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POCalling Inherited IUnknown::Release() in a destructor
 

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    <p>Why does calling the inherited IUnknown::Release() function on a IWICImagingFactory object in a destructor cause a "CXX0030: Error: expression cannot be evaluated" to be shown each entry in the object's virtual function table (__vfptr)?</p> <p>This is in reference to an earlier question I posted but I've since realized that the problem only occurs in the destructor. The virtual function table appears valid anywhere else I have checked. However, once in the destructor all entries are shown with the CXX0030 error and attempting to call the inherited IUknown::Release() fails.</p> <p>Edit: Here is some code to demonstrate:</p> <pre><code>HRESULT DemoApp::CreateDeviceIndependentResources() { HRESULT hr; hr = D2D1CreateFactory(D2D1_FACTORY_TYPE_SINGLE_THREADED, &amp;mpDirect2DFactory); if (SUCCEEDED(hr)) { hr = CoCreateInstance( CLSID_WICImagingFactory, NULL, CLSCTX_INPROC_SERVER, IID_PPV_ARGS(&amp;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, &amp;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-&gt;CreateDecoderFromFilename( uri, NULL, GENERIC_READ, WICDecodeMetadataCacheOnLoad, &amp;pDecoder ); if (SUCCEEDED(hr)) { // Create the initial frame. hr = pDecoder-&gt;GetFrame(0, &amp;pSource); } if (SUCCEEDED(hr)) { // Convert the image format to 32bppPBGRA // (DXGI_FORMAT_B8G8R8A8_UNORM + D2D1_ALPHA_MODE_PREMULTIPLIED). hr = pIWICFactory-&gt;CreateFormatConverter(&amp;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-&gt;GetSize(&amp;originalWidth, &amp;originalHeight); if (SUCCEEDED(hr)) { if (destinationWidth == 0) { FLOAT scalar = static_cast&lt;FLOAT&gt;(destinationHeight) / static_cast&lt;FLOAT&gt;(originalHeight); destinationWidth = static_cast&lt;UINT&gt;(scalar * static_cast&lt;FLOAT&gt;(originalWidth)); } else if (destinationHeight == 0) { FLOAT scalar = static_cast&lt;FLOAT&gt;(destinationWidth) / static_cast&lt;FLOAT&gt;(originalWidth); destinationHeight = static_cast&lt;UINT&gt;(scalar * static_cast&lt;FLOAT&gt;(originalHeight)); } hr = pIWICFactory-&gt;CreateBitmapScaler(&amp;pScaler); if (SUCCEEDED(hr)) { hr = pScaler-&gt;Initialize( pSource, destinationWidth, destinationHeight, WICBitmapInterpolationModeCubic ); } if (SUCCEEDED(hr)) { hr = pConverter-&gt;Initialize( pScaler, GUID_WICPixelFormat32bppPBGRA, WICBitmapDitherTypeNone, NULL, 0.f, WICBitmapPaletteTypeMedianCut ); } } } else // Don't scale the image. { hr = pConverter-&gt;Initialize( pSource, GUID_WICPixelFormat32bppPBGRA, WICBitmapDitherTypeNone, NULL, 0.f, WICBitmapPaletteTypeMedianCut ); } } if (SUCCEEDED(hr)) { // Create a Direct2D bitmap from the WIC bitmap. hr = pRenderTarget-&gt;CreateBitmapFromWicBitmap( pConverter, NULL, ppBitmap ); } SafeRelease(&amp;pDecoder); SafeRelease(&amp;pSource); SafeRelease(&amp;pStream); SafeRelease(&amp;pConverter); SafeRelease(&amp;pScaler); return hr; } //Now I call SafeRelease() in my destructor and the virtual function table entires are showing the error. DemoApp::~DemoApp() { SafeRelease(&amp;mpDirect2DFactory); SafeRelease(&amp;mpWICFactory); //here is the problem apparently SafeRelease(&amp;mpDWriteFactory); SafeRelease(&amp;mpRenderTarget); SafeRelease(&amp;mpBackgroundBitmap); } //SafeRelease is defined as: template&lt;class Interface&gt; inline void SafeRelease(Interface** ppInterfaceToRelease) { if(*ppInterfaceToRelease != NULL) { (*ppInterfaceToRelease)-&gt;Release(); (*ppInterfaceToRelease) = NULL; } } </code></pre> <p>The problem is when I call SafeRelease() on the WICFactory object, I get: First-chance exception at 0x0024e135 in DemoApp.exe: 0xC0000005: Access violation reading location 0x6d5c28f0. Unhandled exception at 0x0024e135 in DemoApp.exe: 0xC0000005: Access violation reading location 0x6d5c28f0.</p>
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    1. COPost complete but minimal example code that exhibits the problem. Also please clarify your description. It is too hazy.
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      1. USCheers and hth. - Alf
    2. CO-1 the question is hazy and without code, and the OP is explaining it piecemeal in comments instead of fixing it.
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      1. USCheers and hth. - Alf
    3. COI updated the post to include code relevant to the object in question and how I am using it along with a better description of the problem. I would fix it but I don't know how other than to call SafeRelease() outside of the destructor but there seems no reason I should have to as far as I can tell.
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