Final managed exception handler in a mixed native/managed executable?

Question

I have an MFC application compiled with /clr and I'm trying to implement a final handler for otherwise un-caught managed exceptions. For native exceptions, overriding CWinApp::ProcessWndProcException works.

The two events suggested in Jeff's CodeProject article, Application.ThreadException and AppDomain.CurrentDomain.UnhandledException, are not raised.

Can anyone suggest a way to provide a final managed exception handler for a mixed executable?

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Update:

It appears that these exception handlers are only triggered downstream of Application.Run or similar (there's a worker thread flavor, can't remember the name.) If you want to truly globally catch a managed exception you do need to install an SEH filter. You're not going to get a System.Exception and if you want a callstack you're going to have to roll your own walker.

In an MSDN forum question on this topic it was suggested to override a sufficiently low-level point of the main MFC thread in a try ... catch (Exception^). For instance, CWinApp::Run. This may be a good solution but I haven't looked at any perf or stability implications. You'll get a chance to log with a call stack before you bail and you can avoid the default windows unahndled exception behavior.

Answer 1

Using those two exception handlers should work. Are you sure you've added them in a place where they're going to be called and properly set (ie, in your application's managed entry point -- you did put one in, right?)

Answer 2

Using those two exception handlers should work.

Why "should?"

The events are not raised using the below:

extern "C" void wWinMainCRTStartup();

// managed entry point
[System::STAThread]
int managedEntry( void )
{
    FinalExceptionHandler^ handler = gcnew FinalExceptionHandler();

    Application::ThreadException += gcnew System::Threading::ThreadExceptionEventHandler(
             handler,
             &FinalExceptionHandler::OnThreadException);

    AppDomain::CurrentDomain->UnhandledException += gcnew UnhandledExceptionEventHandler(
                 handler,
                 &FinalExceptionHandler::OnAppDomainException);

    wWinMainCRTStartup();

    return 0;
}

// final thread exception handler implementation
void FinalExceptionHandler::OnThreadException( Object^ /* sender */, System::Threading::ThreadExceptionEventArgs^ t )
{
    LogWrapper::log->Error( "Unhandled managed thread exception.", t->Exception );
}

// final appdomain exception handler implementation
void FinalExceptionHandler::OnAppDomainException(System::Object ^, UnhandledExceptionEventArgs ^args)
{
    LogWrapper::log->Error( "Unhandled managed appdomain exception.", (Exception^)(args->ExceptionObject) );
}

BOOL CMyApp::InitInstance()
{
    throw gcnew Exception("test unhandled");
    return TRUE;
}

Answer 3

Taking a look around the internets, you'll find that you need to install a filter to get the unmanaged exceptions passing the filters on their way to your AppDomain. From CLR and Unhandled Exception Filters:

The CLR relies on the SEH unhandled exception filter mechanism to catch unhandled exceptions.