Index: src/readlef.h
--- src/readlef.h.orig
+++ src/readlef.h
@@ -27,6 +27,11 @@
 #define DEFAULT_WIDTH 3	   /* Default metal width for routes if undefined */
 #define DEFAULT_SPACING 4  /* Default spacing between metal if undefined  */
 
+#if defined(__APPLE__) || defined(__OpenBSD__)
+// Linux defines a comparison function prototype, the Mac doesn't. . .
+typedef int (*__compar_fn_t)(const void *, const void *);
+#endif
+
 /* Structure holding the counts of regular and special nets */
 
 typedef struct