The CRTP pattern and member function pointer template parameter

Hi,

I wanted to achieve static polymorphism with the CRTP pattern to
create a base class for encapsulating the thread creation with the
pthread API. What I was trying was:

template<class D, void *(D::*F)()>
class ThreadBase
{
static void *start_routine(void *arg);
};

template<class D, void *(D::*F)()>
void *ThreadBase<D,F>::start_routine(void *arg)
{
    D *pThis = static_cast<D *>(arg);
    return (pThis->*F)();
}

where I could have defined a derived class:

class Derived : public ThreadBase<Derived,&Derived::Run>
{
    void *Run();
};

but it does not work. GCC complains that:

incomplete type `Derived' used in nested name specifier.

Right now, I am blinded with my initial design that does not work so I
would like to ask this newsgroup readers for suggestions about the
best way solve my problem.

As a temporary fix, I am going to remove the second parameter F from
the template ThreadBase and hardcode which member function gets called
like this:

template<class D>
void *ThreadBase<D>::start_routine(void *arg)
{
    D *pThis = static_cast<D *>(arg);
    return pThis->Run();
}

but I find it sad to lose the flexibility to choose at compile time
which member function will be called.

Thank you,
Olivier Langlois
http://www.olivierlanglois.net

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