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[Beast] Security issue note
by Artyom Beilis 01 Jul '17

01 Jul '17

Looking into parser/body code I noticed: parser: void on_body(boost::optional< std::uint64_t> const& content_length, error_code& ec) { wr_.emplace(m_); wr_->init(content_length, ec); } string_body: void init(boost::optional< std::uint64_t> content_length, error_code& ec) { if(content_length) { if(*content_length > (std::numeric_limits< std::size_t>::max)()) { ec = make_error_code( errc::not_enough_memory); return; } ec.assign(0, ec.category()); body_.reserve(static_cast< std::size_t>(*content_length)); } } Basically I can exhaust the memory of the server and kill it by providing huge content length from several connections and lead to its crash. Reasonable and configurable limit should be provided for content length. Artyom Beilis

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[Beast] Questions Before Review
by Artyom Beilis 01 Jul '17

01 Jul '17

Hello Vinnie Falco, I have several design questions regarding this library before the review. DISCLIMER: My name is Artyom Beilis. I'm the author of CppCMS C++ Web Framework: http://cppcms.com It may seems like it can be in some competition with Beast but I don't see it this way as Beast is too low level library that does not addresses typical problems of developers needing Web API/Site running using C++. CppCMS addresses totally different problems in different way. So there are my design related questions: Header Only Design --------------------------- As somebody who worked with guys who do web development, it was very clear that compilation time is an issue. A simple build of http_server_small.cpp example requires about 6s(!) of compilation time g++ 5.4 http_server_fast.cpp takes 7s In comparison entire message board containing templates code flow SQL and more leads to only 4s - non paralel build. (https://github.com/artyom-beilis/cppcms/tree/master/examples/message_board ) I understand that you work on base of Boost.Asio - which itself has unacceptable compilation times but having for web application development may be serious deal breaker for big projects. Which Leads me to another design Choice Template Meta-programming Based Design instead of classic Object Oriented Design ---------------------------------------------------------------------------------------------------------------- I see that almost every object there is some kind of template object. It almost mimics the API of Boost.Asio which on its way has its limitations. I remember I needed to implement FastCGI over TCP and Unix domain sockets virtually leading to same code besides some initial bind - and it required to create the entire parser using template programming because the socket itself was template object different for UNIX and TCP. I have strong feeling that lots of stuff can actually be done using classic OOP. Example Question: > Can I implement same server code for both SSL and non SSL HTTP protocol > without use of templates in the class itself? And my current final question Who are the potential users of the library? ------------------------------------------------------- If I need to send a simple http request to server it does not seem to do simple enough job (see your FAQ) so I'll probably be better with feature rich libcurl. If I need to implement complex web server/service I don't have cookies, sessions, forms, html? If I need to implement RESTful API do I have all stuff like URL mapping of different paths to callbacks, protocol abstraction http/https (basic stuff - I don't see it there correct me if I wrong) Is it for web server developers? Maybe I'd be happier with simple HTTP protocol parser that I can integrate to any socket API? Can you please give more accurate description of who is this library intended for? Best Regards, Artyom Beilis

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Follow-up to the CMake follow-up
by Peter Dimov 01 Jul '17

01 Jul '17

Due to the strong interest in my previous follow-up, I'm following it up with a more complete implementation of the support required for CMake scenario #1, installing configuration files during "b2 install" such that subsequent "find_package" calls work (assuming a suitably set CMAKE_PREFIX_PATH). You can find it in branch "feature/install-cmake-config" in the superproject (boostorg/boost). In other words, git clone --recursive --depth 64 -b feature/install-cmake-config https://githib.com/boostorg/boost bootstrap b2 headers b2 install cmake//install variant=debug,release link=static,shared runtime-link=static,shared This doesn't yet support installation with more than one toolset, and I'm sure that some libraries don't work, but a simple test using Filesystem and ProgramOptions does. /// CMakeLists.txt: /// cmake_minimum_required(VERSION 3.5) project(cmake_demo CXX) list(APPEND CMAKE_PREFIX_PATH C:/Boost) find_package(boost_filesystem 1.63.0) find_package(boost_program_options 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::filesystem boost::program_options) /// cmake_demo.cpp: /// #include <boost/filesystem.hpp> #include <boost/program_options.hpp> #include <cerrno> #include <iostream> namespace fs = boost::filesystem; namespace po = boost::program_options; int main( int argc, char const* argv[] ) { po::options_description desc( "Allowed options" ); desc.add_options() ( "help,h", "produce help message" ) ( "path,p", po::value<std::string>(), "set initial path" ) ; po::variables_map vm; try { po::store( po::parse_command_line( argc, argv, desc ), vm ); po::notify( vm ); } catch( std::exception const & x ) { std::cerr << "Error: " << x.what() << std::endl; return 1; } if( vm.count( "help" ) ) { std::cout << desc << std::endl; return 1; } fs::path p = fs::current_path(); if( vm.count( "path" ) ) { p = vm[ "path" ].as<std::string>(); } std::cout << p << std::endl; }

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Does Boost 1.64 support HP-UX?
by 장윤진 30 Jun '17

30 Jun '17

I read about the platform that boost supports on the boost homepage. However, I do not know if it supports HP-UX. http://www.boost.org/doc/libs/1_64_0/libs/log/doc/html/log/installation.htm… Supported compilers and platforms. The library should build and work with a reasonably compliant compiler. The library was successfully built and tested on the following platforms: Windows XP, Windows Vista, Windows 7. MSVC 8.0 SP1, MSVC 9.0 and newer. Linux. GCC 4.5 and newer. Older versions may work too, but it was not tested. Linux. Intel C++ 13.1.0.146 Build 20130121. Linux. Clang 3.2. Does that mean it supports HP-UX?

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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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[sort] pdqsort mini-review
by Александр Зайцев 27 Jun '17

27 Jun '17

Hello. Try to send my thoughts from another email. 1. Are there any specific concerns you have about pdqsort vs. std::sort? 2. Does it compile for you when you try to use it as a replacement for std::sort? 3. How does the performance compare on your system vs. std::sort? 4. Do you think we should include pdqsort in Boost.Sort? 5. Do you have any concerns about switching the default/fallback sort in Boost libraries (including Boost.Sort) from std::sort to pdqsort? 1. Only that pdqsort is really better than std::sort's Introsort 2. Yes, it does. 3. Pdqsort is much faster than std::sort. 4. Yes, i do. I think that pdqsort is really good sort algorithm - it's really fast and pdqsort is already implemented sort algorithm in Rust's libcore as sort_unstable. 5. No, i have not. Best regards, Alexander Zaitsev zamazan4ik(a)gmail.com

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[sort] pdqsort mini-review
by Александр Зайцев 27 Jun '17

27 Jun '17

Hello. Try to send my thoughts from another email. 1. Are there any specific concerns you have about pdqsort vs. std::sort? 2. Does it compile for you when you try to use it as a replacement for std::sort? 3. How does the performance compare on your system vs. std::sort? 4. Do you think we should include pdqsort in Boost.Sort? 5. Do you have any concerns about switching the default/fallback sort in Boost libraries (including Boost.Sort) from std::sort to pdqsort? 1. Only that pdqsort is really better than std::sort's Introsort 2. Yes, it does. 3. Pdqsort is much faster than std::sort. 4. Yes, i do. I think that pdqsort is really good sort algorithm - it's really fast and pdqsort is already implemented sort algorithm in Rust's libcore as sort_unstable. 5. No, i have not. Best regards, Alexander Zaitsev mazahaka2009(a)list.ru

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Interest in another formatting library ?
by Roberto Hinz 27 Jun '17

27 Jun '17

Hi, Is there space for another formatting library in Boost? Anyone interest in this one? doc: https://robhz786.github.io/stringify/doc/html/index.html code: https://github.com/robhz786/stringify

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Cmake
by Peter Dimov 26 Jun '17

26 Jun '17

There is considerable interest in Boost supporting CMake, but it seems that everyone has different ideas as to what this support will entail. After deliberation and discussions, I have identified the following (separate) scenarios: 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). 2. The user brings several Boost libraries as git submodules into his CMake-based project and uses add_subdirectory in his CMakeLists.txt to link to them. 3. The user uses CMake to install an individual Boost library, which is then available for find_package. 4. The user uses CTest to run the tests of an individual Boost library. 5. CMake is supported as a way to build and install the entire Boost, in place of b2. 6. CTest is supported as a way to run the tests for the entire Boost, in place of b2. At the moment, I think that we should concentrate on (1) and (2) as providing most bang for the buck. 5-6 in particular require that all Jamfiles are ported at once, which is a serious undertaking for a questionable benefit as what we have already works. I've done a proof of concept for (2), which can be seen here: https://github.com/pdimov/boost-cmake-demo-2 This repository uses git submodules in ext/ to bring in Boost.System (our guinea pig) and its dependencies, then uses them via add_subdirectory in https://github.com/pdimov/boost-cmake-demo-2/blob/master/CMakeLists.txt The required CMake infrastructure is on branch feature/cmake in those six libraries (assert, config, core, predef, system, winapi.) It consists of CMakeLists.txt in the root: https://github.com/boostorg/system/blob/c306d479e8326a68d07ee7f058a415fe8b6… and supporting .cmake files in cmake/ : https://github.com/boostorg/system/tree/c306d479e8326a68d07ee7f058a415fe8b6… The goal here is for Boost library developers to be able to remain ignorant of CMake if they so choose; so of those files, only sources.cmake requires their input (it's empty for header-only, so those require nothing at all.) BoostVersion.cmake and default.cmake are common for all libraries and are copied from the superproject. dependencies.cmake is automatically generated with boostdep. There is a Jamfile in cmake/ that updates these three files: https://github.com/boostorg/system/blob/c306d479e8326a68d07ee7f058a415fe8b6… and the intent is for this to be done automatically in a superproject script that invokes "b2 cmake" for the superproject: https://github.com/pdimov/boost-cmake-demo/blob/master/cmake/Jamfile which in turn invokes "b2 cmake" in each library having "cmake/Jamfile". Copying BoostVersion.cmake and default.cmake, instead of referring to them, allows libraries to be used without a superproject, to support scenarios (2) and (3) above. (Scenario (3) is also supported by default.cmake.) What remains to be done is (a) to extend this to the rest of the Boost libraries, if we decide to do so, which would require figuring out a way to cope with the numeric/ irregular libraries, and (b) support for scenario (1) above. Scenario (1), that is, `b2 install` making the installed Boost available for CMake find_package use, is an entirely separate undertaking, completely independent of what I've done - except for possibly reusing the dependencies.cmake files. It would entail generating boost_libname-config.cmake and boost_libname-config-version.cmake files for each library, and boost_libname-config-<suffix>.cmake subconfiguration files for each build variant (toolset, variant=debug/release, link=static/shared, runtime-link=static/shared, runtime-debugging=on/off, threading=single/multi, and possibly python-debugging=on/off.) This would probably require us to define CMake variables controlling these features, such as BOOST_BUILD_TOOLSET, BOOST_BUILD_VARIANT, BOOST_LINK_TYPE, BOOST_RUNTIME_LINK, and so on, with them having appropriate default values inferred from the CMake environment. Then, boost_system-config-vc141-mt-gd-1_65.cmake will check these values and if BOOST_BUILD_TOOLSET is "vc141", BOOST_LINK_TYPE is SHARED, BOOST_RUNTIME_LINK is SHARED and BOOST_RUNTIME_DEBUGGING is ON, it will declare an imported target pointing to boost_system-vc141-mt-gd-1_65.lib/dll, otherwise it would do nothing. (Not sure how relevant is threading=single/multi today, but in principle, it should also check BOOST_THREADING == MULTI.) Generating these -config.cmake files would ideally be done as part of the `b2 install` procedure and require no changes to the individual libraries. 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. At this point, I know what needs to be done, but not how to bring it about.

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Re: [boost] What's wrong with top-posting?
by Brian Wood 26 Jun '17

26 Jun '17

David Abrahams writes: > At Tue, 26 Jan 2010 10:09:43 -0800, > Robert Ramey wrote: >> > > I thought I was familiar with the guidelines and never remembered this. >> >> I top-post all the time. It seems much more natural to me when >> it's not convenient to intersperse comments into the previous >> message. Why I like top posting: >> >> a) It means that I don't have to scroll to the bottom of a message >> which is sometimes pretty long. >> b) To me it is more natural to follow the style >> of other communications (artilcle, books, etc) which make >> their point in the main text and refer to footnotes, bibliographies, >> etc at the end of the main text. > > c) You don't confuse or even *upset* (as I've discovered the hard way) > many people in the business world, where top-posting and > overquoting is the accepted standard. Every message drags along > the entire thread history with it, and you keep a record of > everything by storing the final message. (yuck) It's a cultural > thing, and Boost fits into the open-source programmer weenie > culture much more than the business culture. I was getting annoyed by some top-posting here recently, so I dug up this thread. Is an "open-source programmer weenie culture" like a nerdy culture? Anyway, please stop top posting and trim the old parts of the thread that are no longer needed. Brian Ebenezer Enterprises - In G-d we trust. http://webEbenezer.net

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[outcome v2] Please comment on new result<T, EC> reference API docs
by Niall Douglas 26 Jun '17

26 Jun '17

Dear Boost, I've been hard at work refactoring Outcome to match the peer review a few weeks ago. Much comment at the time mentioned the poor experience of the reference API docs, so can I get a community check of this: https://dedi4.nedprod.com/static/result-v2/doc_result.html This was generated by the new C++ reference docs generator https://github.com/foonathan/standardese. You'll no doubt spot quite a few formatting bugs, Jonathan says he's onto them. But the usage of libclang rather than doxygen's broken C++ parser clearly shows a lot of benefit, it's just standardese still remains quite a lot short in terms of necessary features to make output fully correct. I won't give the changelog for Outcome v2 result<T> over Outcome v1 yet. Let's see how you fare with the above reference API docs first. But as you'll note, there is considerable change over before as we now slot into a niche not occupied by Expected nor EitherMonad, indeed this now looks much more like Robert's or Lawrence Crowl's slimmed down object. This result<T> is approx 0.6 CPU cycles per stack frame unwound slower which I feel is acceptable in exchange for no more variant storage, which in turn released lots of SFINAE budget for me. (FYI v2 outcome<T> isn't done yet, but it will extend v2 result<T>) Niall -- ned Productions Limited Consulting http://www.nedproductions.biz/ http://ie.linkedin.com/in/nialldouglas/

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[container] includes nonexistent file
by Peter Dimov 25 Jun '17

25 Jun '17

Primary dependencies for container: (unknown): <boost/intrusive/detail/to_raw_pointer.hpp> from <boost/container/detail/to_raw_pointer.hpp> Boostdep says that <boost/intrusive/detail/to_raw_pointer.hpp> doesn't exist, and I indeed don't see it.

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[program_options] behaviour change for implicit options
by Vladimir Prus 25 Jun '17

25 Jun '17

Hi, I have committed, and merged to master, a change making program_option consider subsequent tokens for values of implicit options. For example, if "foo" is implicit option and "bar" is some other option, then: 1. "--foo --bar" will be parsed as option "foo" followed by "bar", and implicit option for "foo" will be used. 2. "--foo bar" will be parsed as option "foo" with the value of "bar" This is the way things worked prior to 1.59, was changed in 1.59, continued to cause confusion, and is now reverted back. For background, see: - http://permalink.gmane.org/gmane.comp.lib.boost.devel/269832 - https://github.com/boostorg/program_options/issues/25 Just in case client code might need to check this behaviour, I've added a feature macro, BOOST_PROGRAM_OPTIONS_IMPLICIT_VALUE_NEXT_TOKEN, which will be set to 1 starting with 1.65. Thanks, Volodya

1 0

Boost MSM attribute sharing problem
by Denis Kotov 25 Jun '17

25 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*

1 0

Noexcept improvements
by Emil Dotchevski 25 Jun '17

25 Jun '17

I've completed a second iteration on Noexcept, incorporating valuable feedback from the previous discussions here, and I'd like to thank everyone who participated. https://zajo.github.io/boost-noexcept/ The new result<T> type has a hard value-or-error invariant and can be used to transport errors between threads or to temporarily postpone the consumption of function results, e.g. by storing result<T> objects into a queue (of course, as before, users do not need result<T> just to report a failure from a function.) There is also a new macro, BOOST_NOEXCEPT_CHECK, which makes writing error-neutral functions easier and improves error checking in general. The documentation is also much more complete, including better examples and a new section on programming techniques.

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Fw: [stacktrace] [winapi] header out of place
by Peter Dimov 24 Jun '17

24 Jun '17

The header stacktrace: boost/detail/winapi/capture_stack.hpp should probably either be moved to Winapi, as the name suggests, or renamed to reside in boost/stacktrace/detail. And, as a general rule, libraries should strive to keep their headers under boost/<libname>, with the only exception being boost/<libname>.hpp. We have many legacy libraries not following this requirement, but any new ones and any new headers added to existing ones should. The reason for this requirement is that otherwise it's impossible to perform dependency analysis unless all of Boost is checked out so that the tool can tell in what module boost/random-header-name.hpp resides.

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[review] Boost.Nowide is Accepted into Boost
by Frédéric Bron 24 Jun '17

24 Jun '17

Dear all, I would like to thank all the people who took part in the discussions during the review. All contributors admitted that Boost.Nowide addresses a real issue and solves it, at least partially. Moreover we received 8 official reviews with 6 “accept”, 1 “do not accept as is” and 1 “I am not against it”. So Boost.Nowide is accepted for inclusion in Boost. Congratulation and many thanks to Artyom Beilis for this contribution. However, 2 major issues arose in the discussions and they will have to be fixed before inclusion: 1. handling of ill-formed Unicode input should be improved/clarified 2. the documentation needs improvements In particular, this needs to be fixed: * Design: There was a lot of discussions on what to do with ill-formed UTF-16 strings on Windows, in particular coming from the file system while converting them to narrow UTF-8 strings. Basically, 3 options: 1. allow the roundtrip ill formed UTF-16 > UTF-8 > ill formed UTF-16, this is not possible with UTF-8 encoding, WTF-8 (not a standard) may be an option with some issues 2. issue an error (today’s nowide option, even if the author would like to move to 3.) 3. convert as much as possible to fully conformant UTF-8 with character replacement U+FFFD for invalid input. This is what the NT kernel does with functions like RtlUTF8ToUnicodeN. This would allow cout to continue to work after invalid output instead of failing. After reviewing what was chosen for std::filesystem in C++17, I think 3. is the right think to do: - std::filesystem::path::u8string does not convert strings on Posix. If a conversion is done (on Windows) the output is fully conformant UTF-8. - the roundtrip is not guaranteed in std::filesystem::path conversions (implementation defined) but the roundtrip of a converted paths is guaranteed to work which is the case with Boost.Nowide: once in fully conformant UTF-8, narrow > wide > narrow works fine. - the use of the replacement character U+FFFD is what is done by the NT kernel (question: do you have to reimplement RtlUTF8ToUnicodeN and RtlUnicodeToUTF8N, why not using them)? It should been made clear in the doc that this choice does not guarantees the roundtrip on Windows so that ill-formed filename may not be opened. * Documentation: - the main part of the doc (the non-reference part) should be more detailed - it should be clear to the reader that Windows and Posix platforms are not handled the same; on Windows, we get UTF-8 strings while on Posix platforms, the user should not expect UTF-8 encoding, just narrow strings, even if UTF-8 is today the most common encoding (addressed in Q/A but is probably too far away). It must be clear from the beginning that on Posix platforms, the library does nothing (including no checking of UTF-8 conformance), just forward to the standard library. - review the use of UTF-8 so that it do not let think that narrow strings are always UTF-8 as this is not necessary the case on Posix platform; maybe just use narrow string? - clarify what is converted to what and when: for each function, we need to know precisely what is the output for all possible input; in particular, better explain for each function what the library does with ill-formed input (either UTF-16 input or narrow input), in particular for args and getenv; say clearly what happens (failbit, error, exception, invalid character…) - clarify what is done for Windows and what is (not) done for Posix - explain better what is behind nowide::cout, cin, cerr, what is done? - clarify what does the filesystem integration on Windows vs Posix - check if basic_stackstring::swap needs to swap buffer_ when both strings are on the stack - The doc/ directory is missing a Jamfile, and there's also no meta/libraries.json. * Implementation: - The global BOOST_USE_WINDOWS_H macro should probably be respected. When windows.h is not used, the WinAPI prototypes are declared in the global namespace. This can cause issues when windows.h is also included before/after the Nowide headers, and the prototypes don't match exactly (e.g. short vs. wchar_t). Also it pollutes the global namespace. Nowide should do what other Boost libraries do, and declare the prototypes in a private detail namespace instead. Example in <boost/thread/win32/thread_primitives.hpp>. Need to add a namespace around your definitions. - MinGW gcc: fix warnings in c++03 mode and errors in c++11 and above - Cygwin gcc/clang (errors because of missing ::getenv and friends) - when this is fixed, an error remains: in file included from test\test_system.cpp:11:0: ..\../boost/nowide/cenv.hpp: In function 'int boost::nowide::putenv(char*)': ..\../boost/nowide/cenv.hpp:104:41: warning: comparison between pointer and zero character constant [-Wpointer-compare] while(*key_end!='=' && key_end!='\0') - Under MSYS, one test failed Fail: Error boost::nowide::cin.putback(c) in test_iostream.cpp:17 main - filesystem integration should return somehow the previous locale for potential undoing * Misc: - There are no .travis.yml and appveyor.yml files in the root. - a number of copy/paste references to Boost.System (test/Jamfile) and Boost.Locale (index.html), should be corrected This are just suggestions and are not mandatory for acceptance: - implement stat/opendir/readir - integration with boost::interprocess::file_lock - integration with boost::program_options (in particular for correct line breaks when showing options) Frédéric

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Re: [boost] [review] Review of Nowide (Unicode)
by Groke, Paul 23 Jun '17

23 Jun '17

Hi, this is my official review of the Nowide library. I haven't had much time to look at Nowide, but I have noticed some things that might be of interest, so here we go... > - What is your evaluation of the design? Overall the design looks good. Some things I'd suggest to reconsider: * I'm a big fan of "try" names, so I'd suggest to rename the array versions of widen/narrow to try_widen/try_narrow. Makes it more clear that they can fail without throwing. Also I'm not sure about the benefit of returning the output buffer pointer or NULL. I'd simply return bool instead. * nowide_filesystem... to be honest I'm not sure what this does. If it does something related to UTF-8 on POSIX systems, then I smell a potential problem. If it's only for wide->narrow on Windows, it should be OK. * Also not sure what boost::nowide::cin/cout/cerr do. Do they call SetConsoleCP/SetConsoleOutputCP? Will they work with re-directed input/output streams? What will happen if the user uses them AND std::cin/cout/cerr or stdin/stdout/stderr in the same application? * I'm not a big fan of the basic_stackstring classes. I'd suggest to provide template function overloads for narrow/widen instead. Like: users_favorite::wstring_class wstr; if (boost::nowide::try_widen(wstr, str)) use(wstr); else too_bad(); They could write to the target-string using the usual duck-typing - e.g. via clear/push_back or clear/back_inserter. That way the user can use whatever SSO string class he likes and Nowide wouldn't have to provide string classes -- which IMO isn't its job. As a bonus, the user also gets an exception-free (except bad_alloc) function that doesn't require him to provide a raw array output buffer. * The Windows & invalid UTF-16 thing... I still think invalid UTF-16 should round-trip. > - What is your evaluation of the implementation? Haven't had much time to check the implementation. What I did notice is that when windows.h is not used, the WinAPI prototypes are declared in the global namespace. This can cause issues when windows.h is also included before/after the Nowide headers, and the prototypes don't match exactly (e.g. short vs. wchar_t). Also it pollutes the global namespace. I think Nowide should do what other Boost libraries do, and declare the prototypes in a private detail namespace instead. > - What is your evaluation of the documentation? Incomplete. Too few examples and the reference documentation leaves many things unclear. IMO the reference documentation should unequivocally define the contract of each API. Also I think the documentation should make it very clear what Nowide does and doesn't do on different platforms. Especially that it doesn't do anything Unicode-related on POSIX platforms and that using it does NOT mean the application will only have to deal with UTF-8 strings on POSIX platforms. Also parts of the documentation that suggest or even _state_ that systems like Linux internally use UTF-8 should be fixed. > - What is your evaluation of the potential usefulness of the library? I'd say it's useful. > - Did you try to use the library? With what compiler? Did you have any > problems? No. > - How much effort did you put into your evaluation? A glance? A quick > reading? In-depth study? Quick reading of the documentation + some very quick glances at parts of the implementation. > - Are you knowledgeable about the problem domain? More or less. I have never used or written a "nowide" layer myself, but I have spent plenty of time "widening" Windows-only applications. > And most importantly: > - Do you think the library should be accepted as a Boost library? Be sure to > say this explicitly so that your other comments don't obscure your overall > opinion. I certainly wouldn't vote against it. I didn't spend enough time to understand every aspect of it though, so I don't feel qualified to vote for it either. I would however suggest to require a major update of the documentation before accepting it. Regards, Paul Groke

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Re: [boost] [cmake] Minimum viable cmakeification for Boost
by Thomas Heller 23 Jun '17

23 Jun '17

Am 20.06.2017 5:08 nachm. schrieb "Niall Douglas via Boost" < boost(a)lists.boost.org>: >> Niall says that using the global BUILD_SHARED_LIBS is a cmake2ism, and >> that explicit targets are preferred nowadays. > > Niall, can you point me to a reference stating this? Preferably some cmake > documentation telling me what the right(tm) thing to do is. Any cmake construct which requires you to write an if() in a non-root-level CMakeLists is a cmake2-ism. There are a very few places in cmake3 remaining where no good alternative to global variables exist. BUILD_SHARED_LIBS is definitely not one of those. I'll ask again: do you have any reference to those statements? The official cmake docs seem to disagree about this specific case. I would even call it non sensical alltogether. Why should the root cmake be responsible for configuring a specific sub module. This is asking for cluttering everything into one single entity in a (almost) totally unrelated place. Why not keep it local to where it should be used. One concrete example: I have networking layer which supports different transports, say tcp, libfabric, MPI and infiniband verbs. The user of my library doesn't really care about which one is used, so ideally, I would give him a compiled version of my library with the internal settings I believe are best for him. In that case, my network layer module would be configured with one of those options. Naturally, I would think, those options are defined within this very sub project. The root project really doesn't care, nor do I want that this implementation detail leaks into the users CMakeLists.txt. Would you consider that bad practice to begin with? How would you solve this? There are tons of other use cases very similar to that. Having everything clobbering up in the root Cmakelists.txt doesn't sound appealing to me. Shared libraries usually have different settings to static libs and again to header only libs. They have different relationships to their dependencies, different usage requirements for consumers. You can use generator expressions to encode those differences, but then you've hard coded them so external cmake no longer can easily override them. You have just made your non-root CMakeLists hard to reuse by cmake you didn't write nor design. Generator expressions are also hard to write and debug, are overwhelmingly confusing to read, and randomly don't work in some places depending on which build system generator you are using. So best avoid all of that complexity - place no complexity at all outside the rootlevel CMakeLists. Declaration only. Place all custom logic solely in rootlevel CMakeLists only. > Any definite source on what a cmake2ism is or is not would be highly > appreciated. > > > As a general observation, I see a lot of statements along the lines of "I > state that XYZ is preferable over UVW", it would be nice to have to have > background information (pros and cons anyone? what do the cmake > authors/docs have to say about this?) on those statements so that everyone > can form their own opinion instead of having to choose whom to trust about > what's "standard" cmake. I believe Stephen Kelly is negotiating a book deal on this. It'll be some time before that book lands though. Niall -- ned Productions Limited Consulting http://www.nedproductions.biz/ http://ie.linkedin.com/in/nialldouglas/ _______________________________________________ Unsubscribe & other changes: http://lists.boost.org/ mailman/listinfo.cgi/boost

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[build] Use address-model in library filenames
by Vinnie Falco 23 Jun '17

23 Jun '17

Please add the address-model (32 or 64) into the encoded name which describes a library, so that 32-bit and 64-bit libraries may reside in the same dir. I'd like to avoid a lengthy debate, and if no one wants to do it just provide me with working code for accomplishing it and I'll submit a pull request. -- Follow me on Github: https://github.com/vinniefalco

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Outcome/expected/etc/etc/etc
by Gottlob Frege 22 Jun '17

22 Jun '17

I've now read ALL the emails. Here's some thoughts, in no particular order. - I wonder, Niall, if your uses of the empty state could/should be compared to how people sometimes use -1 or 0, etc - ie "special values as errors". I typically don't like that pattern (yet I've done it anyhow - performance/laziness/etc - but typically only in localized cases, not in "APIs"). So I'm wary about this empty state thing. If we do have an empty state, I like it as a separate type - code needs to deal with it separately. I like the idea of taking a possibly-empty type, checking for empty, and creating a never-empty type, and passing that along so future code need not worry. - I think the narrow and wide contracts should be in the same type, not separate types. This is C++. I suggest "access" if you want long names. ie T & val = oc.access_value(); // possible UB (I almost also suggested "deref" but "deref_value" is wrong - you are deref'ing the outcome, not the value) - I agree with Vicente's concern that functions that behave differently need to be named differently. I haven't looked at the new (or old) API carefully enough, but as a (possibly hypothetical) example: wide_type::value() // returns value, or throw if no value narrow_type::value() // returns value, or UB if no value These functions are not the same, and should not be named the same. Since you thus need different names anyhow (ie value and access_value), why not put them both on the same API? I'm not yet sure if you end up with similar examples with possibly_empty_type::something() and never_empty_type::something(). - I see value in the idea that the narrow contract takes more typing, but I actually *like* using * and -> for the narrow contract because I have 30+ years of training in looking at * and -> and recognizing it as "this may be unsafe, examine the code to see how it is guaranteed". Boost.Optional specifically chose * for that very reason. (on the other hand, I have 0 training on spotting access_value(), but on the third hand, it is easy to grep for) - exception() returns error, error() doesn't return exception, etc: would it be better/easier/clearer if we introduced another name, such as "failure" or whatever? ie exception() only returns the stored exception, error() only returns the stored error(), and then has_failure() would return true in either case, failure_exception() returns exception, generates an exception from error if necessary, etc? - I dislike "exceptions are for exceptional circumstances". Yes it is a common thing, but it is usually wrong. Using Outcome to enable the pattern of "handle errors, but totally cancel the operation on exceptions" might actually turn out to be a useful pattern, but I think this is actually slightly different from the "exceptions are for exceptional cases" camp, as they typically use that chant to choose whether their API will use exceptions or errors, not both in a single API. So I agree with Emil - for most APIs, error-codes vs exceptions" is basically trying to handle the same thing - failure (or "disappointment"). Using both error-codes and exceptions in a single API is somewhat new. And interesting. (There is lots of code that almost-unknowingly uses error-codes and exceptions in the same API, but that is because they don't realize push_back throws or they pretend it doesn't, etc - it isn't really an API design choice) - this ring buffer thing sounds interesting. I haven't looked at it at all, so maybe this makes no sense: should it use thread-local? - I think std::expected should always throw something deriving from std::exception. So if E derives from std::exception, we can throw it. If E is exception_ptr we can (re)throw it. If E is error_code/system_error/etc we can figure out what to throw. If E is user-type, then we wrap it in bad_expected or whatever. (And/or allow user E-to-exception customization somehow). This sounds complicated, but it is easily summarized/taught as "the standard always throws std::exceptions" - I HATE the dual interface of std::filesystem. Worse, there is a chance it is setting a precedent for future std APIs (dual APIs have been proposed elsewhere). Let's please kill it before a dual API strikes again. However, the other problem with trying to "single-fy" the std::filesystem (or any other) API is that users who want error codes sometimes don't want the cost of the extra data (paths, etc). The only way to handle that may be with customizable callback functions that capture the error-info however you like, or something similar to callbacks. - I really look forward to Peter's never-empty variant - and have been hoping for one ever since std::variant was finalized. Not because I dislike std::variant, but just because I think the option should be there for those who need/want it. Regardless, std::variant, in my world, is never empty, since it is only empty when a move operator throws, which should be never and/or when I can't allocate 64 bytes, in which case I'm screwed anyhow. Some days I'm like "man just accept empty, it would be a simple API", but then I think "it is stupid for variant<int, double> to be empty". Other days I think "just double buffer when necessary" (I assume that's your direction Peter?), but then I think "I don't want double-buffering variant<list, vector> to go on/off based on whether I use MS std vs libc++ etc" and also "I don't want double buffering for cases that only happen in theory, not in practice". I like the trade-offs of std::variant. I do agree that Boost should have a variant2 with different choices than std::variant - I think that actually helps the standard - we can choose a direction and instead of telling people "tough luck" when they disagree, we can say "use boost variant2 when you want those properties". - Andrzej: > Actually, now I am thinking not about Boost.Outcome but specifying these > preconditions in the Standard. If you want to std::terminate upon some > condition rather than let the program do random things, you could say. > > *Requires:* `!r` with rescue action `std::terminate()`. This sounds a bit like the contracts proposal - where you get to define what happens when contracts are broken. I'm cautiously hopeful that contracts could help with LEWG's constant struggles with wide vs narrow. - I agree with those who were saying (or thinking) that Boost was - and should again be - the place where APIs go before going into the standard. APIs (mostly) shouldn't bypass boost and go to the standard directly. Or at least an API needs a similar user-base (both in scale and diversity - ie an internal google API has scale, but not necessarily diversity). Since I know a number of LEWG members agree with me on this, don't be surprised to see some push-back from the committee for proposals without that kind of backing, and also don't be surprised if Boost gets flooded with "the committee told me to come here first". Of course I don't speak for LEWG, so maybe none of that happens, we haven't had that discussion yet. I actually probably had more to say - I should have made notes as I was reading all... those... emails. Tony

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[review] Review of Nowide (Unicode) starts today
by Frédéric Bron 22 Jun '17

22 Jun '17

Hi Everyone, The formal review of Artyom Beilis' Nowide library starts today and will last until Wed. 21st of June. Your participation is encouraged, as the proposed library is uncoupled, focused and rather small. Nowadays, everyone needs to handle Unicode but this is very difficult using only the standard library in a platform independant way. Nowide offers a very simple way to handle Unicode the same way on Windows/MacOS/Linux. Key features: * work with UTF-8 in your code, Nowide converts to OS encoding * Easy to use functions for converting UTF-8 to/from UTF-16 * A class to fixing argc, argc and env main parameters to use UTF-8 * UTF-8 aware functions: - stdio.h functions (fopen, freopen, remove, rename) - stdlib.h functions (system, getenv, setenv, unsetenv, putenv) - fstream (filebuf, fstream/ofstream/ifstream) - iostream (cout, cerr, clog, cin) Documentation: http://cppcms.com/files/nowide/html GitHub: https://github.com/artyom-beilis/nowide git clone https://github.com/artyom-beilis/nowide.git Latest tarballs: - to be unzipped in boost source: https://github.com/artyom-beilis/nowide/archive/master.zip - as a standalone library: http://cppcms.com/files/nowide/nowide_standalone.zip Nowide has standard boost layout. So, just put it into the boost source tree under libs/nowide directory for building and running tests. Or alternatively - for header only part of the library add the nowide/include path to the include path of your projects. Please post your comments and review to the boost mailing list (preferably), or privately to the Review Manager (to me ;-). Here are some questions you might want to answer in your review: - What is your evaluation of the design? - What is your evaluation of the implementation? - What is your evaluation of the documentation? - What is your evaluation of the potential usefulness of the library? - Did you try to use the library? With what compiler? Did you have any problems? - How much effort did you put into your evaluation? A glance? A quick reading? In-depth study? - Are you knowledgeable about the problem domain? And most importantly: - Do you think the library should be accepted as a Boost library? Be sure to say this explicitly so that your other comments don't obscure your overall opinion. For more information about Boost Formal Review Process, see: http://www.boost.org/community/reviews.html Thank you very much for your time and efforts. Frédéric

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[cmake] Minimum viable cmakeification for Boost
by Niall Douglas 22 Jun '17

22 Jun '17

I've finished the mockup which can be studied at: https://github.com/ned14/boost-bmv-cmake Just Boost.System was cmakeified. Extensive comments are throughout to explain every single line of cmake and why it's there. A small sample program is in the root of the repo to show how this cmake would be used by end user programs. Readme.md follows for those who don't like clicking on links: --- cut --- This is a mock up of a **bare minimum viable** cmakeification of the Boost C++ libraries for the community to study and evaluate. It only cmakeifies Boost.System alone, its upstream dependencies are stubbed/faked. A demo program which shows how one would link against Boost.System is in this directory (`example_client_program`) and it demos linking against boost::system as a header only library, as a static library and as a shared library. # Specific design goals of this mock up: - Modern, **highly reusable by unknown third party cmake** cmake3 only throughout. - Minimum possible cmake complexity, no cmake innovating, even at the cost of extra boilerplate. - No custom macros, functions, nor custom build logic. Only vanilla cmake3. Keep the learning curve for the build system as gentle as is possible. - **Strict** separation of non-fixed configuration and build. Child CMakeLists must only EVER define build and *fixed* configuration like "I need C++ 11 minimum". *Variable* configuration like naming, directory layout for outputs, optimisation flags etc is ALWAYS defined in the **rootmost** CMakeLists. NEVER in child CMakeLists. - All custom build logic should always be placed in rootlevel cmake scripts (command line programs written in cmake, runnable using `cmake -V`, these can take args etc) or rootlevel CMakeLists, or combinations thereof. # Stuff in there we might yet remove: - This cmake mockup explicitly documents dependencies between Boost libraries in cmake, and so when I link against say Boost.System, cmake will also link in the things Boost.System depends against. Moreover this is minimal, so ONLY the stuff minimally necessary to fulfil the need for Boost.System is built. - We allow those Boost libraries support it to present header only, static and dynamic linkage editions of themselves. This does complicate the CMakeLists however. # What we don't do: - Test the boundaries of cmake or push any limits of what's possible. - Bespoke libraries of common functions dragged in wherever. - Complex custom build logic which needs to be documented and learned off by library developers. - Do anything which gets in the way of CMakeLists reuse by any arbitrary third party cmake written by any Boost user. --- cut --- The code should be fairly self explanatory. Yes there are no tests support. We are limiting the scope of discussion to build only for now. Technical questions are welcome. Niall -- ned Productions Limited Consulting http://www.nedproductions.biz/ http://ie.linkedin.com/in/nialldouglas/

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[review] Beast review coming up!
by Michael Caisse 22 Jun '17

22 Jun '17

The Boost formal review of Vinnie Falco’s Beast library will take place July 1 - 10, 2017. 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 protocol vocabulary types and algorithms using the consistent asynchronous model of Boost.Asio. This library will be familiar to programmers that have used Boost.Asio or the Networking TS. Users who wish to use asynchronous interfaces should already know how to create concurrent network programs using callbacks or coroutines. Beast is designed for: * Symmetry: Algorithms are role-agnostic; build clients, servers, or both. * Ease of Use: Boost.Asio users will immediately understand Beast. * Flexibility: Users make the important decisions such as buffer or thread management. * Performance: Build applications handling thousands of connections or more. * Basis for Further Abstraction. Components are well-suited for building upon. Beast can be found here: * Documentation : <http://vinniefalco.github.io/beast/> * Source code : <https://github.com/vinniefalco/Beast> * The FAQ answers real questions that come up : <http://vinniefalco.github.io/beast/beast/design_choices/faq.html> A lightning talk from CppCon 2016 introducing Beast can be found here: <https://www.youtube.com/watch?v=uJZgRcvPFwI> If you find an obvious bug or problem with the library, please open a GitHub Issue <https://github.com/vinniefalco/Beast/issues>. Vinnie has a track record of resolving issues quickly. Please feel free to take an early look at the library and ask questions. Maybe even click that github Star button! The actual review will be against a non-mutating branch starting July 1st. -- Michael Caisse Ciere Consulting ciere.com

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[build] Use full compiler-version in library filenames
by Deniz Bahadir 22 Jun '17

22 Jun '17

Hi list, While reading Vinnie's mail (regarding the Boost library filenames which should additionally contain the address-model) I remembered another problem existing with library filenames. That is, that Boost libraries built with newer GCC versions (since GCC 5) never add the compiler-version into the library filenames. Building with GCC 5 and newer only adds "gcc" into the filename to determine the toolset, while building with earlier versions of GCC (e.g. GCC 4.9 or GCC 4.8) additionally adds the compiler's version (e.g. "gcc49" or "gcc48"). I assume this might be due to the fact that the version-scheme of GCC changed since GCC 5 and somehow the logic in Boost.Build no longer works because of this. But in order to install boost-libraries built by different GCC versions side-by-side in the same directory the version-number is really required in the filename. Maybe someone can fix this again? A bug-report on Github which addresses this issue already exists: https://github.com/boostorg/build/issues/191 Thanks in advance, Deniz -- BENOCS GmbH Dipl.-Inform. Deniz Bahadir Winterfeldtstr. 21 10781 Berlin Germany Phone: +49 - 30 / 577 0004-22 Email: deniz.bahadir(a)benocs.com www.benocs.com Advisory Board (Chairman): Stephan Schröder Board of Management: Dr.-Ing. Oliver Holschke, Dr.-Ing. Ingmar Poese Commercial Register: Amtsgericht Bonn HRB 19378

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[review] Review of Nowide has finished
by Frédéric Bron 22 Jun '17

22 Jun '17

Thanks for you interest and the discussion. Please be patient, it will take a few days for me to compile all the discussions and give the result of the review. Kind regards, Frédéric

1 0

1.65 closes for new libraries and breaking changes this Friday
by Marshall Clow 22 Jun '17

22 Jun '17

[ The calendar says today, but I forgot to send this out, so we're pushing the deadline back two days. ] 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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Re: [boost] [review] Review of Nowide (Unicode)
by Yakov Galka 21 Jun '17

21 Jun '17

Dear all, Here is my review of the library. - What is your evaluation of the design? > I welcome the UTF-8 approach on Window. However, the fact that Nowide does not handle invalid UTF-16 transparently is an issue that has to be addressed. - What is your evaluation of the implementation? > Going through the code I can't spot any implementation issues. > - What is your evaluation of the documentation? > It's clear. No issues found. > - What is your evaluation of the potential usefulness of the library? > I already use this approach through a different implementation. Even though I wouldn't bring Boost just for that single library, for projects that already use Boost it might be a valuable addition. I do think that Nowide offers a superior solution to encoding issues compared to Boost.Filesystem. > - Did you try to use the library? With what compiler? Did you have any > problems? > I did try it years ago when it was first submitted to Boost. I didn't try the recent version, so NO. > - How much effort did you put into your evaluation? A glance? A quick > reading? In-depth study? > 30 minutes reading the code + mailing list discussions. > - Are you knowledgeable about the problem domain? > I rate myself as an expert. I'm a co-author of utf8everywhere.org. DISCLAIMER: I met Artyom a couple times IRL. > - Do you think the library should be accepted as a Boost library? Be > sure to say this explicitly so that your other comments don't obscure > your overall opinion. > Conditional acceptance, subject to transparent invalid UTF-16 resolution. -- Yakov Galka http://stannum.co.il/

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[review] Last day to send your review of Nowide (Unicode)
by Frédéric Bron 21 Jun '17

21 Jun '17

Dear all, This is the last day to submit your review of Artyom Beilis' Nowide library. So far, 12 people participated to the review (not counting the author and the review manager): - Andrzej Krzemienski - Chris Glover - Degski - Edward Diener - Gavin Lambert - Niall Douglas - Norbert Wenzel - Paul Groke - Peter Dimov - Vadim Zeitlin - Yakov Galka - Zach Laine 8 reviews where received including * 6 reviews said nowide should be accepted (with conditions): - Degski, - Peter Dimov - Andrzej Krzemienski - Chris Glover - Norbert Wenzel - Yakov Galka * 1 review did not choose between accept/do not accept: - Paul Groke * 1 review said nowide should not be accepted as is: - Zach Laine Your participation is encouraged, as the proposed library is uncoupled, focused and rather small. Nowadays, everyone needs to handle Unicode but this is very difficult using only the standard library in a platform independant way. Nowide offers a very simple way to handle Unicode the same way on Windows/MacOS/Linux. Key features: * work with UTF-8 in your code, Nowide converts to OS encoding * Easy to use functions for converting UTF-8 to/from UTF-16 * A class to fixing argc, argc and env main parameters to use UTF-8 * UTF-8 aware functions: - stdio.h functions (fopen, freopen, remove, rename) - stdlib.h functions (system, getenv, setenv, unsetenv, putenv) - fstream (filebuf, fstream/ofstream/ifstream) - iostream (cout, cerr, clog, cin) Documentation: http://cppcms.com/files/nowide/html GitHub: https://github.com/artyom-beilis/nowide git clone https://github.com/artyom-beilis/nowide.git Latest tarballs: - to be unzipped in boost source: https://github.com/artyom-beilis/nowide/archive/master.zip - as a standalone library: http://cppcms.com/files/nowide/nowide_standalone.zip Nowide has standard boost layout. So, just put it into the boost source tree under libs/nowide directory for building and running tests. Or alternatively - for header only part of the library add the nowide/include path to the include path of your projects. Please post your comments and review to the boost mailing list (preferably), or privately to the Review Manager (to me ;-). Here are some questions you might want to answer in your review: - What is your evaluation of the design? - What is your evaluation of the implementation? - What is your evaluation of the documentation? - What is your evaluation of the potential usefulness of the library? - Did you try to use the library? With what compiler? Did you have any problems? - How much effort did you put into your evaluation? A glance? A quick reading? In-depth study? - Are you knowledgeable about the problem domain? And most importantly: - Do you think the library should be accepted as a Boost library? Be sure to say this explicitly so that your other comments don't obscure your overall opinion. For more information about Boost Formal Review Process, see: http://www.boost.org/community/reviews.html Thank you very much for your time and efforts. Frédéric

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[sort] Timsort review result
by Steven Ross 21 Jun '17

21 Jun '17

After reviewing the responses, I have rejected Timsort. Here are the reasons: 1. No author/maintainer responses to the questions on boost (except for forwarding some documentation links). We need a maintainer for all our source, and I'm not volunteering to maintain new functions as complex as Timsort. 2. There was no response on the Timsort bug reported during the review, nor any tests for it. 3. We need better tests. 4. Francisco is including a more efficient stable sort as part of his additions to the library, including handling special cases like Timsort handles better than stable_sort does. Francisco will maintain his code. I'd like to note that many people THINK they are experts on sorting because they covered it in class or may have read about it in a textbook, but most do not understand hybrid sorts well. As a specific example, I saw O(N*log(N)) mentioned as the worst-case speed limit of general-case sorts, when in fact Spreadsort beats that as described in its docs: http://www.boost.org/doc/libs/1_61_0/libs/sort/doc/html/index.html#sort.ove… Many people also don't carefully analyze for worst-case performance, which can be tricky. With regards to future sorting library reviews, I'll get at least a one-page doc describing the algorithm for the review in advance, but the boost documentation formatting is an unreasonable request for a simple sorting function, and I don't see the value it adds for these simple reviews. It is useful for a full library, but we'll be integrating the documentation into our full library after a new function is accepted. It isn't accurate to call it a mini-review (as described here: http://www.boost.org/community/reviews.html#Fast-Track) because it's reviewing completely new source we're talking about adding to the library. That said, do you still want me to a call the upcoming one for pdqsort a "mini-review"?

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Re: [boost] [cmake] Minimum viable cmakeification for Boost
by Thomas Heller 20 Jun '17

20 Jun '17

Am 20.06.2017 2:17 nachm. schrieb "Niall Douglas via Boost" < boost(a)lists.boost.org>: On 20/06/2017 07:27, P F wrote: > >> On Jun 19, 2017, at 6:42 PM, Niall Douglas via Boost >> <boost(a)lists.boost.org> wrote: >> >> I've finished the mockup which can be studied at: >> >> https://github.com/ned14/boost-bmv-cmake >> >> Just Boost.System was cmakeified. Extensive comments are throughout >> to explain every single line of cmake and why it's there. A small >> sample program is in the root of the repo to show how this cmake >> would be used by end user programs. > > Here some feedback, I have: > > - Having things like `::hl` or `::sl` is quite strange. In cmake, I > set `BUILD_SHARED_LIBS=On` when I want a shared library or I set it > to `BUILD_SHARED_LIBS=Off` when I want a static library. There should > only be one target `boost::config` or `boost::system` that I use. BUILD_SHARED_LIBS is a cmake2-ism and should not be present in modern cmake. Moreover, cmake now supports header only libraries, and BUILD_SHARED_LIBS causes problems with eventual C++ Modules support. The ::hl suffix means "link against the header only library edition", the ::sl suffix means "link against the static library edition" and the ::dl suffix means "link against the dynamic library edition". Err, I tend to highly disagree here. As a library author, I can not know if my users need a static or shared library. For a header only library, this hardly matters. Having those different conventions greatly increases the complexity for consuming your library (which do I need again in which circumstances?) so we need to depend on variables to link against the right target (so much for cmake2isms). Some bikeshedding over those names occurred off list. They don't hugely matter, they could be boost::system::header, boost::system::static and boost::system::shared if you wanted. Some bikeshedding also occurred over what boost::system with no suffix should mean. I recommend "whatever library edition the maintainer recommends as the best one" which is NOT necessarily the header only edition. For example, in the future with C++ Modules support the additional suffixs ::hlm, ::slm and ::dlm will be needed. Or longer named, boost::system::header_module, boost::system::static_module and boost::system::shared_module. So if C++ Modules were available, the maintainer might recommend the ::dlm variety, but recommend the ::hl variety if they weren't available. I think that will hugely vary per library as C++ Modules won't necessarily be always a win. Also, end users may wish to assemble all of Boost into a single C++ Module. We don't want to get in the way. > - Each project do things like > `include("${CMAKE_CURRENT_SOURCE_DIR}/../../cmake/BoostVersion.cmake”)` > which is broken when built on its own. That was intentional. Some bikeshedding occurred over that too with respect to which Boost library guaranteed to be a dependency for all other libraries ought to host the version setting script. Boost.Config is most likely. So the above is a placeholder. > - Doing `if(NOT TARGET boost::assert::hl)` is wrong. A target does > not have to exists to be able to link against it. Plus, it should > call `find_package(boost_assert)` to bring in the target for when its > not built in the superproject. That part is there solely to enable modular build. If you don't want to bother with modular build as this is a bare minimum viable cmakeification, you can eliminate it. > - There is no installation of the targets Not necessary right now, so out of scope. > - Doing `target_include_directories(boost_core-hl INTERFACE > "include”)` is wrong as this will only add the include directories > for the build. The include directories should be added for the build > and for the installation. As I've repeatedly explained now, installation logic is best implemented by a rootmost CMakeLists. Not in the per-library CMakeLists. We do tell cmake what targets are used by installation via install(TARGETS ...). That's the bare minimum needed for other cmake to implement the remaining installation logic. (On wider picture stuff, install paths need to be absolute I've found, whereas build paths can usually be relative. Relative paths are much nicer during build. In a rootmost CMakeLists which implements some installation logic, you'd iterate the targets for the Boost libraries and configure each programmatically for the appropriate install for that library and that type of library. All the metadata you need to make decisions is available) Niall -- ned Productions Limited Consulting http://www.nedproductions.biz/ http://ie.linkedin.com/in/nialldouglas/ _______________________________________________ Unsubscribe & other changes: http://lists.boost.org/ mailman/listinfo.cgi/boost

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Re: [boost] [cmake] Minimum viable cmakeification for Boost
by Thomas Heller 20 Jun '17

20 Jun '17

Am 20.06.2017 4:21 nachm. schrieb "Peter Dimov via Boost" < boost(a)lists.boost.org>: Thomas Heller wrote: > As a general observation, I see a lot of statements along the lines of "I > state that XYZ is preferable over UVW", it would be nice to have to have > background information (pros and cons anyone? what do the cmake > authors/docs have to say about this?) on those statements so that everyone > can form their own opinion instead of having to choose whom to trust about > what's "standard" cmake. > That's the problem with CMake, there's no way for someone like me who does not follow it to get a definitive answer to what idiomatic CMake 3.5+ is. There are several articles about it, they all say more or less the same thing - use target_*. I get that. But that's not enough. I see a general (and very predictable) trend of moving from imperative to declarative. Programmers like imperative, but a proper build system really prefers declarative, so CMake is trying to evolve towards declarative. Take for example find_package. It's a command, find me this package, now. But it's much better if a library does not issue "find me this package" commands, but rather declares which packages it needs. So we get "best practice" hacks like redefining find_package. I'm sorry, this doesn't feel right. I hear what you're saying. We'll end up innovating cmake, which for me isn't a bad thing. I'm favoring CMake due to its great support for generating for all kinds of different environments (including proper visual studio solutions). To be fair, I haven't invested as much time in boost.build as I did for cmake. For all platforms I work on, both work equally nice with different quircks on different ends. I'm not using an ide though. For the sake of ide support, I'd lean towards cmake. Regarding the discussion of what's right and wrong when writing your CMakeLists.txt files, it's almost bike shedding. If you want to depend on a library, you'll make it work, no matter what, that's what we do. Nevertheless, in terms of cmakeisms, I really like what Paul put together and what Daniel Pfeifer said in his talk makes a lot of sense in a cmake world. _______________________________________________ Unsubscribe & other changes: http://lists.boost.org/mailman /listinfo.cgi/boost

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proposal - modularize Boost build system
by Stefan Seefeld 20 Jun '17

20 Jun '17

One of Boost's bottlenecks is its monolithic build infrastructure. It would be beneficial for many different use cases (testing, packaging, etc.) to decouple the building of Boost libraries (well, those that require building, see the listing in http://www.boost.org/doc/libs/1_64_0/more/getting_started/unix-variants.htm…) such that they may optionally be built stand-alone. At present, building a Boost library requires the entire (super-)repository to be checked out, and the build logic itself involves traversing the entire source tree, looking for a "Jamroot". What would be beneficial to many would be a workflow like this: 1) Have a development environment with (some version of) Boost pre-installed (or at least the parts that the library being built depends on). 2) Check out a single Boost repository (e.g., https://github.com/boostorg/python) 3) Invoke a command to build it (if there is anything to build) 4) Invoke a command to test it 5) Invoke a command to install it 6) Invoke a command to package it (optional) While it's of course already possible to do all the above by adding support for another build infrastructure (point in case: Boost.Python right now uses SCons for this very reason), this means duplication of effort, as Boost as a whole is still built, tested (and even packaged for binary packages) using Boost.Build, meaning I need to maintain two sets of build infrastructure. This proposal thus has two parts: 1) Make the nested build logic independent of the outer bits, so individual libraries can be built stand-alone (for example, using b2 by adding a `--with-boost` set of options to point to the location of the prerequisite parts of Boost). 2) Define a clear interface the outer build logic will use to invoke the nested build commands. Note that for my own case above (Boost.Python), providing 2) would be enough, i.e. by having a way for me to "plug in" my SCons commands to build and test Boost.Python could obsolete the existing Boost.Build logic as defined in Boost.Python (as well as the prerequisite parts in Boost.Build's "python" module). However, as my proposal is *not* actually advocating to move away from Boost.Build, but rather to modularize it, I think 1) is essential to let everyone else (who may not be inclined to use anything other than Boost.Build) to also take advantage of modularization. While I'd rather avoid delving into the technical details of how this could possibly be implemented (if you really must, *please* do so in a new thread !), let me outline a few use-cases that would be made possible by the above: * individual projects would be free to switch to their preferred infrastructure, including CMake, SCons, etc., if they so wish * individual projects could be much more easily developed and contributed to * individual projects could be much more easily tested, notably in CI environments * individual projects could be much more easily packaged All of the above advantages are *huge*, and reflect real-world needs, and the technical issues to solve these are all minor. The question really is whether there is enough will to move into that direction. I'd be very happy to participate in the work needed to implement this. But first we need to agree that this is where we want to go. Thanks, Stefan -- ...ich hab' noch einen Koffer in Berlin...

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Review of Nowide
by Chris Glover 20 Jun '17

20 Jun '17

Hi, The following is my review of the proposed Boost.Nowide library. This is my first official review of a boost library, so please forgive me if I've missed anything. - What is your evaluation of the design? At first I was surprised by lack of a platform agnostic encoding. However, through reading the docs and the discussion in the list, I believe this to be the correct choice. If a user has a need for a common encoding, I believe that would be best served by a different library that would ultimately have different issues and performance characteristics. One thing I'm not sure about is if the overlap between the fstream implementations in filesystem and nowide is necessary. It seems to me that if I set filesystem to be nowide aware (via boost::nowide::nowide_filesystem) then there's little reason for the nowide versions of the stream objects to exist, other than possibly eliminating one string copy on non-windows platforms and avoiding the filesystem dependency (and maybe those are good enough reasons). - What is your evaluation of the implementation? I only gave the implementation a glance. It looks good; clean, organized; with a full test suite and nothing weird stands out. It seems to be of the typical quality I expect from a boost library. - What is your evaluation of the documentation? The documentation is clear and complete, but I think it needs to explain at the top that the library does not present a uniform encoding for strings. This is discussed in the documentation near the end, under "Q & A", but I think it should be near the top. A suggestion is to add a section called "What Boost.Nowide is *not*" directly under the section titled "What is Boost.Nowide", otherwise I expect some users to be surprised. - What is your evaluation of the potential usefulness of the library? It is very useful. I am already using it. - Did you try to use the library? With what compiler? Did you have any problems? I converted one application that was using boost::filesystem::path to transport filenames around to use nowide instead. I had no issues, everything just worked. Some code was also simplified as a result -- not dramatically, but enough that it felt better. I tested the application on windows only using Visual Studio 2017. I also ran the tests under MSYS2 on Windows using gcc-6.3, on Windows using MSVC 2017 and on Ubuntu using gcc-7. Under MSYS, one test failed (Fail: Error boost::nowide::cin.putback(c) in test_iostream.cpp:17 main), but I haven't had a chance to look into why yet. All of the tests passed on the other platforms. - How much effort did you put into your evaluation? A glance? A quick reading? In-depth study? I followed the discussion, read the docs, integrated the library, used the API and tested the resulting program. All in, I think that took me about 4 hours. This seems quick, but to me that is a testament to a solid design and clear documentation because the conversion process was very simple. - Are you knowledgeable about the problem domain? I am aware of the problem and have worked around it in the past by using filesystem::path as a string. However, most of the environments I work in professionally are controlled in a way that allows us to avoid this problem most of the time, so I have not had extensive experience with it. - Do you think the library should be accepted as a Boost library? Yes. I am already using it and expect I will be using it a lot more going forward. -- chris

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[nowide] review
by Andrzej Krzemienski 20 Jun '17

20 Jun '17

Hi All. This is a review of Boost.Nowide library. I am not really familiar with the problem. I used to do trivial tasks with files on Windows, but they were always ASCII, so the problems solved by Boost.Nowide never affected me. I am also not fa,iliar with the problems of converting from Windows encoding (*WTF* seems like the right choice of name) to UTF-8. I have read the documentation, and got some additional information from the author. I have downloaded the library and have run a toy program that plays with names that cannot be encoded in a single code-page. I am testing on Windows 7, MinGW, GCC 6.3, with -std=c++03. Compilation and linking works fine. Tests work fine too. Then, I tried the same example with normal `std::ifstream` and it did not work on Unicode file names and strings, which conforms that Boost.Nowide solves an existing problem. DESIGN: clear, logical, intuitive. IMPLEMENTATION: I did not look at. DOCUMENTATION: clear. POTENTIAL USEFULNESS: as specified in the docs, if you want to do things with multilingual strings in a platform independent way, you need a library like this. I vote to *ACCEPT* the library. I may not be qualified enough (the manager will weigh my vote), but the desctiption of the library, as well as the replies from Artyom convince me that the library addresses the problem in the right way and is reliable. Artyom, thanks for sharing this library, and submitting it for review. One minor thing. In th be docs (http://cppcms.com/files/nowide/html/) we read: boost::nowide::widen <http://cppcms.com/files/nowide/html/namespaceboost_1_1nowide.html#a6baacc1b…> returns std::string. I thing is thsould be std::wstring? Regards, &rzej;

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Atomic Shared Ptr
by Olaf van der Spek 19 Jun '17

19 Jun '17

Hi, Does Boost have anything like concurrency TS' atomic_shared_ptr? Gr, -- Olaf

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Re: [boost] Boost CRC maintainer (Daryle Walker) missing in action?
by Olaf van der Spek 19 Jun '17

19 Jun '17

Hi Daryle, Any luck on your new setup? Gr, Olaf On Mon, Nov 28, 2011 at 1:11 AM, Daryle Walker <darylew(a)gmail.com> wrote: > I can look at it once I've finished my new setup. > > I had to reset my computer after a partial crash years ago. I never > got around to recreating my programming setup. My computer had been > at its maximum Operating System level back then, which is now 3 > versions behind. For the past few months, I've had my sister's old > laptop, with Windows Vista, and am trying to add a programming setup > to it now. > > > On Tue, Nov 22, 2011 at 7:18 AM, Beman Dawes <bdawes(a)acm.org> wrote: >> Hi Daryle, >> >> This guy has volunteered to take over maintenance of Boost CRC. Should >> we take him up on his offer? > >> ---------- Forwarded message ---------- >> From: >> Date: Wed, Nov 2, 2011 at 7:51 AM >> Subject: [boost] Boost CRC maintainer (Daryle Walker) missing in action? >> To: boost(a)lists.boost.org >> >> >> Hi, >> >> It looks like the Boost CRC maintainer (Daryle Walker) is missing in action? >> >> No response to tickets from the past 3 years. What's the procedure in this case? >> >> https://svn.boost.org/trac/boost/ticket/2492 >> https://svn.boost.org/trac/boost/query?component=crc&col=id&col=summary&col… > > -- > Daryle Walker > Mac, Internet, and Video Game Junkie > darylew AT gmail DOT com -- Olaf

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Sanitizer bug or undefined behavior in format?
by Olaf van der Spek 19 Jun '17

19 Jun '17

Hi, I think it's about rdbuf() which doesn't appear to be virtual. Is this a bug in the sanitizer or is this call not allowed? alt_sstream.hpp: basic_oaltstringstream(stringbuf_t * buf) : pbase_type(buf, No_Op() ), stream_t(rdbuf()) { } $ g++ a.cpp -fsanitize=undefined && ./a.out /usr/include/boost/format/alt_sstream.hpp:146:60: runtime error: member call on address 0x7fffdb4f36a0 which does not point to an object of type 'basic_oaltstringstream' 0x7fffdb4f36a0: note: object has invalid vptr 00 00 00 00 00 00 00 00 00 00 00 00 18 3a 4f db ff 7f 00 00 b0 4c 37 fa 66 55 00 00 28 5b 0d 80 ^~~~~~~~~~~~~~~~~~~~~~~ invalid vptr a.cpp: #include <iostream> int main() { std::cout << boost::format("%d") % 1 << std::endl; // std::cout << boost::format("%04d-%02d-%02d") % (date->tm_year + 1900) % (date->tm_mon + 1) % date->tm_mday << std::endl; return 0; } -- Olaf

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Re: [boost] proposal - introduce API & ABI compatibility guidelines
by Brian Wood 19 Jun '17

19 Jun '17

Artyom Beilis writes: > The problem is that it isn't going to change in near future because > it is almost impossible to reach a consensus of some strategic > direction because any major change will find enough developers > who will not want one. > > So today I use boost only in applications and never in libraries. I'm only comfortable using Boost in private/closed source applications. I think on line code generation will help with some of the packaging problems discussed in this thread. Brian Ebenezer Enterprises - Enjoying programming again. http://webEbenezer.net

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proposal - introduce API & ABI compatibility guidelines
by Stefan Seefeld 18 Jun '17

18 Jun '17

Following up on this point made by Peter Dimov in another discussion: > This is part of the price you pay for being accepted as part of Boost > - the duty to act as an integration test for your Boost dependencies. > This is beneficial for you in the long term, because you can detect > breaking changes in your dependencies before they get shipped. If you > only test against 1.56, and 1.64 breaks your library, you won't hear > about it before 1.72. This does you no good, and it does your users no > good. You WANT to know if changes in 1.65's SmartPtr would break you > BEFORE 1.65 gets released. The real problem that you are touching here is Boost's lack of any sort of ABI or even API stability. So Boost 1.X and Boost 1.(X+1) are two distinct packages, as there is no metric that enables even to measure the amount of incompatibility between the two. Any normal library that's used in-production would have strong requirements for backward compatibility, to enable users to reason about the risk of upgrading etc. Thus, to follow up (and not pollute the original discussion about modularization), I'll propose the following: I'd like to see guidelines to be established for: * what API and ABI changes may be applied in a given release * have a clear definition of version numbers (major, minor, bug fix) with associated semantics * impose testing requirements to enforce the above. Stefan -- ...ich hab' noch einen Koffer in Berlin...

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[nowide] request for clarification
by Andrzej Krzemienski 17 Jun '17

17 Jun '17

Hi Everyone, I admit I am not quite familiar with the problem, but I understand that as one of the features, nowide offers a replacement for std::fstream that can be constructed with its string types. At the same time we have boost::filesystem that offers its own replacement for std::fstream that can be constructed with filesystem::path. Now, if I want to use `filesystem::path`s in my program (to be able to tell just any string from a filesystem path), can I still use the benefits of `nowide` library? Also, in the docs for nowide::ifstream, we read, "Same as std::basic_ifstream<char> but accepts UTF-8 strings under Windows." What about other systems? What does it accept on Linux? ascii? In documentation for `nowide::args`, we read, "args is a class that fixes standard main() function arguments and changes them to UTF-8 under Microsoft Windows." Does it write to the input strings in-place? is it even legal in C++? It "fixes", which implies that otherwise the args are "broken". How are args in function main() broken? (other than not being UTF-8)? Regards, &rzej;

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[review] More reviews of Nowide are welcome
by Frédéric Bron 16 Jun '17

16 Jun '17

Hi all, More official reviews are welcome for the boost nowide library. It's a small and very useful library, please consider taking some time to give us your feedback. Please answer the questions at the bottom of this message. Cheers, Frédéric (review manager) ---------- Forwarded message ---------- Date: 2017-06-12 6:20 GMT+02:00 Subject: [boost][review] Review of Nowide (Unicode) starts today Hi Everyone, The formal review of Artyom Beilis' Nowide library starts today and will last until Wed. 21st of June. Your participation is encouraged, as the proposed library is uncoupled, focused and rather small. Nowadays, everyone needs to handle Unicode but this is very difficult using only the standard library in a platform independant way. Nowide offers a very simple way to handle Unicode the same way on Windows/MacOS/Linux. Key features: * work with UTF-8 in your code, Nowide converts to OS encoding * Easy to use functions for converting UTF-8 to/from UTF-16 * A class to fixing argc, argc and env main parameters to use UTF-8 * UTF-8 aware functions: - stdio.h functions (fopen, freopen, remove, rename) - stdlib.h functions (system, getenv, setenv, unsetenv, putenv) - fstream (filebuf, fstream/ofstream/ifstream) - iostream (cout, cerr, clog, cin) Documentation: http://cppcms.com/files/nowide/html GitHub: https://github.com/artyom-beilis/nowide git clone https://github.com/artyom-beilis/nowide.git Latest tarballs: - to be unzipped in boost source: https://github.com/artyom-beilis/nowide/archive/master.zip - as a standalone library: http://cppcms.com/files/nowide/nowide_standalone.zip Nowide has standard boost layout. So, just put it into the boost source tree under libs/nowide directory for building and running tests. Or alternatively - for header only part of the library add the nowide/include path to the include path of your projects. Please post your comments and review to the boost mailing list (preferably), or privately to the Review Manager (to me ;-). Here are some questions you might want to answer in your review: - What is your evaluation of the design? - What is your evaluation of the implementation? - What is your evaluation of the documentation? - What is your evaluation of the potential usefulness of the library? - Did you try to use the library? With what compiler? Did you have any problems? - How much effort did you put into your evaluation? A glance? A quick reading? In-depth study? - Are you knowledgeable about the problem domain? And most importantly: - Do you think the library should be accepted as a Boost library? Be sure to say this explicitly so that your other comments don't obscure your overall opinion. For more information about Boost Formal Review Process, see: http://www.boost.org/community/reviews.html Thank you very much for your time and efforts. Frédéric

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Re: [boost] [review] Review of Nowide (Unicode) starts today
by Artyom Beilis 16 Jun '17

16 Jun '17

How would you therefore do this simple task: 1. get a directory from nowide::getenv -> base_dir (UTF-8 on Windows, unknown narrow on Posix) 2. create a file in base_dir which name is file_name encoded in UTF-8 (because it is created by the application). If I understand well, I should NOT do this: auto f = nowide::ofstream((boost::filesystem::path(base_dir) / file_name).string()); because this is guaranteed to work only on Windows where I have the guarantee that base_dir is UTF-8, right? Actually it is what exactly you should do. Once you turn on **nowide integration** with boost filesystem path::string does not perform any conversions on POSIX platforms. And you can safely concatenate two different strings and valid file will be created. Even if dir is in ISO 8859-1 and file in UTF-8. The file will be valid even if not representable in any encoding. Under windows you'll get the correct conversions from narrow to wide using the utf8/16 facet installed by boost.nowide/Filesystem integration as on Windows boost filesystem uses wide strings Artyom

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[interprocess] how to use lock_file with Unicode file name?
by Frédéric Bron 16 Jun '17

16 Jun '17

Hi, I have been using lock_file with ASCII file names without any trouble. Now I would like to be able to use non ASCII file names. How does it work? Currently, lock_file uses as input const char *. What about the encoding? Cheers, Frédéric http://www.boost.org/doc/libs/1_64_0/doc/html/boost/interprocess/file_lock.… http://www.boost.org/doc/libs/1_64_0/doc/html/interprocess/synchronization_…

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Re: [boost] [review] Review of Nowide (Unicode) starts today
by Frédéric Bron 15 Jun '17

15 Jun '17

> at Linux nowide fstream is > an alias to std::fstream If course! Frédéric

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[config][android] GCC-5 and 6 failures.
by John Maddock 15 Jun '17

15 Jun '17

There are some runtime (segfault) failures running config_test on andoid, see for example: http://www.boost.org/development/tests/develop/developer/CrystaX-apilevel-2… Can anyone with access to this platform (or preferably the test runner) see if defining BOOST_NO_CXX11_THREAD_LOCAL fixes the issue? That would be my hunch for the problem anyway. Many thanks, John. --- This email has been checked for viruses by AVG. http://www.avg.com

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[random] Request for Additional Generators
by degski 15 Jun '17

15 Jun '17

I would like to request the addition of 2 generators to Boost.Random. xoroshiro128+ <http://xoroshiro.di.unimi.it/xoroshiro128plus.c> Web page: http://xoroshiro.di.unimi.it/ A very fast PRNG, (quite a lot) faster than the fastest current boost generator, with a period of 2 ^ 128, which could/would be good for f.e. game programming (except for shuffling, see below). It also has a state of only 16 bytes on x64. The author states that the distribution is of higher quality than f.e. MT19937-64 <http://www.math.sci.hiroshima-u.ac.jp/%7Em-mat/MT/VERSIONS/C-LANG/mt19937-6…>. It's probably best to just read the web-page, as it goes into quite some detail and is in itself the summary of the research conducted in this area. Other than the normal boost complications, it's very easy to implement and I use my simplistic implementation to great satisfaction with the std and boost distributions. In this <https://www.codeproject.com/Tips/1083372/Random-Number-Generator-Recommenda…> article on CodeProject the issue of shuffling is raised. It's appears that shuffling of large arrays of data requires a generator with extremely long periods in order to be able to generate all the possible permutations. To this extent I would like to see in boost a generator like George Marsaglia's SuperKiss <https://groups.google.com/forum/#!topic/comp.lang.fortran/QiTrbq0XeyM> or/and a templated SFMT generator like this <https://sourceforge.net/p/int64/svn/HEAD/tree/snips/sfmt.hpp> one. degski -- "*Ihre sogenannte Religion wirkt bloß wie ein Opiat reizend, betäubend, Schmerzen aus Schwäche stillend.*" - Novalis 1798

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[review] Review of PolyCollection starts today (May 3rd)
by Ion Gaztañaga 15 Jun '17

15 Jun '17

Hi everyone, The formal review of Joaquín M. López Muñoz's PolyCollection library starts today. I'd like to encourage your participation as the proposed library is small and focused, and reviewers don't need to be domain experts to appreciate the potential usefulness of the library and propose improvements. PolyCollection implements fast containers of polymorphic objects. Typically, polymorphic objects cannot be stored directly in regular containers and need be accessed through an indirection pointer, which introduces performance problems related to CPU caching and branch prediction. Boost.PolyCollection implements a novel data structure that is able to contiguously store polymorphic objects without such indirection, thus providing a value-semantics user interface and better performance. Three polymorphic collections are provided: * boost::base_collection * boost::function_collection * boost::any_collection dealing respectively with classic base/derived or OOP polymorphism, function wrapping in the spirit of std::function and so-called duck typing as implemented by Boost.TypeErasure. The library can be found here: Incubator: http://blincubator.com/bi_library/polycollection/?gform_post_id=1643 Github: https://github.com/joaquintides/poly_collection and the documentation here: http://rawgit.com/joaquintides/poly_collection/website/doc/html/index.html Please post your comments and review to the boost mailing list (preferably), the Boost Library Incubator. or privately to the Review Manager (to me ;-). Here are some questions you might want to answer in your review: - What is your evaluation of the design? - What is your evaluation of the implementation? - What is your evaluation of the documentation? - What is your evaluation of the potential usefulness of the library? - Did you try to use the library? With what compiler? Did you have any problems? - How much effort did you put into your evaluation? A glance? A quick reading? In-depth study? - Are you knowledgeable about the problem domain? And most importantly: - Do you think the library should be accepted as a Boost library? For more information about Boost Formal Review Process, see: http://www.boost.org/community/reviews.html Waiting your reviews! Ion

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[review] Review of Nowide (Unicode) continues - summary of the dicussions so far
by Frédéric Bron 15 Jun '17

15 Jun '17

Dear all, The formal review of Artyom Beilis' Nowide library continues until Wed. 21st of June. Here is a summary of the discussions so far: 7 people participate to the review (not counting Artyom and my-self): - Degski - Niall Douglas - Paul Groke - Peter Dimov - Vadim Zeitlin - Yakov Galka - Zach Laine 2 official reviews have been shared, both positive for inclusion in boost (Degski, Peter Dimov). Discussions: Everybody is positive about the usefullness of the library but some major questions arose: 1. how should we handle invalid Unicode sequences (bytes or multi-bytes)? Allow? throws error? 2. there is an unsymmetric way of treatment between Windows and Posix: - on Windows, the conversion from UTF-16 checks for Unicode conformance and returns only valid UTF-8 or fails - on Posix, no check is performed that the input is a valid UTF-8 sequence. 3. in particular, on Windows, the roundtrip conversion UTF-16 -> UTF-8 -> UTF-16 is not guaranted if the initial string is non conformant One main issue is that existing files may have non conformant names and would therefore not been reachable by the nowide API on Windows. On Posix platforms, non conformant paths would work transparently. Different proposals have been made to address this: - convert from UTF-16 to a superset of UTF-8 so that the round-tip conversion is possible, this would mean that the library accepts non conformant strings on Windows as is done on Posix. Question: which enconding should be used (Modified UTF-8, WTF-8, CESU-8)? WTF-8 has the issue of being difficult to handle with string concatenations. - use RtlUTF8ToUnicodeN functions which replace wrong UTF-16 characters by U+FFFD but is this OK for round-trip? - see glib approach - add function to explicitly convert from wide to WTF-8 However, for the Posix case, the issue is that we cannot guarantee that the encoding is always UTF-8 so checking for conformance may be impossible. Hence the choice for not checking on Posix. Minor points: - Missing some documentation on what happens if invalid UTF-8 is provided (getenv, setenv, cout, cerr). - ::setenv on cygwin gives a compile time error (Peter Dimov proposed a fix) - suggestion to add stat and readdir Frédéric

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Packt: Mastering Git - Jakub Narębski
by degski 15 Jun '17

15 Jun '17

To those interested. On Packt, the ebook Mastering Git - Jakub Narębski <https://www.packtpub.com/application-development/mastering-git> is today avaialble for free download, free membership (registration) required. I don't work for Packt. degski -- "*Ihre sogenannte Religion wirkt bloß wie ein Opiat reizend, betäubend, Schmerzen aus Schwäche stillend.*" - Novalis 1798

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[poly_collection] Help with Intel 16.0
by Joaquin M López Muñoz 14 Jun '17

14 Jun '17

Hello, Boost.PolyCollection will be released with Boost 1.65 on Aug 9. So far regression tests are looking OK for MSVC>=14.0, GCC>=5.0 and Clang>=3.7: http://www.boost.org/development/tests/develop/developer/poly_collection.ht… For Intel>=16.0, though, all tests pass except test_algorithm (admittedly the one involving more complex code): http://tinyurl.com/ya52o3e5 As I don't have local access to that compiler it is very difficult for me to try to find the needed workarounds. If someone with interest in Intel and access to the tools wants to volunteer to help fix the offending test case, please be my guest. Contact me either through this list or by private email. Thank you, Joaquín M López Muñoz

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Mangled "From" field in mailing list posts
by Vladimir Prus 14 Jun '17

14 Jun '17

Hi, it seems that most of recent posts to the mailing lists have rather strange "From" field, e.g. From: Daniel James via Boost <boost(a)lists.boost.org> I see this problem both via NTTP and regular mail, including emails that appear to be posted directly with a mail client. That extra "via Boost" adds no value, and clutters mailbox. Is there any change to return back to having "From" field have just the name of the person? Thanks in advance, Volodya

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[trac] Add Boost.Process to Boost.Trac component list
by Ion Gaztañaga 13 Jun '17

13 Jun '17

Hi, I recently received a bug report for Boost.Process. Since it is not selectable in the component list the reporter selected "interprocess" which minimizes the error ;-) Could someone with permissions add "process" to the trac component list? Many thanks! Ion

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[beast] Request for Discussion
by Vinnie Falco 12 Jun '17

12 Jun '17

Beast provides low level HTTP and WebSocket interfaces built on Boost.Asio, the project is here: https://github.com/vinniefalco/Beast The plan is to solicit feedback from the Boost community before submitting a request for a formal review. First a brief update: I have attended CppCon 2016 and provided a 15 minute Lightning Talk on the library. There should be a video up at some point with all the talks, including mine. I spread the word about Beast and discovered that there are several folks in the wild already using the library and happy with it. There are also a couple of commercial products that are using it. One point brought up during the conference is that Beast does not offer sufficient higher level HTTP functionality. This omission is intentional. It is my idea to offer the building blocks (serializing and deserializing HTTP/1 messages, in synchronous and asynchronous flavors, and a universal HTTP message model), upon which other developers more knowledgeable than me could build those interfaces. The higher level pubic operations requested were: 1. Perform HTTP GET or POST and receive the response. Presumably this would handle both plain and TLS connections, handle redirects, and handle HEAD requests. Not sure about traversing proxies. 2. Expose an asynchronous HTTP server class which callers can instantiate with some sort of handler that returns the HTTP response given a request. It should be possible, in a minimal number of lines, to quickly get a server up and running. The requestor informed me that this functionality did not need to provide every possible feature or handle every use case. It just needed to handle the common use-cases. For the record, I am against this higher level functionality for a number of reasons. The higher the level of functionality, the more contentious the feature becomes, and the harder it is to satisfy a quorum of reviewers. No one would dispute that we need the ability to read a complete HTTP message from a socket. But not everyone will agree that a HTTP server needs an option to allow multiple listening sockets with different level of permissions. Another problem with offering higher level functionality is that it could be less likely to be approved for standardization in the C++ standard library. For example, the attributes of ease of use and fully functional oppose each other. If the functionality offered by a hypothetical std::http::client is not sufficient, a developer would be forced to write their own with little possibility to reuse parts of the implementation from the stdlib. I doubt the committee would approve of such a thing. I know I wouldn't. Admittedly I have little experience or knowledge on what would or would not get approved. A point was raised that a low-level-only HTTP implementation in Boost has the potential to discourage new users that need to perform simple operations like HTTP GET from using Boost in the future, given that robustly handling such operations would require the developer to write a significant amount of code. I can see some validity here. On the other hand, if Boost.Asio was submitted for a formal review today, would those same points be raised? Would Asio get rejected because it doesn't offer public interfaces for doing simple tasks like requesting an object from a web server? I wonder if perhaps the Boost formal review process has become defective. For reference here is what the current API offers: Example program that performs HTTP GET, then receives and prints the response: https://github.com/vinniefalco/Beast/blob/master/examples/http_example.cpp This is a high performance asynchronous HTTP server that serves local files as static pages. It is not an official API, it is part of the examples. Users who want a server need to copy the source code and modify it to suit their needs: https://github.com/vinniefalco/Beast/blob/master/examples/http_async_server… My initial purpose for requesting this discussion is two-fold: 1. Determine the level of consensus on the issue that Beast needs to do more for HTTP than the lowest level of functionality (reading and writing messages). I'm open to hearing all arguments for and against. 2. Get feedback on what official public interfaces to higher level functionality might look like. Specifically, a client that handles GET and POST, and a generic asynchronous server. And what features those interfaces would support. For example, is traversing a proxy a necessary feature for an official client interface? The best answers would provide function signatures or class declarations using the existing Beast HTTP types. In case its not clear, I am asking stakeholders and reviewers to help design the library. I'll open a discourse on the HTTP client to illustrate the proposed style of discussion: We want to provide a HTTP client implementation that lets users perform simple tasks like fetch a resource from a remote host. Calling code should be compact, letting people get their job done without getting mired in boilerplate. Here's a possible signature with example use: response_v1<string_body> get(std::string const& url, error_code& ec); error_code ec; auto res = get("http://boost.org", ec); if(! ec) std::cout << res; else std::cerr << ec.message() << '\n'; The get function would automatically perform the name resolution, connect the socket, request the resource with uri "/", and return the result. There's a problem here though, the caller is forced to use a message with std::string as the container for the body. An obvious fix is to add a template parameter: template<class Body = string_body> response_v1<Body> get(std::string const& url, error_code& ec); Better, but what if the body is not DefaultConstructible? We can add some parameters to forward to the Body constructor: template<class Body = string_body, Args&&... args> response_v1<Body> get(std::string const& url, error_code& ec, Args&&... args); We're getting somewhere now. Most users will use the default body, while an option exists for advanced users. But the implementation of get now has a complication. If an error occurs, it still has to construct a return value. This problem is likely surmountable but lets table it and start a new line of reasoning. What if the URI indicates https, e.g. "https://boost.org"? We can hide that under the hood by using a separate code path that uses asio::ssl::stream instead of ip::tcp::socket. But how does the caller provide the root CA certificates? How does the caller provide a client certificate? We are left with a client that satisfies two thirds of users but is unusable for the remaining one third. Is this Boost worthy? Is this std-lib worthy? I think not. Lets revisit the SSL issues later and think about a new problem. What happens to the socket when the request is done? In the proposed interface, the socket is destroyed. This means you can only make one request on a connection. At this point, I think its clear that the current interface is a non-starter. Here's a better idea. Lets define a class called client and make get a member function. Now we can have state, including configurable settings with reasonable defaults. class client { public: template<class Option> void set_option(Option&&); template<class Body = string_body, Args&&... args> response_v1<Body> get(std::string const& url, error_code& ec, Args&&... args); }; client c; error_code ec; auto res = c.get("http://boost.org", ec); if(! ec) std::cout << res; else std::cerr << ec.message() << '\n'; We still have some of the original problems, but other problems are solved. The class can keep the socket around, so that a subsequent call to get with the same server will use the already-open socket. The caller can set options on the client object instance before invoking get, such as any TLS certificates. Unfortunately we have new problems. Where is the io_service? If the class creates it for you, how many threads? How do I use my existing io_service, or is that even necessary? The class interface allows the connection to be kept alive but what if now the caller wants to close it (i.e. specify "Connection: close" in the request)? And there are some problems which are applicable to any interface. How does the caller adjust the parser options, for example change the limit on the size of the body? What if the caller wants the request made using a specific HTTP version? How does this handle basic authentication? How can the caller adjust the headers in the request? etc... This is why I think that offering a HTTP client is a rabbit hole which can only lead to a rejected formal review. Or maybe I am overthinking this? I'd love to hear proposed solutions to the issues (which could be just to say "forget about those features"). Despite my objection I have started work on these features anyway. Here are the beginnings of a HTTP client: https://github.com/vinniefalco/Beast/blob/88b485df7e6216282842f40cf99cc75de… Here is some work on a generic server: https://github.com/vinniefalco/Beast/blob/server/extras/beast/http/async_se… Please reply to this thread instead of starting a new thread, and keep the subject line prefix (e.g. "Re: [boost] [beast] ...") Thank you

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Boost Build configure checks improvement. [config/predef]
by Rene Rivera 12 Jun '17

12 Jun '17

There's been a long standing "issue" with how the b2 configure checks work. Or rather how some times they don't work. In particular the issue is that the set of properties considered relevant for the configuration checks was fixed. As of last night that is now resolved < https://github.com/boostorg/build/commit/450c25c3b52f5ddcb323140f8423adf3b8… >. As the commit mentions the set is no longer fixed and is configurable by users. The changes now mean that: 1. Any subfeatures of the top level relevant feature set are also considered as part of the set. This means that one can a configuration like below to support multiple invocations of the same toolset with different options. In particular the STD options: === user-config.jam === import feature ; using clang ; feature.subfeature toolset clang : std : cxx03 cxx11 cxx14 cxx17 : optional composite propagated ; feature.compose <toolset-clang:std>cxx03 : <cxxflags>-std=c++03 ; feature.compose <toolset-clang:std>cxx11 : <cxxflags>-std=c++11 ; feature.compose <toolset-clang:std>cxx14 : <cxxflags>-std=c++14 ; === And one can then invoke "b2 toolset=clang-cxx14,clang-cxx11" and get non-colliding configuration checks. 2. The set of relevant features is now soft wired as the set of subfeatures of the "<composite>" feature. Which means ones can add to the default set < https://github.com/boostorg/build/blob/develop/src/build/configure.jam#L26>. For example to add threading choice to the relevant features: === user-config.jam === import feature ; import configure ; feature.compose <configure> : <threading> ; === Enjoy. -- -- Rene Rivera -- Grafik - Don't Assume Anything -- Robot Dreams - http://robot-dreams.net -- rrivera/acm.org (msn) - grafikrobot/aim,yahoo,skype,efnet,gmail

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[outcome] Second high level summary of review feedback accepted so far
by Niall Douglas 11 Jun '17

11 Jun '17

Firstly thanks to everyone who has contributed no less than **618** emails at the time of writing to the Outcome review. Despite some on Reddit calling this review a "train wreck" and indeed some lovely things about me personally, I have found this review deeply helpful, and I believe so have most of its contributors in helping us all firm up our differing opinions about what such a vocabulary type ought to be. With regard to the previous high level summary at http://boost.2283326.n4.nabble.com/outcome-High-level-summary-of-review-fee…, I have made only these changes to the changes in that summary: 1. I have been persuaded to use longer more appropriate naming for result<T> and outcome<T>, so now the typedefed varieties with implicit conversions to their empty-capable form indicated by "=>" are: - static_checked_outcome<T> => static_checked_optional_outcome<T> static_checked_result<T> => static_checked_optional_result<T> These have narrow observers which reinterpret_cast and are therefore undefined behaviour if the state does not match, but use __builtin_unreachable() to help static analysis tooling like clang-tidy spot UB where it can be statically deduced. Conceptually, they are a very thin convenience wrap of std::variant<...>. - runtime_checked_outcome<T> => runtime_checked_optional_outcome<T> runtime_checked_result<T> => runtime_checked_optional_result<T> The runtime_checked_optional_* varieties are identical and unchanged to the outcome<T> and result<T> in the submitted library. They have wide observers with a formal empty state and it is never undefined behaviour to call any observer. This allows the programmer to save typing considerable boilerplate knowing that the runtime checks save the programming needing to spell things out. I have not been persuaded to change a single thing in their design yet apart from removing unnecessary member functions, but thanks to everybody who has tried, and if you think I am making a critical mistake, you still have a few days left to persuade me of it! For anyone not familiar with the discussion and feels that the names are excessively long, be aware they are just convenience typedefs of a more complex to configure "template<...> class outcome_impl". It is expected that end users of the library will choose the varieties they want for their code and typedef them into their local namespace as "result<T>" or whatever. Nobody is proposing that end users actually type out the full name each and every time they use them, and the documentation will make that clear. 2. I have been persuaded to replace the implicit conversion from static_checked_* varieties to runtime_checked_* varieties with explicit conversion instead as the implicit conversion could produce runtime failure where the programmer did not expect that to occur. Regarding other changes that I have accepted since the previous high level summary: 1. Outcome's STL exception throw catch to result<T> super-macro was found to be overkill given that current compilers won't replace simple throw...catch sequences with a branch, and still invoke the full throw-catch runtime machinery whatever the case. Therefore an exception to error code conversion function makes more sense than a macro. https://github.com/ned14/boost.outcome/issues/50 2. Outcome's usage of git submodules is felt by some reviewers to be a showstopper for acceptance as they could bring in non-Boost code unexpectedly in the future. I have agreed to make a cronjob script generated Boost.Outcome from standalone Outcome in the same fashion as Boost.ASIO is script generated from standalone ASIO. https://github.com/ned14/boost.outcome/issues/51 - Licensing to be BSL only - No cmake, just bjam - No git submodules at all - std-flavoured, not boost-flavoured - No code to be brought in except that written by me i.e. a hardcoded whitelist applies. - Contents of Boost repo to only contain material directly relevant to Boost. Nothing else. 3. Under the assumption that error_code_extended's use of a static global ring buffer would be controversial in this review, I hacked a quick and dirty solution expecting to have to remove it. Now we know that few disapprove, a more serious implementation will be needed. https://github.com/ned14/boost.outcome/issues/52 4. Given where Vicente appears to be heading next with expected<T, E1, E2, ...> it may be wise to make the static_checked_* varieties use std::variant<...> for storage when being compiled on C++ 17. https://github.com/ned14/boost.outcome/issues/53 Thanks, Niall -- ned Productions Limited Consulting http://www.nedproductions.biz/ http://ie.linkedin.com/in/nialldouglas/

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[sort] Timsort review reminder
by Steven Ross 11 Jun '17

11 Jun '17

The review for C++ Timsort in Boost is ongoing and will continue through June 12. I am the review manager. The code can be found here: https://github.com/boostorg/sort/pull/12 To merge it into a local copy of the Boost.Sort library: git checkout -b ZaMaZaN4iK-feature_branch/TimSort develop git pull https://github.com/ZaMaZaN4iK/sort.git \ feature_branch/TimSort If you want to see a proposed version of the Sort library source with Francisco's changes and Timsort included, download the zip file <https://drive.google.com/file/d/0B4s-GPKYVV0jOGx5ckJUTkZzMWM/view?usp=shari…>. Feel free to compare flat_stable_sort with Timsort. Please answer these questions in reply to this thread: 1. What is your evaluation of the Timsort implementation? 2. What is your evaluation of the comments? 3. Did you try to use the library? With what compiler? Did you have any problems? 4. How much effort did you put into your evaluation? A glance? A quick reading? In-depth study? 5. How familiar are you with the details of hybrid and stable sorts? 6. Would you actually use Timsort if it was in Boost.Sort? If so, how is it better than the next best alternative? 7. Do you think Timsort should be included in Boost.Sort? Please ask Alexander Zaitsev any questions you have about Timsort for this review before submitting your final review. Thanks, Steven Ross

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[static_views] [gsoc17] Proposal for a library
by Tom Westerhout 10 Jun '17

10 Jun '17

Hi! I'm Tom Westerhout, one of this year's GSoC interns. The module I'm planning to work on, StaticViews, is essentially a subset of Ranges TS optimised for usage with compile-time homogeneous datasets. It can be used to implement compile-time associative maps, compile-time checking of non-type constraints, and compile-time generation of datasets from other compile-time datasets. Some more explanation and motivating examples are on this page: https://boostgsoc17.github.io/static-map/doc/123_build/html/getting_started… Do you think this would be a worthwhile addition to Boost? Is the choice to use Ranges TS as inspiration for the API wise, or would a different API (please, suggest one) be better? All comments are welcome. Thanks in advance! Tom

2 1

Repeated super project commits
by Daniel James 10 Jun '17

10 Jun '17

Hi, You might noticed that some of today's super project commits were repeated. I was working on a change to do one commit per push event, and it went a bit wrong. It turns out there was an existing bug, which meant the script wasn't always updating the position in the event queue. I fixed it while writing the new version, but assumed it was a new bug that I'd introduced today. So when the new version started, it replayed the events since the position was last updated. I backed out the change and I'm going to try to make the script a bit more robust before changing it again - even without the bug, a similar thing could happen if someone manually updated a submodule in the super project. Because the commits were all in a single push, and the last commit was correct, it shouldn't cause any real problems, but there are a few wonky commits in the history, so sorry about that. Because of the way the script worked, the bug only affects that batch of commits, older commits are fine. Daniel

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Re: [boost] [Boost-testing] [EXTERNAL] Run.py test failure 'minimal' is an invalid property
by Tom Kent 10 Jun '17

10 Jun '17

On Wed, Jun 7, 2017 at 10:39 PM, Belcourt, Kenneth via Boost-Testing < boost-testing(a)lists.boost.org> wrote: > Hi, > > To followup with more info on this issue, testing is broken on master when > building on the Mac, though not sure why. Here’s what works okay: > > python run.py --tag=develop --runner="Sandia-clang-3.8" > --toolset=clang-darwin --pjl-toolset=darwin --bjam-options="-j8” > > and what fails (same command with —tag=master): > > python run.py —tag=master --runner="Sandia-clang-3.8" > --toolset=clang-darwin --pjl-toolset=darwin --bjam-options="-j8" > > The error from the failed master build is the error below. It seems to be > related to the context library use of alias (highlighted below). Are there > perhaps boost build or context changes that need to be merged to master > into order to fix this issue? From what I can tell, testing master on > MacOS is hosed. > > Noel > > > On Jun 7, 2017, at 6:03 PM, Belcourt, Kenneth via Boost-Testing < > boost-testing(a)lists.boost.org> wrote: > > > > /Users/jenkins/slave/workspace/build-tpls/boost_bb/src/build/property.jam:529: > in property.translate from module property > > error: 'minimal' is not a valid property specification > > /Users/jenkins/slave/workspace/build-tpls/boost_bb/ > src/build/property-set.jam:432: in property-set.create-from-user-input > from module property-set > /Users/jenkins/slave/workspace/build-tpls/boost_bb/ > src/build/property-set.jam:484: in property-set.refine-from-user-input > from module property-set > /Users/jenkins/slave/workspace/build-tpls/boost_bb/src/build/targets.jam:1619: > in targets.main-target-requirements from module targets > /Users/jenkins/slave/workspace/build-tpls/boost_bb/src/build/alias.jam:65: > in test-suite from module alias > *../libs/context/test/Jamfile.v2:97: in modules.load from module * > Jamfile</Users/jenkins/slave/workspace/build-tpls/boost_ > root/libs/context/test> > /Users/jenkins/slave/workspace/build-tpls/boost_bb/src/build/project.jam:325: > in load-jamfile from module project > /Users/jenkins/slave/workspace/build-tpls/boost_bb/src/build/project.jam:64: > in load from module project > /Users/jenkins/slave/workspace/build-tpls/boost_bb/src/build/project.jam:145: > in project.find from module project > Jamfile.v2:118: in run-tests from module Jamfile</Users/jenkins/slave/ > workspace/build-tpls/boost_root/status> > Jamfile.v2:171: in modules.load from module Jamfile</Users/jenkins/slave/ > workspace/build-tpls/boost_root/status> > /Users/jenkins/slave/workspace/build-tpls/boost_bb/src/build/project.jam:325: > in load-jamfile from module project > /Users/jenkins/slave/workspace/build-tpls/boost_bb/src/build/project.jam:64: > in load from module project > /Users/jenkins/slave/workspace/build-tpls/boost_bb/src/build/project.jam:145: > in project.find from module project > /Users/jenkins/slave/workspace/build-tpls/boost_bb/src/build-system.jam:535: > in load from module build-system > /Users/jenkins/slave/workspace/build-tpls/boost_bb/src/kernel/modules.jam:295: > in import from module modules > /Users/jenkins/slave/workspace/build-tpls/boost_bb/src/kernel/bootstrap.jam:139: > in boost-build from module > /Users/jenkins/slave/workspace/build-tpls/boost_root/boost-build.jam:17: > in module scope from module > > I see the same error for master on linux and windows runners. Tom

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[review] **NEXT WEEK** Review of Nowide (Unicode) Mon. 12th -> Wed. 21st June
by Frédéric Bron 10 Jun '17

10 Jun '17

Hi Everyone, ** HEADS UP, NEXT WEEK'S REVIEW ** The formal review of Artyom Beilis' Nowide library starts next week (Mon. 12-June to Wed. 21-June). Your participation is encouraged, as the proposed library is uncoupled and focused. Nowadays, everyone needs to handle Unicode but this is very difficult using only the standard library in a platform independant way. Nowide offers a very simple way to handle Unicode the same way on Windows/MacOS/Linux. Key features: * work with UTF-8 in your code, Nowide converts to OS encoding * Easy to use functions for converting UTF-8 to/from UTF-16 * A class to fixing argc, argc and env main parameters to use UTF-8 * UTF-8 aware functions: - stdio.h functions (fopen, freopen, remove, rename) - stdlib.h functions (system, getenv, setenv, unsetenv, putenv) - fstream (filebuf, fstream/ofstream/ifstream) - iostream (cout, cerr, clog, cin) Documentation: http://cppcms.com/files/nowide/html GitHub: https://github.com/artyom-beilis/nowide git clone https://github.com/artyom-beilis/nowide.git Latest tarball: get it from GitHub (Download as zip) NEXT WEEK (when the public review is started): Please post your comments and review to the boost mailing list (preferably), or privately to the Review Manager (to me ;-). Here are some questions you might want to answer in your review: - What is your evaluation of the design? - What is your evaluation of the implementation? - What is your evaluation of the documentation? - What is your evaluation of the potential usefulness of the library? - Did you try to use the library? With what compiler? Did you have any problems? - How much effort did you put into your evaluation? A glance? A quick reading? In-depth study? - Are you knowledgeable about the problem domain? And most importantly: - Do you think the library should be accepted as a Boost library? Be sure to say this explicitly so that your other comments don't obscure your overall opinion. For more information about Boost Formal Review Process, see: http://www.boost.org/community/reviews.html Thank you very much for your time and efforts. Frédéric

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[Format] User-defined literals for Boost.Format
by Корсунов Игорь 09 Jun '17

09 Jun '17

1 0

Re: [boost] [property_tree] Issue: erase is corrupting the tree
by lukas.exler＠barclays.com 09 Jun '17

09 Jun '17

The minimal code that crashes is: boost::property_tree::ptree loadedJSON; boost::property_tree::read_json("animalList.json", loadedJSON); auto assoc_it = loadedJSON.find("animals"); auto it = loadedJSON.to_iterator(assoc_it); it = it->second.begin(); it++; // move to second item loadedJSON.erase(it); boost::property_tree::write_json("shorterList.json", loadedJSON); Where content of "animalList.json" file is: { "animals" : ["fox","dog","cat"] } -----Original Message----- From: Mert Büyüktuncay [mailto:mert.buyuktuncay@sestek.com] Sent: Tuesday, June 06, 2017 9:22 AM To: boost(a)lists.boost.org Cc: Exler, Lukas: IT (PRG) Subject: RE: [property_tree] Issue: erase is corrupting the tree This mail originated from outside our organisation Do you use "it" iterator after the call to erase in that case you shall use it = loadedJSON.erase(it); instead of it++ If this is not your problem you can share a little more code for us to see in detail what is happening here. May be the code up to the point where "write_json" is being called. Regards Mert -----Original Message----- From: Boost [mailto:boost-bounces@lists.boost.org] On Behalf Of Lukas via Boost Sent: Monday, June 5, 2017 4:08 PM To: boost(a)lists.boost.org Cc: lukas.exler(a)barclays.com Subject: [boost] [property_tree] Issue: erase is corrupting the tree I have following JSON structure loaded into boost::property_tree: { "animals" : ["fox","dog","cat"] } I'm trying to delete the second item from the array by: auto assoc_it = loadedJSON.find("animals"); auto it = loadedJSON.to_iterator(assoc_it); it = it->second.begin(); it++; // move to second item loadedJSON.erase(it); After this, when I try to use boost::property_tree::write_json to write the JSON back the app crashes. Do I use the property tree in a wrong way, or is there a bug? Thanks, Lukas. _______________________________________________ This message is for information purposes only, it is not a recommendation, advice, offer or solicitation to buy or sell a product or service nor an official confirmation of any transaction. It is directed at persons who are professionals and is not intended for retail customer use. Intended for recipient only. This message is subject to the terms at: www.barclays.com/emaildisclaimer. For important disclosures, please see: www.barclays.com/salesandtradingdisclaimer regarding market commentary from Barclays Sales and/or Trading, who are active market participants; and in respect of Barclays Research, including disclosures relating to specific issuers, please see http://publicresearch.barclays.com. _______________________________________________ _______________________________________________ Unsubscribe & other changes: http://lists.boost.org/mailman/listinfo.cgi/boost Bu elektronik posta mesajı ve ekleri sadece gönderildiği kişi veya kuruma özeldir ve gizli bilgiler içerebilir. Eğer bu mesajı hataen aldıysanız lütfen bu durumu gönderen kişiye derhal bildiriniz ve mesajı sisteminizden siliniz. Eğer doğru kişiye ulaşmadığını düşünüyorsanız, bu mesajın gizlenmesi, yönlendirilmesi, kopyalanması veya herhangi bir şekilde kullanılması yasaktır. Internet iletişiminde güvenlik ve hatasız gönderim garanti edilemeyeceğinden, mesajın yerine ulaşmaması, geç ulaşması, içeriğinin bozulması ya da mesajın virüs taşıması gibi problemler oluşabilir. Gönderen taraf bu tip sorunlardan sorumlu tutulmaz. SESTEK Ses ve İletişim Teknolojileri A.Ş. www.sestek.com<http://www.sestek.com> This e-mail message and any attachments are confidential and intended solely for the use of the individual or entity to whom they are addressed. If you have received this message in error, please notify the sender immediately and delete it from your system. If you are not the intended recipient you are hereby notified that any dissemination, forwarding, copying or use of any of the information is prohibited. Internet communications cannot be guaranteed to be secure or error-free as information could be intercepted, corrupted, lost, arrive late or contain viruses. The sender therefore does not accept liability for any errors or omissions in the context of this message which arise as a result of Internet transmission SESTEK INC. www.sestek.com <http://www.sestek.com> Bu elektronik posta mesajı ve ekleri sadece gönderildiği kişi veya kuruma özeldir ve gizli bilgiler içerebilir. Eğer bu mesajı hataen aldıysanız lütfen bu durumu gönderen kişiye derhal bildiriniz ve mesajı sisteminizden siliniz. Eğer doğru kişiye ulaşmadığını düşünüyorsanız, bu mesajın gizlenmesi, yönlendirilmesi, kopyalanması veya herhangi bir şekilde kullanılması yasaktır. Internet iletişiminde güvenlik ve hatasız gönderim garanti edilemeyeceğinden, mesajın yerine ulaşmaması, geç ulaşması, içeriğinin bozulması ya da mesajın virüs taşıması gibi problemler oluşabilir. Gönderen taraf bu tip sorunlardan sorumlu tutulmaz. SESTEK Ses ve İletişim Teknolojileri A.Ş. www.sestek.com<http://www.sestek.com> This e-mail message and any attachments are confidential and intended solely for the use of the individual or entity to whom they are addressed. If you have received this message in error, please notify the sender immediately and delete it from your system. If you are not the intended recipient you are hereby notified that any dissemination, forwarding, copying or use of any of the information is prohibited. Internet communications cannot be guaranteed to be secure or error-free as information could be intercepted, corrupted, lost, arrive late or contain viruses. The sender therefore does not accept liability for any errors or omissions in the context of this message which arise as a result of Internet transmission SESTEK INC. www.sestek.com <http://www.sestek.com> _______________________________________________ This message is for information purposes only, it is not a recommendation, advice, offer or solicitation to buy or sell a product or service nor an official confirmation of any transaction. It is directed at persons who are professionals and is not intended for retail customer use. Intended for recipient only. This message is subject to the terms at: www.barclays.com/emaildisclaimer. For important disclosures, please see: www.barclays.com/salesandtradingdisclaimer regarding market commentary from Barclays Sales and/or Trading, who are active market participants; and in respect of Barclays Research, including disclosures relating to specific issuers, please see http://publicresearch.barclays.com. _______________________________________________

2 1

What is the process for adding a library suggestion?
by Adrian H 07 Jun '17

07 Jun '17

I have a suggestion for adding something to the boost library. It is simple but I believe that it would be useful. Do I just post it here or is there some process? Thanks, A -- ======================================== Adrian Hawryluk BSc. Computer Science ---------------------------------------- Specialising in: OOD Methodologies in UML OOP Methodologies in C, C++ and more RT Embedded Programming GUI Development ========================================

3 2

svn.boost.org schedule maintenance - DOWN TIME
by Michael Caisse 07 Jun '17

07 Jun '17

Hi all - svn.boost.org is scheduled for maintenance on June 8 from 1700 - 1900 UTC. Expect outages for Trac during this time. Happy coding! michael -- Michael Caisse Ciere Consulting ciere.com

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[review] Outcome Review Report
by charleyb123 . 07 Jun '17

07 Jun '17

# Boost.Outcome REVIEW REPORT In conclusion to the Outcome Library Review (19-May to 02-June, 2017): The library is REJECTED. Rejection is principally due to: (1) Unresolved key behavior at conclusion of the review period (2) Misunderstanding/disagreement regarding library’s intended purpose (3) Unclear precedent/implications from accepting this library in its current configuration into the Boost distribution The following weighed heavily to consider accepting the library into Boost: (a) The library demonstrates solutions to fundamental issues (error and exception handling) (b) The library effectively addresses constraints to serve the needs of several user-bases (c) New paradigms/idioms are enabled (d) Implementation is of high quality Some 20+ participants sent 850+ email messages to the public list discussing the Outcome library, plus additional (non-trivial) off-list discussion. Public reviews sent to the list were from: *- Paul Bristow -- ACCEPT (Tue-23-May) *- Deniz Bahadir -- ACCEPT (Wed-24-May) *- Robert Ramey -- REJECT (Fri-26-May) *- Peter Dimov -- REJECT (Sun-28-May) *- Emil Dotchevski -- REJECT (Sun-28-May) *- Vicente J. Botet Escriba -- REJECT (Tue-30-May) *- Andrzej Krzemienski -- REJECT (Wed-31-May) *- Gavin Lambert -- REJECT (May 31) *- Bjorn Reese -- REJECT (Fri-02-June) The remainder of this report is a summary of discussion with select issues specific to the Outcome library, plus some possible topics for further consideration by the Boost Community and Boost Steering Committee. This further elaboration is not intended to be comprehensive regarding issues raised during the review; Rather, it is to: (a) Provide historical “summary/context” for the level of discussion exhibited during this review, and which contributed to the final decision; (b) Highlight issues that may provide assistance in considering “readiness” for a later review for an evolved form of this library (or for a similar library intending to address the same domain); (c) Provide “discussion-points” for the Boost Community and Boost Steering Committee regarding possible future evolution or guidance associated with Boost tooling, distribution, and individual library dependencies (related to topics raised during this review). The conclusions will be: (1) Outcome Library Author: Consider re-submitting for review when... (a) Key behavior/design issues are resolved (see below) (b) Integration plan with Boost is more clear (and consistent with Boost Steering Committee Guidance) (2) Boost Community / Boost Steering Committee: Consider providing guidance to future library submissions regarding... (a) Attempted dual-license, this submission attempted: *- BSL+Apache2 dual-license (b) “Extra-build-steps”, this submission attempted: *- Custom preprocessing to “generate-source” (to significantly improve compile-time speed) (Note: During review, a template-based solution was proposed as a possible replacement mechanism, but code-gen should probably be explicitly addressed) (c) Class/namespace versioning, this submission attempted: *- Stable ABI/versioning mechanism through a framework provided with this submission (to enable multiple versions of this library used by differing third-party libraries to correctly coexist within the same binary) (d) Use of outside source; use of git (git-submodules), this submission attempted: *- Dependency to an outside (git-submodule) lib archive (gsl-lite: https://github.com/martinmoene/gsl-lite.git ) (e) Use of (non-test/Jamfile) for test, this submission attempted: *- Custom test mechanism (because “Boost.Test” won’t work with C++ exceptions disabled; lib needed “boost-lite” to run the test suite) (f) Use of CMake, Dependency upon Boost, this submission attempted: *- No Boost dependency (but provided a “boost-lite” shim to coexist in user-workspaces with-or-without Boost, providing common cmake machinery and test-running) # SUMMARY OVERVIEW As demonstrated through the volume and depth of discussion, the library attracted wide interest, which is consistent with a perception that it attempts to address an active need. Comments suggested the library’s purpose (enabling public APIs to pass <value|error|exception>) was useful, and that enabling a shared handling of <error|exception> to be somewhat novel. Several participants further suggested that the library attempts to serve a role as a “fundamental” library: to provide vocabulary types and pose new idioms, to be used in public APIs as a common <error|exception> exchange mechanism. One reviewer commented that the library’s documentation under-sold the library’s motivation, suggesting it compelling for: *- Cases where errors cannot be propagated by throwing exceptions (e.g., within callbacks where an error value is provided [e.g., ASIO]); *- When passing values between threads, such as in an Actor model where a message queue handles return values (e.g., pass outcome<T> instead of an std::error_code to handle <error|exception> in addition to desired <T>) Many/most reviewers that voted REJECT commented that they would like a similar library to be accepted, or perhaps an evolved form of this library after necessary changes (see below). To accept the importance of the domain which the library attempts to address, one need not agree with the design nor implementation of Outcome (indeed, the library is rejected in its current form at the conclusion of this review). Rather, this summary assertion is that the Outcome proposal successfully demonstrates a need for such a fundamental (and community-endorsed) solution (or direction) for error handling. # ISSUE: Unresolved key behavior at conclusion of the review period Key behavior (or design) issues that did not reach consensus by the end of the review period: (1) Narrow vs. Wide contracts -- consensus is not reached (2) Empty-state (allowed?) remains controversial (3) Ring-buffer appears uncontroversial; but perhaps needs additional scrutiny (a) Separate library implementation (for reuse elsewhere, and to enable evolution without touching the ‘result<>’/’outcome<>’ API)? (b) Bigger buffer? Some of the difficulties in this evaluation likely trace to the (in-progress) evolution of the proposed ‘std::expected<>’ (also discussed during this review). A future Outcome review would likely benefit from the clarity provided by fully resolved semantics for ‘std::expected<>’. # ISSUE: Misunderstanding/disagreement regarding library’s intended purpose The Outcome library attempts to define a paradigm and propose idioms in <error|exception> handling, where few can successfully argue that current practice, libraries, and idioms are sufficient. The review concluded that Outcome proposes a new paradigm that is demonstrated to be useful and effective. However, disagreement exists on the nature of that framework: PURPOSE: Outcome is a unified/universal <error|exception> handling framework for use in public APIs; (a) ...enabling user-customization to address domain-specific constraints ...versus... (b) ...for possible future consideration in a C++ Standards Track, likely within <system_error> The Library Author intended (a), while multiple reviewers advocated for (b). This disagreement-in-vision resulted in many difficult discussions during the review, and ultimately lack of consensus for several important API and design decisions (due to the corresponding implied future limitations). For example: Static-checked vs. Runtime-checked behavior. The library-as-presented attempts to serve both, citing orthogonal user bases with differing (latency) constraints, such as “with-or-without” runtime overhead, and “with-or-without” Undefined Behavior (UB). Current implementation enables integration of arbitrary third-party libraries (each with their own preferred error handling strategy and tradeoffs), with zero-cost conversion and inter-operation. However, this *significantly* complicates the design: The user composes ‘result<>’ and ‘outcome<>’ types with regards to module-specific static or runtime type safety and performance requirements, which (transparently) propagate through the library internals and across threads and public APIs to external modules. In contrast, a C++ Standards Track implementation is likely much simpler, introducing one-or-two vocabulary types merely parameterized on ‘<T>’, providing a simplified (and “standard”) mechanism to bridge <T|error|exception> transport across third-party module boundaries. For example, in advocating for a “Standards-Track” vocabulary type, reviewers argued for a mechanism that would enable user-libraries to obsolete the duplicate “throw/no-throw” APIs with a single API: R filesystem_api(); // throws filesystem_error R filesystem_api( error_code& ec ) noexcept; ...becomes... outcome<R> filesystem_api(); // <R|error|exception> The contrast between the two visions can more distinctly be termed: (a) “Multi-Modal” Usage -- Many varieties of usage style within the API is necessary, because there are a multitude of ways for library abstractions to be used in composition patterns due to domain-specific constraints (likely with some idioms not yet discovered, or not yet in widespread use) (b) “Single-Modal” Usage -- One (single) clean design and use model is encouraged The Library Author states that normal C++ design principles should prefer (b), but due to the vocabulary-type nature of the problem and domain-specific constraints encountered by real-world users, this particular library was forcefully evolved into (a). It is perhaps ironic that the suitability of a proposed library as providing vocabulary types and possibly evolving into a future standard demands that the Library Author change the library’s stated purpose due to this potential popularity; but that seems consistent with the current circumstance. The Library Author (of course) should have authority to characterize the actual intended use-case and resulting behavior provided through the authored work; with the Review Process providing analysis and feedback regarding possible missed opportunity resulting from those decisions. However, this review’s conclusion seems to encounter the curious scenario where the vision itself remains in conflict. Of course, these very differing outlooks resulted in some apparent “impasses” or circular discussions regarding type-safety (and number-of-types), wide or narrow contracts, optimization opportunities, “too-big” (or “cluttered”) interfaces, implicit or explicit conversion, the need for iterator and visitor patterns on ‘outcome<T>’, and the “empty” state and sentinel values. In support of the “Multi-Modal” design, the Library Author posits three main use patterns exist for error-handling objects-returned, and that a single design can serve only two at best: (Quoting the Library Author): > <quote> > (1) User wants failure reason type to be local to only the code to which > it applies. So think custom E type, nonconvertible to any other E type, and > E is never error_code nor exception_ptr. They specifically want to keep > failure handling local a small patch of code e.g. constexpr evaluation > contexts. > > All-narrow observers make sense for this use case as object usage is > tightly integrated to the code using it, and failure is handled entirely > locally. > > (2) User wants failure reason type to be globally understood and will be > choosing either E = std::error_code, or E = std::exception_ptr. They > specifically want failure handling to be able to traverse any or all code, > just like C++ exception throws. This is where Outcome was primarily aimed > at. > > All-wide observers make sense for this use case, as due to handling a wide > degree of uncertainty, most failure handling code is *generic* i.e. we test > for some specific failure causes, and for everything else we either ignore > or hand it off to other code to handle. > > (3) User wants to write functional programming logic using the basic > vocabulary of Maybe, Either and i/o monads and basic operators of bind, > fmap, do etc and probably some subset or refinement of Hana for the > collections monads, though my GSoC student may be making the Ranges TS a > choice here as well later this summer. > > All-narrow observers make sense for this use case as the monadic operators > ensure your function will never be called with the wrong state. > </quote> The Outcome library uses a, “single implementation, multiple personalities” to solve this problem, and makes the intentional decision to attempt targeting (2). # ISSUE: Unclear precedent/implications from including this library in its current configuration into the Boost distribution The library in its current configuration is perceived as setting precedent for changes to the Boost distribution, which reviewers commented added complexity to their analysis. Specific topics: *- Dual-license (BSL and Apache2) confused reviewers *- Add bjam support (author agreed) *- Packaging relied upon git-submodules to an outside lib archive (gsl-lite, https://github.com/martinmoene/gsl-lite.git) *- Library does tricks with the preprocessor to avoid significant compile-time costs; but these tricks were commented by some reviewers as being unnecessarily complex. *- The Author found these tricks necessary to reach reasonable compile metrics for large projects using Outcome in their public APIs, and believes some mechanism must address this build-speed-need. A proposed metaprogramming mechanism may eliminate the need for these preprocessor tricks in the future. # FINAL THOUGHTS In the very active years of “Classic Boost” (such as 2004-2008), fundamental libraries had a good chance of becoming vocabulary types that attempt to establish new Best Practice for the industry (and not merely be “just another library”). This awareness drove much of the review discussion, and underscored the importance of experimentation and “lessons learned” to result in a library that offered: (1) behavior and idioms that are understood; and (2) sufficient experience to make use recommendation to the wider user base in contrast to existing alternative approaches. Consistent with this historical context, it should be relatively uncontroversial to recognize that the Outcome library does not reach that threshold at this time (so it is rejected). However, this review also suggests: (1) A similar library is needed; (2) The community lacks agreement on direction (e.g., “Multi-Modal” vs. “Single-Modal”) In support of experimentation and to expand on our “lessons-learned”, it seems somewhat obvious that Outcome provides a strongly-implemented Multi-Modal low-latency library that will assist the community in gaining experience with these idioms proposed. Since conclusion of the review period, discussion continues (on and off-list) regarding possible evolution to the Outcome library, related to feedback provided during this review, and related to discussions of design evolution for pertinent libraries (e.g., possible changes to std::expected<>, and evolution of a never-empty ‘variant2<>’). It is promising that such a strong library as Outcome continues to receive critical attention and evolution by multiple interested parties. Great thanks to the Boost Community for their tremendous efforts, disciplined review, and detailed exploration of topics in considering this library submission. Sincerest appreciation to Niall Douglas (Author of the Outcome Library) for pushing the envelope for low-latency <error|exception> handling and for submitting his work to the Boost Review process. -- charley (Outcome Review Manager) If there be any in this assembly, any dear friend of Caesar's, to him I say that Brutus' love to Caesar was no less than his. If then that friend demand why Brutus rose against Caesar, this is my answer: not that I loved Caesar less, but that I loved Rome more. (3.2.19-24)

7 8

Deprecation indication
by Raffi Enficiaud 06 Jun '17

06 Jun '17

Hi, Is there anything in eg. boost.config or other that expands to a compiler indication that something is "deprecated", possibly with a message that appears only once? It may expand to `[[deprecated]]` or `[[deprecated("reason")]]` if available and supported, or `__declspec(deprecated)` / `__declspec(deprecated("reason"))`, `__attribute__ ((deprecated))` ... I could not find anything in boost.config. Has anyone an example of this in boost? Is there any indication/policy in boost about deprecation? Thanks in advance, Raffi

1 0

[Nowide] Links to source code
by Artyom Beilis 06 Jun '17

06 Jun '17

Hello Frederic and Boost Developers. I had noticed that the links to the source and git repository at http://www.boost.org/community/review_schedule.html are incorrect. It should be links to github https://github.com/artyom-beilis/nowide Can it be fixed before the review begins in order to prevent confusion? Thanks, Artyom Beilis

1 0

[outcome] High level summary of review feedback accepted so far
by Niall Douglas 05 Jun '17

05 Jun '17

Some reviewers have asked what form Outcome will take in the near future. The following is a high level summary of the changes already made on develop branch or will be made according to https://github.com/ned14/boost.outcome/issues logged from review feedback. I have left out some minor issues, this lists just the major changes. This should help reviewers to decide whether to recommend acceptance or rejection. If there are any questions, please do ask. Major design changes: ===================== - option<T> to be removed https://github.com/ned14/boost.outcome/issues/48 - outcome<T> and result<T> will have their empty state removed, and all observers gain narrow contracts. Default construction is disabled. https://github.com/ned14/boost.outcome/issues/44. Example: ``` result<Foo> v(make_errored_result(std::errc::invalid_argument)); assert(v.has_error()); // true assert(!v.has_value()); // true // As if Foo(reinterpret_cast<Foo &&> // (error_code_extended(std::errc::invalid_argument)); Foo f(std::move(v.value())); assert(v.has_error()); // still true assert(!v.has_value()); // still true ``` (NOTE: expected<T, E> will track whatever LEWG Expected does, but it differs from what will become result<T> by having a wide contract on .value() and narrow contracts on operator*(), .error(), operator->(). result<T> will have narrow contracts on everything, it is basically a thin wrap of std::variant<T, error_code_extended> except with strong never empty warranty) - New typedefs outcome_e<T> and result_e<T> are identical to outcome<T> and result<T> except for adding a formal empty state. Observer contract slightly widens, an attempt to use an empty object throws a bad_outcome_access exception. Implicit conversion from non-empty-capable varieties is permitted to empty-capable varieties, but not the other way round. Default construction is to **empty**. https://github.com/ned14/boost.outcome/issues/44 - New typedefs checked_outcome<T>/checked_result<T>, checked_outcome_e<T>/checked_result_e<T> are added. These mirror the editions just described, but checks and default actions occur on all observer usage so hidden reinterpret_cast<> never occurs. Implicit conversion from non-checked varieties is permitted to checked varieties, but not the other way round. https://github.com/ned14/boost.outcome/issues/47. Examples: ``` // Note result<T> implicitly converts to checked_result<T>, but not // the other way round. So we can use same make_errored_result(). checked_result<Foo> v(make_errored_result(std::errc::invalid_argument)); assert(v.has_error()); // true assert(!v.has_value()); // true // .value() throws std::system_error( // std::make_error_code(std::errc::invalid_argument)); Foo f(std::move(v.value())); ``` ``` checked_result<Foo> v(make_valued_result(Foo())); assert(!v.has_error()); // true assert(v.has_value()); // true // .error() returns a default constructed (null) error_code_extended // when result is valued to indicate "no error here" error_code_extended ec(std::move(v.error())); assert(!ec); // true ``` - The presented library self generates using lots of preprocessor based multiple #include's to stamp out finished editions of implementation. The git repo partially preprocesses this into a nearly finished edition for minimum compile time load for end users. Due to the many more varieties of outcome<T> and result<T> provided, the preprocessor machinery would be replaced with a template based machinery instead. I will look into making optional use of extern template and a static library to retain minimum compile time load, but header only usage will remain possible. Smaller design changes: ======================= - tribool stuff to go away in default configured build. https://github.com/ned14/boost.outcome/issues/22 - .get*() functions will be removed. https://github.com/ned14/boost.outcome/issues/24 - Don't include <windows.h> on winclang. https://github.com/ned14/boost.outcome/issues/39 Documentation changes: ====================== - Licence boilerplate missing on some files. https://github.com/ned14/boost.outcome/issues/38 - Reference API docs need to spell out exact preconditions, postconditions and semantics per API. https://github.com/ned14/boost.outcome/issues/26 - Reference API docs need to describe types void_rebound, *_type and raw_*_type in detail. https://github.com/ned14/boost.outcome/issues/29 - User overridable macros which throw exceptions and provide customisation points have vanished from the docs somehow. https://github.com/ned14/boost.outcome/issues/35 - Landing page and introduction to be broken up into bitesize single page chunks. https://github.com/ned14/boost.outcome/issues/41 Still to be decided: ==================== - Should *_e() varieties provide convenience .get(), .get_error(), .get_exception() which returns T, error_code_extended and std::exception_ptr by value moved from internal state, resetting state afterwards to empty? These would mirror future.get()'s single shot observers. Niall -- ned Productions Limited Consulting http://www.nedproductions.biz/ http://ie.linkedin.com/in/nialldouglas/

10 104

DocBook toolchain: Disable auto toc for just one section's children?
by Vinnie Falco 05 Jun '17

05 Jun '17

My documentation has a reference section whose children are themselves sections automatically generated by a doxygen->xml->xslt->QuickBook chain. I want an automatically generated table of contents, but when I turn that on I get hundreds of entries for all of the individual classes and functions in the reference. Is there a way to disable just the child sections of my Reference section? Perhaps marking the section somehow and passing an xsl:param in the Jamfile or something? This would really help to put that last bit of polish on these docs. I noticed that Boost.Asio docs had the same problem, so the author just disabled the auto-toc and created a very small, manual one. Not the same. Ideas?

3 5

[property_tree] Issue: erase is corrupting the tree
by lukas.exler＠barclays.com 05 Jun '17

05 Jun '17

I have following JSON structure loaded into boost::property_tree: { "animals" : ["fox","dog","cat"] } I'm trying to delete the second item from the array by: auto assoc_it = loadedJSON.find("animals"); auto it = loadedJSON.to_iterator(assoc_it); it = it->second.begin(); it++; // move to second item loadedJSON.erase(it); After this, when I try to use boost::property_tree::write_json to write the JSON back the app crashes. Do I use the property tree in a wrong way, or is there a bug? Thanks, Lukas. _______________________________________________ This message is for information purposes only, it is not a recommendation, advice, offer or solicitation to buy or sell a product or service nor an official confirmation of any transaction. It is directed at persons who are professionals and is not intended for retail customer use. Intended for recipient only. This message is subject to the terms at: www.barclays.com/emaildisclaimer. For important disclosures, please see: www.barclays.com/salesandtradingdisclaimer regarding market commentary from Barclays Sales and/or Trading, who are active market participants; and in respect of Barclays Research, including disclosures relating to specific issuers, please see http://publicresearch.barclays.com. _______________________________________________

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[outcome] non-interface-related concerns
by Andrzej Krzemienski 05 Jun '17

05 Jun '17

The discussion mostly revolves around the design of the interface of `outcome::expected` and even `std::expected`. My questions here are about the way this library will be distributed to users. And I am uncomfortable with the situation. I am not necessarily saying it is wrong, but I do not understand what is going on here. 1. The current GitHub repository consists of sub-repos. Do you (Niall) plan to have it like this when the library is accepted? Is it relevant? 2. This macro BOOST_OUTCOME_DISABLE_PREPROCESSED_INTERFACE_FILE, it controls whether I use this "preprocessed" file versus if I use... what? Normal header files? What is gained by this preprocessed file? Not having to include more than one header, or something else? Can I get different results when compiling with and without this macro? 3. I am recommended to use this macro BOOST_OUTCOME_V1_NAMESPACE. I am told it has something to do with ABI stability? Can you elaborate on how this guarantees ABI stability. Or is its purpose different? I have a certain problem with understanding this philosophy. A couple of days back, I reported the compilation failure in MinGW. I can see that the issue (https://github.com/ned14/boost.outcome/issues/36) is reorted as fixed in branch 'develop'. I would like to confirm that the bug is fixed. I checkout branch develop. There is no branch develop for the sub-repos, so what am I supposed to checkout, master, or some particular commit? I went with master. I do not understand a lot of CMake, but since it is a header-only library, I assume that I can just #include the file "include/boost/outcome.hpp", and my programs (compiled manually) should compile. But the only change in the commit that was supposed to fix the bug, was in a .cmake file, so I cannot see how it would help fix a header only library. Also, would the fix be visible in a "precompiled" header, or normal headres, or both? I am not complaining about this particular fix. I would like to know how in this system of mcros, sub-modules and preprocessed headers, I can figure out what changes will be observed in my program, when I see a particular change in git sub-repo. Regards, &rzej;

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[outcome] Review
by Bjorn Reese 03 Jun '17

03 Jun '17

I apologize in advance for the rather meek review below; I did not have the time to be more thorough. > - What is your evaluation of the design? The review discussions provided many insightful arguments in favour or against various aspects of the design, and I have not formed a final opinion about most of these. I do believe that fixing E for result<T> to error_code is the right decision. I would prefer a design without an empty state, because we already have a vocabulary type for it. The choice of C++14 seems motivated solely by performance considerations. A slower C++11 version should be considered. > - What is your evaluation of the implementation? I did not have enough time to review it. > - What is your evaluation of the documentation? The introduction (Description) only provides a vague description of the purpose of the library. For example, it does not mention that its types are used to carry either a value or an error. Instead, it assumes that the reader can derive this from prior familiarity with expected<T> (or Rust.) The first motivating example is too large (as indeed are the examples in the tutorial.) Instead I suggest a "Tony table" that shows the essense of the library (either value or error.) For example: Before: FILE *file = fopen("myfile", "r"); if (!file) throw std::system_error(errno, std::system_category(), "Error delivered out-of-band by errno"); fclose(file); After: result<FILE *> file = fopen_wrapper("myfile", "r"); if (!file) throw std::system_error(file.error(), "Error delivered in-band by file.error()"); fclose(file.value()); This may not look overly convincing, but it does demonstrate the either value or error aspect in a few lines. The library is weakly motivated -- the motivation boils down to a less expensive alternative to throwing exceptions. A stronger motivation would have been to mention use cases were errors cannot be propagated by throwing exceptions. Here are two examples: One motivating use case where exceptions cannot be throw are callbacks, such as Boost.Asio asynchronous handlers. Here the return value is not returned by the asynchronous operation (the initiating function), but will be passed to the provided callback once the operation completes. In other words, the following synchronous operation return_type operation(arg_type, error_code&); is turned into this asynchronous operation: void async_operation(arg_type, void (*)(return_type, error_code)); Exceptions cannot be thrown into the functions (here the callback), so errors have to be passed as arguments (whether error_code or exception_ptr.) The above works if the return_type has a reasonable "unengaged" value that can be passed as the first argument in case of an error. While this is true for Boost.Asio, where return_type is a std::size_t, it is not necessarily true in general. A much better solution is to pass an outcome<T>, result<T>, or expected<T>: void async_operation(arg_type, void(*)(result<result_type>)); Another motivating use case is passing results between threads. For instance, in the Actor model of concurrency information is passed between actors/threads via a message queue. Some of these messages are replies to requests that may or may not have failed. A queue containing one of the Outcome types is well-suited for this kind of interaction. Apart from the above-mentioned shortcomings, I found the remainder of the documentation quite readable. I did not find the inheritance diagrams in the reference documentation useful though. > - What is your evaluation of the potential usefulness of the library? The idea of an either-value-or-error return type is very useful. > - Do you think the library should be accepted as a Boost library? No, not in its current form. I have two reasons for this rejection. First, some of the design discussions (especially on narrow/wide contracts) are not settled yet, so it would be premature to vote for the design. Second, whilst the lastest offer from the author about a fully-fledged Boost.Outcome repository without a dependency on the non-reviewed library called "boost-lite" is a step in the right direction, it is unclear to me how that repository will end up. Having been surprised by the current submission and the author's opinions, I will defer any vote of acceptance until the a repository is submitted for review.

2 2

[outcome] expected, etc. why are these assignable
by Robert Ramey 03 Jun '17

03 Jun '17

It just occurred to me that for a similar component I created some time ago for my own purposes, I (intentionally?) support of the assignment operator. Copy construction was permitted however. So the only way to use the component is: checked_result<int> = function(...); something void function(checked_result & cr, ....) will be the same as void function(const checked_result & cr, ...) because checked_result only contains const functions. That is, once constructed, it's immutable. Personally I never use an interface which passes a mutable type to a function. To me it violates the mathematical idea of what a function is. Doesn't this simplify things? Doesn't this eliminate the whole questions about about empty state, etc. Doesn't this better model the "mondad" concept we're trying to leverage on. And why the hell are we modifying and an object designed to model a result in the first place? It doesn't make logical sense in terms of we expect a "result" to be. I plunk down my money (a function) and ask for a pepperoni pizza. Either they say they don't have pepperoni and give me my money back or give me a pizza. I don't think of modifying this result - it's an artifact of history. And wouldn't making these things immutable, eliminate a large part of the whole controversy? Just a thought. I think sometimes something is hard because we haven't thought enough about what we're really trying to do - what problem we're trying to solve. Robert Ramey

6 16

[outcome] To variant, or not to variant?
by Gavin Lambert 03 Jun '17

03 Jun '17

I probably should have thought of asking this earlier, but it occurs to me now that my own mental model of how an "outcome"-ish type should act is probably not suited to variant storage at all. So just out of curiosity I thought I'd ask whether people prefer this sort of interface: template<typename T> class outcome { public: bool has_value() const { return m_storage.has<T>(); } T& value() { return m_storage.get<T>(); } bool has_error() const { return m_storage.has<error_code>(); } error_code& error() { return m_storage.get<error_code>(); } bool has_exception() const { return m_storage.has<exception_ptr>(); } exception_ptr& exception() { return m_storage.get<exception_ptr>(); } void set(none_t) { m_storage = none; } void set(const T& val) { m_storage = val; } void set(error_code err) { m_storage = err; } void set(exception_ptr ep) { m_storage = ep; } private: variant<none_t, T, error_code, exception_ptr> m_storage; }; Or this sort of interface: template<typename T> class outcome { public: bool has_value() const { return !!m_value; } T& value() { ensure(); return m_value.value(); } //bool has_error() const { return !!m_error; } const error_code& error() const { return m_error; } //bool has_exception() const { return !!m_exception; } const exception_ptr& exception() const { return m_exception; } void ensure() const { if (m_exception) { rethrow_exception(m_exception); } if (m_error) { throw system_error(m_error); } } void set(none_t) { m_value = none; m_error = error_code(); m_exception = nullptr; } void set(const T& val) { m_value = val; m_error = error_code(); m_exception = nullptr; } void set(error_code err) { m_value = none; m_error = err; m_exception = nullptr; } void set(exception_ptr ep) { m_value = none; m_error = ep ? error_code(errc::has_exception) : error_code(); m_exception = ep; } private: optional<T> m_value; error_code m_error; exception_ptr m_exception; }; (Don't get too hung up on the specifics. This is a sketch, not a real implementation. I've obviously omitted things that a real implementation would need such as more const methods and move support, and construction and assignment rather than using set methods. The focus is on variant vs. non-variant.) Anyway, the point is that this could actually transport multiple things; in particular as above both an error_code and an exception_ptr; perhaps set(error_code) could construct an exception as well, although I've explained elsewhere why I don't like that option. Perhaps this could even be exposed even more so that user code could explicitly provide both a value and an error -- think "here's a value, but it was truncated" or "here's the 5 values you asked for, but there's more", both fairly common in system APIs. Or for things like ambiguous matches where you still return the most likely candidate. Or dictionary insertion (duplicate key, but here's the value that's already there). Or many more such examples. (Though obviously in this case value() couldn't call ensure(). But that should make some people happy.) Also note has_error() and has_exception() don't even need to be provided in this version since you can always call error() and exception() in a boolean context anyway, with the same result. (Or actually a slightly better result than the implementation shown here.) The obvious downside is that it now uses more storage, which might hinder some inlining cases.

9 63

[sort] Timsort review
by Steven Ross 03 Jun '17

03 Jun '17

The review for C++ Timsort in Boost will commence tomorrow, June 3, and continue through June 12. I am the review manager. The code can be found here: https://github.com/boostorg/sort/pull/12 To merge it into a local copy of the Boost.Sort library: git checkout -b ZaMaZaN4iK-feature_branch/TimSort develop git pull https://github.com/ZaMaZaN4iK/sort.git \ feature_branch/TimSort If you want to see a proposed version of the Sort library source with Francisco's changes and Timsort included, download the zip file <https://drive.google.com/file/d/0B4s-GPKYVV0jOGx5ckJUTkZzMWM/view?usp=shari…>. Feel free to compare flat_stable_sort with Timsort. Please answer these questions in reply to this thread: 1. What is your evaluation of the Timsort implementation? 2. What is your evaluation of the comments? 3. Did you try to use the library? With what compiler? Did you have any problems? 4. How much effort did you put into your evaluation? A glance? A quick reading? In-depth study? 5. How familiar are you with the details of hybrid and stable sorts? 6. Would you actually use Timsort if it was in Boost.Sort? If so, how is it better than the next best alternative? 7. Do you think Timsort should be included in Boost.Sort? Please ask Alexander Zaitsev any questions you have about Timsort for this review before submitting your final review. Thanks, Steven Ross

1 0

[poly_collection][VS 2017] Potential compiler bug
by Joaquin M López Muñoz 02 Jun '17

02 Jun '17

Hi, Boost.PolyCollection tests have started to cycle and I found VS 2017 aka MSVC 14.1 fails at test_algorithm.cpp: http://tinyurl.com/yb4zdkys whereas this test compiles and runs OK with VS 2015 aka MSVC 4.0 (_MSC_FULL_VER = 190023026). I've distilled down the problem to this test case: #include <algorithm> #include <utility> template<typename... Ts> struct all_of { template<typename... Args> auto operator()(Args&&... args)const-> decltype(std::all_of<Ts...>(std::forward<Args>(args)...)) { return std::all_of<Ts...>(std::forward<Args>(args)...); } }; int main() { int x; all_of<> alg; alg(&x,&x,[](int){return true;}); } which works fine with GCC and VS 2015 but fails in webcompiler.cloudapp.net with Compiled with /EHsc /nologo /W4 /c main.cpp main.cpp(9): error C3546: '...': there are no parameter packs available to expand main.cpp(18): note: see reference to class template instantiation 'all_of<>' being compiled (_MSC_FULL_VER = 191125331, which I think is VS 2017.3 or something). This looks like a regression to me. Deleting the ->decltype(...) bit makes the problem go away but I need to stay within C+11. * Can someone (STL?) confirm this is indeed a compiler bug? * Any rewording of the code that might be generally applicable to C++11 so that I don't have to include a specific workaround for VS 2017? Thank you, Joaquín M López Muñoz

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[outcome] Outcome Review Period Closes Today (Fri-02-June)
by charleyb123 . 02 Jun '17

02 Jun '17

Hello Everyone, Today concludes the Outcome library review period (Fri-02-June-2017). Great thanks to all that invested so much time and effort to explore in such a disciplined and professional manner the dark corners of error/exception composition and a paradigm/API/implementation proposed by the Outcome library. Your efforts are truly appreciated. Reviews sent to the public list are the following (PLEASE contact me if I've missed your review): *- Paul Bristow (Tue-23-May) *- Daniz Bahadir (Wed-24-May) *- Robert Ramey (Wed-24-May) *- Peter Dimov (Sun-28-May) *- Emil Dotchevski (Sun-28-May) *- Vicente J. Botet Escriba (Tue-20-May) *- Andrzej Krzemienski (Wed-31-May) *- Gavin Lambert (Wed-31-May) My understanding is that as the review concludes today, further reviews are permitted only until the end-of-day UTC. In addition, many notable discussions and topics raised during the review period will also contribute to a final submission decision and summary report. Preparing this report will take some time. I've accumulated extensive notes, but my intention is to review (re-read) all discussion in the context of the "story-arc" and (in some cases) the shifted opinions of some persons during the course of the review (as topics were clarified and alternatives were explored). I assume other "satellite discussions" will continue (e.g., evolution of std::expected<>, suitability of wide vs. narrow contract in APIs, generalization of variant<>, etc.), which I will endeavor to continue to follow as the Outcome Review summary report is prepared (because these continued discussions may further clarify issues previously raised during the Outcome Review); but no more reviews can be accepted after the review period closes. Thank you all (again) for your (often thankless) contributions to the community, where the personal sacrifice in time and effort (and perhaps stressful emotional investment) is quite obviously extensive in many cases. --charley

2 2

[outcome] where is the monadic style tutorial?
by Mathias Gaunard 02 Jun '17

02 Jun '17

Hi, I just took a quick look at outcome today and I don't really understand what it is doing. I expected to have some kind of mechanism to manage control flow with propagation between states only happening if the previous expression in the chain resulted in an expected value, like with the Expected monad. I searched throughout the documentation and didn't find any. Why is there no example of this? More than how the error state is captured and stored or how to capture custom errors, I believe the programming model is what the tutorial should really focus on.

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[outcome] Formal review
by Gavin Lambert 01 Jun '17

01 Jun '17

With the extended review period ending soon (or perhaps slightly overdue, depending on timezone), and given my many posts regarding the library, I feel like I should probably express my thoughts in review form. This is my first formal review and I am not myself a Boost library author (just a user) so please take that into account. - What is your evaluation of the design? A lot of thought has clearly gone into it, though I'm not sure I agree with some of the decisions made. Empty state I'm on the fence about; I can see it's convenient both for optional<T> success return semantics and for not-yet-populated/called pending result semantics, but I'm not sure these are consistently applied as it stands, and they seem at least partly opposed to the "empty state is weird, let's aggressively throw" behaviour in the actual implementation. Simplifying expected<T, E> into result<T> and outcome<T> makes sense, and the design of error_code_extended seems reasonable, including the content and ring buffer history. However I wonder if perhaps some middle ground might be better, where result<T, E> and outcome<T, E> exist but E is constrained to a type with specific characteristics (such as being constructible from error_code and having noexcept move). This might allow for more flexible error payloads. Alternately some way to use a similar error_code_extended-linked-to-ring-buffer system but with a user-defined payload data type. I don't consider this to be a defect or reason to reject the library, though, just something that would be useful if possible. I don't like that result<error_code{,_extended}> is not legal, as this seems like unnecessary asymmetry, though again I don't consider this a rejection reason. - What is your evaluation of the implementation? I have not looked in depth at it. The dual licensing and dual source distribution (preprocessed vs. not) bother me, but that will apparently be addressed in future. I don't like the total duplication of interface methods (get vs. value, error vs. get_error), but this will apparently also be addressed in future. (I am not opposed to having both narrow and wide accessors in the same type, though I prefer that the ones that can cause UB if abused require more typing. I *am* opposed to having multiple names for the exact same behaviour.) I'm not sure why it would be useful to provide const&& overloads of some of the value methods. Usually the only time I've seen these is to explicitly delete that overload. (Unless that is what's actually happening and doxygen is just not showing that correctly.) I like the use of wide contracts by default, such that it is safe to call value(), error(), or exception() without inspecting the underlying type and they will react sensibly (eg. throwing) rather than having UB, although some of the finer points of what a sensible reaction means are still being debated. But I can understand the desire of some people to have the other versions available for specific cases or in environments where static checking is more common. Even so, I hope that the narrow versions will at least BOOST_ASSERT their preconditions. The lack of use of Boost facilities such as Config, Assert, and Core (esp. BOOST_NO_EXCEPTIONS) bothers me more, and I do consider that a rejection reason. Use of StackTrace would be good as well but at this point I don't consider that a defect since it's not quite "in" Boost yet. (Possibly also Exception for boost::throw_exception, though using std::exception_ptr is the correct choice.) There is a critical defect in error_code_extended's backtrace API, which has already been brought to the author's attention and should hopefully be resolved later. - What is your evaluation of the documentation? Generally good, although it seems to spend a lot of time and pages talking about expected<T, E>, and only towards the end adds "but you should probably use outcome<T> instead" as a sort of afterthought, which seems a bit backwards. This is perhaps the correct order in a presentation, but it feels wrong in library documentation somehow. I think it needs to be more up-front about outcome and result (since those are the core types of the library) and recommended usage, and cover the other things as background material afterwards. The documentation refers to "monads" a lot, which is an unfamiliar concept to me. Not sure if this needs more explanation or just rewording. Doxygen's habit of putting hyperlinks that go nowhere in the reference pages is a bit disconcerting as well. - What is your evaluation of the potential usefulness of the library? Direct usefulness to me right now will be limited due to compiler support, but this seems like the sort of thing that would be quite useful in the future, especially to tidy up dual APIs such as those in ASIO. They have a fairly good chance of becoming standard vocabulary types, which of course has also helped drive a lot of the discussion thus far. - Did you try to use the library? With what compiler? Did you have any problems? I have not, as the compilers I use day-to-day are only C++11 or less, not C++14. - How much effort did you put into your evaluation? A glance? A quick reading? In-depth study? Primarily a fairly detailed reading of the documentation, combined with discussion here. - Are you knowledgeable about the problem domain? Mixed. I have experience with exception handling internals in MSVC and regularly work with software in both contexts of using error codes everywhere with exceptions banned, and of allowing exceptions but preferring they never actually be thrown. I also regularly work with both low-latency and fixed-latency environments, in addition to more "normal" software. But other than interaction with ASIO I have not made much use of error_codes to date, or mixing the two environments in the "sea of noexcept" fashion, though I can see the appeal. - Do you think the library should be accepted as a Boost library? Eventually, yes, but currently no (rejection, with encouragement to resubmit). While the author claims that the actual implementation has changed little since initial submission, the changelog in the "review accepted feedback" threads sounds fairly serious, and I'm not sure I like some of its directions (such as separate types for contract variations). Perhaps it will indeed end up being no big deal, but I don't feel like I have a good handle on what the end result will look or behave like so I don't feel comfortable endorsing it until I can get a better look at it. Primarily though I think the Boost integration was done backwards; the library should make use of Boost facilities first (as previously mentioned); if also distributed separately then that separate distribution should have the Boost emulation layer in it, and not the reverse. (To clarify: using std:: facilities is preferred, so using <system_error> is better than using <boost/system/system_error.hpp>, although it would be nice if compatible with the latter without actually depending on it unless requested explicitly. But the main problem is lack of use of Config, Assert, and Core, unless I missed something.)

2 2

[units] Compilation fails on quantity copy-construction
by Pavel Kretov 31 May '17

31 May '17

Hi all! I'm trying to make use of Boost.Units in a simple FDTD simulation program, but found a strange behavior of some kind. Consider the following demonstration example where I try to calculate time step from spatial steps according to the CFL condition [1]: #include <iostream> #include <boost/units/physical_dimensions.hpp> #include <boost/units/systems/si.hpp> #include <boost/units/cmath.hpp> #include <boost/units/io.hpp> int main() { namespace bu = boost::units; namespace si = boost::units::si; using dimless = bu::quantity<si::dimensionless, float>; bu::quantity<si::length, float> dx = 1.0f * si::meter, dy = 1.0f * si::meter; bu::quantity<si::velocity, float> v = 1.0f * si::meter_per_second; bu::quantity<si::time, float> dt = 0.5f / (v * bu::sqrt(1.0f/(dx*dx) + 1.0f/(dy*dy))); std::cout << dt << std::endl; } The code looks okay to me, but when I try to compile it, I get a scary error message: main.cpp:20:19: error: no match for ‘operator/’ (operand types are ‘float’ and ‘<THE_TERROR_THAT_FLAPS_IN_THE_NIGHT>’) dt = 0.5f / (v * bu::sqrt(1.0f/(dx*dx) + 1.0f/(dy*dy))); ~~~~~^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ where the second operand type looks like boost::units::multiply_typeof_helper< boost::units::quantity< boost::units::unit< [{length_base_dimension, static_rational<1l>}, {time_base_dimension, static_rational<-1l, 1l>}], boost::units::si::system, float>, boost::units::quantity< boost::units::unit< [{length_base_dimension, static_rational<-1l, 1l>}], boost::units::si::system, double>>::type In the above expression [{}, {}, ...] is a pseudo-code for static head-tail list of boost::units::dim<Unit, Rat> pairs. Note the 'double' type materialized from barely nowhere: the code explicitly defines everything as 'float', it's the 'bu::sqrt' to blame for it to appear. Note that replacing 'bu::sqrt' with 'bu::pow<1, 2>()' does not help. As I didn't feel happy with the above error message, I mutated the code a bit and made it to work with: bu::quantity<si::time, float> dt; dt = dimless(0.5f) / (v * bu::sqrt(1.0f/(dx*dx) + 1.0f/(dy*dy))); I had to both (a) add 'dimless', and (b) separate variable declaration and definition. Doing only (a) didn't help. Mkay, but what if I need to have a const quantity? (I'm a big fan of making everything 'const'!). The only one thing I could do was to roll out my own 'sqrt' and 'pow' functions. Here they are: #include <boost/units/get_system.hpp> #include <boost/units/get_dimension.hpp> #include <boost/units/static_rational.hpp> #include <boost/units/quantity.hpp> #include <boost/units/dimension.hpp> template<typename Unit, int N, int M = 1> using static_power_helper = boost::units::unit< typename boost::units::static_power< typename boost::units::get_dimension<Unit>::type, typename boost::units::static_rational<N, M>::type>::type, typename boost::units::get_system<Unit>::type>; template<int N, typename Unit, typename Y> auto ratpow(boost::units::quantity<Unit, Y> const &x) -> boost::units::quantity<static_power_helper<Unit, N>, Y> { using std::pow; return decltype(ratpow<N>(x))::from_value(pow(x.value(), N)); } template<int N, int M, typename Unit, typename Y> auto ratpow(boost::units::quantity<Unit, Y> const &x) -> boost::units::quantity<static_power_helper<Unit, N, M>, Y> { using std::pow; return decltype(ratpow<N, M>(x))::from_value(pow(x.value(), (Y) N / M)); } template<typename Unit, typename Y> auto msqrt(boost::units::quantity<Unit, Y> const &x) -> decltype(ratpow<1, 2>(x)) { return ratpow<1, 2>(x); } Using them I was able to compile the original form of the expression (as seen in the very first listing): bu::quantity<si::time, float> const dt = 0.5f / (v * msqrt(1.0f/(dx*dx) + 1.0f/(dy*dy))); The questions: 1. Is it possible to work around the problem without custom 'sqrt'? 2. Is the described behavior intentional, -or- Is there an error in Boost.Units' implementation of 'sqrt'? 3. If the 'boost::unit::sqrt' is fine, is there something wrong with my implementation? ――― Pavel K. [1]: https://en.wikipedia.org/wiki/Courant-Friedrichs-Lewy_condition

2 1

[poly_collection] Questions about merging into Boost
by Joaquin M López Muñoz 31 May '17

31 May '17

Boost.PolyCollection was recently accepted into Boost and I'm planning to integrate it into https://github.com/boostorg/ asap to begin test cycling. I am not sure if the lib will be in a good enough shape for launching with Boost 1.65, though. Questions: 1. The current repository is https://github.com/joaquintides/poly_collection , which has branches master (code) and website (for the online docs). Is the following the right procedure for integration with Boost? a. Rename master to develop (https://gist.github.com/lttlrck/9628955 ) b. Transfer repo to boostorg (https://help.github.com/articles/about-repository-transfers/ ) c. Ask for write permission to github.com/boostorg/poly_collection 2. Can the repo not have a master branch until I decide the lib is ready for launch? Will this result in poly_collection simply not being in Boost releases while still develop tests are cycling? Thank you, Joaquín M López Muñoz

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[outcome] Andrzej's review
by Andrzej Krzemienski 31 May '17

31 May '17

Hi Everyone, This is my review of Boost.Outcome library. First, I want to thank Niall for taking the effort to write the library, promoting it, sharing with the community, and submitting for Boost review. I think that the library has already proven useful regardless of this review's outcome (or should I say 'result'). I recommend to REJECT the library at this point, and encourage the author to re-submit it after the list of what I consider issues -- described below -- has been addressed. Why reject and not conditionally accept? It is possible to say that I accept the library if this "delta" is applied to the current submission's state. Niall has indicated a couple of times that he is willing to apply even big changes, if this is what reviewers wish. But the amount of change that would be required, plus the uncertainty what the "delta" actually is, plus a general confusion as to what library is for, as reported by others (the effect of the current shape of documentation), in total make the conditional acceptance too fragile. What are we reviewing? It would be fair to assume that we are reviewing the master branch, SHA 4851926c1c601c0e9391b2d0d07fb17f634b3ecb, but there is also a "delta" described by Niall in high-level in one of the messages: http://boost.2283326.n4.nabble.com/outcome-High-level-summar y-of-review-feedback-accepted-so-far-td4694767.html. So maybe the master + that delta. It describes that we will have like 10 types, like outcome_e, checked_outcome_e, etc.. Now in another thread I hear there will only be 5 types: optional_outcome and outcome. This makes me believe that the compromise solutions and promises are being made in a hurry, and this will likely result in (1) suboptimal design and (2) misunderstandings as to what we are actually agreeing to. Am I knowledgeable about the problem domain? If the domain is "reporting function failures in predictable-latency environments", then no, I have no experience with this domain. I also have no experience with `expected`, although having worked on formal specification of `std::optional` I am familiar with a number of issues that `expected` also needs to solve. Also, a number of controversies revolves around git sub-modules, dual licensing and Boost distribution process. I do not feel competent in this area either. How much effort did I put into the evaluation? I have read a number of versions of the documentation. Had a long email exchange with Niall in order to understand what the library does. I had a glimpse at the source code to figure out the pieces that were missing from documentation. I have tried running my own test examples on GCC 6.3.0 with MinGW w64 5.0.0 (doesn't work) and GCC 6.3.1 on Fedora (works fine). Is the library useful? Yes. Apparently it solves an important problem in predictable-latency environments. This is confirmed by the user base the library already has managed to acquire. It provides an implementation of the to-be standardized `exceptional`, which allows for experimentation. I believe Boost would benefit from including this library (after the issues have been resolved). I am confident Niall has knowledge about problem domain. Documentation. It has two serious deficiencies. It lacks an introductory part that would clearly and shortly describe what problem the library is solving an how, how can I use it and when should I use it. It is also missing a reference with documented semantics. One cannot tell what outocme's default constructor does, or what function error() does when you have an exception_ptr inside. I believe Niall when he says his users do not need this documentation: they immediately grasp what and how it is doing. But of the Boost library I expect a high-quality documentation. I think that these deficiencies in the documentation prevent a successful review of the library. I bet there are people who were put off by the docs and will not proceed to reviewing the library further, even though they could have given you many valuable insights, or point out defects. Some will stop at criticizing the docs. Any potential flaws in the library will not even be revealed. This may be the reason why things like ring buffer were not opposed: the potential critics may have not gotten that far. This is one of the reasons that I would recommend fixing the docs and staring the review again without the distraction. On the other hand, there is a lot of useful material in the documentation. For sure it is a way better that the original versions. For instance, the usage of ring buffer is documented clearly. Design. The idea to represent either a returned value or a reason for the lack thereof as `variant<T, error_code, exception_ptr>` is sound. Fixing the `E` to a single type is sound. using_error_code extended (along with ring buffer) for carrying payload is sound. I also like the fact that you only have three "monads": `outcome`, `result` and `expected`, and that they are maximally different: expected and result make the opposite decision on practically any aspect. This is a reasonable compromise between many possible combinations of micro-decisions, and the expectation to have a small number of types. `option` should go, I think. I can think of no use case for it. However, the design still changes throughout the review, and has not stabilized yet. The last message is that we may have varieties for narrow versus wide contract or we will have duplicated observers, and this has not been settled on yet. The consequence of using the ring buffer, where the error message can suddenly disappear is unfortunate, but then again, I know of no way to make it better. It might be the best choice of those available. I wish someone from low-latency users stepped in and commented on whether this is the right choice and whether the choice of these particular members (a short string, two unsigned ints) is the optimum in practice. Some aspects of design, to me seem unclear. E.g., what does it mean that `outcome` has value but I am calling `o.error()`? Is it a programmer error, which the function is trying to conceal, or does `o.error()` mean "convert `outcome` to `error_code`, whatever the state? Similarly, when `exception()` also recognizes error_codes, and `error()` does not recognize exception_ptrs looks quite random: I cannot see a mental model behind it. You could document detailed semantics of each function, but this would not be enough. I need a clear mental model, like "every error_code or exception_ptr is collectively called 'exception' in this library". If you do not support `outcome<T&>, I need a clear indication of it and a rationale. Implementation. These dual licensing, testing and git sub-module issues. I am not an expert in how Boost is organized, but a number of people I consider qualified have reported strong objections, and this has to be considered. A Boost library must be compliant with "the way things work in Boost" even if it is felt that things work wrong in Boost. I did not look much, at the implementation, but it looks acceptable on the surface. The assignment (most tricky part, I think) is implemented quite clearly. Sometimes static_assert's constrain too much. A non-default-constructible types should be allowed. Types that throw upon copy/move construction should be allowed provided I do not call the assignment on outcome/expected. I am told `outcome<error_code>` does not work. I am not sure if this is fortunate. It is no longer an `outcome<T>` that works for any Regular T. What if I have a function that optains an error_code and might potentially fail. How can I express this in the interface? (Or do I have to wrap in `outcome<unique<error_code>>`?) `outcome` has function swap overloaded in namespace std. I am not sure if it is legal, but even if so, I would recommend implementing it in `outcome`'s namespace, in order not to mess with `std`. Again, thanks Niall for this library, and for a very educational discussion. Regards, &rzej;

2 1

[units] Compilation fails on quantity copy-construction
by Pavel Kretov 31 May '17

31 May '17

Hi all! I'm trying to make use of Boost.Units in a simple FDTD simulation program, but found a strange behavior of some kind. Consider the following demonstration example where I try to calculate time step from spatial steps according to the CFL condition [1]: #include <iostream> #include <boost/units/physical_dimensions.hpp> #include <boost/units/systems/si.hpp> #include <boost/units/cmath.hpp> #include <boost/units/io.hpp> int main() { namespace bu = boost::units; namespace si = boost::units::si; using dimless = bu::quantity<si::dimensionless, float>; bu::quantity<si::length, float> dx = 1.0f * si::meter, dy = 1.0f * si::meter; bu::quantity<si::velocity, float> v = 1.0f * si::meter_per_second; bu::quantity<si::time, float> dt = 0.5f / (v * bu::sqrt(1.0f/(dx*dx) + 1.0f/(dy*dy))); std::cout << dt << std::endl; } The code looks okay to me, but when I try to compile it, I get a scary error message: main.cpp:20:19: error: no match for ‘operator/’ (operand types are ‘float’ and ‘<THE_TERROR_THAT_FLAPS_IN_THE_NIGHT>’) dt = 0.5f / (v * bu::sqrt(1.0f/(dx*dx) + 1.0f/(dy*dy))); ~~~~~^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ where the second operand type looks like boost::units::multiply_typeof_helper< boost::units::quantity< boost::units::unit< [{length_base_dimension, static_rational<1l>}, {time_base_dimension, static_rational<-1l, 1l>}], boost::units::si::system, float>, boost::units::quantity< boost::units::unit< [{length_base_dimension, static_rational<-1l, 1l>}], boost::units::si::system, double>>::type In the above expression [{}, {}, ...] is a pseudo-code for static head-tail list of boost::units::dim<Unit, Rat> pairs. Note the 'double' type materialized from barely nowhere: the code explicitly defines everything as 'float', it's the 'bu::sqrt' to blame for it to appear. Note that replacing 'bu::sqrt' with 'bu::pow<1, 2>()' does not help. As I didn't feel happy with the above error message, I mutated the code a bit and made it to work with: bu::quantity<si::time, float> dt; dt = dimless(0.5f) / (v * bu::sqrt(1.0f/(dx*dx) + 1.0f/(dy*dy))); I had to both (a) add 'dimless', and (b) separate variable declaration and definition. Doing only (a) didn't help. Mkay, but what if I need to have a const quantity? (I'm a big fan of making everything 'const'!). The only one thing I could do was to roll out my own 'sqrt' and 'pow' functions. Here they are: #include <boost/units/get_system.hpp> #include <boost/units/get_dimension.hpp> #include <boost/units/static_rational.hpp> #include <boost/units/quantity.hpp> #include <boost/units/dimension.hpp> template<typename Unit, int N, int M = 1> using static_power_helper = boost::units::unit< typename boost::units::static_power< typename boost::units::get_dimension<Unit>::type, typename boost::units::static_rational<N, M>::type>::type, typename boost::units::get_system<Unit>::type>; template<int N, typename Unit, typename Y> auto ratpow(boost::units::quantity<Unit, Y> const &x) -> boost::units::quantity<static_power_helper<Unit, N>, Y> { using std::pow; return decltype(ratpow<N>(x))::from_value(pow(x.value(), N)); } template<int N, int M, typename Unit, typename Y> auto ratpow(boost::units::quantity<Unit, Y> const &x) -> boost::units::quantity<static_power_helper<Unit, N, M>, Y> { using std::pow; return decltype(ratpow<N, M>(x))::from_value(pow(x.value(), (Y) N / M)); } template<typename Unit, typename Y> auto msqrt(boost::units::quantity<Unit, Y> const &x) -> decltype(ratpow<1, 2>(x)) { return ratpow<1, 2>(x); } Using them I was able to compile the original form of the expression (as seen in the very first listing): bu::quantity<si::time, float> const dt = 0.5f / (v * msqrt(1.0f/(dx*dx) + 1.0f/(dy*dy))); The questions: 1. Is it possible to work around the problem without custom 'sqrt'? 2. Is the described behavior intentional, -or- Is there an error in Boost.Units' implementation of 'sqrt'? 3. If the 'boost::unit::sqrt' is fine, is there something wrong with my implementation? ――― Pavel K. [1]: https://en.wikipedia.org/wiki/Courant-Friedrichs-Lewy_condition

1 0

[config] C++17 macros wanted
by Tal Lancaster 31 May '17

31 May '17

I have been adding C++17 features to date_time. There are two config macros, I would like to have: Test for C++17’s constexpr inline feature. Maybe call it something like: BOOST_NO_CXX17_CONSTEXPR_INLINE Test for C++17’s structured binding feature. Maybe call it something like: BOOST_NO_CXX17_STRUCT_BIND

3 7

[outcome] How to drop the formal empty state
by Niall Douglas 31 May '17

31 May '17

There has been a fair bit of review feedback that people don't like the formal empty state in outcome<T> and result<T>. I still think this opinion daft, just because it's there doesn't mean you have to use it, but here are some options: 1. Like Expected, we could require the E types to provide a nothrow move constructor. This would allow us to guarantee no empty state, not ever. Default constructing an outcome<T> or result<T> would set a default constructed T state, just like Expected. The only remaining difference now between result<T> and expected<T> would be the wide vs narrow observer functions. outcome<T> still can also carry a std::exception_ptr. 2. We could do the above, but default constructor constructs to some constexpr undefined state that is not state T nor E. 3. We could only provide a guarantee of no empty state if the E types provide nothrow move construction, but if they do not we fall back to an empty state arising if throws occur during assignment. 4. The option for an empty state becomes a template parameter defaulted to false i.e. disabled. This can be combined with any of the above. Thoughts? Niall -- ned Productions Limited Consulting http://www.nedproductions.biz/ http://ie.linkedin.com/in/nialldouglas/

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[review] Review of Outcome (ends Fri-June-2)
by charleyb123 . 31 May '17

31 May '17

Reminder -- On Fri-26-May the Review Wizards approved extending the Outcome review until Fri-02-June. (Notification was sent to the list, but considering the high traffic volume lately, one can be forgiven for having missed that message.) Thank you to everyone for your tremendous efforts in taking part in the review; for keeping up with high message traffic; and for the professional and deep exploration of the many (very broad!) topics touched on during this review. The review continues for several more days, ending Fri-02-June (it will not be extended further). Please consider posting a review to the boost mailing list, or privately to the Review Manager (to me). Here are some questions you might want to answer in your review: - What is your evaluation of the design? - What is your evaluation of the implementation? - What is your evaluation of the documentation? - What is your evaluation of the potential usefulness of the library? - Did you try to use the library? With what compiler? Did you have any problems? - How much effort did you put into your evaluation? A glance? A quick reading? In-depth study? - Are you knowledgeable about the problem domain? And most importantly: - Do you think the library should be accepted as a Boost library? For more information about Boost Formal Review Process, see: http://www.boost.org/community/reviews.html Thank you very much for your time and efforts. --charley

3 2

[gil] where is the mysterious boost::gil::read_image function?
by Frédéric Bron 31 May '17

31 May '17

I would like to read a jpeg image from a memory location, not from a file. According to this post http://boost.2283326.n4.nabble.com/gil-io-new-review-Reading-images-from-in… there is a boost::gil::read_image(input_stream, image, image_tag) function but I cannot find it in the header files. Thanks, Frédéric

1 0

[future.then] Should deferred continuation respect status of original future?
by Tomas Sturm 31 May '17

31 May '17

Hi, consider this code that wraps some library returning a future: // some async library boost::future<intermediate> DoLongAsyncTask() { return myPromise.get_future(); } // intermediate translation layer boost::future<result> GetResult() { return DoLongAsyncTask().then([] (boost::future<intermediate> f) { return TranslateToResult(f.get()); }); } // client event loop void RunInClientContext() { auto myFuture = GetResult(); while (stuffToDo()) { doStuff(); if (SafeToCallFutureGetWithoutBlocking(myFuture)) ProcessResult(myFuture.get()); } } What should the implementation of 'SafeToCallFutureGetWithoutBlocking' be? Normally, one would write something like: myFuture.is_ready() or myFuture.wait_for(chrono::seconds(0)) != future_status::timeout But this doesn't work in case the implementation of intermediate translation layer calls .then with launch::deferred! In Boost 1.63 the future returned from .then(launch::deferred, ...) is always deferred, so wait_for(...) always returns deferred no matter what (and is_ready() always returns false). In fact, there is no way to implement 'SafeToCallFutureGetWithoutBlocking' if the translation is to happen in the context of the client (launch::deferred). Wouldn't it be more natural to respect the status of the original future in this case? The documentation is already very clear that the continuation is executed only after the original future is ready. So in case a client asks whether the continuation future is ready, and the original future is not ready yet, the call should forward to the original future instead. What I propose is this: promise<int> p; future<int> f1 = p.get_future(); future<int> f2 = f1.then(launch::deferred, [] (auto f) { return f.get(); }); assert(f2.wait_for(0) == future_status::timeout); p.set_value(42); assert(f2.wait_for(0) == future_status::deferred); Is there any reason for the continuation future to not behave this way? Regards Tomas

2 1

[outcome] narrow-contract, wide-contract, and value_if
by Andrzej Krzemienski 31 May '17

31 May '17

Hi Everyone, Some comments about `outcome`'s observers with narrow and wide contracts. First, the wide-contract functions. We have a situation when someone assumes that `o` currently stores an error_code, and with this assumption in mind calls `o.error()`, but somehow his assumption is incorrect. What do we want to do? 1. Try to report programmer's bug at run-time? 2. Since in this case it is a bug anyway and are screwed, at least let's make such behavior useful for other situations where `error()` is called conciously on `o` without an error code? The first scenario attempts at identifying a bug, bringing it to attention of developers (maybe in form of a log), and minimizing its consequences by perhaps skipping the execution of some part of the program in hope that the bug will no show symptoms again. The second scenario in a way ignores the bug, and lets the program continue, as though it was correct, and from now on the program is doing something else than what the programmer intended. But the semantics of the function are useful in itself. Users who check `o.has_error()` before calling it can use it as if `error()` had a single purpose and a narrow contract; and users who know the additional semantics can use it for other useful things, like saving themselves of writing some boilerplate code. It is my impression that some of these observer functions in `outcome` follow this second scenario: just do something useful for people who use it unchecked. Saving boilerplate is useful, but let's state it clear: these functions offer no protection against inadvertent mistakes: no run-time or static protection. If I call `o.error()` and it throws when `o.is_empty()`, it is a form of protection. If `o.error()` returns `E{}` when `o.has_value()`, this is no protection, it is convinience function that can be used as a narrow-contract observer. Maybe the interface of `outcome` should make this distinction and offer two sets: one for observers with run-time protection, and the other for nice convenience functions? Second, narrow-contract functions. Narrow functions acheive the following goals: 1. Simple design: function only does one thing, it does not have any if inside. 2. The interface of the library makes a clear distinction of what is valid and what is an invalid usage of the library. It helps in code reviews. For instance, you are looking for a bug in a big code, you find the following piece: ``` auto e = o.error(); ``` and it turns out that `e` contains a value. Did you just find a bug, or was it the author's intention to get an `E{}` at this point? You do not know with wide contracts. With narrow contracts you know: it is a bug. 3. Narrow contracts assist instrumentation in test builds and runs. If I have function `just_value` with a narrow contract, I leave myself the freedom: I can do whatever I want when has_value() is false. What can I do with this freedom: A. In test build, I can check the precondition at run-time and launch the debugger B. I can (run-time) check the precondition, and std::termiante() or throw an exception. C. I can ignore the potential precondition violation, check nothing and aim at some performance gain. D. I can put some code that assists the static analyser (like __builtin_unreachable()) E. I can put some instrumentation code that assists an UB sanitizer (like __builtin_unreachable()) F. I can put hints for optimizer (like __builtin_unreachable(), again) G. Finally, I can put a macro `PRECONDITION(has_value())` which can do any of the above based on the build configuration. Given that, the proposed function `value_if` (which returns a pointer to value) will not satisfy my needs. It has a wide contract, so I cannot put macro `PRECONDITION()` inside. It rturns a pointer. The pointer's operator-> inded does have a narrow contract, but it gives me no room where I can put macro `PRECONDITION()`. So I get some narrow contract, but without the benefits I am looking for. So that is my view of the observer functions. Now my proposal is to provide a pair of observers for each value, error_code and exception -- narrow and wide: `value()` and `just_value()`, `error()` and `just_error()`, `exception()` and `just_exception()` Or maybe, even three for narrow-contract, wide-contract with run-time protection, and for convenience function: `error()` -- wide-contract, runtime-checked precondition `just_error()` -- narrow contract `as_error()` -- convenience function, e.g. returns E{}, on value, monad::has_exception on exception, etc.. Regards, &rzej;

2 2

[outcome] user's experience
by Andrzej Krzemienski 30 May '17

30 May '17

Hi Everyone, In order to test Boost.Outcome, I applied it to the problem I had to solve at work a while ago. For people who do not know what Boost.Outcome is for, this could be an introduction. For me it can be an opportunity to obtain feedback from Niall and Vicente, If I am using `expected` correctly, and they can get some feedback from me. Here is the task. I get an std::string as input: it is a data structure encoded in ASCII text: "1-10|11-20|21-99;1-10|10-50|51-99" Semicolons separate "distributions". Within distribution, vertical bars separate "ranges". Within ranges, dashes separarate integer numbers. There are some additional constrains. like ranges within distribution cannot overlap, no gaps between ranges are allowed, and a couple more. I need to validate if the input matches the required format, and build a corresponding data structure. But the vaidation cannot be just binary valid-invalied answer: I want to give user a description of what exactly is wrong with her input, as detailed as possible. So, I have function parse, that internally calls parse_distribution, which in turn calls parse_range. Each of them can return different parsing error that needs to be propagated up. My original implementation used "out" function parameters for signalling errors. Code was unnecessarily long and it was easy to forget to check results from functions, but I didn't want to use exceptions to indicate validation failures, because there is nothin exceptional about it. You expect input validation to fail -- quite often. Now, this is a more philosophic question: when to use (or not) exceptions. One citerion I sometimes use is, "do I want my debugger to automatically break if this function reports faiure?" So I didn't use exceptions for input validation, but the ugliness of the code forced me to go back to rewrite it with exceptions. The code was shorter, and "saer" in the sense that I could not forget ot pass the failure up the stack. Now with Boost.Outcome I have a third option. It is almost as concise as exceptions, but does not use exceptions. Here is my implementation: https://github.com/akrzemi1/__sandbox__/blob/master/outcome_practical_examp… Note a couple of things. I am creating a number of temporay strings under way, they all can throw bad_alloc. I am fine with that. I am not affraid of throwing an exception, it is only the validation failures that I want to report with `expected`. For other failures I want exceptions. This is input validation. It does not have to be super fast. In the public API of this file, I will not be exposing the information about parsing failues. `process` will consume the error information and just output something. So, the choice of `E` in `expected<T, E>` is internal to a file, and I can choose something specific to my use case. I provid my own type, which encodes different erroneous situations in an enum, and two ints for additional details. ``` struct BadInput { enum { no_distrib = 1, range_count_not_3, distrib_starts_with_no_1, distrib_ends_with_no_99, gap_between_ranges, overlap_between_ranges, inverted_range, no_2_numbers_in_range, not_a_number, } type; int val1; int val2; }; ``` It is quite similar to Outcome's error_code_extended. Now, I also wanted to have an std::string member inside, but `expected` forbids it: It says as per LWG requirements `E` in `expected<T, E>` must not kave a throwing copy constructor. Is that right? In my use case it wouldn't harm anyone: if copying of `expected` throws, entire function `process` is exited, with a bad_alloc, which is fine. No `expected` with partial state will be ever observed. Do we need this restriction? Also, at some point I will be returning an `expected<vector<T>, E>`, which makes me uneasy. Returning vectors wrapped in something: will I get runtime penalty for it? So, I naturally arrived at a pattern that Niall described in the other thread: ``` out::expected<vector<T>, E> parse (...) { out::expected<vector<T>, E> ans {out::value}; vector<T> & vec = ans.value(); // will if statement be ellided?} // fill vec return ans; } ``` (BTW, this constant out::value is not documented in the docs, unlike out::value_t.) It has been mentioned a number of times that an optimizing compiler can remove a redundant if-statement. I know that the if-statement inside `value()` is redundant, but in this particular case, will compiler know it to? Nobody has called `has_value()` before. Also, the following piece of code illustrates how concise the implementation of a single function can be: ``` // I use a shortet alias for macro BOOST_OUTCOME_TRYX. // It is not portable, though. It only works on Clang and GCC. #define TRY(ex) BOOST_OUTCOME_TRYX(ex) out::expected<Range, BadInput> parse_range (const std::string& input) { tokenizer numbers_s {input, sep_3}; auto it = numbers_s.begin(), itEnd = numbers_s.end(); int count = std::distance(it, itEnd); if (count != 2) return out::make_unexpected(BadInput{BadInput::no_2_numbers_in_range, count}); Range r {TRY(parse_int(*it++)), TRY(parse_int(*it++))}; if (r.lo > r.hi) return out::make_unexpected(BadInput{BadInput::inverted_range, r.lo, r.hi}); return r; } ``` It is almost as short as if I used exceptions, except for the TRY macro. Note in particular this line: ``` Range r {TRY(parse_int(*it++)), TRY(parse_int(*it++))}; ``` `parse_int()` returns `out::expected<int, BadInput>`.Now, `TRY(parse_int(...))` is an expression and means, "if parse_int() failed immedaitely return function `parse_range` with the same BadInput, otherwise use its `value()` to initialize `r`. What do you think. Am I using the library correctly? Regards, &rzej;

4 7

[outcome] Exception safety guarantees
by Andrzej Krzemienski 30 May '17

30 May '17

Hi All, This is in connection with Vicente's question: what exception safety should we expect of copy assignment of `expected`? Now, this is really funny because we are talking about exception safety in something that is used as a substitute for exceptions. That is, one of the use cases for `expected` is to be able to get rid of exception handling altogether (while still reporting failures). But this fundamental problem, "what state my object is in if this mutating operation fails" is not specific to exceptions. It is speciffic to operations that might fail; and how (and if) they signal failures is of secondary importance. So, let's talk about *failure safety* rather than 'exception safety'. First, let's consider the use case for `expected`, where we want to disable exception handling altogether. This means `T` or `E` cannot throw on any operation. But copy assignment can still fail, right? Or maybe in these domains you are only using trivially-copyable types as `T` and `E`. Or maybe in these domains you never have a need to copy-assign instances of `expected`? Is so, they provide a *no-fail* guarantee, and any implementation of `expected` will be good and offer no-fail guarantee also. Bus if some copying operation on T or E can fail, how is the failure reported? Through a return value? Output parameter? But whatever the answer, we are arriving at the "nested failure" problem: we are processing a (potential) failure report, and this processing fails. What should we do? report the new error condition and ignore the previous? This is very close to a double-exception during stack unwinding. In C++ it std::terminates, other languages ignore the original error, or build a combined error report. All these solutions not satisfactory, and maybe no satisfactory solution exists. I would like to hear an opinion from people who deal with `expected` in exception-disabled environments. On the other extreme, you fave my example with parsing input (which Vicente observed is not parsing, but matching): https://github.com/akrzemi1/__sandbox__/blob/master/outcome_practical_examp… In that case, If I get an exception anywhere (not only upon copying T or E) I want stack to be unwound so far, that all not `expected` objects will remain. So I only care about basic failure guarantee: just let me correctly destroy these objects. In the middle: you have the situation where you copy-assign an `expected` and a copy-constructor of assignment of T or E throws. But where did this exception come from, given that you are using `excepted` for signalling failures? Or are you signalling some failures with exceptions and some with `expected`? And if so, are exceptions not more panic-like? And in that case yu would like to abandon the processing of any `expected`? Anyway, the most difficulties stem from the case where you are storing an E in `expected` and you want to assign an `expected` storing T. You have to first destroy E, and then may not be able to construct a T. My solution to this would be to go to the advice from the first days of forming exception safety guarantees: provide basic guarantee by default, and strong guarantee only if it does not cost too much. We are used to STL containers providing strong assignment, but this is because they are pointers, and they can implement it for free. But does std::touple provide a strong guarantee? No. Do aggregate types provide stron guarantee? No. And can it result in inconsistent data? It can: ``` struct Man { std::string fist_name, last_name; }; Man m1 = {"April", "Jones"}; Man m2 = {"Theresa", "May"}; try { m2 = m1; } catch(...) { } ``` `m2` may end up being {"April", "May"}. And we are taught to write types like this. But if this hapens, the blame is on whoever allowed these objects to outlive the "stack unwinding bubble". So my view, as of today, is not to strive for a strong or even never-empty guarantee. Provide a conditional guarantee, if types T and E don't throw, you get no-fail guarantee. If they do, you only have a basic guarantee: you can destroy, assign to, or maybe call valueless_by_exception(). Nothing more. I think `std::variant` made the optimal choice. And people should code so that instances of `expected` (at least those with T or E throwing on copy/move) should not outlive the "stack unwinding bubbles". Also, note what vector::push_back does when T is non-opyable and its move constructor is potentially throwing: if T's move throws upon reallocation, the behavior is undefined. Regards, &rzej;

8 42

[outcome] Review of Outcome
by Peter Dimov 30 May '17

30 May '17

What follows is my review of the Outcome library. I. DESIGN --------- The general idea of an error handling framework is sound, extremely appealing, and I found it well explained in the documentation. I like the concept very much and agree with many of the design decisions taken throughout. Specifically, constraining the error type to be the fixed std::error_code (or equivalent) and providing a wide accessor interface. I don't think that option<T> should have been included at all. It duplicates optional<T> and has no good reason to exist other than to showcase that the underlying policy-based implementation can produce it. I don't consider expected<T, E> a particularly needed part of the library; the focus should be on result<T> and outcome<T>, the two classes that represent the error handling philosophy on which the library is built. As already stated, I consider the interface of result<T> and outcome<T> a bit too cluttered. Not everyone shares my design preferences for minimal but complete interfaces, so there's legitimate argument to be had over whether, for instance, operator*, operator-> or value_or ought to be included, but the needless duplication between get() and value() is, well, needless. For an initial submission, it's better to err on the side of too little, rather than too much, because it's easy to add later, hard to remove. The empty state has been a source of controversy, and with reason. My initial stance was that it simply needs to go. This however presents a legitimate design question as to what the behavior of the default constructor ought to be. After seeing the suggestions of leaving the object uninitialized there, I now see the empty state as a significantly lesser evil. Having an empty state without the default constructor putting the object into it however is pointless. I do not agree with the direction things have taken of providing a multitude of result classes instead of a single one. Components that are intended to be used in interfaces should provide one, carefully designed option, which encourages what the designer deems best practices. The idea here, assuming that we shoot for standard acceptance at some point, is to provide std::result<T> and have APIs return it, not provide a bag of options and let everyone pick its own thing. (They already do that today and we're not better for it.) I do not agree with making value() unchecked by default. As I explained, one expression of the error handling philosophy behind the library is the following snippet: auto r = function().value(); where function() is noexcept and returns result<T>, whereas the place where the above line appears is a higher level component that signals errors not via error_code, but via exceptions. This one-liner provides the transition in an elegant way; losing it obscures the vision behind the library. Instead of using std::error_code, the library provides its own error_code_extended, complete with an interesting and very useful ring buffer logging mechanism that stores additional information along with the standard code/category values. Specifically, it returns error_code_extended from result<T>::error(). I would separate things a bit further here, attaching the additional information not to a separate error_code_extended class, but to result<> itself. That is, result<>::error() would return std::error_code, and I'd provide a separate accessor, result<>::error_info(), say, that would return the ring buffer entry associated with this result<>. This for me provides a cleaner separation between the basic result<> functionality, and the extended one, although this is a matter of taste. I would also support chaining result<>s by storing the index of the parent ring buffer entry in the current ring buffer entry. This is a straightforward and very useful extension. Instead of providing a macro BOOST_OUTCOME_CATCH_EXCEPTION_TO_RESULT, I would provide result<T>::set_error_from_exception(std::exception const& e); and outcome<T>::set_error_from_exception(std::exception const& e, std::exception_ptr const & p); that would do more or less what the macro does, except the fallback in the second case would be to store p instead of (EINVAL, e.what()). I'd also use make_error_result and make_value_result instead of make_errored_result and make_valued_result, as the former seem more grammatically correct. II. IMPLEMENTATION ------------------ The implementation, from a cursory look, appears of high quality, which is not surprising given that it was in use for two years. The preprocessed header is not easy to review, but the non-preprocessed form is available and amenable to study. Simple examples using outcome<T> compile and work well, although under VS2017 Clang/C2 windows.h is included, which is unfortunate but fixable. The library does not provide a test/Jamfile, which means that as submitted it will not integrate into Boost's testing infrastructure. Given that a Jamfile that performs the equivalent of withmsvc.bat is trivial to write: import testing ; project : requirements <include>../include/boost/outcome/v1.0 ; run unittests.cpp ; the omission is inexplicable. (Further integration into the Boost test matrix would ideally entail splitting unittests.cpp into separate .cpp tests so that success/failure can be tracked independently.) With the above Jamfile, trying to test the library with Cygwin gcc fails with: D:\tmp2\boost-master\libs\outcome\test>b2 toolset=gcc-cxx14 [...] gcc.compile.c++ ..\..\..\bin.v2\libs\outcome\test\unittests.test\gcc-cxx14-6.3.0\debug\unittests.o In file included from ../include/boost/outcome/outcome.hpp:26:0, from unittests.cpp:34: ../include/boost/outcome/outcome_v1.0.hpp:1446:22: fatal error: execinfo.h: No such file or directory #include <execinfo.h> ^ compilation terminated. I realize that Cygwin is not a supported platform, but this is what I have here and this is what I test with, so I figured I'll give it a try. Trying to test with VS 2017 fails with: D:\tmp2\boost-master\libs\outcome\test>b2 toolset=msvc-14.1 [...] compile-c-c++ ..\..\..\bin.v2\libs\outcome\test\unittests.test\msvc-14.1\debug\threading-multi\unittests.obj unittests.cpp unittests.cpp(780): error C3245: 'boost::outcome::_1_0_std_std_9274c0d4::basic_monad<boost::outcome::_1_0_std_std_9274c0d4::policy::monad_policy<udt>>::is_constructible': use of a variable template requires template argument list d:\tmp2\boost-master\libs\outcome\include\boost\outcome\outcome_v1.0.hpp(4271): note: see declaration of 'boost::outcome::_1_0_std_std_9274c0d4::basic_monad<boost::outcome::_1_0_std_std_9274c0d4::policy::monad_policy<udt>>::is_constructible' unittests.cpp(780): fatal error C1903: unable to recover from previous error(s); stopping compilation I get the same failure with /std:c++latest. Testing with the msvc-14.0 toolset works. The library as submitted contains both a preprocessed, fully self-contained, single header named outcome_v1_0.hpp, which is used by default, and a traditional non-preprocessed form that can be chosen with a macro. For the non-preprocessed form to be functional, a git submodule is incorporated by reference: [submodule "include/boost/outcome/boost-lite"] path = include/boost/outcome/boost-lite url = https://github.com/ned14/boost-lite.git branch = master fetchRecurseSubmodules = true ignore = untracked which in turn incorporates two more submodules: [submodule "include/gsl-lite"] path = include/gsl-lite url = https://github.com/martinmoene/gsl-lite.git branch = master fetchRecurseSubmodules = true ignore = untracked [submodule "pcpp"] path = pcpp url = https://github.com/ned14/pcpp.git branch = master fetchRecurseSubmodules = true ignore = untracked The first of these is not by the library author, and the second is a derived work. It is not possible for a Boost release, say, boost_1_65_0.zip, to incorporate git submodules by reference, so there remains a question of what, exactly, is being submitted for inclusion. My attempts to clarify this with the author have proven unsuccessful. I consider this a critical defect of the submission. It is simply not possible for a reviewer to give an opinion whether the submission ought to be included into Boost releases without it being known what, specifically, is being proposed to be included. There is no problem with the library containing implementation details under its directory, but we need to know what these details are. What the library actually needs as dependencies from boost-lite is not much and it's perfectly possible to extract the necessary parts and prepare a self-contained submission. This should have been done prior to the review. The files in the library contain the following: ``` Licensed under the Apache License, Version 2.0 (the "License"); you may not use this file except in compliance with the License. You may obtain a copy of the License in the accompanying file Licence.txt or at http://www.apache.org/licenses/LICENSE-2.0 Unless required by applicable law or agreed to in writing, software distributed under the License is distributed on an "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the License for the specific language governing permissions and limitations under the License. Distributed under the Boost Software License, Version 1.0. (See accompanying file Licence.txt or copy at http://www.boost.org/LICENSE_1_0.txt) ``` This intends to dual license the library, but as written, it doesn't. What it does is apply the terms of BOTH licenses to distribution and use. This is also a critical defect. If the library is included in a Boost release, it should make it perfectly clear that it's licensed under the Boost license, and not under the intersection of Boost and Apache 2.0. There are several ways to do it, one is to clarify the above to specifically say "ASL2 or BSL, at your option" in the appropriate legalese, another is to license the Boost-included Outcome under BSL and the standalone Outcome under whatever. My recommendation would be to just license the lot under BSL and be done with it. Dual licensing creates unnecessary legal complications and may, from a legal point of view, be more burdensome than just using the BSL. Contributors need to be aware that they are licensing their patches under both licenses, it might not be very clear whether they have been aware, and so on. At times, the library duplicates certain functionality present elsewhere in Boost. I do not consider this a defect. It's a legitimate design decision to avoid intra-Boost dependencies, although the author needs to be aware of the downsides - using Boost components is basically taking advantage of free work instead of having to maintain everything oneself. III. DOCUMENTATION ------------------ I found the documentation perfectly adequate and was able to get a very good outline of how the classes were designed, how they were intended to be used, and what problem they intend to solve. It focuses a bit too much on expected<T, E>, which is not in itself a bad thing but is, for me, not exactly what the library is about. Fixing E to std::error_code is a fundamental (and correct) design decision from which these classes derive much of their utility. The Doxygen-generated reference will not win any awards, but it does the job. It however contains too many implementation details that would ideally either not be there at all, or tucked away in their own separate section. The monadic content is also a bit too high for my taste, and I would prefer if a user of result<> and outcome<> does not encounter the word monad at all. IV. VERDICT ----------- Should Outcome be accepted? In short, eventually. This, at present, is a NO. Ideally, what I would like to see is the library resubmitted in a conventional form, consisting of exactly the files that are intended to go into the libs/outcome directory in boost_1_65_0.zip, licensed under the BSL, only containing the files necessary for the non-preprocessed version of the code to compile and work. In addition, the test/ subdirectory would contain a Jamfile that is ready to integrate into the Boost test matrix.

4 14

[build] conditional run of unit-tests?
by Oliver Kowalke 30 May '17

30 May '17

In the unit tests I want conditionally run some unit-tests - depending on property <target-os>- On Windows systems the unit-test should apply/build with property <context- impl>winfib and on POSIX (non-Windows) <context-impl>ucontext. The Jamfile below doesn't work (Windows version build on POSIX) - xould I get a hint how to fix it (couldn't find a reference of rule 'run'). Oliver [ run test_callcc.cpp : : : <context-impl>fcontext [ requires cxx11_auto_declarations cxx11_constexpr cxx11_defaulted_functions cxx11_final cxx11_hdr_thread cxx11_hdr_tuple cxx11_lambdas cxx11_noexcept cxx11_nullptr cxx11_rvalue_references cxx11_template_aliases cxx11_thread_local cxx11_variadic_templates ] : test_callcc_fcontext ] [ run test_callcc.cpp : : : <context-impl>ucontext [ requires cxx11_auto_declarations cxx11_constexpr cxx11_defaulted_functions cxx11_final cxx11_hdr_thread cxx11_hdr_tuple cxx11_lambdas cxx11_noexcept cxx11_nullptr cxx11_rvalue_references cxx11_template_aliases cxx11_thread_local cxx11_variadic_templates ] : test_callcc_ucontext ] [ run test_callcc.cpp : : : <context-impl>winfib [ requires cxx11_auto_declarations cxx11_constexpr cxx11_defaulted_functions cxx11_final cxx11_hdr_thread cxx11_hdr_tuple cxx11_lambdas cxx11_noexcept cxx11_nullptr cxx11_rvalue_references cxx11_template_aliases cxx11_thread_local cxx11_variadic_templates ] : test_callcc_winfib : <target-os>windows ] ;

2 2

Re: [boost] [outcome] Possible extensions/changes to std::experimental::expected
by Vicente J. Botet Escriba 30 May '17

30 May '17

Hi, I believe that this private mail I sent to Niall could concern the Boost community and the Outcome review. While the post concerns the proposed std::experimental::expected, this is applicable as well to Outcome. I've added a more points at the end and some additional information about possible open points for std expected. Le 24/05/2017 à 01:04, Vicente J. Botet Escriba a écrit : > > Hi, > > > After better understanding of the goals of Boost.Outcome I would like > to share two possible extension of std::experimental::expected > > > 1. Implicit conversion when the errors are convertible and the type is > the same. > > I believe this is a missing constructor. > > EXPLICIT expected<T, E>::expected(expected<T, G>); // E is > convertible from G > > I see that the other constructor is also useful > > EXPLICIT expected<T, E>::expected(expected<U, E>); // T is > convertible from U > > and so > > EXPLICIT expected<T, E>::expected(expected<U, G>); // T is > convertible from U and E is convertible from G > > We could as well have an adapt function that transforms expected error explicitly to do error propagation adapt : (E->G) x expected<T,E> -> expected<T,G> (E->G) stands for a function that takes an E and return a G. > 2. variadic expected<Y, E1, ..., En> > > I suggested this already in revision 2 of the Expected standard proposal. > > expected<Y, E1, ..., En> should be something like variant<Y, E1, ..., > En> but with some syntactic sugar. > > > expected<T, E1, ...., En> could be EXPLICIT convertible from > expected<T, G1, ...., Gm> as far as for all Gj we find a unique Ek > that is convertible to. > We can refine the subsumption relation this could take too long to the compiler (as the previous relation has quadratic complexity as Andrzej reported to me). > > I believe this will cover exactly what outcome covers and in addition > it will let open the error types used by the user. > > It acts as a exception specification, which we have abandoned in C++11. > > expected<T, E1, ...., En> f(); > > T f() throw (E1, ...., En); > > > We can consider that this is bad, as we have abandoned it. > > Anyway, I think that expected<T, E1, ...., En> is a good > generalization of the proposed outcome<T> where E1 could be none_t, E2 > could be error_code and E3 is exception_ptr. > > At the end users could use variant<E, E1, ..., En> are return code, so maybe we could to make their life easier. > > In this way we could have > > template <class T> > > using option = expected<T, nullopt_t>; > > Note that this is different to std::optional as the default is T not > nullopt_t :( > I'm not proposing it. Just to say that this could be a possibility for option. > > template <class T> > > using result = expected<T, error_code_extended>; // and possibly none. > > template <class T> > > using outcome = expected<T, none_t, error_code_extended, exception_ptr>; > > > I believe we would need the syntactic sugar as expected<T, > variant<E1,... En>> should have a lot of user code noise. > In addition it will be less efficient than variant<T, E1,... En>. > > E.g. expected<T, variant<E1,... En>> should be convertible from > unexpected_type<G> as soon a one of the Ek is convertible from G. > > I believe variant<E1,... En> is not convertible from variant<G1,... > Gm> under the conditions described above, but maybe this should be the > case. > Andrzej told to me that this is already the case for optional<T>, but I've not found yet on which paper this was added? > > Of course, the never empty warranties could be supported only if the > types Ek allow it and we need to change the standard to ensure it for > exception_ptr. > > > I will not have time to implement a POC for 2, but I believe I could > do it for 1 before Toronto. Anyway I believe it will be worth > discussing these 2 extensions. > > > Best, > > Vicente > > > P.S. EXPLICIT above has the sense given in the standard. > 3. uninitialized default constructed expected<T,E> I know this could be conflictual, but there are a some advantages to doing it. We don't spend time initializing with something we will assign later. This state corresponds to the moved-from state. Initializing it by default to T() is not better initializing to E(). Is expected<Date, error_code> default constructible even if Date is not? Currently it is not the case. There are of course liabilities. We have now the possibility for uninitialized variables, but static analysis tools will help here. 4. About comparisons Outcome doesn't implement comparisons between Outcomes. He pretend that we don't need them. In addition the mix of comparisons and implicit conversion give us some surprising cases as described in Andrzej blog. [1] A gotcha with Optional - https://akrzemi1.wordpress.com/2014/12/02/a-gotcha-with-optional We have that std::future is not comparable (as exception_ptr is not comparable). Instead of comparison we could specialize std::less<> if we want to use them in ordered containers. What others think? 5. About implicit conversion from T The implicit conversion from T to expected<T,E> is a consequence of wanting that expected<T,E> should behave like a T. But this is not right. A expected<T,E> is not a T. We have in some way that expected<T,E> is explicitly constructible from E bu the use of make_unexpected(e). If we had only and explicit constructor from T the code will be much more uniform. Either you build it with a modified make_expected or with make_unexpected. In my opinion the implicit conversion from T to expected<T> is a mistake. 5. About the exception to throw std::experimental::expected throw bad_expected_access<E>. I adopted the design of optional and bad_optional_access We could have as well a bad_expected_access_base class as Outcome has. My question is why don't throw directly E? Some are requesting a way to get a specific exception from E, but either there is one exception that works for all and we can set it using some kind of trait or we need to add a trait parameter to expected to the the mapping :( Do we really want this to be configurable? 6. Implicit conversion from E outcome::expected<T,E> outcome::expected<T,E> is implicitly convertible from E when there is no risk of ambiguity. std::expected<T,E> is implicitly convertible from unexpected<E>. What people thing we should have? In Boost? in the standard? Vicente

5 21

[build] [config] check_target_builds and feature.subfeature composition
by Edward Diener 30 May '17

30 May '17

The Boost library config uses the check_target_builds rule to provide build time feature testing. Other Boost libraries use config checks in their own build and test jamfiles. I have found that this works reliably when a particular toolset is used in a normal manner. However when using the feature.subfeature and feature.compose rules to extend the toolset-version designation with a subfeature, such that the toolset designation now becomes toolset-version-subfeature, the use of the check_target_builds rule does not work as expected. In particular the individual check_target_builds rule results are put into a subdirectory based on the toolset-version and not based on the toolset-version-subfeature when toolset subfeature composition is used. I also suspect that the cached value reflects setup. This causes wrong results in tests where the toolset designation uses subfeatures, and a library's jamfile is using config and/or predef checks. As an example My toolset designation looks like: using gcc : 6.3 : some_path ; feature.subfeature toolset gcc : cxxstd : c03 c11 c14 c17 : optional composite propagated ; feature.compose <toolset-gcc:cxxstd>c03 : <cxxflags>-std=c++03 ; feature.compose <toolset-gcc:cxxstd>c11 : <cxxflags>-std=c++11 ; feature.compose <toolset-gcc:cxxstd>c14 : <cxxflags>-std=c++14 ; feature.compose <toolset-gcc:cxxstd>c17 : <cxxflags>-std=c++1z ; A library's test looks like: import ../../config/checks/config : requires ; run some_test.cpp : : : [ requires cxx11_hdr_forward_list ] ; If I run some some_test with toolset=gcc-6.3-c03, the config result for checking if forward list is supported is put into a subdirectory reflecting the toolset-version while the test result will be put into a subdirectory reflecting the toolset-version-subfeature. Subsequently if I run some_test with toolset=gcc-6.3-c11 the config result is taken from the subdirectory reflect the toolset-version even though whether the forward list is supported or not depends very much on the subfeature I am designating as part of the toolset. This naturally causes incorrect results for the test. Is this a known problem ? Is it a problem with Boost Build or is it a problem with how config uses the check_target_builds rule ? I have run into this problem extensively in my testing once I started to use the feature.subfeature ability of Boost Build.

5 9

[outcome] Review of Outcome
by Emil Dotchevski 29 May '17

29 May '17

I. Design There is a need in C++ for dealing with failures without using exceptions. This is not so much driven by actual inefficiencies (as opposed to perceived inefficiencies) of exception handling, but by the fact that not all C++ code in existence is exception-safe, and the fact that some C++ programmers work in environments where exception handling is disabled, as ill-advised such a decision may be. In my opinion the library should drop option<T> and result<T> altogether and should be reduced to outcome<T> only, which can be empty, or hold a T, or hold an exception (but not error code, see below.) This is critical for a library that aims to provide a _common_ general mechanism for dealing with failures in interfaces; providing a rich set of alternatives works against that goal. (It seems desirable to get rid of the empty state too but the discussions during the review period show that this might cause more problems than it solves.) Secondly, it is not a good idea to use error codes or any other value as means to dispatch on different kinds of failures because semantically such dispatch should be static: there is some _code_ which detects the error, and there is some other _code_ that needs to bind it and handle it. This is one reason why in C++ catch dispatches by the static type of the exception objects, not by some exception.what() value. Further, using static types to communicate different kinds of failures allows users to recognize and handle an entire class of errors by means of implicit type conversions, by organizing error types in a hierarchy. For example: struct io_error: virtual std::runtime_error { }; struct read_error: virtual io_error { }; struct write_error: virtual io_error { }; struct file_error: virtual io_error { }; struct file_read_error: virtual file_error, virtual read_error { }; struct parse_error: virtual std::runtime_error { }; struct syntax_error: virtual parse_error { }; With this hierarchy, we can use read_error to handle any kind of read errors (not just file-related), file_error to handle any kind of file failures (read or write), etc. That said, outcome<T> should also be able to transport values, however their purpose should not be to tell _what_ went wrong, but to provide additional information. It must be stressed that such additional information should be decoupled from the classification of the error. For example: outcome<parsed_data> parse_file( char const * file_name ); The above function reads a file and returns some parsed_data -or- stores an exception object in the outcome. What are the possible failures? It may be a file_read_error, but also types unrelated to I/O like std::bad_alloc or syntax_error. Regardless of the type of the failure, the outcome object should be able to transport the file name because it is relevant no matter _what_ went wrong. Incidentally, the need to transport contextual information independently of the error classification exists when throwing exceptions as well, so if outcome<T> can hold exception objects (and allow users to dispatch on their static type, like catch does), the exception objects themselves can take care of holding any additional information, for example by using Boost Exception. II. Implementation In general the library should not shy away from integrating with common Boost facilities in an effort to appeal to people who hate Boost. A Boost library should primarily target Boost users and address their concerns. This includes the testing framework as well as boost/config.hpp where applicable (it is okay to not always include boost/config.hpp, but it should be included to get things like BOOST_NO_EXCEPTIONS and other configuration macros.) The library should use BOOST_ASSERT, though I don't see a problem with not #including boost/assert.hpp if BOOST_ASSERT is already defined (by the user). The library should use BOOST_THROW_EXCEPTION to throw. Like in the case of BOOST_ASSERT, it's fine to not #include boost/throw_exception.hpp if BOOST_THROW_EXCEPTION is already defined. That said, avoiding coupling with individual Boost submodules is desirable in general. Also there is no problem with providing facilities to avoid all Boost coupling in order to support non-Boost users. III. Documentation The documentation makes broad claims about the inefficiency of exception handling which seem to be motivated by a desire to appeal to programmers who hold such beliefs. There is no need to make such generally untrue claims in order to justify the need for Outcome. Other than that the documentation does the job. IV. Verdict Should Outcome be accepted into Boost? NO This obviously applies only to the current state of the library.

3 4

[move] BOOST_RV_REF(TypeWithoutMoveEmulation) parameters
by Groke, Paul 29 May '17

29 May '17

Hi, I'd like to use BOOST_RV_REF, with both C++98 and C++11 compilers, for some sink-functions, with types that are not "move-enabled". I.e. types that the sink can "consume"/"move from" by other means (swapping, calling .release(), ...). Some of them I can - eventually - change to be fully move-enabled, others I can not (e.g. STL classes). I just assumed that this was possible by simply passing the argument with boost::move(arg). Apparently it's not though, because boost::move will return a plain T& for types without move emulation. For the time being I have defined my own helper function template "move_any" that will always return a rv<T>&. Is there such a function that I missed? And if not, would you think it'd make sense to provide one (I certainly think it would)? Regards, Paul Groke

3 5

[outcome] On the design and documentation
by Thomas Heller 28 May '17

28 May '17

Hi Niall (and also probably Vicente) I was following the discussion about expected/outcome/result very closely and I can absolutely see the usefulness of such a library (I explicitly discarded option here). I am not sure if this post should count as a review, mainly because I disagree with the fundamental design decisions (that includes expected as defined in D0323R2) and therefor would cast my vote as in "not ready yet", I hope I can convey my points below. First of all, I don't agree with the strong (conceptual) relationship between optional (be it boost:: or std::experimental) in such a way that expected is a generalization of it. From what I understand, the purpose of expected/outcome/ result is to be used as a mechanism to return the result of a function. As such it should also expose the semantics of it. Fortunately, we already have a (asynchronous) return object standardized (std::future). And this is my basic disagreement here: Why not model expected in the lines of future? With the main points being: - expected being movable only - expected<T,E>::value() should always return by value and invalidate this. - (I would really prefer the color .get though ;)) So the question to Vicente/Niall is: what is the motivation to make it "optional-ish"? Do we have use cases which make this design undesirable? By having these constraints, expected of course needs to have an uninitialized state. As such we'd have the three observers: valid(): true when has_value() || has_error(), false otherwise (for example default constructed, invalidated), has_value() and has_error(). Second, I think Niall raised a valid about outcome being a framework for interoperability (completely orthogonal to the first point). However, I totally miss this from the proposed library, most pressing are non intrusive mechanisms. For that purpose I postulate, that a mechanism to transform between different unexpected results, that is: various error codes etc. However, for that to work, one would of course need a properly defined concept, for example, as Vicente suggested "EitherValue", and a mechanism to coerce one error type into another, maybe through ADL, or traits specialization or whatever. With that in place, one could simply define the different EitherValue types, there is no need that everything needs to be in the form of "basic_XXX". For the library under review, this would be perfectly sufficient: template <typename T, typename E> class expected; template <typename T> using result = expected<T, extended_error_info>; template <typename T> using outcome = expected<T, variant<extended_error_info, exception_ptr>>; That is, given that we have either a value or unexpected, we can convert expected<T, E1> to expected<U, E2> if T is convertible to U and E1 "coercable" (with whichever mechanism) to E2. If we then have a generic mechanism to get from a (possibly user defined "E") to an exception, I completely miss the point of the outcome template. Furthermore, I believe that .value/.error should really have a narrow contract, that is that it is UB to call those functions if the respective types are not held (easy to catch this in a debug build...). Why? Probably just a micro optimization, but consider the canonical usage: auto r = some_function_returning_expected(...); if (r.has_value()) // Do something with the value else // An error occurred, PANIC In both branches, we know exactly what's in there ... so why check again when getting the state out? I don't get the "reinterpret_cast" argument. I am one of the persons that believe that UB is a necessary evil for some optimizations... All optimizations can then easily be put as implementation details and the generic expected<T, E> will probably suffice for most use cases, for everything else, we can implement special types which conform to our concepts and implement the error conversion mechanisms. This will most likely also work with different APIs/ABIs. Last but not least, I wanted to give some feedback on the proposed Boost.Outcome documentation. At the very least, I find it highly confusing. When I open its "landing page", I get no idea about the following: - What is the purpose of the library? - Why/when should I use it? - What should I look into next? >From the front page, it looks like a implementation of expected, but only talks about the outcome template, it is very hard to find the documentation for the other three types result, outcome and option. Yet, the documentation explicitly warns about it being unstable and suggests to use its refinements. Useful information is spread across the whole documentation, there is no easy way to find the requirements on T or E. The reference section is anything but complete and doesn't convey any useful information. I did not really look at the actual implementation of the proposed library. I cloned the git repository and had a quick glance, but to be honest, I got lost very early, I have no idea where to start looking first. Cheers, Thomas

6 15

[outcome] outcome without empty state?
by Andrzej Krzemienski 28 May '17

28 May '17

Niall, What do you think about the following alternate interface of outcome types? 1. Remove option<T> altogether. 2. result<T> (and outcome<T>) does not have a separate empty state. 3. A default-constructed result<T> is initialized as if `result<T>{error_code_extended{}}`. 4. Function r.empty() is implemented as `r.has_error() && !error()`. 5. Framework requires that type E in `expected<T, E>` is default-constructible, and its default-constructed value represents no error condition (already the case for exception_ptr, error_code). The rationale behind this is my assumption that `option<T>` is not as useful as the other types. (Or can you give an example to the contrary?) That there was no initial business need for an empty state, and the examples that illustrate its usefulness are just exploring how we can make use of it now that it is there. (Or am I wrong here?) I noticed a number of people report negative feedback about this empty state. Getting rid of it would take result<T> closer to "either T or reason for failure". What do you think? Regards, &rzej;

6 27

[review] Review of Outcome (starts Fri-19-May)
by charleyb123 . 28 May '17

28 May '17

Hi Everyone, The formal review of Niall Douglas' Outcome library starts today (Fri-19-May) and continues until Sun-28-May. Your participation is encouraged, as the proposed library is uncoupled and focused, and reviewers don't need to be domain experts to appreciate the potential usefulness of the library and to propose improvements. Everyone needs (and has suffered) error handling, and can compose an opinion on that topic. Outcome is a header-only C++14 library providing expressive and type-safe ultra-lightweight error handling, suitable for low-latency code bases. Key features: *- Makes using std::error_code from C++11's <system_error> more convenient and safe *- Provides high-quality implementation of proposed std::expected<T,E> (on C++20 standards track) *- Good focus on low-latency (with tests and benchmarks) *- Error-handling algorithmic composition with-or-without C++ exceptions enabled *- No dependencies (not even on Boost) This review is timely, as C++17 brings us std::optional<T>. The upcoming std::expected<T,E> (an implementation provided in Outcome) is a generalization of std::optional<T> that provides a <success|fail> value, where the unhappy result is a 'std::error_code' or an instance of "your-chosen-error-type". The library further provides 'outcome<T,error-code,exception-ptr>' for handling <success|error|exception> to safely wrap throwing APIs. Documentation: https://ned14.github.io/boost.outcome/index.html ACCU 2017 talk including design rationale: https://www.youtube.com/watch?v=XVofgKH-uu4 GitHub: https://github.com/ned14/boost.outcome Latest tarball: https://github.com/ned14/boost.outcome/releases/download/ boost_peer_review3/boost.outcome-v1.0-source-201705111650.tar.xz Note: Tarball might be easiest; but if you want to clone from GitHub directly, after the clone you should run the following command to get the source zip exactly: git submodule update --init --recursive Please post your comments and review to the boost mailing list (preferably), or privately to the Review Manager (to me ;-). Here are some questions you might want to answer in your review: - What is your evaluation of the design? - What is your evaluation of the implementation? - What is your evaluation of the documentation? - What is your evaluation of the potential usefulness of the library? - Did you try to use the library? With what compiler? Did you have any problems? - How much effort did you put into your evaluation? A glance? A quick reading? In-depth study? - Are you knowledgeable about the problem domain? And most importantly: - Do you think the library should be accepted as a Boost library? For more information about Boost Formal Review Process, see: http://www.boost.org/community/reviews.html Thank you very much for your time and efforts. --charley

17 70

[review] Review of Outcome (ends Sun-28-May)
by charleyb123 . 27 May '17

27 May '17

Hi, Everyone, First a (very-)big "thank-you!" to all participating in the ongoing (and vigorous) debate and review for the Outcome library. The spirited discussion touches on tricky issues for composition and error handling (with and without C++ exceptions enabled), where the community is clearly searching for best convention and common ground. Thus far: (a)- some 300+ emails discussing Outcome (and more emails off-list) (b)- participation from: *- Andrzej Krzemienski *- D25fe0be *- Deniz Bahadir *- Emil Dotchevski *- Gavin Lambert *- Glen Fernandes *- Gottlob Frege (Tony) *- Hartmut Kaiser *- Ion Gaztanaga *- Jonathan Muller *- Niall Douglas *- Paul Bristow *- Pete Bartlett *- Peter Dimov *- Robert Ramey *- Thomas Heller *- Vicente J. Botet Escriba *- Vinnie Falco *- ...(apologies if I've missed anyone) (c)- Some points-of-discussion relate to: *- Outcome efficiency (copy/move) on today’s compilers *- Outcome speed/overhead (exceptions) *- Outcome purpose/motivation *- Outcome Tutorials, documentation *- Outcome “formal-empty-state”, default-initialization *- Outcome compiling, compiler support *- Outcome ABI, namespace usage, use of preprocessor *- Outcome alternative APIs *- std::expected proposal, possible changes (d)- Reviews to date (sent publicly to the list): *- Paul Bristow -- accept, conditional (Tue-23-May) *- Deniz Bahadir -- accept, unconditional (Wed-24-May) *- Thomas Heller -- (almost a review), ?reject, "not-ready-yet?" (Wed-24-May) (e)- Significant other discussion also contributes to evaluation of Outcome as a Boost library. However, I encourage further reviews to make clear any conclusions from these discussions that I might have missed. The review continues for several more days, ending Sun-28-May. Please consider posting a review to the boost mailing list, or privately to the Review Manager (to me). Here are some questions you might want to answer in your review: - What is your evaluation of the design? - What is your evaluation of the implementation? - What is your evaluation of the documentation? - What is your evaluation of the potential usefulness of the library? - Did you try to use the library? With what compiler? Did you have any problems? - How much effort did you put into your evaluation? A glance? A quick reading? In-depth study? - Are you knowledgeable about the problem domain? And most importantly: - Do you think the library should be accepted as a Boost library? For more information about Boost Formal Review Process, see: http://www.boost.org/community/reviews.html Thank you very much for your time and efforts. --charley

8 16

Detail headers moved
by Belcourt, Kenneth 26 May '17

26 May '17

Hi, I’m trying to build Boost.Graph and running into missing header files that used to live in boost/detail and now live elsewhere. Here’s a couple of examples of headers that moved and the code that still expects to find them there: detail/container_fwd.hpp libs/functional/include/boost/functional/hash/extensions.hpp: #include <boost/detail/container_fwd.hpp> libs/lambda/include/boost/lambda/detail/operator_return_type_traits.hpp: #include "boost/detail/container_fwd.hpp" libs/phoenix/include/boost/phoenix/stl/algorithm/detail/is_std_list.hpp: #include <boost/detail/container_fwd.hpp> libs/phoenix/include/boost/phoenix/stl/algorithm/detail/is_std_map.hpp: #include <boost/detail/container_fwd.hpp> libs/phoenix/include/boost/phoenix/stl/algorithm/detail/is_std_set.hpp: #include <boost/detail/container_fwd.hpp> detail/indirect_traits.hpp libs/iterator/include/boost/iterator/detail/facade_iterator_category.hpp: #include <boost/detail/indirect_traits.hpp> libs/iterator/include/boost/iterator/indirect_iterator.hpp: #include <boost/detail/indirect_traits.hpp> It seems that indirect_traits.hpp was moved from detail into python/detail, and container_fwd.hpp into container. Just curious but was it intentional to make many Boost libraries depend on Python through boost/iterator/iterator_facade.hpp? Noel

2 4

[outcome] some problems compiling
by Andrzej Krzemienski 26 May '17

26 May '17

So, I am trying to run my first test program with Boost.Outcome. The library fails to compile with GCC 6.3.0 on MinGW on Windows 7. I have filed the issue: https://github.com/ned14/boost.outcome/issues/36 But also, I can see in file <boost/outcome/outcome_v1.0.hpp>, lines 1267 to 1279 ``` #ifdef __cplusplus namespace { #endif typedef struct _IMAGEHLP_LINE64 { unsigned long SizeOfStruct; void *Key; unsigned long LineNumber; wchar_t *FileName; unsigned long long int Address; } IMAGEHLP_LINE64, *PIMAGEHLP_LINE64; ``` 1. Why do you check for __cplusplus? Is it a copy-and-paste of some Windows headers? 2. This class and subsequent functions are defined in anonymous namespace. This means they are redefined and recompiled in each translation unit, and remain a per TU definition. Is that intent? Regards, &rzej;

5 11

Re: [boost] [outcome] Possible extensions/changes to std::experimental::expected
by Andrzej Krzemienski 26 May '17

26 May '17

It looks like part of the discussion accidentally went into a private conversation. So, here we are back. 2017-05-25 22:39 GMT+02:00 Vicente J. Botet Escriba < vicente.botet(a)wanadoo.fr>: > Le 25/05/2017 à 18:40, Andrzej Krzemienski a écrit : > > > > 2017-05-25 17:32 GMT+02:00 Vicente J. Botet Escriba < > vicente.botet(a)wanadoo.fr>: > >> Le 25/05/2017 à 13:18, Andrzej Krzemienski via Boost a écrit : >> >>> 2017-05-25 9:44 GMT+02:00 Vicente J. Botet Escriba via Boost < >>> boost(a)lists.boost.org>: >>> >>> We have now the possibility for uninitialized variables, but static >>> analysis tools will help here. >>> >>> So, more specifically, I understand that you propose the following: >>> >>> - Default constructor works: no T or no E is construced (similar what >>> outcome<> does) >>> >> I was not aware of this. Do you know that from this reference >> documentation? >> >> constexpr outcome () noexcept(is_nothrow_default_constructible) >> Default constructor. >> > > Well, I just assumed that since outcome<> has this empty state, it is > exactly for the purpose of giving semantics to the default constructor. But > now that you have asked, I looked at the docs. They say nothing about what > happens in the default constructor. I tried to look in the code, but was > confused with these policies. So, I just run a small test program, and yes: > default constructor creates an empty state. > > Niall, please could you add an issue in order to document default > constructors (if it doesn't already exists). > This is already logged in https://github.com/ned14/boost.outcome/issues/26 > > >> >> Sorrty, I couldn't interpret it as you. >> But, if it is the case, yes, as outcome does. >> >>> - You can assing to and and destroy such an objetc (similar what >>> outcome<> does) >>> >> I don't catch what you mean here. Are you referring to the conversion >> between expected with convertible value type and error types? >> > > No, I am saying that the following should work: > outcome<T> o; // default-constructed > o = some_outcome<T>(); // this should be safe to execute > > This works already with expected even if it doesn't defaults to empty. > Ok, and you expect it to continue to work. > > >> - You will probably need to add an observer function that checks for >>> this singular state, like `is_singular()`. If not for anything else >>> it >>> would be used for assisting the static analysis tools. (again, >>> similar what >>> outcome<> does) >>> >> No. There will be no such observer. This is essential. There is no >> visible empty state. >> Or do you consider that chrono::duration should tell you if it was >> initialized or not? >> The user know if it is initialized or not, but there is no tool to check >> it. >> This could be against safe programming, but we are here in C++ and we >> should provide first the raw tools and then build on top of them when we >> want more. >> >>> - other observer functions (has_value(), value(), has_error(), >>> error()) >>> cause UB when `is_singular() == true. (this is the only difference >>> from >>> outcome<>) >>> >> Not the only one. >> outcome fixes its error types. I'm proposing an extension to the current >> expected so that it can take care of the Outcome use cases and needs. >> >>> >>> Did I understand your intentions correctly? >>> >> Not completly. I don't want an observer that tells me, attention you have >> not initialized your variable, or you have moved from. This is essential. > > > Very daring. It would be easier to accept if you could show a tool that is > capable of statically analying this kind of "used unintialized" bug for > `expected`. > > > Static analysis to check if uninitialized variables are used (read) works > very well already . I don't remember if it si with clang-tidy that I have > seen this kind of warnings. > Ok. Now I am thinking, another thing you can do, is to internally store something like varient<T, Y, Empty> but do not expose this Empty in the interface. Instead, rewrite observer functions like this: ``` bool has_value() const { if (BOOST_UNLIKELY(_is_in_empty_state())) __builtin_unreachable(); return _is_in_valued_state; } ```

3 12

[outcome] expected<T&>, result<T&>
by Andrzej Krzemienski 25 May '17

25 May '17

Niall, Are Boost.Outcome monads intended to work with references (at least lvalue references)? If I try to compile the following program that tries to use an `result<T&>` (on GCC 6.3.1): ``` #include <boost/outcome.hpp> namespace out = BOOST_OUTCOME_V1_NAMESPACE; int g_count = 0; out::result<int&> get_ref() { return out::result<int&>(g_count); } int main () {} ``` I get lots of compiler errors. But the messages ("constructor cannot be overloaded") indicate that it was just an omission and not a design decision. If I try it with `outcome::expected` I also get these messages, but I also get a static assert saying that as per LWG decision T must be default constructible. Vicente, does this mean you cannot use `std::expected` to return references? Regards, &rzej;

5 8

Re: [boost] [outcome] expected vs. result
by Niall Douglas 25 May '17

25 May '17

> It would be very helpful to have a documentation for comparing all types, > expected, option, outcome, and result, showing the use cases and best > practices. I have some hard time to understand what one can do and the > other can not and in which cases I should prefer one. One thing very obvious in this review so far is how overwraught it has made that choice seem. I think as soon as you start writing some code using Outcome, you'll find the choice flows naturally. Using this library in your code is far, far, far easier and more intuitive than this review makes it seem. They are very simple objects, and very easy to use. Often the simpler the object, the more bikeshedding and strong opinions and noise result. Niall -- ned Productions Limited Consulting http://www.nedproductions.biz/ http://ie.linkedin.com/in/nialldouglas/

3 2

[outcome] Ternary logic -- need an example
by Andrzej Krzemienski 25 May '17

25 May '17

Niall Douglas wrote: > Finally, if you did have some special E value to mean empty, you would > have to write special checks for it in Outcome in order to give it the > stronger abort type semantics it has - if you don't have it being given > alternative semantics, then there is no point in having an empty state. > If you are writing special checks, then you might as well just have a > formal empty state in the first place. > > This argument can be generalised into the argument in favour of ternary > logics over binary logics. Sure, 90% of the time binary logics are > sufficient, but binary is a subset of ternary. And *you don't have to > use* the "other" state in a ternary logic just because it's there. Just > don't use it, so long as its implementation signals its unintentional > usage with a very loud bang, it's a safe design. > > (There is an argument that Outcome's "very loud bang" isn't loud enough. > I'd be pleased to hear feedback on that) Niall, you mention "ternary logic" here, and I guess it has to do with 'module' `tribool` exposed by Outcome library. But I do not believe I have seen in the documentation (I mean the tutorial section) how I am supposed to use it, and how it improves my programs. Or I might have just missed it. Could you give me an example? Regards, &rzej;

7 46

Re: [boost] Boost.Outcome review - First questions
by Hartmut Kaiser 25 May '17

25 May '17

Andrzej, Thanks for attempting to additionally clarify what you said before. > Again, sorry to reply on behalf of Niall, but it is my description that > might have caused the confusion. I'm glad you try to answer my questions as I know I will not get any from Niall directly. > There is still this case where you want to avoid exceptions in one part of > the program, but still use exceptions in other parts of the program. For > one example. in one "task" you launch another task with a callback > function `f`. You might want to throw from `f` and this is valid. But the > framework for launching tasks cannot afford to spill exceptions, so they > have to catch and somehow transport the exception (e.g., by exception_ptr) > then in the other task, you might want to re-convert to an exception. > (something similar to what std::future does.) I understand what you're saying, std::future needs a (conceptual) variant<T, exception_ptr> to store its state. So if I hear you correctly, outcome::expected<T, exception_ptr> could be used for that. > Other situation, is when you are using a third-party library, which throws > exceptions. You want to wrap it into a component that does not throw. > Boost.Outcome also supports in a convenient way this transition from and > to exceptions. Ok. > Also, maybe you will find of use the following example that tries to > illustrate the basic use case of the library: <snipped code example> Thanks, I think I've seen this in the docs. All of this could have been done with a variant<T, some_error_type> without changing the semantics, yes? So I guess the next question I would like to ask is: what is the benefit of using outcome::result<T> over std::optional<T>, and outcome::expected<T, E> over std::variant<T, E>? Regards Hartmut --------------- http://boost-spirit.com http://stellar.cct.lsu.edu

2 3

Re: [boost] Boost.Outcome review - First questions
by Hartmut Kaiser 25 May '17

25 May '17

Andrzej, > Thanks, I think I've seen this in the docs. All of this could have been > done with a variant<T, some_error_type> without changing the semantics, > yes? > > So I guess the next question I would like to ask is: what is the benefit > of using outcome::result<T> over std::optional<T>, and > outcome::expected<T, E> over std::variant<T, E>? > > At some conceptual level, yes, `outcome::expected<T, E>` is like > `variant<T, E>`. Two other types from this library could also be described > in terms of variant: > `outocome::result<T>` is like `variant<T, outcome::error_code_extended, > empty_state>` > `outocome::outcome<T>` is like `variant<T, outcome::error_code_extended, > std::exception_ptr, empty_state>` > Technically, you could use variant everywhere, but the tools from > Boost.Outcome offer an interface tailored to the use cases, loike > contextual conversion to bool. Also, a more focused scope than variant > offers room for optimizations. All of those could be equally well provided by a set of free-standing generic functions. There is no need to introduce yet another inventory type. As said elsewhere, a 'using expected<T, E> = variant<T, E>;' would do us the same in this case. > Having this `empty_state` is under debate. I hope at least the empty state gets dropped on the floor, even if I think the whole expected<> business is overkill and introducing a minimally necessary set of monadic helper functions (Vicente mentioned PossibleValue, MonadError, etc.) would be sufficient in many ways. With those functions a simple variant<T, E> would give us all we need. Thanks! Regards Hartmut --------------- http://boost-spirit.com http://stellar.cct.lsu.edu

1 0

Boost.Outcome review - First questions
by Vicente J. Botet Escriba 25 May '17

25 May '17

Hi, I've tried to read the tutorial, but it is too long for my taste. I will try it later on :( A minor issue * "As inferred in the example code cases earlier, you can check if an |expected<T, E>| has an expected value via a simple test for boolean true or more explicitly via |.has_value()| before retrieving the value using |.value()|." This is not correct. It is correct for the de-reference operator, but .value() don't needs any check with .has_value(). Instead of some deviation, I would expect a report of all deviations and a rationale explaining why it is better to do this way. # "Types |T| and |E| cannot be constructible into one another. This is a fundamental design choice in basic_monad to significantly reduce compile times so it won't be fixed." * "Note though that |expected<void, void>| is permitted (which is legal in the LEWG proposal)." What are the compile time cost |associated the std::experimental::expected<T,E>? | I don't see what |expected<void, void> could mean. | # |unexpected_type<E>| is implemented as an |expected<void, E>| and it lets the basic_monad machinery do the implicit conversion to some |expected<T, E>| through the less representative to more representative conversion rules. Note that our Expected passes the LEWG Expected test suite just fine, so you probably won't notice this implementation detail in your code. The test of my POC implementation couldn't be complete, so this is not a sign of compatibility. Which operation allow to convert expected<void,E> to expected<T,E> and what is the expected behavior if expected<void,E> has a value? # Our |expected<T, E>| defaults E to |std::error_code| rather than |std::error_condition| (the LEWG proposal fixes this in P0323R2). I don't have a strong opinion on which default would be the best. As you suggested, I have added it to the next revision. We don't implement the ordering and hashing operator overloads due to https://akrzemi1.wordpress.com/2014/12/02/a-gotcha-with-optional/. The fact the LEWG proposal does as currently proposed is a defect (it will be discussed by LEWG with P0323R2 in Toronto). As for optional this could be considered a defect. The question is if we want expected to differen from the optional interface. If we considered it a defect, I don't believe that we should remove comparison, but IMHO we should make the constructor from T explicit. I don't expect the committee to fix this for expected and let the issue for optional. We will see. # We don't implement |make_expected_from_call()| as we think it highly likely to be removed from the next version of the proposal due to it conferring little value. This is possible and the function can be implemented very easily. I can live with and without it. # Our |make_expected()| and |make_unexpected()| functions deviate significantly as we believe the LEWG ones to be defective in various ways. This topic will be discussed in Toronto and reconciliation later is highly likely. Please, could you tell how those are defective so that we can fix them? Otherwise I don't see what we could discuss in Toronto. # Our |value_or()| member functions pass through the reference rather than returning by value (we don't understand why the LEWG proposal does except that |std::optional<T>| does, which itself is a bad design choice and it should be changed). Well, what is the advantage to returning by reference? Rather than |void|, our |value_type| and |error_type| typedefs are set to a descriptive compiler error generating type if the Expected is configured with |void|. If you want to know if no type was configured, use the static constexpr bools at |expected<T, E>::has_value_type| and |expected<T, E>::has_error_type| or use |raw_value_type| and |raw_error_type|. The reason for this deviation is to make metaprogramming using Outcome's transports much easier and less error prone. Sorry. I don't understand what is the issue. Could you elaborate? # Our Expected always defines the default, copy and move constructors even if the the type configured is not capable of it. That means |std::is_copy_constructible| etc returns true when they should return false. The reason why is again to significantly improve compile times by hugely reducing the number of templates which need to be instantiated during routine basic_monad usage, and again this won't be fixed. Instead use the static constexpr bools at: Defining these operation when they can not be implemented means that you cannot use SFINAE on this type. Maybe I'm wrong, but I believe we want to check if a type is constructible, ... using the C++ standard type traits. Next follow the first questions I have mainly from the reference documentation of expected<T,E>. In general I find most of the operation not specified enough. I would like to have something in line with the standard way of specifying an interface. * it is not clear from the reference documentation if expected<void,E> is valid? |* |is expected<T,E> the sum type of T, E and empty? and exception_ptr? |"outcome<T>| can be empty, or hold an instance of a type |T|, or hold an instance of |error_code_extended|, or hold an instance of |std::exception_ptr|. This saves you having to wrap an error code into an exception pointer instance, thus also avoiding a memory allocation." std::experimental::expected requires that its Error type to be no throw constructible, copyable and movable. What are the exception warranties for |error_code_extended? | What are the exception warranties for |outcome<T>||? | * inplace construction What is the difference between: constexpr expected (value_t _) noexcept(std::is_nothrow_default_constructible< value_type >::value) Implicit constructor of a valued monad (default constructed) and constexpr expected (in_place_t, Args &&... args) noexcept(std::is_nothrow_constructible< value_type, Arg, Args... >::value) when there is no Args. IMO the second subsumes the first and so there is no need fro the first overload and the value_t tag. * default constructor constexpr expected () noexcept(is_nothrow_default_constructible) Default constructor. This doesn't say what the default constructor does. * Shouldn't constexpr expected (in_place_t, std::initializer_list l) noexcept(std::is_nothrow_constructible< value_type, std::initializer_list>::value) Implicit constructor from an initializer list. be constexpr explicit expected(in_place_t, initializer_list il, Args&&... args); * What is void_rebound and where it is defined constexpr expected (const void_rebound &v) noexcept(std::is_nothrow_copy_constructible< error_type >::value) Implicit constructor from an identically configured basic_monad<void> by copy. * construction from error type What is wrong with template <class... Args> constexpr explicit expected(unexpect_t, Args&&...); template <class U, class... Args> constexpr explicit expected(unexpect_t, initializer_list, Args&&...); Why do you prefer an implicit conversion. This deviation must be in the rationale of the differences. constexpr expected (const error_type &v) noexcept(std::is_nothrow_copy_constructible< error_type >::value) Implicit constructor from a error_type by copy. constexpr expected (error_type &&v) noexcept(std::is_nothrow_move_constructible< error_type >::value) * raw types It is not clear what is the difference between xxx and raw_xxx typedef value_storage_type::value_type value_type The type potentially held by the monad. typedef implementation_policy::value_type raw_value_type The raw type potentially held by the monad. typedef value_storage_type::error_type error_type The error code potentially held by the monad. typedef implementation_policy::error_type raw_error_type The raw error code potentially held by the monad. typedef value_storage_type::exception_type exception_type The exception ptr potentially held by the monad. typedef implementation_policy::exception_type raw_exception_type The raw exception ptr potentially held by the monad. * What is the "The exception ptr potentially held by the monad"? * what is the sizeof expected <T,E>? * is basic_monad something proposed or an implementation detail? If the first, this should be renamed, if the second this class should not appear in the documentation and the word monad should be banned. * What is expected<Policy> in template<class Policy , typename = typename std::enable_if<std::is_same<typename implementation_policy::value_type, typename Policy::value_type>::value || std::is_void<typename Policy::value_type>::value || std::is_constructible<typename implementation_policy::value_type, typename Policy::value_type>::value>::type, typename = typename std::enable_if<std::is_same<typename implementation_policy::error_type, typename Policy::error_type>::value || std::is_constructible<typename implementation_policy::error_type, typename Policy::error_type>::value>::type, typename = typename std::enable_if<std::is_same<typename implementation_policy::exception_type, typename Policy::exception_type>::value || std::is_constructible<typename implementation_policy::exception_type, typename Policy::exception_type>::value>::type> constexpr expected (expected< Policy > &&o, explicit_conversion_from_different_policy=explicit_conversion_from_different_policy()) Explicit move constructor from a basic_monad with a differing implementation policy. For this constructor to be available, value_type, error_type and exception_type must be identical or constructible. * move constructor/copy constructor The reference documentation doesn't says what this does. * Missing move/copy assignment * bool conversion should be explicit * is_ready has nothing to be with expected. * Shouldn't value_or return by value? otherwise what would be the difference between get_or and value_or? * emplace. Missing overload template <class U, class... Args> void emplace(initializer_list, Args&&...); * swap: What is the meaning of swapping an expected with an option? swap must follow the standard signature. * Missing preconditions on the observers, which make them wide operations. Saying that they return an address makes them wide operations however accessing to the contents of this address will be undefined behavior. I prefer the standard way, defining a narrow function and stating clearly the pre-conditions. * what error_or <https://ned14.github.io/boost.outcome/structboost_1_1outcome_1_1v1__xxx_1_1…> returns if it contains an exception? * what is the difference between get_error_or and error_or? https://github.com/ned14/boost.outcome/issues/19 * Missing overload for get_unexpected. In addition it doesn't return an unexpected_type. constexpr const E & get_unexpected () const; Best, Vicente

12 63

boost.interprocess atomic uint64?
by dnj0496 24 May '17

24 May '17

Hi, I am looking at interprocess/detail/atomic.hpp file and all atomic operations seem to be dealing with uint32. Does boost interprocess not support uint64 types? Can it work similar to std::atomic<type>? Thanks. Dk. -- View this message in context: http://boost.2283326.n4.nabble.com/boost-interprocess-atomic-uint64-tp46945… Sent from the Boost - Dev mailing list archive at Nabble.com.

2 2

[outcome] expected vs. result
by Andrzej Krzemienski 24 May '17

24 May '17

Niall, I am trying to summarize differences between `expected<T, error_code>` and `result<T>`. So far, I have identified the following: 1. API/ABI stability guarantees. 2. `result` has empty state - `expected` does not. 3. `result` uses error_code_extended for more error details in the ring-buffer. 4. No ordering (operator<) for `result` Is the above list complete? Regards, &rzej;

2 1

issue in using vector in version 1.64
by Rishabh Arora 24 May '17

24 May '17

Hello, I just build the latest version of boost (1.64) I tried running the following code: http://ideone.com/n6FSKr It didn't compile and instead gave the following error: https://usercontent.irccloud-cdn.com/file/Pf0b8F8L/Screenshot%20from%202017… Can someone please help in understanding and rectifying it. Thanks in advance, Best Regards, Rishabh

4 3

Request for endorsements for mp11
by Peter Dimov 24 May '17

24 May '17

Would anyone be so kind as to formally endorse mp11 as a candidate for Boost? As a reminder, mp11 is a simple C++11 metaprogramming library, available at https://github.com/pdimov/mp11/ CSS-less documentation can be viewed at https://rawgit.com/pdimov/mp11/master/doc/html/mp11.html

9 15

std::auto_ptr in public interfaces
by Daniela Engert 23 May '17

23 May '17

Hi everybody, you are probably aware of the fact that the upcoming C++17 standard is going to remove std:auto_ptr (and other deprecated features), and that MSVC 14.0 and 14.1 no longer supply these deprecated, to-be-removed features when compiling in a 'later than C++14' mode (i.e. /std::c++latest or /std:c++17). Today I've learned that latest versions of libc++ also no longer supply std::auto_ptr when compiled in C++17 mode. Some time ago I've talked about an in-house version of Boost which no longer requires these deprecated features and builds and passes tests in C++17 mode. As of yesterday I've completed my pull-requests against all those libraries using any of these features (¹), to deal with this situation where required - except for two libraries: locale and ptr_container. These two remaining libraries use std::auto_ptr in their public interfaces and replacing std::auto_ptr with std::unique_ptr is not as easy as a replacement of std::auto_ptr used in the bowels of a library or in test code. It would impose respective changes to user code as well. In our company we just got rid of all traces of std::auto_ptr and happily keep on using locale and ptr_container just as before. So guys, what's your opinion of how to deal with this situation? Ciao Dani ¹ algorithm, asio, assign, bimap, container, gil, graph, icl, interprocess, intrusive, lockfree, msm, phoenix, polygon, random, range, regex, statechart, test, typeof, wave, xpressive -- PGP/GPG: 2CCB 3ECB 0954 5CD3 B0DB 6AA0 BA03 56A1 2C4638C5

10 19

[msm] [statechart] unmerged PRs
by András Kucsma 23 May '17

23 May '17

Hi Everyone, There are a couple of PRs for msm and statechart by me and others, which didn't get any attention for many months now. Can the maintainers please take a look at them? https://github.com/boostorg/msm/pulls https://github.com/boostorg/statechart/pulls Thank you, Andras

2 2

[review] PolyCollection formal review results: ACCEPTED into Boost
by Ion Gaztañaga 23 May '17

23 May '17

Hi, Thank you for your participation in the PolyCollection review. I'll try to collect all votes and summarize the agreed changes on the library. ----- Votes ----- I count 8 (all positive) reviews and votes from Pete Bartlett Andrzej Krzemienski Hans Dembinski Thorsten Ottosen Vinnie Falco Edward Diener Brook Milligan Steven Watanabe -------- Comments -------- Additionally the following boosters did some positive comments on the library and made some questions Dominique Devienne Adam Wulkiewicz Myself No comment was blocking for the acceptance of the library so Boost.PolyCollection is accepted into Boost, congratulations to Joaquín! I recommend committing the library to the boostorg repo as soon as possible in order to start regressions and try to include the new library in Boost 1.65. Many of the proposed changes are one-liners in the documentation and code and hopefully will be ready for Boost 1.65. Deeper changes can wait until Boost 1.66. --------------------------------------- Summary of agreed comments and changes: --------------------------------------- ------------------ Dominique Devienne (positive comment) https://lists.boost.org/Archives/boost/2017/05/234672.php ------------------ "I suspect the new poly_collection could be used for more efficient parallel (and/or concurrent) processing of elements, and would be interested in examples and even a ::parallel_for_each() algorithm that leverages the collection's internal storage" Joaquín will try to play with this idea to see how it fares performancewise. ------------------ Pete Bartlett (positive review) https://lists.boost.org/Archives/boost/2017/05/234669.php ------------------ "It may be worth remarking in the docs what facilities are used for the type registries that are presumably behind the scenes. From the reference section I think RTTI is required. Is this a hard limit or could Boost.TypeIndex be used?" Additional comment from the review manager: Consider making RTTI customizable. Boost.TypeInfo should be easily usable. In any case document the use of RTTI in the documentation. Joaquín will consider the customizable RTTI, will document that RTTI is required by the library. ------------------ Andrzej Krzemienski (positive review) https://lists.boost.org/Archives/boost/2017/05/234716.php ------------------ [1] "Based on my experience OO-inheritance solutions are faster that using `variant`. As you say below, I was suggesting the alternative design: `variant_collection`." Joaquín: "Some have asked for a variant_collection to be part of Boost.PolyCollection roadmap." [2] "I am not comfortable with per-segment functions having the same name as container-wide functions" Joaquín: "On the contrary, I like name overloading better, because it looks terser yet sufficiently expressive" [3] "I observed that the following small program crashes (assertion fails). According to the documentation this should throw an exception upon insertion rather than firing assertions" Joaquín: I think the assertion will be removed. [4] Commenting c.insert(x) / c.insert(it,x) reference: "And maybe it is just me, but I cannot make the sense of it" Joaquín: There is a typo that will be fixed. Will reword the reference sections into a more digestible form. ------------------ Ion Gaztañaga (positive comment) https://lists.boost.org/Archives/boost/2017/05/234729.php https://lists.boost.org/Archives/boost/2017/05/234745.php ------------------ [1] Model-based polymorphism: "Wouldn't be a good idea to make this model-based polymorphism (or a refined one) public? Maybe the current model needs more work to support additional polymorphism models." Joaquín: I'd be really conservative here and withhold such a big move until real use cases are found. The problem is once this is made public the design of the lib becomes effectively frozen. Will study it for the future if there's demand. [2] Optimize memory-indirection caused by unique_ptr: "segment_type could directly hold the class derived from segment_backend as packed_segment/split_segment will need the same size and alignment requirements regardless of the ConcreteType they hold (as long as they use std::vector). This could improve insertion times and other operations. This optimization could also make easier to fix the following section (allocator propagation)." Joaquín: In principle if the optimization is reasonably implemented t'd be welcome. [3] Allocator propagation: The library does not correctly propagate the allocator to support the scoped allocator model. Joaquín will fix this. [4] In many operations the dynamic type of the object to be inserted or manipulated can be known at compile, so the internal virtual call overhead can be optimized. Specially in "insert" and "emplace", but many other operations that work with a single segment can be optimized as well. Joaquín will review operations and will try to "staticfy" as much as possible. [5] Documentation should reflect some operations, like size<T>(), empty<T>() and others are not constant-time cheap operations. Thorsten suggested: The documentation should defin k = # of segments in container and add in those operations "Complexity: linear in k" as the explanation. Joaquín will document it. --------------- Adam Wulkiewicz (comment, but positive) https://lists.boost.org/Archives/boost/2017/05/234662.php --------------- [1] Polycollection doesn't meet the requirements of C++ container as defined in the standard, specially section (23.2.1.3). Joaquín: The part about 23.2.1.3 is not listed among the differences, will include it. --------------- Hans Dembinski (positive review) https://lists.boost.org/Archives/boost/2017/05/234694.php --------------- [1] "boost::function_collection was not so clear to me. It is nice to keep the narrative of game development going, but like someone said before, I think it would help to give a simpler example" Joaquín will improve the explanation [2] "I felt that the benefit of using boost::function_collection was not so clearly presented as for boost::base_collection. The function pointers are all the same size, so how exactly does the optimisation enter" Joaquín will improve the explanation. [3] "I tried to compile the tests on a Mac with Apple-clang 8.0.0. It worked after I manually specified "cxxflags=-std=c++11" Note from the review manager: No fix was discovered, I suggest working on this as many Apple users will have this problem. --------------- Thorsten Ottosen (positive review) https://lists.boost.org/Archives/boost/2017/05/234697.php --------------- [1] "OO programming and copyability of classes is not something that everybody is going to like. (...) Would it be possible for the library to pick up a private or protected copy-constructor when needed, possible via a friend declaration? (...) being able to have your hierarchy non-copyable while allowing copyability within the container is important IMO." Moveability is already required to store classes in the segment. Joaquín will study the possibility of using a copying traits class to let users customize this point. [2] "I miss range versions of the various iteration patterns so I can use them directly with a range-based for. E.g. instead of" Joaquín will implement it. [3] "Inside the segments you store std::vector. I could easily imagine the need to store something else, (...) Therefore I would love to have a second defaulted argument set to std::vector" Element contiguity is a key property and this customization requires a lot of work. Deferred for the future if there is demand for it. [4] "Implementation of equality: do we need to be set like semantics (two-pass)? Why don't you just delegate to the segments after checking the size?" Joaquín proposed a new slightly better implementation. [5] "tutorial: consider using override where appropriate" Joaquín will review code to use it. [6] "why ==,!= but not <,>,>=, <=" Joaquín followed the interface of std::unordered_set, [Review manager's comment: Consider explaining this in the documentation] [7] "Clarify that boost::poly_collection::for_each <warrior,juggernaut,goblin,std::string,window>( //restituted types c.begin(),c.end(),[&](const auto& x) loops over all elements or only the specific" Joaquín will clarify it. [8] "It could be good to have a performance test of erase in the middle/front." Joaquín will test it. [9] "using the identifier "concept" may require change in the near future?"s Joaquín will change it. [10] "I wouldn't mind seeing separate graphs for 0-300 elements." Joaquín will add it. [11] 2clarify test are without use of reserve" Joaquín will clarify it. [12] The test are testing best possible scenario; a more realistic test would be to copy pointers to an std::vector<base*>, shuffle it and run update on that. Joaquín will consider this, maybe additionally for 1-1000 elements. --------------- Vinnie Falco (Positive review) https://lists.boost.org/Archives/boost/2017/05/234704.php --------------- [1] "Iterators returned by begin<T>() produce a long, ugly compile error when compared against iterators returned by begin() or end()." Joaquín will study the issue. He's not sure if this can be improved. --------------- Edward Diener (positive review) https://lists.boost.org/Archives/boost/2017/05/234762.php --------------- [1] "It is also hard to understand what the advantage of a poly collection of these objects entail over a more normal C++ collection ( vector, array etc. ) of std::function<Signature> objects, since the latter object type already represents a generalized callable construct in C++." Joaquín will think about how to make the intro part more accessible. [2] "I have mentioned previously that I think the documentation should be more specific about the types being used for the boost::function_collection" Joaquín will take these points, and try to improve docs so as to make these aspects clearer. --------------- Brook Milligan (positive review) https://lists.boost.org/Archives/boost/2017/05/234872.php --------------- [1] "The only problem was that the following test cases needed -std=c++14 (rather than c++11) because std::make_unique is not defined for c++11 on that compiler: algorithms, basic_function, and segmented_structure. Perhaps a mention of the need for c++14 in some examples?" Joaquín will fix in the corresponding Jamfile.v2 and will mention it in the examples. --------------- Steven Watanabe (positive review) https://lists.boost.org/Archives/boost/2017/05/234877.php --------------- [1] Several documentation fixes Joaquín will apply recommended fixes [2] Change type_erasure::is_subconcept<type_erasure::assignable<>,Concept2>::value as Boost.TypeErasure was recently extended to support move assignment. [3] Fix "type_erasure::is_subconcept<type_erasure::typeid_<>,Concept>::value " with "typeid_<remove_cv_t<remove_reference_t<T>>> " [4] Fix "static void* subaddress(T& x){return boost::addressof(x);}" as it does not support multiple inheritance [5] Fix "return r(std::forward<Args>(args)...);" that does not correctly handle "void" return types. Joaquín will fix all of them [6] "make_index_sequence<N>" can be implemented more efficiently: Joaquín will find a better implementation. Review manager's comment: see https://stackoverflow.com/questions/17424477/implementation-c14-make-intege… [7] poly_collection is defined in namespace detail, internal functions can be found by ADL Joaquín will try to limit what ADL can find.

3 2

[config] Need help with clang config
by John Maddock 22 May '17

22 May '17

I've just added travis support to Boost.Config, the problem is that there are a large number of clang failures that I simply don't know how to fix, see: https://travis-ci.org/boostorg/config The errors occur because clang chokes on libstdc++ code, so while <regex> exists (for example), clang won't parse it. Any ideas anyone? Thanks in advance, John. --- This email has been checked for viruses by AVG. http://www.avg.com

5 8

Re: [boost] Request for endorsements for mp11
by Bjorn Reese 22 May '17

22 May '17

I endorse mp11.

1 0

base64 ?
by Greger 22 May '17

22 May '17

Hi all, First: As an introduction: I am new on this list. Joined a few weeks ago. Second:is there any interest in base64? I have a library for encoding and decoding, which I could contribute. Thank you, tc Greger

6 7

Boost.Outcome and the C++ standard proposals
by Vicente J. Botet Escriba 20 May '17

20 May '17

Hi, for those that will follow the Boost.Outcome review I wanted to share some links related to the standard: The draft of the next revision : * D0323R2 -*A proposal to add a utility class to represent expected monad *(Revision 4) - https://github.com/viboes/std-make/blob/master/doc/proposal/expected/d0323r… The monadic interface draft proposal * DXXXX - *C++ Monadic inteface* - https://github.com/viboes/std-make/blob/master/doc/proposal/monads/Monads.md This is based on Hana customization in its pre-Boost version. And last a very draft paper I don't pretend to send to the standard meetings, at least not yet, about how FileSystem TS could be adapted to take in account the proposes status_value and expected classes. * DXXXX -*Refactoring FileSystem TS using **|expected|**or **|status_value|*||- https://github.com/viboes/std-make/blob/master/doc/proposal/expected/DXXXXR… This paper show that there is not silver bullet solution to reporting errors, but that making abstractions as status_value or expected makes the interface more clear, composable and readable (for me at least) than using out parameters error codes. The paper show also that wanting to have exception interfaces and non-exception interface forces to double the interface. Using expected could reduce it at the price of using .value(). I have an POC implementation in https://github.com/viboes/std-make/tree/master/include/experimental/fundame… Look for expected, functor, applicative, monad, monad_error folders for the implementation and std for the customization. My intention is to show that there is something on-going on the standard aside the expected proposal as requested by the committee. Note these drafts are of course not reviewed yet by the committee and I don't know if they will like the direction. We will see in Toronto next July Best, Vicente P.S. The dead line for next meeting is the 19 Jun. Any feedback is welcome, but as this is not C++ standard ML, I will prefer to have this feedback either privately or vi a the std-proposals ML.

2 1

[outcome] Changelog of all changes made since review announcement one week ago
by Niall Douglas 20 May '17

20 May '17

Dear list, The Outcome review begins later today, but so much feedback has landed this past week already that I had better announce what has changed in develop branch to prevent people reraising already fixed things: ## 20170519 boost_peer_review4: - Issue #13 The opcode counting CI tests in test/constexprs was severely broken on POSIX. Thanks to Tom Westerhout for finding the problem and supplying its fix. - unittests.cpp had become clang-tidy unclean, fixed. - Issue #15 Move `outcome::expected<T, E>` into `outcome::experimental::expected<T, E>`. Thanks to Vicente J. Botet Escriba for persuading me to do this. - Issue #14 Removed all the static asserts in the Expected implementation apart from the nothrow move constructor check, which is now correct unlike the incorrect assert from before. Thanks to Vicente J. Botet Escriba for explaining Expected's semantics. - Issue #21 Correct misspelling of `extended_error_code` with `error_code_extended` in the docs. Thanks to Deniz Bahadir for reporting this. - Issue #17 Give credit to Paul Bristow for the name "Outcome". Thanks to Peter Dimov for finding the correct person. - Issue #18 `result<T>` had a `.set_exception()` which it should not have had. Thanks to Peter Dimov for reporting this. - Issue #19 Remove observers `.is_ready()`, `.get_error_or()`, `.get_exception_or()`. Thanks to Peter Dimov and Andrzej Krzemienski for suggesting this. - Issue #20 Rename: - `monad_error` to `bad_outcome` - `monad_errc` to `bad_outcome_errc` - `monad_category` to `bad_outcome_category` - `BOOST_OUTCOME_THROW_MONAD_ERROR` to `BOOST_OUTCOME_THROW_BAD_OUTCOME` Thanks to Peter Dimov, Andrzej Krzemienski and Paul Bristow for suggesting this. If anyone prefers to see these changes in a tarball, you can get a tarball at https://github.com/ned14/boost.outcome/releases/tag/boost_peer_review4 or the boost_peer_review4 tag in git. Note that this tarball was generated straight off develop branch from my laptop and MAY NOT WORK well. I didn't get a chance to implement these outstanding issues before the review began: - https://github.com/ned14/boost.outcome/issues/11 Expected should never have a valueless state - https://github.com/ned14/boost.outcome/issues/12 Copy assignment gets instantiated even when type T cannot be copied - https://github.com/ned14/boost.outcome/issues/16 Default constructor of T is sometimes compiled when T has no default constructor Thanks in advance for your feedback and reviews. As I hope the above shows, it makes a big difference. Niall -- ned Productions Limited Consulting http://www.nedproductions.biz/ http://ie.linkedin.com/in/nialldouglas/

2 2

[context] Windows x64 fiber local storage GS offset
by Elbert Mai 20 May '17

20 May '17

The Windows x64 implementation of Boost.Context saves fiber local storage from GS:[0x18]. For example, in jump_x86_64_ms_pe_masm.asm: ; load NT_TIB mov r10, gs:[030h] ; save fiber local storage mov rax, [r10+018h] mov [rsp+0b0h], rax However, this is the NT_TIB struct as defined in winnt.h typedef struct _NT_TIB { struct _EXCEPTION_REGISTRATION_RECORD *ExceptionList; PVOID StackBase; PVOID StackLimit; PVOID SubSystemTib; union { PVOID FiberData; DWORD Version; }; PVOID ArbitraryUserPointer; struct _NT_TIB *Self; } NT_TIB; This implies that fiber local storage is found in GS:[0x20], not GS:[0x18]. The Windows x86 implementation uses FS:[0x10], which is consistent with the NT_TIB struct. Am I missing something, or does Boost.Context save/restore fiber local storage at the wrong address in Windows x64?

3 3

[Beast] Discussion
by Vinnie Falco 20 May '17

20 May '17

A desire was stated in the 2015 formal review for Boost.Http, that the author would engage the community during the development of the library. I've been doing that throughout the development of Beast and I will continue to do so. So I am inviting you and anyone else who would like to participate in the design and evolution of this library to weigh in with comments on anything that you would like, ahead of the Beast formal review (scheduled July 1st). Your feedback can help make the library better! On Sat, May 20, 2017 at 8:19 AM, Bjorn Reese via Boost <boost(a)lists.boost.org> wrote: > On 05/20/2017 04:17 PM, Vinnie Falco via Boost wrote: > >> I hope readers are convinced that HTTP requests and responses should >> be modeled as self-contained objects with all necessary fields >> prescribed by rfc7230, and that the HTTP status should be neither >> separate nor stored in an error_code. > > > Not really, but that is the subject for a review of a different library. Here's a nice new thread for the discussion.

1 0

[math] Chebyshev polynomial
by Bjorn Reese 20 May '17

20 May '17

Does Boost.Math contain functions for Chebyshev polynomials? Preferably a recurrent chebyshev_next(). I can find functions for Legendre, Laguerre, and Hermite polynomials, but not Chebyshev.

3 3

[review] **NEXT WEEK** Review of Outcome (starts Fri-19-May)
by charleyb123 . 19 May '17

19 May '17

Hi Everyone, ** HEADS UP, NEXT WEEK ** The formal review of Niall Douglas' Outcome library starts next week (Fri-19-May to Sun-28-May). Your participation is encouraged, as the proposed library is uncoupled and focused, and reviewers don't need to be domain experts to appreciate the potential usefulness of the library and to propose improvements. Everyone needs (and has suffered) error handling, and can compose an opinion on that topic. Outcome is a header-only C++14 library providing expressive and type-safe ultra-lightweight error handling, suitable for low-latency code bases. Key features: *- Makes using std::error_code from C++11's <system_error> more convenient and safe *- Provides high-quality implementation of proposed std::expected<T,E> (on C++20 standards track) *- Good focus on low-latency (with tests and benchmarks) *- Error-handling algorithmic composition with-or-without C++ exceptions enabled *- No dependencies (not even on Boost) This review is timely, as C++17 brings us std::optional<T>. The upcoming std::expected<T,E> (an implementation provided in Outcome) is a generalization of std::optional<T> that provides a <success|fail> value, where the unhappy result is a 'std::error_code' or an instance of "your-chosen-error-type". The library further provides 'outcome<T,error-code,exception-ptr>' for handling <success|error|exception> to safely wrap throwing APIs. Documentation: https://ned14.github.io/boost.outcome/index.html ACCU 2017 talk including design rationale: https://www.youtube.com/watch?v=XVofgKH-uu4 GitHub: https://github.com/ned14/boost.outcome Latest tarball: https://github.com/ned14/boost.outcome/releases/ download/boost_peer_review3/boost.outcome-v1.0-source-201705111650.tar.xz Note: Tarball might be easiest; but if you want to clone from GitHub directly, after the clone you should run the following command to get the source zip exactly: git submodule update --init --recursive NEXT WEEK (when the public review is started): Please post your comments and review to the boost mailing list (preferably), or privately to the Review Manager (to me ;-). Here are some questions you might want to answer in your review: - What is your evaluation of the design? - What is your evaluation of the implementation? - What is your evaluation of the documentation? - What is your evaluation of the potential usefulness of the library? - Did you try to use the library? With what compiler? Did you have any problems? - How much effort did you put into your evaluation? A glance? A quick reading? In-depth study? - Are you knowledgeable about the problem domain? And most importantly: - Do you think the library should be accepted as a Boost library? For more information about Boost Formal Review Process, see: http://www.boost.org/community/reviews.html Thank you very much for your time and efforts. --charley

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[outcome] Fix with support for VS2017 Update 1
by Niall Douglas 19 May '17

19 May '17

Earlier today Vinnie Falco found that the peer review edition of Outcome does not compile on Visual Studio 2017 Update 1. I do apologise for this. Update 1 came out a few days before the peer review edition was set in stone. I didn't know it had until now, and I tested against VS2017 RTM, not Update 1. I have applied a fix to develop branch and cherry picked just this fix to the frozen master branch. You can find that fixed peer review edition at this branch: https://github.com/ned14/boost.outcome/tree/master_vs2017_fixed I hope that this does not inconvenience people too much, and once again, sorry. Niall -- ned Productions Limited Consulting http://www.nedproductions.biz/ http://ie.linkedin.com/in/nialldouglas/

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[offtopic] Who has the power to create Trac accounts nowadays?
by Niall Douglas 19 May '17

19 May '17

Sorry for asking boost-dev, but had no reply on boost-steering. I've got some new GSoC mentors wanting to contribute to https://svn.boost.org/trac/boost/wiki/SoC2017 but they need a Trac login to do so. Who has that power, and can they grant me the power to create Trac accounts as this comes up every year? I'm ned14 on Boost Trac. Niall -- ned Productions Limited Consulting http://www.nedproductions.biz/ http://ie.linkedin.com/in/nialldouglas/

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Any Projects that need significant contribution?
by GuillermoReyes 19 May '17

19 May '17

Hi all, My name is Guillermo - I am currently looking to significantly contribute to the boost library. In fact, I recently applied for gsoc17. I am willing to work on the nearly antipodal points issue (astroid problem), but am open to contributing to others as well. I have accepted an internship offer, so my time may be limited to part time work. I really want to contribute to the library :) Thanks Again, Sincerely, Guillermo Reyes -- View this message in context: http://boost.2283326.n4.nabble.com/Any-Projects-that-need-significant-contr… Sent from the Boost - Dev mailing list archive at Nabble.com.

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[review] Review of PolyCollection is finished, thanks!
by Ion Gaztañaga 18 May '17

18 May '17

Hi, The review period for PolyCollection has come to an end. Thanks to all participants for submitting their reviews, and sharing their insights. All votes have been positive, so congratulations to Joaquín, PolyCollection will be accepted. I will collect all the suggestions, fixes and change proposals during this weekend and post an official result announcement in a few days. I encourage everyone to continue discussing further issues that can improve the library in the mailing list. Best, Ion, review manager

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[dynamic_bitset] Comparison operators without assertions
by Pavel Kretov 18 May '17

18 May '17

Hi all. Looking through boost::dynamic_bitset code, I found a interesting inconsistency between its operator== and operator<. Namely, the first works well with bitsets of different size, while the second triggers an assertion: boost::dynamic_bitset<> a(std::string("111")), b(std::string("1110")); a == b; // false a < b; // Assertion `a.size() == b.size()' failed. This means that we cannot reliably use dynamic bitset within ordered containers like std::set or std::map. Since the standard library has distinct concepts of equality and equivalence (see [1]), it's fine to have different comparison behaviors in dynamic_bitset. However, as far as I can judge, equivalence is a metaphysically broader concept than equality, we shouldn't restrict it to bitsets of the same size only. So, the questions: 1. May I remove that assertion? (It won't be a breaking change, after all). 2. How about doing the same thing to bitwise operators, too? Instead of throwing an assertion if sizes don't match, it may be worth to generalize the operators definitions. I can see several possible schemes, but not all of them are consistent enough. 3. Shouldn't BOOST_ASSERT be used instead of the one from assert.h? ――― Pavel K. [1]: http://en.cppreference.com/w/cpp/concept/EqualityComparable

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[poly_collection] Memory allocation and allocator propagation
by Ion Gaztañaga 17 May '17

17 May '17

Hi Joaquín, Some additional comments about the design: ///////////////////////// // Memory indirections ///////////////////////// If I understand code correctly, the internal structure of a poly collection is approximately: 1) poly_collection stores an unordered_map<type_index, segment_type> 2) segment_type stores a unique_ptr<segment_backend> and segment_backend_is an abstract class, so roughly equivalent to unique_ptr<packed_segment/split_segment> (both packed_segment/split_segment derive from segment_backend. 3) packed_segment/split_segment stores a vector of concrete types. So we need 3 memory hops to navigate between the "this" pointer of a PolyCollection to a pointer to a concrete type: poly_collection -> unordered node -> segment in unique_ptr -> vector value. I think the data structure could be optimized to save one indirection. segment_type could directly hold the class derived from segment_backend as packed_segment/split_segment will need the same size and alignment requirements regardless of the ConcreteType they hold (as long as they use std::vector). This could improve insertion times and other operations. This optimization could also make easier to fix the following section (allocator propagation). *Main question 1*: Do you find think PolyCollection should implement this optimization? ///////////////////////// // Allocator propagation ///////////////////////// As mentioned in Adam Wulkiewicz's review PolyCollection currently does not propagate the allocator from the constructor argument of poly_collection to the concrete type. From a practical point of view, the key requirement is that all intermediate memory until the concrete type must be allocated using the same root allocator passed when a poly_collection was constructed, and that allocator must be propagated also to the concrete type. I think this should also be the case of all memory used for auxiliary data like the index vector of split_sequence. Clause 23.2.1.3 was mentioned although I don't think this clause was designed with compound containers in mind, as IMHO all auxiliary data, including metadata that needs dynamic memory should receive the allocator and should be constructed using allocator_traits or a container that uses allocator_traits (yes, even the non-value parts of a node). Otherwise, the original intention of the new standard allocator model (use a single source of memory and propagate it transparently) wouldn't be feasible. I think that a unique memory source for all internal structures and the correct propagation of the allocator using allocator_traits is a very interesting feature for PolyCollection. Even Bjarne Stroustrup commented on this when Joaquín's article was published in isocpp ( https://isocpp.org/blog/2014/05/fast-polymorphic-collections-joaquin-m-lope…) "One thing caught my eye: The elements could be allocated using stack allocators, rather than a general new. That would make the technique applicable to hard real-time systems where general dynamic memory is banned" *Main question 2*: Do you think PolyCollection should support stateful allocator using the scoped allocator model? Some specific notes that might show places where the scoped allocator model has problems.: - PolyCollection uses operator new to allocate the packed/split_segment implementation stored in unique_ptr and also when the segment must be copied. If unique_ptr is avoided and the concrete segment is in-place constructed inside "segment" then all memory will be allocated from the original allocator. - I think "segment" is missing an extended copy and move constructor taking an additional allocator. It also would need an internal allocator_type typedef so that uses_allocator_v is true and unordered_map calls these new constructors when needed. These new constructors should be propagated to split_segment/packed_segment so that these call the extended constructors of internal vectors. - The concrete type wrappers (e.g. value_holder) also would need to support allocators with extended copy/move constructors. - The "emplace" operation uses a placement new to wrapped in a lambda which is type-erased with a captureless lambda. It looks to me that instead of delegating the work into the value_holder, the type erasure arguments should be treated by the segment so that internal vectors propagate the allocator when needed. A test to make sure everything is correctly propagated: -> Create an instance of monotonic_buffer_resource passing a big enough static buffer. -> Create a base_collection< Base, std::polymorphic_allocator<Base> > passing the address of the monotonic_buffer_resource -> Insert types Derived1 and Derived2 in the container, both of which hold a vector<int, polymorphic_allocator<int> > (for Derived1 and Derived2 are uses_allocator_v is true and they propagate the memory resource to the vector). -> After filling base_collection, no heap allocation is made and all objects are constructed in the static buffer. Best, Ion

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Re: [boost] Hello Again From Facebook Engineering
by Yurii Zubrytskyi 16 May '17

16 May '17

Hi Scott, I appreciate the email. Things are going great here, and I'm really happy with Google. Anyway, even if I wanted to change jobs I wouldn't consider Facebook until it opens an office on the Eastside - commuting into Seattle is just too uncomfortable, so I'm not considering any company there Thanks! ________________________________ From: Scott Shay <scottshay(a)fb.com> Sent: Tuesday, April 18, 2017 10:03:15 AM To: Yuriy Zubritsky; boost(a)lists.boost.org Subject: Hello Again From Facebook Engineering Hi Yuriy, Sending a note to say hello again from Facebook! My great teammate, Camila, mentioned that I should reach out and see how things at Google have been going for you? Have you had some time to consider what's next in your career? I understand if this is not the right timing, kindly let me know how we can best keep in touch for when it makes more sense. Thanks a lot and I look forward to hearing back from you. P.S. in case you're curious, here's a resource that highlights some of the technical problems we tackle. https://code.facebook.com/ Scott Shay Engineering Sourcer | Recruiting M: (650) 785-6142 [id:image001.png@01D298C9.4BBDBCE0] facebook.com/careers<https://www.facebook.com/careers>

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crc // wrong poly for crc_xmodem_type
by Sergei Nikulov 16 May '17

16 May '17

Hello All, I've discovered that current typedef crc_xmodem_type uses wrong poly. Current release and master branch: > typedef crc_optimal<16, 0x8408, 0, 0, true, true> crc_xmodem_type; Should be (ref: http://reveng.sourceforge.net/crc-catalogue/16.htm#crc.cat-bits.16) > typedef crc_optimal<16, 0x1021, 0, 0, false, false> Develop branch already have some changes which address this error (for ex. https://github.com/boostorg/crc/commit/328bf50f666c463901e2179aa2d890916c3b…) but master and boost release does not. Who currently owns boost::crc and can fix this issue? Thank you. -- Best Regards, Sergei Nikulov

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[Convert] convert<float> doesn't respect input size
by Olaf van der Spek 15 May '17

15 May '17

Hi, const char* a = "42"; boost::string_ref b(a, 1); float c = boost::convert<float>(b, boost::cnv::strtol(), -1); // returns 42 assert(c == 4); https://github.com/boostorg/convert/issues/29 -- Olaf

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Re: [boost] [http] Boost.Http review report
by Vinnie Falco 15 May '17

15 May '17

On Aug 27, 2015 at 12:21 PM, Bjorn Reese <breese_at_[hidden]> wrote: > The outcome of the formal review of Boost.Http is that the library is > NOT accepted for inclusion into Boost this time. > ... > Judging from the reviews, the following additions will > make a future submission more likely to succeed: > > 1. Involve the community more during the development. This will > both solicit earlier feedback on the design, and help to align > community expectation. I've been trying to involve the community for several months now, offering opportunities to weigh in on design decisions, provide feedback on pull requests, perform code reviews on pending merges. The response has been, to put it nicely, minimal. In particular I have not heard from anyone involved in the other proposed libraries such as Boost.Http or cpp-netlib except some initial contacts in early 2016.

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Re: [boost] [review] **NEXT WEEK** Review of Outcome (starts Fri-19-May)
by Bjorn Reese 14 May '17

14 May '17

On 05/11/2017 06:19 PM, charleyb123 . via Boost wrote: > GitHub: > https://github.com/ned14/boost.outcome The code has a "boost-lite" submodule. Is that part of the review?

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Win10 now allows symlink creation without elevated privileges
by Niall Douglas 14 May '17

14 May '17

In case the list didn't know, from the Creator's Update onwards Windows 10 allows normal users to create symlinks if the machine is put into Developer mode: https://blogs.windows.com/buildingapps/2016/12/02/symlinks-windows-10/ I don't know about others, but this will be a major time saver for me at least, I had been using hard links on Windows which are prone to accidental data loss. Niall

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[poly_collection] User-defined polymorphism model
by Ion Gaztañaga 14 May '17

14 May '17

Hi Joaquín and all reviewers, Before we reach the end of the review period, I wanted to comment an (IMHO) interesting feature used in the internal design of PolyCollection. The library offers three of polymorphism models: base-derived, boost::any and signature-sharing callable types. Under the hood, the library abstracts those polymorphic models into a generic class in the detail namespace: template<typename Model,typename Allocator> class poly_collection; and each concrete container is just implemented in terms of poly_collection: template<typename Base,typename Allocator> class base_collection : public detail::poly_collection<detail::base_model<Base>,Allocator> The first template parameter (Model) is the abstraction ("concept") that implements the non-generic part of each polymorphism model. A model implements the following types and operations (comments on each attribute are my interpretation, they can be completely wrong): template<class ModelArg> class Model { // //Value-related attributes // //The type we want to expose as value_type of the container using value_type= ...; //Is T a subtype of the general type (acceptable as value)? template<class T> using is_subtype= ... //Is T the "most refined type"? template<class T> using is_terminal=... //Id of a value template<class T> static const std::type_info& subtypeid(const T& x); //Obtain a type-erased pointer to the value template<class T> static void* subaddress(T& x); template<typename T> static const void* subaddress(const T& x); // //Segment-related // //Segment iterators that point to type_erased value_types using base_iterator=... using const_base_iterator=... //const<->non-const conversions static base_iterator nonconst_iterator(const_base_iterator it); template<typename T> static iterator<T> nonconst_iterator(const_iterator<T> it); //Concrete iterators for Derived template<typename Derived> using iterator=...; template<typename Derived> using const_iterator=... //Generic type, comparable with base_iterator. //base_iterator == the last returned base_sentinel //means that base_iterator points one-past the last //element of a segment. using base_sentinel=...; using const_base_sentinel=... //Construct a segment for type T using the given allocator and //return it type-erased. template<typename T,typename Allocator> static detail::segment_backend<Model>* make(const Allocator& al); }; I have several questions on this polymorphism model. 1) Wouldn't be a good idea to make this model-based polymorphism (or a refined one) public? Maybe the current model needs more work to support additional polymorphism models. Of course requirements for each operation in a model should be detailed. A correct abstraction to define user-provided polymorphism models is hard but this seems really a great feature that makes this library more valuable for users. 2) If understand this model abstraction correctly, each Model chooses the segment type to store values (it could be any sequence type, I guess). The segment_backend abstraction does not only abstract ConcreteTypes from value_types (using void pointers that will be casted to real types in the implementation of the virtual function), but also the segment type (the sequence holding the concrete values). Current implementation uses two segment types: split_segment (stores Concrete types and generic value_type's in two separate vectors) and packed_segment (stores ConcreteTypes which already contain value_type's as a subobject). function_collection and any_collection use the first segment, base_collection uses the second. Why are different segment types needed? Can't we store value_types and ConcreteTypes in a struct and use only one type of segment? If this is possible, I guess iteration performance would be improved for function_collection and any_collection. Model definition could be simplified. On the other hand, if the sequence type can be left out of the model definition, the underlying sequence type (change vector with deque, small vector or any other) could be made configurable. Would this be useful for users? 3) I understand that caching a base_sentinel in each segment is an optimization to avoid a virtual function call when iterating with base_iterators. Is this assumption correct? Why is a different base_sentinel type needed to mark the end of each segment? Wouldn't a "base_iterator" pointing to that on-past-the end position suffice? Is an optimization (maybe base_sentinel is cheaper) or a must have? Thanks, Ion PD: I have more design questions related to other topics but I will post a different thread for each one.

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Re: [boost] [review] Review of PolyCollection starts today (May 3rd)
by Glen Fernandes 13 May '17

13 May '17

Gavin Lambert wrote: > On that note, do you know of a more-comprehensible-than-standardese guide > on how allocator_traits is supposed to be used for node-based custom > container types? I've tried to figure it out a couple times but I'm sure I'm > missing important points. What do you want to know? 1. The storage for the node should be allocated with the Allocator's 'allocate()', for an allocator instance 'a' whose value_type is the containers node type (i.e. 'a' can be achieved by rebinding an existing allocator instance in the normal way). 2. The node object itself would be constructed in the normal way - e.g. placement new to construct the node object. 3. The containers' value_type object within the node must be constructed by allocator_traits::construct(u, p, args...) where u of type U is a rebound copy of the allocator such that the allocator's value_type is the container's value_type. 4. Similar to 3, for destruction of the container's value_type object should be destroyed by allocator_traits::destroy(u, p) 5. Similar to 2, the node object is destroyed in the normal way - e.g. invoking the destructor of the node type. 6. Similar to 1, the storage for the node is deallocated with the Allocator's deallocate() (for an allocator instance whose value_type is the container's node type). Glen

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[poly_collection] Andrzej's review
by Andrzej Krzemienski 12 May '17

12 May '17

Hi Everyone, Some comments from me about PolyCollection library, First, Joaquín, thank you for writing and sharing this library. I am not an an expert in the domain. In my programs I never needed this optimization. But I have seen it described in a number of publications, and I am convinced it deserves a place in Boost libraries, so that people are not forced to reinvent it. [1] Now, because I have no practical experience with the problem, what I say in this paragraph might be incorrect. But I have a problem here. You will use this library for improved performance, maybe for a game implementation, yet because a game needs super-performance, can a programmer afford to use dynamic dispatch, or RTTI or exceptions? I always imagined taht such library, rather than resembling `ptr_vector` would resemble `vector<variant<A, B, C>>`, that is: I decide and fix the container on a set of types I will be storing inside. This set of tyes is embedded in the type, so I can detect many mis-usages at compile time. The implementation can be faster, because the number of segments is fixed (no segment management), and no registration checks need to be performed. Then, iterate over such collection with a static_visitor (from Boost.Variant). Of course, this would be constraining: I need to know all the types I will be using ahead of time. But maybe in practice this is often the case? If you disagree, maybe it is wort discussing it in the rationale. [2] I am not comfortable with per-segment functions having the same name as container-wide functions, and being only overloaded based on function or template parameters, like `cc.size()` and `cc.size(index)`. These two functions do different things, so they deserve different names. Maybe `cc.segment_size(index)`, or `cc.serment(index).size()`? [3] I downloaded it and tried toy examples with GCC 6.3 on Windows with -std=c++11, and clang 3.8.1 on Fedora with -std=c++11. It compiIes fine. I observed that the following small program crashes (assertion fails): ``` #include <boost/poly_collection/base_collection.hpp> struct Iface { Iface() = default; virtual ~Iface() = 0; }; inline Iface::~Iface() {} struct Type1 : Iface { Type1() = default; Type1(Type1&&) = delete; }; struct Type2 : Iface { Type2() = default; Type2(Type2&&) {} // throwing move // no move assignment }; int main () try { boost::base_collection<Iface> c; c.insert(Type1{}); // fires an assert c.insert(Type2{}); // fires an assert } catch (std::exception const& e) { } ``` Admittedly, `Type1` and `Type2` are not "acceptable", but according to the documentation this should throw an exception upon insertion rather than firing assertions. [4] The documentation is good. As to implementation, I did not look at it in detail. Regards, &rzej;

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[poly_collection] Small review
by Pete Bartlett 11 May '17

11 May '17

> > Dear Ion, Joaquin and boost mailing list, > > I hope this brief review is of some value to you. I don’t expect to be a recognised name on the mailing list but have contributed to it intermittently over the years. I have also used the author’s MultiIndex library in production for about a decade. > > I would recommend that PolyCollection be accepted into Boost. > > I think the design pattern is common enough to be Boost-ified. I have done something very similar to boost::base_collection myself in the past and have achieved useful speed ups over a solution like boost::ptr_vector in a production system. My speed-ups were not quite as good as Joaquin documents, but I can’t tell if this was due to the ineptitude of my own solution or due to lab conditions of the Boost.PolyCollection tests. > > I spent a couple of hours reading the docs and running basic examples on my default compiler (VS2015 x64) and did not experience any significant problems. > > It may be worth remarking in the docs (sorry if I missed it) what facilities are used for the type registries that are presumably behind the scenes. From the reference section I think RTTI is required. Is this a hard limit or could Boost.TypeIndex be used? > > NB the reference section has a note “REVIEW THIS DESIGN DECISION” in it. > > Personally I would attach value to the fact that the author has been a great servant to Boost over the years (as have many others) so it is likely that this would be a well-maintained library. E.g. if algorithms were added to <algorithm> in the future, they would likely end up in <boost/poly_collection/algorithm.hpp> too. > > Regards, > Pete >

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[review][poly_collection] Review period EXTENDED until May 17th
by Ion Gaztañaga 11 May '17

11 May '17

Dear boosters, Some have requested a bit of time to extend the review period in order to have time to submit reviews or issue technical comments. With the approval of Review Wizards, the review of PolyCollection is extended until May 17th. Please feel free to submit review and comments. Best, Ion

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[poly_collection] Two remarks
by Dominique Devienne 10 May '17

10 May '17

Just as Pete Bartlett mentioned, I'm also a fan of Joaquín's Multi-Index, which I'm used in production for many years as well. My only complaint about his proposed Poly-Collection is the fact I can't leverage and thus benefit from the performance of it, in a multi-index scenario, but as Joaquín already answered a few months ago, that's off-topic and by design, I know :) Many of my BMIs have a by-type index, and the type-partitioned storage of those in contiguous memory for by-type scans would be (greatly?) beneficial. I'd be willing to give up some iterator guarantees BMI provides, as a node-based container, for intelligent contiguous storage of elements, without myself having to maintain by-value homogeneous containers with a manually maintained BMI of polymorphic pointers to those containers' elements. My second remark is about parallelism. I suspect the new poly_collection could be used for more efficient parallel (and/or concurrent) processing of elements, and would be interested in examples and even a ::parallel_for_each() algorithm that leverages the collection's internal storage. And perhaps even on the write side, rather than having to make the whole container thread-safe, but external mutexing for example, provide ways for a more granular thread-safety by type or segment perhaps. Again, probably off topic, but hardly something you can "add from the outside" I think, and why I mention it here and now. As merely a user of Boost, I don't feel qualified as a reviewer, beyond the two above remarks. Thanks, --DD

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[build] please review the long standing pull request
by Konstantin Ivlev 10 May '17

10 May '17

Hello, There's a 2 month old pull request https://github.com/boostorg/build/pull/169. Please review and let me know any feedback.

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[Thread] What is the meaning of BOOST_THREAD_USE_LIB?
by Frédéric Bron 09 May '17

09 May '17

Hi, I always use boost as static libraries. For a long time, I have been used to define macro BOOST_THREAD_USE_LIB on windows when cross-compiling from linux to windows with mingw. I have now made a new cross-compiler conformant with pthread (the previous one had only win32 api) but then boost does not build (with threadapi=posix). It seems that not defining BOOST_THREAD_USE_LIB helps. I do not remember why I used to define BOOST_THREAD_USE_LIB a long time ago and cannot find any help in the doc (http://www.boost.org/doc/libs/1_64_0/doc/html/thread/build.html) What is the meaning of BOOST_THREAD_USE_LIB? Frédéric

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gsoc17 and boost.ublas
by Rishabh Arora 09 May '17

09 May '17

Hi Everyone, My name is Rishabh Arora and I have been selected to work with the BoostC++ libraries on the the project, "dataframes in ublas" as a part of GSoC '17. It will be great if someone could provide me with suggestions on how to get started with it. Thank you in advance Best Regards, Rishabh Arora

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[GSOC'17] Project: Optimising Multiplications in uBLAS
by mohammad sharique 09 May '17

09 May '17

Hello Boost Community, My name is Mohd Sharique. I have been selected to work with Boost C++ Libraries under Google Summer of Code '17. My project is "Optimising Multiplications in uBLAS". It would be great if I could get some starting point for the same. Thank you, Your's sincerely, Mohd Sharique

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[integer] Please fix build/test errors..
by Rene Rivera 09 May '17

09 May '17

The Integer library is causing general CI failures: < https://travis-ci.org/boostorg/boost/jobs/230199520#L6396> Please rectify ASAP. -- -- Rene Rivera -- Grafik - Don't Assume Anything -- Robot Dreams - http://robot-dreams.net -- rrivera/acm.org (msn) - grafikrobot/aim,yahoo,skype,efnet,gmail

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[poly_collection] throws upon insertion
by Andrzej Krzemienski 09 May '17

09 May '17

Hi, I am looking at the documentation of poly_collection. I will not be able to thoroughly review and test the library. But judging from the documentation, the problem is worth solving, and the approach to solve it is sound. I have one question/observation though. I am trying to figure out how preventing an incorrect insert() works. In the docs ( http://rawgit.com/joaquintides/poly_collection/website/doc/html/poly_collec…) it says that it will sometimes throw if it cannot determine the most derived type. In the class reference, I get: ( http://rawgit.com/joaquintides/poly_collection/website/doc/html/poly_collec… ) ``` (1) c.insert(x) (2) c.insert(it,x) Effects: If the type of the subobject of t is not registered, then if this type is T and T is acceptable, does the registration, otherwise throws. If t is not a non-const rvalue expression and the type of its subobject is not CopyConstructible, throws. Inserts an element with a subobject move constructed or copy constructed from the subobject of t: (1) at the end of the corresponding segment; (2) just before the position indicated by it, if it points to the corresponding segment, or at the end of the segment otherwise. Returns: An iterator to the newly inserted element. Complexity: Amortized constant time plus linear in the distance from the insertion position to the end of the segment. ``` And maybe it is just me, but I cannot make the sense of it. First, it refers to 't' but in the signatures we have an 'x'. Next, the first sentence has two "if"s and one "otherwise" and I do not know which "if" the "otherwise" binds to. I read it as saying: if T is derived from the interface (like class `warrior`) but is not movable (which implies that T is not "acceptable"), then the program will compile fine but will later throw an exception. Is my interpretation correct? But if so, why not refuse to compile instead? Maybe it would be better tom make the prose longer in "Effects" clause, but to make it harder for misinterpretation. Regards, &rzej;

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[Boost.Test] access to boost::unit_test::framework::master_test_suite().{argc, argv} outside from BOOST_TEST
by Olaf Peter 08 May '17

08 May '17

Hello, my test program uses boost.test datasets. I've wrote a filesystem loader for the input and expected data. Now I run into the problem, that boost::unit_test::framework::master_test_suite().{argc, argv} is only setup inside the tests self. My loader isn't a test case ... I can check it by using a simple mock, like struct app_mock { app_mock(); int const argc; char** const argv; }; app_mock::app_mock() : argc(boost::unit_test::framework::master_test_suite().argc) , argv(boost::unit_test::framework::master_test_suite().argv) { } BOOST_AUTO_TEST_CASE( app_mocker ) { app_mock app; std::cout << "Count = " << app.argc << '\n'; for(int i = 0; i != app.argc; i++) std::cout << "Arg = " << app.argv[i] << '\n'; } $ my_test -- my_args Count = 2 path/to/exe my_args these works, but as mentioned: dataset_loader::dataset_loader(fs::path const& path) { app_mock app; std::cout << "ARGC = " << boost::unit_test::framework::master_test_suite().argc << '\n'; read_files(path); } is always zero. How can I read the argc/argv values? Thanks, Olaf

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[gsoc17] welcome Ruoyun
by Vissarion Fisikopoulos 05 May '17

05 May '17

Hi Ruoyun, congrats and welcome! As mentioned by GSoC this is the community bonding period. So you can start reading the documentation: http://www.boost.org/doc/libs/1_64_0/libs/geometry/doc/html/index.html This wiki is also useful: https://github.com/boostorg/geometry/wiki check for example https://github.com/boostorg/geometry/wiki/Contribution-Tutorial We can also start now discussing and refining you project goals. Best, Vissarion. ---------- Forwarded message ---------- From: Google Summer of Code <summerofcode-noreply(a)google.com> Date: 4 May 2017 at 19:35 Subject: GSoC 2017: You are a mentor for Ruoyun Jing To: fisikop(a)gmail.com [image: Google Summer of Code] Congratulations, you will be spending the next few months working with Ruoyun Jing on GSoC2017 Boost.Geometry:Filtering of compare distance predicates Proposal <https://summerofcode.withgoogle.com/dashboard/organization/4839090517180416…> . Please welcome <http://write.flossmanuals.net/gsoc-mentoring/community-basics/> your student into your community and work with them to plan the milestones they will need to meet. Setting clear expectations early is one of the best ways to help your student succeed. You can read the Mentor Manual <http://write.flossmanuals.net/gsoc-mentoring/about-this-manual/> for some great tips on how to communicate with your student and make a project plan. If you have any questions please contact our Google Open Source Programs team at gsoc-support(a)google.com or email the mentors mailing list if appropriate. -Google Open Source Programs team This email was sent to fisikop(a)gmail.com. You are receiving this email because of your participation in Google Summer of Code 2017. https://summerofcode.withgoogle.com To leave the program and stop receiving all emails, you can go to your profile <https://summerofcode.withgoogle.com/dashboard/profile/> and request deletion of your program profile. For any questions, please contact gsoc-support(a)google.com. Replies to this message go to an unmonitored mailbox. © 2017 Google Inc., 1600 Amphitheatre Parkway, Mountain View, CA 94043, USA

1 0

[1.64] [ublas] Broken/regession due to Boost.Serialization changes
by Peppard 05 May '17

05 May '17

Hi, since the 1.64 release including e.g. boost/numeric/ublas/matrix.hpp gives an error like "no member named 'make_array' in namespace 'boost::serialization'", according to the official(?) test overview (http://www.boost.org/development/tests/master/developer/numeric-ublas.html) on a lot of systems. There have been discussions on this mailing list in Nov/Dec 2016 probably at least related to this ([boost] [serialization][ublas][test] failures in serialization causing regressions) and in Feb 2017 ([boost] [serialization][uBlas] Serialization still breaking anything that uses uBlas?), also there are several pull requests on GitHub, e.g. https://github.com/boostorg/ublas/pull/46. (I assume you are aware of this already, but I wonder why there was a release with a regression like this, maybe due to a maintainer missing? How are cases like these handled?) Thanks! (Sorry if this is a double post but the list address seemed to change from @wowbagger.crest.iu.edu to @lists.boost.org so I tried again.)

3 2

[beast] 1.0.0-b35 has been merged to master
by Vinnie Falco 05 May '17

05 May '17

Beast 1.0.0-b35 has been merged to the master branch. Changes include: API Changes * New HTTP interfaces This version has a freshly written HTTP parser which improves on the performance of the previous parser. New interfaces are provided to allow incremental reading of HTTP messages and better handling for Expect: 100-continue. These are API breaking changes. Beast is a C++11 header-only HTTP and WebSocket library built on Boost.Asio, scheduled for Boost formal review starting July 1st. Official repository: https://github.com/vinniefalco/Beast Documentation: http://vinniefalco.github.io/beast/index.html Stakeholders and interested parties may review version the pull request for 1.0.0-b36 if desired, all feedback welcomed: https://github.com/vinniefalco/Beast/pull/330 Thanks!

1 0

Boost macros for Android
by Vicente J. Botet Escriba 04 May '17

04 May '17

Hi, I would like to inhibit some failing test on Android. Are there any specific BOOST macros for Android? Best, Vicente

3 3

Test - ignore
by Michael Caisse 03 May '17

03 May '17

-- Michael Caisse Ciere Consulting ciere.com

1 0

GMane reflection of Boost mailing list messages
by Edward Diener 03 May '17

03 May '17

I am a user of GMane in regard to Boost mailing lists and it appears that GMane is no longer picking up Boost mailing list changes or allowing users to respond to mailing list posts through the corresponding GMane ng. Does anyone know how to rectify this situation ? I recall that Boost might have changed who was hosting the mailing lists and I am wondering if this is the reason that GMane no longer works with Boost mailing lists. The GMane website appears to be in transition, and all links for contacting anyone at GMane have been removed. I did try to contact Lars Magne Ingebrigtsen, who has been running GMane, but I do not know if this will produce any results.

4 9

Fwd: [clang] clang-cl expansion of macros
by degski 01 May '17

01 May '17

On 16 April 2016 at 17:58, Edward Diener <eldiener(a)tropicsoft.com> wrote: > What I strongly suspect will finally happen is that clang will not fix > these emulation problems because they are too tricky and numerous to do. > Instead they will probably declare that their emulation is good enough for > the majority of preprocessor constructs and that Boost PP, which pushes the > preprocessor to its limits, is not meant to work with their flawed VC++ > emulation. I hope I am wrong about that supposition, but having spent much > time in Boost PP and Boost VMD trying to workaround VC++ non-standard > preprocessor behavior I can envision that having to code "down" to that > behavior in numerous complicated instances will be too much time consuming > work for the clang developers who have chosen to work with VC++ > preprocessor emulation. > I've successfully built boost-1.64 with VC1410 (from the developer command prompt). Trying to use boost with a project using Clang 4.0.0 (both the LLVM and C2 backends) gives me the following PP error messages: 1>------ Rebuild All started: Project: test, Configuration: Debug x64 ------ 1> In file included from test.cpp:16: 1> In file included from z:\vc\x64\include\boost/filesystem.hpp:16: 1> In file included from z:\vc\x64\include\boost/filesystem/path.hpp:28: 1> In file included from z:\vc\x64\include\boost/iterat or/iterator_facade.hpp:12: 1> In file included from z:\vc\x64\include\boost/iterat or/interoperable.hpp:11: 1> In file included from z:\vc\x64\include\boost/mpl/or.hpp:43: 1> In file included from z:\vc\x64\include\boost/mpl/au x_/include_preprocessed.hpp:37: 1>z:\vc\x64\include\boost/mpl/aux_/preprocessed/plain/or.hpp(59,7): error : too many arguments provided to function-like macro invocation 1> 2 1> ^ 1> z:\vc\x64\include\boost/preprocessor/facilities/expand.hpp(26,10): note: macro 'BOOST_PP_EXPAND_I' defined here 1> # define BOOST_PP_EXPAND_I(x) x 1> ^ 1> In file included from test.cpp:16: 1> In file included from z:\vc\x64\include\boost/filesystem.hpp:16: 1> In file included from z:\vc\x64\include\boost/filesystem/path.hpp:28: 1> In file included from z:\vc\x64\include\boost/iterat or/iterator_facade.hpp:12: 1> In file included from z:\vc\x64\include\boost/iterat or/interoperable.hpp:11: 1> In file included from z:\vc\x64\include\boost/mpl/or.hpp:43: 1> In file included from z:\vc\x64\include\boost/mpl/au x_/include_preprocessed.hpp:37: 1>z:\vc\x64\include\boost/mpl/aux_/preprocessed/plain/or.hpp(58,1): error : expected a qualified name after 'typename' 1> BOOST_MPL_AUX_NA_SPEC2( 1> ^ 1> z:\vc\x64\include\boost/mpl/aux_/na_spec.hpp(166,44): note: expanded from macro 'BOOST_MPL_AUX_NA_SPEC2' 1> #define BOOST_MPL_AUX_NA_SPEC2(i, j, name) \ 1> ^ 1> z:\vc\x64\include\boost/mpl/aux_/na_spec.hpp(64,11): note: expanded from macro '\ 1> 1> BOOST_MPL_AUX_NA_SPEC_MAIN' 1> BOOST_MPL_PP_PARAMS(i, typename T) \ 1> ^ 1> z:\vc\x64\include\boost/mpl/aux_/preprocessor/params.hpp(58,11): note: expanded from macro 'BOOST_MPL_PP_PARAMS' 1> , BOOST_MPL_PP_AUX_PARAM_FUNC \ 1> ^ 1> In file included from test.cpp:16: 1> In file included from z:\vc\x64\include\boost/filesystem.hpp:16: 1> In file included from z:\vc\x64\include\boost/filesystem/path.hpp:28: 1> In file included from z:\vc\x64\include\boost/iterat or/iterator_facade.hpp:12: 1> In file included from z:\vc\x64\include\boost/iterat or/interoperable.hpp:11: 1> In file included from z:\vc\x64\include\boost/mpl/or.hpp:43: 1> In file included from z:\vc\x64\include\boost/mpl/au x_/include_preprocessed.hpp:37: 1>z:\vc\x64\include\boost/mpl/aux_/preprocessed/plain/or.hpp(58,1): error : expected ',' or '>' in template-parameter-list Up till now I was using a hacked boost-1.62. So in order to see what would happen, I also built boost-1.63. Apart from a small change in type_with_alignment.hpp (adding a ckeck for _MSC_VER not to exist if __clang__ does exist in line 87), boost-1.63 compiles without a problem (no specific (relevant to the emulation) command line parameters). Is there a macro I should define or is there something else I should set/do in order to use boost-1.64 with Clang 4.0.0 on windows? Any other suggestions? degski -- "*Ihre sogenannte Religion wirkt bloß wie ein Opiat reizend, betäubend, Schmerzen aus Schwäche stillend.*" - Novalis 1798

3 13

[review] Review of PolyCollection will start in a few days
by Ion Gaztañaga 30 Apr '17

30 Apr '17

Dear Boost community, The formal review of Joaquín M López Muñoz's PolyCollection library will start on Wednesday, May 3rd and ends on May 12th. This library implements fast containers of polymorphic objects. Typically, polymorphic objects cannot be stored directly in regular containers and need be accessed through an indirection pointer, which introduces performance problems related to CPU caching and branch prediction. Boost.PolyCollection implements a novel data structure that is able to contiguously store polymorphic objects without such indirection, thus providing a value-semantics user interface and better performance. Three polymorphic collections are provided: * boost::base_collection * boost::function_collection * boost::any_collection dealing respectively with classic base/derived or OOP polymorphism, function wrapping in the spirit of std::function and so-called duck typing as implemented by Boost.TypeErasure. If you are interested, you can start preparing your review with the following information: Repositories: Incubator: http://blincubator.com/bi_library/polycollection/?gform_post_id=1643 Github: https://github.com/joaquintides/poly_collection and the documentation here: http://rawgit.com/joaquintides/poly_collection/website/doc/html/index.html See you on Wednesday! Ion

1 0

[integer][math]Heads up on revised gcd/lcm code
by John Maddock 30 Apr '17

30 Apr '17

First some history.... Some time ago, the old gcd/lcm code was moved from Boost.Math to Boost.Integer as a means of reducing inter-library dependencies. Unfortunately a number of tasks were never completed: the docs weren't added to Boost.Integer, and the Boost.Math code never got updated to redirect to the moved headers. Fast forward a couple of years and when Jeremy Murphy contributed a new version of the gcd/lcm code as part of supporting polynomial gcd, and since I'd completely forgotten about the move, this got integrated into Boost.Math leaving us with two divergent versions. As part of sorting this mess out, I've now pushed to Boost.Integer a "best of both" version of this code, so far as I can tell, all dependent libraries are unaffected by the change, though I do need to do some more work on supporting obsolete compilers I no longer have access to. The main enhancements are: * New mixed binary/Euclid algorithm added, this seems to be the best performing algorithm in most cases, and is now the default for most integer types (performance is deeply dependent on the input though, so your mileage may vary). * In addition to integer and rational support, polynomial gcd is now supported via boost::math::polynomial. * There are new range based gcd-lcm algorithms for calculating the gcd/lcm of all the values in an iterator range, this is primarily for polynomial gcd support. * There are new variadic overloads of gcd/lcm for calculating gcd/lcm over more than 2 values. * The gcd/lcm functions are now constexpr in C++14 land, this means that the old compile time calculation traits classes are rendered obsolete for current compilers. * The gcd/lcm functions are now noexcept where appropriate. * Compiler intrinsics are now used speed up binary-gcd steps where possible, sadly this is incompatible with constexpr support since the intrinsics aren't yet constexpr :( Please do let me know if you find any snags, best, John. --- This email has been checked for viruses by AVG. http://www.avg.com

3 17

Boost MultiIndex slow mass insertion
by miticodonati＠libero.it 29 Apr '17

29 Apr '17

I have the following structure: typedef boost::multi_index_container< MyClass, boost::multi_index::indexed_by< boost::multi_index::hashed_unique<boost::multi_index::member<MyClass, int, &MyClass::label>>, boost::multi_index::ordered_non_unique<boost::multi_index::member<MyClass, double, &MyClass::dist>> > > MyClassSet; If i populate it in a loop: MyClassSet all: for (int y = 0; y < input.rows; ++y) { MyClass c; // .... all.insert(c); } the insertion time is quite slow. It probably need to continuously re-order the underlying implementation. Anyway i would expect that populating it with a single call it would be faster (e.g. sorting the whole set only at the end). Example: std::vector<MyClass> vec; // ... MyClassSet all(vec.begin(), vec.end()); BUT... the times are almost equal. My question is: is this intended behaviour? Is there a faster way to mass populate the container (e.g. not enforcing the invariants/orderings at each 'insert')?

3 2

[clang] clang-cl expansion of macros
by Edward Diener 29 Apr '17

29 Apr '17

You can get clang-cl ( clang-win ) to show its VC++ emulated expansion of macros somewhat by passing the c++ option '-fmacro-backtrace-limit=0' to the compiler. It is still blessedly difficult to see the what and the why of clang's error messages when expanding macro using clang-cl, but at least it gives you a better chance of understanding where clang's emulation of VC++ has gone wrong. I have posted bug 27380 to the llvm/clang bug tracker at https://llvm.org/bugs/show_bug.cgi?id=27380 showing the main failure in VC++ emulation which I see when testing Boost PP with clang-cl.

3 8

[quickbook] diagnosing a missing [endsect]?
by Peter Dimov 28 Apr '17

28 Apr '17

I just noticed a missing [endsect] in the middle of one of the .qbk files in the Core documentation. The main .qbk file contains [include addressof.qbk] [include checked_delete.qbk] [include demangle.qbk] [include enable_if.qbk] [include explicit_operator_bool.qbk] [include ignore_unused.qbk] [include is_same.qbk] [include lightweight_test.qbk] [include no_exceptions_support.qbk] [include noncopyable.qbk] [include null_deleter.qbk] [include ref.qbk] [include scoped_enum.qbk] [include swap.qbk] [include typeinfo.qbk] and in the middle of lightweight_test.qbk an [endsect] was missing. The end result of it was that the following includes went into the [section] opened in lightweight_test.qbk, as subsections. This wasn't noticeable from a cursory look so it went unnoticed for a while. Is it worth diagnosing this problem in some way? We probably can't disallow unbalanced sections in an [include], but this could be a warning? (If someone pays it any attention, of course.) Presumably, at the end of the file there'll be a [section] left open? This could be made an error so it'd be harder to miss.

4 23

[core] [noncopyable] Add nonmoveable?
by Viktor Sehr 27 Apr '17

27 Apr '17

In addition to noncopyable, I sometimes want to force classes to be nonmoveable as well (mainly node-type classes in tree structures which other classes point to). Therefore I'd suggest adding a cousin to noncopyable; boost::nonmoveable which simply prevents an instance to be nonmoveable (as well as noncopyable). Note; even due the delete modifier were added in C++11 I still think inheriting boost:noncopyable\nonmoveable syntactically nicer than manually marking the copy\move constructors\assignment operators delete. /Viktor Sehr

4 8

[1.64][python] not building for Visual x64
by Raffi Enficiaud 27 Apr '17

27 Apr '17

Hi, I have some trouble building boost.python for the freshly released boost 1.64: there is no boost.python binary generated, and "bin.v2/libs" does not contain any folder named "python". Maybe related: the machine has python2.7 and 3.4 installed. The command for building: b2 toolset=msvc-14.0 --layout=versioned --build-type=complete --without-log -j 4 address-model=64 threading=multi runtime-link=shared The same command was used for 1.63 with no issue. What am I missing? Let me know if this is a chair-to-keyboard problem. Best, Raffi PS: logs of the second run attached (the number of messages for the first run is flooding the console).

2 2

[stacktrace] Two days remaining before review ends
by Niall Douglas 27 Apr '17

27 Apr '17

Current summary of votes cast so far: * Peter Dimov: Unconditional acceptance * Vladimir Batov: Unconditional acceptance Am I missing any? If you are going to make a review and a recommendation, please do so soon. Niall -- ned Productions Limited Consulting http://www.nedproductions.biz/ http://ie.linkedin.com/in/nialldouglas/

6 9

[release] Epic fail: Numeric cast in 1.64 does not match trunk
by Antony Polukhin 26 Apr '17

26 Apr '17

Hello, File https://github.com/boostorg/numeric_conversion/blob/master/include/boost/nu… does not match the one in release 1.64 That file was fixed and merged to master a long time ago, however boost_1_64_0.7z archive still has on outdated version (one with std::unary_function). This looks like an issue within some release scripts. Issue was noted here: https://svn.boost.org/trac/boost/ticket/12972 -- Best regards, Antony Polukhin

4 4

How to contribute??
by Saurabh Singh 25 Apr '17

25 Apr '17

Hey, This is Saurabh from New Delhi, India. I want to contribute to Boost and help you guys in fixing bugs. Can you please help me to get started in doing so. Thanks

3 2

[release] 1.65.0 open for merging
by Rene Rivera 24 Apr '17

24 Apr '17

The master branch is open for merging all stable changes from develop, including bug fixes and major upgrades to existing libraries. Breaking changes should be coordinated via the mailing list with the developers of the other libraries affected. New libraries may be added, but require permission of a release manager. In other words, merging does not require permission from a release manager, except for new libraries. Boost Calendar with the release schedule: http://www.boost.org/development/index.html Release schedule explanation: https://github.com/boostorg/boost/wiki/Release-Schedule Release practices for developers: http://svn.boost.org/trac/boost/wiki/ImprovingPractices -- The Boost Release Team

2 3

[context] - Boost.Context fails to build -> Call of overloaded 'callcc(...) is ambiguous'
by Carlos Ferreira 24 Apr '17

24 Apr '17

I was trying to compile Boost 1.64.0 for OpenWRT when the build failed for Arm Cortex A7 (Raspberry Pi 2) using Gcc 5.2 with Musl 1.1.16. The build output with the error follows. Any ideas on what it could be ? gcc.compile.c++ bin.v2/libs/fiber/build/gcc-arm/release/abi-aapcs/boost.locale.iconv-on/boost.locale.posix-off/link-static/threading-multi/context.o libs/fiber/src/context.cpp: In constructor 'boost::fibers::context::context(boost::fibers::dispatcher_context_t, const boost::context::preallocated&, const default_stack&, boost::fibers::scheduler*)': libs/fiber/src/context.cpp:236:14: error: call of overloaded 'callcc(const std::allocator_arg_t&, const boost::context::preallocated&, const default_stack&, boost::fibers::context::context(boost::fibers::dispatcher_context_t, const boost::context::preallocated&, const default_stack&, boost::fibers::scheduler*)::<lambda(boost::context::continuation&&)>)' is ambiguous }); ^ In file included from ./boost/fiber/context.hpp:28:0, from libs/fiber/src/context.cpp:7: ./boost/context/continuation.hpp:469:1: note: candidate: boost::context::continuation boost::context::callcc(std::allocator_arg_t, StackAlloc, Fn&&, Arg ...) [with StackAlloc = boost::context::preallocated; Fn = const boost::context::basic_fixedsize_stack<boost::context::stack_traits>&; Arg = {boost::fibers::context::context(boost::fibers::dispatcher_context_t, const boost::context::preallocated&, const default_stack&, boost::fibers::scheduler*)::<lambda(boost::context::continuation&&)>}] callcc( std::allocator_arg_t, StackAlloc salloc, Fn && fn, Arg ... arg) { ^ ./boost/context/continuation.hpp:483:1: note: candidate: boost::context::continuation boost::context::callcc(std::allocator_arg_t, boost::context::preallocated, StackAlloc, Fn&&, Arg ...) [with StackAlloc = boost::context::basic_fixedsize_stack<boost::context::stack_traits>; Fn = boost::fibers::context::context(boost::fibers::dispatcher_context_t, const boost::context::preallocated&, const default_stack&, boost::fibers::scheduler*)::<lambda(boost::context::continuation&&)>; Arg = {}] callcc( std::allocator_arg_t, preallocated palloc, StackAlloc salloc, Fn && fn, Arg ... arg) { ^ ./boost/context/continuation.hpp:514:1: note: candidate: boost::context::continuation boost::context::callcc(std::allocator_arg_t, boost::context::preallocated, StackAlloc, Fn&&) [with StackAlloc = boost::context::basic_fixedsize_stack<boost::context::stack_traits>; Fn = boost::fibers::context::context(boost::fibers::dispatcher_context_t, const boost::context::preallocated&, const default_stack&, boost::fibers::scheduler*)::<lambda(boost::context::continuation&&)>] callcc( std::allocator_arg_t, preallocated palloc, StackAlloc salloc, Fn && fn) { ^ ./boost/context/continuation.hpp:457:1: note: candidate: boost::context::continuation boost::context::callcc(Fn&&, Arg ...) [with Fn = const std::allocator_arg_t&; Arg = {boost::context::preallocated, boost::context::basic_fixedsize_stack<boost::context::stack_traits>, boost::fibers::context::context(boost::fibers::dispatcher_context_t, const boost::context::preallocated&, const default_stack&, boost::fibers::scheduler*)::<lambda(boost::context::continuation&&)>}; <template-parameter-1-3> = void] callcc( Fn && fn, Arg ... arg) { ^ -- Carlos Miguel Ferreira Researcher at Telecommunications Institute Aveiro - Portugal Work E-mail - cmf(a)av.it.pt Skype & GTalk -> carlosmf.pt(a)gmail.com LinkedIn -> http://www.linkedin.com/in/carlosmferreira

2 2

Supporting boost 1.64 for Visual Studio 2017
by Evgen8 23 Apr '17

23 Apr '17

The "NuGet" system indicates that BC 2017 is supported. *boost_locale-vc141. Compiler: Visual Studio 2017. Platforms: Win32, x64.* But attempts to use this package end with nothing. Regardless of how I install the "boost_locale" - do I get the same result manually or using "NuGet"? Attempts to install it on another machine ran out the same. Is this a bug? /1>libboost_locale-vc141-mt-1_64.lib(generator.obj) : error LNK2001: unresolved external symbol "class boost::system::error_category const & __cdecl boost::system::system_category(void)" (?system_category@system@boost@@YAABVerror_category@12@XZ) 1>libboost_locale-vc141-mt-1_64.lib(localization_backend.obj) : error LNK2001: unresolved external symbol "class boost::system::error_category const & __cdecl boost::system::system_category(void)" (?system_category@system@boost@@YAABVerror_category@12@XZ) 1>libboost_locale-vc141-mt-1_64.lib(lcid.obj) : error LNK2001: unresolved external symbol "class boost::system::error_category const & __cdecl boost::system::system_category(void)" (?system_category@system@boost@@YAABVerror_category@12@XZ) 1>libboost_locale-vc141-mt-1_64.lib(date_time.obj) : error LNK2001: unresolved external symbol "class boost::system::error_category const & __cdecl boost::system::system_category(void)" (?system_category@system@boost@@YAABVerror_category@12@XZ) 1>libboost_locale-vc141-mt-1_64.lib(generator.obj) : error LNK2001: unresolved external symbol "class boost::system::error_category const & __cdecl boost::system::generic_category(void)" (?generic_category@system@boost@@YAABVerror_category@12@XZ) 1>libboost_locale-vc141-mt-1_64.lib(localization_backend.obj) : error LNK2001: unresolved external symbol "class boost::system::error_category const & __cdecl boost::system::generic_category(void)" (?generic_category@system@boost@@YAABVerror_category@12@XZ) 1>libboost_locale-vc141-mt-1_64.lib(lcid.obj) : error LNK2001: unresolved external symbol "class boost::system::error_category const & __cdecl boost::system::generic_category(void)" (?generic_category@system@boost@@YAABVerror_category@12@XZ) 1>libboost_locale-vc141-mt-1_64.lib(date_time.obj) : error LNK2001: unresolved external symbol "class boost::system::error_category const & __cdecl boost::system::generic_category(void)" (?generic_category@system@boost@@YAABVerror_category@12@XZ) 1>E:\Yandex.Disk\Projects\OS\Release\Devs.exe : fatal error LNK1120: 2 unresolved externals/ -- View this message in context: http://boost.2283326.n4.nabble.com/Supporting-boost-1-64-for-Visual-Studio-… Sent from the Boost - Dev mailing list archive at Nabble.com.

3 2

Re: [boost] Supporting boost 1.64 for Visual Studio 2017
by Andrey Semashev 22 Apr '17

22 Apr '17

On 04/23/17 00:11, Nadtochiy Evgeniy wrote: > 22.04.2017, 21:07, "Andrey Semashev" <andrey.semashev(a)gmail.com>: >> >> On 04/22/17 20:29, Evgen8 via Boost wrote: >> >> The "NuGet" system indicates that BC 2017 is supported. >> *boost_locale-vc141. Compiler: Visual Studio 2017. Platforms: >> Win32, x64.* >> But attempts to use this package end with nothing. Regardless of >> how I >> install the "boost_locale" - do I get the same result manually or >> using >> "NuGet"? Attempts to install it on another machine ran out the >> same. Is this >> a bug? >> >> /1>libboost_locale-vc141-mt-1_64.lib(generator.obj) : error LNK2001: >> unresolved external symbol "class boost::system::error_category >> const & >> __cdecl boost::system::system_category(void)" >> >> >> The missing symbols are from Boost.System. Since you're linking static >> libraries, you'll have to specify Boost.Locale dependencies manually to >> link with in your project. >> > How can i do this? There was always enough installation with NuGet... I don't know what NuGet is or how it works, but the libraries to link with are typically specified in VS project settings (look for the linker parameters tab). PS: Also, please, don't top post.

1 0

[1.64][process] Windows line endings in headers
by Andrey Semashev 22 Apr '17

22 Apr '17

Hi, I can see some of the headers in Boost.Process (for example, boost/process/cmd.hpp, boost/process/env.hpp) contain Windows line endings. Regarding 1.64, Windows line endings are also present in the .tar.bz2 package, which is supposed to be targeted for POSIX systems. 1. Could Windows line endings be removed in git? 2. Could the release procedures be updated to ensure that foreign line endings don't creep into the released packages? I understand that 1.64 has sailed, but I think at least a note (preferably, with a patch) would be appropriate in the release notes.

7 11

[Stacktrace] Second review begins today 17th Mar ends 26th Mar
by Niall Douglas 22 Apr '17

22 Apr '17

I am pleased to announce the second review of the proposed Boost.Stacktrace library running from today until Sunday 26th. Stacktrace is an optionally header-only library providing multiple implementation backends. At its very simplest it lets you capture the stack backtrace for the calling thread and to print it to a std::ostream& of your choice. The basic_stacktrace<> class quacks like a STL container of frame object instances. The rest of the API pretty much follows STL design principles for the most part. Use is therefore unsurprising. You can find the documentation at http://apolukhin.github.io/stacktrace/index.html and the github repo at https://github.com/apolukhin/stacktrace. Review guidelines ================= This is a second review of this library with many changes implemented in response to feedback from the previous review. My previous review report can be found at http://lists.boost.org/boost-announce/2017/01/0486.php where I made the following conditions for acceptance: 1. That the documentation more clearly set out what Stacktrace does and especially does not do, and that the default facilities provided are those of the Minimum Viable Product described above i.e. no source file nor line number discovery, no external dependencies on libraries not always provided on the target platform, no invocation of child processes, no async safety during stacktrace parsing. Stacktrace ought to be pared back to the minimum viable product featureset with no external dependencies at all. 2. That suitable predefined macros opt in to additional functionality such as serialisation of offset translated backtraces, retrieval of source code path and line number etc. Enabling these may introduce dependencies on third party libraries not always present on a system such as libunwind, or on third party helper utilities such as addr2line. I would recommend that the APIs the use of which are dependent on such third party items are entirely compiled out of Stacktrace when the macro enabling them is not defined. 3. That the documentation describe ONLY the default minimum viable product functionality in its tutorial and quick start. All extra functionality enabled by macros is to be relocated into a separate documentation section away from the main documentation e.g. "Advanced/optional features". 4. That APIs made available only when a given macro has turned them on are documented as such in the API reference docs. Antony hasn't entirely met my conditions, hence this second review. He has instead implemented this changelog: * Reimplemented boost::stacktrace::basic_stacktrace class to accept allocators and to have a small size * Added outputting of the path to the binary object into the stacktrace, when source location is not available * Allowed to use `libbacktrace` - a defacto standard for GCC/CLANG backtracing that does not fork and has a permissive license * Optimized stacktrace and frames ostreaming * Removed backends and made the default tracing to have only platform basic functionality. Added macros to enable additional functionality. * Fixed (theoretically) MinGW compilation * Added functions for async-safe dumping into memory or descriptor * Changed signal handling example to be async-signal-safe * Allowed users to choose how many frames to skip during stack capture * Removed `boost::stacktrace::stacktrace` functions and other internals from printed stack traces * Updated docs: * examples now use Boost.Exception * removed all the references to "backend" * reduced macro count * "Build, Macros and Backends" section was rewritten and became "Configuration and Build" * added note that library is C++03 * added examples on storing traces into shared memory * updated all the human readable dumps It is up to the Boost community as to whether this revised library is now acceptable without any conditions, or with conditions. Reviews should be submitted to the developer list (boost_at_[hidden]), preferably with '[stacktrace]' in the subject. Or if you don't wish to for some reason or are not subscribed to the developer list you can send them privately to me at 's_sourceforge at nedprod dot com'. If so, please let me know whether or not you'd like your review to be forwarded to the list. For your review you may wish to consider the following questions: - What is your evaluation of the design? - What is your evaluation of the implementation? - What is your evaluation of the documentation? - What is your evaluation of the potential usefulness of the library? - Did you try to use the library? With what compiler? Did you have any problems? - How much effort did you put into your evaluation? A glance? A quick reading? In-depth study? - Are you knowledgeable about the problem domain? And finally, every review should attempt to answer this question: - Do you think the library should be accepted as a Boost library? Be sure to say this explicitly so that your other comments don't obscure your overall opinion. Even if you do not wish to give a full review any technical comment regarding the library is welcome as part of the review period and will help me as the review manager decide whether the library should be accepted as a Boost library. Any questions about the use of the library are also welcome. Niall -- ned Productions Limited Consulting http://www.nedproductions.biz/ http://ie.linkedin.com/in/nialldouglas/

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Locating Visual Studio 2017 on disk
by Andrew Pardoe 20 Apr '17

20 Apr '17

Folks, We had a number of conversations about the fact that VS 2017 could be installed in any location, or multiple locations, and no longer created a registry key pointing to an install location. There's also the problem that an installation of VS 2017 may or may not contain C++ tools (as was the case with VS 2015.) The solution proposed by the VS team-creating a tool called VSWhere-was inadequate for some scenarios such as Boost's because it would have required either caching a binary in your source enlistment or compiling code to locate the compiler. A number of people on this list asked for a more straightforward solution. I'm happy to tell you that your feedback was heard. We're going to start shipping the VSWhere tool in a known location on any machine that has VS 2017. More details can be found in this blog post: https://blogs.msdn.microsoft.com/heaths/2017/04/21/vswhere-is-now-installed… This doesn't fix the problem for all the versions of VS 2017 that are installed already. And this doesn't help our version numbers to make any more sense (although I'm pushing to fix that as well.) But at least in the future you'll be able to locate VS installs from a scripted environment. Thanks for being loud and reaching out to us. As always, I'm happy to help you with any issues you might have with MSVC-just ask. Andrew Pardoe MSVC compiler & tools

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[stacktrace] Please for into boostorg repo
by Antony Polukhin 20 Apr '17

20 Apr '17

Hi, Stacktrace library was accepted into the Boost http://www.boost.org/community/review_schedule.html Please fork the repo https://github.com/apolukhin/stacktrace into boostorg and give me admin rights to that repo. -- Best regards, Antony Polukhin

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Boost Library Incubator Statistics
by Robert Ramey 20 Apr '17

20 Apr '17

In the course of updating the Boost Library Incubator website, I gathered some summary statistics which some might find interesting. 40 Number of libraries submitted 2 libraries not accepted into the incubator of lack docs, test, etc. 11 libraries reviews by boost 9 accepted 2 rejected All in all, I'm thinking these numbers aren't too bad for boost and the incubator. I would like to see more submissions - but the submissions we've received seem to be better than average quality and worthy of consideration. Hopefully this has made the review process more efficient. A couple of libraries have also been accepted (and rejected) without having been placed in the incubator. The number is small. I think this validates the incubator as useful, but not necessary and libraries authors should continue to be encouraged, but not required, to submit library candidates to the incubator. Other than the above, I'm not going to try to draw any conclusions from the above admittedly anecdotal data. I would also remind boosters that if you're logged into the incubator, you can display statistics on viewership for a particular library by using the "Display Statistics" button on the library page. This is a crude but someone engaging way to get an idea of how many people have looked at the library page. The attached shows visits to the safe numerics library page in the last 90 days. Robert Ramey

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List-Id mail header
by Christoph Ludwig 20 Apr '17

20 Apr '17

Hi, starting yesterday, the List-Id header in the mails I get from the Boost mailing list changed. It used to be: List-Id: Boost developers' mailing list <boost.lists.boost.org> Now it is: List-Id: Boost developers' mailing list <boost.wowbagger.crest.iu.edu> Due to this change, the mail filter I have used for years fails to identify the messages as boost mailing list traffic. Therefore, the messages end up in my regular inbox instead of the dedicated folder I have for the mailing list. Of course, I can easily update my mail filter, that's no big deal. I just want to know: Did I miss an announcement, was this change intended? Will the List-Id use the wowbagger identifier from now on? Cheers, Christoph

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[release] Boost 1.64.0
by Rene Rivera 20 Apr '17

20 Apr '17

Release 1.64.0 of the Boost C++ Libraries is now available. These open-source libraries work well with the C++ Standard Library, and are usable across a broad spectrum of applications. The Boost license encourages both commercial and non-commercial use. This release contains one new library and numerous enhancements and bug fixes for existing libraries. For details, including download links, see < http://www.boost.org/users/history/version_1_64_0.html> You can also download directly from: < https://dl.bintray.com/boostorg/release/1.64.0/> To install this release on your system, see < http://www.boost.org/doc/libs/release/more/getting_started/index.html> Thanks to everyone who participated in this release. Thanks, -- The Boost Release Team Vladimir Prus, Rene Rivera, Marshall Clow, Eric Niebler, Daniel James, Beman Dawes

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[release] Boost 1.64.0 Release Candidate 1
by Rene Rivera 19 Apr '17

19 Apr '17

The release candidates for the 1.64.0 release are now available at: <https://dl.bintray.com/boostorg/beta/1.64.0.rc.1/> The SHA256 checksums are as follows: 49c6abfeb5b480f6a86119c0d57235966b4690ee6ff9e6401ee868244808d155 boost_1_64_0_rc1.7z 7bcc5caace97baa948931d712ea5f37038dbb1c5d89b43ad4def4ed7cb683332 boost_1_64_0_rc1.tar.bz2 0445c22a5ef3bd69f5dfb48354978421a85ab395254a26b1ffb0aa1bfd63a108 boost_1_64_0_rc1.tar.gz b99973c805f38b549dbeaf88701c0abeff8b0e8eaa4066df47cac10a32097523 boost_1_64_0_rc1.zip As always, the release managers would appreciate it if you download the candidate of your choice and give building it a try. Please report both success and failure, and anything else that is noteworthy. -- The Boost Release Team -- -- Rene Rivera -- Grafik - Don't Assume Anything -- Robot Dreams - http://robot-dreams.net -- rrivera/acm.org (msn) - grafikrobot/aim,yahoo,skype,efnet,gmail

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[Trac] Spam and suspicious attachments
by Mateusz Loskot 19 Apr '17

19 Apr '17

Hi, I'm not sure what is the correct admin contact to report spam on Trac, so posting here. Number of suspicious attachments (.exe, .jpg) have been submitted to this ticket during recent period of 3 years https://svn.boost.org/trac/boost/ticket/8070 Best regards, -- Mateusz Loskot, http://mateusz.loskot.net

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[ranges] Please merge the long standing pull request
by Antony Polukhin 18 Apr '17

18 Apr '17

Hello, There's a year old pull request https://github.com/boostorg/range/pull/44 Please merge it to the develop branch. The pull request is a blocker for improving Boost.Algorithm (https://github.com/boostorg/algorithm/pull/35) https://github.com/boostorg/range/pull/44 changes were adopted into C++17 standard library.So the change is not innovative. -- Best regards, Antony Polukhin

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Serialization support for colony container
by Brian Wood 17 Apr '17

17 Apr '17

Shalom It's looking like Matthew Bentley's colony container -- http://plflib.org -- is going to pass over Boost on it's way to the standard. I've added serialization support for this container to the C++ Middleware Writer and added some code that tests that support to my repo -- https://bitbucket.org/webenezer/onwards . I enjoyed Jon Kalb's CppChat show where he talked to Matthew about this container -- http://www.slashslash.info/cppchat/ https://www.youtube.com/watch?v=SFAJ238rBNw -- Brian Ebenezer Enterprises - In G-d we trust. http://webEbenezer.net

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Guinea pigs for testing GSoC submission ranking
by Niall Douglas 16 Apr '17

16 Apr '17

Google have removed the ability for the community to rank proposals plus they force proposals to be sent to us in the highly unuseful PDF format. I've come up with a stopgap solution, and need guinea pigs for testing it. If you're game, please send me your google login name and I'll send you instructions. My thanks in advance. Niall -- ned Productions Limited Consulting http://www.nedproductions.biz/ http://ie.linkedin.com/in/nialldouglas/

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[metal] Formal Review - Request for Endorsement
by Bruno Dutra 16 Apr '17

16 Apr '17

Dear Community, I'd like to formalize what has been known to many for some time now and request the formal review of Metal, a modern C++14 library designed to make template metaprogramming intuitive and effectively replace Boost.MPL. Klemens Morgenstern has kindly offered to manage the review process. The library is available on github at https://github.com/brunocodutra/metal The full documentation is available online at http://brunocodutra.github.io/metal/ Up to date benchmarks are uploaded daily to metaben.ch Great effort has been put into making Metal as portable to different compilers as possible. Currently, the following compilers are tested in continuous integration using Travis and Appveyor: * GCC 4.7 and above * Clang 3.4 and above * Xcode 6.4 and above * Visual Studio 14 (2015) and above * MinGW 5 and above Complying with the new Boost policy, I'd like to kindly request those interested in seeing Metal in boost to take a look at it and endorse this request for formal review. Regards, Bruno

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[config] What to call macros to indicate deprecated/removed components
by John Maddock 16 Apr '17

16 Apr '17

We now have several former C++ features which are removed in C++17: auto_ptr random_shuffle binders unary/binary_function And we're getting requests for configuration macros for these, the question is what to call them? We could stick with the (easy to implement) existing naming and just use: BOOST_NO_<FEATURE> or we could use: BOOST_<STD>_REMOVED_<FEATURE> which is a bit more work as all the scripts that rely on the BOOST_NO/BOOST_HAS convention need updating. Any other suggestions/preferences? Thanks, John. --- This email has been checked for viruses by AVG. http://www.avg.com

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[typeof][scope_exit] VS2017 and option /permissive-
by Daniela Engert 16 Apr '17

16 Apr '17

Hello, late last year, VS2017RC gained a compiler option /permissive- which disables some non-conforming behaviour. Source code that was accepted by previous versions of msvc, and still is accepted by msvc 14.1 without this compiler option, is rejected and flagged as an error if /permissive- is engaged. For more on this see https://blogs.msdn.microsoft.com/vcblog/2016/11/16/permissive-switch/. While checking our company's codebase for possible problems related to that I noticed compile errors in Boost.Log and traced the problem back to Boost.Typeof and in particular "libs\typeof\include\boost\typeof\msvc\typeof_impl.hpp". Therein is code emulating the missing __typeof__ keyword by taking advantage of a silent msvc compiler 'bug' as a 'feature'. Parts of this code are duplicated in a msvc-specific workaround in Boost.Scope_Exit. This compiler bug is no longer silent with /permissive- in place but rather a hard error. As it turns out, I'm not the first to be bitten by this: ticket #12900 tells the same story. Many other Boost libraries use Boost.Typeof directly or indirectly and therefore suffer from the same problem (like Boost.Log in my particular case). I've implemented a possible solution and created two pull-requests: - https://github.com/boostorg/typeof/pull/7 - https://github.com/boostorg/scope_exit/pull/3 The patches only affect msvc 14.1. With these patches applied, the test results of the full Boost testsuite are the same as without these patches. I don't know enough about __typeof__ to decide if my emulation is compatible in every aspect, but at least it's good enough to pass the testsuite. There are two other compile failures introduced with /permissive- in place which are compiler bugs which need to be addressed by Microsoft's compiler team. Fortunately these are very specific to just two libraries, Boost.Spirit.Repository (one test case) and Boost.Geometry (two test cases caused by one single function). -- PGP/GPG: 2CCB 3ECB 0954 5CD3 B0DB 6AA0 BA03 56A1 2C4638C5

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Boost licensing information
by Fabrizio Riente 15 Apr '17

15 Apr '17

Dear Boost Members, I'm Fabrizio Riente and I'm a researcher from the Politecnico di Torino in Italy. I'm using some part of boost libraries in our application. In particular we are using boost spirit, odeint and serialization. In the next future, we would like to release this tool for free for research purposes. I read that at the moment boost is released under Boost license. I was wandering if under this license it is possible to distribute the application for free to other universities and interested people without sharing the source code. Thanks in advance for your time. Best regards. Fabrizio Riente -- Fabrizio Riente, Postdoctoral Research Associate Politecnico di Torino, Dept. of Electronics and Telecommunications C.so Duca degli Abruzzi 24, I-10129, Torino, Italy Phone: +39 011 090 4241, Email: fabrizio.riente(a)polito.it

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Header Inclusion practices
by Robert Ramey 15 Apr '17

15 Apr '17

As long as I can remember, it's been my practice to write program code to minimize dependencies on the environment in which it is built. By environment I mean things external to the code itself like environmental and command line variables, directory context etc. As part of this I use rules for header file inclusion: a) use #include "header.hpp" for files in the same directory as the current source file. b) use #include "other directory/header.hpp" for files which are known to be in a specific place relative to the current file. This shows up in things like: #include "../include/header.hpp" for tests and examples. c) use #include <boost/serialization/xml_archive.hpp> for files which are found by looking in directories listed in "-I" switches and environmental variables (INCLUDE). I generally try not to depend upon any environmental variables as I always forget to set them or even how to set them. Come to think about it. I don't know how my build system finds the boost libraries. I presume it's through some IDE/Bjam/CMake setting which I can never remember. d) use #include <iostream> for standard library components. Presumably these are routed to some directory relative to the compiler. So some of my source files look like: // interval.hpp header for safe numerics library #include <limits> #include <cassert> #include <type_traits> #include <array> #include <initializer_list> #include <boost/logic/tribool.hpp> #include <boost/core/demangle.hpp> #include "utility.hpp" // log #include "checked_result.hpp" #include "checked.hpp" and // example using he safe numerics library #include <iostream> #include <limits> #include <boost/integer.hpp> #include "../include/cpp.hpp" #include "../include/exception.hpp" #include "../include/safe_integer.hpp" #include "../include/safe_range.hpp" This has raised consternation in some quarters - but I don't see anything wrong with it. It basically means that only the <boost libraries are depended on the whole b2 business. I didn't want the incubator version of the the safe numeric library to depend on the library having been accepted into boost have have b2 run. Also I don't like adding the library to boost - and having to change all the headers. What if someone want's to run the tests/examples outside of the boost tree. As far as I know this question has never been asked before and I'm curious to know what others might have to say about this. Robert Ramey

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gil: extension/numeric missing in tarball(s)
by Tim Blechmann 14 Apr '17

14 Apr '17

hi all, the complete folder with the gil numeric extensions is not included in the tarball ... is this a bug or a feature? https://github.com/boostorg/gil/tree/develop/include/boost/gil/extension/nu… thnx, tim

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