[PATCH nft 3/3] netlink_linearize: avoid strict-overflow warning in netlink_gen_bitwise()

[Thomas Haller <thaller@xxxxxxxxxx>]

With gcc-13.2.1-1.fc38.x86_64:

  $ gcc -Iinclude -c -o tmp.o src/netlink_linearize.c -Werror -Wstrict-overflow=5 -O3
  src/netlink_linearize.c: In function ‘netlink_gen_bitwise’:
  src/netlink_linearize.c:1790:1: error: assuming signed overflow does not occur when changing X +- C1 cmp C2 to X cmp C2 -+ C1 [-Werror=strict-overflow]
   1790 | }
        | ^
  cc1: all warnings being treated as errors

It also makes more sense this way, where "n" is the hight of the
"binops" stack, and we check for a non-empty stack with "n > 0" and pop
the last element with "binops[--n]".

Signed-off-by: Thomas Haller <thaller@xxxxxxxxxx>
---
 src/netlink_linearize.c | 7 +++----
 1 file changed, 3 insertions(+), 4 deletions(-)

diff --git a/src/netlink_linearize.c b/src/netlink_linearize.c
index c91211582b3d..f2514b012a9d 100644
--- a/src/netlink_linearize.c
+++ b/src/netlink_linearize.c
@@ -712,14 +712,13 @@ static void netlink_gen_bitwise(struct netlink_linearize_ctx *ctx,
 	while (left->etype == EXPR_BINOP && left->left != NULL &&
 	       (left->op == OP_AND || left->op == OP_OR || left->op == OP_XOR))
 		binops[n++] = left = left->left;
-	n--;
 
-	netlink_gen_expr(ctx, binops[n--], dreg);
+	netlink_gen_expr(ctx, binops[--n], dreg);
 
 	mpz_bitmask(mask, expr->len);
 	mpz_set_ui(xor, 0);
-	for (; n >= 0; n--) {
-		i = binops[n];
+	while (n > 0) {
+		i = binops[--n];
 		mpz_set(val, i->right->value);
 
 		switch (i->op) {
-- 
2.41.0