Index: lxc-2.0.4/src/lxc/tools/lxc_snapshot.c
===================================================================
--- lxc-2.0.4.orig/src/lxc/tools/lxc_snapshot.c	2016-08-15 19:37:55.000000000 -0700
+++ lxc-2.0.4/src/lxc/tools/lxc_snapshot.c	2020-02-05 22:02:54.881031322 -0800
@@ -16,6 +16,7 @@
  * with this program; if not, write to the Free Software Foundation, Inc.,
  * 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
  */
+#define _GNU_SOURCE
 
 #include "confile.h"
 #include <stdio.h>