P3D v5 Syntax error in data struct C++

[DragonflightDesign]

This is my first attempt at creating and reading a data definition dynamically. It all works well insofar that the data definition is created and that 'RequestDataOnSimObject' is fired off because

if (pObjData->dwRequestID == REQUEST_PAYLOAD_INFO)

gets hit successfully. The syntax problem occurs when trying to get data out of the definition and into a receiving struct - what is a perfectly legal call for a non-dynamic definition is barfing on the dynamic one with a

Error    C2679    binary '=': no operator found which takes a right-hand operand of type 'payloadData' (or there is no acceptable conversion)

It's the very last line in the code below. Stack Overflow has completely failed to give me code that I can cut'n'paste without understanding what's going on. Seriously though, what should I be doing?

// No. of stations
struct payloadStations
{
    double stations;
};
payloadStations pStations;

// Station definition
struct payloadData
{
    float stations[];
};

// Receiving structure
struct payloadInfo
{
    double station1;
    // etc..
};
payloadInfo pStatWeight;

// ----------------------

    if (pObjData->dwRequestID == REQUEST_PAYLOAD_STATIONS)
    {
        int i = 0;
        char station[64] = "";

        payloadStations* pStationData = (payloadStations*)&pObjData->dwData;
        pStations = *pStationData;

        // Create a definition for payload station weights
        if (pStations.stations != 0)
        {
            // Allocate and size the station data structure
            payloadData* pStationData = (payloadData*)malloc(sizeof(float) * pStations.stations);

            // Build the data definition
            for (i = 1; i <= pStations.stations; i++)
            {
                sprintf (station, "PAYLOAD STATION WEIGHT:%d", i);
                hr = SimConnect_AddToDataDefinition(hSimConnect, DEFINE_PAYLOAD_INFO, station, "pounds", SIMCONNECT_DATATYPE_FLOAT64);
            }
            hr = SimConnect_RequestDataOnSimObject(hSimConnect, REQUEST_PAYLOAD_INFO, DEFINE_PAYLOAD_INFO, SIMCONNECT_OBJECT_ID_USER, SIMCONNECT_PERIOD_SECOND, NULL, NULL, NULL, NULL);
        }
    }

    if (pObjData->dwRequestID == REQUEST_PAYLOAD_INFO)
    {
        payloadData* pPData = (payloadData*)&pObjData->dwData;
        pStatWeight = *pPData;     // <--- Syntax error here
    }

Thank you.

 

[WarpD]

payloadData and payloadInfo are not the same. They can not translate. "float stations[]" is an array of undefined size and payloadInfo is a rather strictly defined grouping of doubles. floats are not doubles, thus it would be literally impossible to translate an array of floats of indeterminant size directly to a group of doubles of set size.

Also this line:

payloadData* pStationData = (payloadData*)malloc(sizeof(float) * pStations.stations);

is a memory leak. You declare it, but I don't see it used anywhere, nor is it disposed of.

 

[DragonflightDesign]

Thanks Ed. I spotted the floats/doubles finger trouble after I'd posted. Your comment about the memory leak has just helped me make sense of a Visual Studio tooltip popup - I think I know where to go from here. I was going to dispose it later in the sequence.

[Edit] Yup - problem fixed. Bit of a mess, wasn't it? Definite noob error

 

[WarpD]

I am firmly against declaring a variable "on the fly" in the manner that C/C++ allows. It provides the ability to write some incredibly dumb code flaws that can be insanely difficult to locate.

 

[DragonflightDesign]

I completely agree Ed, for those very reasons. This was a 'first pass' PoC to be tidied up later. I now have tidy code with no 'on-the-fly' declarations that gets all of the payload station weights. And no potential memory leaks