Re: The CRTP pattern and member function pointer template parameter

From:

Olivier Langlois <olanglois@sympatico.ca>

Newsgroups:

comp.lang.c++.moderated

Date:

Thu, 28 Jun 2007 09:13:17 CST

Message-ID:

<1183037956.165589.190760@k79g2000hse.googlegroups.com>

Hi Uli,

First, thank you very much for your explanations. I will check for
sure the thread support provided by boost. There is only this part
that I want to bring a clarification:

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.

Two things:
1. It is normal with polymorphism that the baseclass dictates which

function

is called, whether it is static or dynamic.
2. You are passing an argument to the static start_routine(). For CRTP,

you

would not make it static but a normal member and then simply
use 'static_cast<Derived*>(this)'. Eventually, both are the same, but it

simply more convenient like this.

Uli

the start_routine signature must be exactly like that because it is
required by the pthread creation function callback parameter.

Greetings and thank you,
Olivier Langlois
http://www.olivierlanglois.net

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