1 files changed, 19 insertions, 0 deletions
diff --git a/lib/util/tsort.h b/lib/util/tsort.h
index 811d6cd..18e82d6 100644
--- a/lib/util/tsort.h
+++ b/lib/util/tsort.h
@@ -37,4 +37,23 @@ do { \
 } while (0)
 #endif
 
+
+#ifndef NUMERIC_CMP
+/*
+ * NUMERIC_CMP is a safe replacement for `a - b` in comparison
+ * functions. It will work on integers, pointers, and floats.
+ *
+ * Rather than
+ *
+ *      return a - b;
+ *
+ * use
+ *
+ *     return NUMERIC_CMP(a, b);
+ *
+ * and you won't have any troubles if a - b would overflow.
+ */
+#define NUMERIC_CMP(a, b) (((a) > (b)) - ((a) < (b)))
+#endif
+
 #endif