Re: [Boost-users] statechart] [gcc-4.7.2] a template state inherited from statechart::state results in compiler error

Subject: Re: [Boost-users] statechart] [gcc-4.7.2] a template state inherited from statechart::state results in compiler error
From: Nikiforov Anatoly (Anatoly.Nikiforov_at_[hidden])
Date: 2013-01-15 10:16:13

>> I'm using Boost.Statechart and have come across a strange gcc-4.7.2 behavior on the attached sample code. The error is:
>>
>> cpp-lab/boost/statechart/main.cpp:89:23: error: expected ')' before 'ctx'
>>
>> If outermost_context() isn't used in Inner3() constructor and statechart::simple_state is used instead of statechart::state everything is OK.
>> If Inner3 is not a template then everything is OK
>>
>> The problem occurs only if a state template class is inherited from statechart::state.
>>
>> Is there any workaround for the issue?
>
> You can't use unqualified inherited names from within a template, because the compler wouldn't search them in the base.
> Try something like this:
>
> template<class T>
> struct Inner3: public sc::state<Inner3<T>, Active> {
>     Inner3(typename sc::state<Inner3<T>, Active>::my_context ctx):
> sc::state<Inner3<T>, Active>::my_base(ctx)
>     {
>         std::cout << "Inner3(): my outermost_context() is '" <<
> this->outermost_context().name() << "'" << std::endl;
>     }
> 
>     ~Inner3() {
>         std::cout << "~Inner3()"<< std::endl;
>     }
> };

That works. Thanks, lesson learned.