IPv4/single: some minor comments after the MISRA changes

[htibosch]

Description

• FreeRTOS_DNS.c

Use xReturn and not uxReturn when the variable is signed.
Call memset() to clear the contents of a struct.

I have seen applications crash on such a statement:

-    struct xDNSBuffer xReceiveBuffer = { 0 };
+    struct xDNSBuffer xReceiveBuffer;
+    memset( xReceiveBuffer, 0, sizeof( xReceiveBuffer ) );

because the compile can be mistaken about the alignment.

• FreeRTOS_DNS_Networking.c

Check the return value of FreeRTOS_recvfrom() before assigning it to an unsigned variable:

-    pxReceiveBuffer->uxPayloadLength = FreeRTOS_recvfrom( xDNSSocket, ... );
-    pxReceiveBuffer->uxPayloadSize = pxReceiveBuffer->uxPayloadLength;
+    lResult = FreeRTOS_recvfrom( xDNSSocket, ... );
+    if( lResult > 0 )
+    {
+        pxReceiveBuffer->uxPayloadLength = ( size_t ) lResult;
+        pxReceiveBuffer->uxPayloadSize = pxReceiveBuffer->uxPayloadLength;
+    }

The result of FreeRTOS_recvfrom() must be tested because a negative value indicates an error.

• FreeRTOS_IP_Utils.c

As I commented here, cast a BaseType_t variable to int when using snprintf():

-( void ) snprintf( pcBuffer, uxLength, "Errno %d", xErrnum );
+( void ) snprintf( pcBuffer, uxLength, "Errno %d", ( int ) xErrnum );

• FreeRTOS_IP.h

Let ipFR_TCP_VERSION_NUMBER depend on the other 3 version macros:

-    #define ipFR_TCP_VERSION_NUMBER    "V2.3.999"
     #define ipFR_TCP_VERSION_MAJOR     2
     #define ipFR_TCP_VERSION_MINOR     3
     /* Development builds are always version 999. */
     #define ipFR_TCP_VERSION_BUILD     999
+    #define __VERSION( v1, v2, v3 )    "V" # v1 "." # v2 "." # v3
+    #define _VERSION( v1, v2, v3 )     __VERSION( v1, v2, v3 )
+
+    /* ipFR_TCP_VERSION_NUMBER makes a string like "V2.3.999". */
+    #define ipFR_TCP_VERSION_NUMBER \
+        _VERSION( ipFR_TCP_VERSION_MAJOR, ipFR_TCP_VERSION_MINOR, ipFR_TCP_VERSION_BUILD )

but I think that Aniruddha has a more elegant solution.

I compare today's mainline with the release on 7th of June. Beside a few minor things I think it is all good. Thanks.

By submitting this pull request, I confirm that you can use, modify, copy, and redistribute this contribution, under the terms of your choice.

[AniruddhaKanhere]

Thank you for this PR @htibosch. I have a couple of comments/suggestions. Can you please take a look at that?

[AniruddhaKanhere]

MISRA doesn't like the use of # operator. Ref: Misra c-2012 rule 20.10 (advisory).

Also, these version numbers are updated together - and only when a release happens. Not completely sold on the value added by using the above expression to generate the ipFR_TCP_VERSION_NUMBER string.

[htibosch]

I have cancelled the change to the macro ipFR_TCP_VERSION_NUMBER.

[ActoryOu]

The logic added in DNS_ReadReply is not needed. Removed that part and update the branch.

        if( lResult > 0 )
        {
            pxReceiveBuffer->uxPayloadLength = ( size_t ) lResult;
            pxReceiveBuffer->uxPayloadSize = pxReceiveBuffer->uxPayloadLength;
        }
        else
        {
            pxReceiveBuffer->uxPayloadLength = 0U;
            pxReceiveBuffer->uxPayloadSize = 0U;
        }