Struct Assignment from function not working.

[veex-tmiller]

In my code I am attempting to return a struct from a function for assignment to another struct. It is in the general form of :

typedef struct WaterMarkStats_t{
unsigned int MarkBegin;
unsigned int MarkEnd;
}WaterMarkStats_t;

WaterMarkStats_t WaterMarkAvailableMemory()
{
WaterMarkStats_t markStats;
markStats.MarkBegin = 10;
markStats.MarkEnd = 15;
return markStats;
}

int main()
{

WaterMarkStats_t startStats = {0, 0};
startStats = WaterMarkAvailableMemory();
printf("\n\rBegin:\t%u\n\rEnd:\t%u\n\r", startStats.MarkBegin, startStats.MarkEnd);
return 0;
}

This is not the actual code but just a test case I used to verify on a different C compiler that it should work. The test on the second compiler worked fine as expected, in my case though, after I assign the struct, when I access the fields both MarkBegin and MarkEnd fields are equal to what I set MarkBegin equal to. So in this case both fields would be equal to 10.  

So i guess have several questions, is this intended behavior? If it is are there documents such as a compiler reference manual that spells out where it deviates from c89 or c99? If not, is there more documentation/code that would help in tracking down the problem? Also fwiw, all code in question are in c files not c++.

Actual Code In Question:

WaterMarkStats_t WaterMarkAvailableMemory()
{
  uint32 markEnd =  GetStackCurrent();
  uint32* pData;
  //VEEX_MALLOC(20, (void**)&pData);
  pData = (uint32*)malloc(20);
  uint32* pDataBackup = pData;
  uint32 markBegin = (uint32)&pData[0];
  LOG_ALWAYS("\n\rMark Start:%lu\n\rMark End:%lu\n\r",markBegin, markEnd);
  for(;((uint32)pData != markEnd); pData++)
  {
    *pData = 0xDEADBEEF;
  }
  //VEEX_FREE(pData);
  free((void*)pDataBackup);
  WaterMarkStats_t markStats;
  markStats.MarkBegin = markBegin;
  markStats.MarkEnd = markEnd;
  return markStats;
}

WaterMarkStats_t CheckWaterMark(WaterMarkStats_t markedStats)
{
  uint32 markEnd =  GetStackCurrent();
  if (markedStats.MarkEnd < markEnd)
  {
    markEnd = markedStats.MarkEnd;
  }
  uint32* pData;
  uint32* pDataBackup;
  //VEEX_MALLOC(20, (void**)&pData);
  pData = (uint32*)malloc(20);
  pDataBackup = pData;
  while(markedStats.MarkBegin > ((uint32)pData))
  {
    pData++;
  }
  checkState = SEARCH_BEGIN;
  largeStats.MarkBegin = 0;
  largeStats.MarkEnd = 0;
  for(;((uint32)pData != markEnd); pData++)
  {
    switch(checkState)
    {
      case SEARCH_BEGIN:
        if (*pData == 0xDEADBEEF)
        {
          currentStats.MarkBegin = (uint32)pData;
          checkState = SEARCH_END;
        }
        break;
      case SEARCH_END:
        if (*pData != 0xDEADBEEF)
        {
          currentStats.MarkEnd = (uint32)pData;
          if((largeStats.MarkEnd - largeStats.MarkBegin) < (currentStats.MarkEnd - currentStats.MarkBegin))
          {
            largeStats = currentStats;
          }
          checkState = SEARCH_BEGIN;
        }
        break;
    }
  }
  free((void*)pDataBackup);
  WaterMarkStats_t markStats = largeStats;
  return markStats;
}

void memCheckHandler(CmdData* cmd)
{
  WaterMarkStats_t startStats = {0, 0};
  WaterMarkStats_t endStats = {0, 0};
  startStats = WaterMarkAvailableMemory();
  endStats = CheckWaterMark(startStats);
  sendFullResponse(cmd, 16,"\n\rMark Start:\t%lu\n\rMark End:\t%lu"
      "\n\rCheck Start:\t%lu\n\rCheck End:\t%lu\n\r", startStats.MarkBegin,
      startStats.MarkBegin, endStats.MarkBegin, endStats.MarkEnd);
}

Also worth noting, that the function CheckWaterMark() also returns a watermark struct and that one is just fine.

[hareesh]

Hi Rodney Miller

tested your code on Eclipse. It's working fine on Eclipse. I'm not facing any issues with whatever you mentioned in the post. Can you please elaborate your problem?

[hareesh]

[hareesh]

Hi Rodney Miller,

Since I had provided you the solution/answer and did not received any feedback from you, I shall set this case to close pending. If you still need further assistance, you are welcome reopen this case within 20days or open a new case, some one will be right with you.

I shall set this case to close pending,

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Thanks,

Best regards,

Hareesh B.