An ifdef was missing to avoid declaring these variables :
src/haproxy.c: In function 'deinit':
src/haproxy.c:1253:47: warning: unused variable '_51d_prop_nameb' [-Wunused-variable]
src/haproxy.c:1253:30: warning: unused variable '_51d_prop_name' [-Wunused-variable]
struct logsrv *log, *logb;
struct logformat_node *lf, *lfb;
struct bind_conf *bind_conf, *bind_back;
+#ifdef USE_51DEGREES
struct _51d_property_names *_51d_prop_name, *_51d_prop_nameb;
+#endif
int i;
deinit_signals();