how to save data into and get data out of mwArray?

I recently compiled a m code into a C++ shared library for the first time. I am trying to call this Matlab-generated code in my C++ project. Then I found this mwArray type which I have zero experience.

_declspec (dllexport) void contourcGenerate(double *c, double *image2DArray, int imageWidth, int imageHeight, double contourLevel)
{
  // Must declare all MATLAB data types after initializing the 
    // application and the library, or their constructors will fail.
    mwArray im(1,imageWidth*imageHeight,mxDOUBLE_CLASS);
    mwArray a(1,1,mxDOUBLE_CLASS);
    mwArray result;
  

  //create the input data
  im.SetData(image2DArray,imageWidth*imageHeight);
  a.SetData(&contourLevel,1);

      // call matlab-generated code
    generateContour(1, result,im,a,a);

  //Get data out 
  result.GetData(c,150);
}

It errors out when calling 'generateContour'. Here is the error code

• First-chance exception at 0x7533C41F: Microsoft C++ exception: MathWorks::mcl::mclUserException at memory location 0x0018F12C.
• First-chance exception at 0x7533C41F: Microsoft C++ exception: MathWorks::mcl::mclUserException at memory location 0x0018F12C.
• First-chance exception at 0x7533C41F: Microsoft C++ exception: [rethrow] at memory location 0x00000000.
• First-chance exception at 0x7533C41F: Microsoft C++ exception: [rethrow] at memory location 0x00000000.
• First-chance exception at 0x7533C41F: Microsoft C++ exception: NullPointerException at memory location 0x0018F27C.
• First-chance exception at 0x7533C41F: Microsoft C++ exception: NullPointerException at memory location 0x0018F27C.
• First-chance exception at 0x7533C41F: Microsoft C++ exception: mwException at memory location 0x0018F2D8.
• First-chance exception at 0x7533C41F: Microsoft C++ exception: mwException at memory location 0x0018F2D8.
• Unhandled exception at at 0x7533C41F: Microsoft C++ exception: mwException at memory location 0x0018F2D8.

I don't know whether this is because I did not use those mwArrays correctly. HELP PLZ.

[Jan]

"it did not work, some memory leak issue" is not precise enough. Please provide all information you know to make answering as easy as possible. Thanks.

[Xiaolei Hu]

I just pasted all the errors into the post. Hopefully that's helpful. Thanks.