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.

1 files changed, 11 insertions, 11 deletions

diff --git a/src/backend/utils/adt/geo_ops.c b/src/backend/utils/adt/geo_ops.c
index 6b6510e8e2..6cb6be5c5f 100644
--- a/src/backend/utils/adt/geo_ops.c
+++ b/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)