Re: Suggested policy for dropping C++03 support in Boost libraries

From: Peter Dimov (pdimov_at_[hidden])
Date: 2019-11-26 17:10:04

Raffi Enficiaud wrote:
> > https://pdimov.github.io/articles/phasing_out_cxx03.html.
>
> Perfectly fine with me/boost.test. *BUT* I see a lot of internal 
> dependencies on boost.test and it looks to me that some of those libraries 
> are not actively maintained.
>
> Would the CMT be taking care of that? Should the libraries be moved to 
> boost.lightweighttest or should it be a copy of boost.test inside each of 
> the libraries?

Good questions without easy answers. We've been slowly moving 
undermaintained libraries to LWT where feasible, but there's still much work 
to do. But the options, were Boost.Test to switch to requiring C++11, would 
in general be either move to LWT, or drop C++03 in the dependent libraries 
as well.

It's a bit more subtle than that though, because some libraries only use 
parts of Boost.Test, such as

uuid:
    <boost/test/included/test_exec_monitor.hpp>
        from <libs/uuid/test/test_generators.cpp>
    <boost/test/test_tools.hpp>
        from <libs/uuid/test/test_generators.cpp>

or

qvm:
    <boost/test/tools/floating_point_comparison.hpp>
        from <libs/qvm/test/test_qvm.hpp>

or

property_map:
    <boost/test/minimal.hpp>
        from <libs/property_map/test/compose_property_map_test.cpp>
        from <libs/property_map/test/dynamic_properties_test.cpp>
        from <libs/property_map/test/function_property_map_test.cpp>
        from <libs/property_map/test/transform_value_property_map_test.cpp>

So the amount of work will depend on whether some of these headers will 
continue to be usable under C++03.

A major goal of my suggested policy is actually to answer this question for 
library users; if the header starts issuing deprecation warnings, C++03 
users of it would need to transition to something else. If it doesn't, they 
wouldn't need to.