Re: [boost] [config] Macro for null pointer

Subject: Re: [boost] [config] Macro for null pointer
From: Jeffrey Lee Hellrung, Jr. (jeffrey.hellrung_at_[hidden])
Date: 2012-12-02 15:10:38

On Fri, Nov 30, 2012 at 12:04 AM, Andrey Semashev <andrey.semashev_at_[hidden]
> wrote:

> On Fri, Nov 30, 2012 at 11:19 AM, Jeffrey Lee Hellrung, Jr.
> <jeffrey.hellrung_at_[hidden]> wrote:
> > On Thu, Nov 29, 2012 at 10:59 PM, Andrey Semashev <
> andrey.semashev_at_[hidden]
> >> wrote:
> >
> >> On Thu, Nov 29, 2012 at 9:51 PM, Jeffrey Lee Hellrung, Jr.
> >> <jeffrey.hellrung_at_[hidden]> wrote:
> >> > On Thu, Nov 29, 2012 at 12:04 AM, Andrey Semashev <
> >> andrey.semashev_at_[hidden]
> >> >> wrote:
> >> >
> >> >> My main point is that
> >> >> nullptr should "just work" (tm) by default.
> >> >>
> >> >
> >> > But, it kinda doesn't "just work" if correct and robust use requires a
> >> > conditional using declaration. And, at that point, what use is the
> "using
> >> > boost::nullptr" at global scope anyway, if it's conditional on a
> >> > configuration macro?
> >>
> >> The config macro is only used to solve problems, should they arise.
> >> Other than that nullptr will work after simply including the header.
> >> And I'm sure in 99.9% of cases this will be the case.
> >
> > Just to be clear, the conditional using declaration I was referring to is
> > the one you suggested clients should use in their code, whereas you seem
> to
> > be referring to the using declaration in the boost/utility/nullptr.hpp
> > header. Is that right, and is my interpretation of your suggestion
> correct?
>
> Yes, I was referring to the global using declaration in
> boost/utility/nullptr.hpp and the BOOST_NO_GLOBAL_NULLPTR config
> macro.
>
> I have little concern about BOOST_USING_NULLPTR macro; I would
> probably use conditional using declaration in a public third party
> library anyway (I prefer explicitness of this solution).
>

Well either way, I reiterate my comment: If we have a conditional
global-scope using declaration, I would imagine we would strongly recommend
that client code likewise include a conditional using declaration (whether
wrapped in a macro or explicitly expressed via #ifndef...#endif) so that
things continue to "just work" whether the global-scope using declaration
is enabled or not.

On the other hand, requiring a user to just have a "BOOST_USING_NULLPTR;"
declaration at the scope they wish to use the nullptr identifier seems
safer (Boost doesn't inject anything into the global scope) and simpler /
more uniform (no need for an additional configuration macro and explanation
for why it's necessary and when one needs to concern oneself with it).

- Jeff