Re: [boost] [fit] Mini Review (consider 1/2 or 1/4 weight)

Subject: Re: [boost] [fit] Mini Review (consider 1/2 or 1/4 weight)
From: Zach Laine (whatwasthataddress_at_[hidden])
Date: 2016-03-20 16:55:20

On Sun, Mar 20, 2016 at 7:53 AM, Gonzalo BG <gonzalobg88_at_[hidden]> wrote:

> I want to make a minor remark about this:
>
> > [...]
> >
> > 1. Inline functions are weak symbols and don't violate ODR
> > 2. Static variables in C++ do violate ODR (btw in C they do not) so
> > basically you COPY every instance of the functions across compilation
> > unit.
> >
> > [...]
>
> FIT (and range-v3, and many other libraries) follow the best practice we
> currently have in C++ < 17 here, which is Eric Niebler's N4381 Suggested
> Design for Customization Points [0].
>
> It seems, however, that from the discussion here and in the other reviews
> of FIT, this best practice is not "common practice" yet.
>
> The failure is only on us for not giving it enough exposure.
>
> IMO all new Boost libraries should be following N4381 as FIT does.
>
> On first encounter, however, a macro like BOOST_FIT_STATIC_LAMBDA
> is going to look very suspicious: why is this required? what about ODR? ...
>
> Since these macros are going to remain the only viable solution for
> a long time (until we drop support for C++<17) we should address these
> questions on first usage in the documentation of new libraries, maybe by
> linking against N4381 directly (which addresses the issue in great detail)
> or by providing a small summary of N4381 in the documentation or the
> Boost wiki.
>
> [0]
>
> http://ericniebler.github.io/std/wg21/D4381.html#no-violations-of-the-one-definition-rule

+1