Re: [boost] Alternative implementation for BOOST_PP_VARIADIC_SIZE

Subject: Re: [boost] Alternative implementation for BOOST_PP_VARIADIC_SIZE
From: Edward Diener (eldiener_at_[hidden])
Date: 2011-11-12 14:42:02

On 11/12/2011 6:52 AM, Gennadiy Rozental wrote:
> Lorenzo Caminiti<lorcaminiti<at>  gmail.com>  writes:
>> On Thu, Nov 10, 2011 at 6:43 PM, Gennadiy Rozental<rogeeff<at>  gmail.com>>
>> Hi,
>>>
>>> Current implementation of subject macro have a very serious shortcoming -
>>> it does not work for empty __VA_ARGS__. After googling around a bit for
>>> some ideas I came up with the following alternative:
>>
>> A while back there was a discussion about the
>> possibility/impossibility to handle empty macro parameters using
>> variadics:
>>
>> http://lists.boost.org/Archives/boost/2011/02/177321.php
>>
>> (Make sure to address the concerns expressed by Paul in the replies to
>> the above thread.)
>
> Frankly, I do not have time to read through the whole discussion. I am not a
> language lawyer, but for what it worth my version works on all compilers I
> have tried and looks to be perfectly legal (to me). I do know about one
> limitation. It's where __VA_ARGS__ ends with macro function which produces
> comma when evaluated. It's very rare case though and even if it's possible
> to implement solution that deals with it (look here:
> https://gustedt.wordpress.com/2010/06/08/detect-empty-macro-arguments/ ),
> I find the complication does not worth the trouble.
>
> If Edward or Paul care to comment it might be easier for them to point to any
> shortcomings in my solution (if any).

I have already commented in a direct reply to your OP. I don't see how 
the link above gets around the function-like macro problem but I will 
study it to see what is involved.