diff --git a/src/subs.c b/src/subs.c
index c860f3af..e723587d 100644
--- a/src/subs.c
+++ b/src/subs.c
@@ -322,13 +322,15 @@ static int sub__add_context(struct mosquitto_db *db, struct mosquitto *context,
 {
 	struct mosquitto__subhier *branch;
 	int topic_index = 0;
+	size_t topiclen;
 
 	/* Find leaf node */
 	while(topics && topics[topic_index] != NULL){
-		HASH_FIND(hh, subhier->children, topics[topic_index], strlen(topics[topic_index]), branch);
+		topiclen = strlen(topics[topic_index]);
+		HASH_FIND(hh, subhier->children, topics[topic_index], topiclen, branch);
 		if(!branch){
 			/* Not found */
-			branch = sub__add_hier_entry(subhier, &subhier->children, topics[topic_index], strlen(topics[topic_index]));
+			branch = sub__add_hier_entry(subhier, &subhier->children, topics[topic_index], topiclen);
 			if(!branch) return MOSQ_ERR_NOMEM;
 		}
 		subhier = branch;
@@ -562,6 +564,7 @@ int sub__add(struct mosquitto_db *db, struct mosquitto *context, const char *sub
 	const char *sharename = NULL;
 	char *local_sub;
 	char **topics;
+	size_t topiclen;
 
 	assert(root);
 	assert(*root);
@@ -570,9 +573,10 @@ int sub__add(struct mosquitto_db *db, struct mosquitto *context, const char *sub
 	rc = sub__topic_tokenise(sub, &local_sub, &topics, &sharename);
 	if(rc) return rc;
 
-	HASH_FIND(hh, *root, topics[0], strlen(topics[0]), subhier);
+	topiclen = strlen(topics[0]);
+	HASH_FIND(hh, *root, topics[0], topiclen, subhier);
 	if(!subhier){
-		subhier = sub__add_hier_entry(NULL, root, topics[0], strlen(topics[0]));
+		subhier = sub__add_hier_entry(NULL, root, topics[0], topiclen);
 		if(!subhier){
 			mosquitto__free(local_sub);
 			mosquitto__free(topics);
diff --git a/src/sys_tree.c b/src/sys_tree.c
index c7d746f5..8e8cf487 100644
--- a/src/sys_tree.c
+++ b/src/sys_tree.c
@@ -45,14 +45,15 @@ unsigned int g_connection_count = 0;
 void sys_tree__init(struct mosquitto_db *db)
 {
 	char buf[64];
+	int len;
 
 	if(db->config->sys_interval == 0){
 		return;
 	}
 
 	/* Set static $SYS messages */
-	snprintf(buf, 64, "mosquitto version %s", VERSION);
-	db__messages_easy_queue(db, NULL, "$SYS/broker/version", SYS_TREE_QOS, strlen(buf), buf, 1, 0, NULL);
+	len = snprintf(buf, 64, "mosquitto version %s", VERSION);
+	db__messages_easy_queue(db, NULL, "$SYS/broker/version", SYS_TREE_QOS, len, buf, 1, 0, NULL);
 }
 
 static void sys_tree__update_clients(struct mosquitto_db *db, char *buf)
@@ -62,6 +63,7 @@ static void sys_tree__update_clients(struct mosquitto_db *db, char *buf)
 	static int client_max = 0;
 	static int disconnected_count = -1;
 	static int connected_count = -1;
+	int len;
 
 	int count_total, count_by_sock;
 
@@ -70,13 +72,13 @@ static void sys_tree__update_clients(struct mosquitto_db *db, char *buf)
 
 	if(client_count != count_total){
 		client_count = count_total;
-		snprintf(buf, BUFLEN, "%d", client_count);
-		db__messages_easy_queue(db, NULL, "$SYS/broker/clients/total", SYS_TREE_QOS, strlen(buf), buf, 1, 60, NULL);
+		len = snprintf(buf, BUFLEN, "%d", client_count);
+		db__messages_easy_queue(db, NULL, "$SYS/broker/clients/total", SYS_TREE_QOS, len, buf, 1, 60, NULL);
 
 		if(client_count > client_max){
 			client_max = client_count;
-			snprintf(buf, BUFLEN, "%d", client_max);
-			db__messages_easy_queue(db, NULL, "$SYS/broker/clients/maximum", SYS_TREE_QOS, strlen(buf), buf, 1, 60, NULL);
+			len = snprintf(buf, BUFLEN, "%d", client_max);
+			db__messages_easy_queue(db, NULL, "$SYS/broker/clients/maximum", SYS_TREE_QOS, len, buf, 1, 60, NULL);
 		}
 	}
 
@@ -89,20 +91,20 @@ static void sys_tree__update_clients(struct mosquitto_db *db, char *buf)
 			 * not last for long, so just cap at zero and ignore. */
 			disconnected_count = 0;
 		}
-		snprintf(buf, BUFLEN, "%d", disconnected_count);
-		db__messages_easy_queue(db, NULL, "$SYS/broker/clients/inactive", SYS_TREE_QOS, strlen(buf), buf, 1, 60, NULL);
-		db__messages_easy_queue(db, NULL, "$SYS/broker/clients/disconnected", SYS_TREE_QOS, strlen(buf), buf, 1, 60, NULL);
+		len = snprintf(buf, BUFLEN, "%d", disconnected_count);
+		db__messages_easy_queue(db, NULL, "$SYS/broker/clients/inactive", SYS_TREE_QOS, len, buf, 1, 60, NULL);
+		db__messages_easy_queue(db, NULL, "$SYS/broker/clients/disconnected", SYS_TREE_QOS, len, buf, 1, 60, NULL);
 	}
 	if(connected_count != count_by_sock){
 		connected_count = count_by_sock;
-		snprintf(buf, BUFLEN, "%d", connected_count);
-		db__messages_easy_queue(db, NULL, "$SYS/broker/clients/active", SYS_TREE_QOS, strlen(buf), buf, 1, 60, NULL);
-		db__messages_easy_queue(db, NULL, "$SYS/broker/clients/connected", SYS_TREE_QOS, strlen(buf), buf, 1, 60, NULL);
+		len = snprintf(buf, BUFLEN, "%d", connected_count);
+		db__messages_easy_queue(db, NULL, "$SYS/broker/clients/active", SYS_TREE_QOS, len, buf, 1, 60, NULL);
+		db__messages_easy_queue(db, NULL, "$SYS/broker/clients/connected", SYS_TREE_QOS, len, buf, 1, 60, NULL);
 	}
 	if(g_clients_expired != clients_expired){
 		clients_expired = g_clients_expired;
-		snprintf(buf, BUFLEN, "%d", clients_expired);
-		db__messages_easy_queue(db, NULL, "$SYS/broker/clients/expired", SYS_TREE_QOS, strlen(buf), buf, 1, 60, NULL);
+		len = snprintf(buf, BUFLEN, "%d", clients_expired);
+		db__messages_easy_queue(db, NULL, "$SYS/broker/clients/expired", SYS_TREE_QOS, len, buf, 1, 60, NULL);
 	}
 }
 
@@ -112,18 +114,19 @@ static void sys_tree__update_memory(struct mosquitto_db *db, char *buf)
 	static unsigned long current_heap = -1;
 	static unsigned long max_heap = -1;
 	unsigned long value_ul;
+	int len;
 
 	value_ul = mosquitto__memory_used();
 	if(current_heap != value_ul){
 		current_heap = value_ul;
-		snprintf(buf, BUFLEN, "%lu", current_heap);
-		db__messages_easy_queue(db, NULL, "$SYS/broker/heap/current", SYS_TREE_QOS, strlen(buf), buf, 1, 60, NULL);
+		len = snprintf(buf, BUFLEN, "%lu", current_heap);
+		db__messages_easy_queue(db, NULL, "$SYS/broker/heap/current", SYS_TREE_QOS, len, buf, 1, 60, NULL);
 	}
 	value_ul =mosquitto__max_memory_used();
 	if(max_heap != value_ul){
 		max_heap = value_ul;
-		snprintf(buf, BUFLEN, "%lu", max_heap);
-		db__messages_easy_queue(db, NULL, "$SYS/broker/heap/maximum", SYS_TREE_QOS, strlen(buf), buf, 1, 60, NULL);
+		len = snprintf(buf, BUFLEN, "%lu", max_heap);
+		db__messages_easy_queue(db, NULL, "$SYS/broker/heap/maximum", SYS_TREE_QOS, len, buf, 1, 60, NULL);
 	}
 }
 #endif
@@ -131,16 +134,17 @@ static void sys_tree__update_memory(struct mosquitto_db *db, char *buf)
 static void calc_load(struct mosquitto_db *db, char *buf, const char *topic, bool initial, double exponent, double interval, double *current)
 {
 	double new_value;
+	int len;
 
 	if (initial) {
 		new_value = *current;
-		snprintf(buf, BUFLEN, "%.2f", new_value);
-		db__messages_easy_queue(db, NULL, topic, SYS_TREE_QOS, strlen(buf), buf, 1, 60, NULL);
+		len = snprintf(buf, BUFLEN, "%.2f", new_value);
+		db__messages_easy_queue(db, NULL, topic, SYS_TREE_QOS, len, buf, 1, 60, NULL);
 	} else {
 		new_value = interval + exponent*((*current) - interval);
 		if(fabs(new_value - (*current)) >= 0.01){
-			snprintf(buf, BUFLEN, "%.2f", new_value);
-			db__messages_easy_queue(db, NULL, topic, SYS_TREE_QOS, strlen(buf), buf, 1, 60, NULL);
+			len = snprintf(buf, BUFLEN, "%.2f", new_value);
+			db__messages_easy_queue(db, NULL, topic, SYS_TREE_QOS, len, buf, 1, 60, NULL);
 		}
 	}
 	(*current) = new_value;
@@ -213,13 +217,14 @@ void sys_tree__update(struct mosquitto_db *db, int interval, time_t start_time)
 
 	double exponent;
 	double i_mult;
+	int len;
 
 	now = mosquitto_time();
 
 	if(interval && now - interval > last_update){
 		uptime = now - start_time;
-		snprintf(buf, BUFLEN, "%d seconds", (int)uptime);
-		db__messages_easy_queue(db, NULL, "$SYS/broker/uptime", SYS_TREE_QOS, strlen(buf), buf, 1, 60, NULL);
+		len = snprintf(buf, BUFLEN, "%d seconds", (int)uptime);
+		db__messages_easy_queue(db, NULL, "$SYS/broker/uptime", SYS_TREE_QOS, len, buf, 1, 60, NULL);
 
 		sys_tree__update_clients(db, buf);
 		bool initial_publish = false;
@@ -287,33 +292,33 @@ void sys_tree__update(struct mosquitto_db *db, int interval, time_t start_time)
 
 		if(db->msg_store_count != msg_store_count){
 			msg_store_count = db->msg_store_count;
-			snprintf(buf, BUFLEN, "%d", msg_store_count);
-			db__messages_easy_queue(db, NULL, "$SYS/broker/messages/stored", SYS_TREE_QOS, strlen(buf), buf, 1, 60, NULL);
-			db__messages_easy_queue(db, NULL, "$SYS/broker/store/messages/count", SYS_TREE_QOS, strlen(buf), buf, 1, 60, NULL);
+			len = snprintf(buf, BUFLEN, "%d", msg_store_count);
+			db__messages_easy_queue(db, NULL, "$SYS/broker/messages/stored", SYS_TREE_QOS, len, buf, 1, 60, NULL);
+			db__messages_easy_queue(db, NULL, "$SYS/broker/store/messages/count", SYS_TREE_QOS, len, buf, 1, 60, NULL);
 		}
 
 		if (db->msg_store_bytes != msg_store_bytes){
 			msg_store_bytes = db->msg_store_bytes;
-			snprintf(buf, BUFLEN, "%lu", msg_store_bytes);
-			db__messages_easy_queue(db, NULL, "$SYS/broker/store/messages/bytes", SYS_TREE_QOS, strlen(buf), buf, 1, 60, NULL);
+			len = snprintf(buf, BUFLEN, "%lu", msg_store_bytes);
+			db__messages_easy_queue(db, NULL, "$SYS/broker/store/messages/bytes", SYS_TREE_QOS, len, buf, 1, 60, NULL);
 		}
 
 		if(db->subscription_count != subscription_count){
 			subscription_count = db->subscription_count;
-			snprintf(buf, BUFLEN, "%d", subscription_count);
-			db__messages_easy_queue(db, NULL, "$SYS/broker/subscriptions/count", SYS_TREE_QOS, strlen(buf), buf, 1, 60, NULL);
+			len = snprintf(buf, BUFLEN, "%d", subscription_count);
+			db__messages_easy_queue(db, NULL, "$SYS/broker/subscriptions/count", SYS_TREE_QOS, len, buf, 1, 60, NULL);
 		}
 
 		if(db->shared_subscription_count != shared_subscription_count){
 			shared_subscription_count = db->shared_subscription_count;
-			snprintf(buf, BUFLEN, "%d", shared_subscription_count);
-			db__messages_easy_queue(db, NULL, "$SYS/broker/shared_subscriptions/count", SYS_TREE_QOS, strlen(buf), buf, 1, 60, NULL);
+			len = snprintf(buf, BUFLEN, "%d", shared_subscription_count);
+			db__messages_easy_queue(db, NULL, "$SYS/broker/shared_subscriptions/count", SYS_TREE_QOS, len, buf, 1, 60, NULL);
 		}
 
 		if(db->retained_count != retained_count){
 			retained_count = db->retained_count;
-			snprintf(buf, BUFLEN, "%d", retained_count);
-			db__messages_easy_queue(db, NULL, "$SYS/broker/retained messages/count", SYS_TREE_QOS, strlen(buf), buf, 1, 60, NULL);
+			len = snprintf(buf, BUFLEN, "%d", retained_count);
+			db__messages_easy_queue(db, NULL, "$SYS/broker/retained messages/count", SYS_TREE_QOS, len, buf, 1, 60, NULL);
 		}
 
 #ifdef REAL_WITH_MEMORY_TRACKING
@@ -322,56 +327,56 @@ void sys_tree__update(struct mosquitto_db *db, int interval, time_t start_time)
 
 		if(msgs_received != g_msgs_received){
 			msgs_received = g_msgs_received;
-			snprintf(buf, BUFLEN, "%lu", msgs_received);
-			db__messages_easy_queue(db, NULL, "$SYS/broker/messages/received", SYS_TREE_QOS, strlen(buf), buf, 1, 60, NULL);
+			len = snprintf(buf, BUFLEN, "%lu", msgs_received);
+			db__messages_easy_queue(db, NULL, "$SYS/broker/messages/received", SYS_TREE_QOS, len, buf, 1, 60, NULL);
 		}
 		
 		if(msgs_sent != g_msgs_sent){
 			msgs_sent = g_msgs_sent;
-			snprintf(buf, BUFLEN, "%lu", msgs_sent);
-			db__messages_easy_queue(db, NULL, "$SYS/broker/messages/sent", SYS_TREE_QOS, strlen(buf), buf, 1, 60, NULL);
+			len = snprintf(buf, BUFLEN, "%lu", msgs_sent);
+			db__messages_easy_queue(db, NULL, "$SYS/broker/messages/sent", SYS_TREE_QOS, len, buf, 1, 60, NULL);
 		}
 
 		if(publish_dropped != g_msgs_dropped){
 			publish_dropped = g_msgs_dropped;
-			snprintf(buf, BUFLEN, "%lu", publish_dropped);
-			db__messages_easy_queue(db, NULL, "$SYS/broker/publish/messages/dropped", SYS_TREE_QOS, strlen(buf), buf, 1, 60, NULL);
+			len = snprintf(buf, BUFLEN, "%lu", publish_dropped);
+			db__messages_easy_queue(db, NULL, "$SYS/broker/publish/messages/dropped", SYS_TREE_QOS, len, buf, 1, 60, NULL);
 		}
 
 		if(pub_msgs_received != g_pub_msgs_received){
 			pub_msgs_received = g_pub_msgs_received;
-			snprintf(buf, BUFLEN, "%lu", pub_msgs_received);
-			db__messages_easy_queue(db, NULL, "$SYS/broker/publish/messages/received", SYS_TREE_QOS, strlen(buf), buf, 1, 60, NULL);
+			len = snprintf(buf, BUFLEN, "%lu", pub_msgs_received);
+			db__messages_easy_queue(db, NULL, "$SYS/broker/publish/messages/received", SYS_TREE_QOS, len, buf, 1, 60, NULL);
 		}
 		
 		if(pub_msgs_sent != g_pub_msgs_sent){
 			pub_msgs_sent = g_pub_msgs_sent;
-			snprintf(buf, BUFLEN, "%lu", pub_msgs_sent);
-			db__messages_easy_queue(db, NULL, "$SYS/broker/publish/messages/sent", SYS_TREE_QOS, strlen(buf), buf, 1, 60, NULL);
+			len = snprintf(buf, BUFLEN, "%lu", pub_msgs_sent);
+			db__messages_easy_queue(db, NULL, "$SYS/broker/publish/messages/sent", SYS_TREE_QOS, len, buf, 1, 60, NULL);
 		}
 
 		if(bytes_received != g_bytes_received){
 			bytes_received = g_bytes_received;
-			snprintf(buf, BUFLEN, "%llu", bytes_received);
-			db__messages_easy_queue(db, NULL, "$SYS/broker/bytes/received", SYS_TREE_QOS, strlen(buf), buf, 1, 60, NULL);
+			len = snprintf(buf, BUFLEN, "%llu", bytes_received);
+			db__messages_easy_queue(db, NULL, "$SYS/broker/bytes/received", SYS_TREE_QOS, len, buf, 1, 60, NULL);
 		}
 		
 		if(bytes_sent != g_bytes_sent){
 			bytes_sent = g_bytes_sent;
-			snprintf(buf, BUFLEN, "%llu", bytes_sent);
-			db__messages_easy_queue(db, NULL, "$SYS/broker/bytes/sent", SYS_TREE_QOS, strlen(buf), buf, 1, 60, NULL);
+			len = snprintf(buf, BUFLEN, "%llu", bytes_sent);
+			db__messages_easy_queue(db, NULL, "$SYS/broker/bytes/sent", SYS_TREE_QOS, len, buf, 1, 60, NULL);
 		}
 		
 		if(pub_bytes_received != g_pub_bytes_received){
 			pub_bytes_received = g_pub_bytes_received;
-			snprintf(buf, BUFLEN, "%llu", pub_bytes_received);
-			db__messages_easy_queue(db, NULL, "$SYS/broker/publish/bytes/received", SYS_TREE_QOS, strlen(buf), buf, 1, 60, NULL);
+			len = snprintf(buf, BUFLEN, "%llu", pub_bytes_received);
+			db__messages_easy_queue(db, NULL, "$SYS/broker/publish/bytes/received", SYS_TREE_QOS, len, buf, 1, 60, NULL);
 		}
 
 		if(pub_bytes_sent != g_pub_bytes_sent){
 			pub_bytes_sent = g_pub_bytes_sent;
-			snprintf(buf, BUFLEN, "%llu", pub_bytes_sent);
-			db__messages_easy_queue(db, NULL, "$SYS/broker/publish/bytes/sent", SYS_TREE_QOS, strlen(buf), buf, 1, 60, NULL);
+			len = snprintf(buf, BUFLEN, "%llu", pub_bytes_sent);
+			db__messages_easy_queue(db, NULL, "$SYS/broker/publish/bytes/sent", SYS_TREE_QOS, len, buf, 1, 60, NULL);
 		}
 
 		last_update = mosquitto_time();