Re: BUG #17858: ExecEvalArrayExpr() leaves uninitialised memory for multidim array with nulls

With a server compiled with flags -DUSE_VALGRIND
-DWRITE_READ_PARSE_PLAN_TREES the following query:
SELECT * FROM generate_series(1, 1) a WHERE a = ANY
(array[array[NULL::int]]);

provokes an incorrect memory access:

Here ExecEvalArrayExpr() performs:
                result = (ArrayType *) palloc(nbytes);
where nbytes includes ARR_OVERHEAD_WITHNULLS(ndims, nitems) for ndims = 2
and nitems = 1, so last 8 bytes in this memory area reserved for a null
bitmap, but only one bit of the bitmap initialised later by
array_bitmap_copy().

Something like:
@@ -2860,6 +2861,9 @@ ExecEvalArrayExpr(ExprState *state, ExprEvalStep
*op)
                result->elemtype = element_type;
                memcpy(ARR_DIMS(result), dims, ndims * sizeof(int));
                memcpy(ARR_LBOUND(result), lbs, ndims * sizeof(int));
+               nullbitmap = ARR_NULLBITMAP(result);
+               if (nullbitmap)
+                       memset(nullbitmap, 0, ARR_OVERHEAD_WITHNULLS(ndims,
nitems) - ARR_OVERHEAD_NONULLS(ndims));

                dat = ARR_DATA_PTR(result);
                iitem = 0;

fixes the issue, just as "result = (ArrayType *) palloc0(nbytes)" does, of
course.