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

Subject: Re: [boost] [config] Using SD-6 macros
From: Niall Douglas (s_sourceforge_at_[hidden])
Date: 2015-06-13 11:51:36

On 13 Jun 2015 at 11:27, Edward Diener wrote:

> > For each feature test, we would need both (e.g.) __cpp_constexpr and
> > __cpp_constexpr_and_implemented_correctly.  The chance of just (e.g.)
> > __cpp_constexpr being reliable enough is low, IMO, particularly for
> > non-trivial feature use (e.g. Boost).
> 
> What you are saying is that we can use SD-6 but that we shouldn't trust 
> that whoever implements it is doing it correctly.

Both GCC and clang have been lenient in letting you use some minor 
C++ 14 constexpr when in C++ 11 constexpr mode (albeit usually with a 
warning).

VS2015 will not be lenient. You get guaranteed as much constexpr as 
is minimally required to implement C++ 11, anything past that is 
gravy.

I've tried feeding test code into the unreleased full constexpr web 
MSVC compiler and so far for me at least it's working. I would like 
to assume someone in Microsoft has tried flipping BOOST_CONSTEXPR on 
in Boost with their latest release, but maybe STL can tell us more on 
that.

One ballsy move might be for Boost to turn on BOOST_CONSTEXPR 
unilaterally for VS2015, and let the bug reports work their magic :)

Niall

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