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PRB: CAxWindow Members Can Cause a Memory Leak

Article ID: 229904 - View products that this article applies to.

This article was previously published under Q229904

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SYMPTOMS

The CAxWindow CreateControl() and AttachControl() functions may leak memory if not used correctly.

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CAUSE

The following two techniques of creating ActiveX controls on composite controls (or any window supporting ATL containment) can result in memory leaks.

//Intialize ATL control containment.
AtlAxWinInit();

//Create container window.
HWND hWndCont = m_ax.Create(m_hWnd, rect, 0, WS_CHILD | WS_VISIBLE);

//Create & activate ActiveX control
HRESULT hr = m_ax.CreateControl("MSCAL.Calendar");

-OR-

//Intialize ATL control containment.
AtlAxWinInit();
//Create container window
HWND hWndCont = m_ax.Create(m_hWnd, rect, 0, WS_CHILD | WS_VISIBLE);

// Create ActiveX control.
CComPtr<IUnknown> spunk;
HRESULT hr = CLSIDFromProgID(OLESTR("MSCAL.Calendar"), &clsid);
hr = CoCreateInstance(clsid, NULL, CLSCTX_ALL, IID_IUnknown, (void**)&spunk);

// Activate ActiveX control.
HRESULT hr = m_ax.AttachControl(spunk);

In both techniques, the calls to Create() results in the creation of a CAxHostWindow object. The call to CreateControl() or AttachControl() also creates another CAxHostWindow Object. Upon destruction, the CAxHostWindow object created by Create() is freed.

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