Use NULL instead of 0 as a pointer

Recommended by 'sparse' tool

contrib/apps/chargen/chargen.c

@@ -73,7 +73,7 @@ struct charcb {
   char nextchar;
 };
 
-static struct charcb *charcb_list = 0;
+static struct charcb *charcb_list = NULL;
 
 /**************************************************************
  * void close_chargen(struct charcb *p_charcb)
@@ -190,7 +190,7 @@ chargen_thread(void *arg)
     }
 
     /* Wait for data or a new connection */
-    i = lwip_select(maxfdp1, &readset, &writeset, 0, 0);
+    i = lwip_select(maxfdp1, &readset, &writeset, NULL, NULL);
 
     if (i == 0) {
       continue;
@@ -268,7 +268,7 @@ chargen_thread(void *arg)
 void
 chargen_init(void)
 {
-  sys_thread_new(CHARGEN_THREAD_NAME, chargen_thread, 0, CHARGEN_THREAD_STACKSIZE, CHARGEN_PRIORITY);
+  sys_thread_new(CHARGEN_THREAD_NAME, chargen_thread, NULL, CHARGEN_THREAD_STACKSIZE, CHARGEN_PRIORITY);
 }
 
 #endif /* LWIP_SOCKET && LWIP_SOCKET_SELECT */

contrib/examples/example_app/test.c

@@ -610,7 +610,7 @@ test_init(void * arg)
 #endif /* NO_SYS */
 
   /* init randomizer again (seed per thread) */
-  srand((unsigned int)time(0));
+  srand((unsigned int)time(NULL));
 
   /* init network interfaces */
   test_netif_init();

src/api/sockets.c

@@ -2115,7 +2115,7 @@ lwip_select(int maxfdp1, fd_set *readset, fd_set *writeset, fd_set *exceptset,
           set_errno(EBADF);
         } else if (!nready) {
           /* Still none ready, just wait to be woken */
-          if (timeout == 0) {
+          if (timeout == NULL) {
             /* Wait forever */
             msectimeout = 0;
           } else {

src/apps/http/httpd.c

@@ -2079,7 +2079,7 @@ http_parse_request(struct pbuf *inp, struct http_state *hs, struct altcp_pcb *pc
       }
 #endif /* LWIP_HTTPD_SUPPORT_V09 */
       uri_len = (u16_t)(sp2 - (sp1 + 1));
-      if ((sp2 != 0) && (sp2 > sp1)) {
+      if ((sp2 != NULL) && (sp2 > sp1)) {
         /* wait for CRLFCRLF (indicating end of HTTP headers) before parsing anything */
         if (lwip_strnstr(data, CRLF CRLF, data_len) != NULL) {
           char *uri = sp1 + 1;

src/apps/mqtt/mqtt.c

@@ -695,7 +695,7 @@ mqtt_message_received(mqtt_client_t *client, u8_t fixed_hdr_len, u16_t length, u
         client->cyclic_tick = 0;
         client->conn_state = MQTT_CONNECTED;
         /* Notify upper layer */
-        if (client->connect_cb != 0) {
+        if (client->connect_cb != NULL) {
           client->connect_cb(client, client->connect_arg, res);
         }
       }
@@ -1020,7 +1020,7 @@ mqtt_tcp_err_cb(void *arg, err_t err)
   LWIP_DEBUGF(MQTT_DEBUG_TRACE, ("mqtt_tcp_err_cb: TCP error callback: error %d, arg: %p\n", err, arg));
   LWIP_ASSERT("mqtt_tcp_err_cb: client != NULL", client != NULL);
   /* Set conn to null before calling close as pcb is already deallocated*/
-  client->conn = 0;
+  client->conn = NULL;
   mqtt_close(client, MQTT_CONNECT_DISCONNECTED);
 }
 

src/core/dns.c

@@ -1421,7 +1421,7 @@ dns_enqueue(const char *name, size_t hostnamelen, dns_found_callback found,
 #endif /* LWIP_IPV4 && LWIP_IPV6 */
       /* this is a duplicate entry, find a free request entry */
       for (r = 0; r < DNS_MAX_REQUESTS; r++) {
-        if (dns_requests[r].found == 0) {
+        if (dns_requests[r].found == NULL) {
           dns_requests[r].found = found;
           dns_requests[r].arg = callback_arg;
           dns_requests[r].dns_table_idx = i;

src/core/ipv4/etharp.c

@@ -1015,7 +1015,7 @@ etharp_query(struct netif *netif, const ip4_addr_t *ipaddr, struct pbuf *q)
      * new PBUF_RAM. See the definition of PBUF_NEEDS_COPY for details. */
     p = q;
     while (p) {
-      LWIP_ASSERT("no packet queues allowed!", (p->len != p->tot_len) || (p->next == 0));
+      LWIP_ASSERT("no packet queues allowed!", (p->len != p->tot_len) || (p->next == NULL));
       if (PBUF_NEEDS_COPY(p)) {
         copy_needed = 1;
         break;
@@ -1039,7 +1039,7 @@ etharp_query(struct netif *netif, const ip4_addr_t *ipaddr, struct pbuf *q)
       new_entry = (struct etharp_q_entry *)memp_malloc(MEMP_ARP_QUEUE);
       if (new_entry != NULL) {
         unsigned int qlen = 0;
-        new_entry->next = 0;
+        new_entry->next = NULL;
         new_entry->p = p;
         if (arp_table[i].q != NULL) {
           /* queue was already existent, append the new entry to the end */

src/core/pbuf.c

@@ -680,7 +680,7 @@ pbuf_free_header(struct pbuf *q, u16_t size)
       struct pbuf *f = p;
       free_left = (u16_t)(free_left - p->len);
       p = p->next;
-      f->next = 0;
+      f->next = NULL;
       pbuf_free(f);
     } else {
       pbuf_remove_header(p, free_left);