I think I'm close and I bet the solution is something stupid.

I have a C++ native DLL where I define the following function:

DllExport bool __stdcall Open(const char* filePath, int *numFrames, void** data);
{
  //creates the list of arrays here... don't worry, lifetime is managed somewhere else

  //foreach item of the list:
  {
      BYTE* pByte = GetArray(i);

      //here's where my problem lives
      *(data + i * sizeofarray) = pByte;
  }
  *numFrames = total number of items in the list
  return true;
}

Basically, given a file path, this function creates a list of byte arrays (BYTE*) and should return a list of pointers via the data param. Each pointing to a different byte array.

I want to pass an array of IntPtr from C# and be able to marshal each individual array in order. Here's the code I'm using:

    [DllImport("mydll.dll",EntryPoint = "Open")]
    private static extern bool MyOpen(
      string filePath, out int numFrames, out IntPtr[] ptr);

    internal static bool Open(
      string filePath, out int numFrames, out Bitmap[] images)
    {
        var ptrList = new IntPtr[512];

        MyOpen(filePath, out numFrames, out ptrList);

        images = new Bitmap[numFrames];
        var len = 100; //for sake of simplicity
        for (int i=0; i<numFrames;i++)
        {
            var buffer = new byte[len];
            Marshal.Copy(ptrList[i], buffer, 0, len);

            images[i] = CreateBitmapFromBuffer(buffer, height, width);
        }

        return true;
    }

Problem is in my C++ code. When I assign *(data + i * sizeofarray) = pByte; it corrupts the array of pointers... what am I doing wrong?