Use FLEXIBLE_ARRAY_MEMBER in a bunch more places.

Replace some bogus "x[1]" declarations with "x[FLEXIBLE_ARRAY_MEMBER]".
Aside from being more self-documenting, this should help prevent bogus
warnings from static code analyzers and perhaps compiler misoptimizations.

This patch is just a down payment on eliminating the whole problem, but
it gets rid of a lot of easy-to-fix cases.

Note that the main problem with doing this is that one must no longer rely
on computing sizeof(the containing struct), since the result would be
compiler-dependent.  Instead use offsetof(struct, lastfield).  Autoconf
also warns against spelling that offsetof(struct, lastfield[0]).

Michael Paquier, review and additional fixes by me.

contrib/cube/cubedata.h

@@ -23,11 +23,10 @@ typedef struct NDBOX
 	unsigned int header;
 
 	/*
-	 * Variable length array. The lower left coordinates for each dimension
-	 * come first, followed by upper right coordinates unless the point flag
-	 * is set.
+	 * The lower left coordinates for each dimension come first, followed by
+	 * upper right coordinates unless the point flag is set.
 	 */
-	double		x[1];
+	double		x[FLEXIBLE_ARRAY_MEMBER];
 } NDBOX;
 
 #define POINT_BIT			0x80000000
@@ -41,9 +40,9 @@ typedef struct NDBOX
 #define LL_COORD(cube, i) ( (cube)->x[i] )
 #define UR_COORD(cube, i) ( IS_POINT(cube) ? (cube)->x[i] : (cube)->x[(i) + DIM(cube)] )
 
-#define POINT_SIZE(_dim) (offsetof(NDBOX, x[0]) + sizeof(double)*(_dim))
-#define CUBE_SIZE(_dim) (offsetof(NDBOX, x[0]) + sizeof(double)*(_dim)*2)
+#define POINT_SIZE(_dim)	(offsetof(NDBOX, x) + sizeof(double)*(_dim))
+#define CUBE_SIZE(_dim)		(offsetof(NDBOX, x) + sizeof(double)*(_dim)*2)
 
-#define DatumGetNDBOX(x)	((NDBOX*)DatumGetPointer(x))
-#define PG_GETARG_NDBOX(x)	DatumGetNDBOX( PG_DETOAST_DATUM(PG_GETARG_DATUM(x)) )
+#define DatumGetNDBOX(x)	((NDBOX *) PG_DETOAST_DATUM(x))
+#define PG_GETARG_NDBOX(x)	DatumGetNDBOX(PG_GETARG_DATUM(x))
 #define PG_RETURN_NDBOX(x)	PG_RETURN_POINTER(x)

contrib/intarray/_int.h

@@ -73,7 +73,7 @@ typedef struct
 {
 	int32		vl_len_;		/* varlena header (do not touch directly!) */
 	int32		flag;
-	char		data[1];
+	char		data[FLEXIBLE_ARRAY_MEMBER];
 } GISTTYPE;
 
 #define ALLISTRUE		0x04
@@ -133,7 +133,7 @@ typedef struct QUERYTYPE
 {
 	int32		vl_len_;		/* varlena header (do not touch directly!) */
 	int32		size;			/* number of ITEMs */
-	ITEM		items[1];		/* variable length array */
+	ITEM		items[FLEXIBLE_ARRAY_MEMBER];
 } QUERYTYPE;
 
 #define HDRSIZEQT	offsetof(QUERYTYPE, items)

contrib/ltree/ltree.h

@@ -10,7 +10,7 @@
 typedef struct
 {
 	uint16		len;
-	char		name[1];
+	char		name[FLEXIBLE_ARRAY_MEMBER];
 } ltree_level;
 
 #define LEVEL_HDRSIZE	(offsetof(ltree_level,name))
@@ -20,7 +20,7 @@ typedef struct
 {
 	int32		vl_len_;		/* varlena header (do not touch directly!) */
 	uint16		numlevel;
-	char		data[1];
+	char		data[FLEXIBLE_ARRAY_MEMBER];
 } ltree;
 
 #define LTREE_HDRSIZE	MAXALIGN( offsetof(ltree, data) )
@@ -34,7 +34,7 @@ typedef struct
 	int32		val;
 	uint16		len;
 	uint8		flag;
-	char		name[1];
+	char		name[FLEXIBLE_ARRAY_MEMBER];
 } lquery_variant;
 
 #define LVAR_HDRSIZE   MAXALIGN(offsetof(lquery_variant, name))
@@ -51,7 +51,7 @@ typedef struct
 	uint16		numvar;
 	uint16		low;
 	uint16		high;
-	char		variants[1];
+	char		variants[FLEXIBLE_ARRAY_MEMBER];
 } lquery_level;
 
 #define LQL_HDRSIZE MAXALIGN( offsetof(lquery_level,variants) )
@@ -72,7 +72,7 @@ typedef struct
 	uint16		numlevel;
 	uint16		firstgood;
 	uint16		flag;
-	char		data[1];
+	char		data[FLEXIBLE_ARRAY_MEMBER];
 } lquery;
 
 #define LQUERY_HDRSIZE	 MAXALIGN( offsetof(lquery, data) )
@@ -107,7 +107,7 @@ typedef struct
 {
 	int32		vl_len_;		/* varlena header (do not touch directly!) */
 	int32		size;
-	char		data[1];
+	char		data[FLEXIBLE_ARRAY_MEMBER];
 } ltxtquery;
 
 #define HDRSIZEQT		MAXALIGN(VARHDRSZ + sizeof(int32))
@@ -208,7 +208,7 @@ typedef struct
 {
 	int32		vl_len_;		/* varlena header (do not touch directly!) */
 	uint32		flag;
-	char		data[1];
+	char		data[FLEXIBLE_ARRAY_MEMBER];
 } ltree_gist;
 
 #define LTG_ONENODE 0x01

contrib/pageinspect/rawpage.c

@@ -192,7 +192,7 @@ page_header(PG_FUNCTION_ARGS)
 	 * Check that enough data was supplied, so that we don't try to access
 	 * fields outside the supplied buffer.
 	 */
-	if (raw_page_size < sizeof(PageHeaderData))
+	if (raw_page_size < SizeOfPageHeaderData)
 		ereport(ERROR,
 				(errcode(ERRCODE_INVALID_PARAMETER_VALUE),
 				 errmsg("input page too small (%d bytes)", raw_page_size)));

contrib/pg_trgm/trgm.h

@@ -63,7 +63,7 @@ typedef struct
 {
 	int32		vl_len_;		/* varlena header (do not touch directly!) */
 	uint8		flag;
-	char		data[1];
+	char		data[FLEXIBLE_ARRAY_MEMBER];
 } TRGM;
 
 #define TRGMHDRSIZE		  (VARHDRSZ + sizeof(uint8))

src/backend/catalog/namespace.c

@@ -261,9 +261,9 @@ RangeVarGetRelidExtended(const RangeVar *relation, LOCKMODE lockmode,
 	 * with the answer changing under them, or that they already hold some
 	 * appropriate lock, and therefore return the first answer we get without
 	 * checking for invalidation messages.  Also, if the requested lock is
-	 * already held, LockRelationOid will not AcceptInvalidationMessages,
-	 * so we may fail to notice a change.  We could protect against that case
-	 * by calling AcceptInvalidationMessages() before beginning this loop, but
+	 * already held, LockRelationOid will not AcceptInvalidationMessages, so
+	 * we may fail to notice a change.  We could protect against that case by
+	 * calling AcceptInvalidationMessages() before beginning this loop, but
 	 * that would add a significant amount overhead, so for now we don't.
 	 */
 	for (;;)
@@ -1075,8 +1075,8 @@ FuncnameGetCandidates(List *names, int nargs, List *argnames,
 		 */
 		effective_nargs = Max(pronargs, nargs);
 		newResult = (FuncCandidateList)
-			palloc(sizeof(struct _FuncCandidateList) - sizeof(Oid)
-				   + effective_nargs * sizeof(Oid));
+			palloc(offsetof(struct _FuncCandidateList, args) +
+				   effective_nargs * sizeof(Oid));
 		newResult->pathpos = pathpos;
 		newResult->oid = HeapTupleGetOid(proctup);
 		newResult->nargs = effective_nargs;
@@ -1597,7 +1597,8 @@ OpernameGetCandidates(List *names, char oprkind, bool missing_schema_ok)
 	 * separate palloc for each operator, but profiling revealed that the
 	 * pallocs used an unreasonably large fraction of parsing time.
 	 */
-#define SPACE_PER_OP MAXALIGN(sizeof(struct _FuncCandidateList) + sizeof(Oid))
+#define SPACE_PER_OP MAXALIGN(offsetof(struct _FuncCandidateList, args) + \
+							  2 * sizeof(Oid))
 
 	if (catlist->n_members > 0)
 		resultSpace = palloc(catlist->n_members * SPACE_PER_OP);

src/backend/commands/prepare.c

@@ -383,10 +383,9 @@ EvaluateParams(PreparedStatement *pstmt, List *params,
 	/* Prepare the expressions for execution */
 	exprstates = (List *) ExecPrepareExpr((Expr *) params, estate);
 
-	/* sizeof(ParamListInfoData) includes the first array element */
 	paramLI = (ParamListInfo)
-		palloc(sizeof(ParamListInfoData) +
-			   (num_params - 1) * sizeof(ParamExternData));
+		palloc(offsetof(ParamListInfoData, params) +
+			   num_params * sizeof(ParamExternData));
 	/* we have static list of params, so no hooks needed */
 	paramLI->paramFetch = NULL;
 	paramLI->paramFetchArg = NULL;

src/backend/executor/functions.c

@@ -896,9 +896,9 @@ postquel_sub_params(SQLFunctionCachePtr fcache,
 
 		if (fcache->paramLI == NULL)
 		{
-			/* sizeof(ParamListInfoData) includes the first array element */
-			paramLI = (ParamListInfo) palloc(sizeof(ParamListInfoData) +
-									  (nargs - 1) * sizeof(ParamExternData));
+			paramLI = (ParamListInfo)
+				palloc(offsetof(ParamListInfoData, params) +
+					   nargs * sizeof(ParamExternData));
 			/* we have static list of params, so no hooks needed */
 			paramLI->paramFetch = NULL;
 			paramLI->paramFetchArg = NULL;

src/backend/executor/spi.c

@@ -2290,9 +2290,8 @@ _SPI_convert_params(int nargs, Oid *argtypes,
 	{
 		int			i;
 
-		/* sizeof(ParamListInfoData) includes the first array element */
-		paramLI = (ParamListInfo) palloc(sizeof(ParamListInfoData) +
-									  (nargs - 1) * sizeof(ParamExternData));
+		paramLI = (ParamListInfo) palloc(offsetof(ParamListInfoData, params) +
+										 nargs * sizeof(ParamExternData));
 		/* we have static list of params, so no hooks needed */
 		paramLI->paramFetch = NULL;
 		paramLI->paramFetchArg = NULL;

src/backend/nodes/params.c

@@ -40,9 +40,8 @@ copyParamList(ParamListInfo from)
 	if (from == NULL || from->numParams <= 0)
 		return NULL;
 
-	/* sizeof(ParamListInfoData) includes the first array element */
-	size = sizeof(ParamListInfoData) +
-		(from->numParams - 1) * sizeof(ParamExternData);
+	size = offsetof(ParamListInfoData, params) +
+		from->numParams * sizeof(ParamExternData);
 
 	retval = (ParamListInfo) palloc(size);
 	retval->paramFetch = NULL;

src/backend/postmaster/syslogger.c

@@ -785,13 +785,13 @@ process_pipe_input(char *logbuffer, int *bytes_in_logbuffer)
 	int			dest = LOG_DESTINATION_STDERR;
 
 	/* While we have enough for a header, process data... */
-	while (count >= (int) sizeof(PipeProtoHeader))
+	while (count >= (int) (offsetof(PipeProtoHeader, data) +1))
 	{
 		PipeProtoHeader p;
 		int			chunklen;
 
 		/* Do we have a valid header? */
-		memcpy(&p, cursor, sizeof(PipeProtoHeader));
+		memcpy(&p, cursor, offsetof(PipeProtoHeader, data));
 		if (p.nuls[0] == '\0' && p.nuls[1] == '\0' &&
 			p.len > 0 && p.len <= PIPE_MAX_PAYLOAD &&
 			p.pid != 0 &&

src/backend/tcop/postgres.c

@@ -1619,9 +1619,8 @@ exec_bind_message(StringInfo input_message)
 	{
 		int			paramno;
 
-		/* sizeof(ParamListInfoData) includes the first array element */
-		params = (ParamListInfo) palloc(sizeof(ParamListInfoData) +
-								  (numParams - 1) * sizeof(ParamExternData));
+		params = (ParamListInfo) palloc(offsetof(ParamListInfoData, params) +
+										numParams * sizeof(ParamExternData));
 		/* we have static list of params, so no hooks needed */
 		params->paramFetch = NULL;
 		params->paramFetchArg = NULL;

src/backend/utils/adt/geo_ops.c

@@ -1390,7 +1390,7 @@ path_in(PG_FUNCTION_ARGS)
 	}
 
 	base_size = sizeof(path->p[0]) * npts;
-	size = offsetof(PATH, p[0]) +base_size;
+	size = offsetof(PATH, p) +base_size;
 
 	/* Check for integer overflow */
 	if (base_size / npts != sizeof(path->p[0]) || size <= base_size)
@@ -1443,12 +1443,12 @@ path_recv(PG_FUNCTION_ARGS)
 
 	closed = pq_getmsgbyte(buf);
 	npts = pq_getmsgint(buf, sizeof(int32));
-	if (npts <= 0 || npts >= (int32) ((INT_MAX - offsetof(PATH, p[0])) / sizeof(Point)))
+	if (npts <= 0 || npts >= (int32) ((INT_MAX - offsetof(PATH, p)) / sizeof(Point)))
 		ereport(ERROR,
 				(errcode(ERRCODE_INVALID_BINARY_REPRESENTATION),
 			 errmsg("invalid number of points in external \"path\" value")));
 
-	size = offsetof(PATH, p[0]) +sizeof(path->p[0]) * npts;
+	size = offsetof(PATH, p) +sizeof(path->p[0]) * npts;
 	path = (PATH *) palloc(size);
 
 	SET_VARSIZE(path, size);
@@ -3476,7 +3476,7 @@ poly_in(PG_FUNCTION_ARGS)
 			  errmsg("invalid input syntax for type polygon: \"%s\"", str)));
 
 	base_size = sizeof(poly->p[0]) * npts;
-	size = offsetof(POLYGON, p[0]) +base_size;
+	size = offsetof(POLYGON, p) +base_size;
 
 	/* Check for integer overflow */
 	if (base_size / npts != sizeof(poly->p[0]) || size <= base_size)
@@ -3530,12 +3530,12 @@ poly_recv(PG_FUNCTION_ARGS)
 	int			size;
 
 	npts = pq_getmsgint(buf, sizeof(int32));
-	if (npts <= 0 || npts >= (int32) ((INT_MAX - offsetof(POLYGON, p[0])) / sizeof(Point)))
+	if (npts <= 0 || npts >= (int32) ((INT_MAX - offsetof(POLYGON, p)) / sizeof(Point)))
 		ereport(ERROR,
 				(errcode(ERRCODE_INVALID_BINARY_REPRESENTATION),
 		  errmsg("invalid number of points in external \"polygon\" value")));
 
-	size = offsetof(POLYGON, p[0]) +sizeof(poly->p[0]) * npts;
+	size = offsetof(POLYGON, p) +sizeof(poly->p[0]) * npts;
 	poly = (POLYGON *) palloc0(size);	/* zero any holes */
 
 	SET_VARSIZE(poly, size);
@@ -4251,7 +4251,7 @@ path_add(PG_FUNCTION_ARGS)
 		PG_RETURN_NULL();
 
 	base_size = sizeof(p1->p[0]) * (p1->npts + p2->npts);
-	size = offsetof(PATH, p[0]) +base_size;
+	size = offsetof(PATH, p) +base_size;
 
 	/* Check for integer overflow */
 	if (base_size / sizeof(p1->p[0]) != (p1->npts + p2->npts) ||
@@ -4393,7 +4393,7 @@ path_poly(PG_FUNCTION_ARGS)
 	 * Never overflows: the old size fit in MaxAllocSize, and the new size is
 	 * just a small constant larger.
 	 */
-	size = offsetof(POLYGON, p[0]) +sizeof(poly->p[0]) * path->npts;
+	size = offsetof(POLYGON, p) +sizeof(poly->p[0]) * path->npts;
 	poly = (POLYGON *) palloc(size);
 
 	SET_VARSIZE(poly, size);
@@ -4468,7 +4468,7 @@ box_poly(PG_FUNCTION_ARGS)
 	int			size;
 
 	/* map four corners of the box to a polygon */
-	size = offsetof(POLYGON, p[0]) +sizeof(poly->p[0]) * 4;
+	size = offsetof(POLYGON, p) +sizeof(poly->p[0]) * 4;
 	poly = (POLYGON *) palloc(size);
 
 	SET_VARSIZE(poly, size);
@@ -4502,7 +4502,7 @@ poly_path(PG_FUNCTION_ARGS)
 	 * Never overflows: the old size fit in MaxAllocSize, and the new size is
 	 * smaller by a small constant.
 	 */
-	size = offsetof(PATH, p[0]) +sizeof(path->p[0]) * poly->npts;
+	size = offsetof(PATH, p) +sizeof(path->p[0]) * poly->npts;
 	path = (PATH *) palloc(size);
 
 	SET_VARSIZE(path, size);
@@ -5181,7 +5181,7 @@ circle_poly(PG_FUNCTION_ARGS)
 				 errmsg("must request at least 2 points")));
 
 	base_size = sizeof(poly->p[0]) * npts;
-	size = offsetof(POLYGON, p[0]) +base_size;
+	size = offsetof(POLYGON, p) +base_size;
 
 	/* Check for integer overflow */
 	if (base_size / npts != sizeof(poly->p[0]) || size <= base_size)

src/backend/utils/cache/catcache.c

@@ -1590,7 +1590,7 @@ SearchCatCacheList(CatCache *cache,
 		oldcxt = MemoryContextSwitchTo(CacheMemoryContext);
 		nmembers = list_length(ctlist);
 		cl = (CatCList *)
-			palloc(sizeof(CatCList) + nmembers * sizeof(CatCTup *));
+			palloc(offsetof(CatCList, members) +nmembers * sizeof(CatCTup *));
 		heap_copytuple_with_tuple(ntp, &cl->tuple);
 		MemoryContextSwitchTo(oldcxt);
 		heap_freetuple(ntp);

src/bin/pg_dump/dumputils.c

@@ -1216,9 +1216,8 @@ simple_string_list_append(SimpleStringList *list, const char *val)
 {
 	SimpleStringListCell *cell;
 
-	/* this calculation correctly accounts for the null trailing byte */
 	cell = (SimpleStringListCell *)
-		pg_malloc(sizeof(SimpleStringListCell) + strlen(val));
+		pg_malloc(offsetof(SimpleStringListCell, val) +strlen(val) + 1);
 
 	cell->next = NULL;
 	strcpy(cell->val, val);

src/bin/pg_dump/dumputils.h

@@ -38,7 +38,7 @@ typedef struct SimpleOidList
 typedef struct SimpleStringListCell
 {
 	struct SimpleStringListCell *next;
-	char		val[1];			/* VARIABLE LENGTH FIELD */
+	char		val[FLEXIBLE_ARRAY_MEMBER];		/* null-terminated string here */
 } SimpleStringListCell;
 
 typedef struct SimpleStringList

src/include/access/gin_private.h

@@ -389,7 +389,7 @@ typedef struct
 {
 	ItemPointerData first;		/* first item in this posting list (unpacked) */
 	uint16		nbytes;			/* number of bytes that follow */
-	unsigned char bytes[1];		/* varbyte encoded items (variable length) */
+	unsigned char bytes[FLEXIBLE_ARRAY_MEMBER]; /* varbyte encoded items */
 } GinPostingList;
 
 #define SizeOfGinPostingList(plist) (offsetof(GinPostingList, bytes) + SHORTALIGN((plist)->nbytes) )

src/include/access/gist_private.h

@@ -47,7 +47,7 @@ typedef struct
 {
 	BlockNumber prev;
 	uint32		freespace;
-	char		tupledata[1];
+	char		tupledata[FLEXIBLE_ARRAY_MEMBER];
 } GISTNodeBufferPage;
 
 #define BUFFER_PAGE_DATA_OFFSET MAXALIGN(offsetof(GISTNodeBufferPage, tupledata))
@@ -131,7 +131,8 @@ typedef struct GISTSearchItem
 		/* we must store parentlsn to detect whether a split occurred */
 		GISTSearchHeapItem heap;	/* heap info, if heap tuple */
 	}			data;
-	double		distances[1];	/* array with numberOfOrderBys entries */
+	double		distances[FLEXIBLE_ARRAY_MEMBER];		/* numberOfOrderBys
+														 * entries */
 } GISTSearchItem;
 
 #define GISTSearchItemIsHeap(item)	((item).blkno == InvalidBlockNumber)

src/include/access/heapam_xlog.h

@@ -132,7 +132,7 @@ typedef struct xl_heap_multi_insert
 {
 	uint8		flags;
 	uint16		ntuples;
-	OffsetNumber offsets[1];
+	OffsetNumber offsets[FLEXIBLE_ARRAY_MEMBER];
 } xl_heap_multi_insert;
 
 #define SizeOfHeapMultiInsert	offsetof(xl_heap_multi_insert, offsets)

src/include/access/spgist_private.h

@@ -426,7 +426,7 @@ typedef struct spgxlogMoveLeafs
 	 * the dead tuple from the source
 	 *----------
 	 */
-	OffsetNumber offsets[1];
+	OffsetNumber offsets[FLEXIBLE_ARRAY_MEMBER];
 } spgxlogMoveLeafs;
 
 #define SizeOfSpgxlogMoveLeafs	offsetof(spgxlogMoveLeafs, offsets)
@@ -534,7 +534,7 @@ typedef struct spgxlogPickSplit
 	 *		list of leaf tuples, length nInsert (unaligned!)
 	 *----------
 	 */
-	OffsetNumber offsets[1];
+	OffsetNumber offsets[FLEXIBLE_ARRAY_MEMBER];
 } spgxlogPickSplit;
 
 #define SizeOfSpgxlogPickSplit offsetof(spgxlogPickSplit, offsets)
@@ -558,7 +558,7 @@ typedef struct spgxlogVacuumLeaf
 	 *		tuple numbers to insert in nextOffset links
 	 *----------
 	 */
-	OffsetNumber offsets[1];
+	OffsetNumber offsets[FLEXIBLE_ARRAY_MEMBER];
 } spgxlogVacuumLeaf;
 
 #define SizeOfSpgxlogVacuumLeaf offsetof(spgxlogVacuumLeaf, offsets)
@@ -571,7 +571,7 @@ typedef struct spgxlogVacuumRoot
 	spgxlogState stateSrc;
 
 	/* offsets of tuples to delete follow */
-	OffsetNumber offsets[1];
+	OffsetNumber offsets[FLEXIBLE_ARRAY_MEMBER];
 } spgxlogVacuumRoot;
 
 #define SizeOfSpgxlogVacuumRoot offsetof(spgxlogVacuumRoot, offsets)
@@ -583,7 +583,7 @@ typedef struct spgxlogVacuumRedirect
 	TransactionId newestRedirectXid;	/* newest XID of removed redirects */
 
 	/* offsets of redirect tuples to make placeholders follow */
-	OffsetNumber offsets[1];
+	OffsetNumber offsets[FLEXIBLE_ARRAY_MEMBER];
 } spgxlogVacuumRedirect;
 
 #define SizeOfSpgxlogVacuumRedirect offsetof(spgxlogVacuumRedirect, offsets)

src/include/access/xact.h

@@ -118,7 +118,7 @@ typedef struct xl_xact_assignment
 {
 	TransactionId xtop;			/* assigned XID's top-level XID */
 	int			nsubxacts;		/* number of subtransaction XIDs */
-	TransactionId xsub[1];		/* assigned subxids */
+	TransactionId xsub[FLEXIBLE_ARRAY_MEMBER];	/* assigned subxids */
 } xl_xact_assignment;
 
 #define MinSizeOfXactAssignment offsetof(xl_xact_assignment, xsub)
@@ -128,7 +128,7 @@ typedef struct xl_xact_commit_compact
 	TimestampTz xact_time;		/* time of commit */
 	int			nsubxacts;		/* number of subtransaction XIDs */
 	/* ARRAY OF COMMITTED SUBTRANSACTION XIDs FOLLOWS */
-	TransactionId subxacts[1];	/* VARIABLE LENGTH ARRAY */
+	TransactionId subxacts[FLEXIBLE_ARRAY_MEMBER];
 } xl_xact_commit_compact;
 
 #define MinSizeOfXactCommitCompact offsetof(xl_xact_commit_compact, subxacts)
@@ -143,7 +143,7 @@ typedef struct xl_xact_commit
 	Oid			dbId;			/* MyDatabaseId */
 	Oid			tsId;			/* MyDatabaseTableSpace */
 	/* Array of RelFileNode(s) to drop at commit */
-	RelFileNode xnodes[1];		/* VARIABLE LENGTH ARRAY */
+	RelFileNode xnodes[FLEXIBLE_ARRAY_MEMBER];
 	/* ARRAY OF COMMITTED SUBTRANSACTION XIDs FOLLOWS */
 	/* ARRAY OF SHARED INVALIDATION MESSAGES FOLLOWS */
 } xl_xact_commit;
@@ -171,7 +171,7 @@ typedef struct xl_xact_abort
 	int			nrels;			/* number of RelFileNodes */
 	int			nsubxacts;		/* number of subtransaction XIDs */
 	/* Array of RelFileNode(s) to drop at abort */
-	RelFileNode xnodes[1];		/* VARIABLE LENGTH ARRAY */
+	RelFileNode xnodes[FLEXIBLE_ARRAY_MEMBER];
 	/* ARRAY OF ABORTED SUBTRANSACTION XIDs FOLLOWS */
 } xl_xact_abort;
 

src/include/c.h

@@ -424,8 +424,8 @@ typedef struct
 	Oid			elemtype;
 	int			dim1;
 	int			lbound1;
-	int16		values[1];		/* VARIABLE LENGTH ARRAY */
-} int2vector;					/* VARIABLE LENGTH STRUCT */
+	int16		values[FLEXIBLE_ARRAY_MEMBER];
+} int2vector;
 
 typedef struct
 {
@@ -435,8 +435,8 @@ typedef struct
 	Oid			elemtype;
 	int			dim1;
 	int			lbound1;
-	Oid			values[1];		/* VARIABLE LENGTH ARRAY */
-} oidvector;					/* VARIABLE LENGTH STRUCT */
+	Oid			values[FLEXIBLE_ARRAY_MEMBER];
+} oidvector;
 
 /*
  * Representation of a Name: effectively just a C string, but null-padded to

src/include/catalog/namespace.h

@@ -34,8 +34,8 @@ typedef struct _FuncCandidateList
 	int			nvargs;			/* number of args to become variadic array */
 	int			ndargs;			/* number of defaulted args */
 	int		   *argnumbers;		/* args' positional indexes, if named call */
-	Oid			args[1];		/* arg types --- VARIABLE LENGTH ARRAY */
-}	*FuncCandidateList;	/* VARIABLE LENGTH STRUCT */
+	Oid			args[FLEXIBLE_ARRAY_MEMBER];	/* arg types */
+}	*FuncCandidateList;
 
 /*
  *	Structure for xxxOverrideSearchPath functions

src/include/commands/dbcommands.h

@@ -22,21 +22,6 @@
 #define XLOG_DBASE_CREATE		0x00
 #define XLOG_DBASE_DROP			0x10
 
-typedef struct xl_dbase_create_rec_old
-{
-	/* Records copying of a single subdirectory incl. contents */
-	Oid			db_id;
-	char		src_path[1];	/* VARIABLE LENGTH STRING */
-	/* dst_path follows src_path */
-}	xl_dbase_create_rec_old;
-
-typedef struct xl_dbase_drop_rec_old
-{
-	/* Records dropping of a single subdirectory incl. contents */
-	Oid			db_id;
-	char		dir_path[1];	/* VARIABLE LENGTH STRING */
-}	xl_dbase_drop_rec_old;
-
 typedef struct xl_dbase_create_rec
 {
 	/* Records copying of a single subdirectory incl. contents */

src/include/commands/tablespace.h

@@ -25,7 +25,7 @@
 typedef struct xl_tblspc_create_rec
 {
 	Oid			ts_id;
-	char		ts_path[1];		/* VARIABLE LENGTH STRING */
+	char		ts_path[FLEXIBLE_ARRAY_MEMBER]; /* null-terminated string */
 } xl_tblspc_create_rec;
 
 typedef struct xl_tblspc_drop_rec

src/include/executor/hashjoin.h

@@ -114,7 +114,7 @@ typedef struct HashMemoryChunkData
 
 	struct HashMemoryChunkData *next; /* pointer to the next chunk (linked list) */
 
-	char		data[1];	/* buffer allocated at the end */
+	char		data[FLEXIBLE_ARRAY_MEMBER];	/* buffer allocated at the end */
 } HashMemoryChunkData;
 
 typedef struct HashMemoryChunkData *HashMemoryChunk;

src/include/nodes/bitmapset.h

@@ -32,8 +32,8 @@ typedef int32 signedbitmapword; /* must be the matching signed type */
 typedef struct Bitmapset
 {
 	int			nwords;			/* number of words in array */
-	bitmapword	words[1];		/* really [nwords] */
-} Bitmapset;					/* VARIABLE LENGTH STRUCT */
+	bitmapword	words[FLEXIBLE_ARRAY_MEMBER];	/* really [nwords] */
+} Bitmapset;
 
 
 /* result of bms_subset_compare */

src/include/nodes/params.h

@@ -71,7 +71,7 @@ typedef struct ParamListInfoData
 	ParserSetupHook parserSetup;	/* parser setup hook */
 	void	   *parserSetupArg;
 	int			numParams;		/* number of ParamExternDatas following */
-	ParamExternData params[1];	/* VARIABLE LENGTH ARRAY */
+	ParamExternData params[FLEXIBLE_ARRAY_MEMBER];
 }	ParamListInfoData;
 
 

src/include/nodes/tidbitmap.h

@@ -41,8 +41,8 @@ typedef struct
 	int			ntuples;		/* -1 indicates lossy result */
 	bool		recheck;		/* should the tuples be rechecked? */
 	/* Note: recheck is always true if ntuples < 0 */
-	OffsetNumber offsets[1];	/* VARIABLE LENGTH ARRAY */
-} TBMIterateResult;				/* VARIABLE LENGTH STRUCT */
+	OffsetNumber offsets[FLEXIBLE_ARRAY_MEMBER];
+} TBMIterateResult;
 
 /* function prototypes in nodes/tidbitmap.c */
 

src/include/postgres.h

@@ -117,20 +117,20 @@ typedef union
 	struct						/* Normal varlena (4-byte length) */
 	{
 		uint32		va_header;
-		char		va_data[1];
+		char		va_data[FLEXIBLE_ARRAY_MEMBER];
 	}			va_4byte;
 	struct						/* Compressed-in-line format */
 	{
 		uint32		va_header;
 		uint32		va_rawsize; /* Original data size (excludes header) */
-		char		va_data[1]; /* Compressed data */
+		char		va_data[FLEXIBLE_ARRAY_MEMBER];		/* Compressed data */
 	}			va_compressed;
 } varattrib_4b;
 
 typedef struct
 {
 	uint8		va_header;
-	char		va_data[1];		/* Data begins here */
+	char		va_data[FLEXIBLE_ARRAY_MEMBER]; /* Data begins here */
 } varattrib_1b;
 
 /* TOAST pointers are a subset of varattrib_1b with an identifying tag byte */
@@ -138,7 +138,7 @@ typedef struct
 {
 	uint8		va_header;		/* Always 0x80 or 0x01 */
 	uint8		va_tag;			/* Type of datum */
-	char		va_data[1];		/* Data (of the type indicated by va_tag) */
+	char		va_data[FLEXIBLE_ARRAY_MEMBER]; /* Type-specific data */
 } varattrib_1b_e;
 
 /*

src/include/postmaster/syslogger.h

@@ -48,7 +48,7 @@ typedef struct
 	int32		pid;			/* writer's pid */
 	char		is_last;		/* last chunk of message? 't' or 'f' ('T' or
 								 * 'F' for CSV case) */
-	char		data[1];		/* data payload starts here */
+	char		data[FLEXIBLE_ARRAY_MEMBER];	/* data payload starts here */
 } PipeProtoHeader;
 
 typedef union

src/include/replication/walsender_private.h

@@ -88,7 +88,7 @@ typedef struct
 	 */
 	bool		sync_standbys_defined;
 
-	WalSnd		walsnds[1];		/* VARIABLE LENGTH ARRAY */
+	WalSnd		walsnds[FLEXIBLE_ARRAY_MEMBER];
 } WalSndCtlData;
 
 extern WalSndCtlData *WalSndCtl;

src/include/storage/bufpage.h

@@ -156,7 +156,7 @@ typedef struct PageHeaderData
 	LocationIndex pd_special;	/* offset to start of special space */
 	uint16		pd_pagesize_version;
 	TransactionId pd_prune_xid; /* oldest prunable XID, or zero if none */
-	ItemIdData	pd_linp[1];		/* beginning of line pointer array */
+	ItemIdData	pd_linp[FLEXIBLE_ARRAY_MEMBER]; /* line pointer array */
 } PageHeaderData;
 
 typedef PageHeaderData *PageHeader;

src/include/storage/fsm_internals.h

@@ -39,7 +39,7 @@ typedef struct
 	 * NonLeafNodesPerPage elements are upper nodes, and the following
 	 * LeafNodesPerPage elements are leaf nodes. Unused nodes are zero.
 	 */
-	uint8		fp_nodes[1];
+	uint8		fp_nodes[FLEXIBLE_ARRAY_MEMBER];
 } FSMPageData;
 
 typedef FSMPageData *FSMPage;

src/include/storage/standby.h

@@ -60,7 +60,7 @@ extern void StandbyReleaseOldLocks(int nxids, TransactionId *xids);
 typedef struct xl_standby_locks
 {
 	int			nlocks;			/* number of entries in locks array */
-	xl_standby_lock locks[1];	/* VARIABLE LENGTH ARRAY */
+	xl_standby_lock locks[FLEXIBLE_ARRAY_MEMBER];
 } xl_standby_locks;
 
 /*
@@ -75,7 +75,7 @@ typedef struct xl_running_xacts
 	TransactionId oldestRunningXid;		/* *not* oldestXmin */
 	TransactionId latestCompletedXid;	/* so we can set xmax */
 
-	TransactionId xids[1];		/* VARIABLE LENGTH ARRAY */
+	TransactionId xids[FLEXIBLE_ARRAY_MEMBER];
 } xl_running_xacts;
 
 #define MinSizeOfXactRunningXacts offsetof(xl_running_xacts, xids)

src/include/tsearch/dicts/regis.h

@@ -21,7 +21,7 @@ typedef struct RegisNode
 				len:16,
 				unused:14;
 	struct RegisNode *next;
-	unsigned char data[1];
+	unsigned char data[FLEXIBLE_ARRAY_MEMBER];
 } RegisNode;
 
 #define  RNHDRSZ	(offsetof(RegisNode,data))

src/include/tsearch/dicts/spell.h

@@ -49,7 +49,7 @@ typedef struct
 typedef struct SPNode
 {
 	uint32		length;
-	SPNodeData	data[1];
+	SPNodeData	data[FLEXIBLE_ARRAY_MEMBER];
 } SPNode;
 
 #define SPNHDRSZ	(offsetof(SPNode,data))
@@ -70,7 +70,7 @@ typedef struct spell_struct
 			int			len;
 		}			d;
 	}			p;
-	char		word[1];		/* variable length, null-terminated */
+	char		word[FLEXIBLE_ARRAY_MEMBER];
 } SPELL;
 
 #define SPELLHDRSZ	(offsetof(SPELL, word))
@@ -120,7 +120,7 @@ typedef struct AffixNode
 {
 	uint32		isvoid:1,
 				length:31;
-	AffixNodeData data[1];
+	AffixNodeData data[FLEXIBLE_ARRAY_MEMBER];
 } AffixNode;
 
 #define ANHRDSZ		   (offsetof(AffixNode, data))

src/include/tsearch/ts_type.h

@@ -63,7 +63,7 @@ typedef uint16 WordEntryPos;
 typedef struct
 {
 	uint16		npos;
-	WordEntryPos pos[1];		/* variable length */
+	WordEntryPos pos[FLEXIBLE_ARRAY_MEMBER];
 } WordEntryPosVector;
 
 
@@ -82,7 +82,7 @@ typedef struct
 {
 	int32		vl_len_;		/* varlena header (do not touch directly!) */
 	int32		size;
-	WordEntry	entries[1];		/* variable length */
+	WordEntry	entries[FLEXIBLE_ARRAY_MEMBER];
 	/* lexemes follow the entries[] array */
 } TSVectorData;
 
@@ -233,7 +233,7 @@ typedef struct
 {
 	int32		vl_len_;		/* varlena header (do not touch directly!) */
 	int32		size;			/* number of QueryItems */
-	char		data[1];		/* data starts here */
+	char		data[FLEXIBLE_ARRAY_MEMBER];	/* data starts here */
 } TSQueryData;
 
 typedef TSQueryData *TSQuery;

src/include/utils/catcache.h

@@ -147,8 +147,8 @@ typedef struct catclist
 	uint32		hash_value;		/* hash value for lookup keys */
 	HeapTupleData tuple;		/* header for tuple holding keys */
 	int			n_members;		/* number of member tuples */
-	CatCTup    *members[1];		/* members --- VARIABLE LENGTH ARRAY */
-} CatCList;						/* VARIABLE LENGTH STRUCT */
+	CatCTup    *members[FLEXIBLE_ARRAY_MEMBER]; /* members */
+} CatCList;
 
 
 typedef struct catcacheheader

src/include/utils/datetime.h

@@ -219,7 +219,7 @@ typedef struct TimeZoneAbbrevTable
 {
 	Size		tblsize;		/* size in bytes of TimeZoneAbbrevTable */
 	int			numabbrevs;		/* number of entries in abbrevs[] array */
-	datetkn		abbrevs[1];		/* VARIABLE LENGTH ARRAY */
+	datetkn		abbrevs[FLEXIBLE_ARRAY_MEMBER];
 	/* DynamicZoneAbbrev(s) may follow the abbrevs[] array */
 } TimeZoneAbbrevTable;
 
@@ -227,7 +227,7 @@ typedef struct TimeZoneAbbrevTable
 typedef struct DynamicZoneAbbrev
 {
 	pg_tz	   *tz;				/* NULL if not yet looked up */
-	char		zone[1];		/* zone name (var length, NUL-terminated) */
+	char		zone[FLEXIBLE_ARRAY_MEMBER];	/* NUL-terminated zone name */
 } DynamicZoneAbbrev;
 
 

src/include/utils/geo_decls.h

@@ -80,7 +80,7 @@ typedef struct
 	int32		npts;
 	int32		closed;			/* is this a closed polygon? */
 	int32		dummy;			/* padding to make it double align */
-	Point		p[1];			/* variable length array of POINTs */
+	Point		p[FLEXIBLE_ARRAY_MEMBER];
 } PATH;
 
 
@@ -115,7 +115,7 @@ typedef struct
 	int32		vl_len_;		/* varlena header (do not touch directly!) */
 	int32		npts;
 	BOX			boundbox;
-	Point		p[1];			/* variable length array of POINTs */
+	Point		p[FLEXIBLE_ARRAY_MEMBER];
 } POLYGON;
 
 /*---------------------------------------------------------------------

src/include/utils/jsonb.h

@@ -194,7 +194,7 @@ typedef struct JsonbContainer
 {
 	uint32		header;			/* number of elements or key/value pairs, and
 								 * flags */
-	JEntry		children[1];	/* variable length */
+	JEntry		children[FLEXIBLE_ARRAY_MEMBER];
 
 	/* the data for each child node follows. */
 } JsonbContainer;

src/include/utils/relmapper.h

@@ -29,7 +29,7 @@ typedef struct xl_relmap_update
 	Oid			dbid;			/* database ID, or 0 for shared map */
 	Oid			tsid;			/* database's tablespace, or pg_global */
 	int32		nbytes;			/* size of relmap data */
-	char		data[1];		/* VARIABLE LENGTH ARRAY */
+	char		data[FLEXIBLE_ARRAY_MEMBER];
 } xl_relmap_update;
 
 #define MinSizeOfRelmapUpdate offsetof(xl_relmap_update, data)

src/include/utils/varbit.h

@@ -26,7 +26,8 @@ typedef struct
 {
 	int32		vl_len_;		/* varlena header (do not touch directly!) */
 	int32		bit_len;		/* number of valid bits */
-	bits8		bit_dat[1];		/* bit string, most sig. byte first */
+	bits8		bit_dat[FLEXIBLE_ARRAY_MEMBER]; /* bit string, most sig. byte
+												 * first */
 } VarBit;
 
 /*