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Subject: Re: [boost] [modularization] proposal and poll
From: Glen Fernandes (glen.fernandes_at_[hidden])
Date: 2014-05-29 20:33:15

On Thu, May 29, 2014 at 1:22 PM, Julian Gonggrijp wrote:
> - Manually: this is cumbersome and generally hard because there are
> many (undocumented) interdependencies between Boost libraries.
> - Automatically: as far as I know Ryppl is the only existing attempt
> at providing automated dependency handling for Boost, but it is a
> very ambitious project that attempts to do much more and it is
> currently neither finished nor being actively developed.
> I think there could be a less ambitious but faster way to provide
> automated dependency handling. It would take no more than some static
> configuration, to list for each library what other Boost libraries it
> depends on, combined with a simple script that automatically traverses
> the dependency graph and clones just the necessary submodules. This
> script may then be hooked into the bootstrap script. I think I could
> write the dependency handler, and I would be willing to, though I
> can't currently provide any indication of when I would be able to
> start.

It would be nice if both approaches (static configuration, automatic
identification) take into account - or allow you to specify -
conditional dependencies (e.g. dependencies based on identification of
supported or unsupported features determined by Boost.Config).

For example:

Boost.Align should only be considered as depending on Boost.TypeTraits
(for boost::alignment_of) if BOOST_NO_CXX11_HDR_TYPE_TRAITS is
defined; otherwise it uses the C++11 standard library (for
std::alignment_of). Similarly, it only depends on Boost.Utility (for
boost::addressof) if BOOST_NO_CXX11_STD_ADDRESSOF is defined;
otherwise it uses the C++11 standard library (for std::addressof).

For anyone wanting to consume Boost.Align, should they have a
conforming C++11 implementation, they should see Boost.Align's
dependencies as only Boost.Config and Boost.Integer. Otherwise,
someone consuming Boost.Align with a totally non-conforming C++11
implementation should see its dependencies as: Boost.Config,
Boost.Integer, Boost.Utility, Boost.TypeTraits.


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