diff --git a/src/dns_client.c b/src/dns_client.c
index bd9fbdd..1784f07 100644
--- a/src/dns_client.c
+++ b/src/dns_client.c
@@ -242,7 +242,7 @@ struct dns_query_struct {
 static struct dns_client client;
 static atomic_t dns_client_sid = ATOMIC_INIT(0);
 static LIST_HEAD(pending_servers);
-pthread_mutex_t pending_server_mutex = PTHREAD_MUTEX_INITIALIZER;
+static pthread_mutex_t pending_server_mutex = PTHREAD_MUTEX_INITIALIZER;
 static int dns_client_has_bootstrap_dns = 0;
 
 /* get addr info */
@@ -452,7 +452,7 @@ errout:
 }
 
 /* add server to group */
-int _dns_client_add_to_group_pending(char *group_name, char *server_ip, int port, dns_server_type_t server_type, int ispending)
+static int _dns_client_add_to_group_pending(char *group_name, char *server_ip, int port, dns_server_type_t server_type, int ispending)
 {
 	struct dns_server_info *server_info = NULL;
 
diff --git a/src/dns_server.c b/src/dns_server.c
index 665656d..335adf6 100644
--- a/src/dns_server.c
+++ b/src/dns_server.c
@@ -2032,7 +2032,6 @@ static int _dns_server_recv(struct dns_server_conn_head *conn, unsigned char *in
 	int qclass;
 	int qtype = DNS_T_ALL;
 
-	_dns_server_conn_get(conn);
 	/* decode packet */
 	tlog(TLOG_DEBUG, "recv query packet from %s, len = %d", gethost_by_addr(name, sizeof(name), (struct sockaddr *)from), inpacket_len);
 	decode_len = dns_decode(packet, DNS_PACKSIZE, inpacket, inpacket_len);
@@ -2083,7 +2082,6 @@ static int _dns_server_recv(struct dns_server_conn_head *conn, unsigned char *in
 		goto errout;
 	}
 
-	_dns_server_conn_release(conn);
 	return ret;
 errout:
 	if (request) {
@@ -2091,7 +2089,6 @@ errout:
 		_dns_server_delete_request(request);
 	}
 
-	_dns_server_conn_release(conn);
 	return ret;
 }
 
@@ -2441,23 +2438,28 @@ static int _dns_server_process_tcp(struct dns_server_conn_tcp_client *dnsserver,
 
 static int _dns_server_process(struct dns_server_conn_head *conn, struct epoll_event *event, unsigned long now)
 {
+	int ret;
 	_dns_server_client_touch(conn);
+	_dns_server_conn_get(conn);
 	if (conn->type == DNS_CONN_TYPE_UDP_SERVER) {
 		struct dns_server_conn_udp *udpconn = (struct dns_server_conn_udp *)conn;
-		return _dns_server_process_udp(udpconn, event, now);
+		ret = _dns_server_process_udp(udpconn, event, now);
 	} else if (conn->type == DNS_CONN_TYPE_TCP_SERVER) {
 		struct dns_server_conn_tcp_server *tcpserver = (struct dns_server_conn_tcp_server *)conn;
-		return _dns_server_tcp_accept(tcpserver, event, now);
+		ret = _dns_server_tcp_accept(tcpserver, event, now);
 	} else if (conn->type == DNS_CONN_TYPE_TCP_CLIENT) {
 		struct dns_server_conn_tcp_client *tcpclient = (struct dns_server_conn_tcp_client *)conn;
-		return _dns_server_process_tcp(tcpclient, event, now);
+		ret = _dns_server_process_tcp(tcpclient, event, now);
 	} else if (conn->type == DNS_CONN_TYPE_TLS_SERVER) {
 		tlog(TLOG_ERROR, "unsupport dns server type %d", conn->type);
-		return -1;
+		ret = -1;
 	} else {
 		tlog(TLOG_ERROR, "unsupport dns server type %d", conn->type);
-		return -1;
+		ret = -1;
 	}
+	_dns_server_conn_release(conn);
+
+	return ret;
 }
 
 static void _dns_server_second_ping_check(struct dns_request *request)
diff --git a/src/fast_ping.c b/src/fast_ping.c
index 04b152a..c9b8caa 100644
--- a/src/fast_ping.c
+++ b/src/fast_ping.c
@@ -984,14 +984,10 @@ static int _fast_ping_get_addr_by_type(PING_TYPE type, const char *ip_str, int p
 		return _fast_ping_get_addr_by_dns(ip_str, port, out_gai, out_ping_type);
 		break;
 	default:
-		goto errout;
 		break;
 	}
 
 	return -1;
-
-errout:
-	return -1;
 }
 
 struct ping_host_struct *fast_ping_start(PING_TYPE type, const char *host, int count, int interval, int timeout, fast_ping_result ping_callback, void *userptr)
@@ -1055,7 +1051,6 @@ struct ping_host_struct *fast_ping_start(PING_TYPE type, const char *host, int c
 	hash_add(ping.addrmap, &ping_host->addr_node, addrkey);
 	pthread_mutex_unlock(&ping.map_lock);
 
-	_fast_ping_host_get(ping_host);
 	_fast_ping_host_get(ping_host);
 	if (_fast_ping_sendping(ping_host) != 0) {
 		goto errout_remove;
@@ -1063,8 +1058,10 @@ struct ping_host_struct *fast_ping_start(PING_TYPE type, const char *host, int c
 
 	ping_host->run = 1;
 	freeaddrinfo(gai);
-	_fast_ping_host_put(ping_host);
 	return ping_host;
+errout_remove:
+	fast_ping_stop(ping_host);
+	ping_host = NULL;
 errout:
 	if (gai) {
 		freeaddrinfo(gai);
@@ -1074,10 +1071,6 @@ errout:
 		free(ping_host);
 	}
 
-	return NULL;
-errout_remove:
-	fast_ping_stop(ping_host);
-	_fast_ping_host_put(ping_host);
 	return NULL;
 }
 
@@ -1270,8 +1263,8 @@ static int _fast_ping_process_icmp(struct ping_host_struct *ping_host, struct ti
 	}
 
 	if (recv_ping_host->seq != seq) {
-		_fast_ping_host_put(recv_ping_host);
 		tlog(TLOG_ERROR, "seq num mismatch, expect %u, real %u", recv_ping_host->seq, seq);
+		_fast_ping_host_put(recv_ping_host);
 		return -1;
 	}
 
@@ -1640,7 +1633,7 @@ errout:
 	return -1;
 }
 
-void _fast_ping_close_fds(void)
+static void _fast_ping_close_fds(void)
 {
 	if (ping.fd_icmp > 0) {
 		close(ping.fd_icmp);
diff --git a/src/include/stringutil.h b/src/include/stringutil.h
index edbf949..c8f8a87 100644
--- a/src/include/stringutil.h
+++ b/src/include/stringutil.h
@@ -20,4 +20,4 @@ static inline char *safe_strncpy(char *dest, const char *src, size_t n)
 	return ret;
 }
 
-#endif
\ No newline at end of file
+#endif
diff --git a/src/lib/art.c b/src/lib/art.c
index 12851f8..1f5b109 100644
--- a/src/lib/art.c
+++ b/src/lib/art.c
@@ -52,23 +52,28 @@ SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
  */
 static art_node* alloc_node(uint8_t type) {
     art_node* n;
-    switch (type) {
+	void *mem = NULL;
+	switch (type) {
         case NODE4:
-            n = (art_node*)calloc(1, sizeof(art_node4));
+            mem = (art_node*)calloc(1, sizeof(art_node4));
             break;
         case NODE16:
-            n = (art_node*)calloc(1, sizeof(art_node16));
+            mem = (art_node*)calloc(1, sizeof(art_node16));
             break;
         case NODE48:
-            n = (art_node*)calloc(1, sizeof(art_node48));
+            mem = (art_node*)calloc(1, sizeof(art_node48));
             break;
         case NODE256:
-            n = (art_node*)calloc(1, sizeof(art_node256));
+            mem = (art_node*)calloc(1, sizeof(art_node256));
             break;
         default:
             abort();
     }
-    n->type = type;
+    if (mem == NULL) {
+		abort();
+	}
+	n = mem;
+	n->type = type;
     return n;
 }
 
diff --git a/src/lib/conf.c b/src/lib/conf.c
index d527ed7..2b6a0be 100644
--- a/src/lib/conf.c
+++ b/src/lib/conf.c
@@ -167,7 +167,6 @@ int conf_parse_args(char *key, char *value, int *argc, char **argv)
 			argv[count] = start;
 			*ptr = '\0';
 			ptr++;
-			start = ptr;
 			count++;
 			sep_flag = ' ';
 			start = NULL;
diff --git a/src/tlog.h b/src/tlog.h
index 235a816..fffcf4a 100644
--- a/src/tlog.h
+++ b/src/tlog.h
@@ -71,7 +71,7 @@ format: Log formats
 #ifndef BASE_FILE_NAME
 #define BASE_FILE_NAME __FILE__
 #endif
-#define tlog(level, format, ...) tlog_ext(level, BASE_FILE_NAME, __LINE__, __func__, 0, format, ##__VA_ARGS__)
+#define tlog(level, format, ...) tlog_ext(level, BASE_FILE_NAME, __LINE__, __func__, NULL, format, ##__VA_ARGS__)
 
 extern int tlog_ext(tlog_level level, const char *file, int line, const char *func, void *userptr, const char *format, ...)
     __attribute__((format(printf, 6, 7))) __attribute__((nonnull (6)));
diff --git a/src/util.c b/src/util.c
index b143dc5..8857dff 100644
--- a/src/util.c
+++ b/src/util.c
@@ -506,7 +506,7 @@ static int _ipset_operate(const char *ipsetname, const unsigned char addr[], int
 	nested[0]->len = (void *)buffer + NETLINK_ALIGN(netlink_head->nlmsg_len) - (void *)nested[0];
 
 	for (;;) {
-		rc = sendto(ipset_fd, buffer, netlink_head->nlmsg_len, 0, (struct sockaddr *)&snl, sizeof(snl));
+		rc = sendto(ipset_fd, buffer, netlink_head->nlmsg_len, 0, (const struct sockaddr *)&snl, sizeof(snl));
 		if (rc >= 0) {
 			break;
 		}
@@ -680,25 +680,10 @@ void SSL_CRYPTO_thread_cleanup(void)
 #ifndef MIN
 #define MIN(X, Y) ((X) < (Y) ? (X) : (Y))
 #endif
-typedef struct Protocol {
-    const char *const name;
-    const uint16_t default_port;
-    int (*const parse_packet)(const char*, size_t, char *, const char **);
-    const char *const abort_message;
-    const size_t abort_message_len;
-} protocol_t;
 
 static int parse_extensions(const char *, size_t, char *, const char **);
 static int parse_server_name_extension(const char *, size_t, char *, const char **);
 
-const struct Protocol *const tls_protocol;
-
-static const protocol_t tls_protocol_st = {
-	.default_port = 443,
-	.parse_packet = &parse_tls_header,
-};
-const protocol_t *const tls_protocol = &tls_protocol_st;
-
 /* Parse a TLS packet for the Server Name Indication extension in the client
  * hello handshake, returning the first servername found (pointer to static
  * array)
@@ -884,4 +869,4 @@ void get_compiled_time(struct tm *tm)
 	tm->tm_hour = hour;
 	tm->tm_min = min;
 	tm->tm_sec = sec;
-}
\ No newline at end of file
+}