Fix MISRA violations (#110)

* Fix MISRA C-2012 Directive 4.6

* Suppress MISRA C-2012 Rule 11.3

* Suppress MISRA C-2012 Rule 8.7

* Suppress MISRA C-2012 Rule 8.9

* Suppress MISRA C-2012 Rule 8.13

* Fix MISRA C-2012 Rule 8.9

* Fix formatting

MISRA.md

@@ -23,4 +23,17 @@ Deviations from the MISRA standard are listed below:
 | Rule 8.13 | Advisory | Functions that are passed as pointers to coreMQTT or the agent must exactly match function signatures with the pointer type definition, so `const` modifiers cannot be added even if a specific function implementation does not modify a given parameter. |
 
 ### Suppressed with Coverity Comments
-*None.*
+To find the deviation references in the source files run grep on the source code
+with ( Assuming rule 11.3 violation; with justification in point 1 ):
+```
+grep 'MISRA Ref 11.3.1' . -rI
+```
+#### Rule 11.3
+
+_Ref 11.3.1_
+
+- MISRA C-2012 Rule 11.3 states that a cast shall not be performed between a pointer to
+  to object type and a pointer to a different object type. In this library, the MQTT stack
+  processes data as byte stream, requiring casting to specific data structure. However this
+  casting is safe because the buffers are aligned to a 4-byte boundaries, ensuring  that no
+  unaligned memory access occurs.

source/core_mqtt_agent.c

@@ -51,21 +51,6 @@
 
 /*-----------------------------------------------------------*/
 
-#if ( MQTT_AGENT_USE_QOS_1_2_PUBLISH != 0 )
-
-/**
- * @brief Array used to maintain the outgoing publish records and their
- * state by the coreMQTT library.
- */
-    static MQTTPubAckInfo_t pOutgoingPublishRecords[ MQTT_AGENT_MAX_OUTSTANDING_ACKS ];
-
-/**
- * @brief Array used to maintain the incoming publish records and their
- * state by the coreMQTT library.
- */
-    static MQTTPubAckInfo_t pIncomingPublishRecords[ MQTT_AGENT_MAX_OUTSTANDING_ACKS ];
-#endif
-
 /**
  * @brief Track an operation by adding it to a list, indicating it is anticipating
  * an acknowledgment.
@@ -562,9 +547,9 @@ static MQTTStatus_t processCommand( MQTTAgentContext_t * pMqttAgentContext,
 
     if( pCommand != NULL )
     {
-        assert( ( unsigned int ) pCommand->commandType < ( unsigned int ) NUM_COMMANDS );
+        assert( ( uint32_t ) pCommand->commandType < ( uint32_t ) NUM_COMMANDS );
 
-        if( ( unsigned int ) pCommand->commandType < ( unsigned int ) NUM_COMMANDS )
+        if( ( uint32_t ) pCommand->commandType < ( uint32_t ) NUM_COMMANDS )
         {
             commandFunction = pCommandFunctionTable[ pCommand->commandType ];
             pCommandArgs = pCommand->pArgs;
@@ -657,6 +642,9 @@ static MQTTAgentContext_t * getAgentFromMQTTContext( MQTTContext_t * pMQTTContex
     MQTTAgentContext_t ctx = { 0 };
     ptrdiff_t offset = ( ( uint8_t * ) &( ctx.mqttContext ) ) - ( ( uint8_t * ) &ctx );
 
+    /* MISRA Ref 11.3.1 [Misaligned access] */
+    /* More details at: https://github.com/FreeRTOS/coreMQTT-Agent/blob/main/MISRA.md#rule-113 */
+    /* coverity[misra_c_2012_rule_11_3_violation] */
     return ( MQTTAgentContext_t * ) &( ( ( uint8_t * ) pMQTTContext )[ 0 - offset ] );
 }
 
@@ -987,6 +975,18 @@ MQTTStatus_t MQTTAgent_Init( MQTTAgentContext_t * pMqttAgentContext,
 {
     MQTTStatus_t returnStatus;
 
+    /**
+     * @brief Array used to maintain the outgoing publish records and their
+     * state by the coreMQTT library.
+     */
+    static MQTTPubAckInfo_t pIncomingPublishRecords[ MQTT_AGENT_MAX_OUTSTANDING_ACKS ];
+
+    /**
+     * @brief Array used to maintain the outgoing publish records and their
+     * state by the coreMQTT library.
+     */
+    static MQTTPubAckInfo_t pOutgoingPublishRecords[ MQTT_AGENT_MAX_OUTSTANDING_ACKS ];
+
     if( ( pMqttAgentContext == NULL ) ||
         ( pMsgInterface == NULL ) ||
         ( pTransportInterface == NULL ) ||

tools/coverity/misra.config

@@ -32,6 +32,14 @@
             "deviation": "Rule 3.1",
             "reason": "Allow nested comments. Documentation blocks contain comments for example code."
         },
+        {
+            "deviation": "Rule 8.7",
+            "reason": "API functions are not used by the library outside of the files they are defined; however, they must be externally visible in order to be used by an application."
+        },
+        {
+            "deviation": "Rule 8.13",
+            "reason": "Allow to not to use const-qualified type for callback function."
+        },
         {
             "deviation": "Rule 11.5",
             "reason": "Allow casts from void *. Contexts are passed as void * and must be cast to the correct data type before use."