Make most of functions const correct (#714)

* Make most of the functions const correct

Used clang-tidy and sonarlint to help find places where const could
pretty easily applied. Also lot of hand work.

This commit does not yet touch handlers and typedefs of those.

* Fix Arduino uno handler_who_is() has extra parenthesis

For some reason there is extra parenthesis. Remove it this is more
likely buildable.

* Bugfix/bacapp: Fix uninitilized array_index

We have changed bacapp_snprintf_value() to be const correct. After that
we got

```
/home/runner/work/bacnet-stack/bacnet-stack/src/bacnet/bacapp.c:3183:27: warning: 4th function call argument is an uninitialized value [core.CallAndMessage]
                ret_val = bacapp_snprintf_weeklyschedule(
                          ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
1 warning generated.
```

So analyzer could now spot that we do not actually initilize array_index
at all. Fix this by setting array_index to zero. Note that I actually do
not know if zeroing is right thing to do here. I choose zero as if this
has worked before it is most likely that it will work with zero value.

* cmake: Add and ignore Wwrite-strings compiler option

Wwrite-strings helps find places where const correctness is broken.

Example it will warn about these

```C

void func1(char* str);

func("test") /* "test" is const so we should not pass it to func1().

char* func2()
{
  return "test"; /* func2() should return const char*.
}
```

We still need to ignore it as not all are fixed but let's add it already
so we remember that it should be opened at some point.

---------

Co-authored-by: Kari Argillander <kari.argillander@fidelix.com>

ports/zephyr/bacnet/datalink/ethernet.h

@@ -71,7 +71,7 @@ extern "C" {
 
     BACNET_STACK_EXPORT
     void bacnet_ethernet_set_my_address(
-        BACNET_ADDRESS * my_address);
+        const BACNET_ADDRESS * my_address);
     BACNET_STACK_EXPORT
     void bacnet_ethernet_get_my_address(
         BACNET_ADDRESS * my_address);

ports/zephyr/bip-init.c

@@ -150,7 +150,7 @@ void bip_get_broadcast_address(BACNET_ADDRESS *dest)
  * @param addr - network IPv4 address
  * @return true if the address was set
  */
-bool bip_set_addr(BACNET_IP_ADDRESS *addr)
+bool bip_set_addr(const BACNET_IP_ADDRESS *addr)
 {
     if (addr) {
         memcpy(&BIP_Address.s_addr, &addr->address[0], IP_ADDRESS_MAX);
@@ -180,7 +180,7 @@ bool bip_get_addr(BACNET_IP_ADDRESS *addr)
  * @param addr - network IPv4 address
  * @return true if the address was set
  */
-bool bip_set_broadcast_addr(BACNET_IP_ADDRESS *addr)
+bool bip_set_broadcast_addr(const BACNET_IP_ADDRESS *addr)
 {
     if (addr) {
         memcpy(&BIP_Broadcast_Addr.s_addr, &addr->address[0], IP_ADDRESS_MAX);
@@ -249,7 +249,8 @@ uint8_t bip_get_subnet_prefix(void)
  * @return Upon successful completion, returns the number of bytes sent.
  *  Otherwise, -1 shall be returned and errno set to indicate the error.
  */
-int bip_send_mpdu(BACNET_IP_ADDRESS *dest, uint8_t *mtu, uint16_t mtu_len)
+int bip_send_mpdu(
+    const BACNET_IP_ADDRESS *dest, const uint8_t *mtu, uint16_t mtu_len)
 {
     struct sockaddr_in bip_dest = { 0 };
 
@@ -267,7 +268,7 @@ int bip_send_mpdu(BACNET_IP_ADDRESS *dest, uint8_t *mtu, uint16_t mtu_len)
     /* Send the packet */
     debug_print_ipv4(
         "Sending MPDU->", &bip_dest.sin_addr, bip_dest.sin_port, mtu_len);
-    return zsock_sendto(BIP_Socket, (char *)mtu, mtu_len, 0,
+    return zsock_sendto(BIP_Socket, (const char *)mtu, mtu_len, 0,
         (struct sockaddr *)&bip_dest, sizeof(struct sockaddr));
 }
 
@@ -404,7 +405,7 @@ int bip_send_pdu(BACNET_ADDRESS *dest,
  * @param ifname [in] The named interface to use for the network layer.
  *        Eg, for Linux, ifname is eth0, ath0, arc0, and others.
  */
-void bip_set_interface(char *ifname)
+void bip_set_interface(const char *ifname)
 {
     struct net_if *iface = 0;
     int index = -1;
@@ -492,7 +493,7 @@ void bip_set_interface(char *ifname)
     }
 }
 
-static int createSocket(struct sockaddr_in *sin)
+static int createSocket(const struct sockaddr_in *sin)
 {
     int sock_fd = -1;
     const int sockopt = 1;

ports/zephyr/bip6-init.c

@@ -51,7 +51,7 @@ static char ipv6_addr_str[] = "";
  * @param a - IPv6 address
  * @return Pointer to global string
  */
-static char *inet6_ntoa(struct in6_addr *a)
+static char *inet6_ntoa(const struct in6_addr *a)
 {
 #if CONFIG_BACNETSTACK_LOG_LEVEL
     uint8_t x = 0;
@@ -226,7 +226,7 @@ void bip6_get_my_address(BACNET_ADDRESS *addr)
  *
  * @param addr - network IPv6 address
  */
-bool bip6_set_addr(BACNET_IP6_ADDRESS *addr)
+bool bip6_set_addr(const BACNET_IP6_ADDRESS *addr)
 {
     return bvlc6_address_copy(&BIP6_Addr, addr);
 }
@@ -246,7 +246,7 @@ bool bip6_get_addr(BACNET_IP6_ADDRESS *addr)
  *
  * @param addr - network IPv6 address
  */
-bool bip6_set_broadcast_addr(BACNET_IP6_ADDRESS *addr)
+bool bip6_set_broadcast_addr(const BACNET_IP6_ADDRESS *addr)
 {
     return bvlc6_address_copy(&BIP6_Broadcast_Addr, addr);
 }
@@ -272,7 +272,8 @@ bool bip6_get_broadcast_addr(BACNET_IP6_ADDRESS *addr)
  * @return Upon successful completion, returns the number of bytes sent.
  *  Otherwise, -1 shall be returned and errno set to indicate the error.
  */
-int bip6_send_mpdu(BACNET_IP6_ADDRESS *dest, uint8_t *mtu, uint16_t mtu_len)
+int bip6_send_mpdu(
+    const BACNET_IP6_ADDRESS *dest, const uint8_t *mtu, uint16_t mtu_len)
 {
     struct sockaddr_in6 bvlc_dest = { 0 };
     uint16_t addr16[8];
@@ -302,8 +303,8 @@ int bip6_send_mpdu(BACNET_IP6_ADDRESS *dest, uint8_t *mtu, uint16_t mtu_len)
     LOG_DBG("BIP6: Sending MPDU to %s", ipv6_addr_str);
     /* Send the packet */
     return zsock_sendto(
-        BIP6_Socket, (char *)mtu, mtu_len, 0, (struct sockaddr *)&bvlc_dest,
-        sizeof(bvlc_dest));
+        BIP6_Socket, (const char *)mtu, mtu_len, 0,
+        (struct sockaddr *)&bvlc_dest, sizeof(bvlc_dest));
 }
 
 /**
@@ -333,7 +334,8 @@ int bip6_send_pdu(
  * @param n - size of the buffer
  * @param addr - BACnet/IPv6 address
  */
-static int bvlc6_snprintf_addr(char *s, size_t n, BACNET_IP6_ADDRESS *addr)
+static int bvlc6_snprintf_addr(
+    char *s, size_t n, const BACNET_IP6_ADDRESS *addr)
 {
     uint16_t addr16[8];
 

ports/zephyr/rs485.h

@@ -32,8 +32,8 @@ extern "C" {
     BACNET_STACK_EXPORT
     void RS485_Send_Frame(
         volatile struct mstp_port_struct_t *mstp_port,  /* port specific data */
-        uint8_t * buffer,       /* frame to send (up to 501 bytes of data) */
-        uint16_t nbytes);       /* number of bytes of data (up to 501) */
+        const uint8_t * buffer,     /* frame to send (up to 501 bytes of data) */
+        uint16_t nbytes);           /* number of bytes of data (up to 501) */
 
     BACNET_STACK_EXPORT
     void RS485_Check_UART_Data(