dotgen edgeposcmpf: 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/dotgen/mincross.c b/lib/dotgen/mincross.c
index 2bb1088185e05ca7f68decd0c1a2d46de8975c50..85bd4f46163aa07c42caf63c688bc0eaf09842be 100644 (file)
--- a/lib/dotgen/mincross.c
+++ b/lib/dotgen/mincross.c
@@ -1843,7 +1843,13 @@ static int nodeposcmpf(node_t ** n0, node_t ** n1)
 
 static int edgeidcmpf(edge_t ** e0, edge_t ** e1)
 {
-    return (AGSEQ(*e0) - AGSEQ(*e1));
+  if (AGSEQ(*e0) < AGSEQ(*e1)) {
+    return -1;
+  }
+  if (AGSEQ(*e0) > AGSEQ(*e1)) {
+    return 1;
+  }
+  return 0;
 }
 
 /* following code deals with weights of edges of "virtual" nodes */