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When multiple clients are concurrently accessing an out of process COM server, client calls may fail unexpectedly. Debugging the server during such failures shows that the server is throwing exception 0xEFFFFFFF.
Recognizing this problem can be difficult because both the client and the server applications may continue running. In particular, this exception does not directly result in causing of the server or the client to stop responding (hang) or a crash.
Rather, the server simply returns a failure to the client. Whether the client continues functioning correctly after such a failure will depend entirely on how the client software is written. Well behaved client applications may silently retry the operation or log an error without being otherwise adversely affected. Clients that do not take care to check the return status of their function calls may experience access violations or other fatal errors.
To confirm whether this problem is the cause of a specific failure, it is necessary to debug the server application, set the debugger to break on this exception, and compare the resultant stack to the one below:
RPCRT4! RpcRaiseException@4 + 49 bytes OLE32! ThreadInvoke(struct _RPC_MESSAGE *) + 524 bytes RPCRT4! DispatchToStubInC@12 + 52 bytes RPCRT4! RPC_INTERFACE::DispatchToStubWorker(struct _RPC_MESSAGE *, unsigned int,long *) + 292 bytes RPCRT4! RPC_INTERFACE::DispatchToStub(struct _RPC_MESSAGE *, unsigned int,long *) + 93 bytes RPCRT4! RPC_INTERFACE::DispatchToStubWithObject(struct _RPC_MESSAGE *, class RPC_UUID *,unsigned int,long *) + 176 bytes RPCRT4! WMSG_SASSOCIATION::DealWithRequestMessage(union _WMSG_MESSAGE *, union _WMSG_MESSAGE *,struct _RPC_MESSAGE *, class WMSG_SBINDING * *,unsigned int,int,int,int) + 826 bytes RPCRT4! WMSG_ADDRESS::HandleRequest(union _WMSG_MESSAGE *, class WMSG_SASSOCIATION *,struct _RPC_MESSAGE *, class WMSG_ENDPOINT *,int,int) + 146 bytes RPCRT4! WMSG_ADDRESS::DealWithWMSGRequest(union _WMSG_MESSAGE *, class WMSG_ENDPOINT * *,struct HWND__ * *, class WMSG_ASSOCIATION *,union _WMSG_MESSAGE * *) + 734 bytes RPCRT4! WMSG_ADDRESS::ReceiveLotsaCalls(void) + 837 bytes RPCRT4! RecvLotsaCallsWrapper(class WMSG_ADDRESS *) + 9 bytes RPCRT4! BaseCachedThreadRoutine(class CACHED_THREAD *) + 156 bytes RPCRT4! ThreadStartRoutine(class THREAD *) + 23 bytes KERNEL32! 77f04f44()
The OLE functions handling typelib marshaling are not completely multithread safe, resulting in a narrow window of opportunity for the exception to take place if two or more clients are making concurrent calls to the server.
To resolve this problem, obtain the latest service pack for Windows NT 4.0 or the individual software update. For information on obtaining the latest service pack, please go to:
Microsoft has confirmed this to be a problem in Windows NT version 4.0. This problem was first corrected in Windows NT 4.0 Service Pack 5.