diff --git a/src/api/api_lib.c b/src/api/api_lib.c
index 444f83a9..f5a16e8f 100644
--- a/src/api/api_lib.c
+++ b/src/api/api_lib.c
@@ -71,7 +71,7 @@ netconn_new_with_proto_and_callback(enum netconn_type t, u8_t proto,
   struct netconn *conn;
   struct api_msg msg;
 
-  conn = netconn_alloc_with_proto_and_callback(t, proto, callback);
+  conn = netconn_alloc(t, callback);
   if (conn != NULL ) {
     msg.function = do_newconn;
     msg.msg.msg.n.proto = proto;
diff --git a/src/api/api_msg.c b/src/api/api_msg.c
index 0a48fd4d..4add74b9 100644
--- a/src/api/api_msg.c
+++ b/src/api/api_msg.c
@@ -338,7 +338,7 @@ accept_function(void *arg, struct tcp_pcb *newpcb, err_t err)
 
   /* We have to set the callback here even though
    * the new socket is unknown. conn->socket is marked as -1. */
-  newconn = netconn_alloc_with_proto_and_callback(conn->type, 0, conn->callback);
+  newconn = netconn_alloc(conn->type, conn->callback);
   if (newconn == NULL) {
     return ERR_MEM;
   }
@@ -446,7 +446,7 @@ do_newconn(struct api_msg_msg *msg)
  *         NULL on memory error
  */
 struct netconn*
-netconn_alloc_with_proto_and_callback(enum netconn_type t, u8_t proto,
+netconn_alloc(enum netconn_type t,
           void (*callback)(struct netconn *, enum netconn_evt, u16_t len))
 {
   struct netconn *conn;
@@ -469,7 +469,7 @@ netconn_alloc_with_proto_and_callback(enum netconn_type t, u8_t proto,
     memp_free(MEMP_NETCONN, conn);
     return NULL;
   }
-  conn->acceptmbox = SYS_MBOX_NULL;
+  conn->acceptmbox   = SYS_MBOX_NULL;
   conn->state        = NETCONN_NONE;
   /* initialize socket to -1 since 0 is a valid socket */
   conn->socket       = -1;
diff --git a/src/api/netdb.c b/src/api/netdb.c
index ea891a62..a0096f85 100644
--- a/src/api/netdb.c
+++ b/src/api/netdb.c
@@ -269,7 +269,7 @@ lwip_getaddrinfo(const char *nodename, const char *servname,
   err_t err;
   struct ip_addr addr;
   struct addrinfo *ai;
-  struct sockaddr_in *sa;
+  struct sockaddr_in *sa = NULL;
   int port_nr = 0;
 
   if (res == NULL) {
diff --git a/src/core/dns.c b/src/core/dns.c
index f1499950..34bd8dcf 100644
--- a/src/core/dns.c
+++ b/src/core/dns.c
@@ -563,7 +563,7 @@ dns_check_entries(void)
  * @params see udp.h
  */
 static void
-dns_recv(void *s, struct udp_pcb *pcb, struct pbuf *p, struct ip_addr *addr, u16_t port)
+dns_recv(void *arg, struct udp_pcb *pcb, struct pbuf *p, struct ip_addr *addr, u16_t port)
 {
   u8_t i;
   char *pHostname;
@@ -578,6 +578,11 @@ dns_recv(void *s, struct udp_pcb *pcb, struct pbuf *p, struct ip_addr *addr, u16
   u8_t* dns_payload;
 #endif /* (DNS_USES_STATIC_BUF == 2) */
 
+  LWIP_UNUSED_ARG(arg);
+  LWIP_UNUSED_ARG(pcb);
+  LWIP_UNUSED_ARG(addr);
+  LWIP_UNUSED_ARG(port);
+
   /* is the dns message too big ? */
   if (p->tot_len > DNS_MSG_SIZE) {
     LWIP_DEBUGF(DNS_DEBUG, ("dns_recv: pbuf too big\n"));
@@ -627,7 +632,7 @@ dns_recv(void *s, struct udp_pcb *pcb, struct pbuf *p, struct ip_addr *addr, u16
 
 #if DNS_DOES_NAME_CHECK
         /* Check if the name in the "question" part match with the name in the entry. */
-        if (dns_compare_name(pEntry->name, (unsigned char *)dns_payload + sizeof(struct dns_hdr)) != 0) {
+        if (dns_compare_name((unsigned char *)(pEntry->name), (unsigned char *)dns_payload + sizeof(struct dns_hdr)) != 0) {
           LWIP_DEBUGF(DNS_DEBUG, ("dns_recv: \"%s\": response not match to query\n", pEntry->name));
           /* call callback to indicate error, clean up memory and return */
           goto responseerr;
@@ -709,7 +714,7 @@ dns_enqueue(const char *name, dns_found_callback found, void *callback_arg)
 {
   u8_t i;
   u8_t lseq, lseqi;
-  struct dns_table_entry *pEntry;
+  struct dns_table_entry *pEntry = NULL;
 
   /* search an unused entry, or the oldest one */
   lseq = lseqi = 0;
diff --git a/src/core/init.c b/src/core/init.c
index ee073daf..5e0b522c 100644
--- a/src/core/init.c
+++ b/src/core/init.c
@@ -103,7 +103,7 @@
 #if (LWIP_TCP && ((TCP_MAXRTX > 12) || (TCP_SYNMAXRTX > 12)))
   #error "If you want to use TCP, TCP_MAXRTX and TCP_SYNMAXRTX must less or equal to 12 (due to tcp_backoff table), so, you have to reduce them in your lwipopts.h"
 #endif
-#if (LWIP_TCP && TCP_LISTEN_BACKLOG && (TCP_DEFAULT_LISTEN_BACKLOG < 0) || (TCP_DEFAULT_LISTEN_BACKLOG > 255))
+#if (LWIP_TCP && TCP_LISTEN_BACKLOG && (TCP_DEFAULT_LISTEN_BACKLOG < 0) || (TCP_DEFAULT_LISTEN_BACKLOG > 0xff))
   #error "If you want to use TCP backlog, TCP_DEFAULT_LISTEN_BACKLOG must fit into an u8_t"
 #endif
 #if (LWIP_IGMP && (MEMP_NUM_IGMP_GROUP<=1))
diff --git a/src/core/mem.c b/src/core/mem.c
index 61139e6e..68d3ab3d 100644
--- a/src/core/mem.c
+++ b/src/core/mem.c
@@ -12,7 +12,7 @@
  * MEM_USE_CUSTOM_POOLS to 1 and create a file "lwippools.h" that includes a list
  * of pools like the this (more pools can be added between _START and _END):
  *
- * /* Define three pools with sizes 256, 512, and 1512 bytes
+ * Define three pools with sizes 256, 512, and 1512 bytes
  * LWIP_MALLOC_MEMPOOL_START
  * LWIP_MALLOC_MEMPOOL(20, 256)
  * LWIP_MALLOC_MEMPOOL(10, 512)
diff --git a/src/core/tcp.c b/src/core/tcp.c
index dbaa8d4f..d8863323 100644
--- a/src/core/tcp.c
+++ b/src/core/tcp.c
@@ -347,6 +347,7 @@ tcp_listen_with_backlog(struct tcp_pcb *pcb, u8_t backlog)
 {
   struct tcp_pcb_listen *lpcb;
 
+  LWIP_UNUSED_ARG(backlog);
   LWIP_ERROR("tcp_listen: pcb already connected", pcb->state == CLOSED, return NULL);
 
   /* already listening? */
diff --git a/src/include/lwip/api_msg.h b/src/include/lwip/api_msg.h
index e755d735..1691a889 100644
--- a/src/include/lwip/api_msg.h
+++ b/src/include/lwip/api_msg.h
@@ -148,8 +148,8 @@ void do_join_leave_group( struct api_msg_msg *msg);
 void do_gethostbyname(void *arg);
 #endif /* LWIP_DNS */
 
-struct netconn* netconn_alloc_with_proto_and_callback(
-  enum netconn_type t, u8_t proto,
+struct netconn* netconn_alloc(
+  enum netconn_type t,
   void (*callback)(struct netconn *, enum netconn_evt, u16_t len));
 
 #ifdef __cplusplus