Fix #1189, fix compiler warnings

Corrects two false alarms about uninitialized vars and another
cast-align warning on the raspbian toolchain (gcc 4.9.3) or
other older versions of gcc (e.g. RHEL/CentOS 7).

- Promotes the CFE_SBR_INVALID_ROUTE_ID constant from the private
  cfe_sbr_priv.h header to the public cfe_sbr.h header (where the
  type itself is defined).
- Pre-Initialize local stack variables that store outputs from other
  functions (avoids false warning about use-before-init).
- Corrects an alignment warning on ARM.

fsw/cfe-core/src/inc/private/cfe_sbr.h

@@ -38,6 +38,13 @@
 #include "cfe_msg_typedefs.h"
 #include "cfe_platform_cfg.h"
 
+/*
+ * Macro Definitions
+ */
+
+/** \brief Invalid route id */
+#define CFE_SBR_INVALID_ROUTE_ID ((CFE_SBR_RouteId_t) {.RouteId = 0})
+
 /******************************************************************************
  * Type Definitions
  */

fsw/cfe-core/src/sb/cfe_sb_api.c

@@ -1397,6 +1397,7 @@ int32  CFE_SB_TransmitMsg(CFE_MSG_Message_t *MsgPtr, bool IncrementSequenceCount
 
     PendingEventID = 0;
     BufDscPtr = NULL;
+    RouteId = CFE_SBR_INVALID_ROUTE_ID;
 
     Status = CFE_SB_TransmitMsgValidate(MsgPtr, &MsgId, &Size, &RouteId);
 
@@ -1886,6 +1887,7 @@ int32  CFE_SB_ReceiveBuffer(CFE_SB_Buffer_t **BufPtr,
     BufDscPtr = NULL;
     DestPtr = NULL;
     BufDscSize = 0;
+    RcvStatus = OS_SUCCESS;
 
     /*
      * Check input args and see if any are bad, which require

fsw/cfe-core/src/sb/cfe_sb_priv.c

@@ -536,15 +536,7 @@ void CFE_SB_RemoveDestNode(CFE_SBR_RouteId_t RouteId, CFE_SB_DestinationD_t *Nod
 int32 CFE_SB_ZeroCopyReleaseAppId(CFE_ES_AppId_t AppId)
 {
     CFE_SB_BufferLink_t *NextLink;
-
-    /* Using a union type permits promotion of CFE_SB_BufferLink_t* to CFE_SB_BufferD_t*
-     * without violating aliasing rules or alignment rules.  Note that the first element
-     * of CFE_SB_BufferD_t is a CFE_SB_BufferLink_t, which makes this possible. */
-    union LocalBufDesc
-    {
-        CFE_SB_BufferLink_t As_Link;
-        CFE_SB_BufferD_t    As_Dsc;
-    } *BufPtr;
+    CFE_SB_BufferD_t    *DscPtr;
 
     /*
      * First go through the "ZeroCopy" tracking list and find all nodes
@@ -560,16 +552,18 @@ int32 CFE_SB_ZeroCopyReleaseAppId(CFE_ES_AppId_t AppId)
         while(!CFE_SB_TrackingListIsEnd(&CFE_SB_Global.ZeroCopyList, NextLink))
         {
             /* Get buffer descriptor pointer */
-            BufPtr = (union LocalBufDesc*)NextLink;
+            /* NOTE: casting via void* here rather than CFE_SB_BufferD_t* avoids a false
+             * alignment warning on platforms with strict alignment requirements */
+            DscPtr = (void *)NextLink;
 
             /* Read the next link now in case this node gets moved */
             NextLink = CFE_SB_TrackingListGetNext(NextLink);
 
             /* Check if it is a zero-copy buffer owned by this app */
-            if (CFE_RESOURCEID_TEST_EQUAL(BufPtr->As_Dsc.AppId, AppId))
+            if (CFE_RESOURCEID_TEST_EQUAL(DscPtr->AppId, AppId))
             {
                 /* If so, decrement the use count as the app has now gone away */
-                CFE_SB_DecrBufUseCnt(&BufPtr->As_Dsc);
+                CFE_SB_DecrBufUseCnt(DscPtr);
             }
         }
 

modules/sbr/private_inc/cfe_sbr_priv.h

@@ -31,12 +31,6 @@
  */
 #include "private/cfe_sbr.h"
 
-/*
- * Macro Definitions
- */
-
-/** \brief Invalid route id */
-#define CFE_SBR_INVALID_ROUTE_ID ((CFE_SBR_RouteId_t) {.RouteId = 0})
 
 /******************************************************************************
  * Function prototypes