Documentation fixes and additions (#373)

### core_mqtt.h:
- fix MQTT_InitRetransmits example (remove phantom `publishClearAllCallback` so example matches the 3-callback signature);
- fix MQTT_InitStatefulQoS docstring (@p pBuffer -> @p pAckPropsBuf);
- Complete the truncated MQTTStatusNotConnected return-value sentence in `MQTT_CheckConnectStatus`.
- Replace C99 compound literals (&(uint8_t){ MQTT_PACKET_TYPE_* }) in all doc examples with the C90-compatible MQTT_PROP_VALIDATE_* macros across core_mqtt.h (5), core_mqtt_serializer.h (1), MigrationGuide.md (26), and MQTTv5Guide.md (9). The one PUBREL case, which has no matching MQTT_PROP_VALIDATE_* macro, uses MQTT_PROP_NO_VALIDATE.

### README.md:
- Add Thread Safety section documenting the MQTT_PRE_STATE_UPDATE_HOOK / MQTT_POST_STATE_UPDATE_HOOK extension points, with a non-recursive FreeRTOS mutex example (verified: the library does not re-enter a hook-protected region).

### core_mqtt_serializer.h:
- Add an explanatory comment block above the MQTT_PACKET_TYPE_*_VAL file-scope statics explaining why they exist and why the MISRA C:2012 Rule 2.2 / 2.8 deviations are accepted (macros cannot be addressed, MQTT_PROP_VALIDATE_* needs a typed const uint8_t *).
- Add source/include/core_mqtt_config_template.h: a commented-out starter template users can copy as core_mqtt_config.h, covering every tunable documented in core_mqtt_config_defaults.h plus the thread-safety
hooks.

Author: AniruddhaKanhere

MQTTv5Guide.md

@@ -310,7 +310,7 @@ status = MQTTPropertyBuilder_Init(&propBuilder, propBuffer, sizeof(propBuffer));
 // Add session expiry
 uint32_t sessionExpiry = 3600;  // 1 hour
 status = MQTTPropAdd_SessionExpiry(&propBuilder, sessionExpiry,
-                                   &(uint8_t){MQTT_PACKET_TYPE_CONNECT});
+                                   MQTT_PROP_VALIDATE_CONNECT);
 
 // Add user property
 MQTTUserProperty_t userProp = {
@@ -320,7 +320,7 @@ MQTTUserProperty_t userProp = {
     .valueLength = strlen("sensor-001")
 };
 status = MQTTPropAdd_UserProp(&propBuilder, &userProp,
-                              &(uint8_t){MQTT_PACKET_TYPE_CONNECT});
+                              MQTT_PROP_VALIDATE_CONNECT);
 ```
 
 3. **Pass the property builder to API functions:**
@@ -532,7 +532,7 @@ MQTTPropertyBuilder_Init(&pubProps, pubPropsBuf, sizeof(pubPropsBuf));
 
 uint16_t topicAlias = 1;
 MQTTPropAdd_TopicAlias(&pubProps, topicAlias,
-                       &(uint8_t){MQTT_PACKET_TYPE_PUBLISH});
+                       MQTT_PROP_VALIDATE_PUBLISH);
 
 MQTTPublishInfo_t publishInfo = {
     .qos = MQTTQoS1,
@@ -560,10 +560,10 @@ MQTTPropertyBuilder_Init(&pubProps, pubPropsBuf, sizeof(pubPropsBuf));
 
 MQTTPropAdd_ResponseTopic(&pubProps, "response/topic",
                           strlen("response/topic"),
-                          &(uint8_t){MQTT_PACKET_TYPE_PUBLISH});
+                          MQTT_PROP_VALIDATE_PUBLISH);
 
 MQTTPropAdd_CorrelationData(&pubProps, "req-123", strlen("req-123"),
-                            &(uint8_t){MQTT_PACKET_TYPE_PUBLISH});
+                            MQTT_PROP_VALIDATE_PUBLISH);
 
 MQTT_Publish(&context, &publishInfo, packetId, &pubProps);
 
@@ -618,7 +618,7 @@ MQTTPropertyBuilder_Init(&connectProps, connectPropsBuf, sizeof(connectPropsBuf)
 // Set session expiry to 1 hour
 uint32_t sessionExpiry = 3600;
 MQTTPropAdd_SessionExpiry(&connectProps, sessionExpiry,
-                          &(uint8_t){MQTT_PACKET_TYPE_CONNECT});
+                          MQTT_PROP_VALIDATE_CONNECT);
 
 // Connect with session expiry
 MQTT_Connect(&context, &connectInfo, NULL, 1000, &sessionPresent,
@@ -640,7 +640,7 @@ MQTTUserProperty_t deviceId = {
     .valueLength = strlen("sensor-001")
 };
 MQTTPropAdd_UserProp(&pubProps, &deviceId,
-                     &(uint8_t){MQTT_PACKET_TYPE_PUBLISH});
+                     MQTT_PROP_VALIDATE_PUBLISH);
 
 MQTTUserProperty_t timestamp = {
     .pKey = "timestamp",
@@ -649,7 +649,7 @@ MQTTUserProperty_t timestamp = {
     .valueLength = strlen("2024-01-23T10:30:00Z")
 };
 MQTTPropAdd_UserProp(&pubProps, &timestamp,
-                     &(uint8_t){MQTT_PACKET_TYPE_PUBLISH});
+                     MQTT_PROP_VALIDATE_PUBLISH);
 
 MQTT_Publish(&context, &publishInfo, packetId, &pubProps);
 ```
@@ -664,7 +664,7 @@ MQTTPropertyBuilder_Init(&disconnectProps, disconnectPropsBuf,
 
 MQTTPropAdd_ReasonString(&disconnectProps, "Shutting down for maintenance",
                          strlen("Shutting down for maintenance"),
-                         &(uint8_t){MQTT_PACKET_TYPE_DISCONNECT});
+                         MQTT_PROP_VALIDATE_DISCONNECT);
 
 MQTTSuccessFailReasonCode_t reason = MQTT_REASON_DISCONNECT_NORMAL_DISCONNECTION;
 MQTT_Disconnect(&context, &disconnectProps, &reason);

MigrationGuide.md

@@ -407,7 +407,7 @@ static bool eventCallback(
         /* PUBREC is not a terminating packet — the library will send PUBREL next.
          * pReasonCode and pSendPropsBuffer are valid here. */
         *pReasonCode = MQTT_REASON_PUBREL_SUCCESS;
-        MQTTPropAdd_ReasonString( pSendPropsBuffer, "Success", 7, &(uint8_t){ MQTT_PACKET_TYPE_PUBREL } );
+        MQTTPropAdd_ReasonString( pSendPropsBuffer, "Success", 7, MQTT_PROP_NO_VALIDATE );
     }
     else
     {
@@ -613,7 +613,7 @@ size bufLength = sizeof(buf);
 MQTTPropertyBuilder_Init(&connectionProperties, buf, bufLength) ;
 
 uint32_t sessionExpiryInterval = 100 ; // 100ms
-MQTTPropAdd_SessionExpiry(&connectionProperties, sessionExpiryInterval, &(uint8_t){ MQTT_PACKET_TYPE_CONNECT } );
+MQTTPropAdd_SessionExpiry(&connectionProperties, sessionExpiryInterval, MQTT_PROP_VALIDATE_CONNECT );
 
 // Can also use the will properties in a similar way.
 
@@ -713,7 +713,7 @@ MQTTPropertyBuilder_Init(&propertyBuilder,
                         sizeof(propertyBuffer));
 
 // Add subscription identifier property
-MQTTPropAdd_SubscriptionId(&propertyBuilder, 1, &(uint8_t){ MQTT_PACKET_TYPE_SUBSCRIBE } );
+MQTTPropAdd_SubscriptionId(&propertyBuilder, 1, MQTT_PROP_VALIDATE_SUBSCRIBE );
 
 status = MQTT_Subscribe(&mqttContext,
                     subscriptionList,
@@ -810,8 +810,8 @@ MQTTPropertyBuilder_Init(&propertyBuilder,
                         sizeof(propertyBuffer));
 
 // Add publish properties
-MQTTPropAdd_PayloadFormat(&propertyBuilder, 1, &(uint8_t){ MQTT_PACKET_TYPE_PUBLISH } );
-MQTTPropAdd_TopicAlias(&propertyBuilder, 1, &(uint8_t){ MQTT_PACKET_TYPE_PUBLISH } );
+MQTTPropAdd_PayloadFormat(&propertyBuilder, 1, MQTT_PROP_VALIDATE_PUBLISH );
+MQTTPropAdd_TopicAlias(&propertyBuilder, 1, MQTT_PROP_VALIDATE_PUBLISH );
 
 status = MQTT_Publish(&mqttContext,
                     &publishInfo,
@@ -913,7 +913,7 @@ MQTTUserProperty_t userProperty = {
     .pValue = "value",
     .valueLength = strlen("value")
 };
-MQTTPropAdd_UserProp(&propertyBuilder, &userProperty, &(uint8_t){ MQTT_PACKET_TYPE_UNSUBSCRIBE } );
+MQTTPropAdd_UserProp(&propertyBuilder, &userProperty, MQTT_PROP_VALIDATE_UNSUBSCRIBE );
 
 status = MQTT_Unsubscribe(&mqttContext,
                         unsubscribeList,
@@ -983,7 +983,7 @@ MQTTPropertyBuilder_Init(&propertyBuilder,
 MQTTPropAdd_ReasonString(&propertyBuilder,
                         "Normal shutdown",
                         strlen("Normal shutdown"),
-                        &(uint8_t){ MQTT_PACKET_TYPE_DISCONNECT });
+                        MQTT_PROP_VALIDATE_DISCONNECT);
 
 MQTTSuccessFailReasonCode_t reason = MQTT_REASON_DISCONNECT_NORMAL_DISCONNECTION;
 status = MQTT_Disconnect(&mqttContext,
@@ -1083,7 +1083,7 @@ MQTTPropertyBuilder_Init(&willProperties,
                         sizeof(willPropBuffer));
 
 // Add properties as needed
-MQTTPropAdd_SessionExpiry(&connectionProperties, 3600, &(uint8_t){ MQTT_PACKET_TYPE_CONNECT } );
+MQTTPropAdd_SessionExpiry(&connectionProperties, 3600, MQTT_PROP_VALIDATE_CONNECT );
 MQTTPropAdd_WillDelayInterval(&willProperties, 60, NULL );
 
 status = MQTT_GetConnectPacketSize(&connectInfo,
@@ -1179,8 +1179,8 @@ MQTTPropertyBuilder_Init(&publishProperties,
                         sizeof(propBuffer));
 
 // Add publish properties
-MQTTPropAdd_TopicAlias(&publishProperties, 1, &(uint8_t){ MQTT_PACKET_TYPE_PUBLISH } );
-MQTTPropAdd_PayloadFormat(&publishProperties, 1, &(uint8_t){ MQTT_PACKET_TYPE_PUBLISH } );
+MQTTPropAdd_TopicAlias(&publishProperties, 1, MQTT_PROP_VALIDATE_PUBLISH );
+MQTTPropAdd_PayloadFormat(&publishProperties, 1, MQTT_PROP_VALIDATE_PUBLISH );
 
 // Get max packet size from CONNACK properties
 uint32_t serverMaxPacketSize = pContext->connectionProperties.serverMaxPacketSize; // Value from server
@@ -1274,7 +1274,7 @@ MQTTPropertyBuilder_Init(&subscribeProperties,
                         sizeof(propBuffer));
 
 // Add subscription identifier
-MQTTPropAdd_SubscriptionId(&subscribeProperties, 1, &(uint8_t){ MQTT_PACKET_TYPE_SUBSCRIBE } );
+MQTTPropAdd_SubscriptionId(&subscribeProperties, 1, MQTT_PROP_VALIDATE_SUBSCRIBE );
 
 // Get max packet size from CONNACK properties
 uint32_t serverMaxPacketSize = pContext->connectionProperties.serverMaxPacketSize; // value from server
@@ -1377,7 +1377,7 @@ MQTTUserProperty_t userProperty = {
     .pValue = "value",
     .valueLength = strlen("value")
 };
-MQTTPropAdd_UserProp(&unsubscribeProperties, &userProperty, &(uint8_t){ MQTT_PACKET_TYPE_UNSUBSCRIBE } );
+MQTTPropAdd_UserProp(&unsubscribeProperties, &userProperty, MQTT_PROP_VALIDATE_UNSUBSCRIBE );
 
 // Get max packet size from CONNACK properties
 uint32_t serverMaxPacketSize = pContext->connectionProperties.serverMaxPacketSize; // Value from server
@@ -1455,11 +1455,11 @@ MQTTPropertyBuilder_Init(&disconnectProperties,
                         sizeof(propBuffer));
 
 // Add disconnect properties
-MQTTPropAdd_SessionExpiry(&disconnectProperties, 0, &(uint8_t){ MQTT_PACKET_TYPE_DISCONNECT } );
+MQTTPropAdd_SessionExpiry(&disconnectProperties, 0, MQTT_PROP_VALIDATE_DISCONNECT );
 MQTTPropAdd_ReasonString(&disconnectProperties,
                         "Normal shutdown",
                         strlen("Normal shutdown"),
-                        &(uint8_t){ MQTT_PACKET_TYPE_DISCONNECT } );
+                        MQTT_PROP_VALIDATE_DISCONNECT );
 
 MQTTSuccessFailReasonCode_t reason = MQTT_REASON_DISCONNECT_NORMAL_DISCONNECTION;
 status = MQTT_GetDisconnectPacketSize(&disconnectProperties,
@@ -1587,8 +1587,8 @@ MQTTPropertyBuilder_Init(&willProperties,
                         sizeof(willPropBuffer));
 
 // Add connect properties
-MQTTPropAdd_SessionExpiry(&connectionProperties, 3600, &(uint8_t){ MQTT_PACKET_TYPE_CONNECT } );
-MQTTPropAdd_MaxPacketSize(&connectionProperties, 1024, &(uint8_t){ MQTT_PACKET_TYPE_CONNECT } );
+MQTTPropAdd_SessionExpiry(&connectionProperties, 3600, MQTT_PROP_VALIDATE_CONNECT );
+MQTTPropAdd_MaxPacketSize(&connectionProperties, 1024, MQTT_PROP_VALIDATE_CONNECT );
 
 // Add will properties if using will message
 MQTTPropAdd_WillDelayInterval(&willProperties, 60, NULL );
@@ -1723,9 +1723,9 @@ MQTTPropertyBuilder_Init(&publishProperties,
                         sizeof(propBuffer));
 
 // Add publish properties
-MQTTPropAdd_PayloadFormat(&publishProperties, 1, &(uint8_t){ MQTT_PACKET_TYPE_PUBLISH } );
-MQTTPropAdd_TopicAlias(&publishProperties, 1, &(uint8_t){ MQTT_PACKET_TYPE_PUBLISH } );
-MQTTPropAdd_MessageExpiry(&publishProperties, 3600, &(uint8_t){ MQTT_PACKET_TYPE_PUBLISH } );
+MQTTPropAdd_PayloadFormat(&publishProperties, 1, MQTT_PROP_VALIDATE_PUBLISH );
+MQTTPropAdd_TopicAlias(&publishProperties, 1, MQTT_PROP_VALIDATE_PUBLISH );
+MQTTPropAdd_MessageExpiry(&publishProperties, 3600, MQTT_PROP_VALIDATE_PUBLISH );
 
 // Get remaining length first
 status = MQTT_GetPublishPacketSize(&publishInfo,
@@ -1863,9 +1863,9 @@ MQTTPropertyBuilder_Init(&publishProperties,
                         sizeof(propBuffer));
 
 // Add publish properties
-MQTTPropAdd_PayloadFormat(&publishProperties, 1, &(uint8_t){ MQTT_PACKET_TYPE_PUBLISH } );
-MQTTPropAdd_TopicAlias(&publishProperties, 1, &(uint8_t){ MQTT_PACKET_TYPE_PUBLISH } );
-MQTTPropAdd_MessageExpiry(&publishProperties, 3600, &(uint8_t){ MQTT_PACKET_TYPE_PUBLISH } );
+MQTTPropAdd_PayloadFormat(&publishProperties, 1, MQTT_PROP_VALIDATE_PUBLISH );
+MQTTPropAdd_TopicAlias(&publishProperties, 1, MQTT_PROP_VALIDATE_PUBLISH );
+MQTTPropAdd_MessageExpiry(&publishProperties, 3600, MQTT_PROP_VALIDATE_PUBLISH );
 
 // Get remaining length first
 status = MQTT_GetPublishPacketSize(&publishInfo,
@@ -2003,7 +2003,7 @@ MQTTPropertyBuilder_Init(&subscribeProperties,
                         sizeof(propBuffer));
 
 // Add subscription identifier
-MQTTPropAdd_SubscriptionId(&subscribeProperties, 1, &(uint8_t){ MQTT_PACKET_TYPE_SUBSCRIBE } );
+MQTTPropAdd_SubscriptionId(&subscribeProperties, 1, MQTT_PROP_VALIDATE_SUBSCRIBE );
 
 // Get remaining length first
 status = MQTT_GetSubscribePacketSize(subscriptionList,
@@ -2141,7 +2141,7 @@ MQTTUserProperty_t userProperty = {
 .pValue = "value",
 .valueLength = strlen("value")
 };
-MQTTPropAdd_UserProp(&unsubscribeProperties, &userProperty, &(uint8_t){ MQTT_PACKET_TYPE_UNSUBSCRIBE } );
+MQTTPropAdd_UserProp(&unsubscribeProperties, &userProperty, MQTT_PROP_VALIDATE_UNSUBSCRIBE );
 
 // Get remaining length first
 status = MQTT_GetUnsubscribePacketSize(subscriptionList,
@@ -2242,11 +2242,11 @@ MQTTPropertyBuilder_Init(&disconnectProperties,
                         sizeof(propBuffer));
 
 // Add disconnect properties
-MQTTPropAdd_SessionExpiry(&disconnectProperties, 0, &(uint8_t){ MQTT_PACKET_TYPE_DISCONNECT } );
+MQTTPropAdd_SessionExpiry(&disconnectProperties, 0, MQTT_PROP_VALIDATE_DISCONNECT );
 MQTTPropAdd_ReasonString(&disconnectProperties,
                         "Normal shutdown",
                         strlen("Normal shutdown"),
-                        &(uint8_t){ MQTT_PACKET_TYPE_DISCONNECT } );
+                        MQTT_PROP_VALIDATE_DISCONNECT );
 
 // Get remaining length first
 MQTTSuccessFailReasonCode_t reason = MQTT_REASON_DISCONNECT_NORMAL_DISCONNECTION;

README.md

@@ -105,6 +105,61 @@ connectInfo.userNameLength = USERNAME_STRING_LENGTH;
 mqttStatus = MQTT_Connect( pMqttContext, &connectInfo, NULL, CONNACK_RECV_TIMEOUT_MS, pSessionPresent, NULL, NULL );
 ```
 
+## Thread Safety
+
+coreMQTT is a single-threaded protocol engine: a given `MQTTContext_t` is
+**not** safe to use concurrently from multiple threads. The `MQTT_ProcessLoop`,
+`MQTT_ReceiveLoop`, and publish/subscribe APIs all read and mutate fields in
+the context (timestamps, state records, in-flight packet IDs, etc.) without
+internal locking.
+
+If your application calls coreMQTT APIs from more than one thread — for
+example, an MQTT receive loop in one task and application-originated
+`MQTT_Publish` calls from another — you must serialize access to the context
+yourself. The library provides two extension points for that purpose:
+
+- `MQTT_PRE_STATE_UPDATE_HOOK( pContext )` — invoked immediately before the
+  library reads or writes shared context state.
+- `MQTT_POST_STATE_UPDATE_HOOK( pContext )` — invoked immediately after the
+  corresponding read or write completes.
+
+Both macros expand to nothing by default. Define them in your
+`core_mqtt_config.h` (or via the compiler command line) to acquire and release
+a mutex that protects the context. Sketch for FreeRTOS:
+
+```c
+/* In core_mqtt_config.h */
+#include "FreeRTOS.h"
+#include "semphr.h"
+
+/* Application provides one mutex per MQTT context and stores a pointer to it
+ * reachable from the context — for example, inside the NetworkContext or a
+ * parallel lookup table keyed by pContext. */
+extern SemaphoreHandle_t getMutexForContext( const MQTTContext_t * pContext );
+
+#define MQTT_PRE_STATE_UPDATE_HOOK( pContext ) \
+    ( void ) xSemaphoreTake( getMutexForContext( pContext ), portMAX_DELAY )
+
+#define MQTT_POST_STATE_UPDATE_HOOK( pContext ) \
+    ( void ) xSemaphoreGive( getMutexForContext( pContext ) )
+```
+
+Notes:
+
+- The library calls the hooks in matched pre/post pairs around individual
+  state accesses; it does not re-enter a hook-protected region from inside
+  another one, so a non-recursive mutex is sufficient. A recursive mutex
+  also works if you prefer one for defense in depth.
+- The hooks surround individual state accesses, not whole API calls. If you
+  also need atomicity across a full `MQTT_Publish` invocation from the
+  application's point of view, take a second application-level lock around
+  the API call.
+- On a single-threaded system (for example, cooperative scheduling with one
+  task owning the MQTT stack), leave the hooks undefined.
+- The transport `send` / `recv` callbacks are not called from inside the
+  hooks, so your transport implementation does not need to be reentrant with
+  respect to the mutex.
+
 ## Upgrading to v5.0.0
 
 coreMQTT v5.0.0 adds MQTT v5.0 protocol support with breaking API changes.

source/include/core_mqtt.h

@@ -520,7 +520,7 @@ MQTTStatus_t MQTT_Init( MQTTContext_t * pContext,
  * @param[in] incomingPublishCount Maximum number of records which can be kept in the memory
  * pointed to by @p pIncomingPublishRecords.
  * @param[in] pAckPropsBuf Pointer to memory which will be used to store properties of outgoing publish-ACKS.
- * @param[in] ackPropsBufLength Length of the buffer pointed to by @p pBuffer.
+ * @param[in] ackPropsBufLength Length of the buffer pointed to by @p pAckPropsBuf.
  * @return #MQTTBadParameter if invalid parameters are passed;<br>
  * #MQTTSuccess otherwise.<br>
  *
@@ -637,8 +637,6 @@ MQTTStatus_t MQTT_InitStatefulQoS( MQTTContext_t * pContext,
  * // User defined callback used to clear a particular copied publish packet
  * bool publishClearCallback(struct MQTTContext* pContext,
  *                           uint16_t packetId);
- * // User defined callback used to clear all copied publish packets
- * bool publishClearAllCallback(struct MQTTContext* pContext);
  *
  * MQTTContext_t mqttContext;
  * TransportInterface_t transport;
@@ -678,8 +676,7 @@ MQTTStatus_t MQTT_InitStatefulQoS( MQTTContext_t * pContext,
  * {
  *      status = MQTT_InitRetransmits( &mqttContext, publishStoreCallback,
  *                                                   publishRetrieveCallback,
- *                                                   publishClearCallback,
- *                                                   publishClearAllCallback );
+ *                                                   publishClearCallback );
  *
  *      // Now unacked Publishes can be resent on an unclean session resumption.
  * }
@@ -700,7 +697,7 @@ MQTTStatus_t MQTT_InitRetransmits( MQTTContext_t * pContext,
  *
  * @return #MQTTBadParameter if invalid parameters are passed;
  * #MQTTStatusConnected if the MQTT connection is established with the broker.
- * #MQTTStatusNotConnected if the MQTT connection is broker.
+ * #MQTTStatusNotConnected if the MQTT connection is not established with the broker.
  * #MQTTStatusDisconnectPending if Transport Interface has failed and MQTT connection needs to be closed.
  *
  * <b>Example</b>
@@ -840,7 +837,7 @@ MQTTStatus_t MQTT_CheckConnectStatus( const MQTTContext_t * pContext );
  *
  *   // Set a property in the connectPropsBuilder
  * uint32_t maxPacketSize = 100 ;
- * status = MQTTPropAdd_MaxPacketSize(&connectPropsBuilder, maxPacketSize, &(uint8_t){ MQTT_PACKET_TYPE_CONNECT });
+ * status = MQTTPropAdd_MaxPacketSize(&connectPropsBuilder, maxPacketSize, MQTT_PROP_VALIDATE_CONNECT);
  *
  * // The last will and testament is optional, it will be published by the broker
  * // should this client disconnect without sending a DISCONNECT packet.
@@ -930,7 +927,7 @@ MQTTStatus_t MQTT_Connect( MQTTContext_t * pContext,
  * size_t propertyBufferLength = sizeof( propertyBuffer );
  * status = MQTTPropertyBuilder_Init( &propertyBuilder, propertyBuffer, propertyBufferLength );
  *
- * status = MQTTPropAdd_SubscriptionId(&propertyBuilder, 1, &(uint8_t){ MQTT_PACKET_TYPE_SUBSCRIBE });
+ * status = MQTTPropAdd_SubscriptionId(&propertyBuilder, 1, MQTT_PROP_VALIDATE_SUBSCRIBE);
  *
  * // Obtain a new packet id for the subscription.
  * packetId = MQTT_GetPacketId( pContext );
@@ -1011,7 +1008,7 @@ MQTTStatus_t MQTT_Subscribe( MQTTContext_t * pContext,
  * status = MQTTPropertyBuilder_Init( &propertyBuilder, propertyBuffer, propertyBufferLength );
  *
  * // Set a property in the propertyBuilder
- * status = MQTTPropAdd_PayloadFormat( &propertyBuilder, 1, &(uint8_t){ MQTT_PACKET_TYPE_PUBLISH });
+ * status = MQTTPropAdd_PayloadFormat( &propertyBuilder, 1, MQTT_PROP_VALIDATE_PUBLISH);
  *
  * // Packet ID is needed for QoS > 0.
  * packetId = MQTT_GetPacketId( pContext );
@@ -1130,7 +1127,7 @@ MQTTStatus_t MQTT_Ping( MQTTContext_t * pContext );
  * userProperty.pValue = "value";
  * userProperty.valueLength = strlen( userProperty.pValue );
  *
- * status = MQTTPropAdd_UserProp( &propertyBuilder, &userProperty, &(uint8_t){ MQTT_PACKET_TYPE_UNSUBSCRIBE });
+ * status = MQTTPropAdd_UserProp( &propertyBuilder, &userProperty, MQTT_PROP_VALIDATE_UNSUBSCRIBE);
  *
  * status = MQTT_Unsubscribe( pContext, &unsubscribeList[ 0 ], NUMBER_OF_SUBSCRIPTIONS, packetId, &propertyBuilder );
  *
@@ -1184,7 +1181,7 @@ MQTTStatus_t MQTT_Unsubscribe( MQTTContext_t * pContext,
  * status = MQTTPropertyBuilder_Init( &propertyBuilder, propertyBuffer, propertyBufferLength );
  *
  * // Set a property in the propertyBuilder
- * status = MQTTPropAdd_ReasonString( &propertyBuilder, "Disconnecting", 13, &(uint8_t){ MQTT_PACKET_TYPE_DISCONNECT });
+ * status = MQTTPropAdd_ReasonString( &propertyBuilder, "Disconnecting", 13, MQTT_PROP_VALIDATE_DISCONNECT);
  *
  * MQTTSuccessFailReasonCode_t reason = MQTT_REASON_DISCONNECT_NORMAL_DISCONNECTION;
  * status = MQTT_Disconnect( pContext, &propertyBuilder, &reason );