Microsoft KB Archive/151491

= FIX: copy Member of _bstr_t in comutl.h Doesn't Copy =

Article ID: 151491

Article Last Modified on 7/5/2005

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APPLIES TO


 * Microsoft Visual C++ 5.0 Enterprise Edition
 * Microsoft Visual C++ 5.0 Professional Edition

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This article was previously published under Q151491



SYMPTOMS
Calling the _bstr_t::copy member function does not return a copy of the contained BSTR and may cause an access violation in OLEAUT32.DLL when debugging. Sample code that demonstrates this bug is included below.



CAUSE
This is due to a bug in the implementation of a helper function of a nested class, _bstr_t::Data_t::Copy. On line 627 of comutil.h the function is passing an uninitialized local variable to ::SysStringByteLen(bstr) instead of passing the member variable, m_wstr.



RESOLUTION
Replace the call to t1.copy with SysAllocString(static_cast(t1)) where t1 is an object of type _bstr_t.



STATUS
Microsoft has confirmed this to be a bug in the Microsoft products listed at the beginning of this article. This bug has been corrected in Visual Studio 97, Service Pack 1.

For additional information about the Visual Studio 97 Service Pack 1, please see the following article in the Microsoft Knowledge Base:

170365 INFO: Visual Studio 97 Service Packs - What, Where, and Why



MORE INFORMATION
By stepping through the following sample code in the debugger, you can see that the string is not copied to t2.

Sample Code
// Compile options needed: /Zi // Libraries needed: oleaut32.lib comsupp.lib #include   #include    int main {     _bstr_t t1 = "Hello"; BSTR t2; t2 = t1.copy; t2 = SysAllocString(static_cast(t1)); // workaround return 0; }

Keywords: kbbug kbfix kbvs97sp1fix kbvs97sp2fix KB151491

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