Re: [boost] [config][mpl][type_traits][integer] BOOST_STATIC_CONSTANT should use constexpr

Subject: Re: [boost] [config][mpl][type_traits][integer] BOOST_STATIC_CONSTANT should use constexpr
From: John Maddock (boost.regex_at_[hidden])
Date: 2013-04-21 07:08:18

>> As for the original question, this is such a pervasive breaking change, I
>> think a new macro is inevitable I'm afraid :-(
>
> New macro will do exactly what the old macro did, but using C++11
> feature. Code in all Boost libraries will be changed to use new macro.
> So the old macro will be required only for users code that use macro
> and attempts to take address of constant...
>
> To me, it looks less obscuring to have one macro and a note for users
> to use BOOST_CONSTEXPR_OR_CONST for out-of-line definition; than two
> macro (which one shall be used by default?) that do the same thing but
> very slightly differ in details.

Here's a radical idea: are there any compilers still around that we care 
about which require the enum workaround?  Certainly not VC6 ;-)

So we could recomend libraries use:

template <class T>
struct foo
{
    BOOST_STATIC_CONSTEXPR bool value = some_value;
};

template <class T>
BOOST_CONSTEXPR_OR_CONST bool foo<T>::value;

Thoughts?

John.