Dilema.cpp

template <M>
class AsyncMessageProcessor {
    Handle() = 0;
    ProcessMessage(M m ) {
        // put message in queue
    }
    Thread tread; // thread pop messages from queue and call Handle for each
    
    void Stop() {
        // forbid push
        // clear queue ( optional)
        thread.join() // process left messages
    }
    virtual ~AsyncMessageProcessor() {}
};

class XMessagePtocessor : public AsyncMessageProcessor<XMessage> {
    void Handle(XMessage m) override {
        // do staff
    }
    ~XMessagePtocessor() {
        Stop(); // I would like to avoid explicitely call Stop in ~XMessagePtocessor
    }
}; 

// Preferable usage : 
{
XMessagePtocessor p;
for (XMessage m: messages) {
    p.ProcessMessage(m)
}
} // there code should safely destroy XMessagePtocessor