Function `strdup' implicitly converted to pointer at xmpp-servers.c:295

--- src/core/xmpp-servers.c
+++ src/core/xmpp-servers.c
@@ -18,5 +18,6 @@
 */

+#define _GNU_SOURCE
 #include <sys/types.h>
 #include <sys/socket.h>
 #include <string.h>