diff -up readline-6.2/chardefs.h.orig readline-6.2/chardefs.h

--- readline-6.2/chardefs.h.orig	2011-08-31 09:24:01.852751855 +0200

+++ readline-6.2/chardefs.h	2011-08-31 09:24:07.143685706 +0200

@@ -72,7 +72,7 @@

 #  define IN_CTYPE_DOMAIN(c) isascii(c)

 #endif

-#if !defined (isxdigit) && !defined (HAVE_ISXDIGIT)

+#if !defined (isxdigit) && !defined (HAVE_ISXDIGIT) && !defined (__cplusplus) 

 #  define isxdigit(c)   (isdigit((c)) || ((c) >= 'a' && (c) <= 'f') || ((c) >= 'A' && (c) <= 'F'))

 #endif