在析构函数中调用 Inherited IUnknown::Release()

Question

为什么在析构函数中对 IWICImagingFactory 对象调用继承的 IUnknown::Release() 函数会导致对象的虚拟函数表 (__vfptr) 中的每个条目显示“CXX0030：错误：无法计算表达式”？

这是参考我之前发布的一个问题，但我后来意识到问题只发生在析构函数中。在我检查过的其他地方，虚拟函数表似乎都是有效的。但是，一旦进入析构函数，所有条目都会显示 CXX0030 错误，并且尝试调用继承的 IUknown::Release() 失败。

编辑：这里有一些代码来演示：

HRESULT DemoApp::CreateDeviceIndependentResources()
{
HRESULT hr;


hr = D2D1CreateFactory(D2D1_FACTORY_TYPE_SINGLE_THREADED, &mpDirect2DFactory);


if (SUCCEEDED(hr))
{
    hr = CoCreateInstance(
        CLSID_WICImagingFactory,
        NULL,
        CLSCTX_INPROC_SERVER,
        IID_PPV_ARGS(&mpWICFactory)
        );
}

//CoCreateInstance returns S_OK.
//Other unrelated code here.
}

HRESULT DemoApp::CreateDeviceResources()
{
HRESULT hr;
//Other unrelated code here for creating device-dependant resources.
//mpBackgroundBitmap is a ID2D1Bitmap*.
    if(SUCCEEDED(hr))
    {
        hr = LoadBitmapFromFile(
            mpRenderTarget,
            mpWICFactory,
            L".\\background.png",
            0,
            0,
            &mpBackgroundBitmap);
    }
}


//The below LoadBitmapFromFile() code is taken directly from an MSDN sample.
//I didn't write it.

HRESULT DemoApp::LoadBitmapFromFile(
ID2D1RenderTarget *pRenderTarget,
IWICImagingFactory *pIWICFactory,
PCWSTR uri,
UINT destinationWidth,
UINT destinationHeight,
ID2D1Bitmap **ppBitmap
)
{
IWICBitmapDecoder *pDecoder = NULL;
IWICBitmapFrameDecode *pSource = NULL;
IWICStream *pStream = NULL;
IWICFormatConverter *pConverter = NULL;
IWICBitmapScaler *pScaler = NULL;

HRESULT hr = pIWICFactory->CreateDecoderFromFilename(
    uri,
    NULL,
    GENERIC_READ,
    WICDecodeMetadataCacheOnLoad,
    &pDecoder
    );

if (SUCCEEDED(hr))
{
    // Create the initial frame.
    hr = pDecoder->GetFrame(0, &pSource);
}
if (SUCCEEDED(hr))
{

    // Convert the image format to 32bppPBGRA
    // (DXGI_FORMAT_B8G8R8A8_UNORM + D2D1_ALPHA_MODE_PREMULTIPLIED).
    hr = pIWICFactory->CreateFormatConverter(&pConverter);

}


if (SUCCEEDED(hr))
{
    // If a new width or height was specified, create an
    // IWICBitmapScaler and use it to resize the image.
    if (destinationWidth != 0 || destinationHeight != 0)
    {
        UINT originalWidth, originalHeight;
        hr = pSource->GetSize(&originalWidth, &originalHeight);
        if (SUCCEEDED(hr))
        {
            if (destinationWidth == 0)
            {
                FLOAT scalar = static_cast<FLOAT>(destinationHeight) / static_cast<FLOAT>(originalHeight);
                destinationWidth = static_cast<UINT>(scalar * static_cast<FLOAT>(originalWidth));
            }
            else if (destinationHeight == 0)
            {
                FLOAT scalar = static_cast<FLOAT>(destinationWidth) / static_cast<FLOAT>(originalWidth);
                destinationHeight = static_cast<UINT>(scalar * static_cast<FLOAT>(originalHeight));
            }

            hr = pIWICFactory->CreateBitmapScaler(&pScaler);
            if (SUCCEEDED(hr))
            {
                hr = pScaler->Initialize(
                        pSource,
                        destinationWidth,
                        destinationHeight,
                        WICBitmapInterpolationModeCubic
                        );
            }
            if (SUCCEEDED(hr))
            {
                hr = pConverter->Initialize(
                    pScaler,
                    GUID_WICPixelFormat32bppPBGRA,
                    WICBitmapDitherTypeNone,
                    NULL,
                    0.f,
                    WICBitmapPaletteTypeMedianCut
                    );
            }
        }
    }
    else // Don't scale the image.
    { 
        hr = pConverter->Initialize(
            pSource,
            GUID_WICPixelFormat32bppPBGRA,
            WICBitmapDitherTypeNone,
            NULL,
            0.f,
            WICBitmapPaletteTypeMedianCut
            );
    }
}
if (SUCCEEDED(hr))
{

    // Create a Direct2D bitmap from the WIC bitmap.
    hr = pRenderTarget->CreateBitmapFromWicBitmap(
        pConverter,
        NULL,
        ppBitmap
        );
}

SafeRelease(&pDecoder);
SafeRelease(&pSource);
SafeRelease(&pStream);
SafeRelease(&pConverter);
SafeRelease(&pScaler);

return hr;
}

//Now I call SafeRelease() in my destructor and the virtual function table entires are showing the error.
DemoApp::~DemoApp()
{
SafeRelease(&mpDirect2DFactory);
SafeRelease(&mpWICFactory); //here is the problem apparently
SafeRelease(&mpDWriteFactory); 
SafeRelease(&mpRenderTarget);
SafeRelease(&mpBackgroundBitmap);

}

//SafeRelease is defined as:
template<class Interface>
inline void SafeRelease(Interface** ppInterfaceToRelease)
{
if(*ppInterfaceToRelease != NULL)
{
    (*ppInterfaceToRelease)->Release();
    (*ppInterfaceToRelease) = NULL;
        }

}

问题是当我在 WICFactory 对象上调用 SafeRelease() 时，我得到： DemoApp.exe 中 0x0024e135 处的首次机会异常：0xC0000005：读取位置 0x6d5c28f0 时发生访问冲突。 DemoApp.exe 中 0x0024e135 处未处理的异常：0xC0000005：读取位置 0x6d5c28f0 时发生访问冲突。

Answer 1

我最近也为这个问题苦苦挣扎。问题在于，IWICImagingFactory 的创建和释放分别依赖于之前和之后调用的CoInitialize/CoUninitialize。在您的应用程序中，很可能在析构函数中释放 IWICImagingFactory 之前调用 CoUninitialize()，这会导致崩溃。请注意，ID2D1RenderTarget 等似乎不受影响，并且在调用 CoUninitialize() 后仍然可以释放。

从 RunMessageLoop() 或任何位置删除对 CoUninitialize() 的调用，并将其放在析构函数中的释放调用之后，崩溃就会消失。

Answer 2

在构造函数或析构函数内调用虚函数不会调用您假设它将调用的函数。它总是导致调用同一类的函数。

您可以假设在构造函数和析构函数中禁用了虚拟调度。

更合适的说法是：

在执行构造函数或析构函数期间，对运行构造函数或析构函数的对象的虚拟调用的行为就像调用中使用的对象表达式的动态类型等于构造函数或析构函数的类一样。

礼貌：在 C++ Lounge 进行了长时间的讨论，最后，@JohannesSchaublitb 提出了这个恰当的定义，我们大多数人似乎都同意这个定义。