pack cmpf: 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/pack/pack.c b/lib/pack/pack.c
index d79864ed8539554bd0693fdb847e70c495ef0814..ca211fe0a663d45f5cae543ae636858d6f704ca8 100644 (file)
--- a/lib/pack/pack.c
+++ b/lib/pack/pack.c
@@ -97,7 +97,13 @@ static int cmpf(const void *X, const void *Y)
     const ginfo *x = *(ginfo *const *) X;
     const ginfo *y = *(ginfo *const *) Y;
     /* flip order to get descending array */
-    return y->perim - x->perim;
+    if (y->perim < x->perim) {
+        return -1;
+    }
+    if (y->perim > x->perim) {
+      return 1;
+    }
+    return 0;
 }
 
 /* fillLine: