Fix most -Wundef warnings

In some cases #if was used instead of #ifdef in an inconsistent style.
Cleaning this up also helps when analyzing cases like
38d8dce6 where this makes a
difference.

There are no behavior changes here, but the change in pg_bswap.h would
prevent possible accidental misuse by third-party code.

Discussion: https://www.postgresql.org/message-id/flat/3b615ca5-c595-3f1d-fdf7-a429e564f614%402ndquadrant.com

contrib/hstore/hstore_compat.c

@@ -299,7 +299,7 @@ hstoreUpgrade(Datum orig)
 
 	if (valid_new)
 	{
-#if HSTORE_IS_HSTORE_NEW
+#ifdef HSTORE_IS_HSTORE_NEW
 		elog(WARNING, "ambiguous hstore value resolved as hstore-new");
 
 		/*

contrib/pg_standby/pg_standby.c

@@ -145,7 +145,7 @@ CustomizableInitialize(void)
 	switch (restoreCommandType)
 	{
 		case RESTORE_COMMAND_LINK:
-#if HAVE_WORKING_LINK
+#ifdef HAVE_WORKING_LINK
 			SET_RESTORE_COMMAND("ln -s -f", WALFilePath, xlogFilePath);
 			break;
 #endif

contrib/pgcrypto/imath.c

@@ -2361,12 +2361,12 @@ s_ucmp(mp_int a, mp_int b)
 static int
 s_vcmp(mp_int a, mp_small v)
 {
-#if _MSC_VER
+#ifdef _MSC_VER
 #pragma warning(push)
 #pragma warning(disable: 4146)
 #endif
 	mp_usmall	uv = (v < 0) ? -(mp_usmall) v : (mp_usmall) v;
-#if _MSC_VER
+#ifdef _MSC_VER
 #pragma warning(pop)
 #endif
 

src/backend/libpq/be-fsstubs.c

@@ -95,7 +95,7 @@ be_lo_open(PG_FUNCTION_ARGS)
 	LargeObjectDesc *lobjDesc;
 	int			fd;
 
-#if FSDB
+#ifdef FSDB
 	elog(DEBUG4, "lo_open(%u,%d)", lobjId, mode);
 #endif
 
@@ -118,7 +118,7 @@ be_lo_close(PG_FUNCTION_ARGS)
 				(errcode(ERRCODE_UNDEFINED_OBJECT),
 				 errmsg("invalid large-object descriptor: %d", fd)));
 
-#if FSDB
+#ifdef FSDB
 	elog(DEBUG4, "lo_close(%d)", fd);
 #endif
 

src/backend/replication/logical/reorderbuffer.c

@@ -3247,7 +3247,7 @@ typedef struct RewriteMappingFile
 	char		fname[MAXPGPATH];
 } RewriteMappingFile;
 
-#if NOT_USED
+#ifdef NOT_USED
 static void
 DisplayMapping(HTAB *tuplecid_data)
 {

src/backend/storage/file/fd.c

@@ -738,7 +738,7 @@ durable_link_or_rename(const char *oldfile, const char *newfile, int elevel)
 	if (fsync_fname_ext(oldfile, false, false, elevel) != 0)
 		return -1;
 
-#if HAVE_WORKING_LINK
+#ifdef HAVE_WORKING_LINK
 	if (link(oldfile, newfile) < 0)
 	{
 		ereport(elevel,

src/backend/utils/hash/dynahash.c

@@ -243,7 +243,7 @@ struct HTAB
  */
 #define MOD(x,y)			   ((x) & ((y)-1))
 
-#if HASH_STATISTICS
+#ifdef HASH_STATISTICS
 static long hash_accesses,
 			hash_collisions,
 			hash_expansions;
@@ -706,7 +706,7 @@ init_htab(HTAB *hashp, long nelem)
 	/* Choose number of entries to allocate at a time */
 	hctl->nelem_alloc = choose_nelem_alloc(hctl->entrysize);
 
-#if HASH_DEBUG
+#ifdef HASH_DEBUG
 	fprintf(stderr, "init_htab:\n%s%p\n%s%ld\n%s%ld\n%s%d\n%s%ld\n%s%u\n%s%x\n%s%x\n%s%ld\n",
 			"TABLE POINTER   ", hashp,
 			"DIRECTORY SIZE  ", hctl->dsize,
@@ -832,7 +832,7 @@ hash_destroy(HTAB *hashp)
 void
 hash_stats(const char *where, HTAB *hashp)
 {
-#if HASH_STATISTICS
+#ifdef HASH_STATISTICS
 	fprintf(stderr, "%s: this HTAB -- accesses %ld collisions %ld\n",
 			where, hashp->hctl->accesses, hashp->hctl->collisions);
 
@@ -933,7 +933,7 @@ hash_search_with_hash_value(HTAB *hashp,
 	HASHBUCKET *prevBucketPtr;
 	HashCompareFunc match;
 
-#if HASH_STATISTICS
+#ifdef HASH_STATISTICS
 	hash_accesses++;
 	hctl->accesses++;
 #endif
@@ -988,7 +988,7 @@ hash_search_with_hash_value(HTAB *hashp,
 			break;
 		prevBucketPtr = &(currBucket->link);
 		currBucket = *prevBucketPtr;
-#if HASH_STATISTICS
+#ifdef HASH_STATISTICS
 		hash_collisions++;
 		hctl->collisions++;
 #endif
@@ -1130,7 +1130,7 @@ hash_update_hash_key(HTAB *hashp,
 	HASHBUCKET *oldPrevPtr;
 	HashCompareFunc match;
 
-#if HASH_STATISTICS
+#ifdef HASH_STATISTICS
 	hash_accesses++;
 	hctl->accesses++;
 #endif
@@ -1204,7 +1204,7 @@ hash_update_hash_key(HTAB *hashp,
 			break;
 		prevBucketPtr = &(currBucket->link);
 		currBucket = *prevBucketPtr;
-#if HASH_STATISTICS
+#ifdef HASH_STATISTICS
 		hash_collisions++;
 		hctl->collisions++;
 #endif

src/backend/utils/mmgr/freepage.c

@@ -164,7 +164,7 @@ static void FreePagePushSpanLeader(FreePageManager *fpm, Size first_page,
 static Size FreePageManagerLargestContiguous(FreePageManager *fpm);
 static void FreePageManagerUpdateLargest(FreePageManager *fpm);
 
-#if FPM_EXTRA_ASSERTS
+#ifdef FPM_EXTRA_ASSERTS
 static Size sum_free_pages(FreePageManager *fpm);
 #endif
 

src/include/port/pg_bswap.h

@@ -139,7 +139,14 @@ pg_bswap64(uint64 x)
  * the same result as a memcmp() of the corresponding original Datums, but can
  * be much cheaper.  It's generally safe to do this on big-endian systems
  * without any special transformation occurring first.
+ *
+ * If SIZEOF_DATUM is not defined, then postgres.h wasn't included and these
+ * macros probably shouldn't be used, so we define nothing.  Note that
+ * SIZEOF_DATUM == 8 would evaluate as 0 == 8 in that case, potentially
+ * leading to the wrong implementation being selected and confusing errors, so
+ * defining nothing is safest.
  */
+#ifdef SIZEOF_DATUM
 #ifdef WORDS_BIGENDIAN
 #define		DatumBigEndianToNative(x)	(x)
 #else							/* !WORDS_BIGENDIAN */
@@ -149,5 +156,6 @@ pg_bswap64(uint64 x)
 #define		DatumBigEndianToNative(x)	pg_bswap32(x)
 #endif							/* SIZEOF_DATUM == 8 */
 #endif							/* WORDS_BIGENDIAN */
+#endif							/* SIZEOF_DATUM */
 
 #endif							/* PG_BSWAP_H */

src/port/snprintf.c

@@ -1052,7 +1052,7 @@ fmtint(long long value, char type, int forcesign, int leftjust,
 	}
 
 	/* disable MSVC warning about applying unary minus to an unsigned value */
-#if _MSC_VER
+#ifdef _MSC_VER
 #pragma warning(push)
 #pragma warning(disable: 4146)
 #endif
@@ -1061,7 +1061,7 @@ fmtint(long long value, char type, int forcesign, int leftjust,
 		uvalue = -(unsigned long long) value;
 	else
 		uvalue = (unsigned long long) value;
-#if _MSC_VER
+#ifdef _MSC_VER
 #pragma warning(pop)
 #endif
 

src/port/win32error.c

@@ -188,7 +188,7 @@ _dosmaperr(unsigned long e)
 			ereport(DEBUG5,
 					(errmsg_internal("mapped win32 error code %lu to %d",
 									 e, doserr)));
-#elif FRONTEND_DEBUG
+#elif defined(FRONTEND_DEBUG)
 			fprintf(stderr, "mapped win32 error code %lu to %d", e, doserr);
 #endif
 			errno = doserr;