August 2017 - Boost - lists.preview.boost.org

[BB++] Consensus
by Phil Bouchard 03 Aug '17

03 Aug '17

After the feedback I got back from the community, people agree they would rather improve C++ than seeing a new language taking off. I definitely agree but I would like professional opinions on how the following could be achieved: - to add instances of an object implicitly as each scope; - to add implicit references to these objects in top-level classes - to overload 'operator .' - to use 'auto' for member variables instead of 'decltype' Thanks for your help I really appreciate. Sincerely, -Phil

2 4

[review][mp11] Review report
by Bjorn Reese 03 Aug '17

03 Aug '17

I. VERDICT Mp11 is accepted unconditionally into Boost. There were 14 accept votes and 1 conditional accept vote. See list at end of this report. II. DESIGN Reviewers evaluated the design as very good. Many agreed with the design principle of using template aliases on type lists, which means that Mp11 can be used on std, boost, and custom type lists. Integration with MPL was discussed. This resulted in a new header file <boost/mp11/mpl.hpp> that enables the conversion between mp_list (and std::tuple) and MPL sequences. A version of mp_eval_if that can apply a metafunction to type lists in both the true and false branch was requested. This is not possible due to C++ limitations (template parameter pack must be at the end.) Instead two alternatives were suggested: (1) use a nested mp_eval_if in the true branch, or (2) use mp_if<>::type with mp_defer in both branches. Extra metafunctions were added for working with map and sets: mp_is_set, mp_is_map, and mp_map_keys which returns a list of all keys. No review without a discussion about names. The mp_ prefix received most comments. The prefix is used to avoid collision between mp11 names and C++ keywords. The argument against the mp_ prefix was that MPL and other Boost libraries already have established trailing underscore as the naming convention. The argument in favor is that the mp_ prefix is better suited for later C++ standardization. Other names that deviate from MPL, such as apply versus fn, were also pointed out, and the names of tuple operations were also discussed. III. IMPLEMENTATION The reviewers who looked at the implementation were generally pleased with its quality and simplicity. A faster version of mp_find was proposed during review. On reviewer pointed out that const lists causes obscure compilation errors. IV. DOCUMENTATION The evaluation of the documentation was more mixed. Some found it good, while others found it too terse. A recurring comment was that the documentation is missing beginner-level explanations and examples. For instance, the tuple_cat example was mentioned as being too advanced for an introduction. More examples with higher-order metafunctions (e.g. mp_bind) was requested. The reference documentation does not state the pre-conditions of the metafunctions. For example, what happens when indices are out of bounds? The description of map (list of lists) lead to confusion. Mp11 map entries have one unique key-type, and zero or more value-types. The ability to have multiple value-types per key-type makes it possible to emulate multi-maps. Some where unsure whether C++11 or C++14 was required for the library. There were plenty of other useful comments that I will omit from the review report for the sake of brevity. V. USEFULNESS The library was generally deemed useful. It was discussed if C++11 (and later) makes it too easy to write our own metaprogramming utilities, and thus not needing a metaprogramming library. This was not directed at Mp11 in particular. Some of the arguments in favor of a metaprogramming library were better performance and portability. I would like to add another advantage of a metaprogramming library, namely that it gives us a common vocabulary. VI. CONCLUSION The library fulfills the quality and usefulness criteria without major outstanding issues. The library is therefore cleared to be included into Boost. My main recommendation as review manager is to make the documentation more beginner-friendly before the library is added to Boost. This is a recommendation, not a requirement. VII. PARTICIPANTS The following formal reviews were posted: * Barrett Adair : Accept * Brook Milligan : Accept * Edward Diener : Accept * Glen Fernandes : Accept * Jason Rice : Accept * Joaquin M López Muñoz : Conditional accept * John P Fletcher : Accept * Lee Clagett : Accept * Paul Fultz : Accept * Peter Koch Larsen : Accept * Robert Ramey : Accept * Roberto Hinz : Accept * Vijayan : Accept * Vinnie Falco : Accept * Zach Laine : Accept I would like to thank all participants for their efforts. I would also like to thank Peter Dimov for bringing such a high-quality library to Boost.

3 2

Warning generated by boost::process code
by Wilfred Smith 02 Aug '17

02 Aug '17

Dear Sir or Madam, In Boost 1.64.0, include/boost/process/detail/posix/wait_group.hpp:131:10: warning: unused variable 'start' [-Wunused-variable] auto start = std::chrono::system_clock::now(); ^ /usr/local/include/boost/process/detail/posix/wait_group.hpp:165:10: warning: unused variable 'start' [-Wunused-variable] auto start = std::chrono::system_clock::now(); ^ I believe these two lines should be removed. This appears to be a “copy and paste” issue. The two routines above these lines use the “start” variable to calculate a relative time. However, the later two routines use an absolute time, and the compiler complains as shown above. Removing these two lines should fix the compiler warning and have no adverse effect. Please let me know if this is the wrong place to complain about issues. \W/

2 1

Boost::Process is broken
by Wilfred Smith 02 Aug '17

02 Aug '17

All, Has anyone tried to build with <boost/process.hpp> included using XCode 9.0? I don’t think this went through code review. include/boost/process/exception.hpp:22:30: error: using declaration cannot refer to a constructor using std::system_error::system_error; ~~~~~~~~~~~~~~~~~~~^ I’m not sure that does what was intended, and the compiler thinks it’s silly talk… Any and all assistance appreciated in advance… \W/

2 1

Reminder: Boost Master branch will close for the 1.65.0 release on Wednesday
by Marshall Clow 02 Aug '17

02 Aug '17

Get your bug fixes and documentation updates in now! -- Mashall Upcoming release schedule: 2-Aug: Release closed for all changes, except by permission of a release manager. 5-Aug: Boost 1.65.0 closed for all changes 9-Aug: Boost 1.65.0 release

7 20

[numeric_conversion] Compilation errors with msvc-14.1 and std:c++latest in master branch
by Adam Wulkiewicz 02 Aug '17

02 Aug '17

Hi, I noticed there are compilation errors in master branch and not in develop branch. Only runs with cxxflags= std:c++latest are failing. See e.g.: http://www.boost.org/development/tests/master/developer/output/teeks99-09-q… Affecting Geometry: http://www.boost.org/development/tests/master/developer/output/teeks99-09-q… Regards, Adam

1 0

[release-1.65] changes in master
by Oliver Kowalke 01 Aug '17

01 Aug '17

Will commits that have been added to branch master in the last days be included into release 1.65? ty, Oliver

2 1

[BB++] 17 minutes long documentary
by Phil Bouchard 01 Aug '17

01 Aug '17

Like I promised, here's a 17 minutes long documentary on BB++ which now shows its internals: https://youtu.be/GrNDYWyasxg Regards, -Phil

3 3