Microsoft KB Archive/216862

= PRB: Access Violation on Chat Server During Callback Registration =

Article ID: 216862

Article Last Modified on 3/4/2004

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APPLIES TO


 * Microsoft Exchange Server 5.5 Standard Edition

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This article was previously published under Q216862



SYMPTOMS
During the callback registration for an Extension Filter to Microsoft Exchange Chat Server, calls to the AddServerEvents and AddChannelEvents methods of the IChatRegistrar object may result in an access violation.

NOTE: The access violation is caught by the Chat Server. To detect an access violation, the Extension Filter must install its own exception handler.



CAUSE
During callback registration, the Chat Server modifies the string parameters that are passed to the methods of the IChatRegistrar object. If the string parameters are hard-coded in the Extension Filter, the buffer that is passed to the Chat Server is marked read-only. When the Chat Server attempts to modify this buffer, it generates an access violation.



RESOLUTION
To avoid this problem, copy the registration string to a temporary buffer, and pass the buffer to the IChatRegistrar object. The following code sample registers the OnNewUser and OnCloseUser events properly: STDMETHODIMP CMyExtension::Init(IChatServer *pServer,                                IChatRegistrar* pRegistrar,                                 long *Result) {  long     nResult; wchar_t sServerEvent[512] = { 0 }; wcscpy(sServerEvent, L"OnNewUser,OnCloseUser");

__try {     pRegistrar->AddServerEvent(sServerEvent, &nResult); if(nResult != 0) OutputDebugString("AddServerEvent failed!\n"); }  __except(TRUE) {     OutputDebugString("Aiiiieeee\n"); }

*pResult = nResult; return S_OK; }



Steps to Reproduce Behavior
The following sample code to register the OnNewUser and OnCloseUser events causes an access violation:

STDMETHODIMP CMyExtension::Init(IChatServer *pServer,                                IChatRegistrar* pRegistrar,                                 long *Result) {  long     nResult;

__try {     pRegistrar->AddServerEvent(L"OnNewUser,OnCloseUser", &nResult); if(nResult != 0) OutputDebugString("AddServerEvent failed!\n"); }  __except(TRUE) {     OutputDebugString("Aiiiieeee\n"); }

*Result = nResult; return S_OK; }

