common increasingrankcmpf: rephrase comparator to avoid arithmetic

cccb8b1d22a18031fc92d93133c7fa14ef7e1361 fixed an integer overflow in a
`memcmp`-/`strcmp`-like comparator. The same situation exists in the code
touched in this commit. Rather than wait for an edge case to expose an overflow
here, this change makes the same update, removing arithmetic and the consequent
possibility of overflow.

diff --git a/lib/common/ns.c b/lib/common/ns.c
index 6968135eb2d25b3fd6427606b6b73c3b9d43ff6c..456a25f8b16d5245292c2cf97d6375d7c6aba8b1 100644 (file)
--- a/lib/common/ns.c
+++ b/lib/common/ns.c
@@ -689,7 +689,13 @@ static int decreasingrankcmpf(node_t **n0, node_t **n1) {
 }
 
 static int increasingrankcmpf(node_t **n0, node_t **n1) {
-  return ND_rank(*n0) - ND_rank(*n1);
+  if (ND_rank(*n0) < ND_rank(*n1)) {
+    return -1;
+  }
+  if (ND_rank(*n0) > ND_rank(*n1)) {
+    return 1;
+  }
+  return 0;
 }
 
 static void TB_balance(void)