Detect integer overflow in array_set_slice().

When provided an empty initial array, array_set_slice() fails to
check for overflow when computing the new array's dimensions.
While such overflows are ordinarily caught by ArrayGetNItems(),
commands with the following form are accepted:

	INSERT INTO t (i[-2147483648:2147483647]) VALUES ('{}');

To fix, perform the hazardous computations using overflow-detecting
arithmetic routines.  As with commit 18b585155a, the added test
cases generate errors that include a platform-dependent value, so
we again use psql's VERBOSITY parameter to suppress printing the
message text.

Reported-by: Alexander Lakhin
Author: Joseph Koshakow
Reviewed-by: Jian He
Discussion: https://postgr.es/m/31ad2cd1-db94-bdb3-f91a-65ffdb4bef95%40gmail.com
Backpatch-through: 12

src/backend/utils/adt/arrayfuncs.c

@@ -2887,7 +2887,14 @@ array_set_slice(Datum arraydatum,
 						 errdetail("When assigning to a slice of an empty array value,"
 								   " slice boundaries must be fully specified.")));
 
-			dim[i] = 1 + upperIndx[i] - lowerIndx[i];
+			/* compute "upperIndx[i] - lowerIndx[i] + 1", detecting overflow */
+			if (pg_sub_s32_overflow(upperIndx[i], lowerIndx[i], &dim[i]) ||
+				pg_add_s32_overflow(dim[i], 1, &dim[i]))
+				ereport(ERROR,
+						(errcode(ERRCODE_PROGRAM_LIMIT_EXCEEDED),
+						 errmsg("array size exceeds the maximum allowed (%d)",
+								(int) MaxArraySize)));
+
 			lb[i] = lowerIndx[i];
 		}