- Boost - lists.preview.boost.org

Test
by Andrey Semashev 26 Jun '24

26 Jun '24

Hello, testing.

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test77
by sam＠cppalliance.org 26 Jun '24

26 Jun '24

qq

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test6
by Sam Darwin 26 Jun '24

26 Jun '24

test6

2 1

test7
by Sam Darwin 30 May '24

30 May '24

test7

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NVCC and Unit Test Framework.
by Allen Sanderson 29 May '24

29 May '24

Hello, I am trying to sort out an odd crash on exit while using NVCC (via Kokkos-CUDA) and the Boost Unit Test Framework. Here my are data points: Kokkos-CUDA with the Boost test tool infrastructure - Crash Kokkos-HIP with the Boost test tool infrastructure - works Kokkos-Serial with the Boost test tool infrastructure - works Pure CUDA with the Boost test tool infrastructure - works Serial with the Boost test tool infrastructure - works Kokkos-CUDA alone (e.g. normal application) - works For the first case I have three scenarios (only used to high the Kokkos usage - the code does not crash in Kokkos::initialize), two of which crash: if(true) Kokkos::initialize(argc,argv); crash in CUDA - SEGFAULTif(false) Kokkos::initialize(argc,argv); crash in elsewhere - Subprocess aborted#if 0 Kokkos::initialize() #endif No crash For the first scenario the call stack is the following: #0 0x00001555521b5d9a in ?? () from ./cuda/12.2.0/lib64/libcudart.so.12 #1 0x00001555521b8c14 in ?? () from ./cuda/12.2.0/lib64/libcudart.so.12 #2 0x000015555219d882 in ?? () from ./cuda/12.2.0/lib64/libcudart.so.12 #3 0x00001555521a072b in ?? () from ./cuda/12.2.0/lib64/libcudart.so.12 #4 0x000015554b3b5797 in __cxa_finalize () from /lib64/libc.so.6 #5 0x0000155551301a87 in __do_global_dtors_aux () from build_kokkos_cuda/library/Operators/libOperators-g.so.5.5.0 #6 0x00007fffffffad10 in ?? () #7 0x000015555532dcee in _dl_fini () at dl-fini.c:141 For second, the call stack is quite deep after the call to __cxa_finalize () otherwise the first four (4-7) are the same. At this point the only culprit I can perhaps point at is nvcc I know at that previous versions of Boost and nvcc did not get along. And such, wondering if the usage is a corner case because I know of another project that is successfully using all three Boost, Kokkos, and CUDA. I am using Boost 1.85, Kokkos 4.3, and CUDA 12.2. Any insight or thoughts ? Our unit test work with Kokkos-HIP so able to validate results. Allen Sanderson SCI Institute University of Utah

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[release] Boost 1.85.0
by Marshall Clow 28 May '24

28 May '24

Release 1.85.0 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 two new libraries: * Boost.Charconv: A high quality implementation of <charconv> in C++11, from Matt Borland. * Boost.Scope: A collection of scope guard utilities and a unique_resource wrapper, from Andrey Semashev. The release also contains numerous enhancements and bug fixes for existing libraries. For details, including download links, see <http://www.boost.org/users/news/version_1.85.0> You can also download directly from: <https://boostorg.jfrog.io/artifactory/main/release/1.85.0/> 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. -- The Boost Release Team Marshall Clow, Glen Fernandes

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[container] Draft development plan for Boost.Container
by Ion Gaztañaga 28 May '24

28 May '24

Hi to all, Boost.Container was accepted in 2011 when container classes were spun off from Boost.Interprocess to form a new library. At that time it offered new features like emulated move semantics for "classic" STL-like containers and some new classes like flat_map and stable_vector. During these years more containers/main features were added: - The scoped allocator Model was added in Boost 1.50 (2012) - static_vector was added in Boost 1.54 (2013) - small_vector was added in Boost 1.58 (2015) - Polymorphic Memory Resources were added in Boost 1.60 (2015) - devector was added in Boost 1.75 (2020) Lately I've been collecting some ideas about how to improve the library and keep it interesting/useful both for other Boost libraries and Boost users. I've somewhat formalized a bit some of those ideas and I'd like to share them here in order to obtain feedback from the developers. Here's the document: https://docs.google.com/document/d/1VdMTheFUczC946dP3VKPseOoUq3sVKjU73oMvK8… Note that this document does not outline a schedule for all those ideas, it's an initial description of possible developments that should be evaluated/prioritized, as developing a substantial subset of the proposals would be a huge task. Thanks in advance for your attention and comments. Best, Ion

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Docs in release tarballs
by Ruben Perez 24 May '24

24 May '24

Hi all, For someone that hasn't been that long involved in Boost, it feels strange to distribute the documentation in the same release tarball as the code, specially considering the usual complains about "Boost size". I'm sure there are reasons behind it, and I'd like to learn about them. This is a candid question, out of being a newbie here. Thanks, Ruben

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OSTIF Boost security audit report
by Andrey Semashev 24 May '24

24 May '24

Hi, Recently, a security audit of several Boost libraries has been conducted. The audited Boost version was 1.83.0. The report is now published here: https://ostif.org/boost-audit-complete/ https://ostif.org/wp-content/uploads/2024/05/OSTIF-Boost-Report-PT-v1.4.pdf In short, the following libraries were audited: - Boost.Beast (1 medium issue) - Boost.DLL (1 informational issue) - Boost.Date_Time - Boost.Filesystem - Boost.GIL - Boost.Graph (1 low and 1 informational issues) - Boost.JSON - Boost.Program_Options - Boost.Regex (3 low issues) - Boost.String_Algo - Boost.URL - Boost.UUID No critical or high severity issues were identified. Of the 7 identified issues, 4 are marked as closed, meaning the issues are fixed. The remaining 3 are open and listed in Boost.Beast (medium), Boost.DLL (informational) and Boost.Graph (informational). During audit, several fuzzing harnesses were developed and added to OSS-Fuzz: https://github.com/google/oss-fuzz/tree/master/projects/boost In the report, there were also a few general recommendations given to improve project security: - Monitor OSS-Fuzz Reports - Implement a Vulnerability Disclosure Process - Implement Supply-Chain Attack Countermeasures - Improve the Documentation with Security Mechanisms and Assumptions - Avoid the Abuse of Asserts Also, one general recommendation to Boost users: - Perform Strict Input Validation You can find more details in the report. I'd like to emphasize the "Implement Supply-Chain Attack Countermeasures" part, which basically comes down to signing git tags and release tarballs. I think, our release process is indeed not very reliable, let's say, which showed during the past few releases: - there was instance when different tarballs for the same RC were generated from different git revisions - git tags for the release were missing or pointing to a wrong git commit Also, release tarballs on GitHub don't have hashsums or signatures attached. https://github.com/boostorg/boost/issues/838 For tarballs on jfrog, thankfully, there are hashsums published in the release notes. Perhaps, we could also publish .sig files for all tarballs, and also publish the public key to verify the signature on the website. Also, under "Implement a Vulnerability Disclosure Process" it is suggested to use GitHub Security Advisories[1] as the mechanism for reporting security issues. I've never used this tool, but perhaps it is worth enabling for boostorg on GitHub. Emailing library maintainers privately might not be a very reliable mechanism for such reports, given that maintainers may become inactive. [1]: https://docs.github.com/en/code-security/security-advisories/working-with-r…

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Boost/CMake
by Robert Ramey 23 May '24

23 May '24

Anyone have first hand experience building/testing a boost library/application with CMake? I've found the github project for boost/Cmake. Can anyone point me to more useful information? Robert Ramey

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Two mqtt libraries
by Robert Ramey 22 May '24

22 May '24

I've been contacted by my friend and sometime collaborator Takatoshi Kondo regarding his submission of a boost library: https://github.com/redboltz/async_mqtt. It has received two endorsements. He has asked me to be review manager and I'm inclined to accept this request as he was very helpful to me during the refinement of the boost serialization library. There is also mqtt client library that is proposed to the Boost. https://github.com/mireo/async-mqtt5 It also has endorsements and a review manager. A cursory examination of the git hub pages suggest considerable overlap between the two submissions. In general, boost has discouraged the acceptance of multiple libraries with this much overlap - and for good reason. An accepted library often becomes the canonical implementation in large parts of the C++ world. Having two high quality libraries that do almost the same thing is not where we would like to be. I would like to propose that we review both libraries simultaneously in order to try to reach a consensus as to which, if either we want to accept. I know this is a difficult task, but I think it is important that we do this. It's going to be tough to reject a well written library because a better one has been accepted. But it would be worse to reject a well written library merely because another one was submitted first. Normally I don't participate as a review manager as I'm pretty bogged down in Boost stuff as it is. But I'm willing to make an exception in this case due to the importance of this case and my strong personal ties to Takatoshi. BTW - who is the review wizard these days? I presume that he will be the one making the decision about this. Robert Ramey

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Re: [boost] modern logic classes
by g.peterhoff＠t-online.de 18 May '24

18 May '24

> At this point I'd like to know if it's possible to thread mathematically the N-bool problem and create a library for generic multidimensional bool that works with templates allowing to determine N at compile time. Because in the future we should have a 8-bool implementation, and so on... Theoretically, it would (probably) be possible to provide N-valued logics. But that is beyond my knowledge. bool3/bool4(Belnap) are still manageable. For N-valued logics N>4, mathematicians would have to be consulted (as I said: I am not one). If you are asking about such things, perhaps temporal logics could also be provided https://en.wikipedia.org/wiki/Temporal_logic. But that's where I completely drop out.

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modern logic classes
by g.peterhoff＠t-online.de 18 May '24

18 May '24

Hello, I would like to provide modern logic classes, please see https://github.com/boostorg/logic/issues/30 What are your opinions/comments on this? thx Gero

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2024 Q1 Transparency report
by Louis Tatta 16 May '24

16 May '24

Hello, Louis Tatta here, CEO of The C++ Alliance, Inc, a registered 501(c)(3) non-profit organization dedicated to the support of C++. This is our Q1 2024 transparency report regarding our charitable work for the Boost C++ Library Collection. First, some background on our operations. The C++ Alliance seeks out highly talented and experienced C++ experts and hires them, usually full-time, so they can focus completely on their open-source projects. Our Staff Engineers maintain existing Boost libraries, write new Boost libraries, and contribute to other Boost projects. We employ IT experts full-time to maintain and improve the infrastructure which supports Boost, including the legacy web server, the Drone continuous integration servers, the scripts used to deploy GitHub Actions for Boost repositories, and the scripts which publish the Boost release. In addition, we provide on-demand technical support services for Boost authors and maintainers who have infrastructure-related problems. The Boost Mailing List continues to be the premier place for high-quality discussion of the Boost libraries and tangential C++ Standards related topics. The C++ Alliance supports the use of the mailing lists going forward. We are upgrading it to the latest Mailman version and building an optional web-based front-end allowing interaction using only a browser. We continue to operate the Official C++ Language Slack Workspace ( https://cpp.al/slack) which hosts the most popular interactive discussions regarding the Boost libraries. The C++ Alliance sponsors a paid plan to provide full history, video and audio conferences, collaboration tools, and unlimited document storage for seventeen dedicated Boost library channels and one main Boost discussion channel. Our largest project for Q1 2024 is the continuation of work on the new Boost website. The new site is a C++ social media portal with rich support for user-generated content and a powerful back-end which has visibility into the contributions made on GitHub and the release process. This allows us to deliver an elevated user experience with the hopes of attracting fresh talent to Boost. Also, note that the graphics on the website are hand-drawn by our contract artist and reflect our level of commitment to ensure that Boost, to put it simply, looks good. In Q1 2024 there were a total of two Boost Formal Reviews. One of the reviewed libraries is authored by a C++ Alliance Staff Engineer. None of the reviews were managed by C++ Alliance team members. Out of a total of sixteen submitted reviews for the quarter, eight were from C++ Alliance team members. This quarter, we increased our efforts to build Boost’s social media presence. There were a total of six messages from the @Boost_Libraries X (formerly Twitter) account, all submitted by C++ Alliance team members. Three of them contained artwork from Bob Ostrom commissioned by us. Messages containing images get three times more engagement than text-only messages. We believe that the X platform has unique strategic value for informing newer generations about the Boost value proposition. A total of $406,000 was spent on Boost-related contributions, broken down thusly (and rounded to the nearest thousand): Staff Engineers Compensation $317,000 Website Software Development $64,000 Server Hosting $25,000 During Q1 2024 we employed a total of 12 individuals to contribute to Boost. Here is a high-level summary of accomplishments: Sam Darwin (Chief Technical Officer) * Boost website maintenance and administration * Boost per-pull-request documentation previews * Boost Release Process development, maintenance, and administration * Boost Mailman services maintenance and upgrade * Boost GitHub Actions self-hosted runner project development * Boost Drone service administration and maintenance * New Boost website deployment, administration, and development Dmitry Arkhipov (Staff Engineer) * Boost.JSON maintenance Alan de Freitas (Staff Engineer) https://cppalliance.org/alan/2024/05/07/AlanQ1Update.html * Boost.URL maintenance * Mr. Docs project management (https://mrdocs.com) * GitHub actions support scripts for Boost CI (https://alandefreitas.github.io/cpp-actions/cpp-actions/index.html) Christian Mazakas (Staff Engineer) * Boost.Unordered evolution project * Boost.Buffers development (new library) * Boost.Http.Proto, Boost.Http.Io development (new libraries) Krystian Stasiowski (Staff Engineer) * Boost.StaticString maintenance * Mr. Docs Lead engineer (https://mrdocs.com/) * Clang/LLVM contributions Peter Turcan (Senior Technical Writer) * Boost User Guide development (new documentation) * Boost Contributor Guide (new documentation) * Boost Formal Reviews (new documentation) Matt Borland (Staff Engineer) * Boost.Decimal (proposed library) * Multi (https://github.com/correaa/Boost-Multi) review manager * Boost.Math maintenance Ruben Perez * Boost.PFR integration and maintenance work * Boost.MySQL maintenance (new, accepted library) * Boost.Charconv * User Guide, Contributor Guide contribution (new documentation) Mohammad Nejati (Staff Engineer) * Boost.Http.Proto and Boost.Buffers (new libraries) * Boost-Gecko (full-text site search) * Boost.Beast maintenance Fernando Pelliccioni (Staff Engineer) * Mr. Docs development (https://mrdocs.com/) Spencer Strickland (Senior Web Developer) * New website front-end and scripting Joaquin M Lopez Munoz (Staff Engineer) * Boost.Unordered evolution project lead * Boost.Bimap * Boost promotion and new website

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Decimal Floating Point Library Beta
by Matt Borland 16 May '24

16 May '24

Hello, For the past year Chris Kormanyos and I have been working on a new library to implement IEEE 754 decimal floating point types. We are pleased to announce the library is now in beta, and can be found at: https://github.com/cppalliance/decimal, and the documentation is at: https://cppalliance.org/decimal/decimal.html First, what are Decimal Floating Point Numbers? They are floating point numbers where the significand is stored in base-10 (decimal) instead of base-2 (binary). This means that numbers can be represented exactly avoiding cases such as the famous 0.1 + 0.2 != 0.3: https://0.30000000000000004.com. The library provides types decimal32, decimal64, and decimal128 as specified in IEEE 754 and STL-like functionality. The library is header-only, has no dependencies, and only requires C++14. It provides most of the STL functionality that you are familiar with such as <cmath>, <cstdlib>, <charconv>, etc. We are proceeding as a beta right now rather than pursuing complete boost review as we are missing STL features such as C++17 special math, and believe we can continue to increase performance. We do intend to go through the review process at a later time. Please give the library a go, and let us know how we can make it better. We look forward to any and all feedback. If you use the Cpplang slack channel I am active (from the Central European Time zone) on both #boost and #boost-decimal. On a personal note as of today I have also moved from being employed half-time to full-time with the C++ Alliance. This affords me a greater opportunity to develop and maintain new and existing Boost libraries. Matt Borland —- C++ Alliance Staff Engineer

8 15

Fwd: shared_mutex lock() issue
by Max 15 May '24

15 May '24

Hi, It looks like threads-devel is abandoned I posted here. I have tried boost::shared_mutex and found an issue. It looks like it doesn't work as expected. The problem is following code: void lock() { #if defined BOOST_THREAD_PROVIDES_INTERRUPTIONS boost::this_thread::disable_interruption do_not_disturb; #endif boost::unique_lock<boost::mutex> lk(state_change); state.exclusive_waiting_blocked=true; exclusive_cond.wait(lk, boost::bind(&state_data::can_lock, boost::ref(state))); state.exclusive=true; } On lines: state.exclusive_waiting_blocked=true; exclusive_cond.wait(lk, boost::bind(&state_data::can_lock, boost::ref(state))); Here the state is changed and new lock_shared() waits because can_lock_shared returns false in this case. It works as I think it should be. The when "old" readers unlocks mutex the last one unlock_shared() executes void unlock_shared() { ... if (state.no_shared()) { if (state.upgrade) { ... } else { state.exclusive_waiting_blocked=false; //lk.unlock(); } release_waiters(); } where resets state.exclusive_waiting_blocked value. Then notify 2 condition variables(in release_waiters): 1 for readers and 1 for writers. If the writer doesn't win this race and one of the waited readers will be the first one, the writer runs state_data::can_lock and it of course returns false. Then the writer goes to sleep again. But exclusive_waiting_blocked is still false. So in the high pressure of readers, this writer never gets a chance to get control in this case anymore until all readers are gone. This bug was introduced in 1.67 version, before the changes the code was: while (state.shared_count || state.exclusive) { state.exclusive_waiting_blocked=true; exclusive_cond.wait(lk); } but it not the same as (because exclusive_waiting_blocked reassigned): state.exclusive_waiting_blocked=true; exclusive_cond.wait(lk, boost::bind(&state_data::can_lock, boost::ref(state))) Best Regards, Maxim

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Re: [boost] Problem with building 1.85.0
by Ted Lyngmo 15 May '24

15 May '24

Andrey Semashev wrote: > > If you're building Boost from git, you should run `./b2 headers` before building Boost. > > The output you posted is missing the actual compilation errors for these files. Check the earlier compiler messages for these files. Or run `./b2 -j8 --with-filesystem` to build specifically Boost.Filesystem and see the output. Ok, I added `./b2 headers` before `./b2 -j8 install` which didn't change anything that I could see. `./b2 -j8 --with-filesystem` then gave me this: ...patience... ...found 3209 targets... ...updating 46 targets... boost-install.generate-cmake-config- bin.v2/libs/headers/build/stage/boost_headers-config.cmake boost-install.generate-cmake-config- bin.v2/libs/filesystem/build/stage/boost_filesystem-config.cmake boost-install.generate-cmake-config-version- bin.v2/libs/headers/build/stage/boost_headers-config-version.cmake common.copy /home/ted/git/boost/stage/lib/libboost_atomic.so.1.85.0 ln-UNIX /home/ted/git/boost/stage/lib/libboost_atomic.so boost-install.generate-cmake-config- bin.v2/libs/atomic/build/stage/boost_atomic-config.cmake boost-install.generate-cmake-config-version- bin.v2/libs/atomic/build/stage/boost_atomic-config-version.cmake common.copy /home/ted/git/boost/stage/lib/libboost_atomic.a common.copy /home/ted/git/boost/stage/lib/cmake/BoostDetectToolset-1.85.0.cmake common.copy /home/ted/git/boost/stage/lib/cmake/boost_filesystem-1.85.0/boost_filesystem-config.cmake common.copy /home/ted/git/boost/stage/lib/cmake/Boost-1.85.0/BoostConfig.cmake common.copy /home/ted/git/boost/stage/lib/cmake/Boost-1.85.0/BoostConfigVersion.cmake common.copy /home/ted/git/boost/stage/lib/cmake/boost_headers-1.85.0/boost_headers-config.cmake common.copy /home/ted/git/boost/stage/lib/cmake/boost_headers-1.85.0/boost_headers-config-version.cmake common.copy /home/ted/git/boost/stage/lib/cmake/boost_atomic-1.85.0/boost_atomic-config-version.cmake common.copy /home/ted/git/boost/stage/lib/cmake/boost_atomic-1.85.0/libboost_atomic-variant-shared.cmake boost-install.generate-cmake-config-version- bin.v2/libs/filesystem/build/stage/boost_filesystem-config-version.cmake common.copy /home/ted/git/boost/stage/lib/cmake/boost_atomic-1.85.0/boost_atomic-config.cmake common.copy /home/ted/git/boost/stage/lib/cmake/boost_atomic-1.85.0/libboost_atomic-variant-static.cmake common.copy /home/ted/git/boost/stage/lib/cmake/boost_filesystem-1.85.0/boost_filesystem-config-version.cmake gcc.compile.c++ bin.v2/libs/filesystem/build/gcc-14/release/threading-multi/visibility-hidden/unique_path.o libs/filesystem/src/unique_path.cpp:57:10: fatal error: boost/scope/unique_fd.hpp: No such file or directory 57 | #include <boost/scope/unique_fd.hpp> | ^~~~~~~~~~~~~~~~~~~~~~~~~~~ compilation terminated. "g++" -fvisibility-inlines-hidden -fPIC -m64 -pthread -O3 -finline-functions -Wno-inline -Wall -fvisibility=hidden -DBOOST_ALL_NO_LIB=1 -DBOOST_ATOMIC_DYN_LINK=1 -DBOOST_COBALT_USE_STD_PMR=1 -DBOOST_FILESYSTEM_DYN_LINK=1 -DBOOST_FILESYSTEM_HAS_DIRENT_D_TYPE -DBOOST_FILESYSTEM_HAS_FALLOCATE -DBOOST_FILESYSTEM_HAS_FDOPENDIR_NOFOLLOW -DBOOST_FILESYSTEM_HAS_INIT_PRIORITY -DBOOST_FILESYSTEM_HAS_POSIX_AT_APIS -DBOOST_FILESYSTEM_HAS_STATX -DBOOST_FILESYSTEM_HAS_STAT_ST_BLKSIZE -DBOOST_FILESYSTEM_HAS_STAT_ST_MTIM -DBOOST_FILESYSTEM_NO_CXX20_ATOMIC_REF -DBOOST_FILESYSTEM_SOURCE -DNDEBUG -I"." -I"libs/filesystem/src" -c -o "bin.v2/libs/filesystem/build/gcc-14/release/threading-multi/visibility-hidden/unique_path.o" "libs/filesystem/src/unique_path.cpp" ...failed gcc.compile.c++ bin.v2/libs/filesystem/build/gcc-14/release/threading-multi/visibility-hidden/unique_path.o... gcc.compile.c++ bin.v2/libs/filesystem/build/gcc-14/release/link-static/threading-multi/visibility-hidden/unique_path.o libs/filesystem/src/unique_path.cpp:57:10: fatal error: boost/scope/unique_fd.hpp: No such file or directory 57 | #include <boost/scope/unique_fd.hpp> | ^~~~~~~~~~~~~~~~~~~~~~~~~~~ compilation terminated. "g++" -fvisibility-inlines-hidden -m64 -pthread -O3 -finline-functions -Wno-inline -Wall -fvisibility=hidden -DBOOST_ALL_NO_LIB=1 -DBOOST_ATOMIC_STATIC_LINK=1 -DBOOST_COBALT_USE_STD_PMR=1 -DBOOST_FILESYSTEM_HAS_DIRENT_D_TYPE -DBOOST_FILESYSTEM_HAS_FALLOCATE -DBOOST_FILESYSTEM_HAS_FDOPENDIR_NOFOLLOW -DBOOST_FILESYSTEM_HAS_INIT_PRIORITY -DBOOST_FILESYSTEM_HAS_POSIX_AT_APIS -DBOOST_FILESYSTEM_HAS_STATX -DBOOST_FILESYSTEM_HAS_STAT_ST_BLKSIZE -DBOOST_FILESYSTEM_HAS_STAT_ST_MTIM -DBOOST_FILESYSTEM_NO_CXX20_ATOMIC_REF -DBOOST_FILESYSTEM_SOURCE -DBOOST_FILESYSTEM_STATIC_LINK=1 -DNDEBUG -I"." -I"libs/filesystem/src" -c -o "bin.v2/libs/filesystem/build/gcc-14/release/link-static/threading-multi/visibility-hidden/unique_path.o" "libs/filesystem/src/unique_path.cpp" ...failed gcc.compile.c++ bin.v2/libs/filesystem/build/gcc-14/release/link-static/threading-multi/visibility-hidden/unique_path.o... gcc.compile.c++ bin.v2/libs/filesystem/build/gcc-14/release/threading-multi/visibility-hidden/directory.o libs/filesystem/src/directory.cpp:42:10: fatal error: boost/scope/unique_fd.hpp: No such file or directory 42 | #include <boost/scope/unique_fd.hpp> | ^~~~~~~~~~~~~~~~~~~~~~~~~~~ compilation terminated. "g++" -fvisibility-inlines-hidden -fPIC -m64 -pthread -O3 -finline-functions -Wno-inline -Wall -fvisibility=hidden -DBOOST_ALL_NO_LIB=1 -DBOOST_ATOMIC_DYN_LINK=1 -DBOOST_COBALT_USE_STD_PMR=1 -DBOOST_FILESYSTEM_DYN_LINK=1 -DBOOST_FILESYSTEM_HAS_DIRENT_D_TYPE -DBOOST_FILESYSTEM_HAS_FALLOCATE -DBOOST_FILESYSTEM_HAS_FDOPENDIR_NOFOLLOW -DBOOST_FILESYSTEM_HAS_INIT_PRIORITY -DBOOST_FILESYSTEM_HAS_POSIX_AT_APIS -DBOOST_FILESYSTEM_HAS_STATX -DBOOST_FILESYSTEM_HAS_STAT_ST_BLKSIZE -DBOOST_FILESYSTEM_HAS_STAT_ST_MTIM -DBOOST_FILESYSTEM_NO_CXX20_ATOMIC_REF -DBOOST_FILESYSTEM_SOURCE -DNDEBUG -I"." -I"libs/filesystem/src" -c -o "bin.v2/libs/filesystem/build/gcc-14/release/threading-multi/visibility-hidden/directory.o" "libs/filesystem/src/directory.cpp" ...failed gcc.compile.c++ bin.v2/libs/filesystem/build/gcc-14/release/threading-multi/visibility-hidden/directory.o... gcc.compile.c++ bin.v2/libs/filesystem/build/gcc-14/release/link-static/threading-multi/visibility-hidden/directory.o libs/filesystem/src/directory.cpp:42:10: fatal error: boost/scope/unique_fd.hpp: No such file or directory 42 | #include <boost/scope/unique_fd.hpp> | ^~~~~~~~~~~~~~~~~~~~~~~~~~~ compilation terminated. "g++" -fvisibility-inlines-hidden -m64 -pthread -O3 -finline-functions -Wno-inline -Wall -fvisibility=hidden -DBOOST_ALL_NO_LIB=1 -DBOOST_ATOMIC_STATIC_LINK=1 -DBOOST_COBALT_USE_STD_PMR=1 -DBOOST_FILESYSTEM_HAS_DIRENT_D_TYPE -DBOOST_FILESYSTEM_HAS_FALLOCATE -DBOOST_FILESYSTEM_HAS_FDOPENDIR_NOFOLLOW -DBOOST_FILESYSTEM_HAS_INIT_PRIORITY -DBOOST_FILESYSTEM_HAS_POSIX_AT_APIS -DBOOST_FILESYSTEM_HAS_STATX -DBOOST_FILESYSTEM_HAS_STAT_ST_BLKSIZE -DBOOST_FILESYSTEM_HAS_STAT_ST_MTIM -DBOOST_FILESYSTEM_NO_CXX20_ATOMIC_REF -DBOOST_FILESYSTEM_SOURCE -DBOOST_FILESYSTEM_STATIC_LINK=1 -DNDEBUG -I"." -I"libs/filesystem/src" -c -o "bin.v2/libs/filesystem/build/gcc-14/release/link-static/threading-multi/visibility-hidden/directory.o" "libs/filesystem/src/directory.cpp" ...failed gcc.compile.c++ bin.v2/libs/filesystem/build/gcc-14/release/link-static/threading-multi/visibility-hidden/directory.o... gcc.compile.c++ bin.v2/libs/filesystem/build/gcc-14/release/threading-multi/visibility-hidden/operations.o libs/filesystem/src/operations.cpp:120:10: fatal error: boost/scope/unique_fd.hpp: No such file or directory 120 | #include <boost/scope/unique_fd.hpp> | ^~~~~~~~~~~~~~~~~~~~~~~~~~~ compilation terminated. "g++" -fvisibility-inlines-hidden -fPIC -m64 -pthread -O3 -finline-functions -Wno-inline -Wall -fvisibility=hidden -DBOOST_ALL_NO_LIB=1 -DBOOST_ATOMIC_DYN_LINK=1 -DBOOST_COBALT_USE_STD_PMR=1 -DBOOST_FILESYSTEM_DYN_LINK=1 -DBOOST_FILESYSTEM_HAS_DIRENT_D_TYPE -DBOOST_FILESYSTEM_HAS_FALLOCATE -DBOOST_FILESYSTEM_HAS_FDOPENDIR_NOFOLLOW -DBOOST_FILESYSTEM_HAS_INIT_PRIORITY -DBOOST_FILESYSTEM_HAS_POSIX_AT_APIS -DBOOST_FILESYSTEM_HAS_STATX -DBOOST_FILESYSTEM_HAS_STAT_ST_BLKSIZE -DBOOST_FILESYSTEM_HAS_STAT_ST_MTIM -DBOOST_FILESYSTEM_NO_CXX20_ATOMIC_REF -DBOOST_FILESYSTEM_SOURCE -DNDEBUG -I"." -I"libs/filesystem/src" -c -o "bin.v2/libs/filesystem/build/gcc-14/release/threading-multi/visibility-hidden/operations.o" "libs/filesystem/src/operations.cpp" ...failed gcc.compile.c++ bin.v2/libs/filesystem/build/gcc-14/release/threading-multi/visibility-hidden/operations.o... ...skipped <pbin.v2/libs/filesystem/build/gcc-14/release/threading-multi/visibility-hidden>libboost_filesystem.so.1.85.0 for lack of <pbin.v2/libs/filesystem/build/gcc-14/release/threading-multi/visibility-hidden>directory.o... ...skipped <p/home/ted/git/boost/stage/lib>libboost_filesystem.so.1.85.0 for lack of <pbin.v2/libs/filesystem/build/gcc-14/release/threading-multi/visibility-hidden>libboost_filesystem.so.1.85.0... ...skipped <p/home/ted/git/boost/stage/lib>libboost_filesystem.so for lack of <p/home/ted/git/boost/stage/lib>libboost_filesystem.so.1.85.0... ...skipped <pbin.v2/libs/filesystem/build/gcc-14/release/threading-multi/visibility-hidden>libboost_filesystem-variant-shared.cmake for lack of <pbin.v2/libs/filesystem/build/gcc-14/release/threading-multi/visibility-hidden>libboost_filesystem.so.1.85.0... ...skipped <p/home/ted/git/boost/stage/lib/cmake/boost_filesystem-1.85.0>libboost_filesystem-variant-shared.cmake for lack of <pbin.v2/libs/filesystem/build/gcc-14/release/threading-multi/visibility-hidden>libboost_filesystem-variant-shared.cmake... gcc.compile.c++ bin.v2/libs/filesystem/build/gcc-14/release/link-static/threading-multi/visibility-hidden/operations.o libs/filesystem/src/operations.cpp:120:10: fatal error: boost/scope/unique_fd.hpp: No such file or directory 120 | #include <boost/scope/unique_fd.hpp> | ^~~~~~~~~~~~~~~~~~~~~~~~~~~ compilation terminated. "g++" -fvisibility-inlines-hidden -m64 -pthread -O3 -finline-functions -Wno-inline -Wall -fvisibility=hidden -DBOOST_ALL_NO_LIB=1 -DBOOST_ATOMIC_STATIC_LINK=1 -DBOOST_COBALT_USE_STD_PMR=1 -DBOOST_FILESYSTEM_HAS_DIRENT_D_TYPE -DBOOST_FILESYSTEM_HAS_FALLOCATE -DBOOST_FILESYSTEM_HAS_FDOPENDIR_NOFOLLOW -DBOOST_FILESYSTEM_HAS_INIT_PRIORITY -DBOOST_FILESYSTEM_HAS_POSIX_AT_APIS -DBOOST_FILESYSTEM_HAS_STATX -DBOOST_FILESYSTEM_HAS_STAT_ST_BLKSIZE -DBOOST_FILESYSTEM_HAS_STAT_ST_MTIM -DBOOST_FILESYSTEM_NO_CXX20_ATOMIC_REF -DBOOST_FILESYSTEM_SOURCE -DBOOST_FILESYSTEM_STATIC_LINK=1 -DNDEBUG -I"." -I"libs/filesystem/src" -c -o "bin.v2/libs/filesystem/build/gcc-14/release/link-static/threading-multi/visibility-hidden/operations.o" "libs/filesystem/src/operations.cpp" ...failed gcc.compile.c++ bin.v2/libs/filesystem/build/gcc-14/release/link-static/threading-multi/visibility-hidden/operations.o... ...skipped <pbin.v2/libs/filesystem/build/gcc-14/release/link-static/threading-multi/visibility-hidden>libboost_filesystem.a(clean) for lack of <pbin.v2/libs/filesystem/build/gcc-14/release/link-static/threading-multi/visibility-hidden>directory.o... ...skipped <pbin.v2/libs/filesystem/build/gcc-14/release/link-static/threading-multi/visibility-hidden>libboost_filesystem.a for lack of <pbin.v2/libs/filesystem/build/gcc-14/release/link-static/threading-multi/visibility-hidden>directory.o... ...skipped <p/home/ted/git/boost/stage/lib>libboost_filesystem.a for lack of <pbin.v2/libs/filesystem/build/gcc-14/release/link-static/threading-multi/visibility-hidden>libboost_filesystem.a... ...skipped <pbin.v2/libs/filesystem/build/gcc-14/release/link-static/threading-multi/visibility-hidden>libboost_filesystem-variant-static.cmake for lack of <pbin.v2/libs/filesystem/build/gcc-14/release/link-static/threading-multi/visibility-hidden>libboost_filesystem.a... ...skipped <p/home/ted/git/boost/stage/lib/cmake/boost_filesystem-1.85.0>libboost_filesystem-variant-static.cmake for lack of <pbin.v2/libs/filesystem/build/gcc-14/release/link-static/threading-multi/visibility-hidden>libboost_filesystem-variant-static.cmake... ...updated 30 targets... ...skipped 10 targets... <p/home/ted/git/boost/stage/lib/cmake/boost_filesystem-1.85.0>libboost_filesystem-variant-shared.cmake <p/home/ted/git/boost/stage/lib/cmake/boost_filesystem-1.85.0>libboost_filesystem-variant-static.cmake <p/home/ted/git/boost/stage/lib>libboost_filesystem.a <p/home/ted/git/boost/stage/lib>libboost_filesystem.so <p/home/ted/git/boost/stage/lib>libboost_filesystem.so.1.85.0 <pbin.v2/libs/filesystem/build/gcc-14/release/link-static/threading-multi/visibility-hidden>libboost_filesystem-variant-static.cmake <pbin.v2/libs/filesystem/build/gcc-14/release/link-static/threading-multi/visibility-hidden>libboost_filesystem.a <pbin.v2/libs/filesystem/build/gcc-14/release/link-static/threading-multi/visibility-hidden>libboost_filesystem.a(clean) <pbin.v2/libs/filesystem/build/gcc-14/release/threading-multi/visibility-hidden>libboost_filesystem-variant-shared.cmake <pbin.v2/libs/filesystem/build/gcc-14/release/threading-multi/visibility-hidden>libboost_filesystem.so.1.85.0 ...failed updating 6 targets... gcc.compile.c++ bin.v2/libs/filesystem/build/gcc-14/release/link-static/threading-multi/visibility-hidden/directory.o gcc.compile.c++ bin.v2/libs/filesystem/build/gcc-14/release/link-static/threading-multi/visibility-hidden/operations.o gcc.compile.c++ bin.v2/libs/filesystem/build/gcc-14/release/link-static/threading-multi/visibility-hidden/unique_path.o gcc.compile.c++ bin.v2/libs/filesystem/build/gcc-14/release/threading-multi/visibility-hidden/directory.o gcc.compile.c++ bin.v2/libs/filesystem/build/gcc-14/release/threading-multi/visibility-hidden/operations.o gcc.compile.c++ bin.v2/libs/filesystem/build/gcc-14/release/threading-multi/visibility-hidden/unique_path.o

4 4

Problem with building 1.85.0
by Ted Lyngmo 13 May '24

13 May '24

Hi! First, I'm not sure if this is the right place for this. https://svn.boost.org/trac/boost seems to be down so I'm not sure where to turn. When I try building 1.85 on Fedora 40 with g++ (GCC) 14.1.1 20240507 (Red Hat 14.1.1-1) I run into a problem. I'm preparing the build like this: git co master && \ git pull -r && \ git co boost-1.85.0 && \ git submodule update --recursive && \ ./bootstrap.sh --with-libraries=all --with-icu \ -with-python-version=3.12.3 --prefix=/home/ted/local && \ echo 'using mpi ;' >> project-config.jam Then building like this: ./b2 -j8 install It however ends like this: ... ...updated 18621 targets... ...skipped 30 targets... <p/home/ted/local/lib/cmake/boost_fiber-1.85.0>libboost_fiber-variant-shared.cmake <p/home/ted/local/lib/cmake/boost_filesystem-1.85.0>libboost_filesystem-variant-shared.cmake <p/home/ted/local/lib/cmake/boost_filesystem-1.85.0>libboost_filesystem-variant-static.cmake <p/home/ted/local/lib/cmake/boost_log-1.85.0>libboost_log-variant-shared.cmake <p/home/ted/local/lib/cmake/boost_log_setup-1.85.0>libboost_log_setup-variant-shared.cmake <p/home/ted/local/lib/cmake/boost_wave-1.85.0>libboost_wave-variant-shared.cmake <p/home/ted/local/lib>libboost_fiber.so <p/home/ted/local/lib>libboost_fiber.so.1.85.0 <p/home/ted/local/lib>libboost_filesystem.a <p/home/ted/local/lib>libboost_filesystem.so <p/home/ted/local/lib>libboost_filesystem.so.1.85.0 <p/home/ted/local/lib>libboost_log.so <p/home/ted/local/lib>libboost_log.so.1.85.0 <p/home/ted/local/lib>libboost_log_setup.so <p/home/ted/local/lib>libboost_log_setup.so.1.85.0 <p/home/ted/local/lib>libboost_wave.so <p/home/ted/local/lib>libboost_wave.so.1.85.0 <pbin.v2/libs/fiber/build/gcc-14/release/threading-multi/visibility-hidden>libboost_fiber-variant-shared.cmake <pbin.v2/libs/fiber/build/gcc-14/release/threading-multi/visibility-hidden>libboost_fiber.so.1.85.0 <pbin.v2/libs/filesystem/build/gcc-14/release/link-static/threading-multi/visibility-hidden>libboost_filesystem-variant-static.cmake <pbin.v2/libs/filesystem/build/gcc-14/release/link-static/threading-multi/visibility-hidden>libboost_filesystem.a <pbin.v2/libs/filesystem/build/gcc-14/release/link-static/threading-multi/visibility-hidden>libboost_filesystem.a(clean) <pbin.v2/libs/filesystem/build/gcc-14/release/threading-multi/visibility-hidden>libboost_filesystem-variant-shared.cmake <pbin.v2/libs/filesystem/build/gcc-14/release/threading-multi/visibility-hidden>libboost_filesystem.so.1.85.0 <pbin.v2/libs/log/build/gcc-14/release/threading-multi/visibility-hidden>libboost_log-variant-shared.cmake <pbin.v2/libs/log/build/gcc-14/release/threading-multi/visibility-hidden>libboost_log.so.1.85.0 <pbin.v2/libs/log/build/gcc-14/release/threading-multi/visibility-hidden>libboost_log_setup-variant-shared.cmake <pbin.v2/libs/log/build/gcc-14/release/threading-multi/visibility-hidden>libboost_log_setup.so.1.85.0 <pbin.v2/libs/wave/build/gcc-14/release/threading-multi/visibility-hidden>libboost_wave-variant-shared.cmake <pbin.v2/libs/wave/build/gcc-14/release/threading-multi/visibility-hidden>libboost_wave.so.1.85.0 ...failed updating 6 targets... gcc.compile.c++ bin.v2/libs/filesystem/build/gcc-14/release/link-static/threading-multi/visibility-hidden/directory.o gcc.compile.c++ bin.v2/libs/filesystem/build/gcc-14/release/link-static/threading-multi/visibility-hidden/operations.o gcc.compile.c++ bin.v2/libs/filesystem/build/gcc-14/release/link-static/threading-multi/visibility-hidden/unique_path.o gcc.compile.c++ bin.v2/libs/filesystem/build/gcc-14/release/threading-multi/visibility-hidden/directory.o gcc.compile.c++ bin.v2/libs/filesystem/build/gcc-14/release/threading-multi/visibility-hidden/operations.o gcc.compile.c++ bin.v2/libs/filesystem/build/gcc-14/release/threading-multi/visibility-hidden/unique_path.o Building boost-1.84.0, or earlier, the same way doesn't show any signs of problems. Is my bootstrapping done in the wrong way? I've used the same way for a long time, but I might just have been lucky that it has worked :) Br, Ted

2 1

What is this "Beman Project Development"?
by René Ferdinand Rivera Morell 12 May '24

12 May '24

I got the email below from discourse.boost.org (I had subscribed long ago). So getting something was not unexpected. What I'm wondering about are this: Q: What is this new "Beman Project Development" thing about? A: It's something from C++Now initiated by The Boost Foundation (DBA) Q: Did they get permission from the Beman family to use Beman Dawes' name this way? A: ?? ---------- Forwarded message --------- From: Jeff Garland via Beman Project <notifications(a)boost.discoursemail.com> Date: Fri, May 3, 2024 at 10:19 AM Subject: [Beman Project] [Beman Project Development] Becoming a member of the beman-project github Jeff-Garland <https://discourse.boost.org/u/jeff-garland> May 3 Please send your github id to @Jeff-Garland <https://discourse.boost.org/u/jeff-garland> @dsankel <https://discourse.boost.org/u/dsankel> or @bretbrownjr <https://discourse.boost.org/u/bretbrownjr> via DM. ------------------------------ Visit Topic <https://discourse.boost.org/t/becoming-a-member-of-the-beman-project-github…> or reply to this email to respond. To unsubscribe from these emails, click here <https://discourse.boost.org/email/unsubscribe/63382355ff9c551129d38f2a59078…> . -- -- René Ferdinand Rivera Morell -- Don't Assume Anything -- No Supone Nada -- Robot Dreams - http://robot-dreams.net

13 43

[boost.QVM] can you explain quaternions in the docs?
by Andrzej Krzemienski 12 May '24

12 May '24

Hi Everyone, I landed on this library docs when trying to learn what quarterions are for. Although the library has a vast documentation it doesn't explain what quaternions are and why they are used. When I was taught algebra for the purpose of computer graphics, vectors and matrices were on the table, but no quaternions. The examples show that I need to create a quaternion only to turn it into a rotation matrix. I am pretty sure there has to be more to it. Could I request an introduction section in the docs that would explain what quaternions are and why one would want to use them? The corresponding GitHub issue: https://github.com/boostorg/qvm/issues/51 Regards, &rzej;

5 5

What is this "Beman Project Development" exactly
by Robert Ramey 10 May '24

10 May '24

I confess that I'm totally mystified by this. I've looked over the web page and it doesn't help me. Here is the "mission statement" from the Boost Foundation website: "The Boost Foundation’s broad C++ mission is: (a) development of high quality, expert reviewed, legally unencumbered, open-source libraries, (b) inspiring standard enhancements, and (c) advancing and disseminating software development best practices. It does this by fostering community engagement, nurturing leaders, providing necessary financial/legal support, and making directional decisions in the event of Boost community deadlock." "Equally important to our mission is the guidance provided by our shared values. These are transparency, inclusivity, consensus-building, federated authorship, and community-driven leadership." Here is the "mission statement" from the Beman Project: "The Beman Project’s mission is to support the efficient design and adoption of the highest quality C++ Standard libraries through implementation experience, user feedback, and technical expertise. Founded at C++Now in 2024 the project strives to aggregate libraries proposed for ISO standardization making a simple usage experience for the C++ Community to try out new libraries. For library authors we assist by helping to make best modern development practices easy. Including CI, coverage, and packaging." Seems to me that they are essentially the same with different wording (excluding the woke paragraph it the Boost Foundation version. A couple miscellaneous questions: a) Why is the Boost Foundation website not part of the Boost.org website? b) So what's the point of all this? Who has promoted/championed it? What is their motivation. Extremely odd to me. add your own questions here. Personally I'd like to see the following: a) consolidation of all this under one umbrella b) More transparency in selection of board of directors. More direct influence on the part of library creators and users. I don't have any idea how to achieve this without creating caos though. c) Distancing Boost from the C++ standard. Boosts original mission was accomplished when the standards committee incorporated a large part of boost directly into the standard. Since then boost's policy of working with the standard library is very confusing. Are we an alternative? or are trying to create new (better?) standard library components. Or are we trying to create canonical implementations of the standard library components? The standard committee is flailing around itself. Three way branch? executors? Does something as elaborate as ranges belong in a standard library? What about testing the standard library? How do we do this? or Not. Do I incorporate the standard library in my heart pacemaker app? Without being able to test any of it? Oh let's not forget "modules" I've been reading up on it and it seems at most a half-baked idea. So boost should only focus on the standard to the extent that it needs to in order to make it's own libraries work. Sorry, I'm just not understanding any of this. Robert Ramey

7 11

Boost Foundation annual meeting in Aspen
by David Sankel 07 May '24

07 May '24

Hi all! We held our annual Boost Foundation meeting at C++Now last week. At this annual meeting we elect officers for an annual term and directors for staggering two-year terms. Glen Fernandes and Peter Dimov had terms expiring this year and were re-elected for another two-year term. We additionally added Matthew Guidry, who has been regularly active in foundation work, to the director roster. Congrats Matthew! Class A (Terms Expiring 2025) - Bob Steagall [BS] - David Sankel [DS] - Michael Caisse [MJC] - Zach Laine [ZL] - Inbal Levi [IL] - Jeff Garland [JG] - Kristen Shaker [KS] Class B (Terms Expiring 2026) - Glen Fernandes [GF] - Peter Dimov [PD] - Matthew Guidry [MG] - (4 vacant slots) We additionally made officer selections. I will continue for another year as Executive Director, but have stepped down as Chair of the Board of Directors. Kristen Shaker has volunteered to take this on (congrats Kristen!). Zach Laine has agreed to take on the Safety and Inclusion Chair role in her place. Here is the list of officers: - Board of Directors, Chair: Kristen Shaker - Board of Directors, Vice Chair: Glen Fernandes - Conference Chair: Bob Steagall - Director of Summer of Code: Inbal Levi - Executive Director: David Sankel - Secretary: Michael Caisse - Treasurer: Zach Laine - Standardization Chair: Jeff Garland - Safety and Inclusion Chair: Zach Laine We also decided to take down discourse.boost.org due to a general lack of interest by those active in the Boost project. The instance will be utilized by the Beman project <https://www.bemanproject.org/>, an independent initiative focused on providing implementations of libraries proposed for the C++ standard. That's all for now! -- David

1 0

Looking for review manager for async_mqtt
by Takatoshi Kondo 06 May '24

06 May '24

Hi, I've proposed a MQTT communication library based on Boost.Asio. https://github.com/redboltz/async_mqtt Fortunately, I got two endorsements, so far. Thank you Klemens and JoaquÃn. https://lists.boost.org/Archives/boost/2024/04/256650.php https://lists.boost.org/Archives/boost/2024/04/index.php However, I couldn't find a review manager, so far. https://www.boost.org/development/submissions.html I think that I am at step4 and step5 in the Boost Library Submission Process. I'm looking for review managers for async_mqtt now. I think that Boost.Beast, Boost.MySQL, and Boost.Redis are developed on Boost.Asio. I referred to those libraries for async_mqtt development. async_mqtt is using Boost.Beast for WebSocket communication. If those libraries developers would be interested in review managers, I would appreciate it. Of course, any other people are welcome. Best Regards, Takatoshi Kondo

1 0

GSOC '24 at Boost
by David Bellot 05 May '24

05 May '24

Hi all, Another year, another GSOC's coming! As you all know now, Inbal is in charge of managing our GSOC program at Boost. Over the past years, I had the pleasure to work with many of you and we had the chance to have many great students and mentors. This year, however, it seems we don't have enough mentors yet. I know it's just the beginning of the year, but I would like to encourage you to join this program as a mentor, and help students to participate in Boost and become great C++ developers. It's a very rewarding journey I took myself years ago and you will learn so much, both on the technical and human side. If you want to become a mentor, just add your name to this shared spreadsheet: https://docs.google.com/spreadsheets/d/1_eUWRsXnhi_JwKZbHZsGQf3WNUESsAPE4lV… Cheers, David

4 3

Compression libraries such as zlib and zstd ought to be first class boost libraries
by Nigel Stewart 05 May '24

05 May '24

Hello all, I've been having a fairly hard time enabling zlib and zstd for boost 1.85.0 so we can make use of the compression support in iostreams module. We do have some specifics - static linking, non-standard file names and not system-installed. Windows and Linux. For various reasons it looks like we're going to copy certain files into our modules, rather than puzzle over making this work. It's not ideal, but workable. But along the way it's become clear that this functionality is not first-class boost citizen. Such as the broken links in the documentation, and various historical questions via google reporting similar issues. There are also other copies of zlib in the beast tree, because it's obviously needed for HTTP stuff too. zstd too? So I did think that I should at least mention that zlib, zstd, bzip2 and xv-utils all ought to be promoted to first-class boost libraries even though the majority of the maintenance is coming from upstream. They ought to be part of the "big tarball" and enabled and built by default regardless of what happens to be installed on the system. The cmake stuff ought to "just work" the way it does for other boost modules. I'm not quite volunteering myself, but it seems like a start to pose the question. The developer experience could be significantly improved for this particular corner of things. - Nigel Stewart

7 24

Proposal for yet another MQTT library for Boost
by Takatoshi Kondo 01 May '24

01 May '24

Dear Boost Developers, I'd like to propose a MQTT library to the Boost Libraries. Repository link: https://github.com/redboltz/async_mqtt Document link: https://redboltz.github.io/async_mqtt/doc/5.0.0/index.html Here is characteristics of async_mqtt: - C++17 or later is required. - async_mqtt supports Boost.Asio style completion tokens. - e.g. use_future, deferred, use_awaitable, callback functions, etc - Not only MQTT client but also MQTT server is supported. - User can use this library to develop MQTT broker. - Sample MQTT broker application is included. - Both MQTT v3.1.1 and v5.0 are supported. - In addition, undetermined protocol version is supported for server implementation. In this case, the protocol version is decided when you receive CONNECT packet. - Continuous packet sending - Users can send the next MQTT packets before the previous sending is not completed (completion handler is not invoked yet). - Auto acquiring/mapping topic alias is supported. - In addition, when resending a PUBLISH packet after reconnecting, the topic alias is removed and the original topic is restored. It is required by MQTT v5.0 spec. - Packet based send()/recv() APIs. - MQTT has various packets and some of their fields are optional. In order to keep simple APIs, async_mqtt uses packet based APIs. - See https://redboltz.github.io/async_mqtt/doc/5.0.0/tutorial/send_recv.html - Layered archtecture - async_mqtt can have predefined TCP, TLS, WS, WSS, and user defined underlying layer. Users can access the underlying layer using next_layer() member function of MQTT endpoint. So you can configure any layers by yourself. e.g. tcp_no_delay, set send/recv buffer size, etc - See https://redboltz.github.io/async_mqtt/doc/5.0.0/tutorial/create_endpoint.ht… - High performance - See https://redboltz.github.io/async_mqtt/doc/5.0.0/performance.html Background I have developed another mqtt library mqtt_cpp https://github.com/redboltz/mqtt_cpp since 2015. It is widely used but has some limitations. For example: - The functions are directly mapped to packets(publish, subscribe, etc), so optional features are not designed cleanly. - Due to set_publish_hander / on_publish style handler design, Completion Token cannot be supported. Based on this 9years experience, I designed the new MQTT library. This is async_mqtt. I would appreciate if you could endorse this library. Regards, Takatoshi Kondo

3 4

Re: [boost] modern logic classes
by g.peterhoff＠t-online.de 29 Apr '24

29 Apr '24

Here is an update. Since a few boost libraries use tribool, these would have to be converted to bool3. Unfortunately it is not that easy to establish a new boost library. Especially if it is incompatible with previous implementations. thx Gero

1 0

Can we get rid of auto-linking?
by René Ferdinand Rivera Morell 29 Apr '24

29 Apr '24

Today I got bit by auto-linking again. As I forgot to define BOOST_ALL_NO_LIB in a CI build. I can't remember a time when auto-linking has been beneficial. And I've lost the number of times I've had to answer user questions with "Auto-linking is getting in the way. Define BOOST_ALL_NO_LIB and link normally." more times than I can count. If there was ever a benefit to auto-linking it has not surpassed the drawbacks. So.. Can we get rid of auto-linking? -- -- René Ferdinand Rivera Morell -- Don't Assume Anything -- No Supone Nada -- Robot Dreams - http://robot-dreams.net

7 15

Emitting complete type information in boost-python docstrings
by Jakob van Santen 29 Apr '24

29 Apr '24

Hello, I’m not sure if this is the right forum for this question, but here goes: I work on a large scientific codebase that is heavily tied to boost, and that most users interact with via boost-python. Lately I have been working on generating PEP 484 type stubs for the ~1000 classes it exposes in order to enable static type checking and code completion in editors. This required some modifications to boost-python itself in order to get complete type information into the generated docstrings, where it can be consumed by external tooling to generate stubs: https://github.com/boostorg/python/pull/417 I have found this quite useful, and suspect it might be useful for others as well to have it in a Boost release. Can anyone give me a pointer as to how to make that happen, or let me know where or whom I should be asking instead? I asked on cplusplus-sig(a)python.org <mailto:cplusplus-sig@python.org>, which was the place many years ago, but that list seems to have died out. Many thanks in advance! Cheers, Jakob ------------------------------------------------------- Jakob van Santen DESY - Deutsches Elektronen-Synchrotron Platanenallee 6, D-15738, Zeuthen Office 2L/32 +49 (0)33762-7-7233 -------------------------------------------------------

2 1

BOOST_THREAD_HAS_EINTR_BUG...
by David Bien 26 Apr '24

26 Apr '24

Not really sure where to bring this issue up. I have a singleton globals object with a session manager, share manager, etc. that is destroyed atexit() on final reference release. There are a few mutexes in the implementation. This functions fine on Windows, MacOS, etc - the globals object is released during atexit() and shutdown proceeds normally. Under Linux when BOOST_THREAD_HAS_EINTR_BUG is defined we SIGABRT at this: ~mutex() { BOOST_VERIFY(!posix::pthread_mutex_destroy(&m)); } The verify fails and we abort(). When I define BOOST_THREAD_HAS_NO_EINTR_BUG we do not abort - which means that posix::pthread_mutex_destroy() returns 0 in the case where BOOST_THREAD_HAS_NO_EINTR_BUG is defined and returns non-zero in the case of it not being defined. Guidance? Also point me at a better place for this discussion if there is such a place. Thanks, David Bien

3 10

question about singleton_pool
by 李重斌 26 Apr '24

26 Apr '24

I want to use singleton_pool to manage memory. This is just an example which tests it. My question: the first time i allocate 100 spot object, and free them. If i allocate some spot objects, and the number of them is less than 100. no more memory is needed, there is no need to allocate memory from os again. but the fact is another memory block is allocated. The first block is 4016 bytes (sizeof(Spot) = 40), the second block is 8016 bytes. This is not as my imagine. Is there something wrong with these code? ///////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////// std::cout << "size of Spot " << sizeof(Spot) << " bytes\n"; std::cout << "test singleton_pool firt time\n"; const size_t NumSpots = 100; Spot* p1 = static_cast<Spot*>(spot_pool::ordered_malloc(NumSpots)); for (size_t i = 0; i < NumSpots; i++) { p1[i].x = 1; p1[i].y = 1; } spot_pool::ordered_free(p1); std::cout << "test singleton_pool second time\n"; Spot* p2 = static_cast<Spot*>(spot_pool::ordered_malloc(NumSpots/2)); for (size_t i = 0; i < NumSpots/2; i++) { p2[i].x = 2; p2[i].y = 2; } spot_pool::ordered_free(p2); /////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////

1 0

UUID design discussion
by Peter Dimov 26 Apr '24

26 Apr '24

We've been discussing some UUID design issues in, well, issues in the Uuid repo, namely https://github.com/boostorg/uuid/issues/96 and, for context, https://github.com/boostorg/uuid/issues/113. This topic might be of wide interest to developers, so I thought it would be better to have this list know about it. Anyone who has an opinion on the matter is welcome to express it in the issue, or here. In addition to the questions raised in #96, namely, how should the constructors and the accessors of `uuid` look like (once we somehow move away from the public `data` member), here are some more topics of interest: * Should a default-constructed `uuid` remain uninitialized, or should the default constructor produce the nil Uuid? (Uninitialized is not a good look in 2024 because safety. On the other hand, `new uuid[ 1048576 ]` will start doing a `memset`.) * At the moment wide strings are processed by the name generators by converting every wchar_t to 32 bit, then hashing the bytes, zeroes and all. This doesn't strike me as correct. I think that the string should be converted to UTF-8 on the fly (with 32 bit wchar_t assumed UTF-16 and 32 bit wchar_t assumed UTF-32.)

5 11

Re: [boost] modern logic classes
by g.peterhoff＠t-online.de 25 Apr '24

25 Apr '24

>> Hello, >> I would like to provide modern logic classes, please see https://github.com/boostorg/logic/issues/30 >> What are your opinions/comments on this? > Interesting idea. > But rather than messing with tribool, I'd prefer to just see a new library quadbool. I would also like tribool to be removed. But until then it still needs to be supported. regards Gero

1 0

[stacktrace] boost_stacktrace_from_exception on non-x86
by Tim Haines 24 Apr '24

24 Apr '24

This feature is guarded by BOOST_STACKTRACE_ALWAYS_STORE_IN_PADDING, but that is only enabled on x86 ( https://github.com/boostorg/stacktrace/blob/a33e198cf660c213e700d6f050a4641…) This means that ./bootstrap.sh --with-toolset=gcc --with-libraries=stacktrace ./b2 install threading=multi toolset=gcc always fails to build on non-x86 platforms. There are three current workarounds: 1) set boost.stacktrace.from_exception=off 2) set BOOST_STACKTRACE_LIBCXX_RUNTIME_MAY_CAUSE_MEMORY_LEAK 3) build with threading=single (1) prevents me from using this feature. (2) shouldn't be needed on it's face because I'm using gcc/libstdc++. (3) affects more than stacktrace. Is this an incidental error, or is there a reason I wasn't able to deduce as to why this feature can't be used on non-x86+libstdc++? It seems like the check for libc++ on non-x86 can't be entirely done at compile time. I definitely understand wanting to alert users to the dangers of using this feature, but there also doesn't seem to be a good way of detecting the presence of libc++ at compile time (hence the need for https://github.com/boostorg/stacktrace/blob/a33e198cf660c213e700d6f050a4641… ). Thanks. - Tim

1 0

Boost board update on website, twitter, etc.
by David Sankel 21 Apr '24

21 Apr '24

Hi all, We're overdue for a Boost website/Twitter status update as it relates to the board. In summary: - The board approved pointing boost.org to C++ Alliance servers running the new website once it's ready - The board is accepting a contribution from the C++ Alliance to upgrade the @Boost_Libraries Twitter account to premium, which simplifies delegation of credentials for posts - The C++ Alliance made their @BoostLibraries Twitter account private which means only its subscribers will see its posts. The website decision was made in the 3/28 board meeting which followed the 3/13 meeting where several on boost-dev were invited to the discussion. You can read the minutes here <https://docs.google.com/document/d/1zMKUX3nfdcOXT6nUIU4M_YRlCU4ywGoG40ouo3I…> . The website decision was not easy. There wasn't consensus in boost-dev nor on the board itself (it passed with 3 in favor, 2 against, and 1 abstention). However, a needed decision was made and I invite everyone to rally behind it and support its success. I want to thank Vinnie and those working for the C++ Alliance for their major Boost website contributions. I want to acknowledge the reviewers, active Boost authors, review managers, folks making releases, bug reporters, infrastructure maintainers, and the many others that contribute to Boost in various ways. These people constitute the Boost libraries project whose consensus is the primary means of community-wide decision making. The Boost Steering Committee (and now the Boost Foundation) was created by the Boost libraries project to make such decisions *only in the rare case of community deadlock*. While the Boost board is more than happy to provide feedback and financial support for Boost libraries initiatives, the board is taking its direction from the project and not the other way around. Thanks everyone for your passionate interest in Boost and I look forward to what comes next! David, Boost Foundation Chair

2 1

On Boost and modules: second part
by Ruben Perez 19 Apr '24

19 Apr '24

Hi all, Following the recent discussion on Boost and C++20 modules, I've been performing further investigations on the possible benefits and costs of offering module support in Boost. I've summarized my findings here: https://anarthal.github.io/cppblog/modules2 TL;DR: * While there isn't too much benefit for clean builds, incremental builds tend to be much faster with modules. * Right now, modularizing requires an effort for each modularized library. * Writing CMake files for module consumption won't be trivial. I'd like to know everyone's opinion on this: do you think these efforts would make sense? In the mid-term, this will require authors to review and merge module-related PRs, at the very least. I'm especially interested in hearing René and Peter's opinions, as maintainers of B2, Boost.CMake and many other core parts (as well as other authors'). If the community decides these efforts may be worthwhile, I volunteer to perform most of the required work. My first step would be to create a working prototype with a modularized Boost.Url (as a maintained, separately compiled library, with non-trivial dependencies), together with CMake tooling, to spot any pitfalls I've missed during my analysis. I'd also like to drag any present MSVC developers' attention on this bug which has nasty consequences on code like Asio: https://developercommunity.visualstudio.com/t/Using-%5f%5ftry-in-an-inline-… Thanks, Ruben.

4 4

[release] Boost 1.85.0 Release Candidate 3 is available
by Marshall Clow 18 Apr '24

18 Apr '24

The third release candidates for the 1.85.0 release are now available at: <https://boostorg.jfrog.io/artifactory/main/release/1.85.0/source/> The SHA256 checksums are as follows: e712fe7eb1b9ec37ac25102525412fb4d74e638996443944025791f48f29408a boost_1_85_0_rc3.zip 7009fe1faa1697476bdc7027703a2badb84e849b7b0baad5086b087b971f8617 boost_1_85_0_rc3.tar.bz2 16d16b9658753117c1434e5450c5eac194957f4b6d0b390b9d07900d37c115a4 boost_1_85_0_rc3.7z be0d91732d5b0cc6fbb275c7939974457e79b54d6f07ce2e3dfdd68bef883b0b boost_1_85_0_rc3.tar.gz The changes from RC1 are: * Boost.ASIO docs generate very long file names that are not usable on Windows. * Boost.Program options does not build in C++23 mode on clang truck (to be clang 19 before boost 1.86.0 is released) Note: It is possible that this is a bug in clang, and it’s in a clang that is not released yet. * Boost.Log has some broken links in its documentation. * A meaningless change to Boost.Array (add a space to a test file) Apparently the RC2 tarballs were mis-buiilt; some of them were missing the required changes. I believe that RC3 resolves that problem. 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 Release managers

10 25

A base64 library?
by Ruben Perez 17 Apr '24

17 Apr '24

Hi all, I've been thinking of writing a base64 encoder/decoder library for some time. I first found the need when writing ServerTech chat (https://github.com/anarthal/servertech-chat) and I couldn't find a library that suited my needs. All the libraries I could find were either forgotten one-day projects with no tests, or private parts of something bigger. >From this issue from Beast (https://github.com/boostorg/beast/issues/1710) it looks like this could be useful to people. My idea would be writing something that is: * Boost quality - extensive testing and fuzzing. * Configurable. My use case in ServerTech required me to not output padding chars, for instance. * Support for a streaming API. * Support for calling in a constexpr context. * I'd prefer to focus on doing base64 only and doing it well, rather than targeting arbitrary bases. I don't have any sample code yet. Following our recommendations, I'm only determining interest. My questions are: * Do you think a library like this could be useful to the C++ community? * If the answer to the above is yes, do you think it could belong to Boost, or would be better as a standalone library? Regards, Ruben.

13 30

Things I Hate (Re: New Website)
by Vinnie Falco 17 Apr '24

17 Apr '24

Now that we're here I want to tell you about some things I hate. To clear out any suspense they are: 1. April Fool's 2. Deadlines 3. New Boost Website April Fool's I can't stand this fauxliday and I refuse to participate. Every year sees the C++ community produce an outsized load of lame jokes. The problem, I think, is that comedy on some level has to come at someone else's expense. Good comedy at least. Our community is so damn politically correct that folks are afraid to make a really good joke for fear of getting canceled at some level. Deadlines I hate deadlines. People ask me "how long will this take" and honestly I have no idea. About a decade ago I stopped trying to estimate how long things take as I never was able to give a reasonably accurate answer. I'm good at writing the code, but figuring out how long it will take - not so much. During development, unanticipated stuff comes up. A discovered design flaw or implementation obstacle, which can't be predicted. These days I just figure that if a project is properly staffed and there is reasonable daily progress, eventually it will get finished. New Boost Website Well I don't hate the whole thing but there is definitely stuff which is bothering me. Like how long the thing is taking. Seems like it is still not ready to go up on boost.org. But more importantly I have to be honest... I'm not feeling this Cairo font. I am just going to come out and say it: the old Quickbook stylesheets are superior to the new stylesheets which render in Cairo. Compare: https://www.boost.org/doc/libs/1_85_0/libs/beast/doc/html/beast/ref/boost__… vs. https://www.boost.io/doc/libs/1_84_0/libs/beast/doc/html/beast/ref/boost__b… or https://www.boost.org/doc/libs/1_85_0/libs/beast/doc/html/beast/concepts/Dy… vs. https://www.boost.io/doc/libs/1_84_0/libs/beast/doc/html/beast/concepts/Dyn… The new one is better than it was a month ago, thanks to Julio our new frontend developer. But it is still not as good as the old one. I cannot in good conscience propose replacing something old with something new unless the new thing is demonstrably superior. Or at the very least, equally as good. So I think we still have work to do. Thanks

4 7

[release] The master branch is now open for all changes
by Marshall Clow 16 Apr '24

16 Apr '24

Next deadline: June 26th - Boost 1.86.0 closed for new libraries and breaking changes` As always, the calendar is at: https://www.boost.org/development/ — Marshall

1 0

Boost.Graph security issues
by Jeremy Murphy 13 Apr '24

13 Apr '24

Dear Boost community, I've recently received a few security issue notifications from both the Google Chrome fuzzer project and Shielder (part of an OSTIF project), and basically I'm not sure how much to worry about them. I don't have time to fix them (but I can review and merge fixes), and I don't know how to draw attention to the need to fix them without publicizing the issues (which are still not published). It all depends on how many people actually are exposed via Boost.Graph and to what severity, right? I have no idea, but my gut tells me not many, as most Boost.Graph users I hear about are just using it internally, not exposing the interfaces to input from the Internet. But I'm not a security expert, that's why I'm asking you. What should I do? Thanks, cheers. Jeremy

3 5

Re: [boost] Boost C++ in Australia
by Jeremy Murphy 13 Apr '24

13 Apr '24

Hi David, Hello from Sydney, at least for the next six months. I'd love to catch up, although finding time is hard. Cheers. Jeremy On Wed, 3 Apr 2024, 8:05 am David Bellot via Boost, <boost(a)lists.boost.org> wrote: > Hi all, > > reading through the Boost mailing list, I've realized several of you live > in the country of kangaroos and cute koalas (and great white sharks and > funnel web spiders too, thinking of it). > > As I am too, why don't we find a good opportunity to gather, hoping that > we're in the same city. If it's not the case, then chances are we are > "just" a few thousands kilometers away from each other! > > Let me know what you think > > Cheers, > David > > _______________________________________________ > Unsubscribe & other changes: > http://lists.boost.org/mailman/listinfo.cgi/boost >

1 0

Technical Excellence?
by Vinnie Falco 12 Apr '24

12 Apr '24

I guess I'm confused. My understanding is that libraries are considered good candidates for the Boost collection based on meeting some or all of certain criteria: * They offer useful, novel functionality not found elsewhere * The API is superior to other libraries that do similar things * The implementation is exceptionally performant * Solving a familiar problem in a particularly elegant fashion * The library is already popular and has field experience * The library offers C++ standard functionality for older compilers But some of the chatter on the mailing list suggests that the bar for a Boost library candidate is lower. That a library just needs to basically work, even if it duplicates functionality found elsewhere, or even if it does not have anything that one might hold up as an example of exceptional engineering. Boost libraries used to be cutting edge, to such an extent that they were adopted into the C++ Standard. And now the progress is in reverse. The Standard introduces a new component, and the Boost library follows (Boost.Charconv for example). In other cases I see libraries with few to no users limping into reviews, or absent discussions which question whether or not the bar for excellence is exceeded. When I used to participate in wg21 I complained about the "direct to standard" pipeline, where people would just write papers for the sake of it with no example code or real-world user experience. I have to wonder if we are not cultivating a "direct to Boost" pipeline by having relaxed or poorly-defined acceptance criteria. There are thousands of open-source libraries for doing things in a fashion that is "good enough." If libraries are not held to technical excellence and high standards during the review process then what is the value proposition of the collection? If libraries of average design and implementation are seen as passable for acceptance then how would this inspire any authors to strive for excellence? When I write a library there are always two factors in my mind: 1. that the use-case is compelling, and 2. that I can bring something to the table which demonstrates technical excellence. These are the libraries that I have contributed thus far and my process for designing them: 1. Boost.Beast This offers something never seen before which is a generic approach to HTTP and Websocket, based on Asio, which offers models and algorithms that are designed well (of course, it still has its flaws). The library already had many users ahead of the review, and was being used to transact economic value in a live product. I will note that my initial motivation for Beast was because the websocketpp library API was just terrible, and the alternatives even worse. 2. Boost.JSON When I needed JSON I looked at the alternatives and while RapidJSON was clearly the best in terms of performance I felt that it made several major design flaws in its API. Boost.JSON pretty much copies all of the good ideas from RapidJSON especially the performant implementation, and offers a redesigned API that follows C++ best practices with respect to copy and move, exceptions, and error codes. Furthermore I added the streaming parser and I introduced a novel means of managing memory resources which I believe corrects a design flaw in the standard. This library already had commercial users and lots of feedback before going into review. 3. Boost.URL Beast users regularly asked for URL parsing. There are some regex patterns floating around and some Spirit based parsers, and also some URL libraries that do the "five std::string data members" thing. I wanted something excellent, but the first two iterations of an API turned out to be crap and I gave up, as I do not like publishing mediocre libraries. Some time passed and with renewed energy I tried again and then I got it right. The URL is stored in its serialized form (just one string), allowing the possibility for having a url_view type in addition to the mutable container. I copied much of the API from a popular JS URL lib because, well hey why duplicate the effort if someone has already gone through the trouble :) Boost.URL offers particularly clean and robust interfaces for reading and modifying the values of each part of the URL both with and without the URL-encoding applied. The mechanism for lazily iterating the path and query sequences is novel. And it offers a strong invariant: the container will always contain a valid URL. The library further innovates by making public its parsing framework which is optimized for the type of grammars found in the Internet RFCs such as HTTP and the fields used in Websocket handshakes. Boost.URL had a bunch of users before the review was conducted. 4. Boost.StaticString This one is just a straightforward string container whose storage is fixed in capacity as a data member. Container libraries are often unexciting but they are necessary. StaticString follows all best practices for modern C++ containers. When I look at a proposed library I try to figure out what is great about it, how well it performs for its users (or even, does it have any users?), what part of the API is exceptionally well designed and ergonomic, but most importantly I want to ask: what makes this library stand out to the extent that it should be part of the library collection? What aspects of the library, if viewed by someone learning C++ or interested in improving their design skills, are inspirational? Is this overly demanding or exclusionary? Am I overthinking things? Should we be asking more of these types of questions and requiring better answers? What is the criteria for determining if a library is good enough to become part of the collection? Thanks

26 78

On Boost and modules
by Ruben Perez 12 Apr '24

12 Apr '24

Hi all, Following a recent conversation on the possibility to somehow enable Boost to be consumed using C++20 modules, I've jumped in and done a small research: https://anarthal.github.io/cppblog/modules René posted the link to r/cpp and it seems to have attracted some interest (https://www.reddit.com/r/cpp/comments/1bxggim/c20_modules_and_boost_an_anal…) It looks like a small fraction of users would consider consuming Boost as modules if there was the possibility (note that considering here is pretty far from actually doing it). Nevertheless, I'd like to know everyone's opinion on the subject. If we find a way to overcome the technical challenges that I manifest in the article, do you think a set of non-intrusive "module bindings" allowing users to consume Boost as a module could add any value to Boost? Thanks, Ruben.

14 62

Re: [boost] [release] Boost 1.85.0 Release Candidate 2 is available
by Glen Fernandes 11 Apr '24

11 Apr '24

I wrote: > I think we saw this before, but I couldn't figure it out: > https://github.com/boostorg/boost/issues/884 Many thanks to Sam Darwin for finding the cause (and looking into a long term solution in the new website release mechanism). Glen

1 0

[release] Boost 1.85.0 Release Candidate 2 is available
by Marshall Clow 11 Apr '24

11 Apr '24

The second release candidates for the 1.85.0 release are now available at: <https://boostorg.jfrog.io/artifactory/main/release/1.85.0/source/> The SHA256 checksums are as follows: 06bdbef025de63a22baf997d49d34f38455975529ee05ab73379338e572d0df4 boost_1_85_0_rc2.zip 623a9e5288bae94c0c01b733873ea12613af35f4fc433059a0ddaa5cf0033ce1 boost_1_85_0_rc2.tar.bz2 f7b6b252f488dc8a386bfc79bf7197772c4400f847f0dee50754bb23847d40d2 boost_1_85_0_rc2.7z ec9347228d2c8a7189685b48fe4609a837d3dde45973d4457a8f2396d2c446da boost_1_85_0_rc2.tar.gz The changes from RC1 are: * Boost.ASIO docs generate very long file names that are not usable on Windows. * Boost.Program options does not build in C++23 mode on clang truck (to be clang 19 before boost 1.86.0 is released) Note: It is possible that this is a bug in clang, and it’s in a clang that is not released yet. * Boost.Log has some broken links in its documentation. 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 Release managers

7 10

Is there an interest for an async JSON-RPC library in boost ?
by Quentin Chateau 11 Apr '24

11 Apr '24

A couple of years ago, I wrote packio, a library implementing asynchronous client and server for msgpack-rpc. Over time it evolved into something more generic, an async implementation of the JSON-RPC (https://www.jsonrpc.org/) spec with customizable serialization. It is built on top of asio, and boost.json is supported serializer. This means that with minimal efforts it could evolve into an implementation of JSON-RPC with no dependencies outside of boost - yet extendable. My question then is: is there an interest for it ? I'd probably need to invest a non trivial amount of time into making it boost-compliant and following up on the review process, so I'm wondering whether it is worth it or not. Note that there are two known limitations in my library: - No support for batch mode - No support for sharing a transport between a client and a server (not part of the spec, but requested by some users) I'm looking forward to get the community's opinion. You can check my library on GitHub (https://github.com/qchateau/packio) Feedback on either community's interest for such library, or plain comments on the library are welcome ! Quentin

6 5

Fwd: A proposal for a modern build-system
by Daniele Lupo 11 Apr '24

11 Apr '24

On 23/03/2024 13:16, Hassan Sajjad wrote: > Hi. > > Could you please confirm if my proposal is under consideration? If so, > when can I expect an update regarding its status? > > Sorry for the delay, I had personal issues during those days. I've read the thread, and since now I can't see any serious issue or problem that make me think that the actual build system must be replaced. Maybe updated, but not replaced. For explaining more in detail my point of view (that, I will not ever repeat too many times, it's my personal one, so other people can have other ideas about it): - Boost does not pay people (as far as I know). You're asking for compensation in the first message, but nodoby will pay it, and nodoby asked for it. - I agree with others that three month of development are a bit too optimistic, and also in this case we must maintain two different build systems instead that one. - In the thread I've read many messages like "b2 can do this", "well, also hmake", but no messages like "hmake can do it and b2 it's not able to do it" "oh really? I'd love to have it!". I don't see any important use case that's requested by the community and that hmake will provide while b2 not. So the community wil use hmake to do the same things that at the moment it does with b2. - There's already another build system, even if not much official, and that's cmake. It works well and it's widely used, and that's supported by many package managers, like vcpkg. I have to say that hmake will not be used by them, so it will be limited to the scope of build boost like b2 actually does. Even in this case, it does not add anything. Basically, in the entire thread, in my opinion, there's not a single point that le me think that hmake will make the like easier to boost community. At most we'll have another tool that make the same things. And, repeating myself, I can see that new features actually not supported by b2, pratically modules, are easier to be implemented in b2 instead of using another build system and obligate the entire community to learn another tool for a feature that for now only a few of them will use. In addition to this, I strongly think that instead of a new build system I'll spend some effort, if necessary, in improving existing alternatives, like cmake, that are already widely used by the developer community around the world. Regards Daniele Lupo

4 6

[release] Boost 1.85.0 Release Candidate 1 is available
by Marshall Clow 08 Apr '24

08 Apr '24

The first release candidates for the 1.85.0 release are now available at: <https://boostorg.jfrog.io/artifactory/main/release/1.85.0/source/> The SHA256 checksums are as follows: de84c538aaadf2388362e006d73d0be783541288d87a9ef68e906995efc2148d boost_1_85_0_rc1.tar.gz dd8baccd0b5ca534ad3717a07b426391fe6d49b6b84bf07d10e72792a5d1ba10 boost_1_85_0_rc1.7z 289ab7784b9297e13938876f698ced91f734f9a80f91099d35803b78d15c0210 boost_1_85_0_rc1.tar.bz2 84c35ef72efde30725de7bca8ccf399cd8d205a0d5b249465cf86c818291b7b7 boost_1_85_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 Release managers

8 22

[release] status of the Boost release
by Marshall Clow 08 Apr '24

08 Apr '24

The RC1 has been tested, and three problems have been reported (so far) * Boost.ASIO docs generate very long file names that are not usable on Windows. * Boost.Program options does not build in C++23 mode on clang truck (to be clang 19 before boost 1.86.0 is released) Note: It is possible that this is a bug in clang, and it’s in a clang that is not released yet. * Boost.Log has some broken links in its documentation. And … Some additional libraries no longer build under C++03. (More than 1.84.0) The first one is the one that will impact the most people. Given that we want to fix that, we should fix the other two. I have asked the maintainers to merge the fixes to master. I will be out “watching the sky” tomorrow, but I will turn an RC2 either tomorrow night or Tuesday AM. This means that the release will almost certainly be delayed a couple of days past Wednesday. — Marshall

1 0

Interest in a library for type-safe bitwise operations?
by tobi＠die-loews.de 06 Apr '24

06 Apr '24

Hi, I would like to gauge interest in a library that makes the usage of flag-like enumerations safer. The library is called Boost.Flags, and its key features are - provides type-safe bitwise operations for flag-like scoped / unscoped enumerations - turns undetected logical errors into type errors Further characteristics are - non-intrusive - only a function overload or a template specialization required to opt-in - single header-file library - no dependencies (only standard-library includes) - everything is constexpr - zero-overhead in optimized builds - requires at least C++11, uses newer features if available From the Boost.Flags documentation: > Why do we use the bits of integer types for Boolean options? > > - easy to define, e.g. as macros, integer constants or enumerators > - language support for setting and querying through bitwise operators > - compact representation in memory > - simple bulk transfer in interfaces (on many platforms an int can > hold up to 32 different Boolean options) > - enforces the usage of names, especially to prevent bool parameters > in interfaces: > - "Boolean arguments loudly declare that the function does more than > one thing. They are confusing and should be eliminated." [C. Martin, > Clean Code] But C++ already has everything to work with integer-based flags, so why do we need Boost.Flags? The answer is type-safety! With integer-based flags we can do too much. E.g. when there are multiple different integer-based flag sets, nothing prevents the programmer from accidentally mixing flags from unrelated flag-sets. And of course, there are problems with the bitwise negation operator~. If you want to know, what possibly could go wrong, read the docs. The Github page: https://github.com/tobias-loew/flags The online docs: https://tobias-loew.github.io/flags Example on Godbolt: https://godbolt.org/z/qbojncnd7 I am looking forward to your comments! Tobias

5 11

Re: [boost] Boost C++ in Australia
by Hans Dembinski 05 Apr '24

05 Apr '24

> [...] you're supposed to refer to these as "megameters" As an educated physicist, I concur (*). Also, it's time that the general public finally uses kilo-, mega-, and gigadollars, to avoid the confusion what a "billion" means in different languages https://en.wikipedia.org/wiki/Long_and_short_scales#Current_usage (*) Actually, not even physicists use megameters for some reason, neither does anyone say megagrams... people are so inconsistent.

3 2

Reminder: The master branch closes for the 1.85.0 release TOMORROW
by Marshall Clow 02 Apr '24

02 Apr '24

Calendar: https://www.boost.org/development/ — Marshall

1 0

Re: [boost] Technical Excellence?
by Peter Dimov 02 Apr '24

02 Apr '24

Ivan Matek wrote: > If there is some boost contributing for dummies so that I don't waste more > time in PR review for maintainers than I saved for them by renaming 8 uses of > boost::array to std::array I would be happy to pick some tasks next weekend. Unfortunately the procedure for bringing a library up to date with C++11 is pretty convoluted in general; it's only easy if the library is actively maintained and has up to date CI, and even then, dependency changes require updating the CMakeLists.txt file. For an "old" library, what I generally do is 1. Update (or add) Github Actions CI 2. Fix any test failures that the above has exposed (this happens surprisingly often and is sometimes not easy) 3. If the library has C++11 dependencies and therefore already requires C++11, update meta/libraries.json with the 11 requirement and drop 03 from CI (if not, add a BOOST_PRAGMA_MESSAGE that C++03 will be dropped two releases from now) 4. Add CMake jobs to CI. This requires adding test/CMakeLists.txt and supporting files. 5. Finally, change boost::array to std::array and remove the include of <boost/array.hpp> 6. Regenerate CMakeLists.txt using `boostdep --cmake libname`, if it was generated, or update it manually, if not, to drop Boost::array 7. See if anything broke on CI, and fix it which... isn't generally something a new contributor can do on his own.

1 0

A few updates...
by David Sankel 02 Apr '24

02 Apr '24

Hi all, I have a few updates regarding Boost organization that I wanted to share with the wider community. First, as many of you are already aware, Vinnie Falco, Rene Rivera, and others from the C++ Alliance have set up a rival Boost website (boost.io vs. boost.org) Boost Twitter account (@BoostLibraries vs. @Boost_Libraries), and LinkedIn account. As this behavior is gravely injurious to the Boost community and amounts to a hostile takeover attempt, it has been decided to ban these individuals from the Boost mailing list for the foreseeable future. Libraries owned by these individuals will be removed from the main Boost distribution in future releases unless others volunteer to continue their maintenance. Additionally, we have initiated legal action to get these false Internet assets taken down under common trademark law. I hope with these steps we will finally put behind us the unfortunate events of the past few months. Second, we have decided to retire the Boost mailing list in favor of discord.boost.org to attract a newer demographic of Boost users and developers who prefer this medium to legacy mailing lists. The transition will not be immediate, but we hope to have it complete by April 1, 2025. I know some of you have been reluctant to this kind of change, but as Roy T Bennett once said, "change begins at the end of your comfort zone." Third, I am very pleased to announce that Microsoft has given the Boost Foundation a $850,000 grant as part of their Rust initiative. These funds will be used primarily to port Boost libraries to the Rust programming language. We will begin by porting recent additions to Boost, such as Boost.Parser, since some of the older libraries (e.g. Boost.SmartPtr) already have equivalents in the Rust standard library. The Boost community is invited to provide additional input as to the priority of various conversions. Finally, and with some regret, I must share the news that the Boost Foundation will be dissolving itself per popular request from Boost developers considering it (incorrectly) be concerned with only the C++Now conference. The Boost Foundation's assets will be held under trust by Robert Ramey and Niall Douglas until more appropriate governance is built. That's all for now. I hope y'all have a great week! -- David Sankel

7 7

[release] Master branch is now open for bug fixes
by Marshall Clow 01 Apr '24

01 Apr '24

The master branch is now open for bug fixes, test and documentation changes. Other changes by release manager permission, as described in https://github.com/boostorg/wiki/wiki/Releases%3A-Beta-Merge-Policy The next deadline: On April 3rd, master closes for all changes. As always, the calendar is at https://www.boost.org/development/ — Marshall

12 22

boost.sqlite seeking endorsement
by Klemens Morgenstern 30 Mar '24

30 Mar '24

A while back I asked about interest in a boost.sqlite library and got enough engagement that I think it's worth proposing. Hence I am seeking an endorsement and would like to see if someone wants to volunteer as review manager. Code: https://github.com/klemens-morgenstern/sqlite Docs: https://klemens.dev/sqlite/

14 28

Slow mail archive and link?
by René Ferdinand Rivera Morell 27 Mar '24

27 Mar '24

I've known this for a long time, but only now decided to bring it up.. The mailman archive is both laggy and unhelpful. There's a significant lag between one sending an email to the list and it being reflected in the archive (https://lists.boost.org/Archives/boost/) I think it took 5 minutes with my latest message. I've noticed that for other mailman web archive lists I subscribe to, like the wg21 lists, there is no significant lag. And they even put a link to the archive for the specific message in the footer of the message immediately. First.. Can the lag be improved? Second.. Can a link to the archive message be included in the message? -- -- René Ferdinand Rivera Morell -- Don't Assume Anything -- No Supone Nada -- Robot Dreams - http://robot-dreams.net

4 5

[Parser] Review Results and Report
by Marshall Clow 27 Mar '24

27 Mar '24

The review of Zach's parser library ran from Feburary 19 -> 28th. If I have mischaracerized/incorrectly stated anyone's position, please let me know in this thread. REVIEW RESULT ----------------------------- The result is Boost.Parser is * ACCEPTED WITH CONDITIONS * into Boost. The following tickets in the parser repo should be addressed before adding this library to boost: Consider changing the way semantic actions are invoked https://github.com/tzlaine/parser/issues/106 Turn on -Wall for GCC and Clang builds https://github.com/tzlaine/parser/issues/107 Clearly indicate which directives create a new parser when used, which do not, and why it matters. https://github.com/tzlaine/parser/issues/161 Enable code coverage on Github project https://github.com/tzlaine/parser/issues/146 Add more examples and use cases to The Parse Context https://github.com/tzlaine/parser/issues/145 ABI-tag __has_include-guarded differing code https://github.com/tzlaine/parser/issues/151 API reference for char_ should explicitly state that it can be used without args https://github.com/tzlaine/parser/issues/150 Add no_case support to symbol tables https://github.com/tzlaine/parser/issues/149 REVIEW REPORT ----------------------------- We recieved 10 reviews during the review period, and two more after the review ended. Six reviews recommended ACCEPT One review recommended ACCEPT WITH CONDITIONS Three reviews reccommended REJECT One review did not reccommend an action. One review was of the documentation only. Thanks to everyone who participated. Thanks to Zach for writing the library, and participating heavily in the review. REVIEW COMMENTS ----------------------------- Several of the reviews sparked discussions, and many of the issues raised were debated back and forth on the mailing list. There was a lot of discussion about the use of Boost.Hana in the library; Zach defended it on the grounds that Hana's tuple has an `operator[]`, which is much more readable than using `std::get`. There was push back from the reviewers on this, not wanting to add a dependency (and learning curve) for yet another library. Currently, this is selectable at compile time; Zach said that he would consider defaulting to use std::tuple instead of Hana::tuple. Phil had trouble with a custom parser that used the double parser; I believe that this was resolved, and this is now captured as a test case: https://github.com/tzlaine/parser/blob/boost_review_changes/test/parse_coor… There was a long discussion about semantic actions, and how they are defined/invoked. https://github.com/tzlaine/parser/issues/106 was created to address this. Several people mentioned compiler error messages one such example is https://github.com/tzlaine/parser/issues/105 and compiler warnings https://github.com/tzlaine/parser/issues/107 Christian thinks that the examples comparing Parser to Spirit3 should emphasize the advantages of Parser. Zach to update the examples. He also asked for general design guidance on writing rules vs. actions. https://github.com/tzlaine/parser/issues/161 Matt (and others) asked for more CI coverage; Zach said that he welcomed help setting it up. https://github.com/tzlaine/parser/issues/146 Alan requested that the numeric parsers use Boost.Charconv for the conversions. He also stated that the section in the docs "The Parse context" is confusing https://github.com/tzlaine/parser/issues/145 David noted some ODR issues https://github.com/tzlaine/parser/issues/151 and he also noted that the docs for the char parser don't say it can be used without arguments: https://github.com/tzlaine/parser/issues/150 He also mentioned that he would really rather see a library design more like Text.Parsec from Haskell. Дмитрий wanted to know why the symbols didn't support 'nocase'. https://github.com/tzlaine/parser/issues/149 He also thought that the attribute for parsers with semantic actions is none is not advertised well enough https://github.com/tzlaine/parser/issues/148 Mohammed asked a question about parsing chunk-encoded HTML bodies efficiently. Zach replied that this wasn't supported directly, but you could write a custom parser to do it. Christian reported a hideous performance overhead when parsing JSON. (100x slower than Boost.JSON) Zach and Peter investigated, and it turned out that the construction of a stringstream for tracing was much of it, and the rest was also part of the tracing mechanism. Zach reworked the tracing code, and now non-debug builds are much faster. https://github.com/tzlaine/parser/issues/152 REVIEW ACKNOWLEDGMENTS ----------------------------- Thanks again to Zach for Boost.Parser Many thanks to our expert reviewers, commenters and watchers. Your contributions keep Boost excellent! Marshall Clow Boost.Parser Review Manager

13 22

Pre-C++14 compilers
by Дмитрий Архипов 26 Mar '24

26 Mar '24

Recently we stopped supporting C++03. Now, the only compilers which support C++11, but do not claim some support of C++14 (that I am aware of) are GCC versions 4.8 and 4.9. But even C++11 support in those GCC versions is fairly buggy and those who still test on them often have to resort to various tricks to make their code build. Those compilers are fairly old, and the systems that use them increasingly go extinct. This makes me consider removing them from CI. Which is why I want to ask the community several questions: 1) Do you still use GCC 4.8 or 4.9? 2) If you do, is there a specific date when you plan to drop them? 2) Do you use some other compiler which supports C++11, but not C++14 (even with flags like -std=c++1y)?

10 12

Re: [boost] [release] Master branch is now open for bug fixes
by Christophe Henry 25 Mar '24

25 Mar '24

Hi Marshall, I would like to merge in MSM this bugfix (2 missing includes): compile break in 1.85.0.beta1 when using favor_compile_time · Issue #70 · boostorg/msm (github.com) <https://github.com/boostorg/msm/issues/70> and this doc fix: Boost 1.85.0: Backend Dokumentation · Issue #69 · boostorg/msm (github.com) <https://github.com/boostorg/msm/issues/69> PR: Feature/1.85 beta by henry-ch · Pull Request #71 · boostorg/msm (github.com) <https://github.com/boostorg/msm/pull/71> Develop builds and tests ok. Regards, Christophe

2 1

A proposal for a modern build-system
by Hassan Sajjad 25 Mar '24

25 Mar '24

Hi. Preface: C++20 modules and header-units are a great addition to C++. There are numerous benefits of these. One of them is a faster compilation. Conventional build-systems however are unable to benefit from C++20 modules or header-units. Boost current build-system b2 does not support C++20 modules or header-units. CMake does not support C++20 header-units https://gitlab.kitware.com/cmake/cmake/-/issues/25293. I developed the build-system HMake https://github.com/HassanSajjad-302/HMake. It is in C++ and MIT Licenced. It supports drop-in header-files to header-units replacement. While compilers support processing a header-file as header-unit, no other build-system supports this feature. With this I compiled SFML with C++20 header-units https://www.reddit.com/r/cpp/comments/1555g6b/hmake_build_system_02_compili…. In the post, I mentioned that 2-3.5x speed-up was achieved but I did some more testing recently and an even better speed-up of 2.7-4.7x was achieved i.e., the speed of header-units is further improving with recent iterations. Proposal: I want to propose my build-system HMake for boost. Besides its already state-of-the-art C++20 modules and header-units support, it will be the first to support https://lists.isocpp.org/sg15/2023/11/2106.php or https://lists.isocpp.org/sg15/2023/11/2146.php if any of this gets implemented. These papers present ideas for faster module adoption and avoiding redundant module compilations. These need support from build-system. This way boost could be a breeding ground for C++20 modules adoption. Also, I have good experience with boost's current build-system b2 as a good portion of HMake's current API is inspired by it. Timeframe: I will complete this proposal in 3 months. Deliverables: 1) 2-months: Boost basic configuration compiled with C++20 header-units. This is more of a lone sprint. 2) 3-months: All boost current configurations + new with header-units and modules + tests and examples. This will require more active involvement by the current maintainers. I will give weekly updates here and will make a video after 2 months presenting the progress made. This will be to help other contributors so they can ensure that their library is fully supported. Cost: Standard C++ Developer Compensation for 3 months (Negotiable). Payments are to be issued monthly. But you can back out at any point in case you are unsatisfied with development speed or direction. Impact: While I don't see any reason for it to be a flop, it is an engineering endeavor so there is some inherent risk. The best-case scenario is that it improves Boost usability and 2.5x compilation speed improvement starts a domino effect for HMake and C++20 header-units and modules adoption. Best, Hassan Sajjad

9 37

Boost::serialize: im doing an Windows MSVC to Linux GCC port and i have a linker error (with a small example)
by Dennis Luehring 25 Mar '24

25 Mar '24

im doing an Linux/GCC port of an huge ~1Mio LOC/15 years grown Windows/MSVC project - my first step was switching over to CMake replacing the Studio-Solution file and in around 2.5 weeks i went from a hell lot of compile errors down to full compilation and nearly full linking - happy state so far :) but i stumbled over an linking problem using Boost::serialize with template types (in static libs and hundreds of them in this project) the code compiles and links with MSVC but not with GCC/Clang ld/lld/mold under Linux tested with Boost 1.84.0 - needs Boost::serialization ---- /usr/lib64/gcc/x86_64-suse-linux/13/../../../../x86_64-suse-linux/bin/ld: CMakeFiles/linux_link_error_test.dir/main.cpp.o: in function `boost::archive::detail::iserializer<boost::archive::text_iarchive, MyType<double, 2ul> >::version() const': main.cpp:(.text._ZNK5boost7archive6detail11iserializerINS0_13text_iarchiveE6MyTypeIdLm2EEE7versionEv[_ZNK5boost7archive6detail11iserializerINS0_13text_iarchiveE6MyTypeIdLm2EEE7versionEv]+0x15): undefined reference to `boost::serialization::version<MyType<double, 2ul> >::value' ---- nm -C shows that the symbol 'boost::serialization::version<MyType<double, 2ul> >::value' is 'U' undefined in the the lib but i don't understand why the linker is looking for this header-only version function - and what MSVC is doing different to accept it as is i reduced the big scenario down to a more or less trivial sample to show the effect loading a dummy type "MyType" it compiles and links with MSVC but GCC gives me the linker error https://github.com/LowLevelMahn/linux_link_error | | build.txt | CMakeLists.txt | +---linux_link_error_lib <-- a static lib with the serializable 'MyType' | CMakeLists.txt | MyType.hpp <-- definition of the dummy type | serialize_MyType.hpp <-- definition of the boost serialization routines | test.cpp <-- dummy code for the static lib | \--linux_link_error_test <-- console app using MyType serialization CMakeLists.txt main.cpp the structure of the sample project, static-library, using different headers for type-definition and its serialize routines is intentionaly like in the original project - so i can maybe easily adapt a solution to my real project, i hope the sample is bare enough :) how to build: mkdir linux_link_error_dev cd linux_link_error_dev git clone https://github.com/LowLevelMahn/linux_link_error.git mkdir _build cd _build # Windows/MSVC cmake -G "Visual Studio 17 2022" -A x64 -DCMAKE_PREFIX_PATH=[boost-path]\lib\cmake ..\linux_link_error # Linux/gcc cmake -DCMAKE_PREFIX_PATH=[boost-path]/lib/cmake ../linux_link_error #or without prefix path if boost is installed as package in your distro cmake ../linux_link_error cmake --build . result: builds on windows on linux with gcc i get the linker error from above my system: recent Tumbleweed SUSE gcc 13.2.1 clang 18.1.1 ld: 2.42.0 lld: 18.1.1 mold: 2.30.0 my boost build: wget https://boostorg.jfrog.io/artifactory/main/release/1.84.0/source/boost_1_84… tar -xf boost_1_84_0.tar.bz2 cd boost_1_84_0 ./bootstrap.sh --prefix=/home/testing/boost_1_84_0_install ./b2 install it could be that all the MSVC magic/micro compiler/linker differences i've learned in the last years don't let me see the truth :(

1 1

Boost BCP tool is abandoned.
by René Ferdinand Rivera Morell 24 Mar '24

24 Mar '24

While making changes to update the various tools I found that the BCP tool is abandoned. As in it hasn't been updated for a couple of years. And because of changes to Boost.Filsystem no longer builds. And since no one has complained about it not building, I'm guessing no one uses it. There's two choices to deal with this: 1. Find someone to maintain it. 2. Delete it and move on with other more important things. I favor #2. -- -- René Ferdinand Rivera Morell -- Don't Assume Anything -- No Supone Nada -- Robot Dreams - http://robot-dreams.net

4 3

Linker errors under Linux on using locale in a tiny example - using my own boost build
by Dennis Luehring 21 Mar '24

21 Mar '24

i can't built a simple locale from_utf using example with my own build boost 1.84.0 [system] SUSE Tumbleweed gcc (SUSE Linux) 13.2.1 20240206 [revision 67ac78caf31f7cb3202177e6428a46d829b70f23] [boost build] using https://boostorg.jfrog.io/artifactory/main/release/1.84.0/source/boost_1_84… tar -xf boost_1_84_0.tar.bz2 cd boost_1_84_0 ./bootstrap.sh --prefix=/home/test/boost_1_84_0_install ./b2 install ---- [CMakeLists.txt] cmake_minimum_required (VERSION 3.14) project (MyTest) set(CMAKE_CXX_STANDARD 17) set(CMAKE_CXX_STANDARD_REQUIRED ON) list(APPEND CMAKE_PREFIX_PATH "/home/test/boost_1_84_0_install/lib/cmake") find_package( Boost REQUIRED COMPONENTS locale ) add_executable( my_test main.cpp) target_link_libraries( my_test PRIVATE Boost::boost ) ---- [main.cpp] #include <boost/locale.hpp> int main() { auto x = boost::locale::conv::from_utf( "blun", "ISO-8859-1" ); return 0; } ---- build: _build>cmake ../MyTest _build>make [ 50%] Building CXX object CMakeFiles/my_test.dir/main.cpp.o [100%] Linking CXX executable my_test /usr/lib64/gcc/x86_64-suse-linux/13/../../../../x86_64-suse-linux/bin/ld: CMakeFiles/my_test.dir/main.cpp.o: in function `std::__cxx11::basic_string<char, std::char_traits<char>, std::allocator<char> > boost::locale::conv::from_utf<char>(char const*, std::__cxx11::basic_string<char, std::char_traits<char>, std::allocator<char> > const&, boost::locale::conv::method_type)': main.cpp:(.text._ZN5boost6locale4conv8from_utfIcEENSt7__cxx1112basic_stringIcSt11char_traitsIcESaIcEEEPKT_RKS8_NS1_11method_typeE[_ZN5boost6locale4conv8from_utfIcEENSt7__cxx1112basic_stringIcSt11char_traitsIcESaIcEEEPKT_RKS8_NS1_11method_typeE]+0x42): undefined reference to `std::__cxx11::basic_string<char, std::char_traits<char>, std::allocator<char> > boost::locale::conv::from_utf<char>(char const*, char const*, std::__cxx11::basic_string<char, std::char_traits<char>, std::allocator<char> > const&, boost::locale::conv::method_type)' collect2: error: ld returned 1 exit status make[2]: *** [CMakeFiles/my_test.dir/build.make:97: my_test] Error 1 make[1]: *** [CMakeFiles/Makefile2:83: CMakeFiles/my_test.dir/all] Error 2 make: *** [Makefile:91: all] Error 2 any idea what is happening here?

3 4

Porting to Openvms
by Barrett Southworth 18 Mar '24

18 Mar '24

I see the source files for setting up config.hpp. But I don't see how to create source files for OpenVMS (the vms.hpp is really out of date). The compiler VSI CXX. Or any of the other options. Is there a guide for setting up the config that I'm missing? If not any suggestions for how to go about setting up those files?

2 2

release clang++ std=c++23/26 trunk version emit diagnostics errors on #include <boost/program_options.hpp>
by Bjørn Roald 17 Mar '24

17 Mar '24

https://gcc.godbolt.org/z/d3PTjdMhr this is fixed by changing suspect throw() declarations with BOOST_NOEXCEPT I have not checked rest of boost for diagnostics with this compiler, but my understanding is that throw() declarations are no longer part of the standard and compilers may emit diagnostics like this. Is there any reason, except for the work to be done, not to use BOOST_NOEXCEPT everywhere? — Bjørn

2 1

Social Media Guidelines
by Vinnie Falco 16 Mar '24

16 Mar '24

I guess I'll take a stab at offering a starting point for social media posting guidelines. When I had access to post to the Boost_Libraries account there were basically two kinds of posts. Official communications from the Developers, and unofficial but relevant announcements. The Developers are defined as the set of members of the boostorg GitHub organization who have the Owner role, plus any proxies they authorize. Official communications include: * When a review starts https://twitter.com/Boost_Libraries/status/1622664075217092609 * When review results are available https://twitter.com/Boost_Libraries/status/1768833941341896756 * When a Boost release is published (usually 3 a year): https://twitter.com/Boost_Libraries/status/1735542393229967849 * When a change in policy for the libraries happens: https://twitter.com/Boost_Libraries/status/1633484289693339648 Official communications are identifiable by the Boost logo watermark appearing at a prescribed location and size in the color Boost Mustard. Examples of unrelated but relevant announcements include: https://twitter.com/Boost_Libraries/status/1716891934986530946 https://twitter.com/Boost_Libraries/status/1748504615371334006 Unofficial posts should have images if possible, but never with a Boost logo watermark, to denote that the post does not presume to speak for or have an association with the Developers. Anyway, these are the set of rules I informally invented when I had posting privileges to Boost_Libraries. I always checked with other developers before posting anything, especially for unofficial posts to ensure that the content was relevant to Boost in some fashion. This could be used as the starting point for explaining the guidelines for operating official Boost accounts. There is a page in the new site docs (a work in progress for sure) which is intended to capture these guidelines in a way that is easily understood by readers: https://www.boost.io/doc/contributor-guide/tweeting.html Disclaimer: That page is probably not be up to date, and is not the product of a consensus-driven process. But it can be, someone just needs to volunteer to do the work. Thanks

1 0

Review schedule update
by Mateusz Loskot 16 Mar '24

16 Mar '24

Folks, I have just updated the review schedule with status of the reviewed libraries as well as Boost versions releasing the new libraries. I'll appreciate if authors of the libraries (from STLInterfaces onwards) could verify if I've got their release version right. p.s. thanks to Christopher Kormanyos for nudging me about the update. Best regards, -- Mateusz Łoskot - on behalf of the Review Wizards Team

2 3

Re: [boost] (Important) Boost Foundation meeting this Wednesday
by Louis Tatta 16 Mar '24

16 Mar '24

On Mon, Mar 11, 2024 at 12:23 PM David Sankel <camior(a)gmail.com> wrote: > Our monthly Boost Foundation meeting is this Wednesday at 3pm Eastern > (12pm Pacific). > To: Boost developer community and Boost Foundation Board Hi everyone, I write to address two important matters regarding recent events. First, upon reviewing my messages with David and conferring with Vinnie, I must apologize for a miscommunication. I did not realize that “copyright assignment” was a term of art which means to transfer all legal rights and title. I thought instead it meant that Boost Foundation would receive a license to reproduce the logo without permission in referential contexts. Vinnie wasn’t involved in this so it is unfair to blame him; in fact, the task of this communication was delegated to me specifically because David suggested that dealing with someone else might be preferable to dealing with Vinnie. Second, as the agenda for the Boost Foundation board meeting occurring on March 13th includes a discussion of the new website, I would reiterate our proposed contribution to the developer community. A transfer of copyrights is not in line with Boost tradition, but it is still possible for us to have a healthy relationship. Thusly we repeat our previous offer: 1. The boost.org domain will point to The C++ Alliance servers running the new website, which we will operate and pay for. 2. Administrative access to the new cloud services will include Sam Darwin (CTO of C++ Alliance), plus anyone appointed by the developer community. 3. The new Boost logo (“B Mark”) will have its copyright and trademark retained by The C++ Alliance, and it will be published under a license which allows for irrevocable, permissionless reproduction in the context of referring to the Boost Libraries. The text for this is being prepared by our legal team, and it will be similar to the wording found under “Foundation name and C++ logo” here https://isocpp.org/home/terms-of-use. 4. Work on the website and documentation will continue in the repositories now under control of the developer community at https://github.com/boostorg/website-v2 and https://github.com/boostorg/website-v2-docs and licensed under the BSL. 5. If and when the developer community feels that the new website, infrastructure, or level of support received does not meet with expectations, the boost.org domain can be pointed away from The C++ Alliance servers. We believe this proposal is fair, generous, and respectful to tradition. It honors contributors by empowering them to continue their work, in a way that preserves the independence of the Boost project. Thank you for your consideration in this matter. Louis Tatta CEO, The C++ Alliance, Inc.

8 17

Suspicious changes to Serialization
by Peter Dimov 14 Mar '24

14 Mar '24

The current Serialization emits the following warning: c:\projects\boost-root\boost\serialization\extended_type_info_typeid.hpp(118) : warning C4700: uninitialized local variable 'ap' used which looks legitimate and is caused by the removal of `va_start(ap, count);` in this commit https://github.com/boostorg/serialization/commit/2805bc3faa8f8fb7ce80ec5181… This looks like a mistake to me, and is probably going to cause problems.

3 3

[release] Boost 1.85.0 beta 1 is available
by Marshall Clow 14 Mar '24

14 Mar '24

Boost release 1.85.0 beta 1 is now available at: https://boostorg.jfrog.io/artifactory/main/beta/1.85.0.beta1/source/ The SHA256 checksums are: c13b76f420684a8d5b2eb0f297c281348ba0311d50354d952c5ce7c689e7879b boost_1_85_0_b1.zip e65d529023c7b08d0b92c53fff24ce9df9568cc0fe667c90caf8a9dbc5e63b0d boost_1_85_0_b1.7z 9c1ce4793342e8e57eb34c61f774a9dac0c6fc036084785e416613a18091bacc boost_1_85_0_b1.tar.gz cf7449faedeac9b76bade8ee59007cc4456a14de375dfcbd9e6e38aabe8a1334 boost_1_85_0_b1.tar.bz2 There was one problem reported during the beta release process; when you build the release using b2, it will emit a warning: [errno 2] failed to scan file '': No such file or directory This is harmless, and will be fixed for the final release. the release notes are available at: https://www.boost.org/users/history/version_1_85_0.html Please try the beta and report any problems you encounter. Thanks to everyone who contributed to the release. -- Boost Release Team

3 4

Github releases for CI
by Peter Dimov 14 Mar '24

14 Mar '24

In addition to the CMake releases on Github, I've modified the action to also create releases for use with b2 (with the headers copied to boost/ and removed from libs/*/include, but without the documentation.) These would be useful for CI, which would hopefully lower the pressure on the official downloads. E.g. https://github.com/boostorg/boost/releases/tag/boost-1.85.0.beta1

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[release] Boost 1.85.0 Release Candidate 1 is available.
by Marshall Clow 12 Mar '24

12 Mar '24

Available at: <https://boostorg.jfrog.io/artifactory/main/beta/1.85.0.beta1/source/> The SHA256 checksums are as follows: fa31215de3a4d2d010c0bc6e42cc63da76be82899f145ea6a6034b5bf3e6e297 boost_1_85_0_b1_rc1.zip 3b16d693acd4ee1745b0d9267555f7e34387527a02817f0c81bf8ec963b7c569 boost_1_85_0_b1_rc1.tar.bz2 20c7d2ccbbddeb56e618aa80960ea4dd38cbc4912b9a05fefef31c290519154e boost_1_85_0_b1_rc1.7z 7a28cd03e8e48b59a898900c953a9194b8f1efbb8c6149703b7faf08642c0cf7 boost_1_85_0_b1_rc1.tar.gz 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 Release Managers

8 17

Reminder: Review for Zach's parsing library starts on Feb 19th
by Marshall Clow 11 Mar '24

11 Mar '24

That’s a week from now. Github: https://github.com/tzlaine/parser Docs: https://tzlaine.github.io/parser — Marshall

14 54

[release] Request to merge B2
by René Ferdinand Rivera Morell 11 Mar '24

11 Mar '24

Can I merge the latest, 5.1.0 (a), release of B2 to master at the next opportunity? By next opportunity I mean whenever the release managers think it's appropriate. :-) [a] Release notes: <https://github.com/bfgroup/b2/releases/tag/5.1.0> -- -- René Ferdinand Rivera Morell -- Don't Assume Anything -- No Supone Nada -- Robot Dreams - http://robot-dreams.net

2 1

New Website: State of the review / pending issues
by Ion Gaztañaga 07 Mar '24

07 Mar '24

Hi to all, We've had quite an intense debate regarding the proposed new website. I've tried to extract the main technical comments expressed in the ML to to determine the current state, fix any misunderstanding and try to establish a constructive thread: ------------------------- ------------------------- 1) Repository: the website code was hosted in cppalliance's github. It was transferred to boostorg. I understand this as an improvement as it's in the same level as other boost libraries. 2) License: Before transferring it to boostorg, a request to change the license to BSL was made. The license change was announced on February 21, and boost.io says it's BSL, so I guess it's solved now. Source files in the repo (https://github.com/boostorg/website-v2) have no copyright notice, I don't think it's something that is required, but usually all Boost source files have the notice and point to the license. I'm not a lawyer, but if the site is open source, anyone can fork and improve it, and ownership and copyright of the source code follows the standard Boost practices (BSL). Anyone with enough technical expertise can put up a server with the original or forked code and re-run the site in case of cpp.al goes away or if there are disagreements. 3) Privacy Policy: There was a comment about information from third parties and the use of Google Analytics, location data... AFAIK there is a new privacy policy page (https://www.boost.io/privacy/) which does not mention any location data and says a notification will be sent to registered users on any change. There is a issue to implement account deletion (https://github.com/boostorg/website-v2/issues/965) opened by Vinnie, so it should be implemented soon. 4) Terms of use: It was suggested that there needed to be a page like "Terms of Use" composed with help of a lawyer. AFAIK there is a new page (https://www.boost.io/terms-of-use/) that is much simpler and easier to read than the original. I'm not sure if Andrey's comments are addressed with the new TOU. Andrey, it's ok now? 5) GDPR: A issue was filed (https://github.com/boostorg/website-v2/issues/960) and there was a discussion in the ML about not having any analytics tool to avoid cookie banners or a couple of analytic tools that were compliant with GDPR. The github issue was resolved stating that: - Google Analytics was removed and Plausible was deployed (e.g. no cookies. IP addresses are anonymized with a hash function and rotating salt value), - YouTube Embed on the homepage was changed to an external link to the video. I understand that with those changes the site is GDPR-compliant. Is that right? 6) Moderation: We had a discussion about how moderation should be performed in the site (mainly as an anti-spam mechanism) and how it's implemented now in the mailing list (volunteers). My understanding is that the new website has some moderation tools so that anyone can submit news, etc... and that the same ML method (volunteers blessed in the ML) should be used to appoint the moderators for the site (not necessarily the same people that moderate the ML). ------------------------- ------------------------- I don't know if this summary is accurate, the aim was synthesize several ML threads into a single post, certainly I could be wrong on several points, please correct me in that case. Now the next question is: *What's missing technically so that the new website can to live?* If technically we have an agreement or we are near that, then we can: - Know if there are non-technical aspects that need to be ironed out. - Know if there is any alternative to be discussed and compared with the proposed website. If so, let's put it on the table, review and compare it. - Schedule a plan so that Boost can have a new modern website soon. Does this make sense? Best, Ion

8 10

[release] The Master branch is now CLOSED for the 1.85.0 beta.
by Marshall Clow 07 Mar '24

07 Mar '24

Please do not commit anything to ‘master’. — Marshall

1 0

Boost.Parser review result delayed
by Marshall Clow 06 Mar '24

06 Mar '24

I had to go out of town for a couple of days, and appear to have brought hone a cold. Sorry for the delay. — Marshall

2 1

[release] Master Branch closes for the release TOMORROW
by Marshall Clow 06 Mar '24

06 Mar '24

As always, the calendar is here: https://www.boost.org/development/ — Marshall

1 0

Boost.Parser Question about digit separator support
by Olaf Peter 04 Mar '24

04 Mar '24

Hi all, In the past I had some attempts with Spirit.x3. C++, VHDL and other languages support literal digit separators. On Stackoverflow.com there are some workarounds (in the context of VHDL's digit separator '_' ) for X3, which works but are unattractive and to unwieldy/unflexible. Is there a native/direct support for it at Boost.Parser? Thanks, Olaf

2 1

Reminder: Master branch closes for the 1.85.0 beta release on WEDNESDAY
by Marshall Clow 03 Mar '24

03 Mar '24

Calendar is here: https://www.boost.org/development/ — Marshall

1 0

Re: [boost] Reminder: Review for Zach's parsing library starts on Feb 19th
by Peter Dimov 02 Mar '24

02 Mar '24

Zach Laine wrote: > On Fri, Mar 1, 2024 at 2:15 AM Peter Dimov <pdimov(a)gmail.com> wrote: > > > > Zach Laine wrote: > > > > > I'm not sure what the tests reported earlier were doing, but I > > > > > definitely don't see orders of magnitude difference. > > > > > > > > I used this file: > > > > > > > > https://github.com/boostorg/json/blob/develop/bench/data/twitter.j > > > > son > > > > > > Using that file, I get similar results to what I already posted (the > > > numbers are different, but the ratios between them are the same). > > > > > > I managed to make a change that was much smaller -- no template > > > parameter required. I consistenty see 1.5x slowdown for Parser vs. > > > Boost.JSON for files around this size, and 2x or so for much larger > > > files (~25MB). > > > > That's probably because you are measuring I/O in addition to parsing. > > > > https://github.com/cmazakas/parser-review/blob/main/test/json.cpp > > > > only measures the parsing part. > > Quite right! After building it locally, I do see an advantage to the template > parameter approach -- that is, controlling the contents of scoped_trace_t with > an NTTP that is true/false when trace is enabled/disabled. scoped_trace_t is > specialized to be empty when the NTTP is false. I'll be committing the template > param-based approach soon. > > For those keeping track, with Christian's test framework, I get 35X worse > performance of the JSON parser example vs. Boost.JSON. This seems like a > reasonable factor to me. I wrote that example in a single, and made no > attempt to optimize it in any way; it is an example. Boost.JSON is a dedicated > JSON parser emphasizing efficiency. There's probably some room for Boost.Parser automatically applying certain optimizations to "naively" written parsers. For example, a lot of the time here is spent in skipping whitespace, using this rule: auto const ws_def = '\x09'_l | '\x0a' | '\x0d' | '\x20'; This generates an or_parser that contains four separate omit_parsers, each with a char_ inside. If I change it by hand to auto const ws_def = bp::omit[ bp::char_( "\x09\x0a\x0d\x20" ) ]; which I assume is equivalent, time improves from 365ms to 316ms (*). And that's still far from optimal, because (1) skipping whitespace can in principle be done with the equivalent of `find_first_not_of` and (2) the characters are a runtime value in the above, but something like `cxchar<'\0x09', '\0x0a', '\0x0d', '\x20'>` could be even faster. It should be possible for the library to automatically turn the "naive" ws_def into something more optimal, and then special-case `skip` for this common case. In the general case this is complicated by the existence of attributes and semantic actions; transforming parsers should take care to preserve those. But in this specific case none are present. (*) Under clang-cl. GCC -O3 has different views of the world and times there are 165ms and 181ms, respectively.

1 0

Late review of Boost.Parser
by David Sankel 02 Mar '24

02 Mar '24

# Are you knowledgeable about the problem domain? Yes. I've written several parser combinator libraries in C++ and used still more in C++ (Spirit v1, v2, and qi) and other programming langauges (Haskell's Parsec, attoparsec, and others). # How much effort did you put into your evaluation? A glance? A quick reading? In-depth study? I read through the tutorial documentation and some of the reference documentation. I also tried to create several examples with the library and made comparisons to Haskell's Parsec. # What is your evaluation of the potential usefulness of the library? Very # What is your evaluation of the documentation? The documentation isn't great. Consider char_ <https://tzlaine.github.io/parser/doc/html/boost/parser/char_.html>'s documentation. It includes no examples and fails to mention it can be used without arguments. It seems strange that the tutorial focuses so much on semantic actions. It seems like the more common case would be to parse into some kind of abstract syntax tree. # What is your evaluation of the design? Much of the wealth of research into parser combinators wasn't incorporated into this library. I didn't see in the documentation, for example, an easy way to "map" one parser's attribute into another. This kind of thing should be a basis operation provided by the library. # What is your evaluation of the implementation? The usage of has_include is a ODR nightmare for large codebases. It would be better to generate some kind of config.hpp that sets these definitions at compile time. For custom variant/tuple types, user specialization of variable templates is also an ODR nightmare. Again, a config.hpp would be better for this. For this, though, I don't think the configurability is worth the complexity. We have standard types for these so we should use them. # Did you try to use the library? With what compiler? Did you have any problems? Yes, I tried to use the library with a modern compiler on a MacOS machine. I didn't have any problems building. # Do you think the library should be accepted as a Boost library? No, I do not think it should be accepted. Overall, I think the syntax has too much focus on magically filling in user-provided structures instead of the basics of monadic parser combinators and basis operations. Consider the following Haskell parser which evaluates simple parenthesized sum expressions. I wasn't able to use Boost.Parser to accomplish this after reading the documentation and several attempts. I'm sure it's possible, but I don't see how it can be done using the combiners and primitives provided. import Text.Parsec.String (Parser)import Text.Parsec integer :: Parser Integerinteger = do n <- many1 digit return (read n) integerPlus :: Parser IntegerintegerPlus = do x <- integer y <- (try $ char '+' >> expression) <|> return 0 return $ x+y parentheses :: Parser Integerparentheses = do char '(' x <- expression char ')' return x expression :: Parser Integerexpression = integerPlus <|> parentheses

5 9

Boost Tools
by Robert Ramey 01 Mar '24

01 Mar '24

For some time I've felt that our Boost tooling could be improved. By boost tooling I mean things like b2, boost unit testing and integration testing, documentation generation, reports like dependencies, website, etc. Currently we rely on certain privileged authors to develop these things then then upload them to the boost directories. This has worked, but it could be better. We spend what seems to me an inordinate amount of time chasing down anomalies, researching errors, responding for requests for help, etc. I think design, robustness, documentation could be improved. I think that the the most natural way for us to do that would be to adopt the practices that we have used successfully for decades to develop superior quality libraries to the design and development of tooling. That is: a) Someone proposes a new tool or improvement in an existing one on this list. His proposal includes a working though likely incomplete prototype, documentation, tests, demo etc. b) This is subjected to the same formal review process that libraries are. c) Subject to this review, the proposal is either rejected, accepted or accepted with conditions. Of course this would only apply to new tools and updates of existing ones. Robert Ramey

1 0

The Review for Zach's parser library has concluded
by Marshall Clow 01 Mar '24

01 Mar '24

Thanks to everyone who participated, and especially to those to submitted reviews. (And Zach, of courser) I’ll have results soon. — Marshall

1 0

Boost.Parser parsing length-prefixed strings efficiently
by Mohammad Nejati [ashtum] 01 Mar '24

01 Mar '24

Hi everyone, I have two questions about the following code, which attempts to parse length-prefixed strings using the proposed Boost.Parser: ``` std::string input = "[5]HELLO[5]WORLD"; unsigned int size = 0; auto action = [&size](auto & ctx) { size = bp::_attr(ctx); }; auto lps_parser = '[' >> bp::uint_[action] >> ']' >> bp::repeat(std::ref(size))[bp::char_]; auto result = bp::parse(input, *lps_parser); ``` 1. Is it possible to eliminate the need for the action and size variable by using some kind of placeholder in bp::repeat that utilizes the attribute of the first parser? 2. How can we make this part of the parser more efficient: bp::repeat(std::ref(size))[bp::char_] The current implementation seems to loop and execute bp::char_ parser on each character, while all it needs to do is chunk a portion of the input string. Regards, Mohammad Nejati

2 1

New website is open-source!
by Vinnie Falco 29 Feb '24

29 Feb '24

The new website and documentation are provided under the BSL, and the source repositories have been transferred to the Boost GitHub organization: https://github.com/boostorg/website-v2 https://github.com/boostorg/website-v2-docs While we sort out the unresolved issues related to the licensing of artwork and logo, the new website has moved to this temporary location for now: https://boost.io Please continue to experience, enjoy, and most importantly test the new website. A gentle reminder: it is not “finished” and likely will not be “perfect” for a while. The launch of the new website is the beginning of the journey rather than the end. Issues opened here will be acted upon by our dedicated website development team: https://github.com/boostorg/website-v2/issues For documentation-related issues, please open and monitor issues here: https://github.com/boostorg/website-v2-docs/issues Pull requests are always welcomed! Thanks

6 6

Boost.Parser questions
by Ruben Perez 29 Feb '24

29 Feb '24

Hi all, Sorry for jumping into this so late. I'll send my review tomorrow (that's still on time, isn't it?). I've been playing with the library and some questions popped up (please note I've no prior experience with Spirit): * What's the rationale for using operator[] for semantic actions (instead of a regular method like .action())? It looks like the parsing problem with inline lambdas could be easily worked around with this. * What's the rationale for using operator[] for directives? repeat(24)[p] looks like an over-complication, where a regular function repeat(24, p) would have just worked fine. * For non-recursive rules, what's the rationale on preferring the macro over something like: constexpr bp::rule<struct replacement_field_tag, std::string> replacement_field { "replacement_field", +bp::char_ }; * My use case involves parsing identifiers that can only contain ASCII lowercase, uppercase, digits and the underscore. I'd usually do this by defining a `bool is_identifier_char(char c)` function. This is what I could do with Boost.Parser - is there a better way (one that doesn't force me to list all valid characters)? constexpr const char name_chars[] = "abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ_0123456789"; constexpr auto name_continuation_rng = std::span<const char>( name_continuation, sizeof(name_continuation) - 1 ); * What's the rationale behind the special naming convention for functions like _attr, _value, _globals and the like? Is there a reason why these can't be member functions of the context? * I've found really frustrating the generic lambda approach for semantic actions, since this completely inhibits tooling like clangd. Is there a reason why we can't have a public definition of the parsing context I could use in my functions? * I started my evaluation using clang-18 (Linux) but builds fail (seems to happen under all clang versions I tried). gcc-12 seems to work fine. Note that I'm using the develop branch, since I understand it contains the bug fixes for the issues that previous reviewers found. Regards, Ruben.

6 9

Boost.Parser review
by Richard 29 Feb '24

29 Feb '24

- Do you think the library should be accepted as a Boost library? Yes, this would be a great addition to Boost as a successor to Spirit. ====================================================================== Details: Note: I've only had time to read through the documentation. I'm familar with Spirit Classic, Spirit V2 and X3 parsing libraries and have done presentations on them using my own written example code. - What is your evaluation of the design? It's very similar to Boost.Spirit in philosophy, but other than the (optional) connection to Boost.Hana feels very decoupled from all the other bits of boost at a user level. Spirit's direct connection to things like Phoenix and Fusion made Spirit more complicated to explain to other developers and more difficult to use IMO. I understand why such things were done at the time of Boost.Spirit's writing, but being a C++17 library frees Boost.Parser from all these digressions which is good. The only thing obviously lacking were the binary parsers from Spirit V2 (bug filed). - What is your evaluation of the implementation? I've only reviewed the documentation, so I haven't had any time to dig into the implementation before the review deadline. I will say that there are no comments in the header files and that could be improved. It means that without consulting the tutorial documentation, I have no information in the included headers to guide me. - What is your evaluation of the documentation? The documentation is well written and follows a logical progression. It could use a math expression example as this is one of the most common reasons for needing to write a parser (typical C style math operators and precedence rules). The JSON example is nice (shows recursive rule parsing), but doesn't deal with operator precedence at all, so another detailed example showing this would be helpful. There were some minor typos and mistakes; I filed github issues on those. The concepts and reference section are just raw code dumps. They could use some additional doxygen style comments to tie things together. - What is your evaluation of the potential usefulness of the library? I would find this library a great successor to Spirit. - Did you try to use the library? With what compiler? Did you have any problems? No, I only had time to read through documentation. - How much effort did you put into your evaluation? A glance? A quick reading? In-depth study? I carefully read through every page of the documentation in the Tutorial section and skimmed over the reference section. - Are you knowledgeable about the problem domain? Yes. -- "The Direct3D Graphics Pipeline" free book <http://tinyurl.com/d3d-pipeline> The Terminals Wiki <http://terminals-wiki.org> The Computer Graphics Museum <http://ComputerGraphicsMuseum.org> Legalize Adulthood! (my blog) <http://LegalizeAdulthood.wordpress.com>

3 2

Boost.Parser review
by Ruben Perez 29 Feb '24

29 Feb '24

Hi all, This is my review of the proposed Boost.Parser. As in other occasions, I've taken a practical approach and used the library to (re)implement an existing, real feature in Boost.MySQL: client-side SQL formatting. This requires parsing a format string with replacement fields (similar to std::format strings). - What is your evaluation of the potential usefulness of the library? I think it's useful. Parsing is a common task, and this library simplifies it. I tend to prefer hand-crafted parsers in general, but libraries like the proposed tend to save time (and bugs). Also, many other users have manifested interest in it. I think the library is too heavyweight regarding compile times to be used in header-only libraries like Boost.MySQL, but it should be fine in compiled libraries and applications. - What is your evaluation of the design? I think it's pretty good in general. It allows you to express complex parsers using little code, which is good. In my opinion, it may be too generic (allowing any forward character range as input, for instance), which tends to increase complexity. I tend to prefer simpler approaches like the one Boost.URL uses - but I understand not everyone thinks like me, and there's a use case for each approach. As we discussed in previous posts, if I was writing this, I would have made some decisions differently (see https://lists.boost.org/Archives/boost/2024/02/256010.php) but I don't think there is any problem with the current design. The author has justified his decisions, and everything makes sense. - What is your evaluation of the implementation? I can tell it's really complex. I've attempted to debug a problem I had for which parser::trace::on wasn't enough (see below), and navigating the code was extremely difficult (reminds me of debugging Asio). This is probably inherent to the level of complexity of the library. This is not a criticism, but a thought I wanted to share. - Did you try to use the library? With what compiler? Did you have any problems? Yes, I did. As mentioned above, I re-implemented Boost.MySQL SQL formatting (see https://www.boost.org/doc/libs/master/libs/mysql/doc/html/mysql/sql_formatt…) using the proposed library. I've uploaded the code to a branch - you can check it here: https://github.com/boostorg/mysql/blob/66c99e31c9e548b6cf5b98e3d08255f22390… For reference, I've also pasted the grammar and the code at the end of this email. I've found the following problems: * Rule parsers using sequence + optional parsers yield unexpected results when the optional rule doesn't match. Making it a regular parser, rather than a rule parser, fixes the problem. The impact is that automatic replacement fields (i.e. `{}`) were being parsed as `{0}`. https://github.com/tzlaine/parser/issues/125 tracks this. * My clang-11 build fails. Looks like a concept is being used without proper protection, and the compiler doesn't support it. https://github.com/tzlaine/parser/issues/129 * My clang-16 build (and my local build attempts with clang 17, 18 and 19) fail because of a non-matching template redeclaration in parser/detail/text/transcode_view.hpp. I don't know if it's clang being picky or a clang bug. https://github.com/tzlaine/parser/issues/130 * My clang-14 build fails. This looks like it's hitting a clang + libstdc++ bug. See https://github.com/tzlaine/parser/issues/131. * My Apple clang 14 build fails. It also looks like an issue in clang or libc++. See https://github.com/tzlaine/parser/issues/133. * My MSVC 14.2 and 14.3 builds under C++17 fail (C++20 works fine). I've completely failed to parse what's the problem here. Description here: https://github.com/tzlaine/parser/issues/132 Some other minor problems: * As reported by other reviewers, enabling warnings=all or warnings=extra issues a lot of warnings. * [[no_unique_address]] (C++20) is used unprotected, which causes warnings under clang-7 (see https://github.com/tzlaine/parser/issues/128) * The CMakeLists.txt is not Boost-compliant (yet). * There is a #include <boost/hana.hpp>, which is not very friendly for compile-times - better replace it by the individual header that is needed. I've submitted the build logs together with all details I've been able to gather. I haven't been able to provide a minimal reproducible example for some of these (they were a lot and I had limited time). Note that all the builds referenced in the issues (except the OSX one) are run in Docker containers. If you have access to Docker, reproducing these environments should be trivial. Since I've done this in the past, should the author need any help with this, please let me know, I'm happy to help. Reading the CI files for the proposed library, I think compiler coverage is insufficient - for instance, there are no Linux clang builds, and the only Apple clang build uses clang 13 and C++17. - What is your evaluation of the documentation? The presentation is really good. I struggled to understand the concepts at first because I had no previous experience with parsers. I ended up reading the Bison concepts section (https://www.gnu.org/software/bison/manual/bison.html#Concepts) after which everything made perfect sense. I'd advise to expand the introduction a bit, or just point to other material for people like me. I fail to understand what RESOLVE means in https://tzlaine.github.io/parser/doc/html/boost_parser__proposed_/tutorial/…. Docs state "RESOLVE() is a notional macro that expands to the resolution of parse argument or evaluation of a parse predicate", but I'd say this resolution hasn't been explained yet - a link here would help. I've found the reference to be more confusing that helpful - it looks like a straight header dump. This is made worse by the concepts not being linked. Although it has many terrible things, the quickbook toolchain is (partly) capable of linking concepts - have a look at https://www.boost.org/doc/libs/master/libs/mysql/doc/html/mysql/ref/boost__…. This still has limitations, but I'd say it's better than what's currently there. If this is something you'd be interested in, please let me know and I will help you with it. - How much effort did you put into your evaluation? A glance? A quick reading? In-depth study? I've spent around 2 full days of work reading about the problem domain, studying the docs, writing my use case, diagnosing the problems I reported and writing this review. - Are you knowledgeable about the problem domain? I've never used a parsing library like this before. I've read about the problem in the past, but wasn't very knowledgeable about it before the review. I've written small parsers like the one for format strings in the past, though. - My conclusion My recommendation is to REJECT the library in its current form. This is not a hard rejection - I completely think this library can be useful to people. But I found too many problems while using it - too many to get it into Boost in its current form. I'd be happy to see this library being proposed again in a couple of months, once all the issues found during the review get fixed. - Affiliation disclosure Please note that I'm affiliated with the C++ Alliance. I'd like to thank Zach for proposing the library, and Marshall for managing the review. Regards, Ruben. - Reference: parsing code in Boost.MySQL /** * format-str = *( text | literal-opening-brace | literal-closing-brace | replacement-field ) * text = *( any characters except {} ) * replacement-field = "{" [ replacement-id ] "}" * replacement-id = ushort | field-name * field-name = (character a-z, A-Z, _) *( any characters 0-9, a-z, A-Z, _ ) */ // Note: globals is a format_state structure, which has member functions // to append raw text and replacement fields to the output string // Actions constexpr auto action_text = [](auto& ctx) { _globals(ctx).append_text(_attr(ctx)); }; constexpr auto action_replacement_field = [](auto& ctx) { const std::optional<std::variant<unsigned short, std::string>>& val = _attr(ctx); format_state& st = _globals(ctx); if (val) { if (const auto* idx = std::get_if<unsigned short>(&*val)) { st.append_indexed_field(*idx); } else { st.append_named_field(std::get<std::string>(*val)); } } else { st.append_auto_field(); } }; constexpr auto action_opening_brace = [](auto& ctx) { _globals(ctx).append_text("{"); }; constexpr auto action_closing_brace = [](auto& ctx) { _globals(ctx).append_text("}"); }; // Character ranges constexpr std::array<const char, 63> name_chars{ 'a', 'b', 'c', 'd', 'e', 'f', 'g', 'h', 'i', 'j', 'k', 'l', 'm', 'n', 'o', 'p', 'q', 'r', 's', 't', 'u', 'v', 'w', 'x', 'y', 'z', 'A', 'B', 'C', 'D', 'E', 'F', 'G', 'H', 'I', 'J', 'K', 'L', 'M', 'N', 'O', 'P', 'Q', 'R', 'S', 'T', 'U', 'V', 'W', 'X', 'Y', 'Z', '_', '0', '1', '2', '3', '4', '5', '6', '7', '8', '9' }; constexpr boost::span<const char, 53> name_start_chars{name_chars.data(), 53}; // Parsers and rules constexpr auto field_name = parser::char_(name_start_chars) >> *(parser::char_(name_chars)); constexpr auto replacement_id = parser::ushort_ | field_name; constexpr auto replacement_field = ('{' >> -replacement_id) > '}'; constexpr auto literal_open_brace = parser::lit("{{"); constexpr auto literal_close_brace = parser::lit("}}"); constexpr auto text = +(parser::char_ - '{' - '}'); constexpr auto format_str_parser = *( text[action_text] | literal_open_brace[action_opening_brace] | literal_close_brace[action_closing_brace] | replacement_field[action_replacement_field] ); // Top-level parsing function inline void parse_format_str(string_view format_str, format_context_base& ctx, span<const format_arg> args) { // By default, parser prints to cerr, which we don't want parser::callback_error_handler handler([](const std::string&) {}); // Create a parsing state format_state st(ctx, args); // Invoke the actual parsing bool result = parser::parse( format_str, parser::with_globals(parser::with_error_handler(format_str_parser, handler), st) ); // If there was an error, report it if (!result) { ctx.add_error(client_errc::format_string_invalid_syntax); } }

2 1

[release] The 1.85.0 release will close for major changes TOMORROW
by Marshall Clow 28 Feb '24

28 Feb '24

Calendar here: https://www.boost.org/development/ Next deadline: The master branch will close for the beta next Wednesday. — The release managers

1 0

Boost.Parser review by Tobias
by tobi＠die-loews.de 27 Feb '24

27 Feb '24

Boost.Parser review Why do we need a DSEL-Parser library in Boost: I think nobody, who once has written a parser with a DSEL (like e.g. Spirit) in C++, ever want's to go back to out off source parser-generators like yacc/bison or ANTLR (or even hand written parsers): it is so convenient having the parser definition as a grammar within the code. Additionally, you can quite easily hook into the parser (e.g. Spirit's Phoenix functions). So, IMHO there is definitely need for such C++ libraries. On the other hand, the task of creating such a library is very challenging and requires high expertise and coding standards, as library-users have to rely on its correctness. So, Boost with its standards and peer-review process is definitely the place for such a library. (Personally, I wouldn't use a parser-library the hasn't gone through such a process.) Should accept Boost.Parser into Boost? There are already three parser libraries in Boost: Spirt and its successors Qi and X3 - Spirit: very outdated interface, IIRC C++98 compatible, superseded by Qi - Qi: Simply a revolution in parsing! It was blowing my mind, when I first used it. The way attributes were composed and semantic actions could applied with Phoenix was totally exciting. But of course, there was also the downside of (very) long compilation-times and frustrating long error-messages when something got wrong. And (again IIRC) Qi came to life before C++11, so it is also C++98. - X3: I only wrote one larger X3 parser, and to be frank, IMHO it never made it to production-level. There are several things that worked perfectly with Qi, which I never got running the same way in X3. Additionally, the Spirit libraries seem no longer to be in active development. Now, let's get to Boost.Parser: First, I don't want to go into the details of the library, as I think other reviewers did a very good job there. I've been following its evolving since I heard of it in 2022. Back then, I did some test with it and reported some Issues, which got resolved. During the last two years many additional features got added to it. So, Boost.Parser is definitely under active development. Furthermore, the author is an expert for Unicode, which is reflected in the built-in Unicode support of the library. It is written in modern C++ (requires C++17). It is compile-time friendly, supports std::ranges and concepts. It offers an option/abstraction to choose between std::tuples, if needed, or the more flexible hana-implementation. It's syntax is close to Qi, so transition for Qi-users should not be too hard. The documentation contains a lot of examples that help to understand how the library works and how it can be used. Finally, I really like the very easy to use trace-mode. Again, should accept Boost.Parser into Boost? Definitely Yes! Tobias

3 2

Boost.Parser Review
by Phil Endecott 26 Feb '24

26 Feb '24

Boost.Parser Review =================== I've been using Spirit for almost 20 years. It has always been an amazing example of pushing the limits of what is possible in C++, even by the standards of Boost. So it has always left me thinking that we just need to wait a few more years until the language has the few more features needed to smooth over its remaining awkwardness. Now a few years have passed and we have, for example, lambdas, auto, constexpr, concepts. So I was excited to see what improvements Zach's proposed library has over Spirit. For example, when Metaparse was reviewed in 2015, compile-time parsing of BNF was discussed. Perhaps we should be able to write actual BNF in compile-time strings now, rather than re-use C++ operators? And now that we have constexpr, should we be able to convert the production rules to tables at compile time and do proper linear-complexity LALR parsing, rather than top-down? We do now have compile-time regular expression libraries than can do something like this. Initial Reaction ---------------- My first reaction when I looked at the docs was: - I'd like to congratulate Zach on choosing a sensible descriptive name for the library. - The rule syntax looks very much like Spirit. The docs look like the Spirit docs. It's more of an evolution than a revolution. - There's an ugly MACRO to define rules! That doesn't look very 2024 to me. Test Case --------- I decided to try to translate an exiting parser from Spirit v2 (qi) to the new library. It's a parser for latitude-longitude coordinates entered by a human, i.e. it is supposed to try to recognise a range of possible formats. Examples: 12.34 N, 56.78 E 56.78,-12.34 12d 30' n 45d 15' 7" w 12 30 45 N, 45 15 7 W 12d 30m 15s S 50d 59m 59s W There are some subtle issues with this grammar. Note for example that 's' could mean seconds or South. One advantage of Bison is that it gives compile-time diagnostics reporting some of these. Neither Spirit nor the new library can do this. The core of the Spirit code is as follows: (I will link to a .zip with the complete code at the end; I bet the mailing list messes up the long lines.) ///////////////////////////////////// degrees_symbol = lit(UTF8_DEGREES) | no_case[ lit("degrees") | lit("deg") | lit('d') ]; minutes_symbol = lit(UTF8_PRIME) | no_case[ lit('\'') | lit("minutes") | lit("min") | lit('m') ]; seconds_symbol = lit(UTF8_DOUBLE_PRIME) | no_case[ lit('"') | lit("seconds") | lit("sec") | lit('s') ]; uint_0_60 %= uint_ [ _pass = _1 < 60U ]; double_0_60 %= basic_udouble [ _pass = _1 < 60 ]; decimal_degrees %= basic_udouble >> -degrees_symbol; degrees_decimal_minutes = (uint_ >> -degrees_symbol >> double_0_60 >> -minutes_symbol) [ _val = _1 + _2/60.0 ]; degrees_minutes_seconds = (uint_ >> -degrees_symbol >> uint_0_60 >> -minutes_symbol >> double_0_60 >> -seconds_symbol) [ _val = _1 + _2/60.0 + _3/3600.0 ]; degrees %= degrees_minutes_seconds // Longest first. | degrees_decimal_minutes | decimal_degrees; northsouth %= no_case[ char_("ns") ]; eastwest %= no_case[ char_("ew") ]; latitude = (degrees >> northsouth) [( _pass = _1 <= 90, _val = if_else(_2=='S' || _2=='s', -_1, _1) )]; longitude = (degrees >> eastwest) [( _pass = _1 <= 180, _val = if_else(_2=='W' || _2=='w', -_1, _1) )]; signed_degrees %= basic_double >> -degrees_symbol; signed_latitude %= signed_degrees [ _pass = -90 <= _1 && _1 <= 90 ]; signed_longitude %= signed_degrees [ _pass = -180 <= _1 && _1 <= 180 ]; latlon = ((latitude >> longitude) [ _val = construct<g2d::Vector>(_2,_1) ]) | ((longitude >> latitude) [ _val = construct<g2d::Vector>(_1,_2) ]) | ((signed_longitude >> signed_latitude) [ _val = construct<g2d::Vector>(_1,_2) ]); ///////////////////////////////////// The complete Boost.Parser code is as follows: ///////////////////////////////////// #include "boost/parser/parser.hpp" #include <cassert> #include <iostream> #include <optional> #include <string> namespace bp = boost::parser; using namespace boost::hana::literals; namespace g2d { struct Vector { double x, y; }; }; bp::rule<struct uint_0_60, unsigned int> uint_0_60 = "uint_0_60"; bp::rule<struct double_0_60, double> double_0_60 = "double_0_60"; bp::rule<struct degrees_decimal_minutes, double> degrees_decimal_minutes = "degrees_decimal_minutes"; bp::rule<struct degrees_minutes_seconds, double> degrees_minutes_seconds = "degrees_minutes_seconds"; bp::rule<struct degrees, double> degrees = "degrees"; bp::rule<struct latitude, double> latitude = "latitude"; bp::rule<struct longitude, double> longitude = "longitude"; bp::rule<struct signed_latitude, double> signed_latitude = "signed_latitude"; bp::rule<struct signed_longitude, double> signed_longitude = "signed_longitude"; bp::rule<struct latlon, g2d::Vector> latlon = "latlon"; //const auto degrees_symbol = bp::no_case[ bp::lit("degrees") | bp::lit("deg") | bp::lit('d') ]; //const auto minutes_symbol = bp::no_case[ bp::lit('\'') | bp::lit("minutes") | bp::lit("min") | bp::lit('m') ]; //const auto seconds_symbol = bp::no_case[ bp::lit('"') | bp::lit("seconds") | bp::lit("sec") | bp::lit('s') ]; // FIXME those rules don't work and I don't know why. They work if the symbol is // the first alternative; it it's any of the other alternatives the double returned // by e.g. decimal_degrees below is always zero. // Use these instead: const auto degrees_symbol = bp::lit('d'); const auto minutes_symbol = bp::lit('m'); const auto seconds_symbol = bp::lit('s'); // Beware, 's' can also mean south. const auto uint_0_60_def = bp::uint_ [( [](auto ctx) { _pass(ctx) = _attr(ctx) < 60U; _val(ctx) = _attr(ctx); } )]; const auto double_0_60_def = bp::double_ [( [](auto ctx) { _pass(ctx) = _attr(ctx) < 60; _val(ctx) = _attr(ctx); } )]; const auto decimal_degrees = bp::double_ >> -degrees_symbol; const auto degrees_decimal_minutes_def = (bp::uint_ >> -degrees_symbol >> double_0_60 >> -minutes_symbol) [( [](auto ctx) { auto d = _attr(ctx)[0_c]; auto m = _attr(ctx)[1_c]; _val(ctx) = d + m/60.0; } )]; // FIXME this rule matches e.g. 150.5 as 150 .5; we want that input to // be matched by the decimal degrees rule as 150.5. In the qi code, which // has the same fundamental problem, it is avoided because the double_ // parser is configured to reject input with a leading decimal point. // It would be more correct to require that either a degrees symbol or // whitepace or both between the degrees and minutes numbers. That's // a bit complicated because the whitespace is handled by the skipper. // In a bottom-up parser I think the ambiguity is resolved by putting // decimal_degrees first in degrees_def below. That doesn't work for a // top-down parser. // FIXME for similar reasons, "150d 0.5m n" fails to parse, because // the degrees_minutes_seconds rule matches 150,0,.5 and then the next // rule up fails to parse the 'm'. const auto degrees_minutes_seconds_def = (bp::uint_ >> -degrees_symbol >> uint_0_60 >> -minutes_symbol >> double_0_60 >> -seconds_symbol) [( [](auto ctx) { auto d = _attr(ctx)[0_c]; auto m = _attr(ctx)[1_c]; auto s = _attr(ctx)[2_c]; _val(ctx) = d + m/60.0 + s/3600.0; } )]; const auto degrees_def = degrees_minutes_seconds | degrees_decimal_minutes | decimal_degrees; const auto northsouth = bp::no_case[ bp::char_("ns") ]; const auto eastwest = bp::no_case[ bp::char_("ew") ]; const auto latitude_def = (degrees >> northsouth) [( [](auto ctx) { auto d = _attr(ctx)[0_c]; auto ns = _attr(ctx)[1_c]; _pass(ctx) = d <= 90; _val(ctx) = ns=='S' || ns=='s' ? -d : d; } )]; const auto longitude_def = (degrees >> eastwest) [( [](auto ctx) { auto d = _attr(ctx)[0_c]; auto ew = _attr(ctx)[1_c]; _pass(ctx) = d <= 180; _val(ctx) = ew=='W' || ew=='w' ? -d : d; } )]; const auto signed_degrees = bp::double_ >> -degrees_symbol; const auto signed_latitude_def = signed_degrees [( [](auto ctx) { auto d = _attr(ctx); _pass(ctx) = -90 <= d && d <= 90; } )]; const auto signed_longitude_def = signed_degrees [( [](auto ctx) { auto d = _attr(ctx); _pass(ctx) = -180 <= d && d <= 180; } )]; const auto latlon_def = ((latitude >> longitude) [( [](auto ctx) { _val(ctx) = g2d::Vector{_attr(ctx)[1_c], _attr(ctx)[0_c]}; } )] ) | ((longitude >> latitude) [( [](auto ctx) { _val(ctx) = g2d::Vector{_attr(ctx)[0_c], _attr(ctx)[1_c]}; } )] ) | ((signed_longitude >> signed_latitude) [( [](auto ctx) { _val(ctx) = g2d::Vector{_attr(ctx)[0_c], _attr(ctx)[1_c]}; } )] ); BOOST_PARSER_DEFINE_RULES(uint_0_60); BOOST_PARSER_DEFINE_RULES(double_0_60); BOOST_PARSER_DEFINE_RULES(degrees_decimal_minutes); BOOST_PARSER_DEFINE_RULES(degrees_minutes_seconds); BOOST_PARSER_DEFINE_RULES(degrees); BOOST_PARSER_DEFINE_RULES(latitude); BOOST_PARSER_DEFINE_RULES(longitude); BOOST_PARSER_DEFINE_RULES(signed_latitude); BOOST_PARSER_DEFINE_RULES(signed_longitude); BOOST_PARSER_DEFINE_RULES(latlon); static std::optional<g2d::Vector> try_parse_latlon(std::string_view s) { auto input = latlon >> bp::eoi; return parse(s,input, bp::ws|bp::lit(',')); } int main(int argc, const char* argv[]) { assert(argc==2); auto opt_coords = try_parse_latlon(argv[1]); if (!opt_coords) { std::cerr << "parse error\n"; return 1; } else { std::cout << opt_coords->x << " " << opt_coords->y << "\n"; return 0; } } ///////////////////////////////////// That Ugly Macro --------------- bp::rule<struct latitude, double> latitude = "latitude"; const auto latitude_def = (degrees >> northsouth) .... ; BOOST_PARSER_DEFINE_RULES(latitude); Is a macro really the best way to do this? Spirit seems to manage without. Despite having a macro this is still very verbose. I've had to write the name of the rule FIVE times in three lines. Once there is a macro you might as well put everything inside it: BOOST_PARSER_DEFINE_RULE(latitude, double, (degrees >> northsouth) ....); Of course if you need to declare the rules before defining them due to recursion or other forward references you will need separate macros for declaration and definition. These rule declarations seem to need to be at global scope (maybe namespace scope?). Is that fundamental? Can't I put them in a class or a function? Semantic Actions ---------------- In Bison I can write semantic actions like this: { $$ = $1 + $2/60.0; } After expanding the $ variables that gets copied verbatim into the bison output, so it can include any code. Spirit clearly wanted to replicate that sort of functionality, but it pre-dates lambdas, so it includes a lot of amazing functionality that allows me to write semantic actions like: [ _val = _1 + _2/60.0 ] This is nice and concise but its limitation is of course that I cannot write arbitrary code in there. (BTW, are we strictly allowed to use identifiers starting with _ like _val?) What should this look like now that we have lambdas in the language? Of course it's going to be a bit more verbose because of the syntax overhead, but I was hoping that it would be something like this: [ [](auto deg, auto min) { return deg + min/60.0; } ] (Aside: That doesn't actually work because [[ can only appear in attributes even if there is a space, so it needs to be written [( [] ... )]. I did wonder if changing from operator[] to operator() might make sense?) That's longer than before, but I have given meaningful names to the parameters (which I can also do in Bison BTW) and I can include any code. But that's not the syntax that the current proposal needs. It needs this: [( [](auto ctx) { _val(ctx) = _attr(ctx)[0_c] + _attr(ctx)[1_c]; } )] Frankly I think that combines the worst of all the other options and adds some extra new verbosity of its own. One other advantage of having the lambda return a result could be improving how the semantic type (aka attribute type) of a rule is set. For example, if I have the rule degrees >> minutes where degrees and minutes return doubles, the semantic type of the combined rule is something like tuple<double,double>. But I'm going to add a semantic action that adds the two values as shown above, returning one double. If the return value of the semantic action's lambda were used as the semantic type of the rule then we could write: auto rule = (degrees >> minutes) [( [](auto d, auto m) { return d + m/60.0; } )]; and rule would return a double to its parent rule. As it is, the semantic action doesn't change the type and we have to explicitly and verbosely declare the rule as returning a double. Of course the context includes more than just the child rule semantic values and a slot for the result; for example it includes the _pass boolean that I use to clamp the range of values in my example: [( [](auto ctx) { _pass(ctx) = _attr(ctx)[0_c] <= 90; } )]; I suggest that either a special lambda signature is used to indicate that it is a predicate, or an additional "directive" e.g. predicate[ ... ] is added. Compilation Times and Errors ---------------------------- Compilation times for my example were: Boost.Parser: 28.6 s Boost.Spirit: 30.1 s but the grammar is not quite identical, so the small difference is not significant. Code size is somewhat larger for Parser than for Spirit. (g++ 12.2.0, -O3, Linux, aarch64.) I did not particularly notice improved error messages compared to Spirit, though they weren't worse. Consider for example this code from my example: return parse(s, input, bp::ws|bp::lit(',')); Originally I had this: auto skipper = bp::ws | bp::lit(','); return parse(s, input, skipper); But that failed to compile, and I got 15 screenfuls of inpenetrable error messages. I fixed it more-or-less by randomly changing things until it worked. If I now change it back I get only two screenfuls that accurately say that I can't return a bool from a function that's supposed to return an optional, but I still don't know why the return type of parse() changes when I move the declaration of the skipper. So I fear that the idea that compile times and error verbosity are improved compared to Spirit are not borne out. Bugs ---- I found a couple of bugs while writing this review which Zach has resolved. I suspect that this code has not had enough varied use to flush out all the issues. Other Issues ------------ The double_ parser is not configurable in the way that the Spirit double_ parser is. This is problematic; in my example 3e6n means "3 east 6 north", not "3000000 north", so I need a double_ parser that doesn't recognise exponents. I'd also like to ignore values with leading .s, i.e. 10.1 should not match int_ >> double_ as "10 0.1", and I really don't want a hacker to sneak a nan or inf into my code if it recognises those. The docs are not bad and are reminiscent of the Spirit docs. Personally I would prefer to see an example early on that takes a chunk of real BNF and translates it into a parser. I had issues with Apple Clang (15.0.0); it would not compile "#include <boost/parser.hpp>" until I turned off concepts. Has anyone tried with other Clangs? If this is not fixable maybe the library should detect this and use non-concepts mode automatically. Compiling with -Wall resulted in lots of unused parameter warnings. These can be fixed by commenting-out the parameter name, leaving just the type. Boost libraries should compile without warnings, some people use -Werror. Conclusion ---------- I was hoping to find a library that was an improvement on Spirit, but I regret to say that that's not what I've found here. The only notable improvement compared to Spirit.Qi that I've found is that no_case[] is propogated to nested rules, which isn't the case with Qi. Rules themselves are essentially the same as Spirit. The method for defining rules is more verbose and now needs an ugly macro. Semantic actions are less readable. It is possible that there are significant advantages compared to Spirit that I have missed, as a result of having used working Spirit code as my starting point, but I have read the doc's comparison with Spirit page. My conclusion is that this library should not be accepted. If others believe it should be accepted then I feel that should be conditional on many of the issues I've mentioned above being resolved, e.g. unused parameter warnings, configuration of the double_ parser, etc. File containing example: https://chezphil.org/tmp/parser_review.zip Regards, Phil.

4 4

Doxygen+Quickbook and C++20 concepts
by Zach Laine 26 Feb '24

26 Feb '24

I've seen concepts just vanish from Doxygen+Quickbook docs in the past. I thought this was just a limitation. However, looking at the Quickbook docs, I see that there's now a conceptref reference link. So, I put this very simple concept in a header (parser.hpp) to test things: /** \concept non_void */ template<typename T> concept non_void = (!std::same_as<T, void>); Doxygen appears to process it ok, or at least it says in its output that it does. Then I see non_void show up in these files: bin/parser_reference-xml.doxygen bin/parser_reference-xml/index.xml bin/parser_reference-xml/parser_8hpp.xml (I put the concept in this header, parser.hpp) bin/parser_reference-xml/conceptboost_1_1parser_1_1non__void.xml However, when I put [conceptref non_void Non-void.] in a .qbk file, all that shows up in the rendered HTML is "Non-void." (it's not a clickable link). Also, the no_void concept is not in the Doxygen reference for that header. Most frustratingly, concept constraints disappear from constrained templates in the Doxygen reference docs. Is there some special sauce that makes Quickbook+Doxygen process concepts? Is it doing it, but I'm not looking in the right place? Zach

1 0

Review of Parser library ends Wednesday, February 28th.
by Marshall Clow 25 Feb '24

25 Feb '24

So far we’ve received five reviews, and one of them was “docs only”. Keep those reviews coming! — Marshall

1 0

Boost.Parser review by Andrzej
by Andrzej Krzemienski 24 Feb '24

24 Feb '24

Hi, This is another review of Boost.Parser. Usefulness If Boost.Parser is a maintained version of Boost.Spirit that is already a worth goal. If Boost.Parser is a better documented version of Boost.Spirit that is already a gain. Note that the docs for Boost.Spirit X3 are hidden, and I was not aware of its existence until the review of Boost.Parser. I hear that the selling point of this library is Unicode support "through and through". I cannot confirm that it works as advertised, nor benefit from this guarantee, as all my use cases for a parser so far only dealt with the ASCII set. Design Boost.Spirit has a great design, and because Boost.Parser adopts the same design, it must be also good. I would intuitively expect that C++17 offers sufficient number of new features that the design for a parser library would be improved over Boost.Spirits. For instance, I am surprised that we still need to use a macro. Not that I can offer a better alternative. I do not know much about the implementation difficulties. so maybe the macro is the best choice. Wouldn't template explicit specializations do the job? The fact that this library automatically adapts aggregate types as attributes in a Boost.PFR way is really cool. I am convinced that compiler error messages could be better. This can be done by using a combination of static_assert and implementation details SFINAEd away based on the same condition as in static_assert. See https://github.com/tzlaine/parser/issues/56 I am unhappy about the fact that as simple task as parsing a JSON-like array of ints `[1, 2, 3]` into a vector requires me to define a rule. Spirit introduced operator% that doesn't work for empty lists, but doe to its clever attribute conversions (at least in Spirit2), I could define: auto array = '[' > ((int_ % ',') | eps) > ']'; And it would deduce the return attribute alright. But because Boost.Parser wants to be more strict about clever attribute conversions this option is gone, and no alternative is provided other than to declare a rule, which I never needed with Boost.Spirit. See https://github.com/tzlaine/parser/issues/67 I am not comfortable that I have to use the macro BOOST_PARSER_DEFINE_RULES. I would expect that template specializations should give a similar effect. But I do not know how to make it better. But if I have to use a macro, maybe it could offer more, like checking if the rule is compatible with its definition (for earlier bug reporting). I am missing a tool that would give me a compile-time answer * can I pass this attribute to that parser when parsing this type of character? * will my rule with its parser compile for a given input character type? * will my rule with its parser compile for at least one input character type? Documentation To me, the tutorial and overview in the documentation were sufficient to understand the library. But this is because I had learned Boost.Spirit before. If this were my first exposure to "a parser implementation via expression templates", I would be overwhelmed. Even though a lot of effort went into preparing a soft introduction to the subject, the subject is so complicated that it requires a super-gentle introduction. Some things remain underdocumented, like the interface of context. See https://github.com/tzlaine/parser/issues/104 After having stared at the docs for more than a month, I still have trouble finding the table with all the parsers listed. The reference section of documentation is missing details, such as what functions throw, what they expect of their arguments, what they guarantee, what is the exception safety level. For instance, see https://github.com/tzlaine/parser/issues/103 Also, the layout of the reference section looks like it is driven by an auto-generation tool run on the header files. It is not very user friendly. for instance, trying to find the specification of function parse() in https://tzlaine.github.io/parser/doc/html/header/boost/parser/parser_hpp.ht… isn't easy: neither visually (the amount of content is overwhelming) nor with grep-like tool (a lot of things there have "parse" in the name). What is good for header organization is not necessarily good for documentation organization. I am uncomfortable with the responses from the author that the reference section is missing parts, such as concepts, because the documentation toolchain does not support them. This would look like a bad choice of the tool. On the other hand, I do not know of any satisfactory tool for good C++ documentation. My testing I spent like a week trying to compile my parser for a text-based game engine, which was previously compiled with Boost.Spirit v2. Here's a sample file to parse (in Polish): https://raw.githubusercontent.com/akrzemi1/wdungeon/master/wdungeon.plot Here's the original Spirit V2 parser: https://raw.githubusercontent.com/akrzemi1/wdungeon/master/parser.cpp The new parser in BoostParser is included below. I didn't have to use rules in the original version. I am forced to use them in Boost.Spirit. I was not interested in performance testing as my use case is to read the config file upon application startup, so I can afford to wait. I tried the library with the newest versions of MSVC, GCC and Clang. It works in all of them. I filed a number of bug reports, to which Zach has been responding extremely quickly. Thank you! I also appreciate the negative responses, as they indicate that the author has a clear and coherent vision of what he wants the library to be. I recommend accepting the library into Boost. I would also like to thank Zach for writing and sharing this library! Regards, &rzej; ``` namespace parser { using namespace plot2; const auto identifier = bp::lexeme[+(bp::digit | bp::lower | bp::upper | bp::char_('_'))]; const bp::rule<struct cond_tag, std::vector<Variable>> cond = "cond"; const bp::rule<struct set_vars_tag, std::vector<Variable>> set_vars = "set_vars"; const bp::rule<struct choice_tag, Choice> choice = "choice"; const bp::rule<struct continuation_tag, Alternative> continuation = "continuation"; const bp::rule<struct map_tag, std::vector<MapStep>> map = "map"; const bp::rule<struct label_tag, std::string> label = "label"; const bp::rule<struct text_tag, std::string> text = "text"; const bp::rule<struct transition_tag, Transition> transition = "transition"; const bp::rule<struct redirection_tag, Redirection> redirection = "redirection"; const bp::rule<struct comment_tag> comment = "comment"; const bp::rule<struct plot_tag, GamePlot> plot = "plot"; const auto cond_def = ("[" >> ((identifier >> "=" > bp::int_) % ",") > "]") | bp::attr(std::vector<Variable>{}); const auto set_vars_def = ("[" >> ((identifier >> ":=" > bp::int_) % ",") > "]") | bp::attr(std::vector<Variable>{}); auto end_tag = bp::lit("[") >> bp::char_("+!") >> bp::lit("]"); auto label_def = bp::lit("[") >> identifier >> bp::lit("]"); auto text_def = bp::lexeme[+(bp::char_ - ']' - '[')]; auto map_step = bp::lit("^") >> -bp::char_("NESW") >> -(bp::lit(".") >> (+bp::char_("STCLPRXHUVD#"))); auto map_def = bp::lit("[") >> +map_step >> bp::lit("]"); auto redirection_def = +(bp::lit("[->]") >> cond >> (-map) >> label >> set_vars); auto option = bp::lit("[#]") >> cond >> text >> (-map) >> label >> (-text) >> set_vars; auto choice_def = bp::lit("[?]") >> text >> (+option); auto continuation_def = redirection | end_tag | choice; auto transition_def = bp::lit("[##]") > label >> -map >> -text > continuation; auto comment_def = bp::lit("[//]") >> bp::omit[*(bp::char_ - ']' - '[')]; auto plot_def = +transition; BOOST_PARSER_DEFINE_RULES(cond, set_vars, choice, continuation, map, label, text, transition, redirection, comment, plot); } ```

2 3

Parsers vs Unicode
by Arno Schoedl 24 Feb '24

24 Feb '24

Since the reviews of Boost.Parser are currently on, I wanted to share an insight we had at think-cell when working with Boost.Spirit. We have standardized on it for years for all custom parsing needs. Most parsers are small, but some are larger, like Excel expressions. Of course, our input is mostly Unicode, either UTF-8 or UTF-16. Matching Unicode is complex. Comparison by code point is usually not the right thing. Instead, we must normalize, for which we even have various choices of what to accept as equal: https://en.wikipedia.org/wiki/Unicode_equivalence Case-insensitive matching is even more complex, slow, and even language-dependent. Input is often not guaranteed to be valid Unicode. For example, file names on Windows are sequences of 16-bit units, allowing unmatched surrogates, same with input from Win32 edit boxes and file content. But we realized that for almost all grammars we have, all this complexity does not matter. The reserved symbols of most grammars (JSON, XML, C++, URLs, etc.) are pure ASCII. Semantically relevant strings are ASCII as well („EXCEL.EXE“). ASCII can be correctly and quickly matched on a per-code-unit basis. Case-insensitive matching for ASCII is simple and fast. User-defined strings, such as JSON string values, may contain Unicode, but then they usually do not affect parsing decisions. The user may want Unicode validation for these strings, but this can be done by the leaf parser for these strings, rather than for the whole input. Since so much matching is against ASCII, we found it useful to have compile-time known ASCII literals in the parser library. With them, the same grammar can be used for all input encodings. When parsing user-defined strings, they will have the encoding of the input, but that’s fine. Any encoding conversion can be dealt with separately from the parser. Finally, we may want to parse more than just strings. Parsing binary files, or sequences of DNA, should be possible and efficient. Thus I recommend separating Unicode processing from the parser library. The parser library operates on an abstract stream of symbols. For Unicode text these would be code units. It provides the composite parsers such as sequences with and without backtracking, alternatives, Kleene star etc., and leaves the interpretation of the symbols entirely to the leaf parsers, which may or may not care about Unicode. We started modifying Boost.Spirit in this direction, and it serves us well. -- Dr. Arno Schödl CTO schoedl(a)think-cell.com<mailto:schoedl@think-cell.com> | +49 30 6664731-0 We are looking for C++ Developers: https://www.think-cell.com/developers think-cell Software GmbH (Web site<https://www.think-cell.com>) Leipziger Str. 51, 10117 Berlin, Germany Main phone +49 30 6664731-0 | US toll-free +1 800 891 8091 Amtsgericht Berlin-Charlottenburg HRB 180042 Directors: Christoph Hobo, Dr. Arno Schödl Please refer to our privacy policy<https://www.think-cell.com/privacy> on how we protect your personal data.

3 4

Odd build error in 1.85 pre-release - filesystem
by Tom Kent 23 Feb '24

23 Feb '24

When building for windows against the 1.85.0 nightly snapshot, I'm seeing an odd error with no info around it: - type_erasure : building - url : building - wave : building ...patience... ...patience... ...patience... ...patience... ...patience... ...patience... ...patience... [errno 22] failed to scan file '': Invalid argument...found 39744 targets... Upping the verbosity in B2, I was able to find that it appears to happen in filesystem: bind -- <object(c-scanner)@8602>boost\filesystem\detail\type_traits\disjunction.hpp: boost\filesystem\detail\type_traits\disjunction.hpp time -- <object(c-scanner)@8602>boost\filesystem\detail\type_traits\disjunction.hpp: 2024-02-22 07:18:09.000000000 +0000 make -- <object(c-scanner)@8602>boost\filesystem\detail\type_traits\disjunction.hpp make -- <object(c-scanner)@8602>boost\filesystem\detail\type_traits\disjunction.hpp time -- <object(c-scanner)@8602>boost\filesystem\detail\type_traits\disjunction.hpp: unbound made stable <object(c-scanner)@8602>boost\filesystem\detail\type_traits\disjunction.hpp make -- <object(c-scanner)@8602>boost\filesystem\detail\header.hpp make -- <object(c-scanner)@8602>boost\filesystem\detail\header.hpp bind -- [errno 22] failed to scan file '': Invalid argument <object(c-scanner)@8602>boost\filesystem\detail\header.hpp: boost\filesystem\detail\header.hpp time -- <object(c-scanner)@8602>boost\filesystem\detail\header.hpp: 2024-02-22 07:18:09.000000000 +0000 make -- <object(c-scanner)@8602>boost\filesystem\detail\header.hpp make -- <object(c-scanner)@8602>boost\filesystem\detail\header.hpp time -- <object(c-scanner)@8602>boost\filesystem\detail\header.hpp: unbound made stable <object(c-scanner)@8602>boost\filesystem\detail\header.hpp Anyone have ideas on what this can be? Why it doesn't show up more like a normal error? Thanks, Tom

3 4

2023 Transparency Report
by Louis Tatta 21 Feb '24

21 Feb '24

Hello, Louis Tatta here, CEO of The C++ Alliance, Inc, a registered 501(c)(3) non-profit organization dedicated to the support of C++. This is our 2023 transparency report regarding our charitable work for the Boost C++ Library Collection. First, some background on our operations. The C++ Alliance seeks out the highly talented and experienced C++ experts and hires them, usually full-time, so they can focus completely on their open-source projects. Our Staff Engineers maintain existing Boost libraries, write new Boost libraries, and contribute to other Boost projects. We employ IT experts full-time to maintain and improve the infrastructure which supports Boost, including the legacy web server, the Drone continuous integration servers, the scripts used to deploy GitHub Actions for Boost repositories, and the scripts which publish the Boost release. In addition, we provide on-demand technical support services for Boost authors and maintainers who have infrastructure related problems. The Boost Mailing List continues to be the premier place for high-quality discussion of the Boost libraries and tangential C++ Standards related topics. The C++ Alliance supports the use of the mailing lists going forward. We are upgrading it to the latest Mailman version, and building an optional web-based front-end allowing interaction using only a browser. We continue to operate the Official C++ Language Slack Workspace (https://cpp.al/slack) which hosts the most popular interactive discussions regarding the Boost libraries. The C++ Alliance sponsors a paid plan to provide full history, video and audio conferences, collaboration tools, and unlimited document storage for seventeen dedicated Boost library channels and one main Boost discussion channel. Our largest project for 2023 is the continuation of work on the new Boost website. The new site is a C++ social media portal with rich support for user-generated content, and a powerful back-end which has visibility into the contributions made on GitHub and the release process. This allows us to deliver an elevated user experience with the hopes of attracting fresh talent to Boost. Also,note that the graphics on the website are hand-drawn by our contract artist and reflect our level of commitment to ensure that Boost, to put it simply, looks good. In 2023 there were a total of four Boost Formal Reviews. One of the reviewed libraries is authored by a C++ Alliance Staff Engineer. Three of the reviews were managed by C++ Alliance team members. Out of a total of twenty-eight submitted reviews for the year, twelve were from C++ Alliance team members. Last year we increased our efforts to build Boost’s social media presence. There were a total of twelve messages from the @Boost_Libraries X (formerly Twitter) account, all submitted by C++ Alliance team members. Three of them contained artwork from Bob Ostrom commissioned by us. Messages containing images get three times more engagement than text-only messages. We believe that the X platform has unique strategic value for informing newer generations about the Boost value proposition. A total of $1,768,000 was spent on Boost-related contributions, broken down thusly (and rounded to the nearest thousand): Staff Engineers Compensation $1,240,000 Website Software Development $570,000 Server Hosting $62,000 C++ Slack Workspace $96,000 Conference Sponsorship $10,000 Conference Attendance $10,000 During 2023 we employed a total of 12 individuals to contribute to Boost. Here is a high-level summary of accomplishments: Sam Darwin (Chief Technical Officer) * Boost website maintenance and administration * Boost per-pull-request documentation previews * Boost Release Process development, maintenance, and administration * Boost Mailman services maintenance and upgrade * Boost GitHub Actions self-hosted runner project development * Boost Drone service administration and maintenance * New Boost website deployment, administration, and development Dmitry Arkhipov (Staff Engineer) * Boost.JSON maintenance Alan de Freitas (Staff Engineer) * Boost.URL maintenance * Mr. Docs project management (https://mrdocs.com) * GitHub actions support scripts for Boost CI (https://alandefreitas.github.io/cpp-actions/cpp-actions/index.html) Christian Mazakas (Staff Engineer) * Boost.Unordered evolution project * Boost.Buffers development (new library) * Boost.Http.Proto, Boost.Http.Io development (new libraries) * Boost.Websocket.Proto, Boost.Websocket.Io development (new libraries) Krystian Stasiowski (Staff Engineer) * Boost.StaticString maintenance * Mr. Docs Lead engineer (https://mrdocs.com/) * Clang/LLVM contributions Peter Turcan (Senior Technical Writer) * Boost User Guide development (new documentation) * Boost Contributor Guide (new documentation) * Boost Formal Reviews (new documentation) Matt Borland (Staff Engineer) * Boost.Charconv (new, accepted library) Ruben Perez * Boost.MySQL maintenance (new, accepted library) * User Guide, Contributor Guide contribution (new documentation) Mohammad Nejati (Staff Engineer) * Boost website full-text search feature * Boost.Beast maintenance Fernando Pelliccioni (Staff Engineer) * Mr. Docs development (https://mrdocs.com/) Spencer Strickland (Senior Web Developer) * New website front-end and scripting Klemens Morgenstern (Staff Engineer) * Boost.Beast maintenance * Boost.Cobalt (new, accepted library) Joaquin M Lopez Munoz (Staff Engineer) * Boost.Unordered evolution project lead * Boost Contributor Guide contributions (new documentation) Our sources of funding are secure and we look forward to continuing our charitable contributions throughout this decade and beyond. It is an honor and a pleasure to support the Boost C++ Library collection. Thank You Louis Tatta

5 4

Reminder: Boost 1.85.0 will be closing for new libraries and breaking changes THIS WEDNESDAY
by Marshall Clow 20 Feb '24

20 Feb '24

As always, look at the calendar at https://www.boost.org/development/ — Marshall

2 1

Review of Parser library begins today
by Marshall Clow 19 Feb '24

19 Feb '24

The review of Zach Laine’s proposed Boost.Parser library begins today and will end on February 28th. From the introduction page of the documentation: Boost.Parser is a parser combinator library. That is, it consists of a set of low-level primitive parsers, and operations that can be used to combine those parsers into more complicated parsers. There are primitive parsers that parse epsilon (the empty string), chars, ints, floats, etc. There are operations which combine parsers to create new parsers. For instance, the Kleene star operation takes an existing parser p and creates a new parser that matches zero or more occurrences of whatever p matches. Both callable objects and operator overloads are used for the combining operations. For instance, operator*() is used for Kleene star, and you can also write repeat(n)[p] to create a parser for exactly n repetitions of p. Boost.Parser also tries to accommodate the multiple ways that people often want to get a parse result out of their parsing code. Some parsing may best be done by returning an object that represents the result of the parse. Other parsing may best be done by filling in a preexisting data structure. Yet other parsing may best be done by parsing small sections of a large document, and reporting the results of subparsers as they are finished, via callbacks. Boost.Parser accommodates all these ways of working, and even makes it possible to do callback-based or non-callback-based parsing without rewriting any code (except by changing the top-level call from parse() to callback_parse()). All of Boost.Parser's public interfaces are sentinel- and range-friendly, just like the interfaces in std::ranges. Boost.Parser is Unicode-aware through and through. When you parse ranges of char, Boost.Parser does not assume any particular encoding — not Unicode or any other encoding. Parsing of inputs other than plain chars assumes that the input is Unicode. In the Unicode-aware code paths, all parsing is done by matching code points. This means that you can feed UTF-8 strings into Boost.Parser, both as input and within your parser, and the right sort of matching occurs. For instance, if your parser is trying to match repetitions of the char '\xcc' (which is a lead byte from a UTF-8 sequence, and so is malformed UTF-8 if not followed by an appropriate UTF-8 code unit), it will not match the start of "\xcc\x80" (UTF-8 for the code point U+0300). Boost.Parser knows that the matching must be whole-code-point, and so it interprets the char '\xcc' as the code point U+00CC. Error reporting is important to get right, and it is important to make errors easy to understand, especially for end-users. Boost.Parser produces runtime parse error messages that are very similar to the diagnostics that you get when compiling with GCC and Clang (it even supports warnings that don't fail the parse). The exact token associated with a diagnostic can be reported to the user, with the containing line quoted, and with a marker pointing right at the token. Boost.Parser takes care of this for you; your parser does not need to include any special code to make this happen. Of course, you can also replace the error handler entirely, if it doesn't fit your needs. Debugging complex parsers can be a real nightmare. Boost.Parser makes it trivial to get a trace of your entire parse, with easy-to-read (and very verbose) indications of where each part of the trace is within the parse, the state of values produced by the parse, etc. Again, you don't need to write any code to make this happen — you just pass a parameter to parse(). Github: https://github.com/tzlaine/parser Docs https://tzlaine.github.io/parser — Marshall

1 0

Re: [boost] Should boost::core::string_view be made public?
by g.peterhoff＠t-online.de 18 Feb '24

18 Feb '24

Have you come to a conclusion how this should be handled (in the future)? The problem is basically that there are different implementations for string_view. I don't know why it was done this way. Presumably it's because various boost libraries want to be independent of others, so that some things are implemented anew each time (within the library) instead of using existing libraries. This will also be due to the fact that boost is not atomistic enough, so that large libraries might have to be included/used, although only a fraction of the functionality is needed. My suggestion: - Throw out boost::utility::string_view - Make boost::core::detail::string_view public, just like all other backports in boost::core. - Check if there are other multiple implementations. If so, pull them out into separate small boost libraries. (For databases, this would be called normalization, but it must not be over-normalized). regards Gero

5 4

Potential Launch of Boost Website: Request for Final Feedback
by Louis Tatta 17 Feb '24

17 Feb '24

Louis here from the C++ Alliance. With the potential launch of the new Boost website on the horizon this week, we're making a final call for your feedback. Your insights a few months ago were incredibly helpful, and as we approach the launch, we'd value your final review. If you have a moment to look over the site again and note any issues or suggestions, it would be of great help. Feedback can be submitted on our GitHub issues page: https://github.com/cppalliance/temp-site/issues. Thank you for your ongoing support and contributions to the Boost community. Looking forward to your feedback. Best regards, Louis C++ Alliance

18 79

Re: [boost] New Website Repositories
by Glen Fernandes 16 Feb '24

16 Feb '24

On 2024-02-16, Vinnie Falco wrote: > On Fri, Feb 16, 2024 at 12:33, Glen Fernandes wrote: > > If you want to follow the tradition of source files, the easiest > > convention to follow is to state that your files, e.g. > > > >  > > We can do that, or alternatively is it possible to just plop a LICENSE > file at the root of the repository? I would prefer both (thanks). Glen

1 0

New Website Repositories
by Vinnie Falco 16 Feb '24

16 Feb '24

All: The contribution of a brand new, mostly complete website at the level of quality of what we at The C++ Alliance have developed (see https://preview.boost.org) is a rare event. We are proud to share this special moment in Boost history. As is the Boost tradition we propose to do the following: * Transfer of all website related repositories to the Boost GitHub organization (these will also be renamed to something sensible): https://github.com/cppalliance/temp-site https://github.com/cppalliance/temp-site-documentation https://github.com/cppalliance/site-docs https://github.com/cppalliance/boost-mailman ...plus any other miscellaneous necessary repositories that Sam has created for the administration of the website, mailing list, and release process. * Whatever is the appropriate license for the artwork to be used on the website, with copyright to "The C++ Alliance, Inc. (https://cppalliance.org)" With respect to the artwork licensing, I have to admit I am not an expert so we will work to find out what the proper solution is. Thanks

3 3

Slack Workspace Link
by Spencer Strickland 16 Feb '24

16 Feb '24

Hi all - I’ve submitted a pull request to add the Official C++ Language Slack Workspace link to the website, can someone please merge this? https://github.com/boostorg/website/pull/815 Adding Slack link by 4down · Pull Request #815 · boostorg/website github.com Thanks, Spencer

2 1

Proposal to make Boost easily citable in academic works with Zenodo
by Hans Dembinski 15 Feb '24

15 Feb '24

Dear all, Nick Smith, an academic colleague, approached me with the question of how to cite Boost in academic works. As far as I am aware, we don't have a policy on that. Here is a proposal, mainly directed towards the admins of the Boost super-project on Github. Since a few years now zenodo.org <http://zenodo.org/> provides an easy to make software citable without requiring us to publish a paper in some journal. You can just sign in to Zenodo with your Github account and enable your repositories. On the next release, a Zenodo entry will be automatically generated, that academics can then cite easily. The procedure (with pictures) is explained here: https://inbo.github.io/tutorials/tutorials/git_zenodo I use Zenodo since a while for my scientific Python libraries and it works well. Once you set it up, it is a maintenance-free solution. It would be great if the admins of https://github.com/boostorg/boost would set this up for the Boost super-project, so that all of Boost becomes citable on the next release. Best regards, Hans

2 2

Preview Site Link for Boost Website Feedback
by Louis Tatta 13 Feb '24

13 Feb '24

In my last email, I forgot to include the preview link for the new Boost website. Here it is: https://www.preview.boost.org/ <http://preview.boost.org>. Please take a look and report any feedback or issues on our GitHub page: https://github.com/cppalliance/temp-site/issues. Thanks for your help. Louis C++ Alliance

3 3

Should boost::core::string_view be made public?
by Дмитрий Архипов 08 Feb '24

08 Feb '24

boost::core::string_view is a string_view implementation that (unlike boost::string_view from Utility) can interconvert with std::string_view. This functionality was necessary for Boost.JSON to drop the standalone mode, because people who have access to C++17 prefer to use std::string_view wherever they can. At the time there was no consensus on whether the type should be made public. Now in addition to Boost.JSON the type is also used at least by Boost.URL. And recently added Charconv is also using it. So, I want to raise the question again: should we make the type public and refer to it directly in our libraries' docs, rather than considering it an implementation detail?

5 21

Re: [boost] [Scope] Peer review conclusion
by Andrey Semashev 06 Feb '24

06 Feb '24

On 2/6/24 22:29, Дмитрий Архипов wrote: > Looks good to me. I consider the review conditions satisfied. Thank you Dmitry. And especially for taking the time to review the documentation and point out errors. > пн, 5 февр. 2024 г. в 03:47, Andrey Semashev <andrey.semashev(a)gmail.com>: > >> >> On 1/15/24 22:50, Дмитрий Архипов via Boost wrote: >>> Dear Boost community, the formal review of Boost.Scope has taken place >>> between 26th of November and 5th of December of the previous year. I >>> have received 5 reviews in total, including 4 here on the mailing list >>> and 1 on Reddit. Two of the reviews recommended unconditional, and 3 >>> conditional acceptance. The >>> reviews came from: >>> - Klemens Morgenstern, >>> - Janko Dedic, >>> - Julien Blanc, >>> - David Sankel, >>> - /u/jonesmz on Reddit. >>> >>> Also, several people have given insightful comments but did not provide a >>> review. I would like to thank all of the people who took their time to write >>> reviews or participate in the discussions. Your effort was very important and >>> valuable. >>> >>> The outcome of the review is that Boost.Scope is ACCEPTED with several minor >>> CONDITIONS. >>> >>> 1. noexcept specification on destructors of scope guards should be properly >>> documented. Andrey has already commented that the technical hurdle that >>> prevented it was eliminated. >>> >>> 2. There should be a good motivating example for scope_success. There was a lot >>> of comments regarding scope_success and its seeming uselessness. Without a >>> good example I see the same pattern occurring with future users. >>> >>> 3. The examples should better describe what they are trying to achieve. Several >>> comments about examples suggested incorrect changes, which signals that readers >>> failed to understand them. >>> >>> After a lot of consideration I decided against requesting the author to remove >>> unique_resource and related functionality from the library. While several >>> reviewers wanted a more "concise" library, all noted that the component is >>> useful. >>> >>> One last thing I wanted to point out is that all reviewers and most commenters >>> were adamant that compatibility with the Technical Specification on which this >>> library was initially based should not be a goal. In fact, Andrzej Krzemienski >>> even noted that such compatibility has prevented him from adequately evaluating >>> the library on its own merit. In my opinion this should be a sign to all of us >>> that people prefer better APIs over standard APIs. I recommend Andrey to >>> re-evaluate those parts of the library's APIs that he copied from the TS and >>> potentially pick better names for member functions. >>> >>> Thanks to Andrey for submitting this library to Boost. And thanks again to the >>> reviewers and everyone who provided feedback, who ultimately made this review >>> possible. >> >> I have updated the library according to review comments and conditions. >> To specifically address the acceptance conditions: >> >> 1. Noexcept specifications for destructors are now present in the docs. >> For example: >> >> https://lastique.github.io/scope/libs/scope/doc/html/boost/scope/defer_guar… >> https://lastique.github.io/scope/libs/scope/doc/html/boost/scope/scope_exit… >> https://lastique.github.io/scope/libs/scope/doc/html/boost/scope/unique_res… >> >> The fix for the BoostBook stylesheets is currently in develop. >> Hopefully, it will get merged to master soon. >> >> 2. I have added an example showing usage of all three conditional scope >> guards, including scope_success, here: >> >> https://lastique.github.io/scope/libs/scope/doc/html/scope/scope_guards.htm… >> >> The example is based on the one I posted during the review. >> >> 3. I have added more comments to some examples, as well as the >> discussion around them. For example, the examples on the front page are >> better commented now: >> >> https://lastique.github.io/scope/libs/scope/doc/html/index.html >> >> Some examples were modified or completely rewritten. For example, the >> locked_write_string was modified to reduce code duplication: >> >> https://lastique.github.io/scope/libs/scope/doc/html/index.html >> >> The leading example for unique_resource was rewritten: >> >> https://lastique.github.io/scope/libs/scope/doc/html/scope/unique_resource.… >> >> And a new example for unique_resource was added on the front page: >> >> https://lastique.github.io/scope/libs/scope/doc/html/index.html >> >> There are many more additions and modifications than I can mention here. >> >> >> There were also changes that were requested by reviewers or were the >> result of the discussion. The changelog here lists most of the changes: >> >> https://lastique.github.io/scope/libs/scope/doc/html/scope/changelog.html >> >> To mention the most prominent changes: >> >> * BOOST_SCOPE_FINAL was renamed to BOOST_SCOPE_DEFER and scope_final to >> defer_guard. >> * The `release()` member of scope guards was removed. `set_active()` is >> still present and is the way to activate and deactivate scope guards. >> * Added `operator bool()` to `unique_resource`. >> * Added a C++17 `unallocated_resource` class template that simplifies >> declaration of resource traits when all unallocated resource values can >> be listed. Along with the recently added to Boost.Core `functor` >> template, this can significantly reduce the amount of code one needs to >> write to declare a `unique_resource`. For example, a `unique_resource` >> for Windows handles could be declared like this: >> >> unique_resource< >> HANDLE, >> functor< CloseHandle >, >> unallocated_resource< INVALID_HANDLE_VALUE, (HANDLE)NULL > >> > handle; >> >> https://lastique.github.io/scope/libs/scope/doc/html/scope/unique_resource.… >> https://www.boost.org/doc/libs/develop/libs/core/doc/html/core/functor.html >> >> * `unique_resource` now enforces requirements on the resource traits >> with static asserts rather than falling back to the "no resource traits" >> mode of operation. >> * `unique_resource` no longer supports the "reduced" resource traits, >> where the traits were only used to customize the default resource value >> but not to distinguish allocated and unallocated resource values. >> * Added documentation sections discussing differences with the Library >> Fundamentals TS: >> >> https://lastique.github.io/scope/libs/scope/doc/html/scope/scope_guards.htm… >> https://lastique.github.io/scope/libs/scope/doc/html/scope/unique_resource.… >> >> * On the front page, removed comparison with Boost.ScopeExit from the >> table. There is a separate section for it: >> >> https://lastique.github.io/scope/libs/scope/doc/html/scope/scope_guards.htm… >> >> Also added another row to the table that shows explicit deactivation of >> the scope guards by calling `set_active(false)`. >> >> * There is now a section discussing caveats of capturing variables by >> reference in scope guards: >> >> https://lastique.github.io/scope/libs/scope/doc/html/scope/scope_guards.htm… >> >> There are probably other changes that I forgot to mention. >> >> >> Dmitry, please let me know if you consider the review conditions >> satisfied or if there needs to be done something more. >> >> If everything's fine, what needs to be done to move the library into >> boostorg? >>

1 0

Re: [boost] critical bugs in charconv
by g.peterhoff＠t-online.de 05 Feb '24

05 Feb '24

> So what's your point? Another example. I had asked for a TypeTrait is_integer and also supplied code for it (https://github.com/boostorg/type_traits/issues/186) The point is that is_integer only returns integer (no character, no bool). John immediately closed my request "We are not responsible for that". Instead of admitting a mistake (of course I make some myself) and saying "we forgot/didn't think of it, we'll do it", the only answer is "we don't care". That's thinking from the wallpaper to the wall. As I said, boost used to be progressive, but now when you make a suggestion, all you get is "We're not responsible for that/we're not interested in that/we might have to change something that's not possible" And this even with such a simple TypeTrait. Single file. No dependencies. And on the other hand, libraries with the most severe buffer overflows (charchonv) are included, where obviously no tests are carried out at all.

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Re: [boost] critical bugs in charconv
by g.peterhoff＠t-online.de 05 Feb '24

05 Feb '24

> So what's your point? a) boost/math/policies/error_handling.hpp manual name_of, although it would be no problem to add a simple nameof in boost/core/demagle.hpp: template <typename Type> inline std::string nameof() { return demangle(typeid(Type).name()); } b) boost/math/policies/policity.hpp manual "variadic templates" c) boost.convert (apart from the fact that this library is unusable due to its design) - no C++23 FP types - no (unsigned)__int128 - no __float128 These are just the things that came to my mind. The whole design and supported types of boost is stuck 25 years ago. As I said, I'm grateful that boost made C++11 possible. But since then you are stuck at this level and changes are *not* welcome.

2 1

critical bugs in charconv
by g.peterhoff＠t-online.de 05 Feb '24

05 Feb '24

Hello Matt, Sorry for submitting a bug report this way. (Having problems with my GitHub account at the moment). Code: Attachment (gcc 13.2 -std=gnu++23 -O3 -Wall -fanalyzer) Errors (normal) - Missing sign - Hex exponent is wrong - Hex is completely wrong - Accuracy is not correct - Error code deviates from the standard ... The backup functions via (quadmath)snprintf do not work. Errors (critical) - If the buffer is too small (e.g. set the array size to 3) there are a lot of buffer overflows. Especially with value ±nan/±inf. The functions should therefore always be structured in the same way: Auxiliary function inline constexpr bool is_valid_range(const char*const first, const char*const last) noexcept { return (first!=nullptr && last!=nullptr) ? first < last : false; } Pseudocode to_chars(...) // FP { to_chars_result result{last, std::errc::value_too_large}; if (is_valid_range(first, last)) [[likely]] { const size_t size = size_t(last - first); if (inf or nan) [[unlikely]] { if (size is large enough) { copy the string values into the range result = ...; Here you could also use #define to specify whether the string values are compatible with the standard or not. "±inf", "±nan" or https://develop.charconv.cpp.al/#to_chars_usage_notes_for_to_chars_for_floa… } } else { convert, detail::implemantation(first, size, ...) result = ...; } } return result; } to_chars(...) // INT { to_chars_result result{last, std::errc::value_too_large}; if (is_valid_range(first, last)) [[likely]] { const size_t size = size_t(last - first); convert, detail::implemantation(first, size, ...) result = ...; } return result; } This can be achieved with templates and typetraits: FP boost::is_floating_point still does not contain any C++23 types. template <typename Type> BOOST_NOINLINE typename std::enable_if<std::is_floating_point<Type>::value, to_chars_result>::type to_chars(char*const first, char*const last, const Type value, const chars_format format, const int precision) noexcept; template <type name Type> BOOST_NOINLINE typename std::enable_if<std::is_floating_point<Type>::value, to_chars_result>::type to_chars(char*const first, char*const last, const Type value, const chars_format format) noexcept; INT (boost)is_integer is unfortunately still missing. template <type name Type> BOOST_NOINLINE typename std::enable_if<boost::is_integer<Type>::value, to_chars_result>::type to_chars(char*const first, char*const last, const Type value, const int base = 10) noexcept; regards Gero

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[Scope] Peer review conclusion
by Дмитрий Архипов 05 Feb '24

05 Feb '24

Dear Boost community, the formal review of Boost.Scope has taken place between 26th of November and 5th of December of the previous year. I have received 5 reviews in total, including 4 here on the mailing list and 1 on Reddit. Two of the reviews recommended unconditional, and 3 conditional acceptance. The reviews came from: - Klemens Morgenstern, - Janko Dedic, - Julien Blanc, - David Sankel, - /u/jonesmz on Reddit. Also, several people have given insightful comments but did not provide a review. I would like to thank all of the people who took their time to write reviews or participate in the discussions. Your effort was very important and valuable. The outcome of the review is that Boost.Scope is ACCEPTED with several minor CONDITIONS. 1. noexcept specification on destructors of scope guards should be properly documented. Andrey has already commented that the technical hurdle that prevented it was eliminated. 2. There should be a good motivating example for scope_success. There was a lot of comments regarding scope_success and its seeming uselessness. Without a good example I see the same pattern occurring with future users. 3. The examples should better describe what they are trying to achieve. Several comments about examples suggested incorrect changes, which signals that readers failed to understand them. After a lot of consideration I decided against requesting the author to remove unique_resource and related functionality from the library. While several reviewers wanted a more "concise" library, all noted that the component is useful. One last thing I wanted to point out is that all reviewers and most commenters were adamant that compatibility with the Technical Specification on which this library was initially based should not be a goal. In fact, Andrzej Krzemienski even noted that such compatibility has prevented him from adequately evaluating the library on its own merit. In my opinion this should be a sign to all of us that people prefer better APIs over standard APIs. I recommend Andrey to re-evaluate those parts of the library's APIs that he copied from the TS and potentially pick better names for member functions. Thanks to Andrey for submitting this library to Boost. And thanks again to the reviewers and everyone who provided feedback, who ultimately made this review possible.

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[charconv] Review Results and Report
by Christopher Kormanyos 02 Feb '24

02 Feb '24

Dear Boost Community, The review of the proposed Boost.Charconv is finished It took place 15-25 January 2024. REVIEW RESULT ----------------------------- The result is Boost.Charconv is unconditionally * ACCEPTED * into Boost. Thank you Matt. Boost.Charconv will enrich Boost and surely be used vigorously. REVIEW REPORT ----------------------------- The review tally is: * 1 Conditional ACCEPT * 4 ACCEPT * 1 Positive Document Review ---------------------------- = 5 ACCEPT, since the single condition has already been satisfied in develop branch. My Comments and Descriptions below are based on limited knowledge and my subjective interpretations. Please correct, add, modify these (and to these) as needed. * Comments: The review atmosphere was highly productive and excellent. Reviews and contributions featured deep technical content and detail. Fact-based statements combined with experienced-based opinions were provided. There was great strength of expression and clarity. Yet there was mutual respect and fairness, even in the course of lively debate. * Descriptions: Ultimately there were three areas receiving the most debate. For background, see references below. 1) The library needs to allocate. Among other conversions, Boost.Charconv handles conversion of floating-point values to chars. Edge-cases may require hundreds or even thousands of bits. * Consensus: Handle the required memory needed, as done, with low-level C-LIB malloc. But do describe this decision with greater depth of clarity in the docs. 2) The project makes use of a variety of methods, including some table-driven methods. One example is RYU (see [1]). A quick glance at Fig. 4 in [1], for instance, reveals the need for relatively large, constant-valued tables. Largescale tables, combined with the C++11 design goal formed a clear indication to produce a compiled library (as opposed to a header-only one). * Consensus: Compiled-library is sound and viable. Tables (especially in constexpr-context) might bloat or not even work in some language-standards environments. Some commenters, however, seemed subjectively to disapprove of this consensus, feeling that header-only offers the best chances at friction-free setup and convenient portability. Other commenters revealed a sense that compiled libraries are gaining traction in the industry. They feel that this is because the community, their available tools, language-skills, specifications, compilers, CI, VMs, etc. have matured significantly and continue to mature. Thereby they embrace a perceived future-oriented trend that views client-builds to be uncomplicated. There were no blockers on the consensus. 3) The top-level interface differs from that of std-<charconv> in points such as overloads and error-handling. Whereas some details are not even fully hashed-out in the Standard. * Consensus: Weigh known opinions and decide interface details based on unbiased majority. My current understanding is: Offer two drop-ins for from_chars, with the caveat that one should provide better error-handling. REVIEW ACKNOWLEDGMENTS ----------------------------- Thanks again, Matt for Boost.Charconv. Many thanks to our expert reviewers, commenters and watchers. Your contributions keep Boost excellent! Kindest regards, Christopher Kormanyos Boost.Charconv Review Manager * References: [1] Ulf Adams, "RYU: fast float-to-string conversion", ACM SIGPLAN Notices, Volume 53, Issue 4, pp 270–282 (ACM 2018) [2] "Number Parsing at a Gigabyte per Second", Daniel Lemire's Blog, https://lemire.me/blog/2021/01/29/number-parsing-at-a-gigabyte-per-second/ [3] https://github.com/lemire/fast_double_parser

1 0

[charconv] Review Results and Report
by Christopher Kormanyos 02 Feb '24

02 Feb '24

Dear Boost Community, The review of the proposed Boost.Charconv is finished It took place 15-25 January 2024. REVIEW RESULT ----------------------------- The result is Boost.Charconv is unconditionally * ACCEPTED * into Boost. Thank you Matt. Boost.Charconv will enrich Boost and surely be used vigorously. REVIEW REPORT ----------------------------- The review tally is: * 1 Conditional ACCEPT * 4 ACCEPT * 1 Positive Document Review ---------------------------- = 5 ACCEPT, since the single condition has already been satisfied in develop branch. My Comments and Descriptions below are based on limited knowledge and my subjective interpretations. Please correct, add, modify these (and to these) as needed. * Comments: The review atmosphere was highly productive and excellent. Reviews and contributions featured deep technical content and detail. Fact-based statements combined with experienced-based opinions were provided. There was great strength of expression and clarity. Yet there was mutual respect and fairness, even in the course of lively debate. * Descriptions: Ultimately there were three areas receiving the most debate. For background, see references below. 1) The library needs to allocate. Among other conversions, Boost.Charconv handles conversion of floating-point values to chars. Edge-cases may require hundreds or even thousands of bits. * Consensus: Handle the required memory needed, as done, with low-level C-LIB malloc. But do describe this decision with greater depth of clarity in the docs. 2) The project makes use of a variety of methods, including some table-driven methods. One example is RYU (see [1]). A quick glance at Fig. 4 in [1], for instance, reveals the need for relatively large, constant-valued tables. Largescale tables, combined with the C++11 design goal formed a clear indication to produce a compiled library (as opposed to a header-only one). * Consensus: Compiled-library is sound and viable. Tables (especially in constexpr-context) might bloat or not even work in some language-standards environments. Some commenters, however, seemed subjectively to disapprove of this consensus, feeling that header-only offers the best chances at friction-free setup and convenient portability. Other commenters revealed a sense that compiled libraries are gaining traction in the industry. They feel that this is because the community, their available tools, language-skills, specifications, compilers, CI, VMs, etc. have matured significantly and continue to mature. Thereby they embrace a perceived future-oriented trend that views client-builds to be uncomplicated. There were no blockers on the consensus. 3) The top-level interface differs from that of std-<charconv> in points such as overloads and error-handling. Whereas some details are not even fully hashed-out in the Standard. * Consensus: Weigh known opinions and decide interface details based on unbiased majority. My current understanding is: Offer two drop-ins for from_chars, with the caveat that one should provide better error-handling. REVIEW ACKNOWLEDGMENTS ----------------------------- Thanks again, Matt for Boost.Charconv. Many thanks to our expert reviewers, commenters and watchers. Your contributions keep Boost excellent! Kindest regards, Christopher Kormanyos Boost.Charconv Review Manager * References: [1] Ulf Adams, "RYU: fast float-to-string conversion", ACM SIGPLAN Notices, Volume 53, Issue 4, pp 270–282 (ACM 2018) [2] "Number Parsing at a Gigabyte per Second", Daniel Lemire's Blog, https://lemire.me/blog/2021/01/29/number-parsing-at-a-gigabyte-per-second/ [3] https://github.com/lemire/fast_double_parser

1 0

Using ASIO to wait on a foreign socket being readable, with a timeout
by Dominique Devienne 31 Jan '24

31 Jan '24

Hi, I'm trying to use ASIO to wait until a socket is ready to read, or timeout. This is a blocking wait. But the socket is not "owned" by ASIO, but is from the libpq PostgreSQL connection. So ASIO should NOT consume any of the input on the socket, just notify me when that socket is "read-ready". I've cobbled together the following test code: ``` const int socket2 = PQsocket(conn2.handle()); BOOST_CHECK(socket2 > 0); int timr_err_code = 0; int sock_err_code = 0; bool timr_aborted = false; bool sock_aborted = false; std::string timr_err_msg; std::string sock_err_msg; bool timed_out = true; auto c1 = "C# 1"sv; conn2.listen(c1); conn1->notify(c1, "wake up!"sv); { boost::asio::io_context io_ctx; boost::asio::ip::tcp::socket io_sock(io_ctx); io_sock.assign(boost::asio::ip::tcp::v4(), socket2); boost::asio::steady_timer io_timer(io_ctx); io_timer.expires_from_now(std::chrono::milliseconds(100)); io_sock.async_wait( io_sock.wait_read, [&](const boost::system::error_code& errc) { if (errc) { sock_err_code = errc.value(); sock_err_msg = errc.message(); sock_aborted = (errc == boost::asio::error::operation_aborted); } timed_out = false; //io_timer.cancel(); io_ctx.stop(); } ); io_timer.async_wait( [&](const boost::system::error_code& errc) { if (errc) { timr_err_code = errc.value(); timr_err_msg = errc.message(); timr_aborted = (errc == boost::asio::error::operation_aborted); } io_sock.cancel(); io_ctx.stop(); } ); io_ctx.run(); // blocks until either async op above runs } // there's a notif to read, so io_sock.async_wait should have completed BOOST_CHECK_EQUAL(timr_err_code, 0); BOOST_CHECK_EQUAL(sock_err_code, 0); BOOST_CHECK_EQUAL(timr_err_msg, ""); BOOST_CHECK_EQUAL(sock_err_msg, ""); BOOST_CHECK_EQUAL(timr_aborted, false); BOOST_CHECK_EQUAL(sock_aborted, false); BOOST_CHECK_EQUAL(timed_out, false); auto notif = conn2.notification(); BOOST_REQUIRE(notif); BOOST_CHECK_EQUAL(notif.backend_pid(), pid1); BOOST_CHECK_EQUAL(notif.channel(), c1); BOOST_CHECK_EQUAL(notif.payload(), "wake up!"sv); ``` The io_sock.async_wait(io_sock.wait_read, ...) succeeds, the IO loop stops as expected, but when I try to PQconsumeInput() from the LIBPQ connection next (as shown in the code below) ``` Notification Connection::notification() { auto [lock, hndl] = ensure_handle(); if (1 != PQconsumeInput(hndl)) { throw std::runtime_error(error_msg()); // <<<<<< THROWS } PGnotify_uptr notif{ PQnotifies(hndl) }; return Notification(std::move(notif)); // may be null } ``` that calls fail with this error message: fatal error: in "NotificationTests/test_across_backends": class std::runtime_error: could not receive data from server: Socket operation on non-socket (0x00002736/10038) LIBPQ didn't like what ASIO somehow did on the socket descriptor. The LIBPQ doc says to select() the descriptor, but I thought ASIO would be cleaner, more C++, and perhaps more cross-platform. Can somehow help, telling me if I'm using ASIO incorrectly here? Thanks, --DD

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Boost.Charconv review runs January 15th - 25th, 2024
by Christopher Kormanyos 31 Jan '24

31 Jan '24

Dear all, The review of Boost.Charconv by Matt Borland runs Monday, January 15th through January 25th, 2024. Code: https://github.com/cppalliance/charconvDocs: https://master.charconv.cpp.al/Review Schedule: https://www.boost.org/community/review_schedule.html Thank you for considering this review. Please optionally provide feedback on the followinggeneral topics: - 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? Christopher KormanyosBoost.Charconv Review Manager

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[charconv] is std::from_chars practical?
by Andrzej Krzemienski 26 Jan '24

26 Jan '24

Hi Everyone, This is about https://github.com/cppalliance/charconv/issues/110, again. Now I understand Peter's point better. std::from_chars is impractical, or one would say "broken", at least for the case of ERANGE. Actually applying a patch in https://cplusplus.github.io/LWG/lwg-active.html#3081 will not make the tool good, it will just make it broken in another way. In that case, maybe the goal of providing literally a *drop-in replacement* for std::from_chars is not a good one? Maybe this is the case similar to variant2, where the community would benefit more from the library motivated by "how would from_chars look like if we designed it instead of WG21". That is, an *alternative to* std::from_chars, rather than a *drop-in-replacement for* std::from_chars. Regards, &rzej;

6 6

Review of proposed CharConv
by Antony Polukhin 25 Jan '24

25 Jan '24

## What is your evaluation of the design? Design follows the C++ Standard library design with all the latest additions. Everything is fine. ## What is your evaluation of the implementation? Fine in general. A few nitpicks/concerns follow. ### Arrays of constants RYU/fast_float/... are used for some of the conversions and most of those algorithms have huge tables full of constants. For example https://github.com/cppalliance/charconv/blob/41a83261c0f65aee575e89ccb71d94… and https://github.com/cppalliance/charconv/blob/41a83261c0f65aee575e89ccb71d94… and https://github.com/cppalliance/charconv/blob/41a83261c0f65aee575e89ccb71d94… Those constants have internal linkage. They are put in every translation unit that includes and uses them. Those constants would not be merged by linker. Moreover, the same constants with different names now exist in Standard Library implementations and are not merged with Boost.Charconv. To reduce the binary size and improve data locality I'd recommend switching to std implementation in sources if the feature test macro tells that std::to_chars/std::from_chars are fine. ### Internal headers in include/ Some of the headers are used only internally during build. It seems reasonable to move them to the src/ directory to make sure that no one uses them and that the library itself does not include them by accident. ### Header only support There is a PR to make the library header only https://github.com/cppalliance/charconv/pull/138 This feature is demanded by users however it raises the constants question again. Marking arrays of constants with `inline` should be done to make the constants externally visible, so that the linker could merge them. ### Constexpr for floats Just a feature request - it would be nice to have constexpr from_chars and constexpr to_chars for floating point types. If is_constant_evaluated() - do slow but constexpr conversion. Otherwise - fallback to std:: version or to the implementation in src/ ### Locales Locales are used in some corner cases along with switching them back and forth https://github.com/cppalliance/charconv/blob/41a83261c0f65aee575e89ccb71d94… Looks like there's no need in that line for locales switching. Just get the decimal point separator from the current locale and if it is not '.' then do the replacement of the first '.' to the locale's separator. ### Nitpicks Looks like zero initialization of the buffers could be skipped in following places: * https://github.com/cppalliance/charconv/blob/41a83261c0f65aee575e89ccb71d94… * https://github.com/cppalliance/charconv/blob/41a83261c0f65aee575e89ccb71d94… * https://github.com/cppalliance/charconv/blob/41a83261c0f65aee575e89ccb71d94… ## What is your evaluation of the documentation? Looks like parts of the docs repeat themself. For example, the reference section duplicates some of the previous descriptions. The latter could be just removed. Another thing that catches an eye are the benchmarks. Please also provide some absolute numbers because "X is five times faster than Y" could easily be that X and Y execute for ~1ns each. Those numbers are profitable for users. Side Note for myself: Seems that LexicalCast shows poor performance in some cases where it should not. Will investigate. ## What is your evaluation of the potential usefulness of the library? Very useful for libraries that wish to support pre-C++17 standards or a wide range of compilers. Useful for experimenting and prototyping new C++ Standard Library proposals ## 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? Just looked through the code and the docs. ## Are you knowledgeable about the problem domain? I'm maintaining the Boost.LexicalCast and implemented a bunch of optimizations for std::to_chars/std::from_chars for the libstdc++. I'm not knowledgeable of RUY internals, but have the general understanding of the <charconv>. ## Do you think the library should be accepted as a Boost library? Yes

3 2

Zach Laine CharConv review
by Zach Laine 25 Jan '24

25 Jan '24

- What is your evaluation of the design? It follows the design of the equivalent facility in std::, so this feels moot. No complaints with that part. My only complaint is that the semantics of boost::charconv::from_chars and boost::charconv::from_chars_strict seem backward to me. I know this was mentioned by other reviewers. I think that with near-identity to the standard version, having the same (or corresponding name within boost::) should imply the same semantics. This is classic adherence to The Principle of Least Surprise. I would much prefer that the varying version have the different name, and that the one with the standard's semantics should be from_chars. I also encourage the authors to track any changes to std::from_chars with boost::charconv::from_chars. - What is your evaluation of the implementation? I mean, there's a lot of it. I'm sure it's all necessary, but I only looked at about 10% of it. What I saw seemed reasonable and well organized. - What is your evaluation of the documentation? It's great. The library is smallish, and the docs are correspondingly bite-sized, with plenty of examples. I might add a little more front matter that explains why someone should use this library. The docs get there, but putting it in the first paragraph is better. Busy people will blow right past everything that isn't in the first paragraph or two. - What is your evaluation of the potential usefulness of the library? High. I think the fact that this is a C++17 feature that we still can't reliably use says it all. The fact that it's about the same as the std:: implementation, or sometimes a little faster, is even better. - Did you try to use the library? With what compiler? Did you have any problems? Yes. I tried it with GCC 12, in a small test program just to see it go. No issues. - How much effort did you put into your evaluation? A glance? A quick reading? In-depth study? I spent about 3 hours, mostly looking at code. I also read all the docs and gave it a quick try. - Are you knowledgeable about the problem domain? Not particularly. I have written lots and lots of parsers, but never a simple low-level one like those in charconv. Zach

3 3

test message 19
by Sam Darwin 24 Jan '24

24 Jan '24

content test message 19

1 0

test message 7
by Sam Darwin 18 Jan '24

18 Jan '24

contents of test message 7 ___

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Review of Parser library scheduled
by Mateusz Loskot 17 Jan '24

17 Jan '24

Folk, Review of Zach Laine's Praser library has been scheduled [1] for February 19, 2024 - February 28, 2024 Big thanks to Marshall Clow for volunteering to be the review manager. [1] https://www.boost.org/community/review_schedule.html Best regards, -- Mateusz Loskot on behalf of Boost Review Wizards

1 0

Making Boost modular. IMPORTANT! URGENT! <insert-superlative-here>!
by René Ferdinand Rivera Morell 17 Jan '24

17 Jan '24

Dear fellow Boost authors, As some of you may have heard.. Some of us have been working on making it possible to fully consume Boost in a modular arrangement. First some FAQs about this: Q: What is a "modular arrangement"? A: It's when the libraries can be used, and hence built, without creating the monolithic headers, without needing the root build files, and without needing the libraries to be arranged in the usual root/libs/<name>. Q: Will a modular Boost remove the Boost release? A: No. The collection of libraries is still a single release. See recent discussions about this. Q: Will this change the testing? A: No, unless you want to. You will still be able to test the same non-modular way. But you could also test the modular way. Q: Will this require that we change the current Boost source structure? A: Yes. Unfortunately there is one restriction that adhering to a modular Boost requires. We would not allow sublibs. That is, that we can't support having libraries in root/libs/thing/<library> style locations. All libraries must be single libraries under the root/libs directory. Thankfully there's only a handful of such libraries. The root/libs/numeric/* group of libraries. Q: Why do we want a modular Boost? A: I'm not going to enumerate the reasons here. But let me just say.. That we've wanted a way to reduce, i.e. modularize, Boost since at least 19 years ago. When we added the "--without-<library>" build option to the root build file <https://github.com/boostorg/boost/blame/master/Jamroot#L107>. Now the work part.. Over the past year or so I've been making patches to the Boost build files, in my own repo, that cleans up the many, many, problems that make libraries depend on the current source structure. I've also made changes to B2 to make it easier/possible/automatic to deal with the new modular freedom. The B2 changes were naturally easy to put in since I control the repo and distribution. And the last bit of them shipped with the 1.83 release last Summer. But now I need to start pushing the changes to the many Boost repos to get this finished. A couple of weeks ago I started posting PRs to incrementally, and unobtrusively, make the changes to the Jamfiles. So far I have these: <https://github.com/boostorg/ublas/pull/189> <https://github.com/boostorg/interval/pull/38> I'm not sure how else to say this so.. PLEASE, PLEASE, merge those and future PRs ASAP. -- -- René Ferdinand Rivera Morell -- Don't Assume Anything -- No Supone Nada -- Robot Dreams - http://robot-dreams.net

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Boost downloads and JFrog
by Glen Fernandes 13 Jan '24

13 Jan '24

Rather than emails and Slack DMs, I would prefer we have this discussion on the mailing list. To summarize what I have repeated in the aforementioned channels: - Yes, our downloads are not working again because the JFrog account is again not active. - No, I cannot do anything about the JFrog account. - Yes, we can update the website to point to downloads hosted elsewhere. It is correct that JFrog does not charge us yet but our traffic has increased from 60TB/month to almost 200TB/month which is no longer supportable for free. We have limited time to find a solution. We are on borrowed time but as far as I know we still have time. the deactivation of the JFrog account in December 31 was not expected, and it was reinstated. Glen

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Request for comments: to_static_string
by Ruben Perez 13 Jan '24

13 Jan '24

Hi all, Since we will be reviewing Boost.CharConv shortly, and my development efforts in Boost.MySQL are currently requiring converting numbers to strings, I've been playing with the utilities we currently have to do so. I've found cases where I just needed to convert something to string, then pass the result to another function taking a string_view as parameter. The most efficient and correct way to do so is using to_chars (stack based, non-throwing, C++23 constexpr and locale-independent). But I still like the simplicity of std::to_string. Since I had some free time this weekend, I took a step forward and implemented a (deadly simple) wrapper around to_chars that looks like std::to_string, but has all the benefits of to_chars. I called this to_static_string. Repo is here: https://github.com/anarthal/to-static-string This is currently a prototype. I want to hear everyone's opinion on this - do you think this may be useful to any of you? I don't think it's big enough to even consider putting it into Boost (my idea is having it as a standalone lib). Any comments are welcome. Thanks, Ruben.

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[scope] Some random thoughts
by Andrzej Krzemienski 10 Jan '24

10 Jan '24

Hi All, Two observations from reading the docs. Why do I need a condition in scope_exit when I have a scope_fail? I recommend putting warning somewhere in the docs that while using scope guards you may inadvertently read an object after move: std::string checked(std::string name) { scope::scope_exit g{[&]{ std::clog << "checked " << name <<std::endl; }}; validate(name); return name; // name becomes moved-from } Regards, &rzej;

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Forthcoming Boost.Charconv review January 15th - 25th, 2024
by Christopher Kormanyos 09 Jan '24

09 Jan '24

Dear all, The review of Boost.Charconv by Matt Borland is scheduledfrom Monday, January 15th to January 25th, 2024. ----------------------------------------------------- About the library: Boost.Charconv provides a highly portable and efficient, C++11 implementation of <charconv>. The API containsfunctions compatible with <charconv>. Boost.Charconv can be highly useful for portability and efficiency. The standard library's <charconv> requires C++17 or higher. Currently only quite modern compilers such as GCC 11+ and MSVC 19.24+ support both integer and floating-point conversions in their implementation of <charconv>. If you are using either of those compilers, Boost.Charconv is at least as performant as <charconv>, and can be up to several times faster. If you are using an older compiler or a language standard lower than C++17, then there is no <charconv> available. In such cases, Boost.Charconv provides a highly-viable, portable and efficient header-only implementation. Boost.Charconv is a compiled library and does require a few other Boost libraries to run. The docs providedirections for how to consume with b2, vcpkg and Conanto facilitate this. Boost.Charconv fits into Boost stylistically and through itshigh quality, its Boost-like testing and its documentation. Boost.Charconv has been well-received and endorsed on the Boost-lists and is already being used for prototyping in several existing Boost libraries. Tool vendors have expressed interest in Boost.Charconv particularly due to its high performance and clarity of implementation details. docs: https://develop.charconv.cpp.al git: https://github.com/cppalliance/charconv --------------------------------------------------- Naturally, you need not wait until the review formally opens to start reviewing the Charconv library. Please always state in your review whether you think the library should be accepted as a Boost library! Please consider giving feedback on the following general topics: - 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? Christopher Kormanyos Boost.Charconv Review Manager ------------------------------

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boost.sqlite
by Klemens Morgenstern 06 Jan '24

06 Jan '24

I've written a boost.sqlite library last year mainly to experiment, but it has been a feature-complete C++ wrapper for a while. Hence I'd like to gauge interest to see if it's worth proposing for boost. It has more features than most C++ sqlite wrappers and uses boost-isms such as system.result, tag_invoke and boost.json. Code: https://github.com/klemens-morgenstern/sqlite Docs: https://klemens.dev/sqlite/

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Re: [boost] Interest in new parsing library?
by tobi＠die-loews.de 06 Jan '24

06 Jan '24

Zach Laine wrote: > - use approximately the same set of directives to influence the parse > (e.g. lexeme[]); It seems there is no directive like Spirit's no_case. Is there a way to match case-insensitivity?

2 2

Google Summar of Code 2024 - Collecting Projects & Mentors! 📢
by Inbal Levi 05 Jan '24

05 Jan '24

Hello all! We would like to collect projects & mentors for the GSOC 2024 :) If you would like to volunteer as a mentor and/or have a proposal for a Boost project which you like to collect volunteers for, please fill in the proper tab: https://docs.google.com/spreadsheets/d/1_eUWRsXnhi_JwKZbHZsGQf3WNUESsAPE4lV… Once we have a list of proposed projects, we will upload them to GitHub. Thanks! Best regards, Inbal Levi ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ *Lead Software Engineer @ Millenium* Isocpp, Boost &"Hamakor" Non-Profits Board Member ISO C++ LEWG Chair & Israeli NB Chair C++Now Program Chair & CoreC++ Conference Organizer ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

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Recommendations for documentation authors
by Andrzej Krzemienski 04 Jan '24

04 Jan '24

Hi Boost Developers, And a happy New Year (at least for those who recognize the Gregorian calendar). While I consider improving the documentation quality of some Boost libraries, I wonder if there are any tool or workflow recommendations for the library authors regarding the documentation. I know we do not force any specific tool or format, so I am only asking about recommendations. I note that page https://www.preview.boost.org has at https://www.preview.boost.org/doc/contributor-guide/docs/documentation-guid… the following: > The format for documentation on the new website is AsciiDoc Syntax Quick Reference <https://docs.asciidoctor.org/asciidoc/latest/syntax-quick-reference/>. Should I treat it as a recommendation to use AsciiDoc? I note that quite a few new libraries choose it. I also see the advantage: you need no special tool for it: a simple web browser knows how to format it. But I found the documentation of libraries that use adoc to be uncomfortable to read. I do not know if this is the tool itself or maybe the correlation between the choice of the tool and the devotion to documentation quality, or maybe something else. It is quite subjective. The older libraries' documentation (using BoostDoc) seemed more friendly and easier to navigate. But to write and maintain such documentation is a challenge. Last year something broke in my pipeline (QuickDoc, xstlproc) and to this day I am not able to determine what it is. So, relying on too complex flows, which become obsolete over time, also doesn't seem like a good idea. I wonder if any of you have similar thoughts, and if you can recommend something for writing good quality and user friendly documentation. Regards, &rzej;

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[website][string_ref] Broken link to the library docs
by Andrey Semashev 02 Jan '24

02 Jan '24

Hi, In the library list for Boost 1.84: https://www.boost.org/doc/libs/1_84_0/ there is an entry for Boost.StringRef. However, that library was removed from libs/utility/meta/libraries.json. Or, more precisely, it was renamed to Boost.StringView (key: utility/string_view). The problem is that the StringRef entry in the above list has a broken link to the library docs, and the rename was supposed to fix it (by having an entry for StringView instead, linking to its docs). I'm not sure where StringRef comes from, but can it be removed? This has been reported a few times already: https://github.com/boostorg/website/issues/763 https://github.com/boostorg/utility/issues/105

1 0

Interest in new parsing library?
by Zach Laine 30 Dec '23

30 Dec '23

I'm trying to gauge interest in a parsing library to replace Boost.Spirit 2/Spirit X3. I'm also looking for endorsements. The library is intended to remedy some shortcomings of Boost.Spirit*. I think these are great libraries, but Spirit 2 was written in pre-11 C++ (I think; certainly its dependencies were). Most-to-all of the downsides stem from that -- long compile times, inscrutable compilation failures, etc. (Boost.Parser compile times are quite low.) I'm calling my proposal Boost.Parser, and it follows many of the conventions of Boost.Spirit 2 and X3, such as the operators used for overloading, the names of many parsers and directives, etc. It requires C++17 or later. >From the introduction in the online docs: """ Boost.Parser is a parser combinator library. That is, it consists of a set of low-level primitive parsers, and operations that can be used to combine those parsers into more complicated parsers. There are primitive parsers that parse epsilon (the empty string), chars, ints, floats, etc. There are operations which combine parsers to create new parsers. For instance, the Kleene star operation takes an existing parser p and creates a new parser that matches zero or more occurrences of whatever p matches. Both callable objects and operator overloads are used for the combining operations. For instance, operator*() is used for Kleene star, and you can also write repeat(n)[p] to create a parser for exactly n repetitions of p. Boost.Parser also tries to accommodate the multiple ways that people often want to get a parse result out of their parsing code. Some parsing may best be done by returning an object that represents the result of the parse. Other parsing may best be done by filling in a preexisting data structure. Yet other parsing may best be done by parsing small sections of a large document, and reporting the results of subparsers as they are finished, via callbacks. Boost.Parser accommodates all these ways of working, and even makes it possible to do callback-based or non-callback-based parsing without rewriting any code (except by changing the top-level call from parse() to callback_parse()). All of Boost.Parser's public interfaces are sentinel- and range-friendly, just like the interfaces in std::ranges. Boost.Parser is Unicode-aware through and through. When you parse ranges of char, Boost.Parser does not assume any particular encoding — not Unicode or any other encoding. Parsing of inputs other than plain chars assumes that the input is Unicode. In the Unicode-aware code paths, all parsing is done by matching code points. This means that you can feed UTF-8 strings into Boost.Parser, both as input and within your parser, and the right sort of matching occurs. For instance, if your parser is trying to match repetitions of the char '\xcc' (which is a lead byte from a UTF-8 sequence, and so is malformed UTF-8 if not followed by an appropriate UTF-8 code unit), it will not match the start of "\xcc\x80" (UTF-8 for the code point U+0300). Boost.Parser knows that the matching must be whole-code-point, and so it interprets the char '\xcc' as the code point U+00CC. Error reporting is important to get right, and it is important to make errors easy to understand, especially for end-users. Boost.Parser produces runtime parse error messages that are very similar to the diagnostics that you get when compiling with GCC and Clang (it even supports warnings that don't fail the parse). The exact token associated with a diagnostic can be reported to the user, with the containing line quoted, and with a marker pointing right at the token. Boost.Parser takes care of this for you; your parser does not need to include any special code to make this happen. Of course, you can also replace the error handler entirely, if it doesn't fit your needs. Debugging complex parsers can be a real nightmare. Boost.Parser makes it trivial to get a trace of your entire parse, with easy-to-read (and very verbose) indications of where each part of the trace is within the parse, the state of values produced by the parse, etc. Again, you don't need to write any code to make this happen — you just pass a parameter to parse(). Dependencies are still a nightmare in C++, so Boost.Parser can be used as a purely standalone library, independent of Boost. """ Boost.Parser aims to be a superset of Boost.Spriit* in most ways. Major things missing from the set of features in Spirit 2 + Spirit X3 are: - A separate lexer. - Binary parsers (meaning for parsing bits, not binary numbers written as text; the latter is fully supported). I've been in touch with Joel de Guzman, Hartmut Kaiser, and Michael Caisse, to make sure I was not toe-stomping, for those who are concerned about that. They gave this new library their blessing. One feature comes entirely from them: Boost.Parser is usable in a Boost-free environment -- as a standalone library -- at the user's option. They said that was the #1 request from users, which surprised me a bit. The Github page is here: https://github.com/tzlaine/parser The online docs are here: https://tzlaine.github.io/parser To see an extended example, here's a JSON parser that passes all the published JSON tests, including most of the optional ones, in only about 300 lines of code, go here: https://tzlaine.github.io/parser/doc/html/boost_parser__proposed_/extended_… Finally, for those wanting to know how this lib differs from Boost.Spirit* without digging through the docs, here is the doc page that explains Boost.Parser's relationship to Boost.Spirit*: """ Boost.Spirit is a library that is already in Boost, and it has been around for a long time. However, it does not suit user needs in some ways. Spirit 2 suffers from very long compile times. Spirit 2 has error reporting that requires a lot of user intervention to work. Spirit 2 requires user intervention, including a (long) recompile, to enable parse tracing. Spirit X3 has rules that do not compose well — the attributes produced by a rule can change depending on the context in which you use the rule. Spirit X3 is missing many of the convenient interfaces to parsers that Spirit 2 had. For instance, you cannot add parameters to a parser. All versions of Spirit have Unicode support, but it is quite difficult to get working. I wanted a library that does not suffer from any of the above limitations. It should be noted that while Spirit X3 only has a couple of flaws in the list above, the one related to rules is a deal-breaker. The ability to write rules, test them in isolation, and then re-use them throughout a complex parser is essential. Though no version of Boost.Spirit (Spirit 2 or Spirit X3) suffers from all those limitations, there also does not exist any one version that avoids all of them. Boost.Parser does so. However, there are a lot of great ideas in Boost.Spirit that have been retained in Boost.Parser. Both libraries: - use the same operator overloads to combine parsers; - use approximately the same set of directives to influence the parse (e.g. lexeme[]); - provide loosely-coupled rules that are separately compilable (at least for Spirit X3); and - are built around a flexible parse context object that has state added to and removed from it during the parse (again, comparing to Spirit X3). """ Zach

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Re: [boost] Interest in new parsing library?
by Zach Laine 29 Dec '23

29 Dec '23

On Fri, Dec 29, 2023 at 12:40 PM Zach Laine <whatwasthataddress(a)gmail.com> wrote: > > On Fri, Dec 29, 2023 at 3:53 AM Andrzej Krzemienski <akrzemi1(a)gmail.com> wrote: > > > > > > > > czw., 28 gru 2023 o 22:05 Zach Laine via Boost <boost(a)lists.boost.org> napisał(a): > >> > >> I'm trying to gauge interest in a parsing library to replace > >> Boost.Spirit 2/Spirit X3. I'm also looking for endorsements. > >> > [snip] > > > > Hi Zach, > > Thank you for writing and sharing this library. I intend to test it on my mini-language early next year. > > That sounds useful. Please let me know how it goes. > > > For now, let me dig a bit about the high-level differences between Boost.Parser and Boost.SpiritX3. > > > > Your introduction mentions "a separate lexer" as a feature that Boost.Spirit is missing. > > How does that square with the entire section for Spirit.Lex in Boost.Spirit docs? > > No, I meant the other way around. *Boost.Parser* is missing that. > Sorry for the confusion. > > > "Boost.Parser aims to be a superset of Boost.Spirit". But Boost.Spirit is also a generator. > > Quite right! I forgot about that; this is another thing that > Boost.Parser is missing vs. Spirit. > > > You mention that "Spirit X3 has rules that do not compose well". I personally never experienced this. Is there an example somewhere that would illustrate this problem? > > The issue for me is that the attribute types generated by X3 parsers > and rules are loose. This is by design. So, say you have a parser > that parses strings, producing a range of char: > > auto p = /* ... */; > > If you then use p to parse into some std::string variable in the > middle of the parse, everything works as you'd expect. But if you use > p to parse into a different std::vector<char> variable in the middle > of the parse, that also works. This is not by itself a problem. > However, I had a problem with this semantic, because there was no way > to lock down the attribute type to a specific, concrete type. So if > at some point in the parse I had: > > auto p_p = p >> p; > > That may be used to generate a std::variant<std::string, > std::vector<char>>, a std::variant<std::vector<char>, std::string>>, > etc. These types are not interconvertible. So, If you made a mistake > somewhere in writing a semantic action or something, you get an error > stating that std::variant<std::string, std::vector<char>> is not > assignable to std::variant<std::vector<char>, std::string>> or > whatever, and figuring out where the error actually lies is very > difficult. If you have a Boost.Parser rule, it has a concrete > attribute type A, and so it always produces As. I find this much, > much easier to diagnose and debug when I make a mistake. > > > What is the recommendation of Boost.Spirit authors to the programmers that need to do parsing? Is Boost.Parser simply the newer and improved version, or do they have disjoint sets of use cases? > > I think Joel answered that above. > > > Personally, skimming through the docs, I find the feature of producing custom error and warning messages very attractive. This is what I was always missing from the parsing libraries. > > > > Thanks again for your effort. > > Thanks for taking a look! Also, I should mention that this is the > easiest library I have ever written, given its complexity. That is > true due to all the very nice design work that came before it, from > Joel, Hartmut, and others. > > Zach I somehow sent only this one reply to Andrzej only; echoing here. Sorry for the borked formatting. Zach

1 0

About weird behavior with boost.asio 1.63 on linux 2.6.15
by Scott Zhang 25 Dec '23

25 Dec '23

Dear All: I have been using boost over 10+ years. The asio library work quite well along with document. Today I get a problem: My development environment: gcc 4.7.3 OABI Linux 2.6.15 boost 1.63 The code looks like below: void myTask(const char *text) { sleep(5); /*for(;;) { //sleep(1); }*/ cout<<"text is "<<text<<endl; // cout<<"out"<<endl; } boost::asio::io_service ioService; ioService.post(boost::bind(myTask,"hello")); ioService.run(); I get 2 problems: 1. If I run program as above, the mytask get executed correctly, but as soon as it returns, the program get "illegal instruction", and program dies. If I call myTask directly, then everything is ok. So what's wrong with io_service.post 2. If I run ioservice within thread using threadpool.create_thread( boost::bind(&boost::asio::io_service::run, &ioService) Then after myTask executed, I get "Killed", using strace says program get SIGKILL. As the test code is so simple, I can't tell where goes wrong. I also noticed, if I don't call io_service.post, everything looks ok. And the threads, in linux ps, shows as many processes. I reread the document of asio 1.63, it says had beed tested against linux 2.4 and 2.6 kernel. so it should be ok. Please help. Thanks.

3 5

The master branch is now open for all changes
by Marshall Clow 14 Dec '23

14 Dec '23

Thanks to everyone who participated in the release! — Marshall

1 0

[release] Boost 1.84.0
by Marshall Clow 14 Dec '23

14 Dec '23

Release 1.84.0 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 contain two new libraries, numerous enhancements and bug fixes for existing libraries. For details, including download links, see <http://www.boost.org/users/news/version_1.84.0> You can also download directly from: <https://boostorg.jfrog.io/artifactory/main/release/1.84.0/source> 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. -- The Boost Release Team Marshall Clow, Glen Fernandes

1 0

[Fiber] aligned_storage is deprecated
by Niall Douglas 12 Dec '23

12 Dec '23

On Boost 1.81 with clang 18 in C++ 23 mode: ``` [build] /usr/include/boost/fiber/future/detail/shared_state.hpp:160:19: warning: 'aligned_storage<4, 4>' is deprecated [-Wdeprecated-declarations] [build] 160 | typename std::aligned_storage< sizeof( R), alignof( R) >::type storage_{}; [build] | ^ [build] /usr/include/boost/fiber/future/promise.hpp:28:22: note: in instantiation of template class 'boost::fibers::detail::shared_state<int>' requested here [build] 28 | typedef typename shared_state< R >::ptr_type ptr_type; ``` It could have been fixed upstream since, I haven't checked. Niall

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[release] Boost 1.84.0 Release Candidate 1 is available
by Marshall Clow 12 Dec '23

12 Dec '23

The first release candidates for the 1.84.0 release are now available at: <https://boostorg.jfrog.io/artifactory/main/release/1.84.0/source/> The SHA256 checksums are as follows: cc4b893acf645c9d4b698e9a0f08ca8846aa5d6c68275c14c3e7949c24109454 boost_1_84_0_rc1.tar.bz2 cc77eb8ed25da4d596b25e77e4dbb6c5afaac9cddd00dc9ca947b6b268cc76a4 boost_1_84_0_rc1.zip 81a4d10075731966477276c47324ecd9cac02da49899d36c48eba66e40014f25 boost_1_84_0_rc1.7z a5800f405508f5df8114558ca9855d2640a2de8f0445f051fa1c7c3383045724 boost_1_84_0_rc1.tar.gz 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 Release managers

4 4

[scope] review
by Julien Blanc 07 Dec '23

07 Dec '23

Hi, This is my review of the proposed boost scope library. * Does this library bring real benefit to C++ developers for real world use-case? Yes. Scope guards are a well-known and widely used feature, nearly every code-base has some implementation of it. The same goes for raii resource wrappers. * Do you have an application for this library? I would consider using it for new projects. It does not, however, offer significant value at the time which would justify migrating from our homebrew scope guard. Worse, it misses some guarantees that makes it less fitted (but arguably it is more generic than what we use now). * Does the API match with current best practices? The API is copied from a TS proposal, for some parts. Most of my griefs against the API also applies to the TS. While I was not fond of it at the start, i think there's a clear value in differentiating scope_success and scope_fail. The first one is allowed to throw, the second is not. This, however, is not a strong requirement, but a general advice. It thus raises the concern about why not simply giving a boolean parameter to the scope_guard handler function, and letting it act accordingly. I suggest making the noexcept-ness of scope_fail executor a strong requirement. scope_success / scope_fail are not default-constructible, although they have a valid empty state. While there's a rationale behind this (it is a bit uncommon to create a scope guard that does nothing), it is a limitation for the sake of nothing. Initializing an empty scope_exit allows scope escaping (useful when initializing the scope guard in the body of an if statement). There will always be the possiblity to do it with an optional, so it just seems that forbidding default construction has no value. To check whether a scope_xxx is active or not, one has to call the active() method. To check whether a unique_resource has a value, one has to call the allocated() method. These are additions compared to the TS. While they may be useful, the names are inconsistent, both are new, also inconsistent with what other nullable types (optional, unique_ptr, variant...) uses. While this is common practice accross the c++ standard, I would not called this *best*. This leads to problems for generic code, and proposals such as this one: https://herbsutter.com/2022/09/25/something-i-implemented-today-is-void/ . In both case, i think at least an operator bool() should be provided, because it's a more widespread and common way to check for emptiness / valid state. scope_success / fails / exit takes an additional parameter (extension over TS), which is the execution condition. scope_success executes when the condition returns false. This is unintuitive, and something i will usually get wrong. While i get the reasoning behind, i think it tells more in favor of a scope_conditional<SuccessHandler, FailureHandler> interface. I'm not sure there's a lot of use-cases for a success_only or fail_only scope guard, especially since you can release in case of success, to avoid the cost of the failure check. About this customizable failure detector, i'm not found of the idea. The default, detection of a current exception, is a sane one. And it allows us to require FailureHandler to be noexcept. That's no longer the case if you allow customizing the failure detector. I'm not sure it's worth the tradeoff, since the failure detection could always be done inside the body of a standard unconditional scope_exit. Finally, i don't get the point of set_active. Sure, it's cheap to implement, but do we really want to encourage dynamically enabling scope guards ? Disabling a scope guard makes a lot of sense, that's what you do to disable a rollback scope_guard upon successful operation. Dynamically enabling it looks more like being hostile to the reader to me. In all cases, it's possible to get this behaviour with a boolean inside the scope guard callback, so this use case is already addressed. There's no need for it to be a first-class citizen. I like the idea of the lighter, unconditional, scope_final, which is missing in the TS. * Is the scope of the library well-defined? unique_resource and scope_exit are quite different beasts. They only have in common being RAII. But that also include unique_lock, unique_ptr, and nobody thought about making them part of the same library. I think it is a mistake to mix them. unique_resource takes three template parameters, the third one being a predicate telling if the resource is valid. I understand the wish to avoid storing an extra information, when there's a possibility to do without by storing an invalid value. But to me, it looks like a more widespread problem already solved, for example by https://github.com/akrzemi1/markable . It would be far better IMHO to get markable in boost, and have unique_resource specialized for markable<X> than replicating most of its functionality into unique_resource. * Is the documentation helpful and clear? The documentation is clear enough, although i could not find some information that i think should be emphasized more (ie, what the library guarantees in terms of pre / post conditions, noexceptness, etc). I don't like the way the reference section subitems are links to the file headers descriptions, and not links to class descriptions. I'd prefer something like: Reference * template< > class scope_exit * template< > class scope_final * ... instead of the headers, for which i usually don't care (i just need to know which header i need to include, and this information is provided in the class description). There are a few examples in the documentation that can be improved. There's always room for improvement, the overall quality is good. * Did you try to use it? What problems or surprises did you encounter? How much time did you spent? I made some small experiments with it. I spent around 6-8 hours reviewing the library and writing this review. Most of the time was spent reading the documentation and checking the behaviour. No problems and no surprises so far. * What is your evaluation of the implementation? The library is big (~2,5k lines of code), given what it offers. Most of this comes from the fact that the library offers a lot of customization points, maybe too much. Others have pointed that it reimplements some standard features, for the sake of not including some headers. I don't like this choice, but I don't know what's boost policy in this regard is. In all cases, a reimplementation with a name is better than nothing. In particular, there are some static_cast<T&&> which would advantagely be replaced by a detail::forward<T>, the latter being far more readable than the former. It's a shame that compact_storage is not provided as a facility: i guess there are several similar implementation across boost. But that's not the library's fault. Outside that, the organisation is clean, and the code largely readable, given that it needs to be compatible with C++11. * What is you final evaluation of the library? My current recommandation is to CONDITIONNALY ACCEPT the library. I think the following should be adressed, but i'd note that several of these comments also applies to the TS: - scope_success and scope_fail should be unified into a single call, taking two callbacks. This will make a slightly bigger object, but if you plan on detecting exceptions then you don't mind the extra cost anyway. And it will allow to evaluate the condition only once, so that may prove a gain in several situations. - scope_success and scope_fail should not take an execution condition. Exception detection should be enough for everyone, or else you should resort to scope_exit. - the failure handler (scope_fail) should be enforced to be noexcept - scope_exit should be default constructible (released by default, equivalent to moved-from state). That does not hold for scope_final, which is not releasable. - the active / released name fiasco should be adressed. At least provide operator bool(). - set_active should be removed. This is encouraging bad practice. - unique_resource should be moved outside the library. I consider that it belongs to a separate library, and i think it has some flaws in its design that should be addressed. Finally, many thanks to Andrey for proposing this library, and for quickly replying to the questions during the review. Regards, Julien

3 5

[release] Master Branch is closed for ALL changes
by Marshall Clow 07 Dec '23

07 Dec '23

Please do not commit anything to the master branch. Other branches are always fine. The 1.84.0 release is scheduled for next Wednesday, 13-December. — Marshall

1 0

[scope] Scope review starts on November 26th
by Дмитрий Архипов 07 Dec '23

07 Dec '23

Dear Boost community. The peer review of the proposed Boost.Scope will start on 26th of November and continue until December 5th. Boost.Scope is a small library implementing utilities defined in <experimental/scope> from C++ Extensions for Library Fundamentals v3 with a few extensions. Namely, the library contains: * A number of scope guards for various use cases. * A unique resource wrapper that automatically frees the resource on destruction. * Utilities for wrapping POSIX-like file descriptors in the unique resource wrapper. You can find the source code of the library at https://github.com/Lastique/scope and read the documentation at https://lastique.github.io/scope/libs/scope/doc/html/index.html. The library is header-only and thus it is fairly easy to try it out. In addition, the library can be used with Conan and vcpkg (see its README for instructions on how to do that). Finally, there's a single header version suitable for Compiler Explorer (https://raw.githubusercontent.com/Lastique/scope/single-header/include/boos…) As the library is not domain-specific, everyone is very welcome to contribute a review either by sending it to the Boost mailing list, or me personally. In your review please state whether you recommend to reject or accept the library into Boost, and whether you suggest any conditions for acceptance. Thanks in advance for your time and effort! Dmitry Arkhipov, Staff Engineer at The C++ Alliance.

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The standard library is better documented
by Niilo Huovila 07 Dec '23

07 Dec '23

By better I mean cppreference.com. There's a page for pretty much everything in the standard library. Related pages are linked. The preconditions and behavior of functions are specified. Consequentially I come to Boost only when the standard library doesn't do enough. If you are going to compete with the standard library instead of just supplementing it, you need outstanding documentation.

14 26

Master branch is now open for bug fixes
by Marshall Clow 06 Dec '23

06 Dec '23

The master branch is now open for bug fixes and documentation changes. Other changes by release manager permission, as described in https://github.com/boostorg/wiki/wiki/Releases%3A-Beta-Merge-Policy The next deadline: On December 6th, master closes for all changes. As always, the calendar is at https://www.boost.org/development/ — Marshall

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[release] Master Branch will close for the 1.84.0 release TOMORROW
by Marshall Clow 05 Dec '23

05 Dec '23

Don’t forget your release notes, too! — Marshall

1 0

[scope] Formal review - David Sankel
by David Sankel 05 Dec '23

05 Dec '23

- What is your evaluation of the design? I'm overall happy with the design. I like the API provided and think it is useful in many scenarios. The one question I have is why unique_resource::allocated instead of a bool conversion. This is the one aspect of the API that makes me hesitate using unique_resource for things like POSIX file descriptors as .allocated() would be quite foreign for users. - What is your evaluation of the implementation? I gave the implementation only a quick glance, but it looked fine to me. - What is your evaluation of the documentation? The documentation was good. I'd suggest the front page focuses on usage examples instead of a Boost.ScopeExit comparison though. Most people reading this page won't know about ScopeExit and are trying to evaluate whether not this library will solve their problem. - What is your evaluation of the potential usefulness of the library? I think this has wide applicability. - Did you try to use the library? With what compiler? Did you have any problems? I did not attempt to use it. - How much effort did you put into your evaluation? A glance? A quick reading? In-depth study? I spent about an hour working through the documentation. - Are you knowledgeable about the problem domain? Yes And finally, every review should 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. Yes, I do.

1 0

Proposal for Inclusion of Async.MQTT5 Library in Boost
by Ivica Siladic 05 Dec '23

05 Dec '23

Dear Boost Developers, we are writing to introduce a new C++ Async.MQTT5 library that we believe would be a valuable addition to Boost. MQTT has become the de-facto standard for IoT communication, with billions of IoT devices relying on it to publish or retrieve data from the cloud. Despite its widespread use, integrating MQTT into a C++ embedded application remains a complex and error-prone task. This challenge primarily arises from the absence of a higher-level library that offers a straightforward interface for message publishing and receiving while abstracting MQTT protocol intricacies and effectively managing various corner cases inherent in MQTT implementation. The primary objective behind developing Async.MQTT5 was to address these challenges comprehensively, allowing developers to focus on the messages they need to send without concerns about underlying network connectivity issues. Async.MQTT5 is a C++20 client implementation of the MQTT 5.0 protocol, leveraging Boost Asio and Boost Spirit. It fully adheres to the Asio asynchronous model, providing comprehensive support for all forms of asynchronous completion tokens, per-operation cancellation, and custom allocators. The library is designed to work seamlessly with any ordered network transport, typically TCP, SSL/TLS over TCP, or WebSockets (secured and unsecured). Our goal with Async.MQTT5 is to offer developers a simple and clear C++ interface for sending and receiving messages using the MQTT 5.0 protocol. Emphasizing code readability was a key design principle of Async.MQTT5. For instance, tedious protocol message parsing/composing is implemented declaratively (partially utilizing Boost Spirit). Additionally, Asio composed operations are implemented using a novel, clear, and highly efficient "chaining functional operators" approach. It is worth noting that the library is already written following Boost style guidelines, and the documentation is crafted and formatted in line with Boost conventions. You can find the library at https://github.com/mireo/async-mqtt5, and the documentation is available at https://spacetime.mireo.com/async-mqtt5/. We highly value your opinion and would appreciate any feedback you can provide on the Async.MQTT5 library. Thank you for your time and consideration. Best regards, Ivica Siladic Bruno Iljazovic Korina Simicevic

9 15

[scope] A few questions
by Julien Blanc 05 Dec '23

05 Dec '23

Hi, I have a few questions regarding the scope library currently being reviewed: * scope_exit is not default constructible. But it can be released and is movable, so a default constructed scope_exit state makes sense (this is the same as a moved-from scope_exit). I find this a rather strange design choice. What is the rationale behind this? There's even a section on the documentation on how to circumvent this: https://lastique.github.io/scope/libs/scope/doc/html/scope/scope_guards.htm… using cleanup_func_t = std::function< void() >; // Create an inactive scope guard first, since the cleanup function is not set yet boost::scope::scope_exit< cleanup_func_t > cleanup(cleanup_func_t(), false); Why can't i just write? boost::scope::scope_exit< std::function< void() > > cleanup; * the documentation says little about memory allocation. I finally found the answer i was looking for in the boost.ScopeExit comparison: scope_xxx objects do not do any heap allocations themselves. Is that a guarantee of the library? Such a guarantee is needed in some code i work with, i need to know if it is a feature of the library that i can rely upon, and not just an optimization that could go away in a further release. * unique_fd is a resource wrapper for files. But on all major systems, closing a file can fail and return an error. It may well be that the file is not completly written correctly, and this is reported not in the write call, but in the final close call. unique_fd silently drops the return value of close. I'm not sure we should encourage this behaviour. Another issue raises when we look at the example code: void write_string(std::string const& filename, std::string const& str) { // Create a unique resource for a file boost::scope::unique_resource< int, fd_deleter > file(open(filename.c_str(), O_CREAT | O_WRONLY)); if (file.get() < 0) { int err = errno; throw std::system_error(err, std::generic_category(), "Failed to open file " + filename); } // Use it to write data to the file const char* p = str.data(); std::size_t size_left = str.size(); while (size_left > 0) { ssize_t written = write(file.get(), p, size_left); if (written < 0) { int err = errno; if (err == EINTR) continue; throw std::system_error(err, std::generic_category(), "Failed to write data"); } p += written; size_left -= written; } } In case of a failure, what we got is an half-baked file, which we know nothing about. A proper write_string function should at least try to do its cleanup and delete the file in case of error. But that defeats the purpose of unique_resource... In my experience, automatically closing file handles is not error handling. But it has its use cases, maybe it would be better demonstrated by an example like: bool compare_files(std::string const& filename1, std::string const& filename2) { boost::scope::unique_resource< int, fd_deleter > file1(open(filename.c_str(), O_CREAT | O_WRONLY)); if (file1.get() < 0) { int err = errno; throw std::system_error(err, std::generic_category(), "Failed to open file " + filename1); } boost::scope::unique_resource< int, fd_deleter > file2(open(filename.c_str(), O_CREAT | O_WRONLY)); if (file2.get() < 0) { int err = errno; throw std::system_error(err, std::generic_category(), "Failed to open file " + filename2); } // do the comparison } Regards, Julien

2 7

[scope] Mr. Docs rendered reference
by Krystian Stasiowski 05 Dec '23

05 Dec '23

Hi everyone, My name is Krystian, and I'm a Staff Engineer at The C++ Alliance. I’ve been working on Mr. Docs, a clang based C++ documentation generator intended to serve as an alternative to Doxygen. Although Mr. Docs is not yet ready for release, I noticed that there was an issue with rendering the exception specification of destructors due to a bug in Boostbook. Thus, I would like to present Mr. Docs as a potential future alternative, and have generated a multi-page reference for Boost.Scope to demonstrate its capabilities: https://mrdocs.com/demos/develop/boost-scope/multi/adoc-asciidoc/boost/scop… The output was created using the built-in Asciidoc generator and converted to HTML with asciidoctor. Since the Asciidoc generator uses handlebars templates to format the output, customizing the rendered documentation is a matter of modifying the templates. Unlike Doxygen, Mr. Docs operates directly on the clang AST. This means that support for new/obscure language features is only limited by the extent of clang’s conformance to the latest C++ standard. Any feedback is greatly appreciated. 🙂 Best, Krystian Stasiowski

5 6

Re: [boost] The standard library is better documented
by Niilo Huovila 05 Dec '23

05 Dec '23

On 12/5/23 1:43 AM, boost-request(a)lists.boost.org wrote: > Date: Mon, 4 Dec 2023 12:36:27 > -0800 From: Marshall Clow <mclow.lists(a)gmail.com> To: > boost(a)lists.boost.org Subject: Re: [boost] The standard library is > better documented Message-ID: > <B135B251-3578-40CA-A9D8-34E165EE6C14(a)gmail.com> Content-Type: > text/plain; charset=utf-8 On Dec 4, 2023, at 12:21 PM, Mateusz Loskot > via Boost <boost(a)lists.boost.org> wrote: >> On Mon, 4 Dec 2023 at 21:05, Niilo Huovila via Boost >> <boost(a)lists.boost.org <mailto:boost@lists.boost.org>> wrote: >>> On 12/4/23 4:36 PM, Hans Dembinski wrote: >>>>> On 2. Dec 2023, at 16:57, Ren? Ferdinand Rivera Morell via Boost<boost(a)lists.boost.org> wrote: >>>>> >>>>> It would be useful if you could point to instances of Boost libraries >>>>> that could use better documentation. >>>> Can we organise a user poll that ranks all Boost libraries on how well documented they are? >>>> >>>> Might be a fun way to approach this and it provides an opportunity to create some publicity for Boost when we advertise this. I can see the news headline: "Boost devs finally respond to user cries for better docs" >>> The secret of cppreference seems to be that it is a wiki. How about >>> that? Users could put their energy to improving the docs instead of >>> complaining. :) >> Users can already do that by submitting pull requests on GitHub. > Or, if they don?t grok Quickbook, they can open a GitHub issue and suggest better wording. They seem relatively heavy-handed ways to add a link or correct spelling. > Date: Tue, 5 Dec 2023 00:12:17 +0300 > From: Andrey Semashev<andrey.semashev(a)gmail.com> > To:boost@lists.boost.org > Subject: Re: [boost] The standard library is better documented > Message-ID:<9e217656-9b05-4e82-a5a3-67c55d949b4f(a)gmail.com> > Content-Type: text/plain; charset=UTF-8 > > On 12/4/23 20:53, Niilo Huovila via Boost wrote: >> On 12/4/23 4:36 PM, Hans Dembinski wrote: >>>> On 2. Dec 2023, at 16:57, Ren? Ferdinand Rivera Morell via Boost >>>> <boost(a)lists.boost.org> wrote: >>>> >>>> It would be useful if you could point to instances of Boost libraries >>>> that could use better documentation. >>> Can we organise a user poll that ranks all Boost libraries on how well >>> documented they are? >>> >>> Might be a fun way to approach this and it provides an opportunity to >>> create some publicity for Boost when we advertise this. I can see the >>> news headline: "Boost devs finally respond to user cries for better docs" >> The secret of cppreference seems to be that it is a wiki. How about >> that? Users could put their energy to improving the docs instead of >> complaining. :) > Wiki is prone to vandalism and edit wars. > > Also, aside from stylistic and wording edits, the documentation is > supposed to be written by people who are very knowledgeable in the > subject. Those people are likely very few, often maintainers only. > > Wiki is good for "public knowledge" kind of documentation. The official > library documentation is very different from that. In fact, it is the > ground truth upon which that public knowledge is built. Would separating the reference from other documentation also separate it from those concerns? Then it could be a wiki and editing the other stuff can be restricted to maintainers.

1 0

[scope] some more thoughts
by Andrzej Krzemienski 04 Dec '23

04 Dec '23

Hi Everyone, I want to share some thoughts regarding the review of Boost.Scope. The fact that it wants to implement 1-to-1 a feature from a TS -- not from the standard -- impedes the review process. The reviewer says, "this feature is bad". The author responds, "but this is how the TS requires it to be". And now what? Should we accept a bad feature because the TS requires so? Being TS-conformant is very constraining for the author. Maybe this is not a worthy goal. Also, my observation from recent years is that putting stuff into a TS may be a polite way of saying, "we respect you, but we do not want this." Also, the goal of having an implementation for a proposed feature is to check if the interface has been battle-tested to be sound. The Boost Review process is such a test. When the feedback is, this feature is wrong, then this feedback should affect the STD proposal. But Boost shouldn't be compromised by an STD proposal that was submitted without a battle-tested implementation. The move assignment operator in scope_exit and friends. It looks like its existence is against the goal of the feature. You define a guard and then you use it. Why would you assign a different guard to it? Why do we have scope_success? An alternative to using scope success is to just put your instructions at the end of the function. Do you have multiple return statements in your function and at the same time you need the same sequence of operations to be performed at each end? This is a good motivation to restructure your function to have a single return. Multiple returns are generally OK, but needing the same sequence warrants a single return. scope_success seems like a solution that is looking for a problem. "But the TS has scope_success" -- this is not a good argument for me. In Boost Review we should be evaluating a library based on its own merit, not based on a similarity with some other design, which can have its own flaws. Mixing unique_resource with scope guards is not a good idea. The STD tends to use big aggregate headers. Boost does not. The solution from the TS should not be ported 1-to-1 to Boost. Boost.Scope offers at least three ways to do the same thing. For instance, to execute some code only upon some inconvenient condition, I can use scope_fail with my condition, or scope_exit with my condition, or I can add set_active on top of either. I consider this to be a bad design. Source code is not only for the flexibility of writing, but also for the ease of reading and learning. Having multiple ways to do the same thing impedes the understanding of the code. While I understand the existence of the triplet `scope_exit`, `scope_fail` and `scope_success` (D uses an analogous triplet), it takes a while to understand the difference between scope_exit and scope_final. And the choice of name doesn't help there. The Standard library chose to use term guard (std::lock_guard) to indicate something small and cheap. Maybe use this name instead. Not perfect either, but at least consistent with what we have in STD. Also, my experience is that one uses scope guards only in rare situations where you need to satisfy complex guarantees, like maintaining the same size of two vectors. And in those situations one is already very cautious, and tries to structure the code for the minimum surprises. One does not use multiple returns or complex control flows. The justification I heard for so many features in Boost.Scope is that there may be complex situations that require it. I think that in these situations restructuring the code is better than adding more features to Boost.Scope. This looks like a lot of harsh words, but I find a subset of the library very useful: * the unconditional execution of the function * the execution based on manual deactivation (active being the initial state) * execution based on the uncaught exception count, with the caveat that it sometimes doesn't work, and it is not cheap. Regards, &rzej;

2 5

[scope] unique_resource vs unique_ptr
by Bruno Martínez 04 Dec '23

04 Dec '23

Hi, unique_ptr can emulate unique_resource: template<auto nullvalue, auto delete_> class unique { using T = decltype(nullvalue); struct generic_delete { class pointer { T t; public: pointer(T t) : t(t) {} pointer(std::nullptr_t = nullptr) : t(nullvalue) { } explicit operator bool() { return t != nullvalue; } friend bool operator ==(pointer lhs, pointer rhs) { return lhs.t == rhs.t; } friend bool operator !=(pointer lhs, pointer rhs) { return lhs.t != rhs.t; } operator T() { return t; } }; void operator()(T p) { delete_(p); } }; public: using type = std::unique_ptr<struct not_used, generic_delete>; }; int main() { using unique_fd = unique<-1, close>::type; static_assert(sizeof(unique_fd) == sizeof(int), "bloated unique_fd"); unique_fd fd1(open("fd.txt", O_WRONLY | O_CREAT | O_TRUNC)); write(fd1.get(), "hello\n", 6); } The std papers say While std::unique_ptr can be tweaked by using a custom deleter type to almost a perfect handler for resources, it is awkward to use for handle types that are not pointers. But what's the awkwardness? Kind regards, Bruno

3 2

Re: [boost] The standard library is better documented
by Niilo Huovila 03 Dec '23

03 Dec '23

On 12/3/23 3:37 AM, boost-request(a)lists.boost.org wrote: > Date: Sat, 2 Dec 2023 17:44:05 +0100 > From: Andrzej Krzemienski <akrzemi1(a)gmail.com> > To: boost(a)lists.boost.org > Subject: Re: [boost] The standard library is better documented > Message-ID: > <CAOenAXhr9fu6jo7PoFC6JTKBhD7Kdw6yxWJUEFxtcPgYkujHwQ(a)mail.gmail.com> > Content-Type: text/plain; charset="UTF-8" > > sob., 2 gru 2023 o 17:21 Andrey Semashev via Boost <boost(a)lists.boost.org> > napisa?(a): > >> On 12/2/23 03:35, Niilo Huovila via Boost wrote: >>> By better I mean cppreference.com. There's a page for pretty much >>> everything in the standard library. Related pages are linked. The >>> preconditions and behavior of functions are specified. Consequentially I >>> come to Boost only when the standard library doesn't do enough. If you >>> are going to compete with the standard library instead of just >>> supplementing it, you need outstanding documentation. >> >> To be fair, as useful as cppreference.com is, it is not quite the same >> kind of documentation as Boost documentation is. It is mostly similar to >> the reference section that you can find in most libraries' docs, as it >> basically translates the standard wording to human language and gives a >> single usage example in the end. There is no rationale, discussion, or >> usage recommendations. It's a feature: there's a time for discussion and rationale, but not when I just want to look up something quickly. >> The unquestionable advantage of cppreference.com is that it has lots of >> cross-links, which makes it very easy to navigate and find what you're >> looking for. Cross-linking is definitely something that Boost docs could >> use more. ^ This. The easy to navigate reference is what I miss the most. Cppreference can be explored like a retailer's magazine. Items are usually sorted to categories. It makes them more discoverable. > True, but for that we would have to have a uniform documentation experience > for all the libraries. And I do not think we are ever going to get there. I agree that it's a daunting task. Actually I thought that the first reaction to my message would be pondering whether competing with the standard library is worth the effort or even feasible. I were surprised when the first reaction was asking which docs need improvement, because cppreference sets the bar so high.

1 0

Re: [boost] [scope] Scope review starts on November 26th
by Janko Dedic 02 Dec '23

02 Dec '23

Thanks for proposing this library. Scope guards are a natural and much needed addition to Boost. The following is my review of the proposed Boost.Scope. The first thing I looked for in this library was a convenience SCOPE_EXIT { ... }; macro that would provide the functionality in the form of a control flow construct. I've managed to quickly find it, but it wasn't exactly what I was expecting. BOOST_SCOPE_FINAL [] { std::cout << "Hello world!" << std::endl; }; I found it rather odd that the capture list is not included in the macro. I looked a bit further into the documentation to find this: BOOST_SCOPE_FINAL std::ref(cleanup_func); Is this use case the reason why the capture list is required? It seems like a very rare one that shouldn't pessimize the interface for 99% of use cases. Performance shouldn't be a concern because the compiler sees all this code and inlines it anyway. In my view, this just makes the interface worse and less pleasant to use. scope_success doesn't seem terribly useful. I have yet to see a legitimate use case of this type. I haven't found a motivating example in the documentation. There should either be one, or this type should be removed from the library. There is no BOOST_SCOPE_FAIL macro. Why is it missing? I found the scope_fail example pretty bad: class collection { std::set< std::shared_ptr< object > > objects; public: void add_object(std::shared_ptr< object > const& obj) { // Create a deactivated scope guard initially std::set< std::shared_ptr< object > >::iterator it; boost::scope::scope_fail rollback_guard{[&, this] { objects.erase(it); }, false}; bool inserted; std::tie(it, inserted) = objects.insert(obj); if (inserted) { // Activate rollback guard rollback_guard.set_active(true); } obj->on_added_to_collection(*this); } }; It could be simply rewritten to not use set_active (which should be discouraged, because it makes code less declarative and harder to follow): class collection { std::set< std::shared_ptr< object > > objects; public: void add_object(std::shared_ptr< object > const& obj) { // Create a deactivated scope guard initially std::set< std::shared_ptr< object > >::iterator it; bool inserted; std::tie(it, inserted) = objects.insert(obj); if (inserted) { boost::scope::scope_fail rollback_guard{[&, this] { objects.erase(it); }}; obj->on_added_to_collection(*this); } } }; Could be made even cleaner by using an early return: if (!inserted) return; All destructor declarations in the documentation lack noexcept specification, which by default means that they're noexcept, but they're actually not if you look at the Throws section, or the implementation. Also, the question presents itself: why are these destructors allowed to throw? I feel like it is common knowledge today that destructors should not throw, and this is heavily frowned upon. I can see the want to "be generic" here, but I don't see why a library should entertain broken code. I also noticed that certain scope guards are move constructible. Why? I cannot imagine myself ever approving of someone moving a scope guard on code review. Scope guards are to be used exclusively as local variables and don't need to be moved. This just opens up room for misuse. I don't see any compelling use cases for scope_exit::set_active in the documentation. The only example I find motivating is this one: void push_back(int x, std::vector<int>& vec1, std::vector<int>& vec2) { vec1.push_back(x); // Revert vec1 modification on failure boost::scope::scope_exit rollback_guard{[&] { vec1.pop_back(); }}; vec2.push_back(x); // Commit vec1 modification rollback_guard.set_active(false); } This could as well have used rollback_guard.release();. This matches my personal experience: only dismiss/release/cancel is necessary for real use cases ("commiting" something and thus disabling the "rollback" action). absl::Cleanup for example, supports only Cancel(). There is value in preventing users from shooting themselves in the foot. I don't like the name scope_exit::release personally. I feel like "dismiss" or "cancel" would be much better. I know that std::experimental::scope_exit calls it "release", but we shouldn't appeal to false authority. I did not like the locked_write_string example. Reading this code locally: // Lock the file while (flock(fd, LOCK_EX) < 0) { err = errno; if (err != EINTR) return; } it's hard to get what's happening, why we're setting err and how big of an impact that has on function behavior. A better way to write this code would be to simply extract this piece into its own function: err = errno; if (err != EINTR) return; together with the ec = std::error_code(err, std::generic_category()), which doesn't require a scope guard. fd_deleter and unique_fd provide some nice handling for EINTR, which wasn't required but I think it's nice to have and it's good that it's a part of this library! I think make_unique_resource_checked approaches the problem from the wrong direction. This code: // Create a unique resource for a file auto file = boost::scope::make_unique_resource_checked( open(filename.c_str(), O_CREAT | O_WRONLY) -1, fd_deleter()); if (!file.allocated()) { int err = errno; throw std::system_error(err, std::generic_category(), "Failed to open file " + filename); } could be this: // Create a unique resource for a file int file = open(filename.c_str(), O_CREAT | O_WRONLY); boost::scope::scope_final close_file(fd_deleter{}); if (file != -1) { int err = errno; throw std::system_error(err, std::generic_category(), "Failed to open file " + filename); } This has the advantage of being able to use `file` directly for the rest of the code instead of `file.get()`. I think a similar utility would be more useful in form of a class template, for example: resource<HANDLE, INVALID_HANDLE_VALUE, ::CloseHandle> windows_handle; resource<SDL_Window*, nullptr, ::SDL_DestroyWindow> sdl_window_handle; This would be very useful for concisely implementing RAII wrappers over C handles (you don't have to manually write destructors, move constructors and move assignment operators). For local use (within a function), I feel like a local handle + scope guard is just more ergonomic than the whole make_unique_resource_checked thing. My overall impression is that this library is trying to be too generic when it's not really necessary. There's definitely useful stuff here that I want to see included, but also a lot of stuff that is too much. I don't personally see the need for any scope guard beyond scope_exit with a release. That covers all the use cases I've ran into very nicely. scope_fail can be more error-prone since the "commit" is not explicit, so you may end up doing rollback even when it's unnecessary. Using the modified example from the documentation: void push_back(int x, std::vector<int>& vec1, std::vector<int>& vec2) { vec1.push_back(x); // Revert vec1 modification on failure boost::scope::scope_fail rollback_guard{[&] { vec1.pop_back(); }}; vec2.push_back(x); do_something_else(); // if this throws, rollback_guard runs } If you use scope_exit with an explicit release, it's clearer IMO: void push_back(int x, std::vector<int>& vec1, std::vector<int>& vec2) { vec1.push_back(x); // Revert vec1 modification on failure boost::scope::scope_exit rollback_guard{[&] { vec1.pop_back(); }}; vec2.push_back(x); rollback_guard.release(); // commit do_something_else(); // if this throws, rollback_guard won't run } The documentation states that "exception_checker is incompatible with C++20 coroutines", which is true in general, but it doesn't have to be (depending on the coroutine library implementation). However, I bring this up because using scope_exit+release is an entirely viable alternative for coroutines. scope_exit+release will work whether you use exceptions, error codes, std::expected, coroutines or all of them combined. This is the beauty of it, which makes me feel like scope_fail is unnecessary. I vote to ACCEPT this library with the following CONDITIONS: - BOOST_SCOPE_FINAL includes the lambda capture list OR another macro that does is provided; - noexcept specification on destructors is properly documented; - move constructors on all scope guard types are deleted; - a motivating example for scope_success is provided, or the type is removed. These are my conditions, but I'm hoping the full review is taken as a recommendation in improving the library and the documentation. Best regards, Janko Dedic

3 18

[scope] The comparison with Boost.ScopeExit is unfair
by Andrzej Krzemienski 02 Dec '23

02 Dec '23

Hi All, This is not a review yet. I am just looking at the front page of the docs, and I think the comparison with Boost.ScopeGuard is unfair. You are comparing C++03 Boost.ScopeGuard with C++11 Boost.Scope. Try comparing it with C++03 Boost.Scope. Otherwise compare C++11 to C++11, and there Boost.ScopeGuard has a nicer syntax: int compute() { // Reset variables on return BOOST_SCOPE_EXIT(this_) { this_->x = 0; this_->y = 0; }; return x + y; } Regarding the example with exceptions, nobody would use Boost.ScopeGuard like this. A robust usage is in Boost.ScopeGuard's docs: void world::add_person(person const& a_person) { bool commit = false; persons_.push_back(a_person); // (1) direct action // Following block is executed when the enclosing scope exits. BOOST_SCOPE_EXIT(&commit, &persons_) { if(!commit) persons_.pop_back(); // (2) rollback action }; // ... // (3) other operations commit = true; // (4) disable rollback actions } Which is longer, but usable in coroutines. Whereas Boost.Scope's solution is not usable in coroutines. Only after these changes are applied, I think is the comparison fair. Regards, &rzej;

2 5

Boost Culture
by Vinnie Falco 02 Dec '23

02 Dec '23

It occurs to me that newcomers to the mailing list will not have any understanding of Boost culture or its development process. For example there is a recurring theme where a new person will ask about "what documentation toolchain does Boost use." The answer of course is that every library has considerable autonomy to define how it wants to generate its documents. The only requirement is that the final result is rendered as HTML. Another example is the idea that there is a "CEO of Boost." Or rather that there are particular individuals who have some sort of decision-making authority for the entire libraries. Or another example, why we use mailing lists over dedicated forum software. We might consider putting together a document which centralizes all of the collected wisdom and knowledge about Boost culture including the history of its evolution and why some things are the way that they are. This would facilitate the entry of newcomers to places like the mailing list which assume that participants already know a lot about Boost culture. This could become a chapter in the new Contributor Guide: https://www.preview.boost.org/doc/contributor-guide/index.html Thanks

4 3

Dead Link
by Brian Salehi 01 Dec '23

01 Dec '23

There is a dead link on page [Machine Learning](https://www.preview.boost.org/doc/user-guide/task-machine-learnin… refering to Boost.uBLAS library. I guess the typo is an extra s letter after /doc which seems to point to the correct page when removed. Regards, Brian

1 0

[scope] Scope review starts on November 26th
by Claudio DeSouza 28 Nov '23

28 Nov '23

It would be helpful if the cmake build was fixed to not require some specific custom setup that was used by the author during development. The cmake list file seems to check for the existence of a cmake test file, to decide whether or not to build the tests. These files seem to have been moved outside reach of the setup in place, under test/test_cmake. Also, it would be better to get rid of this: add_subdirectory(../../../.. "${CMAKE_CURRENT_BINARY_DIR}/boost_superproject") Ideally, these cmake tests should assume scope is a submodule, or a subfolder, of the boost super project. Claudio.

4 3

[release] Boost 1.84.0 beta 1 released
by Marshall Clow 24 Nov '23

24 Nov '23

Boost release 1.84.0 beta 1 is now available at: https://boostorg.jfrog.io/artifactory/main/beta/1.84.0.beta1/source/ The SHA256 checksums are: 224d595cc666c19b91214c5e9cced3988d08063146dfad9f616c481d52626f27 boost_1_84_0_b1.zip de9b35e232e4b1769f4d800ec01255a9c2546639be43e45b16ce6d109c088e99 boost_1_84_0_b1.tar.gz f8a9f21580961536a95fb7fcf9deebde45d7e0e94ddd81402f1e37ae2c590410 boost_1_84_0_b1.tar.bz2 3e4765c41974c763b7d4a67a432569bf75d3367d7a6b72c4ac9458e5004c59dc boost_1_84_0_b1.7z Release notes (still need updates): https://www.boost.org/users/history/version_1_84_0.html Please try the beta and report any problems you encounter. Thanks to everyone who contributed to the release. -- Boost Release Team

3 3

cobalt build is failing
by Alain O' Miniussi 24 Nov '23

24 Nov '23

Hi, The colbalt build fails on master, starting with this message: [...]/boost/libs/cobalt/test/main.cpp:10:21: error: too few arguments to function call, expected 2, have 1 boost::cobalt::main co_main(int argc, char *argv[]) ^~~~~~~ I can provide more details if needed, but first I'd like to know if this is expected. Thanks ---- Alain Miniussi DSI, Pôles Calcul et Genie Log. Observatoire de la Côte d'Azur Tél. : +33609650665

2 2

[1.84][beast] Permission to merge to master
by Mohammad Nejati [ashtum] 17 Nov '23

17 Nov '23

Hi, I’d like to merge this to master: https://github.com/boostorg/beast/compare/master...develop Fixes a narrowing conversion error reported in this issue: https://github.com/boostorg/beast/issues/2766 Thanks, Mohammad Nejati

2 1

[release] Boost 1.84.0 Beta 1 Release Candidate 1 is available
by Marshall Clow 17 Nov '23

17 Nov '23

Available at: <https://boostorg.jfrog.io/artifactory/main/beta/1.84.0.beta1/source/> The SHA256 checksums are as follows: f8a9f21580961536a95fb7fcf9deebde45d7e0e94ddd81402f1e37ae2c590410 boost_1_84_0_b1_rc1.tar.bz2 224d595cc666c19b91214c5e9cced3988d08063146dfad9f616c481d52626f27 boost_1_84_0_b1_rc1.zip 3e4765c41974c763b7d4a67a432569bf75d3367d7a6b72c4ac9458e5004c59dc boost_1_84_0_b1_rc1.7z de9b35e232e4b1769f4d800ec01255a9c2546639be43e45b16ce6d109c088e99 boost_1_84_0_b1_rc1.tar.gz 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 Release Managers

11 28

Do we still want develop branch?
by Andrey Semashev 16 Nov '23

16 Nov '23

Hi, The recent case of a commit in develop that was left unmerged to master made me wondering if people still find the develop branch useful. Historically (since the SVN days), we used a separate branch for active development, which we then merged to the stable branch that was used for creating Boost releases. This allowed to test libraries together before changes propagate to the stable branch. This was useful back when the official test matrix was the primary gauge of the Boost "health", so when something broke, it was rather visible, even if the breakage manifested in downstream libraries. With the adoption of git and CI, the relevance of the test matrix has diminished, and, presumably, people have shifted towards monitoring their libraries' CI. Which means, people are less likely to notice that something broke downstream, unless the downstream developer notices and reports the problem. Although I have been that downstream developer myself quite a few times, I have to admit that this role of the develop branch of "an integration testing field" is not well filled in the current workflow. Noticing the breakage is mostly luck (i.e. a matter of me making a commit to my library and noticing the CI failure caused by an upstream dependency) rather than a rule. Additionally, I have been asked on a few occasions to avoid development directly in the develop branch and use separate feature branches instead. That is, do your commits in a feature branch, let the CI pass, then merge to develop, let the CI pass again, then merge to master. Apparently, some people are using this workflow by default to avoid breakage in develop, which means develop is no longer the branch where the actual development happens. (This workflow actually makes develop meaningless because your CI over the feature branch already tests your changes against develop of the rest of Boost. Which means after merging to develop you're running the same CI again, and might as well just merge to master straight away.) Then there's the recurring problem that led to this post - people forget to merge to master from time to time. Or simply don't have time to merge. Or the library is no longer actively maintained. Or the commit is left out of master for any other reason, which means users don't receive their bug fixes in a release. Personally, I do try to remember the PRs I make during the release cycle and look through them just before the release to make sure they are merged to master. Some of you probably received gentle merge reminders from me. I'm not sure if anyone else is doing this, but I can say this is an active mental effort on my part, which I'd rather not have to make. And even then I can't be sure I remember all PRs or have the time to cycle though them before the release. Which brings me to my question. Do people still find the develop branch useful? Maybe we'd be better off just dropping it and performing all development in feature branches before merging straight to master? Also, if you do find develop useful, what do you think about creating a GitHub Action to automatically merge develop to master once the CI on develop succeeds? Maybe there are other ideas how to avoid commits unmerged to master? Thanks.

8 51

Re: [boost] Do we still want develop branch?
by Jonathan Wakely 13 Nov '23

13 Nov '23

Oops, resending from the address that is actually sub'd the the list ... On Mon, 6 Nov 2023 at 19:13, Jonathan Wakely wrote: > > > On Mon, 6 Nov 2023 at 16:45, Robert Ramey via Boost <boost(a)lists.boost.org> > wrote: > >> On 11/6/23 1:45 AM, Alexander Grund via Boost wrote: >> > I agree here that this is a major issue and maybe the release managers >> > can check (e.g. with Peters script) for that common issue and maybe >> even >> > initiate merges. >> >> Seems to me it would be easy to make a script which the release manager >> would run before release which would flag all libraries which have >> unmerged changes on the development branch dated before the current >> date. This might resolve the whole issue. >> >> > That would imply a rule of thumb that develop should (in general) have no > changes that aren't merged to master ready for a release. > > If you're going to have such a rule, you might as well just get rid of the > two branch model and just use a trunk-based git workflow. So you work on > develop, and then at some point you create a release branch from develop, > call it boost_1_84_0 and that release branch is used for the release. No > manual merging from develop to master, because the release branch comes > straight from develop, not from an unrelated branch which should (in > theory, if the maintainer remembers) match the *content* of develop, but > not the actual history of develop. > > > > https://www.atlassian.com/continuous-delivery/continuous-integration/trunk-… > https://www.toptal.com/software/trunk-based-development-git-flow > https://trunkbaseddevelopment.com/ > >

7 14

[Release] Master branch is closed for beta
by Marshall Clow 09 Nov '23

09 Nov '23

Master is closed for all changes. See the release schedule at: https://www.boost.org/development/index.html -- Release managers

1 0

Re: [boost] [boost.cobalt] A precondition or an error condition?
by Andrzej Krzemienski 09 Nov '23

09 Nov '23

czw., 9 lis 2023 o 17:32 Klemens Morgenstern < klemensdavidmorgenstern(a)gmail.com> napisał(a): > > Actually, your explanation convinces me even stronger that this should > be a different function with a different name. It is a different use case, > it has a different signature, a different return type. > > > > How is the use case different? I got multiple awaitable and I want to > wait for one to finish. The decision of how many is either a runtime > or a compile time decision and we're discussing how to handle the > runtime error. Sounds like the same thing to me. > They have different preconditions: one requires a non-epty variadic pack. One allows promises with different result types, the other doesn't. They differ in return types: one returns a variant, the other returns a pair. So, the following code will look different in either case. Sure they share some similarities. Much like `race` and `left_race` do. But they have two different names. Regards, &rzej;

1 0

[boost.cobalt] A precondition or an error condition?
by Andrzej Krzemienski 09 Nov '23

09 Nov '23

Hi Everyone, I would like to discuss one correctness aspect of Boost.COBALT. We have this list and the Slack channel, so I am not sure which place is better. Let me do it here. In Boost.Cobalt (formerly Boost.Async) we have function cobalt::race (formerly select()) that takes a range of awaitables `p` and returns an awaitable capable on awaiting on one of the elements of `p`: https://www.boost.org/doc/libs/develop/libs/cobalt/doc/html/index.html#race… Example: ``` promise<string> talk_to_server_1(); promise<string> talk_to_server_2(); promise<string> timeout_with_default(); vector<promise<int>> servers = { talk_to_server_1(), talk_to_server_2(), timeout_with_default() }; pair<size_t, string> ans = co_await race(servers); ``` This obviously cannot work when the input range passed to `race` is empty. Boost.COBALT docs say that for this situation "Selecting an empty range will cause an exception to be thrown". But I do not think it is the right approach. The right approach would be to clearly communicate to the user of the library that this is an incorrect usage of the library: if you pass an empty range to `race` you clearly do not know what you are doing, or you simply overlooked it and planted a bug. The library should list it as a *precondition* in the docs: the passed range cannot be empty. If you do it, you cannot expect your program to work correctly. >From the perspective of the library author, you can now, for the event of passing the empty range, putt all the tools that help in debugging: * BOOST_ASSERT * insert a breakpoint And on the next line, you can also throw an exception to avoid an UB. But in that case the exception would not be part of the official contract. If the docs just say "throws an exception" (as today, which I think is wrong) then the library author is not allowed to insert any debugging aids (such as BOOST_ASSERT or breaking into the debugger) because the user may be relying on the exception throw. You do not want the users to rely on the exception throw: you want to prevent the users from passing the empty range. What do others think about it? Regards, &rzej;

3 6

[release] Master branch closes for the 1.84.0 beta release TOMORROW
by Marshall Clow 08 Nov '23

08 Nov '23

Calendar here: https://www.boost.org/development/ — The release managers

3 5

Linking Problems starting with Boost 1.81
by Dennis Luehring 05 Nov '23

05 Nov '23

1.79 links with my software 1.80 links with my software 1.81 does not link 1.82 does not link 1.83 does not link Linux up to date Suse/Tumbleweed gcc 13.2.1 ./bootstrap.sh ./b2 -j16 --toolset=gcc cxxflags=-fPIC --build-dir=./_build address-model=64 architecture=x86 threading=multi --stagedir=./lib64-gcc --build-type=complete --layout=versioned --without-mpi these are the errors on linking when using 1.81 and above ld.lld: error: duplicate symbol: boost::phoenix::placeholders::uarg1 >>> defined at local_256.hpp:16 (/home/linux/dev/3rdparty-linux-gcc/boost_1_83_0/boost/preprocessor/iteration/detail/limits/local_256.hpp:16) >>> Recipe_expression_validator.cpp.o:(boost::phoenix::placeholders::uarg1) in archive ../../implementation/expression_validation/libexpression_validation.a >>> defined at local_256.hpp:16 (/home/linux/dev/3rdparty-linux-gcc/boost_1_83_0/boost/preprocessor/iteration/detail/limits/local_256.hpp:16) >>> parser.cpp.o:(.bss+0xF80) in archive ../../devs/expression_parser_lib/libexpression_parser_lib.a ld.lld: error: duplicate symbol: boost::phoenix::placeholders::uarg2 >>> defined at local_256.hpp:19 (/home/linux/dev/3rdparty-linux-gcc/boost_1_83_0/boost/preprocessor/iteration/detail/limits/local_256.hpp:19) >>> Recipe_expression_validator.cpp.o:(boost::phoenix::placeholders::uarg2) in archive ../../implementation/expression_validation/libexpression_validation.a >>> defined at local_256.hpp:19 (/home/linux/dev/3rdparty-linux-gcc/boost_1_83_0/boost/preprocessor/iteration/detail/limits/local_256.hpp:19) >>> parser.cpp.o:(.bss+0xFC0) in archive ../../devs/expression_parser_lib/libexpression_parser_lib.a ld.lld: error: duplicate symbol: boost::phoenix::placeholders::uarg3 >>> defined at local_256.hpp:22 (/home/linux/dev/3rdparty-linux-gcc/boost_1_83_0/boost/preprocessor/iteration/detail/limits/local_256.hpp:22) >>> Recipe_expression_validator.cpp.o:(boost::phoenix::placeholders::uarg3) in archive ../../implementation/expression_validation/libexpression_validation.a >>> defined at local_256.hpp:22 (/home/linux/dev/3rdparty-linux-gcc/boost_1_83_0/boost/preprocessor/iteration/detail/limits/local_256.hpp:22) >>> parser.cpp.o:(.bss+0x1000) in archive ../../devs/expression_parser_lib/libexpression_parser_lib.a anyone got an idea what changed between 1.80 and 1.81 to let my linking fail with the above errors the expression_parser_lib and expression_validation is my own code

4 8

Reminder: Boost 1.84.0 release cycle starting
by Marshall Clow 04 Nov '23

04 Nov '23

The deadline for “major changes” is next Wednesday, 1-Nov. The beta release will be two weeks later. As always, the release calendar is at: https://www.boost.org/development/index.html — Marshall

5 5

Boost test matrix
by Robert Ramey 04 Nov '23

04 Nov '23

I've merged my develop branch into the the master, waited some time, and reviewed the test results here: https://www.boost.org/development/tests/develop/developer/serialization.html . Given that we intend to release soon, I have a few questions: a) I don't see any windows compilers here. WTF? b) If I switch to "Release View" (upper left hand corner) I expect to see test runs for the master branch. I just get an error message. I can't see how we can think of doing a release with having these issues resolved. Robert Ramey

6 8

error on inclusion of ../boost/math/special_functions/next.hpp
by Robert Ramey 03 Nov '23

03 Nov '23

In reviewing the test matrix: https://www.boost.org/development/tests/develop/developer/serialization.html I'm getting the following error message when on a couple of my tests: > Test output: teeks99-dkr-dc6-17 - serialization - test_complex_text_archive / clang-linux-6.0~c++17 > Rev 1c12b5c15fc82f0cb6d4bd931a057fc050df8a34 / Sun, 29 Oct 2023 21:39:02 +0000 > Compile [2023-10-29 23:34:25 UTC]: fail > > > "clang++-6.0" -fvisibility-inlines-hidden -Wno-c99-extensions -std=c++17 -fPIC -m64 -pthread -O0 -fno-inline -Wall -fvisibility=hidden --target=x86_64-pc-linux -ftemplate-depth-255 -DBOOST_ALL_NO_LIB=1 -DBOOST_ARCHIVE_TEST=text_archive.hpp -DBOOST_ATOMIC_DYN_LINK=1 -DBOOST_BEAST_ALLOW_DEPRECATED -DBOOST_BEAST_SEPARATE_COMPILATION -DBOOST_COBALT_USE_STD_PMR=1 -DBOOST_FILESYSTEM_DYN_LINK=1 -DBOOST_LIB_DIAGNOSTIC=1 -DBOOST_SERIALIZATION_DYN_LINK=1 -DBOOST_WSERIALIZATION_DYN_LINK=1 -I".." -c -o "/var/boost/run/results/boost/bin.v2/libs/serialization/test/test_complex_text_archive.test/clang-linux-6.0~c++17/debug/debug-symbols-off/threading-multi/visibility-hidden/test_complex.o" "../libs/serialization/test/test_complex.cpp" > > In file included from ../libs/serialization/test/test_complex.cpp:19: > In file included from ../boost/math/special_functions/next.hpp:17: > In file included from ../boost/math/special_functions/trunc.hpp:21: > In file included from ../boost/math/ccmath/ldexp.hpp:15: > In file included from ../boost/math/ccmath/abs.hpp:16: > ../boost/math/ccmath/isnan.hpp:35:29: error: no template named 'is_integral_v' in namespace 'std'; did you mean 'is_integral'? > if constexpr (!std::is_integral_v<T>) > ~~~~~^~~~~~~~~~~~~ > is_integral > /usr/bin/../lib/gcc/x86_64-linux-gnu/5.4.0/../../../../include/c++/5.4.0/type_traits:289:12: note: 'is_integral' declared here > struct is_integral > ^ Looks like a minor snafu in ../boost/math/ccmath/isnan.hpp ... or not. Could someone who understands math/special functions took a look into this? On a totally separate note: I'm getting another failure on the same matrix: Test output: teeks99-dkr-dc6-17 - serialization - test_dll_simple / clang-linux-6.0~c++17 Rev 1c12b5c15fc82f0cb6d4bd931a057fc050df8a34 / Sun, 29 Oct 2023 21:39:02 +0000 Lib [2023-10-29 23:34:28 UTC]: fail See boost/bin.v2/libs/serialization/test/clang-linux-6.0~c++17/debug/debug-symbols-off/threading-multi/visibility-hidden where the links points to a file containing: > Test output: boost/bin.v2/libs/serialization/test/clang-linux-6.0~c++17/debug/debug-symbols-off/threading-multi/visibility-hidden > Rev 1c12b5c15fc82f0cb6d4bd931a057fc050df8a34 / Sun, 29 Oct 2023 21:39:02 +0000 > Compile [2023-10-29 23:34:25 UTC]: succeed > > "clang++-6.0" -fvisibility-inlines-hidden -Wno-c99-extensions -std=c++17 -fPIC -m64 -pthread -O0 -fno-inline -Wall -fvisibility=hidden --target=x86_64-pc-linux -DBOOST_ALL_NO_LIB=1 -DBOOST_ATOMIC_DYN_LINK=1 -DBOOST_BEAST_ALLOW_DEPRECATED -DBOOST_BEAST_SEPARATE_COMPILATION -DBOOST_COBALT_USE_STD_PMR=1 -DBOOST_FILESYSTEM_DYN_LINK=1 -I".." -c -o "/var/boost/run/results/boost/bin.v2/libs/serialization/test/clang-linux-6.0~c++17/debug/debug-symbols-off/threading-multi/visibility-hidden/dll_polymorphic_derived2.o" "../libs/serialization/test/dll_polymorphic_derived2.cpp" > > In file included from ../libs/serialization/test/dll_polymorphic_derived2.cpp:13: > In file included from ../libs/serialization/test/polymorphic_derived2.cpp:15: > ../libs/serialization/test/polymorphic_base.hpp:29:13: warning: polymorphic_base imported [-W#pragma-messages] > #pragma message ("polymorphic_base imported") > ^ > In file included from ../libs/serialization/test/dll_polymorphic_derived2.cpp:13: > In file included from ../libs/serialization/test/polymorphic_derived2.cpp:16: > ../libs/serialization/test/polymorphic_derived2.hpp:32:13: warning: polymorphic_derived2 exported [-W#pragma-messages] > #pragma message ("polymorphic_derived2 exported") > ^ > 2 warnings generated. > > Link [2023-10-29 23:34:25 UTC]: succeed > > > "clang++-6.0" -o "/var/boost/run/results/boost/bin.v2/libs/serialization/test/clang-linux-6.0~c++17/debug/debug-symbols-off/threading-multi/visibility-hidden/libdll_polymorphic_derived2.so.1.84.0" -Wl,-soname -Wl,"libdll_polymorphic_derived2.so.1.84.0" -shared -Wl,--start-group "/var/boost/run/results/boost/bin.v2/libs/serialization/test/clang-linux-6.0~c++17/debug/debug-symbols-off/threading-multi/visibility-hidden/dll_polymorphic_derived2.o" "/var/boost/run/results/boost/bin.v2/libs/serialization/test/clang-linux-6.0~c++17/debug/debug-symbols-off/threading-multi/visibility-hidden/libdll_polymorphic_base.so.1.84.0" "/var/boost/run/results/boost/bin.v2/libs/serialization/build/clang-linux-6.0~c++17/debug/debug-symbols-off/threading-multi/visibility-hidden/libboost_serialization.so.1.84.0" "/var/boost/run/results/boost/bin.v2/libs/filesystem/build/clang-linux-6.0~c++17/debug/debug-symbols-off/threading-multi/visibility-hidden/libboost_filesystem.so.1.84.0" -Wl,-Bstatic -Wl,-Bdynamic -lrt -Wl,--end-group -fPIC -m64 -pthread -fvisibility=hidden -fvisibility-inlines-hidden --target=x86_64-pc-linux So .... This parts builds a dll/shared library which is used in the test. There doesn't seem to be anything wrong with this. Does anyone have any ideas? Robert Ramey

3 3

Boost Security Disclosure
by Feuer, Mark 02 Nov '23

02 Nov '23

Is there a written security disclosure policy for Boost? As an example, is there a boost document that says all security vulnerabilities will be reported to NIST? If so, can someone point me to the disclosure form? I've seen in some documentation references to CVEs. Does this mean all security vulnerabilities are required to be submitted to NIST? Thanks, Mark [CONFIDENTIALITY AND PRIVACY NOTICE] Information transmitted by this email is proprietary to Medtronic and is intended for use only by the individual or entity to which it is addressed, and may contain information that is private, privileged, confidential or exempt from disclosure under applicable law. If you are not the intended recipient or it appears that this mail has been forwarded to you without proper authority, you are notified that any use or dissemination of this information in any manner is strictly prohibited. In such cases, please delete this mail from your records. To view this notice in other languages you can either select the following link or manually copy and paste the link into the address bar of a web browser: http://emaildisclaimer.medtronic.com

1 0

[release] Master Branch is closed for major code changes
by Marshall Clow 02 Nov '23

02 Nov '23

The master branch closed for major code changes. Still open for serious problem fixes and docs changes without release manager review. The master branch will close for the 1.84.0 beta release next Wednesday As always, the calendar is available at: https://www.boost.org/development/ — The release managers

1 0

[Release] Boost 1.84.0 closing for major changes TOMORROW
by Marshall Clow 31 Oct '23

31 Oct '23

Release closed for major code changes. Still open for serious problem fixes and docs changes without release manager review. See: https://www.boost.org/development/index.html — Marshall

1 0

[scope] Looking for endorsements and review manager
by Andrey Semashev 31 Oct '23

31 Oct '23

Hi, This is a reminder that Boost.Scope is looking for endorsements and a review manager. Following is an excerpt from the previous announcement, describing the library. Boost.Scope is a small library implementing utilities defined in <experimental/scope> from C++ Extensions for Library Fundamentals v3 with a few extensions. Namely, the library contains: * A number of scope guards for various use cases. * A unique resource wrapper that automatically frees the resource on destruction. * Utilities for wrapping POSIX-like file descriptors in the unique resource wrapper. Compared to <experimental/scope>, some notable extensions are: * A new scope_final scope guard, which is a more lightweight alternative to scope_exit. It is accompanied with the BOOST_SCOPE_FINAL macro that allows to simplify scope guard declaration syntax. * Scope guards can be activated/deactivated multiple times. * Scope guards can be created inactive initially. * Scope guard factory functions, for compatibility with C++11. * Support for optional resource traits in unique_resource wrapper, which improves usage with resources having unallocated values. * unique_resource supports swapping. * unique_resource supports dereferencing for any resource types that support dereferencing, not only pointers. * More flexible constructors for unique_resource. The library requires C++11 at the minimum and will significantly benefit from C++17. Source: https://github.com/Lastique/scope Docs: https://lastique.github.io/scope/libs/scope/doc/html/index.html The library is tested in CI and used in production in one of my projects. Thanks.

5 14

Use of boost::anys::unique_any in place of boost::any
by Bhuyan, Jyotideep 23 Oct '23

23 Oct '23

Hello, As per documentation, Boost::Any is getting deprecated, and it was suggested to use boost::anys::unique_any. I am using boost::any and boost::any_cast heavily in my application code. I am looking for some sample code for best practices on how we can replace boost::any and boost::any_cast with boost::anys::unique_any. I am using VS2022, boost v1.83, and building the code with C++17. Best Regards, Jyotideep Bhuyan (he/him) Please be advised that this email may contain confidential information. If you are not the intended recipient, please notify us by email by replying to the sender and delete this message. The sender disclaims that the content of this email constitutes an offer to enter into, or the acceptance of, any agreement; provided that the foregoing does not invalidate the binding effect of any digital or other electronic reproduction of a manual signature that is included in any attachment. Confidential - Company Proprietary

1 0

[Looking for Feedback] - Fairness lib
by Federico Abrignani 22 Oct '23

22 Oct '23

Dear Boost Community, I am writing to seek feedback on a new C++ library that I have been developing (https://github.com/Sernior/fairness <https://github.com/Sernior/fairness>). This library, named "*Fairness*," is still a work in progress. Nonetheless, I believe that this is an opportune time to begin gathering feedback. *Fairness* is designed to provide fair synchronization primitives. While the standard C++ library offers various tools for managing concurrency, it does not provide mechanisms for handling fairness policies. To introduce the most fundamental component of my library, the "priority_mutex," I would like to share a simple example: /#include <thread>/ /#include <chrono>/ /#include <algorithm>/ /#include <BS_thread_pool.hpp>/ /#include <boost/fairness.hpp>/ / / /static boost::fairness::priority_mutex<4> pm;/ / / /static void busy_wait_nano(int64_t nanoseconds){/ /auto begin = std::chrono::steady_clock::now();/ /for(;std::chrono::duration_cast<std::chrono::nanoseconds>(std::chrono::steady_clock::now() - begin).count() < nanoseconds;)/ / continue;/ /}/ / / /static void thread_function_nano(int p, int preCriticalTime, int postCriticalTime, int criticalTime){/ / busy_wait_nano(preCriticalTime);/ / pm.lock(p);/ / busy_wait_nano(criticalTime);/ / pm.unlock();/ / busy_wait_nano(postCriticalTime);/ /}/ / / /int main()/ /{/ / std::array<int, 8> prios {0, 2, 2, 1, 1, 3, 3, 0};/ / std::array<int, 8> preCT {2000, 1500, 2000, 3000, 1000, 500, 500, 2000};/ / std::array<int, 8> postCT {5000, 3000, 2000, 2500, 1000, 1500, 1500, 4500};/ / int criticalTime = 1000;/ / / / BS::thread_pool pool(8);/ / / / for (int i = 0; i < 8; ++i){/ / pool.push_task(thread_function_nano, prios[i], preCT[i], postCT[i], criticalTime);/ / }/ / pool.wait_for_tasks();/ / / / return 0;/ /} / /// using BS thread pool https://github.com/bshoshany/thread-pool in this example./ / / In this example priorities are not given randomly, you can see that I gave 0 priority (the highest priority) to thread 0 which has 2000 + 1000 + 5000 and thread 7 which has 2000 + 1000 + 4500. Priority mutexes function much like a `std::array`, using a 0-indexed based system. For instance, a `priority_mutex<4>` will manage priorities ranging from 0 to 3, with 0 being the highest priority. Currently, the library comprises priority mutexes, both recursive and shared versions, along with RAII wrappers such as `unique_lock` and `shared_lock`, all of which support priorities. There are, however, some elements still missing, including priority condvars and timed versions of the mutexes. The primary motivation behind creating this library is to enhance throughput in multi-threaded pipelines. To illustrate the concept more simply, imagine a pipeline with N tasks, some of which access a protected resource. In cases of contention, there exists an optimal order of resource accesses that minimizes overall execution time, https://sernior.github.io/fairness/ <https://sernior.github.io/fairness/> the images show 2 different ways of ordering critical sections one of which is much better than the other. This library aims to empower developers, who have profiled their software, to manipulate this order with minimal performance overhead and as simply as possible. In terms of implementation, much of the development has revolved around benchmarking and testing. During this process, I've experimented with over 10 different versions of the priority mutex. Ultimately, I achieved the best results by using a priority spinlock, which is also available to library users, to provide internal atomicity to the rest of the mutexes. An essential consideration in the implementation is ensuring that the internal priority spinlock is 128 bytes away from the rest of the memory used by the mutex especially the memory used to perform the atomic::wait on. This separation helps avoid false sharing. The choice of 128 bytes aligns with processor architectures like AMD Zen 4 (the one I am testing on), as indicated in their optimization manual. I can attest that without those 128 byte separation the PM_LockUnlock benchmark was 10X worse and the PM_pipeline_benchmark_fast was worse than the std counterpart (see below for the benchmarks). Another aspect to note in the implementation is the use of 4 bytes for booleans when only a single byte is needed. This decision is related to the way atomic::wait is implemented. Most standard library implementations of atomic::wait check if the type size is supported by the current platform's wait syscall. For instance, Windows can wait on 1 byte, while Linuxkernel based systems can only wait on 4 bytes. These are some benchmark results: 6.4.0-kali3-amd64 AMD Ryzen 5 7600X 6-Core Processor Now the LockUnlock benchmarks were the most difficult to optimize. Those are 8 threads simply doing: m.lock(); m.unlock(); The pipeline benchmarks (with different lenght) are actual pipelines where each thread has different times before/during/after the critical section and I try to set the priorities accordingly to finish as soon as possible. You can see there is also a mutex called slim_priority_mutex, that is a priority_mutex implementation that can support up to 7 (15 if boost atomic is found and your hardware supports the DWCAS) priorities. Those are light weight versions that only take 128 bits up to 7 priorities and past that, up to 15, 256 bits. I am also testing with a custom wait implementations (https://github.com/Sernior/fairness/blob/main/include/boost/fairness/detail… <https://github.com/Sernior/fairness/blob/main/include/boost/fairness/detail…>) which can be tested by defining BOOST_FAIRNESS_USE_EXPERIMENTAL_WAIT_NOTIFY. At some point I wish to make this wait the default version the lib uses instead of the std one since users of my lib could configure this version using my configs macros (number of fast spins - relaxed spins - yield spins before the wait syscall). As I said in the beginning other than to present my lib, this email has the purpose of obtaining feedback. I would like to see if there is anyone (other than me) interested in what I am doing and, if so, consider that I am still far from finished and I would love suggestions. Thank you all for your attention. Best regards, Federico Abrignani.

3 5

[boost.async] new name
by Klemens Morgenstern 13 Oct '23

13 Oct '23

Given the renaming requirement, I'd like to query the list if there are any objections to any of the following names: async.core await co_async / cosync co20 / cor20 Thanks, Klemens

14 28

[Async] Naming land grab?
by Niall Douglas 12 Oct '23

12 Oct '23

Dear Boost, I have received a non-public review which raises concerns about the naming land grab by proposed Boost.Async i.e. a Boost library called "Async" claims too much through its name. Seeing as nobody here has raised this concern to date, can I confirm everybody here is fine with proposed Boost.Async being called Boost.Async? If you are not, please suggest a preferred alternative name. Niall

21 67

Library proposal - indexed_array
by Julien Blanc 12 Oct '23

12 Oct '23

Hi, I've written and released a (rather small) library which allows defining arrays with arbitrary index mechanisms (hence the name, indexed_array). This especially allows indexing with scoped enums, use non zero-starting indexes, or use sparse indexes. This is not a view, but an array in the sense that it owns the data, and provides the same guarantees and functionalities as std::array, such as triviality propagation, being able to reside in read-only program sections, etc. It also supports multidimensional indexing, and provides an indexed_span template class to access lower dimension content (which can be used outside indexed_array). Finally, it provides an opt-in safer way to initialize the array content, which is especially useful when using complex and/or changing indexing schemes (like based on externally generated files). The library is available here: https://github.com/Julien-Blanc-tgcm/indexed_array And the doc is here: https://julien-blanc-tgcm.github.io/indexed_array/ It requires C++17 and mp11, and has first-class support for describe-d enums. If there is some interest, i'd like to propose it for inclusion in boost. So i'm looking for people who would endorse it. Thanks and best regards, Julien

8 24

Re: [boost] Welcome to our NEW Boost Discourse server! 🥳🎉
by René Ferdinand Rivera Morell 12 Oct '23

12 Oct '23

On Wed, Oct 11, 2023 at 5:33 PM David Sankel <camior(a)gmail.com> wrote: > > On Wed, Oct 11, 2023 at 6:20 PM René Ferdinand Rivera Morell <grafikrobot(a)gmail.com> wrote: >> >> How does one start a new topic in a category through email on this? >> I.e. without using the web UI. Yes, I'm trying to use this thing. > > > It looks like this is something I needed to enable. You can try sending an email to boost+development-4(a)discoursemail.com to post to the boost development category. Why is that not a boost.org email address? Also, where do I find those email addresses? -- -- René Ferdinand Rivera Morell -- Don't Assume Anything -- No Supone Nada -- Robot Dreams - http://robot-dreams.net

2 3

[Async] Peer review report and conditions
by Niall Douglas 12 Oct '23

12 Oct '23

Dear Boost, Proposed Boost.Async by Klemens Morgenstern was reviewed between 8th and 18th August, and again between 22nd September and 2nd October. Reviews or substantially detailed comments came from: - /u/trailing_zero_count on Reddit - Ruben Perez - Marcelo Zimbres Silva - Andrzej Krzemienski - Mohammad Nejati - Janko Dedic - Robert Leahy I would like to thank those above for taking the time to write their detailed comments or reviews, and if I forgot to list anyone, please do forgive me. I did read all reviews and comments as they came in, so even if your name is not listed above, I did take into account your feedback. I would also like to thank all those far too many to list here who gave initial impressions, relaying spelling mistakes in the docs, or otherwise gave feedback of various forms. Boost could not continue without you! The tl;dr; outcome is that proposed Boost.Async is ACCEPTED but with CONDITIONS. Next follows are the **binding** conditions without which the library is not accepted: 1. The library needs to be renamed to something the Boost community doesn’t object to Quite a bit of discussion and feedback surrounded the proposed name “Boost.Async”. Multiple people felt that the name claims too much seeing as it is a C++ 20 coroutines only library, and is from first appearances entirely tied into Boost.ASIO (technically, any ASIO i/o executor can wrap any third party executor, but I can see where people get the strong ASIO association). I agree with Klemens that putting “ASIO” in the new name would be out of character with the other Boost libraries also heavily orientated around Boost.ASIO which do not have ASIO in their name. I find the suggestions that C++ 20 coroutines needs to be somehow in the name convincing. Exactly what form it should take I’ll leave up to the author and community to negotiate, but “Boost.Async” is definitely not a name with good buy-in in the Boost community. It cannot be named “Boost.Async” if it is to enter Boost. 2. The `select()` operation either needs to have its semantics changed, or be renamed Quite a few reviewers found the current semantics unpleasantly surprising, in that a random ready awaitable is chosen and all the others cancelled. This is far away from what `select()` typically means in the C and C++ worlds, and multiple reviewers commented negatively about this. The docs are unclear if it is guaranteed that the first ready awaitable is always chosen, or whether it is _some_ ready awaitable. The difference is important in many kinds of async programming. As this is a single threaded implementation, it should be possible to offer strict guarantees here. The semantics are acceptable if the operation is not called “select”, so I would suggest the easiest course here is to rename that operation to something more acceptable to the Boost community. 3. Channels need to terminate the process if relocated during use, or be made immovable, rather than it being UB to relocate them Some reviewers found the hard UB of moving a channel in use a poor design decision. Hard UB is good if it confers distinct benefits, however reviewers couldn’t see one here, and neither can I. As this library requires C++ 20 in any case, the obvious thing to do is make them immovable, but if that is felt too cumbersome, then they ought to noisily terminate the process or something not footgunny if relocated during use. Other non-binding feedback, which is not a hard condition of acceptance: - Multiple people found the naming of `promise` confusing. A promise is something in C++ land associated with a future, and I suppose in a few years it will also be associated with C++ coroutine awaitables. But here we have an awaitable named `promise`? Yes I know it makes sense in other programming languages, but here in C++ land it just seems weird and confusing for no obvious gain. I personally would suggest `eager_task` and `lazy_task` but I have no especially strong opinions on naming here other than that `promise` is a poor choice for any awaitable type. In fact, I think just don’t put the word “promise” into any awaitable type period. - I am sympathetic to multiple people raising the lack of preconditions and postconditions on operations described in the documentation. I also accept that in an async world, it’s hard to be precise. However, I think it would be a large benefit to the documentation to describe for each operation a list of the ways in which it can fail, and I think this should be added. - Andrzej took issue with the design of the generators, and I can see why. However, out in real world code land, C++ coroutine generators have surprisingly large amount of design variation. I’ve seen ones which you loop on testing them for boolean true, I’ve seen others which loop on their iterators, I’ve even seen ones which don’t implement either boolean true nor iterators and require you to call a `value()` member function which returns an Optional. Why? No idea, people seem to innovate uselessly here for some reason. I think it wise to adhere to `std::generator` from the standard, and do exactly what it does. From my reading of Async’s `generator`, whilst it has extensions e.g. the invocable call operator, the only thing missing is the iterator interface to make it implement `std::generator` and I don’t see any obvious reason why an iterator interface can’t be added here? - I agree with Andrzej about ever throwing `std::logic_error`, it should not be done in newly written code. It is recognised as a mistake by most on the standards committee nowadays. - The Mersenne Twister is a poor PRNG by modern standards. You should use JSF or anything else both much faster and higher quality. - More than one reviewer wants the docs to do a much better job on documenting pseudo-awaitables and awaitables and `await_transform`. - Quite a few times the docs talks about “async” when it really means “C++ coroutines”. - I think the docs does a poor job of disambiguating when what it is describing is part of the C++ standard, or it is part of Boost.Async. The reason this is important is that users need to know when/if they are locking themselves into Boost.Async proprietary extensions vs standard C++ coroutines. Finally, as a personal note on the review, it was notable how much negativity there currently is against C++ coroutines in general from the C++ community. A small number of us have been writing C++ coroutine code for many years now, we have been through the process of getting footgunned over lifetime issues, got frustrated that these coroutines are not the coroutines we were looking for, and eventually came round to understanding what C++ coroutines are good at solving, and more importantly what they are NOT good at solving. Once your head is wrapped around that, then comes the problem of having to reinvent a C++ coroutine support library because all the current open source ones have severe issues, especially around very tight coupling being imposed on your codebase. I don’t personally agree with every design decision in proposed Boost.Async, but I do think this will be a major step forward in making C++ coroutines accessible to many more developers than now, especially because this is to my knowledge the first standards-based loosely coupled C++ coroutines library which is open source. Undoubtedly after it ships with Boost, deficiencies will be found both in this library and in the currently quite poor quality implementation of C++ coroutines in the three major compilers. I very much hope that the increased number of developers using C++ coroutines as a result of this new Boost library will result in large and substantial improvements in implementation and library support of C++ coroutines. My thanks to Klemens for putting the work into what is a controversial and opinionated library design quite unlike any other currently available. It’s not easy to tread new ground without much precedent. My thanks to the Boost and Reddit communities for their ample and detailed review feedback, which made me managing this review possible.

5 13

Welcome to our NEW Boost Discourse server! 🥳🎉
by Inbal Levi 11 Oct '23

11 Oct '23

Hello everyone! Boost board has been working on a few improvements lately, one of which is to create a new *Boost Discourse server: https://discourse.boost.org/ <https://discourse.boost.org/>* The server is meant to allow more interactive and convenient development in the boost community, and we'll be happy to have you all there! *To join the server:* 1. Go to the URL: https://discourse.boost.org/ 2. Login to the discourse server 3. The server contains three categories: 1. Beginners - start here if you're new to Boost or to discourse 2. Boost Development - go here to create a new topic of discussion (roughly, we expect every new library will have its own discussion thread) 3. Community - go here if you'd like to start a thread about community topics, or if you'd like to talk about anything that doesn't fit the first two topics :) *To start a technical discussion:* 1. log-in 2. Go to the "*Boost Development*" category 3. Click on "+ New Topic" (in the right upper corner), and add a new discussion topic for your library! [image: image.png] Please review our Code of Conduct <https://cppnow.org/about/code_of_conduct/> before participation. We expect a respectful and positive discussion! If there are any technical issues, feel free to approach me at: sinbal2lextra(a)gmail.com or any other of the server admins: jeff(a)crystalclearsoftware.com, camior(a)gmail.com, whatwasthataddress(a)gmail.com Looking forward to seeing you all in our new discourse server! 🤗 Thanks, Inbal Levi, in the name of the Boost Foundation board members ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ *Lead Software Engineer @ Millenium* Isocpp, Boost &"Hamakor" Non-Profits Board Member ISO C++ LEWG Chair & Israeli NB Chair C++Now Program Chair & CoreC++ Conference Organizer ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

6 8

Mutual respect
by David Sankel 10 Oct '23

10 Oct '23

Some comments in the boost Async discussion were unconstructive and disrespectful. I want to remind folks that this is not how this community operates and thrives. Technical disagreements are, of course, fine and encouraged but we don't cross into putting people down, imputing nefarious motives, or disrespecting people's efforts. Thanks, -- David

2 1

Raising minimum target Windows version
by Andrey Semashev 08 Oct '23

08 Oct '23

Hi, I'm considering raising minimum target Windows version for my libraries to at least Windows 7. This means dropping workarounds for missing WinAPI functions that are present (but, for a very long time now, untested) for Windows XP. This specifically pertains to Boost.Atomic, Boost.Filesystem and Boost.Log. I'm also tempted to raise the requirement to Windows 8 to have access to WaitOnAddress & co., but I'm hesitant since Windows 7 might still be wide spread (perhaps, not on desktop but embedded). The current plan is to announce this in the release notes for the upcoming 1.84 release and drop the support in 1.85. This will mean the dependent libraries and tools will similarly drop support for older Windows versions. Additionally, I'm proposing to raise the default target Windows version in Boost.WinAPI to Windows 10, provided that the Windows SDK that is detected in compile time supports it. This means that by default many Boost libraries that rely on Boost.WinAPI for WinAPI definitions will target Windows 10. Which, in particular, means the prebuilt binaries we distribute will require Windows 10, unless libraries take explicit measures to stay compatible with older versions. I have no fixed time frame for the proposed Boost.WinAPI change, but it could be done as soon as in 1.84, since this doesn't remove anything, just changing the default. Comments? Objections? Counter-proposals? I'm especially interested in comments regarding Windows 7 as the new baseline - am I being too conservative? Thanks.

6 10

issue with boost::any documentation
by jepessen＠wteam.it 06 Oct '23

06 Oct '23

Hi. I was reading the online documentation for boost::any, when I went to this page: https://www.boost.org/doc/libs/1_83_0/doc/html/any/ValueType.html clicking on the next arrow will go to this page https://www.boost.org/doc/libs/1_83_0/doc/html/reference_section.html that seems a page of boost::PFR instead of boost::any. In fact, by clicking on next and previous arrows, allows navigating to PFR documentation. Im not an expert on about how documentation works, so I dont know how fix it and make a pull request. What should I do? Daniele Lupo

2 1

[Async] Review from Janko Dedic
by Niall Douglas 02 Oct '23

02 Oct '23

This was sent to me privately with an express wish it be posted here. I don't know if the author is subscribed here, so I don't know if replies will be seen. This is the first REJECT review. Niall --- cut --- What follows is my review of the proposed Boost.Async library. >Please state your experience with C++ coroutines and ASIO in your review, and how many hours you spent on the review. I have considerable experience with C++ coroutines as I've been implementing my own coroutine types in the past. I have used Asio before in a professional setting, although I wouldn't call myself an Asio expert. My experience involved using Beast/Asio to perform HTTP requests and sending fan-out notifications to external subscribers. Notably, I have a lot of experience with asynchronous programming in other programming languages, mainly Java, Kotlin and JavaScript, but I'm also very familiar with how it works in Go and Rust. I would say I've spent around 10 hours evaluating the proposed library. When I first saw this library being proposed, I was hoping it would provide a more modern, capable and ergonomic version of asynchronous programming, like other modern programming languagues and unlike Asio. The goal of this library is seemingly not to provide such an out-of-the-box seamless solution, but very specifically to provide certain coroutine-related utilities and enable composition of different coroutine types, including user-defined coroutine types (unlike `asio::awaitable`). However, I don't think either characterization is entirely correct, and Boost.Async finds itself in an awkward middle. On one hand, it does not build on top of Asio to provide a modern and seamless experience which would completely replace the direct usage of Asio (which is exposed front-and-center in the interface and code using this library has to also use Asio a lot to get the job done). On the other hand, it's also not a completely generic "coroutine library" that only provides abstractions based on C++ coroutines that could be used by any library (because it depends on Asio specifically). In my view, the correct way to characterize this library would be to regard it as a bundle of coroutine-related utilities on top of Asio. However, the library is evidently not entirely compatible with any kind of Asio usage as it's focused on "simple single threaded asynchronicity." It can certainly be used in conjunction with Asio, but it definitely brings some additional nuance and complexity (which I don't think is good, considering that Asio has a lot of complexity of its own). When it comes to added functionality, there are definitely some welcome additions in the form of `async::with` for asynchronous clean-up, `async::select`, generators. What mainly stands out to me is channels, which are a very important bread-and-butter feature for many languages. However, we should keep in mind that Asio has some experimental support for channels as well, and users of this library would probably be faced with an unnecessary choice sometime in the future. One of the most advertised features is the ability to "compose arbitrary third party awaitables without any additional effort, which lets you tie together third party libraries with ease and convenience". Firstly, I don't think this is a goal worth pursuing. As a user, I would definitely want as few coroutine types as possible in my codebase (ideally one). `asio::awaitable` already nicely fits the bill. I very well understand that we need at least a few more for sync/async generators, but that's where I'd draw the line. Secondly, this library does not exactly fulfill the promise of "tying together third-party libraries with ease". Boost.Async does not work with any coroutine library out of the box. For example, my coroutine types are incompatible with it and the code doesn't compile. Same goes for `asio::awaitable`. There is definitely some integration effort necessary to wrangle these distinct types to work together. Related to this, I also dislike exposing the whole C++ coroutine machinery as some kind of a first-class "standard" API for integrating different coroutine types together. There is evidently no "standard" API for integrating different coroutine types as arbitrary coroutine types won't simply work together out of the box. Additionally, having used the standard coroutine customization points myself, I can't say I like this API at all and I consider it a necessary evil. It is very subtle, error-prone and hard to reason about. This is definitely not something that should be exposed to the users of the library, even experts. Implementing one coroutine type is hard enough, but making sure that two coroutine types from different authors work together is even harder. Considering the complexity of the standard coroutine API, even if my coroutine types compiled with this library's types, I would not trust the whole thing to actually work in all the edge cases. I believe `asio::awaitable` made the right choice here. I have built the library and played with the examples a bit. I've tried integrating it with my own coroutine types as I've described above. The documentation is filled with examples, which is good, but the reference section is lacking a bit in a sense that it doesn't document the signature, arguments, the return type, preconditions etc. as you would expect. I don't see this is a major issue because the documentation can always be improved, and perhaps we still have to discover how to effectively document coroutines because of how unique and different they are. I vote to REJECT this library on the basis outlined above. This is definitely an admirable effort and I want to see more progress for C++ in this direction, because the standardization efforts are not promising and there are still no open-source libraries comparable to the likes of Rust's Tokio and Kotlin's standard library. Unfortunately, I don't think this library is a step in the right direction. All the best, Janko Dedic

2 1

PSA: C++11 libraries need to update their libraries.json and CMakeLists.txt
by Peter Dimov 02 Oct '23

02 Oct '23

Libraries that now require C++11, such as Atomic, TypeIndex, LexicalCast, need to update their libraries.json files to now state "cxxstd": 11, and to add the C++11 requirement to their CMakeLists.txt files, e.g. target_compile_features(boost_lexical_cast INTERFACE cxx_std_11) boostdep --cmake looks at libraries.json and automatically adds the above requirement, so for generated CMakeLists.txt files (such as the one in lexical_cast), a simple regeneration with e.g. `boostdep --cmake lexical_cast` will suffice. Note that cxx_std_11 requires CMake 3.8, so the cmake_minimum_required line may need to be adjusted as well. (`boostdep --cmake` does that automatically.)

2 4

Windows Regression Runners - Failing on Develop
by Tom Kent 02 Oct '23

02 Oct '23

Starting sometime between 3am and 5pm on September 11, 2023, all the windows regression runners started failing on the develop branch. Master branch runners on the same VM are still doing fine ( https://www.boost.org/development/tests/master/developer/summary.html) The output doesn't have anything jump out at me. Nor were there any commits to the develop branch in that window that seem suspicious to me. The regression run output ends with: ...found 1 target... # Searching for "process_jam_log.exe" in "C:\teeks99-09\run\boost_regression\stage\bin"... Traceback (most recent call last): File "run.py", line 71, in <module> runner(root) File "C:\teeks99-09\run\boost_regression_src\regression.py", line 286, in __init__ self.main() File "C:\teeks99-09\run\boost_regression_src\regression.py", line 623, in main getattr(self,action_m)() File "C:\teeks99-09\run\boost_regression_src\regression.py", line 580, in command_regression self.command_setup() File "C:\teeks99-09\run\boost_regression_src\regression.py", line 351, in command_setup self.build_if_needed(self.process_jam_log,self.pjl_toolset) File "C:\teeks99-09\run\boost_regression_src\regression.py", line 714, in build_if_needed tool[ 'build_path' ] = self.tool_path( tool ) File "C:\teeks99-09\run\boost_regression_src\regression.py", line 739, in tool_path , '\n'.join( [ name_or_spec[ 'path' ], build_dir ] ) Exception: Cannot find "process_jam_log.exe" in any of the following locations: C:\teeks99-09\run\boost_regression\stage\bin\process_jam_log.exe C:\teeks99-09\run\boost_regression\stage\bin With the full output available here: https://gist.github.com/teeks99/bb4230f6a1efdd7af11bd93341c950bf Any ideas on this would be much appreciated.

5 15

Dropping support for InPlaceFactory from Optional
by Andrzej Krzemienski 01 Oct '23

01 Oct '23

Hi Everyone, I would like to get the community's advice on removing the support for InPlaceFactory from Boost.Optional. The motivation for this is to reduce dependencies among Boost libraries. Boost.Optional is surprisingly heavy. This is mostly due to the dependency on InPlaceFactory and OptionalPointee from Boost.Utility. https://pdimov.github.io/boostdep-report/develop/module-weights.html#weight… InPlaceFactory ( https://www.boost.org/doc/libs/1_83_0/libs/utility/doc/html/utility/utiliti…) used to be a workaround for the missing "perfect forwarding" in C++03, it emulated both "universal references" and variadic templates. It is unnecessary for C++11 where Boost.optional offers a superior interface. But removing the support for InPlaceFactory would break code for people that happen to use it. When the user switches to C++11 (C++03 support is deprecated for Boost.Optional) they should expect their programs to still compile. But if I remove the InPlaceFactory, it forces the users to change their code, even if they are already on C++11. Can InPlaceFactory be moved to a separate library? Or is it so useless now that it has to be eradicated even at the cost of breaking users' code? I would welcome any suggestions. Regards, &rzej;

3 3

[boost.async] Andrzej's review
by Andrzej Krzemienski 01 Oct '23

01 Oct '23

Hi Everyone, I would like to thank Klemens for writing and sharing the Async library. It is something the community needs, and it is clear that a lot of thought and effort was put in it. I am not an expert on C++ coroutines or coroutines in general. I have played with a few echo-server examples in the past from Boost.ASIO, and created some toy examples of C++ coroutines. I devoted something like twelve evenings studying the Boost.Async: reading docs, testing toy examples (Windows 11, MSVC 2022), debugging and asking Klemens a lot of questions. Still, I cannot say I understand the library well enough to be able to responsibly give a recommendation. But I can still share my observations. On the design. Although my knowledge is superficial, I will risk a claim that the synchronization mechanisms and supporting features (`with`, channels, work_group) are the strong part of the design. (I disagree with the overload set for `select`, but I guess this is a non-design bug.) Regarding the choice and design of "coroutine types", I have certain reservations. It is still not clear to me why we have two -- promise and task -- and when I should use which. The docs give some answer: promise is eager, task can be awaited/spawned on another executor than it was created on. But is that it? I sense that there is a good reason to have them as two types, a better/clearer one than this described in the docs.But I fail to see it, and the docs do not explain it clearly enough, I think. I am uneasy about the design for `generator`. I filed a couple of issues: https://github.com/klemens-morgenstern/async/issues/101 https://github.com/klemens-morgenstern/async/issues/70 One problem is how the `generator` signals that it has finished. In all the examples it has to create a dummy value. I hear from Klemens that it is a necessity imposed by the coroutine design in C++. I do not feel competent to confirm it or not. But I note that std::generator does not require the user to `co_return` anything. And that asio::experimental::coro does allow the user to specify that they do not want to co_return even if they co_yield things. Regarding the value-returning generators, I have even more reservations. As noted in one of the quoted GitHub issues, the fact that it has a different interface than the normal generator, and that it has to be lazy to be usable, It looks to me like it qualifies for a separate coroutine type. On the documentation. The only other library offering coroutine support and any documentation that I know of is Boost.ASIO. In comparison to Boost.ASIO, Boost.Async has a waaay better documentation. It is big (in a positive sense), it has a lot of tutorial materials, lots of ideas explained, it is still being improved. It is waaay above the average quality of a library documentation that you can find on the web. But still I would greatly appreciate an even better one, however arrogant that seems. My reasoning is that for the next couple of years people who will consider Boost.Async will not only be unfamiliar with the library but also with C++ coroutines in general. They will need additional extra help to be able to use the library responsibly. To be more specific, I would expect more full compiling examples (those in folder examples) that illustrate different aspects of the library. For instance: * A convincing example of value-returning generator * timeout implemented in terms of `async::select`. I would expect a more detailed explanation of concepts used in this library: * interruption and cancellation, and how they differ, and when/if I should care about them. * being detaching and being detached, and how it is different from spawning. I got a response in one of GitHub issues that, "Interrupt is [...] meant to make select work lossless. What gets detached is the co_await itself, not the awaited thing." I feel the documentation should explain it more cleanly, and perhaps introduce some more well defined terms. The library does not cleanly communicate preconditions on the operations. I think it sometimes decides to throw an exception when a precondition is more appropriate. In other places it is silent about the corner cases. It also does not specify clearly what is guaranteed of the provided operations. Klemens correctly points out that postconditions are tricky in the case of asynchronous operations, but (1) some things in the library are not asynchronous and (2) this library (like any other) does offer some guarantees, if not on individual function calls, then for the entire expressions. For instance `co_await select(aw1, aw2)` does provide a guarantee that the result of one of the awaitables will be returned and the others will be interrupted. It should be specified in the synopsis of `select`. On the implementation. It is mostly magic to me, so I do not have much to say. There are a lot of awaitable types created whose existence I could not predict from studying the docs. I cannot say if this is a deficiency of the documentation, or is this how the C++ coroutines work: you might need a lot of awaitables that are implementation details. I find the design of the overload set of functions `select` bad and generic-programming-unfriendly. I explained it in detail in: https://github.com/klemens-morgenstern/async/issues/103 Functions that do slightly different things should have different names. Returning different types for special cases breaks generic code, and causes surprises, sometimes runtime surprises. Also, because the overload for value-returning promises returns a variant, I have run into an interesting situation when trying to add a timeout support to the echo server example. I get the following statement: ``` variant2::variant<variant2::monostate, tcp_socket> ans = co_await async::select( timer.async_wait(async::use_op), acceptor.async_accept() ); ``` And now I have a variant to unpack inside a coroutine. Normally, the recommended way to unpack a variant is to use a visitor: ``` struct visitor { void operator()(tcp_socket&& sock) { co_yield std::move(sock); // ERROR } void operator()(variant2::monostate&&) { } }; visit(visitor{}, std::move(ans)); ``` But this doesn't work, because now I am co_yield-ing from a non-coroutine. And I have to resort to manually inspecting the variant, which is taught to be error prone. I guess this is the right choice to use variant for the return type of `select`, and that it is the limitation of variant, until C++ gets pattern matching. But still, it would be helpful if the documentation (or examples) illustrated what potential difficulties the user can expect. Should the library be accepted to Boost? Again, I am not competent enough in the domain of coroutines, to responsibly say that the library meets the bar, but because I think the community desperately needs this kind of library with Boost-quality docs and support, I will risk saying that Boost.async should be conditionally accepted. The conditions being: * Address the design of generators (either change it or provide a clearer rationale) * Improve the docs - clearly describe the notions of interrupting, canceling, detaching, spawning. - provide a more detailed synopses for functions and classes with preconditions, described effects, and the guarantees. I filed this as a list of issues in the GitHub: https://github.com/klemens-morgenstern/async/issues/120 https://github.com/klemens-morgenstern/async/issues/119 https://github.com/klemens-morgenstern/async/issues/117 https://github.com/klemens-morgenstern/async/issues/115 https://github.com/klemens-morgenstern/async/issues/114 https://github.com/klemens-morgenstern/async/issues/103 https://github.com/klemens-morgenstern/async/issues/101 https://github.com/klemens-morgenstern/async/issues/100 https://github.com/klemens-morgenstern/async/issues/70 https://github.com/klemens-morgenstern/async/issues/64 Finally, while the above might look like a list of complaints, I really appreciate the work that was done in order to provide this library, and the solutions that were applied (like the clever use of await_transform). I learned a lot from studying this library, and my intuition tells me that it will end up being a great addition to Boost. I also appreciate the responsiveness of the author. Klemens has been answering a lot of my questions in a timely fashion, and improving the docs based on feedback. Thanks! Regards, &rzej;

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[Async] Second attempt at review of proposed Boost.Async begins
by Niall Douglas 01 Oct '23

01 Oct '23

Dear Boost, Due to too few reviews last time, we are going to try again the review of this library. This review shall run between Friday 22nd September and Monday 2nd October. Please do consider contributing a review! My thanks to Marcelo Zimbres Silva for the only formal review last time, and to the others including those on Reddit /r/cpp and by private email who submitted feedback. All your reviews and feedback have been retained and will be reused for this review. To remind you all, Boost.Async is a C++ coroutine programming library based around Boost.ASIO as the executor, with a unique set of properties which make it incomparable to most existing C++ coroutine programming libraries. To be specific, it lets you compose arbitrary third party awaitables without any additional effort, which lets you tie together third party libraries with ease and convenience. Changes to proposed Boost.Async since the last review: 1. Major doc improvements & bug fixes 2. PMR is optional 3. optimized associated allocator for use_op 4. lazy generator support 5. public unique_handle & more examples with custom awaitables 6. as_result/as_tuple support (akin to the asio stuff, but takes an awaitables, i.e. co_await as_result(foo())) - reduces unnecessary exceptions. 7. with supports return values. You can read the documentation at https://klemens.dev/async/ and study or try out the code at https://github.com/klemens-morgenstern/async. Anyone with experience using C++ coroutines is welcome to contribute a review at the Boost mailing list (https://lists.boost.org/mailman/listinfo.cgi/boost) at /r/cpp on Reddit, via email to me personally, or any other mechanism where I the review manager will see it. In your review please state at the end whether you recommend acceptance, acceptance with conditions, or rejection. Please state your experience with C++ coroutines and ASIO in your review, and how many hours you spent on the review. Thanks in advance for your time and reviews! Niall

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boost::any_cast gives build errors with VS2022, boost v1.82 and C++17
by Bhuyan, Jyotideep 01 Oct '23

01 Oct '23

Hi, I was using VS2019, boost v1.78, and C++14 version and the below code was working well. Same code gives build error with VS2022, boost v1.82, and C++17 due to "o << *boost::any_cast<T>(&a); " Instruction. I wanted to know why it behaves differently. Code : class any_out { struct streamer { virtual void print(std::ostream& o, const boost::any& a) = 0; virtual streamer* clone() = 0; virtual ~streamer() {} }; public: any_out() : m_streamer(nullptr) { } ~any_out() { delete m_streamer; } template <typename T> any_out(const T& value) : m_streamer(new streamer_imp<T>), m_object(value) { } any_out(const any_out& a) : m_streamer(a.m_streamer ? a.m_streamer->clone() : nullptr), m_object(a.m_object) { } template <typename T> any_out& operator=(const T& r) { any_out(r).swap(*this); return *this; } any_out& operator=(const any_out& r) { any_out(r).swap(*this); return *this; } any_out& swap(any_out& r) noexcept { std::swap(m_streamer, r.m_streamer); std::swap(m_object, r.m_object); return *this; } friend std::ostream& operator<<(std::ostream& o, const any_out& a) { if(a.m_streamer) { a.m_streamer->print(o, a.m_object); } return o; } boost::any& get() { return m_object; } const boost::any get()const { return m_object; } bool empty() const { return m_object.empty(); } private: template <typename T> struct streamer_imp : public streamer { virtual void print(std::ostream& o, const boost::any& a) { try { if (a.empty()) { o << "<empty>"; } else { o << *boost::any_cast<T>(&a); } } } virtual streamer* clone() { return new streamer_imp<T>(); } }; // Members streamer* m_streamer; boost::any m_object; }; I have migrated to VS2022, boost v1.82, and C++17, and due to a build error, I have changed the code below. virtual void print(std::ostream& o, const boost::any& a) { try { if (a.empty()) { o << "<empty>"; } else { o << boost::any_cast<T*>(a); } } } any_out anyTest; anyTest = 100; std::string actualStr; actualStr = make_string() << anyTest; actualStr prints nullptr (0000000) instated of value 100 for VS2022, boost v1.82 and C++17 Best Regards, Jyotideep (JD) Please be advised that this email may contain confidential information. If you are not the intended recipient, please notify us by email by replying to the sender and delete this message. The sender disclaims that the content of this email constitutes an offer to enter into, or the acceptance of, any agreement; provided that the foregoing does not invalidate the binding effect of any digital or other electronic reproduction of a manual signature that is included in any attachment. Confidential - Company Proprietary

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[Async] Reminder that peer review ends on Monday
by Niall Douglas 29 Sep '23

29 Sep '23

A reminder to Boost folk that the proposed Boost.Async review ends on Monday 2nd October. I have received no new reviews since this second review began. You can read the documentation at https://klemens.dev/async/ and study or try out the code at https://github.com/klemens-morgenstern/async. Niall

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Re: [boost] Fwd: [boost.async] Andrzej's review
by Niall Douglas 29 Sep '23

29 Sep '23

Andrzej, Firstly, it's weird I don't see this on the Boost mailing list. In fact, I seem to only get about half the mail to the Boost mailing list ever since they fiddled with the servers. So thanks for sending this review to me directly. I've also caught up with all your other posts on Boost.Async from https://lists.boost.org/Archives/boost/2023/09/index.php, none of which I had seen before now. Thanks for the review. If you don't mind if I jump in with a few bits myself which are intentionally not about the review itself ... On 29/09/2023 14:08, Andrzej Krzemienski wrote: > Regarding the choice and design of "coroutine types", I have certain > reservations. > It is still not clear to me why we have two -- promise and task -- and > when I should use which. The docs give some answer: promise is > eager, task can be awaited/spawned on another executor than it was > created on. But is that it? I sense that there is a good reason to have > them as two types, a better/clearer one than this described in the > docs.But I fail to see it, and the docs do not explain it clearly > enough, I think. Outcome calls the same thing eager and lazy. I felt lazy is a more descriptive name than task. I mean, why should a task be lazy rather than eager? The reason is simply because Lewis Baker happened to choose that default, and it's stuck since, but there isn't any strong rational for "task ~= lazy" other than convention. > One problem is how the `generator` signals that it has finished. In all > the examples it has to create a dummy value. I hear from Klemens that it > is a necessity imposed by the coroutine design in C++. I do not feel > competent to confirm it or not. But I note that std::generator does not > require the user to `co_return` anything. And that > asio::experimental::coro does allow the user to specify that they do not > want to co_return even if they co_yield things. It's been a while since I used coroutine generators, but my memory is when the coroutine exits then the generator returns its end iterator value. I don't remember dummy values. But then I 99.9% use C++ coroutines with Result, to avoid ever throwing C++ exceptions through C++ coroutine machinery which *still* is riddled with showstopper bugs in current compilers. > On the documentation. The only other library offering coroutine support > and any documentation that I know of is Boost.ASIO. There are actually a good few Boost libraries with C++ coroutine support now in one form or other. Outcome is obviously one, but there is at least one other apart from ASIO (somebody else may remind me which one now). Boost.Async's are much fuller featured obviously, but even Outcome's simple ones are usually good enough for most use cases. You don't need to use them with Result either. > But this doesn't work, because now I am co_yield-ing from a > non-coroutine. And I have to resort to manually inspecting the variant, > which is taught to be error prone. BTW tip for the future: just use helper coroutine lambdas if you need to do coroutine stuff from within normal code. These normally don't work with the Coroutine support from cppcoro, stdexec, libunifex nor ASIOs because their coroutines don't allow it. But Boost.Async's does, as does Boost.Outcome's. It cannot be understated the usefulness of being able to dip in and out of "coroutine land" using inline lambdas from normal code. It makes C++ coroutines vastly more convenient to use. Niall

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[fiber] Moving fibers between threads
by Niall Douglas 28 Sep '23

28 Sep '23

Dear Boost, At work I need to move a Boost Fiber from one kernel thread to another. There is a dedicated documentation page for this: https://www.boost.org/doc/libs/1_83_0/libs/fiber/doc/html/fiber/migration.h… What that page doesn't say is how to migrate yourself if you're currently within a Fiber to another kernel thread, as the docs only talk about migrating Fibers currently not executing and in the ready not sleeping state. I guess this would work: 1. Create a new Fiber, and go into a loop giving up the current execution. 2. When that new Fiber executes, migrate the original fiber to its new kernel thread, then have it exit the loop so it proceeds. Then self immolate, as you're done. But now you're creating and destroying a whole Fiber just to migrate a Fiber between kernel threads, and that feels icky. I don't suppose there's a better way e.g. some sort of way of asking the current thread's Fiber scheduler to call a function when it's next not executing a Fiber? That would avoid the needless Fiber creation and destruction per migration of a Fiber across kernel threads. Thanks for help in advance. Niall

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