Re: [boost] [config] Using SD-6 macros

Subject: Re: [boost] [config] Using SD-6 macros
From: Edward Diener (eldiener_at_[hidden])
Date: 2015-06-12 23:00:10

On 6/12/2015 6:54 PM, Stephen Kelly wrote:
> Edward Diener wrote:
>
>> On 6/12/2015 12:06 PM, John Maddock wrote:
>> Some of it, although very clever, seems like educated "guesswork". Isn't
>> it better if the compiler tells us what is omplemented ?
>
> For come compiler versions/cxx features the answer is no: For some Clang
> releases which support SD-6 macros, they didn't implement the SD-6 macro
> for
> features which they documented as available.

As long as they don't give the wrong answer for the SD-6 they 
implemented it does not matter.

>
> In some cases, they implemented the __has_feature macro for a feature but
> not the SD-6, and in other cases vice-versa.

My view is to use SD-6 and fall back to our current implementation when 
it is not available.

>
>> About what std lib features are you speaking ? Most of the things I see
>> at
>> https://isocpp.org/std/standing-documents/sd-6-sg10-feature-test-recommendations
>> are predefined. Are you saying that because the compiler implementations
>> of SD-6 most likely have to include standard library headers in order to
>> implement SD-6 correctly that we should avoid using SD-6 ?
>
> The reason for this

"this" meaning what ? That predefined macros are enforced rather than 
macros in standard library headers ?

> is literally that the chair of SG-10 didn't want to
> require the stdlib implementor to have to open another file in their editor
> to add the macro there.
>
>   http://thread.gmane.org/gmane.comp.lang.c++.isocpp.features/17/focus=22
>
> I get headaches thinking of all the reasons that that's absurd.