Pass an array of double with a pointer as argument-CodePudding

I want to fill an array of doubles from a pointer and then pass the entire array to a C# function.

I declare and initialize the array in the main script as:

double values[3];
for (uint32_t index = 0; index < 3; index  )
{
    std::cout << "[EXE] Set the value for ";
    std::cin >> values[index];
}

setValuesFcn(values); // Call the function passing the pointer

I pass the pointer because on my header I declare the function as bool setValuesFcn(double* values);

The implementation of the function (here is where I have the problem) is:

bool setValuesFcn(double *values)
{
    array<double>^ setValues;

    std::cout << "[DLL] Entering into setMultipleSignals()... " << std::endl;

    for (uint32_t index = 0 ; index < 3; index  )
    {
        setValues[index] = values[index];   // ERROR HERE!
        std::cout << "[DLL] Value[" << index << "]: " << setValues[index] << std::endl;
    }
    if (!veristand_wrapper_cs::VeriStand_dll::SetMultipleSignals(setValues))
        return true;
    else
        return false;
}

I receive an error of System.NullReferenceException that says: Object reference not set to an instance of an object.

I have tried to only print the values with std::cout << "[DLL] Value[" << index << "]: " << values[index] << std::endl; and it works, so my function is able to know the data with a pointer as argument.

Is it possible that the error is due to trying to assign the values of double[] to one of array^? In this case... Is there any solution?

PD: I need that the array that I am trying to fill is of type array<double>^ because the function SetMultipleSignals is allocated in a C# DLL that I have implemented and it expects to get this type of data. The declaration of this function is public static bool SetMultipleSignals(double[] values)

CodePudding user response：

You never instantiated setValues.

values is a stack-allocated array, but setValues is a ^-pointer, which is a pointer to memory allocated and managed by the runtime. Except, you never allocated that memory and the pointer is null, so trying to dereference it gives you a NullReferenceException.

You need:

array<double>^ setValues = gcnew array<double>(3);

See How to: Use Arrays in C /CLI.

One big clue is that you got an exception from the CLR, which means the error was accessing a managed object, and values is unmanaged, so the error can't be with accessing values. Another clue is that you never specified the capacity for setValues anywhere