+ size_t len = strlen(s) + 3; /* see len comments below */
+
+#define isoctal(chr) (((chr) >= '0') && ((chr) <= '7'))
+#define isalnumx(chr) ((((chr) >= '0') && ((chr) <= '9')) \
+ || (((chr) >= 'a') && ((chr) <= 'z')) \
+ || (((chr) >= 'A') && ((chr) <= 'Z')) \
+ || (chr) == '_')