[boost] Statechart bug? [Fwd: [Boost-users] [statechart] Template States, Compile Error]

From: David Greene (greened_at_[hidden])
Date: 2006-02-27 14:59:25

Forwarding because this might be a library bug.  I can't figure
out why these error messages are generated.

                          -Dave


attached mail follows:

The attached testcase doesn't compile with g++ 4.0.2 or g++ 3.2.3.
The compiler generates a series of error messages like this:

boost/statechart/simple_state.hpp:189: error: no type named
'inner_context_type' in 'struct Test::NormalMode<int>'

I hastily sketched this out based on a larger code.  If there
are typos or other mistakes, let me know but the main problem I'm
trying to solve is the "no type named" problem.  I typedef it
right in the template definition for NormalMode!

This is using the current CVS for statechart, 1.33.1 for mpl.

Is it possibly a compiler bug?

Thanks!

                             -Dave

----------------
Testcase

#include <boost/statechart/state_machine.hpp>
#include <boost/statechart/simple_state.hpp>
#include <boost/statechart/event.hpp>
#include <boost/statechart/custom_reaction.hpp>
#include <boost/statechart/state.hpp>
#include <boost/statechart/transition.hpp>
#include <boost/mpl/list.hpp>

#include <iostream>

// Switch finite state machine for multiplexor schedule policy
namespace Test {
   namespace sc = boost::statechart;
   namespace mpl = boost::mpl;

   // Inner states
   template <typename Type> struct On;
   template <typename Type> struct Off;

   template <typename Type> struct Error;

   // Outer states
   template <typename Type> struct NormalMode;
   template <typename Type> struct ErrorMode;

   // Events
   struct End : public sc::event<End> {};

   struct UnconsumedEvent : public sc::event<UnconsumedEvent> {
         std::string st;
         UnconsumedEvent(const std::string &s) : st(s) {};
        
         const std::string &state(void) const { return(st); };
   };

   template<typename Derived, typename Type>
   struct SwitchEvent : public sc::event<Derived> {
         typedef Type value_type;

         value_type ev;

         SwitchEvent(value_type e) : ev(e) {};

         value_type value(void) const { return(ev); }
   };

   template<typename Type>
   struct TurnOn : public SwitchEvent<TurnOn<Type>, Type> {
         TurnOn(Type value) : SwitchEvent<TurnOn<Type>, Type>(value) {};
   };

   template<typename Type>
   struct TurnOff : public SwitchEvent<TurnOff<Type>, Type> {
         TurnOff(Type value) : SwitchEvent<TurnOff<Type>, Type>(value) {};
   };

   template<typename Type> struct Switch;

   namespace detail {
      template<typename Type>
      struct typedefs {
            typedef Type value_type;
        
            typedef Switch<value_type> switch_context;
        
            typedef TurnOn<value_type> turn_on;
            typedef TurnOff<value_type> turn_off;

            typedef On<value_type> on;
            typedef Off<value_type> off;
      };
   };

   // The state machine
   template<typename Type>
   struct Switch :
         public sc::state_machine<Switch<Type>,
                                  NormalMode<Type> >,
         public detail::typedefs<Type>
   {
         typedef sc::state_machine<Switch<Type>,
                                   NormalMode<Type> > Base;
         typedef Switch<Type> This;

         std::string state(void) const {
            if (this->template state_cast<const typename This::on *>()) {
               return("ON");
            }
            else if (this->template state_cast<const typename This::off *>()) {
               return("OFF");
            }
            else {
               std::cerr << "Unknown state" << std::endl;
               std::abort();
               return("ERROR");
            }
         };

         // Abort on unexpected events
         void unconsumed_event(const sc::event_base &event)
         {
            std::cerr << "Unexpected event in state " << state() << std::endl;
            std::abort();
            this->post_event(new UnconsumedEvent(state()));
         };
   };

   // Define states

   // Outer
   template<typename Type>
   struct NormalMode : public sc::simple_state<NormalMode<Type>,
                                               Switch<Type>,
                                               Off<Type> >,
                       public detail::typedefs<Type> {
         typedef sc::simple_state<NormalMode<Type>,
                                  Switch<Type>,
                                  Off<Type> >
         state_base;
        
         typedef typename state_base::inner_context_type inner_context_type;
   };

   template<typename Type>
   struct ErrorMode : public sc::simple_state<ErrorMode<Type>,
                                              Switch<Type>,
                                              Error<Type> >,
                      public detail::typedefs<Type> {
         typedef sc::simple_state<ErrorMode<Type>,
                                  Switch<Type>,
                                  Error<Type> >
         state_base;

         typedef typename state_base::inner_context_type inner_context_type;
   };

   // Inner
   template<typename Type>
   struct Off : public sc::simple_state<Off<Type>,
                                        NormalMode<Type> >,
                public detail::typedefs<Type> {
         typedef Off<Type> This;
        
         typedef mpl::list<
            sc::custom_reaction<typename This::on>,
            sc::custom_reaction<End>
	 > reactions;

         sc::result react(const typename This::on &) {
            this->template context<typename
This::switch_context>().transit("OFF", "ON");
            return(this->template transit<typename This::on>());
         };

         sc::result react(const End &) {
            this->terminate();
         };
   };

   template<typename Type>
   struct On : public sc::simple_state<On<Type>,
                                       NormalMode<Type> >,
               public detail::typedefs<Type> {
         typedef On<Type> This;

         typedef mpl::list<
            sc::custom_reaction<typename This::off>,
            sc::custom_reaction<End>
	 > reactions;

         sc::result react(const typename This::off &) {
            this->template context<typename
This::switch_context>().transit("ON", "OFF");
            return(this->template transit<typename This::off>());
         };

         sc::result react(const End &) {
            this->terminate();
         };
   };

   template<typename Type>
   struct Error : sc::simple_state<Error<Type>,
                                   ErrorMode<Type> >,
                  public detail::typedefs<Type> {
   };
};

int main(void)
{
   Test::Switch<int> machine;

   machine.initiate();

   machine.process_event( Test::TurnOn<int>(0) );
   std::cout << "Now in state " << machine.state() << std::endl;
   machine.process_event( Test::TurnOff<int>(0) );
   std::cout << "Now in state " << machine.state() << std::endl;
   machine.process_event( Test::TurnOff<int>(0) );  // Should produce error
   std::cout << "Now in state " << machine.state() << std::endl;

   machine.process_event( Test::End() );
}
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