-/* Walk the array backwards to get substring-conflict names */
-for (i = nopt-1; i >= 0; i--) if (*(s = opts[i].name) && *s != '*')
+/* The 'previously-defined-substring' rule for macros in config file
+lines is done so for these builtin macros: we know that the table
+we source from is in strict alpha order, hence the builtins portion
+of the macros list is in reverse-alpha (we prepend them) - so longer
+macros that have substrings are always discovered first during
+expansion. */
+
+for (i = 0; i < nopt; i++) if (*(s = opts[i].name) && *s != '*')