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Noexcept
by Emil Dotchevski 30 Jun '17

30 Jun '17

The lively debates during the Outcome review show that there is a great deal of interest in solving the problem of error handling in environments where C++ exception handling is unavailable. Noexcept is a new C++11 library that implements a different approach to solving the same problem. Any feedback is welcome. https://zajo.github.io/boost-noexcept/ Emil

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[review] Mp11 review starts in two weeks
by Bjorn Reese 29 Jun '17

29 Jun '17

The formal review of Peter Dimov's Mp11 library is scheduled for July 15 - July 24, 2017 [1]. Mp11 is a C++11 metaprogramming library for compile-time manipulation of data structures that contain types. It’s based on template aliases and variadic templates and implements the approach outlined in the article "Simple C++ metaprogramming" [2] and its sequel [3]. These articles are useful background information for the review. * Mp11 aims to make simple usage simple, and to support complex usage without complicating the simple use cases. * Mp11 works on any type-list, whether its own type-list mp_list, or standard type-lists such as std::tuple and std::variant, or user-defined type-lists. * Mp11 works with any meta-function, such as C++11 or Boost type-traits, or user-defined type-traits. Mp11 can be found here: * Documentation: https://rawgit.com/pdimov/mp11/master/doc/html/mp11.html * Source code: https://github.com/pdimov/mp11 [1] http://www.boost.org/community/review_schedule.html [2] http://pdimov.com/cpp2/simple_cxx11_metaprogramming.html [3] http://pdimov.com/cpp2/simple_cxx11_metaprogramming_2.html

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CMake followup
by Peter Dimov 29 Jun '17

29 Jun '17

In a previous post I identified several scenarios for CMake support, where number one was 1. The user installs a Boost release as usual with `b2 install`, which makes the installation visible to CMake and usable via find_package(boost_libname). For this, I said "The changes to the `b2 install` procedure significantly exceed my bjam-fu however, so if we decide to proceed with this - and I don't see how we could claim CMake support in a meaningful way without it - the interested parties would need to figure out a way to make that happen." but I lied. (Well, not entirely, I had a lot of help.) Here https://github.com/pdimov/boost-cmake-demo is a proof-of-concept implementation that more or less works for our beloved test case of Boost.System. To test (the instructions are for Windows, where I tested), clone the repo, do b2 headers b2 --build-type=complete install as usual, then b2 cmake//install variant=debug,release link=static,shared runtime-link=shared (or whatever combination of options you prefer.) This should install -config.cmake files into $prefix/libs/cmake. Then, in a CMakeLists.txt, cmake_minimum_required(VERSION 3.5) project(cmake_demo CXX) #set(BOOST_BUILD_VARIANT RELEASE) #set(BOOST_LINK_TYPE SHARED) #set(BOOST_RUNTIME_LINK STATIC) find_package(boost_core 1.63.0) find_package(boost_system 1.63.0) # disable autolink globally # could also do it per-target add_definitions(-DBOOST_ALL_NO_LIB=1) # sample program add_executable(cmake_demo cmake_demo.cpp) target_link_libraries(cmake_demo boost::core boost::system) or similar. Ideally, cmake//install would be integrated into the install target (and cmake//stage into stage, respectively.)

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[iterator][utility] Move utility/next_prior.hpp to Iterator module?
by Michel Morin 29 Jun '17

29 Jun '17

Andrzej Krzemienski wrote: >> Do you mean coupling of Boost.Iterator and Boost.Range? I think that would >> be fine, since Boost.Range already couples with Boost.Iterator. >> Boost.Range's `boost::distance` should call Boost.Iterator's >> `boost::distance`. >> > > I meant `next()` and `prior()` that are located in Utility: > http://www.boost.org/doc/libs/1_64_0/libs/utility/utility.htm Ah ok, got it. I think it would be better to move utility/next_prior.hpp to the Boost.Iterator module. After the move, the Boost.Iterator module will have: - include/boost/iterator/next_prior.hpp * Contains the actual code for `next` and `prior`. (Personally, I'd like to add `boost::prev` as a synonym of `boost::prior`.) - include/boost/utility/next_prior.hpp * Just includes <boost/iterator/next_prior.hpp>. This is how utility/declval.hpp was moved to the Boost.TypeTraits module. Regards, Michel

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[beast] Formal "review" branch frozen
by Vinnie Falco 29 Jun '17

29 Jun '17

The "review" branch of Beast is now available and frozen for modifications. It contains the snapshot of the repository which will undergo the Boost formal review starting on July 1 and lasting for 10 days. Currently the review branch is even with the master branch, at version 70. The review branch repository is here: https://github.com/vinniefalco/Beast/tree/review The review documentation snapshot: http://vinniefalco.github.io/stage/beast/review/ Autobahn WebSocket Implementation Test Report: http://vinniefalco.github.io/autobahn/index.html Beast is a C++ header-only library serving as a foundation for writing interoperable networking libraries by providing low-level HTTP/1, WebSocket, and networking protocolvocabulary types and algorithms using the consistent asynchronous model of Boost.Asio. Beast empowers users to create their own libraries, clients, and servers using HTTP/1 and WebSocket. Code will be easier and faster to implement, understand, and maintain, because Beast takes care of the low-level protocol details. Please don't forget to "star" the repository on GitHub, the increased exposure will vitalize Beast and Boost with the new generation of programmers! Thanks! -- Follow me on Github: https://github.com/vinniefalco

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Boost MSM attribute sharing problem
by Christophe Henry 28 Jun '17

28 Jun '17

>Hello everyone, > >I have an issue with* Boost MSM*. >Using *Boost MSM eUML* I have created a >state machine. Actually I created *HSM* (Hierarchical State Machine) or >Composite State Machine as second name. >And I faced with issue: How to >share attributes between Parent State Machine and Sub-State Machines >(or Child State Machine) ?? > >I have not found an answer on this question ... >Could anyone possibly help me ? > >*Thanks,* > >*Best RegardsDenis Kotov* Hi Denis, I think the best way is to have your attributes owned by the top-level state machine, then passed to the composite as say, a pointer. The top-level can call get_state, then set the attribute. For example, with eUML, supposing you declared the attribute with BOOST_MSM_EUML_DECLARE_ATTRIBUTE (or without for other front-ends): get_state<Composite&>().get_attribute(some_attribute) = &top_attribute; HTH, Christophe

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Boost.Build and Microsoft C2 clang
by Niall Douglas 28 Jun '17

28 Jun '17

Can someone who has this working right please tell me how they persuaded Boost.Build to correctly invoke Microsoft C2 clang as the compiler and get it to link properly? My GSoC student has tried: - Configuring clang-win, this is a no-go, C2 clang comes in GCC arguments accepting form, not MSVC arguments accepting form. And no there is no clang-cl program supplied by Microsoft. - Configuring mingw gcc but with the C2 clang executable, this compiles code okay but fails at the link stage for some reason, probably it's trying to invoke the mingw linker and we want the Microsoft linker. Any help much appreciated. Niall -- ned Productions Limited Consulting http://www.nedproductions.biz/ http://ie.linkedin.com/in/nialldouglas/

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[thread] Interaction between interruption points and condition_variable
by David Stone 28 Jun '17

28 Jun '17

Assume 1) A thread is waiting on a condition_variable 2) That condition_variable has been notified that its condition is now true 3) The thread has been interrupted Given this, the interruption is processed rather than the condition_variable unblocking normally regardless of the order in which the notify and the interruption occur. That means that this program would eventually fail even though the notify always comes before the interrupt. #include <boost/thread/condition_variable.hpp> #include <boost/thread/lock_types.hpp> #include <boost/thread/mutex.hpp> #include <boost/thread/thread.hpp> #include <cassert> struct flag_t { using lock_type = boost::unique_lock<boost::mutex>; void notify() { auto lock = lock_type(m_mutex); m_flag = true; m_cv.notify_one(); } void wait() { auto lock = lock_type(m_mutex); m_cv.wait(lock, [=]{ return m_flag; }); } private: bool m_flag = false; boost::mutex m_mutex; boost::condition_variable m_cv; }; struct test_t { unsigned value = 0; ~test_t() { assert(value != 0); assert(value != 1); assert(value == 2); } }; int main() { while (true) { flag_t flag; test_t test; auto thread = boost::thread([&]{ test.value = 1; boost::this_thread::interruption_requested(); flag.wait(); test.value = 2; }); flag.notify(); thread.interrupt(); thread.join(); } } If we move the `flag.notify()` line before the thread creation, this program never terminates. This is because `boost::condition_variable::wait(lock_type &, function)` is defined as only blocking when the function returns false. The only way this program can terminate is if `thread` begins execution and executes `flag.wait()` before `flag.notify()` is called, then `thread.interrupt()` runs before `thread` is unblocked. It seems more intuitive to me that if a thread is blocked on a condition_variable and it is interrupted that it would unblock normally rather than throwing boost::thread_interrupted. Under that behavior, users who want the current behavior can always check after they leave a condition_variable::wait using `boost::this_thread::interruption_requested()` and throw rather than processing data. Under the current behavior, I do not believe there is any way to process the data in a function that does not have access to the thread object without losing the fact that an interruption was requested. This would only be possible if we had a function like `boost::this_thread::interrupt()`, but that does not exist. I do not know what code (if any) depends on the current behavior of interruptions always taking precedence over notifications, but it appears that the current behavior is undocumented. Is there a justification for the current behavior or is it just the way it happened to be implemented? Is this something we could change, or at least allow users to implement the behavior I outlined?

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Reminder: 1.65 closes for major changes tomorrow
by Marshall Clow 28 Jun '17

28 Jun '17

Upcoming release dates: 28-Jun: Boost 1.65.0 closed for major changes 5-Jul: Boost 1.65.0 closed for all changes, except by permission of a release manager. 8-Jul: Boost 1.65.0 closed for all changes 12-Jul: Boost 1.65.0 beta; master branch re-opened 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 -- Marshall

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Testing for ML Admin
by Alexander Zaitsev 28 Jun '17

28 Jun '17

Hello. Â I am simple letter and i want to be a part of boost mailing list. Â Hey, see - i have body. Head and body. Â --Â Best regards, Alexander Zaitsev Â

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