When compiling the examples (statechart library downloaded from sf 18 Aug), I get the following warnings: <warnings format=edited> /usr/local/boost_1_33_0/boost/statechart/detail/state_base.hpp: In instantiation of `boost::statechart::detail::state_base<std::allocator<void>, boost::statechart::detail::rtti_policy>': /usr/local/boost_1_33_0/boost/statechart/state_machine.hpp:443: instantiated from `boost::statechart::state_machine<Machine, Greeting, std::allocator<void>, boost::statechart::null_exception_translator>' ../main.cpp:12: instantiated from here /usr/local/boost_1_33_0/boost/statechart/detail/state_base.hpp:74: warning: `class boost::statechart::detail::state_base<std::allocator<void>, boost::statechart::detail::rtti_policy>' has virtual functions but non-virtual destructor [snip] /usr/local/boost_1_33_0/boost/statechart/simple_state.hpp:189: instantiated from `boost::statechart::simple_state<Greeting, Machine, boost::mpl::list<mpl_::na, mpl_::na, mpl_::na, mpl_::na, mpl_::na, mpl_::na, mpl_::na, mpl_::na, mpl_::na, mpl_::na, mpl_::na, mpl_::na, mpl_::na,mpl_::na, mpl_::na, mpl_::na, mpl_::na, mpl_::na, mpl_::na, mpl_::na>, has_no_history>' ../main.cpp:14: instantiated from here /usr/local/boost_1_33_0/boost/statechart/detail/leaf_state.hpp:27: warning: `class boost::statechart::detail::leaf_state<std::allocator<void>, boost::statechart::detail::rtti_policy>' has virtual functions but non-virtual destructor </warnings> I changed ~simple_State() and ~state_base() to virtual and the warnings disappeared. However, ~state_base() contains the following annotation: // This destructor is not virtual for performance reasons. The library // ensures that a state object is never deleted through a state_base // pointer but only through a pointer to the most-derived type. ~state_base() {} As a quick, not-definitive check, I built PingPong* with both the virtual and non-virtual dtorS using gcc 3.4.2 on an old i386-redhat-linux machine. The results appear to be the reverse of what I would expect, but I checked to verify that I have the correct result/config correspendence. ..................non-virtual.....virtual PingPongSingle.... 4.08 ..... 3.71 PingPongMulti1.... 6.01997 ..... 5.85999 PingPongMulti2.... 19.53 ..... 19.55 Reminds me of the old joke: "I see fine. I just don't understand what I'm looking at." Two questions: 1) will making the dtorS virtual lead to adverse consequences I simply haven't encountered yet; and 2) can someone help me understand what I did wrong in setting up this test? <extra_credit ot=true my_understanding=faulty> With a well-developed pipelined architecture and a reasonably rich set of addressing operations, shouldn't there be little or no difference between direct and indirect access times - given that the bookeeping normally associated with virtual classes has already been paid for? </extra_credit> Thanks to any/all for help with this. Regards, Dick Bridges "Multithreading is just one damn thing after, before, or simultaneous with another." Scott Meyers and Andrei Alexandrescu