+/* *INDENT-OFF* */
+static char *session_error_str[] = {
+#define _(sym, str) str,
+ foreach_session_error
+#undef _
+};
+/* *INDENT-ON* */
+
+static inline u8 *
+format_session_error (u8 * s, va_list * args)
+{
+ session_error_t error = va_arg (*args, session_error_t);
+ if (-error >= 0 && -error < SESSION_N_ERRORS)
+ s = format (s, "%s", session_error_str[-error]);
+ else
+ s = format (s, "invalid session err %u", -error);
+ return s;
+}