AccessViolationException未处理C＃

Question

我在Warper.dll文件中有以下C ++函数签名

extern "C" DLLEXPORTED unsigned char* UpdateWarp
(int warperId, int x, int y, int *xRet, int *yRet, int *width, int *height, int* scanWidth);

C ++函数

    unsigned char* UpdateWarp(int warperId, int x, int y, 
                int *xRet, int *yRet, int *width, int *height, int* scanWidth)
{
    if(xRet && yRet && width && height && scanWidth)
    {
        Warper* warper = getMapItem<Warper*>(m_warpers, warperId);
        if (warper)
        {
            WarpedImage* warpedImg = warper->UpdateWarp(Point(x, y));
            *xRet = warpedImg->Position.X;
            *yRet = warpedImg->Position.Y;
            *width = warpedImg->Image.Width;
            *height = warpedImg->Image.Height;
            *scanWidth = warpedImg->Image.ScanWidth;

            m_warpedImages[warperId] = warpedImg;

            return warpedImg->Image.Data;
        }
    }
    return NULL;
}

在C＃中我声明为

 [DllImport("Warper.dll", EntryPoint = "UpdateWarp")]
    private static extern IntPtr UpdateWarp(int warperId, int x, int y,
        ref int xRet, ref int yRet, ref int width, ref int height, ref int scanWidth);

并呼叫为

IntPtr ptrRawData = UpdateWarp(m_iWarperId, pt.X, pt.Y, ref x, ref y, ref w, ref h, ref iScanWidth);

执行代码时，它在Debug和Release模式下都会出现 AccessViolationException未处理错误。错误是将值传递给函数我认为不返回值。 可能是什么原因。