PRB: Access Violation in GetAmbientDisplayName (190149)
The information in this article applies to:
- The Microsoft Active Template Library (ATL) 3.0, when used with:
- Microsoft Visual C++, 32-bit Enterprise Edition 6.0
- Microsoft Visual C++, 32-bit Professional Edition 6.0
- Microsoft Visual C++, 32-bit Learning Edition 6.0
- Microsoft Visual C++ .NET (2003)
- Microsoft Visual C++ .NET (2002)
This article was previously published under Q190149 SYMPTOMS An Access Violation may occur in GetAmbientDisplayName if
the BSTR parameter passed to it is uninitialized. This is most likely to occur
if the BSTR was declared as a local variable. CAUSE In Visual C++ 6. and Visual C++ .Net, the ATL
implementation of GetAmbientDisplayName assumes that all non-NULL BSTRs are
initialized, and passes them to ::SysFreeString. This assumption can cause
problems because any uninitialized BSTR declared inside a function could be
non-NULL. RESOLUTION Set any uninitialized BSTRs to NULL before calling
GetAmbientDisplayName. STATUS This behavior is by design. MORE INFORMATION The ATL implementation of GetAmbientDisplayName in Visual
C++ 5.0 assumes all BSTRs are uninitialized and does not free memory before
using them, which can cause leaks. Also, no memory is allocated for the BSTR
and the value of the BSTR is set to memory that is then freed, which can cause
access violations.
These problems have been corrected in Visual C++
6.0.
(c) Microsoft Corporation 1998, All Rights Reserved.
Contributions by Kelly Marie Ward, Microsoft Corporation.
| Modification Type: | Major | Last Reviewed: | 9/18/2003 |
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| Keywords: | kbprb KB190149 |
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