FIX: Interfaces Not Released by _com_ptr_t::CreateInstance() (200292)


The information in this article applies to:

  • Microsoft Visual C++, 32-bit Enterprise Edition 5.0
  • Microsoft Visual C++, 32-bit Professional Edition 5.0
This article was previously published under Q200292

SYMPTOMS

Smart pointers object creation (using _com_ptr_t::CreateInstance() ) does not release interface pointers to local or remote servers on failure.

RESOLUTION

For local and remote servers, use the CoCreateInstance() API instead of the function, _com_ptr_t::CreateInstance(). Then use the smart pointer wrapper to call methods on the object by calling _com_ptr_t::Attach(). Once the smart pointer goes out of scope, Release() is called for the interface pointer.

STATUS

Microsoft has confirmed that this is a bug in the Microsoft products that are listed at the beginning of this article.

This bug was corrected in Microsoft Visual C++, version 6.0.

MORE INFORMATION

For local and remote servers, call CoCreateInstance() directly, as in the following sample code: 
HRESULT hr = CoCreateInstance(..., ..., IID_IUnknown, (LPVOID*)&pUnk);
if (FAILED(hr))
    //Do error handling.

hr = OleRun(pUnk);

if (FAILED(hr)) {
    pUnk->Release();
    //Do error handling
}

// Query for the required interface, such as IFoo.
hr = pUnk->QueryInterface( IID_IFoo, pFoo);

if (FAILED(hr)) {
    pUnk->Release();
    //Do error handling
}

Once you have the interface, you can use the smart pointer wrapper by calling _com_ptr_t::Attach(), as in the following sample code:
// Declare the smart pointer for the IFoo interface.
IFooPtr m_pFoo;

// Attach the raw interface pointer which you got above
// to the smart pointer wrapper.
m_pFoo.Attach(pFoo);

REFERENCES

(c) Microsoft Corporation 1999, All Rights Reserved. Contributions by Jaganathan Thangavelu, Microsoft Corporation.

Modification Type:MajorLast Reviewed:10/24/2003
Keywords:kbBug kbfix kbVC600fix KB200292
©2003 Microsoft Corporation. All rights reserved.