Re: [boost] [Config] Big changes in C++0x detection...

Subject: Re: [boost] [Config] Big changes in C++0x detection...
From: Daniel Walker (daniel.j.walker_at_[hidden])
Date: 2011-03-23 12:54:39

On Wed, Mar 23, 2011 at 12:42 PM, Eric Niebler <eric_at_[hidden]> wrote:
> On 3/18/2011 7:35 AM, Stephan T. Lavavej wrote:
>> [Eric Niebler]
>>> Yes. So the behavior of vc10's decltype wrt this issue is in conformance with /current/
>>> working paper -- which is broken, according to n3233. It will be discussed soon in Madrid.
>>> If the proposed wording is accepted (and I hope to god it is), then VC10's decltype --along
>>> with everybody else's-- will need to be fixed.
>>> But please fix it anyway. :-)
>>
>> I'll ask the compiler team for a fix. I don't always get what I want, but the STL is the compiler's first and best customer, and I've been looking forward to making result_of 95% powered by decltype.
>>
>> (Keeping track of rvalue references v2, lambdas v1.1, rvalue references v2.1, rvalue references v3 - I actually don't know if that one was reverted in the Working Paper - and now decltype v1.1 can be exhausting!)
>
> And just to keep everybody abreast, N3233 was moved to "immediately
> ready" in Madrid today, with fairly minor wording tweaks. That means two
> things, one good and one bad:
>
> Bad: Every decltype implementation is broken.
> Good: Once they're fixed, we'll have a decltype-based result_of that
> actually works.
>
> I, for one, am euphoric and would like to thanks James Widman and Doug
> Gregor for helping to make this happen. Getting the committee to make
> *any* changes at this point is a major accomplishment.

That's good news! I'm glad you guys pushed for this. Congratulations!

>
> It means one other thing: we should have a config macro for detecting
> this standards-related decltype bug, because several major compilers
> have now shipped with it, and I'll need the macro in Proto. I suggest:
>
>  BOOST_NO_DECLTYPE_N3276
>
> (N3276 will be the number of the redrafted N3233.) I can provide a
> config test for this.

Good idea.

Daniel Walker