[master] better reporting of xml/json unavailability

- error if "configure --with-libxml2" but the library isn't available
- log a warning on startup if only JSON or only XML can be served

bin/named/statschannel.c

@@ -2923,7 +2923,20 @@ ns_statschannels_configure(ns_server_t *server, const cfg_obj_t *config,
 			      NS_LOGMODULE_SERVER, ISC_LOG_WARNING,
 			      "statistics-channels specified but not effective "
 			      "due to missing XML and/or JSON library");
-#endif
+#else /* EXTENDED_STATS */
+#ifndef HAVE_LIBXML2
+		isc_log_write(ns_g_lctx, NS_LOGCATEGORY_GENERAL,
+			      NS_LOGMODULE_SERVER, ISC_LOG_WARNING,
+			      "statistics-channels: XML library missing, "
+			      "only JSON stats will be available");
+#endif /* !HAVE_LIBXML2 */
+#ifndef HAVE_JSON
+		isc_log_write(ns_g_lctx, NS_LOGCATEGORY_GENERAL,
+			      NS_LOGMODULE_SERVER, ISC_LOG_WARNING,
+			      "statistics-channels: JSON library missing, "
+			      "only XML stats will be available");
+#endif /* !HAVE_JSON */
+#endif /* EXTENDED_STATS */
 
 		for (element = cfg_list_first(statschannellist);
 		     element != NULL;

configure

@@ -16482,8 +16482,14 @@ case "$use_libxml2" in
 			libxml2_cflags=`xml2-config --cflags`
 			;;
 		*)
-			libxml2_libs=
-			libxml2_cflags=
+			if test "$use_libxml2" = "yes" ; then
+				{ $as_echo "$as_me:${as_lineno-$LINENO}: result: no" >&5
+$as_echo "no" >&6; }
+				as_fn_error $? "required libxml2 version not available" "$LINENO" 5
+			else
+				libxml2_libs=
+				libxml2_cflags=
+			fi
 			;;
 		esac
 		;;

configure.in

@@ -2067,8 +2067,13 @@ case "$use_libxml2" in
 			libxml2_cflags=`xml2-config --cflags`
 			;;
 		*)
-			libxml2_libs=
-			libxml2_cflags=
+			if test "$use_libxml2" = "yes" ; then
+				AC_MSG_RESULT(no)
+				AC_MSG_ERROR(required libxml2 version not available)
+			else
+				libxml2_libs=
+				libxml2_cflags=
+			fi
 			;;
 		esac
 		;;