FIX: COleDispatchDriver::InvokeHelperV Causes Memory Leaks |
Q124066
The information in this article applies to:
- The Microsoft Foundation Classes (MFC), included with:
- Microsoft Visual C++, version 1.5
SYMPTOMS
Creating a COleDispatchDriver derived class from an automation object's type library for a particular object may result in a memory leak when subsequently calling its member functions. This leak is caused by a bug in the InvokeHelperV member function of the COleDispatchDriver class used by the member functions of the derived class to call the OLE automation object's methods.
CAUSE
COleDispatchDriver::InvokeHelperV function, eventually called by all method member functions, incorrectly calculates the parameter information and will not free memory associated with BSTR (String) parameters. The error is marked below in a small segment taken from the COleDispatchDriver::InvokeHelperV function:
void COleDispatchDriver::InvokeHelperV(DISPID dwDispID, WORD wFlags, VARTYPE vtRet, void* pvRet, const BYTE FAR* pbParamInfo, va_list, argList) { ... // cleanup any arguments that need cleanup if (dispparams.cArgs != 0) { VARIANTARG FAR* pArg = dispparams.rgvarg; // BUG: wrong start address // the correct line included in Visual C++ 1.51: // VARIANTARG FAR* pArg = dispparams.rgvarg + dispparams.cArgs - 1; const BYTE FAR* pb = pbParamInfo; while (*pb != 0) { switch ((VARTYPE)*pb) { case VT_BSTR: VariantClear(pArg); // BUG: wrong address gets passed since // initial calculation was wrong break; ... } ++pArg; // BUG: wrong direction for parameters (they're in reverse order) // the correct line included in Visual C++ 1.51: // --pArg; ++pb; } } .... }
STATUS
Microsoft has confirmed this to be a bug in the Microsoft products listed at the beginning of this article. This bug was corrected in the Microsoft Foundation Classes version 2.51 that was included with Microsoft Visual C++ version 1.51 for Windows.
Additional query words: 1.50 2.50
Keywords : kb16bitonly
Issue type :
Technology : kbAudDeveloper kbMFC
Last Reviewed: May 8, 2001 |