind;
 
+#define PGSS_NUMKIND (PGSS_EXEC + 1)
+
 /*
  * Hashtable key that defines the identity of a hashtable entry.  We separate
  * queries by user and by database even if they are otherwise identical.

src/backend/postmaster/autovacuum.c

@@ -247,9 +247,10 @@ typedef enum
 {
 	AutoVacForkFailed,			/* failed trying to start a worker */
 	AutoVacRebalance,			/* rebalance the cost limits */
-	AutoVacNumSignals,			/* must be last */
 }			AutoVacuumSignal;
 
+#define AutoVacNumSignals (AutoVacRebalance + 1)
+
 /*
  * Autovacuum workitem array, stored in AutoVacuumShmem->av_workItems.  This
  * list is mostly protected by AutovacuumLock, except that if an item is

src/bin/pg_dump/pg_backup.h

@@ -74,9 +74,10 @@ enum _dumpPreparedQueries
 	PREPQUERY_DUMPTABLEATTACH,
 	PREPQUERY_GETCOLUMNACLS,
 	PREPQUERY_GETDOMAINCONSTRAINTS,
-	NUM_PREP_QUERIES			/* must be last */
 };
 
+#define NUM_PREP_QUERIES (PREPQUERY_GETDOMAINCONSTRAINTS + 1)
+
 /* Parameters needed by ConnectDatabase; same for dump and restore */
 typedef struct _connParams
 {

src/include/storage/pmsignal.h

@@ -40,10 +40,10 @@ typedef enum
 	PMSIGNAL_BACKGROUND_WORKER_CHANGE,	/* background worker state change */
 	PMSIGNAL_START_WALRECEIVER, /* start a walreceiver */
 	PMSIGNAL_ADVANCE_STATE_MACHINE, /* advance postmaster's state machine */
-
-	NUM_PMSIGNALS				/* Must be last value of enum! */
 } PMSignalReason;
 
+#define NUM_PMSIGNALS (PMSIGNAL_ADVANCE_STATE_MACHINE+1)
+
 /*
  * Reasons why the postmaster would send SIGQUIT to its children.
  */

src/include/storage/procsignal.h

@@ -47,10 +47,10 @@ typedef enum
 	PROCSIG_RECOVERY_CONFLICT_BUFFERPIN,
 	PROCSIG_RECOVERY_CONFLICT_STARTUP_DEADLOCK,
 	PROCSIG_RECOVERY_CONFLICT_LAST = PROCSIG_RECOVERY_CONFLICT_STARTUP_DEADLOCK,
-
-	NUM_PROCSIGNALS				/* Must be last! */
 } ProcSignalReason;
 
+#define NUM_PROCSIGNALS (PROCSIG_RECOVERY_CONFLICT_LAST + 1)
+
 typedef enum
 {
 	PROCSIGNAL_BARRIER_SMGRRELEASE, /* ask smgr to close files */